University of Leeds scientists have invented a new type of
polymer gel that can be used to manufacture cheaper lithium batteries without
compromising performance.
The technology,
developed by Professor Ian Ward FRS, a Research Professor of Physics at the University of Leeds, has been licensed to the American
company Polystor Energy Corporation, which is conducting trials to commercialize
cells for portable consumer electronics.
Professor Ward
believes the new material could replace the liquid electrolytes currently used
in rechargeable lithium cells. Furthermore, the gel can be made into a thin,
flexible film via a fully automated process that is fast, efficient, and low
cost.
Rechargeable
lithium-ion batteries are now the power of choice for a wide range of portable
consumer electronics such as laptops, digital cameras, mobile phones, and MP3
players.
Traditional
lithium-ion batteries are based on cells (sealed containers) which contain a
porous polymer film separator plus liquid chemical filler. This allows lithium
ions carrying charge to flow between the two electrodes and also acts as a
barrier, holding the electrodes apart to prevent short-circuiting.
The polymer gel
developed by Professor Ward and his team removes the need for this separator. They
have also developed a patented manufacturing process called
extrusion/lamination which sandwiches the gel between an anode and cathode at
high speed (10 m/min) to create a highly-conductive strip that is just nanometers
thick.
The resultant polymer
gel film can be cut to any size and permits a fully automated process which is
cost effective and safe. The lamination process also seals the electrodes
together so that there is no excess flammable solvent and liquid electrolyte.
“The polymer gel
looks like a solid film, but it actually contains about 70% liquid
electrolyte” says Professor Ward. “It’s made using the same
principles as making a jelly: you add lots of hot water to ‘gelatine’—in this
case there is a polymer and electrolyte mix—and as it cools it sets to form a
solid but flexible mass”.
As well as being safe
and damage tolerant, the flexible cells can be shaped and bent to fit the
geometries of virtually any device.
