Cathode for lithium-sulfur battery and preparation method therefor

1. A cathode for a lithium-sulfur battery comprising:

a cathode active part comprising a sulfur-carbon composite; and

a cathode coating layer provided on at least a portion of a surface of the cathode active part and including an inorganic oxide,

wherein a content of the inorganic oxide of the cathode coating layer is 0.5 to 10 wt % based on a total weight of the cathode,

wherein the cathode coating layer has a thickness of 0.1 to 20 μm,

wherein the cathode coating layer comprises pores having an average diameter of 0.5 to 10 μm, and

wherein a porosity of the cathode coating layer is 20 to 70% based on a total volume of the cathode for a lithium-sulfur battery.

2. The cathode for a lithium-sulfur battery of claim 1 , wherein the inorganic oxide is a hydrophilic inorganic oxide.

3. The cathode for a lithium-sulfur battery of claim 2 , wherein the hydrophilic inorganic oxide comprises one or more selected from the group consisting of SrTiO 3 , SnO 2 , CeO 2 , MgO, NiO, CaO, ZnO, ZrO 2 , Y 2 O 3 , Al 2 O 3 , TiO 2 , SiC, BaTiO 3 , HfO 2 , Pb(Zr,Ti)O 3 (PZT), Pb 1-x La x Zr 1-y Ti y O 3 (PLZT, 0≤x≤1, 0≤y≤1) and PB(Mg 3 Nb 2/3 )O 3 —PbTiO 3 (PMN-PT).

4. The cathode for a lithium-sulfur battery of claim 1 , wherein the inorganic oxide is an inorganic oxide having lithium ion transfer capacity.

5. The cathode for a lithium-sulfur battery of claim 4 , wherein the inorganic oxide having lithium ion transfer capacity comprises one or more selected from the group consisting of lithium phosphate (Li 3 PO 4 ), lithium titanium phosphate (Li x Ti y (PO 4 ) 3 , 0<x<2, 0<y<1, 0<z<3), lithium aluminum titanium phosphate (Li x Al y Ti z (PO 4 ) 3 , 0<x<2, 0<y<1, 0<z<3), (LiAlTiP) x O y -based glass (0<x<4, 0<y<13), lithium lanthanum titanate (Li x La y TiO 3 , 0<x<2, 0<y<3), lithium germanium thiophosphate (Li x Ge y P z S w , 0<x<4, 0<y<1, 0<z<1, 0<w<5), lithium nitride (Li x N y , 0<x<4, 0<y<2), SiS 2 (Li x Si y S z , 0<x<3, 0<y<2, 0<z<4)-based glass and P 2 S 5 (Li x P y S z , 0<x<3, 0<y<3, 0<z<7)-based glass.

6. The cathode for a lithium-sulfur battery of claim 1 , wherein the cathode active part has a thickness of 20 to 100 μm.

7. The cathode for a lithium-sulfur battery of claim 1 , wherein the cathode coating layer is provided on the entire surface of the cathode active part.

8. The cathode for a lithium-sulfur battery of claim 1 , wherein the sulfur-carbon composite is formed by applying sulfur particles on porous carbon.

9. The cathode for a lithium-sulfur battery of claim 1 , wherein the sulfur-carbon composite is formed by dissolving sulfur particles and mixing the sulfur particles with carbon.

10. The cathode for a lithium-sulfur battery of claim 1 , wherein the cathode active part further comprises one or more additives selected from transition metal elements, IIIA Group elements, IVA Group elements, sulfur compounds of these elements, and alloys of these elements and sulfur.

11. A lithium-sulfur battery comprising:

an anode comprising lithium metal or a lithium alloy as an anode active material;

the cathode for a lithium-sulfur battery of claim 1 ;

a separator positioned between the cathode and the anode; and

an electrolyte impregnated in the anode, the cathode and the separator and comprising a lithium salt and an organic solvent.

12. The lithium-sulfur battery of claim 11 , wherein the lithium salt comprises one or more selected from the group consisting of LiSCN, LiBr, LiI, LiPF 6 , LiBF 4 , LiSO 3 CF 3 , LiClO 4 , LiSO 3 CH 3 , LiB(Ph) 4 , LiC(SO 2 CF 3 ) 3 and LiN(SO 2 CF 3 ) 2 .

13. The lithium-sulfur battery of claim 11 , wherein the lithium alloy is an alloy of lithium and metal selected from the group consisting of Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Ba, Ra, Al and Sn.

14. The lithium-sulfur battery of claim 11 , wherein the organic solvent is a single solvent or a mixed organic solvent of two or more solvents.

15. A battery module comprising the lithium-sulfur battery of claim 11 as a unit cell.

16. A method of preparing a lithium-sulfur battery, the method comprising:

forming a cathode active part comprising a sulfur-carbon composite; and

forming a cathode coating layer comprising an inorganic oxide on at least a portion of a surface of the cathode active part,

wherein a content of the inorganic oxide of the cathode coating layer is 0.5 to 10 wt % based on a total weight of the cathode,

wherein the cathode coating layer has a thickness of 0.1 to 20 μm,

wherein the cathode coating layer comprises pores having an average diameter of 0.5 to 10 μm, and

wherein a porosity of the cathode coating layer is 20 to 70% based on a total volume of the cathode for a lithium-sulfur battery.

17. The method of claim 16 , wherein the forming of the coating layer uses a method of dip coating, die coating, comma coating, gravure coating or bar coating.

18. The cathode for a lithium-sulfur battery of claim 1 , wherein the cathode active part further comprises a conductive material.

19. The method of preparing a lithium-sulfur battery of claim 16 , wherein the cathode active part further comprises a conductive material.