The invention uses a molten salt composed of two metals. Under electrolysis, the salt separates into the metal components — one of which is lighter than the salt and floats to the top, the other being denser and sinks to the bottom.
Put energy in and the salt separates — the metal layers get thicker and the salt layer gets thinner. Reverse the process to take energy out — salt is formed and the metal layers get thinner.
Supposedly more power density than lithium batteries, and a good match for installing at fixed locations, such as the base of windmills."