Numerical Simulation and Validation of Distributed Thermal Runaway Propagation in Lithium-Ion Battery Packs

The contradiction between the widespread application of large-scale module-level lithium-ion batteries and their thermal runaway safety hazards is becoming increasingly prominent. To reveal the propagation laws of thermal runaway in battery modules, this paper takes lithium-ion battery packs as the research object, constructs a multiphysics coupling model, and systematically investigates the effects of single-point and distributed thermal triggering modes as well as battery pack scale on the dynamic response of thermal runaway. The results show that: after thermal runaway is triggered, the system enters a completely uncontrollable stage within 15–20 s; single-point triggering exhibits a single-point initiation—adjacent propagation; under distributed conditions, thermal triggering presents a typical chain propagation cascade effect; and the number of cells and the discharge rate of the battery pack are significantly positively correlated with the thermal diffusion rate. Validation experiments show that after thermal runaway is triggered, the voltage of the lithium battery drops suddenly 15–30 s before the runaway, providing a powerful early warning window. The revealed multiphysics thermal diffusion evolution laws of distributed batteries provide theoretical basis and technical support for the safety design and thermal management optimization of module-level lithium-ion battery systems.