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

Abstract

The present invention provides: a carbon nanotube aggregate by which it is possible to fabricate a battery having excellent cycle characteristics, the aggregate satisfying the conditions (1) and (2); and an application thereof. (1) The amorphous carbon content is greater than or equal to 0.1 mass% and less than 2.0 mass% relative to the total mass of the carbon nanotube aggregate. (2) The carbon nanotube aggregate includes a bundle structure, and in an observation region observed by a scanning electron microscope, the area ratio of bundles having a bundle diameter of greater than or equal to 100 nm is greater than 0.1.

Description

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

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

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

[0003] For example, Patent Document 1 describes a method for removing carbonaceous impurities from carbon nanotubes, comprising a first step of providing sulfur and carbon nanotubes in a sealed space, and a second step of sulfurizing the surface of the carbon nanotubes in order to remove impurities attached to the carbon nanotubes. Patent Document 2 describes a CNT aggregate that satisfies the following conditions: a 2θ peak exists at 24°±2° by powder X-ray diffraction analysis, the height ratio of the G band to the D band (G / D ratio) by Raman spectroscopy at a wavelength of 532 nm is 30 or more, and the combustion peak temperature is 550°C or more and 700°C or less. Patent Document 3 describes a CNT aggregate that has a bundle structure, the bundles have a diameter greater than 0.3 μm, and the average diameter is 0.5 μm or more.

[0004] Japanese Patent Publication No. 2007-008803, Japanese Patent Publication No. 2009-029695, Chinese Patent Application Publication No. 116111043

[0005] When manufacturing batteries using CNT assemblies, there were times when excellent cycle characteristics were required.

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

[0007] <1> A carbon nanotube aggregate that satisfies the following conditions (1) and (2). (1) The amorphous carbon content is 0.1% by mass or more and less than 2.0% by mass of the total mass of the carbon nanotube aggregate. (2) It contains a bundle structure, and in the area observed by a scanning electron microscope, the area ratio of bundles with a bundle diameter of 100 nm or more is greater than 0.1. <2> The carbon nanotube aggregate described in <1> that satisfies the following condition (3). (3) When the carbon nanotube aggregate is mixed with water and the liquid temperature is 25°C and the concentration is 0.20% by mass, the common logarithm of the viscosity of the dispersion is greater than 1.0 and less than 3.5. The unit of viscosity is mPa·s. <3> A conductive material containing the carbon nanotube aggregate described in <1> or <2>. <4> An electrode containing an electrode active material and the conductive material described in <3>. <5> A secondary battery equipped with the electrode described in <4>. <6> A planar aggregate containing the carbon nanotube aggregate described in <1> or <2>. <7> A laminate comprising a substrate and the planar aggregate described in <6>. <8> A filter using the planar aggregate described in <6>. <9> An electromagnetic shield using the planar aggregate described in <6>. <10> An extreme ultraviolet pellicle using the planar aggregate described in <6>.

[0008] According to one embodiment of the present disclosure, a carbon nanotube aggregate capable of producing a battery with excellent cycle characteristics is provided. According to another embodiment of the present disclosure, a conductive material, an electrode, a secondary battery, and a planar aggregate comprising the carbon nanotube aggregate are provided. According to another embodiment of the present disclosure, a laminate comprising the planar aggregate is provided. According to another embodiment of the present disclosure, a filter, an electromagnetic shield, and an extreme ultraviolet pellicle using the planar aggregate are provided.

[0009] This is a scanning electron microscope image showing one aspect of CNT aggregate 1 of Example 1. This is a scanning electron microscope image showing one aspect of CNT aggregate 2 of Example 2. This is a scanning electron microscope image showing one aspect of CNT aggregate 3 of Example 3. This is a scanning electron microscope image showing one aspect of CNT aggregate 4 of Example 4. This is a scanning electron microscope image showing one aspect of CNT aggregate 5 of Example 5. This is a scanning electron microscope image showing one aspect of CNT aggregate 6 of Example 6. This is a scanning electron microscope image showing one aspect of powdered CNT aggregate 7 of Comparative Example 1. This is a scanning electron microscope image showing one aspect of powdered CNT aggregate 8 of Comparative Example 2.

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

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

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

[0013] [CNT aggregate] The CNT aggregate according to this disclosure satisfies the following conditions (1) and (2): (1) The amorphous carbon content is 0.1% by mass or more and less than 2.0% by mass of the total mass of the CNT aggregate. (2) It contains a bundle structure, and in the area observed by a scanning electron microscope, the area ratio of bundles with a bundle diameter of 100 nm or more is greater than 0.1.

[0014] A CNT assembly that satisfies conditions (1) and (2), i.e., the CNT assembly according to this disclosure, can be used to produce a battery with excellent cycle characteristics. On the other hand, Patent Documents 1 to 3 do not contain any descriptions that focus on conditions (1) and (2).

[0015] In Patent Document 1, amorphous carbon is removed as an impurity that inhibits the inherent properties of CNTs, such as high conductivity. However, while removing amorphous carbon makes it easier for CNTs to exhibit their inherent properties, it also increases the aggregation of CNTs too much. As a result, the dispersibility of the CNT aggregate in solvents, etc., decreases, and it may become unsuitable for use as a conductive additive. On the other hand, CNTs containing an excess of amorphous carbon tend to lose their inherent properties, such as physical robustness (tensile strength and fracture strength) and high conductivity. Furthermore, in Patent Documents 2 and 3, the control of the bundle diameter was insufficient. In contrast, the CNT aggregate according to the present disclosure can produce a battery with excellent cycle characteristics by satisfying conditions (1) and (2).

[0016] <Condition (1)> The CNT aggregate relating to this disclosure has an amorphous carbon content of 0.1% by mass or more and less than 2.0% by mass of the total mass of the CNT aggregate.

[0017] The CNT aggregate relating to this disclosure includes amorphous carbon.

[0018] CNT aggregates may contain amorphous carbon, for example, adsorbed on the surface of the CNT aggregate, or incorporated into the interior of fibrous CNT aggregates formed during manufacturing.

[0019] Amorphous carbon is produced as a by-product in the manufacturing process of carbon nanotubes (CNTs). Since amorphous carbon and CNTs have different physical and chemical properties, controlling the amorphous carbon content is important. For example, in the synthesis of CNTs using chemical vapor deposition (CVD), amorphous carbon is generated when hydrocarbon gas is decomposed at high temperatures. In this process, carbon atoms are deposited on the catalyst metal surface and CNTs grow, while amorphous carbon is simultaneously generated 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 this disclosure, the battery cycle characteristics are improved by controlling the amorphous carbon content to 0.1% by mass or more and less than 2.0% by mass.

[0020] From the viewpoint of further improving the battery's cycle characteristics, the amorphous carbon content is preferably 0.1% by mass or more and less than 1.9% by mass relative to the total mass of the CNT aggregate. Furthermore, the amorphous carbon content is preferably 0.20% by mass or more and less than 2.0% by mass, more preferably 0.22% by mass or more and less than 2.0% by mass, even more preferably 0.22% by mass or more and less than 1.9% by mass, particularly preferably 0.22% by mass or more and less than 1.85% by mass, and most preferably 0.24% by mass or more and 1.80% by mass or less, relative to the total mass of the CNT aggregate.

[0021] By having an amorphous carbon content of 0.1% to less than 2.0% by mass relative to the total mass of the CNT aggregate, the amorphous carbon is appropriately dispersed on the surface of the CNTs, resulting in improved conductivity and mechanical strength as an electrode material. Specifically, the amorphous carbon reduces contact resistance between CNTs, promoting efficient current flow. The scattering of amorphous carbon on the surface of the CNTs weakens the van der Waals forces between CNTs and suppresses aggregation, making it easier to disperse widely within the electrode. This allows for the formation of a uniform conductive path within the electrode through communication between electrode active materials. Furthermore, the amorphous carbon stabilizes the bundle structure of the CNTs, improving the structural stability of the electrode and mitigating volume changes and stress during the cycle. Therefore, it is believed that a battery with excellent cycle characteristics can be obtained. In addition, it suppresses electrode degradation due to swelling and shrinkage of the electrode active material during charging and discharging, thereby improving the battery's cycle characteristics.

[0022] The amorphous carbon content in the CNT aggregates relating to this disclosure is calculated by thermogravimetric differential thermal analysis (TG-DTA). In thermogravimetric differential thermal analysis (TG-DTA), the constituent elements and quality of the carbon material are evaluated by analyzing the peak combustion temperature and residues after heating to approximately 900°C at a rate of approximately 10°C / min. For example, carbon material obtained by suspended catalytic chemical vapor deposition (FCCVD) is a mixture of metals (e.g., iron (Fe)) contained in the catalyst raw materials, CNTs, amorphous carbon, and graphite 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 graphite carbon begin burning at around 400°C and completely burn at around 700°C. Therefore, the amorphous carbon content can be calculated from the difference in weight loss between 200°C and 400°C.

[0023] When measuring the amorphous carbon content, a powder of CNT aggregates is used as the measurement sample. If the CNT aggregates are in a form other than powder (e.g., fibers or sheets), the CNT aggregates can be pulverized to obtain a powder. The pulverization process is not particularly limited; any pulverization process that can break the CNT aggregates into small pieces can be used. As a pulverization process, freeze-drying can be used.

[0024] <Condition (2)> The CNT aggregate relating to this disclosure includes a bundle structure, and in the area observed by a scanning electron microscope (SEM), the area ratio of bundles with a bundle diameter of 100 nm or more is greater than 0.1.

[0025] The CNT aggregates relating to this disclosure include bundle structures. A bundle structure refers to an aggregate in which multiple CNTs are aggregated together by van der Waals forces or the like, forming a bundle. It is presumed that including bundle structures of an appropriate size in a CNT aggregate improves the handling properties of the CNT aggregate and further enhances its stability. On the other hand, if the bundle structures included in the CNT aggregate become too large, the size of the CNT aggregate itself becomes too large, and it becomes difficult to separate and disperse the CNTs included in the bundle structure, which may reduce its dispersibility in the dispersion medium.

[0026] The bundle structure in the CNT aggregate can be formed, for example, by controlling the catalyst particle size distribution during manufacturing by chemical vapor deposition (CVD) or by controlling the cooling rate during the cooling process.

[0027] From the viewpoint of achieving both the handling properties and dispersibility in the solvent of the CNT aggregate, the width of the individual bundle structures contained in the CNT aggregate, i.e., the size in the width direction of the fiber bundle, is preferably 5 nm to 500 nm, and more preferably 10 nm to 300 nm. The content of bundle structures in the CNT aggregate is preferably 10% to 100% by mass, and more preferably 20% to 90% by mass, based on the total mass of the CNT aggregate. The presence or absence of bundle structures in the CNT aggregate can be confirmed by observing the CNT aggregate with an optical microscope, a scanning electron microscope (SEM), etc. The width of the bundle structure can be determined by identifying the location where the bundle structure exists in the CNT aggregate and measuring the length using an image of the bundle structure.

[0028] In the CNT aggregate according to this disclosure, the area ratio of bundles with a bundle diameter of 100 nm or more exceeds 0.1 in the SEM observation area, resulting in the appropriate formation of a CNT bundle structure and improved mechanical strength and conductivity as an electrode material. Specifically, a bundle diameter of 100 nm or more strengthens the bonding between CNTs, making the electron transport pathways connecting electrode active materials more robust, thereby improving the structural stability of the electrode. Furthermore, a large bundle diameter increases the electron conduction pathways within the electrode, promoting efficient current flow. This reduces the internal resistance of the battery and improves charge-discharge efficiency. Therefore, in the SEM observation area, a battery with excellent cycle characteristics can be obtained by having an area ratio of bundles with a bundle diameter of 100 nm or more exceeding 0.1.

[0029] In particular, the area ratio of the above bundle is preferably greater than 0.1 and 0.6 or less, more preferably greater than 0.1 and 0.55 or less, even more preferably greater than 0.1 and less than 0.5, especially preferably 0.13 or more and less than 0.5, even more preferably 0.13 or more and 0.45 or less, and particularly preferably 0.13 or more and 0.41 or less. Furthermore, the area ratio of the above bundle is preferably greater than 0.1 and less than 0.8, more preferably 0.11 or more and less than 0.6, and even more preferably 0.12 or more and 0.55 or less. Within this range, the bundle structure of the CNTs is appropriately formed, and the bonding between the CNTs is strengthened, thereby improving the mechanical strength of the electrode. In addition, an appropriate bundle diameter improves the dispersibility of the CNTs and ensures a uniform conductive path within the electrode. As a result, the conductivity of the entire electrode is improved and the internal resistance of the battery is reduced, resulting in excellent cycle characteristics.

[0030] Furthermore, from the viewpoint of increasing the elongation at break, the area ratio of the bundle is more preferably 0.20 to 0.55, and particularly preferably 0.20 to 0.45. A higher elongation at break improves the flexibility and durability of the material containing the CNT aggregate. Moreover, an area ratio of 0.20 to 0.55 is also particularly preferred. A higher elongation at break improves the flexibility and durability of the material containing the CNT aggregate.

[0031] Furthermore, it is preferable that the area ratio of the bundle is greater than 0.1 and less than or equal to 0.55. Within this range, the bundle diameter of the CNTs becomes appropriately small, increasing the surface area as an electrode material and widening the contact area with the electrode active material. This promotes ion movement and improves the charge and discharge efficiency of the battery. In addition, an appropriately small bundle diameter also has the effect of increasing the flexibility of the electrode and improving its resistance to volume changes during the cycle. Therefore, the cycle characteristics of the battery are further improved.

[0032] Furthermore, in SEM observation, the bundle diameter at which 90% of the total volume is cumulative is preferably greater than 90 nm and less than or equal to 300 nm. When the bundle diameter at which 90% of the total volume is cumulative is greater than 90 nm, the bundles of CNTs gather together, making it easier to form long-distance conductive networks. Also, when the bundle diameter at which 90% of the total volume is cumulative is less than or equal to 300 nm, the dispersibility in the dispersion medium is good, making it easier to ensure conductivity. The bundle diameter at which 90% of the total volume is cumulative is preferably greater than 90 nm and less than or equal to 250 nm, and more preferably greater than 100 nm and less than or equal to 250 nm.

[0033] The bundle diameter of the CNT aggregate is measured by observation using a scanning electron microscope (SEM). Multiple SEM images are obtained by photographing the CNT aggregate at a magnification of 100,000x. The imaging method using the SEM is not particularly limited and can be carried out using known methods.

[0034] -Imaging- Images of the CNT aggregate are obtained by imaging using an SEM device (for example, Hitachi High-Technologies Corporation, S-4800) under the following conditions. From the viewpoint of reducing the variance of the analyzed bundle diameter, it is preferable to obtain five or more images. Acceleration voltage: 0.5 kV Emission current: 10 μA Magnification: 100,000x Image size: 1280 pixels × 960 pixels

[0035] - Image Selection - From the obtained images, select two or more images in which CNT bundles are frequently observed.

[0036] - Overview of Bundle Diameter Analysis using Image Analysis - Image processing and image analysis are performed on the selected image using Python. In image processing, the contours and centerlines of the CNTs are detected and combined with the original image. In image analysis, the bundle diameter is determined by calculating the distance from the centerline to the contour in the created image. Then, the product of the bundle diameter and the length of the centerline is calculated to determine the area occupied by the CNTs in the image.

[0037] -Detection of CNT contours using image analysis- 1. Binarize the image to distinguish between CNTs and the background. 2. Create contours for the CNT portions using the edge detection function of the OpenCV library.

[0038] -Detection of CNT centerlines using image analysis- 1. Adjust parameters to distinguish between CNTs and background and perform binarization. 2. Create a skeleton for the CNT portion using the skeletonize function of the scikit-image library. 3. For each coordinate of the skeleton, count the number of skeletons in the surrounding 2 pixels and recognize coordinates with 5 or more skeletons as skeleton intersections. 4. Divide the skeleton at the intersections by converting the intersections to background pixels. The resulting skeletons are called regions. 5. Measure the length of the regions and delete the shorter regions. 6. Perform linear approximation for each region. 7. For each created line, obtain the X-axis coordinate of the region from which the approximation was made. Convert the line into a line segment based on the interval in which the obtained X-coordinate exists. Treat the line segment obtained here as the centerline of the CNT. 8. Calculate the similarity based on the center coordinates and angles for all sets of centerlines. If the distance between the center coordinates is within 10 pixels and the angle between the two line segments is less than 10 degrees, treat the pair of center lines as duplicate center lines and delete the shorter one. 9. Overlay the CNT contour and center lines onto the original image and save. The contour will be treated in red, and the center lines in blue.

[0039] -Detection of CNT bundle diameter by image analysis- 1. Load an image created by image processing and recognize CNTs, contours, background, and center lines using hue recognition. 2. Measure the length of each center line. 3. Select a random point on the center line and draw a perpendicular line from the point to the center line. 4. Detect the intersection point of the perpendicular line and the contour, and save the distance from the random point on the center line to the intersection point as the bundle diameter. 5. Calculate the occupied area as the product of the length of the center line segment and the bundle diameter. Save the data as a histogram with the bundle diameter on the horizontal axis and the occupied area on the vertical axis.

[0040] - Obtaining Bundle Diameter Parameters - Using the calculated bundle diameter histogram data, the bundle diameter features of each sample are calculated using the following method: 1. Add the bundle diameters and occupied areas of multiple fields of view of the same sample and normalize so that the sum is 1. With normalization, the unit of the vertical axis is set to occupied area ratio. 2. Find the sum of the occupied area ratios of bundles with a bundle diameter of 100 nm or more. 3. Calculate the cumulative occupied area ratio and determine the bundle diameter at which this value first exceeds 0.9 as the cumulative 90% bundle diameter.

[0041] <Condition (3)> The CNT aggregate relating to this disclosure has a common logarithm of viscosity greater than 1.0 and less than 3.5 when the CNT aggregate is mixed with water at a liquid temperature of 25°C and a concentration of 0.20% by mass. The unit of viscosity is mPa·s.

[0042] When the common logarithm of the viscosity of the above dispersion is greater than 1.0 and less than 3.5, the dispersibility of CNTs is improved, and the performance as an electrode material is optimized.

[0043] The common logarithm of the viscosity of the above dispersion is more preferably 1.1 or more and less than 3.5, and even more preferably 1.5 or more and less than 3.5. Furthermore, the common logarithm of the viscosity of the above dispersion is more preferably greater than 1.0 and less than 3.3, even more preferably 1.1 or more and less than 3.3, even more preferably 1.5 or more and less than 3.3, and particularly preferably 1.52 or more and 2.98 or less. By appropriately controlling the viscosity of the dispersion, the dispersibility of CNTs is improved and the performance as an electrode material is optimized. Specifically, when the common logarithm of the viscosity of the above dispersion is 1.1 or more and less than 3.5, the dispersion of CNTs is maintained uniformly, and conductive paths are efficiently formed within the electrode. As a result, the conductivity of the electrode is improved and the internal resistance of the battery is reduced, so the charge-discharge efficiency of the battery is improved and the cycle characteristics are further improved. Furthermore, when the common logarithm of the viscosity of the above dispersion is greater than 1.0 and less than 3.3, the dispersion of CNTs is further improved and the mechanical strength as an electrode material is improved. This allows the electrodes to be more durable against volume changes and stress during the cycle, contributing to battery life. In particular, when the common logarithm of the viscosity of the dispersion is between 1.1 and 3.3, the balance between the dispersibility and conductivity of the CNTs is optimized, and the performance as an electrode material is maximized. Within this range, uniform dispersion of CNTs and high conductivity can be achieved simultaneously, and a significant improvement in the battery's cycle characteristics is expected.

[0044] The viscosity of the CNT dispersion is measured using a cone-plate viscometer (also known as an E-type viscometer). For example, the Brookfield DV-II+Pro Programmable Viscometer is used as a cone-plate viscometer. The measurement conditions are as follows: Measurement fixture: Cone-plate; Measurement mode: Rotational mode; Shear speed: 0.6 s －１ ~384 simultaneous －１ Temperature: 25°C. From the obtained data, read the viscosity at the following shear rate: Shear rate = 12s －１

[0045] The CNT aggregates according to this disclosure have a high affinity for the dispersion medium, which tends to result in a lower viscosity of the dispersion. When the viscosity of the dispersion is within an appropriate range, it can be determined that the dispersibility of the aggregates according to this disclosure in the dispersion medium is good. The viscosity of the dispersion is preferably 10 mPa·s to 1600 mPa·s, more preferably 10 mPa·s to 1500 mPa·s, even more preferably 30 mPa·s to 1300 mPa·s, particularly preferably 100 mPa·s to 1200 mPa·s, even more preferably 100 mPa·s to 1000 mPa·s, especially preferably 300 mPa·s to 980 mPa·s, and particularly preferably 127.4 mPa·s to 953.2 mPa·s. In other embodiments, from the viewpoint of achieving both dispersibility and battery performance, the viscosity of the dispersion is more preferably 30 mPa·s to 1600 mPa·s, even more preferably 300 mPa·s to 1600 mPa·s, and particularly preferably 400 mPa·s to 1600 mPa·s. In yet another embodiment, from the viewpoint of prioritizing dispersibility more than other factors in achieving both dispersibility and battery performance, the viscosity of the dispersion is more preferably 30 mPa·s to 1600 mPa·s, even more preferably 30 mPa·s to 1300 mPa·s, particularly preferably 30 mPa·s to 1200 mPa·s, even more preferably 30 mPa·s to 1000 mPa·s, and especially preferably 33.2 mPa·s to 953.2 mPa·s.

[0046] <Other matters concerning CNT aggregates> In this disclosure, the CNTs included in the CNT aggregate may be SWCNTs or MWCNTs. From the viewpoint that having a layer distribution and slightly lower uniformity contributes to satisfying conditions (1) and (2), it is preferable that the CNT aggregate includes SWCNTs and MWCNTs.

[0047] The maximum length of the CNTs included in the CNT aggregate relating to this disclosure is not particularly limited.

[0048] In one embodiment, the CNT aggregate may mainly consist of CNTs with a maximum length of 500 μm or less, and may not contain CNTs with a length greater than 500 μm and less than or equal to 30,000 μm. Here, "main component" means that 90% by mass or more of the CNTs constituting the CNT aggregate are CNTs with a maximum length of 500 μm or less. The CNT aggregate may also contain CNTs with a maximum length of 500 μm or less.

[0049] The CNT aggregates according to this disclosure include, for example, CNTs having a maximum length of 10 μm to 30,000 μm. The CNT aggregates according to this disclosure preferably include CNTs having a maximum length of 500 μm or more, more preferably include CNTs having a maximum length of 500 μm to 30,000 μm, and even more preferably include CNTs having a maximum length of 1,000 μm to 30,000 μm (i.e., ULCNTs).

[0050] ULCNTs are longer in length and can take the form of fibers compared to general-purpose CNTs. When the maximum length of the CNTs included in the CNT aggregate according to this disclosure is 500 μm or more, the entanglement between the CNTs becomes moderately strong, and the CNTs tend to form a network structure more easily.

[0051] By taking the form of fibers, ULCNTs have a tendency to entangle with each other. A CNT aggregate is preferably an aggregate containing multiple ULCNTs, as this allows the CNTs to entangle with each other and form a more stable aggregate. Hereinafter, an aggregate containing ULCNTs may be abbreviated as an "ULCNT aggregate."

[0052] Here, the term "fiber" is generally used to refer to a structure in which one dimension is larger than the other two dimensions. The fiber may be a thread-like fiber with a circular cross-section, a ribbon-like fiber with a rectangular cross-section, hollow, or have other shapes. From the viewpoint of improving conductivity, the cross-section of the CNTs contained in the CNT aggregate is preferably circular and preferably hollow.

[0053] The CNT aggregate may be an aggregate of three-dimensional structures in which the CNTs are intertwined. The intertwined state of the CNTs in the CNT aggregate according to this disclosure can be confirmed by SEM observation.

[0054] The length of individual carbon nanotubes (CNTs) within a CNT aggregate can be measured by focusing on a single CNT and observing multiple SEM images within adjacent fields of view. Here, "CNT length" refers to the measured length in the longitudinal direction of the CNT, and the maximum value among the measured lengths is defined as the "maximum length." If, by observing the SEM images, one CNT with a maximum length in the range of 1,000 μm to 30,000 μm is observed within the field of view of the SEM image, it can be confirmed that the observed CNT contains a ulcerative colloidal cell (ULCNT).

[0055] It is preferable that multiple ULCNs are present within the field of view of the SEM image. Focusing on 100 CNTs included in the field of view of the SEM image, the maximum length of each is measured, and of the observed CNTs, it is preferable that 10% or more (in numerical terms) of the CNTs have a maximum length in the range of 1000 μm to 30000 μm (i.e., ULCNs), from the viewpoint of further improving the stability of the CNT aggregate due to the entanglement of ULCNs, more preferably 20% or more, even more preferably 30% or more, and particularly preferably 50% or more.

[0056] The diameter of an ULCNT can be measured by observing a SEM (Surface-Emission Microscope) or transmission electron microscope (TEM) image. Here, diameter refers to the length in the direction perpendicular to the longitudinal direction of the ULCNT. The diameter is measured at 10 different points on a single ULCNT, and the average value is taken as the diameter of that ULCNT.

[0057] The length of the ULCNT is in the range of 1,000 μm to 30,000 μm, preferably in the range of 1,050 μm to 25,000 μm, more preferably in the range of 1,100 μm to 20,000 μm, even more preferably in the range of 1,200 μm to 18,000 μm, and particularly preferably in the range of 1,300 μm to 15,000 μm. The diameter of the ULCNT is preferably in the range of 1 nm to 100 nm, more preferably in the range of 2 nm to 80 nm, even more preferably in the range of 3 nm to 50 nm, and particularly preferably in the range of 5 nm to 30 nm.

[0058] The length / diameter ratio, or aspect ratio, of the ULCNT is preferably 1000 or more, more preferably 3000 or more, even more preferably 5000 or more, and particularly preferably 10000 or more. The aspect ratio can be calculated from the ratio of the maximum length to the diameter of a single ULCNT. From the viewpoint of measurement accuracy, it is preferable to use the average value of the measurements of 20 or more ULCNTs.

[0059] Furthermore, from the viewpoint of dispersibility, the specific gravity of the ULCNT aggregate is preferably in the range of 1.5 to 2.5, more preferably in the range of 1.7 to 2.4, and even more preferably in the range of 1.8 to 2.2. The specific gravity of the ULCNT aggregate can be measured by the method described in JIS Z8807:2012 "Method for measuring the density and specific gravity of solids".

[0060] The purity of carbon as CNTs in an ULCNT aggregate can be measured by thermogravimetric analysis. For example, a thermogravimetric (TG) curve and a differential thermal analysis (DTA) curve of the ULCNT aggregate are obtained using a thermal analyzer (Shimadzu Corporation, DTG-60). In the DTA curve, where the peak top appears around 650°C to 750°C, the largest exothermic peak is considered to be the combustion of CNTs, and other exothermic peaks are considered to be the combustion of substances other than CNTs. The purity of the CNTs is determined from the weight loss rate of the TG curve. From the viewpoint of the resulting conductivity, the purity of the ULCNT aggregate is preferably 50% by mass or more, more preferably 65% ​​by mass or more, even more preferably 80% by mass or more, and particularly preferably 95% by mass or more.

[0061] The obtained fibrous ULCNT is preferably flexible and strong. Also, the conductivity of the ULCNT itself is preferably 5000 ohm －１ ·m －１ or more, and more preferably 10000 ohm －１ ·m －１ or more. Note that the conductivity of the ULCNT itself is usually 1000000 ohm －１ ·m －１ or less.

[0062] <Method for manufacturing CNT> The method for manufacturing CNT in the present disclosure is not particularly limited. For example, as the method for manufacturing CNT in the present disclosure, methods such as a 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.

[0063] The CNT 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.

[0064] Hereinafter, the method for manufacturing CNT in the present disclosure will be described with examples. However, the method for manufacturing CNT in the present disclosure is not limited to the following examples.

[0065] = Manufacturing method X = As an example of the method for manufacturing CNT 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 outside the reaction region (hereinafter, also referred to as "manufacturing method X").

[0066] According to manufacturing method X, CNT containing ULCNT can be obtained in the form of fibrous aggregates or other aggregates that are easy to handle.

[0067] In manufacturing method X, the force applied to the product particles may be a mechanical force. If the aggregate is fibrous CNT, the mechanical force applied to the product particles can be applied by a rotating spindle around which the aggregate is wound. The fibrous CNT may be collected on the spindle, or it may be accumulated elsewhere after being rotated around the spindle once or more times, as the spindle is continuously unwound.

[0068] Preferably, the spindle axis is positioned perpendicular or parallel to the flow direction of one or more gaseous reactants, but it may be positioned in other orientations. For example, a spindle with its axis positioned at a 25° angle to the flow direction of the gaseous reactants can also be suitably used to apply mechanical force to product particles.

[0069] The spindle can rotate around two axes (for example, two vertical axes). In particular, the spindle can rotate around axes perpendicular and parallel to the flow direction of the gaseous reactant. Such a spindle allows for the pulling and twisting of aggregates, which are fibrous carbon nanotubes, to control the number of twists and length.

[0070] The spindle material may be metal, ceramic, or resin. The spindle can take on different suitable shapes depending on the material properties and the intended use of the CNTs. The spindle can be used, for example, as a mold for producing carbon products by a spin-coating process. Preferred spindle shapes are rod-shaped or box-shaped.

[0071] Fibrous carbon nanotubes (CNTs) are accumulated on the spindle or elsewhere, and the coating thickness and orientation can be controlled by controlling the reaction time and reaction conditions, or by applying an electric field or other field to the carbon product. The coating thickness and orientation of the carbon product can be controlled, for example, by the fluidity of the gas.

[0072] The spindle rotation speed is preferably 0.01 rpm (revolutions per minute; the same applies hereafter) to 10,000 rpm, and more preferably 0.1 rpm to 100 rpm. The spinning speed (i.e., the spindle rotation speed) may be adjusted so that the material is recovered at the same rate as it is produced. The spindle rotation speed may be used to control the thickness of the accumulated fibrous CNTs. In one preferred embodiment, as the spindle rotates, the fibrous CNTs are processed in the axial direction of the spindle. In this processing, the fibrous CNTs are wound evenly along the spindle, rather than being wound at only one specific point on the spindle.

[0073] Fibrous CNTs may be recovered onto the reactor wall, for example, by a substrate placed in the reactor. The substrate may be a fixed substrate or a rotating guide used to apply a strong and equal force to the fibrous CNTs when they are recovered. A suitable substrate arrangement used in fiber technology is a substrate consisting of two guides positioned orthogonally to each other.

[0074] In manufacturing method X, the mechanical force applied to the product particles may be a force applied by an accelerating gas flow. The accelerating gas flow can be generated by passing the product particles through a reactor having a narrow diameter or through a capillary tube located downstream of the reaction region. A vacuum may be applied to the product particles.

[0075] Other forces applied to the product particles include electrostatic forces appropriately applied by a charged plate. When using electrostatic forces, the product particles must be charged. By using a charged plate, CNTs can be generated on the plate in the form of intertwined sheets.

[0076] Furthermore, other forces applied to the generated particles may include magnetic force or photon pressure applied by a light source.

[0077] The raw material for CNTs may be injected in the form of a liquid containing a carbon source, instead of a gaseous reactant containing a carbon source. When a liquid is used as the raw material for CNTs, it can be injected through a single inlet or multiple inlets, for example, in a showerhead configuration.

[0078] One or more gaseous reactants are preferably reacted at 500°C to 1600°C, and more preferably at 1000°C to 1500°C. The temperature gradient is maintained within the reactor, and the reaction region is preferably kept at a higher temperature than the product region of the reactor.

[0079] The gaseous reactant may be used in combination with one or more gases that act as diluents. The gaseous reactant may also be used in combination with gases that do not play a direct role in the reaction but play an auxiliary role. If amorphous carbon is produced as a byproduct, it is also preferable to use a gas as a diluent that can react with amorphous carbon to maintain the reaction sites on the catalyst and produce nanotubes.

[0080] Gases that can be used as diluents include argon or other inert gases, hydrogen, nitrogen, ammonia, carbon dioxide, and helium. Among these, hydrogen is particularly preferred as a diluent.

[0081] The composition of the product particles can be controlled by monitoring the aggregates and changing the reaction conditions based on the information obtained. For example, aggregates can be monitored by online Raman spectroscopy. Online Raman spectroscopy provides data indicating whether the aggregates are single-layer or multi-layer CNTs. It also provides data indicating the diameter and crystallinity of the CNTs. Aggregates can also be monitored by online conductivity measurement, gas analysis, measurement of the opacity of the reaction region, and / or measurement of the winding force.

[0082] When removing aggregates from the reactor, it is preferable to prevent air from entering the reactor. Preventing air inflow is particularly important, for example, when the diluent gas contains hydrogen, as it helps to prevent the formation of an explosive mixture of hydrogen and air in the reactor.

[0083] The product particles produced in manufacturing method X contain ULCN. Depending on the manufacturing conditions, SWCNTs and MWCNTs may also be present.

[0084] The product particles may be generated by chemical vapor deposition. When the product particles are generated by chemical vapor deposition, the carbon source, which is a gaseous reactant, reacts in the presence of a catalyst.

[0085] Suitable carbon-containing compounds as carbon sources include carbon monoxide, carbon dioxide, aromatic hydrocarbons (e.g., benzene, toluene, xylene, cumene, ethylbenzene, naphthalene, or mesitylene), non-aromatic hydrocarbons (e.g., methane, ethane, propane, butane, pentane, hexane, cyclohexane, ethylene, propylene, or acetylene), and oxygen-containing hydrocarbons (e.g., formaldehyde, acetaldehyde, acetone, methanol, ethanol, diethyl ether, polyethylene glycol, 1-propanol, ethyl formate, or hydrocarbons containing two or more of these). Carbon monoxide, methane, ethylene, or acetylene are preferred as carbon-containing compounds.

[0086] The carbon source preferably contains oxygen. Ethanol is a particularly preferred carbon source. Oxygen can be introduced into the reactor by other means, for example, by using a carbon source containing a diluent gas or water.

[0087] As catalysts, transition metals are preferred, particularly chromium (Cr), molybdenum (Mo), tungsten (W), or VIII-B transition metals. Specifically, preferred catalysts include, for example, iron (Fe), cobalt (Co), nickel (Ni), ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os), iridium (Ir), and platinum (Pt) or manganese (Mn), or mixtures thereof. Metals from the lanthanide and actinide series (e.g., yttrium (Y)) can also be used as catalysts. Fe, Ni, Co, Mo, and mixtures thereof are preferred, for example, a mixture of Ni and Co (mass ratio: 50 / 50), a mixture of Fe and Ni, or a mixture of Fe and Mo are more preferred. Any of these transition metals can be used alone or in combination with any of the other transition metals listed above to function as catalysts for the growth of CNTs. The catalyst is particularly preferably a mixture of two or more of the listed metals.

[0088] The catalyst is preferably formed by the decomposition of a precursor. The precursor is preferably a thermal, photocatalytic, or plasma-degradable compound of one or more of the above-mentioned metals, such as a carbonyl or cyclopentadienyl organometallic compound. Ferrocene, iron pentacarbonyl, nickerocene, and cobaltocene are particularly preferred as precursors. In some embodiments, at least 0.01% by mass of the precursor is contained in the carbon source, preferably 0.2% to 30% by mass of the precursor, and more preferably 0.2% to 20% by mass of the precursor. In some embodiments, 0.23% to 2.3% by mass of the precursor may be contained in the carbon source, and 0.02% to 20% by mass of the precursor. The catalyst may also be used supported on a carrier. Preferred carriers include silica and magnesium oxide.

[0089] The carbon source is preferably reacted in the presence of an accelerator. Suitable accelerators are one or more of sulfur, phosphorus, molybdenum, and organic compounds of these elements. Thiophene is also a preferred accelerator. Preferably, the accelerator is contained in the carbon source at a concentration of up to 10% by mass. Preferably, the accelerator is contained in the carbon source at a concentration of 0.2% to 6% by mass. When high or low concentrations of thiophene are used as the accelerator, MWCNTs are formed.

[0090] According to manufacturing method X, fibrous CNTs having a length of at least 500 μm, for example, at least 1 mm, can be obtained. The fibrous CNTs can take the form of threads or sheets. The length of the fibrous CNTs can be controlled, for example, by the winding capacity of the spindle used when manufacturing the fibrous CNTs.

[0091] The manufacturing method X preferably includes the steps of generating CNTs by reacting a carbon source in the reaction region of a reactor, and agglomerating the CNTs into aggregates by applying force to them. This manufacturing method makes it possible to easily produce fibrous CNTs.

[0092] The manufacturing method X preferably further includes a step of passing the obtained CNT aggregates through a sieve after the step of agglomerating the CNTs into aggregates. It is also preferable to recover the CNTs that have passed through the sieve. By passing the obtained CNT aggregates through a sieve, CNT aggregates that satisfy conditions (1) and (2) are more easily obtained.

[0093] The method of passing the material through the sieve is not particularly limited and can be carried out by commonly known methods. The mesh size of the sieve is, for example, 0.1 mm to 3.0 mm, preferably 0.5 mm to 2.0 mm, and more preferably 1.0 mm to 1.5 mm. The material of the sieve is not particularly limited and may be metal or resin. When the CNT aggregate is applied to an electrode (especially an electrode 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 aggregate through the sieve, the CNT aggregate may be cut into appropriate sizes beforehand.

[0094] Furthermore, it is preferable to use two types of sieves with different mesh sizes and pass the material through the sieves two or more times. By using the sieve with the relatively smaller mesh size among the two types of sieves, it is possible to remove amorphous carbon and other particles that have become dusty. Alternatively, by using the sieve with the relatively larger mesh size among the two types of sieves, it is possible to remove foreign matter and coarse CNTs that may have entered from the outside.

[0095] By passing the obtained CNT aggregates through a sieve and recovering the CNTs that pass through the sieve, coarse CNTs are removed, improving the stability of the CNT dispersion. In addition, while foreign matter introduced from the outside is generally removed during electrode manufacturing, passing the obtained CNT aggregates through a sieve allows for a simpler method of removing foreign matter introduced from the outside.

[0096] In other embodiments, the method may include generating CNTs containing ULCNTs in a reaction region by the above method, condensing them to form CNTs containing ULCNTs, and continuously withdrawing CNTs from near the reaction region. In yet other embodiments, the method may include generating CNTs containing ULCNTs in a reaction region, continuously electrostatically attracting CNTs containing ULCNTs from the reaction region, and recovering CNTs containing ULCNTs.

[0097] =Manufacturing Method Y= In this disclosure, as an example of a method for manufacturing CNTs, the manufacturing method described in Japanese Patent Publication No. 2021-527611 can be referenced. That is, a mixture containing a main catalyst precursor and a co-catalyst precursor is γ-Al ２ O ３ A manufacturing method (hereinafter also referred to as "manufacturing method Y") includes the steps of: (1) supporting the active support on a material to produce an active support; (2) drying the active support by multi-stage drying including vacuum drying; (3) heat-treating the dried active support to produce a supported catalyst; and (4) producing CNTs in the presence of the supported catalyst.

[0098] Step (1) Step (1) involves mixing a main catalyst precursor and a co-catalyst precursor in γ-Al ２ O ３ The active support is manufactured by supporting it on a material.

[0099] The main catalyst precursor and co-catalyst precursor are γ-Al ２ O ３ To ensure uniform support, the mixture may further contain a solvent, and the main catalyst precursor and co-catalyst precursor may be dissolved in the solvent. The solvent may be one or more selected from the group consisting of water, methanol, and ethanol, with water being preferred.

[0100] γ-Al ２ O ３ Because it has high porosity and a spinel structure, the main catalyst and co-catalyst are γ-Al ２ O ３ They can be arranged irregularly. CNTs grown from an irregularly arranged main catalyst can be produced in an entangled manner.

[0101] The main catalyst may be one or more selected from the group consisting of cobalt, iron, nickel, manganese, and chromium, with cobalt being preferred.

[0102] 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.

[0103] The main catalyst precursor is Co(NO ３ ) ２ Co(NO ３ ) ２ 6H ２ O, Co ２ (CO) ８ Co ２ (CO) ６ [HC=C(C(CH ３ ) ３ ) ], Co (CH ３ CO ２ ) ２ Fe(NO ３ ) ３ Fe(NO ３ ) ２ nH ２ O, Fe(CH ３ CO ２ ) ２ Ni (NO ３ ) ２ Ni (NO ３ ) ２ 6H ２O, Mn (NO ３ ) ２ , Mn(NO ３ ) ２ 6H ２ O, Mn(CH ３ CO ２ ) ２ ・n(H ２ O) and Mn(CO) ５ It may be one or more selected from the group consisting of Br, and among these, Co(NO ３ ) ２ 6H ２ O, Fe (NO ３ ) ２ nH ２ O, Ni (NO ３ ) ２ 6H ２ O is preferred.

[0104] The co-catalyst improves the dispersibility of the main catalyst and may be one or more selected from the group consisting of vanadium and molybdenum.

[0105] The co-catalyst precursor is NH ４ VO ３ NaVO ３ , V ２ O ５ , V(C ５ H ７ O ２ ) ３ , and (NH ４ ) ６ Mo ７ O ２４ 4H ２ It may be one or more selected from the group consisting of O, and NH ４ VO ３ and (NH ４ ) ６ Mo ７ O ２４ 4H ２ It is preferable to select one or more from the group consisting of O.

[0106] When the mixture contains two or more co-catalyst precursors, that is, when it contains both a vanadium precursor and a molybdenum precursor, the molar ratio of the sum of vanadium and molybdenum to vanadium can be 1:0.45 to 1:0.95 or 1:0.5 to 1:0.9, and is preferably 1:0.5 to 1:0.9. When the above conditions are met, the structure of the CNTs can be stably maintained and CNTs with the desired pore volume can be produced.

[0107] The mixture may contain a main catalyst precursor and a 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, with a preferred ratio of 1:0.1 to 1:0.25. Satisfying the above molar ratios improves the dispersibility of the main catalyst and allows for the production of CNTs with the desired pore volume.

[0108] The mixture may further contain an organic acid that plays a role in suppressing the precipitation of the main catalyst precursor and the co-catalyst precursor.

[0109] 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.

[0110] The mixture can contain the organic acid and the co-catalyst precursor in a molar ratio of 1:1 to 1:20, 1:2 to 1:10, or 1:3 to 1:6, with a ratio of 1:3 to 1:6 being preferred. Satisfying the above range has the advantage of enabling the production of a transparent catalyst metal solution during catalyst manufacturing and the production of a catalyst with suppressed fine powder formation during impregnation.

[0111] The process may further include a maturation step after step (1).

[0112] The maturation process may be carried out for 1 to 60 minutes or 10 to 50 minutes. It is preferable to carry it out for 10 to 50 minutes. When the above conditions are met, γ-Al ２ O ３The main catalyst precursor and co-catalyst precursor can be sufficiently supported on the support. Furthermore, bubbles present within the support are removed to the maximum extent possible, allowing the main catalyst precursor and co-catalyst precursor to be sufficiently supported even in the fine pores inside the support.

[0113] Step (2) Next, the active support is dried by multi-stage drying, which includes vacuum drying.

[0114] Multi-stage drying can mean that a drying process, including vacuum drying, is performed two or more times. Specifically, multi-stage drying may include atmospheric pressure drying and vacuum drying, or it may include vacuum drying alone two or more times.

[0115] Vacuum drying may be carried out at 80°C to 300°C or 120°C to 250°C, with 120°C to 250°C being preferred. When the above conditions are met, the main catalyst precursor, i.e., the coordination bond of the main catalyst, can be easily decomposed to form the main catalyst oxide, and energy consumption can be minimized.

[0116] Vacuum drying may be performed at 1 mbar to 200 mbar or 30 mbar to 150 mbar, and is preferably performed at 30 mbar to 150 mbar. When the above conditions are met, the main catalyst precursor, i.e., the coordination bond of the main catalyst, is rapidly decomposed and discharged, so that the main catalyst oxide can be formed more easily under vacuum conditions and energy consumption can be minimized.

[0117] Vacuum drying can be performed for 10 minutes to 3 hours or 10 minutes to 2 hours, with 10 minutes to 2 hours being preferred. When the above conditions are met, the main catalyst precursor can be easily decomposed and converted into the main catalyst oxide, and energy consumption can be minimized.

[0118] On the other hand, if multi-stage drying includes atmospheric pressure drying and vacuum drying, atmospheric pressure drying can be performed before the vacuum drying described above, and atmospheric pressure drying can remove any solvents that may be present in the active carrier.

[0119] Atmospheric pressure drying may be carried out at 80°C to 160°C or 100°C to 140°C, and is preferably carried out at 100°C to 140°C. When the above conditions are met, the solvent present in the active carrier can be sufficiently removed, and energy consumption can be minimized.

[0120] Atmospheric pressure drying may be carried out at 900 mbar to 1,100 mbar, and preferably at 950 mbar to 1,050 mbar. When the above conditions are met, the solvent present in the active carrier can be sufficiently removed, and energy consumption can be minimized.

[0121] Atmospheric pressure drying may be carried out for 1 to 12 hours, and preferably for 3 to 9 hours. When the above conditions are met, the solvent present in the active carrier can be sufficiently removed, and energy consumption can be minimized.

[0122] On the other hand, if multi-stage drying includes two or more vacuum drying steps, it may include two or more vacuum drying steps performed at different temperatures, more specifically, a primary vacuum drying step performed at a first temperature and a secondary vacuum drying step performed at a second temperature higher than the first temperature.

[0123] Primary vacuum drying can remove any solvents that may be present in the active carrier.

[0124] The first temperature may be between 80°C and 160°C, and is preferably between 100°C and 140°C. When the above conditions are met, the solvent present in the active carrier can be sufficiently removed, and energy consumption can be minimized.

[0125] Primary vacuum drying can be performed for 1 to 12 hours, preferably 3 to 9 hours. When the above conditions are met, the solvent present in the active carrier can be sufficiently removed, and energy consumption can be minimized.

[0126] The primary vacuum drying may be carried out at 1 mbar to 200 mbar, 1 mbar to 150 mbar or 80 mbar to 150 mbar, and is preferably carried out at 80 mbar to 150 mbar. When the above conditions are satisfied, the solvent present in the active support can be sufficiently removed, and the energy consumption can be minimized.

[0127] The description of the secondary vacuum drying is as described in the above description of the vacuum drying.

[0128] The second temperature may be 175 to 300 °C, and is preferably 180 to 280 °C. When the above conditions are satisfied, the main catalyst precursor, that is, the coordination compound of the main catalyst, can be easily decomposed to form the main catalyst oxide, and the energy consumption can be minimized.

[0129] The secondary vacuum drying may be carried out at 1 mbar to 200 mbar, 1 mbar to 150 mbar or 1 mbar to 70 mbar, and is more preferably carried out at 1 mbar to 70 mbar. When the above conditions are satisfied, the main catalyst precursor, that is, the coordination compound of the main catalyst, is rapidly decomposed and discharged, so that the main catalyst oxide can be more easily formed under vacuum conditions, and the energy consumption can be minimized.

[0130] The secondary vacuum drying may be carried out for 10 minutes to 3 hours or 10 minutes to 2 hours, and is preferably carried out for 10 minutes to 2 hours. When the above conditions are satisfied, the main catalyst precursor can be easily decomposed and converted into the main catalyst oxide, and the energy consumption can be minimized.

[0131] - Step (3) Then, the dried active support is heat-treated to produce a supported catalyst.

[0132] When the heat treatment is carried out, a supported catalyst in which the main catalyst and the promoter are coated on the surface and pores of γ-Al ２ O ３ is produced.

[0133] The heat treatment may be carried out at 600 °C to 800 °C or 620 °C to 750 °C, and is preferably carried out at 620 °C to 750 °C. When the above conditions are satisfied, the main catalyst and the promoter are γ-Al２ O ３ The supported catalyst can be manufactured with a uniform coating on the surface and pores, while minimizing energy consumption.

[0134] The heat treatment may be carried out for 1 to 12 hours or 2 to 8 hours, and is preferably carried out for 2 to 8 hours. When the above time is met, the catalyst precursor is γ-Al ２ O ３ A supported catalyst can be manufactured that exists in a state where it is uniformly coated on the surface and pores.

[0135] Step (4) Next, CNTs are produced in the presence of a supported catalyst.

[0136] In detail, carbon nanotubes (CNTs) can be produced by contacting a supported catalyst with a carbon-based compound. Specifically, this may be done by chemical vapor phase synthesis.

[0137] To describe in detail the steps for producing CNTs, first, a supported catalyst can be introduced into a horizontal fixed-bed reactor or a fluidized-bed reactor. Next, a gaseous carbon-based compound, or a mixed gas of a gaseous carbon-based compound, a reducing gas (e.g., hydrogen), and a carrier gas (e.g., nitrogen), is injected at a temperature above the thermal decomposition temperature of the gaseous carbon-based compound or below the melting point of the catalyst supported on the catalyst, and CNTs can be grown by chemical vapor-phase synthesis through the decomposition of the gaseous carbon-based compound.

[0138] CNTs produced by the chemical vapor phase synthesis method described above have crystal growth directions that are nearly parallel to the tube axis, and the graphite structure exhibits high crystallinity along the length of the tube. As a result, CNTs with small unit diameters and high conductivity and strength can be produced.

[0139] The chemical vapor phase synthesis method may be carried out at 600°C to 800°C or 650°C to 750°C, and is preferably carried out at 650°C to 750°C. By satisfying the above temperature range, CNTs can be produced while minimizing the generation of amorphous carbon.

[0140] Possible heat sources for the reaction include induction heating, radiant heat, lasers, IR, microwaves, plasma, and surface plasmon heating.

[0141] Furthermore, carbon-based compounds can be used without particular restrictions, as long as they can supply carbon and exist in a gaseous state at temperatures above 300°C.

[0142] The carbon-based compound may be a carbon-based compound having six or fewer carbon atoms, and may be one or more selected from the group consisting of carbon monoxide, methane, ethane, ethylene, ethanol, acetylene, propane, propylene, butane, butadiene, pentane, pentene, cyclopentadiene, hexane, cyclohexane, benzene, and toluene.

[0143] After growing CNTs by the reaction described above, a cooling step may be selectively performed to further align the CNTs in a more regular manner. Specifically, the cooling step can be carried out by natural cooling by removing the heat source or by using a cooler or the like.

[0144] The above-described manufacturing methods X and Y are examples, and the manufacturing methods for CNTs that may be included in a CNT aggregate are not limited to those described above.

[0145] [Carbon Nanotube Dispersion] The carbon nanotube dispersion (CNT dispersion) according to this disclosure comprises a CNT aggregate and a dispersion medium. The CNT dispersion exhibits good dispersibility of the CNT aggregate in the dispersion medium and has excellent conductivity. The CNT dispersion is preferably used for electrode formation, transparent conductive film formation, resin additives, conductive inks, coatings, antistatic agents, paints, and the like.

[0146] <CNT aggregates> The CNT aggregates contained in the CNT dispersion are the same as the CNT aggregates related to this disclosure described above, so their explanation is omitted here.

[0147] <Dispersion Medium> The dispersion medium preferably contains water, and more preferably contains water as its main component. "Containing water as its main component" means that the proportion of water in the dispersion medium is more than 50% by mass. The proportion of water in the dispersion medium is preferably 90% by mass or more, more preferably 95% by mass or more, even more preferably 99% by mass or more, and may be, for example, 100% by mass.

[0148] The water is not particularly limited, but it is preferable to use distilled water, deionized water, or pure water, for example, because it contains fewer impurities.

[0149] 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.

[0150] The CNT dispersion may further contain other components that can be used in the dispersion, in addition to the CNT aggregate and dispersion medium. Examples of other components include dispersants, defoamers, antistatic agents, and conductive additives other than the conductive additives described herein. It may also further contain trace amounts of impurities, so-called unavoidable impurities.

[0151] <Dispersant> The CNT dispersion may contain a dispersant for the purpose of further improving the dispersibility and dispersion stability of the CNT aggregate. The dispersant is not particularly limited and, for example, various surfactants can be used. Polymer compounds such as resins can also be used as dispersants. A surfactant is preferred as the dispersant. The surfactant may be an ionic surfactant or a nonionic surfactant and is not particularly limited. In the CNT dispersion, the surfactant can be used alone or in a mixture of two or more types.

[0152] Examples of ionic surfactants include anionic surfactants, cationic surfactants, and amphoteric surfactants. Examples of anionic surfactants include aromatic sulfonic acid-based surfactants such as alkylbenzene sulfonates (e.g., dodecylbenzenesulfonic acid) and dodecylphenyl ether sulfonates; ether sulfate-based surfactants; phosphate-based surfactants; and carboxylic acid-based surfactants. Examples of cationic surfactants include alkylamine salts and quaternary ammonium salts. Examples of amphoteric surfactants include alkylbetaine-based surfactants and amine oxide-based surfactants. As for ionic surfactants, ionic surfactants having an aromatic ring (so-called aromatic ionic surfactants) are preferred, and aromatic sulfonic acid-based surfactants such as alkylbenzene sulfonates and dodecylphenyl ether sulfonates are more preferred. Aromatic ionic surfactants tend to have excellent dispersibility, dispersion stability, and high concentration properties for CNT aggregates.

[0153] Examples of nonionic surfactants include sugar ester surfactants such as sorbitan fatty acid esters and polyoxyethylene sorbitan fatty acid esters; fatty acid ester surfactants such as polyoxyethylene resin acid esters and polyoxyethylene fatty acid diethyl; ether surfactants such as polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, and polyoxyethylene polypropylene glycol; and aromatic nonionic surfactants such as polyoxyalkylene octylphenyl ether, polyoxyalkylene nonylphenyl ether, polyoxyalkyldibutylphenyl ether, polyoxyalkyl styrylphenyl ether, polyoxyalkyl benzylphenyl ether, polyoxyalkylbisphenyl ether, polyoxyalkylcumylphenyl ether, and polyoxyalkylene phenyl ether. As nonionic surfactants, ionic surfactants having aromatic rings (so-called aromatic nonionic surfactants) are preferred, polyoxyalkylene phenyl ether is more preferred, and polyoxyethylene phenyl ether is even more preferred. Aromatic nonionic surfactants tend to have excellent dispersibility, dispersion stability, and high concentration properties for CNT aggregates.

[0154] Other dispersants that excel in dispersibility, dispersion stability, and high concentration of CNTs include: Demol (registered trademark: hereinafter the same) N, Demol RN, and Demol T (manufactured by Kao Corporation), sodium salt of β-naphthalene sulfonic acid formalin condensate; Brij S 100 (manufactured by Sigma-Aldrich), polyvinylpyrrolidone K30 (e.g., manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.); carboxymethylcellulose (CMC) (e.g., manufactured by Daicel Mirise Co., Ltd.); sodium deoxycholate (e.g., manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.); and SOLSPERSE. ＴＭ W100, SOLSPERSE ＴＭ Examples include W150 (manufactured by Lubrizol Japan Co., Ltd.). CMC is particularly preferred from the viewpoint of excellent dispersion ability, dispersion stability, and high concentration of CNT aggregates.

[0155] When the CNT dispersion contains a dispersant, the amount of dispersant used is not particularly limited and can be set appropriately depending on the type of dispersant, the amount of CNT aggregate, the amount of dispersion medium, etc.

[0156] [Method for Manufacturing CNT Dispersion] The method for manufacturing a CNT dispersion is not particularly limited. A CNT dispersion can be manufactured by dispersing CNT aggregates in a dispersion medium. That is, a CNT dispersion can be manufactured by a method that includes a step of dispersing CNT aggregates in a dispersion medium (also called the "dispersion step"). The dispersion mediums that can be used in the dispersion step are as described above.

[0157] The dispersion method is not particularly limited. Examples of dispersion methods include using dispersion devices such as a stirrer, homogenizer, colloid mill, flow jet mixer, dissolver, paint conditioner, Manton emulsifier, jet mill, and ultrasonic device. Other examples of dispersion methods include using known grinding means, such as ball milling (e.g., ball mill, vibrating ball mill, planetary ball mill, bead mill, etc.), sand milling, colloid milling, jet milling, roller milling, vertical or horizontal agitator mill, attritor, colloid mill, three-roll mill, pearl mill, super mill, impeller, disperser, KD mill, dynatron, and pressurized kneader. The method using a jet mill is preferred, and the method using a wet jet mill is more preferred. A wet jet mill is a dispersion device that pumps a mixture in a solvent as a high-speed flow from a nozzle placed in a sealed state inside a pressure vessel. In a wet jet mill, CNT aggregates are dispersed within a pressure vessel by collisions between opposing flows, collisions with the vessel wall, turbulence and shear flow generated by high-speed flow, etc. A suitable wet jet mill is an ultra-high pressure homogenizer manufactured by Jōkō Co., Ltd. (model numbers: NAGS20, NAGS100, JAGS200, NAGS1000, etc.). However, the wet jet mill is not limited to these. When using the above-mentioned ultra-high pressure homogenizer as the dispersion device, the dispersion processing pressure is preferably 10 MPa to 250 MPa.

[0158] The method for producing a CNT dispersion may include a step of drying the CNT aggregate (also called a "drying step") before the dispersion step described above.

[0159] If moisture adheres to the CNTs, the surface tension of the water can cause the CNTs to stick together, raising concerns about reduced dispersibility. Therefore, by performing a drying step of the conductive additive before the dispersion step, moisture adhering to the CNTs is removed, preventing the CNTs from sticking together due to moisture, and further improving the dispersibility of the CNTs in the dispersion medium. The drying method is not particularly limited. Examples of drying methods include heating drying, vacuum drying, and heating vacuum drying. Heating vacuum drying is preferred as the drying method. The drying temperature is not particularly limited, but is preferably, for example, 40°C to 100°C. The drying time is not particularly limited and can be set appropriately depending on the drying temperature, the degree of moisture adhering to the CNT aggregate in this disclosure, etc.

[0160] The following are examples of CNT dispersion manufacturing methods, but the manufacturing of CNT dispersions is not limited to those shown below.

[0161] <Manufacturing Example 1: Example of Dispersion Production> 0.040 g of the CNT aggregate according to this disclosure is weighed and placed in a three-necked flask. After adding the CNT aggregate, a large excess of deionized water, which is the dispersion medium, is poured into the flask (for example, 20 mL), and the mixture is stirred at room temperature (25°C, the same applies hereafter). At this time, a known dispersant (for example, carboxymethylcellulose) may be added as appropriate. Next, the conductive additive is dispersed in the dispersion medium using a known dispersion device (for example, an ultrasonic irradiation device or a wet jet mill). The obtained dispersion is further stirred with a stirrer at room temperature for a long time (for example, 1 hour to 48 hours). In this way, a CNT dispersion is obtained.

[0162] [Conductive Material] The conductive material according to this disclosure includes a CNT aggregate. As described above, the CNT aggregate contained in the conductive material according to this disclosure has excellent conductivity when dispersed, and is therefore suitable as a conductive additive. Because the conductive material according to this disclosure includes the CNT aggregate according to this disclosure, it has excellent conductivity efficiency and can effectively impart high conductivity to the object to be used.

[0163] The conductive material relating to this disclosure may contain known conductive additives such as graphite and Ketjenblack. Furthermore, the conductive material relating to this disclosure may contain CNTs other than specific CNT aggregates.

[0164] The conductive material relating to this disclosure can be used as one of the electrode materials. An example of an electrode formed using the electrode material is an electrode provided in a secondary battery. An embodiment of an electrode and a secondary battery equipped with the electrode will be described below.

[0165] <Electrode> The electrode according to this disclosure includes an electrode active material and a conductive material according to this disclosure. Because the electrode according to this disclosure includes a conductive material according to this disclosure, it has excellent conductivity for forming conductive paths within the electrode. Therefore, the secondary battery according to this disclosure has excellent cycle characteristics.

[0166] In electrodes, CNT aggregates can function as conductive additives. The CNT aggregates included in the electrodes described below are synonymous with the CNT aggregates in this disclosure, and the preferred embodiments are also the same; therefore, a description of the CNT aggregates will be omitted below.

[0167] The electrode may consist of at least one of a positive electrode and a negative electrode. The electrode may include an electrode active material layer, or it may include a current collector and an electrode active material layer disposed on the current collector.

[0168] The current collector is not particularly limited as long as it does not induce chemical changes in the battery and is conductive. Examples of current collectors include copper, stainless steel, aluminum, nickel, titanium, calcined carbon, and aluminum or stainless steel surfaces that have been surface-treated with carbon, nickel, titanium, silver, etc. Specifically, transition metals with good carbon adsorption properties, such as copper and nickel, may be used as current collectors.

[0169] The electrode active material layer can contain an electrode active material. The electrode active material is preferably electrode active material particles. When the electrode is a positive electrode, the electrode active material is not particularly limited, and the electrode active material layer can contain a positive electrode active material commonly used in positive electrode materials for electrodes. Specifically, examples of the positive electrode active material include layered compounds such as lithium cobalt oxide (LiCoO ２ ), lithium nickel oxide (LiNiO ２ ), etc.; compounds substituted with one or more transition metals; lithium iron oxides such as LiFe ３ O ４ ; lithium manganese oxides with chemical formulas Li １＋ｃ１ Mn ２－ｃ１ O ４ (0 ≤ c1 ≤ 0.33), LiMnO ３ , LiMn ２ O ３ , LiMnO ２ , etc.; lithium copper oxide (Li ２ CuO ２ ); vanadium oxides such as LiV ３ O ８ , V ２ O ５ , Cu ２ V<00​​​​​​​​​​​​​​​​​​​​​​​​These are some examples.

[0170] When the electrode is a negative electrode, the electrode active material is not particularly limited, and the electrode active material layer may include negative electrode active materials commonly used for negative electrode materials. Specifically, the negative electrode active material may include graphite-based active material particles or silicon-based active material particles. As graphite-based active material particles, at least one selected from the group consisting of artificial graphite, natural graphite, graphitized carbon fiber, and graphitized mesocarbon microbeads may be used. By using artificial graphite as graphite-based active material particles, rate characteristics can be improved. As silicon-based active material particles, at least one selected from the group consisting of Si, SiOx (0 < x < 2), Si-C composite, and Si-Y alloy (where Y is an element selected from the group consisting of alkali metals, alkaline earth metals, transition metals, group 13 elements, group 14 elements, rare earth elements, and combinations thereof) may be used. By using silicon-based active material particles, the battery capacity can be increased.

[0171] The electrode active material layer may further contain a binder. The binder is not particularly limited, and the electrode active material layer may include binders commonly used in electrode materials. Examples of binders include at least one polymer selected from the group consisting of polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene propylene diene monomer (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, and polyacrylic acid, as well as polymers in which the hydrogen atoms of these polymers are substituted with Li, Na, Ca, etc.

[0172] <Secondary Battery> The secondary battery according to this disclosure comprises electrodes according to this disclosure. The secondary battery may include a negative electrode, a positive electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte. At least one of the positive electrode and the negative electrode is an electrode according to this disclosure.

[0173] A separator separates the negative electrode from the positive electrode and provides a passage for lithium ions to move. It is generally not limited to any separator commonly used in secondary batteries. Preferably, the separator has low resistance to ion movement in the electrolyte and excellent electrolyte moisture absorption capacity. Specifically, a porous polymer film can be used as a separator. The porous polymer film may be, for example, a porous polymer film made from polyolefin polymers such as ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, or ethylene / methacrylate copolymer, or a laminated structure in which two or more of these films are laminated. Alternatively, the separator may be a conventional porous nonwoven fabric, such as a nonwoven fabric made of high-melting-point glass fibers or polyethylene terephthalate fibers. Furthermore, the separator may be coated with a ceramic component or polymer substance to ensure heat resistance or mechanical strength. The separator can selectively have a single-layer or multi-layer structure.

[0174] The electrolyte is not particularly limited and can include, for example, organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, and molten inorganic electrolytes that can be used in the manufacture of lithium secondary batteries.

[0175] Specifically, the electrolyte may include non-aqueous organic solvents and metal salts. Examples of non-aqueous organic solvents include N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, γ-butyrolactone, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, triester phosphate, trimethoxymethane, dioxolane derivatives, sulfolane, methylsulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ethers, methyl propionate, and ethyl propionate, which are aprotic organic solvents.

[0176] Among carbonate-based organic solvents, cyclic carbonates such as ethylene carbonate and propylene carbonate are preferred as non-aqueous organic solvents because they have high dielectric constants as high-viscosity organic solvents and readily dissociate lithium salts. It is even more preferable to use a mixture of such cyclic carbonates with low-viscosity, low-dielectric-constant linear carbonates such as dimethyl carbonate and diethyl carbonate in appropriate proportions as a non-aqueous organic solvent, as this yields an electrolyte with high electrical conductivity.

[0177] The metal salt may also be a lithium salt. Lithium salts are readily soluble in non-aqueous electrolytes. For example, the anion portion of the lithium salt may be F － , Cl － , I － NO ３ － , N (CN) ２ － BF ４ － , ClO ４ － , PF ６ － (CF ３ ) ２ PF ４ － (CF３ ) ３ PF ３ － 、(CF ３ ) ４ PF ２ － 、(CF ３ ) ５ PF － 、(CF ３ ) ６ P － 、CF ３ SO ３ － 、CF ３ CF ２ SO ３ － 、(CF ３ SO ２ ) ２ N － 、(FSO ２ ) ２ N － 、CF ３ CF ２ (CF ３ ) ２ CO － 、(CF ３ SO ２ ) ２ CH － 、(SF ５ ) ３ C － 、(CF ３ SO ２ ) ３ C － 、CF ３ (CF ２ ) ７ SO ３ － 、CF ３ CO ２ － 、CH ３ CO ２ － 、SCN － 、及び、(CF ３ CF ２ SO ２ ) ２ N － が挙げられる。

[0178] In addition to non-aqueous organic solvents and metal salts, the electrolyte may further contain one or more additives for the purpose of improving battery life characteristics, suppressing the decrease in battery capacity, and improving battery discharge capacity, such as haloalkylene carbonate compounds like difluoroethylene carbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ethers, ethylenediamine, n-glycemic (glyme), hexalic acid triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salts, pyrrole, 2-methoxyethanol, and aluminum trichloride.

[0179] The secondary battery described above can constitute a battery module containing the secondary battery as a unit cell, and a battery pack containing the battery module. The battery module and battery pack can be used as a power source for medium to large devices selected from the group consisting of electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, and power storage systems.

[0180] <Planar Assembly> The planar assembly relating to this disclosure includes the CNT assembly relating to this disclosure. The proportion of the CNT assembly relating to this disclosure contained in the planar assembly relating to this disclosure is usually 1% by mass or more with respect to the total mass of the planar assembly. The planar assembly relating to this disclosure may contain components other than the CNT assembly relating to this disclosure.

[0181] Examples of planar aggregates relating to this disclosure include films containing the CNT aggregate relating to this disclosure.

[0182] The planar assemblies relating to this disclosure are useful, for example, in filters, electromagnetic shields, and pellicles for extreme ultraviolet (EUV) radiation.

[0183] The method for producing the planar aggregate according to this disclosure is not particularly limited. The planar aggregate according to this disclosure can be produced, for example, as a nonwoven fabric-like planar aggregate by dispersing the CNT aggregate according to this disclosure in water or other fluid and filtering it once or twice or more.

[0184] <Laminate> The laminate according to this disclosure comprises a substrate and a planar assembly according to this disclosure. The substrate and the planar assembly may be in direct contact, or other layers may be arranged between the substrate and the planar assembly. Alternatively, the planar assembly according to this disclosure may be arranged on the substrate, and yet another layer may be arranged on the planar assembly.

[0185] The material constituting the substrate may be resin, glass, or fiber. Examples of resins include polyethylene terephthalate (PET), polycarbonate (PC), polymethyl methacrylate (PMMA), cyclic olefin polymer (COP), triacetate (TAC), cyclic olefin copolymer (COC), poly(vinyl chloride) (PVC), polyethylene 2,6-naphthalate (PEN), polyimide (PI), polypropylene (PP), polyethylene (PE), polystyrene (PS), polyamide (PA), polyacetal (POM), polyurethane (PU), acrylonitrile butadiene styrene (ABS), polyphenylene ether (PPE), polysulfone (PSU), polyether ether ketone (PEEK), and polyamide-imide (PAI). Examples of glass include float glass (SiO2). ２ Na ２ Examples include sodium chloride (containing O, CaO, and MgO), soda lime, aluminosilicate glass, and borosilicate glass. Examples of fibers include synthetic fibers such as polyester fibers, polyamide fibers, polyolefin fibers, and acrylic fibers; and natural fibers such as cotton, linen, silk, wool, cashmere, mohair, alpaca, jute, hemp, and ramie.

[0186] The planar aggregate preferably contains a binder in addition to the CNT aggregate according to this disclosure. The binder is preferably a polymer and preferably contains at least one selected from the group consisting of polymers containing constituent units derived from vinylidene chloride (e.g., polyvinylidene chloride, vinylidene chloride-vinyl chloride copolymer, vinylidene chloride-vinyl acetate copolymer, etc.), polyimide, polysiloxane, and epoxy resin.

[0187] The following examples will provide a more detailed explanation of the CNT aggregates, etc., related to this disclosure. This disclosure is not limited to the following examples, unless it exceeds the spirit of the disclosure.

[0188] (Example 1) 1. Production of Sheet-Shaped CNT Assembly 1 Sheet-shaped CNT assembly 1 was produced by a floating catalyst method (CVD method) in which the self-assembly of CNT bundles directly interacts in the gas phase. A cylindrical reactor with an inner diameter of 85 mm was used as the CNT reactor. First, ferrocene, as a metal catalyst precursor containing Fe atoms, and thiophene, as an accelerator, were introduced into a continuous flow of carrier gas in a once-through reactor whose temperature was controlled to 200°C to 800°C. Hydrogen gas was used as the carrier gas. By maintaining the temperature in the once-through reactor within the above range, the metal catalyst precursor decomposes. The region in which the metal catalyst precursor decomposes is referred to as the first temperature zone.

[0189] Next, methane, the carbon source, was released into the carrier gas stream. The metal catalyst and carbon source were supplied to a second temperature zone, temperature-controlled at 1400°C, located downstream of the first temperature zone. The total gas supply flow rate for the carrier gas and source gas was set to 34 NL / min (NL is normal liters). The thiophene / hydrogen gas flow rate ratio was set to range A in Table 1. The second temperature zone was maintained at a temperature sufficient to generate carbon nanotube aggregates.

[0190]

[0191] In the second temperature zone, a reaction field was generated within the temperature-controlled flow reactor, forming catalytic nuclei and causing rapid growth of CNTs, thereby generating CNT aggregates. The aggregates were discharged as continuous discharge through the outlet of the flow-type reactor, which was temperature-controlled between 200°C and 700°C, and sheet-like CNT aggregates were collected. The obtained sheet-like CNT aggregates were washed with pure water for 10 seconds, crushed into a powder, and then passed through a sieve with a mesh size of 1.0 mm twice. The CNT aggregates that passed through the sieve were collected and designated as CNT aggregate 1.

[0192] 2. Preparation of CNT dispersion 1 The following materials were mixed and pre-dispersed by treating them with an Ace homogenizer manufactured by Nippon Seiki Co., Ltd. for 1 hour to obtain pre-dispersion 1.

[0193] (Dispersion composition) - CNT aggregate 1 obtained above... 1.1 g - CARBOXYMETHYL CELLULOSE SODIUM SALT HIGH VISCOSITY (manufactured by MP Biomedicals)... 1.65 g - Purified water... 547.25 g

[0194] The pre-dispersion 1 was subjected to the final dispersion using a high-pressure homogenizer (model number: NAGS100) manufactured by Jōkō Co., Ltd. as a wet jet mill under the following conditions to obtain a CNT dispersion 1 with a concentration of 0.20% by mass. (Dispersion conditions) Nozzle diameter: 0.22 mm Pressure: 85 MPa Number of passes: 8 Method: Circulation method

[0195] <Amorphous carbon content relative to the total mass of CNT aggregates> The amount of amorphous carbon was quantified by thermogravimetric differential thermal analysis (TG-DTA). Thermogravimetric differential thermal analysis was performed using a thermal analyzer (model: STA200, manufactured by Hitachi High-Tech Corporation) under air circulation at a heating rate of 10°C / min. Approximately 10 mg of the sample was weighed into a Pt pan and heated to 900°C at a rate of 10°C / min. The amorphous carbon content was calculated from the difference in weight loss between 200°C and 400°C.

[0196] <Area ratio of bundles with a diameter of 100 nm or more> For the CNT aggregate 1 of Example 1, imaging was performed using a scanning electron microscope (SEM), and two images in which CNT bundles were clearly observed were selected from the obtained images (one of which is Figure 1). Image processing and image analysis were performed on the selected images using Python. In image processing, the contours and centerlines of the CNTs were detected and combined with the original image. In image analysis, the bundle diameter was determined by calculating the distance from the centerline to the contour of the created image. Then, the product of the bundle diameter and the length of the centerline was calculated to determine the area occupied by the CNTs in the image. A histogram of bundle diameter and occupied area was obtained.

[0197] Using the calculated bundle diameter histogram, the bundle diameter features of each sample were calculated using the following method: 1. The bundle diameters and occupied areas of multiple fields of view of the same sample were added together and normalized so that the sum equaled 1. Following normalization, the unit of the vertical axis was set to occupied area ratio. 2. The total occupied area ratio of bundles with a bundle diameter of 100 nm or more was calculated. As a result, the area ratio of bundles with a bundle diameter of 100 nm or more was 0.17.

[0198] <Viscosity of CNT dispersion> The viscosity of CNT dispersion 1 was measured using a cone-plate viscometer (also known as an E-type viscometer). Specifically, a cone-plate viscometer (BROOKFIELD DV-II+Pro PROGRAMMABLE VISCOMETER) was used to measure the viscosity. Measurement fixture: Cone-plate Measurement mode: Rotation mode Shear rate: 0.6 s －１ ~384 simultaneous －１ Temperature: 25°C. From the obtained data, the shear rate was 12 s. －１ The viscosity was measured. The viscosity of the dispersion was 434.0 mPa·s. Table 2 shows the common logarithm of the viscosity.

[0199] <Elongation at Break> CNT dispersion 1 was poured onto a 22 mm x 75 mm x 3 mm slide glass type silicon plate (manufactured by Dosaka E-M Co., Ltd., #08-1044), heated to 100°C, and dried for 30 minutes to be used as the measurement sample. The measurement sample was fixed to the gripping part of a tensile testing apparatus (manufactured by Shimadzu Corporation, Autograph AG-IS), and a tensile test was performed at a speed of 1 mm / min. The point where the test force was maximum was considered the breaking point, and the elongation at break was calculated. The elongation at break was 1.5%.

[0200] (Example 2) 1. Manufacturing of CNT assembly 2 CNT assembly 2 was manufactured in the same manner as CNT assembly 1, except that the temperature of the second temperature zone was controlled to 1320°C and the total gas supply flow rate of the carrier gas and raw material gas was set to 17 NL / min.

[0201] 2. Preparation of CNT dispersion 2 Using the obtained CNT aggregate 2, a pre-dispersion 2 was obtained in the same manner as in Example 1.

[0202] The main dispersion of pre-dispersion 2 was carried out using a high-pressure homogenizer (model number: NAGS100) manufactured by Jōkō Co., Ltd. as a wet jet mill under the following conditions to obtain CNT dispersion 2. (Dispersion conditions) Nozzle diameter: 0.22 mm Pressure: 200 MPa Number of cycles: 8 Method: Circulation method The viscosity of the dispersion measured in the same manner as in Example 1 was 33.2 mPa·s.

[0203] 3. Evaluation Example 2: The CNT aggregate 2 of Example 2 was evaluated in the same manner as in Example 1, except that imaging was performed using a SEM, and three images in which the CNT bundle was clearly observed were selected from the obtained images (one of which is shown in Figure 2). The evaluation results are shown in Table 2.

[0204] (Example 3) 1. Manufacturing of CNT Assembly 3 CNT assembly 3 was manufactured by mixing the following CNT assembly 3A and CNT assembly 3B. CNT assembly 3A was manufactured in the same manner as CNT assembly 1, except that the total gas supply flow rate of the carrier gas and raw material gas was set to 35 NL / min. CNT assembly 3B was manufactured in the same manner as CNT assembly 1, except that the total gas supply flow rate of the carrier gas and raw material gas was set to 36 NL / min.

[0205] 2. Preparation of CNT dispersion 3 A pre-dispersion 3 was obtained using the obtained CNT aggregate 3 in the same manner as in Example 1.

[0206] The main dispersion of the pre-dispersion 3 was carried out using a high-pressure homogenizer (model number: NAGS100) manufactured by Jōkō Co., Ltd. as a wet jet mill under the following conditions to obtain the specific CNT dispersion 3. (Dispersion conditions) Nozzle diameter: 0.22 mm Pressure: 50 MPa Number of times: 3 Method: Circulation method The viscosity of the dispersion measured in the same manner as in Example 1 was 798.2 mPa·s.

[0207] 3. Evaluation Example 3: The CNT aggregate 3 of Example 3 was imaged using a SEM, and four images in which the CNT bundle was clearly observed were selected from the obtained images (one of which is shown in Figure 3). The evaluation was performed in the same manner as in Example 1. The evaluation results are shown in Table 2.

[0208] (Example 4) 1. Manufacturing of CNT assembly 4 CNT assembly 4 was manufactured in the same manner as CNT assembly 1, except that the temperature of the second temperature zone was controlled to 1400°C and the total gas supply flow rate of the carrier gas and raw material gas was set to 34.2 NL / min.

[0209] 2. Preparation of CNT dispersion 4 A pre-dispersion 4 was obtained using the obtained CNT aggregate 4 in the same manner as in Example 1.

[0210] The pre-dispersion 4 was subjected to the final dispersion using a high-pressure homogenizer (model number: NAGS100) manufactured by Jōkō Co., Ltd. as a wet jet mill under the following conditions to obtain the CNT dispersion 4. (Dispersion conditions) Nozzle diameter: 0.22 mm Pressure: 85 MPa Number of cycles: 8 Method: Circulation method The viscosity of the dispersion measured in the same manner as in Example 1 was 953.2 mPa·s.

[0211] 3. Evaluation Example 4: The CNT aggregate 4 was imaged using a SEM, and three images were selected from the obtained images in which the CNT bundle was clearly observed (one of which is shown in Figure 4). The evaluation was carried out in the same manner as in Example 1. The evaluation results are shown in Table 2.

[0212] (Example 5) 1. Manufacturing of CNT assembly 5 CNT assembly 5 was manufactured in the same manner as CNT assembly 1, except that the temperature of the second temperature zone was controlled to 1400°C and the total gas supply flow rate of the carrier gas and raw material gas was set to 34.1 NL / min.

[0213] 2. Preparation of CNT dispersion 5 Using the obtained CNT aggregate 5, a pre-dispersion 5 was obtained in the same manner as in Example 1.

[0214] The pre-dispersion 5 was subjected to final dispersion using a high-pressure homogenizer (model number: NAGS100) manufactured by Jōkō Co., Ltd. as a wet jet mill under the following conditions to obtain the CNT dispersion 5. (Dispersion conditions) Nozzle diameter: 0.22 mm Pressure: 150 MPa Number of cycles: 8 Method: Circulation method The viscosity of the dispersion measured in the same manner as in Example 1 was 127.4 mPa·s.

[0215] 3. Evaluation Example 5: The CNT aggregate 5 was evaluated in the same manner as in Example 1, except that imaging was performed using a SEM, and three images in which the CNT bundle was clearly observed were selected from the obtained images (one of which is shown in Figure 5). The evaluation results are shown in Table 2.

[0216] (Example 6) 1. Manufacturing of CNT assembly 6 CNT assembly 6 was manufactured in the same manner as CNT assembly 1, except that the second temperature zone was controlled to 1400°C, the total gas supply flow rate of the carrier gas and raw material gas was set to 41.9 NL / min, and the flow rate ratio of thiophene / hydrogen gas was set to range B in Table 1.

[0217] 2. Preparation of CNT dispersion 6 A pre-dispersion 6 was obtained using the obtained CNT aggregate 6 in the same manner as in Example 1.

[0218] The pre-dispersion 6 was subjected to final dispersion using a high-pressure homogenizer (model number: NAGS100) manufactured by Jōkō Co., Ltd. as a wet jet mill under the following conditions to obtain the CNT dispersion 6. (Dispersion conditions) Nozzle diameter: 0.22 mm Pressure: 250 MPa Number of cycles: 8 Method: Circulation method The viscosity of the dispersion measured in the same manner as in Example 1 was 14.4 mPa·s.

[0219] 3. Evaluation Example 6: The CNT aggregate 6 of Example 6 was imaged using a SEM, and three images in which the CNT bundle was clearly observed were selected from the obtained images (one of which is shown in Figure 6). The evaluation was carried out in the same manner as in Example 1. The evaluation results are shown in Table 2.

[0220] (Comparative Example 1) 1. Preparation of Powdered CNT Assembly 7 As the powdered CNT assembly 7, carbon nanotubes manufactured by C-nano Co., Ltd. (catalog number: FT9100) were prepared.

[0221] 2. Preparation of CNT dispersion 7: Using the prepared powdered CNT aggregate 7, a CNT dispersion 7 was obtained in the same manner as in Example 1.

[0222] 3. Evaluation of the powdered CNT aggregate 7 of Comparative Example 1 was performed using SEM imaging, and three images in which the CNT bundles were clearly observed were selected from the obtained images (one of which is shown in Figure 7). The evaluation was carried out in the same manner as in Example 1. The evaluation results are shown in Table 2.

[0223] (Comparative Example 2) 1. Preparation of Powdered CNT Assembly 8 As Powdered CNT Assembly 8, carbon nanotubes manufactured by C-nano Co., Ltd. (catalog number: FT7000) were prepared.

[0224] 2. Preparation of CNT dispersion 8: Using the prepared powdered CNT aggregate 8, a CNT dispersion 8 was obtained in the same manner as in Example 1.

[0225] 3. Evaluation of the powdered CNT aggregate 8 of Comparative Example 2 was performed using SEM imaging, and two images in which the CNT bundles were clearly observed were selected from the obtained images (one of which is shown in Figure 8). The evaluation was performed in the same manner as in Example 1. The results are shown in Table 2.

[0226] Next, we fabricated a lithium-ion secondary battery.

[0227] 1. Fabrication of positive electrode for lithium secondary battery: Positive electrode active material (LiNi ０．８ Co ０．１ Mn ０．１ O ２ A positive electrode mixture was prepared by mixing a conductive material (acetylene black) and a binder (PVdF) in a ratio of positive electrode active material:conductive material:binder = 92:5:3 (mass ratio), and then kneading with N-methyl-2-pyrrolidone. The obtained positive electrode mixture was applied to a 15 μm thick Al foil to be used as a current collector, vacuum-dried at 80°C for 1 hour, and then roll-pressed to obtain a positive electrode for a lithium secondary battery. The positive electrode area was 1.65 cm², and the basis weight was 16 mg / cm². ２ The density is 3.0 g / cm³. ３ I adjusted it so that it would be as follows.

[0228] 2. Preparation of a Negative Electrode for Lithium Secondary Batteries A negative electrode for lithium secondary batteries was prepared by mixing artificial graphite MAG-E and carbon-coated SiO in a 9:1 (mass ratio) ratio as the negative electrode active material, using CLPA-C07 (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) as a binder, and adding the above CNT dispersion as a conductive additive, so that the composition was negative electrode active material:binder:conductive additive = 94.9:5.0:0.1 (weight ratio), and kneading to prepare a paste-like negative electrode mixture. Ion-exchanged water was used as the solvent during the preparation of the negative electrode mixture. The obtained negative electrode mixture was coated onto a 20 μm thick Cu foil using a single-sided continuous coating machine, dried at 120°C, and then roll-pressed to obtain a negative electrode for lithium secondary batteries. The negative electrode area was 1.77 cm². ２ The estimated amount is 9.3 mg / cm³. ２ The density is 1.4 g / cm³. ３ I adjusted it so that it would be as follows.

[0229] 3. Fabrication of a Lithium Secondary Battery The positive electrode for the lithium secondary battery was placed on the lower cover of a part for the coin-type battery R2032 (manufactured by Hosen Co., Ltd.), and a laminated film separator, which consists of a 16 μm heat-resistant porous layer laminated on a polyethylene porous film, was placed on top of it. 300 μL of electrolyte was injected into this. As the electrolyte, a 20:75:5 (volume ratio) mixture of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate was added, to which 1 volume% of vinylene carbonate was added, and LiPF was added. ６ A solution of 1.3 mol / L was used. Next, the negative electrode for the lithium secondary battery was placed on top of the laminated film separator, the top cover was placed on top via a gasket, and the lithium secondary battery of coin-type full cell R2032 was fabricated by crimping with a crimping machine. These operations were performed in a glove box under an argon atmosphere.

[0230] 4. Cycle Test Using the manufactured lithium-ion battery, a cycle test was conducted for 200 cycles under the conditions shown below, and the discharge capacity retention rate after 200 cycles was calculated using the following formula. Note that a higher discharge capacity retention rate after 200 cycles indicates better lifespan characteristics. Discharge capacity retention rate after 200 cycles (%) = Discharge capacity at 200th cycle / Discharge capacity at 1st cycle × 100

[0231] <Cycle Test Conditions> Test temperature: 25°C Charging conditions: Constant current constant voltage charging, maximum charging voltage 4.2V, charging time 5 hours, charging current 0.3CA Rest time after discharge: 10 minutes Discharge conditions: Constant current discharge, minimum discharge voltage 2.5V, discharge current 0.3CA Rest time after charge: 10 minutes In this test, one cycle is defined as the process of charging, resting the discharge, discharging, and resting the charge in sequence.

[0232] The evaluation results for Examples 1 to 6, Comparative Example 1, and Comparative Example 2 are shown in Table 2.

[0233]

[0234] As shown in Table 2, the CNT assemblies of Examples 1 to 6 satisfy conditions (1) and (2), and were found to have a high discharge capacity retention rate and excellent cycle characteristics.

Claims

1. A carbon nanotube aggregate that satisfies the following conditions (1) and (2): (1) The amorphous carbon content is 0.1% by mass or more and less than 2.0% by mass of the total mass of the carbon nanotube aggregate. (2) It contains a bundle structure, and in the area observed by a scanning electron microscope, the area ratio of bundles with a bundle diameter of 100 nm or more is greater than 0.

1.

2. The carbon nanotube aggregate according to claim 1, satisfying the following condition (3): (3) When the carbon nanotube aggregate is mixed with water and the liquid temperature is 25°C and the concentration is 0.20% by mass, the common logarithm of the viscosity of the dispersion is greater than 1.0 and less than 3.

5. The unit of viscosity is mPa·s.

3. A conductive material comprising the carbon nanotube aggregate described in claim 1 or 2.

4. An electrode comprising an electrode active material and the conductive material described in claim 3.

5. A secondary battery comprising the electrode described in claim 4.

6. A planar aggregate comprising the carbon nanotube aggregate described in claim 1 or 2.

7. A laminate comprising a substrate and the planar assembly described in claim 6.

8. A filter using the planar assembly described in claim 6.

9. An electromagnetic shield using the planar assembly described in claim 6.

10. A pellicle for extreme ultraviolet radiation using the planar aggregate described in claim 6.

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