Silicon-carbon nanocomposite seeks to boost lithium-ion performance

March 16, 2010 // Paul Buckley

A high-performance anode structure based on silicon-carbon nanocomposite materials developed by the Georgia Institute of Technology is aiming to improve the performance of lithium-ion batteries used in a wide range of applications from hybrid vehicles to portable electronics.

Employing a "bottom-up" self-assembly technique, the anode’s structure takes advantage of nanotechnology to fine-tune its materials properties, addressing the shortcomings of earlier silicon-based battery anodes. The low-cost fabrication technique was designed to be easily scaled up and compatible with existing battery manufacturing.

"Development of a novel approach to producing hierarchical anode or cathode particles with controlled properties opens the door to many new directions for lithium-ion battery technology," said Gleb Yushin, an assistant professor in the School of Materials Science and Engineering at the Georgia Institute of Technology. "This is a significant step toward commercial production of silicon-based anode materials for lithium-ion batteries."

Existing lithium-ion batteries rely on anodes made from graphite, a form of carbon. Silicon-based anodes theoretically offer as much as a ten-fold capacity improvement over graphite but have so far not been stable enough for practical use.

Graphite anodes use particles ranging in size from 15 to 20 microns. If silicon particles of that size are simply substituted for the graphite, expansion and contraction as the lithium ions enter and leave the silicon creates cracks that quickly cause the anode to fail.

The new nanocomposite material solves that degradation problem, potentially allowing battery designers to tap the capacity advantages of silicon and enabling a higher power output from a given battery size – or allow a smaller battery to produce a required amount of power.

Electrical measurements of the new composite anodes in small coin cells have shown a capacity more than five times greater than the theoretical capacity of graphite.

Details of the new self-assembly approach were published online in the journal Nature Materials on March 14.

Related link: www. gatech.edu

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