Thermal runaway and fire behavior investigation of lithium ion batteries using modified cone calorimeter

The lithium ion battery has been widely used, but it has high fire risk due to its flammable materials. In this study, a series of combustion tests are conducted on the 18650-type lithium ion batteries using the modified cone calorimeter. The temperature and voltage variation of the battery, heat release rate and gas generation during combustion are measured in this study. The battery is heated evenly by the self-made heater, and the reliable trigger temperatures of thermal runaway are obtained for different states of charge (SOCs) batteries in this study. The fire behavior of the 100% SOC batteries is shown in this paper. The net heat absorption by the battery before thermal runaway is calculated based on the heat transfer theory. It ranges from 56.81 to 64.05kJ for 0 to 100% SOC batteries, which shows a decreasing trend as SOC increases. The peak combustion heat release rate of 100% SOC batteries is 3.747 +/- 0.858kW. CH4 and CO gases are detected before and after thermal runaway. The generation of CO shows an increasing trend as SOC increases. Some suggestions on the early warning system of battery thermal runaway are proposed based on this study.