Effects of ambient temperature and convective heat transfer coefficient on the thermal–gas–mechanical coupling behavior of LiFePO4 batteries during thermal runaway

This study establishes a multiphysics model coupling thermal, gas, and mechanical behaviors for a prismatic LiFePO 4 battery. The influences of ambient temperature and convective heat transfer coefficient on thermal runaway (TR) characteristics, internal pressure evolution, gas generation, and expansion force response are systematically investigated. It is found that higher ambient temperature or lower heat transfer coefficient accelerates temperature rise and increases the maximum temperature. Kinetic analysis reveals that the early exothermic stage is primarily governed by SEI decomposition and the anode–electrolyte reaction, with side reaction rates reaching earlier and higher peaks at higher ambient temperatures or lower heat transfer coefficients. Internal pressurization is initially dominated by electrolyte vapor and subsequently by reaction gases. Accordingly, venting occurs earlier at higher ambient temperatures or lower heat transfer coefficients. With a fixed venting threshold, such conditions enhance the contribution of electrolyte vapor while reducing the accumulation of reaction gases at venting. The total expansion force is governed primarily by internal pressure. Using an expansion force rise rate of 5 N/s as the warning threshold, the warning lead time relative to venting increases at higher ambient temperatures or lower heat transfer coefficients.