Implementation of gas formation into a finite-element model for the mechanical swelling simulation of lithium-ion batteries

Lithium-ion batteries (LIBs) are playing an increasingly vital role in electric vehicles. LIBs are assembled into modules with a preload force to ensure stability and safety. During cycling, battery swelling increases the force within the module. In addition, gas formation, resulting from the battery aging mechanisms, may impact swelling behavior and impair battery performance and safety. While researchers have developed various models to analyze swelling mechanisms, few have considered implementing gas formation into mechanical swelling models. However, the effect of gas formation should not be overlooked, as it has a significant impact on aged batteries. Herein, we implement gas formation into a simplified finite element model to better evaluate the swelling mechanism of LIBs. We found that, for the model of an aged cell with 1900 cycles, it achieves a mean absolute percentage error (MAPE) of 10.24% for force change and 15.12% for thickness change with gas formation (as compared with experimental results), versus the 565.05% for force change and 228.30% for thickness change achieved without gas formation, thus underscoring the critical impact of gas formation on cell swelling mechanisms. These findings suggest that gas formation is a needed consideration in a swelling model to predict a change in battery thickness and swelling-related force fluctuation. The approach in our study is crucial for evaluating the impact of gas on battery mechanical behavior and can be applied to determine the optimal preload force in further investigations. • Gas formation is implemented into a finite-element battery swelling model. • Gas formation contributes to the reduction of battery compression modulus. • Model with gas formation shows higher accuracy for battery swelling behavior than the non-gas model.