Effect of a compressed separator on the electrochemical performance of Li-ion battery

This work investigates the effects of compressed separators on the electrochemical performance of Li-ion batteries (LIBs) and the underpinning mechanisms. Two typical commercial separators (polypropylene (PP) and polyethylene (PE)) with different compressive behaviours were used in this study. The tortuosity values of compressed PP and PE separators were determined using Electrochemical Impedance Spectrum (EIS) tests, showing that the PP separator has a higher tortuosity than that of the PE separator under given compressive stress. LIBs with the compressed PP and PE separators were tested for their capacity performance. It is found that the onset strain of densifications can be considered as the critical compressive strain for the significant reduction of LIB's capacity. The experimental observations are supported by COMSOL modelling results.