Evaluation of the mechanical properties evolution of battery pads due to charging-discharging cycles in prismatic Li-ion battery cells

Swelling force is a critical factor impacting battery capacity and safety degradation. Battery designers utilize battery pads to mitigate the effects of swelling force within the module by absorbing stress and preventing thermal runaway. Battery pad mechanical properties are essential for accurately predicting swelling forces, as certain models incorporate these characteristics. However, no prior research has explored the evolution of the mechanical properties of pads subjected to cyclic loading from the charging and discharging processes of the battery. This study investigates the evolution of mechanical properties in circular silicone foam battery pads subjected to cyclic compression, simulating charging-discharging cycles, at 20°C and 60°C. Samples were cyclically compressed, and strain energy density and tangent modulus were evaluated. Two-way ANOVA analysis of the test results demonstrates that increasing the number of cycles significantly decreases both strain energy density (p < 0.05) and tangent modulus (p < 0.05). The strain energy density decreased exponentially with cycle count, while temperature primarily influenced the tangent modulus only in the elastic region (p < 0.05). Moreover, there is no interaction between the cyclic loading and temperature factors. These findings provide a basis for enhancing swelling force prediction models by incorporating the evolution of pad mechanical properties with cycling and temperature, leading to more robust battery module designs and improved lifespan predictions.