Silicon Increases Li-ion Battery Capacity

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"Treated silicon could increase battery energy storage tenfold."

Rice University and Lockheed Martin scientists have found that silicon can radically increase the capacity of lithium-ion batteries.

"The anode, or negative, side of today's batteries is made of graphite, which works. It's everywhere, but it's maxed out. You can't stuff anymore lithium into graphite than we already have," said Michael Wong, a professor of chemical and biomolecular engineering and of chemistry.

Silicon has the highest theoretical capacity of any material for storing lithium, but after a couple of cycles of swelling and shrinking, it cracks. Putting micron-sized pores into the surface of a silicon wafer gives the material sufficient room to expand.

While common lithium-ion batteries hold about 300 milliamp hours per gram of carbon-based anode material, they determined the treated silicon could theoretically store more than 10 times that amount.

The straightforward process makes it highly adaptable for manufacturing.

"The other advantage is that we've seen fairly long lifetimes. Our current batteries have 200-250 cycles, much longer than nanowire batteries," the researchers noted.

The researchers are confident that cheap, plentiful silicon combined with ease of manufacture could help push their idea into the mainstream, as it significantly increase the performance of lithium-ion batteries, which are used in a wide range of commercial, military and aerospace applications.

"Our goal is to develop a model of the strain that silicon undergoes in cycling lithium. Once we understand that, we'll have a much better idea of how to maximize its potential," Wong said.

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