MUNICH, Germany — In the quest for more powerful automotive batteries, researchers from the Technical University of Graz (Austria) have achieved significant progress: They have invented a gel that helps to increase the power density by a factor of two or more.

In today's lithium-ion batteries, one of the electrodes is typically made of graphite. If the electrode is coated with silicon, the lithium ion storage capability is increased by a factor of ten — but the vapor deposition method to coat the electrode led to inadequate results since the silicon features volume changes over temperature.

The Austrian researchers have along with German battery manufacturer Varta Microbatteries AG developed a silicon-containing gel that avoids these drawbacks. Thus, the research team was able to reduce the mechanical stress generated by the volume change of the silicon, explained project manager Stefan Koller.

However, the material still does not keep the promise of a tenfold increase in lithium ion storage capacity. "Not all elements are active ones, and the counter electrode still remains a challenge," Koller explained. Nevertheless, the process developed by the research team enables designers to build lithium ion batteries with twice the energy content of today's batteries.

Koller was unable to specify when volume production of such a battery could begin. "The research team made a 'precursor' model", he said. "Commercial production would require building an industrial-scale manufacturing line."

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