Mechanistic investigation of interfacial stability in composite cathode for all-solid-state batteries

In all-solid-state batteries (ASSBs), the solid-solid interfaces (SSIs) between active particles and solid electrolyte (SE) undergo instability and debonding due to cyclic swelling and contraction of active particles, impairing Li transport within the composite cathode and exacerbating intergranular cracks. However, the mechanistic role of coupled electrochemical–mechanical fields in driving interfacial decohesion and particle rupture remains unresolved. Here, we present an interface collaborative model to investigate the effects of operational pressure, internal pores, open-pore cracks, Young's modulus (E), and Poisson's ratio (v) on the composite cathode. Our simulations reveal a dynamically synergistic evolution of interface debonding and intragranular cracking. Results show that interfacial debonding starts during charging, hindering Li transport between particles and SE. Meanwhile, concentration gradient polarization triggers and exacerbates intergranular cracks in anisotropic primary particles. The synergistic interaction between interfacial debonding and intergranular fracture accelerates battery performance degradation and leads to failure. Quantitative comparisons further indicate that operational pressure and controlled internal defects preserve interface integrity and mitigate stress, while exploring varied combinations of mechanical properties provides valuable guidance for composite cathode material design. This work provides theoretical guidance for elucidating the electrochemical-mechanical failure mechanisms in ASSBs composite cathode and supports the development of more robust composite cathode.