A new type of polymer gel that can be used to manufacture cheaper lithium batteries without compromising performance has been invented University of Leeds scientists. The technology, developed by Professor Ian Ward FRS, a Research Professor of Physics, has been licensed to the American company Polystor Energy Corporation, which is conducting trials to commercialise cells for portable consumer electronics. 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 removes the need for this separator. The team has also developed a patented manufacturing process called extrusion/lamination which sandwiches the gel between an anode and cathode at high speed (10m/minute) 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. The polymer gel looks like a solid film, but it actually contains about 70% liquid electrolyte. Besides being safe and damage tolerant, the flexible cells can be shaped and bent to fit the geometries of virtually any device.