Multi-walled carbon nanotube aggregate, multi-walled carbon nanotube dispersion, conductive material, electrode, secondary battery, planar aggregate, filter, electromagnetic shield, and protective film for extreme ultraviolet

Abstract

Provided are a multiwalled carbon nanotube assembly having high conductivity and good dispersibility in a dispersion medium, a multiwalled carbon nanotube dispersion liquid, a conductive material, an electrode, a secondary battery, a planar assembly, a filter, an electromagnetic shield, and an extreme ultraviolet protective film. A multi-walled carbon nanotube assembly, a multi-walled carbon nanotube dispersion, a conductive material, an electrode, a secondary battery, a planar assembly, a filter, an electromagnetic shield, and an extreme ultraviolet protective film, wherein the multi-walled carbon nanotube assembly contains Fe atoms and multi-walled carbon nanotubes having a maximum length of 1000-30000 [mu] m, and the Fe atom content ratio relative to the total mass of the assembly is 0.5 mass% or more but less than 10 mass%. The invention also provides a multi-walled carbon nanotube dispersion, a conductive material, an electrode, a secondary battery, a planar assembly, a filter, an electromagnetic shield, and an extreme ultraviolet protective film.

Description

TECHNICAL FIELD

[0001] The present application relates to a multi-walled carbon nanotube aggregate, a multi-walled carbon nanotube dispersion liquid, a conductive material, an electrode, a secondary battery, a planar aggregate, a filter, an electromagnetic shield, and a protective film for extreme ultraviolet. BACKGROUND

[0002] Carbon nanotubes have good mechanical properties and electronic properties, and are expected to be used for various purposes.

[0003] As carbon nanotubes (hereinafter can be referred to as "CNT"), single-walled carbon nanotubes (hereinafter can be referred to as "SWCNT") and multi-walled carbon nanotubes (hereinafter can be referred to as "MWCNT") of several μm to several tens of μm in length are known.

[0004] SWCNT is a seamless cylindrical tube formed of a single layer of graphene, and has a high specific surface area, and thus is expected to have high conductivity, and thus is attracting attention as a conductive aid.

[0005] On the other hand, MWCNT is composed of a plurality of concentric cylindrical tubes. As a product with a large number of layers, there is also a MWCNT composed of several tens of layers.

[0006] MWCNT has a larger diameter of the cylindrical tube than SWCNT, and has a smaller specific surface area than SWCNT, and thus is slightly easier to handle than SWCNT, but has a problem that it is difficult to achieve high conductivity as in SWCNT.

[0007] In addition, CNT of several μm to several tens of μm in length is in a powder form, and the main component is carbon, and thus is basically difficult to handle, and the dispersibility of CNT in a dispersion medium also becomes a problem.

[0008] In recent years, longer CNT, specifically long fiber MWCNT of several mm in length, has attracted attention. Long fiber MWCNT has a low specific surface area, but is expected to have higher conductivity than short MWCNT because of the long length. In addition, it is easy to handle compared to powder-like CNT.

[0009] Conventionally, long fiber MWCNT has been difficult to manufacture, but in recent years, production technology has been explored, and it is expected to be more easily available.

[0010] For example, a method of orienting and aggregating a plurality of CNTs in the longitudinal direction to obtain a long-sized CNT aggregate wire or a CNT aggregate wire bundle has been proposed (for example, refer to Patent Literature 1). According to the technology described in Patent Literature 1, it is described that the length of the CNT aggregate wire can be made to be 10 cm or more.

[0011] PRIOR ART DOCUMENTS

[0012] PATENT LITERATURE

[0013] Patent Literature 1: International Publication No. 2020 / 138379 SUMMARY

[0014] PROBLEMS TO BE SOLVED BY THE INVENTION

[0015] The CNT aggregate obtained by the technology described in Patent Literature 1 contains an aggregate of long fibers oriented by CNT fibers. In Patent Literature 1, dispersibility in a dispersion medium, which is important for CNT applications, is not focused on.

[0016] An object of one embodiment of the present application is to provide a multi-walled carbon nanotube aggregate having high conductivity and good dispersibility in a dispersion medium, a conductive material containing the multi-walled carbon nanotube aggregate, an electrode, a secondary battery, and a planar aggregate.

[0017] An object of another embodiment of the present application is to provide a multi-walled carbon nanotube dispersion liquid containing a multi-walled carbon nanotube aggregate having high conductivity.

[0018] An object of still another embodiment of the present application is to provide a planar aggregate containing a multi-walled carbon nanotube powder, a filter, an electromagnetic shield, and a protective film for extreme ultraviolet light using the planar aggregate.

[0019] MEANS FOR SOLVING THE PROBLEMS

[0020] <1> A multi-walled carbon nanotube aggregate containing multi-walled carbon nanotubes having a maximum length of 1000 μm to 30000 μm and Fe atoms, the ratio of the Fe atoms with respect to the total mass of the aggregate being 0.5 mass% or more and less than 10 mass%.

[0021] <2> The multi-walled carbon nanotube aggregate described in <1>, which is a conductive aid.

[0022] <3> A multi-walled carbon nanotube dispersion liquid containing the multi-walled carbon nanotube aggregate described in <1> or <2>, and a dispersion medium.

[0023] <4> A conductive material containing the multi-walled carbon nanotube aggregate described in <1> or <2>.

[0024] <5> The multi-walled carbon nanotube dispersion liquid described in <3>, which is an ink composition for forming a lithium battery negative electrode.

[0025] <6> An electrode containing an electrode active material and the conductive material described in <4>.

[0026] <7> A secondary battery provided with the electrode described in <6>.

[0027] <8> A composition comprising the multi-walled carbon nanotube aggregate according to <1> or <2>, and at least one selected from the group consisting of a resin, a ceramic, and a concrete.

[0028] <9> A multi-walled carbon nanotube aggregate comprising multi-walled carbon nanotubes having a tensile strength of 10 MPa to 100 MPa and Fe atoms, the ratio of the Fe atoms being 0.5 mass% or more and less than 10 mass% with respect to the total mass of the aggregate.

[0029] <10> The multi-walled carbon nanotube aggregate according to <9>, which is a conductive aid.

[0030] <11> A multi-walled carbon nanotube dispersion liquid comprising the multi-walled carbon nanotube aggregate according to <9> or <10>, and a dispersion medium.

[0031] <12> An electrically conductive material comprising the multi-walled carbon nanotube aggregate according to <9> or <10>.

[0032] <13> The multi-walled carbon nanotube dispersion liquid according to <11>, which is an ink composition for forming a lithium battery negative electrode.

[0033] <14> An electrode comprising an electrode active material, and the electrically conductive material according to <12>.

[0034] <15> A secondary battery provided with the electrode according to <14>.

[0035] <16> A composition comprising the multi-walled carbon nanotube aggregate according to <9> or <10>, and at least one selected from the group consisting of a resin, a ceramic, and a concrete.

[0036] <17> A composition comprising a multi-walled carbon nanotube aggregate, and at least one selected from the group consisting of a dispersion medium, a resin, a ceramic, and a concrete, the multi-walled carbon nanotube aggregate comprising multi-walled carbon nanotubes and Fe atoms, the ratio of the Fe atoms being 0.5 mass% or more and less than 10 mass% with respect to the total mass of the aggregate.

[0037] <18> A multi-walled carbon nanotube dispersion liquid comprising multi-walled carbon nanotubes having a tensile strength of 10 MPa to 100 MPa, and a dispersion medium.

[0038] <19> A planar aggregate comprising the multi-walled carbon nanotube aggregate according to <1>, <2>, <9>, or <10>.

[0039] <20> A filter using the planar aggregate according to <19>.

[0040] <21> An electromagnetic shielding body, which is used in <19> The aforementioned planar aggregate.

[0041] <22> An extreme ultraviolet protective film, its use includes <19> The aforementioned planar aggregate.

[0042] Invention Effects

[0043] According to one embodiment of the present invention, it is possible to provide a multi-walled carbon nanotube assembly with high conductivity and good dispersibility in a dispersion medium, a conductive material comprising the multi-walled carbon nanotube assembly, an electrode, a secondary battery, and a planar assembly.

[0044] According to another embodiment of the present invention, it is possible to provide a multi-walled carbon nanotube dispersion comprising an aggregate of multi-walled carbon nanotubes with high conductivity.

[0045] According to another embodiment of the present invention, it is possible to provide a planar assembly comprising multi-walled carbon nanotube powder, a filter using the planar assembly, an electromagnetic shield, and an extreme ultraviolet protective film. Attached Figure Description

[0046]

【 Figure 1 [Image 1] is a scanning electron microscope image showing one manner of the multi-walled carbon nanotube assembly of the present invention. Detailed Implementation

[0047] In this invention, the numerical range represented by “~” refers to the range in which the values ​​recorded before and after “~” are respectively taken as the minimum and maximum values.

[0048] In the numerical ranges recorded in segments in this invention, the upper or lower limit of a certain numerical range can be replaced with the upper or lower limit of other numerical ranges recorded in segments.

[0049] Furthermore, within the numerical range described in this invention, the upper or lower limit of a certain numerical range can be replaced with the values ​​shown in the embodiments.

[0050] In this invention, a combination of two or more preferred methods is a more preferred method.

[0051] In this invention, the amount of each component refers to the total amount of the multiple substances when there are multiple substances belonging to each component, unless otherwise stated.

[0052] In this specification, the term "process" refers not only to an independent process, but also to any process that can be clearly distinguished from other processes, as long as it achieves the intended purpose of the process.

[0053] <Multi-walled carbon nanotube assemblies: First embodiment>

[0054] The multi-walled carbon nanotube assembly of the present invention comprises multi-walled carbon nanotubes with a maximum length of 1000 μm to 30000 μm and Fe atoms, and the Fe atoms contain a ratio of 0.5% by mass or more and less than 10% by mass relative to the total mass of the assembly.

[0055] The multi-walled carbon nanotube aggregates of the present invention can take the form of sheets, fibers, etc.

[0056] Here, sheet-like aggregates refer to aggregates of multi-walled carbon nanotubes that have a sheet-like morphology.

[0057] Furthermore, fibrous aggregates refer to multi-walled carbon nanotubes in the form of filaments. Fibrous aggregates can contain multi-walled carbon nanotubes in a monofilament (single fiber) state, or they can contain multifilaments, that is, multiple multi-walled carbon nanotube fibers twisted together to form filaments.

[0058] Multi-walled carbon nanotubes

[0059] The multi-walled carbon nanotube assembly of the present invention (hereinafter referred to as "the assembly of the present invention") comprises multi-walled carbon nanotubes with a maximum length of 1000 μm to 30000 μm. Hereinafter, "multi-walled carbon nanotubes with a maximum length of 1000 μm to 30000 μm" is sometimes abbreviated as "ULMWCNT".

[0060] The maximum length of ULMWCNT ranges from 1000μm to 30000μm, which is longer than that of conventional MWCNT, and it can be in a fibrous form.

[0061] Here, the term "fiber" is usually used to refer to a structure in which one dimension is larger than the other two dimensions. A fiber can be a thread-like fiber with a circular cross-section, or a ribbon-like fiber with a rectangular cross-section; it can be hollow, or it can have other shapes.

[0062] From the perspective of improving the conductivity of the assembly of the present invention, the cross-section of ULMWCNT is preferably circular, and preferably hollow.

[0063] Due to their fibrous morphology, ULMWCNTs have the property of easily intertwining. The assembly of the present invention contains at least one ULMWCNT, and from the perspective of the ease with which MWCNTs intertwine to form a more stable assembly, an assembly containing multiple ULMWCNTs is preferred. Hereinafter, an assembly containing ULMWCNTs will sometimes be simply referred to as an "ULMWCNT assembly".

[0064] The assembly of the present invention can be an assembly of three-dimensional structures that are intertwined.

[0065] Figure 1This is a scanning electron microscope (SEM) image showing one embodiment of the assembly of the present invention. From Figure 1 As shown in the SEM image, multiple fibrous ULMWCNTs are wound together to form a sheet-like aggregate. This SEM observation confirms the winding state of the ULMWCNTs within the aggregate of the present invention.

[0066] The length of a ULMWCNT can be determined by observing multiple SEM images of adjacent fields of view for a single ULMWCNT. Here, length refers to the longitudinal length of the ULMWCNT, and the maximum value among the length measurements is taken as the "maximum length".

[0067] As described above, if a ULMWCNT with a maximum length in the range of 1000μm to 30000μm is observed within the field of view of the SEM image, it can be confirmed that the observed assembly is the assembly of the present invention.

[0068] Preferably, ULMWCNTs with a maximum length in the range of 1000μm to 30000μm as measured above are present in multiple roots within the field of view of the SEM image.

[0069] From the perspective of further improving the stability of the assembly through the entanglement of ULMWCNTs, the maximum length of each of the 100 MWCNTs contained in the field of view of the SEM image is measured by the above method. Preferably, the number of ULMWCNTs with a maximum length in the range of 1000μm to 30000μm is 10% or more, more preferably 20% or more, even more preferably 30% or more, and particularly preferably 50% or more.

[0070] The diameter of a ULMWCNT can be determined by observing SEM or transmission electron microscopy (TEM) images. Here, the diameter refers to the length in a direction orthogonal to the longitudinal direction of the ULMWCNT. The diameter is measured at 10 different points on a single ULMWCNT, and the average value is taken as the diameter of that ULMWCNT.

[0071] The length of the ULMWCNTs included in the assembly of the present invention 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 ULMWCNTs included in the assembly of the present invention 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.

[0072] The length-to-diameter ratio of the ULMWCNT, also known as the aspect ratio, is preferably 1000 or more, more preferably 3000 or more, even more preferably 5000 or more, and particularly preferably 10000 or more.

[0073] The aspect ratio can be calculated based on the ratio of the maximum length to the diameter of a single ULMWCNT. From the perspective of measurement accuracy, it is preferable to use the average value of measurements from more than 20 ULMWCNTs.

[0074] Furthermore, from the perspective 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.

[0075] The specific gravity of ULMWCNT aggregates can be determined using the method described in JIS Z8807-2012 "Methods for Determination of Density and Specific Gravity of Solids".

[0076] The purity of the ULMWCNT aggregate, expressed as MWCNTs, can be determined by thermogravimetric analysis (TGA). For example, using a thermal analysis apparatus (manufactured by Shimadzu Corporation, DTG-60), thermogravimetric (TG) and differential thermal analysis (DTA) curves of the ULMWCNT aggregate are obtained. The largest exothermic peak in the DTA curve, which peaks around 650°C to 750°C, is taken as the combustion of MWCNTs, and exothermic peaks elsewhere are taken as the combustion of substances other than MWCNTs. The purity of MWCNTs is determined based on the weight loss rate of the TG curve. From the perspective of the conductivity of the obtained aggregate, the purity of the ULMWCNT aggregate 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.

[0077] ULMWCNTs may contain 0.01% to 50% by mass of Fe atoms derived from the iron catalyst used in the manufacturing process. ULMWCNTs may contain Fe atoms in, for example, in a state adsorbed on the surface of ULMWCNTs or in a state introduced into the interior of fibrous ULMWCNTs formed during manufacturing.

[0078] The resulting fibrous ULMWCNT preferably has both flexibility and strength.

[0079] Furthermore, the conductivity of ULMWCNT itself is preferably 5000Ω. -1 ·m -1 The above, preferably 10000Ω -1 ·m -1 That's all. Additionally, the conductivity of ULMWCNT itself is typically 1,000,000 Ω. -1 ·m -1 the following.

[0080] There are no particular limitations on the manufacturing method of the ULMWCNT included in the assembly of the present invention.

[0081] As a method for manufacturing ULMWCNT in this invention, conventionally known methods such as chemical vapor deposition (CVD) and methods for reacting gaseous reactants containing a carbon source in the presence of a catalyst can be applied.

[0082] The MWCNT in this invention can be manufactured, for example, by referring to the manufacturing method described in Japanese Patent Application Publication No. 2016-102047.

[0083] The following is an example of the method for manufacturing MWCNTs according to the present invention. However, the method for manufacturing MWCNTs according to the present invention is not limited to the following example.

[0084] As an example of the manufacturing method of ULMWCNT in this invention, the manufacturing method disclosed in Japanese Patent Application Publication No. 2016-102047 can be cited, namely, a manufacturing method comprising the following steps (hereinafter also referred to as "manufacturing method X"): passing one or more gaseous reactants containing a carbon source through a reactor; reacting one or more gaseous reactants in the reaction zone of the reactor in the presence of a catalyst to form carbon-containing product particles; aggregating the product particles into aggregates; and applying force to the aggregates to continuously move the aggregates outside the reaction zone.

[0085] According to manufacturing method X, MWCNTs containing ULMWCNTs can be obtained in the form of easily handled fibrous aggregates or other aggregates.

[0086] In manufacturing method X, the force applied to the product particles can be a mechanical force.

[0087] When the aggregate contains fibrous CNTs, the mechanical force applied to the product particles can be applied by rotating a spindle around the aggregate containing the fibrous CNTs. In this way, the fibrous CNTs can be recovered as an aggregate on the spindle, or the spindle can be continuously unwound after rotating around the spindle once or more, storing the aggregate volume of the fibrous CNTs in other locations.

[0088] The spindle is preferably configured such that its axis is perpendicular or parallel to the flow direction of one or more gaseous reagents, but the spindle axis can also be configured in other orientations. For example, a spindle with its axis configured at a 25° angle to the airflow direction can also be suitably used to impart mechanical force to product particles.

[0089] The spindle can rotate about two axes, for example, about two perpendicular axes. In particular, the spindle can rotate about axes that are perpendicular to and parallel to the flow direction of the gaseous reactant, respectively. The twist and length of such a spindle can be controlled by drawing or twisting an aggregate containing fibrous CNTs.

[0090] The spindle can be made of metal, ceramic or resin.

[0091] Depending on the properties of the aforementioned materials and the intended use of the ULMWCNT assembly, the spindle can take on various suitable shapes. For example, the spindle can be used as a mold for manufacturing carbon products via spin coating. Preferred spindle shapes are rod-shaped or box-shaped.

[0092] Fibrous MWCNTs accumulate on spindles or other locations. 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 also be controlled, for example, by the dynamics of the gas flow.

[0093] The spindle rotation speed is preferably between 0.01 rpm and 10,000 rpm, more preferably between 0.1 rpm and 100 rpm. The spinning speed, i.e., the spindle rotation speed, can be adjusted to recover at the same rate as the material generation rate. The thickness of the fibrous ULMWCNT aggregate can be controlled by the rotation speed. In a preferred embodiment, the fibrous ULMWCNT aggregate is processed along the axial direction of the spindle as the spindle rotates. This processing means that the fibrous ULMWCNTs are not simply stacked at one location on the spindle, but are uniformly wound along the spindle.

[0094] Other techniques used in fiber technology can also be used to form aggregates based on fibrous ULMWCNT clusters.

[0095] Aggregates of fibrous ULMWCNTs can be recovered onto the reactor wall, for example, by a matrix placed in the reactor. The matrix can be a fixed matrix or a rotating guide used to apply a strong and uniform force to the ULMWCNTs during recovery. As a suitable matrix configuration for fiber technology, a matrix consisting of two guides in mutually orthogonal positions can be cited as an example.

[0096] In manufacturing method X, the mechanical force applied to the product particles can be a force applied by an accelerating gas flow. The accelerating 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.

[0097] Other forces applied to product particles include electrostatic forces appropriately applied by charged plates. When using electrostatic forces, the product particles need to be charged. By using charged plates, MWCNTs can be generated on the charged plates in an intertwined felt-like form.

[0098] In addition, other forces applied to the product particles can be magnetic force or light pressure applied by a light source.

[0099] The raw material for CNTs can be injected in liquid form containing a carbon source instead of gaseous reactants containing a carbon source. When using liquid as the raw material for CNTs, it can be injected through a single injection port or multiple injection ports, for example, through a spray nozzle.

[0100] One or more gaseous reactants are preferably reacted at 500°C to 1600°C, more preferably at 1000°C to 1500°C or 1600°C (especially 1000°C to 1500°C). It is preferable to maintain a temperature gradient within the reactor, with the reaction zone maintained at a higher temperature than the product zone of the reactor.

[0101] Gaseous reactants can be mixed with one or more gases that act as diluents. Gaseous reactants can also be mixed with gases that do not play a direct role in the reaction but play an auxiliary role. For example, when generating amorphous carbon as a byproduct, it is preferable to use a gas that, by reacting with amorphous carbon, maintains normal reaction sites on the catalyst so that it can be used to generate nanotubes as a diluent.

[0102] Gases that can be used as diluents include, for example, argon or other inert gases, hydrogen, nitrogen, ammonia, carbon dioxide, or helium. Among these, hydrogen is particularly preferred. 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.

[0103] The gas pressure of the gaseous reactants and any diluent 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. When gas flows out of the reactor, the outflowing gas can be recycled, either cleaned or not.

[0104] By monitoring the aggregated products and adjusting reaction conditions based on the obtained information, the composition of the products can be controlled. For example, the products can be monitored using online Raman spectroscopy. Regarding carbon nanotubes, data indicating whether the nanotubes are single-walled or multi-walled, their diameter, and their crystallinity can be obtained. The products can also be monitored through online conductivity measurements, gas analysis, monitoring of the opacity of the reaction zone, and / or monitoring of the entrainment force. Reaction conditions can be changed by the operator or automatically.

[0105] When removing the aggregate from the reactor, it is preferable to prevent air from entering the reactor. When the diluent gas contains hydrogen, preventing air inflow is particularly important from the perspective of, for example, suppressing the formation of an explosive mixture of hydrogen and air in the reactor.

[0106] The product particles produced by the above manufacturing method contain ULMWCNTs. Furthermore, depending on the manufacturing conditions, in addition to multi-walled carbon nanotubes, single-walled carbon nanotubes may also be included.

[0107] Fibrous ULMWCNTs can be generated by chemical vapor deposition, in which case the carbon source, acting as a gaseous reactant, reacts in the presence of a catalyst.

[0108] Suitable carbon-containing compounds as carbon sources include, for example, carbon monoxide, carbon dioxide, aromatic hydrocarbons (e.g., benzene, toluene, xylene, cumene, ethylbenzene, naphthalene, or mesitylene), non-aromatic hydrocarbons (e.g., methane, ethane, propane, butane, pentane, hexane, cyclohexane, ethylene, propylene, or acetylene), and oxygen-containing hydrocarbons (e.g., formaldehyde, acetaldehyde, acetone, methanol, ethanol, diethyl ether, polyethylene glycol, 1-propanol, ethyl formate, and hydrocarbons containing two or more of these).

[0109] As a carbon-containing compound, carbon monoxide, methane, ethylene, or acetylene are preferred.

[0110] The carbon source preferably contains oxygen. Ethanol is a particularly preferred carbon source.

[0111] Oxygen can be introduced into the reactor by other methods, such as by using a carbon source containing diluent gas or water.

[0112] The gaseous reactants used as carbon sources are 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.

[0113] 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. More preferred are Fe, Ni, Co, Mo, and mixtures thereof, such as mixtures of Ni and Co (mass ratio: 50 / 50), mixtures of Fe and Ni, or mixtures of Fe and Mo.

[0114] Any of these transition metals can be used alone or in combination with any of the other listed transition metals to function as a CNT growth catalyst. A mixture of two or more of the listed metals is particularly preferred as the catalyst.

[0115] The catalyst is preferably formed by the decomposition of a precursor. The precursor is preferably a thermal, photochemical, 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 precursors. Suitably, the carbon source 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.

[0116] The catalyst can be used supported on a carrier. Preferred carriers include silica and magnesium oxide.

[0117] 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. Suitably, the carbon source contains up to 10% by mass (less than 10% by mass) of promoter. Preferably, the carbon source contains 0.2% to 6% by mass of promoter. When high or low concentrations of thiophene are used as promoters, MWCNTs can be formed.

[0118] For example, MWCNTs can be well formed using ethanol containing 0% or 1.5% to 4.0% by mass of thiophene and 1.0% to 10.0% by mass (especially 2.3% by mass) of ferrocene, at an injection rate of 5.0 mL / h to 30.0 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.

[0119] 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 be in the form of filaments or felt.

[0120] The length of fibrous CNTs can be controlled, for example, by the winding capability of the spindle used in manufacturing fibrous CNTs.

[0121] Manufacturing method X preferably includes: a step of reacting a carbon source to generate CNTs within the reaction zone of a reactor; and a step of agglomerating the CNTs into aggregates by applying force to the CNTs. According to this manufacturing method, fibrous CNT aggregates can be readily manufactured.

[0122] Alternatively, the following steps can be taken: generating ULMWCNTs in the reaction region using the method described above, aggregating the ULMWCNTs to form the aforementioned aggregate, and continuously extracting the aforementioned aggregate from the vicinity of the reaction region.

[0123] Alternatively, the following steps can be taken: generating ULMWCNTs in the reaction region, continuously electrostatically attracting ULMWCNTs from the reaction region, and recovering ULMWCNTs as the aforementioned aggregate.

[0124] The manufacturing method X described above is just one example, and the manufacturing method of MWCNT containing ULMWCNT is not limited to the above.

[0125] [Fe atom]

[0126] The aggregate of the present invention contains Fe atoms, and the proportion of Fe atoms relative to the total mass of the aggregate is 0.5% by mass or more and less than 10% by mass.

[0127] ULMWCNTs contain carbon and are expected to be conductive. However, when ULMWCNTs are manufactured in the presence of catalysts containing metal atoms such as Fe, the Fe atoms from the catalyst source are included in the ULMWCNTs, raising concerns about reduced conductivity. Traditionally, after the manufacture of ULMWCNTs, they are cleaned with acid to remove metal atoms, represented by Fe atoms.

[0128] However, according to the inventors' research, it has been found that by including ULMWCNTs with a maximum length of 1000 μm to 30000 μm, and ensuring that the maximum length of the CNTs is within the above range, and that the Fe atom content relative to the total mass of the aggregate is 0.5% by mass or more and less than 10% by mass, the dispersibility in the dispersion medium can be further improved while maintaining the conductivity of the aggregate.

[0129] The Fe atom content relative to the total mass of the aggregate of the present invention is 0.5% by mass or more and less than 10% by mass, preferably more than 1.0% by mass and less than 10% by mass, more preferably 1.2% by mass to 9.5% by mass, further preferably 1.5% by mass to 9% by mass, particularly preferably 2% by mass to 8% by mass, and especially preferably 3% by mass to 7% by mass.

[0130] The ratio of Fe atoms relative to the total mass of the aggregate can be determined, for example, by the following methods.

[0131] The aggregate of the present invention is completely dissolved in an acid such as hydrochloric acid or nitric acid. To ensure complete dissolution in the acid, pretreatments such as dry ashing, wet ashing, or melt treatment can be performed. The solution in which the aggregate of the present invention is completely dissolved in the acid is then subjected to inductively coupled plasma atomic emission spectrometry (ICP-AES) or inductively coupled plasma mass spectrometry (ICP-MS) to determine the Fe atom content. ICP-MS is preferred due to its higher sensitivity.

[0132] As mentioned above, ULMWCNTs may contain 0.01% to 50% by mass of Fe atoms derived from the iron catalyst used in the manufacturing process. ULMWCNTs may contain Fe atoms, for example, in a state adsorbed on the surface of ULMWCNTs or in a state introduced into the interior of fibrous ULMWCNTs formed during manufacturing.

[0133] That is, in this invention, the Fe atoms contained in the aggregate may include Fe atoms derived from the catalyst used to manufacture multi-walled carbon nanotubes.

[0134] In the assembly of the present invention, it is preferable to consider the content of Fe atoms derived from the catalyst contained in the aforementioned ULMWCNT, and adjust it to a target Fe atom content ratio within a range of 0.5% by mass or more and less than 10% by mass relative to the total mass of the assembly. Furthermore, it goes without saying that when the content ratio of Fe atoms derived from the catalyst relative to the total mass of the assembly is already the target content ratio, it is not necessary to take special measures to adjust the Fe atom content ratio.

[0135] When the Fe atom content relative to the total mass of the aggregate is 10% by mass or more, the Fe atom content relative to the total mass of the aggregate can be adjusted to less than 10% by mass by using known methods, such as washing the aggregate with water, acid or an aqueous solution of acid (e.g., an aqueous solution of hydrochloric acid of 1% to 37% by mass, especially 35% by mass), to wash and remove a portion of the Fe atoms.

[0136] When the Fe atom content relative to the total mass of the aggregate is less than 0.5% by mass, the Fe atom content relative to the total mass of the aggregate can be adjusted to a level of 0.5% by mass or more by immersing the aggregate in an aqueous solution of ferric nitrate (1% to 46% by mass, particularly about 5% by mass) or an aqueous solution of ferric chloride (1% to 47% by mass, particularly about 40% by mass) as a source of Fe atom supply, thereby causing Fe atoms to adsorb onto the surface of the fibrous ULMWCNT.

[0137] The mechanism by which the aggregate of the present invention improves conductivity and dispersion is not yet clear, but it is speculated as follows. However, the following speculation is not intended to limit the aggregate of the present invention, but is provided as an example.

[0138] When known short CNTs contain Fe atoms, the presence of Fe atoms narrows the contact area between them, making it difficult to connect conductive paths and resulting in reduced conductivity.

[0139] In the aggregate of the present invention, since the maximum length of the included ULMWCNTs is in the range of 1000 μm to 30000 μm, the contact area between them is wide, making aggregation prone to occur. Here, with an appropriate amount of Fe atoms attached to the surface of the ULMWCNTs, by including Fe atoms in the aggregate, the contact between multiple ULMWCNTs is moderately hindered by the Fe atoms, thereby suppressing aggregation and presumably improving dispersibility. When the aggregation of ULMWCNTs is suppressed, conductivity generally decreases, but since the maximum length of the ULMWCNTs included in the aggregate of the present invention is in the range of 1000 μm to 30000 μm, even if the presence of Fe atoms suppresses aggregation, sufficient contact area can be ensured, and it is believed that both improved dispersibility and good conductivity can be achieved.

[0140] In ULMWCNTs with an Fe atom content of 10% by mass or more, even within ULMWCNTs, the presence of Fe atoms narrows the contact areas between them, making it difficult to connect conductive pathways and reducing conductivity. Furthermore, in ULMWCNTs with an Fe atom content of less than 0.5% by mass, the aggregation-inhibiting effect of the presence of Fe atoms is ineffective, the contact areas become wider, and although conductivity is good, dispersibility is reduced.

[0141] Since the Fe atom content relative to the total mass of the assembly of the present invention is within the above range, the specific gravity of the ULMWCNT assembly is slightly increased due to the presence of Fe atoms.

[0142] For example, when the Fe atom content in an aggregate is 5% by mass, the specific gravity is approximately 2.2.

[0143] When the aggregate of the present invention is used as the conductive additive described later, since the specific gravity of the carbon material graphite in the electrode is 2.2 and the specific gravity of Ketjen black is 2.7, the specific gravity of the aggregate increases due to the Fe atoms, thereby having the additional effect of reducing the specific gravity difference with the carbon material and improving its dispersibility in the carbon material.

[0144] In addition, the method for determining the specific gravity of aggregates is as described in the section on multi-walled carbon nanotubes.

[0145] <Multi-walled carbon nanotube assemblies: Second embodiment>

[0146] As a second embodiment of the multi-walled carbon nanotube assembly of the present invention, an example is a multi-walled carbon nanotube assembly comprising multi-walled carbon nanotubes with a tensile strength of 10 MPa to 100 MPa and Fe atoms, wherein the Fe atom content relative to the total mass of the assembly is 0.5% by mass or more and less than 10% by mass.

[0147] The second embodiment of the multi-walled carbon nanotube assembly of the present invention comprises multi-walled carbon nanotubes with a tensile strength of 10 MPa to 100 MPa and Fe atoms, wherein the Fe atoms contain a ratio of 0.5% by mass or more and less than 10% by mass relative to the total mass of the assembly.

[0148] In this invention, the "tensile strength" is determined with reference to the tensile test described in ISO 527-1 standard.

[0149] The tensile strength of the multi-walled carbon nanotubes of the second embodiment of the present invention is expressed as a value measured in a stretchable state such as sheet or fiber.

[0150] When the multi-walled carbon nanotube assembly is in sheet form, the sheet assembly is cut into 75mm×10mm pieces as test specimens, fixed in the clamping part of a tensile testing machine (manufactured by Shimadzu Corporation, Autograph AGS-X series), and a tensile test is performed at a speed of 1mm / min. The fracture strength of the test specimen at the point of fracture is taken as the tensile strength.

[0151] When multi-walled carbon nanotubes are in the form of filaments, the fibrous multi-walled carbon nanotubes are cut into 500mm lengths as test specimens, fixed in the clamping part of a tensile testing machine (manufactured by Shimadzu Corporation, Autograph AGS-X series), and a tensile test is performed using a wire clamp (manufactured by Shimadzu Corporation) at a speed of 1mm / min. The tensile strength is taken as the fracture strength of the test specimen.

[0152] In addition, when the sheet-shaped test specimen does not reach the above-mentioned size, or the filament-shaped test specimen does not reach the above-mentioned length, the test specimen is used directly to determine the tensile strength.

[0153] The tensile strength of the multi-walled carbon nanotubes of the present invention is preferably 10 MPa to 100 MPa, more preferably 30 MPa to 85 MPa, and even more preferably 50 MPa to 70 MPa. When the tensile strength of the multi-walled carbon nanotubes is 50 MPa or higher, the maximum length of the multi-walled carbon nanotubes is sufficient, making it easy to ensure the conductivity of the multi-walled carbon nanotubes. When the tensile strength of the multi-walled carbon nanotubes is 70 MPa or lower, the force required to pulverize the sheet-like or fibrous multi-walled carbon nanotubes as needed is small, thus allowing for easy pulverization as a post-processing step.

[0154] The multi-walled carbon nanotubes of the present invention have a tensile strength of 10 MPa to 100 MPa. When pulverizing these nanotubes as needed, a pulverization method can be used, for example, cryogenic pulverization. Cryogenic pulverization is a process where, regardless of whether the multi-walled carbon nanotube assembly is in sheet or fibrous form, the assembly is rapidly cooled with liquid nitrogen, causing the elasticity of the multi-walled carbon nanotubes to disappear, thus making them easier to pulverize. Alternatively, known pulverization methods such as ball milling can also be used.

[0155] The aforementioned multi-walled carbon nanotube assembly contains Fe atoms, with the Fe atom content being more than 0.5% by mass and less than 10% by mass relative to the total mass of the assembly.

[0156] In the second embodiment of the assembly of the present invention, the Fe atom content relative to the total mass is 0.5% by mass or more and less than 10% by mass, preferably more than 1.0% by mass and less than 10% by mass, more preferably 1.2% by mass to 9.5% by mass, further preferably 1.5% by mass to 9% by mass, particularly preferably 2% by mass to 8% by mass, and especially preferably 3% by mass to 7% by mass.

[0157] In addition, unless otherwise stated, "the collection of the present invention" refers to the collection of the first embodiment of the present invention.

[0158] <Method for manufacturing the assembly of the present invention>

[0159] The assembly of the present invention can be obtained by adjusting the Fe atom content ratio relative to the total mass of the assembly to a range of 0.5% by mass or more and less than 10% by mass from the assemblies containing ULMWCNTs obtained by the above manufacturing method. The method for adjusting the Fe atom content ratio is as described above.

[0160] First, the proportion of Fe atoms derived from the reaction catalyst in the ULMWCNT-containing aggregate is determined. Then, considering this proportion, Fe atoms are removed or further adsorbed to adjust the Fe atom content. If the Fe atom content in the ULMWCNT-containing aggregate is within the target range, no special adjustment of the Fe atom content is required.

[0161] <Physical Properties of the Assembly in this Invention>

[0162] 1. Rsp value

[0163] The Rsp value of the aggregate relative to the dispersion medium of the present invention is preferably 300 to 10000, more preferably 500 to 7000, further preferably 1000 to 5000, and particularly preferably 3500 to 4500.

[0164] Rsp value is a standard for affinity with the dispersion medium and can be determined by pulsed nuclear magnetic resonance (pulse NMR). Pulse NMR can be used without diluting the dispersion and does not approximate the shape of the dispersed phase as spherical, making it suitable for determining the affinity of dispersions such as the aggregates of the present invention with the dispersion medium. When the Rsp value of the aggregates of the present invention relative to the dispersion medium is within an appropriate range, it can be determined that the aggregates of the present invention have good dispersibility in the dispersion medium.

[0165] Rsp values ​​can be obtained by comparing the relaxation time T measured when the dispersion is placed in a sample tube using a pulsed NMR apparatus. 2s The relaxation time T, compared to that measured when only the dispersion medium is placed in a test tube. 2b It can be calculated using the following formula.

[0166] Rsp = (T 2b / T 2s )- 1

[0167] 2. Viscosity

[0168] As described above, the aggregates of the present invention have a high affinity for the dispersion medium, thus the viscosity of the dispersion tends to be lower. When the viscosity of the dispersion is within an appropriate range, it can be determined that the aggregates of the present invention have good dispersibility in the dispersion medium.

[0169] The dispersion shear rate is 1 s. -1 The viscosity at this time is preferably 0.1 Pa·s to 4.8 Pa·s, more preferably 0.5 Pa·s to 4.5 Pa·s, and even more preferably 1.0 Pa·s to 4.2 Pa·s. The dispersion shear rate is 100 s⁻¹. -1 The viscosity at that time is preferably 0.001 Pa·s to 0.11 Pa·s, more preferably 0.005 Pa·s to 0.1 Pa·s, and even more preferably 0.01 Pa·s to 0.09 Pa·s.

[0170] Viscosities at various shear rates can be obtained from rheometer measurements. For example, using a viscoelasticity measuring apparatus (Anton Paar, MCR302), the shear rate dependence of viscosity can be evaluated under the following measurement conditions.

[0171] Measuring fixture: cone plate

[0172] Measurement mode: Rotation mode

[0173] Shear rate: 0.01s -1 ~1000s -1

[0174] Temperature: 25℃

[0175] From the obtained data, read the viscosity at the following shear rates.

[0176] Shear rate = 1s -1

[0177] Shear rate = 100s -1

[0178] 3. Electrical conductivity

[0179] The aggregate of the present invention has good electrical conductivity because its main component is carbon.

[0180] The conductivity of the polymer of the present invention can be determined by its volume resistivity. When the volume resistivity measured under the following conditions is lower than a specified value, it can be determined that the polymer of the present invention has good conductivity.

[0181] The conductivity of the assembly of the present invention, calculated from the volume resistivity, is preferably 1.5 × 10⁻⁶ under a pressure of 5 kN. -2 Below Ω·cm, more preferably 1.0×10 -5 Ω·cm~1.2×10 -2 Ω·cm, more preferably 5.0 × 10⁻⁶ -5 Ω·cm~1.0×10 -2 Ω·cm, preferably 1.0×10 -4 Ω·cm~9.9×10 -3 Ω·cm.

[0182] The volume resistivity of the assembly of the present invention was measured using a resistivity meter at 25°C via a four-probe method. A Loresta apparatus can be used as the resistivity meter.

[0183] Specifically, using the Loresta apparatus (product name: MCP-PD51 powder resistivity measurement system, Loresta-GP low resistivity meter, MCP-PD511 low resistance probe for powder (constant current application method four-probe method), all manufactured by Nitto Seiko Analytical Technology Co., Ltd.), the multi-walled carbon nanotube assembly is introduced into the powder resistivity measurement probe unit. Using the attached hydraulic pump, a pressure of 5 kN is applied. After reaching the target load, the volume resistivity (Ω·cm) is measured.

[0184] When measuring the volume resistivity of the assembly of the present invention, if it is necessary to pulverize the assembly, as described above, for example, a cryogenic pulverization method can be used. Alternatively, a known pulverization method such as a ball mill can be used for pulverization.

[0185] The volume resistivity of the assembly of the present invention can also be calculated based on the surface resistance value measured by the following method.

[0186] The surface resistivity of the ULMWCNT assembly was measured using the four-probe resistivity test conforming to JIS K 7149-1994, employing a Loresta EP MCP-T360 (manufactured by Dia Instrument Co., Ltd.). The volume resistivity was calculated by multiplying the surface resistivity obtained through the four-probe method by the film thickness of the assembly. The conductivity of the assembly was then calculated from the obtained volume resistivity.

[0187] The film thickness of the assembly of the present invention can be measured according to the thickness measurement method ISO method A in JIS L 1913-2010 "General Test Methods for Nonwoven Fabrics", using a thickness measuring device with two circular horizontal plates.

[0188] [Conductive additives]

[0189] As described above, the aggregate of the present invention exhibits good electrical conductivity. Therefore, the aggregate of the present invention can be used as a conductive additive (preferably a conductive additive for the negative electrode).

[0190] Conductive additives, by coexisting with conductive materials such as positive electrode active materials and negative electrode active materials, can further improve the conductivity of conductive materials.

[0191] Since the aggregate of the present invention contains ULMWCNT, the aggregate of the present invention can also be used as a conductive additive, in addition to known conductive additives such as graphite and Ketjen black, as an active material for conductive materials.

[0192] As described above, the aggregate of the present invention contains Fe atoms in a specified ratio. Therefore, the specific gravity of the aggregate of the present invention tends to be slightly higher than that of ULMWCNT aggregates with a typical specific gravity in the range of 1.8 to 2.0.

[0193] For example, when the Fe atom content in the aggregate is 5% by mass, the specific gravity of the aggregate is about 2.2, which is smaller than the specific gravity difference between the carbon materials graphite (specific gravity 2.2) and Ketjen black (specific gravity 2.7) used as conductive additives. In addition to the dispersibility of the aggregate of the present invention in the dispersion medium, the dispersibility in the carbon materials used in the aggregate is also better.

[0194] As an example of its use as a conductive additive, for instance, in the manufacture of the positive electrode of a battery, the positive electrode active material, the conductive additive which is part of the above-described composite of the present invention, and the binder are mixed in a prescribed mass ratio, a solvent is added to the mixture to prepare a slurry, which is then coated onto a current collector for the positive electrode, dried, and rolled to produce the positive electrode, etc.

[0195] Another example of its use as a conductive additive is, for instance, in the manufacture of the negative electrode of a battery, the negative electrode active material, the conductive additive which is part of the above-described composite of the present invention, and the binder are mixed in a prescribed mass ratio, a solvent is added to the mixture to prepare a slurry, which is then coated onto a current collector for the negative electrode, dried, and rolled to produce the negative electrode, etc.

[0196] The foregoing describes the combination of carbon materials as conductive materials and conductive additives as the aggregate of the present invention, but the use of the present invention as a conductive additive is not limited to the foregoing.

[0197] When the aggregate of the present invention is used as a conductive additive, the content ratio relative to the total mass of the solid components of the material containing the conductive material and the conductive additive can be used in any proportion.

[0198] Furthermore, the assembly of the present invention can also be used as a conductive material. The conductive material of the present invention comprises the assembly of the present invention described above.

[0199] As a conductive material, its applications include batteries, such as electrode materials in lithium-ion batteries, specifically as negative electrode active materials, positive electrode active materials, etc.

[0200] Multi-walled carbon nanotube dispersion

[0201] The aggregates of the present invention are well dispersible and therefore can be suitably used as dispersions.

[0202] The multi-walled carbon nanotube dispersion of the present invention comprises the aggregate of the present invention and the dispersion medium described above.

[0203] Another multi-walled carbon nanotube dispersion of the present invention comprises multi-walled carbon nanotubes with a tensile strength of 10 MPa to 100 MPa and a dispersion medium.

[0204] These multi-walled carbon nanotube dispersions can be simply referred to as the dispersions of this invention.

[0205] [Dispersion medium]

[0206] The dispersion medium that may be included in the dispersion of the present invention will be described.

[0207] The dispersion medium preferably contains water, and more preferably contains water as the main component.

[0208] "Containing water as a main component" means that the proportion of water in the dispersion medium is more than 50% by mass. The proportion of water in the dispersion medium is preferably 90% by mass or more, more preferably 95% by mass or more, even more preferably 99% by mass or more, and for example, it can also be 100% by mass.

[0209] There are no particular limitations on the water, but distilled water, ion-exchange water, or pure water are preferred in terms of having fewer impurities.

[0210] The dispersion medium can be a mixture of water and a hydrophilic solvent.

[0211] 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.

[0212] 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.

[0213] In addition to the aggregate and dispersion medium of the present invention, the dispersion of the present invention may further contain other components that can be used in the dispersion.

[0214] Other components may include dispersants, defoamers, antistatic agents, CNTs other than the ULMWCNT of this invention, and carbon materials other than CNTs. Furthermore, trace amounts of impurities, i.e., so-called unavoidable impurities, may also be included.

[0215] [Dispersant]

[0216] In order to further improve the dispersibility and dispersion stability of the aggregate of the present invention, the dispersion of the present invention may contain a dispersant.

[0217] There are no particular limitations on what can be considered a dispersant; for example, various surfactants can be listed. Furthermore, polymers such as resins can also be listed as dispersants.

[0218] Surfactants are preferred as dispersants.

[0219] Surfactants can be either ionic or nonionic, without any particular limitation.

[0220] Surfactants can be used alone or in combination of two or more.

[0221] Examples of ionic surfactants include anionic surfactants, cationic surfactants, and amphoteric surfactants.

[0222] 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.

[0223] Examples of cationic surfactants include alkylamine salts and quaternary ammonium salts.

[0224] Examples of amphoteric surfactants include alkyl betaine surfactants and amine oxide surfactants.

[0225] As ionic surfactants, ionic surfactants having aromatic rings are preferred (so-called aromatic ionic surfactants), and aromatic sulfonic acid surfactants such as alkylbenzene sulfonates and dodecyl phenyl ether sulfonates are more preferred.

[0226] Aromatic ionic surfactants tend to have excellent dispersion ability, dispersion stability and high concentration of multi-walled carbon nanotube aggregates.

[0227] Examples of nonionic surfactants include glycol ester surfactants such as sorbitan fatty acid esters and polyoxyethylene sorbitan fatty acid esters; fatty acid ester surfactants such as polyoxyethylene resin esters and polyoxyethylene diethyl fatty acid esters; ether surfactants such as polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, and polyoxyethylene / polypropylene glycol; and aromatic nonionic surfactants such as polyoxyalkylene octylphenyl ether, polyoxyalkylene nonylphenyl ether, polyoxyalkylene dibutylphenyl ether, polyoxyalkylene styrene phenyl ether, polyoxyalkylene benzylphenyl ether, polyoxyalkylene diphenyl ether, polyoxyalkylene cumylphenyl ether, and polyoxyalkylene phenyl ether.

[0228] 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.

[0229] Aromatic nonionic surfactants tend to have excellent dispersion ability, dispersion stability and high concentration of multi-walled carbon nanotube aggregates.

[0230] Other dispersants that enhance the dispersion, dispersion stability, and high concentration of multi-walled carbon nanotube aggregates include β-naphthalenesulfonic acid formaldehyde condensate sodium salt Demol (registered trademark: same below) N, Demol RN, Demol T (manufactured by Kao Corporation), polyoxyethylene stearyl ether Brij S 100 (manufactured by Sigma-Aldrich), polyvinylpyrrolidone K30 (e.g., manufactured by Fujifilm and Kojun Pharmaceutical Co., Ltd.), carboxymethyl cellulose (CMC) (e.g., manufactured by Caillou Miwa Co., Ltd.), sodium deoxycholate (e.g., manufactured by Fujifilm and Kojun Pharmaceutical Co., Ltd.), and SOLSPERSE. TM W100, SOLSPERSE TM W150 (manufactured by Lubrizol Corporation, Japan), etc. From the perspective of excellent dispersion ability, dispersion stability and high concentration of multi-walled carbon nanotube aggregates, CMC is particularly preferred.

[0231] When the dispersion of the present invention contains a dispersant, the amount of dispersant used is not particularly limited and can be appropriately set according to the type of dispersant, the amount of multi-walled carbon nanotube aggregates, the amount of dispersion medium, etc.

[0232] [Method for manufacturing dispersion]

[0233] The method for manufacturing the dispersion of the present invention is not particularly limited.

[0234] The dispersion of the present invention can be manufactured by dispersing the aggregate of the present invention in a dispersion medium. That is, the dispersion of the present invention can be manufactured by a method comprising a step (also referred to as a "dispersion step") of dispersing the multi-walled carbon nanotube aggregate of the present invention in a dispersion medium.

[0235] The dispersion media that can be used in the dispersion process are as described above.

[0236] There are no particular restrictions on the method of dispersion.

[0237] Examples of dispersion methods include those using dispersion devices such as agitators, homogenizers, colloid mills, flow jet mixers, dissolvers, paint conditioners, Manton emulsifiers, jet mills, and ultrasonic devices.

[0238] In addition, dispersion methods also include, for example, the use of 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 stirred mills, grinders, colloid mills, three-roll mills, pearl mills, super mills, impeller mixers, dispersers, KD mills, Dyno mills, pressure kneaders, and other dispersing machines.

[0239] As a dispersion method, jet milling is preferred, and wet jet milling is more preferred.

[0240] A wet jet mill is a dispersion device that uses a mixture in a solvent as a high-speed flow, pressurized and conveyed through a sealed nozzle located within a pressure vessel. In a wet jet mill, multi-walled carbon nanotube aggregates are dispersed through 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, NAGS200, NAGS1000, etc.) can be appropriately used as wet jet mills. However, wet jet mills are not limited to these.

[0241] When using the above-mentioned ultra-high pressure homogenizer as a dispersion device, the dispersion processing pressure is preferably 10MPa to 250MPa.

[0242] The method for manufacturing the dispersion of the present invention may include a step of drying the aggregate of the present invention (also referred to as the "drying step") before the above-described dispersion step.

[0243] If multi-walled carbon nanotubes (MWCNTs) are attached to water, they tend to adhere to each other due to the surface tension of water, raising concerns about reduced dispersibility. Therefore, by performing a drying process on the aggregate before the dispersion process to remove water adhering to the surface of the MWCNTs contained in the aggregate, the adhesion of MWCNTs to each other due to water adhesion can be suppressed, thereby further improving the dispersibility of the aggregate of the present invention in the dispersion medium.

[0244] There are no particular restrictions on the drying method.

[0245] Examples of drying methods include heating drying, vacuum drying, and heated vacuum drying.

[0246] As a drying method, heating and vacuum drying is preferred.

[0247] There is no particular limitation on the drying temperature, but it is preferably 40°C to 100°C.

[0248] There is no particular limitation on the drying time, which can be set appropriately according to the drying temperature, the degree of moisture adhesion on the aggregate of the present invention, etc.

[0249] [Application of Dispersions]

[0250] The dispersion of the present invention has good dispersibility in the dispersion medium and excellent conductivity, and therefore can be used for various applications.

[0251] Applications of dispersions include conductive inks, antistatic agents, conductive materials for circuit patterning, materials for transparent electrodes, and water-soluble polymer fillers, with conductive inks being the preferred application.

[0252] The dispersion of the present invention is preferably used in conductive inks, and is particularly suitable for use in ink compositions for forming lithium battery anodes.

[0253] By using the dispersion of the present invention as an ink composition for forming lithium battery anodes, lithium battery anodes with good conductivity can be easily manufactured.

[0254] When the dispersion of the present invention is applied to conductive ink, it can be manufactured by the same method as the dispersion of the present invention, except that it further contains viscosity modifiers, antioxidants, etc., which are components of conductive ink.

[0255] As one application of the assembly of the present invention, examples include electrodes and secondary batteries in which the assembly of the present invention is used as a conductive additive.

[0256] Electrodes containing the conductive additives of the present invention exhibit excellent conductivity pathway formation within the electrode. Therefore, secondary batteries containing the aforementioned electrodes exhibit excellent cycle characteristics.

[0257] The electrode may contain the conductive additives of the present invention described above. The conductive additives contained in the electrode are the same as those of the present invention, and the description of the conductive additives is omitted below.

[0258] The electrode can be at least one of the positive and negative electrodes.

[0259] The electrode may include a layer of electrode active material. The electrode may include a current collector and a layer of electrode active material disposed on the current collector.

[0260] 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. For example, copper, stainless steel, aluminum, nickel, titanium, calcined coke, or materials whose surfaces have been surface-treated with carbon, nickel, titanium, silver, etc., can be used as current collectors. Specifically, transition metals such as copper and nickel, which can effectively adsorb carbon, can be used as current collectors.

[0261] The electrode active material layer may contain electrode active materials.

[0262] The electrode active material is preferably electrode active material particles.

[0263] When the electrode is the positive electrode, there are no particular limitations on the electrode active material particles, and they may include the positive electrode active materials commonly used in positive electrode materials for electrodes. Specifically, examples of the positive electrode active material include layered compounds such as lithium cobalt oxide (LiCoO2) and lithium nickel oxide (LiNiO2), compounds substituted with one or more transition metals; lithium iron oxides such as LiFe3O4; and a chemical formula Li 1+c1 Mn 2-c1 O4 (0 ≤ c1 ≤ 0.33), lithium manganese oxides such as LiMnO3, LiMn2O3, and LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, V2O5, and Cu2V2O7; a Ni-site substituted lithium nickel oxide represented by the chemical formula LiNi 1-c2 M c2 O2 (where M is at least any one selected from Co, Mn, Al, Cu, Fe, Mg, B, and Ga, satisfying 0.01 ≤ c2 ≤ 0.66); a lithium manganese composite oxide represented by the chemical formula LiMn 2-c3 M c3 O2 (where M is at least any one selected from Co, Ni, Fe, Cr, Zn, and Ta, satisfying 0.01 ≤ c3 ≤ 0.1) or Li2Mn3MO8 (where M is at least any one selected from Fe, Co, Ni, Cu, and Zn); LiMn2O4 in which a part of Li in the chemical formula is substituted with an alkaline earth metal ion, etc.

[0264] When the electrode is the negative electrode, there are no particular limitations on the electrode active material, and it may include the negative electrode active materials commonly used in negative electrode materials for electrodes.

[0265] Specifically, the negative electrode active material may include graphite-based active material particles or silicon-based active material particles. As the graphite-based active material particles, one or more selected from artificial graphite, natural graphite, graphitized carbon fiber, and graphitized mesophase carbon microspheres can be used. By using artificial graphite, the rate performance can be improved.

[0266] As the silicon-based active material particles, one or more selected from Si, SiOx (0 < x < 2), Si-C composite, and Si-Y alloy (where Y is an element selected from 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 battery can be made to have a high capacity.

[0267] The electrode active material layer may further include a binder.

[0268] There are no particular limitations on the binder, and it may include the binders commonly used in electrode materials.

[0269] As an adhesive, examples include at least one polymer selected from polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-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, as well as polymers in which the hydrogen atoms of these polymers are replaced by Li, Na, Ca, etc.

[0270] Secondary batteries

[0271] A secondary battery may comprise 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 of the present invention, preferably the negative electrode.

[0272] The separator is used to separate the negative and positive electrodes and provide a migration channel for lithium ions. Generally, any separator used in a secondary battery will suffice, without particular restrictions. Preferably, the separator has low impedance to ion migration in the electrolyte and excellent electrolyte wetting ability.

[0273] As a diaphragm, porous polymer membranes can be specifically cited. Porous polymer membranes can be, for example, porous polymer membranes made of polyolefin polymers such as ethylene homopolymers, propylene homopolymers, ethylene / butene copolymers, ethylene / hexene copolymers, and ethylene / methacrylate copolymers, or laminated structures formed by stacking two or more of these membranes.

[0274] In addition, the diaphragm can also 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, it can also be a coated diaphragm containing ceramic components or polymeric substances. The diaphragm can be selectively configured as a single-layer or multi-layer structure.

[0275] As electrolytes, examples that can be used in the manufacture of lithium-ion secondary batteries include organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, and molten inorganic electrolytes, but are not limited to these.

[0276] Specifically, electrolytes can contain non-aqueous organic solvents and metal salts.

[0277] 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, tetrahydrofuran, 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-imidazolinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ethers, methyl propionate, and ethyl propionate, among other non-protic organic solvents.

[0278] Among carbonate-based organic solvents, ethylene carbonate and propylene carbonate, as cyclic carbonates, are high-viscosity organic solvents with high dielectric constants, enabling them to readily dissociate lithium salts. Therefore, they are preferred as non-aqueous organic solvents. Furthermore, if such cyclic carbonates are mixed in appropriate proportions with low-viscosity, low-dielectric-constant linear carbonates such as dimethyl carbonate and diethyl carbonate, an electrolyte with high conductivity can be obtained, which is even more preferable.

[0279] As a metal salt, it can be a lithium salt.

[0280] Lithium salts are substances that are readily soluble in non-aqueous electrolytes.

[0281] As the anionic moiety of lithium salts, examples include those selected from F. - Cl - I - NO3 - N(CN)2 - BF4 - ClO4 - PF6 - (CF3)2PF4 - (CF3)3PF3 - (CF3)4PF2 - (CF3)5PF - (CF3)6P - CF3SO3 - CF3CF2SO3 - (CF3SO2)2N - (FSO2)2N - CF3CF2(CF3)2CO - (CF3SO2)2CH - (SF5)3C - (CF3SO2)3C - CF3(CF2)7SO3 - CF3CO2- CH3CO2 - SCN - and (CF3CF2SO2)2N - One or more of them.

[0282] In addition to non-aqueous organic solvents and metal salts, the electrolyte may also contain one or more additives to improve battery life, suppress battery capacity reduction, and increase battery discharge capacity. These additives may include: halogenated alkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ethers, ethylenediamine, dimethyl ethylene glycol ether (glyme), triammonium hexaphosphate, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N,N-substituted imidazolines, dialkyl ethylene glycol ethers, ammonium salts, pyrrole, 2-methoxyethanol, or aluminum trichloride.

[0283] The aforementioned secondary batteries can be configured as battery modules comprising individual secondary batteries and battery packs comprising battery modules. Battery modules and battery packs can be used as power sources for medium to large-sized equipment selected from electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, and energy storage systems.

[0284] <Composition>

[0285] [Resin, ceramics, and concrete, etc.]

[0286] The composition of the present invention comprises the aggregate of the present invention, and a composition selected from at least one of resin, ceramic and concrete.

[0287] Another composition of the present invention comprises a multi-walled carbon nanotube aggregate and at least one selected from a dispersion medium, resin, ceramic and concrete, wherein the multi-walled carbon nanotube aggregate comprises multi-walled carbon nanotubes and Fe atoms, and the Fe atom content relative to the total mass of the aggregate is 0.5% by mass or more and less than 10% by mass.

[0288] 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.

[0289] As ceramics, examples include crystalline ceramics and amorphous ceramics.

[0290] As for concrete, silicate cement concrete can be cited as an example.

[0291] The compositions of the present invention may further contain other components such as water and organic solvents.

[0292] In the composition of the present invention, when the content of the aggregate of the present invention is 100 parts by weight, the content of at least one selected from resin, ceramic and concrete is generally 10 to 1,000,000 parts by weight, preferably 100 to 100,000 parts by weight, more preferably 1,000 to 40,000 parts by weight, and when other components are included, it is preferably 1 to 10,000 parts by weight, more preferably 10 to 1,000 parts by weight.

[0293] In the composition of the present invention, the aggregate, resin, ceramic, concrete, and other components may each contain one or more of the following:

[0294] [Method for manufacturing the composition]

[0295] The compositions of the present invention can be manufactured, for example, by mixing the aggregates of the present invention with resin, ceramics, or pre-hardened concrete. The resin may be in the form of powder, granules, solution, or dispersion. The ceramic may be in the form of powder, precursor solution, or dispersion.

[0296] The compositions of the present invention can also be manufactured, for example, by dispersing the aggregates of the present invention in a solution of resin, a ceramic precursor or dispersion, or in concrete before hardening and then molding them.

[0297] [Use of the composition]

[0298] When the compositions of the present invention contain resin or ceramic, they are useful, for example, as structural materials, conductive materials, thermal management materials, or antistatic materials.

[0299] When the composition of the present invention contains concrete, it is useful as a lightweight, durable building material, or (if necessary) an energy storage device impregnated with electrolyte.

[0300] <Planar aggregate>

[0301] The planar aggregate of the present invention comprises the multi-walled carbon nanotube aggregate of the present invention. The content of the multi-walled carbon nanotube aggregate of the present invention in the planar aggregate of the present invention is typically 1% by mass or more relative to the total mass of the planar aggregate. The planar aggregate of the present invention may also comprise other components such as carbon nanotube aggregates with a maximum length of less than 1000 μm, particularly multi-walled carbon nanotube aggregates with a maximum length of less than 1000 μm.

[0302] [Methods for constructing planar aggregates]

[0303] The method for manufacturing the planar assembly of the present invention is not particularly limited.

[0304] The planar aggregate of the present invention can be made by dispersing the multi-walled carbon nanotube aggregate of the present invention, or the multi-walled carbon nanotube aggregate of the present invention, as well as carbon nanotube aggregates with a maximum length of less than 1000 μm, especially multi-walled carbon nanotube aggregates with a maximum length of less than 1000 μm, and other components in water or other fluids, and filtering them once or twice or more, for example, to form a non-woven fabric-like planar aggregate.

[0305] As one embodiment of the planar assembly of the present invention, a thin film can be cited as an example.

[0306] The planar assembly of the present invention is useful, for example, for filters, electromagnetic shields, and protective films for extreme ultraviolet (EUV) radiation.

[0307]

Example

[0308] The following examples illustrate the aggregates and dispersions comprising the aggregates of the present invention in more detail. The aggregates and dispersions of the present invention are not limited to the following examples as long as they do not depart from their spirit.

[0309] In addition, unless otherwise stated, "%" means "quality%".

[0310] (Example 1)

[0311] 1. Manufacturing of sheet-like ULMWCNT assembly 1

[0312] The sheet-like ULMWCNT aggregate 1 was prepared by a floating catalyst method (CVD) that directly interacts with the self-assembly of CNT bundles in the gas phase.

[0313] First, ferrocene, a precursor for a metal catalyst containing Fe atoms, and thiophene, a promoter, are introduced into a continuous flow of carrier gas in a cross-flow reactor where the temperature is controlled between 400°C and 700°C. 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).

[0314] By maintaining the temperature within the transverse reactor within the aforementioned range, the metal catalyst precursor is generated as a granular metal catalyst. The region where the metal catalyst is generated is called the first temperature zone.

[0315] Next, methane, serving as a carbon source, is released into the carrier gas stream. The metal catalyst and carbon source are then supplied to a second temperature zone, located downstream of the first temperature zone and controlled at 1400°C. The second temperature zone is maintained at a temperature sufficient to generate carbon nanotube aggregates.

[0316] In the second temperature zone, an electric field is generated within the temperature-controlled continuous flow reactor, thereby generating aggregates of ULMWCNT.

[0317] The aggregates are ULMWCNT aggregates discharged continuously from the outlet of a continuous flow reactor with the temperature controlled between 100℃ and 500℃. The sheet-like ULMWCNT aggregates are collected by continuous discharge.

[0318] The resulting sheet-like ULMWCNT aggregate contains ULMWCNT and MWCNT.

[0319] To adjust the Fe atom content ratio, the obtained sheet-like ULMWCNT aggregate was washed with deionized water for 10 seconds to obtain sheet-like ULMWCNT aggregate 1.

[0320] 2. Preparation of Dispersion 1

[0321] The following materials were mixed and pre-dispersed using an ACE homogenizer manufactured by Nippon Seiki Co., Ltd. for 1 hour to obtain pre-dispersion liquid 1. In order to prevent the sheet-like ULMWCNT aggregate 1 from tangling on the blades of the homogenizer, the sheet-like ULMWCNT aggregate 1 was cut into small fragments of about 1cm × 1cm with scissors before mixing.

[0322] (Dispersion composition)

[0323] • The above-obtained sheet-like ULMWCNT aggregate 1: 1.1g

[0324] • High viscosity sodium carboxymethyl cellulose (manufactured by MP Biomedicals): 1.65g

[0325] • Pure water: 547.2g

[0326] As a wet jet mill, a high-pressure homogenizer (model: NAGS100) manufactured by Tokimitsu Corporation was used to perform the formal dispersion of the pre-dispersion liquid 1 to obtain dispersion liquid 1.

[0327] Nozzle diameter: 0.22mm

[0328] Pressure: 85MPa

[0329] Number of times: 8

[0330] Method: Looping

[0331] 3. Evaluation

[0332] 3-1. Proportion of ULMWCNTs with a maximum length of 1000μm to 30000μm

[0333] First, in multiple adjacent SEM images (magnification: 5000x) of the sheet-like ULMWCNT aggregate 1 obtained in Example 1 above, 100 MWCNTs were observed. The results showed that the proportion of ULMWCNTs with a maximum length of 1000μm to 30000μm was 75%, and the maximum length of the observed 100 MWCNTs was 3500μm.

[0334] 3-2. Fe atom content ratio relative to the total mass of the aggregate

[0335] The Fe atom content of the sheet-like ULMWCNT aggregate 1 of Example 1 was determined using an inductively coupled plasma mass spectrometry (ICP-MS) apparatus (PerkinElmer, NexION 2000C). As a pretreatment, the sheet-like ULMWCNT aggregate 1 was subjected to low-temperature ashing / acid dissolution, and the determination was performed using the above apparatus. The results showed that the Fe atom content of the sheet-like ULMWCNT aggregate 1 of Example 1 was 5.6% by mass relative to the total mass of the aggregate.

[0336] 3-3. Rsp value

[0337] The dispersion 1 obtained by dispersing and liquefying the sheet-like ULMWCNT aggregate 1 of Example 1 using the above method was placed into a sample tube, and the relaxation time T was measured using a pulsed nuclear magnetic resonance (pulse NMR) device (Bruker, the Minispec MQ20). 2s .

[0338] In addition, pure water was placed in the sample tube, and the relaxation time T was measured. 2b The Rsp value is calculated using the following formula.

[0339] Rsp = (T 2b / T 2s )- 1

[0340] The results are shown in Table 1.

[0341] 3-4. Viscosity

[0342] The viscosity of dispersion 1 was obtained from a rheometer. The shear rate dependence of viscosity was evaluated using a viscoelasticity measuring apparatus (Antonpah, MCR302) under the following conditions.

[0343] Measuring fixture: cone plate

[0344] Measurement mode: Rotation mode

[0345] Shear rate: 0.01s -1 ~1000s -1

[0346] Temperature: 25℃

[0347] From the obtained data, read the viscosity at the following shear rates.

[0348] Shear rate = 1s -1

[0349] Shear rate = 100s -1

[0350] The results are shown in Table 1.

[0351] 3-5. Volume resistivity

[0352] The sheet-like ULMWCNT assembly 1 of 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, Low Resistance Probe MCP-PD511 for Powder (Constant Current Application Method, Four-Probe Method), all manufactured by Nitto Seiko Analytical Technology Co., Ltd.), the pulverized sheet-like ULMWCNT assembly 1 was introduced into the powder resistivity measurement probe unit. Using the attached hydraulic pump, a pressure of 5 kN was applied until the target load was reached, and the volume resistivity (Ω·cm) was measured.

[0353] The measured volume resistivity at 5 kN was 9.2 × 10⁻⁶. -3 Ω·cm.

[0354] 3-6. Tensile strength

[0355] The sheet-like ULMWCNT assembly 1 of Example 1 was cut into 5mm×100mm pieces as test specimens, fixed in the clamping part of a tensile testing machine (manufactured by Shimadzu Corporation, Autograph AG-IS), and subjected to a tensile test at a speed of 1mm / min.

[0356] The tensile strength was measured to be 11.3 MPa.

[0357] (Example 2)

[0358] 1. Manufacturing of fibrous ULMWCNT aggregate 2

[0359] The fibrous ULMWCNT aggregate 2, like the sheet-like ULMWCNT aggregate 1, was also produced by a floating catalyst method (CVD) that directly interacts with the self-assembly of CNT bundles in the gas phase.

[0360] First, ferrocene, a precursor for a metal catalyst containing Fe atoms, and thiophene, a promoter, are introduced into a continuous flow of carrier gas within a cross-flow reactor at a temperature controlled between 400°C and 700°C. A mixture of nitrogen and argon is used as the carrier gas. The carrier gas flow rate is set to 30,000 sccm.

[0361] By maintaining the temperature within the transverse reactor within the aforementioned range, the metal catalyst precursor is generated as a granular metal catalyst. The region where the metal catalyst is generated is called the first temperature zone.

[0362] Next, methane, serving as a carbon source, is released into the carrier gas stream. The metal catalyst and carbon source are then supplied to a second temperature zone, located downstream of the first temperature zone and controlled at 1400°C. The second temperature zone is maintained at a temperature sufficient to generate carbon nanotube aggregates.

[0363] In the second temperature zone, an electric field is generated within the temperature-controlled continuous flow reactor, thereby generating fibrous ULMWCNT aggregates.

[0364] The aggregates were discharged as carbon nanotube aggregates through the outlet of a continuous flow reactor with the temperature controlled between 100℃ and 500℃. The fibrous ULMWCNT aggregates were collected by continuous discharge.

[0365] The resulting fibrous ULMWCNT aggregate contains ULMWCNT and MWCNT.

[0366] To adjust the Fe atom content ratio, the obtained fibrous ULMWCNT aggregate was washed with deionized water for 10 seconds to obtain fibrous ULMWCNT aggregate 2.

[0367] 2. Preparation of Dispersion 2

[0368] Using the obtained fibrous ULMWCNT aggregate 2, a dispersion 2 was obtained in the same manner as in Example 1. In order to prevent the fibrous ULMWCNT aggregate 2 from tangling on the blades of the homogenizer, the fibrous ULMWCNT aggregate 2 was cut into lengths of about 1 cm with scissors before mixing.

[0369] 3. Evaluation

[0370] In the determination of tensile strength, except that the fibrous ULMWCNT aggregate 2 of Example 2 was cut into 100 mm lengths, fixed in the clamping part of the tensile testing machine (manufactured by Shimadzu Corporation, Autograph AG-IS), and tensile test was performed at a speed of 1 mm / min using a wire clamp (manufactured by Shimadzu Corporation), the fibrous ULMWCNT aggregate 2 and dispersion 2 of Example 2 were evaluated in the same manner as in Example 1.

[0371] The results are shown in Table 1.

[0372] (Comparative Example 1)

[0373] 1. Manufacturing of sheet-like ULMWCNT assembly 3

[0374] The sheet-like ULMWCNT aggregates collected in Example 1 were immersed in a polytetrafluoroethylene (PTFE) tray containing hydrochloric acid (manufactured by Fujifilm and Koichi Chemical Co., Ltd., premium reagent) for 24 hours. Afterwards, the sheet-like ULMWCNT aggregates were removed from the tray and rinsed with deionized water until the pH of the rinsing water became 7, yielding sheet-like ULMWCNT aggregate 3.

[0375] 2. Preparation of Dispersion 3

[0376] Using the sheet-like ULMWCNT aggregate 3 obtained in Comparative Example 1, a dispersion 3 was obtained in the same manner as in Example 1.

[0377] 3. Evaluation

[0378] The sheet-like ULMWCNT aggregate 3 and dispersion 3 of Comparative Example 1 were evaluated in the same manner as in Example 1.

[0379] The results are shown in Table 1.

[0380] (Comparative Example 2)

[0381] 1. Preparation of powdered MWCNT aggregate 1

[0382] As a powdered MWCNT assembly 1, "multi-walled carbon nanotubes" (product number: FT7000, manufactured by C-nano Corporation) were prepared.

[0383] 2. Preparation of Dispersion 4

[0384] Dispersion 4 was obtained using the powdered MWCNT1 of Comparative Example 2, in the same manner as in Example 1.

[0385] 3. Evaluation

[0386] In the determination of tensile strength, in addition to casting the dispersion 4 onto a 22mm×75mm×3mm glass slide-shaped silicon plate (manufactured by Dosaka EM Co., Ltd., #08-1044), heating it to 100°C to dry it, and using this as the test specimen, the tensile test was performed on the clamping part of the tensile testing machine (manufactured by Shimadzu Corporation, Autograph AG-IS) at a speed of 1mm / min. The powdered MWCNT aggregate 1 and dispersion 4 of Comparative Example 2 were evaluated in the same manner as in Example 1.

[0387] The results are shown in Table 1.

[0388] (Comparative Example 3)

[0389] 1. Preparation of powdered MWCNT aggregate 2

[0390] As a powdered MWCNT assembly 2, "multi-walled carbon nanotubes" (product number: FT6120, manufactured by C-nano Corporation) were prepared.

[0391] 2. Preparation of Dispersion 5

[0392] Using the powdered MWCNT aggregate 2 of Comparative Example 3, a dispersion 5 was obtained in the same manner as in Example 1.

[0393] 3. Evaluation

[0394] In the determination of tensile strength, the dispersion 5 was cast onto a 22mm×75mm×3mm glass slide-shaped silicon plate (manufactured by Dosaka EM Co., Ltd., #08-1044), heated to 100°C to dry it, and used as the test specimen. The specimen was fixed in the clamping part of the tensile testing machine (manufactured by Shimadzu Corporation, Autograph AG-IS) and a tensile test was performed at a speed of 1mm / min. The powdered MWCNT aggregate 2 and dispersion 5 of Comparative Example 3 were evaluated in the same manner as in Example 1.

[0395] The results are shown in Table 1.

[0396] (Comparative Example 4)

[0397] 1. Preparation of powdered SWCNT aggregate 1

[0398] As a powdered SWCNT aggregate 1, "single-walled carbon nanotubes" (product number: TUBALL, manufactured by OCSiAl) were prepared.

[0399] 2. Preparation of Dispersion 6

[0400] As a dispersion of the powdered SWCNT aggregate 1 in Comparative Example 4, dispersion 6 (trade name: TUBALL) was used. TM BATT H2O, an aqueous solution of single-walled carbon nanotubes (CNTs), manufactured by OCSiAl. The concentration of CNTs was adjusted to 0.2% by mass.

[0401] 3. Evaluation

[0402] In the determination of tensile strength, in addition to casting the dispersion 6 onto a 22mm×75mm×3mm glass slide-shaped silicon plate (manufactured by Dosaka EM Co., Ltd., #08-1044), heating it at 100°C to dry it, and using this as the test specimen, the tensile test was performed on the clamping part of the tensile testing machine (manufactured by Shimadzu Corporation, Autograph AG-IS) at a speed of 1mm / min. The powdered SWCNT aggregate 1 and dispersion 6 of Comparative Example 4 were evaluated in the same manner as in Example 1.

[0403] The results are shown in Table 1.

[0404] Table 1

[0405]

[0406] As shown in Table 1, the sheet-like ULMWCNT aggregate 1 (Example 1) and the fibrous ULMWCNT aggregate 2 (Example 2) of the embodiments are ULMWCNT aggregates, which have the property of easily entangled with each other, thus exhibiting high conductivity. Furthermore, since the Fe atom content is 0.5% by mass or more but less than 10% by mass, the resulting dispersion has a high Rsp value, good affinity with the dispersion medium, and a viscosity suitable for practical applications. Therefore, it can be seen that the aggregates of the embodiments have high conductivity and good dispersibility in the dispersion medium.

[0407] On the other hand, the comparative example's sheet-like ULMWCNT aggregate 3 (Comparative Example 1), containing less than 0.5% by mass of Fe atoms, although being an ULMWCNT aggregate and possessing the property of easily entangled with each other, thus exhibiting high conductivity, did not adequately hinder the contact between multiple ULMWCNTs, and aggregation was not suppressed. Therefore, the resulting dispersion had a low Rsp value, problematic affinity with the dispersion medium, and low viscosity, especially a shear rate of 100 s. -1 The value is high, at a level insufficient for practical use. Therefore, it can be seen that its dispersibility in the dispersion medium is poor compared to the assembly of the embodiments.

[0408] Comparative Examples 1 (Comparative Example 2) and 2 (Comparative Example 3) of powdered MWCNT aggregates have short maximum lengths and poor entanglement properties, resulting in low electrical conductivity. Furthermore, due to their poor entanglement properties, MWCNTs do not readily aggregate, and regardless of the Fe atom content ratio, the resulting dispersion has a low Rsp value, problematic affinity with the dispersion medium, and low viscosity, making it impractical for practical applications.

[0409] Comparative Example 4 (comparative example 1) is a powdered SWCNT aggregate, which has higher conductivity than MWCNTs due to being SWCNTs. However, SWCNTs aggregate more strongly than MWCNTs, and even when the Fe atom content is set to 10.0% by mass or more, the aggregation of SWCNTs is not suppressed. Therefore, the resulting dispersion has a low Rsp value, poor affinity with the dispersion medium, and a high viscosity, which is not practical.

Claims

1. A multi-walled carbon nanotube aggregate comprising multi-walled carbon nanotubes with a maximum length of 1000 μm to 30000 μm and Fe atoms. The Fe atom content relative to the total mass of the aggregate is more than 0.5% by mass and less than 10% by mass.

2. The multi-walled carbon nanotube assembly according to claim 1, wherein it is a conductive additive.

3. A multi-walled carbon nanotube dispersion comprising the multi-walled carbon nanotube aggregate as described in claim 1 or claim 2, and a dispersion medium.

4. A conductive material comprising the multi-walled carbon nanotube assembly as described in claim 1 or claim 2.

5. The multi-walled carbon nanotube dispersion according to claim 3 is an ink composition for forming a lithium battery negative electrode.

6. An electrode comprising an electrode active material and the conductive material of claim 4.

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

8. A composition comprising the multi-walled carbon nanotube assembly of claim 1 or claim 2, and at least one selected from resins, ceramics and concrete.

9. A multi-walled carbon nanotube assembly comprising multi-walled carbon nanotubes with a tensile strength of 10 MPa to 100 MPa and Fe atoms. The Fe atom content relative to the total mass of the aggregate is more than 0.5% by mass and less than 10% by mass.

10. The multi-walled carbon nanotube assembly according to claim 9, wherein it is a conductive additive.

11. A multi-walled carbon nanotube dispersion comprising the multi-walled carbon nanotube aggregate of claim 9 or claim 10, and a dispersion medium.

12. A conductive material comprising the multi-walled carbon nanotube assembly of claim 9 or claim 10.

13. The multi-walled carbon nanotube dispersion according to claim 11 is an ink composition for forming a lithium battery negative electrode.

14. An electrode comprising an electrode active material and the conductive material of claim 12.

15. A secondary battery comprising the electrode as described in claim 14.

16. A composition comprising the multi-walled carbon nanotube assembly of claim 9 or claim 10, and at least one selected from resins, ceramics, and concrete.

17. A composition comprising an aggregate of multi-walled carbon nanotubes, and at least one selected from a dispersion medium, resin, ceramics, and concrete. The multi-walled carbon nanotube assembly comprises multi-walled carbon nanotubes and Fe atoms, with the Fe atom content relative to the total mass of the assembly being more than 0.5% by mass and less than 10% by mass.

18. A multi-walled carbon nanotube dispersion comprising multi-walled carbon nanotubes with a tensile strength of 10 MPa to 100 MPa, and a dispersion medium.

19. A planar assembly comprising the multi-walled carbon nanotube assembly of claim 1, claim 2, claim 9 or claim 10.

20. A filter that uses the planar assembly as described in claim 19.

21. An electromagnetic shielding body that uses the planar assembly as described in claim 19.

22. An extreme ultraviolet protective film, which uses the planar aggregate as described in claim 19.

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