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JOHNSON MATTHEY
TECHNOLOGY REVIEW www.technology.matthey.com

Johnson Matthey Technol. Rev ., 2015, 59 , (1), 2–3 http://dx.doi.org/10.1595/205651315X686723
JOHNSON MATTHEY
TECHNOLOGY REVIEW www.technology.matthey.com
It may surprise some readers to see an edition of this journal dedicated largely to lithium-ion batteries, but this is a technology that Johnson Matthey considers a major new business area for the company.
Johnson Matthey has been involved in research and development (R&D) in the battery materials space for several years and launched its commercial business operations in the sector in 2012. Since then, the company has made a series of acquisitions to establish itself both as a global supplier of cathode materials and of advanced battery systems. Complemented by its lithium-ion battery research group at the Technology
Centres in Sonning Common, UK, and in Singapore, the Battery Technology business of Johnson Matthey sits within its New Business Division. It represents a further expansion of the company’s core strengths and expertise in chemistry and advanced materials to develop new, high technology products.
Johnson Matthey Battery Technologies brings together the company’s activities in lithium-ion and next generation batteries and operates at two points in the value chain for lithium-ion batteries ( Figure 1 ).
Through a combination of in-house R&D and acquisition the company is establishing itself as a signifi cant player in the sector. From an initial position in lithium iron phosphate materials, further investments in the coming years will expand the product range, working with cell developers to commercialise improved and next generation materials.
There are big challenges to deliver the performance required for advanced lithium-ion cells, not just initial performance but durability and long term safety, as well as cost. Good cell design and effi cient manufacture are critical elements but the functional materials used are also important contributors and big improvements are still required. We believe that Johnson Matthey’s deep understanding of functional materials design can be applied to some of these challenges and we think that solving them is a huge opportunity.
At the other end of the chain we will continue to work on the design and supply of complex, high performance battery systems for demanding customers in both automotive and non-automotive sectors. In addition to
Raw materials e.g. precursors
Cell materials e.g. cathodes
Cell manufacture
Engineering, optimisation & fabrication
System design
Engineering & manufacture
OEM customer e.g. vehicle producers
Fig. 1. Johnson Matthey Battery Systems’ input into the value chain for lithium-ion batteries
2 © 2015 Johnson Matthey

http://dx.doi.org/10.1595/205651315X686723 Johnson Matthey Technol. Rev ., 2015, 59 , (1) being an attractive growth sector in its own right the battery systems activities help defi ne future materials requirements through providing deep applications knowledge in the sector.
Taken together Johnson Matthey’s Battery businesses will have three major manufacturing operations in
China, Canada and Poland together with R&D facilities in the UK, in Germany and in Singapore.
As well as looking at today’s lithium-ion chemistries
Johnson Matthey continues to invest in longer term research in the sector, covering next generation lithiumion and also other systems such as metal-air and metalsulfur chemistries.
Examples of collaborative, EU-funded programmes in which Johnson Matthey is involved include the Lithium
Sulfur Superbattery Exploitating Nanotechnology
(LISSEN) project. This project is aimed at the electrode and electrolyte materials to promote the practical implementation of the very high energy lithium-sulfur battery. It is expected that this battery will offer an energy density at least three times higher than that available from the present lithium battery technology, a comparatively long cycle life, a much lower cost (replacement of cobalt-based with a sulfur-based cathode) and a high degree of safety
(no use of lithium metal). The project will benefi t from the support of a laboratory expert in battery modelling, large research laboratories having modern battery production facilities and chemical and battery manufacturing industry partners.
Stable Interfaces for Rechargeable Batteries
(SIRBATT) is a multisite collaborative project consisting of 12 full partners from the European area (six universities, one research institute and fi ve industrial partners). Collaboration with leading battery research groups in the USA and Japan is also considered.
SIRBATT will develop microsensors to monitor internal temperature and pressure of lithium cells in order to maintain optimum operating conditions to allow long-life times that can be scaled for use in grid scale batteries.
The scientifi c aim of SIRBATT is a radical improvement in the fundamental understanding of the structure and reactions occurring at lithium battery electrode/ electrolyte interfaces.
The Practical Lithium Air Batteries (PLAB) project brings together a range of academic and industrial partners with complementary skills to work on improved lithium-air battery single cells and assess their feasibility in future battery pack and system design, viability for use in automotive applications. Academic partners Queens University Belfast and Liverpool
University, both in the UK, will work on synthesising and characterising the new electrolytes, whilst Johnson
Matthey Technology Centre will produce novel cathode and anode materials, optimise electrode structures and perform electrochemical testing. The participation of Jaguar Land Rover as an end user and Johnson
Matthey Battery Systems (formerly Axeon) will provide an applications focused approach and they will perform a paper feasibility study on how high performing lithiumair single cells would be incorporated into automotive systems in the future. The fi nal output will assess the feasibility for lithium air battery systems to achieve a
400 Wh kg –1 power density.
MARS-EV aims to overcome the ageing phenomenon in Li-ion cells by focusing on the development of highenergy electrode materials (250 Wh kg –1 at cell level) via sustainable scaled-up synthesis and safe electrolyte systems with improved cycle life (> 3000 cycles at 100% depth of discharge (DOD)). Through industrial prototype cell assembly and testing coupled with modelling
MARS-EV will improve the understanding of the ageing behaviour at the electrode and system levels. Finally, it will address a full life cycle assessment of the developed technology. MARS-EV brings together partners with complementary skills and expertise, including industry and covering the complete chain from active materials suppliers to cell and battery manufacturers, thus ensuring that developments in MARS-EV will directly improve European battery production capacities.
Johnson Matthey is excited to be involved in these and many other projects in the fi eld of lithium battery research. We hope that readers will enjoy the articles about lithium batteries in this issue, and look out for future articles and reviews on this topic in future issues.
MARTIN GREEN
Director, Battery Technologies
Johnson Matthey Plc, 5th Floor, 25 Farringdon St,
London, EC4A 4AB, UK
Email : martin.green@matthey.com
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http://dx.doi.org/10.1595/205651315X685445
Johnson Matthey Technol. Rev ., 2015, 59 , (1), 4–13
Johnson Matthey Battery Systems, Orchard Road,
Royston, Hertfordshire, SG8 5HE, UK
Email: peter.miller@matthey.com
Recently lithium-ion batteries have started to be used in a number of automotive passenger car applications.
This paper will review these applications and compare the requirements of the applications with the capabilities of the lithium-ion chemistries that are actually being used. The gaps between these requirements and capabilities will be highlighted and future developments that may be able to fill these gaps will be discussed.
It is concluded that while improvements to the lithiumion cell chemistry will help reduce the weight of battery packs for electric vehicle applications the largest weight gains will come from the pack design. e –
3 V
Li x
C
6
Graphite
Li + conducting electrolyte
Li + charge
Lithium-ion cells ( Figure 1 ) (1), in their most common form, consist of a graphite anode, a lithium metal oxide cathode and an electrolyte of a lithium salt and an organic solvent. Lithium is a good choice for an electrochemical cell due to its large standard electrode potential (–3.04 V) resulting in a high operating voltage
(which helps both power and energy) and the fact that it is the metal with the lowest density (which reduces weight).
The construction of a typical cylindrical cell is shown in Figure 2 , while Figure 3 shows a typical pouch cell. Such cells provide a relatively light and small source of energy and are now manufactured in very large quantities (>1 billion cells per year) (2). In an automotive application a lithium-ion battery consists of tens to thousands of individual cells packaged together to provide the required voltage, power and energy. e –
LiCoO
2 e – e –
Fig. 1. Diagrammatic view of a lithium-ion cell (1)
4
Li + discharge
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http://dx.doi.org/10.1595/205651315X685445 Johnson Matthey Technol. Rev ., 2015, 59 , (1)
+ve/–ve Terminals
+ve/–ve Terminals and safety vent
Metal case
Anode
Separator
Cathode
Fig. 2. Internal construction of a typical cylindrical cell (1)
Metallised foil pouch
Anode
Separator
Cathode
Fig. 3. Internal construction of a typical pouch cell (1)
Individual cells are normally mounted into a number of modules, which are then assembled into the complete battery pack as shown in Figure 4 .
Many countries have now put in place binding carbon dioxide emissions targets for cars, for example in
Europe the requirements are for fleet average CO
2 emissions of 130 g km –1 by 2015 and 95 g km –1 by
2021 (3). It will be shown in Section 2 of this paper that by using a (lithium-ion) battery it is possible to significantly reduce a car’s CO
2
emissions. More lithium-ion batteries are now being used in automotive applications for this reason.
The structure of this paper is as follows. In Section 2 a number of automotive passenger car applications for lithium-ion batteries are presented and their key requirements listed. Section 3 will give a brief overview of the capabilities of a number of lithium-ion chemistries currently in use for automotive applications and Section 4 will compare the requirements (from
Section 2) with the capabilities listed in Section 3.
Section 5 will look at future developments, while
Section 6 will offer some conclusions.
Fig. 4. CAD of disassembled battery module, assembled module and whole battery package (1)
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http://dx.doi.org/10.1595/205651315X685445 Johnson Matthey Technol. Rev ., 2015, 59 , (1)
There are a range of applications for batteries in passenger cars (4). The ones that will be considered here were selected either because they already use lithium-ion batteries or because they could potentially do so in the future. Note that there are a number of standard automotive requirements that all lithium-ion batteries used in cars need to meet: these include life
(8–15 years are typical requirements), temperature range (–40°C to at least +60°C, ideally 80°C) and vibration resistance (at least 4.5 root-mean-squareacceleration (grms)) (5). Each application will now be briefly described.
Starting lighting ignition (SLI) is the ‘car battery’ that has been in almost every car for the last 100 years.
Commonly this is called a ‘12 V battery’, but its normal voltage (while in use in the car and being charged by the alternator) is nearer 14 V. In almost all current production cars this is a lead-acid battery, but there are a few cars now that use a lithium-ion battery either as standard (for example, the McLaren P1) or as an option (for example, some Porsche models). In the
Porsche Boxster Spyder the lithium-ion battery is a
US$1700 option and has the same form factor and mounting points as the standard lead-acid battery, but weighs only 6 kg which is 10 kg lighter than the leadacid option. It should be noted that Porsche supply a conventional lead-acid battery as well as the lithium-ion one for use in cold temperatures where the lithium-ion pack may not be able to provide enough power to crank the engine (see Section 3).
This is a system that is now fitted to the majority of
European vehicles which switches the combustion engine off whenever the vehicle is stationary, restarting it when you go to drive off (4). It offers around a 5% saving in fuel economy at an estimated system cost of around US$350 (4), which makes it an attractive solution for original equipment manufacturers (OEMs) looking to meet the European 2015 CO
2
limits. The requirements for a battery for this application are very similar to those of an SLI battery, but the more frequent starting and stopping of the engine requires a longer cycle life. The vast majority of batteries for this application are still lead-acid, but a number of other options are used including ultracapacitors and lithium-ion which was first used in 2002 on the Toyota
Vitz CVT, which to the author’s knowledge was the first production car to use a lithium-ion battery pack.
Many idle stop systems also intelligently control the vehicle’s alternator, for example using it to generate maximum power when the vehicle is slowing down
(giving a limited degree of regenerative braking capability) and these systems are frequently called micro hybrids.
In a mild hybrid the electrical energy is used to supplement the energy from the combustion engine.
By use of a suitable control system to decide how to mix these two energy sources significant savings in fuel (typically 10%–15%, but up to 30% has been shown in some demonstrator vehicles) can be obtained for a moderate increase in system cost (4). Batteries for this application only require a small amount of power and energy. Most batteries for this application at present are nickel metal hydride (NiMH), with lithium-ion first used in 2010 for the Mercedes S400 hybrid. As this paper is focused on lithium-ion batteries,
NiMH batteries (which is an older technology that offers lower energy density than lithium-ion) will not be covered in further detail here.
Note that the number of mild hybrids produced is soon expected to significantly increase due to the use of 48 V systems within a vehicle. This shift is driven by the
European 2020 fleet CO
2
requirements (3). The use of 48 V was originally proposed in 2011 by Audi, BMW,
Daimler, Porsche and Volkswagen (6) and resulted in the LV 148 standard (7). Audi recently stated that they expect such systems to be in production within the next two years (8) and it is expected that all 48 V systems will be based on lithium-ion batteries.
It should also be noted that most fuel cell vehicles will also be hybrids (4). For example, Toyota has recently announced that it will start sales of a fuel cell sedan in early 2015 and this is a mild hybrid using a small battery to supplement the fuel cell and increase the vehicle’s overall efficiency (9).
In a full hybrid, the approach is similar to that of the mild hybrid, but the electrical power and stored energy are now high enough to power the car purely from electrical energy. The battery energy available normally limits the range in this mode to a few kilometres. An example of
6 © 2015 Johnson Matthey

http://dx.doi.org/10.1595/205651315X685445 Johnson Matthey Technol. Rev ., 2015, 59 , (1) this sort of vehicle is the Toyota Prius (although this currently uses a NiMH battery pack), which is by far the most successful hybrid vehicle sold so far. It has around a 1 mile range in electric vehicle (EV) mode.
Fuel consumption savings in a full hybrid are typically
30%–40%, for example on the 2014 Toyota Yaris the
1.33 gasoline (98 bhp / 73 kW) produces 114 g km –1 of
CO
2
emissions, while the hybrid (also 98 bhp / 73 kW) achieves 75 g km –1 , a 34% reduction.
Batteries for this application must provide more power
(to act as the sole source of power in the vehicle) and more energy than for a mild hybrid application. Most applications (by volume) are still NiMH, but a significant number of vehicles are now lithium-ion based, including the BMW Active Hybrid 3 which can drive for 2.5 miles at up to 37 mph on electric power alone. Hybrid electric vehicle (HEV) is a phrase that has been used to describe mild hybrid and a full hybrid vehicles and has even been applied to some vehicles with little more than idle-stop systems (micro hybrids).
The plug in hybrid electric vehicle (PHEV) could be considered to be a full hybrid with the ability to charge the battery from the grid. The vehicle is designed to initially preferentially use the electrical energy from its last charge until this is depleted, at which time it behaves like a full hybrid vehicle. Thus the energy obtained by charging from the grid replaces some energy that would have been required from the liquid fuel (gasoline or diesel), further lowering fuel consumption (and hence tailpipe CO
2
emissions). The
VW XL1 is a PHEV that offers 313 mpg and 24 g km –1 of CO
2
, but the Vauxhall Ampera (GM Volt) and Toyota
Prius PHEV (note the Toyota Prius PHEV is a different vehicle to the ‘standard’ Toyota Prius which is a full hybrid vehicle) are more affordable options. All use lithium-ion batteries. The power required from the battery is similar to that required in a full hybrid, but more energy needs to be stored to make the effort to recharge from the grid worthwhile.
For the purposes of this paper a range extended electric vehicle (REEV) will be considered a type of PHEV.
An EV has the battery as its only source of energy. An example of this type of vehicle is the Nissan Leaf. An
EV has zero tailpipe emissions, although the Leaf is estimated to emit 66.83 g km on the CO
2
–1 CO
2
in the UK based
produced by the mains electricity used to refuel it. The power required from an EV battery is the same as for a PHEV (both need to be able to power the car), but in an EV as much energy as practical is fitted to give a reasonable range (typically ~100 miles).
This large energy requirement explains the ‘low cost’ requirement (in $/kWh terms) for EVs in Table I , as the battery cost needs to be compared with a conventional fuel tank (~€100 or ~US$130).
All of the applications listed above are summarised in
Table I . The typical properties and requirements of the battery technology for each application are shown.The power and energy data in Table I can also be viewed as a chart, as shown in Figure 5 .
Lithium-ion cells, in their most common form, consist of a graphite anode and a lithium metal oxide cathode and an electrolyte of a lithium salt and an organic solvent.
Table I Typical Passenger Car Applications for Lithium-ion Batteries
Application
Typical voltage(s), V
Typical Power levels, kW
Typical energy, kWh
SLI
Idle stop
Mild hybrid
Full Hybrid
PHEV
EV
14
14
48–200
300–600
300–600
300–600
60
60
3
3
10–30
60
0.7
0.7
0.3
1–2.5
4–10
15+
Commonest battery type today
Lead-acid
Lead-acid
NiMH
NiMH
Li-ion
Li-ion
Special requirements
Cranking at cold
Cranking at cold
Long cycle life
Long cycle life
Long cycle life
Low cost
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http://dx.doi.org/10.1595/205651315X685445 Johnson Matthey Technol. Rev ., 2015, 59 , (1)
25
20
EV
15
10
PHEV
5
0
SLI/idle stop Mild hybrid
Full hybrid
0 10 20 30 40 50 60 70
Power, kW
Fig. 5. Power and energy requirements for different passenger vehicle battery applications
While the basic format remains constant for all lithiumion cells the detailed chemistry (i.e. cathode and/or anode) can be changed, altering the properties of the cell. It is not the aim of this paper to give a detailed explanation of the manufacture of the various cells or their chemistries as this is well covered elsewhere (see for example (1, 2, 10)).
The main lithium-ion chemistries used in automotive applications are summarised in Table II (1). In all cases the anode is graphite apart from the sixth entry in which the anode is a titanate.
This table can be summarised in terms of key parameters that are required for commercial application of these battery technologies in passenger vehicles, as in Table III below. Note that price has not been included in this table as all the ranges effectively overlap, with the exception of the more expensive titanate containing system.
While all these cell chemistries have been used in passenger vehicles and hence can be made adequately safe, the temperature at which thermal runaway starts is used here to illustrate the differences between the chemistries – the higher this temperature the safer the chemistry is considered to be. Life is given in Table II in terms of cycle life, while the ranking in Table III can be considered to also include calendar life.
Note that the chemistry that provides the best power (lithium iron phosphate (LiFePO
4
)) is the
Table II Summary of the Main Lithium-ion Variants
Cell level energy density,
Wh kg –1
Cell level energy density,
Wh l –1
Durability cycle life,
100% DoD
Price estimate,
US$ Wh –1
LiCoO
2
LiFePO
4
(EV/PHEV)
LiFePO
4
(HEV)
170–185
90–125
80–108
NCM (HEV) 150
NCM (EV/
PHEV)
Titanate vs.
NCM/LMO
Manganese spinel (EV/
PHEV)
155–190
65–100
90–110
450–490
130–300
200–240
270–290
330–365
118–200
280
500
2000
2000
1500
1500
12,000
>1000
0.31–0.46
0.3–0.6
0.4–1.0
0.5–0.9
0.5–0.9
1–1.7
0.45–0.55
Power
C-rate
1 C
5 C cont.
10 C pulse
30 C cont.
50 C pulse
20 C cont.
40 C pulse
1 C cont.
5 C pulse
10 C cont.
20 C pulse
3–5 C cont.
Safety thermal runaway onset, °C
170
270
270
215
Potential,
V
Temperature range in ambient conditions,
°C
3.6
–20 to 60
3.2
–20 to 60
3.2
3.7
215 3.7
Not susceptible 2.5
255 3.8
–20 to 60
–20 to 60
–20 to 60
–50 to 75
–20 to 50
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http://dx.doi.org/10.1595/205651315X685445
Table III Key Parameters of Lithium-ion Chemistries
Parameter Highest performing chemistry(s)
Safety
Power
Energy
Life
Titanate, LiFePO
4
LiFePO
4
LiCoO
2
, NCM
Titanate, LiFePO
4
Johnson Matthey Technol. Rev ., 2015, 59 , (1)
Lowest performing chemistry
LiCoO
2
LiCoO
2
LiFePO
4
LiCoO
2 worst for energy. Both power and energy need to be considered when selecting candidate chemistries for applications and this idea will be explored further in Section 4.
The last parameter for consideration is low temperature performance and this is best shown by a graph ( Figure 6 which is based on data from (11) with lithium-ion added by the present author based on measurements of an automotive LiFePO
4
lithium-ion cell).
This graph shows that valve-regulated lead-acid
(VRLA) battery technology offers significantly higher power at cold temperatures and so is better suited for cold cranking applications (which require the ability to crank the engine at –40°C).
One way to view the suitability of lithium-ion for various applications is to compare the power:energy ratio for the cells vs.
the applications as shown in
Figure 7 . Here the yellow lines show the power:energy ratios for the various chemistries (from Table II ), while the dots show the requirements for each of the applications ( Figure 5 ). The lines closest to the dots are likely to be the best fit to the application from a power and energy viewpoint, as chemistries with lines a long way away will have a significant excess of power or energy beyond the requirements. This is likely to make them a more expensive solution (in terms of cost, weight and volume) than solutions with lines close to the dot.
It can be seen that there are good matches for the mild and full hybrid and PHEV, but not a particularly good match for the EV requirements.
This means that companies offering a range of different types of hybrid vehicle will normally need to select multiple chemistries (which also normally means multiple suppliers). For example BMW uses A123
LiFePO
4
cells in its hybrids, while it uses Samsung SDI
(nickel-manganese-cobalt (NMC)) for its EV and PHEV vehicles (12), both of which can be seen to be sensible choices based on Figure 3 . However there is no industry consensus, for example while BMW selected
NMC for its EVs, Honda uses a titanate chemistry in its Fit EV and Renault uses spinel lithium manganese oxide (LMO) in the ZOE EV (13).
It should be noted that while lithium-ion batteries are in use in production cars, low temperature operation (see
1800
1600
1400
1200
1000
800
600
400
200
0
–40 –20 0 20 40 60
Temperature, ºC
Fig. 6. Low temperature performance of selected battery chemistries
VRLA (W kg –1 ) (11)
NiMH (W kg –1 ) (11)
Li-ion (W kg –1 )
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25
20
LiCoO
2
EV
Spinel
15
NCM-EV
10
5
0
SLI/idle stop Mild hybrid
PHEV
Full hybrid
LiFePO
4
-EV
Titanate
NCM-HEV
LiFePO
4
-HEV
0 10 20 30 40 50 60 70
Fig. 7. Power and energy and capabilities of various chemistries
Power, kW
Section 3), life (especially calendar life), temperature range, safety and cost are all areas that ideally need to be improved and these challenges still remain after many years of research and development (10). Some progress has been made, for example battery packs have improved from 80 Wh kg –1 in the Mitsubishi iMiEV
(launched in 2009) and Nissan Leaf (launched in 2010) to 97 Wh kg –1 in the new Kia Soul EV (launched in May
2014) (14) which is a 4% per year average (compound) improvement. This is partly due to the automotive industry’s long timescales (five or more years from part selection to volume production is common), but also due to the need for improvements without adversely impacting other parameters.
Much research is ongoing into lithium-ion batteries. The review of lithium batteries (2) dates from 2009 but it is still a useful overview and many of the research topics it discusses have yet to make it into volume automotive applications. A theoretical model created at Rice
University and Lawrence Livermore National laboratory which predicts how carbon components will perform as electrodes (15) also has the potential to significantly benefit future lithium-ion cell developments.
A recent overview which focuses on energy and cost (and is so most relevant to EV applications) (16) suggests that lithium-ion chemistries will improve by probably no more than 30% in terms of energy per unit weight and proposes a range of potential replacement chemistries. However, it should be remembered that an automotive battery pack is much more than just the chemistry, as the cells themselves have to be packaged using a pouch or can and then hundreds or possibly thousands of these cells need to be packaged in the car together with thermal management and electronic control equipment. A typical automotive battery pack today achieves 82 Wh kg –1 (for example, the Nissan
Leaf) which is considerably lower than that achievable from the cells alone.
Recently prototype battery packs have been developed with significantly higher energy density. For example the SmartBatt programme (17) has recently demonstrated an EV battery pack with 148 Wh kg –1 while meeting all other automotive requirements, this pack was shown as CAD in Figure 4 and the assembled pack is shown in Figure 8 . This was achieved by combining 1408 relatively high energy lithium-ion cells
(each of 181 Wh kg –1 ) with innovative materials (including an aluminium hybrid foam sandwich material) and state of the art engineering (including a large number of crash test simulations to optimise the design).
Table IV gives the weight breakdown of the SmartBatt pack. The 85% gain in energy per unit weight obtained by the SmartBatt pack far exceeds the long term projections of a 30% improvement in energy per unit weight from lithium-ion chemistry improvements and together they suggest that a 100% gain in energy per unit weight (to around 160 Wh kg –1 ) may be possible at the pack level for EV packs.
This paper has shown the range of applications for automotive batteries and summarised the different requirements for each. This has shown that while lithium-ion based battery packs could be used in all the major passenger car battery applications, they are best suited to use in PHEV and EV applications
10 © 2015 Johnson Matthey

http://dx.doi.org/10.1595/205651315X685445 Johnson Matthey Technol. Rev ., 2015, 59 , (1)
Fig. 8. SmartBatt battery pack
Table IV SmartBatt Weight Breakdown
Component
Housing
Mass, kg
8.5
Fraction, %
5.5
Module without cells
Cells
Electrical components
Electrical connections
TOTAL
16.6
125.3
2.1
2.9
155.4
10.7
80.6
1.4
1.9
– and are least suited to SLI applications. Even for the applications where lithium-ion is being used, it has been shown that different vehicle OEMs have selected different chemistries for the same application based on different interpretations of the trade-offs between the chemistries’ performance and the requirements of the specific application.
It has been stated that new lithium-ion chemistries offer limited potential for improvement (~30% in terms of Wh kg –1 ) which has resulted in significant research in non lithium-ion based chemistries which offer the promise of significantly higher gains (16). However it is shown here that, especially for EV battery packs, major weight gains can come from the overall design of the battery pack and these together with better chemistries suggest that a doubling of the energy per unit weight for EV battery packs is possible in the relatively near future.
The author wishes to thank the anonymous referees and the editor for their constructive comments as well as Johnson Matthey for permission to publish this paper.
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11 © 2015 Johnson Matthey

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Storage Conference (IRES II), Bonn, Germany, 19th–
21st November, 2007
11. M. J. Weighall, J. Power Sources , 2003, 116 , (1–2), 151
12. P. Buckley, ‘Samsung SDI Batteries to Drive Future
BMW EVs’, EE Times Europe , 15th July, 2014
Johnson Matthey Technol. Rev ., 2015, 59 , (1)
13. C. Garnier, ‘Renault ZE: Path Toward EV Battery
Production’, CAPIRE Workshop, Brussels, Belgium,
10th April, 2013
14. ‘Bosch Set to Double Battery Energy Density’,
Automotive Engineer , 2014, 39 , (2), 5
15 Y. Liu, Y. M. Wang, B. I. Yakobson and B. C. Wood,
Phys. Rev. Lett., 2014, 113 , 028304
16. R. Van Noorden, Nature , 2014, 507 , (7490), 26
17. H. Kapeller, ‘SmartBatt: Smart and Safe Integration of
Batteries in Electric Vehicles’, The 27th International
Electric Vehicle Symposium (EVS27), Barcelona,
Spain, 17th–20th November, 2013
In December 2013 Dr Peter Miller took up the role of Chief Electronics Technologist at Johnson
Matthey Battery Systems. Prior to this he was the Director, Electrical/Electronic Engineering at
Ricardo and until 2001 he was the European Director of Technology at Motorola Automotive/
Industrial Electronics Group. His primary interests relate to the design, control and use of lithiumion batteries. Dr Miller is the author of a large number papers and patents. He holds a BSc and
PhD from Hull University, UK, is a Chartered Engineer, a fellow of the Institute of Engineering and
Technology (IET) and a member of the Institute of Electrical and Electronics Engineers (IEEE) and the Association of Computing Machinery (ACM).
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Johnson Matthey Battery Systems is a leading independent provider of battery design, development and supply for demanding automotive applications, such as performance hybrids and PHEVs. We also manufacture high volumes of batteries for e-bikes, power tools and mobile technologies
What we do - Battery Design, Development and Supply for Demanding Applications
13
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Johnson Matthey Technol. Rev ., 2015, 59 , (1), 14–25 http://dx.doi.org/10.1595/205651315X685346
JOHNSON MATTHEY
TECHNOLOGY REVIEW www.technology.matthey.com
The Institute of Problems of Chemical Physics of the
Russian Academy of Sciences, Academician Semenov avenue 1, Chernogolovka, Moscow Region,
142432, Russia
Email: irenmak@icp.ac.ru
Traditional Fischer-Tropsh synthesis for the conversion of gas into liquids for fuels and chemicals is uneconomic for many stranded natural and remote gas sources. This review presents platinum group metal (pgm)-catalysed carbonylation as the basis of a new generation of alternative GTL processes to produce petrochemical products from hydrocarbon gases. The pgm route may allow monetisation of stranded natural and associated petroleum gases by converting them into marketable products with high added value, including for example acetic acid, methyl acetate, ethylidene diacetate, propanal, methyl propanoate, vinyl acetate, oligoketones and oligoesters.
As global energy demand and crude oil prices rise, alternative production routes for hydrocarbons and petrochemicals are becoming more and more economically and ecologically attractive. Thus, gasto-liquids (GTL) processes intended for the production of synthetic liquid fuels as well as other chemical and petrochemical products (for example methanol, lubricants and waxes) from hydrocarbon gases have been of interest for the past three decades. This is at least partly driven by a desire to diversify the utilisation of large or stranded gas reserves by gas conversion into marketable products with high added value.
GTL today is largely dominated by Fischer-Tropsch
(FT) synthesis converting synthesis gas into synthetic fuels for the transport fuel market. Manufacturing GTL fuels is extremely expensive: conventional FT GTL technologies consist of three steps (1): (a) production of synthesis gas or syngas (carbon monoxide and hydrogen) by oxidation of high purity natural gas or any methane-rich feedstock in the presence of nickelbased catalysts (this step is the most energy intensive and comprises more than 50% of the total GTL capital cost); (b) FT synthesis – the conversion of syngas in the presence of cobalt or iron catalysts to produce a mixture of hydrocarbons in the form of a synthetic crude oil (syncrude) (this step consumes ≥ 25% of the GTL capital investment); and (c) hydrocracking and hydroisomerisation of the synthesised syncrude using precious metal catalysts and syncrude re fi ning processes to give marketable products (this step comprises 15% to 25% of the total capital cost).
Unfortunately, today the established processes for natural gas transformation into syngas and consequent
FT synthesis require large investments which are prohibitive for the exploitation of small and stranded natural gas reservoirs which make up approximately one third of the world’s natural gas reserves.
Various attempts are being undertaken by many researchers worldwide to avoid the costly production of syngas required by a conventional GTL route
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(hydrocarbon gas  syngas → FT → GTL products).
For example, scientists working on the European Union
(EU)-funded project “Innovative Catalytic Technologies and Materials for Next Gas to Liquid Processes” (NEXT-
GTL) are addressing the main cost and technical challenges associated with conventional GTL processes
(2). They are exploring unconventional novel routes for catalytic syngas formation, including H
2 separation by membrane. They are also investigating direct catalytic conversion (without the syngas intermediary) of methane to methanol/dimethyl ether (DME).
Methanol is an important product of GTL technologies.
Therefore special attention is paid to the second (in scale of production) route of GTL performance that leads to methanol (gas-to-methanol (GTM) process): hydrocarbon gas → syngas → methanol. The Nobel
Prize Winner George Olah proposed the use of methanol as a basic feedstock not only for the chemical industry but also for the whole power industry in the near future (3). Methanol is already a key component of various process fl ow-sheets allowing a broad range of technologies to be used for manufacturing high valueadded products.
Another EU project, “Oxidative Coupling of Methane
Followed by Oligomerisation to Liquids” (OCMOL), was aimed at developing a new liquefaction route adapted to the exploitation of small gas reservoirs. The OCMOL process was based on oxidative coupling of methane into ethene followed by subsequent oligomerisation of ethene to linear α -ole fi ns and synthetic fuels including gasoline and diesel (4). The OCMOL route aimed to develop a process with economic operation at capacities of 100 kT year –1 and more uniform pressures with low if not zero CO
2
emission.
Among the attempts to develop alternative GTL processes a direct non-catalytic partial oxidation of hydrocarbon gases is of great interest. A new route to convert hydrocarbon gas → methanol without the step of syngas production has been developed at the institutes of the Russian Academy of Sciences (5). Depending on reaction conditions, the oxidative conversion of hydrocarbon gases at temperatures of 700°C–750°C may lead to formation of ole fi ns (6, 7) which can also be used in a number of reactions. Methanol and ole fi ns produced via this method may potentially be involved in carbonylation or oligomerisation reactions in the presence of catalysts, giving a wide assortment of marketable petrochemicals.
At present a number of well-known carbonylation processes are used industrially for large scale production. The most effective carbonylation catalysts are based on platinum group metals (pgms) such as rhodium, iridium and palladium. The aim of this article is to review and discuss pgm-catalysed carbonylation as the basis of a new generation of alternative GTL processes. For the purposes of this article, the term
‘carbonylation’ will refer to all reactions that include
CO additions to various substrates. The latter may be methanol, ethene, ethanol, formaldehyde and certain other substrates formed during the direct non-catalytic partial oxidation of hydrocarbon gases.
As a rule pgm catalysts in carbonylation processes are metal complexes with various organic heteroatom ligands providing selectivity to the required product.
Sometimes relatively cheap zeolite catalysts and catalysts based on late transition metals are also used in carbonylation. However, such catalysts are less active in comparison with pgm catalysts and therefore they cannot be effectively used for the carbonylation of mixtures with low substrate content (methanol, ethene). Such mixtures are known to be formed during the partial oxidation of natural hydrocarbon gases.
The pgms are used to catalyse many reactions involving CO, H
2
and even molecular nitrogen (8).
In general, pgm catalysts are active under milder conditions and show much higher selectivity compared to other metals. The pgms have many other key characteristics and are widely applied in industrial catalysis, despite their high prices ( Table I ).
Previous research at the Institute of Problems of
Chemical Physics of the Russian Academy of Sciences
Table I Johnson Matthey Base Prices a (9)
Platinum Group Metal Pt
US$ per oz 1264.69
a Month average for all time zones, October 2014
Pd
782.87
Rh
1229.31
Ir
583.30
Ru
58.96
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(IPCP RAS) includes the development of catalysts based on pgms (Pd, Pt, Rh, Ir). These catalysts were intended for a number of processes, particularly liquidphase hydrogenation and dehydrodechlorination of organic compounds (10, 11), activation of C–H bonds
(12) and copolymerisation of ethene and CO (13).
Possible products of oxidative conversion of hydrocarbon gases, including methanol, ethene and
CO, may undergo various reactions to form products which are in high demand. There are currently a range of oxidative conversion processes at different stages of commercialisation. The most promising for alternative
GTL processes are addition reactions of CO to low molecular weight substrates, such as carbonylation of methanol to acetic acid and methyl acetate; production of ethylidene diacetate; hydroformylation of ethene to propanal; formation of methyl propanoate during ethene methoxycarbonylation and vinyl acetate by reaction of ethene with acetic acid; and the cooligimerisation of ethene and CO with formation of oligoketones and oligoesters.
The carbonylation of methanol to acetic acid is one of the major commercialised processes using CO,
Equation (i):
CH
3
OH + CO → CH
3
COOH (i)
The process was described by BASF in 1913 and was modi fi ed in 1941 to use late transition metal carbonyl complexes in place of transition metal salts.
Co-catalysed carbonylation was initially commercialised by BASF in 1963. The use of Co-based catalysts required extremely harsh process conditions (~250°C,
600 bar) with an acetic acid yield up to 90% based on methanol and up to 70% based on CO (14).
In the 1960s Monsanto developed an improved low pressure method for methanol carbonylation using an iodide-promoted rhodium complex catalyst with much higher catalytic activity and selectivity, allowing for milder reaction conditions (~175°C, 30 bar) (15).
The fi rst plant based on this technology was put into operation in Texas City, USA, in 1970. This process has since become used in all industrialised countries.
The achieved selectivity is more than 99% (based on methanol) due to the catalytic mechanism proceeding on Rh active species. This mechanism may be achieved when the catalyst is promoted by iodide ions because methanol itself cannot participate in the basic catalytic cycle ( Figure 1 ).
The selectivity of the process is about 85% to CO. The low selectivity is caused primarily by the occurrence of the water gas shift reaction (WGSR), Equation (ii):
CO + H
2
O → CO
2
+ H
2
(ii)
Because this reaction is also catalysed by Rh complexes, it cannot be avoided by changing the operating conditions. Catalysts based on Ir complexes do not have this shortcoming.
The effect of hydrogen (syngas) on methanol carbonylation has also been investigated (17, 18).
It was shown that the availability of hydrogen cannot prevent the carbonylation of methanol to acetic acid and methyl acetate.
In 1983 Eastman Chemical developed a process of acetic anhydride production by Rh-catalysed iodidepromoted carbonylation of methyl acetate, with a plant capacity of 320,000 tons per year (15, 19). Production of methyl acetate is performed using standard acetic acid production technology supplemented by esteri fi cation of excess methanol under reactive distillation conditions.
Another option to produce acetic acid via methanol carbonylation is the Cativa TM process developed by
BP Chemicals in the early 1990s. This process applies an Ir-based catalyst and a ruthenium promoter. The technology was commercialised in 1995. The catalytic cycle of methanol carbonylation includes Ir-containing active species. In contrast to the Monsanto process, the oxidative addition of methyl iodide to Ir-based catalysts proceeds 150 times faster than for Rh catalysts (20).
The selectivity to acetic acid may exceed 99% because the Ir catalyst prevents the formation of propanoic acid as a side product.
The production of acetic acid by carbonylation of methanol is considered the most economical of all commercial methods (oxidation of acetaldehyde and oxidation of C
4
–C
7
hydrocarbons). All new plants under construction based on this technology have a capacity of about 0.5 million tons acetic acid per year for each plant. The capital cost of such plants is estimated at
US$500 million each.
The global acetic acid market was valued at
US$6 billion in 2011 and is expected to reach US$10 billion by 2018, growing at an annual growth rate of 9.3% over the forecast period from 2012 to 2018 (21). Global demand
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I
I CO
–
Rh
CO
I
I
I
CO
Rh
CO
O
CH
3
– H
3
C
O
H
3
C
O
I
OH
H
2
O
HI
H
3
C I
H
3
C OH
I
I
I
CO
Rh
C
H
3
CO
–
CO
I
I
I
Rh
CO
CH
3
–
Fig. 1. Catalytic cycle for rhodium-complex-catalysed methanol carbonylation (Monsanto) (16) for acetic acid has been steadily increasing over the last ten years (10.25 million tons in 2011 compared to 6.11 million tons in 2000) and is estimated to reach
15.5 million tons by 2020. Demand in advanced countries has largely stabilised, while emerging economies like China and India have huge consumption potential in acetic acid downstream segments such as vinyl acetate monomer, puri fi ed terephthalic acid, ethyl acetate and acetic anhydride (22).
via
As mentioned above, when carbonylation is carried out in excess methanol, methyl acetate may be synthesised as well as acetic acid (23). Further reductive carbonylation of methyl acetate leads to formation of ethylidene diacetate (24), which after hydrolysis yields vinyl acetate. Vinyl acetate monomer is well-known as one of the most important chemical raw materials (25),
Equations (iii) and (iv):
2 СН
3
СООСН
3
+ 2 СО + Н
2
→ СН
3
СН ( ОСОСН
3
)
2
+ СООН (iii)
СН
3
СН ( ОСОСН
3
)
2
→ СН
2
= СНОСОСН
3
+ СООН (iv)
These syntheses were fi rst proposed by Halcon in the 1980s. It was found that they are 30%–40% more ef fi cient than traditional reaction routes. It has recently been shown (26) that the best feedstock for production of ethylidene diacetate and vinyl acetate is DME (24) which ensures the highest selectivity, because the
WGSR is not possible (27).
Hydroformylation (oxo synthesis) of unsaturated substrates was discovered by Otto Roelen in 1938
(28, 29) and was originally performed using a heterogeneous Co catalyst. Further research revealed a range of metals (Rh, Co, Ir, Ru, Mn and Fe) able to catalyse the process ( Table II ) (30).
In commercial processes different metal-based catalysts are used and the most effective among them are Rh-based complexes. As can be seen from Table II , the activity of the Rh catalyst
[HRh(CO)(PPh
3
)
3
] exceeds that of the Co catalyst
[HCo(CO)
4
] by three orders of magnitude. The
Rh-based catalyst is more selective (linear:branched aldehyde ratio 19:1 compared with 4:1) and can be operated at lower pressures (7 atm–25 atm compared with 200 atm–300 atm) (31). The bene fi t of using a
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http://dx.doi.org/10.1595/205651315X685346
Table II Relative Activity of Different Metals in Hydroformylation (30)
М etal
Lg A
Rh
3
Co
0
Ir
–1
Ru
–2
Johnson Matthey Technol. Rev ., 2015, 59 , (1)
Mn
–4
Fe
–6
Rh-based catalyst in hydroformylation is economic ef fi ciency, especially after the two-stage Ruhrchemie/
Rhone-Poulenc (RCH/RP) process was developed, eliminating the need to separate the used catalyst from the products (21).
At present commercial hydroformylation is the key step in production of fatty alcohols based on dimers and trimers of propylene and butenes.
Alternate copolymerisation of ole fi ns and CO is usually carried out in the presence of Pd-containing catalysts and leads to the formation of 1,4-polyketones ( γ -polyketones).
The latter represent copolymers with unique properties
(high crystallinity, excellent mechanical properties and high chemical stability) (32, 33).
Shell developed commercial production of the fi rst polyketone in 1996, but discontinued it in 2000 (34, 35).
The product, marketed under the trade name of Carilon ® , was an ole fi n/CO alternate copolymer containing ethene and a small amount (5%–10%) of propylene units. Today
SRI International, USA, offers polyketone thermoplastic polymers. The material is currently produced under the brand name Karilon by industrial conglomerate Hyosung
Corporation, South Korea, in a pilot plant, but there are plans for a continuous plant that would come on-stream in 2015 (36).
A similar reaction of ethene and CO proceeding in methanol can lead to low molecular weight products.
The latter represent valuable raw materials for the production of methyl methacrylate, among them methyl propanoate (37) and diethyl ketone as a ‘green’ solvent
( Figure 2 ) (38). These reactions are catalysed by Pd complexes with phosphine ligands under relatively low pressures (39, 40). A source of hydrogen that leads to
C
2
H
4
+ CO
CH
3
OH
R
O
Fig. 2. Feasible products during interaction of CO and ethene in methanol in the presence of pgm catalysts chain termination and the formation of diketones may help the WGSR. The reaction was therefore promoted by the addition of amines into the reaction mixture.
Both selectivity of oligomerisation and the chain length of products obtained strongly depend on the nature and the structure of the phosphine ligand (33).
One of the low molecular weight products which can be formed during the cooligomerisation of ethene and CO in the presence of methanol, involving the isomerisation of active centres, is methyl propanoate. Synthesis of methyl propanoate by methoxycarbonylation of ethene requires the participation of equimolar quantities of ethene, methanol and CO ( Figure 2 , R = OMe). The synthesis is catalysed by Pd complexes with the sterically bulky bidentate phosphine ligands.
Methoxycarbonylation of ethene was commercialised while developing the Lucite Alpha process in 2008
(41). The fi rst step is interaction of ethene, CO and methanol to produce methyl propanoate; the second step is the reaction of methyl propanoate and formaldehyde to form methyl methacrylate ( Figure 3 ).
The carbonylation step has a complex highly selective mechanism with two kinds of catalytic cycles starting from both methoxy- and hydrido-Pd species ( Figure 4 ).
This reaction is catalysed by adducts of Pd salts with biphosphine that have tertiary substituents at the phosphorus atom allowing the polymerisation process to be suppressed (42). The commercial Lucite Alpha process uses 1,2-bis(ditert -butylphosphinomethyl)benzene as a phosphine ligand.
Methyl methacrylate monomer is an important marketable product. Its main applications are the production of polymethylmethacrylate and acrylic resin. Global growth in the consumption of methyl methacrylate is forecast to be 4.0% on average annually during 2011–2017 and its global market will reach 3.2 million tons by 2017 (43).
It is worth mentioning carbonylation processes which do not use CO as a direct raw material (44). In such cases different carbonyl-containing compounds (most often formates) are used as carbonyl group donors.
An example is the formation of methyl propanoate by reaction of ethene with methyl formate, catalysed by Ru
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http://dx.doi.org/10.1595/205651315X685346 Johnson Matthey Technol. Rev ., 2015, 59 , (1)
OMe
H
2
CO
C
2
H
4
+ CO + CH
3
OH
O
Fig. 3. Scheme of Lucite Alpha methyl methacrylate process
O
OMe
C
2
H
4
[Pd] H
O
O
MeOH
[Pd] OMe CO
P
P
Pd
H
2
C
CH
2
H
+
[Pd]
A
[Pd]
O
[Pd]
CO
Fig. 4. Mechanism of ethene methoxycarbonylation
[Pd] =
P
P
Pd
MeOH
+
O
O
B
[Pd]
O
O
C
2
H
4 catalysts ( Figure 5 ). This reaction is more ecologically friendly than the reaction that directly uses CO. The methyl formate needed for this reaction may be formed by copper-catalysed methanol carbonylation (45).
Synthesis of methyl formate and further formation of methyl propanoate taken together represent an alternative to methoxycarbonylation processes.
C
2
H
4
+
H
O
OMe
[Ru]
O
OMe
O [Ru]
CO + MeOH
H OMe
Fig. 5. Ruthenium-catalysed reaction of ethene and methyl formate
Vinyl acetate is another important monomer for the production of various polymers. Its world production is estimated as 6.5 million tons per year (46). The global vinyl acetate monomer market is expected to grow at an average rate of 5% over the forecast period from 2012 to 2020, and at a much higher rate in the
Asia-Pacific region, particularly in China. Process modernisation means that BP has decreased its operating costs by a factor of three; similarly,
Celanese managed to increase productivity by 95%
(Praxair – by 5%) and to decrease costs by 15%.
In addition to the production of vinyl acetate from ethylidene diacetate which in turn can be produced by the reductive carboxylation of methyl acetate, vinyl acetate can be produced by the reaction of ethene with acetic acid ( Figure 6 ). This reaction is catalysed by the homogeneous catalyst PdCl
2
/CuCl
2
at optimal temperatures of 110°C–130°C and pressures of
30 atm–40 atm. However, such operating conditions are extremely corrosive to the processing equipment.
Heterogeneous Pd/Au catalysts have now been developed that avoid this shortcoming. The newly designed catalysts ensure selectivity of up to 94% to ethene and up to 99% to acetic acid. When the process is carried out in a fl uidised bed reactor the capital costs may decrease by 30% (46). Recently a
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http://dx.doi.org/10.1595/205651315X685346 Johnson Matthey Technol. Rev ., 2015, 59 , (1)
O
C
2
H
4
+ CH
3
COOH
O
Fig. 6. Palladium-catalysed vinyl acetate production from ethene and acetic acid by Co; however, pgm catalysts are increasingly being used. Such catalysts possess higher activity and selectivity, ensuring higher relative ef fi ciency of the whole process.
number of large scale vinyl acetate plants have been constructed in China, India, Iran and Saudi Arabia.
Those pgm-catalysed carbonylation processes mentioned above that have been successfully commercialised are listed in Table III . It can be seen from Table III that there is signi fi cant commercial experience in the realisation of processes including pgm-catalysed carbonylation to form a wide range of valuable petrochemicals. A number of these processes may be performed only in the presence of pgm catalysts. Hydroformylation was originally catalysed
A new route for alternative GTL based on carbonylation has been proposed recently by the present authors (55).
It consists of direct partial oxidation of hydrocarbon gases into methanol and/or ethene followed by catalytic carbonylation of the latter. The main steps of conventional GTL and the suggested alternative GTL process are shown in Figure 7 .
The fi rst step of the suggested alternative GTL process consists of direct oxidative conversion; for example: the partial oxidation of methane to methanol
(56); the partial oxidation of heavy components of associated petroleum gas to methanol and CO (57); or the oxidative cracking of heavy components of associated petroleum gas to form ethene and CO
Table III Commercial Processes Including the Step of Methanol and Ethene Carbonylation
Process Products
Hydroformylation of ethene and propylene (oxosynthesis)
Aldehydes, alcohols
Metal/
Catalyst
Rh
H[Rh(CO)
(PAr)
3
]
Operating temperature,
°C
100
Operating pressure, atm
20
Licensor
Union
Carbide
Company
Ruhrchemie/
Rhone-
Poulenc
Startup time
1948
1986
Production Reference overall on
Rh ~2.3×10 t/a (2002)
6 (47, 29)
Carbonylation of methanol
Acetic acid, methyl acetate
Interaction of ethene and acetic acid
Rh
[Rh(CO)
2
I
2
] −
(active species)
Ir
[Ir(CO)
2
I
2
] −
Vinyl acetate
Pd
PdCl
2
Pd/Au
/CuCl
2 or supported
180
130
30
40
Monsanto
Celanese
BP (Cativa TM process)
National
Distillers
Products
Bayer-
Hoechst
1970 ~10.5×10 6 t/a
(2012)
1996
(2007)
6 t/a
(22, 48, 49)
(50–52)
Ethene-CO copolymerisation Polyketone
Ethene
Carbomethoxyation
Methyl methacrylate
Pd various Pd- phosphine complexes
Pd
Pd
2
(dba) methyl) benzene
3
+
1,2-bis(ditert butylphosphino-
100
120
20
20
Shell
(Carilon ® )
BP (Ketonex ® )
1996
Lucite (Alpha process)
1998
7000 t/a
(discontinued in 2000)
(53)
0.1×10 6 t/a
(2008)
0.1×10 6 t/a (under construction)
(41, 54)
20 © 2015 Johnson Matthey

http://dx.doi.org/10.1595/205651315X685346 Johnson Matthey Technol. Rev ., 2015, 59 , (1)
I. Oxidation step
CONVENTIONAL GTL TECHNOLOGIES
II. Catalytic step III. Hydroprocessing step
Natural or associated petroleum gas
Syngas generation
Syngas
Co, Fe
Fischer-
Tropsch synthesis
Syncrude
Hydroprocessing
Fuels
Lubricants
ALTERNATIVE GTL TECHNOLOGIES
I. Oxidation step
Natural or associated petroleum gas
Oxidative conversion
II. Catalytic step
Methanol, ethylene,
CO
Carbonylation
Pd, Rh, Ir,
Ru
Petrochemicals
Fig. 7. The main steps of conventional and suggested alternative GTL-technologies
(58). The further processing of gas-vapour mixtures containing methanol, ethene and CO may give a broad assortment of value-added GTL products.
This approach to gas conversion is particularly attractive because CO can be formed, along with the substrates (methanol and ethene), during the partial oxidation of natural gas in quantities suf fi cient for a further carbonylation step. Therefore there is no need for energy consuming steam conversion or oxidation of methane into syngas. This allows the development of an integrated two-stage gas conversion process that gives a broad range of GTL products such as diethylketone, methylacetate, dimethylcarbonate, methylpropanoate, ethylidene diacetate, oligoketones and polyketones
( Figure 8 ), without the need to separate intermediate products.
Shell, Sasol, ChevronTexaco, Retch, Syntroleum Corp,
Statoil and other petrochemical companies are currently developing GTL technologies for the production of sulfur-free synthetic fuels with high octane numbers
(59). Among them the only companies with industrial scale FT GTL facilities are Shell (Malaysia and Qatar),
Sasol (South Africa and Qatar), PetroSA (South Africa) and Chevron (Nigeria).
Current FT-based GTL technologies are most effective as large scale projects with a capacity of 30,000–150,000 barrels per day (bpd). GTL plants in use at Oryx GTL and Pearl GTL (Qatar),
Escravos (Nigeria) and Nippon GTL (Japan), as well as Bintulu (Malaysia) and Mossel Bay (South
Africa) which are under construction at the time of writing, represent extremely complex and energy- and capital-intensive facilities. The capital cost of the megaproject Shell Pearl in Qatar with a capacity of 140,000 bpd exceeds US$20 billion, meaning that the capital cost per 1 bpd of synthetic oil is more than US$140,000. Chevron Escravos in Nigeria had a total capital cost of US$8.4 billion, i.e. the capital cost per 1 bpd of synthetic oil is around US$200,000.
The evolution of GTL processes using Fe and Co
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http://dx.doi.org/10.1595/205651315X685346 Johnson Matthey Technol. Rev ., 2015, 59 , (1)
Methanol +
CO
Ethylene +
CO
Acetic acid
Methylacetate
Ethylidendiacetate
Vinylacetate
Methylpropanoate
Propanal
Diethylketone
Oligoketones
Fig. 8. Potential marketable products of catalytic carbonylation
Rh, Ir, 30 atm, 180ºC
Rh carbonylation,
Reactive distillation
Rh/PPh
3
, 25–50 atm,
150–200ºC
Pd, 30–40 atm, 110–130ºC
Pd, 70–120ºC, 1–200 atm
Rh, 100ºC, 20 atm
Pd, 30–70ºC, 1 atm
Pd, Rh catalysts seems unlikely due to the difficulty of increasing their productivity any further.
Thus, despite the interest, the main challenges and restrictions to the broad expansion of GTL-FT technologies are capital costs, changes in the oil/gas price ratio and volatile prices of GTL products. GTL products also have to compete with cheaper products from crude oil (gasoline, diesel, jet and stove fuel) in the consumer market. In recent years, the stimulus of GTL has turned to another force: the desire to transform stranded or fl ared natural gases into money by converting these into high value-added marketable chemicals.
For example, Sasol’s GTL-FT facilities are flexible for the production of not only synthetic liquid fuels but also a broad assortment of different petrochemicals with high added value (60). This approach lowers the investment risks in comparison with production of synthetic fuel as the only marketable product.
Sasol produces more than 100 products (acids, alcohols, ketones, olefins) from its high-temperature
FT process for supply to the market, among them only a few fuels. This demonstrates the potential for alternative GTL to produce value-added products.
The operating characteristics of conventional GTL technologies based on FT synthesis in comparison with the suggested integrated process including carbonylation in the presence of pgm catalysts are given in Table IV .
Table IV Comparative Data on Conventional FT GTL and Integrated Process including Platinum Group
Metal Catalysed Carbonylation
Parameter
Temperature, ° С
Conventional FT GTL Carbonylation based GTL
220–330 100–200
Pressure, atm 20–30 10–60
Catalysts Co, Fe
Speci fi c activity of catalyst, kg/kg h
1.1–0.3 (conventional);
Up to 2 (microchannel) pgm
250–400
(for Rh-catalysed hydroformylation)
(Continued)
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Table IV Comparative Data on Conventional FT GTL and Integrated Process including Platinum Group
Metal Catalysed Carbonylation (Continued)
Parameter Conventional FT GTL Carbonylation based GTL
Reactor size Huge Ordinary
Expensive step for syngas production Not required
Oxidant (industrial O
2
)
Required
Steam conversion: no need for O
2
;
Partial oxidation and ATR: need for O
2
Need for O
2
Additional step for reductive isomerisation
Final products
Product puri fi cation
Availability for small-scale production or direct use in oil/gas fi elds
Capital cost per unit, US$/bpd
Required
Syncrude, fuels, lubricants
Required
Economically unreasonable
Not required
Petrochemicals
Required
Economically reasonable
˃ 140,000 ~50,000
The present review indicates that in some cases alternative GTL processes based on carbonylation will be able to take their own segment in the existing petrochemical markets, especially for remote areas and short life oil/gas pools. In order to perform such alternative processes it is advisable to use pgm catalysts because of their high activity and selectivity.
This type of process can be used for the monetisation of stranded natural and associated petroleum gases by converting them into marketable products with high added value.
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Iren A. Makaryan obtained her PhD in Chemistry from the Institute of Problems of Chemical Physics at the Russian Academy of Sciences (RAS), Chernogolovka, Moscow Region, Russia, under the supervision of Professor Valery I. Savchenko. She is currently Head of the Techno-Economic and
Market Research Group. Her research interests include kinetics and mechanism of pgm catalysed reactions, commercialisation of newly designed processes and market analysis.
Igor V. Sedov obtained his PhD in Chemistry from the Institute of Problems of Chemical Physics
RAS, Chernogolovka, under the supervision of Professor Petr E. Matkovskiy in 2011. He is now Head of the Petrochemical Processes Laboratory at the institute. His interests include organometallic catalysis, chemical technology and engineering.
Professor Valery I. Savchenko has been Head of the Department of Chemical Technology at the
Institute of Problems of Chemical Physics RAS, Chernogolovka, since 1991. He also lectures on Modern Petrochemical Processes at the Lomonosov Moscow State University, Russia. His research is devoted to a wide range of problems in the fi eld of chemical physics and chemical technology, including catalysis, kinetics, reaction mechanisms and reaction engineering. He has helped develop and commercialise a number of novel chemical and petrochemical processes.
25 © 2015 Johnson Matthey

Johnson Matthey Technol. Rev ., 2015, 59 , (1), 26–29 http://dx.doi.org/10.1595/205651315X685526
JOHNSON MATTHEY
TECHNOLOGY REVIEW www.technology.matthey.com
Johnson Matthey Technology Centre, Blounts Court,
Sonning Common, Reading, RG4 9NH, UK
Email: ballsc@matthey.com
“Nanomaterials for Lithium-Ion Batteries: Fundamentals and Applications” is edited by Rachid Yazami and is published by Pan Stanford Publishing Pte Ltd. The book covers the latest developments in new materials for lithium-ion batteries including examples of novel alloys, oxides and conversion materials for use as anodes and phosphates, high voltage spinels and layered oxides for use as cathodes. Composite structures incorporating reduced graphene oxide are considered along with thin fi lms and nanowires. Emphasis is also placed on combining electrochemical test data with materials characterisation and detailed explanation of the mechanisms occurring.
Chapter 1, ‘Silicon Nanowire Electrodes for Lithium-Ion
Battery Negative Electrodes’ by Candace K. Chan
(Arizona State University, USA) and Matthew T.
McDowell and Yi Cui (Stanford University, USA), describes the advantages and challenges of nanostructured silicon as an anode material. The signi fi cantly enhanced capacity of silicon over conventional graphite electrodes is also associated with a huge volume change of ~300% on lithiation of silicon electrodes. The chapter describes how the preparation of thin layers or nanoscale structures can mitigate this volume change ( Figure 1 ), but other aspects such as instability of the solid electrolyte interphase (SEI), cracking and detachment from the current collector with cycles are also important considerations. Methods to make silicon nanowires are discussed and the structural changes from the initial crystalline state to an amorphous structure after the fi rst cycle are explained.
Chapter 2, ‘Nanoscale Anodes of Silicon and
Germanium for Lithium Batteries’ by Jason Graetz and
Feng Wang (Brookhaven National Laboratory, USA), extends the discussion to cover additional elements which can alloy with Li, then focuses on Si and Ge, both of which can achieve high capacity at a low voltage.
Again the use of nanostructures is key to mitigate volume expansion issues and dissipate strain more readily during the expansion observed on lithiation of the material. Electrochemistry and cycling behaviour of thin fi lms of Si and Ge are compared and the chapter concludes by commenting on the possible bene fi ts of
Si and Ge electrodes in solid state batteries and the requirement for materials engineering of composite structures to stop pulverisation and decrepitation with cycles.
Chapter 3, ‘Nano-Electrochemical Approach for
Improvement of Lithium-Tin Alloy Anode’ by Tetsuya
Osaka, Hiroki Nara and Hitomi Mukaibo (Waseda
University, Japan), describes the promise of tin and tin alloys as Li storage materials. The approach of adding an inert spacer or scaffold element such as nickel to the tin is described, as Ni does not react with Li. Results
26 © 2015 Johnson Matthey

http://dx.doi.org/10.1595/205651315X685526
(a) Initial substrate After cycling
Johnson Matthey Technol. Rev ., 2015, 59 , (1)
Film
(b)
Particles
Nanowires
Ef fi cient 1D electron transport
Facile strain relaxation
Good contact with current collector
Fig. 1. Schematic of morphological changes that occur in Si during electrochemical cycling. (Reproduced with permission from (1). Copyright (2008) Nature Publishing Group) of electrochemical testing and characterisation (X-ray diffraction (XRD), transmission electron microscopy
(TEM) and electron diffraction) are shown for fi lms with various Sn:Ni ratios to illustrate the phases formed and the processes occurring; fi lm composition Sn:Ni 62:38 showed the best performance. Calculations and in situ methods to measure stress on the electrode layer as a result of volume expansion are also described.
Preparation of mesoporous Sn is also covered which shows improved cycling performance over denser Sn anodes.
Chapter 4, ‘Alloy Electrode and Its Breakthrough
Technology’ by Kiyotaka Yasuda (Mitsui Mining and
Smelting Co Ltd, Japan) provides a more historical perspective on the different types of anodes (Li metal and various alloy types) and also describes the different types of alloying reactions (internal displacement, phase separation and mixed reaction). The approach used by Mitsui in its SILX project on silicon based anodes is then discussed. Si particles are covered with a thin copper layer and formed into an electrode structure with ~30% cavity space. These features lead to good conductivity, prevent unwanted reaction of the electrolyte with Si and mitigate volume expansion issues, all of which lead to good performance and cyclability, especially at lower temperatures.
Chapter 5, ‘Nanometer Anode Materials for Li-Ion
Batteries’ by Xuejie Huang and Hong Li (Chinese
Academy of Sciences, China) describes the important features of anodes (low Li insertion and removal voltage, high capacity, low volume change, stability to electrolyte reactions, abundance and low cost) and also the various types of anode material (oxide, alloy, conversion) that are available. Examples of these different anode Li storage approaches are also provided, in particular the properties of transition metal oxide conversion materials. In such materials the metal oxide is converted to metal nanoparticles within a matrix of Li oxide by the lithiation process. The importance of achieving high mass and also high volumetric capacity for novel materials when comparing with currently used graphites is also emphasised.
Chapter 6, ‘Lithium Reaction with Metal Nano fi lms’ by Rachid Yazami provides a concise and systematic description of the properties of different metal nano fi lms during lithiation covering both non-alloying metals
27 © 2015 Johnson Matthey

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(where the only modes of Li storage are reaction with surface oxides and storage in micro cracks) and alloying metals (where incorporation of Li into the metal also takes place).
In Chapter 7, ‘High-Rate Li-Ion Intercalation in
Nanocrystalline Cathode Materials for High-Power
Li-ion Batteries’, Masashi Okubo (National Institute of Advanced Industrial Science and Technology,
Japan) and Itaru Honma (Institute of Multidisciplinary
Research for Advanced Materials, Japan) discuss the properties of lithium cobalt oxide (LiCoO
2
) which is currently widely used as a lithium-ion battery cathode material. Theoretical and experimental aspects of this material are covered, such as correlation between lithium diffusion distances and high rate capability.
Chapters 8 and 9 cover an alternative cathode material, lithium iron phosphate (LiFePO
4
), which is safer, lower cost and effective at high rates when made at nanosize and carbon coated ( Figure 2 ). Chapter 8, ‘LiFePO
4
:
From an Insulator to a Robust Cathode Material’ by
Miran Gaberš č ek (National Institute of Chemistry,
Slovenia) et al . is excellent, covering theoretical and experimental properties of LiFePO
4
from single crystals through to nanomaterials in electrode layers. The effect of size, models for different types of electrochemical contacting of active particles and network effects in cathode layers are all well explained. Chapter 9,
‘Redox Reaction in Size-Controlled Li x
FePO
4
by
Atsuo Yamada (The University of Tokyo, Japan) further elucidates the behaviour of LiFePO
4
, covering redox reactions and the effect of particle size on the phase diagram; the adverse effects of exposure of LiFePO
4 to air which causes oxidation of surface Fe are also discussed.
5 nm
5 nm
2 nm
2 nm
2 nm 5 nm
Fig. 2. TEM images of carbon coated LiFePO
4
Chapter 10, ‘Reduced Graphene Oxide–Based Hybrid
Materials for High-Rate Lithium Ion Batteries’ by Seong
Min Bak, Hyun Kyung Kim, Sang Hoon Park and
Kwang Bum Kim (Yonsei University, Republic of Korea) summarises the advantages and requirements for reduced graphene oxide (RGO) composite materials for both cathodes and anodes. These advantages include good conductivity and the ability to form small, well dispersed metal oxide particles on the RGO surface, preventing agglomeration of oxide particles and restacking of RGO and hence allowing good capacity and performance at high C-rates. Such materials may be made by microwave assisted hydrothermal synthesis and cathode (lithium manganese oxide (LiMnO
4
)/RGO) and anode (Li
4
Ti
5
O
12
/RGO) are both covered.
The fi nal chapter of this book turns to more practical considerations and how the advanced materials already discussed can be effectively utilised to give high power and/or high energy in real cells. Chapter 11, ‘High-
Energy and High-Power Li-Ion Cells: Practical Interest/
Limitation of Nanomaterials and Nanostructuration’ is by S. Jouanneau, S. Patoux, Y. Reynier and
S. Martinet (Commissariat à l’énergie atomique et aux
énergies alternatives (CEA) Laboratory for Innovation in New Energy Technologies and Nanomaterials
(LITEN), France). The advantages and challenges of a wide range of nanomaterials for cathodes, including
28 © 2015 Johnson Matthey

http://dx.doi.org/10.1595/205651315X685526 olivine type lithium metal phosphates, layered oxides and high voltage spinels with various metal contents, are discussed. Experience with novel Si/C composite anodes and titanium oxides and titanates is also reviewed. The requirements for more stable high voltage electrolytes or appropriate additives to accompany these advanced materials are also considered along with binder and processing aspects. The chapter provides an overview of the potential usefulness of nanomaterials for battery applications.
This book provides a very useful introduction to the forthcoming advanced nanomaterials for lithium-ion anodes and cathodes. Bene fi ts and disadvantages of a wide range of materials types are presented both in the context of fundamental materials properties and challenges of incorporating nanomaterials into practical electrodes and cells. Common themes within the chapters are the bene fi ts of nanosizing materials in terms of shorter diffusion lengths, improved conductivity and better rate capability, but disadvantages such as low density and increased surface area leading to greater irreversible capacity and unstable SEI are also
Johnson Matthey Technol. Rev ., 2015, 59 , (1) highlighted. Strategies to control volume expansion and limit material degradation with cycles via the preparation of composite materials and nanostructures, coatings or doping also feature across a wide number of the examples used.
1. C. K. Chan, H. Peng, G. Liu, K. McIlwrath, X. F. Zhang,
R. A. Huggins and Y. Cui, Nature Nanotechnol.
,
2008,
3
, (1), 31
"Nanomaterials for
Lithium-ion Batteries"
Dr Sarah Ball is a Senior Principal Scientist at the Johnson Matthey Technology Centre, Sonning
Common, UK. In the last two years she has been involved in work on lithium air and lithium-ion batteries. Previously she was involved in fuel cell research on novel cathode materials including assessment of electrochemical stability, performance and properties.
29 © 2015 Johnson Matthey

Johnson Matthey Technol. Rev ., 2015, 59 , (1), 30–33 http://dx.doi.org/10.1595/205651315X685517
JOHNSON MATTHEY
TECHNOLOGY REVIEW www.technology.matthey.com
Johnson Matthey Technology Centre, Blounts Court,
Sonning Common, Reading, RG4 9NH, UK
Email: ballsc@matthey.com
“Electrolytes for Lithium and Lithium-Ion Batteries”, published in 2014 by Springer, is Volume 58 in the
Modern Aspects of Electrochemistry series. The volume is edited by T. Richard Jow, Kang Xu, Oleg
Borodin and Makoto Ue. In the preface the Editors set out their purpose in compiling this volume, which was to provide a comprehensive overview of electrolytes for lithium-ion batteries. It covers electrolyte research and development in the last ten years and may be used as a foundation for future work and directions. The volume succeeds in covering the multifaceted area of electrolytes in a logical and highly comprehensive manner.
Chapter topics include lithium salts, advances in solvents, additives and ionic liquids, then progressing to understanding of the cathode and anode interphases, reviewing various characterisation approaches, a discussion of modelling approaches and fi nally future technologies such as lithium air batteries.
Chapter 1, ‘Nonaqueous Electrolytes: Advances in Lithium Salts’ by Wesley A. Henderson (Pacifi c
Northwest National Laboratory, USA) begins with information on desirable salt properties such as ionic conductivity, solubility, stability (to oxidation and hydrolysis) and ability to form an optimal interphase at the electrodes. The chapter then provides an extremely comprehensive coverage of the different types of lithium salts and their properties, ranging from established salts such as lithium hexafl uorophosphate (LiPF
6
) and lithium bis(bistrifl uoromethanesulphonyl)imide (LiTFSI) to more advanced examples including organoborates, phosphates and aluminates. Structure diagrams are included for all examples which greatly aid the reader and the chapter concludes by highlighting adoption criteria for new salts; the chapter also includes over
700 references.
Chapter 2, ‘Nonaqueous Electrolytes with Advances in Solvents’ by Makoto Ue, Yukio Sasaki (Tokyo
Polytechnic University, Japan), Yasutaka Tanaka
(Shizuoka University, Japan) and Masayuki Morita
(Yamaguchi University, Japan), reviews the important solvent properties including high electrolytic conductivity, high chemical and electrochemical stability, wide operating temperature range and high safety. Phase diagrams for a range of solvent mixtures are shown and properties such as viscosity, conductivity and stability are discussed for a range of cyclic and linear carbonates and fl uorinated versions thereof. The typical requirement to blend at least two electrolytes together to achieve optimal properties, for example a combination of a cyclic carbonate (high dielectric constant to aid salt dissociation) and a linear carbonate (to lower viscosity) is discussed, along with benefi ts of fl uorinated solvents to increase electrochemical performance and stability, use of organoborates to reduce weight, cost and toxicity and the addition of phosphates as fl ame retardants.
Polymer gel electrolytes and sulfur containing solvents are also reviewed.
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Chapter 3, ‘Nonaqueous Electrolytes and Advances in Additives’ by Koji Abe (UBE Industries Ltd, Japan), is partly told from a historical perspective, but also classifi es the different additive types according to their function and safety. The intentional addition of additives to control the solid electrolyte interphase (SEI) by forming a controlled thin layer with lower resistance to
Li mobility and additives for the formation of a stable cathode interphase are discussed. Safety aspects such as addition of species which can prevent thermal runaway via surface polymerisation and additives such as redox shuttles (for example, anisoles) and other approaches to overcharge protection and fl ame retardant additives such as phosphates are also reviewed.
Chapter 4, ‘Recent Advances in Ionic Liquids for
Lithium Secondary Batteries’ by Hajime Matsumoto
(National Institute of Advanced Industrial Science and
Technology (AIST), Japan) describes the benefi cial properties of ionic liquids (ILs) such as reduced fl ammability and volatility and covers examples of their exploratory usage in full-cells. Important recent developments are the formulation of new anions
(in particular asymmetric versions) which impact viscosity and improve mobility/conductivity, to achieve performance comparable to conventional electrolytes using ILs. The high stability reported for ILs in individual component analysis (thermal decomposition) is also shown to be reduced in the presence of active battery components, illustrating the importance of realistic testing scenarios.
Chapter 5, ‘Interphases Between Electrolytes and
Anodes in Li-Ion Battery’ by Mengqing Xu, Lidan Xing and Weishan Li (South China Normal University) covers the anode electrolyte interphase (referred to as the SEI). It begins with a historical overview of initial work with Li anodes and graphite highlighting how the unstable interphase formed with graphite and propylene carbonate (PC) electrolytes hampered initial studies and was revolutionised by the change to ethylene carbonate (EC) and other electrolytes which form a stable SEI with graphite anodes. The mechanisms of SEI formation (two-dimensional (2D) and three-dimensional (3D)) and reduction products for various linear and cyclic carbonate solvent species that create the SEI are discussed and the energy barriers to
Li motion through the interphase described ( Figure 1 ).
In addition various characterisation techniques
(including nuclear magnetic resonance (NMR) and
X-ray photoelectron spectroscopy (XPS)) to explore the SEI composition are discussed. The extension to more advanced anodes such as silicon and additives to aid SEI formation for various systems are also covered.
Chapter 6, ‘On the Surface Chemistry of Cathode
Materials for Li-Ion Batteries’ by Susai Francis Amalraj,
Ronit Sharabi, Hadar Sclar and Doron Aurbach
(Bar-Ilan University, Israel) provides a concise and practical introduction to the different cathode chemistry types (including layered oxides, spinels and olivines) and diagnostic methods to assess the cathodeelectrolyte interphase. Issues such as metal dissolution from the cathode and subsequent precipitation at the anode (leading to performance loss) and the use of additives or active materials coatings to control the cathode interphase and limit unwanted side reactions are described. References to greater details in a number of their own publications are also provided.
Chapter 7, ‘Tools and Methodologies for the
Characterization of Electrode–Electrolyte Interfaces’ by
Jordi Cabana (Lawrence Berkeley National Laboratory,
USA and University of Illinois, USA), provides a thorough and authoritative introduction to the various techniques to analyse electrode-electrolyte interfaces.
Electrochemical techniques, various types of spectroscopy (Raman, infrared (IR), XPS, NMR, X-ray and neutron techniques), ellipsometry and microscopy are all discussed with illustrative examples. To date many experiments have been made ex situ , necessarily requiring a washing and electrolyte removal step that may infl uence the surface, so advances in cell design to allow measurement in the presence of electrolyte are key to future progress. Also, the importance of combining complementary techniques to fully assess the interface properties is stressed along with possible overlaps with other areas in electrocatalysis.
Chapter 8, ‘Molecular Modeling of Electrolytes’ by Oleg
Borodin describes the different methodologies for the modelling of electrolytes and stresses the importance of considering clusters and systems rather than just the individual molecules and components. Validation of models against experimental data and also the dangers of combining experimental results from different sources (where details such as experimental procedures and reference scales may vary) are
31 © 2015 Johnson Matthey

http://dx.doi.org/10.1595/205651315X685517
 G ≠
Johnson Matthey Technol. Rev ., 2015, 59 , (1)
60~70 kJ mol
–1
“Charge-transfer” activation energy
Diffusion of solvated
Li
+
in bulk solution
Reaction coordinate
Li + diffusion through SEI fi lm
0.35 mm
Breakup of Li + solvation sheath
Li + diffusion in graphene bulk
Fig. 1. Schematic description of energy barrier for “Li transfer” at graphite/electrolyte interphase (Reprinted with permission from
(1). Copyright (2010) American Chemical Society) highlighted. The use of molecular dynamics (MD) simulations to explore Li mobility within the SEI and the different anode substrates (graphite, lithium titanate and lithium lanthanum titanate) and hence decouple Li mobility in SEI from Li desolvation effects is described.
Chapter 9, ‘Prediction of Electrolyte and Additive
Electrochemical Stabilities’ by Johan Scheers and
Patrik Johansson (Chalmers University of Technology,
Sweden), covers different approaches to modelling the potentials of oxidation and reduction of solvent, salt and additive components of the electrolyte. Signifi cant variations in predicted trends are found depending on the reaction products (linear or cyclic), route, mechanism and intermediates. Again issues with cross comparison against different experimental results in the literature are pointed out, including varying sweep rates, working electrodes, cut off currents and also variations in the reference energies. In the case of redox shuttle, accurate predictions of potentials are particularly important, as their behaviour links to battery safety. The advantages of increasing computer power are also discussed, as more complex systems may be modelled and in particular realistic electrode materials depictions, surfaces and multicomponent systems can be explored more accurately.
The book closes with Chapter 10, ‘Aprotic Electrolytes in
Li-Air Batteries’ by Kah Chun Lau, Rajeev S. Assary and
Larry A. Curtiss (Argonne National Laboratory, USA).
Lithium air batteries in theory present the possibility of exceptionally high capacities due to their low mass constituents. However, the lack of stability of current electrolytes in the presence of the superoxide radical generated in the cathode oxygen reduction reaction is thought to be the greatest barrier to success in these systems. For many years common Li-ion electrolytes such as PC were used in lithium air systems. However, superoxide attack results in formation of irreversible lithium carbonate species, rather than the desired lithium peroxide ( Figure 2 ). This chapter summarises
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http://dx.doi.org/10.1595/205651315X685517 Johnson Matthey Technol. Rev ., 2015, 59 , (1)
200 nm
Fig. 2. Lithium peroxide toroids formed on discharge in a lithium air cathode. (Picture courtesy of the Analytical
Department, Johnson Matthey Technology Centre, Sonning
Common, UK) the characterisation methods used to confi rm the unsuitability of PC and the somewhat improved results with ether based solvent and stresses the importance of understanding the reaction mechanisms and of interlinking theory and experiment to enable the search for an improved electrolyte system.
Throughout the book certain themes emerge, including the importance of carefully correlating experimental results with modelling data and addressing multicomponent systems under realistic conditions rather than considering the individual constituents in isolation. It is also apparent that no one technique can ever provide all the answers. This book provides an excellent guide to the plethora of salt, electrolyte and additive options and their functionalities and properties; the historical overview is also particularly helpful to those who are new to the fi eld.
In summary, this book will be useful to battery researchers in academia and industry, providing historical context, reference information on a wide range of electrolyte components and their functionality and highlighting directions for further work and the challenges that lie ahead. The use of examples to illustrate materials properties, interplay between components, the different analytical techniques and modelling approaches is particularly helpful along with the large number of literature references cited on the different topics.
1. K. Xu, A. von Cresce and U. Lee, Langmuir , 2010,
26
,
(13), 11538
Electrolytes for Lithium and
Lithium-ion Batteries
Dr Sarah Ball is a Senior Principal Scientist at the Johnson Matthey Technology Centre, Sonning
Common, UK. In the last two years she has been involved in work on lithium air and lithium-ion batteries. Previously she was involved in fuel cell research on novel cathode materials including assessment of electrochemical stability, performance and properties.
33 © 2015 Johnson Matthey

Johnson Matthey Technol. Rev ., 2015, 59 , (1), 34–44 http://dx.doi.org/10.1595/205651314X685824
JOHNSON MATTHEY
TECHNOLOGY REVIEW www.technology.matthey.com
Helmholtz Institute Ulm (HIU), Electrochemistry 1,
Helmholtzstraße 11, 89081 Ulm, Germany; and
Karlsruhe Institute of Technology (KIT), PO Box 3640,
76021 Karlsruhe, Germany
Johnson Matthey Technology Centre, Blount’s Court,
Sonning Common, Reading, RG4 9NH, UK
Email: *stefano.passerini@kit.edu;
**mark.copley@matthey.com
Following the development of commercial secondary lithium-ion batteries (LIBs), this article illustrates the progress of therein-utilised anode materials from the fi rst successful commercialisation to recent research activities. First, early scienti fi c achievements and industrial developments in the fi eld of LIBs, which enabled the remarkable evolution within the last 20 years of this class of batteries, are reviewed. Afterwards, the characteristics of state-of-the-art commercially available anode materials are highlighted with a particular focus on their lithium storage mechanism.
Finally, a new class of anode active materials exhibiting a different storage mechanism, namely combined conversion and alloying, is described, which might successfully address the challenges and issues lithiumion battery anodes are currently facing.
Rechargeable (i.e. secondary) LIBs are now our everyday companions, powering our laptops, cellular phones, tablets, portable audio players, etc. Due to their high speci fi c energy, superior coulombic ef fi ciency and outstanding cycle life compared to earlier battery systems like lead-acid, nickel cadmium or nickel metal hydride (1), LIBs quickly conquered the battery market for consumer electronics (2) and are at present the power source of choice for these applications (3). In view of limited crude oil resources and climate endangering emissions (e.g. CO
2
) deriving from the consumption of fossil fuels, LIB technology is currently facing a new great challenge: its implementation in large-scale devices like (hybrid) electric vehicles and stationary energy storage to balance the intermittent supply of renewable energy sources such as wind, solar and tidal (3–5). Although some electric and hybrid vehicles are now becoming available, the energy density of LIBs still needs to be substantially increased by a factor of two to fi ve compared to the existing state-of-the-art technology (150 Wh kg –1 ) to push these vehicles out of the niche market sector, paving the way for a fully sustainable transportation system (6). However, the conversion of electrical energy to chemical energy
(and vice versa ), corresponding to the charge (and discharge) of a LIB, is a complicated process due to the various participating components in a lithium-ion cell, their (electro-)chemical properties and their extensive interdependencies (4).
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http://dx.doi.org/10.1595/205651314X685824 Johnson Matthey Technol. Rev ., 2015, 59 , (1)
Generally, LIBs are built of two electrodes (anode and cathode), separated by an electrically insulating though ionically conducting liquid electrolyte supported on a porous separator to ensure the transfer of charge carriers (lithium-ions) from one electrode to the other (7,
8). It appears noteworthy that the separator-electrolyte system may also consist of a non-porous polymer layer, i.e. a solid-state polymer electrolyte (SPE) membrane, occasionally swollen by a liquid electrolyte, i.e. a gel polymer electrolyte (GPE) (9). A deep understanding of the chemical and electrochemical interactions of these components throughout the lifetime of a LIB is certainly crucial to develop new concepts for advanced lithiumbased battery technologies in future (3). However, in a fi rst step each component of the cell has to be addressed solely, keeping the other cell parameters constant.
This article reviews the development of lithiumion anode materials ( Section 2 ), focusing initially on those materials that were or are already employed in commercial batteries ( Section 3 ). Subsequently, promising alternatives for these currently utilised anode materials are brie fl y reviewed, in particular those materials storing lithium by a combined alloying and conversion mechanism ( Section 4 ). Interdependencies of these lithium-ion anode materials and other cell components are also addressed.
The most elementary anode material for lithium-based batteries is obviously metallic lithium, which has been used for primary (i.e. non-rechargeable) batteries since the early 1960s (10, 11). By possessing the lowest standard potential (–3.05 V vs. a standard hydrogen electrode (SHE) (12)) and the lowest atomic weight (6.94 g mol –1 ; speci fi c gravity: ρ = 0.53 g cm –3 ) among all metals, the utilisation of metallic lithium as an anode offers the realisation of galvanostatic cells having an extremely high energy density (10, 13, 14).
Consequently, metallic lithium was also considered the candidate of choice for secondary lithium-based batteries (10, 15, 16). However, lithium metal cells have one severe drawback, namely, inhomogeneous lithium plating, which halted their commercial development three decades ago. This uneven deposition of lithium onto the anode surface upon charge results in the formation of so-called dendrites (11, 17, 18). These dendrites consist of high surface area, highly branched lithium metal structures, which continuously grow, eventually penetrate the separator and electrically connect the anode and cathode leading to a short circuit of the cell. This spontaneous and uncontrolled event results in local heat evolution and – in the most unfortunate case – thermal runaway of the cell (19, 20).
To circumvent this severe safety issue, in the 1970s several researchers developed the concept of lithiumion host structures, later commonly named insertion compounds, thus avoiding the risk of super fi cial
(dendritic) lithium growth (21–24). In the course of these developments Scrosati and Lazzari proposed the ‘rocking chair battery’, which marked the fi rst practical realisation of two host materials reversibly shuttling lithium-ions from the anode to the cathode upon discharge and vice versa upon charge (7, 8).
Nowadays, all commercially available secondary
LIBs make use of this concept, although they employ different active materials as cathode and anode.
Regarding the anode side, carbonaceous materials are generally used as the lithium-ion host framework
(10, 11). The fi rst commercial secondary LIB, released by Sony Corporation in 1991, comprised LiCoO
2
as cathode and a soft carbon (more precisely coke; soft carbons can be graphitised by thermal treatment at about 2300ºC) as an anode ( Figure 1 ). This LIB provided an energy density and speci fi c energy of
200 Wh l –1 and 80 Wh kg –1 , respectively, outperforming all other battery technologies present in the market at that time. Moreover, this battery showed a highly reversible and stable cycling behaviour and an extremely high cell voltage of about 4 V, employing propylene carbonate (PC) as electrolyte solvent
(10, 15). The replacement of soft carbon by hard carbon
( Figure 1 ) (i.e. non-graphitisable carbon), offering enhanced speci fi c capacities, led to an increase of the achievable volumetric and gravimetric energy density up to 295 Wh l –1 and 120 Wh kg –1 , respectively
(10, 15). The hard carbon anode facilitated the increase of the upper cut-off potential to 4.2 V, while presenting excellent cyclability in the – at that time – commonly used PC-based electrolytes (10, 15).
In summary, it can be stated that (by carefully controlling the heat treatment temperature) hard and soft carbons can be obtained, providing acceptable speci fi c capacities, low initial irreversible charge loss and relatively low (dis-)charge hysteresis, enabling ef fi cient energy conversion and storage (25, 26).
Nevertheless, the desired application of LIBs in cellular phones required the replacement of such anode
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(a)
(b)
(c)
Soft (disordered, graphitisable)
Hard (disordered, nongraphitisable)
Graphite
1.2
1.0
0.8
0.6
2.0
1.8
1.6
1.4
0.6
0.4
0.2
0
1.4
1.2
1.0
0.8
1.2
1.0
0.8
0.6
0.4
0.4
0.2
0
1.4
Li + uptake
Li + uptake
Li + release
Li + release
Li + release
0.2
0
Li + uptake
0 100 200 300 400 500 600 700
Speci fi c capacity, mAh g –1
Fig. 1. Schematic illustration (left side) of: (a) soft carbon; (b) hard carbon; and (c) graphite structures and (right side) their typical potential pro fi les (Figure redrawn from (15, 16)) materials, as the voltage drop in the potential pro fi le of both carbonaceous materials (13) upon (dis-)charge
( Figure 1 ) results in a substantially varying overall cell voltage. However, cellular phones need an operational voltage of at least 3 V (27). In addition, the utilisation of these anode materials suffered a severe safety issue.
In order to achieve the maximum speci fi c capacity, the cathodic cut-off potential (i.e. the end-of-charge potential for the anode) must be set close to 0 V vs.
Li/
Li + (16), thus, again posing the risk of metallic – in worst case dendritic – lithium plating on the carbon particles surface. For these reasons a new anode material was required. Graphite advantageously addresses all these issues rather satisfactorily and is thus still the most commonly employed anode material in today’s commercial LIBs (5).
In contrast to soft and hard carbons, graphite shows a rather fl at potential pro fi le when reversibly hosting lithium-ions at potentials below 0.5 V vs.
Li/Li + ( Figure 1 )
(25, 28, 29). Additionally, it offers a signi fi cantly higher speci fi c capacity of 372 mAh g –1 (corresponding to one lithium per hexagonal carbon ring, i.e. LiC
6
) with limited irreversible capacity (10, 13, 15). Graphite is composed of graphene layers, stacked in AB or ABC sequence and held together by van der Waals forces (13). Upon (dis-) charge lithium-ions (de-)intercalate into the layered structure by a so-called staging mechanism, resulting in an AA stacking con fi guration once it is fully lithiated
(25, 28, 29). Another great advantage of graphite is its high electronic conductivity, originating from the sp 2 hybridisation ( p -orbitals building a delocalised electron network) of the carbon atoms located in the planar, hexagonally structured graphene layers (13).
A major obstacle for the implementation of graphitebased anodes, however, was their incompatibility with the standard electrolyte solvent PC (10, 15). In 1970,
Dey and Sullivan observed the electrochemically induced degradation of the graphite structure in
PC-based electrolytes (30). As reported in later studies, the reason for this degradation was the co-intercalation of solvent molecules, i.e. the solvation shell of the
36 © 2015 Johnson Matthey

http://dx.doi.org/10.1595/205651314X685824 Johnson Matthey Technol. Rev ., 2015, 59 , (1) lithium-ions in the electrolyte, leading to a volume expansion of ~150% and subsequent exfoliation of the single graphene layers (13). Furthermore, lithium-ion intercalation occurs at potentials beyond the electrochemical stability window of common electrolytes. Therefore, a continuous reductive decomposition of the electrolyte components takes place, leading to a drying-out of the cell and hence a rapid capacity fading. The implementation of graphite as lithium-ion anode was made possible, fi nally, by replacing PC with mixtures of short-chain linear alkyl carbonates (low viscosity) and – most importantly – ethylene carbonate (EC, high dielectric constant (28)).
These solvents are also not stable (thermodynamically) at such low potentials, but the initial decomposition of
EC results in the formation of a stable, electronically insulating, ionically conductive fi lm on the graphite particles surface, preventing direct contact of the active material and the electrolyte while at the same time inhibiting the co-intercalation of solvent molecules
( Figure 2 ) (17, 18, 28, 29, 31, 32). Following an early study by Peled, this protective surface fi lm is now known as the solid electrolyte interphase (SEI) (31).
The replacement of hard carbon by graphite as an anode led to a further jump in volumetric and gravimetric energy density up to 400 Wh l –1 and 165 Wh kg –1 , respectively (10, 15). As the theoretical capacity of graphite has now been mostly achieved, recent research efforts to further improve the performance of LIBs are basically dedicated to minimising the fi rst cycle irreversible capacity, for instance by modifying the graphite surface. An extensive description of these research activities is certainly beyond the scope of this review and the interested reader is referred to Bresser
Activation barrier
Graphite SEI Electrolyte
Fig. 2. Schematic illustration of the SEI on graphite, emphasising its role in the desolvation process of lithium ions prior to the intercalation of lithium into the graphite host material (Reproduced with permission from (32). Copyright
2009 American Chemical Society) et al . (27) (and references cited therein), who provide a more detailed overview on this subject.
As mentioned earlier, graphite is still the most used anode material in commercial LIBs. However, as with soft and hard carbons, it entails the inherent risk of metallic lithium plating, an intrinsically limited high rate capability upon charge and a very high reactivity towards the electrolyte in the lithiated state, which might result in thermal runaway and occasionally the event of a fi re if the SEI gets damaged or decomposes due to the overall temperature of the cell exceeding
130ºC (11, 17, 18, 33–37).
4
5
12
A very promising alternative for graphite is spinelstructured Li
4
Ti
5
O
12
(LTO), which was fi rst reported in
1994 (38). The reversible (de-)insertion of Li + in the
LTO framework occurs at a comparably high potential
(about 1.55 V vs.
Li/Li + ) and the theoretical speci fi c capacity is relatively low (175 mAh g –1 ). Consequently, the achievable energy density of a lithium-ion cell employing LTO is much lower compared to graphitebased cells (38–40). However, LTO exhibits several great advantages compared to graphite, resulting in steadily growing interest regarding its commercial application (41–43). While the rather high operating potential of LTO certainly restricts the overall energy density, it allows the realisation of inherently safer LIBs.
Since common electrolytes are thermodynamically stable at 1.55 V vs . Li/Li + , no vigorous electrolyte decomposition occurs, thus avoiding issues related to the growth or breakdown of the SEI.The operating potential is far from the region where metallic lithium plates onto the anode surface and consequently no dendritic formation can occur (34, 38, 39, 42, 44). In addition, the negligible volume expansion (39, 45) of LTO upon (de-)lithiation results in an outstanding cycling stability for more than tens of thousands of fast
(dis-)charge cycles (46, 47).
As apparent from Figure 3 , LTO exhibits a desirable fl at potential pro fi le corresponding to a two-phase
(spinel to rock-salt) electrochemical lithium (de-) insertion process (48):
Li
4
Ti
5
O
12
+ 3 Li + + 3 e –  Li
7
Ti
5
O
12
The insulating character (49) of spinel phase LTO, however, is a major obstacle for fast (de-)lithiation processes. Hence, several strategies were pursued to improve its electronic conductivity. Inter alia , nanostructuring of the LTO particles leading to shorter
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http://dx.doi.org/10.1595/205651314X685824 Johnson Matthey Technol. Rev ., 2015, 59 , (1)
2.0
1.5
1.0
Li + deinsertion
Li + insertion
Speci fi c capacity, mAh g –1
Fig. 3. Typical potential pro fi le for a LTO electrode showing a fl at Li + (de-)insertion plateau and a low voltage hysteresis
(Image courtesy of Guk Tae Kim, Helmholtz Institute Ulm
(HIU), Ulm, Germany) diffusion pathways for lithium-ions and electrons and an increased electrode/electrolyte contact area resulted in a remarkable enhancement of its electrochemical performance, particularly at high (dis-)charge rates
(14, 44, 47, 50). Further improvement was achieved by coating the (nanosized) particles with conductive surface layers (e.g. carbon) or by introducing LTO in highly conductive mesoporous (carbonaceous) matrices (48, 50–52). As a result, LTO appears highly attractive for the realisation of substantially safer, high power LIBs (5, 45, 53).
Several elements (e.g. Sn, Pb, Al, Sb, Zn, Si) are able to reversibly form alloys with lithium at low potential
(54, 55). In contrast to the already discussed lithium storage by intercalation and insertion, the alloying mechanism is fundamentally different, giving rise to multiple new issues. However, with appealing theoretical speci fi c capacities (exceeding that of graphite up to tenfold) and hence, energy densities, alloying anodic materials are currently intensely researched (56–58). Clearly, one of the major issues regarding alloying materials in general is the large volume expansion/contraction upon (de-)lithiation, leading to the fracturing of active material particles, the subsequent loss of electronic contact and fi nally the pulverization of the electrode (57, 59).
More than ten years ago an amorphous tin-oxygenbased composite was developed by Fuji Photo
Film Corporation (60). However, it has never been successfully commercialised for various reasons. Upon initial lithiation, in a partially irreversible step, Li
2
O and metallic Sn are formed, followed by a reversible alloying reaction of lithium and tin (61). It was assumed that the electrochemically inert ‘matrix’ of Li
2
O separating the initially formed tin nanograins would prevent the latter from aggregation upon cycling (62, 63), but not least due to the substantial volume expansion of ~200% (56) accompanying the alloying reaction, the comprised tin still aggregates upon long-term cycling (64, 65). This leads to rather rapid capacity fading after several cycles.
Therefore, research efforts were focused on creating secondary particle structures or matrices which are capable of buffering this volume expansion/contraction stress. Such research efforts comprised inter alia the preparation of hollow carbon nanospheres (66), core-shell nanostructures (67–69) and submicron- or micron-sized carbonaceous matrices (70–73).
Despite these very promising approaches, to date only one tin-based alloying material – a composite of tin, cobalt and carbon – has been successfully employed in commercial LIBs (56, 74). It is reported that upon lithiation this Sn-Co-C composite initially forms a
Li-Sn-Co phase, which subsequently separates into a
Li-Sn alloy (75) and amorphous cobalt, provided that a suf fi cient amount of cobalt is present in the initial composite (76). Upon discharge, the delithiated tin alloys with the amorphous cobalt. This rather complex mechanism is supposedly the origin of the improved cycle life compared to pure Sn- or SnO
2
-based anodes
(77–80).
It may be noted that very recently silicon-based anodes
(more precisely, carbon-coated silicon nanostructures) were commercialised, promising substantially higher speci fi c energies (81, 82) compared to pure graphite or graphite-based anodes containing a relatively low content of silicon (83).
Research activities for the next generation of lithiumion anodes are now focusing on the development of materials capable of surpassing graphite anodes in terms of energy, power and safety, while maintaining (if not improving) the level of environmental friendliness and raw material availability. Presently, nanosized alternative active materials (5, 84, 85) reversibly hosting lithium by both mechanisms discussed so far, insertion
(e.g. N -doped carbonaceous materials or titanium
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http://dx.doi.org/10.1595/205651314X685824 Johnson Matthey Technol. Rev ., 2015, 59 , (1) dioxide) as well as alloying (e.g. silicon or silicon oxide), are attracting world-wide scienti fi c interest (27) and several excellent reviews are available for these very promising anode materials (44, 84, 86, 87).
In this review we focus on the latest upcoming research area characterised by a completely different lithium storage mechanism: chemical displacement or so-called conversion reactions.
Initially, displacement (i.e. conversion) reactions were considered to be irreversible at room temperature due to the extensive energy demand for bond breakage, atomic reorganisation, and the formation of new bonds
(24). In 2000, Poizot et al . (86) reported for the fi rst time reversible lithium storage using transition metal oxides as active materials, providing speci fi c capacities of more than 700 mAh g –1 . Since then a growing interest in battery materials following a conversion mechanism
( Figure 4 ) (88) can be noted, including transition metal oxides, sul fi des, nitrides, phosphides, fl uorides and other phases (89).
The conversion mechanism can be generally described as follows (85):
TM x
A y
+ z e – + z Li + x TM 0 + Li z
A y
Upon lithiation the transition metal (TM) is reduced to its metallic state and embedded in the simultaneously formed lithium-comprising compound Li z
A y
(where A stands for O, N, P, F and others). Due to the inherent physico-chemical properties of the initially formed TM nanograins, the formation of Li z
A y
becomes reversible
(86). It might be noted that very recently also the reversible formation of lithium silicate, starting from cobalt silicate, was reported (90).
Nevertheless, despite the growing knowledge about nanosized materials there is still a lack of fundamental understanding of the processes occurring in conversion materials, boosting the scienti fi c interest regarding this class of materials
(56). Commonly, nanostructured materials bene fi t
8 Li + + 8e –
Co
3
O
4
Li
22
Nanosized Co 0
(diameter 2–3 nm)
Fig. 4. Schematic illustration of the conversion mechanism shown exemplarily for spinel cobalt oxide (Figure redrawn from (88)) from enhanced electron and lithium-ion transport due to shorter diffusion (or more generally transport) pathways and reduced internal stress during volume expansion/contraction upon (de-)lithiation (56). For a more detailed insight into the (dis)advantages arising from using nanostructured materials for LIB applications the interested reader is referred to Bruce et al . (84), Scrosati et al . (74), Lee and Cho (87), and more recently Bresser et al . (91). De fi nitely, the most appealing feature of conversion materials is their ability to store more equivalents of lithium (two to eight per unit formula of the starting material) than any insertion compound (up to two), resulting in substantially higher speci fi c capacities as displayed in Table I (3, 14).
However, conversion materials exhibit a series of severe drawbacks which necessarily need to be overcome before they can be seriously considered for commercial applications (89). The conversion reaction inherently causes a massive structural reorganisation, which potentially leads to a loss of electrical contact and electrode pulverisation (89). Moreover, conversion materials suffer from a very high reactivity towards commonly used electrolytes and a marked (dis-)charge voltage hysteresis, considerably affecting the energy storage ef fi ciency of such electrodes (14, 89, 92). The elevated operational potentials of many conversion materials also limit the achievable energy density (14,
56) and the large fi rst-cycle irreversible capacity is unacceptable for practical applications and requires special electrode treatments for compensation (56,
89). Taking into account the surface area which is frequently high (an intrinsic feature of nanostructured particles) and, as already mentioned, reactive, as well as the SEI instability known from compounds
Table I Comparison of Theoretical Specifi c
Capacities of Selected Insertion and
Conversion Materials a
Material type
Anode material
Soft carbons
Theoretical capacity, mAh g
–1
200–1000
Hard carbons 200–600
Insertion
Graphite 300–375
LTO 175
TiO
2
Metal oxides
Conversion
Metal phosphides, sul fi des or nitrides a Table prepared according to (13, 85)
330
500–1200
500–1800
39 © 2015 Johnson Matthey

http://dx.doi.org/10.1595/205651314X685824 Johnson Matthey Technol. Rev ., 2015, 59 , (1) experiencing considerable volume changes (56, 86), conversion materials have just reached the early stage of development. For a detailed summary concerning the different types of conversion materials the interested reader is referred to Cabana et al . (89), Nitta and
Yushin (56) or Goriparti et al.
(85).
Conversion-alloying materials mark another step forward in developing high energy and high power lithium-ion anode materials. The idea behind this new class of active materials is to further increase the uptake of lithium per unit formula of starting material by using mixed metal oxides in which one of the comprised metals can further alloy with lithium after being initially reduced to the metallic state (93, 94).
This obviously results in higher speci fi c capacities than theoretically achievable for ‘pure’ conversion materials.
Exploiting, for instance, the lithium alloying capability of zinc, iron is partially substituted by zinc in the commonly known conversion material Fe
3
O
4
, giving e.g. ZnFe
2
O
4
. Upon lithiation metallic zinc and iron are formed. Subsequently, zinc can further reversibly alloy with lithium. Overall, nine equivalents of lithium per unit formula can be stored in ZnFe
2
O
4 speci fi c capacity: 1000.5 mAh g
(theoretical
–1 ) compared to only eight equivalents of lithium per unit formula in Fe
3
O
4
(926 mAh g –1 ) (94).
Analogously to other conversion materials, the chemical reaction of spinel-structured zinc ferrite and lithium, fi rst reported in 1986 (95), was initially considered to be irreversible. Nevertheless, after conclusive proof of reversible lithium uptake in
ZnFe
2
O
4
thin fi lms in 2004 (96), research efforts were focused on achieving high reversibility and increased speci fi c capacities. Early studies nonetheless obtained neither stable cycling performance nor the material’s theoretical capacity. Additionally, the rate performance, i.e. the achievable speci fi c capacity at elevated speci fi c currents, remained a severe issue (97–101). The apparently inevitable capacity fading was attributed to the formation of an insulating polymeric layer related to an ongoing electrolyte decomposition (44) and/or signi fi cant volume changes upon (de-)lithiation (98).
Transferring their knowledge about electronically conductive carbonaceous percolating networks
(102) to conversion-alloying materials, Bresser et al .
(94) very recently succeeded in overcoming these issues by coating ZnFe
2
O
4
nanoparticles with an amorphous carbon layer. The use of rather stiff sodiumcarboxymethyl cellulose (CMC; water-based) as binder further enhanced the electrochemical performance, preventing the electrode morphology upon cycling
(94), while the choice of the carbon precursor obviously also had a great impact on the cycling stability (103).
After investigating the reaction kinetics of the involved electrochemical mechanisms of the carbon-coated
ZnFe
2
O
4
(94), very recently Varzi et al . (104) were able to realise a high-power LIB, comprising carbon-coated
ZnFe
2
O
4 nanoparticles as an anode and a composite of
LiFePO
4
and multiwalled carbon nanotubes as cathode
( Figure 5 ). This lithium-ion full-cell retained 85% of its initial capacity after 10,000 cycles at a current rate as high as 10 C with respect to the (capacity-limiting) cathode or about 3 C in regard to the ZnFe
2
O
4
-C anode. To compensate the high fi rst-cycle irreversible capacity Varzi et al . investigated different degrees of partial pre-lithiation of the anode. Remarkably, even the most extensive lithium doping (600 mAh g –1 ) did not signi fi cantly affect the rate performance of the carboncoated ZnFe
2
O
4 nanoparticles, while at the same time the degree of pre-lithiation allowed the overall voltage of the lithium-ion full-cell to be tailored (104). These promising results con fi rm that the concept of using conversion or preferably conversion-alloying high capacity anodes – despite the manifold issues these materials are facing – is a valuable approach to future challenges for LIBs.
140
120
100
80
100
80
60
60
40
40
20
Ef fi ciency
Charge
Discharge
20
0 0
0 2500 5000 7500 10,000
Cycles
Fig. 5. Long-term cycling stability of a ZFO-C/LFP-CNT full-cell, applying a high current density (3 mA cm –2 ) (Image courtesy of Alberto Varzi, Helmholtz Institute Ulm (HIU),
Ulm, Germany)
This brief overview of commercial secondary LIB anodes re fl ects only partially the intensive and continuously growing research efforts carried out within the past 25 years in this speci fi c segment of
40 © 2015 Johnson Matthey

http://dx.doi.org/10.1595/205651314X685824 Johnson Matthey Technol. Rev ., 2015, 59 , (1)
LIB technology. It is also evident as the strict industrial requirements have so far allowed only a few materials to reach a commercial level, for which the guarantee of reliable performance is doubtlessly the most important requirement. As this article shows, even the change of basic reaction mechanisms from intercalation/ insertion to alloying and conversion has not yet led to a breakthrough in LIB technology. We still do not have satisfactory solutions for the challenges within sight, but the encouraging advances and manifold developments of anode materials (and LIBs in general) from the fi rst commercial device up to the present ones provide a solid basis for exploring the next generation of LIBs.
The authors would like to thank Dr Guk Tae Kim,
Helmholtz Institute Ulm (HIU), Ulm, Germany, for providing the potential pro fi le of LTO ( Figure 3 ) and
Dr Alberto Varzi, Helmholtz Institute Ulm (HIU), Ulm,
Germany, for providing the cycling data of ZFOC/LFP-
CNT full-cells ( Figure 5 ).
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Nicholas Loef fl er is a second year PhD student in the group of Professor Stefano Passerini, formerly at the Institute of Physical Chemistry & MEET Battery Research Centre at the University of Münster, Germany, now working at the Helmholtz Institute Ulm (HIU) of the Karlsruhe Institute of Technology (KIT), Germany. His main research activities are focused on the processing of electrode formulations in aqueous media as well as investigation of suitable binder systems and additives and their in fl uence on the electrochemical performance of lithium-ion batteries.
Dominic Bresser is a third year PhD student in the group of Professor Stefano Passerini, formerly at the Institute of Physical Chemistry & MEET Battery Research Centre at the University of Münster, now working at the Helmholtz Institute Ulm (HIU) of the Karlsruhe Institute of Technology (KIT).
His main research activities are focused on the development and investigation of nanostructured materials for lithium and lithium-ion batteries as well as the design and study of carbonaceous coatings and matrices and its in fl uence on the electrochemical performance of nanosized active materials.
43 © 2015 Johnson Matthey

http://dx.doi.org/10.1595/205651314X685824 Johnson Matthey Technol. Rev ., 2015, 59 , (1)
Stefano Passerini has been a Professor at the Karlsruhe Institute of Technology (KIT) since 2014, carrying out his activities in the Helmholtz Institute Ulm (HIU), the joint research facility of KIT,
University of Ulm, Germany, the German Aerospace Center (DLR), and the Centre for Solar Energy and Hydrogen Research (ZSW). Before then, he co-founded the MEET Battery Research Center at the University of Münster, Germany. His research activities are focused on electrochemical energy storage in batteries and supercapacitors. He is (co-)author of more than 250 scienti fi c papers, a few book chapters, and several international patents. In 2012, he was awarded the Research
Award of the Electrochemical Society Battery Division. Since 2013 he has been appointed as
European Editor of Journal of Power Sources .
Mark Copley is a Principal Scientist at the Johnson Matthey Technology Centre, Sonning Common,
UK. His work focuses on the development of nanomaterials for use as active electrode materials in lithium-ion secondary batteries. He gained his PhD (2006), under the supervision on Professor
Trevor Spalding University College Cork, Ireland. The thesis focused on the development of ordered mesoporous structures, their tunable synthesis and applications in catalysis.
44 © 2015 Johnson Matthey

Johnson Matthey Technol. Rev ., 2015, 59 , (1), 45–51 http://dx.doi.org/10.1595/205651315X685553
JOHNSON MATTHEY
TECHNOLOGY REVIEW www.technology.matthey.com
Johnson Matthey Technology Centre, Blounts Court,
Sonning Common, Reading, RG4 9NH, UK
Email: xavier.quek@matthey.com
Jointly organised by the Aseanian Membrane Society, the European Membrane Society and the North
American Membrane Society, the 10th International
Congress on Membrane and Membrane Processes
(ICOM) was held at Suzhou, China from 20th to
25th July 2014. ICOM is a highly regarded triennial conference in the membrane community, attracting scientists from around the world for scienti fi c dissemination and discussion on membranes. The
10th ICOM attracted approximately 1300 delegates representing 39 countries. The programme consists of four plenary lectures, 86 keynote lectures, 424 oral presentations (split into nine parallel sessions) and
662 poster presentations. With such a vast selection of presentations, only selected highlights on themes related to gas separation, liquid separation, polymeric membranes, inorganic membranes and novel membrane processes and applications are discussed in this review.
Further information on the 10th ICOM can be found on the conference website (1).
The following challenges in applying membranes to large scale separations were highlighted by William
Koros (Georgia Institute of Technology, USA) in his
William J. Koros
(Georgia Institute of
Technology, USA)
Yiqun Fan (Nanjing
University of
Technology, China)
Membrane Technology
Pathways to Low
Energy Intensive Large
Scale Gas Separations
Inorganic Membranes for Sustainable Industry
Processes
Tai-Shung Chung
(National University of Singapore,
Singapore)
Matthias Wessling
(Rheinisch
Westfälische
Technische
Hochschule (RWTH)
Aachen University,
Germany)
Polymeric Membranes for Clean Water
Production and
Osmotic Power
Generation
Geometry Matters plenary lecture:
• Gas fluxes (flow rate per unit area) across polymeric membranes are two orders of magnitude lower than liquid fluxes
• Trade-off relationship between flux and selectivity is much higher for gas than liquid separation
• Kinetic diameter differences between molecules in gas separation are much smaller than for liquid separation.
45 © 2015 Johnson Matthey

http://dx.doi.org/10.1595/205651315X685553 Johnson Matthey Technol. Rev ., 2015, 59 , (1)
This section on gas separation will cover carbon dioxide removal, paraf fi n/ole fi n separation and hydrocarbon separation.
A key observation from this conference is that there has been an increase in the use of carbon molecular sieves and membrane contactors for CO
2
removal (in both natural gas puri fi cation and carbon capture). In addition, there were several lectures which emphasised the need for better understanding of the use of membranes in a process.
Under high CO
2
partial pressure and in the presence of hydrogen sul fi de (H
2
S) in the stream, polymeric membranes are known to swell, causing deteriorated separation performance. Koros showed in his plenary lecture that cross-linking of polymeric membranes is effective in stabilising the membranes and preventing swelling. However further improvements in membrane performance can only be achieved using membranes with molecular sieving abilities such as carbon molecular sieves (CMS). The performance of a CMS membrane was shown to exceed the present upper bound of Robeson’s trade-off graph.
Membrane contactors, which combine the advantages of membrane technology and solvent absorption, are a promising technology for CO
2
removal. Shiguang Li
(Gas Technology Institute (GTI), USA) presented on a pilot scale study for post-combustion CO
2
capture using poly(ether ether ketone) (PEEK) hollow fi bre membrane contactors. The membrane contactor GTI is developing can be used in both the absorber and the desorber section. Laboratory testing has found that the performance of the PEEK membrane contactor is not affected by impurities such as oxygen or oxides of sulfur (SOx) and nitrogen (NOx). Initial pilot studies were carried out using a slip stream from Joliet power station and future tests will be conducted at the National
Carbon Capture Centre.
Christophe Castel (Université de Lorraine, France) used a fl ue gas slip stream from one of Compagnie
Parisienne de Chauffage Urbain (CPCU)’s power plants as a feed to their membrane contactor.
Commercially available polytetra fl uoroethylene (PTFE) hollow fi bre membrane from PolyMem and 30% monoethanolamine (MEA) solution was used in their membrane contactor. Their pilot study is still at a very early phase in comparison to GTI’s work.
Emphasis on understanding membrane processes was re fl ected by a signi fi cant number of presentations dedicated to engineering studies on membrane processes.
A series of presentations by Membrane Technology and Research, Inc (MTR) on post-combustion carbon capture demonstrated the importance of understanding the processes in order to better utilise the membranes.
Richard Baker (MTR, USA) emphasised the importance of pressure ratio. Through their studies, the typical economical pressure ratio range is about 5 to 10.
Pingjiao Hao (MTR, USA) showed that combining a conventional CO
2
separation membrane with a gas/gas membrane contactor ( Figure 1(a) ) (2) is more effective for carbon capture than a standalone membrane unit.
Xiaotong Wei (MTR, USA) showed that carbon capture from a natural gas power plant is more complex than from a coal power plant ( Figure 1(b) ) (3). This is due to signi fi cantly lower CO
2
concentration in the fl ue gas being emitted from a natural gas plant.
Numerous other presentations have also emphasised the importance of using process engineering tools to understand membrane processes at very different scales. Eric Favre (Université de Lorraine, France) used process engineering tools to design membrane processes and evaluate their economic bene fi ts in carbon capture. Maria Grätz (Helmholtz-Zentrum
Geesthacht, Germany) used simulations to investigate the effects of various process parameters for precombustion carbon capture using membranes. Iran
Chary-Prada (Saudi Aramco, Saudi Arabia) investigated the con fi gurations and economics for two- and threestage membrane processes used for bulk acid gas removal from natural gas.
Separation of paraf fi n/ole fi n mixtures is one of the most challenging processes due to the small differences in the kinetic diameter. Several reports demonstrated promising progress in the separation of paraf fi n/ole fi n mixtures using inorganic membranes and facilitated transport membranes.
William Koros showed that polymer derived CMS membranes are effective for paraf fi n/ole fi n separation. The membrane was proposed to be used for debottlenecking of existing distillation processes. Thinner CMS selective layers can increase the fl ux of propylene through the membrane. Jerry Lin (Arizona State University, USA) has shown that thinner CMS membranes were prepared by coating the surface of α -Al
2
O
3
support with  -Al
2
O
3
. The smaller pores of  -Al
2
O
3
allow a thinner defect-free CMS layer to be prepared.
46 © 2015 Johnson Matthey

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CO
Steam turbine
20% CO
2
2
purge
70–80% CO
2
Nitrogen purge
2% CO
10% CO
2
2
GT
Natural gas Compressor
CO
2 capture membrane
Selective recycle membrane
Blower
Air
Expander
Cleaned exhaust
HRSG
Air + CO
2
CO
2
CO
2
Selective
CO
2
purge
8% CO
2
18% O
2
Selective membrane contactor
Air
Water knockout
CO
2 compressor
Water removal
CO
2
Coal
CO
2
puri fi cation membrane
Fig. 1. Block fl ow diagram of MTR’s proposed post-combustion carbon capture in: (a) an integrated gasi fi cation combined cycle power plant (Reprinted with permission from (2). Copyright 2014 Elsevier); and (b) a natural gas combined cycle power plant
(Reprinted with permission from (3). Copyright 2013 American Chemical Society)
Due to their molecular sieving ability, zeolite membranes have also been investigated in paraf fi n/ ole fi n separation. Masahiko Matsukata (Waseda
University, Japan) showed that in a propane-rich stream, the propylene permeance and separation factor for zeolite membranes are better than the values reported for CMS. However membrane performance is strongly in fl uenced by the feed composition.
Facilitated ole fi n transport membranes incorporate a reactive carrier (Ag + ) in the membrane for separation.
The major technological hurdle for commercialising facilitated transport membranes is the stability of the
Ag + carrier. Yong Soo Kang (Hanyang University,
Korea) investigated membranes using Ag nanoparticles with positively induced charge, as a stable reactive carrier. An electron acceptor ligand is coordinated to the Ag nanoparticles to induce a positive change on the particles. These positively charged Ag nanoparticles, which are embedded into a polymeric matrix, show long term stability in ole fi n/paraf fi n separation.
Yuri Yampolskii (Russian Academy of Sciences) reviewed the membranes used for C
2+
removal from natural gas. Rubbery membranes are commonly used in this application, where the current state-of-the-art membranes are polyacetylene type polymers. A recent development is a novel norbornene polymer membrane with a fl exible Si-O group. Although selectivity of these novel membranes is lower than polyacetylene type membranes, the permeance is much higher. Despite high separation factors being observed for C
4
/C
1 separation, the C n
/C n –1
separation factors for these membranes are very low ( Figure 2 ) (4).
50
40
30
C
C n n
/ C
/ C
1 n –1
20
10
0
Ethane Propane Butane
Fig. 2. Highest C
4
/C data reported in (4)
1
membrane separation, plotted from
This section on liquid separation will discuss advancement in membranes for pervaporation, organic solvent nano fi ltration and waste water treatment.
Pervaporation was fi rst commercialised by GFT in the 1980s based on cross-linked poly(vinyl alcohol)
(PVA) composite membranes. Wilfredo Yave (Sulzer
Chemtech, Switzerland) presented the recent
47 © 2015 Johnson Matthey

http://dx.doi.org/10.1595/205651315X685553 Johnson Matthey Technol. Rev ., 2015, 59 , (1) improvements made to the PREVAP™ membrane, which is a PVA composite membrane. The membrane was modi fi ed to improve its separation performance, stability and also lifetime. The major improvement made was to have multiple selective layers instead of a single layer as used in their previous generation of membranes.
Inorganic membranes have been investigated and used in pervaporation to avoid swelling which is often encountered by polymeric membranes. The plenary lecture by Yiqun Fan (Nanjing University of
Technology; and Jiuwu Hi-Tech, China) discussed the use of polydimethylsiloxane (PDMS) supported on ceramic for pervaporation. The purpose of using a ceramic support is to constrain the swelling of the
PDMS. Another pervaporation membrane supplied by
Jiuwu Hi-Tech is a hydrophilic NaA zeolite membrane.
Masahiko Matsukata (Waseda University, Japan) shared his work on zeolite membranes for pervaporation in isopropyl alcohol (IPA) dehydration. Y-type zeolite and SSZ-13 tubular membranes were developed and tested on a bench-scale rig located next to an IPA production plant as shown in Figure 3 . The product stream from the plant was used as a feed for the test.
Process engineering tools are essential to evaluate the bene fi ts of using a membrane for separation.
Masahiko Matsukata evaluated the process design and economic bene fi ts for his studies on IPA dehydration using zeolite membranes as presented above. Three different methods of implementing membranes in an IPA dehydration process were considered. Results show that co-production of IPA with a membrane would yield a higher energy saving compared to the other methods.
Ivy Huang (MTR, USA) looked at applying pervaporation membranes to ethanol dehydration from a process engineering viewpoint. Various con fi gurations were investigated to use membranes together with other unit operations. Heat integration within the membrane process and with other separation units was identi fi ed to be the key to reduce operating cost. Debottlenecking has been identi fi ed as a possible opportunity to implement membranes in bioethanol separation.
Andrew Livingston (Imperial College, UK) presented on the use of membrane separation in organic liquids. The main challenges in organic solvent nano fi ltration are to increase the stability of the membrane (chemical, thermal and operational), increase permeance and to obtain more precise separation. Stability can be enhanced by performing cross-linking or using polymers which are inherently stable in organics. A recent development is to prepare thin fi lm composite membranes by interfacial polymerisation, followed by post-treatment to remove oligomers. This membrane was found to have higher fl ux and better molecular weight cut off rejection.
Cheryl Tanardi (University of Twente, Netherlands) presented on the use of polymer grafted ceramic membranes for organic solvent nano fi ltration. A layer of  -Al
2
O
3
was coated on the  -Al
2
O
3
support to provide more functional groups for grafting PDMS on to the support.
Ludmila Peeva (Imperial College) demonstrated the use of organic solvent nano fi ltration in a continuous catalytic Heck coupling reaction, where a homogeneous catalyst is used. Different materials were investigated and PEEK was identi fi ed as the most suitable material.
Fig. 3. JX-Nippon Oil and Energy’s IPA production plant and the bench-scale zeolite membrane located beside the plant (Image courtesy of Masahiko Matsukata, Waseda University, Japan (5))
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The use of a membrane reactor resulted in a lower concentration of catalyst contamination in the product.
The plenary lecture by Neal Chung (National University of Singapore) was on the use of membranes for clean water production. Nano fi ltration for heavy metal ion removal was achieved by using a dual charge membrane. This membrane comprises of a selective layer and support with opposite charges. A similar concept was used to synthesise a membrane with both hydrophobic and hydrophilic properties for membrane distillation, where the membrane fl ux was increased. A dual skin membrane with a selective layer for forward osmosis (FO) on one side and nano fi ltration on the other side of a support was used for shale gas waste water treatment. The nano fi ltration prevents fouling of the membrane due to the substrate becoming clogged by stabilised emulsi fi ed oil droplets. The advantages of using a combination of FO and reverse osmosis (RO) for desalination were also discussed.
Thomas Schiestel (Fraunhofer Institute for Interfacial
Engineering and Biotechnology IGB, Germany) presented on the use of composite adsorber membranes. Polymers coordinated on hydrogel particles, which can adsorb neodymium, silver, copper and lead ions, were embedded in a micro fi ltration membrane. Stability of the membrane in fi ve adsorptiondesorption cycles was demonstrated.
In the fi nal plenary lecture of ICOM 2014, Matthias
Wessling (RWTH Aachen University, Germany) showed the importance of membrane geometry for both the transport properties and the membrane performance. By introducing nanometre thick dots and striped structures to the surface of an electrodialysis membrane, concentration polarisation can be minimised. Another example shows the use of twisted fi nned hollow fi bres in a membrane bioreactor, which improves the secondary fl ow and minimises the buildup of particles on the surface. When twisted spacers are used in ultra fi ltration (UF), higher yield fl ux and also sharper molecular weight cut-off was obtained.
Zhenjie He (MTR) presented on MTR’s development on per fl uoropolymer composite membranes. Surface fl uorination of polyimide membranes improves the membrane permeability and selectivity. However the performance of these surface fl uorinated membranes decays during storage. MTR have recently developed a new per fl uoropolymer membrane from fl uorinated polymers commonly used in optical fi bres. Compared to their existing membrane, these new membranes exhibit three times higher selectivity with comparable fl ux.
Mathias Ulbricht (Universität Duisburg-Essen,
Germany) discussed the different methods to tailor the surface properties of polymeric membranes.
One method is to synthesise the membrane from functionalised polymers or blend established membrane polymer materials with functionalised copolymers. Another method to introduce functionality into membranes is via post-synthesis functionalisation. This can be achieved by using ultraviolet (UV) radiation or using a copolymer with an attached macro-initiator.
Peter Budd (University of Manchester, UK) summarised the development of polymers of intrinsic microporosity (PIM) membranes. Many new PIMs have been developed but PIM-1 is still the most widely studied material. Chemical modi fi cation of the polymer precursor to introduce amines to PIMs was shown to be effective in increasing the CO
2
adsorption. UV and thermal treatment of PIM membranes is able to increase the selectivity while maintaining the fl ux. PIMs are also widely investigated in mixed matrix membranes
(MMMs). It was found that the different forms of
CC3 introduced into PIM-1 caused minor changes in free volume but resulted in signi fi cant change in gas permeation.
Cher Hon Lau (Commonwealth Scienti fi c and
Industrial Research Organisation (CSIRO),
Australia) used MMMs as a means to improve the stability of super glassy polymeric membranes. By incorporating porous aromatic frameworks (PAF-1) into polytrimethylsilylpropyne (PTMSP), membrane ageing was prevented.
Inorganic membranes were shown to exhibit better separation rates, withstand higher temperatures and pressures and also display better resistance towards chemicals and moisture compared to polymeric membranes. However, inorganic membranes are expensive, dif fi cult to process and prone to the formation of non-selective defects.
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The higher cost of manufacturing inorganic membranes was addressed by Yiqun Fan (Nanjing
University of Technology, China). Some of the methods used to reduce costs include co-sintering, hot compressive sintering and the use of more environmentally benign precursors.
In order to avoid the formation of non-selective defects in inorganic membranes, Aisheng Huang (Ningbo
Institute of Material Technology and Engineering, China) used polydopamine (PDA) functionalised supports to synthesise zeolites and metal-organic framework
(MOF) membranes. The adhesive property of PDA on the support favours nucleation and growth of uniform zeolites and MOFs on the support. Seeding of the parent zeolite or MOF on the support was not required.
ZIF-8, ZIF-90 and LTA type zeolite membranes were synthesised using this method.
Miao Yu (University of South Carolina, USA) gave an overview on graphene and graphene oxide membranes. Graphene membranes show potential applications in both liquid and gas separation. A graphene membrane supported on polyamide was shown to prevent irreversible membrane fouling and also exhibit higher fl ux than polyamide membranes for oil/water separation. In gas separation, graphene membranes perform better in H
2
/CO
2
separation compared to polymeric and zeolite membranes. One of the main challenges ahead for graphene membranes is to control the porosity. The stability of graphene membranes under real gas conditions is also poorly understood.
quadruple stimuli responsive membranes have been reported.
One of the novel membrane processes reported at
ICOM is the cyclic pressure-vacuum swing permeation process described by Xianshe Feng (University of
Waterloo, Canada). This process, as shown in Figure 4
(6), is a non-steady state process which makes use of transient conditions to maintain high permeance through the membrane. This process uses a single pump to pressurise the feed and also to extract vacuum for permeate removal. The process switches between three modes, namely: (a) feed pressurisation,
(b) permeate evacuation and (c) retentate venting.
This process would be an advantage for a feed with low pressure.
V4
V2
P
F
V5
V1
Pump
Membrane module
V3
P
P
Fig. 4. Pressure-vacuum swing permeation process as reported in (6). Red line shows the path for permeate evacuation (Reprinted with permission from (6). Copyright
2014 Elsevier)
One class of membrane which is considerably different from other membranes reported at ICOM 2014 are stimuli-responsive membranes, which have the ability to respond to a change in the environment. Liang-Yin Chu
(Sichuan University, China) gave a general overview on this type of membrane, which contains an arti fi cial smart gate where the presence of an external in fl uence can open or close the pores of the material. The smart gate can be introduced before, during or after membrane synthesis. These membranes can be made to respond to temperature, pH, light, electric fi eld, magnetic fi eld, ions, chemical species and biological species. Membranes can also be designed to respond to more than one type of stimuli; dual, triple and
This section summarises the use of membranes in less commonly discussed applications presented at
ICOM2014 such as biore fi nery, pharmaceutical and biopharmaceutical uses.
Mathias Wessling (RWTH Aachen University,
Germany) proposed several areas where nano fi ltration can be utilised in a biore fi nery. One such use is for the recovery of oxalic acid. Oxalic acid is used to disintegrate lignocellulose to its individual fractions
(lignin, hemi-cellulose and cellulose). Separation occurs via molecular weight-cut off and charge exclusion. Another use of nano fi ltration in a biore fi nery is to aid downstream recovery of itaconic acid, which is an important intermediate. Nano fi ltration is used to concentrate the feed from the fermenter and itaconic acid can be recovered by crystallisation.
50 © 2015 Johnson Matthey

http://dx.doi.org/10.1595/205651315X685553 Johnson Matthey Technol. Rev ., 2015, 59 , (1)
Andrew Livingston (Imperial College) demonstrated the use of organic solvent nano fi ltration in liquid phase peptide synthesis for pharmaceutical applications.
This permits the use of lower amino acid excess in each sequential coupling step, while allowing ease of separation. The membrane is used to remove unreacted amino acid and solvent between each step. This synthesis method can also be used to synthesise monodispersed heterobifunctional polyethylene glycol (PEG).
Dieter Melzner (Sartorius-Stedim Biotech GmbH,
Germany) presented on the use of membranes for virus separation. Separation is via size exclusion and/ or adsorptive mechanisms. Membrane chromatography is also used in virus processing, which can operate in two modes: (i) bind and elute mode, used to purify virus particles; and (ii) polishing mode, used to adsorb impurities while allowing the virus product to fl ow through.
The study and understanding of membranes and membrane processes continues to be an essential part of research to develop better fundamental understanding and allow possible industrial exploitation.
This review covers emerging areas in gas separation and liquid separation and also recent innovations in membrane materials. Novel membrane processes and applications were also brie fl y discussed. However this review only represents a small portion of the work presented at ICOM 2014.
In general, there was a good mix of talks focusing on both new membrane material development and applications of membranes in processes. However, more attendees were observed in the material talks especially those on novel membrane materials such as graphene. Despite the massive scale and number of attendees, ICOM 2014 was very well organised with plenty of opportunities to network. The next ICOM will be held in San Francisco, USA, in 2017.
1 The 10th International Congress on Membranes and
Membrane Processes, Suzhou, China, 20th–25th
July, 2014
2 P. Hao, J. G. Wijmans, J. Kniep and R. W. Baker, J.
Membrane Sci.
, 2014, 462 , 131
3 T. C. Merkel, X. Wei, Z. He, L. S. White, J. G. Wijmans and R. W. Baker, Ind. Eng. Chem. Res.
, 2013, 52 , (3),
1150
4 Yu. Yampolskii, L. Starannikova, N. Belov, M.
Bermeshev, M. Gringolts and E. Finkelshtein,
J.
Membrane Sci.
, 2014, 453 , 532
5 M. Matsukata, ‘Prospects of Zeolite Membrane
Technologies for Energy and Chemical Processes’, in Proceedings of the 10th International Congress on Membranes and Membrane Processes, Suzhou,
China, 20th–25th July, 2014
6 Y. Chen, D. Lawless and X. Feng, Sep. Purif. Technol.
,
2014, 125 , 301
Xavier (Xian-Yang) Quek graduated with a BEng in Chemical Engineering from Nanyang
Technological University, Singapore, and a PhD in heterogeneous catalysis from Eindhoven
University of Technology, the Netherlands. In 2013, he joined the Low Carbon Technology group at Johnson Matthey Technology Centre, Sonning Common, UK. His current research focuses on the use of Pd and Pd-alloy membranes for pre-combustion carbon capture. He also has a wider interest in membranes and the use of membranes in various processes.
51 © 2015 Johnson Matthey

Johnson Matthey Technol. Rev ., 2015, 59 , (1), 52–55 http://dx.doi.org/10.1595/205651315X685706
JOHNSON MATTHEY
TECHNOLOGY REVIEW www.technology.matthey.com
Julie Macpherson is a Professor in the Department of Chemistry at the University of Warwick, UK.
Her research focuses on the development of sensors based on different forms of carbon, including conducting diamond, carbon nanotubes and graphene, with a range of applications in environmental monitoring, healthcare technologies and water research. She has published over 150 papers and 14 patents.
About the Research
Carbon is an extremely interesting element which can be arranged in different forms, two of which are of interest in the group’s research: diamond (sp 3 ) and carbon nanotubes (sp 2 ). The group is working towards an electrochemical understanding of the different forms of carbon and how the material can be appropriately structured in order to produce the most ef fi cient sensor for a wide range of applications. As the sensor is often based on electrochemical principles, the material must conduct. For sp 2 carbon this is not a problem; for diamond it is. Hence during synthesis diamond is doped with boron (boron doped diamond
(BDD)). At suf fi cient doping levels the material turns black and electrically behaves as a semi-metal. In the conducting diamond arena, work with the industrial diamond company Element Six has focused on methods to produce BDD electrodes in any geometry, where the electrode component is insulated in diamond; this has led to a variety of solution-based sensing applications. All-diamond electrodes enable the sensor to be placed in extreme or complex environments, where other electrode materials fail,
• Name: Julie Macpherson
• Position: Professor/Royal Society Industry Fellow
• Department: Chemistry
• University: University of Warwick
• Street: Gibbet Hill Road
• City: Coventry
• Post Code: CV4 7AL
• Country: UK
• Email Address: j.macpherson@warwick.ac.uk
for long periods of time, continuously monitoring.
BDD is also extremely robust when subject to high applied potentials, for example, for the production of ozone or other oxidative species in water treatment processes. Figure 1 shows two examples of alldiamond sensors, from the group.
The use of a dual electrode con fi guration has been used, for example, as a means of controlling the local pH environment of the sensing electrode.
52 © 2015 Johnson Matthey

http://dx.doi.org/10.1595/205651315X685706
(a) Insulating diamond (b) Insulating diamond
BDD
Johnson Matthey Technol. Rev ., 2015, 59 , (1)
BDD
Fig. 1. (a) Ring-disc all-diamond sensor structure. The disc has a diameter of 3 mm; (b) all-diamond multiple band electrode sensor. The width of the diamond chip is ~1 cm × 1 cm. For both images the black tracks are BDD and the transparent areas are insulating diamond (Image copyright Jon C. Newland, University of Warwick, UK)
The outer or upstream BDD electrode (in a fl uidic fl ow cell) can be used to electrochemically break down water, creating a controlled pH environment over the detector electrode to optimise the sensing process of interest. These structures have been successfully deployed to detect heavy metal (for example, mercury) ions and dissolved hydrogen sul fi de in water ( Figure 2 ) in far from ideal pH conditions. The BDD electrodes can also be combined with other measurement techniques to further enhance analytical capabilities. For example, electrochemical X-ray fl uorescence is a recently emerged technique based on BDD electrodes which enables unique chemical identi fi cation and quanti fi cation of complex ‘soups’ of metal ions in solution, with the ultimate aim being to measure these directly at the source.
The group is also investigating the electrochemical sensing capabilities of single walled carbon nanotubes (SWNTs), with a focus on healthcare applications. Growth of SWNTs takes place in the laboratory. For trace level analysis, the optimal arrangement in terms of sensitivity, time and cost was a two dimensional network of SWNTs grown directly onto insulating substrates. When incorporated into a suitable microfluidic flow system, these electrodes were shown to be capable of sub-nanomolar detection of dopamine and ferrocene labelled molecules
( Figure 3 ) in biologically relevant solutions.
Working with high resolution electrochemical imaging techniques it was also possible to elucidate the electrochemical behaviour and sensing capabilities of SWNTs at the single tube level, showing that the entire sidewall is active
( Figure 4 ).
(a)
H +
H +
H +
H +
H +
Intrinsic diamond
H + H +
Hg 00
H
BDD ring
+
BDD disc
(b)
H
2
O
H
2
S
H
2
O
H
2
S
H
2
O
Insulating diamond
H
2
O
OH p
K
H
2 a
= 6.88
S  HS – p K
 S 2– a
= 14.15
OH –
OH –
HS
OH –
–
– generator HS –
S 0
detector
Fig. 2. pH optimisation of a dual detector electrode using two different con fi gurations: (a) generation of H + by the ring to control the pH environment of the disc (Adapted with permission from T. L. Read, E. Bitziou, M. B. Joseph and J. V. Macpherson, Anal.
Chem ., 2014, 86 , (1), 367. Copyright (2014) American Chemical Society); (b) upstream generation of OH – in a fl ow device fl oods the downstream detector electrode, optimising the pH of the sensor (Reprinted with permission from E. Bitziou, M. B.
Joseph, T. L. Read, N. Palmer, T. Mollart, M. E. Newton and J. V. Macpherson, Anal. Chem ., 2014, 86 , (21), 10834. Copyright
(2014) American Chemical Society)
53 © 2015 Johnson Matthey

http://dx.doi.org/10.1595/205651315X685706
(a)
(b)
Johnson Matthey Technol. Rev ., 2015, 59 , (1)
(c)
10
5
0
–5
30
25
20
15
100 nM
70 nM
25 nM
–10
–15
–20
–25
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8
E/V vs.
Ag/AgCl
Fig. 3. (a) Optical picture of a SWNT network chip for sensing applications (Image copyright Petr Dudin, University of Warwick,
UK); (b) electron microscope image of a SWNT network electrode (10 μ m × 10 μ m); (c) cyclic voltammogram for FcTMA + detection – red line shows a detection cyclic voltammogram for 25 nM (Reprinted with permission from P. Bertoncello,
J. P. Edgeworth, J. V. Macpherson and P. R. Unwin,
J. Am. Chem. Soc
., 2007,
129
, (36), 10982. Copyright (2007) American
Chemical Society)
(a)
V
1
V
2
I
2
Red Ox
12
8
4
0
I
EC
SECCM
V
Appl
= 0.4 V
Fig. 4. (a) Set-up for scanning electrochemical cell imaging of a single SWNT; (b) electrochemical image of a single SWNT. As the potential on the SWNT is successively increased the SWNT current increases. The sidewall is shown to be active (Reprinted with permission from A. G. Güell, K. E. Meadows, P. V. Dudin, N. Ebejer, J. V. Macpherson and P. R. Unwin, Nano Lett.
, 2014,
14 , (1), 220. Copyright (2014) American Chemical Society)
54 © 2015 Johnson Matthey

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J. V. Macpherson,
Phys. Chem. Chem. Phys
., 2015, doi:
10.1039/C4CP04022H
E. Bitziou, M. B. Joseph, T. L. Read, N. Palmer, T. Mollart,
M. E. Newton and J. V. Macpherson,
Anal. Chem
.,
2014,
86
, (21), 10834
T. L. Read, E. Bitziou, M. B. Joseph and J. V. Macpherson,
Anal. Chem
., 2014,
86
, (1), 367
L. A. Hutton, G. D. O’Neil, T. L. Read, Z. J. Ayres, M. E.
Newton and J. V. Macpherson, Anal. Chem ., 2014, 86 ,
(9), 4566
M. B. Joseph, E. Bitziou, T. L. Read, L. Meng, N. L. Palmer,
T. P. Mollart. M. E. Newton and J. V. Macpherson,
Anal. Chem
., 2014,
86
, (11), 5238
A. G. Güell, K. E. Meadows, P. V. Dudin, N. Ebejer, J. V.
Macpherson and P. R. Unwin, Nano Lett ., 2014, 14 ,
(1), 220
S. Sansuk, E. Bitziou, M..B. Joseph, J. A. Covington,
M. G. Boutelle, P. R. Unwin and J. V. Macpherson,
Anal. Chem
., 2013,
85
, (1), 163
L. A. Hutton, J. G. Iacobini, E. Bitziou, R. B. Channon,
M. E. Newton and J. V. Macpherson, Anal. Chem .,
2013,
85
, (15), 7230
H. V. Patten, K. E. Meadows, L. A. Hutton, J. G. Iacobini,
D. Battistel, K. McKelvey, A. W. Colburn, M. E. Newton,
J. V. Macpherson and P. R. Unwin,
Angew. Chem. Int.
Ed ., 2012, 51 , (28), 7002
P. V. Dudin, M. E. Snowden, J. V. Macpherson and P. R.
Unwin,
ACS Nano
, 2011,
5
, (12), 10017
I. Dumitrescu, J. P. Edgeworth, P. R. Unwin and J. V.
Macpherson, Adv. Mater ., 2009, 21 , (30), 3105
I. Dumitrescu, P. R. Unwin and J. V. Macpherson, Chem.
Comm
., 2009, (45), 6886
P. Bertoncello, J. P. Edgeworth, J. V. Macpherson and
P. R. Unwin, J. Am. Chem. Soc ., 2007, 129 , (36),
10982
Johnson Matthey Technol. Rev ., 2015, 59 , (1)
55 © 2015 Johnson Matthey

Johnson Matthey Technol. Rev ., 2015, 59 , (1), 56–63 http://dx.doi.org/10.1595/205651315X685733
JOHNSON MATTHEY
TECHNOLOGY REVIEW www.technology.matthey.com
Johnson Matthey Technology Centre, Sonning
Common, Reading, RG4 9NH, UK
*Email: mario.joost@matthey.com
Within the last 20 years, publication numbers in the fi eld of lithium battery research have increased from a few hundred in the mid 1990s to more than
4500 publications in 2013 ( Figure 1 ). It has grown to a major research topic, with many universities, state laboratories and commercial research and development (R&D) facilities involved. The number of meetings dedicated to battery work has increased likewise. The International Meeting on
Lithium Batteries (IMLB) has been held biannually since 1982 and is one of the top meetings in the Li battery community. It is organised by an international executive committee, currently comprising of 24 international scientists. Following Jeju, Korea, in
2012, this year’s meeting was held in Como, Italy.
It was co-organised by the Electrochemical Society
(ECS) which will also publish dedicated special issues in Journal of the Electrochemical Society and ECS
Transactions . Around 1000 people attended the meeting with 40+ keynote speakers, presenting in nine plenary sessions and three large poster sessions with more than 500 contributions. Further details on the
17th IMLB meeting including details of the scienti fi c programme and biographies of the invited speakers can be found on the conference website (1).
1000
100
10
Related to:
Li-ion Li-air
Li-sulfur Sodium
1000
100
10
1
1980 1985 1990 1995 2000 2005 2010
Year
1
Fig. 1. Numbers of scienti fi c publications related to different types of battery. The search was run on keywords in the manuscript titles and abstracts. Note that the numbers for sodium batteries include the (high-temperature) molten salt and Na-sulfur systems
56 © 2015 Johnson Matthey

http://dx.doi.org/10.1595/205651315X685733 Johnson Matthey Technol. Rev ., 2015, 59 , (1)
In recent years there has been increasing interest in next-generation, ‘beyond lithium-ion’ battery technologies, especially in Li-air, Li-sulfur and sodium based chemistries. A major theme of the meeting addressed recent advances in beyond Li-ion batteries, where novelty was a key requirement for paper acceptance. The main areas of interest were Li battery related science and technology such as, but not limited to: electrode materials, electrolytes, Li-air, Li-sulfur, sodium batteries, new analytical tools, computational work and safety.
Due to the huge amount of contributions during this conference, only a few highlights of each main topic are included in this review. For a detailed overview of the conference contents, the interested reader is referred to the conference homepage (1).
100 nm
Fig. 2. Li
2
O
2
toroidal discs on a porous carbon electrode
No other battery system is the subject of such controversial discussion as Li-oxygen. The list of
‘unsolvable’ problems is long and small successes are contrasted by big setbacks. The many reports on stability issues of electrolyte solvents are just one example (2–4). Reaction mechanisms of the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) are still not explained satisfactorily (5) and side reactions are omnipresent. Contamination originating from the cathode, which is open to the environment, cannot be blocked suf fi ciently (6).
From the start, the question of the preferred morphology of Li
2
O
2
deposition was heavily discussed amongst the speakers. Together with her coworkers, Yang Shao-Horn (Massachusetts Institute of
Technology (MIT), USA) studied the effect of solvation on Li-O
2
redox reactions. The results revealed the formation of very small Li
2
O
2
particles at high discharge rates and/or when using a solvent with low solvation power (here: dimethylether (DME)). At low rates and/or when using solvents with higher donor numbers (here: dimethyl sulfoxide (DMSO)), larger, disc-like particles
( Figure 2 ) are formed (7). Lower overpotential (i.e. higher discharge voltage) was observed in the latter case. Increased solvation power due to high donor numbers lowers the energy levels of the Li/Li + redox reaction and increases that of the O
2
/2*O 2– reaction.
Larger particles seemed to improve the kinetics and better fi ll the volume of carbon pores, whereas smaller particles have a reduced overpotential (5).
Large, toroidal shaped discs in high donor number solvents were also found by Peter Bruce’s group
(University of Oxford, UK). According to his theory, high solubility of the superoxide radical in the electrolyte leads to Li
2
O
2
growth from the solution rather than from the electrode surface. The addition of redox mediators was discussed to aid the dissolution of Li
2
O
2
on charge and therefore increase the rate capability (8). Also focused on the donor abilities of electrolyte solvents, K. M. Abraham’s (Northeastern
University, USA) approach was based on the ‘hard and soft acids and bases’ (HSAB) concept. Ionic liquids (ILs) with soft cations (such as 1-methyl-1butyl-pyrrolidinium bis(tri fl ouromethanesulfonyl)imide
(Pyr
14
TFSI) and 1-ethyl-3-methylimidazolium bis-
(tri fl uoromethanesulfonyl)imide (EMITFSI)) reduce the
Li + acidity in organic electrolytes and therefore increase the lifetime of initially formed O
2
– (9). The potential of
Pyr
14
TFSI was demonstrated by Jakub Reiter (BMW
Group, Germany) when he presented results of an ionic liquid electrolyte (Pyr
14
TFSI/LiTFSI (9:1)), applied in a Li-air battery using a Super-P ® cathode and a Limetal anode (10).
Tailoring Li
2
O
2
morphology by providing an optimised cathode structure was the idea of Xin-Bo Zhang and coworkers (Chinese Academy of Sciences, China). A freestanding honeycomb-like palladium modi fi ed hollow spherical carbon was applied as Li-air cathode, which led to organised, toroidal nanosheets of Li
2
O than 100 cycles at a current density of 300 mA g
2
–1
. More
and a speci fi c capacity limit of 1000 mAh g –1 were presented
(11). In contrast to the results discussed before, Li
2
O
2 was observed to form rapidly if the superoxide binds
57 © 2015 Johnson Matthey

http://dx.doi.org/10.1595/205651315X685733 Johnson Matthey Technol. Rev ., 2015, 59 , (1) well on the cathode surface. Atomically dispersed
Fe/N/C composite as bifunctional catalysts showed better performance, exhibiting fewer side reactions than a classic α -manganese(IV) oxide (MnO
2
) catalyst
(12).
The possible instability of the carbon cathode and the related importance of the 2e – per O
2
ratio for the
ORR and OER was a key message from Peter Bruce
(13–15). Arumugam Manthiram (University of Texas,
USA) suggested hybrid Li-air batteries as a solution to the aforementioned problems. The bene fi ts of an aqueous cathodic compartment and a non-aqueous anodic compartment can compensate for the increased complexity of the system (16, 17). Novel catalysts like iridium(IV) oxide (IrO
2
) (18), low-temperature Li
1– x
CoO
2 or LiMn
1.5
Ni
0.5
O
4
were successfully employed (19).
Other workers used a cobalt phthalocyanine-derived catalyst to enable the full reduction of O
2
to Li
2
O, thus utilising the full theoretical range of a Li-air cell (20). To reduce safety issues, replacing the Li metal anode with
SnC, Fe
0.1
Zn
0.9
O or SiC was suggested (10).
Lithium-sulfur (Li-S) batteries are expected to be closer to a marketable product than Li-air batteries. A major remaining challenge, addressed in many contributions, is the high solubility of polysul fi de intermediates formed during the stepwise (but in no case straightforward) reduction from S
8
to the fi nal discharge product Li
2
S
(21, 22). These polysul fi des migrate to the anode, ending up as a self-discharge promoting redox shuttle or as a deposit blocking the anode surface (23, 24).
Yi Cui (Stanford University, USA) started with a quick overview of the recent evolution of Li-S cathodes (from sulfur/carbon mixtures to encapsulated hollow particles) and he summarised by stating that no satisfying solution to ‘capture’ the sulfur has been found yet. Tin-doped indium oxide was found to fi x polysul fi de to carbon (25).
Core-shell material showed increased sulfur ‘trapping’ but still lost polysul fi des during cycling (26, 27). Yu-
Guo Guo (Chinese Academy of Sciences) tried to start from smaller sulfur homologues (S
2–4
) which could be successfully trapped inside microporous carbon or carbon nanotubes (CNTs) (28). The group of Linda F.
Nazar (University of Waterloo, Canada) replaced the carbon support with titania (TiO
2
), alumina (Al
2
O
3
) and titanium oxide (Ti
4
O
7
) and successfully reduced the fade rate (29).
A second approach to stop polysul fi de migration would be an electrolyte which would act as a polysul fi de barrier. A polymer electrolyte made from poly ethylene(oxide) with 10 wt% ZrO
2
, LiCF
3
SO
3 and Li
2
S was presented by Jusef Hassoun (Sapienza
University of Rome, Italy). Cells had to be operated at 70ºC to deliver 900 mAh g –1 (30). Doping the electrolyte (tetraglyme) with a polysul fi de (Li
2
S
8
) proved to decrease the internal resistance and seemed to buffer further polysul fi de dissolution (31).
The incorporation of ionic liquids might also be a viable solution to the problem. Aleksandar Matic (Chalmers
University, Sweden) presented imidazolium- and pyrrolidinium-based electrolytes (32), some of them mixed with 1,3-dioxolane or glymes (33). Linda F.
Nazar could achieve decreased polysul fi de dissolution in electrolyte systems based on 1,3-dioxolane,
1,2-dimethoxyethane and bis(tri fl uoromethylsulfonyl)imide (TFSI) salts (34). She also presented an in operando X-ray absorption spectroscopy technique to identify the different sulfur species (35). As an alternative approach, a membrane-free polysul fi de fl ow battery was presented by Yi Cui (36).
High-temperature Na batteries were developed as molten Na-S or Na-NiCl
2
(ZEBRA) batteries in the 1980s. However, these systems were quickly pushed aside by the success of Li-ion batteries. Lowtemperature sodium systems, like Li-ion technology, have now started to gain interest within the last few years ( Figure 1 ). They can certainly bene fi t from experience in the Li-ion fi eld but knowledge transfer will not be as straightforward as it may seem.
‘Walking on the sodium side’ was the slogan of
Maria Rosa Palacín (Institut de Ciència de Materials de Barcelona-Consejo Superior de Investigaciones
Cientí fi cas (ICMAB-CSIC), Spain) as she opened the
Na-ion related talks. Major safety concerns come with the use of Na metal as anode, which reacts more fi ercely with water than Li. Carbon would be one alterative (37), but Ti-based insertion materials, especially Na
2
Ti
3
O
7
, could also give reasonable performance, with Na insertion potentials as low as 0.3 V vs . Na + /Na (38,
39). Young-Jun Kim (Korea Electronics Technology
Institute) would employ sodium metal in systems like
Na-S, Na-NiCl
2
, Na-O
2
and Na-ion when electrolytes like NaAlCl
4
*SO
2
or organic liquids would prove
58 © 2015 Johnson Matthey

http://dx.doi.org/10.1595/205651315X685733 Johnson Matthey Technol. Rev ., 2015, 59 , (1) suitable. However, side reactions with the electrolyte are an issue for sodium. Maria Rosa Palacín’s group found ethylene carbonate and/or propylene carbonate based solutions with sodium perchlorate (NaClO
4
) to be relatively stable (40). Laurence Croguennec (Institut de Chimie de la Matière Condensée de Bordeaux-
Centre National de la Recherche Scienti fi que (ICMCB-
CNRS), France) suggested fl uorophosphates as high energy density positive electrodes for Na (and Li) batteries. In particular the compound Na
3
V
2
(PO
4
)
2
F
3 was investigated, since vanadium offers a wide range of stable oxidation states and structures in Na (41, 42) and Li (43) containing compounds.
There is a large drive to increase the operating potential of Li-ion batteries in order to increase the gravimetric energy density. The gravimetric energy density is the product of capacity and the mean operating voltage and therefore can be altered by changing either of these material properties. Layered metal oxides have been used as Li-ion battery cathodes since the fi rst commercial battery produced by Sony in the early
1990s. These materials are made up of slabs of edge sharing MO
6
octahedra (where M is Ni, Co and/ or Mn) separated by layers of Li cations ( Figure 3 ).
The elemental composition of these materials has changed signi fi cantly since Sony fi rst used LiCoO
2
as
Fig. 3. Structure of LiMO
2 and red = oxygen (O)
: green = lithium, purple = metal (M) an intercalation cathode. Modern versions are doped with Ni and Mn (known as NMC) with the formula
Li[Ni x
Mn y
Co z
]O
2
, where x + y + z = 1. The transition metal ratios can be altered to control properties such as capacity and operating potential.
One major issue with NMC type compounds is structural instability caused by either collapse of the
MO
6
layers on Li removal or by migration of transition metals into the empty Li positions. Increasing the Ni content in Li[Ni x
Mn y
Co z
]O
2
leads to increased capacity but also decreased capacity retention and concomitant decrease in structural stability. When x is as high as
0.85, the material has a higher initial capacity, but 90% of the structure collapses during cycling, leading to fast capacity loss. Therefore Yang-Kook Sun (Hangyang
University, Korea) described a core-shell material with increased capacity in the core and good stability (and therefore high safety) on the surface (44). However, these materials do not perform well due to separation of the shell from the core during cycling, caused by different volume change ratios. Applying a gradient throughout the whole particle, using a slow concentration change in the core and a fast concentration change in the shell, led to mechanically stable particles while keeping the capacity and stability advantages (45, 46).
Al
2
O
3
coatings as an alternative method for stabilising
NMC particles were described by Kuniaki Tatsumi
(National Institute of Advanced Industrial Science and
Technology (AIST), Japan). Li[Ni
1/3
Mn
1/3
Co
1/3
]O
2
was mechanochemically coated, the Al
2
O
3
was uniformly distributed on the surface with no migration into the bulk particle. The material showed greatly improved cycling performance, even at elevated temperatures. The
Al
2
O
3
coating suppressed crack formation, reduced degradation of charge transfer sites and increased cycling stability at 1 C. Without coating, carbonates and LiF formed on the particle surfaces, concomitant with an increase in the detrimental cubic NMC phase at particle surfaces (47).
A third strategy to increase the stability of NMC based layered compounds is to make a composite of Li
2
MnO
3
and LiNi x
Mn y
Co z
O
2
, also known as
Li-rich NMC. Li
2
MnO
3
is structurally related to
LiNi x
Mn y
Co z
O
2
; however excess Li resides in the transition metal layers. This results in the presence of electrochemically inactive Mn 4+ which acts as a structural scaffold and prevents collapse of the metal oxide layers. The resulting compound has a reversible capacity as high as 200 mAh g –1 . However, transition metal cations migrate from the transition metal layers
59 © 2015 Johnson Matthey

http://dx.doi.org/10.1595/205651315X685733 Johnson Matthey Technol. Rev ., 2015, 59 , (1) to the Li layers, leading to voltage fade over time.
The cause of this migration is not fully understood, however, Jean-Marie Tarascon shed some light on the problem using simpli fi ed compounds like
Li
2
Ru(IV)
1– y
Sn(IV) y
O
3
(as opposed to Li
2
MnO
3
). This
3 d -metal-free compound could be cycled over 100 times, delivering reasonably high capacity. X-ray diffraction (XRD) was used to show the onset of large disorder on charging which was recovered on discharge. High-angle annular darkfi eld-scanning transmission electron microscopy (HAADF-STEM) showed massive cationic migration to the Li layers on charging which returned to the completely ordered state when subsequently discharged. Despite this cationic migration the Li
2
Ru(IV)
1– y
Sn(IV) y
O
3
structure shows no voltage fade over time. Testing the impact of ion size (Sn 4+ >Ti 4+ >Mn 4+ ), the titanium compound
Li
2
Ru
0.75
Ti
0.25
O
3
was synthesised. It showed the worst voltage fade. A combination of X-ray photoelectron spectroscopy (XPS) and electron microscopy showed that upon cycling, Ti 4+ accumulates in tetrahedral sites between the metal oxide and Li layers where it is no longer active. Preventing metals entering these tetrahedral sites will prevent voltage fade in layeredlayered compounds. Sn 4+ is therefore attractive to reduce voltage fade, however replacing Mn with Sn has not worked. Compounds with the stoichiometry
Li
4
(M n + ,M m + )O
6
where m + n = 8 are considered best as an answer to the voltage fade issue in Li-rich
NMCs (48, 49).
Future anode materials are more likely to be conversion or alloying type materials rather than insertion materials like the state-of-the-art graphite anode. Complex reaction mechanisms and high volume changes present challenges for these materials. Nanostructuring and coating with polymers or carbons are two approaches to protect materials against side reactions and ensure good cycling, even at high rates.
Fe
3
O
4
is a conversion material which reacts with Li + to form Li
2
O and Fe metal. The Fe metal produced can also alloy with Li as the battery continues to discharge.
Fe
3
O
4
has in the past been doped with Zn to produce
ZnFe
2
O
4
, however this material has poor coulombic ef fi ciency. Stefano Passerini (Helmholtz Institute, Ulm,
Germany) presented his group’s work in which ZnFe
2
O
4 was coated with carbon using glucose as precursor. In addition to the particle coating, a carbon matrix was formed in which many particles were combined to form macroscopically sized particles. These ‘carbon coated matrix’ particles showed improved performance compared to micron sized particles (50, 51). In a separate piece of work TiO
2
nanorods were carbon coated using polyacrylonitrile (PAN) as precursor. The block copolymer was anchored to the TiO
2
surface before carbonising to create an even carbon layer.
The performance of these new nanorods was greatly improved with respect to the uncoated sample (52).
Karim Zaghib (Hydro-Québec, Canada) described the latest advances in trying to stabilise reactive Li metal anodes with polymer coatings. The challenges and opportunities in developing thin Li metal with a stable solid electrolyte interphase (SEI) as the negative electrode were discussed in this presentation. In a unique process, Li metal was extruded to 20 μ m thin fi lms at a speed of 30 m min –1 . The surface was treated with a special solution and pressed against a solid polymer electrolyte fi lm (dry polymer and ionic liquidpolymer electrolytes). Due to the surface treatment, the very clean conditions and constant pressure on the stack, long term cycling (3000 cycles at C/3 and 80ºC) without major fading and dendrite growth was possible.
Nanostructuring has become a key requirement for the utilisation of high capacity silicon anodes. Whilst these anodes have very high capacities they can be dif fi cult to utilise, due to a large volume change of around 300% occurring on lithiation. Fei Luo (Chinese
Academy of Sciences) described how the volume variation in Si/C composites is very anisotropic. Si/C particles were synthesised as nanorods attached to the substrate which allowed for the large volume expansion. There was a complex evolution of particle shape caused by amorphous to amorphous diffusioncontrolled phase transitions; however porous fi lms did not prevent cracking. Isolated Si column structures showed much less cracking than dense fi lms (53).
Increasing the operational potential of the cathodes brings new challenges for the electrolyte. Jeff Dahn and Laura Downie (Dalhousie University, Canada) described their approach to tackle increased side reactions originating from electrolyte oxidation on high voltage material surfaces. Commonly used carbonate based electrolyte solutions show increasing reaction rates above 4.2 V vs . Li + /Li. Additives such as vinylidene carbonate (VC), tris(trimethylsilyl)phosphite
60 © 2015 Johnson Matthey

http://dx.doi.org/10.1595/205651315X685733 Johnson Matthey Technol. Rev ., 2015, 59 , (1)
(TTSPi) and methylene methanedisulfonate (MMDS)
(54) can be used to increase this maximum operating potential (55). NMC pouch cells were cycled at C/10 with low temperature impedance measurements made every 10 cycles. The results of this study showed that there was a very large increase in charge transfer resistance when cells are cycled above 4.4 V. Increased electrolyte oxidation is correlated to increased parasitic heat fl ow, detected via isothermal microcalorimetry.
When more than 100 μ V of heat is generated during cycling, the entire electrolyte of an A5 pouch cell would be consumed within one year (56–58). Jeff
Dahn carefully summarised that the electrolyte stability usually increases with the number of additives.
Ceramic solid state electrolytes as a safe highvoltage solution were presented by Chihiro Yada
(Toyota Motor Europe). A main problem is the huge charge-transfer resistance at the interfaces due to fast Li-ion depletion upon load. Dielectric modi fi cation of these layers using BaTiO
3
could decrease this resistance and increase the quantity of Li at the interface. Li
1.1
(Nb
0.5
Ta
0.5
)
0.9
O
3– δ
was identi fi ed as a promising material with high permeation and Li-ion mobility (59). Flexible solid state electrolytes which can be printed in any shape were presented as a key component for future electronic devices (wearable technology, fl exible devices) by Sang-Young Lee
(Ulsan National Institute of Science and Technology
(UNIST), Korea). The plastic crystal electrolyte (PCE) consists of alumina/silica ceramic nanoparticles, ethylene carbonate, succinonitrile and an ultraviolet
(UV) cross linker. The electrolyte ink has no additional processing solvents and shows thixotropic behaviour. Addition of ethoxylated trimethylolpropane triacrylate (ETPTA) successfully suppresses dendrite growth. Cells can be stretched and bent during operation (60, 61). Maria Forsyth (Deakin University,
Australia) presented organic ionic plastic crystals
(OIPCs, solidi fi ed ionic liquids), which show good electrochemical behaviour. Phosphonium based
OIPCs incorporating Na salts show electrochemical properties similar to Li containing analogues
(62–64). However, the presence of multiple phases, high viscosity and high-temperature eutectics remain issues which can be altered by a careful choice of ion combination (65).
The fact that polymer electrolytes are still solid, after 30 years of research, was no cause for concern for Michel
Armand (CIC EnergiGUNE, Spain). Poly(ethylene oxide) (PEO) suffers from increasing glass transition temperature (T g
) (and therefore decreased conductivity) with increasing salt concentration. In poly(ethylene carbonate) (PEC) it is the other way around and this might be an interesting solution for the problem of low conductivity at sub-ambient temperatures (66).
Polyelectrolytes have the anion attached to the backbone and the Li transport number should therefore be 1, since Li + is the only mobile species. However, the overall conductivity remains low for these systems so far. Armand’s group linked TFSI anions and PEO elements to a polystyrene backbone which could achieve conductivities around 10 –5 S cm –1 at 60ºC
(67, 68). The question of whether PEO based systems can successfully suppress Li dendrite formation was investigated by the group of Noboyuki Imanishi (Mie
University, Japan). A PEO
18
LiTFSI with 10 wt% BaTiO
3 system was swollen with ionic liquid which reduced the bulk resistance of the battery and increased the cycle performance. In situ scanning electron microscopy investigations showed that dendrite growth could be retarded.
This conference was loaded with excellent talks and an enormous number of interesting poster contributions.
It was a very well organised event and the beautiful weather underlined the lovely venue. It was obvious that the research on post Li-ion systems is a quickly growing fi eld, which already generate dedicated conferences.
One can happily look forward to the next IMLB meeting in 2016 which will be held in Chicago, USA.
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Mario Joost obtained his Diploma and PhD in physical chemistry from the University of Münster,
Germany. He spent a postdoctoral year at the Münster Electrochemical Energy Technology
(MEET) battery research centre before joining the battery materials research team at the Johnson
Matthey Technology Centre, Sonning Common, UK, in 2013. His current research is focused on the development of novel electrolytes for next generation battery systems, including Li-air and Li-sulfur.
Sam Alexander obtained a Masters degree in Chemistry from the University of Shef fi eld, UK, before completing a PhD in Materials Chemistry at University College London, UK, in 2012, focusing on solid state synthesis of complex metal oxides. Subsequently he joined the Johnson
Matthey Technology Centre, Sonning Common, in 2012. His current research is focused on the development of high energy cathode materials for Li-ion batteries.
63 © 2015 Johnson Matthey

Johnson Matthey Technol. Rev ., 2015, 59 , (1), 64–67 http://dx.doi.org/10.1595/205651315X686011
JOHNSON MATTHEY
TECHNOLOGY REVIEW www.technology.matthey.com
Johnson Matthey Inc, Emission Control Technologies,
456 Devon Park Drive, Wayne, Pennsylvania, 19087,
USA
*Email: chenh@jmusa.com
Three-way catalysts (TWCs) have been widely applied on stoichiometric-burn gasoline engine powered vehicles to reduce the tailpipe emissions of hydrocarbons (HC), carbon monoxide (CO) and nitrogen oxides (NOx). A conventional TWC can convert the three pollutants at nearly 100% conversion ef fi ciency once it reaches its operation temperature, typically above 400ºC. As the exhaust temperature can rapidly exceed 400ºC on current gasoline engines, all gasoline vehicles produced today are capable of meeting the stringent government emission standards in the USA.
Starting in 2017, US federal regulations will mandate a signi fi cant improvement in fuel economy and reduction of greenhouse gases (GHG) for light duty vehicles (1, 2) at the same time as continued reductions of tailpipe pollutant emissions. Advanced engines and powertrain systems with improved fuel ef fi ciency can reduce CO
2 emissions substantially, but the exhaust temperature of these systems is expected to be much lower and can be below the normal operation temperature of a conventional TWC. This poses signi fi cant challenges to the emission control system, demanding the catalysts to function at low temperatures.
Many factors can in fl uence the low-temperature performance of a TWC. Among them, the nature of the support materials for the platinum group metals (pgms) plays a critical role (3–5). Ceria/zirconia (CeO
2
/ZrO
2
) mixed oxides have become an essential component in a TWC because of their unique oxygen storage and release properties. CeO
2
/ZrO
2
mixed oxides not only enhance the intrinsic catalytic activity of the pgm components, but also provide oxygen storage capacity
(OSC) to the system, minimising the air:fuel ratio deviation from the stoichiometric point; both signi fi cantly improve the TWC performance of the system. Most commercially available CeO
2
/ZrO
2
mixed oxides lose their surface area considerably after high-temperature exposure. As a result, even though a fresh TWC can exhibit excellent catalytic activity below 400ºC, much of the low-temperature performance is lost when the catalyst is aged.
In this study, we developed a novel alumina/ceria/ zirconia Al
2
O
3
/CeO
2
/ZrO
2
mixed oxide that shows much improved thermal stability compared to a conventional CeO
2
/ZrO
2
mixed oxide with a similar composition, exhibits higher OSC especially at low temperatures and reduces the light-off temperature by nearly 50ºC.
A novel Al
2
O
3
/CeO
2
/ZrO
2
mixed oxide was developed in-house. The material was prepared by a co-precipitation method. For comparison purposes, a conventional CeO
2
/ZrO
2
mixed oxide was prepared following the same co-precipitation method, then
64 © 2015 Johnson Matthey

http://dx.doi.org/10.1595/205651315X686011 Johnson Matthey Technol. Rev ., 2015, 59 , (1) blended with γ -Al
2
O
3
powder. Pd-loaded catalyst powders were made by impregnating Pd onto the
Al
2
O
3
/CeO
2
/ZrO
2
mixed oxide and the
(Al
2
O
3
+ CeO
2
/ZrO
2
) mixture, respectively. The Pd loading was 1 wt% in both samples. Fully formulated
TWCs were prepared using the Al
2
O
3
/CeO
2
/ZrO
2 mixed oxide and the (Al
2
O
3
+ CeO
2
/ZrO
2
) mixture, respectively, as the Pd support. Full experimental details and characterisation data are published elsewhere (6).
2
3
2
2
The Al
2
O
3
(Al
2
O
3
/CeO
2
/ZrO
2
mixed oxide and the
+ CeO
2
/ZrO
2
) mixture were evaluated as support materials for Pd. The Pd-impregnated catalysts were redox aged at 1050ºC for 36 hours prior to the tests.
Light-off activity of the aged catalysts was measured in a gas mixture containing a stoichiometric amount of
HC/CO/NO/O
2
without perturbation and the results are plotted in Figure 1 .
The Al
2
O
3
/CeO
2
/ZrO
2
mixed oxide supported Pd catalyst shows rapid light-off for HC/CO and reaches
100% conversion at temperatures above 320ºC.
As a comparison, the (Al
2
O
3
+ CeO
2
/ZrO
2
) mixture supported Pd catalyst shows more gradual HC/CO light-off, and does not reach 100% conversion until the temperature goes above 390ºC. As Pd catalysts are in general relatively inactive for NOx reduction, it is not surprising that neither of the two catalysts show appreciable NOx conversion in these tests. In a fully formulated TWC, a separate Rh component will be incorporated into the formulation to enhance the NOx performance. Nevertheless, the Al
2
O
3
/CeO
2
/ZrO
2 mixed oxide supported Pd catalyst is clearly more active than the (Al
2
O
3
+ CeO
2
/ZrO
2
) mixture supported
Pd catalyst and is therefore considered more suitable for applications with low exhaust temperatures.
To understand why the Al
2
O
3
/CeO
2
/ZrO
2
mixed oxide supported catalyst has better light-off activity, the 1050ºC/36 h redox aged powder catalysts were analysed by transmission electron microscopy (TEM).
The dark fi eld images together with the elemental images of Ce and Pd are shown in Figure 2 .
Comparing the two dark fi eld images in combination with the Ce elemental images, it is apparent that the
CeO
2
/ZrO
2
mixed oxide particles on the Al
2
O
3
/CeO
2
/
ZrO
2
sample are about one order of magnitude smaller than the CeO
2
/ZrO
2
mixed oxides in the (Al
2
O
3
+ CeO
2
/
ZrO
2
) sample. The elemental images of Pd further indicate that high Pd dispersion is maintained on the
1050ºC/36 h redox aged Al
2
O
3
/CeO
2
/ZrO
2
sample, whereas noticeable Pd sintering has occurred on the
(Al
2
O
3
+ CeO
2
/ZrO
2
) sample as evidenced by the two large Pd particles in the image.
The results above suggest that depositing CeO
2
/ZrO
2 mixed oxides directly on alumina supports can minimise the sintering of the CeO
2
/ZrO
2
mixed oxides, hence
(a)
100
80
60
40
20
Al
Al
2
O
3
Al
Al
Al
2
2
2
2
O
O
O
O
3
3
3
3
Al
2
O
3
/CeO
+   CeO
2
/CeO
2
2
/ZrO
/ZrO
2
/ZrO
+   CeO
2
2
2
C
3
H
6
CO
/ZrO
2
/CeO
2
/ZrO
2
+   CeO
2
/ZrO
C
3
NO
2
H
CO
NO
6
0
550
Temperature, ºC
Fig. 1. Light-off activity of the Al
2 and the (Al
2
O
3
+ CeO
2
/ZrO
2 after 1050ºC/36 h redox ageing
O
3
/CeO
2
/ZrO
2
mixed oxide
) mixture supported Pd catalysts
30 nm
(b)
Ce Pd
200 nm
Ce Pd
Fig. 2. TEM images of the Al
2
O
3
/CeO
2
/ZrO
2
mixed oxide and the (Al
2
O
3
+ CeO
2
/ZrO
2
) mixture supported Pd catalysts after 1050ºC/36 h redox ageing: (a) Al supported Pd catalyst; (b) (Al
2
O
3
2
O
3
/CeO
2
/ZrO
2
+ CeO
2
/ZrO
2
) supported
Pd catalyst
65 © 2015 Johnson Matthey

http://dx.doi.org/10.1595/205651315X686011 Johnson Matthey Technol. Rev ., 2015, 59 , (1) improving their thermal stability and OSC properties.
The material can also maintain Pd in high dispersion even after severe ageing. All these features contribute to the superior light-off activity of the Al
2
O
3
/CeO
2
/ZrO
2 supported Pd catalyst.
2
3
2
2
A TWC was formulated using the Al
2
O
3
/CeO
2
/ZrO
2 mixed oxide as the Pd support in combination with a Rh component. As a reference, a conventional TWC using the (Al
2
O
3
+ CeO
2
/ZrO
2
) mixture as the Pd support and the same Rh component was also prepared. Both catalysts were coated on ceramic monolith substrates with a cell density of 62 cells cm –2 and a wall thickness of 64  m (or 400 cpsi and 2.5 mil). The dimension of the substrates is 10.6 cm in diameter and 7.8 cm in length. The pgm loadings of the catalysts were kept at relatively low levels (1.34 g l –1 Pd and 0.07 g l –1 Rh) to better differentiate their performance. The catalysts were aged on a 4.6 l gasoline engine under
4-mode conditions for 100 hours with the catalyst bed temperatures averaging 925ºC. The aged catalysts were evaluated on a separate 4.6 l gasoline engine that was capable of changing the air-to-fuel ratio from
13.5 to 15.5 with a perturbation frequency of 1 Hz and amplitude of 0.5. The CO/NOx crossover conversion and the corresponding HC conversion measured at a space volume of 112,000 h –1 at 400ºC and 350ºC are summarised in Table I . At 400ºC, both catalysts achieve high NOx/CO/HC conversions. At 350ºC, the
Al
2
O
3
/CeO
2
/ZrO
2
mixed oxide supported catalyst still maintains high NOx/CO/HC conversion ef fi ciency.
The (Al
2
O
3
+ CeO
2
/ZrO
2
) mixture supported catalyst, however, is nearly inactive.
Table I. Engine Sweep CO/NOx Crossover
Conversion (%) and the Corresponding HC
Conversion (%) at 400°C and 350°C
Pd:Rh TWC
400°C
CO/NOx,
%
81
THC,
%
84
350°C
CO/
NOx, %
51
THC,
%
55 Al
2
O
3
/CeO
ZrO
2
2
/
(Al
2
O
3
+ CeO
2
/
ZrO
2
)
70 82 9 10
The engine dynamometer evaluation results on fully formulated TWCs are in line with the laboratory reactor results on the supported Pd powder catalysts. Both demonstrate that the Al
2
O
3
/CeO
2
/ZrO
2
mixed oxide developed in this study can offer signi fi cant advantages for applications with low exhaust temperatures.
2
3
2
2
A 2010 model year vehicle equipped with an advanced
3.5 l GTDI engine and a turbo charger was selected to evaluate the performance of a TWC system based on the Al
2
O
3
/CeO
2
/ZrO
2
mixed oxide. Compared to other vehicles in the same class with traditional naturally aspirated engines, this vehicle represents approximately 20% better fuel ef fi ciency and 15% reduction of GHG emissions. As a result, the exhaust temperature of the vehicle is also substantially lower.
Catalyst systems with either the Al
2
O
3
/CeO
2
/ZrO
2 mixed oxide or the (Al
2
O
3
+ CeO
2
/ZrO
2
) mixture as the
Pd support were evaluated. Prior to vehicle evaluation, the TWC systems were aged under 4-mode conditions to simulate the end of their useful life performance.
The non-methane hydrocarbon (NMHC) and NOx emissions of the aged systems under federal test procedure (FTP) testing cycles are summarised in
Table II . While the two systems show comparable NOx performance, the Al
2
O
3
/CeO
2
/ZrO
2
mixed oxide based system clearly demonstrates better HC conversion and
7 mg mile –1 lower NMHC emissions from the tailpipe.
Table II. NMHC/NOx Emissions under FTP
Testing Cycles on a Vehicle with a 3.5 l GTDI
Engine
TWC systems NMHC (g mile –1 ) NOx (g mile –1 )
Al
2
O
3
/CeO
2
/ZrO mixed oxide
2
(Al
2
O
3
ZrO
2
+ CeO
2
) mixture
/
0.021
0.028
0.034
0.036
The cumulative tailpipe total HC (THC) emissions of the two systems during the cold start period are shown in Figure 3 . The majority of the THC is emitted in the initial 250 seconds while the temperature of the catalyst system is warming up. During this period, the
Al
2
O
3
/CeO
2
/ZrO
2
mixed oxide based TWC system has approximately 25% lower tailpipe HC emissions than the (Al
2
O
3
+ CeO
2
/ZrO
2
) mixture based system.
66 © 2015 Johnson Matthey

http://dx.doi.org/10.1595/205651315X686011 Johnson Matthey Technol. Rev ., 2015, 59 , (1)
0.04
0.03
0.02
0.01
Al
2
O
3
Al
2
/CeO
2
/ZrO
2
O
3
+   CeO
2
/ZrO
Vehicle speed
2
200
150
100
50
0
0 100 200 300 400 500
0
Time, s
Fig. 3. Cumulative total THC emissions during the cold start period of FTP 75 testing cycles
A novel Al
2
O
3
/CeO
2
/ZrO
2
mixed oxide was developed in this study. Compared to a conventional CeO
2
/ZrO
2 mixed oxide that has the same composition, the Al
2
O
3
/
CeO
2
/ZrO
2
mixed oxide is thermally more stable and exhibits much improved OSC properties especially at low temperatures. As a support material for Pd, the material improves the light-off activity of the catalyst.
TWC formulations based on the new material show noticeable advantages on a fuel-ef fi cient vehicle with low exhaust temperatures. Future optimisation of catalyst systems will enable fuel-ef fi cient gasoline engine powered vehicles to meet stringent government standards both for the criteria pollutant and the GHG emissions.
This article is an abridged form of a full paper presented at the Society of Automotive Engineers (SAE) in 2014, and is published with the permission of the SAE (6).
1. ‘LEV III and Tier 3 Exhaust Emission Control
Technologies for Light-Duty Gasoline Vehicles’,
Manufacturers of Emission Controls Association,
Arlington, Virginia, USA, April 2013
2. ‘EPA and NHTSA Set Standards to Reduce
Greenhouse Gases and Improve Fuel Economy for Model Years 2017–2025 Cars and Light
Trucks’, Regulatory Announcement, United
States Environmental Protection Agency, Of fi ce of
Transportation and Air Quality, Washington, DC, USA,
August 2012
3. P. Andersen and T. Ballinger, ‘Improvements in Pd:Rh and Pt:Rh Three Way Catalysts’, SAE Technical Paper
1999-01-0308, 1999
4. E. Rohart, S. Verdier, H. Takemori, E. Suda and K.
Yokota, ‘High OSC CeO
2
/ZrO
2
Mixed Oxides Used as
Preferred Metal Carriers for Advanced Catalysts’, SAE
Technical Paper 2007-01-1057, 2007
5. Y. Hirasawa, K. Katoh, T. Yamada and A. Kohara,
‘Study on New Characteristic CeO
2
-ZrO
2
Based
Material for Advanced TWC’, SAE Technical Paper
2009-01-1078, 2009
6. H.-L. Chang, H.-Y. Chen, K. Koo, J. Rieck and P.
Blakeman, ‘Gasoline Cold Start Concept (gCSC™)
Technology for Low Temperature Emission Control’,
SAE Technical Paper 2014-01-1509, 2014
Dr Hai-Ying Chen is a Product Development Manager at Emission Control Technologies, Johnson
Matthey Inc, USA. He obtained his BSc and PhD in Chemistry from Fudan University, Shanghai,
China. Following this he was a Postdoctoral Fellow at the Center for Catalysis and Surface Science,
Northwestern University, Evanston, Illinois, USA. Since joining Johnson Matthey in 2000 he has been working extensively on the development of catalysts for emissions control.
Hsiao-Lan (Russell) Chang received his PhD in Materials Science from Drexel University,
Philadelphia, USA. He is currently a Staff Scientist at Emission Control Technologies, Johnson
Matthey Inc, USA. Since joining Johnson Matthey in 1999, his main responsibility is to develop new materials for catalyst applications on exhaust emissions control.
67 © 2015 Johnson Matthey

Johnson Matthey Technol. Rev ., 2015, 59 , (1), 68–70 http://dx.doi.org/10.1595/205651315X686039
JOHNSON MATTHEY
TECHNOLOGY REVIEW www.technology.matthey.com
‘Solid State Platinum Speciation from X-ray Absorption
Spectroscopic Studies of Fresh and Road Aged Three
Way and Diesel Vehicle Emission Control Catalysts’
T. I. Hyde and G. Sankar, in “Platinum Metals in the
Environment”, eds. F. Zereini and C. L. S. Wiseman,
Environmental Science and Engineering, Springer-
Verlag Berlin, Heidelberg, Germany, 2015, pp. 289–308,
ISBN: 978-3-662-44558-7 (Print); 978-3-662-44559-4
(Online)
A series of studies were carried out in a variety of locations in Europe and North America on fresh and road-aged automotive catalysts. Platinum L3 and L2 edge X-ray absorption spectroscopy (XAS) was used alongside detailed laboratory based characterisation.
X-ray absorption near edge structure (XANES) was found not suf fi cient to determine the nature of
Pt species present in multi-component catalysts.
Therefore detailed analysis of the extended X-ray absorption fi ne structure (EXAFS) was performed at the Pt L3 and L2 edges and this revealed mainly oxidic species to be present in the fresh catalysts, while metallic and bimetallic components were the dominant species in the road aged catalysts. Taken together, with the addition of Cl K-edge XANES analysis, it is concluded that no environmentally signi fi cant quantities of chloroplatinate species were present in the fresh or road-aged samples.
‘Cu/Zeolite SCR Catalysts for Automotive Diesel NOx
Emission Control’
H.-Y. Chen, in “Urea-SCR Technology for deNOx After
Treatment of Diesel Exhausts”, eds. I. Nova and E.
Tronconi, Fundamental and Applied Catalysis, Springer,
New York, USA, 2014, pp. 123–147, ISBN: 978-1-4899-
8070-0 (Print); 978-1-4899-8071-7 (Online)
The use of Cu/zeolite catalysts for the selective catalytic reduction (SCR) of NOx with NH
3
is reviewed. Cu/zeolite SCR catalysts exhibit higher
NOx conversion ef fi ciency than titania supported vanadia SCR catalysts, and are also more tolerant to high temperature excursions. This is crucial for automotive applications, in which temperatures above
650ºC must be applied periodically to regenerate the diesel particulate fi lter (DPF). At lower temperatures
(200ºC–300ºC), Cu/zeolite catalysts are more active than alternative Fe/zeolite SCR catalysts. The chemistry and functionality of this class of catalyst is discussed in this book chapter, along with the deactivation mechanisms of previous generations of Cu/zeolite catalysts, the development of smallpore zeolite supported Cu SCR catalysts and recent literature studies on the understanding of their hydrothermal stability and performance.
Halotriazolium Axle Functionalised [2]Rotaxanes for
Anion Recognition: Investigating the Effects of Halogen-
Bond Donor and Preorganisation
J. M. Mercurio, R. C. Knighton, J. Cookson and P. D.
Beer, Chem. Eur. J.
, 2014, 20 , (37), 11740
Three novel halogen-bonding 5-halo-1,2,3-triazolium axle containing [2]rotaxanes were prepared by anion-templated synthesis. Different halogen-bond donor atoms and the degree of inter-component preorganisation affected the anion-recognition properties of the interlocked host. This knowledge is vital for designing a potent anion receptor. Bromide was found to be the most effective template from the investigation into the ability of bromotriazolium motif to direct the halide-anion templated assembly of interpenetrated [2]pseudorotaxanes. The fi rst bromotriazolium axle containing [2]rotaxane was synthesised by bromine anion templation and the anion-binding properties were analysed by 1 H NMR spectroscopic titration. The results showed an enhanced bromide and iodide recognition relative to a hydrogen-bonding protic triazolium rotaxane analogue.
Two halogen-bonding [2]rotaxanes with bromo- and iodotriazolium motifs arranged into shortened axles designed to extend inter-component preorganisation were also prepared and the rotaxanes were able to bind halide anions even more strongly with the iodotriazolium axle integrated rotaxane capable of recognising halides in aqueous solvent media.
68 © 2015 Johnson Matthey

http://dx.doi.org/10.1595/205651315X686039
Synthesis and Catalytic Applications of an Extended
Range of Tethered Ruthenium(II)/ η
Complexes
6 -Arene/Diamine
R. Hodgkinson, V. Jur č ík, A. Zanotti-Gerosa, H. G.
Nedden, A. Blackaby, G. J. Clarkson and M. Wills,
Organometallics , 2014, 33 , (19), 5517
Novel enantiopure Ru(II) complexes were prepared by introducing a tethering group between the η 6 -arene and chiral diamine. An increase in stability and activity at lower catalyst loadings was shown by the complexes and was tested in the asymmetric reduction of various ketones.
The presence of bulky sulfonyl groups can in fl uence the reactivity and enantioselectivity of the catalysts.
The In fl uence of the Hubbard U Parameter in Simulating the Catalytic Behaviour of Cerium Oxide
L. J. Bennett and G. Jones, Phys. Chem. Chem. Phys .,
2014, 16 , (39), 21032
The localisation of f -electrons and the self-interaction error linked with DFT can affect the theoretical treatment of ceria. These errors are commonly corrected by
DFT + U when investigating speci fi c physical material properties. However, rectifying certain bulk properties may not lead to the correct description of catalytic reactivity at surfaces due to the empirical nature of the U correction. A new method for choosing the U parameter using adsorption properties was proposed in this study.
The combination of derived ceria energetics with those of adsorption at metal surfaces enables the construction of transition metal-oxide pairings and a redox screening model for catalysis can be developed.
Water-Splitting Electrocatalysis in Acid Conditions
Using Ruthenate-Iridate Pyrochlores
K. Sardar, E. Petrucco, C. I. Hiley, J. D. B. Sharman, P.
P. Wells, A. E. Russell, R. J. Kashtiban, J. Sloan and R.
I. Walton, Angew. Chem. Int. Ed.
, 2014, 53 , (41), 10960
Hydrothermal synthesis was used to prepare for the fi rst time a series of conducting mixed ruthenium–iridium
A
2
B
2
O
7
pyrochlore materials with A = Na, Ce(IV) and
B = Ru(IV), Ir(IV) as nanocrystalline powders. A solid solution of pyrochlore was used as a catalyst layer for the electrochemical evolution of oxygen from water at pH
<7. The new composition produces electrode coatings with better charge densities than a typical (Ru,Ir)O
2 catalyst. The catalyst was studied in situ using XANES.
There was no evidence for Ru or Ir in oxidation states +6 or higher. Both Ru and Ir were shown to contribute to the electrocatalytic activity.
The Role of the sp
2 : sp
3 Substrate Content in Carbon
Supported Nanotube Growth
R. J. Cartwright, S. Esconjauregui, R. S. Weatherup, D.
Johnson Matthey Technol. Rev ., 2015, 59 , (1)
Hardeman, Y. Guo, E. Wright, D. Oakes, S. Hofmann and J. Robertson, Carbon , 2014, 75 , 327
Direct growth is the most promising method for incorporating carbon nanotubes (CNTs) into a composite matrix to take advantage of their high tensile strength and surface area to volume ratio for use as nanoscale reinforcement in hierarchical carbon fi bre–CNT composites and fuel cell electrodes. In this study, CNTs were grown into ‘forests’ up to 0.2 mm high on an 85:15 sp
2 : sp
3 carbon support with Fe catalyst. The catalyst was pretreated in inert atmosphere to avoid the growth of defective CNTs. Graphite, tetrahedral amorphous carbon and pure diamond were also found to produce defective CNTs. The importance of the substrate in controlling the growth of CNTs on carbon fi bres has been emphasised.
Degradation Mechanisms of Platinum Nanoparticle
Catalysts in Proton Exchange Membrane Fuel Cells:
The Role of Particle Size
K. Yu, D. J. Groom, X. Wang, Z. Yang, M. Gummalla,
S. C. Ball, D. J. Myers and P. J. Ferreira, Chem. Mater .,
2014, 26 , (19), 5540
Morphological changes in the Pt nanoparticle catalysts during fuel cell operation, particularly in the cathode, are associated with performance degradation. This article presents the fi rst systematic study by transmission electron microscopy (TEM) analysis of the in fl uence of nanoparticle size on active degradation mechanisms and hence on the electrochemical performance of membrane electrode assemblies (MEAs). Five MEAs with different average sizes of Pt nanoparticles in the cathode were analysed before and after potential cycling
(see Figure ). In most cases, the smallest initial particle size catalysts ended up with the largest particle sizes after 10,000 cycles, meaning that the ECA loss for Pt nanoparticle catalysts with smaller initial sizes (2.2 nm and
3.5 nm) was greater than for particles with sizes from 5.0 nm to 11.3 nm. Mechanisms for the particle size changes are discussed.
d = 10.3 nm
10 nm
After cycling
Reprinted with permission from K. Yu, D. J. Groom, X. Wang,
Z. Yang, M. Gummalla, S. C. Ball, D. J. Myers and P. J.
Ferreira, Chem. Mater ., 2014, 26 , (19), 5540. Copyright
(2014) American Chemical Society
69 © 2015 Johnson Matthey

http://dx.doi.org/10.1595/205651315X686039 Johnson Matthey Technol. Rev ., 2015, 59 , (1)
Record Activity and Stability of Dealloyed Bimetallic
Catalysts for Proton Exchange Membrane Fuel Cells
B. Han, C. E. Carlton, A. Kongkanand, R. S. Kukreja,
B. R. Theobald, L. Gan, R. O’Malley, P. Strasser, F. T.
Wagner and Y. Shao-Horn, Energy Environ. Sci ., 2015, doi:10.1039/C4EE02144D
The highest catalyst activity and device durability yet achieved in PEMFCs under automotive testing conditions is reported. A family of dealloyed core-shell
Pt-Ni nanoparticles were developed as catalysts for the cathode. Smaller particle size, non-oxidative acid treatment and post-acid-treatment annealing was found to reduce transition metal leaching from catalyst nanoparticles, and suppress nanoporosity formation.
This insight led to the ability to design more stable and active Pt-Ni catalysts. The details of alloy structure and compositions that lead to long-term PEMFC device stability were analysed using SEM and EDS.
The resulting catalyst meets and exceeds the of fi cial
2017 DOE targets for the oxygen reduction reaction
(ORR).
FCC Additive Improves Residue Processing Economics with High Iron Feeds
T. Hochheiser, Y. Tang, M. Allahverdi and B. De Graaf,
American Fuel and Petrochemical Manufacturers
(AFPM) Annual Meeting, Orlando, USA, 23rd–25th
March, 2014
Johnson Matthey’s FCC INTERCAT
JM
additive
CAT-AID TM is used by many re fi neries to trap contaminants due to its ability to improve the pro fi tability of the FCC operation. Lower quantities of fresh catalyst and fl ushing Ecat are needed and the product selectivities are improved, in particular diminishing delta coke. This study includes three commercial examples and the use of CAT-AID TM to reduce delta coke and improve residue processing is demonstrated.
Insights into Brønsted Acid Sites in the Zeolite Mordenite
D. B. Lukyanov, T. Vazhnova, N. Cherkasov, J. L. Casci and J. J. Birtill, J. Phys. Chem. C , 2014, 118 , (41), 23918
The purpose of this study was to identify the exact number and locations of Brønsted acid sites (BAS) in acidic and partially Na-exchanged samples of zeolite mordenite
(MOR). The catalytic properties of MOR are notably in fl uenced by the local environment of the BAS (O1–
O10 atoms), see Figure . At least six distinct BAS in the
MOR structure were identi fi ed by a comprehensive FT-IR investigation and Fourier self-deconvolution (FSD) analysis of the IR spectra. The results showed that ~25% of BAS are located in the eight-membered ring (8-MR) channels
(O1–H and O9–H) in the purely acidic H-MOR sample,
~13% of BAS are found at the intersections between the side pockets and 12-MR channels (O5–H hydroxyls) and ~62% of BAS are located in 12-MR channels (~39% correlate to O2–H and/or O10–H hydroxyls and the remaining 23% to O3–H and O7–H hydroxyls). The acid sites were found to be distributed quite evenly between oxygen atoms in the various crystallographic positions.
O9
O6
I
O1
T atoms
O5
O8
O2
O3
O7
IV
T1
O10
T4 T3
T2
VI
O4
Oxygen atoms
Reprinted with permission from D. B. Lukyanov, T.
Vazhnova, N. Cherkasov, J. L. Casci and J. J. Birtill,
J.
Phys. Chem. C
, 2014,
118
, (41), 23918. Copyright (2014)
American Chemical Society
70 © 2015 Johnson Matthey

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