Lithium ions react
with silicon to form a new compound, which causes
the electrode to
expand. Researchers found that flouroethylene carbonate molecules
produce a rubber-like
protective layer that can accommodate the electrode expansion.
Infographic by Sana
Sandler/Sarah Schlieder
(August 6, 2015) Imagine
a cell a phone that charges in less than an hour and lasts for three to four
days or an electric car that runs for hundreds of miles before needing to be
plugged in.
Researchers at the U.S. Department of Energy’s Argonne
National Laboratory are working to make this dream a reality by developing
lithium-ion batteries containing silicon-based materials. The most commonly
used commercial lithium-ion batteries are graphite-based, but scientists are
becoming increasingly interested in silicon because it can store roughly 10
times more lithium than graphite.
“When we talk about batteries, we talk in terms of the
amount of energy that can be stored,” said Daniel Abraham, materials scientist
in Argonne’s Chemical Sciences and Engineering Division. “Silicon-based
batteries could double or even triple the energy stored in conventional
batteries, which would greatly benefit the consumer electronics market and the
automotive industry.”
There’s just one problem: current batteries based on silicon
materials don’t last long.
The problem lies in the battery’s chemistry. The electrolyte
inside the battery transports lithium ions back and forth between positive and
negative electrodes as the battery charges and discharges. The positive
electrode contains a lithium-bearing compound, while the negative electrode
contains materials such as graphite or silicon.