Carbon nanotube dispersion composition for electrodes of non-aqueous electrolyte secondary batteries, slurry for electrodes of non-aqueous electrolyte secondary batteries, electrode sheets, and non-aqueous electrolyte secondary batteries, and method for manufacturing slurry for electrodes of non-aqueous electrolyte secondary batteries, electrode sheets, and non-aqueous electrolyte secondary batteries.

Abstract

The present invention provides a CNT dispersion composition containing single-walled carbon nanotubes (CNTs) that, when used as a source of conductive additives in the formation of the electrode active material layer of a non-aqueous electrolyte secondary battery, can result in a non-aqueous electrolyte secondary battery with high energy density and high output characteristics; an electrode slurry using this CNT dispersion composition; an electrode sheet formed using this electrode slurry; a non-aqueous electrolyte secondary battery incorporating this electrode sheet; and methods for manufacturing these. [Solution] A CNT dispersion composition for electrodes of a non-aqueous electrolyte secondary battery, comprising single-walled carbon nanotubes (WYST), a dispersant, and a dispersion medium, wherein the dispersion medium is an organic solvent, the WYST content is 1.2 to 10.0% by mass, and the resistance value of the dispersion composition is 15 to 80000 Ω·cm, a CNT dispersion composition, an electrode sheet, a non-aqueous electrolyte secondary battery, and a method for manufacturing the same.

Description

[Technical Field]

[0001] The present invention relates to a carbon nanotube dispersion composition for electrodes of a non-aqueous electrolyte secondary battery, a slurry for electrodes of a non-aqueous electrolyte secondary battery, an electrode sheet, and a non-aqueous electrolyte secondary battery, as well as a method for manufacturing a slurry for electrodes of a non-aqueous electrolyte secondary battery, an electrode sheet, and a non-aqueous electrolyte secondary battery. [Background technology]

[0002] Non-aqueous electrolyte secondary batteries, such as lithium-ion batteries, have high energy density, excellent storage performance, and low-temperature operation capabilities, and are widely used in portable electronic devices such as mobile phones and laptop computers. Furthermore, larger batteries are being used in transportation equipment, including automobiles, and their use as storage devices for electricity generated from off-peak hours and renewable energy sources is also progressing.

[0003] With the expanding applications of non-aqueous electrolyte secondary batteries, there is a growing demand for higher energy density (higher capacity) in these batteries. For example, when using non-aqueous electrolyte secondary batteries as a power source for EVs (Electric Vehicles) and drones, increasing the battery capacity can extend the driving range of EVs and allow drones to fly for longer periods.

[0004] To increase the energy density of non-aqueous electrolyte secondary batteries, it is necessary to increase the amount of electrode active material in the electrodes. Consequently, the amount of conductive additives, which are essential materials for efficient electron conduction, must be reduced in the electrodes. Until now, conductive materials in the form of non-fibrous particles such as carbon black have been widely used as conductive additives. However, recently, fibrous conductive additives such as carbon nanotubes (CNTs), which can form conductive networks with smaller concentrations, have come into use. Among these, single-walled carbon nanotubes (WYSNs) have particularly excellent electron conductivity and are expected to be a conductive additive that can contribute to increasing the capacity of non-aqueous electrolyte secondary batteries with the addition of small amounts.

[0005] For example, Patent Document 1 contains: A conductive material dispersion comprising a conductive material, a copolymer (A), a base (B), and water, The conductive material contains single-walled carbon nanotubes with an average outer diameter of 1-4 nm. A conductive material dispersion characterized in that the copolymer (A) is a copolymer containing 10% to 99% by mass of units derived from (meth)acrylonitrile and 1% to 50% by mass of carboxyl group-containing monomer units, based on 100% by mass of the total units, the base (B) has a pKb of 5 or less at 25°C in water and a solubility of 1 g / 100 ml or more at 25°C in water, and the solid content mass ratio (B) / (A) of the copolymer (A) to the base (B) is 0.2 to 1.0. This is disclosed. According to the technology described in Patent Document 1, a conductive material dispersion is provided in which carbon nanotubes with excellent compatibility with binders and storage stability are dispersed, and it is said that the output and cycle life of secondary batteries can be improved by using this conductive material dispersion.

[0006] Furthermore, Patent Document 2 contains, A carbon nanotube dispersion is disclosed, comprising carbon nanotubes, a dispersant, and a solvent, characterized in that it satisfies the following conditions (1) to (4). (1) In the Raman spectrum of carbon nanotubes, 1560-1600 cm⁻¹ -1 G represents the maximum peak intensity within the range of 1310-1350 cm. -1 When the maximum peak intensity within the specified range is denoted as D, the G / D ratio of carbon nanotubes is between 5 and 100. (2) The carbon nanotube contains 30 parts by mass or more but less than 250 parts by mass of dispersant per 100 parts by mass of carbon nanotube. (3) The complex modulus of the carbon nanotube dispersion at 25°C and a frequency of 1Hz is 5 Pa or more and less than 650 Pa, and the phase angle is 5° or more and less than 50°. (4) The BET specific surface area of ​​carbon nanotubes is 550-1200 m². 2 / g Patent Document 2 states that single-walled carbon nanotubes are preferred as the carbon nanotubes. According to the technology described in Patent Document 2, a resin composition, a mixture slurry, and an electrode film with excellent electrode strength and adhesion can be obtained, and a non-aqueous electrolyte secondary battery with excellent rate characteristics and cycle characteristics can be obtained. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2021-190330 [Patent Document 2] Japanese Patent Publication No. 2022-63234 [Overview of the project] [Problems that the invention aims to solve]

[0008] The electrodes (positive and negative electrodes) of a non-aqueous electrolyte secondary battery have an electrode active material layer (positive electrode active material layer or negative electrode active material layer), which contains at least electrode active material particles capable of intercalating or releasing lithium ions during charging and discharging, and a conductive additive. The electrode active material layer is usually formed by preparing a slurry (composition) in which the electrode active material and conductive additive are dispersed in a solvent (liquid medium) by the action of a dispersant, and then drying the coating film formed from this slurry. When single-walled carbon nanotubes (WYSTs) are used as conductive additives, WYSTs have low dispersibility in solvents. Therefore, a CNT dispersion composition is prepared in advance and mixed with other components such as electrode active materials (Patent Documents 1 and 2). For example, Patent Document 2 discloses that the amount of CNTs in the CNT dispersion is 0.2 to 1.5 parts by mass per 100 parts by mass of the dispersion, and an N-methylpyrrolidone dispersion containing 0.4% by mass of CNTs is shown in the examples. However, a CNT dispersion composition that can fully bring out the inherent conductive network-forming ability of WYSTs when used as an electrode has not yet been realized.

[0009] In selecting the solvent for the electrode slurry described above, affinity with the dispersant (organic polymer) is considered, and while water is sometimes used as the solvent as described in Patent Document 1, organic solvents are also frequently used. When an organic solvent is used as the solvent for the electrode slurry described above, it is required that the CNT dispersion composition formulated during the preparation of the electrode slurry also uses an organic solvent as the dispersion medium.

[0010] The present invention aims to provide a CNT dispersion composition containing single-walled carbon nanotubes (WNTs) that, when used as a source of conductive additives in the formation of the electrode active material layer of a non-aqueous electrolyte secondary battery, can result in a non-aqueous electrolyte secondary battery with high energy density and high output characteristics. The present invention also aims to provide an electrode slurry for a non-aqueous electrolyte secondary battery using this CNT dispersion composition as a source of conductive additives, an electrode sheet for a non-aqueous electrolyte secondary battery formed using this electrode slurry, and a non-aqueous electrolyte secondary battery incorporating this electrode sheet. Furthermore, the present invention aims to provide a method for manufacturing these electrode slurry, electrode sheet, and non-aqueous electrolyte secondary battery. [Means for solving the problem]

[0011] In view of the above problems, the inventors have conducted extensive research and have found that by using a CNT dispersion composition containing single-walled carbon nanotubes (WYSIW) as a conductive additive and an organic solvent as a liquid medium, and by controlling the WYSIW content to a specific high-content range and the resistance value of the CNT dispersion composition to a specific range, the electrode sheet formed from a slurry of this CNT dispersion composition and an active material can be made to have lower resistance, thereby achieving a higher level of high capacity and high output characteristics in a non-aqueous electrolyte secondary battery obtained using this electrode sheet. The present invention was completed after further research based on this finding.

[0012] The above-mentioned problems of the present invention were solved by the following means. [1] A carbon nanotube dispersion composition for electrodes of a non-aqueous electrolyte secondary battery, comprising single-walled carbon nanotubes, a dispersant, and a dispersion medium, The dispersion medium is an organic solvent, the content of single-walled carbon nanotubes in the dispersion composition is 1.2 to 10.0% by mass, the resistance value of the dispersion composition is 15 to 80000 Ω·cm, A carbon nanotube dispersion composition. [2] The carbon nanotube dispersion composition according to [1], wherein the adsorption rate of the dispersant to the single-walled carbon nanotubes is 5 to 55%. [3] The carbon nanotube dispersion composition according to [1] or [2], wherein the content of the dispersant in the dispersion composition is 0.02 to 2.00% by mass. [4] The carbon nanotube dispersion composition according to any one of [1] to [3], wherein the GD ratio (D / G) of the single-walled carbon nanotubes is 0.020 to 0.060. [5] The carbon nanotube dispersion composition according to any one of [1] to [4], wherein the viscosity at a shear rate of 10 / s is 500 to 30000 mPa·s. [6] A slurry for an electrode of a non-aqueous electrolyte secondary battery, comprising the carbon nanotube dispersion composition according to any one of [1] to [5] and an electrode active material. [7] An electrode sheet having an electrode active material layer formed using the slurry for an electrode according to [6]. [8] A non-aqueous electrolyte secondary battery having the electrode sheet according to [7] as an electrode. [9] A method for producing a slurry for an electrode, comprising mixing the carbon nanotube dispersion composition according to any one of [1] to [5] and an electrode active material.

[10] A method for producing an electrode sheet, comprising forming an electrode active material layer using the slurry for an electrode according to [6].

[11] A method for producing a non-aqueous electrolyte secondary battery, comprising incorporating the electrode sheet according to [7] as an electrode.

[0013] In the description of this invention, a numerical range represented by "~" means a range that includes the numbers written before and after "~" as the lower limit and upper limit, respectively. In this invention, "non-aqueous electrolyte" means an electrolyte that substantially does not contain water. That is, the "non-aqueous electrolyte" may contain a small amount of water as long as it does not hinder the effects of the present invention. In this invention, the "non-aqueous electrolyte" has a water concentration of 200 ppm (by mass) or less, preferably 100 ppm or less, and more preferably 20 ppm or less. It should be noted that it is practically difficult to make a non-aqueous electrolyte completely anhydrous, and it usually contains 1 ppm or more of water. [Effects of the Invention]

[0014] The carbon nanotube dispersion composition for electrodes of a non-aqueous electrolyte secondary battery of the present invention (also referred to as the CNT dispersion composition of the present invention) can be used as a source of conductive additive in the formation of the electrode active material layer of a non-aqueous electrolyte secondary battery, thereby enabling the resulting non-aqueous electrolyte secondary battery to have high energy density and high output characteristics. The electrode slurry for a non-aqueous electrolyte secondary battery of the present invention (also referred to as the electrode slurry of the present invention) can enable the electrode sheet obtained using it to have lower resistance. By using the electrode sheet of the present invention as the electrode active material layer of a non-aqueous electrolyte secondary battery, the resulting non-aqueous electrolyte secondary battery can have high energy density and high output characteristics. The non-aqueous electrolyte secondary battery of the present invention has excellent energy density and output characteristics. According to the method for manufacturing an electrode slurry of the present invention, the electrode slurry of the present invention can be obtained. According to the method for manufacturing an electrode sheet of the present invention, the electrode sheet of the present invention can be obtained. According to the method for manufacturing a non-aqueous electrolyte secondary battery of the present invention, the non-aqueous electrolyte secondary battery of the present invention can be obtained. [Brief explanation of the drawing]

[0015] [Figure 1] Figure 1 is a longitudinal cross-sectional view schematically showing the basic stacked structure of one embodiment of the secondary battery according to the present invention. [Modes for carrying out the invention]

[0016] Preferred embodiments of the present invention will be described, but the present invention is not limited to these forms other than those specified herein.

[0017] [Carbon nanotube dispersion composition for electrodes of non-aqueous electrolyte secondary batteries] The CNT dispersion composition of the present invention comprises single-walled carbon nanotubes (WYSIWY), a dispersant, and a dispersion medium. The CNT dispersion composition of the present invention is suitable as a source of conductive additive in the preparation of electrodes for non-aqueous electrolyte secondary batteries. More specifically, the CNT dispersion composition of the present invention is suitable for incorporation as a source of conductive additive in the preparation of electrode slurries for non-aqueous electrolyte secondary batteries, and can effectively disperse single-walled carbon nanotubes in the electrode slurry. The CNT dispersion composition of the present invention uses an organic solvent as the dispersion medium. In the CNT dispersion composition of the present invention, the content of single-walled carbon nanotubes is 1.2 to 10.0% by mass, and the resistance value of the CNT dispersion composition of the present invention is 15 to 80000 Ω·cm.

[0018] The CNT dispersion composition of the present invention controls the content of single-walled carbon nanotubes (WYSIWY) in the CNT dispersion composition and the resistance value of the CNT dispersion composition to the above-mentioned specific ranges. By incorporating this composition as a source of conductive additives during the preparation of electrode slurry, the electrode active material layer formed using this electrode slurry can be made low-resistance, and the energy density and output characteristics of the non-aqueous electrolyte secondary battery having this electrode active material layer can be increased. The reason for this is not entirely clear, but the following is considered to be the cause. The CNT dispersion composition of the present invention is considered to be in a specific state of dispersion or aggregation of single-walled carbon nanotubes (WCNTs) in the CNT dispersion composition, by controlling the single-walled carbon nanotube (WCNT) content and resistance value within the above-mentioned specific ranges. Focusing on the CNT content, conventional CNT dispersion compositions cannot adequately disperse CNTs if the CNT content is high, and conventional techniques have had to limit the amount of CNTs that can be included in the CNT dispersion composition. When an electrode slurry is prepared using a CNT dispersion composition with a low CNT content in this way, the amount of solvent in the electrode slurry increases, which makes the CNTs more prone to aggregation, resulting in inferior performance of the resulting electrode sheet and secondary battery. In the CNT dispersion composition of the present invention, a stable dispersion composition is achieved by devising dispersion conditions while increasing the single-walled CNT content in the CNT dispersion composition. This CNT dispersion composition has a resistance that is not too low, thus easily forming a conductive network, and also has a resistance that is not too high, containing aggregates in a certain proportion, resulting in excellent uniformity with other components.

[0019] The content of single-walled carbon nanotubes in the CNT dispersion composition is 1.2 to 10.0% by mass, preferably 1.2 to 8.0% by mass, more preferably 1.5 to 7.0% by mass, even more preferably 1.5 to 6.0% by mass, even more preferably 1.5 to 5.0% by mass, even more preferably 1.8 to 4.0% by mass, and even more preferably 1.8 to 3.0% by mass.

[0020] The resistivity of the CNT dispersion composition is 15 to 80,000 Ω·cm, preferably 100 to 70,000 Ω·cm, more preferably 400 to 60,000 Ω·cm, even more preferably 600 to 40,000 Ω·cm, even more preferably 1,000 to 20,000 Ω·cm, even more preferably 2,000 to 10,000 Ω·cm, even more preferably 3,000 to 10,000 Ω·cm, even more preferably 5,000 to 9,000 Ω·cm, and even more preferably 6,500 to 8,000 Ω·cm. The resistance of the CNT dispersion composition can be controlled by the type and content of single-walled carbon nanotubes, dispersion conditions, and other factors. The resistance of the CNT dispersion composition can be measured by the method described in the examples.

[0021] In the CNT dispersion composition of the present invention, the GD ratio (D / G) of single-walled CNTs is preferably 0.020 to 0.060, more preferably 0.020 to 0.045, even more preferably 0.020 to 0.040, and still more preferably 0.020 to 0.030. The above GD ratio is derived from the graphite structure in the Raman spectrum of single-walled carbon nanotubes, specifically the G-band (1600 cm⁻¹). -1 ) Peak intensity and defect-derived D-band (1350cm) -1 This is the ratio of the peak intensities of ). The above GD ratio is a value measured for single-walled carbon nanotubes contained in the CNT dispersion composition of the present invention, and can be determined by Raman spectroscopy, specifically by the method described in the examples. The smaller the GD ratio, the less defects are estimated to be present in the single-walled carbon nanotubes. A GD ratio within the above range means that the single-walled carbon nanotubes in the CNT dispersion composition have good electronic conductivity. The GD ratio of single-walled carbon nanotubes (WCNTs) in a CNT dispersion composition can be controlled by the GD ratio of the WCNTs used, the concentration of WCNTs during the preparation of the CNT dispersion composition, and the dispersion conditions. For example, the more grinding treatment described later, the lower the GD ratio tends to be. It is thought that the grinding treatment eliminates the aggregation state of the WCNTs, exposing WCNTs with fewer defects, thus lowering the GD ratio.

[0022] The components constituting the CNT dispersion composition of the present invention will be described in more detail below.

[0023] <Single-walled carbon nanotubes (Single-walled CNTs)> A single-walled carbon nanotube (WNT) is a tubular structure made up solely of carbon atoms, with a single layer of carbon in the tube. Generally, the tube has a diameter of 0.4 to 4.0 nm and a length of 0.1 to 10.0 μm. Single-walled carbon nanotubes (WNTs) may contain residual metals (Fe, Al, Co, etc.) used as catalysts during their preparation, but it is preferable to have as little residual metal as possible. Generally, it is preferable for the residual metal content in WNTs to be less than 8000 ppm. Single-walled carbon nanotubes (SWCNTs) may be manufactured by methods such as arc discharge, laser ablation, or chemical vapor deposition. Specific examples of single-walled carbon nanotubes (WNTs) include TUBALL 01RW02, 01RW03 (both product names, manufactured by OCSiAl), SG101 (product name, manufactured by Nippon Zeon Corporation), JENOTUBE 3A (product name, manufactured by JEIO Corporation), EC1.5P (product name, manufactured by Meijo Nanocarbon Corporation), and TNSR (product name, manufactured by Timesnano Corporation). These can be used individually or in combination of two or more types.

[0024] <Dispersant> The dispersant is not particularly limited to low-molecular-weight compounds or high-molecular-weight compounds, as long as it can disperse single-walled carbon nanotubes in the dispersion medium. In the present invention, the dispersant is preferably a high-molecular-weight compound, and more preferably an organic polymer. Furthermore, a dispersant that can be appropriately adsorbed onto single-walled carbon nanotubes is preferred.

[0025] The adsorption rate of the dispersant to single-walled carbon nanotubes is preferably 5-55%, more preferably 10-50%, even more preferably 15-40%, and still more preferably 20-35%. The adsorption rate of the dispersant to single-walled carbon nanotubes (WYSIW) is a value measured for the adsorption rate of the dispersant contained in the CNT dispersion composition of the present invention to the WYSIW contained in the CNT dispersion composition, and can be measured specifically by the method described in the examples. The adsorption rate of the above-mentioned dispersant to single-walled carbon nanotubes can be controlled by the components of the dispersant, the type and amount of adsorbent groups it possesses, and so on.

[0026] The above dispersant preferably contains at least one of the following groups: amino group, cyano group, carboxyl group, phosphate group, phosphonic acid group, sulfo group, hydroxyl group, carbamoyl group, alkyl group, and aromatic group (hereinafter also referred to as an adsorbent group). Such adsorbent groups exhibit adsorption to single-walled carbon nanotubes (WYSIWNs) and contribute to improving the affinity between the dispersant and the WYSIWNs. The above amino group may be an unsubstituted amino group, a monosubstituted amino group, or a disubstituted amino group. If the amino group is a substituted amino group, the substituent on the amino group is preferably an alkyl group (preferably having 1 to 10 carbon atoms, more preferably 1 to 6 carbon atoms, even more preferably 1 to 4 carbon atoms, and even more preferably methyl or ethyl). The carboxyl group, phosphate group (-OP(=O)(-OH)OH), phosphonic acid group (-P(=O)(-OH)OH), and sulfo group mentioned above may also be in the form of a salt. They may also be in the form of an acid anhydride. In other words, in this invention, when we simply refer to a "carboxyl group," it includes not only the carboxyl group (-COOH), but also salts of the carboxyl group and groups obtained by dehydration condensation of a carboxyl group. The same applies to the phosphate group, phosphonic acid group, and sulfo group. The amino group of the above carbamoyl group (aminocarbonyl group) may be an unsubstituted amino group, a monosubstituted amino group, or a disubstituted amino group. If the amino group of the carbamoyl group is a substituted amino group, the substituent on this amino group is preferably an alkyl group (preferably having 1 to 10 carbon atoms, more preferably 1 to 6 carbon atoms, even more preferably 1 to 4 carbon atoms, and even more preferably methyl or ethyl). The alkyl group described above refers to a monovalent group obtained by removing one hydrogen atom from a hydrocarbon. The number of carbon atoms in the alkyl group is preferably 1 to 20, more preferably 5 to 19, and even more preferably 10 to 18. The above-mentioned aromatic group refers to a monovalent group obtained by removing one hydrogen atom from an aromatic ring. The aromatic group may be an aromatic hydrocarbon group or an aromatic heterocyclic group, with the aromatic hydrocarbon group being more preferred. The above-mentioned aromatic group may have substituents. Therefore, the above-mentioned aromatic hydrocarbon group and the above-mentioned aromatic heterocyclic group may also have substituents. The aromatic ring constituting the aromatic group may be a monocyclic ring or a fused ring, with the monocyclic ring being preferred. The above-mentioned aromatic group is particularly preferably a phenyl group.

[0027] When the dispersant is a low molecular weight compound, the dispersant is preferably one having the above-mentioned adsorbent group, such as sodium deoxycholate or phosphate esters.

[0028] When the dispersant is a polymer compound, the polymer compound may be a polymer (hereinafter referred to as polymer(I)), and this polymer may be a homopolymer or a copolymer, but is usually a copolymer. The polymerization form of the copolymer may be random or block. Polymer (I) may be a polymer produced by addition polymerization or a polymer produced by condensation polymerization, with polymers produced by addition polymerization (polymers whose main chain is composed of carbon-carbon bonds) being preferred. Examples of polymers having carbon-carbon bonds in their main chain include fluoropolymers (fluorine-containing polymers), hydrocarbon polymers, vinyl polymers, and (meth)acrylic polymers. Polymer (I) may be in a form having the above-mentioned adsorbent group, or it may be in a form not having the above-mentioned adsorbent group. If polymer (I) is in a form having an adsorbent group, the target polymer (I) can be obtained by introducing the adsorbent group into the polymer obtained by addition polymerization or condensation polymerization. Examples of monomers for introducing the adsorbent group include (meth)acrylic acid; maleic anhydride; (meth)acrylamide; styrene; vinyl compounds or acrylic compounds having an amino group, cyano group, phosphoric acid group, phosphonic acid group, sulfo group, hydroxyl group, or carbamoyl group. It is also preferable that polymer (I) has constituent components derived from alkyl (meth)acrylate, aryl (meth)acrylate, N-vinylpyrrolidone, N-alkylmaleimide, etc. The alkyl group in the (meth)acrylate alkyl ester is preferably having 1 to 15 carbon atoms, more preferably 2 to 12 carbon atoms, even more preferably 2 to 8 carbon atoms, and even more preferably methyl or ethyl. The alkyl group in N-alkylmaleimide is preferably having 1 to 15 carbon atoms, more preferably 2 to 12 carbon atoms, even more preferably 2 to 8 carbon atoms, and even more preferably methyl or ethyl. When polymer (I) is a fluoropolymer, examples of fluoropolymers include polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), polytetrafluoroethylene (PTFE), and perfluoroalkoxyalkane (PFA). Polymer (I) may be modified by an acid or the like.

[0029] In the present invention, preferred polymers (I) include modified styrene-maleic acid copolymer, copolymer of N-alkylmaleimide and alkyl (meth)acrylate, polyvinylpyrrolidone, and polyvinylidene fluoride (PVDF). In a copolymer of N-alkylmaleimide and alkyl (meth)acrylate, the N-alkylmaleimide-derived component is preferably 50-80% by mass, more preferably 50-75% by mass, and even more preferably 50-70% by mass. The alkyl (meth)acrylate-derived component is preferably 20-50% by mass, more preferably 25-50% by mass, and even more preferably 30-50% by mass.

[0030] When the dispersant is a polymer compound, the polymer compound may be a polysaccharide. Examples of polysaccharides include starch, carboxymethylcellulose, cellulose, diacetylcellulose, methylcellulose, hydroxyethylcellulose, and hydroxypropylcellulose.

[0031] When the dispersant is a polymer compound, the polymer compound may be rubber. Examples of rubber include hydrogenated nitrile rubber (H-NBR) and styrene-butadiene rubber (SBR). In the present invention, hydrogenated nitrile rubber is preferred as the rubber.

[0032] The following products can be used as dispersants: ET3002, ET3004, ET3034 (all product names, manufactured by BYK), PVP-K30, PVP-K25, PVP-K90 (all product names, manufactured by Fujifilm Wako Pure Chemical Industries), Luna Ace (product name, manufactured by Kao Corporation), Methylcellulose 15 (product name, manufactured by Fujifilm Wako Pure Chemical Industries), #7208 (product name, manufactured by Kureha Corporation), H-NBR (product name, manufactured by Zeon Corporation)

[0033] When the dispersant is a polymer compound, the weight-average molecular weight (Mw) of the dispersant is not particularly limited, but is preferably 2,000 to 100,000, more preferably 2,500 to 30,000, and even more preferably 3,500 to 20,000.

[0034] (Measurement of weight-average molecular weight) In this invention, the weight-average molecular weight of the polymer is measured by gel permeation chromatography (GPC). The weight-average molecular weight is the weight-average molecular weight on a polyethylene oxide basis. As a general rule, the weight-average molecular weight is measured by the method described below. However, depending on the type of polymer, an appropriate eluent may be selected and used as appropriate. Measuring instrument: HLC-8320GPC (product name, manufactured by Tosoh Corporation) Columns: TOSOH TSKgel guardcolumn SuperHZ-L, Super HZM-H, Super HZ4000, Super HZ2000 (product names, manufactured by Tosoh Corporation) Carrier: THF (tetrahydrofuran) solution Measurement temperature: 40℃ Carrier flow rate: 0.35 ml / min Sample concentration: 0.2% by mass Detector: RI (refractive index) detector

[0035] The dispersant content in the CNT dispersion composition is preferably 0.02 to 2.00% by mass, more preferably 0.02 to 1.80% by mass, even more preferably 0.02 to 1.50% by mass, and still more preferably 0.10 to 1.50% by mass.

[0036] <Dispersion medium> The dispersion medium constituting the CNT dispersion composition of the present invention is an organic solvent, and a non-aqueous solvent is preferred. In this invention, "non-aqueous solvent" means a solvent that is substantially free of water. That is, the "non-aqueous solvent" may contain trace amounts of water as long as it does not hinder the effects of the present invention. In this invention, the "non-aqueous solvent" has a water concentration of 200 ppm (by mass) or less, preferably 100 ppm or less, and more preferably 20 ppm or less. It should be noted that it is practically difficult to make a non-aqueous solvent completely anhydrous, and it usually contains 1 ppm or more of water. As the organic solvent used as the dispersion medium, aprotic organic solvents are preferred, and among them, aprotic organic solvents having 2 to 10 carbon atoms are more preferred. Examples of such organic solvents include linear or cyclic carbonate compounds, lactone compounds, linear or cyclic ether compounds, ester compounds, nitrile compounds, amide compounds, oxazolidinone compounds, nitro compounds, linear or cyclic sulfone or sulfoxide compounds, and phosphate ester compounds. The organic solvent is preferably an alkylpyrrolidone compound, and more preferably an N-alkylpyrrolidone compound. Preferable specific examples of the organic solvent include, for example, ethylene carbonate, fluoroethylene carbonate, vinylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, γ-butyrolactone, γ-valerolactone, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, tetrahydropyran, 1,3-dioxolane, 4-methyl-1,3-dioxolane, 1,3-dioxane, 1,4-dioxane, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, methyl butyrate, butyl butyrate, methyl isobutyrate, methyl trimethylacetate, ethyl trimethylacetate, acetonitrile, glutaronitrile, adiponitrile, methoxyacetonitrile, 3-methoxypropionitrile, N,N-dimethylformamide, N-methylpyrrolidone, N-methyloxazolidinone, N,N'-dimethylimidazolidinone, nitromethane, nitroethane, sulfolane, trimethyl phosphate, dimethyl sulfoxide or dimethyl sulfoxide phosphate, etc. These may be used alone or in combination of two or more. In the present invention, the dispersion medium is preferably N-methylpyrrolidone (NMP), N-ethylpyrrolidone or cyclohexanone, and more preferably NMP.

[0037] In the CNT dispersion composition, the content of the dispersion medium is preferably an amount such that the total of the above-mentioned single-walled CNT and the dispersant is 100% by mass.

[0038] <Other properties of the CNT dispersion composition> The CNT dispersion composition of the present invention preferably has a viscosity of 500 to 30000 mPa·s at a shear rate of 10 / s, more preferably 800 to 28000 mPa·s, even more preferably 1000 to 20000 mPa·s, even more preferably 1500 to 15000 mPa·s, even more preferably 2000 to 10000 mPa·s, even more preferably 2500 to 7000 mPa·s, even more preferably 2700 to 7000 mPa·s, even more preferably 3000 to 6000 mPa·s, and even more preferably 3000 to 5000 mPa·s. The viscosity described above can be measured by the method described in the examples.

[0039] [Method for preparing carbon nanotube dispersion compositions for electrodes of non-aqueous electrolyte secondary batteries] The CNT dispersion composition of the present invention can be prepared by mixing single-walled carbon nanotubes (WYNS) with a dispersant and a dispersion medium, dispersing the WYNS, and controlling the resistance value. The apparatus used for this mixing and / or dispersion, and the conditions for mixing and / or dispersion, are not particularly limited as long as the resistance value of the CNT dispersion composition can be controlled within the above range. The mixing and / or dispersion method is not particularly limited; the mixtures may be mixed and dispersed all at once, or they may be mixed and dispersed sequentially. It is preferable that the single-walled carbon nanotubes (WNTs) be subjected to pulverization or crushing (hereinafter collectively referred to as "pulverization") before mixing with the dispersant and dispersion medium. This pulverization can be carried out, for example, using a powder processing device. By performing the pulverization multiple times or for an extended period, the resistance value of the CNT dispersion composition tends to decrease. Also, by performing the pulverization multiple times or for an extended period, the viscosity of the CNT dispersion composition tends to increase. Furthermore, by performing the pulverization multiple times or for an extended period, the GD ratio of the WNTs in the CNT dispersion composition tends to decrease. The conditions for the grinding process depend on the characteristics of the single-walled carbon nanotubes used, but for example, it is preferable to grind them at 20,000 to 50,000 rpm for about 10 to 30 seconds. The mixing of single-walled carbon nanotubes (WNTs), a dispersant, and a dispersion medium can be performed using conventional mixing equipment. For example, planetary ball mills and thin-film swirling high-speed mixers can be suitably used. Mixing using these devices may be performed continuously.

[0040] The CNT dispersion composition of the present invention is suitable for mixing with an electrode active material to prepare an electrode slurry. It is preferable to add the CNT dispersion composition of the present invention to an electrode slurry such that the single-walled carbon nanotubes (WCNTs) content is 0.03 to 4.00% by mass of the solid content, more preferably 0.03 to 2.00% by mass, and even more preferably 0.05 to 1.00% by mass. The CNT dispersion composition of the present invention can be suitably used in preparing an electrode slurry for forming a positive electrode active material layer.

[0041] [Slurry for electrodes of non-aqueous electrolyte secondary batteries] The electrode slurry of the present invention comprises at least an electrode active material (negative electrode active material layer or positive electrode active material layer) and the CNT dispersion composition of the present invention. The electrode slurry of the present invention may optionally contain, in addition to the electrode active material, a binder, an ionic liquid, a thickener, an antifoaming agent, a leveling agent, a dehydrating agent, an antioxidant, and the like. Since the CNT dispersion composition of the present invention contains a dispersion medium, it is usually not necessary to add a solvent when preparing the electrode slurry. However, the viscosity of the electrode slurry may be adjusted by adding more solvent. The electrode active material, binder, solvent, ionic liquid, thickener, defoamer, leveling agent, dehydrating agent, antioxidant, etc. contained in the electrode slurry are not particularly limited. The electrode active material, binder, solvent, ionic liquid, thickener, defoamer, leveling agent, dehydrating agent, antioxidant, etc. can be those commonly used in non-aqueous electrolyte secondary batteries. The electrode active material is preferably a positive electrode active material, and as the positive electrode active material, a lithium-containing transition metal oxide having a (MA) layered rock salt type structure is preferred, LiNi 0.33 Co 0.33 Mn 0.33 O2 is more preferable. The type of organic polymer used as a binder is not particularly limited, and any binder that can be commonly used in electrodes of non-aqueous electrolyte secondary batteries can be used as appropriate. For example, polyvinylidene fluoride (PVDF) is suitable as a binder. The content of single-walled carbon nanotubes in the electrode slurry of the present invention is preferably 0.03 to 3.00% by mass, more preferably 0.03 to 2.00% by mass, and even more preferably 0.05 to 1.00% by mass, based on the solid content. The content of the electrode active material in the electrode slurry of the present invention is preferably 96.00 to 99.50% by mass, more preferably 96.00 to 99.00% by mass, and even more preferably 97.00 to 98.00% by mass, based on the solid content. The binder content in the electrode slurry of the present invention is preferably 0.10 to 3.00% by mass, more preferably 0.20 to 2.50% by mass, and even more preferably 0.20 to 2.00% by mass, relative to the solid content.

[0042] [Method for manufacturing electrode slurry] The method for producing an electrode slurry of the present invention includes at least mixing the CNT dispersion composition of the present invention with an electrode active material. Except for using the CNT dispersion composition of the present invention as a source of conductive additive, the same steps as those used for conventional electrode slurry production methods can be employed.

[0043] [Electrode Sheet] The electrode sheet of the present invention has an electrode active material layer (positive electrode active material layer or negative electrode active material layer) formed using an electrode slurry containing the CNT dispersion composition of the present invention. In this invention, the term "electrode sheet" simply refers to both the form in which it is incorporated as a component in a non-aqueous electrolyte secondary battery (the state in which it is incorporated into the secondary battery) and the form in which it is an electrode material before being incorporated into a non-aqueous electrolyte secondary battery. In other words, the structure of the electrode sheet (area, thickness, etc.) is sufficient as long as it is a structure that can be used as an electrode, or a structure that can be processed into a structure that can be used as an electrode. The electrode sheet of the present invention may be any electrode sheet having an electrode active material layer formed using an electrode slurry containing the CNT dispersion composition of the present invention described above. The electrode active material layer may be formed on a substrate such as a current collector, or it may be a sheet without a substrate, formed only of the electrode active material layer (negative electrode active material layer or positive electrode active material layer). This electrode sheet is usually a sheet in which the electrode active material layer is laminated on a current collector. The electrode sheet of the present invention may also have other layers, such as a protective layer or coating layer, such as a release sheet. In the electrode sheet of the present invention, it is preferable that the electrode active material layer is laminated in direct contact with the electrode current collector. The electrode sheet of the present invention can be suitably used as a material constituting the negative electrode active material layer or the positive electrode active material layer of a secondary battery, or as a laminate of a negative electrode current collector and a negative electrode active material layer (negative electrode layer) or a laminate of a positive electrode current collector and a positive electrode active material layer (positive electrode layer). The electrode sheet of the present invention may be a negative electrode sheet or a positive electrode sheet, but it is preferable that it be a positive electrode sheet.

[0044] When the electrode sheet of the present invention has a current collector, the current collector constituting the electrode sheet of the present invention is an electron transporter and is usually in the form of a film sheet. The current collector can be appropriately selected depending on the electrode active material. Examples of materials that make up the positive electrode current collector include aluminum, aluminum alloys, stainless steel, nickel, and titanium, with aluminum or aluminum alloys being preferred. Furthermore, a positive electrode current collector may also be made by treating the surface of aluminum or stainless steel with carbon, nickel, titanium, or silver to form a coating layer (thin film). Examples of materials that make up the negative electrode current collector include aluminum, copper, copper alloys, stainless steel, nickel, and titanium, with aluminum, copper, copper alloys, or stainless steel being preferred. Furthermore, negative electrode current collectors may also be made by treating the surface of aluminum, copper, copper alloys, or stainless steel with carbon, nickel, titanium, or silver to form a coating layer (thin film).

[0045] The electrode sheet of the present invention can be incorporated as at least one of the electrodes (positive electrode and negative electrode) of a non-aqueous electrolyte secondary battery to manufacture a non-aqueous electrolyte secondary battery.

[0046] The resistance value (electrode resistance value) of the electrode sheet of the present invention is preferably 150 to 510 Ω·cm, more preferably 150 to 430 Ω·cm, even more preferably 155 to 300 Ω·cm, and still more preferably 155 to 200 Ω·cm. The resistance value of the electrode sheet can be measured by the method described in the example.

[0047] [Method for manufacturing electrode sheets] The method for manufacturing an electrode sheet of the present invention includes at least forming an electrode active material layer using the electrode slurry of the present invention. Apart from using the electrode slurry of the present invention, the process can be the same as that for conventional electrode sheet manufacturing methods. For example, the electrode sheet of the present invention can be manufactured by forming a film using the electrode slurry of the present invention. More specifically, it can be prepared by using the electrode current collector or the like as a substrate and forming the electrode active material layer thereon. Using the electrode current collector as a substrate, the electrode slurry of the present invention can be applied thereon (may be through other layers) to form a coating film, which is then dried to obtain an electrode sheet having an electrode active material layer (coated and dried layer) on the substrate. The coating film may be subjected to pressing as needed. The method for applying the electrode slurry to the electrode current collector is not particularly limited, and a conventional method can be used.

[0048] [Nonaqueous electrolyte secondary battery] The non-aqueous electrolyte secondary battery of the present invention (hereinafter, also referred to as "the secondary battery of the present invention") has the electrode sheet of the present invention as at least one of the electrodes. The secondary battery of the present invention can have the same configuration as a normal non-aqueous electrolyte secondary battery except that it has the electrode sheet of the present invention as at least one of the electrodes. That is, the secondary battery of the present invention can be obtained by incorporating the electrode sheet of the present invention as at least one of the electrodes of a normal non-aqueous electrolyte secondary battery.

[0049] The structure of a general non-aqueous electrolyte secondary battery will be described below. FIG. 1 is a cross-sectional view schematically showing the laminated structure of a general non-aqueous electrolyte secondary battery 10, including the operating parts when operating as a battery. The non-aqueous electrolyte secondary battery 10 has a laminated structure (hereinafter, also referred to as an electrode laminate) having, in this order from the negative electrode side, a negative electrode current collector 1, a negative electrode active material layer 2, a separator 3, a positive electrode active material layer 4, and a positive electrode current collector 5. The negative electrode active material layer 2 and the positive electrode active material layer 4 and the space therebetween are filled with a non-aqueous electrolyte (not shown) and are separated by the separator 3. The separator 3 has pores and functions as a separation membrane between the positive and negative electrodes that insulates between the positive and negative electrodes while allowing the electrolyte and ions to permeate through these pores in the normal use state of the battery. With such a structure, for example, in the case of a lithium-ion secondary battery, during charging, electrons (e - ) are supplied to the negative electrode side through an external circuit, and at the same time, lithium ions (Li + ) move from the positive electrode through the electrolyte and accumulate at the negative electrode. On the other hand, during discharging, the lithium ions (Li + ) accumulated at the negative electrode return to the positive electrode side through the electrolyte, and electrons are supplied to the operating part 6. In the illustrated example, a light bulb is adopted for the operating part 6 and is made to light up by discharging. The secondary battery of the present invention has the electrode sheet of the present invention in place of at least one of the positive electrode active material layer 4 and the positive electrode current collector 5 in the above general non-aqueous electrolyte secondary battery.

[0050] The secondary battery of the present invention is equipped with the positive electrode sheet of the present invention as at least one of the electrodes of the secondary battery, but other components such as the positive electrode active material layer, positive electrode current collector, negative electrode active material layer, negative electrode current collector, electrolyte (aqueous electrolyte, non-aqueous electrolyte) or solid electrolyte material, separator, etc., are not particularly limited. These materials and components can be those commonly used in secondary batteries. Furthermore, the method for manufacturing the secondary battery of the present invention can be a conventional method, except that the electrode sheet of the present invention is used as at least one of the positive electrode and negative electrode. For components and manufacturing methods commonly used in these secondary batteries, refer to, for example, Japanese Patent Publication No. 2016-201308, Japanese Patent Publication No. 2005-108835, Japanese Patent Publication No. 2012-185938 and International Publication No. 2020 / 067106, etc., as appropriate.

[0051] The secondary battery of the present invention can be installed in electronic devices such as laptop computers, pen-input computers, mobile computers, e-book players, mobile phones, cordless phone handsets, pagers, handheld terminals, portable fax machines, portable copiers, portable printers, headphone stereos, video cameras, LCD televisions, handheld vacuum cleaners, portable CD players, MiniDiscs, electric shavers, transceivers, electronic organizers, calculators, memory cards, portable tape recorders, radios, backup power supplies, and more. It can also be used in consumer applications such as automobiles, electric vehicles, motors, lighting fixtures, toys, game consoles, road conditioners, clocks, strobes, cameras, and medical devices (pacemakers, hearing aids, shoulder massagers, etc.). Furthermore, it can be used for various military and space applications. It can also be combined with solar cells.

[0052] [Method for manufacturing non-aqueous electrolyte secondary battery] The present invention relates to a method for manufacturing a non-aqueous electrolyte secondary battery, which includes incorporating the electrode sheet of the present invention as at least one of the electrodes of the non-aqueous electrolyte secondary battery. Aside from using the electrode sheet of the present invention, the same steps as those used for manufacturing a conventional non-aqueous electrolyte secondary battery can be employed.

[0053] The present invention will be described in more detail below based on examples. However, the present invention is not intended to be limited thereto. [Examples]

[0054] [Platement of carbon nanotube dispersion composition]

[0055] 1. Preparation of the dispersant The following polymer was used as a dispersant. Polymer P1: Modified styrene-maleic acid copolymer (ET3002 (trade name), manufactured by BYK) Polymer P2: Copolymer containing 75 parts by mass of N-ethylmaleimide and 25 parts by mass of ethyl acrylate Polymer P3: Copolymer of 50 parts by mass of N-ethylmaleimide and 50 parts by mass of ethyl acrylate Polymer P4: Copolymer containing 50 parts by mass of N-ethylmaleimide and 50 parts by mass of octyl acrylate Polymer P5: Copolymer containing 50 parts by mass of N-ethylmaleimide and 50 parts by mass of lauryl acrylate Polymer P6: Polyvinylpyrrolidone (PVP-K30 (trade name), manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) Polymer P7: Polyvinylidene fluoride (PVDF) (#7208 (product name), manufactured by Kureha Corporation) Polymer P8: Hydrogenated nitrile rubber (H-NBR (product name), manufactured by Zeon Corporation)

[0056] Polymers P2 to P5 were prepared as follows.

[0057] <Preparation of Polymer P2> Solution A was prepared by mixing 15 g of N-ethylmaleimide, 5 g of ethyl acrylate, 3.5 g of azobisisobutyronitrile, and 40 g of methyl ethyl ketone at room temperature. A three-necked flask equipped with a stirrer, thermometer, reflux condenser, thermostat, and dropper pump was purged with nitrogen, and 100 g of methyl ethyl ketone was added. The mixture was then heated to 85°C while stirring. Solution A was then added to the flask dropwise at a constant rate over 1 hour using the dropper pump. After the dropwise addition was complete, the mixture was stirred at the same temperature, and the reaction was terminated after 5 hours. After the reaction was complete, the solution was concentrated to remove the methyl ethyl ketone, thereby obtaining polymer P2. The weight-average molecular weight (Mw) of the obtained polymer P2 was approximately 4000.

[0058] <Preparation of Polymer P3> Polymer P3 was prepared in the same manner as polymer P2, except that 10 g of N-ethylmaleimide and 10 g of ethyl acrylate were used in the preparation of polymer P2.

[0059] <Preparation of Polymer P4> Polymer P4 was prepared in the same manner as polymer P3, except that ethyl acrylate was replaced with octyl acrylate.

[0060] <Preparation of Polymer P5> Polymer P5 was prepared in the same manner as polymer P3, except that ethyl acrylate was replaced with lauryl acrylate.

[0061] 2. Preparation of carbon nanotube dispersion composition Using the above polymer as a dispersant, carbon nanotube dispersion compositions (CNT dispersion compositions) for experiments No. 1 to 21 were obtained as follows.

[0062] <Experiments No. 1-11, 14, 16-18> Single-walled carbon nanotubes (TUBALL 01RW03 (product name), manufactured by OCSiAl) (hereinafter also referred to as single-walled carbon nanotubes 1) were subjected to a single crushing treatment at 20,000 rpm for 10 seconds using a powder processing device, Drystroke (DB-100L (product name), manufactured by Sugino Machine Co., Ltd.). Next, the single-walled carbon nanotubes (WNTs), the dispersant listed in Table 1, and the dispersion medium were mixed so that each component was present in the amounts listed in Table 1. The mixture was then mixed in a planetary ball mill (P-6 (trade name), manufactured by Fritsch) using 1 mm diameter beads at 650 rpm for 16 hours. Subsequently, it was mixed in a thin-film swirling high-speed mixer (Filmix-56L (trade name), manufactured by Primix) at 16,000 rpm for 120 seconds. Finally, the mixture was subjected to five dispersion treatments at 150 MPa for 2 seconds each using a high-pressure dispersion device (Starburst (trade name), manufactured by Sugino Machine Co., Ltd.) to obtain the carbon nanotube dispersion compositions of Experiments No. 1-11, 14, and 16-18. The NMP used above had a water content of 200 ppm or less.

[0063] <Experiment No. 12> The carbon nanotube dispersion composition of Experiment No. 12 was obtained in the same manner as in Experiment No. 11, except that the decomposition treatment by dry strut was performed twice.

[0064] <Experiment No. 13> In Experiment No. 3, the carbon nanotube dispersion composition of Experiment No. 13 was obtained in the same manner as in Experiment No. 3, except that the descaling treatment by dry strut was not performed.

[0065] <Experiment No. 15> In Experiment No. 6, the carbon nanotube dispersion composition of Experiment No. 15 was obtained in the same manner as in Experiment No. 6, except that the descaling treatment by dry strut was not performed.

[0066] <Experiment No. 19> In Experiment No. 3, the carbon nanotube dispersion composition of Experiment No. 19 was obtained in the same manner as in Experiment No. 3, except that the decomposition treatment by dry strut was performed 10 times.

[0067] <Experiment No. 20> In Experiment No. 3, the carbon nanotube dispersion composition of Experiment No. 20 was obtained in the same manner as in Experiment No. 3, except that water was used as the dispersion medium.

[0068] <Experiment No. 21> In Experiment No. 3, the carbon nanotube dispersion composition of Experiment No. 21 was obtained in the same manner as in Experiment No. 3, except that single-walled carbon nanotubes (SG101 (trade name), manufactured by Nippon Zeon Co., Ltd.) (hereinafter also referred to as single-walled carbon nanotube 2) were used.

[0069] [Measurement of adsorption rate to CNTs] The adsorption rate of each dispersant (polymer) to single-walled carbon nanotubes was measured as follows. H-NMR measurements were performed on each CNT dispersion composition, and the peak intensity of the peak with the highest peak intensity among the peaks derived from the dispersant was identified. The peak intensity value of this peak was defined as the "H-NMP peak intensity in the dispersion composition." Subsequently, the carbon nanotube dispersion composition was filtered, and the resulting liquid component was subjected to H-NMR measurement. The peak intensity of the peak with the highest peak intensity among the dispersant-derived peaks remaining in the liquid component was identified. This peak intensity value was defined as the "H-NMP peak intensity in the liquid component." The adsorption rate of the dispersant to single-walled carbon nanotubes was determined using the following formula. Adsorption rate of dispersant (%) = 100 - {[H-NMP peak intensity in liquid component] / [H-NMP peak intensity in dispersion composition]} × 100

[0070] [Resistance measurement of CNT dispersion composition] The resistance values ​​of each CNT dispersion composition obtained above were measured as follows. A Loresta-GX resistivity meter (product name, manufactured by Nitto Seikou Analytech Co., Ltd.) was used, and a PSP probe (product name, manufactured by Nitto Seikou Analytech Co., Ltd.) was used as the probe. The probe was brought into contact with each CNT dispersion composition, and the resistance was measured at a current of 100 mA. This measurement was performed five times (N5), and the average of the obtained measurements was taken as the resistance value (Ω·cm) of each CNT dispersion composition.

[0071] [Method for measuring the viscosity of CNT dispersion compositions] The viscosity of each CNT dispersion composition was measured as follows. The test was performed using an E-type viscometer (TV-35 (product name), manufactured by Toki Sangyo Co., Ltd.) and a standard cone rotor (1"34' × R24). The sample cup was preheated to 25°C, 1.1 mL of the CNT dispersion composition obtained above was added, and the sample cup was placed in the main unit and maintained for 5 minutes until the temperature became constant. The viscosity measured thereafter at a shear rate of 10 / s was taken as the viscosity value.

[0072] [Raman method for evaluating the GD ratio] The GD ratio of single-walled carbon nanotubes contained in each CNT dispersion composition was measured as follows. 200 μL of the CNT dispersion composition obtained above was dropped onto a glass slide and dried at 120°C. A Raman spectrum was obtained from this sample using a confocal Raman microscope (inVia Qontor (trade name), Renishaw) irradiated with a 532 nm laser. The baseline was determined using an approximation curve based on a polynomial (6th degree). The G-band of the Raman spectrum (wavenumber 1600 cm⁻¹) -1 D-band (wavenumber 1350 cm) relative to the peak intensity of ) -1 The peak intensity ratio (D / G ratio) was determined. The above measurement was performed at 10 arbitrary points on the sample, and the average value of the obtained peak intensity ratios was taken as the GD ratio.

[0073] [Electrode resistance value, energy density evaluation, and output characteristic evaluation] Using the CNT dispersion composition obtained above, electrode sheets and secondary batteries were fabricated, and the electrode resistance value of the positive electrode sheet and the energy density and output characteristics of the secondary battery were evaluated. The test equipment used was a charge / discharge evaluation device (TOSCAT3000 (product name), manufactured by Toyo System Co., Ltd.).

[0074] <Rechargeable battery manufacturing> (1) Preparation of non-aqueous electrolyte E1 A non-aqueous electrolyte (non-aqueous electrolyte E1) was prepared by mixing ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) in a mass ratio of EC:DMC:EMC = 3:4:3, and then adding LiPF6 as a lithium salt to a concentration of 1 M.

[0075] (2) Preparation of the positive electrode sheet NCM111 (LiNi 0.33 Co 0.33 Mn 0.33 A positive electrode slurry was prepared by mixing 97.95 parts by mass of O2 (manufactured by Toyoshima Seisakusho), a carbon nanotube dispersion composition as described in Table 1 as a conductive additive in an amount that resulted in a CNT content of 0.05 parts by mass, and 2.00 parts by mass of polyvinylidene fluoride (PVDF) (#7208 (product name), manufactured by Kureha Corporation) as a binder, and stirring the mixture at 2000 rpm for 360 seconds using a centrifugal planetary mixer (Sinky Co., Ltd., product name Awatori Rentaro). The positive electrode slurry was applied to one side of a 12 μm thick positive electrode current collector (aluminum foil) and dried at 120°C until the dispersion medium completely evaporated. Then, a press process was performed using a roll press to obtain a sheet-like positive electrode (positive electrode sheet). In this positive electrode sheet, the thickness of the positive electrode active material layer was 70 μm, and the density was 3.1 g / cm³. 3 That was the case.

[0076] (3) Preparation of the negative electrode sheet A negative electrode slurry was obtained by mixing a negative electrode active material (artificial graphite), styrene-butadiene copolymer (SBR) as a binder, carboxymethylcellulose (CMC) as a thickener, and water as a solvent in a mass ratio of negative electrode active material:SBR:CMC:water = 60:1.5:0.5:38. The above-mentioned negative electrode slurry was coated onto one side of a 12 μm thick negative electrode current collector (copper foil), and dried at 120°C until the solvent completely evaporated. Then, a press process was performed using a roll press to obtain a sheet-like negative electrode (negative electrode sheet). The thickness of the negative electrode active material layer in this negative electrode sheet was approximately 180 μm.

[0077] (4) Fabrication of a non-aqueous electrolyte secondary battery The positive electrode sheet and negative electrode sheet obtained above were laminated with a separator in between to obtain an electrode laminate consisting of a positive electrode current collector, a positive electrode active material layer, a separator, a negative electrode active material layer, and a negative electrode current collector. Aluminum tabs were attached to the ends of the positive electrode current collector and nickel tabs were attached to the ends of the negative electrode current collector by ultrasonic welding. A battery assembly was fabricated by housing this electrode laminate in an aluminum laminate container. After injecting the non-aqueous electrolyte E1 with the liquid injection port open, the liquid injection port was sealed and the container was sealed to produce a non-aqueous electrolyte secondary battery for evaluation testing.

[0078] <Method for measuring electrode resistance> After fabricating the positive electrode sheet described above, another aluminum current collector was placed on top of the positive electrode active material layer of the positive electrode sheet. Aluminum tabs were attached to the two aluminum current collectors by ultrasonic welding, sandwiched between two aluminum laminate films, and then heat-sealed and vacuum-sealed to fabricate an electron conductivity evaluation cell. A constant voltage of 10 mV was applied to this cell and resistance measurements were performed. This measurement was performed three times (N3), and the average of the obtained measurements was calculated as the electrode resistance (Ω·cm). -Evaluation Criteria- A: 200Ω cm or less B: More than 200Ω·cm, less than 300Ω·cm C: More than 300Ω·cm, less than 400Ω·cm D: More than 400Ω·cm, less than 500Ω·cm E: More than 500Ω cm

[0079] <Measurement of volumetric energy density> The positive electrode sheets used in the preparation of each of the above non-aqueous electrolyte secondary batteries were punched out to a diameter of 10 mm, the positive electrode current collector was removed from the resulting punched piece, and the thickness of the positive electrode active material layer was measured. The thickness of the negative electrode active material layer was measured in the same manner. The thickness of the power generation element was determined by adding the thickness of the positive electrode current collector, the thickness of the positive electrode active material layer, the thickness of the separator, the thickness of the negative electrode active material layer, and the thickness of the negative electrode current collector. The thickness of each constituent layer was measured using a constant-pressure thickness measuring instrument (PG-20J (product name), manufactured by Teclock Co., Ltd.). The volume (L) of the power generation element was determined by multiplying the thickness of the power generation element by the area of ​​the circular surface of the power generation element. The non-aqueous electrolyte secondary battery was charged and discharged under "Charge / Discharge Condition I" described later, and the reference discharge capacity (Ah) was measured. The average voltage (V) during discharge was also measured, and the energy (Wh) was calculated by multiplying the reference discharge capacity (Ah) by the average voltage (V). The volumetric energy density of the non-aqueous electrolyte secondary battery was calculated by dividing the amount of electrical energy (Wh) obtained in this way by the volume of the power generation element (L) determined above. The obtained value was then evaluated according to the evaluation criteria below. -Evaluation Criteria- A:500Wh / L or more B: 490 Wh / L or more, less than 500 Wh / L C: 480 Wh / L or more, less than 490 Wh / L D: 470Wh / L or more, less than 480Wh / L E: Less than 470 Wh / L (Charge / discharge condition I) Constant current-constant voltage (CC-CV) charging: Current value 25mA, upper voltage limit 4.2V, cutoff current value 2.5mA Constant current (CC) discharge: Current value 25mA, cutoff voltage value 3.0V

[0080] <Output Characteristics Evaluation> After charging and discharging according to the "Charge / Discharge Condition I" described above, one side of the laminate container was cut, and unwanted gases generated during the charging and discharging process under "Charge / Discharge Condition I" were removed from each battery. The container was then resealed using a vacuum sealer. After charging under "Charge / Discharge Condition I" and degassing the batteries, output characteristic tests were conducted under the following conditions. Specifically, under "Charge / Discharge Condition II" below, the batteries were charged to 4.2V by CC-CV charging and discharged to 3.0V by CC discharge to measure the reference discharge capacity. Then, under "Charge / Discharge Condition III" below, the batteries were charged to 4.2V by CC-CV charging and discharged to 3.0V by CC discharge to measure the output evaluation discharge capacity. Furthermore, the discharge capacity retention rate was calculated using the following formula and evaluated according to the evaluation criteria below. Charge / discharge conditions II (standard discharge capacity) CC-CV charging: Current value 25mA, upper voltage limit 4.2V, cutoff current value 2.5mA CC discharge: Current value 25mA, cutoff voltage value 3.0V Charge / Discharge Condition III (Output Evaluation Discharge Capacity) CC-CV charging: Current value 25mA, upper voltage limit 4.2V, cutoff current value 2.5mA CC discharge: Current value 1500mA, cutoff voltage value 3.0V Discharge capacity maintenance rate (%) = Output evaluation discharge capacity / Reference discharge capacity × 100 -Evaluation Criteria- A: Over 80% B: 70% or more, less than 80% C: 65% or more, less than 70% D: 60% or more, less than 65% E: Less than 60%

[0081] The results obtained are shown in Tables 1 and 2.

[0082] [Table 1]

[0083] In Table 1, the content of single-walled carbon nanotubes, dispersant, and dispersion medium is expressed in "mass%".

[0084] [Table 2]

[0085] The CNT dispersion compositions in Experiments No. 1, 6, 13-15, and 19 did not contain single-walled carbon nanotubes (WYSTs) in the amount specified in this invention, and / or the resistance values ​​of the CNT dispersion compositions were not within the range specified in this invention. In all of these Experiments No. 1, 6, 13-15, and 19, when a positive electrode active material layer was formed using a positive electrode slurry containing these CNT dispersion compositions, the electrode resistance value was 560 Ω·cm or higher, indicating high resistance. Furthermore, when these positive electrodes were incorporated into a secondary battery, the energy density was less than 470 Wh / L, and the discharge capacity retention rate was less than 60%, resulting in inferior energy density and output characteristics. Furthermore, the CNT dispersion composition in Experiment No. 20 uses water as the dispersion medium. When the positive electrode active material layer was formed using a positive electrode slurry containing this CNT dispersion composition in Experiment No. 20, the electrode resistance was 522 Ω·cm, which was high. Moreover, when this positive electrode was incorporated into a secondary battery, the energy density was less than 470 Wh / L, and the discharge capacity retention rate was less than 60%, resulting in inferior performance in both energy density and output characteristics. In contrast, the CNT dispersion compositions of Experiments No. 2-5, 7-12, 16-18, and 21 contained single-walled carbon nanotubes (WYSTs) in the amount specified in this invention, and the resistance values ​​of the CNT dispersion compositions were within the range specified in this invention. In all of these Experiments No. 2-5, 7-12, 16-18, and 21, when a positive electrode active material layer was formed using a positive electrode slurry containing these CNT dispersion compositions and used as the positive electrode, the electrode resistance value was below 500 Ω·cm, indicating low resistance. Furthermore, when these positive electrodes were incorporated into a secondary battery, the energy density was 470 Wh / L or higher, and the discharge capacity retention rate was 60% or higher, resulting in excellent energy density and output characteristics. [Explanation of Symbols]

[0086] 10 Nonaqueous electrolyte secondary battery 1 Negative electrode current collector 2 Negative electrode active material layer 3 Separators 4 Cathode active material layer 5 Positive electrode current collector 6. Operating parts (light bulbs)

Claims

1. A carbon nanotube dispersion composition for electrodes of a non-aqueous electrolyte secondary battery, comprising single-walled carbon nanotubes, a dispersant, and a dispersion medium, The dispersion medium is an organic solvent. The content of single-walled carbon nanotubes in the dispersion composition is 1.2 to 10.0% by mass. The resistivity of the aforementioned dispersion composition is 15 to 80,000 Ω·cm. Carbon nanotube dispersion composition.

2. The carbon nanotube dispersion composition according to claim 1, wherein the adsorption rate of the dispersant to the single-walled carbon nanotube is 5 to 55%.

3. The carbon nanotube dispersion composition according to claim 1, wherein the content of the dispersant in the dispersion composition is 0.02 to 2.00% by mass.

4. The carbon nanotube dispersion composition according to claim 1, wherein the GD ratio (D / G) of the single-walled carbon nanotubes is 0.020 to 0.

060.

5. The carbon nanotube dispersion composition according to claim 1, wherein the viscosity at a shear rate of 10 / s is 500 to 30,000 mPa·s.

6. A slurry for electrodes of a non-aqueous electrolyte secondary battery, comprising the carbon nanotube dispersion composition and an electrode active material according to any one of claims 1 to 5.

7. An electrode sheet having an electrode active material layer formed using the electrode slurry described in claim 6.

8. A non-aqueous electrolyte secondary battery having the electrode sheet described in claim 7 as an electrode.

9. A method for producing an electrode slurry, comprising mixing a carbon nanotube dispersion composition according to any one of claims 1 to 5 with an electrode active material.

10. A method for manufacturing an electrode sheet, comprising forming an electrode active material layer using the electrode slurry described in claim 6.

11. A method for manufacturing a non-aqueous electrolyte secondary battery, comprising incorporating the electrode sheet described in claim 7 as an electrode.

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