Synthesis of a Li3−xInCl6−x solid electrolyte and its application in all-solid-state batteries

The ionic conductivity and electrochemical stability of Li₃InCl₆ solid electrolytes (SEs) can be enhanced through covalent substitutions of In and Cl. Although the ionic conductivity of Li3InCl6 has been extensively studied, the dynamics of Li ions in these systems have been rarely reported. In this study, Li_3−xInCl_6−x (0 ≤ x ≤ 0.1) SEs were synthesized via planetary ball-milling, followed by heat treatment at 260 °C for 4 h in a dry Ar atmosphere. The structures of the resulting samples were characterized using X-ray diffraction and scanning electron microscopy–energy-dispersive spectroscopy. Crystal structures were confirmed via Rietveld refinement using Fullprof software, and the mean crystallite size was estimated using the Halder–Wagner–Langford plot. Lattice strain was determined using the Williamson–Hall equation. The sample with x = 0.05 exhibited the highest ionic conductivity (4.57 × 10⁻³ Scm⁻¹) at 30 °C. Results show that ion carrier formation is the main barrier to Li ion movement in the Li_3−xInCl_6−x (0 ≤ x ≤ 0.1). Furthermore, an all-solid-state cell with Li_2.95InCl_5.95 SE remained stable after 50 cycles, demonstrating the compatibility of the SE with bare LiNi_0.5Mn_0.3Co_0.2O₂.