A Review of Modification Methods of Solid Electrolytes for All‐Solid‐State Sodium‐Ion Batteries

All‐solid‐state sodium‐ion battery (ASSIB) is a promising new energy storage device due to the excellent thermal stability, low flammability, high impermeability and nonvolatility, as well as riskless fire and explosion properties. The solid electrolyte plays a core role in the ASSIBs to determine their electrochemical performance. Herein, close attention is paid to effective approaches to improve the performance of solid electrolytes, including ion doping and substitution, composite method, coating method, crystal transformation method, ceramization and vitrification, etc. In particular, electrochemical window, ionic conductivity, electrochemical stability, and structural stability are also reviewed. The future development of solid electrolytes and the possible directions for improving the properties of the ASSIBs in practical applications are also prospects. This review will guide the development of solid electrolytes for the ASSIBs in future.