Characterization of a Novel Chloride Li-ion Conductor Li₂LuCl₅ (Supporting Information)

Materials with a high Li-ion conductivity and deformability are garnering interest for the facile fabrication of safe all-solid-state batteries with high energy densities. Hence, increasing attention has been focused on Li-containing chloride materials that meet these requirements since they were first reported in 2018 (Asano et al. Advanced Materials 2018, 30 (44), 1803075). In this paper, we report a novel Li-containing chloride of Li₃LuCl₆ with a high Li-ion conductivity (σ_{25 °C} = 3.1 × 10⁻⁴ S cm⁻¹) and sufficient deformability. Furthermore, its defect derivative of Li_3−xLuCl_6−x (x = 1), i.e., Li₂LuCl₅ with a higher Li-ion conductivity (σ_{25 °C} = 5.2 × 10⁻⁴ S cm⁻¹), is synthesized. Scanning electron microscopy confirms the dense packing of both Li₃LuCl₆ and Li₂LuCl₅ as compressed pellets. Hence, Li₂LuCl₅ is presented as a promising solid electrolyte with a high Li-ion conductivity and deformability, which presents a novel opportunity for exploring the composition of Li₂MCl₅ (M: trivalent metal ion) compounds and indicates potential applications as an all-solid-state battery material. Furthermore, as there are no reported cases of high-Li-ion-conductivity chloride materials with the Li₂MCl₅ composition until this work, this study is expected to increase the progress in future studies of LiCl-deficient Li₂MCl₅ compositions with a Li₃MCl₆ composition.