Tuning the interface by a soldering method for high performance garnet-type solid-state Li metal battery

Garnet-type solid electrolytes are promising lithium (Li) ion conductors for all-solid-state batteries. However, their poor compatibilities towards Li metal due to their inherently lithiophobic properties severely hinder their practical application in garnet-based solid-state Li metal batteries (SSLBs). Here, we demonstrated a soldering method to modify the surface of garnet ceramic by forming a thin artificial sulfur layer, which results in a homogeneous and stable Li/solid electrolyte interface. This artificial interface effectively enhances the compatibility between the garnet-type solid electrolyte and the Li metal anode. Consequently, the interfacial resistance of sulfur-coated garnet electrolyte is significantly reduced from 1750 Ω cm2 to 160 Ω cm2 based on the electrochemical impedance spectroscopy (EIS) measurements on Li symmetric cells. Besides, the symmetric cell exhibits an excellent lifetime of more than 1100 h at a steady state of voltage hysteresis, which indicates a stable and dendrite-free garnet/Li metal interface. The fabricated Li|garnet|LiCoO2 SSLB using this novel interfacial treatment delivers a high specific capacity of 126 mAh g−1 and good cycling stability.