Thermal Runaway Behavior of Li 6 PS 5 Cl Solid Electrolytes for LiNi 0.8 Co 0.1 Mn 0.1 O 2 and LiFePO 4 in All-Solid-State Batteries

All-solid-state batteries (ASSBs) have received much attention because of their high energy density and safety. However, the safety of argyrodite-type Li 6 PS 5 Cl (LPSCl)-based ASSBs is still not assured because their thermal stability has been assessed under selected mild conditions. Herein, we introduce the poor thermal stability of LPSCl with Ni-rich layered oxide cathode materials as the trigger of thermal runaway. The charged composite cathode pellets containing Li 1– x Ni 0.8 Co 0.1 Mn 0.1 O 2 and LPSCl are explosively burned at 150 °C even in Ar. Moreover, the mechanical abuse gives rise to violent burning at room temperature. This is due to vigorous exothermic chemical reactions between delithiated Li 1– x Ni 0.8 Co 0.1 Mn 0.1 O 2 and LPSCl. However, LPSCl with LiFePO 4 exhibits excellent thermal stability, such as no violent exothermic reactions even at 350 °C. This is because …