Scientists have designed a lithium-ion battery that self-regulates according to temperature, to prevent itself from overheating. Reaching extreme temperatures, the battery is able to shut itself down, only restarting once it has cooled. The researchers designed the battery to shut down and restart itself over a repeated heating and cooling cycle, without compromising performance. A polyethylene film is applied to one of the electrodes, which expands and shrinks depending on temperature, to create a conductive/non-conductive material.