Sulfur-carbon composite, method for producing same, and lithium secondary battery including same

1. A sulfur-carbon composite comprising:

porous carbon;

diisopropenylbenzene; and

sulfur,

wherein the diisopropenylbenzene and sulfur are supported in pores of the porous carbon and on a surface of the porous carbon,

wherein the pores of the porous carbon contain first mesopores having a diameter of 2 nm to 8 nm and second mesopores having a diameter of 20 nm to 50 nm,

wherein the porous carbon comprises the first mesopores and the second mesopores in a pore volume ratio of 1:20 to 70,

wherein the diisopropenylbenzene and sulfur are covalently bonded, and

wherein the porous carbon is a spherical particle having a particle diameter of 2 μm to 10 μm.

2. The sulfur-carbon composite of claim 1 , wherein a pore volume of the second mesopores is at least 3.5 cm 3 /g.

3. The sulfur-carbon composite of claim 1 , wherein a specific surface area of the porous carbon is 1000 cm 2 /g to 1300 cm 2 /g.

4. The sulfur-carbon composite of claim 1 , wherein the diisopropenylbenzene is present in an amount of 5% by weight to 30% by weight based on a total weight of the sulfur-carbon composite.

5. A method for preparing the sulfur-carbon composite according to claim 1 , comprising the steps of:

(1) dispersing porous silica in an organic solvent, and mixing a hydrate for introducing an Al acid site to prepare a porous silica dispersion;

(2) evaporating the organic solvent from the porous silica dispersion to obtain porous silica particles;

(3) performing a first heat treatment on the porous silica particles to obtain porous silica particles having the Al acid site introduced therein;

(4) impregnating pores of the porous silica particles having the Al acid site introduced therein with a carbon precursor, and then performing a second heat treatment to obtain a carbon-silica composite;

(5) etching silica from the carbon-silica composite to obtain porous carbon;

(6) preparing a solution by dissolving diisopropenylbenzene and sulfur;

(7) dispersing the porous carbon into the solution of diisopropenylbenzene and sulfur to prepare a mixture; and

(8) performing a third heat treatment on the mixture to support diisopropenylbenzene and sulfur in pores of the porous carbon and on a surface of the porous carbon.

6. The method for preparing the sulfur-carbon composite of claim 5 , wherein the hydrate for introducing the Al acid site is aluminum chloride hexahydrate.

7. The method for preparing the sulfur-carbon composite of claim 5 , wherein the first heat treatment is heated to 500° C. to 600° C. at a rate of 0.5° C./min to 3° C./min.

8. The method for preparing the sulfur-carbon composite of claim 5 , wherein the carbon precursor is at least one selected from the group consisting of furfuryl alcohol, sucrose and glucose.

9. The method for preparing the sulfur-carbon composite of claim 5 , wherein the second heat treatment is performed for 7 hours to 10 hours at 70° C. to 100° C.

10. The method for preparing the sulfur-carbon composite of claim 5 , further comprising:

after the second heat treatment, heat-treating for 1 hour to 5 hours at 700° C. to 1000° C. by increasing the temperature at a rate of 0.5° C./min to 3° C./min under an inert atmosphere.

11. The method for preparing the sulfur-carbon composite of claim 5 , wherein an etching solution used in the etching is a solution comprising at least one selected from the group consisting of hydrofluoric acid, hydrogen peroxide, nitric acid, potassium hydroxide and sodium hydroxide.

12. The method for preparing the sulfur-carbon composite of claim 5 , wherein a solvent into which diisopropenylbenzene and sulfur are dissolved comprises at least one selected from the group consisting of CS 2 , ethylenediamine, acetone and ethanol.

13. The method for preparing the sulfur-carbon composite of claim 5 , wherein the diisopropenylbenzene and sulfur are mixed in a weight ratio of 5:95 to 30:70.

14. The method for preparing the sulfur-carbon composite of claim 5 , wherein the third heat treatment is performed for 1 minute to 30 minutes at a temperature of 100° C. to 200° C.

15. A positive electrode for a lithium secondary battery comprising the sulfur-carbon composite of claim 1 .

16. The positive electrode for the lithium secondary battery of claim 15 , wherein the positive electrode for the lithium secondary battery is a positive electrode for a lithium-sulfur battery.

17. A lithium secondary battery comprising a positive electrode; a negative electrode; a separator interposed between the positive electrode and the negative electrode and an electrolyte, wherein the positive electrode is the positive electrode of claim 15 .

18. The lithium secondary battery of claim 17 , wherein the lithium secondary battery is a lithium-sulfur battery.