Exploring Aliovalent Substitutions in the Lithium Halide Superionic Conductor Li3-xIn1-x ZrxCl6 (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.

Automated summary

This study delves into the impact of Zr substitution on the structure and ionic conductivity of Li3InCl6, revealing new lithium positions and cation disorder, and confirming an increase in ionic conductivity in the solid solution series due to Zr substitution. The findings demonstrate nonuniform volume changes and an increasing number of vacancies induced by Zr substitution.