Many electronic devices -- from notebooks to cell phones -- rely on
batteries for operation. Rechargeable batteries account for much of the weight in
today’s electronic devices so the size of the battery has to be tempered with
battery life to get an ideal product.
Stanford assistant professor of materials science and engineering Yi Cui,
graduate student Candace Chan and five other researchers made a breakthrough
for lithium-ion batteries. The researchers used silicon nanowires in the
battery anodes to design new
lithium-ion batteries that can hold ten times the electrical charge of current
batteries of the same size.
Cui told the Stanford News Service, “It's not a small improvement.
It's a revolutionary development.” Cui and his team were able to get the
greatly increased electrical storage capacity by growing silicon nanowires on a
stainless steel substrate, which provides excellent electrical conduction.
Researchers say that the amount of energy a currently lithium-ion battery
can store is dependent on the amount of lithium it can store in its anode
typically made from carbon. Silicon has a higher storage capacity than carbon.
The use of silicon in lithium-ion batteries had been attempted before but the
growing and shrinking process caused by adding and removing lithium caused the
silicon to break down severely degrading the performance of the battery.
Chan says, “The people kind of gave up on it [silicon] because the capacity
wasn't high enough and the cycle life wasn't good enough. And it was just
because of the shape they were using. It was just too big, and they couldn't
undergo the volume changes.”
The silicon nanowires used in the researcher’s batteries are tiny at about
one-thousandth of the thickness of a sheet of paper and are able to inflate to
four times their normal size as they take in lithium without breaking during
the duty cycle of the battery. The researchers say that the infrastructure
behind silicon is mature meaning the new technology could be pushed to market
quickly.
Cui has filed a patent application and is considering starting a company to
product batteries based on the technology or collaborating with an established
battery maker. This development could also mean much smaller and lighter
batteries than we have today that store as much electricity, which would be a
huge boon for mobile electronics.
Cui sees the new and improved lithium-ion batteries as being particularly
interesting to electric vehicle makers such as GM with its Chevy
Volt due in 2010.
