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

Abstract

Provided is a carbon nanotube assembly with which a battery having excellent cycle characteristics can be manufactured. The carbon nanotube assembly satisfies conditions (1), (2) and (3) below. (1) The carbon nanotube assembly does not contain at least one first metal type selected from the group consisting of Si, Mn, Ni, Cr, Mo, and Co, or contains the first metal, and the total content of the first metal is 1000 ppm by mass or less with respect to the total mass of the carbon nanotube assembly. (2) The carbon nanotube assembly does not contain at least one second metal type selected from the group consisting of Na, K, Ca, and Al, or contains the second metal, and the total content of the second metal is 1000 ppm by mass or less with respect to the total mass of the carbon nanotube assembly. (3) The carbon nanotube assembly includes at least one of the first metal and the second metal.

Description

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

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

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

[0003] For example, Patent Document 1 describes a carbon nanotube aggregate that satisfies the following conditions (1), (2), and (3): (1) It contains at least one Fe atom and a Co atom, and the total content of Fe atoms and Co atoms is 2,000 ppm to 60,000 ppm relative to the total mass of the carbon nanotube aggregate. (2) It contains at least one Na atom and a K atom, and the total content of Na atoms and K atoms is 50 ppm to 700 ppm relative to the total mass of the carbon nanotube aggregate. (3) The ratio of the volume resistivity under a 20 kN pressurization to the volume resistivity under a 1 kN pressurization is 0.21 or higher. Patent Document 2 describes a carbon nanotube that satisfies the following conditions (1) to (3): (1) In differential thermal analysis when the temperature is raised from 200°C to 1000°C at a rate of 10°C / min, it has an exothermic peak between 600°C and 800°C. (2) In the Raman spectrum, the maximum peak intensity in the range of 1560–1600 cm⁻¹ is G, and 1310–1350 cm⁻¹ is rated. －１ (3) The total content of cobalt, iron, copper, zinc, nickel, chromium, manganese, and molybdenum is 5000 ppm or less.

[0004] Japanese Patent Publication No. 7556170, Japanese Unexamined Patent Publication No. 2024-095722

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

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

[0007] <1> A carbon nanotube aggregate that satisfies the conditions of (1), (2), and (3). (1) Does not contain at least one first metal selected from the group consisting of Si, Mn, Ni, Cr, Mo, and Co, or contains the first metal, and the total content of the first metal is 1000 ppm by mass or less with respect to the total mass of the carbon nanotube aggregate. (2) Does not contain at least one second metal selected from the group consisting of Na, K, Ca, and Al, or contains the second metal, and the total content of the second metal is 1000 ppm by mass or less with respect to the total mass of the carbon nanotube aggregate. (3) Contains at least one of the first metal and the second metal. <2> The carbon nanotube aggregate described in <1> that satisfies the condition of (4) below. (4) Contains a bundle structure, and in the area observed by a scanning electron microscope, the area ratio of bundles with a bundle diameter of 100 nm or more is greater than 0.1. <3> A carbon nanotube aggregate according to <1> or <2> that satisfies the following condition (5): (5) It contains a bundle structure, and in the area observed by a scanning electron microscope, the bundle diameter that is 90% cumulative is greater than 90 nm and less than or equal to 400 nm. <4> A conductive material containing a carbon nanotube aggregate according to any one of <1> to <3>. <5> An electrode containing an electrode active material and the conductive material according to <4>. <6> A secondary battery equipped with the electrode according to <5>. <7> A planar aggregate containing a carbon nanotube aggregate according to any one of <1> to <3>. <8> A laminate comprising a substrate and the planar aggregate according to <7>. <9> A filter using the planar aggregate according to <7>. <10> An electromagnetic shield using the planar aggregate according to <7>. <11> An extreme ultraviolet pellicle using the planar aggregate according to <7>.

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

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

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

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

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

[0013] [CNT Assembly] The CNT assembly according to this disclosure satisfies the following conditions (1), (2), and (3): (1) It does not contain at least one first metal selected from the group consisting of Si, Mn, Ni, Cr, Mo, and Co, or it contains a first metal, and the total content of the first metal is 1000 ppm by mass or less with respect to the total mass of the CNT assembly. (2) It does not contain at least one second metal selected from the group consisting of Na, K, Ca, and Al, or it contains a second metal, and the total content of the second metal is 1000 ppm by mass or less with respect to the total mass of the CNT assembly. (3) It contains at least one of the first metal and the second metal.

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

[0015] For example, the CNT aggregate described in Patent Document 1 has a total content of Fe atoms and Co atoms of 2,000 ppm to 60,000 ppm relative to the total mass of the CNT aggregate, and does not satisfy condition (1) in the CNT aggregate according to the present disclosure. Furthermore, Patent Document 1 does not contain any description focusing on cycle characteristics. Patent Document 2 does not contain any description focusing on the first metal and the second metal. Furthermore, Patent Document 2 does not contain any description focusing on cycle characteristics. In contrast, the CNT aggregate according to the present disclosure can produce a battery with excellent cycle characteristics by satisfying conditions (1), (2), and (3).

[0016] <Condition (1)> The CNT aggregate according to this disclosure does not contain at least one first metal selected from the group consisting of Si, Mn, Ni, Cr, Mo, and Co, or contains a first metal, wherein the total content of the first metal is 1000 ppm by mass or less with respect to the total mass of the CNT aggregate. Hereinafter, "at least one selected from the group consisting of Si, Mn, Ni, Cr, Mo, and Co" will also be simply referred to as "first metal". By having a total content of the first metal of 1000 ppm by mass or less, the deterioration of battery performance is suppressed when the CNT aggregate is used in a secondary battery (for example, as a conductive additive in a lithium-ion battery). If the total content of the first metal exceeds 1000 ppm by mass, side reactions are more likely to occur in the battery, and the battery performance tends to deteriorate, so adjusting the total content of the first metal is important.

[0017] As described in condition (3), the CNT aggregates relating to this disclosure contain at least one of the first and second metals, and therefore do not need to contain the first metal. However, if the content of Si, Mn, Cr, Mo, and Co is less than 10 ppm by mass, it becomes technically difficult to detect peaks originating from these elements using ICP-MS or ICP-AES, and it may be difficult to accurately calculate the content. For this reason, content less than 10 ppm by mass may be treated as 0 ppm by mass. It is difficult from the viewpoint of CNT synthesis and handling to reduce the total content of the first metal to less than 300 ppm by mass, and further to 100 ppm or less. Specifically, in the CNT manufacturing process, it is unavoidable that trace amounts of Si, Mn, Cr, Mo, and Co, which are raw materials for the reactor material, are mixed in as impurities, and it is technically difficult to achieve a total content of the first metal to less than 300 ppm by mass, and further to 100 ppm or less. The contamination of primary metals from the manufacturing process is presumed to originate from the reaction tube, raw material container, injector, and recovery machine. Ceramic materials containing Si, Al, etc., are sometimes used for the reaction tube due to their excellent heat resistance. Furthermore, materials such as SUS316L, SUS304, Alloy601, and Alloy600, each containing 10% or more by mass of Ni and Cr as active ingredients, are sometimes used for the raw material container, injector, and recovery machine. Under harsh conditions, such as high temperatures, it is possible that trace amounts of primary metals may be released from the reactor during the manufacturing process and adhere to the CNT aggregate.

[0018] Our inventors' research has shown that if the total content of the first metal is 100 ppm by mass or more, and moreover 300 ppm by mass or more, stable CNTs can be obtained in the manufacturing process. Furthermore, even if the total content of the first metal is 100 ppm by mass or more, and moreover 300 ppm by mass or more, the conductivity of the CNT aggregate does not tend to decrease.

[0019] From the above viewpoint, if the CNT aggregate contains a first metal, the content of the first metal may be 100 ppm by mass or more and 1000 ppm by mass or less, 250 ppm by mass or more and 1000 ppm by mass or less, or 300 ppm by mass or more and 1000 ppm by mass or less.

[0020] Methods for reducing the total content of the first metal to 1000 ppm by mass or less include, for example, washing the CNT aggregate with water, acid, an aqueous acid solution (for example, a 35% by mass aqueous solution of hydrochloric acid), or an aqueous chelating agent solution. This method can reduce the content of the first metal. In particular, when reducing the Si content, washing with an aqueous solution containing hydrofluoric acid or an aqueous solution containing a tetraalkylammonium salt of fluoride ions is effective. Another method involves immersing the CNT aggregate in an aqueous nitrate solution or an aqueous chloride solution containing approximately 5% by mass of the first metal to adsorb the first metal onto the surface of the CNT aggregate. This method can improve the total content of the first metal relative to the total mass of the CNT aggregate, and thus adjust the total content of the first metal. However, such adjustments to the content increase the process load and lead to increased costs, so it is preferable to avoid them.

[0021] In other embodiments, the CNT aggregate according to this disclosure contains a first metal. The CNT aggregate contains at least one first metal selected from the group consisting of Si, Ni, Mo, and Co, and the total content of the first metal is 1000 ppm by mass or less with respect to the total mass of the CNT aggregate. In other embodiments, the CNT aggregate according to this disclosure contains a first metal. The CNT aggregate contains at least one first metal selected from the group consisting of Si, Ni, and Mo, and the total content of the first metal is 1000 ppm by mass or less with respect to the total mass of the CNT aggregate. In other embodiments, the CNT aggregate according to this disclosure contains a first metal. The CNT aggregate contains either one of the first metals, Si or Ni, and the total content of the first metal is 1000 ppm by mass or less with respect to the total mass of the CNT aggregate. In other embodiments, the CNT aggregate according to this disclosure contains a first metal. The CNT aggregate contains Si among the primary metals, and the total content of the primary metal is 1000 ppm or less relative to the total mass of the CNT aggregate.

[0022] The total content of the primary metal can be adjusted to 1000 ppm by mass or less by selecting materials for reaction tubes, raw material containers, injectors, and recovery machines that minimize the release of the primary metal, and by controlling the reaction conditions to prevent them from becoming too harsh. In this case, no further adjustment of the content is necessary.

[0023] Within the above range, the dispersibility of the CNT aggregate as a dispersion, and the balance between the appropriate viscosity and conductivity of the dispersion can be optimized, resulting in improved battery performance. Furthermore, the refining cost when removing the first metal from the CNTs can be kept within an appropriate range.

[0024] In this disclosure, the content (mass ppm) of Si, Mn, Ni, Cr, Mo, and Co relative to the total mass of the CNT aggregate can be measured, for example, by the following method: The CNT aggregate is completely dissolved in an acid such as hydrochloric acid or nitric acid. Pretreatment such as dry ashing, wet ashing, or melting may be performed to completely dissolve the CNT aggregate in the acid. By using a solution obtained by completely dissolving a CNT aggregate in acid as a sample, the content of Si, Mn, Ni, Cr, Mo, and Co relative to the total mass of the CNT aggregate can be measured by inductively coupled plasma atomic emission spectroscopy (ICP-AES) or inductively coupled plasma mass spectrometry (ICP-MS). In the CNT aggregate of this disclosure, the Si content is measured using ICP-AES. The content of Mn, Ni, Cr, Mo, and Co is measured using ICP-MS.

[0025] Furthermore, if the content of Si, Mn, Ni, Cr, Mo, and Co in a CNT aggregate is less than 10 ppm by mass, it may be technically difficult to detect the peaks originating from Si, Mn, Ni, Cr, Mo, and Co, even when using ICP-MS or ICP-AES, making it difficult to accurately calculate the content. For this reason, in this disclosure, if the content of Si, Mn, Ni, Cr, Mo, and Co determined by the above measurement is less than 10 ppm by mass, the content of Si, Mn, Ni, Cr, Mo, and Co may be treated as 0 ppm by mass. However, the fact that the content of Si, Mn, Ni, Cr, Mo, and Co is 0 ppm by mass does not negate the presence of Si, Mn, Ni, Cr, Mo, and Co in the CNT aggregate.

[0026] From the above viewpoint, the total content of the first metal is 1,000 ppm by mass or less, preferably 900 ppm by mass or less, more preferably 850 ppm by mass or less, even more preferably 800 ppm by mass or less, and particularly preferably 750 ppm by mass or less.

[0027] The total content of the first metal may be greater than 0 ppm by mass, 10 ppm or more by mass, 20 ppm or more by mass, 30 ppm or more by mass, 40 ppm or more by mass, 50 ppm or more by mass, 60 ppm or more by mass, 70 ppm or more by mass, 80 ppm or more by mass, 90 ppm or more by mass, or 100 ppm or more by mass.

[0028] The content of Si, Mn, Ni, Cr, Mo, and Co relative to the total mass of the CNT aggregate is 1000 ppm by mass or less, preferably 900 ppm by mass or less, more preferably 850 ppm by mass or less, particularly preferably 800 ppm by mass or less, and even more preferably 750 ppm by mass or less.

[0029] Furthermore, if the CNT aggregate according to this disclosure contains a first metal, the content of Si, Mn, Ni, Cr, Mo, and Co relative to the total mass of the CNT aggregate may be greater than 0 ppm by mass, 10 ppm or more by mass, or 20 ppm or more by mass.

[0030] In one preferred embodiment, the total content of the first metal is greater than 0 ppm by mass and 1000 ppm by mass or less, 0 ppm by mass and 950 ppm by mass or less, 0 ppm by mass and 900 ppm by mass or less, 0 ppm by mass and 850 ppm by mass or less, 0 ppm by mass and 800 ppm by mass or less, and 0 ppm by mass and 750 ppm by mass or less. In another preferred embodiment, the total content of the first metal is greater than 10 ppm by mass and 1000 ppm by mass or less, 10 ppm by mass and 950 ppm by mass or less, 10 ppm by mass and 900 ppm by mass or less, 10 ppm by mass and 850 ppm by mass or less, 10 ppm by mass and 800 ppm by mass or less, 10 ppm by mass and 750 ppm by mass or less, and 10 ppm by mass and 720 ppm by mass or less. In another preferred configuration, the total content of the first metal is 100 ppm by mass or more and 1000 ppm by mass or less, 100 ppm by mass or more and 950 ppm by mass or less, 100 ppm by mass or more and 900 ppm by mass or less, 100 ppm by mass or more and 850 ppm by mass or less, 100 ppm by mass or more and 800 ppm by mass or less, 100 ppm by mass or more and 750 ppm by mass or less, and 100 ppm by mass or more and 720 ppm by mass or less. In another preferred configuration, the total content of the first metal is 250 ppm by mass or more and 1000 ppm by mass or less, 250 ppm by mass or more and 950 ppm by mass or less, 250 ppm by mass or more and 900 ppm by mass or less, 250 ppm by mass or more and 850 ppm by mass or less, 250 ppm by mass or more and 800 ppm by mass or less, 250 ppm by mass or more and 750 ppm by mass or less, and 250 ppm by mass or more and 720 ppm by mass or less. In another, more preferred embodiment, the total content of the first metal is 50 ppm by mass or more and 1000 ppm by mass or less, 60 ppm by mass or more and 950 ppm by mass or less, 70 ppm by mass or more and 900 ppm by mass or less, 80 ppm by mass or more and 850 ppm by mass or less, 90 ppm by mass or more and 800 ppm by mass or less, 100 ppm by mass or more and 750 ppm by mass or less, and 250 ppm by mass or more and 720 ppm by mass or less.

[0031] <Condition (2)> The CNT aggregate relating to this disclosure does not contain at least one secondary metal selected from the group consisting of Na, K, Ca, and Al, or it contains a secondary metal, and the total content of the secondary metal is 1000 ppm by mass or less with respect to the total mass of the CNT aggregate. Hereinafter, "at least one selected from the group consisting of Na, K, Ca, and Al" will also be simply referred to as "secondary metal".

[0032] The secondary metals contained in the CNT assemblies are thought to originate from the catalyst or catalyst support used during CNT production. For example, the reactivity during CNT production is sometimes adjusted by incorporating secondary metals into the catalyst. By adjusting the total content of secondary metals in the catalyst, the total content of secondary metals in the CNT assemblies can be controlled. On the other hand, if CNTs are obtained with a total content of secondary metals exceeding a predetermined range, the total content of secondary metals in the CNT assemblies can be controlled by, for example, applying an appropriate acid washing treatment to remove some of Na, K, Ca, and Al.

[0033] Since Na, K, Ca, and Al are presumed to exist in the form of oxides or inorganic salts, when the total content of the secondary metal is 10 ppm by mass or more, hydrophilicity improves and dispersibility in polar solvents containing water improves. Specifically, the adsorption of the secondary metal onto the surface of the CNTs changes the surface energy of the CNTs, strengthening the interaction with the polar solvent. As a result, the dispersion of CNT aggregates shows uniform dispersion and dispersibility improves. Furthermore, when the total content of the secondary metal is 1000 ppm by mass or less, the deterioration of battery performance is suppressed, for example, when used as a conductive additive in lithium-ion batteries. When the total content of the secondary metal exceeds 1000 ppm by mass, side reactions are more likely to occur in the battery, and battery performance tends to deteriorate, making it important to adjust the total content of the secondary metal. When the total content of the secondary metal is 1000 ppm by mass or less, a CNT dispersion with excellent conductivity and appropriate viscosity can be obtained. As a result, battery performance improves.

[0034] Methods for reducing the total content of the secondary metal to 1000 ppm by mass or less include, for example, washing the CNT aggregate with water, acid, an acidic aqueous solution (for example, a 35% by mass aqueous solution of hydrochloric acid), or an aqueous solution of a chelating agent. This method can reduce the content of the secondary metal. Another method involves immersing the CNT aggregate in an aqueous solution of nitrate or chloride salt containing approximately 5% by mass of the secondary metal to adsorb the secondary metal onto the surface of the CNT aggregate. This method can increase the total content of the secondary metal relative to the total mass of the CNT aggregate, thereby adjusting the total content of the secondary metal. However, such adjustments to the content increase the process load and lead to increased costs, so it is preferable to avoid them.

[0035] The total content of the secondary metal can be adjusted to 1000 ppm by mass or less by selecting a catalyst or catalyst support material that is less prone to the release of the secondary metal during CNT production, and by controlling the reaction conditions so that they do not become too harsh. In this case, no further adjustment of the content is necessary.

[0036] In this disclosure, the respective content (mass ppm) of Na, K, Ca, and Al relative to the total mass of the CNT aggregate can be measured, for example, by the following method: The CNT aggregate is completely dissolved in an acid such as hydrochloric acid or nitric acid. Pretreatment such as dry ashing, wet ashing, or melting treatment may be performed to completely dissolve the CNT aggregate in the acid. The respective content of Na, K, Ca, and Al relative to the total mass of the CNT aggregate can be measured by performing inductively coupled plasma atomic emission spectroscopy (ICP-AES) or inductively coupled plasma mass spectrometry (ICP-MS) on the solution in which the CNT aggregate has been completely dissolved in the acid. In the CNT aggregates of this disclosure, the content of Na, K, Ca, and Al is measured using ICP-MS.

[0037] Furthermore, if the Na, K, Ca, and Al content in the CNT aggregate is less than 10 ppm by mass, it may be technically difficult to detect the peaks originating from Na, K, Ca, and Al, even when using ICP-MS or ICP-AES, making it difficult to accurately calculate the content. For this reason, in this disclosure, if the Na, K, Ca, and Al content obtained by the above measurement is less than 10 ppm by mass, the Na, K, Ca, and Al content may be treated as 0 ppm by mass. However, the fact that the Na, K, Ca, and Al content is 0 ppm by mass does not negate the presence of Na, K, Ca, and Al in the CNT aggregate.

[0038] As described in condition (3), the CNT aggregates relating to this disclosure contain at least one of the first metal and the second metal, and therefore do not necessarily contain the second metal. From the above viewpoint, the total content of the second metal is 1000 ppm by mass or less, preferably 960 ppm by mass or less, more preferably 920 ppm by mass or less, even more preferably 880 ppm by mass or less, even more preferably 850 ppm by mass or less, even more preferably 750 ppm by mass or less, even more preferably 700 ppm by mass or less, particularly preferably 600 ppm by mass or less, extremely preferably 550 ppm by mass or less, and most preferably 500 ppm by mass or less.

[0039] The total content of the second metal may be greater than 0 ppm by mass, 10 ppm or more by mass, 20 ppm or more by mass, 30 ppm or more by mass, 40 ppm or more by mass, 50 ppm or more by mass, or 60 ppm or more by mass. In another embodiment, the total content of the second metal may be greater than 0 ppm by mass, 20 ppm or more by mass, 30 ppm or more by mass, 50 ppm or more by mass, 70 ppm or more by mass, 80 ppm or more by mass, 100 ppm or more by mass, 110 ppm or more by mass, or 120 ppm by mass.

[0040] The respective contents of Na, K, Ca, and Al relative to the total mass of the CNT aggregate are 1000 ppm by mass or less, preferably 960 ppm by mass or less, more preferably 920 ppm by mass or less, preferably 880 ppm by mass or less, preferably 850 ppm by mass or less, preferably 840 ppm by mass or less, preferably 750 ppm by mass or less, more preferably 700 ppm by mass or less, more preferably 600 ppm by mass or less, more preferably 550 ppm by mass or less, even more preferably 500 ppm by mass or less, most preferably 480 ppm by mass or less, and particularly preferably 470 ppm by mass or less. In another embodiment, the content of Na, K, Ca, and Al relative to the total mass of the CNT aggregate is 1000 ppm by mass or less, preferably 960 ppm by mass or less, more preferably 920 ppm by mass or less, preferably 880 ppm by mass or less, preferably 840 ppm by mass or less, preferably 750 ppm by mass or less, more preferably 600 ppm by mass or less, more preferably 500 ppm by mass or less, more preferably 400 ppm by mass or less, even more preferably 300 ppm by mass or less, and most preferably 250 ppm by mass or less.

[0041] The respective contents of Na, K, Ca, and Al relative to the total mass of the CNT aggregate may be greater than 0 ppm by mass, 10 ppm or more by mass, 20 ppm or more by mass, 30 ppm or more by mass, 40 ppm or more by mass, 50 ppm or more by mass, or 60 ppm or more by mass. In another embodiment, the respective contents of Na, K, Ca, and Al relative to the total mass of the CNT aggregate may be greater than 0 ppm by mass, 20 ppm or more by mass, 40 ppm or more by mass, 60 ppm or more by mass, 80 ppm or more by mass, 90 ppm or more by mass, 100 ppm or more by mass, or 120 ppm or more by mass.

[0042] In one preferred embodiment, the total content of the second metal is greater than 0 ppm by mass and 1000 ppm by mass or less, 0 ppm by mass and 960 ppm by mass or less, 0 ppm by mass and 920 ppm by mass or less, 0 ppm by mass and 880 ppm by mass or less, 0 ppm by mass and 850 ppm by mass or less, and 0 ppm by mass and 750 ppm by mass or less. In another preferred embodiment, the total content of the second metal is greater than 10 ppm by mass and 1000 ppm by mass or less, 10 ppm by mass and 960 ppm by mass or less, 10 ppm by mass and 920 ppm by mass or less, 10 ppm by mass and 880 ppm by mass or less, 10 ppm by mass and 850 ppm by mass or less, 10 ppm by mass and 840 ppm by mass or less, and 10 ppm by mass and 750 ppm by mass or less. In another preferred embodiment, the total content of the second metal is 100 ppm by mass or more and 1000 ppm by mass or less, 100 ppm by mass or more and 950 ppm by mass or less, 100 ppm by mass or more and 900 ppm by mass or less, 100 ppm by mass or more and 850 ppm by mass or less, 100 ppm by mass or more and 840 ppm by mass or less, 100 ppm by mass or more and 800 ppm by mass or less, 100 ppm by mass or more and 750 ppm by mass or less, and 120 ppm by mass or more and 470 ppm by mass or less. In another preferred embodiment, the total content of the second metal is 250 ppm or more and 1000 ppm or less, 250 ppm or more and 950 ppm or less, 250 ppm or more and 900 ppm or less, 250 ppm or more and 850 ppm or less, 250 ppm or more and 840 ppm or less, 250 ppm or more and 800 ppm or less, 250 ppm or more and 750 ppm or less, and 250 ppm or more and 470 ppm or less. In yet another embodiment, the CNT aggregate according to the present disclosure contains at least one second metal selected from the group consisting of Na, K, Ca, and Al. The CNT aggregate contains at least one second metal selected from the group consisting of Na, K, and Al, and the total content of the second metal is 1000 ppm or less with respect to the total mass of the CNT aggregate.In another embodiment, the CNT aggregate according to the present disclosure contains one secondary metal, either Na or Al, and the total content of the secondary metal is 1,000 ppm by mass or less with respect to the total mass of the CNT aggregate.

[0043] <Condition (4)> The CNT aggregate according to this disclosure includes a bundle structure, and it is preferable that the area ratio of bundles with a bundle diameter of 100 nm or more in the area observed by a scanning electron microscope (SEM) is greater than 0.1.

[0044] The CNT aggregates according to this disclosure preferably include bundle structures. A bundle structure refers to an aggregate in which multiple CNTs are aggregated together by van der Waals forces or the like, forming a bundle. It is presumed that including bundle structures of an appropriate size in a CNT aggregate improves the handling properties of the CNT aggregate and further enhances its stability. On the other hand, if the bundle structures included in the CNT aggregate become too large, the size of the CNT aggregate itself becomes too large, and it becomes difficult to separate and disperse the CNTs included in the bundle structure, which may reduce its dispersibility in the dispersion medium.

[0045] The bundle structure in the CNT aggregate can be formed, for example, by controlling the catalyst particle size distribution during manufacturing by chemical vapor deposition (CVD) or by controlling the cooling rate during the cooling process.

[0046] From the viewpoint of achieving both the handling properties and dispersibility in the solvent of the CNT aggregate, the individual bundle diameters contained in the CNT aggregate are preferably 5 nm to 500 nm, and more preferably 10 nm to 300 nm. The content of bundle structures in the CNT aggregate is preferably 10% to 100% by mass, and more preferably 20% to 90% by mass, based on the total mass of the CNT aggregate. The presence or absence of bundle structures in the CNT aggregate can be confirmed by observing the CNT aggregate with an optical microscope, a scanning electron microscope (SEM), etc. The bundle diameter can be determined by identifying the locations where bundle structures exist in the CNT aggregate and measuring the length using images of the bundle structures.

[0047] In the CNT aggregate according to this disclosure, the area ratio of bundles with a bundle diameter of 100 nm or more exceeds 0.1 in the SEM observation area, resulting in the appropriate formation of a CNT bundle structure and improved mechanical strength and conductivity as an electrode material. Specifically, a bundle diameter of 100 nm or more strengthens the bonding between CNTs, making the electron transport pathways connecting electrode active materials more robust, thereby improving the structural stability of the electrode. Furthermore, a large bundle diameter increases the electron conduction pathways within the electrode, promoting efficient current flow. This reduces the internal resistance of the battery and improves charge-discharge efficiency. Therefore, in the SEM observation area, a battery with excellent cycle characteristics can be obtained by having an area ratio of bundles with a bundle diameter of 100 nm or more exceeding 0.1.

[0048] In particular, the area ratio of the above bundles is preferably greater than 0.1 and less than 0.6, more preferably greater than 0.1 and less than 0.55, even more preferably greater than 0.1 and less than 0.5, particularly preferably 0.14 or more and less than 0.5, even more preferably 0.14 or more and 0.45 or less, particularly preferably 0.14 or more and 0.40 or less, especially preferably 0.14 or more and 0.35 or less, particularly preferably 0.14 or more and 0.30 or less, and even more preferably 0.14 or more and 0.26 or less. In another preferred embodiment, the area ratio of the above bundles is preferably greater than 0.2 and less than 0.5, and more preferably 0.2 or more and 0.45 or less. Within this range, the bundle structure of the CNTs is appropriately formed, and the bonding between the CNTs is strengthened, thereby improving the mechanical strength of the electrode. In addition, an appropriate bundle diameter improves the dispersibility of the CNTs, and a uniform conductive path is ensured within the electrode. This improves the overall conductivity of the electrodes and reduces the internal resistance of the battery, resulting in a battery with excellent cycle characteristics.

[0049] Furthermore, from the viewpoint of increasing the elongation at break, the area ratio of the bundle is particularly preferably 0.14 to 0.45. A higher elongation at break improves the flexibility and durability of the material containing the CNT aggregate.

[0050] Furthermore, it is preferable that the area ratio of the bundle is greater than 0.1 and less than or equal to 0.45. Within this range, the bundle diameter of the CNTs becomes appropriately small, increasing the surface area as an electrode material and widening the contact area with the electrode active material. This promotes ion movement and improves the charge and discharge efficiency of the battery. In addition, an appropriately small bundle diameter also has the effect of increasing the flexibility of the electrode and improving its durability against volume changes during the cycle. Therefore, the cycle characteristics of the battery are further improved.

[0051] <Condition (5)> The CNT aggregate according to this disclosure includes a bundle structure, and preferably the bundle diameter at which 90% of the total volume is accumulated (hereinafter also referred to as the "90% bundle diameter") is greater than 90 nm and less than or equal to 400 nm in the area observed by a scanning electron microscope. Furthermore, the bundle diameter at which 90% of the total volume is accumulated may be 350 nm or less, 300 nm or less, 250 nm or less, or 200 nm or less. Furthermore, the bundle diameter at which 90% of the total volume is accumulated may be 100 nm or more, or 110 nm or more.

[0052] In SEM observation, the CNT aggregates described herein have a cumulative 90% bundle diameter exceeding 90 nm, which facilitates the aggregation of CNT bundles and the formation of long-distance conductive networks. Furthermore, a cumulative 90% bundle diameter of 400 nm or less results in good dispersibility in the dispersion medium and facilitates the assurance of conductivity.

[0053] Specifically, a cumulative 90% bundle diameter exceeding 90 nm allows the CNTs to aggregate appropriately, forming efficient conductive paths. This improves the conductivity of the CNT aggregate and optimizes its performance as an electrode material. Furthermore, a cumulative 90% bundle diameter of 350 nm or less ensures good dispersibility in the dispersion medium, resulting in uniform dispersion. This maintains the viscosity of the dispersion containing the CNT aggregate within an appropriate range, improving dispersibility. As a result, the battery's cycle performance is improved.

[0054] In particular, the cumulative 90% bundle diameter is preferably greater than 90 nm and 350 nm or less, more preferably greater than 90 nm and 300 nm or less, more preferably greater than 90 nm and 280 nm or less, even more preferably greater than 90 nm and 250 nm or less, extremely preferably greater than 90 nm and 220 nm or less, and particularly preferably greater than 90 nm and 200 nm or less. Furthermore, the cumulative 90% bundle diameter is preferably 100 nm or more and 350 nm or less, more preferably greater than 100 nm and 300 nm or less, more preferably greater than 100 nm and 250 nm or less, even more preferably 100 nm or more and 220 nm or less, and particularly preferably 100 nm or more and 200 nm or less. Furthermore, the cumulative 90% bundle diameter is preferably 110 nm or more and 200 nm or less, more preferably 120 nm or more and 190 nm or less, and even more preferably 120 nm or more and 150 nm or less. In another preferred embodiment, the cumulative 90% bundle diameter is more preferably 130 nm to 220 nm, particularly preferably 130 nm to 200 nm, more preferably 130 nm to 190 nm, and even more preferably 130 nm to 150 nm. Within this range, the appropriate control of the CNT bundle diameter reduces the contact resistance between CNTs and efficiently forms electron conduction paths, thereby improving conductivity. Furthermore, the appropriate control of the bundle diameter maintains the viscosity of the dispersion containing the CNT aggregates within an appropriate range, improving dispersibility. As a result, the battery's cycle performance is improved.

[0055] <Matters concerning bundle diameter and bundle diameter parameters> The CNT aggregate according to this disclosure preferably includes a bundle structure. A bundle structure refers to an aggregate in which multiple CNTs are aggregated together by van der Waals forces or the like, forming a bundle. The width of the bundle structure, that is, the size in the width direction of the fiber bundle, is the bundle diameter. It is presumed that including a bundle structure with an appropriate bundle diameter in the CNT aggregate improves the handling properties of the CNT aggregate and further improves its stability. On the other hand, if the bundle structure included in the CNT aggregate becomes too large, the size of the CNT aggregate itself becomes too large, and it becomes difficult to separate and disperse the CNTs included in the bundle structure, which may reduce the dispersibility in the dispersion medium. The bundle diameter of the CNT aggregate is measured by observation using a SEM. Multiple SEM images are obtained by photographing the CNT aggregate at a magnification of 100,000 times. The imaging method using the SEM is not particularly limited and can be carried out by known methods.

[0056] -Imaging- Images of the CNT aggregate are obtained by imaging using an SEM device (for example, Hitachi High-Technologies Corporation, S-4800) under the following conditions. From the viewpoint of reducing the variance of the analyzed bundle diameter, it is preferable to obtain five or more images. Acceleration voltage: 0.5 kV Emission current: 10 μA Magnification: 100,000x Image size: 1280 pixels × 960 pixels

[0057] - Image Selection - From the obtained images, select two or more images in which CNT bundles are frequently observed.

[0058] - Overview of Bundle Diameter Analysis using Image Analysis - Image processing and image analysis are performed on the selected image using Python. In image processing, the contours and centerlines of the CNTs are detected and combined with the original image. In image analysis, the bundle diameter is determined by calculating the distance from the centerline to the contour in the created image. Then, the product of the bundle diameter and the length of the centerline is calculated to determine the area occupied by the CNTs in the image.

[0059] -Detection of CNT contours using image analysis- 1. Binarize the image to distinguish between CNTs and the background. 2. Create contours for the CNT portions using the edge detection function of the OpenCV library.

[0060] -Detection of CNT centerlines using image analysis- 1. Adjust parameters to distinguish between CNTs and background and perform binarization. 2. Create a skeleton for the CNT portion using the skeletonize function of the scikit-image library. 3. For each coordinate of the skeleton, count the number of skeletons in the surrounding 2 pixels and recognize coordinates with 5 or more skeletons as skeleton intersections. 4. Divide the skeleton at the intersections by converting the intersections to background pixels. The resulting skeletons are called regions. 5. Measure the length of the regions and delete the shorter regions. 6. Perform linear approximation for each region. 7. For each created line, obtain the X-axis coordinate of the region from which the approximation was made. Convert the line into a line segment based on the interval in which the obtained X-coordinate exists. Treat the line segment obtained here as the centerline of the CNT. 8. Calculate the similarity based on the center coordinates and angles for all sets of centerlines. If the distance between the center coordinates is within 10 pixels and the angle between the two line segments is less than 10 degrees, treat the pair of center lines as duplicate center lines and delete the shorter one. 9. Overlay the CNT contour and center lines onto the original image and save. The contour will be treated in red, and the center lines in blue.

[0061] -Detection of CNT bundle diameter by image analysis- 1. Load an image created by image processing and recognize CNTs, contours, background, and center lines using hue recognition. 2. Measure the length of each center line. 3. Select a random point on the center line and draw a perpendicular line from the point to the center line. 4. Detect the intersection point of the perpendicular line and the contour, and save the distance from the random point on the center line to the intersection point as the bundle diameter. 5. Calculate the occupied area as the product of the length of the center line segment and the bundle diameter. Save the data as a histogram with the bundle diameter on the horizontal axis and the occupied area on the vertical axis.

[0062] - Obtaining Bundle Diameter Parameters - Using the calculated bundle diameter histogram data, the bundle diameter features of each sample are calculated using the following method: 1. Add the bundle diameters and occupied areas of multiple fields of view of the same sample and normalize so that the sum is 1. With normalization, the unit of the vertical axis is set to occupied area ratio. 2. Find the sum of the occupied area ratios of bundles with a bundle diameter of 100 nm or more. 3. Calculate the cumulative occupied area ratio and determine the bundle diameter at which this value first exceeds 0.9 as the cumulative 90% bundle diameter.

[0063] <Viscosity of dispersion containing CNT aggregates> The viscosity of the dispersion containing CNT aggregates according to this disclosure is preferably 10 mPa·s to 1500 mPa·s, more preferably 30 mPa·s to 1300 mPa·s, particularly preferably 35 mPa·s to 1300 mPa·s, and even more preferably 100 mPa·s to 1200 mPa·s. In another embodiment, the viscosity of the dispersion is preferably 10 mPa·s to 1600 mPa·s, more preferably 100 mPa·s to 1600 mPa·s, and even more preferably 100 mPa·s to 1400 mPa·s.

[0064] The viscosity of the dispersion containing the CNT aggregate according to this disclosure is the viscosity obtained by measuring the viscosity using a dispersion prepared by mixing the CNT aggregate with 700 kDa of carboxymethylcellulose sodium and water, at a liquid temperature of 25°C, with a concentration of 0.20% by mass of the CNT aggregate and a concentration of 0.30% by mass of the carboxymethylcellulose sodium.

[0065] The viscosity of the dispersion containing the CNT aggregates according to this disclosure is measured using a cone-plate viscometer (also known as an E-type viscometer). For example, a Brookfield DV-II+Pro Programmable Viscometer is used as the cone-plate viscometer. The measurement conditions are as follows: Measurement fixture: Cone-plate; Measurement mode: Rotational mode; Shear speed: 0.6 s －１ ~384 simultaneous －１ Temperature: 25°C. From the obtained data, read the viscosity at the following shear rate: Shear rate = 12s－１

[0066] The CNT aggregates relating to this disclosure have a high affinity for the dispersion medium, which tends to result in a lower viscosity of the dispersion. When the viscosity of the dispersion is within an appropriate range, it can be determined that the dispersibility of the aggregates relating to this disclosure in the dispersion medium is good.

[0067] <Elongation at Break, Tensile Strength, and Energy Density at Break> The CNT aggregate according to this disclosure preferably has an elongation at break of more than 0% and 5.0% or less, measured by the following measurement method, a tensile strength of more than 4.0 MPa and 50.0 MPa or less, and an energy density at break of more than 7.0 MPa·% and 100 MPa·% or less.

[0068] -Method for measuring tensile strength, elongation at break, and energy density at break- A CNT dispersion is prepared by mixing a CNT aggregate, 700 kDa of carboxymethylcellulose sodium, and water, so that the concentration of the CNT aggregate is 0.20 mass% and the concentration of carboxymethylcellulose sodium is 0.30 mass%. 15 mL of the obtained CNT dispersion is poured onto a slide glass type silicon plate with inner dimensions of 22 mm × 75 mm × 3 mm, and heated at 100°C for 30 minutes to dry and obtain a measurement sample. The obtained measurement sample is fixed to the gripping part of a tensile testing device, and a tensile test is performed at a speed of 1 mm / min. The point where the stress is maximum is considered the fracture point, and the elongation at break is calculated from the length of the measurement sample at the fracture point and the length of the measurement sample before measurement. The maximum test force is calculated as the tensile strength. Furthermore, the energy density at break is calculated from the product of the elongation at break and the tensile strength.

[0069] When the elongation at break of the CNT aggregate according to this disclosure exceeds 0% (preferably 0.5% or more), the length of the CNTs is sufficiently long, making it easier to ensure conductivity. Specifically, the sufficient length of the CNTs increases the number of contact points between CNTs, allowing for smoother electron movement, thus improving the conductivity of the entire CNT aggregate. Furthermore, by maintaining an appropriate length of CNTs, conductive paths are efficiently formed, optimizing conductivity. When the elongation at break of the CNT aggregate according to this disclosure is 5.0% or less, it is easy to process into a dispersion and ensure dispersibility in the dispersion. Specifically, an elongation at break of 5.0% or less maintains the flexibility of the CNTs appropriately, enabling uniform dispersion of CNTs in the dispersion. This appropriately maintains the viscosity of the dispersion, improves dispersibility, and further enhances durability against volume changes and stress during the battery cycle. This further improves the maintenance rate of discharge capacity. Therefore, having a fracture elongation rate of the CNT aggregate in the range of over 0% and 5.0% or less plays an important role in improving the battery cycle characteristics of the CNT aggregate.

[0070] Furthermore, the elongation rate at break of the CNT aggregate can be adjusted by the length, diameter, and other factors of the CNT aggregate.

[0071] The tensile strength of the CNT aggregate according to this disclosure is preferably greater than 3.0 MPa and 50.0 MPa or less, more preferably between 3.5 MPa and 35.0 MPa, and even more preferably between 4.6 MPa and 32.6 MPa. When the tensile strength of the CNT aggregate according to this disclosure is greater than 3.0 MPa, the length of the CNTs according to this disclosure is sufficiently long, making it possible to manufacture a battery with excellent cycle characteristics. Specifically, the sufficient length of the CNTs increases the contact points between the CNTs, allowing for smoother electron movement, which improves the conductivity of the entire CNT aggregate and improves the cycle characteristics of the battery (i.e., the rate of maintenance of discharge capacity). When the tensile strength of the CNT aggregate according to this disclosure is 50.0 MPa or less, it is easy to process into a dispersion and easy to ensure dispersibility in the dispersion. Specifically, when the tensile strength is 35.0 MPa or less, the flexibility and mechanical strength of the CNTs are well balanced, and uniform dispersion of CNTs in the dispersion is achieved. This ensures that the viscosity of the dispersion is properly maintained, further improving its resistance to volume changes and stress during the battery cycle. This, in turn, further improves the retention rate of discharge capacity.

[0072] Furthermore, the tensile strength of the CNT aggregate can be adjusted by the length, diameter, and other factors of the CNT aggregate.

[0073] The fracture energy density of the CNT aggregate according to this disclosure is preferably greater than 8.0 MPa·% and 100.0 MPa·% or less, more preferably 9.0 MPa·% to 100.0 MPa·%, even more preferably 10.0 MPa·% to 100.0 MPa·%, particularly preferably 14.0 MPa·% to 100.0 MPa·%, preferably greater than 17.9 MPa·% and 100.0 MPa·% or less, more preferably 20.0 MPa·% to 90.0 MPa·%, and even more preferably 21.0 MPa·% to 80.0 MPa·%. When the fracture energy density of the CNT aggregate according to this disclosure is greater than 17.9 MPa·% (preferably 20.0 MPa·% or more), the length of the CNTs according to this disclosure is sufficiently long, making it possible to manufacture a battery with excellent cycle characteristics. Specifically, sufficient length of the CNTs increases the contact points between them, allowing for smoother electron movement. This improves the overall conductivity of the CNT assembly and enhances the battery's cycle characteristics (i.e., the rate of discharge capacity retention). When the fracture energy density of the CNT assembly according to this disclosure is 100.0 MPa·% or less, it is easy to process into a dispersion and ensure dispersibility in the dispersion. Specifically, a fracture energy density of 100.0 MPa·% or less maintains a good balance between the flexibility and mechanical strength of the CNTs, enabling uniform dispersion of the CNTs in the dispersion. This appropriately maintains the viscosity of the dispersion, further improving the battery's resistance to volume changes and stress during the cycle. This further improves the rate of discharge capacity retention.

[0074] Furthermore, the fracture energy density of a CNT aggregate can be adjusted by the length, diameter, and other factors of the CNT aggregate.

[0075] <Surface Resistivity> The surface resistivity of the film containing the CNT aggregate according to this disclosure is preferably 0.01 Ω / □ to 15.4 Ω / □, more preferably 0.1 Ω / □ to 12.0 Ω / □, even more preferably 0.2 Ω / □ to 10.0 Ω / □, particularly preferably 0.3 Ω / □ to 8.0 Ω / □, and extremely preferably 0.2 Ω / □ to 6.5 Ω / □, further preferably 0.80 Ω / □ to 5.0 Ω / □, more preferably 0.80 Ω / □ to 4.0 Ω / □, even more preferably 0.80 Ω / □ to 3.0 Ω / □, particularly preferably 0.80 Ω / □ to 2.0 Ω / □, and extremely preferably 0.90 Ω / □ to 1.24 Ω / □.

[0076] In this disclosure, the surface resistivity is measured by the following method. A CNT dispersion is prepared by mixing a CNT aggregate with 700 kDa of carboxymethylcellulose sodium and water, so that the concentration of the CNT aggregate is 0.20 mass% and the concentration of carboxymethylcellulose sodium is 0.30 mass%. A sample is prepared by pouring 15 mL of the prepared CNT dispersion onto a slide glass type silicon plate with inner dimensions of 22 mm × 75 mm × 3 mm and heating and drying it at 100°C. The surface resistivity of the prepared sample is measured at five arbitrarily selected locations on the film using a resistivity meter with a four-probe method, and the average value of the five measured values ​​is taken as the surface resistivity W.

[0077] <Other matters concerning CNT aggregates> In this disclosure, the CNTs included in the CNT aggregate may be SWCNTs or MWCNTs. From the viewpoint that having a layer distribution and slightly lower uniformity contributes to satisfying conditions (1) and (2), it is preferable that the CNT aggregate includes SWCNTs and MWCNTs.

[0078] The maximum length of the CNTs included in the CNT aggregate relating to this disclosure is not particularly limited.

[0079] In one embodiment, the CNT aggregate may mainly consist of CNTs with a maximum length of 500 μm or less, and may not contain CNTs with a length greater than 500 μm and less than or equal to 30,000 μm. Here, "main component" means that 90% by mass or more of the CNTs constituting the CNT aggregate are CNTs with a maximum length of 500 μm or less. The CNT aggregate may also contain CNTs with a maximum length of 500 μm or less.

[0080] The CNT aggregates according to this disclosure include, for example, CNTs having a maximum length of 10 μm to 30,000 μm. The CNT aggregates according to this disclosure preferably include CNTs having a maximum length of 500 μm or more, more preferably include CNTs having a maximum length of 500 μm to 30,000 μm, and even more preferably include CNTs having a maximum length of 1,000 μm to 30,000 μm (i.e., ULCNTs).

[0081] ULCNTs are longer in length and can take the form of fibers compared to general-purpose CNTs. When the maximum length of the CNTs included in the CNT aggregate according to this disclosure is 500 μm or more, the entanglement between the CNTs becomes moderately strong, and the CNTs tend to form a network structure more easily.

[0082] By taking the form of fibers, ULCNTs have a tendency to entangle with each other. A CNT aggregate is preferably an aggregate containing multiple ULCNTs, as this allows the CNTs to entangle with each other and form a more stable aggregate. Hereinafter, an aggregate containing ULCNTs may be abbreviated as an "ULCNT aggregate."

[0083] Here, the term "fiber" is generally used to refer to a structure in which one dimension is larger than the other two dimensions. The fiber may be a thread-like fiber with a circular cross-section, a ribbon-like fiber with a rectangular cross-section, hollow, or have other shapes. From the viewpoint of improving conductivity, the cross-section of the CNTs contained in the CNT aggregate is preferably circular and preferably hollow.

[0084] The CNT aggregate may be an aggregate of three-dimensional structures in which the CNTs are intertwined. The intertwined state of the CNTs in the CNT aggregate according to this disclosure can be confirmed by SEM observation.

[0085] The length of individual carbon nanotubes (CNTs) within a CNT aggregate can be measured by focusing on a single CNT and observing multiple SEM images within adjacent fields of view. Here, "CNT length" refers to the measured length in the longitudinal direction of the CNT, and the maximum value among the measured lengths is defined as the "maximum length." If, by observing the SEM images, one CNT with a maximum length in the range of 1,000 μm to 30,000 μm is observed within the field of view of the SEM image, it can be confirmed that the observed CNT contains a ulcerative colloidal cell (ULCNT).

[0086] It is preferable that multiple ULCNs are present within the field of view of the SEM image. Focusing on 100 CNTs included in the field of view of the SEM image, the maximum length of each is measured, and of the observed CNTs, it is preferable that 10% or more (in numerical terms) of the CNTs have a maximum length in the range of 1000 μm to 30000 μm (i.e., ULCNs), from the viewpoint of further improving the stability of the CNT aggregate due to the entanglement of ULCNs, more preferably 20% or more, even more preferably 30% or more, and particularly preferably 50% or more.

[0087] The diameter of an ULCNT can be measured by observing a SEM (Surface-Emission Microscope) or transmission electron microscope (TEM) image. Here, diameter refers to the length in the direction perpendicular to the longitudinal direction of the ULCNT. The diameter is measured at 10 different points on a single ULCNT, and the average value is taken as the diameter of that ULCNT.

[0088] The length of the ULCNT is in the range of 1,000 μm to 30,000 μm, preferably in the range of 1,050 μm to 25,000 μm, more preferably in the range of 1,100 μm to 20,000 μm, even more preferably in the range of 1,200 μm to 18,000 μm, and particularly preferably in the range of 1,300 μm to 15,000 μm. The diameter of the ULCNT is preferably in the range of 1 nm to 100 nm, more preferably in the range of 2 nm to 80 nm, even more preferably in the range of 3 nm to 50 nm, and particularly preferably in the range of 5 nm to 30 nm.

[0089] The length / diameter ratio, or aspect ratio, of the ULCNT is preferably 1000 or more, more preferably 3000 or more, even more preferably 5000 or more, and particularly preferably 10000 or more. The aspect ratio can be calculated from the ratio of the maximum length to the diameter of a single ULCNT. From the viewpoint of measurement accuracy, it is preferable to use the average value of the measurements of 20 or more ULCNTs.

[0090] Furthermore, from the viewpoint of dispersibility, the specific gravity of the ULCNT aggregate is preferably in the range of 1.5 to 2.5, more preferably in the range of 1.7 to 2.4, and even more preferably in the range of 1.8 to 2.2. The specific gravity of the ULCNT aggregate can be measured by the method described in JIS Z8807:2012 "Method for measuring the density and specific gravity of solids".

[0091] The purity of carbon as CNTs in an ULCNT aggregate can be measured by thermogravimetric analysis. For example, a thermogravimetric (TG) curve and a differential thermal analysis (DTA) curve of the ULCNT aggregate are obtained using a thermal analyzer (Shimadzu Corporation, DTG-60). In the DTA curve, where the peak top appears around 650°C to 750°C, the largest exothermic peak is considered to be the combustion of CNTs, and other exothermic peaks are considered to be the combustion of substances other than CNTs. The purity of the CNTs is determined from the weight loss rate of the TG curve. From the viewpoint of the resulting conductivity, the purity of the ULCNT aggregate is preferably 50% by mass or more, more preferably 65% ​​by mass or more, even more preferably 80% by mass or more, and particularly preferably 95% by mass or more.

[0092] The obtained fibrous ULCNTs are preferably flexible and strong. Further, the conductivity of the ULCNT itself is 5000 ohm －１ ·m －１ or more, more preferably 10000 ohm －１ ·m －１ or more. The conductivity of the ULCNT itself is usually 1000000 ohm －１ ·m －１ or less.

[0093] <Method for Producing CNTs> The method for producing CNTs in the present disclosure is not particularly limited. For example, as the method for producing CNTs in the present disclosure, conventionally known methods such as a chemical vapor deposition (CVD) method and a method of reacting a gaseous reactant containing a carbon source in the presence of a catalyst can be applied.

[0094] The CNTs in the present disclosure can be produced with reference to, for example, the methods described in Japanese Patent Application Laid-Open No. 2016-102047, Japanese National Publication of International Patent Application No. 2021-527611, and the like.

[0095] Hereinafter, the method for producing CNTs in the present disclosure will be described by way of examples. However, the method for producing CNTs in the present disclosure is not limited to the following examples.

[0096] =Production Method X= An example of the method for producing CNTs referred to in the present disclosure includes the production method described in Japanese Patent Application Laid-Open No. 2016-102047. That is, the production method comprises: a step of passing a gaseous reactant containing one or more carbon sources through a reactor; a step of reacting one or more gaseous reactants in the presence of a catalyst within a reaction region of the reactor to form product particles containing carbon; a step of aggregating the product particles into an aggregate; and a step of applying a force to the aggregate to continuously move the aggregate out of the reaction region (hereinafter, also referred to as "Production Method X").

[0097] According to Production Method X, CNTs including ULCNTs can be obtained in the form of easily handleable fibrous aggregates or other forms of aggregates.

[0098] In manufacturing method X, the force applied to the product particles may be a mechanical force. If the aggregate is fibrous CNT, the mechanical force applied to the product particles can be applied by a rotating spindle around which the aggregate is wound. The fibrous CNT may be collected on the spindle, or it may be accumulated elsewhere after being rotated around the spindle once or more times, as the spindle is continuously unwound.

[0099] Preferably, the spindle axis is positioned perpendicular or parallel to the flow direction of one or more gaseous reactants, but it may be positioned in other orientations. For example, a spindle with its axis positioned at a 25° angle to the flow direction of the gaseous reactants can also be suitably used to apply mechanical force to product particles.

[0100] The spindle can rotate around two axes (for example, two vertical axes). In particular, the spindle can rotate around axes perpendicular and parallel to the flow direction of the gaseous reactant. Such a spindle allows for the pulling and twisting of aggregates, which are fibrous carbon nanotubes, to control the number of twists and length.

[0101] The spindle material may be metal, ceramic, or resin. The spindle can take on different suitable shapes depending on the material properties and the intended use of the CNTs. The spindle can be used, for example, as a mold for producing carbon products by a spin-coating process. Preferred spindle shapes are rod-shaped or box-shaped.

[0102] Fibrous carbon nanotubes (CNTs) are accumulated on the spindle or elsewhere, and the coating thickness and orientation can be controlled by controlling the reaction time and reaction conditions, or by applying an electric field or other field to the carbon product. The coating thickness and orientation of the carbon product can be controlled, for example, by the fluidity of the gas.

[0103] The spindle rotation speed is preferably 0.01 rpm (revolutions per minute; the same applies hereafter) to 10,000 rpm, and more preferably 0.1 rpm to 100 rpm. The spinning speed (i.e., the spindle rotation speed) may be adjusted so that the material is recovered at the same rate as it is produced. The spindle rotation speed may be used to control the thickness of the accumulated fibrous CNTs. In one preferred embodiment, as the spindle rotates, the fibrous CNTs are processed in the axial direction of the spindle. In this processing, the fibrous CNTs are wound evenly along the spindle, rather than being wound at only one specific point on the spindle.

[0104] Fibrous CNTs may be recovered onto the reactor wall, for example, by a substrate placed in the reactor. The substrate may be a fixed substrate or a rotating guide used to apply a strong and equal force to the fibrous CNTs when they are recovered. A suitable substrate arrangement used in fiber technology is a substrate consisting of two guides positioned orthogonally to each other.

[0105] In manufacturing method X, the mechanical force applied to the product particles may be a force applied by an accelerating gas flow. The accelerating gas flow can be generated by passing the product particles through a reactor having a narrow diameter or through a capillary tube located downstream of the reaction region. A vacuum may be applied to the product particles.

[0106] Other forces applied to the product particles include electrostatic forces appropriately applied by a charged plate. When using electrostatic forces, the product particles must be charged. By using a charged plate, CNTs can be generated on the plate in the form of intertwined sheets.

[0107] Furthermore, other forces applied to the generated particles may include magnetic force or photon pressure applied by a light source.

[0108] The raw material for CNTs may be injected in the form of a liquid containing a carbon source, instead of a gaseous reactant containing a carbon source. When a liquid is used as the raw material for CNTs, it can be injected through a single inlet or multiple inlets, for example, in a showerhead configuration.

[0109] One or more gaseous reactants are preferably reacted at 500°C to 1600°C, and more preferably at 1000°C to 1500°C. The temperature gradient is maintained within the reactor, and the reaction region is preferably kept at a higher temperature than the product region of the reactor.

[0110] The gaseous reactant may be used in combination with one or more gases that act as diluents. The gaseous reactant may also be used in combination with gases that do not play a direct role in the reaction but play an auxiliary role. If amorphous carbon is produced as a byproduct, it is also preferable to use a gas as a diluent that can react with amorphous carbon to maintain the reaction sites on the catalyst and produce nanotubes.

[0111] Gases that can be used as diluents include argon or other inert gases, hydrogen, nitrogen, ammonia, carbon dioxide, and helium. Among these, hydrogen is particularly preferred as a diluent.

[0112] The composition of the product particles can be controlled by monitoring the aggregates and changing the reaction conditions based on the information obtained. For example, aggregates can be monitored by online Raman spectroscopy. Online Raman spectroscopy provides data indicating whether the CNTs are single-layer or multi-layer. It also provides data indicating the diameter and crystallinity of the CNTs. Aggregates can also be monitored by online conductivity measurement, gas analysis, measurement of the opacity of the reaction region, and / or measurement of the winding force.

[0113] When removing aggregates from the reactor, it is preferable to prevent air from entering the reactor. Preventing air inflow is particularly important, for example, when the diluent gas contains hydrogen, as it helps to prevent the formation of an explosive mixture of hydrogen and air in the reactor.

[0114] In manufacturing method X, it is preferable to control the reactor temperature to 200°C to 700°C when removing the aggregates from the reactor. The bundle diameter of the CNTs can be controlled by the temperature of the reaction region of the CNTs and the reactor temperature when removing the aggregates from the reactor. The higher the reactor temperature when removing the aggregates from the reactor, the larger the bundle diameter of the CNTs can be. For example, by setting the reactor temperature to about 150°C when removing the aggregates from the reactor, the bundle diameter, which is 90% of the cumulative CNTs, can be set to 110 nm to 170 nm. By setting the reactor temperature to about 500°C when removing the aggregates from the reactor, the bundle diameter, which is 90% of the cumulative CNTs, can be set to 190 nm to 230 nm. By setting the reactor temperature to about 750°C when removing the aggregates from the reactor, the bundle diameter, which is 90% of the cumulative CNTs, can be set to 300 nm to 400 nm. The "reactor temperature" refers to the temperature determined by measuring the gas temperature at the outlet from which the condensed material is removed from the reactor.

[0115] The product particles produced in manufacturing method X contain ULCN. Depending on the manufacturing conditions, SWCNTs and MWCNTs may also be present.

[0116] The product particles may be generated by chemical vapor deposition. When the product particles are generated by chemical vapor deposition, the carbon source, which is a gaseous reactant, reacts in the presence of a catalyst.

[0117] Suitable carbon-containing compounds as carbon sources include carbon monoxide, carbon dioxide, aromatic hydrocarbons (e.g., benzene, toluene, xylene, cumene, ethylbenzene, naphthalene, or mesitylene), non-aromatic hydrocarbons (e.g., methane, ethane, propane, butane, pentane, hexane, cyclohexane, ethylene, propylene, or acetylene), and oxygen-containing hydrocarbons (e.g., formaldehyde, acetaldehyde, acetone, methanol, ethanol, diethyl ether, polyethylene glycol, 1-propanol, ethyl formate, or hydrocarbons containing two or more of these). Carbon monoxide, methane, ethylene, or acetylene are preferred as carbon-containing compounds.

[0118] The carbon source preferably contains oxygen. Ethanol is a particularly preferred carbon source. Oxygen can be introduced into the reactor by other means, for example, by using a carbon source containing a diluent gas or water.

[0119] As catalysts, transition metals are preferred, particularly chromium (Cr), molybdenum (Mo), tungsten (W), or VIII-B transition metals. Specifically, preferred catalysts include, for example, iron (Fe), cobalt (Co), nickel (Ni), ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os), iridium (Ir), and platinum (Pt) or manganese (Mn), or mixtures thereof. Metals from the lanthanide and actinide series (e.g., yttrium (Y)) can also be used as catalysts. Fe, Ni, Co, Mo, and mixtures thereof are preferred, for example, a mixture of Ni and Co (mass ratio: 50 / 50), a mixture of Fe and Ni, or a mixture of Fe and Mo are more preferred. Any of these transition metals can be used alone or in combination with any of the other transition metals listed above to function as catalysts for the growth of CNTs. The catalyst is particularly preferably a mixture of two or more of the listed metals.

[0120] The catalyst is preferably formed by the decomposition of a precursor. The precursor is preferably a thermal, photocatalytic, or plasma-degradable compound of one or more of the above-mentioned metals, such as a carbonyl or cyclopentadienyl organometallic compound. Ferrocene, iron pentacarbonyl, nickerocene, and cobaltocene are particularly preferred as precursors. In some embodiments, at least 0.01% by mass of the precursor is contained in the carbon source, preferably 0.2% to 30% by mass of the precursor, and more preferably 0.2% to 20% by mass of the precursor. In some embodiments, 0.23% to 2.3% by mass of the precursor may be contained in the carbon source, and 0.02% to 20% by mass of the precursor. The catalyst may also be used supported on a carrier. Preferred carriers include silica and magnesium oxide.

[0121] The carbon source is preferably reacted in the presence of an accelerator. Suitable accelerators are one or more of sulfur, phosphorus, molybdenum, and organic compounds of these elements. Thiophene is also a preferred accelerator. Preferably, the accelerator is contained in the carbon source at a concentration of up to 10% by mass. Preferably, the accelerator is contained in the carbon source at a concentration of 0.2% to 6% by mass. When high or low concentrations of thiophene are used as the accelerator, MWCNTs are formed.

[0122] According to manufacturing method X, fibrous CNTs having a length of at least 500 μm, for example, at least 1 mm, can be obtained. The fibrous CNTs can take the form of threads or sheets. The length of the fibrous CNTs can be controlled, for example, by the winding capacity of the spindle used when manufacturing the fibrous CNTs.

[0123] The manufacturing method X preferably includes the steps of generating CNTs by reacting a carbon source in the reaction region of a reactor, and agglomerating the CNTs into aggregates by applying force to them. This manufacturing method makes it possible to easily produce fibrous CNTs.

[0124] The manufacturing method X preferably further includes a step of purifying the obtained CNT aggregates after the step of agglomerating CNTs into aggregates. Specifically, first, the CNT aggregates are washed with alcohol (e.g., methanol, ethanol, etc.). Next, they are washed with an alkaline solution (e.g., ammonia water). The pH of the alkaline solution is, for example, 8 to 11. Furthermore, they are washed with pure water.

[0125] The cleaning method is not particularly limited and may involve spraying a cleaning solution onto the CNT aggregates or immersing the CNT aggregates in a cleaning solution. Cleaning with alcohol removes alcohol-soluble components contained in the CNT aggregates. Cleaning with an alkaline solution hydrolyzes and removes impurities contained in the CNT aggregates. Cleaning with an acidic solution may also be performed.

[0126] It is preferable to dry the CNT aggregates after washing. The drying method is not particularly limited and can be carried out by commonly known methods.

[0127] By purifying the aggregates of carbon nanotubes (CNTs), the metal content in the CNTs can be reduced.

[0128] The manufacturing method X preferably further includes a step of passing the purified CNT aggregates through a sieve after the step of purifying the CNT aggregates. It is also preferable to recover the CNTs that have passed through the sieve.

[0129] The method of passing the material through the sieve is not particularly limited and can be carried out by commonly known methods. The mesh size of the sieve is, for example, 0.1 mm to 3.0 mm, preferably 0.5 mm to 2.0 mm, and more preferably 1.0 mm to 1.5 mm. The material of the sieve is not particularly limited and may be metal or resin. When the CNT aggregate is applied to an electrode (especially an electrode for a lithium-ion battery), it is preferable that the material does not impair the performance of the battery. The number of times the material is passed through the sieve is, for example, 1 to 3 times. Before passing the CNT aggregate through the sieve, the CNT aggregate may be crushed to an appropriate size beforehand. Crushing can be done using a crusher. Examples of crushers include roll mills, cutter mills, hammer mills, etc.

[0130] By passing the obtained CNT aggregates through a sieve and recovering the CNTs that pass through the sieve, coarse CNTs are removed, improving the stability of the CNT dispersion. In addition, while foreign matter introduced from the outside is generally removed during electrode manufacturing, passing the obtained CNT aggregates through a sieve allows for a simpler method of removing foreign matter introduced from the outside.

[0131] In other embodiments, the method may include generating CNTs containing ULCNTs in a reaction region by the above method, condensing them to form CNTs containing ULCNTs, and continuously withdrawing CNTs from near the reaction region. In yet other embodiments, the method may include generating CNTs containing ULCNTs in a reaction region, continuously electrostatically attracting CNTs containing ULCNTs from the reaction region, and recovering CNTs containing ULCNTs.

[0132] =Manufacturing Method Y= In this disclosure, as an example of a method for manufacturing CNTs, the manufacturing method described in Japanese Patent Publication No. 2021-527611 can be referenced. That is, a mixture containing a main catalyst precursor and a co-catalyst precursor is γ-Al ２ O ３A manufacturing method (hereinafter also referred to as "manufacturing method Y") includes the steps of: (1) supporting the active support on a material to produce an active support; (2) drying the active support by multi-stage drying including vacuum drying; (3) heat-treating the dried active support to produce a supported catalyst; and (4) producing CNTs in the presence of the supported catalyst.

[0133] Step (1) Step (1) involves mixing a main catalyst precursor and a co-catalyst precursor in γ-Al ２ O ３ The active support is manufactured by supporting it on a material.

[0134] The main catalyst precursor and co-catalyst precursor are γ-Al ２ O ３ To ensure uniform support, the mixture may further contain a solvent, and the main catalyst precursor and co-catalyst precursor may be dissolved in the solvent. The solvent may be one or more selected from the group consisting of water, methanol, and ethanol, with water being preferred.

[0135] γ-Al ２ O ３ Because it has high porosity and a spinel structure, the main catalyst and co-catalyst are γ-Al ２ O ３ They can be arranged irregularly. CNTs grown from an irregularly arranged main catalyst can be produced in an entangled manner.

[0136] The main catalyst may be one or more selected from the group consisting of cobalt, iron, nickel, manganese, and chromium, with cobalt being preferred.

[0137] 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.

[0138] The main catalyst precursor is Co(NO ３ ) ２ Co(NO ３ ) ２ 6H ２ O, Co ２ (CO) ８ Co ２ (CO) ６ [HC=C(C(CH ３ )３ ) ], Co (CH ３ CO ２ ) ２ Fe(NO ３ ) ３ Fe(NO ３ ) ２ nH ２ O, Fe(CH ３ CO ２ ) ２ Ni (NO ３ ) ２ Ni (NO ３ ) ２ 6H ２ O, Mn (NO ３ ) ２ , Mn(NO ３ ) ２ 6H ２ O, Mn(CH ３ CO ２ ) ２ ・n(H ２ O) and Mn(CO) ５ It may be one or more selected from the group consisting of Br, and among these, Co(NO ３ ) ２ 6H ２ O, Fe (NO ３ ) ２ nH ２ O, Ni (NO ３ ) ２ 6H ２ O is preferred.

[0139] The co-catalyst improves the dispersibility of the main catalyst and may be one or more selected from the group consisting of vanadium and molybdenum.

[0140] The co-catalyst precursor is NH ４ VO ３ NaVO ３ , V ２ O ５ , V(C ５ H ７ O ２ ) ３ , and (NH ４ ) ６ Mo ７ O ２４ 4H ２ It may be one or more selected from the group consisting of O, and NH４ VO ３ and (NH ４ ) ６ Mo ７ O ２４ 4H ２ It is preferable to select one or more from the group consisting of O.

[0141] When the mixture contains two or more co-catalyst precursors, that is, when it contains both a vanadium precursor and a molybdenum precursor, the molar ratio of the sum of vanadium and molybdenum to vanadium can be 1:0.45 to 1:0.95 or 1:0.5 to 1:0.9, and is preferably 1:0.5 to 1:0.9. When the above conditions are met, the structure of the CNTs can be stably maintained and CNTs with the desired pore volume can be produced.

[0142] The mixture may contain a main catalyst precursor and a co-catalyst precursor in molar ratios of 1:0.01 to 1:0.5, 1:0.1 to 1:0.4, or 1:0.1 to 1:0.25, with a preferred ratio of 1:0.1 to 1:0.25. Satisfying the above molar ratios improves the dispersibility of the main catalyst, enabling the production of CNTs with the desired pore volume.

[0143] The mixture may further contain an organic acid that plays a role in suppressing the precipitation of the main catalyst precursor and the co-catalyst precursor.

[0144] 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.

[0145] The mixture can contain the organic acid and the co-catalyst precursor in a molar ratio of 1:1 to 1:20, 1:2 to 1:10, or 1:3 to 1:6, with a ratio of 1:3 to 1:6 being preferred. Satisfying the above range has the advantage of enabling the production of a transparent catalyst metal solution during catalyst manufacturing and the production of a catalyst with suppressed fine powder formation during impregnation.

[0146] The process may further include a maturation step after step (1).

[0147] The maturation process may be carried out for 1 to 60 minutes or 10 to 50 minutes. It is preferable to carry it out for 10 to 50 minutes. When the above conditions are met, γ-Al ２ O ３ The main catalyst precursor and co-catalyst precursor can be sufficiently supported on the support. Furthermore, bubbles present within the support are removed to the maximum extent possible, allowing the main catalyst precursor and co-catalyst precursor to be sufficiently supported even in the fine pores inside the support.

[0148] Step (2) Next, the active support is dried by multi-stage drying, which includes vacuum drying.

[0149] Multi-stage drying can mean that a drying process, including vacuum drying, is performed two or more times. Specifically, multi-stage drying may include atmospheric pressure drying and vacuum drying, or it may include vacuum drying alone two or more times.

[0150] Vacuum drying may be carried out at 80°C to 300°C or 120°C to 250°C, with 120°C to 250°C being preferred. When the above conditions are met, the main catalyst precursor, i.e., the coordination bond of the main catalyst, can be easily decomposed to form the main catalyst oxide, and energy consumption can be minimized.

[0151] Vacuum drying may be performed at 1 mbar to 200 mbar or 30 mbar to 150 mbar, and is preferably performed at 30 mbar to 150 mbar. When the above conditions are met, the main catalyst precursor, i.e., the coordination bond of the main catalyst, is rapidly decomposed and discharged, so that the main catalyst oxide can be formed more easily under vacuum conditions and energy consumption can be minimized.

[0152] Vacuum drying can be performed for 10 minutes to 3 hours or 10 minutes to 2 hours, with 10 minutes to 2 hours being preferred. When the above conditions are met, the main catalyst precursor can be easily decomposed and converted into the main catalyst oxide, and energy consumption can be minimized.

[0153] On the other hand, if multi-stage drying includes atmospheric pressure drying and vacuum drying, atmospheric pressure drying can be performed before the vacuum drying described above, and atmospheric pressure drying can remove any solvents that may be present in the active carrier.

[0154] Atmospheric pressure drying may be carried out at 80°C to 160°C or 100°C to 140°C, and is preferably carried out at 100°C to 140°C. When the above conditions are met, the solvent present in the active carrier can be sufficiently removed, and energy consumption can be minimized.

[0155] Atmospheric pressure drying may be carried out at 900 mbar to 1,100 mbar, and preferably at 950 mbar to 1,050 mbar. When the above conditions are met, the solvent present in the active carrier can be sufficiently removed, and energy consumption can be minimized.

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

[0157] On the other hand, if multi-stage drying includes two or more vacuum drying steps, it may include two or more vacuum drying steps performed at different temperatures, more specifically, a primary vacuum drying step performed at a first temperature and a secondary vacuum drying step performed at a second temperature higher than the first temperature.

[0158] Primary vacuum drying can remove any solvents that may be present in the active carrier.

[0159] The first temperature may be between 80°C and 160°C, and is preferably between 100°C and 140°C. When the above conditions are met, the solvent present in the active carrier can be sufficiently removed, and energy consumption can be minimized.

[0160] Primary vacuum drying can be performed for 1 to 12 hours, preferably 3 to 9 hours. When the above conditions are met, the solvent present in the active carrier can be sufficiently removed, and energy consumption can be minimized.

[0161] The primary vacuum drying may be performed at 1 mbar to 200 mbar, 1 mbar to 150 mbar, or 80 mbar to 150 mbar, and is preferably performed at 80 mbar to 150 mbar. When the above conditions are satisfied, the solvent present in the active support can be sufficiently removed, and energy consumption can be minimized.

[0162] The description regarding the secondary vacuum drying is as described in the above description regarding vacuum drying.

[0163] The second temperature may be 175°C to 300°C, and is preferably 180°C to 280°C. When the above conditions are satisfied, the main catalyst precursor, that is, the coordination conjugate of the main catalyst, can be easily decomposed to form the main catalyst oxide, and energy consumption can be minimized.

[0164] The secondary vacuum drying may be performed at 1 mbar to 200 mbar, 1 mbar to 150 mbar, or 1 mbar to 70 mbar, and is more preferably performed at 1 mbar to 70 mbar. When the above conditions are satisfied, the main catalyst precursor, that is, the coordination conjugate of the main catalyst, is rapidly decomposed and discharged, so that the main catalyst oxide can be formed more easily under vacuum conditions, and energy consumption can be minimized.

[0165] The secondary vacuum drying may be performed for 10 minutes to 3 hours or 10 minutes to 2 hours, and is preferably performed for 10 minutes to 2 hours. When the above conditions are satisfied, the main catalyst precursor can be easily decomposed and converted into the main catalyst oxide, and energy consumption can be minimized.

[0166] • Step (3) Next, the dried active support is subjected to heat treatment to produce a supported catalyst.

[0167] When the heat treatment is performed, the main catalyst and the co-catalyst are supported on γ-Al ２ O ３ A supported catalyst that exists in a coated state on the surface and pores of is produced.

[0168] The heat treatment may be performed at 600°C to 800°C or 620°C to 750°C, and is preferably performed at 620°C to 750°C. When the above conditions are satisfied, the main catalyst and the co-catalyst are supported on γ-Al２ O ３ The supported catalyst can be manufactured with a uniform coating on the surface and pores, while minimizing energy consumption.

[0169] The heat treatment may be carried out for 1 to 12 hours or 2 to 8 hours, and is preferably carried out for 2 to 8 hours. When the above time is met, the catalyst precursor is γ-Al ２ O ３ A supported catalyst can be manufactured that exists in a state where it is uniformly coated on the surface and pores.

[0170] Step (4) Next, CNTs are produced in the presence of a supported catalyst.

[0171] In detail, carbon nanotubes (CNTs) can be produced by contacting a supported catalyst with a carbon-based compound. Specifically, this may be done by chemical vapor phase synthesis.

[0172] To describe in detail the steps for producing CNTs, first, a supported catalyst can be introduced into a horizontal fixed-bed reactor or a fluidized-bed reactor. Next, a gaseous carbon-based compound, or a mixed gas of a gaseous carbon-based compound, a reducing gas (e.g., hydrogen), and a carrier gas (e.g., nitrogen), is injected at a temperature above the thermal decomposition temperature of the gaseous carbon-based compound or below the melting point of the catalyst supported on the catalyst, and CNTs can be grown by chemical vapor-phase synthesis through the decomposition of the gaseous carbon-based compound.

[0173] CNTs produced by the chemical vapor phase synthesis method described above have crystal growth directions that are nearly parallel to the tube axis, and the graphite structure exhibits high crystallinity along the length of the tube. As a result, CNTs with small unit diameters and high conductivity and strength can be produced.

[0174] The chemical vapor phase synthesis method may be carried out at 600°C to 800°C or 650°C to 750°C, and is preferably carried out at 650°C to 750°C. By satisfying the above temperature range, CNTs can be produced while minimizing the generation of amorphous carbon.

[0175] Possible heat sources for the reaction include induction heating, radiant heat, lasers, IR, microwaves, plasma, and surface plasmon heating.

[0176] Furthermore, carbon-based compounds can be used without particular restrictions, as long as they can supply carbon and exist in a gaseous state at temperatures above 300°C.

[0177] The carbon-based compound may be a carbon-based compound having six or fewer carbon atoms, and may be one or more selected from the group consisting of carbon monoxide, methane, ethane, ethylene, ethanol, acetylene, propane, propylene, butane, butadiene, pentane, pentene, cyclopentadiene, hexane, cyclohexane, benzene, and toluene.

[0178] After growing CNTs by the reaction described above, a cooling step may be selectively performed to further align the CNTs in a more regular manner. Specifically, the cooling step can be carried out by natural cooling by removing the heat source or by using a cooler or the like.

[0179] The above-described manufacturing methods X and Y are examples, and the manufacturing methods for CNTs that may be included in a CNT aggregate are not limited to those described above.

[0180] [Carbon Nanotube Dispersion] The carbon nanotube dispersion (CNT dispersion) according to this disclosure comprises a CNT aggregate and a dispersion medium. The CNT dispersion exhibits good dispersibility of the CNT aggregate in the dispersion medium and has excellent conductivity. The CNT dispersion is preferably used for electrode formation, transparent conductive film formation, resin additives, conductive inks, coatings, antistatic agents, paints, and the like.

[0181] <CNT aggregates> The CNT aggregates contained in the CNT dispersion are the same as the CNT aggregates related to this disclosure described above, so their explanation is omitted here.

[0182] <Dispersion Medium> The dispersion medium preferably contains water, and more preferably contains water as its main component. "Containing water as its main component" means that the proportion of water in the dispersion medium is more than 50% by mass. The proportion of water in the dispersion medium is preferably 90% by mass or more, more preferably 95% by mass or more, even more preferably 99% by mass or more, and may be, for example, 100% by mass.

[0183] The water is not particularly limited, but it is preferable to use distilled water, deionized water, or pure water, for example, because it contains fewer impurities.

[0184] 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.

[0185] The CNT dispersion may further contain other components that can be used in the dispersion, in addition to the CNT aggregate and dispersion medium. Examples of other components include dispersants, defoamers, antistatic agents, and conductive additives other than the conductive additives described herein. It may also further contain trace amounts of impurities, so-called unavoidable impurities.

[0186] <Dispersant> The CNT dispersion may contain a dispersant for the purpose of further improving the dispersibility and dispersion stability of the CNT aggregate. The dispersant is not particularly limited and, for example, various surfactants can be used. Polymer compounds such as resins can also be used as dispersants. A surfactant is preferred as the dispersant. The surfactant may be an ionic surfactant or a nonionic surfactant and is not particularly limited. In the CNT dispersion, the surfactant can be used alone or in a mixture of two or more types.

[0187] Examples of ionic surfactants include anionic surfactants, cationic surfactants, and amphoteric surfactants. Examples of anionic surfactants include aromatic sulfonic acid-based surfactants such as alkylbenzene sulfonates (e.g., dodecylbenzenesulfonic acid) and dodecylphenyl ether sulfonates; ether sulfate-based surfactants; phosphate-based surfactants; and carboxylic acid-based surfactants. Examples of cationic surfactants include alkylamine salts and quaternary ammonium salts. Examples of amphoteric surfactants include alkylbetaine-based surfactants and amine oxide-based surfactants. As for ionic surfactants, ionic surfactants having an aromatic ring (so-called aromatic ionic surfactants) are preferred, and aromatic sulfonic acid-based surfactants such as alkylbenzene sulfonates and dodecylphenyl ether sulfonates are more preferred. Aromatic ionic surfactants tend to have excellent dispersibility, dispersion stability, and high concentration properties for CNT aggregates.

[0188] As nonionic surfactants, examples include sugar ester-based surfactants such as sorbitan fatty acid esters and polyoxyethylene sorbitan fatty acid esters; fatty acid ester-based surfactants such as polyoxyethylene resin acid esters and polyoxyethylene fatty acid diethyl; ether-based surfactants such as polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenyl ethers, and polyoxyethylene-polypropylene glycol; and aromatic nonionic surfactants such as polyoxyalkylene octyl phenyl ethers, polyoxyalkylene nonyl phenyl ethers, polyoxyalkyl dibutyl phenyl ethers, polyoxyalkyl styryl phenyl ethers, polyoxyalkyl benzyl phenyl ethers, polyoxyalkyl bisphenyl ethers, polyoxyalkyl cumyl phenyl ethers, and polyoxyalkylene phenyl ethers. As the nonionic surfactant, an ionic surfactant having an aromatic ring (so-called aromatic nonionic surfactant) is preferable, polyoxyalkylene phenyl ether is more preferable, and polyoxyethylene phenyl ether is even more preferable. Aromatic nonionic surfactants tend to be excellent in the dispersibility, dispersion stability and high concentration achievement of CNT aggregates.

[0189] As other dispersants excellent in the dispersibility, dispersion stability and high concentration achievement of CNTs, there may be mentioned Demol N, which is a sodium salt of β-naphthalenesulfonic acid-formalin condensate (registered trademark: the same applies hereinafter), Demol RN, Demol T (manufactured by Kao Corporation), Brij S 100 of polyoxyethylene stearyl ether (manufactured by Sigma-Aldrich), polyvinylpyrrolidone K30 (for example, manufactured by Fujifilm Wako Pure Chemical Corporation), carboxymethyl cellulose (CMC) (for example, manufactured by Daicel Miraizu Ltd.), sodium deoxycholate (for example, manufactured by Fujifilm Wako Pure Chemical Corporation), SOLSPERSE ＴＭ W100, SOLSPERSE ＴＭ W150 (manufactured by Nippon Lubrizol Co., Ltd.) and the like. From the viewpoint of being excellent in the dispersibility, dispersion stability and high concentration achievement of CNT aggregates, CMC is particularly preferable.

[0190] When the CNT dispersion contains a dispersant, the amount of dispersant used is not particularly limited and can be set appropriately depending on the type of dispersant, the amount of CNT aggregate, the amount of dispersion medium, etc.

[0191] [Method for Manufacturing CNT Dispersion] The method for manufacturing a CNT dispersion is not particularly limited. A CNT dispersion can be manufactured by dispersing CNT aggregates in a dispersion medium. That is, a CNT dispersion can be manufactured by a method that includes a step of dispersing CNT aggregates in a dispersion medium (also called the "dispersion step"). The dispersion mediums that can be used in the dispersion step are as described above.

[0192] The dispersion method is not particularly limited. Examples of dispersion methods include using dispersion devices such as a stirrer, homogenizer, colloid mill, flow jet mixer, dissolver, paint conditioner, Manton emulsifier, jet mill, and ultrasonic device. Other examples of dispersion methods include using known grinding means, such as ball milling (e.g., ball mill, vibrating ball mill, planetary ball mill, bead mill, etc.), sand milling, colloid milling, jet milling, roller milling, vertical or horizontal agitator mill, attritor, colloid mill, three-roll mill, pearl mill, super mill, impeller, disperser, KD mill, dynatron, and pressurized kneader. The method using a jet mill is preferred, and the method using a wet jet mill is more preferred. A wet jet mill is a dispersion device that pumps a mixture in a solvent as a high-speed flow from a nozzle placed in a sealed state inside a pressure vessel. In a wet jet mill, CNT aggregates are dispersed within a pressure vessel by collisions between opposing flows, collisions with the vessel wall, turbulence and shear flow generated by high-speed flow, etc. A suitable wet jet mill is an ultra-high pressure homogenizer manufactured by Jōkō Co., Ltd. (model numbers: NAGS20, NAGS100, JAGS200, NAGS1000, etc.). However, the wet jet mill is not limited to these. When using the above-mentioned ultra-high pressure homogenizer as the dispersion device, the dispersion processing pressure is preferably 10 MPa to 250 MPa.

[0193] The method for producing a CNT dispersion may include a step of drying the CNT aggregate (also called a "drying step") before the dispersion step described above.

[0194] If moisture adheres to the CNTs, the surface tension of the water can cause the CNTs to stick together, raising concerns about reduced dispersibility. Therefore, by performing a drying step of the conductive additive before the dispersion step, moisture adhering to the CNTs is removed, preventing the CNTs from sticking together due to moisture, and further improving the dispersibility of the CNTs in the dispersion medium. The drying method is not particularly limited. Examples of drying methods include heating drying, vacuum drying, and heating vacuum drying. Heating vacuum drying is preferred as the drying method. The drying temperature is not particularly limited, but is preferably, for example, 40°C to 100°C. The drying time is not particularly limited and can be set appropriately depending on the drying temperature, the degree of moisture adhering to the CNT aggregate in this disclosure, etc.

[0195] The following are examples of CNT dispersion manufacturing methods, but the manufacturing of CNT dispersions is not limited to those shown below.

[0196] <Manufacturing Example 1: Example of Dispersion Production> 0.040 g of the CNT aggregate according to this disclosure is weighed and placed in a three-necked flask. After adding the CNT aggregate, a large excess of deionized water, which is the dispersion medium, is poured into the flask (for example, 20 mL), and the mixture is stirred at room temperature (25°C, the same applies hereafter). At this time, a known dispersant (for example, carboxymethylcellulose) may be added as appropriate. Next, the conductive additive is dispersed in the dispersion medium using a known dispersion device (for example, an ultrasonic irradiation device or a wet jet mill). The obtained dispersion is further stirred with a stirrer at room temperature for a long time (for example, 1 hour to 48 hours). In this way, a CNT dispersion is obtained.

[0197] [Conductive Material] The conductive material according to this disclosure includes the CNT aggregate according to this disclosure. As described above, the CNT aggregate contained in the conductive material according to this disclosure has excellent conductivity when dispersed, and is therefore suitable as a conductive additive. Because the conductive material according to this disclosure includes the CNT aggregate according to this disclosure, it has excellent conductivity efficiency and can effectively impart high conductivity to the object to be used.

[0198] The conductive material relating to this disclosure may contain known conductive additives such as graphite and Ketjenblack. Furthermore, the conductive material relating to this disclosure may contain CNTs other than the CNT aggregate relating to this disclosure.

[0199] The conductive material relating to this disclosure can be used as one of the electrode materials. An example of an electrode formed using the electrode material is an electrode provided in a secondary battery. An embodiment of an electrode and a secondary battery equipped with the electrode will be described below.

[0200] <Electrode> The electrode according to this disclosure includes an electrode active material and a conductive material according to this disclosure. Because the electrode according to this disclosure includes a conductive material according to this disclosure, it has excellent conductivity for forming conductive paths within the electrode. Therefore, the secondary battery according to this disclosure has excellent cycle characteristics.

[0201] In electrodes, CNT aggregates can function as conductive additives. The CNT aggregates included in the electrodes described below are synonymous with the CNT aggregates in this disclosure, and the preferred embodiments are also the same; therefore, a description of the CNT aggregates will be omitted below.

[0202] The electrode may consist of at least one of a positive electrode and a negative electrode. The electrode may include an electrode active material layer, or it may include a current collector and an electrode active material layer disposed on the current collector.

[0203] The current collector is not particularly limited as long as it does not induce chemical changes in the battery and is conductive. Examples of current collectors include copper, stainless steel, aluminum, nickel, titanium, calcined carbon, and aluminum or stainless steel surfaces that have been surface-treated with carbon, nickel, titanium, silver, etc. Specifically, transition metals with good carbon adsorption properties, such as copper and nickel, may be used as current collectors.

[0204] The electrode active material layer may contain electrode active material. Preferably, the electrode active material is electrode active material particles. When the electrode is a positive electrode, the electrode active material is not particularly limited, and the electrode active material layer may contain positive electrode active material commonly used for positive electrode materials. Specifically, as the positive electrode active material, lithium cobalt oxide (LiCoO) ２ ), lithium nickel oxide (LiNiO ２ ) Layered compounds such as, compounds substituted with one or more transition metals; LiFe ３ O ４ Lithium iron oxides such as Li １＋ｃ１ Mn ２－ｃ１ O ４ (0≦c1≦0.33), LiMnO ３ LiMn ２ O ３ LiMnO ２ Lithium manganese oxides such as lithium copper oxide (Li ２ CuO ２ ); LiV ３ O ８ , V ２ O ５ ,Cd ２ V ２ O ７ Vanadium oxides such as LiNi; chemical formula LiNi １－ｃ２ M ｃ２ O ２ Ni-site type lithium nickel oxide represented by the chemical formula LiMn (where M is at least one selected from the group consisting of Co, Mn, Al, Cu, Fe, Mg, B, and Ga, and satisfies 0.01 ≤ c² ≤ 0.66). ２－ｃ３ M ｃ３ O ２ (Here, M is at least one selected from the group consisting of Co, Ni, Fe, Cr, Zn, and Ta, satisfying 0.01 ≤ c3 ≤ 0.1.), or Li ２ Mn ３ MO ８ Lithium manganese composite oxide represented by (where M is at least one selected from the group consisting of Fe, Co, Ni, Cu, and Zn); LiMn in which part of the Li in the chemical formula is substituted with an alkaline earth metal ion. ２ O ４These are some examples.

[0205] When the electrode is a negative electrode, the electrode active material is not particularly limited, and the electrode active material layer may include negative electrode active materials commonly used for negative electrode materials. Specifically, the negative electrode active material may include graphite-based active material particles or silicon-based active material particles. As graphite-based active material particles, at least one selected from the group consisting of artificial graphite, natural graphite, graphitized carbon fiber, and graphitized mesocarbon microbeads may be used. By using artificial graphite as graphite-based active material particles, rate characteristics can be improved. As silicon-based active material particles, at least one selected from the group consisting of Si, SiOx (0 < x < 2), Si-C composite, and Si-Y alloy (where Y is an element selected from the group consisting of alkali metals, alkaline earth metals, transition metals, group 13 elements, group 14 elements, rare earth elements, and combinations thereof) may be used. By using silicon-based active material particles, the battery capacity can be increased.

[0206] The electrode active material layer may further contain a binder. The binder is not particularly limited, and the electrode active material layer may include binders commonly used in electrode materials. Examples of binders include at least one polymer selected from the group consisting of polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene propylene diene monomer (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, and polyacrylic acid, as well as polymers in which the hydrogen atoms of these polymers are substituted with Li, Na, Ca, etc.

[0207] <Secondary Battery> The secondary battery according to this disclosure comprises electrodes according to this disclosure. The secondary battery may include a negative electrode, a positive electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte. At least one of the positive electrode and the negative electrode is an electrode according to this disclosure.

[0208] A separator separates the negative electrode from the positive electrode and provides a passage for lithium ions to move. It is generally not limited to any separator commonly used in secondary batteries. Preferably, the separator has low resistance to ion movement in the electrolyte and excellent electrolyte moisture absorption capacity. Specifically, a porous polymer film can be used as a separator. The porous polymer film may be, for example, a porous polymer film made from polyolefin polymers such as ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, or ethylene / methacrylate copolymer, or a laminated structure in which two or more of these films are laminated. Alternatively, the separator may be a conventional porous nonwoven fabric, such as a nonwoven fabric made of high-melting-point glass fibers or polyethylene terephthalate fibers. Furthermore, the separator may be coated with a ceramic component or polymer substance to ensure heat resistance or mechanical strength. The separator can selectively have a single-layer or multi-layer structure.

[0209] The electrolyte is not particularly limited and can include, for example, organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, and molten inorganic electrolytes that can be used in the manufacture of lithium secondary batteries.

[0210] Specifically, the electrolyte may include non-aqueous organic solvents and metal salts. Examples of non-aqueous organic solvents include N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, γ-butyrolactone, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, triester phosphate, trimethoxymethane, dioxolane derivatives, sulfolane, methylsulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ethers, methyl propionate, and ethyl propionate, which are aprotic organic solvents.

[0211] Among carbonate-based organic solvents, cyclic carbonates such as ethylene carbonate and propylene carbonate are preferred as non-aqueous organic solvents because they have high dielectric constants as high-viscosity organic solvents and readily dissociate lithium salts. It is even more preferable to use a mixture of such cyclic carbonates with low-viscosity, low-dielectric-constant linear carbonates such as dimethyl carbonate and diethyl carbonate in appropriate proportions as a non-aqueous organic solvent, as this yields an electrolyte with high electrical conductivity.

[0212] The metal salt may also be a lithium salt. Lithium salts are readily soluble in non-aqueous electrolytes. For example, the anion portion of the lithium salt may be F － , Cl － , I － NO ３ － , N (CN) ２ － BF ４ － , ClO ４ － , PF ６ － (CF ３ ) ２ PF ４ － (CF３ ) ３ PF ３ － , (CF ３ ) ４ PF ２ － , (CF ３ ) ５ PF － , (CF ３ ) ６ P － , CF ３ SO ３ － , CF ３ CF ２ SO ３ － , (CF ３ SO ２ ) ２ N － , (FSO ２ ) ２ N － , CF ３ CF ２ (CF ３ ) ２ CO － , (CF ３ SO ２ ) ２ CH － , (SF ５ ) ３ C － , (CF ３ SO ２ ) ３ C － , CF ３ (CF ２ ) ７ SO ３ － , CF ３ CO ２ － , CH ３ CO ２ － , SCN － and (CF ３ CF ２ SO ２ ) ２ N － may be mentioned.

[0213] In addition to non-aqueous organic solvents and metal salts, the electrolyte may further contain one or more additives for the purpose of improving battery life characteristics, suppressing the decrease in battery capacity, and improving battery discharge capacity, such as haloalkylene carbonate compounds like difluoroethylene carbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ethers, ethylenediamine, n-glycemic (glyme), hexalic acid triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salts, pyrrole, 2-methoxyethanol, and aluminum trichloride.

[0214] The secondary battery described above can constitute a battery module containing the secondary battery as a unit cell, and a battery pack containing the battery module. The battery module and battery pack can be used as a power source for medium to large devices selected from the group consisting of electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, and power storage systems.

[0215] <Planar Assembly> The planar assembly relating to this disclosure includes the CNT assembly relating to this disclosure. The proportion of the CNT assembly relating to this disclosure contained in the planar assembly relating to this disclosure is usually 1% by mass or more with respect to the total mass of the planar assembly. The planar assembly relating to this disclosure may contain components other than the CNT assembly relating to this disclosure.

[0216] Examples of planar aggregates relating to this disclosure include films containing the CNT aggregate relating to this disclosure.

[0217] The planar assemblies relating to this disclosure are useful, for example, in filters, electromagnetic shields, and pellicles for extreme ultraviolet (EUV) radiation.

[0218] The method for producing the planar aggregate according to this disclosure is not particularly limited. The planar aggregate according to this disclosure can be produced, for example, as a nonwoven fabric-like planar aggregate by dispersing the CNT aggregate according to this disclosure in water or other fluid and filtering it once or twice or more.

[0219] The planar assemblies relating to this disclosure are useful, for example, in filters, electromagnetic shields, and pellicles for extreme ultraviolet (EUV) applications.

[0220] <Laminate> The laminate according to this disclosure comprises a substrate and a planar assembly according to this disclosure. The substrate and the planar assembly may be in direct contact, or other layers may be arranged between the substrate and the planar assembly. Alternatively, the planar assembly according to this disclosure may be arranged on the substrate, and yet another layer may be arranged on the planar assembly.

[0221] The material constituting the substrate may be resin, glass, or fiber. Examples of resins include polyethylene terephthalate (PET), polycarbonate (PC), polymethyl methacrylate (PMMA), cyclic olefin polymer (COP), triacetate (TAC), cyclic olefin copolymer (COC), poly(vinyl chloride) (PVC), polyethylene 2,6-naphthalate (PEN), polyimide (PI), polypropylene (PP), polyethylene (PE), polystyrene (PS), polyamide (PA), polyacetal (POM), polyurethane (PU), acrylonitrile butadiene styrene (ABS), polyphenylene ether (PPE), polysulfone (PSU), polyether ether ketone (PEEK), and polyamide-imide (PAI). Examples of glass include float glass (SiO2). ２ Na ２ Examples include sodium chloride (containing O, CaO, and MgO), soda lime, aluminosilicate glass, and borosilicate glass. Examples of fibers include synthetic fibers such as polyester fibers, polyamide fibers, polyolefin fibers, and acrylic fibers; and natural fibers such as cotton, linen, silk, wool, cashmere, mohair, alpaca, jute, hemp, and ramie.

[0222] The planar aggregate preferably contains a binder in addition to the CNT aggregate according to this disclosure. The binder is preferably a polymer and preferably contains at least one selected from the group consisting of polymers containing constituent units derived from vinylidene chloride (e.g., polyvinylidene chloride, vinylidene chloride-vinyl chloride copolymer, vinylidene chloride-vinyl acetate copolymer, etc.), polyimide, polysiloxane, and epoxy resin.

[0223] The following examples will provide a more detailed explanation of the CNT aggregates, etc., related to this disclosure. This disclosure is not limited to the following examples, unless it exceeds the spirit of the disclosure.

[0224] (Example 1) 1. Production of Sheet-like CNT Assembly 1 Sheet-like CNT assembly 1 was produced by a floating catalyst method (CVD method) in which the self-assembly of CNT bundles directly interacts with the catalyst in the gas phase. A cylindrical reactor with an inner diameter of 85 mm was used as the CNT reactor. First, ferrocene, as a metal catalyst precursor containing Fe atoms, and thiophene, as an accelerator, were introduced into a continuous flow of carrier gas in a once-through reactor whose temperature was controlled to 120°C. Hydrogen gas was used as the carrier gas. By maintaining the temperature in the once-through reactor within the above range, the metal catalyst precursor decomposes. The region in which the metal catalyst precursor decomposes is referred to as the first temperature zone.

[0225] Next, methane, the carbon source, was released into the carrier gas stream. The metal catalyst and carbon source were supplied to a second temperature zone, located downstream of the first temperature zone and controlled to 1320°C. The total gas supply flow rate for the carrier gas and source gas was set to 17 NL / min (NL is normal liters). The second temperature zone was maintained at a temperature sufficient to generate carbon nanotube aggregates.

[0226] In the second temperature zone, a reaction field was created within the temperature-controlled flow reactor, forming catalytic nuclei and rapidly growing CNTs, thereby generating CNT aggregates. The aggregates were discharged as continuous discharge through the outlet of the flow-type reactor, which was temperature-controlled to 500°C, and sheet-like CNT aggregates were collected.

[0227] The obtained sheet-like CNT aggregates were immersed in a pH 10 diluted aqueous ammonia solution for 10 minutes, washed with pure water for 10 minutes, dried, crushed into a powder, and then passed through a 1.0 mm mesh sieve twice. The CNT aggregates that passed through the sieve were collected and designated as CNT aggregate 1.

[0228] 2. Preparation of CNT dispersion 1 The following materials were mixed and pre-dispersed by treating them with an Ace homogenizer manufactured by Nippon Seiki Co., Ltd. for 1 hour to obtain pre-dispersion 1.

[0229] (Dispersion composition) - CNT aggregate 1 obtained above... 1.1 g - CARBOXYMETHYL CELLULOSE SODIUM SALT HIGH VISCOSITY (manufactured by MP Biomedicals)... 1.65 g - Purified water... 547.25 g

[0230] The main dispersion of pre-dispersion 1 was carried out using a high-pressure homogenizer (model number: NAGS100) manufactured by Jōkō Co., Ltd. as a wet jet mill under the following conditions to obtain CNT dispersion 1 with a concentration of 0.20% by mass. (Dispersion conditions) Nozzle diameter: 0.22 mm Pressure: 200 MPa Number of cycles: 8 Method: Circulation method

[0231] 3. Evaluation <Content of Si, Mn, Ni, Cr, Mo, and Co relative to the total mass of the CNT aggregate> The content of Si atoms relative to the total mass of CNT aggregate 1 was measured using an inductively coupled plasma mass spectrometer (ICP-AES) (NexION 2000C, Perkin Elmer). The CNT aggregate 1 obtained above was pretreated by ashing / alkaline fusion / acid dissolution and measured using the above instrument. The content of Mn, Ni, Cr, Mo, and Co relative to the total mass of CNT aggregate 1 was measured using an inductively coupled plasma mass spectrometer (ICP-MS) (NexION 2000C, Perkin Elmer). The CNT aggregate 1 obtained above was pretreated by low-temperature ashing / acid dissolution and measured using the above instrument.

[0232] The Si content was 700 ppm by mass, the Mn content was 0 ppm by mass, the Ni content was 20 ppm by mass, the Cr content was 0 ppm by mass, the Mo content was 0 ppm by mass, and the Co content was 0 ppm by mass. The total content of the first metal (at least one selected from the group consisting of Si, Mn, Ni, Cr, Mo, and Co) was 720 ppm by mass.

[0233] <Content of Na, K, Ca, and Al relative to the total mass of the CNT aggregate> The content of Na, K, Ca, and Al relative to the total mass of CNT aggregate 1 was measured using an inductively coupled plasma mass spectrometer (ICP-MS) (NexION 2000C, PerkinElmer). The sheet-like CNT aggregate 1 obtained above was pretreated by low-temperature ashing / acid dissolution and then measured using the above apparatus.

[0234] The Na content was 40 ppm by mass, the K content was 300 ppm by mass, the Ca content was 30 ppm by mass, and the Al content was 100 ppm by mass. The total content of the secondary metal (at least one selected from the group consisting of Na, K, Ca, and Al) was 470 ppm by mass.

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

[0236] Using the calculated bundle diameter histogram, the bundle diameter features of each sample were calculated using the following method: 1. The bundle diameters and occupied areas of multiple fields of view of the same sample were added together and normalized so that the sum equaled 1. Following normalization, the unit of the vertical axis was set to occupied area ratio. 2. The total occupied area ratio of bundles with a bundle diameter of 100 nm or more was calculated. As a result, the area ratio of bundles with a bundle diameter of 100 nm or more was 0.43. The cumulative 90% bundle diameter was 190 nm.

[0237] <Viscosity of CNT dispersion> The viscosity of CNT dispersion 1 was measured using a cone-plate viscometer (also known as an E-type viscometer). Specifically, a cone-plate viscometer (BROOKFIELD DV-II+Pro PROGRAMMABLE VISCOMETER) was used to measure the viscosity. Measurement fixture: Cone-plate Measurement mode: Rotation mode Shear rate: 0.6 s －１ ~384 simultaneous －１ Temperature: 25°C. From the obtained data, the shear rate was 12 s. －１ The viscosity was measured. The viscosity of the dispersion was 33.2 mPa·s. It was determined that a CNT dispersion with appropriate viscosity was obtained if the viscosity of the dispersion was within the range of 10 mPa·s to 1500 mPa·s.

[0238] <Tensile Strength, Elongation at Break, Energy Density at Break> A CNT dispersion 1 was prepared by mixing CNT aggregate 1, 700 kDa of carboxymethylcellulose sodium, and water, with a concentration of CNT aggregate 1 at 0.20 mass% and a concentration of carboxymethylcellulose sodium at 0.30 mass%. The obtained CNT dispersion 1 (15 mL) was poured onto a slide glass type silicon plate with inner dimensions of 22 mm × 75 mm × 3 mm, and heated at 100°C for 30 minutes to dry and obtain a measurement sample. The measurement sample was fixed to the gripping part of a tensile testing apparatus (Shimadzu Corporation, Autograph AG-IS), and a tensile test was performed at a speed of 1 mm / min. The maximum test force was calculated as the tensile strength. The point at which the test force was maximum was considered the breaking point, and the elongation at break was calculated. Furthermore, the energy density at break was calculated from the product of the elongation at break and the tensile strength. As a result, the tensile strength was 4.6 MPa, the elongation at break was 2.0%, and the energy density at break was 9.2 MPa·%.

[0239] <Surface Resistivity> A sample was prepared by pouring 15 mL of CNT dispersion 1 onto a slide glass type silicon plate (manufactured by Dosaka E-M Co., Ltd., #08-1044) with inner dimensions of 22 mm × 75 mm × 3 mm, and heating and drying it at 100°C. The surface resistivity of the film was measured using a Loresta GXII manufactured by Nitto Seikou Analytech Co., Ltd. Measurements were taken at five locations on the film, and the average of the five measured values ​​was taken as the surface resistivity. The measured surface resistivity was 6.09 Ω / □.

[0240] (Example 2) 1. Manufacturing of CNT Assembly 2 CNT assembly 2 was manufactured by mixing CNT assembly 2A and CNT assembly 2B described below. CNT assembly 2A was manufactured in the same manner as CNT assembly 1, except that the total gas supply flow rate of the carrier gas and raw material gas was set to 35 NL / min, the second temperature zone was controlled to 1400°C, and the aggregates were continuously discharged through the outlet of a flow-through reactor controlled to 150°C. CNT assembly 2B was manufactured in the same manner as CNT assembly 1, except that the total gas supply flow rate of the carrier gas and raw material gas was set to 36 NL / min, the second temperature zone was controlled to 1400°C, and the aggregates were continuously discharged through the outlet of a flow-through reactor controlled to 150°C.

[0241] 2. Preparation of CNT dispersion 2 Using the obtained CNT aggregate 2, a pre-dispersion 2 was obtained in the same manner as in Example 1.

[0242] The pre-dispersion 2 was subjected to the final dispersion using a high-pressure homogenizer (model number: NAGS100) manufactured by Jōkō Co., Ltd. as a wet jet mill under the following conditions to obtain CNT dispersion 2. (Dispersion conditions) Nozzle diameter: 0.22 mm Pressure: 50 MPa Number of passes: 3 Method: Circulation method

[0243] 3. Evaluation <Contents of Si, Mn, Ni, Cr, Mo, and Co relative to the total mass of the CNT aggregate> Measurements were taken in the same manner as in Example 1, except that CNT aggregate 2 was used. The Si content was 300 ppm by mass, the Mn content was 0 ppm by mass, the Ni content was 10 ppm by mass, the Cr content was 0 ppm by mass, the Mo content was 0 ppm by mass, and the Co content was 0 ppm by mass. The total content of the first metal was 310 ppm by mass.

[0244] <Contents of Na, K, Ca, and Al relative to the total mass of the CNT aggregate> The measurements were taken in the same manner as in Example 1, except that CNT aggregate 2 was used. The Na content was 20 ppm by mass, the K content was 0 ppm by mass, the Ca content was 40 ppm by mass, and the Al content was 100 ppm by mass. The total content of the second metal was 160 ppm by mass.

[0245] <Bundle Diameter Features> For the CNT aggregate 2 of Example 2, imaging was performed using a scanning electron microscope (SEM), and four images in which CNT bundles were clearly observed were selected from the obtained images (one of which is shown in Figure 2). Image processing and image analysis were performed on the selected images using Python. In image processing, the contours and midlines of the CNTs were detected and combined with the original image. In image analysis, the bundle diameter was determined by calculating the distance from the midline to the contour of the created image. Then, the product of the bundle diameter and the length of the midline was calculated to determine the area occupied by the CNTs in the image. A histogram of bundle diameter and occupied area was then created.

[0246] Using the calculated bundle diameter histogram, the bundle diameter features of each sample were calculated using the following method: 1. The bundle diameters and occupied areas of multiple fields of view of the same sample were added together and normalized so that the sum equaled 1. Following normalization, the unit of the vertical axis was set to occupied area ratio. 2. The total occupied area ratio of bundles with a bundle diameter of 100 nm or more was calculated. As a result, the area ratio of bundles with a bundle diameter of 100 nm or more was 0.26. The cumulative 90% bundle diameter was 150 nm.

[0247] <Viscosity of CNT dispersion> The viscosity of CNT dispersion 2 was measured using a cone-plate viscometer (also known as an E-type viscometer). Specifically, a cone-plate viscometer (BROOKFIELD DV-II + Pro PROGRAMMABLE VISCOMETER) was used to measure the viscosity. Measurement fixture: Cone-plate Measurement mode: Rotation mode Shear rate: 0.6 s －１ ~384 simultaneous －１ Temperature: 25°C. From the obtained data, the shear rate was 12 s. －１ The viscosity was read. The viscosity of the dispersion was 798.2 mPa·s. It was determined that a CNT dispersion with appropriate viscosity was obtained if the viscosity of the dispersion was within the range of 10 mPa·s to 1500 mPa·s.

[0248] <Tensile Strength, Elongation at Break, and Energy Density at Break> These were calculated in the same manner as in Example 1, except that CNT dispersion 2 was used. As a result, the tensile strength was 15.5 MPa, the elongation at break was 2.6%, and the energy density at break was 40.3 MPa·%.

[0249] <Surface Resistivity> The surface resistivity was measured in the same manner as in Example 1, except that CNT dispersion 2 was used. The measured surface resistivity was 0.90 Ω / □.

[0250] (Example 3) 1. Manufacturing of CNT aggregate 3 CNT aggregate 3 was manufactured in the same manner as CNT aggregate 1, except that the total gas supply flow rate of the carrier gas and raw material gas was set to 42 NL / min, and the temperature of the second temperature zone was controlled to 1400°C. 2. Preparation of CNT dispersion 3 Using the obtained CNT aggregate 3, a pre-dispersion 3 was obtained in the same manner as in Example 1.

[0251] The pre-dispersion 3 was subjected to the final dispersion using a high-pressure homogenizer (model number: NAGS100) manufactured by Jōkō Co., Ltd. as a wet jet mill under the following conditions to obtain the CNT dispersion 3. (Dispersion conditions) Nozzle diameter: 0.22 mm Pressure: 150 MPa Number of passes: 8 Method: Circulation method

[0252] 3. Evaluation <Contents of Si, Mn, Ni, Cr, Mo, and Co relative to the total mass of the CNT aggregate> The measurements were performed in the same manner as in Example 1, except that CNT aggregate 3 was used. The Si content was 1000 ppm by mass, the Mn content was 0 ppm by mass, the Ni content was 0 ppm by mass, the Cr content was 0 ppm by mass, the Mo content was 0 ppm by mass, and the Co content was 0 ppm by mass. The total content of the first metal was 1000 ppm by mass.

[0253] <Contents of Na, K, Ca, and Al relative to the total mass of the CNT aggregate> The measurements were taken in the same manner as in Example 1, except that CNT aggregate 3 was used. The Na content was 100 ppm by mass, the K content was 600 ppm by mass, the Ca content was 60 ppm by mass, and the Al content was 80 ppm by mass. The total content of the second metal was 840 ppm by mass.

[0254] <Bundle Diameter Features> For the CNT aggregate 3 of Example 3, imaging was performed using a scanning electron microscope (SEM), and six images in which CNT bundles were clearly observed were selected (one of which is shown in Figure 3). Image processing and image analysis were performed on the selected images using Python. In image processing, the contours and midlines of the CNTs were detected and combined with the original image. In image analysis, the bundle diameter was determined by calculating the distance from the midline to the contour of the created image. Then, the product of the bundle diameter and the length of the midline was calculated to determine the area occupied by the CNTs in the image. A histogram of bundle diameter and occupied area was then created.

[0255] Using the calculated bundle diameter histogram, the bundle diameter features of each sample were calculated using the following method: 1. The bundle diameters and occupied areas of multiple fields of view of the same sample were added together and normalized so that the sum equaled 1. Following normalization, the unit of the vertical axis was set to occupied area ratio. 2. The total occupied area ratio of bundles with a bundle diameter of 100 nm or more was calculated. As a result, the area ratio of bundles with a bundle diameter of 100 nm or more was 0.41. The cumulative 90% bundle diameter was 200 nm.

[0256] <Viscosity of CNT dispersion> The viscosity of CNT dispersion 3 was measured using a cone-plate viscometer (also known as an E-type viscometer). Specifically, a cone-plate viscometer (BROOKFIELD DV-II + Pro PROGRAMMABLE VISCOMETER) was used to measure the viscosity. Measurement fixture: Cone-plate Measurement mode: Rotation mode Shear rate: 0.6 s －１ ~384 simultaneous －１ Temperature: 25°C. From the obtained data, the shear rate was 12 s. －１ The viscosity was measured. The viscosity of the dispersion was 34.6 mPa·s. It was determined that a CNT dispersion with appropriate viscosity was obtained if the viscosity of the dispersion was within the range of 10 mPa·s to 1500 mPa·s.

[0257] <Tensile strength, elongation at break, and energy density at break> These were calculated in the same manner as in Example 1, except that CNT dispersion 3 was used. As a result, the tensile strength was 3.5 MPa, the elongation at break was 4.1%, and the energy density at break was 14.4 MPa·%.

[0258] <Surface Resistivity> The surface resistivity was measured in the same manner as in Example 1, except that CNT dispersion 3 was used. The measured surface resistivity was 4.21 Ω / □.

[0259] (Example 4) 1. Manufacturing of CNT aggregate 4 CNT aggregate 4 was manufactured in the same manner as CNT aggregate 1, except that the total gas supply flow rate of the carrier gas and raw material gas was set to 34 NL / min, and the temperature of the second temperature zone was controlled to 1400°C. 2. Preparation of CNT dispersion 4 Using the obtained CNT aggregate 4, a pre-dispersion 4 was obtained in the same manner as in Example 1.

[0260] The pre-dispersion 4 was subjected to the final dispersion using a high-pressure homogenizer (model number: NAGS100) manufactured by Jōkō Co., Ltd. as a wet jet mill under the following conditions to obtain the CNT dispersion 4. (Dispersion conditions) Nozzle diameter: 0.22 mm Pressure: 85 MPa Number of passes: 8 Method: Circulation method

[0261] 3. Evaluation <Contents of Si, Mn, Ni, Cr, Mo, and Co relative to the total mass of the CNT aggregate> The measurements were performed in the same manner as in Example 1, except that CNT aggregate 4 was used. The Si content was 100 ppm by mass, the Mn content was 0 ppm by mass, the Ni content was 0 ppm by mass, the Cr content was 0 ppm by mass, the Mo content was 0 ppm by mass, and the Co content was 0 ppm by mass. The total content of the first metal was 100 ppm by mass.

[0262] <Contents of Na, K, Ca, and Al relative to the total mass of the CNT aggregate> The measurements were taken in the same manner as in Example 1, except that CNT aggregate 4 was used. The Na content was 200 ppm by mass, the K content was 50 ppm by mass, the Ca content was 0 ppm by mass, and the Al content was 0 ppm by mass. The total content of the second metal was 250 ppm by mass.

[0263] <Bundle Diameter Features> For the CNT aggregate 4 of Example 4, imaging was performed using a scanning electron microscope (SEM), and six images in which CNT bundles were clearly observed were selected (one of which is Figure 4). Image processing and image analysis were performed on the selected images using Python. In image processing, the contours and centerlines of the CNTs were detected and combined with the original image. In image analysis, the bundle diameter was determined by calculating the distance from the centerline to the contour in the created image. Then, the product of the bundle diameter and the length of the centerline was calculated to determine the area occupied by the CNTs in the image. A histogram of bundle diameter and occupied area was then created.

[0264] Using the calculated bundle diameter histogram, the bundle diameter features of each sample were calculated using the following method: 1. The bundle diameters and occupied areas of multiple fields of view of the same sample were added together and normalized so that the sum equaled 1. Following normalization, the unit of the vertical axis was set to occupied area ratio. 2. The total occupied area ratio of bundles with a bundle diameter of 100 nm or more was calculated. As a result, the area ratio of bundles with a bundle diameter of 100 nm or more was 0.23. The cumulative 90% bundle diameter was 130 nm.

[0265] <Viscosity of CNT dispersion> The viscosity of CNT dispersion 4 was measured using a cone-plate viscometer (also known as an E-type viscometer). Specifically, a cone-plate viscometer (BROOKFIELD DV-II + Pro PROGRAMMABLE VISCOMETER) was used to measure the viscosity. Measurement fixture: Cone-plate Measurement mode: Rotation mode Shear rate: 0.6 s －１ ~384 simultaneous －１ Temperature: 25°C. From the obtained data, the shear rate was 12 s. －１ The viscosity was measured. The viscosity of the dispersion was 705.2 mPa·s. It was determined that a CNT dispersion with appropriate viscosity was obtained if the viscosity of the dispersion was within the range of 10 mPa·s to 1500 mPa·s.

[0266] <Tensile Strength, Elongation at Break, and Energy Density at Break> These were calculated in the same manner as in Example 1, except that CNT dispersion 4 was used. As a result, the tensile strength was 11.3 MPa, the elongation at break was 2.4%, and the energy density at break was 27.5 MPa·%.

[0267] <Surface Resistivity> The surface resistivity was measured in the same manner as in Example 1, except that CNT dispersion 4 was used. The measured surface resistivity was 1.24 Ω / □.

[0268] (Example 5) 1. Manufacturing of CNT aggregate 5 CNT aggregate 5 was manufactured in the same manner as CNT aggregate 1, except that the total gas supply flow rate of the carrier gas and raw material gas was set to 34.1 NL / min, and the temperature of the second temperature zone was controlled to 1400°C. 2. Preparation of CNT dispersion 5 Using the obtained CNT aggregate 5, a pre-dispersion 5 was obtained in the same manner as in Example 1.

[0269] The pre-dispersion 5 was subjected to the final dispersion using a high-pressure homogenizer (model number: NAGS100) manufactured by Jōkō Co., Ltd. as a wet jet mill under the following conditions to obtain the CNT dispersion 5. (Dispersion conditions) Nozzle diameter: 0.22 mm Pressure: 85 MPa Number of passes: 8 Method: Circulation method

[0270] 3. Evaluation <Contents of Si, Mn, Ni, Cr, Mo, and Co relative to the total mass of the CNT aggregate> The measurements were performed in the same manner as in Example 1, except that CNT aggregate 5 was used. The Si content was 400 ppm by mass, the Mn content was 0 ppm by mass, the Ni content was 0 ppm by mass, the Cr content was 0 ppm by mass, the Mo content was 0 ppm by mass, and the Co content was 0 ppm by mass. The total content of the first metal was 400 ppm by mass.

[0271] <Contents of Na, K, Ca, and Al relative to the total mass of the CNT aggregate> The measurements were taken in the same manner as in Example 1, except that CNT aggregate 5 was used. The Na content was 10 ppm by mass, the K content was 0 ppm by mass, the Ca content was 50 ppm by mass, and the Al atom content was 60 ppm by mass. The total content of the second metal was 120 ppm by mass.

[0272] <Bundle Diameter Features> For the CNT aggregate 5 of Example 5, imaging was performed using a scanning electron microscope (SEM), and six images in which CNT bundles were clearly observed were selected (one of which is Figure 5). Image processing and image analysis were performed on the selected images using Python. In image processing, the contours and centerlines of the CNTs were detected and combined with the original image. In image analysis, the bundle diameter was determined by calculating the distance from the centerline to the contour of the created image. Then, the product of the bundle diameter and the length of the centerline was calculated to determine the area occupied by the CNTs in the image. A histogram of bundle diameter and occupied area was created.

[0273] Using the calculated bundle diameter histogram, the bundle diameter features of each sample were calculated using the following method: 1. The bundle diameters and occupied areas of multiple fields of view of the same sample were added together and normalized so that the sum equaled 1. Following normalization, the unit of the vertical axis was set to occupied area ratio. 2. The total occupied area ratio of bundles with a bundle diameter of 100 nm or more was calculated. As a result, the area ratio of bundles with a bundle diameter of 100 nm or more was 0.14. The cumulative 90% bundle diameter was 120 nm.

[0274] <Viscosity of CNT dispersion> The viscosity of CNT dispersion 5 was measured using a cone-plate viscometer (also known as an E-type viscometer). Specifically, a cone-plate viscometer (BROOKFIELD DV-II + Pro PROGRAMMABLE VISCOMETER) was used to measure the viscosity. Measurement fixture: Cone-plate Measurement mode: Rotation mode Shear rate: 0.6 s －１ ~384 simultaneous －１ Temperature: 25°C. From the obtained data, the shear rate was 12 s. －１ The viscosity was read. The viscosity of the dispersion was 435.5 mPa·s. It was determined that a CNT dispersion with appropriate viscosity was obtained if the viscosity of the dispersion was in the range of 10 mPa·s to 1500 mPa·s.

[0275] <Tensile Strength, Elongation at Break, and Energy Density at Break> These were calculated in the same manner as in Example 1, except that CNT dispersion 5 was used. As a result, the tensile strength was 32.6 MPa, the elongation at break was 2.3%, and the energy density at break was 75.1 MPa·%.

[0276] <Surface Resistivity> The surface resistivity was measured in the same manner as in Example 1, except that CNT dispersion 5 was used. The measured surface resistivity was 1.07 Ω / □.

[0277] (Comparative Example 1) 1. Preparation of Powdered CNT Assembly 6 As the powdered CNT assembly 6, carbon nanotubes manufactured by C-nano Co., Ltd. (catalog number: FT7000) were prepared.

[0278] 2. Preparation of CNT dispersion 6 A pre-dispersion 6 was obtained using the obtained CNT aggregate 6 in the same manner as in Example 1.

[0279] The pre-dispersion 6 was subjected to the final dispersion using a high-pressure homogenizer (model number: NAGS100) manufactured by Jōkō Co., Ltd. as a wet jet mill under the following conditions to obtain the CNT dispersion 6. (Dispersion conditions) Nozzle diameter: 0.22 mm Pressure: 85 MPa Number of passes: 8 Method: Circulation method

[0280] 3. Evaluation <Contents of Si, Mn, Ni, Cr, Mo, and Co relative to the total mass of the CNT aggregate> The measurements were performed in the same manner as in Example 1, except that CNT aggregate 6 was used. The Si content was 0 ppm by mass, the Mn content was 100 ppm by mass, the Ni content was 20 ppm by mass, the Cr content was 20 ppm by mass, the Mo content was 900 ppm by mass, and the Co content was 0 ppm by mass. The total content of the first metal was 1040 ppm by mass.

[0281] <Contents of Na, K, Ca, and Al relative to the total mass of the CNT aggregate> The measurements were taken in the same manner as in Example 1, except that CNT aggregate 6 was used. The Na content was 200 ppm by mass, the K content was 2000 ppm by mass, the Ca content was 500 ppm by mass, and the Al content was 7000 ppm by mass. The total content of the second metal was 9700 ppm by mass.

[0282] <Bundle Diameter Features> For the CNT aggregate 6 of Comparative Example 1, imaging was performed using a scanning electron microscope (SEM), and two images in which CNT bundles were clearly observed were selected (one of which is Figure 6). Image processing and image analysis were performed on the selected images using Python. In image processing, the contours and midlines of the CNTs were detected and combined with the original image. In image analysis, the bundle diameter was determined by calculating the distance from the midline to the contour of the created image. Then, the product of the bundle diameter and the length of the midline was calculated to determine the area occupied by the CNTs in the image. A histogram of bundle diameter and occupied area was then created.

[0283] Using the calculated bundle diameter histogram, the bundle diameter features of each sample were calculated using the following method: 1. The bundle diameters and occupied areas of multiple fields of view of the same sample were added together and normalized so that the sum was 1. Following normalization, the unit of the vertical axis was set to the occupied area ratio. 2. The total occupied area ratio of bundles with a bundle diameter of 100 nm or more was calculated. The bundle diameter features were calculated using the following method, in the same manner as in Example 1, except for using CNT aggregate 6. As a result, the area ratio of bundles with a bundle diameter of 100 nm or more was 0.10. The cumulative 90% bundle diameter was 90 nm.

[0284] <Viscosity of CNT dispersion> The viscosity of the CNT dispersion 6 was measured using a cone-plate viscometer (also known as an E-type viscometer). Specifically, a cone-plate viscometer (BROOKFIELD DV-II+Pro PROGRAMMABLE VISCOMETER) was used to measure the viscosity. Measurement fixture: Cone-plate Measurement mode: Rotation mode Shear rate: 0.6 s －１ ~384 simultaneous －１ Temperature: 25°C. From the obtained data, the shear rate was 12 s. －１ The viscosity was measured. The viscosity of the dispersion was 6.4 mPa·s. It was determined that a CNT dispersion with appropriate viscosity was obtained if the viscosity of the dispersion was within the range of 10 mPa·s to 1500 mPa·s.

[0285] <Tensile strength, elongation at break, and energy density at break> These were calculated in the same manner as in Example 1, except that CNT dispersion 6 was used. As a result, the tensile strength was 6.9 MPa, the elongation at break was 2.6%, and the energy density at break was 17.9 MPa·%.

[0286] <Surface Resistivity> The surface resistivity was measured in the same manner as in Example 1, except that CNT dispersion 6 was used. The measured surface resistivity was 16.52 Ω / □.

[0287] (Comparative Example 2) 1. Preparation of Powdered CNT Assembly 7 As the powdered CNT assembly 7, carbon nanotubes manufactured by C-nano Co., Ltd. (catalog number: FT9100) were prepared.

[0288] 2. Preparation of CNT dispersion 7 A dispersion 5 was obtained using the obtained CNT aggregate 7 in the same manner as in Comparative Example 1.

[0289] 3. Evaluation <Contents of Si, Mn, Ni, Cr, Mo, and Co relative to the total mass of the CNT aggregate> The measurements were performed in the same manner as in Example 1, except that CNT aggregate 7 was used. The Si content was 0 ppm by mass, the Mn content was 0 ppm by mass, the Ni content was 0 ppm by mass, the Cr content was 0 ppm by mass, the Mo content was 900 ppm by mass, and the Co content was 0 ppm by mass. The total content of the first metal was 900 ppm by mass.

[0290] <Contents of Na, K, Ca, and Al relative to the total mass of the CNT aggregate> The measurements were taken in the same manner as in Example 1, except that CNT aggregate 7 was used. The content of Na was 0 ppm by mass, the content of K was 0 ppm by mass, the content of Ca was 0 ppm by mass, and the content of Al was 5000 ppm by mass. The total content of the second metal was 5000 ppm by mass.

[0291] <Bundle Diameter Features> For the CNT aggregate 7 of Comparative Example 2, imaging was performed using a scanning electron microscope (SEM), and two images in which CNT bundles were clearly observed were selected (one of which is Figure 7). Image processing and image analysis were performed on the selected images using Python. In image processing, the contours and centerlines of the CNTs were detected and combined with the original image. In image analysis, the bundle diameter was determined by calculating the distance from the centerline to the contour in the created image. Then, the product of the bundle diameter and the length of the centerline was calculated to determine the area occupied by the CNTs in the image. A histogram of bundle diameter and occupied area was then created.

[0292] Using the calculated bundle diameter histogram, the bundle diameter features of each sample were calculated using the following method: 1. The bundle diameters and occupied areas of multiple fields of view of the same sample were added together and normalized so that the sum was 1. Following normalization, the unit of the vertical axis was set to the occupied area ratio. 2. The total occupied area ratio of bundles with a bundle diameter of 100 nm or more was calculated. The bundle diameter features were calculated using the following method, in the same manner as in Example 1, except for using CNT aggregate 7. As a result, the area ratio of bundles with a bundle diameter of 100 nm or more was 0.08. The cumulative 90% bundle diameter was 80 nm.

[0293] <Viscosity of CNT dispersion> The viscosity of the CNT dispersion 7 was measured using a cone-plate viscometer (also known as an E-type viscometer). Specifically, a cone-plate viscometer (BROOKFIELD DV-II + Pro PROGRAMMABLE VISCOMETER) was used to measure the viscosity. Measurement fixture: Cone-plate Measurement mode: Rotation mode Shear rate: 0.6 s －１ ~384 simultaneous －１ Temperature: 25°C. From the obtained data, the shear rate was 12 s. －１ The viscosity was measured. The viscosity of the dispersion was 5.7 mPa·s. It was determined that a CNT dispersion with appropriate viscosity was obtained if the viscosity of the dispersion was within the range of 10 mPa·s to 1500 mPa·s.

[0294] <Tensile Strength, Elongation at Break, and Energy Density at Break> These were calculated in the same manner as in Example 1, except that CNT dispersion 7 was used. As a result, the tensile strength was 2.3 MPa, the elongation at break was 1.9%, and the energy density at break was 4.4 MPa·%.

[0295] <Surface Resistivity> The surface resistivity was measured in the same manner as in Example 1, except that CNT dispersion 7 was used. The measured surface resistivity was 15.54 Ω / □.

[0296] Next, we fabricated a lithium-ion secondary battery.

[0297] 1. Fabrication of positive electrode for lithium secondary battery: Positive electrode active material (LiNi ０．８ Co ０．１ Mn ０．１ O ２ A positive electrode mixture was prepared by mixing a conductive material (acetylene black) and a binder (PVdF) in a ratio of positive electrode active material:conductive material:binder = 92:5:3 (mass ratio), and then kneading with N-methyl-2-pyrrolidone. The obtained positive electrode mixture was applied to a 15 μm thick Al foil to be used as a current collector, vacuum-dried at 80°C for 1 hour, and then roll-pressed to obtain a positive electrode for a lithium secondary battery. The positive electrode area was 1.65 cm², and the basis weight was 16 mg / cm². ２ The density is 3.0 g / cm³. ３ I adjusted it so that it would be as follows.

[0298] 2. Preparation of a Negative Electrode for Lithium Secondary Batteries A negative electrode for lithium secondary batteries was prepared by mixing artificial graphite MAG-E and carbon-coated SiO in a 9:1 (mass ratio) ratio as the negative electrode active material, using CLPA-C07 (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) as a binder, and adding the above CNT dispersion as a conductive additive, so that the composition was negative electrode active material:binder:conductive additive = 94.9:5.0:0.1 (mass ratio), and kneading to prepare a paste-like negative electrode mixture. Ion-exchanged water was used as the solvent during the preparation of the negative electrode mixture. The obtained negative electrode mixture was coated onto a 20 μm thick Cu foil using a single-sided continuous coating machine, dried at 120°C, and then roll-pressed to obtain a negative electrode for lithium secondary batteries. The negative electrode area was 1.77 cm². ２ The estimated amount is 9.3 mg / cm³. ２The density is 1.4 g / cm³. ３ I adjusted it so that it would be as follows.

[0299] 3. Fabrication of a Lithium Secondary Battery The positive electrode for the lithium secondary battery was placed on the lower cover of a part for the coin-type battery R2032 (manufactured by Hosen Co., Ltd.), and a laminated film separator, which consists of a 16 μm heat-resistant porous layer laminated on a polyethylene porous film, was placed on top of it. 300 μL of electrolyte was injected into this. As the electrolyte, a 20:75:5 (volume ratio) mixture of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate was added, to which 1 volume% of vinylene carbonate was added, and LiPF was added. ６ A solution of 1.3 mol / L was used. Next, the negative electrode for the lithium secondary battery was placed on top of the laminated film separator, the top cover was placed on top via a gasket, and the lithium secondary battery of coin-type full cell R2032 was fabricated by crimping with a crimping machine. These operations were performed in a glove box under an argon atmosphere.

[0300] 4. Cycle Test Using the manufactured lithium-ion battery, a cycle test was conducted for 200 cycles under the conditions shown below, and the discharge capacity retention rate after 200 cycles was calculated using the following formula. Note that a higher discharge capacity retention rate after 200 cycles indicates better lifespan characteristics. Discharge capacity retention rate after 200 cycles (%) = Discharge capacity at 200th cycle / Discharge capacity at 1st cycle × 100

[0301] <Cycle Test Conditions> Test temperature: 25°C Charging conditions: Constant current constant voltage charging, maximum charging voltage 4.2V, charging time 5 hours, charging current 0.3C Rest time after discharge: 10 minutes Discharge conditions: Constant current discharge, minimum discharge voltage 2.5V, discharge current 0.3CA Rest time after charge: 10 minutes In this test, one cycle is defined as the process of charging, resting the discharge, discharging, and resting the charge in sequence.

[0302] Table 1 shows the evaluation results for Examples 1, 2, 3, 4, 5, Comparative Example 1, and Comparative Example 2. In Table 1, the units for the values ​​of the first metal and the second metal are "mass ppm," and the units for the values ​​in the column for cumulative 90% bundle diameter are "nm." "Percentage of bundles with a bundle diameter of 100 nm or more" refers to "the area percentage of bundles with a bundle diameter of 100 nm or more."

[0303]

[0304] As shown in Table 1, the CNT assemblies of Examples 1, 2, 3, 4, and 5 satisfy conditions (1), (2), and (3), and it was found that a carbon nanotube dispersion with appropriate viscosity can be obtained, and a battery with high discharge capacity retention and excellent cycle characteristics can be fabricated.

Claims

1. A carbon nanotube aggregate that satisfies the following conditions (1), (2), and (3): (1) Does not contain at least one first metal selected from the group consisting of Si, Mn, Ni, Cr, Mo, and Co, or contains the first metal, and the total content of the first metal is 1000 ppm by mass or less with respect to the total mass of the carbon nanotube aggregate. (2) Does not contain at least one second metal selected from the group consisting of Na, K, Ca, and Al, or contains the second metal, and the total content of the second metal is 1000 ppm by mass or less with respect to the total mass of the carbon nanotube aggregate. (3) Contains at least one of the first metal and the second metal.

2. A carbon nanotube aggregate according to claim 1, satisfying the following condition (4): (4) comprising a bundle structure, wherein the area ratio of bundles with a bundle diameter of 100 nm or more in the area observed by a scanning electron microscope is greater than 0.

1.

3. A carbon nanotube aggregate according to claim 1, satisfying the following condition (5): (5) It contains a bundle structure, and in the area observed by a scanning electron microscope, the bundle diameter that is 90% cumulative is greater than 90 nm and less than or equal to 400 nm.

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

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

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

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

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

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

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

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

Images