Carbon-based fiber sheet and lithium-sulfur battery including same

Abstract

The carbon-based fiber sheet for the lithium-sulfur battery according to the present invention is doped with a high concentration of nitrogen and thus plays a role of preventing diffusion by adsorbing lithium polysulfide eluted from a positive electrode during charging and discharging, thereby suppressing a shuttle reaction and thus improving capacity and lifecycle properties of the lithium-sulfur battery.

1 . A carbon-based fiber sheet for lithium-sulfur battery doped with a high concentration of nitrogen. 
     
     
         2 . The carbon-based fiber sheet for the lithium-sulfur battery according to  claim 1 , wherein the nitrogen is doped at a doping concentration of 5 to 30% by weight in the carbon-based fiber sheet. 
     
     
         3 . The carbon-based fiber sheet for the lithium-sulfur battery according to  claim 1 , wherein the carbon-based fiber may be at least one selected from the group consisting of carbon fiber, carbon nanofiber, graphite fiber and graphene fiber. 
     
     
         4 . The carbon-based fiber sheet for the lithium-sulfur battery according to  claim 1 , wherein the carbon-based fiber sheet has at least one fabric form selected from the group consisting of felt, mat, paper and cloth. 
     
     
         5 . The carbon-based fiber sheet for the lithium-sulfur battery according to  claim 1 , wherein the carbon-based fiber sheet has a thickness of 0.1 to 100 μm. 
     
     
         6 . The carbon-based fiber sheet for the lithium-sulfur battery according to  claim 1 , wherein the carbon-based fiber sheet is made of a carbon-based fiber having a diameter of 0.01 to 100 μm. 
     
     
         7 . The carbon-based fiber sheet for the lithium-sulfur battery according to  claim 1 , wherein the carbon-based fiber sheet has a pore size of 0.1 to 10 μm and a porosity of 5 to 90%. 
     
     
         8 . The carbon-based fiber sheet for the lithium-sulfur battery according to  claim 1 , wherein the carbon-based fiber sheet has a specific surface area of 5 to 500 m 2 /g and a bulk density of 0.05 to 0.2 g/cm 3 . 
     
     
         9 . A preparation method of a carbon-based fiber sheet for the lithium-sulfur battery comprising,
 i) preparing a spinning solution comprising a carbon-based precursor;   ii) spinning the spinning solution to prepare a sheet in a form of a fibrous web;   iii) stabilizing the sheet through heat treatment in the presence of oxygen; and   iv) carbonizing the sheet in an inert atmosphere,   wherein the carbon-based precursor contains a nitrogen element in the molecular structure.   
     
     
         10 . The preparation method of the carbon-based fiber sheet for the lithium-sulfur battery according to  claim 9 , wherein the carbon-based precursor in step i) is at least one selected from the group consisting of polyacrylonitrile, polyaniline, polypyrrole, polyimide, polybenzimidazole, polypyrrolidone, polyamide, polyamideimide, polyaramid, melamine, melamine-formaldehyde and fluorine mica. 
     
     
         11 . The preparation method of the carbon-based fiber sheet for the lithium-sulfur battery according to  claim 9 , wherein the carbon-based precursor includes from 5 to 20% of nitrogen atoms in the molecular structure. 
     
     
         12 . The preparation method of the carbon-based fiber sheet for the lithium-sulfur battery according to  claim 9 , wherein the heat treatment in step iii) is carried out at 100 to 400° C. 
     
     
         13 . The preparation method of the carbon-based fiber sheet for the lithium-sulfur battery according to  claim 9 , wherein the heat treatment in step iii) is carried out in the oxidizing atmosphere. 
     
     
         14 . The preparation method of the carbon-based fiber sheet for the lithium-sulfur battery according to  claim 9 , wherein the carbonization in the step iv) is carried out at 600 to 1500° C. 
     
     
         15 . The preparation method of the carbon-based fiber sheet for the lithium-sulfur battery according to  claim 9 , wherein the carbonization in step iv) is carried out in the inert gas atmosphere. 
     
     
         16 . A lithium-sulfur battery comprising: a positive electrode; an negative electrode; a separator interposed between the positive electrode and the negative electrode; and an electrolyte impregnated thereinto,
 wherein the carbon-based fiber sheet of  claim 1  is interposed between the positive electrode and the separator.