Zn doping for enhanced sodium-ion conductivity and air stability in Na₃SbS₄ solid electrolyte

Solid electrolytes equipped battery show promise in solving energy storage and ecological concerns owing to their excellent electrical conductivity and chemical stability. Only a limited number of substances satisfy the demanding criterion of high ionic conductivity (≥ 10⁻³ S/cm), while using non-toxic elements. In this work, the designed Na_3.3Zn_0.1Sb_0.9S₄ electrolyte, a zinc-doped sodium sulfide ion conductor, with a maximum conductivity of 1.48 × 10⁻³ S/cm under normal conditions, and a low activation energy of 0.128 eV was achieved. This was ruled by substituting low-valence Zinc for antimony in the SbS₄³⁻ cell, maintaining efficient ion transport pathways. Additionally, the electrolyte demonstrated strong air stability under humid conditions and emitted minimal H₂S. The origin of heterovalent ion doping and the impact of thermal effects on electrochemical performance were discussed in detail, which were crucial to promote the development of sodium-ion solid electrolytes.