JP7088150B2 - Carbon nanotube dispersion liquid and its use - Google Patents

Description

The present invention relates to a dispersion liquid of carbon nanotubes. More specifically, the present invention relates to a resin composition containing a carbon nanotube dispersion liquid and a resin, a mixed material slurry containing a carbon nanotube dispersion liquid, a resin and an active material, and an electrode film coated with the mixture slurry.

In recent years, with the spread of mobile phones and notebook personal computers, lithium-ion batteries have been attracting attention. A lithium ion battery usually includes a negative electrode made of a carbon-based material, a positive electrode containing an active material that reversibly moves lithium ions in and out, and a non-aqueous electrolyte that immerses them. It is manufactured by applying an electrode paste made of a conductive material and a binder to a current collector plate.

In the positive electrode, the conductivity of the active material is enhanced by blending the conductive material, but if the dispersion of the conductive material with respect to the active material is insufficient, the improvement of the conductivity is also insufficient. Therefore, there has been proposed a slurry for forming an electrode of a lithium ion battery, which contains an electrode active material, a conductive material, a binder and a polar solvent, and has an average particle size of 500 nm or less when the conductive material is dispersed. (See, for example, Patent Document 1.).

As the conductive material, carbon black, Ketjen black, fullerene, graphene, fine carbon material and the like are used. In particular, carbon nanotubes, which are a type of fine carbon fiber, are tubular carbons with a diameter of 1 μm or less, and their use as conductive materials for lithium-ion batteries has been studied because of their high conductivity based on their unique structure. ing. Among them (see, for example, Patent Documents 2, 3 and 4), multi-walled carbon nanotubes having an outer diameter of 10 nm to several tens of nm are relatively inexpensive and are expected to be put into practical use.

When carbon nanotubes having a small average outer diameter are used, a conductive network can be efficiently formed with a small amount, and the amount of conductive material contained in the positive electrode and the negative electrode for a lithium ion battery can be reduced. However, since carbon nanotubes having a small average outer diameter have strong cohesive force and are difficult to disperse, it has not been possible to obtain a carbon nanotube dispersion liquid having sufficient dispersibility.

Therefore, various attempts have been made to improve the dispersibility of carbon nanotubes with respect to the dispersion medium. For example, a method of dispersing carbon nanotubes in acetone while applying ultrasonic waves (see Patent Document 5) has been proposed. However, there is a problem that carbon nanotubes start to aggregate when the irradiation is completed even if they can be dispersed while the ultrasonic waves are being irradiated, and the carbon nanotubes aggregate when the concentration of the carbon nanotubes increases.

In addition, a method for dispersing and stabilizing carbon nanotubes using various dispersants has been proposed. For example, dispersion in water and NMP using a polymer-based dispersant such as the water-soluble polymer polyvinylpyrrolidone (hereinafter, PVP) has been proposed (see Patent Documents 2, 3 and 6). However, in Cited Document 2, although the electrode produced by using carbon nanotubes having an outer diameter of 10 to 15 nm is evaluated, there is a problem that the electrode resistance is high. Further, in Cited Document 3, a dispersion liquid using carbon nanotubes having a small DBP oil absorption is proposed, but there is a problem that it is difficult to obtain high conductivity although the dispersibility is improved. In Cited Document 6, dispersion using a single-walled CNT having a small outer diameter has been studied, but it has been difficult to disperse carbon nanotubes in a solvent at a high concentration. Further, in Cited Document 7, carbon nanotubes in which a 2θ peak exists at 24 ° ± 2 ° when powder X-ray diffraction analysis is performed and the half-value width of the peak is 6.27 ° are examined. It is a mixed composition of single-walled carbon nanotubes and double-walled carbon nanotubes, and it was necessary to perform dispersion treatment using an ultrasonic homogenizer. Therefore, obtaining a carbon nanotube dispersion liquid in which carbon nanotubes having a small outer diameter are uniformly dispersed in a dispersion medium at a high concentration has been an important issue for expanding applications.

Japanese Unexamined Patent Publication No. 2006-309958 Japanese Unexamined Patent Publication No. 2011-070908 Japanese Unexamined Patent Publication No. 2014-19619 Japanese Unexamined Patent Publication No. 2008-285368 Japanese Unexamined Patent Publication No. 2000-86219 Japanese Unexamined Patent Publication No. 2005-162877 Japanese Unexamined Patent Publication No. 2008-230947

An object to be solved by the present invention is to solve the above-mentioned conventional problems, and to provide a carbon nanotube dispersion liquid using carbon nanotubes having a small average outer diameter.

Further, an object to be solved by the present invention is to provide a carbon nanotube dispersion liquid and a carbon nanotube resin composition for obtaining an electrode film having high conductivity.

The inventors of the present invention have diligently studied to solve the above problems. The inventors have an average outer diameter of more than 3 nm and less than 10 nm, and in powder X-ray diffraction, a peak exists at a diffraction angle of 2θ = 25 ° ± 2 °, and the half-value width of the peak is 3 ° to 6 ° C. It has been found that a carbon nanotube dispersion liquid having excellent conductivity can be obtained by using carbon nanotubes at °. The inventors have come up with the present invention based on such a discovery.

That is, the present invention is a carbon nanotube (A) characterized by satisfying the following (1), (2) and (3). Regarding.
(1) The average outer diameter of carbon nanotubes is more than 3 nm and less than 10 nm.
(2) In powder X-ray diffraction analysis, a peak exists at a diffraction angle of 2θ = 25 ° ± 2 °, and the half-value width of the peak is 3 ° to 6 °.
(3) G / D when the maximum peak intensity in the range of 1560 to 1600 cm ^-1 is G and the maximum peak intensity in the range of 1310 to 1350 cm ^-1 is D in the Raman spectrum of the carbon nanotube (A). The ratio should be 0.5-4.5.

The present invention also relates to the carbon nanotube (A), wherein the standard deviation of the outer diameter of the carbon nanotube (A) is more than 0.7 nm and 3.5 nm or less.

The present invention also relates to the carbon nanotube ( A ) characterized in that the volume resistivity of the carbon nanotube (A) is 1.0 × 10 ⁻² to 2.5 × 10 ⁻² Ω · cm.

Further, in the present invention, when the maximum peak intensity in the range of 1560 to 1600 cm ^-1 is G and the maximum peak intensity in the range of 1310 to 1350 cm ^-1 is D in the Raman spectrum of the carbon nanotube (A). The present invention relates to the carbon nanotube (A) characterized by having a G / D ratio of 1.0 to 3.0.

Further, in the present invention, when the average outer diameter of the carbon nanotube (A) is X and the standard deviation of the outer diameter of the carbon nanotube is σ, X ± σ is 5.0 nm ≦ X ± σ ≦ 14.0 nm. The present invention relates to the carbon nanotube (A) , which is characterized by filling.
The present invention also relates to a secondary battery comprising the carbon nanotube (A).
The present invention also relates to the method for producing carbon nanotubes according to any one of claims 1 to 5, wherein the steps (1), (2) and (3) below are sequentially included.
(1) Step of installing a heat-resistant container containing carbon nanotubes in the furnace
(2) A step of raising the temperature in the furnace to 1000 to 1600 ° C. at the maximum temperature after reducing the oxygen concentration in the furnace to 0.1% or less.
(3) Step of introducing chlorine gas after reaching the maximum temperature

By using the carbon nanotube dispersion liquid of the present invention, a resin composition, a mixture slurry and an electrode film having excellent conductivity can be obtained. Therefore, the carbon nanotube dispersion liquid of the present invention can be used in various fields of application where high conductivity is required.

FIG. 1 is a graph showing the relationship between the outer diameter of carbon nanotubes and the number of carbon nanotubes used in Example 1 when 300 carbon nanotubes are arbitrarily observed using a transmission electron microscope. FIG. 2 is a graph showing the relationship between the outer diameter of carbon nanotubes and the number of carbon nanotubes used in Example 2 when 300 carbon nanotubes are arbitrarily observed using a transmission electron microscope. FIG. 3 is a graph showing the relationship between the outer diameter of carbon nanotubes and the number of carbon nanotubes used in Example 3 when 300 carbon nanotubes are arbitrarily observed using a transmission electron microscope. FIG. 4 is a graph showing the relationship between the outer diameter of carbon nanotubes and the number of carbon nanotubes used in Example 4 when 300 carbon nanotubes are arbitrarily observed using a transmission electron microscope. FIG. 5 is a graph showing the relationship between the outer diameter of carbon nanotubes and the number of carbon nanotubes used in Example 5 when 300 carbon nanotubes are arbitrarily observed using a transmission electron microscope. FIG. 6 is a graph showing the relationship between the outer diameter of carbon nanotubes and the number of carbon nanotubes used in Example 6 when 300 carbon nanotubes are arbitrarily observed using a transmission electron microscope. FIG. 7 is a graph showing the relationship between the outer diameter of carbon nanotubes and the number of carbon nanotubes used in Comparative Example 1 when 300 carbon nanotubes are arbitrarily observed using a transmission electron microscope. FIG. 8 is a graph showing the relationship between the outer diameter of carbon nanotubes and the number of carbon nanotubes used in Comparative Example 2 when 300 carbon nanotubes are arbitrarily observed using a transmission electron microscope. FIG. 9 is a graph showing the relationship between the outer diameter of carbon nanotubes and the number of carbon nanotubes used in Comparative Example 3 when 300 carbon nanotubes are arbitrarily observed using a transmission electron microscope. FIG. 10 is a graph showing the relationship between the outer diameter of carbon nanotubes and the number of carbon nanotubes used in Comparative Example 4 when 300 carbon nanotubes are arbitrarily observed using a transmission electron microscope.

Hereinafter, the carbon nanotube dispersion liquid, the resin composition, the mixture slurry, and the electrode film coated on the mixture slurry of the present invention will be described in detail.

(1) Carbon nanotube (A)
The carbon nanotube (A) of the present embodiment has a shape in which flat graphite is wound in a cylindrical shape. The carbon nanotube (A) may be a mixture of single-walled carbon nanotubes. Single-walled carbon nanotubes have a structure in which one layer of graphite is wound. Multi-walled carbon nanotubes have a structure in which two or three or more layers of graphite are wound. Further, the side wall of the carbon nanotube (A) does not have to have a graphite structure. For example, a carbon nanotube having a side wall having an amorphous structure can also be used as the carbon nanotube (A).

The shape of the carbon nanotube (A) of the present embodiment is not limited. Examples of such a shape include various shapes including a needle shape, a cylindrical tube shape, a fish bone shape (fishbone or cup laminated type), a playing card shape (platelet), and a coil shape. In the present embodiment, the shape of the carbon nanotube (A) is preferably needle-shaped or cylindrical tube-shaped. The carbon nanotube (A) may be a single shape or a combination of two or more kinds of shapes.

Examples of the form of the carbon nanotube (A) of the present embodiment include graphite whisker, carbonentas carbon, graphite fiber, ultrafine carbon tube, carbon tube, carbon fibril, carbon microtube and carbon nanofiber. Not limited to. The carbon nanotube (A) may have a single form thereof or a combination of two or more kinds thereof.

The average outer diameter of the carbon nanotube (A) of the present embodiment is more than 3 nm and less than 10 nm. Above all, it is preferably more than 4 nm and less than 10 nm, and more preferably more than 4 nm and less than 8 nm.

The standard deviation of the outer diameter of the carbon nanotube (A) of the present embodiment is preferably more than 0.7 nm and 3.5 nm or less, and preferably more than 1.4 nm and 3.5 nm or less. It is more preferably more than 4 nm and 3 nm or less.

The average outer diameter of the carbon nanotube (A) of the present embodiment is X ± σ [nm] when the average outer diameter of the carbon nanotube is X [nm] and the standard deviation of the outer diameter of the carbon nanotube is σ [nm]. Is preferably 5.0 nm ≦ X ± σ ≦ 14.0 nm, and more preferably 5.0 nm ≦ X ± σ ≦ 10.0 nm. X ± 2σ [nm] is preferably 2.0 nm ≦ X ± 2σ ≦ 17.0 nm, more preferably 3.0 nm ≦ X ± 2σ ≦ 13.5 nm, and more preferably 3.0 nm ≦ X ± 2σ. It is more preferably ≦ 12.0 nm.

The outer diameter and the average outer diameter of the carbon nanotube (A) of the present embodiment are obtained as follows. First, the carbon nanotube (A) is observed and imaged by a transmission electron microscope. Next, in the observation photograph, any 300 carbon nanotubes (A) are selected and the outer diameter of each is measured. Next, the average outer diameter (nm) of the carbon nanotube (A) is calculated as the number average of the outer diameters.

The fiber length of the carbon nanotube (A) of the present embodiment is preferably 0.1 to 150 μm, more preferably 1 to 10 μm.

The carbon purity of the carbon nanotube (A) of the present embodiment is represented by the content (% by mass) of carbon atoms in the carbon nanotube (A). The carbon purity is preferably 90% by mass or more, more preferably 95% by mass or more, further preferably 99% by mass or more, still more preferably 99.5% by mass or more, based on 100% by mass of the carbon nanotube (A).

The amount of metal contained in the carbon nanotube (A) of the present embodiment is preferably less than 10% by mass, more preferably less than 5% by mass, still more preferably less than 1% by mass, based on 100% by mass of the carbon nanotube (A). , Less than 0.5% by mass is more preferable. Examples of the metal contained in the carbon nanotube (A) include a metal and a metal oxide used as a catalyst in synthesizing the carbon nanotube (A). Specific examples thereof include metals such as cobalt, nickel, aluminum, magnesium, silica, manganese and molybdenum, metal oxides and composite oxides thereof.

The carbon nanotube (A) of this embodiment usually exists as a secondary particle. The shape of the secondary particles may be, for example, a state in which carbon nanotubes (A), which are general primary particles, are intricately intertwined. It may be an aggregate of straight carbon nanotubes (A). Secondary particles, which are aggregates of linear carbon nanotubes (A), are easier to unravel than those that are intertwined. Further, the linear one has better dispersibility than the entangled one, and therefore can be suitably used as the carbon nanotube (A).

The carbon nanotube (A) of the present embodiment may be a carbon nanotube that has been surface-treated. Further, the carbon nanotube (A) may be a carbon nanotube derivative to which a functional group typified by a carboxyl group is imparted. Further, carbon nanotubes (A) containing a substance typified by an organic compound, a metal atom, or fullerene can also be used.

The layer structure of the carbon nanotube (A) can be analyzed by powder X-ray diffraction analysis by the following method.

First, the carbon nanotube (A) is packed in a predetermined sample holder so that the surface is flat, set in a powder X-ray diffraction analyzer, and the irradiation angle of the X-ray source is changed from 15 ° to 35 ° for measurement. As the X-ray source, for example, CuKα ray is used. The carbon nanotube (A) can be evaluated by reading the diffraction angle 2θ at which the peak appears at that time. In graphite, a peak of 2θ is usually detected near 26 °, and it is known that this is a peak due to interlayer diffraction. Since the carbon nanotube (A) also has a graphite structure, a peak due to graphite interlayer diffraction is detected in the vicinity thereof. However, since carbon nanotubes have a cylindrical structure, their values are different from those of graphite. By the appearance of the peak at the position where the value 2θ is 25 ° ± 2 °, it can be determined that the composition having a multi-layer structure is contained instead of the single layer. Since the peak appearing at this position is a peak due to the interlayer diffraction of the multilayer structure, it is possible to determine the number of layers of the carbon nanotube (A). Since the single-walled carbon nanotubes have only one layer, no peak appears at the position of 25 ° ± 2 ° with the single-walled carbon nanotubes alone. However, even single-walled carbon nanotubes are not 100% single-walled carbon nanotubes, and peaks may appear at positions where 2θ is 25 ° ± 2 ° when multi-walled carbon nanotubes and the like are mixed. ..

In the carbon nanotube (A) of the present embodiment, a peak appears at a position where 2θ is 25 ° ± 2 °. The layer structure can also be analyzed from the half-value width of the peak of 25 ° ± 2 ° detected by powder X-ray diffraction analysis. That is, it is considered that the smaller the half-value width of this peak, the larger the number of layers of the multi-walled carbon nanotubes (A). On the contrary, it is considered that the larger the half-value range of this peak is, the smaller the number of layers of carbon nanotubes is.

The carbon nanotube (A) of the present embodiment has a peak at a diffraction angle of 2θ = 25 ° ± 2 ° when powder X-ray diffraction analysis is performed, and the half-value width of the peak is 3 ° to 6 °. It is preferably 4 ° to 6 °, more preferably 5 ° to 6 °.

The G / D ratio of the carbon nanotube (A) of the present embodiment is obtained by Raman spectroscopy. In the carbon nanotube (A) of the present embodiment, when the maximum peak intensity in the range of 1560 to 1600 cm ^-1 is G and the maximum peak intensity in the range of 1310 to 1350 cm ^-1 is D in the Raman spectrum, the maximum peak intensity is D. The G / D ratio is 0.5 to 4.5, preferably 0.7 to 3.0, and more preferably 1.0 to 3.0.

There are various laser wavelengths used in Raman spectroscopy, but 532 nm and 632 nm are used here. The Raman shift seen near 1590 cm ^-1 in the Raman spectrum is called the G band derived from graphite, and the Raman shift seen near 1350 cm ^-1 is called the D band derived from defects of amorphous carbon or graphite. The higher the G / D ratio, the higher the degree of graphitization.

Since the wave number of Raman spectroscopic analysis may fluctuate depending on the measurement conditions, the wave number specified here shall be specified by the wave number ± 10 cm ^-1 .

The volume resistivity of the carbon nanotube (A) of the present embodiment is preferably 1.0 × 10 ⁻² to 2.5 × 10 ⁻² Ω · cm, preferably 1.0 × 10 ⁻² to 2.0 ×. It is preferably 10 ⁻² Ω · cm, and more preferably 1.2 × 10 ⁻² to 1.8 × 10 ⁻² Ω · cm. The volume resistivity of the carbon nanotube (A) can be measured using a powder resistivity measuring device (manufactured by Mitsubishi Chemical Analytech Co., Ltd .: Lorester GP powder resistivity measuring system MCP-PD-51)). ..

The BET specific surface area of the carbon nanotube (A) of this embodiment is 200 to 1000 m ² /
The amount of g is preferable, the amount of 300 to 900 m ² / g is more preferable, and the amount of 400 to 800 m ² / g is particularly preferable.

The carbon nanotube (A) of the present embodiment has an average outer diameter of more than 3 nm and less than 10 nm, and has a peak at a diffraction angle of 2θ = 25 ° ± 2 ° in powder X-ray diffraction analysis, which is half of the peak. The value width is 3 ° to 6 °, and G / when the maximum peak intensity in the range of 1560 to 1600 cm ^-1 is G and the maximum peak intensity in the range of 1310 to 1350 cm ^-1 is D in the Raman spectrum. The D ratio is not particularly limited as long as it is 0.5 to 3.0, and carbon nanotubes produced by any method may be used. For example, carbon nanotubes (A) can be obtained by a laser ablation method, an arc discharge method, a thermal CVD method, a plasma CVD method, and a combustion method.

(2) Solvent (B)
The solvent (B) of the present embodiment is not particularly limited as long as the carbon nanotubes (A) can be dispersed, but is a mixed solvent consisting of one or more of water and / or a water-soluble organic solvent. Is preferable.

Water-soluble organic solvents include alcohols (methanol, ethanol, propanol, isopropanol, butanol, isobutanol, secondary butanol, tertiary butanol, benzyl alcohol, etc.) and polyhydric alcohols (ethylene glycol, diethylene glycol, triethylene glycol, polyethylene). Glycol, propylene glycol, dipropylene glycol, polypropylene glycol, butylene glycol, hexanediol, pentanediol, glycerin, hexanetriol, thiodiglycol, etc.), polyhydric alcohol ethers (ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene) Glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monobutyl ether, ethylene glycol monomethyl ether acetate, triethylene glycol monomethyl ether, triethylene glycol monoethyl Ether, triethylene glycol monobutyl ether, ethylene glycol monophenyl ether, propylene glycol monophenyl ether, etc.), amine-based (ethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, morpholin, N-ethylmorpholin , Ethylenediamine, diethylenediamine, triethylenetetramine, tetraethylenepentamine, polyethyleneimine, pentamethyldiethylenetriamine, tetramethylpropylenediamine, etc.), amides (N-methyl-2-pyrrolidone (NMP), N-ethyl-2-pyrrolidone) (NEP), N, N-dimethylformamide, N, N-dimethylacetamide, N, N-diethylacetamide, N-methylcaprolactam, etc.), heterocyclic system (cyclohexylpyrrolidone, 2-oxazolidone, 1,3-dimethyl-2) -Imidazolidinone, γ-butyrolactone, etc.), sulfoxide type (dimethylsulfoxide, etc.), sulfone type (hexamethylphosphorotriamide, sulfolane, etc.), lower ketone type (acetone, methylethylketone, etc.), etc., tetrahydrofuran, urea, aceto Nitrile and the like can be used. Of these, water or an amide-based organic solvent is more preferable, and among the amide-based solvents, N-methyl-2-pyrrolidone and N-ethyl-2-pyrrolidone are particularly preferable.

When only an amide-based organic solvent is used as the solvent (B) of the present embodiment, the water content in the solvent (B) is preferably 500 ppm or less, more preferably 300 ppm or less, and further preferably 100 ppm or less. Is particularly preferred.

(3) Dispersant (C)
The dispersant (C) of the present embodiment is not particularly limited as long as the carbon nanotube (A) can be dispersed and stabilized, and a surfactant and a resin-type dispersant can be used. Surfactants are mainly classified into anionic, cationic, nonionic and amphoteric. A dispersant of an appropriately suitable type can be used in a suitable blending amount according to the characteristics required for the dispersion of the carbon nanotube (A).

When selecting an anionic surfactant, the type thereof is not particularly limited. Specifically, fatty acid salts, polysulfonates, polycarboxylates, alkylsulfate esters, alkylarylsulfonates, alkylnaphthalene sulfonates, dialkylsulfonates, dialkylsulfosuccinates, alkylphosphates, polyoxys. Examples thereof include ethylene alkyl ether sulfate, polyoxyethylene alkylaryl ether sulfate, naphthalene sulfonic acid formalin condensate, polyoxyethylene alkyl phosphate sulfonate, glycerol volate fatty acid ester and polyoxyethylene glycerol fatty acid ester. Not limited to. Further, specific examples thereof include sodium dodecylbenzene sulfonate, sodium lauryl sulfate, sodium polyoxyethylene lauryl ether sulfate, polyoxyethylene nonylphenyl ether sulfate ester salt and sodium salt of β-naphthalene sulfonate formalin condensate. , Not limited to these.

Further, examples of the cationic surfactant include alkylamine salts and quaternary ammonium salts. Specifically, stearylamine acetate, trimethyl palmammonium chloride, trimethyl beef ammonium chloride, dimethyldiolylammonium chloride, methyloleyldiethanol chloride, tetramethylammonium chloride, laurylpyridinium chloride, laurylpyridinium bromide, laurylpyridinium disulfate, cetylpyridinium bromide. , 4-Alkylmercaptopyridine, poly (vinylpyridine) -dodecyl bromide and dodecylbenzyl triethylammonium chloride, but are not limited thereto. Further, examples of the amphoteric surfactant include, but are not limited to, aminocarboxylates.

Examples of the nonionic surfactant include, but are not limited to, polyoxyethylene alkyl ether, polyoxyalkylene derivative, polyoxyethylene phenyl ether, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester and alkyl allyl ether. Specific examples thereof include, but are not limited to, polyoxyethylene lauryl ether, sorbitan fatty acid ester and polyoxyethylene octylphenyl ether.

The surfactant selected is not limited to a single surfactant. Therefore, it is also possible to use two or more kinds of surfactants in combination. For example, a combination of anionic surfactant and nonionic surfactant, or a combination of cationic surfactant and nonionic surfactant can be used. The blending amount at that time is preferably a blending amount suitable for each surfactant component. As the combination, a combination of an anionic surfactant and a nonionic surfactant is preferable. The anionic surfactant is preferably a polycarboxylate. The nonionic surfactant is preferably polyoxyethylene phenyl ether.

Specific examples of the resin-type dispersant include cellulose derivatives (cellulose acetate, cellulose acetate butyrate, cellulose butyrate, cyanoethyl cellulose, ethyl hydroxyethyl cellulose, nitrocellulose, methylcellulose, ethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, and hydroxypropylmethylcellulose. Etc.), polyvinyl alcohol, polyvinyl butyral, polyvinylpyrrolidone and the like. In particular, methyl cellulose, ethyl cellulose, polyvinyl alcohol, polyvinyl butyral, and polyvinylpyrrolidone are preferable.

(4) Carbon Nanotube Dispersion Liquid The carbon nanotube dispersion liquid of the present embodiment contains a carbon nanotube (A), a solvent (B), and a dispersant (C).

In order to obtain the carbon nanotube dispersion liquid of the present embodiment, it is preferable to carry out a treatment of dispersing the carbon nanotubes (A) in the solvent (B). The dispersive device used to perform such processing is not particularly limited.

As the disperser, a disperser usually used for pigment dispersion or the like can be used. For example, mixers such as dispersers, homomixers, planetary mixers, homogenizers (BRANSON Advanced Digital Sonifer®, MODEL 450DA, M-Technique "Clearmix", PRIMI.
X company "Philmix" etc., Silverson company "Abramix" etc.), paint conditioner (Red Devil company), colloid mill (PUC company "PUC colloid mill")
, IKA "colloidal mill MK"), cone mill (IKA "corn mill MKO", etc.), ball mill, sand mill (Simmal Enterprises "Dynomill", etc.), attritor, pearl mill (Erich "DCP", etc.) Mills, etc.), media-type dispersers such as colloid mills, wet jet mills (Genus PY manufactured by Genus, Starburst manufactured by Sugino Machine Limited, Nanomizer manufactured by Nanomizer, etc.), Claire manufactured by M-Technique Examples include, but are not limited to, medialess dispersers such as "SS-5" and "MICROS" manufactured by Nara Machinery Co., Ltd., and other roll mills.

The solid content of the carbon nanotube dispersion liquid of the present embodiment is preferably 0.1 to 30% by mass, preferably 0.5 to 25% by mass, and 1 to 10% by mass with respect to 100% by mass of the carbon nanotube dispersion liquid. % Is preferable, and 1 to 5% by mass is particularly preferable.

The amount of the dispersant (C) in the carbon nanotube dispersion liquid of the present embodiment is preferably 3 to 300% by mass with respect to 100% by mass of the carbon nanotube (A). Further, from the viewpoint of conductivity, it is preferable to use 5 to 100% by mass, further preferably 5 to 50% by mass, and particularly preferably 5 to 25% by mass.

The fiber length of the carbon nanotube (A) in the carbon nanotube dispersion liquid of the present embodiment is preferably 0.1 to 10 μm, preferably 0.2 to 5 μm, and particularly preferably 0.3 to 2 μm.

(4) Binder (D)
The binder (D) is a resin that binds substances together.

Examples of the binder (D) of the present embodiment include ethylene, propylene, vinyl chloride, vinyl acetate, vinyl alcohol, maleic acid, acrylic acid, acrylic acid ester, methacrylic acid, methacrylic acid ester, acrylonitrile, styrene, vinyl butyral, and the like. Polymers or copolymers containing vinyl acetal, vinyl pyrrolidone, etc. as constituent units; polyurethane resin, polyester resin, phenol resin, epoxy resin, phenoxy resin, urea resin, melamine resin, alkyd resin, acrylic resin, formaldehyde resin, silicon resin , Fluorine resin; Cellulosic resin such as carboxymethyl cellulose; styrene-butadiene rubber, rubbers such as fluororubber; conductive resins such as polyaniline and polyacetylene. Further, modified products and mixtures of these resins and copolymers may be used. In particular, from the viewpoint of resistance, it is preferable to use a polymer compound having a fluorine atom in the molecule, for example, polyvinylidene fluoride, polyvinyl fluoride, tetrafluoroethylene and the like.

The weight average molecular weight of these resins as the binder (D) of the present embodiment is preferably 10,000 to 2,000,000, more preferably 100,000 to 1,000,000, and 200,000 to 1. Million is particularly preferred. If the molecular weight is small, the resistance and adhesion of the binder may decrease. Although the resistance and adhesion of the binder are improved when the molecular weight is increased, the viscosity of the binder itself is increased, the workability is lowered, and the particles act as a flocculant, and the dispersed particles may be remarkably aggregated.

From the industrial availability assumed by the present invention, the binder (D) preferably contains a polymer compound having a fluorine atom, preferably a polymer compound having a fluorine atom, and is a vinylidene fluoride-based compound. It is more preferably a polymer, and particularly preferably polyvinylidene fluoride.

(5) Carbon Nanotube Resin Composition The carbon nanotube resin composition of the present embodiment contains a carbon nanotube (A), a solvent (B), a dispersant (C), and a binder (D).

In order to obtain the carbon nanotube resin composition of the present embodiment, it is preferable to mix and homogenize the carbon nanotube dispersion liquid (C) and the binder (D). As the mixing method, various conventionally known methods can be used. The carbon nanotube resin composition can be produced by using the dispersant described in the carbon nanotube dispersion liquid.

(6) Active substance (E)
The active material (E) of the present embodiment is a material that is the basis of a battery reaction. The active material is divided into a positive electrode active material and a negative electrode active material according to the electromotive force.

The positive electrode active material is not particularly limited, but a metal oxide capable of doping or intercalating lithium ions, a metal compound such as a metal sulfide, a conductive polymer, or the like can be used. Examples thereof 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, transition metal oxide powders such as MnO, V ₂ O ₅ , V ₆ O ₁₃ , TiO ₂ , layered lithium nickelate, lithium cobaltate, lithium manganate, lithium manganate having a spinel structure, etc. Examples thereof include a composite oxide powder of lithium and a transition metal, a lithium iron phosphate-based material which is a phosphoric acid compound having an olivine structure, and a transition metal sulfide powder such as TiS ₂ and FeS. Further, conductive polymers such as polyaniline, polyacetylene, polypyrrole, and polythiophene can also be used. Further, the above-mentioned inorganic compounds and organic compounds may be mixed and used.

The negative electrode active material is not particularly limited as long as it can be doped with or intercalated with lithium ions. For example, metal Li, alloys such as tin alloys, silicon alloys, and lead alloys, Li _X Fe ₂ O ₃ , Li _X Fe ₃ O ₄ , and Li _X WO ₂ (x is a number of 0 <x <1). ), Metal oxides such as lithium titanate, lithium vanadium, lithium siliconate, conductive polymers such as polyacetylene and poly-p-phenylene, and amorphous carbonaceous materials such as soft carbon and hard carbon. Examples thereof include artificial graphite such as high graphite carbon material, carbonaceous powder such as natural graphite, carbon black, mesophase carbon black, resin fired carbon material, air layer growth carbon fiber, and carbon fiber such as carbon fiber. These negative electrode active materials may be used alone or in combination of two or more.

The positive electrode active material is preferably a composite oxide with lithium containing a transition metal such as Al, Fe, Co, Ni, and Mn, and is a composite oxidation with lithium containing any one of Al, Co, Ni, and Mn. It is more preferably a product, and particularly preferably a composite oxide with lithium containing Ni and / or Mn. When these active substances are used, particularly good effects can be obtained.

The BET specific surface area of the active material is preferably 0.1 to 10 m ² / g, more preferably 0.2 to 5 m ² / g, and even more preferably 0.3 to 3 m ² / g.

The average particle size of the active material is preferably in the range of 0.05 to 100 μm, more preferably in the range of 0.1 to 50 μm. The average particle size of the active material as used herein is an average value of the particle size of the active material measured with an electron microscope.

(7) Mixed Material Slurry The mixed material slurry of the present embodiment contains carbon nanotubes (A), a solvent (B), a dispersant (C), a binder (D), and an active material (E).

In order to obtain the mixed material slurry of the present embodiment, it is preferable to add an active material to the carbon nanotube resin composition and then disperse it. The dispersive device used to perform such processing is not particularly limited. As the mixed material slurry, the mixed material slurry can be obtained by using the disperser described in the carbon nanotube dispersion liquid.

The amount of the active material (E) in the mixed material slurry is preferably 20 to 85% by mass, particularly preferably 40 to 85% by mass, based on 100% by mass of the mixed material slurry.

The amount of carbon nanotubes (A) in the mixture slurry is preferably 0.05 to 10% by mass, preferably 0.1 to 5% by mass, based on 100% by mass of the active material. It is preferably ~ 3% by mass.

The amount of the binder (A) in the mixture slurry is preferably 0.5 to 20% by mass, more preferably 1 to 10% by mass, and 1 to 5% by mass with respect to 100% by mass of the active material. % Is particularly preferable.

The solid content of the mixed material slurry is preferably 30 to 90% by mass, preferably 40 to 85% by mass, based on 100% by mass of the mixed material slurry.

The water content in the mixture slurry is preferably 500 ppm or less, more preferably 300 ppm or less, and particularly preferably 100 ppm or less.

(7) Electrode film The electrode film of the present embodiment is a coating film having an electrode mixture layer formed by applying and drying a mixture slurry on a current collector.

The material and shape of the current collector used for the electrode film of the present embodiment are not particularly limited, and those suitable for various secondary batteries can be appropriately selected. For example, examples of the material of the current collector include metals and alloys such as aluminum, copper, nickel, titanium, and stainless steel. As the shape, a foil on a flat plate is generally used, but a roughened surface, a perforated foil, or a mesh-shaped current collector can also be used.

The method of applying the mixture slurry on the current collector is not particularly limited, and a known method can be used. Specific examples include a die coating method, a dip coating method, a roll coating method, a doctor coating method, a knife coating method, a spray coating method, a gravure coating method, a screen printing method, an electrostatic coating method, and the like, and drying. As the method, a stand-alone dryer, a blower dryer, a warm air dryer, an infrared heater, a far-infrared heater, and the like can be used, but the method is not particularly limited thereto.

Further, after coating, rolling processing may be performed by a lithographic press, a calendar roll, or the like. The thickness of the electrode mixture layer is generally 1 μm or more and 500 μm or less, preferably 10 μm or more and 300 μm or less.

It was found that the mixed material slurry using the carbon nanotube dispersion liquid as described above has good conductivity.

The reason why the conductivity is good is that the average outer diameter is more than 3 nm and less than 10 nm, and in powder X-ray diffraction analysis, a peak exists at a diffraction angle of 2θ = 25 ° ± 2 °, and the half-value width of the peak is present. This is because the carbon nanotubes having a temperature of 3 ° to 6 ° have a smaller outer diameter and a smaller layer thickness than general carbon nanotubes, so that it is easy to form a conductive path.

Hereinafter, the present invention will be described in more detail with reference to examples. The present invention is not limited to the following examples as long as the gist of the present invention is not exceeded. In the examples, "carbon nanotubes" may be abbreviated as "CNT".

<Measurement method of physical properties>
The physical characteristics of the CNTs used in each of the examples and comparative examples described later were measured by the following methods.

<Volume resistivity of CNT>
Using a powder resistivity measuring device (manufactured by Mitsubishi Chemical Analytech Co., Ltd .: Lorester GP powder resistivity measuring system MCP-PD-51)), the sample mass was 1.2 g, and the probe unit for powder (four probes). Needle / ring electrode, electrode spacing 5.0 mm, electrode radius 1.0 mm, sample radius 12.5 mm) allows the applied voltage limiter to be 90 V, and the volume resistivity [Ω · cm] of the conductive powder under various pressurization. It was measured. The value of the volume resistivity of CNT at a density of 1 g / cm ³ was evaluated.

<Radan spectroscopic analysis of CNT>
A CNT was installed in a Raman microscope (XploRA, manufactured by HORIBA, Ltd.), and measurement was performed using a laser wavelength of 532 nm. The measurement conditions were an capture time of 60 seconds, an integration frequency of 2 times, a dimming filter of 10%, an objective lens magnification of 20 times, a confocus hole of 500, a slit width of 100 μm, and a measurement wavelength of 100 to 3000 cm ^-1 . The CNTs for measurement were separated on a slide glass and flattened using a spatula. Among the obtained peaks, the maximum peak intensity is G in the range of 1560 to 1600 cm ^-1 in the spectrum, the maximum peak intensity is D in the range of 1310 to 1350 cm ^-1 , and the G / D ratio is G / of CNT. It was set to D ratio.

<CNT powder X-ray diffraction analysis>
A CNT was placed in the central recess of an aluminum sample plate (outer diameter φ46 mm, thickness 3 mm, sample portion φ26.5 mm, thickness 2 mm) and flattened using a slide glass. Then, a medicine wrapping paper was placed on the surface on which the sample was placed, and a load of 1 ton was applied to the surface on which the aluminum high sheet packing was placed to flatten the surface. Then, the medicine wrapping paper and the aluminum high sheet packing were removed to obtain a sample for powder X-ray diffraction analysis of CNT. After that, a sample for powder X-ray diffraction analysis of CNT was placed in an X-ray diffractometer (Ultima2100, manufactured by Rigaku Co., Ltd.) and operated from 15 ° to 35 ° for analysis. Sampling is performed every 0.02 °, and the scan speed is 2 ° / min. And said. The voltage was 40 kV, the current was 40 mA, and the X-ray source was CuKα ray. The plots appearing at the diffraction angle 2θ = 25 ° ± 2 ° obtained at this time were simply moved averaged at 11 points, and the half-value range of the peak was defined as the half-value range of CNT. The baseline was a line connecting the plots of 2θ = 16 ° and 2θ = 34 °.

<Measurement of CNT purity>
The CNT was acid-decomposed using a microwave sample pretreatment device (ETHOS1 manufactured by Milestone General Co., Ltd.) to extract the metal contained in the CNT. Then, analysis was performed using a multi-type ICP emission spectrophotometer (720-ES, manufactured by Agilent), and the amount of metal contained in the extract was calculated. The purity of CNT was calculated as follows.
CNT purity (%) = ((mass of CNT-mass of metal in CNT) ÷ mass of CNT) × 100

<Volume resistivity of electrode film>
The mixture slurry was applied onto the aluminum foil to a size of 70 ± 10 μm using an applicator, and then the coating film was dried at 120 ° C. ± 5 ° C. for 25 minutes in an electric oven. Then, the surface resistivity (Ω / □) of the coating film after drying was measured using Lorester GP and MCP-T610 manufactured by Mitsubishi Chemical Analytech Co., Ltd. After the measurement, the thickness of the electrode mixture layer formed on the aluminum foil was multiplied to obtain the volume resistivity (Ω · cm) of the electrode film. The thickness of the electrode mixture layer is determined by subtracting the thickness of the aluminum foil from the average value measured at three points in the electrode film using a film thickness meter (DIKION, DIGIMICRO MH-15M). The volume resistivity (Ω · cm) was used.

<Peeling strength of electrode film>
The mixture slurry was applied onto the aluminum foil to a size of 70 ± 10 μm using an applicator, and then the coating film was dried at 120 ° C. ± 5 ° C. for 25 minutes in an electric oven. Then, two pieces were cut into a rectangle of 90 mm × 20 mm with the coating direction as the major axis. A desktop tensile tester (Strograph E3, manufactured by Toyo Seiki Seisakusho Co., Ltd.) was used to measure the peel strength, and the peel strength was evaluated by a 180-degree peel test method. Specifically, a 100 mm × 30 mm size double-sided tape (No. 5000NS, manufactured by Nitoms Co., Ltd.) was attached onto a stainless steel plate, and the produced battery electrode mixture layer was brought into close contact with the other surface of the double-sided tape. Peeling was performed while pulling from the bottom to the top at a constant speed (50 mm / min), and the average value of stress at this time was taken as the peel strength.

<Catalyst for CNT synthesis and production example of CNT>
The CNTs used in each of the examples and comparative examples described later were prepared by the following methods.

Catalyst for CNT synthesis (A)
Weigh 60 parts by mass of cobalt hydroxide, 138 parts by mass of magnesium acetate / tetrahydrate, and 16.2 parts by mass of manganese acetate in a heat-resistant container, and dry them at a temperature of 170 ± 5 ° C. for 1 hour using an electric oven. After evaporating the water content, the SPEED dial was adjusted to 3 using a crusher (Wonder Crusher WC-3, manufactured by Osaka Chemical Co., Ltd.) and pulverized for 1 minute. After that, each crushed powder was adjusted to 2 on the dial of SPPED using a crusher (Wonder Crusher WC-3, manufactured by Osaka Chemical Co., Ltd.), mixed for 30 seconds, and the catalyst precursor (A) for CNT synthesis. Was produced. Then, the catalyst precursor (A) for CNT synthesis is transferred to a heat-resistant container, fired in a muffle furnace (FO510, manufactured by Yamato Kagaku Co., Ltd.) for 30 minutes in an air atmosphere at 450 ± 5 ° C. The catalyst (A) for CNT synthesis was obtained by pulverizing in a mortar.

Catalyst for CNT synthesis (B)
Heat resistance of 60 parts by mass of cobalt hydroxide, 138 parts by mass of magnesium acetate / tetrahydrate, 16.2 parts by mass of manganese carbonate, and 4.0 parts by mass of Aerosil (AEOSIL® 200, manufactured by Nippon Aerosil Co., Ltd.). Weigh it into a container, dry it at a temperature of 170 ± 5 ° C. for 1 hour using an electric oven to evaporate the water content, and then use a crusher (Wonder Crusher WC-3, manufactured by Osaka Chemical Co., Ltd.) to make SPEED. The dial was adjusted to 3 and crushed for 1 minute. Then, using a crusher (Wonder Crusher WC-3, manufactured by Osaka Chemical Co., Ltd.), adjust the dial of SPEED to 2 and mix for 30 seconds to mix each crushed powder for CNT synthesis catalyst precursor (B). Was produced. Then, the catalyst precursor (B) for CNT synthesis is transferred to a heat-resistant container, fired in a muffle furnace (FO510, manufactured by Yamato Kagaku Co., Ltd.) for 30 minutes in an air atmosphere at 450 ± 5 ° C. The catalyst (B) for CNT synthesis was obtained by pulverizing in a mortar.

Catalyst for CNT synthesis (C)
After weighing 1000 parts by mass of magnesium acetate tetrahydrate in a heat-resistant container and drying it at an ambient temperature of 170 ± 5 ° C. for 6 hours using an electric oven, a crusher (Sample Mill KIIW-I type, Co., Ltd.) A 1 mm screen was attached using (manufactured by Dalton Corporation) and pulverized to obtain a magnesium acetate dry pulverized product. Magnesium acetate dry crushed product 45.8 parts, manganese carbonate 8.1 parts, silicon oxide (SiO ₂ , manufactured by Aerosil Japan, Inc .: AEROSIL® 200)
) 1.0 part and 200 parts of steel beads (bead diameter 2.0 mmφ) were charged into an SM sample bottle (manufactured by Sansho Co., Ltd.), and pulverized and mixed for 30 minutes using a paint conditioner manufactured by Red Devil. Then, using a stainless sieve, the pulverized and mixed powder and steel beads (bead diameter 2.0 mmφ) were separated to obtain a catalyst carrier for CNT synthesis. Then, 30 parts by mass of cobalt (II) hydroxide was weighed in a heat-resistant container and dried at an atmospheric temperature of 170 ± 5 ° C. for 2 hours to obtain a cobalt composition containing CoHO ₂ . After that, 54.9 parts by mass of the catalyst carrier for CNT synthesis and 29 parts by mass of the cobalt composition were charged into a crusher (Wonder Crusher WC-3, manufactured by Osaka Chemical Co., Ltd.), a standard lid was attached, and the SPEED dial was set to 2. And pulverized and mixed for 30 seconds to obtain a catalyst precursor for CNT synthesis. The catalyst precursor for CNT synthesis is transferred to a heat-resistant container, fired in a muffle furnace (FO510, manufactured by Yamato Kagaku Co., Ltd.) for 30 minutes in an air atmosphere and at 450 ± 5 ° C., and then pulverized in a mortar. A catalyst for CNT synthesis (C) was obtained.

Catalyst for CNT synthesis (D)
A catalyst for CNT synthesis (D) was obtained by the same method as in Example 1 of Japanese Patent Application Laid-Open No. 2015-123410.

<Synthesis of CNT (A)>
A quartz glass heat-resistant dish sprayed with 2 g of the CNT synthesis catalyst (A) was installed in the center of a horizontal reaction tube having an internal volume of 10 L, which can be pressurized and heated by an external heater. Evacuation was performed while injecting nitrogen gas, the air in the reaction tube was replaced with nitrogen gas, and the atmosphere in the horizontal reaction tube was set to an oxygen concentration of 1% by volume or less. Then, it was heated by an external heater until the center temperature in the horizontal reaction tube reached 680 ° C. After reaching 680 ° C., propane gas was introduced into the reaction tube at a flow rate of 2 L / min as a carbon source, and the contact reaction was carried out for 1 hour. After completion of the reaction, the gas in the reaction tube was replaced with nitrogen gas, the gas in the reaction tube was replaced with nitrogen gas, and the temperature of the reaction tube was cooled to 100 ° C. or lower and taken out to obtain CNT (A). ..

<Synthesis of CNT (B)>
The CNT (B) was obtained by the same method as the synthesis of the CNT (A) except that the catalyst for CNT synthesis (A) was changed to the catalyst for CNT synthesis (B).

<Synthesis of CNT (C)>
A quartz glass heat-resistant dish sprayed with 1 g of the CNT synthesis catalyst (C) was installed in the center of a horizontal reaction tube having an internal volume of 10 L, which can be pressurized and heated by an external heater. Exhaust was performed while injecting nitrogen gas, the air in the reaction tube was replaced with nitrogen gas, and the mixture was heated until the atmospheric temperature in the horizontal reaction tube reached 710 ° C. After reaching 710 ° C., ethylene gas as a hydrocarbon was introduced into the reaction tube at a flow rate of 2 L / min, and the contact reaction was carried out for 7 minutes. After completion of the reaction, the gas in the reaction tube was replaced with nitrogen gas, and the temperature of the reaction tube was cooled to 100 ° C. or lower and taken out to obtain CNT (C).

<Synthesis of CNT (D)>
CNT (D) was obtained by the same method as the synthesis of CNT (C) except that the contact reaction time was changed from 7 minutes to 15 minutes.

<CNT (E)>
Multi-walled carbon nanotubes (JENOTUBE 8S manufactured by JEIO) were used as CNTs (E).

<Synthesis of CNT (F)>
1000 g of CNT (E) was weighed in a heat-resistant container made of carbon. After that, a carbon heat-resistant container containing CNT was installed in the furnace. After that, the inside of the furnace was 1 Torr (133 Pa).
) The vacuum was exhausted below, and the carbon heater was energized to raise the temperature inside the furnace to 1000 ° C. Next, argon gas was introduced into the furnace to adjust the pressure in the furnace to 70 Torr (9.33 kPa), and then 1 L of argon gas per minute was introduced into the furnace. After that, chlorine gas was introduced in addition to argon gas, and the pressure in the furnace was adjusted to 90 Torr (11.99 kPa). After the pressure was reached, 0.3 L of chlorine gas per minute was added to the furnace. Introduced to. In the same state, after holding for 1 hour, the energization was stopped, the introduction of argon gas and chlorine gas was stopped, and the vacuum was cooled. Finally, vacuum cooling was performed at a pressure of 1 Torr (133 Pa) or less for 12 hours, and after confirming that the inside of the furnace was cooled to room temperature, nitrogen gas was introduced into the furnace until the pressure reached atmospheric pressure, and heat resistance was obtained. The sex vessel was taken out to obtain purified CNT (F).

<Synthesis of CNT (G)>
10 kg was weighed in a heat-resistant container of CNT (E) 120 L, and the heat-resistant container containing CNT was installed in the furnace. After that, nitrogen gas was introduced into the furnace to discharge the air in the furnace while maintaining the positive pressure. After the oxygen concentration in the furnace became 0.1% or less, the mixture was heated to 1600 ° C. over 30 hours. Chlorine gas was introduced at a rate of 50 L / min for 50 hours while maintaining the temperature inside the furnace at 1600 ° C. Then, nitrogen gas was introduced at 50 L / min and cooled while maintaining the positive pressure to obtain CNT (G).

<Synthesis of CNT (H)>
CNT (H) was obtained by the same method as in Example 9 of Japanese Patent Application Laid-Open No. 2015-123410 except that the catalyst for CNT synthesis (D) was used.

(Example 1)
In a glass bottle (M-225, manufactured by Kashiwayo Glass Co., Ltd.), 3.9 parts of CNT (A), 1.95 parts of dispersant (polyvinylpyrrolidone K-30 manufactured by Nippon Catalyst Co., Ltd.), 124 parts of NMP. 200 parts and 200 parts of zirconia beads (bead diameter 1.25 mmφ) were charged and subjected to dispersion treatment for 10 hours using a paint conditioner manufactured by Red Devil, and then the zirconia beads were separated to obtain a CNT dispersion liquid (A). ..

(Examples 2 to 4), (Comparative Examples 1 to 5)
CNT dispersions (B) to (D) and (H) to (L) were obtained by the same method except that the CNTs were changed to those listed in Table 1.

(Example 5)
In a glass bottle (M-225, manufactured by Kashiwayo Glass Co., Ltd.), 1.95 parts of CNT (E), 0.98 parts of dispersant (polyvinylpyrrolidone K-30 manufactured by Nippon Catalyst Co., Ltd.), 127 parts of NMP. 200 parts and 200 parts of zirconia beads (bead diameter 1.25 mmφ) were charged and subjected to dispersion treatment for 10 hours using a paint conditioner manufactured by Red Devil, and then the zirconia beads were separated to obtain a CNT dispersion liquid (E). ..
(Examples 6 and 7)
CNT dispersions (F) to (G) were obtained by the same method except that the CNTs listed in Table 1 were changed.

(Example 8)
PVDF (Solvay, Solef # 5) in a plastic container with a capacity of 150 cm ³
NMP in which 8% by mass of 130) was dissolved was weighed in 4.7 parts by mass. Then, 0.5 part by mass of the CNT dispersion liquid (A) was added, and the mixture was stirred at 2000 rpm for 30 seconds using a rotation / revolution mixer (Awatori Rentaro manufactured by Shinki Co., Ltd., ARE-310). Further, 5.7 parts by mass of the CNT dispersion liquid (A) was added, and the mixture was stirred again at 2000 rpm for 30 seconds using a rotation / revolution mixer (Awatori Rentaro, ARE-310) to form a carbon nanotube resin composition. (A) was obtained. After that, 36.9 parts by mass of a positive electrode active material (BASF Toda Battery Materials GK, HED (registered trademark) NCM-111 1100) was added, and a rotation / revolution mixer (Awatori Rentaro, ARE-310) was added. It was stirred at 2000 rpm for 2.5 minutes. Finally, 2.2 parts by mass of NMP was added, and the mixture was stirred at 2000 rpm for 2.5 minutes using a rotation / revolution mixer (Awatori Rentaro, ARE-310) to obtain a mixed material slurry (A).

(Examples 9 to 11), (Comparative Examples 6 to 10)
A carbon nanotube resin composition and a mixed material slurry were obtained by the same method as in Example 8 except that the CNT dispersion liquid shown in Table 2 was changed.

(Example 12)
PVDF (Solvay, Solef # 5) in a plastic container with a capacity of 150 cm ³
NMP in which 8% by mass of 130) was dissolved was weighed in 4.3 parts by mass. Then, 0.5 part by mass of the CNT dispersion liquid (E) was added, and the mixture was stirred at 2000 rpm for 30 seconds using a rotation / revolution mixer (Awatori Rentaro, ARE-310). Further, 11.1 parts by mass of the CNT dispersion liquid (E) was added, and the mixture was stirred again at 2000 rpm for 30 seconds using a rotation / revolution mixer (Awatori Rentaro, ARE-310) to form a carbon nanotube resin composition ( E) was obtained. After that, 34.1 parts by mass of a positive electrode active material (BASF Toda Battery Materials GK, HED (registered trademark) NCM-111 1100) was added, and a rotation / revolution mixer (Awatori Rentaro, ARE-310) was added. It was stirred at 2000 rpm for 2.5 minutes. Finally, using a rotation / revolution mixer (Awatori Rentaro, ARE-310), the mixture was stirred at 2000 rpm for 2.5 minutes to obtain a mixed material slurry (E).

(Examples 13 and 14)
The carbon nanotube resin compositions (F), (G) and the mixture slurry (F) were prepared by the same method as in Example 12 except that the CNT dispersion liquid (E) was changed to the CNT dispersion liquids (F) and (G). , (G) was obtained.

(Example 15)
PVDF (Solvay, Solef # 5) in a plastic container with a capacity of 150 cm ³
NMP in which 8% by mass of 130) was dissolved was weighed in 4.3 parts by mass. Then, 0.5 part by mass of the CNT dispersion liquid (E) was added, and the mixture was stirred at 2000 rpm for 30 seconds using a rotation / revolution mixer (Awatori Rentaro, ARE-310). Further, 8.7 parts by mass of the CNT dispersion liquid (E) was added, and the mixture was stirred again at 2000 rpm for 30 seconds using a rotation / revolution mixer (Awatori Rentaro, ARE-310) to form a carbon nanotube resin composition ( M) was obtained. After that, 34.2 parts by mass of a positive electrode active material (BASF Toda Battery Materials GK, HED (registered trademark) NCM-111 1100) was added, and a rotation / revolution mixer (Awatori Rentaro, ARE-310) was added. It was stirred at 2000 rpm for 2.5 minutes. Finally, 2.3 parts by mass of NMP was added, and the mixture was stirred at 2000 rpm for 2.5 minutes using a rotation / revolution mixer (Awatori Rentaro, ARE-310) to obtain a mixed material slurry (M).

(Examples 16 and 17)
The carbon nanotube resin composition (N), (O) and the mixture slurry (N) were prepared by the same method as in Example 15 except that the CNT dispersion liquid (E) was changed to the CNT dispersion liquid (F) and (G). , (O) was obtained.

Table 3 shows the carbon nanotube resin compositions and mixture slurries prepared in Examples 12 to 17.

(Example 18)
The mixture slurry (A) was applied onto an aluminum foil to a size of 70 ± 10 μm using an applicator, and then the coating film was dried at 120 ° C. ± 5 ° C. for 25 minutes in an electric oven.

(Examples 19 to 27), (Comparative Examples 11 to 15)
Electrode films (B) to (O) were obtained by the same method as in Example 18 except that the mixture slurry was changed to the one shown in Table 4.

Table 5 shows the evaluation results of the mixed material slurries prepared in Examples 18 to 27 and Comparative Examples 11 to 15. The evaluation criteria are as follows. For conductivity evaluation, the volume resistivity (Ω · cm) of the electrode film is +++ (excellent) when it is less than 6, ++ (good) when it is 6 or more and less than 8, (possible) when it is 8 or more and less than 10, and-(possible) when it is more than 10. Impossible). For adhesion evaluation, peel strength (N / cm) of 0.4 or more is +++ (excellent), 0.2 or more and less than 0.4 is ++ (good), and 0.1 or more and less than 0.2 is + (possible). Less than 0.1 was defined as- (impossible). In the comprehensive evaluation, the sum of the + numbers of the conductivity evaluation and the adhesion evaluation is 4 or more and does not include- (excellent), and the sum of the + numbers of the conductivity evaluation and the adhesion evaluation is 2 or more. Those that did not contain-were marked as ◯ (good), and those that contained-in the conductivity evaluation or adhesion evaluation were marked as x (impossible).

(Example 28)
In a glass bottle (M-225, manufactured by Kashiwayo Glass Co., Ltd.), 1.95 parts of CNT (E), 0.98 parts of dispersant (polyvinylpyrrolidone K-30 manufactured by Nippon Catalyst Co., Ltd.), ion-exchanged water. 127 parts and 200 parts of zirconia beads (bead diameter 1.25 mmφ) were charged, and after performing dispersion treatment for 10 hours using a paint conditioner manufactured by Red Devil, the zirconia beads were separated and CNT dispersion liquid (WA) was applied. Obtained.

(Example 29)
A degree of etherification as a thickener 0.45 to 0.5 in a plastic container with a capacity of 150 cm ³
Carboxymethyl cellulose of No. 5 (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., cellogen PL-15), 7.4 parts by mass of a 2 mass% aqueous solution, and a 40 mass% solution of SBR emulsion as a binder (manufactured by Nippon Zeon Corporation, product name). : BM-400B) 0.9 parts by mass was weighed. Then, 0.5 part by mass of the CNT dispersion liquid (S) was added, and the mixture was stirred at 2000 rpm for 30 seconds using a rotation / revolution mixer (Awatori Rentaro manufactured by Shinki Co., Ltd., ARE-310). Further, 11.5 parts by mass of CNT dispersion liquid (WA) was added, and the mixture was stirred again at 2000 rpm for 30 seconds using a rotation / revolution mixer (Awatori Rentaro, ARE-310) to form a carbon nanotube resin composition. (WA) was obtained. After that, 3 positive electrode active materials (LiFePO ₄ having a carbon coating amount of 5% by mass) were added.
5.5 parts by mass was added, and the mixture was stirred at 2000 rpm for 2.5 minutes using a rotation / revolution mixer (Awatori Rentaro, ARE-310). Finally, using a rotation / revolution mixer (Awatori Rentaro, ARE-310), the mixture was stirred at 2000 rpm for 2.5 minutes to obtain a mixed material slurry (WA).

Table 6 shows the evaluation results of the mixed material slurry prepared in Example 29. The evaluation criteria are as follows. For conductivity evaluation, the volume resistivity (Ω · cm) of the electrode film is +++ (excellent) when it is less than 6, ++ (good) when it is 6 or more and less than 8, (possible) when it is 8 or more and less than 10, and-(possible) when it is more than 10. Impossible). For adhesion evaluation, peel strength (N / cm) of 0.4 or more is +++ (excellent), 0.2 or more and less than 0.4 is ++ (good), and 0.1 or more and less than 0.2 is + (possible). Less than 0.1 was defined as- (impossible). In the comprehensive evaluation, the sum of the + numbers of the conductivity evaluation and the adhesion evaluation is 4 or more and does not include- (excellent), and the sum of the + numbers of the conductivity evaluation and the adhesion evaluation is 2 or more. Those that did not contain-were marked as ◯ (good), and those that contained-in the conductivity evaluation or adhesion evaluation were marked as x (impossible).

Table 7 shows the evaluation results of the CNT dispersion liquid, the mixture slurry, and the electrode film prepared by using the CNTs used in Examples 1 to 7 and 29 and Comparative Examples 1 to 5. The comprehensive evaluation was the same as the comprehensive evaluation of the electrode film.

In the above embodiment, CNTs having an average outer diameter of more than 3 nm and less than 10 nm and a half-value range of 3 to 6 ° were used. In the comparative example, CNTs having a half-value range of less than 3 ° were used. In the examples, an electrode film having higher conductivity than that of the comparative example was obtained. Since an electrode film having high conductivity can be obtained with a small amount of addition, it has been clarified that the present invention can provide an electrode film having conductivity which is difficult to realize with a conventional CNT dispersion liquid.

Although the invention of the present application has been described above with reference to the embodiments, the invention of the present application is not limited to the above. Various changes that can be understood by those skilled in the art can be made within the scope of the invention in the configuration and details of the invention of the present application.

Claims (7)

A carbon nanotube (A) characterized by satisfying the following (1), (2) and (3).
(1) The average outer diameter of carbon nanotubes is more than 3 nm and less than 10 nm.
(2) In powder X-ray diffraction analysis, a peak exists at a diffraction angle of 2θ = 25 ° ± 2 °, and the half-value width of the peak is 3 ° to 6 °.
(3) G / D when the maximum peak intensity in the range of 1560 to 1600 cm ^-1 is G and the maximum peak intensity in the range of 1310 to 1350 cm ^-1 is D in the Raman spectrum of the carbon nanotube (A). The ratio should be 1.0 to 4.5. The carbon nanotube (A) according to claim 1, wherein the standard deviation of the outer diameter of the carbon nanotube (A) is more than 0.7 nm and 3.5 nm or less. The carbon nanotube (A) according to claim 1 or 2, wherein the carbon nanotube (A) has a volume resistivity of 1.0 × 10 − ² to 2.5 × 10 − ² Ω · cm. In the Raman spectrum of carbon nanotube (A), the G / D ratio is 1 when the maximum peak intensity in the range of 1560 to 1600 cm ^-1 is G and the maximum peak intensity in the range of 1310 to 1350 cm ^-1 is D. The carbon nanotube (A) according to any one of claims 1 to 3, characterized in that it is 0.0 to 3.0. When the average outer diameter of the carbon nanotube (A) is X and the standard deviation of the outer diameter of the carbon nanotube is σ, X ± σ satisfies 5.0 nm ≦ X ± σ ≦ 14.0 nm. The carbon nanotube (A) according to any one of claims 1 to 4. A secondary battery comprising a carbon nanotube (A) satisfying the following (1), (2) and (3) .
(1) The average outer diameter of carbon nanotubes is more than 3 nm and less than 10 nm.
(2) In powder X-ray diffraction analysis, a peak exists at a diffraction angle of 2θ = 25 ° ± 2 °, and the half-value width of the peak is 3 ° to 6 °.
(3) G / D when the maximum peak intensity in the range of 1560 to 1600 cm ^-1 is G and the maximum peak intensity in the range of 1310 to 1350 cm ^-1 is D in the Raman spectrum of the carbon nanotube (A). The ratio should be 0.5-4.5. A method for producing a carbon nanotube (A) that satisfies the following (1), (2) and (3).
A method for producing carbon nanotubes, which comprises the following steps (1), (2) and (3) in order.

(1) The average outer diameter of carbon nanotubes is more than 3 nm and less than 10 nm.
(2) In powder X-ray diffraction analysis, a peak exists at a diffraction angle of 2θ = 25 ° ± 2 °, and the half-value width of the peak is 3 ° to 6 °.
(3) G / D when the maximum peak intensity in the range of 1560 to 1600 cm ^-1 is G and the maximum peak intensity in the range of 1310 to 1350 cm ^-1 is D in the Raman spectrum of the carbon nanotube (A). The ratio should be 0.5-4.5.

Step (1) Step of installing a heat-resistant container containing carbon nanotubes in the furnace
Step (2) A step of raising the temperature in the furnace to 1000 to 1600 ° C. at the maximum temperature after reducing the oxygen concentration in the furnace to 0.1% or less.
Step (3) Step of introducing chlorine gas after reaching the maximum temperature

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