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Posted by jim on January 4, 2008, 9:54 am
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> (from
> http://news-service.stanford.edu/news/2008/january9/nanowire-010908.html)
>
> Stanford Report, December 18, 2007
> Stanford's nanowire battery holds 10 times the charge of existing ones
>
> BY DAN STOBER
>
>
> 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."
>
> Also contributing to the paper in Nature Nanotechnology were Halin Peng
> and Robert A. Huggins of Materials Science and Engineering at Stanford,
> Gao Liu of Lawrence Berkeley National Laboratory, and Kevin McIlwrath and
> Xiao Feng Zhang of the electron microscope division of Hitachi High
> Technologies in Pleasanton, Calif
You do realize that that means that a Tesla raodster could go up to 2500
miles on a single charge!
Wow!
Now maybe we can do something about automobile pollution, at least.
I know all about the percentages of pollution so don't get your geek in a
wad. But reducing (or eliminating) auto exhaust will definitely improve
local air quality and may even help cool cities off a couple of degrees in
the summer. Not to mention the new quiet engines.....
jim
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