Effects of Halogen and Sulfur Mixing on Lithium-Ion Conductivity in Li 7– x – y (PS 4 )(S 2– x – y Cl x Br y ) Argyrodite and the Mechanism for Enhanced Lithium Conduction

作者：Naoya Masuda, Kiyoshi Kobayashi, Futoshi Utsuno, Tetsuo Uchikoshi, Naoaki Kuwata · 发表于：The Journal of Physical Chemistry C · 年份：2022 · DOI：10.1021/acs.jpcc.2c03780 · 被引用次数：28 · 研究领域：Advanced Battery Materials and Technologies、Advancements in Battery Materials、Chemical Synthesis and Characterization

All-solid-state lithium-ion batteries containing phosphorus sulfides are promising next-generation batteries because they have higher energy densities than their liquid-electrolyte counterparts. Halogen-rich argyrodites, Li 7−α (PS 4 )(S 2−α X α ) (X = Cl, Br, I; α > 1), exhibit higher ionic conductivities than other phosphorus sulfides; varying the content of a single anion enables halogen substitution. However, there is no appropriate model for the ion-conducting path in these argyrodites. Herein, we discuss a range of composition maps to explain the lithium-ion conductivity of Li 7– x – y (PS 4 )(S 2– x – y Cl x Br y ) ( x + y > 1). The ionic conductivities (∼11.6 mS/cm) of Li 5.4 (PS 4 )(S 0.4 Cl 1.0 Br 0.6 ) and Li 5.4 (PS 4 )(S 0.4 Cl 0.6 Br 1.0 ) are among the highest reported. Bond valence sum mapping and maximum entropy methods for Li 7– x – y (PS 4 )(S 2– x – y Cl x Br y ) ( x + y > 1) were used. The results showed that these argyrodites have a lithium-cage structure surrounding the halide or sulfide ions at the 4d sites and a lithium-ion-conduction path between the cages via an interstitial site (16e). The degree of disorder of chloride, bromide, and sulfide ions on the 4a and 4d sites controls the conduction path length between the cages; a short lithium-ion-conduction path between the cages enhances lithium-ion conductivity. These results could inspire the development of halogen-rich compositions of Li 7−α (PS 4 )(S 2−α X α ) (α > 1) with enhanced ionic conductiv...