Lithium ion-conducting sulfide-based solid electrolyte containing selenium and method for preparing the same

A method for preparing a lithium ion-conducting sulfide-based solid electrolyte containing selenium comprising:

• preparing a mixture comprising lithium sulfide (Li2S), diphosphorus pentasulfide (P2S5) and lithium halide (LiX);
• and
• grinding the mixture,
• wherein the grinding of the mixture is carried out by adding selenium (Se) and simple-substance phosphorus to the mixture to substitute a part of sulfur elements by a selenium element, as shown in the following Formula 1:
• Li6PS5-aSeaX [Formula 1]
• wherein X is at least one halogen element selected from the group consisting of fluorine (F), chlorine (Cl), bromine (Br) and iodine (I) elements;
• and
• a satisfies 0<a<3.