University of Leeds scientists have invented a new type of polymer gel that can be used to make cheaper lithium batteries.
The technology, funded by the Engineering and Physical Sciences Research Council and Yorkshire Concept, has been licensed to the American company Polystor Energy Corporation, which is conducting trials to commercialise cells for portable consumer electronics.
Physics Research Professor Ian Ward developed the new gel, which can be made into a thin, flexible film through a speedy and low-cost fully automated process.
He believes it could replace the liquid electrolytes currently used in rechargeable lithium cells.
“The polymer gel looks like a solid film, but it actually contains about 70 per cent liquid electrolyte,” Professor Ward explained.
“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”.
Rechargeable lithium-ion batteries are used in a wide range of portable consumer electronics including laptops, digital cameras, mobile phones and MP3 players.
Traditional lithium-ion batteries are based on cells which contain a porous polymer film separator and 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, and they have also developed a patented manufacturing process called extrusion/lamination which sandwiches the gel between an anode and cathode at high speed to create a highly-conductive strip that is just nanometres 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.
As well as being safe and damage tolerant, the flexible cells can be shaped and bent to fit the geometries of virtually any device.