Despite it's benefits as being a relatively cheap and lightweight battery material, silicon tends to expand when charging and shrink back when discharged. This often results in cracks which cause the silicon to break off from the electrode, which degrades battery life. Researchers at Stanford used a "stretchy polymer that coats the electrode, binds it and spontaneously heals tiny cracks that develop". This self-heals and seals the silicon, allowing it to extend battery life much further than before. Chao Wang, Stanford associate professor had this to say:
Self-healing is very important for the survival and long lifetimes of animals and plant. We want to incorporate this feature into lithium ion batteries so they will have a long lifetime as well. 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...
Their capacity for storing energy is in the practical range now, but we would certainly like to push that. The electrodes worked for about 100 charge-discharge cycles without significantly losing their energy storage capacity. That's still quite a way from the goal of about 500 cycles for cell phones and 3,000 cycles for an electric vehicle, but the promise is there, and from all our data it looks like it's working.
While this all sounds promising, it could be some time before we get self-healing batteries in our notebooks and other devices but it is a step in the right direction. When used in combination with flexible batteries we could end up with lighter devices that last longer in the long run.
[Source]
COMMENTS