High-density carbon nanotube composition, method for producing the same, carbon nanotube dispersion containing the same, and positive electrode slurry composition

Abstract

The present invention provides a method for manufacturing a semiconductor device having a volume density defined by Equation 1 of 500 to 2500 / mm 3 The carbon nanotube composition of the present invention has excellent dispersibility and productivity because the carbon nanotubes in the carbon nanotube composition maintain a bundled structure and have a high bulk density.

Description

[Technical Field]

[0001] This application claims the benefit of priority based on Korean Patent Application Nos. 10-2023-0028574 and 10-2023-0028575, filed March 3, 2023, and all contents disclosed in the documents of said Korean patent applications are incorporated herein by reference.

[0002] The present invention relates to a carbon nanotube composition having high packing density and bulk density, a method for producing the same, and a dispersion and a positive electrode slurry composition containing the carbon nanotube composition. [Background technology]

[0003] Carbon nanomaterials include fullerenes, carbon nanotubes (CNTs), graphene, and graphite nanoplates depending on the shape of the material. Of these, carbon nanotubes are giant molecules in which a hexagonal honeycomb-shaped graphite sheet, in which one carbon atom is bonded to three different carbon atoms, is rolled up with a nano-sized diameter.

[0004] Carbon nanotubes are hollow and lightweight, with electrical conductivity as good as copper, thermal conductivity as good as diamond, and tensile strength comparable to that of steel. Depending on the coiled form, they can be divided into single-walled carbon nanotubes (SWCNT), multi-walled carbon nanotubes (MWCNT), and rope carbon nanotubes.

[0005] Recently, the field of lithium secondary batteries has been the most active area of ​​research into the application of carbon nanotubes. The ultimate goal of lithium secondary batteries is to store more electrical energy in a smaller size. Research is being conducted into the use of carbon nanotubes as a conductive material as one way to improve the electrode density of lithium secondary batteries and thereby manufacture electrodes with higher energy density per unit volume. High-density electrodes are typically formed by high-pressure pressing electrode active material particles ranging in size from several micrometers to several tens of micrometers. This process can lead to particle deformation, reducing the interparticle space and reducing electrolyte permeability. To address this issue, materials with excellent electrical conductivity and strength are used as conductive materials during electrode fabrication. Carbon nanotubes are also widely used as such due to their excellent strength and electrical conductivity. When conductive materials are used in electrode fabrication, they are dispersed among the compressed electrode active material, maintaining micropores between the active material particles, facilitating electrolyte permeation. Furthermore, their excellent conductivity can reduce resistance within the electrode.

[0006] However, the most problematic aspect of using carbon nanotubes as a conductive material is their low dispersibility. Due to their strong van der Waals attractive forces, carbon nanotubes cannot be stably dispersed in aqueous solutions, resulting in aggregation. Aggregation of carbon nanotubes in the dispersion reduces the processability of the dispersion, making it difficult to apply the dispersion uniformly. Therefore, it is preferable to apply the dispersion with its viscosity minimized.

[0007] Carbon nanotubes are classified into bundled and entangled types depending on their morphology. The bundled type refers to a secondary shape in which multiple carbon nanotube units are aligned parallel with the longitudinal axes of the units in substantially the same orientation, or are aligned and then twisted or entangled, forming a bundle or rope. On the other hand, the entangled type refers to a shape in which carbon nanotube units are entangled without a specific shape, such as a bundle or rope. Of the bundled and entangled carbon nanotubes, the bundled type has superior dispersibility. However, bundled carbon nanotubes have limitations in that they have low bulk density in powder form, resulting in low productivity during synthesis. Therefore, research is needed to improve the dispersibility of carbon nanotubes by increasing their bulk density in powder form while maintaining their bundled morphology, thereby also increasing productivity. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] KR10-2018-0106929 A Summary of the Invention [Problem to be solved by the invention]

[0009] An object of the present invention is to provide carbon nanotubes that maintain a bundled shape and have a high bulk density, and therefore are excellent in both dispersibility and productivity, and a method for producing the same.

[0010] In addition, the present invention provides a carbon nanotube dispersion containing bundled carbon nanotubes, which has low viscosity and excellent processability, and exhibits electrical conductivity at a level equal to or higher than that of conventional carbon nanotube dispersions containing entangled carbon nanotubes, and a positive electrode slurry composition containing the same. [Means for solving the problem]

[0011] In order to solve the above-mentioned problems, the present invention provides a carbon nanotube composition, a method for producing a carbon nanotube composition, a carbon nanotube dispersion, and a positive electrode slurry composition. More specifically, (1) the present invention provides a method for manufacturing a porous ceramic material having a volume density of 500 to 2500 / mm3 as defined by the following formula 1: 3 The present invention provides a carbon nanotube composition comprising: [Formula 1] Volumetric density = yield of carbon nanotubes / volume of carbon nanotube composition The yield of the carbon nanotubes is calculated by (mass of the carbon nanotube composition - mass of the catalyst in the carbon nanotube composition) / (mass of the catalyst in the carbon nanotube composition).

[0012] (2) The present invention provides the carbon nanotube composition according to (1) above, wherein the particle size density defined by the following formula 2 is 50 to 120 / mm: [Formula 2] Particle size density = carbon nanotube yield / volume average particle size of carbon nanotubes The yield of the carbon nanotubes is calculated in the same manner as in Equation 1.

[0013] (3) The present invention provides the above (1) or (2), wherein the bulk density is 40 to 85 kg / m 3 The present invention provides a carbon nanotube composition comprising:

[0014] (4) The present invention provides the carbon nanotube composition according to any one of (1) to (3) above, wherein the yield of the carbon nanotubes is 30% or more.

[0015] (5) In any one of the above (1) to (4), the present invention is characterized in that the specific surface area of ​​the carbon nanotubes is 160 m 2 / g or more.

[0016] (6) The present invention provides a carbon nanotube composition according to any one of the above (1) to (5), which contains bundled carbon nanotubes.

[0017] (7) The present invention provides a method for producing a carbon nanotube composition according to any one of (1) to (6), comprising the steps of: (S1) loading a fluidized bed reactor with a supported catalyst in which Co and V are supported on boehmite and a carbon nanotube powder for fluidized bed; and (S2) supplying a carbon source gas into the fluidized bed reactor while reacting the gas to synthesize carbon nanotubes.

[0018] (8) The present invention provides a method for producing a carbon nanotube composition according to (7), wherein the supported catalyst has a Co content of 16 to 22 wt % and a molar ratio of Co to V in the supported catalyst of 2:1 to 4:1.

[0019] (9) The present invention provides the method for producing a carbon nanotube composition according to (7) or (8), wherein in the step S2, the fluidized bed reactor is heated so that the internal temperature thereof becomes 650 to 750°C.

[0020] (10) The present invention provides a method for producing a carbon nanotube composition according to any one of (7) to (9), wherein the S2 step supplies both a carbon source gas and a fluidizing gas, and the supply flow rate ratio of the carbon source gas to the fluidizing gas is 1:1 to 1:10.

[0021] (11) The present invention provides a carbon nanotube dispersion liquid containing the carbon nanotube composition according to any one of (1) to (6) above and a dispersion medium.

[0022] (12) The present invention provides the carbon nanotube dispersion according to (11), wherein the content of the carbon nanotube composition in the dispersion is 0.5 to 5% by weight.

[0023] (13) The present invention provides a carbon nanotube dispersion according to (11) or (12), wherein the dispersion contains one or more dispersants selected from the group consisting of styrene butylene rubber (SBR), carboxymethyl cellulose (CMC), hydrogenated acrylonitrile butatiene rubber (H-NBR), polyvinylpyrrolidone (PVP), and polyvinylbutyral (PVB).

[0024] (14) The present invention provides a carbon nanotube dispersion liquid according to any one of the above (11) to (13), which has an initial viscosity of 15,000 cP or less.

[0025] (15) The present invention provides a positive electrode slurry composition comprising the carbon nanotube dispersion liquid according to any one of (11) to (14) above, a positive electrode active material, a binder, and a solvent. [Effects of the Invention]

[0026] The carbon nanotube composition of the present invention maintains the bundle shape, has a high bulk density, and is excellent in both dispersibility and productivity.

[0027] In addition, the carbon nanotube dispersion of the present invention has low viscosity and excellent processability, and can contain a relatively high content of carbon nanotubes. Therefore, it is easy to process when preparing a positive electrode slurry, and can maintain excellent electrical properties. [Brief explanation of the drawings]

[0028] [Figure 1] FIG. 2 is a diagram showing the morphology of the carbon nanotubes of Example 1 observed by SEM at ×3000 magnification. [Figure 2]FIG. 1 is a SEM image at ×3000 magnification of the morphology of the carbon nanotubes of Comparative Example 3. [Figure 3] FIG. 1 is a SEM image at ×3000 magnification of the morphology of the carbon nanotubes of Comparative Example 4. [Figure 4] FIG. 10 is a SEM image at ×400 magnification of the morphology of the carbon nanotubes of Example 8. [Figure 5] FIG. 10 is a SEM image at ×400 magnification of the morphology of the carbon nanotubes of Example 9. [Figure 6] FIG. 10 is a SEM image at ×400 magnification of the morphology of the carbon nanotubes of Example 10. [Figure 7] FIG. 10 is a SEM image at ×400 magnification of the morphology of the carbon nanotubes of Example 11. DETAILED DESCRIPTION OF THE INVENTION

[0029] The present invention will now be described in more detail.

[0030] The terms and words used in this specification and claims should not be interpreted in a limited way to their ordinary or dictionary meanings, but should be interpreted in a way that is consistent with the technical idea of ​​the present invention, based on the principle that the inventors can appropriately define the concepts of terms in order to best describe their invention.

[0031] The term "carbon nanotube" used in the present invention refers to a secondary structure formed by the complete or partial assembly of carbon nanotube units. The carbon nanotube units are graphite sheets with a cylindrical shape of nanometer-sized diameter and an sp2 bond structure. Depending on the angle and structure of the graphite sheet, the carbon nanotube units can exhibit conductive or semiconductive properties. Depending on the number of bonds forming the wall, carbon nanotube units are classified as single-walled carbon nanotubes (SWCNTs), double-walled carbon nanotubes (DWCNTs), and multi-walled carbon nanotubes (MWCNTs). The thinner the wall, the lower the resistance.

[0032] The carbon nanotube of the present invention may include one or more of single-wall, double-wall, and multi-wall carbon nanotube units.

[0033] In the present invention, the bundled carbon nanotube refers to a carbon nanotube having a secondary shape in the form of a bundle or rope, in which a plurality of carbon nanotube units are arranged parallel to each other with the longitudinal axes of the units substantially in the same orientation, or are arranged and then twisted or entangled.

[0034] In the present invention, the entangled carbon nanotube refers to a carbon nanotube in which the carbon nanotube units are entangled without forming a specific shape such as a bundle or rope.

[0035] In the present invention, the carbon nanotube composition refers to a product obtained from a carbon nanotube production process using a fluidized bed reactor, and refers to a mixture containing synthesized carbon nanotubes and a supported catalyst used for the synthesis. More specifically, the carbon nanotube composition includes a supported catalyst and carbon nanotubes grown from the supported catalyst.

[0036] Carbon nanotube composition As is well known, bundled carbon nanotubes have the advantage of being highly dispersible and therefore have excellent electrical properties, but have the disadvantage of having a relatively low carbon nanotube content per unit volume, resulting in a low carbon nanotube content per batch in the manufacturing process. Therefore, if it is possible to obtain carbon nanotubes that maintain the secondary bundled shape and have individual carbon nanotube bundles that are more densely packed, it will be possible to provide carbon nanotubes that are excellent in both performance and productivity.

[0037] In order to solve this problem, the present invention provides a method for manufacturing a porous ceramic material having a volume density of 500 to 2500 / mm3 as defined by the following formula 1: 3 The present invention provides a carbon nanotube composition comprising:

[0038] [Formula 1] Volumetric density = yield of carbon nanotubes / volume of carbon nanotube composition

[0039] The yield of the carbon nanotubes is calculated by (mass of the carbon nanotube composition - mass of the catalyst in the carbon nanotube composition) / (mass of the catalyst in the carbon nanotube composition).

[0040] The volume density is an index showing the amount of carbon nanotubes contained per unit volume of the carbon nanotube composition obtained after the synthesis reaction is completed. In particular, since the volume density is also affected by the yield of carbon nanotubes, the volume density can be obtained when the yield of carbon nanotubes is above a predetermined level and the volume of the carbon nanotube composition is within a specific range.

[0041] The volume density is 500 to 2500 / mm 3 and preferably 500 / mm 3 Above, 510 / mm 3 Above, 520 / mm 3 Above, 530 / mm 3 or more or 540 / mm 3 or more and 2500 / mm 3 Below, 2400 / mm 3 Below, 2300 / mm 3 Below, 2200 / mm 3 Below, 2100 / mm 3 Below, 2000 / mm 3 Below, 1900 / mm 3 Below, 1850 / mm 3 Below, 1800 / mm 3 or less or 1780 / mm 3 If the volume density exceeds the above range, the secondary shape of the carbon nanotubes may change from a bundle type to an entangled type, which may reduce the electrochemical performance of the carbon nanotubes themselves.

[0042] In the carbon nanotube composition provided by the present invention, the carbon nanotube composition may have a particle size density defined by the following formula 2 of 50 to 120 / mm.

[0043] [Formula 2] Particle size density = carbon nanotube yield / volume average particle size of carbon nanotubes

[0044] The yield of the carbon nanotubes is calculated in the same manner as in Equation 1.

[0045] Like the volume density, the particle size density is an index that represents the number of carbon nanotubes contained in a composition based on the volume average particle size of the carbon nanotubes, and like the volume density, it is also an index related to the density of the carbon nanotubes.

[0046] The particle size density may be 50 to 120 / mm, preferably 50 / mm or more, 53 / mm or more, 55 / mm or more, 57 / mm or more, 60 / mm or more, 62 / mm or more, 64 / mm or more, or 66 / mm or more, and may be 120 / mm or less, 118 / mm or less, 115 / mm or less, 113 / mm or less, 110 / mm or less, 107 / mm or less, 105 / mm or less, or 102 / mm or less. If the particle size density exceeds the above range, the secondary shape of the carbon nanotubes may change from a bundle type to an entangled type, which may reduce the electrochemical performance of the carbon nanotubes themselves.

[0047] The carbon nanotube composition of the present invention has a bulk density of 40 to 85 kg / m 3 and preferably 40 kg / m 3 More than 45kg / m 3 More than 50kg / m 3 More than 55kg / m 3 or more than 57 kg / m 3 or more and 80 kg / m 3 Below, 77kg / m 3 or less than 75 kg / m 3 The bulk density of the carbon nanotube composition of the present invention is higher than that of conventional bundled carbon nanotubes, which means that the carbon nanotube content per unit volume of the carbon nanotube composition of the present invention is high, and therefore the productivity per batch is high. Meanwhile, the bulk density can be calculated by filling a 50 ml container with the carbon nanotube composition by free fall, measuring the weight of the carbon nanotubes in the container, and dividing the weight by the container volume of 50 ml.

[0048] In the carbon nanotube composition provided by the present invention, the carbon nanotube yield may be 23 or more, preferably 23 or more, 23.5 or more, or 24 or more, and may be 45 or less, 43 or less, or 40 or less. The yield is an index indicating the amount of carbon nanotubes obtained relative to the weight of the catalyst, and a yield within the above range means that the carbon nanotube composition of the present invention is obtained with a high yield from the supported catalyst. In other words, the carbon nanotube composition of the present invention has excellent productivity, similar to conventional entangled carbon nanotubes. Meanwhile, the carbon nanotube yield may be calculated by (mass of carbon nanotube composition - mass of catalyst in carbon nanotube composition) / (mass of catalyst in carbon nanotube composition). More specifically, the mass of catalyst in the carbon nanotube composition may be determined by oxidizing the carbon nanotube composition in an alumina crucible at 750°C under atmospheric conditions for 4 hours to burn off all the carbon nanotubes, leaving only the supported catalyst in the composition, and then measuring the weight of the remaining supported catalyst.

[0049] In the carbon nanotube composition provided by the present invention, the specific surface area of ​​the carbon nanotubes is 160 m 2 / g or more, and preferably 163m 2 / g or more, 165m 2 / g or more or 168m 2 / g or more and 220m 2 / g or less, 210m 2 / g or less or 205m 2 The range of the specific surface area is similar to that of conventional bundled carbon nanotubes, and the carbon nanotube composition of the present invention has a bulk density similar to that of entangled carbon nanotubes as described above, and therefore exhibits high productivity, and is similar to conventional bundled carbon nanotubes in terms of specific surface area, and is superior in terms of dispersibility and electrical conductivity.

[0050] The carbon nanotube composition of the present invention may contain bundled carbon nanotubes, more specifically, the carbon nanotubes in the composition may be entirely bundled carbon nanotubes. As described above, the carbon nanotubes in the carbon nanotube composition of the present invention have the bundled structure and the technical advantages of entangled carbon nanotubes, and the content of bundled carbon nanotubes in the composition may be as high as the above range.

[0051] Method for producing carbon nanotube composition The present invention provides a method for producing the above-mentioned carbon nanotube composition, specifically, the method includes a step (S1) of packing a supported catalyst in which Co and V are supported on boehmite and a carbon nanotube powder for fluidized bed into a fluidized bed reactor, and a step (S2) of supplying a carbon source gas into the fluidized bed reactor and reacting the gas to synthesize carbon nanotubes.

[0052] 1) S1 step catalyst The catalyst used in the method for producing a carbon nanotube composition of the present invention is characterized by using a boehmite support, with Co and V simultaneously supported on the support. Boehmite is an aluminum-based support represented by γ-AlO(OH), and the main catalyst component Co and the co-catalyst component V are uniformly supported on the surface via hydroxyl groups.

[0053] Meanwhile, the number average particle size of the boehmite may be 20 to 100 μm, preferably 40 to 60 μm. When the number average particle size of the boehmite is within the above range, Co and V can be efficiently supported, and the specific surface area of ​​the carbon nanotubes produced from the catalyst can be particularly high.

[0054] The boehmite has a specific surface area of ​​150 to 250 m 2 / g, preferably 170 to 220 m 2 The boehmite may have a bulk density of 500 to 1200 kg / m 3 and preferably 700 to 1000 kg / m 3 When the physical properties of the boehmite are within the above ranges, there are technical advantages in that the support has excellent durability and can support a large amount of metal components without difficulty.

[0055] The shape of the boehmite is not particularly limited, but may be spherical or potato-shaped. The boehmite may have a porous structure, a molecular sieve structure, a honeycomb structure, or the like so as to have a relatively high surface area per unit mass or unit volume.

[0056] In the catalyst used in the method for producing a carbon nanotube composition of the present invention, Co is the main catalytic component and directly reduces the activation energy of the reaction in which carbon nanotubes are synthesized from a carbon source gas, thereby facilitating the carbon nanotube synthesis reaction. In particular, using Co rather than Ni or Fe as the main catalytic component has the technical advantage of facilitating the development of activity in the grain region of the main catalytic component on the support, thereby more easily forming a carbon nanotube bundle structure than using Ni or Fe as the main catalytic component. Furthermore, using a catalyst in which Co is supported on boehmite produces carbon nanotubes at a higher yield than using a catalyst in which Ni or Fe is supported on boehmite. Meanwhile, V, as a promoter, enhances the catalytic activity of Co. V, particularly, has an excellent synergistic effect with Co, thereby suppressing Co agglomeration during the production process.

[0057] Meanwhile, the Co content of the supported catalyst may be 16 to 22 wt%, preferably 18 to 20 wt%. The molar ratio of Co to V in the supported catalyst may be 2:1 to 4:1, preferably 2.5:1 to 3.5:1. When the contents of Co and V contained in the supported catalyst are within the above ranges, a carbon nanotube composition having the volume density targeted by the present invention can be produced.

[0058] The catalyst can be prepared by adding the boehmite support to a solution containing a Co precursor and a V precursor, followed by drying and calcination. The calcination temperature during the catalyst preparation process can be 660°C or higher and 740°C or lower, preferably 660°C or higher or 670°C or higher, and 740°C or lower, 730°C or lower, or 720°C or lower. If the calcination temperature during the catalyst preparation process is not appropriate, the particle size density and volume density of the carbon nanotubes obtained from the catalyst may deviate from the range required by the present invention.

[0059] Carbon nanotube powder for fluidized beds In the method for producing a carbon nanotube composition of the present invention, a carbon nanotube powder for fluidization is introduced into a fluidized bed reactor together with the catalyst. The carbon nanotube powder for fluidization is pre-synthesized carbon nanotube powder introduced together with the catalyst to maintain the reaction temperature within the fluidized bed reactor. Specifically, if only the supported catalyst is introduced without the carbon nanotube powder, 1) if a sufficient amount of supported catalyst is introduced, carbon nanotubes may overgrow from each catalyst, resulting in the production of carbon nanotubes that exceed the internal volume of the fluidized bed reactor, which may result in the production of carbon nanotubes with uniform properties. To prevent this, 2) if a small amount of supported catalyst is introduced, the volume occupied by the supported catalyst within the internal space of the fluidized bed reactor is small, which may result in the supported catalyst not being heated to a sufficiently high temperature during the reaction. On the other hand, when the supported catalyst and the carbon nanotube powder for fluidized bed are both introduced into a fluidized bed reactor to form a fluidized bed, the two components occupy a predetermined ratio or more of the internal space of the fluidized bed reactor, thereby ensuring a sufficient reaction temperature. Furthermore, after the reaction is completed, there is no need to separate the carbon nanotube powder for fluidized bed introduced to form the fluidized bed, and the final product can be easily obtained.

[0060] The carbon nanotubes used as the carbon nanotube powder for the fluidized bed are not particularly limited, however, from the viewpoint of obtaining a more uniform carbon nanotube composition, it is preferable to use carbon nanotubes having similar characteristics to the produced carbon nanotubes, such as bulk density, specific surface area, and particle size, as the carbon nanotube powder for the fluidized bed.

[0061] 2) S2 step In the previous step, after the supported catalyst and the carbon nanotube powder for fluidizing are filled into the fluidized bed reactor, a carbon source gas can be injected into the fluidized bed reactor to synthesize carbon nanotubes.

[0062] The carbon source gas is a carbon-containing gas that can be decomposed at high temperatures to form carbon nanotubes, and various carbon-containing compounds can be used, such as aliphatic alkanes, aliphatic alkenes, aliphatic alkynes, and aromatic compounds. More specifically, compounds such as methane, ethane, ethylene, acetylene, ethanol, methanol, acetone, carbon monoxide, propane, butane, benzene, cyclohexane, propylene, butene, isobutene, toluene, xylene, cumene, ethylbenzene, naphthalene, phenanthrene, anthracene, acetylene, formaldehyde, and acetaldehyde can be used. Ethylene is particularly preferred as the carbon source gas.

[0063] The carbon source gas is injected into the fluidized bed reactor, and the internal temperature of the fluidized bed reactor is increased to decompose the carbon source gas and synthesize carbon nanotubes. The internal temperature of the fluidized bed reactor in this step is preferably 650 to 750°C, and more preferably 670 to 730°C. The carbon nanotube composition of the present invention can be produced by using the above-mentioned supported catalyst and adjusting the reaction temperature within the above-mentioned range. If the reaction temperature is lower than this range, the yield of the carbon nanotube composition may be too low, and if it is higher than this range, problems such as further decomposition of the synthesized carbon nanotubes may occur.

[0064] Meanwhile, in this step, a fluidizing gas can be supplied into the fluidized bed reactor together with the carbon source gas. The fluidizing gas is used to further increase the fluidity of the pre-charged catalyst particles and the carbon nanotube powder for the fluidized bed. The fluidizing gas can be a gas that does not react with the carbon source gas or the carbon nanotubes and has high thermal stability. For example, nitrogen gas or an inert gas can be used as the fluidizing gas.

[0065] The supply flow ratio of the carbon source gas to the fluidizing gas may be 1:1 to 1:10, preferably 1:2 to 1:8, based on volume. When the supply flow ratio between the two gases is within the above range, the carbon nanotube composition can be obtained in high yield.

[0066] Carbon nanotube dispersion The present invention provides a carbon nanotube dispersion containing the above-mentioned carbon nanotube composition. More specifically, the present invention provides a carbon nanotube dispersion containing the above-mentioned carbon nanotube composition and a dispersion medium.

[0067] dispersion medium In the carbon nanotube dispersion liquid of the present invention, the dispersion medium may be either an aqueous solvent or an organic solvent, and examples thereof include water; amide-based polar organic solvents such as dimethylformamide (DMF), diethylformamide, dimethylacetamide (DMAc), and N-methylpyrrolidone (NMP); alcohols such as methanol, ethanol, 1-propanol, 2-propanol (isopropyl alcohol), 1-butanol (n-butanol), 2-methyl-1-propanol (isobutanol), 2-butanol (sec-butanol), 1-methyl-2-propanol (tert-butanol), pentanol, hexanol, heptanol, and octanol; glycols such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, 1,3-propanediol, 1,3-butanediol, 1,5-pentanediol, and hexylene glycol; glycerin, trimethylol, and the like. Examples of suitable dispersion media include polyhydric alcohols such as propane, pentaerythritol, and sorbitol; glycol ethers such as ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, triethylene glycol monomethyl ether, tetraethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monoethyl ether, triethylene glycol monoethyl ether, tetraethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, and tetraethylene glycol monobutyl ether; ketones such as acetone, methyl ethyl ketone, methyl propyl ketone, and cyclopentanone; and esters such as ethyl acetate, γ-butyrolactone, and ε-propiolactone. These may be used singly or in combination. More specifically, in consideration of the effect of improving the dispersibility of the carbon nanotubes and the dispersant, the dispersion medium may be an amide-based polar organic solvent, particularly N-methylpyrrolidone.

[0068] The carbon nanotube dispersion of the present invention may further include a dispersant to further enhance dispersibility. The dispersant may be an aqueous or organic dispersant. The aqueous dispersant may be selected from styrene butylene rubber (SBR) or carboxymethyl cellulose (CMC), and the organic dispersant may be hydrogenated acrylonitrile butatiene rubber (H-NBR), polyvinylpyrrolidone (PVP), or polyvinylbutyral (PVB).

[0069] In the carbon nanotube dispersion of the present invention, the initial viscosity of the dispersion may be 15,000 cP or less, preferably 12,000 cP or less, 10,000 cP or less, 8,000 cP or less, 7,000 cP or less, 6,000 cP or less, 5,000 cP or less, 4,500 cP or less, 4,000 cP or less, or 3,500 cP or less, and may be 200 cP or more, 500 cP or more, 700 cP or more, 1,000 cP or more, 1,200 cP or more, or 1,400 cP or more. By including the carbon nanotube composition described above, the dispersion of the present invention can maintain the above-mentioned relatively low viscosity. Meanwhile, the viscosity can be measured using a viscometer, specifically, at a spindle rotation of 12 rpm and a measurement temperature of 20 to 25°C.

[0070] In the carbon nanotube dispersion of the present invention, the content of the carbon nanotube composition in the dispersion may be 0.5 to 5 wt %, and preferably 1 to 5 wt %. Since the viscosity of the dispersion increases as the carbon nanotube content increases, an appropriate content of carbon nanotubes must be included for smooth processing of the dispersion. If the carbon nanotube content in the dispersion is lower than the above range, electrical conductivity may decrease when the slurry is subsequently applied. If the carbon nanotube content is higher than the above range, the viscosity of the dispersion may increase excessively, making processing difficult.

[0071] In the carbon nanotube dispersion of the present invention, the carbon nanotube particles dispersed in the dispersion may have a volume average particle size (Mv) of 3 μm or more, 4 μm or more, 5 μm or more, 6 μm or more, 6.5 μm or more, or 7 μm or more, and 30 μm or less, 25 μm or less, 20 μm or less, 18 μm or less, 15 μm or less, or 13 μm or less. The carbon nanotube particles may have a D10 value of 1.8 μm or more, 2.0 μm or more, 2.2 μm or more, 2.4 μm or more, 2.5 μm or more, 2.6 μm or more, or 2.7 μm or more, and 10 μm or less, 9 μm or less, 8 μm or less, 7 μm or less, 6 μm or less, 5 μm or less, or 4.5 μm or less. The carbon nanotube particles may have a D50 value of 2.5 μm or more, 3 μm or more, 4 μm or more, 4.5 μm or more, or 5 μm or more, and 15 μm or less, 14 μm or less, 13 μm or less, 12 μm or less, 11 μm or less, 10 μm or less, or 9 μm or less. The carbon nanotube particles may have a D90 value of 8 μm or more, 9 μm or more, 10 μm or more, 11 μm or more, 12 μm or more, or 13 μm or more, and 30 μm or less, 29 μm or less, 28 μm or less, 27 μm or less, 26 μm or less, or 25 μm or less. Furthermore, the span ((D90-D10) / D50) value obtained from the particle size distribution of the carbon nanotube particles may be 1.6 or more, 1.65 or more, 1.7 or more, 1.75 or more, or 1.78 or more, and 3.0 or less, 2.7 or less, 2.5 or less, 2.4 or less, or 2.3 or less. When the span value in the particle size distribution obtained for the carbon nanotube particles dispersed in the dispersion is within the above range, the dispersion has the advantages of low viscosity and excellent electrical conductivity.

[0072] The carbon nanotube dispersion liquid can be prepared by mixing a carbon nanotube composition with a dispersion medium. In the process of preparing the carbon nanotube dispersion liquid, a pretreatment step (S0) of milling the carbon nanotube composition before mixing can be performed first. By pre-milling the carbon nanotube composition and then mixing it with a dispersion medium, the viscosity of the dispersion liquid can be further reduced. The milling can be performed by a conventional method known as a milling method, such as ball milling. The milling time is not particularly limited, but is preferably 10 hours or less, since excessive milling may cause structural collapse of the carbon nanotubes themselves.

[0073] The mixing process may be carried out using a high-pressure homogenizer. Mixing using a high-pressure homogenizer allows for the preparation of a uniform dispersion in a short period of time. Mixing using a high-pressure homogenizer may be carried out once or repeatedly carried out 2 to 5 times, and the more times the mixing is repeated, the lower the viscosity of the dispersion may become. Since it is important that the viscosity of the dispersion be within an appropriate range when applying the slurry, the number of times mixing is repeated using a high-pressure homogenizer may be determined and carried out depending on the desired viscosity value of the dispersion.

[0074] Positive electrode slurry The present invention provides a positive electrode slurry containing the carbon nanotube dispersion. The carbon nanotube dispersion has an appropriate viscosity and excellent electrical conductivity, making it particularly suitable for use as a conductive material. Therefore, the dispersion can be used as a positive electrode slurry by mixing it with a positive electrode active material, a binder, and a solvent.

[0075] The positive electrode active material, binder, and solvent used in the positive electrode slurry of the present invention can be used in the present invention without any particular limitation, so long as they are commonly used.

[0076] Hereinafter, the present invention will be described in detail with reference to examples and experimental examples in order 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 into various other forms, and the scope of the present invention should not be interpreted as being limited to the examples detailed below. The examples of the present invention are provided to more completely explain the present invention to those skilled in the art.

[0077] Catalyst production example 1-1 A catalyst composition was prepared by dissolving 109.4 g of Co(NO3)2·6H2O and 14.6 g of NH4VO3 in 146 g of water, followed by dissolving 10.5 g of anhydrous citric acid with multicarboxylic acid. The catalyst composition was thoroughly stirred and then poured onto a boehmite support. The catalyst was then dried in an oven at 170°C for 6 hours and calcined at 690°C for 1 hour to obtain a catalyst. The Co content in the catalyst obtained in this Example 1 was 19 wt%, and the molar ratio of Co to V was 3:1.

[0078] Catalyst manufacturing examples 1-2 to 1-9 The weight of the cobalt and vanadium precursors used in Catalyst Preparation Example 1-1 was taken as 100% of the supported amount, and catalysts were obtained by varying the supported amount and the catalyst calcination temperature as shown in Table 1 below.

[0079] [Table 1]

[0080] Catalyst production example 2 A catalyst composition was prepared by dissolving 58.9 g of Co(NO3)2·6H2O and 2.4 g of NH4VO3 in 78.8 g of water, followed by dissolving 2.4 g of anhydrous citric acid with multicarboxylic acid. The catalyst composition was thoroughly stirred and then poured onto a boehmite support. The catalyst was then dried in an oven at 190°C for 6 hours and calcined at 690°C for 1 hour to obtain a catalyst. The Co content in the catalyst obtained in this Example 1 was 13 wt%, and the molar ratio of Co to V was 10:1.

[0081] Examples and Comparative Examples 800 g of the catalyst prepared in the catalyst preparation example and a pre-synthesized carbon nanotube composition were placed in a fluidized bed reactor, and the reactor was heated to a predetermined temperature while injecting ethylene gas and nitrogen gas into the reactor. The reaction was continued for 100 minutes to obtain a carbon nanotube composition containing the catalyst and synthesized carbon nanotubes.

[0082] The type of catalyst used in each example and comparative example, the weight of the pre-synthesized carbon nanotube composition (bed) pre-loaded into the fluidized bed reactor, the flow rate ratio (volume basis) of ethylene gas to nitrogen gas, and the reaction temperature are summarized in Table 2 below.

[0083] [Table 2A]

[0084] [Table 2B]

[0085] Comparative Example 4 We used the FT9100 product, an entangled carbon nanotube manufactured by CNano.

[0086] Comparative Example 5 Bulk density is 123.7 kg / m 3 and the specific surface area is 194m 2 The entangled carbon nanotube composition used had a mass of 1000 sq m / g, a purity of 97.5%, and a yield of 39.2 times.

[0087] Experimental Example 1: Confirmation of the properties of carbon nanotube compositions of Examples and Comparative Examples The carbon nanotube compositions obtained in the examples and comparative examples were examined for the following properties by the following methods.

[0088] 1) Bulk density: The carbon nanotube composition thus obtained was allowed to fall freely into a 50 ml container until it was filled to capacity, and the weight of the carbon nanotube composition filled into the container was measured. The measured weight was divided by the volume of the container, 50 ml, to calculate the bulk density.

[0089] 2) Specific surface area: Measured by standard method using Trista 2000 manufactured by Microtrac.

[0090] 3) Purity: The weight of the obtained carbon nanotube composition was measured, and the obtained carbon nanotube composition was placed in an alumina crucible and oxidized for 4 hours under atmospheric conditions at 750°C, and the weight of the remaining ash (catalyst) was measured. From this, the weight of the oxidized carbon nanotubes and the weight of the remaining catalyst were calculated, and the purity was calculated using the following formula.

[0091] Purity (wt%)=(mass of carbon nanotube composition−mass of catalyst in carbon nanotube composition) / (mass of carbon nanotube composition)*100%

[0092] 4) Yield: The weight of the obtained carbon nanotube composition was measured, and the obtained carbon nanotube composition was placed in an alumina crucible and oxidized for 4 hours under atmospheric conditions at 750°C, and the weight of the remaining ash (catalyst) was measured. Then, the yield was calculated using the following formula.

[0093] Yield=(mass of carbon nanotube composition−mass of catalyst in carbon nanotube composition) / (mass of catalyst in carbon nanotube composition)

[0094] 5) Mv (volume average particle size, μm): After 0.1 g of the carbon nanotube composition was dispersed in 50 g of water, the particle size distribution and the volume average particle size were measured using a spectrometer.

[0095] 6) Volumetric density: Calculated using the following formula 1.

[0096] [Formula 1] Volumetric density = yield of carbon nanotubes / volume of carbon nanotube composition

[0097] 7) Particle size density: Calculated using the following formula 2.

[0098] [Formula 2] Particle size density = carbon nanotube yield / volume average particle size of carbon nanotubes

[0099] The measurement and calculation results are summarized in Table 3 below.

[0100] [Table 3A]

[0101] [Table 3B]

[0102] As can be seen from Table 3, the carbon nanotube compositions according to the examples of the present invention have higher yields and bulk densities than the carbon nanotube compositions according to Comparative Examples 2 and 3. Comparative Example 2 is a bundled carbon nanotube composition produced using a catalyst calcined at a higher temperature, and Comparative Example 3 is a conventional bundled carbon nanotube composition. This means that the carbon nanotube composition of the present invention contains more carbon nanotubes per unit volume than the conventional bundled carbon nanotube composition, and can therefore be obtained with higher productivity.

[0103] On the other hand, the specific surface area and volume average particle size were similar between Example and Comparative Example 3. This confirms that the carbon nanotube composition of the present invention can be obtained with higher productivity than Comparative Example 3, and that the physical properties of the carbon nanotubes themselves are similar to those of conventional bundled carbon nanotubes. From these results, it can be predicted that the carbon nanotube composition of the present invention will exhibit electrical conductivity at a level similar to that of conventional bundled carbon nanotube compositions.

[0104] Meanwhile, among the results in Table 2, Examples 1 and 10 used catalysts prepared under the same conditions, and the differences in the numerical values ​​of Examples 1 and 10 are due to errors in the catalyst synthesis and carbon nanotube synthesis processes.

[0105] Experimental Example 2: Examples and Comparative Examples: Confirmation of the Properties of Carbon Nanotube Composition in a Dispersion State Carbon nanotube dispersions were prepared using the carbon nanotube compositions of Examples 8 to 11 and Comparative Examples 3 to 5, which used the same catalyst but different synthesis temperatures. Specifically, each carbon nanotube composition was milled using zirconium balls with a diameter of 10 mm at a rotation speed of 175 rpm. 18 g of the milled carbon nanotube composition was mixed with 578.5 g of N-methylpyrrolidone, and 3.5 g of HNBR was added as a dispersant to prepare a carbon nanotube dispersion with a carbon nanotube content of 3 wt %.

[0106] The prepared dispersion was measured for viscosity, slurry powder resistance, and particle size distribution in the dispersion state. Each property was measured by the following methods.

[0107] 1) Viscosity: Measurement was performed using a viscometer at a spindle rotation of 12 rpm and a measurement temperature of 20±1°C.

[0108] 2) Slurry powder resistance: 19 g of the prepared dispersion was added to the NCM cathode material (chemical formula: LiNi 0.5 Co 0.2 Mn 0.3 74g of cellulose acetate was mixed with 1g of PVDF as a binder and 32g of 1-methyl-2-pyrrolidone as a solvent and stirred to produce a slurry. The slurry was then coated onto an aluminum plate and dried at 130°C in a convection oven to form an electrode layer. After peeling off the electrode layer, the particles were collected and a predetermined amount was placed in a powder resistivity measurement module (MCP-PD51, manufactured by Nittoseiko Analytech). The powder resistivity was measured while increasing the pressure within the module from 4 to 20kN, and the powder resistivity value at a density of 2.7g / cc was calculated.

[0109] 3) Particle size distribution in the dispersion state (Mv, D10, D50, D90, SPAN ((D90-D10) / D50)): Using a laser diffraction particle size analyzer (Malvern Panalytic, Mastersizer 3000), the particle size and distribution were analyzed after adding a diluted solution of carbon nanotube dispersion. Among the analytical values, the volume average particle size (Mv), D10, D50 and D90 values ​​were derived, and the SPAN value was calculated using the derived D10, D50 and D90 values.

[0110] The results are summarized in Table 4 below.

[0111] [Table 4]

[0112] As can be seen from the results in Table 4, the carbon nanotube composition dispersion of the present invention contains bundled carbon nanotubes, and therefore exhibits electrical conductivity at a similar level to that of Comparative Example 3, which also contains bundled carbon nanotubes, and the viscosity in the dispersion state is significantly lower and processability is far superior to that of the dispersion of Comparative Example 3. On the other hand, in the case of the dispersions of Comparative Examples 4 and 5, which contain entangled carbon nanotubes, the entangled carbon nanotubes are easily dispersed during the dispersion preparation process, so that they exhibit superior effects in terms of viscosity compared to the Examples, but in terms of electrical conductivity, it can be seen that the slurry powder resistance is significantly higher than that of the Examples of the present invention.

[0113] This confirms that the carbon nanotube composition of the present invention simultaneously possesses the excellent electrical conductivity that is an advantage of bundled carbon nanotubes and the excellent dispersibility and processability that are advantages of entangled carbon nanotubes.

[0114] Experimental Example 3. Observation of the morphology of carbon nanotubes in Examples and Comparative Examples The morphology of the carbon nanotube compositions obtained in the examples and comparative examples was observed using SEM images. First, the morphologies of the carbon nanotubes obtained in Example 1 and Comparative Examples 3 and 4 were observed using SEM images at 3000x magnification, and the images are shown in Figures 1 to 3, respectively.

[0115] 1 to 3, the carbon nanotubes of Comparative Example 3 were bundled, and the carbon nanotubes of Comparative Example 4 were entangled, and it was confirmed that the carbon nanotubes according to the examples of the present invention were very similar in morphology to the bundled carbon nanotubes of Comparative Example 3. This confirmed that the carbon nanotube composition of the present invention was similar to the entangled carbon nanotubes in terms of bulk density and yield, but was actually shaped like bundled carbon nanotubes.

[0116] Furthermore, to compare the morphology of carbon nanotubes depending on volume and particle size density, the morphology of the carbon nanotubes obtained in Examples 8 to 11 was observed using SEM images at 400x magnification, and these are shown in Figures 4 to 7, respectively. As can be seen from Figures 4 to 7, as the density of the carbon nanotube composition increases, the morphology partially changes from a bundle type to an entangled type in which fine carbon nanotube bundles are entangled and agglomerated. This is thought to be because as the carbon nanotube synthesis temperature increases, the yield of carbon nanotubes increases, the grain size of the catalyst on the support increases, and the density within the carbon nanotube particles increases.

Claims

1. The volume density defined by the following formula 1 is 500 / mm ３ Above, 2500 / mm ３ A carbon nanotube composition, which is: [Formula 1] Volume density = yield of carbon nanotubes / volume of carbon nanotube composition The yield of the carbon nanotubes is calculated by (mass of the carbon nanotube composition - mass of the catalyst in the carbon nanotube composition) / (mass of the catalyst in the carbon nanotube composition).

2. 2. The carbon nanotube composition according to claim 1, wherein the particle size density defined by the following formula 2 is 50 / mm or more and 120 / mm or less. [Formula 2] Particle size density = carbon nanotube yield / volume average particle size of carbon nanotubes The yield of the carbon nanotubes is calculated in the same manner as in Equation 1.

3. Bulk density is 40 kg / m ３ Above, 85kg / m ３ 2. The carbon nanotube composition of claim 1, wherein:

4. The carbon nanotube composition according to claim 1 , wherein the yield of the carbon nanotubes is 30% or more.

5. The specific surface area of ​​the carbon nanotube is 160 m ２ The carbon nanotube composition according to claim 1 , wherein the carbon nanotube composition has a molecular weight of 1 / g or more.

6. The carbon nanotube composition of claim 1 , comprising bundled carbon nanotubes.

7. Step (S1) of packing a supported catalyst in which Co and V are supported on boehmite and a carbon nanotube powder for fluidized bed into a fluidized bed reactor; and (S2) supplying a carbon source gas into the fluidized bed reactor while reacting the gas to synthesize carbon nanotubes.

8. The Co content of the supported catalyst is 16 wt% or more and 22 wt% or less, 8. The method for producing a carbon nanotube composition according to claim 7, wherein the molar ratio of Co to V in the supported catalyst is 2:1 to 4:

1.

9. 8. The method for producing a carbon nanotube composition according to claim 7, wherein the fluidized bed reactor is heated to an internal temperature of 650°C or more and 750°C or less in the step S2.

10. The step S2 includes supplying both a carbon source gas and a fluidizing gas; 8. The method for producing a carbon nanotube composition according to claim 7, wherein the ratio of the supply flow rate of the carbon source gas to the flowing gas is 1:1 to 1:

10.

11. The carbon nanotube composition according to any one of claims 1 to 6, A carbon nanotube dispersion comprising:

12. The carbon nanotube dispersion according to claim 11 , wherein the content of the carbon nanotube composition in the dispersion is 0.5% by weight or more and 5% by weight or less.

13. The carbon nanotube dispersion according to claim 11, wherein the dispersion contains one or more dispersants selected from the group consisting of styrene butylene rubber (SBR), carboxymethyl cellulose (CMC), hydrogenated acrylonitrile butadiene rubber (H-NBR), polyvinylpyrrolidone (PVP), and polyvinyl butyral (PVB).

14. The carbon nanotube dispersion according to claim 11, having an initial viscosity of 15,000 cP or less.

15. The carbon nanotube dispersion liquid according to claim 11, a positive electrode active material; Binder and a solvent.

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