Under development since 2017, this liquid metal battery (LMB) is about to be let loose on the globe. Consisting of 3 liquid layers; 2 of molten metals and a middle layer of molten salts. The system is self-heating and insulated, but contains no combustible materials - so they can't burn. And they retain all of their charge capacity for at least 5000 cycles (think decades, not years). Modular, safer and cheaper than lithium-ion batteries.