Preparation method for solid electrolyte, solid electrolyte prepared thereby, and all-solid-state battery comprising same

A method for preparing an alkali metal ion-conductive chalcogenide-based solid electrolyte, which comprises:

• (1) preparing a first precursor solution in which a precursor of an alkali metal ion-conductive chalcogenide-based solid electrolyte is completely dissolved in a polar aprotic solvent;
• (2) adding an alkali metal or an alkali metal-containing material to the first precursor solution to prepare a slurry in which a second precursor is dispersed;
• (3) recovering the second precursor in a powder form from the slurry;
• and
• (4) thermally treating the second precursor powder.