A multiscale study on the effect of compression on lithium-ion battery separators

Separators play a vital role within Li-ion batteries. Separators allow rapid Li-ion transport while isolating the cathode and anode to prevent electrical short circuits. Herein, the effects of compression on the mechanical and transport properties of the separator were investigated using a multiscale approach. The microscale domain of the separator was stochastically reconstructed based on the scanning electron microscopy images of a Celgard 2400 membrane. The reconstructed model was then imported to perform explicit dynamic simulations to investigate the mechanical behavior of the separator at different compression ratios. A pore-scale model was employed to calculate the effective transport properties of the deformed models. This was then used in a 3D macroscopic multiphysics model to evaluate the impact of compression on the battery performance. The simulation results revealed the effect of compression on the separator's mechanical properties and battery performance from the microscale to macroscale level. The compression of the separator was found to adversely influence the charging performance of the Li-ion battery. When the compression ratio reaches 40 %, the charging performance of the battery decreased significantly. The present study demonstrates a multiscale approach for investigating the effect of compression on Li-ion battery separators. This is a powerful method for optimizing separators in the future.