Numerical analysis on the combustion and explosion characteristics of lithium-ion battery vent gases based on a skeletal mechanism

The accidental ignition of flammable gases generated after thermal runaway of lithium-ion battery (LIB) is a direct cause of battery fire or explosion accidents. In this work, the combustion and explosion characteristics of LIB vent gases were analyzed numerically. A skeletal mechanism (25 species, 145 reactions) was proposed to simulate the combustion of LIB vent gases. Three typical accident scenarios of LIB vent gases were investigated. First, the morphology, temperature and distribution of free radicals of LIB vent gases jet flame were analyzed. It demonstrated that the high temperature zone was consist of pyrolysis of CH₃ and reaction of OH. Then, the characteristic of LIB vent gases flame propagation in pipeline was investigated. The highest flame velocity was about 20.4 m/s and the highest overpressure was about 0.595 MPa. The results suggested that the intensity and thickness of distribution of free radicals was decreasing with the flame propagation process. Furthermore, the explosion process of LIB vent gases in energy storage container was explored. The maximum explosion overpressure was about 23 kPa, because the venting of pressure relief panels and door could greatly decrease the overpressure. The maximum distance of damage caused by the explosion pressure was about 10 m.