Thermal runaway propagation behavior and cooling effect of water mist within a 18650-type LiFePO4 battery module under different conditions

Abstract

The thermal runaway (TR) propagation behavior of lithium-ion batteries (LIBs) and mitigation strategies to suppress TR of LIBs have gained significant attention. This study conducted a series of tests to investigate the TR propagation behavior of LiFePO4 battery modules arranged in a one-dimensional linear arrangement and a square configuration. The influence of flames on the TR propagation was analyzed. Furthermore, the cooling effects of water mist (WM) on single cells and battery modules at different stages of TR were explored. Flaming combustion could induced more cells to TR and significantly accelerate the propagation speed of TR. The mitigation effect of WM on the TR propagation is notable, however, as TR progresses, the duration of WM required to prevent TR or completely cool the cells increases. Under the same water usage conditions, intermittent WM releases significantly extend the low-temperature duration of the cells, enhancing the cooling effectiveness. This work provides essential guidance for ensuring process safety and designing fire protection measures for 18650-type LiFePO4 battery systems.