Researchers from Stanford University in California have developed a thin polyethylene film that prevents lithium-ion batteries from overheating, then restarts the battery when it cools. The design is an enhancement of a wearable sensor that monitors human body temperature. The sensor consists of a plastic material embedded with tiny particles of nickel with nanoscale spikes protruding from the surface. For the battery, the researchers coated the spiky nickel particles with graphene and embedded the particles in a thin film of elastic polyethylene. To conduct electricity, the spiky particles have to physically touch one another. Due to thermal expansion during use, the polyethylene stretches, which disconnects the particles stopping the flow of electricity. When the battery cools, the polyethylene shrinks, bringing the particles in contact again.
Source: Stanford University