Composite made of porous carbon and sulfur-containing active material as well as method for producing same

Abstract

The invention relates to a composite made of a porous carbon and an active material containing sulphur and to method for producing same. A method for producing a composite made of a porous carbon structure and sulphur is disclosed, said composite being characterised by a high capacitance and a low capacitance loss, when used as an electrode material for a lithium-sulphur secondary battery. According to the invention, a dispersion of carbon powder, an active material containing sulphur and an aqueous medium are treated hydrothermally at a temperature sufficient for melting sulphur. The liquid phase which forms, which contains the melted sulphur and water, infiltrates the pores of the porous carbon.

1 . A method for producing a composite consisting of porous carbon and sulfur-containing active material, said method comprising:
 (a) providing a carbon powder of porous carbon;   (b) preparing a dispersion of the carbon powder, the sulfur-containing active material, and an aqueous medium;   (c) performing a hydrothermal treatment of the dispersion at a temperature sufficient for melting sulfur so as to form a liquid phase containing sulfur melt and water and to cause infiltration of pores of the porous carbon with the liquid phase; and   (d) removing the water and insulating the composite.   
     
     
         2 . The method according to  claim 1 , wherein the liquid phase is present in an amount sufficient for fully covering the porous carbon. 
     
     
         3 . The method according to  claim 1 , wherein a weight ratio of a weight of the aqueous medium to a weight of solid phase in the dispersion is between 0.5:1 and 3:1. 
     
     
         4 . The method according to  claim 1 , wherein the hydrothermal treatment has a duration that is at least 180 min. 
     
     
         5 . The method according to  claim 1 , wherein the sulfur-containing active material in the composite powder makes up a weight percentage of 1% [-] to 90%. 
     
     
         6 . The method according to  claim 1 , wherein the removal of the water and the insulation of the composite include a flotation step. 
     
     
         7 . The method according to  claim 1 , wherein the provision of the carbon powder comprises a template method in which a carbon skeleton is built up around a structure-directing template of a porous SiO 2  soot template material, and the template material is thereupon removed. 
     
     
         8 . The method according to  claim 7 , wherein the template is provided in a form of porous SiO 2  granulate particles with non-spherical morphology, and wherein said porous SiO 2  granulate particles are obtained by producing a SiO 2  soot layer by gas phase deposition, thermally solidifying the SiO 2  soot layer into a porous soot plate, and comminuting said porous soot plate into the porous SiO 2  granulate particles. 
     
     
         9 . The method according to  claim 7 , wherein for the template method of a mixture of template particles and of particles of a meltable precursor substance for carbon is heated, such that the precursor substance melts and penetrates into pores of the template material, and the precursor substance is carbonized prior to the removal of the template material. 
     
     
         10 . The method according to  claim 1 , wherein the composite is present in the form of porous carbon flakes of carbon layers having a mean layer thickness ranging from 10 μm to 500 μm and has a hierarchical pore structure. 
     
     
         11 . The method according to  claim 1 , wherein the amount of the active material measured in at.% on a surface within the pores of the porous carbon is higher at least by a factor of 1.5 than the amount of the active material measured on a surface outside the pores of the porous carbon. 
     
     
         12 . A composite of porous carbon and sulfur-containing active material, said composite comprising:
 a porous carbon structure that has an outer surface and inner walls defining interconnected cavities therein that can be accessed via pore channels from the outer surface,   wherein the active material is present in an amount measured in at.% in the pore channels and the inner walls that is higher by at least the factor 1.5 than an amount thereof on the outer surface, and   wherein, in the pore channels and the inner walls, the active material is present in an amount determined by EDX analysis in at.% that is higher by at least a factor of 1.5 than an amount of carbon therein determined by EDX analysis in at.%.   
     
     
         13 . The composite according to  claim 12 , wherein the amount of the active material measured in at.% in the pore channels and the inner walls is higher by at least a factor of 3 than the amount of the active material measured in at. % on the outer surface. 
     
     
         14 . The composite according to  claim 12 , wherein in the pore channels and the inner walls the amount of the active material determined by means of EDX analysis in at.% is higher by at least a factor of 3 than the amount of carbon determined by means of EDX analysis in at.%. 
     
     
         15 . The method according to  claim 1 , wherein the sulfur-containing active material in the composite makes up a weight percentage of 50% to 80%. 
     
     
         16 . The method according to  claim 1 , wherein the composite is present in the form of porous carbon flakes of carbon layers having a mean layer thickness ranging from 20 μm to 100 μm and has a hierarchical pore structure. 
     
     
         17 . The method according to  claim 1 , wherein the composite is present in the form of porous carbon flakes of carbon layers having a mean layer thickness not less than 20 μm and less than 50 μm and has a hierarchical pore structure.