New battery lasts 10 times as long | January 2, 2008 | Palo Alto Weekly | Palo Alto Online |

Palo Alto Weekly

Cover Story - January 2, 2008

New battery lasts 10 times as long

Silicon Valley legacy of innovation continues — with silicon

by Arden Pennell

Imagine rarely having to recharge the battery of your new, all-electric car. Saving gas is just one potential benefit of a new battery that lasts 10 times longer than standard models, creator and Stanford University researcher Yi Cui said.

"It can be used in laptops. You can do international flights without charging up" or it can be used in iPods or cell phones, said Cui, an assistant professor in the Materials Science and Engineering Department.

Cui and colleagues announced the break-through battery last month, capping two years of research, he said.

The notion of a battery based on nanotechnology came about when Cui got to Stanford in 2005.

"I was very excited when this idea was demonstrated to work for the first time," Cui said.

The new battery generates 10 times as much energy as traditional batteries by getting around the tendency of silicon to break down through normal use, he said.

In standard lithium-ion batteries, the silicon expands during charging as it absorbs lithium ions, then shrinks during use as the tiny particles flow back out.

The expand-and-contract cycle causes silicon, which is in the shape of particles or layers, to degrade. But Cui's new battery uses a forest of tiny silicon wires to store ions, he said.

The nanowires, each with a diameter of one-thousandth the thickness of a sheet of paper, grow to four times their normal size but don't fracture as other silicon shapes do, he said.

With silicon intact, the battery keeps going — including in electric-car engines, a use Cui is particularly excited about.

"You don't need to burn gasoline. You can use the battery. It has high enough energy to drive really long distances," he said.

He plans to run more lab tests to determine the battery's exact duration, but it could hit commercial markets in as little as five years, he said.

He plans to either start his own company or license the technology to others, he said.

And with abundant supply and pre-existing technology, it shouldn't cost too much, he said.

"Silicon is really abundant, the second most abundant element. The semiconductor industry is mature. [So] the cost is low," he said.

As the region's nickname implies, silicon played a crucial local role in high-tech innovations as an ideal material for semiconductors and later computer chips.

But nanotechnology, or the ability to make such small objects, is only about a decade old, Cui said.

"In previous research, they couldn't solve this problem" of preventing silicon breakage, because the pieces were too large, he said.

And while silicon has the highest known charge capacity, or ability to store lithium ions, that potential could not be unlocked earlier due to its tendency to wear out, Cui and others said in a letter describing their findings.

Cui has received phone calls from all over the world since the letter's publication online in the journal Nature Nanotechnology, he said.

Staff Writer Arden Pennell can be e-mailed at


Posted by Ken Edwards, a resident of another community
on Mar 13, 2008 at 6:53 am

Regarding the coal/NG pollution needed to generate the electricity for charging electric vehicles, take a look at the "well-to-wheel" efficiency data at the link below:
Web Link
You should also take into account the emissions from power generation in California. See the chart at: Web Link
Of course if you install solar panels and generate your own power for recharging you'll get what we're all lookiing for -- zero emissions from generation to use. In Connecticut, where I live, we also generate power using nuclear plants.

Posted by Another Engineer, a resident of Duveneck/St. Francis
on Mar 13, 2008 at 11:00 pm

Hello Mr Edwards

Thanks for the links. This concisely-presented well to wheel analysis is exactly the right tool for evaluating propulsion options, and the metric, km/MJ, is appropriate.

However, the authors do not show how they developed the MJ numbers or what energy items comprise them. This is important, since the bookkeeping would be significantly different between an all-electric powerplant and fuel-based or hybrid propulsion. These are smart people, but engineers always want to look under the hood themselves.

In any case, the authors are spot on in promoting all-solar charging.

As for the second link: It certainly shows California is ahead of the nation with its generating choices, but the grid we plug into is national. As all freshman electrical engineers learn, it is impossible to apportion the energy delivered to a given load in a network to the various sources in the network, with so many watts coming from this generator, such and such watts from that one, and so on. Power is not linear. I suspect that you and I probably toast our bagels with a power mix closely reflecting the national blend, but we'll never know for sure.

Posted by another engineer, a resident of Another Palo Alto neighborhood
on Mar 16, 2008 at 1:10 am

There are several troubling comments in this article.

"The battery generates 10 times the energy-------." Batteries don't generate any energy. They store energy. Why would he imply that they generate energy? Maybe to fool uneducated investors??

They can generate energy because the silicon dosen't break down?? A strange way to put it.

No matter how you put it the energy source for 10's of millions of cars will probably be coal as Nuclear is for all practical purposes banned in the U.S..

5 years to develop the technology and probably another 10 years to bring the price down below $20,000 for batteries for cars.

Posted by Another Engineer, a resident of Duveneck/St. Francis
on Mar 17, 2008 at 11:14 am

"The battery generates 10 times the energy-------." Batteries don't generate any energy. They store energy. Why would he imply that they generate energy? Maybe to fool uneducated investors?? - another engineer

I'd chalk these misstatements up to a non-techie reporter and not a deliberate attempt to mislead.

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