Oxygen-induced thermal runaway mechanisms of Ah-level solid-state lithium metal pouch cells

Solid-state electrolyte is a potential choice to handle the safety risks of lithium mental batteries. However, the thermal stability of solid-state lithium metal batteries at practical working conditions is few explored. We investigated the thermal features of 3.8-Ah lithium-LiNi_0.5Co_0.2Mn_0.3O₂ pouch cells based on Li₆PS₅Cl electrolyte. The solid-state lithium metal battery without thermal runaway is obtained at 0% state-of-charge due to the high thermal stability between lithium and Li₆PS₅Cl. There is significant heat generation between oxygen induced by the decomposition of cathode and Li₆PS₅Cl in the 100% state-of-charge cell after 275.5 °C, which directly leads to the thermal runway. The reaction of electrolytes with cathodes is preferential to that with lithium metal occurring after 302.4 °C. The excellent thermal performance of solid-state lithium metal batteries has been strongly proven benefiting from the intrinsically high thermal stability of lithium metal anode against Li₆PS₅Cl electrolyte and the released oxygen.