In situ Microscopy Techniques for Understanding Li Plating and Stripping in Solid-State Batteries

Solid-state batteries have potential to realize a rechargeable Li metal anode. However, several challenges persist in the charging and discharging processes of the Li metal anode, which require a fundamental understanding of Li plating and stripping across the interface of solid-state electrolytes to address. This review overviews studies on Li metal anodes in solid-state batteries using in situ observation techniques with an emphasis on Li electrodeposition and dissolution using scanning electron microscopy (SEM) and solid electrolytes (SEs) such as lithium phosphorus oxynitride (LiPON) and garnet-type compounds such as Li7La3Zr2O12 (LLZ). Previous research is categorized into three topics: (1) Li nucleation, growth, and dissolution at the anode-free interface, (2) Electrochemical reduction of SE, and (3) Short-circuit phenomena in SE. The current trends of each topic are summarized.