Sulfur-carbon composite comprising a highly graphitic carbon material for lithium-sulfur batteries and process for preparing the same

1. A process for preparing a sulfur-carbon composite, wherein the sulfur-carbon composite comprises a highly graphitic carbon material and sulfur, wherein the highly graphitic carbon material has a porous structure and a high graphitization degree characterized by a ratio of the intensity of G band to the intensity of D band in Raman spectrum being more than 1.0, said material being a core-shell material with a conductive core coated by a graphitic microporous carbon layer, and wherein sulfur is encapsulated into the porous structure of the highly graphitic carbon material,

the process comprising:

mixing an aqueous suspension of the conductive core with an aqueous solution of transition metal-containing salt, keeping at 60-120° C. for 2-12 h, carrying out a hydrothermal reaction by adding carbon source to the obtained product, followed by centrifuging, washing and drying; or alternatively, mixing an aqueous suspension of the conductive core with an aqueous solution of transition metal-containing salt and carbon source at the same time, then carrying out a hydrothermal reaction, followed by centrifuging, washing and drying,

pyrolyzing the obtained material at a temperature of 500-900° C. for 1-12 h;

removing the transition metal oxide by an acid solution; and

loading of sulfur.

2. A process for preparing a sulfur-carbon composite, wherein the sulfur-carbon composite comprises a highly graphitic carbon material and sulfur, wherein the highly graphitic carbon material has a porous structure and a high graphitization degree characterized by a ratio of the intensity of G band to the intensity of D band in Raman spectrum being more than 1.0, said material being a graphitic microporous carbon substrate, and wherein sulfur is encapsulated into the porous structure of the highly graphitic carbon material,

the process comprising the steps of:

dispersing microporous carbon substrate in an aqueous solution of transition metal-containing salt, stirring and heating at 60-120° C. for 2-12 h;

pyrolyzing the obtained material at a temperature of 500-900° C. for 1-12 h to carbonize and graphitize the microporous carbon substrate;

removing the transition metal oxide by an acid solution; and

loading of sulfur.

3. The process according to claim 1 , wherein said carbon source is one or more selected from the group consisting of sucrose, D-glucose, fructose, polyaniline, polyacetylene, polythiophene, dopamine and sodium alginate.

4. The process according to claim 1 , wherein the transition metal-containing salt is selected from the group consisting of chloride, sulfate, nitrate, acetate, carbonate and phosphate of Fe, Co and Ni.

5. The process according to claim 1 , wherein the sulfur loading comprises mixing homogeneously the carbon material obtained after removing the transition metal oxide with a solution of sulfur dissolved in a non-polar solvent by ultrasonication, and then adding a polar solvent to precipitate sulfur particles from the solution and deposite into the carbon material, followed by drying.

6. The process according to claim 2 , wherein the transition metal-containing salt is selected from the group consisting of chloride, sulfate, nitrate, acetate, carbonate and phosphate of Fe, Co and Ni.

7. The process according to claim 2 , wherein the sulfur loading comprises mixing homogeneously the carbon material obtained after removing the transition metal oxide with a solution of sulfur dissolved in a non-polar solvent by ultrasonication, and then adding a polar solvent to precipitate sulfur particles from the solution and deposite into the carbon material, followed by drying.