SOLID ELECTROLYTE SEPARATOR, ALL-SOLID SECONDARY BATTERY INCLUDING THE SAME, AND METHOD OF MANUFACTURING THE SOLID ELECTROLYTE SEPARATOR

Provided are a solid electrolyte separator, an all-solid secondary battery including the same, and a method of manufacturing the solid electrolyte separator, the solid electrolyte separator including a sulfide-based solid electrolyte and a composite of LiS and a lithium salt, wherein the composite of LiS and the lithium salt is represented by LiS-LiX where 1≤a≤5 and 1≤b≤5, and X is I, Br, Cl, F, H, O, Se, Te, N, P, As, Sb, Al, B, OCl, PF, BF, SbF, AsF, ClO, AlO, AlCl, NO, CO, BH, SO, BOs, PO, NCl, NCl, BN, or a combination thereof.