Origin of Superionic Li<sub>3</sub>Y<sub>1–<i>x</i></sub>In<sub><i>x</i></sub>Cl<sub>6</sub> Halide Solid Electrolytes with High Humidity Tolerance
Xiaona Li, Jianwen Liang, Keegan R. Adair, Junjie Li, Weihan Li, Feipeng Zhao, Yongfeng Hu, Tsun‐Kong Sham, Li Zhang, Shangqian Zhao, Shigang Lu, Huan Huang, Ruying Li, Ning Chen, Xueliang Sun
Abstract
The high ionic conductivity, air/humidity tolerance, and related chemistry of Li3MX6 solid-state electrolytes (SSEs, M is a metal element, and X is a halogen) has recently gained significant interest. However, most of the halide SSEs suffer from irreversible chemical degradation when exposed to a humid atmosphere, which originates from hydrolysis. Herein, the function of the M atom in Li3MX6 was clarified by a series of Li3Y1–xInxCl6 (0 ≤ x < 1). When the ratio of In3+ was increased, a gradual structural conversion from the hexagonal-closed-packed (hcp) anion arrangement to cubic-closed-packed (ccp) anion arrangement has been traced. Compared to hcp anion sublattice, the Li3MX6 with ccp anion sublattice reveals faster Li+ migration. The tolerance of Li3Y1–xInxCl6 towards humidity is highly improved when the In3+ content is high enough due to the formation of hydrated intermediates. The correlations among composition, structure, Li+ migration, and humidity stability presented in this work provide insights for designing new halide-based SSEs.