Carbon nanotube dispersion composition, slurry for electrode and method for producing same, electrode sheet and method for producing same, and nonaqueous electrolyte secondary battery and method for producing same

Abstract

The present invention provides: a CNT dispersion composition which contains single-walled CNTs, a dispersant and a dispersion medium, wherein the content of the single-walled CNTs is 0.40 mass% or more, the average fiber length of the single-walled CNTs is 2.5 µm or more, and a composition A, in which the content of the single-walled CNTs is adjusted to 0.40 mass% by using the CNT dispersion composition as is or by diluting the CNT dispersion composition, exhibits specific viscoelastic properties; an electrode sheet; a nonaqueous electrolyte secondary battery; and methods for producing the CNT dispersion composition, the electrode sheet and the nonaqueous electrolyte secondary battery.

Description

Carbon nanotube dispersion composition, electrode slurry and method for manufacturing the same, electrode sheet and method for manufacturing the same, and non-aqueous electrolyte secondary battery and method for manufacturing the same

[0001] The present invention relates to a carbon nanotube dispersion composition, an electrode slurry and a method for producing the same, an electrode sheet and a method for producing the same, and a non-aqueous electrolyte secondary battery and a method for producing the same.

[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] 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. Until now, conductive materials that are 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 a conductive network with a smaller content, have come into use. Among these, single-walled carbon nanotubes (WYSIWY) have particularly excellent electronic 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. When using single-walled carbon nanotubes (WYNTs) as a conductive additive, WYNTs have low dispersibility in solvents. Therefore, a CNT dispersion composition is prepared in advance and mixed with other components such as electrode active materials.

[0005] For example, Patent Document 1 discloses a carbon nanotube dispersion containing carbon nanotubes, a dispersant, and a solvent, characterized in that it satisfies the following conditions (1) to (4): (1) The Raman spectrum of the carbon nanotubes is 1560 to 1600 cm⁻¹ －１ The maximum peak intensity within the range is G, 1310-1350 cm. －１ (1) The G / D ratio of carbon nanotubes is 5 to 100 when the maximum peak intensity within the range is denoted as D. (2) The dispersion contains 30 to less than 250 parts by mass of dispersant per 100 parts by mass of carbon nanotubes. (3) The complex modulus of the carbon nanotube dispersion is 5 Pa or more and less than 650 Pa at 25°C and a frequency of 1 Hz, and the phase angle is 5° or more and less than 50°. (4) The BET specific surface area of ​​the carbon nanotubes is 550 to 1200 m². ２The value should be / g. Patent Document 1 states that single-walled carbon nanotubes are preferred as the carbon nanotubes. According to the technology described in Patent Document 1, 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.

[0006] For example, Patent Document 2 discloses a carbon nanotube dispersion comprising carbon nanotubes, a first polymer containing at least one selected from the group consisting of hydroxyl group-containing structural units and heterocyclic-containing structural units, but not containing nitrile group-containing structural units, a second polymer containing nitrile group-containing structural units, and a solvent, wherein the carbon nanotubes comprise at least two types of carbon nanotubes with different fiber diameter distributions in the range of 100 nm or less as measured by a scanning electron microscope, and the two types of carbon nanotubes comprise a component exhibiting a first fiber diameter distribution and a component exhibiting a second fiber diameter distribution. According to the technology described in Patent Document 2, a carbon nanotube dispersion and a carbon nanotube dispersion composition having high concentration and high dispersibility are provided, and by using this dispersion composition, a non-aqueous electrolyte secondary battery having excellent rate characteristics and cycle characteristics can be provided.

[0007] Japanese Patent Publication No. 2022-63234 Japanese Patent Publication No. 2022-99288

[0008] With the expanding applications of non-aqueous electrolyte secondary batteries, there is a growing demand for improved rapid charging capabilities (high current and short charging time). For example, when using non-aqueous electrolyte secondary batteries as a power source for electric vehicles, improved rapid charging capabilities enable charging in a short time, allowing for smoother travel. It also makes it possible to secure a sufficient power source quickly in emergencies or other critical situations.

[0009] To improve rapid charging performance, it is necessary to increase the mobility of charge carriers (e.g., lithium ions) and electrons in the electrodes. To increase the mobility of charge carriers and electrons, it is necessary to reduce the resistance in the electrodes. In rapid charging, if the resistance is sufficiently low, high-current charging can be maintained for a certain period of time, albeit for a short time, and the charging capacity can be secured in a short charging time. In addition, heat generation and side reactions are suppressed, and it is possible to prevent a decrease in discharge capacity. Conductive additives play an important role in improving the efficiency of electron movement (electron conduction). As mentioned above, single-walled carbon nanotubes (SWCNTs) are considered promising as conductive additives, but a CNT dispersion composition that can fully utilize the inherent conductive network-forming ability of SWCNTs and effectively improve rapid charging performance has not yet been realized.

[0010] The present invention aims to provide a CNT dispersion composition containing single-walled carbon nanotubes (WNTs) that can effectively enhance the electronic conductivity (significantly reduce resistance) of various components by being used as a source of WNTs responsible for electronic conductivity in these components. Furthermore, the present invention aims to provide an electrode slurry 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. The present invention also aims to provide a method for manufacturing these electrode slurry, electrode sheet, and non-aqueous electrolyte secondary battery.

[0011] In view of the above problems, the inventors of the present invention conducted extensive research and found that, in a CNT dispersion composition containing a certain amount or more of single-walled carbon nanotubes (WWNTs) as a conductive additive, by setting the average fiber length of the WWNTs to a specific length or more and controlling the composition to exhibit unique viscoelastic properties by devising dispersion conditions, etc., the electronic conductivity of components such as those incorporating this CNT dispersion composition as a source of WWNTs can be effectively enhanced (resistance can be sufficiently suppressed). The present invention was completed after further research based on this finding.

[0012] The above problems of the present invention have been solved by the following means. [1] A carbon nanotube dispersion composition comprising single-walled carbon nanotubes, a dispersant and a dispersion medium, wherein the content of the single-walled carbon nanotubes in the dispersion composition is 0.40% by mass or more, and the average fiber length is 2.5 μm or more, and composition A, in which the content of the single-walled carbon nanotubes is 0.40% by mass by using the dispersion composition as is or by diluting it with a dispersion medium of the same type as the dispersion medium, satisfies at least one of the following conditions (1) and (2). Condition (1): In the measurement of the strain dependence of the storage modulus and loss modulus of composition A, the strain rate at the intersection of the storage modulus and the loss modulus is 10% or more, and the storage modulus is greater than the loss modulus in the region where the strain rate is smaller than the strain rate at the intersection. Condition (2): In the measurement of the shear rate dependence of the viscosity of composition A, the viscosity ratio represented by the following (formula I) is 250 or more. [1] The carbon nanotube dispersion composition according to [1], wherein the average value of the storage modulus of composition A in the range of strain rate of 0.01% to 0.1% is 25 to 200 Pa. [3] The carbon nanotube dispersion composition according to [1] or [2], wherein the average fiber length of the single-walled carbon nanotubes in the dispersion composition is 10.0 μm or less. [4] The carbon nanotube dispersion composition according to any one of [1] to [3], wherein the dispersant is insoluble in a non-aqueous electrolyte. [5] The carbon nanotube dispersion composition according to any one of [1] to [4], wherein the content of the dispersant in the dispersion composition is 10 to 70 parts by mass per 100 parts by mass of the single-walled carbon nanotubes. [6] The carbon nanotube dispersion composition according to any one of [1] to [5], wherein the dispersant contains a lactone ring structure or an aliphatic hydrocarbon ring structure. [7] The carbon nanotube dispersion composition according to any one of [1] to [6], wherein the content of the single-walled carbon nanotubes in the dispersion composition is 1.20% by mass or more.[8] An electrode slurry comprising a carbon nanotube dispersion composition according to any one of [1] to [7] and an electrode active material. [9] An electrode sheet having an electrode active material layer formed using the electrode slurry according to [8].

[10] A non-aqueous electrolyte secondary battery having the electrode sheet according to [9] as an electrode.

[11] A method for producing an electrode slurry, comprising mixing a carbon nanotube dispersion composition according to any one of [1] to [7] and an electrode active material.

[12] A method for producing an electrode sheet, comprising forming an electrode active material layer using the electrode slurry according to [8].

[13] A method for producing a non-aqueous electrolyte secondary battery, comprising incorporating the electrode sheet according to [9] as an electrode.

[0013] In the description of this invention, numerical ranges expressed using "~" mean a range that includes the values ​​written before and after "~" as the lower and upper limits. 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 this 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.

[0014] The carbon nanotube dispersion composition of the present invention (also referred to as the CNT dispersion composition of the present invention) can be used in various materials as a source of single-walled carbon nanotubes responsible for electronic conductivity, thereby effectively increasing the electronic conductivity of these materials (sufficiently reducing resistance). For example, it is suitable as a source of conductive additives in the formation of the electrode active material layer of a non-aqueous electrolyte secondary battery, and the resulting non-aqueous electrolyte secondary battery can be made to have excellent rapid charging properties. The electrode slurry of the present invention can be used to form an electrode sheet, and by using this electrode sheet as an electrode in a non-aqueous electrolyte secondary battery, for example, the resulting non-aqueous electrolyte secondary battery can be made to have excellent rapid charging properties. The non-aqueous electrolyte secondary battery of the present invention has excellent rapid charging properties. According to the manufacturing methods of the electrode slurry, electrode sheet, and non-aqueous electrolyte secondary battery of the present invention, the electrode slurry, electrode sheet, and non-aqueous electrolyte secondary battery of the present invention can be obtained, respectively.

[0015] This is an example of a graph obtained by measuring the strain dependence of composition A obtained from the CNT dispersion composition of the present invention, and is a graph obtained from the CNT dispersion composition of Experiment No. 6 described later. Figure 2 is a longitudinal cross-sectional view schematically showing the basic stacked structure of one embodiment of the secondary battery according to the present invention.

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

[0017] [Carbon Nanotube Dispersion Composition] The CNT dispersion composition of the present invention comprises single-walled carbon nanotubes (WYSIW) and a dispersant and a dispersion medium. The CNT dispersion composition of the present invention is suitable as a source of conductive additive in various components, elements, devices, etc., that contain WYSIW as a conductive additive. The CNT dispersion composition of the present invention is suitable, for example, as a source of conductive additive used in electrodes of secondary batteries such as non-aqueous electrolyte secondary batteries. Furthermore, the CNT dispersion composition of the present invention can be used, for example, as a source of electronically conductive WYSIW in capacitors, electronic components (e.g., semiconductor devices) and their transport materials, wiring materials, electrostatic components, electromagnetic wave shielding components, etc.

[0018] The CNT dispersion composition of the present invention contains 0.40% by mass or more of the single-walled carbon nanotubes. The average fiber length of the single-walled carbon nanotubes is 2.5 μm or more. Composition A, obtained by diluting the CNT dispersion composition of the present invention with a dispersion medium of the same type as the above dispersion medium as necessary, so that the single-walled CNT content is 0.40% by mass, satisfies at least one of the following conditions (1) and (2). Condition (1): In the measurement of the strain dependence of the storage modulus and loss modulus of composition A, the strain rate at the intersection of the storage modulus and the loss modulus is 10% or more, and the storage modulus is greater than the loss modulus in the region where the strain rate is smaller than the strain rate at the intersection. Condition (2): In the measurement of the shear rate dependence of the viscosity of composition A, the viscosity ratio represented by the following formula (I) is 250 or more. Viscosity ratio = (Viscosity Vα at shear rate 0.01 / sec) / (Viscosity Vβ at shear rate 1000 / sec) ... (Equation I)

[0019] In the "measurement of strain dependence of storage modulus and loss modulus" under condition (1) above, composition A is subjected to viscoelastic measurement, and a graph is obtained by plotting the storage modulus and loss modulus (vertical axis) against the strain rate (horizontal axis). In this graph, if the intersection point of the storage modulus and the loss modulus is located at a strain rate of 10% or more, and the storage modulus is greater than the loss modulus in the region where the strain rate is smaller than the intersection point, then condition (1) above is satisfied.

[0020] In the following description, the CNT dispersion composition of the present invention will be mainly explained using non-aqueous electrolyte secondary batteries as an example, but as stated above, the applications of the CNT dispersion composition of the present invention are not limited to non-aqueous electrolyte secondary batteries or their components.

[0021] The CNT dispersion composition of the present invention contains single-walled CNTs of a specific average fiber length and satisfies the above conditions (1) or (2). In other words, it forms a stable CNT network, resulting in enhanced electronic conductivity, and therefore exhibits high elasticity or thixotropy. Furthermore, this CNT network also exhibits excellent stability over time. Therefore, the CNT dispersion composition of the present invention can be used, for example, in combination with an electrode active material to prepare an electrode slurry, and the coating film of this slurry can be dried as needed to form an electrode active material layer, thereby obtaining an electrode active material layer with lower resistance. As a result, if this electrode active material layer is used as an electrode in a non-aqueous electrolyte secondary battery, the rapid charging performance can be further enhanced, and the rapid charging performance can be maintained even after long-term storage.

[0022] The content of single-walled carbon nanotubes (WYSIW) in the CNT dispersion composition is preferably 0.50% by mass or more, more preferably 0.70% by mass or more, even more preferably 1.00% by mass or more, even more preferably 1.20% by mass or more, and even more preferably 1.50% by mass or more. The content of single-walled carbon nanotubes (WYSIW) in the CNT dispersion composition is preferably 0.40 to 10.00% by mass, more preferably 0.50 to 8.00% by mass, even more preferably 0.70 to 7.00% by mass, even more preferably 1.00 to 6.00% by mass, even more preferably 1.20 to 4.00% by mass, and even more preferably 1.60 to 3.00% by mass.

[0023] The average fiber length of single-walled carbon nanotubes (WLA) is preferably 2.8 μm or more, more preferably 3.0 μm or more, and even more preferably 3.5 μm or more. There is no particular upper limit to the average fiber length of single-walled carbon nanotubes, but it is preferably 25.0 μm or less, more preferably 20.0 μm or less, even more preferably 18.0 μm or less, even more preferably 15.0 μm or less, even more preferably 10.0 μm or less, even more preferably 8.0 μm or less, and even more preferably 6.0 μm or less. The average fiber length of single-walled carbon nanotubes (WLA) is preferably 2.5 to 25.0 μm, more preferably 2.8 to 20.0 μm, even more preferably 3.0 to 18.0 μm, even more preferably 3.0 to 15.0 μm, even more preferably 3.0 to 10.0 μm, even more preferably 3.5 to 8.0 μm, and even more preferably 3.5 to 6.0 μm. The average fiber length of single-walled carbon nanotubes (WYNA) can be determined as follows: -Method for measuring single-walled CNT fiber length- The CNT dispersion composition is imaged using a scanning electron microscope (JEOL Corporation) and the fiber length is measured. The fiber length of 100 WYNA is measured, and the arithmetic mean of the 100 measured values ​​is taken as the average fiber length. If the concentration of the CNT dispersion composition is too high and it is difficult to measure the fiber diameter, the CNT dispersion composition can be appropriately diluted before measurement.

[0024] The CNT dispersion composition of the present invention exhibits viscoelastic properties that satisfy at least one of the above conditions (1) and (2) when the amount of single-walled carbon nanotubes is 0.40% by mass (state of composition A). In determining whether the above conditions (1) and (2) are satisfied, the CNT dispersion composition of the present invention is diluted with a dispersion medium as necessary to prepare composition A so that the amount of single-walled carbon nanotubes is 0.40% by mass. As this dispersion medium, the same type of dispersion medium as that which constitutes the CNT dispersion composition is used. If the CNT dispersion composition of the present invention contains 0.40% by mass of single-walled carbon nanotubes, the CNT dispersion composition of the present invention can be used as composition A without dilution.

[0025] The CNT dispersion composition of the present invention may satisfy only condition (1), may satisfy only condition (2), or may satisfy both condition (1) and condition (2). When condition (1) is satisfied, condition (2) is often satisfied, and when condition (2) is satisfied, condition (1) is often satisfied. Therefore, it can be said that condition (1) and condition (2) define approximately equivalent viscoelastic properties in terms of improving and maintaining electronic conductivity.

[0026] The above condition (1) will be described more specifically with reference to FIG. 1. FIG. 1 is an example of a graph obtained by strain dependence measurement of composition A, which is a graph obtained for composition A of Experiment No. 6 described later. In this graph, the horizontal axis represents strain ratio (%), and the vertical axis represents storage elastic modulus (Pa) and loss elastic modulus (Pa). Both axes are logarithmic scales. The storage elastic modulus line is shown by a solid line, and the loss elastic modulus line is shown by a dotted line. The magnitudes of storage elastic modulus and loss elastic modulus are interchanged at intersection IP (the positional relationship in the vertical axis direction is interchanged). In FIG. 1, the intersection of the solid line of storage elastic modulus and the dotted line of loss elastic modulus is located at the position of a strain ratio of 10%, and in the region where the strain ratio is smaller than this intersection, the storage elastic modulus is larger than the loss elastic modulus.

[0027] Intersection IPs may be located at a strain rate of 10% or more, more preferably at a strain rate of 15% or more, even more preferably at a strain rate of 20% or more, and even more preferably at a strain rate of 30% or more. There is no particular upper limit to the strain rate at which the intersection IP is located. The upper limit of the strain rate at which the intersection IP is located is preferably 800% or less, more preferably 600% or less, even more preferably 400% or less, even more preferably 200% or less, even more preferably 100% or less, and even more preferably 50% or less. Intersection IPs are preferably located at a strain rate of 10 to 800%, more preferably at a strain rate of 15 to 800%, even more preferably at a strain rate of 20 to 800%, and even more preferably at a strain rate of 30 to 800%. The intersection IP is preferably located at a strain rate of 10-600%, 15-400%, 20-200%, and 30-100%. The location of the above intersection IP can be determined by the following method: -Method for determining the intersection of the storage modulus and loss modulus of a CNT dispersion composition- For composition A, strain dependence measurements are performed at 25°C and a frequency of 1 Hz in the range of strain rates from 0.01% to 1000%. A rheometer (HAAKE MARS40 (trade name), manufactured by Thermo Fisher Scientific) and a cone with a diameter of 60 mm and an angle of 4° are used for the measurement. A graph is created with the strain rate on the horizontal axis and the storage modulus and loss modulus on the vertical axis, and the point where the magnitudes of the storage modulus and loss modulus are reversed (the point where the positions in the vertical axis direction are swapped) is defined as the intersection IP.

[0028] In a region where the strain rate is lower than the intersection point IP, the storage elastic modulus is larger than the loss elastic modulus. In the strain dependency measurement for the composition A, when an average value of the storage elastic modulus in a strain rate range of 0.01% or more and 0.1% or less is defined as an average storage elastic modulus, and an average value of the loss elastic modulus in a strain rate range of 0.01% or more and 0.1% or less is defined as an average loss elastic modulus, it is preferable that the average storage elastic modulus and the average loss elastic modulus satisfy the following conditions. The average value of the storage elastic modulus and the average value of the loss elastic modulus for the composition A in the strain rate range of 0.01% or more and 0.1% or less can be automatically calculated by a rheometer during the measurement for determining the intersection point IP. The difference between the average storage elastic modulus and the average loss elastic modulus (average storage elastic modulus - average loss elastic modulus) is preferably 5 Pa or more, and more preferably 10 Pa or more. The difference between the average storage elastic modulus and the average loss elastic modulus is not particularly limited, practically it is 500 Pa or less, preferably 400 Pa or less, and more preferably 200 Pa or less. The difference between the average storage elastic modulus and the average loss elastic modulus is preferably 5 to 500 Pa, more preferably 10 to 400 Pa, and still more preferably 20 to 200 Pa. The average storage elastic modulus is preferably 1 to 10000 Pa, more preferably 1 to 1000 Pa, still more preferably 10 to 800 Pa, further preferably 10 to 600 Pa, further preferably 20 to 400 Pa, further preferably 25 to 300 Pa, further preferably 25 to 200 Pa, further preferably 30 to 200 Pa, further preferably 40 to 200 Pa, and further preferably 50 to 200 Pa. The average loss elastic modulus only needs to be smaller than the average storage elastic modulus, and is preferably 0.1 to 100 Pa, more preferably 0.1 to 80 Pa, still more preferably 1 to 60 Pa, further preferably 2 to 40 Pa, further preferably 2.5 to 30 Pa, further preferably 2.5 to 20 Pa, further preferably 3 to 20 Pa, further preferably 4 to 20 Pa, and further preferably 5 to 20 Pa.

[0029] Next, we will explain condition (2) in more detail. Condition (2) is an indicator of so-called thixotropy. The viscosity ratio in condition (2) can be determined by measuring the shear rate dependence of viscosity. More specifically, it can be calculated by the following method. -Method for measuring the shear rate dependence of a CNT dispersion composition- For composition A, the shear rate dependence of viscosity is measured at 25°C in the range of shear rates from 1000 / sec to 0.01 / sec. For the measurement, a rheometer (HAAKE MARS40 (trade name), manufactured by Thermo Fisher Scientific) and a cone with a diameter of 60 mm and an angle of 4° are used. From the obtained flow curve, the viscosity Vα at a shear rate of 0.01 / sec and the viscosity Vβ at a shear rate of 1000 / sec are determined, and the viscosity ratio is obtained by (formula I) above. The viscosity ratio is preferably 270 or higher, more preferably 300 or higher, and even more preferably 400 or higher. There is no particular upper limit to the viscosity ratio. For example, 600 is practical. Therefore, the viscosity ratio can be 250 to 600, 300 to 600, or 400 to 600.

[0030] The viscosity Vα at a shear rate of 0.01 / second is not particularly limited as long as the above (2) is satisfied. Vα can be 10,000 to 500,000 mPa·s, and can also be 100,000 to 400,000 mPa·s. The viscosity Vβ at a shear rate of 1,000 / second is not particularly limited as long as the above (2) is satisfied. Vβ can be 10 to 4,000 mPa·s, and can also be 20 to 3,000 mPa·s.

[0031] The components constituting the CNT dispersion composition of the present invention will be described in more detail below.

[0032] <Single-walled carbon nanotubes (WYSIW)> Single-walled carbon nanotubes (WYSIW) are tubular structures made up of only carbon atoms, with a single layer of tubes. Generally, the diameter of the tubes is about 0.4 to 4.0 nm, and the length is about 0.1 to 10.0 μm. Single-walled carbon nanotubes may contain residual metals (Fe, Al, Co, etc.) used as catalysts during the preparation of WYSIW, but it is preferable to have as little residual metal as possible. Generally, it is preferable that the amount of residual metal in WYSIW is less than 8000 ppm. Single-walled carbon nanotubes 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.

[0033] <Dispersant> The dispersant is not limited to low-molecular-weight compounds or high-molecular-weight compounds, as long as it can disperse single-walled carbon nanotubes (WNTs) 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 adsorb appropriately to the WNTs is preferred.

[0034] The above dispersant preferably contains at least one of the following (hereinafter also referred to as an adsorbent group): an amino group, a carboxyl group, a phosphate group, a phosphonic acid group, a sulfo group, a hydroxyl group, a carbamoyl group, an alkyl group, and an aromatic group. Such adsorbent groups exhibit adsorption to single-walled carbon nanotubes (WNTs) and contribute to improving the affinity between the dispersant and the WNTs. 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 above carboxyl group, phosphate group (-OP(=O)(-OH)OH), phosphonic acid group (-P(=O)(-OH)OH), and sulfo group may be in the form of a salt. They may also be in the form of an acid anhydride. In other words, in the present 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 phosphate groups, phosphonic acid groups, and sulfo groups. 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. When the amino group of the carbamoyl group is a substituted amino group, the substituent of 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 above alkyl group means 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 aromatic group means 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 aromatic group may have substituents. Therefore, the aromatic hydrocarbon group and the aromatic heterocyclic group may also have substituents. The aromatic ring constituting the aromatic group may be a monocyclic or fused ring, with the monocyclic being preferred. The aromatic group is particularly preferably a phenyl group.

[0035] 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.

[0036] When the dispersant is a polymer compound, the polymer compound may be a polymer (hereinafter referred to as polymer (I)). This polymer may be a homopolymer or a copolymer, and 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, and a polymer produced by addition polymerization (a polymer whose main chain is composed of carbon-carbon bonds) is preferred. Examples of polymers having carbon-carbon bonds in their main chain include fluoropolymers (fluorine-containing polymers), hydrocarbon polymers, vinyl polymers, (meth)acrylic polymers, etc. Polymer (I) may be in a form having the above-mentioned adsorbent groups or in a form without the above-mentioned adsorbent groups. When polymer (I) is in a form having adsorbent groups, the target polymer (I) can be obtained by introducing the above-mentioned adsorbent groups into the polymer produced by addition polymerization or a polymer produced by condensation polymerization. Examples of monomers for introducing the above-mentioned adsorbent groups include (meth)acrylic acid; maleic anhydride; (meth)acrylamide; styrene; vinyl compounds or acrylic compounds having an amino group, phosphate group, phosphonic acid group, sulfo group, hydroxyl group, or carbamoyl group. Polymer (I) may also preferably have components derived from alkyl (meth)acrylates, aryl (meth)acrylates, N-vinylpyrrolidone, N-alkylmaleimide, etc. The alkyl group of alkyl (meth)acrylates preferably has 1 to 20 carbon atoms, more preferably 5 to 20, even more preferably 10 to 20, and even more preferably 15 to 20 carbon atoms. The alkyl group of N-alkylmaleimide preferably has 1 to 15 carbon atoms, more preferably 2 to 12, and even more preferably 2 to 8 carbon atoms. The alkyl group of N-alkylmaleimide may also preferably be 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).From the viewpoint of reducing the resistance in the electrode, polymer (I) is preferably not a fluoropolymer. Polymer (I) may be modified with an acid or the like.

[0037] It is also preferable that polymer (I) has a form including a lactone ring structure or an aliphatic hydrocarbon ring structure in its structure. Polymer (I) including a lactone ring structure or an aliphatic hydrocarbon ring structure preferably contains the following component (a) in its structure. When polymer (I) is in a form having component (a), the target polymer (I) can be obtained by introducing the component (a) into the polymer obtained by the addition polymerization or the polymer obtained by the condensation polymerization described above. Polymer (I) having component (a) can be obtained, for example, by using the above-mentioned monomer for introducing the adsorptive group and, if necessary, a monomer that derives a structure represented by any of the following formulas (i) to (iii).

[0038] — Component (a) — The structure of component (a) is represented by any one of the following (i) to (iii).

[0039]

[0040] In (i) to (iii) above, R １１ and R ２１ each represent a hydrogen atom or an alkyl group. R １１ and R ２１ are preferably an alkyl group having 1 to 6 carbon atoms, more preferably an alkyl group having 1 to 4 carbon atoms, still more preferably methyl or ethyl, and even more preferably methyl. When R １１ and R ２１ are an alkyl group, a hetero atom (e.g., an oxygen atom, a sulfur atom, a nitrogen atom) may be incorporated in the middle of the carbon chain of the alkyl group. When R １１ and R ２１ are an alkyl group, a halogen atom may be bonded in place of a hydrogen atom of the alkyl group. As R １１ and R ２１ , a hydrogen atom, methyl or methoxymethyl is preferable, and a hydrogen atom is more preferable.

[0041] R １２R indicates a substituent containing a lactone ring structure. ２２ and R ３ This indicates a substituent containing a lactone ring structure or an aliphatic hydrocarbon ring structure.

[0042] The lactone ring structure described above is preferably a 4- to 7-membered ring, more preferably a 5- to 6-membered ring, and even more preferably a 5-membered ring. Note that when referring to a Z-membered ring (where Z is a number), Z represents the number of ring-constituting atoms directly making up the ring. Therefore, the oxygen atom of the carbonyl group in the lactone ring structure (the oxygen atom bonded to the ring-constituting carbon atom) is not a ring-constituting atom. The lactone ring structure may contain multiple oxygen atoms (preferably two) as ring-constituting atoms. The lactone ring structure may also include a structure in which other ring structures are fused to the 4- to 7-membered lactone ring structure in the form of a bicyclo or spiro structure. It is preferable that the lactone ring structure is not a fused ring structure. The lactone ring structure may have substituents. Examples of substituents that the lactone ring structure may have include alkyl groups having 1 to 4 carbon atoms. １２ , R ２２ , and R ３ Examples of possible lactone ring structures include a γ-butyrolactone ring (5-membered ring), a δ-valerolactone ring (6-membered ring), a mevalonolactone ring (6-membered ring), a 5,3-bicyclo[2.2.1]heptanecarbolactone ring (a structure in which a bicyclo[2.2.1]heptane ring is fused to a 5-membered lactone ring). Substituents containing the above lactone ring structure only need to have a lactone ring structure, and may be a ring group obtained by removing one hydrogen atom from the lactone ring structure, or a group in which the lactone ring structure is bonded to a linking group. Examples of linking groups include aliphatic hydrocarbon groups, which may have an oxygen atom. More specifically, alkylene groups, -O-, -COO-, -OCO-, -CO-, or divalent linking groups combining these are preferred. The number of carbon atoms in the linking group is preferably 1 to 6, more preferably 1 to 4, and even more preferably 1 or 2.

[0043] The above aliphatic hydrocarbon ring structure may be a cycloalkane structure or a cycloalkene structure, with the cycloalkane structure being preferred. Furthermore, the above aliphatic hydrocarbon ring structure may be a monocyclic structure or a condensed ring structure formed by the condensation of monocyclic aliphatic hydrocarbon rings. For example, it may be a cyclo ring, a dicyclo ring, or a tricyclo ring structure. A monocyclic structure is preferred for the aliphatic hydrocarbon ring structure. The number of carbon atoms in the aliphatic hydrocarbon ring structure is preferably 4 to 20, more preferably 4 to 15, and even more preferably 5 to 10. The aliphatic hydrocarbon ring structure may have substituents. Examples of substituents that the aliphatic hydrocarbon ring structure may have include C1 to C4 alkyl groups, C1 to C4 alkoxy groups, and halogen atoms (e.g., fluorine atoms, chlorine atoms, bromine atoms). It is preferable that the aliphatic hydrocarbon ring structure does not have substituents. １２ , R ２２ , and R ３ Examples of aliphatic hydrocarbon ring structures that can be possessed include cyclopentane, cycloheptane, and adamantane. Substituents containing the above aliphatic hydrocarbon ring structure only need to have an aliphatic hydrocarbon ring structure, and may be a ring group obtained by removing one hydrogen atom from an aliphatic hydrocarbon ring structure, or a structure in which an aliphatic hydrocarbon ring structure is bonded to a linking group. Examples of linking groups include aliphatic hydrocarbon groups, and these aliphatic hydrocarbon groups may have an oxygen atom. More specifically, the linking group is preferably an alkylene group, -O-, -COO-, -OCO-, -CO-, or a divalent linking group that combines these. The number of carbon atoms in the linking group is preferably 1 to 6, more preferably 1 to 4, and even more preferably 1 or 2.

[0044] R １２ The substituent is preferably a ring group obtained by removing one hydrogen atom from a non-fused lactone ring structure, or a substituent in which a fused lactone ring structure is bonded to a linking group, more preferably a ring group obtained by removing one hydrogen atom from a non-fused lactone ring structure, even more preferably a ring group obtained by removing one hydrogen atom from a mevalonolactone ring structure, and a ring group obtained by removing one hydrogen atom from γ-butyrolactone. ２２The ring group is preferably obtained by removing one hydrogen atom from an aliphatic hydrocarbon ring structure, more preferably obtained by removing one hydrogen atom from an aliphatic hydrocarbon ring having 5 to 10 carbon atoms, even more preferably obtained by removing one hydrogen atom from a monocyclic aliphatic hydrocarbon ring having 5 to 7 carbon atoms, and cyclopentyl is even more preferred. ３ The ring group is preferably obtained by removing one hydrogen atom from an aliphatic hydrocarbon ring structure, and cyclohexyl is more preferred.

[0045] The substituent containing the above-mentioned lactone ring structure or aliphatic hydrocarbon ring structure preferably has a chemical formula weight of 40 to 400, more preferably 40 to 250, even more preferably 50 to 200, and still more preferably 70 to 150.

[0046] The structure of component (a) is preferably (i) or (ii), and more preferably (ii).

[0047] The structures represented by formulas (i) to (iii) above are shown below as preferred specific examples of monomers that lead to each structure, but the present invention is not limited to these specific examples.

[0048] (i) monomers that lead to the constituent components

[0049]

[0050] monomers that derive the constituent components represented by (ii)

[0051]

[0052] monomers that derive the constituent components represented by (iii)

[0053]

[0054] Polymer (I) preferably contains 20% by mass or more of component (a), more preferably 30% by mass or more, and even more preferably 40% by mass or more, from the viewpoint of improving dispersibility and oxidation resistance. The upper limit is not particularly limited and can be 80% by mass. Therefore, the content of component (a) in polymer (I) is preferably 20 to 80% by mass, more preferably 30 to 70% by mass, and even more preferably 40 to 60% by mass.

[0055] In the present invention, the polymer (I) is preferably polyvinylpyrrolidone (preferably a polymer of N-vinyl-2-pyrrolidone); a copolymer of the vinylpyrrolidone and an alkyl (meth)acrylate; a copolymer of a monomer that leads to the component represented by (i) (e.g., γ-butyrolactone acrylate) and an alkyl (meth)acrylate; or a copolymer of a monomer that leads to the component represented by (iii) (e.g., cyclohexylmaleimide) and an alkyl (meth)acrylate. In the copolymer of vinylpyrrolidone and an alkyl (meth)acrylate, the vinylpyrrolidone-derived component is preferably 20 to 80% by mass, more preferably 30 to 70% by mass, and even more preferably 40 to 60% by mass. In a copolymer of a monomer (e.g., γ-butyrolactone acrylate) that leads to the component represented by (i) and an alkyl (meth)acrylate, the monomer-derived component that leads to the component represented by (i) is preferably 20 to 80% by mass, more preferably 30 to 70% by mass, and even more preferably 40 to 60% by mass. In a copolymer of a monomer (e.g., cyclohexylmaleimide) that leads to the component represented by (iii) and an alkyl (meth)acrylate, the monomer-derived component that leads to the component represented by (iii) is preferably 20 to 80% by mass, more preferably 30 to 70% by mass, and even more preferably 40 to 60% by mass.

[0056] From the viewpoint of reducing the resistance within the electrode, it is preferable that polymer (I) does not have an acetal structure.

[0057] 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.

[0058] 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.

[0059] The dispersant may be soluble in the dispersion medium or insoluble, but it is preferable that it be soluble in the dispersion medium.

[0060] The dispersant is preferably insoluble in the non-aqueous electrolyte. By using a dispersant insoluble in the non-aqueous electrolyte, even when the CNT dispersion composition of the present invention is used to form the electrode active material layer to prepare a non-aqueous electrolyte secondary battery, the dissolution of the dispersant into the non-aqueous electrolyte can be suppressed. In other words, the decrease in ionic conductivity of the non-aqueous electrolyte over time can be suppressed. As a result, the rapid charging performance is further improved, and a high level of rapid charging performance can be maintained even after long-term storage. Here, insolubility means that when 0.5 g of the dispersant is added to 10 ml of the non-aqueous electrolyte, the turbidity measured with a turbidimeter (haze meter NDH4000 (product name), manufactured by Nippon Denshoku Industries Co., Ltd.) is 50 or higher. The non-aqueous electrolyte used to determine "insolubility" above is a mixed solvent of ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) in a mass ratio of EC:DMC:EMC = 3:4:3, with LiPF as the lithium salt. ６ Prepare a non-aqueous electrolyte by mixing the components to a concentration of 1 M.

[0061] Commercially available dispersants can also be used, for example, the following products: ET3004, ET3034 (all trade names, manufactured by BYK Corporation), PVP-K30, PVP-K25, PVP-K90 (all trade names, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), Methylcellulose 15 (trade name, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), CMC#1140 (trade name, manufactured by Daicel Corporation), #7208 (trade name, manufactured by Kureha Corporation), H-NBR (trade name, manufactured by Zeon Corporation).

[0062] 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.

[0063] - 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 value measured by the following method shall be used for the measurement of the weight-average molecular weight. 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) Column: TOSOH TSKgel guardcolumn SuperHZ-L, Super HZM-H, Super HZ4000, Super HZ2000 (product name, manufactured by Tosoh Corporation) Carrier: THF (tetrahydrofuran) solution Measurement temperature: 40℃ Carrier flow rate: 0.35 ml / min Sample concentration: 0.2 mass% Detector: RI (refractive index) detector

[0064] The content of the dispersant in the CNT dispersion composition is preferably 10 to 100 parts by mass, more preferably 10 to 70 parts by mass, even more preferably 10 to 50 parts by mass, even more preferably 10 to 30 parts by mass, even more preferably 10 to 25 parts by mass, and even more preferably 10 to 20 parts by mass, per 100 parts by mass of single-walled carbon nanotubes. The content of the dispersant 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 even more preferably 0.10 to 1.50% by mass.

[0065] <Dispersion Medium> The dispersion medium constituting the CNT dispersion composition of the present invention is water or an organic solvent, and a non-aqueous solvent is preferred. In the present invention, "non-aqueous solvent" means a solvent that substantially does not contain 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 the present 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 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. Specific examples of preferred organic solvents include, for example, ethylene carbonate, fluorinated ethylene 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, Examples include 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.These may be used individually or in combination of two or more. In the present invention, the dispersion medium is preferably water, N-methylpyrrolidone (NMP), N-ethylpyrrolidone, or cyclohexanone, and more preferably NMP.

[0066] In the CNT dispersion composition, the amount of the dispersion medium is preferably such that the total amount of the single-walled CNTs and the dispersant is 100% by mass.

[0067] [Method for preparing a carbon nanotube dispersion composition] The CNT dispersion composition of the present invention can be prepared by mixing single-walled carbon nanotubes (WYNATs), a dispersant, and a dispersion medium, and dispersing the WYNATs in the dispersion medium by the action of the dispersant so that the viscoelastic properties satisfy at least one of (1) and (2) above. The apparatus used for this mixing and / or dispersion, and the conditions for mixing and / or dispersion, are not particularly limited as long as they can be controlled so that the viscoelastic properties of the CNT dispersion composition satisfy at least one of (1) and (2) above. The mixing and / or dispersion method is not particularly limited, and the materials may be mixed and dispersed all at once, or mixed and dispersed sequentially.

[0068] The single-walled carbon nanotubes (WNTs) may be subjected to grinding or crushing (hereinafter collectively referred to as "grinding") before mixing with the dispersant and dispersion medium. This grinding can be carried out, for example, using a powder processing device. By performing the grinding multiple times or for an extended period, the average storage modulus of the CNT dispersion composition usually increases, and the viscosity ratio in the CNT dispersion composition tends to increase as the grinding is performed multiple times or for an extended period. The conditions for the grinding depend on the characteristics of the WNTs used, but for example, when using a high-speed rotary grinder, it is preferable to grind at 20,000 to 50,000 rpm for about 10 to 30 seconds.

[0069] The satisfaction of conditions (1) and (2) above can be controlled by optimizing the mixing conditions of the single-walled carbon nanotubes (WNTs), the dispersant, and the dispersion medium. For example, it is preferable to disperse the WNTs in the dispersion medium by controlling the mixing conditions using a planetary ball mill, a thin-film swirling high-speed mixer, etc. For example, by not performing the dispersion too many times or for a short time, the average fiber length of the WNTs in the CNT dispersion composition tends to increase. Also, by not performing the dispersion too many times or for a short time, the strain rate at which the intersection IP of condition (1) is located tends to increase. Also, by not performing the dispersion too many times or for a short time, the viscosity ratio of condition (2) tends to increase. When using a bead mill, it is preferable to use beads with a diameter of 1 to 5 mm. By reducing the diameter of the beads, the strain rate at which the intersection IP of condition (1) exists tends to increase. Also, by reducing the diameter of the beads, the viscosity ratio of condition (2) usually tends to increase. The material of the beads is not particularly limited, but zirconia is preferred. When using a bead mill, dispersion is preferably carried out for about 1 to 20 hours, more preferably for 1 to 15 hours, even more preferably for 1 to 10 hours, even more preferably for 1 to 8 hours, and even more preferably for 1 to 6 hours. The shorter the dispersion time, the better the average fiber length of the single-walled CNTs can be maintained, the larger the strain rate at which the above intersection IP is located in condition (1), and the larger the viscosity ratio in condition (2). When using a bead mill, it is preferable to use beads with a diameter of 1 to 5 mm and to mix at 500 to 1000 rpm for about 1 to 20 hours.

[0070] 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 the electrode slurry so that the single-layer CNT 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 to prepare an electrode slurry for forming a positive electrode active material layer.

[0071] [Electrode Slurry] 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. In addition to the electrode active material, the electrode slurry of the present invention may optionally contain a binder, ionic liquid, thickener, defoamer, leveling agent, dehydrating agent, antioxidant, etc. 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 a solvent further. 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, and those commonly used in non-aqueous electrolyte secondary batteries can be appropriately adopted. 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 O ２ This 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 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.

[0072] [Method for Manufacturing Electrode Slurry] The method for manufacturing electrode slurry of the present invention comprises 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 process as for manufacturing a conventional electrode slurry can be employed.

[0073] [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 the present invention, when simply referred to as "electrode sheet," it encompasses 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 a secondary battery) and the form in which it is an electrode material before being incorporated into a non-aqueous electrolyte secondary battery. That is, the structure (area, thickness, etc.) of the electrode sheet 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 is an electrode sheet having an electrode active material layer formed using an electrode slurry containing the CNT dispersion composition of the present invention described above, and the electrode active material layer may be a sheet formed on a substrate such as a current collector, or a sheet that does not have a substrate and is formed only of an electrode active material layer (negative electrode active material layer or positive electrode active material layer). This electrode sheet is usually a sheet with an electrode active material layer laminated on a current collector. The electrode sheet of the present invention may have other layers, such as a protective layer such as a release sheet or a coating layer. 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, and it is preferable that it be a positive electrode sheet.

[0074] 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 carrier and is usually in the form of a film sheet. The current collector can be appropriately selected according to the electrode active material. Examples of constituent materials for the positive electrode current collector include aluminum, aluminum alloy, stainless steel, nickel, titanium, etc., with aluminum or aluminum alloy being preferred. As a positive electrode current collector, a coating layer (thin film) may be formed by treating the surface of aluminum or stainless steel with carbon, nickel, titanium, or silver. Examples of constituent materials for the negative electrode current collector include aluminum, copper, copper alloy, stainless steel, nickel, titanium, etc., with aluminum, copper, copper alloy, or stainless steel being preferred. As a negative electrode current collector, a coating layer (thin film) may be formed by treating the surface of aluminum, copper, copper alloy, or stainless steel with carbon, nickel, titanium, or silver.

[0075] 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.

[0076] [Method for Manufacturing an Electrode Sheet] 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 manufacturing an electrode sheet in the ordinary. 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, the electrode slurry of the present invention can be applied to the electrode current collector as a substrate (may be applied via other layers) to form a coating film, which can then be 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 ordinary methods can be used.

[0077] [Non-aqueous 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 (positive electrode or negative electrode). 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.

[0078] The following describes the structure of a typical non-aqueous electrolyte secondary battery. Figure 2 is a schematic cross-sectional view showing the stacked structure of a typical non-aqueous electrolyte secondary battery 10, including the operating parts when the battery is in operation. The non-aqueous electrolyte secondary battery 10 has a stacked structure (hereinafter also referred to as an electrode stack) in the following order when viewed from the negative electrode side: negative electrode current collector 1, negative electrode active material layer 2, separator 3, positive electrode active material layer 4, and positive electrode current collector 5. The negative electrode active material layer 2 and positive electrode active material layer 4 and the space between them are filled with a non-aqueous electrolyte (not shown) and separated by a separator 3. The separator 3 has pores and, in the normal operating state of the battery, functions as a positive and negative electrode separation membrane that insulates the positive and negative electrodes while allowing the electrolyte and ions to pass through these pores. With such a structure, for example, in the case of a lithium-ion secondary battery, during charging, electrons (e) pass through an external circuit to the negative electrode side. － ) is supplied, and at the same time lithium ions (Li) are supplied from the positive electrode via the electrolyte. ＋ ) move and accumulate on the negative electrode. On the other hand, during discharge, lithium ions (Li) accumulated on the negative electrode move and accumulate on the negative electrode. ＋ The discharge is returned to the positive electrode side via the electrolyte, and electrons are supplied to the working part 6. In the illustrated example, a light bulb is used for the working part 6, and it is designed to light up when discharge occurs. The secondary battery of the present invention has, in the above general non-aqueous electrolyte secondary battery, the electrode sheet of the present invention in place of at least one of the positive electrode active material layer 4 and the negative electrode active material layer 2, or in place of at least one of the positive electrode consisting of the positive electrode active material layer 4 and the positive electrode assembly 5 and the negative electrode consisting of the negative electrode active material layer 2 and the negative electrode current collector 1.

[0079] The secondary battery of the present invention is provided with the electrode sheet of the present invention as at least one of the electrodes of the secondary battery, but other than that, 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 and other components 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 such 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 as appropriate.

[0080] 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, and backup power supplies. It can also be used for 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.

[0081] [Method for Manufacturing a Non-Aqueous Electrolyte Secondary Battery] The method for manufacturing a non-aqueous electrolyte secondary battery of the present invention includes incorporating the electrode sheet of the present invention as at least one of the electrodes of the non-aqueous electrolyte secondary battery. Apart from using the electrode sheet of the present invention, the same process as for manufacturing a conventional non-aqueous electrolyte secondary battery can be employed.

[0082] The present invention will be described in more detail below based on examples. However, the present invention is not intended to be limited thereto.

[0083] [Preparation of Carbon Nanotube Dispersion Composition] 1. Preparation of Dispersant The following polymers were used as dispersants. Polymer P1: Polyvinylpyrrolidone (PVP-K30 (trade name), manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) Polymer P2: Copolymer of 50 parts by mass of vinylpyrrolidone and 50 parts by mass of stearyl acrylate Polymer P3: Copolymer of 50 parts by mass of γ-butyrolactone acrylate and 50 parts by mass of stearyl acrylate Polymer P4: Copolymer of 50 parts by mass of N-cyclohexylmaleimide and 50 parts by mass of stearyl acrylate Polymer P5: Carboxymethylcellulose (CMC#1140 (trade name), manufactured by Daicel Corporation) Polymer P6: Hydrogenated nitrile rubber (H-NBR (trade name), manufactured by Zeon Corporation)

[0084] Polymers P2 to P4 were prepared as follows: <Preparation of Polymer P2> 15 g of vinylpyrrolidone (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), 15 g of stearyl acrylate (manufactured by Tokyo Chemical Industries, Ltd.), 35 g of N-methylpyrrolidone (NMP) (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), and 0.1 g of polymerization initiator V-601 (trade name, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) were added to a 100 mL graduated cylinder to prepare monomer solution a. 35 g of N-methylpyrrolidone was added to a 300 mL three-necked flask and heated to 80°C under a nitrogen atmosphere while stirring. The monomer solution a was added dropwise to this three-necked flask over 2 hours. After the dropwise addition was complete, the temperature was raised to 90°C and stirred for 2 hours to obtain polymer solution S1 containing polymer P2, which includes a structure derived from vinylpyrrolidone and a structure derived from stearyl acrylate as component (a), and NMP as a dispersion medium. The weight-average molecular weight (Mw) of the obtained polymer P2 was 5800. The solid content concentration of the polymer solution S1 was 30% by mass.

[0085] <Preparation of Polymer P3> Polymer P3 and its polymer solution were prepared in the same manner as in the preparation of Polymer P2, except that 15 g of γ-butyrolactone acrylate was used instead of vinylpyrrolidone. The weight-average molecular weight (Mw) of the obtained Polymer P3 was 6200.

[0086] <Preparation of Polymer P4> Polymer P4 and its polymer solution were prepared in the same manner as in the preparation of Polymer P2, except that 15 g of N-cyclohexylmaleimide was used instead of vinylpyrrolidone. The weight-average molecular weight (Mw) of the obtained Polymer P4 was 6000.

[0087] The solubility of P1 to P6 in non-aqueous electrolytes was measured as described above, and the results are shown in Table 1. Table 1 also shows whether P1 to P6 have a lactone ring or an aliphatic hydrocarbon ring in their structure. When using P2 to P4 as dispersants in the preparation of the carbon nanotube dispersion compositions described below, the respective polymer solutions described above should be used to adjust the content of the dispersant (solids) in the carbon nanotube dispersion composition to the content shown in Table 1.

[0088] 2. Preparation of Carbon Nanotube Dispersion Compositions Using the above polymer as a dispersant, carbon nanotube dispersion compositions (CNT dispersion compositions) No. 1, 2, 4-6, 8, 10-12, 14, 15, 17-20, and 22-24 were obtained as follows. Furthermore, CNT dispersion compositions No. 3, 7, 9, 13, 16, and 21 can be prepared as follows. Details are described below.

[0089] <CNT dispersion compositions for Experiments No. 1 and No. 2: Starburst> Single-walled carbon nanotubes (TUBALL 01RW03 (product name), manufactured by OCSiAl) (hereinafter also referred to as single-walled carbon nanotubes 1; indicated as SWCNT in the table) were subjected to a crushing treatment once at 20,000 rpm for 30 seconds using a powder processing device (Dryst DB-100L (product name), manufactured by Sugino Machine Co., Ltd.). Next, the crushed single-walled carbon nanotubes (WNTs) 1, the dispersant shown in Table 1, and the dispersion medium were mixed so that the WNTs 1 and dispersant reached the concentrations shown in Table 1. The mixture was then mixed at 16,000 rpm for 120 seconds using a thin-film swirling high-speed mixer (Filmix-56L (trade name), manufactured by Primix Corporation). After that, the mixture was subjected to five dispersion treatments at 150 MPa using a wet high-pressure dispersion apparatus (Starburst (trade name), manufactured by Sugino Machine Co., Ltd.) to obtain the CNT dispersion compositions for Experiments No. 1 and No. 2. In the table, the above crushing and dispersion treatments are referred to as "Starburst".

[0090] <CNT Dispersion Composition for Experiment No. 3: Bead Dispersion 1> Single-walled CNT 1 is crushed once for 30 seconds at 20,000 rpm using a powder processing device (Drystrob DB-100L (product name), manufactured by Sugino Machine Co., Ltd.). Next, the crushed single-walled CNT 1, the dispersant listed in Table 1, and the dispersion medium are mixed so that the concentrations of single-walled CNT 1 and dispersant are as shown in Table 1. The mixture is then mixed for 16 hours at 650 rpm using 2 mm diameter beads (YTZ zirconia balls (product name), manufactured by Nikatoh) in a planetary ball mill (P-6 (product name), manufactured by Fritsch). In this way, the CNT dispersion composition for Experiment No. 3 can be prepared. In the table, the above crushing and dispersion treatment is indicated as "Bead Dispersion 1". (Hereafter, the name of the dispersion treatment will be shown next to the Experiment No.).

[0091] <CNT Dispersion Compositions of Experiment No. 4 and Experiment No. 21: Bead Dispersion 2> The carbon nanotube dispersion composition of Experiment No. 4 was obtained in the same manner as in Experiment No. 3, except that the dispersion time using a planetary ball mill was changed to 12 hours. The CNT dispersion composition of Experiment No. 21 can be prepared in the same manner as in Experiment No. 4, except that the dispersant is P3 and the single-walled CNTs 1, dispersant, and dispersion medium are mixed so that the concentrations of single-walled CNTs 1 and dispersant are as shown in Table 1.

[0092] <CNT dispersion composition of Experiment No. 5: Bead dispersion 3> The CNT dispersion composition of Experiment No. 5 was obtained in the same manner as in Experiment No. 3, except that the dispersion time using a planetary ball mill was changed to 10 hours.

[0093] <CNT dispersion composition of Experiment No. 6: Bead dispersion 4> The CNT dispersion composition of Experiment No. 6 was obtained in the same manner as in Experiment No. 3, except that beads with a diameter of 1 mm were used and the dispersion time using a planetary ball mill was changed to 10 hours.

[0094] <CNT dispersion composition of Experiment No. 7: Bead dispersion 5> The CNT dispersion composition of Experiment No. 7 can be prepared in the same manner as in Experiment No. 6, except that the dispersion time using a planetary ball mill is changed to 8 hours.

[0095] <CNT dispersion compositions of Experiment No. 8 and Experiment No. 22: Bead dispersion 6> The CNT dispersion composition of Experiment No. 8 was obtained in the same manner as in Experiment No. 6, except that the dispersion time using a planetary ball mill was changed to 6 hours. The CNT dispersion composition of Experiment No. 22 was obtained in the same manner as in Experiment No. 8, except that the dispersant and dispersion medium listed in Table 1 were used, and the single-walled CNT 1, dispersant and dispersion medium were mixed so that the concentrations of single-walled CNT 1 and dispersant were as listed in Table 1.

[0096] <CNT dispersion composition for Experiment No. 9: Bead dispersion 7> The CNT dispersion composition for Experiment No. 9 can be prepared in the same manner as in Experiment No. 6, except that the dispersion time using a planetary ball mill is changed to 2 hours.

[0097] <CNT dispersion composition of Experiment No. 10: Bead dispersion 8> The CNT dispersion composition of Experiment No. 10 was obtained in the same manner as in Experiment No. 6, except that the dispersion time using a planetary ball mill was changed to 1 hour.

[0098] <CNT dispersion compositions of Experiment No. 11, Experiment Nos. 12-20, 23-24: Bead dispersion 9> In Experiment No. 8, the CNT dispersion composition of Experiment No. 11 was obtained in the same manner as in Experiment No. 8, except that the decomposition treatment by dry strumming was performed twice. In Experiment No. 11, the CNT dispersion compositions of Experiments No. 12, 14, 15, 17-20, 23-24 were obtained in the same manner as in Experiment No. 11, except that the dispersant and dispersion medium listed in Table 1 were used, and the single-walled CNT 1, dispersant and dispersion medium were mixed so that the single-walled CNT 1 and dispersant were at the concentrations listed in Table 1. CNT dispersion compositions 13 and 16 can be prepared. In Experiment No. 24, multilayered CNTs (JENOTUBE 10B (trade name), manufactured by JEIO) (hereinafter also referred to as MWCNTs) were used instead of single-walled CNTs 1.

[0099] Table 1 shows the average fiber length of the CNTs contained in the CNT dispersion compositions for Experiments No. 1 to 24. The average fiber length was measured by the method described above.

[0100] For the CNT dispersion compositions of Experiments No. 1 to 24, the strain rates at which the intersection of the storage modulus and loss modulus, as determined according to condition (1), are located are shown in "Location of Intersection IP" in Table 1. Furthermore, Figure 1 shows a graph plotting the storage modulus and loss modulus based on strain-dependent measurements for composition A of the CNT dispersion composition of Experiment No. 6. Note that when plotting the storage modulus and loss modulus for composition A of the CNT dispersion compositions of Experiments No. 1 to 5 and 7 to 24, similar to Figure 1, the storage modulus shows a greater value than the loss modulus line in the region of strain rates smaller than the strain rate at which the intersection is located. The average storage modulus is shown in Table 1. Additionally, the viscosity ratios determined according to condition (2) are shown in Table 1. The determination methods for all of these are as described above.

[0101] [Evaluation of rapid charging performance and rapid charging performance after long-term storage] For electrode sheets and secondary batteries obtained using each of the CNT dispersion compositions in Experiments No. 1 to 24 described above, the rapid charging performance and rapid charging performance after long-term storage are summarized in Table 1. Rapid charging performance and rapid charging performance after long-term storage are evaluated by the following method. A charge / discharge evaluation device (TOSCAT3000 (product name), manufactured by Toyo System Co., Ltd.) is used as the test equipment.

[0102] <Battery Fabrication> (1) Preparation of Non-Aqueous Electrolyte E1> A mixed solvent of ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) in a mass ratio of EC:DMC:EMC = 3:4:3 is mixed with LiPF as the lithium salt. ６ (2) Preparation of positive electrode sheet NCM111 (LiNi) is used as the positive electrode active material. ０．３３ Co ０．３３ Mn ０．３３ O ２Mix 97.95 parts by mass of (manufactured by Toyoshima Seisakusho), the CNT dispersion composition listed in Table 1 as a conductive additive in an amount that results in a CNT content of 0.05 parts by mass, and 2 parts by mass of polyvinylidene fluoride (PVDF) (#7208 (trade name), manufactured by Kureha Corporation) as a binder, and stir at 2000 rpm for 360 seconds using a centrifugal planetary mixer (Awatori Rentaro (trade name), manufactured by Shinky Co., Ltd.) to prepare a positive electrode slurry. Coat one side of a 12 μm thick positive electrode current collector (aluminum foil) with the above positive electrode slurry and dry at 120°C until the dispersion medium has completely evaporated. Then, perform a pressing process 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 is 70 μm and the density is 3.1 g / cm³. ３ (3) Preparation of the negative electrode sheet The negative electrode active material (artificial graphite), styrene-butadiene copolymer (SBR) as a binder, carboxymethylcellulose (CMC) as a thickener, and water as a solvent are mixed in a mass ratio of negative electrode active material:SBR:CMC:water = 60:1.5:0.5:38 to obtain a negative electrode slurry. The negative electrode slurry is coated onto one side of a 12 μm thick negative electrode current collector (copper foil) and dried at 120°C until the solvent has completely evaporated. After that, a press process is performed using a roll press machine to obtain a sheet-like negative electrode (negative electrode sheet). The thickness of this negative electrode is approximately 180 μm. (4) Fabrication of a non-aqueous electrolyte secondary battery The obtained positive electrode sheet and negative electrode sheet are laminated with a separator in between to obtain an electrode laminate consisting of a positive electrode current collector - positive electrode active material layer - separator - negative electrode active material layer - negative electrode current collector. Aluminum tabs are attached to the ends of the positive electrode current collector and nickel tabs are attached to the ends of the negative electrode current collector using ultrasonic welding. This electrode stack is then housed in an aluminum laminate container to create a battery assembly. After injecting the non-aqueous electrolyte E1 with the injection port open, the injection port is sealed to enclose the container. In this way, a non-aqueous electrolyte secondary battery for evaluation testing is produced.

[0103] <Pre-test charging and discharging> The above secondary battery will be subjected to constant current-constant voltage (CC-CV) charging and constant current (CC) discharging under the following condition I. (Condition I) CC-CV charging: Current value 25mA, upper limit voltage 4.2V, cutoff current value 2.5mA CC discharging: Current value 25mA, cutoff voltage value 3.0V

[0104] <Rapid Charging Performance Evaluation> Rapid charging performance is evaluated using the discharge capacity retention rate as an indicator. After charging and discharging according to "Condition I" above, a piece of the laminate container is cut, and unwanted gases generated during charging and discharging according to "Condition I" are removed from each battery, and the container is resealed with a vacuum sealer. A rapid charging performance test is performed on the batteries that have been degassed after charging and discharging according to "Condition I" above, under the following conditions. Specifically, under "Charge / Discharge Condition II" below, the batteries are 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 are charged to 4.2V by CC charging and discharged to 3.0V by CC discharge to measure the discharge capacity after rapid charging. Furthermore, the discharge capacity retention rate is calculated using the following formula and evaluated according to the evaluation criteria below. (Charge / Discharge Condition II: Reference Discharge Capacity) CC-CV Charging: Current 25mA, Upper Voltage 4.2V, End Current 2.5mA CC Discharge: Current 25mA, End Voltage 3.0V (Charge / Discharge Condition III: Discharge Capacity After Rapid Charging) CC Charging: Current 1500mA, Upper Voltage 4.2V CC Discharge: Current 25mA, End Voltage 3.0V Discharge Capacity Retention Rate (%) = Discharge Capacity After Rapid Charging / Reference Discharge Capacity × 100 -Evaluation Criteria- A: 70% or more B: 65% or more, less than 70% C: 60% or more, less than 65% D: 55% or more, less than 60% E: 50% or more, less than 55% F: 45% or more, less than 50% G: Less than 45%

[0105] <Method for Evaluating Rapid Charging Performance After Long-Term Storage> Rapid charging performance after long-term storage is evaluated using the discharge capacity retention rate after long-term storage as an indicator. After the lithium-ion secondary battery following the above <Rapid Charging Performance Evaluation> is stored at 45°C and 50% relative humidity for 50 days, the rapid charging performance after long-term storage is evaluated in the same manner as the above <Rapid Charging Performance Evaluation>. -Evaluation Criteria- A: 70% or more B: 65% or more, less than 70% C: 60% or more, less than 65% D: 55% or more, less than 60% E: 50% or more, less than 55% F: 45% or more, less than 50% G: Less than 45%

[0106] The results obtained are shown in Table 1.

[0107]

[0108] SWCNT: Single-walled carbon nanotube MWCNT: Multi-walled carbon nanotube "Electrolyte solubility" of the dispersant: Indicates "Soluble" if dissolved in the electrolyte used in battery fabrication, and "Insoluble" if not dissolved. "Lactone ring or aliphatic hydrocarbon ring" of the dispersant: Indicates "Present" if the dispersant contains a lactone ring or aliphatic hydrocarbon ring in its structure, and "Absent" if it does not. DP ratio: Ratio of dispersant content to 100 parts by mass of single-walled carbon nanotube NMP: N-methylpyrrolidone (NMP) (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) Regarding the dispersion method: "Starburst": Disintegration treatment using the above starburst "Bead dispersion 1-9": Bead dispersion 1-9 Average fiber length: Average fiber length of cellulose fibers Position of intersection IP: Strain rate at which the intersection IP of condition (1) above is located

[0109] Experiments No. 1-5, 21, and 22, in which the intersection of the storage modulus and the loss modulus lies at a strain rate of less than 10% and the viscosity ratio is less than 250 (neither condition (1) nor (2) is met), exhibit poor rapid charging properties and rapid charging properties after long-term storage. The same is true when MWCNTs are used (experiment No. 24). On the other hand, the CNT dispersion compositions of Experiments No. 6-20 and 23, which maintain a cellulose fiber length of 2.5 μm and satisfy both conditions (1) and (2), all exhibit excellent rapid charging properties and rapid charging properties after long-term storage.

[0110] Although we have described the present invention along with its embodiments, we do not intend to limit our invention in any detail of the description unless specifically designated, and we believe that it should be interpreted broadly without contradicting the spirit and scope of the invention as set forth in the appended claims.

[0111] This application claims priority based on Japanese Patent Application No. 2025-054452, filed in Japan on 27 March 2025, the contents of which are incorporated herein by reference as part of this specification.

[0112] 10 Non-aqueous electrolyte secondary battery 1 Negative electrode current collector 2 Negative electrode active material layer 3 Separator 4 Positive electrode active material layer 5 Positive electrode current collector 6 Working part (light bulb)

Claims

1. A carbon nanotube dispersion composition comprising single-walled carbon nanotubes, a dispersant, and a dispersion medium, wherein the content of single-walled carbon nanotubes in the dispersion composition is 0.40% by mass or more, and the average fiber length is 2.5 μm or more, and composition A, obtained by reducing the content of single-walled carbon nanotubes to 0.40% by mass, either as is or by diluting the dispersion composition with the same type of dispersion medium, satisfies at least one of the following conditions (1) and (2): Condition (1): In the measurement of the strain dependence of the storage modulus and loss modulus of composition A, the strain rate at the intersection of the storage modulus and the loss modulus is 10% or more, and the storage modulus is greater than the loss modulus in the region where the strain rate is smaller than the strain rate at the intersection. Condition (2): In the measurement of the shear rate dependence of the viscosity of composition A, the viscosity ratio represented by the following formula (I) is 250 or more. Viscosity ratio = (Viscosity Vα at shear rate 0.01 / sec) / (Viscosity Vβ at shear rate 1000 / sec) ... (Equation I) 2. The carbon nanotube dispersion composition according to claim 1, wherein the average value of the storage modulus of composition A in the range of strain rate of 0.01% to 0.1% is 25 to 200 Pa.

3. The carbon nanotube dispersion composition according to claim 1, wherein the average fiber length of the single-walled carbon nanotubes in the dispersion composition is 10.0 μm or less.

4. The carbon nanotube dispersion composition according to claim 1, wherein the dispersant is insoluble in a non-aqueous electrolyte.

5. The carbon nanotube dispersion composition according to claim 1, wherein the amount of the dispersant in the dispersion composition is 10 to 70 parts by mass per 100 parts by mass of the single-walled carbon nanotube.

6. The carbon nanotube dispersion composition according to claim 1, wherein the dispersant comprises a lactone ring structure or an aliphatic hydrocarbon ring structure.

7. The carbon nanotube dispersion composition according to claim 1, wherein the content of the single-walled carbon nanotube in the dispersion composition is 1.20% by mass or more.

8. An electrode slurry comprising a carbon nanotube dispersion composition according to any one of claims 1 to 7 and an electrode active material.

9. An electrode sheet having an electrode active material layer formed using the electrode slurry described in claim 8.

10. A non-aqueous electrolyte secondary battery having the electrode sheet described in claim 9 as an electrode.

11. A method for producing an electrode slurry, comprising mixing a carbon nanotube dispersion composition according to any one of claims 1 to 7 with an electrode active material.

12. A method for manufacturing an electrode sheet, comprising forming an electrode active material layer using the electrode slurry described in claim 8.

13. A method for manufacturing a non-aqueous electrolyte secondary battery, comprising incorporating the electrode sheet described in claim 9 as an electrode.

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