Influence of Reduced Na Vacancy Concentrations in the Sodium Superionic Conductors Na_11+xSn₂P_1–xM_xS₁₂ (M = Sn, Ge)

Abstract

Exploration of sulfidic sodium solid electrolytes and their design contributes to advances in solid state sodium batteries. Such design is guided by a better understanding of fast sodium transport, for instance in the herein studied Na 11 Sn 2 PS 12 -type materials. By using Rietveld refinements against synchrotron X-ray diffraction and electrochemical impedance spectroscopy, the influence of aliovalent substitution onto the structure and transport in Na 11+x Sn 2 P 1−x M x S 12 with M = Ge and Sn is investigated. Whereas Sn induces stronger structural changes than Ge, the found influence on the sodium sublattice and the ionic transport properties are comparable. Overall, a reduced in-grain activation energy of Na + transport can be found with the reducing Na + vacancy concentration. This work explores previously unreported phases in the Na 11 Sn 2 PS 12 structure type that, based on their determined properties reveal Na + vacancy concentrations to be an important factor guiding further understanding within Na 11 Sn 2 PS 12 -type materials. File list (2) download file view on ChemRxiv manuscript.pdf (1.80 MiB) download file view on ChemRxiv Supporting Information.pdf (2.83 MiB)

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