Influence of Reduced Na Vacancy Concentrations in the Sodium Superionic Conductors Na11+ xSn2P1- xMxS12(M = Sn, Ge)
Marvin A. Kraft (Universität Münster)
Lara M. Gronych (Universität Münster)
T. Famprikis (TU Delft - RST/Storage of Electrochemical Energy)
Wolfgang G. Zeier (FZ Jülich, Universität Münster)
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Abstract
Exploration of sulfidic sodium solid electrolytes and their design contributes to advances in solid-state sodium batteries. Such a design is guided by a better understanding of fast sodium transport, for instance, in the herein studied Na11Sn2PS12-type materials. By using Rietveld refinements against synchrotron X-ray diffraction and electrochemical impedance spectroscopy, the influence of aliovalent substitution on the structure and transport in Na11+xSn2P1-xMxS12 with M = Ge and Sn is investigated. Although Sn induces stronger structural changes than Ge, the influence on the sodium sublattice and the ionic transport properties is 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 Na11Sn2PS12 structure type based on their determined properties revealing Na+ vacancy concentrations to be an important factor providing a further understanding of Na11Sn2PS12-type materials.