Metal and nitrogen-including argyrodite solid electrolyte, electrochemical cell including solid electrolyte, and method of preparing solid electrolyte oxide

An all-solid-state secondary battery comprising:

• a cathode layer;
• an anode layer;
• and
• a solid electrolyte layer disposed between the cathode layer and the anode layer,
• wherein, the solid electrolyte layer and the cathode layer comprises a solid electrolyte, and the solid electrolyte comprising a compound represented by Formula 1, and
• the solid electrolyte of the cathode layer has an average particle diameter, which is smaller than an average particle diameter of the solid electrolyte used in the solid electrolyte layer:
• (Li1-aMa)7-d+xPS6-d-x+kNxXd Formula 1
• wherein, in Formula 1,
• M is Na, K, Ca, Fe, Mg, Ag, Cu, Zr, Zn, or a combination thereof,
• X is at least two of CI, Br, F, I, or a pseudohalogen, and
• 0.1≤x≤0.125, 0<a<1, 0<d≤1, and 0≤k<1, and
• wherein the compound has an argyrodite crystal structure.

A method of preparing a solid electrolyte comprising a compound of Formula 1, the method comprising:

• providing a Li precursor, a S precursor, a P precursor, an X precursor, a N precursor, and an M precursor;
• mixing the Li precursor, the S precursor, the P precursor, the X precursor, the N precursor, and the M precursor, to prepare a solid electrolyte precursor;
• and
• heat-treating the solid electrolyte precursor at a temperature equal to or greater than about 300° C. to prepare the solid electrolyte comprising a compound of Formula 1,
• (Li1-aMa)7-d+xPS6-d-x+kNxXd Formula 1
• wherein, in Formula 1,
• M is Na, K, Ca, Fe, Mg, Ag, Cu, Zr, Zn, or a combination thereof;
• X is at least two of CI, Br, F, I, or a pseudohalogen;
• and
• 0.1≤x≤0.125, 0<a<1, 0<d≤1, and 0≤k<1,
• wherein the compound of Formula 1 has an argyrodite crystal structure.