Regulating the Interfacial\nPerformance of All-Solid-State\nSodium Batteries Using Lanthanum Substitution in a Na<sub>3</sub>Zr<sub>2</sub>Si<sub>2</sub>PO<sub>12</sub> Solid Electrolyte

The main issues currently facing solid-state batteries\nare the\nlow ionic conductivity of solid electrolytes and high interfacial\nresistance. By employing a doping strategy to introduce La<sup>3+</sup> into the Na<sub>3</sub>Zr<sub>2</sub>Si<sub>2</sub>PO<sub>12</sub> solid electrolyte increases the ionic conductivity to as high as\n1.1 mS cm<sup>–1</sup>, promotes Na<sub>3</sub>La(PO<sub>4</sub>)<sub>2</sub> interphase formation, and enhances interfacial charge\ntransfer and cycling stability. The anode interfacial resistance of\nthe Na<sub>3.1</sub>Zr<sub>1.9</sub>La<sub>0.1</sub>Si<sub>2</sub>PO<sub>12</sub> electrolyte decreased to 75 Ω cm<sup>2</sup> at room temperature, merely one-fourth smaller than that of Na<sub>3</sub>Zr<sub>2</sub>Si<sub>2</sub>PO<sub>12</sub>. Moreover, Na<sub>3.1</sub>Zr<sub>1.9</sub>La<sub>0.1</sub>Si<sub>2</sub>PO<sub>12</sub> achieves superior stable sodium plating/stripping cycling over 1800\nh, and its performance exceeds that of most reported sodium solid\nelectrolytes. A solid-state Na<sub>3</sub>V<sub>2</sub>(PO<sub>4</sub>)<sub>3</sub>/Na<sub>3.1</sub>Zr<sub>1.9</sub>La<sub>0.1</sub>Si<sub>2</sub>PO<sub>12</sub>/sodium battery is assembled, demonstrating\nstable cycling performance with 84.5% capacity retention after 750\ncycles. The enhancement of ionic conductivity in the solid electrolyte\nand the improvement of anode interfacial wettability have facilitated\nthe advancement of solid-state sodium batteries.