Researchers at the U.K.’s University of Leeds have developed a polymer gel for producing rechargeable lithium-ion batteries more safely and inexpensively than traditional ones. This advance could lead to lighter laptop computers and more efficient electric cars that run on lower-cost batteries without the risk of “thermal runaway.”
In 2006, Dell recalled numerous laptops because the batteries overheated and could catch fire. Dell’s redesigned batteries addressed the safety, but the batteries were bigger. Apple redesigned its batteries too, but power output suffered. Electric car makers have designed batteries with safeguards that ended up adding significant cost and weight to the vehicles.
Hamish Pritchard, a science reporter for the BBC, writes that the new batteries are safe and cost 10-20% less than traditional lithium batteries. He adds:
The secret to their success lies in blending a rubber-like polymer with a conductive, liquid electrolyte into a thin, flexible film of gel that sits between the battery electrodes.
Traditional lithium-ion batteries have sealed containers filled with electrolytes, and the containers are separated by a porous polymer film. Lithium ions carrying charge flow between the two electrodes. The film also prevents short-circuiting by acting as a barrier and holding the electrodes apart.
Ian Ward’s team at Leeds developed the gel and its patented manufacturing process. The high-speed extrusion/lamination process sandwiches the gel between an anode and cathode, and seals the electrodes together so there is no excess flammable solvent and liquid electrolyte. The resulting strip is highly-conductive, flexible, and is nanometeres in thickness. It can be cut to any size as well as shaped and bent to fit the geometry of any device, in addition to being safe and tolerant to damage, according to a press release.
“The polymer gel looks like a solid film, but it actually contains about 70% liquid electrolyte,” Ward said in a statement. “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.”
The technology has been licensed to the American company Polystor Energy Corporation, which is conducting trials to commercialize cells for portable consumer electronics, according to a press release.
Source: “Jelly batteries: Safer, cheaper, smaller, more powerful,” BBC, 9/10/11
Source: “Material World,” BBC’s Radio 4, 9/12/11
Source: “Polymer batteries for next-generation electronics,” University of Leeds press release, 9/9/11
Image by Ed Yourdon, used under its Creative Commons license.
Rachel Petkewich is a freelance science writer and editor. She has worked as a research scientist in the chemical industry and spent eight years as a staff writer and editor at various science journals and magazines, including Chemical & Engineering News.