Experimental validation and numerical analysis of cyclic mechanical damage in composite electrodes of all-solid-state lithium-ion batteries

Recent advances in lithium-ion battery technology have renewed attention to cyclic mechanical damage in electrodes, driven by diffusion-induced stresses (DIS) during lithiation–delithiation cycles that compromise both safety and capacity. In this work, electrode degradation under coupled electrochemical–mechanical conditions is conceptualized as a fatigue process, characterized by (i) the complex interplay among electrochemical reactions, species diffusion, and stress evolution, and (ii) stress–strain hysteresis governed by cumulative fatigue damage. A finite element electrode model was developed in COMSOL Multiphysics, and a systematic workflow was established to implement the proposed fatigue assessment methodology. Validation against experimental data confirms the model’s predictive ability for progressive fatigue damage accumulation. A strategy is also introduced to connect electrochemically measured degradation with underlying mechanical fatigue mechanisms. Following parameterization, cycling tests and fatigue simulations at different C-rates were performed to further validate the approach. For LiFePO 4 (LFP) electrodes, experimental cycling results were used to parameterize the fatigue model, which was then applied in numerical simulations to elucidate diffusion effects and stress–strain evolution during electrochemical degradation. The simulations indicate that electrode regions adjacent to the separator are particularly susceptible to crack initiation under cyclic operation. Overall, this study demonstrates the applicability of mechanical fatigue theory for characterizing and predicting the gradual failure of composite battery electrodes subjected to repeated electrochemical cycling.