Strategies to Enhance Ionic Conductivity of Na ₃ Zr ₂ Si ₂ PO ₁₂ Solid Electrolyte for Advanced Solid‐State Sodium Batteries

ABSTRACT Solid‐state sodium batteries (SSSBs) have been highly prized as a promising alternative to conventional battery systems using organic liquid electrolytes due to their improved safety, higher energy density, and substantial resources and low cost of sodium. Na ₃ Zr ₂ Si ₂ PO ₁₂ (NZSP) solid electrolyte is attracting considerable interest owing to its excellent thermal and chemical stability and favorable compatibility with Na metal anode and high‐voltage cathode. However, two main challenges of poor room‐temperature ionic conductivity and high interfacial resistance limit the application of NZSP electrolyte in SSSBs. So far, intensive efforts have been devoted to developing modification strategies to improve the room‐temperature ionic conductivity of NZSP. This review aims to provide a comprehensive summary and discussion of some optimization strategies for enhancing the room‐temperature ionic conductivity of the NZSP solid electrolyte. These optimization strategies are categorized into foreign‐ion doping or substitution, sintering behavior modulation, and regulation of chemical composition based on precursors, and their optimization mechanisms are also elaborated. Finally, the prospects of NZSP‐based solid electrolytes are presented. This review is expected to offer better guidance for designing and developing high‐performance NZSP‐based solid electrolytes for accelerating the practical application of SSSBs.