Thermal runaway routes of large-format lithium-sulfur pouch cell batteries

Lithium-sulfur (Li-S) batteries emerge as one of the most attractive energy storage systems due to their ultra-high theoretical energy densities, but the pace of their thermal safety assessment is obviously lagging behind. Herein, by investigating the thermal runaway behavior of Li-S pouch cells from the materials level, we unprecedentedly revealed that the thermal runaway route starts from cathode-induced reactions and then gets accelerated by reactions from the anode. Besides, the solvent vaporization is verified to dominate pressure building up during thermal runaway. Moreover, Li-S batteries employing varied electrolytes with different thermal stabilities, even inorganic all solid-state electrolytes, all undergo rapid thermal runaway at a narrow temperature range due to the intrinsic thermal features of the sulfur cathode and Li metal anode sublimating, melting, and cross-reacting at high temperatures. The in-depth depicted thermal runaway routes will deliver great inspiration for mitigating the safety issues of next generation batteries.