Carbon nanotube aggregate, carbon nanotube dispersion, conductive material, electrode, secondary battery, planar aggregate, filter, electromagnetic wave shield, and extreme ultraviolet protection film

Abstract

Provided is a carbon nanotube aggregate having excellent conductivity when a carbon nanotube dispersion liquid is produced, and applications thereof. A carbon nanotube aggregate, a carbon nanotube dispersion liquid, a conductive material, an electrode, a secondary battery, a planar aggregate, a filter, an electromagnetic wave shield, and an extreme ultraviolet protective film satisfy conditions (1), (2), and (3), (1) contain at least one of Fe atoms and Co atoms, the total content of the Fe atoms and the Co atoms is 2000 mass ppm to 100000 mass ppm relative to the total mass of the carbon nanotube aggregate; (2) contain at least one of Na atoms and K atoms, the total content of the Na atoms and the K atoms is 50 mass ppm to 1000 mass ppm relative to the total mass of the carbon nanotube aggregate; and (3) the ratio of the volume resistivity under 20 kN pressure to the volume resistivity under 1 kN pressure is 0.21 or more.

Description

Technical Field

[0001] This disclosure relates to carbon nanotube aggregates, carbon nanotube dispersions, conductive materials, electrodes, secondary batteries, planar aggregates, filters, electromagnetic wave shields, and protective films for extreme ultraviolet radiation. Background Technology

[0002] Carbon nanotubes are materials with a cylindrical structure formed by rolling graphene sheets with carbon atoms arranged in a hexagonal honeycomb pattern into a tube. Carbon nanotubes are broadly classified into single-walled carbon nanotubes formed from a single layer of graphene sheets and multi-walled carbon nanotubes formed from multiple layers of graphene sheets. Carbon nanotubes possess excellent mechanical and electronic properties, making them promising for various applications. In recent years, various attempts have been made to further improve the properties of carbon nanotubes.

[0003] For example, Patent Document 1 describes a carbon nanotube, a dispersion and its application, which has a cobalt content of 1000ppm to 30000ppm, contains particles containing metal atoms with specific mass magnetic susceptibility, and has a Raman spectrum G / D ratio of 0.7 to 1.5.

[0004] Patent document 2 describes a conductive material for secondary batteries containing carbon nanotubes. The carbon nanotubes have a spherical secondary structure formed by the entanglement of carbon nanotube units with a diameter of 20 nm to 150 nm. The ratio of true density (TD) to apparent density (BD) (TD / BD) is 30 to 120, and the metal content is less than 50 ppm.

[0005] [Existing Technical Documents]

[0006] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 2023-089806

[0008] [Patent Document 2] Japanese Patent Application Publication No. 2018-530854 Summary of the Invention

[0009] [The problem the invention aims to solve]

[0010] One embodiment of this disclosure aims to solve the problem of providing a carbon nanotube aggregate with excellent conductivity when prepared as a carbon nanotube dispersion.

[0011] Another problem to be solved by this disclosure is to provide a carbon nanotube dispersion containing the above-mentioned carbon nanotube aggregate and having excellent electrical conductivity.

[0012] Another problem to be solved by this disclosure is to provide a conductive material, an electrode, and a secondary battery comprising the above-described carbon nanotube aggregate.

[0013] Another problem to be solved by this disclosure is to provide a planar assembly comprising the above-described carbon nanotube assembly and comprising carbon nanotube assemblies with a maximum length of 1000 μm to 30000 μm.

[0014] Another problem to be solved by this disclosure is to provide a filter, an electromagnetic wave shield, and an extreme ultraviolet protective film using the above-described planar assembly.

[0015] [Methods used to solve problems]

[0016] <1> A carbon nanotube aggregate that satisfies the following conditions (1), (2) and (3).

[0017] (1) Contains at least one of Fe atoms and Co atoms,

[0018] The combined content of Fe and Co atoms relative to the total mass of the carbon nanotube assembly is 2000 ppm to 100000 ppm.

[0019] (2) Contains at least one of Na atoms and K atoms, and the total content of Na atoms and K atoms relative to the total mass of the carbon nanotube assembly is 50 ppm to 1000 ppm by mass;

[0020] (3) The ratio of volume resistivity under 20kN pressure to volume resistivity under 1kN pressure is less than 0.21.

[0021] <2> according to <1> The carbon nanotube assembly includes a bundle structure.

[0022] <3> according to <1> or <2> The carbon nanotube aggregate described herein has a pore volume of 0.60 cm³. 3 / g~3.20cm 3 / g.

[0023] <4> A carbon nanotube dispersion comprising <1> ~ <3> The carbon nanotube aggregate and dispersion medium described in any one of the following.

[0024] <5> A conductive material comprising <1> ~ <3> The carbon nanotube assembly described in any one of the following statements.

[0025] <6> An electrode comprising an electrode active material and <5> The aforementioned conductive material.

[0026] <7> A secondary battery, which has <6> The aforementioned electrode.

[0027] <8> A planar aggregate, which is <1> ~ <3> The carbon nanotube assembly according to any one of the following methods, wherein the carbon nanotube assembly comprises carbon nanotubes with a maximum length of 1000 μm to 30000 μm.

[0028] <9> A filter that is used <8> The aforementioned planar aggregate.

[0029] <10> An electromagnetic wave shield, which is used <8> The aforementioned planar aggregate.

[0030] <11> A protective film for extreme ultraviolet radiation, its use <8> The planar aggregate protective film.

[0031] <12> A composition comprising a carbon nanotube aggregate satisfying conditions (1) and (2) below, and at least one selected from the group consisting of a dispersion medium, resin, ceramic, and concrete.

[0032] (1) Containing at least one of Fe atoms and Co atoms, wherein the total content of Fe atoms and Co atoms is 2,500 ppm to 60,000 ppm relative to the total mass of the carbon nanotube assembly;

[0033] (2) Containing at least one of Na atoms and K atoms, wherein the total content of Na atoms and K atoms is 50 ppm to 700 ppm relative to the total mass of the carbon nanotube assembly.

[0034] <13> A composition comprising a carbon nanotube aggregate satisfying conditions (1) and (2) below, and at least one selected from the group consisting of a dispersion medium, resin, ceramic, and concrete.

[0035] (1) Containing at least one of Fe atoms and Co atoms, wherein the total content of Fe atoms and Co atoms is 2,500 ppm to 60,000 ppm relative to the total mass of the carbon nanotube assembly;

[0036] (2) The ratio of volume resistivity under 20kN pressure to volume resistivity under 1kN pressure is greater than 0.21.

[0037] [Invention Effects]

[0038] According to one embodiment of the present disclosure, a carbon nanotube aggregate with excellent conductivity when prepared as a carbon nanotube dispersion can be provided.

[0039] According to another embodiment of this disclosure, a carbon nanotube dispersion containing the above-described carbon nanotube aggregate and exhibiting excellent electrical conductivity can be provided.

[0040] According to another embodiment of this disclosure, a conductive material, an electrode, and a secondary battery comprising the above-described carbon nanotube aggregate can be provided. Attached Figure Description

[0041]

【 Figure 1 [A scanning electron microscope image showing one manner of a specific CNT assembly] Detailed Implementation

[0042] The following provides a detailed description of the carbon nanotube aggregates, carbon nanotube dispersions, conductive materials, electrodes, and secondary batteries disclosed herein. The following description is sometimes based on representative embodiments of this disclosure, but this disclosure is not limited to such embodiments, and appropriate modifications can be made to implement it within the scope of the purposes of this disclosure.

[0043] In this disclosure, the numerical range indicated by “~” means that the numerical values ​​recorded before and after “~” are included as the minimum and maximum values, respectively.

[0044] In the numerical ranges described in this disclosure, the upper or lower limit value recorded in a certain numerical range can be replaced with the upper or lower limit value of other numerical ranges described in different segments. Furthermore, in the numerical ranges described in this disclosure, the upper or lower limit value recorded in a certain numerical range can be replaced with the values ​​shown in the embodiments.

[0045] In this disclosure, a combination of two or more preferred methods is a more preferred method.

[0046] In this disclosure, where there are multiple substances that conform to each component, unless otherwise stated, the amount of each component refers to the total amount of the multiple substances.

[0047] In this specification, the term "process" includes not only independent processes, but also processes that can not be clearly distinguished from other processes, as long as the intended purpose of the process can be achieved.

[0048] In this disclosure, the terms “carbon nanotube”, “single-walled carbon nanotube”, “multi-walled carbon nanotube”, “multi-walled carbon nanotube with a maximum length of 1000 μm to 30000 μm”, “carbon nanotube aggregate” and “carbon nanotube dispersion” are sometimes abbreviated as “CNT”, “SWCNT”, “MWCNT”, “ULMWCNT”, “CNT aggregate” and “CNT dispersion”, respectively.

[0049] [Carbon nanotube assembly]

[0050] One embodiment of this disclosure is a carbon nanotube assembly that satisfies the conditions (1), (2), and (3) below.

[0051] (1) Contains at least one of Fe atoms and Co atoms, and the total content of Fe atoms and Co atoms relative to the total mass of the aggregate is 2,000 ppm to 100,000 ppm.

[0052] (2) Contains at least one of Na atoms and K atoms, and the total content of Na atoms and K atoms relative to the total mass of the aggregate is 50 ppm to 1000 ppm.

[0053] (3) The ratio of volume resistivity under 20kN pressure to volume resistivity under 1kN pressure is greater than 0.21.

[0054] Hereinafter, the carbon nanotube assembly of this embodiment will also be referred to as a "specific CNT assembly".

[0055] The carbon nanotube dispersion exhibits excellent conductivity when prepared according to a specific CNT aggregate. That is, the carbon nanotube dispersion (hereinafter also referred to as "specific CNT dispersion") containing a specific CNT aggregate and a dispersion medium that satisfy the conditions (1), (2) and (3) above has excellent conductivity.

[0056] The specific CNT dispersion is another embodiment of this disclosure, and details regarding the specific CNT dispersion, other than the specific CNT aggregate, will be described later.

[0057] On the other hand, Patent Document 1, from the viewpoint of obtaining a carbon nanotube dispersion with excellent conductivity, specifies the content of Co atoms, but does not focus on controlling the total content of N atoms and K atoms, nor does it specify the ratio of volume resistivity under 20 kN pressure to volume resistivity under 1 kN pressure as a condition.

[0058] Patent document 2, from the viewpoint of obtaining a carbon nanotube dispersion with excellent conductivity, specifies the ratio of true density (TD) to apparent density (BD) (TD / BD), but does not focus on the total content of Fe atoms and Co atoms, the total content of N atoms and K atoms, and further does not focus on the ratio of volume resistivity under 20 kN pressure to volume resistivity under 1 kN pressure as a specified condition.

[0059] The following is a detailed description of a specific set of CNTs. However, the speculations described below are not intended to limit the interpretation of the specific set of CNTs, but are provided as examples.

[0060] <Condition (1)>

[0061] A specific CNT aggregate contains at least one of Fe atoms and Co atoms, and the total content of Fe atoms and Co atoms relative to the total mass of the specific CNT aggregate is 2000 ppm to 100000 ppm.

[0062] The Fe and Co atoms contained in a particular CNT assembly are believed to originate from the metal catalyst used in the manufacture of CNTs.

[0063] When CNTs are manufactured in the presence of catalysts containing metal atoms such as Fe and Co, Fe and Co atoms from the catalyst may be included in the CNTs, raising concerns about reduced conductivity. In the past, after the CNTs were manufactured, metal atoms, primarily Fe and Co atoms, were removed by cleaning with acid.

[0064] However, according to the research of the present invention, it has been found that by making the total content of Fe atoms and Co atoms relative to the total mass of a specific CNT aggregate 2,000 ppm to 100,000 ppm by mass, the dispersibility in the dispersion medium can be further improved while maintaining the conductivity of the CNT aggregate.

[0065] The total content of Fe atoms and Co atoms is 2,000 ppm to 100,000 ppm by mass, preferably 2,500 ppm to 80,000 ppm by mass, and more preferably 3,000 ppm to 60,000 ppm by mass.

[0066] Fe and Co atoms are located in close positions in the periodic table, and their mechanisms of action can be considered similar.

[0067] It can be assumed that by keeping the total content of Fe and Co atoms relative to the total mass of a specific CNT aggregate in the range of 2000 ppm to 100000 ppm, the contact sites between the CNTs contained in the specific CNT aggregate are maintained within an appropriate range, thus making it easy to connect the conductive pathways and obtain good conductivity in the resulting specific dispersion.

[0068] As a catalyst containing Fe or Co atoms for CNT manufacturing, a main catalyst such as iron (Fe) or cobalt (Co) can be used alone as a metal catalyst, or the main catalyst can be used together with a co-catalyst such as molybdenum (Mo), vanadium (V), or chromium (Cr) in the form of a main catalyst-co-catalyst composite catalyst. Specifically, examples of composite catalysts include FeCo, CoMo, CoV, FeCoMo, FeMoV, FeV, or FeCoMoV, and any one or a mixture of two or more of these can be used. Furthermore, the co-catalyst can be used in an amount of 0.01 moles to 1 mole, more specifically 0.05 moles to 0.5 moles, relative to 1 mole of the main catalyst.

[0069] The content (mass ppm) of Fe and Co atoms relative to the total mass of a specific CNT aggregate can be determined, for example, by the following methods.

[0070] Specific CNT aggregates are completely dissolved in acids such as hydrochloric acid and nitric acid. To ensure complete dissolution, pretreatment methods such as dry ashing, wet ashing, and melt treatment can be performed. The content of Fe and Co atoms can be determined by performing inductively coupled plasma atomic emission spectrometry (ICP-AES) or inductively coupled plasma mass spectrometry (ICP-MS) on the solution containing the completely dissolved CNT aggregates. ICP-MS is preferred due to its higher sensitivity.

[0071] Furthermore, when the content of Fe atoms and Co atoms is below 10 ppm, it becomes technically difficult to detect the peaks originating from these elements using ICP-MS or ICP-AES, and it is sometimes difficult to calculate the content accurately. Therefore, the content below 10 ppm can be treated as 0.

[0072] CNTs sometimes contain 0.01% to 50% by mass of iron Fe or Co atoms derived from the catalyst used in their manufacture. Additionally, when CNTs contain Fe or Co atoms, it may be in the form of adsorption on the surface of the CNT or encapsulated within the fibrous CNTs formed during manufacturing.

[0073] That is, in this disclosure, the Fe atoms and Co atoms contained in a particular CNT assembly may respectively contain Fe atoms and Co atoms derived from the catalyst used in the manufacture of MWCNT.

[0074] In a specific CNT aggregate, considering the content of Fe and Co atoms derived from the catalyst contained in the CNTs, preferably, the total content of Fe and Co atoms relative to the total mass of the aggregate is adjusted to a target total content of Fe and Co atoms, within the range of 4000 ppm to 60000 ppm. Furthermore, when the total content of Fe or Co atoms derived from the catalyst is a target content relative to the total mass of the aggregate, it is of course unnecessary to take special measures to adjust the Fe atom content.

[0075] When the total content of Fe and Co atoms relative to the total mass of a particular CNT aggregate exceeds 60,000 ppm by mass, the total content of Fe and Co atoms relative to the total mass of the particular CNT aggregate can be adjusted to below 60,000 ppm by mass by washing the aggregate with known methods, such as water, acid, or an aqueous solution of acid (e.g., a 35% aqueous solution of hydrochloric acid), to wash and remove a portion of the Fe atoms.

[0076] When the total content of Fe and Co atoms relative to the total mass of a specific CNT aggregate is less than 2000 ppm by mass, the total content of Fe and Co atoms can be adjusted to 2000 ppm by mass or more by immersing the aggregate in an aqueous solution of approximately 5% by mass of ferric nitrate or approximately 40% by mass of ferric chloride, which serves as a source of Fe atoms. This causes Fe atoms to adsorb onto the surface of the fibrous ULMWCNT, thereby increasing the Fe atom content relative to the total mass of the aggregate. Furthermore, the total content of Fe and Co atoms can be adjusted to 2000 ppm by mass or more by immersing the aggregate in an aqueous solution of approximately 5% by mass of cobalt nitrate or approximately 40% by mass of cobalt chloride, which serves as a source of Co atoms. This causes Co atoms to adsorb onto the surface of the fibrous ULMWCNT, thereby increasing the Co atom content relative to the total mass of the aggregate.

[0077] <Condition (2)>

[0078] A specific CNT aggregate contains at least one of Na atoms and K atoms, and the total content of Na atoms and K atoms relative to the total mass of the specific CNT aggregate is 50 ppm to 1000 ppm by mass.

[0079] The total content of Na and K atoms relative to the total mass of a specific CNT aggregate is preferably 60 ppm to 900 ppm by mass, more preferably 70 ppm to 700 ppm by mass.

[0080] The Na and K atoms contained in a specific CNT aggregate are believed to originate from the catalyst raw materials used in CNT manufacturing. Preferably, the Na and K atoms originate from impurities contained in catalyst raw materials such as ferrocene.

[0081] Dispersants used to prepare CNT dispersions sometimes contain Na and K atoms as counter ions. According to our research, the Na and K atoms are considered to originate from the catalyst raw material and are present either adsorbed on the surface of the CNTs or encapsulated within the fibrous CNTs formed during manufacturing. This is effective for improving the conductivity of the carbon nanotube dispersion. This is likely because the adsorption of Na and K ions in the dispersant for CNTs in the dispersion is unstable.

[0082] The effect of improving the conductivity of a specific CNT dispersion by making the total content of Na and K atoms relative to the total mass of a specific CNT aggregate 50 ppm to 1000 ppm by mass is not yet clear, but the inventors have considered the following.

[0083] Following the reaction during CNT manufacturing, the surfaces of Fe and Co atoms derived from the catalyst are partially covered by oxides. It is speculated that the presence of at least one atom selected from Na and K atoms during CNT manufacturing leads to the formation of a composite oxide. It can be assumed that the formation of the composite oxide increases the affinity of the specific CNT aggregate for water, allowing for more stable dispersion in the dispersion. Consequently, the resulting CNT dispersion readily forms conductive pathways, achieving good conductivity.

[0084] Examples of composite oxides include NaFeO3, Na2FeO4, NaCoO3, Na2CoO4, KFeO3, K2FeO4, KCoO3, and K2CoO4. It is speculated that the aforementioned effects are achieved because these composite oxides are formed in trace amounts on the surface of Fe and Co atoms in the catalyst residue.

[0085] In a specific CNT aggregate, if the combined content of Fe and Co atoms is too high, there is a tendency to hinder the formation of conductive pathways; if the combined content of Fe and Co atoms is too low, CNTs are prone to aggregation, and the dispersibility of the CNT aggregate in solvents such as water tends to decrease, making it difficult to achieve the effect of improving the conductivity of the dispersion.

[0086] Furthermore, it can be argued that if the combined content of Na and K atoms is too high, the ionic strength of the surface becomes too strong, which may make it difficult to form conductive pathways due to electrostatic repulsion between CNTs; if the combined content of Na and K atoms is too low, it is sometimes difficult to achieve the effect of improving the dispersibility of CNT aggregates in solvents such as water, and it is difficult to achieve the effect of improving the conductivity of the dispersion.

[0087] The content of Na and K atoms in a specific CNT aggregate can be determined using the same method as the method for determining the content of Fe atoms described above.

[0088] The total content of Na and K atoms in a specific CNT aggregate can be adjusted by controlling the content of Na and K atoms as impurities in catalyst raw materials such as ferrocene.

[0089] For example, when using ferrocene synthesized from sodium cyclopentadienyl and ferric chloride as a starting material for a catalyst, the content of Na atoms as impurities can sometimes be high. Therefore, by using sodium or potassium compounds as starting materials for the catalyst, the content of Na and K atoms in the resulting CNTs can be increased to the required levels.

[0090] On the other hand, when the total content of Na and K atoms in CNTs exceeds the specified range, some Na and K atoms can be removed by appropriately performing the acid cleaning treatment as described above, thereby adjusting the total content to the specified range.

[0091] <Condition (3)>

[0092] The ratio of the volume resistivity of a specific CNT assembly under 20kN pressure to its volume resistivity under 1kN pressure (hereinafter also referred to simply as the "resistivity ratio") is 0.21 or less.

[0093] Because the resistivity ratio of certain CNT aggregates is above 0.21, their aggregation in powder form is not very high, resulting in good dispersibility in the dispersion medium and wide micro-dispersion in the dispersion liquid. Therefore, it is speculated that the conductive pathways formed between CNTs in the dispersion liquid can easily reach an appropriate length, thus creating a dispersion with excellent conductivity.

[0094] Furthermore, there is no particular upper limit to the resistivity ratio in a specific CNT assembly, but since the contact between CNTs is moderately enhanced and conductive paths are easily and stably formed, it can be set to 0.35 or less.

[0095] In one embodiment, the resistivity ratio of a particular CNT assembly is preferably 0.21 or higher and 0.24 or lower.

[0096] When the resistivity ratio is above 0.21 and below 0.24, the aggregation of specific CNT aggregates in the powder state is not very high, which makes it easy to ensure the dispersibility of the dispersion medium. Therefore, it is possible to ensure the connectivity between the micro-dispersed CNTs in the dispersion, and it is speculated that the conductivity of the dispersion will be improved.

[0097] In another embodiment, the resistivity ratio of the specific CNT aggregate is preferably 0.25 or higher and 0.29 or lower. It is speculated that when the resistivity ratio is 0.25 or higher and 0.29 or lower, the aggregation in the powder state will not be too high, and the conductivity of the specific CNT dispersion can be more easily and stably ensured.

[0098] In this disclosure, the volume resistivity of the CNT assembly is measured using a resistivity meter at 25°C via a four-probe method. A Loresta apparatus can be used as the resistivity meter.

[0099] Specifically, using the Loresta apparatus (product name: MCP-PD51 powder resistance measurement system, Loresta-GP low resistivity meter, MCP-PD511 low resistance probe for powder (constant current application method 4-probe method), all manufactured by Nitto Seiko Analytical Technology Co., Ltd.), the sample to be measured is introduced into the resistivity measurement probe unit, and the accompanying hydraulic pump is used to apply pressure at 1kN or 20kN. After reaching the target load, the volume resistivity (Ω·cm) is measured.

[0100] As a sample for measuring volume resistivity, powder of CNT aggregates is used.

[0101] When the CNT aggregates are in a form other than powder (e.g., fibers or sheets), the CNT aggregates can be pulverized to become powder. There are no particular limitations on the pulverization process; any pulverization method capable of breaking the CNT aggregates into small pieces can be used. Cryogenic pulverization can be used as a pulverization process.

[0102] In this disclosure, the resistivity ratio is calculated by dividing the measured volume resistivity under 20 kN pressure by the volume resistivity under 1 kN pressure, and rounding off the third decimal place.

[0103] The resistivity ratio of a specific CNT assembly can be adjusted using conventional methods.

[0104] Methods for adjusting the resistivity ratio of a specific CNT assembly include, for example, controlling the content of impurities in the CNT, controlling the structural defects of the CNT, controlling the length of the CNT, and controlling the specific surface area of ​​the CNT.

[0105] Regarding impurities contained in CNTs, it can be considered that at low load pressures, impurities trapped between CNTs significantly obstruct the conductive path, leading to an increase in resistivity. Conversely, as the load pressure increases, the number of contact points between CNTs increases, reducing the impact of the resistance increase caused by impurities and decreasing the resistivity. Therefore, for example, the resistivity ratio can be controlled by controlling the content of Fe atoms and / or Co atoms, which are important impurities derived from the catalyst.

[0106] The structural defects of CNTs can be quantified by the G / D intensity ratio in Raman spectroscopy. A high G / D intensity ratio indicates fewer structural defects, thus the resistivity tends to decrease. The G / D intensity ratio can be controlled by selecting the conditions of the CNT manufacturing method described later.

[0107] As the length of a CNT increases, its resistivity tends to decrease. Taking this into account, methods for incorporating ULMWCNTs are also cited as one control method. ULMWCNTs can be obtained, for example, by controlling the manufacturing method of the CNT.

[0108] The resistivity ratio of a specific CNT assembly can also be controlled by the specific surface area of ​​the CNTs. It is speculated that if the specific surface area is small, it is difficult to ensure contact points between CNTs, but the increase in contact points due to applied load will be significant. Conversely, it is speculated that if the specific surface area is large, it is easier to ensure contact points between CNTs, but the increase in contact points due to applied load will be smaller. The specific surface area of ​​CNTs can be controlled by adjusting the conditions in the CNT manufacturing method described later. For example, the mixing ratio of CNTs with large specific surface areas to CNTs with small G / D strength ratios can be controlled, and the two can be uniformly mixed before use.

[0109] <Bundle Structure>

[0110] From the perspective of improved operability, a particular CNT assembly preferably includes a bundle structure.

[0111] A bundle structure refers to a collection of multiple CNTs that are aggregated together by van der Waals forces, forming a bundle-like or handle-like structure. It is speculated that a particular CNT assembly, by containing a bundle structure of a suitable size, exhibits improved operability and stability. However, on the other hand, if the bundle structure within a particular CNT assembly is too large, the CNT assembly itself may become excessively large, making it difficult to separate and disperse the CNTs within the bundle structure, thus reducing its dispersibility in the dispersion medium.

[0112] Therefore, from the viewpoint of balancing the operability of CNT assemblies and their dispersibility with solvents, the width of each bundle structure contained in a specific CNT assembly, i.e., the width dimension of the fiber bundle, is preferably 5 nm to 500 nm, and more preferably 10 nm to 300 nm.

[0113] The content of bundle structures in a specific CNT assembly is preferably 10% to 100% by mass, more preferably 20% to 90% by mass, relative to the total mass of the specific CNT assembly.

[0114] The presence or absence of bundle structures within a specific CNT assembly can be confirmed by observing the assembly using optical microscopy or scanning electron microscopy (SEM). The width of the bundle structure is determined by identifying the locations within the assembly where bundle structures are present and measuring their length using images captured from the bundle structures.

[0115] Bundle structures in specific CNT aggregates, for example in the manufacture by chemical vapor deposition (CVD), can be formed by controlling the catalyst particle size distribution and the cooling rate during the cooling process.

[0116] <Porous volume>

[0117] The preferred pore volume of the specific CNT aggregate disclosed herein is 0.60 cm³. 3 / g~3.20cm 3 / g.

[0118] It is speculated that the specific CNT aggregate has a pore volume of 0.60 cm³. 3 / g~3.20cm 3 / g, so the friction between specific CNT aggregates is within a suitable range, and when made into a dispersion, it is easy to stably form a conductive path, thus improving the conductivity of the dispersion.

[0119] In contrast, it is speculated that for pore volumes below 0.60 cm³... 3 / g of CNT aggregates, due to the scarcity of surface irregularities on the CNT aggregates, the friction between the CNT aggregates is small, making it difficult to maintain a stable contact state, thus making the conductive path unstable.

[0120] Additionally, it is speculated that for pore volumes greater than 3.20 cm³... 3 / g of CNT aggregates, due to the increased friction between the CNT aggregates, their dispersion in the dispersion solution becomes insufficient, which is not conducive to the formation of conductive pathways.

[0121] Furthermore, if the stomatal volume is greater than 3.20 cm³ 3If the volume of pores is too large (e.g., the amount of voids in the CNT aggregate increases, which may reduce the physical strength of the CNT aggregate. Due to the reduced physical strength, the CNT aggregate may not withstand shear forces applied to it during processes such as dispersing the CNT aggregate (e.g., partial blockage of pores, partial destruction of the CNT aggregate), making this undesirable. Furthermore, if the pore volume is too large, the amount of voids in the CNT aggregate increases, potentially leading to excessively long conductive pathways and increased resistance, which is also undesirable.

[0122] In this disclosure, the pore volume of a CNT aggregate is defined as the pore volume (cm³) of a CNT aggregate per unit mass (g). 3 The morphology of CNT aggregates, which are the objects of pore volume measurement, is not limited and can be any form of powder, fiber, sheet, etc.

[0123] In this disclosure, the pore volume of the CNT aggregate is determined using a constant volume method. A specific surface area / pore distribution measuring device can be used as the measuring apparatus.

[0124] Pore ​​volume of CNT aggregates (cm³) 3 / g), specifically, is determined by the steps shown below.

[0125] First, the CNT aggregates to be measured were subjected to vacuum degassing at 300°C for 3 hours to prepare samples for measurement.

[0126] For the prepared samples, nitrogen-based adsorption-desorption isotherms were determined using the constant volume method. The BJH method was used for the analysis to calculate the pore volume.

[0127] Measuring Apparatus: Specific Surface Area / Pore Distribution Measuring Apparatus (Product Name "BEL SORP-miniII", manufactured by MicrotracBEL)

[0128] Measurement temperature: 77K

[0129] Adsorbate: Nitrogen

[0130] Saturated vapor pressure: Measured value

[0131] Adsorbate cross-sectional area: 0.162 nm 2

[0132] Waiting time after adsorption equilibrium is reached: 500 seconds

[0133] <Other matters concerning specific CNT collections>

[0134] In this disclosure, the CNTs contained in a particular CNT set may be SWCNTs or MWCNTs, but from the viewpoint that they have a layered distribution and slightly lower uniformity, thus making it easier to improve dispersion, MWCNTs are preferred.

[0135] Typically, SWCNTs have lower volume resistivity than MWCNTs, and lower volume resistivity means a smaller resistivity change caused by applied load. The number of CNT layers can be controlled by selecting the CNT manufacturing method.

[0136] As the length of a CNT increases, its volume resistivity tends to decrease. The length of a CNT can be controlled by selecting the manufacturing method.

[0137] In one embodiment, a specific CNT assembly may comprise MWCNTs with a maximum length of 500 μm or less as the principal component, and may not comprise an assembly of MWCNTs exceeding 500 μm but less than 30,000 μm. Here, a principal component refers to MWCNTs with a maximum length of 500 μm or less comprising at least 90% by mass of the CNTs constituting the specific CNT assembly. The specific CNT assembly may also comprise SWCNTs with a maximum length of 500 μm or less.

[0138] In one embodiment, a particular CNT assembly preferably comprises MWCNTs with a maximum length of 10 μm to 30,000 μm. In another embodiment, the MWCNTs preferably comprise ULMWCNTs.

[0139] ULMWCNTs are MWCNTs with a maximum length of 1000μm to 30000μm. Compared with general MWCNTs, they are longer and can be designed in fiber shape.

[0140] By being shaped like fibers, ULMWCNTs have the property of easily entangled with each other. MWCN contains at least one type of ULMWCNT, and from the viewpoint that MWCNTs can easily form a more stable aggregate by entanglement, an aggregate containing multiple ULMWCNTs is preferred. Hereinafter, an aggregate containing ULMWCNTs will sometimes be simply referred to as an "ULMWCNT aggregate".

[0141] Here, the term "fiber" is generally used to refer to a structure in which one dimension is larger than the other two dimensions. A fiber can be a filamentous fiber with a circular cross-section, a ribbon-like fiber with a rectangular cross-section, a hollow fiber, or have other shapes. From the viewpoint of improving conductivity, it is preferable that the ULMWCNT has a circular cross-section, and more preferably a hollow one.

[0142] An assembly of MWCNTs can also be an assembly of intertwined three-dimensional structures.

[0143] Figure 1 This is a scanning electron microscope (SEM) image showing one manner of assembling MWCNTs in this disclosure. From Figure 1 The SEM images shown reveal that multiple fibrous ULMWCNTs are intertwined and form aggregates. This SEM observation confirms the entangled state of the ULMWCNTs in this disclosure.

[0144] The length of a ULMWCNT can be determined by observing multiple SEM images of adjacent field-of-view angles focusing on a single ULMWCNT. Here, "length of ULMWCNT" refers to the measured length along the long side of the ULMWCNT, and the maximum value among the measured lengths is taken as the "maximum length".

[0145] When a MWCNT with a maximum length ranging from 1000 μm to 30000 μm is observed within the field of view of a SEM image, it can be confirmed that the observed MWCNT contains a ULWMCNT.

[0146] It is preferable that multiple ULMWCNTs are present in the field of view of the SEM image. Considering 100 MWCNTs contained in the field of view of the SEM image, the maximum length of each MWCNT is measured. From the viewpoint of further improving the stability of the MWCNT aggregate caused by the entanglement of ULMWCNTs, it is preferable that 10% or more of the MWCNTs (i.e., ULMWCNTs) with a maximum length in the range of 1000 μm to 30000 μm are present, more preferably more than 20%, more preferably more than 30%, and particularly preferably more than 50%.

[0147] The diameter of a ULMWCNT can be determined by observing SEM or transmission electron microscopy (TEM) images. Here, the diameter refers to the length of a direction orthogonal to the long side of the ULMWCNT. The diameter is measured at 10 different locations for a single ULMWCNT, and the average value is taken as the diameter of that ULMWCNT.

[0148] The length of the ULMWCNT is in the range of 1000 μm to 30000 μm, preferably in the range of 1050 μm to 25000 μm, more preferably in the range of 1100 μm to 20000 μm, even more preferably in the range of 1200 μm to 18000 μm, and particularly preferably in the range of 1300 μm to 15000 μm. The diameter of the ULMWCNT is preferably 1 nm to 100 nm, more preferably 2 nm to 80 nm, even more preferably 3 nm to 50 nm, and particularly preferably 5 nm to 30 nm.

[0149] The length-to-diameter ratio of the ULMWCNT, also known as the aspect ratio, is preferably 1,000 or more, more preferably 3,000 or more, even more preferably 5,000 or more, and particularly preferably 10,000 or more.

[0150] The length-to-diameter ratio can be calculated from the ratio of the maximum length to the diameter of a single ULMWCNT. From the viewpoint of measurement accuracy, it is preferable to use the average value of measurements from 20 or more ULMWCNTs.

[0151] Furthermore, from the viewpoint of dispersion, the specific gravity of the ULMWCNT 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.

[0152] The specific gravity of ULMWCNT aggregates can be determined by the method described in JIS Z8807:2012 "Determination of density and specific gravity of solids".

[0153] The purity of MWCNTs, which are ULMWCNT aggregates, can be determined by thermogravimetric analysis (TGA). For example, using a thermal analysis apparatus (manufactured by Shimadzu Corporation, DTG-60), thermogravimetric (TG) curves and differential thermal analysis (DTA) curves of the ULMWCNT aggregates are obtained. The maximum exothermic peak appearing near 650°C to 750°C in the DTA curve is taken as the combustion of MWCNTs, and exothermic peaks appearing elsewhere are taken as the combustion of substances other than MWCNTs. The purity of MWCNTs is determined from the weight loss rate of the TG curves. From the viewpoint of the obtained electrical conductivity, the purity of the ULMWCNT aggregates is preferably 50% by mass or more, more preferably 65% ​​by mass or more, further preferably 80% by mass or more, and particularly preferably 95% by mass or more.

[0154] ULMWCNTs sometimes contain 0.01% to 50% by mass of Fe atoms derived from iron (which is a catalyst used in the manufacturing process). When ULMWCNTs contain Fe atoms, it is sometimes in the form of adsorption on the surface of ULMWCNTs or encapsulated inside the fibrous ULMWCNTs formed during manufacturing.

[0155] The resulting fibrous ULMWCNTs are preferably soft and have high strength.

[0156] In addition, the conductivity of ULMWCNT itself is preferably 5000 ohms. -1 ·m -1 The above, more preferably 10000 ohms -1 ·m -1 That's all. Furthermore, the conductivity of ULMWCNT itself is typically 1,000,000 ohms.-1 ·m -1 or less.

[0157] <Method for producing CNTs>

[0158] The method for producing CNTs in the present disclosure is not particularly limited. For example, as the method for producing MWCNTs in the present disclosure, conventionally known methods such as a chemical vapor deposition (CVD) method, a method of reacting a gaseous reactive substance containing a carbon source in the presence of a catalyst, and the like can be applied.

[0159] The CNTs in the present disclosure can be produced, for example, by referring to the methods described in Japanese Patent Laid-Open No. 2016-102047, Japanese Patent National Publication of International Application No. 2021-527611, and the like.

[0160] 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.

[0161] =Production Method X=

[0162] As one example of the method for producing CNTs referred to in the present disclosure, the production method described in Japanese Patent Laid-Open No. 2016-102047 can be mentioned. That is, a production method (hereinafter also referred to as "Production Method X") including the following steps can be mentioned: a step of passing a gaseous reactive substance containing one or more carbon sources through a reactor; a step of reacting one or more gaseous reactive substances in the presence of a catalyst in the reaction zone of the reactor to form carbon-containing product particles; 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 zone.

[0163] According to Production Method X, MWCNTs containing ULMWCNTs can be obtained in the form of easily handleable fibrous aggregates or other forms of aggregates.

[0164] In Production Method X, the force applied to the product particles may also be a mechanical force.

[0165] When the aggregate is a fibrous MWCNT, the mechanical force applied to the product particles can be applied by a rotating mandrel that winds the aggregate. The fibrous CNTs can be collected on the mandrel, or after rotating around the mandrel one or more times, can be accumulated in another location by continuously unwinding the mandrel.

[0166] The mandrel is preferably arranged with its axis perpendicular or parallel to the flow direction of the one or more gaseous reactive substances, but may also be arranged in other orientations. For example, a mandrel arranged at an angle of 25° relative to the flow direction of the gaseous reactive substances can also be suitably used to apply a mechanical force to the product particles.

[0167] The mandrel can rotate about two axes (e.g., two perpendicular axes). In particular, the mandrel can rotate about axes perpendicular and parallel to the flow direction of the gaseous reactants, respectively. With such a mandrel, the aggregates of fibrous CNTs can be drawn and twisted to control the twist count and length.

[0168] The mandrel can be made of metal, ceramic or resin.

[0169] Depending on the material properties and the intended use of MWCNTs, the mandrel can take on different suitable shapes. The mandrel can be produced by spin coating, for example, as a mold for manufacturing carbon products. Preferred mandrel shapes are rod-shaped or box-shaped.

[0170] Fibrous MWCNTs accumulate on the mandrel or other sites. The coating thickness and orientation can be controlled by adjusting the reaction time and conditions, or by applying an electric field or other field to the carbon products. The coating thickness and the orientation of the carbon products can be controlled, for example, by the dynamics of the gas flow.

[0171] The rotational speed of the mandrel is preferably 0.01 rpm to 10,000 rpm, more preferably 0.1 rpm to 100 rpm.

[0172] The spinning speed (i.e., the rotation speed of the mandrel) can be adjusted to be the same speed as the generated material. The thickness of the accumulated fibrous MWCNTs can be controlled by the rotation speed of the mandrel. In a preferred embodiment, the fibrous CNTs are processed along the axial direction of the mandrel as the mandrel rotates. In the above processing, the fibrous MWCNTs are not wound only at a specific location on the mandrel, but are wound uniformly along the mandrel.

[0173] Fibrous MWCNTs can be recovered, for example, from the reactor wall using a matrix placed within the reactor. The matrix can be a stationary matrix, or, in the case of recovering fibrous MWCNTs, a rotating guide component for applying a strong and uniform force to the fibrous MWCNTs. As a suitable matrix configuration for fiber technology, a matrix consisting of two guide components positioned orthogonally to each other can be cited as an example.

[0174] In manufacturing method X, the mechanical force applied to the product particles can be a force applied by accelerating a gas flow. Accelerating the gas flow can be generated by passing the product particles through a reactor with a narrow diameter, or through a capillary located downstream of the reaction zone. A vacuum can also be applied to the product particles.

[0175] As another force applied to the product particles, an example is the electrostatic force appropriately applied via a charged electrode plate. When using an electrostatic force, the product particles need to be charged. By using a charged electrode plate, MWCNTs can be generated on the charged electrode plate in the form of intertwined sheets.

[0176] Alternatively, other forces applied to the product particles could be magnetic force or photon pressure applied by a light source.

[0177] The raw material for CNTs can replace the gaseous reactants containing a carbon source, and can be injected in liquid form containing a carbon source. When using liquid as the raw material for CNTs, injection can be performed through a single injection port or multiple injection ports, for example, injection can be performed using a spray head configuration.

[0178] One or more gaseous reactants are preferably reacted at 500°C to 1600°C, more preferably at 1000°C to 1500°C. It is preferable to maintain a temperature gradient within the reactor and keep the reaction zone at a higher temperature than the product zone of the reactor.

[0179] The gaseous reactant can be mixed with one or more gases that act as a diluent. The gaseous reactant can also be mixed with a gas that does not play a direct role in the reaction but plays an auxiliary role. In the case of generating amorphous carbon as a byproduct, it is preferable to use a gas that can properly maintain the reaction sites on the catalyst and generate nanotubes by reacting with amorphous carbon as a diluent.

[0180] Examples of 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. The flow rate of the gas used as a diluent is preferably 2000 mL / min or less, more preferably 400 mL / min to 800 mL / min.

[0181] The pressure of the gaseous reactants and optional diluents is preferably 0.1 bar to 50 bar, more preferably 0.5 bar to 5 bar, and even more preferably 1 bar to 2 bar. In the presence of gas outflow from the furnace, the outflowing gas can be recycled with or without purging.

[0182] The composition of the product particles can be controlled by monitoring the aggregates and adjusting the reaction conditions based on the obtained information. For example, the aggregates can be monitored using online Raman spectroscopy. Online Raman spectroscopy can provide data indicating whether the CNTs are single-walled or multi-walled. Additionally, data indicating the diameter and crystallinity of the CNTs can also be obtained. The aggregates can also be monitored using online conductivity measurements, gas analysis, opacity measurements of the reaction zone, and / or winding force measurements.

[0183] When removing the aggregates from the reactor, it is preferable to prevent air from entering the reactor. This is especially important when the gas used as a diluent contains hydrogen, for example, from the viewpoint of suppressing the formation of an explosive mixture of hydrogen and air in the reactor.

[0184] The product particles produced in manufacturing method X contain ULMWCNTs. Additionally, depending on the manufacturing conditions, SWCNTs may sometimes be present in addition to MWCNTs.

[0185] Product particles can also be generated via chemical vapor deposition. In the case of product particles generated via chemical vapor deposition, the carbon source, which is a gaseous reactant, reacts in the presence of a catalyst.

[0186] 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, and mixtures of two or more of these).

[0187] As a carbon-containing compound, carbon monoxide, methane, ethylene, or acetylene are preferred.

[0188] The carbon source preferably contains oxygen. Ethanol is a particularly preferred carbon source.

[0189] Oxygen can be introduced into the reactor by other methods, such as by using a carbon source containing diluent gas or water.

[0190] The gaseous reactant, which serves as a carbon source, is preferably injected into the reactor at a rate of 0.01 mL / min to 10 mL / min, and more preferably at a rate of 0.08 mL / min to 0.25 mL / min.

[0191] As catalysts, transition metals, particularly Group VIB chromium (Cr), molybdenum (Mo), tungsten (W), or VIIIB transition metals, are preferred. Specifically, as catalysts, 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, are preferred. Metals from the lanthanides and actinides (e.g., yttrium (Y)) can also be used as catalysts. Fe, Ni, Co, Mo, and mixtures thereof are more preferred, such as mixtures of Ni and Co (mass ratio: 50 / 50), mixtures of Fe and Ni, or mixtures of Fe and Mo.

[0192] Any of these transition metals can be used alone or in combination with any of the other listed transition metals to function as a catalyst for CNT growth. The catalyst is particularly preferably a mixture of two or more of the listed metals.

[0193] The catalyst is preferably formed by the decomposition of a precursor. The precursor is preferably a thermally decomposable, photodecomposable, or plasma-decomposable compound of one or more of the aforementioned metals, such as a carbonyl or cyclopentadienyl organometallic compound. Ferrocene, iron pentacarbonyl, nickel dicene, and cobalt dicene are particularly preferred as precursors. The carbon source preferably contains at least 0.01% by mass of the precursor, preferably 0.2% to 2.5% by mass. In one embodiment, the carbon source contains 0.23% to 2.3% by mass of the precursor.

[0194] The catalyst can be supported on a carrier. Preferred carriers include silica and magnesium oxide.

[0195] The carbon source preferably reacts in the presence of a promoter. Suitable promoters are one or more of sulfur, phosphorus, molybdenum, and organic compounds of these elements. Thiophene is also a preferred promoter. The carbon source preferably contains up to 10% by mass of the promoter. Preferably, the carbon source contains 0.2% to 6% by mass of the promoter. When high or low concentrations of thiophene are used as the promoter, MWCNTs will form.

[0196] For example, MWCNTs can be well formed using ethanol containing 0% or 1.5% to 4.0% by mass of thiophene and 0.5% to 5.0% by mass (especially 2.3% by mass) of ferrocene, at an injection rate of 3.0 mL / h to 12.0 mL / h (especially 7.5 mL / h), a hydrogen flow rate of 400 mL / min to 800 mL / min, and a synthesis temperature of 1100°C to 1180°C.

[0197] According to manufacturing method X, fibrous CNTs with a length of at least 500 μm, for example, at least 1 mm, can be obtained. The fibrous CNTs can take the form of filaments or sheets.

[0198] The length of fibrous CNTs can be controlled, for example, by the winding capability of the mandrel used in manufacturing fibrous CNTs.

[0199] Manufacturing method X preferably includes: a step of reacting a carbon source in the reaction zone of a reactor to generate CNTs; and a step of applying force to the CNTs to cause them to aggregate into aggregates. According to this manufacturing method, fibrous CNTs can be easily manufactured.

[0200] Alternatively, the following methods can be used: after generating MWCNTs containing ULMWCNTs in the reaction zone using the above method, condense them to form MWCNTs containing ULMWCNTs; and continuously extract MWCNTs from the vicinity of the reaction zone.

[0201] Alternatively, the following methods may be employed: generating MWCNTs containing ULMWCNTs in the reaction zone; continuously electrostatically attracting MWCNTs containing ULMWCNTs from the reaction zone; and recovering MWCNTs containing ULMWCNTs.

[0202] =Manufacturing Method Y=

[0203] In this disclosure, as an example of a method for manufacturing CNTs, reference can be made to the manufacturing method described in Japanese Patent Application Publication No. 2021-527611. That is, a manufacturing method including the following steps (hereinafter also referred to as "manufacturing method Y") can be cited: Step (1), supporting a mixture containing a main catalyst precursor and a co-catalyst precursor on γ-Al2O3 to manufacture an active support; Step (2), drying the active support by multi-stage drying including vacuum drying; Step (3), subjecting the dried active support to heat treatment to manufacture a supported catalyst; and Step (4), manufacturing CNTs in the presence of the supported catalyst.

[0204] Process (1)

[0205] In step (1), a mixture containing a main catalyst precursor and a co-catalyst precursor is supported on γ-Al2O3 to produce an active support.

[0206] To ensure that the main catalyst precursor and the co-catalyst precursor are uniformly supported on γ-Al₂O₃, the mixture may further contain a solvent, wherein the main catalyst precursor and the co-catalyst precursor may be dissolved in the solvent. The solvent may be one or more selected from the group consisting of water, methanol, and ethanol, preferably water.

[0207] Due to the high porosity and spinel structure of γ-Al₂O₃, the main catalyst and co-catalyst can be irregularly arranged on γ-Al₂O₃. CNTs grown from the irregularly arranged main catalyst can be fabricated in an entangled manner.

[0208] The main catalyst may be selected from one or more of the group consisting of cobalt, iron, nickel, manganese and chromium, with cobalt being preferred.

[0209] The precursor of the main catalyst can be one or more selected from the group consisting of nitrates, sulfates, carbonates and acetates of the main catalyst, preferably nitrates of the main catalyst.

[0210] The main catalyst precursor can be one or more selected from the group consisting of Co(NO3)2, Co(NO3)2·6H2O, Co2(CO)8, Co2(CO)6[HC=C(C(CH3)3)], Co(CH3CO2)2, Fe(NO3)3, Fe(NO3)2·nH2O, Fe(CH3CO2)2, Ni(NO3)2, Ni(NO3)2·6H2O, Mn(NO3)2, Mn(NO3)2·6H2O, Mn(CH3CO2)2·n(H2O) and Mn(CO)5Br, among which Co(NO3)2·6H2O, Fe(NO3)2·nH2O and Ni(NO3)2·6H2O are preferred.

[0211] A co-catalyst is a substance that improves the dispersibility of the main catalyst and can be one or more selected from the group consisting of vanadium and molybdenum.

[0212] The catalyst precursor can be selected from NH4VO3, NaVO3, V2O5, V(C5H7O2)3, and (NH4)6Mo7O 24 One or more of the group consisting of 4H2O, preferably free from NH4VO3 and (NH4)6Mo7O. 24 One or more of the groups consisting of ·4H2O.

[0213] When the mixture contains two or more co-catalyst precursors, i.e., when it contains both a vanadium precursor and a molybdenum precursor, it can be contained in such a way that the total molar ratio of vanadium and molybdenum to vanadium is 1:0.45 to 1:0.95 or 1:0.5 to 1:0.9, preferably in a way that is 1:0.5 to 1:0.9. When the above conditions are met, the structure of CNTs can be stably maintained, and CNTs with the target pore volume can be manufactured.

[0214] The mixture can contain the main catalyst to the co-catalyst in a molar ratio of 1:0.01 to 1:0.5, 1:0.1 to 1:0.4, or 1:0.1 to 1:0.25, preferably in a molar ratio of 1:0.1 to 1:0.25. Satisfying the above molar ratio improves the dispersibility of the main catalyst and enables the production of CNTs with the target pore volume.

[0215] The mixture may further contain organic acids that inhibit the precipitation of the main catalyst precursor and the co-catalyst precursor.

[0216] 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.

[0217] The mixture may contain organic acids and co-catalyst precursors in a molar ratio of 1:1 to 1:20, 1:2 to 1:10, or 1:3 to 1:6, preferably 1:3 to 1:6. Meeting these ranges provides the advantage that a transparent catalyst metal solution can be produced during catalyst manufacturing, and that a catalyst with suppressed microparticles can be produced during impregnation.

[0218] After step (1), a maturation step may be further included.

[0219] The maturation process can be carried out for 1 to 60 minutes or 10 to 50 minutes. Preferably, it is carried out for 10 to 50 minutes. When the above conditions are met, the main catalyst precursor and the co-catalyst precursor can be adequately supported on γ-Al₂O₃. Furthermore, bubbles present within the support are removed to the maximum extent, and the main catalyst precursor and the co-catalyst precursor can be adequately supported within the micropores of the support.

[0220] Process (2)

[0221] Next, the active support is dried through a multi-stage drying process, including vacuum drying.

[0222] Multi-stage drying can refer to drying processes that include vacuum drying, performed two or more times. Specifically, multi-stage drying can include atmospheric pressure drying and vacuum drying, or it can include only two or more vacuum drying processes.

[0223] Vacuum drying can be carried out at 80℃~300℃ or 120℃~250℃, preferably at 120℃~250℃. When the above conditions are met, the main catalyst precursor, i.e., the coordination compound of the main catalyst, can be easily decomposed to form the main catalyst oxide, and energy consumption can be minimized.

[0224] Vacuum drying can be carried out at 1 mbar to 200 mbar or 30 mbar to 150 mbar, preferably at 30 mbar to 150 mbar. When the above conditions are met, the main catalyst precursor, i.e., the coordination compound of the main catalyst, will be rapidly decomposed and discharged. Therefore, the main catalyst oxide can be formed more easily under vacuum conditions, and energy consumption can be minimized.

[0225] Vacuum drying can be carried out 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.

[0226] On the other hand, in the case of multi-stage drying including atmospheric pressure drying and vacuum drying, atmospheric pressure drying can be carried out before the aforementioned vacuum drying, and solvents that may be present in the active support can be removed by atmospheric pressure drying.

[0227] Drying under normal pressure can be carried out at 80℃~160℃ or 100℃~140℃, preferably at 100℃~140℃. When the above conditions are met, the solvent present in the active support can be completely removed, and energy consumption can be minimized.

[0228] Drying at atmospheric pressure can be carried out at 900 mbar to 1,100 mbar, preferably at 950 mbar to 1,050 mbar. Meeting these conditions ensures thorough removal of the solvent present in the active support while minimizing energy consumption.

[0229] Drying under normal pressure can be carried out over 1 to 12 hours, preferably 3 to 9 hours. When the above conditions are met, the solvent present in the active support can be completely removed, and energy consumption can be minimized.

[0230] On the other hand, in the case where multi-stage drying only includes two or more vacuum drying processes, it can include two or more vacuum drying processes performed at different temperatures. More specifically, it can include one vacuum drying process performed at a first temperature and a second vacuum drying process performed at a second temperature higher than the first temperature.

[0231] Solvents that may be present in the active support can be removed by a single vacuum drying process.

[0232] The first temperature can be 80℃ to 160℃, preferably 100℃ to 140℃. When the above conditions are met, the solvent present in the active support can be completely removed, and energy consumption can be minimized.

[0233] A single vacuum drying process can last from 1 hour to 12 hours, preferably from 3 hours to 9 hours. When the above conditions are met, the solvent present in the active support can be completely removed, and energy consumption can be minimized.

[0234] A single vacuum drying operation can be performed at 1 mbar to 200 mbar, 1 mbar to 150 mbar, or 80 mbar to 150 mbar, preferably at 80 mbar to 150 mbar. Meeting these conditions ensures thorough removal of the solvent from the active support and minimizes energy consumption.

[0235] The explanation of secondary vacuum drying is as described in the above explanation of vacuum drying.

[0236] The second temperature can be 175–300°C, preferably 180–280°C. When the above conditions are met, the main catalyst precursor, i.e., the coordination compound of the main catalyst, can be easily decomposed to form the main catalyst oxide, and energy consumption can be minimized.

[0237] Secondary vacuum drying can be carried out at 1 mbar to 200 mbar, 1 mbar to 150 mbar, or 1 mbar to 70 mbar, more preferably at 1 mbar to 70 mbar. When the above conditions are met, the main catalyst precursor, i.e., the coordination compound of the main catalyst, will be rapidly decomposed and discharged, thus making it easier to form the main catalyst oxide under vacuum conditions and minimizing energy consumption.

[0238] Secondary vacuum drying can be carried out for 10 minutes to 3 hours or 10 minutes to 2 hours, preferably 10 minutes to 2 hours. 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.

[0239] Process (3)

[0240] Next, the dried active support is heat-treated to produce a supported catalyst.

[0241] If heat treatment is performed, a supported catalyst is produced in which the main catalyst and co-catalyst are coated on the surface and pores of γ-Al2O3.

[0242] The heat treatment can be carried out at 600℃~800℃ or 620℃~750℃, preferably at 620℃~750℃. When the above conditions are met, the supported catalyst can be manufactured with the main catalyst and the co-catalyst uniformly coated on the surface and pores of γ-Al2O3, and energy consumption can be minimized.

[0243] The heat treatment can be carried out for 1 hour to 12 hours or 2 hours to 8 hours, preferably 2 hours to 8 hours. When the above time is met, a supported catalyst can be produced in which the catalyst precursor is uniformly coated on the surface and pores of γ-Al2O3.

[0244] Process (4)

[0245] Next, CNTs are manufactured in the presence of a supported catalyst.

[0246] Specifically, CNTs can be manufactured by contacting a supported catalyst with a carbonaceous compound. More specifically, substances synthesized using a chemical vapor phase method can also be used.

[0247] The steps for manufacturing CNTs are described in detail. First, a supported catalyst can be added to a horizontal fixed-bed reactor or a fluidized-bed reactor. Next, at a temperature above the thermal decomposition temperature of the gaseous carbonaceous compound or below the melting point of the catalyst supported on the catalyst, a gaseous carbonaceous compound, or a mixture of a gaseous carbonaceous compound, a reducing gas (e.g., hydrogen), and a carrier gas (e.g., nitrogen), is injected. Through the decomposition of the gaseous carbonaceous compound, CNTs can be grown using a chemical vapor phase synthesis method.

[0248] CNTs manufactured using the chemical vapor deposition method described above exhibit crystal growth directions that are approximately parallel to the tube axis, and sometimes show higher crystallinity of the graphite structure along the tube length. As a result, it is possible to produce CNTs with small unit diameters, high conductivity, and high strength.

[0249] Chemical vapor phase synthesis can be carried out at 600℃~800℃ or 650℃~750℃, preferably at 650℃~750℃. Meeting these temperatures allows for the fabrication of CNTs while minimizing the generation of amorphous carbon.

[0250] As a heat source for the reaction, induction heating, radiant heat, laser, IR, microwave, plasma, surface plasma heating, etc. can be used.

[0251] In addition, 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.

[0252] Carbon-based compounds can be carbon-based compounds with 6 or fewer carbon atoms, or they can be one or more compounds selected from the group consisting of carbon monoxide, methane, ethane, ethylene, ethanol, acetylene, propane, propylene, butane, butadiene, pentane, pentene, cyclopentadiene, hexane, cyclohexane, benzene, and toluene.

[0253] After CNTs are grown through the above-described reaction, a selective cooling process can be performed to further refine the arrangement of the CNTs. Specifically, the cooling process can be carried out through natural cooling accompanied by the removal of the heat source, or by using a cooler.

[0254] The manufacturing methods X and Y described above are just examples; the manufacturing methods of CNTs that can be included in a specific CNT collection are not limited to the methods described above.

[0255] [Carbon nanotube dispersion]

[0256] The carbon nanotube dispersions (specific CNT dispersions) disclosed herein comprise specific CNT aggregates and a dispersion medium.

[0257] In specific CNT dispersions, the specific CNT aggregates disclosed herein exhibit good dispersibility in the dispersion medium and excellent conductivity.

[0258] Certain CNT dispersions are preferred for use in forming electrodes, forming transparent conductive films, resin additives, conductive inks, coating agents, antistatic agents, paints, etc.

[0259] <Specific CNT Collection>

[0260] The specific CNT aggregate contained in a particular CNT dispersion is the same as the specific CNT aggregate involved in this disclosure, and therefore description is omitted here.

[0261] <Dispersion Medium>

[0262] The dispersion medium preferably contains water, and more preferably contains water as the main component.

[0263] "Contains water as a main component" means that water accounts for more than 50% of the dispersion medium 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 for example, it can also be 100% by mass.

[0264] There are no particular limitations on the water, but distilled water, ion-exchanged water, or pure water are preferred in terms of having fewer impurities.

[0265] The dispersion medium can be a mixture of water and a hydrophilic solvent.

[0266] Examples of hydrophilic solvents include carbonate compounds such as ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, and butenyl carbonate; ether compounds such as tetrahydrofuran; ketone compounds such as acetone; lower alcohol compounds such as methanol and ethanol; and solvents such as acetonitrile.

[0267] 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.

[0268] In addition to specific CNT aggregates and dispersion media, a particular CNT dispersion may further contain other components that can be used in the dispersion.

[0269] Other components may include dispersants, defoamers, antistatic agents, and conductive additives other than those disclosed herein. Additionally, it may contain trace amounts of impurities, i.e., so-called unavoidable impurities.

[0270] <Dispersant>

[0271] To further improve the dispersibility and dispersion stability of specific CNT aggregates, carbon nanotube dispersions may contain dispersants.

[0272] There are no particular limitations on the dispersant; for example, various surfactants can be cited. Additionally, polymers such as resins can also be cited as dispersants.

[0273] Surfactants are preferred as dispersants.

[0274] Surfactants can be either ionic or nonionic, without any particular limitation.

[0275] In a specific CNT dispersion, a single surfactant may be used alone, or two or more surfactants may be used in combination.

[0276] Examples of ionic surfactants include anionic surfactants, cationic surfactants, and amphoteric surfactants.

[0277] Examples of anionic surfactants include aromatic sulfonic acid surfactants such as alkylbenzene sulfonates (e.g., dodecylbenzene sulfonic acid) and dodecylphenyl ether sulfonates; ether sulfate surfactants; phosphate surfactants; and carboxylic acid surfactants.

[0278] Examples of cationic surfactants include alkylamine salts and quaternary ammonium salts.

[0279] Examples of amphoteric surfactants include alkyl betaine surfactants and amine oxide surfactants.

[0280] As ionic surfactants, ionic surfactants having aromatic rings (so-called aromatic ionic surfactants) are preferred, and aromatic sulfonic acid surfactants such as alkylbenzene sulfonates and dodecyl phenyl ether sulfonates are more preferred.

[0281] Aromatic ionic surfactants tend to excel in dispersing ability, dispersion stability, and high concentration of multi-walled carbon nanotubes.

[0282] Examples of nonionic surfactants include sorbitan fatty acid esters and polyoxyethylene sorbitan fatty acid esters; fatty acid esters such as polyoxyethylene resin esters and polyoxyethylene diethyl fatty acid esters; ethers such as polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, and polyoxyethylene-polypropylene glycol; and aromatic nonionic surfactants such as polyoxyalkylene octylphenyl ether, polyoxyalkylene nonylphenyl ether, polyoxyalkylene dibutylphenyl ether, polyoxyalkylene styrene phenyl ether, polyoxyalkylene benzylphenyl ether, polyoxyalkylene diphenyl ether, polyoxyalkylene cumylphenyl ether, and polyoxyalkylene phenyl ether.

[0283] As a nonionic surfactant, an ionic surfactant having an aromatic ring (so-called aromatic nonionic surfactant) is preferred, polyoxyalkylene phenyl ether is more preferred, and polyoxyethylene phenyl ether is even more preferred.

[0284] Aromatic nonionic surfactants tend to excel in dispersing ability, dispersion stability and high concentration of multi-walled carbon nanotubes.

[0285] Other dispersants that excel in dispersing ability, dispersion stability, and high concentration of CNTs include Demol N, Demol RN, and Demol T (manufactured by Kao Corporation) of sodium β-naphthalenesulfonic acid formaldehyde condensate; Brij S 100 (manufactured by Sigma-Aldrich) of polyoxyethylene stearyl ether; polyvinylpyrrolidone K30 (manufactured by Fujifilm and Kojun Pharmaceutical Co., Ltd., for example); carboxymethyl cellulose (CMC) (manufactured by Daicel Miraizu Co., Ltd., for example); sodium deoxycholate (manufactured by Fujifilm and Kojun Pharmaceutical Co., Ltd., for example); and SOLSPERSE. TM W100, SOLSPERSE TM W150 (manufactured by Lubrizol Corporation, Japan), etc. From the viewpoint of its superior dispersion ability, dispersion stability and high concentration of multi-walled carbon nanotubes, CMC is particularly preferred.

[0286] When a specific CNT dispersion contains a dispersant, there is no particular limitation on the amount of dispersant used. It can be appropriately set according to the type of dispersant, the amount of multi-walled carbon nanotubes, the amount of dispersion medium, etc.

[0287] [Method for manufacturing specific CNT dispersions]

[0288] There are no particular limitations on the manufacturing method of a specific CNT dispersion.

[0289] A specific CNT dispersion can be manufactured by dispersing a specific CNT aggregate in a dispersion medium. That is, a specific CNT dispersion can be manufactured by a method that includes a step of dispersing the specific CNT aggregate in a dispersion medium (also known as a "dispersion step").

[0290] The dispersion media that can be used in the dispersion process are as described above.

[0291] There are no particular restrictions on the method of dispersion.

[0292] Examples of dispersion methods include those using dispersion devices such as agitators, homogenizers, colloid mills, jet mixers, dissolving machines, paint conditioners, paint emulsifying devices, jet mills, and ultrasonic devices.

[0293] In addition, as a dispersion method, examples include the use of well-known pulverizing means, such as ball mills (e.g., ball mills, vibratory ball mills, planetary ball mills, bead mills, etc.), sand mills, colloid mills, jet mills, roller mills, vertical or horizontal agitator mills, grinding mills, colloid mills, three-roll mills, pearl mills, super mills, impeller mills, dispersers, KD mills, Dynatron, pressure kneaders, and other dispersing machines.

[0294] As a dispersion method, jet milling is preferred, and wet jet milling is more preferred.

[0295] A wet jet mill is a dispersion device that uses a mixture in a solvent as a high-speed flow, pressurized through nozzles arranged in a sealed pressure vessel. In a wet jet mill, multi-walled carbon nanotubes are dispersed due to collisions between opposing flows within the pressure vessel, collisions with the vessel walls, turbulence generated by the high-speed flow, and shear flow. Ultra-high pressure homogenizers manufactured by Tsunemitsu Corporation (models: NAGS20, NAGS100, JAGS200, NAGS1000, etc.) can be suitable as wet jet mills. However, wet jet mills are not limited to these models.

[0296] When the above-mentioned ultra-high pressure homogenizer is used as a dispersion device, the dispersion processing pressure is preferably 10MPa to 250MPa.

[0297] The method for manufacturing a specific CNT dispersion may include a step of drying the specific CNT aggregate (also known as a "drying step") prior to the dispersion step described above.

[0298] When moisture adheres to CNTs, the surface tension of water causes the CNTs to easily adhere to each other, which may reduce dispersibility. Therefore, by performing a drying process of the conductive additive before the dispersion process, the moisture adhering to the CNTs is removed, and the adhesion of multi-walled carbon nanotubes caused by moisture is suppressed, which can further improve the dispersibility of CNTs in the dispersion medium.

[0299] There are no particular restrictions on the drying method.

[0300] Examples of drying methods include heating drying, vacuum drying, and heated vacuum drying.

[0301] As a drying method, heating and vacuum drying is preferred.

[0302] There is no particular limitation on the drying temperature, but it is preferably 40°C to 100°C.

[0303] There is no particular limitation on the drying time, which can be appropriately set according to the drying temperature, the degree of moisture adhesion of the multi-walled carbon nanotubes in this disclosure, etc.

[0304] The following shows a specific example of the manufacture of a CNT dispersion, but the manufacture of a specific CNT dispersion is not limited to the following.

[0305] <Manufacturing Example 1: Manufacturing Example of Dispersion>

[0306] 0.040 g of the specific CNT aggregate disclosed herein is measured and added to a three-necked flask. A large excess of ion-exchanged water (e.g., 20 mL) as the dispersion medium is added to the flask, and the mixture is stirred at room temperature (25°C). At this time, a known dispersant (e.g., carboxymethyl cellulose) may be added as appropriate. Next, the conductive additive is dispersed in the dispersion medium using a known dispersion apparatus (e.g., an ultrasonic irradiation device or a wet jet mill). The resulting dispersion is further stirred at room temperature using a magnetic stirrer for an extended period (e.g., 1 hour to 48 hours). Thus, a specific CNT dispersion is obtained.

[0307] [Conductive Materials]

[0308] The conductive materials disclosed herein comprise specific CNT aggregates.

[0309] The specific CNT aggregates contained in the conductive materials disclosed herein, as previously described, are suitable as conductive additives due to their excellent conductivity when formed into dispersions.

[0310] Since the conductive material disclosed herein contains the specific CNT aggregates disclosed herein, it has excellent conductivity and can effectively impart high conductivity to the object to be used.

[0311] The conductive materials disclosed herein may contain known conductive additives such as graphite and Ketjen black. Furthermore, the conductive materials disclosed herein may contain CNTs other than specific CNT aggregates.

[0312] The conductive material disclosed herein can be used as one of the electrode materials. As an example of an electrode formed using this electrode material, the electrode of a secondary battery can be cited. Hereinafter, an embodiment of the electrode and a secondary battery having the electrode will be described.

[0313] [Electrodes and secondary batteries]

[0314] The electrodes disclosed herein comprise electrode active materials and conductive materials as described herein. The secondary batteries disclosed herein possess the electrodes described herein.

[0315] Because the electrodes disclosed herein contain the conductive materials disclosed herein, the formation of conductive pathways within the electrodes is excellent. Therefore, the secondary batteries disclosed herein exhibit excellent cycle characteristics.

[0316] The following describes one embodiment of the electrode and the secondary battery having the electrode.

[0317] <Electrode>

[0318] Electrodes may contain specific CNT aggregates.

[0319] In electrodes, specific CNT aggregates can function as conductive aids.

[0320] The CNT aggregates contained in the electrodes described below are synonymous with specific CNT aggregates and have the same preferred method, so the description of CNT aggregates is omitted below.

[0321] The electrode can be either a positive electrode or a negative electrode.

[0322] An 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.

[0323] There are no particular restrictions on the current collector as long as it does not induce chemical changes in the battery and has electrical conductivity.

[0324] As a current collector, it can be, for example, copper, stainless steel, aluminum, nickel, titanium, sintered carbon, or a material whose surface has been treated with carbon, nickel, titanium, silver, etc. Specifically, transition metals such as copper and nickel, which have good adsorption properties for carbon, can also be used as current collectors.

[0325] The electrode active material layer may contain electrode active materials.

[0326] The electrode active material is preferably electrode active material particles.

[0327] When the electrode is a positive electrode, there are no particular limitations on the electrode active material, and the electrode active material layer may contain the positive electrode active material commonly used in positive electrode materials.

[0328] Specifically, examples of positive electrode active materials include layered compounds such as lithium cobalt oxide (LiCoO2) and lithium nickel oxide (LiNiO2), compounds replaced by one or more transition metals; lithium iron oxides such as LiFe3O4; and compounds with the chemical formula Li 1+ c1 Mn 2-c1 Lithium manganese oxides such as O4 (0≦c1≦0.33), LiMnO3, LiMn2O3, and LiMnO2; lithium copper oxides (Li2CuO2); vanadium oxides such as LiV3O8, V2O5, and Cu2V2O7; and those with the chemical formula LiNi 1-c2 M c2O2 (wherein M is at least one selected from the group consisting of Co, Mn, Al, Cu, Fe, Mg, B and Ga, and 0.01≦c2≦0.66 is satisfied.) represented Ni-site type lithium nickel oxide; the chemical formula LiMn 2-c3 M c3 O2 (wherein M is at least one selected from the group consisting of Co, Ni, Fe, Cr, Zn and Ta, and 0.01≦c3≦0.1 is satisfied.), or Li2Mn3MO8 (wherein M is at least one selected from the group consisting of Fe, Co, Ni, Cu and Zn.) represented lithium-manganese composite oxide; LiMn2O4 in which part of Li in the chemical formula is substituted with alkaline earth metal ions, and the like.

[0329] When the electrode is a negative electrode, the electrode active material is not particularly limited, and the electrode active material layer may contain a negative electrode active material commonly used in negative electrode electrode materials.

[0330] Specifically, the negative electrode active material may contain graphite-based active material particles or silicon-based active material particles.

[0331] As the graphite-based active material particles, at least one selected from the group consisting of artificial graphite, natural graphite, graphitized carbon fibers, and graphitized mesophase carbon microbeads can be used. By using artificial graphite as the graphite-based active material particles, rate characteristics can be improved.

[0332] As the silicon-based active material particles, at least one selected from the group consisting of Si, SiOx (0<x<2), Si-C composite, and Si-Y alloy (herein, 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.) can be used. By using the silicon-based active material particles, the high capacity of the battery can be achieved.

[0333] The electrode active material layer may further contain a binder.

[0334] The binder is not particularly limited, and the electrode active material layer may contain a binder commonly used in electrode materials.

[0335] Examples of the binder include those selected from the group consisting of polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF -At least one polymer from the group consisting of co-HFP, polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene propylene diene monomer (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, and polyacrylic acid, and polymers in which hydrogen atoms of these polymers are replaced by Li, Na, Ca, etc.

[0336] Secondary batteries

[0337] A secondary battery can be constructed by comprising a negative electrode, a positive electrode, a separator between the positive and negative electrodes, and an electrolyte. At least one of the positive and negative electrodes is an electrode formed using a conductive material containing specific CNT aggregates as the electrode material.

[0338] The separator separates the negative electrode from the positive electrode and provides a pathway for lithium ions to move. Generally, there are no particular limitations on the material used as a separator in a secondary battery. Preferably, the separator has low resistance to ion movement in the electrolyte and excellent electrolyte impregnation capacity.

[0339] As a diaphragm, a specific example is a porous polymer film.

[0340] Porous polymer films can be porous polymer films made from polyolefin polymers such as ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, and ethylene / methacrylate copolymer, or they can be laminated structures formed by stacking two or more of these films.

[0341] Alternatively, the diaphragm can be a typical porous nonwoven fabric, such as a nonwoven fabric composed of high-melting-point glass fiber or polyethylene terephthalate fiber. Furthermore, to ensure heat resistance or mechanical strength, the diaphragm can also be a material coated with ceramic components or polymers.

[0342] The diaphragm can be optionally designed as a single-layer or multi-layer structure.

[0343] There are no particular limitations on electrolytes. Examples of electrolytes that can be used in the manufacture of lithium secondary batteries include organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, and molten inorganic electrolytes.

[0344] Specifically, electrolytes can contain non-aqueous organic solvents and metal salts.

[0345] Examples of non-aqueous organic solvents include N-methyl-2-pyrrolidone, propylene carbonate, ethylene carbonate, butenyl carbonate, dimethyl carbonate, diethyl carbonate, γ-butyrolactone, 1,2-dimethoxyethane, tetrahydroxyfuran, 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, triphosphate, trimethoxymethane, dioxolane derivatives, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolium ketone, propylene carbonate derivatives, tetrahydrofuran derivatives, ethers, methyl propionate, and ethyl propionate.

[0346] Among carbonate-based organic solvents, ethylene carbonate and propylene carbonate, being cyclic carbonates, are preferred as non-aqueous organic solvents due to their high dielectric constant and ability to effectively dissociate lithium salts. Furthermore, for the purpose of obtaining an electrolyte with high conductivity, it is even more preferable to use a mixture of low-viscosity, low-dielectric-constant linear carbonates such as dimethyl carbonate and diethyl carbonate in appropriate proportions as a non-aqueous organic solvent.

[0347] The metal salt can be a lithium salt.

[0348] Lithium salts are substances that are readily soluble in non-aqueous solutions.

[0349] For example, F can be used as the anion portion of lithium salts. - Cl - I - NO3 - N(CN)2 - BF4 - ClO4 - PF6 - (CF3)2PF4 - (CF3)3PF3 - (CF3)4PF2 - (CF3)5PF - (CF3)6P - CF3SO3 - CF3CF2SO3 - (CF3SO2)2N - (FSO2)2N - CF3CF2(CF3)2CO - (CF3SO2)2CH - (SF5)3C - (CF3SO2)3C - CF3(CF2)7SO3- CF3CO2 - CH3CO2 - SCN - and (CF3CF2SO2)2N - .

[0350] In addition to non-aqueous organic solvents and metal salts, the electrolyte may further contain one or more additives such as halogenated alkylene carbonate compounds such as ethylene difluorocarbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ethers, ethylenediamine, n-glycol dimethyl ether (glyme), triammonium hexaphosphate, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidinyl ethers, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, and aluminum trichloride, for purposes such as improving battery life characteristics, suppressing battery capacity reduction, and increasing battery discharge capacity.

[0351] The aforementioned secondary batteries can be used to construct battery modules that include secondary batteries as unit cells, and battery packs that include battery modules.

[0352] Battery modules and battery packs can be used as power sources for medium to large-sized devices selected from groups consisting of electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, and energy storage systems.

[0353] The planar aggregate disclosed herein is a carbon nanotube aggregate comprising carbon nanotubes with a maximum length of 1000 μm to 30000 μm.

[0354] The proportion of carbon nanotubes with a maximum length of 1000 μm to 30000 μm contained in the planar aggregate of this disclosure is typically 1% by mass or more. The planar aggregate of this disclosure may also include carbon nanotube aggregates containing carbon nanotubes with a maximum length of less than 1000 μm, carbon nanotube aggregates that do not contain carbon nanotubes with a maximum length of 1000 μm to 30000 μm, and other components.

[0355] The planar aggregate disclosed herein can be manufactured by dispersing a carbon nanotube aggregate containing carbon nanotubes with a maximum length of 1000 μm to 30000 μm, or the carbon nanotube aggregate and other components such as a carbon nanotube aggregate containing carbon nanotubes with a maximum length of less than 1000 μm, in water or other fluids, and filtering it once or twice or more, thereby enabling it to be configured as a planar aggregate in the form of a nonwoven fabric, for example.

[0356] A planar assembly as an example of this disclosure is a thin film.

[0357] The planar assemblies disclosed herein can be used, for example, in filters, electromagnetic wave shields, and protective films for extreme ultraviolet (EUV) radiation.

[0358] [Composition]

[0359] The compositions disclosed herein are compositions comprising the CNT aggregates disclosed herein and at least one selected from the group consisting of a dispersion medium, resin, ceramic and concrete.

[0360] As a dispersion medium, it is preferable to contain water, more preferably to contain water as the main component, and even more preferably water.

[0361] N-methylpyrrolidone is a preferred solvent, second only to water.

[0362] Examples of resins include thermoplastic resins and thermosetting resins, with preferred resins being olefin-based resins, polycarbonate-based resins, polyester-based resins, polyamide-based resins, thermoplastic polyurethane resins, polysulfone-based resins, and silicone resins.

[0363] As ceramics, examples include crystalline ceramics and amorphous ceramics.

[0364] As for concrete, Portland cement concrete is an example.

[0365] The compositions disclosed herein may further include other components such as water and organic solvents.

[0366] In the compositions disclosed herein, when the content of the CNT aggregate is set to 100 parts by mass, the content of at least one selected from the group consisting of resin, ceramic and concrete is generally 10 to 1,000,000 parts by mass, preferably 100 to 100,000 parts by mass, more preferably 1,000 to 40,000 parts by mass. In addition, when other components are included, the content is preferably 1 to 10,000 parts by mass, more preferably 10 to 1,000 parts by mass.

[0367] In the compositions disclosed herein, the CNT aggregate, resin, ceramic, concrete, and other components may each contain one or more of the following:

[0368] <Method for manufacturing the composition>

[0369] The compositions disclosed herein can be manufactured, for example, by incorporating the CNT aggregates of this disclosure into a resin, ceramic, or pre-hardened concrete. The resin may be in the form of a powder, granules, solution, or dispersion. The ceramic may be in the form of a powder, precursor solution, or dispersion.

[0370] The compositions disclosed herein can also be manufactured, for example, by dispersing the CNT dispersion disclosed herein in a solution of resin, a ceramic precursor or dispersion, or in concrete before hardening and then molding it.

[0371] <Uses of the Composition>

[0372] The compositions disclosed herein are useful, for example, as structural materials, conductive materials, thermal management materials, and antistatic materials, when they contain resin or ceramics.

[0373] The compositions disclosed herein are useful as lightweight, durable building materials, or as energy storage devices (impregnated with electrolytes, if necessary), when they contain concrete.

[0374]

Example

[0375] The following examples illustrate specific CNT aggregates and dispersions containing such CNT aggregates as described in this disclosure. Without departing from its spirit, the aggregates and dispersions of this disclosure are not limited to the following examples.

[0376] In addition, unless otherwise stated, “%” means “mass%” and “ppm” means “mass ppm”.

[0377] (Example 1)

[0378] 1. Manufacturing of sheet-like CNT aggregate 1

[0379] The sheet-like CNT aggregate 1 was fabricated by a suspension catalyst method (CVD) that directly interacts with the self-assembly of CNT bundles in the gas phase.

[0380] First, ferrocene, as a precursor for a metal catalyst containing Fe atoms, and thiophene, as a promoter, are introduced into a continuous flow of carrier gas in a cross-flow reactor where the temperature is controlled between 400℃ and 700℃. A mixture of nitrogen and argon is used as the carrier gas. The flow rate of the carrier gas is set to 30,000 sccm (standard cubic centimeters per minute).

[0381] By maintaining the temperature within the transverse reactor within the aforementioned range, the metal catalyst precursor is generated as a particulate metal catalyst. The region where the metal catalyst is generated is referred to as the first temperature zone.

[0382] Next, methane, serving as a carbon source, is released in the carrier gas flow. The metal catalyst and carbon source are then supplied to a second temperature zone downstream of the first temperature zone, where the temperature is controlled at 1400°C. The second temperature zone is maintained at a temperature sufficient to generate carbon nanotube aggregates.

[0383] In the second temperature zone, an electric field is generated within the temperature-controlled flow reactor, thereby generating aggregates of CNTs.

[0384] The aggregates of CNTs are discharged continuously through the outlet of a flow-through reactor with the temperature controlled between 100°C and 500°C, and the sheet-like CNT aggregates are collected by continuous discharge.

[0385] The resulting sheet-like CNT aggregate 1 contains MWCNTs.

[0386] To adjust the content of Fe atoms, Co atoms, Na atoms, and K atoms, the obtained sheet-like CNT aggregate was washed with pure water for 10 seconds to obtain sheet-like CNT aggregate 1 as a specific CNT aggregate.

[0387] 2. Preparation of CNT Dispersion 1

[0388] The following materials were mixed and pre-dispersed by processing them for 1 hour using an Ace homogenizer manufactured by Nippon Seiki Co., Ltd., to obtain a pre-dispersion liquid 1. In order to prevent the sheet-like CNT aggregate 1 from tangling on the blades of the homogenizer, the sheet-like CNT aggregate 1 was cut into small fragments of 1cm × 1cm with scissors before mixing.

[0389] (Dispersion composition)

[0390] • The above-obtained sheet-like CNT aggregate 1 1.1g

[0391] ·CARBOXYMETHYL CELLULOSE SODIUM SALT HIGH VISCOSITY (manufactured by MP Biomedicals) 1.65g

[0392] ·Pure water 547.25g

[0393] Using a high-pressure homogenizer (model: NAGS100) manufactured by Tokimitsu Corporation as a wet jet mill, the pre-dispersion liquid 1 was subjected to primary dispersion under the following conditions to obtain CNT dispersion 1 as a specific CNT dispersion.

[0394] (Dispersion conditions)

[0395] Nozzle diameter: 0.22mm

[0396] Pressure: 85MPa

[0397] Number of times: 8

[0398] Method: Looping

[0399] 3. Evaluation

[0400] 3-1. The content of Fe atoms, Co atoms, Na atoms, and K atoms relative to the total mass of the aggregate.

[0401] The contents of Fe, Co, Na, and K atoms in the sheet-like CNT aggregate 1 of Example 1 were determined using an inductively coupled plasma mass spectrometry (ICP-MS) apparatus (PerkinElmer, NexION 2000C). The sheet-like CNT aggregate 1 was pretreated by low-temperature ashing / acid dissolution. The results showed that the Fe atom content relative to the total mass of the aggregate in the sheet-like CNT aggregate 1 of Example 1 was 56,000 ppm, the Co atom content was less than 10 ppm (below the detection limit), the Na atom content was 100 ppm, and the K atom content was 500 ppm. That is, the total Fe and Co atom content was 56,000 ppm, and the total Na and K atom content was 600 ppm.

[0402] 3-2. Volume resistivity

[0403] The sheet-like CNT aggregate 1 from Example 1 was pulverized using a cryogenic pulverization method. Using a Loresta apparatus (product name: Powder Resistance Measurement System MCP-PD51, Low Resistivity Meter Loresta-GP, Powder Low Resistance Probe MCP-PD511 (Constant Current Application Method 4 Probe Method), all manufactured by Nitto Seiko Analytical Technology Co., Ltd.), the pulverized sheet-like CNT aggregate 1 was introduced into the powder resistivity measurement probe unit. Using the accompanying hydraulic pump, pressure was applied at 1 kN and 20 kN. After reaching the target load, the volume resistivity (Ω·cm) was measured.

[0404] As a result, the volume resistivity is 1.7 × 10⁻⁶ at 1 kN. -2 Ω·cm, which is 5.0 × 10⁻⁶ at 20 kN. -3 Ω·cm. The ratio of the volume resistivity at 20 kN to that at 1 kN (referred to as "resistivity ratio" in Table 1) is 0.29.

[0405] 3-3. Electrical conductivity of dispersions

[0406] One drop of CNT dispersion was added to a glass substrate (10cm × 10cm), and a film was formed using a stainless steel applicator with a gap size of 150μm. The film was then dried on a hot plate at 110°C for 10 minutes.

[0407] The surface resistivity of the membrane was measured using a Loresta GXII sensor manufactured by Nitto Seiko Analytical Technology Co., Ltd. Measurements were taken at five locations on the membrane, and the average of the five values ​​was used as the surface resistivity.

[0408] As a result, the surface resistivity is 164.42 Ω / □.

[0409] 3-4. Confirmation of the bundle structure

[0410] The sheet-like CNT assembly 1 of Example 1 was observed using SEM (device name: S-4800, manufactured by Hitachi High Technology Co., Ltd.), and the result confirmed that it contained a bundle structure. The length was measured at 20 locations and the average value was calculated. The width of the bundle structure was 70 nm.

[0411] 3-5. Pore volume

[0412] Pore ​​volume was measured using a gas adsorption capacity measuring device (product name "BELSORP-miniII", manufactured by MicrotracBEL).

[0413] The sheet-like CNT aggregate 1 obtained in Example 1 was used as the sample for measurement.

[0414] The pore volume was determined after the sheet-like CNT aggregate 1 was vacuum degassed at 300°C for 3 hours using a pretreatment device (product name "BELPREP-vacII", manufactured by MicrotracBEL).

[0415] For the sheet-like CNT aggregate 1 after vacuum degassing, nitrogen-based adsorption-desorption isotherms were determined using the constant volume method.

[0416] The measurement temperature was set to 77 K, the adsorbate to nitrogen, the saturated vapor pressure to the measured value, and the adsorbate cross-sectional area to 0.162 nm. 2 The waiting time after reaching adsorption equilibrium is set to 500 seconds.

[0417] The BJH method was used to calculate the pore volume based on the obtained adsorption-desorption isotherms.

[0418] As a result, the pore volume of the sheet-like CNT aggregate 1 was 2.06 cm³. 3 / g.

[0419] The evaluation results are shown in Table 1. In addition, in the section on bundle structure confirmation, "Yes" is recorded when a bundle structure is confirmed, and "-" is recorded when it is not confirmed.

[0420] (Example 2)

[0421] 1. Manufacturing of fibrous CNT aggregates 2

[0422] The fibrous CNT aggregate 2, like the sheet-like CNT aggregate 1, was also prepared by a suspension catalyst method (CVD) in which the CNT bundles directly interact with each other in the gas phase through self-assembly.

[0423] First, ferrocene, as a precursor for a metal catalyst containing Fe atoms, and thiophene, as a promoter, are introduced into a continuous flow of carrier gas within a cross-flow reactor where the temperature is controlled between 400℃ and 700℃. A mixture of nitrogen and argon is used as the carrier gas. The carrier gas flow rate is set to 30,000 sccm.

[0424] By maintaining the temperature within the transverse reactor within the aforementioned range, the metal catalyst precursor is generated as a particulate metal catalyst. The region where the metal catalyst is generated is referred to as the first temperature zone.

[0425] Next, methane, serving as a carbon source, is released in the carrier gas flow. The metal catalyst and carbon source are then supplied to a second temperature zone downstream of the first temperature zone, where the temperature is controlled at 1400°C. The second temperature zone is maintained at a temperature sufficient to generate carbon nanotube aggregates.

[0426] In the second temperature zone, an electric field is generated within the temperature-controlled flow reactor, thereby generating aggregates of fibrous CNTs.

[0427] The carbon nanotube aggregates are discharged continuously through the outlet of a flow-through reactor with the temperature controlled between 100°C and 500°C, and the fibrous CNT aggregates are collected by continuous discharge.

[0428] The resulting fibrous CNT aggregates contain MWCNTs.

[0429] To adjust the content of Fe, Co, Na and K atoms, the obtained fibrous CNT aggregate was washed with pure water for 10 seconds to obtain fibrous CNT aggregate 2.

[0430] 2. Preparation of CNT Dispersion 2

[0431] Using the obtained fibrous CNT aggregate 2, a CNT dispersion 2 was obtained in the same manner as in Example 1.

[0432] 3. Evaluation

[0433] The fibrous CNT aggregate 2 and CNT dispersion 2 of Example 2 were evaluated in the same manner as in Example 1. The evaluation results are shown in Table 1.

[0434] (Example 3)

[0435] 1. Manufacturing of sheet-like CNT aggregate 3

[0436] The sheet-like CNT aggregates obtained in Example 1 were immersed in a polytetrafluoroethylene (PTFE) tray containing hydrochloric acid (manufactured by Fujifilm and Kojun Chemical Co., Ltd., reagent grade) for 24 hours. Subsequently, the sheet-like CNT aggregates were removed from the tray and rinsed with deionized water until the pH of the rinsing water reached 7, yielding sheet-like CNT aggregate 3.

[0437] 2. Preparation of CNT Dispersion 3

[0438] Using the obtained sheet-like CNT aggregate 3, a CNT dispersion 3 was obtained in the same manner as in Example 1.

[0439] 3. Evaluation

[0440] The sheet-like CNT aggregate 3 and CNT dispersion 3 of Comparative Example 1 were evaluated in the same manner as in Example 1. The evaluation results are shown in Table 1.

[0441] (Comparative Example 1)

[0442] 1. Preparation of powdered CNT aggregate 4

[0443] As a powdered CNT assembly 4, “multi-walled carbon nanotubes” (catalog number: 901019, 50-90nm diameter, >95% carbon basis, manufactured by Sigma-Aldrich) were prepared.

[0444] 2. Preparation of CNT Dispersion 4

[0445] Using the prepared powdered CNT aggregate 4, a CNT dispersion 4 was obtained in the same manner as in Example 1.

[0446] 3. Evaluation

[0447] The powdered CNT aggregate 4 and CNT dispersion 4 of Comparative Example 1 were evaluated in the same manner as in Example 1. The evaluation results are shown in Table 1.

[0448] (Comparative Example 2)

[0449] 1. Preparation of powdered CNT aggregate 5

[0450] As a powdered CNT assembly 5, "multi-walled carbon nanotubes" (catalog number: FT7000, manufactured by C-nano Corporation) were prepared.

[0451] 2. Preparation of CNT Dispersion 5

[0452] Using the prepared powdered CNT aggregate 4, a CNT dispersion 5 was obtained in the same manner as in Example 1.

[0453] 3. Evaluation

[0454] The powdered CNT aggregate 5 and CNT dispersion 5 of Comparative Example 2 were evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0455] (Comparative Example 3)

[0456] 1. Preparation of powdered CNT aggregate 6

[0457] As a powdered CNT aggregate 6, prepare "single-walled carbon nanotubes" (catalog number: TUBALL). TM (Made by OCSiAl Company).

[0458] 2. Preparation of CNT Dispersion 6

[0459] Using the prepared powdered CNT aggregate 6, a CNT dispersion 6 was obtained in the same manner as in Example 1.

[0460] 3. Evaluation

[0461] The powdered CNT aggregate 6 and CNT dispersion 6 of Comparative Example 3 were evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0462] (Comparative Example 4)

[0463] 1. Preparation of powdered CNT aggregate 7

[0464] As a powdered CNT assembly 7, “multi-walled carbon nanotubes” (catalog number: FT6120, manufactured by C-nano Corporation) were prepared.

[0465] 2. Preparation of CNT Dispersion 7

[0466] Using the prepared powdered CNT aggregate 7, a CNT dispersion 7 was obtained in the same manner as in Example 1.

[0467] 3. Evaluation

[0468] The powdered CNT aggregate 7 and CNT dispersion 7 of Comparative Example 4 were evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0469] Table 1

[0470]

[0471] As shown in Table 1, the CNT dispersion obtained by dispersing the CNT aggregates of the examples has good conductivity.

[0472] On the other hand, the CNT aggregates of Comparative Examples 1 and 2, whose combined Na and K atom content was less than 50 ppm or more than 1000 ppm, and whose volume resistivity at 20 kN to volume resistivity at 1 kN ratio was less than 0.21, had problems with the conductivity of the CNT dispersions obtained by preparing them into dispersions. It can be seen that the CNT aggregates of Comparative Examples 1 and 2 are poor conductive materials.

[0473] Furthermore, the CNT aggregate of Comparative Example 3, with a combined Fe and Co atom content greater than 100,000 ppm and a combined Na and K atom content greater than 1,000 ppm, and the CNT aggregate of Comparative Example 4, with a combined Fe and Co atom content less than 2,000 ppm, both exhibited problems in the conductivity of the CNT dispersions obtained by preparing them into dispersions. It is evident that the CNT aggregates of Comparative Examples 3 and 4 are poor conductive materials.

Claims

1. A carbon nanotube aggregate that satisfies the following conditions (1), (2) and (3), (1) Containing at least one of Fe atoms and Co atoms, wherein the total content of Fe atoms and Co atoms relative to the total mass of the carbon nanotube assembly is 2,000 ppm to 100,000 ppm; (2) Containing at least one of Na atoms and K atoms, wherein the total content of Na atoms and K atoms is 50 ppm to 1000 ppm by mass relative to the total mass of the carbon nanotube assembly; (3) The ratio of volume resistivity under 20kN pressure to volume resistivity under 1kN pressure is greater than 0.

21.

2. The carbon nanotube assembly according to claim 1, comprising a bundle structure.

3. The carbon nanotube assembly of claim 1 or claim 2, wherein, Pore volume is 0.60 cm 3 / g ~ 3.20 cm 3 / g.

4. A carbon nanotube dispersion comprising the carbon nanotube aggregate and dispersion medium as described in claim 1 or claim 2.

5. A conductive material comprising the carbon nanotube assembly of claim 1 or claim 2.

6. An electrode comprising an electrode active material and the conductive material of claim 5.

7. A secondary battery comprising the electrode as described in claim 6.

8. A planar aggregate, which is the carbon nanotube aggregate according to claim 1 or claim 2. The carbon nanotube assembly comprises carbon nanotubes with a maximum length of 1000 μm to 30000 μm.

9. A filter that uses the planar assembly of claim 8.

10. An electromagnetic wave shielding body that uses the planar assembly as described in claim 8.

11. A protective film for extreme ultraviolet radiation, which uses the planar assembly as described in claim 8.

12. A composition comprising a carbon nanotube aggregate satisfying conditions (1) and (2) below, and at least one selected from the group consisting of a dispersion medium, a resin, a ceramic, and concrete. (1) Containing at least one of Fe atoms and Co atoms, wherein the total content of Fe atoms and Co atoms is 2,500 ppm to 60,000 ppm relative to the total mass of the carbon nanotube assembly; (2) Containing at least one of Na atoms and K atoms, wherein the total content of Na atoms and K atoms is 50 ppm to 700 ppm relative to the total mass of the carbon nanotube assembly.

13. A composition comprising a carbon nanotube aggregate satisfying conditions (1) and (2) below, and at least one selected from the group consisting of a dispersion medium, a resin, a ceramic, and concrete. (1) Containing at least one of Fe atoms and Co atoms, wherein the total content of Fe atoms and Co atoms is 2,500 ppm to 60,000 ppm relative to the total mass of the carbon nanotube assembly; (2) The ratio of volume resistivity under 20kN pressure to volume resistivity under 1kN pressure is greater than 0.21.

Images