Configurational and Dynamical Heterogeneity in Superionic Li5.3PS4.3Cl1.7−xBrx

• Published in: Advanced functional materials 2023-12, Vol.33 (51), p.n/a
• Main Authors: Wang, Pengbo, Patel, Sawankumar, Liu, Haoyu, Chien, Po‐Hsiu, Feng, Xuyong, Gao, Lina, Chen, Benjamin, Liu, Jue, Hu, Yan‐Yan
• Format: Article
• Language: English
• Subjects: Anions; Cations; Conductors; Dynamic structural analysis; Heterogeneity; high entropy; Ion currents; Ion migration; lattice dynamics; Materials science; Maximum entropy method; mixed anion; Molecular dynamics; Neutron scattering; Neutrons; NMR; Nuclear magnetic resonance; Resonance scattering; solid‐state nuclear magnetic resonance; Structural engineering; superionic conductors
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.202307954

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. This study explores Li+ conductors in the argyrodite family, uncovering how anion lattice chemistry affects cation migration. The results reveal anion sublattices of high chemical and structural disorder enhance PS43− re‐orientation, leading to fast Li+‐ion conduction with low activation energy barriers via correlated Li+‐PS43− motion.