Influence of Reduced Na Vacancy Concentrations in the Sodium Superionic Conductors Na11+xSn2P1−xMxS12 (M = Sn, Ge)

Abstract

<p>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<sub>11</sub>Sn<sub>2</sub>PS<sub>12</sub>-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<sub>11+<i>x</i></sub>Sn<sub>2</sub>P<sub>1−<i>x</i></sub><i>M<sub>x</sub></i>S<sub>12</sub> with <i>M</i> = 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<sup>+</sup> transport can be found with the reducing Na<sup>+</sup> vacancy concentration. This work explores previously unreported phases in the Na<sub>11</sub>Sn<sub>2</sub>PS<sub>12</sub> structure type that, based on their determined properties reveal Na<sup>+</sup> vacancy concentrations to be an important factor guiding further understanding within Na<sub>11</sub>Sn<sub>2</sub>PS<sub>12</sub>-type materials.</p>

Facilitating Layered Oxide Cathodes Based on Orbital Hybridization for Sodium‐Ion Batteries: Marvelous Air Stability, Controllable High Voltage, and Anion Redox Chemistry

“…[194,195] Moreover, the complex anionic redox presence of oxygen release, multiphase transitions, slow kinetics, etc., can be mitigated by selecting elemental substitutions with high covalency (e.g., Li/Mg/Zn/Cu/Ti) and forming a stable superstructures as well as introducing vacancies in the structure. [196][197][198] Nowadays, SIBs has a huge opportunity for large-scale energy storage because of its low cost and enormous storage capacity. In order to better understand the potential of discovering sodium layered oxide cathodes, the air stability, phase transition, orbital hybridization methods and electrochemical characteristic of some representative layered oxide cathodes are shown in Table 1.…”