Experimental and numerical studies on the thermomechanical deformation of lithium-ion battery pack housing under thermal runaway propagation condition

Lithium-ion battery can experience the risk of thermal runaway propagation due to various reasons. The emission of high-temperature vent gas from the cell during thermal runaway leads to the build-up of internal pressure and the excessive temperature rise of the mechanical component of the pack, which are the causes of deformation or failure of the structure such as the pack top cover. In this work, the numerical model is developed and validated through the mini-module sized test jig with top cover made of steel. The magnitude of top cover deformation, temperature distributions on the outer surface, and temporal variation of internal pressure are measured simultaneously under thermal runaway propagation condition. Degraded mechanical properties of top cover material at elevated temperatures are measured by tensile coupon tests and applied as input data of the model. It is found that the overall magnitude of the deformation of top cover during thermal runaway propagation is determined by the degree of the initial pressure rise, and the detailed behavior is more sensitive to the local temperature distribution. The present numerical model can capture the dynamic deformation behavior of the top cover with a relatively good accuracy, and highly detailed location-specific temperature and pressure gradient information can improve the accuracy. This research provides novel methodologies of experiment and simulation for the investigation of thermomechanical behavior of battery pack steel housing, and can help further the design of safe and robust pack structure.