Ionic conductivity

Valence (chemistry)

Solid solution

Electrochemistry

Metallurgy

Materials science

Crystal structure

Physical chemistry

Organic chemistry

Monoclinic crystal system

Neutron diffraction

Conductivity

Crystallography

Chemistry

Electrode

Electrolyte

Rietveld refinement

Fast ion conductor

Chemical Engineering Journal

Newly emerging halide superionic conductors with excellent (electro)chemical oxidation stability and deformability are considered as the enabler for high-performance all-solid-state batteries. Compared to close-packed monoclinic Li3InCl6 or Li3ScCl6, despite the same structural framework, the lower ionic conductivity of Li2ZrCl6 is intriguing. Herein, the structural evolution and Li+ migration of aliovalent-substituted Li2ZrCl6 with In3+ (or Sc3+) are investigated. A monoclinic crystal structure over the entire range of substitution (0 ≤ x ≤ 1.0 in Li2+xZr1-xInxCl6) is identified by the Rietveld refinement of neutron diffraction. By the aliovalent substitution, the Li+ conductivity of Li2ZrCl6 is increased drastically from 7.1 × 10-6 to max. 2.1 × 10-3 S cm−1 at 30 °C. It is revealed that the aliovalent substitution results in anisotropic lattice volume expansion and redistribution of Li in the lattice. Specifically, the increased concentration of Li+ in the (0 0 2) plane renders the Li+ migration more favorable. The bond valence energy level calculations also disclose two dimensionally (2D) preferable 3D Li+ migration channels, which emphasizes a tetrahedral Li site in the (0 0 2) plane as the key for facile Li+ migration. Furthermore, the excellent electrochemical performance of all-solid-state batteries using In-substituted Li2ZrCl6 is demonstrated for single-crystalline LiNi0.88Co0.11Mn0.01O2 cathode.

Li+ conduction in aliovalent-substituted monoclinic Li2ZrCl6 for all-solid-state batteries: Li2+xZr1-xMxCl6 (M = In, Sc)