Interface issues and challenges for NASICON-based solid-state sodium-metal batteries

All-solid-state sodium (Na)-metal batteries (ASSSMBs) are considered promising candidates for large-scale energy storage systems due to their abundant sodium resources, unparalleled safety performance, and impressive energy density. Na superionic conductors (NASICONs) are among the best enablers of ASSSMBs in view of their high ionic conductivity, ease of synthesis, and excellent thermal stability and good electrochemical/chemical compatibility with common electrodes. However, challenges surrounding the NASICON/electrode interface, such as high interfacial resistance and dendrite formation, have hindered the development of practical ASSSMBs based on NASICONs. This review starts with an explicit summary of the interface problems between the metallic Na anode and NASICON arising from mechanical, chemical, and electrochemical aspects (i.e., poor interface contact, insulating side-reaction products, and irregular dendrite growth). Subsequently, we systematically analyze and logically categorize modification strategies for addressing anode interface problems and provide a comprehensive discussion on the underlying enhancement mechanisms. As such, we identify underlying and universal interface enhancement mechanisms by comparatively studying various modification strategies. Furthermore, we briefly summarize the challenges in the cathode/electrolyte interface and early-stage research efforts in constructing stable cathode/electrolyte interface and fabricating high-performance composite cathodes. Finally, key suggestions and future prospectives for the advancement of NASICON-based ASSSMBs are outlined.