Sulfur-Carbon Composite, Method for Preparing Same and Lithium Secondary Battery Comprising Same

Abstract

A sulfur-carbon composite including a porous carbon material; and sulfur present in at least a part of pores of the porous carbon material and on an outer surface of the porous carbon material, wherein an inner surface and the outer surface of the porous carbon material are doped with a carbonate compound. Also, a positive electrode and a secondary battery including the same. Further, a method of preparing a sulfur-carbon composite and a method of preparing a positive electrode.

1 . A method for manufacturing a positive electrode for a lithium-sulfur battery, comprising steps of:
 (i) forming a sulfur-carbon composite comprising the steps of:
 (a) preparing a porous carbon material; 
 (b) mixing a carbonate compound with a volatile solvent to prepare a doping composition; 
 (c) mixing the porous carbon material of step (a) with the doping composition of step (b), and then drying the resulting mixture to prepare a porous carbon material doped with the carbonate compound; and 
 (d) mixing sulfur in the porous carbon material doped with the carbonate compound, and heat-treating the resulting mixture to prepare the sulfur-carbon composite; 
   (ii) mixing the sulfur-carbon composite with a conductive material and a binder to form a slurry;   (iii) coating the slurry on a current collector to form a coated current collector; and   (iv) drying the coated current collector to obtain the positive electrode for the lithium-sulfur battery.   
     
     
         2 . The method for manufacturing the positive electrode for the lithium-sulfur battery according to  claim 1 , wherein the porous carbon material is at least one selected from the group consisting of graphite, graphene, carbon black, carbon nanotube, carbon fiber, and activated carbon. 
     
     
         3 . The method for manufacturing the positive electrode for the lithium-sulfur battery according to  claim 1 , wherein the volatile solvent is at least one selected from the group consisting of ethanol and THF. 
     
     
         4 . The method for manufacturing the positive electrode for the lithium-sulfur battery according to  claim 1 , wherein the carbonate compound is at least one selected from the group consisting of propylene carbonate, and butylene carbonate. 
     
     
         5 . The method for manufacturing the positive electrode for the lithium-sulfur battery according to  claim 1 , wherein an amount of the carbonate compound is from 0.5 to 5.0 wt. % based on a total weight of the sulfur-carbon composite. 
     
     
         6 . The method for manufacturing the positive electrode for the lithium-sulfur battery according to  claim 1 , wherein an amount of the carbonate compound is from 1.0 to 3.0 wt. % based on a total weight of the sulfur-carbon composite. 
     
     
         7 . The method for manufacturing the positive electrode for the lithium-sulfur battery according to  claim 1 , wherein conductive material is carbon black. 
     
     
         8 . The method for manufacturing the positive electrode for the lithium-sulfur battery according to  claim 1 , wherein the binder is at least one selected from the group consisting of polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), styrene-butadiene rubber, acrylonitrile-butadiene rubber, styrene-isoprene rubber, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, and regenerated cellulose, polyalcohol-based binders, polyethylene, polypropylene, polyimide-based binders, polyester-based binders, silane-based binders, acrylate-based binder, and acrylate-based copolymer binder. 
     
     
         9 . The method for manufacturing the positive electrode for the lithium-sulfur battery according to  claim 1 , wherein in step (d), when mixing the sulfur and the porous carbon material, the weight ratio of sulfur and the porous carbon material ranges from 9:1 to 5:5.