Mechano-Electrochemical Coupling Enabled by Triple-Gradient Interface Engineered Garnet for Durable All-Solid-State...

All-solid-state lithium metal batteries are promising for next-generation energy storage but remain limited by interfacial instability arising from coupled electrochemical and mechanical failures. Here, we propose a triple-gradient interface engineering strategy to resolve this challenge by simultaneously regulating chemical functionality, mechanical compliance, and lithium-ion transport across inorganic-organic interfaces. Garnet-type Li_6.4La₃Zr_1.4Ta_0.6O₁₂ (LLZTO) is transformed into a hierarchical core-bridging-coordinating architecture through sequential adhesion, covalent bridging, and adaptive polymerization. A polydopamine-derived adhesion layer enhances polymer affinity, a silane-mediated bridging layer passivates surface Li₂CO₃ and mitigates interfacial stress, and an outer poly(dioxolane) shell provides dynamic Li⁺ coordination and stress buffering. The resulting triple-gradient composite electrolyte exhibits a high ionic conductivity of 2.62 × 10^-4 S cm^-1 at 60°C and a Li⁺ transference number of 0.86. Symmetric Li‖Li cells cycle stably for over 2400 h, while full cells deliver excellent long-term stability, demonstrating an effective mechano-electrochemical regulation paradigm for durable solid-state lithium metal batteries.