The investigation of thermal runaway propagation of lithium-ion batteries under different vertical distances

The time of safety valve cracks and thermal runaway propagation are influenced seriously by vertical distance and the stage of charge (SOC). In this study, a series of experiments with four lithium-ion batteries has been finished to evaluate the fire hazards by in situ calorimeter. The temperature of safety valve crack is inversely proportional to the SOC. For upper batteries of 0, 50 and 100% SOC, the safety valve was not cracked at 3, 5 and 8 cm, respectively. The safety valve crack time is an exponential function of distance for 50% and 100% SOC. The SO2 can be obviously found under a high temperature for the fully charged batteries.