li ions

ion exchange

lithium

ionic conductivity

li ion

state lithium batteries

conductivity cm

solid electrolyte

Chemical Engineering Journal

• In 3+ -substituted Li 2 ZrCl 6 shows a maximum conductivity of 2.1 mS cm −1 at 30 °C. • The monoclinic structure of Li 2+x Zr 1-x M x Cl 6 (0 ≤ x ≤ 1) with a space group of C2/m . • 2D-preferable 3D Li + diffusion channels disclosed by neutron diffraction analysis. • Excellent performance of all-solid-state batteries employing Li 2.5 Zr 0.5 In 0.5 Cl 6 . 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 Li 3 InCl 6 or Li 3 ScCl 6 , despite the same structural framework, the lower ionic conductivity of Li 2 ZrCl 6 is intriguing. Herein, the structural evolution and Li + migration of aliovalent-substituted Li 2 ZrCl 6 with In 3+ (or Sc 3+ ) are investigated. A monoclinic crystal structure over the entire range of substitution (0 ≤ x ≤ 1.0 in Li 2+x Zr 1-x In x Cl 6 ) is identified by the Rietveld refinement of neutron diffraction. By the aliovalent substitution, the Li + conductivity of Li 2 ZrCl 6 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 Li 2 ZrCl 6 is demonstrated for single-crystalline LiNi 0.88 Co 0.11 Mn 0.01 O 2 cathode.

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