Quantifying the solid electrolyte interphase stress induced capacity fading of lithium-ion batteries via a multiscale mechanical-electrochemical coupling model

The solid electrolyte interphase (SEI) is widely recognized as a critical factor leading to the capacity fading of lithium-ion batteries (LIBs). Although SEI stress-related mechanical failure caused by the expansion or contraction of active materials upon cycles is well documented, previously reported SEI components and overpotential varying phenomena due to SEI stress and their effects on the electrochemical performance are poorly understood. Here, we establish a quantitative correlation between capacity fading and the SEI stress by considering its effects on side reactions, especially SEI component evolution, in a multiscale mechanical-electrochemical coupling model. Furthermore, the capacity fading behaviors of two typical cells (Li[NiMnCo]O₂ as the cathode, and graphite and silicon as the anode, respectively) were adopted as numerical examples to demonstrate its potential utility and applications. Stress within the SEI was indeed found to play a predominant role in the capacity fading of the graphite and silicon anodes, resulting in 27% and 69% of the total capacity loss after 200 and 100 cycles at 1 C, respectively. This study provides valuable mechanical insights into the variations of SEI properties related to the capacity degradation and SEI optimization and design for LIBs.