A self-heating battery was developed that can charge an electrical vehicle in 10 minutes for a 200- to 300-mile range while maintaining 2,500 charging cycles or the equivalent of half a million miles of travel.
Lithium-ion batteries degrade when rapidly charged at ambient temperatures under 50 °F because, rather than the lithium ions smoothly being inserted into the carbon anodes, the lithium deposits in spikes on the anode surface. This lithium plating reduces cell capacity but also can cause electrical spikes and unsafe battery conditions. Batteries heated above the lithium plating threshold, whether by external or internal heating, will not exhibit lithium plating.
Researchers discovered that if the batteries could heat up to 140 °F for 10 minutes and then rapidly cool to ambient temperatures, lithium spikes would not form and heat degradation of the battery would also not occur. The rapid cooling of the battery would be accomplished using the cooling system designed into the car. The large difference from 140 to about 75 °F will also help increase the speed of cooling.
The self-heating battery uses a thin nickel foil with one end attached to the negative terminal and the other extending outside the cell to create a third terminal. A temperature sensor attached to a switch causes electrons to flow through the nickel foil to complete the circuit. This rapidly heats up the nickel foil through resistance heating and warms the inside of the battery.