On the Lithium Distribution in Halide Superionic Argyrodites by Halide Incorporation in Li7−xPS6−xClx
<p>Superionic lithium argyrodites are attractive as solid electrolytes for all-solid-state-batteries. These materials of composition Li<sub>6</sub>PS<sub>5</sub>X (X = Cl, Br, and I) exhibit structural disorder between the X<sup>−</sup>/S<sup>2−</sup> positions, with higher disorder realizing better Li<sup>+</sup> transport. Further replacement of the sulfide by chloride anions (for the series Li<sub>7</sub><sub>−x</sub>PS<sub>6</sub><sub>−x</sub>Cl<sub>x</sub>) has been shown to increase the ionic conductivity. However, the underlying changes to the lithium substructure are still relatively unknown. Here we explore a larger range of nominal halide compositions in this material from x = 0.25 to x = 1.5 and explore the changes with neutron diffraction and impedance spectroscopy. The replacement of S<sup>2−</sup> by Cl<sup>−</sup>causes a lowered average charge in the center of the prevalent Li<sup>+</sup> “cages”, which in turn causes weaker interactions with Li<sup>+</sup> ions. Analysis of neutron diffraction data reveals that the increased Cl<sup>−</sup> content causes these clustered Li<sup>+</sup> “cages” to become more interconnected, thereby increasing Li<sup>+</sup> conductivity through the structure. This study explores the understanding of the fundamental structure–transport correlations in the argyrodites, specifically structural changes withinthe Li<sup>+</sup> ion substructure upon changing anionic charge distribution.</p>