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.