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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
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
.
