Exploring Aliovalent Substitutions in the Lithium Halide Superionic Conductor Li3–xIn1–xZrxCl6 (0 ≤ x ≤ 0.5)

In recent years, ternary halides Li3MX6 (M = Y, Er, In; X = Cl, Br, I) have garnered attention as solid electrolytes due to their wide electrochemical stability window and favorable room-temperature conductivities. In this material class, the influences of iso- or aliovalent substitutions are so far rarely studied in depth, despite this being a common tool for correlating structure and transport properties. In this work, we investigate the impact of Zr substitution on the structure and ionic conductivity of Li3InCl6 (Li3–xIn1–xZrxCl6 with 0 ≤ x ≤ 0.5) using a combination of neutron diffraction, nuclear magnetic resonance, and impedance spectroscopy. The analysis of high-resolution diffraction data shows the presence of an additional tetrahedrally coordinated lithium position together with a cation-site disorder, both of which have not been reported previously for Li3InCl6. This Li+ position and cation disorder lead to the formation of a three-dimensional lithium-ion diffusion channel, instead of the expected two-dimensional diffusion. Upon Zr4+ substitution, the structure exhibits nonuniform volume changes along with an increasing number of vacancies, all of which lead to increasing ionic conductivity in this series of solid solutions.

近年来，三元卤化物Li3MX6（M = Y、Er、In；X = Cl、Br、I）凭借其宽电化学稳定窗口与优异的室温电导率，作为固体电解质受到广泛关注。这类材料中，尽管同价或异价取代是关联结构与输运性质的常用手段，但目前对其影响的深入研究仍较为匮乏。在本工作中，我们结合中子衍射、核磁共振（Nuclear Magnetic Resonance, NMR）与阻抗谱技术，探究了Zr取代对Li3InCl6结构与离子电导率的影响（对应化学式为Li3–xIn1–xZrxCl6，其中0 ≤ x ≤ 0.5）。对高分辨衍射数据的分析表明，体系中存在额外的四面体配位锂位点与阳离子位点无序现象，这两种特征在此前的Li3InCl6研究中均未被报道。该锂离子位点与阳离子无序共同促成了三维锂离子扩散通道的形成，而非预期的二维扩散路径。随着Zr4+取代量增加，材料体系呈现出不均匀体积变化与逐渐增多的空位，这些因素共同提升了该系列固溶体的离子电导率。