Study of thermal runaway and the combustion behavior of lithium-ion batteries overcharged with high current rates

•The thermal runaway characteristics of high current rate overcharged 18,650 lithium-ion batteries were studied.•The thermal runaway processes of lithium-ion batteries were recorded by infrared and visible light cameras.•The combustion and explosion law of two times of thermal runaway was studied.•The higher the current rate, the more intense the thermal runaway reaction of lithium battery. Overcharged lithium-ion batteries can experience thermal runaway that can cause spontaneous combustion or an explosion. By measuring the heat release rate, surface temperature, flame temperature, positive and negative electrode temperature and mass loss of 18650 NCM lithium-ion battery, the combustion and explosion characteristics of lithium-ion battery under different current rates were analyzed. The results show that the 18650 lithium-ion battery undergoes two thermal runaway behaviors when overcharge at a high current rate. The first thermal runaway leads to a continuous explosion reaction, while the second thermal runaway has a combustion and explosion reaction that is more violent than the first thermal runaway. As the current rate increases from 1 C to 3 C, the time for the first thermal runaway to occur decreases from 1554 to 360 s, the time for the second thermal runaway to occur decreases from 2515 to 522 s, and the explosive response becomes more violent. : [Display omitted]