Bonded Interface Enabled Durable Solid‐state Lithium Metal Batteries with Ultra‐low Interfacial Resistance of 0.25 Ω cm²

Abstract The solid‐state batteries (SSBs) with Li anode present one of the most promising energy storage systems due to their enhanced energy density and safety. However, interfacial problems between Li anode and solid‐state electrolyte hinder the advancement of SSBs. Among them, insufficient solid‐solid interfacial contact is the main issue, which causes large resistance and hinders Li⁺ diffusion, leading to current distribution unevenness and lithium dendrites growth. To meet these challenges, a silver/carbon interlayer composed of ultrafine Ag nanoparticles (≈5 nm) grown on COOH‐CNTs (nano‐Ag@COOH‐CNTs) is constructed. In which, nano‐Ag is designed to guide homogeneous Li deposition, while CNTs substrate bonds with Li_6.5La₃Zr_1.5Ta_0.5O₁₂ (LLZTO) electrolyte by reactions between ─COOH groups and LLZTO alkaline surface, thus transforming loose physical solid‐solid contact to chemical bonding contact. In addition, nano‐Ag is immobilized by CNTs, avoiding the migration of Li⁺ implanted nano‐Ag during cycling. Therefore, nano‐Ag@COOH‐CNTs interlayer can boost Li⁺ transport at LLZTO/Li interface and inhibit Li dendrites, achieving an ultra‐low interfacial resistance of 0.25 Ω cm², a high critical current density of 1.7 mA cm⁻² and a long cycling over 2155 h at 0.5 mA cm⁻². The modified SSBs with LiNi_0.83Co_0.12Mn_0.05O₂ cathode cycles stably over 500 cycles. Moreover, high‐loading SSBs operate stably for 85 cycles.