tz9b00322_si_002.cif (6.31 kB)
A New Superionic Plastic Polymorph of the Na+ Conductor Na3PS4
dataset
posted on 2019-11-10, 15:14 authored by Theodosios Famprikis, James A. Dawson, François Fauth, Oliver Clemens, Emmanuelle Suard, Benoit Fleutot, Matthieu Courty, Jean-Noël Chotard, M. Saiful Islam, Christian MasquelierNa3PS4 is one of the most promising Na+ conductors, relevant for applications that can leverage its
high ionic conductivity, such as solid-state batteries. Currently,
two crystalline phases of the material have been identified, and it
has been thought to melt above 500 °C. In contrast, based on diffraction, ab initio simulations,
impedance spectroscopy, and thermal analysis, we show that Na3PS4 remains solid above this temperature and transforms
to a third polymorph, γ, exhibiting fast-ion conduction and
an orthorhombic crystal structure. We show that the fast Na+-conduction is associated with rotational motion of the thiophosphate
polyanions pointing to a plastic crystal. These findings are of major
importance for the development and understanding of new polyanion-based
solid electrolytes.