High ionic conductivity of multivalent cation doped Li₆PS₅Cl solid electrolytes synthesized by mechanical milling

The performances of next generation all-solid-state batteries might be improved by using multi-valent cation doped Li₆PS₅Cl solid electrolytes. This study provided solid electrolytes at room temperature using planetary ball milling without heat treatment. Li₆PS₅Cl was doped with a variety of multivalent cations, where an electrolyte comprising 98% Li₆PS₅Cl with 2% YCl₃ doping exhibited an ionic conductivity (13 mS cm^-1) five times higher than pure Li₆PS₅Cl (2.6 mS cm^-1) at 50 °C. However, this difference in ionic conductivity at room temperature was slight. No peak shifts were observed, including in the synchrotron XRD measurements, and the electron diffraction patterns of the nano-crystallites (ca. 10-30 nm) detected using TEM exhibited neither peak shifts nor new peaks. The doping element remained at the grain boundary, likely lowering the grain boundary resistance. These results are expected to offer insights for the development of other lithium-ion conductors for use in all-solid-state batteries.