Development of a P2D-based model for battery swelling prediction under mechanical constraints

Lithium-ion batteries (LIBs) for electric vehicles are typically assembled into modules with mechanical constraints that exert external pressure on individual cells to improve stability and performance. During operation, battery swelling behavior under mechanical constraint generates external pressure fluctuation that can lead to structural degradation, including electrode cracking, separator deformation, and accelerated side reactions. This ultimately increases the risk of safety issues such as internal short circuits and thermal runaway. While existing battery simulation models provide insights into the mechanisms of battery swelling, many overlook the influence of external mechanical pressure. However, these effects should not be overlooked, as they impact the behavior of battery swelling. In this study, we present a pseudo-two-dimensional (P2D) model which integrates lithium ion transport dynamics with pressure-dependent parameters to enable swelling prediction of LIBs under mechanical constraints without requiring real-time sensors during operation. We found that the model predicts cell thickness changes during 1C discharge at 0.164 MPa with a mean absolute percentage error (MAPE) of 6.87% compared to experimental results. These findings bridge the gap in predicting changes in cell thickness under mechanical constraints. The approach in our study is crucial for the safety assessment of mechanically constrained battery systems.