Carbon nanotube and method for manufacturing same

Abstract

The present invention relates to a novel carbon nanotube having excellent electrical conductivity while exhibiting excellent storage and transportation efficiency, a method for manufacturing the carbon nanotube, a carbon nanotube dispersion, an electrode structure comprising the carbon nanotube, and a secondary battery comprising the carbon nanotube.

Description

Carbon nanotubes and their manufacturing methods

[0001] The present invention relates to a novel carbon nanotube having excellent electrical conductivity and excellent storage and transport efficiency, a method for producing the carbon nanotube, a carbon nanotube dispersion, an electrode structure including a carbon nanotube, and a secondary battery including a carbon nanotube.

[0002] Carbon nanomaterials are classified into fullerene, carbon nanotubes (CNT), graphene, and graphite nanoplates depending on their shape. Among these, carbon nanotubes are nanocarbon materials formed by rolling graphene sheets, in which one carbon atom is bonded to three other carbon atoms to form a hexagonal honeycomb structure, into a cylindrical shape with a diameter in the nanometer range. Carbon nanotubes have excellent electrical conductivity, high strength, and excellent thermal conductivity, and thus have diverse potential applications. In particular, they are being actively researched for use as electrode conductive materials in electronic devices, composite materials, and energy storage devices, for example.

[0003]

[0004] Carbon nanotubes are cutting-edge materials with diverse applications, including electronic devices and energy storage devices. These applications demand both superior electrical performance and efficient storage and transport properties. While carbon nanotubes inherently possess excellent electrical conductivity, in actual powder form, agglomeration and clumping often reduce connectivity between carbon nanotubes and reduce surface reactivity, preventing them from achieving the expected electrical conductivity. Furthermore, carbon nanotubes generally have a low bulk density, limiting the amount that can be stored per volume. This limits their storage and transport efficiency.

[0005]

[0006] In particular, electrical conductivity and storage / transport efficiency are known to be in a trade-off relationship. Lowering bulk density to increase electrical conductivity reduces storage and transport efficiency. Conversely, increasing bulk density to improve storage and transport efficiency can exacerbate aggregation, which can reduce electrical conductivity. Therefore, the development of carbon nanotubes that can simultaneously satisfy these conflicting characteristics of electrical conductivity and storage / transport efficiency is needed.

[0007]

[0008] Prior art literature

[0009] [Patent Document 1] Republic of Korea Publication No. 10-2017-0111973

[0010] [Patent Document 2] Republic of Korea Publication No. 10-2014-0032349

[0011]

[0012] The present invention aims to provide a novel carbon nanotube having excellent electrical conductivity and excellent storage and transport efficiency, a method for producing the carbon nanotube, a carbon nanotube dispersion, an electrode structure including the carbon nanotube, and a secondary battery including the carbon nanotube.

[0013] One aspect of the present invention is

[0014] A carbon nanotube satisfying the following equation 1 is provided.

[0015] [Formula 1]

[0016]

[0017] (In the above equation 1,

[0018] BD is a number representing the bulk density (unit: kg / m³) of carbon nanotubes,

[0019] BET is a number that represents the specific surface area of ​​carbon nanotubes (BET specific surface area, unit: m² / g).

[0020] P is a number indicating the purity of carbon nanotubes (unit: wt%),

[0021] R is a number representing the powder resistance of carbon nanotubes (unit: mΩ·cm),

[0022] y is 8.2 to 9.0.)

[0023] In the above equation 1, y can be in the range of 8.3 to 9.0.

[0024] The bulk density of the above carbon nanotubes is 70 to 160 kg / m 3 It could be.

[0025] The specific surface area of ​​the above carbon nanotubes is 220 to 310 m 2 / g may be.

[0026] The powder resistance of the above carbon nanotube may be 6 to 12 mΩ·cm.

[0027] The purity of the above carbon nanotubes may be 94 to 99.9 wt%.

[0028]

[0029] Another aspect of the present invention is

[0030] (S1) A step of preparing a catalyst by mixing an active ingredient including cobalt, molybdenum, and citric acid and a catalyst support;

[0031] (S2) A step of filling the catalyst into the reactor;

[0032] (S3) a step of heating the reactor; and

[0033] (S4) A step of injecting carbon source gas into the above reactor;

[0034] A method for manufacturing a carbon nanotube satisfying the following formula 1 is provided:

[0035] [Formula 1]

[0036]

[0037] (In the above equation 1,

[0038] BD is a number representing the bulk density (unit: kg / m³) of carbon nanotubes,

[0039] BET is a number that represents the specific surface area of ​​carbon nanotubes (BET specific surface area, unit: m² / g).

[0040] P is a number indicating the purity of carbon nanotubes (unit: wt%),

[0041] R is a number representing the powder resistance of carbon nanotubes (unit: mΩ·cm),

[0042] y is 8.2 to 9.0.)

[0043] The molar ratio of citric acid to molybdenum (CA / Mo) in the catalyst manufactured in the above step (S1) may be 0 or more and less than 2.4. Preferably, the molar ratio of citric acid to molybdenum may be 0 to 1.6.

[0044] The molar ratio of molybdenum to cobalt (Mo / Co, molybdenum to cobalt molar ratio) in the catalyst manufactured in the above step (S1) may be 0.1 or more and less than 0.7. Preferably, the molar ratio of molybdenum to cobalt may be 0.1 to 0.5.

[0045] In the above step (S1), the catalyst support may include one or more metal oxides or metal hydroxides selected from the group consisting of hydrotalcite, alumina (Al2O3), magnesium peroxide (MgO2), magnesium oxide (MgO), and boehmite.

[0046] In the above step (S1), the catalyst precursor in which the active ingredient and the catalyst support are mixed can be calcined at 350°C to 750°C.

[0047]

[0048] Another aspect of the present invention is

[0049] A carbon nanotube dispersion comprising carbon nanotubes according to one aspect of the present invention is provided.

[0050]

[0051] Another aspect of the present invention is

[0052] An electrode structure manufactured using the above carbon nanotube dispersion is provided.

[0053]

[0054] Another aspect of the present invention is

[0055] An electrode structure including a carbon nanotube according to one aspect of the present invention is provided.

[0056]

[0057] Another aspect of the present invention is

[0058] A secondary battery including an electrode structure manufactured using the above carbon nanotube dispersion is provided.

[0059] The carbon nanotubes according to the present invention have a high bulk density, resulting in a large storage capacity per volume, and excellent flowability and handleability in powder form, which can dramatically improve transport and storage efficiency. Furthermore, their low powder resistance facilitates smooth electron transfer between carbon nanotubes, thereby maintaining high electrical conductivity. In particular, the carbon nanotubes of the present invention have a high purity, minimizing deterioration and degradation of electrical properties due to impurities. Furthermore, their large surface area enhances reactivity at the interface, making them highly useful as electrode materials.

[0060] This combination of properties effectively overcomes the problems of conventional carbon nanotubes, such as reduced conductivity due to aggregation and clumping, and reduced volume utilization due to low density. Therefore, the carbon nanotubes of the present invention not only exhibit excellent performance in various fields of application, such as electrode additives for energy storage devices such as lithium-ion batteries and supercapacitors, antistatic coating agents, fillers for conductive composite materials, EMI shielding materials, and fuel cells, but can also provide high efficiency and economy in industrial-scale production, transportation, and processing processes.

[0061] As a result, the carbon nanotube according to the present invention has high industrial value as a high-performance material that overcomes the trade-off between electrical performance and process efficiency, and can be utilized as a key component in the development of various high-functionality electronic materials and energy materials.

[0062] Hereinafter, the present invention will be described in more detail.

[0063] Terms or words used in this specification and claims should not be interpreted as limited to their usual or dictionary meanings, but should be interpreted as meanings and concepts that conform to the technical idea of ​​the present invention, based on the principle that the inventor can appropriately define the concept of the term to explain his or her own invention in the best way.

[0064] The term “carbon nanotube (CNT)” used herein includes a structure composed of one or more carbon nanotube units, and may include not only a single CNT (SWCNT, DWCNT or MWCNT), but also a secondary structure in which these CNTs are assembled in whole or in part in a bundle form or in a group form in which multiple CNTs are mixed. The carbon nanotube units are sp 2A graphene sheet, which is a flat carbon atomic layer in a hexagonal honeycomb structure with a bonding structure, has a cylindrical rolled structure with a diameter of nanometers. At this time, the graphene sheet can exhibit the properties of a conductor or a semiconductor depending on the rolling angle (or chiral angle) and structure. Carbon nanotubes can be classified into single-walled carbon nanotubes (SWCNT, Single-Walled Carbon Nanotube), double-walled carbon nanotubes (DWCNT, Double-Walled Carbon Nanotube), and multi-walled carbon nanotubes (MWCNT, Multi-Walled Carbon Nanotube) depending on the number of layers forming the wall, and generally, the thinner the wall thickness, the lower the resistance. The bundled carbon nanotube according to the present invention may include one or more of single-walled, double-walled, and multi-walled carbon nanotubes, or two or more.

[0065] The term “bundle type” as used herein, unless otherwise stated, refers to a secondary shape in the form of a bundle or rope in which a plurality of carbon nanotube units are arranged in parallel with their longitudinal axes substantially in the same orientation, or are arranged and then twisted or entangled.

[0066] The term “bulk density” used herein refers to the mass occupied by carbon nanotubes (powder) in a specific volume, which represents the density based on the entire volume, including not only the interior of the carbon nanotube particles but also the porosity between particles. The bulk density of carbon nanotubes is expressed in units of g / cm³ or kg / m³ and has a significant impact on the productivity of carbon nanotubes. In general, carbon nanotubes with low bulk density have a large volume and weak inter-particle bonding, which causes the powder to easily swell or disperse. Due to these characteristics, separate compression or molding processes are required for transport and handling, which increases production time and cost and may further negatively affect the dispersibility and uniformity of the carbon nanotubes. On the other hand, the carbon nanotubes according to the present invention have a high bulk density, so they can be efficiently transported and delivered without a separate compression process during transportation and handling.

[0067]

[0068] 1. Carbon nanotubes

[0069] One aspect of the present invention provides a carbon nanotube satisfying the following equation 1.

[0070] [Formula 1]

[0071]

[0072] (In the above equation 1,

[0073] BD is a number representing the bulk density (unit: kg / m³) of carbon nanotubes,

[0074] BET is a number that represents the specific surface area of ​​carbon nanotubes (BET specific surface area, unit: m² / g).

[0075] P is a number indicating the purity of carbon nanotubes (unit: wt%),

[0076] R is a number representing the powder resistance of carbon nanotubes (unit: mΩ·cm),

[0077] y is 8.2 to 9.0.)

[0078] In the above formula 1, y may be 8.2 to 9.0. Specifically, in the above formula 1, y may be 8.2 or more, 8.25 or more, 8.3 or more, 8.35 or more, or 8.4 or more, and 9.0 or less, 8.95 or less, or 8.9 or less. For example, in the above formula 1, y may be 8.2 to 9.0, 8.25 to 9.0, 8.3 to 9.0, 8.3 to 8.95, 8.35 to 8.95, 8.4 to 8.95, or 8.4 to 8.9. Carbon nanotubes manufactured within this range simultaneously satisfy high bulk density and specific surface area while exhibiting low powder resistance, and have physical properties optimized as a conductive material. This significantly improves the dispersibility of the conductive material dispersion, enabling stable and uniform dispersion. This improved dispersibility can maximize electrode performance and enhance electrochemical performance. Furthermore, carbon nanotubes satisfying the y value within the above range are expected to offer superior conductivity and enhanced mechanical stability, which can enable efficient energy storage and delivery in batteries and other electronic devices.

[0079] The bulk density of the above carbon nanotubes is 70 to 160 kg / m 3 It could be. The bulk density of the above carbon nanotube is specifically 70 kg / m 3 Above, 71 kg / m 3 Above, 72 kg / m 3 Above, 73 kg / m 3 Above, 74 kg / m 3 Above, 75 kg / m 3 Above, 76 kg / m 3 Above, 77 kg / m 3 Above, 78 kg / m3 or more than 79 kg / m 3 It can be more than 160 kg / m 3 Below 155 kg / m 3 Below 150 kg / m 3 Below 145 kg / m 3 Below 140 kg / m 3 Below, 135 kg / m 3 Below 130 kg / m 3 Below 125 kg / m 3 or less, or 120 kg / m 3 It may be less than or equal to 10 ... 3 Up to 160 kg / m 3 , 71 kg / m 3 Up to 155 kg / m 3 , 72 kg / m 3 Up to 150 kg / m 3 , 73 kg / m 3 Up to 150 kg / m 3 , 74 kg / m 3 Up to 145 kg / m 3 , 75 kg / m 3 Up to 140 kg / m 3 , 76 kg / m 3 Up to 135 kg / m 3 , 77 kg / m 3 Up to 130 kg / m 3 , 78 kg / m 3 Up to 125 kg / m 3 , or 79 kg / m 3 Up to 120 kg / m 3 It could be. The bulk density of the above carbon nanotube is 70 kg / m 3If it is less than 10 ...

[0080] The specific surface area of ​​the above carbon nanotube is 220 m 2 / g to 310 m 2 / g can be. The specific surface area of ​​the above carbon nanotube is 220 m 2 If the specific surface area of ​​the carbon nanotube is less than / g, the electrical conductivity may be reduced, making it unsuitable as a conductive material for secondary batteries, and if the specific surface area of ​​the carbon nanotube is less than 310 m 2 / g, the carbon nanotubes may clump or form aggregates, which may reduce the dispersibility. The specific surface area of ​​the carbon nanotubes can be measured by a method commonly used in this technical field. For example, the specific surface area of ​​the carbon nanotubes measured by the BET (Brunauer-Emmett-Teller) method can be calculated by obtaining the nitrogen gas adsorption amount at liquid nitrogen temperature (77K) using BELSORP-mini II of BEL Japan.

[0081] The powder resistance of the carbon nanotube may be 6 mΩ·cm to 12 mΩ·cm. Specifically, the powder resistance of the carbon nanotube may be 6 mΩ·cm or more, 6.5 mΩ·cm or more, 7 mΩ·cm or more, 7.5 mΩ·cm or more, 8 mΩ·cm or more, 8.5 mΩ·cm or more, 9 mΩ·cm or more, 9.5 mΩ·cm or more, or 10 mΩ·cm or more, and 12 mΩ·cm or less, 11.9 mΩ·cm or less, 11.8 mΩ·cm or less, 11.7 mΩ·cm or less, 11.6 mΩ·cm or less, 11.5 mΩ·cm or less, 11.4 mΩ·cm or less, 11.3 mΩ·cm or less, or 11.2 mΩ·cm or less. For example, the powder resistance of the carbon nanotube may be 6 mΩ·cm to 12 mΩ·cm, 6.5 mΩ·cm to 11.9 mΩ·cm, 7 mΩ·cm to 11.8 mΩ·cm, 7.5 mΩ·cm to 11.7 mΩ·cm, 8 mΩ·cm to 11.6 mΩ·cm, 8.5 mΩ·cm to 11.5 mΩ·cm, 9 mΩ·cm to 11.4 mΩ·cm, 9.5 mΩ·cm to 11.3 mΩ·cm, or 10 mΩ·cm to 11.2 mΩ·cm. When the powder resistance of the carbon nanotube is less than 6 mΩ·cm, the carbon nanotube may have excessively high conductivity, which may cause electrical interference or short-circuit problems. When the powder resistance of the carbon nanotube exceeds 12 mΩ·cm, the electrical conductivity may be reduced, making it unsuitable as a conductive material for secondary batteries. The powder resistance of the carbon nanotube can be measured by a method commonly used in this technical field. For example, the powder resistance of the carbon nanotube can be calculated by measuring the resistance according to pressure when the compression density is 1 g / cc using the MCP-PD51 equipment of Nittoseiko Analytech Co., Ltd.

[0082] The purity of the carbon nanotubes may be 94 to 99.9 wt%. Specifically, the purity of the carbon nanotubes may be 94 wt% or more, 94.1 wt% or more, 94.2 wt% or more, 94.3 wt% or more, 94.4 wt% or more, 94.5 wt% or more, 94.6 wt% or more, 94.7 wt% or more, 94.8 wt% or more, 94.9 wt% or more, or 95 wt% or more. For example, the purity of the carbon nanotubes may be 94 wt% to 99.9 wt%, 94.1 wt% to 99.9 wt%, 94.2 wt% to 99.9 wt%, 94.3 wt% to 99.9 wt%, 94.4 wt% to 99.9 wt%, 94.5 wt% to 99.9 wt%, 94.6 wt% to 99.9 wt%, 94.7 wt% to 99.9 wt%, 94.8 wt% to 99.9 wt%, 94.9 wt% to 99.9 wt%, or 95 wt% to 99.9 wt%. The purity of the carbon nanotubes refers to the content of carbon nanotubes remaining after impurities in the carbon nanotubes are removed, and can be calculated based on the weight change obtained by burning the carbon nanotubes:

[0083] Purity (%) = {(Carbon nanotube weight - Carbon nanotube weight after combustion) / Carbon nanotube weight} x 100

[0084] According to one aspect of the present invention, carbon nanotubes exhibit optimized physical properties as a conductive material, with bulk density, specific surface area, purity, and powder resistivity regulated to satisfy specific relationships. In particular, satisfying these relationships significantly improves dispersibility within a conductive material dispersion, enabling stable and uniform dispersion. This maximizes electrode performance and is expected to enhance electrochemical properties.

[0085] The carbon nanotube according to one aspect of the present invention, i.e., the carbon nanotube satisfying the conditions of the above formula 1, can be obtained by controlling the manufacturing raw materials, catalyst, manufacturing conditions, etc. This will be described in detail below.

[0086]

[0087] 2. Method for manufacturing carbon nanotubes

[0088] Another aspect of the present invention is

[0089] (S1) A step of preparing a catalyst by mixing an active ingredient including cobalt, molybdenum, and citric acid and a catalyst support;

[0090] (S2) A step of filling the catalyst into the reactor;

[0091] (S3) a step of heating the reactor; and

[0092] (S4) A step of injecting carbon source gas into the above reactor;

[0093] and provides a method for manufacturing a carbon nanotube satisfying the following equation 1.

[0094] [Formula 1]

[0095]

[0096] (In the above equation 1,

[0097] BD is a number representing the bulk density (unit: kg / m³) of carbon nanotubes,

[0098] BET is a number that represents the specific surface area of ​​carbon nanotubes (BET specific surface area, unit: m² / g).

[0099] P is a number indicating the purity of carbon nanotubes (unit: wt%),

[0100] R is a number representing the powder resistance of carbon nanotubes (unit: mΩ·cm),

[0101] y is 8.2 to 9.0.)

[0102] In the above step (S1), cobalt precursors may include, but are not limited to, cobalt nitrate hexahydrate (Co(NO₃)₂·6H₂O), cobalt chloride dihydrate (CoCl₂·2H₂O), cobalt sulfate heptahydrate (CoSO₄·7H₂O), cobalt acetate tetrahydrate (Co(CH₃COO)₂·4H₂O), cobalt oxalate dihydrate (CoC₂O₄·2H₂O), cobalt acetylacetone complex (Co(acac)₂), cobalt carbonate (CoCO₃), or cobalt oxide (Co₃O₄).

[0103] In the above step (S1), ammonium molybdate ((NH₄)MoO₂₄·4H₂O), sodium molybdate (Na₂MoO₄), potassium molybdate (K₂MoO₄), molybdenum trioxide (MoO₃), ammonium molybdate ((NH₄)₂MoO₄), molybdenum oxochloride (MoO₂Cl₂), molybdenum oxoacetylacetone (MoO₂(acac)₂), molybdenum trichloride (MoCl₃), or molybdenum oxofluoride (MoOF₄) may be used as a precursor of molybdenum, but is not limited thereto.

[0104] The molar ratio of citric acid to molybdenum (CA / Mo) in the catalyst manufactured in the above step (S1) may be 0 or more and less than 2.4. For example, the molar ratio of citric acid to molybdenum may be 0 to 2.3, 0 to 2.2, 0 to 2.1, 0 to 2.0, 0 to 1.9, 0 to 1.8, 0 to 1.7, or 0 to 1.6. Preferably, the molar ratio of citric acid to molybdenum may be 0 to 1.6. When the molar ratio of citric acid to molybdenum is 2.4 or more, the specific surface area may excessively increase, the powder resistivity may exceed 12 mΩ·cm, and carbon nanotubes with reduced purity may be generated.

[0105] The molar ratio of molybdenum to cobalt (Mo / Co) in the catalyst manufactured in the above step (S1) may be 0.1 or more and less than 0.7. For example, the molar ratio of molybdenum to cobalt may be 0.1 to 0.6, or 0.1 to 0.5. Preferably, the molar ratio of molybdenum to cobalt may be 0.1 to 0.5. When the molar ratio of molybdenum to cobalt is 0.7 or more, the bulk density is 70 kg / m 3 Carbon nanotubes with a thickness of less than 10 μm can be manufactured.

[0106] In the above step (S1), a porous metal oxide may be used as the catalyst support. For example, the porous metal oxide may be at least one metal oxide or metal hydroxide selected from the group consisting of hydrotalcite, alumina (Al2O3), magnesium peroxide (MgO2), magnesium oxide (MgO), and boehmite.

[0107] In the above step (S1), the catalyst precursor in which the active ingredient and the catalyst support are mixed can be dried at 180°C to 200°C for 1 to 5 hours and then calcined for 30 minutes to 3 hours to form a catalyst. The calcination temperature can be 350 to 750°C. Specifically, the calcination temperature can be 350°C or higher, 360°C or higher, 370°C or higher, 380°C or higher, 390°C or higher, or 400°C or higher, and can be 750°C or lower, 700°C or lower, 650°C or lower, 600°C or lower, 550°C or lower, or 500°C or lower. For example, the firing temperature may be 350°C to 750°C, 350°C to 700°C, 350°C to 650°C, 350°C to 600°C, 350°C to 550°C, 360°C to 540°C, 370°C to 530°C, 380°C to 520°C, 390°C to 510°C, or 400°C to 500°C. When the firing temperature is in the range of 350°C to 750°C, carbon nanotubes having a powder resistivity of 12 mΩ·cm or less can be produced. On the other hand, when the firing temperature is less than 350°C, carbon nanotubes having a powder resistivity exceeding 12 mΩ·cm can be produced.

[0108] In the above step (S2), the reactor may include a chemical vapor deposition reactor, a fixed bed reactor or a fluidized bed reactor.

[0109] The step of heating the reactor in the above step (S3) may be performed at a temperature of 600 to 800°C. For example, the step of heating the reactor may be performed at a temperature of 600°C to 800°C, 610°C to 790°C, 620°C to 780°C, 630°C to 770°C, 640°C to 760°C, or 650°C to 750°C.

[0110] In the above step (S4), the carbon source gas is a carbon-containing gas that can be decomposed at high temperatures to form carbon nanotubes, and an aliphatic alkane, an aliphatic alkene, an aliphatic alkyne, or an aromatic compound may be used. For example, the carbon source gas may be at least one selected from the group consisting of ethane, ethylene, acetylene, ethanol, methanol, acetone, carbon monoxide, propane, butane, benzene, cyclohexane, propylene, butene, isobutene, toluene, xylene, cumene, ethylbenzene, naphthalene, phenanthrene, anthracene, formaldehyde, and acetaldehyde.

[0111]

[0112] 3. Carbon nanotube dispersion

[0113] Another aspect of the present invention is

[0114] A carbon nanotube dispersion liquid including a carbon nanotube satisfying the following equation 1 and a dispersion medium is provided.

[0115] [Formula 1]

[0116]

[0117] (In the above equation 1,

[0118] BD is a number representing the bulk density (unit: kg / m³) of carbon nanotubes,

[0119] BET is a number that represents the specific surface area of ​​carbon nanotubes (BET specific surface area, unit: m² / g).

[0120] P is a number indicating the purity of carbon nanotubes (unit: wt%),

[0121] R is a number representing the powder resistance of carbon nanotubes (unit: mΩ·cm),

[0122] y is 8.2 to 9.0.)

[0123] The above dispersion medium may be at least one selected from the group consisting of N-methylpyrrolidone, pyridine, dimethylaminobenzene, and diethylaminobenzene.

[0124] The content of carbon nanotubes in the above dispersion may be 0.05 to 10 wt%. Within the above range, sufficient electrical conductivity is secured while suppressing aggregation of carbon nanotubes, thereby maintaining an appropriate viscosity, thereby advantageously achieving excellent processability of the dispersion.

[0125]

[0126] Another aspect of the present invention is

[0127] An electrode structure manufactured including the above carbon nanotube dispersion is provided. The electrode structure may be, for example, a secondary battery electrode structure.

[0128]

[0129] Another aspect of the present invention is

[0130] An electrode structure including the above carbon nanotubes is provided. The carbon nanotubes satisfy the following equation 1 and can exist in the electrode structure in a dried solid state, and the electrode structure can be, for example, a secondary battery electrode structure.

[0131] [Formula 1]

[0132]

[0133] (In the above equation 1,

[0134] BD is a number representing the bulk density (unit: kg / m³) of carbon nanotubes,

[0135] BET is a number that represents the specific surface area of ​​carbon nanotubes (BET specific surface area, unit: m² / g).

[0136] P is a number indicating the purity of carbon nanotubes (unit: wt%),

[0137] R is a number representing the powder resistance of carbon nanotubes (unit: mΩ·cm),

[0138] y is 8.2 to 9.0.)

[0139] In addition, the carbon nanotubes may be included in the electrode structure, for example, as a conductive material. The carbon nanotubes exhibit excellent dispersibility in the conductive material dispersion, thereby enhancing the uniformity and stability of the electrode slurry, thereby contributing to improved electrochemical performance.

[0140]

[0141] Another aspect of the present invention is

[0142] A secondary battery comprising an electrode structure manufactured by including the above-described carbon nanotube dispersion is provided. The secondary battery can stably exhibit excellent discharge capacity, output characteristics, and capacity retention due to the uniform dispersion of carbon nanotubes within the electrode structure. As a result, the secondary battery can be usefully used in portable devices such as mobile phones, laptop computers, and digital cameras, and electric vehicles such as hybrid electric vehicles (HEVs).

[0143] Hereinafter, the present invention will be described in more detail with examples and experimental examples to specifically explain the present invention. However, the present invention is not limited to these examples and experimental examples. The examples according to the present invention can be modified in various different forms, and the scope of the present invention should not be construed as being limited to the examples described below. The examples of the present invention are provided to more fully explain the present invention to those of average skill in the art.

[0144]

[0145] <Catalyst Manufacturing Example>

[0146] (NH₄)6Mo7O as a molybdenum precursor 24·4H2O was first dissolved in water, then citric acid (CA), a multicarboxylic acid, was added as a complexing agent, followed by Co(NO3)2·6H2O, a cobalt precursor, to prepare a precursor solution. The catalyst precursor composition was sufficiently stirred and then supported on hydrotalcite, a support. Subsequently, it was dried in an oven at 190°C for 4 hours, and then calcined for 1 hour at the temperature shown in Table 1 below, to prepare a catalyst. The molar ratio of citric acid to molybdenum (CA / Mo) and the molar ratio of molybdenum to cobalt (Mo / Co) confirmed in the final manufactured catalyst are as shown in Table 1 below.

[0147] Catalyst CA / MoMo / Co Calcination temperature (℃) Manufacturing example 100.5500 Manufacturing example 20.40.5500 Manufacturing example 30.80.5500 Manufacturing example 41.20.5500 Manufacturing example 50.40.3500 Manufacturing example 60.80.3500 Manufacturing example 71.20.3500 Manufacturing example 81.60.3500 Manufacturing example 91.20.1500 Manufacturing example 102.40.1500 Manufacturing example 1140.1500 Manufacturing example 1260.1500 Manufacturing example 131.20.7500 Manufacturing example 140.150.3300 Manufacturing example 150.150.3400 Manufacturing example 160.150.3500

[0148] <Examples and Comparative Examples>

[0149] Carbon nanotubes were produced using the catalyst prepared in the above catalyst preparation example. Specifically, 6.4 g of the prepared catalyst was charged into a fluidized bed reactor, nitrogen gas was injected into the reactor at 3,000 sccm, and the internal temperature of the reactor was heated to 690°C. Thereafter, ethylene gas, a carbon source gas, was injected at 1,000 sccm, and the reaction was continued for 120 minutes to produce carbon nanotubes. The catalysts used in the examples and comparative examples are shown in Table 2 below.

[0150] Catalyst used in the classification Catalyst characteristics CA / MoMo / Co Calcination temperature (℃) Example 1 Manufacturing example 100.5500 Example 2 Manufacturing example 20.40.5500 Example 3 Manufacturing example 30.80.5500 Example 4 Manufacturing example 41.20.5500 Example 5 Manufacturing example 50.40.3500 Example 6 Manufacturing example 60.80.3500 Example 7 Manufacturing example 71.20.3500 Example 8 Manufacturing example 91.20.1500 Example 9 Manufacturing example 150.150.3400 Example 10 Manufacturing example 160.150.3500 Example 11 Manufacturing example 81.60.3500 Comparative example 1 Manufacturing example 102.40.1500Comparative Example 2Manufacturing Example 1140.1500Comparative Example 3Manufacturing Example 1260.1500Comparative Example 4Manufacturing Example 131.20.7500Comparative Example 5Manufacturing Example 140.150.3300

[0151] <Experimental Example>

[0152] Confirmation of the physical properties of carbon nanotubes

[0153] The bulk density, specific surface area, powder resistivity, and purity of the carbon nanotubes manufactured according to the above examples and comparative examples were measured by the following methods. All measurements were performed under room temperature (23 ± 2°C), atmospheric pressure (approximately 1 atm), and relative humidity of 40 to 60% unless otherwise stated.

[0154]

[0155] 1) Bulk Density

[0156] The measurement was performed using a 50 ml stainless steel (SUS) quantitative cup (Ray-Ran) according to ASTM D1895. When measuring, the CNT powder was filled into the quantitative cup by free-fall from a height of about 5 cm from the top of the cup, and the total weight of the powder filled in a natural state without overflowing the top of the cup was measured using an electronic balance (Mettler Toledo, Balance XPR204V, precision: ± 0.0001 g), and this was divided by the volume of the cup (50 ml) to convert it to bulk density (kg / m³). The measurement was repeated three times, and the average value was used as the final bulk density.

[0157] 2) Specific Surface Area

[0158] Nitrogen gas adsorption isotherm was measured at liquid nitrogen temperature (77 K) using BELSORP-mini II equipment from BEL Japan, and the specific surface area was calculated according to the BET (Brunauer-Emmett-Teller) method. Before measurement, the sample was vacuum-dried at 150°C for more than 90 minutes, and the equipped sample chamber was 10 - It was maintained at a vacuum of less than ²Pa.

[0159] 3) Powder Resistivity

[0160] Density-Volume Resistivity mode was used for measurement using Nittoseiko Analytech's MCP-PD51 equipment (maximum load 20 kN, probe volume 20 × 50 mm, 4-point probe). 0.5–5 g of CNT powder was weighed and filled into the measurement cell between the electrodes. A hydraulic pump was used to apply a total of five loads of 4, 8, 12, 16, and 20 kN, and the electrical resistance at each load was measured. The powder resistivity at 1 g / cc was then calculated through interpolation.

[0161] 4) Purity

[0162] After the reaction was completed, the CNT powder was heated to 750°C for 2 hours, maintained for 4 hours, and burned. The purity was calculated based on the weight change.

[0163] Purity (%) = {(Carbon nanotube weight - Carbon nanotube weight after combustion) / Carbon nanotube weight} x 100

[0164] 5) [Formula 1]

[0165]

[0166] (In the above equation 1, BD is a number representing the bulk density (unit: kg / m³) of the carbon nanotube, BET is a number representing the specific surface area (BET specific surface area, unit: m² / g) of the carbon nanotube, P is a number representing the purity (unit: wt%) of the carbon nanotube, R is a number representing the powder resistance (unit: mΩ·cm) of the carbon nanotube, and y is 8.2 to 9.0.)

[0167] The measured physical properties and whether Equation 1 is satisfied are shown in Table 3 below.

[0168] Bulk density (kg / m) 3 )Specific surface area (m 2 / g) Purity (wt%) Powder resistance (mΩ·cm) (BD × BET × (P / (100-P))) / R²y Formula 1 Example 1 99.222 496.110.74782.455 2598.472709O Example 2 94.425 9.695.911.24569.570 5578.427 175O Example 3 80.827 5.996.810.56 116.5966 448.718761O Example 4 79.828 5.396.510.85 381.66 20378.590 753O Example 598.2245.495.710.94514.1556798.414973O Example 6108.3282.595.510.65778.6452778.661925O Example 783.3285.696.610.66015.7486658.702136O Example 8111.2274.89510.65167.2965478.550105O Example 9114.3238.896.210.66149.7901678.724173O Example 10102.2234.796.1105910.480198.684482O Example 1188.2308.796.810.87061.2743068.862380811O Comparative Example 1125.1281.292.312.82573.7340177.853113X Comparative Example 2126.3302.691.913.52379.223447.774529X Comparative Example 3130.8303.189.716.91208.8585587.097432X Comparative Example 461.2289.396.211.53389.1879268.128346X Comparison Example 5116.3242.29613.83549.8248278.174654X

[0169] As can be seen from the above Table 3, Examples 1 to 11 according to the present invention simultaneously satisfy the physical properties of bulk density of 70 kg / m³ or more, specific surface area of ​​220 to 310 m² / g, powder resistivity of 12 mΩ·cm or less, and purity of 94 wt% or more, and it was confirmed that the y values ​​calculated based on these parameters all fall within the range of Equation 1 (8.2 to 9.0). That is, Equation 1 of the present invention proves to function as an index that can select carbon nanotubes with excellent physical properties as a conductive material by defining an optimal condition range in which multiple characteristic values ​​(BD, BET, R, P) work harmoniously with each other. On the other hand, Comparative Examples 1 to 5 did not satisfy the range of Equation 1, and thus at least one parameter was outside the standard value. For example, Comparative Examples 1 to 3, in which the molar ratio of CA / Mo was 2.4 or more, exhibited low purity and high powder resistance exceeding 12 mΩ·cm, Comparative Example 4, in which Mo / Co was 0.7 or more, had a low bulk density of 61.2 kg / m³, and Comparative Example 5, in which the sintering temperature was 300°C, exhibited high powder resistance of 13.7 mΩ·cm.

[0170]

[0171] Therefore, the range (8.2 to 9.0) of Equation 1 according to the present invention is a quantitative index that comprehensively considers multiple major properties such as bulk density (BD), specific surface area (BET), powder resistivity (R), and purity (P), rather than a single property condition, and can be said to be a standard that scientifically presents the optimal conditions that can simultaneously secure the electrical performance and process suitability of carbon nanotubes. This range of Equation 1 goes beyond a simple comparison of properties and functions as a technical means that can quantitatively evaluate the balance between multiple characteristics that may be conflicting and select carbon nanotubes with excellent properties. This is a new approach that has not been proposed in the existing technology, and it is expected to be an industrially very useful technical standard for performance prediction and quality control of carbon nanotubes for conductive materials.

[0172] The carbon nanotube according to the present invention has high industrial value as a high-performance material that overcomes the trade-off between electrical performance and process efficiency, and can be utilized as a key component in the development of various high-functionality electronic materials and energy materials.

Claims

1. A carbon nanotube satisfying the following equation 1. [Formula 1] (In the above equation 1, BD is a number representing the bulk density (unit: kg / m³) of carbon nanotubes, BET is a number that represents the specific surface area of ​​carbon nanotubes (BET specific surface area, unit: m² / g). P is a number indicating the purity of carbon nanotubes (unit: wt%), R is a number representing the powder resistance of carbon nanotubes (unit: mΩ·cm), y is 8.2 to 9.0) 2. In paragraph 1, In the above formula 1, y is a carbon nanotube in the range of 8.3 to 9.

0.

3. In paragraph 1, The bulk density of the above carbon nanotubes is 70 to 160 kg / m 3 In, carbon nanotubes.

4. In paragraph 1, The specific surface area of ​​the above carbon nanotubes is 220 to 310 m 2 / g, carbon nanotubes.

5. In paragraph 1, A carbon nanotube having a powder resistance of 6 to 12 mΩ·cm.

6. In paragraph 1, A carbon nanotube having a purity of 94 to 99.9 wt%. 7.(S1) A step of preparing a catalyst by mixing an active ingredient including cobalt, molybdenum, and citric acid and a catalyst support; (S2) A step of filling the catalyst into the reactor; (S3) a step of heating the reactor; and (S4) A step of injecting carbon source gas into the above reactor; A method for manufacturing a carbon nanotube, which includes and satisfies the following formula 1. [Formula 1] (In the above equation 1, BD is a number representing the bulk density (unit: kg / m³) of carbon nanotubes, BET is a number that represents the specific surface area of ​​carbon nanotubes (BET specific surface area, unit: m² / g). P is a number indicating the purity of carbon nanotubes (unit: wt%), R is a number representing the powder resistance of carbon nanotubes (unit: mΩ·cm), y is 8.2 to 9.0) 8. In paragraph 7, A method for producing a carbon nanotube, wherein the molar ratio of citric acid to molybdenum (CA / Mo) in the catalyst produced in the above step (S1) is 0 or more and less than 2.

4.

9. In paragraph 7, A method for producing carbon nanotubes, wherein the molar ratio of citric acid to molybdenum (CA / Mo) in the catalyst produced in the above step (S1) is 0 to 1.

6.

10. In paragraph 7, A method for producing carbon nanotubes, wherein the molar ratio of molybdenum to cobalt (Mo / Co) in the catalyst produced in the above step (S1) is 0.1 or more and less than 0.

7.

11. In paragraph 7, A method for producing a carbon nanotube, wherein the molar ratio of molybdenum to cobalt (Mo / Co) in the catalyst produced in the above step (S1) is 0.1 to 0.

5.

12. In paragraph 7, A method for producing a carbon nanotube, wherein in the step (S1), the catalyst support comprises at least one metal oxide or metal hydroxide selected from the group consisting of hydrotalcite, alumina (Al2O3), magnesium peroxide (MgO2), magnesium oxide (MgO), and boehmite.

13. In paragraph 7, A method for producing carbon nanotubes, wherein a catalyst precursor in which an active ingredient and a catalyst support are mixed in the above step (S1) is calcined at 350°C to 750°C.

14. A carbon nanotube dispersion comprising a carbon nanotube according to any one of claims 1 to 6.

15. An electrode structure manufactured using a carbon nanotube dispersion according to Article 14.

16. An electrode structure comprising a carbon nanotube according to any one of claims 1 to 6.

17. A secondary battery comprising an electrode structure manufactured using a carbon nanotube dispersion according to Article 14.

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