In Situ Lithiophilic Layer from H⁺/Li⁺ Exchange on Garnet Surface for the Stable Lithium-Solid Electrolyte Interface

Garnet-type solid-state electrolytes (SSEs) show a promising application in solid-state Li batteries. Poor interfacial contact with lithium causing large interfacial impedance and dendrite penetration is a problem. Inspired by unique H⁺/Li⁺ exchange of garnet electrolyte, we used an AgNO₃ aqueous solution induced strategy to construct a lithiophilic layer in situ on the garnet surface without any specific apparatus. Experimental analysis reveals the uniform distribution of Ag nanoparticles and significantly enhanced affinity between the solid state electrolyte (SSE) and Li anode for the Li-Ag alloying. As expected, the interfacial area specific resistance (ASR) is greatly reduced to ∼4.5 Ω cm², accompanying with long-cycling stability for ∼3500 h at 0.2 mA cm^-2 and high critical current density of 0.75 mA cm^-2. With modified SSEs, quasi-solid-state batteries with a LiFePO₄ or LiNi_0.5Co_0.2Mn_0.3O₂ cathode operate well at room temperature and an all-solid-state LiFePO₄/garnet/Li battery displays good cycling stability for over 200 cycles at 60 °C.