A jelly lithium battery has been developed that is safer and cheaper than traditional lithium-ion batteries
Scientists at the University of Leeds have paved the way to smaller, cheaper and lighter gadgets with the invention of a jelly lithium battery.
The flexible polymer gel batteries can be shaped and bent to fit virtually any device and can be made just nanometres thick at a rate of ten metres per minute.
Most portable electronics such as laptops, digital cameras, mobile phones and MP3 players rely on rechargeable lithium-ion batteries for power.
To prevent short circuiting, the electrodes of these cell-based batteries are kept apart by separator elements but the polymer gel developed by the university team removes the need for this.
“The polymer gel looks like a solid film, but it actually contains about 70 percent liquid electrolyte” said Professor Ian Ward FRS, a research professor of physics at the University of Leeds. “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.”
Patent manufacturing process
Professor Ward’s team has 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 can be cut to any size.
The lamination process also seals the electrodes together so that there is no excess flammable solvent and liquid electrolyte.
In 2006, Dell, Toshiba, Apple and Lenovo all recalled laptops amid fears that overheating could damage their batteries’ separators and potentially result in explosion. The batteries were all made by Sony. Hewlett-Packard has recalled batteries several times since then
One Lenovo ThinkPad burst into flames at a Los Angeles airport prompted wide ranging restrictions on laptop use on planes for a period.
Apple replaced its batteries with a solid lithium-polymer but had to accept a reduction in power output. The BBC reports that the Leeds-based researchers promise their batteries perform at the level of liquid-filled batteries and are as safe as polymer ones but are just 10 to 20 percent of the price.
Professor Peter Bruce from the University of St Andrews, who was not involved in the Leeds study, told the BBC: “Safety is of paramount importance in lithium batteries. Conventional lithium batteries use electrolytes based on organic liquids; this is what you see burning in pictures of lithium batteries that catch fire. Replacing liquid electrolytes by a polymer or gel electrolyte should improve safety and lead to an all-solid-state cell.”
Leeds University has licensed the polymer gel technology to American company Polystor Energy Corporation, which is conducting trials to commercialise cells for portable consumer electronics.
The research was funded by the Engineering and Physical Sciences Research Council and Yorkshire Concept.
Materials scientists are approaching the problem of batteries from several directions. Sumitomo Electric has developed a very porous solid metal foam called aluminium celmet which meets the structural requirements of a battery and can increase the contact area between the metal and the electrolyte in a battery.