Sc-doping in Na3Zr2Si2PO12 electrolytes enables preeminent performance of solid-state sodium batteries in a wide temperature range

Solid-state sodium batteries (SSSBs) display great potential in scale energy storage for their safety, cost and sustainability. However, it is a great challenge to achieve high ionic conductivity and temperature adaptability for most sodium-ion solid electrolytes. Here, we first demonstrate that Sc 3+ -doped Na 3 Zr 2 Si 2 PO 12 (NASICON) is a promising electrolyte for a wide temperature range utilizing in SSSBs from 0 to 80 °C. Optimal Na 3.4 Zr 1.6 Sc 0.4 Si 2 PO 12 shows a superior Na-ion conductivity, up to 1.77 × 10 −3  S cm −1 at room temperature, and excellent Na metal compatibility, as confirmed by a symmetrical cell test. Furthermore, the solid-state sodium battery with the configuration of Na 3 V 2 (PO 4 ) 3 /Na 3.4 Zr 1.6 Sc 0.4 Si 2 PO 12 /Na maintains a discharge capacity of 98.7 mAh g −1 at 1C after 300 cycles at room temperature. Even at 0 °C, the battery still displays a reversible capacity of 99.2 mAh g −1 at 0.1C after 100 cycles. Through the structure analysis and ex-situ and in-situ electrochemical characterizations, the reasons that dominate the excellent performance of the assembled all-solid-state sodium battery with NASICON electrolytes are initially revealed.