Catalyst for producing carbon nanotubes and carbon nanotubes produced using same

Abstract

The present invention relates to a catalyst for manufacturing carbon nanotubes, and particularly, to a catalyst for manufacturing thin-walled carbon nanotubes, carbon nanotubes produced using the catalyst, a carbon nanotube dispersion, an electrode structure comprising the carbon nanotubes, and a secondary battery comprising the carbon nanotubes.

Description

Catalyst for manufacturing carbon nanotubes and carbon nanotubes manufactured using the same

[0001] The present invention relates to a catalyst for manufacturing carbon nanotubes, and more specifically, to a catalyst for manufacturing thin-walled carbon nanotubes, carbon nanotubes manufactured using said catalyst, a carbon nanotube dispersion, an electrode structure comprising carbon nanotubes, and a secondary battery comprising carbon nanotubes.

[0002] Carbon nanomaterials are classified into fullerene, carbon nanotube (CNT), graphene, and graphite nanoplate according to their shape. Among these, carbon nanotubes are nano carbon materials formed by rolling a graphene sheet, in which one carbon atom is bonded to three other carbon atoms to form a hexagonal honeycomb structure, into a cylindrical shape with a nanometer-sized diameter.

[0003] Carbon nanotubes possess excellent electrical conductivity, high strength, and outstanding thermal conductivity, making them highly promising for use in various application fields. In particular, their utilization as conductive materials for electrodes in electronic devices, composite materials, and energy storage devices is being actively researched.

[0004] Carbon nanotubes are classified into single-walled carbon nanotubes (SWCNTs), multi-walled carbon nanotubes (MWCNTs), and rope carbon nanotubes based on their structure. Each of these forms differs in electrical, mechanical, and thermal properties.

[0005] Among them, single-walled carbon nanotubes (SWCNT) with one wall and multi-walled carbon nanotubes (MWCNT) with two to five walls are typically classified as thin-walled carbon nanotubes. These thin-walled carbon nanotubes provide a higher specific surface area and superior electrical and mechanical properties compared to multi-walled carbon nanotubes with more than five walls. Due to these characteristics, thin-walled carbon nanotubes have significant potential for application in various fields, such as electronic devices, energy storage devices, and high-strength composite materials.

[0006] Currently, single-walled carbon nanotubes boast very high electrical performance, but multi-walled carbon nanotubes with equivalent electrical performance have not yet been reported. Under these circumstances, thin-walled carbon nanotubes with 1 to 5 walls are attracting attention as structures with the potential to exhibit electrical performance similar to that of single-walled carbon nanotubes, and accordingly, research on the synthesis of thin-walled carbon nanotubes has recently been actively conducted.

[0007]

[0008] Meanwhile, crystallinity and yield are used as key indicators to evaluate the quality and performance of carbon nanotubes. Crystallinity represents the regularity and purity of the carbon nanotube structure; higher crystallinity leads to superior performance in terms of electrical conductivity, mechanical strength, and thermal conductivity. Yield indicates the amount of carbon nanotubes produced in a given process and is closely related to commercial productivity. High yield serves as a particularly important indicator for mass production, as it allows for the production of more carbon nanotubes from the same amount of raw material.

[0009] However, achieving both high crystallinity and high yield simultaneously is a highly challenging task. Maintaining high crystallinity requires precise control of reaction conditions, which induces the formation of carbon nanotube structures with regularly arranged carbon atoms; however, this process can lead to slower production speeds or demanding reaction conditions, potentially resulting in lower yield. Conversely, optimizing reaction conditions to maximize yield may lead to lower crystallinity, which can result in an increase in impurities within the carbon nanotubes or the occurrence of structural defects.

[0010]

[0011] Due to this trade-off, simultaneously optimizing high crystallinity and high yield presents a technical challenge. To achieve this, it is essential to develop innovative manufacturing processes capable of mass-producing high-performance CNTs, along with precise control of reaction conditions.

[0012]

[0013] Prior art literature

[0014] [Patent Document 1] Republic of Korea Published Patent No. 10-2016-0107524

[0015] The present invention confirmed that thin-walled carbon nanotubes satisfying both high yield and high crystallinity can be produced by adding a chelating agent during the metal precursor dissolution process when manufacturing a catalyst, and by controlling the catalyst composition ratio and the content of the chelate.

[0016]

[0017] Accordingly, the present invention aims to provide a method for manufacturing a catalyst for manufacturing thin-walled carbon nanotubes having an average number of walls of 1 to 5, carbon nanotubes manufactured using said catalyst, a carbon nanotube dispersion, an electrode structure including carbon nanotubes, and a secondary battery including carbon nanotubes.

[0018] One aspect of the present invention is

[0019] (S1) A metal salt of a catalyst component comprising a main catalyst precursor (A), a co-catalyst precursor (B), and a support precursor (C) in the following molar ratios; and a step of adding a chelating agent to an aqueous solvent to form a metal precursor solution;

[0020] A : B : C = x : y : z

[0021] (In the above formula

[0022] A is one or more metal precursors selected from Fe, Ni, and Co, and

[0023] B is one or more metal precursors selected from Mo, Mn, V, and W, and

[0024] C is one or more metal precursors selected from Mg, Al, and Si, and

[0025] 0.5≤x≤5, 0.05≤y≤0.5, and 85≤z≤90, and

[0026] The molar ratio of the chelating agent to the above co-catalyst precursor is 0.5 to 5.

[0027] (S2) A step of adding a co-precipitating agent to the metal precursor solution to obtain a metal precursor solution containing a co-precipitating agent;

[0028] (S3) A step of obtaining a slurry by aging the above-mentioned metal precursor solution containing a co-precipitating agent at a temperature of 90°C to 180°C for 1 hour to 30 hours; and

[0029] (S4) A step comprising separating, drying, and washing the above slurry,

[0030] A method for manufacturing a catalyst for manufacturing thin-walled carbon nanotubes is provided.

[0031] In step (S1) above, A : B : C = x : y : z, 2≤x≤3.3, 0.2≤y≤0.33, and 87≤z≤89.

[0032] In step (S1) above, the chelating agent may include citric acid, glycine, tartaric acid, oxalic acid, ethylenediaminetetraacetic acid, or a combination thereof. Preferably, the chelating agent may be citric acid.

[0033] In the above step (S1), the chelating agent is citric acid and can be added in a molar ratio of 0.5 to 2 based on the co-catalyst precursor.

[0034] The above thin-walled carbon nanotubes may have an average of 1 to 5 walls.

[0035]

[0036] Another aspect of the present invention is

[0037] (S1) A step of introducing the catalyst prepared according to the method for preparing the catalyst for producing thin-walled carbon nanotubes into a chemical vapor deposition reactor;

[0038] (S2) A step of synthesizing Pristine carbon nanotubes by heating the chemical vapor deposition reactor and then injecting a carbon source gas;

[0039] (S3) A step of obtaining carbon nanotubes by heat-treating the above pristine carbon nanotubes at 400 to 600 ℃; and

[0040] (S4) A step of purifying the carbon nanotubes obtained above

[0041] A method for manufacturing carbon nanotubes is provided, comprising and satisfying the following (1) to (3):

[0042] (1) The average diameter of the carbon nanotubes is 1.0 to 1.6 nm,

[0043] (2) I of carbon nanotubes G / I D is 21.5 to 40 days, and

[0044] (3) The average number of walls of the carbon nanotubes is 1 to 5.

[0045] Here, the above I G / I D1550–1650 cm in the Raman spectrum of carbon nanotubes -1 The maximum peak intensity within the range of the G band intensity (I G It is called ), and 1250~1400cm -1 The maximum peak intensity within the range of the D band intensity (I D When referring to ), the strength of the G-band (I G ) and D-band strength (I D The ratio of )(I G / I D It represents ).

[0046] I of the pristine carbon nanotubes synthesized in the above step (S2) G / I D The value is 13 to 20, and the yield can be 31 to 50%.

[0047]

[0048] Another aspect of the present invention is

[0049] A carbon nanotube satisfying (1) to (3) below is provided.

[0050] (1) The average diameter of the carbon nanotubes is 1.0 to 1.6 nm,

[0051] (2) I of carbon nanotubes G / I D is 21.5 to 40 days, and

[0052] (3) The average number of walls of the carbon nanotubes is 1 to 5.

[0053] Here, the above I G / I D 1550–1650 cm in the Raman spectrum of carbon nanotubes -1 The maximum peak intensity within the range of the G band intensity (I G It is called ), and 1250~1400cm -1 The maximum peak intensity within the range of the D band intensity (I D When referring to ), the strength of the G-band (I G ) and D-band strength (I D The ratio of )(I G / ID It represents ).

[0054] The specific surface area of ​​the above carbon nanotube is 900 to 1200 m² 2 It can be / g.

[0055] The carbon nanotubes may have an average number of walls of 1 to 4. Preferably, the average number of walls of the carbon nanotubes may be 1 to 3.

[0056]

[0057] Another aspect of the present invention is

[0058] A carbon nanotube dispersion comprising carbon nanotubes according to one aspect of the present invention is provided.

[0059]

[0060] Another aspect of the present invention is

[0061] An electrode structure manufactured using the above carbon nanotube dispersion is provided.

[0062]

[0063] Another aspect of the present invention is

[0064] An electrode structure comprising carbon nanotubes according to one aspect of the present invention is provided.

[0065]

[0066] Another aspect of the present invention is

[0067] A secondary battery comprising an electrode structure manufactured using the above carbon nanotube dispersion is provided.

[0068] The catalyst according to the present invention is at 1550–1650 cm in the Raman spectrum -1 The maximum peak intensity within the range of the G band intensity (I G ) and 1250~1400cm -1 The maximum peak intensity within the range of the D band intensity (I D When referring to ), the strength of the G-band (I G ) and D-band strength (I D The ratio of )(I G / ID It enables the production of carbon nanotubes that have a high crystallinity structure of 21.5 or higher and a thin-walled structure with an average number of walls of 1 to 5.

[0069] In addition, carbon nanotubes produced using the catalyst according to the present invention have high crystallinity and a thin-walled structure with an average number of walls of 1 to 5, and simultaneously possess a fine diameter and a high specific surface area. Due to these excellent structural characteristics, they exhibit excellent electrical conductivity and charge mobility, and can perform well in electronic devices and energy storage devices.

[0070] Furthermore, improved mechanical strength and flexibility are expected to make it highly effective as a reinforcing material for high-strength composites. In addition, the high specific surface area can significantly contribute to increased reaction efficiency and expanded active surface area in various chemical and electronic applications, such as catalysts, adsorbents, and electrode materials.

[0071] Therefore, the carbon nanotubes according to the present invention are expected to secure an outstanding technological advantage as next-generation nanomaterials capable of playing a key role in improving quality and performance in various industrial fields requiring high functionality and high performance.

[0072] Figure 1 shows an SEM image of a catalyst prepared according to Preparation Example 1.

[0073] The present invention will be described in more detail below.

[0074] Terms and words used in this specification and claims should not be interpreted as being limited to their ordinary or dictionary meanings, but should be interpreted in a meaning and concept consistent with the technical spirit of the invention, based on the principle that the inventor can appropriately define the concept of the terms to best describe his invention.

[0075] As used herein, the term “Carbon Nanotube (CNT)” refers to a structure comprising one or more carbon nanotube units, and may include not only a single CNT (SWCNT, DWCNT, or MWCNT) but also a secondary structure assembled in whole or in part in a bundle form or in a group form in which multiple units are mixed. The carbon nanotube units are sp 2 A graphene sheet, which is a planar carbon atomic layer with a hexagonal honeycomb structure having a bonding structure, has a structure in which it is rolled into a cylindrical shape to have a nanometer-sized diameter. At this time, depending on the rolling angle (or chiral angle) and structure of the graphene sheet, it may exhibit conductive or semiconductor properties. Carbon nanotubes can be classified into single-walled carbon nanotubes (SWCNT), double-walled carbon nanotubes (DWCNT), and multi-walled carbon nanotubes (MWCNT) depending on the number of layers forming the walls, and generally, the thinner the wall thickness, the lower the resistance. Meanwhile, the term “pristine carbon nanotube” as used in this specification refers to a carbon nanotube in its original form in which no chemical functional groups have been introduced to the surface, that is, without undergoing chemical modification or surface alteration.

[0076] The term “thin-walled carbon nanotube” as used in this specification refers to a carbon nanotube having an average number of walls of 1 to 5, and may include any one or a combination of single-walled, double-walled, triple-walled, quadruple-walled, and pentruple-walled carbon nanotube units.

[0077] As used herein, the term “crystallinity” refers to the degree to which atoms or molecules within carbon nanotubes form a regular and repetitive crystal lattice structure. A higher degree of crystallinity is evaluated as having fewer defects and a more uniform atomic arrangement within the carbon nanotubes, resulting in superior electrical, mechanical, and thermal properties. The crystallinity is [related to] the G band of the Raman spectrum (1550–1650 cm⁻¹). -1 ) and D band (1250~1400cm) -1 It can be evaluated by measuring the peak intensity in the ) region. Here, the G band represents a regular graphene layer structure, and the D band represents structural defects or irregularities. Therefore, the intensity of the G band (I G ) and D band strength (I D The ratio of ) (I G / I D The larger ) is, the fewer defects and the better the crystal lattice is formed, that is, it indicates a high degree of crystallization.

[0078]

[0079] 1. Method for manufacturing a catalyst

[0080] One aspect of the present invention is

[0081] (S1) A metal salt of a catalyst component comprising a main catalyst precursor (A), a co-catalyst precursor (B), and a support precursor (C) in the following molar ratios; and a step of adding a chelating agent to an aqueous solvent to form a metal precursor solution;

[0082] A : B : C = x : y : z

[0083] (In the above formula

[0084] A is one or more metal precursors selected from Fe, Ni, and Co, and

[0085] B is one or more metal precursors selected from Mo, Mn, V, and W, and

[0086] C is one or more metal precursors selected from Mg, Al, and Si, and

[0087] 0.5≤x≤5, 0.05≤y≤0.5, and 85≤z≤90, and

[0088] The molar ratio of the chelating agent to the above co-catalyst precursor is 0.5 to 5.)

[0089] (S2) A step of adding a co-precipitating agent to the metal precursor solution to obtain a metal precursor solution containing a co-precipitating agent;

[0090] (S3) A step of obtaining a slurry by aging the above-mentioned metal precursor solution containing a co-precipitating agent at a temperature of 90°C to 180°C for 1 hour to 30 hours; and

[0091] (S4) A step comprising separating, drying, and washing the above slurry,

[0092] A method for manufacturing a catalyst for manufacturing thin-walled carbon nanotubes is provided.

[0093] In a method for preparing a catalyst for manufacturing thin-walled carbon nanotubes according to one aspect of the present invention, the addition of a chelating agent prevents pre-precipitation of a co-catalyst such as Mo in an all-metal precursor solution and can maximize the dispersion of the active metal through ligand binding of the metal chelating agent. When the dispersion of the active metal is improved, not only is the average diameter of the carbon nanotubes grown on the catalyst reduced, but it is also advantageous for the synthesis of carbon nanotubes with an average number of walls of 1 to 5, preferably 1 to 4, and more preferably 1 to 3, making it suitable for synthesizing thin-walled carbon nanotubes. Furthermore, when the dispersion of the active metal is improved, the activation energy of the reactants can be effectively lowered, allowing for the synthesis of highly crystalline carbon nanotubes with a higher yield and promoting the length growth of carbon nanotubes relative to the same reactants.

[0094] In step (S1) above, the ratio of main catalyst precursor (A) : co-catalyst precursor (B) : support precursor (C) = x : y : z may be 2≤x≤3.3, 0.2≤y≤0.33, and 87≤z≤89. When carbon nanotubes are manufactured using a catalyst in which the molar ratio of the main catalyst precursor (A) : co-catalyst precursor (B) : support precursor (C) satisfies the above range, thin-walled carbon nanotubes with high yield and crystallinity can be manufactured.

[0095] In step (S1) above, the chelating agent may include citric acid, glycine, tartaric acid, oxalic acid, ethylenediaminetetraacetic acid, or a combination thereof. Preferably, the chelating agent may be citric acid. When preparing the catalyst according to the present invention, the chelating agent is added in step (S1) of forming a metal precursor solution. In this process, the chelating agent prevents pre-precipitation of a co-catalyst, such as Mo, in the metal precursor solution before the addition of the co-precipitating agent, and can maximize the dispersion of the active metal through ligand binding of the metal chelating agent.

[0096] In step (S1) above, the molar ratio of the chelating agent to the co-catalyst precursor may be 0.1 or more and less than 10. For example, the molar ratio of the chelating agent to the co-catalyst precursor may be 0.1 to 9, 0.1 to 8, 0.1 to 7, 0.1 to 6, 0.1 to 5, 0.1 to 4, 0.1 to 3, or 0.1 to 2. If the molar ratio of the chelating agent to the co-catalyst precursor is less than 0.1, the active sites of the catalyst may be incompletely or unevenly distributed, which may degrade the catalyst performance, and if the molar ratio of the chelating agent to the co-catalyst precursor is 10 or more, the metal ions may be excessively stabilized, which may result in less exposure of the catalyst active sites.

[0097] In the above step (S1), the aqueous solvent may include water, lower alcohols having 1 to 4 carbon atoms, or a combination thereof.

[0098] In step (S2) above, the co-precipitating agent may include ammonium hydroxide (NH4OH), ammonium carbonate ((NH4)2CO3), ammonium bicarbonate (NH4HCO3), or a combination thereof. The co-precipitating agent may be added in a molar ratio of 1.5 to 3.0 based on the metal of the catalyst component. If the molar ratio of the co-precipitating agent to the metal of the catalyst component is less than 1.5, the structure of the catalyst may be incompletely formed due to unstable precipitation, and if the molar ratio of the co-precipitating agent to the metal of the catalyst component exceeds 3.0, there is a risk that unnecessary by-products will be generated or the active site of the catalyst will be contaminated.

[0099] The catalyst prepared according to the above-mentioned sun may have a spherical, elliptical, or amorphous particle structure.

[0100] The average diameter of the catalyst prepared according to the above-mentioned sun may be 100 nm to 2 μm.

[0101] Carbon nanotubes grown on a catalyst prepared according to the above-mentioned sun can satisfy (1) to (3) below:

[0102] (1) The average diameter of the carbon nanotubes is 1.0 to 1.6 nm,

[0103] (2) I of carbon nanotubes G / I D is 21.5 to 40 days, and

[0104] (3) The average number of walls of the carbon nanotubes is 1 to 5.

[0105] (Here, the above I G / I D 1550–1650 cm in the Raman spectrum of carbon nanotubes -1 The maximum peak intensity within the range of the G band intensity (I G It is called ), and 1250~1400cm -1 The maximum peak intensity within the range of the D band intensity (I D When referring to ), the strength of the G-band (I G ) and D-band strength (I DThe ratio of )(I G / I D It represents ).

[0106] As an example, a method for manufacturing the catalyst for producing the above thin-walled carbon nanotubes is:

[0107] (s1) a metal salt of a catalyst component comprising iron (Fe), molybdenum (Mo) and magnesium (Mg) in the following molar ratios; and a step of forming a metal precursor solution by adding a chelating agent to an aqueous solvent in a molar ratio of 0.5 to 5 based on molybdenum;

[0108] Fe : Mo : Mg = x : y : z

[0109] (In the above equation, 2≤x≤3.3, 0.2≤y≤0.33, and 87≤z≤89)

[0110] (s2) A step of adding a co-precipitating agent to the metal precursor solution to obtain a metal precursor solution containing a co-precipitating agent;

[0111] (s3) a step of obtaining a slurry by aging the above-mentioned metal precursor solution containing a co-precipitating agent at a temperature of 90°C to 180°C for 1 hour to 30 hours; and

[0112] (s4) The above slurry may include the steps of separating, drying, and washing.

[0113]

[0114] 2. Method for manufacturing carbon nanotubes

[0115] Another aspect of the present invention is

[0116] (S1) A step of introducing the catalyst prepared according to the method of preparing the catalyst of 1. above into a chemical vapor deposition reactor; and

[0117] (S2) A step of synthesizing Pristine carbon nanotubes by heating the chemical vapor deposition reactor and then injecting a carbon source gas;

[0118] (S3) A step of obtaining carbon nanotubes by heat-treating the above pristine carbon nanotubes at 400 to 600 ℃; and

[0119] (S4) A step of purifying the carbon nanotubes obtained above

[0120] A method for manufacturing carbon nanotubes is provided that includes and satisfies the following (1) to (3):

[0121] (1) The average diameter of the carbon nanotubes is 1.0 to 1.6 nm,

[0122] (2) I of carbon nanotubes G / I D is 21.5 to 40 days, and

[0123] (3) The average number of walls of the carbon nanotubes is 1 to 3.

[0124] (Here, the above I G / I D 1550–1650 cm in the Raman spectrum of carbon nanotubes -1 The maximum peak intensity within the range of the G band intensity (I G It is called ), and 1250~1400cm -1 The maximum peak intensity within the range of the D band intensity (I D When referring to ), the strength of the G-band (I G ) and D-band strength (I D The ratio of )(I G / I D It represents ).

[0125] In the above step (S2), the temperature of the reactor may be 800 to 900°C. If the temperature of the reactor is below 800°C, there may be a problem with carbon nanotubes not being manufactured well, and if the temperature of the reactor exceeds 900°C, not only is the cost incurred, but the catalyst particles themselves may decompose.

[0126] In step (S2) above, the carbon source gas may include an aliphatic alkane, an aliphatic alkene, an aliphatic alkyne, an aromatic compound, or a combination thereof. For example, the carbon source gas may include methane, ethane, ethylene, acetylene, ethanol, methanol, acetone, carbon monoxide, propane, butane, benzene, cyclohexane, propylene, butene, isobutene, toluene, xylene, cumene, ethylbenzene, naphthalene, phenanthrene, anthracene, formaldehyde, or acetaldehyde.

[0127] In the above step (S2), a flowing gas may be injected into the reactor along with the carbon source gas. For example, the flowing gas may include hydrogen, helium, argon, nitrogen, oxygen, carbon dioxide, or methane.

[0128] I of the pristine carbon nanotubes synthesized in the above step (S2) G / I D can be 13 to 20. I of the above pristine carbon nanotube G / I D Specifically, it may be 13 or more, 13.2 or more, 13.4 or more, or 13.5 or more, and may be 20 or less, 19 or more, 18 or less, or 17 or less. For example, I of the above pristine carbon nanotube G / I D It may be 13 to 20, 13.2 to 19, 13.4 to 18, or 13.5 to 17.

[0129] The yield of the pristine carbon nanotubes synthesized in step (S2) above may be 31 to 50%. Specifically, the yield of the pristine carbon nanotubes may be 31% or more, 32% or more, or 33% or more, and 50% or less, 49% or less, 48% or less, 47% or less, 46% or less, or 45% or less. For example, the yield of the pristine carbon nanotubes may be 31% to 50%, 31% to 49%, 32% to 48%, 32% to 47%, 33% to 46%, or 33% to 45%.

[0130]

[0131] 3. Carbon nanotubes

[0132] Another aspect of the present invention is

[0133] A carbon nanotube satisfying (1) to (3) below is provided.

[0134] (1) The average diameter of the carbon nanotubes is 1.0 to 1.6 nm,

[0135] (2) I of carbon nanotubes G / I D is 21.5 to 40 days, and

[0136] (3) The average number of walls of the carbon nanotubes is 1 to 5.

[0137] (Here, the above I G / I D 1550–1650 cm in the Raman spectrum of carbon nanotubes -1 The maximum peak intensity within the range of the G band intensity (I G ) and 1250~1400cm -1 The maximum peak intensity within the range of the D band intensity (I D When referring to ), the strength of the G-band (I G ) and D-band strength (I D The ratio of )(I G / I D It represents ).

[0138] The average diameter of the carbon nanotube may be 1.0 to 1.6 nm. Specifically, the average diameter of the carbon nanotube may be 1.0 nm or more, 1.1 nm or more, 1.2 nm or more, or 1.3 nm or more, and may be 1.6 nm or less, or 1.5 nm or less. For example, the average diameter of the carbon nanotube may be 1.0 nm to 1.6 nm, 1.1 nm to 1.6 nm, 1.2 nm to 1.5 nm, or 1.3 nm to 1.5 nm. When the average diameter of the carbon nanotube falls within the above range, it mainly corresponds to single-walled carbon nanotubes (SWCNT), double-walled carbon nanotubes (DWCNT), or triple-walled carbon nanotubes (TWCNT), and can exhibit excellent electronic and mechanical properties due to their thin-walled structure.

[0139] I of the above carbon nanotube G / I D can be 21.5 to 40. I of the carbon nanotube G / I D Specifically, it may be 21.5 or more, 22 or more, 22.5 or more, or 23 or more, and may be 40 or less, 39 or less, 38 or less, 37 or less, 36 or less, 35 or less, 34 or less, 33 or less, 32 or less, 31 or less, or 30 or less. For example, I of the carbon nanotube above G / I D It may be 21.5 to 40, 21.5 to 39, 21.5 to 38, 22 to 37, 22 to 36, 22.5 to 35, 22.5 to 34, 22.5 to 33, 23 to 32, 23 to 31, or 23 to 30. I of the carbon nanotube G / I D If the value is less than 22, the electrical and thermal conductivity of the carbon nanotubes may decrease. Carbon nanotubes in this range have fewer defects and higher crystallinity, so they may have excellent electrical and thermal conductivity, excellent mechanical strength, and excellent chemical stability.

[0140] The carbon nanotubes may have an average number of walls of 1 to 5, preferably 1 to 4, more preferably 1 to 3, and most preferably 1 or 2.

[0141] The specific surface area of ​​the above carbon nanotube is 900 to 1200 m² 2 It can be / g. Specifically, the specific surface area of ​​the carbon nanotube is 900 m² 2 / g or more, 910 m 2 / g or more, or 920 m 2 It can be greater than / g, and 1200 m 2 / g or less, 1150 m 2 / g or less, or 1100 m 2 It may be less than / g. For example, the specific surface area of ​​the carbon nanotube is 900 m² 2 / g to m 2 / g 1200, 910 m 2 / g to 1150 m 2 / g, or 920 m 2 / g to 1200 m 2 It may be / g. The specific surface area of ​​the carbon nanotube can be measured by methods commonly used in this field of technology. For example, the specific surface area of ​​the carbon nanotube measured by the BET (Brunauer-Emmett-Teller) method can be calculated by determining the amount of nitrogen gas adsorbed at liquid nitrogen temperature (77K) using the BELSORP-mini II from BEL Japan.

[0142] According to one aspect of the present invention, carbon nanotubes have an average diameter, I G / I D With optimized ratio, average wall number, and specific surface area, it can demonstrate excellent performance in various applications. As the average diameter falls within the fine range of 1.0 to 1.6 nm, the formation of uniform nanostructures is possible, and precise control of electrical properties and physical properties can be achieved. In addition, I G / I D With a high ratio of 21.5 or higher, it exhibits excellent crystallinity and low defect density, resulting in superior electrical and thermal conductivity, making it suitable for precision electronic applications such as electronic devices, electrode materials, and sensors. It has a thin-walled structure with an average number of walls ranging from 1 to 5, preferably 1 to 4, and more preferably 1 to 3, providing excellent mechanical flexibility and strength. Furthermore, it has a large specific surface area of ​​900 to 1200 m² / g, which exhibits excellent reactivity and a large number of surface active sites, making it highly advantageous for applications such as catalyst supports, adsorbents, and electrode materials for energy storage devices. These characteristics enable the carbon nanotubes of the present invention to serve as next-generation nanomaterials possessing high purity, high functionality, and high performance simultaneously, playing a key role in various industrial fields such as electrical and electronic, energy, composite materials, environment, and bio.

[0143]

[0144] Another aspect of the present invention is

[0145] We intend to provide a carbon nanotube dispersion comprising a carbon nanotube satisfying (1) to (3) below and a dispersion medium.

[0146] (1) The average diameter of the carbon nanotubes is 1.0 to 1.6 nm,

[0147] (2) I of carbon nanotubes G / I D It shall be 21.5 to 40 days,

[0148] (3) The average number of walls of the carbon nanotubes is 1 to 5.

[0149] In the above carbon nanotube dispersion, one or more dispersion media selected from the group consisting of N-methylpyrrolidone, pyridine, dimethylaminobenzene, and diethylaminobenzene may be used.

[0150]

[0151] Another aspect of the present invention is

[0152] An electrode structure prepared by including the above-described carbon nanotube dispersion is provided. The electrode structure may be, for example, a secondary battery electrode structure.

[0153]

[0154] Another aspect of the present invention is

[0155] An electrode structure comprising the above carbon nanotube is provided. The carbon nanotube satisfies the conditions of (1) to (3) below and may exist in a dried solid state within the electrode structure, and the electrode structure may be, for example, a secondary battery electrode structure.

[0156] (1) The average diameter of the carbon nanotubes is 1.0 to 1.6 nm,

[0157] (2) I of carbon nanotubes G / I D is 21.5 to 40 days, and

[0158] (3) The average number of walls of the carbon nanotubes is 1 to 5.

[0159]

[0160] In addition, the carbon nanotubes may be included in the electrode structure, for example, as a conductive material. Due to their excellent electrical conductivity and high crystallinity, the carbon nanotubes improve the electrical properties of the electrode and can contribute to improving the output characteristics and high-rate characteristics of the battery by improving the uniformity of current flow and the charge transfer efficiency within the electrode.

[0161]

[0162] Another aspect of the present invention is

[0163] The present invention provides a secondary battery comprising an electrode structure manufactured including the above-described carbon nanotube dispersion. Due to the excellent electrical conductivity and high crystallinity of the carbon nanotubes within the electrode structure, the secondary battery can exhibit excellent and stable electrochemical performance in terms of discharge capacity, output characteristics, and capacity retention rate.

[0164] As a result, the secondary battery of the present invention can be usefully applied to portable electronic devices such as mobile phones, laptop computers, and digital cameras, as well as electric vehicles requiring high performance, such as hybrid electric vehicles (HEVs).

[0165] Hereinafter, the present invention will be described in more detail through examples and experimental examples to specifically explain the invention, but the present invention is not limited by these examples and experimental examples. The embodiments according to the present invention may be modified in various different forms, and the scope of the present invention should not be interpreted as being limited to the embodiments described below. The embodiments of the present invention are provided to more completely explain the invention to those with average knowledge in the art.

[0166]

[0167] <Catalyst Preparation Example>

[0168] As metal precursors, Iron Nitrate Nonahydrate, Ammonium Molybdate Tetrahydrate, and Magnesium Nitrate Hexahydrate were dissolved in distilled water to prepare an aqueous metal precursor solution. At this time, the molar ratios of Fe, Mo, and Mg were adjusted and added within the ranges of Fe: 2–6.6 and Mo: 0.2–0.66, while Mg was fixed at 88. Next, a chelating agent according to Table 1 below was added to the aqueous metal precursor solution in the range of 0.5–10 relative to the molar amount of Mo, and NH4OH was added as a co-precipitating agent at a molar ratio of 2:1 relative to the metal component to prepare a slurry solution. The slurry solution was aged at a temperature of 150 °C for 24 hours, and the solids were recovered from the aged slurry solution through a vacuum filter and then washed with distilled water. Next, the washed solid was dried at a temperature of 90 ℃ and calcined at 700 ℃ to finally obtain a metal oxide hydrothermal synthesis catalyst. The molar ratios of Fe, Mo, and Mg and the molar ratio of the chelating agent to molybdenum (CA / Mo) identified in the finally prepared catalyst are shown in Table 1 below.

[0169] Classification Catalyst Composition FeMoMgCA*CA / Mo Preparation Example 1 3.30.3388 Citric acid 1.0 Preparation Example 2 20.288 Citric acid 1.0 Preparation Example 3 20.288 Citric acid 0.5 Preparation Example 4 3.30.3388 Citric acid 0.5 Preparation Example 5 3.30.3388 Citric acid 2.0 Preparation Example 6 3.30.3388 Oxalic acid 1.0 Preparation Example 7 3.30.3388 EDTA 1.0 Preparation Example 8 6.60.6688 Citric acid 1.0 Preparation Example 9 3.30.3388 Citric acid 10.0 Preparation Example 10 3.30.3388 Oxalic acid 10.0 Preparation Example 11 3.30.3388 EDTA 10.0 Preparation Example 1220.288 Manufacturing Example 133.30.3388 Manufacturing Example 146.60.6688

[0170] *CA: Chelating Agent SEM images of the catalyst prepared according to Preparation Example 1 above are shown in Figure 1, and SEM image observation was performed using JSM-7610F (JEOL). As a result, it was confirmed that the catalyst prepared according to Preparation Example 1 contains spherical, elliptical, and amorphous small particle structures, and the interior consists of a slit shape of 2 μm or less.

[0171]

[0172] <Examples and Comparative Examples>

[0173] 1. Preparation and Characterization of Pristine Carbon Nanotubes

[0174] Carbon nanotubes were synthesized using the catalyst prepared in the above catalyst preparation example. Specifically, 0.5 g of the prepared catalyst was loaded into a CCVD (Catalytic Chemical Vapor Deposition) reactor, argon gas was injected into the reactor at 540 sccm, and the internal temperature of the reactor was heated to 850°C. Subsequently, methane gas, which is the carbon source gas, was introduced into the Ar:CH4 Pristine carbon nanotubes were synthesized by injecting at a ratio of 540:105 sccm and sustaining the reaction for 30 minutes. The yield and I of the synthesized carbon nanotubes G / I D It was measured in the following manner. Unless otherwise noted, all measurements were performed at room temperature (23 ± 2℃), atmospheric pressure (about 1 atm), and relative humidity (40–60%).

[0175] 1) CNT Yield (%)

[0176] [(Generated CNT + Catalyst) Weight - Catalyst Weight] / Catalyst Weight]

[0177] 2) CNT Raman Spectrum Analysis (I G / I D )

[0178] CNTs were mounted on a Thermo Scientific DXR Raman Microscope, and measurements were performed using a laser wavelength of 532 nm. The measurement conditions were an infusion time of 10 seconds, 5 accumulator cycles, an objective lens magnification of 50x, a slit width of 50 μm, and a measurement wavelength of 100–3000 cm⁻¹. -1 It was set to . The CNTs for measurement were transferred onto a glass slide and flattened using a spatula. Among the obtained peaks, the 1550–1650 cm⁻¹ range in the spectrum -1 The maximum peak intensity within the range of the G band intensity (I G ) and 1250~1400cm -1 The maximum peak intensity within the range of the D band intensity (I D It was set to ), and the intensity of the G band (I G ) and D-band strength (I D The ratio of ) to CNT's I G / I D It was defined as a ratio. This analysis was performed without applying baseline correction.

[0179] The measurement results are shown in Table 2 below.

[0180] Classification | Catalyst Used | Catalyst Composition | Pristine CNT | Physical Properties | FeMoMgCA | CA / Mo | Yield %I G / I DExample 1 Preparation Example 1 3.30.3388 Citric acid 1.04 4.2 17.0 Example 2 Preparation Example 2 20.288 Citric acid 1.03 3.4 16.1 Example 3 Preparation Example 3 20.288 Citric acid 0.54 0.2 16.0 Example 4 Preparation Example 4 3.30.3388 Citric acid 0.53 9.9 16.1 Example 5 Preparation Example 5 3.30.3388 Citric acid 2.04 1.5 16.0 Example 6 Preparation Example 6 3.30.3388 Oxalic acid 1.03 8.2 14.9 Example 7 Preparation Example 7 3.30.3388 EDTA 1.03 7.8 13.5 Comparative Example 1 Preparation Example 86.60.6688 Citric acid 1.029.410.7 Comparative Example 2 Manufacturing Example 93.30.3388 Citric acid 10.019.611.6 Comparative Example 3 Manufacturing Example 103.30.3388 Oxalic acid 10.024.813.6 Comparative Example 4 Manufacturing Example 113.30.3388 EDTA 10.024.712.9 Comparative Example 5 Manufacturing Example 1220.28830.914.5 Comparative Example 6 Manufacturing Example 133.30.338829.213.7 Comparative Example 7 Manufacturing Example 146.60.668823.011.6

[0181] When a chelating agent is added during catalyst preparation according to Examples 1 to 7 of the present invention, the yield and I of carbon nanotubes compared to Comparative Examples 5 to 7, in which a chelating agent was not added G / I D The ratio increased significantly. In particular, when the molar ratio of Fe : Mo : Mg was within the range of 2~3.3 : 0.2~0.33 : 88 and the molar ratio of the chelating agent to molybdenum (Mo) was less than 10, the yield of carbon nanotubes improved significantly to over 33%, and I G / I D It was confirmed that carbon nanotubes with excellent crystallinity were obtained, as the ratio was also maintained at a high level of 13 or higher.

[0182]

[0183] 2. Evaluation of Physical Properties of Carbon Nanotubes

[0184] The carbon nanotubes according to the above examples and comparative examples were heat-treated at 500 °C and purified by stirring in a 2 M aqueous hydrochloric acid solution at room temperature for 2 hours to remove the catalyst metal. Subsequently, the average diameter, specific surface area, and I of the carbon nanotubes G / I D The average wall count was measured in the following manner. Unless otherwise noted, all measurements were performed at room temperature (23 ± 2℃), atmospheric pressure (approx. 1 atm), and relative humidity (40–60%).

[0185] 1) Average CNT diameter (nm)

[0186] The average diameter of the CNTs was measured using a Thermo Scientific Raman analyzer. Measurements were performed under conditions of a laser wavelength of 532 nm, a laser power of 2 mW, an exposure time of 10 seconds, and a cumulative number of measurements of 5. Based on the position of the Radial Breathing Mode (RBM) peaks in the measured Raman spectrum, the diameter d (nm) was calculated according to the relationship ω (wavenumber cm⁻¹) = 246 / d (nm). The calculated average diameter of the CNTs is the arithmetic mean value derived from the RBM peaks measured for multiple CNTs, with n being 30 or more and the standard deviation also indicated.

[0187] 2) CNT specific surface area (m 2 / g)

[0188] Measurements were performed using the Brunauer-Emmett-Teller (BET) method with a Trista 2000 (Microtrac) instrument. Prior to measurement, the samples were degassed at 150°C for more than 4 hours under vacuum conditions (10² Torr or less), and then nitrogen adsorption-desorption isotherms were measured under liquid nitrogen (-196°C) conditions. The specific surface area was calculated by analyzing the adsorption data within a relative pressure range (P / P0: 0.05–0.30) using the BET equation.

[0189] 3) CNT Raman Spectrum Analysis (I G / I D )

[0190] CNTs were mounted on a Thermo Scientific DXR Raman Microscope, and measurements were performed using a laser wavelength of 532 nm. The measurement conditions were an infusion time of 10 seconds, 5 accumulator cycles, an objective lens magnification of 50x, a slit width of 50 μm, and a measurement wavelength of 100–3000 cm⁻¹. -1 It was set to . The CNTs for measurement were transferred onto a glass slide and flattened using a spatula. Among the obtained peaks, the 1550–1650 cm⁻¹ range in the spectrum -1 The maximum peak intensity within the range of the G band intensity (I G ) and 1250~1400cm -1 The maximum peak intensity within the range of the D band intensity (I D It was set to ), and the intensity of the G band (I G ) and D-band strength (I D The ratio of ) to CNT's I G / I D It was defined as a ratio. This analysis was performed without applying baseline correction.

[0191] 4) TEM (Transmission Electron Microscopy) Analysis

[0192] To prepare the TEM sample, 1.6 g of SDS (Sodium dodecyl sulfate) was dissolved in 200 mL of water, 0.2 g of CNT was added, and the mixture was dispersed by sonication (20 minutes, 200 W). The dispersion was placed on a TEM grid and dried to prepare the sample. TEM analysis was performed using a Titan G2 80-200 Field Emission Transmission Electron Microscope at an acceleration voltage of 200 kV, and the number of CNT walls was analyzed at high magnification (1,000,000x).

[0193] The measurement results are shown in Table 3 below.

[0194] Diameter (nm) Specific surface area (m²) 2 / g)I G / I D Average number of walls (pieces) Example 1 1.5±0.029 26 27.71~2 Example 2 1.3±0.0210 23 24.81~2 Example 3 1.3±0.0210 26 29.31~2 Example 4 1.3±0.0293 7 23.41~2 Example 5 1.3±0.0294 6 23.71~2 Example 6 1.4±0.02925 25.41~2 Example 7 1.4±0.0295 226.61~2 Comparative Example 11.8±0.028 29 21.41~2 Comparative Example 2 1.7±0.02794 18.61~2 Comparative Example 3 1.7±0.02-(Unmeasured) 16.81~2 Comparative Example 41.7±0.02-(Unmeasured)19.31~2 Comparative Example 51.7±0.0285321.31~2 Comparative Example 61.8±0.0282520.71~2 Comparative Example 71.8±0.0281717.91~2

[0195] As can be seen from Table 3 above, the carbon nanotubes prepared according to Examples 1 to 7 of the present invention have a uniform and fine average diameter of about 1.3 to 1.5 nm (standard deviation ±0.02), a high specific surface area of ​​900 m² / g or more, and I G / I D It simultaneously exhibited high crystallinity with a ratio of 23.4 to 29.3. On the other hand, the carbon nanotubes according to Comparative Examples 1 to 7 had a relatively large average diameter of 1.7 to 1.8 nm, and in most cases, the specific surface area was low at 850 m² / g or less, and I G / I D The ratio was relatively low at 21.4 or lower, showing a tendency for reduced crystallinity.

[0196] These results clearly demonstrate that the catalyst composition and manufacturing process of the present invention can stably produce uniform and high-quality carbon nanotubes. In particular, the fine diameter distribution, high specific surface area, and excellent crystallinity are expected to serve as key factors for exhibiting superior performance and durability in various industrial fields, such as electrochemical devices, catalyst supports, and composite materials.

[0197] Therefore, the carbon nanotubes of the present invention possess significant superiority over competing technologies as high-performance nanomaterials.

Claims

1. (S1) A metal salt of a catalyst component comprising a main catalyst precursor (A), a co-catalyst precursor (B), and a support precursor (C) in the following molar ratios; and a step of adding a chelating agent to an aqueous solvent to form a metal precursor solution; A : B : C = x : y : z (In the above formula A is one or more metal precursors selected from Fe, Ni, and Co, and B is one or more metal precursors selected from Mo, Mn, V, and W, and C is one or more metal precursors selected from Mg, Al, and Si, and 0.5≤x≤5, 0.05≤y≤0.5, and 85≤z≤90, and The molar ratio of the chelating agent to the above co-catalyst precursor is 0.5 to 5. (S2) A step of adding a co-precipitating agent to the metal precursor solution to obtain a metal precursor solution containing a co-precipitating agent; (S3) A step of obtaining a slurry by aging the above-mentioned metal precursor solution containing a co-precipitating agent at a temperature of 90°C to 180°C for 1 hour to 30 hours; and (S4) A step comprising separating, drying, and washing the above slurry, Method for manufacturing a catalyst for manufacturing thin-walled carbon nanotubes.

2. In Paragraph 1, A method for manufacturing a catalyst for manufacturing thin-walled carbon nanotubes, wherein in step (S1) above, A : B : C = x : y : z, 2≤x≤3.3, 0.2≤y≤0.33, and 87≤z≤89.

3. In Paragraph 1, A method for preparing a catalyst for manufacturing thin-walled carbon nanotubes, wherein the chelating agent in step (S1) comprises citric acid, glycine, tartaric acid, oxalic acid, ethylenediaminetetraacetic acid, or a combination thereof.

4. In Paragraph 1, A method for manufacturing a catalyst for manufacturing thin-walled carbon nanotubes, wherein in step (S1) above, the chelating agent is citric acid and is added in a molar ratio of 0.5 to 2 based on the co-catalyst precursor.

5. (S1) A step of introducing a catalyst prepared according to any one of claims 1 to 4 above into a chemical vapor deposition reactor; (S2) A step of synthesizing Pristine carbon nanotubes by heating the chemical vapor deposition reactor and then injecting a carbon source gas; (S3) A step of obtaining carbon nanotubes by heat-treating the above pristine carbon nanotubes at 400 to 600 ℃; and (S4) A step of purifying the carbon nanotubes obtained above A method for manufacturing carbon nanotubes comprising and satisfying (1) to (3) below: (1) The average diameter of the carbon nanotubes is 1.0 to 1.6 nm, (2) I of carbon nanotubes G / I D is 21.5 to 40 days, and (3) The average number of walls of the carbon nanotubes is 1 to 5. (Here, the above I G / I D 1550–1650 cm in the Raman spectrum of carbon nanotubes -1 The maximum peak intensity within the range of the G band intensity (I G It is called ), and 1250~1400cm -1 The maximum peak intensity within the range of the D band intensity (I D When referring to ), the strength of the G-band (I G ) and D-band strength (I D The ratio of )(I G / I D It represents ).

6. In Paragraph 5, I of the pristine carbon nanotubes synthesized in the above step (S2) G / I D A method for manufacturing carbon nanotubes, wherein the amount is 13 to 20 and the yield is 31 to 50%.

7. Carbon nanotube satisfying (1) to (3) below: (1) The average diameter of the carbon nanotubes is 1.0 to 1.6 nm, (2) I of carbon nanotubes G / I D is 21.5 to 40 days, and (3) The average number of walls of the carbon nanotubes is 1 to 5. (Here, the above I G / I D 1550–1650 cm in the Raman spectrum of carbon nanotubes -1 The maximum peak intensity within the range of the G band intensity (I G It is called ), and 1250~1400cm -1 The maximum peak intensity within the range of the D band intensity (I D When referring to ), the strength of the G-band (I G ) and D-band strength (I D The ratio of )(I G / I D It represents ).

8. In Paragraph 7, The average number of walls of the carbon nanotubes is 1 to 4, and the carbon nanotubes.

9. In Paragraph 7, Carbon nanotubes having an average wall count of 1 to 3.

10. In Paragraph 7, The specific surface area of ​​the above carbon nanotube is 900 to 1200 m² 2 / g phosphorus, carbon nanotube.

11. A carbon nanotube dispersion comprising carbon nanotubes according to any one of claims 7 to 10.

12. An electrode structure manufactured using a carbon nanotube dispersion according to paragraph 11.

13. An electrode structure comprising carbon nanotubes according to any one of claims 7 to 10.

14. A secondary battery comprising an electrode structure manufactured using a carbon nanotube dispersion according to paragraph 11.

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