A team of researchers from Stanford University and the Department of Energy’s (DOE) SLAC National Accelerator Laboratory have made the first battery electrode that heals itself, opening a new and potentially commercially viable path for making the next generation of lithium ion batteries.
The secret is a stretchy polymer that coats the electrode, binds it together and spontaneously heals tiny cracks that develop during battery operation. The self-healing polymer is already being developed as a flexible electronic skin for use in robots, sensors, prosthetic limbs, and other applications. For the battery project they added tiny nanoparticles of carbon to the polymer so it would conduct electricity and found that silicon electrodes lasted 10 times longer when coated with the self-healing polymer.
The electrodes worked for about 100 charge-discharge cycles without significantly losing their energy storage capacity. The research say that the promise is there to increase to their goal of about 500 cycles.
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 self-healing electrode, which is made from silicon microparticles that are widely used in the semiconductor and solar cell industries, is the first solution that seems to offer a practical road forward, they said. The researchers said they think this 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.