Carbon composite material for positive electrode of lithium-sulfur battery and method for manufacturing same

Abstract

The present invention relates to a carbon composite material for use in a positive electrode of a lithium-sulfur battery, the carbon composite material including a porous carbon material; and vanadium nitride particles formed on a surface of the porous carbon material. A lithium-sulfur battery using the carbon composite material has improved stability by rapidly converting lithium polysulfide into lithium sulfide.

Description

Technical Field

[0001] This invention relates to a carbon composite material for the cathode of lithium-sulfur batteries and a method for manufacturing the same.

[0002] This application claims priority to Korean Patent Application No. 2022-0110385, filed on August 31, 2022, and Korean Patent Application No. 2022-0187899, filed on December 28, 2022, the disclosures of which are incorporated herein by reference. Background Technology

[0003] Lithium-sulfur batteries are battery systems that use sulfur-sulfur (SS) bonds in sulfur-based materials as the positive electrode active material and lithium metal as the negative electrode active material. Sulfur, the main component of the positive electrode active material, is abundant in nature and widely available worldwide; it is non-toxic and has a low atomic weight.

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

[0005] During discharge, the lithium-sulfur battery undergoes oxidation at the negative electrode active material (lithium) by releasing electrons into lithium cations, and reduction at the positive electrode active material (sulfur-based material) by accepting electrons. Through the reduction reaction, the sulfur-based material accepts two electrons via S-S bonds to transform into sulfide anions. The lithium cations generated from the lithium oxidation reaction migrate via the electrolyte to the positive electrode and combine with the sulfide anions generated from the reduction reaction of the sulfur compounds to form a salt. Specifically, the sulfur before discharge has a cyclic S8 structure, and the sulfur is converted into lithium polysulfide (Li₂S₂) through the reduction reaction. x (x = 8, 6, 4, 2) and completely reduced to lithium sulfide (Li2S).

[0006] In this situation, lithium polysulfides generated during charging / discharging readily dissolve in the electrolyte, causing battery capacity decay and reduced battery performance. To overcome the lithium polysulfide dissolution problem, extensive research has been conducted on the impregnation of sulfur into the pores of various porous carbon materials used in cathodes. In particular, because the synthesis of carbon with a large specific surface area requires high production costs, research has mainly focused on the physical and chemical modification of carbon materials with low specific surface area used in cathodes.

[0007] However, although these studies have proposed some solutions to the problem of lithium polysulfide leaching, they have failed to promote the conversion reaction of lithium polysulfides to lithium sulfides (Li2S). Summary of the Invention

[0008] Technical issues

[0009] The present invention aims to provide a carbon composite material for the positive electrode of lithium-sulfur batteries and a method for manufacturing the same, wherein the carbon composite material is used to promote the conversion of lithium polysulfides to lithium sulfides.

[0010] Technical solution

[0011] To achieve the above objectives, according to one aspect of the present invention, a carbon composite material with the following embodiments is provided.

[0012] The carbon composite material according to the first embodiment comprises: a porous carbon material; and vanadium nitride particles formed on the surface of the porous carbon material.

[0013] According to the second implementation scheme, in the first implementation scheme, the specific surface area of ​​the carbon composite material can be 250 m². 2 / g or more.

[0014] According to the third embodiment, in the first or second embodiment, the pore volume of the carbon composite material can be 1.0 cm³. 3 / g or more.

[0015] According to the fourth embodiment, in any one of the first to third embodiments, the average pore size of the carbon composite material can be above 10 nm.

[0016] According to the fifth implementation scheme, in any one of the first to fourth implementation schemes, the average particle size of vanadium nitride particles can be below 200 nm.

[0017] According to the sixth embodiment, in any one of the first to fifth embodiments, the content of vanadium nitride particles based on 100 parts by weight of carbon composite material can be 3 to 50 parts by weight.

[0018] According to the seventh embodiment, in any of the first to sixth embodiments, the porous carbon material may comprise carbon nanotubes (CNTs), reduced graphene oxide (rGO), or mixtures thereof.

[0019] According to another aspect of the present invention, a positive electrode active material, a positive electrode, and a battery are provided according to the following embodiments.

[0020] The positive electrode active material according to the eighth embodiment comprises: a carbon composite material according to any one of the first to seventh embodiments; and a sulfur-containing compound loaded into the pores of the carbon composite material.

[0021] According to the ninth implementation plan, in the eighth implementation plan, the weight ratio of sulfur-containing compounds to carbon composite materials can be from 1:1 to 9:1.

[0022] The positive electrode according to the tenth embodiment comprises: a current collector; and a positive electrode active material layer formed on at least one surface of the current collector, and comprising the positive electrode active material according to the eighth or ninth embodiment and an adhesive.

[0023] The battery according to the eleventh embodiment includes: a positive electrode, a negative electrode, a separator between the positive electrode and the negative electrode, and an electrolyte, wherein the positive electrode is as defined in the tenth embodiment.

[0024] The positive electrode according to the twelfth embodiment comprises: a current collector; and a positive electrode active material layer formed on at least one surface of the current collector, and comprising a positive electrode active material, a binder, and a positive electrode additive, wherein the positive electrode active material comprises a sulfur-containing compound, and the positive electrode additive comprises a carbon composite material according to any one of the first to seventh embodiments.

[0025] According to the thirteenth implementation plan, in the twelfth implementation plan, based on a total of 100 parts by weight of positive electrode active material layer, the content of positive electrode additive can be from 0.01 to 30 parts by weight.

[0026] The battery according to the fourteenth embodiment includes: a positive electrode, a negative electrode, a separator between the positive electrode and the negative electrode, and an electrolyte, wherein the positive electrode is as defined in the twelfth or thirteenth embodiment.

[0027] According to another aspect of the present invention, a method for manufacturing a carbon composite material according to the following embodiments is provided.

[0028] The method for manufacturing carbon composite materials according to the fifteenth embodiment includes:

[0029] First step: Add and disperse porous carbon material, vanadium nitride or its precursor, and reducing agent in a solvent;

[0030] The second step: Filter the product from the first step to remove the solvent and dry it; and

[0031] Third step: Heat treat the product obtained in the second step under an inactive atmosphere.

[0032] The third step includes:

[0033] First process: heat treatment at 350℃ to 650℃; and

[0034] The second step: heat treatment at 650℃ to 1400℃.

[0035] Beneficial effects

[0036] By using the carbon composite material according to the present invention as a positive electrode additive for lithium-sulfur batteries or a carrier for sulfur-containing compounds in lithium-sulfur batteries, lithium polysulfides can be rapidly converted into lithium sulfides.

[0037] Furthermore, the method for manufacturing carbon composite materials according to the present invention enables the catalyst to be uniformly loaded onto a porous carbon support without the use of harmful gases such as NH3 and strong acids such as HF. Attached Figure Description

[0038] The accompanying drawings illustrate exemplary embodiments of the invention and, together with the foregoing description, serve to provide a further understanding of the technical aspects of the invention; therefore, the invention should not be construed as limited to the drawings.

[0039] Figure 1 This is a graph showing the specific surface area of ​​a carbon composite material according to one embodiment of the present invention.

[0040] Figure 2 This is a scanning electron microscope (SEM) image of a carbon composite material according to one embodiment of the present invention.

[0041] Figure 3 This is a SEM image of a carbon composite material according to an embodiment of the present invention.

[0042] Figure 4 These are SEM images of the carbon composite material according to a comparative example of the present invention.

[0043] Figure 5 This is a charging / discharging performance evaluation diagram of a lithium-sulfur battery according to one embodiment of the present invention.

[0044] Figure 6 This is a charging / discharging performance evaluation diagram of a lithium-sulfur battery according to a comparative example of the present invention.

[0045] Figure 7 This is a charging / discharging performance evaluation diagram of a lithium-sulfur battery according to a comparative example of the present invention.

[0046] Figure 8 This is a performance evaluation diagram of a lithium-sulfur battery according to one embodiment of the present invention.

[0047] Figure 9 This is a performance evaluation diagram of a lithium-sulfur battery according to one embodiment of the present invention. Detailed Implementation

[0048] The present invention will be described in detail below. However, the invention is not limited to the description below, and the elements may be modified or selectively combined as necessary. Therefore, it should be understood that the invention encompasses all variations, equivalents, or substitutions included within the aspects and scope of the invention.

[0049] In this specification, the terms “comprising” or “including” specify the presence of the said element, but do not exclude the presence or addition of more than one other element unless expressly stated otherwise.

[0050] As used in this article, “A and / or B” means “A, or B, or both”.

[0051] Regarding the properties described herein, without detailed description of the measurement conditions and methods, these properties are measured using the measurement conditions and methods commonly used by those skilled in the art.

[0052] As used in this article, the term "polysulfide" includes "polysulfide ions (S...)". x 2- "x = 8, 6, 4, 2)" and "lithium polysulfide (Li2S)" x or LiS x The concept of "x = 8, 6, 4, 2".

[0053] As used in this article, the term "composite material" refers to a combination of two or more materials that have different physicochemical phases and perform more effective functions.

[0054] This invention provides a carbon composite material that can be used in lithium-sulfur batteries.

[0055] According to one aspect of the invention, carbon composite materials can be used in the positive electrode of lithium-sulfur batteries.

[0056] In one embodiment of the present invention, a carbon composite material can be used as a positive electrode additive, which is added separately from the positive electrode active material in the positive electrode of a lithium-sulfur battery.

[0057] In another embodiment of the invention, the carbon composite material can be used as a porous carbon support for the positive electrode active material (specifically a sulfur-containing compound) in the positive electrode of an impregnated lithium-sulfur battery.

[0058] In another embodiment of the present invention, the carbon composite material can be used as a positive electrode additive and positive electrode active material in the positive electrode of a lithium-sulfur battery.

[0059] The carbon composite material according to one aspect of the invention comprises a porous carbon material; and vanadium nitride particles formed on the surface of the porous carbon material.

[0060] Typically, during the charging / discharging of lithium-sulfur batteries, the dissolution of lithium polysulfides occurs at the positive electrode. When a carbon composite material according to one aspect of the invention is used as at least one of a positive electrode additive or a carrier of sulfur-containing compounds in a lithium-sulfur battery, the vanadium nitride particles contained in the carbon composite material act as a catalyst to rapidly convert lithium polysulfides into lithium sulfides, thereby preventing the dissolution of lithium polysulfides in the electrolyte.

[0061] In one embodiment of the invention, the "porous carbon material" can function as a support for vanadium nitride particles used as catalysts.

[0062] In one embodiment of the invention, the porous carbon material may be at least partially or completely crystallized to improve the catalytic activity of vanadium nitride particles. For example, when an amorphous porous carbon material is used as at least a portion of the cathode additive and / or cathode active material, the amorphous carbon portion acts as a resistor in the electrochemical reaction of the battery, causing a decrease in battery performance. Therefore, when the porous carbon material is at least partially or completely crystallized, it can be used to reduce the resistance in the electrode and improve the catalytic activity through the vanadium nitride particles, but the mechanism of the invention is not limited thereto.

[0063] In one embodiment of the invention, the crystallinity of porous carbon materials can be measured by X-ray diffraction (XRD) analysis. "XRD" is a diffraction analysis caused by the scattering and interference of X-rays by electrons surrounding atoms when a sample is irradiated with X-rays (Bragg condition: 2dsinθ = nλ: the distance between two planes is d, the angle between the plane and the X-ray is θ, any integer is n, and the wavelength of the X-ray is λ), and is used to determine the phase, amount, crystal size, or crystallinity of a component.

[0064] For example, the presence of at least one independent peak in the XRD spectrum indicates that the porous carbon material is at least partially crystalline. In this case, the measured signal is at least 1, 1.5, 2, 5, or 10 times stronger than the noise at the independent peak.

[0065] In one embodiment of the invention, when the porous carbon material is at least partially crystalline, the porous carbon material may have higher elasticity than the amorphous carbon material. Here, for example, the amorphous carbon material may be the carbon material disclosed by Liu et al., Nanoscale, 2018, 10 5246-5253.

[0066] In one embodiment of the invention, when the porous carbon material is fully crystalline, the porous carbon material can have much higher elasticity than the amorphous carbon material.

[0067] In one embodiment of the invention, the porous carbon material may comprise a plurality of micropores on its outer surface and interior, and the average diameter of the micropores may be, for example, in the range of 1 nm to 200 nm, such as 1 nm to 100 nm, 10 nm to 80 nm, or 20 nm to 50 nm. The average diameter of the pores may be measured according to ISO 15901:2019, as known in the relevant art, but is not limited thereto.

[0068] Furthermore, in one embodiment of the invention, the porosity (or void fraction) of the porous carbon material can range from 10% to 90% of the total volume of the porous carbon material. The porosity of the porous carbon material can be measured according to the method known in the relevant technical field, ISO 15901:2019, but the measurement method is not limited thereto.

[0069] In one embodiment of the present invention, the pore volume of the porous carbon material can be, for example, 1 cm³. 3 / g to 20cm 3 / g or 1cm 3 / g to 10cm 3 / g. For example, the pore volume can be a measurement calculated by analyzing the N2 isotherm obtained based on liquid nitrogen adsorption. When the pore volume of the porous carbon material is within the above range, a sufficient amount of vanadium nitride particles, which can be used as a catalyst, can be placed on the surface of the porous carbon material, but the invention is not limited thereto.

[0070] Pore ​​volume can be measured according to ASTM D4641 using the AUTOSORB iQ series (manufactured by Quantachrome), and the pore volume can be a measured value calculated by N2 isotherm analysis obtained based on liquid nitrogen adsorption.

[0071] In one embodiment of the invention, the average particle size (D) of the porous carbon material is... 50 The particle size can range from 10 μm to 80 μm. For example, multiple porous carbon materials as primary particles can be formed into porous carbon materials in the form of secondary particles, and in this case, the average particle size (D) of the porous carbon materials as primary particles is... 50 It can be within the above value range.

[0072] Average particle size (D) 50 The particle size distribution refers to the particle size at the 50% percentile of the cumulative volumetric particle size distribution. Particle size can be measured using laser diffraction. Specifically, the particle size distribution is calculated by dispersing the target powder in a dispersion medium and measuring the difference in diffraction pattern with particle size as the particles pass through a laser beam using a commercially available laser diffraction particle size measurement device (e.g., Microtrac S3500). 50 The particle size can be measured by calculating the particle size at 50% of the cumulative volumetric particle size distribution in the measuring device.

[0073] In one embodiment of the present invention, the specific surface area of ​​the porous carbon material can be, for example, 100 to 2000 m². 2 / g, 300 to 2000m 2 / g, 400 to 1800m 2 / g, 450 to 1500m 2 / g or 500 to 1200m 2 / g. Specific surface area can be measured by the BET method according to ISO 15901:2019, which is known in the relevant technical field, but is not limited thereto. When the specific surface area of ​​the porous carbon material is within the above range, vanadium nitride particles can be sufficiently loaded, but the present invention is not limited thereto.

[0074] In one embodiment of the present invention, the porous carbon material may comprise, for example, at least one selected from the following: carbon nanotubes (CNT), graphene, graphene oxide (GO), reduced graphene oxide (rGO), carbon black, graphite, graphite nanofibers (GNF), carbon nanofibers (CNF), activated carbon fibers (ACF), natural graphite, artificial graphite, expandable graphite, activated carbon, or fullerene.

[0075] In one embodiment of the present invention, the porous carbon material may comprise at least one selected from carbon nanotubes and reduced graphene oxide.

[0076] In one embodiment of the invention, the porous carbon material may be doped with at least one element selected from nitrogen, oxygen, or phosphorus.

[0077] In another embodiment of the invention, the porous carbon material may comprise: carbon nanotubes doped with at least one element selected from nitrogen, oxygen, or phosphorus; reduced graphene oxide doped with at least one element selected from nitrogen, oxygen, or phosphorus; or mixtures thereof.

[0078] Carbon nanotubes are tubes made of carbon atoms connected in a hexagonal shape. According to one embodiment of the invention, depending on the number of layers of carbon atoms forming the carbon nanotubes (referred to as "carbon walls"), the carbon nanotubes may comprise at least one of single-walled carbon nanotubes (SWCNTs) or multi-walled carbon nanotubes (MWCNTs). There is no particular limitation on the length of each carbon nanotube.

[0079] In another embodiment of the invention, the carbon nanotubes may comprise two or more carbon nanotubes entangled in close contact with each other by cohesive forces therebetween.

[0080] Specifically, in one embodiment of the invention, carbon nanotubes can be provided as: a carbon nanotube dispersion in which single chains are dispersed in a dispersion medium; or a secondary structure formed by the aggregation of primary carbon nanotubes. In this regard, when the porous carbon material contains carbon nanotubes, the carbon nanotubes can contain at least one of bundled secondary structures or entangled secondary structures. A bundled secondary structure of carbon nanotubes refers to an aggregation of primary structures along the length of the carbon nanotubes by bonds between carbon atoms (each primary structure is a single chain of carbon nanotubes) and can be referred to as bundled CNTs.

[0081] The carbon nanotubes contained in the carbon composite material may contain more than one twisted or entangled carbon nanotube, and the carbon composite material may have a porous structure with spaces between the carbon nanotubes.

[0082] Reduced graphene oxide may comprise bent reduced graphene oxide, and may comprise both bent and entangled reduced graphene oxide. Alternatively, reduced graphene oxide may comprise wrinkled reduced graphene oxide. The reduced graphene oxide contained in the carbon composite material may comprise more than one entangled or wrinkled reduced graphene oxide, and the carbon composite material may have a porous structure with spaces between the reduced graphene oxides.

[0083] The carbon composite material according to the invention comprises vanadium nitride particles formed on the surface of a porous carbon material.

[0084] Vanadium nitride (VN) is a compound of nitrogen and vanadium. Vanadium nitride particles exist on the surface of porous carbon materials.

[0085] In one embodiment of the present invention, "vanadium nitride particles" can react with sulfur (S8), lithium sulfide (Li2S), and lithium polysulfides (Li2S). x The oxidation and reduction reactions of disulfides or mixtures thereof (2≤x≤8) are catalytically active.

[0086] In one embodiment of the invention, vanadium nitride particles may be present on at least one of the outer surface or the surface inside the pores of the porous carbon material. Specifically, vanadium nitride particles may be adsorbed and present on the outer surface of the porous carbon material.

[0087] In one embodiment of the invention, since carbon nanotubes are tubes made of carbon connected in a hexagonal shape, the carbon composite material may contain vanadium nitride particles formed on the inner and / or outer surfaces of the tubular carbon nanotubes. Specifically, the vanadium nitride particles may be present on the outer surface of the carbon nanotubes. Here, the method of placing vanadium nitride on the surface of the porous carbon material is not limited to a specific method, but rather, for example, vanadium nitride may be attached to or deposited on the surface of the porous carbon material.

[0088] In one embodiment of the present invention, the average particle size of the vanadium nitride particles can be below 200 nm. Specifically, the average particle size (D...) 50 The average particle size of vanadium nitride particles can be below 190 nm, 180 nm, 170 nm, 160 nm, or 20 nm. Furthermore, the average particle size of vanadium nitride particles can be above 1 nm or above 2 nm. When the average particle size of vanadium nitride particles is within the above range, the specific surface area of ​​the vanadium nitride particles used as a catalyst increases, thereby improving the reaction with lithium polysulfides. The surface is not completely covered by lithium sulfides generated during discharge, thus enabling a reversible reaction, and a larger amount of catalyst can be present on the surface of the porous carbon material. The average particle size of vanadium nitride particles (D...) 50 It can be measured in the same way as the particle size measurement method for carbon composites.

[0089] In one embodiment of the invention, the content of vanadium nitride particles based on 100 parts by weight of carbon composite material can be 3 to 50 parts by weight. Specifically, based on 100 parts by weight of carbon composite material, this content can be 3 to 40 parts by weight, 3 to 30 parts by weight, 40 to 50 parts by weight, 35 to 50 parts by weight, 10 to 40 parts by weight, or 20 to 30 parts by weight. When the content of vanadium nitride particles is within the above-mentioned range, the vanadium nitride particles can rapidly convert lithium polysulfides into lithium sulfides, preventing the dissolution of lithium polysulfides in the electrolyte and maintaining optimal resistance and weight.

[0090] In one embodiment of the invention, at least a portion of the surface of vanadium nitride may be coated with a carbon layer. Alternatively, the entire surface of vanadium nitride may be coated with a carbon layer. Specifically, in the presence of a carbon layer, the thickness of the carbon layer may be less than 5 nm. The thickness of the carbon layer can be measured by transmission electron microscopy (TEM). When the thickness of the carbon layer meets the above-mentioned range, the stability of the vanadium nitride catalyst can be improved while maintaining the catalyst's effectiveness.

[0091] In one embodiment of the invention, the carbon layer coated on vanadium nitride can be 1 to 3 layers or 1 to 5 layers. In this case, the total thickness of the carbon layer can be less than 5 nm.

[0092] In one embodiment of the present invention, the specific surface area of ​​the carbon composite material can be, for example, 250 m². 2 / g or more, specifically 260m 2 / g or more, 270m 2 / g or more, 280m 2 / g or more, 290m 2 / g or more or 300m 2 / g or more, and can be 400m 2 / g or less or 500m 2Less than / g. When the specific surface area of the carbon composite material is within the above range, a sufficient amount of vanadium nitride can exist on the surface of the carbon composite material, so that the conversion performance of polysulfide lithium to lithium sulfide can be improved by the sufficient amount of vanadium nitride on the surface, and the surface of the carbon composite material is not completely covered by polysulfide lithium or lithium sulfide generated during discharge, thus enabling a reversible reaction to occur.

[0093] The specific surface area is measured by the BET method. Specifically, it can be calculated from the amount of adsorbed nitrogen at liquid nitrogen temperature (77K) using BELSORP mino II of BEL Japan.

[0094] In one embodiment of the present invention, the pore volume of the carbon composite material can be, for example, 1.0 cm 3 / g or more. Specifically, the pore volume of the carbon composite material can be 1.1 cm 3 / g or more, 1.2 cm 3 / g or more, 1.3 cm 3 / g or more, or 1.4 cm 3 / g or more, and can be 2.5 cm 3 / g or less, 2.7 cm 3 / g or less, 3.0 cm 3 / g or less. When the pore volume of the carbon composite material is within the above range, the electrolyte of the battery using the carbon composite material in the positive electrode can be fully impregnated in the pores, thereby improving ion conductivity, improving the loading efficiency of sulfur (S8) through the pores of the carbon composite material, or improving the conductivity of the positive electrode, but the present invention is not limited thereto.

[0095] In one embodiment of the present invention, the average pore size of the carbon composite material can be 10 nm or more. Specifically, the average pore size of the carbon composite material can be 15 nm or more and 50 nm or less, 70 nm or less, 100 nm or less. When the average pore size of the carbon composite material satisfies the above range, polysulfide lithium can be effectively adsorbed, and the electrolyte can easily enter the pores, thereby maintaining the best ion conductivity and improving the reactivity.

[0096] The average pore size can be, for example, a measured value calculated by N2 isotherm analysis based on nitrogen adsorption at liquid nitrogen temperature.

[0097] In one embodiment of the present invention, the carbon composite material can contain trace amounts of V generated from by-products when forming vanadium nitride particles x O y (0 < x < 2, 0 < y < 5). Based on the total weight of the vanadium nitride particles contained in the carbon composite material, V x O y(0 < x < 2, 0 < y < 5) may be less than 1% by weight. In this case, the amount can be measured by calculating the residual mass at 950 °C using a thermogravimetric analyzer (TGA).

[0098] In one embodiment of the present invention, the XRD peak of the carbon composite material appears at 2θ.

[0099] In one embodiment of the present invention, the intensity ratio (I D / I G ratio) in the Raman spectrum peak of the carbon composite material can be 2.0 or less. Specifically, the I D / I G ratio can be 0.5 or more and 2.0 or less. The intensity ratio (I D / I G ratio) can be measured from the peak intensities I G and I D values obtained from the spectrum of the carbon composite material obtained by Raman spectroscopy. I G refers to the peak of the crystalline part (G peak, 1573 / cm), and I D refers to the peak of the amorphous part (D peak, 1309 / cm). Therefore, in this case, it means that as the ratio of I D / I G becomes smaller, the crystallinity becomes higher. When the ratio satisfies the above range, the optimal conductivity and mechanical strength can be maintained.

[0100] In one embodiment of the present invention, the crystallinity of the carbon composite material can be, for example, 70% or more. The crystallinity is measured using at least one of Raman spectroscopy analysis or XRD analysis. When the crystallinity is within the above range, it is possible to prevent a decrease in catalyst performance while maintaining the optimal conductivity and keep the resistance below a predetermined level.

[0101] According to another aspect of the present invention, there is provided a positive electrode active material including the above carbon composite material.

[0102] Specifically, the positive electrode active material can be a positive electrode active material for a lithium-sulfur battery.

[0103] The positive electrode active material according to one embodiment of the present invention includes a carbon composite material as a carrier and may include a sulfur-containing compound loaded into the pores of the carbon composite material.

[0104] In one embodiment of the present invention, the sulfur-containing compound loaded into the pores of the carbon composite material may include at least one selected from the following: inorganic sulfur (S8); Li2S n(n≥1); disulfide compounds such as 2,5-dimercapto-1,3,4-thiadiazole and 1,3,5-trithiocyanate; and organic sulfur compounds. Preferably, the sulfur-containing compounds may include inorganic sulfur (S8).

[0105] In one embodiment of the invention, the weight ratio of the sulfur-containing compound to the carbon composite material can be, for example, 1:1 to 9:1. Specifically, the weight ratio of the sulfur-containing compound to the carbon composite material can be 2:1 to 8:1, 5:1 to 9:1, or 8:1 to 9:1. When this weight ratio meets the above range, aggregation of the sulfur-containing compound can be prevented, which facilitates electron acceptance and allows direct participation in the electrode reaction. Furthermore, the optimal amount of binder required to prepare the positive electrode slurry can be controlled, thereby preventing an increase in the surface resistance of the electrode or a decrease in battery performance.

[0106] According to another aspect of the present invention, a positive electrode comprising a positive active material is provided.

[0107] The positive electrode includes a current collector and a positive electrode active material layer formed on at least one surface of the current collector and comprising the aforementioned positive electrode active material and binder. If necessary, the positive electrode active material layer may further comprise a conductive material.

[0108] In one embodiment of the invention, the adhesive is used to retain the positive electrode active material on the positive electrode current collector and organically connect the positive electrode active material to increase the bonding strength between them, and may comprise any adhesive known in the relevant art. For example, the adhesive may comprise any of the following: fluoropolymer adhesives, including polyvinylidene fluoride (PVdF) or polytetrafluoroethylene (PTFE); rubber adhesives, including styrene-butadiene rubber (SBR), nitrile rubber, and styrene-isoprene rubber; cellulose adhesives, including carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, and regenerated cellulose; polyol adhesives; polyolefin adhesives, including polyethylene and polypropylene; polyimide adhesives; polyester adhesives; polyacrylate adhesives; and silane adhesives; or mixtures or copolymers thereof.

[0109] In one embodiment of the present invention, when the total weight of the positive electrode active material layer is 100 parts by weight, the amount of binder added can be, for example, 0.5 to 30 parts by weight. When the amount of binder meets the above range, the physical properties of the positive electrode can be improved, the separation of the active material and the conductive material in the positive electrode can be prevented, and the optimal ratio of the active material and the conductive material in the positive electrode can be controlled, thereby ensuring the battery capacity.

[0110] In one embodiment of the invention, the conductive material is a material that electrically connects the electrolyte to the positive electrode active material and serves as a channel for the movement of electrons from the current collector to the positive electrode active material, and may contain any type of material with conductive properties without limitation. In one embodiment, the conductive material may contain at least one of the following: carbon black materials such as Super-P, Danka Black, acetylene black, Ketjen Black, channel black, furnace black, lamp black, thermal cracking black, and carbon black; carbon derivatives such as carbon nanotubes, graphene, and fullerene; conductive fibers such as carbon fibers or metal fibers; fluorocarbons, metal powders such as aluminum powder and nickel powder; or conductive polymers such as polyaniline, polythiophene, polyacetylene, and polypyrrole. Furthermore, the conductive material may contain carbon composite materials according to the invention.

[0111] In one embodiment of the present invention, when a conductive material is included, the content of the conductive material can be from 0.01 to 30 parts by weight based on 100 parts by weight of the positive electrode active material layer.

[0112] In one embodiment of the invention, the current collector is not limited to a specific type and can comprise any material that supports the positive electrode active material layer and has high conductivity without causing any chemical change to the corresponding battery. For example, the current collector may comprise: copper, stainless steel, aluminum, nickel, titanium, palladium, sintered carbon, copper or stainless steel surface-treated with carbon, nickel or silver, and aluminum-cadmium alloys.

[0113] In one embodiment of the present invention, the current collector may have fine irregularities on its surface to enhance the bonding strength with the positive electrode active material, and may be of various types, such as membrane, sheet, foil, sieve, mesh, porous body, foam, non-woven fabric, etc.

[0114] In one embodiment of the invention, the thickness of the current collector is not limited to a specific range, but can be, for example, in the range of 3 μm to 500 μm.

[0115] According to another aspect of the present invention, a battery using the above-described positive electrode can be provided, particularly a lithium secondary battery, specifically a lithium-sulfur battery.

[0116] A battery consists of a positive electrode, a negative electrode, a separator between the positive and negative electrodes, and an electrolyte.

[0117] Regarding the positive electrode, please refer to the description above.

[0118] In one embodiment of the invention, the negative electrode and separator are not limited to a particular type and can include any type of negative electrode and separator used in lithium-sulfur batteries without departing from the purpose of the invention. The negative electrode may contain, for example, lithium metal.

[0119] In one embodiment of the invention, the separator can comprise any type of separator commonly used in lithium-sulfur batteries without limitation.

[0120] In one embodiment of the invention, the membrane may comprise a porous polyolefin substrate, and, if necessary, may further comprise inorganic particles on at least one surface of the porous polyolefin substrate. Furthermore, if necessary, the membrane may further comprise an adhesive to bind the inorganic particles.

[0121] In another embodiment of the invention, the separator may be a membrane-like electrolyte membrane containing a solid electrolyte, and may further include a binder to bond the solid electrolyte, if necessary. The solid electrolyte may include, but is not limited to, any type of solid electrolyte commonly used in lithium-sulfur batteries, such as polymeric solid electrolytes, inorganic solid electrolytes, or mixtures thereof.

[0122] In one embodiment of the invention, the electrolyte may comprise any type of electrolyte commonly used in lithium-sulfur batteries. The electrolyte may comprise lithium salts and non-aqueous solvents.

[0123] The lithium salt can comprise any type of lithium salt commonly used in lithium-sulfur battery electrolytes without limitation. The lithium salt can include at least one of, 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, lower aliphatic carboxylic acids, lithium tetraphenylborate, or lithium imide, but not limited to these.

[0124] Non-aqueous solvents may include any type of non-aqueous solvent commonly used in electrolytes for lithium-sulfur batteries without limitation. Non-aqueous solvents may include, for example, cyclic carbonate solvents, linear carbonate solvents, ester solvents, ketone solvents, or mixtures of two or more of these, but are not limited thereto.

[0125] In one embodiment of the invention, the electrolyte may contain (CF3SO2)2NLi as a lithium salt and, as a non-aqueous solvent, may contain a two-component system of dioxolane (DOL) / dimethoxyethane (DME). For example, the electrolyte may further contain commonly used additives, such as LiNO3.

[0126] In one embodiment of the invention, the lithium-sulfur battery can be, for example, coin-shaped, cylindrical, pouch-shaped, or prismatic, and the shape of the battery is not limited to a specific shape. Furthermore, the lithium-sulfur battery can be used not only in individual battery cells as power sources for small devices, but also as unit cells in medium to large-sized battery modules comprising multiple individual battery cells, and is not limited to specific applications.

[0127] According to another aspect of the present invention, there exists a positive electrode comprising the above-described carbon composite material as a positive electrode additive.

[0128] In one embodiment of the present invention, the positive electrode comprises: a current collector; and a positive electrode active material layer formed on at least one surface of the current collector and comprising a positive electrode active material, a binder and a positive electrode additive, wherein the positive electrode active material comprises a sulfur-containing compound and the positive electrode additive comprises the aforementioned carbon composite material.

[0129] In one embodiment of the present invention, when the positive electrode additive is the aforementioned carbon composite material, the content of the positive electrode additive can be from 0.1 to 30 parts by weight based on a total of 100 parts by weight of the positive electrode active material layer. Specifically, the content of the positive electrode additive can be from 0.5 to 20 parts by weight, 1 to 10 parts by weight, or 1 to 5 parts by weight based on a total of 100 parts by weight of the positive electrode active material layer. When the content of the positive electrode additive is within the above-mentioned range, the conductivity between active material particles or between the active material and the current collector can be improved, and the resistance in the electrode can be reduced. In addition, the positive electrode additive is dispersed between the compressed active material particles and maintains the micropores between the active material particles, which makes it easy for the electrolyte to penetrate.

[0130] According to another aspect of the present invention, a battery is provided, the battery comprising a positive electrode using the above-described carbon composite material as a positive electrode additive.

[0131] The battery includes a positive electrode, a negative electrode, a separator between the positive and negative electrodes, and an electrolyte, and the positive electrode contains the aforementioned carbon composite material as a positive electrode additive.

[0132] In this case, refer to the foregoing description regarding the negative electrode, membrane, and electrolyte.

[0133] According to another aspect of the present invention, a method for manufacturing the above-described carbon composite material is provided.

[0134] The carbon composite material comprises: porous carbon material; and vanadium nitride particles formed on the surface of the porous carbon material as described above.

[0135] Methods for manufacturing carbon composite materials include:

[0136] First step: Add and disperse porous carbon materials, vanadium nitride or its precursors and reducing agents in a solvent;

[0137] The second step: Filter the product obtained in the first step to remove the solvent and dry it; and

[0138] Third step: Heat treat the product obtained in the second step under an inactive atmosphere.

[0139] In one embodiment of the present invention, the vanadium nitride precursor may include at least one selected from dicyandiamide, ammonium metavanadate (NH4VO3), vanadium oxide, ammonia (NH3), and ammonium chloride.

[0140] For example, vanadium nitride can be produced through the synthesis reaction of dicyandiamide and ammonium metavanadate.

[0141] In one embodiment of the present invention, the reducing agent may comprise at least one selected from glucose, sucrose, lactose, fructose, starch, polydopamine, and tannic acid.

[0142] In one embodiment of the invention, the solvent used in the first step may comprise at least one organic solvent selected from the following: dimethyl carbonate, dimethylformamide, N-methylformamide, sulfolane (tetrahydrothiophene-1,1-dioxide), 3-methylsulfolane, N-butyl sulfone, dimethyl sulfoxide, pyrrolidone (HEP), dimethylpiperidone (DMPD), N-methylpyrrolidone (NMP), N-methylacetamide, dimethylacetamide (DMAc), N,N-dimethylformamide (DMF), diethylacetamide (DEAc), dipropylacetamide (DPAc), ethanol, propanol, butanol, hexanol, ethylene glycol, tetrachloroethylene, propylene glycol, toluene, turpentine, methyl acetate, ethyl acetate, petroleum ether, acetone, cresol, and glycerol.

[0143] In one embodiment of the invention, based on 100 parts by weight of porous carbon material added in the first step, the amount of vanadium nitride or its precursor can be 1 to 100 parts by weight or 5 to 40 parts by weight, and the amount of reducing agent can be 10 to 100 parts by weight or 20 to 80 parts by weight. When the amounts of vanadium nitride or its precursor and the reducing agent meet the above ranges, an optimal level of vanadium nitride catalyst particles can be uniformly formed on the surface of the porous carbon material. Furthermore, it is possible to minimize amorphous carbon with low electrical conductivity and maximize the exposure of the catalyst surface while maintaining a large specific surface area, thereby maximizing the reactivity of lithium polysulfides and preventing dissolution in the electrolyte, but is not limited thereto.

[0144] In one embodiment of the invention, in the first step, dispersion can be carried out by ultrasonic treatment and / or magnetic stirring.

[0145] In one embodiment of the invention, solvent removal in the second step can be performed by vacuum filtration. Furthermore, drying can be carried out at a temperature of 50°C to 150°C. Additionally, drying can be carried out, for example, for 1 to 48 hours.

[0146] In one embodiment of the invention, the third step may include a first step of heat treatment at a low temperature and a second step of heat treatment at a high temperature. Specifically, the first step may be performed to generate vanadium nitride through the pyrolysis and reduction of vanadium nitride precursors, and the second step may be performed by bonding vanadium nitride particles to the surface of a porous carbon material through a carbonization reaction.

[0147] In one embodiment of the invention, the third step may include a first step of heat treatment at 350°C to 650°C and a second step of heat treatment at 650°C to 1400°C.

[0148] In one embodiment of the present invention, specifically, the first step can be performed at 350°C to 650°C, 500°C to 650°C, or 550°C to 650°C.

[0149] In one embodiment of the present invention, specifically, the second step can be performed at 650°C to 1400°C, 700°C to 900°C, or 750°C to 850°C.

[0150] In one embodiment of the invention, the third step can be carried out in an inactive atmosphere, and the inactive atmosphere can be formed using at least one gas selected from helium, neon, argon, carbon dioxide and nitrogen.

[0151] In one embodiment of the present invention, the method for manufacturing carbon composite materials may be characterized by not using NH3, HF and acids with a pKa of less than 4.0.

[0152] The invention will be described in more detail below by way of examples, but the examples are provided for illustrative purposes only and the scope of the invention is not limited thereto.

[0153] [Manufacturing of carbon composite materials]

[0154] Example 1

[0155] 1.6g carbon nanotubes, 24g dicyandiamide, 0.8g ammonium metavanadate and 0.2g glucose were mixed in 500mL of a solvent containing ethanol and water in a 1:1 volume ratio, and dissolved and dispersed by ultrasonic treatment and magnetic stirring.

[0156] Subsequently, the solvent, excluding the vanadium nitride precursor, adsorbed on the surface of the carbon nanotubes was removed by vacuum filtration.

[0157] Subsequently, it was dried in an oven at 80°C for 12 hours.

[0158] Subsequently, the carbon composite material was heat-treated at 600°C for 3 hours and then at 800°C for 2 hours in a tube furnace under an inactive atmosphere to obtain a carbon composite material in which vanadium nitride particles are present on the surface of carbon nanotubes. In this case, the amount of vanadium nitride particles was 20 parts by weight based on 100 parts by weight of the obtained carbon composite material. The amount of vanadium nitride particles was measured using a thermogravimetric analyzer (TGA).

[0159] Example 2

[0160] Except for using reduced graphene oxide instead of carbon nanotubes, the method of Example 1 was performed to obtain a carbon composite material in which vanadium nitride particles are present on the surface of reduced graphene oxide. In this case, based on 100 parts by weight of the resulting carbon composite material, the amount of vanadium nitride particles was 20 parts by weight. The amount of vanadium nitride particles was measured using a thermogravimetric analyzer (TGA).

[0161] Comparative Example 1

[0162] 24g of dicyandiamide, 0.8g of ammonium metavanadate and 0.8g of glucose were mixed in 500mL of a solvent containing ethanol and water in a 1:1 volume ratio, and dissolved and dispersed by ultrasonic treatment and magnetic stirring.

[0163] Subsequently, the solvents other than dicyandiamide and ammonium metavanadate are removed by vacuum filtration.

[0164] Subsequently, it was dried in an oven at 80°C for 12 hours.

[0165] Subsequently, the carbon composite material was heat-treated at 600°C for 3 hours and then at 800°C for 2 hours in a tube furnace under an inactive atmosphere to obtain a carbon composite material in which vanadium nitride particles exist on the surface of amorphous carbon produced by a carbonization process of glucose.

[0166] In this case, based on 100 parts by weight of the resulting carbon composite material, the amount of vanadium nitride particles is 20 parts by weight. The amount of vanadium nitride particles was measured using a thermogravimetric analyzer (TGA).

[0167] Performance evaluation of carbon composite materials

[0168] The specific surface area, pore volume, and average pore size of the carbon composite materials manufactured in Examples 1, 2, and Comparative Example 1 were measured by calculating the amount of nitrogen adsorbed using BELSORP mino II from BEL Japan at liquid nitrogen temperature (77 K).

[0169] Furthermore, the crystallinity of carbon in the carbon composite material was measured using Raman spectroscopy, and I was derived from the spectra obtained from the measurement results. D / I G Compare.

[0170] The property values ​​evaluated using the above method are shown in Table 1 below.

[0171] [Table 1]

[0172]

[0173] Figure 1 The 77KN2 isotherm measurements of the carbon composite materials according to Example 1, Example 2 and Comparative Example 1 are shown.

[0174] Figure 2 The image shows a scanning electron microscope (SEM) image of the carbon composite material of Example 1, in which vanadium nitride particles are present on the surface of carbon nanotubes. Figure 2 The SEM image was obtained at a magnification of 2,000 times over an area of ​​10 μm × 10 μm.

[0175] Figure 3 The image shows a SEM image of the carbon composite material from Example 2, in which vanadium nitride particles are present on the surface of reduced graphene oxide. Figure 3 The SEM image was obtained at a magnification of 2,000 times over an area of ​​10 μm × 10 μm.

[0176] Figure 4 The image shows a SEM image of the carbon composite material observed in Comparative Example 1, in which vanadium nitride particles are present on the surface of carbon nanotubes, which are amorphous carbon. Figure 4 The SEM image was obtained at a magnification of 2,000 times over an area of ​​10 μm × 10 μm.

[0177] Reference Figures 2 to 4 It was confirmed that vanadium nitride particles are uniformly distributed on the surfaces of carbon nanotubes, reduced graphene oxide, and amorphous carbon. The average size (D) of the vanadium nitride particles formed on the surface of amorphous carbon was also confirmed. 50 The average size (Dm) of vanadium nitride particles is 1 μm, suggesting significant aggregation of vanadium nitride particles. Conversely, this confirms that the average size (Dm) of vanadium nitride particles formed on the surface of reduced graphene oxide or carbon nanotubes is much smaller. 50 The size is below 0.1 μm.

[0178] [Manufacturing of lithium-sulfur batteries]

[0179] Example 3

[0180] <The Manufacturing of the Positive Electrode>

[0181] For the positive electrode active material, a porous carbon support in which sulfur is loaded on carbon nanotubes was prepared. In this case, the weight ratio of carbon composite material to sulfur (S8) was 1:3. The carbon composite material of Example 1, used as a positive electrode additive, and polyacrylic acid (PAA), used as a binder, were mixed with the positive electrode active material to prepare a positive electrode slurry.

[0182] In this case, the weight ratio of the positive electrode active material, the positive electrode additive, and the binder is 88:5:7.

[0183] The slurry was coated onto aluminum foil using a Mathis coating machine and dried at 50°C for 24 hours, followed by rolling to produce the positive electrode.

[0184] <Manufacturing of Lithium-Sulfur Batteries>

[0185] For the negative electrode, a 45 μm thick lithium metal film was prepared, and for the electrolyte, a mixture of 1 M lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and 1 wt% lithium nitrate (LiNO3) was prepared in an organic solvent of 1,3-dioxolane and dimethyl ether (DOL:DME = 1:1 (volume ratio)).

[0186] The prepared positive and negative electrodes are placed facing each other, with a polyethylene separator of 16 μm thickness and 46% porosity inserted between them, and 70 μl of electrolyte is injected to manufacture a lithium-sulfur battery.

[0187] Example 4

[0188] The lithium-sulfur battery was manufactured using the same method as in Example 3, except that the carbon composite material of Example 2 was used instead of the carbon composite material of Example 1 as the cathode additive.

[0189] Example 5

[0190] <The Manufacturing of the Positive Electrode>

[0191] A positive electrode active material was prepared by loading sulfur onto the carbon composite material manufactured in Example 1 via a melt-loading method. Specifically, the carbon composite material was blended and uniformly mixed with sulfur (S8). Subsequently, it was heat-treated in an oven at 150°C for 30 minutes to impregnate the sulfur into the carbon composite material. In this case, the weight ratio of carbon composite material to sulfur was 1:3.

[0192] A positive electrode slurry is prepared by mixing a polyacrylic acid (PAA) binder and a carbon fiber conductive material with the positive electrode active material. In this case, the weight ratio of the positive electrode active material, the conductive material, and the binder in the slurry is 88:5:7.

[0193] The slurry was coated onto aluminum foil using a Mathis coating machine and dried at 50°C for 24 hours, followed by rolling to produce the positive electrode.

[0194] <Manufacturing of Lithium-Sulfur Batteries>

[0195] For the negative electrode, a 45 μm thick lithium metal film was prepared, and for the electrolyte, a mixture of 1 M lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and 1 wt% lithium nitrate (LiNO3) was prepared in an organic solvent of 1,3-dioxolane and dimethyl ether (DOL:DME = 1:1 (volume ratio)).

[0196] The prepared positive and negative electrodes are placed facing each other, with a polyethylene separator of 16 μm thickness and 46% porosity inserted between them, and 70 μl of electrolyte is injected to manufacture a lithium-sulfur battery.

[0197] Comparative Example 2

[0198] The lithium-sulfur battery was manufactured using the same method as in Example 3, except that carbon nanotubes (CNTs) were used instead of the carbon composite material in Example 1 for the cathode additive.

[0199] Comparative Example 3

[0200] The lithium-sulfur battery was manufactured using the same method as in Example 3, except that the carbon composite material of Comparative Example 1 was used instead of the carbon composite material of Example 1 as the cathode additive.

[0201] Comparative Example 4

[0202] Except that carbon nanotubes (CNTs) were used instead of the carbon composite material of Example 1 as a cathode additive, the cathode and lithium-sulfur battery were manufactured by the same method as in Example 5.

[0203] Comparative Example 5

[0204] <The Manufacturing of the Positive Electrode>

[0205] A positive electrode active material was prepared in which sulfur was loaded onto carbon nanotubes via a melt-loading method. Specifically, carbon nanotubes were blended and uniformly mixed with sulfur (S8). Subsequently, the mixture was heat-treated in an oven at 150°C for 30 minutes to impregnate the sulfur into the carbon composite material. In this case, the weight ratio of the carbon composite material to sulfur was 1:3.

[0206] A positive electrode slurry was prepared by adding polyacrylic acid (PAA) binder, polyvinyl alcohol (PVA) thickener, and carbon nanotube conductive material to the positive electrode active material and mixing them together. In this slurry, the weight ratio of the positive electrode active material, binder, thickener, and conductive material was 88:6.5:0.5:5.

[0207] The slurry was coated onto aluminum foil using a Mathis coating machine and dried at 50°C for 24 hours, followed by rolling to produce the positive electrode.

[0208] <Manufacturing of Lithium-Sulfur Batteries>

[0209] For the negative electrode, a 45 μm thick lithium metal film was prepared, and for the electrolyte, a mixture of 1 M lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and 1 wt% lithium nitrate (LiNO3) was prepared in an organic solvent of 1,3-dioxolane and dimethyl ether (DOL:DME = 1:1 (volume ratio)).

[0210] The prepared positive and negative electrodes are placed facing each other, with a polyethylene separator of 16 μm thickness and 46% porosity inserted between them, and 70 μl of electrolyte is injected to manufacture a lithium-sulfur battery.

[0211] [Evaluation of Lithium-Sulfur Battery Performance]

[0212] The performance of the lithium-sulfur batteries of Examples 3 to 5 and Comparative Examples 2 to 5 was evaluated using the cyclic current-voltage method (CV), and the results are presented below. Figures 5 to 9 middle.

[0213] Specifically, at 1.7V to 2.8V (relative to Li / Li + Within the voltage range of ), the battery under evaluation was repeatedly charged / discharged at a current density of 0.1C for the first three cycles, 0.3C for the next three cycles, and 0.5C for subsequent cycles. The capacity-voltage curve for the first cycle is shown. Figure 5 , Figure 7 , Figure 8 Voltage-current density curves ( Figure 6 ) and cycle-specific capacity curve ( Figure 9 ).

[0214] Reference Figure 5 It was confirmed that, compared to the battery of Comparative Example 5, the batteries of Examples 3 and 4 using carbon composite materials containing vanadium nitride particles on porous carbon materials as cathode additives exhibited improved battery performance due to the catalytic activity of the vanadium nitride particles. Therefore, it was confirmed that vanadium nitride particles can prevent overvoltage in lithium-sulfur batteries and improve the conversion rate of lithium polysulfides to lithium sulfides. In particular, it was confirmed that Example 3, using carbon nanotubes, exhibited higher performance than Example 4, using reduced graphene oxide.

[0215] In addition, refer to Figure 6 and Figure 7The battery in Comparative Example 3, which uses a carbon composite material with a small specific surface area, few pores, and vanadium nitride particles formed on the surface of amorphous carbon as a positive electrode additive, has increased resistance due to the low conductivity of amorphous carbon. Conversely, the performance of Comparative Example 3 is lower than that of Comparative Example 5, which uses a positive electrode without vanadium nitride particles.

[0216] Reference Figure 8 and Figure 9 It was confirmed that the lithium-sulfur battery of Example 5 exhibited improved performance through overvoltage mitigation and the promotion of the conversion reaction. Therefore, it was confirmed that the performance of lithium-sulfur batteries can be improved by loading sulfur (S8) onto a carbon composite material containing vanadium nitride particles on a porous carbon material and using it as the positive electrode active material.

[0217] Although the invention has been described with reference to a limited number of embodiments and accompanying drawings, the invention is not limited thereto, and it will be apparent to those skilled in the art that various modifications and alterations can be made to it within the scope of the technical aspects of the invention and its appended claims and equivalents.

Claims

1. A positive electrode, said positive electrode comprising: Current collector; and A positive electrode active material layer is formed on at least one surface of the current collector and comprises a positive electrode active material, a binder, and a positive electrode additive. in, The positive electrode active material contains sulfur-containing compounds, and The positive electrode additive comprises a carbon composite material, which includes: Porous carbon materials that are at least partially crystalline; and Vanadium nitride particles formed on the surface of the porous carbon material.

2. The positive electrode according to claim 1, wherein, The specific surface area of ​​the carbon composite material is 250 m². 2 / g or more.

3. The positive electrode according to claim 1, wherein, The specific surface area of ​​the carbon composite material is 280 m². 2 / g to 500 m 2 / g.

4. The positive electrode according to claim 1, wherein, The specific surface area of ​​the carbon composite material is 300 m². 2 / g to 400 m 2 / g.

5. The positive electrode according to claim 1, wherein, The carbon composite material has a pore volume of 1.0 cm³. 3 / g or more.

6. The positive electrode according to claim 1, wherein, The carbon composite material has a pore volume of 1.2 cm³. 3 / g to 3.0 cm 3 / g.

7. The positive electrode according to claim 1, wherein, The carbon composite material has a pore volume of 1.4 cm³. 3 / g to 2.5 cm 3 / g.

8. The positive electrode according to claim 1, wherein, The average pore size of the carbon composite material is greater than 10 nm.

9. The positive electrode according to claim 1, wherein, The average pore size of the carbon composite material is 15 nm to 100 nm.

10. The positive electrode according to claim 1, wherein, The intensity ratio I in the Raman spectrum of the carbon composite material D / I G The ratio is below 2.

0.

11. The positive electrode according to claim 1, wherein, The carbon composite material has a crystallinity of over 70%.

12. The positive electrode according to claim 1, wherein, The average particle size of the vanadium nitride particles is less than 200 nm.

13. The positive electrode according to claim 1, wherein, The vanadium nitride particles have an average particle size of 1 nm to 190 nm.

14. The positive electrode according to claim 1, wherein, The vanadium nitride particles have an average particle size of 2 nm to 180 nm.

15. The positive electrode according to claim 1, wherein, Based on 100 parts by weight of the carbon composite material, the content of the vanadium nitride particles is from 3 parts by weight to 50 parts by weight.

16. The positive electrode according to claim 1, wherein, Based on 100 parts by weight of the carbon composite material, the content of the vanadium nitride particles is from 10 parts by weight to 40 parts by weight.

17. The positive electrode according to claim 1, wherein, Based on 100 parts by weight of the carbon composite material, the content of the vanadium nitride particles is 20 to 30 parts by weight.

18. The positive electrode according to claim 1, wherein, At least a portion of the surface of the vanadium nitride is coated with a carbon layer.

19. The positive electrode according to claim 18, wherein, The thickness of the carbon layer is less than 5 nm.

20. The positive electrode according to claim 18, wherein, The carbon layer consists of 1 to 5 layers, and the total thickness of the carbon layer is less than 5 nm.

21. The positive electrode according to claim 1, wherein, The porous carbon material comprises carbon nanotubes (CNTs), reduced graphene oxide (rGO), or mixtures thereof.

22. The positive electrode according to claim 1, wherein, The porous carbon material comprises multiple micropores on its outer surface and inside, with the average diameter of the micropores ranging from 1 nm to 200 nm.

23. The positive electrode according to claim 1, wherein, The porosity of the porous carbon material is in the range of 10% to 90% of the total volume of the porous carbon material.

24. The positive electrode according to claim 1, wherein, The porous carbon material has a pore volume of 1 cm³. 3 / g to 20 cm 3 Within the range of / g.

25. The positive electrode according to claim 1, wherein, The porous carbon material has a pore volume of 1 cm³. 3 / g to 10 cm 3 Within the range of / g.

26. The positive electrode according to claim 1, wherein, The average particle size D of the porous carbon material 50 The range is from 10 μm to 80 μm.

27. The positive electrode according to claim 1, wherein, The porous carbon material has a specific surface area of ​​100 m². 2 / g to 2000m 2 / g.

28. The positive electrode according to claim 1, wherein, The porous carbon material is doped with at least one element selected from nitrogen, oxygen, or phosphorus.

29. The positive electrode according to claim 1, wherein, The porous carbon material comprises at least one selected from the following: carbon nanotubes (CNT), graphene, graphene oxide (GO), reduced graphene oxide (rGO), carbon black, graphite, graphite nanofibers (GNF), carbon nanofibers (CNF), activated carbon fibers (ACF), natural graphite, artificial graphite, expandable graphite, activated carbon, or fullerene.

30. The positive electrode according to claim 1, wherein, The sulfur-containing compound comprises at least one selected from the following: inorganic sulfur S8; Li2S n , where n≥1; disulfide compounds; and organosulfur compounds.

31. The positive electrode according to claim 1, wherein, Based on a total of 100 parts by weight of the positive electrode active material layer, the content of the positive electrode additive is from 0.01 parts by weight to 30 parts by weight.

32. The positive electrode according to claim 1, wherein, Based on a total of 100 parts by weight of the positive electrode active material layer, the content of the positive electrode additive is from 0.5 parts by weight to 20 parts by weight.

33. The positive electrode according to claim 1, wherein, Based on a total of 100 parts by weight of the positive electrode active material layer, the content of the positive electrode additive is from 1 part by weight to 10 parts by weight.

34. A battery comprising: Positive electrode, negative electrode, membrane between the positive and negative electrodes, and electrolyte. in, The positive electrode is the positive electrode according to claim 1.

35. The battery according to claim 34, wherein, The battery is a lithium-sulfur battery.

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