A new study tackled a long-held assumption that adding some liquid electrolyte to improve performance would make solid-state batteries unsafe. Instead, the research team found that in many cases solid-state batteries with a little liquid electrolyte were safer than their lithium-ion counterparts. They also found, if the battery were to short-circuit, releasing all its stored energy, the theoretically super-safe, all-solid-state battery could put out a dangerous amount of heat.