Positive electrode material for lithium-sulfur battery and lithium-sulfur battery comprising same

Abstract

The present invention relates to a carbon composite for use in a positive electrode of a lithium-sulfur battery and a method for manufacturing the same, and the carbon composite comprises: a porous carbon material; and a catalyst on at least one of an outer surface of the porous carbon material and an inner surface of pores of the porous carbon material, where the catalyst includes transition metal alloy particles and a carbon coating on at least a portion of a surface of the transition metal alloy particles, where the transition metal alloy particles include cobalt (Co) and iron (Fe), and wherein at least a portion of the carbon coating comprises crystalline carbon.

Description

Technical Field

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

[0002] This application claims priority from Korean Patent Application No. 10-2023-0125127 filed in Korea on September 19, 2023, and Korean Patent Application No. 10-2024-0119502 filed in Korea on September 3, 2024, the disclosures of which are incorporated herein by reference. Background Art

[0003] Lithium-sulfur batteries (LSBs) use a sulfur-based material with sulfur-sulfur (SS) bonds as the positive electrode active material and lithium metal as the negative electrode active material. Sulfur, the primary component of the positive electrode active material, is abundant in nature, can be found worldwide, is non-toxic, and has a low atomic weight.

[0004] As secondary batteries are used in a wide range of applications including electric vehicles (EVs) and energy storage systems (ESS), lithium-sulfur batteries, which have a theoretically higher gravimetric energy storage density (approximately 2,600 Wh / kg) compared to lithium-ion secondary batteries with a lower gravimetric energy storage density (approximately 250 Wh / kg), are attracting attention.

[0005] During discharge, the lithium-sulfur battery undergoes oxidation to become lithium cations by releasing electrons at the negative electrode active material lithium, and undergoes reduction by accepting electrons at the positive electrode active material sulfur-based material. Through the reduction reaction, the sulfur-based material accepts two electrons through the SS bond and is converted into sulfur anions. The lithium cations generated by the oxidation reaction of lithium move to the positive electrode via the electrolyte and bond with the sulfur anions generated by the reduction reaction of the sulfur compound to form a salt. Specifically, sulfur has a cyclic S8 structure before discharge, and it is converted into lithium polysulfide (Li2S) through the reduction reaction. x ) and is completely reduced to lithium sulfide (Li2S).

[0006] On the other hand, among the many factors that determine the price and energy density of lithium-sulfur batteries, the amount of electrolyte in a lithium-sulfur battery is the most important consideration. First, among the materials used to make lithium-sulfur batteries, lithium-sulfur batteries are generally quite expensive to manufacture because they contain a very thin lithium anode and an electrolyte based on expensive lithium salts. In contrast, the energy density of a lithium-sulfur battery depends on how much energy the manufactured battery produces compared to its total weight. The ratio of total battery weight to generated energy is affected by the sulfur loading per unit area of ​​the positive electrode and the proportion of sulfur in the composite, but is more significantly influenced by the electrolyte-to-sulfur ratio (E / S), or the ratio of the amount of electrolyte to the amount of sulfur in the positive electrode. Furthermore, the ratio of generated energy to total battery weight is more affected by the capacity generated by the lithium-sulfur electrochemical reaction than by the operating voltage. Therefore, there is a need to design stable lithium-sulfur batteries that minimize the amount of electrolyte and achieve high reversible capacity in batteries with a low E / S ratio.

[0007] In particular, since sulfur used in the positive electrode active material is a non-conductor, the movement of electrons generated by the electrochemical reaction is suppressed, and polysulfide (LiS x ) dissolution and the problem of reduced battery life and rate characteristics due to the slow kinetic activity in the electrochemical reaction caused by the low electrical conductivity of sulfur and lithium sulfide. Under these circumstances, many studies have been conducted recently to improve the performance of lithium-sulfur secondary batteries by using platinum (Pt), which is mainly used as an electrochemical catalyst, to improve the kinetic activity of the redox reaction of sulfur during charge and discharge. However, precious metal catalysts such as platinum are difficult to commercialize due to their high cost and have a risk of poisoning due to the redox reaction of sulfur during charge and discharge, and are therefore not easy to use as positive electrode materials for lithium-sulfur secondary batteries. Therefore, it is necessary to develop positive electrode materials to improve the kinetic activity in the electrochemical reaction during charge and discharge of lithium-sulfur secondary batteries and the cost-effectiveness of commercialization. Summary of the Invention

[0008] Technical issues

[0009] The present invention aims to solve the above-mentioned problems, and therefore, the present invention aims to provide a cathode material having improved lithium polysulfide adsorption and increased kinetic activity in sulfur redox reactions.

[0010] In particular, the present invention aims to provide a carbon composite that exhibits high mobility under electrolyte-poor conditions while maintaining a good catalytic effect in accelerating lithium polysulfide conversion reactions. Consequently, the present invention aims to provide a lithium-sulfur battery cathode material having improved reversible capacity and lifetime stability, as well as high energy density under electrolyte-poor conditions, and a lithium-sulfur battery including the cathode material.

[0011] Technical Solution

[0012] In order to solve the above-mentioned problems, according to one aspect of the present invention, a carbon composite according to the following embodiments is provided.

[0013] A carbon composite according to a first embodiment includes:

[0014] porous carbon materials, and

[0015] a catalyst located on at least one of an outer surface of the porous carbon material and an inner surface of the pores of the porous carbon material,

[0016] wherein the catalyst comprises transition metal alloy particles and a carbon coating on at least a portion of the surface of the transition metal alloy particles,

[0017] wherein the transition metal alloy particles comprise cobalt (Co) and iron (Fe), and

[0018] At least a portion of the carbon coating comprises crystalline carbon.

[0019] According to the second embodiment, in the first embodiment,

[0020] The transition metal alloy particles may comprise cobalt-iron alloy particles having a body-centered cubic structure.

[0021] According to a third embodiment, in the first embodiment or the second embodiment,

[0022] The average particle size of the carbon composite (D 50 ) can be in the range between 100 nm and 100 μm.

[0023] According to a fourth embodiment, in any one of the first to third embodiments,

[0024] The average particle size of the catalyst (D 50 ) can be less than 100 nm.

[0025] According to a fifth embodiment, in any one of the first to fourth embodiments,

[0026] The thickness of the carbon coating is related to the average particle size of the transition metal alloy particles (D 50 ) can be less than 40%.

[0027] According to a sixth embodiment, in any one of the first to fifth embodiments,

[0028] The thickness of the carbon coating can be less than 10 nm.

[0029] According to a seventh embodiment, in any one of the first to sixth embodiments,

[0030] The carbon coating layer may have a single-layer structure or a multi-layer structure of 10 layers or less.

[0031] According to an eighth embodiment, in any one of the first to seventh embodiments,

[0032] The amount of the catalyst may be in the range of 5 wt % to 50 wt % based on 100 wt % of the carbon composite.

[0033] According to a ninth embodiment, in any one of the first to eighth embodiments,

[0034] The porous carbon material may include carbon nanotubes (CNTs), graphene, graphene oxide (GO), reduced graphene oxide (rGO), carbon black, graphite, graphite nanofibers (GNFs), carbon nanofibers (CNFs), activated carbon fibers (ACFs), activated carbon, fullerenes, or two or more thereof.

[0035] According to a tenth embodiment, in any one of the first to ninth embodiments,

[0036] The porous carbon material may comprise carbon nanotubes (CNTs), and

[0037] The carbon nanotubes may include entangled CNTs.

[0038] According to another aspect of the present invention, a method of manufacturing a carbon composite according to the following embodiments is provided.

[0039] A method for manufacturing a carbon composite according to an eleventh embodiment may include manufacturing the carbon composite according to any one of the first to tenth embodiments. The method includes:

[0040] mixing a cobalt (Co)-containing precursor, an iron (Fe)-containing precursor, a carbon layer precursor, and a porous carbon material to obtain a transition metal-carbon layer precursor polymer / porous carbon material (M-CPP / C), and

[0041] The transition metal-carbon layer precursor polymer / porous carbon material is heat-treated to obtain a carbon composite.

[0042] According to the twelfth embodiment, in the eleventh embodiment,

[0043] The carbon layer precursor may include dopamine, polydopamine, melamine, 1,10-phenanthroline, polyaniline, carbon nitride (g-CN), glucose, phenylenediamine, or a mixture thereof.

[0044] According to the thirteenth embodiment, in the eleventh embodiment or the twelfth embodiment,

[0045] The heat treatment may be performed at a temperature ranging from 600°C to 1,000°C.

[0046] According to another aspect of the present invention, there are provided a positive electrode active material and a lithium-sulfur battery of the following embodiments.

[0047] The positive electrode active material according to the fourteenth embodiment may include:

[0048] A carbon composite and a sulfur compound of any one of the first to tenth embodiments.

[0049] The lithium-sulfur battery according to the fifteenth embodiment includes:

[0050] A positive electrode, a negative electrode, and an electrolyte,

[0051] where the positive electrode may include the positive electrode active material of the fourteenth embodiment.

[0052] According to the sixteenth embodiment, in the fifteenth embodiment,

[0053] The E / S ratio may be 8 μL / mg or less, and the sulfur loading in the positive electrode may be 2.25 mg s / cm 2 or more. Here, the E / S ratio may represent the ratio of the volume of the electrolyte to the weight of sulfur in the positive electrode.

[0054] According to the seventeenth embodiment, in the fifteenth or sixteenth embodiment,

[0055] The E / S ratio may be 3 μL / mg or less, and the energy density may be 380 Wh / kg or more.

[0056] Advantageous Effects

[0057] The carbon composite according to an embodiment of the present invention has improved polysulfide (LiPS, Li2S x , 1 < x ≤ 8) adsorption through a metal catalyst. In addition, the carbon composite provides improved kinetic activity in the redox reaction of sulfur.

[0058] In addition, since the carbon composite according to an embodiment of the present invention includes a catalyst that is weakly attached to the surface of the carbon material and has a certain degree of mobility on the surface of the carbon material, the proximity of polysulfides to the catalyst surface / electrolyte / carbon material three-phase interface can be improved at a low E / S ratio.

[0059] Thereby, a lithium-sulfur battery having a high energy density and life stability can be provided by suppressing a decrease in catalytic activity under poor electrolyte conditions.

[0060] For example, according to one aspect of the present invention, when the E / S ratio is 10 μL / mg or less, specifically 2.5 μL / mg or less, a high energy density can be achieved, such as an energy density of 300 Wh / kg or more or 380 Wh / kg or more, but the effects of the present invention are not limited thereto. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] Figure 1 is a graph showing the reaction that occurs in the conversion reaction of a cathode material with low kinetic activity in lithium sulfide (Li2S) and polysulfide (Li2S x , 1 < x). Figure 1 Shows the conversion reaction of lithium sulfide (Li2S) and polysulfide (Li2S x , 1 < x) and by-products on the surface and in the pores of the porous carbon material and the porous carbon material.

[0062] Figure 2 is a graph showing the polysulfide conversion reaction using a carbon composite according to an embodiment of the present invention.

[0063] Figure 3 Shows the scanning transmission electron microscope (STEM) image (a) and energy dispersive X-ray spectroscopy (EDX) mapping results (b) of a carbon composite according to an embodiment of the present invention.

[0064] Figure 4 Shows the high-resolution transmission electron microscope (HRTEM) image (a) of a carbon composite according to an embodiment of the present invention and a graph (b) showing the result of measuring the distance between (110) planes by d-spacing measurement.

[0065] Figure 5 Shows the X-ray diffraction analysis (XRD) analysis results of a carbon composite according to an embodiment of the present invention. <​​​​​​​​​​​​​​​​These are cyclic voltammetry (CV) graphs of a lithium-sulfur battery (FeCo) using the carbon composite of Example 1 of this specification and a lithium-sulfur battery (Ref) using the carbon composite of Comparative Example 1.

[0071] Figure 9 These are electrochemical impedance spectroscopy (EIS) graphs of a lithium-sulfur battery (FeCo) using the carbon composite of Example 1 of this specification and a lithium-sulfur battery (Ref) using the carbon composite of Comparative Example 1.

[0072] Figure 10a 1 is a voltage-capacity graph obtained at the 10th cycle using each of the lithium-sulfur batteries of Example 1 and Comparative Example 1 in this specification.

[0073] Figure 10b This is a discharge capacity-cycle graph of a lithium-sulfur battery with an E / S of 10 μL / mg using Example 1 and Comparative Example 1 in this specification.

[0074] Figure 10c The positive electrode loading amount of Example 1 and Comparative Example 1 in this specification is 7 mg. s / cm 2 And the discharge capacity-cycle diagram of lithium-sulfur battery with E / S of 6 μL / mg.

[0075] Figure 11 This is a graph showing the results of measuring the energy density changes over cycles of lithium-sulfur batteries using two E / S ratio conditions of Example 1 in this specification and a lithium-sulfur battery using Comparative Example 1. DETAILED DESCRIPTION

[0076] Hereinafter, the present invention will be described in more detail.

[0077] In this specification, unless explicitly stated otherwise, the term "comprising" specifies the presence of stated elements, but does not exclude the presence or addition of one or more other elements.

[0078] In this specification, "A and / or B" means A or B or both.

[0079] The term "composite" as used herein refers to a material in which two or more materials are combined to form physically or chemically different phases and exhibit more effective functions.

[0080] As used herein, the term "(poly)sulfide" encompasses "(poly)sulfide ions (S x 2- , 1≤x≤8)" and "lithium (poly)sulfide (Li2S x or Li2S x - , 1≤x≤8)” concept.

[0081] As used herein, the term "polysulfide" encompasses the concepts of "polysulfide ions (S x 2- , 1 < x ≤ 8)" and "lithium polysulfide (Li2S x or Li2S x - , 1 < x ≤ 8)".

[0082] Unless otherwise specified, the unit "mg s / cm 2 " as used herein represents the weight of sulfur (S) per unit area and can be used interchangeably with other expressions such as mg(s) / cm 2 , mAh / gs, etc. [[ID=2@]]

[0083] During charge and discharge, lithium-sulfur batteries exhibit a lower capacity than the theoretical capacity due to the dissolution of lithium polysulfide generated by the reduction reaction of sulfur (S8) at the positive electrode into the electrolyte.

[0084] According to one aspect of the present invention, there is provided a carbon composite having improved lithium polysulfide adsorption and improved mobility on the surface of a carbon material, providing enhanced kinetic activity under lean electrolyte conditions and being usable in high-performance lithium-sulfur batteries.

[0085] Figure 1 is a graph showing the reaction that occurs in the conversion reaction of a positive electrode material with low kinetic activity in lithium sulfide (Li2S) and lithium polysulfide (Li2S x , 1 < x). Refer to Figure 1 , due to the slow conversion reaction of lithium polysulfide, the pores and surface of a porous carbon material (such as carbon nanotubes) are covered with lithium sulfide (Li2S) and by-products, which further increases the irreversible capacity of the positive electrode, resulting in rapid degradation of the lithium-sulfur battery.

[0086] Figure 2 is a graph showing the reaction using the carbon composite according to one aspect of the present invention. Refer to Figure 2 , alloy particle catalysts containing cobalt (Co) and iron (Fe) are located on the outer surface of a porous carbon material (such as carbon nanotubes) and / or the inner surface of the pores of the porous carbon material. Due to the adsorption of lithium polysulfide, the catalyst can play a role in increasing the adsorption strength between the carbon composite and lithium polysulfide. Therefore, adding alloy particle catalysts containing cobalt (Co) and iron (Fe) can accelerate the conversion reaction of lithium sulfide (Li2S) and lithium polysulfide (Li2S x , 1 < x), thereby increasing the reversible capacity of the lithium-sulfur positive electrode using the same.

[0087] Specifically, the carbon composite according to one aspect of the present invention may include bimetallic nanoparticles, iron (Fe) particles that accelerate reduction, and cobalt (Co) particles that accelerate oxidation as catalysts to accelerate the conversion reaction during charge and discharge. Thereby, a higher reversible capacity and stable charge and discharge can be achieved under lean electrolyte conditions, thus realizing a lithium-sulfur battery with high energy density.

[0088] In one embodiment of the present invention, the catalyst has catalytic activity in the oxidation and reduction reactions of sulfur compounds such as sulfur (S8), lithium sulfide (Li2S), polysulfide (Li2S x , 1 < x ≤ 8), disulfide compounds, and mixtures thereof, which are used as the positive electrode active material of the lithium-sulfur battery. However, the function of the material included as the catalyst is not limited thereto.

[0089] In one embodiment of the present invention, the catalyst may be located on the outer surface of the porous carbon material, or on the inner surface of the pores of the porous carbon material, or on both.

[0090] The carbon composite according to one aspect of the present invention includes: a porous carbon material, and a catalyst located on at least one of the outer surface of the porous carbon material and the inner surface of the pores of the porous carbon material, and the catalyst includes transition metal alloy particles and a carbon coating on at least a part of the surface of the transition metal alloy particles. Specifically, the transition metal alloy particles include cobalt (Co) and iron (Fe), and at least a part of the carbon coating includes crystalline carbon.

[0091] According to one embodiment of the present invention, the catalyst includes bimetallic particles, which include: cobalt (Co) that accelerates the oxidation reaction and iron (Fe) that accelerates the reduction reaction in the conversion reaction of inorganic sulfur (S8) ↔ polysulfide (Li2S x , x > 1) ↔ lithium sulfide (Li2S).

[0092] Figure 3 Shows a scanning transmission electron microscope (STEM) image (a) of a carbon composite according to one embodiment of the present invention and an energy-dispersive X-ray spectroscopy (EDX) map obtained by elemental analysis of the catalyst.

[0093] Reference Figure 3 , the transition metal alloy particles included in the carbon composite according to one embodiment of the present invention may include nanoparticles of cobalt (Co)-iron (Fe) alloy.

[0094] In one embodiment of the present invention, the catalyst includes transition metal alloy particles as the active ingredient of the catalyst in the core. Specifically, the core of the catalyst may only include transition metal alloy particles.

[0095] In one embodiment of the present invention, the transition metal alloy particles included in the core of the catalyst may include only cobalt-iron alloy particles. Specifically, the sum of the amounts of cobalt and iron may be 100 mol % based on 100 mol % of the transition metal alloy particles.

[0096] In another embodiment of the present invention, in addition to the cobalt-iron alloy particles, the core of the catalyst may further comprise, without prejudice to the purpose of the present invention, at least one metal element selected from the group consisting of zinc (Zn), vanadium (V), chromium (Cr), manganese (Mn), nickel (Ni), copper (Cu), zirconium (Zr), niobium (Nb), molybdenum (Mo), technetium (Tc), rubidium (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), and indium (In). Specifically, the core of the catalyst may further comprise alloy particles of cobalt-iron and the selected transition metal, but the present invention is not limited thereto. In this case, the sum of the cobalt and iron contents of the core may preferably be 90 mol% or more or 95 mol% or more based on 100 mol% of the elements, but the present invention is not limited thereto.

[0097] In one embodiment of the present invention, the transition metal alloy particles may be metal particles grown from a transition metal-containing precursor, and may have, for example, spherical, elliptical or ovoid, flake, plate, fiber, needle, or hollow shapes.

[0098] In one embodiment of the present invention, the catalyst may contain alloy particles containing both cobalt and iron. Specifically, the catalyst may contain cobalt-iron alloy particles having a body-centered cubic (BCC) structure.

[0099] Figure 4 Shown are a high-resolution transmission electron microscope (HRTEM) image (a) of a carbon composite according to one embodiment of the present invention and a diagram (b) showing the result of measuring the distance between (110) planes by d-spacing.

[0100] Figure 5 Shown are XRD analysis results of a carbon composite according to one embodiment of the present invention.

[0101] refer to Figure 4 and 5 , as a result of analyzing the d spacing of the catalyst (specifically, cobalt-iron alloy particles) contained in the carbon composite according to one embodiment of the present invention, the d spacing (110) matches the distance between the planes, thereby confirming that the cobalt-iron alloy particles have a body-centered cubic structure.

[0102] In one embodiment of the present invention, the average particle size (D 50 ) can be, for example, between 1 nm and 90 nm. Specifically, the average particle size (D 50 ) can be in the range of 1 nm to 80 nm, 2 nm to 50 nm, 5 nm to 40 nm, 5 nm to 35 nm, 5 nm to 30 nm, or 10 nm to 20 nm. When the size of the transition metal alloy particles is within the above range, this can have beneficial effects on high electronic and / or ionic conductivity and improved battery performance and manufacturing processes, but the present invention is not limited thereto.

[0103] In this specification, particle size can be measured by a common method, and the measuring method is not limited to a specific method. For example, particle size can be measured by a scanning electron microscope (SEM), a field emission electron microscope or laser diffraction. The measurement using laser diffraction can be performed, for example, using a commercially available laser diffraction particle size analyzer (such as Microtrac MT 3000). Average particle size (D 50 ) refers to the particle size at 50% of the cumulative volume distribution.

[0104] Specifically, the catalyst has a structure in which at least a portion of the surface of transition metal alloy particles is coated with a carbon coating layer.

[0105] The carbon coating layer can control the size of the transition metal alloy particles and provide sites for bonding with a porous carbon material carrying a catalyst, thereby enabling loading onto the porous carbon material. Furthermore, the carbon coating layer can stably maintain the metallic phase of the core transition metal alloy particles. For example, the carbon coating layer can hinder direct chemical bonding between lithium polysulfide in the electrolyte and the surface of the transition metal alloy particles, thereby stably maintaining the catalytic activity of the transition metal alloy particles during operation of the lithium-sulfur battery. In the present invention, the functions of the carbon coating layer are not limited to those described above.

[0106] In one embodiment of the present invention, the surface area of ​​the core covered by the carbon coating is not limited thereto, but may be, for example, more than 50%, more than 60%, more than 70%, more than 80%, more than 90%, more than 95% or more than 99% of the total surface area of ​​the core.

[0107] In one embodiment of the present invention, the carbon coating may cover the entire surface of the core. As described below, when the carbon coating is formed on the entire surface of the core, this can have a beneficial effect on stabilizing the activity of the transition metal alloy particles brought about by the carbon coating, but the present invention is not limited to this. For example, when transition metal alloy particles are loaded onto a carbon composite without applying a carbon coating, transition metal alloy particles of uneven size may be formed, resulting in low catalyst stability and, in turn, poor battery life stability during operation of a battery using the same, but the present invention is not limited to this.

[0108] In this specification, the surface area of ​​the core covered by the carbon coating can be measured, for example, by TEM. The TEM can use Tencai's G2 F30 S-Twin, but is not limited thereto.

[0109] In one embodiment of the present invention, the thickness of the carbon coating is proportional to the average particle size (D 50 For example, the thickness of the carbon coating layer is proportional to the average particle size (D 50 ) can be 30% or less, 25% or less, 20% or less, or 15% or less. For example, the thickness of the carbon coating layer is about the average particle size (D 50 ) can be 1% or more, 5% or more, 7.5% or more, or 10% or more. For example, the thickness of the carbon coating layer is proportional to the average particle size (D 50 ) can be in the range of 10% to 20% or 10% to 15%. When the ratio of the thickness of the carbon coating layer to the average particle size of the transition metal alloy particles is within the above range, this can have a beneficial effect on stabilizing the activity of the transition metal alloy particles brought about by the carbon coating layer, but the present invention is not limited thereto. In addition, the carbon coating layer can cover the surface of the transition metal alloy particles with a small thickness, thereby loading transition metal alloy particles of uniform size onto the porous carbon material and enhancing the catalytic activity of the transition metal alloy particles. For example, when the thickness of the carbon coating layer is less than 40% of the total thickness of the transition metal alloy particles, a good interaction between the transition metal alloy particles located in the carbon coating layer and the lithium polysulfide from the outside of the carbon coating layer can be maintained.

[0110] In one embodiment of the present invention, the carbon coating layer covering the surface of the transition metal alloy particle may have a uniform thickness. For example, the standard deviation (Δd) of the thickness of the carbon coating layer formed on the surface of the core measured at ten random points may be 0.5 nm or less.

[0111] In one embodiment of the present invention, the carbon coating layer may cover the entire surface of the transition metal alloy particle, and the standard deviation (Δd) of thickness measured at 100 random points on the entire surface of the carbon coating layer may be 0.5 nm or less.

[0112] In one embodiment of the present invention, since the thickness of the carbon coating is relatively small, the interaction between the transition metal particles and lithium polysulfide can be improved, thereby improving the catalytic activity brought about by the transition metal particles, but the present invention is not limited thereto.

[0113] In one embodiment of the present invention, the thickness of the carbon coating layer may be, for example, 10 nm or less. Specifically, the thickness of the carbon coating layer may be 5 nm or less. In one embodiment of the present invention, the thickness of the carbon coating layer may be, for example, 0.5 nm or more. More specifically, the thickness of the carbon coating layer may be, for example, in the range of 1 nm to 5 nm or 0.5 nm to 2 nm.

[0114] For example, the thickness of the carbon coating layer may be measured by microscopic observation in an SEM image or a TEM image of the carbon composite, but the method of measuring the thickness of the carbon coating layer is not limited thereto.

[0115] Unless explicitly stated otherwise, SEM images were obtained using Hitachi’s S-4800 field emission, and TEM images were obtained using Tencai’s G2 F30 S-Twin.

[0116] In one embodiment of the present invention, the carbon coating may be a single layer.

[0117] In another embodiment of the present invention, the carbon coating layer may have a multilayer structure of two or more layers. For example, the carbon coating layer may have a multilayer structure of two or more layers and ten or fewer layers. Specifically, the carbon coating layer may have a multilayer structure of two to ten layers, a multilayer structure of two to five layers, a multilayer structure of two to four layers, or a multilayer structure of two to three layers. When the carbon coating layer is multilayered, this may have a beneficial effect on the catalytic activity of the carbon composite, but the present invention is not limited thereto.

[0118] In one embodiment of the present invention, the carbon coating may comprise crystalline carbon. For example, in another embodiment of the present invention, the carbon coating may consist of crystalline carbon. For example, the carbon coating may be formed by carbonization of a carbon precursor and may comprise only crystalline carbon.

[0119] In this specification, "crystalline" carbon means carbon that exists in three dimensions at the atomic level. For example, whether it is crystalline can be confirmed by diffraction techniques, melting enthalpy measurement, TEM, etc. For example, whether it is crystalline can be confirmed by at least one clear peak for each carbon in the XRD spectrum.

[0120] Reference again Figure 4 It was confirmed that the catalyst includes transition metal alloy particles as cores and a carbon coating layer covering at least a portion of the surface of the cores. Specifically, it was confirmed that at least a portion of the carbon coating layer includes crystalline carbon.

[0121] In one embodiment of the present invention, the carbon coating may contain at least one foreign element other than carbon as a doping element. For example, the foreign element may contain one or more selected from nitrogen (N), sulfur (S), and oxygen (O).

[0122] As described below, to produce a carbon composite, a porous carbon material, a cobalt (Co)-containing precursor, an iron (Fe)-containing precursor, and a carbon layer precursor may be mixed and then heat-treated. In this case, the carbon layer precursor may contain at least one foreign element selected from nitrogen, sulfur, and oxygen. Thus, a carbon coating layer may be formed on the surface of the transition metal alloy particles using carbon derived from the carbon layer precursor, and the foreign element derived from the carbon layer precursor may be doped into at least one of the porous carbon material and the carbon coating layer.

[0123] As described above, according to one embodiment of the present invention, the carbon coating layer may have a multilayer structure of, for example, 2 to 3 layers, covering the entire surface of the transition metal alloy particle, and may include crystalline carbon having a total thickness of 5 nm or less and doped with at least one nitrogen.

[0124] In one embodiment of the present invention, the average particle size (D 50 ) can be 100 nm or less. For example, the average particle size (D 50 ) may be in the range of 2 nm to 100 nm, 2 nm to 90 nm, 5 nm to 80 nm, 5 nm to 75 nm, 5 nm to 60 nm, 5 nm to 50 nm, 5 nm to 40 nm, 5 nm to 30 nm, 5 nm to 25 nm, 5 nm to 21 nm, 10 nm to 21 nm, or 11 nm to 21 nm. When the size of the transition metal composite particles is within the above range, this may have beneficial effects on high electronic and / or ionic conductivity and improved battery performance and manufacturing process, but the present invention is not limited thereto.

[0125] Figure 6 TEM images of carbon composites according to one embodiment of the present invention at different magnifications are shown. Specifically, Figure 6 TEM images of carbon composites are shown in which a catalyst comprising cobalt-iron alloy particles is located on the surface of carbon nanotubes (CNTs) as a porous carbon material. Figure 6 (a), it was observed that the catalyst was located on the outer surface of the porous carbon material and / or the inner surface of the pores of the porous carbon material. Figure 6 (b), it can be seen that the particle size of the catalyst is below 100 nm, for example, between 10 nm and 30 nm.

[0126] According to one aspect of the present invention, the catalyst is located on the outer surface of the porous carbon material and / or on the inner surface of the pores of the porous carbon material.

[0127] In one embodiment of the present invention, the porous carbon material improves the conductivity of the catalyst and has a function of providing a host for the catalyst as an electrode component.

[0128] In the present invention, the catalyst can be used alone as a catalyst in the positive electrode of a lithium-sulfur battery to impart activity to the reduction reaction of lithium polysulfide. However, according to the present invention, when the catalyst is located on the outer surface of the porous carbon material and / or the inner surface of the pores of the porous carbon material, the adsorption of lithium polysulfide and the activation of the sulfur oxidation / reduction reaction can be further improved.

[0129] The porous carbon material contains a material including a plurality of micropores, and the catalyst is supported on at least one of an outer surface of the porous carbon material and an inner surface of pores of the porous carbon material.

[0130] In one embodiment of the present invention, the porous carbon material may further include at least one foreign element other than carbon as a doping element. Specifically, the foreign element may include one or more selected from nitrogen (N), sulfur (S) and oxygen (O).

[0131] Specifically, in one embodiment of the present invention, at least one carbon atom present in the porous carbon material and / or the carbon coating layer may have a structure in which it is substituted with a foreign element.

[0132] In another embodiment of the present invention, when both the porous carbon material and the carbon coating in the catalyst contain at least one foreign element other than carbon as a doping element, the foreign element may be derived from the same precursor as described below, and therefore, they may contain the same element.

[0133] In another embodiment of the present invention, the heterogeneous elements contained in the porous carbon material and the carbon coating layer may each independently contain one or more elements selected from nitrogen, sulfur, and oxygen. Specifically, the heterogeneous elements doped in the porous carbon material may be derived from a precursor different from that contained in the carbon coating layer. For example, in order to improve the bonding with lithium polysulfide in the catalyst or electrolyte, the porous carbon material may be doped with a precursor containing one or more elements selected from nitrogen, sulfur, and oxygen, and mixed with the transition metal particles to form a carbon composite.

[0134] In one embodiment of the present invention, the catalyst may be located on at least one of the outer surface of the porous carbon material and the inner surface of the pores of the porous carbon material by chemical and / or physical bonding.

[0135] In one embodiment of the present invention, the catalyst may be physically adsorbed on the outer surface of the porous carbon material and / or the inner surface of the pores of the porous carbon material. Alternatively, the catalyst may be chemically bonded to the outer surface of the porous carbon material and / or the inner surface of the pores of the porous carbon material through C-C covalent bonds and / or π-π interactions between the elements present in the catalyst and the carbon of the porous carbon material. In addition, both physical adsorption and chemical bonding may exist between the catalyst and the porous carbon material.

[0136] In one embodiment of the present invention, the porous carbon material contains a plurality of micropores on its outer surface and in its interior. The average diameter of the micropores may be, for example, in the range of 5 nm to 100 nm, specifically in the range of 5 nm to 80 nm, 5 nm to 60 nm, or 5 nm to 50 nm. The average diameter of the micropores represents the pore diameter at 50% of the pore size distribution. The pore diameter can be measured, for example, by performing TEM analysis on the pore diameter in a direction perpendicular to the surface of the porous carbon material, but the measurement method is not limited thereto.

[0137] The porous carbon material is not limited to a specific material and may include any material that includes a plurality of micropores and supports the above-mentioned catalyst.

[0138] In one embodiment of the present invention, the specific material of the porous carbon material may include, for example, carbon nanotubes (CNTs), graphene, graphene oxide (GO), reduced graphene oxide (rGO), carbon black, graphite nanofibers (GNFs), carbon nanofibers (CNFs), activated carbon fibers (ACFs), natural graphite, artificial graphite, expanded graphite, activated carbon, fullerenes, or two or more thereof.

[0139] In one embodiment of the present invention, when the porous carbon material comprises carbon nanotubes, the carbon nanotubes may comprise single-walled carbon nanotubes (SWCNTs), multi-walled carbon nanotubes (MWCNTs), or both.

[0140] In another embodiment of the present invention, when the porous carbon material includes carbon nanotubes, the carbon nanotubes may include entangled CNTs formed into a secondary structure, ie, an aggregate of a plurality of primary structures, the carbon nanotubes being the primary structure.

[0141] According to one embodiment of the present invention, entangled-type CNTs may have improved porosity compared to primary-structured carbon nanotubes due to interstitial volumes formed by entanglement of the primary-structured carbon nanotubes.

[0142] In one embodiment of the present invention, the size of the porous carbon material may be, for example, in the range of 10 μm to 100 μm, specifically in the range of 20 μm to 50 μm, but is not limited thereto. When the size of the porous carbon material is within the above range, this can have a beneficial effect on solid content adjustment when preparing the slurry for forming the electrode active material layer, as well as electrode properties such as adhesion strength and battery performance (output and capacity).

[0143] In one embodiment of the present invention, the pore volume of the porous carbon material may be, for example, from 1 cm 3 / g to 5 cm 3 / g, specifically from 1 cm 3 / g to 4 cm 3 For example, the pore volume may be a measured value calculated by N2 isotherm analysis obtained based on liquid nitrogen adsorption.

[0144] In one embodiment of the present invention, the BET specific surface area of ​​the porous carbon material may be, for example, from 150 m 2 / g to 2,000 m 2 / g, specifically from 250 m 2 / g to 700 m 2 / g, but not limited thereto.

[0145] The BET specific surface area can be measured by the BET method and can represent a value measured by a known method for measuring the BET specific surface area. For example, the BET specific surface area can be a value calculated from the volume of nitrogen gas adsorbed at liquid nitrogen temperature (77 K) using a BELSORP-mini II from BEL Japan.

[0146] As described above, according to one aspect of the present invention, there is provided a carbon composite including a catalyst on at least one of the outer surface of a porous carbon material and the inner surface of the pores of the porous carbon material.

[0147] In one embodiment of the present invention, the average particle size (D 50 ) can be, for example, between 100 nm and 100 μm, specifically between 10 μm and 50 μm. In addition, the pore volume of the carbon composite can be, for example, between 0.5 cm 3 / g to 4 cm 3 / g, specifically within 1 cm 3 / g to 3 cm 3 In addition, the BET specific surface area of ​​the carbon composite can be, for example, between 150 m 2 / g to 500 m 2 / g, specifically between 250 m 2 / g to 300 m 2 / g.

[0148] In one embodiment of the present invention, the amount of the catalyst may be, for example, 50% by weight or less, based on a total of 100% by weight of the carbon composite. Specifically, the amount of the catalyst may be in a range of 5% to 50% by weight, 5% to 30% by weight, 10% to 20% by weight, or 10% to 15% by weight, based on a total of 100% by weight of the carbon composite. When the amount of the catalyst is within the above range, this may have a beneficial effect on sufficient catalytically active sites and electronic and / or ionic conductivity in the electrode. Therefore, the performance of a battery using the catalyst may be improved, but the present invention is not limited thereto.

[0149] In another embodiment of the present invention, the weight ratio of the porous carbon material to the catalyst in the carbon composite may be, for example, in the range of 95:5 to 70:30. Specifically, the weight ratio of the porous carbon material to the catalyst may be in the range of 90:10 to 80:20 or from 95:5 to 85:15. When the weight ratio of the porous carbon material to the catalyst is within the above range, this may have a beneficial effect on sufficient catalytic active sites and inhibiting or preventing catalyst agglomeration, thereby improving resistance characteristics. Therefore, the performance of a battery using the same may be improved, but the present invention is not limited thereto.

[0150] Figure 7 : is a graph showing the results of analyzing the amount of cobalt-iron alloy particles by thermogravimetric analysis (TGA) of the carbon composite according to one embodiment of the present invention. Figure 7 , the analysis showed that the amount of the cobalt-iron alloy particles in the carbon composite was 14.7 wt % based on 100 wt % of the carbon composite.

[0151] In one embodiment of the present invention, the carbon composite contains a foreign element in at least one of the porous carbon material and the carbon coating. In one embodiment of the present invention, the amount of the foreign element may be, for example, 0.1% by weight or more or 0.5% by weight or more based on 100% by weight of the carbon composite. Furthermore, the amount of the foreign element may be, for example, 20% by weight or less or 10% by weight or less based on 100% by weight of the carbon composite, but is not limited thereto. Specifically, the amount of the foreign element may be, for example, in the range of 0.1% by weight to 20% by weight, specifically in the range of 0.5% by weight to 10% by weight, based on 100% by weight of the carbon composite. When the amount of the foreign element is within the above range, it may have a beneficial effect on accelerating the catalytic activity of the transition metal alloy particles and the adsorption of lithium polysulfide.

[0152] In one embodiment of the present invention, as described above, the core of the catalyst comprises transition metal alloy particles formed by bonding between transition metal atoms.

[0153] In another embodiment of the present invention, the carbon composite may further contain free transition metal atoms from transition metal particles in a single atomic state without hindering the catalytic activity of the carbon composite.

[0154] For example, the state of transition metal atoms contained in the carbon composite can be confirmed by extended X-ray absorption fine structure (EXAFS) analysis. Specifically, when transition metal atoms of transition metal particles are contained in the carbon composite in a single-atom state without metallic bonds, the bond between the transition metal element and the heterogeneous element can be confirmed based on the EXAFS analysis results. Conversely, when two or more transition metal atoms are contained in the carbon composite in a metallic particle state via metallic bonds, the bond between the transition metal elements can be confirmed based on the EXAFS analysis results.

[0155] In one embodiment of the present invention, when bonds between elements in the carbon composite are confirmed by EXAFS analysis, the number of bonds between transition metal elements contained in the carbon composite may be greater than the number of bonds between the transition metal element and the foreign element. In another embodiment of the present invention, when bonds between elements in the carbon composite are confirmed by EXAFS analysis, the peak intensity of bonds between transition metal elements may be, for example, at least 10 times higher, specifically at least 20 times higher, and more specifically at least 50 times higher, than the peak intensity of bonds between transition metal elements and the foreign element.

[0156] The carbon composite of the present invention can provide sites for bonding with lithium polysulfide and exhibit catalytic activity in sulfur redox reactions, thereby improving the lifespan stability of lithium-sulfur batteries using the composite. Furthermore, the catalyst in the carbon composite can be mobile on the surface of the porous carbon material, enabling lithium-sulfur batteries using the composite to achieve stable performance and high energy density under electrolyte-poor conditions. However, the mechanism of the present invention is not limited to this.

[0157] According to one embodiment of the present invention, as a positive electrode active material, a carbon composite can be used, which is combined with a sulfur compound as a carrier of the positive electrode active material such as the sulfur compound. Alternatively, the carbon composite itself can be used as an additive for the positive electrode.

[0158] According to one embodiment of the present invention, the carbon composite may be used as an additive for a separator of a lithium-sulfur battery.

[0159] Another aspect of the present invention provides a method of making a carbon composite.

[0160] The carbon composite can be produced by a method for producing a carbon composite, but the method for producing a carbon composite is not limited thereto.

[0161] The method of making the carbon composite comprises:

[0162] mixing a cobalt (Co)-containing precursor, an iron (Fe)-containing precursor, a carbon layer precursor, and a porous carbon material to obtain a transition metal-carbon layer precursor polymer / porous carbon material (M-CPP / C), and

[0163] The transition metal-carbon layer precursor polymer / porous carbon material is heat-treated to obtain a carbon composite.

[0164] As described above, according to one embodiment of the present invention, the carbon layer precursor may include at least one foreign element selected from nitrogen (N), sulfur (S), and oxygen (O), but the present invention is not limited thereto.

[0165] First, each of the cobalt-containing precursor and the iron-containing precursor can be a precursor for the transition metal alloy particles contained in the core of the catalyst. The cobalt-containing precursor and the iron-containing precursor can be a precursor containing cobalt and a precursor containing iron, respectively, but a single material containing both cobalt and iron can be added as a precursor. That is, the present invention is not limited to each of the cobalt-providing material and the iron-providing material, or a single material, as the raw material.

[0166] In one embodiment of the present invention, each of the cobalt-containing precursor and the iron-containing precursor may include a cobalt- and / or iron-containing metal salt, metal acetylacetonate, metal hydroxide, metal chloride, metal oxide, metal chloride hydrate, or two or more thereof.

[0167] In another embodiment of the present invention, each of the cobalt-containing precursor and the iron-containing precursor may contain only a metal salt containing a transition metal element. When only metal salts are contained as the cobalt-containing precursor and the iron-containing precursor, the method for manufacturing the catalyst can be simplified, the size of the manufactured catalyst can be easily controlled, and the catalytic activity can be improved.

[0168] For example, in one embodiment of the present invention, the cobalt-containing precursor may include cobalt acetylacetonate, cobalt hydroxide, cobalt chloride, cobalt oxide, cobalt chloride hydrate, or two or more thereof as the cobalt metal salt.

[0169] In one embodiment of the present invention, the cobalt-containing precursor may include cobalt chloride hexahydrate as the cobalt metal salt.

[0170] For example, in one embodiment of the present invention, the iron-containing precursor may include iron acetylacetonate, iron hydroxide, iron chloride, iron oxide, iron hydrate, or two or more thereof as the iron metal salt.

[0171] In one embodiment of the present invention, the iron-containing precursor may include iron chloride hexahydrate as the iron metal salt.

[0172] In one embodiment of the present invention, in addition to the cobalt-containing precursor and the iron-containing precursor, the raw material may further include a precursor containing any other transition metal element as a transition metal-containing precursor. In this case, the transition metal element that may be included may include, for example, at least one selected from the following substances: zinc (Zn), vanadium (V), chromium (Cr), manganese (Mn), nickel (Ni), copper (Cu), zirconium (Zr), niobium (Nb), molybdenum (Mo), technetium (Tc), rubidium (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) and indium (In). For example, the transition metal-containing precursor that may be included may also include nickel acetylacetonate, nickel hydroxide, nickel chloride, nickel oxide, nickel hydrate or two or more thereof, but the present invention is not limited thereto.

[0173] In one embodiment of the present invention, the carbon layer precursor is a precursor for forming a carbon coating layer, and is used to coat at least a portion of the surface of the transition metal alloy particle.

[0174] In the present invention, the carbon layer precursor may contain at least one foreign element selected from nitrogen, sulfur, and oxygen to function as a precursor for doping the foreign element into at least one of the carbon coating layer and the porous carbon material.

[0175] In one embodiment of the present invention, the carbon layer precursor may contain a foreign element other than carbon, and the foreign element may be at least one selected from nitrogen, sulfur and oxygen as described above. The carbon precursor is not limited to a specific type and may include any carbon precursor that provides a crystalline carbon coating by carbonization.

[0176] The carbon layer precursor may contain, for example, carbon and nitrogen, and may include dopamine, polydopamine, melamine, 1,10-phenanthroline, polyaniline, carbon nitride (g-CN), glucose, phenylenediamine, or a mixture thereof.

[0177] In one embodiment of the present invention, reference is made to the above description regarding the porous carbon material.

[0178] The method of making a carbon composite includes mixing a cobalt (Co)-containing precursor, an iron (Fe)-containing precursor, a carbon layer precursor, and a porous carbon material.

[0179] In one embodiment of the present invention, the weight ratio of the cobalt-containing precursor, the iron-containing precursor and the carbon layer precursor can be, for example, 1-3:1-3:1-3, specifically 1-2:1-2:1-2, more specifically 1-1.5:1-1.5:1-1.5, but the present invention is not limited thereto.

[0180] In one embodiment of the present invention, the weight ratio of the total weight of the cobalt-containing precursor and the iron-containing precursor to the porous carbon material can be, for example, in the range of 1:1 to 1:10, specifically in the range of 1:1 to 1:8, more specifically in the range of 1:1 to 1:5 or 1:1 to 1:3, but the present invention is not limited thereto.

[0181] In one embodiment of the present invention, the weight ratio of the carbon layer precursor to the porous carbon material can be, for example, in the range of 1:10 to 1:5, specifically in the range of 1:1 to 1:3, more specifically in the range of 1:1 to 1:2.5 or 1:2 to 1:2.5, but the present invention is not limited thereto.

[0182] In one embodiment of the present invention, when the weight ratio of the cobalt-containing precursor, the iron-containing precursor, the carbon layer precursor, and the porous carbon material is within the above range, this may have a beneficial effect on the properties of the manufactured carbon composite, but the present invention is not limited thereto.

[0183] In one embodiment of the present invention, a method for manufacturing a carbon composite may include first mixing a cobalt-containing precursor, an iron-containing precursor, and a carbon layer precursor, then mixing with a porous carbon material and heat-treating the mixture. When the cobalt-containing precursor, the iron-containing precursor, and the carbon layer precursor are first mixed and then mixed with the porous carbon material to manufacture the carbon composite, this may have a beneficial effect on the uniformity of the carbon coating thickness and the uniformity of the catalyst size, but the present invention is not limited thereto.

[0184] In one embodiment of the present invention, a method of making a carbon composite may include:

[0185] (S1) mixing a cobalt-containing precursor, an iron-containing precursor, and a carbon layer precursor to form a transition metal-carbon layer precursor polymer (MC precursor polymer),

[0186] (S2) mixing a transition metal-carbon layer precursor polymer and a porous carbon material to obtain a transition metal-carbon layer precursor polymer / porous carbon material (M-CPP / C), and

[0187] (S3) Heat-treating the transition metal-carbon layer precursor polymer / porous carbon material (M-CPP / C) to obtain a carbon composite.

[0188] Step (S1) may include mixing a cobalt-containing precursor, an iron-containing precursor, and a carbon layer precursor to generate a metal-carbon layer precursor complex (MC precursor complex) by physical and / or chemical bonding of the carbon layer precursor to surfaces of the cobalt-containing precursor and the iron-containing precursor.

[0189] In one embodiment of the present invention, the cobalt-containing precursor, the iron-containing precursor, and the carbon layer precursor may be mixed in a suitable solvent and stirred. In this case, when each of the cobalt-containing precursor and the iron-containing precursor is a metal salt, the solvent may preferably be water, but is not limited thereto.

[0190] In one embodiment of the present invention, in step (S1), the mixing may be performed at room temperature, for example, at a temperature between 23°C and 25°C.

[0191] In one embodiment of the present invention, in step (S1), when stirring is performed during mixing, the stirring may be performed, for example, at 200 rpm to 250 rpm, specifically at 220 rpm to 240 rpm. When stirring is performed under the above conditions, this may have a beneficial effect on the uniformity of the size of the produced transition metal alloy particles, but the present invention is not limited thereto.

[0192] The step (S2) is performed to form M-CPP / C, wherein the MC precursor complex is supported on at least one of the outer surface of the porous carbon material and the inner surface of the pores of the porous carbon material.

[0193] In one embodiment of the present invention, the M-CPP may be present in a dispersed state in the solvent used in step (S1), such as water. The porous carbon material may be added to the dispersion in which the M-CPP is dispersed to prepare a dispersion in which the M-CPP and the porous carbon material are dispersed.

[0194] In one embodiment of the present invention, in order to produce M-CPP / C, the pH of the dispersion liquid in which M-CPP and the porous carbon material are dispersed may be in the range of, for example, 8 to 9.

[0195] In another embodiment of the present invention, step (S2) may further include adding a pH adjuster to adjust the acidity of the mixture of the M-CPP and the porous carbon material (e.g., a dispersion in which the M-CPP and the porous carbon material are dispersed). The pH adjuster may be a basic compound or an acidic compound, depending on the pH of the prepared dispersion.

[0196] In one embodiment of the present invention, the pH adjuster may include a basic compound, and the basic compound may include, for example, an amine compound. The amine compound may include, for example, tris(hydroxymethyl)aminomethane (TRIS).

[0197] In another embodiment of the present invention, the pH regulator may include an acidic compound, and the acidic compound may include, for example, an organic carboxylic acid. The organic carboxylic acid may include, for example, formic acid, acetic acid, propionic acid, butyric acid, pivalic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, acrylic acid, benzoic acid, phthalic acid, or two or more thereof.

[0198] In one embodiment of the present invention, step (S2) may include stirring. The stirring may be performed at room temperature for 12 to 48 hours, specifically 20 to 30 hours, for example 24 hours.

[0199] In one embodiment of the present invention, step (S2) may further include filtering and washing steps after stirring.

[0200] In one embodiment of the present invention, washing can be carried out, for example, using water, an organic solvent or a mixture thereof. For example, washing can be carried out by washing with water one to three times and then washing once with an alcoholic organic solvent such as ethanol, but the present invention is not limited thereto.

[0201] In one embodiment of the present invention, step (S2) may further include mixing the M-CPP with the porous carbon material, filtering, washing and drying.

[0202] In one embodiment of the present invention, the drying may be performed, for example, in a vacuum, and may be performed at a temperature between 50°C and 70°C, specifically at 60°C.

[0203] Step (S3) may include heat-treating the M-CPP / C to produce a carbon composite, wherein a catalyst containing transition metal alloy particles containing cobalt and iron and a carbon coating layer on at least a portion of the surface of the transition metal alloy particles is supported on at least one of the outer surface of the porous carbon material and the inner surface of the pores of the porous carbon material.

[0204] In one embodiment of the present invention, a foreign element contained in the carbon layer precursor may be doped into at least one of the porous carbon material and the carbon coating layer by heat treatment.

[0205] In one embodiment of the present invention, the heat treatment may be performed, for example, at 600° C. to 1,000° C. Specifically, the heat treatment may be performed at a temperature between 750° C. and 850° C., for example, 800° C.

[0206] In one embodiment of the present invention, the heat treatment may include increasing the temperature while uniformly maintaining a rate selected from the range of 0.5° C. / min to 10° C. / min.

[0207] In one embodiment of the present invention, the heat treatment may be performed while increasing the temperature at a rate of 5° C. / min.

[0208] According to the above method, the above-mentioned carbon composite can be produced.

[0209] According to another aspect of the present invention, a positive electrode active material and a positive electrode including the same are provided. The positive electrode active material includes a carbon composite and a sulfur compound.

[0210] The positive electrode may include a carbon composite as a carrier of the positive electrode active material and a composite of a sulfur compound as the positive electrode active material as the positive electrode active material.

[0211] In one embodiment of the present invention, the sulfur compound may include, for example, sulfur (S8), lithium sulfide (Li2S), polysulfide (Li2S x , 1 < x ≤ 8) or a disulfide compound or a mixture thereof, but is not limited thereto.

[0212] In one embodiment of the present invention, the carbon composite and the sulfur compound may be mixed at a mixing ratio of 1:9 to 9:1. Specifically, the mixing ratio may be 1:9 to 5:5, more specifically 2:8 to 4:6.

[0213] In one embodiment of the present invention, the positive electrode active material may be formed by mixing a carbon composite with a sulfur compound and then performing heat treatment. The heat treatment may be carried out, for example, at a temperature between 130 °C and 200 °C, specifically between 130 °C and 180 °C or between 150 °C and 160 °C.

[0214] In one embodiment of the present invention, in addition to the positive electrode active material containing a carbon composite and a sulfur compound, the positive electrode for a lithium-sulfur battery may further include a binder. The binder is not limited to a specific type and may include any type of binder that can be used in the positive electrode of a lithium-sulfur battery.

[0215] In one embodiment of the present invention, the binder may include, for example, polyvinylidene fluoride (PVDF), specifically PVDF dispersed in N-methyl-2-pyrrolidone (NMP).

[0216] In another embodiment of the present invention, the binder may include, for example, an aqueous binder such as styrene-butadiene rubber (SBR), acrylonitrile copolymer, and specifically may include an aqueous binder dispersed in an aqueous solvent such as water.

[0217] In one embodiment of the present invention, the binder may include a commercially available LA132(TOB) binder, but the present invention is not limited thereto.

[0218] In another embodiment of the present invention, in addition to the positive electrode active material and the binder, the positive electrode for a lithium-sulfur battery may further include a conductive material and an additive. In this case, the binder, the conductive material, and the additive include the binders, conductive materials, and additives commonly used in the art, and their descriptions are omitted.

[0219] In another embodiment of the present invention, the positive electrode for a lithium-sulfur battery may include a positive electrode current collector, and may include a positive electrode active material layer in which the positive electrode active material and the binder are coated on one or both surfaces of the current collector.

[0220] In this case, the positive electrode current collector is not limited to a specific kind and may include any kind of positive electrode current collector that does not cause any chemical change to the corresponding battery and is highly conductive.

[0221] In one embodiment of the present invention, a positive electrode including the carbon composite may have improved initial capacity and cycle stability, but the effects of the present invention are not limited thereto.

[0222] In one embodiment of the present invention, for example, the sulfur (S) loading of the positive electrode for lithium-sulfur batteries can be 2 mg s / cm 2 Above, specifically 5 mg s / cm 2 More, for example 2 to 10 mg s / cm 2 2.5 to 10 mg s / cm 2 or 5 to 8 mg s / cm 2 , but the present invention is not limited thereto.

[0223] A lithium-sulfur battery according to 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, wherein the positive electrode includes a carbon composite and a sulfur compound as positive electrode active materials.

[0224] In one embodiment of the present invention, the negative electrode and the separator are not limited to specific kinds and may include negative electrodes and separators used in lithium-sulfur batteries without hindering the purpose of the present invention.

[0225] In one embodiment of the present invention, the negative electrode may include, for example, lithium metal. Alternatively, the negative electrode may include a lithium alloy, and the lithium alloy may include, for example, an alloy of lithium (Li) and a metal selected from the group consisting of sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), francium (Fr), beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), radium (Ra), aluminum (Al), and tin (Sn).

[0226] Preferably, the negative electrode active material may be lithium metal, specifically in the form of lithium metal foil or lithium metal powder.

[0227] In one embodiment of the present invention, the separator may include, but is not limited to, those separators commonly used as lithium-sulfur battery separators.

[0228] In one embodiment of the present invention, the separator may include a porous polyolefin substrate and, if necessary, inorganic particles may be further included on at least one surface of the porous polyolefin substrate. In addition, if necessary, the separator may further include a binder for holding the inorganic particles together.

[0229] In another embodiment of the present invention, the separator may be a membrane-shaped electrolyte membrane comprising a solid electrolyte and, if necessary, a binder to tightly bind the solid electrolyte. The solid electrolyte may include, but is not limited to, any solid electrolyte commonly used in lithium-sulfur batteries, such as a polymer solid electrolyte, an inorganic solid electrolyte, or a mixture thereof.

[0230] In one embodiment of the present invention, the electrolyte comprises any electrolyte commonly used in lithium-sulfur batteries. The electrolyte may comprise a lithium salt and a non-aqueous solvent.

[0231] The lithium salt may include, but is not limited to, any lithium salt commonly used in the electrolyte of lithium-sulfur batteries. The lithium salt may include, for example: LiCl, LiBr, LiI, LiClO4, LiBF4, LiB 10 Cl 10 , LiPF6, LiCF3SO3, LiCF3CO2, LiC4BO8, LiAsF6, LiSbF6, LiAlCl4, CH3SO3Li, CF3SO3Li, (CF3SO2)2NLi, (C2F5SO2)2NLi, (SO2F)2NLi, (CF3SO2)3CLi, lithium chloroborane, lithium lower aliphatic carboxylate, lithium tetraphenylborate, lithium imide or two or more thereof, but not limited thereto.

[0232] The non-aqueous solvent may include, but is not limited to, any non-aqueous solvent commonly used in the electrolyte of lithium-sulfur batteries. The non-aqueous solvent may include, for example, an ether solvent, a carbonate solvent, an ester solvent, a ketone solvent, or a mixture thereof, but is not limited thereto.

[0233] In one embodiment of the present invention, the ether solvent may include acyclic ether, cyclic ether or a mixture thereof.

[0234] In one embodiment of the present invention, the acyclic ether may include, for example, at least one selected from the group consisting of dimethyl ether, diethyl ether, dipropyl ether, dibutyl ether, diisobutyl ether, ethyl methyl ether, ethyl propyl ether, ethyl tert-butyl ether, dimethoxymethane, trimethoxymethane, dimethoxyethane, diethoxyethane, dimethoxypropane, diethylene glycol, diethylene glycol diethyl ether, triethylene glycol, tetraethylene glycol, ethylene glycol divinyl ether, diethylene glycol divinyl ether, triethylene glycol divinyl ether, dipropylene glycol dimethylene ether, butylene glycol ether, diethylene glycol ethyl methyl ether, diethylene glycol isopropyl methyl ether, diethylene glycol butyl methyl ether, diethylene glycol tert-butyl ethyl ether, and ethylene glycol ethyl methyl ether. Preferably, the acyclic ether may include at least one selected from the group consisting of dimethoxyethane, diethoxyethane, diethylene glycol, triethylene glycol, and tetraethylene glycol, more preferably dimethoxyethane.

[0235] In one embodiment of the present invention, the cyclic ether may include, for example, at least one selected from the group consisting of 2-methylfuran, 1,3-dioxolane, 4,5-dimethyl-dioxolane, 4,5-diethyl-dioxolane, 4-methyl-1,3-dioxolane, 4-ethyl-1,3-dioxolane, tetrahydrofuran, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, 2,5-dimethoxytetrahydrofuran, , 2-ethoxytetrahydrofuran, 2-methyl-1,3-dioxolane, 2-vinyl-1,3-dioxolane, 2,2-dimethyl-1,3-dioxolane, 2-methoxy-1,3-dioxolane, 2-ethyl-2-methyl-1,3-dioxolane, tetrahydropyran, 1,4-dioxane, 1,2-dimethoxybenzene, 1,3-dimethoxybenzene, 1,4-dimethoxybenzene and isosorbide dimethyl ether. Preferably, the cyclic ether may comprise at least one selected from the group consisting of 2-methylfuran, 1,3-dioxolane, tetrahydrofuran, 2-methyltetrahydrofuran and 2,5-dimethyltetrahydrofuran, more preferably 2-methylfuran.

[0236] In one embodiment of the present invention, the electrolyte may include (CF3SO2)2NLi as a lithium salt and may include a two-component system of dioxolane (DOL) / dimethoxyethane (DME) as a non-aqueous solvent. For example, the electrolyte may further include any commonly used additives, such as LiNO3.

[0237] In another embodiment of the present invention, the electrolyte may include one selected from these lithium salts or a mixture thereof, and a mixture of dimethoxyethane (DME) and 2-methylfuran (2-MeF) as the non-aqueous solvent, but the present invention is not limited thereto.

[0238] In one embodiment of the present invention, the lithium-sulfur battery may be shaped, for example, as a coin, cylinder, pouch, or prismatic shape, but the battery shape is not limited thereto. Furthermore, the lithium-sulfur battery can be used not only in battery cells used as power sources for small devices but also in unit cells for medium- to large-sized battery modules comprising a plurality of battery cells, and its application is not limited thereto.

[0239] In one embodiment of the present invention, a lithium-sulfur battery using a positive electrode including a carbon composite may not only have improved kinetic activity in sulfur redox reactions but also have improved battery initial capacity and cycle stability, but the effects of the present invention are not limited thereto.

[0240] In one embodiment of the present invention, a lithium-sulfur battery may have improved energy density by increasing the sulfur loading in the electrode and stably operate under a lean electrolyte condition, but the effects of the present invention are not limited thereto.

[0241] In one embodiment of the present invention, the electrolyte / sulfur (E / S) ratio of the lithium-sulfur battery can be, for example, 8 μL / mg or less. Low activity of the positive electrode limits the reduction of the E / S ratio, but the present invention can stably reduce the E / S ratio. Therefore, the E / S ratio of the lithium-sulfur battery can have a value greater than the above range. It should be apparent to those skilled in the art that the lower limit is not limited to a specific value, and the present invention is not limited thereto.

[0242] In this specification, the E / S ratio may represent the ratio of the volume of the electrolyte to the weight of sulfur in the positive electrode.

[0243] In one embodiment of the present invention, the lithium-sulfur battery can be manufactured to have an E / S ratio of, for example, 8 μL / mg or less, 5 μL / mg or less, 3 μL / mg or less, or 2.9 μL / mg or less.

[0244] In one embodiment of the present invention, the E / S ratio of the lithium-sulfur battery can be calculated by the ratio of the weight of the electrolyte to the weight of sulfur in the sulfur-carbon composite of the positive electrode added in a manufacturing step immediately after manufacturing the lithium-sulfur battery.

[0245] In another embodiment of the present invention, the E / S ratio of the lithium-sulfur battery can be calculated by analyzing the ratio of the weight of the electrolyte to the weight of the sulfur in the sulfur-carbon composite of the positive electrode, as analyzed after disassembling the battery.

[0246] As an example, when analyzing the E / S ratio of a lithium-sulfur battery after disassembling the battery, the total weight of the charged lithium-sulfur battery can be measured by subtracting the weight of the positive electrode, negative electrode, separator, and shell from the total weight of the battery, after measuring the total weight of the battery, disassembling the battery, washing the positive electrode, negative electrode, separator, and shell with a solvent, drying, and calculating the sum of their weights. In this case, the washing solvent can preferably include any solvent that extracts the electrolyte from the positive electrode, negative electrode, separator, and shell. Then, after separating the positive electrode active material layer and current collector from the dried positive electrode, the weight of sulfur derived from the sulfur-carbon composite present in the positive electrode active material layer can be measured to measure the weight of sulfur in the positive electrode. The E / S ratio of the lithium-sulfur battery can be calculated as the ratio of the electrolyte weight to the weight of sulfur in the positive electrode sulfur-carbon composite.

[0247] In one embodiment of the present invention, a method of measuring the weight of sulfur derived from the sulfur-carbon composite present in the positive electrode active material layer may include, for example, measuring the amount of sulfur (S) derived from the active material by performing thermogravimetric analysis (TGA) on the resultant obtained by scraping off the obtained positive electrode active material layer, but the measurement method is not limited thereto.

[0248] In one embodiment of the present invention, the state of charge (SOC) when disassembling the lithium-sulfur battery can be SOC 100%, i.e., a fully charged state. In another embodiment of the present invention, the SOC when disassembling the lithium-sulfur battery can be in a range from SOC 95% to SOC 100%. In one embodiment of the present invention, for safety reasons, the lithium-sulfur battery must be disassembled in an inert atmosphere while in a charged state. For example, the lithium-sulfur battery can be disassembled in an Ar atmosphere.

[0249] In one embodiment of the present invention, the energy density of the lithium-sulfur battery can be, for example, 300 Wh / kg or greater. For example, the energy density of the lithium-sulfur battery can be 350 Wh / kg or greater, such as 380 Wh / kg or greater. The energy density of the lithium-sulfur battery can be, for example, in the range of 300 Wh / kg to 2,600 Wh / kg, 300 Wh / kg to 1,600 Wh / kg, 300 Wh / kg to 1,000 Wh / kg, 300 Wh / kg to 800 Wh / kg, 300 Wh / kg to 450 Wh / kg, 330 Wh / kg to 400 Wh / kg, 350 Wh / kg to 400 Wh / kg, or 380 Wh / kg to 400 Wh / kg.

[0250] In one embodiment of the present invention, the energy density of the lithium-sulfur battery can be measured by a commonly used method, and the measurement method is not limited to a specific method. For example, the energy density of the lithium-sulfur battery can be calculated according to the following mathematical formula based on the specific capacity measured after one or more cycles of discharge and charge in the range of 1.8 V to 2.7 V at room temperature and then 0.1 C discharge. In one embodiment of the present invention, the initial discharge and charge can each be performed at a rate of 0.1 C to 0.3 C. Specifically, the initial discharge and charge can each be performed at a rate of 0.1 C to 0.2 C, for example, 0.1 C. In addition, in one embodiment of the present invention, the initial discharge and charge can each be repeated three times at a rate of 0.1 C.

[0251] In the following mathematical formula, the discharge capacity may be measured in mAh, the operating voltage may be measured in V, and the battery weight may be measured in kg.

[0252] [Mathematical formula]

[0253] Energy density (Wh / kg) = {[(discharge capacity (mAh) × operating voltage (V)) / 1000] / (battery weight (kg))}

[0254] In one embodiment of the present invention, the room temperature may be, for example, from 23°C to 25°C, specifically 23°C.

[0255] In one embodiment of the present invention, the charge / discharge rate may be in the range of 0.1 C to 0.5 C, for example 0.3 C, but not limited thereto, and charging and discharging may be performed at any rate within the above rate range.

[0256] According to another aspect of the present invention, a positive electrode active material including a sulfur compound, a positive electrode including a carbon composite as a positive electrode additive, and a lithium-sulfur battery including the same may be provided.

[0257] In one embodiment of the present invention, in contrast to one aspect of the present invention in which the positive electrode includes a carbon composite as a support in combination with a sulfur compound as a positive electrode active material, the carbon composite may be included in the positive electrode as an additive separately from the positive electrode active material.

[0258] In one embodiment of the present invention, when the carbon composite is used as a cathode additive, it can not only improve the capacity of the battery but also improve the reactivity with lithium polysulfide, thereby improving the battery performance.

[0259] In one embodiment of the present invention, when a carbon composite is used as a positive electrode additive, the content of the carbon composite may be 1 wt % to 25 wt %, for example, 1 wt % to 15 wt % or 1 wt % to 10 wt %, based on the total weight of the positive electrode active material, the binder and the carbon composite contained in the positive electrode active material layer, but is not limited thereto.

[0260] In one embodiment of the present invention, the positive electrode may include a sulfur compound or a sulfur compound supported on a conventional carbon support as the positive electrode active material. For details of the sulfur compound, reference is made to the description of the positive electrode according to the above aspects. In addition, the conventional carbon support may be, for example, the aforementioned porous carbon material itself, but is not limited thereto.

[0261] The lithium-sulfur battery according to one aspect of the present invention may be used, for example, in electric vehicles (EVs), drones, or urban air mobility systems (UAM), but the scope of application of the present invention is not limited thereto.

[0262] The following describes in detail a method for producing a carbon composite according to an embodiment of the present invention and the results of measuring the performance of a lithium-sulfur battery using the same through examples. However, the following examples are provided to describe the present invention for illustrative purposes only and the scope of the present invention is not limited thereto.

[0263] [Preparation of Carbon Composite]

[0264] Example 1 (FeCo / CNT)

[0265] First, 568 mg of ferrous chloride hydrate (FeCl2·6H2O, 99%, Sigma-Aldrich), 502 mg of cobalt chloride hydrate (CoCl2·6H2O, 99%, Sigma-Aldrich), and 800 mg of dopamine hydrochloride (98%, Sigma-Aldrich) were added to 2 L of distilled water and stirred at 230 rpm for 30 min at room temperature (23°C) to prepare a transition metal-carbon layer precursor polymer (MC precursor polymer).

[0266] 1.8 g of multi-walled carbon nanotubes (MWCNTs) (BET surface area of ​​275 m 2 / g, Carbon Nano-material Technology Co., Ltd.) and stirred at room temperature for 30 minutes to prepare a dispersion. Subsequently, the pH of the prepared dispersion was maintained at 8.5 by adding 3.602 g of Trizma base (tris (hydroxymethyl) aminomethane, TRIS). The obtained dispersion was stirred at room temperature for 24 hours, filtered, washed three times with distilled water, then washed once with ethanol and dried at 60 ° C to obtain Fe-Co-polydopamine / carbon nanotube composite (M-PDA / CNT) as transition metal-carbon layer precursor polymer / porous carbon material (M-CPP / C).

[0267] The obtained M-PDA / CNT was placed in an electric heating tube furnace and heat treated at 800°C for 2 hours (heating rate of 5°C / min) under argon atmosphere to obtain a carbon composite (D 50 The obtained carbon composite comprises: MWCNTs as a porous carbon material; a catalyst located on at least one of the outer surface of the MWCNTs and the inner surface of the pores of the MWCNTs, wherein the catalyst comprises transition metal alloy particles and a carbon coating on at least a portion of the surface of the transition metal alloy particles, the transition metal alloy particles comprising cobalt and iron; and doped nitrogen. In this case, the thickness of the carbon coating is proportional to the average particle size (D 50 ) ratio is 15%.

[0268] Comparative Example 1 (Ref)

[0269] Multi-walled carbon nanotubes (MWCNTs) (BET surface area of ​​275 m 2 / g) as a carbon composite without supporting a catalyst.

[0270] [Structure determination of carbon composites]

[0271] Structural observation of carbon composites

[0272] Figure 3 shows the STEM image of the carbon composite prepared in Example 1,

[0273] Figure 4 HRTEM images and d-spacing diagrams are shown,

[0274] Figure 5 The XRD analysis diagram is shown.

[0275] Figure 6 TEM images are shown.

[0276] refer to Figure 3 and 6, it was confirmed that the carbon composite of Example 1 contained a catalyst comprising cobalt-iron alloy particles uniformly on the surface of MWCNT and a carbon coating covering the surface. In particular, referring to Figure 5 (b) XRD analysis of four particles prepared according to the above method confirmed that the carbon composite had reproducible properties. In addition, it was confirmed that the size of the catalyst in the carbon composite was uniform, ranging from 10 nm to 20 nm.

[0277] refer to Figure 4 , it was confirmed that the carbon composite of Example 1 had a crystalline carbon coating on the surface of the transition metal alloy particles, and that the transition metal alloy particles had a body-centered cubic structure.

[0278] Determination of the amount of catalyst

[0279] TGA analysis was performed to measure the amount of transition metal alloy particles supported on the carbon composite prepared in Example 1, and the results are shown in FIG. Figure 7 TGA analysis measured the weight loss of the prepared carbon composite while increasing the temperature from 100° C. to 800° C. (at a heating rate of 10° C. / min).

[0280] refer to Figure 7 Since the weight at the point where no temperature change occurs when the temperature is increased corresponds to the weight of the transition metal alloy particles (FeCo), it was confirmed that the loading amount of the cobalt-iron alloy particles as the transition metal alloy particles in the carbon composite of Example 1 was 14.7 wt%.

[0281] [Preparation of lithium-sulfur batteries]

[0282] In order to evaluate the performance of lithium-sulfur batteries using the carbon composites prepared in Example 1 and Comparative Example 1, lithium-sulfur batteries were prepared as follows.

[0283] Cathode manufacturing

[0284] 25 wt % of the prepared carbon composite and 75 wt % of sulfur (sulfur powder, Sigma Aldrich) were mixed and subjected to isothermal heat treatment at 155° C. for 2 hours to obtain a positive electrode active material.

[0285] To fabricate a working electrode, the prepared cathode active material and polyacrylonitrile binder (PAN binder, LA 132) were mixed at a weight ratio of 9:1 using N-methyl-2-pyrrolidone (NMP) solvent to prepare a cathode slurry.

[0286] The prepared cathode slurry was coated on a carbon-coated Al foil and dried at 60° C. for 8 h. Subsequently, the electrode was rolled and cut into a shell shape to fabricate a cathode.

[0287] Battery manufacturing

[0288] A positive electrode, a negative electrode, and a separator therebetween are placed in a case along with an electrolyte to manufacture a battery.

[0289] The positive electrode was the one produced as described above, and a porous polypropylene film (Celgard 2400, Welcos Co., Ltd.) was prepared as a separator. Lithium metal (200 μm thickness) was used for each of the reference electrode and the counter electrode.

[0290] The electrolyte was a solution containing 1.0 M lithium bis(trifluoromethane)sulfonamide (LiTFSI) as an electrolyte and 2.0 wt % LiNO3 (99.99% metal base, Sigma-Aldrich) as an additive in a solvent (1,3-dioxolane and dimethoxymethane (DOL / DME) in a 1:1 volume ratio, produced by Panax E-Tec, Korea).

[0291] The sulfur loading in the cathode is 2.5 mg s / cm 2 , and the E / S ratio of the battery is 10 μL / cm 2 Coin-type cells were fabricated using the CR2032 standard, and for the following electrochemical performance tests, 200 μm thick lithium metal was used as the reference electrode and the counter electrode.

[0292] In addition, for the experiments under lean electrolyte conditions, each lithium-sulfur battery was fabricated with a sulfur loading of 7 mg in the cathode. s / cm 2 , and the E / S ratio of the battery is 6 μL / mg.

[0293] [Performance evaluation of lithium-sulfur batteries]

[0294] Determination of the reactivity of sulfur conversion based on carbon composites

[0295] Figure 8 are CV graphs obtained by operating lithium-sulfur batteries each using the carbon composite of Example 1 and the carbon composite of Comparative Example 1,

[0296] Figure 9 An EIS measurement graph is shown.

[0297] refer to Figure 8 and Figure 9 , the electrochemical reaction of sulfur conversion occurred in both the carbon composite of Example 1 (FeCo) and the carbon composite of Comparative Example 1 (Ref), and when the carbon composite of Example 1 was used, it was confirmed that the resistance to the sulfur conversion reaction was low and the kinetic activity was further improved.

[0298] Charge and discharge curve distribution

[0299] First, lithium-sulfur batteries each using the carbon composite of Example 1 and the carbon composite of Comparative Example 1 were charged and discharged within a range between 1.7 V and 2.8 V at a current density of 0.2 C. Figure 10a The voltage-capacity curve obtained at the 10th cycle is shown. Figure 10b The discharge capacity-cycle curve of the fabricated lithium-sulfur battery with an E / S of 10 μL / mg is shown.

[0300] also, Figure 10c The fabricated positive electrode loading is 7 mg. s / cm 2 The discharge capacity-cycle curve of the lithium-sulfur battery with an E / S of 6 μL / mg during the 0.1 C charge and discharge process.

[0301] according to Figure 10a , it was confirmed that the use of the carbon composite according to one embodiment of the present invention increases the utilization of sulfur, thereby improving the discharge capacity. Figure 10b , confirmed that the use of the carbon composite according to one embodiment of the present invention improves the battery cycle life. In particular, according to Figure 10c , it was confirmed that the use of the carbon composite according to one embodiment of the present invention significantly improved the life stability of the battery under high loading and poor electrolyte conditions.

[0302] Energy density evaluation

[0303] Lithium-sulfur batteries were manufactured using the carbon composite of Example 1 and the carbon composite of Comparative Example 1, respectively, using the same method as described above. The E / S ratios of the lithium-sulfur battery using the carbon composite of Example 1 were 2.4 μL / mg and 2.8 μL / mg, and the E / S ratio of the lithium-sulfur battery using the carbon composite of Comparative Example 1 was 2.4 μL / mg. The lithium-sulfur batteries were charged and discharged at a current density of 0.2 C in the range of 1.7 V to 2.8 V, and the discharge capacity was evaluated. Figure 11 A cycle-energy density diagram based on the measurement results is shown.

Claims

1. A carbon composite, comprising: porous carbon materials, and a catalyst located on at least one of an outer surface of the porous carbon material and an inner surface of pores of the porous carbon material, wherein the catalyst comprises transition metal alloy particles and a carbon coating on at least a portion of the surface of the transition metal alloy particles, wherein the transition metal alloy particles comprise cobalt (Co) and iron (Fe), and wherein at least a portion of the carbon coating comprises crystalline carbon.

2. The carbon composite according to claim 1, The transition metal alloy particles comprise cobalt-iron alloy particles having a body-centered cubic structure.

3. The carbon composite according to claim 1, The average particle size of the carbon composite (D 50 ) is in the range of 100 nm to 100 μm.

4. The carbon composite according to claim 1, The average particle size of the catalyst (D 50 ) is less than 100 nm.

5. The carbon composite according to claim 1, The thickness of the carbon coating is related to the average particle size (D 50 ) is less than 40%.

6. The carbon composite according to claim 1, The thickness of the carbon coating is less than 10 nm.

7. The carbon composite according to claim 1, The carbon coating layer has a single-layer structure or a multi-layer structure of 10 layers or less.

8. The carbon composite according to claim 1, The amount of the catalyst is in a range of 5 wt % to 50 wt % based on 100 wt % of the carbon composite.

9. The carbon composite according to claim 1, The porous carbon material comprises carbon nanotubes (CNTs), graphene, graphene oxide (GO), reduced graphene oxide (rGO), carbon black, graphite, graphite nanofibers (GNFs), carbon nanofibers (CNFs), activated carbon fibers (ACFs), activated carbon, fullerenes, or two or more thereof.

10. The carbon composite according to claim 1, wherein the porous carbon material comprises carbon nanotubes (CNTs), and The carbon nanotubes include entangled CNTs.

11. A method for producing the carbon composite according to any one of claims 1 to 10, the method comprising: mixing a cobalt (Co)-containing precursor, an iron (Fe)-containing precursor, a carbon layer precursor, and a porous carbon material to obtain a transition metal-carbon layer precursor polymer / porous carbon material (M-CPP / C), and The transition metal-carbon layer precursor polymer / porous carbon material is heat-treated to obtain the carbon composite.

12. The method for producing a carbon composite according to claim 11, The carbon layer precursor comprises dopamine, polydopamine, melamine, 1,10-phenanthroline, polyaniline, carbon nitride (g-CN), glucose, phenylenediamine or a mixture thereof.

13. The method for producing a carbon composite according to claim 11, The heat treatment is performed at a temperature ranging from 600°C to 1,000°C. 14 . A positive electrode active material comprising the carbon composite according to claim 1 and a sulfur compound.

15. A lithium-sulfur battery, comprising: positive electrode, negative electrode and electrolyte, The positive electrode comprises the positive electrode active material according to claim 14 .

16. The lithium-sulfur battery according to claim 15, The E / S ratio is less than 8 μL / mg, and the sulfur loading in the positive electrode is 2.25 mg. s / cm 2 above, and The E / S ratio represents the ratio of the volume of the electrolyte to the weight of sulfur in the positive electrode.

17. The lithium-sulfur battery according to claim 15, The E / S ratio is less than 3 μL / mg and the energy density is greater than 380 Wh / kg.

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