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Silicon Nanowires Before and After Absorbing Lithium  (Source: Stanford News Service)
New lithium-ion battery using silicon nanowires will store ten times the energy of current lithium-ion batteries

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.



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Recycycle
By AlvinCool on 12/20/2007 11:08:08 AM , Rating: 2
It would be great if by not using carbon and using silica it allowed for better recycling. Hybrids using these batterys would be awesome. Hand tools are already showing extended time and more power but one of our biggest wasters are lawn mowers. With these batterys it may be possible to convert everyone to electric lawn mowers!! Much less the cars stated in the article. If they can do this I hope the first thing they do is make them in AA and AAA so we stop filling our landfills with throw aways and rechargables




RE: Recycycle
By mcnabney on 12/20/2007 11:43:43 AM , Rating: 2
You are right! I never thought of lawn mowers as being a target for this. Those nasty inefficient 2 stroke engines pollute more in one mowing than my two cars do in a week. Except for the commercial ones that are used all the time, most mowers aren't used for more than 2 hours at a time.

And they can't replace the current crop of batteries we use. Li-Ion voltage is too high. 3.6V per cell I believe, which is more than double the 1.5V standard. NiMH run at 1.2 and I have never known why that isn't more of a problem.


RE: Recycycle
By TomZ on 12/20/2007 12:22:13 PM , Rating: 1
Lawn mower engines are 4-stroke, not 2-stroke, at least in the US.


RE: Recycycle
By fic2 on 12/20/2007 1:39:24 PM , Rating: 2
Yes, they are 4-stroke, but they have little, if any pollution controls on them.


RE: Recycycle
By TomZ on 12/20/2007 9:14:28 PM , Rating: 1
Agreed, but they're not burning tons of oil like 2-strokes.


RE: Recycycle
By AlexandertheBlue on 12/20/2007 9:41:43 PM , Rating: 2
Not necessarily. You are assuming that all lawn mowers are new. Many old lawn mowers, especially lawn boys, are 2 stroke.

However that said, I have always preferred gas mowers over electric as they have had more power and are thus able to cut longer grass more easily. With the new battery density hopefully thay are able to remedy this and give decent operating time and recharge time.


RE: Recycycle
By fic2 on 12/20/2007 12:01:33 PM , Rating: 2
Lawn mowers, leaf blowers, weed wackers, etc. All a huge source of environmental pollution including noise pollution. If these could be converted to electrical it would be a huge win.


RE: Recycycle
By Spuke on 12/20/2007 1:27:36 PM , Rating: 2
I'm surprised this isn't done already. Are any of these offered in electric only?


RE: Recycycle
By Spuke on 12/20/2007 1:34:52 PM , Rating: 2
Just checked and there are already electric lawn mowers. I saw them on Sears.com. They don't seem to be anymore expensive than regular mowers.


RE: Recycycle
By kingpotnoodle on 12/21/2007 8:50:42 AM , Rating: 2
Electric lawnmowers (at least in UK) have been available for decades... sure most of the larger "sit-on" mowers are diesel/petrol powered like a small tractor but a great many garden appliances for the average home user are electric... they are not that much quieter than 2 stroke engines though. If you have a garden that's not far from your house then it is hardly a hassle to buy a 20m extension reel, indeed many new houses have electric sockets with built in safety cut out positioned in their garages or near the garden.


RE: Recycycle
By fic2 on 12/20/2007 1:37:43 PM , Rating: 2
Usually electric mowers are plug-in which some people will deal with, but most won't. Same with weed-wackers and leaf blowers.

A lot of lawn work is not done by commercial lawn maintenance people and would need long battery life to think about switching to electric.

I would think with this, current electric motors, the price of gas and the hassle of getting a gas mower started every spring that people might be willing to switch if someone came out with a good battery powered mower.


RE: Recycycle
By Dfere on 12/21/2007 9:31:46 AM , Rating: 2
Uh Uh. When you factor how often you have to throw the whole lawn mower away, I think not. The electric mowers rely on a plastic shim in case the blade encounters resistant to give or strip. I think this is because the something inside the motor would take the direct shock and break instead. I have tried two for my rentals over the last ten years and had to throw both away for lack of replacement parts. Any heavy use strips this shim as well.

For trimming your little yard once a week, perhaps these fit, but I have real estate to mow.


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