Researchers at the Stanford University Department of Materials Science
and Engineering have developed a technique for making lithium ion
batteries that hold ten times more charge than current models. This
could extend the driving time of electric cars and the life of mobile
devices such as cell phones, music players and cameras by the same
amount, making a typical laptop battery last 40 hours instead of four..
"It's not a small improvement," researcher Yi Cui said. "It's a
revolutionary development."
Traditional lithium ion batteries
<http://www.naturalnews.com/batteries.html> use graphite as the anode,
or the part of the battery that positive current flows into.
Scientists have long known that a much higher theoretical charge could
be achieved with a silicon anode, but due to a quirk of silicon's
nature, until now such anodes have been impossible.
Silicon expands when charged with lithium ions, and then contracts
again as the charge flows out. Typically, one such charge-discharge
cycle causes the silicon to be pulverized, making it ineffective for
future cycles.
Cui and his fellow researchers overcame the problem by growing a
cluster of silicon nanowires directly onto the stainless steel that
serves as the battery's current collector. While these nanowires,
originally on thousandth the thickness of a sheet of paper, swell to
about four times their size when charged with lithium, they do not
fracture when they shrink back down.
On the first charge cycle, the anode attained silicon's maximum
theoretical charge. Subsequent cycles achieved 75 percent of that
charge and maintained it even over many charge-discharge cycles.
Cui expressed optimism that the technology could be commercialized
within "several years."
"We are working on scaling up and evaluating the cost of our
technology," he said.
Cui has filed a patent for the technology and says that he is
considering either starting his own company or forming a partnership
with an existing battery company to further develop and market it
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