LAUSR

Summary The influence of interfaces represents a critical factor affecting the use of solid-state batteries (SSBs) in a wide range of practical industrial applications. However, our current understanding of this key issue remains somewhat limited. Therefore, this review presents the mechanisms and advanced characterization techniques associated with interfaces in SSBs. First, we compare liquid- and solid-state batteries and emphasize the challenges in solid-solid interfaces. Second, we discuss different aspects of interfaces including interphase formation, cathode-electrolyte interface, anode-electrolyte interface, and interparticle interface, which contain a detailed description of the formation mechanisms and current research. Third, the characterization strategies for effective interfacial observation and analysis are summarized and discussed. In particular, two unique characterization techniques, vibrational sum-frequency generation spectroscopy and on-chip single-nanowire battery characterization, are highlighted. Lastly, we summarize the scientific issues associated with solid-solid interfaces and provide our perspectives to better understand the fundamental issues and improve the performance of SSBs.