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Stanford's nanowire battery
holds 10 times the charge of existing ones
Other Topics:
Nanotech Revolution,
Nanotech Semiconductor,
Nanotech Coatings
Stanford University
December 18, 2007
Palo Alto, CA -- 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. |
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"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. |
