Research progress on the interfaces of solid-state lithium metal batteries

Solid-state lithium metal batteries (SSLMBs) with the advantages of brilliant safety, superior energy density, and improved thermal stability are regarded as one of the most promising energy storage devices. However, intrinsic defects of the solid-solid rigid interface, such as insufficient wettability and compatibility manifesting as poor interfacial contact, side reactions, space charge layer (SCL) effect, etc., lead to a rapid degradation in interfacial stability. This yields unsatisfactory electrochemical performance of SSLMBs. In this review, the origin of inferior stability and kinetics on solid-solid interfaces are first clarified. Second, recent achievements in stabilizing the interfacial stability using an interfacial buffer layer, composite electrode, liquid phase therapy, etc. are summarized from the physical and chemical/electrochemical aspects. In particular, issues related to electrode-electrolyte interfaces such as lithium dendrites, SCL effect, deficient physical contact, and parasitic reactions are emphasized. Finally, remaining challenges such as the degradation mechanism, advanced characterization techniques, and commercialization, as well as future development directions, are prospected. This review will provide certain new insights for formulating target-oriented studies on high-performance SSLMBs.