Li Metal Surface Modification to Stabilize Lithium-Argyrodite Interface for Sulfide-Based All-Solid-State Lithium Metal Batteries

Since the commercialization of lithium-ion batteries, they have faced limitation in safety and energy density. All-solid-state lithium metal batteries (ASSLMBs) can be a solution to address these issues. Among many types of solid electrolytes, sulfide-based solid electrolytes have been attracted great attention because of their high ion conductivity and ductile property. However, many researchers have reported that the interface between lithium metal and solid electrolyte is highly unstable. The lithium dendrite growth can be also occurred in the ASSLMBs by voids, cracks, grain boundaries in solid electrolyte and side reactions between lithium metal and solid electrolyte. Therefore, it is imperative to develop a protective layer that can suppress lithium dendrites and side reactions. In our work, we removed native resistive surface layer formed on pristine lithium metal and reconstructed solid electrolyte interphases (SEI) with uniform, ion-conductive and excellent physical properties by dipping solution containing lithium nitrate in nitromethane and dimethoxyethane. The modified lithium metal is denoted as Li@NDL (lithium @ nitromethane-dimethoxyethane-lithium nitrate). We confirmed that nitromethane reacted with LiOH and Li 2 O on native surface of lithium to form Li 3 N and organic layer, which enhanced ionic conductivity and mechanical strength. The symmetric lithium cell with Li@NDL increased critical current density to 2.8 mA cm -2 and exhibited outstanding cycling stability without short circuit over 1000 hours. ASSLMB comprising Li@NDL anode and 4 mAh cm -2 NCM composite cathode maintained 80% retention after 200th cycles at 0.5 C, demonstrating our work can provide a novel surface modification of lithium metal for ASSLMBs.