XPS and SEM analysis between Li/Li3PS4 interface with Au thin film for all-solid-state lithium batteries

Li metal is an attractive negative electrode to achieve all-solid-state batteries with high energy density. Interface formation between Li metal and solid electrolytes is a key for the improvement of them. Here, we investigated effects of inserting a gold thin film to the Li/Li3PS4 interface on the structure of the electrolyte and morphology change of Li metal. XPS analysis revealed that Li3PS4 electrolytes in the vicinity of Li metal were partially reduced regardless of the insertion of the Au thin film. The reduced product layer had a low resistance and excellent stability. On the other hand, SEM observation exhibited that the Au thin film between Li metal and Li3PS4 electrolytes prevented void generation after the initial Li dissolution and increased the sites for Li deposition. The more uniform morphology changes of Li metal contributed to the better reversibility of Li utilization for the cell with the Au thin film.