Experimental study on the internal pressure evolution of large-format LiFePO4 battery during thermal runaway

The safety problems of lithium-ion batteries, such as fire and explosion, have become the main issues constraining the rapid development of electrochemical energy storage. This paper proposes a new method to obtain the internal pressure and gas components of battery under adiabatic condition. Subsequently, the internal pressure evolution of a fully charged 300 Ah LiFePO4 (LFP) cell during thermal runaway (TR) are analyzed. At the temperature of safety venting (SV), the internal peak pressure recorded is 412 kPa and the gas release of H2 and CO are 35.2 % and 23.7 %, respectively. Basing on the analysis, the gas release temperature calculated by internal pressure is about 5 K lower than self-generated heat temperature. Before SV, the electrolyte volatilization and gas releasing are decoupled, and the gas release is about 0.009 mol. The internal pressure evolution of battery can be divided into three stages. At stage C, the gas release which cause SV account for 43.97 % of the gas volume and the reactions releasing H2 and CO gas are the prime chemical reason for SV. These results are of great significance to the setting of early warning system and the emergency response to TR.