Superionic Conduction in the Plastic Crystal Polymorph of Na4P2S6

Scholz, Tanja; Schneider, Christian; Terban, Maxwell W.; Deng, Zeyu; Eger, Roland; Etter, Martin; Dinnebier, Robert E.; Canepa, Pieremanuele and Lotsch, Bettina V. (2022): Superionic Conduction in the Plastic Crystal Polymorph of Na4P2S6. In: ACS Energy Letters, Vol. 7, No. 4: pp. 1403-1411

Abstract

Sodium thiophosphates are promising materials for large-scale energystorage applications benefiting from high ionic conductivities and the geopoliticalabundance of the elements. A representative of this class is Na4P2S6, which currently showstwo known polymorphs-alpha and beta. This work describes a third polymorph of Na4P2S6,gamma,that forms above 580 degrees C, exhibits fast-ion conduction with low activation energy, and ismechanically soft. Based on high-temperature diffraction, pair distribution functionanalysis, thermal analysis, impedance spectroscopy, andab initiomolecular dynamicscalculations, the gamma-Na4P2S6phase is identified to be a plastic crystal characterized bydynamic orientational disorder of the P2S64-anions translationallyfixed on a body-centered cubic lattice. The prospect of stabilizing plastic crystals at operating temperatures of solid-state batteries, withbenefits from their high ionic conductivities and mechanical properties, could have a strong impact in thefield of solid-statebattery research.

• Item Type: Journal article
• Faculties: Chemistry and Pharmacy > Department of Chemistry
• Subjects: 500 Science > 540 Chemistry
• ISSN: 2380-8195
• Language: English