context: In general, the solid electrolytes used to develop Na-ion solid state battery systems are based on inorganic solid materials; in particular, oxide-based materials that have high ionic conductivity and are electrochemically and thermally stable are being studied. Among oxide-based materials, Na-β-alumina materials have been mainly studied. Because of their high ionic conductivity, they have been used in all-solid-state batteries until recently. However, they have the disadvantage of being vulnerable to moisture. Another stable oxide-based material is Na3Zr2Si2PO12 (Na super-ionic conductor, NASICON). NASICON solid electrolytes are promising oxide-based Na-ion conducting materials, with a high ionic conductivity of over 10−4 S cm−1 at room temperature and stability to air and moisture. NASICON ceramics are electrochemically stable up to 7 V, making them suitable for use in high voltage batteries. Owing to its stability advantages, efforts have been made to use NASICON in solid-state NIB systems. However, there remains a critical problem in the resistance between solid particle interfaces caused by the fragile and rigid nature of the oxide material itself, regardless of how high the pressure of the solid electrolyte powder is, making it difficult to utilize it in a solid-state battery system.
answer: NASICON