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Unraveling the electrolyte properties of Na3SbS4 through computation and experiment

Larry E. Rush, Jr., Zachary D. Hood, and N. A. W. Holzwarth
Physical Review Materials 1 075405 (2017)   (local copy)

Solid-state sodium electrolytes are expected to improve next-generation batteries on the basis of favorable energy density and reduced cost. Na3SbS4 represents a new solid-state ion conductor with high ionic conductivities in the mS/cm range. Here, we explore the tetragonal phase of Na3SbS4 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—Na/Na3SbS4/Na— show that a conductive solid electrolyte interphase forms. Computer simulations infer that the interface is likely to be related to Na3SbS3, involving the conversion of the tetrahedral SbS3−4 ions of the bulk electrolyte into trigonal pyramidal SbS3−3 ions at the interface.