Experimental study of the cooling effect of water mist on 18650 lithium-ion battery at different initial temperatures

The depletion of fossil fuels has led to the rapid development of environmentally friendly lithium ion battery (LIB). However, exposure of LIB to elevated temperatures frequently leads to battery failure, thermal runaway (TR), or even TR propagation. In this study, a series of experiments are conducted on the LIBs with and without water mist at different initial temperatures (50 °C and 106–206 °C) in a novel designed battery module to investigate the cooling effect of water mist. The results show that water mist reduces the possibility of battery failure and inhibits TR. The critical temperature of TR is enhanced by 36 °C. Moreover, using water mist to suppress the TR propagation requires reducing the temperature of a cell that undergoing TR to below 126 °C. Analysis of cooling rate indicates that there are four cooling modes ((Ⅰ) rapid cooling and quasi-steady state, (Ⅱ) rapid cooling and slow cooling, (Ⅲ) transitional stage, and (Ⅳ) rapid heating and rapid cooling) of water mist. The heat absorbed by water mist is distinct in four cooling modes. These results reveal that water mist has better cooling effect and the cooling mode changes with the increase of temperature, which may provide insight into the thermal safety performance of cells.