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Influence of Lattice Polarizability on the Ionic Conductivity in the Lithium Superionic Argyrodites Li 6 PS 5 X (X = Cl, Br, I)

DOI: 10.1021/jacs.7b06327 DOI Help

Authors: Marvin A. Kraft (Justus-Liebig-University Giessen) , Sean P. Culver (Justus-Liebig-University Giessen) , Mario Calderon (Michigan State University) , Felix Böcher (Justus-Liebig-University Giessen) , Thorben Krauskopf (Justus-Liebig-University Giessen) , Anatoliy Senyshyn (Technische Universität München) , Christian Dietrich (Justus-Liebig-University Giessen) , Alexandra Zevalkink (Michigan State University) , Jürgen Janek (Justus-Liebig-University Giessen) , Wolfgang G. Zeier (Justus-Liebig-University Giessen)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Journal Of The American Chemical Society

State: Published (Approved)
Published: July 2017
Diamond Proposal Number(s): 13560

Abstract: In the search for novel solid electrolytes for solid-state batteries, thiophosphate ionic conductors have been in recent focus owing to their high ionic conductivities, which are believed to stem from a softer, more polarizable anion framework. Inspired by the oft-cited connection between a soft anion lattice and ionic transport, this work aims to provide evidence on how changing the polarizability of the anion sublattice in one structure affects ionic transport. Here, we systematically alter the anion framework polarizability of the superionic argyrodites Li6PS5X by controlling the fractional occupancy of the halide anions (X = Cl, Br, I). Ultrasonic speed of sound measurements are used to quantify the variation in the lattice stiffness and Debye frequencies. In combination with electrochemical impedance spectroscopy and neutron diffraction, these results show that the lattice softness has a striking influence on the ionic transport: the softer bonds lower the activation barrier and simultaneously decrease the prefactor of the moving ion. Due to the contradicting influence of these parameters on ionic conductivity, we find that it is necessary to tailor the lattice stiffness of materials in order to obtain an optimum ionic conductivity.

Subject Areas: Chemistry, Materials

Instruments: I15-Extreme Conditions