Rational Design of Lamellar Mixed Ion/Electron Conductive Layer for Dendrite-Free Garnet-Based Solid State Batteries

Garnet-based lithium metal solid-state batteries are a promising alternative for next generation energy storage due to it large energy density and high safety. However, the growth of lithium dendrite during the alloying/dealloying process hinders its commercial application. Herein, we construct a high-performance Cu/Li–Ag lamellar mixed ion/electron conductive layer (LMCL) by in situ conversion of Cu/Ag sputtered on the surface of garnet solid electrolyte (Li6.25Ga0.25La3Zr2O12, LGLZO) with metal lithium. It is found that Cu provides uniform charge distribution at the interface, while the Li–Ag alloy improves the interfacial wettability and greatly slows the growth of lithium dendrites. Consequently, the Li|LMCL@LGLZO|Li exhibits a low interface area-specific resistance of only 20.86 Ω cm2 and a high critical current density of 1.85 mA/cm2, and it can stably plated/stripped for over 3000 h at 0.2 mA/cm2. Meanwhile, the Li|LMCL@LGLZO|LiFePO4 full cell showed superior electrochemical performance. This study provides a new reference for designing an interlayer to stabilize solid-state lithium–metal batteries.