Research progress of inorganic sodium ion conductors for solid-state batteries

For large-scale energy storage devices, all-solid-state sodium-ion batteries (SIBs) have been revered for the abundant resources, low cost, safety performance and a wide operating temperature range. Na-ion solid-state electrolytes (Na-ion SSEs) are the critical parts and mostly determine the electrochemical performance of SIBs. Among the studied ones, inorganic Na-ion SSEs stand out for their good safety performance and high ionic conductivity. In this review, we outline the research progress of inorganic SSEs in SIBs based on the perspectives of crystal structure, performance optimization, synthesis methods, all-solid-state SIBs, interface modification and related characterization techniques. We hope to provide some ideas for the design of future high-performance Na-ion SSEs.