Carbon nanotube assembly, conductive material, electrode, secondary battery, planar assembly, filter, electromagnetic wave shield, and extreme ultraviolet pellicle

Abstract

Provided is a carbon nanotube assembly having higher tensile strength compared to the past. This carbon nanotube assembly satisfies conditions (1) and (2) below. (1) The carbon nanotube assembly contains Si, and the Si content is more than 0 mass ppm but less than 1,000 mass ppm relative to the total mass of the carbon nanotube assembly. (2) The surface resistivity W as measured according to the measurement method set forth in the specification is more than 0 Ω / □ but not more than 4.0 Ω / □.

Description

Carbon nanotube aggregates, conductive materials, electrodes, secondary batteries, planar aggregates, filters, electromagnetic shielding, and pellicles for extreme ultraviolet radiation.

[0001] This disclosure relates to carbon nanotube aggregates, conductive materials, electrodes, secondary batteries, planar aggregates, filters, electromagnetic shielding, and pellicles for extreme ultraviolet radiation.

[0002] Carbon nanotubes (hereinafter also referred to as "CNTs") are materials having a cylindrical structure formed by rolling up graphene sheets, which are composed of six-membered ring structures of carbon, in a single or multilayer configuration on the same axis. CNTs are broadly classified into single-walled CNTs, which are formed from a single layer of graphene sheet, and multilayered CNTs, which are formed from multiple layers of graphene sheet. CNTs exhibit excellent mechanical, electrical, and chemical properties, and these properties are expected to lead to applications in fields such as materials, catalysts, energy, and electronics. Various attempts have been proposed to further enhance the properties of CNTs.

[0003] For example, Patent Document 1 describes a carbon nanotube comprising at least one element selected from aluminum (Al), magnesium (Mg), and silicon (Si), and at least one metal selected from cobalt (Co), nickel (Ni), iron (Fe), manganese (Mn), and molybdenum (Mo), wherein the intensity ratio (ID / IG) measured by Raman spectroscopy is about 1.10 or less, and the carbon purity is about 98% or more. Patent Document 2 describes a dispersion of fibrous carbon nanostructures comprising fibrous carbon nanostructures whose t-plot obtained from adsorption isotherms shows an upwardly convex shape, molecular additives, and a solvent.

[0004] U.S. Published Patent No. 2015 / 0093576, Japanese Patent Publication No. 2017-114756

[0005] In some cases, high tensile strength was required for CNT aggregates.

[0006] This disclosure has been made in view of the above circumstances. One embodiment of this disclosure aims to solve the problem of providing a carbon nanotube aggregate with higher tensile strength compared to conventional materials. Another embodiment of this disclosure aims to solve the problem of providing a conductive material, electrode, secondary battery, and planar aggregate containing the carbon nanotube aggregate. Another embodiment of this disclosure aims to solve the problem of providing a laminate comprising the planar aggregate. Another embodiment of this disclosure aims to solve the problem of providing a filter, electromagnetic shield, and extreme ultraviolet pellicle using the planar aggregate.

[0007] <1> A carbon nanotube aggregate that satisfies the following conditions (1) and (2). (1) It contains Si, and the Si content is greater than 0 ppm by mass and less than 1000 ppm by mass relative to the total mass of the carbon nanotube aggregate. (2) The surface resistivity measured by the following measurement method is greater than 0 Ω / □ and 4.0 Ω / □ or less. (Method for measuring surface resistivity) A carbon nanotube dispersion is prepared by mixing the carbon nanotube aggregate, 700 kDa of carboxymethylcellulose sodium, and water, so that the concentration of the carbon nanotube aggregate is 0.20% by mass and the concentration of carboxymethylcellulose sodium is 0.30% by mass. 15 mL of the prepared carbon nanotube dispersion is poured onto a slide glass type silicon plate with inner dimensions of 22 mm × 75 mm × 3 mm and heated and dried at 100°C to prepare a measurement sample. For the prepared measurement sample, the surface resistivity of five arbitrarily selected locations on the film is measured using a resistivity meter with a four-probe method, and the average of the five measured values ​​is taken as the surface resistivity. <2> A carbon nanotube aggregate as described in <1> that satisfies the following condition (3). (3) When the carbon nanotube aggregate, 700 kDa of carboxymethylcellulose sodium, and water are mixed, and the liquid temperature is 25°C, the concentration of the carbon nanotube aggregate is 0.20 mass%, and the concentration of the carboxymethylcellulose sodium is 0.30 mass%, the common logarithm of the viscosity of the dispersion is 2.0 or higher. The unit of viscosity is mPa·s. <3> A conductive material containing the carbon nanotube aggregate as described in <1> or <2>. <4> An electrode containing an electrode active material and the conductive material as described in <3>. <5> A secondary battery equipped with the electrode as described in <4>. <6> A planar aggregate containing the carbon nanotube aggregate as described in <1> or <2>. <7> A laminate comprising a substrate and the planar assembly described in <6>. <8> A filter using the planar assembly described in <6>. <9> An electromagnetic shield using the planar assembly described in <6>. <10> An extreme ultraviolet pellicle using the planar assembly described in <6>.

[0008] According to one embodiment of the present disclosure, a carbon nanotube aggregate with higher tensile strength than conventional materials is provided. According to another embodiment of the present disclosure, a conductive material, an electrode, a secondary battery, and a planar aggregate comprising the carbon nanotube aggregate are provided. According to another embodiment of the present disclosure, a laminate comprising the planar aggregate is provided. According to another embodiment of the present disclosure, a filter, an electromagnetic shield, and an extreme ultraviolet pellicle using the planar aggregate are provided.

[0009] This is a scanning electron microscope image showing one aspect of CNT aggregate 1 of Example 1. This is a scanning electron microscope image showing one aspect of CNT aggregate 2 of Example 2. This is a scanning electron microscope image showing one aspect of CNT aggregate 3 of Example 3. This is a scanning electron microscope image showing one aspect of CNT aggregate 4 of Example 4. This is a scanning electron microscope image showing one aspect of CNT aggregate 5 of Example 5. This is a scanning electron microscope image showing one aspect of CNT aggregate 6 of Comparative Example 1. This is a scanning electron microscope image showing one aspect of CNT aggregate 7 of Comparative Example 2.

[0010] The carbon nanotube assemblies, conductive materials, electrodes, secondary batteries, planar assemblies, laminates, filters, electromagnetic shields, and extreme ultraviolet pellicles related to this disclosure will be described in detail below. The following descriptions may be based on typical embodiments of this disclosure, but this disclosure is not limited to such embodiments and can be implemented with appropriate modifications within the scope of the purpose of this disclosure.

[0011] In this disclosure, numerical ranges indicated using "~" mean ranges that include the numbers before and after "~" as the minimum and maximum values, respectively. In numerical ranges described in stages in this disclosure, the upper or lower limit stated in one numerical range may be replaced with the upper or lower limit of another numerical range described in stages. Also, in numerical ranges described in this disclosure, the upper or lower limit stated in one numerical range may be replaced with the values ​​shown in the examples. In this disclosure, a combination of two or more preferred embodiments is a more preferred embodiment. In this disclosure, the amount of each component means the total amount of multiple substances if there are multiple substances corresponding to each component, unless otherwise specified. In this specification, the term "process" includes not only independent processes but also processes that cannot be clearly distinguished from other processes, as long as the intended purpose of the process is achieved.

[0012] In this disclosure, the terms "carbon nanotube," "single-walled carbon nanotube," "multi-walled carbon nanotube," "carbon nanotube aggregate," "carbon nanotube having a maximum length of 1,000 μm to 30,000 μm," and "carbon nanotube dispersion" may be abbreviated as "CNT," "SWCNT," "MWCNT," "CNT aggregate," "ULCNT," and "CNT dispersion," respectively.

[0013] [CNT aggregate] The CNT aggregate according to this disclosure satisfies the following conditions (1) and (2): (1) It contains Si, and the Si content is greater than 0 ppm by mass and less than 1000 ppm by mass relative to the total mass of the CNT aggregate. (2) The surface resistivity measured by the following measurement method is greater than 0 Ω / □ and 4.0 Ω / □ or less. (Method for measuring surface resistivity) A CNT dispersion is prepared by mixing a carbon nanotube aggregate, 700 kDa sodium carboxymethylcellulose, and water, with a concentration of CNT aggregate of 0.20% by mass and a concentration of sodium carboxymethylcellulose of 0.30% by mass. 15 mL of the prepared CNT dispersion is poured onto a slide glass type silicon plate with inner dimensions of 22 mm × 75 mm × 3 mm and heated and dried at 100°C to prepare a measurement sample. For the prepared sample, the surface resistivity at five arbitrarily selected locations on the film is measured using a resistivity meter with a four-probe method, and the average of the five measured values ​​is taken as the surface resistivity.

[0014] A CNT aggregate that satisfies conditions (1) and (2), i.e., the CNT aggregate according to this disclosure, has higher tensile strength compared to conventional aggregates. On the other hand, Patent Documents 1 and 2 do not contain any descriptions that focus on conditions (1) and (2).

[0015] Patent Document 1 does not describe the specific Si content, nor does it describe the surface resistivity. Furthermore, Patent Document 1 does not focus on tensile strength. Patent Document 2 describes a carbon nanotube dispersion containing Si. However, the carbon nanotube dispersion described in Patent Document 2 is coated onto a substrate and then fired in air at a temperature of 250°C, and is not obtained as a carbon nanotube aggregate. In contrast, the CNT aggregate according to the present disclosure has higher tensile strength compared to conventional materials by satisfying conditions (1) and (2).

[0016] <Condition (1)> The CNT aggregate according to this disclosure has a Si content of more than 0 ppm by mass and less than 1000 ppm by mass relative to the total mass of the CNT aggregate. The Si is presumed to originate from the Si used in the manufacturing method of the CNT aggregate and exists in the form of silica or the like. Si may be used as a catalyst support as silica, or as a constituent material of ceramic reaction tubes, and it is thought to originate from either or both. Silica is a relatively hard substance with a Mohs hardness of about 7 and has the effect of dispersing unwanted aggregation of CNT aggregates. In addition, water and silica are compatible and have the effect of increasing the affinity of the CNT aggregate to water. For this reason, the CNTs interact with each other gently in the dispersion, and a basis for efficiently forming conductive paths in the film obtained from the dispersion is created, so the surface resistivity of the film can be kept in a low range. This is a suitable property for use as a conductive additive and contributes to maintaining the tensile strength of the obtained film in a desirable range.

[0017] Specifically, the adsorption of Si onto the surface of CNTs strengthens the bonding force between CNT aggregates. It is believed that the chemical adsorption of Si onto the surface of CNTs strengthens the interactions between CNTs, thereby improving the overall mechanical strength of the CNT aggregate. This effect is due to the change in the surface free energy of the CNTs caused by Si, which strengthens the bonds between CNTs. As a result, the tensile strength of the CNT aggregate is improved.

[0018] By having a Si content of less than 1000 ppm by mass, for example, when the CNT aggregate of this disclosure is used as a reinforcing material for a composite material, embrittlement of the composite material due to the presence of excess Si is suppressed. The appropriate presence of Si on the surface of the CNTs strengthens the bonding force between CNTs, while the presence of excess Si can reduce the flexibility of the CNTs. The tensile strength of the CNT aggregate is optimized by having an appropriate Si content. Therefore, the tensile strength of the CNT aggregate is efficiently improved by having an appropriate Si atom content in the CNT aggregate.

[0019] The CNT aggregates according to this disclosure contain Si. However, from a synthesis standpoint, it is technically difficult to reduce the Si content in the CNT aggregates to less than 10 ppm by mass. Specifically, in the CNT manufacturing process, it is unavoidable that trace amounts of Si will be introduced as impurities from the reactor. Therefore, it is difficult to achieve a Si content of less than 10 ppm by mass. Attempting to remove even more Si would require extreme processing conditions, which are undesirable from the standpoint of manufacturing costs. Furthermore, applying harsh processing conditions may introduce unexpected functional groups to the surface of the CNT aggregates or damage the framework of the CNT aggregates, potentially leading to a decrease in conductivity. If the Si content is 10 ppm by mass or more, stable CNTs can be obtained in the manufacturing process.

[0020] From the above viewpoint, the Si content may be 10 ppm by mass or more and less than 1000 ppm by mass.

[0021] Methods to reduce the Si content to less than 1000 ppm by mass include, for example, washing the CNT aggregate with water, acid, an acidic aqueous solution (e.g., hydrofluoric acid aqueous solution), or an aqueous solution of a quaternary ammonium salt containing fluoride ions. This method can reduce the Si content. By immersing the CNT aggregate in tetraethoxysilane and hydrolyzing it, Si can be adsorbed onto the surface of the CNT aggregate, thereby increasing the Si content relative to the total mass of the CNT aggregate. However, such adjustments to the Si content increase the process load and lead to increased costs, so it is preferable to avoid them. Furthermore, it is possible to adjust the Si content to less than 1000 ppm by mass by avoiding the use of silica as a catalyst support, appropriately selecting a ceramic reaction tube material that is less prone to Si removal, and controlling the reaction conditions so that they are not too harsh. In this case, no further adjustment of the Si content is necessary.

[0022] Within the range described above, the adsorption of Si onto the CNT surface strengthens the interactions between CNTs, thereby improving tensile strength. Specifically, Si atoms chemically adsorb onto the CNT surface, forming Si-C bonds and Si-O-C bonds, which strengthens the bonding force between CNTs. This reinforces van der Waals forces and π-π interactions between CNTs, improving the overall mechanical strength of the CNT aggregate. As a result, the tensile strength of the CNT aggregate is optimized. Furthermore, within the range described above, having an appropriate Si atom content optimizes the balance between flexibility and strength when using the CNT aggregate as a reinforcing material in composite materials. Therefore, by adjusting the Si content to an appropriate range, the tensile strength of the CNT aggregate can be efficiently improved. In addition, having a Si content within the above range allows the refining cost of the CNT aggregate to be kept within an appropriate range. This makes it possible to optimize the balance between improved tensile strength and cost efficiency.

[0023] In this disclosure, the Si content (mass ppm) relative to the total mass of a CNT aggregate can be measured, for example, by the following method: The CNT aggregate is completely dissolved in an alkali. Pretreatment such as dry ashing or wet ashing may be performed to completely dissolve the CNT aggregate in an alkali. After dissolving in an alkali, it is dissolved in an acid. The Si content relative to the total mass of the CNT aggregate can be measured by performing inductively coupled plasma atomic emission spectroscopy (ICP-AES) on a solution obtained by completely dissolving the CNT aggregate in an acid as a sample.

[0024] Furthermore, if the Si content in the CNT aggregate is less than 10 ppm by mass, it may be technically difficult to detect peaks originating from Si atoms, even when using ICP-MS or ICP-AES, making it difficult to accurately calculate the Si content. For this reason, in this disclosure, if the Si atom content obtained by the above measurement is less than 10 ppm by mass, the Si atom content may be treated as 0.

[0025] The Si content is less than 1000 ppm by mass, and may be 950 ppm by mass or less, 900 ppm by mass or less, 850 ppm by mass or less, 800 ppm by mass or less, 750 ppm by mass or less, or 700 ppm by mass or less.

[0026] The Si content may be 15 ppm or more by mass, 20 ppm or more by mass, 25 ppm or more by mass, 30 ppm or more by mass, 35 ppm or more by mass, 40 ppm or more by mass, 45 ppm or more by mass, 50 ppm or more by mass, 60 ppm or more by mass, 70 ppm or more by mass, 80 ppm or more by mass, 90 ppm or more by mass, or 100 ppm or more by mass.

[0027] In one preferred embodiment, the Si content is greater than 0 ppm by mass and 800 ppm by mass or less, greater than 0 ppm by mass and less than 750 ppm by mass, and greater than 0 ppm by mass and 700 ppm by mass or less. In another preferred embodiment, the Si content is 10 ppm by mass or more and 800 ppm by mass or less, 10 ppm by mass or more and 750 ppm by mass or less, and 10 ppm by mass or more and 700 ppm by mass or less. In another preferred embodiment, the Si content is 15 ppm by mass or more and 800 ppm by mass or less, 15 ppm by mass or more and 750 ppm by mass or less, and 15 ppm by mass or more and 700 ppm by mass or less. In another preferred embodiment, the Si content is 20 ppm by mass or more and 800 ppm by mass or less, 20 ppm by mass or more and 750 ppm by mass or less, and 20 ppm by mass or more and 700 ppm by mass or less. In another preferred embodiment, the Si content is 25 ppm or more and 800 ppm or less, 25 ppm or more and 750 ppm or less, and 25 ppm or more and 700 ppm or less. In another preferred embodiment, the Si content is 30 ppm or more and 800 ppm or less, 30 ppm or more and 750 ppm or less, and 30 ppm or more and 700 ppm or less. In another preferred embodiment, the Si content is 35 ppm or more and 800 ppm or less, 35 ppm or more and 750 ppm or less, and 35 ppm or more and 700 ppm or less. In another preferred embodiment, the Si content is 40 ppm or more and 800 ppm or less, 40 ppm or more and 750 ppm or less, and 40 ppm or more and 700 ppm or less. In another preferred embodiment, the Si content is 45 ppm by mass or more and 800 ppm by mass or less, 45 ppm by mass or more and 750 ppm by mass or less, and 45 ppm by mass or more and 700 ppm by mass or less. In another preferred embodiment, the Si content is 50 ppm by mass or more and 800 ppm by mass or less, 50 ppm by mass or more and 750 ppm by mass or less, and 50 ppm by mass or more and 700 ppm by mass or less.In another preferred embodiment, the Si content is 100 ppm by mass or more and 800 ppm by mass or less, 100 ppm by mass or more and 750 ppm by mass or less, and 100 ppm by mass or more and 700 ppm by mass or less.

[0028] In a more preferred embodiment, the Si content is 10 ppm to 700 ppm by mass, 20 ppm to 700 ppm by mass, 30 ppm to 700 ppm by mass, 40 ppm to 700 ppm by mass, 50 ppm to 700 ppm by mass, and 100 ppm to 700 ppm by mass. A Si content of 700 ppm by mass or less is preferred because it strengthens the interaction between CNTs and improves tensile strength.

[0029] <Condition (2)> The CNT aggregate relating to this disclosure has a surface resistivity measured by the following measurement method that is greater than 0 Ω / □ and less than or equal to 4.0 Ω / □. (Method for measuring surface resistivity) A CNT dispersion is prepared by mixing a CNT aggregate, 700 kDa of carboxymethylcellulose sodium, and water, with a concentration of 0.20 mass% of CNT aggregate and a concentration of 0.30 mass% of carboxymethylcellulose sodium. A measurement sample is prepared by pouring 15 mL of the prepared CNT dispersion onto a slide glass type silicon plate with inner dimensions of 22 mm × 75 mm × 3 mm and heating and drying it at 100°C. The surface resistivity of the prepared measurement sample is measured at five arbitrarily selected locations on the film using a resistivity meter with a four-probe method, and the average value of the five measured values ​​is taken as the surface resistivity.

[0030] The surface resistivity may be 3.9 Ω / □ or less, 3.8 Ω / □ or less, 3.7 Ω / □ or less, 3.6 Ω / □ or less, 3.5 Ω / □ or less, 3.4 Ω / □ or less, 3.3 Ω / □ or less, 3.2 Ω / □ or less, 3.1 Ω / □ or less, or 3.0 Ω / □ or less.

[0031] The surface resistivity may be 0.01 Ω / □ or higher, 0.02 Ω / □ or higher, 0.03 Ω / □ or higher, 0.04 Ω / □ or higher, 0.05 Ω / □ or higher, 0.06 Ω / □ or higher, 0.07 Ω / □ or higher, 0.08 Ω / □ or higher, 0.09 Ω / □ or higher, 0.1 Ω / □ or higher, 0.2 Ω / □ or higher, 0.3 Ω / □ or higher, 0.5 Ω / □ or higher, 0.7 Ω / □ or higher, or 0.9 Ω / □ or higher.

[0032] The surface resistivity is preferably 0.01 Ω / □ or more and 4.0 Ω / □ or less, more preferably 0.02 Ω / □ or more and 4.0 Ω / □ or less, even more preferably 0.04 Ω / □ or more and 4.0 Ω / □ or less, particularly preferably 0.06 Ω / □ or more and 4.0 Ω / □ or less, extremely preferably 0.08 Ω / □ or more and 4.0 Ω / □ or less, even more extremely preferably 0.1 Ω / □ or more and 4.0 Ω / □ or less, even more extremely preferably 0.2 Ω / □ or more and 4.0 Ω / □ or less, and most preferably 0.9 Ω / □ or more and 4.0 Ω / □ or less. The surface resistivity is preferably 0.01 Ω / □ or more and 3.5 Ω / □ or less, more preferably 0.02 Ω / □ or more and 3.5 Ω / □ or less, even more preferably 0.04 Ω / □ or more and 3.5 Ω / □ or less, particularly preferably 0.06 Ω / □ or more and 3.5 Ω / □ or less, extremely preferably 0.08 Ω / □ or more and 3.5 Ω / □ or less, even more extremely preferably 0.1 Ω / □ or more and 3.5 Ω / □ or less, even more extremely preferably 0.2 Ω / □ or more and 3.5 Ω / □ or less, and most preferably 0.9 Ω / □ or more and 3.5 Ω / □ or less. The surface resistivity is preferably 0.01 Ω / □ or more and 3.31 Ω / □ or less, more preferably 0.02 Ω / □ or more and 3.31 Ω / □ or less, even more preferably 0.04 Ω / □ or more and 3.31 Ω / □ or less, particularly preferably 0.06 Ω / □ or more and 3.31 Ω / □ or less, extremely preferably 0.08 Ω / □ or more and 3.31 Ω / □ or less, even more extremely preferably 0.1 Ω / □ or more and 3.31 Ω / □ or less, even more extremely preferably 0.2 Ω / □ or more and 3.31 Ω / □ or less, and most preferably 0.91 Ω / □ or more and 3.31 Ω / □ or less.

[0033] When the surface resistivity is within the above range, the aggregation of CNT aggregates is appropriately controlled, and uniform dispersion of CNT aggregates in the dispersion is achieved. Mechanical strength can also be ensured. In particular, when added to electrodes as a conductive additive, good mechanical strength can be maintained, thereby suppressing volume changes of the electrodes and improving the durability of the battery. In particular, when the surface resistivity is in the range of 0.01 to 4.0, the aggregation of CNT aggregates is moderately small and tends to be uniform, so aggregation of CNT aggregates in the dispersion is suppressed and dispersibility is improved. It is thought that the low surface resistivity of the CNT aggregates makes it easier to build a loose network of CNTs in the dispersion, making it easier to incorporate dispersion medium molecules, resulting in further improvement of dispersibility. When such a loose network is formed, for example, when CNT aggregates are incorporated into electrodes, it suppresses swelling and shrinkage by enveloping the electrode active material, contributing to improved mechanical properties and thus leading to an improvement in battery life. Furthermore, the reduced electrostatic charge in the CNT aggregate makes it less likely for clumps to form due to static electricity, thus reducing blocking during dispersion. Therefore, by satisfying condition (2), high tensile strength can be obtained.

[0034] <Condition (3)> The CNT aggregate according to this disclosure is obtained by mixing the CNT aggregate with 700 kDa of carboxymethylcellulose sodium and water, and the common logarithm of the viscosity of the dispersion when the liquid temperature is 25°C, the concentration of the CNT aggregate is 0.20% by mass, and the concentration of the carboxymethylcellulose sodium is 0.30% by mass is 2.0 or higher. The unit of viscosity is preferably mPa·s.

[0035] By having a common logarithm of the viscosity of the above dispersion of 2.0 or higher, the tensile strength of the CNT aggregate is improved, and the performance as a composite material is optimized.

[0036] The common logarithm of the viscosity of the above dispersion is preferably 2.0 or more and 3.5 or less, more preferably 2.0 or more and 3.4 or less, particularly preferably 2.0 or more and 3.3 or less, even more preferably 2.0 or more and 3.1 or less, even more preferably 2.0 or more and 3.0 or less, particularly preferably 2.01 or more and 2.85 or less, and especially preferably 2.47 or more and 2.85 or less.

[0037] When the common logarithm of the viscosity of the above dispersion is between 2.0 and 3.5, the dispersion of CNTs is maintained uniformly, and a network structure is efficiently formed within the composite material. This improves the tensile strength of the composite material and optimizes the overall mechanical properties of the material.

[0038] Furthermore, when the common logarithm of the viscosity of the dispersion is between 2.1 and 3.5, the dispersion of CNTs is further improved, and the mechanical strength of the composite material is enhanced. As a result, the composite material can be more durable against external stress, extending its service life.

[0039] In particular, when the common logarithm of the viscosity of the dispersion is between 2.4 and 3.5, the balance between the dispersibility and tensile strength of the CNTs is optimized, and the performance of the composite material is maximized. Within this range, uniform dispersion of CNTs and high tensile strength can be achieved simultaneously, and a significant improvement in the material's mechanical properties can be expected.

[0040] <Bundle Structure> The CNT aggregate according to this disclosure preferably includes a bundle structure. A bundle structure refers to an aggregate in which multiple CNTs are aggregated together by van der Waals forces or the like, forming a bundle. It is presumed that including a bundle structure of an appropriate size in the CNT aggregate improves the handling properties of the CNT aggregate and further improves its stability. On the other hand, if the bundle structure included in the CNT aggregate becomes too large, the size of the CNT aggregate itself becomes too large, and it becomes difficult to separate and disperse the CNTs included in the bundle structure, which may reduce its dispersibility in the dispersion medium.

[0041] The bundle structure in the CNT aggregate can be formed, for example, by controlling the catalyst particle size distribution during manufacturing by chemical vapor deposition (CVD) or by controlling the cooling rate during the cooling process.

[0042] From the viewpoint of achieving both the handling properties and dispersibility in the solvent of the CNT aggregate, the individual bundle diameters contained in the CNT aggregate are preferably 5 nm to 500 nm, and more preferably 10 nm to 300 nm. The content of bundle structures in the CNT aggregate is preferably 10% to 100% by mass, and more preferably 20% to 90% by mass, based on the total mass of the CNT aggregate. The presence or absence of bundle structures in the CNT aggregate can be confirmed by observing the CNT aggregate with an optical microscope, a scanning electron microscope (SEM), etc. The bundle diameter can be determined by identifying the locations where bundle structures exist in the CNT aggregate and measuring the length using images of the bundle structures.

[0043] <Area ratio of bundles with a bundle diameter of 100 nm or more> The CNT aggregate according to this disclosure includes a bundle structure, and it is preferable that the area ratio of bundles with a bundle diameter of 100 nm or more in the area observed by a scanning electron microscope (SEM) is greater than 0.1. In the CNT aggregate according to this disclosure, having an area ratio of bundles with a bundle diameter of 100 nm or more in the area observed by an SEM of greater than 0.1 allows for the appropriate formation of the CNT bundle structure, improving the mechanical strength. Specifically, a bundle diameter of 100 nm or more strengthens the bonds between CNTs, improving the tensile strength of the entire aggregate. In addition, a large bundle diameter stabilizes the network structure of the CNTs, improving durability against external stress. As a result, the mechanical properties of the material are significantly improved.

[0044] In particular, the area ratio of the bundles is preferably greater than 0.1 and less than 0.6, more preferably greater than 0.1 and less than 0.55, more preferably greater than 0.1 and less than 0.5, and even more preferably between 0.12 and 0.45. Within this range, the bundle structure of the CNTs is appropriately formed, and the bonds between the CNTs are strengthened, thereby improving the tensile strength of the CNT aggregate. Furthermore, an appropriate bundle diameter improves the dispersibility of the CNTs, appropriately maintains the viscosity of the dispersion, resulting in good processability and ensuring a uniform network structure within the material. As a result, the overall mechanical properties of the material are improved.

[0045] The CNT aggregates of this disclosure preferably have a bundle diameter of 100 nm or more and 500 nm or less, and preferably the area ratio of bundles with a bundle diameter of 100 nm or more in the SEM observation area is greater than 0.1 and less than 0.5.

[0046] Furthermore, the area ratio of the bundle is preferably greater than 0.1 and less than or equal to 0.45. Within this range, the bundle diameter of the CNTs becomes appropriately small, increasing the surface area of ​​the material and expanding the contact area with other components. This improves the tensile strength of the material. In addition, an appropriately small bundle diameter also has the effect of increasing the flexibility of the material and improving its resistance to external stress. Therefore, the mechanical properties of the material are further improved.

[0047] <Cumulative 90% Bundle Diameter> The CNT aggregate according to this disclosure includes a bundle structure, and in the observation area by scanning electron microscopy, the cumulative 90% bundle diameter (hereinafter also referred to as the "cumulative 90% bundle diameter") is usually 500 nm or less, and preferably more than 80 nm and less than or equal to 500 nm. The cumulative 90% bundle diameter may also be 400 nm or less, 350 nm or less, 300 nm or less, 250 nm or less, 220 nm or less, 200 nm or less, or 190 nm or less. The cumulative 90% bundle diameter may also be 90 nm or more, 100 nm or more, 110 nm or more, or 120 nm or more. The cumulative 90% bundle diameter may also be more than 180 nm or more than 200 nm.

[0048] In particular, in one embodiment, the cumulative 90% bundle diameter is preferably 80 nm to 500 nm, more preferably 90 nm to 400 nm, even more preferably 100 nm to 300 nm, especially preferably 100 nm to 250 nm, even more preferably 110 nm to 230 nm, particularly preferably 110 nm to 200 nm, and even more preferably 120 nm to 190 nm. When the cumulative 90% bundle diameter is greater than 80 nm, the bundles of CNTs gather together, making it easier to form long-distance conductive networks. Also, when the cumulative 90% bundle diameter is 500 nm or less, the dispersibility in the dispersion medium is good, making it easier to ensure tensile strength.

[0049] <Matters concerning bundle diameter and bundle diameter parameters> The CNT aggregate according to this disclosure preferably includes a bundle structure. A bundle structure refers to an aggregate in which multiple CNTs are aggregated together by van der Waals forces or the like, forming a bundle. The width of the bundle structure, that is, the size in the width direction of the fiber bundle, is the bundle diameter. It is presumed that including a bundle structure with an appropriate bundle diameter in the CNT aggregate improves the handling properties of the CNT aggregate and further improves its stability. On the other hand, if the bundle structure included in the CNT aggregate becomes too large, the size of the CNT aggregate itself becomes too large, and it becomes difficult to separate and disperse the CNTs included in the bundle structure, which may reduce the dispersibility in the dispersion medium.

[0050] The bundle diameter of the CNT aggregate is measured by observation using a scanning electron microscope (SEM). Multiple SEM images are obtained by photographing the CNT aggregate at a magnification of 100,000x. The imaging method using the SEM is not particularly limited and can be carried out using known methods.

[0051] -Imaging- Images of the CNT aggregate are obtained by imaging using an SEM device (for example, Hitachi High-Technologies Corporation, S-4800) under the following conditions. From the viewpoint of reducing the variance of the analyzed bundle diameter, it is preferable to obtain five or more images. Acceleration voltage: 0.5 kV Emission current: 10 μA Magnification: 100,000x Image size: 1280 pixels × 960 pixels

[0052] - Image Selection - From the obtained images, select two or more images in which CNT bundles are frequently observed.

[0053] - Overview of Bundle Diameter Analysis using Image Analysis - Image processing and image analysis are performed on the selected image using Python. In image processing, the contours and centerlines of the CNTs are detected and combined with the original image. In image analysis, the bundle diameter is determined by calculating the distance from the centerline to the contour in the created image. Then, the product of the bundle diameter and the length of the centerline is calculated to determine the area occupied by the CNTs in the image.

[0054] -Detection of CNT contours using image analysis- 1. Binarize the image to distinguish between CNTs and the background. 2. Create contours for the CNT portions using the edge detection function of the OpenCV library.

[0055] -Detection of CNT centerlines using image analysis- 1. Adjust parameters to distinguish between CNTs and background and perform binarization. 2. Create a skeleton for the CNT portion using the skeletonize function of the scikit-image library. 3. For each coordinate of the skeleton, count the number of skeletons in the surrounding 2 pixels and recognize coordinates with 5 or more skeletons as skeleton intersections. 4. Divide the skeleton at the intersections by converting the intersections to background pixels. The resulting skeletons are called regions. 5. Measure the length of the regions and delete the shorter regions. 6. Perform linear approximation for each region. 7. For each created line, obtain the X-axis coordinate of the region from which the approximation was made. Convert the line into a line segment based on the interval in which the obtained X-coordinate exists. Treat the line segment obtained here as the centerline of the CNT. 8. Calculate the similarity based on the center coordinates and angles for all sets of centerlines. If the distance between the center coordinates is within 10 pixels and the angle between the two line segments is less than 10 degrees, treat the pair of center lines as duplicate center lines and delete the shorter one. 9. Overlay the CNT contour and center lines onto the original image and save. The contour will be treated in red, and the center lines in blue.

[0056] -Detection of CNT bundle diameter by image analysis- 1. Load an image created by image processing and recognize CNTs, contours, background, and center lines using hue recognition. 2. Measure the length of each center line. 3. Select a random point on the center line and draw a perpendicular line from the point to the center line. 4. Detect the intersection point of the perpendicular line and the contour, and save the distance from the random point on the center line to the intersection point as the bundle diameter. 5. Calculate the occupied area as the product of the length of the center line segment and the bundle diameter. Save the data as a histogram with the bundle diameter on the horizontal axis and the occupied area on the vertical axis.

[0057] - Obtaining Bundle Diameter Parameters - Using the calculated bundle diameter histogram data, the bundle diameter features of each sample are calculated using the following method: 1. Add the bundle diameters and occupied areas of multiple fields of view of the same sample and normalize so that the sum is 1. With normalization, the unit of the vertical axis is set to occupied area ratio. 2. Find the sum of the occupied area ratios of bundles with a bundle diameter of 100 nm or more. 3. Calculate the cumulative occupied area ratio and determine the bundle diameter at which this value first exceeds 0.9 as the cumulative 90% bundle diameter.

[0058] <Cumulative 50% particle size D50> The CNT aggregate according to this disclosure preferably has a cumulative 50% particle size D50 in the volume-based particle size distribution that is less than 25.0 μm.

[0059] The cumulative 50% particle size D50 may be 24.0 μm or less, 23.0 μm or less, 22.0 μm or less, 21.0 μm or less, 20.0 μm or less, 19.0 μm or less, 18.0 μm or less, 17.0 μm or less, 16.0 μm or less, 15.0 μm or less, 14.0 μm or less, 13.0 μm or less, 12.0 μm or less, 11.0 μm or less, 10.5 μm or less, 10.0 μm or less, 9.8 μm or less, or 9.6 μm or less.

[0060] The cumulative 50% particle size D50 may be 0.5 μm or larger, or 1.0 μm or larger. The cumulative 50% particle size D50 may be 0.5 μm or larger and less than 25.0 μm, 0.5 μm or larger and 24.0 μm or smaller, 0.5 μm or larger and 23.0 μm or smaller, 0.5 μm or larger and 22.0 μm or smaller, or 0.5 μm or larger and 21.0 μm or smaller. It may be 0.5 μm or more and less than 20.0 μm, 0.5 μm or more and 19.0 μm or less, 0.5 μm or more and 18.0 μm or less, 0.5 μm or more and 17.0 μm or less, 0.5 μm or more and 16.0 μm or less, 0.5 μm or more and 15.0 μm or less, 0.5 μm or more and 14.0 μm or less, 0.5 μm or more and 13.0 μm or less, 0.5 μm or more and 12.0 μm or less, 0.5 μm or more and 11.0 μm or less, 0.5 μm or more and 10.0 μm or less, or 0.5 μm or more and 9.53 μm or less. In particular, the cumulative 50% particle size D50 is preferably 0.5 μm or more and 15.0 μm or less, more preferably 0.6 μm or more and 15.0 μm or less, especially preferably 0.7 μm or more and 15.0 μm or less, even more preferably 0.8 μm or more and 15.0 μm or less, extremely preferably 0.9 μm or more and 15.0 μm or less, and most preferably 1.0 μm or more and 15.0 μm or less, as this improves dispersibility in the dispersion medium and makes it easier to ensure conductivity. Furthermore, the cumulative 50% particle size D50 is preferably 1.0 μm or more and 13.0 μm or less, more preferably 1.0 μm or more and 12.0 μm or less, even more preferably 1.0 μm or more and 11.0 μm or less, particularly preferably 1.0 μm or more and 10.0 μm or less, even more preferably 1.18 μm or more and 9.53 μm or less, especially preferably 1.30 μm or more and 9.53 μm or less, and particularly preferably 1.47 μm or more and 9.53 μm or less.

[0061] By having the cumulative 50% particle size D50 within the above range, the particle size of the CNT aggregate is appropriately controlled, achieving uniform dispersion of the CNT aggregate in the dispersion. Furthermore, by appropriately controlling the particle size, the interaction between CNTs is optimized, improving the tensile strength of the entire aggregate. Specifically, an appropriate particle size distribution strengthens the bonds between CNTs, improving the mechanical strength of the aggregate. As a result, when using the CNT aggregate as a composite material, it is expected that the overall durability and mechanical properties of the material will be improved.

[0062] The cumulative 50% particle size D50 in the volume-based particle size distribution of a CNT aggregate is measured as follows: The CNT dispersion is thoroughly stirred and then diluted with pure water. The resulting diluted solution is used as a sample, and the cumulative particle size D50 of the CNT dispersion is measured using a particle size analyzer (LA-960, laser diffraction particle size analyzer, Horiba, Ltd.). The particle refractive index of the CNTs to be measured is assumed to be 1.920–0.522i. The refractive index of the solvent is assumed to be 1.333. During measurement, the CNT dispersion is diluted by dropping it into pure water while observing the transmittance, and the measurement is performed after confirming that the particle size distribution on the monitor is stable.

[0063] <Matters concerning tensile strength, elongation at break, and energy density at break> In this disclosure, tensile strength and elongation at break are measured by the following method. A CNT dispersion is prepared by mixing a CNT aggregate, 700 kDa of sodium carboxymethylcellulose, and water, so that the concentration of the CNT aggregate is 0.20 mass% and the concentration of sodium carboxymethylcellulose is 0.30 mass%. 15 mL of the prepared CNT dispersion is poured onto a slide glass type silicon plate with inner dimensions of 22 mm × 75 mm × 3 mm and heated and dried at 100°C to prepare a measurement sample. The prepared measurement sample is fixed to the gripping part of a tensile testing apparatus, and a tensile test is performed at a tensile speed of 1 mm / min to measure the tensile strength. The point where the stress is maximum in the tensile test is considered to be the fracture point, and the elongation at break is calculated from the length of the measurement sample at the fracture point and the length of the measurement sample before the tensile test. The energy density at break is the product of the tensile strength and the elongation at break.

[0064] <Tensile Strength> The tensile strength of the CNT aggregate according to this disclosure is preferably 1.0 MPa or more and 60.0 MPa or less. When the tensile strength of the CNT aggregate according to this disclosure is 1.0 MPa or more, the length of the CNTs according to this disclosure is sufficiently long, making it easier to ensure mechanical strength. Specifically, the sufficient length of the CNTs increases the number of contact points between the CNTs, increasing the frictional force under tension and thus improving mechanical strength. When the tensile strength of the CNT aggregate according to this disclosure is 60.0 MPa or less, it is easy to process into a dispersion and easy to ensure dispersibility in the dispersion. Specifically, when the tensile strength is 50.0 MPa or less, the flexibility and mechanical strength of the CNTs are well balanced, and uniform dispersion of CNTs in the dispersion is achieved.

[0065] Furthermore, the tensile strength of the CNT aggregate can be adjusted by the length, diameter, and other factors of the CNT aggregate.

[0066] <Fracture Energy Density> The fracture energy density of the CNT aggregate according to this disclosure is preferably 14.5 MPa·% or more (particularly greater than 14.5 MPa·%) and 100 MPa or less.

[0067] If the fracture energy density of the CNT aggregate relating to this disclosure is 14.5 MPa・% or higher, the mechanical strength is improved because the length of the CNTs relating to this disclosure is sufficiently long. Specifically, the sufficient length of the CNTs increases the number of contact points between the CNTs, which increases the frictional force under tension and thus the tensile strength, and the increased length that can be stretched under tension also improves the mechanical strength.

[0068] If the fracture energy density of the CNT aggregate according to this disclosure is 100 MPa·% or less, it is easy to process into a dispersion and easy to ensure dispersibility in the dispersion. Specifically, by having a fracture energy density of 100 MPa·% or less, the flexibility of the CNTs is appropriately maintained and uniform dispersion of CNTs in the dispersion is achieved. Therefore, by having a fracture energy density within the above range, the conductivity and tensile strength of the CNT aggregate are improved. From the above viewpoint, the fracture energy density of the CNT aggregate according to this disclosure is preferably 14.5 MPa·% or more and 100 MPa·% or less, more preferably 14.5 MPa·% or more and 90.0 MPa·% or less, particularly preferably 14.5 MPa·% or more and 80.0 MPa·% or less, even more preferably 25.0 MPa·% or more and 80.0 MPa·% or less. Furthermore, the fracture energy density of the CNT aggregate is preferably 26.0 MPa·% to 78.0 MPa·%, more preferably 26.5 MPa·% to 77.0 MPa·%, particularly preferably 27.0 MPa·% to 76.0 MPa·%, and particularly preferably 27.5 MPa·% to 75.1 MPa·%.

[0069] <Viscosity of dispersion containing CNT aggregates> The viscosity of the dispersion containing CNT aggregates according to this disclosure is preferably 10 mPa·s to 1600 mPa·s, more preferably 10 mPa·s to 1500 mPa·s, even more preferably 30 mPa·s to 1300 mPa·s, particularly preferably 35 mPa·s to 1300 mPa·s, and even more preferably 100 mPa·s to 1200 mPa·s. In other embodiments, the viscosity of the dispersion is more preferably 10 mPa·s to 1600 mPa·s, preferably 10 mPa·s to 1400 mPa·s, and even more preferably 100 mPa·s to 1400 mPa·s.

[0070] The viscosity of the dispersion containing the CNT aggregate according to this disclosure is the viscosity obtained by measuring the viscosity using a dispersion prepared by mixing the CNT aggregate with 700 kDa of carboxymethylcellulose sodium and water, at a liquid temperature of 25°C, with a concentration of 0.20% by mass of the CNT aggregate and a concentration of 0.30% by mass of the carboxymethylcellulose sodium.

[0071] The viscosity of the dispersion containing the CNT aggregates according to this disclosure is measured using a cone-plate viscometer (also known as an E-type viscometer). For example, a Brookfield DV-II+Pro Programmable Viscometer is used as the cone-plate viscometer. The measurement conditions are as follows: Measurement fixture: Cone-plate; Measurement mode: Rotational mode; Shear speed: 0.6 s －１ ~384 simultaneous －１ Temperature: 25°C. From the obtained data, read the viscosity at the following shear rate: Shear rate = 12s －１

[0072] The CNT aggregates relating to this disclosure have a high affinity for the dispersion medium, which tends to result in a lower viscosity of the dispersion. When the viscosity of the dispersion is within an appropriate range, it can be determined that the dispersibility of the aggregates relating to this disclosure in the dispersion medium is good.

[0073] <Other matters concerning CNT aggregates> In this disclosure, the CNTs included in the CNT aggregate may be SWCNTs or MWCNTs. From the viewpoint that having a layer distribution and slightly lower uniformity contributes to satisfying conditions (1) and (2), it is preferable that the CNT aggregate includes SWCNTs and MWCNTs.

[0074] The maximum length of the CNTs included in the CNT aggregate relating to this disclosure is not particularly limited.

[0075] In one embodiment, the CNT aggregate may mainly consist of CNTs with a maximum length of 500 μm or less, and may not contain CNTs with a length greater than 500 μm and less than or equal to 30,000 μm. Here, "main component" means that 90% by mass or more of the CNTs constituting the CNT aggregate are CNTs with a maximum length of 500 μm or less. The CNT aggregate may also contain CNTs with a maximum length of 500 μm or less.

[0076] The CNT aggregates according to this disclosure include, for example, CNTs having a maximum length of 10 μm to 30,000 μm. The CNT aggregates according to this disclosure preferably include CNTs having a maximum length of 500 μm or more, more preferably include CNTs having a maximum length of 500 μm to 30,000 μm, and even more preferably include CNTs having a maximum length of 1,000 μm to 30,000 μm (i.e., ULCNTs).

[0077] ULCNTs are longer in length and can take the form of fibers compared to general-purpose CNTs. When the maximum length of the CNTs included in the CNT aggregate according to this disclosure is 500 μm or more, the entanglement between the CNTs becomes moderately strong, and the CNTs tend to form a network structure more easily.

[0078] By taking the form of fibers, ULCNTs have a tendency to entangle with each other. A CNT aggregate is preferably an aggregate containing multiple ULCNTs, as this allows the CNTs to entangle with each other and form a more stable aggregate. Hereinafter, an aggregate containing ULCNTs may be abbreviated as an "ULCNT aggregate."

[0079] Here, the term "fiber" is generally used to refer to a structure in which one dimension is larger than the other two dimensions. The fiber may be a thread-like fiber with a circular cross-section, a ribbon-like fiber with a rectangular cross-section, hollow, or have other shapes. From the viewpoint of improving conductivity, the cross-section of the CNTs contained in the CNT aggregate is preferably circular and preferably hollow.

[0080] The CNT aggregate may be an aggregate of three-dimensional structures in which the CNTs are intertwined. The intertwined state of the CNTs in the CNT aggregate according to this disclosure can be confirmed by SEM observation.

[0081] The length of individual carbon nanotubes (CNTs) within a CNT aggregate can be measured by focusing on a single CNT and observing multiple SEM images within adjacent fields of view. Here, "CNT length" refers to the measured length in the longitudinal direction of the CNT, and the maximum value among the measured lengths is defined as the "maximum length." If, by observing the SEM images, one CNT with a maximum length in the range of 1,000 μm to 30,000 μm is observed within the field of view of the SEM image, it can be confirmed that the observed CNT contains a ulcerative colloidal cell (ULCNT).

[0082] It is preferable that multiple ULCNs are present within the field of view of the SEM image. Focusing on 100 CNTs included in the field of view of the SEM image, the maximum length of each is measured, and of the observed CNTs, it is preferable that 10% or more (in numerical terms) of the CNTs have a maximum length in the range of 1000 μm to 30000 μm (i.e., ULCNs), from the viewpoint of further improving the stability of the CNT aggregate due to the entanglement of ULCNs, more preferably 20% or more, even more preferably 30% or more, and particularly preferably 50% or more.

[0083] The diameter of an ULCNT can be measured by observing a SEM (Surface-Emission Microscope) or transmission electron microscope (TEM) image. Here, diameter refers to the length in the direction perpendicular to the longitudinal direction of the ULCNT. The diameter is measured at 10 different points on a single ULCNT, and the average value is taken as the diameter of that ULCNT.

[0084] The length of the ULCNT is in the range of 1,000 μm to 30,000 μm, preferably in the range of 1,050 μm to 25,000 μm, more preferably in the range of 1,100 μm to 20,000 μm, even more preferably in the range of 1,200 μm to 18,000 μm, and particularly preferably in the range of 1,300 μm to 15,000 μm. The diameter of the ULCNT is preferably in the range of 1 nm to 100 nm, more preferably in the range of 2 nm to 80 nm, even more preferably in the range of 3 nm to 50 nm, and particularly preferably in the range of 5 nm to 30 nm.

[0085] The length / diameter ratio, or aspect ratio, of the ULCNT is preferably 1000 or more, more preferably 3000 or more, even more preferably 5000 or more, and particularly preferably 10000 or more. The aspect ratio can be calculated from the ratio of the maximum length to the diameter of a single ULCNT. From the viewpoint of measurement accuracy, it is preferable to use the average value of the measurements of 20 or more ULCNTs.

[0086] Furthermore, from the viewpoint of dispersibility, the specific gravity of the ULCNT aggregate is preferably in the range of 1.5 to 2.5, more preferably in the range of 1.7 to 2.4, and even more preferably in the range of 1.8 to 2.2. The specific gravity of the ULCNT aggregate can be measured by the method described in JIS Z8807:2012 "Method for measuring the density and specific gravity of solids".

[0087] The purity of carbon as CNTs in an ULCNT aggregate can be measured by thermogravimetric analysis. For example, a thermogravimetric (TG) curve and a differential thermal analysis (DTA) curve of the ULCNT aggregate are obtained using a thermal analyzer (Shimadzu Corporation, DTG-60). In the DTA curve, where the peak top appears around 650°C to 750°C, the largest exothermic peak is considered to be the combustion of CNTs, and other exothermic peaks are considered to be the combustion of substances other than CNTs. The purity of the CNTs is determined from the weight loss rate of the TG curve. From the viewpoint of the resulting conductivity, the purity of the ULCNT aggregate is preferably 50% by mass or more, more preferably 65% ​​by mass or more, even more preferably 80% by mass or more, and particularly preferably 95% by mass or more.

[0088] The resulting fibrous ULCNT is preferably flexible and strong. Further, the conductivity of the ULCNT itself is 5000 ohm －１ ·m －１ or more, more preferably 10000 ohm －１ ·m －１ or more. Note that the conductivity of the ULCNT itself is usually 1000000 ohm －１ ·m －１ or less.

[0089] <Method for Producing CNT> The method for producing CNT in the present disclosure is not particularly limited. For example, as the method for producing CNT in the present disclosure, conventionally known methods such as a chemical vapor deposition (CVD) method and a method of reacting a gaseous reactant containing a carbon source in the presence of a catalyst can be applied.

[0090] The CNT in the present disclosure can be produced with reference to, for example, the methods described in Japanese Patent Application Laid-Open No. 2016-102047, Japanese National Publication of International Patent Application No. 2021-527611, and the like.

[0091] Hereinafter, the method for producing CNT in the present disclosure will be described with examples. However, the method for producing CNT in the present disclosure is not limited to the following examples.

[0092] =Production Method X= As an example of the method for producing CNT referred to in the present disclosure, the production method described in Japanese Patent Application Laid-Open No. 2016-102047 can be mentioned. That is, the production method includes the steps of: passing a gaseous reactant containing one or more carbon sources through a reactor; reacting the one or more gaseous reactants in a reaction region of the reactor in the presence of a catalyst to form product particles containing carbon; aggregating the product particles into an aggregate; and applying a force to the aggregate to continuously move the aggregate out of the reaction region (hereinafter also referred to as "Production Method X").

[0093] According to Production Method X, CNT containing ULCNT can be obtained in the form of easily handled fibrous aggregates or other forms of aggregates.

[0094] In manufacturing method X, the force applied to the product particles may be a mechanical force. If the aggregate is fibrous CNT, the mechanical force applied to the product particles can be applied by a rotating spindle around which the aggregate is wound. The fibrous CNT may be collected on the spindle, or it may be accumulated elsewhere after being rotated around the spindle once or more times, as the spindle is continuously unwound.

[0095] Preferably, the spindle axis is positioned perpendicular or parallel to the flow direction of one or more gaseous reactants, but it may be positioned in other orientations. For example, a spindle with its axis positioned at a 25° angle to the flow direction of the gaseous reactants can also be suitably used to apply mechanical force to product particles.

[0096] The spindle can rotate around two axes (for example, two vertical axes). In particular, the spindle can rotate around axes perpendicular and parallel to the flow direction of the gaseous reactant. Such a spindle allows for the pulling and twisting of aggregates, which are fibrous carbon nanotubes, to control the number of twists and length.

[0097] The spindle material may be metal, ceramic, or resin. The spindle can take on different suitable shapes depending on the material properties and the intended use of the CNTs. The spindle can be used, for example, as a mold for producing carbon products by a spin-coating process. Preferred spindle shapes are rod-shaped or box-shaped.

[0098] Fibrous carbon nanotubes (CNTs) are accumulated on the spindle or elsewhere, and the coating thickness and orientation can be controlled by controlling the reaction time and reaction conditions, or by applying an electric field or other field to the carbon product. The coating thickness and orientation of the carbon product can be controlled, for example, by the fluidity of the gas.

[0099] The spindle rotation speed is preferably 0.01 rpm (revolutions per minute; the same applies hereafter) to 10,000 rpm, and more preferably 0.1 rpm to 100 rpm. The spinning speed (i.e., the spindle rotation speed) may be adjusted so that the material is recovered at the same rate as it is produced. The spindle rotation speed may be used to control the thickness of the accumulated fibrous CNTs. In one preferred embodiment, as the spindle rotates, the fibrous CNTs are processed in the axial direction of the spindle. In this processing, the fibrous CNTs are wound evenly along the spindle, rather than being wound at only one specific point on the spindle.

[0100] Fibrous CNTs may be recovered onto the reactor wall, for example, by a substrate placed in the reactor. The substrate may be a fixed substrate or a rotating guide used to apply a strong and equal force to the fibrous CNTs when they are recovered. A suitable substrate arrangement used in fiber technology is a substrate consisting of two guides positioned orthogonally to each other.

[0101] In manufacturing method X, the mechanical force applied to the product particles may be a force applied by an accelerating gas flow. The accelerating gas flow can be generated by passing the product particles through a reactor having a narrow diameter or through a capillary tube located downstream of the reaction region. A vacuum may be applied to the product particles.

[0102] Other forces applied to the product particles include electrostatic forces appropriately applied by a charged plate. When using electrostatic forces, the product particles must be charged. By using a charged plate, CNTs can be generated on the plate in the form of intertwined sheets.

[0103] Furthermore, other forces applied to the generated particles may include magnetic force or photon pressure applied by a light source.

[0104] The raw material for CNTs may be injected in the form of a liquid containing a carbon source, instead of a gaseous reactant containing a carbon source. When a liquid is used as the raw material for CNTs, it can be injected through a single inlet or multiple inlets, for example, in a showerhead configuration.

[0105] One or more gaseous reactants are preferably reacted at 500°C to 1600°C, and more preferably at 1000°C to 1500°C. The temperature gradient is maintained within the reactor, and the reaction region is preferably kept at a higher temperature than the product region of the reactor.

[0106] The gaseous reactant may be used in combination with one or more gases that act as diluents. The gaseous reactant may also be used in combination with gases that do not play a direct role in the reaction but play an auxiliary role. If amorphous carbon is produced as a byproduct, it is also preferable to use a gas as a diluent that can react with amorphous carbon to maintain the reaction sites on the catalyst and produce nanotubes.

[0107] Gases that can be used as diluents include argon or other inert gases, hydrogen, nitrogen, ammonia, carbon dioxide, and helium. Among these, hydrogen is particularly preferred as a diluent.

[0108] The composition of the product particles can be controlled by monitoring the aggregates and changing the reaction conditions based on the information obtained. For example, aggregates can be monitored by online Raman spectroscopy. Online Raman spectroscopy provides data indicating whether the CNTs are single-layer or multi-layer. It also provides data indicating the diameter and crystallinity of the CNTs. Aggregates can also be monitored by online conductivity measurement, gas analysis, measurement of the opacity of the reaction region, and / or measurement of the winding force.

[0109] When removing aggregates from the reactor, it is preferable to prevent air from entering the reactor. Preventing air inflow is particularly important, for example, when the diluent gas contains hydrogen, as it helps to prevent the formation of an explosive mixture of hydrogen and air in the reactor.

[0110] In manufacturing method X, it is preferable to control the reactor temperature to 200°C to 700°C when removing the aggregates from the reactor. The bundle diameter of the CNTs can be controlled by the temperature of the reaction region of the CNTs and the reactor temperature when removing the aggregates from the reactor. The higher the reactor temperature when removing the aggregates from the reactor, the larger the bundle diameter of the CNTs can be. For example, by setting the reactor temperature when removing the aggregates from the reactor to about 150°C, the bundle diameter, which is 90% of the cumulative CNTs, can be set to 110 nm to 170 nm. By setting the reactor temperature when removing the aggregates from the reactor to about 500°C, the bundle diameter, which is 90% of the cumulative CNTs, can be set to 200 nm to 230 nm. By setting the reactor temperature when removing the aggregates from the reactor to about 750°C, the bundle diameter, which is 90% of the cumulative CNTs, can be set to 300 nm to 400 nm. The "reactor temperature" refers to the temperature determined by measuring the gas temperature at the outlet from which the condensed material is removed from the reactor.

[0111] The product particles produced in manufacturing method X contain ULCN. Depending on the manufacturing conditions, SWCNTs and MWCNTs may also be present.

[0112] The product particles may be generated by chemical vapor deposition. When the product particles are generated by chemical vapor deposition, the carbon source, which is a gaseous reactant, reacts in the presence of a catalyst.

[0113] Suitable carbon-containing compounds as carbon sources include carbon monoxide, carbon dioxide, aromatic hydrocarbons (e.g., benzene, toluene, xylene, cumene, ethylbenzene, naphthalene, or mesitylene), non-aromatic hydrocarbons (e.g., methane, ethane, propane, butane, pentane, hexane, cyclohexane, ethylene, propylene, or acetylene), and oxygen-containing hydrocarbons (e.g., formaldehyde, acetaldehyde, acetone, methanol, ethanol, diethyl ether, polyethylene glycol, 1-propanol, ethyl formate, or hydrocarbons containing two or more of these). Carbon monoxide, methane, ethylene, or acetylene are preferred as carbon-containing compounds.

[0114] The carbon source preferably contains oxygen. Ethanol is a particularly preferred carbon source. Oxygen can be introduced into the reactor by other means, for example, by using a carbon source containing a diluent gas or water.

[0115] As catalysts, transition metals are preferred, particularly chromium (Cr), molybdenum (Mo), tungsten (W), or VIII-B transition metals. Specifically, preferred catalysts include, for example, iron (Fe), cobalt (Co), nickel (Ni), ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os), iridium (Ir), and platinum (Pt) or manganese (Mn), or mixtures thereof. Metals from the lanthanide and actinide series (e.g., yttrium (Y)) can also be used as catalysts. Fe, Ni, Co, Mo, and mixtures thereof are preferred, for example, a mixture of Ni and Co (mass ratio: 50 / 50), a mixture of Fe and Ni, or a mixture of Fe and Mo are more preferred. Any of these transition metals can be used alone or in combination with any of the other transition metals listed above to function as catalysts for the growth of CNTs. The catalyst is particularly preferably a mixture of two or more of the listed metals.

[0116] The catalyst is preferably formed by the decomposition of a precursor. The precursor is preferably a thermal, photocatalytic, or plasma-degradable compound of one or more of the above-mentioned metals, such as a carbonyl or cyclopentadienyl organometallic compound. Ferrocene, iron pentacarbonyl, nickerocene, and cobaltocene are particularly preferred as precursors. In some embodiments, at least 0.01% by mass of the precursor is contained in the carbon source, preferably 0.2% to 30% by mass of the precursor, and more preferably 0.2% to 20% by mass of the precursor. In some embodiments, 0.23% to 2.3% by mass of the precursor may be contained in the carbon source, and 0.02% to 20% by mass of the precursor. The catalyst may also be used supported on a carrier. Preferred carriers include silica and magnesium oxide.

[0117] The carbon source is preferably reacted in the presence of an accelerator. Suitable accelerators are one or more of sulfur, phosphorus, molybdenum, and organic compounds of these elements. Thiophene is also a preferred accelerator. Preferably, the accelerator is contained in the carbon source at a concentration of up to 10% by mass. Preferably, the accelerator is contained in the carbon source at a concentration of 0.2% to 6% by mass. When high or low concentrations of thiophene are used as the accelerator, MWCNTs are formed.

[0118] According to manufacturing method X, fibrous CNTs having a length of at least 500 μm, for example, at least 1 mm, can be obtained. The fibrous CNTs can take the form of threads or sheets. The length of the fibrous CNTs can be controlled, for example, by the winding capacity of the spindle used when manufacturing the fibrous CNTs.

[0119] The manufacturing method X preferably includes the steps of generating CNTs by reacting a carbon source in the reaction region of a reactor, and agglomerating the CNTs into aggregates by applying force to them. This manufacturing method makes it possible to easily produce fibrous CNTs.

[0120] The manufacturing method X preferably further includes a step of purifying the obtained CNT aggregates after the step of agglomerating CNTs into aggregates. Specifically, first, the CNT aggregates are washed with alcohol (e.g., methanol, ethanol, etc.). Next, they are washed with an alkaline solution (e.g., ammonia water). The pH of the alkaline solution is, for example, 8 to 11. Furthermore, they are washed with pure water.

[0121] The cleaning method is not particularly limited and may involve spraying a cleaning solution onto the CNT aggregates or immersing the CNT aggregates in a cleaning solution. Cleaning with alcohol removes alcohol-soluble components contained in the CNT aggregates. Cleaning with an alkaline solution hydrolyzes and removes impurities contained in the CNT aggregates. Cleaning with an acidic solution may also be performed.

[0122] It is preferable to dry the CNT aggregates after washing. The drying method is not particularly limited and can be carried out by commonly known methods.

[0123] By purifying the aggregates of carbon nanotubes (CNTs), the metal content in the CNTs can be reduced.

[0124] The manufacturing method X preferably further includes a step of passing the purified CNT aggregates through a sieve after the step of purifying the CNT aggregates. It is also preferable to recover the CNTs that have passed through the sieve.

[0125] The method of passing the material through the sieve is not particularly limited and can be carried out by commonly known methods. The mesh size of the sieve is, for example, 0.1 mm to 3.0 mm, preferably 0.5 mm to 2.0 mm, and more preferably 1.0 mm to 1.5 mm. The material of the sieve is not particularly limited and may be metal or resin. When the CNT aggregate is applied to an electrode (especially an electrode for a lithium-ion battery), it is preferable that the material does not impair the performance of the battery. The number of times the material is passed through the sieve is, for example, 1 to 3 times. Before passing the CNT aggregate through the sieve, the CNT aggregate may be crushed to an appropriate size beforehand. Crushing can be done using a crusher. Examples of crushers include roll mills, cutter mills, hammer mills, etc.

[0126] By passing the obtained CNT aggregates through a sieve and recovering the CNTs that pass through the sieve, coarse CNTs are removed, improving the stability of the CNT dispersion. In addition, while foreign matter introduced from the outside is generally removed during electrode manufacturing, passing the obtained CNT aggregates through a sieve allows for a simpler method of removing foreign matter introduced from the outside.

[0127] In other embodiments, the method may include generating CNTs containing ULCNTs in a reaction region by the above method, condensing them to form CNTs containing ULCNTs, and continuously withdrawing CNTs from near the reaction region. In yet other embodiments, the method may include generating CNTs containing ULCNTs in a reaction region, continuously electrostatically attracting CNTs containing ULCNTs from the reaction region, and recovering CNTs containing ULCNTs.

[0128] =Manufacturing Method Y= In this disclosure, as an example of a method for manufacturing CNTs, the manufacturing method described in Japanese Patent Publication No. 2021-527611 can be referenced. That is, a mixture containing a main catalyst precursor and a co-catalyst precursor is γ-Al ２ O ３A manufacturing method (hereinafter also referred to as "manufacturing method Y") includes the steps of: (1) supporting the active support on a material to produce an active support; (2) drying the active support by multi-stage drying including vacuum drying; (3) heat-treating the dried active support to produce a supported catalyst; and (4) producing CNTs in the presence of the supported catalyst.

[0129] Step (1) Step (1) involves mixing a main catalyst precursor and a co-catalyst precursor in γ-Al ２ O ３ The active support is manufactured by supporting it on a material.

[0130] The main catalyst precursor and co-catalyst precursor are γ-Al ２ O ３ To ensure uniform support, the mixture may further contain a solvent, and the main catalyst precursor and co-catalyst precursor may be dissolved in the solvent. The solvent may be one or more selected from the group consisting of water, methanol, and ethanol, with water being preferred.

[0131] γ-Al ２ O ３ Because it has high porosity and a spinel structure, the main catalyst and co-catalyst are γ-Al ２ O ３ They can be arranged irregularly. CNTs grown from an irregularly arranged main catalyst can be produced in an entangled manner.

[0132] The main catalyst may be one or more selected from the group consisting of cobalt, iron, nickel, manganese, and chromium, with cobalt being preferred.

[0133] The main catalyst precursor may be one or more selected from the group consisting of nitrates, sulfates, carbonates, and acetates of the main catalyst, with nitrates of the main catalyst being preferred.

[0134] The main catalyst precursor is Co(NO ３ ) ２ Co(NO ３ ) ２ 6H ２ O, Co ２ (CO) ８ Co ２ (CO) ６ [HC=C(C(CH ３ )３ ) ], Co (CH ３ CO ２ ) ２ Fe(NO ３ ) ３ Fe(NO ３ ) ２ nH ２ O, Fe(CH ３ CO ２ ) ２ Ni (NO ３ ) ２ Ni (NO ３ ) ２ 6H ２ O, Mn (NO ３ ) ２ , Mn(NO ３ ) ２ 6H ２ O, Mn(CH ３ CO ２ ) ２ ・n(H ２ O) and Mn(CO) ５ It may be one or more selected from the group consisting of Br, and among these, Co(NO ３ ) ２ 6H ２ O, Fe (NO ３ ) ２ nH ２ O, Ni (NO ３ ) ２ 6H ２ O is preferred.

[0135] The co-catalyst improves the dispersibility of the main catalyst and may be one or more selected from the group consisting of vanadium and molybdenum.

[0136] The co-catalyst precursor is NH ４ VO ３ NaVO ３ , V ２ O ５ , V(C ５ H ７ O ２ ) ３ , and (NH ４ ) ６ Mo ７ O ２４ 4H ２ It may be one or more selected from the group consisting of O, and NH４ VO ３ and (NH ４ ) ６ Mo ７ O ２４ 4H ２ It is preferable to select one or more from the group consisting of O.

[0137] When the mixture contains two or more co-catalyst precursors, that is, when it contains both a vanadium precursor and a molybdenum precursor, the molar ratio of the sum of vanadium and molybdenum to vanadium can be 1:0.45 to 1:0.95 or 1:0.5 to 1:0.9, and is preferably 1:0.5 to 1:0.9. When the above conditions are met, the structure of the CNTs can be stably maintained and CNTs with the desired pore volume can be produced.

[0138] The mixture may contain a main catalyst precursor and a co-catalyst precursor in molar ratios of 1:0.01 to 1:0.5, 1:0.1 to 1:0.4, or 1:0.1 to 1:0.25, with a preferred ratio of 1:0.1 to 1:0.25. Satisfying the above molar ratios improves the dispersibility of the main catalyst, enabling the production of CNTs with the desired pore volume.

[0139] The mixture may further contain an organic acid that plays a role in suppressing the precipitation of the main catalyst precursor and the co-catalyst precursor.

[0140] The organic acid may be one or more selected from the group consisting of citric acid, tartaric acid, fumaric acid, malic acid, acetic acid, butyric acid, palmitic acid, and oxalic acid, with citric acid being preferred.

[0141] The mixture can contain the organic acid and the co-catalyst precursor in a molar ratio of 1:1 to 1:20, 1:2 to 1:10, or 1:3 to 1:6, with a ratio of 1:3 to 1:6 being preferred. Satisfying the above range has the advantage of enabling the production of a transparent catalyst metal solution during catalyst manufacturing and the production of a catalyst with suppressed fine powder formation during impregnation.

[0142] The process may further include a maturation step after step (1).

[0143] The maturation process may be carried out for 1 to 60 minutes or 10 to 50 minutes. It is preferable to carry it out for 10 to 50 minutes. When the above conditions are met, γ-Al ２ O ３ The main catalyst precursor and co-catalyst precursor can be sufficiently supported on the support. Furthermore, bubbles present within the support are removed to the maximum extent possible, allowing the main catalyst precursor and co-catalyst precursor to be sufficiently supported even in the fine pores inside the support.

[0144] Step (2) Next, the active support is dried by multi-stage drying, which includes vacuum drying.

[0145] Multi-stage drying can mean that a drying process, including vacuum drying, is performed two or more times. Specifically, multi-stage drying may include atmospheric pressure drying and vacuum drying, or it may include vacuum drying alone two or more times.

[0146] Vacuum drying may be carried out at 80°C to 300°C or 120°C to 250°C, with 120°C to 250°C being preferred. When the above conditions are met, the main catalyst precursor, i.e., the coordination bond of the main catalyst, can be easily decomposed to form the main catalyst oxide, and energy consumption can be minimized.

[0147] Vacuum drying may be performed at 1 mbar to 200 mbar or 30 mbar to 150 mbar, and is preferably performed at 30 mbar to 150 mbar. When the above conditions are met, the main catalyst precursor, i.e., the coordination bond of the main catalyst, is rapidly decomposed and discharged, so that the main catalyst oxide can be formed more easily under vacuum conditions and energy consumption can be minimized.

[0148] Vacuum drying can be performed for 10 minutes to 3 hours or 10 minutes to 2 hours, with 10 minutes to 2 hours being preferred. When the above conditions are met, the main catalyst precursor can be easily decomposed and converted into the main catalyst oxide, and energy consumption can be minimized.

[0149] On the other hand, if multi-stage drying includes atmospheric pressure drying and vacuum drying, atmospheric pressure drying can be performed before the vacuum drying described above, and atmospheric pressure drying can remove any solvents that may be present in the active carrier.

[0150] Atmospheric pressure drying may be carried out at 80°C to 160°C or 100°C to 140°C, and is preferably carried out at 100°C to 140°C. When the above conditions are met, the solvent present in the active carrier can be sufficiently removed, and energy consumption can be minimized.

[0151] Atmospheric pressure drying may be carried out at 900 mbar to 1,100 mbar, and preferably at 950 mbar to 1,050 mbar. When the above conditions are met, the solvent present in the active carrier can be sufficiently removed, and energy consumption can be minimized.

[0152] Atmospheric pressure drying may be carried out for 1 to 12 hours, and preferably for 3 to 9 hours. When the above conditions are met, the solvent present in the active carrier can be sufficiently removed, and energy consumption can be minimized.

[0153] On the other hand, if multi-stage drying includes two or more vacuum drying steps, it may include two or more vacuum drying steps performed at different temperatures, more specifically, a primary vacuum drying step performed at a first temperature and a secondary vacuum drying step performed at a second temperature higher than the first temperature.

[0154] Primary vacuum drying can remove any solvents that may be present in the active carrier.

[0155] The first temperature may be between 80°C and 160°C, and is preferably between 100°C and 140°C. When the above conditions are met, the solvent present in the active carrier can be sufficiently removed, and energy consumption can be minimized.

[0156] Primary vacuum drying can be performed for 1 to 12 hours, preferably 3 to 9 hours. When the above conditions are met, the solvent present in the active carrier can be sufficiently removed, and energy consumption can be minimized.

[0157] The primary vacuum drying may be performed at 1 mbar to 200 mbar, 1 mbar to 150 mbar, or 80 mbar to 150 mbar, and is preferably performed at 80 mbar to 150 mbar. When the above conditions are satisfied, the solvent present in the active support can be sufficiently removed, and energy consumption can be minimized.

[0158] The description regarding the secondary vacuum drying is as stated in the above description regarding vacuum drying.

[0159] The second temperature may be 175°C to 300°C, and is preferably 180°C to 280°C. When the above conditions are satisfied, the main catalyst precursor, that is, the coordination conjugate of the main catalyst, can be easily decomposed to form the main catalyst oxide, and energy consumption can be minimized.

[0160] The secondary vacuum drying may be performed at 1 mbar to 200 mbar, 1 mbar to 150 mbar, or 1 mbar to 70 mbar, and is more preferably performed at 1 mbar to 70 mbar. When the above conditions are satisfied, the main catalyst precursor, that is, the coordination conjugate of the main catalyst, is rapidly decomposed and discharged, so the main catalyst oxide can be formed more easily under vacuum conditions, and energy consumption can be minimized.

[0161] The secondary vacuum drying may be performed for 10 minutes to 3 hours or 10 minutes to 2 hours, and is preferably performed for 10 minutes to 2 hours. When the above conditions are satisfied, the main catalyst precursor can be easily decomposed and converted into the main catalyst oxide, and energy consumption can be minimized.

[0162] • Step (3) Next, the dried active support is subjected to heat treatment to produce a supported catalyst.

[0163] When the heat treatment is performed, the main catalyst and the cocatalyst are supported on γ-Al ２ O ３ A supported catalyst that exists in a coated state on the surface and pores of is produced.

[0164] The heat treatment may be performed at 600°C to 800°C or 620°C to 750°C, and is preferably performed at 620°C to 750°C. When the above conditions are satisfied, the main catalyst and the cocatalyst are supported on γ-Al２ O ３ The supported catalyst can be manufactured with a uniform coating on the surface and pores, while minimizing energy consumption.

[0165] The heat treatment may be carried out for 1 to 12 hours or 2 to 8 hours, and is preferably carried out for 2 to 8 hours. When the above time is met, the catalyst precursor is γ-Al ２ O ３ A supported catalyst can be manufactured that exists in a state where it is uniformly coated on the surface and pores.

[0166] Step (4) Next, CNTs are produced in the presence of a supported catalyst.

[0167] In detail, carbon nanotubes (CNTs) can be produced by contacting a supported catalyst with a carbon-based compound. Specifically, this may be done by chemical vapor phase synthesis.

[0168] To describe in detail the steps for producing CNTs, first, a supported catalyst can be introduced into a horizontal fixed-bed reactor or a fluidized-bed reactor. Next, a gaseous carbon-based compound, or a mixed gas of a gaseous carbon-based compound, a reducing gas (e.g., hydrogen), and a carrier gas (e.g., nitrogen), is injected at a temperature above the thermal decomposition temperature of the gaseous carbon-based compound or below the melting point of the catalyst supported on the catalyst, and CNTs can be grown by chemical vapor-phase synthesis through the decomposition of the gaseous carbon-based compound.

[0169] CNTs produced by the chemical vapor phase synthesis method described above have crystal growth directions that are nearly parallel to the tube axis, and the graphite structure exhibits high crystallinity along the length of the tube. As a result, CNTs with small unit diameters and high conductivity and strength can be produced.

[0170] The chemical vapor phase synthesis method may be carried out at 600°C to 800°C or 650°C to 750°C, with 650°C to 750°C being preferred. By satisfying the above temperature range, CNTs can be produced while minimizing the generation of amorphous carbon.

[0171] Possible heat sources for the reaction include induction heating, radiant heat, lasers, IR, microwaves, plasma, and surface plasmon heating.

[0172] Furthermore, carbon-based compounds can be used without particular restrictions, as long as they can supply carbon and exist in a gaseous state at temperatures above 300°C.

[0173] The carbon-based compound may be a carbon-based compound having six or fewer carbon atoms, and may be one or more selected from the group consisting of carbon monoxide, methane, ethane, ethylene, ethanol, acetylene, propane, propylene, butane, butadiene, pentane, pentene, cyclopentadiene, hexane, cyclohexane, benzene, and toluene.

[0174] After growing CNTs by the reaction described above, a cooling step may be selectively performed to further align the CNTs in a more regular manner. Specifically, the cooling step can be carried out by natural cooling by removing the heat source or by using a cooler or the like.

[0175] The above-described manufacturing methods X and Y are examples, and the manufacturing methods for CNTs that may be included in a CNT aggregate are not limited to those described above.

[0176] [Carbon Nanotube Dispersion] The carbon nanotube dispersion (CNT dispersion) according to this disclosure comprises a CNT aggregate and a dispersion medium. The CNT dispersion exhibits good dispersibility of the CNT aggregate in the dispersion medium and has excellent conductivity. The CNT dispersion is preferably used for electrode formation, transparent conductive film formation, resin additives, conductive inks, coatings, antistatic agents, paints, and the like.

[0177] <CNT aggregates> The CNT aggregates contained in the CNT dispersion are the same as the CNT aggregates related to this disclosure described above, so their explanation is omitted here.

[0178] <Dispersion Medium> The dispersion medium preferably contains water, and more preferably contains water as its main component. "Containing water as its main component" means that the proportion of water in the dispersion medium is more than 50% by mass. The proportion of water in the dispersion medium is preferably 90% by mass or more, more preferably 95% by mass or more, even more preferably 99% by mass or more, and may be, for example, 100% by mass.

[0179] The water is not particularly limited, but it is preferable to use distilled water, deionized water, or pure water, for example, because it contains fewer impurities.

[0180] The dispersion medium may be a mixture of water and a hydrophilic solvent. Examples of hydrophilic solvents include carbonate compounds such as ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, and butylene carbonate; ether compounds such as tetrahydrofuran; ketone compounds such as acetone; lower alcohol compounds such as methanol and ethanol; and solvents such as acetonitrile. When the dispersion medium contains a hydrophilic solvent, the proportion of the hydrophilic solvent in the dispersion medium is preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 1% by mass or less.

[0181] The CNT dispersion may further contain other components that can be used in the dispersion, in addition to the CNT aggregate and dispersion medium. Examples of other components include dispersants, defoamers, antistatic agents, and conductive additives other than the conductive additives described herein. It may also further contain trace amounts of impurities, so-called unavoidable impurities.

[0182] <Dispersant> The CNT dispersion may contain a dispersant for the purpose of further improving the dispersibility and dispersion stability of the CNT aggregate. The dispersant is not particularly limited and, for example, various surfactants can be used. Polymer compounds such as resins can also be used as dispersants. A surfactant is preferred as the dispersant. The surfactant may be an ionic surfactant or a nonionic surfactant and is not particularly limited. In the CNT dispersion, the surfactant can be used alone or in a mixture of two or more types.

[0183] Examples of ionic surfactants include anionic surfactants, cationic surfactants, and amphoteric surfactants. Examples of anionic surfactants include aromatic sulfonic acid-based surfactants such as alkylbenzene sulfonates (e.g., dodecylbenzenesulfonic acid) and dodecylphenyl ether sulfonates; ether sulfate-based surfactants; phosphate-based surfactants; and carboxylic acid-based surfactants. Examples of cationic surfactants include alkylamine salts and quaternary ammonium salts. Examples of amphoteric surfactants include alkylbetaine-based surfactants and amine oxide-based surfactants. As for ionic surfactants, ionic surfactants having an aromatic ring (so-called aromatic ionic surfactants) are preferred, and aromatic sulfonic acid-based surfactants such as alkylbenzene sulfonates and dodecylphenyl ether sulfonates are more preferred. Aromatic ionic surfactants tend to have excellent dispersibility, dispersion stability, and high concentration properties for CNT aggregates.

[0184] Examples of nonionic surfactants include sugar ester surfactants such as sorbitan fatty acid esters and polyoxyethylene sorbitan fatty acid esters; fatty acid ester surfactants such as polyoxyethylene resin acid esters and polyoxyethylene fatty acid diethyl; ether surfactants such as polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, and polyoxyethylene polypropylene glycol; and aromatic nonionic surfactants such as polyoxyalkylene octylphenyl ether, polyoxyalkylene nonylphenyl ether, polyoxyalkyldibutylphenyl ether, polyoxyalkyl styrylphenyl ether, polyoxyalkyl benzylphenyl ether, polyoxyalkylbisphenyl ether, polyoxyalkylcumylphenyl ether, and polyoxyalkylene phenyl ether. As nonionic surfactants, ionic surfactants having aromatic rings (so-called aromatic nonionic surfactants) are preferred, polyoxyalkylene phenyl ether is more preferred, and polyoxyethylene phenyl ether is even more preferred. Aromatic nonionic surfactants tend to have excellent dispersibility, dispersion stability, and high concentration properties for CNT aggregates.

[0185] Other dispersants that excel in dispersibility, dispersion stability, and high concentration of CNTs include: Demol (registered trademark: hereinafter the same) N, Demol RN, and Demol T (manufactured by Kao Corporation), sodium salt of β-naphthalene sulfonic acid formalin condensate; Brij S 100 (manufactured by Sigma-Aldrich), polyvinylpyrrolidone K30 (e.g., manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.); carboxymethylcellulose (CMC) (e.g., manufactured by Daicel Mirise Co., Ltd.); sodium deoxycholate (e.g., manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.); and SOLSPERSE. ＴＭ W100, SOLSPERSE ＴＭ Examples include W150 (manufactured by Lubrizol Japan Co., Ltd.). CMC is particularly preferred from the viewpoint of excellent dispersion ability, dispersion stability, and high concentration of CNT aggregates.

[0186] When the CNT dispersion contains a dispersant, the amount of dispersant used is not particularly limited and can be set appropriately depending on the type of dispersant, the amount of CNT aggregate, the amount of dispersion medium, etc.

[0187] [Method for Manufacturing CNT Dispersion] The method for manufacturing a CNT dispersion is not particularly limited. A CNT dispersion can be manufactured by dispersing CNT aggregates in a dispersion medium. That is, a CNT dispersion can be manufactured by a method that includes a step of dispersing CNT aggregates in a dispersion medium (also called the "dispersion step"). The dispersion mediums that can be used in the dispersion step are as described above.

[0188] The dispersion method is not particularly limited. Examples of dispersion methods include using dispersion devices such as a stirrer, homogenizer, colloid mill, flow jet mixer, dissolver, paint conditioner, Manton emulsifier, jet mill, and ultrasonic device. Other examples of dispersion methods include using known grinding means, such as ball milling (e.g., ball mill, vibrating ball mill, planetary ball mill, bead mill, etc.), sand milling, colloid milling, jet milling, roller milling, vertical or horizontal agitator mill, attritor, colloid mill, three-roll mill, pearl mill, super mill, impeller, disperser, KD mill, dynatron, and pressurized kneader. The method using a jet mill is preferred, and the method using a wet jet mill is more preferred. A wet jet mill is a dispersion device that pumps a mixture in a solvent as a high-speed flow from a nozzle placed in a sealed state inside a pressure vessel. In a wet jet mill, CNT aggregates are dispersed within a pressure vessel by collisions between opposing flows, collisions with the vessel wall, turbulence and shear flow generated by high-speed flow, etc. A suitable wet jet mill is an ultra-high pressure homogenizer manufactured by Jōkō Co., Ltd. (model numbers: NAGS20, NAGS100, JAGS200, NAGS1000, etc.). However, the wet jet mill is not limited to these. When using the above-mentioned ultra-high pressure homogenizer as the dispersion device, the dispersion processing pressure is preferably 10 MPa to 250 MPa.

[0189] The method for producing a CNT dispersion may include a step of drying the CNT aggregate (also called a "drying step") before the dispersion step described above.

[0190] If moisture adheres to the CNTs, the surface tension of the water can cause the CNTs to stick together, raising concerns about reduced dispersibility. Therefore, by performing a drying step of the conductive additive before the dispersion step, moisture adhering to the CNTs is removed, preventing the CNTs from sticking together due to moisture, and further improving the dispersibility of the CNTs in the dispersion medium. The drying method is not particularly limited. Examples of drying methods include heating drying, vacuum drying, and heating vacuum drying. Heating vacuum drying is preferred as the drying method. The drying temperature is not particularly limited, but is preferably, for example, 40°C to 100°C. The drying time is not particularly limited and can be set appropriately depending on the drying temperature, the degree of moisture adhering to the CNT aggregate in this disclosure, etc.

[0191] The following are examples of CNT dispersion manufacturing methods, but the manufacturing of CNT dispersions is not limited to those shown below.

[0192] <Manufacturing Example 1: Example of Dispersion Production> 0.040 g of the CNT aggregate according to this disclosure is weighed and placed in a three-necked flask. After adding the CNT aggregate, a large excess of deionized water, which is the dispersion medium, is poured into the flask (for example, 20 mL), and the mixture is stirred at room temperature (25°C, the same applies hereafter). At this time, a known dispersant (for example, carboxymethylcellulose) may be added as appropriate. Next, the conductive additive is dispersed in the dispersion medium using a known dispersion device (for example, an ultrasonic irradiation device or a wet jet mill). The obtained dispersion is further stirred with a stirrer at room temperature for a long time (for example, 1 hour to 48 hours). In this way, a CNT dispersion is obtained.

[0193] [Conductive Material] The conductive material according to this disclosure includes the CNT aggregate according to this disclosure. As described above, the CNT aggregate contained in the conductive material according to this disclosure has excellent conductivity when dispersed, and is therefore suitable as a conductive additive. Because the conductive material according to this disclosure includes the CNT aggregate according to this disclosure, it has excellent conductivity efficiency and can effectively impart high conductivity to the object to be used.

[0194] The conductive material relating to this disclosure may contain known conductive additives such as graphite and Ketjenblack. Furthermore, the conductive material relating to this disclosure may contain CNTs other than the CNT aggregate relating to this disclosure.

[0195] The conductive material relating to this disclosure can be used as one of the electrode materials. An example of an electrode formed using the electrode material is an electrode provided in a secondary battery. An embodiment of an electrode and a secondary battery equipped with the electrode will be described below.

[0196] <Electrode> The electrode according to this disclosure includes an electrode active material and a conductive material according to this disclosure. Because the electrode according to this disclosure includes a conductive material according to this disclosure, it has excellent conductivity for forming conductive paths within the electrode. Therefore, the secondary battery according to this disclosure has excellent cycle characteristics.

[0197] In electrodes, CNT aggregates can function as conductive additives. The CNT aggregates included in the electrodes described below are synonymous with the CNT aggregates in this disclosure, and the preferred embodiments are also the same; therefore, a description of the CNT aggregates will be omitted below.

[0198] The electrode may consist of at least one of a positive electrode and a negative electrode. The electrode may include an electrode active material layer, or it may include a current collector and an electrode active material layer disposed on the current collector.

[0199] The current collector is not particularly limited as long as it does not induce chemical changes in the battery and is conductive. Examples of current collectors include copper, stainless steel, aluminum, nickel, titanium, calcined carbon, and aluminum or stainless steel surfaces that have been surface-treated with carbon, nickel, titanium, silver, etc. Specifically, transition metals with good carbon adsorption properties, such as copper and nickel, may be used as current collectors.

[0200] The electrode active material layer may contain an electrode active material. The electrode active material is preferably electrode active material particles. When the electrode is a positive electrode, the electrode active material is not particularly limited, and the electrode active material layer may include a positive electrode active material that is commonly used for positive electrode materials for electrodes. Specifically, examples of the positive electrode active material include lithium cobalt oxide (LiCoO ２ ), layered compounds such as lithium nickel oxide (LiNiO ２ ), and compounds substituted with one or more transition metals; LiFe ３ O ４ and other lithium iron oxides; the chemical formula Li １＋ｃ１ Mn ２－ｃ１ O ４ (0≦c1≦0.33), LiMnO ３ , LiMn ２ O ３ , LiMnO ２ and other lithium manganese oxides; lithium copper oxide (Li ２ CuO ２ ); LiV ３ O ８ , V ２ O ５ , Cu ２ V ２ O ７ and other vanadium oxides; Ni-site type lithium nickel oxide represented by the chemical formula LiNi １－ｃ２ M ｃ２ O ２ (wherein M is at least one selected from the group consisting of Co, Mn, Al, Cu, Fe, Mg, B and Ga, and satisfies 0.01≦c2≦0.66); lithium manganese composite oxide represented by the chemical formula LiMn ２－ｃ３ M ｃ３ O ２ (wherein M is at least one selected from the group consisting of Co, Ni, Fe, Cr, Zn and Ta, and satisfies 0.01≦c3≦0.1), or Li ２ Mn ３ MO ８ (wherein M is at least one selected from the group consisting of Fe, Co, Ni, Cu and Zn); LiMn in which part of Li in the chemical formula is substituted with alkaline earth metal ions ２ O ４These are some examples.

[0201] When the electrode is a negative electrode, the electrode active material is not particularly limited, and the electrode active material layer may include negative electrode active materials commonly used for negative electrode materials. Specifically, the negative electrode active material may include graphite-based active material particles or silicon-based active material particles. As graphite-based active material particles, at least one selected from the group consisting of artificial graphite, natural graphite, graphitized carbon fiber, and graphitized mesocarbon microbeads may be used. By using artificial graphite as graphite-based active material particles, rate characteristics can be improved. As silicon-based active material particles, at least one selected from the group consisting of Si, SiOx (0 < x < 2), Si-C composite, and Si-Y alloy (where Y is an element selected from the group consisting of alkali metals, alkaline earth metals, transition metals, group 13 elements, group 14 elements, rare earth elements, and combinations thereof) may be used. By using silicon-based active material particles, the battery capacity can be increased.

[0202] The electrode active material layer may further contain a binder. The binder is not particularly limited, and the electrode active material layer may include binders commonly used in electrode materials. Examples of binders include at least one polymer selected from the group consisting of polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene propylene diene monomer (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, and polyacrylic acid, as well as polymers in which the hydrogen atoms of these polymers are substituted with Li, Na, Ca, etc.

[0203] <Secondary Battery> The secondary battery according to this disclosure comprises electrodes according to this disclosure. The secondary battery may include a negative electrode, a positive electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte. At least one of the positive electrode and the negative electrode is an electrode according to this disclosure.

[0204] A separator separates the negative electrode from the positive electrode and provides a passage for lithium ions to move. It is generally not limited to any separator commonly used in secondary batteries. Preferably, the separator has low resistance to ion movement in the electrolyte and excellent electrolyte moisture absorption capacity. Specifically, a porous polymer film can be used as a separator. The porous polymer film may be, for example, a porous polymer film made from polyolefin polymers such as ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, or ethylene / methacrylate copolymer, or a laminated structure in which two or more of these films are laminated. Alternatively, the separator may be a conventional porous nonwoven fabric, such as a nonwoven fabric made of high-melting-point glass fibers or polyethylene terephthalate fibers. Furthermore, the separator may be coated with a ceramic component or polymer substance to ensure heat resistance or mechanical strength. The separator can selectively have a single-layer or multi-layer structure.

[0205] The electrolyte is not particularly limited and can include, for example, organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, and molten inorganic electrolytes that can be used in the manufacture of lithium secondary batteries.

[0206] Specifically, the electrolyte may include non-aqueous organic solvents and metal salts. Examples of non-aqueous organic solvents include N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, γ-butyrolactone, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, triester phosphate, trimethoxymethane, dioxolane derivatives, sulfolane, methylsulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ethers, methyl propionate, and ethyl propionate, which are aprotic organic solvents.

[0207] Among carbonate-based organic solvents, cyclic carbonates such as ethylene carbonate and propylene carbonate are preferred as non-aqueous organic solvents because they have high dielectric constants as high-viscosity organic solvents and readily dissociate lithium salts. It is even more preferable to use a mixture of such cyclic carbonates with low-viscosity, low-dielectric-constant linear carbonates such as dimethyl carbonate and diethyl carbonate in appropriate proportions as a non-aqueous organic solvent, as this yields an electrolyte with high electrical conductivity.

[0208] The metal salt may also be a lithium salt. Lithium salts are readily soluble in non-aqueous electrolytes. For example, the anion portion of the lithium salt may be F － , Cl － , I － NO ３ － , N (CN) ２ － BF ４ － , ClO ４ － , PF ６ － (CF ３ ) ２ PF ４ － (CF３ ) ３ PF ３ － , (CF ３ ) ４ PF ２ － , (CF ３ ) ５ PF － , (CF ３ ) ６ P － , CF ３ SO ３ － , CF ３ CF ２ SO ３ － , (CF ３ SO ２ ) ２ N － , (FSO ２ ) ２ N － , CF ３ CF ２ (CF ３ ) ２ CO － , (CF ３ SO ２ ) ２ CH － , (SF ５ ) ３ C － , (CF ３ SO ２ ) ３ C － , CF ３ (CF ２ ) ７ SO ３ － , CF ３ CO ２ － , CH ３ CO ２ － , SCN － and (CF ３ CF ２ SO ２ ) ２ N － may be mentioned.

[0209] In addition to non-aqueous organic solvents and metal salts, the electrolyte may further contain one or more additives for the purpose of improving battery life characteristics, suppressing the decrease in battery capacity, and improving battery discharge capacity, such as haloalkylene carbonate compounds like difluoroethylene carbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ethers, ethylenediamine, n-glycemic (glyme), hexalic acid triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salts, pyrrole, 2-methoxyethanol, and aluminum trichloride.

[0210] The secondary battery described above can constitute a battery module containing the secondary battery as a unit cell, and a battery pack containing the battery module. The battery module and battery pack can be used as a power source for medium to large devices selected from the group consisting of electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, and power storage systems.

[0211] <Planar Assembly> The planar assembly relating to this disclosure includes the CNT assembly relating to this disclosure. The proportion of the CNT assembly relating to this disclosure contained in the planar assembly relating to this disclosure is usually 1% by mass or more with respect to the total mass of the planar assembly. The planar assembly relating to this disclosure may contain components other than the CNT assembly relating to this disclosure.

[0212] Examples of planar aggregates relating to this disclosure include films containing the CNT aggregate relating to this disclosure.

[0213] The planar assemblies relating to this disclosure are useful, for example, in filters, electromagnetic shields, and pellicles for extreme ultraviolet (EUV) radiation.

[0214] The method for producing the planar aggregate according to this disclosure is not particularly limited. The planar aggregate according to this disclosure can be produced, for example, as a nonwoven fabric-like planar aggregate by dispersing the CNT aggregate according to this disclosure in water or other fluid and filtering it once or twice or more.

[0215] The planar assemblies relating to this disclosure are useful, for example, in filters, electromagnetic shields, and pellicles for extreme ultraviolet (EUV) applications.

[0216] <Laminate> The laminate according to this disclosure comprises a substrate and a planar assembly according to this disclosure. The substrate and the planar assembly may be in direct contact, or other layers may be arranged between the substrate and the planar assembly. Alternatively, the planar assembly according to this disclosure may be arranged on the substrate, and yet another layer may be arranged on the planar assembly.

[0217] The material constituting the substrate may be resin, glass, or fiber. Examples of resins include polyethylene terephthalate (PET), polycarbonate (PC), polymethyl methacrylate (PMMA), cyclic olefin polymer (COP), triacetate (TAC), cyclic olefin copolymer (COC), poly(vinyl chloride) (PVC), polyethylene 2,6-naphthalate (PEN), polyimide (PI), polypropylene (PP), polyethylene (PE), polystyrene (PS), polyamide (PA), polyacetal (POM), polyurethane (PU), acrylonitrile butadiene styrene (ABS), polyphenylene ether (PPE), polysulfone (PSU), polyether ether ketone (PEEK), and polyamide-imide (PAI). Examples of glass include float glass (SiO2). ２ Na ２ Examples include sodium chloride (containing O, CaO, and MgO), soda lime, aluminosilicate glass, and borosilicate glass. Examples of fibers include synthetic fibers such as polyester fibers, polyamide fibers, polyolefin fibers, and acrylic fibers; and natural fibers such as cotton, linen, silk, wool, cashmere, mohair, alpaca, jute, hemp, and ramie.

[0218] The planar aggregate preferably contains a binder in addition to the CNT aggregate according to this disclosure. The binder is preferably a polymer and preferably contains at least one selected from the group consisting of polymers containing constituent units derived from vinylidene chloride (e.g., polyvinylidene chloride, vinylidene chloride-vinyl chloride copolymer, vinylidene chloride-vinyl acetate copolymer, etc.), polyimide, polysiloxane, and epoxy resin.

[0219] The following examples will provide a more detailed explanation of the CNT aggregates, etc., related to this disclosure. This disclosure is not limited to the following examples, unless it exceeds the spirit of the disclosure.

[0220] (Example 1) 1. Production of Sheet-like CNT Assembly 1 Sheet-like CNT assembly 1 was produced by a floating catalyst method (CVD method) in which the self-assembly of CNT bundles directly interacts with the catalyst in the gas phase. A cylindrical reactor with an inner diameter of 85 mm was used as the CNT reactor. First, ferrocene, as a metal catalyst precursor containing Fe atoms, and thiophene, as an accelerator, were introduced into a continuous flow of carrier gas in a once-through reactor whose temperature was controlled to 120°C. Hydrogen gas was used as the carrier gas. By maintaining the temperature in the once-through reactor within the above range, the metal catalyst precursor decomposes. The region in which the metal catalyst precursor decomposes is referred to as the first temperature zone.

[0221] Next, methane, the carbon source, was released into the carrier gas stream. The metal catalyst and carbon source were supplied to a second temperature zone, controlled to 1400°C, located downstream of the first temperature zone. The total gas supply flow rate for the carrier gas and source gas was set to 34 NL / min (NL is normal liters). The flow rate ratio of methane / thiophene gas was set to range A in Table 1. The second temperature zone was maintained at a temperature sufficient to generate carbon nanotube aggregates.

[0222]

[0223] In the second temperature zone, a reaction field was created within the temperature-controlled flow reactor, forming catalytic nuclei and rapidly growing CNTs, thereby generating CNT aggregates. The aggregates were discharged as continuous discharge through the outlet of the flow reactor, which was temperature-controlled to 150°C, and sheet-like CNT aggregates were collected.

[0224] The obtained sheet-like CNT aggregates were washed with methanol, immersed in a pH 10 diluted aqueous ammonia solution for 10 minutes, washed with pure water for 10 minutes, dried, crushed into a powder, and then passed through a sieve with a mesh size of 1.0 mm twice. The CNT aggregates that passed through the sieve were collected and designated as CNT aggregate 1.

[0225] 2. Preparation of CNT dispersion 1 The following materials were mixed and pre-dispersed by treating them with an Ace homogenizer manufactured by Nippon Seiki Co., Ltd. for 1 hour to obtain pre-dispersion 1.

[0226] (Dispersion composition) - CNT aggregate 1 obtained above... 1.1 g - CARBOXYMETHYL CELLULOSE SODIUM SALT HIGH VISCOSITY (manufactured by MP Biomedicals)... 1.65 g - Purified water... 547.25 g

[0227] The pre-dispersion 1 was subjected to the final dispersion using a high-pressure homogenizer (model number: NAGS100) manufactured by Jōkō Co., Ltd. as a wet jet mill under the following conditions to obtain a CNT dispersion 1 with a concentration of 0.20% by mass. (Dispersion conditions) Nozzle diameter: 0.22 mm Pressure: 85 MPa Number of passes: 8 Method: Circulation method

[0228] <Evaluation of CNT aggregate dispersion 1: Viscosity> The viscosity of CNT dispersion 1 was measured using a cone-plate viscometer (also known as an E-type viscometer). Specifically, a cone-plate viscometer (BROOKFIELD DV-II+Pro PROGRAMMABLE VISCOMETER) was used to measure the viscosity. Measurement fixture: Cone-plate Measurement mode: Rotation mode Shear rate: 0.6 s －１ ~384 simultaneous －１ Temperature: 25°C. From the obtained data, the shear rate was 12 s. －１The viscosity was measured. The viscosity of the dispersion was 705.2 mPa·s. The common logarithm of the viscosity was 2.85.

[0229] 3. Evaluation

[0230] <Si content relative to the total mass of the CNT aggregate> The Si content relative to the total mass of CNT aggregate 1 was measured using an inductively coupled plasma mass spectrometer (ICP-AES) (NexION 2000C, PerkinElmer). The CNT aggregate 1 obtained above was pretreated by ashing / alkali fusion / acid dissolution and then measured using the above apparatus. The Si content was 100 ppm by mass.

[0231] <Tensile Test> A sample was prepared by pouring 15 mL of CNT dispersion 1 onto a slide-type silicon plate (manufactured by Dosaka E-M Co., Ltd., #08-1044) with inner dimensions of 22 mm × 75 mm × 3 mm, and heating and drying it at 100°C for 30 minutes. The prepared sample was fixed to the gripping part of a tensile testing apparatus (manufactured by Shimadzu Corporation, Autograph AG-IS), and a tensile test was performed at a tensile speed of 1 mm / min to measure the tensile strength. The point at which the stress was maximum in the tensile test was considered the fracture point, and the elongation at fracture was calculated from the length of the sample at the fracture point and the length of the sample before the tensile test. As a result, the tensile strength was 11.3 MPa, the elongation at fracture was 2.4%, and the energy density at fracture was 27.5 MPa·%.

[0232] <Surface Resistivity> The surface resistivity of the prepared sample was measured using the four-probe method with a Loresta GXII manufactured by Nitto Seiko Analytech Co., Ltd. Measurements were taken at five locations on the film, and the average of the five values ​​was taken as the surface resistivity. As a result, the surface resistivity was 1.24 Ω / □.

[0233] <Measurement of cumulative 50% particle size D50 in volume-based particle size distribution> CNT dispersion 1 was thoroughly stirred and then diluted with pure water. The resulting diluted solution was used as a sample, and the cumulative particle size D50 of the CNT dispersion was measured using a particle size analyzer (LA-960, laser diffraction particle size analyzer, Horiba, Ltd.). The particle refractive index of the CNTs was set to 1.920-0.522i. The refractive index of the solvent was set to 1.333. During measurement, CNT dispersion 1 was diluted by dropping it into pure water while observing the transmittance, and the measurement was performed after confirming that the particle size distribution on the monitor was stable. As a result, the cumulative 50% particle size D50 in the volume-based particle size distribution of CNT aggregate 1 was 6.65 μm.

[0234] <Bundle diameter characteristics>

[0235] For the CNT aggregate 1 of Example 1, imaging was performed using a scanning electron microscope (SEM), and six images in which CNT bundles were clearly observed were selected (one of which is shown in Figure 1). Image processing and image analysis were performed on the selected images using Python. In image processing, the contours and midlines of the CNTs were detected and combined with the original image. In image analysis, the bundle diameter was determined by calculating the distance from the midline to the contour of the created image. Then, the product of the bundle diameter and the length of the midline was calculated to determine the area occupied by the CNTs in the image. A histogram of bundle diameter and occupied area was then created.

[0236] Using the calculated bundle diameter histogram, the bundle diameter features of each sample were calculated using the following method: 1. The bundle diameters and occupied areas of multiple fields of view of the same sample were added together and normalized so that the sum equaled 1. Following normalization, the unit of the vertical axis was set to occupied area ratio. 2. The total occupied area ratio of bundles with a bundle diameter of 100 nm or more was calculated. As a result, the area ratio of bundles with a bundle diameter of 100 nm or more was 0.23. The cumulative 90% bundle diameter was 130 nm.

[0237] (Example 2) 1. Manufacturing of CNT aggregate 2 CNT aggregate 2 was manufactured in the same manner as CNT aggregate 1, except that the total gas supply flow rate of the carrier gas and raw material gas was set to 39 NL / min, and the aggregates were continuously discharged through the outlet of a flow-through reactor with a temperature controlled to 500°C. 2. Preparation of CNT dispersion 2 Using the obtained CNT aggregate 2, a pre-dispersion 2 was obtained in the same manner as in Example 1.

[0238] The pre-dispersion 2 was subjected to the final dispersion using a high-pressure homogenizer (model number: NAGS100) manufactured by Jōkō Co., Ltd. as a wet jet mill under the following conditions to obtain CNT dispersion 2. (Dispersion conditions) Nozzle diameter: 0.22 mm Pressure: 150 MPa Number of passes: 8 Method: Circulation method

[0239] <Evaluation of CNT aggregate dispersion 2: Viscosity> The viscosity of CNT dispersion 2 was measured using the same method as in Example 1. The viscosity of the dispersion was 292.9 mPa·s. The common logarithm of the viscosity was 2.47.

[0240] 3. Evaluation

[0241] <Si atom content relative to the total mass of the CNT aggregate> The measurement was performed in the same manner as in Example 1, except that CNT aggregate 2 was used. The Si atom content was 700 ppm by mass.

[0242] <Tensile Test> A tensile test was performed in the same manner as in Example 1, except that CNT dispersion 2 was used. The results showed a tensile strength of 10.6 MPa, an elongation at break of 2.8%, and an energy density at break of 29.7 MPa·%.

[0243] <Surface Resistivity> The surface resistivity was measured in the same manner as in Example 1, except that the measurement sample from Example 2 was used. As a result, the surface resistivity was 2.85 Ω / □.

[0244] <Measurement of cumulative 50% particle size D50 in volume-based particle size distribution> For CNT dispersion 2, the cumulative 50% particle size D50 in volume-based particle size distribution was measured in the same manner as in Example 1. As a result, the cumulative 50% particle size D50 in volume-based particle size distribution of CNT aggregate 2 was 1.18 μm.

[0245] <Bundle Diameter Features> For CNT aggregate 2 of Example 2, imaging was performed using SEM, and six images in which CNT bundles were clearly observed were selected from the obtained images (one of which is shown in Figure 2). Except for this, the bundle diameter features were calculated in the same manner as in Example 1. As a result, the area ratio of bundles with a bundle diameter of 100 nm or more was 0.40. The cumulative 90% bundle diameter was 210 nm.

[0246] (Example 3) 1. Manufacturing of CNT aggregate 3 CNT aggregate 3 was manufactured in the same manner as CNT aggregate 1, except that the total gas supply flow rate of the carrier gas and raw material gas was set to 34 NL / min. 2. Preparation of CNT dispersion 3 Using the obtained CNT aggregate 3, a CNT dispersion 3 was obtained in the same manner as in Example 1.

[0247] <Evaluation of CNT aggregate dispersion 3: Viscosity> The viscosity of CNT dispersion 3 was measured using the same method as in Example 1. The viscosity of the dispersion was 435.5 mPa·s. The common logarithm of the viscosity was 2.64.

[0248] 3. Evaluation

[0249] <Si atom content relative to the total mass of the CNT aggregate> The measurement was performed in the same manner as in Example 1, except that CNT aggregate 3 was used. The Si atom content was 400 ppm by mass.

[0250] <Tensile Test> A tensile test was performed in the same manner as in Example 1, except that CNT dispersion 3 was used. The results showed a tensile strength of 32.6 MPa, an elongation at break of 2.3%, and an energy density at break of 75.1 MPa·%.

[0251] <Surface Resistivity> The surface resistivity was measured in the same manner as in Example 1, except that the sample used was the same as in Example 3. As a result, the surface resistivity was 1.07 Ω / □.

[0252] <Measurement of cumulative 50% particle size D50 in volume-based particle size distribution> For the CNT dispersion 3, the cumulative 50% particle size D50 in volume-based particle size distribution was measured in the same manner as in Example 1. As a result, the cumulative 50% particle size D50 in volume-based particle size distribution of the CNT aggregate 3 was 1.47 μm.

[0253] <Bundle Diameter Features> For the CNT aggregate 3 of Example 3, imaging was performed using an SEM, and five images in which CNT bundles were clearly observed were selected from the obtained images (one of which is shown in Figure 3). Except for this, the bundle diameter features were calculated in the same manner as in Example 1. As a result, the area percentage of bundles with a bundle diameter of 100 nm or more was 0.14. The cumulative 90% bundle diameter was 120 nm.

[0254] (Example 4) 1. Manufacturing of CNT Assembly 4 CNT assembly 4 was manufactured in the same manner as CNT assembly 1, except that the temperature of the second temperature zone was controlled to 1320°C, the total gas supply flow rate of the carrier gas and raw material gas was set to 17.2 NL / min, and the flow rate ratio of methane / thiophene gas was set to range C in Table 1. 2. Preparation of CNT Dispersion 4 Using the obtained CNT assembly 4, a pre-dispersion 4 was obtained in the same manner as in Example 1.

[0255] The pre-dispersion 4 was subjected to the final dispersion using a high-pressure homogenizer (model number: NAGS100) manufactured by Jōkō Co., Ltd. as a wet jet mill under the following conditions to obtain the CNT dispersion 4. (Dispersion conditions) Nozzle diameter: 0.22 mm Pressure: 85 MPa Number of passes: 8 Method: Circulation method

[0256] <Evaluation of CNT aggregate dispersion 4: Viscosity> The viscosity of CNT dispersion 4 was measured using the same method as in Example 1. The viscosity of the dispersion was 542.5 mPa·s. The common logarithm of the viscosity was 2.73.

[0257] 3. Evaluation

[0258] <Si atom content relative to the total mass of the CNT aggregate> The measurement was performed in the same manner as in Example 1, except that CNT aggregate 4 was used. The Si atom content was 700 ppm by mass.

[0259] <Tensile Test> A tensile test was performed in the same manner as in Example 1, except that CNT dispersion 4 was used. The results showed a tensile strength of 15.1 MPa, an elongation at break of 2.0%, and an energy density at break of 30.6 MPa·%.

[0260] <Surface Resistivity> The surface resistivity was measured in the same manner as in Example 1, except that the sample used for measurement in Example 4 was used. As a result, the surface resistivity was 0.91 Ω / □.

[0261] <Measurement of cumulative 50% particle size D50 in volume-based particle size distribution> For the CNT dispersion 4, the cumulative 50% particle size D50 in volume-based particle size distribution was measured in the same manner as in Example 1. As a result, the cumulative 50% particle size D50 in volume-based particle size distribution of the CNT aggregate 1 was 9.53 μm.

[0262] <Bundle Diameter Features> For the CNT aggregate 4 of Example 4, imaging was performed using an SEM, and six images in which CNT bundles were clearly observed were selected from the obtained images (one of which is shown in Figure 4). Except for this, the bundle diameter features were calculated in the same manner as in Example 1. As a result, the area percentage of bundles with a bundle diameter of 100 nm or more was 0.43. The cumulative 90% bundle diameter was 190 nm.

[0263] (Example 5) 1. Manufacturing of CNT aggregate 5 CNT aggregate 5 was manufactured in the same manner as CNT aggregate 1, except that the total gas supply flow rate of the carrier gas and raw material gas was set to 38.9 NL / min. 2. Preparation of CNT dispersion 5 Using the obtained CNT aggregate 5, a pre-dispersion 5 was obtained in the same manner as in Example 1.

[0264] The pre-dispersion 5 was subjected to the final dispersion using a high-pressure homogenizer (model number: NAGS100) manufactured by Jōkō Co., Ltd. as a wet jet mill under the following conditions to obtain the CNT dispersion 5. (Dispersion conditions) Nozzle diameter: 0.22 mm Pressure: 150 MPa Number of passes: 8 Method: Circulation method

[0265] <Evaluation of CNT aggregate dispersion 5: Viscosity> The viscosity of CNT dispersion 5 was measured using the same method as in Example 1. The viscosity of the dispersion was 102.2 mPa·s. The common logarithm of the viscosity was 2.01.

[0266] 3. Evaluation

[0267] <Si atom content relative to the total mass of the CNT aggregate> The measurement was performed in the same manner as in Example 1, except that CNT aggregate 5 was used. The Si atom content was 700 ppm by mass.

[0268] <Tensile Test> A tensile test was performed in the same manner as in Example 1, except that CNT dispersion 5 was used. The results showed a tensile strength of 28.5 MPa, an elongation at break of 2.5%, and an energy density at break of 71.5 MPa·%.

[0269] <Surface Resistivity> The surface resistivity was measured in the same manner as in Example 1, except that the sample used for measurement in Example 5 was used. As a result, the surface resistivity was 3.31 Ω / □.

[0270] <Measurement of cumulative 50% particle size D50 in volume-based particle size distribution> For the CNT dispersion 5, the cumulative 50% particle size D50 in volume-based particle size distribution was measured in the same manner as in Example 1. As a result, the cumulative 50% particle size D50 in volume-based particle size distribution of the CNT aggregate 1 was 1.07 μm.

[0271] <Bundle Diameter Features> For the CNT aggregate 5 of Example 5, imaging was performed using an SEM, and six images in which CNT bundles were clearly observed were selected from the obtained images (one of which is shown in Figure 5). Except for this, the bundle diameter features were calculated in the same manner as in Example 1. As a result, the area percentage of bundles with a bundle diameter of 100 nm or more was 0.23. The cumulative 90% bundle diameter was 160 nm.

[0272] (Comparative Example 1) 1. Manufacturing of CNT Assembly 6 CNT assembly 6 was manufactured in the same manner as CNT assembly 1, except that the total gas supply flow rate of the carrier gas and raw material gas was set to 42 NL / min. 2. Preparation of CNT Dispersion 6 Using the obtained CNT assembly 6, a CNT dispersion 6 was obtained in the same manner as in Example 2.

[0273] <Evaluation of CNT aggregate dispersion 6: Viscosity> The viscosity of the dispersion was 34.6 mPa·s. The common logarithm of the viscosity was 1.54.

[0274] 3. Evaluation <Si atom content relative to the total mass of the CNT aggregate> The measurement was performed in the same manner as in Example 1, except that CNT aggregate 6 was used. The Si atom content was 1000 ppm by mass.

[0275] <Tensile Test> A tensile test was performed in the same manner as in Example 1, except that CNT dispersion 6 was used. The results showed a tensile strength of 3.5 MPa, an elongation at break of 4.1%, and a fracture energy density of 14.2 MPa·%.

[0276] <Surface Resistivity> The surface resistivity was measured in the same manner as in Example 1, except that the measurement sample from Comparative Example 1 was used. As a result, the surface resistivity was 4.21 Ω / □.

[0277] <Measurement of cumulative 50% particle size D50 in volume-based particle size distribution> For the CNT dispersion 6, the cumulative 50% particle size D50 in volume-based particle size distribution was measured in the same manner as in Example 1. As a result, the cumulative 50% particle size D50 in volume-based particle size distribution of the CNT aggregate 6 was 0.44 μm.

[0278] <Bundle Diameter Feature> For the CNT aggregate 6 of Comparative Example 1, imaging was performed using SEM, and six images in which CNT bundles were clearly observed were selected from the obtained images (one of which is shown in Figure 4). Except for this, the bundle diameter feature was calculated in the same manner as in Example 1. As a result, the area percentage of bundles with a bundle diameter of 100 nm or more was 0.41. The cumulative 90% bundle diameter was 200 nm.

[0279] (Comparative Example 2) 1. Manufacturing of CNT Assembly 7 CNT assembly 7 was manufactured in the same manner as CNT assembly 1, except that the total gas supply flow rate of the carrier gas and raw material gas was set to 38.1 NL / min. 2. Preparation of CNT Dispersion 7 Using the obtained CNT assembly 7, a pre-dispersion 7 was obtained in the same manner as in Example 1.

[0280] The pre-dispersion 7 was subjected to the final dispersion using a high-pressure homogenizer (model number: NAGS100) manufactured by Jōkō Co., Ltd. as a wet jet mill under the following conditions to obtain the CNT dispersion 7. (Dispersion conditions) Nozzle diameter: 0.22 mm Pressure: 250 MPa Number of passes: 8 Method: Circulation method

[0281] <Evaluation of CNT aggregate dispersion 7: Viscosity> The viscosity of the dispersion was 73.2 mPa·s. The common logarithm of the viscosity was 1.86.

[0282] 3. Evaluation <Si atom content relative to the total mass of the CNT aggregate> The measurement was performed in the same manner as in Example 1, except that CNT aggregate 7 was used. The Si atom content was 1300 ppm by mass.

[0283] <Tensile Test> A tensile test was performed in the same manner as in Example 1, except that CNT dispersion 7 was used. The results showed a tensile strength of 5.9 MPa, an elongation at break of 2.3%, and an energy density at break of 13.5 MPa·%.

[0284] <Surface Resistivity> The surface resistivity was measured in the same manner as in Example 1, except that the measurement sample from Comparative Example 2 was used. As a result, the surface resistivity was 5.76 Ω / □.

[0285] <Measurement of cumulative 50% particle size D50 in volume-based particle size distribution> For the CNT dispersion 7, the cumulative 50% particle size D50 in volume-based particle size distribution was measured in the same manner as in Example 1. As a result, the cumulative 50% particle size D50 in volume-based particle size distribution of the CNT aggregate 7 was 0.98 μm.

[0286] <Bundle Diameter Feature> For the CNT aggregate 7 of Comparative Example 2, imaging was performed using SEM, and four images in which CNT bundles were clearly observed were selected from the obtained images (one of which is shown in Figure 7). Except for this, the bundle diameter feature was calculated in the same manner as in Example 1. As a result, the area ratio of bundles with a bundle diameter of 100 nm or more was 0.16. The cumulative 90% bundle diameter was 130 nm.

[0287] Next, we fabricated a lithium-ion secondary battery.

[0288] 1. Fabrication of positive electrode for lithium secondary battery: Positive electrode active material (LiNi ０．８ Co ０．１ Mn ０．１ O ２A positive electrode mixture was prepared by mixing a conductive material (acetylene black) and a binder (PVdF) in a ratio of positive electrode active material:conductive material:binder = 92:5:3 (mass ratio), and then kneading with N-methyl-2-pyrrolidone. The obtained positive electrode mixture was applied to a 15 μm thick Al foil to be used as a current collector, vacuum-dried at 80°C for 1 hour, and then roll-pressed to obtain a positive electrode for a lithium secondary battery. The positive electrode area was 1.65 cm². ２ The estimated amount is 16 mg / cm³. ２ The density is 3.0 g / cm³. ３ I adjusted it so that it would be as follows.

[0289] 2. Preparation of a Negative Electrode for Lithium Secondary Batteries A negative electrode for lithium secondary batteries was prepared by mixing artificial graphite MAG-E and carbon-coated SiO in a 9:1 (mass ratio) ratio as the negative electrode active material, using CLPA-C07 (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) as a binder, and adding the CNT dispersion 1 from Example 1 as a conductive additive, so that the composition was negative electrode active material:binder:conductive additive = 94.9:5.0:0.1 (weight ratio), and kneading to prepare a paste-like negative electrode mixture. Ion-exchanged water was used as the solvent during the preparation of the negative electrode mixture. The obtained negative electrode mixture was coated onto a 20 μm thick Cu foil using a single-sided continuous coating machine, dried at 120°C, and then roll-pressed to obtain a negative electrode for lithium secondary batteries. The negative electrode area was 1.77 cm². ２ The estimated amount is 9.3 mg / cm³. ２ The density is 1.4 g / cm³. ３ I adjusted it so that it would be as follows.

[0290] 3. Fabrication of a Lithium Secondary Battery The positive electrode for the lithium secondary battery was placed on the lower cover of a part for the coin-type battery R2032 (manufactured by Hosen Co., Ltd.), and a laminated film separator, which consists of a 16 μm heat-resistant porous layer laminated on a polyethylene porous film, was placed on top of it. 300 μL of electrolyte was injected into this. As the electrolyte, a 20:75:5 (volume ratio) mixture of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate was added, to which 1 volume% of vinylene carbonate was added, and LiPF was added. ６A solution of 1.3 mol / L was used. Next, the negative electrode for the lithium secondary battery was placed on top of the laminated film separator, the top cover was placed on top via a gasket, and the lithium secondary battery of coin-type full cell R2032 was fabricated by crimping with a crimping machine. These operations were performed in a glove box under an argon atmosphere.

[0291] The evaluation results for Example 1, Example 2, Example 3, Example 4, Example 5, Comparative Example 1, and Comparative Example 2 are shown in Table 2.

[0292]

[0293] As shown in Table 2, the CNT aggregates of Examples 1 to 5 satisfy conditions (1) and (2), and were found to have excellent tensile strength.

Claims

A carbon nanotube aggregate that satisfies the following conditions (1) and (2). (1) Contains Si, and the Si content is greater than 0 ppm by mass and less than 1000 ppm by mass relative to the total mass of the carbon nanotube aggregate. (2) The surface resistivity measured by the following measurement method is greater than 0 Ω / □ and less than or equal to 4.0 Ω / □. (Method for measuring surface resistivity) A carbon nanotube dispersion is prepared by mixing a carbon nanotube aggregate, 700 kDa sodium carboxymethylcellulose, and water, so that the concentration of the carbon nanotube aggregate is 0.20 mass% and the concentration of sodium carboxymethylcellulose is 0.30 mass%. 15 mL of the prepared carbon nanotube dispersion is poured onto a glass slide-type silicon plate with inner dimensions of 22 mm × 75 mm × 3 mm and heated and dried at 100°C to prepare a measurement sample. For the prepared measurement sample, the surface resistivity of five arbitrarily selected locations on the film is measured using a resistivity meter with a four-probe method, and the average of the five measured values ​​is taken as the surface resistivity. 　 A carbon nanotube aggregate according to claim 1, satisfying the following condition (3). (3) When the carbon nanotube aggregate, 700 kDa of carboxymethylcellulose sodium, and water are mixed, and the liquid temperature is 25°C, the concentration of the carbon nanotube aggregate is 0.20% by mass, and the concentration of the carboxymethylcellulose sodium is 0.30% by mass, the common logarithm of the viscosity of the dispersion is 2.0 or higher. The unit of viscosity is mPa·s. 　 A conductive material comprising a carbon nanotube aggregate according to claim 1 or 2. 　 An electrode comprising an electrode active material and the conductive material described in claim 3. 　 A secondary battery comprising the electrode described in claim 4. 　 A planar aggregate comprising the carbon nanotube aggregate according to claim 1 or 2. 　 A laminate comprising a substrate and the planar assembly described in claim 6. 　 A filter using the planar assembly described in claim 6. 　 Electromagnetic shielding using the planar assembly described in claim 6. 　 A pellicle for extreme ultraviolet radiation using the planar aggregate described in claim 6.

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