Graphene composite material, methods for making graphene and graphene composite material, and lithium sulfur battery using the same

Abstract

A method for making graphene-based material is disclosed. A graphene oxide dispersion includes graphene oxide dispersed in solvent. A hydrogen sulfide gas is introduced to the graphene oxide dispersion at a reacting temperature to achieve a graphene dispersion. The hydrogen sulfide reduces graphene oxide into graphene, and elemental sulfur produced from the hydrogen sulfide is deposited on surfaces of the graphene. The solvent is removed to achieve a graphene composite material. Further, a graphene composite material and a lithium sulfur battery using the graphene composite material are also disclosed.

What is claimed is: 
     
         1 . A method for making graphene based material comprising steps:
 providing a graphene oxide dispersion comprising graphene oxide dispersed in solvent;   introducing a hydrogen sulfide gas to the graphene oxide dispersion at a reacting temperature to achieve a graphene dispersion, wherein the hydrogen sulfide reduces graphene oxide into graphene, and elemental sulfur produced from the hydrogen sulfide is deposited on surfaces of the graphene; and   removing the solvent to achieve a graphene composite material.   
     
     
         2 . The method of  claim 1 , wherein the reacting temperature is in a range from about 5° C. to about 260° C. 
     
     
         3 . The method of  claim 1 , wherein the removing the solvent comprises freeze-drying the graphene dispersion. 
     
     
         4 . The method of  claim 1 , further comprising introducing a sulfur dioxide gas to the graphene dispersion to form an additional elemental sulfur on the surfaces of the graphene. 
     
     
         5 . The method of  claim 1 , wherein the removing the solvent comprises at least one of evaporating the solvent from the graphene dispersion at room temperature, vacuum heating, heating at atmosphere, in a protective gas, and supercritical drying. 
     
     
         6 . The method of  claim 1 , wherein the solvent is selected from the group consisting of water, ethanol, isopropanol, ethylene glycol, N,N-dimethylformamide, N-methylpyrrolidone, tetrahydrofuran, and combinations thereof. 
     
     
         7 . The method of  claim 1 , wherein a concentration of graphene oxide in the graphene oxide dispersion is in a range from about 0.05 mg/mL to about 30 mg/mL. 
     
     
         8 . The method of  claim 1 , the removing the solvent from the graphene dispersion comprising filtering the graphene dispersion to achieve a graphene composite film. 
     
     
         9 . The method of  claim 1  further comprising a step of solvothermal reacting the graphene dispersion to achieve a graphene based gel. 
     
     
         10 . The method of  claim 9 , wherein the solvothermal reacting is processed at a temperature from about 50° C. to about 360° C. for about 0.1 hours to about 120 hours. 
     
     
         11 . The method of  claim 1  further comprising a step of removing the elemental sulfur from the surface of the graphene. 
     
     
         12 . The method of  claim 11 , wherein the removing the elemental sulfur comprises a thermal treatment step to evaporate the elemental sulfur from the surface of the graphene at a temperature from about 150° C. to about 1000° C. 
     
     
         13 . The method of  claim 11 , wherein the removing the elemental sulfur comprises a washing step using an organic liquid to dissolve the elemental sulfur on the surface of the graphene. 
     
     
         14 . The method of  claim 13 , wherein the organic liquid is selected from the group consisting of carbon disulfide, carbon tetrachloride, benzene, toluene, and combinations thereof. 
     
     
         15 . A graphene composite material comprising a three dimensional porous graphene macrostructure and elemental sulfur deposited on surfaces of the three dimensional porous graphene macrostructure, wherein the three dimensional porous graphene macrostructure is a free-standing structure. 
     
     
         16 . The graphene composite material of  claim 15 , wherein the element sulfur is located in pores of the three dimensional porous graphene macrostructure. 
     
     
         17 . The graphene composite material of  claim 15 , wherein a mass percentage of the elemental sulfur is in a range of about 5% to about 95%. 
     
     
         18 . The graphene composite material of  claim 15 , wherein a pore volume of the three dimensional porous graphene macrostructure is about 0.05 cm 3 /g to about 5.2 cm 3 /g. 
     
     
         19 . The graphene composite material of  claim 15 , wherein a pore size distribution is about 0.4 nm to about 10 μm. 
     
     
         20 . A lithium sulfur battery comprising a cathode electrode plate, an anode electrode plate, a separator, and an electrolyte, wherein the cathode electrode plate comprises a graphene composite material comprising a three dimensional porous graphene macrostructure and elemental sulfur deposited on surfaces of the three dimensional porous graphene macrostructure, the three dimensional porous graphene macrostructure being a free-standing structure.