Carbon nanotube dispersion composition, secondary battery electrode composition, electrode film, secondary battery, and vehicle

Abstract

A carbon nanotube dispersion composition according to the present invention comprises carbon nanotubes, a dispersant, and water, wherein the carbon nanotubes include carbon nanotube aggregates in which two or more carbon nanotube units having an average outer diameter of 3-8 nm and the number of layers of 3-15 are bundled in parallel by interaction, and the average outer diameter of the carbon nanotube aggregates is 10-50 nm.

Description

Carbon nanotube dispersion composition, composition for secondary battery electrodes, electrode film, secondary battery, and vehicle

[0001] This disclosure relates to a carbon nanotube dispersion composition and its use. More specifically, this disclosure relates to a carbon nanotube dispersion composition, a secondary battery electrode composition comprising the carbon nanotube dispersion composition and an active material, an electrode film formed by creating the secondary battery electrode composition in a film form, and a secondary battery comprising the electrode film and an electrolyte.

[0002] With the spread of electric vehicles and the miniaturization, weight reduction, and increased performance of portable devices, there is a growing demand for secondary batteries with high energy density and higher capacity. Against this backdrop, non-aqueous electrolyte secondary batteries, particularly lithium-ion secondary batteries, which use non-aqueous electrolytes, are increasingly being used in many devices due to their high energy density and high voltage characteristics.

[0003] In the electrode materials used in these lithium-ion secondary batteries, carbon materials with a low potential close to lithium (Li) and a large charge / discharge capacity per unit mass are used as negative electrode materials; graphite is a typical example. However, because these electrode materials are used up to near their theoretical charge / discharge capacity per unit mass, the energy density per unit mass of the battery is approaching its limit. Therefore, in order to increase the utilization rate of the electrodes, attempts are being made to reduce conductive additives and binders that do not contribute to the charge / discharge capacity.

[0004] Conductive additives used include carbon black, Ketjenblack, fullerene, graphene, and fine carbon materials. Carbon nanotubes, a type of fine carbon fiber, are particularly frequently used. For example, it is known that adding carbon nanotubes to a graphite or silicon negative electrode improves the conductivity of the electrode, electrode strength such as adhesion and expansion / contraction resistance, and the rate characteristics and cycle characteristics of lithium-ion secondary batteries (see, for example, Patent Document 1). Studies have also been conducted to reduce electrode resistance by adding carbon nanotubes to the positive electrode (see, for example, Patent Documents 2, 3, and 4).

[0005] Thus, it is known that using carbon nanotubes with a small average outer diameter and long fiber length allows for the efficient formation of a conductive network with a small amount of material, thereby reducing the amount of conductive additive contained in the positive and negative electrodes of lithium-ion secondary batteries.

[0006] Japanese Patent Publication No. 2021-72279, Japanese Patent Publication No. 2019-210173, International Publication No. 2017 / 171291, Japanese Patent Publication No. 2022-521422

[0007] However, because carbon nanotubes are fibrous and have strong cohesive forces, it is difficult to obtain a carbon nanotube dispersion that is uniformly dispersed and maintains its dispersibility over a long period of time.

[0008] Patent Document 1 describes a material with an average outer diameter greater than 3 nm and less than or equal to 25 nm, and a BET specific surface area of ​​150 m². ２ / g to 800m ２ A carbon nanotube dispersion composition with a fiber length of 0.8 to 3.5 μm is prepared by dispersing carbon nanotubes at a concentration of 1 / g, a dispersant, and a solvent using a high-pressure homogenizer. In Patent Document 2, carbon nanotubes with a G / D ratio of 1.5 to 5.0 are prepared by heat-treating carbon nanotubes, and polyvinylpyrrolidone is added as a dispersant. These are then dispersed using zirconia beads to prepare a carbon nanotube dispersion. The carbon nanotube dispersion prepared as described above is dispersed in a state where the carbon nanotubes have been broken down to individual units. While the conductivity of the electrode is improved, the rigidity due to the twisting and aggregation of carbon nanotube aggregates is impaired, resulting in insufficient electrode strength.

[0009] Based on the above, one embodiment of the present invention provides a carbon nanotube dispersion composition that is excellent in terms of time stability and can be applied to various application fields where durability is required in addition to high conductivity. Another embodiment of the present invention provides an electrode film with high conductivity and excellent electrode strength using the above carbon nanotube dispersion composition or a secondary battery electrode composition using the above carbon nanotube dispersion composition. Furthermore, another embodiment of the present invention provides a secondary battery having excellent cycle characteristics.

[0010] One embodiment of the present invention relates to a carbon nanotube dispersion composition comprising carbon nanotubes, a dispersant, and water, wherein the carbon nanotubes include carbon nanotube aggregates in which two or more carbon nanotube units, each having an average outer diameter of 3 nm to 8 nm and 3 to 15 layers, are bundled together in parallel by interaction, and the average outer diameter of the carbon nanotube aggregates is 10 nm to 50 nm. Another embodiment of the present invention relates to a secondary battery electrode composition comprising the carbon nanotube dispersion composition of the above embodiment. Another embodiment of the present invention relates to an electrode film comprising a coating film of the secondary battery electrode composition of the above embodiment. Another embodiment of the present invention relates to a secondary battery comprising the electrode film of the above embodiment. Another embodiment of the present invention relates to a vehicle comprising the secondary battery of the above embodiment.

[0011] By using a carbon nanotube dispersion composition according to one embodiment of the present invention, an electrode film with not only high conductivity but also excellent electrode strength, and a secondary battery electrode composition capable of forming such an electrode film can be obtained. Furthermore, a secondary battery with excellent cycle characteristics can be obtained. Thus, according to one embodiment of the present invention, a carbon nanotube dispersion composition can be obtained that is excellent in terms of time stability and applicable to various application fields where high conductivity and durability are required.

[0012] Figure 1 is a photograph of the carbon nanotube (A-1) prepared in the manufacturing example, observed at 1,000,000x magnification using a transmission electron microscope. Figure 2 is a photograph of the carbon nanotube dispersion composition (D1-2) prepared in Example 1-2, observed at 500,000x magnification using a transmission electron microscope. Figure 3 shows the viscoelasticity measurement results of the secondary battery electrode compositions prepared in Example 2-2, Comparative Example 2-6, and Comparative Example 2-7. Figure 4 shows the viscosity measurement results of the secondary battery electrode compositions prepared in Example 2-2, Comparative Example 2-6, and Comparative Example 2-7.

[0013] The following describes specific embodiments of the present invention, including carbon nanotube dispersion compositions, secondary battery electrode compositions, electrode films, and secondary batteries. However, the present invention is not limited to these embodiments and can include a variety of other embodiments.

[0014] The numerical values ​​specified in this specification are those obtained by the methods disclosed in the embodiments or examples. In this specification, the numerical range specified using "~" includes the numerical values ​​before and after "~" as the lower and upper limits. In this specification, carbon nanotubes may be written as "CNT". In this specification, a carbon nanotube unit may be called a "CNT unit", a carbon nanotube aggregate may be called a "CNT aggregate", and a carbon nanotube dispersion composition may be called a "CNT dispersion composition", or simply a "dispersion composition". A carbon nanotube aggregate in which two or more are bundled in parallel by interaction is also called a "bundled CNT". Unless otherwise noted, the various components described in this specification may be used individually or in combination of two or more.

[0015] Furthermore, the term "CNT dispersion composition" refers to the state before the addition of active material. In this respect, CNT dispersion compositions are distinguished from secondary battery electrode compositions that contain active material. That is, CNT dispersion compositions substantially do not contain active material. This concept excludes the state in which active material is intentionally added to the CNT dispersion composition. More specifically, the content of active material relative to the total mass of the CNT dispersion composition may be 1% by mass or less, 0.5% by mass or less, or 0.1% by mass or less, or even 0% by mass. The active material will be described later.

[0016] A carbon nanotube dispersion composition, which is one embodiment of the present invention, comprises carbon nanotubes, a dispersant, and water, wherein the carbon nanotubes include carbon nanotube aggregates in which two or more carbon nanotube units, each having an average outer diameter of 3 nm to 8 nm and 3 to 15 layers, are bundled together in parallel by interaction, and the average outer diameter of the carbon nanotube aggregates is 10 nm to 50 nm.

[0017] A CNT unit is an individual carbon nanotube fiber, possessing a specific average outer diameter and number of layers. A CNT aggregate is a form in which multiple CNT units aggregate together through interactions such as van der Waals forces, forming bundles of two or more parallel strands, resulting in a bundle-like or condensed structure. By controlling the average outer diameter of the CNT aggregates in the CNT dispersion composition to be between 10 nm and 50 nm, a CNT dispersion composition with not only high conductivity but also good durability can be obtained. The CNT dispersion composition may contain some CNT units that do not form CNT aggregates, as well as some CNT aggregates other than those described above.

[0018] The average outer diameter of the CNT aggregate can be adjusted by controlling the dispersion method so that small-diameter, easily broken CNTs are not excessively broken down during dispersion, and the bundled state is maintained without over-unraveling each individual CNT, as described in the method for producing the CNT dispersion composition later. Examples of dispersion control methods include crushing of the CNT aggregate using collision energy from media dispersion, crushing of the CNT aggregate using shear energy from medialess dispersion, control of resin adsorption to CNTs and suppression of re-aggregation of CNTs by adjusting the amount of dispersant, adjustment of interaction with solvent or resin by modifying or surface treating CNTs, and suppression of CNT re-aggregation and sedimentation by stabilizers or thickeners.

[0019] In the CNT dispersion composition, the CNTs are formed by two or more CNT units being bundled together in parallel by interaction, forming a CNT aggregate. Such CNT aggregates are also called bundled CNTs and are widely known to those skilled in the art. The carbon nanotube dispersion composition of this embodiment is characterized by containing CNT aggregates (bundled CNTs) having an average outer diameter of 10 nm to 50 nm, and the CNT aggregate being formed from two or more CNT units having an average outer diameter of 3 nm to 8 nm and 3 to 15 layers. In this embodiment, the average outer diameter of the CNT aggregates (bundled CNTs) may be 10 nm to 50 nm. The average outer diameter may be 15 nm or more, 18 nm or more, or 20 nm or more. The average outer diameter may be 40 nm or less, 35 nm or less, or 30 nm or less. In some embodiments, the average outer diameter is preferably 18 nm to 30 nm. If the average outer diameter of the CNT aggregates falls within the above range, it can be determined that the CNT aggregates are sufficiently dispersed and unraveled. As a result, the number of CNT aggregates in the CNT dispersion composition becomes sufficient, enabling the formation of an efficient conductive network. Furthermore, the carbon nanotubes, arranged in a mesh-like structure within the electrode film, act as a structural reinforcement, improving electrode strength. The average outer diameter of the CNT aggregates in the CNT dispersion composition can be determined by measuring the outer diameters of 50 randomly selected CNT aggregates using a transmission electron microscope and calculating the arithmetic mean. Specifically, it can be measured by the method described in the examples.

[0020] The standard deviation of the outer diameter of the CNT aggregate is preferably 20 nm or less, and more preferably 10 nm or less. When the standard deviation of the outer diameter is within the above range, the storage modulus of the secondary battery electrode composition becomes appropriate, the bundled CNTs are uniformly dispersed within the electrode, and the electrode strength and the cycle characteristics of the secondary battery are further improved.

[0021] The average fiber length of the CNTs in the CNT dispersion composition is preferably 0.8 to 5 μm, and more preferably 1 to 3.5 μm. When the average fiber length is within the above range, a conductive network can be efficiently formed with a small amount, and the amount of CNTs contained in the positive and negative electrodes of the secondary battery can be reduced. When the average fiber length of the CNTs is 0.8 μm or more, the CNTs are spread in a mesh-like manner within the electrode film and act as a structural reinforcement material, thereby further improving the strength of the electrode film (electrode). Furthermore, by using CNTs with a larger fiber length, the amount of CNTs contained in the electrode is reduced, which can suppress an increase in the surface area of ​​the electrode, suppress the decomposition of the electrolyte during high-temperature storage in the secondary battery, and further improve the cycle characteristics. Also, when the average fiber length of the CNTs is 5 μm or less, a sufficient amount of CNTs can be contained in the electrode, and a conductive network can be efficiently formed.

[0022] The average fiber length of CNTs in the above-mentioned CNT dispersion composition is essentially the average fiber length of the CNT aggregates, and can be measured specifically by the following method. The CNT dispersion composition is diluted with water to a CNT concentration of 0.0001% to 0.001% by mass, and then a few drops of the CNT dispersion composition are dropped onto a mica substrate. After that, it is dried on a hot plate at 100°C to prepare a substrate for observing the CNT fiber length. The prepared substrate is photographed using a scanning electron microscope, and the obtained SEM images are analyzed using image analysis software such as "WinROOF2015" (manufactured by Mitani Corporation) or "ImageJ" (open-source image processing and analysis software developed by the National Institutes of Health, USA). The fiber length of 100 CNT aggregates is measured, and the average fiber length of CNTs in the CNT dispersion composition can be determined by the arithmetic mean.

[0023] <Carbon Nanotubes> The CNT dispersion composition of this embodiment contains carbon nanotubes, and the carbon nanotubes include CNT aggregates in which two or more CNT units, each having an average outer diameter of 3 nm or more and 8 nm or less and 3 to 15 layers, are bundled together in parallel by interaction.

[0024] The average outer diameter of the CNT units is between 3 nm and 8 nm. Preferably, it is between 3 nm and 6 nm, and more preferably between 3 nm and 5 nm. By using CNT units with an average outer diameter within the above range, electrodes with excellent conductivity and electrode strength can be obtained. The average outer diameter of the CNT units can be obtained by observing the CNT units constituting the CNT aggregate using a transmission electron microscope, measuring the outer diameter of 50 arbitrarily extracted CNT units, and taking the arithmetic mean of the measured values.

[0025] The standard deviation of the outer diameter of the CNT unit is preferably 2 nm or less, more preferably 1.5 nm or less, and even more preferably 1.2 nm or less. When the standard deviation of the outer diameter of the CNT unit is within the above range, an electrode with superior electrode strength can be easily obtained when used as a composition for secondary battery electrodes.

[0026] The number of layers in the CNT unit may be 3 or more and 15 or less. In some embodiments, the number of layers may be preferably 5 or more, more preferably 8 or more, and even more preferably 10 or more. The number of layers may be preferably 14 or less. In some embodiments, the number of layers may be preferably 3 or more and 13 or less, and even more preferably 8 or more and 13 or less. When the number of layers in the CNT unit is within this range, the viscoelasticity of the secondary battery electrode composition is good when the CNTs are dispersed, the electrode strength is easily improved, and the cycle characteristics of the secondary battery can be improved. The CNT unit may be a mixture of single-walled CNTs and multi-walled CNTs.

[0027] The number of layers in a CNT unit can be determined from the crystallite size (Lc002) and average interplanar spacing (d002) obtained by powder X-ray diffraction analysis of the CNTs, and can be calculated using the following formula (1). Formula (1): Number of layers = Crystallite size (Lc002) / Average interplanar spacing (d002) In the above formula (1), the crystallite size (Lc002) and average interplanar spacing (d002) are the crystallite size (Lc002) and average interplanar spacing (d002) of the maximum peak at the diffraction angle 2θ = 25° ± 2° in powder X-ray diffraction analysis using CuKα rays.

[0028] Specifically, the number of layers in a CNT unit can be determined, for example, by powder X-ray diffraction analysis using the following method. First, the CNTs are packed into a predetermined sample holder so that the surface is flat, and then set in a powder X-ray diffraction analyzer. Measurements are performed under CuKa line conditions (wavelength: 1.54 Å) at a scanning speed of 87.5 seconds for every 0.02° from 2-Theta 10° to 90°. The CNTs can be evaluated by reading the diffraction angle 2θ at which the peak appears. In graphite, a peak is usually detected around 26° for 2θ, and this is known to be a peak due to interlayer diffraction. Since CNTs also have a graphite structure, a peak due to graphite interlayer diffraction is detected in this vicinity, but because CNTs have a cylindrical structure, 2θ will differ from that of graphite. The presence or absence of a peak at a position of 25° ± 2° for 2θ can be used to determine whether the composition includes single-walled CNTs and / or CNTs with a multilayer structure (multilayer CNTs). The peak appearing at 2θ ± 2° is due to interlayer diffraction in a multilayer structure. Therefore, in monowalled carbon nanotubes (SNAFUs) with only one layer and no multilayer structure, the peak at 2θ ± 2° does not appear. On the other hand, if the material is not composed solely of SNAFUs but also contains multilayered carbon nanotubes, the peak may appear at 2θ ± 2°.

[0029] The CNT can measure the full width at half maximum (FWHM) of the (002) crystal peak appearing at a 2θ of 20° to 30° and the full width at half maximum of the (100) crystal peak appearing around 38° to 50°, and then calculate the (Lc002) and (La100) values ​​using the Scherrer formula.

[0030] The crystallite size (Lc002) of the CNTs is preferably 1.0 nm or larger, more preferably 1.9 nm or larger, and even more preferably 2.5 nm or larger. A crystallite size (Lc002) of 1.0 nm or larger allows π electrons to move easily within the crystal layer, enabling the creation of electrodes with excellent conductivity even with a small amount of additive. Alternatively, the crystallite size (Lc002) of the CNTs is preferably less than 5.3 nm, and may be less than 4.8 nm. A crystallite size (Lc002) of less than 5.3 nm allows for the creation of electrode films with excellent flexibility, durability, and other strengths with a small amount of additive.

[0031] The crystallite size (La100) of the CNT is preferably 10 to 100, more preferably 20 to 100, and even more preferably 30 to 100. The crystallite size (La100) is a parameter that reflects the length and crystallinity of the growth unit of the CNT. CNTs with a crystallite size (La100) within the above range tend to have fewer nodes, are not excessively fractured even when subjected to dispersion treatment using shear energy or collision energy, and can maintain a long fiber length, thus providing electrodes with good conductivity and strength, making them preferable.

[0032] The BET specific surface area of ​​CNT is 100 m². ２ / g to 300m ２ It is preferable that it be / g, 100m ２ / g to 250m ２ It is more preferable that the BET specific surface area is 100 m². In some embodiments, the BET specific surface area is 100 m². ２ / g~199m ２ / g. When the BET specific surface area is within the above range, when the CNT dispersion treatment is performed, the refinement of CNT due to excessive dispersion can be suppressed, and a secondary battery electrode composition with good conductivity can be easily obtained. Further, when a secondary battery is used, the decomposition of the electrolytic solution on the electrode surface can be suppressed, and the cycle characteristics of the secondary battery tend to be good. The BET specific surface area can be measured by the BET method of JIS Z 8830:2013.

[0033] The G / D ratio of the CNT may be 1.5 or more and 20 or less. The above G / D ratio may be 1.8 or more and 2.5 or more. The above G / D ratio may be 15 or less, 10 or less, 6 or less. In some embodiments, the G / D ratio is preferably 1.5 to 15, preferably 1.8 to 10, and more preferably 2.5 to 6. In some embodiments, the above G / D ratio is preferably 3 to 20, and more preferably 5.1 to 15. The G / D ratio is the ratio of G / D when the maximum peak intensity in the range of 1560 to 1600 cm －１ is taken as G, and the maximum peak intensity in the range of 1310 to 1350 cm －１ is taken as D. The Raman spectrum can be measured using a laser beam with a wavelength of 532 nm according to the Raman spectroscopy method. When the G / D ratio of the CNT is 1.5 or more, a more highly crystalline CNT can form a conductive network with excellent electrical conductivity. Further, the network is toughened and the toughness of the film is improved. When the G / D ratio is 20 or less, a certain degree of defects remain, so that both toughness and flexibility can be achieved, the contact surface with the active material increases, and an efficient conductive network can be formed.

[0034] The volume resistivity of the CNT is preferably 1.0×10 －３ Ω·cm to 1.5×10 －２ Ω·cm, and more preferably 1.0×10 －３ Ω·cm to 1.3×10 －２ Ω·cm. In some embodiments, the volume resistivity of the CNT is 1.0×10 －３ Ω·cm to 1.0×10 －２The volume resistivity may be Ω·cm. The volume resistivity of the CNT can be measured using a powder resistivity measuring device (Rolestar GP Powder Resistivity Measuring System MCP-PD-51, manufactured by Nitto Seikou Analytech Co., Ltd.). When the volume resistivity is within the above range, the conductivity of the electrode film is good, and a secondary battery with excellent rate characteristics and cycle characteristics can be obtained.

[0035] The carbon purity of the CNTs is preferably high, preferably 90% by mass or more, preferably 98% by mass or more, more preferably 99.5% by mass or more, even more preferably 99.8% by mass or more, and particularly preferably 99.9% by mass or more, based on 100% by mass of CNTs. In other words, the content of metal foreign particles is preferably low, preferably 2.0% by mass or less, more preferably 0.5% by mass or less, even more preferably 0.2% by mass or less, and particularly preferably 0.1% by mass or less, based on 100% by mass of CNTs. By using CNTs produced by a method that does not use a metal catalyst as a core, or CNTs obtained by conventionally known purification methods such as acid treatment, the content of metal foreign particles in the CNT dispersion composition can be reduced to 2.0% by mass or less per 100% by mass of CNTs, thereby improving the cycle characteristics of the secondary battery. The carbon purity of the CNTs can be determined by the method described in the examples using an ICP emission spectrometer.

[0036] The iron content of the CNTs is preferably 5,000 ppm or less, and more preferably 3,000 ppm or less. When the iron content of the CNTs is within the above range, gas generation due to electrolyte decomposition in the secondary battery is suppressed, and the cycle characteristics of the secondary battery tend to be good. In addition, the iron content of the CNT dispersion composition described later can be easily reduced.

[0037] The CNTs may be pulverized CNTs. Pulverization is a process of pulverizing CNTs without substantially involving any liquid substance, and is also called dry pulverization. Pulverization mainly has the effect of reducing the size of the secondary particles of CNTs, thereby improving the dispersibility of CNTs. Dry pulverization equipment can include dry attritors, ball mills, vibratory mills, bead mills, jet mills, hammer mills, etc., and the physical properties of CNTs can be controlled by optimizing the pulverization conditions. When using a pulverization device, the pulverization process can be batch, pass, or circulating, but the pass or circulating method is preferred, and the circulating method is more preferred, due to the ease of controlling the physical properties of the CNTs. The batch method is a method in which the processing is carried out using only the dispersion device body without using piping, etc. The pass method is a method in which the pulverization device body is equipped with a tank that supplies CNTs via piping and a tank that receives CNTs, and the CNTs pass through the pulverization device body. The circulating method is a method in which the CNTs that have passed through the dispersion device body are returned to the tank that supplies CNTs and processed while being circulated. In all cases, the longer the processing time, the more the grinding process progresses, so it is sufficient to pass or recirculate the material until the desired state is reached, and the processing volume can be increased by changing the size of the tank or the processing time. As for the grinding equipment, grinders that are normally used for grinding pigments can be used. Examples include bead mills such as the "Dynamic Mill" from Nippon Coke Industries Co., Ltd. and the "Drystar" from Ajisawa Fine Tech Co., Ltd., dry jet mills such as the "Nanojetmizer" from Aisin Nano Technologies Co., Ltd., the "Single Track Jet Mill" from Seishin Enterprise Co., Ltd., the "Spiral Jet Mill" and "Counter Jet Mill" from Hosokawa Micron Corporation, and hammer mills such as the "ACM Pulperizer" from Hosokawa Micron Corporation, the "Turbo Mill" from Freund Turbo Co., Ltd., and the "Drystr" from Sugino Machine Co., Ltd.

[0038] CNTs can be manufactured using any method. CNTs can generally be manufactured by laser ablation, arc discharge, FCCVD, thermal CVD, plasma CVD, and combustion methods, but are not limited to these.

[0039] The CNTs may be surface-treated CNTs. Alternatively, the CNTs may be CNT derivatives to which functional groups, such as carboxyl groups, have been added. Furthermore, CNTs containing organic compounds, metal atoms, or substances such as fullerenes can also be used.

[0040] <Dispersant> The carbon nanotube dispersion composition of this embodiment includes a dispersant. The dispersant has the function of dispersing and stabilizing the CNTs in the dispersion composition, and other dispersants may be used in combination to the extent that they do not inhibit the effect. Although not particularly limited, it can be one or more selected from surfactants (anionic surfactants, cationic surfactants, amphoteric surfactants, nonionic surfactants) and resin-type dispersants.

[0041] When selecting anionic surfactants, the type is not particularly limited. Specifically, examples include, but are not limited to, fatty acid salts, polysulfonates, polycarboxylates, alkyl sulfates, alkylaryl sulfonates, alkylnaphthalene sulfonates, dialkyl sulfonates, dialkyl sulfosuccinates, alkyl phosphates, polyoxyethylene alkyl ether sulfates, polyoxyethylene alkylaryl ether sulfates, naphthalene sulfonic acid formalin condensates, polyoxyethylene alkyl phosphate sulfonates, glycerol borate fatty acid esters, and polyoxyethylene glycerol fatty acid esters.

[0042] Cationic surfactants include alkylamine salts and quaternary ammonium salts. Specifically, these include, but are not limited to, stearylamine acetate, trimethyl coconut ammonium chloride, trimethyl beef tallow ammonium chloride, dimethyl dioleyl ammonium chloride, methyl oleyl diethanol chloride, tetramethyl ammonium chloride, laurylpyridinium chloride, laurylpyridinium bromide, laurylpyridinium disulfate, cetylpyridinium bromide, 4-alkyl mercaptopyridine, poly(vinylpyridine)-dodecyl bromide, and dodecylbenzyltriethylammonium chloride. Amphoteric surfactants include, but are not limited to, aminocarboxylate salts.

[0043] Examples of nonionic surfactants include, but are not limited to, polyoxyethylene alkyl ethers, polyoxyalkylene derivatives, polyoxyethylene phenyl ethers, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, and alkyl allyl ethers. Specifically, examples include, but are not limited to, polyoxyethylene lauryl ethers, sorbitan fatty acid esters, and polyoxyethylene octylphenyl ethers.

[0044] The selected surfactant is not limited to a single surfactant. Therefore, it is possible to use two or more surfactants in combination. For example, a combination of an anionic surfactant and a nonionic surfactant, or a combination of a cationic surfactant and a nonionic surfactant can be used. In such cases, the amount blended should preferably be an amount suitable for each surfactant component. A combination of an anionic surfactant and a nonionic surfactant is preferred. The anionic surfactant is preferably a polycarboxylate salt or a naphthalene sulfonic acid formalin condensate. The nonionic surfactant is preferably a polyoxyethylene phenyl ether.

[0045] Specific examples of resin-type dispersants include cellulose derivatives (cellulose acetate, cellulose acetate butyrate, cellulose butyrate, cyanoethylcellulose, ethyl hydroxyethylcellulose, nitrocellulose, methylcellulose, ethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, hydroxypropylmethylcellulose, carboxymethylcellulose, etc.), polyvinyl alcohol, polyvinyl butyral, polyvinylpyrrolidone, polyacrylic acid, and polyacrylonitrile polymers. Cellulose derivatives, polyvinyl butyral, polyvinylpyrrolidone, polyacrylic acid, and polyacrylonitrile polymers are particularly preferred. Among cellulose derivatives, methylcellulose, ethylcellulose, and carboxymethylcellulose are preferred. Carboxymethylcellulose, polyacrylic acid, polyvinylpyrrolidone, and polyacrylonitrile polymers are preferred resin-type dispersants, with carboxymethylcellulose, polyacrylic acid, and polyacrylonitrile polymers being particularly preferred.

[0046] As a resin-type dispersant, carboxymethylcellulose can be used in the form of a salt, such as a sodium salt of carboxymethylcellulose, in which the hydroxyl groups of carboxymethylcellulose are replaced with carboxymethyl sodium groups. The degree of etherification of carboxymethylcellulose as a resin-type dispersant is preferably 0.5 to 1.5, and more preferably 0.6 to 1.0. The degree of etherification of carboxymethylcellulose can be measured according to conventional methods. By setting the degree of etherification within the above range, it is possible to provide appropriate affinity to water and CNTs. Furthermore, when used in secondary batteries, it is possible to prevent problems such as the dispersant dissolving in the electrolyte within the battery and increasing the viscosity of the electrolyte. The degree of etherification can be measured, for example, by the following method.

[0047] Weigh approximately 2.0 g of the sample accurately and place it in a 300 mL stoppered Erlenmeyer flask. Add methanol nitrate (1 L of anhydrous methanol and special grade concentrated HNO3). ３Add 100 mL of the solution (after adding 100 mL), shake for 2 hours to convert Na-CMC to H-CMC. Quantitatively transfer the H-CMC to a 1G3 glass filter and filter by suction, then wash with 200 mL of 80% methanol. After that, replace with 50 mL of anhydrous methanol, filter by suction, and dry at 105°C for 2 hours. Accurately weigh 1 to 1.5 g of the oven-dried H-CMC, place in a 300 mL stoppered Erlenmeyer flask, and wet the H-CMC with 15 mL of 80% methanol. Ｎ／１０ Add 50 mL of NaOH and shake at room temperature for 2 hours, using phenol-phthalein as an indicator. Ｎ／１０ H ２ SO ４ The excess NaOH is back-titrated. The degree of etherification is calculated by the following formula: Formula: Degree of etherification (M / c6) = (0.162A / (1 - 0.058A)) A = ((50 × F' - Ｎ／１０ H ２ SO ４ (mL) × F) / (Dry weight of H-CMC (g)) × (1 / 10) F: Ｎ／１０ H ２ SO ４ Factor F': Ｎ／１０ Factors of NaOH

[0048] The polyacrylonitrile polymer is a polymer having nitrile group-containing structural units, and may be a copolymer having nitrile group-containing structural units and structural units other than nitrile group-containing structural units. When the polyacrylonitrile polymer is a copolymer, the content of nitrile group-containing structural units is preferably 15% by mass or more and 60% by mass or less, more preferably 20% by mass or more and 55% by mass or less, and even more preferably 25% by mass or more and 50% by mass or less. Examples of structural units other than nitrile group-containing structural units, based on the total structural units contained in the copolymer, include alkylene structural units, amide group-containing structural units, carboxyl group-containing structural units, etc. The polyacrylonitrile polymer preferably contains a copolymer (sometimes referred to as "copolymer N") having alkylene structural units in a content of 50% by mass or more and 75% by mass or less, and nitrile group-containing structural units in a content of 25% by mass or more and 50% by mass or less.

[0049] The weight-average molecular weight (Mw) of the resin-type dispersant is preferably 5,000 to 500,000, preferably 10,000 to 300,000, and more preferably 10,000 to 100,000. Using a dispersant with an appropriate weight-average molecular weight (Mw) improves adsorption to carbon nanotubes and further improves the stability of the carbon nanotube dispersion composition. Furthermore, if a dispersant exceeding the above range is used, the viscosity of the carbon nanotube dispersion composition increases, and the dispersion efficiency may decrease when using a disperser through which the composition to be dispersed passes through narrow channels, such as a nozzle-type or valve-type high-pressure homogenizer. Here, the weight-average molecular weight (Mw) of the resin-type dispersant can be measured using gel permeation chromatography (GPC) equipped with a differential refractive index (RI) detector.

[0050] <Inorganic Bases, Inorganic Metal Salts> In addition to a dispersant, the CNT dispersion composition may also contain an inorganic base and / or an inorganic metal salt. The inorganic base and inorganic metal salt are preferably compounds having at least one of an alkali metal and an alkaline earth metal. More specifically, examples include chlorides, hydroxides, carbonates, nitrates, sulfates, phosphates, tungstates, vanadates, molybdates, niobates, and borates of alkali metals and alkaline earth metals. Among these, alkali metal and alkaline earth metal chlorides, hydroxides, and carbonates are preferred because they can easily supply cations. Examples of alkali metal hydroxides include lithium hydroxide, sodium hydroxide, and potassium hydroxide. Examples of alkaline earth metal hydroxides include calcium hydroxide and magnesium hydroxide. Examples of alkali metal carbonates include lithium carbonate, lithium bicarbonate, sodium carbonate, sodium bicarbonate, potassium carbonate, and potassium bicarbonate. Examples of alkaline earth metal carbonates include calcium carbonate and magnesium carbonate. Among these, lithium hydroxide, sodium hydroxide, lithium carbonate, and sodium carbonate are more preferred.

[0051] <Acid> The CNT dispersion composition may contain an acid in addition to the dispersant. Adding an acid can change the charge state and the balance between hydrophilic and hydrophobic parts in the dispersion system, which may improve dispersibility. The type of acid is not particularly limited, and one type or a combination of several types may be used. The acid may be, for example, an organic acid or inorganic acid having 6 or fewer carbon atoms. Examples include oxalic acid, lactic acid, citric acid, acetic acid, malonic acid, hydrochloric acid, nitric acid, sulfuric acid, boric acid, and phosphoric acid. If the active material contained in the secondary battery electrode composition described later is, for example, a lithium-containing negative electrode active material and is basic, the dispersibility of the carbon nanotube dispersion composition may be disrupted and it may thicken. However, if an acid is included in addition to the dispersant, the pH change during the manufacture of the electrode composition can be mitigated, and the rapid thickening of the secondary battery electrode composition can be suppressed. As a result, the storage stability of the secondary battery electrode composition is excellent, coating unevenness of electrodes using the secondary battery electrode composition can be suppressed, and the quality of the secondary battery can be easily stabilized.

[0052] <Antifoaming agent> The CNT dispersion composition may further contain an antifoaming agent. Any commercially available antifoaming agent, wetting agent, etc., that has an antifoaming effect can be used, and one type may be used alone or two or more types may be used in combination.

[0053] <Optional Components> The CNT dispersion composition may optionally contain other additives such as wetting agents, pH adjusters, wetting and penetrating agents, leveling agents, and other conductive materials other than CNTs, as long as they do not hinder the objectives of the present invention. Optional components can be added at any time, such as before the preparation of the CNT dispersion composition, during mixing, after mixing, or in combination thereof.

[0054] <Method for Producing CNT Dispersion Composition> A CNT dispersion composition can be produced, for example, by dispersing CNTs in water. The raw material CNTs to be used may be added in one or more stages at any time during the dispersion process. The dispersion method for performing such a process is not particularly limited.

[0055] In this embodiment, it is important to break down the CNT aggregates, which are tightly bound together by interactions such as van der Waals forces, to an optimal thickness. To achieve this, it is preferable to use a device such as a high-pressure homogenizer to disperse them under high pressure conditions and strong shear force. However, if the shear force is excessive, the CNT aggregates will be completely broken down, reaching the individual CNT units. While this improves the conductivity of the electrodes, it impairs the rigidity caused by the twisted CNT aggregates, making it impossible to improve the durability, such as electrode strength.

[0056] In contrast, in some embodiments, it is preferable to use CNTs as raw materials that have properties that make it easy to maintain CNT aggregates without crushing them down to the CNT units, even when dispersion processing with strong shear force using a high-pressure homogenizer. For example, CNTs that have been adjusted to the predetermined range described above for one or more requirements selected from the group consisting of the average outer diameter of the CNT units, the number of CNT layers, the crystallite size, the BET specific surface area, and the G / D ratio can be suitably used. For CNT units to twist together and form a CNT aggregate, interactions such as van der Waals forces are necessary, and these interactions depend on the crystallinity of the CNTs (G / D ratio, crystallite size La(100)) and the number of units per unit weight (number of CNT layers, crystallite size Lc(002), BET specific surface area). Therefore, it is presumed that by using CNTs that have been adjusted to the predetermined range for the above requirements, interactions between multiple CNT units will easily occur. For example, the higher the crystallinity, the smoother the graphite surfaces between CNTs and the larger the contact area. Also, the more CNTs there are per unit weight, the closer the adjacent CNTs become. Thus, it is presumed that by using CNTs that meet specific requirements as raw materials, the CNT units become easier to twist together, making it easier to maintain the CNT aggregate. Although not particularly limited, specific examples of CNTs that can be suitably used as raw materials include the CNTs prepared in the examples described later, and these CNTs satisfy at least the requirements of crystallite size La and the number of CNT layers.

[0057] Furthermore, the CNTs used as raw materials in this embodiment may be in the form of cut sheet-like raw materials. In the case of sheet-like CNTs, in order to more quickly finish the cut or crushed CNTs to a fiber length of several micrometers, it is also effective to break them by impact force using bead dispersion or by shear force using plastmill dispersion. The cutting method is not particularly limited, but for example, scissors can be used.

[0058] In the CNT dispersion composition of this embodiment, in addition to the essential component, CNT aggregates with an average outer diameter of 10 nm to 50 nm, CNT aggregates and / or CNT units with an average outer diameter outside the above range may also be present. As the proportion of CNT units in the CNT dispersion composition increases, the conductivity of the electrode improves, but the rigidity due to the twisting and aggregation of CNT aggregates is impaired, and the electrode strength tends to become insufficient. Therefore, from the viewpoint of obtaining excellent electrode strength, in some embodiments, it is preferable that the CNT dispersion composition substantially does not contain CNT units. For example, the ratio of CNT aggregates to CNT units in the CNT dispersion composition may be 98.0 / 2.0 to 99.0 / 1.0, 99.5 / 0.5 to 99.0 / 0.1, or 100 / 0. The above proportions are values ​​obtained by visually confirming the shape of the CNTs from multiple photographs of the CNT dispersion composition observed using a transmission electron microscope, similar to the method described in the examples later, and it is preferable that no CNT units existing independently from the CNT aggregates can be confirmed. As described above, when CNTs that meet the requirements such as crystallite size La and the number of CNT layers are used as raw materials, a CNT dispersion composition in which the presence of CNT units cannot be confirmed by observation using a transmission electron microscope can be easily obtained.

[0059] As the dispersion device, a disperser commonly used for pigment dispersion, etc., can be used. For example, either a medialess disperser or a media-type disperser may be used. Examples of medialess dispersers include mixers such as dispersers, homomixers, and planetary mixers; homogenizers (such as Branson's Advanced Digital Sonifer®, MODEL 450DA, M-Technique's "Clearmix", Primix's "Filmix", Silverson's "Abramix", etc.); paint conditioners (Red Devil), colloid mills (PUC's "PUC Colloid Mill", IKA's "Colloid Mill MK"), and cone mills (such as IKA's "Corn Mill MKO"). Examples of media-type dispersers include ball mills, sand mills (such as Shinmaru Enterprises' "Dino Mill"), attritors, pearl mills (such as Eirich's "DCP Mill"), ball mills, bead mills (Mugen Flow®, manufactured by Ashizawa Finetech), and media-type paint conditioners. Furthermore, examples include high-pressure homogenizers (such as Genus's "Genus PY", Sugino Machine's "Starburst", and Nanomizer's "Nanomizer"), media-less dispersers such as M-Technique's "CREA SS-5" and Nara Machinery's "MICROS", and other roll mills. Dispersers are not limited to these. There are no particular restrictions on the disperser, but for example, it is preferable to use a high-pressure homogenizer from the viewpoint of adjusting the fiber length of the CNTs in the CNT dispersion composition to a preferred range, a high-shear mixer from the viewpoint of promoting wetting of the CNTs and breaking down coarse particles and agglomerations, and a media-type disperser such as a bead mill from the viewpoint of crushing agglomerated and solidified particles. Furthermore, it is more preferable to select and combine multiple of the above dispersers for dispersion, and the order of the dispersers can be changed arbitrarily. The pressure when using the high-pressure homogenizer is not particularly limited, but for example, it is preferably 30 to 150 MPa, and more preferably 60 to 150 MPa.

[0060] Dispersion methods using a dispersion device include batch dispersion, pass dispersion, and circulating dispersion. Any of these methods may be used, and two or more methods may be combined. Batch dispersion is a method in which dispersion is performed using only the dispersion device itself, without the use of piping. Because it is easy to handle, it is preferable for small-scale production. Pass dispersion is a dispersion method in which the dispersion device is equipped with a tank to supply the liquid to be dispersed via piping and a tank to receive the liquid to be dispersed, and the liquid is dispersed by passing it through the dispersion device. Circulating dispersion is a method in which the liquid to be dispersed, after passing through the dispersion device, is returned to the tank to supply the liquid and dispersed while being circulated. In all cases, dispersion progresses as the processing time increases, so it is sufficient to repeat the pass or circulation until the desired dispersion state is achieved, and the processing volume can be increased by changing the size of the tank or the processing time. Pass dispersion is preferable to circulating dispersion because it is easier to achieve a uniform dispersion state. Circulating dispersion is preferable to pass dispersion because the work and manufacturing equipment are simpler. In the dispersion process, the disintegration of aggregated particles, the unraveling of CNTs, wetting, stabilization, etc., proceed sequentially or simultaneously. Since the final dispersion state differs depending on how these processes proceed, it is preferable to control the dispersion state in each dispersion process by using various evaluation methods. For example, this can be controlled by the method described in the examples below.

[0061] The CNT dispersion composition of this embodiment may contain iron particles or dissolved iron ions derived from the manufacturing processes of the CNTs, dispersant, and other materials, and iron particles or iron ions may also be introduced during the manufacturing process of the CNT dispersion composition. Since the presence of iron inside a secondary battery poses a risk of short-circuiting and ignition, removing iron contained in the CNT dispersion composition is extremely important from a safety standpoint when applying it to vehicle applications. In the manufacturing process of the CNT dispersion composition, the iron content in the CNT dispersion composition can be easily reduced by using CNTs produced by a manufacturing method that does not use the aforementioned metal catalyst as a nucleus, or CNTs obtained by a purification method. Alternatively, it is preferable to include a step to remove contaminants such as iron particles (foreign matter removal step) at any arbitrary timing. From the viewpoint of efficiency, it is preferable to perform the foreign matter removal step in the middle of the dispersion process of the CNT dispersion composition and / or at the end of the dispersion process. The foreign matter removal step may be performed multiple times.

[0062] In the foreign matter removal process, the method for removing iron particles from the CNT dispersion composition is not particularly limited, and examples include removal by filtration using a filter, removal by centrifugal separation, and removal by magnetic force. Among these, since iron particles are magnetic, removal by magnetic force is preferred, and a method combining the process of removal by magnetic force and the process of removal by filtration using a filter is more preferred.

[0063] The method of removal by magnetism is not particularly limited as long as it can remove iron particles, but from the viewpoint of productivity and removal efficiency, it is preferable to remove the CNT dispersion composition by placing a magnetic filter in the manufacturing line of the CNT dispersion composition and passing the composition through it. The step of removing iron particles from the CNT dispersion composition by placing a magnetic filter and passing the composition through it is preferably carried out by passing the composition through a magnetic filter having a magnetic flux density of 1,000 gauss or more. Since the removal efficiency of iron particles decreases if the magnetic flux density is low, it is preferably 5,000 gauss or more, more preferably 10,000 gauss or more, and most preferably 12,000 gauss or more, considering the removal of weakly magnetic iron particles such as stainless steel. Since iron particles may pass through the magnetic filter depending on the filtration flow rate, when placing a magnetic filter in the manufacturing line, it is preferable to include a step upstream of the magnetic filter to remove contaminants such as iron particles by filtration using a filter such as a cartridge filter. Furthermore, while passing the CNT dispersion composition through a magnetic filter only once is effective, it is more preferable to pass it through two or more times using a circulating system. Passing the CNT dispersion composition through a magnetic filter two or more times improves the efficiency of iron particle removal. When a magnetic filter is placed in the production line of the CNT dispersion composition, there are no particular restrictions on the placement of the magnetic filter, but it is preferable to place it before the filtration filter if there is a filtration step using a filtration filter immediately before filling the CNT dispersion composition into containers. By placing it in this way, if iron detaches from the magnetic filter, the iron particles can be captured by the filtration filter, preventing contamination of the product.

[0064] The amount of CNTs in the CNT dispersion composition of this embodiment is preferably 0.1 parts by mass or more, more preferably 0.2 to 20 parts by mass, even more preferably 0.5 to 10 parts by mass, and particularly preferably 0.5 to 3 parts by mass, per 100 parts by mass of the CNT dispersion composition. By setting the amount within the above range, the dispersibility of the CNT dispersion composition can be maintained more effectively. Furthermore, because the dispersibility of the CNT dispersion composition is maintained, when an electrode film is made using the secondary battery electrode composition, the CNTs maintain linearity in the electrode film, the number of active material particles in contact with the CNTs increases, and the performance of the secondary battery can be further improved.

[0065] The amount of dispersant in the CNT dispersion composition of this embodiment is preferably 20 parts by mass or more, more preferably 40 parts by mass or more, and even more preferably 60 parts by mass or more, per 100 parts by mass of CNT. Furthermore, it is preferably 200 parts by mass or less, more preferably 150 parts by mass or less, and even more preferably 120 parts by mass or less. When the amount is within the above range, the dispersibility of the CNT dispersion composition is good, and the initial viscosity and stability over time tend to be good. If the conductivity and strength of the electrode film described later are considered more important than the ease of handling such as the initial viscosity and stability over time of the CNTs in the CNT dispersion composition of this embodiment, the amount of dispersant in the CNT dispersion composition of this embodiment may be adjusted as appropriate according to the amount of CNT added to the electrode film, and may be 10 parts by mass or more but less than 100 parts by mass, 100 parts by mass or more but less than 200 parts by mass, or 200 parts by mass or more but less than 300 parts by mass.

[0066] If the CNT dispersion composition contains components other than CNTs, a dispersant, and water, the amount of the other components in the CNT dispersion composition may be 0.1 to 10 parts by mass, 0.5 to 5 parts by mass, or 1 to 3 parts by mass per 100 parts by mass of the CNT dispersion composition.

[0067] If the CNT dispersion composition contains a basic compound, the amount of the basic compound in the CNT dispersion composition may be 0.01 to 1 part by mass, 0.02 to 0.5 parts by mass, or 0.04 to 0.1 parts by mass per 100 parts by mass of the CNT dispersion composition. If the CNT dispersion composition contains a basic compound, the amount of the basic compound in the CNT dispersion composition may be 1 to 20 parts by mass, 2 to 10 parts by mass, or 4 to 8 parts by mass per 100 parts by mass of the dispersant.

[0068] If the CNT dispersion composition contains an antifoaming agent, the amount of the antifoaming agent in the CNT dispersion composition may be 0.01 to 1 part by mass, 0.02 to 0.5 parts by mass, or 0.04 to 0.1 parts by mass per 100 parts by mass of the CNT dispersion composition.

[0069] While not particularly limited, an example of a method for producing a CNT dispersion composition according to this embodiment is a method comprising: (1) crushing CNTs; (2) dispersing the crushed CNTs obtained in (1), a dispersant, a solvent containing water, and various additives as needed to obtain a dispersion; and (3) removing foreign matter from the dispersion obtained in (2). In the above method, step (1) is preferably carried out using a dry grinding device. Dry grinding tends to make it easier to adjust the BET specific surface area and G / D ratio of the CNTs to a preferred range. A bead mill can be suitably used as an example of a dry grinding device. The grinding process using the above grinding device may be either a pass-type or a circulating type. Furthermore, step (2) can be carried out using the various dispersion devices exemplified above, but it is preferable to carry it out in combination of two or more dispersion devices. For example, it is preferable to perform dispersion using a high-shear mixer followed by further dispersion using a high-pressure homogenizer. Dispersion makes it easier to adjust the average outer diameter of the CNT aggregate to a preferred range. The distributed processing can be either a pass-type or a circulating type. Furthermore, step (3) can be carried out by applying the method exemplified above, but it is preferable to carry it out by combining two or more methods. For example, it is preferable to carry it out by combining the removal of foreign matter by magnetic force and the removal of foreign matter by filtration using a filter.

[0070] The above manufacturing method may further include a step (0) of manufacturing CNTs to be used as raw materials prior to step (1). In step (0), it is preferable to perform vacuum firing. The conditions during vacuum firing can be adjusted as appropriate. In some embodiments, the furnace pressure during vacuum firing is set to 10 －２ ~10 －３ Pa is preferred, and the furnace temperature is preferably 1350 to 1800°C. By performing reduced-pressure firing under these conditions, the iron content in the CNTs can be easily reduced. In addition, in some embodiments, by adjusting the conditions in step (0), it tends to be easy to adjust the BET specific surface area and the G / D ratio. Although not particularly limited, examples of CNTs that can be suitably used as raw materials in the method for producing the CNT dispersion composition according to this embodiment include CNT(A-1) to CNT(A-25) prepared in the examples described later. Among these, CNT(A-1) to (A-12) and (A-15) to (A-25) can be used more preferably.

[0071] <Physical Properties of CNT Dispersion Composition> [Iron Content] The iron content of the CNT dispersion composition can be calculated using an ICP emission spectrometer after drying the CNT dispersion composition to remove water, as described in the example. The iron content detected by ICP analysis includes iron particles and dissolved iron ions. In other words, the iron content of the CNT dispersion composition after the foreign matter removal process includes iron particles that could not be completely removed and dissolved iron ions.

[0072] The iron content of the CNT dispersion composition is preferably 50 ppm or less, and more preferably 30 ppm or less, based on 100% by mass of the CNT dispersion composition. By setting the iron content of the CNT dispersion composition within the above range, side reactions due to the decomposition of the electrolyte in the secondary battery electrode film are less likely to occur, and a secondary battery with superior cycle characteristics can be obtained.

[0073] [pH] The pH of the CNT dispersion composition is preferably 3 to 6, more preferably 4 to 6, and even more preferably 4 to 5. The pH may also be 9 to 11. The pH of the CNT dispersion composition can be measured using a pH meter (pH METER F-52, manufactured by Horiba, Ltd.). When the pH of the CNT dispersion composition is within the above range, a CNT dispersion composition with excellent viscosity stability is easily obtained due to the repulsion of surface charges of the CNTs.

[0074] [20-degree specular gloss] The dispersion state of a CNT dispersion composition can also be evaluated from the 20-degree specular gloss of the CNT dispersion composition. The 20-degree specular gloss of the CNT dispersion composition is the gloss level (i.e., the intensity of reflected light at 20 degrees relative to the angle of incidence) measured at 20 degrees using a coating obtained by coating a PET (polyethylene terephthalate) film and baking and drying it. If the dispersant content in the CNT dispersion composition is high, the 60-degree specular gloss measured according to method 3 described in JIS standard Z8741:1997 will show a high gloss level, which may reduce the accuracy of the measurement. For this reason, it is preferable to measure the 20-degree specular gloss according to method 5 described in JIS standard Z8741:1997. Although not particularly limited, in some embodiments, the above specular gloss may be 20 to 170, preferably 25 to 150, more preferably 30 to 130, and even more preferably 35 to 100. When the above-mentioned specular gloss is within the above range, it is considered that the aggregation of CNTs in the CNT dispersion composition is suppressed, while at the same time, fine cleavage is suppressed, which tends to facilitate the formation of an efficient conductive network.

[0075] [Viscosity ratio (V1 / V2)] The CNT dispersion composition was measured using a rheometer at a shear rate of 10 s. －１ Viscosity (V1) at 25°C measured by [method / tool ​​name] and shear rate 100 s －１ The viscosity ratio (V1 / V2) of the viscosity (V2) measured at 25°C is preferably 4.0 or higher, more preferably 5.0 or higher, and even more preferably 6.0 or higher. It is also preferable that it be 7.5 or lower. Shear rate 10s －１ and 100s －１By determining the ratio of shear viscosities (V1 / V2) in the fibrous CNT, the degree of structural viscosity derived from the fibrous CNT can be determined. When the fiber length of the CNT is large, the viscosity ratio (V1 / V2) increases regardless of dispersibility, and when the viscosity ratio is within the above range, the fiber length of the CNT is within an appropriate range, so a conductive network can be efficiently formed with a small amount, and the amount of CNT contained in the positive and negative electrodes of the secondary battery can be reduced. In the case of CNTs with a fiber length such that the viscosity ratio (V1 / V2) is 4.0 or higher, the CNTs form a network state with each other, and the effect of improving the strength of the electrode film is obtained. In addition, by using CNTs with a large fiber length, the increase in the surface area of ​​the electrode can be suppressed, the decomposition of the electrolyte during high-temperature storage in the secondary battery can be suppressed, and the cycle characteristics can be improved. Furthermore, in the case of CNTs with a fiber length such that the viscosity ratio (V1 / V2) is 7.5 or lower, the CNTs are broken down to an appropriate fiber length, which increases the number of effective CNTs contained in the electrode film, and a conductive network can be efficiently formed with a small amount.

[0076] The viscosity of the CNT dispersion composition was determined by standing the CNT dispersion composition in a constant temperature bath at 25°C for at least one hour, then thoroughly stirring the CNT dispersion composition, and measuring it using a rheometer with a 25 mm diameter, 2° cone at 25°C and a shear rate of 10 s. －１ and 100s －１ The shear viscosity can be measured and determined. If the measured value includes decimal places, it should be rounded to an integer according to rule B of JIS Z 8401:1999.

[0077] [Complex Modulus and Phase Angle] The dispersibility of a CNT dispersion composition can be evaluated by the complex modulus and phase angle determined by dynamic viscoelasticity. The complex modulus indicates the hardness of the CNT dispersion composition, and it decreases as the dispersibility of the CNTs is good and the viscosity of the CNT dispersion composition decreases. However, when the fiber length of the CNTs is large, even if the CNTs are uniformly and stably unraveled in water, the structural viscosity of the CNTs themselves may result in a high value for the complex modulus. The phase angle refers to the phase shift of the stress wave when the strain applied to the CNT dispersion composition is a sine wave, and thus indicates the flowability of the dispersion composition. The complex modulus of the CNT dispersion composition is preferably 300 Pa or less, more preferably 150 Pa or less, and even more preferably 50 Pa or less. It is also preferably 1 Pa or more, more preferably 5 Pa or more, and even more preferably 10 Pa or more. Furthermore, the phase angle of the CNT dispersion composition is preferably 5° or more, more preferably 8° or more, and even more preferably 10° or more. It is also preferably 80° or less, more preferably 59° or less, and even more preferably 50° or less. When the phase angle and complex modulus of the CNT dispersion composition are within the above ranges, the dispersibility of the CNTs is good, and an electrode film with excellent conductivity and strength can be easily obtained.

[0078] <<Composition for Secondary Battery Electrodes>> The secondary battery electrode composition of this embodiment comprises at least a CNT dispersion composition and an active material. That is, the secondary battery electrode composition comprises at least CNTs, a dispersant, a solvent, and an active material. It is also preferable to include a binder resin.

[0079] A binder resin is a resin used to bond substances together. There are no particular restrictions on the binder resin, but examples include polymers or copolymers containing fluororesins, ethylene, propylene, vinyl chloride, vinyl acetate, vinyl alcohol, maleic acid, acrylic acid, acrylic acid esters, methacrylic acid, methacrylic acid esters, acrylonitrile, styrene, vinyl butyral, vinyl acetal, vinylpyrrolidone, etc. as constituent units; polyurethane resins, polyester resins, phenolic resins, epoxy resins, phenoxy resins, urea resins, melamine resins, alkyd resins, acrylic resins, formaldehyde resins, silicone resins, fluororesins; cellulose resins such as carboxymethylcellulose; rubbers such as styrene-butadiene rubber; and conductive resins such as polyaniline and polyacetylene. Among these, the use of styrene-butadiene rubber or fluororesins as binder resins is preferred from the viewpoint of electrochemical oxidation-reduction resistance.

[0080] As for the fluororesin, polyvinylidene fluoride, polyvinyl fluoride, and polytetrafluoroethylene are preferred, for example.

[0081] Active material refers to the material that forms the basis of a battery reaction. Active material can be divided into positive electrode active material and negative electrode active material based on its electromotive force. In this specification, positive electrode active material and negative electrode active material may sometimes be simply referred to as "active material." Active material refers to the material that forms the basis of a battery reaction. Active material can be divided into positive electrode active material and negative electrode active material based on its electromotive force.

[0082] The positive electrode active material is not particularly limited, but metal compounds such as metal oxides and metal sulfides that can be doped or intercalated with lithium ions, and conductive polymers can be used. For example, examples include oxides of transition metals such as Fe, Co, Ni, and Mn, composite oxides with lithium, and inorganic compounds such as transition metal sulfides. Specifically, MnO, V ２ O ５ , V ６ O １３ , TiO ２Transition metal oxide powders such as, lithium and transition metal composite oxide powders such as layered lithium nickelate, lithium cobaltate, lithium manganate, and spinel-structured lithium manganate, lithium iron phosphate-based materials which are olivine-structured phosphate compounds, and TiS ２ Examples include transition metal sulfide powders such as FeS. Conductive polymers such as polyaniline, polyacetylene, polypyrrole, and polythiophene can also be used. Furthermore, the above inorganic and organic compounds may be mixed and used.

[0083] The negative electrode active material is not particularly limited as long as it can be doped or intercalated with lithium ions. For example, metallic Li, alloys thereof such as tin alloys, silicon alloys, lead alloys, etc. Ｘ Fe ２ O ３ Li Ｘ Fe ３ O ４ Li Ｘ WO ２ Examples of anode active materials include metal oxides such as lithium titanate, lithium vanadate, and lithium siliconate; conductive polymers such as polyacetylene and poly-p-phenylene; amorphous carbonaceous materials such as soft carbon and hard carbon; artificial graphite such as high-graphitization carbon materials; carbonaceous powders such as natural graphite; carbon black; mesophase carbon black; resin-fired carbon materials; vapor-grown carbon fibers; and carbon fibers. These anode active materials can be used individually or in combination. Among these, alloy-based anode active materials are preferred, and silicon alloys are particularly preferred. Although alloy-based anode active materials have a large theoretical capacity, they undergo large volume changes during charging and discharging of secondary batteries. However, by combining them with the carbon nanotube dispersion composition of this embodiment, electrode degradation due to volume changes of the alloy-based active material can be suppressed, and the cycle characteristics of the secondary battery can be improved.

[0084] The BET specific surface area of ​​the negative electrode active material is 0.1 m². ２ / g or more 30m ２ It is preferable that the amount is less than or equal to 1.0 m ２ / g or more 20m２ It is more preferable that it be less than or equal to 5.0 m ２ / g or more 15m ２ It is even more preferable that the amount is less than or equal to / g. The BET specific surface area can be measured by the BET method according to JIS Z 8830:2013.

[0085] Cumulative particle size D of the negative electrode active material １０ The particle size is preferably 0.05 μm or more and 2 μm or less, and more preferably 0.1 μm or more and 1 μm or less. Cumulative particle size D ５０ The particle size is preferably 0.5 μm to 5 μm, and more preferably 1 μm to 3 μm. Cumulative particle size D ９０ The particle size is preferably 3 μm to 10 μm, and more preferably 3.0 to 5.0 μm. The cumulative particle size of the active material can be measured by the particle size analysis - laser diffraction and scattering method of JIS Z 8825:2013. As a measuring device, for example, a laser diffraction particle size distribution analyzer (SALD-2300, manufactured by Shimadzu Corporation) can be used, and the light intensity of the sample can be adjusted to 15 to 20% for measurement. When the cumulative particle size of the active material is within the above range, even if the negative electrode active material is an alloy system with a large volume change during charging and discharging of the secondary battery, the carbon nanotube dispersion composition of this embodiment maintains a strong conductive network, resulting in good cycle characteristics of the secondary battery.

[0086] To obtain a secondary battery electrode composition, it is preferable to add an active material to the CNT dispersion composition and then perform a dispersion process. The dispersion apparatus used for this process is not particularly limited. The secondary battery electrode composition can be obtained using the dispersion apparatus described above for the CNT dispersion composition. In the case of a secondary battery electrode composition containing a binder resin, the active material, binder resin, and a solvent may be added and mixed before adding and dispersing the CNT dispersion composition. Alternatively, the CNT dispersion resin may be added to the CNT dispersion composition to form a CNT dispersion resin composition, and then the active material may be added to obtain the secondary battery electrode composition.

[0087] In viscoelasticity measurements, when the shear strain of the secondary battery electrode composition is measured in the range of 0.01% to 500%, the difference between the storage modulus at 1% shear strain and the storage modulus at 100% shear strain is preferably less than 8 Pa, more preferably less than 7 Pa, and even more preferably less than 6 Pa. It is also preferably 1 Pa or more, and even more preferably 2 Pa or more. A secondary battery electrode composition with a large difference in storage modulus indicates that the hardness changes greatly depending on the shear force, i.e., it has a hard and brittle structure. On the other hand, a secondary battery electrode composition with a small difference in storage modulus indicates that the internal structure is stable and less prone to breakage. When the difference in storage modulus is within the above range, uneven coating during electrode film fabrication is less likely to occur, improving productivity, and the peel strength of the electrode and the uniformity of the coating film are improved, resulting in a secondary battery with stable quality.

[0088] The amount of active material in the secondary battery electrode composition is preferably 20 to 85 parts by mass, and particularly preferably 40 to 85 parts by mass, based on 100 parts by mass of the secondary battery electrode composition.

[0089] The amount of CNTs in the secondary battery electrode composition is preferably 0.01 to 5 parts by mass, more preferably 0.05 to 2 parts by mass, and even more preferably 0.1 to 1 part by mass, based on 100 parts by mass of active material.

[0090] The amount of dispersant in the secondary battery electrode composition is preferably 10 to 300 parts by mass, more preferably 20 to 150 parts by mass, and even more preferably 40 to 120 parts by mass, based on 100 parts by mass of CNT.

[0091] When the secondary battery electrode composition contains a binder resin, the amount of binder resin in the secondary battery electrode composition is preferably 0.5 to 20 parts by mass, more preferably 1 to 10 parts by mass, and particularly preferably 1 to 5 parts by mass, based on 100 parts by mass of active material.

[0092] The solid content concentration of the secondary battery electrode composition is preferably 30% to 90% by mass, and more preferably 40% to 85% by mass, based on 100% by mass of the secondary battery electrode composition.

[0093] ≪Electrodes and Electrode Films≫ The electrodes comprise a current collector and an electrode film formed from a secondary battery electrode composition. The electrode film is a coated film of the secondary battery electrode composition, for example, a coated film formed by coating the secondary battery electrode composition onto the current collector and drying it to form a secondary battery electrode composition layer.

[0094] The material and shape of the current collector are not particularly limited, and can be appropriately selected to suit various types of secondary batteries. For example, the material of the current collector can be a metal or alloy such as aluminum, copper, nickel, titanium, or stainless steel. In terms of shape, a flat foil is generally used, but current collectors with roughened surfaces, perforated foils, and mesh-shaped current collectors can also be used.

[0095] There are no particular limitations on the method for coating a secondary battery electrode composition onto a current collector to form an electrode film, and known methods can be used. Specifically, die coating, dip coating, roll coating, doctor coating, knife coating, spray coating, gravure coating, screen printing, or electrostatic coating methods can be used, and drying methods such as standing drying, forced-air drying, hot-air drying, infrared heating, and far-infrared heating can be used, but are not limited to these.

[0096] Furthermore, rolling may be performed after coating using a flatbed press or calender roll. The thickness of the electrode film (composition layer for secondary battery electrodes) is generally 1 μm or more and 500 μm or less, preferably 10 μm or more and 300 μm or less.

[0097] <<Secondary Battery>> The secondary battery of this embodiment comprises an electrode having an electrode film and an electrolyte. The secondary battery comprises a positive electrode and a negative electrode, and at least one of the positive electrode and the negative electrode may have the above-mentioned electrode film. In the carbon nanotube dispersion composition of this embodiment, carbon nanotubes exist as bundled aggregates within the electrodes of the secondary battery, contributing to good conductivity and improved electrode strength. As a result, the active material is utilized homogeneously during charging and discharging, and electrode degradation due to volume changes can be suppressed, thus improving the cycle characteristics of the secondary battery.

[0098] As the positive electrode, an electrode film can be used that has been prepared by coating a current collector with a composition for secondary battery electrodes containing a positive electrode active material and drying it.

[0099] As the negative electrode, an electrode film can be used that has been prepared by coating a secondary battery electrode composition containing a negative electrode active material onto a current collector and drying it.

[0100] As the electrolyte, various conventionally known substances in which ions can move can be used. For example, LiBF ４ LiClO ４ LiPF ６ LiAsF ６ LiSbF ６ LiCF ３ SO ３ , Li(CF ３ SO ２ ) ２ N, LiC ４ F ９ SO ３ , Li(CF ３ SO ２ ) ３ C, LiI, LiBr, LiCl, LiAlCl, LiHF ２ LiSCN, or LiBPh ４ Examples include those containing lithium salts (where Ph is a phenyl group), but are not limited to these, and those containing sodium salts can also be used. The electrolyte is preferably dissolved in a non-aqueous solvent and used as an electrolyte solution.

[0101] Non-aqueous solvents are not particularly limited, but examples include carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate; lactones such as γ-butyrolactone, γ-valerolactone, and γ-octanoic lactone; glycines such as tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, 4-methyl-1,3-dioxolane, 1,2-methoxyethane, 1,2-ethoxyethane, and 1,2-dibutoxyethane; esters such as methyl formate, methyl acetate, and methyl propionate; sulfoxides such as dimethyl sulfoxide and sulfolane; and nitriles such as acetonitrile. These solvents may be used individually or in combination of two or more.

[0102] The secondary battery of this embodiment preferably includes a separator. Examples of separators include polyethylene nonwoven fabric, polypropylene nonwoven fabric, polyamide nonwoven fabric, and those treated to be hydrophilic, but are not limited to these.

[0103] The structure of the secondary battery in this embodiment is not particularly limited, but it typically consists of a positive electrode, a negative electrode, and a separator provided as needed, and can take on various shapes depending on the intended use, such as paper type, cylindrical type, button type, or laminated type.

[0104] The secondary battery of this embodiment is not particularly limited in its applications. Specifically, it can be used as a power source for consumer electronics such as mobile phones, laptop computers, and digital cameras; as an emergency power source for hospitals, factories, and buildings; and for vehicle applications such as hybrid vehicles, plug-in hybrid vehicles, electric vehicles, electric assist bicycles, and railway vehicles. The secondary battery, for example, recovers regenerative energy from the power of a vehicle.

[0105] In particular, because it is a secondary battery with high charge / discharge performance and excellent cycle characteristics, it can be suitably used in vehicles, resulting in vehicles that are highly safe and can be expected to improve fuel efficiency. Furthermore, it can demonstrate excellent performance even in vehicle applications where high-current charging and discharging are desired.

[0106] The mounting location of the secondary battery in the vehicle of this embodiment is not particularly limited. For example, when the secondary battery is installed in an automobile, it can be installed in the engine compartment, at the rear of the vehicle, or under the seats.

[0107] The following are examples of typical embodiments of the present invention. <1> A carbon nanotube dispersion composition comprising carbon nanotubes, a dispersant, and water, wherein the carbon nanotubes include carbon nanotube aggregates in which two or more carbon nanotube units, each having an average outer diameter of 3 nm or more and 8 nm or less and 3 to 15 layers, are bundled together in parallel by interaction, and the average outer diameter of the carbon nanotube aggregates is 10 nm or more and 50 nm or less. <2> The carbon nanotube dispersion composition according to <1> above, wherein the iron content of the carbon nanotube dispersion composition is 50 ppm or less. <3> The BET specific surface area of ​​the carbon nanotubes is 100 m ２ / g or more 300m ２ A carbon nanotube dispersion composition according to <1> or <2> above, wherein the amount is less than or equal to / g. <4> A carbon nanotube dispersion composition according to any one of <1> to <3> above, wherein the G / D ratio of the carbon nanotubes is 5.1 or more and 15 or less. <5> A carbon nanotube dispersion composition according to any one of <1> to <4> above, wherein the 20-degree specular gloss of the carbon nanotube dispersion composition is 50 or more and 170 or less. <6> A shear rate of 10s for the carbon nanotube dispersion composition. －１ Viscosity (V1) at 25°C measured by [method / tool ​​name] and shear rate 100 s －１A carbon nanotube dispersion composition according to any one of <1> to <5> above, wherein the viscosity ratio (V1 / V2) to the viscosity (V2) measured at 25°C is 4.0 or more and 7.5 or less. <7> A composition for secondary battery electrodes comprising the carbon nanotube dispersion composition according to any one of <1> to <6> above. <8> An electrode film comprising a coating film of the secondary battery electrode composition according to <7> above. <9> A secondary battery comprising the electrode film according to <8> above. <10> A vehicle comprising the secondary battery according to <9> above.

[0108] This disclosure relates to the subject matter described in Japanese Patent Application No. 2024-230628, filed on 26 December 2024, and all disclosures herein are incorporated herein by reference.

[0109] The present invention will be described in more detail below with reference to examples. The present invention is not limited to the following examples unless it exceeds the gist of the invention. Unless otherwise specified, "parts" refers to "parts by mass" and "%" refers to "percentage by mass".

[0110] 《Methods for measuring and evaluating physical properties》 The physical properties of CNTs, CNT dispersion compositions, secondary battery electrode compositions, electrode films, and secondary batteries were measured and evaluated by the following methods.

[0111] <Average outer diameter of CNT units> The CNT dispersion composition was diluted 50 to 200 times with deionized water, dropped onto a microgrid (Nisshin EM Holey Microgrid U1003), air-dried, and then observed using a transmission electron microscope (JEM2800, JEOL Ltd.). The observation was performed with an acceleration voltage of 200 kV and a magnification of 1,000,000x. Multiple photographs containing 10 or more CNT aggregates in the field of view were taken, and the outer diameters of 50 arbitrarily extracted CNTs were measured. The average outer diameter of the CNT units (nm) was taken from the arithmetic mean, and the standard deviation was taken from the standard deviation value of the CNT unit outer diameter (nm).

[0112] <Number of Layers in CNT Units> CNTs were placed in the recess of a glass sample plate (outer diameter 5.0 cm × 3.5 cm, thickness 3 mm, sample area 2.0 cm × 2.0 cm, thickness 2 mm) and planarized using a glass slide. Then, a sample for powder X-ray diffraction analysis of carbon material was placed in a fully automated multi-purpose X-ray diffractometer (SmartLab, Rigaku Corporation) and analyzed by operating it from 15° to 35°. Sampling was performed every 0.01°, and the scan speed was 1° / min. The voltage was 40 kV, the current was 40 mA, and the X-ray source was CuKα rays. The number of layers in the CNT units was calculated using the following equation (1) with respect to the average interplanar spacing (d002) and crystallite size (Lc002) of the peak obtained at the diffraction angle 2θ = 25° ± 2°. Equation (1): Number of layers = Crystallite size (Lc002) / Average interplanar spacing (d002)

[0113] <Average outer diameter of CNT aggregates> The CNT dispersion composition was diluted 50 to 200 times with deionized water, dropped onto a microgrid (Nisshin EM Holey Microgrid U1003), air-dried, and then observed using a transmission electron microscope (JEM2800, JEOL Ltd.). The observation was performed with an acceleration voltage of 200 kV and a magnification of 500,000x. Multiple photographs were taken containing 10 or more CNT aggregates in the field of view, and the outer diameters of 50 arbitrarily extracted CNT aggregates were measured. The arithmetic mean was used to determine the average outer diameter (nm) of the CNT aggregates, and the standard deviation was used to determine the standard deviation of the outer diameter (nm). The CNTs contained in the CNT dispersion composition (D1-1 to D1-56) were CNT aggregates in which multiple CNTs had orientation, and two or more CNT units were bundled together in parallel by interaction. The CNTs contained in the CNT dispersion compositions (D1-57 to D1-58) were broken down to individual CNT units and were not CNT aggregates. Therefore, the average outer diameter and standard deviation of the CNT aggregates in Table 3 are indicated as "-".

[0114] <Average Fiber Length of CNTs in CNT Dispersion Composition> The CNT dispersion composition was diluted with water to a CNT concentration of 0.0001% to 0.001% by mass, and then several drops of the CNT dispersion composition were dropped onto a mica substrate. The substrate was then dried on a hot plate at 100°C to prepare a substrate for observing the CNT fiber length. The prepared substrate was photographed using a scanning electron microscope (SEM), and the obtained SEM images were analyzed using the image analysis software "ImageJ" (open-source image processing and analysis software developed by the National Institutes of Health, USA). The fiber length of 100 CNTs was measured, and the average fiber length of CNTs in the CNT dispersion composition was calculated by arithmetic mean. The average fiber length of CNTs obtained in this way was evaluated according to the following criteria. [Evaluation Criteria] A: 1.0 μm or more and less than 3.5 μm B: 0.8 μm or more and less than 1.0 μm C: 3.5 μm or more and less than 5.0 μm D: Less than 0.8 μm, or 5.0 μm or more

[0115] <Image Observation of CNTs> The state of the CNT aggregates of powdered CNTs was confirmed by image observation using the following method. Powdered CNTs were diluted 50 to 200 times with a mixed solvent of acetone and MEK (acetone:MEK = 1:1), dropped onto a microgrid (Nisshin EMHoley Microgrid U1003), and air-dried. Using a JEM2800 (JEOL, transmission electron microscope), 10 to 12 samples were measured based on a scale bar for arbitrarily selected CNTs using transmission electron imaging at an acceleration voltage of 200 kV and a magnification of 1,000,000x, and the mean and standard deviation were calculated for all samples.

[0116] <BET Specific Surface Area of ​​CNTs> 0.03 g of CNTs was weighed using an electronic balance (MSA225S100DI, manufactured by Sartorius), and then dried at 110°C for 15 minutes while degassing. After that, the BET specific surface area of ​​the CNTs was measured using a fully automatic specific surface area measuring device (MOUNTECH, HM-model 1208). The BET specific surface area was measured in accordance with the BET method of JIS Z 8830:2013.

[0117] <G / D ratio of CNTs> CNTs were mounted on a Raman microscope (XploRA, manufactured by Horiba, Ltd.) and measured using a laser wavelength of 532 nm. The measurement conditions were: acquisition time 60 seconds, number of integrations 2, light-reducing filter 10%, objective lens magnification 20x, confocus hole 500, slit width 100 μm, and measurement wavelength 100 cm. －１ ~3,000 cm －１ The carbon nanotubes for measurement were separated onto a glass slide and flattened using a spatula. Of the obtained peaks, the peak at 1,560 cm⁻¹ in the spectrum was selected. －１ ~1,600cm －１ Within this range, the maximum peak intensity is G, 1,310 cm. －１ ~1,350cm －１ Within the specified range, the maximum peak intensity was defined as D, and the G / D ratio was defined as the G / D ratio of CNTs.

[0118] <Iron Content of CNTs> CNT powder was acid-decomposed using a microwave sample preparation device (Milestone General, ETHOS1) to extract the metals contained in the carbon nanotubes. Subsequently, analysis was performed using a multi-type ICP emission spectrometer (Agilant, 720-ES) to calculate the iron content in the extract, which was then determined as the iron content of the CNT powder.

[0119] <Iron Content of CNT Dispersion Composition> After drying the CNT dispersion composition using a hot air oven, the metals contained in the carbon nanotubes were extracted by acid decomposition using a microwave sample pretreatment device (Milestone General, ETHOS1). Subsequently, analysis was performed using a multi-type ICP emission spectrometer (Agilant, 720-ES) to calculate the iron content in the extract, which was then determined as the iron content of the CNT dispersion composition.

[0120] <20° specular gloss of CNT dispersion composition>The CNT dispersion composition was dropped in an amount of 1 mL onto a PET (polyethylene terephthalate) film and coated at 2 cm / second using a No. 7 bar coater. Then, using a gloss meter (VG-7000, manufactured by Nippon Denshoku Industries Co., Ltd.), three locations within the film surface excluding the edges were randomly selected, and the 20° measurement in the parallel light method was performed once each in accordance with JIS standard Z8741:1997. The average value was taken as the gloss of the CNT dispersion composition.

[0121] <Viscosity ratio of CNT dispersion composition>After the CNT dispersion composition was allowed to stand in a thermostatic bath at 25°C for 1 hour or more, using a rheometer (MCR302e, manufactured by Anton Paar) with a cone having a diameter of 25 mm and an angle of 2°, the shear viscosity at 25°C and a shear rate from 0.01 s －１ to 1,000 s －１ was measured. The viscosity ratio (V1 / V2) was determined from the viscosity (V1) at 25°C measured at a shear rate of 10 s －１ and the viscosity (V2) at 25°C measured at a shear rate of 100 s －１ . The obtained viscosity ratio (V1 / V2) was evaluated according to the following evaluation criteria. [Evaluation criteria] A: 6.0 or more and 7.5 or less B: 5.0 or more and less than 6.0 C: Less than 5.0 or exceeding 7.5 and 8.0 or less D: Less than 4.0 or exceeding 8.0

[0122] <Complex elastic modulus and phase angle of CNT dispersion composition> After the CNT dispersion composition was allowed to stand in a thermostatic bath at 25°C for 1 hour or more, using a rheometer (MCR302e, manufactured by Anton Paar) with a cone having a diameter of 25 mm and an angle of 2°, dynamic viscoelasticity measurement was performed at 25°C and a frequency of 1 Hz in the range of shear strain from 0.01% to 5% to determine the complex elastic modulus and the phase angle.

[0123] <Viscosity of CNT Dispersion Composition over Time> The secondary battery electrode composition was left to stand in a 40°C constant temperature bath for one week, then left to stand in a 25°C constant temperature bath for more than three hours, and then immediately subjected to viscosity testing using a B-type viscometer rotor at a rotation speed of 30 rpm. Rotor No. 4 was used. If the viscosity over time was less than 200 mPa·s, rotor No. 3 was used. The lower the viscosity over time of the CNT dispersion composition, the better the viscosity stability when used as a secondary battery electrode composition, the more coating unevenness can be suppressed, and a homogeneous electrode film and secondary battery can be obtained. The evaluation criteria for viscosity over time are as follows. [Evaluation Criteria] ◎ (Excellent): Less than 4,000 mPa·s 〇 (Good): 4,000 mPa·s or more and less than 6,000 mPa·s △ (Acceptable): 6,000 mPa·s or more and less than 9,000 mPa·s × (Unacceptable): 9,000 mPa·s or more

[0124] <Viscosity of the composition for secondary battery electrodes> After standing the composition for secondary battery electrodes in a constant temperature bath at 25°C for at least one hour, the viscosity was measured using a rheometer (MCR302e, manufactured by Anton Paar) with a 25 mm diameter, 2° cone at 25°C and a shear rate of 0.01 s. ―１ from 1,000s －１ The shear viscosity was measured and evaluated. When the viscosity of the secondary battery electrode composition is within the following range, it can be said that the CNTs contained in the secondary battery electrode composition are uniformly dispersed, and the conductivity and strength of the electrode film can be easily improved. The viscosity of the secondary battery electrode composition is measured at a shear rate of 1 s. －１ The viscosity was measured and evaluated based on the measured values. The evaluation criteria are as follows: [Evaluation Criteria] ◎ (Excellent): 2,000 mPa·s or more and less than 6,000 mPa·s 〇 (Good): 6,000 mPa·s or more and less than 8,000 mPa·s △ (Acceptable): 8,000 mPa·s or more and less than 10,000 mPa·s × (Unacceptable): Less than 2,000 mPa·s or more and greater than 10,000 mPa·s

[0125] <Electrode Strength of Secondary Battery Electrode Compositions> After leaving the secondary battery electrode composition in a constant temperature bath at 25°C for more than one hour, dynamic viscoelasticity measurements were performed using a rheometer (MCR302e, manufactured by Anton Paar) with a 25 mm diameter, 2° cone at 25°C and a frequency of 1 Hz, in the range of shear strain from 0.01% to 5%. The electrode strength was evaluated by the storage modulus, which was determined by the difference between the storage modulus G' at 1% shear strain and 100% shear strain. At 1% shear strain, the evaluation was performed in the region where strain is less likely to occur (e.g., during standing), and at 100% shear strain, the evaluation was performed in the region where the liquid structure is more likely to strain due to increased force (e.g., during liquid transfer). For example, as shown in Figures 3 and 4, when CNTs are mixed without dispersion as in Comparative Example 2-6, the elastic modulus changes even with slight strain, so the internal structure of the secondary battery electrode composition is considered to be easily damaged. In Example 2-2 and Comparative Example 2-7, both were stable in the unstrained region. However, Comparative Example 2-7 had an inappropriate dispersion state, resulting in high viscoelasticity during standing and a tendency to gel during standing. This is thought to affect the unevenness of the electrode at the start of coating and the handling of the product. A smaller storage modulus value indicates less electrode unevenness and less internal structure breakdown, resulting in better electrode strength. Therefore, electrode strength was evaluated based on the storage modulus value. The evaluation criteria are as follows: [Evaluation Criteria] ◎ (Excellent): Less than 6 Pa 〇 (Good): 6 Pa or more and less than 7 Pa △ (Acceptable): 7 Pa or more and less than 8 Pa × (Unacceptable): 8 Pa or more

[0126] <Evaluation of Negative Electrode Conductivity> The composition for the negative electrode secondary battery electrode was evaluated using an applicator, and the basis weight per unit area of ​​the electrode was 8 mg / cm². ２ After coating the copper foil in this manner, the coating was dried in an electric oven at 120°C ± 5°C for 25 minutes. Subsequently, it was rolled using a roll press (manufactured by Sanku Metal Co., Ltd., 3t hydraulic roll press) to obtain a density of 1.6 g / cm³ for the secondary battery electrode composition layer. ３A negative electrode was fabricated. Subsequently, the negative electrode was punched out to a size of 50 mm × 45 mm, and the volume resistivity and interfacial resistance of the composition layer for the secondary battery electrode were measured using an electrode resistance measuring device (electrode resistance measurement system RM2610, manufactured by Hioki Electric Co., Ltd.). The measurement conditions were set as follows: the operation mode was set to "potential measurement + calculation", the measurement speed was set to "MEDIUM", and the measurement range was set to "AUTO". The thickness of the composition layer for the secondary battery electrode and the thickness of the copper foil were input, and the volume resistivity of the copper foil "1.7000E-06" was selected. The film thickness of the composition layer for the secondary battery electrode was obtained by subtracting the film thickness of the copper foil from the measured negative electrode film thickness using a film thickness gauge (a combination of Nikon Solutions Co., Ltd.'s Digimicrohead MH-15M (standard), measurement stand MS-5C, and counter TC-101). The conductivity of the negative electrode was evaluated based on the value of the volume resistivity (Ω·cm) of the negative electrode obtained as described above. The evaluation criteria are as follows. [Evaluation Criteria] ◎ (Excellent): Less than 0.08: 〇 (Good): 0.08 or more and less than 0.1 △ (Fair): 0.1 or more and less than 0.12 × (Poor): 0.12 or more

[0127] <Fabrication of Battery Evaluation Cell> The negative electrode was punched out to a diameter of 16 mm and used as the working electrode. A metal lithium foil (thickness 0.2 mm) was used as the counter electrode. A separator made of porous polypropylene film was inserted and laminated between the working electrode and the counter electrode. After injecting 100 μL of an electrolytic solution (a non-aqueous electrolytic solution in which LiPF ６ was dissolved at a concentration of 1 M in a mixed solvent of ethylene carbonate, diethyl carbonate, dimethyl carbonate, fluoroethylene carbonate, and vinylene carbonate in a ratio of 38:30:28:3:1 (weight ratio)), a two-electrode cell (manufactured by Nippon Tomcell Co., Ltd.) was assembled to fabricate a cell for battery evaluation.

[0128] <Evaluation of Cycle Characteristics of Secondary Batteries> A cell for battery evaluation was placed in a constant temperature room at 25°C, and charge / discharge measurements were performed using a charge / discharge device (SM-8, manufactured by Hokuto Denko Co., Ltd.). After performing constant current / constant voltage discharge (0.025C) with a discharge current of 0.2C and a discharge termination voltage of 0V, constant current charging was performed with a charging current of 0.2C and a charge termination voltage of 1.5V. This operation was repeated 25 times. Note that 1C was defined as the current value required to charge the theoretical capacity of the negative electrode in 1 hour. The cycle characteristics were calculated at 25°C as the ratio of the maximum 0.2C charge capacity among the 1st to 25th cycles to the charge capacity at the 25th cycle, i.e., using the following equation 2. (Equation 2) Cycle characteristics = 0.2C charge capacity at the 25th cycle / Maximum charge capacity among the 1st to 25th cycles × 100 (%) The cycle characteristics values ​​obtained as described above were evaluated according to the following evaluation criteria. [Evaluation Criteria] ◎ (Excellent): 98% or higher 〇 (Good): 97% or higher but less than 98% △ (Acceptable): 96% or higher but less than 97% × (Poor): Less than 96%

[0129] <Manufacturing of CNTs> (Manufacturing Example 1; CNT (A-1)) CNT (A-1) was obtained by manufacturing in the same manner as the sheet-like CNT aggregate 1 described in Example 1 of Japanese Patent No. 7528392, and cutting it with scissors until it became a sheet piece of about 1 mm x 3 mm.

[0130] (Manufacturing Example 2; CNT (A-2)) CNT (A-2) was obtained in the same manner as in Manufacturing Example 1, except that the second temperature zone was changed from 1400°C to 1350°C.

[0131] (Manufacturing Example 3; CNT (A-3)) CNT (A-3) was obtained in the same manner as in Manufacturing Example 1, except that the carrier gas flow rate was changed from 30,000 sccm to 45,000 sccm.

[0132] (Manufacturing Example 4; CNT (A-4)) Ten parts of CNT (A-1) prepared in Manufacturing Example 1 were placed in a graphite crucible with a diameter of 10 cm and a height of 10 cm. The crucible containing the CNTs was placed in a multi-purpose high-temperature furnace (High Multi 5000, manufactured by Fuji Denpa Kogyo Co., Ltd.) and subjected to heat treatment under reduced pressure and vacuum as follows. First, nitrogen gas was introduced into the multi-purpose high-temperature furnace, and the nitrogen gas substitution operation was performed twice. Next, the furnace pressure was reduced using an oil rotary pump and adjusted to 9.8 to 9.5 Pa, and then further reduced using an oil diffusion pump to adjust the furnace pressure to 0.03 to 2 Pa. Subsequently, while maintaining the reduced pressure by the oil diffusion pump, the temperature was raised to 1,500°C at a heating rate of 20°C / min and held at 1,500°C for 2 hours. After that, it was allowed to cool naturally until the furnace temperature fell below 50°C to obtain CNT (A-4).

[0133] (Manufacturing Example 5; CNT (A-5)) CNT (D) was crushed using a dry jet mill "NJ-50" (product name) manufactured by Aisin Nanotechnologies Inc., with a crushing air pressure of 1.2 MPa and a flow rate of 100 g / h, in a circulating crushing method to obtain CNT (A-5) at a processing speed of 30 g / h.

[0134] (Manufacturing Example 6; CNT (A-6)) CNT (D) was processed using a bead mill of a 60L capacity dynamic mill (manufactured by Nippon Coke Industries Co., Ltd.) with 8mm diameter zirconia beads as the grinding media at a packing rate of 70%. 100 kg was supplied at a flow rate of 120 ± 20 kg / h (hour), and the process was carried out for 3 hours in a circulating grinding system at a peripheral speed of 3 m / s (seconds) to obtain CNT (A-6).

[0135] (Manufacturing Example 7; CNT (A-7)) CNT (A-7) was obtained in the same manner as in Manufacturing Example 4, except that the carrier gas flow rate was changed from 30,000 sccm to 60,000 sccm, and CNTs manufactured in the same manner as in Manufacturing Example 1 were used.

[0136] (Manufacturing Example 8; CNT (A-8)) CNT (A-8) was obtained in the same manner as in Manufacturing Example 4, except that the carrier gas flow rate was changed from 30,000 sccm to 105,000 sccm, and CNTs manufactured in the same manner as in Manufacturing Example 1 were used.

[0137] (Manufacturing Example 9; CNT (A-9)) CNT (A-9) was obtained by the same method as in Manufacturing Example 4, except that the temperature was raised to 1,800°C at a heating rate of 20°C / min and held at 1,800°C for 2 hours.

[0138] (Manufacturing Example 10; CNT (A-10)) CNT (A-9) was processed using a bead mill of a 60L dynamic mill (manufactured by Nippon Coke Industries Co., Ltd.) with 8mm diameter zirconia beads as the grinding media at a packing rate of 70%. 100 kg was supplied at a flow rate of 120 ± 20 kg / h (hour), and the process was carried out for 3 hours in a circulating grinding system at a peripheral speed of 3 m / s (seconds) to obtain CNT (A-10).

[0139] (Manufacturing Example 11; CNT (A-11)) CNT (A-11) was obtained in the same manner as in Manufacturing Example 9, except that CNT (A-3) was used instead of CNT (A-1).

[0140] - CNT (A-12): MIRALON (manufactured by HUNTSMAN, multilayer CNT) - CNT (A-13): CNT described in Example 4 of Japanese Patent No. 6586197 - CNT (A-14): CNT described in paragraph 0133 of Japanese Patent No. 6801806

[0141] (Manufacturing Example 12; CNT (A-15)) Ten portions of CNT (A-1) prepared in Manufacturing Example 1 were placed in a graphite crucible with a diameter of 10 cm and a height of 10 cm. The crucible containing the CNTs was placed in a multi-purpose high-temperature furnace (High Multi 5000, manufactured by Fuji Denpa Kogyo Co., Ltd.) and subjected to heat treatment under reduced pressure and vacuum as follows. First, nitrogen gas was introduced into the multi-purpose high-temperature furnace, and the nitrogen gas substitution operation was performed twice. Next, the furnace pressure was reduced using an oil rotary pump and adjusted to 9.8 to 9.5 Pa, and then further reduced using an oil diffusion pump to adjust the furnace pressure to 0.01 to 0.05 Pa. Subsequently, while maintaining the reduced pressure using the oil diffusion pump, the temperature was raised to 1,500°C at a heating rate of 20°C / min and held at 1,500°C for 24 hours. Subsequently, the CNTs obtained by allowing the furnace temperature to cool naturally to below 50°C were subjected to dry processing as follows. First, using a 50L capacity dynamic mill (manufactured by Nippon Coke Industries Co., Ltd.) bead mill, 3mm diameter zirconia beads were loaded as grinding media at a packing rate of 70%, and 60 kg of CNTs were supplied at a flow rate of 50 ± 20 kg / h (hour). The CNTs were processed for 10 hours using a circulating grinding method at a peripheral speed of 3 m / s (seconds) to obtain CNTs (A-15).

[0142] (Manufacturing Example 13; CNT (A-16)) Ten portions of CNT (A-1) prepared in Manufacturing Example 1 were placed in a graphite crucible with a diameter of 10 cm and a height of 10 cm. The crucible containing the CNTs was placed in a multi-purpose high-temperature furnace (High Multi 5000, manufactured by Fuji Denpa Kogyo Co., Ltd.) and subjected to heat treatment under reduced pressure and vacuum as follows. First, nitrogen gas was introduced into the multi-purpose high-temperature furnace, and the nitrogen gas substitution operation was performed twice. Next, the furnace pressure was reduced using an oil rotary pump and adjusted to 9.8 to 9.5 Pa, and then further reduced using an oil diffusion pump to adjust the furnace pressure to 0.01 to 0.05 Pa. Subsequently, while maintaining the reduced pressure by the oil diffusion pump, the temperature was raised to 1,500°C at a heating rate of 20°C / min and held at 1,500°C for 24 hours. Subsequently, the CNTs obtained by allowing the furnace temperature to cool naturally to below 50°C were subjected to dry processing as follows. First, using a 50L capacity dynamic mill (manufactured by Nippon Coke Industries Co., Ltd.) bead mill, 3mm diameter zirconia beads were loaded as grinding media at a packing rate of 70%, and 60 kg of CNTs were supplied at a flow rate of 50 ± 20 kg / h (hours). The CNTs were processed for 21 hours using a circulating grinding method at a peripheral speed of 3 m / s (seconds) to obtain CNTs (A-16).

[0143] (Manufacturing Example 14; CNT (A-17)) Ten portions of CNT (A-2) prepared in Manufacturing Example 2 were placed in a graphite crucible with a diameter of 10 cm and a height of 10 cm. The crucible containing the CNTs was placed in a multi-purpose high-temperature furnace (High Multi 5000, manufactured by Fuji Denpa Kogyo Co., Ltd.) and subjected to heat treatment under reduced pressure and vacuum as follows. First, nitrogen gas was introduced into the multi-purpose high-temperature furnace, and the nitrogen gas substitution operation was performed twice. Next, the furnace pressure was reduced using an oil rotary pump and adjusted to 9.8 to 9.5 Pa, and then further reduced using an oil diffusion pump to adjust the furnace pressure to 0.01 to 0.05 Pa. Subsequently, while maintaining the reduced pressure by the oil diffusion pump, the temperature was raised to 1,500°C at a heating rate of 20°C / min and held at 1,500°C for 24 hours. Subsequently, the CNTs obtained by allowing the furnace temperature to cool naturally to below 50°C were subjected to dry processing as follows. First, using a 50L capacity dynamic mill (manufactured by Nippon Coke Industries Co., Ltd.) bead mill, 8mm diameter zirconia beads were loaded as grinding media at a packing rate of 70%, and 60 kg of CNTs were supplied at a flow rate of 50 ± 20 kg / h (hours). The CNTs were processed for 23 hours using a circulating grinding method at a peripheral speed of 3 m / s (seconds) to obtain CNTs (A-17).

[0144] (Manufacturing Example 15; CNT (A-18)) Ten portions of CNT (A-2) prepared in Manufacturing Example 2 were placed in a graphite crucible with a diameter of 10 cm and a height of 10 cm. The crucible containing the CNTs was placed in a multi-purpose high-temperature furnace (High Multi 5000, manufactured by Fuji Denpa Kogyo Co., Ltd.) and subjected to heat treatment under reduced pressure and vacuum as follows. First, nitrogen gas was introduced into the multi-purpose high-temperature furnace, and the nitrogen gas substitution operation was performed twice. Next, the furnace pressure was reduced using an oil rotary pump and adjusted to 9.8 to 9.5 Pa. Subsequently, the pressure was further reduced using an oil diffusion pump and adjusted to 0.01 to 0.05 Pa. Then, while maintaining the reduced pressure using the oil diffusion pump, the temperature was raised to 1,500°C at a heating rate of 20°C / min and held at 1,500°C for 24 hours. Subsequently, the CNTs obtained by allowing the furnace temperature to cool naturally to below 50°C were subjected to dry processing as follows. First, using a 50L capacity dynamic mill (manufactured by Nippon Coke Industries Co., Ltd.) bead mill, 3mm diameter zirconia beads were loaded as grinding media at a packing rate of 70%, and 60 kg of CNTs were supplied at a flow rate of 50 ± 20 kg / h (hours). The CNTs were processed for 10 hours using a circulating grinding method at a peripheral speed of 3 m / s (seconds) to obtain CNTs (A-18).

[0145] (Manufacturing Example 16; CNT (A-19)) Ten portions of CNT (A-2) prepared in Manufacturing Example 2 were placed in a graphite crucible with a diameter of 10 cm and a height of 10 cm. The crucible containing the CNTs was placed in a multi-purpose high-temperature furnace (High Multi 5000, manufactured by Fuji Denpa Kogyo Co., Ltd.) and subjected to heat treatment under reduced pressure and vacuum as follows. First, nitrogen gas was introduced into the multi-purpose high-temperature furnace, and the nitrogen gas substitution operation was performed twice. Next, the furnace pressure was reduced using an oil rotary pump and adjusted to 9.8 to 9.5 Pa, and then further reduced using an oil diffusion pump to adjust the furnace pressure to 0.01 to 0.05 Pa. Subsequently, while maintaining the reduced pressure by the oil diffusion pump, the temperature was raised to 1,500°C at a heating rate of 20°C / min and held at 1,500°C for 24 hours. Subsequently, the CNTs obtained by allowing the furnace temperature to cool naturally to below 50°C were subjected to dry processing as follows. First, using a 50L capacity dynamic mill (manufactured by Nippon Coke Industries Co., Ltd.) bead mill, 3mm diameter zirconia beads were loaded as grinding media at a packing rate of 70%, and 60 kg of CNTs were supplied at a flow rate of 50 ± 20 kg / h (hours). The CNTs were processed for 21 hours using a circulating grinding method at a peripheral speed of 3 m / s (seconds) to obtain CNTs (A-19).

[0146] (Manufacturing Example 17; CNT (A-20)) Referring to "Mapping carbon nanotube aspect ratio, concentration and spinning in FGGVD synthesis controlled by sulphur (Carbon Trends 15(2024) 100355)" by Miguel Vazquez-Pufleau et al., CNTs were manufactured in the same manner as described in the above-mentioned document, except that the sulfur (S) / carbon (C) ratio (hereinafter referred to as the S / C ratio) was changed to 0.05. The obtained CNTs were subjected to heat treatment under reduced pressure and vacuum as follows. Ten parts of CNTs were placed in a graphite crucible with a diameter of 10 cm and a height of 10 cm. The crucible containing the above CNTs was placed in a multi-purpose high-temperature furnace (High Multi 5000, manufactured by Fuji Denpa Kogyo Co., Ltd.), and heat treatment under reduced pressure and vacuum was performed as follows. First, nitrogen gas was introduced into the multi-purpose high-temperature furnace, and the nitrogen gas substitution operation was performed twice. Next, the furnace pressure was reduced using an oil rotary pump and adjusted to 9.8–9.5 Pa. Subsequently, the pressure was further reduced using an oil diffusion pump and adjusted to 0.01–0.05 Pa. Then, while maintaining the reduced pressure by the oil diffusion pump, the temperature was raised to 1,500°C at a heating rate of 20°C / min and held at 1,500°C for 24 hours. After that, the CNTs obtained by allowing the furnace temperature to cool naturally to below 50°C were subjected to dry processing as follows. First, in a 50L capacity Ajisawa Finetech Co., Ltd. "Drystar SDA50", 3 mm diameter zirconia beads were loaded as grinding media at a packing rate of 70%, 60 kg of CNTs were supplied at an average flow rate of 120 ± 20 kg / h, and processed for 10 hours in a circulating grinding method at a peripheral speed of 3.0 m / s to obtain CNTs (A-20). During the processing step, the powder was cooled by flowing cooling water (10°C) through the vessel (flow rate 10 L / min) so that the outlet powder temperature was 65 ± 10°C.

[0147] (Manufacturing Example 18; CNT (A-21)) Using CNTs obtained in the same manner as described in the above-mentioned document "Carbon Trends 15 (2024) 100355", except that the S / C ratio was changed to 0.1, heat treatment under reduced pressure and vacuum was performed as follows. Ten parts of CNTs were placed in a graphite crucible with a diameter of 10 cm and a height of 10 cm. The crucible containing the CNTs was placed in a multi-purpose high-temperature furnace (High Multi 5000, manufactured by Fuji Denpa Kogyo Co., Ltd.), and heat treatment under reduced pressure and vacuum was performed as follows. First, nitrogen gas was introduced into the multi-purpose high-temperature furnace, and the nitrogen gas substitution operation was performed twice. Next, the furnace pressure was reduced using an oil rotary pump and adjusted to 9.8 to 9.5 Pa, and then further reduced using an oil diffusion pump to adjust the furnace pressure to 0.01 to 0.05 Pa. Next, while maintaining reduced pressure using an oil diffusion pump, the temperature was raised to 1,500°C at a heating rate of 20°C / min and held at 1,500°C for 24 hours. After that, the CNTs obtained by allowing natural cooling until the furnace temperature fell below 50°C were used for dry processing as follows. First, in a 50L capacity Ajisawa Finetech Co., Ltd. "Drystar SDA50" furnace, 3mm diameter zirconia beads were loaded as grinding media at a packing rate of 70%, and 60kg of CNTs were supplied at an average flow rate of 120±20kg / h. The processing was carried out for 10 hours using a circulating grinding method at a peripheral speed of 3.0m / s to obtain CNTs (A-21). During the processing, the outlet powder temperature was cooled by flowing cooling water (10°C) through the vessel (flow rate 10L / min) so that it reached 65±10°C.

[0148] (Manufacturing Example 19; CNT (A-22)) Using CNTs obtained in the same manner as described in the above-mentioned document "Carbon Trends 15 (2024) 100355", except that the S / C ratio was changed to 0.5, heat treatment under reduced pressure and vacuum was performed as follows. Ten parts of CNTs were placed in a graphite crucible with a diameter of 10 cm and a height of 10 cm. The crucible containing the CNTs was placed in a multi-purpose high-temperature furnace (High Multi 5000, manufactured by Fuji Denpa Kogyo Co., Ltd.), and heat treatment under reduced pressure and vacuum was performed as follows. First, nitrogen gas was introduced into the multi-purpose high-temperature furnace, and the nitrogen gas substitution operation was performed twice. Next, the furnace pressure was reduced using an oil rotary pump and adjusted to 9.8 to 9.5 Pa, and then further reduced using an oil diffusion pump to adjust the furnace pressure to 0.01 to 0.05 Pa. Next, while maintaining reduced pressure using an oil diffusion pump, the temperature was raised to 1,500°C at a heating rate of 20°C / min and held at 1,500°C for 24 hours. After that, the CNTs obtained by allowing natural cooling until the furnace temperature was below 50°C were used for dry processing as follows. First, in a 50L capacity Ajisawa Finetech Co., Ltd. "Drystar SDA50" furnace, 3mm diameter zirconia beads were loaded as grinding media at a packing rate of 70%, and 60kg of CNTs were supplied at an average flow rate of 120±20kg / h. The processing was carried out for 10 hours using a circulating grinding method at a peripheral speed of 3.0m / s to obtain CNTs (A-22). During the processing, the outlet powder temperature was cooled by flowing cooling water (10°C) through the vessel (flow rate 10L / min) so that it reached 65±10°C.

[0149] (Manufacturing Example 20; CNT (A-23)) Using CNTs obtained in the same manner as described in the above-mentioned document "Carbon Trends 15 (2024) 100355", except that the S / C ratio was changed to 1, heat treatment under reduced pressure and vacuum was performed as follows. Ten parts of CNTs were placed in a graphite crucible with a diameter of 10 cm and a height of 10 cm. The crucible containing the CNTs was placed in a multi-purpose high-temperature furnace (High Multi 5000, manufactured by Fuji Denpa Kogyo Co., Ltd.), and heat treatment under reduced pressure and vacuum was performed as follows. First, nitrogen gas was introduced into the multi-purpose high-temperature furnace, and the nitrogen gas substitution operation was performed twice. Next, the furnace pressure was reduced using an oil rotary pump and adjusted to 9.8 to 9.5 Pa, and then further reduced using an oil diffusion pump to adjust the furnace pressure to 0.01 to 0.05 Pa. Next, while maintaining reduced pressure using an oil diffusion pump, the temperature was raised to 1,500°C at a heating rate of 20°C / min and held at 1,500°C for 24 hours. After that, the CNTs obtained by allowing natural cooling until the furnace temperature fell below 50°C were used for dry processing as follows. First, in a 50L capacity Ajisawa Finetech Co., Ltd. "Drystar SDA50" furnace, 3mm diameter zirconia beads were loaded as grinding media at a packing rate of 70%, and 60kg of CNTs were supplied at an average flow rate of 120±20kg / h. The processing was carried out for 10 hours using a circulating grinding method at a peripheral speed of 3.0m / s to obtain CNTs (A-23). ​​During the processing, the outlet powder temperature was cooled by flowing cooling water (10°C) through the vessel (flow rate 10L / min) so that it reached 65±10°C.

[0150] (Manufacturing Example 21; CNT (A-24)) Using CNTs obtained in the same manner as described in the above-mentioned document "Carbon Trends 15 (2024) 100355", except that the S / C ratio was changed to 3, heat treatment under reduced pressure and vacuum was performed as follows. Ten parts of CNTs were placed in a graphite crucible with a diameter of 10 cm and a height of 10 cm. The crucible containing the CNTs was placed in a multi-purpose high-temperature furnace (High Multi 5000, manufactured by Fuji Denpa Kogyo Co., Ltd.), and heat treatment under reduced pressure and vacuum was performed as follows. First, nitrogen gas was introduced into the multi-purpose high-temperature furnace, and the nitrogen gas substitution operation was performed twice. Next, the furnace pressure was reduced using an oil rotary pump and adjusted to 9.8 to 9.5 Pa, and then further reduced using an oil diffusion pump to adjust the furnace pressure to 0.01 to 0.05 Pa. Next, while maintaining reduced pressure using an oil diffusion pump, the temperature was raised to 1,500°C at a heating rate of 20°C / min and held at 1,500°C for 24 hours. After that, the CNTs obtained by allowing natural cooling until the furnace temperature fell below 50°C were used for dry processing as follows. First, in a 50L capacity Ajisawa Finetech Co., Ltd. "Drystar SDA50" furnace, 3mm diameter zirconia beads were loaded as grinding media at a packing rate of 70%, and 60kg of CNTs were supplied at an average flow rate of 120±20kg / h. The processing was carried out for 10 hours using a circulating grinding method at a peripheral speed of 3.0m / s to obtain CNTs (A-24). During the processing, the outlet powder temperature was cooled by flowing cooling water (10°C) through the vessel (flow rate 10L / min) so that it reached 65±10°C.

[0151] (Manufacturing Example 22; CNT (A-25)) Using CNTs obtained in the same manner as described in the above-mentioned document "Carbon Trends 15 (2024) 100355", except that the S / C ratio was changed to 5, heat treatment under reduced pressure and vacuum was performed as follows. Ten parts of CNTs were placed in a graphite crucible with a diameter of 10 cm and a height of 10 cm. The crucible containing the CNTs was placed in a multi-purpose high-temperature furnace (High Multi 5000, manufactured by Fuji Denpa Kogyo Co., Ltd.), and heat treatment under reduced pressure and vacuum was performed as follows. First, nitrogen gas was introduced into the multi-purpose high-temperature furnace, and the nitrogen gas substitution operation was performed twice. Next, the furnace pressure was reduced using an oil rotary pump and adjusted to 9.8 to 9.5 Pa, and then further reduced using an oil diffusion pump to adjust the furnace pressure to 0.01 to 0.05 Pa. Next, while maintaining reduced pressure using an oil diffusion pump, the temperature was raised to 1,500°C at a heating rate of 20°C / min and held at 1,500°C for 24 hours. After that, the CNTs obtained by allowing natural cooling until the furnace temperature fell below 50°C were used for dry processing as follows. First, in a 50L capacity Ajisawa Finetech Co., Ltd. "Drystar SDA50" furnace, 3mm diameter zirconia beads were loaded as grinding media at a packing rate of 70%, and 60kg of CNTs were supplied at an average flow rate of 120±20kg / h. The processing was carried out for 10 hours using a circulating grinding method at a peripheral speed of 3.0m / s to obtain CNTs (A-25). During the processing, the outlet powder temperature was cooled by flowing cooling water (10°C) through the vessel (flow rate 10L / min) so that it reached 65±10°C.

[0152] <Dispersants> ・Dispersant (B-1): Polyacrylic acid (AC-10LP, weight-average molecular weight 50,000, manufactured by Toagosei Co., Ltd.) ・Dispersant (B-2): Polyacrylic acid (AC-10P, weight-average molecular weight 9,000, manufactured by Toagosei Co., Ltd.) ・Dispersant (B-3): Polyacrylic acid (molecular weight 1,000,000 to 1,600,000, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) ・Dispersant (B-4): Carboxymethylcellulose (Sunrose A, APP-084, weight-average molecular weight 18,000, manufactured by Nippon Paper Industries Co., Ltd.) ・Dispersant (B-5): Polyvinyl alcohol (Kuraray Poval, SD1000, manufactured by Kuraray Co., Ltd.) ・Dispersant (B-6): Polyvinylpyrrolidone (PVP) (K-30, weight-average molecular weight 40,000, manufactured by Nippon Shokubai Co., Ltd.)

[0153] (Production Example 23; Dispersant (B-7)) 100 parts of acetonitrile were charged into a reaction vessel equipped with a gas inlet tube, thermometer, condenser, and stirrer, and the vessel was purged with nitrogen gas. The reaction vessel was heated to 70°C, and a mixture of 85.0 parts acrylonitrile, 15.0 parts acrylic acid, and 5.0 parts of 2,2'-azobis(2,4-dimethylvaleronitrile) (manufactured by NOF Corporation; V-65) was added dropwise over 2 hours to carry out the polymerization reaction. After the dropwise addition was complete, the reaction was continued at 70°C for another hour, then 0.5 parts of barbutyl O was added, and the reaction was continued at 70°C for another hour. Subsequently, the conversion rate was confirmed to be over 98% by measuring the non-volatile content, and the dispersion medium was completely removed by reducing the pressure and concentrating to obtain dispersant (B-7). The weight-average molecular weight (Mw) of dispersant (B-7) was 38,000.

[0154] (Method for measuring the weight-average molecular weight (Mw) of dispersants (B-1 to B-7)) The weight-average molecular weight (Mw) of dispersants (B-1 to B-7) was measured using gel permeation chromatography (GPC) equipped with an RI detector, selecting either measurement method 1 or measurement method 2 depending on the solubility of the dispersant in water. The dispersant was added to a mixture of purified water / methanol = 3 / 7 (volume ratio) to a concentration of 0.2 mass%, and sonicated for 10 minutes. If the dispersant was completely dissolved, it was measured using measurement method 1. On the other hand, if the dispersant did not completely dissolve, precipitate formed, or remained in a suspended state, it was measured using measurement method 2. (Measurement Method 1) A Shodex GPC-101 apparatus (manufactured by Showa Denko Corporation) was used. Four columns were connected in series as separation columns: three Showa Denko Corporation "OHpak SB-806M HQ" columns and one Showa Denko Corporation "OHpak SB-802.5 HQ" column. The oven temperature was 40°C, and a 50 mM lithium chloride purified water / methanol = 3 / 7 (volume ratio) solution was used as the eluent. The measurement was performed at a flow rate of 1.0 mL / min. The sample was prepared at a concentration of 0.2 mass% in the mixture of the above eluent and 0.1 mL was injected. Molecular weight is calculated on a polyethylene glycol basis. From the above measurement results, the weight-average molecular weight (Mw) of the dispersants (B-1 to B-7) was calculated. (Measurement Method 2) The apparatus used was an HLC-8320GPC (manufactured by Tosoh Corporation). Tosoh Corporation's "TSK-GELSUPER AW-4000", "AW-3000", and "AW-2500" were connected in series as separation columns. The oven temperature was 40°C, and a 30 mM triethylamine and 10 mM lithium bromide N,N-dimethylformamide solution was used as the eluent. Measurements were taken at a flow rate of 0.6 mL / min. The sample was prepared in a solvent consisting of the above eluent at a concentration of 0.2 mass%, and 10 μL was injected. Molecular weight is the polystyrene equivalent. From the above measurement results, the weight-average molecular weight (Mw) of the dispersants (B-1) to (B-7) was calculated.

[0155] 1. CNT Dispersion Compositions The properties of the CNTs used in the examples and comparative examples described later, which were produced by the manufacturing method described above, are shown in Table 1.

[0156]

[0157] Table 2 shows the dispersion conditions for producing the CNT dispersion compositions prepared in the examples and comparative examples described later. The CNT dispersion compositions were prepared by combining the first, second, third, and fourth dispersion steps.

[0158]

[0159] (Example 1-1) 98.05 parts of deionized water were added to a stainless steel container, and while stirring with a disperser, 0.90 parts of dispersant (B-1) and 0.05 parts of sodium carbonate were added and stirred with the disperser until homogeneous. Then, 1 part of CNT (A-4) was weighed and added while stirring with the disperser, and a square-hole high-shear screen was attached to a high-shear mixer (L5M-A, manufactured by SILVERSON), and batch dispersion was performed at a speed of 8,000 rpm until the entire mixture was homogeneous. This process is designated as the first dispersion process. Subsequently, the dispersion liquid was supplied from the stainless steel container to a nozzle-type high-pressure homogenizer (Starburst Lab HJP-17007, manufactured by Sugino Machine Co., Ltd.) via piping, and a circulating dispersion process was performed. The dispersion process used a single nozzle chamber, and 33 passes were performed with a nozzle diameter of 0.20 mm and a pressure of 150 MPa. This process is designated as the second dispersion process. These processes were performed to obtain the CNT dispersion composition (D-1).

[0160] (Examples 1-2 to 1-3) CNT dispersion compositions (D-2 to D-3) were obtained in the same manner as in Example 1-1, except that the second dispersion step was changed to the dispersion conditions described in Table 2.

[0161] (Example 1-4) A CNT dispersion composition (D-4) was obtained in the same manner as in Example 1-1, except that a valve-type high-pressure homogenizer (H3-1D, manufactured by Sanmaru Machinery Industry Co., Ltd.) was used instead of a nozzle-type high-pressure homogenizer (Starburst Lab HJP-17007, manufactured by Sugino Machinery Co., Ltd.) and subjected to 50 passes at a pressure of 100 MPa.

[0162] (Examples 1-5) 98.05 parts of deionized water were added to a stainless steel container, and while stirring with a disperser, 0.90 parts of dispersant (B-1) and 0.05 parts of additive were added and stirred with the disperser until homogeneous. Then, 1 part of CNT (A-4) was weighed and added while stirring with the disperser, and a square-hole high-shear screen was attached to a high-shear mixer (L5M-A, manufactured by SILVERSON), and batch dispersion was performed at a speed of 8,000 rpm until the entire mixture was homogeneous. This process is designated as the first dispersion process. Next, the mixture was transferred from the stainless steel container via piping to a bead mill (Ashizawa Finetech Co., Ltd. "Star Mill LMZ2", bead filling rate 80%) filled with 1.0 mmφ zirconia beads, and circulating dispersion was performed at a peripheral speed of 12 m / s for 16 minutes. This process is designated as the second dispersion process. Next, the dispersion liquid was supplied from the stainless steel container to a valve-type high-pressure homogenizer (H3-1D, manufactured by Sanmaru Machinery Industry Co., Ltd.) via piping, and a circulating dispersion process was performed. A flat valve was used for the homogenization section, and the process was carried out for 50 passes at a pressure of 100 MPa. This process was designated as the third dispersion process. These processes were performed to obtain the CNT dispersion composition (D-5).

[0163] (Example 1-6) 98.05 parts of deionized water were added to a stainless steel container, and while stirring with a disperser, 0.90 parts of dispersant (B-1) and 0.05 parts of additive were added and stirred with the disperser until homogeneous. Then, 1 part of CNT (A-4) was weighed and added while stirring with the disperser, and a square-hole high-shear screen was attached to a high-shear mixer (L5M-A, manufactured by SILVERSON), and batch dispersion was performed at a speed of 8,000 rpm until the entire mixture was homogeneous. This process is designated as the first dispersion process. Next, the mixture was transferred from the stainless steel container via piping to a bead mill (Ashizawa Finetech Co., Ltd. "Star Mill LMZ2", bead filling rate 80%) filled with 1.0 mmφ zirconia beads, and circulating dispersion was performed at a peripheral speed of 12 m / s for 16 minutes. This process is designated as the second dispersion process. Next, the dispersion liquid was supplied from the stainless steel container to a nozzle-type high-pressure homogenizer (Starburst Lab HJP-17007, manufactured by Sugino Machine) via piping, and a circulating dispersion process was performed. The dispersion process used a single nozzle chamber, with a nozzle diameter of 0.20 mm and a pressure of 150 MPa, and 40 passes were performed. This process was designated as the third dispersion step. These processes were performed to obtain the CNT dispersion composition (D-6).

[0164] (Examples 1-7 to 1-11) CNT dispersion compositions (D-7 to D-11) were obtained in the same manner as in Example 1-6, except that the second and third dispersion steps were changed to the bead diameter, dispersion time, nozzle diameter, pressure, and number of passes as shown in Table 2.

[0165] (Example 1-12) 98.05 parts of deionized water were added to a stainless steel container, and while stirring with a disperser, 0.90 parts of dispersant (B-1) and 0.05 parts of additive were added and stirred with the disperser until homogeneous. Then, 1 part of CNT (A-4) was weighed and added while stirring with the disperser, and a square-hole high-sear screen was attached to a high-sear mixer (L5M-A, manufactured by SILVERSON), and batch dispersion was performed at a speed of 8,000 rpm until the entire mixture was homogeneous. This process is designated as the first dispersion process. Next, the mixture was transferred from the stainless steel container via piping to a bead mill (DinoMill MULTI LAB, manufactured by Shinmaru Enterprises, with a bead filling rate of 80%) filled with 2.0 mmφ zirconia beads, and circulating dispersion was performed at a peripheral speed of 12 m / s for 16 minutes. This process is designated as the second dispersion process. Next, a circulating dispersion process was performed from a stainless steel container through piping using a bead mill (Ashizawa Finetech Co., Ltd. "Star Mill LMZ2", bead filling rate 80%) filled with 1.0 mm diameter zirconia beads until the peripheral speed was 12 m / s and the retention time was 16 minutes. This process is designated as the second dispersion process. Subsequently, the dispersion liquid was supplied from the stainless steel container through piping to a nozzle-type high-pressure homogenizer (Starburst Lab HJP-17007, Sugino Machine Co., Ltd.) and a circulating dispersion process was performed. The dispersion process was performed using a single nozzle chamber, with a nozzle diameter of 0.20 mm and a pressure of 150 MPa for 40 passes. This process is designated as the fourth dispersion process. By performing these processes, a CNT dispersion composition (D-12) was obtained.

[0166] (Examples 1-13) 14.4 parts by mass of dispersant (B-1), 16 parts by mass of CNT (A-4), and 69.6 parts by mass of deionized water were charged into a Laboplast Mill (manufactured by Toyo Seiki Seisakusho Co., Ltd.) and dispersed until the cumulative energy reached 2,000 MJ. This process was designated as the first dispersion process. Subsequently, the mixture was transferred to a stainless steel container, and 2,565.6 parts by mass of deionized water and 1.07 parts by mass of sodium carbonate were added. A square-hole high-sear screen was attached to a high-sear mixer (L5M-A, manufactured by SILVERSON) and the mixture was stirred at a speed of 7,000 rpm until uniform. This process was designated as the second dispersion process. The dispersion liquid was supplied from the stainless steel container to a high-pressure homogenizer (Starburst Lab HJP-17007, manufactured by Sugino Machine) via piping, and a circulating dispersion process was performed. The dispersion process was performed using a single nozzle chamber, with a nozzle diameter of 0.20 mm and a pressure of 150 MPa, for a total of 40 passes. This process was designated as the third dispersion step. These processes were carried out to obtain the CNT dispersion composition (D-13).

[0167] (Example 1-14) 14.4 parts by mass of dispersant (B-1), 16 parts by mass of CNT (A-4), and 69.6 parts by mass of deionized water were charged into a Laboplast Mill (manufactured by Toyo Seiki Seisakusho Co., Ltd.) and dispersed until the cumulative energy reached 2,000 MJ. This process was designated as the first dispersion process. Subsequently, the mixture was transferred to a stainless steel container, and 2,565.6 parts by mass of deionized water and 1.07 parts by mass of sodium carbonate were added. A square-hole high-sear screen was attached to a high-sear mixer (L5M-A, manufactured by SILVERSON) and the mixture was stirred at a speed of 7,000 rpm until uniform. This process was designated as the second dispersion process. The dispersion liquid was supplied from the stainless steel container to a high-pressure homogenizer (Starburst Lab HJP-17007, manufactured by Sugino Machine) via piping, and a circulating dispersion process was performed. The dispersion process was performed using a single nozzle chamber, with a nozzle diameter of 0.20 mm and a pressure of 150 MPa, for a total of 40 passes. This process is designated as the third dispersion step. Next, a circulating dispersion process was performed using a bead mill (Ashizawa Finetech Co., Ltd. "Star Mill LMZ2", bead filling rate 80%) filled with 1.0 mmφ zirconia beads from a stainless steel container via piping, at a peripheral speed of 12 m / s until the material was retained for 16 minutes. This process is designated as the fourth dispersion step. These processes were performed to obtain the CNT dispersion composition (D-14).

[0168] (Example 1-15) 14.4 parts by mass of dispersant (B-1), 16 parts by mass of CNT (A-4), and 69.6 parts by mass of deionized water were charged into a Laboplast Mill (manufactured by Toyo Seiki Seisakusho Co., Ltd.) and dispersed until the cumulative energy reached 2,000 MJ. This process is designated as the first dispersion process. Subsequently, the mixture was transferred to a stainless steel container, and 2,565.6 parts by mass of deionized water and 1.07 parts by mass of sodium carbonate were added. A square-hole high-sear screen was attached to a high-sear mixer (L5M-A, manufactured by SILVERSON) and the mixture was stirred at a speed of 7,000 rpm until uniform. This process is designated as the second dispersion process. Next, the mixture was transferred from the stainless steel container via piping to a bead mill (Ashizawa Finetech Co., Ltd. "Star Mill LMZ2", bead filling rate 80%) filled with 1.0 mmφ zirconia beads, and a circulating dispersion process was performed at a peripheral speed of 12 m / s for 16 minutes. This process is designated as the third dispersion step. The dispersion liquid was supplied from a stainless steel container through piping to a high-pressure homogenizer (Starburst Lab HJP-17007, manufactured by Sugino Machine Co., Ltd.) and a circulating dispersion process was performed. The dispersion process was carried out using a single nozzle chamber, with a nozzle diameter of 0.20 mm and a pressure of 150 MPa for 40 passes. This process is designated as the fourth dispersion step. By performing these processes, a CNT dispersion composition (D-15) was obtained.

[0169] CNT dispersion compositions (D-16 to D-58) were prepared by changing the CNT, dispersant, additives, water type and amount (parts by mass), and dispersion conditions described in Tables 3-1 to 3-3 (Examples 1-16 to 1-53).

[0170] (Examples 1-54 to 1-64) CNT dispersion compositions (D-59 to D-69) were prepared by changing the CNT, dispersant, additives, water type and amount (parts by mass), and dispersion conditions as described in Table 3-3.

[0171] Tables 3-4 to 3-6 show the composition, physical properties, and evaluation results of the CNT dispersion compositions prepared in the examples and comparative examples.

[0172]

[0173]

[0174]

[0175]

[0176]

[0177]

[0178] 2. Composition for secondary battery electrodes (Example 2-1) Capacity 150 cm³ ３ In a plastic container, 0.63 parts by mass of CNT dispersion composition (D-1), 12.5 parts by mass of an aqueous solution containing 2% by mass of CMC (manufactured by Daicel Finechem Co., Ltd., #1190), and 13.8 parts by mass of ion-exchanged water were weighed out. Then, using a rotation / revolution mixer (Awatori Rentaro, ARE-310, manufactured by Thinky Co., Ltd.), the mixture was stirred at 2,000 rpm for 30 seconds to obtain CNT resin composition (D-1). Subsequently, 2.92 parts by mass of silicon monoxide (SILICON MONOOXIDE, manufactured by Osaka Titanium Technologies Co., Ltd., SiO₂ 1.3C 5μm / 5μm) was added, and the mixture was stirred at 1,500 rpm for 10 minutes using a disperser. Furthermore, 21.44 parts by mass of artificial graphite (manufactured by Nippon Graphite Industry Co., Ltd., CGB-20) was added, and the mixture was stirred at 6,000 rpm for 10 minutes using a disperser. Subsequently, 0.78 parts by mass of styrene-butadiene emulsion (manufactured by ENEOS Material Co., Ltd., TRD2001) was added, and the mixture was stirred at 2,000 rpm for 30 seconds using the above-mentioned rotation-revolution mixer to obtain secondary battery electrode composition (D-1).

[0179] (Examples 2-2 to 2-53), (Comparative Examples 2-1 to 2-53) Secondary battery electrode compositions (D-2 to D-58) were obtained in the same manner as in Example 2-1, except that the CNT dispersion compositions listed in Tables 4-1 to 4-3 were used and the amounts of CNT dispersion composition and ion-exchanged water added were adjusted so that the amount of CNT in 100% by mass of the secondary battery electrode composition was 0.025% by mass.

[0180] (Comparative Example 2-6) A secondary battery electrode composition (D-59) was obtained in the same manner as in Example 2-1, except that the amount of CNT (A-4) and ion-exchanged water added was adjusted to replace the CNT dispersion composition so that the amount of CNT in 100% by mass of the secondary battery electrode composition was 0.025% by mass.

[0181] (Comparative Example 2-7) A secondary battery electrode composition (D-60) was obtained in the same manner as in Example 2-1, except that the amount of a single-layer CNT dispersion (manufactured by OCSiAl, TUBALL BATT 02H017) containing carboxymethylcellulose with a CNT concentration of 0.4% by mass and the amount of deionized water added were adjusted so that the amount of CNT in 100% by mass of the secondary battery electrode composition was 0.025% by mass.

[0182] (Examples 2-54 to 2-64) Secondary battery electrode compositions (D-61 to D-71) were obtained in the same manner as in Example 2-1, except that the CNT dispersion composition was changed to the one shown in Table 4-3, and the amount of CNT dispersion composition and ion-exchanged water added was adjusted so that the amount of CNT in 100% by mass of the secondary battery electrode composition was 0.025% by mass.

[0183] Table 4 shows the evaluation results of the secondary battery electrode compositions prepared in the examples and comparative examples.

[0184]

[0185]

[0186]

[0187] 3. Electrode (negative electrode) characteristics (Example 3-1) The composition for secondary battery electrodes (D-1) was applied using an applicator, and the basis weight per unit area of ​​the electrode was 7.2 mg / cm². ２ After coating the copper foil in this manner, it was dried on a hot plate at 80°C for 10 minutes, and then the coating was dried in an electric oven at 120°C for 15 minutes to obtain electrode film D-1). Subsequently, the electrode film was rolled using a roll press (manufactured by Sanku Metal Co., Ltd., 3t hydraulic roll press) to obtain a composite layer density of 1.6 g / cm³. ３ A negative electrode (D-1) was fabricated.

[0188] (Examples 3-2 to 3-53), (Comparative Examples 3-1 to 3-7) Negative electrodes (D-2 to D-60) were prepared in the same manner as in Example 3-1, except that the secondary battery electrode composition (D-1) was changed to secondary battery electrode compositions (D-2 to D-60).

[0189] (Examples 3-54 to 3-64) Negative electrodes (D-61 to D-71) were prepared in the same manner as in Example 3-1, except that the secondary battery electrode composition (D-1) was changed to secondary battery electrode compositions (D-61 to D-71).

[0190] Tables 5-1 to 5-3 show the evaluation results of the negative electrodes prepared in the examples and comparative examples.

[0191]

[0192]

[0193]

[0194] 4. Characteristics of the secondary battery (Example 4-1) The negative electrode (D-1) was punched out to a diameter of 16 mm to serve as the working electrode, and a metallic lithium foil (thickness 0.2 mm) was used as the counter electrode. A separator made of porous polypropylene film was inserted and laminated between the working electrode and the counter electrode. The electrolyte (ethylene carbonate, diethyl carbonate, dimethyl carbonate, fluoroethylene carbonate, and vinylene carbonate were mixed in a ratio of 38:30:28:3:1 (by weight), and then LiPF was added to the mixed solvent) ６ After injecting 100 μL of a non-aqueous electrolyte (dissolved at a concentration of 1 M), a two-electrode cell (manufactured by Nippon Tom Cell Co., Ltd.) was assembled to produce a secondary battery (D-1).

[0195] (Examples 4-2 to 4-53), (Comparative Examples 4-1 to 4-7) A secondary battery (D-2 to D-60) was manufactured in the same manner as in Example 4-1, except that the negative electrode (D-1) was changed to the negative electrodes (D-2 to D-60).

[0196] (Examples 4-54 to 4-64) Secondary batteries (D-61 to D-71) were manufactured in the same manner as in Example 4-1, except that the negative electrode (D-1) was changed to the negative electrodes (D-61 to D-71).

[0197] Tables 6-1 to 6-3 show the evaluation results of the secondary batteries prepared in the examples and comparative examples.

[0198]

[0199]

[0200]

[0201] In the above embodiment, a CNT dispersion composition comprising CNTs, a dispersant, and water was used, wherein the CNTs included CNT aggregates in which two or more CNT units, each having an average outer diameter of 3 nm to 8 nm and 3 to 15 layers, were bundled in parallel by interaction, and the average outer diameter of the CNT aggregates was 10 nm to 50 nm. The CNT dispersion composition of this embodiment having the above configuration was found to have excellent stability over time and to be applicable to various application fields where high conductivity and durability are required.

[0202] Furthermore, in the above embodiment, the CNT dispersion composition exhibited superior stability over time compared to the comparative example, resulting in a secondary battery electrode composition with excellent viscosity and peel strength, and a secondary battery with excellent cycle characteristics. Therefore, it has become clear that this embodiment can provide a secondary battery with high capacity, high output, and high durability, which is difficult to achieve with conventional CNT dispersion compositions. In addition, since the secondary battery of this embodiment has high charge / discharge performance and excellent cycle characteristics, when a vehicle is constructed using the secondary battery of this embodiment, a vehicle with high safety and improved fuel efficiency can be obtained.

[0203] Although the present invention has been described above in accordance with specific embodiments, the present invention is not limited thereto. The configuration and details of the present invention can be modified in various forms that can be understood by those skilled in the art within the scope of the invention.

Claims

1. A carbon nanotube dispersion composition comprising carbon nanotubes, a dispersant, and water, wherein the carbon nanotubes include carbon nanotube aggregates in which two or more carbon nanotube units, each having an average outer diameter of 3 nm or more and 8 nm or less and 3 to 15 layers, are bundled together in parallel by interaction, and the average outer diameter of the carbon nanotube aggregates is 10 nm or more and 50 nm or less.

2. The carbon nanotube dispersion composition according to claim 1, wherein the iron content of the carbon nanotube dispersion composition is 50 ppm or less.

3. The BET specific surface area of ​​the carbon nanotube is 100 m². ２ / g or more 300m ２ A carbon nanotube dispersion composition according to claim 1 or 2, wherein the amount is less than or equal to / g.

4. The carbon nanotube dispersion composition according to any one of claims 1 to 3, wherein the G / D ratio of the carbon nanotubes is 1.5 or more and 15 or less.

5. Shear rate of the carbon nanotube dispersion composition at 10 s. －１ Viscosity (V1) at 25°C measured by [method / tool ​​name] and shear rate 100 s －１ A carbon nanotube dispersion composition according to any one of claims 1 to 4, wherein the viscosity ratio (V1 / V2) of the viscosity (V2) measured at 25°C is 4.0 or more and 7.5 or less.

6. A composition for secondary battery electrodes comprising the carbon nanotube dispersion composition according to any one of claims 1 to 5.

7. An electrode film comprising a coating film of the secondary battery electrode composition described in claim 6.

8. A secondary battery comprising the electrode film described in claim 7.

9. A vehicle comprising the secondary battery described in claim 8.

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