Advancing NASICON-structured solid-state sodium-ion batteries through compositional and interfacial engineering.

NASICON-type ceramics are promising solid electrolytes (SEs) for next-generation solid-state batteries (SSBs), but their practical application is constrained by moderate ionic conductivity and high interfacial resistance. This article reviews recent advancements in overcoming these challenges through a dual strategy: (1) compositional engineering- co-doping NaZrSiPO with Yb/Sc, Ce/Sc, and Mg/Si-to enhance Na conductivity through structural modifications; and (2) interfacial engineering-including wetting agent insertion, composite cathode formation, and the use of infiltrated cathodes-to enlarge interfacial solid-solid contact between cathode and rigid SE and improve electrochemical stability. By integrating these approaches, this work offers a unified framework for the rational design of NASICON-based SSBs. Importantly, SSBs incorporating Mg/Si co-doped NZSP as the SE, a Na metal anode, and an infiltrated cathode achieve high active mass loading (∼2.2 mg cm), with an initial discharge capacity of 103.8 mA h g at 0.2C and 95% retention after 50 cycles. Finally, this article provides a road map outlining key milestones and future research directions for advancing NASICON-based SSB technology.