Interphase Design Enabling Stable Cycling of All-Solid-state Lithium Metal Batteries by In-Situ X-ray Photoelectron Spectroscopy Lithium Metal Sputtering

Interface compatibility is one of the key issues for all -solid-state lithium metal batteries (ASSLMBs). The interface problems include the formation of lithiophobic phases (e.g., Li 2 CO 3 ) on the surface of the solid electrolytes to worsen the solid -solid interface contact and the continuous parasitic reactions between the highly reactive lithium metal and the electrolyte during cycling. In this work, the in -situ XPS (X-ray Photoelectron Spectroscopy) characterization is used to study the interface between lithium metal and Li 1.5 Al 0.5 Ge 1.5 (PO 4 ) 3 (LAGP) solid electrolyte using different modification strategies. An ultra -thin composite modification layer of 6 nm Au -6 nm LiF is deposited on the LAGP, which is called C-LAGP. The Li|C-LAGP|Li symmetric cell can be stably cycled for more than 800 h at room temperature at the current density of 0.1 mA cm -2 , and the critical current density can reach 1 mA cm -2 . The LiFePO 4 |C-LAGP|Li solid-state battery delivers good cycling stability and high reversible capacity at room temperature. All these good electrochemical performances are resulted from the wellconstructed interfacial structure at the solid electrolyte/Li contact. This work provides new ideas and characterization methods for the design of artificial modification layers to solve the interface issues for all -solid-state lithium metal batteries.