Enhancing Cycling Stability of All‐Solid‐State Batteries With 3D‐Architectured Interfaces via Controlled Yield Stress and Internal Stress Relaxation

During charge–discharge cycling, irreversible volume changes in all‐solid‐state batteries (ASSBs) impair electrode–electrolyte contact and elevate interfacial resistance, necessitating several MPa of external pressure. However, such high‐pressure conditions hinder commercialization, underscoring the need for interfacial engineering strategies to ensure stable operation under low‐pressure conditions. This study shows that 3D microscale interfacial architectures significantly enhance the cycling stability of ASSBs. The structure is fabricated through sequential imprinting with polymer molds, a free‐standing sulfide electrolyte membrane, and the formation of mechanically stable interfaces. The symmetric cell with 3D interfaces maintains stable cycling up to 600 h, outperforming that with flat interfaces (400 h). The full cell exhibits improved electrochemical performance with enhanced capacity and retention. Microstructural analysis after long‐term cycling reveals continuous and rigid interfaces in 3D interfacial cell. A finite element model simulation demonstrates that out‐of‐plane stresses are relaxed to in‐plane directions, thereby accommodating electrode expansion/contraction. The impedance distribution of relaxation times quantitatively confirms that the resistance increases of the 3D interfacial cell during cycling are smaller than those observed for flat interfacial cell, both for the charge transfer resistance (from 1275.12 to 2679.81 Ω vs. from 2177.44 to 6486.42 Ω) and diffusion‐related resistance (from 28.46 to 104.21 Ω vs. from 33.02 to 153.79 Ω).