Cathode material for lithium-sulfur battery and lithium-sulfur battery including same

Abstract

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

Description

A cathode material for a lithium-sulfur battery, and a lithium-sulfur battery containing the same

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

[0002] This application claims priority to Korean Patent Application No. 10-2023-0125127, filed with the Korean Intellectual Property Office on September 19, 2023, and Korean Patent Application No. 10-2024-0119502, filed with the Korean Intellectual Property Office on September 3, 2024, the entire contents of which are incorporated herein by reference.

[0003] Lithium-sulfur batteries are battery systems that use a sulfur-based material with a sulfur-sulfur bond as the positive electrode active material and lithium metal as the negative electrode active material. Sulfur, the primary ingredient in the positive electrode active material, is abundant worldwide, is non-toxic, and has the advantages of a low per-atom weight.

[0004] As the application areas of secondary batteries expand to include electric vehicles (EVs) and energy storage systems (ESS), lithium-sulfur battery technology, which can theoretically achieve a high energy storage density per weight (~2,600 Wh / kg) compared to lithium-ion secondary batteries with a relatively low energy storage density per weight (~250 Wh / kg), is attracting attention.

[0005] In a lithium-sulfur battery, when discharging, the negative active material lithium is oxidized by giving up electrons and ionizing into lithium cations, and the positive active material sulfur-based material is reduced by accepting electrons. Here, through the reduction reaction of the sulfur-based material, the S-S bond accepts two electrons and is converted into a sulfur anion. The lithium cation produced by the oxidation reaction of lithium is transferred to the positive electrode through the electrolyte, and this combines with the sulfur anion produced by the reduction reaction of the sulfur-based compound to form a salt. Specifically, before discharge, sulfur has a cyclic S8 structure, which is converted into lithium polysulfide (Li2Sx) through the reduction reaction, and is completely reduced to produce lithium sulfide (Li2S).

[0006] Meanwhile, the amount of electrolyte within a lithium-sulfur battery is one of the most important variables to consider among the various variables that determine the price and energy density of a lithium-sulfur battery. First, looking at the materials that generally make up a lithium-sulfur battery, the manufacturing cost of a lithium-sulfur battery is considerably high due to the use of a very thin lithium anode and an electrolyte based on expensive lithium salts. On the other hand, the energy density of a lithium-sulfur battery is critically determined by the amount of energy that the manufactured cell can express relative to its total weight. The ratio of the expressible energy to the total cell weight is influenced by the sulfur loading per unit area of ​​the cathode and the sulfur ratio within the composite, but is relatively more significantly affected by the ratio of the amount of sulfur in the cathode to the amount of electrolyte (E / S, electrolyte to sulfur). Furthermore, the energy expression ratio relative to the total cell weight is more significantly affected by the capacity generated from the lithium-sulfur electrochemical reaction than by the operating voltage. Therefore, it is necessary to design a stable lithium-sulfur battery that can express high reversible capacity in a cell with a low E / S ratio while minimizing the amount of electrolyte.

[0007] In particular, sulfur, which is used in the cathode active material, is an insulator, making it difficult for electrons generated by the electrochemical reaction to move. In addition, there were problems with the release of polysulfide (LiSx) generated during the charge / discharge process, and the slow kinetic activity of the electrochemical reaction due to the low electrical conductivity of sulfur and lithium sulfide, which resulted in reduced battery life and rate characteristics. In relation to this, recent studies have been conducted to improve the performance of lithium-sulfur secondary batteries by improving the kinetic activity of the sulfur redox reaction during the charge / discharge process of lithium-sulfur secondary batteries using platinum (Pt), which has been widely used as an electrochemical catalyst. However, noble metal catalysts such as platinum are expensive, making them difficult to commercialize. In addition, there is a problem that they are not easy to use as cathode materials for lithium-sulfur secondary batteries due to the possibility of poisoning by sulfur redox reactions during the charge / discharge process. Therefore, there is a continuous need for technological development for cathode materials that can improve the kinetic activity of the electrochemical reaction during charge / discharge of lithium-sulfur secondary batteries and are advantageous for commercialization in terms of cost.

[0008] Therefore, the problem that the present invention seeks to solve is to solve the above-described problem,

[0009] The present invention aims to provide a cathode material having excellent adsorption capacity with lithium polysulfide and increasing the kinetic activity of sulfur oxidation / reduction reactions.

[0010] In particular, the present invention seeks to provide a carbon composite that exhibits high mobility even under lean electrolyte conditions and maintains excellent catalytic activity that promotes the conversion reaction of lithium polysulfide. Through this, the present invention aims to provide a cathode material for a lithium-sulfur battery, and a lithium-sulfur battery comprising the same, that enhances reversible capacity and cycle stability, and further enables high energy density even under lean electrolyte conditions.

[0011] To solve the above problem,

[0012] According to one aspect of the present invention, carbon composites of the following embodiments are provided.

[0013] The carbon composite according to the first embodiment is:

[0014] porous carbon materials, and

[0015] A catalyst is included which is positioned on at least one of the outer surface and the inner surface of the pores of the porous carbon material,

[0016] The catalyst comprises a transition metal alloy particle and a carbon coating layer covering at least a portion of the surface of the transition metal alloy particle,

[0017] The above transition metal alloy particles include cobalt (Co) and iron (Fe),

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

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

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

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

[0022] The average particle diameter (D) of the above carbon composite 50 ) can be 100 nm to 100 μm.

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

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

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

[0026] The average particle diameter (D) of the above transition metal alloy particles 50 ) The ratio of the thickness of the carbon coating layer may be 40% or less.

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

[0028] The thickness of the above carbon coating layer may be 10 nm or less.

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

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

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

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

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

[0034] The above porous carbon material may include carbon nanotubes (CNT), graphene, graphene oxide (GO), reduced graphene oxide (rGO), carbon black, graphite, graphite nanofibers (GNF), carbon nanofibers (CNF), activated carbon fibers (ACF), activated carbon, fullerene, or two or more of these materials.

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

[0036] The above porous carbon material includes carbon nanotubes (CNTs),

[0037] The above carbon nanotubes may include entangled carbon nanotubes (CNTs).

[0038]

[0039] According to another aspect of the present invention, a method for producing a carbon composite according to the following embodiments is provided.

[0040] The method for manufacturing a carbon composite according to the 11th embodiment is as follows:

[0041] It may be a method of manufacturing a carbon composite according to any one of the first to tenth embodiments.

[0042] The above manufacturing method comprises: 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

[0043] It includes heat treating the above transition metal-carbon layer precursor polymer / porous carbon material to obtain the carbon composite.

[0044] According to the 12th embodiment, in the 11th embodiment,

[0045] The carbon layer precursor may include dopamine, polydopamine, melamine, 1,10-phenanthroline, polyaniline, carbon nitride (g-CN), glucose, phenylenediamine, or a mixture thereof.

[0046] According to the 13th embodiment, in the 11th embodiment or the 12th embodiment,

[0047] The above heat treatment can be performed at a temperature of 600°C to 1,000°C.

[0048]

[0049] According to another aspect of the present invention, a cathode active material and a lithium sulfur battery of the following embodiments are provided.

[0050] The positive electrode active material according to the 14th embodiment is

[0051] It may include a carbon composite according to any one of the first to tenth embodiments, and a sulfur series compound.

[0052] A lithium sulfur battery according to the 15th embodiment,

[0053] Containing a positive electrode, a negative electrode and an electrolyte,

[0054] The above positive electrode may include a positive electrode active material according to the 14th embodiment.

[0055] According to the 16th embodiment, in the 15th embodiment,

[0056] The E / S ratio is 8 μL / mg or less, and the sulfur loading amount in the anode is 2.25 mg. s / cm 2 It may be ideal. Here, the E / S ratio represents the ratio of the volume of the electrolyte and the weight of sulfur in the anode.

[0057] According to the 17th embodiment, in the 15th embodiment or the 16th embodiment,

[0058] The E / S ratio is 3 μL / mg or less, and the energy density can be 380 Wh / kg or more.

[0059] A carbon composite according to one embodiment of the present invention comprises lithium polysulfide (LiPS, Li2Sx, 1) through a metal catalyst. <x≤8)와의 흡착력이 우수한 효과가 있다. 또한, 상기 탄소 복합체는 황의 산화 / 환원 반응에 우수한 동역학적 활성을 제공하는 효과가 있다.

[0060] Furthermore, the carbon composite according to one embodiment of the present invention can exhibit the effect of improving the accessibility of polysulfide to the catalyst surface / electrolyte / carbon material three-phase interface at a low E / S ratio by including a catalyst having a relatively weak fixation to the carbon material surface and a certain degree of mobility on the carbon material surface.

[0061] Through this, the degree of decrease in catalyst activity can be suppressed even under lean electrolyte conditions, thereby providing a lithium-sulfur battery exhibiting high energy density and lifespan stability.

[0062] For example, according to one aspect of the present invention, it is possible to achieve an effect of realizing a high energy density, for example, an energy density of 300 Wh / kg or more, or 380 Wh / kg or more, even under conditions where the E / S ratio is 10 μL / mg or less, specifically 2.5 μL / mg or less, but the effect of the present invention is not limited thereto.

[0063] Figure 1 shows lithium sulfide (Li2S) and lithium polysulfide (Li2Sx, 1 <x)의 전환 반응에 대한 동역학적 활성이 저하된 양극재에서 일어나는 반응 모식도이다. 도 1에는 리튬설파이드(Li2S)와 리튬폴리설파이드(Li2Sx, 1<x)의 전환 반응과 다공성 탄소재 및 다공성 탄소재의 표면 및 기공에 부산물이 덮인 양상이 나타난다.

[0064] Figure 2 is a schematic diagram showing a conversion reaction of lithium polysulfide using a carbon composite according to one embodiment of the present invention.

[0065] FIG. 3 is a scanning transmission electron microscope (STEM) image (a) and an energy dispersive X-ray spectroscopy (EDX) mapping result (b) for a carbon composite according to one embodiment of the present invention.

[0066] FIG. 4 shows a HRTEM (High Resolution Transmission Electron Microscopy) image (a) of a carbon composite according to one embodiment of the present invention and a graph (b) showing the results of measuring the (110) interplanar distance through d-spacing.

[0067] Figure 5 illustrates XRD analysis results for carbon composites according to one embodiment of the present invention. (a) is an XRD analysis graph for porous carbon materials (CNTs), cobalt metal particles, iron metal particles, and cobalt-iron alloy particles, and (b) is an XRD analysis graph for four different carbon composites to confirm reproducibility.

[0068] FIG. 6 shows TEM images at different magnifications of a carbon composite according to one embodiment of the present invention.

[0069] Figure 7 is a graph showing the results of analyzing the content of cobalt-iron alloy particles through thermal decomposition analysis (TGA) for a carbon composite according to one embodiment of the present invention.

[0070] Figure 8 is a CV result graph of a lithium sulfur battery (FeCo) using the carbon composite of Example 1 in the present specification and a lithium sulfur battery (Ref) using the carbon composite of Comparative Example 1.

[0071] Figure 9 is a graph showing the EIS results of a lithium-sulfur battery (FeCo) using the carbon composite of Example 1 in the present specification and a lithium-sulfur battery (Ref) using the carbon composite of Comparative Example 1.

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

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

[0074] Figure 10c shows the results of Example 1 and Comparative Example 1 in the present specification with a positive electrode loading of 7 mg. s / cm 2 , is a discharge capacity-cycle graph of a lithium-sulfur battery manufactured with E / S 6 μL / mg.

[0075] Figure 11 is a graph showing the results of measuring the change in energy density according to the cycle repetition of a lithium-sulfur battery manufactured with two conditions of E / S ratio using Example 1 in the present specification and a lithium-sulfur battery manufactured using Comparative Example 1.

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

[0077] In this specification, when a configuration is said to “include” a component, this does not mean that it excludes other components, but rather that it may include other components, unless otherwise specifically stated.

[0078] In this specification, the description of “A and / or B” means A or B, or both.

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

[0080] The term "(poly)sulfide" as used herein means "(poly)sulfide ion (S x 2- , 1≤ x ≤8)" and "lithium (poly)sulfide (Li2S x or Li2S x - , 1≤ x ≤8)" is a concept that includes all of them.

[0081] In this specification, the term "polysulfide" means "polysulfide ion (S x 2- , 1< x ≤8)" and "lithium polysulfide (Li2S x or Li2S x - , 1< x ≤8)" is a concept that includes all of them.

[0082] The unit "mg" used in this specification s / cm 2" is intended to represent the weight of sulfur (S) per unit area, unless otherwise stated, mg(s) / cm 2 , may be used interchangeably with other expressions such as mAh / gs.

[0083] Lithium-sulfur batteries have a problem in that lithium polysulfide, which is formed by the reduction reaction of sulfur (S8) at the positive electrode during charging and discharging, is eluted from the positive electrode into the electrolyte, and as a result, the capacity of the battery does not represent the theoretical capacity.

[0084] According to one aspect of the present invention, a carbon composite is provided that has excellent adsorption capacity for lithium polysulfide, has improved mobility on the surface of a carbon material, and provides excellent dynamic activity even under dilute electrolyte conditions, thereby being usable in a high-performance lithium-sulfur battery.

[0085] Figure 1 shows lithium sulfide (Li2S) and lithium polysulfide (Li2Sx, 1 <x)의 전환 반응에 대한 동역학적 활성이 저하된 양극재에서 일어나는 반응 모식도가 도시되어 있다. 도 1을 참고하면, 리튬폴리설파이드의 느린 전환 반응으로 인해 리튬설파이드(Li2S)와 부산물들이 다공성 탄소재(예를 들어, 카본나노튜브)의 기공과 표면을 덮으면서 양극의 비가역적 용량이 더욱 증가하여 리튬황 전지의 퇴화를 촉진하는 것이 설명될 수 있다.

[0086] FIG. 2 is a schematic diagram of a reaction using a carbon composite according to one aspect of the present invention. Referring to FIG. 2, a cobalt (Co) and iron (Fe)-containing alloy particle catalyst is positioned on the outer surface and / or the inner surface of the pores of a porous carbon material (e.g., carbon nanotube). The catalyst exhibits an adsorption capacity with lithium polysulfide, thereby increasing the adsorption strength of the carbon composite and lithium polysulfide. Accordingly, the introduction of the cobalt (Co) and iron (Fe)-containing alloy particle catalyst can lead to the formation of lithium sulfide (Li2S) and lithium polysulfide (Li2Sx, 1). <x)의 전환 반응이 촉진되어 이를 이용한 리튬황 양극의 가역 용량이 증가하는 것이 설명될 수 있다.

[0087] In particular, the carbon composite according to one aspect of the present invention can exhibit the advantage of promoting conversion reactions during both charge and discharge processes by including bimetallic nanoparticles as catalysts, including iron (Fe) particles that promote reduction and cobalt (Co) particles that promote oxidation. Through this, higher reversible capacity expression and stable charge and discharge are possible even under conditions of extremely small amounts of electrolyte, and thus, it can exhibit the advantage of enabling the implementation of a high-energy-density lithium-sulfur battery.

[0088] In one embodiment of the present invention, the catalyst is a cathode active material of a lithium sulfur battery, including sulfur (S8), lithium sulfide (Li2S), and lithium polysulfide (Li2Sx, 1 <x≤8), 디설파이드 화합물 및 이들 중 2 이상의 혼합물 등과 같은 황 계열 화합물의 산화 및 환원 반응에 대한 촉매 활성을 갖는다. 다만, 상기 촉매로서 포함되는 물질의 기능이 이에 한정되는 것은 아니다.

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

[0090] A carbon composite according to one aspect of the present invention comprises a porous carbon material and a catalyst positioned on at least one of an outer surface and an inner surface of pores of the porous carbon material, wherein the catalyst comprises transition metal alloy particles and a carbon coating layer covering at least a portion of the surface of the transition metal alloy particles. Specifically, the transition metal alloy particles comprise cobalt (Co) and iron (Fe), and at least a portion of the carbon coating layer comprises crystalline carbon.

[0091] According to one embodiment of the present invention, the above-described catalyst comprises inorganic sulfur (S8)↔lithium polysulfide (Li2Sx, 1 <x)↔리튬설파이드(Li2S)의 전환반응에 있어서 산화 반응을 촉진하는 코발트(Co) 및 환원 반응을 촉진하는 철(Fe)을 동시에 포함하는 이원금속 입자를 포함한다.

[0092] FIG. 3 shows a STEM (Scanning Transmission Electron Microscope) image (a) of a carbon composite according to one embodiment of the present invention and an EDX (Energy Dispersive X-ray Spectroscopy) map showing elemental analysis of the catalyst.

[0093] Referring to FIG. 3, the transition metal alloy particles included in the carbon composite according to one embodiment of the present invention may include nanoparticles in which cobalt (Co) and iron (Fe) form an alloy.

[0094] In one embodiment of the present invention, the catalyst includes transition metal alloy particles as an active component of the catalyst in a core portion, and specifically, the core portion of the catalyst may be composed only of the transition metal alloy particles.

[0095] In one embodiment of the present invention, the transition metal alloy particles included in the core portion of the catalyst may be composed solely of the cobalt-iron alloy particles. Specifically, the sum of the contents 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, the core part of the catalyst may further include, in addition to the cobalt-iron alloy particles, one or more metal elements selected from, for example, 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), gallium (Gd), scandium (Sc), titanium (Ti), gallium (Ga), and indium (In), as long as the purpose of the present invention is not impaired. Specifically, alloy particles alloyed with cobalt-iron and the transition metal selected above may be further included, but the present invention is not limited thereto. In this case, it is preferable that the core portion have a sum of the cobalt and iron elements content of 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 are grown as metal particles from a transition metal-containing precursor, and may have a shape such as a sphere, an ellipse, a sheet, a plate, a fiber, a needle, or a hollow shape.

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

[0099] FIG. 4 shows an HRTEM (High Resolution Transmission Electron Microscopy) image (a) of a carbon composite according to one embodiment of the present invention and a graph (b) showing the results of measuring the (110) interplanar distance through d-spacing.

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

[0101] Referring to FIGS. 4 and 5, the d-spacing analysis results of the catalyst included in the carbon composite according to one embodiment of the present invention, specifically the cobalt-iron alloy particles, are consistent with the (110) interplanar distance, confirming that the cobalt-iron alloy particles have a body-centered cubic structure.

[0102] In one embodiment of the present invention, the transition metal alloy particles have an average particle diameter (D) of, for example, 1 nm to 90 nm. 50 ) may have. Specifically, the average particle diameter (D) of the transition metal alloy particles 50 ) may be 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-described range, the conductivity of electrons and / or ions is excellent, and thus, the performance of the battery may be improved and an advantageous effect may be exhibited in the manufacturing process, but the present invention is not limited thereto.

[0103] In the present specification, the size of the particles can be measured according to a known method for measuring the same, and the measuring method is not particularly limited. For example, the size of the particles can be measured according to a scanning electron microscope (SEM), a field emission electron microscope (laser diffraction method), or a laser diffraction method. The measurement using the laser diffraction method can be, for example, using a commercially available laser diffraction particle size measuring device (for example, Microtrac MT 3000). The average particle diameter (D 50 ) means the particle size at the 50% point of the volume cumulative distribution.

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

[0105] The carbon coating layer may have the function of controlling the size of the transition metal alloy particles and providing a bonding site with the porous carbon material on which the catalyst is supported so that the catalyst can be supported in the porous carbon material. In addition, the carbon coating layer may have the function of stably maintaining the metallic phase of the transition metal alloy particles in the core portion. For example, the carbon coating layer may have the function of inhibiting lithium polysulfide in the electrolyte from directly chemically bonding to the surface of the transition metal alloy particles so that the catalytic activity by the transition metal alloy particles can be stably maintained when the lithium-sulfur battery is operated. In the present invention, the function of the carbon coating layer is not limited to the above-described function.

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

[0107] In one embodiment of the present invention, the carbon coating layer may cover the entire surface of the core portion. As described below, since the carbon coating layer is formed on the entire surface of the core portion, it may exhibit an advantageous effect in terms of stabilizing the activity of the transition metal alloy particles by the carbon coating layer, but the present invention is not limited thereto. For example, if the transition metal alloy particles are supported on the carbon composite without covering with a carbon coating layer, the size of the transition metal alloy particles may be formed unevenly, which may cause a problem of deterioration in catalyst stability, and accordingly, when a battery using the same is operated, there may be a problem of poor battery life stability, but the present invention is not limited thereto.

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

[0109] In one embodiment of the present invention, the average particle diameter (D) of the transition metal alloy particles 50 ) may be less than or equal to 40% of the thickness of the carbon coating layer. For example, the average particle diameter (D) of the transition metal alloy particles 50 ) the ratio of the thickness of the carbon coating layer may be 30% or less, 25% or less, 20% or less, or 15% or less. For example, the average particle diameter (D) of the transition metal alloy particles 50) the ratio of the thickness of the carbon coating layer may be 1% or more, 5% or more, 7.5% or more, or 10% or more. For example, the average particle diameter (D) of the transition metal alloy particles 50 ) may be 10% to 20% or 10% to 15% in comparison to the average particle diameter of the transition metal alloy particles. When the ratio of the thickness of the carbon coating layer to the average particle diameter of the transition metal alloy particles is within the above-described range, an advantageous effect may be exhibited in terms of stabilizing the activity of the transition metal alloy particles by the carbon coating layer, but the present invention is not limited thereto. In addition, the carbon coating layer covers the surface of the transition metal alloy particles with a thin thickness, thereby enabling the transition metal alloy particles to be supported on the porous carbon material with a uniform size, while also enabling the transition metal alloy particles to exhibit excellent catalytic activity. For example, when the thickness of the carbon coating layer is formed to be within 40% of the total thickness of the transition metal alloy particles, it is possible to maintain smooth interaction between the transition metal alloy particles located inside the carbon coating layer and lithium polysulfide approaching from the outside of the carbon coating layer.

[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 (△d) of the thickness measured at any 10 points of the carbon coating layer formed on the surface of the core portion may be 0.5 nm or less.

[0111] In one embodiment of the present invention, the carbon coating layer covers the entire surface of the transition metal alloy particle, and the carbon coating layer may exhibit a standard deviation (△d) of the thickness measured at 100 arbitrary points over the entire surface of 0.5 nm or less.

[0112] In one embodiment of the present invention, as the thickness of the carbon coating layer becomes thinner, the interaction between the transition metal particles and lithium polysulfide is improved, and thus, a favorable effect can be exhibited in terms of catalytic activity by the transition metal particles, but the present invention is not limited thereto.

[0113] In one embodiment of the present invention, the carbon coating layer may have a thickness of, 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, 1 nm to 5 nm or 0.5 nm to 2 nm.

[0114] The thickness of the carbon coating layer can be measured through microscopic observation, such as an SEM image or TEM image of the carbon composite, for example, but the method for measuring the thickness of the carbon coating layer is not limited thereto.

[0115] In this specification, unless otherwise specified, SEM images may be obtained using S-4800 field emission, Hitachi, and TEM images may be obtained using G2 F30 S-Twin, Tencai.

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

[0117] In another embodiment of the present invention, the carbon coating layer may be composed of a multilayer structure of two or more layers. For example, the carbon coating layer may have a multilayer structure composed of two or more layers and ten or less layers. Specifically, the carbon coating layer may be composed of a multilayer structure composed of two to ten layers, a multilayer structure composed of two to five layers, a multilayer structure composed of two to four layers, or a multilayer structure composed of two to three layers. When the carbon coating layer is composed of multiple layers, there may be an advantageous effect in terms of 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 layer may comprise crystalline carbon. For example, in another embodiment of the present invention, the carbon coating layer may be composed of crystalline carbon. For example, the carbon coating layer may be formed by carbonization of a carbon precursor and may be composed solely of crystalline carbon.

[0119] As used herein, the term "crystalline" carbon refers to the presence of carbon in three dimensions at the atomic level. For example, the presence of crystalline carbon can be confirmed through diffraction techniques, heat of fusion measurements, TEM, etc. For example, the presence of crystallinity can be confirmed through the presence of at least one distinct peak for each carbon in an XRD spectrum.

[0120] Referring again to FIG. 4, it can be confirmed that the catalyst comprises a core portion of the transition metal alloy particle and a carbon coating layer covering at least one surface of the core portion. Specifically, it can be confirmed that at least a portion of the carbon coating layer comprises crystalline carbon.

[0121] In one embodiment of the present invention, the carbon coating layer may include at least one heterogeneous element as a doping element in addition to carbon. For example, the heterogeneous element may include one or more selected from nitrogen (N), sulfur (S), and oxygen (O).

[0122] As described below, a step of mixing the porous carbon material, a cobalt (Co)-containing precursor, an iron (Fe)-containing precursor, and a carbon layer precursor and then performing a heat treatment may be performed to manufacture the carbon composite. At this time, the carbon layer precursor may include one or more heterogeneous elements selected from nitrogen, sulfur, and oxygen. Accordingly, a carbon coating layer is formed on the surface of the transition metal alloy particle by the carbon derived from the carbon layer precursor, and the heterogeneous element derived from the carbon layer precursor may be doped onto at least one of the porous carbon material and the carbon coating layer.

[0123] Thus, according to one embodiment of the present invention, the carbon coating layer may be a multilayer structure of, for example, two to three layers covering the entire surface of the transition metal alloy particle, having a total thickness of 5 nm or less, and composed of crystalline carbon doped with at least one nitrogen element.

[0124] In one embodiment of the present invention, the average particle diameter (D) of the catalyst 50 ) may be less than 100 nm. For example, the average particle diameter (D) of the catalyst 50) may be 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 in the above-described range, the conductivity of electrons and / or ions is excellent, and thus, the performance of the battery may be improved and an advantageous effect may be exhibited in the manufacturing process, but the present invention is not limited thereto.

[0125] FIG. 6 illustrates TEM images at different magnifications of a carbon composite according to an embodiment of the present invention. Specifically, the TEM image illustrates a carbon composite in which a catalyst composed of cobalt-iron alloy particles is positioned on the surface of carbon nanotubes (CNTs) as a porous carbon material. Referring to FIG. 5(a), it can be confirmed that the catalyst is positioned on the outer surface and / or the inner surface of the pores of the porous carbon material. In addition, referring to FIG. 5(b), it can be confirmed that the particle size of the catalyst is 100 nm or less, for example, 10 nm to 30 nm.

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

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

[0128] In the present invention, the catalyst can be used alone as a catalyst in the positive electrode of a lithium-sulfur battery to provide activity in the reduction reaction of lithium polysulfide. However, according to the present invention, by positioning the catalyst on the external surface and / or the internal surface of the pores of the porous carbon material, it can exhibit the effect of further enhancing the adsorption of lithium polysulfide and the activation of the oxidation / reduction reaction of sulfur.

[0129] The above porous carbon material is a material containing a large number of microscopic pores, and the catalyst is supported on at least one of the outer surface and the inner surface of the pores of the porous carbon material.

[0130] In one embodiment of the present invention, the porous carbon material may include at least one heterogeneous element as a doping element in addition to carbon. Specifically, the heterogeneous element may include one or more elements 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 carbon coating layer may have a structure in which the carbon atom is substituted by the heterogeneous element.

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

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

[0134] In one embodiment of the present invention, the catalyst may be chemically and / or physically bound to one or more locations of the outer surface and the inner surface of the pores of the porous carbon material.

[0135] In one embodiment of the present invention, the catalyst may be physically adsorbed to the outer surface and / or the inner surface of the pores of the porous carbon material. Alternatively, the catalyst may be chemically bonded to the outer surface and / or the inner surface of the pores of the porous carbon material by CC covalent bonding and / or pi-pi interactions between elements present in the catalyst and carbon of the porous carbon material. Furthermore, the aforementioned physical adsorption and chemical bonding may exist simultaneously between the catalyst and the porous carbon material.

[0136] In one embodiment of the present invention, the porous carbon material includes a plurality of micropores on the outer surface and the interior. The average diameter of the micropores may be, for example, 5 nm to 100 nm, specifically 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 the 50% point in a pore size distribution according to pore size. The pore diameter may be measured, for example, through TEM analysis of the diameter of the pores 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 described above is not particularly limited in its material as long as it contains a large number of micropores as described above and can support the catalyst.

[0138] In one embodiment of the present invention, the material of the porous carbon material may include, for example, carbon nanotubes (CNT), graphene, graphene oxide (GO), reduced graphene oxide (rGO), carbon black, graphite nanofibers (GNF), carbon nanofibers (CNF), activated carbon fibers (ACF), natural graphite, artificial graphite, expanded graphite, activated carbon, fullerene, or two or more of these materials.

[0139] In one embodiment of the present invention, when the porous carbon material includes carbon nanotubes, the carbon nanotubes may include 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 as a material, the carbon nanotubes may include entangled carbon nanotubes (CNTs) in which a plurality of primary structures are aggregated to form a secondary structure with carbon nanotubes as the primary structure.

[0141] According to one embodiment of the present invention, the intertwined carbon nanotube may have a characteristic of improved porosity compared to the carbon nanotube of the primary structure due to an interstitial volume formed by intertwining the carbon nanotubes of the primary structure.

[0142] In one embodiment of the present invention, the size of the porous carbon material is not limited thereto, but may be, for example, 10 μm to 100 μm, specifically 20 μm to 50 μm. When the size of the porous carbon material is within the above-described range, it can exhibit advantageous effects in terms of solid content control and electrode properties, such as adhesive strength, and battery performance (output and capacity, etc.) during the preparation of a slurry for forming an electrode active material layer.

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

[0144] In one embodiment of the present invention, the BET specific surface area of ​​the porous carbon material is not limited thereto, but is, for example, 150 m 2 / g to 2,000 m 2 / g, specifically 250 m 2 / g to 700 m2 / g may be.

[0145] The above BET specific surface area is measured by the BET method, and may represent a value measured according to a known method for measuring the BET specific surface area. For example, the above BET specific surface area may be a value calculated from the nitrogen gas adsorption amount at liquid nitrogen temperature (77K) using BELSORP-mino II of BEL Japan.

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

[0147] In one embodiment of the present invention, the carbon composite has an average particle diameter (D) of, for example, 100 nm to 100 ㎛, specifically, 10 ㎛ to 50 ㎛. 50 ) can have. In addition, the carbon composite may have, for example, 0.5 cm 3 / g to 4 cm 3 / g, specifically 1 cm 3 / g to 3 cm 3 / g of pore volume. In addition, the carbon composite may have a pore volume of, for example, 150 m 2 / g to 500 m 2 / g, specifically 250 m 2 / g to 300 m 2 / g can have a BET surface area.

[0148] In one embodiment of the present invention, the content of the catalyst may be, for example, 50 wt% or less based on 100 wt% of the entire carbon composite. Specifically, the content of the catalyst may be 5 wt% to 50 wt%, 5 wt% to 30 wt%, 10 wt% to 20 wt%, or 10 wt% to 15 wt% based on 100 wt% of the entire carbon composite. When the content of the catalyst is within the above-described range, a site exhibiting catalytic activity can be sufficiently secured, while exhibiting advantageous effects in terms of the conductivity of electrons and / or ions within the electrode. Accordingly, an excellent effect can be exhibited in terms of improving the performance of a battery using the same, but the present invention is not limited thereto.

[0149] In another embodiment of the present invention, the weight ratio of the porous carbon material and the catalyst in the carbon composite may be, for example, 95:5 to 70:30. Specifically, the weight ratio of the porous carbon material and the catalyst may be 90:10 to 80:20 or 95:5 to 85:15. When the weight ratio of the porous carbon material and the catalyst is within the above-described range, the position exhibiting catalytic activity is sufficiently secured, while the agglomeration phenomenon between catalysts is improved, thereby exhibiting the effect of improving resistance characteristics. Accordingly, it may exhibit an excellent effect in terms of improving the performance of a battery using the same, but the present invention is not limited thereto.

[0150] Figure 7 is a graph illustrating the results of analyzing the content of cobalt-iron alloy particles through thermal decomposition analysis (TGA) of a carbon composite according to one embodiment of the present invention. Referring to Figure 7, it can be confirmed that the content of cobalt-iron alloy particles in the carbon composite is analyzed to be 14.7 wt% based on 100 wt% of the carbon composite.

[0151] In one embodiment of the present invention, the carbon composite includes a heterogeneous element in at least one of the porous carbon material and the carbon coating layer. In one embodiment of the present invention, the content of the heterogeneous element may be, for example, 0.1 wt% or more, or 0.5 wt% or more, based on 100 wt% of the carbon composite. In addition, the content of the heterogeneous element may be, for example, 20 wt% or less, or 10 wt% or less, based on 100 wt% of the carbon composite, but is not limited thereto. Specifically, the content of the heterogeneous element may be, for example, 0.1 wt% to 20 wt%, specifically 0.5 wt% to 10 wt%, based on 100 wt% of the total carbon composite. When the content of the heterogeneous element is within the above-described range, it may exhibit an advantageous effect in terms of adsorbing lithium polysulfide while promoting the catalytic activity of transition metal alloy particles.

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

[0153] In another embodiment of the present invention, the carbon composite may further include a transition metal element liberated from the transition metal particle in a single atomic state within a range that does not inhibit the catalytic activity of the carbon composite.

[0154] The form in which the transition metal atoms are included in the carbon composite can be confirmed, for example, through extended X-ray absorption fine structure (EXAFS) analysis. Specifically, if the transition metal atoms in the transition metal particles in the carbon composite are not metal-bonded but are included in a single-atom state, the EXAFS analysis results confirm a bond between the transition metal element and the heterogeneous element. On the other hand, if two or more transition metal atoms are metal-bonded to each other and are included in a metal particle state, the EXAFS analysis results confirm a bond between the transition metal elements.

[0155] In one embodiment of the present invention, when confirming the bonds between elements in the carbon composite by EXAFS analysis, the carbon composite may include a number of bonds between the transition metal elements greater than the number of bonds between the transition metal elements and the heterogeneous element. In another embodiment of the present invention, when confirming the bonds between elements in the carbon composite by EXAFS analysis, the peak intensity indicating the bonds between the transition metal elements may be, for example, 10 times or more, specifically 20 times or more, and more specifically 50 times or more, as compared to the peak intensity indicating the bonds between the transition metal elements and the heterogeneous element.

[0156] The carbon composite of the present invention, as described above, provides a bonding site for lithium polysulfide and exhibits catalytic activity for sulfur redox reactions, thereby improving the lifespan stability of lithium-sulfur batteries using the composite. In addition, since the catalyst within the carbon composite secures mobility on the surface of the porous carbon material, it exhibits stable performance even in a lithium-sulfur battery using the composite under lean electrolyte conditions, thereby achieving a high energy density. However, the mechanism of the present invention is not limited thereto.

[0157] According to one embodiment of the present invention, the carbon composite may be used as a positive electrode active material by additionally complexing with the sulfur-based compound as a carrier supporting a positive electrode active material, or the carbon composite itself may be used as an additive to the positive electrode.

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

[0159]

[0160] Another aspect of the present invention provides a method for producing the above-described carbon composite.

[0161] The above-described carbon composite can be manufactured through the above-described method for manufacturing the carbon composite, but the method for manufacturing the carbon composite is not limited thereto.

[0162] The method for producing the above carbon composite includes 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 heat-treating the transition metal-carbon layer precursor polymer / porous carbon material to obtain the carbon composite.

[0163] As described above, according to one embodiment of the present invention, the carbon layer precursor may include one or more heterogeneous elements selected from nitrogen (N), sulfur (S), and oxygen (O), but the present invention is not limited thereto.

[0164] First, the cobalt-containing precursor and the iron-containing precursor are each precursors for forming transition metal alloy particles included in the core portion of the catalyst. The cobalt-containing precursor and the iron-containing precursor may be each introduced, but a single substance containing both cobalt and iron may also be introduced as the precursor. In other words, as long as cobalt and iron can be provided as raw materials, there is no limitation to introducing separate substances separately or introducing a single substance.

[0165] In one embodiment of the present invention, each of the cobalt-containing precursor and the iron-containing precursor may include a metal salt, metal acetyl acetonate, metal hydroxide, metal chloride, metal oxide, metal chloride hydrate, or two or more thereof containing the cobalt and / or iron elements.

[0166] In another embodiment of the present invention, the cobalt-containing precursor and the iron-containing precursor may each contain only a metal salt containing the transition metal element. By containing only the metal salt as the cobalt-containing precursor and the iron-containing precursor, not only can the catalyst manufacturing method be simplified, but also the size of the manufactured catalyst can be easily controlled, and there may be advantageous effects in terms of improving catalytic activity.

[0167] In one embodiment of the present invention, the cobalt-containing precursor may be a cobalt metal salt, for example, cobalt acetyl acetonate, cobalt hydroxide, cobalt chloride, cobalt oxide, cobalt chloride hydrate, or two or more thereof.

[0168] In one embodiment of the present invention, the cobalt-containing precursor may include cobalt chloride hexahydrate as a cobalt metal salt.

[0169] In one embodiment of the present invention, the iron-containing precursor may be an iron metal salt, for example, iron acetyl acetonate, iron hydroxide, iron chloride, iron oxide, iron hydrate, or two or more thereof.

[0170] In one embodiment of the present invention, the iron-containing precursor may include iron chloride hexahydrate as an iron metal salt.

[0171] In one embodiment of the present invention, the raw material may further include a precursor containing another transition metal element in addition to a cobalt-containing precursor and an iron-containing precursor as a transition metal-containing precursor. At this time, the transition metal element that may be further included may be, for example, one or more selected from 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), gallium (Gd), scandium (Sc), titanium (Ti), gallium (Ga), and indium (In). For example, it may further include nickel acetyl acetonate, nickel hydroxide, nickel chloride, nickel oxide, nickel hydrate, or two or more thereof, but the present invention is not limited thereto.

[0172] In one embodiment of the present invention, the carbon layer precursor is a precursor for forming a carbon coating layer for covering at least a portion of the surface of the transition metal alloy particle.

[0173] In the present invention, the carbon layer precursor can serve as a precursor for doping a heterogeneous element into at least one of the carbon coating layer and the porous carbon material by including at least one heterogeneous element selected from nitrogen, sulfur, and oxygen.

[0174] In one embodiment of the present invention, the carbon layer precursor includes, in addition to carbon, at least one heterogeneous element selected from nitrogen, sulfur, and oxygen as described above, and the carbon precursor may be used without particular limitation as long as it can be carbonized to provide a crystalline carbon coating layer.

[0175] The carbon layer precursor may include, for example, carbon and nitrogen elements, and may include dopamine, polydopamine, melamine, 1,10-phenanthroline, polyaniline, carbon nitride (g-CN), glucose, phenylenediamine, or a mixture thereof.

[0176] In one embodiment of the present invention, the porous carbon material is referred to as described above.

[0177] The method for manufacturing the above carbon composite includes mixing a cobalt (Co)-containing precursor, an iron (Fe)-containing precursor, a carbon layer precursor, and a porous carbon material.

[0178] In one embodiment of the present invention, the weight ratio of the cobalt-containing precursor, the iron-containing precursor, and the carbon layer precursor may be, for example, 1 to 3:1 to 3:1 to 3, specifically 1 to 2:1 to 2:1 to 2, and more specifically 1 to 1.5:1 to 1.5:1 to 1.5, but the present invention is not limited thereto.

[0179] In one embodiment of the present invention, the weight ratio of the total amount of the cobalt-containing precursor and the iron-containing precursor to the porous carbon material may be, for example, 1:1 to 1:10, specifically 1:1 to 1:8, more specifically 1:1 to 1:5 or 1:1 to 1:3, but the present invention is not limited thereto.

[0180] In one embodiment of the present invention, the weight ratio of the carbon layer precursor and the porous carbon material may be, for example, 1:10 to 1:5, specifically 1:1 to 1:3, more specifically 1:1 to 1:2.5 or 1:2 to 1:2.5, but the present invention is not limited thereto.

[0181] 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-described range, a carbon composite produced may exhibit advantageous effects in terms of performance, but the present invention is not limited thereto.

[0182] In one embodiment of the present invention, the method for producing the carbon composite may include a step of first mixing the cobalt-containing precursor, the iron-containing precursor, and the carbon layer precursor, and then mixing and heat-treating the porous carbon material. When the cobalt-containing precursor, the iron-containing precursor, and the carbon layer precursor are first mixed to produce the carbon composite, and then the porous carbon material is mixed, there may be advantageous effects in terms of thickness uniformity of the carbon coating layer and size uniformity of the catalyst, but the present invention is not limited thereto.

[0183] In one embodiment of the present invention, the method for producing the carbon composite comprises:

[0184] (S1) After mixing the cobalt-containing precursor, iron-containing precursor, and carbon layer precursor, a transition metal-carbon layer precursor polymer (MC precursor polymer) is formed.

[0185] (S2) After mixing the above transition metal-carbon layer precursor polymer and porous carbon material, a transition metal-carbon layer precursor polymer / porous carbon material (M-CPP / C) is obtained.

[0186] (S3) It may include heat treating the above transition metal-carbon layer precursor polymer / porous carbon material (M-CPP / C) to obtain a carbon composite.

[0187] The above step (S1) is to produce a metal-carbon layer precursor complex (MC precursor complex) in which the carbon layer precursor is physically and / or chemically bonded to the surfaces of the cobalt-containing precursor and the iron-containing precursor by mixing the cobalt-containing precursor, the iron-containing precursor, and the carbon layer precursor.

[0188] In one embodiment of the present invention, the mixing of the cobalt-containing precursor, the iron-containing precursor, and the carbon layer precursor may be performed in a suitable solvent, and may involve stirring. In this case, when the cobalt-containing precursor and the iron-containing precursor are each metal salts, the solvent may preferably be water, but is not limited thereto.

[0189] In one embodiment of the present invention, the mixing in step (S1) may be performed at room temperature, for example, at 23°C to 25°C.

[0190] In one embodiment of the present invention, when stirring is performed during mixing in step (S1), the stirring may be performed at, for example, a speed of 200 rpm to 250 rpm, specifically, a speed of 220 rpm to 240 rpm. When the stirring is performed under the above-described conditions, it may have a beneficial effect in terms of uniformity of the size of the transition metal alloy particles produced, but the present invention is not limited thereto.

[0191] The above step (S2) is to form the transition metal-carbon layer precursor complex / porous carbon material (M-CPP / C) in which the metal-carbon layer precursor complex formed above is supported on at least one of the outer surface and the inner surface of the pores of the porous carbon material.

[0192] In one embodiment of the present invention, the transition metal-carbon layer precursor (M-CPP) may be present in a dispersed form in a solvent, such as water, used in step (S1). The method may include adding the porous carbon material to a dispersion in which the M-CPP is dispersed, thereby producing a dispersion in which the M-CPP and the porous carbon material are dispersed.

[0193] In one embodiment of the present invention, for the production of the M-CPP / C, the pH of the dispersion in which the M-CPP and the porous carbon material are dispersed may be, for example, 8 to 9.

[0194] In another embodiment of the present invention, the step (S2) may further include a step of adding a pH adjuster to control the acidity of the mixture of the M-CPP and the porous carbon material, for example, 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.

[0195] In one embodiment of the present invention, the pH adjuster may include a basic compound, and the basic compound may be, for example, an amine compound. The amine compound may include, for example, tris(hydroxymethyl)aminomethane (TRIS).

[0196] In another embodiment of the present invention, the pH adjuster may include an acidic compound, and the acidic compound may be, 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.

[0197] In one embodiment of the present invention, the step (S2) may involve stirring. The stirring may be performed, for example, at room temperature, for 12 to 48 hours, specifically 20 to 30 hours, such as 24 hours.

[0198] In one embodiment of the present invention, the step (S2) may further include a step of filtering and washing after the stirring.

[0199] In one embodiment of the present invention, the washing may be performed using, for example, water, an organic solvent, or a mixed solvent thereof. For example, the washing may be performed once to three times with water, followed by one time with an alcohol-based organic solvent such as ethanol, but the present invention is not limited thereto.

[0200] In one embodiment of the present invention, the step (S2) may further include a step of mixing the transition metal-carbon layer precursor polymer (M-CPP) and the porous carbon material, then filtering, washing, and drying.

[0201] In one embodiment of the present invention, the drying may be performed, for example, in a vacuum, and may be performed under conditions of 50°C to 70°C, specifically 60°C.

[0202] The above step (S3) is to manufacture a carbon composite supported with a catalyst including transition metal alloy particles containing cobalt and iron on at least one of the outer surface and the inner surface of the pores of the porous carbon material and a carbon coating layer covering at least a portion of the surface of the transition metal alloy particles by heat-treating the transition metal-carbon layer precursor polymer / porous carbon material (M-CPP / C) manufactured above.

[0203] In one embodiment of the present invention, the heterogeneous 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 the heat treatment.

[0204] In one embodiment of the present invention, the heat treatment may be performed at, for example, 600°C to 1,000°C. Specifically, it may be performed at a temperature of 750°C to 850°C, for example, 800°C.

[0205] In one embodiment of the present invention, the heat treatment may involve increasing the temperature while maintaining a constant rate selected from the range of 0.5°C / min to 10°C / min.

[0206] In one embodiment of the present invention, the heat treatment may be performed by increasing the temperature at a rate of 5°C / min.

[0207] According to the above method, the above-described carbon composite can be manufactured.

[0208]

[0209] According to another aspect of the present invention, a positive electrode active material comprising the above-described carbon composite and sulfur series compound, and a positive electrode comprising the same are provided.

[0210] The above positive electrode may include a composite formed by using the above-described carbon composite as a carrier for the positive electrode active material and mixing it with a sulfur-based compound, which is a positive electrode active material, as the positive electrode active material.

[0211] In one embodiment of the present invention, the sulfur series compound is, for example, sulfur (S8), lithium sulfide (Li2S), lithium polysulfide (Li2Sx, 1 <x≤8), 디설파이드 화합물 또는 이들 중 2 이상의 혼합물을 들 수 있으나, 이에 제한되는 것은 아니다.

[0212] In one embodiment of the present invention, the carbon complex and the sulfur series compound may be mixed in a content ratio of, for example, 1:9 to 9:1. Specifically, they may be mixed in a content ratio of 1:9 to 5:5, and 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 the carbon composite and a sulfur-based compound and then heat-treating the mixture. The heat treatment may be performed at a temperature of, for example, 130°C to 200°C, specifically 130°C to 180°C or 150°C to 160°C.

[0214] In one embodiment of the present invention, the positive electrode for a lithium-sulfur battery may further include a binder in addition to the positive electrode active material including a carbon composite and a sulfur-based compound. The binder may be used without particular limitation as long as it is a 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, PVDF (polyvinylidene fluoride), and specifically, PVDF dispersed in NMP (N-methyl-2-pyrrolidone).

[0216] In another embodiment of the present invention, the binder may include an aqueous binder such as, for example, SBR (styrene butadiene rubber) or an acrylonitrile multi-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 be a commercially available LA132 (TOB Co.) binder, but the present invention is not limited thereto.

[0218] In another embodiment of the present invention, the positive electrode for the lithium-sulfur battery may further include a conductive agent, an additive, etc., in addition to the positive electrode active material and the binder. In this case, the specific types of the binder, conductive agent, and additive may be conventional ones, and thus a description thereof will be omitted.

[0219] In another embodiment of the present invention, the positive electrode for the 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 is applied to one or both sides of the current collector together with a binder.

[0220] At this time, the positive electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery.

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

[0222] In one embodiment of the present invention, the positive electrode for the lithium sulfur battery comprises, for example, 2 mg s / cm 2 Above, specifically 5 mg s / cm 2 Ideally, for example, 2 to 10 mg s / cm 2 , 2.5 to 10 mg s / cm 2or 5 to 8 mg s / cm 2 It may have a sulfur (S) loading amount, but the present invention is not limited thereto.

[0223]

[0224] According to another aspect of the present invention, a lithium-sulfur battery comprises a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte, wherein the positive electrode comprises the above-described carbon composite as a positive electrode active material, and a sulfur-based compound.

[0225] In one embodiment of the present invention, the negative electrode and separator may be used without particular limitation as long as they can be used in a lithium-sulfur battery within a range that does not impede the purpose of the present invention.

[0226] In one embodiment of the present invention, the negative electrode may use, for example, lithium metal. Alternatively, the negative electrode may use a lithium alloy, and the lithium alloy may be an alloy of a metal selected from the group consisting of, for example, lithium (Li) and 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).

[0227] Preferably, the negative active material may be lithium metal, and specifically, may be in the form of a lithium metal thin film or lithium metal powder.

[0228] In one embodiment of the present invention, the separator may be used without limitation as long as it is a separator that can be commonly used as a separator for a lithium-sulfur battery.

[0229] In one embodiment of the present invention, the separator may include a porous polyolefin substrate, and may further include inorganic particles on at least one surface of the porous polyolefin substrate, if necessary. In addition, the separator may further include a binder that binds the inorganic particles, if necessary.

[0230] In another embodiment of the present invention, the separator may be a film-shaped electrolyte membrane containing a solid electrolyte, and may further include a binder for binding the solid electrolyte, if necessary. The solid electrolyte may be any one commonly used in lithium-sulfur batteries, such as a polymer-based solid electrolyte, an inorganic-based solid electrolyte, or a mixture thereof, without limitation.

[0231] In one embodiment of the present invention, the electrolyte comprises one commonly used in lithium-sulfur batteries. The electrolyte may comprise a lithium salt and a non-aqueous solvent.

[0232] The above lithium salt can be used without limitation as long as it is a lithium salt that can be commonly used in the electrolyte of a lithium-sulfur battery. The above lithium salt includes, 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 4-phenylborate, lithium imide or two or more thereof, but are not limited thereto.

[0233] The non-aqueous solvent described above may be used without limitation as long as it is a solvent commonly used in the electrolyte of a lithium-sulfur battery. The non-aqueous solvent may include, but is not limited to, an ether solvent, a carbonate solvent, an ester solvent, a ketone solvent, or a mixed solvent of two or more thereof.

[0234] In one embodiment of the present invention, the ether solvent may include an acyclic ether, a cyclic ether, or a mixture thereof.

[0235] In one embodiment of the present invention, the acyclic ether may include at least one selected from the group consisting of, for example, dimethyl ether, diethyl ether, dipropyl ether, dibutyl ether, diisobutyl ether, ethyl methyl ether, ethylpropyl ether, ethyl tertbutyl 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 tertbutyl ethyl ether, and ethylene glycol ethyl methyl ether. Preferably, it may include at least one selected from the group consisting of dimethoxyethane, diethoxyethane, diethylene glycol, triethylene glycol and tetraethylene glycol, and more preferably, it may include dimethoxyethane.

[0236] In one embodiment of the present invention, the cyclic ether is, for example, 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, It may include at least one selected from the group consisting of 1,2-dimethoxybenzene, 1,3-dimethoxybenzene, 1,4-dimethoxybenzene, and isosorbide dimethyl ether. Preferably, it may include at least one selected from the group consisting of 2-methylfuran, 1,3-dioxolane, tetrahydrofuran, 2-methyltetrahydrofuran, and 2,5-dimethyltetrahydrofuran, and more preferably, it may include 2-methylfuran.

[0237] In one embodiment of the present invention, the electrolyte may include (CF3SO2)2NLi as a lithium salt and a binary system of dioxolane (DOL) / dimethoxyethane (DME) as a non-aqueous solvent. For example, the electrolyte may further include a conventional additive such as LiNO3.

[0238] In another embodiment of the present invention, the electrolyte may include one or a mixture of two or more selected from the lithium salts described above, and may include a mixture of dimethoxyethane (DME) and 2-methylfuran (2-MeF) as a non-aqueous solvent, but the present invention is not limited thereto.

[0239] In one embodiment of the present invention, the external shape of the lithium-sulfur battery may be, for example, a coin shape, a cylinder shape, a pouch shape, or a square shape, and the external shape of the battery is not particularly limited. In addition, the lithium-sulfur battery may be used not only as a battery cell used as a power source for a small device, but may also be used as a unit battery in a medium- to large-sized battery module including a plurality of battery cells, and there is no particular limitation on the form of use thereof.

[0240] In one embodiment of the present invention, a lithium-sulfur battery using a positive electrode including the carbon composite not only has excellent kinetic activity for sulfur redox reactions, but also exhibits excellent effects in terms of initial capacity and cycle stability of the battery, but the effects of the present invention are not limited thereto.

[0241] In one embodiment of the present invention, the lithium-sulfur battery can exhibit an effect of improving energy density by increasing the sulfur loading amount in the electrode and operating stably even under lean electrolyte conditions, but the effect of the present invention is not limited thereto.

[0242] In one embodiment of the present invention, the lithium-sulfur battery may have an electrolyte / sulfur (E / S) ratio of, for example, 8 μL / mg or less. While there was a limit to lowering the E / S ratio due to low activity of the conventional positive electrode, the present invention has the effect of stably lowering the E / S ratio. Therefore, it is apparent to those skilled in the art that the E / S ratio of the lithium-sulfur battery may have a value greater than the above-described range, and that the lower limit thereof is not limited, and the present invention is not limited thereto.

[0243] In this specification, the E / S ratio may represent the ratio of the volume of the electrolyte to the weight of sulfur in the anode.

[0244] In one embodiment of the present invention, the lithium-sulfur battery can be manufactured so that the El / S ratio is, for example, 8 μL / mg or less, 5 μL / mg or less, 3 μL / mg or less, or 2.9 μL / mg or less.

[0245] 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 sulfur in the sulfur-carbon composite of the positive electrode introduced in the manufacturing step immediately after manufacturing the lithium-sulfur battery to the weight of the introduced electrolyte.

[0246] In another embodiment of the present invention, the E / S ratio of the lithium-sulfur battery can be calculated by the ratio of the weight of sulfur in the sulfur-carbon complex of the positive electrode analyzed by disassembling the battery and the weight of the electrolyte introduced.

[0247] For example, when analyzing the E / S ratio of a lithium-sulfur battery by disassembling the battery, the total weight of the lithium-sulfur battery is measured in a charged state, and then the battery is disassembled, the positive electrode, the negative electrode, the separator, and the case are washed and dried with a solvent, and the sum of their respective weights is calculated, and the weight of the electrolyte is measured by deducting the weight of the positive electrode, the negative electrode, the separator, and the case from the measured total weight of the battery. At this time, it is preferable to use a solvent for the washing that can extract the electrolyte attached to the positive electrode, the negative electrode, the separator, and the case. Next, the positive electrode active material layer and the current collector are separated from the dried positive electrode, and then the weight of sulfur derived from the sulfur-carbon complex present in the positive electrode active material layer is measured, thereby measuring the weight of sulfur in the positive electrode. The E / S ratio of the lithium-sulfur battery can be calculated by the ratio of the weight of sulfur in the sulfur-carbon complex of the positive electrode obtained in this way to the weight of the introduced electrolyte.

[0248] In one embodiment of the present invention, a method for measuring the weight of sulfur derived from a sulfur-carbon complex present in the positive electrode active material layer may be, for example, measuring the content of sulfur (S) derived from the active material through thermal gravimetric analysis (TGA) on the result obtained by scraping off the obtained positive electrode active material layer, but the measuring method is not limited thereto.

[0249] In one embodiment of the present invention, the state of charge for disassembling the lithium-sulfur battery may be a full state of charge, i.e., a state of charge of 100%. In another embodiment of the present invention, the state of charge for disassembling the lithium-sulfur battery may be from 95% of the state of charge to 100% of the state of charge. In one embodiment of the present invention, when disassembling the lithium-sulfur battery in the charged state, it must be performed under an inert atmosphere from a safety perspective. For example, disassembly of the lithium-sulfur battery may be performed under an Ar atmosphere.

[0250] In one embodiment of the present invention, the energy density of the lithium-sulfur battery may be, for example, 300 Wh / kg or more. For example, the energy density of the lithium-sulfur battery may be, for example, 350 Wh / kg or more, for example, 380 Wh / kg or more. The energy density of the lithium-sulfur battery may be, for example, 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.

[0251] In one embodiment of the present invention, the energy density of the lithium-sulfur battery may be measured according to a known method for measuring the energy density, and the measuring method is not particularly limited. For example, the energy density of the lithium-sulfur battery may be calculated according to the following formula based on the specific capacity measured by discharging and charging at 0.1C at least once in the range of 1.8 V to 2.7 V at room temperature. In one embodiment of the present invention, the initial discharge and charge may be performed at a rate of 0.1 C to 0.3 C, respectively. Specifically, the initial discharge and charge may be performed at a rate of 0.1 C to 0.2 C, for example, at a rate of 0.1 C, respectively. In addition, in one embodiment of the present invention, the initial discharge and charge may be performed three times, each at a rate of 0.1 C, respectively.

[0252] In the following equation, the discharge capacity may be measured in mAh, the driving voltage in V, and the cell weight in kg.

[0253] [ceremony]

[0254] Energy density (Wh / kg) = {[(discharge capacity (mAh) X operating voltage (V)) / 1000] / (cell weight (kg))}

[0255] In one embodiment of the present invention, the room temperature may be, for example, a temperature of 23°C to 25°C, and specifically, may be measured at 23°C.

[0256] In one embodiment of the present invention, the charge / discharge rate may be 0.1 C rate to 0.5 C rate, and for example, charging and discharging may be performed at 0.3 C rate, but is not particularly limited thereto as long as charging and discharging are performed within the above-described rate range.

[0257]

[0258] According to another aspect of the present invention, a cathode active material including a sulfur series compound and a cathode including the above-described carbon composite as a cathode additive and a lithium sulfur battery including the same can be provided.

[0259] In one embodiment of the present invention, separately from one aspect of the present invention in which the carbon composite is included in the positive electrode in the form of a positive electrode active material formed by complexing the carbon composite with a sulfur-based compound as a support, the carbon composite may be included as an additive separately from the positive electrode active material.

[0260] In one embodiment of the present invention, when the carbon composite is used as a cathode additive, not only can the capacity of the battery be improved, but also the battery performance can be improved due to improved reactivity with lithium polysulfide.

[0261] In one embodiment of the present invention, when the carbon composite is used as a positive electrode additive, the carbon composite may be included in an amount of 1 to 25 wt%, for example, 1 to 15 wt% or 1 to 10 wt%, based on the total weight of the positive electrode active material, binder, and carbon composite included in the positive electrode active material layer, but is not limited thereto.

[0262] In one embodiment of the present invention, the positive electrode may use a sulfur-based compound as the positive electrode active material, or a sulfur-based compound supported on a conventional carbon carrier. The sulfur-based compound will be used in the configuration of the positive electrode according to the aforementioned aspect. Furthermore, the conventional carbon carrier may be, for example, the porous carbon material itself as described above, but is not limited thereto.

[0263] A lithium-sulfur battery according to one aspect of the present invention can be used, for example, in an electric vehicle (EV), a drone, or urban air mobility (UAM), but the use of the present invention is not limited thereto.

[0264]

[0265] Hereinafter, a method for manufacturing a carbon composite according to one embodiment of the present invention and the results of verifying the performance of a lithium-sulfur battery using the same are described in detail through examples. However, the following examples are intended to illustrate the present invention and are not intended to limit the scope of the present invention solely to these examples.

[0266] [Manufacture of carbon composites]

[0267] Example 1 (FeCo / CNT)

[0268] First, 568 mg of iron hydrochloride hydrate (FeCl2·6H2O, 99%, Sigma-Aldrich), 502 mg of cobalt hydrochloride hydrate (CoCl2·6H2O, 99%, Sigma-Aldrich), and 800 mg of dopamine hydrochloride (98 wt%, Sigma-Aldrich) were added to 2 L of distilled water, and stirred at 230 rpm for 30 minutes at room temperature (23°C) to prepare a transition metal-carbon layer precursor polymer (MC precursor polymer).

[0269] Here, 1.8 g of MWCNT (multi-walled carbon nanotube) (BET surface area 275 m 2 / g, Carbon Nano-material Technology Co., LTD) was added and stirred at room temperature for 30 minutes to prepare a dispersion. Then, 3.602 g of Trizma base (Tris(hydroxymethyl)aminomethane, TRIS) was added to the prepared dispersion to maintain the pH at 8.5. The obtained dispersion was stirred at room temperature for 24 hours, filtered, washed three times with distilled water and then once with ethanol, and dried at 60°C to obtain a Fe-Co-polydopamine / carbon nanotube composite (M-PDA / CNT) as a transition metal-carbon layer precursor polymer / porous carbon material (M-CPP / C).

[0270] The obtained M-PDA / CNT was placed in a tube electric furnace under an argon atmosphere and heat-treated at 800°C for 2 hours (heating rate 5°C / min), and a carbon composite (D 50 35 ㎛) was obtained. The obtained carbon composite comprises a porous carbon material, MWCNT; a catalyst comprising transition metal alloy particles including cobalt and iron, located on at least one of the outer surface and the inner surface of the pores of the MWCNT, and a carbon coating layer covering at least a portion of the surface of the transition metal alloy particles; and a doped nitrogen element. At this time, the average particle diameter (D) of the catalyst 50 ) The ratio of the thickness of the carbon coating layer to the above was 15%.

[0271]

[0272] Comparative Example 1 (Ref)

[0273] Without catalyst support, MWCNT (multi-walled carbon nanotube) as a carbon composite (BET surface area 275 m 2 / g) was prepared.

[0274]

[0275] [Confirmation of the structure of carbon complexes]

[0276] Structural observation of carbon complexes

[0277] The STEM image of the carbon composite of Example 1 prepared above is shown in FIG. 3, the HRTEM image and d-spacing graph are shown in FIG. 4, the XRD analysis graph is shown in FIG. 5, and the TEM image is shown in FIG. 6.

[0278] Referring to FIGS. 3 and 6, it was confirmed that the carbon composite of Example 1 formed a catalyst having cobalt-iron alloy particles uniformly on the surface of MWCNTs and a carbon coating layer covering the surface thereof. In particular, referring to FIG. 5(b), the XRD analysis results for the four manufactured particles confirmed that the reproducibility of the carbon composite was secured according to the above method. In addition, it was confirmed that the size of the catalyst within the carbon composite was uniform, ranging from 10 nm to 20 nm.

[0279] Referring to Fig. 4, the carbon composite of Example 1 was confirmed to have a crystalline carbon coating layer formed on the surface of the transition metal alloy particles, and the transition metal alloy particles had a body-centered cubic structure.

[0280]

[0281] Check the catalyst content

[0282] In order to measure the content of transition metal alloy particles supported on the carbon composite of Example 1 prepared above, TGA analysis was performed, and the results are shown in Fig. 7. The TGA analysis measured the weight loss while heating the manufactured carbon composite from 100°C to 800°C (heating rate 10°C / min).

[0283] Referring to Fig. 7, the weight at the point where the temperature change no longer appears upon heating corresponds to the weight of the transition metal alloy particles (FeCo), so it was confirmed that the carbon composite of Example 1 contained 14.7 wt% of cobalt-iron alloy particles as transition metal alloy particles.

[0284]

[0285] [Manufacturing of lithium-sulfur batteries]

[0286] In order to evaluate the performance of a lithium-sulfur battery using the carbon composites of Example 1 and Comparative Example 1 prepared above, a lithium-sulfur battery was prepared as follows.

[0287] Manufacturing of anodes

[0288] 25 wt% of each carbon composite prepared above and 75 wt% of sulfur (sulfur powder, Sigma Aldrich) were mixed and isothermally heat-treated at 155°C for 2 hours to obtain a cathode active material.

[0289] To manufacture a working electrode, a cathode slurry was prepared by mixing the cathode active material manufactured above and polyacrylonitrile binder (PAN binder, LA 132) as a binder at a weight ratio of 9:1 using NMP (N-methyl-2-pyrrolidone) solvent.

[0290] The prepared cathode slurry was coated on a carbon-coated Al foil and dried at 60°C for 8 hours. Afterwards, the electrode was pressed and cut to fit the case size to manufacture the cathode.

[0291]

[0292] Battery manufacturing

[0293] A battery was manufactured by placing a positive electrode, a negative electrode, and a separator between the positive and negative electrodes, and placing them in a case together with an electrolyte.

[0294] The anode manufactured above was prepared as the positive electrode, and a porous polypropylene membrane (Celgard 2400, Welcos Ltd) was prepared as the separator. Lithium metal (200 μm thick) was prepared as the reference electrode and counter electrode, respectively.

[0295] As an electrolyte, a solution containing 1.0 M LiTFSI (bis(trifluoromethane) sulfonamide lithium salt) as an electrolyte and 2.0 wt% LiNO3 (99.99% metal basis, Sigma-Aldrich) as an additive was used in a solvent (PANAX E-TEC Co., Korea) containing 1,3-dioxolane and dimethoxymethane (DOL / DME) in a 1:1 volume ratio.

[0296] The sulfur loading at the anode is 2.5 mg s / cm 2 , and the E / S ratio of the battery was 10 μL / cm 2 The coin-type battery was manufactured to have the CR2032 standard, and lithium metal with a thickness of 200 ㎛ was used as the reference electrode and counter electrode, respectively, for the following electrochemical performance experiments.

[0297] Additionally, for experiments under lean electrolyte conditions, the loading of sulfur at the anode was 7 mg. s / cm 2 And, lithium-sulfur batteries having an E / S ratio of 6 μL / mg were manufactured.

[0298]

[0299] [Performance Evaluation of Lithium Sulfur Battery]

[0300] Confirmation of sulfur conversion reactivity according to carbon complex

[0301] First, the CV results obtained by operating a lithium-sulfur battery using each of the carbon composites of Example 1 and Comparative Example 1 are shown in Fig. 8, and the EIS measurement graph is shown in Fig. 9.

[0302] Referring to FIGS. 8 and 9, both the carbon composite (FeCo) of Example 1 and the carbon composite (Ref) of Comparative Example 1 undergo an electrochemical reaction for sulfur conversion, and it was confirmed that the carbon composite of Example 1 has lower resistance to the sulfur conversion reaction and better kinetic activity.

[0303]

[0304] Charge / discharge curve profile

[0305] First, a lithium-sulfur battery using each of the carbon composites of Example 1 and Comparative Example 1 was charged and discharged at a current density of 0.2 C in the range of 1.7 V to 2.8 V. The voltage-capacity curve obtained in the 10th cycle is shown in Fig. 10a, and the discharge capacity-cycle curve of the lithium-sulfur battery manufactured with E / S of 10 μL / mg is shown in Fig. 10b.

[0306] Additionally, the anode loading amount was 7 mg s / cm 2 , the discharge capacity-cycle curve of a lithium-sulfur battery manufactured with E / S 6 μL / mg and subjected to 0.1C charge / discharge is shown in Fig. 10c.

[0307] According to Fig. 10a, it was confirmed that the discharge capacity can be improved by increasing the sulfur utilization rate by using a carbon composite according to an embodiment of the present invention. In addition, according to Fig. 10b, it was confirmed that the battery life according to the cycle repetition is improved by using a carbon composite according to an embodiment of the present invention. In particular, according to Fig. 10c, it was confirmed that the life stability of the battery can be dramatically improved even under high-loading lean electrolyte conditions by using a carbon composite according to an embodiment of the present invention.

[0308]

[0309] Energy density assessment

[0310] A lithium-sulfur battery was manufactured using the same method as described above using the carbon composite of Example 1 and the carbon composite of Comparative Example 1, respectively, but the lithium-sulfur battery was manufactured such that the E / S ratio of the lithium-sulfur battery using the carbon composite of Example 1 was 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 battery was charged and discharged at a current density of 0.2 C in the range of 1.7 V to 2.8 V to evaluate the discharge capacity, and a cycle-energy density graph was plotted in Fig. 11 according to the measurement results.

Claims

1. Porous carbon material, and A catalyst is included which is positioned on at least one of the outer surface and the inner surface of the pores of the porous carbon material, The catalyst comprises a transition metal alloy particle and a carbon coating layer covering at least a portion of the surface of the transition metal alloy particle, The above transition metal alloy particles include cobalt (Co) and iron (Fe), A carbon composite, wherein at least a portion of the carbon coating layer comprises crystalline carbon.

2. In claim 1, A carbon composite, wherein the above transition metal alloy particles include cobalt-iron alloy particles having a body-centered cubic structure.

3. In claim 1, The average particle diameter (D) of the above carbon composite 50 ) is a carbon composite having a size of 100 nm to 100 μm.

4. In claim 1, The average particle diameter (D) of the above catalyst 50 ) is a carbon composite having a size of less than 100 nm.

5. In claim 1, The average particle diameter (D) of the above transition metal alloy particles 50 ) A carbon composite having a ratio of the thickness of the carbon coating layer to the thickness of the carbon composite of 40% or less.

6. In claim 1, A carbon composite having a thickness of the carbon coating layer of 10 nm or less.

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

8. In claim 1, A carbon composite having a content of the catalyst of 5 to 50 wt% based on 100 wt% of the carbon composite.

9. In claim 1, The above porous carbon material is a carbon composite including carbon nanotubes (CNT), graphene, graphene oxide (GO), reduced graphene oxide (rGO), carbon black, graphite, graphite nanofibers (GNF), carbon nanofibers (CNF), activated carbon fibers (ACF), activated carbon, fullerene, or two or more of these materials.

10. In claim 1, The above porous carbon material includes carbon nanotubes (CNTs), The above carbon nanotube is a carbon composite including entangled carbon nanotubes (entangled CNTs).

11. A method for producing a carbon composite according to any one of claims 1 to 10, 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 A method for producing a carbon composite, comprising heat-treating the above transition metal-carbon layer precursor polymer / porous carbon material to obtain the carbon composite.

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

13. In claim 11, A method for producing a carbon composite, wherein the above heat treatment is performed at a temperature of 600°C to 1,000°C.

14. A cathode active material comprising a carbon composite according to any one of claims 1 to 10 and a sulfur-based compound.

15. Containing anode, cathode and electrolyte, A lithium-sulfur battery comprising the positive electrode active material according to claim 14.

16. In claim 15, The E / S ratio is 8 μL / mg or less, and the sulfur loading amount in the anode is 2.25 mg. s / cm 2 That's all, A lithium-sulfur battery, wherein the E / S ratio represents the ratio of the volume of the electrolyte to the weight of sulfur in the positive electrode.

17. In claim 15, A lithium-sulfur battery having an E / S ratio of 3 μL / mg or less and an energy density of 380 Wh / kg or more.

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