[access-uk] New battery technology
- From: "Darren Brewer" <darren.m.brewer@xxxxxxxxxxxxxxxx>
- To: <access-uk@xxxxxxxxxxxxx>
- Date: Fri, 21 Dec 2007 13:32:17 -0000
Hi All.
Below is a small article about new developments in battery technology that
may interest some list members. It's a bit technical so if you're not
bothered, hit delete now.
New nano wire battery holds 10 times the charge of existing ones.
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 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. Candace Chan,
a graduate student of Cui, 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."
The breakthrough is described in detail 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.
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, California.
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