Recent Progress in Oxide‐Based Na‐Ion Conductors

Oxide‐based sodium‐ion conductors are gaining renewed interest as solid electrolytes for all‐solid‐state sodium batteries, owing to their intrinsic safety, chemical stability, and abundance of constituent elements. This review highlights recent progress in key material families: β / β″ ‐alumina, NASICON‐type compounds, and Na 5 YSi 4 O 12 ‐type (N5) silicates. NASICON materials have achieved room temperature ionic conductivities approaching ~1 × 10 −2 S cm −1 , rivaling those of sulfide‐based electrolytes, while maintaining compatibility with cosintering processes. N5‐type silicates have also emerged as promising candidates, reaching mid‐10 −3 S cm −1 range at room temperature through compositional tuning and controlled processing. These advances have been complemented by progress in scalable fabrication techniques such as tape casting. Perovskite‐ and layered‐type multifunctional sodium‐ion conductors are also being explored. The review further discusses critical design considerations such as electrochemical stability, sinterability, and interfacial compatibility, which are essential for enabling practical all‐solid‐state battery technologies based on oxide electrolytes.