Interfacial Contact Mechanics Governing Resistance Evolution in All-Solid-State Batteries

In all-solid-state batteries, the absence of liquid electrolytes eliminates interfacial wetting and adaptive filling, making ionic transport strongly dependent on direct solid–solid contact at electrode–electrolyte interfaces. Due to inherent surface roughness, the real contact area is significantly smaller than the nominal area, leading to pronounced interfacial resistance and nonlinear performance degradation under varying stack pressure and electrochemically induced deformation. To quantitatively describe this behavior, a mesoscopic interface model based on rough contact mechanics is developed, in which the electrode–electrolyte interface is represented as a statistical ensemble of asperities in contact with an elastic substrate. By incorporating asperity height distributions, elastic deformation superposition, and asperity interactions under quasi-static conditions, the model captures the nonlinear evolution of real contact area and interfacial stress as functions of external pressure and chemical strain. The Holm contact resistance model is further employed to establish a physics-based mapping between interfacial contact state and interfacial resistance, which is dynamically updated by embedding the contact model into a coupled electrochemical–mechanical framework. Experimental validation using atomic force microscopy characterization and electrochemical testing under controlled preload pressures demonstrates that interfacial contact resistance dominates Ohmic losses at low pressures and decreases markedly with progressive interfacial compaction, while differences in electrode surface roughness lead to distinct pressure sensitivities. This work establishes a quantitative link between interfacial mechanical evolution and macroscopic battery performance, providing a predictive framework for interface design and stack pressure optimization.