Study on the Effectiveness of Water Mist on Suppressing Thermal Runaway in LiFePO4 Batteries

Lithium-ion batteries experience rapid temperature increases with a high risk of combustion and explosion during thermal runaway, and water mist has been considered as one of the most effective cooling strategies. The water mist field can be impacted by the safety valve airflow, subsequently affecting the cooling characteristics. In this paper, the water mist nozzle with a fixed working pressure is located 1 m above the 100 Ah LiFePO4 battery to suppress the thermal runaway, and the cooling characteristics under various stages have been compared and analyzed. The results show that the development of thermal runaway can be inhibited before thermal runaway is initiated, and the water mist presents a better cooling effect after the battery safety valve is opened. The critical accumulation heat density of 155 kJ/kg has been identified, which is the threshold for thermal runaway suppression. The confrontation between water mist and the flame has been analyzed, and the water mist droplets cannot fall on the battery surface, resulting in a poor cooling rate of 0.57 kW. This means the suppression effect of water mist will be affected by the airflow impact of the safety valve.