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

Abstract

Provided is a carbon nanotube aggregate and the like that can produce a battery with excellent cycle characteristics. The carbon nanotube aggregate has a sparsity-density factor Σ, as determined by formula (α), of 0.075 or more and less than 1.0.　Resistance factor P is the product of film surface resistivity (ρs) and film absorbance (Abs). Two types of film thicknesses are prepared and the resistance factor Pthick of the thick film and Pthin of the thin film are calculated. In addition, the concentration Cthick of the carbon nanotube aggregate in the thick film and the concentration Cthin of the carbon nanotube aggregate in the thin film are prepared. Pthick, Pthin, Cthick, and Cthin are applied to formula (α).

Description

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

[0001] This disclosure relates to carbon nanotube aggregates, conductive materials, electrodes, secondary batteries, planar aggregates, laminates, 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 discloses a multi-walled carbon nanotube aggregate having high conductivity. It is described that the multi-walled carbon nanotubes are intertwined with each other, forming a large network structure that can exist stably in an aqueous dispersion.

[0004] Patent Document 2 describes how, by utilizing the structurally stable network structure of CNTs and the chemically stable polystyrene sulfonic acid (PSS), a conductive material can be provided that achieves high conductivity, long-term stability in atmospheric environments, high-temperature stability (heat resistance), and high-humidity stability by thinly adsorbing PSS acid onto the CNT surface, as well as a conductive film and solar cell utilizing this material.

[0005] International Publication No. 2025 / 013505, Japanese Patent Publication No. 2021-140999

[0006] When using CNT assemblies as conductive additives, there is room for improvement in the challenge of stably constructing conductive paths and ensuring conductivity, which sometimes resulted in inferior cycle characteristics in the fabricated batteries.

[0007] 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 powder that can be used to produce a battery with excellent cycle characteristics. Another embodiment of this disclosure aims to solve the problem of providing a conductive material, an electrode, a secondary battery, and a planar assembly containing the carbon nanotube powder. Another embodiment of this disclosure aims to solve the problem of providing a laminate comprising the planar assembly. Another embodiment of this disclosure aims to solve the problem of providing a filter, an electromagnetic shield, and an extreme ultraviolet pellicle using the planar assembly.

[0008] The means for solving the above problem include the following embodiments: <1> A carbon nanotube aggregate in which the density factor Σ, calculated by the following formula (α), is 0.075 or more and less than 1.0.

[0009] The resistivity factor P is the product of the film's surface resistivity (ρs) and its absorbance (Abs). Two different film thicknesses were prepared, and the resistivity factor P of the thick film was calculated. thick , thin film P thin The concentration C of carbon nanotube aggregates in the thick film is calculated. thick , concentration C of carbon nanotube aggregates in thin films thin Prepare P thick , P thin , C thick and C thin Apply this to equation (α).

[0010] <2> A carbon nanotube aggregate according to <1>, comprising a bundle structure, wherein the bundle diameter W of 90% of the cumulative bundles in the area observed by a scanning electron microscope is greater than 80 nm and less than 500 nm. <3> A carbon nanotube aggregate according to <1> or <2>, comprising a bundle structure, wherein the area ratio Z of bundles with a bundle diameter of 100 nm or more in the area observed by a scanning electron microscope is greater than 0.1. <4> A conductive material comprising the carbon nanotube aggregate according to any one of <1> to <3>. <5> An electrode comprising an electrode active material and the conductive material according to <4>. <6> A secondary battery comprising the electrode according to <5>. <7> A planar aggregate comprising the carbon nanotube aggregate according to any one of <1> to <3>. <8> A laminate comprising a substrate and the planar aggregate according to <7>. <9> A filter using the planar aggregate according to <7>. <10> An electromagnetic shield using the planar aggregate according to <7>. <11> A pellicle for extreme ultraviolet radiation using the planar aggregate described in <7>.

[0011] According to one embodiment of the present disclosure, a carbon nanotube aggregate capable of producing a battery with excellent cycle characteristics 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.

[0012] This is an image of carbon nanotube aggregate 1 from Example 1, obtained using a scanning electron microscope. This is another image of carbon nanotube aggregate 2 from Example 2, obtained using a scanning electron microscope. This is yet another image of carbon nanotube aggregate 3 from Example 3, obtained using a scanning electron microscope. This is an image of carbon nanotube aggregate 4 from Example 4, obtained using a scanning electron microscope. This is an image of carbon nanotube aggregate 5 from Example 5, obtained using a scanning electron microscope. This is an image of carbon nanotube aggregate 6 from Example 6, obtained using a scanning electron microscope. This is an image of carbon nanotube aggregate 7 from Example 7, obtained using a scanning electron microscope. This is yet another image of carbon nanotube aggregate 8 from Comparative Example 1, obtained using a scanning electron microscope.

[0013] The present disclosure is described in detail below. In this specification, a numerical range expressed using "~" means a range that includes the numbers written before and after "~" as the lower and upper limits. In this specification, in numerical ranges described in stages, 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 specification, the upper or lower limit stated in one numerical range may be replaced with the values ​​shown in the examples. In this specification, the term "process" is included not only in the sense of an independent process, but also in the sense of a process that is not clearly distinguishable from other processes, as long as the intended purpose of that process is achieved.

[0014] 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.

[0015] (Carbon nanotube aggregate) The carbon nanotube aggregate (also referred to as "CNT aggregate") according to the present disclosure has a density factor Σ calculated by the following formula (α) of 0.075 or more and less than 1.0.

[0016] The resistance factor P is the product of the surface resistivity (ρs) of the film and the absorbance (Abs) of the film. Two types of film thickness are prepared, and the resistance factor P of the thick film thick , P of the thin film thin is calculated. Further, the concentration C of the carbon nanotube aggregate in the thick film thick , the concentration C of the carbon nanotube aggregate in the thin film thin is prepared. P thick , P thin , C thick and C thin are applied to formula (α).

[0017] According to the CNT aggregate according to the present disclosure, a carbon nanotube (CNT) dispersion with appropriate viscosity can be obtained, and a battery having excellent cycle characteristics can be produced. On the other hand, Patent Document 1 and Patent Document 2 do not include any description focusing on the density factor Σ calculated by formula (α).

[0018] For example, Patent Document 1 describes the relationship between the median diameter in the volume-based particle size distribution obtained by centrifugal sedimentation when multi-walled carbon nanotubes are dispersed in an aqueous dispersion of a specific concentration, and the structure formed by the entanglement of multi-walled carbon nanotubes. However, it does not focus on the density factor described in the present invention, and does not mention that a carbon nanotube dispersion of appropriate viscosity can be obtained and that it exhibits excellent cycle characteristics in secondary battery evaluation. For example, Patent Document 2 describes a conductive film and solar cell composited with polystyrene sulfonic acid in which carbon nanotubes have a network structure, but it does not focus on the density factor described in the present invention, and does not mention that a carbon nanotube dispersion of appropriate viscosity can be obtained and that it exhibits excellent cycle characteristics in lithium-ion secondary battery evaluation. In contrast, with the CNT aggregate according to the present disclosure, since the density factor Σ obtained by formula (α) is less than 1.0, a carbon nanotube dispersion of appropriate viscosity can be obtained and a battery with excellent cycle characteristics can be manufactured.

[0019] <Density Factor Σ> The density factor is calculated using the following formula. When a thick CNT film is designated as CNT film A and a thin CNT film as CNT film B, the ratio of the resistivity factors of A and B is (surface resistivity of CNT film A / surface resistivity of CNT film B) × (absorbance of CNT film A / absorbance of CNT film B), and the density factor is (resistivity of CNT film A ÷ resistance factor of CNT film B) × (concentration of carbon nanotube aggregates in CNT film B ÷ concentration of carbon nanotube aggregates in CNT film A). The calculated density factor is greater than 0 and less than 1.00. The density factor corresponds to the ratio of the volume resistivity of the thick CNT film and the thin CNT film, and represents the network properties of the CNTs. The larger the value of the density factor, the better the network properties of the CNTs.

[0020] Herein, we provide a theoretical explanation for calculating the density factor Σ obtained by the above equation (α).

[0021] - Overview of the Density Factor - Derivation of the formula The surface resistivity ρs of a resistor is a physical quantity that includes the film thickness t, expressed as ρs = ρv / t, where ρv is the volume resistivity and t is the film thickness. Absorbance Abs is expressed as Abs = εCt, where ε is the molar extinction coefficient, C is the concentration of the substance, and t is the film thickness. Therefore, when the surface resistivity ρs is multiplied by the absorbance, the film thickness t cancels out, and it is expressed as ρs × Abs = ρv × ε × C. Since the dimension of this parameter is Ohm, we define this as the resistance factor P.

[0022]

[0023] When the same CNT species is used, the molar extinction coefficient ε of the CNT itself is constant. In CNT films deposited by varying the filtration rate when a CNT dispersion is suction filtered, the ratio of the resistivity factor of the thick film to the resistivity factor of the thin film is the product of the ratio of the carbon nanotube aggregate concentration C to the volume resistivity ρv. Below, the physical quantities of the thick film and thin film will be denoted by the subscripts thick and thin, respectively.

[0024]

[0025] The concentration C is proportional to the amount filtered when the CNT dispersion is suction filtered, and is therefore a constant. In other words, the ratio of the resistance factors P is proportional to the ratio of the volume resistivity. Rearranging the above equation yields the following:

[0026]

[0027] The value obtained by multiplying the resistance factor on the right-hand side by the inverse ratio of the concentrations corresponds to the ratio of volume resistivity and represents the network properties of CNTs. Since thick and thin CNT filtration membranes are used, the density factor is defined as Σ.

[0028]

[0029] When the density factor is 1, the volume resistivity remains unchanged between thin and thick films, which is the ideal value. Normally, it takes a value of 1 or less, and a larger density factor means that the difference in volume resistivity between sparse and dense CNT aggregates is smaller, indicating good network properties.

[0030] The density factor Σ obtained by formula (α) above may be 0.700 or less, 0.500 or less, 0.400 or less, 0.300 or less, 0.200 or less, or 0.100 or less. Furthermore, the density factor Σ may be 0.075 or more, 0.076 or more, 0.077 or more, 0.078 or more, 0.079 or more, 0.080 or more, 0.081 or more, 0.082 or more, 0.083 or more, 0.084 or more, or 0.085 or more. The upper and lower limits of the density factor Σ can be arbitrarily combined. In particular, it is preferable that it be 0.075 or more and 0.700 or less, more preferably 0.080 or more and 0.700 or less, and even more preferably 0.084 or more and 0.700 or less. In other embodiments, it is preferable that the value is 0.075 or more and 0.500 or less, more preferably 0.080 or more and 0.500 or less, and even more preferably 0.084 or more and 0.500 or less. In other embodiments, it is preferable that the value is 0.075 or more and 0.200 or less, more preferably 0.080 or more and 0.200 or less, and even more preferably 0.084 or more and 0.200 or less. In other embodiments, it is preferable that the value is 0.075 or more and 0.200 or less, more preferably 0.075 or more and 0.100 or less, more preferably 0.080 or more and 0.190 or less, even more preferably 0.080 or more and 0.180 or less, particularly preferably 0.083 or more and 0.180 or less, and especially preferably 0.084 or more and 0.170 or less. In other embodiments, it is preferable that the value is greater than 0.083 and 0.200 or less, more preferably greater than 0.083 and 0.170 or less, and particularly preferable greater than 0.083 and 0.161 or less. In other embodiments, it is preferable that the value is 0.086 or more and 0.200 or less, more preferably 0.086 or more and 0.170 or less, and particularly preferable 0.086 or more and 0.161 or less.

[0031] Specifically, a density factor Σ of 0.075 or higher facilitates the formation of bundles between CNTs, resulting in thicker conductive paths and reduced resistivity of the conductive paths. This improves the conductivity of the CNT aggregate and optimizes its performance as an electrode material. Furthermore, a density factor of 0.700 or lower allows for the formation of conductive paths through network structures in addition to CNT bundles, while preventing the network structure from becoming too narrow and suppressing the resistivity of the conductive paths. Additionally, a density factor of 0.700 or lower ensures particularly good dispersibility of the CNT aggregate in the solvent, and when used as a conductive additive in batteries, it also improves the adhesion of the CNT aggregate to the electrode active material within the electrode. This increases the structural stability within the electrode, improving durability against volume changes and stress during battery cycling, and enhancing the battery's cycle characteristics.

[0032] The ratio of the film thicknesses of CNT film A (thick film) and CNT film B (thin film) is preferably CNT film A:CNT film B = 30:1 to 2:1, more preferably 20:1 to 3:1, and even more preferably 10:1 to 4:1. Having the film thickness ratio within this range allows for the calculation of the density factor in the absorbance comparison between CNT film A and CNT film B without being affected by differences in scattering due to excessive differences in film thickness.

[0033] The density factor can be adjusted by the length and diameter of the carbon nanotube aggregate.

[0034] <Surface Resistivity of CNT Film> In this disclosure, the surface resistivity of the CNT film is determined by the surface resistivity of the CNT film obtained by diluting a dispersion containing CNT aggregates with a large excess of pure water, filtering it, transferring the filtration film formed on the filter onto a glass substrate, and drying it. The surface resistivity can be measured by the 4-terminal 4-probe method in accordance with the standard JIS K7194:1994. As a resistivity meter, for example, Loresta GXII manufactured by Nitto Seiko Analytech Co., Ltd. is used. From the viewpoint of ensuring conductivity as a conductive additive and the stability of the dispersion, the surface resistivity of the CNT film is preferably 0.1 Ω / □ to 1000 Ω / □, more preferably 1.0 Ω / □ to 500 Ω / □, even more preferably 10 Ω / □ to 300 Ω / □, particularly preferably 15 Ω / □ to 200 Ω / □, and most preferably 20 Ω / □ to 200 Ω / □. The center of the film is preferable as the measurement point because it is easier to ensure accuracy. If measurements are taken at the edges of the film, there is a possibility that measurement errors will increase due to electric field leakage.

[0035] <Concentration of CNT film> In this disclosure, the concentration of the CNT film can be estimated from the amount of dispersion used, for example, when the film is obtained by filtering the dispersion. However, since the ratio of the concentrations of the thick film to the thin film is important in calculating the density factor in this disclosure, the individual concentrations of the CNT films themselves are not that important.

[0036] <Measurement of Absorbance> The absorbance of CNT film A and CNT film B is measured at 550 nm by ultraviolet-visible spectroscopy (UV-vis). An example of a UV-vis spectrophotometer is the Cary 5000 UV-Vis-NIR spectrophotometer (manufactured by Agilent Technologies). In calculating the density factor in this disclosure, the ratio of the absorbance of the thick CNT film to the absorbance of the thin CNT film is important, so the absorbance of each individual CNT film is not that important.

[0037] <Preparation of CNT film> -Implantation of CNT film onto substrate for density factor measurement- More specifically, the CNT film is prepared by the following procedure. 12 μL of 0.2% by mass CNT dispersion is diluted with 25 mL of pure water and filtered by suction using a membrane filter to obtain filtration film A on the membrane filter. Optionally, the surface of the glass substrate is subjected to known treatments such as aminosilane coupling agent treatment or UV ozone cleaning treatment. While the membrane filter is still wet, it is immersed in pure water to release filtration film A, which is then attached to the glass substrate. The glass substrate is dried on a hot plate at 100°C for 10 minutes to obtain CNT film A. CNT film B is obtained in the same manner as CNT film A, except that 2 μL of 0.2% by mass CNT dispersion is used. The surface resistivity of the CNT film is the same as that measured for CNT film A.

[0038] <Preparation of CNT dispersion> In the preparation of the CNT membrane in this disclosure, a CNT dispersion can be suitably used. By filtering and washing, excess dispersant can be removed, and the network structure itself can be evaluated more accurately.

[0039] -Preparation of CNT dispersion- A CNT dispersion is prepared in which the concentration of CNTs is 0.2% by mass relative to the total volume of the CNT dispersion. The method for preparing a CNT dispersion in which the concentration of CNTs is 0.2% by mass relative to the total volume of the CNT dispersion is not particularly limited and can be prepared by known methods. More specifically, first, a CNT aggregate, water, and sodium carboxymethylcellulose are mixed to obtain a mixture in which the concentration of CNTs is 0.2% by mass relative to the total volume and the concentration of sodium carboxymethylcellulose is 0.3% by mass relative to the total volume. Next, the mixture is subjected to a pre-dispersion treatment using a homogenizer for 1 hour, and then subjected to a final dispersion treatment using a wet jet mill to obtain a CNT dispersion in which the concentration of CNTs is 0.2% by mass. That is, a CNT aqueous dispersion in which the concentration of CNTs is 0.2% by mass relative to the total volume of the CNT dispersion is prepared.

[0040] The detailed conditions for the pre-dispersion treatment are not particularly limited; for example, dispersion treatment can be performed using a homogenizer at a speed of 500 rpm to 20,000 rpm. The detailed conditions for this dispersion treatment are also not particularly limited; for example, dispersion treatment can be performed using a wet jet mill with the following conditions: nozzle diameter: 0.15 mm to 0.70 mm, pressure: 10 MPa to 250 MPa, number of cycles: 1 to 30, method: circulating method.

[0041] <Bundle Diameter W> The CNT aggregate according to this disclosure includes a bundle structure, and in the area observed by a scanning electron microscope, the bundle diameter W at 90% cumulative (hereinafter also referred to as the "90% cumulative bundle diameter") is greater than 80 nm and less than 500 nm.

[0042] The CNT aggregates according to this disclosure preferably include 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 enhances its stability.

[0043] 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.

[0044] 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.

[0045] In SEM observation, the CNT aggregates described herein have a cumulative 90% bundle diameter exceeding 80 nm, which facilitates the aggregation of CNT bundles and the formation of long-distance conductive networks. Furthermore, having a cumulative 90% bundle diameter of less than 500 nm results in good dispersibility in the dispersion medium and makes it easier to ensure conductivity.

[0046] Specifically, a cumulative 90% bundle diameter exceeding 80 nm allows the CNTs to aggregate appropriately, forming efficient conductive paths. This improves the conductivity of the CNT aggregate and optimizes its performance as an electrode material. Furthermore, a cumulative 90% bundle diameter of less than 500 nm ensures good dispersibility in the dispersion medium, resulting in uniform dispersion. This maintains the viscosity of the dispersion containing the CNT aggregate within an appropriate range, further improving dispersibility.

[0047] In particular, the cumulative 90% bundle diameter is preferably greater than 90 nm and less than or equal to 450 nm. Within this range, by appropriately controlling the bundle diameter of the CNTs, the contact resistance between CNTs is reduced, and electron conduction paths are efficiently formed, thereby improving conductivity. Furthermore, by appropriately controlling the bundle diameter, the viscosity of the dispersion containing the CNT aggregate is maintained within an appropriate range, improving dispersibility.

[0048] In SEM observation, the CNT aggregates described herein have a cumulative 90% bundle diameter of 100 nm or more, which facilitates the aggregation of CNT bundles and the formation of long-distance conductive networks. Furthermore, when the cumulative 90% bundle diameter is 400 nm or less, dispersibility in the dispersion medium is improved, and conductivity is easily ensured.

[0049] Specifically, a cumulative 90% bundle diameter of 100 nm or more allows the CNTs to aggregate appropriately, forming efficient conductive paths. This improves the conductivity of the CNT aggregate and optimizes its performance as an electrode material. Furthermore, a cumulative 90% bundle diameter of 400 nm or less ensures good dispersibility in the dispersion medium, resulting in uniform dispersion. This maintains the viscosity of the dispersion containing the CNT aggregate within an appropriate range, further improving dispersibility.

[0050] In particular, the cumulative 90% bundle diameter is preferably 100 nm to 350 nm, more preferably between 110 nm and 350 nm, and especially preferably between 110 nm and 340 nm. Within this range, by appropriately controlling the bundle diameter of the CNTs, the contact resistance between CNTs is reduced and electron conduction paths are efficiently formed, thereby improving conductivity. Furthermore, by appropriately controlling the bundle diameter, the viscosity of the dispersion containing the CNT aggregate is maintained within an appropriate range, improving dispersibility.

[0051] <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) exceeds 0.1. The area ratio of bundles with a bundle diameter of 100 nm or more is calculated by dividing the area of ​​bundles with a bundle diameter of 100 nm or more in the SEM image of the CNT aggregate by the total area of ​​the CNT aggregate.

[0052] The details regarding the bundle structure contained in the CNT aggregate have been described previously, and will not be explained here.

[0053] In the CNT aggregate according to this disclosure, when the area ratio of bundles with a bundle diameter of 100 nm or more exceeds 0.1 in the SEM observation area, the bundle structure of the CNTs is appropriately formed, improving the mechanical strength and conductivity as an electrode material. Specifically, when the bundle diameter is 100 nm or more, the bonding between CNTs is strengthened, and the electron transport pathways connecting the electrode active materials become more robust, thereby improving the structural stability of the electrode. In addition, the large bundle diameter increases the electron conduction pathways within the electrode, promoting efficient current flow. As a result, the internal resistance of the battery is reduced, and the charge and discharge efficiency is improved. Therefore, when the area ratio of bundles with a bundle diameter of 100 nm or more exceeds 0.1 in the SEM observation area, a battery with excellent cycle characteristics can be obtained.

[0054] In particular, the area ratio of the bundle is preferably greater than 0.1 and less than 0.7, more preferably greater than 0.1 and less than 0.6, even more preferably greater than 0.1 and less than 0.55, especially preferably greater than 0.1 and less than 0.5, even more preferably 0.11 or more and less than 0.5, even more preferably 0.13 or more and less than 0.5, especially preferably 0.15 or more and less than 0.5, and particularly preferably 0.20 or more and less than 0.5. Within this range, the bundle structure of the CNTs is appropriately formed, and the bonding between the CNTs is strengthened, thereby improving the mechanical strength of the electrode. In addition, an appropriate bundle diameter improves the dispersibility of the CNTs and ensures a uniform conductive path within the electrode. As a result, the conductivity of the entire electrode is improved, the internal resistance of the battery is reduced, and excellent cycle characteristics are obtained.

[0055] Furthermore, from the viewpoint of increasing the elongation at break, it is particularly preferable that the area ratio of the above bundle be greater than 0.17 and less than or equal to 0.49. A higher elongation at break improves the flexibility and durability of the material containing the CNT aggregate.

[0056] Furthermore, the area ratio of the bundle is preferably 0.13 or more and less than 0.5, and more preferably 0.15 or more and less than 0.5. Within this range, the bundle diameter of the CNTs becomes appropriately small, increasing the surface area as an electrode material and widening the contact area with the electrode active material. This promotes ion movement and improves the charge and discharge efficiency of the battery. In addition, an appropriately small bundle diameter also has the effect of increasing the flexibility of the electrode and improving its durability against volume changes during the cycle. Therefore, the cycle characteristics of the battery are further improved.

[0057] 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.

[0058] -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

[0059] - Image Selection - From the obtained images, select two or more images in which CNT bundles are frequently observed.

[0060] - 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.

[0061] -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.

[0062] -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.

[0063] -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.

[0064] - 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.

[0065] <Tensile Strength> The CNT aggregate according to this disclosure preferably has a tensile strength of 2.0 MPa or more and 50.0 MPa or less, as measured by the measurement method described below, and preferably has a fracture elongation of more than 0% and 5.0% or less.

[0066] -Method for measuring tensile strength and elongation at break- A carbon nanotube dispersion is prepared by mixing a carbon nanotube aggregate, 700 kDa of carboxymethylcellulose sodium, and water, so that the concentration of the carbon nanotube aggregate is 0.20 mass% and the concentration of carboxymethylcellulose sodium is 0.30 mass%. The obtained carbon nanotube dispersion is poured onto a 22 mm × 75 mm × 3 mm slide glass type silicon plate and heated at 100°C for 30 minutes to dry and obtain 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.

[0067] The elongation at break of the CNT aggregate relating to this disclosure is preferably greater than 0% and 5.0% or less, more preferably 1.0% or more and 5.0% or less, and even more preferably 1.0% or more and 4.5% or less.

[0068] When the elongation at break of the CNT aggregate according to this disclosure exceeds 0%, the length of the CNTs is sufficiently long, making it easier to ensure conductivity. Specifically, the sufficient length of the CNTs increases the number of contact points between CNTs, allowing for smoother electron movement, thus improving the conductivity of the entire CNT aggregate. Furthermore, maintaining an appropriate length of CNTs allows for efficient formation of conductive paths, optimizing conductivity. When the elongation at break of the CNT aggregate according to this disclosure is 5.0% or less, it is easy to process into a dispersion, and dispersibility in the dispersion is easily ensured. Specifically, an elongation at break of 5.0% or less maintains the flexibility of the CNTs appropriately, enabling uniform dispersion of CNTs in the dispersion. This appropriately maintains the viscosity of the dispersion, improves dispersibility, and further enhances durability against volume changes and stress during the battery cycle. This further improves the maintenance rate of discharge capacity. Therefore, having a fracture elongation rate of the CNT aggregate in the range of over 0% and 5.0% or less plays an important role in improving the battery cycle characteristics of the CNT aggregate.

[0069] Furthermore, the elongation rate at break of the CNT aggregate can be adjusted by the length, diameter, and other factors of the CNT aggregate.

[0070] The tensile strength of the CNT aggregate according to this disclosure is preferably 2.5 MPa or more and 50.0 MPa or less, more preferably 2.5 MPa or more and 40.0 MPa or less, and even more preferably greater than 3.5 MPa and 35.0 MPa or less. When the tensile strength of the CNT aggregate according to this disclosure is 2.5 MPa or more, the length of the CNTs according to this disclosure is sufficiently long, making it possible to manufacture a battery with excellent cycle characteristics. Specifically, the sufficient length of the CNTs increases the contact points between the CNTs, allowing for smooth electron movement, which improves the conductivity of the entire CNT aggregate and improves the cycle characteristics of the battery (i.e., the rate of maintenance of discharge capacity). When the tensile strength of the CNT aggregate according to this disclosure is 50.0 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. This ensures that the viscosity of the dispersion is properly maintained, further improving its resistance to volume changes and stress during the battery cycle. This, in turn, further improves the retention rate of discharge capacity.

[0071] Furthermore, the tensile strength of the CNT aggregate can be adjusted by the length, diameter, and other factors of the CNT aggregate.

[0072] <Applications of Carbon Nanotube Assemblies> The applications of the CNT aggregates according to this disclosure are not particularly limited. Because the CNT aggregates according to this disclosure have high conductivity, they can be suitably used, for example, as conductive additives (especially conductive additives for negative electrodes). Because the CNTs in the CNT aggregates according to this disclosure intertwine with each other and easily form conductive paths, they can be used, for example, in combination with conductive materials such as positive electrode active materials and negative electrode active materials within an electrode to further improve the conductivity of the conductive materials. The CNT aggregates according to this disclosure can be used, for example, together with known conductive additives such as graphite and Ketjenbrak.

[0073] <Method for producing CNTs> The method for producing the CNTs constituting the CNT aggregates according to this disclosure is not particularly limited. For example, as a method for producing CNTs in this disclosure, conventionally known methods such as chemical vapor deposition (CVD) and a method of reacting a gaseous reactant containing a carbon source in the presence of a catalyst can be applied.

[0074] The CNTs in this disclosure can be manufactured by referring to, for example, the methods described in Japanese Patent Publication No. 2016-102047, Japanese Patent Publication No. 2021-527611, etc.

[0075] The following describes the manufacturing method of CNTs in this disclosure with examples. However, the manufacturing method of CNTs in this disclosure is not limited to the following examples.

[0076] =Manufacturing Method X= An example of a method for manufacturing CNTs as referenced in this disclosure is the manufacturing method described in Japanese Patent Application Publication No. 2016-102047. That is, a manufacturing method (hereinafter also referred to as "Manufacturing Method X") that includes the steps of passing a gaseous reactant containing one or more carbon sources through a reactor, reacting one or more gaseous reactants in the reaction region of the reactor in the presence of a catalyst to form carbon-containing product particles, agglomerating the product particles into aggregates, and applying force to the aggregates to continuously move the aggregates out of the reaction region.

[0077] 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.

[0078] According to manufacturing method X, CNTs containing ULCNTs can be obtained in the form of easily handled fibrous aggregates or other aggregates.

[0079] 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.

[0080] 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.

[0081] 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.

[0082] 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.

[0083] 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.

[0084] 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.

[0085] 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.

[0086] 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.

[0087] 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.

[0088] Furthermore, other forces applied to the generated particles may include magnetic force or photon pressure applied by a light source.

[0089] 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.

[0090] 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.

[0091] 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.

[0092] 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.

[0093] 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.

[0094] 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.

[0095] The product particles produced in manufacturing method X contain ULCN. Depending on the manufacturing conditions, SWCNTs and MWCNTs may also be present.

[0096] 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.

[0097] 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.

[0098] 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.

[0099] 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.

[0100] 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.

[0101] 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.

[0102] 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.

[0103] 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.

[0104] 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.

[0105] 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.

[0106] 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.

[0107] By purifying the aggregates of carbon nanotubes (CNTs), the metal content in the CNTs can be reduced.

[0108] 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.

[0109] 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.

[0110] 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.

[0111] 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.

[0112] =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.

[0113] 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.

[0114] 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.

[0115] 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.

[0116] The main catalyst may be one or more selected from the group consisting of cobalt, iron, nickel, manganese, and chromium, with cobalt being preferred.

[0117] 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.

[0118] 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.

[0119] 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.

[0120] 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 O, and one or more selected from the group consisting of the above is preferable.

[0121] When the mixture contains two or more cocatalyst precursors, that is, when it contains both a vanadium precursor and a molybdenum precursor, the mixture may be contained such that the molar ratio of the sum of vanadium and molybdenum to vanadium is 1:0.45 to 1:0.95 or 1:0.5 to 1:0.9, and it is preferable that the mixture is contained such that the molar ratio is 1:0.5 to 1:0.9. When the above conditions are satisfied, the structure of CNTs can be stably maintained, and CNTs having a target pore volume can be produced.

[0122] The mixture may contain the main catalyst precursor and the cocatalyst precursor such that the molar ratio of the main catalyst to the cocatalyst is 1:0.01 to 1:0.5, 1:0.1 to 1:0.4, or 1:0.1 to 1:0.25, and it is preferable that the mixture is contained such that the molar ratio is 1:0.1 to 1:0.25. When the above molar ratio is satisfied, the dispersibility of the main catalyst can be improved, and CNTs having a target pore volume can be produced.

[0123] The mixture may further contain an organic acid that functions to suppress precipitation of the main catalyst precursor and the cocatalyst precursor.

[0124] 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, and citric acid is preferable.

[0125] The mixture may contain the organic acid and the cocatalyst precursor in a molar ratio of 1:1 to 1:20, 1:2 to 1:10, or 1:3 to 1:6, and a molar ratio of 1:3 to 1:6 is preferable. When the above range is satisfied, there are advantages that a transparent catalytic metal solution can be produced during catalyst production, and a catalyst with reduced fine powder during impregnation can be produced.

[0126] After step (1), a ripening step may be further included.

[0127] 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.

[0128] Step (2) Next, the active support is dried by multi-stage drying, which includes vacuum drying.

[0129] 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.

[0130] 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.

[0131] 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.

[0132] 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.

[0133] 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.

[0134] 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.

[0135] 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.

[0136] 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.

[0137] 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.

[0138] Primary vacuum drying can remove any solvents that may be present in the active carrier.

[0139] 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.

[0140] 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.

[0141] 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.

[0142] The description of the secondary vacuum drying is as described in the above description of vacuum drying.

[0143] 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 bond compound of the main catalyst, can be easily decomposed to form the main catalyst oxide, and energy consumption can be minimized.

[0144] 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 bond compound 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.

[0145] 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.

[0146] Step (3) Next, the dried active support is subjected to heat treatment to produce a supported catalyst.

[0147] 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.

[0148] 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.

[0149] 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.

[0150] Step (4) Next, CNTs are produced in the presence of a supported catalyst.

[0151] 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.

[0152] 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.

[0153] 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.

[0154] The chemical vapor phase synthesis method may be carried out at 600°C to 800°C or 650°C to 750°C, and is preferably carried out at 650°C to 750°C. By satisfying the above temperature range, CNTs can be produced while minimizing the generation of amorphous carbon.

[0155] Possible heat sources for the reaction include induction heating, radiant heat, lasers, IR, microwaves, plasma, and surface plasmon heating.

[0156] 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.

[0157] 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.

[0158] 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.

[0159] 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.

[0160] <Carbon Nanotube Dispersion> In this disclosure, a carbon nanotube dispersion (CNT dispersion) is a dispersion containing 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, etc.

[0161] -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.

[0162] -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.

[0163] 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.

[0164] 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.

[0165] 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.

[0166] - 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.

[0167] 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.

[0168] 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.

[0169] Other dispersants that excel in dispersing ability, dispersion stability, and high concentration of CNTs include Demol (registered trademark: hereinafter the same) N, Demol RN, and Demol T (manufactured by Kao Corporation), which are sodium salts of β-naphthalene sulfonic acid formalin condensate; Brij S 100 (manufactured by Sigma-Aldrich), which is polyoxyethylene stearyl ether; 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.); SOLSPERSET™ W100 and SOLSPERSET™ W150 (manufactured by Nippon Lubrizol Co., Ltd.). CMC is particularly preferred from the viewpoint of excelling in dispersing ability, dispersion stability, and high concentration of CNT aggregates.

[0170] 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.

[0171] -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.

[0172] 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.

[0173] 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.

[0174] 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.

[0175] The following are examples of CNT dispersion manufacturing methods, but the manufacturing of CNT dispersions is not limited to those shown below.

[0176] -Example of Dispersion Preparation- 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 added to the flask (e.g., 20 mL), and the mixture is stirred at room temperature (25°C, the same applies hereafter). At this time, a known dispersant (e.g., carboxymethylcellulose) may be added as appropriate. Next, the conductive additive is dispersed in the dispersion medium using a known dispersion device (e.g., 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 (e.g., 1 hour to 48 hours). In this way, a CNT dispersion is obtained.

[0177] (Conductive Material) The conductive material relating to this disclosure includes the CNT aggregate relating to this disclosure. As described above, the CNT aggregate contained in the conductive material relating to this disclosure has high conductivity and excellent dispersibility when dispersed, making it suitable as a conductive additive. Because the conductive material relating to this disclosure includes the CNT aggregate relating to this disclosure, it has excellent conductivity and can effectively impart high conductivity to the object to be used.

[0178] 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.

[0179] 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.

[0180] (Electrodes) The electrodes may include the CNT aggregates described herein. In the electrodes, the CNT aggregates according to this disclosure may function as conductive additives. The CNT aggregates included in the electrodes described below are synonymous with the CNT aggregates according to this disclosure, and the preferred embodiments are also the same; therefore, a description of the CNT aggregates will be omitted below.

[0181] 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.

[0182] 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.

[0183] The electrode active material layer may contain electrode active material. Preferably, the electrode active material is 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 contain positive electrode active material commonly used for positive electrode materials. Specifically, as the positive electrode active material, lithium cobalt oxide (LiCoO) ２ ), lithium nickel oxide (LiNiO ２ ) Layered compounds such as, compounds substituted with one or more transition metals; LiFe３ O ４ Lithium iron oxides such as Li １＋ｃ１ Mn ２－ｃ１ O ４ (0≦c1≦0.33), LiMnO ３ LiMn ２ O ３ LiMnO ２ Lithium manganese oxides such as lithium copper oxide (Li ２ CuO ２ ); LiV ３ O ８ , V ２ O ５ ,Cd ２ V ２ O ７ Vanadium oxides such as LiNi; chemical formula LiNi １－ｃ２ M ｃ２ O ２ Ni-site type lithium nickel oxide represented by the chemical formula LiMn (where 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). ２－ｃ３ M ｃ３ O ２ (Here, M is at least one selected from the group consisting of Co, Ni, Fe, Cr, Zn, and Ta, satisfying 0.01 ≤ c3 ≤ 0.1.), or Li ２ Mn ３ MO ８ Lithium manganese composite oxide represented by (where M is at least one selected from the group consisting of Fe, Co, Ni, Cu, and Zn); LiMn in which part of the Li in the chemical formula is substituted with an alkaline earth metal ion. ２ O ４ These are some examples.

[0184] 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.

[0185] 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.

[0186] (Secondary Battery) A secondary battery may comprise a negative electrode, a positive electrode, a separator interposed between the positive and negative electrodes, and an electrolyte. At least one of the positive and negative electrodes is an electrode formed using an electrode material including a CNT aggregate according to this disclosure.

[0187] 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.

[0188] 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.

[0189] 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.

[0190] 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.

[0191] 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.

[0192] 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.

[0193] 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.

[0194] (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 also contain other components such as CNT assemblies (in particular CNT assemblies) with a maximum length of less than 1000 μm.

[0195] <Method for producing a planar aggregate> 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, or the CNT aggregate according to this disclosure and other components such as CNT aggregates with a maximum length of less than 1000 μm (particularly CNT aggregates) in water or other fluid and filtering it once or twice or more.

[0196] Examples of planar aggregates relating to this disclosure include films.

[0197] The planar assemblies relating to this disclosure are useful, for example, in filters, electromagnetic shielding, and extreme ultraviolet (EUV) pellicles.

[0198] (Laminate) The laminate according to the present disclosure comprises a substrate and a planar assembly according to the present 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 the present disclosure may be arranged on the substrate, and yet another layer may be arranged on the planar assembly.

[0199] 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.

[0200] 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.

[0201] 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.

[0202] (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.

[0203] 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, temperature-controlled at 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 second temperature zone was maintained at a temperature sufficient to generate carbon nanotube aggregates.

[0204] In the second temperature zone, a reaction field was generated within the temperature-controlled flow reactor, forming catalytic nuclei and causing rapid growth of CNTs, thereby generating CNT aggregates. The aggregates were discharged as continuous discharge through the outlet of the flow-type reactor, which was temperature-controlled to 150°C, and sheet-like CNT aggregates were collected. The obtained sheet-like CNT aggregates were 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 1.0 mm mesh sieve twice. The CNT aggregates that passed through the sieve were collected and designated as CNT aggregate 1.

[0205] 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.

[0206] (Dispersion composition) - 1.1 g of the CNT aggregate obtained above - 1.65 g of CARBOXYMETHYL CELLULOSE SODIUM SALT HIGH VISCOSITY (manufactured by MP Biomedicals) - 547.25 g of purified water

[0207] 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

[0208] 3. Evaluation <Calculation of Density Factor Σ> - Manufacturing of CNT membrane A1 - The CNT membrane A1 of this example was manufactured by suction filtration. 12 μL of CNT dispersion 1 and 25 mL of pure water were mixed and suction filtered onto a hydrophilic cellulose ester membrane filter (VCWP, pore diameter 0.1 μm, Merck Millipore, Darmstadt, Germany) to obtain filtration membrane A1, which was placed on the membrane filter. The membrane filter was carefully immersed in pure water before the filtration membrane A1 dried. The filtration membrane A1 was transferred from the membrane filter onto a glass substrate. Finally, the filtration membrane A1 on the substrate was dried on a hot plate at 100°C for 10 minutes to obtain CNT membrane A1. From the amount of dispersion used and the filtration area, the CNT concentration of the membrane was 0.011 mg / cm². ２ This was the estimated value.

[0209] - Preparation of CNT membrane B1 - CNT membrane B1 was obtained in the same manner as CNT membrane A1, except that the amount of CNT dispersion 1 was changed from 12 μL to 2 μL. Based on the amount of dispersion used and the filtration area, the CNT concentration of the membrane was 0.0018 mg / cm². ２ This was the estimated value.

[0210] - Absorbance Measurement - The absorbance Abs of CNT films A1 and B1 of the examples and comparative examples was measured at 550 nm using ultraviolet-visible spectroscopy (UV-vis) with a Carry 5000 UV-Vis-NIR spectrophotometer (Agilent Technologies). The absorbance Abs were 0.54 and 0.11, respectively.

[0211] - Measurement of Surface Resistivity - The surface resistivity of CNT films A1 and B1 of Example 1 was measured by transferring the films, which were placed on a membrane filter, onto a glass substrate in pure water, drying them, and then measuring the central part of the films using the four-probe method with a Loresta GXII manufactured by Nitto Seiko Analytech Co., Ltd. As a result, the surface resistivity of CNT film A1 was 77.33 Ω / □. The surface resistivity of CNT film B1 was 667.6 Ω / □.

[0212] - Calculation of Resistivity - The resistance factor P is the product of the surface resistivity ρs and the absorbance Abs. The resistance factor P of CNT film A1 was 41.5 Ω / □, and the resistance factor P of CNT film B1 was 74.5 Ω / □. The ratio of the resistance factors of CNT film A1 to CNT film B1 was 0.56.

[0213] - Calculation of the Dense-Sparse Factor - The density-sparse factor Σ was calculated using the following formula: Dense-sparse factor Σ = (Resistivity of CNT film A1 × Absorbance of CNT film A1) ÷ (Resistivity of CNT film B1 × Absorbance of CNT film B1) As a result, the density-sparse factor Σ was calculated to be 0.093.

[0214] <Bundle Diameter Features> For the CNT aggregate 1 of Example 1, imaging was performed using a scanning electron microscope (SEM), and two images in which CNT bundles were clearly observed were selected (one of which is 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 created.

[0215] 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. 3. The cumulative occupied area ratio was calculated, and the bundle diameter at which this value first exceeded 0.9 was determined as the cumulative 90% bundle diameter. As a result, the area ratio of bundles with a bundle diameter of 100 nm or more was 0.17. The cumulative 90% bundle diameter was 170 nm.

[0216] <Tensile Test> CNT dispersion 1 was poured onto a 22 mm x 75 mm x 3 mm slide glass type silicon plate (manufactured by Dosaka E-M Co., Ltd., #08-1044), heated at 100°C for 30 minutes and dried to prepare the sample for measurement. The sample for measurement 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 speed of 1 mm / min. The point at which the test force was maximum was considered the breaking point, and the tensile strength and elongation at break were calculated. As a result, the tensile strength was 12.6 MPa and the elongation at break was 1.5%.

[0217] (Example 2) 1. Manufacturing of CNT Assembly 2 CNT assembly 2 was manufactured by mixing CNT assembly 2A and CNT assembly 2B described below. CNT assembly 2A 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 35 NL / min. CNT assembly 2B 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 36 NL / min.

[0218] 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.

[0219] 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: 50 MPa Number of passes: 3 Method: Circulation method

[0220] <Calculation of the density factor Σ> - Manufacturing of CNT film A2 - CNT film A2 was obtained in the same manner as in Example 1, except that CNT dispersion 2 was used.

[0221] -Production of CNT film B2- CNT film B2 was obtained in the same manner as in Example 1, except that CNT dispersion 2 was used.

[0222] -Calculation of the Density Factor Σ- The density factor Σ was calculated using CNT films A2 and B2 in the same manner as in Example 1, except that CNT dispersion 2 was used instead of CNT dispersion 1. As a result, the surface resistivity of CNT film A2 was 87.27 Ω / □, and the surface resistivity of CNT film B2 was 639.5 Ω / □. The absorbance of CNT film A2 was 0.42, and the absorbance of CNT film B2 was 0.11. The resistance factor of CNT film A2 was 36.5, and the resistance factor of CNT film B2 was 70.7. The ratio of the resistance factors of CNT film A2 to CNT film B2 was 0.52. The density factor Σ was 0.086.

[0223] <Bundle Diameter Features> For CNT aggregate 2 of 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 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 0.26. The cumulative 90% bundle diameter was 150 nm.

[0224] <Tensile Strength, Elongation at Break> A tensile test was performed in the same manner as in Example 1, except that CNT dispersion 2 was used. As a result, the tensile strength was 15.5 MPa and the elongation at break was 2.6%.

[0225] (Example 3) 1. Manufacturing of CNT aggregate 3 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 42 NL / min, and the CNT aggregates were continuously discharged through the outlet of a flow-through reactor with a temperature controlled to 500°C.

[0226] 2. Preparation of CNT dispersion 3 A pre-dispersion 3 was obtained using the obtained CNT aggregate 3 in the same manner as in Example 1.

[0227] The pre-dispersion 3 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 3. (Dispersion conditions) Nozzle diameter: 0.22 mm Pressure: 150 MPa Number of passes: 8 Method: Circulation method

[0228] <Calculation of the density factor Σ> - Manufacturing of CNT film A3 - CNT film A3 was obtained in the same manner as in Example 1, except that CNT dispersion 3 was used.

[0229] -Production of CNT film B3- CNT film B3 was obtained in the same manner as in Example 1, except that CNT dispersion 3 was used.

[0230] -Calculation of the Density Factor Σ- The density factor Σ was calculated using CNT films A3 and B3 in the same manner as in Example 1, except that CNT dispersion 3 was used instead of CNT dispersion 1. As a result, the surface resistivity of CNT film A3 was 210.9 Ω / □, and the surface resistivity of CNT film B3 was 2098 Ω / □. The absorbance of CNT film A3 was 0.62, and the absorbance of CNT film B3 was 0.12. The resistance factor of CNT film A3 was 130.7, and the resistance factor of CNT film B3 was 261.1. The ratio of the resistance factors of CNT film A3 to CNT film B3 was 0.50. The density factor Σ was 0.083.

[0231] <Bundle Diameter Features> For the CNT aggregate 3 of Example 3, 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 3). 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 0.41. The cumulative 90% bundle diameter was 200 nm.

[0232] <Tensile Test> A tensile test was performed in the same manner as in Example 1, except that CNT dispersion 3 was used. As a result, the tensile strength was 3.5 MPa and the elongation at break was 4.1%.

[0233] (Example 4) 1. Manufacturing of CNT aggregate 4 CNT aggregate 4 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 36 NL / min in, and the CNT aggregates were continuously discharged through the outlet of a flow-through reactor with a temperature controlled to 500°C.

[0234] 2. Preparation of CNT dispersion 4 A pre-dispersion 4 was obtained using the obtained CNT aggregate 4 in the same manner as in Example 3.

[0235] <Viscosity of CNT aggregate dispersion> The viscosity was calculated in the same manner as in Example 1, except that CNT dispersion 4 was used. The viscosity of the dispersion was 142.6 mPa·s.

[0236] <Calculation of the density factor Σ> - Manufacturing of CNT film A4 - CNT film A4 was obtained in the same manner as in Example 1, except that CNT dispersion 4 was used.

[0237] -Production of CNT film B4- CNT film B4 was obtained in the same manner as in Example 1, except that CNT dispersion 4 was used.

[0238] -Calculation of the Density Factor Σ- The density factor Σ was calculated using CNT films A4 and B4 in the same manner as in Example 1, except that CNT dispersion 4 was used instead of CNT dispersion 1. As a result, the surface resistivity of CNT film A4 was 162.1 Ω / □, and the surface resistivity of CNT film B3 was 1485 Ω / □. The absorbance of CNT film A4 was 0.54, and the absorbance of CNT film B4 was 0.10. The resistance factor of CNT film A4 was 87.5, and the resistance factor of CNT film B4 was 154.1. The ratio of the resistance factors of CNT film A4 and CNT film B4 was 0.57. The density factor Σ was 0.095.

[0239] <Bundle Diameter Features> For the CNT aggregate 4 of Example 4, imaging was performed using an SEM, and eight images in which CNT bundles were clearly observed were selected from the obtained images (one of which is Figure 4). 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 0.49. The cumulative 90% bundle diameter was 230 nm.

[0240] <Tensile Strength, Elongation at Break> A tensile test was performed in the same manner as in Example 1, except that CNT dispersion 4 was used. As a result, the tensile strength was 8.0 MPa and the elongation at break was 1.1%.

[0241] (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 NL / min, and the CNT aggregates were continuously discharged through the outlet of a flow-through reactor with a temperature controlled to 750°C.

[0242] 2. Preparation of CNT dispersion 5 A CNT dispersion 5 was obtained using the obtained CNT aggregate 5 in the same manner as in Example 3.

[0243] <Calculation of the density factor Σ> - Manufacturing of CNT film A5 - CNT film A5 was obtained in the same manner as in Example 1, except that CNT dispersion 5 was used.

[0244] - Manufacturing of CNT film B5 - CNT film B5 was obtained in the same manner as in Example 1, except that CNT dispersion 5 was used.

[0245] -Calculation of the Density Factor Σ- The density factor Σ was calculated using CNT films A5 and B5 in the same manner as in Example 1, except that CNT dispersion 5 was used instead of CNT dispersion 1. As a result, the surface resistivity of CNT film A5 was 126.0 Ω / □, and the surface resistivity of CNT film B5 was 1286 Ω / □. The absorbance of CNT film A5 was 0.56, and the absorbance of CNT film B5 was 0.10. The resistance factor of CNT film A5 was 69.9, and the resistance factor of CNT film B5 was 126.4. The ratio of the resistance factors of CNT film A5 and CNT film B5 was 0.55. The density factor Σ was 0.092.

[0246] <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 ratio of bundles with a bundle diameter of 100 nm or more was 0.43. The cumulative 90% bundle diameter was 340 nm.

[0247] <Tensile Test> A tensile test was performed in the same manner as in Example 1, except that CNT dispersion 5 was used. As a result, the tensile strength was 15.3 MPa and the elongation at break was 2.2%.

[0248] (Example 6) 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 33.9 NL / min.

[0249] 2. Preparation of CNT dispersion 6 A CNT dispersion 6 was obtained using the obtained CNT aggregate 6 in the same manner as in Example 3.

[0250] <Calculation of the density factor Σ> - Manufacturing of CNT film A6 - CNT film A6 was obtained in the same manner as in Example 1, except that CNT dispersion 6 was used.

[0251] -Production of CNT film B6- CNT film B6 was obtained in the same manner as in Example 1, except that CNT dispersion 6 was used.

[0252] -Calculation of the Density Factor Σ- The density factor Σ was calculated using CNT films A6 and B6 in the same manner as in Example 1, except that CNT dispersion 6 was used instead of CNT dispersion 1. As a result, the surface resistivity of CNT film A6 was 118.1 Ω / □, and the surface resistivity of CNT film B6 was 599 Ω / □. The absorbance of CNT film A6 was 0.40, and the absorbance of CNT film B6 was 0.08. The resistance factor of CNT film A6 was 47.0, and the resistance factor of CNT film B6 was 49.0. The ratio of the resistance factors of CNT film A6 and CNT film B6 was 0.96. The density factor Σ was 0.161.

[0253] <Bundle Diameter Features> For the CNT aggregate 6 of Example 6, 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 6). 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 0.14. The cumulative 90% bundle diameter was 110 nm.

[0254] <Tensile Test> A tensile test was performed in the same manner as in Example 1, except that CNT dispersion 6 was used. As a result, the tensile strength was 26.2 MPa and the elongation at break was 2.3%.

[0255] (Example 7) 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 34.1 NL / min.

[0256] 2. Preparation of CNT dispersion 7 A CNT dispersion 7 was obtained using the obtained CNT aggregate 7 in the same manner as in Example 1.

[0257] <Calculation of the density factor Σ> - Manufacturing of CNT film A7 - CNT film A7 was obtained in the same manner as in Example 1, except that CNT dispersion 7 was used.

[0258] - Manufacturing of CNT film B7 - CNT film B7 was obtained in the same manner as in Example 1, except that CNT dispersion 7 was used.

[0259] -Calculation of the Density Factor Σ- The density factor Σ was calculated using CNT films A7 and B7 in the same manner as in Example 1, except that CNT dispersion 7 was used instead of CNT dispersion 1. As a result, the surface resistivity of CNT film A7 was 62.16 Ω / □, and the surface resistivity of CNT film B7 was 350 Ω / □. The absorbance of CNT film A7 was 0.43, and the absorbance of CNT film B7 was 0.11. The resistance factor of CNT film A7 was 27.0, and the resistance factor of CNT film B7 was 38.0. The ratio of the resistance factors of CNT film A7 to CNT film B7 was 0.70. The density factor Σ was 0.117.

[0260] <Bundle Diameter Features> For the CNT aggregate 7 of Example 7, 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 7). 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 0.14. The cumulative 90% bundle diameter was 120 nm.

[0261] <Tensile Test> A tensile test was performed in the same manner as in Example 1, except that CNT dispersion 7 was used. As a result, the tensile strength was 32.6 MPa and the elongation at break was 2.3%.

[0262] (Comparative Example 1) 1. Preparation of Powdered CNT Assembly 8 As Powdered CNT Assembly 8, carbon nanotubes manufactured by C-nano Co., Ltd. (catalog number: FT9100) were prepared.

[0263] 2. Preparation of CNT dispersion 8: Using the prepared powdered CNT aggregate 8, a CNT dispersion 8 was obtained in the same manner as in Example 1.

[0264] <Calculation of the density factor Σ> - Production of CNT film A8 - CNT film A8 was obtained in the same manner as in Example 1, except that 24 μL of CNT dispersion 8 was used instead of 12 μL of CNT dispersion 1.

[0265] - Preparation of CNT film B8 - CNT film B8 was obtained in the same manner as in Example 1, except that 4 μL of CNT dispersion 8 was used instead of 2 μL of CNT dispersion 1.

[0266] - Calculation of the Density Factor Σ - The density factor Σ was calculated using CNT film A8 and CNT film B8. As a result, the surface resistivity of CNT film A8 was 1349 Ω / □, and the surface resistivity of CNT film B8 was 17940 Ω / □. The absorbance of CNT film A8 was 1.13, and the absorbance of CNT film B8 was 0.19. The resistivity factor of CNT film A8 was 1526.9, and the resistivity factor of CNT film B8 was 3449.6. The ratio of the resistivity factors of CNT film A8 to CNT film B8 was 0.44. The density factor Σ was 0.074.

[0267] <Bundle Diameter Feature> For the CNT aggregate 8 of Comparative Example 1, imaging was performed using SEM, and three images in which CNT bundles were clearly observed were selected from the obtained images (one of which is Figure 8). 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 0.08. The cumulative 90% bundle diameter was 80 nm.

[0268] <Tensile Test> A tensile test was performed in the same manner as in Example 1, except that CNT dispersion 8 was used. As a result, the tensile strength was 2.3 MPa and the elongation at break was 1.9%.

[0269] [Fabrication of Lithium-ion Rechargeable Batteries] Next, lithium-ion rechargeable batteries were fabricated.

[0270] 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.

[0271] 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 above CNT dispersion 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.

[0272] 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.

[0273] 4. Cycle Test Using the manufactured lithium-ion batteries, a cycle test was conducted for 200 cycles under the conditions shown below, and the discharge capacity retention rate after 200 cycles was calculated using the following formula. In Table 1, this is labeled as "Capacity Retention Rate after 200 Cycles," and a higher discharge capacity retention rate after 200 cycles indicates better lifespan characteristics. Discharge capacity retention rate after 200 cycles (%) = Discharge capacity at 200th cycle / Discharge capacity at 1st cycle × 100

[0274] <Cycle Test Conditions> Test temperature: 25°C Charging conditions: Constant current constant voltage charging, maximum charging voltage 4.2V, charging time 5 hours, charging current 0.3CA Rest time after discharge: 10 minutes Discharge conditions: Constant current discharge, minimum discharge voltage 2.5V, discharge current 0.3CA Rest time after charge: 10 minutes In this test, one cycle is defined as the process of charging, resting the discharge, discharging, and resting the charge in sequence.

[0275] The evaluation results for Examples 1 to 7 and Comparative Example 1 are shown in Table 1. In Table 1, "Percentage of bundles with a bundle diameter of 100 nm or more" refers to "Area percentage Z of bundles with a bundle diameter of 100 nm or more."

[0276]

[0277] As shown in Table 1, the CNT assemblies of Examples 1 to 7, in which the density factor Σ calculated by formula (α) is 0.075 or more and less than 1.0, were found to have a higher discharge capacity retention rate and superior cycle characteristics compared to the CNT assemblies of Comparative Example 1.

Claims

1. A carbon nanotube aggregate, wherein a density-nonuniformity factor Σ obtained by the following formula (α) is 0.075 or more and less than 1.

0. The resistance factor P is a product of a surface resistivity (ρs) of a film and an absorbance (Abs) of the film. Two types of film thicknesses are prepared, the resistance factor P of the thick film thick , and P of the thin film thin are calculated. Further, a concentration C of the carbon nanotube aggregate in the thick film thick , and a concentration C of the carbon nanotube aggregate in the thin film thin are prepared. P thick , P thin , C thick and C thin are applied to formula (α).

2. The carbon nanotube aggregate according to claim 1, comprising a bundle structure, wherein the bundle diameter W, which represents 90% of the cumulative bundle in the area observed by a scanning electron microscope, is greater than 80 nm and less than 500 nm.

3. The carbon nanotube aggregate according to claim 1, comprising a bundle structure, wherein the area ratio Z of bundles with a bundle diameter of 100 nm or more in the area observed by a scanning electron microscope is greater than 0.

1.

4. A conductive material comprising a carbon nanotube aggregate according to any one of claims 1 to 3.

5. An electrode comprising an electrode active material and the conductive material described in claim 4.

6. A secondary battery comprising the electrodes described in claim 5.

7. A planar aggregate comprising a carbon nanotube aggregate as described in any one of claims 1 to 3.

8. A laminate comprising a substrate and the planar assembly described in claim 7.

9. A filter using the planar assembly described in claim 7.

10. An electromagnetic shield using the planar assembly described in claim 7.

11. A pellicle for extreme ultraviolet radiation using the planar aggregate described in claim 7.

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