Mitigating overcharge induced thermal runaway of large format lithium ion battery with water mist

Thermal runaway (TR) is one of the ringleaders of lithium ion battery (LIB) hazard, which has become a major safety concern. Especially to the large-scale LIBs, the TR has been intensified owing to the expanded capacity. Hence, effective countermeasures are urgently needed. In this study, the cooling control capacity of water mist (WM) on mitigating the overcharge induced TR for large-scale LIB is experimentally studied. The thermal hazard processes with and without WM have been comprehensively investigated. Results show that the battery flame experiences rapid increasing process from 0.02 m to 0.9 m, which intensifies the inhomogeneity of temperature distribution. The total heat accumulation of the LIB reaches 1971.0 kJ, over 80% of which is generated after TR. A critical inflection point during TR development has been identified, where the WM has been introduced to successfully suppress the TR. For cases with continuous overcharge current, the occurrence of TR is unstoppable, but the hazard has been significantly mitigated with the maximum temperature decreases to 122.1 degrees C, and over 1000 kJ heat has been dissipated during WM release. This work confirms the excellent cooling capacity of WM on the large-scale LIB, and the overcharge induced TR can be effectively mitigated.