Chemomechanically Adaptive MXene–Si–Ag Dual‐Seed Interlayer Enabling Low‐Pressure Sulfide all‐Solid‐State Batteries

ABSTRACT Sulfide‐based all‐solid‐state batteries (ASSBs) promise high safety and energy density; however, sustaining stable operation under low stack pressure remains challenging due to chemo‐mechanical instability at solid‐solid interfaces. Here, we report a chemomechanically adaptive MXene–Si–Ag hybrid interlayer that stabilizes Li metal‐based anode interfaces in sulfide ASSBs. A mechanically compliant MXene framework maintains intimate contact with the sulfide solid electrolyte and accommodates interfacial stress evolution, while immobile Si and mobile Ag function as complementary lithiophilic seeds. Si provides persistent interfacial anchoring and continuous ionic pathways owing to its negligible solubility in Li, whereas Ag dynamically redistributes along Li flux to regulate nucleation and interfacial reaction kinetics. This immobile‐mobile dual‐seed synergy homogenizes Li transport without requiring strict spatial overlap of the seeds. When paired with high‐loading NCM811 cathodes, the interlayer enables an areal capacity of 4.56 mAh cm −2 with 84.5% capacity retention over 500 cycles at 1C under 40 MPa. Notably, stable cycling is preserved even under ultralow stack pressure (0.21 MPa), delivering an initial Coulombic efficiency of 82.7% and 72.4% capacity retention after 200 cycles. This work demonstrates that coupling mechanical adaptability with dynamic lithiophilic regulation provides a practical pathway toward pressure‐tolerant, high‐energy sulfide ASSBs.