Configurational and Dynamical Heterogeneity in Superionic Li_5.3PS_4.3Cl_1.7−xBr_x

Abstract

The correlation between lattice chemistry and cation migration in high‐entropy Li+ conductors is not fully understood due to challenges in characterizing anion disorder. To address this issue, argyrodite family of Li+ conductors, which enables structural engineering of the anion lattice, is investigated. Specifically, new argyrodites, Li5.3PS4.3Cl1.7−xBrx (0 ≤ x ≤ 1.7), with varying anion entropy are synthesized and X‐ray diffraction, neutron scattering, and multinuclear high‐resolution solid‐state nuclear magnetic resonance (NMR) are used to determine the resulting structures. Ion and lattice dynamics are determined using variable‐temperature multinuclear NMR relaxometry and maximum entropy method analysis of neutron scattering, aided by constrained ab initio molecular dynamics calculations. 15 atomic configurations of anion arrangements are identified, producing a wide range of local lattice dynamics. High entropy in the lattice structure, composition, and dynamics stabilize otherwise metastable Li‐deficient structures and flatten the energy landscape for cation migration. This resulted in the highest room‐temperature ionic conductivity of 26 mS cm−1 and a low activation energy of 0.155 eV realized in Li5.3PS4.3Cl0.7Br, where anion disorder is maximized. This study sheds light on the complex structure–property relationships of high‐entropy superionic conductors, highlighting the significance of heterogeneity in lattice dynamics.

Enhanced Ion Conduction via a Diverse Cl-PS4 Anion Lattice in Li3PS4–xLiCl

“…High-performance SSBs rely on state-of-the-art solid electrolytes to enable rapid ion conduction. Recent research on Li-argyrodites has showcased how fine-tuning the anion substructures can lead to enhanced Li + -ion conduction, − opening a promising avenue for improving Li + ion conductivity in other materials. Among the thiophosphates, Li 3 PS 4 has garnered substantial attention, leading to the development of various novel solid electrolytes, such as crystalline Li 10 P 3 S 12 I, Li 7 P 2 S 8 I, Li 7 P 2 S 8 X (X = I, Br), Li 15 P 4 S 16 Cl 3 , Li 3 PS 4 -LiBr, and Li 3 PS 4 -LiI .…”