Carbon nanotube aggregate, conductive material, electrode, secondary battery, planar aggregate, laminate, filter, electromagnetic wave shield, pellicle for extreme ultraviolet rays, and method for measuring mean curvature

Abstract

Provided is a carbon nanotube aggregate or the like that has excellent electrical conductivity when made into a carbon nanotube dispersion liquid. The carbon nanotube structure has a mean curvature Z (um) in the observation area using a scanning electron microscope. -1 ) is 0.005 or more and less than 0.088, and a cumulative 50% particle size D50 in a volume-based particle size distribution exceeds 0.65 μm.

Description

[Technical Field]

[0001] The present disclosure relates to a carbon nanotube aggregate, a conductive material, an electrode, a secondary battery, a planar aggregate, a laminate, a filter, an electromagnetic wave shield, a pellicle for extreme ultraviolet rays, and a method for measuring mean curvature. [Background technology]

[0002] Carbon nanotubes (hereinafter also referred to as "CNTs") are substances with a cylindrical structure in which graphene sheets, which are composed of six-membered carbon ring structures, are rolled up coaxially in single or multiple layers. CNTs are broadly classified into single-walled CNTs formed from a single layer of graphene sheets and multi-walled CNTs formed from multiple layers of graphene sheets. CNTs exhibit excellent mechanical, electrical, and chemical properties, and these properties are expected to be utilized for applications in fields such as materials, catalysts, energy, and electronics. Various attempts have been proposed to further enhance the properties of CNTs.

[0003] For example, Patent Document 1 describes a multi-walled carbon nanotube aggregate that includes multi-walled carbon nanotubes having a maximum length of 1000 μm to 30000 μm and Fe atoms, and the content ratio of Fe atoms to the total mass of the aggregate is 0.5 mass% or more and less than 10 mass%. Furthermore, a scanning electron microscope (SEM) photograph showing one embodiment shows that a plurality of fibrous multi-walled carbon nanotubes are entangled to form a sheet-like aggregate. Patent Document 2 describes that a conductive additive containing a pulverized multi-walled carbon nanotube powder having a tensile strength of 10 MPa to 100 MPa and an angle of repose of 10 degrees to 90 degrees has an excellent effect of improving conductivity. Furthermore, a scanning electron microscope (SEM) photograph showing one embodiment shows that a plurality of fibrous multi-walled carbon nanotubes are entangled to form a sheet-like aggregate. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2025 / 013504 [Patent Document 2] Japanese Patent Application Laid-Open No. 2025-010479 Summary of the Invention [Problem to be solved by the invention]

[0005] When CNT aggregates are dispersed, they are sometimes required to have excellent electrical conductivity.

[0006] The present disclosure has been made in consideration of the above circumstances. An object of one embodiment of the present disclosure is to provide an aggregate of carbon nanotubes that has excellent electrical conductivity when made into a carbon nanotube dispersion liquid. Another problem to be solved by another embodiment of the present disclosure is to provide a conductive material, an electrode, a secondary battery, and a planar assembly, each including the carbon nanotube aggregate. Another problem to be solved by another embodiment of the present disclosure is to provide a laminate including the above-mentioned planar assembly. Another problem to be solved by another embodiment of the present disclosure is to provide a filter, an electromagnetic wave shield, and a pellicle for extreme ultraviolet rays using the above-mentioned planar assembly. Another problem to be solved by another embodiment of the present disclosure is to provide a novel method for measuring the mean curvature of a carbon nanotube aggregate. [Means for solving the problem]

[0007] The means for solving the above problems include the following aspects. <1> The mean curvature Z(um) of the carbon nanotube structure in the observation area by scanning electron microscope -1 ) is 0.005 or more and less than 0.088, and a cumulative 50% particle size D50 in a volume-based particle size distribution exceeds 0.65 μm. <2> It includes a bundle structure, and in the observation area by a scanning electron microscope, the bundle diameter X of 90% of the cumulative total is more than 90 nm and less than 500 nm. <1> The carbon nanotube aggregate according to claim 1. <3> The area ratio Y of bundles having a bundle diameter of 100 nm or more in an observation area using a scanning electron microscope is greater than 0.1. <1> or <2> The carbon nanotube aggregate according to claim 1. <4> <1> ~ <3> A conductive material comprising the aggregate of carbon nanotubes according to any one of the above. <5> an electrode active material; <4> and an electrode comprising the conductive material according to claim 1. <6> <5> A secondary battery comprising the electrode according to claim 1. <7> <1> ~ <3> 1. A planar aggregate comprising the carbon nanotube aggregate according to any one of 1. to 1. <8> A substrate; <7> A laminate comprising the planar assembly according to claim 1. <9> <7> A filter using the planar assembly described in 1. <10> <7> An electromagnetic wave shield using the planar assembly described in 1. <11> <7> A pellicle for extreme ultraviolet radiation using the planar assembly described in . <12> This method for measuring the mean curvature of a carbon nanotube aggregate involves performing steps 1 to 3 below on two or more images of the carbon nanotube aggregate using the image analysis software ImageJ (version 1.54g) and the Kappa plugin (version 2.0.0) to calculate the mean curvature. 1. Adjust the image size using Image:Adjust:Size, Width=1280. Set the image size to 1280 x 960 and the width to 1410 nm. 2. Fine-tune the curve so that it follows the center of the fiber under the conditions of Plugin:Analyze:Kappa, File:OpenActiveImage, and CurveFittingOptions:ChoosePoints=100, DataThreshold=10, Scale(μm / pixel)=0.16. 3. After calculating approximately eight central lines per field of view, calculate each curvature and the average curvature. [Effects of the Invention]

[0008] According to one embodiment of the present disclosure, an aggregate of carbon nanotubes is provided that has excellent electrical conductivity when made into a carbon nanotube dispersion liquid. According to another embodiment of the present disclosure, there are provided a conductive material, an electrode, a secondary battery, and a planar assembly, each including the carbon nanotube aggregate. According to another embodiment of the present disclosure, there is provided a laminate including the above-described planar assembly. According to other embodiments of the present disclosure, there are provided a filter, an electromagnetic wave shield, and a pellicle for extreme ultraviolet radiation, which use the planar assembly. According to another embodiment of the present disclosure, a novel method for measuring the mean curvature of a carbon nanotube aggregate is provided. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is an image of the carbon nanotube aggregate 1 of Example 1 obtained using a scanning electron microscope. [Figure 2] 1 is an image of a carbon nanotube aggregate 2 of Example 2 obtained using a scanning electron microscope. [Figure 3] 10 is an image of a carbon nanotube aggregate 3 of Example 3 obtained using a scanning electron microscope. [Figure 4] 10 is an image of a carbon nanotube aggregate 4 of Example 4 obtained using a scanning electron microscope. [Figure 5] 10 is an image of carbon nanotube aggregate 5 of Example 5 obtained using a scanning electron microscope. [Figure 6] 1 is an image of a carbon nanotube aggregate 6 of Comparative Example 1 obtained using a scanning electron microscope. [Figure 7] 10 is an image of an aggregate of carbon nanotubes 7 of Comparative Example 2 obtained using a scanning electron microscope. DETAILED DESCRIPTION OF THE INVENTION

[0010] The present disclosure will be described in detail below. In this specification, a numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the lower and upper limits. In the present specification, in the numerical ranges described in stages, the upper or lower limit value described in a certain numerical range may be replaced with the upper or lower limit value of another numerical range described in stages. Furthermore, in the numerical ranges described in the present specification, the upper or lower limit value described in a certain numerical range may be replaced with a value shown in the examples. In this specification, the term "process" includes not only an independent process but also a process that cannot be clearly distinguished from other processes, as long as the intended purpose of the process is achieved.

[0011] In the present disclosure, the terms "carbon nanotubes," "single-walled carbon nanotubes," "multi-walled carbon nanotubes," "carbon nanotube aggregate," "carbon nanotubes having a maximum length of 1000 μm to 30000 μm," and "carbon nanotube dispersion" may be abbreviated as "CNT," "SWCNT," "MWCNT," "CNT aggregate," "ULCNT," and "CNT dispersion," respectively.

[0012] (carbon nanotube aggregates) The carbon nanotube aggregate (also referred to as "CNT aggregate") according to the present disclosure has a mean curvature Z (um -1 , um represents the unit meter) is 0.005 or more and less than 0.088, and the cumulative 50% particle size D50 in the volume-based particle size distribution exceeds 0.65 μm. Here, the unit of mean curvature Z is um -1The term "um (unit meter)" in the following will be explained. "um" is a unit corresponding to the analysis based on the image size and set scale set in this invention, and is also used in the analysis of the examples and comparative examples in this specification. 1 μm calculated in Kappa is defined as 1 um. Note that the scale in Kappa is set to a value different from the scale of the actual image, and the conversion to the scale of the actual image is 1 um = 6.885 nm. Curvature is the value obtained by using a circle inscribed in the curve and calculating the reciprocal of the radius of the inscribed circle (um). -1 " is the unit of measurement, and by standardizing the screen size and scale, it becomes possible to compare the average curvature Z of each carbon nanotube structure. Using the image analysis software ImageJ (version 1.54g), adjust the image size to 1280 x 960 and the width to 1410 nm using Image:Adjust:Size, Width=1280. When analyzing with the Kappa plugin (version 2.0.0), set Scale (μm / pixel) = 0.16. Standardizing the image size and scale here allows for comparison between images.

[0013] According to the CNT aggregate according to the present disclosure, a battery can be produced that can obtain a carbon nanotube dispersion liquid with an appropriate viscosity. On the other hand, Patent Documents 1 and 2 do not mention anything that focuses on the curvature of the carbon nanotube structure.

[0014] Patent Document 1 describes the length of multi-walled carbon nanotubes and the entangled aggregates, but does not particularly describe the shape of the carbon nanotube aggregates. Also, although it describes the viscosity, it does not specifically describe the conductivity. Patent Document 2 describes the tensile strength of multi-walled carbon nanotubes before pulverization, but does not describe the tensile strength after pulverization. Furthermore, regarding electrical conductivity, although it describes the volume resistivity of the powder under pressure, it does not describe dispersibility. In contrast, the CNT aggregate according to the present disclosure has excellent conductivity when made into a carbon nanotube dispersion liquid, since the mean curvature Z of the carbon nanotube structure and the cumulative 50% particle size D50 in the volume-based particle size distribution satisfy the above ranges.

[0015] <Average curvature Z> According to the CNT aggregate according to the present disclosure, when used as a conductive additive in an electrode, the carbon nanotube aggregate improves the cycle characteristics of a battery. The mean curvature Z (um -1 ) is greater than or equal to 0.005 and less than 0.088.

[0016] The average curvature (um) of the carbon nanotube structure in the CNT aggregate according to the present disclosure -1 ) is 0.005 or more and less than 0.088, and may be 0.008 or more and 0.080 or less, 0.010 or more and 0.080 or less, 0.010 or more and 0.070 or less, 0.010 or more and 0.060 or less, 0.010 or more and 0.050 or less, 0.010 or more and 0.040 or less, 0.010 or more and 0.035 or less, 0.010 or more and 0.030 or less, 0.010 or more and 0.025 or less, or 0.010 or more and 0.021 or less. Among these, the value is preferably 0.010 or more and 0.035 or less, more preferably 0.010 or more and 0.030 or less, even more preferably 0.010 or more and 0.025 or less, and particularly preferably 0.010 or more and 0.021 or less. The average curvature Z(um) of the carbon nanotube structure in the CNT aggregate -1) is preferably 0.005 or more, since it appropriately suppresses the aggregation of CNT aggregates, prevents the bundle diameter from becoming too large, and improves dispersibility in the dispersion solvent. -1 ) is preferably less than 0.088, since the electrical conductivity of the CNT aggregate is improved.

[0017] Specifically, the mean curvature Z (um -1 ) is between 0.010 and 0.035, the linearity of the CNT aggregates is maintained and the network structure becomes more linear in parts. This prevents excessive entanglement between the CNT aggregates and promotes uniform dispersion in the dispersion liquid. It also improves electrical conductivity. In one embodiment, the average curvature Z (um -1 ) is greater than 0.010 and equal to or less than 0.025, the cycle characteristics are improved when the CNT aggregate according to the present disclosure is used as a conductive additive for a lithium ion battery, for example. Although the mechanism is unclear, it is thought that when carbon nanotube aggregates take a linear shape, they form a network structure and a conductive path, which shortens the conductive distance and reduces electrical resistance. Furthermore, the linear shape of the carbon nanotube aggregates increases their rigidity, and the tightly packed carbon nanotube aggregates effectively suppress the swelling and shrinkage of the electrode active material due to charge and discharge.

[0018] -Average curvature: Calculation of the average curvature- The mean curvature Z(um -1 ) can be measured, for example, by the following method. Examples of images to be used include those in which bundles of CNT aggregates are clearly captured, such as scanning electron microscope (SEM) photographs. The imaging method and imaging conditions using SEM will be described later.

[0019] Using the image, the average value of the curvature of the CNT structure is calculated by image analysis. More specifically, the following steps 1 to 3 were performed on two or more images of the carbon nanotube aggregate using the image analysis software ImageJ (Wayne Rasband (NIH) Version) (version 1.54g) and Kappa plug-in (version 2.0.0). and calculate the average curvature. 1. Adjust the image size using Image:Adjust:Size, Width=1280. Set the screen size to 1280 x 960 and the width to 1410 nm. 2. Fine-tune the curve so that it follows the center of the fiber under the conditions of Plugin:Analyze:Kappa, File:OpenActiveImage, and CurveFittingOptions:ChoosePoints=100, DataThreshold=10, Scale(μm / pixel)=0.16. 3. After calculating approximately eight central lines per field of view, calculate each curvature and the average curvature.

[0020] <d50> The carbon nanotube aggregate according to the present disclosure has a cumulative 50% particle size D50 in a volume-based particle size distribution that exceeds 0.35 μm, and from the viewpoint of electrical conductivity, it is preferably more than 0.35 μm and not more than 45.0 μm, more preferably more than 0.35 μm and not more than 20.0 μm, more preferably more than 0.35 μm and not more than 15 μm, even more preferably more than 0.35 μm and not more than 14 μm, particularly preferably more than 0.35 μm and not more than 13 μm, and most preferably more than 0.35 μm and not more than 12 μm. In another aspect, it is preferably more than 0.35 μm and not more than 11 μm, more preferably more than 0.35 μm and not more than 10 μm, even more preferably more than 0.35 μm and not more than 9.0 μm, and particularly preferably more than 0.35 μm and not more than 8.0 μm. Furthermore, from the viewpoint of achieving both electrical conductivity and mechanical durability, it is preferably more than 0.35 μm and not more than 45.0 μm, more preferably more than 0.40 μm and not more than 30.0 μm, even more preferably more than 0.41 μm and not more than 20.0 μm, particularly preferably more than 0.42 μm and not more than 15.0 μm, even more preferably more than 0.43 μm and not more than 14.0 μm, and even more preferably 0.44 μm or more and not more than 13.05 μm. Furthermore, from the viewpoint of achieving both electrical conductivity and dispersibility, the cumulative 50% particle size D50 in the volume-based particle size distribution is preferably more than 0.65 μm and not more than 45 μm, more preferably more than 0.65 μm and not more than 20 μm, even more preferably more than 0.65 μm and not more than 15 μm, still more preferably more than 0.65 μm and not more than 14 μm, particularly preferably more than 0.65 μm and not more than 13 μm, and most preferably more than 0.65 μm and not more than 10 μm. When the cumulative 50% particle diameter D50 is in the above range, the particle size of the CNT aggregate is appropriately controlled, and uniform dispersion of the CNT aggregate in the dispersion liquid is achieved. In particular, when the cumulative 50% particle diameter D50 is in the range of more than 0.65 μm and not more than 45 μm, more preferably more than 0.65 μm and not more than 15 μm, the particle size of the CNT aggregate is appropriately small and uniform, so aggregation of the CNT aggregate in the dispersion is suppressed and dispersibility is improved. It is believed that the increased surface area and enhanced interaction with the dispersion medium result in improved dispersibility. Furthermore, the uniform particle size distribution stabilizes the viscosity of the CNT aggregate dispersion, improving processability when forming electrodes using the CNT aggregate and ease of handling during use. Furthermore, when the cumulative 50% particle size D50 is more than 0.65 μm and 8.0 μm or less, the particle size of the CNT aggregate is appropriately controlled, and a more uniform dispersion is achieved when a dispersion is prepared using the CNT aggregate. Therefore, by satisfying the above conditions, the dispersibility of the CNT aggregates is further improved and the viscosity of the dispersion is optimized, making it possible to provide a high-performance CNT dispersion that is excellent in conductivity and handleability.

[0021] The cumulative 50% particle size D50 in the volume-based particle size distribution of the CNT aggregate is measured as follows. The CNT dispersion was thoroughly stirred and further diluted with pure water. Using the resulting diluted solution as a sample, the cumulative particle size D50 of the CNT dispersion was measured using a particle size distribution analyzer (LA-960, laser diffraction particle size distribution analyzer, manufactured by Horiba, Ltd.). The particle refractive index of the CNT to be measured is 1.920-0.522i. The refractive index of the solvent is set to 1.333. When measuring, the CNT dispersion is diluted by adding it dropwise to pure water while observing the transmittance, and measurements are carried out after confirming that the particle size distribution on the monitor has stabilized. The CNT dispersion liquid is prepared by mixing carbon nanotube aggregates, 700 kDa sodium carboxymethyl cellulose, and water, and the concentration of the carbon nanotube aggregates is 0.20 mass % and the concentration of the sodium carboxymethyl cellulose is 0.30 mass %.

[0022] <Bundle structure> The CNT aggregate according to the present disclosure includes a bundle structure, and in the region observed by a scanning electron microscope, the bundle diameter at 90% of the cumulative size (hereinafter also referred to as "cumulative 90% bundle diameter") is preferably more than 90 nm and less than 500 nm. Furthermore, the bundle diameter at 90% of the cumulative size may be 450 nm or less, 400 nm or less, 350 nm or less, 300 nm or less, or 250 nm or less. Furthermore, the bundle diameter at 90% of the cumulative size may be 100 nm or more, or 110 nm or more. Within the range of the bundle diameter at 90% of the cumulative size, these upper and lower limit values ​​can be selected arbitrarily.

[0023] In the present disclosure, the bundle structure contained in a CNT aggregate refers to an aggregate in which a plurality of CNTs are agglomerated together by van der Waals forces or the like to form a bundle. It is presumed that the inclusion of a bundle structure of an appropriate size in a CNT aggregate improves the handleability of the CNT aggregate and further improves its stability.

[0024] The bundle structure in the CNT aggregate can be formed, for example, by controlling the catalyst particle size distribution in production by chemical vapor deposition (CVD) method, or by controlling the cooling rate in the cooling step.

[0025] From the viewpoint of achieving both ease of handling of the CNT aggregate and dispersibility in a solvent, the diameter of each bundle contained in the CNT aggregate is preferably 5 nm to 500 nm, and more preferably 10 nm to 300 nm. The content of the bundle structure in the CNT aggregate is preferably 10% by mass to 100% by mass, and more preferably 20% by mass to 90% by mass, relative to the total mass of the CNT aggregate. The presence or absence of a bundle structure in a 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 location where the bundle structure exists in the CNT aggregate and measuring the length using a photographed image of the bundle structure.

[0026] When the CNT aggregate according to the present disclosure is observed by SEM, the 90% cumulative bundle diameter exceeds 90 nm, which makes it easier for the CNT bundles to come together and form a long-distance conductive network. Furthermore, when the 90% cumulative bundle diameter is less than 500 nm, the dispersibility in the dispersion medium is improved and the conductivity is easily ensured.

[0027] Specifically, when the cumulative 90% bundle diameter exceeds 90 nm, CNTs can be appropriately gathered together to form efficient conductive paths. This improves the conductivity of the CNT aggregate and optimizes its performance as an electrode material. Furthermore, when the cumulative 90% bundle diameter is 400 nm or less, the dispersibility in the dispersion medium is improved, achieving uniform dispersion. This maintains the viscosity of the dispersion containing the CNT aggregate within an appropriate range, improving dispersibility. As a result, battery performance can be improved.

[0028] In particular, the cumulative 90% bundle diameter is preferably more than 90 nm and not more than 350 nm, more preferably more than 90 nm and not more than 300 nm, more preferably more than 90 nm and not more than 250 nm, even more preferably more than 90 nm and not more than 230 nm, and particularly preferably more than 90 nm and not more than 200 nm. Furthermore, the cumulative 90% bundle diameter is preferably from 100 nm to 350 nm, more preferably from 100 nm to 300 nm, more preferably from 100 nm to 250 nm, even more preferably from 100 nm to 230 nm, and particularly preferably from 100 nm to 200 nm. Furthermore, the cumulative 90% bundle diameter is preferably from 110 nm to 350 nm, more preferably from 110 nm to 300 nm, even more preferably from 110 nm to 250 nm, particularly preferably from 110 nm to 230 nm, and particularly preferably from 110 nm to 200 nm. Within this range, the CNT bundle diameter is appropriately controlled, reducing the contact resistance between CNTs and efficiently forming electron conduction paths, thereby improving conductivity. Furthermore, by appropriately controlling the bundle diameter, the viscosity of the dispersion containing the CNT aggregates is maintained within an appropriate range, improving dispersibility. As a result, battery performance can be improved.

[0029] Furthermore, in the CNT aggregate according to the present disclosure, the area ratio of bundles having a bundle diameter of 100 nm or more is preferably greater than 0.1 when observed by SEM. The area ratio of the bundles may be 0.11 or greater, 0.12 or greater, or 0.13 or greater. Furthermore, the area ratio of bundles having a bundle diameter of 100 nm or greater may be 0.8 or less, 0.7 or less, 0.6 or less, 0.55 or less, or 0.5 or less. The area ratio of bundles having a bundle diameter of 100 nm or more is calculated by dividing the area of ​​bundles having a bundle diameter of 100 nm or more in an SEM image of the CNT aggregate by the total area of ​​the CNT aggregate. The area ratio of the bundle is preferably more than 0.1 and not more than 0.8, more preferably 0.11 or more and not more than 0.8, even more preferably 0.12 or more and not more than 0.8, and particularly preferably 0.13 or more and not more than 0.8. In another aspect, the area ratio of the bundle is preferably more than 0.1 and not more than 0.6, more preferably 0.11 or more and not more than 0.6, even more preferably 0.12 or more and not more than 0.6, and particularly preferably 0.13 or more and not more than 0.6. In another aspect, the area ratio of the bundle is preferably greater than 0.1 and not greater than 0.6, more preferably greater than 0.1 and not greater than 0.55, even more preferably greater than 0.1 and not greater than 0.5, particularly preferably 0.11 or greater and not greater than 0.5, even more preferably 0.12 or greater and not greater than 0.5, and especially preferably 0.13 or greater and not greater than 0.5. By ensuring that the area ratio of bundles with a bundle diameter of 100 nm or greater is within the above-mentioned range, the CNT bundles gather together, making it easier to form a long-distance conductive network, making it easier to ensure conductivity and improving dispersibility in the dispersion medium.

[0030] In addition, in one embodiment, from the viewpoint of mechanical strength and electrical conductivity, the area ratio of the bundle is preferably greater than 0.1 and not greater than 0.7, more preferably 0.11 or greater and not greater than 0.7, even more preferably 0.12 or greater and not greater than 0.7, and particularly preferably 0.13 or greater and not greater than 0.7.

[0031] The bundle diameter of the CNT aggregate is measured by observation using an SEM. The CNT aggregate is photographed at a magnification of 100,000 to obtain multiple SEM photographs. The imaging method using an SEM is not particularly limited, and can be performed by a known method.

[0032] -Image capture- Using an SEM device (for example, S-4800 manufactured by Hitachi High-Technologies Corporation), images are taken under the following conditions to obtain multiple images of the CNT aggregate. From the viewpoint of reducing the variance of the analytical values ​​of the bundle diameter, it is preferable to obtain five or more images. Acceleration voltage: 0.5 kV Emission current: 10μA Measurement magnification: 100,000 times Image size: 1280 pixels x 960 pixels

[0033] -Image selection- From the obtained images, select two or more images in which CNT bundles are clearly observed.

[0034] - Overview of bundle diameter analysis using image analysis - The selected image is subjected to image processing and analysis using Python. In image processing, the CNT outline and center line are detected and combined with the original image. In image analysis, the bundle diameter is determined by calculating the distance from the center line to the outline of the created image. The product of the bundle diameter and the length of the center line is then calculated to calculate the area occupied by the CNT in the image.

[0035] -Detecting the outline of CNTs using image analysis- 1. The image is binarized to distinguish between CNTs and the background. 2. Create a contour for the CNT part using the edge detection function of the OpenCV library.

[0036] -Detecting CNT centerlines using image analysis- 1. Adjust the parameters to distinguish between CNTs and the background and perform binarization. 2. Create a skeleton for the CNT part using the skeletonize function of the scikit-image library. 3. For each coordinate of the skeleton, the number of skeletons within the surrounding two pixels is counted, and coordinates where five or more exist are recognized as skeleton intersections. 4. The skeleton is divided at the intersections by converting the intersections into background pixels. The divided skeleton is called a region. 5. Measure the length of the region and delete the short region. 6. Linear approximation is performed for each region. 7. For each line created, obtain the X-axis coordinate of the region that was the source of approximation. Convert the line into a line segment based on the range in which the obtained X-coordinate exists. Treat the line segment obtained here as the center line of the CNT. 8. Calculate the similarity between all pairs of center lines based on their center coordinates and angles. Pairs of center lines whose center coordinates are within 10 pixels of each other and whose angle between the two line segments is less than 10 degrees are treated as overlapping center lines, and the shorter one is deleted. 9. The CNT outline and center line are superimposed on the original image and saved. The outline is displayed in red and the center line in blue.

[0037] -Detecting CNT bundle diameter using image analysis- 1. The image created by image processing is read and the CNT, outline, background, and center line are recognized by color recognition. 2. Measure the length of each center line. 3. Choose a random point on the center line and draw a perpendicular line from the point to the center line. 4. Find the intersection of the perpendicular line and the contour, and save the distance from a random point on the centerline to the intersection as the bundle diameter. 5. Calculate the area occupied by the bundle by multiplying the length of the center line segment by the bundle diameter. Save the data as a histogram with the bundle diameter on the horizontal axis and the area occupied on the vertical axis.

[0038] - Obtaining bundle diameter parameters - Using the calculated bundle diameter histogram data, the feature amount of the bundle diameter of each sample is calculated by the following method. 1. The bundle diameters and occupied areas of multiple fields of view for the same sample are added together and normalized so that the total sum is 1. Following normalization, the unit of the vertical axis is the occupied area ratio. 2. Calculate the total area ratio of bundles with a bundle diameter of 100 nm or more. 3. Calculate the cumulative exclusive area ratio, and determine the bundle diameter when this value exceeds 0.9 for the first time as the cumulative 90% bundle diameter.

[0039] <Viscosity> The aggregate of carbon nanotubes according to the present disclosure is preferably a dispersion liquid obtained by mixing the aggregate of carbon nanotubes, 700 kDa sodium carboxymethyl cellulose, and water, in which the concentration of the aggregate of carbon nanotubes is 0.20 mass% and the concentration of the sodium carboxymethyl cellulose is 0.30 mass%, and the common logarithm of the viscosity of the dispersion liquid is 1.0 or more (the unit of viscosity is mPa·s). Note that the viscosity in the present disclosure is the viscosity at 25°C.

[0040] In one embodiment, the viscosity of the dispersion may be 7.0 mPa·s to 5000 mPa·s, 15 mPa·s to 5000 mPa·s, 20 mPa·s to 5000 mPa·s, 25 mPa·s to 5000 mPa·s, or 30 mPa·s to 5000 mPa·s. Furthermore, it may be 30 to 3000 mPa·s, 30 to 2000 mPa·s, 30 to 1600 mPa·s, 50 to 1600 mPa·s, 80 to 900 mPa·s, 110 to 800 mPa·s, or 142.6 to 798.2 mPa·s.

[0041] The common logarithm of the viscosity of the dispersion is preferably 1.0 or more and 5.0 or less, and the upper limit may be 4.5 or less, 4.0 or less, 3.5 or less, 3.2 or less, 3.1 or less, 3.0 or less, or 2.90 or less. The lower limit may be 1.1 or more, 1.2 or more, 1.3 or more, 1.4 or more, 1.5 or more, or 1.6 or more. Furthermore, the upper and lower limits may be combined in any manner.

[0042] When the common logarithm of the viscosity of the dispersion is 1.0 or more, the dispersibility of the CNTs is improved, and the performance as an electrode material is optimized.

[0043] The common logarithm of the viscosity of the dispersion is more preferably 1.1 or more and 3.5 or less, even more preferably 1.2 or more and 3.2 or less, particularly preferably 1.3 or more and 3.2 or less, more preferably 1.4 or more and 3.2 or less, even more preferably 1.5 or more and 3.2 or less, particularly preferably 1.54 or more and 2.90 or less. Furthermore, when the common logarithm of the viscosity of the dispersion is 1.1 or more and 3.5 or less, the dispersion of the CNTs is further improved, and the tensile strength of the CNT aggregate is improved. Specifically, when the common logarithm of the viscosity of the dispersion is 1.6 or more and 3.2 or less, CNT bundles gather together to easily form a long-distance conductive network, and the dispersion medium is well-dispersed, making it easier to ensure conductivity. As a result, when the dispersion is added to an electrode as a conductive additive, for example, the conductivity of the electrode is improved and the internal resistance of the battery is reduced, thereby improving the charge / discharge efficiency of the battery and further improving its cycle characteristics. Therefore, by making the common logarithm of the viscosity 1.0 or more, it is possible to obtain a CNT film with excellent conductivity and also obtain a dispersion with an appropriate viscosity.

[0044] The aggregate of carbon nanotubes according to the present disclosure is preferably a dispersion liquid obtained by mixing the aggregate of carbon nanotubes, 700 kDa sodium carboxymethyl cellulose, and water, in which the concentration of the aggregate of carbon nanotubes is 0.20 mass % and the concentration of the sodium carboxymethyl cellulose is 0.30 mass %, and the common logarithm of the viscosity of the dispersion liquid is 1.6 or more (the unit of viscosity is mPa·s).

[0045] The common logarithm of the viscosity of the dispersion is 1.54 or more and 5.0 or less, or 1.6 or more and 5.0 or less, and the upper limit may be 4.5 or less, 4.0 or less, 3.5 or less, 3.3 or less, 3.2 or less, 3.1 or less, 3.0 or less, or 2.90 or less. The lower limit may be 1.7 or more, 1.8 or more, 1.9 or more, 2.0 or more, 2.01 or more, or 2.1 or more. Furthermore, the upper limit and lower limit may be combined in any manner. The common logarithm of the viscosity of the dispersion is more preferably 1.8 or more and 3.2 or less, even more preferably 2.0 or more and 3.0 or less, and particularly preferably 2.1 or more and 2.9 or less. By properly controlling the viscosity of CNTs, the dispersibility of CNTs improves, and the tensile strength increases. Specifically, when the common logarithm of the viscosity of the dispersion is 1.8 to 3.2, the CNTs are uniformly dispersed and the electrical conductivity is easily ensured. As a result, when the dispersion is added to an electrode as a conductive additive, the electrical conductivity of the electrode is improved and the internal resistance of the battery is reduced, thereby improving the charge / discharge efficiency of the battery and further improving its cycle characteristics.

[0046] Furthermore, when the common logarithm of the viscosity of the dispersion is 2.0 or more and 3.0 or less, the dispersion of the CNTs is further improved, and the conductivity is enhanced. As a result, when the dispersion is added to an electrode as a conductive additive, for example, the electrode can be made more durable against volume changes and stress during cycling, contributing to the life of the battery. In particular, when the logarithm of the viscosity of the dispersion is between 2.1 and 2.9, the balance between CNT dispersibility and conductivity is optimized, and when added to an electrode as a conductive additive, the electrode's performance is maximized. Within this range, both uniform CNT dispersion and high conductivity are achieved, and significant improvements in the cycle characteristics of the battery are expected. Therefore, by satisfying the above viscosity range, it is possible to obtain a CNT film with excellent conductivity and also obtain a dispersion with an appropriate viscosity.

[0047] The viscosity of the dispersion containing the CNT aggregate according to the present disclosure is measured using a cone-and-plate viscometer (also known as an E-type viscometer). Examples of cone-and-plate viscometers include the DV-II+Pro PROGRAMMABLE VISCOMETER manufactured by BROOKFIELD. R is used. The measurement conditions are as follows. Measuring tool: cone and plate Measurement mode: Rotation mode Shear rate: 0.6s -1 ~384s -1 Temperature: 25℃ From the data obtained, the viscosity is read at the following shear rates: Shear rate=12s -1

[0048] The CNT aggregate according to the present disclosure has a high affinity for the dispersion medium, and therefore tends to have a low viscosity when dispersed in a dispersion medium. When the viscosity of the dispersion is within an appropriate range, it can be determined that the dispersibility of the aggregate according to the present disclosure in the dispersion medium is good.

[0049] <Surface resistivity> In the present disclosure, the surface resistivity of the molded film can be measured by a four-terminal four-probe method in accordance with the standard JIS K7194:1994. As a resistivity meter, for example, a Loresta GXII manufactured by Nitto Seiko Analytech Co., Ltd. is used. The method for preparing the molded film will be described later.

[0050] In the present disclosure, the surface resistivity of the tensile test film is preferably 0.01 Ω / □ to 15.4 Ω / □ from the viewpoint of easily ensuring conductivity as a conductive additive and from the viewpoint of the stability of the dispersion, more preferably 0.1 Ω / □ to 10.0 Ω / □, even more preferably 0.2 Ω / □ to 8.0 Ω / □, particularly preferably 0.3 Ω / □ to 5.0 Ω / □, even more preferably 0.9 Ω / □ to 3.5 Ω / □, particularly preferably 0.90 Ω / □ to 3.31 Ω / □, and most preferably 0.90 Ω / □ to 2.59 Ω / □.

[0051] <Elongation at break, tensile strength, and breaking energy density> The CNT aggregate according to the present disclosure preferably has a breaking elongation of more than 0% and not more than 5.0%, a tensile strength of 2.5 MPa or more and 50.0 MPa or less, and a breaking energy density of more than 4.3 MPa·% and not more than 100 MPa·% as measured by the following measurement method.

[0052] -Methods for measuring tensile strength, elongation at break, and breaking energy density- Carbon nanotube aggregates, 700 kDa sodium carboxymethylcellulose, and water are mixed to prepare a carbon nanotube dispersion with a carbon nanotube aggregate concentration of 0.20 mass% and a sodium carboxymethylcellulose concentration of 0.30 mass%. 15 mL of the resulting carbon nanotube dispersion is poured onto a glass-slide silicon plate with inner dimensions of 22 mm x 75 mm x 3 mm, heated at 100 °C for 30 minutes, and dried to obtain a measurement sample. The resulting measurement sample is fixed to the grip of a tensile testing device and subjected to a tensile test at a rate of 1 mm / min. The point at which the stress is maximum is considered to be the break point. The breaking elongation is calculated from the length of the measurement sample at the break point and the length of the measurement sample before the measurement. The maximum test force is also calculated as the tensile strength. Furthermore, the breaking energy density is calculated from the product of the breaking elongation and the tensile strength.

[0053] When the elongation at break of the CNT aggregate according to the present disclosure exceeds 0% (preferably 0.5% or more), the CNTs are sufficiently long, making it easy to ensure electrical conductivity. Specifically, sufficient CNT length increases the number of contact points between CNTs, allowing for smooth electron transfer, improving the electrical conductivity of the entire CNT aggregate. Furthermore, maintaining an appropriate CNT length allows for efficient formation of conductive paths, optimizing electrical conductivity. When the breaking elongation of the CNT aggregate according to the present disclosure is 6.0% or less, more preferably 5.0% or less, it is easy to process it into a dispersion and ensure its dispersibility in the dispersion. Specifically, a breaking elongation of 5.0% or less maintains the flexibility of the CNTs appropriately, realizing uniform dispersion of the CNTs in the dispersion. This maintains the viscosity of the dispersion appropriately, improves dispersibility, and further improves durability against volume changes and stress during battery cycling. This further improves the discharge capacity retention rate. Therefore, it plays an important role in improving the cycle characteristics of a battery made of a CNT aggregate that the breaking elongation rate of the CNT aggregate is in the range of more than 0% and not more than 6.0%, more preferably more than 0% and not more than 5.0%. In particular, the breaking elongation of the CNT aggregate is more preferably in the range of 0.5% to 6.0%, even more preferably in the range of 0.7% to 5.7%, and particularly preferably in the range of 1.1% to 5.4%.

[0054] The breaking elongation of the CNT aggregate can be adjusted by the length, diameter, etc. of the CNT aggregate.

[0055] The tensile strength of the CNT aggregate according to the present disclosure is preferably 2.5 MPa or more and 50.0 MPa or less, more preferably 4.0 MPa or more and 50.0 MPa or less, even more preferably 5.0 MPa or more and 50.0 MPa or less, and particularly preferably 7.0 MPa or more and 50.0 MPa or less. In another embodiment, the pressure is preferably 3.0 MPa or more and 80.0 MPa or less, more preferably 5.0 MPa or more and 70.0 MPa or less, even more preferably 8.0 MPa or more and 60.0 MPa or less, particularly preferably 8.0 MPa or more and 50.0 MPa or less, and even more preferably 8.0 MPa or more and 32.6 MPa or less. When the tensile strength of the CNT aggregate according to the present disclosure is 2.5 MPa or more, the CNTs according to the present disclosure are sufficiently long, making it possible to produce a battery with excellent cycle characteristics. Specifically, when the CNTs are sufficiently long, the number of contact points between the CNTs increases, allowing for smooth electron transfer, improving the conductivity of the entire CNT aggregate and improving the cycle characteristics of the battery (i.e., the retention rate of discharge capacity). When the tensile strength of the CNT aggregate according to the present disclosure is 50.0 MPa or less, it is easy to process it into a dispersion and ensure its dispersibility in the dispersion. Specifically, a tensile strength of 50.0 MPa or less maintains a good balance between the flexibility and mechanical strength of the CNTs, realizing uniform dispersion of the CNTs in the dispersion. This maintains the viscosity of the dispersion appropriately, further improving durability against volume changes and stress during battery cycling. This further improves the discharge capacity retention rate.

[0056] The tensile strength of the CNT aggregate can be adjusted by the length, diameter, etc. of the CNT aggregate.

[0057] The breaking energy density of the CNT aggregate according to the present disclosure is preferably more than 4.3 MPa·% and not more than 100.0 MPa·%, more preferably 5.0 MPa·% or more and 95.0 MPa·% or less, still more preferably 6.0 MPa·% or more and 90.0 MPa·% or less, even more preferably 8.0 MPa·% or more and 80.0 MPa·% or less, and particularly preferably 8.6 MPa·% or more and 75.1 MPa·% or less. When the breaking energy density of the CNT aggregate according to the present disclosure exceeds 4.3 MPa·% (preferably 6.0 MPa·% or more), the CNTs according to the present disclosure are sufficiently long, making it possible to fabricate a battery with excellent cycle characteristics. Specifically, when the CNTs are long enough, the number of contact points between the CNTs increases, allowing for smooth electron transfer, improving the conductivity of the entire CNT aggregate and improving the cycle characteristics of the battery (i.e., the discharge capacity retention rate). When the breaking energy density of the CNT aggregate according to the present disclosure is 100.0 MPa·% or less, it is easy to process it into a dispersion and ensure its dispersibility in the dispersion. Specifically, a breaking energy density of 100.0 MPa·% or less maintains a good balance between the flexibility and mechanical strength of the CNTs, achieving uniform dispersion of the CNTs in the dispersion. This maintains the viscosity of the dispersion appropriately, further improving durability against volume changes and stress during battery cycling. This further improves the discharge capacity retention rate.

[0058] The breaking energy density of the CNT aggregate can be adjusted by the length, diameter, etc. of the CNT aggregate.

[0059] <Amorphous carbon> The CNT aggregate according to the present disclosure preferably contains amorphous carbon. In the CNT aggregate according to the present disclosure, the content of amorphous carbon is preferably less than 2.0 mass % with respect to the total mass of the CNT aggregate.

[0060] The CNT aggregate may contain amorphous carbon, for example, in a state where it is adsorbed on the surface of the CNT aggregate or in a state where it is incorporated into the interior of the fibrous CNT aggregate formed during production.

[0061] Amorphous carbon is produced as a by-product during the CNT manufacturing process. Because amorphous carbon and CNTs have different physical and chemical properties, controlling the amorphous carbon content is important. For example, amorphous carbon is produced when hydrocarbon gas is decomposed at high temperatures during CNT synthesis using chemical vapor deposition (CVD). During this process, carbon atoms precipitate on the catalyst metal surface, resulting in CNT growth, while amorphous carbon is simultaneously produced on the catalyst surface and substrate. The amorphous carbon content can be controlled by appropriately adjusting the CNT growth conditions (e.g., temperature, gas flow rate, catalyst type, etc.). In particular, in the CNT aggregate according to the present disclosure, controlling the amorphous carbon content to less than 2.0 mass% improves electrical conductivity.

[0062] From the viewpoint of improving the electrical conductivity of the CNT aggregate, the content of amorphous carbon is preferably less than 1.8 mass%, more preferably less than 1.7 mass%, even more preferably 1.6 mass% or less, and particularly preferably less than 1.6 mass%, relative to the total mass of the CNT aggregate. Furthermore, from the viewpoint of improving the dispersibility and electrical conductivity of the CNT aggregate, the content of amorphous carbon is preferably 0 mass%, relative to the total mass of the CNT aggregate, but from the viewpoint of maintaining the electrical conductivity of the CNT aggregate, it may be 0.01 mass% or more, 0.02 mass% or more, or 0.03 mass% or more. The above upper and lower limits can be combined arbitrarily. The content of amorphous carbon is preferably 0.01 mass% or more and less than 2.0 mass%, more preferably 0.01 mass% or more and less than 1.8 mass%, even more preferably 0.01 mass% or more and less than 1.7 mass%, and particularly preferably 0.01 mass% or more and less than 1.6 mass%, more preferably 0.01 mass% or more and less than 1.6 mass%, even more preferably 0.02 mass% or more and less than 1.6 mass%, and particularly preferably 0.04 mass% or more and less than 1.43 mass%, relative to the total mass of the CNT aggregate.

[0063] The amorphous carbon content in the CNT aggregate according to the present disclosure is calculated by thermogravimetric differential thermal analysis (TG-DTA). In thermogravimetric differential thermal analysis (TG-DTA), the temperature is raised to about 900°C at about 10°C / min, and the peak combustion temperature and residue are analyzed to evaluate the constituent elements and quality of the carbon material. For example, carbon materials obtained by floating catalyst chemical vapor deposition (FCCVD) are mixtures of metals (e.g., iron (Fe)) contained in the catalyst raw material, CNTs, amorphous carbon, and graphitic carbon. When the carbon material is heated under the above conditions, if it contains metals such as iron (Fe), an increase in mass due to oxidation of the metal is observed. Typically, amorphous carbon burns at around 300°C to 400°C, while CNTs and graphitic carbon begin to burn at around 400°C and are completely burned at around 700°C. Therefore, the amorphous carbon content can be calculated from the difference in the weight loss between 200°C and 400°C.

[0064] When measuring the content of amorphous carbon, a powder of CNT aggregates is used as the measurement sample. When the CNT aggregate is in a form other than powder (for example, fiber or sheet), the CNT aggregate may be pulverized to obtain a powder. The pulverization method is not particularly limited, and any pulverization method capable of crushing the CNT aggregate into small pieces may be used. As the pulverization method, a freeze-pulverization method may be used.

[0065] <Uses of carbon nanotube aggregates> The use of the CNT aggregate according to the present disclosure is not particularly limited. The CNT aggregate according to the present disclosure has high conductivity and can therefore be suitably used, for example, as a conductive additive (particularly, a conductive additive for a negative electrode). In the CNT aggregate according to the present disclosure, the CNTs are easily entangled with each other to form conductive paths. Therefore, for example, by allowing the CNT aggregate to coexist with conductive materials such as a positive electrode active material and a negative electrode active material within an electrode, the conductivity of the conductive material can be further improved. The CNT aggregate according to the present disclosure can be used, for example, together with graphite, ketjen black, etc., which are known conductive aids.

[0066] <Method for manufacturing CNT> The method for manufacturing CNTs constituting the CNT aggregate according to the present disclosure is not particularly limited. For example, as the method for manufacturing CNTs in the present disclosure, methods such as the conventionally known chemical vapor deposition (CVD) method, a method of reacting a gaseous reactant containing a carbon source in the presence of a catalyst, etc. can be applied.

[0067] The CNTs in the present disclosure can be manufactured, for example, by referring to the methods described in JP-A-2016-102047, JP-T-2021-527611, etc.

[0068] Hereinafter, the method for manufacturing CNTs in the present disclosure will be described with examples. However, the method for manufacturing CNTs in the present disclosure is not limited to the following examples.

[0069] =Manufacturing method X= As an example of the method for manufacturing CNTs referred to in the present disclosure, the manufacturing method described in JP-A-2016-102047 can be mentioned. That is, a step of passing a gaseous reactant containing one or more carbon sources through a reactor, a step of reacting one or more gaseous reactants in the reaction region of the reactor in the presence of a catalyst to form product particles containing carbon, a step of aggregating the product particles into aggregates, and a step of applying a force to the aggregates to continuously move the aggregates out of the reaction region (hereinafter, also referred to as "manufacturing method X").

[0070] According to manufacturing method X, CNTs containing ULCNTs can be obtained in the form of fibrous aggregates or other aggregate forms that are easy to handle.

[0071] In manufacturing method X, the force applied to the product particles may be a mechanical force. When the agglomerates are fibrous CNTs, the mechanical force applied to the product particles can be exerted by a rotating spindle around which the agglomerates are wound, and the fibrous CNTs can be collected on the spindle or accumulated elsewhere by rotating around the spindle one or more times and then successively unwinding the spindle.

[0072] The spindle is preferably oriented with its axis perpendicular or parallel to the flow direction of the gaseous reactant(s), although other orientations are also possible, for example, a spindle with its axis oriented at a 25° angle to the flow direction of the gaseous reactants may also be suitable for applying mechanical forces to the product particles.

[0073] The spindle can rotate around two axes (e.g., two perpendicular axes). In particular, the spindle can rotate around axes perpendicular and parallel to the flow direction of the gaseous reactants. Such a spindle can pull and twist the fibrous CNT aggregates to control the twist number and length.

[0074] The spindle may be made of metal, ceramic, or resin. The spindle can have different suitable shapes depending on the material properties and the intended use of the CNTs. The spindle can be used as a mold for producing carbon products, for example, by a spin-coating process. Preferred spindle shapes are rod-shaped or box-shaped.

[0075] Fibrous CNTs are deposited on a spindle or elsewhere, and the coating thickness and orientation can be controlled by controlling the reaction time and conditions, or by the application of electric or other fields to the carbon product. The coating thickness and orientation of the carbon product can be controlled, for example, by gas flow forces.

[0076] The rotation speed of the spindle is preferably 0.01 rpm (revolutions / minute; the same applies hereinafter) to 10,000 rpm, and more preferably 0.1 rpm to 100 rpm. The spinning speed (i.e., the rotational speed of the spindle) may be adjusted so that the material is collected at a similar rate as it is produced. The rotational speed of the spindle may also control the thickness of the accumulated CNT fiber. In a preferred embodiment, as the spindle rotates, the CNT fiber is processed in the axial direction of the spindle. This processing ensures that the CNT fiber is evenly wrapped along the spindle, rather than being wrapped only at one specific point on the spindle.

[0077] The CNT fibers may be collected, for example, on the reactor wall 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 CNT fibers as they are collected. A suitable substrate arrangement for fiber technology is a substrate consisting of two guides positioned at right angles to each other.

[0078] In production method X, the mechanical force applied to the product particles may be a force applied by an accelerating gas flow. The accelerating gas flow may be generated by passing the product particles through a reactor having a narrow diameter or through a capillary tube downstream of the reaction zone. A vacuum may be applied to the product particles.

[0079] Another force that can be applied to the product particles is electrostatic force, which is suitably applied by a charged plate. Electrostatic force requires that the product particles be charged. By using a charged plate, the CNTs can be grown in the form of intertwined sheets on the charged plate.

[0080] Other forces applied to the product particles may also be magnetic forces or photon pressure applied by a light source.

[0081] Instead of a gaseous reactant containing a carbon source, the CNT precursor may be injected in the form of a liquid containing a carbon source. When a liquid is used as the CNT precursor, it can be injected through a single inlet or multiple inlets, for example, in a showerhead configuration.

[0082] Preferably, the gaseous reactant(s) are reacted at a temperature between 500° C. and 1600° C., more preferably between 1000° C. and 1500° C. A temperature gradient is preferably maintained within the reactor, with the reaction zone being maintained at a higher temperature than the product zone of the reactor.

[0083] The gaseous reactants may be mixed with one or more gases that act as diluents. The gaseous reactants may also be mixed with gases that play a supporting but not direct role in the reaction. It is also preferred to use a diluent gas that can react with the amorphous carbon by-product, if any, to keep the reactive sites on the catalyst intact and produce nanotubes.

[0084] Gases that can be used as a diluent include argon or other inert gases, hydrogen, nitrogen, ammonia, carbon dioxide, helium, etc. Among these, hydrogen is particularly preferred as a gas that can be used as a diluent.

[0085] The composition of the product particles can be controlled by monitoring the agglomerates and modifying the reaction conditions based on the information obtained. For example, the agglomerates can be monitored by online Raman spectroscopy, which provides data indicating whether the CNTs are single-walled or multi-walled. It also provides data indicating the diameter and crystallinity of the CNTs. The agglomerates can also be monitored by online conductivity measurements, gas analysis, measuring the opacity of the reaction zone, and / or measuring the winding force.

[0086] When the agglomerate is removed from the reactor, it is preferable to prevent air from entering the reactor, which is particularly important when the diluent gas contains hydrogen, for example, in order to prevent an explosive mixture of hydrogen and air from forming in the reactor.

[0087] In production method X, it is preferable to control the temperature of the reactor to 200°C to 700°C when removing the agglomerates from the reactor. The CNT bundle diameter can be controlled by the temperature of the CNT reaction region and the temperature of the reactor when removing the agglomerates from the reactor. The higher the reactor temperature when removing the agglomerates from the reactor, the larger the CNT bundle diameter can be. For example, by setting the temperature of the reactor at about 150° C. when the aggregates are removed from the reactor, the bundle diameter, which is 90% of the cumulative diameter of the CNTs, can be set to 110 nm to 170 nm. By setting the temperature of the reactor at about 500° C. when the aggregates are removed from the reactor, the bundle diameter, which is 90% of the cumulative diameter of the CNTs, can be set to 200 nm to 230 nm. By setting the temperature of the reactor at about 750° C. when the aggregates are removed from the reactor, the bundle diameter, which is 90% of the cumulative diameter of the CNTs, can be set to 300 nm to 400 nm. The "reactor temperature" is a temperature determined by measuring the gas temperature at the outlet through which the condensate is taken out of the reactor.

[0088] The product particles in production method X contain ULCNTs. Depending on the production conditions, SWCNTs and MWCNTs may also be contained.

[0089] The product particles may be produced by chemical vapor deposition, where a gaseous reactant, a carbon source, is reacted in the presence of a catalyst.

[0090] Carbon-containing compounds suitable 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, and hydrocarbons containing mixtures of two or more thereof). The carbon-containing compound is preferably carbon monoxide, methane, ethylene or acetylene.

[0091] Preferably, the carbon source contains oxygen. Ethanol is a particularly preferred carbon source. Oxygen can be introduced into the reactor by other methods, such as by using a diluent gas or a carbon source containing water.

[0092] The catalyst is preferably a transition metal, particularly a group VIB transition metal such as chromium (Cr), molybdenum (Mo), or tungsten (W), or a group VIIIB transition metal. Specifically, the catalyst is preferably, for example, iron (Fe), cobalt (Co), nickel (Ni), ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os), iridium (Ir), platinum (Pt), or manganese (Mn), or a mixture 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, such as a mixture of Ni and Co (50 / 50 by mass), a mixture of Fe and Ni, or a mixture of Fe and Mo, are more preferred. Any of these transition metals, either alone or in combination with any of the other transition metals listed, can serve as a catalyst for CNT growth, with it being particularly preferred that the catalyst be a mixture of two or more of the listed metals.

[0093] The catalyst is preferably formed by decomposition of a precursor. The precursor is preferably a thermally, photo-, or plasma-decomposable compound of one or more of the above metals, such as a carbonyl or cyclopentadienyl organometallic compound. Ferrocene, iron pentacarbonyl, nickelocene, and cobaltocene are particularly preferred precursors. In one embodiment, 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 one embodiment, 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 may be contained in the carbon source. The catalyst may be used supported on a carrier, and preferred carriers include silica and magnesium oxide.

[0094] The carbon source is preferably reacted in the presence of a promoter. Suitable promoters are one or more of sulfur, phosphorus, molybdenum, and organic compounds of these elements. Thiophene is also a preferred promoter. Suitably, up to 10% by weight of the promoter is included in the carbon source. Preferably, 0.2% to 6% by weight of the promoter is included in the carbon source. When high or low concentrations of thiophene are used as the promoter, MWCNTs are formed.

[0095] According to production method X, it is possible to obtain fibrous CNTs having a length of at least 500 μm, for example, at least 1 mm. The fibrous CNTs can be in the form of threads or sheets. The length of the fibrous CNT can be controlled, for example, by the winding capacity of the spindle used in producing the fibrous CNT.

[0096] The manufacturing method X preferably includes the steps of reacting a carbon source in a reaction zone of a reactor to produce CNTs, and aggregating the CNTs into aggregates by applying force to the CNTs. This manufacturing method makes it possible to easily produce fibrous CNTs.

[0097] Preferably, production method X further comprises, after the step of aggregating CNTs into aggregates, a step of purifying the resulting CNT aggregates. Specifically, first, the CNT aggregates are washed with alcohol (for example, methanol, ethanol, etc.). Next, they are washed with an alkaline solution (for example, ammonia water). The pH of the alkaline solution is, for example, 8 to 11. Then, they are washed with pure water.

[0098] The cleaning method is not particularly limited, and may be a method of spraying a cleaning liquid onto the CNT aggregates, or a method of immersing the CNT aggregates in the cleaning liquid. Washing with alcohol removes alcohol-soluble components contained in the CNT aggregates. Furthermore, washing with an alkaline solution hydrolyzes and removes impurities contained in the CNT aggregates. Incidentally, washing with an acid solution may also be carried out.

[0099] After washing, the CNT aggregates are preferably dried. The drying method is not particularly limited, and can be carried out by a commonly known method.

[0100] By purifying the CNT agglomerates, the metal content in the CNTs can be reduced.

[0101] Preferably, production method X further comprises, after the step of purifying the CNT agglomerates, a step of passing the purified CNT agglomerates through a sieve. Also, it is preferable to recover the CNTs that have passed through the sieve.

[0102] The method for passing the material through a sieve is not particularly limited, and any commonly known method can be used. 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 (particularly an electrode of 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 agglomerates through a sieve, they may be crushed to an appropriate size. Crushing can be carried out using a crusher. Examples of crushers include a roll mill, a cutter mill, and a hammer mill.

[0103] The resulting CNT agglomerates are passed through a sieve and the CNTs that pass through the sieve are collected, thereby removing coarse CNTs and improving the stability of the CNT dispersion. Furthermore, in general, in the manufacture of electrodes, foreign matter that has been mixed in from the outside is removed, but by passing the obtained CNT agglomerates through a sieve, it is possible to more easily remove foreign matter that has been mixed in from the outside.

[0104] In another embodiment, a method may be adopted in which CNTs containing ULCNTs are generated in a reaction region by the above method, and then condensed to form CNTs containing ULCNTs, and the CNTs are continuously withdrawn from the vicinity of the reaction region. In another embodiment, a method may be adopted that includes producing CNTs containing ULCNTs in a reaction region, continuously electrostatically attracting the CNTs containing ULCNTs from the reaction region, and recovering the CNTs containing ULCNTs.

[0105] =Manufacturing method Y= In the present disclosure, the manufacturing method described in JP-A 2021-527611 can be referred to as an example of a method for manufacturing CNTs. That is, the manufacturing method includes a step (1) of supporting a mixture containing a main catalyst precursor and a co-catalyst precursor on γ-Al2O3 to manufacture an active support, a step (2) of drying the active support by multistage drying including vacuum drying, a step (3) of subjecting the dried active support to a heat treatment to manufacture a supported catalyst, and a step (4) of manufacturing CNTs in the presence of the supported catalyst (hereinafter also referred to as "manufacturing method Y").

[0106] ·Process (1) In step (1), a mixture containing a main catalyst precursor and a co-catalyst precursor is supported on γ-Al 2 O 3 to produce an active support.

[0107] In order to uniformly support the main catalyst precursor and the co-catalyst precursor on γ-AlO, the mixture may further contain a solvent, and the main catalyst precursor and the 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, and water is preferred.

[0108] γ-Al2O3 has high porosity and a spinel structure, making it suitable for use as both a main catalyst and a co-catalyst. The CNTs grown from the randomly arranged primary catalyst can be produced in an entangled state.

[0109] The main catalyst may be one or more selected from the group consisting of cobalt, iron, nickel, manganese and chromium, with cobalt being preferred.

[0110] 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.

[0111] The main catalyst precursor may be one or more selected from the group consisting of Co(NO3)2, Co(NO3)2·6H2O, Co2(CO)8, Co2(CO)6[HC=C(C(CH3)3)], Co(CH3CO2)2, Fe(NO3)3, Fe(NO3)2·nH2O, Fe(CH3CO2)2, Ni(NO3)2, Ni(NO3)2·6H2O, Mn(NO3)2, Mn(NO3)2·6H2O, Mn(CH3CO2)2·n(H2O) and Mn(CO)5Br, of which Co(NO3)2·6H2O, Fe(NO3)2·nH2O and Ni(NO3)2·6H2O are preferred.

[0112] The promoter improves the dispersibility of the main catalyst, and may be one or more selected from the group consisting of vanadium and molybdenum.

[0113] The promoter precursors were NH4VO3, NaVO3, V2O5, V(C5H7O2)3, and (NH4)6Mo7O. 24 4H2O, NH4VO3 and (NH4)6Mo7O 24 Preferably, one or more selected from the group consisting of 4H2O.

[0114] When the mixture contains two or more promoter precursors, i.e., when it contains both a vanadium precursor and a molybdenum precursor, the molar ratio of the sum of vanadium and molybdenum to vanadium can be 1:0.45 to 1:0.95 or 1:0.5 to 1:0.9, and preferably 1:0.5 to 1:0.9. When the above conditions are met, the CNT structure can be stably maintained and CNTs with the desired pore volume can be produced.

[0115] The mixture may contain the main catalyst precursor and the co-catalyst precursor such that the molar ratio of the main catalyst to the co-catalyst is 1:0.01 to 1:0.5, 1:0.1 to 1:0.4, or 1:0.1 to 1:0.25, and preferably 1:0.1 to 1:0.25. Satisfying the above molar ratio improves the dispersibility of the main catalyst, enabling the production of CNTs with the desired pore volume.

[0116] The mixture may further include an organic acid which serves to inhibit precipitation of the main catalyst precursor and the co-catalyst precursor.

[0117] The organic acid may be one or more selected from the group consisting of citric acid, tartaric acid, fumaric acid, malic acid, acetic acid, butyric acid, palmitic acid and oxalic acid, with citric acid being preferred.

[0118] The mixture may contain the organic acid and the co-catalyst precursor in a molar ratio of 1:1 to 1:20, 1:2 to 1:10, or 1:3 to 1:6, preferably 1:3 to 1:6. When the above range is satisfied, it is possible to produce a transparent catalyst metal solution during catalyst production, and it is advantageous in that it is possible to produce a catalyst in which fine particles are suppressed during impregnation.

[0119] After step (1), a step of aging may be further included.

[0120] The aging may be carried out for 1 to 60 minutes or 10 to 50 minutes. Preferably, it is carried out for 10 to 50 minutes. When the above conditions are satisfied, the main catalyst precursor and the co-catalyst precursor can be sufficiently supported on the γ-Al2O3. In addition, air bubbles present in the support are removed to the maximum extent possible, and the main catalyst precursor and the co-catalyst precursor can be sufficiently supported even in the fine pores inside the support.

[0121] ·Process (2) The active support is then dried by multi-stage drying, including vacuum drying.

[0122] Multi-stage drying may mean that a drying process including vacuum drying is performed two or more times. Specifically, multi-stage drying may include atmospheric drying and vacuum drying, or may include vacuum drying two or more times.

[0123] The vacuum drying may be carried out at 80° C. to 300° C. or 120° C. to 250° C., preferably at 120° C. to 250° C. If the above conditions are met, the main catalyst precursor, i.e., the coordinate bond of the main catalyst, can be easily decomposed to form the main catalyst oxide, and energy consumption can be minimized.

[0124] The vacuum drying may be performed at 1 mbar to 200 mbar or 30 mbar to 150 mbar, preferably 30 mbar to 150 mbar. When the above conditions are met, the main catalyst precursor, i.e., the main catalyst coordinated compound, is rapidly decomposed and discharged, making it easier to form the main catalyst oxide under vacuum conditions and minimizing energy consumption.

[0125] The vacuum drying can be performed for 10 minutes to 3 hours or 10 minutes to 2 hours, preferably 10 minutes to 2 hours. If 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.

[0126] On the other hand, when the multi-stage drying includes atmospheric drying and vacuum drying, atmospheric drying can be performed before the above-mentioned vacuum drying, and the atmospheric drying can remove solvent that may be present in the active support.

[0127] Drying at normal pressure 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. If the above conditions are met, the solvent present in the active support can be sufficiently removed, and energy consumption can be minimized.

[0128] Drying at atmospheric pressure may be performed at 900 mbar to 1,100 mbar, preferably 950 mbar to 1,050 mbar. If the above conditions are met, the solvent present in the active support can be sufficiently removed and energy consumption can be minimized.

[0129] Drying under atmospheric pressure may be carried out for 1 to 12 hours, preferably 3 to 9 hours. If the above conditions are met, the solvent present in the active support can be sufficiently removed and energy consumption can be minimized.

[0130] On the other hand, when the multi-stage drying includes two or more vacuum dryings, the multi-stage drying may include two or more vacuum dryings performed at different temperatures, more specifically, a primary vacuum drying performed at a first temperature and a secondary vacuum drying performed at a second temperature higher than the first temperature.

[0131] The primary vacuum drying can remove any solvent that may be present in the active support.

[0132] The first temperature may be 80° C. to 160° C., and preferably 100° C. to 140° C. If the above conditions are met, the solvent present in the active support can be sufficiently removed, and energy consumption can be minimized.

[0133] The primary vacuum drying can be carried out for 1 to 12 hours, preferably 3 to 9 hours. If the above conditions are met, the solvent present in the active support can be sufficiently removed and energy consumption can be minimized.

[0134] 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. If the above conditions are met, the solvent present in the active support can be sufficiently removed, and energy consumption can be minimized.

[0135] The secondary vacuum drying is as described above in the description of vacuum drying.

[0136] The second temperature may be 175° C. to 300° C., and preferably 180° C. to 280° C. If the above conditions are met, the main catalyst precursor, i.e., the coordinated bond of the main catalyst, can be easily decomposed to form the main catalyst oxide, and energy consumption can be minimized.

[0137] 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 more preferably at 1 mbar to 70 mbar. If the above conditions are met, the main catalyst precursor, i.e., the main catalyst coordinated compound, is rapidly decomposed and discharged, making it easier to form the main catalyst oxide under vacuum conditions and minimizing energy consumption.

[0138] The secondary vacuum drying may be performed for 10 minutes to 3 hours or 10 minutes to 2 hours, preferably 10 minutes to 2 hours. If 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.

[0139] ·Process (3) The dried active support is then subjected to a heat treatment to produce a supported catalyst.

[0140] By carrying out the heat treatment, a supported catalyst is produced in which the main catalyst and the promoter are present in a coated state on the surface and in the pores of γ-Al2O3.

[0141] The heat treatment may be carried out at 600 to 800°C or 620 to 750°C, preferably at 620 to 750°C. If the above conditions are met, a supported catalyst can be produced in which the main catalyst and the co-catalyst are uniformly coated on the surface and pores of the γ-Al2O3, and energy consumption can be minimized.

[0142] The heat treatment may be carried out for 1 to 12 hours or 2 to 8 hours, preferably 2 to 8 hours. When the above-mentioned time is satisfied, a supported catalyst can be produced in which the catalyst precursor is uniformly coated on the surface and in the pores of γ-AlO.

[0143] ·Process (4) CNTs are then produced in the presence of a supported catalyst.

[0144] Specifically, CNTs can be produced by contacting a supported catalyst with a carbon-based compound, and specifically, by chemical vapor synthesis.

[0145] To explain the steps for producing CNTs in detail, first, a supported catalyst is loaded into a horizontal fixed-bed reactor or a fluidized-bed reactor. Next, the gaseous carbon-based compound or a mixture of the 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 supported catalyst. CNTs can be grown by chemical vapor synthesis through the decomposition of the gaseous carbon-based compound.

[0146] The CNTs produced by the above-mentioned chemical vapor synthesis method have a crystal growth direction that is nearly parallel to the tube axis, and the graphite structure has high crystallinity along the tube length. As a result, CNTs with small unit diameters and high conductivity and strength can be produced.

[0147] The chemical vapor 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. If the above temperature is satisfied, CNTs can be produced while minimizing the generation of amorphous carbon.

[0148] The heat source for the reaction may be induction heating, radiant heat, laser, IR, microwave, plasma, surface plasmon heating, or the like.

[0149] Any carbonaceous compound can be used without particular limitations as long as it can supply carbon and can exist in a gaseous state at temperatures of 300° C. or higher.

[0150] The carbon-based compound may be a carbon-based compound having 6 or less carbon atoms, and may be one or more compounds 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.

[0151] After growing CNTs by the above-mentioned reaction, a cooling step may be optionally performed to align the CNTs more regularly. Specifically, the cooling step may be performed by natural cooling by removing the heat source or by using a cooler.

[0152] The above manufacturing methods X and Y are merely examples, and the manufacturing methods for CNTs that can be contained in a CNT aggregate are not limited to the above.

[0153] <Carbon nanotube dispersion> In the present disclosure, a carbon nanotube dispersion (CNT dispersion) is a dispersion containing CNT aggregates and a dispersion medium. The CNT dispersion liquid has good dispersibility of the CNT aggregate according to the present disclosure in the dispersion medium and is excellent in electrical conductivity. The CNT dispersion liquid is preferably used for forming electrodes, forming transparent conductive films, resin additives, conductive inks, coating agents, antistatic agents, paints, and the like.

[0154] -CNT aggregate- The CNT aggregate contained in the CNT dispersion liquid is the same as the CNT aggregate according to the present disclosure described above, and therefore a description thereof will be omitted here.

[0155] -Dispersion medium- The dispersion medium preferably contains water, and more preferably contains water as the main component. "Containing water as a 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, and even more preferably 99% by mass or more, and may be, for example, 100% by mass.

[0156] The water is not particularly limited, but is preferably distilled water, ion-exchanged water, pure water, or the like, which contains fewer impurities.

[0157] 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.

[0158] The CNT dispersion may further contain other components that can be used in the dispersion in addition to the CNT aggregates and the dispersion medium. Examples of other components include dispersants, antifoaming agents, antistatic agents, conductive assistants other than the conductive assistant according to the present disclosure, etc. Furthermore, the composition may further contain trace amounts of impurity components, so-called inevitable impurities, etc.

[0159] -Dispersant- The CNT dispersion may contain a dispersant for the purpose of further improving the dispersibility and dispersion stability of the CNT aggregates. The dispersant is not particularly limited and may be, for example, various surfactants. The dispersant may also be a polymer compound such as a resin. The dispersant is preferably a surfactant. The surfactant may be an ionic surfactant or a nonionic surfactant, and is not particularly limited. In the CNT dispersion, the surfactant may be used alone or in combination of two or more.

[0160] Examples of ionic surfactants include anionic surfactants, cationic surfactants, and amphoteric surfactants. Examples of anionic surfactants include aromatic sulfonic acid surfactants such as alkylbenzenesulfonates (e.g., dodecylbenzenesulfonic acid) and dodecylphenyl ether sulfonates; ether sulfate surfactants; phosphate surfactants; and carboxylic acid surfactants. Examples of cationic surfactants include alkylamine salts and quaternary ammonium salts. Examples of amphoteric surfactants include alkylbetaine surfactants and amine oxide surfactants. As the ionic surfactant, an ionic surfactant having an aromatic ring (so-called aromatic ionic surfactant) is preferred, and aromatic sulfonic acid surfactants such as alkylbenzene sulfonate and dodecyl phenyl ether sulfonate are more preferred. Aromatic ionic surfactants tend to be excellent in dispersibility, dispersion stabilization, and concentration of CNT aggregates.

[0161] 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 esters; ether surfactants such as polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenyl ethers and polyoxyethylene polypropylene glycols; and aromatic nonionic surfactants such as polyoxyalkylene octyl phenyl ether, polyoxyalkylene nonyl phenyl ether, polyoxyalkyl dibutyl phenyl ether, polyoxyalkyl styryl phenyl ether, polyoxyalkyl benzyl phenyl ether, polyoxyalkyl bisphenyl ether, polyoxyalkyl cumyl phenyl ether and polyoxyalkylene phenyl ether. As the nonionic surfactant, an ionic surfactant having an aromatic ring (so-called aromatic nonionic surfactant) is preferred, polyoxyalkylene phenyl ether is more preferred, and polyoxyethylene phenyl ether is even more preferred. Aromatic nonionic surfactants tend to be excellent in dispersibility, dispersion stabilization, and concentration of CNT aggregates.

[0162] Other dispersants that are excellent in CNT dispersibility, dispersion stability, and concentration enhancement include β-naphthalenesulfonic acid formalin condensate sodium salts such as DEMOL (registered trademark; the same applies hereinafter) N, DEMOL RN, and DEMOL T (manufactured by Kao Corporation), polyoxyethylene stearyl ether Brij S 100 (manufactured by Sigma-Aldrich), polyvinylpyrrolidone K30 (manufactured by, for example, Fujifilm Wako Pure Chemical Industries, Ltd.), carboxymethyl cellulose (CMC) (manufactured by, for example, Daicel Miraize Co., Ltd.), sodium deoxycholate (manufactured by, for example, Fujifilm Wako Pure Chemical Industries, Ltd.), SOLSPERSE™ W100, and SOLSPERSE™ W150 (manufactured by The Lubrizol Japan Co., Ltd.). CMC is particularly preferred from the viewpoint of excellent CNT aggregate dispersibility, dispersion stability, and concentration enhancement.

[0163] When the CNT dispersion liquid contains a dispersant, the amount of the dispersant used is not particularly limited and can be set appropriately depending on the type of dispersant, the amount of CNT aggregates, the amount of dispersion medium, and the like.

[0164] -Method of manufacturing CNT dispersion- The method for producing the CNT dispersion liquid is not particularly limited. A CNT dispersion can be produced by dispersing a CNT aggregate in a dispersion medium. That is, a CNT dispersion can be produced by a method including a step of dispersing a CNT aggregate in a dispersion medium (also referred to as a "dispersion step"). The dispersion medium that can be used in the dispersion step is as described above.

[0165] The dispersion method is not particularly limited. Examples of the dispersion method include methods using a dispersion device such as a stirrer, homogenizer, colloid mill, flow jet mixer, dissolver, paint conditioner, Manton emulsifier, jet mill, and ultrasonic device. Further, examples of the dispersion method include methods using known pulverization means, such as ball milling (e.g., ball mill, vibration ball mill, planetary ball mill, bead mill, etc.), sand milling, colloid milling, jet milling, roller milling, a vertical or horizontal agitator mill, an attritor, a colloid mill, a three-roll mill, a pearl mill, a super mill, an impeller, a disperser, a KD mill, a dynatron, a pressure kneader, or the like. As a dispersion method, a method using a jet mill is preferred, and a 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 through a nozzle arranged in a sealed pressure-resistant container. In a wet jet mill, CNT aggregates are dispersed by collisions between opposing flows in the pressure-resistant container, collisions with the container wall, turbulence caused by the high-speed flow, shear flow, and the like. An ultra-high-pressure homogenizer (model numbers: NAGS20, NAGS100, JAGS200, NAGS1000, etc.) manufactured by Joko Co., Ltd. can be suitably used as the wet jet mill. However, the wet jet mill is not limited to this. When the ultra-high pressure homogenizer is used as the dispersing device, the processing pressure for dispersion is preferably 10 MPa to 250 MPa.

[0166] The method for producing a CNT dispersion may include a step of drying the CNT aggregate (also referred to as a "drying step") before the dispersion step.

[0167] If water adheres to the CNTs, the surface tension of the water makes them more likely to adhere to each other, which can lead to a decrease in dispersibility. Therefore, by performing a drying process for the conductive additive before the dispersion process, the water adhering to the CNTs is removed, preventing the CNTs from adhering to each other due to water adhesion, and further improving the dispersibility of the CNTs in the dispersion medium. The drying method is not particularly limited. Drying methods include, for example, heat drying, vacuum drying, and heat vacuum drying. The drying method is preferably heated vacuum drying. The drying temperature is not particularly limited, and is preferably 40°C to 100°C, for example. The drying time is not particularly limited and can be set appropriately depending on the drying temperature, the degree of moisture adhesion to the CNT aggregate in the present disclosure, and the like.

[0168] An example of producing a CNT dispersion liquid will be shown below, but the production of a CNT dispersion liquid is not limited to the following.

[0169] -Dispersion liquid manufacturing example- 0.040 g of the CNT aggregate according to the present disclosure is weighed and placed in a three-neck flask. After the CNT aggregate is placed in the flask, a large excess of ion-exchanged water (e.g., 20 mL) is poured into the flask and stirred at room temperature (25°C, the same applies below). At this time, a known dispersant (e.g., carboxymethyl cellulose) may be added as appropriate. Next, a 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 period of time (e.g., 1 hour to 48 hours). In this way, a CNT dispersion is obtained.

[0170] (Conductive materials) The conductive material according to the present disclosure includes the CNT aggregate according to the present disclosure. As described above, the CNT aggregate according to the present disclosure contained in the conductive material according to the present disclosure has high conductivity and excellent dispersibility when made into a dispersion, and is therefore suitable as a conductive auxiliary agent. Since the conductive material according to the present disclosure contains the CNT aggregate according to the present disclosure, it has excellent conductive efficiency and It can effectively impart high conductivity to the object to which it is used.

[0171] The conductive material according to the present disclosure may contain a known conductive aid such as graphite, Ketjen black, etc. Furthermore, the conductive material according to the present disclosure may contain CNTs other than the CNT aggregate according to the present disclosure.

[0172] The conductive material according to the present disclosure can be used as one of electrode materials. An example of an electrode formed using the electrode material is an electrode included in a secondary battery. Hereinafter, an embodiment of the electrode and the secondary battery including the electrode will be described.

[0173] (electrode) The electrode can include the CNT aggregate according to the present disclosure described above. In an electrode, the CNT aggregate according to the present disclosure can function as a conductive additive. The CNT aggregate contained in the electrode described below is synonymous with the CNT aggregate according to the present disclosure, and preferred embodiments are also the same, so description of the CNT aggregate will be omitted below.

[0174] The electrode may be at least one of a positive electrode and a negative electrode. The electrode may include an electrode active material layer, or may include a current collector and an electrode active material layer disposed on the current collector.

[0175] The current collector is not particularly limited as long as it does not induce chemical changes in the battery and has conductivity. The current collector may be, for example, copper, stainless steel, aluminum, nickel, titanium, baked carbon, or aluminum or stainless steel whose surface has been treated with carbon, nickel, titanium, silver, etc. Specifically, a transition metal such as copper or nickel that has good carbon adsorption properties may be used as the current collector.

[0176] The electrode active material layer can include an electrode active material. The electrode active material is preferably electrode active material particles. When the electrode is a positive electrode, the electrode active material is not particularly limited, and the electrode active material layer can contain a positive electrode active material that is commonly used as an electrode material for a positive electrode. Specifically, the positive electrode active material may be a layered compound such as lithium cobalt oxide (LiCoO2) or lithium nickel oxide (LiNiO2), or a compound substituted with one or more transition metals; a lithium iron oxide such as LiFe3O4; or a compound having the chemical formula Li 1+c1 Mn 2-c1 Lithium manganese oxides such as MnO4 (0 ≦ c1 ≦ 0.33), LiMnO3, LiMn2O3, LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, V2O5, Cu2V2O7; chemical formula LiNi 1-c2 M c2 O2 (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).); Ni-site type lithium nickel oxide represented by chemical formula LiMn 2-c3 M c3 O2 (where M is at least one selected from the group consisting of Co, Ni, Fe, Cr, Zn, and Ta, and satisfies 0.01 ≦ c3 ≦ 0.1), or lithium manganese composite oxide represented by Li2Mn3MO8 (where M is at least one selected from the group consisting of Fe, Co, Ni, Cu, and Zn). Examples include LiMn2O4 in which a part of the Li in the chemical formula is substituted with an alkaline earth metal ion.

[0177] When the electrode is the negative electrode, the electrode active material is not particularly limited, and the electrode active material layer can contain a negative electrode active material usually used for negative electrode materials. Specifically, the negative electrode active material can contain graphite-based active material particles or silicon-based active material particles. As the 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 the graphite-based active material particles, the rate characteristics can be improved. As the 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 can be made to have a higher capacity.

[0178] The electrode active material layer may further contain a binder. The binder is not particularly limited, and the electrode active material layer can contain a binder that is 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, polymethylmethacrylate, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, 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 have been substituted with Li, Na, Ca, or the like.

[0179] (Secondary battery) The secondary battery may include a negative electrode, a positive electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte, wherein at least one of the positive electrode and the negative electrode is an electrode formed using an electrode material including the CNT aggregate according to the present disclosure.

[0180] The separator separates the negative electrode from the positive electrode and provides a path for lithium ions to move, and is not particularly limited as long as it is a separator that is typically used as a separator in a secondary battery. The separator preferably has low resistance to ion movement of the electrolyte and is excellent in the ability to retain moisture in the electrolyte solution. A specific example of the separator is a porous polymer film. The porous polymer film may be, for example, a porous polymer film made from a polyolefin polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, or an ethylene / methacrylate copolymer, or a laminate structure in which two or more layers of these films are laminated. The separator may also be a typical porous nonwoven fabric, such as a nonwoven fabric made of high-melting-point glass fiber, polyethylene terephthalate fiber, etc. The separator may also be coated with a ceramic component or a polymeric substance to ensure heat resistance or mechanical strength. The separator may optionally be of a single layer or multi-layer structure.

[0181] The electrolyte is not particularly limited, and examples thereof include electrolytes such as 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 producing lithium secondary batteries.

[0182] Specifically, the electrolyte can include a non-aqueous organic solvent and a metal salt. Examples of non-aqueous organic solvents include aprotic organic solvents such as 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, phosphoric acid triester, trimethoxymethane, dioxolane derivatives, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ethers, methyl propionate, and ethyl propionate.

[0183] Among carbonate organic solvents, cyclic carbonates such as ethylene carbonate and propylene carbonate are preferred as non-aqueous organic solvents because they have high viscosity and high dielectric constants and dissociate lithium salts well. It is more preferred to use a non-aqueous organic solvent obtained by mixing such cyclic carbonates with linear carbonates having low viscosity and low dielectric constants, such as dimethyl carbonate and diethyl carbonate, in an appropriate ratio, in order to obtain an electrolyte having high electrical conductivity.

[0184] The metal salt may be a lithium salt. Lithium salts are substances that are easily dissolved in non-aqueous electrolytes. The anion portion of the lithium salt may be, for example, F - , Cl - , I - , NO3 - , N(CN)2 - , BF4 - , ClO4 - , PF6 - , (CF3)2PF4 - , (CF3)3PF3 - , (CF3)4PF2 - , (CF3)5PF - , (CF3)6P - , CF3SO3 - , CF3CF2SO3 - , (CF3SO2)2N - , (FSO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , (SF5)3C - , (CF3SO2)3C - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN - , and (CF3CF2SO2)2N - Examples include:

[0185] In addition to the non-aqueous organic solvent and metal salt, the electrolyte may further contain one or more additives such as haloalkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ethers, ethylenediamine, n-glyme, hexaphosphoric acid triamide, nitrobenzene derivatives, sulfur, quinoneimine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, and aluminum trichloride, for the purposes of improving the battery's life characteristics, suppressing a decrease in battery capacity, and improving the battery's discharge capacity.

[0186] The above-described secondary battery can be used to form a battery module including the secondary battery as a unit cell, and a battery pack including the battery module. The battery module and the battery pack can be used as a power source for a medium to large device selected from the group consisting of, for example, an electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, and a power storage system.

[0187] (Planar aggregate) The planar aggregate according to the present disclosure includes the CNT aggregate according to the present disclosure. The ratio of the CNT aggregate according to the present disclosure contained in the planar aggregate according to the present disclosure is usually 1 mass % or more relative to the total mass of the planar aggregate. The planar aggregate according to the present disclosure may contain other components such as CNT aggregates (particularly CNT aggregates) having a maximum length of less than 1000 μm.

[0188] <Method for producing planar assembly> The method for producing the planar assembly according to the present disclosure is not particularly limited. The planar aggregate according to the present disclosure can be produced, for example, as a nonwoven fabric-like planar aggregate, by dispersing the CNT aggregate according to the present disclosure, or the CNT aggregate according to the present disclosure and other components, such as a CNT aggregate (particularly a CNT aggregate) having a maximum length of less than 1000 μm, in water or other fluid and filtering once or twice or more times.

[0189] An example of the planar assembly according to the present disclosure is a film.

[0190] Planar assemblies according to the present disclosure are useful, for example, in filters, electromagnetic shields, and extreme ultraviolet (EUV) pellicles.

[0191] (Laminate) A laminate according to the present disclosure includes a substrate and a planar assembly according to the present disclosure. The substrate and the planar assembly may be in direct contact with each other, or another layer may be disposed between the substrate and the planar assembly. Alternatively, the planar assembly according to the present disclosure may be disposed on a substrate, and another layer may be disposed on the planar assembly.

[0192] 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). Glasses include, for example, float glass (containing SiO2, Na2O, CaO, 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.

[0193] The planar aggregate preferably contains a binder in addition to the CNT aggregate according to the present disclosure. The binder is preferably a polymer, and preferably contains at least one selected from the group consisting of polymers containing structural 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.

[0194] (Method for measuring the average curvature of a carbon nanotube aggregate) The method for measuring the mean curvature of a carbon nanotube aggregate according to the present disclosure involves performing the following steps 1 to 3 on two or more images of the carbon nanotube aggregate using image analysis software ImageJ (version 1.54g) and Kappa plug-in (version 2.0.0) to calculate the mean curvature. 1. Adjust the image size using Image:Adjust:Size, Width=1280. Set the screen size to 1280 x 960 and the width to 1410 nm. 2. Fine-tune the curve so that it follows the center of the fiber under the conditions of Plugin:Analyze:Kappa, File:OpenActiveImage, and CurveFittingOptions:ChoosePoints=100, DataThreshold=10, Scale(μm / pixel)=0.16. 3. After calculating approximately eight central lines per field of view, calculate each curvature and the average curvature.

[0195] ImageJ is an open-source, public domain image processing software. By using this and the curvature analysis mode Kappa, it becomes possible to draw a line on each bundle in the carbon nanotube aggregate for analysis, and the curvature of each bundle can be easily calculated. [Example]

[0196] The CNT aggregate and the like according to the present disclosure will be described more specifically below with reference to examples. The present disclosure is not limited to the following examples as long as it does not deviate from the gist of the disclosure.

[0197] Example 1 1. Production of sheet-shaped CNT aggregate 1 Sheet-like CNT aggregate 1 was produced by the floating catalyst method (CVD method), which directly interacts with the self-assembly of CNT bundles 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 a promoter were introduced into a continuous flow of carrier gas in a once-through reactor temperature-controlled at 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 is decomposed. The region where the metal catalyst precursor is decomposed is referred to as the first temperature zone.

[0198] Next, methane, a carbon source, was released into the carrier gas flow. The metal catalyst and carbon source were supplied to a second temperature zone downstream of the first temperature zone, which was temperature-controlled at 1400°C. The total gas supply flow rate of the carrier gas and source gas was 36 NL / min (NL is normal liters). The second temperature zone was maintained at a temperature sufficient to produce carbon nanotube aggregates.

[0199] In the second temperature zone, a reaction field was created in a temperature-controlled flow reactor to form catalytic nuclei and rapidly grow CNTs, thereby producing CNT aggregates. The aggregates of CNTs were continuously discharged through the outlet of a flow reactor whose temperature was controlled at 500°C, and the sheet-like CNT aggregates were collected.

[0200] The obtained sheet-like CNT aggregate was washed with methanol, immersed in a diluted ammonia water solution of pH 10 for 10 minutes, washed with pure water for 10 minutes, dried, crushed into powder, and passed through a sieve with 1.0 mm openings twice. The CNT aggregate that passed through the sieve was collected and designated as CNT aggregate 1.

[0201] 2. Preparation of CNT Dispersion 1 The following materials were mixed and pre-dispersed by processing for 1 hour using an Ace Homogenizer manufactured by Nippon Seiki Co., Ltd., to obtain pre-dispersion liquid 1.

[0202] -Dispersion composition- 1.1g of the CNT aggregate obtained above ·CARBOXYMETHYL CELLULOSE SODIUM SALT HIGH VISCOSITY (manufactured by MP Biomedicals): 1.65g ·Pure water: 547.25g

[0203] The pre-dispersion liquid 1 was subjected to main dispersion using an ultra-high pressure homogenizer (model number: NAGS100) manufactured by Joko Co., Ltd. as a wet jet mill under the following conditions to obtain a CNT dispersion liquid 1 with a concentration of 0.20 mass %. -Dispersion conditions- Nozzle diameter: 0.22 mm Pressure: 150 MPa Number of times: 8 Method: Circulation method

[0204] 3. Evaluation <Calculation of mean curvature> Images of the CNT aggregate 1 of Example 1 were taken using a scanning electron microscope (SEM), and eight images in which the CNT bundles were clearly observed were selected from the obtained images (one of which is shown in FIG. 1).

[0205] Using the above image, the average value of the curvature of the CNT structure was calculated by image analysis. More specifically, the curvature was calculated for each of the captured images using image analysis software (ImageJ) according to the following procedure.

[0206] -Calculation procedure- 1.Image:Adjust:Size, Width=1280 2. Plugin:Analyze:Kappa 3. File:OpenActiveImage 4.CurveFittingOptions:ChoosePoints=100, DataThreshold=10, Scale(μm / pixel)=0.16 5. Select the ControlPointTool and left-click along the center line of the CNT structure. 6. Press Enter and fine-tune the curve to follow the center of the fiber. 7. After calculating approximately eight central lines per field of view, click Export Average Points.

[0207] Based on the curvature calculated for each image, the average value of the curvature was calculated. -1 ) was 0.010.

[0208] <Features of bundle diameter> Image processing and analysis were performed on the selected images using Python. In image processing, the CNT outline and center line were detected and combined with the original image. In image analysis, the bundle diameter was determined by calculating the distance from the center line to the outline of the created image. The product of the bundle diameter and the length of the center line was then calculated to calculate the area occupied by the CNTs in the image. A histogram of the bundle diameter and the area occupied was created.

[0209] Using the calculated bundle diameter histogram, the feature amount of the bundle diameter of each sample was calculated by the following method. 1. The bundle diameters and exclusive areas of multiple fields of view of the same sample were added together and normalized so that the sum became 1. Along with the normalization, the unit of the vertical axis was set as the exclusive area ratio. 2. The total value of the exclusive area ratios of the bundles with a bundle diameter of 100 nm or more was determined. As a result, the ratio of the bundles with a bundle diameter of 100 nm or more was 0.49. The cumulative 90% bundle diameter was 230 nm.

[0210] <Measurement of the cumulative 50% particle size D50 in the volume-based particle size distribution> CNT dispersion liquid 1 was sufficiently stirred and further diluted by adding pure water. Using the obtained diluted liquid as a sample, the cumulative particle size D50 of the CNT dispersion liquid was measured using a particle size distribution analyzer (manufactured by Horiba, Ltd., laser diffraction particle size distribution analyzer, LA-960). The particle refractive index of CNT was set as 1.920 - 0.522i. The refractive index of the solvent was set as 1.333. During the measurement, while observing the transmittance, CNT dispersion liquid 1 was dropped into pure water for dilution, and it was confirmed that the particle size distribution on the monitor was stable before performing the measurement. As a result, the cumulative 50% particle size D50 in the volume-based particle size distribution of CNT aggregate 1 was 1.25 μm. The evaluation results are shown in Table 1 below.

[0211] <Viscosity of the dispersion liquid of CNT aggregate> The viscosity of CNT dispersion liquid 1 was measured using a cone and plate viscometer (also known as an E-type viscometer). Specifically, the viscosity was measured using a cone and plate viscometer (DV-II + Pro PROGRAMMABLE VISCOMETER manufactured by BROOKFIELD). Measurement jig: Cone and plate Measurement mode: Rotation mode Shear rate: 0.6 s -1 ~384 s -1 Temperature: 25 °C From the obtained data, the viscosity at a shear rate of 12 s -1 was read. The viscosity of the dispersion was 142.6 mPa·s. The common logarithm notation of the viscosity was 2.15. In addition, when the viscosity of the dispersion is in the range of 10 mPa·s to 1500 mPa·s, it was determined that a CNT dispersion with an appropriate viscosity was obtained.

[0212] <Evaluation of CNT Aggregate Dispersion 1: Tensile Strength, Elongation at Break, and Fracture Energy Density> CNT aggregate 1, 700 kDa sodium carboxymethyl cellulose, and water were mixed to prepare a carbon nanotube dispersion in which the concentration of the carbon nanotube aggregate was 0.20% by mass and the concentration of sodium carboxymethyl cellulose was 0.30% by mass. 15 mL of the obtained carbon nanotube dispersion was poured onto a slide glass-shaped silicon plate with an inner diameter of 22 mm × 75 mm × 3 mm and heated at 100°C for 30 minutes to dry to obtain a measurement sample. The measurement sample was fixed to the gripping part of a tensile testing machine (Autograph AG-IS, manufactured by Shimadzu Corporation) and a tensile test was conducted at a speed of 1 mm / min. The maximum test force was calculated as the tensile strength. Also, the point at which the test force was maximum was regarded as the fracture point, and the elongation at break was calculated. Furthermore, the fracture energy density was calculated from the product of the elongation at break and the tensile strength. As a result, the tensile strength was 8.0 MPa, the elongation at break was 1.1%, and the fracture energy density was 8.6 MPa·%.

[0213] <Evaluation of CNT Aggregate Dispersion 1: Surface Resistivity> CNT aggregate 1, 700 kDa sodium carboxymethyl cellulose, and water were mixed to prepare a carbon nanotube dispersion in which the concentration of the carbon nanotube aggregate was 0.20% by mass and the concentration of sodium carboxymethyl cellulose was 0.30% by mass. 15 mL of the obtained carbon nanotube dispersion was poured onto a slide glass-shaped silicon plate with an inner diameter of 22 mm × 75 mm × 3 mm and heated at 100°C for 30 minutes to dry to obtain a measurement sample. The surface resistivity of the film was measured using Loresta GXII manufactured by Nitto Seiko Analytic Co., Ltd. The measurement was carried out at five locations on the film, and the average value of the five numerical values was taken as the surface resistivity. As a result, the surface resistivity was 2.59 Ω / sq. The results are shown in Table 1 below.

[0214] <Content of amorphous carbon with respect to the total mass of the CNT aggregate> For CNT aggregate 1, the amount of amorphous carbon was quantified by thermogravimetric differential thermal analysis (TG-DTA). Using a thermal analyzer (model number: STA200, manufactured by Hitachi High-Tech Corporation), thermogravimetric differential thermal analysis was performed under air flow at a heating rate of 10 °C / min. Approximately 10 mg of the sample was weighed into a Pt pan, and the content of amorphous carbon was calculated from the difference in weight loss at 200 °C and 400 °C when the temperature was raised to 900 °C at a rate of 10 °C / min. As a result, the content of amorphous carbon in CNT aggregate 1 was 0.04% by mass.

[0215] (Example 2) 1. Production of CNT aggregate 2 CNT aggregate 2 was prepared in the same manner as CNT aggregate 1, except that the total gas supply flow rate of the carrier gas and the raw material gas was set to 39 NL / min, and continuous discharge was performed through the outlet of a flow-type reactor temperature-controlled at 150 °C.

[0216] 2. Preparation of CNT dispersion 2 Using the obtained CNT aggregate 2, CNT dispersion 2 was obtained in the same manner as in Example 1.

[0217] 3. Evaluation <Calculation of average curvature> Using CNT aggregate 2, the average curvature was calculated in the same manner as in Example 1, except that 7 SEM images were selected (one of which is Figure 2). The average curvature Z (μm -1 ) was found to be 0.021.

[0218] <Characteristic quantity of bundle diameter> Calculated in the same manner as in Example 1 except that the CNT aggregate 2 was used. As a result, the ratio of bundles having a bundle diameter of 100 nm or more was 0.23. The cumulative 90% bundle diameter was 160 nm.

[0219] <Measurement of the cumulative 50% particle size D50 in the volume-based particle size distribution> Measured in the same manner as in Example 1 except that the CNT dispersion 2 was used. As a result, the cumulative 50% particle size D50 in the volume-based particle size distribution was 1.07 μm. The evaluation results are shown in Table 1 below.

[0220] <Viscosity of the dispersion of the CNT aggregate> Measured in the same manner as in Example 1 except that the CNT dispersion 2 was used. The viscosity of the dispersion was 102.2 mPa·s. The common logarithm notation of the viscosity was 2.01.

[0221] <Tensile strength, elongation at break, and breaking energy density> Calculated in the same manner as in Example 1 except that the CNT dispersion 2 was used. As a result, the tensile strength was 2 8.5 MPa, the elongation at break was 2.5%, and the breaking energy density was 71.5 MPa·%.

[0222] <Surface resistivity> The surface resistivity was measured in the same manner as in Example 1 except that the CNT dispersion 2 was used. As a result, the surface resistivity was 3.31 Ω / □. The results are shown in Table 1 below.

[0223] <Content of amorphous carbon> The amount of amorphous carbon was quantified in the same manner as in Example 1 except that the CNT aggregate 2 was used. As a result, the content of amorphous carbon was 0.10% by mass.

[0224] (Example 3) 1. Production of CNT aggregate 3 The CNT aggregate 3 was produced in the same manner as the CNT aggregate 1, except that the total gas supply flow rate of the carrier gas and the raw material gas was set to 34 NL / min, and continuous discharge was performed through the outlet of a flow-type reactor whose temperature was controlled to 150°C.

[0225] 2. Preparation of CNT dispersion 3 Using the obtained CNT aggregate 3, a preliminary dispersion 3 was obtained in the same manner as in Example 1.

[0226] The final dispersion of the preliminary dispersion 3 was carried out using a high-pressure homogenizer (model number: NAGS100) manufactured by Tokuyama Corporation as a wet jet mill under the following conditions to obtain a CNT dispersion 3 with a concentration of 0.20% by mass. - Dispersion conditions - Nozzle diameter: 0.22 mm Pressure: 85 MPa Number of passes: 8 times Method: Circulation method

[0227] 3. Evaluation <Calculation of average curvature> Using the CNT aggregate 3, the average curvature was calculated in the same manner as in Example 1, except that 5 SEM images were selected (one of which is shown in Figure 3). The average curvature Z (μm -1 ) was 0.012.

[0228] <Characteristic quantity of bundle diameter> The calculation was carried out in the same manner as in Example 1, except that the CNT aggregate 4 was used. As a result, the ratio of bundles with a bundle diameter of 100 nm or more was 0.14. The cumulative 90% bundle diameter was 120 nm.

[0229] <Measurement of cumulative 50% particle size D50 in volume-based particle size distribution> The measurement was carried out in the same manner as in Example 1, except that the CNT dispersion 4 was used. As a result, the cumulative 50% particle size D50 in the volume-based particle size distribution was 1.47 μm. The evaluation results are shown in Table 1 below.

[0230] <Viscosity of CNT aggregate dispersion> Measurement was carried out in the same manner as in Example 1, except that CNT Dispersion 3 was used. The viscosity of the dispersion was 34.6 mPa·s. The common logarithm of the viscosity was 1.54.

[0231] <Tensile strength, elongation at break, energy density at break> The calculation was carried out in the same manner as in Example 1 except that CNT dispersion 3 was used. The fracture energy density was 75.1 MPa·%.

[0232] <Surface resistivity> The surface resistivity was measured in the same manner as in Example 1, except for using CNT dispersion liquid 3. As a result, the surface resistivity was 1.07 Ω / □. The results are shown in Table 1 below.

[0233] <Amorphous carbon content> The amount of amorphous carbon was quantified in the same manner as in Example 1 except for using the CNT aggregate 3. As a result, the amorphous carbon content was 0.39 mass %.

[0234] Example 4 1. Preparation of CNT aggregate 4 The CNT aggregate 4 was produced by mixing the following CNT aggregate 4A and the following CNT aggregate 4B. CNT aggregate 4A was produced 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 35 NL / min, and the gas was continuously discharged through the outlet of a flow-type reactor whose temperature was controlled at 150°C. CNT aggregate 4B was produced 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, and the gas was continuously discharged through the outlet of a flow-type reactor whose temperature was controlled at 150°C.

[0235] 2. Preparation of CNT Dispersion 4 Using the obtained CNT aggregate 4, a pre-dispersion liquid 4 was obtained in the same manner as in Example 1.

[0236] The secondary dispersion of the pre-dispersion liquid 4 was carried out using a high-pressure homogenizer (model number: NAGS100) manufactured by Tsunehikari Co., Ltd. as a wet jet mill under the following conditions to obtain the CNT dispersion liquid 4. -Dispersion conditions- Nozzle diameter: 0.22 mm Pressure: 50 MPa Number of times: 3 times Method: Circulation method

[0237] 3. Evaluation <Calculation of average curvature> Using the CNT aggregate 4, four SEM images were selected (one of which is shown in Figure 4), and the average curvature was calculated in the same manner as in Example 1. The average curvature Z (μm -1 ) was 0.010.

[0238] <Characteristic quantity of bundle diameter> The calculation was carried out in the same manner as in Example 1 except for using the CNT aggregate 4. As a result, the ratio of bundles with a bundle diameter of 100 nm or more was 0.26. The cumulative 90% bundle diameter was 150 nm.

[0239] <Measurement of cumulative 50% particle size D50 in volume-based particle size distribution> The measurement was carried out in the same manner as in Example 1 except for using the CNT dispersion liquid 4. As a result, the cumulative 50% particle size D50 in the volume-based particle size distribution was 13.05 μm. The evaluation results are shown in Table 1 below.

[0240] <Viscosity of the dispersion liquid of CNT aggregate> The measurement was carried out in the same manner as in Example 1 except for using the CNT dispersion liquid 4. The viscosity of the dispersion liquid was 798.2 mPa·s. The common logarithm notation of the viscosity was 2.90.

[0241] <Tensile strength, elongation at break, and breaking energy density> The calculation was carried out in the same manner as in Example 1 except for using the CNT dispersion liquid 4. As a result, the tensile strength was 1 5.5 MPa, the elongation at break was 2.6%, and the breaking energy density was 40.6 MPa·%.

[0242] <Surface resistivity> The surface resistivity was measured in the same manner as in Example 1, except for using CNT dispersion liquid 4. As a result, the surface resistivity was 0.90 Ω / □. The results are shown in Table 1 below.

[0243] <Amorphous carbon content> The amount of amorphous carbon was quantified in the same manner as in Example 1 except for using the CNT aggregate 4. As a result, the amorphous carbon content was 1.43 mass %.

[0244] Example 5 1. Production of CNT aggregate 5 CNT aggregate 5 is a CNT aggregate produced in the same manner as CNT aggregate 1, except that the total gas supply flow rate of the carrier gas and raw material gas was set to 34.2 NL / min.

[0245] 2. Preparation of CNT Dispersion 5 Using the obtained CNT aggregate 5, a pre-dispersion liquid 5 was obtained in the same manner as in Example 1.

[0246] The pre-dispersion liquid 5 was subjected to main dispersion using an ultra-high pressure homogenizer (model number: NAGS100) manufactured by Joko Co., Ltd. as a wet jet mill under the following conditions to obtain CNT dispersion liquid 5. -Dispersion conditions- Nozzle diameter: 0.22 mm Pressure: 85 MPa Number of times: 8 Method: Circulation method

[0247] 3. Evaluation <Calculation of mean curvature> Using the CNT aggregate 5, four SEM images were selected (one of which is shown in FIG. 5), and the average curvature was calculated in the same manner as in Example 1. -1 ) was 0.011.

[0248] <Features of bundle diameter> Calculation was performed in the same manner as in Example 1 except that the CNT aggregate 5 was used. As a result, the ratio of bundles having a bundle diameter of 100 nm or more was 0.13. The cumulative 90% bundle diameter was 110 nm.

[0249] <Measurement of cumulative 50% particle diameter D50 in volume-based particle size distribution> Measurement was performed in the same manner as in Example 1 except that the CNT dispersion 5 was used. As a result, the cumulative 50% particle diameter D50 in the volume-based particle size distribution was 40.1 μm. The evaluation results are shown in Table 1 below.

[0250] <Viscosity of CNT aggregate dispersion> Measurement was performed in the same manner as in Example 1 except that the CNT dispersion 5 was used. The viscosity of the dispersion was 499.1 mPa·s. The common logarithm notation of the viscosity was 2.70.

[0251] <Tensile strength, elongation at break, and fracture energy density> Calculation was performed in the same manner as in Example 1 except that the CNT dispersion 5 was used. As a result, the tensile strength was 1 5.6 MPa, the elongation at break was 2.2%, and the fracture energy density was 34.7 MPa·%.

[0252] <Surface resistivity> The surface resistivity was measured in the same manner as in Example 1 except that the CNT dispersion 5 was used. As a result, the surface resistivity was 1.40 Ω / □. The results are shown in Table 1 below.

[0253] <Content of amorphous carbon> Quantification of the amount of amorphous carbon was performed in the same manner as in Example 1 except that the CNT aggregate 5 was used. As a result, the content of amorphous carbon was 0.24% by mass.

[0254] (Comparative Example 1) 1. Preparation of powdered CNT aggregate 6 As the powdered CNT aggregate 6, carbon nanotubes (catalog number: FT7000) manufactured by C-nano were prepared. 2. Preparation of CNT dispersion 6 Using the obtained CNT aggregate 6, a pre-dispersion liquid 6 was obtained in the same manner as in Example 1.

[0255] The present dispersion of the pre-dispersion liquid 6 was carried out using an ultra-high pressure homogenizer (model number: NAGS100) manufactured by Tsunehiro Co., Ltd. as a wet jet mill under the following conditions to obtain a CNT dispersion liquid 6. - Dispersion conditions - Nozzle diameter: 0.22 mm Pressure: 85 MPa Number of times: 8 times Method: Circulation method

[0256] 3. Evaluation <Calculation of average curvature> Using the CNT aggregate 6, except for selecting 2 SEM images (one of which is Figure 6), the average curvature was calculated in the same manner as in Example 1. The average curvature Z (μm -1 ) was 0.095.

[0257] <Characteristic quantity of bundle diameter> Except for using the CNT aggregate 6, it was calculated in the same manner as in Example 1. As a result, the ratio of bundles with a bundle diameter of 100 nm or more was 0.10. The cumulative 90% bundle diameter was 90 nm.

[0258] <Measurement of cumulative 50% particle size D50 in volume-based particle size distribution> Except for using the CNT dispersion liquid 6, it was measured in the same manner as in Example 1. As a result, the cumulative 50% particle size D50 in the volume-based particle size distribution was 0.65 μm. The evaluation results are shown in Table 1 below.

[0259] <Viscosity of dispersion liquid of CNT aggregate> Except for using the CNT dispersion liquid 6, it was measured in the same manner as in Example 1. The viscosity of the dispersion liquid was 6.4 mPa·s. The common logarithm notation of the viscosity was 0.81.

[0260] <Tensile strength, elongation at break, fracture energy density> Except for using the CNT dispersion liquid 6, it was calculated in the same manner as in Example 1. As a result, the tensile strength was 6 .9MPa, elongation at break was 2.6%, and energy density at break was 18.0MPa·%.

[0261] <Surface resistivity> The surface resistivity was measured in the same manner as in Example 1, except for using CNT dispersion liquid 6. As a result, the surface resistivity was 16.52 Ω / □. The results are shown in Table 1 below.

[0262] <Amorphous carbon content> The amount of amorphous carbon was quantified in the same manner as in Example 1 except for using the CNT aggregate 6. As a result, the amorphous carbon content was 0.07 mass %.

[0263] (Comparative Example 2) 1. Preparation of Powdered CNT Aggregates 7 As the powdered CNT aggregate 7, carbon nanotubes manufactured by C-nano (catalog number: FT9100) were prepared.

[0264] 2. Preparation of CNT Dispersion 7 Using the obtained CNT aggregate 7, a CNT dispersion 7 was obtained in the same manner as in Comparative Example 1.

[0265] 3. Evaluation <Calculation of mean curvature> Using the CNT aggregate 7, three SEM images were selected (one of which is shown in FIG. 7), and the average curvature was calculated in the same manner as in Example 1. -1 ) was 0.088.

[0266] <Features of bundle diameter> Calculation was carried out in the same manner as in Example 1, except that CNT aggregate 7 was used. As a result, the proportion of bundles having a bundle diameter of 100 nm or more was 0.08. The cumulative 90% bundle diameter was 80 nm.

[0267] <Measurement of cumulative 50% particle size D50 in volume-based particle size distribution> Measurement was carried out in the same manner as in Example 1 except that CNT dispersion 7 was used. As a result, the cumulative 50% particle size D50 in the volume-based particle size distribution was 0.35 μm. The evaluation results are shown in Table 1 below.

[0268] <Viscosity of CNT aggregate dispersion> Measurement was carried out in the same manner as in Example 1 except that CNT dispersion 7 was used. The viscosity of the dispersion was 5.7 mPa·s. The common logarithm notation of the viscosity was 0.75.

[0269] <Tensile strength, elongation at break, fracture energy density> Calculation was carried out in the same manner as in Example 1 except that CNT dispersion 7 was used. As a result, the tensile strength was 2 .3 MPa, the elongation at break was 1.9%, and the fracture energy density was 4.3 MPa·%.

[0270] <Surface resistivity> The surface resistivity was measured in the same manner as in Example 1 except that CNT dispersion 7 was used. As a result, the surface resistivity was 15.49 Ω / □. The results are shown in Table 1 below.

[0271] <Content of amorphous carbon> Quantification of the amount of amorphous carbon was carried out in the same manner as in Example 1 except that CNT aggregate 7 was used. As a result, the content of amorphous carbon was 0.09 mass%.

[0272] [Preparation of lithium-ion secondary battery] Next, a lithium-ion secondary battery was prepared.

[0273] 1. Preparation of positive electrode for lithium secondary battery The positive electrode active material (LiNi 0.8 Co 0.1 Mn 0.1 O2), the conductive material (acetylene black), and the binder (PVdF) were mixed at a ratio such that the composition of the positive electrode active material: conductive material: binder = 92:5:3 (mass ratio), and N-methyl-2-pyrrolidone was added and kneaded to prepare a paste-like positive electrode mixture. The resulting positive electrode mixture was applied to a 15 μm thick Al foil as a current collector, and the resulting mixture was vacuum dried at 80°C for 1 hour, followed by roll pressing to obtain a positive electrode for a lithium secondary battery. The positive electrode area was 1.65 cm. 2 , basis weight 16mg / cm 2 , density is 3.0g / cm 3 It was adjusted so that

[0274] 2. Preparation of a negative electrode for lithium secondary batteries The negative electrode for the lithium secondary battery was prepared by mixing a 9:1 (mass ratio) mixture of artificial graphite MAG-E and carbon-coated SiO as the negative electrode active material, CLPA-C07 (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) as the binder, and the CNT dispersion as the conductive additive in a mass ratio of 94.9:5.0:0.1 to prepare a paste-like negative electrode mixture. Ion-exchanged water was used as the solvent for preparing the negative electrode mixture. The resulting negative electrode mixture was applied to a 20 μm thick Cu foil using a single-sided continuous coater, dried at 120°C, and then roll-pressed to obtain a negative electrode for a lithium secondary battery. The negative electrode area was 1.77 cm. 2 , basis weight 9.3mg / cm 2 , density is 1.4g / cm 3 It was adjusted so that

[0275] 3. Fabrication of Lithium Secondary Batteries The positive electrode for the lithium secondary battery was placed on the bottom cover of a coin-type battery R2032 (manufactured by Hosen Co., Ltd.), and a laminated film separator consisting of a polyethylene porous film with a 16 μm heat-resistant porous layer laminated thereon was placed on top of it. 300 μL of electrolyte was poured into the separator. The electrolyte was a 20:75:5 (volume ratio) mixture of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate, with 1% vinylene carbonate added by volume, and LiPF6 dissolved therein to a concentration of 1.3 mol / L. Next, the negative electrode for the lithium secondary battery was placed on top of the laminated film separator, and the top cover was placed with a gasket in between. The assembly was then crimped using a crimping machine to produce a coin-type full-cell R2032 lithium secondary battery. These operations were carried out in a glove box under an argon atmosphere.

[0276] 4. Cycle test The fabricated lithium ion battery was subjected to a 200-cycle cycle test under the conditions shown below, and the discharge capacity retention rate after 200 cycles was calculated using the following formula: A higher discharge capacity retention rate after 200 cycles indicates better life characteristics. Discharge capacity retention rate after 200 cycles (%) = 200th discharge capacity / 1st discharge capacity × 100

[0277] <Cycle test conditions> Test temperature: 25℃ Charging conditions: Constant current constant voltage charging, maximum charging voltage 4.2V, charging time 5 hours, charging current 0.3CA Pausing time after discharge: 10 minutes Discharge conditions: Constant current discharge, minimum discharge voltage 2.5V, discharge current 0.3CA Downtime after charging: 10 minutes In this test, one cycle was defined as a cycle in which charging, discharging, discharging, and charging were performed in that order.

[0278] The evaluation results for Examples 1 to 5 and Comparative Examples 1 and 2 are shown in Table 1.

[0279] [Table 1]

[0280] The CNT dispersions obtained by dispersing the CNT aggregates of Examples 1, 2, 3, 4, and 5 satisfy the ranges of the mean curvature Z and D50, and are therefore found to have excellent conductivity. The surface resistivity values ​​of Examples 1, 2, 3, 4, and 5 were 2.59 Ω / □, 3.31 Ω / □, 1.07 Ω / □, 0.90 Ω / □, and 1.40 Ω / □, respectively, and the viscosities of the dispersions were 142.6 mPa·s, 102.2 mPa·s, 34.6 mPa·s, 798.2 mPa·s, and 499.1 mPa·s, respectively, and the common logarithm notation of the viscosities showed appropriate values ​​of 2.15, 2.01, 2.11, 2.90, and 2.70. This confirms that the CNT aggregates of Examples have excellent conductivity and dispersibility. Therefore, it is clear that the CNT aggregates of Examples 1, 2, 3, 4, and 5 are excellent as conductive materials. On the other hand, the surface resistivity values ​​of the CNT dispersions of Comparative Examples 1 and 2 were high at 16.52 Ω / □ and 15.49 Ω / □, respectively, indicating low conductivity. The viscosities of the dispersions were also 6.4 mPa·s and 5.7 mPa·s, respectively, with common logarithm notation of viscosity being 0.81 and 0.75, respectively, which were too low for ease of handling, making them difficult to use as dispersions and resulting in poor workability. These evaluation results demonstrate that the CNT aggregates of Comparative Examples 1 and 2 are inferior as conductive materials. Therefore, it was confirmed that the CNT aggregate of the present disclosure has excellent conductivity when made into a CNT dispersion, and furthermore, it is possible to provide a CNT aggregate from which a CNT dispersion having excellent dispersibility and an appropriate viscosity can be obtained.

Claims

1. The mean curvature Z (um) of the carbon nanotube structure in the observation area by the scanning electron microscope －１ ) is equal to or greater than 0.005 and less than 0.088; The cumulative 50% particle size D50 in the volume-based particle size distribution is greater than 0.65 μm. Carbon nanotube aggregates.

2. including a bundle structure, 2. The carbon nanotube aggregate according to claim 1, wherein a cumulative 90% bundle diameter X in an observation area under a scanning electron microscope is more than 90 nm and less than 500 nm.

3. including a bundle structure, 2. The carbon nanotube aggregate according to claim 1, wherein an area ratio Y of bundles having a bundle diameter of 100 nm or more exceeds 0.1 in an observation region with a scanning electron microscope.

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

5. An electrode comprising an electrode active material and the conductive material according to claim 4 .

6. A secondary battery comprising the electrode according to claim 5 .

7. A planar aggregate comprising the carbon nanotube aggregate according to any one of claims 1 to 3.

8. A laminate comprising a substrate and the planar assembly according to claim 7.

9. A filter using the planar assembly according to claim 7.

10. An electromagnetic wave shield using the planar assembly according to claim 7.

11. A pellicle for extreme ultraviolet rays, which uses the planar assembly according to claim 7.

12. The following steps 1 to 3 are carried out on two or more images of the carbon nanotube aggregate using image analysis software ImageJ to calculate the mean curvature: A method for measuring the average curvature in a carbon nanotube aggregate.

1. Adjust the image size using Image:Adjust:Size, Width = 1280. Set the screen size to 1280 x 960 and the width to 1410 nm.

2. Fine-tune the curve so that it follows the center of the fiber under the conditions of Plugin: Analyze: Kappa, File: OpenActiveImage, and CurveFittingOptions: ChoosePoints = 100, DataThreshold = 10, Scale (μm / pixel) = 0.

16.

3. After calculating approximately eight center lines per field of view, each curvature and the average curvature are calculated.

Images