Affiliation:
1. Department of Chemistry and the Waterloo Institute for Nanotechnology University of Waterloo N2L 3G1 Waterloo Ontario Canada
2. Joint Centre for Energy Storage Research Argonne National Laboratory 60439 Argonne IL USA
3. Physical & Computational Science Directorate Pacific Northwest National Laboratory 99354 Richland WA USA
Abstract
AbstractWe report a new sodium fast‐ion conductor, Na3B5S9, that exhibits a high Na ion total conductivity of 0.80 mS cm−1 (sintered pellet; cold‐pressed pellet=0.21 mS cm−1). The structure consists of corner‐sharing B10S20 supertetrahedral clusters, which create a framework that supports 3D Na ion diffusion channels. The Na ions are well‐distributed in the channels and form a disordered sublattice spanning five Na crystallographic sites. The combination of structural elucidation via single crystal X‐ray diffraction and powder synchrotron X‐ray diffraction at variable temperatures, solid‐state nuclear magnetic resonance spectra and ab initio molecular dynamics simulations reveal high Na‐ion mobility (predicted conductivity: 0.96 mS cm−1) and the nature of the 3D diffusion pathways. Notably, the Na ion sublattice orders at low temperatures, resulting in isolated Na polyhedra and thus much lower ionic conductivity. This highlights the importance of a disordered Na ion sublattice—and existence of well‐connected Na ion migration pathways formed via face‐sharing polyhedra—in dictating Na ion diffusion.
Funder
Office of Science
Natural Sciences and Engineering Research Council of Canada