Scientists working at Stanford University have developed a new lithium-ion battery that will not overheat. Instead, it shuts itself off when temperatures get too high and powers back on once it cools down, a study in Nature Energy reports.
This important new technology, which prevents batteries from overheating, should be able to prevent battery fires in many popular electronics, such as laptops and hoverboards.
Most rechargeable lithium-ion batteries are made up of two lithium electrodes–one positive and one negative–and an intermediary electrolyte liquid that transfers electrons from one end to the other, UPI reports. While this allows the battery to function, sometimes the constant cycle of charging and discharging can raise the temperature of the battery’s electrolyte material to above 300 degrees Fahrenheit. When that happens, the battery can ignite.
While hoverboards have risen in popularity over the past few months, they are known to spontaneously burst into flames because of battery overheating. To combat this, researchers installed a thin film of elastic polyethylene in the battery between the electrodes and the electrolyte. The film contains spiky nanoparticles made of nickle and graphene to enhance conductivity.
“We attached the polyethylene film to one of the battery electrodes so that an electric current could flow through it,” said Zheng Chen, lead author of the study, in a statement. “To conduct electricity, the spiky particles have to physically touch one another. But during thermal expansion, polyethylene stretches. That causes the particles to spread apart, making the film nonconductive so that electricity can no longer flow through the battery.”
The researchers also were able to calibrate the film to separate at different temperatures. This allowed them to expand the film at the right pace for the nanoparticles to separate and the battery to shut down above 160 degrees Fahrenheit.
Using a hot air gun, the scientists tested the new technology and found the safety mechanism to be accurate, effective, and reversible. After the battery shuts down, it quickly begins to work again once it cools below that 160 degree Fahrenheit threshold.
People have tried to solve the problem of accidental lithium-ion fires in the past, but this method is much more reliable than previous approaches. It is the first design that allows a battery to be shut down and reliably revived again and again without lowering the performance of the battery itself.