New self-healing battery electrode increases lithium ion battery lifespans

Nov. 20 (UPI) -- Researchers at Stanford University have made the first self healing battery electrode, which could mean longer charges and a prolonged life span.

The new battery works using a stretchy polymer that coats the its electrodes, strengthens them and fills in small cracks that may appear during battery operation. Adding tiny particles of carbon to the polymer meant it could conduct electricity.

“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.”

Researchers have been upbeat about the use of silicon as a battery electrode due to its high capacity for soaking up lithium ions from the battery fluid during charging and then releasing them when the battery is put to work.

But this performance comes at a price. The silicon electrodes swell to three times their size and shrink back down as they charge and discharge respectively. This causes the material to develop cracks and degrade over time.

The polymer, which will expand and shrink with the electrode, helped the electrodes last ten times longer and fixed the cracks with a few hours. To do this the researchers had to weaken the bonds of the polymer which meant they could expand, but the chemical ends were drawn to each other and so could easily shrink back.

"Their capacity for storing energy is in the practical range now, but we would certainly like to push that," said Yi Cui, an associate professor at SLAC. "That's still quite a way from the goal of about 500 cycles for cell phones and 3,000 cycles for an electric vehicle."