In Situ Visualization of Electrochemical Processes in Solid-State Lithium Batteries

Solid-state lithium batteries (SSLBs) are considered one of the most promising energy storage systems due to their high energy density and long-range safety; however, they suffer from severe interfacial issues. To improve the interfacial compatibility and electrochemical performance of SSLBs, it is crucial to investigate the dynamic evolution of electrodes, solid-state electrolytes, and their interfaces in real time during the charge/discharge process and to deeply understand the interfacial mechanism. This review mainly focuses on the key in situ visualization methods, such as scanning probe microscopy, electron microscopy, X-ray microscopy, and optical microscopy, which reveal the evolution of morphology and structure in a working SSLB, including (1) the phase transition of the cathode material and the formation of the cathode/electrolyte interfacial layer; (2) the dynamic evolution of the solid-state electrolyte; and (3) lithium deposition/dissolution at the anode/electrolyte interface, the kinetics of lithium dendrites growth, and the formation of solid electrolyte interphases. It provides straightforward evidence for the interfacial evolution and degradation mechanism in SSLBs, which is beneficial to guide the optimization and improvement of battery materials and electrochemical performance.