Solid electrolyte and lithium battery including the same
A solid electrolyte material represented by Formula 1: L 1+2x (M1) 1−x (M2)(M3) 4 Formula 1 wherein 0.25<x<1, L is at least one element selected from a Group 1 element, M1 is at least one element selected from a Group 2 element, a Group 3 element, a Group 12 element, and a Group 13 element, M2 is at least one element selected from a Group 5 element, a Group 14 element, and a Group 15 element, and M3 is at least one element selected from a Group 16 element, and wherein the solid electrolyte material has an I-4 crystal structure.
1. A solid electrolyte material represented by Formula 1:
Li 1+2x Zn 1−x PS 4 Formula 1
wherein 0.05≤x<1,
wherein the solid electrolyte material has an I-4 crystal structure, and
wherein the solid electrolyte material has a peak at about 18° two-theta, when analyzed by X-ray diffraction using CuKα radiation.
2. The solid electrolyte material of claim 1 , wherein x of Formula 1 satisfies 0.625≤x≤0.8.
3. The solid electrolyte material of claim 1 , wherein the solid electrolyte material does not comprise a disulfide bond.
4. The solid electrolyte material of claim 1 , wherein the solid electrolyte material has an ionic conductivity of greater than 2.9×10 −8 Siemen per centimeter as measured at room temperature.
5. A method of preparing a solid electrolyte, the method comprising:
contacting LiZnPS 4 and amorphous Li 3 PS 4 to obtain a mixture; and
heat-treating the mixture to obtain the solid electrolyte of claim 1 .
6. The method of claim 5 , wherein the LiZnPS 4 is prepared by:
providing a mixture of Li 2 S, ZnS, and P 2 S 5 ; and
heat-treating the mixture to obtain the LiZnPS 4 .
7. The method of claim 6 , wherein Li 2 S, ZnS, and P 2 S 5 are contained in the mixture at a molar ratio of 1:2:1.
8. The method of claim 5 , wherein the amorphous Li 3 PS 4 is prepared by mixing Li 2 S and P 2 S 5 at a molar ratio of 3:1.
9. The method of claim 5 , wherein the LiZnPS 4 and the amorphous Li 3 PS 4 are contained in the mixture at a molar ratio of 1:3.
10. The method of claim 6 , wherein the heat-treating of the mixture of Li 2 S, ZnS, and P 2 S 5 comprises heat-treating at a temperature in a range of about 200° C. to about 500° C.
11. The method of claim 5 , wherein the heat-treating of the LiZnPS 4 and the Li 3 PS 4 comprises heat-treating at a temperature in a range of about 200° C. to about 230° C.
12. A secondary battery comprising:
a positive electrode comprising a positive active material;
a negative electrode comprising a negative active material; and
a solid electrolyte layer between the positive electrode and the negative electrode, the solid electrolyte layer comprising the solid electrolyte material of claim 1 .
13. The solid electrolyte material of claim 1 , wherein the solid electrolyte material has peaks at about 29.5° two-theta, about 34° two-theta, about 35.5° two-theta, about 43.5° two-theta, about 46.5° two-theta, about 52° two-theta, and about 54° two-theta, when analyzed by X-ray diffraction using CuKα radiation.
14. The solid electrolyte material of claim 1 , wherein x of Formula 1 satisfies 0.25≤x<1.
15. The solid electrolyte material of claim 1 , wherein a structure of the solid electrolyte material comprises a body centered cubic anion sublattice.
16. The solid electrolyte material of claim 15 , wherein the structure of the solid electrolyte material comprises adjacent tetrahedral lithium sites.
17. The solid electrolyte material of claim 1 , wherein [P 2 S 6 ] 4− and (P 2 S 7 ) 4− are absent based on Raman analysis for peaks at 380 inverse centimeters and 400 inverse centimeters, respectively.
18. The solid electrolyte material of claim 1 , wherein the solid electrolyte material has a peak at position of about 17.8° two-theta to about 18.4° two-theta, when analyzed by X-ray diffraction using CuKα radiation.
19. The solid electrolyte material of claim 1 , wherein the solid electrolyte material has peaks at about 29.4° two-theta to about 29.8° two-theta, about 33.9° two-theta to about 34.2° two-theta, about 35.4° two-theta to about 36.3° two-theta, about 43.2° two-theta to about 44.4° two-theta, about 46.3° two-theta to about 46.8° two-theta, about 51.9° two-theta to about 52.10 two-theta, and about 53.3° two-theta to about 54.4° two-theta, when analyzed by X-ray diffraction using CuKα radiation.
20. A solid electrolyte material represented by Formula 1:
Li 1+2x Zn 1−x PS 4 Formula 1
wherein 0.05≤x<1, and
wherein [PS 4 ] 3− anions of the solid electrolyte define a body centered cubic sublattice.
21. The solid electrolyte material of claim 20 wherein x of Formula 1 satisfies 0.25≤x<1.
22. The solid electrolyte material of claim 20 , wherein the solid electrolyte material has peak at about 18° two-theta, when analyzed by X-ray diffraction using CuKα radiation.
23. The solid electrolyte material of claim 22 , wherein a structure of the solid electrolyte comprises adjacent tetrahedral lithium sites.
24. A solid electrolyte material prepared by:
contacting Li 2 S, ZnS, and P 2 S 5 to obtain LiZnPS 4 ; and
combining the LiZnPS 4 and amorphous Li 3 PS 4 to form the solid electrolyte material,
wherein the solid electrolyte material has an I-4 crystal structure,
wherein the solid electrolyte material has an ionic conductivity of greater than 2×10 −4 Siemen per centimeter, and
wherein the solid electrolyte material has a peak at position of about 18°±0.50 two-theta, when analyzed by X-ray diffraction using CuKα radiation.