German researchers have unveiled details of a non-flammable lithium-ion battery based on a polymer electrolyte.

Unlike the liquid electrolyte in conventional lithium-ion batteries, polymer electrolytes are not flammable.

The technology has been developed by researchers at the Fraunhofer Institute for Silicate Research in Würzburg.

"We have succeeded in replacing the inflammable organic electrolytes with a non-flammable polymer that retains its shape," said ISC team leader Dr Kai-Christian Möller.

"This considerably enhances the safety of lithium-ion batteries. What's more, because it is a solid substance, the electrolyte cannot leak out of the battery. "

The boffins point out that traditional lithium-ion batteries have organic electrolytes that are flammable and can easily catch fire. This flaw has resulted in several fires and subsequent recall campaigns for manufactures including Sony.

The polymer for the new battery is derived from the Ormocer group of substances, a compound with silicon-oxygen chains that form an inorganic structure to which organic side chains become attached.

"Normally, the more solid a polymer the less conductive it becomes. But we had numerous parameters that we could adjust," said Möller.

"For example, we can use coupling elements with two, three or four arms. As a result, we have more possibilities with Ormocers than with a single type of plastic."

A prototype of the new lithium-ion battery already exists, but the scientists warned that it will be three to five years before the battery will be available in laptops, PDAs and other devices.