Universal Electro-Chemo-Mechanical Interface Engineering toward Dendrite-Free Solid-State Lithium Metal Batteries

Solid-state batteries (SSBs) with lithium metal anodes offer high energy density and safety but are limited by lithium dendrite formation arising from unstable Li/solid electrolyte (SE) interfaces. Here, a universal electro-chemo-mechanical interface engineering strategy is proposed to suppress dendrite growth. Parallel redox reactions between weak acids and lithium release hydrogen, avoiding the formation of electron-conductive species. An in situ formed LiI/Li2O/LiPAA composite interlayer with a graded structure stabilizes sulfide SE interfaces, blocks electron transport, and converts garnet SEs from lithiophobic to lithiophilic, reducing interfacial resistance by an order of magnitude. The interlayer also inhibits dendrite penetration in polymer SEs due to balanced rigidity and flexibility. As a result, uniform lithium deposition is achieved in symmetric and full cells. This work provides fundamental insight into SE interfacial chemistry and demonstrates a broadly applicable strategy for dendrite-free lithium metal SSBs.