Fast Li-ion Conductor of Li<sub>3</sub>HoBr<sub>6</sub> for Stable All-Solid-State Lithium–Sulfur Battery

Rare-earth (RE) solid-state halide\nelectrolytes have been extensively\nstudied recently in the field of lithium (Li) ion all-solid-state\nbatteries (ASSBs) due to their excellent electrochemical performances.\nHerein, a new RE-based solid halide electrolyte Li₃HoBr₆ (LHB) has been synthesized and exhibits high Li ion conductivity\nup to mS cm^–1 at room temperature. Theoretical calculations\nhave identified four different Li ion migration pathways, in which\nthe out-of-plane pathways are much more favorable than the direct\nin-plane pathways. In addition, LHB has a wider electrochemical window\nin comparison to a sulfide solid electrolyte and good deformability.\nThe LHB-based Li-sulfur ASSB assembled by cold pressing can exhibit\ngood cycling stability with high Coulombic efficiency, which shows\nthat LHB has potential application in ASSBs.