Chemomechanical modeling of lithiation-induced failure based on strain gradient plasticity theory

• A porous electrode model coupling the electrochemical reaction with strain gradient plasticity is developed. • A failure mechanism diagram is constructed considering the damage and crack. • This model could predict the damage and fracture of the electrode interface. Porous silicon (Si) anodes in lithium-ion batteries (LIBs) experience significant diffusion-induced stress gradients during electrochemical cycling, leading to crack propagation and active material pulverization. To systematically predict such failure behaviors, this study proposes a chemo-mechanical coupling framework by integrating strain gradient plasticity (SGP) theory with damage mechanics. The theoretical model explicitly resolves the interplay among lithiation kinetics, dislocation-mediated plasticity, and progressive damage accumulation in porous Si structures. Finite element method (FEM) simulations reveal the spatiotemporal evolution of lithium concentration fields, stress-strain distributions, and microcrack patterns. Parametric analyses identify critical structural parameters (e.g., pore radius, porosity) governing stress localization and interfacial delamination. Additionally, this work constructs a quantitative failure mechanism diagram that correlates state-of-charge (SOC), porosity, and pore geometry with fracture thresholds. The diagram offers actionable guidance for optimizing electrode architectures to mitigate stress-induced degradation in high-capacity LIB anodes.