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While lithium-ion batteries provide high energy density and voltage, they suffer from one major flaw: the organic electrolytes they contain are inflammable. This has resulted in a number of cases of laptop computers spontaneously catching fire and has forced several PC manufacturers to stage expensive battery recalls.
Now researchers at the Fraunhofer Institute for Silicate Research (ISC) say they have removed this hazard. “We have succeeded in replacing the inflammable organic electrolytes with a non-flammable polymer that retains its shape,” says ISC team leader 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 polymer used by the researchers based on a hybrid inorganic/organic polymer called Ormocer that was discovered by Fraunhofer researchers.
This compound has silicon-oxygen chains that form an inorganic structure to which organic side chains become attached. The challenge in using this material is to ensure that it will efficiently conduct lithium ions.
“Normally, the more solid a polymer is, the less conductive it becomes. But we had numerous parameters that we could adjust – for example, we can use coupling elements with two, three or four arms. As a result, we have more possibilities with Ormocer than with a single type of plastic,” says Möller.
A prototype of the new lithium-ion batteries will be on display at the Industrial Technology exhibition at Hannover Messe next week. The need for further improvements and the length of the investment cycles in battery manufacturing mean it will be between three and five years before the batteries are available.