Excellent sodium ion conductivity and air stability of manganese-substituted Na3SbS4 solid electrolytes

Abstract

Solid electrolytes are promising candidates for addressing energy and environmental problems due to their excellent electrical conductivity and extremely high safety. To date, only a few alternative materials can meet the high ionic conductivity requirements of at least ≥1 mS cm⁻¹ when using nontoxic and economical elements. For the first time, we report an Mn-doped sodium sulfide ion conductor Na_3.24Mn_0.08Sb_0.92S₄ that shows a maximum conductivity of 2.05 × 10⁻³ S cm⁻¹ at 25 °C. In its sulfide superionic conductor structure, the antimony in the SbS₄³⁻ cell is replaced with manganese with a low valence state, maintaining a good transport pathway and accelerating ion transport. This electrolyte exhibits good air stability in a humid environment and minimal H₂S release. Moreover, its ionic conductivity is almost unchanged after the conductor is stored at room temperature for many days, which is crucial for promoting the development of sodium ion solid electrolytes. The stability of the conductor and sodium metal has also been evaluated, further studying its potential for practical applications.