Carbon nanotube dispersion and preparation method therefor

Abstract

The present invention relates to a carbon nanotube dispersion having low viscosity and little change in viscosity over time, the carbon nanotube dispersion comprising carbon nanotubes, a dispersant, and a dispersion medium, wherein the dispersant includes a first dispersant and a second dispersant in a weight ratio of 100: 10 to 90, the first dispersant is an N atom-containing dispersant, the second dispersant is a compound including, in the molecular structure thereof, a sulfone group, a hydroxyl group, and an aromatic ring, and a weight ratio of the carbon nanotubes and the dispersant is 100: 25 to 500.

Description

Carbon nanotube dispersion and method for producing the same Cross-citation with related applications This application claims the benefit of priority to Korean Patent Application No. 10-2023-0085868, filed July 3, 2023, the entire contents of which are incorporated herein by reference. Technology field The present invention relates to a carbon nanotube dispersion and a method for producing the same, and more specifically, to a carbon nanotube dispersion having low viscosity and little change in viscosity over time, and a method for producing the same. With the increasing technological development and demand for mobile devices, the demand for secondary batteries as an energy source is rapidly increasing. Among these secondary batteries, lithium secondary batteries, which boast high energy density and voltage, long cycle life, and low self-discharge rates, are commercialized and widely used. Furthermore, active research is being conducted on methods to improve electrode density and produce electrodes with higher energy density per unit volume as electrodes for these high-capacity lithium secondary batteries. In general, high-density electrodes are formed by molding electrode active material particles having a size of several μm to several tens of μm using a high-pressure press. During the molding process, the particles may be deformed and the space between the particles may be reduced, so that the electrolyte permeability is likely to deteriorate. To address the above issues, conductive materials with superior electrical conductivity and strength are used during electrode manufacturing. These conductive materials are positioned between the electrode active materials, and even during the molding process, they maintain micropores between the active material particles, facilitating the penetration of the electrolyte. Their superior electrical conductivity reduces electrode resistance. Among these conductive materials, carbon nanotubes, a fibrous carbon-based conductive material that can further reduce electrode resistance by forming electrically conductive paths within the electrode, are increasingly being used. Carbon nanotubes, a type of microscopic carbon fiber, are tubular carbon fibers with a diameter of less than 1 ㎛. Their unique structure, resulting in high conductivity, tensile strength, and heat resistance, has raised expectations for practical application in various fields. However, carbon nanotubes have low dispersibility and are prone to agglomeration due to the strong van der Waals forces between them due to their high surface area. To address these issues, mechanical dispersion techniques, such as ultrasonic treatment, have been proposed to disperse carbon nanotubes in a dispersion medium. However, mechanical dispersion techniques suffer from the problem of carbon nanotubes agglomerating immediately after ultrasonic irradiation. Accordingly, there is a need to develop a method for producing a carbon nanotube dispersion that can improve the dispersibility of carbon nanotubes, while having low viscosity and suppressing the increase in viscosity over time. The present invention is intended to solve the problems of the above-mentioned prior art, and to provide a carbon nanotube dispersion having excellent dispersibility, low viscosity, and little change in viscosity over time by including a compound containing an N atom and a compound containing a sulfonic group, a hydroxyl group, and an aromatic ring in a molecular structure at a certain weight ratio and a certain content. In addition, the present invention aims to provide a negative electrode slurry composition for a lithium secondary battery comprising the carbon nanotube dispersion. In addition, the present invention aims to provide a method for producing the carbon nanotube dispersion. To solve the above problem, the present invention provides a carbon nanotube dispersion. [1] The present invention is a carbon nanotube dispersion comprising carbon nanotubes, a dispersant, and a dispersion medium, wherein the carbon nanotubes have a specific surface area (BET) of 800 m 2 / g or less, and the dispersion comprises a first dispersant and a second dispersant in a weight ratio of 100:10 to 90, the first dispersant is a compound containing an N atom, the second dispersant is a compound containing all of a sulfonic group, a hydroxyl group, and an aromatic ring, and the weight ratio of the carbon nanotubes and the dispersant is 100:25 to 500. [2] In the present invention, in the above [1], the specific surface area (BET) of the carbon nanotube is 200 m 2 / g or more than 800 m 2 / g or less carbon nanotube dispersion is provided. [3] The present invention provides a carbon nanotube dispersion according to [1] or [2], wherein the carbon nanotube is a multi-walled carbon nanotube. [4] The present invention provides a carbon nanotube dispersion, wherein the carbon nanotube is contained in an amount of 0.1 to 7 parts by weight based on 100 parts by weight of the carbon nanotube dispersion in any one of the above [1] to [3]. [5] The present invention provides a carbon nanotube dispersion, wherein in any one of the above [1] to [4], the first dispersant is at least one selected from the group consisting of polyvinylpyrrolidone, polyacrylic acid hydrazide, poly-N-vinyl-5-methoxazolidon, N-alkyl polyimine, N-acetyl polyimine, polyacrylamide, poly-L-lysine hydrobromide, benzyl-dodecyl-dimethylammonium chloride, and polyethylenimine. [6] The present invention provides a carbon nanotube dispersion according to any one of the above [1] to [5], wherein the second dispersant is a lignosulfonate compound. [7] The present invention provides a carbon nanotube dispersion according to any one of the above [1] to [6], wherein the second dispersant is sodium lignosulfonate, calcium lignosulfonate or a mixture thereof. [8] The present invention provides a carbon nanotube dispersion comprising a first dispersant and a second dispersant in a weight ratio of 100:15 to 75 in any one of the above [1] to [7]. [9] The present invention provides a carbon nanotube dispersion in which the weight ratio of the carbon nanotube and the dispersant is 100:25 to 150 in any one of the above [1] to [8].

[0010] The present invention provides a carbon nanotube dispersion in any one of the above [1] to

[0010] , wherein the dispersion medium is at least one selected from the group consisting of an amide-based polar organic solvent, an alcohol-based solvent, a glycol-based solvent, a glycol ether-based solvent, a ketone-based solvent, an ester-based solvent, and an aqueous solvent.

[0011] The present invention provides a carbon nanotube dispersion having a viscosity of 10 to 1,000 cps in any one of the above [1] to

[0010] . In addition, in order to solve the above other problems, the present invention provides an electrode slurry composition for a lithium secondary battery including the carbon nanotube dispersion.

[0012] The present invention provides an electrode slurry composition for a lithium secondary battery comprising a carbon nanotube dispersion according to any one of the above [1] to

[0011] and an electrode active material. In addition, in order to solve the above other problems, the present invention provides a method for producing a carbon nanotube dispersion.

[0013] The present invention provides a method for producing a carbon nanotube dispersion, comprising the steps of (1) preparing a mixture by mixing carbon nanotubes, a dispersant, and a dispersion medium; and (2) performing a dispersion treatment on the mixture, wherein the dispersant comprises a first dispersant and a second dispersant in a weight ratio of 100:10 to 90, the first dispersant is a dispersant containing an N atom, the second dispersant is a compound containing a sulfonic group, a hydroxyl group, and an aromatic ring in its molecular structure, and the weight ratio of the carbon nanotubes and the dispersant is 100:50 to 500, the method for producing a carbon nanotube dispersion according to any one of [1] to

[0011] . The carbon nanotube dispersion of the present invention contains a dispersant containing N atoms and a compound containing a sulfonic group, a hydroxyl group, and an aromatic ring in its molecular structure, so that the carbon nanotube dispersion has excellent dispersibility, low viscosity, and little change in viscosity over time, and is therefore advantageous in storage and use. Terms or words used in this specification and claims should not be interpreted as limited to their usual or dictionary meanings, but should be interpreted as meanings and concepts that conform to the technical idea of ​​the present invention, based on the principle that the inventor can appropriately define the concept of the term to explain his or her own invention in the best way. The terminology used herein is for the purpose of describing exemplary embodiments only and is not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise. In this specification, it should be understood that the terms “include,” “comprising,” or “having” are intended to specify the presence of a feature, number, step, component, or combination thereof, but do not preclude the possibility of the presence or addition of one or more other features, numbers, steps, components, or combinations thereof. In this specification, “%” means weight percent unless explicitly indicated otherwise. In this specification, the average particle size "D 50 " means the particle size corresponding to 50% of the volume accumulation, and "D 90 " means the particle size corresponding to 90% of the volume accumulation. The above D 50 and D 90 For example, it can be measured using the laser diffraction method. The laser diffraction method can generally measure particle sizes from the submicron range to several mm, and can obtain results with high reproducibility and high resolution. In this specification, the “specific surface area” is measured by the BET method, and can be specifically calculated from the nitrogen gas adsorption amount at liquid nitrogen temperature (77 K) using BELSORP-mino II of BEL Japan. Hereinafter, the present invention will be described in detail. The carbon nanotube dispersion according to the present invention is a carbon nanotube dispersion comprising carbon nanotubes, a dispersant, and a dispersion medium, wherein the specific surface area (BET) of the carbon nanotubes is 800 m 2 / g or less, and the dispersion contains a first dispersant and a second dispersant in a weight ratio of 100:10 to 90, the first dispersant is a compound containing an N atom, the second dispersant is a compound containing all of a sulfonic group, a hydroxyl group, and an aromatic ring, and the weight ratio of the carbon nanotube and the dispersant is 100:25 to 500. carbon nanotube dispersion The carbon nanotube dispersion according to the present invention is a carbon nanotube dispersion comprising carbon nanotubes, a dispersant, and a dispersion medium, wherein the specific surface area (BET) of the carbon nanotubes is 800 m 2 / g or less, and the dispersion contains a first dispersant and a second dispersant in a weight ratio of 100:10 to 90, the first dispersant is a compound containing an N atom, the second dispersant is a compound containing all of a sulfonic group, a hydroxyl group, and an aromatic ring, and the weight ratio of the carbon nanotube and the dispersant is 100:25 to 500. Below, each component of the carbon nanotube dispersion of the present invention is described in detail. (1) Carbon nanotubes The term 'carbon nanotube' used in the present invention refers to a secondary structure formed by assembling carbon nanotube units in a bundle shape, in whole or in part, wherein the carbon nanotube units have a graphite sheet in the shape of a cylinder with a nano-sized diameter, and sp 2 It has a bonding structure. At this time, depending on the angle and structure at which the graphite plane is rolled, it can exhibit the characteristics of a conductor or a semiconductor. The carbon nanotube unit can be classified into a single-walled carbon nanotube (SWCNT, single-walled carbon nanotube), a double-walled carbon nanotube (DWCNT, double-walled carbon nanotube), and a multi-walled carbon nanotube (MWCNT, multi-walled carbon nanotube) depending on the number of bonds forming the wall. The term 'bundle type' used in the present invention, unless otherwise stated, refers to a secondary shape in the form of a bundle or rope in which a plurality of carbon nanotube units are arranged in a parallel manner with their longitudinal axes substantially in the same orientation, or are arranged and then twisted or entangled. The term 'non-bundle type' or 'entangled type' refers to a shape in which carbon nanotube units are entangled without a definite shape such as a bundle or rope. Carbon nanotubes are highly conductive, but they tend to coagulate due to the van der Waals forces that form between them. When a conductive material coagulates, it fails to properly form a conductive path. This leads to the use of a relatively larger amount of conductive material, which reduces the amount of active material and can actually degrade electrode performance. Consequently, commercializing carbon nanotubes as a conductive material has been challenging. The carbon nanotube dispersion according to the present invention includes a compound containing an N atom as a dispersant and a compound containing a sulfonic group, a hydroxyl group, and an aromatic ring in its molecular structure, so that it has excellent dispersibility for carbon nanotubes, can suppress changes in the viscosity of the carbon nanotube dispersion over time, and thus exhibits a low viscosity increase rate, and can exhibit advantageous effects in the storage and use of the carbon nanotube dispersion. In addition, when the carbon nanotube dispersion according to the present invention is applied to the production of an electrode slurry, the carbon nanotubes are uniformly positioned between the active materials, so that even when the electrode slurry is coated, dried, and then rolled to produce an electrode, the microscopic spaces between the electrode active materials can be maintained at a constant level. In addition, the carbon nanotubes are uniformly distributed without agglomeration, so that even a small amount of carbon nanotubes can sufficiently form a conductive path. A carbon nanotube dispersion according to an example of the present invention may include at least one of single-walled, double-walled, and multi-walled carbon nanotube units as the carbon nanotubes, and specifically may include single-walled carbon nanotubes (SWCNTs). The above carbon nanotube is 800 m 2 / g may have a specific surface area (BET) of less than 200 m 2 / g or more, 220 m 2 / g or more, 240 m 2 / g or more, 260 m 2 / g or more, 280 m 2 / g or more, 290 m 2 / g or more, 300 m 2 / g or more, 800 m 2 / g less than 780 m 2 / g less than 760 m 2 / g less than 740 m 2 / g less than 720 m 2 / g less than 700 m 2 / g less than 650 m 2 / g or less. The carbon nanotube dispersion of the present invention exhibits excellent dispersibility by including a compound containing an N atom as a dispersant and a compound containing a sulfonic group, a hydroxyl group, and an aromatic ring in its molecular structure, so that it has a surface area of ​​800 m 2 It can exhibit excellent dispersibility for carbon nanotubes having a low specific surface area (BET) of less than / g, so that the carbon nanotube dispersion exhibits low viscosity and has the effect of little change in viscosity over time. The carbon nanotubes may be included in an amount of 0.1 to 7 parts by weight, specifically 0.5 to 5 parts by weight, and more specifically 1 to 4 parts by weight, based on 100 parts by weight of the conductive dispersion. A carbon nanotube dispersion according to an example of the present invention includes a dispersant having excellent dispersibility, and thus can exhibit excellent dispersibility even for carbon nanotubes having a high specific surface area, so that carbon nanotubes having a high specific surface area can be uniformly dispersed. It can have a high carbon nanotube content compared to conventional carbon nanotube dispersions generally used in the above range. When a carbon nanotube dispersion having a low carbon nanotube content is used in the production of an electrode slurry, the solid content of the produced electrode slurry decreases, so that the thickness (wet thickness) before applying and drying the electrode slurry becomes thick, and the rolling ratio measured after subsequent drying and rolling processes increases, so that the difference in the thickness ratio before and after drying and rolling becomes large. In this way, if the rolling ratio increases, the compositions inside the slurry, including the positive electrode active material, may be damaged during the process, which may cause a problem of deterioration in the performance of the battery. (2) Dispersant The carbon nanotube dispersion according to the present invention comprises a first dispersant and a second dispersant in a weight ratio of 100:10 to 90 to improve the dispersibility of the carbon nanotubes. In addition, the first dispersant is a compound containing an N atom, and the second dispersant is a compound containing a sulfonic group, a hydroxyl group, and an aromatic ring in its molecular structure. The compound including an N atom included as the first dispersant and the compound including a sulfone group, a hydroxyl group and an aromatic ring in the molecular structure included as the second dispersant serve to increase the dispersibility of carbon nanotubes as a dispersant in the carbon nanotube dispersion, and can exert the effect of suppressing an increase in viscosity of the carbon nanotube dispersion and a change in viscosity over time. In particular, the carbon nanotube dispersion according to the present invention includes, in addition to the compound containing the N atom as the first dispersant, a compound containing a sulfonic group, a hydroxyl group, and an aromatic ring in its molecular structure as a second dispersant, so that it exhibits superior dispersibility compared to a carbon nanotube dispersion containing only one type of dispersant that has been conventionally used, and thus the slurry composition exhibits less particle agglomeration, a low sedimentation rate, low viscosity, and excellent adhesion to a membrane substrate. Since the second dispersant includes a sulfone group, a hydroxyl group, and an aromatic ring together in its molecular structure, the bulky structure of the compound and the influence of the sulfone group and hydroxyl group can reduce the viscosity of the carbon nanotube dispersion, particularly the aqueous carbon nanotube dispersion, compared to the prior art, and can significantly improve the increase in viscosity over time. As the first dispersant, a compound containing an N atom can be used, and when a specific dispersant containing a compound containing an N atom in its structure, such as an amine structure, an amide structure, an imine structure, an ammonium structure, etc., is applied as the first dispersant, a more enhanced viscosity improvement effect and an effect of suppressing changes in viscosity over time can be exhibited. The dispersant containing the above N atom may be one that can be dissolved in water, and may be, for example, at least one selected from the group consisting of polyvinylpyrrolidone, polyacrylic acid hydrazide, poly-N-vinyl-5-methoxazolidon, N-alkyl polyimine, N-acetyl polyimine, polyacrylamide, poly-L-lysine hydrobromide, benzyl-dodecyl-dimethylammonium chloride, and polyethylenimine. Additionally, a compound containing a sulfonic acid group, a hydroxyl group, and an aromatic ring within its molecular structure may be used as the second dispersant, and the compound containing a sulfonic acid group, a hydroxyl group, and an aromatic ring within its molecular structure may be, for example, a lignosulfonate compound. Specifically, the second dispersant may be sodium lignosulfonate, calcium lignosulfonate, or a mixture thereof. When the above dispersant includes a dispersant containing an N atom as a first dispersant and a compound containing a sulfonic acid group, a hydroxyl group, and an aromatic ring in its molecular structure as a second dispersant, the interaction between the aromatic ring and the carbon nanotubes in the carbon nanotube dispersion and the interaction through hydrogen bonding between the hydroxyl group and the polymer dispersant are appropriately balanced, thereby exhibiting an effect of reducing the viscosity of the carbon nanotube dispersion and suppressing an increase in viscosity over time. In addition, the sulfonic acid group having a negative charge can induce an electrostatic shielding effect, thereby suppressing aggregation between carbon nanotubes. The above dispersant may include a first dispersant and a second dispersant together in a weight ratio of 100:10 to 90, specifically a weight ratio of 100:10 to 80, or a weight ratio of 100:15 to 75, and more specifically a weight ratio of 100:15 to 50. When the carbon nanotube dispersion liquid includes the first dispersant and the second dispersant as the dispersant in the weight ratio, the carbon nanotubes are uniformly dispersed in the carbon nanotube dispersion liquid, and the viscosity can be maintained at a constant level over time with low viscosity. The weight ratio of the carbon nanotubes and the dispersant may be 100:25 to 500, specifically 100:25 to 300, 100:25 to 250, 100:25 to 200, 100:25 to 180, 100:25 to 160, 100:25 to 150, 100:25 to 140, 100:25 to 120, 100:25 to 100, 100:25 to 90, 100:30 to 500, 100:30 to 300, 100:30 to 250, 100:30 to 200, 100:30 to 180, 100:30 to 160, 100:30 to It can be 150, 100:30 to 140, 100:30 to 120, 100:30 to 100, or 100:30 to 90. In addition, in one embodiment of the present invention, the weight ratio of the carbon nanotubes and the dispersant may be more specifically 100:30 to 90, 100:30 to 75, 100:30 to 60, or 100:30 to 45. If the dispersant is included in an excessive amount beyond the above range, the conductivity of the electrode may be impaired when the carbon nanotube dispersion is applied to the electrode due to the excessive amount of dispersant, and the dispersant may act as an impurity in the electrode. On the other hand, if the dispersant is included in an amount less than the above range, the effect of improving dispersibility, the effect of reducing viscosity, and the effect of suppressing changes in viscosity over time may be insufficient. (3) Dispersant The above dispersion medium is a dispersion medium for dispersing the carbon nanotubes and the dispersant, and can be used to first pre-disperse the carbon nanotubes and supply them as a carbon nanotube dispersion liquid in order to prevent agglomeration from occurring when the powdered carbon nanotubes are directly applied to the production of an electrode slurry composition. The above dispersion medium may be one that can dissolve or disperse the carbon nanotubes and dispersant to a certain level or higher. The dispersion medium may be included in an amount that allows the electrode slurry composition to have an appropriate viscosity, taking into account the coating properties of the electrode slurry composition manufactured using the carbon nanotube dispersion liquid, etc. The above dispersion medium is not particularly limited as long as it is one commonly used in the art for the purpose of dispersing the carbon nanotubes and dispersant, and may be, for example, at least one selected from the group consisting of an amide-based polar organic solvent, an alcohol-based solvent, a glycol-based solvent, a glycol ether-based solvent, a ketone-based solvent, an ester-based solvent, and an aqueous solvent. The above amide-based polar organic solvent may be at least one selected from the group consisting of dimethylformamide (DMF), diethylformamide, dimethyl acetamide (DMAc), N-methyl pyrrolidone (NMP), 3-methoxy-N,N-dimethylpropanamide (Ecamide M100, manufactured by Idemisu Kosan), and 3-butoxy-N,N-dimethylpropanamide (Ecamide B100, manufactured by Idemisu Kosan). The above alcohol solvent may be at least one selected from the group consisting of methanol, ethanol, 1-propanol, 2-propanol (or isopropyl alcohol), 1-butanol, 2-methyl-1-propanol, 2-butanol, 1-methyl-2-propanol, pentanol, hexanol, heptanol, octanol, glycerin, trimethylolpropane, pentaerythritol, and sorbitol. The above glycol solvent may be at least one selected from the group consisting of ethylene glycol, diethyl glycol, triethylene glycol, propylene glycol, 1,3-propanediol, 1,3-butanediol, 1,5-pentanediol, and hexylene glycol. The above glycol ether solvent may be at least one selected from the group consisting of ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, triethylene glycol monomethyl ether, tetraethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monoethyl ether, triethylene glycol monoethyl ether, tetraethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, and tetraethylene glycol monobutyl ether. The above ketone solvent may be at least one selected from the group consisting of acetone, methyl ethyl ketone, methyl propyl ketone, and cyclopentanone. The above ester solvent may be at least one selected from the group consisting of ethyl acetate, gamma-butyrolactone, and epsilon-propiolactone. Additionally, the aqueous solvent may be water. The carbon nanotube dispersion of the present invention containing the above components has excellent dispersibility, so that the viscosity of the dispersion is low and the degree of increase in viscosity over time is small. The above carbon nanotube dispersion may have a viscosity of 10 to 1,000 cps when the viscosity is measured using a viscometer (TOKI SANGYO, viscometer TV-25) at 25°C, Rotor 1, and 1 rpm, and specifically, may have a viscosity of 20 cps or more, 30 cps or more, 40 cps or more, 50 cps or more, 60 cps or more, 70 cps or more, 1,000 cps or less, 800 cps or less, 600 cps or less, 500 cps or less, 400 cps or less, or 300 cps or less. When the carbon nanotube dispersion has a viscosity within the above range, an electrode slurry can be manufactured more smoothly using the same, and an electrode slurry including the carbon nanotube dispersion can have an appropriate viscosity for forming an electrode. In addition, the carbon nanotube dispersion may have a viscosity of 20 cps or more, 30 cps or more, 40 cps or more, 50 cps or more, 60 cps or more, 70 cps or more, 1,500 cps or less, 1,300 cps or less, 1,000 cps or less, 800 cps or less, 600 cps or less, 500 cps or less, or 400 cps or less when the viscosity is measured at 25°C, Rotor 1, and 1 rpm using a viscometer (TOKI SANGYO, viscometer TV-25) after 2 weeks from the time of manufacture. In addition, the carbon nanotube dispersion may have a viscosity increase rate of 50% or less, specifically 40% or less, 35% or less, 30% or less, or 25% or less when left at 25°C for one week. Method for producing carbon nanotube dispersion Hereinafter, a method for producing a carbon nanotube dispersion will be described. The method for producing a conductive dispersion according to the present invention includes the steps of (1) producing a mixture by mixing carbon nanotubes, a dispersant, and a dispersion medium; and (2) dispersing the mixture. Here, the dispersant includes a first dispersant and a second dispersant in a weight ratio of 100:10 to 90, the first dispersant is a compound containing an N atom, the second dispersant is a compound containing a sulfonic group, a hydroxyl group, and an aromatic ring in its molecular structure, and the weight ratio of the carbon nanotubes and the dispersant is 100:25 to 500. In step (1), a mixture is prepared by mixing carbon nanotubes, a dispersant, and a dispersion medium. The above mixture preparation step can be performed under temperature conditions in which the physical properties of the mixture, including viscosity, do not change due to evaporation of the dispersion medium. For example, it can be performed at a temperature of 50°C or lower, more specifically, from 5°C to 50°C. In step (2), the above mixture is dispersed to prepare a carbon nanotube dispersion. The above dispersion can be performed by a milling method such as a ball mill, a bead mill, a disc mill, a basket mill, a high pressure homogenizer, etc., and more specifically, it can be performed by a milling method using a disc mill or a high pressure homogenizer. In the milling using the above bead mill, the size of the beads can be appropriately determined depending on the type and amount of carbon nanotubes and the type of dispersant, and specifically, the diameter of the beads can be 0.1 mm to 5 mm, and more specifically, 0.5 mm to 4 mm. In addition, the bead milling process can be performed at a speed of 1,000 rpm to 15,000 rpm, and more specifically, can be performed at a speed of 2,000 rpm to 12,000 rpm. The dispersion process can be performed depending on the degree of dispersion of the carbon nanotube dispersion, and specifically, can be performed for 30 minutes to 120 minutes, and more specifically, 60 minutes to 90 minutes. The milling using the high-pressure homogenizer is performed by pressurizing the mixture using, for example, a plunger pump of the high-pressure homogenizer and pushing it through a gap in a homogenization valve, thereby generating forces such as cavitation, shear, impact, and explosion when the mixture passes through the gap. The pressure of the high-pressure homogenizer may be 5,000 psi to 40,000 psi, specifically 10,000 psi to 30,000 psi, and more specifically 14,000 psi to 25,000 psi. The dispersion treatment using the high-pressure homogenizer may be performed 1 to 15 times, specifically 2 to 10 times, and more specifically 3 to 7 times. Electrode slurry composition In addition, the present invention provides an electrode slurry composition for a lithium secondary battery comprising the carbon nanotube dispersion and an electrode active material. The above-mentioned electrode slurry composition for a lithium secondary battery may be a positive electrode slurry composition or a negative electrode slurry composition, and specifically, may be a negative electrode slurry composition. The above-described electrode slurry composition for a lithium secondary battery may include the carbon nanotube dispersion, a positive electrode active material or a negative electrode active material as an electrode active material, a binder, a solvent, and / or other additives as needed. As the positive electrode active material, positive electrode active materials well known in the art can be used without limitation, and for example, lithium cobalt-based oxide, lithium nickel-based oxide, lithium manganese-based oxide, lithium iron phosphate, lithium nickel manganese cobalt-based oxide, or a combination thereof can be used. Specifically, the positive electrode active material includes LiCoO2, LiNiO2, LiMn2O4, LiCoPO4, LiFePO4, and LiNi a Mn b Co c O2 (where 0 < a, b, c < 1) can be used, but is not limited thereto. The above negative active materials include natural graphite, artificial graphite, carbonaceous materials; lithium-containing titanium composite oxide (LTO); metals (Me) such as Si, Sn, Li, Zn, Mg, Cd, Ce, Ni or Fe; alloys composed of the above metals (Me); oxides (MeO) of the above metals (Me). x ); and one or more types of negative electrode active materials selected from the group consisting of a complex of the above metal (Me) and carbon. The negative electrode active material may be included in an amount of 60 to 98 wt%, more preferably 70 to 98 wt%, based on the total weight of solids excluding the solvent in the negative electrode slurry. The above binder is a component that assists in the bonding of the active material and the conductive material and the bonding to the current collector, and is typically added in an amount of 1 to 30 wt% based on the total weight of the mixture including the electrode active material. Examples of such binders include polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene-butadiene rubber, fluororubber, and various copolymers. The solvents mentioned above include organic solvents such as N-methyl pyrrolidone (NMP), dimethyl formamide (DMF), acetone, dimethyl acetamide, etc., or water, and these solvents may be used alone or in combination of two or more. The amount of solvent used is sufficient to dissolve and disperse the electrode active material, binder, and conductive agent, taking into account the coating thickness of the slurry and the manufacturing yield. The above viscosity modifier may be carboxymethylcellulose, polyacrylic acid, or the like, and by adding it, the viscosity of the electrode slurry can be adjusted to facilitate the manufacturing of the electrode slurry and the application process on the electrode current collector. The above filler is optionally used as a component that suppresses the expansion of the electrode, and is not particularly limited as long as it is a fibrous material that does not cause a chemical change in the battery. For example, olefin polymers such as polyethylene and polypropylene; fibrous materials such as glass fiber and carbon fiber are used. When the above electrode slurry composition is a composition of a positive electrode slurry for forming a positive electrode, the positive electrode can be manufactured by applying the composition of the positive electrode slurry onto a positive electrode current collector, followed by drying and rolling. Alternatively, the positive electrode slurry can be manufactured by casting the positive electrode slurry onto a separate support, and then laminating the film obtained by peeling it off from the support onto the positive electrode current collector. The thickness of the positive electrode active material layer formed by the positive electrode slurry may vary depending on the loading amount, loading speed, etc. for applying the positive electrode slurry. The above-described positive electrode current collector generally has a thickness of 3 μm to 500 μm. The positive electrode current collector is not particularly limited as long as it has high conductivity and does not cause chemical changes in the battery. For example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. can be used. In addition, the surface of the positive electrode current collector may be formed with fine irregularities to strengthen the bonding strength of the positive electrode active material, and it can be used in various forms such as a film, sheet, foil, net, porous body, foam, or non-woven fabric. When the above electrode slurry composition is a composition of a negative electrode slurry for forming a negative electrode, the negative electrode can be manufactured by applying the composition of the negative electrode slurry onto a negative electrode current collector, followed by drying and rolling. Alternatively, the negative electrode slurry can be manufactured by casting the negative electrode slurry onto a separate support, and then laminating the resulting film onto the negative electrode current collector by peeling it off from the support. The thickness of the negative electrode active material layer formed by the above negative electrode slurry may vary depending on the loading amount, loading speed, etc. for applying the negative electrode slurry. The above negative electrode current collector generally has a thickness of 3 ㎛ to 500 ㎛. The negative electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, and for example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., aluminum-cadmium alloy, etc. can be used. In addition, like the negative electrode current collector, the bonding strength of the negative electrode active material can be strengthened by forming fine unevenness on the surface, and can be used in various forms such as a film, sheet, foil, net, porous body, foam, non-woven fabric, etc. lithium secondary battery A lithium secondary battery includes a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and an electrolyte. The positive electrode and the negative electrode are the same as those described above, so a detailed description thereof will be omitted. The above separator separates the negative electrode and the positive electrode and provides a passage for lithium ions to move. Any separator commonly used in lithium secondary batteries can be used without any particular restrictions, and in particular, one having low resistance to ion movement of the electrolyte and excellent electrolyte moisture absorption capacity is preferable. Specifically, a porous polymer film, for example, a porous polymer film made of a polyolefin polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, and an ethylene / methacrylate copolymer, or a laminated structure of two or more layers thereof, may be used. In addition, a conventional porous nonwoven fabric, for example, a nonwoven fabric made of high-melting-point glass fiber, polyethylene terephthalate fiber, etc. may be used. In addition, a coated separator containing a ceramic component or a polymer material to secure heat resistance or mechanical strength may be used, and may optionally be used in a single-layer or multi-layer structure. The electrolyte may be, but is not limited to, an organic liquid electrolyte, an inorganic liquid electrolyte, a solid polymer electrolyte, a gel-type polymer electrolyte, a solid inorganic electrolyte, a molten inorganic electrolyte, etc. that can be used in the manufacture of a lithium secondary battery. Specifically, the electrolyte may include an organic solvent and a lithium salt. The organic solvent may be used without any particular limitation as long as it can serve as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, the organic solvent may include ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether solvents such as dibutyl ether or tetrahydrofuran; ketone solvents such as cyclohexanone; aromatic hydrocarbon solvents such as benzene and fluorobenzene; Carbonate solvents such as dimethylcarbonate (DMC), diethylcarbonate (DEC), methylethylcarbonate (MEC), ethylmethylcarbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC); alcohol solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (wherein R is a C2 to C20 linear, branched, or cyclic hydrocarbon group, and may include a double-bonded aromatic ring or an ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes can be used. Among these, a carbonate solvent is preferable, and a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate, etc.) having high ionic conductivity and high dielectric constant that can improve the charge / discharge performance of the battery and a linear carbonate compound having low viscosity (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate, etc.) is more preferable.In this case, the performance of the electrolyte may be excellent when the cyclic carbonate and the chain carbonate are mixed and used in a volume ratio of about 1:1 to about 1:9. The lithium salt may be used without any particular limitation as long as it is a compound capable of providing lithium ions used in a lithium secondary battery. Specifically, the lithium salt may be LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAl04, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2. LiCl, LiI, or LiB(C2O4)2. It is preferable that the concentration of the lithium salt be used within the range of 0.1M to 2.0M. When the concentration of the lithium salt is within the above range, the electrolyte can exhibit excellent electrolyte performance because it has appropriate conductivity and viscosity, and lithium ions can move effectively. In addition to the electrolyte components, the electrolyte may further include one or more additives, such as haloalkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethylphosphite, triethanolamine, cyclic ethers, ethylene diamine, n-glyme, hexaphosphoric acid triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, or aluminum trichloride, for the purpose of improving the life characteristics of the battery, suppressing battery capacity decrease, and improving the discharge capacity of the battery. At this time, the additives may be included in an amount of 0.1 wt% to 5 wt% based on the total weight of the electrolyte. A lithium secondary battery comprising an electrode manufactured using a carbon nanotube dispersion according to the present invention, specifically a lithium secondary battery comprising an anode manufactured using a carbon nanotube dispersion, has carbon nanotubes uniformly dispersed within the anode, and can reduce the content thereof compared to a case where a conductive material such as conventional carbon black is included, thereby stably exhibiting excellent discharge capacity and output characteristics. As a result, the lithium secondary battery can be usefully used in portable devices such as mobile phones, laptop computers, and digital cameras, and electric vehicles such as hybrid electric vehicles (HEVs). Accordingly, according to another embodiment of the present invention, a lithium secondary battery, a battery module including the lithium secondary battery as a unit cell, and a battery pack including the same can be provided. The above battery module or battery pack can be used as a power source for one or more medium- to large-sized devices, such as a power tool; an electric vehicle (EV), a hybrid electric vehicle, and a plug-in hybrid electric vehicle (PHEV); or a power storage system. Hereinafter, the present invention will be described in more detail by way of examples. However, the following examples are intended to illustrate the present invention and are not intended to limit the scope of the present invention solely to these examples. Example Example 1 A 300 g mixture was prepared by mixing 0.72 wt% polyvinylpyrrolidone (PVP K15, Zhangzhou Huafu Chemical), 0.18 wt% sodium lignosulfonate (Borregaard), and water as a dispersion medium. An impeller and a vessel were installed in a dissolver (VMA-Getzmann, Dispermat-CA), and the mixture was rotated at 400 rpm for 10 minutes to mix the dispersant and dispersion medium. Surface area 380 m 2 3 wt% of multi-walled carbon nanotubes (MWCNT, BT2001M, LG Chemical) was added and dispersed at 10,000 rpm for 60 minutes. The resultant was treated three times at 20,000 psi using a high-pressure disperser (PICOMAX, Micronox) to produce a carbon nanotube dispersion. Examples 2 to 8 A carbon nanotube dispersion was prepared in the same manner as in Example 1, except that the contents of polyvinylpyrrolidone and sodium lignosulfonate were changed as shown in Table 1 below. Example 9 A carbon nanotube dispersion was prepared in the same manner as in Example 1, except that polyethyleneimine (Sigma-Aldrich) was used instead of polyvinylpyrrolidone in the amounts shown in Table 1 below. Examples 10 and 11 A carbon nanotube dispersion was prepared in the same manner as in Example 1, except that calcium lignosulfonate (Borregaard) was used instead of sodium lignosulfonate in the amounts shown in Table 1 below. Comparative Example 1 A carbon nanotube dispersion was prepared in the same manner as in Example 1, except that sodium lignosulfonate was not used and the content of polyvinylpyrrolidone was changed to 1.35%. Comparative Example 2 A carbon nanotube dispersion was prepared in the same manner as in Example 1, except that polyvinylpyrrolidone was not used and the content of sodium lignosulfonate was changed to 1.35%. Comparative Examples 3 to 7 A carbon nanotube dispersion was prepared in the same manner as in Example 1, except that polyphenol (Tannic acid, Sigma-Aldrich) was used instead of sodium lignosulfonate and the content was varied as shown in Table 1 below. Comparative examples 8 and 9 A carbon nanotube dispersion was prepared in the same manner as in Example 1, except that the contents of polyvinylpyrrolidone and sodium lignosulfonate were changed as shown in Table 1 below. Comparative Examples 10 and 11 A carbon nanotube dispersion was prepared in the same manner as in Example 1, except that polyethyleneimine was used as the first dispersant and polyphenol was used as the second dispersant, but their contents were different as shown in Table 1 below. Comparative Examples 12 and 13 A carbon nanotube dispersion was prepared in the same manner as in Example 1, except that polyvinylpyrrolidone was used as the first dispersant and sodium dodecylbenzenesulfonate (Sigma-Aldrich) was used as the second dispersant, but the contents thereof were different as shown in Table 1 below. Comparative Example 14 A carbon nanotube dispersion was prepared in the same manner as in Example 1, except that the contents of polyvinylpyrrolidone and sodium lignosulfonate were changed as shown in Table 1 below. CNT content (weight %) First dispersant (polymer) Second dispersant Dispersant ratio CNT to dispersant type Dosage (weight %) Type Dosage (weight %) Example 13 PVP 0.72 Sodium lignosulfonate 0.18 1:0.25 1:0.3 Example 23 PVP 1.08 Sodium lignosulfonate 0.27 1:0.25 1:0.45 Example 33 PVP 1.44 Sodium lignosulfonate 0.36 1:0.25 1:0.6 Example 43 PVP 1.8 Sodium lignosulfonate 0.45 1:0.25 1:0.75 Example 53 PVP 2.16 Sodium lignosulfonate 0.54 1:0.25 1:0.9 Example 63 PVP 0.9 Sodium Lignosulfonate 0.45 1:0.5 1:0.45 Example 73 PVP 1.0 125 Sodium Lignosulfonate 0.33 7 5 1:0.33 1:0.45 Example 83 PVP 1.125 Sodium Lignosulfonate 0.22 5 1:0.17 1:0.45 Example 93 PEI 1.08 Sodium Lignosulfonate 0.27 1:0.25 1:0.45 Example 103 PVP 1.08 Calcium Lignosulfonate 0.27 1:0.25 1:0.45 Example 113 PVP 2.16 Calcium Lignosulfonate 0.54 1:0.25 1:0.9 Comparative Example 13 PVP 1.35---1:0.45 Comparative Example 23--Sodium Lignosulfonate 1.35-1:0.45 Comparative Example 33 PVP 0.72 Polyphenol 0.18 1:0.25 1:0.3 Comparative Example 43 PVP 1.08 Polyphenol 0.27 1:0.25 1:0.45 Comparative Example 53 PVP 1.44 Polyphenol 0.36 1:0.25 1:0.6 Comparative Example 63 PVP 1.8 Polyphenol 0.45 1:0.25 1:0.75 Comparative Example 73 PVP 2.16 Polyphenol 0.54 1:0.25 1:0.9 Comparative Example 83 PVP 0.48 Sodium Lignosulfonate 0.12 1:0.25 1:0.2 Comparative Example 93 PVP 0.675 Sodium Lignosulfonate 0.67 5 1:11:0.45 Comparative Example 103PEI1.08Polyphenol0.271:0.251:0.45Comparative Example 113PEI2.16Polyphenol0.541:0.251:0.9Comparative Example 123PVP1.08Sodium dodecylbenzenesulfonate0.271:0.251:0.45Comparative Example 133PVP2.16Sodium dodecylbenzenesulfonate0.541:0.251:0.0Comparative Example 143PVP1.29Sodium lignosulfonate0.061:0.051:0.45 Experimental example The initial viscosity of the carbon nanotube dispersions manufactured in each of the above examples and comparative examples was measured after dispersion, and the viscosity was measured again after leaving them at 25°C for one week, and the results are shown in Table 2 below. Viscosity was measured using a viscometer (viscometer TV-25, manufactured by TOKI) at 25°C, Rotor 1, and 1 rpm. CNT content (wt%)Viscosity (cps)Ratio between dispersantsCNT to dispersantIncrease rate after initial 2 weeks after dispersion(%)Example 13150170131:0.251:0.3Example 23120110-81:0.251:0.45Example 3310010001:0.251:0.6Example 43909561:0.251:0.75Example 53858501:0.251:0.9Example 63270300111:0.51:0.45Example 7314015071:0.331:0.45Example 83130160231:0.171:0.45Example 93160190201:0.251:0.45 Example 103140180301:0.251:0.45 Example 113130160201:0.251:0.9 Comparative Example 1310,00018,00080-1:0.45 Comparative Example 2315,00025,00067-1:0.45 Comparative Example 337,70013,000691:0.251:0.3 Comparative Example 432,88013,0003511:0.251:0.45 Comparative Example 534607,8001,5951:0.251:0.6 Comparative Example 632202,8001,1731:0.251:0.75Comparative example 731002001001:0.251:0.9Comparative example 832505001001:0.251:0.2Comparative example 931,1202,4001141:11:0.45Comparative example 1033,50013,002701:0.251:0.45Comparative example 11340012003001:0.251:0.9Comparative example 1233601,5003201:0.251:0.45Comparative example 133250Phase separation occurred 1:0.251:0.9Comparative example 1438,00018,0001251:0.051:0.45 As can be confirmed in Table 2 above, Examples 1 to 11 maintained the viscosity of the carbon nanotube dispersions even after being left at 25°C for one week, and even when the viscosity increased, it showed only a very low level of increase rate. Comparative Examples 1 and 2 are carbon nanotube dispersions using only PVP and carbon nanotube dispersions using only sodium lignosulfonate, respectively, and had a high initial viscosity after dispersion due to low dispersibility, and showed a significantly higher viscosity increase rate than Examples 1 to 8 even after two weeks. In addition, Comparative Examples 3 to 7 used the same first and second dispersants as the examples, but the second dispersant used a polyphenol containing only a hydroxyl group and an aromatic ring, rather than a compound containing all of a sulfone group, a hydroxyl group, and an aromatic ring. When the amount of dispersant used compared to carbon nanotubes was increased, the initial viscosity after dispersion could be lowered, but the viscosity increase rate increased after two weeks, and when the amount of dispersant used compared to carbon nanotubes was increased from 1:0.6 to 1:0.7 and 1:0.9, the viscosity increase rate decreased after two weeks, but the viscosity increase rate was still significantly higher than that of Examples 1 to 8. Comparative Example 8, which used less dispersant than carbon nanotubes, exhibited a low initial viscosity after dispersion, but a low viscosity increase rate after two weeks. This confirms that an appropriate amount of dispersant must be used for carbon nanotubes to suppress viscosity increase. Comparative Example 9 is an example in which the first dispersant and the second dispersant were used in a weight ratio of 1:1, and since the relative amount of the second dispersant used was large, the initial viscosity after dispersion and the viscosity increase rate after 2 weeks increased significantly. Comparative Example 14 is an example in which the first dispersant and the second dispersant were used in a weight ratio of 1:0.05, in contrast to Comparative Example 9, and since the relative amount of the second dispersant used was too small, the initial viscosity was very high, and the viscosity increase rate was also high. Through this, it was confirmed that an appropriate content ratio must be satisfied when using the first and second dispersants. Comparative Examples 10 and 11 are examples in which the polyethyleneimine used in the examples of the present invention was used as the first dispersant, but a polyphenol without a sulfone group was used as the second dispersant. Not only was the initial viscosity itself higher than that of the examples, but the viscosity increase rate after 2 weeks was also significantly higher. Comparative Examples 12 and 13 are also examples in which the polyvinylpyrrolidone used in the examples of the present invention was used as the first dispersant, but sodium dodecylbenzenesulfonate without a hydroxyl group was used as the second dispersant. These examples also showed higher initial viscosity than the examples, and the viscosity increase rate after 2 weeks was either very high or phase separation occurred. From this, it was confirmed that the second dispersant used in combination with the first dispersant of the present invention must contain all of a sulfone group, a hydroxyl group, and an aromatic ring to achieve the effect of lowering the initial viscosity and the effect of improving the stability of the viscosity.

Claims

1. A carbon nanotube dispersion comprising carbon nanotubes, a dispersant, and a dispersion medium, The specific surface area (BET) of the above carbon nanotube is 800 m 2 / less than g, The above dispersion contains a first dispersant and a second dispersant in a weight ratio of 100:10 to 90, The first dispersant is a compound containing an N atom, and the second dispersant is a compound containing all of a sulfonic group, a hydroxyl group, and an aromatic ring. A carbon nanotube dispersion, wherein the weight ratio of the carbon nanotubes and the dispersant is 100:25 to 500.

2. In paragraph 1, The specific surface area (BET) of the above carbon nanotube is 200 m 2 / g or more than 800 m 2 Carbon nanotube dispersion having a mass of less than / g.

3. In paragraph 1, The above carbon nanotube is a carbon nanotube dispersion that is a multi-walled carbon nanotube.

4. In paragraph 1, A carbon nanotube dispersion, wherein the carbon nanotube is contained in an amount of 0.1 to 7 parts by weight based on 100 parts by weight of the carbon nanotube dispersion.

5. In paragraph 1, A carbon nanotube dispersion, wherein the first dispersant is at least one selected from the group consisting of polyvinylpyrrolidone, polyacrylic acid hydrazide, poly-N-vinyl-5-methoxazolidon, N-alkyl polyimine, N-acetyl polyimine, polyacrylamide, poly-L-lysine hydrobromide, benzyl-dodecyl-dimethylammonium chloride, and polyethylenimine.

6. In paragraph 1, The above second dispersant is a carbon nanotube dispersion which is a lignosulfonate compound.

7. In paragraph 1, The second dispersant is a carbon nanotube dispersion comprising sodium lignosulfonate, calcium lignosulfonate or a mixture thereof.

8. In paragraph 1, The above dispersant is a carbon nanotube dispersion comprising a first dispersant and a second dispersant in a weight ratio of 100:15 to 75.

9. In paragraph 1, A carbon nanotube dispersion having a weight ratio of the carbon nanotubes and the dispersant of 100:25 to 150.

10. In paragraph 1, A carbon nanotube dispersion liquid in which the above dispersion medium is at least one selected from the group consisting of an amide-based polar organic solvent, an alcohol-based solvent, a glycol-based solvent, a glycol ether-based solvent, a ketone-based solvent, an ester-based solvent, and an aqueous solvent.

11. In paragraph 1, A carbon nanotube dispersion having a viscosity of 10 to 1,000 cps.

12. An electrode slurry composition for a lithium secondary battery comprising a carbon nanotube dispersion according to Article 1 and an electrode active material. 13.(1) A step of preparing a mixture by mixing carbon nanotubes, a dispersant, and a dispersion medium; and (2) A method for producing a carbon nanotube dispersion liquid, comprising a step of dispersing the mixture, The above dispersant comprises a first dispersant and a second dispersant in a weight ratio of 100:10 to 90, The first dispersant is a compound containing an N atom, and the second dispersant is a compound containing a sulfonic group, a hydroxyl group, and an aromatic ring in its molecular structure. A method for producing a carbon nanotube dispersion according to claim 1, wherein the weight ratio of the carbon nanotubes and the dispersant is 100:25 to 500.