Nanowire battery holds 10 times the charge of existing ones

December 18, 2007

Stanford researchers have found a way to use silicon nanowires to reinvent the rechargeable lithium-ion batteries that power laptops, iPods, video cameras, cell phones, and countless other devices.

The new version, developed through research led by Yi Cui, assistant professor of materials science and engineering, produces 10 times the amount of electricity of existing lithium-ion, known as Li-ion, batteries. A laptop that now runs on battery for two hours could operate for 20 hours, a boon to ocean-hopping business travelers.

"It's not a small improvement," Cui said. "It's a revolutionary development."

The breakthrough is described in a paper, "High-performance lithium battery anodes using silicon nanowires," published online Dec. 16 in Nature Nanotechnology, written by Cui, his graduate chemistry student Candace Chan and five others.

The greatly expanded storage capacity could make Li-ion batteries attractive to electric car manufacturers. Cui suggested that they could also be used in homes or offices to store electricity generated by rooftop solar panels.

"Given the mature infrastructure behind silicon, this new technology can be pushed to real life quickly," Cui said.

The electrical storage capacity of a Li-ion battery is limited by how much lithium can be held in the battery's anode, which is typically made of carbon. Silicon has a much higher capacity than carbon, but also has a drawback.

Silicon placed in a battery swells as it absorbs positively charged lithium atoms during charging, then shrinks during use (i.e., when playing your iPod) as the lithium is drawn out of the silicon. This expand/shrink cycle typically causes the silicon (often in the form of particles or a thin film) to pulverize, degrading the performance of the battery.

Cui's battery gets around this problem with nanotechnology. The lithium is stored in a forest of tiny silicon nanowires, each with a diameter one-thousandth the thickness of a sheet of paper. The nanowires inflate four times their normal size as they soak up lithium. But, unlike other silicon shapes, they do not fracture.

Research on silicon in batteries began three decades ago. Chan explained: "The people kind of gave up on it 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."

Then, along came silicon nanowires. "We just kind of put them together," Chan said.

For their experiments, Chan grew the nanowires on a stainless steel substrate, providing an excellent electrical connection. "It was a fantastic moment when Candace told me it was working," Cui said.

Cui said that a patent application has been filed. He is considering formation of a company or an agreement with a battery manufacturer. Manufacturing the nanowire batteries would require "one or two different steps, but the process can certainly be scaled up," he added. "It's a well understood process."

Source: Stanford University

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3.3 / 5 (3) Dec 19, 2007
Nothing was said about why this design geometry prevents the silicon fracturing after shrink/swell cycles.
1 / 5 (1) Dec 19, 2007
" The nanowires inflate four times their normal size as they soak up lithium. But, unlike other silicon shapes, they do not fracture. "

I'm guessing because they say it's a forest formation of nanowires that it's probably because of the increased surface area or more efficient deposits of lithium bonds because of the nanoscaled ordering of the silicon.
Jan 05, 2008
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not rated yet Aug 04, 2008
Wow I hope they not let this improvement disapear like all the other cool stuff which was invented.
not rated yet Aug 04, 2008
yeah i agree. i was thinking about this invention nowadays that im searching for a laptop. too bad its still not ready :P
not rated yet May 18, 2009
It's been 18 months. What is the status of this?
1 / 5 (1) May 18, 2009
my friends say the same thing! I have proof i invented the same type of silicon nanowire lithium battery three years before they did. I applied for a NYSERDA grant in 2004 for the same design. NYSERDA said I had to come up with matching funding so we lost out on funding and the race to construct a world record capacity battery.
not rated yet May 19, 2009
I have proof i invented the same type of silicon nanowire lithium battery three years before they did.
No you don't Neil. You have claimed inventions in everything from cold fusion to genetic engineering, yet have produced nothing yet accept your useless butt-glue. No patents, no research, no products. Nothing but false claims.

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