Self-healing Electrode Could Pave Way for Next-generation Lithium Ion Batteries

The invention of the first self-healing battery electrode may lay the foundation for next-generation lithium ion batteries used in electric cars and cellphones, among other devices.

A current race is underway in labs throughout the world as scientists work to increase lithium ion batteries' performance while simultaneously decreasing their weight by storing more energy in their negative electrodes.

Due to its ability to soak up lithium ions from battery fluid during charging and subsequently release them when the battery is operating, silicon currently ranks as the leader of promising electrode materials. However, it is not without its drawbacks, namely that silicon electrodes triple in size and then deflate every time the battery charges and discharges, causing the material to crack and hurting battery performance.

To solve this, researchers from Stanford University and the Department of Energy's SLAC National Accelerator Laboratory weakened some of the chemical bonds within the chain-like molecules known as polymers. As a result, while the material breaks apart easily, the broken ends are able to quickly reassemble again. The result is a self-healing polymer that coats the electrode, binding it together and healing any cracks that develop while the battery is operating.

"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," Zhenan Bao, a professor of chemical engineering, said in a statement.

The self-healing polymer was created by adding tiny nanoparticles of carbon to a flexible electronic skin Stanford scientists were developing for use in robotics, prosthetics and other applications. And unlike many attempts at keeping silicon electrodes intact and improving their performance, this new method calls for widely available materials and scalable production techniques.

"Self-healing is very important for the survival and long lifetimes of animals and plants," said Chao Wang, a postdoctoral researcher at Stanford and one of two principal authors of the paper. "We want to incorporate this feature into lithium ion batteries so they will have a long lifetime as well."

The study outlining the discovery was published in the journal Nature Chemistry.