Achievement of high ionic conductivity and electrochemical stability by W/Sn-doped Na3SbS4 conductors designed for all-solid-state sodium-ion batteries†

All-solid-state sodium-ion batteries are emerging as a highly promising substitute for lithium-ion batteries, primarily owing to their rich natural resources and superior safety performance. Solid electrolytes are integral components of all-solid-state batteries and have attracted much attention due to their remarkable safety and chemical stability. This study examines a novel solid electrolyte Na₃(WSn)_xSb_1−2xS₄ by modifying the W/Sn ratio and achieves a high ionic conductivity of 11.3 mS cm⁻² at room temperature. Structural analysis demonstrates that the inclusion of tungsten facilitates the formation of cubic phase Na₃SbS₄ by more sodium vacancies. Furthermore, the co-dopant Sn ensures pure cubic conductors by removing impurities WS₂ and increasing the element solubility. This efficiently enhances the movement of sodium ions and promotes ion transportation. The W/Sn-optimized Na₃SbS₄ (NBS) electrolyte also exhibited stable cycling for about 323 hours, which is about eight times longer than the Na₃SbS₄ base electrolyte. The efficient enhancement of the critical current density demonstrated the improvement of the structural stability at the interface where sodium dendrites formed easily. The formed Na–Sn alloy provides a protective barrier for the normal transport of ions. In addition, the small release of H₂S also proves the stability of the electrolyte structure. These characteristics make it a highly promising electrolyte material for all-solid-state electrolytes.