Lithium-metal batteries — which can hold up to 10 times more charge than the lithium-ion batteries that currently power our phones, laptops and cars — haven’t been commercialized because of a fatal flaw: as these batteries charge and discharge, lithium is deposited unevenly on the electrodes. This buildup cuts the lives of these batteries too short to make them viable, and more importantly, can cause the batteries to short-circuit and catch fire.