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Composite anode could boost lithium batteries

Posted: 18 Mar 2003 ?? ?Print Version ?Bookmark and Share

Keywords:composite anode? silicon? graphite? sandia national laboratories? lithium-ion battery?

A new class of composite anode formed from silicon and graphite has been invented by the Department of Energy's Sandia National Laboratories, which could provide a major performance boost to Li-ion batteries.

If technical issues with battery cycling can be worked out, the new anode material could lead to batteries with more power, longer life, and smaller sizes than today. In collaboration with Sandia's lithium battery R&D department on the main campus at Los Alamos, New Mexico, the inventors at Livermore estimate that the silicon-graphite anodes may result in a doubling in performance for rechargeable lithium batteries.

"We believe that only silicon-containing electrode materials can compete with the large capacities that our silicon/graphite composites have demonstrated," said Jim Wang, an analytical materials science manager at Sandia.

For three years, the team tried various combinations on the graphite anode, including non-graphitic carbons, intermetallics, oxides, nitrides, and composites, finally settling on the silicon-graphite composite.

Silicon-graphite offers 10 times the battery capacity of graphite alone, but has not been possible before because of problems during the battery's cycling phase. However, by adding silicon microparticles into a graphite matrix, the rapid capacity loss during cycling was eliminated, according to Sandia.

According to Sandia, the material's principle improvement is its power capacity, which is retained during cycling, plus an ability to tune the material to specific applications by changing the microstructure of the underlying graphite base.

Sandia is currently looking to head off a potential roadblock to the technology - fading of long-term cycling capacity, an inherent disadvantage of using silicon. By moving to carbon composites, according to Sandia, the fading can be mitigated.

"We predict smaller, more robust, long lasting, and higher-powered microsystems," said Wang. "Our newly discovered anode materials can improve the performance of microsystems by allowing more powerful electronic components to be reduced in size and weight."

- R. Colin Johnson

EE Times

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