August 6, 2015

Protective shells may boost silicon lithium-ion batteries

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.

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