Uncovering LiH Triggered Thermal Runaway Mechanism of a High‐Energy LiNi 0.5 Co 0.2 Mn 0.3 O 2 /Graphite Pouch Cell

Abstract The continuous energy density increase of lithium ion batteries (LIBs) inevitably accompanies with the rising of safety concerns. Here, the thermal runaway characteristics of a high‐energy 5 Ah LiNi 0.5 Co 0.2 Mn 0.3 O 2 /graphite pouch cell using a thermally stable dual‐salt electrolyte are analyzed. The existence of LiH in the graphite anode side is innovatively identified in this study, and the LiH/electrolyte exothermic reactions and H 2 migration from anode to cathode side are proved to contribute on triggering the thermal runaway of the pouch cell, while the phase transformation of lithiated graphite anode and the O 2 ‐releasing from cathode are just accelerating factors for thermal runaway. In addition, heat determination during cycling at two boundary scenarios of adiabatic and isothermal environment clearly states the necessity of designing an efficient and smart battery thermal management system for avoiding heat accumulation. These findings will shed promising lights on thermal runaway route map depiction and thermal runaway prevention, as well as formulation of electrolyte for high energy safer LIBs.