Molten-salt battery

Molten-salt batteries (including liquid-metal batteries) are a class of battery that uses molten salts as an electrolyte and offers both a high energy density and a high power density. Traditional "use once" thermal batteries can be stored in their solid state at room temperature for long periods of time before being activated by heating. Rechargeable liquid-metal batteries are used for electric vehicles and potentially also for grid energy storage, to balance out intermittent renewable power sources such as solar panels and wind turbines.

For comparison, LiFePO₄ lithium iron phosphate batteries store 90–110 Wh/kg, and the more common LiCoO₂ lithium-ion batteries store 150–200 Wh/kg. A nano lithium-titanate battery stores 72 Wh/kg and can provide a power of 760 W/kg.

Thermal batteries originated during World War II when German scientist Georg Otto Erb developed the first practical cells using a salt mixture as an electrolyte. Erb developed batteries for military applications, including the V-1 flying bomb and the V-2 rocket, and artillery fuzing systems. None of these batteries entered field use during the war. Afterwards, Erb was interrogated by British intelligence. His work was reported in "The Theory and Practice of Thermal Cells". This information was subsequently passed on to the United States Ordnance Development Division of the National Bureau of Standards. When the technology reached the United States in 1946, it was immediately applied to replacing the troublesome liquid-based systems that had previously been used to power artillery proximity fuzes. They were used for ordnance applications (e.g., proximity fuzes) since WWII and later in nuclear weapons. The same technology was studied by Argonne National Laboratories in the 1980s for use in electric vehicles.

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