Abstract: Sodium ion batteries have become a research hotspot in the field of energy storage due to their low cost and relatively high energy density. However, traditional liquid-state electrolytes have potential safety hazards such as leakage and flammability, and it is urgent to develop stable and reliable solid-state electrolytes. In this study, a series of Na_3+xZr_2-xY_xSi₂PO₁₂ (x=0, 0.05, 0.10, 0.15) solid-state electrolytes were prepared by Y³⁺ heterovalent doping Na₃Zr₂Si₂PO₁₂ to improve its compactness, ionic conductivity, and interface stability. The samples were analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results show that the appropriate amount of Y³⁺-doping (x=0.10) significantly improves the density (91.93%) and room temperature ionic conductivity (8.91×10^-4 S·cm^-1) of NASICON-type Na₃Zr₂Si₂PO₁₂ without destroying the crystal structure. The Y³⁺-doped samples have smaller interface polarization voltage and impedance growth rate, showing excellent interface stability. The solid-state sodium battery assembled based on Na_3.10Zr_1.90Y_0.10Si₂PO₁₂ has a capacity retention rate of 98.55% after 100 cycles at 0.1 C at room temperature. This study reveals the synergistic regulation of Y³⁺-doping on crystal structure and interface behavior, which provides an important reference for the design and interface optimization of sodium ion solid-state electrolyte materials.

Key words: NASICON-type solid-state electrolyte, Na₃Zr₂Si₂PO₁₂, Y³⁺-doping, sodium-ion conductivity, crystal structure regulation, interface stability, solid-state sodium battery