Products for batteries
Industry information 2244
Contents
1
2
Introduction
Description of different battery types
3
2
Electrolyte
4
2.1.
AEROSIL® for lead acid gel batteries
4
2.2
Dynasylan® for (Li-ion) batteries
5
3
Separators
6
3.1.
Separators in lead acid batteries (SIPERNAT®)
6
3.2.
Separators for Li-ion batteries (AEROSIL®, AEROXIDE®)
7
4
Electrodes
9
4.1.
Electrodes for Li-ion batteries (AEROXIDE®)
9
4.2.
Titania as precursor material for lithium titanate
9
5
Global presence
10
6
Literature of Evonik
11
7
Product recommendation
11
1. Introduction
The world of rechargeable batteries is changing. For
the last decades, lead acid starter batteries have been
the most prominent type of battery on the market.
But since the greenhouse effect and global warming
are regarded as global threats and since energy costs
are increasing significantly, scientists and technicians
are looking for new energy concepts worldwide.
Battery technology plays an important role in solving
the current problems and in making energy available
in a better way.
Renewable energy sources, like wind and solar energy, are becoming more and more important and the
necessity for efficient intermediate energy storage is
increasing. This can be solved, for example, by lead
acid gel batteries (LAB) or lithium-ion batteries
(Li-ion).
Nowadays, high-energy and high-power Li-ion batteries play an important role for new energy storage
concepts in automobiles. Hybrid electric vehicles
(HEV) as well as full electric vehicles (EV) are reliant
on these battery technologies, which are currently
developed intensively.
Additionally, the new electric bike generation
(e-bikes) requires an efficient rechargeable
battery system based on advanced lead acid (gel,
AGM / SiO2) or Li-ion technologies.
These few examples demonstrate the growing
demand for new materials and technologies for
efficient and environmentally friendly batteries.
Evonik Industries, as one of the most important
chemical suppliers to the battery industry, provides
many sophisticated solutions for present and future
battery systems.
In gel batteries fumed silica is applied as thickening
agent in the electrolyte. Precipitated silica is used
as filler in separators for LAB while fumed products
are used as filler and as well for coatings in Li-ion
separator technology. Fumed titania is suitable as
precursor material for the production of lithium titanate Li4Ti5O12 – an anode active material for Li-ion
batteries. These are just a few examples from the
extensive portfolio of Evonik for the battery industry.
Ask us, challenge us – we will find the right solution
for your application. Our applied technology experts
will provide optimum solutions for your advanced
battery technology.
Description of different battery types
In general, batteries can be classified using the
concept of physical and chemical batteries. The class
of physical batteries consists of thermal cells and
solar power batteries, while their chemical analogues
include primary (non-rechargeable) and secondary
(rechargeable) batteries.
Various types of rechargeable batteries are known,
including the four most common ones:
• Lead acid batteries
• Nickel cadmium batteries
• Nickel metal hydride batteries
• Lithium-ion batteries
Solar battery
Physical battery
Thermal cell
Battery
Primary battery
(not rechargeable)
Chemical battery
Rechargeable
battery
Lead acid battery
Lithium-ion battery
Lithium polymer
battery
Nickel cadmium
battery
Nickel metal
hydride battery
Other rechargeable
batteries
3
General principle of a rechargeable battery
2.1. AEROSIL® for lead acid gel batteries
ee-
CATHODE
ANODE
Lead acid batteries are one of the oldest types of
rechargeable batteries. Even though their energy-toweight ratio is low, the ability of the cells to supply a
high surge current results in a high power-to-weight
ratio.
Due to their low costs, lead acid batteries are still
gaining market shares, especially in these fields,
where new battery systems are either too expensive or too demanding, particularly with regard to
maintenance.
Lead acid batteries are still the most cost effective
battery type for the following applications:
Discharge and Charge
Both, lead acid and Li-ion batteries consist of the
same major components – the two electrodes (anode
and cathode), a separator in between them and
finally an electrolyte, which is responsible for the ion
transfer during charge and discharge processes.
Evonik products are present in the following
battery components
Electrode
material
2. Electrolyte
Separator
Electrolyte
Lead acid
battery
–
SIPERNAT®
AEROXIDE®
AEROSIL®
Lithium ion
battery
AEROXIDE®
AEROSIL®
AEROXIDE®
Dynasylan®
• Starter batteries for automotive engines
• Traction batteries for golf caddies, fork-lifts,
wheelchairs, cleaning machines
• Stationary batteries as power back-up for telecommunication and data centers, power plants,
hospitals, renewable energy systems, emergency
lighting, green energy plants
History of lead acid gel batteries
Conventional flooded cell lead acid batteries are
problematic in view of safety, due to their liquid
acidic electrolyte. Therefore, they should be used
only in an upright position in order to prevent
leaking or spilling of the highly corrosive sulphuric
acid.
In the late fifties, a new class of advanced lead acid
battery based on gel technology was introduced.
The gel battery is a type of valve-regulated leadacid battery (VRLA). In VRLA batteries no water
needs to be added during their lifetime and the
battery is sealed with valves. The acidic electrolyte
is either fixed in the form of a gel or is absorbed in
a glass fleece.
4
The advantages of gel batteries are:
• Almost maintenance-free
• Spillage-free
• Can be used in different positions / no need to
be kept upright / operation irrespective of its
position
• Possibility of high discharge currents
• Resistance to vibration, shock, extreme
temperatures
• No acid stratification
• Deep discharge
Fumed silica is used to gelify the sulfuric acid.
The requirements for gel forming agents are
challenging:
• High purity
• Chemical stable towards sulphuric acid, lead oxide,
and lead
• Thickening and thixotropic behavior
• Medium to high surface area
AEROSIL® fumed silica fulfills these demands and
provides our customers with the following benefits:
•
•
•
•
•
•
Highly effective thickening
Thixotropic behavior
Electrochemically and chemically inert
Stable viscosity
High purity
Prevention of acid stratification
2. 2. Dynasylan® for Li-ion batteries
Due to their special properties, organofunctional
silanes act as highly efficient surface modifiers, as
water and HF scavengers, and as solvents. Hence,
they can act as additives for electrolytes in lithium ion
batteries. In addition to increased reliability due to
higher thermal stability and the lower risk of hydrogen and oxygen formation, increased durability and
a higher number of load cycles can also be expected.
5
3. Separators
3.1. Separators in lead acid batteries (SIPERNAT®)
The function of the separator is to prevent the physical contact of cathode and anode from eachother
to avoid a short-circuit. Additionally, it must be
permeable for ions, which move freely between the
electrodes.
To fulfill those contradicting properties, the separator has to be mechanical stable and porous at the
same time.
Due to the high porosity, protons can migrate from
one electrode to the other and close the electrical
circuit. Because of the non-conducting separator the
electrodes are not in direct contact with each other.
Separators for lead acid batteries can be made up
of different polymers, such as polyethylene (PE),
polyvinylchloride (PVC), resins or rubber. They vary
regarding design (thickness, ribs), porosity, and
composition of the ingredients. In comparison to
the other polymers, the polyethylene based separators show a high flexibility and weld ability, making
PE suitable for a preferred application in starter
batteries.
The main raw materials are PE (UHMW-PE),
silica and oil. Selected additives are used, such as
lubricants, wetting agents, carbon black.
Benefits of the PE separator compared to other
materials are: puncture resistance, flexibility, ability
to be folded and sealed, oxidation resistance and low
acid displacement.
The function of silica is to make the separator
porous. This is achieved by mixing the raw materials
and by extruding the mixture to form a sheet. The oil
is extracted from the sheet and the sheet becomes
porous. The silica remains in the porous sheet and
makes the surface of the PE separator hydrophilic
and wettable for sulfuric acid – allowing the protons
to pass through the separator.
The silica for battery separators needs to be tailormade to achieve the following properties: low
electrical resistance of the separator material, good
processing properties for the manufacturing process,
specific morphology to control the separator shrinkage behavior during manufacturing and in service,
and specific requirements for purity and trace
elements.
The Evonik grades SIPERNAT® 325 C,
SIPERNAT® 325 AP, SIPERNAT® BG–2, SIPERNAT®
325 E and possibly new grades fulfill these market
requirements excellently.
Materials for separators in lead acid batteries
6
PE
PVC
Rubber
Rubber / PE
Phenolic resin
Strength
Excellent
Good
Fair
Excellent
Good
Flexibility
Flexible
Rigid
Flexible
Flexible
Rigid
Mean pore
diameter (µm)
0.10
0.07
0.22
0.15
0.06
0.10
0.50
0.34
Pore Volume (%)
55 – 65
60 – 70
45 – 55
50 – 60
60 – 70
ER (Ωcm²)
0.120
0.130
0.250
0.110
0.140
Oxidation
resistance
Excellent
Excellent
Good
Good
Excellent
Resists to Antimony
transfer
No
No
Yes
Yes
No
3. 2. Separators for Li-ion batteries
(AEROSIL®, AEROXIDE®)
Similar to lead acid batteries, the basic function of
the separator in Li-ion batteries is to prevent physical
contact of anode and cathode from each other, while
allowing lithium ions to move freely between the
electrodes.
Therefore, the separator is made of electrically insulating materials, exhibiting a high porosity. The basis
of all micro porous membranes is a thermoplastic
material, that prevents short circuiting by separating
the electrodes and blocking ionic conductivity in case
of thermal runaway. The separator itself does not
participate in the chemical reaction.
The performance of the battery, including energy
and power density, cycle life and safety is directly
affected by the separator. Various separator types are
known for Li-ion batteries, including:
1 Micro porous membranes
2 Solid ion conductors
3 Gel polymer electrolytes
The application of Li-ion batteries as energy storage
systems in HEVs and full EVs requires an improvement of the currently used separators in order to
increase the safety function significantly.
Modification of these micro porous membranes
with inorganic nanostructured particles, e.g. silica or
alumina as fillers or coatings, results in an improved
inorganic-organic hybrid membrane with a high
porosity and enhanced thermal stability. Furthermore, the mechanical strength and electrolyte wetability is significantly increased.
These inorganic fillers can either be integrated
directly into the thermoplastic material or into a
separate layer that is coated, laminated or coextruded
on top of the membrane.
Such a ceramic modified separator enhances enhances the mechanical stability and, therefore, leads
additionally to an advanced protection against lithium
dendrite growth inside the cell.
7
Requirements for Li-Ion battery separators
8
Parameter
Goal
Thickness
< 25 µm
Porosity
> 40 %
Pore size
< 1 µm
Electrical resistance
2 ohms · cm–2
Wettability
Complete wetting by typical
electrolytes
Puncture strength
> 300 g · mil–1
Shrinkage
< 5 % @ 90 °C for 1 h
High-temperature melt
integrity
> 150 °C
Shutdown temperature
~ 130 °C
Dimensional stability
Should lay flat and not curl on
the edges
Inorganic fillers like AEROSIL® and ceramic layers
with AEROXIDE® greatly influence the characteristics
and properties of the micro porous separator:
• Improve thermal stabiliy
(high temperature melt integrity)
• Enhance mechanical strength
• improve electrolyte wettability
• Increase porosity
4. Electrodes
4. 1. Electrodes for Li-ion batteries
(AEROXIDE®)
The two electrodes of a Li-ion battery act as host
materials for the insertation of small Li+ ions. Upon
charge / discharge of the battery Li ions start to
migrate out of one electrode active material, diffuse
through the electrolyte filled separator, to finally
insertate into the other electrode.
As appropriate anode materials a huge variety of different carbonaceous compounds (natural & artificial
graphite, hard and soft carbons) were used as hosts
for the reversible storage of Li ions in between the
carbon sheets.
In general, the electrodes are formulated from the
following materials:
1
2
3
4
5
Current collector
Electrode active material
Conductive material (e.g. carbon black)
Binder
Additives
4.2. Titania as precursor material for lithium
titanate
Carbon based anode materials exhibit a disadvantage: the formation of an (irregular) solid electrolyte interface (SEI) and the subsequent irreversible
capacity decline upon first-time battery cycling.
This phenomenon can lead to a decreased cycle life
of the battery and represents additionally a safety
risk, because of the potentially growth of lithium
dendrites. Therefore, other types of anode active
materials, especially for those batteries, which are
designed for HEVs and full EVs, are currently developed intensively.
Lithium titanate Li4Ti5O12 seems to be an appropriate anode active material, mainly due its high safety.
During the charge / discharge, i.e. lithiation and delithiation process, a significant volume change of the
host material is not observed (zero-strain material),
resulting in a stable anode structure.
Furthermore, the formation of a SEI between the
anode material and the electrolye does not occur,
avoiding the irreversible capacity decline upon firsttime battery cycling.
Li titanate can be synthesized from different Ti
sources like Ti(OR)4, TiCl4 or TiO2 and the use of
a variety of Li salts (see table below). Two types
of AEROXIDE® materials – AEROXIDE® P 25 and
AEROXIDE® P 90 – are recommended precursor
compounds for the synthesis of Li4Ti5O12.
Different synthesis methods for the production
of Li4Ti5O12
Li source
(examples)
Method
Ti source
Sol-gel
Ti(OR)4, TiCl4
Li2CO3, Li(COOR),
Li(OR)
Electrochemical
insertion
TiO2
LiClO4, LiAsF6,
LiCF3SO3
Solid-state reaction
TiO2
Li2CO3, LiOH, Li2O
Electrochemical
TiO2
LiCl (molten)
Hydrothermal
TiO2
LiOH
9
5. Sites for production and applied technologies (AT)
of SIPERNAT®, AEROSIL® and AEROXIDE®
Antwerpen, Belgium
Roussillon, France
Portland, USA
AT-Center, Piscataway, USA
Mobile, USA
Waterford, USA
Chester, PA, USA
Wesseling, Germany
AT-Center, Hanau-Wolfgang, Germany
Leverkusen, Germany
Rheinfelden, Germany
Zubillaga-Lantaron, Spain
Adapazari, Turkey
Akoh, Japan
Yokkaichi, Japan
AT-Center, Shanghai,
(Production, AT-Center)
China
Nanping, China
Gajraula, Indien
Ta Yuan, Taiwan
Map Ta Phut, Thailand
10
6. Literature of Evonik
•
•
•
•
Specialty Silica, Product Overview
AEROSIL® Product Overview
Dynasylan® Product Range
Technical Overview: AEROSIL® - Fumed silica
7. Product recommendation
Lead acid batteries
AEROSIL®
Separator
Electrolyte (gel)
SIPERNAT®
SIPERNAT® 325 C
SIPERNAT® 325 AP
SIPERNAT® BG–2
SIPERNAT® 22 S
AEROSIL® 200
AEROSIL® 200 V
AEROSIL® 200 VS*
*Regionally restricted availability
Li-ion batteries
AEROSIL®/ AEROXIDE®
Precursors for electrode active materials
AEROXIDE® TiO2 P 25
AEROXIDE TiO2 P 90
AERODISP® W 740 X
Separator
AEROSIL®
AEROXIDE® Alu C
AEROXIDE Alu 65
AEROXIDE Alu 130
AEROXIDE C 805
Dynasylan®
Dynasylan® VTMO
AEROXIDE® TiO2 P 25
AERODISP® W 740 X
AERODISP® W 630
Electrolyte
Dynasylan®
(aminofunctional silanes as HF
scavengers)
11
This information and any recommendations,
technical or otherwise, are presented in good faith
and believed to be correct as of the date prepared.
Recipients of this information and recommendations
must make their own determination as to its
suitability for their purposes. In no event shall
Evonik assume liability for damages or losses of any
kind or nature that result from the use of or reliance
upon this information and recommendations.
EVONIK EXPRESSLY DISCLAIMS ANY
REPRESENTATIONS AND WARRANTIES OF
ANY KIND, WHETHER EXPRESS OR IMPLIED,
AS TO THE ACCURACY, COMPLETENESS, NONINFRINGEMENT, MERCHANTABILITY AND/
OR FITNESS FOR A PARTICULAR PURPOSE
(EVEN IF EVONIK IS AWARE OF SUCH PURPOSE)
WITH RESPECT TO ANY INFORMATION AND
RECOMMENDATIONS PROVIDED. Reference
to any trade names used by other companies is
neither a recommendation nor an endorsement of
the corresponding product, and does not imply that
similar products could not be used. Evonik reserves
the right to make any changes to the information
and/or recommendations at any time, without prior
or subsequent notice.
Europe / Middle-East /
Africa / Latin America
North America
Asia / Pacific
Evonik Resource Efficiency GmbH
Business Lines Silica & Silanes
Rodenbacher Chausse 4
63457 Hanau-Wolfgang
Germany
Evonik Corporation
Business Lines Silica & Silanes
299 Jefferson Road
Parsippany, NJ 07054-0677
USA
Evonik (SEA) Pte. Ltd.
Business Lines Silica & Silanes
3 International Business Park
#07-18 Nordic European Centre
Singapore 609927
 +49 6181 59-12532
 +49 6181 59-712532
ask-si@evonik.com
 +1 800 233-8052
 +1 973 929-8502
ask-si-nafta@evonik.com
 +65 6809-6877
 +65 6809-6677
ask-si-asia@evonik.com
www.evonik.com
07-2015
AEROSIL®, AEROXIDE®, AERODISP®, SIPERNAT®
and Dynasylan® are registered trademark of Evonik
Industries or its subsidiaries.