The Impact of Relaxation Time on Cell Degradation across the Life Cycle under diverse operating temperatures

This work investigates the effect of relaxation periods within cyclic tests on the degradation phenomenon of a lithium-ion cell. Conventionally, it is believed that the rest period improves the cell performance; for example, providing rest periods after discharge and charge periods improves the overall cyclic life. However, in this study, it is observed that relaxation periods have varied effects on individual degradation phenomena - solid electrolyte interphase (SEI) layer growth and lithium plating. Moreover, even the placement of rest periods within a charge-discharge cycle impacts the capacity fade differently. Simulations are carried out on the pseudo-2D model of the LGM50 21700 cylindrical cell at diverse ambient temperatures to validate the rest period behavior at different operating conditions. Our simulations reveal the intricate interplay between relaxation periods and cell degradation corresponding to different ambient temperatures. The reliability of the pseudo-2D model utilized in this work is ensured by performing experimental validation within the laboratory under a controlled environment.