Solid electrolyte, preparation method thereof, and all-solid-state battery employing the same
The present disclosure provides a solid electrolyte including an oxysulfide-based compound represented by Li a P b M c S d O e X (Formula 1) and having excellent stability against moisture, a method of manufacturing the solid electrolyte, and an all-solid-state battery showing superior manufacturing processability. In Formula 1, M is one selected from a group consisting of Zr, Nb, Hf, Ta, Ga, In, Ti, Pb, Bi, Ge, As, Sb, Si, B, Al, and a combination thereof. X is one selected from a group consisting of F, Cl, Br, and I. Also, 6<a≤7, 0<b<1, 0<c<1, 4<d<5, and 0<e<1.
1. A solid electrolyte comprising an oxysulfide-based compound represented by
Li a P b M c S d O e X (Formula 1)
wherein M is one selected from a group consisting of Zr, Nb, Hf, Ta, Ga, In, Ti, Pb, Bi, Ge, As, Sb, Si, B, Al, and a combination thereof,
wherein X is one selected from a group consisting of F, Cl, Br, and I,
wherein 6<a≤7, 0<b<1, 0<c<1, 4<d<5, and 0<e<1.
2. The solid electrolyte of claim 1 , wherein M is Si, Al, B, Ge, or a combination thereof.
3. The solid electrolyte of claim 1 , wherein M is Si.
4. The solid electrolyte of claim 1 , wherein X is CI or Br.
5. The solid electrolyte of claim 1 , wherein 6<a≤6.5, 0.5b<1, 0<c≤0.5, 4.5≤d<5, and 0<e≤0.5.
6. The solid electrolyte of claim 1 , wherein 6<a≤6.3, 0.7≤b≤0.9, 0.1≤c≤0.3, 4.6≤d≤4.8, and 0.2≤e≤0.4.
7. The solid electrolyte of claim 1 , wherein b and c satisfy a relationship b+c=1.
8. The solid electrolyte of claim 1 , wherein d and e satisfy a relationship d+e=1.
9. The solid electrolyte of claim 1 , wherein the oxysulfide-based compound comprises a crystal phase of an argyrodite-type crystal structure.
10. The solid electrolyte of claim 1 , wherein an ionic conductivity of the solid electrolyte ranges from 0.1×10 −3 S/cm to 10×10 −3 S/cm at room temperature (25° C.).
11. The solid electrolyte of claim 1 , wherein the oxysulfide-based compound is Li 6.15 P 0.85 Si 0.15 S 4.7 O 0.3 Cl.
12. A method of manufacturing the solid electrolyte of Formula 1 according to claim 1 , comprising:
(a) mixing lithium sulfide, P 2 S 5 , oxide of a metal M, and LiX (where, M is one or more selected from a group consisting of Zr, Nb, Hf, Ta, Ga, In, Ti, Pb, Bi, Ge, As, Sb, Si, B, and Al, and X is F, CI, Br, and I);
(b) compressing a compound mixed in operation (a) to prepare pellets;
(c) heat-treating the pellets prepared in operation (b) in a vacuum atmosphere; and
(d) cooling and grinding the pellets heat-treated in operation (c).
13. The method of claim 12 , wherein the mixing in the operation (a) comprises:
milling at 200 rpm to 600 rpm for 1 hour to 3 hours.
14. The method of claim 12 , wherein a degree of vacuum of the vacuum atmosphere in the operation (c) is less than 0.1 mmHg.
15. The method of claim 12 , wherein the heat-treating in the operation (c) is performed at a temperature ranging from 400° C. to 700° C. for 5 hours to 7 hours.
16. The method of claim 12 , wherein the operations (a) through (d) are performed in a condition of not being exposed to moisture and oxygen.
17. An all-solid-state battery comprising the solid electrolyte of claim 1 .