Abstract: In order to explore the composition and concentration changes of smoke during thermal runaway propagation, three commonly used cylindrical ternary lithium-ion batteries with different diameters (10440 type, 14500 type and 18650 type) were used as experimental objects, and the influence mechanisms of battery energy density and different states of charge on the composition of smoke components and the corresponding total amount of generation during thermal runaway propagation were analyzed. The results show that the maximum value of gas mass generation basically corresponds to the peak temperature point at which each cell reaches thermal runaway, the trends of acidic non-flammable gas concentration curves such as HF and HCl are basically similar, and the trends of relatively flammable gas mass concentration curves such as NO2, NH3, N2O and CO are basically similar. The flammable NO2, NH3, N2O and CO in the thermal runaway propagation process of lithium batteries gas composition during the thermal runaway propagation of lithium-ion battery is positively correlated with the thermal runaway propagation duration, while non-flammable acidic gases such as HCl and HF are positively correlated with the battery energy density and state of charge. Finally, the prediction model of acidic gas generation during the thermal runaway propagation of the battery is derived by the linear coefficient fitting method.

Key words:  ternary lithium-ion battery, smoke component, energy density, SOC, thermal runaway propagation time