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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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RE: Awesome
By Doormat on 12/20/2007 11:43:46 AM , Rating: 2
I would expect that we'd see much lighter devices with 5-8 hours on a charge. I doubt we'd see many devices with more than 12 hours, the manufacturers will just size down the battery to make it smaller and lighter. It'd be great to have a 3G cell phone that lasts a week on a charge, or an iPod touch that would last an entire 8 hour transpacific flight.

But yea, the biggest implication for these batteries seems to be in electric vehicles. Being able to do 100+ miles on a single charge would be outstanding. The issue is how quickly you can get charge in and out of the battery - how long will it take to charge and how fast can you drive on electric power.

RE: Awesome
By FITCamaro on 12/20/2007 2:17:57 PM , Rating: 2
I think it's going to be a long time before a purely electric car will be a full-time replacement for a gas powered one. They're good for running around town or going to work and back. Not for long trips though. Even if it can make it 100 miles, thats not that far. The average car can make it 300-400 miles on a tank of gas. Sure the size of the tank varies but the point is that they can make it that far. And if you're running low, it only takes 5 minutes to stop at a gas station and fill up. You're likely never going to see a battery than can boast that.

Hence why I still think hydrogen fuel cells are the answer. It'll have to be modified a little but our current distribution system can be used for it.

RE: Awesome
By Doormat on 12/20/2007 3:43:26 PM , Rating: 2
H2 wont do anything. I'd be willing to venture out on a limb and say that 95% of people's daily driving is under 100 miles. If a vehicle can go 100mi on a single charge then fine.

What we'll probably end up seeing is some cars having an optional small 600rpm diesel engine w/ gas tank, where the engine's entire purpose is to recharge the battery on longer trips. You can engineer the engine to operate at its peak efficiency at a constant speed because its only generating electricity, instead of having to go up and down like a standard engine + transmission when you drive and stop, drive and stop.

Now you only use gasoline on trips of more than 100mi/day. The fuel consumption of the people who actually use the engine will be great and since so few people will use the engine anyways, the worldwide consumption of fuel declines dramatically.

RE: Awesome
By FITCamaro on 12/20/2007 6:47:20 PM , Rating: 2
The issue isn't daily driving. It's that people don't want to have to own one car for daily driving and one to take vacations with. And you're still not going to be able to go as far or as fast with just a small diesel engine trying to charge the battery.

With the Chevy Volt it will have a system somewhat like that. But its not meant for driving across the country.

RE: Awesome
By alan328 on 12/23/2007 9:20:15 AM , Rating: 2
The issue isn't daily driving. It's that people don't want to have to own one car for daily driving and one to take vacations with.

Hi everyone, i am from Hong Kong.
Hong Kong is famous for danger level of air polution.
Everyday, on the news is like this: "Tomorrow polution index is HIGH to VERY HIGH. People are recommended to stay indoor."

Believe it or not... it is the daily life of HK people...

HK urgently needed to replace all cars with EVs. And, 100 miles per a charge is more than enough for HK, because it means you can drive around the whole city many many times.

But why HK people are still not using EVs? the answer is cost of the battery. A pack of battery cost $40K to 100K HK$, and you need to replace the battery every 3 - 5 years. That is simplely not cost effective when comparing with the cost of gas you may consume in the same duration (a lot of car owners told me the same answer when i ask them why don't they change to EVs in HK).

What dose this new technology mean to HK car owners? For the same capicity of battery, the size of battery will be decrease to 1/10.... which also means Li-ion material inside the battery decease to 1/10.... the result is the cost of replacing the battery is a lot cheaper.

If replacing the battery every 3 - 5 years is still much cheaper than the gas one would consume during the same period, everyone will change to EV. Wish that day come soon.

RE: Awesome
By FITCamaro on 12/20/2007 6:49:39 PM , Rating: 2
And why wouldn't Hydrogen do anything? It's a clean source of fuel that can be stored just like gas (not quite as easily but still). The only issue is finding a way to produce it in mass qualities cheaply and efficiently. And there's been research done in that area too.

RE: Awesome
By CubicleDilbert on 12/20/2007 2:24:13 PM , Rating: 4
You are forgetting Murphy's general "Law of Inertia"!

such as:
The weight of a bicycle is constant, regardless of technology. The lighter and more advanced the bicycle, the heavier the accompanying metal lock.


The working performance of a computer is constant. The more powerful the system, the more power hungry the software. Which says, writing a letter in MS Office anno 1992 takes the same amount of time as writing it in 2007. The perceived speed of the PC is constant. Pentium 1 and Windows 95 is speed-wise similar to Pentium Core and Vista.

The battery time of any device is constant, regardless of the underlying battery.
Thinkpad 755 (1994) 3-4h
Thinkpad 570 (1998) 3-4h
Thinkpad T23 (2002) 3-4h
Thinkpad T40 (2004) 3-4h
Thinkpad T60 (2007) 3-4h

same with cell phones!
Any new battery performance will be sucked up with more powerful systems and gadget features.

Siemens C25 (1998) 1 day talking
Siemens C45 (2002) 1 day talking
Nokia N95 (2007) 1 day talking

Summa summarum:
a device with this new battery will perform EXACTLY as before (but will have a lot of more performance doing in the end exactly the same work as a generation before)

"We’re Apple. We don’t wear suits. We don’t even own suits." -- Apple CEO Steve Jobs
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