Carbon nanotube aggregates, conductive materials, electrodes, secondary batteries, planar aggregates, laminates, filters, electromagnetic wave shields, and pellicles for extreme ultraviolet rays

Abstract

Provided is a carbon nanotube aggregate and the like that can be used to fabricate a battery having excellent cycle characteristics. [Solution] Carbon nanotube aggregates in which the density factor Σ calculated by formula (α) is less than 1.0, and the common logarithm of the viscosity of a dispersion liquid obtained by mixing carbon nanotube aggregates, carboxymethylcellulose sodium having a molecular weight of 700 kDa, and water, in which the concentration of the carbon nanotube aggregate is 0.20 mass % and the concentration of carboxymethylcellulose sodium is 0.30 mass %, is 1.0 or more (the unit of viscosity is mPa·s). The resistance factor P is the product of the surface resistivity (ρs) of the film and the absorbance (Abs) of the film. Two types of film thickness are prepared, and the resistance factor P of the thick film is thick , thin film P thin Calculate the concentration of carbon nanotube aggregates in the thick film, C thick , the concentration of carbon nanotube aggregates in the thin film, C thin Prepare the P thick , P thin , C thick and C thin applies. JPEG0007785234000009.jpg12110

Description

[Technical Field]

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

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

[0003] For example, Patent Document 1 discloses an aggregate of multi-walled carbon nanotubes having high electrical conductivity. It states that the multi-walled carbon nanotubes are thought to be entangled with each other to form a gigantic network structure that can exist stably in an aqueous dispersion.

[0004] Patent Document 2 describes that by utilizing the structurally stable network structure of CNT and the characteristics of chemically stable polystyrene sulfonic acid (PSS) and thinly adsorbing PSS acid onto the CNT surface, it is possible to provide a conductive material that can achieve high conductivity, long-term stability in atmospheric environments, high-temperature stability (heat resistance), and high-humidity stability, as well as a conductive film and solar cell that utilize this material. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2025 / 013505 [Patent Document 2] Japanese Patent Publication No. 2021-140999 Summary of the Invention [Problem to be solved by the invention]

[0006] There are cases where high tensile strength is required for CNT aggregates.

[0007] The present disclosure has been made in consideration of the above circumstances. An object of an embodiment of the present disclosure is to provide an aggregate of carbon nanotubes that can be used to fabricate a battery having excellent cycle characteristics. Another problem to be solved by another embodiment of the present disclosure is to provide a conductive material, an electrode, a secondary battery, and a planar assembly that include the carbon nanotube powder. Another problem to be solved by another embodiment of the present disclosure is to provide a laminate including the above-mentioned planar assembly. Another problem to be solved by another embodiment of the present disclosure is to provide a filter, an electromagnetic wave shield, and a pellicle for extreme ultraviolet rays using the above-mentioned planar assembly. [Means for solving the problem]

[0008] The means for solving the above problems include the following aspects. <1> The density factor Σ calculated by the following formula (α) is less than 1.0, and the carbon nanotube A carbon nanotube aggregate, a dispersion liquid obtained by mixing a carbon nanotube aggregate with carboxymethylcellulose sodium having a molecular weight of 700 kDa and water, in which the concentration of the carbon nanotube aggregate is 0.20 mass % and the concentration of carboxymethylcellulose sodium is 0.30 mass %, has a viscosity whose common logarithm is 1.0 or more (the unit of viscosity is mPa·s).

[0009]

number

[0010] <2> <1> A conductive material comprising the carbon nanotube aggregate according to claim 1. <3> an electrode active material; <2> and an electrode comprising the conductive material according to claim 1. <4> <3> A secondary battery comprising the electrode according to claim 1. <5> <1> A planar aggregate comprising the carbon nanotube aggregate according to claim 1. <6> A substrate; <5> A laminate comprising the planar assembly according to claim 1. <7> <5> A filter using the planar assembly described in 1. <8> <5> An electromagnetic wave shield using the planar assembly described in 1. <9> <5> A pellicle for extreme ultraviolet radiation using the planar assembly described in . [Effects of the Invention]

[0011] According to one embodiment of the present disclosure, there is provided an aggregate of carbon nanotubes from which a carbon nanotube dispersion liquid having a higher tensile strength than conventional ones can be obtained. According to another embodiment of the present disclosure, there are provided a conductive material, an electrode, a secondary battery, and a planar assembly, each including the carbon nanotube aggregate. According to another embodiment of the present disclosure, there is provided a laminate including the above-described planar assembly. According to other embodiments of the present disclosure, there are provided a filter, an electromagnetic wave shield, and a pellicle for extreme ultraviolet radiation, which use the planar assembly. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is an image of the carbon nanotube aggregate 1 of Example 1 obtained using a scanning electron microscope. [Figure 2] 10 is another image of the carbon nanotube aggregate 2 of Example 2 obtained using a scanning electron microscope. [Figure 3] 10 is still another image obtained by using a scanning electron microscope for the carbon nanotube aggregate 3 of Example 3. [Figure 4] 10 is an image of a carbon nanotube aggregate 4 of Example 4 obtained using a scanning electron microscope. [Figure 5] 10 is an image of carbon nanotube aggregate 5 of Example 5 obtained using a scanning electron microscope. [Figure 6] 10 is an image of a carbon nanotube aggregate 6 of Example 6 obtained using a scanning electron microscope. [Figure 7] 10 is yet another image obtained by using a scanning electron microscope for the carbon nanotube aggregate 7 of Comparative Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0013] The present disclosure will be described in detail below. In this specification, a numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the lower and upper limits. In the present specification, in the numerical ranges described in stages, the upper or lower limit value described in a certain numerical range may be replaced with the upper or lower limit value of another numerical range described in stages. Furthermore, in the numerical ranges described in the present specification, the upper or lower limit value described in a certain numerical range may be replaced with a value shown in the examples. In this specification, the term "process" includes not only an independent process but also a process that cannot be clearly distinguished from other processes, as long as the intended purpose of the process is achieved.

[0014] In the present disclosure, the terms "carbon nanotubes," "single-walled carbon nanotubes," "multi-walled carbon nanotubes," "carbon nanotube aggregate," "carbon nanotubes having a maximum length of 1000 μm to 30000 μm," and "carbon nanotube dispersion" may be abbreviated as "CNT," "SWCNT," "MWCNT," "CNT aggregate," "ULCNT," and "CNT dispersion," respectively.

[0015] (carbon nanotube aggregates) The carbon nanotube aggregate (also referred to as "CNT aggregate") according to the present disclosure has a density factor Σ calculated by the following formula (α) of less than 1.0, and the common logarithm of the viscosity of a dispersion liquid obtained by mixing the carbon nanotube aggregate, sodium carboxymethyl cellulose having a molecular weight of 700 kDa, and water, in which the concentration of the carbon nanotube aggregate is 0.20 mass % and the concentration of the sodium carboxymethyl cellulose is 0.30 mass %, is 1.0 or more (the unit of viscosity is mPa s).

[0016]

number

[0017] According to the CNT aggregate according to the present disclosure, a carbon nanotube dispersion liquid having higher tensile strength than conventional ones can be obtained. On the other hand, Patent Documents 1 and 2 do not include any description that focuses on the density factor Σ and viscosity.

[0018] For example, Patent Document 1 describes the relationship between the median diameter in the volumetric particle size distribution obtained by centrifugal sedimentation when multi-walled carbon nanotubes are dispersed in water at a specific concentration, and the structure formed by entanglement of multi-walled carbon nanotubes. However, it does not pay any attention to the density factor described in the present disclosure, and does not describe that a carbon nanotube dispersion with high tensile strength can be obtained. For example, Patent Document 2 describes a conductive film and a solar cell in which carbon nanotubes have a network structure and are combined with polystyrene sulfonic acid, but does not pay any attention to the density factor described in the present invention, and does not describe that a carbon nanotube dispersion liquid with high tensile strength is obtained and that it has excellent cycle characteristics in evaluation of a lithium ion secondary battery. In contrast to this, with the CNT aggregate according to the present disclosure, by satisfying the conditions of the density factor Σ and viscosity, it is possible to obtain a carbon nanotube dispersion liquid having a higher tensile strength than conventional ones.

[0019] <Denseness factor Σ> The sparseness / denseness factor is calculated from the following relational expression. When the thick CNT film is CNT film A and the thin CNT film is CNT film B, the ratio of the resistance factors of A and B is (surface resistivity of CNT film A / surface resistivity of CNT film B) × (absorbance of CNT film A / absorbance of CNT film B), and the density factor is (resistance factor of CNT film A ÷ resistance factor of CNT film B) × (concentration of carbon nanotube aggregates in CNT film B ÷ concentration of carbon nanotube aggregates in CNT film A). The calculated sparseness / denseness factor is greater than 0 and less than 1.00. The density factor corresponds to the ratio of the volume resistivity of a thick CNT film to that of a thin CNT film, and represents the network properties of the CNT. The larger the density factor, the better the network properties of the CNT.

[0020] The theoretical explanation for the calculation of the sparseness / denseness factor Σ obtained by the above formula (α) will be given below.

[0021] -Overview of density factors- Derivation of the formula The surface resistivity ρs of a resistor is a physical quantity that includes the film thickness t and is expressed as ρs = ρv / t, where ρv is the volume resistivity and t is the film thickness. The absorbance Abs is expressed as Abs = εCt, where ε is the molar absorptivity coefficient, C is the concentration of the substance, and t is the film thickness. Therefore, when the surface resistivity ρs is multiplied by the absorbance, the film thickness t is canceled out, and it can be expressed as ρs × Abs = ρv × ε × C. As the dimension of this parameter is Ohm, it is defined as the resistance factor P.

[0022]

number

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

[0024]

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[0025] The concentration C is proportional to the amount of filtration when the CNT dispersion is suction filtered, and is a constant. In other words, the ratio of the resistance factors P can be said to be proportional to the ratio of the volume resistivities. The above formula can be rearranged as follows:

[0026]

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

[0028]

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[0029] An ideal value is one where the volume resistivity remains the same between thin and thick films. Normally, the value is less than 1, and the larger the density factor, the smaller the difference in volume resistivity between films with sparse and dense CNT aggregates, indicating better network properties.

[0030] The sparse / dense factor Σ calculated by the formula (α) may be 0.700 or less, 0.500 or less, 0.300 or less, 0.200 or less, or 0.100 or less. The sparseness / denseness factor Σ is preferably 0.075 or more, and may be 0.076 or more, 0.077 or more, 0.078 or more, 0.079 or more, 0.080 or more, 0.081 or more, 0.082 or more, 0.083 or more, 0.084 or more, or 0.085 or more. The upper and lower limit values ​​of the sparseness / denseness factor Σ can be combined arbitrarily. Among these, it is preferably 0.075 or more and 0.700 or less, more preferably 0.080 or more and 0.700 or less, even more preferably 0.083 or more and 0.700 or less, and particularly preferably 0.084 or more and 0.700 or less. In another embodiment, it is preferably 0.075 or more and 0.500 or less, more preferably 0.080 or more and 0.500 or less, and even more preferably 0.084 or more and 0.500 or less. In another embodiment, it is preferably 0.075 or more and 0.200 or less, more preferably 0.080 or more and 0.200 or less, and even more preferably 0.084 or more and 0.200 or less. In another aspect, the ratio is preferably 0.075 or more and 0.100 or less, more preferably 0.080 or more and 0.100 or less, even more preferably 0.083 or more and 0.100 or less, particularly preferably 0.084 or more and 0.100 or less, even more preferably 0.086 or more and 0.100 or less, and especially preferably 0.086 or more and 0.095 or less.

[0031] Specifically, when the density factor Σ is 0.075 or more, the CNTs gather appropriately, making it easier to form a network structure. Furthermore, the number of contacts between CNT aggregates increases, improving the tensile strength. In addition, the CNTs are more likely to form bundles, making the conductive path thicker and reducing the resistivity of the conductive path. As a result, the conductivity of the CNT aggregate is improved, and the performance as an electrode material is optimized. Also, when the density factor is 0.700 or less, while there is a situation where conductive paths are formed by the network structure in addition to the bundles of CNTs, the network structure does not become too thin and the resistivity of the conductive path is suppressed. Also, when the density factor is 0.700 or less, the bundle diameter of the CNTs becomes appropriately small, and the contactable area between the bundles increases. As a result, the frictional force between the bundles increases, improving the tensile strength of the CNT aggregate. In addition, particularly good dispersibility of the CNT aggregate in a solvent can be ensured. Furthermore, when used as a conductive aid for a battery, the adhesion of the CNT aggregate to the electrode active material in the electrode is also good. As a result, the structural stability in the electrode is enhanced, the durability against volume changes and stress during battery cycling is improved, and the cycle characteristics of the battery are improved.

[0032] The ratio of the film thickness of CNT film A (thick film) to CNT film B (thin film) is preferably CNT film A:CNT film B = 30:1 to 2:1, more preferably 20:1 to 3:1, and even more preferably 10:1 to 4:1. When the ratio of the film thickness is within this range, in the comparison of the absorbance of CNT film A and CNT film B, the density factor can be calculated without being affected by differences in the degree of scattering due to an excessive film thickness difference.

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

[0034] <Surface resistivity of CNT film> In the present disclosure, the surface resistivity of the CNT film shall be determined by the surface resistivity of the CNT film obtained by diluting a dispersion containing the CNT aggregate with a large excess of pure water, filtering, transferring the formed filter membrane onto a glass substrate, and drying. The surface resistivity can be measured by the four-terminal four-probe method in accordance with the standard of JIS K7194:1994. As the resistivity meter, for example, Loresta GXII manufactured by Nitto Seiko Analytic Co., Ltd. is used. In the present disclosure, the surface resistivity is measured by the following method. For the prepared measurement sample, the surface resistivity at one point in the center of the film is measured by the four-probe method using a resistivity meter, and is designated as the surface resistivity W.

[0035] From the viewpoints of ensuring conductivity as a conductive aid and the stability of the dispersion liquid, the surface resistivity of the CNT film is preferably 0.1 Ω / sq to 1000 Ω / sq, more preferably 1.0 Ω / sq to 500 Ω / sq, still more preferably 10 Ω / sq to 300 Ω / sq, particularly preferably 15 Ω / sq to 200 Ω / sq, and most preferably 20 Ω / sq to 200 Ω / sq. As the measurement location, the center of the film is preferable from the viewpoint of easily ensuring accuracy. When measuring at the edge of the film, measurement errors may increase due to electric field leakage.

[0036] <Concentration of CNT film> In the present disclosure, for example, when obtaining a film by filtering a dispersion liquid, the concentration of the CNT film can be estimated from the amount of the dispersion liquid used. However, since the ratio of the concentrations of thick and thin films is important for calculating the density factor of the present disclosure, the concentration itself of each CNT film is not so important.

[0037] <Measurement of absorbance> The absorbances of CNT film A and CNT film B are measured by ultraviolet-visible spectroscopy (UV-vis) at 550 nm. As the measurement apparatus for ultraviolet-visible spectroscopy (UV-vis), for example, Cary 5000 UV-Vis-NIR spectrophotometer (manufactured by Agilent Technologies) can be mentioned. In calculating the density factor in the present disclosure, since the ratio of the absorbances of thick and thin CNT films is important, the absorbance itself of each CNT film is not so important.

[0038] <Preparation of CNT Film> -Attachment of CNT Film to Substrate for Measuring Density Factor- More specifically, the CNT film is prepared according to the following procedure. After diluting 12 μL of a 0.2 mass% CNT dispersion in 25 mL of pure water, suction filtration is performed using a membrane filter to obtain a filtration membrane A on the membrane filter. Optionally, the surface of the glass substrate is treated with an amino silane coupling material or a known treatment such as UV ozone cleaning treatment. While the membrane filter is wet, it is immersed in pure water to release the filtration membrane A, which is then attached onto the glass substrate. The glass substrate is dried on a hot plate at 100 °C for 10 minutes to obtain a CNT film A. A CNT film B is obtained in the same manner as the CNT film A, except that 2 μL of a 0.2 mass% CNT dispersion is used. The surface resistivity of the CNT film is measured for the CNT film A.

[0039] <Preparation of CNT Dispersion> In the preparation of the CNT film in the present disclosure, a CNT dispersion can be preferably used. By filtering and washing, excess dispersant can be removed, enabling a more accurate evaluation of the network structure itself.

[0040] -Preparation of CNT Dispersion- A CNT dispersion with a CNT concentration of 0.2 mass% relative to the total amount of the CNT dispersion is prepared. The method for preparing a CNT dispersion with a CNT concentration of 0.2 mass% relative to the total amount of the CNT dispersion is not particularly limited and can be prepared by a known method. More specifically, first, a mixture is obtained by mixing CNT aggregates, water, and sodium carboxymethylcellulose so that the CNT concentration is 0.2 mass% and the sodium carboxymethylcellulose concentration is 0.3 mass%. The mixture is then subjected to a pre-dispersion treatment using a homogenizer for one hour, and then to a main dispersion treatment using a wet jet mill, thereby obtaining a CNT dispersion with a CNT concentration of 0.2 mass%. In other words, a CNT aqueous dispersion with a CNT concentration of 0.2 mass% is prepared.

[0041] The detailed conditions for the pre-dispersion treatment are not particularly limited, and for example, the dispersion treatment is carried out using a homogenizer under conditions of 500 rpm to 20,000 rpm. The detailed conditions for this dispersion treatment are not particularly limited, and for example, the dispersion treatment is carried out using a wet jet mill under the following conditions: nozzle diameter: 0.15 mm to 0.70 mm, pressure: 10 MPa to 250 MPa, number of times: 1 to 30 times, method: circulation method.

[0042] <Viscosity> The aggregate of carbon nanotubes according to the present disclosure is a dispersion liquid obtained by mixing an aggregate of carbon nanotubes, sodium carboxymethyl cellulose having a molecular weight of 700 kDa, and water, in which the concentration of the aggregate of carbon nanotubes is 0.20 mass % and the concentration of sodium carboxymethyl cellulose is 0.30 mass %, and the common logarithm of the viscosity of the dispersion liquid is 1.0 or more (the unit of viscosity is mPa·s). Note that the viscosity in the present disclosure is the viscosity at 25°C.

[0043] The common logarithm of the viscosity of the dispersion is preferably 1.0 or more and 5.0 or less, and the upper limit may be 4.5 or less, 4.0 or less, 3.5 or less, 3.2 or less, 3.1 or less, 3.0 or less, or 2.9 or less. The lower limit may be 1.0 or more, 1.1 or more, or 1.15 or more. Furthermore, the upper limit and lower limit may be combined in any manner.

[0044] When the common logarithm of the viscosity of the dispersion is 1.0 or more, the dispersibility of the CNTs is improved, and the performance as an electrode material is optimized.

[0045] The common logarithm of the viscosity of the dispersion is more preferably 1.1 or more and 3.5 or less, even more preferably 1.2 or more and 3.2 or less, particularly preferably 1.3 or more and 3.2 or less, more preferably 1.4 or more and 3.2 or less, even more preferably 1.5 or more and 3.2 or less, particularly preferably 1.6 or more and 3.2 or less. In another embodiment, the ratio is more preferably 1.1 or more and 3.5 or less, even more preferably 1.1 or more and 3.2 or less, particularly preferably 1.1 or more and 3.0 or less, and even more preferably 1.15 or more and 2.90 or less. Furthermore, when the common logarithm of the viscosity of the dispersion is 1.1 or more and 3.5 or less, the dispersion of the CNTs is further improved, and the tensile strength of the CNT aggregate is improved. Specifically, when the logarithm of the viscosity of the dispersion is 1.6 or more and 3.2 or less, the CNTs are uniformly dispersed and the tensile strength is easily ensured. As a result, when the dispersion is added to an electrode as a conductive additive, the conductivity of the electrode is improved and the internal resistance of the battery is reduced, thereby improving the charge / discharge efficiency of the battery and further improving its cycle characteristics. Therefore, when the common logarithm of the viscosity is 1.0 or more, it becomes possible to obtain a CNT film with excellent mechanical properties.

[0046] The carbon nanotube aggregate according to the present disclosure is preferably a dispersion liquid obtained by mixing the carbon nanotube aggregate, sodium carboxymethylcellulose having a molecular weight of 700 kDa, and water, in which the concentration of the carbon nanotube aggregate is 0.20 mass % and the concentration of sodium carboxymethylcellulose is 0.30 mass %, and the common logarithm of the viscosity of the dispersion liquid is preferably 1.54 or more, more preferably 1.6 or more (the unit of viscosity is mPa·s).

[0047] The common logarithm of the viscosity of the dispersion is 1.54 or more, more preferably 1.6 or more and 5.0 or less, and the upper limit may be 4.5 or less, 4.0 or less, 3.5 or less, 3.3 or less, 3.2 or less, 3.1 or less, 3.0 or less, or 2.9 or less. The lower limit may be 1.7 or more, 1.8 or more, 1.9 or more, 2.0 or more, or 2.1 or more. Furthermore, the upper limit and lower limit may be combined in any manner. The common logarithm of the viscosity of the dispersion is more preferably 1.8 or more and 3.2 or less, even more preferably 2.0 or more and 3.0 or less, and particularly preferably 2.1 or more and 2.9 or less. By properly controlling the viscosity of CNTs, the dispersibility of CNTs improves, and the tensile strength increases. Specifically, when the common logarithm of the viscosity of the dispersion is 1.8 to 3.2, the CNTs are uniformly dispersed and the tensile strength is easily ensured. As a result, when the dispersion is added to an electrode as a conductive additive, the conductivity of the electrode is improved and the internal resistance of the battery is reduced, thereby improving the charge / discharge efficiency of the battery and further improving its cycle characteristics.

[0048] Furthermore, when the logarithm of the viscosity of the dispersion is 2.0 to 3.2, more preferably 2.0 to 3.0, the dispersion of the CNTs is further improved, and the tensile strength is increased. As a result, when the dispersion is added to an electrode as a conductive additive, the electrode can be made more durable against volume changes and stress during cycling, contributing to the life of the battery. In particular, when the logarithm of the viscosity of the dispersion is 2.1 or more and 3.1 or less, more preferably 2.1 or more and 2.9 or less, the balance between CNT dispersibility and tensile strength is optimized, and when added to an electrode as a conductive additive, for example, the electrode's performance is maximized. Within this range, both uniform CNT dispersion and high conductivity are achieved, and significant improvements in the cycle characteristics of the battery are expected.

[0049] <Bundle structure> The CNT aggregate according to the present disclosure preferably includes a bundle structure. A bundle structure refers to an aggregate in which multiple CNTs are aggregated together by van der Waals forces, etc., to form a bundle. It is presumed that when a CNT aggregate contains a bundle structure of an appropriate size, it becomes easier to handle as a CNT aggregate and its stability is further improved.

[0050] The bundle structure in the CNT aggregate can be formed, for example, by controlling the catalyst particle size distribution in production by chemical vapor deposition (CVD) method, or by controlling the cooling rate in the cooling step.

[0051] From the viewpoint of achieving both ease of handling of the CNT aggregate and dispersibility in a solvent, the diameter of each bundle contained in the CNT aggregate is preferably 5 nm to 500 nm, and more preferably 10 nm to 300 nm. The content of the bundle structure in the CNT aggregate is preferably 10% by mass to 100% by mass, and more preferably 20% by mass to 90% by mass, relative to the total mass of the CNT aggregate. The presence or absence of a bundle structure in a CNT aggregate can be confirmed by observing the CNT aggregate with an optical microscope, a scanning electron microscope (SEM), etc. The bundle diameter can be determined by identifying the location where the bundle structure exists in the CNT aggregate and measuring the length using a photographed image of the bundle structure.

[0052] The CNT aggregate according to the present disclosure preferably includes a bundle structure, and in an area observed with a scanning electron microscope, the cumulative 90% bundle diameter (hereinafter also referred to as "cumulative 90% bundle diameter") is more than 80 nm and less than 500 nm. In the CNT aggregate according to the present disclosure, when observed by SEM, the cumulative 90% bundle diameter exceeds 80 nm, which makes it easier for the CNT bundles to gather and form a long-distance network. Furthermore, when the cumulative 90% bundle diameter is less than 500 nm, it becomes easier to ensure tensile strength.

[0053] Specifically, when the cumulative 90% bundle diameter is greater than 80 nm, CNTs can be gathered together appropriately and come into efficient contact with each other to form a network structure. This improves the tensile strength of the CNT aggregate. Furthermore, when the cumulative 90% bundle diameter is 500 nm or less, it becomes easier to ensure an area where bundles can contact each other. This increases the frictional force between the bundles, improving the tensile strength of the CNT aggregate.

[0054] In particular, the cumulative 90% bundle diameter is preferably greater than 90 nm and less than or equal to 450 nm. In this range, the CNT bundle diameter is appropriately controlled, ensuring sufficient contact points between CNTs and efficiently forming a network structure, thereby improving tensile strength. It also makes it easier to ensure sufficient contact area between bundles. This increases the frictional force between bundles, improving the tensile strength of the CNT aggregate.

[0055] When the CNT aggregate according to the present disclosure has a cumulative 90% bundle diameter of 100 nm or more as observed by SEM, the CNT bundles gather together and tend to form a long-distance network. Furthermore, when the cumulative 90% bundle diameter is 400 nm or less, it becomes easier to ensure tensile strength.

[0056] Specifically, by having a cumulative 90% bundle diameter of 100 nm or more, CNTs can be gathered together appropriately and come into efficient contact with each other to form a network structure. This improves the tensile strength of the CNT aggregate. Furthermore, by having a cumulative 90% bundle diameter of 400 nm or less, it becomes easier to ensure an area where bundles can contact each other. This increases the frictional force between the bundles, improving the tensile strength of the CNT aggregate.

[0057] In particular, the cumulative 90% bundle diameter is preferably more than 110 nm and not more than 350 nm, more preferably 130 nm or more and 340 nm or less, and even more preferably 150 nm or more and 340 nm or less. By appropriately controlling the bundle diameter of CNTs within this range, sufficient contact points between CNTs are ensured, and a network structure is efficiently formed, improving the tensile strength. Furthermore, by appropriately controlling the bundle diameter, the frictional force between bundles increases, improving the tensile strength of the CNT aggregate.

[0058] The CNT aggregate according to the present disclosure preferably includes a bundle structure, and in an area observed with a scanning electron microscope (SEM), the area ratio of bundles having a bundle diameter of 100 nm or more exceeds 0.1. The area ratio of bundles having a bundle diameter of 100 nm or more is calculated by dividing the area of ​​bundles having a bundle diameter of 100 nm or more in an SEM image of the CNT aggregate by the total area of ​​the CNT aggregate.

[0059] The matters relating to the bundle structure contained in the CNT aggregate are as described above, and therefore a description thereof will be omitted here.

[0060] In the CNT aggregate according to the present disclosure, the area ratio of bundles having a bundle diameter of 100 nm or more exceeds 0.1 in the region observed by SEM, which allows the CNT bundle structure to be formed appropriately and improves tensile strength. Specifically, a bundle diameter of 100 nm or more allows the CNTs to gather together appropriately and efficiently form a network structure. This improves the mechanical strength of the CNT aggregate, thereby improving tensile strength.

[0061] In particular, the area ratio of the bundle is preferably more than 0.1 and less than 0.6, more preferably more than 0.1 and less than 0.55, more preferably more than 0.1 and less than 0.5, more preferably 0.11 or more and less than 0.5, even more preferably 0.15 or more and less than 0.5, and preferably 0.17 or more and 0.49 or less. Within this range, the CNT bundle diameter can be appropriately controlled to increase the number of contact points between CNTs, efficiently forming a network structure and improving tensile strength. This makes it easier to ensure a sufficient contact area between bundles. This increases the frictional force between the bundles and improves the tensile strength of the CNT aggregate.

[0062] Furthermore, from the viewpoint of increasing the breaking elongation, it is particularly preferable that the area ratio of the bundles is more than 0.17 and not more than 0.48. A high breaking elongation improves the flexibility and durability of the material containing the CNT aggregate.

[0063] Furthermore, the area ratio of the bundles is preferably 0.15 or more and 0.55 or less, more preferably 0.15 or more and less than 0.5. Within this range, the CNT bundle diameter is appropriately controlled, increasing the number of contact points between CNTs and efficiently forming a network structure, thereby improving tensile strength. This makes it easier to ensure an area where bundles can contact each other. This increases the frictional force between the bundles, improving the tensile strength of the CNT aggregate.

[0064] The bundle diameter of the CNT aggregate is measured by observation using an SEM. The CNT aggregate is photographed at a magnification of 100,000 to obtain multiple SEM photographs. The imaging method using an SEM is not particularly limited, and can be performed by a known method.

[0065] -Image capture- Using an SEM device (for example, S-4800 manufactured by Hitachi High-Technologies Corporation), images are taken under the following conditions to obtain multiple images of the CNT aggregate. From the viewpoint of reducing the variance of the analytical values ​​of the bundle diameter, it is preferable to obtain five or more images. Acceleration voltage: 0.5 kV Emission current: 10μA Measurement magnification: 100,000 times Image size: 1280 pixels x 960 pixels

[0066] -Image selection- From the obtained images, select two or more images in which CNT bundles are clearly observed.

[0067] - Overview of bundle diameter analysis using image analysis - The selected image is subjected to image processing and analysis using Python. In image processing, the CNT outline and center line are detected and combined with the original image. In image analysis, the bundle diameter is determined by calculating the distance from the center line to the outline of the created image. The product of the bundle diameter and the length of the center line is then calculated to calculate the area occupied by the CNT in the image.

[0068] -Detecting the outline of CNTs using image analysis- 1. The image is binarized to distinguish between CNTs and the background. 2. Create a contour for the CNT part using the edge detection function of the OpenCV library.

[0069] -Detecting CNT centerlines using image analysis- 1. Adjust the parameters to distinguish between CNTs and the background and perform binarization. 2. Create a skeleton for the CNT part using the skeletonize function of the scikit-image library. 3. For each coordinate of the skeleton, the number of skeletons within the surrounding two pixels is counted, and coordinates where five or more exist are recognized as skeleton intersections. 4. The skeleton is divided at the intersections by converting the intersections into background pixels. The divided skeleton is called a region. 5. Measure the length of the region and delete the short region. 6. Linear approximation is performed for each region. 7. For each line created, obtain the X-axis coordinate of the region that was the source of approximation. Convert the line into a line segment based on the range in which the obtained X-coordinate exists. Treat the line segment obtained here as the center line of the CNT. 8. Calculate the similarity based on the center coordinates and angle for all pairs of center lines. Pairs of center lines whose center coordinates are within 10 pixels of each other and whose angle between the two line segments is less than 10 degrees are treated as overlapping center lines, and the shorter one is deleted. 9. The CNT outline and center line are superimposed on the original image and saved. The outline is displayed in red and the center line in blue.

[0070] -Detecting CNT bundle diameter using image analysis- 1. The image created by image processing is read and the CNT, outline, background, and center line are recognized by color recognition. 2. Measure the length of each center line. 3. Choose a random point on the center line and draw a perpendicular line from the point to the center line. 4. Find the intersection of the perpendicular line and the contour, and save the distance from a random point on the centerline to the intersection as the bundle diameter. 5. Calculate the area occupied by the 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 area occupied on the vertical axis.

[0071] - Obtaining bundle diameter parameters - Using the calculated bundle diameter histogram data, the feature amount of the bundle diameter of each sample is calculated by the following method. 1. The bundle diameters and occupied areas of multiple fields of view for the same sample are added together and normalized so that the total sum is 1. Following normalization, the unit of the vertical axis is the occupied area ratio. 2. Calculate the total area ratio of bundles with a bundle diameter of 100 nm or more. 3. Calculate the cumulative exclusive area ratio, and determine the bundle diameter when this value exceeds 0.9 for the first time as the cumulative 90% bundle diameter.

[0072] <Tensile strength> The CNT aggregate according to the present disclosure has a tensile strength measured by the following measurement method of preferably 1.0 MPa or more and 70.0 MPa or less, and more preferably 2.0 MPa or more and 50.0 MPa or less, and also has a breaking elongation of preferably more than 0% and 7.0% or less, and more preferably more than 0% and 5.0% or less.

[0073] -Method for measuring tensile strength and elongation at break- Carbon nanotube aggregates, sodium carboxymethylcellulose with a molecular weight of 700 kDa, and water are mixed to prepare a carbon nanotube dispersion with a carbon nanotube aggregate concentration of 0.20 mass% and a sodium carboxymethylcellulose concentration of 0.30 mass%. 15 mL of the resulting carbon nanotube dispersion is poured onto a glass slide-type silicon plate with inner dimensions of 22 mm x 75 mm x 3 mm, and heated and dried at 100 °C for 30 minutes to obtain a measurement sample. The prepared measurement sample is fixed to the grip of a tensile testing device, and a tensile test is performed at a tensile speed of 1 mm / min to measure the tensile strength. The point at which the stress is maximum in the tensile test is considered to be the breaking point, and the breaking elongation is calculated from the length of the measurement sample at the breaking point and the length of the measurement sample before the tensile test.

[0074] The breaking elongation of the CNT aggregate according to the present disclosure is more than 0% and not more than 6.0%, preferably not less than 1.0% and not more than 6.0%, and more preferably not less than 1.1% and not more than 5.4%.

[0075] When the breaking elongation of the CNT aggregate according to the present disclosure exceeds 0%, the CNTs according to the present disclosure are sufficiently long, and therefore the tensile strength is likely to be improved. Specifically, when the CNTs are sufficiently long, the CNTs gather together appropriately, making it easier to form a network structure. Furthermore, the number of contact points between the CNTs increases, improving the tensile strength. When the CNT aggregate according to the present disclosure has a breaking elongation of 6.0% or less, it is easy to process it into a dispersion and ensure its dispersibility in the dispersion. Specifically, a breaking elongation of 6.0% or less maintains the flexibility of the CNTs appropriately, realizing uniform dispersion of the CNTs in the dispersion. This maintains the viscosity of the dispersion appropriately, further improving durability against volume changes and stress during battery cycling. This further improves the discharge capacity retention rate. Therefore, it is important for the breaking elongation of the CNT aggregate to be in the range of more than 0% and not more than 6.0% in order to improve the tensile strength of the CNT aggregate and further improve the dispersibility.

[0076] The breaking elongation of the CNT aggregate can be adjusted by the length, diameter, etc. of the CNT aggregate.

[0077] The tensile strength of the CNT aggregate according to the present disclosure is preferably 1.0 MPa or more and 70.0 MPa or less, more preferably 1.5 MPa or more and 65.0 MPa or less, and even more preferably more than 2.0 MPa and 60.0 MPa or less. When the tensile strength of the CNT aggregate according to the present disclosure is 1.0 MPa or more, more preferably 2.5 MPa or more, and even more preferably more than 3.5 MPa, the CNTs according to the present disclosure are sufficiently long, making it possible to produce a battery with excellent cycle characteristics. Specifically, when the CNTs are sufficiently long, the number of contact points between the CNTs increases, allowing for smooth electron transfer, improving the conductivity of the entire CNT aggregate and improving the cycle characteristics of the battery (i.e., the retention rate of discharge capacity). When the tensile strength of the CNT aggregate according to the present disclosure is 70.0 MPa or less, more preferably 50.0 MPa or less, it is easy to process it into a dispersion and to ensure dispersibility in the dispersion. Specifically, a tensile strength of 70.0 MPa or less, more preferably 50.0 MPa or less, maintains a good balance between the flexibility and mechanical strength of the CNTs, realizing uniform dispersion of the CNTs in the dispersion. This maintains the viscosity of the dispersion appropriately, further improving durability against volume changes and stress during battery cycling. This further improves the discharge capacity retention rate.

[0078] Note that the tensile strength of the CNT aggregate can be adjusted by the length, diameter, etc. of the CNT aggregate.

[0079] <Uses of Carbon Nanotube Aggregates> The uses of the CNT aggregate according to the present disclosure are not particularly limited. Since the CNT aggregate according to the present disclosure has high conductivity, it can be suitably used, for example, as a conductive aid (particularly, a conductive aid for a negative electrode). Since the CNTs in the CNT aggregate according to the present disclosure are intertwined with each other and easily form a conductive path, for example, in an electrode, by coexisting with a conductive material such as a positive electrode active material and a negative electrode active material, the conductivity of the conductive material can be further improved. The CNT aggregate according to the present disclosure can be used together with, for example, graphite, ketjen black, etc., which are known conductive aids.

[0080] <Method for Producing CNT> The method for producing the CNT constituting the CNT aggregate according to the present disclosure is not particularly limited. For example, as the method for producing the CNT in the present disclosure, methods such as a conventionally known chemical vapor deposition (CVD) method and a method of reacting a gaseous reactant containing a carbon source in the presence of a catalyst can be applied.

[0081] The CNT in the present disclosure can be produced, for example, by referring to the methods described in JP-A-2016-102047, JP-T-2021-527611, etc.

[0082] Hereinafter, the method for producing the CNT in the present disclosure will be described with examples. However, the method for producing the CNT in the present disclosure is not limited to the following examples.

[0083] =Production Method X= An example of a CNT manufacturing method referred to in this disclosure is described in JP 2016-102047 A. That is, the manufacturing method includes the steps of passing gaseous reactants containing one or more carbon sources through a reactor, reacting the one or more gaseous reactants in a reaction zone of the reactor in the presence of a catalyst to form product particles containing carbon, aggregating the product particles into aggregates, and applying force to the aggregates to continuously move the aggregates out of the reaction zone (hereinafter also referred to as "Manufacturing Method X").

[0084] According to production method X, CNTs including ULCNTs can be obtained in the form of fibrous aggregates or other aggregate forms that are easy to handle.

[0085] In production method X, the force applied to the product particles may be a mechanical force. When the agglomerates are fibrous CNTs, the mechanical force applied to the product particles can be exerted by a rotating spindle around which the agglomerates are wound, and the fibrous CNTs can be collected on the spindle or accumulated elsewhere by rotating around the spindle one or more times and then successively unwinding the spindle.

[0086] The spindle is preferably oriented with its axis perpendicular or parallel to the flow direction of the gaseous reactant(s), although other orientations are also possible, for example, a spindle with its axis oriented at a 25° angle to the flow direction of the gaseous reactants may also be suitable for applying mechanical forces to the product particles.

[0087] The spindle can rotate around two axes (e.g., two perpendicular axes). In particular, the spindle can rotate around axes perpendicular and parallel to the flow direction of the gaseous reactants. Such a spindle can pull and twist the fibrous CNT aggregates to control the twist number and length.

[0088] The spindle may be made of metal, ceramic, or resin. The spindle can have different suitable shapes depending on the material properties and the intended use of the CNTs. The spindle can be used as a mold for producing carbon products, for example, by a spin-coating process. Preferred spindle shapes are rod-shaped or box-shaped.

[0089] Fibrous CNTs are deposited on a spindle or elsewhere, and the coating thickness and orientation can be controlled by controlling the reaction time and conditions, or by the application of electric or other fields to the carbon product. The coating thickness and orientation of the carbon product can be controlled, for example, by gas flow forces.

[0090] The rotation speed of the spindle is preferably 0.01 rpm (revolutions / minute; the same applies hereinafter) to 10,000 rpm, and more preferably 0.1 rpm to 100 rpm. The spinning speed (i.e., the rotational speed of the spindle) may be adjusted so that the material is collected at a similar rate as it is produced. The rotational speed of the spindle may also control the thickness of the accumulated CNT fiber. In a preferred embodiment, as the spindle rotates, the CNT fiber is processed in the axial direction of the spindle. This processing ensures that the CNT fiber is evenly wrapped along the spindle, rather than being wrapped only at one specific point on the spindle.

[0091] The CNT fibers may be collected, for example, on the reactor wall by a substrate placed in the reactor. The substrate may be a fixed substrate or a rotating guide used to apply a strong and equal force to the CNT fibers as they are collected. A suitable substrate arrangement for fiber technology is a substrate consisting of two guides positioned at right angles to each other.

[0092] In production method X, the mechanical force applied to the product particles may be a force applied by an accelerating gas flow. The accelerating gas flow may be generated by passing the product particles through a reactor having a narrow diameter or through a capillary tube downstream of the reaction zone. A vacuum may be applied to the product particles.

[0093] Another force that can be applied to the product particles is electrostatic force, which is suitably applied by a charged plate. Electrostatic force requires that the product particles be charged. By using a charged plate, the CNTs can be grown in the form of intertwined sheets on the charged plate.

[0094] Other forces applied to the product particles may also be magnetic forces or photon pressure applied by a light source.

[0095] Instead of a gaseous reactant containing a carbon source, the CNT precursor may be injected in the form of a liquid containing a carbon source. When a liquid is used as the CNT precursor, it can be injected through a single inlet or multiple inlets, for example, in a showerhead configuration.

[0096] Preferably, the gaseous reactant(s) are reacted at a temperature between 500° C. and 1600° C., more preferably between 1000° C. and 1500° C. A temperature gradient is preferably maintained within the reactor, with the reaction zone being maintained at a higher temperature than the product zone of the reactor.

[0097] The gaseous reactants may be mixed with one or more gases that act as diluents. The gaseous reactants may also be mixed with gases that play a supporting but not direct role in the reaction. It is also preferred to use a diluent gas that can react with the amorphous carbon by-product, if any, to keep the reactive sites on the catalyst intact and produce nanotubes.

[0098] Gases that can be used as a diluent include argon or other inert gases, hydrogen, nitrogen, ammonia, carbon dioxide, helium, etc. Among these, hydrogen is particularly preferred as a gas that can be used as a diluent.

[0099] The composition of the product particles can be controlled by monitoring the agglomerates and modifying the reaction conditions based on the information obtained. For example, the agglomerates can be monitored by online Raman spectroscopy, which provides data indicating whether the CNTs are single-walled or multi-walled. It also provides data indicating the diameter and crystallinity of the CNTs. The agglomerates can also be monitored by online conductivity measurements, gas analysis, measuring the opacity of the reaction zone, and / or measuring the winding force.

[0100] When the agglomerate is removed from the reactor, it is preferable to prevent air from entering the reactor. When the diluent gas contains hydrogen, preventing air from entering the reactor is particularly important, for example, from the viewpoint of preventing an explosive mixture of hydrogen and air from forming in the reactor.

[0101] In production method X, it is preferable to control the temperature of the reactor to 200°C to 700°C when removing the agglomerates from the reactor. The CNT bundle diameter can be controlled by the temperature of the CNT reaction region and the temperature of the reactor when removing the agglomerates from the reactor. The higher the reactor temperature when removing the agglomerates from the reactor, the larger the CNT bundle diameter can be. For example, by setting the temperature of the reactor at about 150° C. when the aggregates are removed from the reactor, the bundle diameter, which is 90% of the cumulative diameter of the CNTs, can be set to 110 nm to 170 nm. By setting the temperature of the reactor at about 500° C. when the aggregates are removed from the reactor, the bundle diameter, which is 90% of the cumulative diameter of the CNTs, can be set to 200 nm to 230 nm. By setting the temperature of the reactor at about 750° C. when the aggregates are removed from the reactor, the bundle diameter, which is 90% of the cumulative diameter of the CNTs, can be set to 300 nm to 400 nm. The "reactor temperature" is a temperature determined by measuring the gas temperature at the outlet through which the condensate is taken out of the reactor.

[0102] The product particles in production method X contain ULCNTs. Depending on the production conditions, SWCNTs and MWCNTs may also be contained.

[0103] The product particles may be produced by chemical vapor deposition, where a gaseous reactant, a carbon source, is reacted in the presence of a catalyst.

[0104] Carbon-containing compounds suitable as carbon sources include carbon monoxide, carbon dioxide, aromatic hydrocarbons (e.g., benzene, toluene, xylene, cumene, ethylbenzene, naphthalene, or mesitylene), non-aromatic hydrocarbons (e.g., methane, ethane, propane, butane, pentane, hexane, cyclohexane, ethylene, propylene, or acetylene), and oxygen-containing hydrocarbons (e.g., formaldehyde, acetaldehyde, acetone, methanol, ethanol, diethyl ether, polyethylene glycol, 1-propanol, ethyl formate, and hydrocarbons containing mixtures of two or more thereof). The carbon-containing compound is preferably carbon monoxide, methane, ethylene or acetylene.

[0105] Preferably, the carbon source contains oxygen. Ethanol is a particularly preferred carbon source. Oxygen can be introduced into the reactor by other methods, such as by using a diluent gas or a carbon source containing water.

[0106] The catalyst is preferably a transition metal, particularly a group VIB transition metal such as chromium (Cr), molybdenum (Mo), or tungsten (W), or a group VIIIB transition metal. Specifically, the catalyst is preferably, for example, iron (Fe), cobalt (Co), nickel (Ni), ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os), iridium (Ir), platinum (Pt), or manganese (Mn), or a mixture thereof. Metals from the lanthanide and actinide series (e.g., yttrium (Y)) can also be used as catalysts. Fe, Ni, Co, Mo, and mixtures thereof, such as a mixture of Ni and Co (50 / 50 by mass), a mixture of Fe and Ni, or a mixture of Fe and Mo, are more preferred. Any of these transition metals, either alone or in combination with any of the other transition metals listed, can serve as a catalyst for CNT growth, with it being particularly preferred that the catalyst be a mixture of two or more of the listed metals.

[0107] The catalyst is preferably formed by decomposition of a precursor. The precursor is preferably a thermally, photo-, or plasma-decomposable compound of one or more of the above metals, such as a carbonyl or cyclopentadienyl organometallic compound. Ferrocene, iron pentacarbonyl, nickelocene, and cobaltocene are particularly preferred precursors. In one embodiment, at least 0.01% by mass of the precursor is contained in the carbon source, preferably 0.2% to 30% by mass of the precursor, and more preferably 0.2% to 20% by mass of the precursor. In one embodiment, 0.23% to 2.3% by mass of the precursor may be contained in the carbon source, and 0.02% to 20% by mass of the precursor may be contained in the carbon source. The catalyst may be used supported on a carrier, and preferred carriers include silica and magnesium oxide.

[0108] The carbon source is preferably reacted in the presence of a promoter. Suitable promoters are one or more of sulfur, phosphorus, molybdenum, and organic compounds of these elements. Thiophene is also a preferred promoter. Suitably, up to 10% by weight of the promoter is included in the carbon source. Preferably, 0.2% to 6% by weight of the promoter is included in the carbon source. When high or low concentrations of thiophene are used as the promoter, MWCNTs are formed.

[0109] According to production method X, it is possible to obtain fibrous CNTs having a length of at least 500 μm, for example, at least 1 mm. The fibrous CNTs can be in the form of threads or sheets. The length of the fibrous CNT can be controlled, for example, by the winding capacity of the spindle used in producing the fibrous CNT.

[0110] The manufacturing method X preferably includes the steps of reacting a carbon source in a reaction zone of a reactor to produce CNTs, and aggregating the CNTs into aggregates by applying force to the CNTs. This manufacturing method makes it possible to easily produce fibrous CNTs.

[0111] Preferably, production method X further comprises, after the step of aggregating CNTs into aggregates, a step of purifying the resulting CNT aggregates. Specifically, first, the CNT aggregates are washed with alcohol (for example, methanol, ethanol, etc.). Next, they are washed with an alkaline solution (for example, ammonia water). The pH of the alkaline solution is, for example, 8 to 11. Then, they are washed with pure water.

[0112] The cleaning method is not particularly limited, and may be a method of spraying a cleaning liquid onto the CNT aggregates, or a method of immersing the CNT aggregates in the cleaning liquid. Washing with alcohol removes alcohol-soluble components contained in the CNT aggregates. Furthermore, washing with an alkaline solution hydrolyzes and removes impurities contained in the CNT aggregates. Incidentally, washing with an acid solution may also be carried out.

[0113] After washing, the CNT aggregates are preferably dried. The drying method is not particularly limited, and can be carried out by a commonly known method.

[0114] By purifying the CNT agglomerates, the metal content in the CNTs can be reduced.

[0115] Preferably, production method X further comprises, after the step of purifying the CNT agglomerates, a step of passing the purified CNT agglomerates through a sieve. Also, it is preferable to recover the CNTs that have passed through the sieve.

[0116] The method for passing the material through a sieve is not particularly limited, and can be carried out by a commonly known method. The mesh size of the sieve is, for example, 0.1 mm to 3.0 mm, preferably 0.5 mm to 2.0 mm, and more preferably 1.0 mm to 1.5 mm. The material of the sieve is not particularly limited, and may be metal or resin. When the CNT aggregate is applied to an electrode (particularly an electrode of a lithium ion battery), it is preferable that the material does not impair the performance of the battery. The number of times the material is passed through the sieve is, for example, 1 to 3 times. Before passing the CNT agglomerates through a sieve, they may be crushed to an appropriate size. Crushing can be carried out using a crusher. Examples of crushers include a roll mill, a cutter mill, and a hammer mill.

[0117] The resulting CNT agglomerates are passed through a sieve and the CNTs that pass through the sieve are collected, thereby removing coarse CNTs and improving the stability of the CNT dispersion. Furthermore, in general, in the manufacture of electrodes, foreign matter that has been mixed in from the outside is removed, but by passing the obtained CNT agglomerates through a sieve, it is possible to more easily remove foreign matter that has been mixed in from the outside.

[0118] In another embodiment, a method may be adopted in which CNTs containing ULCNTs are generated in a reaction region by the above method, and then condensed to form CNTs containing ULCNTs, and the CNTs are continuously withdrawn from the vicinity of the reaction region. In another embodiment, a method may be adopted that includes producing CNTs containing ULCNTs in a reaction region, continuously electrostatically attracting the CNTs containing ULCNTs from the reaction region, and recovering the CNTs containing ULCNTs.

[0119] =Manufacturing method Y= In the present disclosure, the manufacturing method described in JP-A 2021-527611 can be referred to as an example of a method for manufacturing CNTs. That is, the manufacturing method includes a step (1) of supporting a mixture containing a main catalyst precursor and a co-catalyst precursor on γ-Al2O3 to manufacture an active support, a step (2) of drying the active support by multistage drying including vacuum drying, a step (3) of subjecting the dried active support to a heat treatment to manufacture a supported catalyst, and a step (4) of manufacturing CNTs in the presence of the supported catalyst (hereinafter also referred to as "manufacturing method Y").

[0120] ·Process (1) In step (1), a mixture containing a main catalyst precursor and a co-catalyst precursor is supported on γ-Al 2 O 3 to produce an active support.

[0121] In order to uniformly support the main catalyst precursor and the co-catalyst precursor on γ-AlO, the mixture may further contain a solvent, and the main catalyst precursor and the co-catalyst precursor may be dissolved in the solvent. The solvent may be one or more selected from the group consisting of water, methanol, and ethanol, and water is preferred.

[0122] Because γ-Al2O3 has high porosity and a spinel structure, the main catalyst and promoter can be randomly arranged in γ-Al2O3. CNTs grown from the randomly arranged main catalyst can be produced in an entangled state.

[0123] The main catalyst may be one or more selected from the group consisting of cobalt, iron, nickel, manganese and chromium, with cobalt being preferred.

[0124] 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.

[0125] The main catalyst precursor may be one or more selected from the group consisting of Co(NO3)2, Co(NO3)2·6H2O, Co2(CO)8, Co2(CO)6[HC=C(C(CH3)3)], Co(CH3CO2)2, Fe(NO3)3, Fe(NO3)2·nH2O, Fe(CH3CO2)2, Ni(NO3)2, Ni(NO3)2·6H2O, Mn(NO3)2, Mn(NO3)2·6H2O, Mn(CH3CO2)2·n(H2O) and Mn(CO)5Br, of which Co(NO3)2·6H2O, Fe(NO3)2·nH2O and Ni(NO3)2·6H2O are preferred.

[0126] The promoter improves the dispersibility of the main catalyst, and may be one or more selected from the group consisting of vanadium and molybdenum.

[0127] The promoter precursors were NH4VO3, NaVO3, V2O5, V(C5H7O2)3, and (NH4)6Mo7O. 24 4H2O, NH4VO3 and (NH4)6Mo7O 24 Preferably, one or more selected from the group consisting of 4H2O.

[0128] When the mixture contains two or more promoter precursors, i.e., when it contains both a vanadium precursor and a molybdenum precursor, the molar ratio of the sum of vanadium and molybdenum to vanadium can be 1:0.45 to 1:0.95 or 1:0.5 to 1:0.9, and preferably 1:0.5 to 1:0.9. When the above conditions are met, the CNT structure can be stably maintained and CNTs with the desired pore volume can be produced.

[0129] The mixture may contain the main catalyst precursor and the co-catalyst precursor such that the molar ratio of the main catalyst to the co-catalyst is 1:0.01 to 1:0.5, 1:0.1 to 1:0.4, or 1:0.1 to 1:0.25, and preferably 1:0.1 to 1:0.25. Satisfying the above molar ratio improves the dispersibility of the main catalyst, enabling the production of CNTs with the desired pore volume.

[0130] The mixture may further include an organic acid which serves to inhibit precipitation of the main catalyst precursor and the co-catalyst precursor.

[0131] 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.

[0132] The mixture may contain the organic acid and the co-catalyst precursor in a molar ratio of 1:1 to 1:20, 1:2 to 1:10, or 1:3 to 1:6, preferably 1:3 to 1:6. When the above range is satisfied, it is possible to produce a transparent catalyst metal solution during catalyst production, and it is advantageous in that it is possible to produce a catalyst in which fine particles are suppressed during impregnation.

[0133] After step (1), a step of aging may be further included.

[0134] The aging may be carried out for 1 to 60 minutes or 10 to 50 minutes. Preferably, it is carried out for 10 to 50 minutes. When the above conditions are satisfied, the main catalyst precursor and the co-catalyst precursor can be sufficiently supported on the γ-Al2O3. In addition, air bubbles present in the support are removed to the maximum extent possible, and the main catalyst precursor and the co-catalyst precursor can be sufficiently supported even in the fine pores inside the support.

[0135] ·Process (2) The active support is then dried by multi-stage drying, including vacuum drying.

[0136] Multi-stage drying may mean that a drying process including vacuum drying is performed two or more times. Specifically, multi-stage drying may include atmospheric drying and vacuum drying, or may include vacuum drying two or more times.

[0137] The vacuum drying may be carried out at 80° C. to 300° C. or 120° C. to 250° C., preferably at 120° C. to 250° C. If the above conditions are met, the main catalyst precursor, i.e., the coordinate bond of the main catalyst, can be easily decomposed to form the main catalyst oxide, and energy consumption can be minimized.

[0138] The vacuum drying may be performed at 1 mbar to 200 mbar or 30 mbar to 150 mbar, preferably 30 mbar to 150 mbar. When the above conditions are met, the main catalyst precursor, i.e., the main catalyst coordinated compound, is rapidly decomposed and discharged, making it easier to form the main catalyst oxide under vacuum conditions and minimizing energy consumption.

[0139] The vacuum drying can be performed for 10 minutes to 3 hours or 10 minutes to 2 hours, preferably 10 minutes to 2 hours. If the above conditions are met, the main catalyst precursor can be easily decomposed and converted into the main catalyst oxide, and energy consumption can be minimized.

[0140] On the other hand, when the multi-stage drying includes atmospheric drying and vacuum drying, atmospheric drying can be performed before the above-mentioned vacuum drying, and the atmospheric drying can remove solvent that may be present in the active support.

[0141] Drying at normal pressure may be carried out at 80°C to 160°C or 100°C to 140°C, and is preferably carried out at 100°C to 140°C. If the above conditions are met, the solvent present in the active support can be sufficiently removed, and energy consumption can be minimized.

[0142] Drying at atmospheric pressure may be performed at 900 mbar to 1,100 mbar, preferably 950 mbar to 1,050 mbar. If the above conditions are met, the solvent present in the active support can be sufficiently removed and energy consumption can be minimized.

[0143] Drying under atmospheric pressure may be carried out for 1 to 12 hours, preferably 3 to 9 hours. If the above conditions are met, the solvent present in the active support can be sufficiently removed and energy consumption can be minimized.

[0144] On the other hand, when the multi-stage drying includes two or more vacuum dryings, the multi-stage drying may include two or more vacuum dryings performed at different temperatures, more specifically, a primary vacuum drying performed at a first temperature and a secondary vacuum drying performed at a second temperature higher than the first temperature.

[0145] The primary vacuum drying can remove any solvent that may be present in the active support.

[0146] The first temperature may be 80° C. to 160° C., and preferably 100° C. to 140° C. If the above conditions are met, the solvent present in the active support can be sufficiently removed, and energy consumption can be minimized.

[0147] The primary vacuum drying can be carried out for 1 to 12 hours, preferably 3 to 9 hours. If the above conditions are met, the solvent present in the active support can be sufficiently removed and energy consumption can be minimized.

[0148] The primary vacuum drying may be performed at 1 mbar to 200 mbar, 1 mbar to 150 mbar, or 80 mbar to 150 mbar, and is preferably performed at 80 mbar to 150 mbar. If the above conditions are met, the solvent present in the active support can be sufficiently removed, and energy consumption can be minimized.

[0149] The secondary vacuum drying is as described above in the description of vacuum drying.

[0150] The second temperature may be 175° C. to 300° C., and preferably 180° C. to 280° C. If the above conditions are met, the main catalyst precursor, i.e., the coordinated bond of the main catalyst, can be easily decomposed to form the main catalyst oxide, and energy consumption can be minimized.

[0151] The secondary vacuum drying may be performed at 1 mbar to 200 mbar, 1 mbar to 150 mbar, or 1 mbar to 70 mbar, and more preferably at 1 mbar to 70 mbar. If the above conditions are met, the main catalyst precursor, i.e., the main catalyst coordinated compound, is rapidly decomposed and discharged, making it easier to form the main catalyst oxide under vacuum conditions and minimizing energy consumption.

[0152] The secondary vacuum drying may be performed for 10 minutes to 3 hours or 10 minutes to 2 hours, preferably 10 minutes to 2 hours. If the above conditions are met, the main catalyst precursor can be easily decomposed and converted into the main catalyst oxide, and energy consumption can be minimized.

[0153] ·Process (3) The dried active support is then subjected to a heat treatment to produce a supported catalyst.

[0154] By carrying out the heat treatment, a supported catalyst is produced in which the main catalyst and the promoter are present in a coated state on the surface and in the pores of γ-Al2O3.

[0155] The heat treatment may be carried out at 600 to 800°C or 620 to 750°C, preferably at 620 to 750°C. If the above conditions are met, a supported catalyst can be produced in which the main catalyst and the co-catalyst are uniformly coated on the surface and pores of the γ-Al2O3, and energy consumption can be minimized.

[0156] The heat treatment may be carried out for 1 to 12 hours or 2 to 8 hours, preferably 2 to 8 hours. When the above-mentioned time is satisfied, a supported catalyst can be produced in which the catalyst precursor is uniformly coated on the surface and in the pores of γ-AlO.

[0157] ·Process (4) CNTs are then produced in the presence of a supported catalyst.

[0158] Specifically, CNTs can be produced by contacting a supported catalyst with a carbon-based compound, and specifically, by chemical vapor synthesis.

[0159] To explain the steps for producing CNTs in detail, first, a supported catalyst is loaded into a horizontal fixed-bed reactor or a fluidized-bed reactor. Next, the gaseous carbon-based compound or a mixture of the gaseous carbon-based compound, a reducing gas (e.g., hydrogen), and a carrier gas (e.g., nitrogen) is injected at a temperature above the thermal decomposition temperature of the gaseous carbon-based compound or below the melting point of the catalyst supported on the supported catalyst. CNTs can be grown by chemical vapor synthesis through the decomposition of the gaseous carbon-based compound.

[0160] The CNTs produced by the above-mentioned chemical vapor synthesis method have a crystal growth direction that is nearly parallel to the tube axis, and the graphite structure has high crystallinity along the tube length. As a result, CNTs with small unit diameters and high conductivity and strength can be produced.

[0161] The chemical vapor synthesis method may be carried out at 600° C. to 800° C. or 650° C. to 750° C., and is preferably carried out at 650° C. to 750° C. If the above temperature is satisfied, CNTs can be produced while minimizing the generation of amorphous carbon.

[0162] The heat source for the reaction may be induction heating, radiant heat, laser, IR, microwave, plasma, surface plasmon heating, or the like.

[0163] Any carbonaceous compound can be used without particular limitations as long as it can supply carbon and can exist in a gaseous state at temperatures of 300° C. or higher.

[0164] The carbon-based compound may be a carbon-based compound having 6 or less carbon atoms, and may be one or more compounds selected from the group consisting of carbon monoxide, methane, ethane, ethylene, ethanol, acetylene, propane, propylene, butane, butadiene, pentane, pentene, cyclopentadiene, hexane, cyclohexane, benzene, and toluene.

[0165] After growing CNTs by the above-mentioned reaction, a cooling step may be optionally performed to align the CNTs more regularly. Specifically, the cooling step may be performed by natural cooling by removing the heat source or by using a cooler.

[0166] The above manufacturing methods X and Y are merely examples, and the manufacturing methods for CNTs that can be contained in a CNT aggregate are not limited to the above.

[0167] <Carbon nanotube dispersion> In the present disclosure, a carbon nanotube dispersion (CNT dispersion) is a dispersion containing CNT aggregates and a dispersion medium. The CNT dispersion liquid has good dispersibility of the CNT aggregate according to the present disclosure in the dispersion medium and is excellent in electrical conductivity. The CNT dispersion liquid is preferably used for forming electrodes, forming transparent conductive films, resin additives, conductive inks, coating agents, antistatic agents, paints, and the like.

[0168] -CNT aggregate- The CNT aggregate contained in the CNT dispersion liquid is the same as the CNT aggregate according to the present disclosure described above, and therefore a description thereof will be omitted here.

[0169] -Dispersion medium- The dispersion medium preferably contains water, and more preferably contains water as the main component. "Containing water as a main component" means that the proportion of water in the dispersion medium is more than 50% by mass. The proportion of water in the dispersion medium is preferably 90% by mass or more, more preferably 95% by mass or more, and even more preferably 99% by mass or more, and may be, for example, 100% by mass.

[0170] The water is not particularly limited, but is preferably distilled water, ion-exchanged water, pure water, or the like, which contains fewer impurities.

[0171] 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.

[0172] The CNT dispersion may further contain other components that can be used in the dispersion in addition to the CNT aggregates and the dispersion medium. Examples of other components include dispersants, antifoaming agents, antistatic agents, conductive assistants other than the conductive assistant according to the present disclosure, etc. Furthermore, the composition may further contain trace amounts of impurity components, so-called inevitable impurities, etc.

[0173] -Dispersant- The CNT dispersion may contain a dispersant for the purpose of further improving the dispersibility and dispersion stability of the CNT aggregates. The dispersant is not particularly limited and may be, for example, various surfactants. Further, the dispersant may also be a polymer compound such as a resin. The dispersant is preferably a surfactant. The surfactant may be an ionic surfactant or a nonionic surfactant, and is not particularly limited. In the CNT dispersion, the surfactant may be used alone or in combination of two or more.

[0174] Examples of ionic surfactants include anionic surfactants, cationic surfactants, and amphoteric surfactants. Examples of anionic surfactants include aromatic sulfonic acid surfactants such as alkylbenzenesulfonates (e.g., dodecylbenzenesulfonic acid) and dodecylphenyl ether sulfonates; ether sulfate surfactants; phosphate surfactants; and carboxylic acid surfactants. Examples of cationic surfactants include alkylamine salts and quaternary ammonium salts. Examples of amphoteric surfactants include alkylbetaine surfactants and amine oxide surfactants. As the ionic surfactant, an ionic surfactant having an aromatic ring (so-called aromatic ionic surfactant) is preferred, and aromatic sulfonic acid surfactants such as alkylbenzene sulfonate and dodecyl phenyl ether sulfonate are more preferred. Aromatic ionic surfactants tend to be excellent in dispersibility, dispersion stabilization, and concentration of CNT aggregates.

[0175] Examples of nonionic surfactants include sugar ester surfactants such as sorbitan fatty acid esters and polyoxyethylene sorbitan fatty acid esters; fatty acid ester surfactants such as polyoxyethylene resin acid esters and polyoxyethylene fatty acid diethyl esters; ether surfactants such as polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenyl ethers and polyoxyethylene polypropylene glycols; and aromatic nonionic surfactants such as polyoxyalkylene octyl phenyl ether, polyoxyalkylene nonyl phenyl ether, polyoxyalkyl dibutyl phenyl ether, polyoxyalkyl styryl phenyl ether, polyoxyalkyl benzyl phenyl ether, polyoxyalkyl bisphenyl ether, polyoxyalkyl cumyl phenyl ether and polyoxyalkylene phenyl ether. As the nonionic surfactant, an ionic surfactant having an aromatic ring (so-called aromatic nonionic surfactant) is preferred, polyoxyalkylene phenyl ether is more preferred, and polyoxyethylene phenyl ether is even more preferred. Aromatic nonionic surfactants tend to be excellent in dispersing ability, dispersion stabilizing ability, and concentration enhancement for CNT aggregates.

[0176] Other dispersants that are excellent in CNT dispersibility, dispersion stability, and concentration enhancement include β-naphthalenesulfonic acid formalin condensate sodium salts such as DEMOL (registered trademark; the same applies hereinafter) N, DEMOL RN, and DEMOL T (manufactured by Kao Corporation), polyoxyethylene stearyl ether Brij S 100 (manufactured by Sigma-Aldrich), polyvinylpyrrolidone K30 (manufactured by, for example, Fujifilm Wako Pure Chemical Industries, Ltd.), carboxymethyl cellulose (CMC) (manufactured by, for example, Daicel Miraize Co., Ltd.), sodium deoxycholate (manufactured by, for example, Fujifilm Wako Pure Chemical Industries, Ltd.), SOLSPERSE™ W100, and SOLSPERSE™ W150 (manufactured by The Lubrizol Japan Co., Ltd.). CMC is particularly preferred from the viewpoint of excellent CNT aggregate dispersibility, dispersion stability, and concentration enhancement.

[0177] When the CNT dispersion liquid contains a dispersant, the amount of the dispersant used is not particularly limited and can be set appropriately depending on the type of dispersant, the amount of CNT aggregates, the amount of dispersion medium, and the like.

[0178] -Method of manufacturing CNT dispersion- The method for producing the CNT dispersion liquid is not particularly limited. A CNT dispersion can be produced by dispersing a CNT aggregate in a dispersion medium. That is, a CNT dispersion can be produced by a method including a step of dispersing a CNT aggregate in a dispersion medium (also referred to as a "dispersion step"). The dispersion medium that can be used in the dispersion step is as described above.

[0179] The dispersion method is not particularly limited. Examples of the dispersion method include methods using a dispersion device such as a stirrer, homogenizer, colloid mill, flow jet mixer, dissolver, paint conditioner, Manton emulsifier, jet mill, and ultrasonic device. Further, examples of the dispersion method include methods using known pulverization means, such as ball milling (e.g., ball mill, vibration ball mill, planetary ball mill, bead mill, etc.), sand milling, colloid milling, jet milling, roller milling, a vertical or horizontal agitator mill, an attritor, a colloid mill, a three-roll mill, a pearl mill, a super mill, an impeller, a disperser, a KD mill, a dynatron, a pressure kneader, or the like. As a dispersion method, a method using a jet mill is preferred, and a method using a wet jet mill is more preferred. A wet jet mill is a dispersion device that pumps a mixture in a solvent as a high-speed flow through a nozzle arranged in a sealed pressure-resistant container. In a wet jet mill, CNT aggregates are dispersed by collisions between opposing flows in the pressure-resistant container, collisions with the container wall, turbulence caused by the high-speed flow, shear flow, and the like. An ultra-high-pressure homogenizer (model numbers: NAGS20, NAGS100, JAGS200, NAGS1000, etc.) manufactured by Joko Co., Ltd. can be suitably used as the wet jet mill. However, the wet jet mill is not limited to this. When the ultra-high pressure homogenizer is used as the dispersing device, the processing pressure for dispersion is preferably 10 MPa to 250 MPa.

[0180] The method for producing a CNT dispersion may include a step of drying the CNT aggregate (also referred to as a "drying step") before the dispersion step.

[0181] If water adheres to the CNTs, the surface tension of the water makes them more likely to adhere to each other, which can lead to a decrease in dispersibility. Therefore, by performing a drying process for the conductive additive before the dispersion process, the water adhering to the CNTs is removed, preventing the CNTs from adhering to each other due to water adhesion, and further improving the dispersibility of the CNTs in the dispersion medium. The drying method is not particularly limited. Drying methods include, for example, heat drying, vacuum drying, and heat vacuum drying. The drying method is preferably heated vacuum drying. The drying temperature is not particularly limited, and is preferably 40°C to 100°C, for example. The drying time is not particularly limited and can be set appropriately depending on the drying temperature, the degree of moisture adhesion to the CNT aggregate in the present disclosure, and the like.

[0182] An example of producing a CNT dispersion liquid will be shown below, but the production of a CNT dispersion liquid is not limited to the following.

[0183] -Dispersion liquid manufacturing example- 0.040 g of the CNT aggregate according to the present disclosure is weighed and placed in a three-neck flask. After the CNT aggregate is placed in the flask, a large excess of ion-exchanged water (e.g., 20 mL) is poured into the flask and stirred at room temperature (25°C, the same applies below). At this time, a known dispersant (e.g., carboxymethyl cellulose) may be added as appropriate. Next, a conductive additive is dispersed in the dispersion medium using a known dispersion device (e.g., an ultrasonic irradiation device or a wet jet mill). The obtained dispersion is further stirred with a stirrer at room temperature for a long period of time (e.g., 1 hour to 48 hours). In this way, a CNT dispersion is obtained.

[0184] (Conductive materials) The conductive material according to the present disclosure includes the CNT aggregate according to the present disclosure. As described above, the CNT aggregate according to the present disclosure contained in the conductive material according to the present disclosure has high conductivity and excellent dispersibility when made into a dispersion, and is therefore suitable as a conductive auxiliary agent. Since the conductive material according to the present disclosure contains the CNT aggregate according to the present disclosure, it has excellent conductive efficiency and It can effectively impart high conductivity to the object to which it is used.

[0185] The conductive material according to the present disclosure may contain a known conductive aid such as graphite, Ketjen black, etc. Furthermore, the conductive material according to the present disclosure may contain CNTs other than the CNT aggregate according to the present disclosure.

[0186] The conductive material according to the present disclosure can be used as one of electrode materials. An example of an electrode formed using the electrode material is an electrode included in a secondary battery. Hereinafter, an embodiment of the electrode and the secondary battery including the electrode will be described.

[0187] (electrode) The electrode can include the CNT aggregate according to the present disclosure described above. In an electrode, the CNT aggregate according to the present disclosure can function as a conductive additive. The CNT aggregate contained in the electrode described below is synonymous with the CNT aggregate according to the present disclosure, and preferred embodiments are also the same, so description of the CNT aggregate will be omitted below.

[0188] The electrode may be at least one of a positive electrode and a negative electrode. The electrode may include an electrode active material layer, or may include a current collector and an electrode active material layer disposed on the current collector.

[0189] The current collector is not particularly limited as long as it does not induce chemical changes in the battery and has conductivity. The current collector may be, for example, copper, stainless steel, aluminum, nickel, titanium, baked carbon, or aluminum or stainless steel whose surface has been treated with carbon, nickel, titanium, silver, etc. Specifically, a transition metal such as copper or nickel that has good carbon adsorption properties may be used as the current collector.

[0190] The electrode active material layer can include an electrode active material. The electrode active material is preferably electrode active material particles. When the electrode is a positive electrode, the electrode active material is not particularly limited, and the electrode active material layer can contain a positive electrode active material that is commonly used as an electrode material for a positive electrode. Specifically, the positive electrode active material may be a layered compound such as lithium cobalt oxide (LiCoO2) or lithium nickel oxide (LiNiO2), or a compound substituted with one or more transition metals; a lithium iron oxide such as LiFe3O4; or a compound having the chemical formula Li 1+c1 Mn 2-c1 O4 (0≦c1≦0.33), lithium manganese oxides such as LiMnO3, LiMn2O3, and LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, V2O5, and Cu2V2O7; chemical formula LiNi 1-c2 M c2 Ni-site type lithium nickel oxide represented by the chemical formula LiMnO2 (wherein M is at least one selected from the group consisting of Co, Mn, Al, Cu, Fe, Mg, B, and Ga, and satisfies 0.01≦c2≦0.66); 2-c3 M c3 Examples of suitable lithium manganese composite oxides include lithium manganese composite oxides represented by Li2Mn3MO8 (wherein M is at least one selected from the group consisting of Co, Ni, Fe, Cr, Zn, and Ta, and satisfies 0.01≦c3≦0.1) or Li2Mn3MO8 (wherein M is at least one selected from the group consisting of Fe, Co, Ni, Cu, and Zn); and LiMn2O4 in which part of the Li in the chemical formula is substituted with an alkaline earth metal ion.

[0191] When the electrode is a negative electrode, the electrode active material is not particularly limited, and the electrode active material layer can contain a negative electrode active material commonly used for negative electrode materials. Specifically, the negative electrode active material can contain graphite-based active material particles or silicon-based active material particles. As the graphite-based active material particles, at least one selected from the group consisting of artificial graphite, natural graphite, graphitized carbon fiber, and graphitized mesocarbon microbeads may be used. By using artificial graphite as the graphite-based active material particles, the rate characteristics can be improved. As the silicon-based active material particles, at least one selected from the group consisting of Si, SiOx (0 < x < 2), Si-C composite, and Si-Y alloy (where Y is an element selected from the group consisting of alkali metals, alkaline earth metals, transition metals, group 13 elements, group 14 elements, rare earth elements, and combinations thereof) may be used. By using silicon-based active material particles, the battery can be made to have a higher capacity.

[0192] The electrode active material layer can further contain a binder. The binder is not particularly limited, and the electrode active material layer can contain a binder commonly used for electrode materials. Examples of the binder 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, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene propylene diene monomer (EPDM), sulfonated EPDM, styrene butadiene rubber (SBR), fluorine rubber, and polyacrylic acid, and polymers in which hydrogen atoms of these polymers are substituted with Li, Na, Ca, etc.

[0193] (Secondary battery) The secondary battery may include a negative electrode, a positive electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte, wherein at least one of the positive electrode and the negative electrode is an electrode formed using an electrode material including the CNT aggregate according to the present disclosure.

[0194] The separator separates the negative electrode from the positive electrode and provides a path for lithium ions to move, and is not particularly limited as long as it is a separator that is typically used as a separator in a secondary battery. The separator preferably has low resistance to ion movement of the electrolyte and is excellent in the ability to retain moisture in the electrolyte solution. A specific example of the separator is a porous polymer film. The porous polymer film may be, for example, a porous polymer film made from a polyolefin polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, or an ethylene / methacrylate copolymer, or a laminate structure in which two or more layers of these films are laminated. The separator may also be a typical porous nonwoven fabric, such as a nonwoven fabric made of high-melting-point glass fiber, polyethylene terephthalate fiber, etc. The separator may also be coated with a ceramic component or a polymeric substance to ensure heat resistance or mechanical strength. The separator may optionally be of a single layer or multi-layer structure.

[0195] The electrolyte is not particularly limited, and examples thereof include electrolytes such as organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, and molten inorganic electrolytes that can be used in producing lithium secondary batteries.

[0196] Specifically, the electrolyte can include a non-aqueous organic solvent and a metal salt. Examples of non-aqueous organic solvents include aprotic organic solvents such as N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, γ-butyrolactone, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, phosphoric acid triester, trimethoxymethane, dioxolane derivatives, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ethers, methyl propionate, and ethyl propionate.

[0197] Among carbonate organic solvents, cyclic carbonates such as ethylene carbonate and propylene carbonate are preferred as non-aqueous organic solvents because they have high viscosity and high dielectric constants and dissociate lithium salts well. It is more preferred to use a non-aqueous organic solvent obtained by mixing such cyclic carbonates with linear carbonates having low viscosity and low dielectric constants, such as dimethyl carbonate and diethyl carbonate, in an appropriate ratio, in order to obtain an electrolyte having high electrical conductivity.

[0198] The metal salt may be a lithium salt. Lithium salts are substances that are easily dissolved in non-aqueous electrolytes. The anion portion of the lithium salt may be, for example, F - , Cl - , I - , NO3 - , N(CN)2 - , BF4 - , ClO4 - , PF6 - , (CF3)2PF4 - , (CF3)3PF3 - , (CF3)4PF2 - , (CF3)5PF - , (CF3)6P - , CF3SO3- , CF3CF2SO3 - , (CF3SO2)2N - , (FSO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , (SF5)3C - , (CF3SO2)3C - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN - , and (CF3CF2SO2)2N - Examples include:

[0199] In addition to the non-aqueous organic solvent and metal salt, the electrolyte may further contain one or more additives such as haloalkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ethers, ethylenediamine, n-glyme, hexaphosphoric acid triamide, nitrobenzene derivatives, sulfur, quinoneimine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, and aluminum trichloride, for the purposes of improving the battery's life characteristics, suppressing a decrease in battery capacity, and improving the battery's discharge capacity.

[0200] The above-described secondary battery can be used to form a battery module including the secondary battery as a unit cell, and a battery pack including the battery module. The battery module and the battery pack can be used as a power source for a medium to large device selected from the group consisting of, for example, an electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, and a power storage system.

[0201] (Planar aggregate) The planar aggregate according to the present disclosure includes the CNT aggregate according to the present disclosure. The ratio of the CNT aggregate according to the present disclosure contained in the planar aggregate according to the present disclosure is usually 1 mass % or more relative to the total mass of the planar aggregate. The planar aggregate according to the present disclosure may contain other components such as CNT aggregates (particularly CNT aggregates) having a maximum length of less than 1000 μm.

[0202] <Method for producing planar assembly> The method for producing the planar assembly according to the present disclosure is not particularly limited. The planar aggregate according to the present disclosure can be produced, for example, as a nonwoven fabric-like planar aggregate, by dispersing the CNT aggregate according to the present disclosure, or the CNT aggregate according to the present disclosure and other components, such as a CNT aggregate (particularly a CNT aggregate) having a maximum length of less than 1000 μm, in water or other fluid and filtering once or twice or more times.

[0203] An example of the planar assembly according to the present disclosure is a film.

[0204] Planar assemblies according to the present disclosure are useful, for example, in filters, electromagnetic shields, and extreme ultraviolet (EUV) pellicles.

[0205] (Laminate) A laminate according to the present disclosure includes a substrate and a planar assembly according to the present disclosure. The substrate and the planar assembly may be in direct contact with each other, or another layer may be disposed between the substrate and the planar assembly. Alternatively, the planar assembly according to the present disclosure may be disposed on a substrate, and another layer may be disposed on the planar assembly.

[0206] The material constituting the substrate may be resin, glass, or fiber. Examples of resins include polyethylene terephthalate (PET), polycarbonate (PC), polymethyl methacrylate (PMMA), cyclic olefin polymer (COP), triacetate (TAC), cyclic olefin copolymer (COC), poly(vinyl chloride) (PVC), polyethylene 2,6-naphthalate (PEN), polyimide (PI), polypropylene (PP), polyethylene (PE), polystyrene (PS), polyamide (PA), polyacetal (POM), polyurethane (PU), acrylonitrile butadiene styrene (ABS), polyphenylene ether (PPE), polysulfone (PSU), polyether ether ketone (PEEK), and polyamide imide (PAI). Glasses include, for example, float glass (containing SiO2, Na2O, CaO, MgO), soda lime, aluminosilicate glass, and borosilicate glass. Examples of fibers include synthetic fibers such as polyester fibers, polyamide fibers, polyolefin fibers, and acrylic fibers; and natural fibers such as cotton, linen, silk, wool, cashmere, mohair, alpaca, jute, hemp, and ramie.

[0207] The planar aggregate preferably contains a binder in addition to the CNT aggregate according to the present disclosure. The binder is preferably a polymer, and preferably contains at least one selected from the group consisting of polymers containing structural units derived from vinylidene chloride (e.g., polyvinylidene chloride, vinylidene chloride-vinyl chloride copolymer, vinylidene chloride-vinyl acetate copolymer, etc.), polyimide, polysiloxane, and epoxy resin. [Example]

[0208] The CNT aggregate and the like according to the present disclosure will be described more specifically below with reference to examples. The present disclosure is not limited to the following examples as long as it does not deviate from the gist of the disclosure.

[0209] Example 1 1. Production of sheet-shaped CNT aggregate 1 Sheet-like CNT aggregate 1 was produced by the floating catalyst method (CVD method), which directly interacts with the self-assembly of CNT bundles in the gas phase. A cylindrical reactor with an inner diameter of 85 mm was used as the CNT reactor. First, ferrocene as a metal catalyst precursor containing Fe atoms and thiophene as a promoter were introduced into a continuous flow of carrier gas in a once-through reactor temperature-controlled at 120°C. Hydrogen gas was used as the carrier gas. By maintaining the temperature in the once-through reactor within the above range, the metal catalyst precursor is decomposed. The region where the metal catalyst precursor is decomposed is referred to as the first temperature zone.

[0210] Next, methane, a carbon source, was released into the carrier gas flow. The metal catalyst and carbon source were supplied to a second temperature zone downstream of the first temperature zone, which was temperature-controlled at 1400°C. The total gas supply flow rate of the carrier gas and source gas was 34 NL / min (NL is normal liters). The second temperature zone was maintained at a temperature sufficient to produce carbon nanotube aggregates.

[0211] In the second temperature zone, a reaction field was created in a temperature-controlled flow reactor to form catalytic nuclei and rapidly grow CNTs, thereby producing CNT aggregates. The aggregates of CNTs were continuously discharged through the outlet of a flow reactor whose temperature was controlled at 150°C, and the sheet-like CNT aggregates were collected. The obtained sheet-like CNT aggregate was immersed in a diluted ammonia water solution of pH 10 for 10 minutes, washed with pure water for 10 minutes, dried, crushed into powder, and passed through a sieve with 1.0 mm openings twice. The CNT aggregate that passed through the sieve was collected and designated as CNT aggregate 1.

[0212] 2. Preparation of CNT Dispersion 1 The following materials were mixed and pre-dispersed by processing for 1 hour using an Ace Homogenizer manufactured by Nippon Seiki Co., Ltd., to obtain pre-dispersion liquid 1.

[0213] (Dispersion liquid composition) 1.1g of the CNT aggregate obtained above ·Sodium carboxymethyl cellulose high viscosity (manufactured by MP Biomedicals): 1.65 g ·Purified water: 547.25 g

[0214] The main dispersion of the pre-dispersion liquid 1 was carried out using a high-pressure homogenizer (model number: NAGS100) manufactured by Tsunehiro Co., Ltd. as a wet jet mill under the following conditions to obtain a CNT dispersion liquid 1 with a concentration of 0.20% by mass. -Dispersion conditions- Nozzle diameter: 0.22 mm Pressure: 85 MPa Number of times: 8 times Method: Circulation method

[0215] <Viscosity of the CNT aggregate dispersion liquid> The viscosity of the CNT dispersion liquid 1 was measured using a cone-plate viscometer (also known as an E-type viscometer). Specifically, the viscosity was measured using a cone-plate viscometer (DV-II+Pro PROGRAMMABLE VISCOMETER manufactured by BROOKFIELD). Measuring fixture: Cone-plate Measurement mode: Rotation mode Shear rate: 0.6 s -1 ~384 s -1 Temperature: 25 °C From the obtained data, the viscosity at a shear rate of 12 s -1 was read. The viscosity of the dispersion liquid was 434.0 mPa·s.

[0216] 3. Evaluation <Calculation of the packing factor Σ> -Manufacture of CNT film A1- The CNT membrane A1 of this example was produced by suction filtration. 12 μL of CNT dispersion 1 and 25 mL of pure water were mixed and suction filtered onto a hydrophilic cellulose ester membrane filter (VCWP, 0.1 μm pore diameter, Merck Millipore, Darmstadt, Germany). The resulting filtration membrane A1 was placed on the membrane filter. The membrane filter was carefully immersed in pure water before drying. The filtration membrane A1 was then transferred from the membrane filter onto a glass substrate. Finally, the filtration membrane A1 on the substrate was dried on a hot plate at 70°C for 10 minutes, yielding the CNT membrane A1. The CNT concentration in the membrane was 0.011 mg / cm based on the amount of dispersion used and the filtration area. 2 It was estimated that:

[0217] -Production of CNT film B1- A CNT film B1 was obtained in the same manner as for the CNT film A1, except that the amount of CNT dispersion liquid 1 was changed from 12 μL to 2 μL. Based on the amount of dispersion used and the filtration area, the CNT concentration in the membrane was 0.0018 mg / cm 2 It was estimated that:

[0218] -Measurement of absorbance- The absorbance Abs of the CNT film A1 and CNT film B1 of the examples and comparative examples was measured using a Cary 5000 Measurements were performed by ultraviolet-visible spectroscopy (UV-vis) at 550 nm using a UV-Vis-NIR spectrophotometer (Agilent Technologies). The absorbances (Abs) were 0.54 and 0.11, respectively.

[0219] -Measurement of surface resistivity- The surface resistivities of the CNT films A1 and B1 of Example 1 were measured by transferring the films on the membrane filter to a glass substrate in pure water, drying them, and then measuring the center of the film using a Loresta GXII manufactured by Nitto Seiko Analytech Co., Ltd. using the four-probe method. As a result, the surface resistivity of the CNT film A1 was 77.33 Ω / □. The surface resistivity of the CNT film B1 was 667.6 Ω / □.

[0220] - Calculation of resistance factor - The resistance factor P is the product of the surface resistivity ρs and the absorbance Abs. The resistance factor P of the CNT film A1 was 41.5 Ω / □, and the resistance factor P of the CNT film B1 was 74.5 Ω / □. The ratio of the resistance factors of the CNT film A1 and CNT film B1 was 0.56.

[0221] -Calculation of density factor- The sparseness / denseness factor Σ was calculated from the following relational expression. Density factor Σ = (resistivity of CNT film A1 × absorbance of CNT film A1) ÷ (resistivity of CNT film B1 × absorbance of CNT film B1) As a result, the sparseness / denseness factor Σ was calculated to be 0.093.

[0222] <Features of bundle diameter> Images of the CNT aggregate 1 of Example 1 were taken using a scanning electron microscope (SEM), and two images in which the CNT bundles were clearly observed were selected from the obtained images (one of which is FIG. 1). The selected images were subjected to image processing and analysis using Python. In image processing, the CNT contours and center lines were detected and combined with the original image. In image analysis, the bundle diameter was determined by calculating the distance from the center line to the contour in the created image. The product of the bundle diameter and the length of the center line was then calculated to calculate the area occupied by the CNTs in the image. A histogram of the bundle diameter and the occupied area was created.

[0223] Using the calculated bundle diameter histogram, the feature amount of the bundle diameter of each sample was calculated by the following method. 1. The bundle diameters and occupied areas of multiple fields of view for the same sample were added together and normalized so that the total sum was 1. Following normalization, the unit of the vertical axis was changed to the occupied area ratio. 2. The total value of the occupied area ratio of bundles with a bundle diameter of 100 nm or more was calculated. 3. The cumulative exclusive area ratio was calculated, and the bundle diameter when this value exceeded 0.9 for the first time was determined as the cumulative 90% bundle diameter. As a result, the area ratio of bundles with a bundle diameter of 100 nm or more was 0.17, and the cumulative 90% bundle diameter was 170 nm.

[0224] <Tensile test> CNT dispersion liquid 1 was poured onto a 22 mm x 75 mm x 3 mm slide-glass type silicon plate (Dosaka EM Co., Ltd., #08-1044), and dried at 100°C for 30 minutes to prepare a measurement sample. The measurement sample was fixed to the grip of a tensile testing device (Shimadzu Corporation, Autograph AG-IS), and a tensile test was carried out at a speed of 1 mm / min. The point where the test force was maximum was regarded as the breaking point, and the tensile strength and breaking elongation were calculated. The tensile strength was 12.6 MPa, and the breaking elongation was 1.5%.

[0225] Example 2 1. Production of CNT aggregate 2 The CNT aggregate 2 was produced by mixing the following CNT aggregate 2A and the following CNT aggregate 2B. The CNT aggregate 2A was produced in the same manner as the CNT aggregate 1, except that the total gas supply flow rate of the carrier gas and the raw material gas was set to 35 NL / min. The CNT aggregate 2B was produced in the same manner as the CNT aggregate 1, except that the total gas supply flow rate of the carrier gas and the raw material gas was set to 36 NL / min.

[0226] 2. Preparation of CNT Dispersion 2 Using the obtained CNT aggregate 2, a pre-dispersion liquid 2 was obtained in the same manner as in Example 1.

[0227] The pre-dispersion liquid 2 was subjected to main dispersion using an ultra-high pressure homogenizer (model number: NAGS100) manufactured by Joko Co., Ltd. as a wet jet mill under the following conditions to obtain CNT dispersion liquid 2. (Dispersion conditions) Nozzle diameter: 0.22 mm Pressure: 50 MPa Number of times: 3 Method: Circulation method

[0228] <Viscosity of CNT Aggregate Dispersion> The viscosity was calculated in the same manner as in Example 1 except that CNT dispersion 2 was used. The viscosity of the dispersion was 798.2 mPa·s.

[0229] <Calculation of Closeness Factor Σ> -Manufacture of CNT Film A2- CNT film A2 was obtained in the same manner as in Example 1 except that CNT dispersion 2 was used.

[0230] -Manufacture of CNT Film B2- CNT film B2 was obtained in the same manner as in Example 1 except that CNT dispersion 2 was used.

[0231] -Calculation of Closeness Factor Σ- The closeness factor Σ was calculated in the same method as in Example 1 except that CNT dispersion 2 was used instead of CNT dispersion 1. using CNT film A2 and CNT film B2. As a result, the surface resistivity of CNT film A2 was 87.27 Ω / □, and the surface resistivity of CNT film B2 was 639.5 Ω / □. The absorbance of CNT film A2 was 0.42, and the absorbance of CNT film B2 was 0.11. The resistance factor of CNT film A2 was 36.5, and the resistance factor of CNT film B2 was 70.7. The ratio of the resistance factors of CNT film A2 and CNT film B2 was 0.52. The closeness factor Σ was 0.086.

[0232] <Feature Quantity of Bundle Diameter> Regarding the CNT aggregate 2 of Example 2, imaging was performed using SEM, and among the obtained images, 4 images in which CNT bundles were well observed were selected (one of which is shown in Figure 2), and the feature quantity of the bundle diameter was calculated in the same manner as in Example 1. As a result, the area ratio of bundles with a bundle diameter of 100 nm or more was 0.26. The cumulative 90% bundle diameter was 150 nm.

[0233] <Tensile Strength, Elongation at Break> A tensile test was conducted in the same manner as in Example 1, except that CNT dispersion liquid 2 was used. As a result, the tensile strength was 15.5 MPa and the elongation at break was 2.6%.

[0234] (Example 3) 1. Production of CNT aggregate 3 CNT aggregate 2 was produced in the same manner as CNT aggregate 1, except that the total gas supply flow rate of the carrier gas and the raw material gas was set to 42 NL / min, and the continuous discharge of the aggregates was performed through the outlet of a flow-type reactor whose temperature was controlled at 500 °C.

[0235] 2. Preparation of CNT dispersion liquid 3 Using the obtained CNT aggregate 3, a preliminary dispersion liquid 3 was obtained in the same manner as in Example 1.

[0236] The final dispersion of the preliminary dispersion liquid 3 was carried out using a high-pressure homogenizer (model number: NAGS100) manufactured by Tsunehiro Co., Ltd. as a wet jet mill under the following conditions to obtain CNT dispersion liquid 3. (Dispersion conditions) Nozzle diameter: 0.22 mm Pressure: 150 MPa Number of times: 8 times Method: Circulation method

[0237] <Viscosity of the dispersion liquid of CNT aggregate> The viscosity was calculated in the same manner as in Example 1, except that CNT dispersion liquid 3 was used. The viscosity of the dispersion liquid was 34.6 mPa·s.

[0238] <Calculation of the packing factor Σ> -Manufacture of CNT film A3- CNT film A3 was obtained in the same manner as in Example 1, except that CNT dispersion liquid 3 was used.

[0239] -Manufacture of CNT film B3- CNT film B3 was obtained in the same manner as in Example 1, except that CNT dispersion liquid 3 was used.

[0240] -Calculation of the packing factor Σ- The density factor Σ was calculated using the CNT film A3 and the CNT film B3 in the same manner as in Example 1, except that the CNT dispersion 3 was used instead of the CNT dispersion 1. As a result, the surface resistivity of CNT film A3 was 210.9 Ω / □, and the surface resistivity of CNT film B3 was 2098 Ω / □. The absorbance of CNT film A3 was 0.62, and the absorbance of CNT film B3 was 0.12. The resistance factor of CNT film A3 was 130.7, and the resistance factor of CNT film B3 was 261.1. The ratio of the resistance factors of CNT film A3 and CNT film B3 was 0.50. The sparseness / denseness factor Σ was 0.083.

[0241] <Features of bundle diameter> For the CNT aggregate 3 of Example 3, images were taken using an SEM, and six images in which the CNT bundles were clearly observed were selected from the obtained images (one of which is Figure 3), and the feature value of the bundle diameter was calculated in the same manner as in Example 1. As a result, the area ratio of bundles with a bundle diameter of 100 nm or more was 0.41, and the cumulative 90% bundle diameter was 200 nm.

[0242] <Tensile test> A tensile test was carried out in the same manner as in Example 1, except for using CNT dispersion liquid 3. As a result, the tensile strength was 3.5 MPa and the elongation at break was 4.1%.

[0243] Example 4 1. Preparation of CNT aggregate 4 CNT aggregate 4 was produced in the same manner as CNT aggregate 1, except that the total gas supply flow rate of the carrier gas and raw material gas was set to 36 NL / min, and the aggregate was continuously discharged through the outlet of a flow-type reactor whose temperature was controlled at 500°C.

[0244] 2. Preparation of CNT Dispersion 4 Using the obtained CNT aggregate 4, a pre-dispersion liquid 4 was obtained in the same manner as in Example 3. The main dispersion of the pre-dispersion liquid 4 was carried out using a super high-pressure homogenizer (model number: NAGS100) manufactured by Tsunehiro Co., Ltd. as a wet jet mill under the following conditions to obtain the CNT dispersion liquid 4. (Dispersion conditions) Nozzle diameter: 0.22 mm Pressure: 150 MPa Number of times: 8 times Method: Circulation method

[0245] <Viscosity of the CNT aggregate dispersion liquid> The viscosity was calculated in the same manner as in Example 1 except that the CNT dispersion liquid 4 was used. The viscosity of the dispersion liquid was 142.6 mPa·s.

[0246] <Calculation of the packing factor Σ> -Manufacture of CNT film A4- A CNT film A4 was obtained in the same manner as in Example 1 except that the CNT dispersion liquid 4 was used.

[0247] -Manufacture of CNT film B4- A CNT film B4 was obtained in the same manner as in Example 1 except that the CNT dispersion liquid 4 was used.

[0248] -Calculation of the packing factor Σ- The packing factor Σ was calculated using the CNT film A4 and the CNT film B4 in the same method as in Example 1 except that the CNT dispersion liquid 4 was used instead of the CNT dispersion liquid 1. As a result, the surface resistivity of the CNT film A4 was 162.1 Ω / □, and the surface resistivity of the CNT film B3 was 1485 Ω / □. The absorbance of the CNT film A4 was 0.54, and the absorbance of the CNT film B4 was 0.10. The resistance factor of the CNT film A4 was 87.5, and the resistance factor of the CNT film B4 was 154.1. The ratio of the resistance factors of the CNT film A4 and the CNT film B4 was 0.57. The packing factor Σ was 0.095.

[0249] <Characteristic quantity of the bundle diameter> Regarding the CNT aggregate 4 of Example 4, imaging was performed using SEM. Among the obtained images, eight images in which CNT bundles were well observed were selected (one of which is shown in FIG. 4). Except for this, the calculation of the characteristic quantity of the bundle diameter was performed in the same manner as in Example 1. As a result, the area ratio of the bundles with a bundle diameter of 100 nm or more was 0.49. The cumulative 90% bundle diameter was 230 nm.

[0250] <Tensile strength, elongation at break> A tensile test was conducted in the same manner as in Example 1, except that the CNT dispersion liquid 4 was used. As a result, the tensile strength was 8.0 MPa and the elongation at break was 1.1%.

[0251] (Example 5) 1. Production of CNT aggregate 5 The CNT aggregate 5 was produced in the same manner as the CNT aggregate 1, except that the total gas supply flow rate of the carrier gas and the raw material gas was set to 38 NL / min, and the discharge of the aggregates was continuously discharged through the outlet of the flow-type reactor whose temperature was controlled to 750°C.

[0252] 2. Preparation of CNT dispersion liquid 5 Using the obtained CNT aggregate 5, a CNT dispersion liquid 5 was obtained in the same manner as in Example 3.

[0253] <Viscosity of the dispersion liquid of the CNT aggregate> The viscosity was calculated in the same manner as in Example 1, except that the CNT dispersion liquid 5 was used. The viscosity of the dispersion liquid was 201.5 mPa·s.

[0254] <Calculation of the packing factor Σ> -Production of CNT film A5- A CNT film A5 was obtained in the same manner as in Example 1, except that the CNT dispersion liquid 5 was used.

[0255] -Production of CNT film B5- A CNT film B5 was obtained in the same manner as in Example 1, except that the CNT dispersion liquid 5 was used.

[0256] -Calculation of the sparseness / denseness factor Σ- The sparseness / dense factor Σ was calculated using CNT film A5 and CNT film B5 in the same manner as in Example 1, except that CNT dispersion liquid 5 was used instead of CNT dispersion liquid 1. As a result, the surface resistivity of CNT film A5 was 126.0 Ω / □, and the surface resistivity of CNT film B5 was 1286 Ω / □. The absorbance of CNT film A5 was 0.56, and the absorbance of CNT film B5 was 0.10. The resistance factor of CNT film A5 was 69.9, and the resistance factor of CNT film B5 was 126.4. The ratio of the resistance factors of CNT film A5 and CNT film B5 was 0.55. The sparseness / denseness factor Σ was 0.092.

[0257] <Features of bundle diameter> For the CNT aggregate 5 of Example 5, images were taken using an SEM, and six images in which the CNT bundles were clearly observed were selected from the obtained images (one of which is FIG. 5), and the feature value of the bundle diameter was calculated in the same manner as in Example 1. As a result, the area ratio of bundles with a bundle diameter of 100 nm or more was 0.43, and the cumulative 90% bundle diameter was 340 nm.

[0258] <Tensile test> A tensile test was carried out in the same manner as in Example 1, except for using CNT dispersion liquid 5. As a result, the tensile strength was 15.3 MPa and the elongation at break was 2.2%.

[0259] Example 6 1. Production of CNT aggregate 6 The CNT aggregate 6 was produced in the same manner as the CNT aggregate 1, except that the total gas supply flow rate of the carrier gas and the raw material gas was set to 41.9 NL / min.

[0260] 2. Preparation of CNT Dispersion 6 Using the obtained CNT aggregate 6, a pre-dispersion liquid 6 was obtained in the same manner as in Example 1.

[0261] The uniform dispersion of the pre-dispersion liquid 6 was carried out under the following conditions using a high-pressure homogenizer (model number: NAGS100) manufactured by Tsunehiro Co., Ltd. as a wet jet mill to obtain the CNT dispersion liquid 6. (Dispersion conditions) Nozzle diameter: 0.22 mm Pressure: 250 MPa Number of times: 8 times Method: Circulation method

[0262] <Viscosity of the CNT aggregate dispersion liquid> The viscosity was calculated in the same manner as in Example 1 except that the CNT dispersion liquid 6 was used. The viscosity of the dispersion liquid was 14.1 mPa·s.

[0263] <Calculation of the porosity factor Σ> -Manufacture of CNT film A6- A CNT film A6 was obtained in the same manner as in Example 1 except that the CNT dispersion liquid 6 was used.

[0264] -Manufacture of CNT film B6- A CNT film B6 was obtained in the same manner as in Example 1 except that the CNT dispersion liquid 6 was used.

[0265] -Calculation of the porosity factor Σ- The porosity factor Σ was calculated using the CNT film A6 and the CNT film B6 in the same method as in Example 1 except that the CNT dispersion liquid 6 was used instead of the CNT dispersion liquid 1. As a result, the surface resistivity of the CNT film A6 was 187.6 Ω / □, and the surface resistivity of the CNT film B6 was 2505 Ω / □. The absorbance of the CNT film A6 was 0.51, and the absorbance of the CNT film B6 was 0.07. The resistance factor of the CNT film A6 was 95.5, and the resistance factor of the CNT film B6 was 248.5. The ratio of the resistance factors of the CNT film A6 and the CNT film B6 was 0.38. The porosity factor Σ was 0.094.

[0266] <Characteristic quantity of the bundle diameter> Regarding the CNT aggregate 6 of Example 6, imaging was performed using SEM. Among the obtained images, four images in which CNT bundles were well observed were selected (one of which is shown in FIG. 6). Except for this, the calculation of the characteristic quantity of the bundle diameter was performed in the same manner as in Example 1. As a result, the area ratio of the bundles with a bundle diameter of 100 nm or more was 0.41. The cumulative 90% bundle diameter was 200 nm.

[0267] <Tensile test> A tensile test was performed in the same manner as in Example 1, except that the CNT dispersion 6 was used. As a result, the tensile strength was 57.8 MPa and the elongation at break was 5.4%.

[0268] (Comparative Example 1) 1. Preparation of powder CNT aggregate 7 As the powder CNT aggregate 7, carbon nanotubes manufactured by C-nano (catalog number: FT9100) were prepared.

[0269] 2. Preparation of CNT dispersion 7 Using the prepared powder CNT aggregate 7, a CNT dispersion 7 was obtained in the same manner as in Example 1.

[0270] <Viscosity of CNT aggregate dispersion> The viscosity was calculated in the same manner as in Example 1, except that the CNT dispersion 7 was used. The viscosity of the dispersion was 5.7 mPa·s. The common logarithm notation of the viscosity was 0.76.

[0271] <Calculation of packing factor Σ> -Manufacture of CNT film A7- A CNT film A7 was obtained in the same manner as in Example 1, except that 24 μL of the CNT dispersion 7 was used instead of 12 μL of the CNT dispersion 1.

[0272] -Manufacture of CNT film B7- A CNT film B7 was obtained in the same manner as in Example 1, except that 4 μL of the CNT dispersion 7 was used instead of 2 μL of the CNT dispersion 1.

[0273] -Calculation of the sparseness / denseness factor Σ- The density factor Σ was calculated using CNT film A7 and CNT film B7. As a result, the surface resistivity of CNT film A7 was 1349 Ω / □, and the surface resistivity of CNT film B7 was 17940 Ω / □. The absorbance of CNT film A7 was 1.13, and the absorbance of CNT film B7 was 0.19. The resistance factor of CNT film A7 was 1526.9, and the resistance factor of CNT film B7 was 3449.6. The ratio of the resistance factors of CNT film A7 and CNT film B7 was 0.44. The sparseness / denseness factor Σ was 0.074.

[0274] <Features of bundle diameter> For the CNT aggregate 7 of Comparative Example 1, images were taken using an SEM, and from the obtained images, three images in which the CNT bundles were clearly observed were selected (one of which is FIG. 7), and the feature value of the bundle diameter was calculated in the same manner as in Example 1. As a result, the area ratio of bundles with a bundle diameter of 100 nm or more was 0.08, and the cumulative 90% bundle diameter was 80 nm.

[0275] <Tensile test> A tensile test was carried out in the same manner as in Example 1, except for using CNT dispersion liquid 7. As a result, the tensile strength was 2.3 MPa and the elongation at break was 1.9%.

[0276] [Fabrication of Lithium-ion Secondary Battery] Next, a lithium ion secondary battery was fabricated.

[0277] 1. Preparation of a positive electrode for lithium secondary batteries Cathode active material (LiNi 0.8 Co 0.1 Mn 0.1 O2), a conductive material (acetylene black), and a binder (PVdF) were mixed in a ratio of positive electrode active material:conductive material:binder = 92:5:3 (mass ratio), and N-methyl-2-pyrrolidone was added and kneaded to prepare a paste-like positive electrode mixture. The resulting positive electrode mixture was applied to a 15 μm thick Al foil as a current collector, and the resulting mixture was vacuum dried at 80°C for 1 hour, followed by roll pressing to obtain a positive electrode for a lithium secondary battery. The positive electrode area was 1.65 cm. 2 , basis weight 16mg / cm 2 , density is 3.0g / cm 3 It was adjusted so that

[0278] 2. Preparation of a negative electrode for lithium secondary batteries The negative electrode for the lithium secondary battery was prepared by mixing a 9:1 (mass ratio) mixture of artificial graphite MAG-E and carbon-coated SiO as the negative electrode active material, CLPA-C07 (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) as the binder, and the CNT dispersion as the conductive additive in a weight ratio of 94.9:5.0:0.1 to prepare a paste-like negative electrode mixture. Ion-exchanged water was used as the solvent for preparing the negative electrode mixture. The resulting negative electrode mixture was applied to a 20 μm thick Cu foil using a single-sided continuous coater, dried at 120°C, and then roll-pressed to obtain a negative electrode for a lithium secondary battery. The negative electrode area was 1.77 cm. 2 , basis weight 9.3mg / cm 2 , density is 1.4g / cm 3 It was adjusted so that

[0279] 3. Fabrication of Lithium Secondary Batteries The positive electrode for the lithium secondary battery was placed on the bottom cover of a coin-type battery R2032 (manufactured by Hosen Co., Ltd.), and a laminated film separator consisting of a polyethylene porous film with a 16 μm heat-resistant porous layer laminated thereon was placed on top of it. 300 μL of electrolyte was poured into the separator. The electrolyte was a 20:75:5 (volume ratio) mixture of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate, with 1% vinylene carbonate added by volume, and LiPF6 dissolved therein to a concentration of 1.3 mol / L. Next, the negative electrode for the lithium secondary battery was placed on top of the laminated film separator, and the top cover was placed with a gasket in between. The assembly was then crimped using a crimping machine to produce a coin-type full-cell R2032 lithium secondary battery. These operations were carried out in a glove box under an argon atmosphere.

[0280] 4. Cycle test Using the fabricated lithium-ion batteries, a 200-cycle cycle test was conducted under the conditions shown below, and the discharge capacity retention rate after 200 cycles was calculated using the following formula. Note that in Table 1, this is referred to as "capacity retention rate after 200 cycles," and a higher discharge capacity retention rate after 200 cycles indicates better life characteristics. Discharge capacity retention rate after 200 cycles (%) = 200th discharge capacity / 1st discharge capacity × 100

[0281] <Cycle test conditions> Test temperature: 25℃ Charging conditions: Constant current constant voltage charging, maximum charging voltage 4.2V, charging time 5 hours, charging current 0.3CA Pausing time after discharge: 10 minutes Discharge conditions: Constant current discharge, minimum discharge voltage 2.5V, discharge current 0.3CA Downtime after charging: 10 minutes In this test, one cycle was defined as a cycle in which charging, discharging, discharging, and charging were performed in that order.

[0282] Table 1 shows the evaluation results for Examples 1 to 6 and Comparative Example 1. In Table 1, "proportion of bundles with a diameter of 100 nm or more" refers to "area proportion Z of bundles with a bundle diameter of 100 nm or more."

[0283] [Table 1]

[0284] As shown in Table 1, it was found that the CNT aggregates of Examples 1 to 6, in which the density factor Σ calculated by formula (α) is less than 1.0 and the common logarithm of the viscosity is 1.0 or more, have higher tensile strength than the CNT aggregate of Comparative Example 1. It was found that the elongation at break is appropriate and a CNT dispersion suitable as a conductive additive can be obtained.

Claims

1. The sparse / dense factor Σ calculated by the following formula (α) is less than 1.0, A dispersion liquid is prepared by mixing aggregates of carbon nanotubes, sodium carboxymethyl cellulose having a molecular weight of 700 kDa, and water, and the concentration of the aggregates of carbon nanotubes is 0.20% by mass, and the concentration of sodium carboxymethyl cellulose is 0.30% by mass. The common logarithm of the viscosity of the dispersion liquid is 1.0 or more (the unit of viscosity is mPa s). Carbon nanotube aggregates. [Equation 1] The resistance factor P is the product of the surface resistivity (ρs) of the film and the absorbance (Abs) of the film. Two types of film thickness were prepared, and the resistance factor P of the thick film was thick , thin film P thin Also, the carbon in the thick film is calculated. Concentration of carbon nanotube aggregates C thick , the concentration of carbon nanotube aggregates in the thin film C thin Prepare the following. thick , P thin , C thick and C thin is applied to equation (α).

2. A conductive material comprising the carbon nanotube aggregate according to claim 1 .

3. An electrode comprising an electrode active material and the conductive material according to claim 2 .

4. A secondary battery comprising the electrode according to claim 3 .

5. A planar aggregate comprising the carbon nanotube aggregate according to claim 1 .

6. A laminate comprising a substrate and the planar assembly according to claim 5 .

7. A filter using the planar assembly according to claim 5.

8. An electromagnetic wave shield using the planar assembly according to claim 5.

9. A pellicle for extreme ultraviolet rays, which uses the planar assembly according to claim 5.

Images