Catalyst for carbon nanotube production and method for producing carbon nanotubes

Abstract

One embodiment of the present specification provides a method for producing a catalyst for producing carbon nanotubes, comprising: (a) dissolving a metal precursor in a solvent to prepare a precursor solution; (b) spraying the precursor solution into a reactor and pyrolyzing it; and (c) obtaining a catalyst, the catalyst comprising a metal component represented by the following formula 1: <Expression 1> Co x :[M1,Zr] y :M2 z In the above formula, Co represents cobalt, an oxide or a derivative thereof, M1 represents at least one metal selected from Al, Ca, Si, Ti and Mg, an oxide or a derivative thereof, Zr represents zirconium, an oxide or a derivative thereof, M2 represents at least one metal selected from W, V, Mn and Mo, an oxide or a derivative thereof, and 0.2≦x / y≦2.6, 6≦x / z≦13.

Description

[Technical Field]

[0001] This specification relates to catalysts for carbon nanotube production and methods for producing carbon nanotubes. [Background technology]

[0002] As interest in and importance of environmentally friendly energy and electric vehicles grow, the demand for rechargeable batteries is rapidly increasing. High-capacity rechargeable batteries for electric vehicles require high energy density, long lifespan, and low self-discharge rate. To ensure these properties, the development of highly electrically conductive materials is essential. Conductive materials function as pathways for the movement of charge within the battery, and carbon-based conductive materials such as graphite, carbon black, graphene, and carbon nanotubes may be used. Conventionally, conductive carbon black has been mainly used.

[0003] Carbon nanotubes are materials with a tubular structure consisting of a hexagonal honeycomb lattice in which one carbon atom is bonded to three different carbon atoms. Due to their excellent electrical conductivity, they are attracting attention as a next-generation conductive material for secondary batteries. When carbon nanotubes are used as a conductive material, the energy density and lifespan of secondary batteries can be improved, and the size of the batteries can be reduced. However, conventional carbon nanotubes have problems with their solubility in solvents and dispersibility within solvents, making them difficult to use as a conductive material for secondary batteries.

[0004] Various attempts have been made to solve these problems, such as physical post-processing using ball mills and pink crusher, but these have created new problems of operational difficulties and increased costs. Furthermore, although catalysts for carbon nanotube production with various metal component combinations and physical properties have been developed, it remains difficult to achieve the dispersion suitable for use as a conductive material in high-capacity secondary batteries. Therefore, there is a need for the development of carbon nanotubes and catalysts for their production that have excellent electrical conductivity and dispersibility and can be used as a conductive material in secondary batteries. [Overview of the project] [Problems that the invention aims to solve]

[0005] The information contained herein is intended to solve the problems of the prior art described above, and one of the objectives of this specification is to provide a method for producing a catalyst for carbon nanotube production that produces carbon nanotubes with excellent electrical conductivity and dispersibility.

[0006] Another objective of this specification is to provide a method for producing carbon nanotubes for secondary battery conductive materials that have excellent electrical conductivity and dispersibility. [Means for solving the problem]

[0007] According to one embodiment, the present invention provides a method for producing a catalyst for carbon nanotube production, comprising the steps of (a) dissolving a metal precursor in a solvent to produce a precursor solution, (b) spraying the precursor solution into a reactor and thermally decomposing it, and (c) obtaining a catalyst, wherein the catalyst contains a metal component represented by the following formula 1.

[0008] <Expression 1> Co x :[M1,Zr] y :M2 z In the above formula, Co represents cobalt, its oxide or derivative; M1 is at least one metal selected from Al, Ca, Si, Ti, and Mg, its oxide or derivative; Zr represents zirconium, its oxide or derivative; and M2 is at least one metal selected from W, V, Mn, and Mo, its oxide or derivative, with 0.2 ≤ x / y ≤ 2.6 and 6 ≤ x / z ≤ 13.

[0009] In one embodiment, step (a) may include (a1) a step of dissolving a Co precursor, a Zr precursor, and at least one metal precursor selected from Al, Ca, Si, Ti, and Mg in a solvent to produce a first precursor solution, and (a2) a step of adding at least one metal precursor selected from W, V, Mn, and Mo to the first precursor solution to produce a second precursor solution.

[0010] In one embodiment, the temperature of the first precursor solution in step (a2) may be less than 30°C.

[0011] In one embodiment, step (a2) may include a step of adding the metal precursor and then stirring under a nitrogen atmosphere.

[0012] In one embodiment, step (b) may include (b1) spraying the precursor solution into a reactor with 1 to 3 bar of air, and (b2) thermally decomposing the sprayed precursor solution at 600 to 1,000°C.

[0013] In one embodiment, the above formula may also have 0.5 ≤ x / y ≤ 2.0 and 8 ≤ x / z ≤ 9.

[0014] In another embodiment, a method for producing carbon nanotubes is provided, which includes the steps of (1) introducing a carbon nanotube production catalyst produced by the above method into a chemical vapor deposition reactor, and (2) synthesizing carbon nanotubes by injecting a carbon-based gas and a transport gas.

[0015] In one embodiment, the chemical vapor deposition reactor may be a fluidized bed chemical vapor deposition reactor.

[0016] In one embodiment, the temperature in the chemical vapor deposition reactor may be 600 to 1,000 °C.

[0017] In one embodiment, the carbon-based gas may be one selected from the group consisting of saturated or unsaturated hydrocarbons having 1 to 4 carbon atoms, carbon monoxide, benzene, and mixtures of two or more of these.

[0018] In one embodiment, the carrier gas may be one selected from the group consisting of helium, nitrogen, argon, and mixtures of two or more of these.

Advantages of the Invention

[0019] The catalyst for producing carbon nanotubes according to one aspect of the present specification may be applied to the synthesis of carbon nanotubes having excellent electrical conductivity and dispersibility.

[0020] In addition, the carbon nanotubes produced according to another aspect of the present specification have excellent physical properties including electrical conductivity and dispersibility, and when used as a conductive material for secondary batteries, the capacity and life characteristics of the secondary batteries can be improved.

[0021] The effects of one aspect of the present specification are not limited to the above effects, and should be understood to include all effects that can be inferred from the configurations described in the detailed description or claims of the present specification.

Brief Description of the Drawings

[0022] [Figure 1] FIG. 1 and FIG. 2 are FE-SEM images of carbon nanotubes produced using the catalyst for producing carbon nanotubes according to one embodiment of the present specification. [Figure 2] FIG. 1 and FIG. 2 are FE-SEM images of carbon nanotubes produced using the catalyst for producing carbon nanotubes according to one embodiment of the present specification. [Modes for carrying out the invention]

[0023] Hereinafter, an embodiment of this specification will be described with reference to the attached drawings. However, the provisions of this specification may be embodied in various forms and are therefore not limited to the embodiments described herein. Furthermore, in order to clearly illustrate an embodiment of this specification in the drawings, parts unrelated to the description have been omitted, and similar parts throughout the specification are denoted by similar reference numerals.

[0024] Throughout the specification, when a part is described as being "connected" to another part, this includes not only cases where it is "directly connected" but also cases where it is "indirectly connected" through other components in between. Furthermore, when a part is described as "containing" a certain component, this does not mean that it excludes other components, but rather that it may further contain other components, unless otherwise stated.

[0025] When a range of numerical values ​​is described herein, unless otherwise specified, the value shall have the precision of significant figures provided in accordance with the standard rules in chemistry for significant figures. For example, 10 includes the range of 5.0 to 14.9, and the figure 10.0 includes the range of 9.50 to 10.49.

[0026] Hereinafter, an embodiment of this specification will be described in detail with reference to the attached drawings.

[0027] Method for manufacturing catalysts for carbon nanotube production A method for producing a catalyst for carbon nanotube production according to one aspect of this specification comprises the steps of (a) dissolving a metal precursor in a solvent to produce a precursor solution, (b) spraying the precursor solution into a reactor and thermally decomposing it, and (c) obtaining a catalyst, wherein the catalyst contains a metal component represented by the following formula 1.

[0028] <Expression 1> Co x :[M1,Zr] y:M2 z In the above formula, Co can represent cobalt, its oxide, or a derivative thereof. The Co can act as the main catalyst in the catalyst for carbon nanotube production. Using the catalyst, a structure with relatively excellent dispersibility can be grown during the synthesis of carbon nanotubes.

[0029] In the above formula, M1 is at least one metal selected from Al, Ca, Si, Ti, and Mg, its oxide, or derivative, and Zr can represent zirconium, its oxide, or derivative.

[0030] The [M1, Zr] is an inert support capable of supporting the main catalyst and co-catalyst components. The [M1, Zr] indicates that M1 and Zr are present in the same or different mole amounts, and for example, M1 may be present in an amount of 1.5 times or more, 2 times or more, 2.5 times or more, or 3 times or more moles relative to Zr, but is not limited thereto.

[0031] The composition and proportions of the main catalyst, co-catalyst, and inert support determine the crystal structure of the catalyst, which can alter the growth morphology and properties of carbon nanotubes. For example, using a catalyst containing M1 and Zr as the inert support can achieve electrical conductivity suitable for use as a conductive material during carbon nanotube synthesis, as well as the necessary levels of solubility and dispersibility for electrode coating.

[0032] In the above formula, M2 may be at least one metal selected from W, V, Mn, and Mo, or an oxide or derivative thereof. M2 can act as a co-catalyst, an active component that assists the action of the main catalyst in the carbon nanotube production catalyst. This allows for improved synthesis efficiency while maintaining the aforementioned structural properties of the carbon nanotubes.

[0033] In the above formula, 0.2 ≤ x / y ≤ 2.6 is also possible. x / y represents the mole fraction of the main catalyst relative to the support, and may be, for example, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, or a range between two of these values. If the x / y mole fraction is lower than the above range, the activity of the catalyst and the resulting carbon nanotube synthesis yield may decrease, the dispersibility of the produced carbon nanotubes will decrease, and they will become unsuitable as conductive materials for secondary batteries. If the x / y mole fraction is higher than the aforementioned range, the support content may be relatively low, reducing the durability of the catalyst. The synthesized carbon nanotubes may exhibit an intangled structure, leading to a decrease in BET specific surface area and powder resistance properties, resulting in insufficient dispersibility and electrical conductivity, making them unsuitable as conductive materials for secondary batteries.

[0034] In the above formula, 6 ≤ x / z ≤ 13 is also possible. The x / z represents the mole fraction of the main catalyst relative to the co-catalyst, and may be, for example, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10, 10.5, 11, 11.5, 12, 12.5, 13, or a range between two of these values. If the x / z mole fraction is lower than the above range, the growth of carbon nanotubes during the reaction may be hindered due to an excess of the co-catalyst, resulting in a decrease in the yield, and the powder resistance of the produced carbon nanotubes will decrease, making them unsuitable as a conductive material for secondary batteries. If the x / z mole fraction is higher than the above range, the growth activity of carbon nanotubes during the reaction may decrease due to a deficiency of the co-catalyst, resulting in a decrease in the yield, and the powder resistance of the synthesized carbon nanotubes will decrease, making them unsuitable as a conductive material for secondary batteries.

[0035] Step (a) above is a step of preparing a precursor solution containing a precursor of a metal component contained in a catalyst for carbon nanotube production, which may include a step of adding the metal precursor to a solvent and then stirring under a nitrogen atmosphere.

[0036] The metal precursor may be, but is not limited to, one selected from the group consisting of nitrates, sulfates, alkoxides, chlorides, acetates, carbonates, and mixtures of two or more of these metals.

[0037] In step (a) above, the solvent may be a polar solvent, and may be water, methanol, ethanol, propanol, isopropanol, butanol, or a mixture of two or more of these, for example, deionized water may be used, but is not limited thereto. Using deionized water as the solvent can minimize impurities in the precursor solution, thereby improving the purity of the final catalyst produced. This improvement in catalyst purity consequently means an improvement in the purity of the carbon nanotubes.

[0038] Step (a) may include (a1) dissolving a Co precursor, a Zr precursor, and at least one metal precursor selected from Al, Ca, Si, Ti, and Mg in a solvent to produce a first precursor solution, and (a2) adding at least one metal precursor selected from W, V, Mn, and Mo to the first precursor solution to produce a second precursor solution. The order of steps (a1) and (a2) is not limited.

[0039] Step (a1) is a step of dissolving the main catalyst precursor and the support precursor in a solvent, and the first precursor solution may be, but is not limited to, an acidic solution.

[0040] Step (a2) above is the step of introducing a precursor of the co-catalyst, and the precursor of the co-catalyst is basic, but is not limited to that.

[0041] In step (a2) above, the temperature of the first precursor solution may be less than 30°C. For example, it may be 29.9°C, 29.5°C, 29°C, 28.5°C, 28°C, 27.5°C, 27°C, 26.5°C, 26°C, 25.5°C, 25°C, 24.5°C, 24°C, 23.5°C, 23°C, 22.5°C, 22°C, 21.5°C, 21°C, 20.5°C, 20°C, within a range between two of these values, or less than 20°C. If the temperature of the first precursor solution is 30°C or higher, thermal side reactions may occur, causing precipitation, which may reduce the productivity and uniformity of the catalyst quality.

[0042] The step in (a2) above may include a step of stirring under a nitrogen atmosphere after adding the metal precursor. If the mixture is stirred under an atmosphere other than nitrogen, such as air, after adding the metal precursor, a precipitation phenomenon may occur due to the reaction between the acidic first precursor solution and the basic co-catalyst precursor, which may reduce the productivity and uniformity of the catalyst quality.

[0043] The (b) step may include (b1) spraying the precursor solution into the reactor with 1 to 3 bar of air, and (b2) thermally decomposing the sprayed precursor solution at 600 to 1,000°C.

[0044] In step (b1) above, the precursor solution can be sprayed into the reactor to convert it into finer droplets in order to control the particle size and apparent density of the catalyst. When spraying the precursor solution, the pressure can be adjusted within the range of 1 to 3 bar. If the spray pressure is less than 1 bar, the particle size and apparent density of the catalyst will not be adjusted within a certain range, which may reduce the purity of the synthesized carbon nanotubes. If the spray pressure exceeds 3 bar, the particle size of the droplets will become excessively small, and the resulting catalyst may aggregate with each other.

[0045] In step (b2) above, the catalyst can be produced by heating the droplets to evaporate the solvent and decompose the precursor. At this time, the temperature of the reactor may be 600 to 1,000°C. For example, it may be 600°C, 650°C, 700°C, 750°C, 800°C, 850°C, 900°C, 950°C, 1,000°C, or a range between two of these values. If the reactor temperature is lower than the above range, the catalyst will not dry properly, requiring additional steps, which is economically disadvantageous, and the purity and physical properties of the carbon nanotubes produced may decrease. If the reactor temperature is higher than the above range, it will not only result in excessive costs for equipment and facility construction and lead to economic losses, but the catalytic performance may also decrease due to the formation of solid solutions and deformation of the crystal structure.

[0046] In the above formula, 0.5 ≤ x / y ≤ 2.0 and 8 ≤ x / z ≤ 9 may be used, but are not limited to these. If the catalyst is a catalyst containing a quaternary element system, it is easier to control the process conditions for producing the desired carbon nanotubes if the proportions between each component satisfy the above range, but are not limited to this.

[0047] Step (c) above is the step of finally obtaining the manufactured carbon nanotube manufacturing catalyst, which can be obtained in powder form, but is not limited to that.

[0048] The carbon nanotube production catalyst produced by the above method may be used in chemical vapor deposition (CVA) methods for synthesizing carbon nanotubes, for example, in fluidized bed CVA or fixed-bed CVA methods, but is not limited thereto.

[0049] The carbon nanotube production catalyst produced by the above method may be applied to the production of carbon nanotubes with excellent electrical conductivity and dispersibility.

[0050] Method for manufacturing carbon nanotubes Another embodiment of this specification provides a method for producing carbon nanotubes, comprising the steps of (1) introducing the carbon nanotube production catalyst produced by the above method into a chemical vapor deposition reactor, and (2) synthesizing carbon nanotubes by injecting a carbon-based gas and a transport gas.

[0051] The chemical vapor deposition reactor may, but is not limited to, a fluidized bed chemical vapor deposition reactor. Unlike conventional catalysts that can only be used in fixed-bed chemical vapor deposition reactors due to issues such as apparent density, catalyst morphology, and strength, the catalyst may be used in both fixed-bed and fluidized bed chemical vapor deposition reactors.

[0052] While fixed-bed chemical vapor deposition (CVA) reactors allow for the use of a relatively wide variety of catalysts, their productivity and the uniformity of the synthesized carbon nanotubes are insufficient. Fluidized-bed CVA reactors are advantageous for mass production and the manufacture of uniform carbon nanotubes, but the types of catalysts that can be used may be limited.

[0053] The temperature inside the chemical vapor deposition reactor may be between 600 and 1,000°C. For example, it may be 600°C, 650°C, 700°C, 750°C, 800°C, 850°C, 900°C, 950°C, 1,000°C, or a range between two of these values. If the reactor temperature is too low, the growth of carbon nanotubes may be impossible or delayed. If the reactor temperature is too high, the synthesized carbon nanotubes may be thermally decomposed or unable to bond with each other and maintain their shape.

[0054] The carbon-based gas may be one selected from the group consisting of saturated or unsaturated hydrocarbons having 1 to 4 carbon atoms, carbon monoxide, benzene, and mixtures of two or more of these, and may, for example, be ethylene, propylene, acetylene, or methane, but is not limited thereto.

[0055] The transport gas may be, but is not limited to, one selected from the group consisting of helium, nitrogen, argon, and mixtures of at least two of these.

[0056] In step (2) above, the carbon-based gas decomposed by high-temperature heat may permeate and saturate the catalyst composition, after which carbon may precipitate and carbon nanotubes may grow, but this is not limited to the above.

[0057] According to the above manufacturing method, a large quantity of carbon nanotubes for use as conductive materials in secondary batteries can be effectively produced.

[0058] The carbon nanotubes produced by the above method may be aggregates of carbon nanotubes grown on the catalyst. The carbon nanotube aggregate can be understood as a concept that includes both the catalyst composition and the carbon nanotubes. The carbon nanotube aggregate includes carbon nanotubes grown from the catalyst seed described above. When the growth pattern and purity of the carbon nanotubes are determined by the catalyst and applied as a conductive material, the electrical conductivity, dispersibility, solubility, etc. may change. Therefore, even if the diameter, length, purity, etc. of the carbon nanotubes are similar, if they are produced with catalysts of different compositions, the properties such as dispersibility, solubility, and electrical conductivity may change.

[0059] In one example, the carbon nanotube aggregate may contain individual carbon nanotubes in linear, curved, or mixed forms. Each of the carbon nanotubes may be a single-walled, double-walled, or multi-walled carbon nanotube.

[0060] In one example, the carbon nanotube aggregate may include bundle-shaped carbon nanotubes in which multiple carbon nanotubes are aggregated together. These bundle-shaped carbon nanotubes may exist in linear, curved, or mixed forms.

[0061] In one example, the carbon nanotube aggregate may include multi-walled carbon nanotubes having an average number of walls of 3 to 20. Even when using multi-walled carbon nanotubes, which are known to have a relatively low conductivity compared to single-walled carbon nanotubes, the necessary physical properties as a conductive material for a secondary battery can be realized.

[0062] The purity of the carbon nanotubes produced by the method may be 90% or more. For example, it may be 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or more, but is not limited thereto. If the purity is outside the above range, the electrical conductivity may be insufficient, or impurities may react inside the battery and a safety accident may occur.

[0063] The BET specific surface area of the carbon nanotube aggregate produced by the method may be 130 to 260 m 2 / g. For example, 130 m 2 / g, 140 m 2 / g, 150 m 2 / g, 160 m 2 / g, 170 m 2 / g, 180 m 2 / g, 190 m 2 / g, 200 m 2 / g, 210 m 2 / g, 220 m 2 / g, 230 m 2 / g, 240 m 2 / g, 250 m 2 / g, 260 m 2 / g or may be in the range between two of these values. If the BET specific surface area is smaller than the above range, the electrical conductivity decreases and it becomes unsuitable as a conductive material for a secondary battery. If it is higher than the range, the dispersibility may decrease.

[0064] The apparent density (bulk density) of the carbon nanotube aggregate produced by the above method may be between 0.005 and 0.10 g / ml. For example, it may be 0.005 g / ml, 0.01 g / ml, 0.02 g / ml, 0.03 g / ml, 0.04 g / ml, 0.05 g / ml, 0.06 g / ml, 0.07 g / ml, 0.08 g / ml, 0.09 g / ml, 0.10 g / ml, or a range between two of these values. The apparent density may be measured using powdered carbon nanotubes. If the apparent density falls outside the above range, problems of excessive scattering of carbon nanotubes may occur, or the dispersibility and solubility may be insufficient when producing conductive material slurries.

[0065] The average fiber diameter of the carbon nanotubes produced by the above method may be 3 to 30 nm. For example, it may be 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, 11 nm, 12 nm, 13 nm, 14 nm, 15 nm, 16 nm, 17 nm, 18 nm, 19 nm, 20 nm, 21 nm, 22 nm, 23 nm, 24 nm, 25 nm, 26 nm, 27 nm, 28 nm, 29 nm, 30 nm, or a range between two of these values. If the average fiber diameter falls outside this range, the synthesized carbon nanotubes may have structural problems or the desired carbon nanotube properties may not be adequately realized.

[0066] The average powder resistance of carbon nanotubes produced by the above method may be 0.005 to 0.045 Ω·cm. For example, 0.005 Ω·cm, 0.006 Ω·cm, 0.007 Ω·cm, 0.008 Ω·cm, 0.009 Ω·cm, 0.01 Ω·cm, 0.011 Ω·cm, 0.012 Ω·cm, 0.013 Ω·cm, 0.014 Ω·cm, 0.015 Ω·cm, 0.016 Ω·cm, 0.017 Ω·cm, 0.018 Ω·cm, 0.019 Ω·cm, 0.02 Ω·cm, 0.021 Ω·cm, 0.022 Ω·cm, 0.023 Ω·cm, 0.024 Ω·cm, 0.025 Ω·cm, 0.026 The resistance may be Ω·cm, 0.027Ω·cm, 0.028Ω·cm, 0.029Ω·cm, 0.03Ω·cm, 0.031Ω·cm, 0.032Ω·cm, 0.033Ω·cm, 0.034Ω·cm, 0.035Ω·cm, 0.036Ω·cm, 0.037Ω·cm, 0.038Ω·cm, 0.039Ω·cm, 0.04Ω·cm, 0.041Ω·cm, 0.042Ω·cm, 0.043Ω·cm, 0.044Ω·cm, 0.045Ω·cm, or a range between two of these values. If the powder resistance is higher than the above range, the electrical conductivity will decrease, making it unsuitable as a conductive material for secondary batteries.

[0067] Among the methods for analyzing the structure of the carbon nanotubes, Raman spectroscopy, which analyzes the surface state of the carbon nanotubes, may be usefully used. As used herein, "Raman spectroscopy" refers to a spectroscopic method for determining the vibrational frequency of a molecule in the Raman effect, which is a phenomenon in which scattered light with a difference equal to the vibrational frequency of the molecule is produced when monochromatic excitation light, such as laser light, is irradiated. Through such Raman spectroscopy, the crystallinity of carbon nanotubes can be quantified and measured.

[0068] Of the Raman spectra of the carbon nanotubes mentioned above, wavenumber 1580±50 cm⁻¹ -1 The peak present in this region is called the G band, and this represents the sp of carbon nanotubes. 2 This peak indicates bonding and can show a carbon crystal without structural defects. Also, at a wavenumber of 1360±50 cm⁻¹, this peak is present.-1 The peak present in this region is called the D band, and this represents the sp of carbon nanotubes. 3 This peak indicates bonding and can represent carbon atoms containing structural defects.

[0069] Furthermore, the peak values ​​of the G band and D band are respectively I G and I D The ratio between the two is called the Raman spectral intensity ratio (I G / I D The crystallinity of carbon nanotubes can be quantified and measured through this method. In other words, a higher Raman spectral intensity ratio indicates fewer structural defects in the carbon nanotubes, so using carbon nanotubes that exhibit a high Raman spectral intensity ratio can result in superior electrical conductivity.

[0070] The Raman spectroscopy intensity ratio (I) of carbon nanotubes produced by the above method G / I D The Raman spectral intensity ratio may be between 0.5 and 2.0. For example, it may be 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, or a range between two of these values. If the Raman spectral intensity ratio falls outside this range, the dispersibility of carbon nanotubes decreases, making it difficult to achieve uniform electrical conductivity when coated onto electrodes.

[0071] The surface resistance of the carbon nanotubes produced by the above method may be 100 to 250 Ω / sq. For example, it may be 100 Ω / sq, 110 Ω / sq, 120 Ω / sq, 130 Ω / sq, 140 Ω / sq, 150 Ω / sq, 160 Ω / sq, 170 Ω / sq, 180 Ω / sq, 190 Ω / sq, 200 Ω / sq, 210 Ω / sq, 220 Ω / sq, 230 Ω / sq, 240 Ω / sq, 250 Ω / sq, or a range between two of these values. If the surface resistance is higher than the above range, the electrical conductivity will decrease, making it unsuitable as a conductive material for secondary batteries.

[0072] The carbon nanotubes produced by the above method exhibit excellent physical properties, including electrical conductivity and dispersibility. When used as a conductive material for secondary batteries, they can improve the capacity and lifespan characteristics of secondary batteries, thereby making them applicable to the production of high-capacity secondary batteries with high energy density and low self-discharge rate.

[0073] Unlike conventional carbon nanotubes, which have insufficient solubility during the manufacturing of electrode material slurries and are difficult to apply to conductive materials, the carbon nanotube aggregate is easy to manufacture as a slurry and has excellent dispersibility. The conductive material for secondary batteries can suppress safety accidents caused by localized current concentration.

[0074] The carbon nanotubes produced by the above method exhibit superior powder resistance compared to carbon black, which is conventionally used as a conductive material for secondary batteries. This allows for increased energy density even with smaller quantities, thereby improving the charging speed and efficiency of secondary batteries. Furthermore, using this conductive material for secondary batteries allows for sufficient current characteristics even when containing a relatively large amount of electrode material.

[0075] The examples of this specification will be described in more detail below. However, the experimental results described below represent only representative results from the aforementioned examples, and the scope and content of this specification cannot be narrowed or limited by the examples. The effects of some of the specific examples of this specification not explicitly shown below will be described in detail in the relevant sections.

[0076] Examples 1-6 and Comparative Examples 1-4 Co(NO3)3·6H2O, Al(NO3)3·9H2O, ZrO(NO3)2·2H2O, and deionized water were added to the reactor and stirred under a nitrogen atmosphere to produce the first precursor solution. NH4VO3 was added to the first precursor solution, which was maintained at a temperature below 30°C, and stirred under a nitrogen atmosphere to produce the second precursor solution. At this time, each precursor was added in the required amount according to the catalyst composition shown in Table 1 below. The catalyst composition was obtained by spraying the second precursor solution with air into a spray pyrolysis reactor at a rate of 3 L / hr and pyrolysis. The air spray pressure was set to 1-3 bar, and the temperature inside the spray pyrolysis reactor was set to 750°C.

[0077] [Table 1]

[0078] Comparative Example 5 A catalyst composition was prepared in the same composition and manner as in Example 1, except that the temperature of the first precursor solution was maintained at 50°C.

[0079] Comparative Example 6 A catalyst composition was prepared in the same composition and manner as in Example 1, except that NH4VO3 was added to the first precursor solution and stirred under air.

[0080] Manufacturing example The catalyst compositions according to the above examples and comparative examples were placed in a 350 mm diameter fluidized bed chemical vapor deposition reactor, and the temperature inside the reactor was raised and maintained at 700-800°C under a nitrogen atmosphere. Then, a gas mixture of nitrogen and ethylene was supplied at a rate of 150 L / min, and the reaction was carried out for 50 minutes to synthesize carbon nanotubes.

[0081] Experimental Example 1 The structure, fiber diameter, and wall number of carbon nanotubes synthesized according to the above manufacturing example were confirmed through FE-SEM imaging, and the BET specific surface area (BET) and powder resistivity were measured and are shown in Table 2 below. The BET specific surface area was measured using a TriStar II 3020 (Micrometritics). For powder resistivity, the bulk density was measured using an HPRM-FA2 (Hantek), and then the volume resistivity (Ω·cm) trend curve based on apparent density was used to calculate the volume resistivity value when the density was 0.65 ± 0.01 g / ml.

[0082] Figures 1 and 2 are FE-SEM images of carbon nanotubes synthesized by the production example using the catalyst compositions of Example 6 and Comparative Example 1, respectively.

[0083] [Table 2]

[0084] The carbon nanotubes synthesized using the catalyst compositions of Examples 1 to 6 exhibited a bundle-like structure as shown in Figure 1, and demonstrated excellent BET specific surface area and powder resistance properties, confirming their applicability as conductive materials for secondary batteries.

[0085] Carbon nanotubes synthesized using the catalyst composition of Comparative Example 1, which had a high Co / (Al+Zr) mole fraction of 3.18, exhibited an intangled structure as shown in Figure 2, and showed a decrease in BET specific surface area and powder resistance properties compared to the examples.

[0086] Carbon nanotubes synthesized using the catalyst composition of Comparative Example 2, which had a low Co / (Al+Zr) mole fraction of 0.18, exhibited excellent powder resistance due to their very high BET specific surface area. However, the high BET specific surface area resulted in reduced dispersibility during dispersion preparation.

[0087] Carbon nanotubes synthesized using the catalyst composition of Comparative Example 3, which had a low Co / V mole fraction of 3.45, were produced in a reduced yield because the growth of the carbon nanotubes during the reaction was hindered by an excess of the co-catalyst, which is the active component, and the powder resistance of the synthesized carbon nanotubes was lower compared to the examples.

[0088] Carbon nanotubes synthesized using the catalyst composition of Comparative Example 4, which had a high Co / V molar fraction of 17.29, showed reduced yield due to a lack of co-catalysts, which are active components, resulting in lower growth activity of the carbon nanotubes during the reaction. Compared to the examples, the powder resistance of the synthesized carbon nanotubes was lower.

[0089] Experimental Example 2 To evaluate the electrical conductivity and dispersibility of the carbon nanotubes synthesized by the above manufacturing example, the surface resistance of the carbon nanotubes was measured and the dispersion was evaluated, and the results are shown in Table 3 below.

[0090] The surface resistance of carbon nanotubes was measured using a 4-point probe after bar coating. The carbon nanotube dispersion was evaluated by adding 5% by weight of carbon nanotubes to N-methylpyrrolidone (NMP) and using a bead mill. The dispersion evaluation was completed and the manufacturing time measured when the viscosity no longer decreased during manufacturing using a Rotate Ring Mill (RRG). If dispersion did not occur after 48 hours or more, it was determined that dispersion was not possible.

[0091] [Table 3]

[0092] Carbon nanotubes synthesized using the catalyst composition of Example 6 were found to have low surface resistance, excellent electrical conductivity, and high dispersibility.

[0093] The carbon nanotubes synthesized using the catalyst composition of Comparative Example 1 exhibited an intangled structure. Although the dispersion preparation time was short, the dispersion was not properly performed, resulting in reduced electrical conductivity compared to the examples.

[0094] Carbon nanotubes synthesized using the catalyst composition of Comparative Example 2 failed to disperse as the BET specific surface area became very high, resulting in the failure to produce a 5% dispersion.

[0095] Experimental Example 3 In the above examples and comparative examples, the solution precipitation phenomenon by the method for producing the second precursor solution was evaluated and is shown in Table 4 below.

[0096] [Table 4]

[0097] Comparing Example 1 with Comparative Example 5, when the temperature of the first precursor solution was 30°C or higher, a thermal side reaction occurred, resulting in precipitation.

[0098] Comparing Example 1 with Comparative Example 6, it was confirmed that when the second precursor solution is prepared under a nitrogen atmosphere, the precipitation phenomenon that occurs during the reaction between the acidic first precursor solution and the basic NH4VO3 precursor can be suppressed.

[0099] We confirmed that when solution precipitation occurs, the productivity and uniformity of the catalyst composition are significantly reduced.

[0100] The descriptions herein provided herein are illustrative, and a person with ordinary skill in the art to which one aspect of this specification belongs will understand that it is possible to easily modify the invention in other specific forms without altering the technical ideas or essential features described herein. Therefore, the embodiments described herein should be understood in all respects as illustrative and not limiting. For example, each component described as a single type may be implemented in a distributed manner, and similarly, components described as distributed may be implemented in a combined manner.

[0101] The scope of this specification is defined by the claims set forth below, and all modifications or alterations derived from the meaning and scope of the claims and the concept of equivalents thereof should be construed as being included within the scope of this specification.

Claims

1. (a) A step of dissolving a metal precursor in a solvent to produce a precursor solution, (b) A step of spraying the precursor solution into the reactor and thermally decomposing it, (c) The step of obtaining a catalyst, A method for producing a catalyst for carbon nanotubes, wherein the catalyst is a catalyst composition containing the following metals in the molar ratio represented by the following formula 1. <Formula 1> Co ｘ :[M1, Zr] ｙ :M2 ｚ In the above formula, [M1, Zr] represents M1 and Zr, indicating that both M1 and Zr are included. Co stands for cobalt, M1 is Al, Zr stands for zirconium. M2 is V, M1 is present in a mole count of 1.5 times or more relative to Zr. 0.53 ≤ x / y ≤ 1.64 and 8.60 ≤ x / z ≤ 8.71; In the catalyst composition, Cobalt may be included in the form of its oxide or derivative. Al may be included in the form of its oxide or derivative. Zirconium may be included in the form of its oxide or derivative. V may be included in the form of its oxide or derivative.

2. The above step (a) is, (a1) A step of dissolving a Co precursor, a Zr precursor, and an Al precursor in a solvent to produce a first precursor solution, (a2) A method for producing a catalyst for carbon nanotube production according to claim 1, comprising the step of adding a V precursor to the first precursor solution to produce a second precursor solution.

3. The method for producing a catalyst for carbon nanotubes according to claim 2, wherein in step (a2), the temperature of the first precursor solution is less than 30°C.

4. The method for producing a catalyst for carbon nanotubes according to claim 2, further comprising the step of adding the metal precursor in step (a2) and stirring under a nitrogen atmosphere.

5. The aforementioned step (b) is, (b1) A step of spraying the precursor solution into the reactor together with 1 to 3 bar of air, (b) The step of thermally decomposing the sprayed precursor solution at 600 to 1,000°C, A method for producing a catalyst for carbon nanotube manufacturing according to claim 1.

6. (1) The step of introducing the carbon nanotube production catalyst manufactured according to claim 1 into a chemical vapor deposition reactor, (2) A method for producing carbon nanotubes, comprising the step of synthesizing carbon nanotubes by injecting a carbon-based gas and a transport gas.

7. The method for producing carbon nanotubes according to claim 6, wherein the chemical vapor deposition reactor is a fluidized bed chemical vapor deposition reactor.

8. The method for producing carbon nanotubes according to claim 6, wherein the temperature inside the chemical vapor deposition reactor is 600 to 1,000°C.

9. The method for producing carbon nanotubes according to claim 6, wherein the carbon-based gas is one selected from the group consisting of saturated or unsaturated hydrocarbons having 1 to 4 carbon atoms, carbon monoxide, benzene, and mixtures of two or more of these.

10. The method for producing carbon nanotubes according to claim 6, wherein the transport gas is one selected from the group consisting of helium, nitrogen, argon, and mixtures of two or more of these.

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