Recent advance on NASICON electrolyte in solid-state sodium metal batteries

Because of the low cost, reliable safety, and desirable energy density, all-solid-state sodium metal batteries have already been recognized as promising alternative to commercial lithium-ion batteries. The research and development of sodium super ionic conductor (NASICON)-structure electrolytes well matching metallic Na anode and high-voltage sodium ion cathodes, are quite meaningful for all-solid-state sodium metal batteries. In this review, the characteristics of Na₃Zr₂Si₂PO₁₂-based ceramic electrolytes, including structural features, conduction mechanism, and the strategies for further elevating the conductivity of NASICON are well summarized. Moreover, the interfacial issues within the Na/NASICON/cathode solid-state batteries are elaborately discussed. At the same time, the challenges and approaches for fixing these interfacial issues between Na₃Zr₂Si₂PO₁₂-based ceramic electrolytes and solid electrodes are also reviewed. Additionally, we also summarize the expanded utilization of Na₃Zr₂Si₂PO₁₂ such as inorganic fillers of composite polymer electrolytes and ionic conductive additives to composite cathode. Finally, the challenges and the future research directions for expediting the practical application of Na₃Zr₂Si₂PO₁₂-based all-solid-state sodium metal batteries are put forward.