Researchers at Stanford University have revamped lithium ion (Li-Ion) battery technology to create a more power-dense construction using silicon nano wires. Yi Cui, assistant professor of materials science and engineering at Stanford and his team of researchers have implemented silicon nanowires in Li-Ion batteries to replace the existing carbon-based batteries found in devices such as iPods and laptops.
“Silicon can combine with a lot of lithium ions, ten times more than carbon,” says Cui, meaning that the power density of a silicon-based Li-Ion battery would be ten times greater than a carbon-based Li-Ion battery.
Silicon nanowires don’t run the risk of breaking because of their small size. “When you break big things you break them into small ones, and there’s always a certain size limit; it’s harder to break it into even smaller and smaller,” says Cui.
The only other obstacle left in building the batteries is the volume expansion of lithium silicide, the newly formed lithium silicon compound. “Because you push a lot of lithium into silicon, the more you push in the more volume expansion you will have,” says Cui. “Same thing for carbon — carbon will swell too but since carbon doesn’t have so many lithium ions in it, they just don’t swell as much.”
Once all the kinks are hammered out, Cui predicts that this new construction for Li-Ion batteries will take about five years to make it to market. “We have a lot of silicon in the world and we also have a mature infrastructure; we have big industry behind silicon,” he says. “We know the process about silicon, so it will be easy for pushing silicon nanowire technology to the real applications because we have this mature infrastructure.” According to Cui, these new batteries could have potential use in the electric vehicles market because of their high power density.
Photos taken by a scanning electron microscope of silicon nanowires before (left) and after (right) absorbing lithium. Both photos were taken at the same magnification. Photos courtesy of Nature Nanotechnology.
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