Abstract: In order to improve the use safety of electric vehicle and reveal the mechanism and behavior features of NCM battery runaway in extreme conditions, thermal runaway experiments on an automotive 12 A·h NCM lithium battery under three abuse conditions including over-temperature, overcharge and internal short-circuit are conducted to explore the changes of key parameters such as the voltage and temperature of battery in the course of thermal runaway and comparatively analyze the features of three thermal runaway behaviors. The results show that there is an obvious evolution process of NCM battery thermal runaway, and abnormal changes of battery voltage, which sharply rises suddenly and then sharply fall rapidly, can be taken as the condition to judge the occurrence of thermal runaway caused by overcharge. There is a certain reaction time between the occurrence of overcharge thermal runaway and severely burn out of battery, and under the same conditions, the extents of severity and destruction of overcharge runaway are larger than that of thermal runaway caused by internal short-circuit and over-temperature. In the end, suggestions are given based on experiment results for improving the safety of NCM battery under thermal, electric and mechanical abuse conditions

Key words: electric vehicle, NCM battery, safety, thermal runaway, experimental study