This patent can help solve thermal runaway issues in EV batteries. The mitigation solution involves combining a lithium-ion battery with a metal-air one to prevent it from catching fire. (Image Credit: USTPO)
Other than increasing energy density and decreasing battery costs, electric car manufacturers have one common goal: making their vehicles safer. One method involves safely mitigating thermal runaway, the most frequent cause of an EV catching fire and exploding. What happens is that the lithium-ion battery overheats, ejecting the hot gases that burn everything around it. A new Tesla patent, granted on September 1st, 2020, describes that it can be prevented by connecting a metal-air battery pack to the main one. The patent was originally filed on January 16th, 2017. This new battery technology, among others, could be unveiled on Tesla Battery Day, set to take place on September 22nd, 2020.
What exactly is an air-metal battery? It's an electrochemical cell that uses an anode made from pure metal and an external cathode of ambient air with an aqueous or aprotic electrolyte. These batteries have a higher capacity and energy density than lithium-ion. This can be used in electric vehicles since it extends the vehicle's range while maintaining a low volumetric space for cell storage.
There is a wide range of issues with the metal anodes, catalysts, and electrolytes that need to be addressed before being used in electric vehicles. Thermal runaways are not one of those problems for a simple reason: they need air in order to function. However, non-metal-air cells are prone to thermal runaway, which is what Tesla's patent can help resolve.
How these solution works are relatively simple. According to the patent, both non-metal and metal-air battery packs are connected by tubes and valves. If a thermal runaway were to occur, the valves open, allowing the hot gas to flow through the metal-air battery pack. This causes the gas to cool down before escaping to the vehicle's surroundings. In addition to solving thermal runaway, the patent discusses how an EV can be powered by combining lithium-ion battery cells and metal-air battery cells. Power is also distributed from the combined metal-air and lithium-ion battery pack system to a drive train by using a controller.
It's not clear how harmful the hot gas coming from a lithium-ion battery would be to the metal-air one, but it likely poses a danger to it. This is the least of anyone's concerns, considering that this patent is a mitigation solution that minimizes risk.
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