RealizingRoom TemperatureStable Rhombohedral Phase NASICON Electrolyte with High Ionic Conductivitythrough ScF₃ Substitution

NASICON-type (Na₃Zr₂Si₂PO₁₂) electrolytes are regarded as one of the most promising solid-state sodium-ion electrolytes due to their exceptional air stability and extensive electrochemical stability window. Nevertheless, the ionic conductivity still requires further enhancement in comparison to that of a conventional liquid electrolyte. This study presents a strategy to enhance the performance of NASICON electrolytes via ScF₃ substitution. Through the optimization of substitution concentration, a rhombohedral phase NASICON that maintains stability at room temperature was synthesized successfully, attaining an ionic conductivity of 2.1 × 10^–3 S cm^–1. The NVP|NZSP-0.5ScF₃|Na battery, which added 10 μL of liquid electrolyte to wet the NVP/NZSP-0.5ScF₃ interface, achieved a capacity retention of 88.21% (89.74 mA h g^–1) after 5000 cycles at the 5C rate. Even at a 20C discharge rate, the battery sustained 88.78% of its capacity (88.32 mA h g^–1) after 3500 cycles, demonstrating remarkable cycling performance. This work provides a promising approach for the application of solid-state sodium batteries and advances high-performance energy storage technologies.