January 26, 2009
Silicon nanowires boost batteries
Coat crystalline silicon nanowires with amorphous silicon and you have highly efficient electrodes for lithium-ion batteries.
Silicon has a much higher storage capacity and faster charge rate than graphite, which is widely used in today's lithium-ion batteries, but silicon is brittle and quickly breaks down from repeated charge-discharge cycles. Lithium batteries store electricity by filling the anode with lithium ions, which stresses the anode's crystal structure.
The amorphous silicon of the coated nanowires withstands the charge-discharge stress, and prototype nanowire electrodes are able to retain 90 percent of their charge capacity after 100 cycles.
The nanowire structure gives the electrodes a large surface area and the crystalline silicon at the nanowires' cores conducts electricity well. The prototypes stored three times as much electricity and charged 20 times faster than graphite electrodes.
Crystalline-Amorphous Core-Shell Silicon Nanowires for High Capacity and High Current Battery Electrodes
Nano Letters, published online December 23, 2008
Yi Cui Group
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