Researchers: Nanowires could boost battery life 10X

Redesigned lithium-ion batteries could go in laptops, iPods -- even electric cars

Researchers at Stanford University are using silicon nanowires that allow lithium-ion batteries to hold 10 times the charge they could before.

That means a laptop that now holds a four-hour charge could last for 40 hours using the new battery, according to Yi Cui, assistant professor of materials science and engineering at Stanford. "This is really a revolutionary result," said Cui, who has worked on the nanotech project for more than a year. "We're talking about a 10-times improvement. It's a big jump."

The batteries could be a boon for business travelers tired of having their laptops or other devices run out of juice on long flights. Cui said the batteries would also work for iPods, cell phones and even electric vehicles. Also, the batteries could be used in homes and commercial buildings to store energy from solar panels.

As it stands now, a lithium-ion battery's capacity is limited by how much lithium its anode can hold. Anodes now are generally made of carbon; silicon, however, has a much higher storage capacity.

The nanowires, explained Cui, act as an active battery material that stores the lithium-ion. The silicon nanowires replace the carbon in the battery. When the nanowires touch the lithium-ion, they form a new material -- lithium silicide. Cui said the battery's energy is stored in the lithium silicide, which has a much greater capacity.

The lithium is stored in a large group of miniscule silicon nanowires. Each wire is 1,000 times thinner than a human hair, although they can inflate to four times their normal size as they soak up the lithium.

Cui also noted that when the energy is used up, the lithium silicide material reverts back to being silicon, so the batteries are rechargeable.

The Stanford research team now is working on ways to mass produce the batteries. "Given the mature infrastructure behind silicon, this new technology can be pushed to real life quickly," Cui said.

Several companies have shown an interest in the technology from Cui and his research team, but he declined to say who he's in talks with. He did say that he's filed a patent for the technology, and is considering either starting his own business or forging an agreement with a battery manufacturer.

In October, a researcher with the University of Edinburgh School of Engineering and Electronics said because of advances in nanowires, supercomputers will be able to fit in the palm of a hand within 10 to 15 years. And early in November, a researcher at Arizona State University said nanotechnology -- specifically nanowires -- will replace magnetic disk drives in iPods, laptops and servers within five to 10 years, making them more durable, lighter and faster.

Copyright © 2007 IDG Communications, Inc.

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