Sodium ion conductivities in Na₂O–Sm₂O₃–SiO₂ ceramics

Ceramic solid electrolytes are promising candidates for advanced solid-state batteries (SSBs) owing to their good ionic conductivity, wide electrochemical stability window, excellent thermal stability and enhanced safety compared to organic liquid electrolytes. In this study, we developed a series of sodium samarium silicates via a conventional solid-state approach using NaNO₃, Sm₂O₃, and SiO₂ precursor powders. By incorporating varying amounts of NaNO₃, we optimized the ionic conductivity influenced by sodium, and a higher Na content increased the ionic conductivity of silicates to an extent. Among the compositions prepared, N5Sm exhibited the lowest grain boundary resistance and achieved the highest total ionic conductivity of 1.33 × 10⁻³ S cm⁻¹ at 25 °C after being sintered at 975 °C. The best ion conducting composition demonstrated an electronic conductivity of 9.47 × 10−10 S cm⁻¹, seven orders of magnitude lower than the ionic conductivity. These silicates also showed exceptional electrochemical stability up to 9 V, making them highly suitable for advanced high-voltage sodium battery applications. These findings underscore the potential of silicate electrolytes in developing next-generation batteries.