Coming soon: Self-healing batteries
In
a first, scientists have invented a battery electrode that heals
itself, paving way for next generation of long-lasting batteries for
electric cars, cell phones and other electronic devices.
The self-healing electrode is madesilicon microparticles that are widely used in the semiconductor and solar cell industry.
The
secret behind the invention is a stretchy polymer that coats the
electrode, binds it together and spontaneously heals tiny cracks that
develop during battery operation, according to Stanford University
researchers and colleagues.
Chao Wang, a
postdoctoral researcher at Stanford and one of two principal authors of
the paper, developed the self-healing polymer in the lab of Zhenan Bao, a
professor of chemical engineering at Stanford, whose group has been
working on flexible electronic skin for use in robots, sensors,
prosthetic limbs and other applications.
For the battery project, Chao added tiny nanoparticles of carbon to the polymer so it would conduct electricity.
"We
found that silicon electrodes lasted 10 times longer when coated with
the self-healing polymer, which repaired any cracks within just a few
hours," Bao said.
The electrodes worked for about 100ge-discharge cycles without significantly losing their energy storage capacity.
"That's
still quite a waythe goal of about 500 cycles for cell phones and 3,000
cycles for an electric vehicle," Yi Cui, an associate professor at
Stanford said, "but the promise is there, andall our data it looksit's
working."
Researchers worldwide are racing to
find ways to store more energy in the negative electrodes of lithium ion
batteries to achieve higher performance while reducing weight.
To
make the self-healing coating, scientists deliberately weakened some of
the chemical bonds within polymers - long, chain-like molecules with
many identical units.
The resulting material
breaks easily, but the broken ends are chemically drawn to each other
and quickly link up again, mimicking the process that allows biological
molecules such as DNA to assemble, rearrange and break down.
The
researchers said they think their approach could work for other
electrode materials as well, and they will continue to refine the
technique to improve the silicon electrode's performance and longevity.
The study appears in the journal Nature Chemistry.
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