Positive electrode material for lithium sulfur battery and lithium sulfur battery containing the same

Abstract

To provide a carbon composite used for a positive electrode of a lithium sulfur battery, and a manufacturing method therefor.SOLUTION: A carbon composite contains: a porous carbon material in which at least one sulfur is doped; and at least one catalyst containing a transition metal. The catalyst is positioned at at least one of an external front surface of the porous carbon material in which the at least one sulfur is doped and an internal front surface of a pore.SELECTED DRAWING: Figure 2a

Description

Technical Field

[0001] The present invention relates to a positive electrode material for a lithium-sulfur battery and a lithium-sulfur battery including the same.

[0002] This application claims priority based on Korean Application No. 2022-0044174 filed on April 8, 2022, and Korean Application No. 2022-0140744 filed on October 27, 2022, and all of the contents disclosed in the specification of the applications are incorporated herein.

Background Art

[0003] A lithium-sulfur battery is a battery system that uses a sulfur-based material having an S-S bond (sulfur-sulfur bond) as a positive electrode active material and lithium metal as a negative electrode active material. Sulfur, which is the main material of the positive electrode active material, has advantages of abundant global resources, no toxicity, and low weight per atom.

[0004] As the application fields of secondary batteries expand to electric vehicles (EVs) and energy storage systems (ESSs), etc., compared with lithium-ion secondary batteries having a relatively low energy storage density (~250 Wh / kg) with respect to weight, lithium-sulfur battery technology that can theoretically achieve a high energy storage density (~2,600 Wh / kg) with respect to weight has been in the spotlight.

[0005] In a lithium-sulfur battery, during discharge, lithium, which is the negative electrode active material, is oxidized while releasing electrons and ionizing into lithium cations. At the same time, a sulfur-based material, which is the positive electrode active material, is reduced while accepting electrons. Here, due to the reduction reaction of the sulfur-based material, the S-S bond accepts two electrons and is converted into a sulfur anion form. The lithium cations generated by the oxidation reaction of lithium are transmitted to the positive electrode through the electrolyte, and this combines with the sulfur anions generated by the reduction reaction of the sulfur-based compound to form a salt. Specifically, sulfur before discharge has a cyclic S8 structure, which is converted into lithium polysulfide (Li2S x ) by a reduction reaction and is completely reduced to generate lithium sulfide (Li2S).

[0006] Since sulfur used as the positive electrode active material in this way is an insulator, it is difficult for the electrons generated by the electrochemical reaction to move, and there are problems such as the elution problem of polysulfide (LiS x ) and the slow kinetic activity of the electrochemical reaction due to the low electrical conductivity of sulfur and lithium sulfide, which lead to a decrease in the battery life characteristics and rate characteristics.

[0007] In relation to this, recently, research has been conducted to realize the high performance of lithium-sulfur secondary batteries by improving the kinetic activity of the redox reaction of sulfur during the charge and discharge process of lithium-sulfur secondary batteries using platinum (Pt), which is widely used as an electrochemical catalyst. However, noble metal catalysts such as platinum are not only expensive and difficult to commercialize, but also have the problem that they are likely to be poisoned by the redox reaction of sulfur during the charge and discharge process, so it is not easy to be used as a positive electrode material for lithium-sulfur secondary batteries.

[0008] In addition, research on single atomic catalyst materials is underway to enhance the lithium-sulfur secondary battery's performance by increasing the atomic utilization efficiency to a level close to 100% and minimizing the catalyst content inside the positive electrode. However, most single atomic catalysts have a low adsorption rate with lithium sulfide, resulting in low conversion performance. Therefore, the current situation is that their effect on improving the performance of lithium-sulfur secondary batteries is still insufficient. As a result, research on using single atomic catalysts together with particle-type catalysts has also been carried out. However, in that case, the atomic utilization efficiency decreases again, so the problem of ineffectiveness still exists.

[0009] Therefore, there is a continuous demand for the development of a positive electrode material that can improve the kinetic activity of the electrochemical reaction during charge and discharge of lithium-sulfur secondary batteries and is commercially advantageous in terms of cost at the same time.

Summary of the Invention

Problems to be Solved by the Invention

[0010] Therefore, the problem to be solved by the present invention is to solve the above-mentioned problems and provide a positive electrode material that has excellent adsorption power with lithium polysulfide and enhances the kinetic activity of the sulfur oxidation / reduction reaction.

[0011] Thereby, a high-performance lithium-sulfur secondary battery is provided.

Means for Solving the Problems

[0012] To solve the above problems, according to one aspect of the present invention, a carbon composite of the following embodiment is provided.

[0013] The carbon composite according to the first embodiment is At least one sulfur-doped porous carbon material and at least one catalyst containing one or more transition metals, wherein the catalyst is located on at least one of the outer surface and the inner surface of the pores of the at least one sulfur-doped porous carbon material.

[0014] According to a second aspect, in the first aspect, The closest interatomic distance between the transition metal contained in the catalyst and at least one sulfur doped in the porous carbon material can be 10 nm or less.

[0015] According to a third aspect, in the first aspect or the second aspect, The closest interatomic distance between the transition metal contained in the catalyst and at least one sulfur doped in the porous carbon material can be 2 nm or less.

[0016] According to a fourth aspect, in any one of the first aspect to the third aspect, The carbon composite may have a BET specific surface area of 200 m 2 / g or more.

[0017] According to a fifth aspect, in any one of the first aspect to the fourth aspect, The catalyst may further include the transition metal and at least one non-metal element that forms a ligand with the transition metal.

[0018] According to a sixth aspect, in any one of the first aspect to the fifth aspect, The catalyst may further include the transition metal, at least one non-metal element that forms a ligand with the transition metal, and an organic support.

[0019] According to a seventh aspect, in any one of the first aspect to the sixth aspect, The catalyst includes a single atom catalyst containing one or more transition metals, and the one or more transition metals may be dispersed in the form of single atom size in the carbon composite.

[0020] According to the eighth aspect, in any one of the first to seventh aspects, the catalyst may not contain a metal bond between two or more transition metals contained therein.

[0021] According to the ninth aspect, in any one of the first to eighth aspects, the catalyst contains particles containing one or more transition metals, and the average diameter (D 50 ) of the particles can be 1 to 30 nm of the diameter of a single atom constituting the transition metal.

[0022] According to the tenth aspect, in any one of the first to ninth aspects, the catalyst contains particles containing one or more transition metals, and the average diameter (D 50 ) of the particles can be 1 to 5 times the diameter of a single atom constituting the transition metal.

[0023] According to the eleventh aspect, in any one of the first to tenth aspects, the transition metal may include zinc (Zn), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zirconium (Zr), niobium (Nb), molybdenum (Mo), technetium (Tc), ruthenium (Ru), rhodium (Rh), palladium (Pd), silver (Ag), cadmium (Cd), lanthanum (La), hafnium (Hf), tantalum (Ta), tungsten (W), osmium (Os), iridium (Ir), cerium (Ce), gadolinium (Gd), scandium (Sc), titanium (Ti), gallium (Ga), indium (In), or two or more thereof.

[0024] According to the twelfth aspect, in any one of the first to eleventh aspects, the transition metal may include iron (Fe).

[0025] According to the thirteenth aspect, in any one of the first to twelfth aspects, The transition metal contains iron (Fe), and the diameter (D 50 ) of the iron contained in the carbon composite may be 0.3 nm to 5 nm.

[0026] According to the 14th aspect, in any one of the 1st to 13th aspects, the molar ratio of sulfur doped in the porous carbon material to one or more transition metals contained in the catalyst may be 0.5 to 8.

[0027] According to the 15th aspect, in any one of the 1st to 14th aspects, the at least one sulfur may be doped in the form of sulfur atoms or sulfur compounds.

[0028] According to the 16th aspect, in any one of the 1st to 15th aspects, the porous carbon material doped with the at least one sulfur contains at least one of the first structure according to the following formula 1 and the second structure according to the following formula 2 in the structure, and the ratio of the first structure to the second structure is the molar ratio of the first structure / the second structure and may be 1 or less.

[0029] [Formula 1] -C-SO2-C- [Formula 2] -C-S-C-

[0030] According to the 17th aspect, in the 16th aspect, the molar ratio of the first structure / the second structure may be 0.1 to 0.7.

[0031] According to the 18th aspect, in any one of the 1st to 17th aspects, Among all the pores of the carbon composite, when the number of pores with a pore diameter of less than 10 nm is N(nano) and the number of pores with a pore diameter of 10 nm or more is N(macro), the ratio [N(macro) / N(nano)] of N(macro) to N(nano) may be 1 or more.

[0032] According to the 19th aspect, in any one of the 1st to 18th aspects, the Raman peak intensity ratio (I G / I D ratio) of the porous carbon material may be 1 or less.

[0033] According to another aspect of the present invention, a method for producing a carbon composite of the following aspect is provided.

[0034] The method for producing a carbon composite according to the 20th aspect is (S1) doping at least one sulfur in the porous carbon material; and (S2) impregnating the product of the step (S1) into a transition metal-containing precursor solution and then removing the solvent, wherein the step (S1) includes a step of heat-treating in a state where the sulfur doping precursor and the porous carbon material are in contact.

[0035] According to the 21st aspect, in the 20th aspect, the heat treatment may be performed at a temperature of 800 °C to 1,000 °C.

[0036] According to the 22nd aspect, in the 20th or 21st aspect, the sulfur doping precursor may include dibenzyl disulfide (DBDS), sodium metabisulfite (Na2S2O5), sodium pyrosulfate (Na2S2O7), sodium thiosulfate (Na2S2O3), thiourea (CH4N2S), sodium sulfide (Na2S), potassium thiocyanate (KSCN), benzyl mercaptan (C7H8S), benzothiophene (C8H6S), dibenzothiophene (C 12 H8S), or a mixture thereof.

[0037] According to the 23rd aspect, in any one of the 20th to 22nd aspects, The transition metal-containing precursor solution in the step (S2) may include an organic solvent, a precursor compound of a non-metallic element, and a precursor compound of a transition metal.

[0038] According to still another aspect of the present invention, a positive electrode active material, a positive electrode, a lithium-sulfur battery, and a battery according to the following aspects are provided.

[0039] According to the 24th aspect, A positive electrode active material including a carbon composite according to any one of the 1st to 19th aspects and a sulfur-based compound is provided.

[0040] According to the 25th aspect, A positive electrode including the positive electrode active material according to the 24th aspect is provided.

[0041] According to the 26th aspect, A lithium-sulfur battery including a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolytic solution, wherein the positive electrode is the positive electrode according to the 25th aspect is provided.

[0042] According to the 27th aspect, A positive electrode including a positive electrode active material containing a sulfur-based compound and a carbon composite according to any one of the 1st to 19th aspects is provided.

[0043] According to the 28th aspect, A lithium-sulfur battery including a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolytic solution, wherein the positive electrode is the positive electrode according to the 27th aspect is provided.

[0044] According to the 29th aspect, A battery including a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolytic solution, wherein at least one of the positive electrode and the negative electrode contains a carbon composite according to any one of the 1st to 19th aspects is provided.

Effects of the Invention

[0045] According to one aspect of the present invention, the carbon composite has an excellent effect on the adsorption force with lithium polysulfide (LiPS, Li2S x , 2≦x≦8). Moreover, the carbon composite has characteristics advantageous for ion transfer and electron transfer essential for the conversion reaction of lithium polysulfide.

[0046] In addition, the carbon composite has an effect of providing excellent kinetic activity in the oxidation / reduction reaction of sulfur.

[0047] Furthermore, the carbon composite has an effect of improving the atomic utilization rate as a catalyst.

[0048] Thereby, a lithium-sulfur secondary battery applying the carbon composite as a carrier supporting a cathode additive and / or a cathode active material suppresses the elution of lithium polysulfide into the electrolyte and improves the conversion rate of sulfur, thereby achieving stable high performance.

[0049] In particular, a lithium-sulfur battery according to one aspect of the present invention has an excellent effect in terms of the initial capacity, the capacity retention rate by charge / discharge cycles, and the energy density of the battery.

[0050] The drawings attached to this specification illustrate desirable embodiments of the present invention and are for the purpose of further understanding the technical idea of the present invention together with the content of the invention. Therefore, the present invention is not construed as being limited only to the matters described in the drawings.

Brief Description of the Drawings

[0051]

Figure 1

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Figure 2b

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Figure 9a

Figure 9b

Figure 9c

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Figure 11

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Figure 13

Mode for Carrying Out the Invention

[0052] Hereinafter, the present invention will be described in detail. However, it is not limited only by the following content, and each component can be variously modified or selectively mixed as necessary. Therefore, it is understood to include all modifications, equivalents, and alternatives included in the spirit and technical scope of the present invention.

[0053] In this specification, when a certain configuration "includes" a certain component, this means, unless otherwise specified, that it does not exclude other components and may further include other components.

[0054] In this specification, the description "A and / or B" means "A or B or both of them".

[0055] The specific terms used in this specification are for convenience and not limiting. For example, terms indicating positions such as "upper", "lower", "left", "right", "front", "rear", "inner" and "outer" do not indicate absolute positions, but can be used to indicate the relative positions and directions between components or to indicate the positions and directions in the referenced drawings. The above terms include, in addition to themselves, words containing them, their derivatives and words with similar meanings.

[0056] According to one aspect of the present invention, there is provided a carbon composite that can be used as an electrochemical catalyst in the positive electrode of a lithium-sulfur secondary battery.

[0057] Figure 1 schematically shows various functions indicating that the carbon composite according to the present invention functions as an electrochemical catalyst at the positive electrode during charge and discharge of a lithium-sulfur secondary battery. Referring to Figure 1, since the carbon composite is used as an electrochemical catalyst at the positive electrode, lithium polysulfide (Li2S x or LiS x - , x = 8, 6, 4, 2) can be adsorbed to suppress elution into the electrolyte. In addition, it shows activity in the conversion reaction between lithium polysulfides and induces rapid conversion, and can prevent the release of lithium sulfide (Li2S).

[0058] The carbon composite according to one aspect of the present invention includes a porous carbon material doped with at least one sulfur and at least one catalyst containing one or more transition metals, and the catalyst is located on at least one of the outer surface and the inner surface of the pores of the porous carbon material doped with the sulfur.

[0059] In one embodiment of the present invention, the catalyst containing the transition metal may be chemically and / or physically bonded to at least one of the outer surface and the inner surface of the pores of the sulfur-doped porous carbon material.

[0060] In one embodiment of the present invention, the catalyst may be physically adsorbed on the outer surface and / or the inner surface of the pores of the porous carbon material, and / or may be chemically bonded by a covalent bond between the elements contained in the catalyst and the carbon of the porous carbon material.

[0061] In the carbon composite of the present invention, at least one sulfur is present at a position close to the catalyst present on the outer surface and / or inside the pores of the porous carbon material. Here, in this specification, the "close" position means a position where the closest interatomic distance between the catalyst and at least one sulfur doped in the porous carbon material is 10 nm or less.

[0062] In this specification, the closest interatomic distance refers to the distance between the centers of two atoms at the closest distance. The closest interatomic distance can represent a value measured according to a known method for measuring the interatomic distance, and is not particularly limited to the measurement method. For example, the closest interatomic distance can be measured using a transmission electron microscope (TEM), an atomic force microscope (AFM), a field-emission electron microscope (FE-SEM), or a laser diffraction method.

[0063] In one embodiment of the present invention, the closest interatomic distance between the catalyst and at least one sulfur doped in the porous carbon material can be 10 nm or less, specifically 5 nm or less, more specifically 2 nm or less, for example 1.5 nm or less or 1 nm or less.

[0064] For example, the closest interatomic distance between the catalyst and at least one sulfur doped in the porous carbon material can represent the closest interatomic distance between the transition metal element contained in the catalyst and at least one sulfur doped in the porous carbon material.

[0065] In the carbon composite, the position where the sulfur is doped can act as an Electron Exchangeable Binding (EEB) site. Also, the sulfur can adjust the orbital level of the transition metal via electron exchange with the transition metal in the catalyst. For example, when the catalyst contains iron (Fe) as a transition metal, the sulfur can adjust the d-orbital level of iron via electron exchange with iron (Fe). Thereby, the carbon composite can promote the kinetic activity for the reduction reaction of lithium polysulfide, but the mechanism of the present invention is not limited thereto.

[0066] In the present invention, the catalyst containing the transition metal can be used alone as a catalyst for the positive electrode of a lithium-sulfur battery and can impart activity to the reduction reaction of lithium polysulfide. However, according to the present invention, when such a catalyst is located on the outer surface and / or the inner surface of the pores of the porous carbon material doped with the at least one sulfur, there is an effect that the adsorption of lithium polysulfide and the activation of the oxidation / reduction reaction of sulfur can be further improved.

[0067] In one aspect of the present invention, the catalyst is not limited as long as it contains a transition metal as an active component of the catalyst and can mediate the oxidation / reduction reaction of sulfur.

[0068] In another aspect of the present invention, the catalyst may further include the transition metal and at least one non-metal element that forms a ligand with the transition metal. At this time, the transition metal and / or non-metal element present in the catalyst may be physically adsorbed and / or chemically bonded to the carbon of the porous carbon material.

[0069] In still another aspect of the present invention, the catalyst may further include the transition metal, at least one non-metal element that forms a ligand with the transition metal, and an organic support. When the catalyst further includes an organic support for supporting the transition metal and the non-metal element, it can have the effect of improving the catalyst utilization rate of the carbon composite according to one aspect of the present invention by improving the dispersibility of the transition metal.

[0070] In still another aspect of the present invention, the catalyst includes an organic support, a transition metal, and at least one non-metal element that forms a ligand with the transition metal, and the catalyst may include a bond between carbon and the transition metal in the organic support, a bond between the carbon and the non-metal element, and a bond between the transition metal and the non-metal element.

[0071] In one aspect of the present invention, the catalyst may include a transition metal in the form of metal particles formed by the bond between the transition metal atoms. However, from the perspective of the atomic utilization rate of the catalyst, it is preferable to include a transition metal that exists as a single atom without being bonded between the transition metal atoms.

[0072] Thereby, according to one aspect of the present invention, the catalyst may include a single-atom catalyst containing one or more transition metals. Thereby, one or more transition metals contained in the catalyst may have a form dispersed in the carbon composite in a single-atom size.

[0073] As used herein, the "single atom catalyst (SAC)" is a catalyst in which the catalytically active site is represented in atomic units, and the carbon composite may include a single atom catalyst containing a transition metal as a catalyst.

[0074] According to one aspect of the present invention, the catalyst may not contain a metal bond between transition metals in its structure. That is, the catalyst may not contain metal particles formed through a metal bond between two or more transition metal atoms in its structure. Specifically, the carbon composite according to one aspect of the present invention does not contain a metal bond between two or more transition metals contained in the catalyst.

[0075] In one aspect of the present invention, the fact that the transition metal is contained in a form dispersed in a single-atom size on a porous carbon material and / or an organic support can be confirmed, for example, by microscopic observation such as scanning electron microscope (SEM), transmission electron microscope (TEM), or scanning transmission electron microscope (STEM) for the carbon composite and / or the catalyst.

[0076] In another aspect of the present invention, the catalyst contained in the carbon composite may include particles containing one or more transition metals. At this time, the average diameter (D 50 ) of the particles can be, for example, 1 to 30 nm times the diameter of a single atom constituting the transition metal. Specifically, the average diameter (D 50 ) of the particles can have a diameter of 1 to 5 times the diameter of a single atom constituting the transition metal. Preferably, the average diameter (D 50 ) of the particles can be 1 to 3 times the diameter of a single atom constituting the transition metal, and more preferably, 1 times the diameter of a single atom constituting the transition metal. That is, it is most preferable that the catalyst has a form in which the transition metal is dispersed in a single-atom size in the carbon composite.

[0077] In one aspect of the present invention, the fact that the catalyst does not contain a metal bond between two or more transition metals can be confirmed, for example, by X-ray diffraction (XRD) analysis of the carbon composite and / or the catalyst.

[0078] In one aspect of the present invention, the transition metal contained in the catalyst is not particularly limited as long as it can exhibit activity in the oxidation / reduction reaction of sulfur in the positive electrode of a lithium-sulfur battery. For example, zinc (Zn), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zirconium (Zr), niobium (Nb), molybdenum (Mo), technetium (Tc), ruthenium (Ru), rhodium (Rh), palladium (Pd), silver (Ag), cadmium (Cd), lanthanum (La), hafnium (Hf), tantalum (Ta), tungsten (W), osmium (Os), iridium (Ir), cerium (Ce), gadolinium (Gd), scandium (Sc), titanium (Ti), gallium (Ga), indium (In), or two or more of these may be used.

[0079] In another aspect of the present invention, the transition metal contained in the catalyst may be iron (Fe).

[0080] In one aspect of the present invention, the known diameter of an iron (Fe) atom is 300 pm. When the catalyst contained in the carbon composite of the present invention contains iron (Fe), the transition metal present in the carbon composite has, for example, a diameter (D 50 ) of 0.3 nm to 5 nm. For example, the diameter (D 50 ) of iron contained in the carbon composite may be 0.5 nm to 2 nm, 0.3 nm to 1.5 nm, 0.3 nm to 1 nm, or 0.3 nm to 0.5 nm.

[0081] In one aspect of the present invention, the non-metallic element that forms a ligand with the transition metal in the catalyst can be appropriately selected according to the type of the transition metal and is not particularly limited.

[0082] In another aspect of the present invention, the non-metallic element that forms a ligand with the transition metal in the catalyst is, for example, hydrogen (H), boron (B), nitrogen (N), oxygen (O), fluorine (F), neon (Ne), silicon (Si), phosphorus (P), chlorine (Cl), bromine (Br), iodine (I), or two or more of these may be used.

[0083] In still another aspect of the present invention, when the catalyst contains iron (Fe) as a transition metal, it may contain nitrogen (N) as the non-metal element. It may be advantageous for the catalyst to exhibit excellent catalytic activity when the iron forms a ligand with nitrogen, but the present invention is not limited thereto.

[0084] In one aspect of the present invention, when the catalyst contains iron (Fe) as a transition metal and nitrogen (N) as a non-metal element, the catalyst may include a structure in which one iron (Fe) atom is bonded to four nitrogen (N) atoms adjacent to the iron atom. When the catalyst includes a structure in which one iron atom is bonded to four adjacent nitrogen atoms, it can have an advantageous effect on the active stability of the carbon composite, but the present invention is not limited thereto.

[0085] As described above, since the catalyst is located on the outer surface and / or the inner surface of the pores of the at least one sulfur-doped carbon material, the carbon composite according to the present invention can improve the catalytic activity in the oxidation / reduction reaction of sulfur.

[0086] In one aspect of the present invention, the at least one sulfur-doped porous carbon material can be a porous carbon material obtained by carbonizing various carbon material precursors and doped with at least one sulfur.

[0087] The porous carbon material produced by carbonizing the precursors of the various carbon materials is not particularly limited as long as it is commonly used in the technical field. For example, the porous carbon material may include graphite; graphene; reduced graphene oxide (rGO); carbon black such as Denka black, acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black; carbon nanotubes (CNT) such as single-walled carbon nanotubes (SWCNT) and multi-walled carbon nanotubes (MWCNT); carbon fibers such as graphite nanofibers (GNF), carbon nanofibers (CNF), and activated carbon fibers (ACF); graphite and activated carbon such as natural graphite, artificial graphite, and expanded graphite; fullerenes; or activated carbon obtained by activating carbon materials, etc.

[0088] According to the present invention, the carbon composite has a structure in which at least one sulfur is doped into the porous carbon material as described above.

[0089] In the present invention, the porous carbon material doped with at least one sulfur indicates that at least one carbon atom (C) of the porous carbon material is replaced by sulfur.

[0090] In one aspect of the present invention, the content of sulfur doped into the porous carbon material may be, for example, a content such that the molar ratio of sulfur doped into the porous carbon material to one or more transition metals contained in the catalyst is 0.5 to 8. Specifically, the molar ratio of sulfur doped into the porous carbon material to one or more transition metals contained in the catalyst may be 0.5 to 5 or 1 to 3. When the molar ratio of the transition metal to sulfur is within the above range, an advantageous effect in terms of catalytic activity can be achieved, but the present invention is not limited thereto.

[0091] The molar ratio of sulfur doped in the porous carbon material to the transition metal in the catalyst can be measured, for example, by inductively coupled plasma mass spectrometry (ICP-MS). When the content of the doped sulfur is trace, it may be advantageous to use a high-resolution device for measurement accuracy, but the present invention is not limited thereto.

[0092] In one aspect of the present invention, the at least one sulfur can be doped in the form of sulfur atoms or sulfur compounds.

[0093] Specifically, the fact that the sulfur is doped in the form of sulfur atoms indicates that within the structure of the porous carbon material, a -C-S-C- structure is included where carbon atoms are substituted by sulfur atoms. Also, the fact that the sulfur is doped in the form of a sulfur compound indicates that within the structure of the porous carbon material, a -C-SY-C- structure (where SY represents a sulfur compound) is included where carbon atoms are substituted by sulfur compounds.

[0094] In one aspect of the present invention, the form of the sulfur compound can be, for example, a sulfur oxide (SO x , where 0.1 ≤ x ≤ 4).

[0095] In one aspect of the present invention, the porous carbon material doped with the at least one sulfur may include a structure in which sulfur is doped in the form of sulfur dioxide (SO2). Specifically, the porous carbon material doped with sulfur may include a -C-SO2-C- structure within the structure.

[0096] In one aspect of the present invention, the porous carbon material doped with the at least one sulfur may include a first structure according to Formula 1 below and / or a second structure according to Formula 2 below within the structure.

[0097] [Formula 1] -C-SO2-C- [Formula 2] -C-S-C-

[0098] In one aspect of the present invention, the at least one sulfur in the carbon composite can adjust the orbital energy level of the transition metal present in the catalyst. For example, electrons can move between the position doped with the sulfur (i.e., the EEB site) and the transition metal.

[0099] At this time, according to the type of the transition metal, the order of the orbital energy levels of the transition metal and the EEB site is determined. The transition metal may function as an electron donor and the EEB site may function as an electron acceptor, or the transition metal may function as an electron acceptor and the EEB site may function as an electron donor.

[0100] In one aspect of the present invention, the carbon composite may contain iron (Fe) as a transition metal in the catalyst and may include the first structure and the second structure within the structure of the porous carbon material doped with the at least one sulfur. At this time, according to the ratio (first structure / second structure) of the first structure and the second structure at positions capable of forming a coordination bond with the transition metal in the one catalyst, the roles of the transition metal as an electron donor and / or an electron acceptor with respect to the EEB site may be determined.

[0101] In one aspect of the present invention, the electron donor / acceptor relationship between the transition metal and the EEB site can be confirmed by measuring their orbital energy levels, but the mechanism of the present invention is not limited thereto.

[0102] For example, when the orbital energy level of the transition metal showing catalytic activity in the carbon composite is low, electrons transfer from the transition metal to the EEB site, or when the orbital energy level of the transition metal is high, electrons transfer from the EEB site to the transition metal.

[0103] In one aspect of the present invention, if the ratio of the first structure / second structure is high, the d-orbital energy level of iron (Fe) is lowered due to the stabilization of the d-orbital of -SO2, and thus it may have the activity of electrons moving from iron to the EEB site.

[0104] In another aspect of the present invention, if the ratio of the first structure to the second structure is low, the stabilizing effect decreases and the d-orbital (orbital) level of iron increases, whereby electrons may have the activity to move from the EEB site to iron.

[0105] In the present specification, the ratio of the first structure to the second structure can represent, for example, a molar ratio.

[0106] Accordingly, in one aspect of the present invention, when the transition metal in the catalyst of the carbon composite contains iron (Fe), the catalytic activity can be further improved by the movement of electrons from the EEB site to the iron (Fe). Therefore, the ratio (first structure / second structure ratio) of the first structure and the second structure in the structure of the at least one sulfur-doped porous carbon material can preferably be 1 or less. The ratio (first structure / second structure ratio) of the first structure to the second structure can be, for example, 1 or less, 0.9 or less, 0.8 or less, 0.7 or less, 0.6 or less, 0.5 or less, 0.4 or less, 0.3 or less, 0.2 or less, or 0.15 or less. Also, the ratio of the first structure to the second structure can be 0.01 or more, 0.05 or more, or 0.1 or more. For example, the ratio of the first structure to the second structure can be 0.01 or more and 1 or less, 0.05 or more and 0.8 or less, 0.10 or more and 0.7 or less, 0.10 or more and 0.5 or less, or 0.10 or more and 0.2 or less, but the present invention is not limited thereto.

[0107] The carbon composite according to one aspect of the present invention, when used as a positive electrode, contains a large number of fine pores for supporting a positive electrode active material and / or for supporting a catalyst in the carbon composite.

[0108] In one aspect of the present invention, the carbon composite includes a large number of fine pores on its outer surface and inside. At this time, the fine pores can be classified into nano pores with a diameter of less than 10 nm and macro pores with a diameter of 10 nm or more according to their sizes.

[0109] In one aspect of the present invention, the diameter of the nano-pores is less than 10 nm, specifically, it can be 1 to 9.5 nm, 2 to 9 nm, 3 to 8 nm, 3.5 to 7 nm, 4 to 6 nm, 4 to 5 nm, or 4.0 to 4.5 nm.

[0110] In another aspect of the present invention, the diameter of the macro-pores is 10 nm or more, specifically, it can be 10 nm or more and 50 nm or less, 40 nm or less, 30 nm or less, or 20 nm or less. More specifically, the diameter of the macro-pores can be 10 nm to 19 nm, 10 nm to 18 nm, 12 to 18 nm, 13 to 17 nm, or 14 to 15 nm.

[0111] The diameter of the micropores can be measured by a known method in the art for measuring the pore diameter of a porous material, and the measurement method is not particularly limited. For example, the diameter of the micropores can be measured using a scanning electron microscope (SEM), a field-emission electron microscope (FE-SEM), or a laser diffraction method.

[0112] In one aspect of the present invention, when the total number of macro-pores in the carbon composite is larger than the total number of nano-pores, it can be more advantageously mixed with the active material to mediate the activation of the conversion reaction of lithium polysulfide.

[0113] In another aspect of the present invention, among all the pores of the carbon composite, when the number of pores with a diameter less than 10 nm is N(nano) and the number of pores with a diameter of 10 nm or more is N(macro), the ratio of N(macro) to N(nano) is the ratio of N(macro) / N(nano), which can be 1 or more.

[0114] In one aspect of the present invention, the average particle size (D 50 ) of the carbon composite can be, for example, 0.5 μm to 200 μm, 0.5 μm to 200 μm, 1 μm to 150 μm, or 10 μm to 150 μm.

[0115] In one aspect of the present invention, for the usefulness of the lithium-sulfur battery, the BET specific surface area of the carbon composite is, for example, 200 m 2 / g or more, but is not limited thereto.

[0116] Specifically, the upper limit of the BET specific surface area of the carbon composite is not particularly limited, but for example, 200 m 2 / g or more, 300 m 2 / g or more, 400 m 2 / g or more, 500 m 2 / g or more, 600 m 2 / g or more, 700 m 2 / g or more to 1,500 m 2 / g or less, 1,000 m 2 / g or less, 900 m 2 / g or less, 800 m 2 / g or less, 780 m 2 / g or less, 750 m 2 / g or less. The carbon composite according to the present invention contains a large number of fine pores, and the catalyst supported thereon can have a form in which transition metals of single atom size are dispersed in a porous carbon material and / or an organic support, so it has the advantage of a very large specific surface area.

[0117] The BET specific surface area is measured by the BET method and can represent a value measured according to a known method for measuring the BET specific surface area. For example, the BET specific surface area can be a value calculated from the nitrogen gas adsorption amount at liquid nitrogen temperature (77K) using BELSORP-mino II manufactured by BEL Japan.

[0118] In one aspect of the present invention, the pore volume of the carbon composite is, for example, 1 to 10 cm 3 / g. Specifically, the pore volume of the carbon composite is 1 to 10 cm 3 / g, 2 to 8 cm 3 / g, 3 to 6 cm 3 / g, 4 to 5 cm 3 / g, 1 to 3 cm 3 / g, or 1 - 2 cm 3 It may be / g, but is not limited thereto.

[0119] The pore volume can be a value calculated and measured, for example, by N2 isotherm analysis obtained based on the adsorption of liquid nitrogen.

[0120] In one aspect of the present invention, the carbon composite has a Raman peak intensity ratio (I G / I D ratio) that can be 1 or less. For example, the I G / I D ratio can be 0.1 - 1, 0.5 - 1, or 0.8 - 1.0. When the I G / I D ratio is within the above range, it can show an advantageous effect in terms of the loading efficiency of the catalyst and / or the sulfur doping efficiency on the porous carbon material, but the present invention is not limited thereto.

[0121] The Raman peak intensity ratio can be measured by the I G and I D values obtained from the spectrum of the carbon composite obtained by Raman spectroscopy. In the obtained spectrum, I G means the peak of the crystalline part (G - peak, 1573 / cm), and I D means the peak of the amorphous part (D - peak, 1309 / cm). Therefore, at this time, the smaller the ratio value of I G / I D , the lower the crystallinity.

[0122] In one aspect of the present invention, the content of the transition metal in the carbon composite may be, for example, 1 wt% to 20 wt%, specifically 1 wt% to 10 wt% based on the total weight of the carbon composite. When the content of the transition metal is within the above range, while showing an excellent catalytic effect by the carbon composite, it may be advantageous in terms of the effect of well-dispersing the transition metal in single-atom size and increasing the specific surface area of the carbon composite. For example, when the content of the transition metal in the carbon composite exceeds the above range, the carbon composite may form a metal bond between the transition metals and contain the transition metal in the form of metal particles.

[0123] In one aspect of the present invention, the content of sulfur (S) in the carbon composite may be, for example, 0.1 wt% to 10 wt%, specifically 1 wt% to 5 wt% based on the total weight of the carbon composite. When the content of the sulfur is within the above range, it may be advantageous in terms of the effect of enhancing the catalytic efficiency of the transition metal.

[0124] In another aspect of the present invention, as described above, the carbon composite may contain iron as a transition metal, and in the catalyst, iron is dispersed in single-atom size on the organic support and may have a form in which iron forms a ligand with 4 surrounding nitrogen atoms. That is, when such a structure is represented as Fe-N4, sulfur doped in the porous carbon material exists around the Fe-N4, and the sulfur capable of forming a coordination bond with the iron of Fe-N4 may exist in the structure of -C-SO2-C- (first structure) and / or -C-S-C- (second structure). At this time, the ratio of the first structure / second structure may be 1 or less as described above, specifically 0.1 to 0.7. The content of sulfur in the carbon composite may be determined within the range that satisfies the above ratio. At this time, the ratio of the first structure / second structure can be expressed as a molar ratio as described above.

[0125] The ratio of the first structure to the second structure can be, for example, 1 or less, 0.9 or less, 0.8 or less, 0.7 or less, 0.6 or less, 0.5 or less, 0.4 or less, 0.3 or less, 0.2 or less, or 0.15 or less. Further, the ratio of the first structure to the second structure can be, for example, 0.01 or more, 0.05 or more, or 0.1 or more. For example, the ratio of the first structure to the second structure can be 0.01 or more and 1 or less, 0.05 or more and 0.8 or less, 0.10 or more and 0.7 or less, 0.10 or more and 0.5 or less, or 0.10 or more and 0.2 or less, but the present invention is not limited thereto.

[0126] The carbon composite of the present invention as described above can exchange electrons with a transition metal around a catalyst containing the transition metal, and at the same time, there is sulfur that can provide an additional binding site with lithium polysulfide. Therefore, when used as a positive electrode of a lithium-sulfur battery, it can play a role in improving battery efficiency, but the mechanism of the present invention is not limited thereto.

[0127] According to one aspect of the present invention, the carbon composite is a carrier that supports a sulfur-based compound as a positive electrode active material, and is additionally complexed with the sulfur-based compound and used as a positive electrode active material, or the carbon composite itself can be used instead of a conductive material.

[0128] In particular, in the carbon composite of the present invention, the transition metal is dispersed in a single atomic size, which can exhibit the effect of significantly improving the atomic utilization rate of the carbon composite, but the mechanism of the present invention is not limited thereto.

[0129] Another aspect of the present invention provides a method for manufacturing the above-described carbon composite.

[0130] According to another aspect of the present invention, a method for manufacturing a carbon composite includes: (S1) doping at least one sulfur in a porous carbon material; and (S2) impregnating the result of the step (S1) into a transition metal-containing precursor solution and then removing the solvent. Specifically, the step (S1) includes heat-treating in a state where a sulfur doping precursor and the porous carbon material are in contact.

[0131] The step (S1) is a step for doping sulfur into a porous carbon material to form an electron-exchangeable bond (EEB) site for the catalyst.

[0132] In one aspect of the present invention, the step (S1) may include, for example, wetting (impregnating) the porous carbon material with a sulfur-containing solution containing a sulfur doping precursor and then heat-treating.

[0133] In one aspect of the present invention, the step (S1) may be performed, for example, by wetting (impregnating) the porous carbon material with a sulfur-containing solution, grinding until the solvent evaporates, and then heat-treating, but the present invention is not limited thereto. ""

[0134] In one aspect of the present invention, wetting the porous carbon material with a sulfur-containing solution may be performed, for example, by impregnating the porous carbon material with the sulfur-containing solution or immersing the porous carbon material in the sulfur-containing solution, but the present invention is not limited thereto.

[0135] In one aspect of the present invention, the heat treatment may be performed, for example, at 800 °C to 1,000 °C to form a low ratio of -C-SO2-C- (first structure) / -C-S-C- (second structure) at the EEB site.

[0136] In one aspect of the present invention, the heat treatment may include raising the temperature while maintaining a constant rate selected from the range of 2 °C / min to 10 °C / min.

[0137] In one aspect of the present invention, the heat treatment can be performed while increasing the temperature at a rate of 5 °C / min.

[0138] In one aspect of the present invention, after the porous carbon material is brought into contact with the sulfur-containing solution as described above, sulfur is uniformly doped into the porous carbon by pulverization and heat treatment, whereby a uniform EEB is formed in the porous carbon. As a result, the catalyst described later may have a form in which transition metals are uniformly dispersed in the form of single atomic sizes, but the manufacturing method of the present invention is not limited thereto.

[0139] The sulfur-containing solution may be a solution in which a sulfur doping precursor is dissolved in a solvent. The sulfur doping precursor may be, for example, dibenzyldisulfide (DBDS), sodium metabisulfite (Na2S2O5), sodium pyrosulfate (Na2S2O7), sodium thiosulfate (Na2S2O3), thiourea (CH4N2S), sodium sulfide (Na2S), potassium thiocyanate (KSCN), benzyl mercaptan (C7H8S), benzothiophene (C8H6S), dibenzothiophene (C 12 H8S, dibenzohiophene), or a mixture thereof. The solvent can be appropriately selected and used as a solvent for the sulfur doping precursor while being excellent in wettability with the porous carbon material, and is not particularly limited.

[0140] According to one aspect of the present invention, depending on the type of the sulfur doping precursor, the form and structure in which sulfur is doped into the porous carbon material may be different. At this time, since sulfur serves as an EEB site, from the viewpoint that sulfur can supply electrons abundantly to the transition metal, the sulfur doping can be performed using dibenzyldisulfide dissolved in an alcohol-based solvent such as ethanol.

[0141] According to one aspect of the present invention, the doping of sulfur can be carried out using dibenzyl disulfide, and the ratio of -C-SO2-C- (the first structure) / -C-S-C- (the second structure) in the carbon composite produced at this time can be 0.1 to 0.5.

[0142] According to another aspect of the present invention, the doping of sulfur may be carried out using sodium sulfite, and the ratio of -C-SO2-C- (the first structure) / -C-S-C- (the second structure) in the carbon composite produced at this time can be 0.5 to 1.

[0143] The step (S2) may include a step of producing a precursor solution for producing a catalyst supported on the sulfur-doped porous carbon material.

[0144] In one aspect of the present invention, the transition metal-containing precursor solution is a precursor solution for producing a catalyst, and may include an organic solvent and a precursor compound of a transition metal.

[0145] In one aspect of the present invention, the transition metal-containing precursor solution is a precursor solution for producing a catalyst, and may include an organic solvent, a precursor compound of a non-metal element, and a precursor compound of a transition metal.

[0146] In one aspect of the present invention, the precursor compound of the transition metal can be, for example, an oxide, a halide, an acetate, a nitrate, a sulfate, a cyanide, a fatty acid salt or a phosphonate of a saturated or unsaturated carbon chain of the transition metal, or a mixture of two or more of these.

[0147] In one aspect of the present invention, the halide of the transition metal can be, for example, a fluoride of the transition metal, a chloride of the transition metal, a bromide of the transition metal, or an iodide of the transition metal.

[0148] In another aspect of the present invention, the precursor solution may contain iron(III) chloride (FeCl3), ferrocene, iron acetylacetonate, iron nitrate, ferrous sulfate, potassium iron ferricyanide, or a mixture of two or more of these.

[0149] In one aspect of the present invention, the precursor compound of the non-metal element may be an organic compound containing at least one non-metal element.

[0150] In one aspect of the present invention, the organic compound containing at least one non-metal element is a compound containing the non-metal element described above. The non-metal element may be, for example, nitrogen (N), and the organic compound containing nitrogen may be, for example, 1,10-phenanthroline, polyaniline, polydopamine, melamine, carbon nitride (g-CN, carbon nitride), phenylenediamine, or a mixture of two or more of these.

[0151] In one aspect of the present invention, the organic solvent is a solvent for the organic compound containing at least one non-metal element and the halide of the transition metal, and can be appropriately selected and used, and is not particularly limited.

[0152] In one aspect of the present invention, the molar ratio of the precursor compound of the non-metal element to the halide of the transition metal in the precursor solution may be, for example, 50:1 to 1:1, 40:1 to 1:1, 20:1 to 1:1, 10:1 to 1:1, or 5:1 to 1:1, but is not limited thereto.

[0153] In one aspect of the present invention, the molar ratio of the precursor compound of the non-metal element to the halide of the transition metal in the precursor solution may be, for example, 4:1.

[0154] In one aspect of the present invention, it may further include a step of manufacturing a transition metal-containing precursor solution before the step (S2). At this time, the step of manufacturing the transition metal-containing precursor solution can be performed in any order in relation to the step (S1). For example, the step of manufacturing the transition metal-containing precursor solution is performed after the step (S1), or the step (S1) is performed after the step of manufacturing the transition metal-containing precursor solution, or the step of manufacturing the transition metal-containing precursor solution is performed simultaneously while performing the step (S1). Thus, the execution order of the step (S1) and the step of manufacturing the transition metal-containing precursor solution is not particularly limited.

[0155] The step (S2) is a step of positioning at least one catalyst containing a transition metal on at least one of the outer surface and the inner surface of the pores of at least one sulfur-doped porous carbon material manufactured in (S1).

[0156] For this purpose, the step (S2) includes a step of removing the solvent after impregnating the result of the step (S1) into the transition metal-containing precursor solution.

[0157] In one aspect of the present invention, the step (S2) may include a step of pulverizing and drying after impregnating the result of the step (S1) into the transition metal-containing precursor solution. The drying can be performed, for example, at 70°C to 100°C, but is not limited thereto. According to another aspect of the present invention, after the drying, it may further include a step of heat-treating at, for example, 800°C to 1,000°C.

[0158] In one aspect of the present invention, after the step (S2), it may further include a step of acid-treating after cooling the result obtained from the step (S2) to room temperature in (S3).

[0159] According to the method as described above, at least one sulfur-doped porous carbon material and at least one catalyst containing one or more transition metals are included, and a carbon composite in which the catalyst is located on at least one of the outer surface and the inner surface of the pores of the at least one sulfur-doped porous carbon material can be produced.

[0160] According to still another aspect of the present invention, a positive electrode including the carbon composite and a positive electrode active material including a sulfur-based compound as described above is provided.

[0161] The positive electrode may use the carbon composite as described above as a carrier of the positive electrode active material, and include, as the positive electrode active material, a composite formed by mixing this with a sulfur-based compound as the positive electrode active material.

[0162] In one aspect of the present invention, the sulfur-based compound may be, for example, sulfur (S8), lithium sulfide (Li2S), lithium polysulfide (Li2S x , 2 ≤ x ≤ 8), a disulfide compound, or a mixture of two or more of these, but is not limited thereto.

[0163] In one aspect of the present invention, the carbon composite and the sulfur-based compound are determined according to the content of sulfur in the carbon composite and the type of sulfur-based compound, and are not particularly limited. For example, the carbon composite and the sulfur-based compound may be mixed at a content ratio of 1:9 to 9:1. Specifically, they may be mixed at a content ratio of 1:9 to 5:5, and more specifically, at a content ratio of 2:8 to 4:6.

[0164] In one aspect of the present invention, the positive electrode active material can be formed by heat-treating after mixing the carbon composite and the sulfur-based compound. The heat treatment can be performed, for example, at a temperature of 130°C to 180°C, specifically 150°C to 160°C.

[0165] In one aspect of the present invention, the positive electrode for the lithium-sulfur battery may further include a binder in addition to the positive electrode active material containing the carbon composite and the sulfur-based compound. The binder is not particularly limited as long as it is a binder used for the positive electrode of the lithium-sulfur battery.

[0166] In another aspect of the present invention, the positive electrode for the lithium-sulfur battery may further include a conductive material, an additive, etc. in addition to the positive electrode active material and the binder. At this time, since ordinary ones can be used as the binder, the conductive material, and the additive, the description of specific types is omitted.

[0167] In still another aspect of the present invention, the positive electrode for the lithium-sulfur battery includes a positive electrode current collector, and may include a positive electrode active material layer in which the positive electrode active material is coated on one side or both sides of the current collector together with a binder.

[0168] At this time, the positive electrode current collector is not particularly limited as long as it has high conductivity without inducing a chemical change in the battery.

[0169] In one aspect of the present invention, the positive electrode containing the carbon composite can exhibit excellent effects in terms of initial capacity and cycle stability, but the effects of the present invention are not limited thereto.

[0170] In one aspect of the present invention, the positive electrode for the lithium-sulfur battery may have a sulfur (S) loading amount of, for example, 1.0 mg / cm 2 or more. For example, the loading amount of sulfur in the positive electrode for the lithium-sulfur battery is 1 mg / cm 2 or more, 1.5 mg / cm 2 or more, 2 mg / cm 2 or more. For example, it is 2 mg / cm 2 to 10 mg / cm 2 and can exhibit the effect of showing driving stability.

[0171] The lithium-sulfur battery according to still another aspect of the present invention includes a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte, and the positive electrode contains the above carbon composite and sulfur-based compound as a positive electrode active material.

[0172] In one aspect of the present invention, the negative electrode, separator, and electrolyte can be used without particular limitation as long as they can be used in a lithium-sulfur battery without impairing the object of the present invention, and thus the description of their specific types is omitted.

[0173] In one aspect of the present invention, the outer shape of the lithium-sulfur battery can be, for example, coin type, cylindrical type, pouch type, or square type, etc., but is not particularly limited. Further, the lithium-sulfur battery can be used not only as a battery cell used as a power source for small devices, but also as a unit cell of a medium and large-sized battery module including a plurality of battery cells, and there is no particular limitation on its usage form.

[0174] In one aspect of the present invention, the lithium-sulfur battery using the positive electrode containing the carbon composite is excellent not only in terms of initial capacity and cycle stability, but also can exhibit excellent effects in terms of the energy density of the battery, but the effects of the present invention are not limited thereto.

[0175] In one aspect of the present invention, the lithium-sulfur battery can exhibit the effect of significantly improving the energy density by increasing the loading amount of sulfur in the electrode and reducing the amount of the electrolyte, but the effects of the present invention are not limited thereto.

[0176] In one aspect of the present invention, the lithium-sulfur battery may have an electrolyte / sulfur (E / S) ratio of 10 μL / mg or less. For example, the E / S ratio of the lithium-sulfur battery may be 10 μL / mg or less, 8 μL / mg or less, 6 μL / mg or less, 4 μL / mg or less, or 2 μL / mg or less. Conventionally, there has been a limit to reducing the E / S ratio due to the low activity of the positive electrode. However, since the present invention has the effect of stably reducing the E / S ratio, the E / S ratio of the lithium-sulfur battery may be a value exceeding the above range, and it is obvious to those skilled in the art that there is no lower limit, and the present invention is not limited thereto.

[0177] In another aspect of the present invention, the lithium-sulfur battery may have an electrolyte / capacity (E / C) ratio of 10 μL / mAh or less. For example, the E / C ratio of the battery for the lithium-sulfur battery may be 10 μL / mAh or less, 9 μL / mAh or less, 8 μL / mAh or less, 7 μL / mAh or less, 5 μL / mAh, or 4 μL / mAh or less, but the present invention is not limited thereto. The electrolyte / capacity (E / C) ratio of the lithium-sulfur battery may be, for example, 1 μL / mAh or more, but the present invention is not limited thereto.

[0178] According to still another aspect of the present invention, there is provided a positive electrode containing the above-described carbon composite as a positive electrode additive and a sulfur-based compound as a positive electrode active material.

[0179] In one aspect of the present invention, apart from one aspect of the present invention in which the carbon composite is included in the positive electrode in the form of a positive electrode active material formed by being complexed with a sulfur-based compound using the carbon composite as a carrier, the carbon composite may be included as an additive that replaces the conductive material in the positive electrode.

[0180] In one aspect of the present invention, when the carbon composite is used as a positive electrode additive, there may be an effect that not only can the capacity of the battery be improved, but also the battery performance can be improved by improving the reactivity with lithium polysulfide.

[0181] In one aspect of the present invention, when the carbon composite is used as a positive electrode additive, the carbon composite may be contained in an amount of 1 to 25% by weight, for example, 1 to 15% by weight, or 1 to 10% by weight, based on the total weight of the positive electrode active material, binder, and carbon composite contained in the positive electrode active material layer, but is not limited thereto.

[0182] In one aspect of the present invention, a sulfur-based compound as a positive electrode active material or a material in which the sulfur-based compound is supported on a normal carbon carrier can be used for the positive electrode. For the sulfur-based compound, the configuration of the positive electrode according to the above-described aspect is incorporated. Further, the normal carbon carrier may be, for example, carbon nanotubes, but is not limited thereto.

[0183] According to still another aspect of the present invention, as described above, a lithium-sulfur battery including a positive electrode using a carbon composite as a positive electrode additive, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte is provided.

[0184] According to still another aspect of the present invention, a battery including the carbon composite as described above in at least one of the positive electrode and the negative electrode is provided. At this time, the battery may include a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte, and is not particularly limited to a lithium-sulfur battery.

[0185] At this time, for the other components of the negative electrode, separator, electrolyte, and positive electrode other than the carbon composite, the configuration of the battery according to the above-described aspect is incorporated.

[0186] FIG. 2a shows a schematic diagram of a flowchart for producing a carbon composite by forming a transition metal-containing catalyst after doping at least one sulfur into porous carbon according to one aspect of the present invention, and using the same to mix with a sulfur-based compound to produce a positive electrode active material.

[0187] Hereinafter, a method for producing a carbon composite according to an aspect of the present invention and a method for producing a positive electrode active material using the same will be described in detail with reference to examples. However, the following examples are merely for illustrating the present invention, and the scope of the present invention is not limited by these examples.

[0188] Production Example 1. Synthesis of Porous Carbon Material (MSU-F-C) The porous carbon material was synthesized using the hard template method as follows.

[0189] First, poly(ethylene glycol)-block-polypropylene glycol)-block-poly(ethylene glycol) (P123, Mn: ~5800 g / mol, manufactured by Sigma-Aldrich) was dissolved in distilled water (DI water) (160 ml) and glacial acetic acid (99.8%, SAMCHUN Pure Chemical Co., Ltd.) (4.58 ml). Next, mesitylene (manufactured by Merck Millipore) (9.26 ml) was added dropwise and stirred for 1 hour to prepare a P123 solution.

[0190] Sodium silicate (manufactured by Sigma-Aldrich) (15.5 ml) was dissolved in distilled water (240 ml) to prepare a sodium silicate solution. The prepared sodium silicate solution was added to the P123 solution prepared above, stirred for 5 minutes, and then stored at 40°C for 20 hours without stirring. Thereafter, it was aged in an oven at 100°C for 24 hours. The aged solution was filtered and redissolved in a mixture of distilled water (200 ml) and HCl solution (35.0 - 37.0%, SAMCHUN Pure Chemical Co., Ltd.) (5 ml). After 3 hours, the solution was filtered again and calcined at 550°C for 4 hours to obtain mesoporous silica (MSU-F-SiO2).

[0191] The obtained mesoporous silica was uniformly dispersed in ethanol, and AlCl3·6H2O (98%, Kanto Chemical Co., Inc.) (0.21 g) was mixed to obtain a uniform mixture. Next, the obtained mixture was dried in an oven at 60 °C to remove ethanol, and the mixture was calcined at 550 °C for 4 hours to obtain mesoporous silica (Al-MSU-F-SiO2) into which Al acid sites were introduced.

[0192] The Al-MSU-F-SiO2 as a hard mold was impregnated with furfuryl alcohol (manufactured by Sigma-Aldrich) as a carbon precursor, and then heat-treated at 850 °C for 4 hours in an Ar atmosphere. After cooling to room temperature, the Al-MSU-F-SiO2 mold was etched with an HF solution (manufactured by JT baker) to produce the porous carbon material (MSU-F-C) of Production Example 1.

[0193] Example 1. Production of carbon composite (FeNC-EEB-1) Step 1. Doping of sulfur in the porous carbon material (formation of EEB sites) Dibenzyl disulfide (DBDS, 98%) was dissolved in ethanol (100 ml) to prepare a DBDS solution.

[0194] The porous carbon material (MSU-F-C) produced above was uniformly impregnated with the DBDS solution, and then repeatedly ground until the ethanol was completely evaporated. Next, the DBDS-impregnated porous carbon (DBDS-impregnated MSU-F-C) was dried at 80 °C for 1 hour and then heat-treated at 900 °C for 1 hour in an Ar atmosphere to form EEB sites with a low molar ratio of -SO2 / -S.

[0195] Step 2. Introduction of transition metal catalyst To support the transition metal catalyst on the external surface of the porous carbon and the internal surface of the pores where the EEB sites were formed, FeCl3·6H2O (manufactured by Sigma-Aldrich) and 1,10-phenanthroline (99%, manufactured by Sigma-Aldrich) in ethanol were dissolved to produce a transition metal-containing precursor solution. Next, the precursor solution was immersed in the porous carbon material with EEB sites formed, and then pulverized. After drying the mixture at 80 °C for 1 hour, it was heat-treated at 900 °C for 1 hour under an Ar atmosphere. After cooling to room temperature, it was stirred with 1M HCl to remove the aggregated Fe metal residues, and the titled carbon composite (FeNC-EEB-1) was produced.

[0196] Example 2. Production of carbon composite (FeNC-EEB-2) A carbon composite (FeNC-EEB-2) was produced in the same manner as in Example 1, except that Na2S2O5 (97%, manufactured by Sigma-Aldrich) was used instead of DBDS for the formation of EEB sites.

[0197] Comparative Example 1. Production of carbon composite (FeNC) A carbon composite (FeNC) was produced in the same manner as in Example 1, except that the EEB sites were not formed by not performing Step 1 and the transition metal catalyst was introduced.

[0198] [Confirmation of sulfur doping] The 2p spectra of sulfur atoms (S) in the carbon composites of Example 1 and Example 2 were obtained using X-ray spectroscopy (XPS: X-ray spectroscopy) (VG Scientific Escalab 250, Al Kα), and the results are shown in Fig. 2b (Example 1) and Fig. 2c (Example 2), respectively.

[0199] According to FIGS. 2b and 2c, it was confirmed that both Example 1 and Example 2 showed two characteristic peaks of -S at 163.7 eV (C-S-C 2p 3 / 2) and 164.9 eV (C-S-C 2p 1 / 2) in the -C-S-C- structure formed by doping sulfur atoms in porous carbon, and a characteristic peak of -SO2 at 168.0 eV (Oxidized S) in the -C-SO2-C- structure formed by doping sulfur dioxide.

[0200] As a result, it was confirmed that both Example 1 and Example 2 contained a structure in which sulfur was doped in porous carbon.

[0201] Next, for the carbon composites of Example 1, Example 2, and Comparative Example 1, the Fe content and the molar ratio of the -SO2 / -S structure were measured using inductively coupled plasma atomic emission spectroscopy (ICP-AES), and the results are shown in FIG. 2d.

[0202] According to FIG. 2d, it was confirmed that the -SO2 / -S molar ratios at the EEB sites of Example 1 and Example 2 were different. Specifically, the -SO2 / -S molar ratio of Example 1 was 0.12, and the -SO2 / -S molar ratio of Example 2 was 0.63, which was confirmed to be about 5 times higher than that of Example 1. It was speculated that this was because Na2S2O5, which is the precursor for sulfur doping in Example 2, had a higher oxygen fraction than DBDS, and thus formed -SO2 species more stably at high temperatures.

[0203] In addition, the mapping images obtained by the energy dispersive X-ray spectrometer (EDS) according to Example 1 and Example 2 are shown in Fig. 3. The mapping images by EDS were obtained from the distribution results of Fe single atoms and other components using a high-performance TEM (HR-TEM; Titan cubed G2 60-300). According to Fig. 3, it was confirmed that the respective Fe, N, C, S, and O atoms in Example 1 and Example 2 were uniformly distributed along the particles. Thereby, it was confirmed that EEB sites were formed by doping with a transition metal-containing catalyst and sulfur in the carbon composite. In particular, according to Fig. 3, it was confirmed that the nearest-neighbor atomic distance between the Fe element and the S element in the carbon composites of Example 1 and Example 2 was formed to be 2 nm or less.

[0204] [Structural Analysis of Carbon Composite] The structures of the carbon composites of Example 1, Example 2, and Comparative Example 1 manufactured above were confirmed by the following method.

[0205] Microscopic Observation Images obtained using SEM (S-4800 field emission, Hitachi, Ltd.) and TEM (G2 F30 S-Twin, Tencai) for each of the carbon composites of Example 1, Example 2, and Comparative Example 1 are shown in Fig. 4. In Fig. 4, FeNC represents the carbon composite according to Comparative Example 1, FeNC-EEB-1 represents the carbon composite according to Example 1, and FeNC-EEB-2 represents the carbon composite according to Example 2. In each figure, the left figure shows the SEM image, and the right figure shows the TEM image.

[0206] Analysis of Pore Characteristics For each of the carbon composites of Example 1, Example 2, and Comparative Example 1, the pore diameter (left) and relative pressure (right) were confirmed by the nitrogen physical adsorption analysis method, and the results are shown in Fig. 5.

[0207] Specifically, the specific surface area and pore analysis of the manufactured comparative examples and examples were performed by the following method.

[0208] First, in order to remove moisture physically adsorbed in the pores, etc., a pretreatment was carried out to dry the analyte overnight in vacuo at 120°C. Next, liquid nitrogen at 77K was physically adsorbed on the surface and pores of the analyte until the pressure was equilibrated in vacuo. At this time, the specific surface area of the porous material was calculated using the BET (Brunauer-Emmett-Teller) method with respect to the N2 isotherm obtained by measurement. Furthermore, based on the obtained N2 isotherm, the pore volume value was obtained by BJH (Barrett-Joyner-Halenda) method calculation.

[0209] The measurement results of the surface area, pore diameter, and pore volume of the carbon composites of Example 1, Example 2, and Comparative Example 1 are shown in Table 1 below.

[0210] As can be seen from FIG. 5, as a result of analyzing the pore diameter, the distribution of the pore diameter appeared in a bimodal form. In Table 1 below, the peak that appears at the smaller diameter among the two peaks is shown as the first pore diameter peak, and the peak that appears at the larger diameter is shown as the second pore diameter peak.

[0211]

Table 1

[0212] According to the results of FIGS. 4 and 5 and Table 1, each of the carbon composites of Example 1, Example 2, and Comparative Example 1 has a porous structure, and the BET specific surface area is 700 m 2 / g or more, and it was confirmed that they each contain pores of 4 to 5 nm and 10 to 15 nm.

[0213] Confirmation of the distribution of transition metals For Comparative Example 1, Example 1, and Example 2, images obtained using a high-angle annular dark-field scanning transmission electron microscope (HAADF-STEM) are shown in Fig. 6. The images by HAADF-STEM were obtained based on the distribution results of Fe single atoms and other components using a high-performance TEM (HR-TEM; Titan cubed G2 60-300). According to Fig. 6, in Comparative Example 1, Example 1, and Example 2, it was confirmed that the transition metal Fe was dispersed in the porous carbon in single-atom size.

[0214] In addition, the results of Fourier-transformed extended X-ray absorption fine structure (FT-EXAFS) for Comparative Example 1, Example 1, and Example 2 are shown in Fig. 7. To compare the chemical state of the iron element distributed in the carbon composite with the chemical state of iron metal, the evaluation results for an Fe foil are also shown in Fig. 7.

[0215] According to Fig. 7, while an Fe-Fe metal bond (2.2 Å) was confirmed for the Fe foil, in Comparative Example 1, Example 1, and Example 2, it was confirmed that the Fe-Fe metal bond disappeared and new Fe-N (1.4 Å) and Fe-C (2.4 Å) peaks were formed. Thereby, it was confirmed that the catalyst (Fe-N-C) present in Comparative Example 1, Example 1, and Example 2 did not contain an Fe-Fe metal bond, that is, Fe metal particles.

[0216] [Confirmation of Catalytic Function of Carbon Composite] For the carbon composites of Example 1, Example 2, and Comparative Example 1, graphs obtained using Fe K-edge XANES (X-ray absorption near-edge structure) analysis method are shown in Fig. 8.

[0217] According to the results of Fig. 8, it was confirmed that the white line intensity of Example 1 was lower than that of Comparative Example 1, and the white line intensity of Example 2 was higher than that of Comparative Example 2. That is, it was confirmed that Example 1 had a low -SO2 / -S ratio and showed an upshift of the Fe d-band center, and thus had the activity of electron transfer from the EEB site to Fe.

[0218] On the other hand, it was confirmed that Example 2 had a high -SO2 / -S ratio and showed a downshift of the Fe d-band center, and thus had the activity of electron transfer from Fe to the EEB site.

[0219] Thereby, it was confirmed that the d-orbital (orbital) energy level of the carbon composite could be adjusted by electron exchange according to the doping structure of sulfur capable of coordinate bonding with the transition metal around the catalyst, that is, the ratio of -SO2 / -S.

[0220] [Manufacture of Lithium-Sulfur Coin-Type Battery] In order to confirm the conversion reaction activity of sulfur and polysulfide of the carbon composite manufactured above, a lithium-sulfur coin-type battery was manufactured as follows.

[0221] Example 3 [Manufacture of Positive Electrode] 30 wt% of the carbon composite (FeNC-EEB-1) of Example 1 manufactured above and 70 wt% of sulfur (sulfur powder, manufactured by Sigma-Aldrich) were mixed and heated at 155 °C for 8 hours to obtain a positive electrode active material.

[0222] For the manufacture of the working electrode, using an NMP (N-methyl-2-pyrrolidone) solvent, the positive electrode active material manufactured above and PVDF (polyvinylidene fluoride) as a binder were mixed at a weight ratio of 9:1 to manufacture a positive electrode slurry.

[0223] The prepared positive electrode slurry was coated on carbon-coated Al foil and then dried at 60 °C for 8 hours. Thereafter, the electrode was pressed and cut into coin shape to fabricate the positive electrode.

[0224] Fabrication of Battery A separator was interposed between the positive electrode, the negative electrode, and the positive and negative electrodes, and this was placed in a case together with the electrolyte to fabricate the battery.

[0225] The positive electrode fabricated above was prepared as the positive electrode, and a porous polypropylene membrane (Celgard 2400, Welcos Ltd) was prepared as the separator. Lithium metal (200 μm thick) was prepared as the reference electrode and the counter electrode, respectively. As the electrolyte, a solution containing 1.0 M LiTFSI (lithium bis(trifluoromethane)sulfonamide) as the electrolyte and 2.0 wt% LiNO3 (99.99% metal-based, manufactured by Sigma-Aldrich) as the additive was used in a solvent obtained by mixing dimethoxymethane and 1,3-dioxolane (DME / DOL) at a volume ratio of 1:1 (PANAX E-TEC Co., Korea).

[0226] The sulfur loading in the positive electrode was 2.0 mg / cm 2 and the E / S ratio of the battery was 10 μL / mg.

[0227] Example 4 A battery was fabricated in the same manner as in Example 3, except that Example 2 (FeNC-EEB-2) was used as the carbon composite during the fabrication of the positive electrode.

[0228] Comparative Example 2 A battery was fabricated in the same manner as in Example 3, except that Comparative Example 1 (FeNC) was used as the carbon composite during the fabrication of the positive electrode.

[0229] Production Example 2 A battery was fabricated in the same manner as in Example 3, except that the porous carbon material (MSU-F-C) of Production Example 1 was used instead of the carbon composite during the fabrication of the positive electrode.

[0230] [Performance Evaluation of Lithium-Sulfur Coin-Type Batteries] Using the lithium-sulfur coin-type batteries manufactured above, the redox kinetic activity of lithium sulfide (Li2S) was evaluated by the following method.

[0231] First, Fig. 9a shows the Tafel plots obtained to evaluate the redox kinetics of sulfur. According to Fig. 9a, it was confirmed that the Tafel plot of Example 3 in the positive electrode reaction was much lower than that of Comparative Example 2, while the Tafel plot of Example 4 was slightly lower than that of Comparative Example 2. On the other hand, in the negative electrode reaction, both Example 3 and Example 4 showed lower Tafel slots than Comparative Example 2, which proves that the doped sulfur around the catalyst, that is, the -SO2 / -S EEB site, improved the redox kinetics of sulfur.

[0232] Next, in order to better understand the electrochemical kinetics of sulfur by the EEB site on the nucleation / decomposition behavior of lithium sulfide in the batteries of Example 3 and Example 4, constant voltage analysis was performed, and the results are shown in Figs. 9b and 9c. In Figs. 9b and 9c, the capacity was calculated based on the weight of sulfur in the electrode.

[0233] According to Fig. 9b, the maximum current time t during constant voltage discharge at 2.05V m was 227 s (Example 3), 320 s (Example 4), and 400 s (Comparative Example 2), respectively. Considering that the t m value is highly related to the nucleation density (N0) and growth rate (k 2 ) of lithium sulfide as shown in the following formula, it was confirmed that the improvement of lithium sulfide nucleation in the battery of Example 3 induced a higher lithium sulfide nucleation capacity (213.3 mAh / g). Next, in Example 4 (196.8 mAh / g), although the capacity was slightly lower than that of Example 3 (213.3 mAh / g), it was confirmed that it had better capacity characteristics than Comparative Example 2 (185.3 mAh / g).

[0234] tm =(2πN0k 2 )-0.5

[0235] According to FIG. 9c, during the constant voltage charging at 2.35 V, Example 3 has a lower t m (468 s) and a higher Li2S dissociation capacity (323.5 mAh / g) than Comparative Example 2 (t m : 468 s, Li2S dissociation capacity: 323.5 mAh / g). It was also confirmed that Example 4 has a higher t m (489 s) and a higher Li2S dissociation capacity (381.5 mAh / g) than Comparative Example 2.

[0236] Thus, (i) by comparing the results of Comparative Example 2, Example 3, and Example 4, it was confirmed that introducing -SO2 / -S EEB sites formed by sulfur doping around the transition metal-containing catalyst can improve the kinetics of the conversion reaction involving lithium sulfide on the catalyst. In particular, (ii) it was confirmed that EEB sites with a low -SO2 / -S ratio (Example 3) are more effective in promoting the nucleation / decomposition reaction of lithium sulfide on the catalyst than EEB sites with a high -SO2 / -S ratio (Example 4).

[0237] Next, in order to evaluate the charge-discharge performance of the batteries of Comparative Example 2, Example 3, and Example 4, for the batteries of Comparative Example 2, Example 3, and Example 4, the charge-discharge performance was evaluated at a current density of 0.2 - 3.0 C rate (1 C rate - 1675 mA / g) and a voltage range of 1.7 - 2.8 V (vs. Li / Li + ), and the results are shown in FIG. 10.

[0238] FIG. 10(a) shows the initial voltage characteristics of the batteries of Comparative Example 2, Example 3, and Example 4 at a 0.2 C rate. According to this, it was confirmed that Comparative Example 2 also has a high initial discharge capacity (1125 mAh / g) due to the presence of the catalyst (FeNC), but it was confirmed that the batteries of Example 3 (1324 mAh / g) and Example 4 (1179 mAh / g) have higher initial discharge capacities.

[0239] In the results of Fig. 10(b), in addition to using FeNC-EEB-1 as a comparative group, the results of a battery (Production Example 2) in which a positive electrode was produced using the porous carbon (MSU-F-C) according to Production Example 1 are both shown. According to the results of Fig. 10(b), also in the case of the polarization degree, it was confirmed that the batteries of Example 3 (0.17 V) and Example 4 (0.185 V) were further improved compared to Comparative Example 2 (0.205 V).

[0240] In Fig. 10(c), the measurement results of the discharge capacity ratio (rate capability) measured at different current densities of 0.3 to 2.0 C rates for the batteries of Comparative Example 2, Example 3, and Example 4 are shown. According to the results of Fig. 10(c), also in the case of the discharge capacity ratio, it was measured in the order of Comparative Example 2 < Example 4 < Example 3, and it was confirmed that the improvement degree of the discharge capacity ratio of Example 3 was the best.

[0241] Fig. 11 is a graph showing the measurement results of the discharge capacity measured while repeating charge and discharge 200 times at 0.2 C. According to Fig. 11, the battery of Comparative Example 2 showed a capacity of 864 mAh / g after 200 cycles, whereas the battery of Example 4 showed a capacity of 925 mAh / g, which was about 7% higher than that of Comparative Example 2, and the battery of Example 3 showed a capacity of 1030 mAh / g, which was about 10% higher than that of Example 4. As a result, it was confirmed that the batteries of Example 3 and Example 4 showed a high capacity retention rate even after repeating 200 charge and discharge cycles and had excellent cycle stability.

[0242] Fig. 12 shows, by additional experiments, that during the production of the positive electrode of Example 3, the sulfur loading amounts were 1.5 mg / cm 2 、3.5 mg / cm 2 、5.0 mg / cm 2It was changed to [specific value], the E / S ratio was adjusted to 4.0 μL / mg, and after repeating charge and discharge 100 times under the condition of 0.1 C rate, the measurement results of the discharge capacity are shown. According to Figure 12, when the carbon composite of FeNC-EEB-1 was used, it was confirmed that the performance of the lithium-sulfur battery was excellent even under harsh conditions.

[0243] Based on the above results, it was confirmed that the catalyst introduced with the -SO2 / -S EEB sites formed by doping sulfur around the transition metal-containing catalyst has excellent effects on the high capacity, cycle stability, discharge capacity ratio, and low polarity of the lithium-sulfur battery.

[0244] In particular, it was confirmed that the carbon composite introduced with the EEB sites having a low -SO2 / -S ratio is more effective in improving the performance of the lithium-sulfur battery than the carbon composite introduced with the EEB sites having a high -SO2 / -S ratio. This was confirmed by additional experiments that the -S structure around the catalyst has a more effective function in adjusting the binding energy of LiPS and the energy barrier of the conversion reaction between Li2S4 and Li2S than the -SO2 structure.

[0245] [Battery Manufacture] Example 5 Manufacture of the positive electrode 75 wt% of sulfur (sulfur powder, manufactured by Sigma-Aldrich) was supported on 25 wt% of carbon nanotubes (CNT, BET specific surface area 150 - 350 m 2 / g) to obtain the positive electrode active material.

[0246] Using NMP (N-methyl-2-pyrrolidone) solvent, the positive electrode active material manufactured above, carbon nanotubes (CNT, BET specific surface area 150 - 350 m 2 / g) as the conductive material, the carbon composite (FeNC-EEB-1) of Example 1 manufactured above as the additive, and PVDF (polyvinylidene fluoride) as the binder were mixed at a weight ratio of 90:2.5:2.5:5 respectively to manufacture the positive electrode slurry.

[0247] After coating the manufactured positive electrode slurry on carbon-coated Al foil, it was dried at 60 °C for 8 hours. Then, the electrode was pressed and cut into coin shape to manufacture the positive electrode.

[0248] Manufacture of Battery A battery was manufactured in the same manner as in Example 3, except that the positive electrode manufactured above was used.

[0249] The loading amount of sulfur in the positive electrode was 3.5 mg / cm 2 was.

[0250] Comparative Example 3 A battery was manufactured in the same manner as in Example 5, except that the positive electrode active material, the conductive material, and the binder were mixed at a weight ratio of 90:5:5, respectively, without mixing the carbon composite (FeNC-EEB-1).

[0251] The loading amount of sulfur in the positive electrode was 3.5 mg / cm 2 was.

[0252] [Evaluation of Battery Performance] To evaluate the charge-discharge performance of the batteries of Example 5 and Comparative Example 3, for the batteries of Example 5 and Comparative Example 3, the charge-discharge performance was evaluated at a current density of 0.1C rate and a voltage range of 1.7~2.6V (vs.Li / Li + ), and the results are shown in Fig. 13.

[0253] Fig. 13 shows the initial voltage characteristics of the batteries of Example 5 and Comparative Example 3 at 0.1C rate. According to this, in Example 5, by using the carbon composite (FeNC-EEB-1) as the positive electrode additive, it was confirmed that not only the initial discharge capacity was improved, but also the battery reactivity could be improved.

[0254] It can be presumed that this is because the carbon composite according to the present invention has an effect as a catalyst additive that adsorbs lithium polysulfide and plays a role of a catalyst that promotes its conversion reaction as compared with a normal conductive material used for a positive electrode, but the effect of the present invention is not limited thereto.

Claims

1. At least one sulfur-doped porous carbon material, At least one catalyst containing one or more transition metals, comprising, The catalyst is a carbon composite located on at least one of the outer surface and the inner surface of the pores of the at least one sulfur-doped porous carbon material.

2. The carbon composite according to Claim 1, wherein the nearest atomic distance between the transition metal contained in the catalyst and at least one sulfur doped in the porous carbon material is 10 nm or less.

3. The carbon composite according to Claim 1, wherein the nearest atomic distance between the transition metal contained in the catalyst and at least one sulfur doped in the porous carbon material is 2 nm or less.

4. The carbon composite has a BET specific surface area of 200 m ２ / g or more, the carbon composite according to claim 1.

5. The carbon composite according to Claim 1, wherein the catalyst further comprises the transition metal and at least one non-metallic element that forms a ligand with the transition metal.

6. The carbon composite according to Claim 1, wherein the catalyst further comprises the transition metal, at least one non-metallic element that forms a ligand with the transition metal, and an organic support.

7. The catalyst includes a single-atom catalyst containing one or more transition metals, The carbon composite according to Claim 1, wherein the one or more transition metals are dispersed in the carbon composite in a single-atom size.

8. The carbon composite according to Claim 1, wherein no metal bond is included between two or more transition metals contained in the catalyst.

9. The catalyst includes particles containing one or more transition metals, The average diameter (D ５０ ) of the particles is 1 to 30 nm times the diameter of a single atom constituting the transition metal, and the carbon composite according to claim 1.

10. The catalyst includes particles containing one or more transition metals, The average diameter (D ５０ ) of the particles is 1 to 5 times the diameter of a single atom constituting the transition metal, and the carbon composite according to claim 1.

11. The transition metal is zinc (Zn), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zirconium (Zr), niobium (Nb), molybdenum (Mo), technetium (Tc), ruthenium (Ru), rhodium (Rh), palladium (Pd), silver (Ag), cadmium (Cd), lanthanum (La), hafnium (Hf), tantalum (Ta), tungsten (W), osmium (Os), iridium (Ir), cerium (Ce), gadolinium (Gd), scandium (Sc), titanium (Ti), gallium (Ga), indium (In), or two or more of these. The carbon composite according to Claim 1.

12. The carbon composite according to Claim 1, wherein the transition metal includes iron (Fe).

13. The transition metal contains iron (Fe), The diameter (D ５０ ) of the iron contained in the carbon composite is 0.3 nm to 5 nm, and the carbon composite according to claim 1.

14. For one or more transition metals contained in the catalyst, the molar ratio of sulfur doped in the porous carbon material is 0.5 to 8. The carbon composite according to Claim 1.

15. The at least one sulfur is doped in the form of sulfur atoms or sulfur compounds. The carbon composite according to Claim 1.

16. The porous carbon material doped with the at least one sulfur contains at least one of the first structure according to the following formula 1 and the second structure according to the following formula 2 in its structure, The ratio of the first structure to the second structure is the molar ratio of the first structure / the second structure and is 1 or less, [Formula 1] -C-SO ２ -C- 「Formula 2」 -C-S-C- The carbon composite according to Claim 1.

17. The molar ratio of the first structure / the second structure is 0.1 to 0.

7. The carbon composite according to Claim 16.

18. Among all the pores of the carbon composite, when the number of pores with a pore diameter of less than 10 nm is N(nano) and the number of pores with a pore diameter of 10 nm or more is N(macro), The ratio [N(macro) / N(nano)] of N(macro) to N(nano) is 1 or more. The carbon composite according to Claim 1.

19. The Raman peak intensity ratio (I Ｇ / I Ｄ ratio) of the porous carbon material is 1 or less. The carbon composite according to claim 1.

20. A method for producing the carbon composite according to Claim 1, (S1) A step of doping at least one sulfur in the porous carbon material, (S2) A step of impregnating the result of the step (S1) into a transition metal-containing precursor solution and then removing the solvent, including, The step (S1) includes a step of heat-treating in a state where the sulfur doping precursor and the porous carbon material are in contact. A method for producing a carbon composite.

21. The heat treatment is performed at a temperature of 800°C to 1,000°C. The method for producing a carbon composite according to Claim 20.

22. The sulfur-doped precursor is dibenzyl disulfide (DBDS), sodium pyrosulfite (Na ２ S ２ O ５ ), sodium pyrosulfate (Na ２ S ２ O ７ ), sodium thiosulfate (Na ２ S ２ O ３ ), thiourea (CH ４ N ２ S), sodium sulfide (Na ２ S), potassium thiocyanate (KSCN), benzyl mercaptan (C ７ H ８ S), benzothiophene (C ８ H ６ S), dibenzothiophene (C １２ H ８ S), or a mixture thereof, for the method for producing a carbon composite according to claim 20.

23. The transition metal-containing precursor solution in the step (S2) includes an organic solvent, a precursor compound of a non-metallic element, and a precursor compound of a transition metal. The method for producing a carbon composite according to Claim 20.

24. A positive electrode active material including the carbon composite according to any one of Claims 1 to 19 and a sulfur-based compound.

25. A positive electrode including the positive electrode active material according to Claim 24.

26. including a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte solution, The lithium-sulfur battery, wherein the positive electrode is the positive electrode according to claim 25.

27. A positive electrode comprising a positive electrode active material containing a sulfur-based compound and the carbon composite according to any one of claims 1 to 19.

28. A lithium-sulfur battery comprising a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte, wherein the positive electrode is the positive electrode according to claim 27.

29. A battery comprising a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte, wherein at least one of the positive electrode and the negative electrode contains the carbon composite according to any one of claims 1 to 19.

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