Researchers at Stanford University think they have come up with a solution to improve the lithium-ion battery, which could lead to improvements in the next generation of mobile phones and electric cars.
Currently lithium-ion batteries contain silicon electrodes. Although silicon is a great material because it has a high capacity for absorbing and releasing lithium ions during charging and discharging, it also swells to three times the size and shrinks again during a charge-discharge cycle. This means they often don’t last very long.
A poor service life may not be a big issue if it is in a smartphone as people tend to replace them frequently anyway but it becomes a much bigger problem when someone has purchased something more pricey, like an electric car for example. When a person wants to sell the car on, they expect it not to need any major component replacements and in an electric car, the battery is a pretty major component.
This is one of the reasons why the motor industry is so reluctant to produce more battery cars. Even Tesla Motors, who is well-known for electric cars, has admitted that battery life could be a major problem for the company as its cars get older.
So what have the experts at Stanford University come up with? Well, they have been able to develop a strong and stretchy polymer which can be used to coat a silicon electrode. As cracks form during the charge and discharge process, the coating is able to “heal” the cracks.
“Self-healing is very important for the survival and long lifetimes of animals and plants,” says Chao Wang, a postdoc researcher at Stanford. “We want to incorporate this feature into lithium ion batteries so they will have a long lifetime as well.”
At the moment the researchers have been only been able to get this marriage of silicon and polymer coating to last for 100 charge cycles before it starts to lose performance. There is still ground to cover, with the goal being to reach 500 cycles for a phone and 3,000 for an electric vehicle. But as Professor Yi Cui points out “the promise is there, and from all our data it looks like it’s working.”