First-principles study on electrode-contact chemical stability and Na ion dynamics of Na3SbS4 solid electrolyte for all-solid-state Na ion batteries*

To enhance safety, the replacement of the combustible organic-/liquid-based electrolyte in sodium ion batteries with a ceramic-based solid electrolyte has been sought. In this talk, we present our results on thermodynamic and ion dynamics analyses of Na3SbS4 solid electrolyte using first-principles calculations. Based from the calculated chemical potential diagram when Na3SbS4 is in contact with possible layered cathode compounds Na[TM]O₂ (where TM = {V, Cr, Mn, Fe, Co, Ni}), sulfur has the driving force to migrate across the electrolyte-cathode interface which may partly explain the experimentally observed formation of interface reaction layer in such all-solid state battery interfaces. From space-time correlation analysis of molecular dynamics trajectory, we determined a concerted migration behavior for Na ions which can explain for the material's superionic conductivity behavior (>10^-3 S/cm). The effects of halide doping on the conductivity behavior of Na3SbS4 will also be discussed.