Experimental and numerical study of expansion of pouch lithium-ion cell considering electrochemical-thermal-mechanical coupling

Abstract

During the charging and discharging process, the volume expansion change of lithium-ion batteries (LIBs) can cause a series of mechanical damage affecting the state-of-health (SOH) and performance. Therefore, the reasonable monitoring and analyzing the mechanical signal changes of LIBs are key to advancing battery condition monitoring technology. In this study, the changes in the expansion displacement of the battery under different constant current charging and discharging rates are experimentally studied and an electrochemical-thermal-mechanical (ETM) coupling model for battery volume expansion is established. The coupling model innovatively considers the effect of solid electrolyte interphase (SEI) formation and porosity on battery expansion, which can more accurately simulate the battery expansion process at different C-rates. The results show that the cell volume expansion is caused by intercalation reaction, thermal expansion and SEI growth. In addition, the relationship between SEI and expansion displacement is investigated by using $\mathrm{dU}/\mathrm{dQ}$ and $\mathrm{dV}/\mathrm{dQ}$ curves. The expansion displacement caused by SEI formation is calculated by the established model. Finally, the non-uniform distribution of SEI films in space is analyzed. This study is of benefit to understand the factors that lead to battery volume expansion. It also has potential applications in enhancing mechanical signal prediction for LIBs management systems.