Carbon nanotube dispersion and preparation method thereof

Abstract

The present invention relates to a carbon nanotube dispersion containing carbon nanotubes, a first dispersant containing a nitrogen atom, a second dispersant containing a compound represented by Formula 1, and a solvent, and a method for preparing the same. The content of the compound represented by Formula 1 is as defined in the specification.

Description

Technical Field

[0001] This application claims the benefit of priority based on Korean Patent Application Nos. 10-2023-0099704, filed on July 31, 2023, 10-2023-0099719, filed on July 31, 2023, 10-2023-0099741, filed on July 31, 2023, 10-2023-0099761, filed on July 31, 2023, 10-2024-0100228, filed on July 29, 2024, 10-2024-0100234, filed on July 29, 2024, 10-2024-0100254, filed on July 29, 2024, and 10-2024-0100258, filed on July 29, 2024, the entire contents of which are incorporated herein by reference as part of this specification.

[0002] The present invention relates to a carbon nanotube dispersion and a method for preparing the same. Background Art

[0003] With the technological development and increasing demand for mobile devices, the demand for secondary batteries as an energy source has rapidly increased. Among these secondary batteries, lithium secondary batteries having high energy density and voltage, long cycle life, and low self-discharge rate have been commercialized and widely used. In addition, research is actively underway on methods for manufacturing electrodes having a higher energy density per unit volume as electrodes for high-capacity lithium secondary batteries by improving electrode density.

[0004] Generally, a high-density electrode is formed by molding electrode active material particles having a size of several μm to several tens of μm using high-pressure pressing. However, during the molding process, the particles may be deformed and the space between the particles may be reduced, which may easily reduce the electrolyte solution permeability.

[0005] To solve the above problems, a conductive material having excellent conductivity and strength is used during the manufacture of the electrode. The conductive material is positioned between the electrode active materials, and even when undergoing the molding process, they maintain the micropores between the active material particles, thereby making it easy for the electrolyte solution to penetrate and having excellent conductivity, thereby reducing the resistance within the electrode. Among these conductive materials, the use of carbon nanotubes, which are fiber-type carbon-based conductive materials that can further reduce the electrode resistance by forming a conductive path within the electrode, is increasing.

[0006] Carbon nanotubes are a type of micro carbon fiber, which are tubular carbon fibers with a diameter of 1 μm or less. Due to their high electrical conductivity, tensile strength, and heat resistance caused by their specific structure, they are expected to be applied in various fields and commercialized in various fields. However, carbon nanotubes have the problem that they have low dispersibility and agglomeration occurs due to the strong van der Waals force between them because of their high specific surface area.

[0007] To solve these problems, a method of dispersing carbon nanotubes in a dispersion medium by mechanical dispersion treatment such as ultrasonic treatment has been proposed. However, in the case of the mechanical dispersion treatment method, there is a problem that once the ultrasonic irradiation ends, the carbon nanotubes agglomerate, or they agglomerate again over time after dispersion.

[0008] Therefore, there is a need to develop a method for preparing a carbon nanotube dispersion that can improve the dispersibility of carbon nanotubes while having a low viscosity and suppressing the increase in viscosity over time.

[0009] [Prior Art Documents]

[0010] [Patent Documents]

[0011] (Patent Document 1) US Patent Application Publication No. 2017-0129804 (May 11, 2017)

[0012] (Patent Document 2) Chinese Patent Application Publication No. 001699155 (November 23, 2005) Summary of the Invention

[0013] Technical Problem

[0014] An object of the present invention is to provide a carbon nanotube dispersion comprising carbon nanotubes, a first dispersant containing a nitrogen atom, a second dispersant containing a compound represented by Formula 1, and a solvent, which has excellent dispersibility, and thus has a low viscosity of the dispersion and a small particle size of the dispersed particles, and has a small change in viscosity over time.

[0015] [Formula 1]

[0016]

[0017] Wherein,

[0018] Ar1 and Ar2 are each independently a substituted or unsubstituted C6-C30 aryl group, and

[0019] L1 is a substituted or unsubstituted C6-C30 arylene group.

[0020] Another object of the present invention is to provide a method for preparing the carbon nanotube dispersion.

[0021] Technical solution

[0022] One embodiment of the present invention provides a carbon nanotube dispersion, which comprises carbon nanotubes, a first dispersant containing a nitrogen atom, a second dispersant containing a compound represented by the following formula 1, and a solvent.

[0023] [Formula 1]

[0024]

[0025] Wherein,

[0026] Ar1 and Ar2 are each independently a substituted or unsubstituted C6-C30 aryl group, and

[0027] L1 is a substituted or unsubstituted C6-C30 arylene group.

[0028] Ar1 and Ar2 in formula 1 can be represented by the following formula 2 or formula 3 respectively.

[0029] [Formula 2]

[0030]

[0031] [Formula 3]

[0032]

[0033] In formula 2,

[0034] R1 to R8 are the same as or different from each other, and are each independently hydrogen; deuterium; halogen; cyano group; sulfonate group; hydroxyl group; amino group; nitro group; substituted or unsubstituted C1-C10 alkyl group; substituted or unsubstituted C1-C10 alkoxy group; or a part connected to formula 2, provided that any one of R1 to R8 is a part connected to the azo group in formula 1, and

[0035] In formula 3,

[0036] R9 to R14 are the same as or different from each other, and are each independently hydrogen; deuterium; halogen; cyano group; sulfonate group; amino group; nitro group; substituted or unsubstituted C1-C10 alkyl group; substituted or unsubstituted C1-C10 alkoxy group; or a part connected to formula 3, provided that any one of R9 to R14 is a part connected to the azo group in formula 1.

[0037] L1 in formula 1 can be represented by the following formula 4 or formula 5:

[0038] [Formula 4]

[0039]

[0040] [Formula 5]

[0041]

[0042] In Formula 4,

[0043] R15 to R18 are the same as or different from each other and are each independently hydrogen; deuterium; halogen; cyano; sulfonate group; hydroxyl group; amino group; nitro group; or a moiety linked to Formula 1, provided that any one of R15 to R18 is a moiety linked to the nitrogen atom not linked to Ar1 among the two nitrogen atoms of the azo group linked to Ar1 in the two azo groups of Formula 1, and R19 to R22 are the same as or different from each other and are each independently hydrogen; deuterium; halogen; cyano; sulfonate group; hydroxyl group; amino group; nitro group; or a moiety linked to Formula 1, provided that any one of R19 to R22 is a moiety linked to the nitrogen atom not linked to Ar2 among the two nitrogen atoms of the azo group linked to Ar2 in the two azo groups of Formula 1, and

[0044] In Formula 5,

[0045] R23 to R27 are the same as or different from each other and are each independently hydrogen; deuterium; halogen; cyano; sulfonate group; hydroxyl group; amino group; nitro group; substituted or unsubstituted C1-C5 alkyl group; substituted or unsubstituted C1-C5 alkoxy group; or a moiety linked to the nitrogen atom not linked to Ar1 among the two nitrogen atoms of the azo group linked to Ar1 in the two azo groups of Formula 1, provided that any one of R23 to R27 is a moiety linked to the nitrogen atom not linked to Ar1 among the two nitrogen atoms of the azo group linked to Ar1 in the two azo groups of Formula 1, and R28 to R32 are the same as or different from each other and are each independently hydrogen; deuterium; halogen; cyano; sulfonate group; hydroxyl group; amino group; nitro group; substituted or unsubstituted C1-C5 alkyl group; substituted or unsubstituted C1-C5 alkoxy group; or a moiety linked to the nitrogen atom not linked to Ar2 among the two nitrogen atoms of the azo group linked to Ar2 in the two azo groups of Formula 1, provided that any one of R28 to R32 is a moiety linked to the nitrogen atom not linked to Ar2 among the two nitrogen atoms of the azo group linked to Ar2 in the two azo groups of Formula 1, and

[0046] Z is a single bond; substituted or unsubstituted C2-C10 alkenylene; or substituted or unsubstituted C2-C10 alkynylene.

[0047] The second dispersant may contain a compound represented by any one of the following Formulas 1-1a to 1-1d:

[0048] [Formula 1-1a]

[0049]

[0050] Among them,

[0051] R1 to R5, R7 to R11, and R13 to R18 are the same as or different from each other, and each independently is hydrogen; deuterium; a halogen; a cyano group; a sulfonate group; a hydroxyl group; an amino group; or a nitro group,

[0052] [Formula 1-1b]

[0053]

[0054] Among them,

[0055] R1 to R7 and R9 to R15 are the same as or different from each other, and each independently is hydrogen; deuterium; a halogen; a cyano group; a sulfonate group; a hydroxyl group; an amino group; a substituted or unsubstituted C1-C10 alkyl group; a substituted or unsubstituted C2-C10 alkenyl group; a substituted or unsubstituted C2-C10 alkynyl group; a substituted or unsubstituted C1-C10 alkoxy group; or a substituted or unsubstituted C6-C20 aryl group, provided that at least one of R1 to R7 is a sulfonate group, and at least one of R9 to R15 is a sulfonate group,

[0056] [Formula 1-1c]

[0057]

[0058] Among them,

[0059] R1 to R5 and R7 to R11 are the same as or different from each other, and each independently is hydrogen; deuterium; a halogen; a cyano group; a sulfonate group; a hydroxyl group; a substituted or unsubstituted C1-C10 alkyl group; a substituted or unsubstituted C2-C10 alkenyl group; a substituted or unsubstituted C2-C10 alkynyl group; a substituted or unsubstituted C1-C10 alkoxy group; a substituted or unsubstituted C6-C20 aryl group; or a substituted or unsubstituted C2-C20 heteroaryl group, provided that at least one of R1 to R5 is a hydroxyl group, and at least one of R7 to R11 is a hydroxyl group, and

[0060] R13 to R20 are the same as or different from each other, and each independently is hydrogen; deuterium; a halogen; a cyano group; a sulfonate group; a hydroxyl group; a substituted or unsubstituted C1-C10 alkyl group; a substituted or unsubstituted C2-C10 alkenyl group; a substituted or unsubstituted C2-C10 alkynyl group; a substituted or unsubstituted C1-C10 alkoxy group; a substituted or unsubstituted C6-C20 aryl group; or a substituted or unsubstituted C2-C20 heteroaryl group, provided that at least one of R13 to R16 is a sulfonate group, and at least one of R17 to R20 is a sulfonate group,

[0061] [Formula 1-1d]

[0062]

[0063] Wherein,

[0064] R1 to R7 and R9 to R15 are the same as or different from each other, and each independently is hydrogen; deuterium; halogen; cyano; sulfonate group; hydroxyl group; amino group; or nitro, and

[0065] R17 to R20 and R22 to R25 are the same as or different from each other, and each independently is hydrogen; deuterium; halogen; cyano; sulfonate group; hydroxyl group; amino group; nitro; substituted or unsubstituted C1 to C5 alkyl; or substituted or unsubstituted C1 to C5 alkoxy group.

[0066] Based on 100 parts by weight of the carbon nanotube dispersion, the carbon nanotubes can be included in an amount of 0.05 parts by weight to 5 parts by weight.

[0067] The BET specific surface area of the carbon nanotubes can be 800 m 2 / g to 2,000 m 2 / g.

[0068] The first dispersant can be at least one selected from the following: polyvinylpyrrolidone, polyacrylic acid hydrazide, poly-N-vinyl-5-methyl oxazolidone, N-alkyl polyimine, N-acetyl polyimine, polyacrylamide, poly-L-lysine hydrobromide, benzyl-dodecyl-dimethylammonium chloride, and polyethyleneimine.

[0069] Based on 100 parts by weight of the carbon nanotube dispersion, the first dispersant can be included in an amount of 0.01 parts by weight to 10 parts by weight.

[0070] Based on 100 parts by weight of the carbon nanotube dispersion, the second dispersant can be included in an amount of 0.001 parts by weight to 9 parts by weight.

[0071] The first dispersant and the second dispersant can be included in a weight ratio of 100:10 to 100:90.

[0072] The initial viscosity of the carbon nanotube dispersion measured at 25°C and 1 rpm can be 1 Pa·s to 10 Pa·s.

[0073] The viscosity increase rate of the carbon nanotube dispersion represented by the following Equation 1 can be 15% or less.

[0074] [Equation 1]

[0075] Viscosity increase rate (%) = {(Viscosity measured after standing for 1 week at 25°C - Initial viscosity) / Initial viscosity} × 100

[0076] Another embodiment of the present invention provides a method for preparing a carbon nanotube dispersion, the method comprising the steps of: (1) preparing a primary dispersion of carbon nanotubes by mixing carbon nanotubes, a first dispersant containing a nitrogen atom, a second dispersant containing a compound represented by Formula 1, and a solvent; and (2) dispersing the primary dispersion of carbon nanotubes to prepare a secondary dispersion of carbon nanotubes.

[0077] Advantageous effects

[0078] The carbon nanotube dispersion according to the present invention uses a first dispersant containing a nitrogen atom and a second dispersant containing a compound represented by Formula 1, and thus, it has the following characteristics: Although carbon nanotubes having a large specific surface area are used, the change in viscosity of the dispersion with time is small, the viscosity is relatively low, and the carbon nanotubes are uniformly and effectively dispersed, and thus the particle size of the dispersed particles is small. Detailed description of the invention

[0079] Hereinafter, embodiments of the present invention will be described in detail. Before that, the terms or words used in this specification and claims should not be construed as limited to their ordinary meanings or dictionary meanings, and should be construed in accordance with the technical idea of the present invention based on the principle that the inventor can appropriately define the terms in order to best explain his own invention. Therefore, it should be understood that the configurations described in the embodiments described in this specification are only one of the most preferred embodiments of the present invention and do not represent all the technical ideas of the present invention, and thus, at the time of filing this application, there may be various equivalent alternatives and modifications that can replace these.

[0080] In this specification, the term "substituted" means that a hydrogen atom bonded to a carbon atom of a compound becomes another substituent, and the position of substitution is not limited as long as the position is a position where a hydrogen atom can be substituted (i.e., a position where a substituent can be substituted), and when two or more substitutions are made, the two or more substituents may be the same or different from each other.

[0081] In this specification, the term "substituted or unsubstituted" means substituted or unsubstituted with one or more substituents selected from the following: deuterium; halogen; cyano; straight-chain or branched C1-C60 alkyl; straight-chain or branched C2-C60 alkenyl; straight-chain or branched C2-C60 alkynyl; monocyclic or polycyclic C3-C60 cycloalkyl; monocyclic or polycyclic C2-C60 heterocycloalkyl; monocyclic or polycyclic C6-C60 aryl; monocyclic or polycyclic C2-C60 heteroaryl; C1-C20 alkylamino; monocyclic or polycyclic C6-C60 arylamino; and monocyclic or polycyclic C2-C60 heteroarylamino, or substituted or unsubstituted with a substituent formed by linking two or more substituents selected from the substituents exemplified above.

[0082] Throughout this specification, when a part is referred to as "comprising" a component, unless otherwise specifically stated, this does not mean that it does not contain other components, but rather that it may also contain other components.

[0083] Throughout this specification, unless otherwise clearly stated, "%" means weight %.

[0084] In this specification, the average particle size "D 50 " means the particle size corresponding to 50% of the volume accumulation. D 50 It can be measured, for example, by 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.

[0085] In this specification, the "specific surface area" is measured by Brunauer-Emmett-Teller analysis, and specifically, it can be calculated from the nitrogen adsorption amount at liquid nitrogen temperature (77K) using BELSORP-minoII of BEL Japan company.

[0086] Carbon nanotube dispersion

[0087] The carbon nanotube dispersion according to the present invention comprises carbon nanotubes, a first dispersant containing a nitrogen atom, a second dispersant containing a compound represented by Formula 1, and a solvent. Hereinafter, each component of the carbon nanotube dispersion of the present invention will be described in detail.

[0088] (1) Carbon nanotubes

[0089] The term "carbon nanotube" used in the present invention refers to a secondary structure formed by assembling carbon nanotube units to form a bundle type wholly or partially, wherein the carbon nanotube unit is a graphite sheet in the form of a cylinder having a nanosize diameter and having sp 2Bonding structure. At this time, depending on the angle and structure of the rolled-up graphene sheet, it can exhibit the characteristics of a conductor or a semiconductor. Carbon nanotube units can be classified into single-walled carbon nanotubes (SWCNT), double-walled carbon nanotubes (DWCNT), and multi-walled carbon nanotubes (MWCNT) according to the number of bonds forming the wall.

[0090] Unless otherwise specified, the term "bundled type" used in the present invention refers to a secondary shape in the form of a bundle or cord, in which a plurality of carbon nanotube units are arranged in parallel with the longitudinal axes of the units substantially in the same orientation, or are twisted or entangled after the arrangement. "Non-bundled or entangled type" refers to a form in which carbon nanotube units are entangled without a specific shape (such as a bundle or cord).

[0091] Carbon nanotubes have high conductivity, but they have high agglomeration characteristics due to the van der Waals forces generated between carbon nanotubes. When the conductive material agglomerates, a conductive path cannot be properly formed within the electrode, and more conductive material is used to increase conductivity, and thus the amount of the active material is relatively reduced, so the performance of the electrode such as capacity may be reduced. Therefore, it is difficult to commercialize carbon nanotubes as a conductive material.

[0092] The carbon nanotube dispersion according to the present invention contains a first dispersant containing a nitrogen atom and a second dispersant containing a compound represented by Formula 1, and thus can significantly reduce the initial viscosity of the carbon nanotube dispersion, suppress the change in viscosity over time, and at the same time maintain a low particle size of the dispersed particles.

[0093] The carbon nanotube dispersion according to an embodiment of the present invention may contain at least one of single-walled carbon nanotubes, double-walled carbon nanotubes, and multi-walled carbon nanotubes as the carbon nanotubes, but is not limited thereto, and specifically may contain single-walled carbon nanotubes. Since single-walled carbon nanotubes or double-walled carbon nanotubes have a higher specific surface area than multi-walled carbon nanotubes, they are more effective in improving the cycle characteristics when applied to secondary batteries.

[0094] Meanwhile, the carbon nanotubes can have an average diameter of, for example, from 0.6 nm to 10 nm, preferably from 0.8 nm to 5 nm, more preferably from 0.8 nm to 3 nm, and can have an average diameter of 0.8 nm or greater, 0.9 nm or greater, 1.0 nm or greater, 1.1 nm or greater, 1.2 nm or greater, 1.3 nm or greater, 1.4 nm or greater, 1.5 nm or greater, 1.6 nm or greater, 1.7 nm or greater, 1.8 nm or greater, or 1.9 nm or greater, and can have an average diameter of 3.0 nm or less, 2.9 nm or less, 2.8 nm or less, 2.7 nm or less, 2.6 nm or less, 2.5 nm or less, 2.4 nm or less, 2.3 nm or less, 2.2 nm or less, 2.1 nm or less, or 2.0 nm or less.

[0095] In addition, the carbon nanotubes can have an average length of from 0.5 μm to 20 μm, preferably from 1 μm to 20 μm, more preferably from 5 μm to 20 μm, and can have an average length of 5 μm or greater, 7 μm or greater, 9 μm or greater, 11 μm or greater, or 13 μm or greater, and can have an average length of 20 μm or less, 18 μm or less, 16 μm or less, or 14 μm or less. If the average diameter and average length of the carbon nanotubes satisfy the above ranges, they are effective in reducing the viscosity of the dispersion and improving the storage stability, and can also achieve excellent cycle characteristics when applied to the electrode active material.

[0096] In these cases, the average diameter of the carbon nanotubes can be measured by photographing the carbon nanotube powder with a scanning electron microscope, and the average length of the carbon nanotubes can be measured by photographing the carbon nanotube dispersion with a scanning electron microscope.

[0097] Based on a total of 100 parts by weight of the carbon nanotube dispersion, the carbon nanotubes may be included in an amount of 0.05 parts by weight to 5 parts by weight, and may be included in the following amounts: 0.05 parts by weight or more, 0.1 parts by weight or more, 0.2 parts by weight or more, 0.3 parts by weight or more, 0.4 parts by weight or more, 0.5 parts by weight or more, 0.6 parts by weight or more, 0.7 parts by weight or more, 0.8 parts by weight or more, 0.9 parts by weight or more, 1.0 parts by weight or more, 1.1 parts by weight or more, 1.2 parts by weight or more, 1.3 parts by weight or more, 1.4 parts by weight or more, 1.5 parts by weight or more, 1.6 parts by weight or more, 1.7 parts by weight or more, 1.8 parts by weight or more, 1.9 parts by weight or more, 2.0 parts by weight or more, 2.1 parts by weight or more, 2.2 parts by weight or more, 2.3 parts by weight or more, 2.4 parts by weight or more, or 2.5 parts by weight or more, and may be included in the following amounts: 5 parts by weight or less, 4.9 parts by weight or less, 4.8 parts by weight or less, 4.7 parts by weight or less, 4.6 parts by weight or less, 4.5 parts by weight or less, 4.4 parts by weight or less, 4.3 parts by weight or less, 4.2 parts by weight or less, 4.1 parts by weight or less, 4 parts by weight or less, 3.9 parts by weight or less, 3.8 parts by weight or less, 3.7 parts by weight or less, 3.6 parts by weight or less, 3.5 parts by weight or less, 3.4 parts by weight or less, 3.3 parts by weight or less, 3.2 parts by weight or less, 3.1 parts by weight or less, 3 parts by weight or less, 2.9 parts by weight or less, 2.8 parts by weight or less, 2.7 parts by weight or less, or 2.6 parts by weight or less. If the content of the carbon nanotubes satisfies the above range, the effect of improving the viscosity of the dispersion and the effect of improving the conductivity of the secondary battery manufactured from the carbon nanotube dispersion are excellent.

[0098] The BET specific surface area of the carbon nanotubes may be 800 m 2 / g to 2,000 m 2 / g. For example, it may be 800 m 2 / g or more, 810 m 2 / g or more, 820 m 2 / g or more, 830 m 2 / g or more, 840 m 2 / g or more, 850 m 2 / g or more, 860 m 2 / g or more, 870 m 2 / g or more, 880 m 2 / g or more, 890 m 2 / g or more, 900 m 2 / g or more, 910 m 2 / g or greater, 920m 2 / g or greater, 930m 2 / g or greater, 940m 2 / g or greater, 950m 2 / g or greater, 960m 2 / g or greater, 970m 2 / g or greater, 980m 2 / g or greater, 990m 2 / g or greater, 1,000m 2 / g or greater, 1,010m 2 / g or greater, 1,020m 2 / g or greater, 1,030m 2 / g or greater, 1,040m 2 / g or greater, 1,050m 2 / g or greater, 1,060m 2 / g or greater, 1,070m 2 / g or greater, 1,080m 2 / g or greater, 1,090m 2 / g or greater, 1,100m 2 / g or greater, 1,110m 2 / g or greater, 1,120m 2 / g or greater, 1,130m 2 / g or greater, 1,140m 2 / g or greater, 1,150m 2 / g or greater, 1,160m 2 / g or greater, 1,170m 2 / g or greater, 1,180m 2 / g or greater, 1,190m 2 / g or greater, 1,200m 2 / g or greater, 1,210m 2 / g or greater, 1,220m 2 / g or greater, 1,230m 2 / g or greater, 1,240m 2 / g or greater, 1,250m 2 / g or greater, 1,260m 2 / g or greater, 1,270m 2 / g or greater, 1,280m 2 / g or greater, 1,290m 2 / g or greater, 1,300m 2 / g or greater, 1,310m 2 / g or greater, 1,320m2 / g or greater, 1,330 m 2 / g or greater, 1,340 m 2 / g or greater, 1,350 m 2 / g or greater, 1,360 m 2 / g or greater, 1,370 m 2 / g or greater, 1,380 m 2 / g or greater, 1,390 m 2 / g or greater or 1,400 m 2 / g or greater, and can be 2,000 m 2 / g or less, 1,990 m 2 / g or less, 1,980 m 2 / g or less, 1,970 m 2 / g or less, 1,960 m 2 / g or less, 1,950 m 2 / g or less, 1,940 m 2 / g or less, 1,930 m 2 / g or less, 1,920 m 2 / g or less, 1,910 m 2 / g or less, 1,900 m 2 / g or less, 1,890 m 2 / g or less, 1,880 m 2 / g or less, 1,870 m 2 / g or less, 1,860 m 2 / g or less, 1,850 m 2 / g or less, 1,840 m 2 / g or less, 1,830 m 2 / g or less, 1,820 m 2 / g or less, 1,810 m 2 / g or less, 1,800 m 2 / g or less, 1,790 m 2 / g or less, 1,780 m 2 / g or less, 1,770 m 2 / g or less, 1,760 m 2 / g or less, 1,750 m 2 / g or less, 1,740 m 2 / g or less, 1,730 m 2 / g or less, 1,720 m 2 / g or less, 1,710 m 2 / g or less, 1,700 m 2 / g or less, 1,690 m 2 / g or less, 1,680 m 2 / g or less, 1,670 m 2 / g or less, 1,660 m 2 / g or less, 1,650 m 2 / g or less, 1,640 m 2 / g or less, 1,630 m 2 / g or less, 1,620 m 2 / g or less, 1,610 m 2 / g or less, 1,600 m 2 / g or less, 1,590 m 2 / g or less, 1,580 m 2 / g or less, 1,570 m 2 / g or less, 1,560 m 2 / g or less, 1,550 m 2 / g or less, 1,540 m 2 / g or less, 1,530 m 2 / g or less, 1,520 m 2 / g or less, 1,510 m 2 / g or less, 1,500 m 2 / g or less, 1,490 m 2 / g or less, 1,480 m 2 / g or less, 1,470 m 2 / g or less, 1,460 m 2 / g or less, 1,450 m 2 / g or less, 1,440 m 2 / g or less, 1,430 m 2 / g or less, 1,420 m 2 / g or less or 1,410 m 2 / g or less. If carbon nanotubes with a high BET specific surface area as described above are used, the formation of the conductive network between the electrode active materials is excellent, and thus the cycle characteristics of the secondary battery manufactured through the carbon nanotube dispersion can be improved.

[0099] The carbon nanotube dispersion according to an embodiment of the present invention may have a relatively high carbon nanotube content because the carbon nanotubes can be uniformly dispersed. If a carbon nanotube dispersion with a low carbon nanotube content is used in the preparation of the electrode paste, since the solid content of the prepared electrode paste is reduced, the thickness (wet thickness) before applying the electrode paste and drying it becomes thicker, and the rolling ratio measured after subsequent drying and rolling processes becomes higher, and thus the difference in the thickness ratio before and after drying and rolling becomes larger. Therefore, if the rolling ratio increases, during this process, the composition within the paste containing the positive electrode active material may be damaged, which may lead to a problem of reduced battery performance.

[0100] (2) Dispersant

[0101] The carbon nanotube dispersion according to the present invention contains a dispersant to improve the dispersibility of the carbon nanotubes, and contains a first dispersant containing a nitrogen atom and a second dispersant containing a compound represented by the following formula 1 as the dispersant.

[0102] [Formula 1]

[0103]

[0104] Wherein,

[0105] Ar1 and Ar2 are each independently a substituted or unsubstituted C6 - C30 aryl group,

[0106] L1 is a substituted or unsubstituted C6 - C30 arylene group.

[0107] In the carbon nanotube dispersion, the first dispersant and the second dispersant function to improve the dispersibility of the carbon nanotubes such that the carbon nanotubes can be uniformly dispersed in the dispersion without agglomeration, and in particular, function to inhibit the change in the viscosity of the carbon nanotube dispersion over time and reduce the average particle size of the dispersed particles.

[0108] In the carbon nanotube dispersion according to an embodiment of the present invention, the first dispersant containing a nitrogen atom can be soluble in the aqueous solvent to be described later, and can be, for example, at least one selected from the following: polyvinylpyrrolidone, polyacrylic hydrazide, poly - N - vinyl - 5 - methyl oxazolidone, N - alkyl polyimine, N - acetyl polyimine, polyacrylamide, poly - L - lysine hydrobromide, benzyl - dodecyl - dimethylammonium chloride, and polyethyleneimine, and preferably can be polyvinylpyrrolidone. The carbon nanotube dispersion according to an embodiment of the present invention can exhibit the effects of improving the viscosity of the dispersion and inhibiting the change in viscosity over time by containing the first dispersant containing a nitrogen atom.

[0109] In one embodiment of the present invention, based on 100 parts by weight of the carbon nanotube dispersion, the first dispersant may be included in an amount of 0.01 to 10 parts by weight. For example, it may be included in the following amounts: 0.01 part by weight or more, 0.1 part by weight or more, 0.2 part by weight or more, 0.3 part by weight or more, 0.4 part by weight or more, 0.5 part by weight or more, 0.6 part by weight or more, 0.7 part by weight or more, 0.8 part by weight or more, 0.9 part by weight or more, 1 part by weight or more, 1.1 part by weight or more, 1.2 part by weight or more, 1.3 part by weight or more, 1.4 part by weight or more, 1.5 part by weight or more, 1.6 part by weight or more, 1.7 part by weight or more, 1.8 part by weight or more, 1.9 part by weight or more, 2 part by weight or more, 2.1 part by weight or more, 2.2 part by weight or more, 2.3 part by weight or more, 2.4 part by weight or more, 2.5 part by weight or more, 2.6 part by weight or more, 2.7 part by weight or more, 2.8 part by weight or more, 2.9 part by weight or more, 3 part by weight or more, 3.1 part by weight or more, 3.2 part by weight or more, 3.3 part by weight or more, 3.4 part by weight or more, 3.5 part by weight or more, 3.6 part by weight or more, 3.7 part by weight or more, 3.8 part by weight or more, 3.9 part by weight or more, 4 part by weight or more, 4.1 part by weight or more, 4.2 part by weight or more, 4.3 part by weight or more, 4.4 part by weight or more, 4.5 part by weight or more, 4.6 part by weight or more, 4.7 part by weight or more, 4.8 part by weight or more, 4.9 part by weight or more or 5 part by weight or more, and may be included in the following amounts: 10 part by weight or less, 9.9 part by weight or less, 9.8 part by weight or less, 9.7 part by weight or less, 9.6 part by weight or less, 9.5 part by weight or less, 9.4 part by weight or less, 9.3 part by weight or less, 9.2 part by weight or less, 9.1 part by weight or less, 9 part by weight or less, 8.9 part by weight or less, 8.8 part by weight or less, 8.7 part by weight or less, 8.6 part by weight or less, 8.5 part by weight or less, 8.4 part by weight or less, 8.3 part by weight or less, 8.2 part by weight or less, 8.1 part by weight or less, 8 part by weight or less, 7.9 part by weight or less, 7.8 part by weight or less, 7.7 part by weight or less, 7.6 part by weight or less, 7.5 part by weight or less, 7.4 part by weight or less, 7.3 part by weight or less, 7.2 part by weight or less, 7.1 part by weight or less, 7 part by weight or less, 6.9 part by weight or less, 6.8 part by weight or less, 6.7 part by weight or less, 6.6 part by weight or less, 6.5 part by weight or less, 6.4 part by weight or less, 6.3 part by weight or less, 6.2 part by weight or less, 6.1 part by weight or less, 6 part by weight or less, 5.9 part by weight or less, 5.8 parts by weight or less, 5.7 parts by weight or less, 5.6 parts by weight or less, 5.5 parts by weight or less, 5.4 parts by weight or less, 5.3 parts by weight or less, 5.2 parts by weight or less, or 5.1 parts by weight or less.

[0110] If, based on 100 parts by weight of the carbon nanotube dispersion, the content of the first dispersant is less than 0.01 part by weight, there may be a problem that the content of the dispersant is insufficient, so that the dispersion does not have a sufficient dispersion effect, and thus the viscosity of the dispersion does not become low and the viscosity increases with time. If the content of the first dispersant exceeds 10 parts by weight, there may be a problem that due to the excessive content of the first dispersant, agglomeration occurs between the solids in the dispersion, and the viscosity of the dispersion becomes high.

[0111] In addition, in order to solve the problem that the viscosity of the dispersion increases as the content of the carbon nanotubes increases in the carbon nanotube dispersion containing only the first dispersant, the carbon nanotube dispersion according to an embodiment of the present invention contains, in addition to the first dispersant, a second dispersant containing a compound represented by the following formula 1, and thus, it has excellent dispersibility compared with a conventional carbon nanotube dispersion using only a dispersant, and it can exhibit effects such as less agglomeration of particles of the slurry composition and a low sedimentation rate.

[0112] [Formula 1]

[0113]

[0114] Wherein,

[0115] Ar1 and Ar2 are each independently a substituted or unsubstituted C6-C30 aryl group, and

[0116] L1 is a substituted or unsubstituted C6-C30 arylene group.

[0117] In one embodiment of the present invention, Ar1 in formula 1 may be a substituted or unsubstituted C6-C30 aryl group.

[0118] In one embodiment of the present invention, Ar1 in formula 1 may be a substituted or unsubstituted C6-C20 aryl group.

[0119] In one embodiment of the present invention, Ar1 in formula 1 may be a substituted or unsubstituted C6-C10 aryl group.

[0120] In one embodiment of the present invention, Ar1 in formula 1 may be a substituted or unsubstituted phenyl group; or a substituted or unsubstituted naphthyl group.

[0121] In one embodiment of the present invention, Ar2 in Formula 1 may be a substituted or unsubstituted C6-C30 aryl group.

[0122] In one embodiment of the present invention, Ar2 in Formula 1 may be a substituted or unsubstituted C6-C20 aryl group.

[0123] In one embodiment of the present invention, Ar2 in Formula 1 may be a substituted or unsubstituted C6-C10 aryl group.

[0124] In one embodiment of the present invention, Ar2 in Formula 1 may be a substituted or unsubstituted phenyl group; or a substituted or unsubstituted naphthyl group.

[0125] In one embodiment of the present invention, L1 in Formula 1 may be a substituted or unsubstituted C6-C30 arylene group.

[0126] In one embodiment of the present invention, L1 in Formula 1 may be a substituted or unsubstituted C6-C20 arylene group.

[0127] In one embodiment of the present invention, L1 in Formula 1 may be a substituted or unsubstituted C6-C10 arylene group.

[0128] In one embodiment of the present invention, Ar1 and Ar2 in Formula 1 may be represented by the following Formula 2 or Formula 3, respectively.

[0129] [Formula 2]

[0130]

[0131] [Formula 3]

[0132]

[0133] In Formula 2,

[0134] R1 to R8 are the same as or different from each other, and each independently is hydrogen; deuterium; halogen; cyano; sulfonate group; hydroxyl group; amino group; nitro group; substituted or unsubstituted C1-C10 alkyl group; substituted or unsubstituted C1-C10 alkoxy group; or a moiety connected to Formula 2, provided that any one of R1 to R8 is a moiety connected to the azo group in Formula 1, and

[0135] In Formula 3,

[0136] R9 to R14 are the same as or different from each other, and each independently is hydrogen; deuterium; a halogen; a cyano group; a sulfonate group; an amino group; a nitro group; a substituted or unsubstituted C1-C10 alkyl group; a substituted or unsubstituted C1-C10 alkoxy group; or a moiety linked to Formula 3, provided that any one of R9 to R14 is a moiety linked to the azo group in Formula 1.

[0137] In one embodiment of the present invention, Ar1 in Formula 1 is represented by Formula 2, and R1 to R8 in Formula 2 are the same as or different from each other, and each independently is hydrogen; deuterium; a halogen; a sulfonate group; a hydroxyl group; or a moiety linked to Formula 1, provided that any one of R1 to R8 can be a moiety linked to the azo group in Formula 1.

[0138] In one embodiment of the present invention, Ar2 in Formula 1 is represented by Formula 2, and R1 to R8 in Formula 2 are the same as or different from each other, and each independently is hydrogen; deuterium; a halogen; a sulfonate group; a hydroxyl group; or a moiety linked to Formula 1, provided that any one of R1 to R8 can be a moiety linked to the azo group in Formula 1.

[0139] In one embodiment of the present invention, Ar1 in Formula 1 is represented by Formula 3, and R9 to R14 in Formula 3 are the same as or different from each other, and each independently is hydrogen; deuterium; a halogen; a sulfonate group; a hydroxyl group; or a moiety linked to Formula 1, provided that any one of R9 to R14 can be a moiety linked to the azo group in Formula 1.

[0140] In one embodiment of the present invention, Ar2 in Formula 1 is represented by Formula 3, and R9 to R14 in Formula 3 are the same as or different from each other, and each independently is hydrogen; deuterium; a halogen; a sulfonate group; a hydroxyl group; or a moiety linked to Formula 1, provided that any one of R9 to R14 can be a moiety linked to the azo group in Formula 1.

[0141] In one embodiment of the present invention, Ar1 in Formula 1 is represented by Formula 2, and at least one of the remaining groups in R1 to R8 in Formula 2 other than the moiety linked to the azo group in Formula 1 can be a sulfonate group.

[0142] In one embodiment of the present invention, Ar2 in Formula 1 is represented by Formula 2, and at least one of the remaining groups in R1 to R8 in Formula 2 other than the moiety linked to the azo group in Formula 1 can be a sulfonate group.

[0143] In one embodiment of the present invention, Ar1 in Formula 1 is represented by Formula 3, and at least one of the remaining groups in R9 to R14 in Formula 3 other than the moiety linked to the azo group in Formula 1 can be a halogen group.

[0144] In one embodiment of the present invention, Ar2 in Formula 1 is represented by Formula 3, and at least one of the remaining groups among R9 to R14 in Formula 3, except for the part connected to the azo group in Formula 1, may be a halogen group.

[0145] In one embodiment of the present invention, Ar1 in Formula 1 is represented by Formula 3, and at least one of the remaining groups among R9 to R14 in Formula 3, except for the part connected to the azo group in Formula 1, may be a hydroxyl group.

[0146] In one embodiment of the present invention, Ar2 in Formula 1 is represented by Formula 3, and at least one of the remaining groups among R9 to R14 in Formula 3, except for the part connected to the azo group in Formula 1, may be a hydroxyl group.

[0147] In one embodiment of the present invention, Ar1 in Formula 1 is represented by Formula 3, and in addition to the part of R9 to R14 in Formula 3 that is connected to the azo group in Formula 1, it may include at least one chlorine group, a sulfonate group, and a hydroxyl group.

[0148] In one embodiment of the present invention, Ar2 in Formula 1 is represented by Formula 3, and in addition to the part of R9 to R14 in Formula 3 that is connected to the azo group in Formula 1, it may include at least one chlorine group, a sulfonate group, and a hydroxyl group.

[0149] In one embodiment of the present invention, Ar1 in Formula 1 is represented by Formula 3, and in addition to the part of R9 to R14 in Formula 3 that is connected to the azo group in Formula 1, it may include at least one hydroxyl group and at least two sulfonate groups.

[0150] In one embodiment of the present invention, Ar2 in Formula 1 is represented by Formula 3, and in addition to the part of R9 to R14 in Formula 3 that is connected to the azo group in Formula 1, it may include at least one hydroxyl group and at least two sulfonate groups.

[0151] In one embodiment of the present invention, Ar1 in Formula 1 is represented by Formula 3, and in addition to the part of R9 to R14 in Formula 3 that is connected to the azo group in Formula 1, it may include at least one hydroxyl group, two or more sulfonate groups, and an amine group.

[0152] In one embodiment of the present invention, Ar2 in Formula 1 is represented by Formula 3, and in addition to the part of R9 to R14 in Formula 3 that is connected to the azo group in Formula 1, it may include at least one hydroxyl group, two or more sulfonate groups, and an amine group.

[0153] In one embodiment of the present invention, when at least one of R1 to R14 in Formula 2 and Formula 3 is a sulfonate group, the anion of the sulfonate group may be in the form of a salt combined with a metal cation, and specifically, it may be the sodium salt or calcium salt of the sulfonate group.

[0154] In one embodiment of the present invention, L1 of Formula 1 may be represented by the following Formula 4 or Formula 5.

[0155] [Formula 4]

[0156]

[0157] [Formula 5]

[0158]

[0159] In Formula 4,

[0160] R15 to R18 are the same as or different from each other, and each independently is hydrogen; deuterium; halogen; cyano; sulfonate group; hydroxyl group; amino group; nitro group; or a moiety connected to Formula 1, provided that any one of R15 to R18 is a moiety connected to the nitrogen atom not connected to Ar1 among the two nitrogen atoms of the azo group connected to Ar1 in the two azo groups of Formula 1, and R19 to R22 are the same as or different from each other, and each independently is hydrogen; deuterium; halogen; cyano; sulfonate group; hydroxyl group; amino group; nitro group; or a moiety connected to Formula 1, provided that any one of R19 to R22 is a moiety connected to the nitrogen atom not connected to Ar2 among the two nitrogen atoms of the azo group connected to Ar2 in the two azo groups of Formula 1, and

[0161] In Formula 5,

[0162] R23 to R27 are the same as or different from each other, and each independently is hydrogen; deuterium; halogen; cyano; sulfonate group; hydroxyl group; amino group; nitro group; substituted or unsubstituted C1-C5 alkyl group; substituted or unsubstituted C1-C5 alkoxy group; or a part connected to the nitrogen atom not connected to Ar1 among the two nitrogen atoms of the azo group connected to Ar1 in the two azo groups of Formula 1, provided that any one of R23 to R27 is a part connected to the nitrogen atom not connected to Ar1 among the two nitrogen atoms of the azo group connected to Ar1 in the two azo groups of Formula 1, and R28 to R32 are the same as or different from each other, and each independently is hydrogen; deuterium; halogen; cyano; sulfonate group; hydroxyl group; amino group; nitro group; substituted or unsubstituted C1-C5 alkyl group; substituted or unsubstituted C1-C5 alkoxy group; or a part connected to the nitrogen atom not connected to Ar2 among the two nitrogen atoms of the azo group connected to Ar2 in the two azo groups of Formula 1, provided that any one of R28 to R32 is a part connected to the nitrogen atom not connected to Ar2 among the two nitrogen atoms of the azo group connected to Ar2 in the two azo groups of Formula 1, and

[0163] Z is a single bond; substituted or unsubstituted C2-C10 alkenylene group; or substituted or unsubstituted C2-C10 alkynylene group.

[0164] In one embodiment of the present invention, in addition to the part connected to the nitrogen atom not connected to Ar1 among the two nitrogen atoms of the azo group connected to Ar1 in the two azo groups of Formula 1, at least one of R15 to R18 in Formula 4 may include at least a sulfonate group and a hydroxyl group, and in addition to the part connected to the nitrogen atom not connected to Ar2 among the two nitrogen atoms of the azo group connected to Ar2 in the two azo groups of Formula 1, at least one of R19 to R22 in Formula 4 may include at least a sulfonate group and a hydroxyl group.

[0165] In one embodiment of the present invention, in addition to the part connected to the nitrogen atom not connected to Ar1 among the two nitrogen atoms of the azo group connected to Ar1 in the two azo groups of Formula 1, at least one of R23 to R27 in Formula 5 may include at least one sulfonate group, and in addition to the part connected to the nitrogen atom not connected to Ar1 among the two nitrogen atoms of the azo group connected to Ar1 in the two azo groups of Formula 1, at least one of R28 to R32 in Formula 5 may include at least one sulfonate group.

[0166] In one embodiment of the present invention, except for the portion connected to the nitrogen atom not connected to Ar1 among the two nitrogen atoms of the azo group connected to Ar1 in the two azo groups of Formula 1, at least one of R23 to R27 in Formula 5 may include at least a substituted or unsubstituted C1-C3 alkyl group; or a substituted or unsubstituted C1-C3 alkoxy group, and except for the portion connected to the nitrogen atom not connected to Ar1 among the two nitrogen atoms of the azo group connected to Ar1 in the two azo groups of Formula 1, at least one of R28 to R32 in Formula 5 may include at least a substituted or unsubstituted C1-C3 alkyl group; or a substituted or unsubstituted C1-C3 alkoxy group.

[0167] In one embodiment of the present invention, except for the portion connected to the nitrogen atom not connected to Ar1 among the two nitrogen atoms of the azo group connected to Ar1 in the two azo groups of Formula 1, at least one of R23 to R27 in Formula 5 may include at least a substituted or unsubstituted methyl group; or a substituted or unsubstituted methoxy group, and except for the portion connected to the nitrogen atom not connected to Ar1 among the two nitrogen atoms of the azo group connected to Ar1 in the two azo groups of Formula 1, at least one of R28 to R32 in Formula 5 may include at least a substituted or unsubstituted methyl group; or a substituted or unsubstituted methoxy group.

[0168] In one embodiment of the present invention, the second dispersant may contain a compound represented by any one of the following Formulas 1-1a to 1-1d.

[0169] [Formula 1-1a]

[0170]

[0171] Wherein,

[0172] R1 to R5, R7 to R11, and R13 to R18 are the same as or different from each other, and each independently is hydrogen; deuterium; a halogen; a cyano group; a sulfonate group; a hydroxyl group; an amino group; or a nitro group,

[0173] [Formula 1-1b]

[0174]

[0175] Wherein,

[0176] R1 to R7 and R9 to R15 are the same as or different from each other, and each independently is hydrogen; deuterium; a halogen; a cyano group; a sulfonate group; a hydroxyl group; an amino group; a substituted or unsubstituted C1-C10 alkyl group; a substituted or unsubstituted C2-C10 alkenyl group; a substituted or unsubstituted C2-C10 alkynyl group; a substituted or unsubstituted C1-C10 alkoxy group; or a substituted or unsubstituted C6-C20 aryl group, provided that at least one of R1 to R7 is a sulfonate group, and at least one of R9 to R15 is a sulfonate group,

[0177] [Formula 1-1c]

[0178]

[0179] wherein,

[0180] R1 to R5 and R7 to R11 are the same as or different from each other, and each independently is hydrogen; deuterium; a halogen; a cyano group; a sulfonate group; a hydroxyl group; a substituted or unsubstituted C1-C10 alkyl group; a substituted or unsubstituted C2-C10 alkenyl group; a substituted or unsubstituted C2-C10 alkynyl group; a substituted or unsubstituted C1-C10 alkoxy group; a substituted or unsubstituted C6-C20 aryl group; or a substituted or unsubstituted C2-C20 heteroaryl group, provided that at least one of R1 to R5 is a hydroxyl group, and at least one of R7 to R11 is a hydroxyl group, and

[0181] R13 to R20 are the same as or different from each other, and each independently is hydrogen; deuterium; a halogen; a cyano group; a sulfonate group; a hydroxyl group; a substituted or unsubstituted C1-C10 alkyl group; a substituted or unsubstituted C2-C10 alkenyl group; a substituted or unsubstituted C2-C10 alkynyl group; a substituted or unsubstituted C1-C10 alkoxy group; a substituted or unsubstituted C6-C20 aryl group; or a substituted or unsubstituted C2-C20 heteroaryl group, provided that at least one of R13 to R16 is a sulfonate group, and at least one of R17 to R20 is a sulfonate group,

[0182] [Formula 1-1d]

[0183]

[0184] wherein,

[0185] R1 to R7 and R9 to R15 are the same as or different from each other, and each independently is hydrogen; deuterium; a halogen; a cyano group; a sulfonate group; a hydroxyl group; an amino group; or a nitro group, and

[0186] R17 to R20 and R22 to R25 are the same as or different from each other, and each independently is hydrogen; deuterium; a halogen; a cyano group; a sulfonate group; a hydroxyl group; an amino group; a nitro group; a substituted or unsubstituted C1 to C5 alkyl group; or a substituted or unsubstituted C1 to C5 alkoxy group.

[0187] In one embodiment of the present invention, R1 to R5 and R7 to R11 in Formula 1-1a may be the same as or different from each other, and may each independently be hydrogen; a halogen; a sulfonate group; or a hydroxyl group.

[0188] In one embodiment of the present invention, R13 to R18 in Formula 1-1a may be the same as or different from each other, and may each independently be hydrogen; a sulfonate group; or a hydroxyl group.

[0189] In one embodiment of the present invention, if the second dispersant is a compound represented by Formula 1-1a, it may include a compound represented by the following Formula 6 (chlorosulfophenol S).

[0190] [Formula 6]

[0191]

[0192] In the carbon nanotube dispersion according to one embodiment of the present invention, since the compound represented by Formula 1-1a contained in the second dispersant contains at least one hydroxyl group, it forms a hydrogen bond with the solvent in the dispersion, so that the "carbon nanotube-dispersant" complex is stably maintained in a dispersed state in the solvent.

[0193] Furthermore, in the carbon nanotube dispersion according to one embodiment of the present invention, since the compound represented by Formula 1-1a contained in the second dispersant contains at least one sulfonate group, the dispersant ionizes when dissolved in the solvent, thereby forming an electrostatic repulsion between the sulfonate anions to prevent aggregation between adjacent dispersants and enabling the "carbon nanotube-dispersant" complex to be stably maintained in a dispersed state in the solvent.

[0194] In one embodiment of the present invention, R1 to R7 in Formula 1-1b are the same as or different from each other, and each independently is hydrogen; a sulfonate group; or a hydroxyl group, provided that at least one of R1 to R7 may be a sulfonate group. In one embodiment of the present invention, R9 to R15 in Formula 1-1b are the same as or different from each other, and each independently is hydrogen; a sulfonate group; or a hydroxyl group, provided that at least one of R9 to R15 may be a sulfonate group.

[0195] In one embodiment of the present invention, if the second dispersant is a compound represented by Formula 1-1b, it may be at least one selected from Direct Red 28, Direct Red 2, Direct Red 7, Direct Red 46, and Direct Red 56, and it is not limited to the above types as long as it is a substituted azo compound that contains at least two sulfonate groups in the molecule and can improve the dispersibility of carbon nanotubes.

[0196] In one embodiment of the present invention, if the second dispersant is a compound represented by Formula 1-1b, it may further contain at least two amine groups.

[0197] If the second dispersant is a compound represented by Formula 1-1b, since it further contains at least two amine groups, it forms hydrogen bonds with the solvent so that the "carbon nanotube - dispersant" complex can be stably maintained in a dispersed state in the solvent, and since the hydrogen bond interaction between the nitrogen atom contained in the first dispersant and the amine group of the second dispersant is appropriately balanced, the effect of reducing the viscosity of the carbon nanotube dispersion and the effect of suppressing the increase in viscosity over time can also be improved.

[0198] In one embodiment of the present invention, R1 to R5 in Formula 1-1c are the same as or different from each other, and are each independently hydrogen; or a hydroxyl group, provided that at least one of R1 to R5 may be a hydroxyl group.

[0199] In one embodiment of the present invention, R7 to R11 in Formula 1-1c are the same as or different from each other, and are each independently hydrogen; or a hydroxyl group, provided that at least one of R7 to R11 may be a hydroxyl group.

[0200] In one embodiment of the present invention, R13 to R16 in Formula 1-1c are the same as or different from each other, and are each independently hydrogen; or a sulfonate group, provided that at least one of R13 to R16 may be a sulfonate group.

[0201] In one embodiment of the present invention, R17 to R20 in Formula 1-1c are the same as or different from each other, and are each independently hydrogen; or a sulfonate group, provided that at least one or more of R17 to R20 may be a sulfonate group.

[0202] In one embodiment of the present invention, if the second dispersant is a compound represented by Formula 1-1c, specific examples thereof may include Direct Yellow 4 in Formula 7 below, and it is not limited to the above types as long as it is a substituted azo compound that contains at least two sulfonate groups and at least two hydroxyl groups in the molecule and can improve the dispersibility of carbon nanotubes.

[0203] [Formula 7]

[0204]

[0205] In one embodiment of the present invention, R1 to R7 in Formula 1-1d are the same as or different from each other, and are each independently hydrogen; a sulfonate group; a hydroxyl group; or an amino group, provided that R1 to R7 may include at least one hydroxyl group and at least two sulfonate groups.

[0206] In one embodiment of the present invention, R9 to R15 in Formula 1-1d are the same as or different from each other, and are each independently hydrogen; a sulfonate group; a hydroxyl group; or an amino group, provided that R9 to R15 may include at least one hydroxyl group and at least two sulfonate groups.

[0207] In one embodiment of the present invention, R17 to R20 in Formula 1-1d may be the same as or different from each other, and may each independently be hydrogen; or a substituted or unsubstituted C1 to C5 alkyl group.

[0208] In one embodiment of the present invention, R22 to R25 in Formula 1-1d may be the same as or different from each other, and may each independently be hydrogen; or a substituted or unsubstituted C1 to C5 alkyl group.

[0209] In one embodiment of the present invention, if the second dispersant is a compound represented by Formula 1-1d, it may be at least one selected from Direct Blue 1, Direct Blue 14, Direct Blue 15, and Direct Blue 53.

[0210] In a carbon nanotube dispersion according to one embodiment of the present invention, since the compound represented by Formula 1-1d contained in the second dispersant contains at least one hydroxyl group, it forms a hydrogen bond with the solvent in the dispersion, so that the "carbon nanotube - dispersant" complex is stably maintained in a dispersed state in the solvent.

[0211] Furthermore, in a carbon nanotube dispersion according to one embodiment of the present invention, since the compound represented by Formula 1-1d contained in the second dispersant contains at least two sulfonate groups, the dispersant ionizes when dissolved in the solvent, thereby forming an electrostatic repulsion between the sulfonate anions to prevent aggregation between adjacent dispersants and enabling the "carbon nanotube - dispersant" complex to be stably maintained in a dispersed state in the solvent.

[0212] If the carbon nanotube dispersion does not contain the second dispersant according to the present invention, the area on the surface of the carbon nanotubes that is not sufficiently covered by the dispersant may increase, and as a result, a strong binding force greater than an appropriate level may be generated between the carbon nanotubes, and the viscosity of the dispersion may become high as a result of aggregation between the carbon nanotubes.

[0213] In addition, if the second dispersant contains, for example, three or more aromatic rings in its molecular structure, since the molecules are linearly angled or form a dense structure, it is not conducive to the surface adsorption of carbon nanotubes with a small diameter, especially single-walled carbon nanotubes. In addition, due to the strong π-π interaction between the unadsorbed dispersants and the aggregation of the dispersants being aggravated, the viscosity of the dispersion becomes high, and the viscosity of the dispersion may increase significantly over time.

[0214] In one embodiment of the present invention, based on 100 parts by weight of the carbon nanotube dispersion, the second dispersant may be included in an amount of 0.001 to 9 parts by weight. For example, it may be included in the following amounts: 0.001 parts by weight or more, 0.01 parts by weight or more, 0.1 parts by weight or more, 0.2 parts by weight or more, 0.3 parts by weight or more, 0.4 parts by weight or more, 0.5 parts by weight or more, 0.6 parts by weight or more, 0.7 parts by weight or more, 0.8 parts by weight or more, 0.9 parts by weight or more, 1 part by weight or more, 1.1 parts by weight or more, 1.2 parts by weight or more, 1.3 parts by weight or more, 1.4 parts by weight or more, 1.5 parts by weight or more, 1.6 parts by weight or more, 1.7 parts by weight or more, 1.8 parts by weight or more, 1.9 parts by weight or more, 2 parts by weight or more, 2.1 parts by weight or more, 2.2 parts by weight or more, 2.3 parts by weight or more, 2.4 parts by weight or more, 2.5 parts by weight or more, 2.6 parts by weight or more, 2.7 parts by weight or more, 2.8 parts by weight or more, 2.9 parts by weight or more, 3 parts by weight or more, 3.1 parts by weight or more, 3.2 parts by weight or more, 3.3 parts by weight or more, 3.4 parts by weight or more, 3.5 parts by weight or more, 3.6 parts by weight or more, 3.7 parts by weight or more, 3.8 parts by weight or more, 3.9 parts by weight or more, 4 parts by weight or more, 4.1 parts by weight or more, 4.2 parts by weight or more, 4.3 parts by weight or more, 4.4 parts by weight or more, or 4.5 parts by weight or more, and may be included in the following amounts: 9 parts by weight or less, 8.9 parts by weight or less, 8.8 parts by weight or less, 8.7 parts by weight or less, 8.6 parts by weight or less, 8.5 parts by weight or less, 8.4 parts by weight or less, 8.3 parts by weight or less, 8.2 parts by weight or less, 8.1 parts by weight or less, 8 parts by weight or less, 7.9 parts by weight or less, 7.8 parts by weight or less, 7.7 parts by weight or less, 7.6 parts by weight or less, 7.5 parts by weight or less, 7.4 parts by weight or less, 7.3 parts by weight or less, 7.2 parts by weight or less, 7.1 parts by weight or less, 7 parts by weight or less, 6.9 parts by weight or less, 6.8 parts by weight or less, 6.7 parts by weight or less, 6.6 parts by weight or less, 6.5 parts by weight or less, 6.4 parts by weight or less, 6.3 parts by weight or less, 6.2 parts by weight or less, 6.1 parts by weight or less, 6 parts by weight or less, 5.9 parts by weight or less, 5.8 parts by weight or less, 5.7 parts by weight or less, 5.6 parts by weight or less, 5.5 parts by weight or less, 5.4 parts by weight or less, 5.3 parts by weight or less, 5.2 parts by weight or less, 5.1 parts by weight or less, 5 parts by weight or less, 4.9 parts by weight or less, 4.8 parts by weight or less, 4.7 parts by weight or less, or 4.6 parts by weight or less.

[0215] If, based on 100 parts by weight of the carbon nanotube dispersion, the content of the second dispersant is less than 0.001 part by weight, there may be a problem that since an effective dispersion effect is not achieved, the viscosity of the dispersion may not be formed to be low, and the viscosity increases with time. If the content of the second dispersant exceeds 9 parts by weight, there may be a problem that due to the excessive content of the second dispersant, agglomeration occurs between the solid components in the dispersion, thereby increasing the viscosity of the dispersion.

[0216] In one embodiment of the present invention, the first dispersant and the second dispersant in the carbon nanotube dispersion may be included in a weight ratio of 100:10 to 100:90. For example, the ratio of the first dispersant to the second dispersant may be 100:10 or greater, 100:15 or greater, 100:17.65 or greater, 100:20 or greater, 100:25 or greater, 100:30 or greater, 100:33.33 or greater, 100:35 or greater, 100:40 or greater, 100:45 or greater, 100:50 or greater or 100:55 or greater, and the ratio of the first dispersant to the second dispersant may be 100:90 or less, 100:85 or less, 100:80 or less, 100:75 or less, 100:70 or less, 100:65 or less or 100:60 or less.

[0217] If the contents of the first dispersant and the second dispersant are included in the carbon nanotube dispersion in the above weight ratio, the carbon nanotubes are uniformly dispersed in the carbon nanotube dispersion, and thus the viscosity can be maintained at a constant level as a low viscosity over time.

[0218] (3) Solvent

[0219] The solvent of the carbon nanotube dispersion according to one embodiment of the present invention is a dispersion medium for dispersing the carbon nanotubes, the first dispersant, and the second dispersant, and is used to pre-disperse the carbon nanotubes in a powder state and supply them as a carbon nanotube dispersion to prevent agglomeration that occurs when directly using the carbon nanotubes in a powder state to prepare an electrode paste composition.

[0220] The solvent can dissolve or disperse the carbon nanotubes, the first dispersant, and the second dispersant to a certain level or higher. Considering the coating characteristics of the electrode paste composition prepared using the carbon nanotube dispersion later, the aqueous solvent may be, for example, water, and the aqueous solvent may be included in an amount such that the electrode paste composition can have an appropriate viscosity.

[0221] The carbon nanotube dispersion according to an embodiment of the present invention enables a first dispersant and a second dispersant to uniformly disperse carbon nanotubes in the solvent as described above, and thus can reduce the average particle size distribution of the dispersed particles (e.g., the complex of carbon nanotubes and each dispersant) contained in the dispersion.

[0222] The average particle size distribution (D 50 ) of the dispersed particles contained in the dispersion can be, for example, 0.5 μm to 10 μm, 1 μm to 10 μm, 1 μm to 8 μm, preferably 1 μm to 5 μm.

[0223] The carbon nanotube dispersion of the present invention containing the above components has excellent dispersibility, and thus the viscosity of the dispersion is low, and the degree of increase in viscosity over time is small.

[0224] The initial viscosity measured using a viscometer (viscometer TV-25, rotor code 01, manufactured by TOKI SANGYO company) for the carbon nanotube dispersion can be from 1 Pa·s to 8 Pa·s at 25 °C and 1 rpm. For example, it can be 1 Pa·s or greater, 1.1 Pa·s or greater, 1.2 Pa·s or greater, 1.3 Pa·s or greater, 1.4 Pa·s or greater, 1.5 Pa·s or greater, 1.6 Pa·s or greater, 1.7 Pa·s or greater, 1.8 Pa·s or greater, 1.9 Pa·s or greater, 2 Pa·s or greater, 2.1 Pa·s or greater, 2.2 Pa·s or greater, 2.3 Pa·s or greater, 2.4 Pa·s or greater, 2.5 Pa·s or greater, 2.6 Pa·s or greater, 2.7 Pa·s or greater, 2.8 Pa·s or greater, 2.9 Pa·s or greater, 3 Pa·s or greater, 3.1 Pa·s or greater, 3.2 Pa·s or greater, 3.3 Pa·s or greater, 3.4 Pa·s or greater, 3.5 Pa·s or greater, 3.6 Pa·s or greater, 3.7 Pa·s or greater, 3.8 Pa·s or greater, 3.9 Pa·s or greater, 4 Pa·s or greater, 4.1 Pa·s or greater, 4.2 Pa·s or greater, 4.3 Pa·s or greater, 4.4 Pa·s, 4.5 Pa·s or greater, 4.6 Pa·s or greater, 4.7 Pa·s or greater, 4.8 Pa·s or greater, 4.9 Pa·s or greater, 5 Pa·s or greater, 5.1 Pa·s or greater, 5.2 Pa·s or greater, 5.3 Pa·s or greater, 5.4 Pa·s or greater or 5.5 Pa·s or greater, and can be 10 Pa·s or less, 9.9 Pa·s or less, 9.8 Pa·s or less, 9.7 Pa·s or less, 9.6 Pa·s or less, 9.5 Pa·s or less, 9.4 Pa·s or less, 9.3 Pa·s or less, 9.2 Pa·s or less, 9.1 Pa·s or less, 9 Pa·s or less, 8.9 Pa·s or less, 8.8 Pa·s or less, 8.7 Pa·s or less, 8.6 Pa·s or less, 8.5 Pa·s or less, 8.4 Pa·s or less, 8.3 Pa·s or less, 8.2 Pa·s or less, 8.1 Pa·s or less, 8 Pa·s or less, 7.9 Pa·s or less, 7.8 Pa·s or less, 7.7 Pa·s or less, 7.6 Pa·s or less, 7.5 Pa·s or less, 7.4 Pa·s or less, 7.3 Pa·s or less, 7.2 Pa·s or less, 7.1 Pa·s or less, 7 Pa·s or less, 6.9 Pa·s or less, 6.8 Pa·s or less, 6.7 Pa·s or less, 6.6 Pa·s or less, 6.5 Pa·s or less, 6.4 Pa·s or less, 6.3 Pa·s or less, 6.2 Pa·s or less, 6.1 Pa·s or less, 6 Pa·s or less, 5.9 Pa·s or less, 5.8 Pa·s or less, 5.7 Pa·s or less, or 5.6 Pa·s or less. If the carbon nanotube dispersion has an initial viscosity within the above range, an electrode paste can be manufactured more smoothly using the same, and the electrode paste containing the carbon nanotube dispersion can have an appropriate viscosity for forming an electrode.

[0225] In addition, the viscosity increase rate calculated by the following Equation 1 when the carbon nanotube dispersion is left standing at 25°C for one week can be 0.1% to 15% or less. Specifically, the viscosity increase rate can be 15% or less, 14.5% or less, 14% or less, 13.5% or less, 13% or less, 12.5% or less, 12.3% or less, 12% or less, 11.5% or less, 11% or less, 10.5% or less, 10% or less, 9.5% or less, 9% or less, 8.5% or less, 8% or less, 7.5% or less, 7% or less, 6.8% or less, 6.5% or less, 6.1% or less, 6% or less, 5.5% or less, 5% or less, 4.5% or less, 4% or less, 3.5% or less, 3% or less, 2.5% or less, 2.4% or less, 2% or less, 1.5% or less, or 1% or less.

[0226] [Equation 1]

[0227] Viscosity increase rate (%) = { (viscosity measured after standing at 25°C for 1 week - initial viscosity) / initial viscosity} × 100

[0228] At this time, the viscosity after standing for 1 week and the initial viscosity are measured at 25°C and 1 rpm.

[0229] Method for preparing carbon nanotube dispersion

[0230] Hereinafter, a method for preparing a carbon nanotube dispersion according to an embodiment of the present invention will be described.

[0231] The method for preparing a carbon nanotube dispersion according to the present invention includes the following steps: (1) preparing a primary dispersion of carbon nanotubes by mixing carbon nanotubes, a first dispersant containing a nitrogen atom, a second dispersant containing a compound represented by the following Formula 1, and a solvent; and (2) dispersing the primary dispersion of carbon nanotubes to prepare a secondary dispersion of carbon nanotubes.

[0232] [Formula 1]

[0233]

[0234] Wherein,

[0235] Ar1 and Ar2 are each independently a substituted or unsubstituted C6-C30 aryl group, and L1 is a substituted or unsubstituted C6-C30 arylene group.

[0236] In step (1), a carbon nanotube, a first dispersant containing a nitrogen atom, a second dispersant containing a compound represented by the following formula 1, and a solvent are mixed to prepare a primary dispersion of carbon nanotubes. The step of preparing the primary dispersion of carbon nanotubes is carried out by a wet process in which the respective components are uniformly mixed.

[0237] Since the specific descriptions of the carbon nanotubes, the first dispersant containing a nitrogen atom, the second dispersant containing a compound represented by the following formula 1, and the solvent according to the method for preparing the carbon nanotube dispersion are the same as those described above, the specific descriptions will be omitted hereinafter.

[0238] The mixing for preparing the primary dispersion of carbon nanotubes can be carried out using a conventional mixing method. Specifically, the mixing device can be, for example, a small mixer, a tank-changing mixer, a Hobert mixer, a planetary mixer, a butterfly mixer, a stone mill, a homogenizer, a bead mill, a ball mill, a basket mill, a grinder, a general stirrer, a transparent mixer, or a TK mixer, and can include a step of mixing at a rotation speed of 300 rpm to 5,000 rpm for 30 minutes to 7 hours.

[0239] In addition, when mixing is carried out to prepare the primary dispersion of carbon nanotubes, cavitation dispersion treatment can also be carried out to improve the miscibility of the carbon nanotubes and the solvent, or the dispersibility of the carbon nanotubes in the solvent. The cavitation dispersion treatment is a dispersion treatment method using the shock wave generated by the explosion of the vacuum bubbles formed in water when high energy is applied to the liquid, and the carbon nanotubes can be dispersed by such a dispersion treatment method without damaging their properties. Specifically, the cavitation dispersion treatment can be carried out by ultrasonic waves, jet milling, or shear dispersion treatment.

[0240] The step of preparing the primary dispersion of carbon nanotubes can be carried out under temperature conditions under which the physical properties (including viscosity) of the mixture do not change due to the evaporation of the solvent. For example, it can be carried out at 50°C or lower, more specifically, at a temperature of 5°C to 50°C.

[0241] In step (2), the primary dispersion of carbon nanotubes is dispersed to prepare a secondary dispersion of carbon nanotubes.

[0242] The process of preparing the secondary dispersion of carbon nanotubes can be carried out by methods such as a ball mill, a bead mill, a disk mill, or a basket mill, a high-pressure disperser (high-pressure homogenizer), and more specifically, it can be carried out by a dispersion method using a high-pressure disperser (high-pressure homogenizer).

[0243] Dispersion through the high-pressure disperser is achieved by, for example, pressurizing the mixture with a plunger pump of the high-pressure disperser and pushing it through the gap of the dispersion valve, thereby causing forces such as cavitation, shear, impact, and explosion when passing through the gap.

[0244] The dispersion process can be carried out according to the degree of dispersion of the carbon nanotube dispersion, and specifically, it can be carried out at a pressure of 5,000 psi to 30,000 psi for 30 minutes to 120 minutes, more specifically, 60 minutes to 90 minutes, and the above process can be repeated 1 time to 10 times.

[0245] The carbon nanotube dispersion according to the present invention can mean a secondary dispersion of carbon nanotubes.

[0246] Electrode paste composition for lithium secondary battery

[0247] In addition, the present invention provides an electrode paste composition for lithium secondary battery, which contains the carbon nanotube dispersion and an electrode active material.

[0248] The electrode paste composition for lithium secondary battery can be a positive electrode paste composition or a negative electrode paste composition, and specifically, it can be a negative electrode paste composition.

[0249] The electrode paste composition for lithium secondary battery can contain 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).

[0250] As the positive electrode active material, positive electrode active materials well-known in the art can be used without limitation. For example, lithium cobalt-based oxides, lithium nickel-based oxides, lithium manganese-based oxides, lithium iron phosphate oxides, lithium nickel manganese cobalt-based oxides, or combinations thereof can be used. Specifically, as the positive electrode active material, LiCoO2, LiNiO2, LiMn2O4, LiCoPO4, LiFePO4, and LiNiaMnbCocO2 (where 0 < a, b, c < 1) can be used, but not limited thereto.

[0251] The negative electrode active material can include one or more negative electrode active materials selected from the following: natural graphite, artificial graphite, carbonaceous materials; lithium-containing titanium composite oxides (LTO); metals (Me) such as Si, Sn, Li, Zn, Mg, Cd, Ce, Ni, or Fe; alloys composed of metals (Me); oxides of metals (MeO x );and composites of metals (Me) and carbon. Based on the total weight of the solids other than the solvent in the negative electrode paste, the negative electrode active material can be included in an amount of 60% by weight to 98% by weight, more preferably 70% by weight to 98% by weight.

[0252] The binder is a component that helps the active material to bind to the conductive material and to the current collector, and is usually added in an amount of 1 wt% to 30 wt% based on the total weight of the mixture containing the electrode active material. Examples of such binders can 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, various copolymers, etc.

[0253] The solvent can include organic solvents such as N-methylpyrrolidone (NMP), dimethylformamide (DMF), acetone, dimethylacetamide, etc., or water, and these solvents can be used alone or in a mixture of two or more. By considering the coating thickness of the slurry and the preparation yield, the amount of the solvent is sufficient as long as the solvent used can dissolve and disperse the electrode active material, the binder, and the conductive material.

[0254] The viscosity modifier can be carboxymethyl cellulose, polyacrylic acid, etc., and by adding it, the viscosity of the electrode slurry can be adjusted to facilitate the preparation of the electrode slurry and the application process on the electrode current collector.

[0255] Optionally, a filler is used as a component to inhibit electrode swelling, and the filler is not particularly limited as long as it is a fibrous material that does not cause chemical changes to the battery. For example, an olefin polymer such as polyethylene and polypropylene is used; fibrous materials such as glass fiber and carbon fiber are used.

[0256] If the electrode slurry composition is a positive electrode slurry composition for forming a positive electrode, the positive electrode slurry composition can be applied to the positive electrode current collector, and then dried and roll-pressed to manufacture the positive electrode. Alternatively, the positive electrode can also be manufactured by casting the positive electrode slurry on a separate support, peeling it from the support to obtain a film, and laminating it on the positive electrode current collector.

[0257] The thickness of the positive electrode active material layer formed from the positive electrode slurry can be changed according to the loading amount, loading speed, etc. of the applied positive electrode slurry.

[0258] The thickness of the positive electrode current collector is generally from 3 μm to 500 μm. The positive electrode current collector is not particularly limited as long as it has high electrical conductivity and does not cause chemical changes in the relevant battery. For example, stainless steel; aluminum; nickel; titanium; sintered carbon; or aluminum or stainless steel whose surface is treated with carbon, nickel, titanium, silver, etc. can be used. In addition, the positive electrode current collector may have minute irregularities formed on its surface to enhance the bonding force with the positive electrode active material, and can be formed in various forms (such as film, sheet, foil, net, porous body, foam, nonwoven fabric, etc.).

[0259] If the electrode paste composition is a negative electrode paste composition for forming a negative electrode, the negative electrode can be manufactured by applying the negative electrode paste composition onto a negative electrode current collector, followed by drying and rolling. Alternatively, the negative electrode can also be manufactured by casting the negative electrode paste on a separate support, peeling it off from the support to obtain a film, and laminating it on the negative electrode current collector.

[0260] The thickness of the negative electrode active material layer formed from the negative electrode paste can be changed according to the coating amount of the negative electrode paste applied, the coating speed, etc.

[0261] The thickness of the negative electrode current collector is generally from 3 μm to 500 μm. The negative electrode current collector is not particularly limited as long as it has high electrical conductivity and does not cause chemical changes in the relevant battery. For example, copper; stainless steel; aluminum; nickel; titanium; sintered carbon; or copper or stainless steel whose surface is treated with carbon, nickel, titanium, silver, etc.; or an aluminum - cadmium alloy can be used. In addition, similar to the positive electrode current collector, the negative electrode current collector may have minute irregularities formed on its surface to enhance the bonding force with the negative electrode active material, and can be formed in various forms (such as film, sheet, foil, net, porous body, foam, nonwoven fabric, etc.).

[0262] Lithium secondary battery

[0263] The lithium secondary battery includes a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte solution. Since the positive electrode and the negative electrode are the same as those described above, their detailed descriptions are omitted.

[0264] The separator separates the negative electrode and the positive electrode and provides a path for the movement of lithium ions. The separator can be used without any particular limitation as long as it is generally used as a separator in a lithium secondary battery. As the separator, it is particularly preferable to have low resistance to the ion movement of the electrolyte and excellent electrolyte solution impregnation ability. Specifically, a porous polymer film can be used, such as a porous polymer film made of a polyolefin-based polymer such as ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, ethylene / methacrylate copolymer, etc., or a laminated structure of two or more layers thereof. In addition, a conventional porous nonwoven fabric can also be used, such as a nonwoven fabric made of high melting point glass fiber, polyethylene terephthalate fiber, etc. In addition, a coated separator containing a ceramic component or a polymer material can be used to ensure heat resistance or mechanical strength, and the separator can be selectively used in a single-layer or multi-layer structure.

[0265] The electrolyte can include, but is not limited to, organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, and melt-type inorganic electrolytes that can be used to manufacture lithium secondary batteries. Specifically, the electrolyte can contain an organic solvent and a lithium salt.

[0266] The organic solvent can be used without any particular limitation as long as it can be used as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, the organic solvent can be an ester-based solvent such as methyl acetate, ethyl acetate, γ-butyrolactone, or ε-caprolactone; an ether-based solvent such as dibutyl ether or tetrahydrofuran; a ketone-based solvent such as cyclohexanone; an aromatic hydrocarbon-based solvent such as benzene or fluorobenzene; a carbonate-based solvent such as dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), or propylene carbonate (PC); an alcohol-based solvent such as ethanol or isopropyl alcohol; a nitrile such as R-CN (R is a C2 to C20 linear, branched, or cyclic hydrocarbon group and may include a double bond aromatic ring or an ether bond); an amide such as dimethylformamide; a dioxolane such as 1,3-dioxolane; or sulfolane. Among them, carbonate-based solvents are preferred, and a mixture of a cyclic carbonate having high ionic conductivity and high dielectric constant (e.g., ethylene carbonate or propylene carbonate, etc.) and a linear carbonate-based compound having low viscosity (e.g., methyl ethyl carbonate, dimethyl carbonate, or diethyl carbonate, etc.) that can improve the charge / discharge performance of the battery is more preferred. In this case, when the cyclic carbonate and the chain carbonate are mixed at a volume ratio of about 1:1 to about 1:9, the performance of the electrolyte can be excellent.

[0267] The lithium salt can be used without particular limitation as long as it is a compound capable of providing lithium ions used in a lithium secondary battery. Specifically, the lithium salt can be LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, or LiB(C2O4)2. The concentration of the lithium salt is preferably used in the range of 0.1 M to 2.0 M. If the concentration of the lithium salt is within the above range, since the electrolyte has appropriate conductivity and viscosity, excellent electrolyte performance can be exhibited, and lithium ions can move effectively.

[0268] In the electrolyte, in addition to the above electrolyte components, for the purpose of improving the life characteristics of the battery, suppressing the reduction of the battery capacity, and improving the discharge capacity of the battery, for example, one or more additives can also be included, such as, for example, a compound based on a haloalkyl carbonate such as difluoroethylene carbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ether, ethylenediamine, n-glycol dimethyl ether, hexaphosphoric triamide, nitrobenzene derivative, sulfur, quinone imine dye, N-substituted oxazolidone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxyethanol, or aluminum trichloride. In this case, based on the total weight of the electrolyte, the additive can be included in an amount of 0.1% by weight to 5% by weight.

[0269] A lithium secondary battery including an electrode manufactured using the carbon nanotube dispersion according to the present invention, specifically, a lithium secondary battery including a negative electrode manufactured using the carbon nanotube dispersion, can stably exhibit excellent discharge capacity and output characteristics because the carbon nanotubes are uniformly dispersed in the negative electrode, and the content of the carbon nanotubes can be reduced compared to the case of including a conductive material such as conventional carbon black. Therefore, it can be used in the fields of portable devices (such as mobile phones, laptop computers, and digital cameras) and electric vehicles (such as hybrid electric vehicles (HEV)).

[0270] Therefore, according to another embodiment of the present invention, a battery module including a lithium secondary battery as a unit cell and a battery pack including the same can be provided.

[0271] A battery module or battery pack can be used as a power source for any one or more of the following medium and large-sized devices: power tools; electric vehicles, including electric vehicles (EVs), hybrid electric vehicles, and plug-in hybrid electric vehicles (PHEVs); or power storage systems; and so on.

[0272] Embodiments of the Invention

[0273] Hereinafter, specific embodiments of the present invention are presented. However, the embodiments described below are only for specifically exemplifying or explaining the present invention, and the present invention is not limited thereto. In addition, since those skilled in the art can sufficiently infer technically what is not described herein, its description is omitted.

[0274] Example

[0275] Example 1a

[0276] (1) 5.625 g (1.125 parts by weight relative to a total of 100 parts by weight of the carbon nanotube dispersion) of polyvinylpyrrolidone (PVP) (PVP K15, prepared by Zhangzhou Huafu Chemical Company) as a first dispersant containing nitrogen atoms, 1.875 g (0.375 parts by weight relative to a total of 100 parts by weight of the carbon nanotube dispersion) of sodium calcium salt of chlorosulfophenol S as a second dispersant containing the compound represented by Formula 1 (prepared by Sigma Aldrich Company), and 487.5 g of water as a solvent were mixed to prepare a 495 g mixed solution. The mixed solution was placed in a dissolution tank (dissolver, Dispermat-CA, prepared by VMA-GETZMANN Company) equipped with an impeller and a container, and mixed by stirring at 400 rpm for 10 minutes.

[0277] (2) 5.0 g (1.0 part by weight relative to a total of 100 parts by weight of the carbon nanotube dispersion) of single-walled carbon nanotubes (SWCNTs, TUBALL, prepared by OCSiAl Company) having a specific surface area of 1,160 m 2 / g and an average particle size (D 50 ) of 5 μm were additionally added to the above mixture, and the mixture was stirred at 8,000 rpm for 60 minutes to prepare a primary dispersion of a total of 500 g of carbon nanotubes.

[0278] (3) Use a high-pressure disperser (PICOMAX, manufactured by Micronox company) to uniformly disperse the primary dispersion of carbon nanotubes 7 times at a pressure of 20,000 psi to prepare a secondary dispersion of carbon nanotubes.

[0279] Example 2a

[0280] Prepare a carbon nanotube dispersion in the same manner as in Example 1a, except that in Example 1a above, the content of the first dispersant is 5.0 g (1.0 wt% relative to a total of 100 parts by weight of the carbon nanotube dispersion), and the content of the second dispersant is 2.5 g (0.5 wt% relative to a total of 100 parts by weight of the carbon nanotube dispersion).

[0281] Example 3a

[0282] Prepare a carbon nanotube dispersion in the same manner as in Example 1a, except that in Example 1a above, the content of the first dispersant is 3.375 g (0.675 wt% relative to a total of 100 parts by weight of the carbon nanotube dispersion), the content of the second dispersant is 1.125 g (0.225 wt% relative to a total of 100 parts by weight of the carbon nanotube dispersion), and the content of the carbon nanotubes is 3.0 g (0.6 wt% relative to a total of 100 parts by weight of the carbon nanotube dispersion).

[0283] Example 1b

[0284] (1) Mix 4.5 g (0.9 wt% relative to a total of 100 parts by weight of the carbon nanotube dispersion) of polyvinylpyrrolidone (PVP) (PVP K15, prepared by ZhangzhouHuafu Chemicalcompany), which is a first dispersant (a polymer dispersant containing a nitrogen atom), 1.5 g (0.3 wt% relative to a total of 100 parts by weight of the carbon nanotube dispersion) of Direct Red 28 (prepared by Sigma Aldrich company), which is a second dispersant containing a compound having at least two azo groups and two or more sulfonate groups, and 490 g of water as a solvent to prepare a 496 g mixed solution. Place the mixed solution in a dissolution tank (dissolver, Dispermat-CA, manufactured by VMA-GETZMANNcompany) equipped with an impeller and a container, and mix by stirring at 400 rpm for 10 minutes.

[0285] (2) Add an additional 4.0 g (0.8 wt% relative to a total of 100 parts by weight of the carbon nanotube dispersion) having a specific surface area of 1,160 m 2 / g and an average particle size of 5 μm (D50 ) single-walled carbon nanotubes (SWCNT, TUBALL, prepared by OCSiAl company), and the mixture was stirred at 8,000 rpm for 60 minutes to prepare a primary dispersion of a total of 500 g of carbon nanotubes.

[0286] (3) Using a high-pressure disperser (PICOMAX, manufactured by Micronox company), the primary dispersion of carbon nanotubes was uniformly dispersed 7 times at a pressure of 14,000 psi to prepare a carbon nanotube dispersion.

[0287] Example 2b

[0288] A carbon nanotube dispersion was prepared in the same manner as in Example 1b, except that in the above Example 1b, the content of carbon nanotubes was 1.0 parts by weight relative to a total of 100 parts by weight of the carbon nanotube dispersion, the content of the first dispersant was 1.125 parts by weight relative to a total of 100 parts by weight of the carbon nanotube dispersion, and the content of the second dispersant was 0.375 parts by weight relative to a total of 100 parts by weight of the carbon nanotube dispersion.

[0289] Example 3b

[0290] A carbon nanotube dispersion was prepared in the same manner as in Example 1b, except that in the above Example 1b, the content of carbon nanotubes was 1.0 parts by weight relative to a total of 100 parts by weight of the carbon nanotube dispersion, the content of the first dispersant was 1.12 parts by weight relative to a total of 100 parts by weight of the carbon nanotube dispersion, and the content of the second dispersant was 0.3 parts by weight relative to a total of 100 parts by weight of the carbon nanotube dispersion.

[0291] Example 4b

[0292] A carbon nanotube dispersion was prepared in the same manner as in Example 1b, except that in the above Example 1b, the content of carbon nanotubes was 1.0 parts by weight relative to a total of 100 parts by weight of the carbon nanotube dispersion, the content of the first dispersant was 1.0 parts by weight relative to a total of 100 parts by weight of the carbon nanotube dispersion, and the content of the second dispersant was 0.5 parts by weight relative to a total of 100 parts by weight of the carbon nanotube dispersion.

[0293] Example 5b

[0294] A carbon nanotube dispersion was prepared in the same manner as in Example 1b, except that in the above Example 1b, 1.5 g (0.3 parts by weight relative to a total of 100 parts by weight of the carbon nanotube dispersion) of Direct Red 7 (prepared by SigmaAldrich company) was used instead of Direct Red 28.

[0295] Example 1c

[0296] (1) 4.5 g (0.9 parts by weight relative to a total of 100 parts by weight of the carbon nanotube dispersion) of polyvinylpyrrolidone K15 (PVP K15, prepared by Zhangzhou Huafu Chemical company), which is a first dispersant and a polymer dispersant containing a nitrogen atom, 1.5 g (0.3 parts by weight relative to a total of 100 parts by weight of the carbon nanotube dispersion) of Direct Yellow 4 (prepared by Sigma Aldrich company), which is a second dispersant and a compound containing at least two azo groups, two or more sulfonate groups, and two or more hydroxyl groups, and 490 g of water as a solvent were mixed to prepare 496 g of a mixed solution. The mixed solution was placed in a dissolution tank (dissolver, Dispermat - CA, manufactured by VMA - GETZMANN company) equipped with an impeller and a container, and mixed by stirring at 400 rpm for 10 minutes.

[0297] To the above mixture, an additional 4.0 g (0.8 parts by weight relative to a total of 100 parts by weight of the carbon nanotube dispersion) of single - wall carbon nanotubes (SWCNT, TUBALL, prepared by OCSiAl company) having a specific surface area of 1,160 m 2 / g and an average particle size (D 50 ) of 5 μm was added, and the mixture was stirred at 8,000 rpm for 60 minutes to prepare a primary dispersion of 500 g of carbon nanotubes in total.

[0298] (2) The primary dispersion of carbon nanotubes was uniformly dispersed 7 times at a pressure of 14,000 psi using a high - pressure disperser (PICOMAX, manufactured by Micronox company) to prepare a carbon nanotube dispersion.

[0299] Example 2c

[0300] A carbon nanotube dispersion was prepared in the same manner as in Example 1c, except that in Example 1c above, the content of the first dispersant was 0.96 parts by weight relative to a total of 100 parts by weight of the carbon nanotube dispersion, and the content of the second dispersant was 0.24 parts by weight relative to a total of 100 parts by weight of the carbon nanotube dispersion.

[0301] Example 3c

[0302] A carbon nanotube dispersion was prepared in the same manner as in Example 1c, except that in Example 1c above, the content of the first dispersant was 0.8 parts by weight relative to a total of 100 parts by weight of the carbon nanotube dispersion, and the content of the second dispersant was 0.4 parts by weight relative to a total of 100 parts by weight of the carbon nanotube dispersion.

[0303] Example 4c

[0304] A carbon nanotube dispersion was prepared in the same manner as in Example 1c, except that in Example 1c above, the content of the first dispersant was 1.0 parts by weight relative to a total of 100 parts by weight of the carbon nanotube dispersion, and the content of the second dispersant was 0.8 parts by weight relative to a total of 100 parts by weight of the carbon nanotube dispersion.

[0305] Example 5c

[0306] A carbon nanotube dispersion was prepared in the same manner as in Example 1c, except that in Example 1c above, the content of the first dispersant was 2.4 parts by weight relative to a total of 100 parts by weight of the carbon nanotube dispersion, and the content of the second dispersant was 1.2 parts by weight relative to a total of 100 parts by weight of the carbon nanotube dispersion.

[0307] Example 1d

[0308] (1) 4.5 g (0.9 parts by weight relative to a total of 100 parts by weight of the carbon nanotube dispersion) of polyvinylpyrrolidone (PVP K15, prepared by Zhangzhou Huafu Chemical company) as the first dispersant containing a nitrogen atom, 1.5 g (0.3 parts by weight relative to a total of 100 parts by weight of the carbon nanotube dispersion) of Direct Blue 53 (prepared by Sigma Aldrich company) as the second dispersant containing the compound represented by Formula 1, and 490 g of water as the solvent were mixed to prepare a 496 g mixed solution. The mixed solution was placed in a dissolution tank (dissolver, Dispermat-CA, manufactured by VMA-GETZMANN company) equipped with an impeller and a container, and mixed by stirring at 400 rpm for 10 minutes.

[0309] To the above mixture, 4.0 g (0.8 parts by weight relative to a total of 100 parts by weight of the carbon nanotube dispersion) of single-walled carbon nanotubes (SWCNT, TUBALL, prepared by OCSiAl company) having a specific surface area of 1,160 m 2 / g and an average particle size (D 50 ) of 5 μm was further added, and the mixture was stirred at 8,000 rpm for 60 minutes to prepare a primary dispersion of 500 g of carbon nanotubes in total.

[0310] (3) Using a high-pressure disperser (PICOMAX, manufactured by Micronox company), the primary dispersion of carbon nanotubes was uniformly dispersed 7 times at a pressure of 14,000 psi to prepare a secondary dispersion of carbon nanotubes.

[0311] Example 2d

[0312] A carbon nanotube dispersion was prepared in the same manner as in Example 1d, except that in Example 1d above, the content of the first dispersant was 4.8 g (0.96 wt% relative to a total of 100 wt% of the carbon nanotube dispersion), and the content of the second dispersant was 1.2 g (0.24 wt% relative to a total of 100 wt% of the carbon nanotube dispersion).

[0313] Example 3d

[0314] A carbon nanotube dispersion was prepared in the same manner as in Example 1d, except that in Example 1d above, the content of the first dispersant was 4.0 g (0.8 wt% relative to a total of 100 wt% of the carbon nanotube dispersion), and the content of the second dispersant was 2.0 g (0.4 wt% relative to a total of 100 wt% of the carbon nanotube dispersion).

[0315] Comparative Example 1a

[0316] A carbon nanotube dispersion was prepared in the same manner as in Example 1a, except that in Example 1a above, the second dispersant was not added.

[0317] Comparative Example 2a

[0318] A carbon nanotube dispersion was prepared in the same manner as in Example 1a, except that in Example 1a above, the content of the carbon nanotubes was 3.0 g (0.6 wt% relative to a total of 100 wt% of the carbon nanotube dispersion), the content of the first dispersant was 4.5 g (0.9 wt% relative to a total of 100 wt% of the carbon nanotube dispersion), and the second dispersant was not added.

[0319] Comparative Example 3a

[0320] A carbon nanotube dispersion was prepared in the same manner as in Example 1a, except that in Example 1a above, the content of the first dispersant was 7.275 g (1.455 wt% relative to a total of 100 wt% of the carbon nanotube dispersion), and the content of the second dispersant was 0.225 g (0.045 wt% relative to a total of 100 wt% of the carbon nanotube dispersion).

[0321] Comparative Example 4a

[0322] A carbon nanotube dispersion was prepared in the same manner as in Example 1a, except that in Example 1a above, no first dispersant was added and the content of the second dispersant was 7.5 g (1.5 parts by weight relative to a total of 100 parts by weight of the carbon nanotube dispersion).

[0323] Comparative Example 5a

[0324] A carbon nanotube dispersion was prepared in the same manner as in Example 1a, except that in Example 1a above, the content of the first dispersant was 0.225 g (0.045 parts by weight relative to a total of 100 parts by weight of the carbon nanotube dispersion) and the content of the second dispersant was 7.275 g (1.455 parts by weight relative to a total of 100 parts by weight of the carbon nanotube dispersion).

[0325] Comparative Example 6a

[0326] A carbon nanotube dispersion was prepared in the same manner as in Example 1a, except that in Example 3a above, 1.125 g (0.225 parts by weight relative to a total of 100 parts by weight of the carbon nanotube dispersion) of triphenylstyryl phenol ethoxylate was used instead of calcium sodium salt of chlorosulfophenol S as the second dispersant.

[0327] Comparative Example 7a

[0328] A carbon nanotube dispersion was prepared in the same manner as in Example 1a, except that in Example 3a above, 1.125 g (0.225 parts by weight relative to a total of 100 parts by weight of the carbon nanotube dispersion) of styrene maleic acid copolymer was used instead of calcium sodium salt of chlorosulfophenol S as the second dispersant.

[0329] Comparative Example 1b

[0330] A carbon nanotube dispersion was prepared in the same manner as in Example 1b, except that in Example 1b above, the content of the carbon nanotubes was 1.0 part by weight relative to a total of 100 parts by weight of the carbon nanotube dispersion, the content of the first dispersant was 1.125 parts by weight relative to a total of 100 parts by weight of the carbon nanotube dispersion, and no second dispersant was added.

[0331] Comparative Example 2b

[0332] A carbon nanotube dispersion was prepared in the same manner as in Example 1b, except that in the above Example 1b, the content of the carbon nanotubes was 1.0 parts by weight relative to a total of 100 parts by weight of the carbon nanotube dispersion, the content of the first dispersant was 0.75 parts by weight relative to a total of 100 parts by weight of the carbon nanotube dispersion, and the content of the second dispersant was 0.75 parts by weight relative to a total of 100 parts by weight of the carbon nanotube dispersion.

[0333] Comparative Example 3b

[0334] A carbon nanotube dispersion was prepared in the same manner as in Example 1b, except that in the above Example 1b, the content of the carbon nanotubes was 1.0 parts by weight relative to a total of 100 parts by weight of the carbon nanotube dispersion, the content of the first dispersant was 1.4 parts by weight relative to a total of 100 parts by weight of the carbon nanotube dispersion, and the content of the second dispersant was 0.1 parts by weight relative to a total of 100 parts by weight of the carbon nanotube dispersion.

[0335] Comparative Example 4b

[0336] A carbon nanotube dispersion was prepared in the same manner as in Example 1b, except that in the above Example 1b, the first dispersant was not added, and the content of the second dispersant was 1.2 parts by weight relative to a total of 100 parts by weight of the carbon nanotube dispersion.

[0337] Comparative Example 5b

[0338] A carbon nanotube dispersion was prepared in the same manner as in Example 1b, except that in the above Example 1b, the content of the carbon nanotubes was 0.6 parts by weight relative to a total of 100 parts by weight of the carbon nanotube dispersion, the content of the first dispersant was 0.675 parts by weight relative to a total of 100 parts by weight of the carbon nanotube dispersion, and the content of tri-styryl phenol ethoxylate, which replaced direct red 28 as the second dispersant, was 0.225 parts by weight relative to a total of 100 parts by weight of the carbon nanotube dispersion.

[0339] Comparative Example 6b

[0340] A carbon nanotube dispersion was prepared in the same manner as in Example 1b, except that in the above Example 1b, the content of the carbon nanotubes was 0.6 parts by weight relative to a total of 100 parts by weight of the carbon nanotube dispersion, the content of the first dispersant was 0.675 parts by weight relative to a total of 100 parts by weight of the carbon nanotube dispersion, and the content of styrene maleic anhydride copolymer, which replaced direct red 28 as the second dispersant, was 0.225 parts by weight relative to a total of 100 parts by weight of the carbon nanotube dispersion.

[0341] Comparative Example 1c

[0342] A carbon nanotube dispersion was prepared in the same manner as in Example 1c, except that in the above Example 1c, the content of the first dispersant was 1.2 parts by weight relative to a total of 100 parts by weight of the carbon nanotube dispersion, and the second dispersant was not added.

[0343] Comparative Example 2c

[0344] A carbon nanotube dispersion was prepared in the same manner as in Example 1c, except that in the above Example 1c, the content of the first dispersant was 0.6 parts by weight relative to a total of 100 parts by weight of the carbon nanotube dispersion, and the content of the second dispersant was 0.6 parts by weight relative to a total of 100 parts by weight of the carbon nanotube dispersion.

[0345] Comparative Example 3c

[0346] A carbon nanotube dispersion was prepared in the same manner as in Example 1c, except that in the above Example 1c, the content of the first dispersant was 1.12 parts by weight relative to a total of 100 parts by weight of the carbon nanotube dispersion, and the content of the second dispersant was 0.08 parts by weight relative to a total of 100 parts by weight of the carbon nanotube dispersion.

[0347] Comparative Example 4c

[0348] A carbon nanotube dispersion was prepared in the same manner as in Example 1c, except that in the above Example 1c, the first dispersant was not added, and the content of the second dispersant was 1.2 parts by weight relative to a total of 100 parts by weight of the carbon nanotube dispersion.

[0349] Comparative Example 5c

[0350] A carbon nanotube dispersion was prepared in the same manner as in Example 1c, except that in the above Example 1c, the content of the carbon nanotubes was 0.6 parts by weight relative to a total of 100 parts by weight of the carbon nanotube dispersion, the content of the first dispersant was 0.675 parts by weight relative to a total of 100 parts by weight of the carbon nanotube dispersion, and the content of triphenylvinylphenol ethoxylate, which replaced direct yellow 4 as the second dispersant, was 0.225 parts by weight relative to a total of 100 parts by weight of the carbon nanotube dispersion.

[0351] Comparative Example 6c

[0352] A carbon nanotube dispersion was prepared in the same manner as in Example 1c, except that in the above Example 1c, the content of carbon nanotubes was 0.6 parts by weight relative to a total of 100 parts by weight of the carbon nanotube dispersion, the content of the first dispersant was 0.675 parts by weight relative to a total of 100 parts by weight of the carbon nanotube dispersion, and the content of a styrene maleic acid copolymer as the second dispersant instead of direct yellow 4 was 0.225 parts by weight relative to a total of 100 parts by weight of the carbon nanotube dispersion.

[0353] Comparative Example 1d

[0354] A carbon nanotube dispersion was prepared in the same manner as in Example 1d, except that in the above Example 1d, the content of the first dispersant was 6.0 g (1.2 parts by weight relative to a total of 100 parts by weight of the carbon nanotube dispersion), and the second dispersant was not added.

[0355] Comparative Example 2d

[0356] A carbon nanotube dispersion was prepared in the same manner as in Example 1d, except that in the above Example 1d, the content of the first dispersant was 3.0 g (0.6 parts by weight relative to a total of 100 parts by weight of the carbon nanotube dispersion), and the content of the second dispersant was 3.0 g (0.6 parts by weight relative to a total of 100 parts by weight of the carbon nanotube dispersion).

[0357] Comparative Example 3d

[0358] A carbon nanotube dispersion was prepared in the same manner as in Example 1d, except that in the above Example 1d, the content of the first dispersant was 5.6 g (1.12 parts by weight relative to a total of 100 parts by weight of the carbon nanotube dispersion), and the content of the second dispersant was 0.4 g (0.08 parts by weight relative to a total of 100 parts by weight of the carbon nanotube dispersion).

[0359] Comparative Example 4d

[0360] A carbon nanotube dispersion was prepared in the same manner as in Example 1d, except that in the above Example 1d, the content of the second dispersant was 6.0 g (1.2 parts by weight relative to a total of 100 parts by weight of the carbon nanotube dispersion), and the first dispersant was not added.

[0361] Comparative Example 5d

[0362] A carbon nanotube dispersion was prepared in the same manner as in Example 1d, except that in Example 3d above, the content of the first dispersant was 3.375 g (0.6 parts by weight relative to a total of 100 parts by weight of the carbon nanotube dispersion), and the content of triphenylvinylphenol ethoxylate, which replaced direct blue 53 (prepared by Sigma Aldrich company) as the second dispersant, was 1.125 g (0.225 parts by weight relative to a total of 100 parts by weight of the carbon nanotube dispersion).

[0363] Comparative Example 6d

[0364] A carbon nanotube dispersion was prepared in the same manner as in Example 1d, except that in Example 3d above, the content of the first dispersant was 3.375 g (0.6 parts by weight relative to a total of 100 parts by weight of the carbon nanotube dispersion), and the content of styrene maleic anhydride copolymer, which replaced direct blue 53 (prepared by Sigma Aldrich company) as the second dispersant, was 1.125 g (0.225 parts by weight relative to a total of 100 parts by weight of the carbon nanotube dispersion).

[0365] Experimental example

[0366] The viscosities of the carbon nanotube dispersions of Examples 1a to 3a and Comparative Examples 1a to 7a were measured, and the viscosities were measured again after leaving them at 25 °C for one week, and the results are shown in Table 1 below.

[0367] The viscosities of the carbon nanotube dispersions of Examples 1b to 5b and Comparative Examples 1b to 6b were measured, and the viscosities were measured again after leaving them at 25 °C for one week, and the results are shown in Table 2 below.

[0368] The viscosities of the carbon nanotube dispersions of Examples 1c to 5c and Comparative Examples 1c to 6c were measured, and the viscosities were measured again after leaving them at 25 °C for one week, and the results are shown in Table 3 below.

[0369] The viscosities of the carbon nanotube dispersions of Examples 1d to 3d and Comparative Examples 1d to 6d were measured, and the viscosities were measured again after leaving them at 25 °C for one week, and the results are shown in Table 4 below.

[0370] The viscosity was measured at 25 °C and 1 rpm using a viscometer (viscometer TV-25, rotor code 01, manufactured by TOKISANGYO company).

[0371] [Table 1]

[0372]

[0373]

[0374] (*The contents of the CNT, the first dispersant, and the second dispersant are based on a total of 100 parts by weight of the carbon nanotube dispersion*)

[0375] Referring to Table 1, it can be determined that, compared with the carbon nanotube dispersion of Comparative Example 1a containing only polyvinylpyrrolidone as the first dispersant, the carbon nanotube dispersions of Examples 1a to 3a containing the first dispersant and sodium calcium salt of chlorosulphonophenol S represented by Formula 1 of the present invention as the second dispersant have a low initial viscosity immediately after dispersing the carbon nanotubes in an aqueous solvent, and in particular, very effectively suppress the increase in the viscosity of the carbon nanotube dispersion over time.

[0376] In the case of the carbon nanotube dispersion of Comparative Example 2a, it can be seen that, compared with the carbon nanotube dispersion of Comparative Example 1a, the content of carbon nanotubes is reduced, so that the initial viscosity immediately after dispersing the carbon nanotubes in an aqueous solvent and the viscosity of the dispersion after 1 week are lower than those of the carbon nanotube dispersion of Comparative Example 1a. However, like the carbon nanotube dispersion of Comparative Example 1a, since it does not contain the second dispersant containing the compound represented by Formula 1 of the present invention as compared with Examples 1a to 3a, it does not show the effect of suppressing the increase in the viscosity of the dispersion over time.

[0377] In the case of the carbon nanotube dispersion of Comparative Example 3a, it can be seen that since the second dispersant represented by Formula 1 of the present invention is included in an amount less than a certain content, the initial viscosity immediately after dispersing the carbon nanotubes in an aqueous solvent is high.

[0378] In the case of the carbon nanotube dispersions of Comparative Examples 4a and 5a, since they do not contain the first dispersant (Comparative Example 4a) or the first dispersant is included in an amount less than a certain content (Comparative Example 5a) as compared with the carbon nanotube dispersions of Examples 1a to 3a, the carbon nanotubes cannot be completely dispersed in the aqueous solvent, and agglomeration of the dispersion occurs, making it impossible to measure the viscosity.

[0379] In the case of the carbon nanotube dispersions of Comparative Examples 6a and 7a, it can be seen that since the compound represented by Formula 1 of the present invention is not used as the second dispersant as compared with the carbon nanotube dispersions of Examples 1a to 3a, the initial viscosity immediately after dispersing the carbon nanotubes in an aqueous solvent is high, and it does not show the effect of suppressing the increase in the viscosity of the carbon nanotube dispersion over time.

[0380] [Table 2]

[0381]

[0382] (*The contents of CNT, the first dispersant, and the second dispersant are based on a total of 100 parts by weight of the carbon nanotube dispersion*)

[0383] Referring to Table 2 above, it can be determined that, compared with the carbon nanotube dispersion of Comparative Example 1b containing only polyvinylpyrrolidone as the first dispersant, the carbon nanotube dispersions of Examples 1b to 5b containing the first dispersant and the second dispersant containing Direct Red 28 (which is a compound containing at least two azo groups and two or more sulfonate groups) have a low initial viscosity immediately after dispersing the carbon nanotubes in an aqueous solvent, and in particular, very effectively suppress the increase in the viscosity of the carbon nanotube dispersion over time.

[0384] In the case of the carbon nanotube dispersions of Comparative Examples 2b and 3b, it can be seen that by including the first dispersant and the second dispersant in the carbon nanotube dispersion, the initial viscosity immediately after dispersion is reduced compared with Comparative Example 1b. However, since the weight ratio of the second dispersant to the first dispersant in the carbon nanotube dispersion exceeds 100:90, strong electrostatic repulsion between the second dispersants containing at least two sulfonate groups is formed (Comparative Example 2b), or since the weight ratio of the second dispersant is less than 100:10, the interaction between the second dispersant and the carbon nanotubes and between the dispersants cannot be smoothly formed, making it impossible to maintain the stable dispersion state of the carbon nanotube dispersion, and thus the effect of suppressing the increase in the viscosity of the dispersion over time is not exhibited (Comparative Examples 2b and 3b).

[0385] In the case of the carbon nanotube dispersion of Comparative Example 4b, it can be seen that since it does not contain the first dispersant compared with the carbon nanotube dispersions of Examples 1b to 5b, the second dispersant exceeds 145 parts by weight based on 100 parts by weight of carbon nanotubes in the carbon nanotube dispersion, and thus strong electrostatic repulsion between the second dispersants is formed, making it impossible to maintain the stable dispersion state of the carbon nanotube dispersion, and agglomeration of the dispersion occurs, and thus the effect of suppressing the increase in the viscosity of the dispersion over time is not exhibited.

[0386] In the case of the carbon nanotube dispersions of Comparative Examples 5b and 6b, it can be seen that since the materials containing compounds having at least two azo groups and two or more sulfonate groups used in Examples 1b to 5b are not used as the second dispersant, the initial viscosity immediately after dispersing the carbon nanotubes in an aqueous solvent is high (Comparative Example 5b), and the effect of suppressing the increase in the viscosity of the carbon nanotube dispersion over time is not exhibited (Comparative Examples 5b and 6b).

[0387] [Table 3]

[0388]

[0389]

[0390] (*The contents of the CNT, the first dispersant, and the second dispersant are based on a total of 100 parts by weight of the carbon nanotube dispersion*)

[0391] Referring to Table 3 above, it can be determined that, compared with the carbon nanotube dispersion of Comparative Example 1c containing only polyvinylpyrrolidone as the first dispersant, the carbon nanotube dispersions of Examples 1c to 5c containing the first dispersant and the second dispersant containing Direct Yellow 4 (a compound containing at least two azo groups, two or more sulfonate groups, and two or more hydroxyl groups) have a low initial viscosity immediately after dispersing the carbon nanotubes in an aqueous solvent, and in particular, very effectively suppress the increase in the viscosity of the carbon nanotube dispersion over time.

[0392] In the case of the carbon nanotube dispersions of Comparative Examples 2c and 3c, it can be seen that by including the first dispersant and the second dispersant in the carbon nanotube dispersion, compared with Comparative Example 1c, the initial viscosity immediately after dispersion is reduced. However, since the weight ratio of the second dispersant to the first dispersant in the carbon nanotube dispersion exceeds 100:90, strong electrostatic repulsion between the second dispersants containing hydroxyl groups and at least two sulfonate groups and hydrogen bonds between the dispersant and the solvent are formed (Comparative Example 2c), or since the weight ratio of the second dispersant is less than 100:10, the interaction between the second dispersant and the carbon nanotubes and between the dispersants cannot be smoothly formed, making it impossible to maintain the stable dispersion state of the carbon nanotube dispersion, and thus no effect of suppressing the increase in the viscosity of the dispersion over time is exhibited (Comparative Examples 2c and 3c).

[0393] In the case of the carbon nanotube dispersion of Comparative Example 4c, it can be seen that since the first dispersant is not included compared with the carbon nanotube dispersions of Examples 1c to 5c, the second dispersant exceeds 150 parts by weight based on 100 parts by weight of the carbon nanotubes in the carbon nanotube dispersion, and thus strong electrostatic repulsion between the second dispersants and hydrogen bonds between the dispersant and the solvent are formed, making it impossible to maintain the stable dispersion state of the carbon nanotube dispersion, and agglomeration of the dispersion occurs, and thus no effect of suppressing the increase in the viscosity of the dispersion over time is exhibited.

[0394] In the case of the carbon nanotube dispersions of Comparative Examples 5c and 6c, it can be seen that, since the materials containing a compound having at least two azo groups, two or more sulfonate groups, and two or more hydroxyl groups of Examples 1c to 5c were not used as the second dispersant, the initial viscosity immediately after dispersing the carbon nanotubes in the aqueous solvent was high (Comparative Example 5c), and the effect of suppressing the increase in the viscosity of the carbon nanotube dispersion with time was not exhibited (Comparative Examples 5c and 6c).

[0395] [Table 4]

[0396]

[0397] (*The contents of CNT, the first dispersant, and the second dispersant are based on a total of 100 parts by weight of the carbon nanotube dispersion)

[0398] (*"Ratio" is the weight ratio of the second dispersant to the first dispersant)

[0399] Referring to Table 4 above, it can be determined that, compared with the carbon nanotube dispersions of Comparative Example 1d containing only polyvinylpyrrolidone as the first dispersant, the carbon nanotube dispersions of Examples 1d to 3d containing Direct Blue 53, which is a compound represented by Formula 1 of the present invention, as the second dispersant have a lower initial viscosity immediately after dispersing the carbon nanotubes in the aqueous solvent, and particularly, very effectively suppress the increase in the viscosity of the carbon nanotube dispersion with time.

[0400] In the case of the carbon nanotube dispersions of Comparative Examples 2d and 3d, it can be seen that, since the second dispersant was contained in an excessive amount (Comparative Example 2d) or in an amount less than a certain content (Comparative Example 3d) compared with the carbon nanotube dispersions of Examples 1d to 3d, the initial viscosity immediately after dispersing the carbon nanotubes in the aqueous solvent was high, and the effect of suppressing the increase in the viscosity of the dispersion with time was not exhibited.

[0401] In the case of the carbon nanotube dispersion of Comparative Example 4d, it can be determined that there is a problem that the viscosity of the carbon nanotube dispersion increases rapidly with time because the first dispersant is absent compared with the carbon nanotube dispersions of Examples 1d to 3d.

[0402] In the case of the carbon nanotube dispersions of Comparative Examples 5d and 6d, it can be seen that, since the compound represented by Formula 1 according to the present invention was not used as the second dispersant compared with the carbon nanotube dispersions of Examples 1d to 3d, the initial viscosity immediately after dispersing the carbon nanotubes in the aqueous solvent was high, and the effect of suppressing the increase in the viscosity of the carbon nanotube dispersion with time was not exhibited.

[0403] Therefore, it was determined that only when the carbon nanotube dispersion formed by dispersing carbon nanotubes in an aqueous solvent contains a first dispersant containing a nitrogen atom according to the present invention and a second dispersant containing a compound represented by Formula 1, and the first dispersant and the second dispersant are included in a certain weight ratio, the carbon nanotube dispersion exhibits a low viscosity and an increase in viscosity over time can be suppressed.

[0404] In the above, although the preferred embodiments of the present invention have been described in detail, the scope of the present invention is not limited thereto, and various modifications and improvements made by those skilled in the art using the basic concept of the present invention defined in the appended claims also fall within the scope of the present invention.

Claims

1. A carbon nanotube dispersion, comprising: Carbon nanotubes; A first dispersant containing a nitrogen atom; A second dispersant containing a compound represented by Formula 1; and A solvent: [Formula 1] Wherein, Ar1 and Ar2 are each independently a substituted or unsubstituted C6-C30 aryl group, and L1 is a substituted or unsubstituted C6-C30 arylene group.

2. The carbon nanotube dispersion according to claim 1, wherein Ar1 and Ar2 in Formula 1 are respectively represented by Formula 2 or Formula 3: [Formula 2] [Formula 3] In Formula 2, R1 to R8 are the same as or different from each other, and are each independently hydrogen; deuterium; halogen; cyano group; sulfonate group; hydroxyl group; amino group; nitro group; substituted or unsubstituted C1-C10 alkyl group; substituted or unsubstituted C1-C10 alkoxy group; or a moiety connected to Formula 2, provided that any one of R1 to R8 is a moiety connected to the azo group in Formula 1, and In Formula 3, R9 to R14 are the same as or different from each other, and are each independently hydrogen; deuterium; halogen; cyano group; sulfonate group; amino group; nitro group; substituted or unsubstituted C1-C10 alkyl group; substituted or unsubstituted C1-C10 alkoxy group; or a moiety connected to Formula 3, provided that any one of R9 to R14 is a moiety connected to the azo group in Formula 1.

3. The carbon nanotube dispersion according to claim 1, wherein L1 in Formula 1 is represented by the following Formula 4 or Formula 5: [Formula 4] [Formula 5] In Formula 4, R15 to R18 are the same as or different from each other, and are each independently hydrogen; deuterium; halogen; cyano group; sulfonate group; hydroxyl group; amino group; nitro group; or a moiety connected to Formula 1, provided that any one of R15 to R18 is a moiety connected to the nitrogen atom not connected to Ar1 among the two nitrogen atoms of the azo group connected to Ar1 in the two azo groups of Formula 1, and R19 to R22 are the same as or different from each other, and are each independently hydrogen; deuterium; halogen; cyano group; sulfonate group; hydroxyl group; amino group; nitro group; or a moiety connected to Formula 1, provided that any one of R19 to R22 is a moiety connected to the nitrogen atom not connected to Ar2 among the two nitrogen atoms of the azo group connected to Ar2 in the two azo groups of Formula 1, and In Formula 5, R23 to R27 are the same as or different from each other, and each independently is hydrogen; deuterium; halogen; cyano; sulfonate group; hydroxyl group; amino group; nitro group; substituted or unsubstituted C1-C5 alkyl group; substituted or unsubstituted C1-C5 alkoxy group; or a part that is connected to the nitrogen atom not connected to Ar1 among the two nitrogen atoms of the azo group connected to Ar1 in the two azo groups of Formula 1, provided that any one of R23 to R27 is a part that is connected to the nitrogen atom not connected to Ar1 among the two nitrogen atoms of the azo group connected to Ar1 in the two azo groups of Formula 1, and R28 to R32 are the same as or different from each other, and each independently is hydrogen; deuterium; halogen; cyano; sulfonate group; hydroxyl group; amino group; nitro group; substituted or unsubstituted C1-C5 alkyl group; substituted or unsubstituted C1-C5 alkoxy group; or a part that is connected to the nitrogen atom not connected to Ar2 among the two nitrogen atoms of the azo group connected to Ar2 in the two azo groups of Formula 1, provided that any one of R28 to R32 is a part that is connected to the nitrogen atom not connected to Ar2 among the two nitrogen atoms of the azo group connected to Ar2 in the two azo groups of Formula 1, and Z is a single bond; substituted or unsubstituted C2-C10 alkenylene; or substituted or unsubstituted C2-C10 alkynylene.

4. The carbon nanotube dispersion according to claim 1, wherein the second dispersant comprises a compound represented by any one of the following Formulas 1-1a to 1-1d: [Formula 1-1a] Wherein, R1 to R5, R7 to R11, and R13 to R18 are the same as or different from each other, and each independently is hydrogen; deuterium; halogen; cyano; sulfonate group; hydroxyl group; amino group; or nitro group, [Formula 1-1b] Wherein, R1 to R7 and R9 to R15 are the same as or different from each other, and each independently is hydrogen; deuterium; halogen; cyano; sulfonate group; hydroxyl group; amino group; substituted or unsubstituted C1-C10 alkyl group; substituted or unsubstituted C2-C10 alkenyl group; substituted or unsubstituted C2-C10 alkynyl group; substituted or unsubstituted C1-C10 alkoxy group; or substituted or unsubstituted C6-C20 aryl group, provided that at least one of R1 to R7 is a sulfonate group, and at least one of R9 to R15 is a sulfonate group, [Formula 1-1c] Wherein, R1 to R5 and R7 to R11 are the same as or different from each other, and each independently is hydrogen; deuterium; halogen; cyano; sulfonate group; hydroxyl group; substituted or unsubstituted C1-C10 alkyl group; substituted or unsubstituted C2-C10 alkenyl group; substituted or unsubstituted C2-C10 alkynyl group; substituted or unsubstituted C1-C10 alkoxy group; substituted or unsubstituted C6-C20 aryl group; or substituted or unsubstituted C2-C20 heteroaryl group, provided that at least one of R1 to R5 is a hydroxyl group, and at least one of R7 to R11 is a hydroxyl group, and R13 to R20 are the same as or different from each other, and each independently is hydrogen; deuterium; a halogen; a cyano group; a sulfonate group; a hydroxyl group; a substituted or unsubstituted C1 to C10 alkyl group; a substituted or unsubstituted C2 to C10 alkenyl group; a substituted or unsubstituted C2 to C10 alkynyl group; a substituted or unsubstituted C1 to C10 alkoxy group; a substituted or unsubstituted C6 to C20 aryl group; or a substituted or unsubstituted C2 to C20 heteroaryl group, provided that at least one of R13 to R16 is a sulfonate group, and at least one of R17 to R20 is a sulfonate group, [Formula 1-1d] wherein, R1 to R7 and R9 to R15 are the same as or different from each other, and each independently is hydrogen; deuterium; a halogen; a cyano group; a sulfonate group; a hydroxyl group; an amino group; or a nitro group, and R17 to R20 and R22 to R25 are the same as or different from each other, and each independently is hydrogen; deuterium; a halogen; a cyano group; a sulfonate group; a hydroxyl group; an amino group; a nitro group; a substituted or unsubstituted C1 to C5 alkyl group; or a substituted or unsubstituted C1 to C5 alkoxy group.

5. The carbon nanotube dispersion according to claim 1, wherein based on 100 parts by weight of the carbon nanotube dispersion, the carbon nanotubes are included in an amount of 0.05 part by weight to 5 parts by weight.

6. The carbon nanotube dispersion according to claim 1, wherein the BET specific surface area of the carbon nanotubes is 800 m 2 / g to 2,000 m 2 / g.

7. The carbon nanotube dispersion according to claim 1, wherein the first dispersant is at least one selected from the following: polyvinylpyrrolidone, polyacrylic hydrazide, poly-N-vinyl-5-methyl oxazolidone, N-alkyl polyimine, N-acetyl polyimine, polyacrylamide, poly-L-lysine hydrobromide, benzyl-dodecyl-dimethyl ammonium chloride, and polyethyleneimine.

8. The carbon nanotube dispersion according to claim 1, wherein based on 100 parts by weight of the carbon nanotube dispersion, the first dispersant is included in an amount of 0.01 part by weight to 10 parts by weight.

9. The carbon nanotube dispersion according to claim 1, wherein based on 100 parts by weight of the carbon nanotube dispersion, the second dispersant is included in an amount of 0.001 part by weight to 9 parts by weight.

10. The carbon nanotube dispersion according to claim 1, wherein the first dispersant and the second dispersant are included in a weight ratio of 100:10 to 100:

90.

11. The carbon nanotube dispersion according to claim 1, wherein the initial viscosity of the carbon nanotube dispersion measured at 25 °C and 1 rpm is 1 Pa·s to 10 Pa·s.

12. The carbon nanotube dispersion according to claim 1, wherein the viscosity increase rate of the carbon nanotube dispersion represented by the following Equation 1 is 15% or less: [Equation 1] Viscosity increase rate (%) = { (viscosity measured after standing at 25 °C for 1 week - initial viscosity) / initial viscosity} × 100.

13. A method for preparing the carbon nanotube dispersion according to claim 1, comprising the following steps: (1) preparing a primary dispersion of carbon nanotubes by mixing carbon nanotubes, a first dispersant containing a nitrogen atom, a second dispersant containing a compound represented by the following Formula 1, and a solvent; and (2) dispersing the primary dispersion of the carbon nanotubes to prepare a secondary dispersion of the carbon nanotubes: [Formula 1] wherein, Ar1 and Ar2 are each independently a substituted or unsubstituted C6 to C30 aryl group, and L1 is a substituted or unsubstituted C6 to C30 arylene group.

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