Characterization of a Novel Chloride Li-ion Conductor Li<sub>2</sub>LuCl<sub>5</sub>

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 (σ25 °C = 3.1 × 10 -4 S cm -1 ) and sufficient deformability.Furthermore, its defect derivative of Li3-xLuCl6-x (x = 1), i.e., Li2LuCl5 with a higher Li-ion conductivity (σ25 °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.