The NEWSLETTER
Winter 2013
Reel-to-Reel
Manufacture of High
Energy Density, AllSolid-State Lithium-Ion
Cells
the large scale use of organic solvents,
By Professor Ian M Ward University of Leeds, UK
overheating within the cells.
The Challenge – Improved Safety at Lower
Recent efforts to address safety issues, such
Cost
as chemical electrolyte additives and novel
numerous instances of large scale fires within
production
plants
have
Historically
there
are
been
also
reported.
many
well
documented cases of fires and explosions
involving lithium-ion batteries resulting from
mechanical
damage,
short
circuits
and
separator materials, have done nothing to
A well-publicised recent spate of fires involving
address the underlying issues.
electric vehicles in the US has once again
opened the debate on the safety of lithium-ion
The Innovation
batteries as sources of automotive power.
Whether or not large-scale batteries are less
The team at Leeds has been working on two
safe than tanks of highly flammable petroleum
inter-related, patented technologies – a solid
products is beyond the scope of this article.
state polymer gel electrolyte and a high speed
However, the fact remains that question marks
extrusion/lamination,
still hang over lithium-ion batteries not only in
manufacturing process.
terms of safety but in terms of cost and
Polymer
performance.
being
polyvinylidene fluoride (PVDF) and lithium
addressed at the University of Leeds by a
salts were invented at Leeds University as part
team headed by Professor Ian Ward FRS. The
of a major project in the IRC in Polymer
basis of the work is the development of a new
Science and Technology. The technological
class of materials that offers an approach to
breakthrough has been to produce semi-rigid
improved safety, maximum performance and
films with very high levels of ionic conductivity
high speed cost effective manufacturing of
- in the region of 10-3 Scm-1, comparable to
lithium-ion cells.
conventional liquid electrolytes.
Conventional lithium-ion batteries use solvent
The solid-state flexible gel creates a dry
based
porous
system eliminating flammable solvents in the
mechanical separator to hold the electrodes
finished product and the need for a separator.
apart. Individual cells are effectively sealed
Furthermore, being
containers that are filled with liquid in a
electrolyte film is ideal for use with high
manufacturing process that is cumbersome
swelling advanced electrode materials.
and often hazardous; the solvents employed
Besides the obvious safety aspects associated
are highly toxic and highly flammable. Besides
with a dry system, elimination of the separator
liquid
Such
issues
electrolytes
are
with
a
gel
reel-to-reel
electrolytes
based
on
highly compliant, the
the obvious environmental issues surrounding
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Winter 2013
can account for significant material cost
reductions.
Figure 1: Cells based on gel electrolytes are allsolid-state, thin, flexible and safe.
The robust, semi-flexible laminate can be
Figure 3: Pouch cells are thin, flexible and can be
cut and packaged into a wide range of shapes,
produced in a wide range of sizes and capacities.
such as flat wide sheets, folded to suit device
Cell Manufacture
geometries or stacked to facilitate large scale
overall
cell
A patented extrusion/lamination process has
thickness is around 0.3 – 0.4 mm.
No
also been developed for the fabrication of cells
separator is required as the gel “micro-
in which the solid polymer gel electrolyte is
encapsulates” the electrolyte to produce a dry
simultaneously coated by both anode and
“pouch” cell.
cathode in a fully automated reel-to-reel
multi-cell
batteries.
Typical
Other
Foils
process.
Cathode
Separator
Anode
Electrolyte
Figure
2:
Conventional
lithium
battery
cost
structure. The separator is a major cost component.
Unlike conventional cells, pouch cells vent at
low pressure, before thermal runaway, with
Figure 4. A pilot line has been constructed to
minimal electrolyte escape on venting or
produce cells of high specific capacity and high
puncture.
The thin, flat shapes provide
energy density for rechargeable lithium batteries.
excellent heat transfer and as the electrodes
The process is high speed and fully automated
are not subjected to high compressive forces
offering
there is less likelihood of shorting.
the
cost
savings
and
repeatability
associated with continuous processes.
Continuous high speed production requires no
separator, eliminates complex mixing and
drying operations and readily allows cutting,
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stacking and packaging of large format cells.
be stored and transported in a given volume.
Variable geometry permits a wide range of cell
In order to meet demands for higher energy
size and capacity. Combined with the solid
densities, an essential requirement if electric
state
offers
vehicles are to become mainstream, new
significant savings in manufacturing costs
chemistries are being developed such as
when
of
silicon alloy nanocomposites. A part of the
conventional liquid electrolyte cells. The pilot
Leeds program has been to demonstrate the
line developed in Leeds can run at 10 m/min
compatibility of the gel electrolyte with a wide
with a projected speed of 100 m/min for
range of electrode materials including:
gel
electrolyte
compared
the
with
process
the
assembly
commercial scale equipment. The process is
fully
scalable
allowing
the
high

speed
manufacture of wide format cells tailored to
Conventional
carbon
anodes
with
LCO, NCA and LFP cathodes

high capacity rechargeable battery packs.
BASF’s
next
generation,
high
performance HE NCM cathode

3M’s high energy Si alloy anode
Figure 5. Laminated electrodes. The extrusion
lamination process enables high speed production
of thin polymer batteries with an estimated 1/3 less
Figure 6. Projected cell energy densities based on
capital investment and up to 25% lower material
Leeds gel electrolyte with various anodes versus
costs compared with cylindrical battery cells.
BASF HE NCM in 5-12 amp-hour pouch cells.
Compatibility and Performance
In
a
recent
development
program,
in
collaboration with PolyStor Energy Corp and
Cell capacity tests comparing the polymer gel
funded by DARPA, cells have been built and
electrolyte with conventional separators have
tested using Leeds gel electrolyte with BASF
shown that Leeds cells typically have equal or
HE NCM and 3M SiA electrode materials
higher
cells.
which enabled the construction of a BB-2590
However, in any lithium battery system cell
battery – a military standard battery used in a
performance is governed by the electrodes,
wide range of field operations including
specifically the number of lithium ions that can
communications and robotics. The battery was
Page 3
energy
than
conventional
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independently tested and shown to have a
capacity of 600 watt-hours. Conventional BB2590’s are < 200 watt-hours.
Proposition Position Today
Both
the
gel
electrolyte
and
the
extrusion/lamination technology have granted
patents.
The Leeds team is responding to
industry drivers in both product development &
customisation of the manufacturing process
with a number of developing collaborations
and alliances in the UK and overseas.
This publication contains general information and,
although SMMT endeavours to ensure that the content is
accurate and up-to-date at the date of publication, no
representation or warranty, express or implied, is made as
to its accuracy or completeness and therefore the
information in this publication should not be relied upon.
Readers should always seek appropriate advice from a
suitably qualified expert before taking, or refraining from
taking, any action. The contents of this publication should
not be construed as advice or guidance and SMMT
disclaims liability for any loss, howsoever caused, arising
directly or indirectly from reliance on the information in this
publication.
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