Tin Interlayer at the Li/Li3PS4 Interface for Improved Li Stripping/Plating Performance

Li metal is a promising negative electrode material for the development of all-solid-state batteries with high energy densities. However, the short-circuiting of batteries owing to Li dendrite formation is challenging. To solve this issue, it is crucial to form a suitable interface between the Li metal and solid electrolyte. This study demonstrates that the incorporation of a Sn interlayer at the interface between the Li metal and Li3PS4 (LPS) electrolyte improved the Li stripping/plating performance of all-solid-state Li symmetrical cells. The cycling performance was further enhanced by replacing pure Li metal with a Li–Mg alloy. Galvanostatic cycling tests were conducted on a symmetrical cell of Li–Mg/Sn/LPS/Sn/Li–Mg at a current density of 1.0 mA cm–2 and a temperature of 100 °C. The operation of the cell was stable for 5000 h without short-circuiting. X-ray diffraction (XRD) and scanning electron microscopy (SEM) revealed that Sn film incorporation into the Li or Li–Mg/LPS interface suppressed the reductive LPS decomposition and maintained a stable interface. These findings will facilitate the development of interfacial modifications between Li metal and sulfide solid electrolytes to enhance the cycling performance of all-solid-state Li metal batteries.