Polymer gel holds promise for flexible lithium ion batteries

The technology, developed by Professor Ian Ward and his team, can be made into a thin, flexible film via a fully automated process that is fast, efficient and low cost - paving the way for cheaper and safer Li-ion batteries with more power. The researchers have also developed and patented a manufacturing process called extrusion/lamination which sandwiches the gel between an anode and cathode at high speed (10m per minute) to create a highly conductive strip that is just nanometres thick. According to Prof Ward, 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." 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". As well as being safe and damage tolerant, the flexible cells can be shaped and bent to fit the geometries of virtually any device. The technology has been licensed to American firm Polystor Energy, which is currently conducting trials to commercialise cells for portable consumer electronics.