Unraveling the electrolyte properties of Na3SbS4 through computation and experiment

Abstract

Solid-state sodium electrolytes are expected to improve next-generation batteries on the basis of favorable energy density and reduced cost. ${\mathrm{Na}}_{3}{\mathrm{SbS}}_{4}$ represents a new solid-state ion conductor with high ionic conductivities in the mS/cm range. Here, we explore the tetragonal phase of ${\mathrm{Na}}_{3}{\mathrm{SbS}}_{4}$ and its interface with metallic sodium anode using a combination of experiments and first-principles calculations. The computed Na-ion vacancy migration energies of 0.1 eV are smaller than the value inferred from experiment, suggesting that grain boundaries or other factors dominate the experimental systems. Analysis of symmetric cells of the electrolyte---${\mathrm{Na}/\mathrm{Na}}_{3}{\mathrm{SbS}}_{4}/\mathrm{Na}$---show that a conductive solid electrolyte interphase forms. Computer simulations infer that the interface is likely to be related to ${\mathrm{Na}}_{3}{\mathrm{SbS}}_{3}$, involving the conversion of the tetrahedral ${\mathrm{SbS}}_{4}^{3\ensuremath{-}}$ ions of the bulk electrolyte into trigonal pyramidal ${\mathrm{SbS}}_{3}^{3\ensuremath{-}}$ ions at the interface.