Carbon nanotube dispersion and its manufacturing method

Abstract

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

Description

[Technical Field]

[0001] This application is a joint application of Korean Patent Application No. 10-2023-0099704 filed on July 31, 2023, Korean Patent Application No. 10-2023-0099719 filed on July 31, 2023, Korean Patent Application No. 10-2023-0099741 filed on July 31, 2023, Korean Patent Application No. 10-2023-0099761 filed on July 29, 2024, and Korean Patent Application No. 10-2023-0099772 filed on July 31, 2023. The present application claims the benefit of priority to Korean Patent Application No. 4-0100228, Korean Patent Application No. 10-2024-0100234, Korean Patent Application No. 10-2024-0100254, Korean Patent Application No. 10-2024-0100258, dated July 29, 2024, and the entire contents of the documents of the relevant Korean patent applications are incorporated herein by reference.

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

[0003] As technological development and demand for mobile devices increase, demand for secondary batteries as an energy source is rapidly increasing. Among these secondary batteries, lithium secondary batteries, which have high energy density and voltage, long cycle life, and low self-discharge rate, have been commercialized and widely used. In addition, active research is being conducted on methods for improving electrode density and manufacturing electrodes with higher energy density per unit volume for such high-capacity lithium secondary batteries.

[0004] Generally, high-density electrodes are formed by molding particles of electrode active material having a size of several μm to several tens of μm using a high-pressure press. During the molding process, the particles may deform and the spaces between the particles may decrease, which may reduce the permeability of the electrolyte.

[0005] To address these issues, conductive materials with excellent electrical conductivity and strength are used in the manufacture of electrodes. These conductive materials are located between the electrode active materials, maintaining micropores between the active material particles even during the molding process, allowing the electrolyte to easily penetrate. They also have excellent electrical conductivity and can reduce the resistance within the electrode. Among these conductive materials, carbon nanotubes, a fibrous carbon-based conductive material, are increasingly being used, as they can further reduce electrode resistance by forming electrical conductive paths within the electrode.

[0006] Carbon nanotubes, a type of fine carbon fiber, are tubular carbon fibers with a diameter of less than 1 μm. Their unique structure gives them high electrical conductivity, tensile strength, and heat resistance, making them promising for practical application in a variety of fields. However, due to their high specific surface area, carbon nanotubes have the problem of poor dispersibility and aggregation due to the strong van der Waals forces between them.

[0007] To solve this problem, a method of dispersing carbon nanotubes in a dispersion medium through a mechanical dispersion process such as ultrasonic treatment has been proposed. However, the mechanical dispersion process has problems such as the carbon nanotubes agglomerating immediately after the ultrasonic treatment is stopped or re-agglomerating over time after dispersion.

[0008] Therefore, there is a need to develop a method for producing a carbon nanotube dispersion liquid that can improve the dispersibility of carbon nanotubes, has low viscosity, and is inhibited from increasing in viscosity over time. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] U.S. Patent Publication No. 2017-0129804 (May 11, 2017) [Patent Document 2] China Published Patent Publication No. 001699155 (November 23, 2005) Summary of the Invention [Problem to be solved by the invention]

[0010] The object of the present invention is to provide a carbon nanotube dispersion comprising carbon nanotubes, a first dispersant containing nitrogen atoms, a second dispersant containing a compound represented by the following chemical formula 1, and a solvent, which has excellent dispersibility, low viscosity of the dispersion, low particle size of the dispersed particles, and little change in viscosity over time.

[0011] [ka]

[0012] In the above Chemical Formula 1, Ar1 and Ar2 each independently represent a substituted or unsubstituted C6 to C30 aryl group; L1 is a substituted or unsubstituted C6 to C30 arylene group.

[0013] It is still another object of the present invention to provide a method for producing the carbon nanotube dispersion liquid. [Means for solving the problem]

[0014] One embodiment of the present invention provides a carbon nanotube dispersion liquid including carbon nanotubes, a first dispersant containing a nitrogen atom, a second dispersant containing a compound represented by the following Chemical Formula 1, and a solvent.

[0015] [ka]

[0016] In the above Chemical Formula 1, Ar1 and Ar2 each independently represent a substituted or unsubstituted C6 to C30 aryl group; L1 is a substituted or unsubstituted C6 to C30 arylene group.

[0017] Ar1 and Ar2 in the above Chemical Formula 1 may be represented by the following Chemical Formula 2 or Chemical Formula 3, respectively.

[0018] [ka]

[0019] [ka]

[0020] In the above Chemical Formula 2, R1 to R8 are the same or different and each independently represent hydrogen, deuterium, a halogen, a cyano group, a sulfonate group, a hydroxyl group, an amine group, a nitro group, a substituted or unsubstituted C1 to C10 alkyl group, a substituted or unsubstituted C1 to C10 alkoxy group, or a moiety that is linked to Chemical Formula 1, and any one of R1 to R8 is a moiety that is linked to the azo group in Chemical Formula 1, In the above Chemical Formula 3, R9 to R14 are the same or different and each independently represent hydrogen; deuterium; halogen; cyano group; sulfonate group; amine group; nitro group; substituted or unsubstituted C1 to C10 alkyl group; substituted or unsubstituted C1 to C10 alkoxy group; or a moiety connecting to Chemical Formula 1, and any one of R9 to R14 is a moiety connecting to the azo group in Chemical Formula 1.

[0021] L1 in Chemical Formula 1 may be represented by Chemical Formula 4 or Chemical Formula 5 below.

[0022] [ka]

[0023] [ka]

[0024] In the above Chemical Formula 4, R15 to R18 are the same or different and each independently represent hydrogen; deuterium; halogen; cyano group; sulfonate group; hydroxyl group; amine group; nitro group; or a moiety connecting to Chemical Formula 1, wherein any one of R15 to R18 is a moiety connecting to the nitrogen atom not connected to Ar1 among the two nitrogen atoms of the azo group to which Ar1 is linked among the two azo groups in Chemical Formula 1; R19 to R22 are the same or different and each independently represent hydrogen; deuterium; halogen; cyano group; sulfonate group; hydroxyl group; amine group; nitro group; or a moiety connecting to Chemical Formula 1, wherein any one of R19 to R22 is a moiety connecting to the nitrogen atom not connected to Ar2 among the two nitrogen atoms of the azo group to which Ar2 is linked among the two azo groups in Chemical Formula 1; In the above Chemical Formula 5, R23 to R27 are the same or different and each independently represent hydrogen; deuterium; halogen; cyano group; sulfonate group; hydroxyl group; amine group; nitro group; substituted or unsubstituted C1 to C5 alkyl group; substituted or unsubstituted C1 to C5 alkoxy group; or a moiety that is bonded to a nitrogen atom that is not bonded to Ar1 among the two nitrogen atoms of the azo group to which Ar1 is bonded among the two azo groups of Chemical Formula 1, and any one of R23 to R27 is a moiety that is bonded to a nitrogen atom that is not bonded to Ar1 among the two nitrogen atoms of the azo group to which Ar1 is bonded among the two azo groups of Chemical Formula 1, R28 to R32 are the same or different and each independently represent hydrogen; deuterium; halogen; cyano group; sulfonate group; hydroxyl group; amine group; nitro group; substituted or unsubstituted C1 to C5 alkyl group; substituted or unsubstituted C1 to C5 alkoxy group; or a moiety that is bonded to a nitrogen atom that is not bonded to Ar2 among the two nitrogen atoms of the azo group to which Ar2 is bonded among the two azo groups in Chemical Formula 1, and any one of R28 to R32 is a moiety that is bonded to a nitrogen atom that is not bonded to Ar2 among the two nitrogen atoms of the azo group to which Ar2 is bonded among the two azo groups in Chemical Formula 1, Z is a single bond; a substituted or unsubstituted C2-C10 alkenylene group; or a substituted or unsubstituted C2-C10 alkynylene group.

[0025] The second dispersant may include a compound represented by any one of the following Chemical Formulas 1-1a to 1-1d.

[0026] [ka]

[0027] In the above chemical formula 1-1a, R1 to R5, R7 to R11, and R13 to R18 are the same as or different from one another and each independently represent hydrogen, deuterium, a halogen, a cyano group, a sulfonate group, a hydroxyl group, an amine group, or a nitro group; [ka]

[0028] In the above chemical formula 1-1b, R1 to R7 and R9 to R15 are the same or different and each independently represent hydrogen, deuterium, a halogen, a cyano group, a sulfonate group, a hydroxyl group, an amine 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, or a substituted or unsubstituted C6 to C20 aryl group, and at least one of R1 to R7 is a sulfonate group, and at least one of R9 to R15 is a sulfonate group; [ka]

[0029] In the above chemical formula 1-1c, R1 to R5 and R7 to R11 are the same or different and each independently represent 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, wherein at least one of R1 to R5 is a hydroxyl group and at least one of R7 to R11 is a hydroxyl group; R13 to R20 are the same or different and each independently represent 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, and at least one of R13 to R16 is a sulfonate group, and at least one of R17 to R20 is a sulfonate group; [ka]

[0030] In the above chemical formula 1-1d, R1 to R7 and R9 to R15 are the same or different and each independently represent hydrogen; deuterium; halogen; cyano group; sulfonate group; hydroxyl group; amine group; or nitro group; R17 to R20 and R22 to R25 are the same or different and each independently represent hydrogen, deuterium, a halogen, a cyano group, a sulfonate group, a hydroxyl group, an amine group, a nitro group, a substituted or unsubstituted C1 to C5 alkyl group, or a substituted or unsubstituted C1 to C5 alkoxy group.

[0031] The carbon nanotube dispersion may contain 0.05 to 5 parts by weight of carbon nanotubes based on 100 parts by weight of the carbon nanotube dispersion.

[0032] The BET specific surface area of ​​the carbon nanotubes is 800 to 2,000 m 2 / g.

[0033] The first dispersant may be at least one selected from the group consisting of polyvinylpyrrolidone, polyacrylic acid hydrazide, poly-N-vinyl-5-methoxazolidone, N-alkyl polyimine, N-acetyl polyimine, polyacrylamide, poly-L-lysine hydrobromide, benzyl-dodecyl-dimethylammonium chloride, and polyethyleneimine.

[0034] The first dispersant may be contained in an amount of 0.01 to 10 parts by weight based on 100 parts by weight of the carbon nanotube dispersion liquid.

[0035] The second dispersant may be contained in an amount of 0.001 to 9 parts by weight based on 100 parts by weight of the carbon nanotube dispersion liquid.

[0036] The first dispersant and the second dispersant may be included in a weight ratio of 100:10 to 100:90.

[0037] The carbon nanotube dispersion may have an initial viscosity of 1 to 10 Pa·s measured at 25° C. and 1 rpm.

[0038] The carbon nanotube dispersion may have a viscosity increase rate represented by the following formula (1) of 15% or less.

[0039] [Formula 1] Viscosity increase rate (%) = {(viscosity measured after leaving at 25°C for 1 week - initial viscosity) / initial viscosity} x 100 Another embodiment of the present invention provides a method for producing a carbon nanotube dispersion, comprising: (1) mixing carbon nanotubes, a first dispersant containing nitrogen atoms, a second dispersant containing the compound represented by Chemical Formula 1, and a solvent to produce a primary dispersion of carbon nanotubes; and (2) dispersing the primary dispersion of carbon nanotubes to produce a secondary dispersion of carbon nanotubes. [Effects of the Invention]

[0040] The carbon nanotube dispersion according to the present invention uses a first dispersant containing a nitrogen atom together with a second dispersant containing the compound represented by Chemical Formula 1. This allows the dispersion to exhibit a relatively low viscosity with little change in viscosity over time despite the use of carbon nanotubes with a large specific surface area, and also allows the carbon nanotubes to be uniformly and effectively dispersed, resulting in a small particle size of the dispersed particles. BEST MODE FOR CARRYING OUT THE INVENTION

[0041] Hereinafter, embodiments of the present invention will be described in detail. Prior to this, the terms and words used in the present specification and claims should not be construed in a limited manner based on their ordinary or dictionary meanings, but should be construed in a manner that is consistent with the technical concept of the present invention, based on the principle that the inventor can appropriately define the concept of terms in order to best describe his or her invention. Therefore, it should be understood that the configurations described in the embodiments of the present specification are merely the most preferred embodiments of the present invention and do not represent the entire technical concept of the present invention, and therefore, at the time of filing this application, various equivalents and modifications that can replace them may exist.

[0042] As used herein, the term "substituted" means that a hydrogen atom bonded to a carbon atom of a compound is replaced with another substituent, and the position of substitution is not limited as long as it is a position at which a hydrogen atom is substituted, i.e., a position at which a substituent can be substituted. When two or more substituents are substituted, the two or more substituents may be the same or different.

[0043] In this specification, the term "substituted or unsubstituted" means substituted or unsubstituted by one or more substituents selected from the group consisting of deuterium; halogen; cyano group; C1 to C60 linear or branched alkyl group; C2 to C60 linear or branched alkenyl group; C2 to C60 linear or branched alkynyl group; C3 to C60 monocyclic or polycyclic cycloalkyl group; C2 to C60 monocyclic or polycyclic heterocycloalkyl group; C6 to C60 monocyclic or polycyclic aryl group; C2 to C60 monocyclic or polycyclic heteroaryl group; C1 to C20 alkylamine group; C6 to C60 monocyclic or polycyclic arylamine group; and C2 to C60 monocyclic or polycyclic heteroarylamine group, or substituted or unsubstituted by a substituent in which two or more substituents selected from the above-mentioned substituents are linked.

[0044] Throughout this specification, when a part "comprises" a certain element, this does not mean that it excludes other elements, but that it may further include other elements, unless otherwise specified.

[0045] Throughout this specification, "%" means % by weight unless expressly indicated otherwise.

[0046] In this specification, the average particle size "D 50 " means the particle size corresponding to 50% of the cumulative volume. 50 can be measured, for example, by using a laser diffraction method. The laser diffraction method generally enables measurement of particle sizes from the submicron range to several mm, and provides results with high reproducibility and high resolution.

[0047] In this specification, the "specific surface area" is measured by the BET method (Brunauer-Emmett-Teller analysis), and specifically, is calculated from the amount of nitrogen gas adsorbed at liquid nitrogen temperature (77K) using a BELSORP-mino II manufactured by BEL Japan.

[0048] Carbon nanotube dispersion The carbon nanotube dispersion according to the present invention comprises carbon nanotubes, a first dispersant containing nitrogen atoms, a second dispersant containing the compound represented by Chemical Formula 1, and a solvent. Each component of the carbon nanotube dispersion according to the present invention will be described in detail below.

[0049] (1) Carbon nanotubes The term "carbon nanotube" used in the present invention refers to a secondary structure formed by the aggregation of carbon nanotube units in a bundle type, either entirely or partially. The carbon nanotube units have a cylindrical shape with a nano-sized diameter graphite sheet, and are separated by a sp 2 Carbon nanotubes have a bond structure. Depending on the angle and structure of the graphite plane, they can exhibit conductive or semiconductive properties. Carbon nanotubes are classified into single-walled carbon nanotubes (SWCNT), double-walled carbon nanotubes (DWCNT), and multi-walled carbon nanotubes (MWCNT) depending on the number of bonds forming the wall.

[0050] The term "bundle type" as used herein, unless otherwise specified, refers to a secondary shape in the form of a bundle or rope in which multiple carbon nanotube units are aligned with their longitudinal axes in substantially the same direction, or are twisted or tangled after being aligned. The term "non-bundle type or entangled type" refers to a shape in which the carbon nanotube units are tangled rather than in a fixed shape like a bundle or rope.

[0051] Carbon nanotubes have high conductivity, but they also tend to aggregate due to the van der Waals force that occurs between them. If the conductive material aggregates, it cannot properly form a conductive path within the electrode. Therefore, more conductive material must be used to increase conductivity, which reduces the amount of active material relatively, resulting in a decrease in performance such as the capacity of the electrode. Therefore, it has been difficult to commercialize carbon nanotubes as a conductive material.

[0052] The carbon nanotube dispersion according to the present invention comprises a first dispersant containing a nitrogen atom and a second dispersant containing a compound represented by Chemical Formula 1, thereby significantly reducing the initial viscosity of the carbon nanotube dispersion and suppressing viscosity changes over time while maintaining a low particle size of the dispersed particles.

[0053] The carbon nanotube dispersion according to an embodiment of the present invention may include, but is not limited to, one or more of single-walled, double-walled, and multi-walled carbon nanotubes as the carbon nanotubes. The single-walled or double-walled carbon nanotubes have a higher specific surface area than multi-walled carbon nanotubes, and therefore are more effective in improving cycle characteristics when used in secondary batteries.

[0054] On the other hand, the average diameter of the carbon nanotubes may be, for example, 0.6 to 10 nm, preferably 0.8 to 5 nm, and more preferably 0.8 to 3 nm, or may be 0.8 nm or more, 0.9 nm or more, 1.0 nm or more, 1.1 nm or more, 1.2 nm or more, 1.3 nm or more, 1.4 nm or more, 1.5 nm or more, 1.6 nm or more, 1.7 nm or more, 1.8 nm or more, or 1.9 nm or more, or may be 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.

[0055] The carbon nanotubes may have an average length of 0.5 to 20 μm, preferably 1 to 20 μm, and more preferably 5 to 20 μm, and may be 5 μm or more, 7 μm or more, 9 μm or more, 11 μm or more, or 13 μm or more, or 20 μm or less, 18 μm or less, 16 μm or less, or 14 μm or less. When the average diameter and average length of the carbon nanotubes satisfy the above ranges, it is effective in reducing the viscosity of the dispersion and improving storage stability, and when used as an electrode active material, it is possible to realize excellent cycle characteristics.

[0056] At this time, 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.

[0057] The carbon nanotubes may be contained in an amount of 0.05 to 5 parts by weight based on a total of 100 parts by weight of the carbon nanotube dispersion, and may be contained in an amount of 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. The carbon nanotube content may be 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 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. When the carbon nanotube content satisfies this range, the effect of improving the viscosity of the dispersion and the effect of improving the conductivity of a secondary battery manufactured using the carbon nanotube dispersion are excellent.

[0058] The BET specific surface area of ​​the carbon nanotubes is 800 m 2 / g~2,000m 2 / g, for example 800m 2 / g or more, 810m 2 / g or more, 820m 2 / g or more, 830m 2 / g or more, 840m 2 / g or more, 850m 2 / g or more, 860m 2 / g or more, 870m 2 / g or more, 880m 2 / g or more, 890m 2 / g or more, 900m 2 / g or more, 910m 2 / g or more, 920m2 / g or more, 930m 2 / g or more, 940m 2 / g or more, 950m 2 / g or more, 960m 2 / g or more, 970m 2 / g or more, 980m 2 / g or more, 990m 2 / g or more, 1,000m 2 / g or more, 1,010m 2 / g or more, 1,020m 2 / g or more, 1,030m 2 / g or more, 1,040m 2 / g or more, 1,050m 2 / g or more, 1,060m 2 / g or more, 1,070m 2 / g or more, 1,080m 2 / g or more, 1,090m 2 / g or more, 1,100m 2 / g or more, 1,110m 2 / g or more, 1,120m 2 / g or more, 1,130m 2 / g or more, 1,140m 2 / g or more, 1,150m 2 / g or more, 1,160m 2 / g or more, 1,170m 2 / g or more, 1,180m 2 / g or more, 1,190m 2 / g or more, 1,200m 2 / g or more, 1,210m 2 / g or more, 1,220m 2 / g or more, 1,230m 2 / g or more, 1,240m 2 / g or more, 1,250m 2 / g or more, 1,260m 2 / g or more, 1,270m 2 / g or more, 1,280m 2 / g or more, 1,290m 2 / g or more, 1,300m 2 / g or more, 1,310m 2 / g or more, 1,320m 2 / g or more, 1,330m 2 / g or more, 1,340m2 / g or more, 1,350m 2 / g or more, 1,360m 2 / g or more, 1,370m 2 / g or more, 1,380m 2 / g or more, 1,390m 2 / g or more or 1,400m 2 / g or more, and 2 / g or less, 1,990m 2 / g or less, 1,980m 2 / g or less, 1,970m 2 / g or less, 1,960m 2 / g or less, 1,950m 2 / g or less, 1,940m 2 / g or less, 1,930m 2 / g or less, 1,920m 2 / g or less, 1,910m 2 / g or less, 1,900m 2 / g or less, 1,890m 2 / g or less, 1,880m 2 / g or less, 1,870m 2 / g or less, 1,860m 2 / g or less, 1,850m 2 / g or less, 1,840m 2 / g or less, 1,830m 2 / g or less, 1,820m 2 / g or less, 1,810m 2 / g or less, 1,800m 2 / g or less, 1,790m 2 / g or less, 1,780m 2 / g or less, 1,770m 2 / g or less, 1,760m 2 / g or less, 1,750m 2 / g or less, 1,740m 2 / g or less, 1,730m 2 / g or less, 1,720m 2 / g or less, 1,710m 2 / g or less, 1,700m 2 / g or less, 1,690m 2 / g or less, 1,680m 2 / g or less, 1,670m 2 / g or less, 1,660m2 / g or less, 1,650m 2 / g or less, 1,640m 2 / g or less, 1,630m 2 / g or less, 1,620m 2 / g or less, 1,610m 2 / g or less, 1,600m 2 / g or less, 1,590m 2 / g or less, 1,580m 2 / g or less, 1,570m 2 / g or less, 1,560m 2 / g or less, 1,550m 2 / g or less, 1,540m 2 / g or less, 1,530m 2 / g or less, 1,520m 2 / g or less, 1,510m 2 / g or less, 1,500m 2 / g or less, 1,490m 2 / g or less, 1,480m 2 / g or less, 1,470m 2 / g or less, 1,460m 2 / g or less, 1,450m 2 / g or less, 1,440m 2 / g or less, 1,430m 2 / g or less, 1,420m 2 / g or less or 1,410m 2 The use of carbon nanotubes having such a high BET specific surface area allows for excellent formation of a conductive network between electrode active materials, thereby improving the cycle characteristics of a secondary battery manufactured using the carbon nanotube dispersion.

[0059] A carbon nanotube dispersion according to an embodiment of the present invention can have a relatively high carbon nanotube content because carbon nanotubes can be uniformly dispersed. When a carbon nanotube dispersion with a low carbon nanotube content is used to prepare an electrode slurry, the solid content of the prepared electrode slurry decreases, the thickness (wet thickness) of the electrode slurry before coating and drying is thick, and the rolling ratio measured after subsequent drying and rolling processes increases, resulting in a large difference in the thickness ratio before and after drying and rolling. If the rolling ratio increases, the components inside the slurry, including the positive electrode active material, may be damaged during the process, resulting in a problem of reduced battery performance.

[0060] (2) Dispersant The carbon nanotube dispersion according to the present invention includes a dispersant to improve the dispersibility of the carbon nanotubes, and the dispersant includes a first dispersant containing a nitrogen atom and a second dispersant containing a compound represented by the following Chemical Formula 1:

[0061] [ka]

[0062] In the above Chemical Formula 1, Ar1 and Ar2 each independently represent a substituted or unsubstituted C6 to C30 aryl group; L1 is a substituted or unsubstituted C6 to C30 arylene group.

[0063] In the carbon nanotube dispersion, the first dispersant and the second dispersant serve to increase the dispersibility of the carbon nanotubes so that the carbon nanotubes are uniformly dispersed without agglomerating in the dispersion, and in particular, serve to suppress the change in viscosity of the carbon nanotube dispersion over time and reduce the average particle size of the dispersed particles.

[0064] In the carbon nanotube dispersion according to an embodiment of the present invention, the first dispersant containing a nitrogen atom may be soluble in an aqueous solvent, as described below, and may be, for example, one or more selected from the group consisting of polyvinylpyrrolidone, polyacrylic acid hydrazide, poly-N-vinyl-5-methoxazolidone, N-alkyl polyimine, N-acetyl polyimine, polyacrylamide, poly-L-lysine hydrobromide, benzyl-dodecyl-dimethylammonium chloride, and polyethyleneimine, and preferably, polyvinylpyrrolidone. The carbon nanotube dispersion according to an embodiment of the present invention includes the first dispersant containing a nitrogen atom, thereby improving the viscosity of the dispersion and suppressing the change in viscosity over time.

[0065] In one embodiment of the present invention, the first dispersant may be included in an amount of 0.01 to 10 parts by weight based on 100 parts by weight of the carbon nanotube dispersion liquid, and may be, for example, 0.01 part by weight or more, 0.1 part 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. Part 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, 4.5 parts by weight or more, 4.6 parts by weight or more, 4.7 parts by weight The amount may be 10 parts by weight or less, 4.8 parts by weight or more, 4.9 parts by weight or more, 5 parts by weight or more, 10 parts by weight or less, 9.9 parts by weight or less, 9.8 parts by weight or less, 9.7 parts by weight or less, 9.6 parts by weight or less, 9.5 parts by weight or less, 9.4 parts by weight or less, 9.3 parts by weight or less, 9.2 parts by weight or less, 9.1 parts by weight or less, 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 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, or 5.1 parts by weight or less.

[0066] If the content of the first dispersant is less than 0.01 parts by weight based on 100 parts by weight of the carbon nanotube dispersion, the insufficient content of the dispersant may result in insufficient dispersion effect, resulting in the dispersion not being formed with a low viscosity and increasing in viscosity over time. If the content of the first dispersant is more than 10 parts by weight, the excessive content of the first dispersant may result in aggregation of solids in the dispersion, resulting in the dispersion being formed with a high viscosity.

[0067] In addition, in order to solve the problem that the viscosity of the dispersion increases as the carbon nanotube content increases in a carbon nanotube dispersion containing only the first dispersant, the carbon nanotube dispersion according to one embodiment of the present invention contains a second dispersant containing a compound represented by the following chemical formula 1 together with the first dispersant. As a result, the carbon nanotube dispersion has better dispersibility than carbon nanotube dispersions that use only conventional dispersants, and the particles of the slurry composition are less likely to agglomerate, resulting in a lower settling rate.

[0068] [ka]

[0069] In the above Chemical Formula 1, Ar1 and Ar2 each independently represent a substituted or unsubstituted C6 to C30 aryl group; L1 is a substituted or unsubstituted C6 to C30 arylene group.

[0070] In one embodiment of the present invention, Ar1 in the above Formula 1 may be a substituted or unsubstituted C6 to C30 aryl group.

[0071] In one embodiment of the present invention, Ar1 in the above Formula 1 may be a substituted or unsubstituted C6 to C20 aryl group.

[0072] In one embodiment of the present invention, Ar1 in the above Formula 1 may be a substituted or unsubstituted C6 to C10 aryl group.

[0073] In one embodiment of the present invention, Ar1 in the above Chemical Formula 1 may be a substituted or unsubstituted phenyl group; or a substituted or unsubstituted naphthalene group.

[0074] In one embodiment of the present invention, Ar2 in the above Formula 1 may be a substituted or unsubstituted C6 to C30 aryl group.

[0075] In one embodiment of the present invention, Ar2 in the above Formula 1 may be a substituted or unsubstituted C6 to C20 aryl group.

[0076] In one embodiment of the present invention, Ar2 in the above Formula 1 may be a substituted or unsubstituted C6 to C10 aryl group.

[0077] In one embodiment of the present invention, Ar2 in the above formula 1 may be a substituted or unsubstituted phenyl group; or a substituted or unsubstituted naphthalene group.

[0078] In one embodiment of the present invention, L1 in the above Chemical Formula 1 may be a substituted or unsubstituted C6 to C30 arylene group.

[0079] In one embodiment of the present invention, L1 in the above Chemical Formula 1 may be a substituted or unsubstituted C6 to C20 arylene group.

[0080] In one embodiment of the present invention, L1 in the above Chemical Formula 1 may be a substituted or unsubstituted C6 to C10 arylene group.

[0081] In one embodiment of the present invention, Ar1 and Ar2 in Formula 1 may be represented by Formula 2 or Formula 3 below, respectively.

[0082] [ka]

[0083] [ka]

[0084] In the above Chemical Formula 2, R1 to R8 are the same or different and each independently represent hydrogen, deuterium, a halogen, a cyano group, a sulfonate group, a hydroxyl group, an amine group, a nitro group, a substituted or unsubstituted C1 to C10 alkyl group, a substituted or unsubstituted C1 to C10 alkoxy group, or a moiety that is linked to Chemical Formula 1, and any one of R1 to R8 is a moiety that is linked to the azo group in Chemical Formula 1, In the above Chemical Formula 3, R9 to R14 are the same or different and each independently represent hydrogen; deuterium; halogen; cyano group; sulfonate group; amine group; nitro group; substituted or unsubstituted C1 to C10 alkyl group; substituted or unsubstituted C1 to C10 alkoxy group; or a moiety connecting to Chemical Formula 1, and any one of R9 to R14 is a moiety connecting to the azo group in Chemical Formula 1.

[0085] In one embodiment of the present invention, Ar1 in Chemical Formula 1 is represented by Chemical Formula 2, and R1 to R8 in Chemical Formula 2 may be the same or different and each independently represent hydrogen; deuterium; halogen; sulfonate group; hydroxyl group; or a moiety connecting to Chemical Formula 1, and any one of R1 to R8 may be a moiety connecting to the azo group in Chemical Formula 1.

[0086] In one embodiment of the present invention, Ar2 in Chemical Formula 1 is represented by Chemical Formula 2, and R1 to R8 in Chemical Formula 2 may be the same or different and each independently represent hydrogen; deuterium; halogen; sulfonate group; hydroxyl group; or a moiety connecting to Chemical Formula 1, and any one of R1 to R8 may be a moiety connecting to the azo group in Chemical Formula 1.

[0087] In one embodiment of the present invention, Ar1 in Chemical Formula 1 is represented by Chemical Formula 3, and R9 to R14 in Chemical Formula 3 may be the same or different and each independently represent hydrogen; deuterium; halogen; sulfonate group; hydroxyl group; or a moiety connecting to Chemical Formula 1, and any one of R9 to R14 may be a moiety connecting to the azo group in Chemical Formula 1.

[0088] In one embodiment of the present invention, Ar2 in Chemical Formula 1 is represented by Chemical Formula 3, and R9 to R14 in Chemical Formula 3 may be the same or different and each independently represent hydrogen; deuterium; halogen; sulfonate group; hydroxyl group; or a moiety connecting to Chemical Formula 1, and any one of R9 to R14 may be a moiety connecting to the azo group in Chemical Formula 1.

[0089] In one embodiment of the present invention, Ar1 in Chemical Formula 1 is represented by Chemical Formula 2, and at least one of R1 to R8 in Chemical Formula 2, excluding the site connected to the azo group in Chemical Formula 1, may be a sulfonate group.

[0090] In one embodiment of the present invention, Ar2 in Chemical Formula 1 is represented by Chemical Formula 2, and at least one of R1 to R8 in Chemical Formula 2, excluding the site connected to the azo group in Chemical Formula 1, may be a sulfonate group.

[0091] In one embodiment of the present invention, Ar1 in Chemical Formula 1 is represented by Chemical Formula 3, and at least one of R9 to R14 in Chemical Formula 3, excluding the site connected to the azo group in Chemical Formula 1, may be a halogen group.

[0092] In one embodiment of the present invention, Ar2 in Chemical Formula 1 is represented by Chemical Formula 3, and at least one of R9 to R14 in Chemical Formula 3, excluding the site connected to the azo group in Chemical Formula 1, may be a halogen group.

[0093] In one embodiment of the present invention, Ar1 in Chemical Formula 1 is represented by Chemical Formula 3, and at least one of R9 to R14 in Chemical Formula 3, excluding the site connected to the azo group in Chemical Formula 1, may be a hydroxyl group.

[0094] In one embodiment of the present invention, Ar2 in Chemical Formula 1 is represented by Chemical Formula 3, and at least one of R9 to R14 in Chemical Formula 3, excluding the site connected to the azo group in Chemical Formula 1, may be a hydroxyl group.

[0095] In one embodiment of the present invention, Ar1 in Chemical Formula 1 is represented by Chemical Formula 3, and among R9 to R14 in Chemical Formula 3, at least one of a chloro group, a sulfonate group, and a hydroxyl group may be included, excluding the site connected to the azo group in Chemical Formula 1.

[0096] In one embodiment of the present invention, Ar2 in Chemical Formula 1 is represented by Chemical Formula 3, and among R9 to R14 in Chemical Formula 3, excluding the site connected to the azo group in Chemical Formula 1, may contain at least one chloro group, sulfonate group, and hydroxyl group.

[0097] In one embodiment of the present invention, Ar1 in Chemical Formula 1 is represented by Chemical Formula 3, and among R9 to R14 in Chemical Formula 3, excluding the site connected to the azo group in Chemical Formula 1, it may contain at least one hydroxyl group and two or more sulfonate groups.

[0098] In one embodiment of the present invention, Ar2 in Chemical Formula 1 is represented by Chemical Formula 3, and among R9 to R14 in Chemical Formula 3, excluding the site connected to the azo group in Chemical Formula 1, may contain at least one hydroxyl group and two or more sulfonate groups.

[0099] In one embodiment of the present invention, Ar1 in Chemical Formula 1 is represented by Chemical Formula 3, and among R9 to R14 in Chemical Formula 3, excluding the site connected to the azo group in Chemical Formula 1, may include at least one hydroxyl group, two or more sulfonate groups, and an amine group.

[0100] In one embodiment of the present invention, Ar2 in Chemical Formula 1 is represented by Chemical Formula 3, and among R9 to R14 in Chemical Formula 3, excluding the site connected to the azo group in Chemical Formula 1, may include at least one hydroxyl group, two or more sulfonate groups, and an amine group.

[0101] In one embodiment of the present invention, when at least one of R1 to R14 in Formulas 2 and 3 is a sulfonate group, the anion of the sulfonate group may be in the form of a salt combined with a metal cation, specifically, a sodium salt or calcium salt of the sulfonate group.

[0102] In one embodiment of the present invention, L1 in Formula 1 may be represented by Formula 4 or 5 below.

[0103] [ka]

[0104] [ka]

[0105] In the above Chemical Formula 4, R15 to R18 are the same or different and each independently represent hydrogen; deuterium; halogen; cyano group; sulfonate group; hydroxyl group; amine group; nitro group; or a moiety connecting to Chemical Formula 1, wherein any one of R15 to R18 is a moiety connecting to the nitrogen atom not connected to Ar1 among the two nitrogen atoms of the azo group to which Ar1 is linked among the two azo groups in Chemical Formula 1; R19 to R22 are the same or different and each independently represent hydrogen; deuterium; halogen; cyano group; sulfonate group; hydroxyl group; amine group; nitro group; or a moiety connecting to Chemical Formula 1, wherein any one of R19 to R22 is a moiety connecting to the nitrogen atom not connected to Ar2 among the two nitrogen atoms of the azo group to which Ar2 is linked among the two azo groups in Chemical Formula 1; In the above Chemical Formula 5, R23 to R27 are the same or different and each independently represent hydrogen; deuterium; halogen; cyano group; sulfonate group; hydroxyl group; amine group; nitro group; substituted or unsubstituted C1 to C5 alkyl group; substituted or unsubstituted C1 to C5 alkoxy group; or a moiety that is bonded to a nitrogen atom that is not bonded to Ar1 among the two nitrogen atoms of the azo group to which Ar1 is bonded among the two azo groups of Chemical Formula 1, and any one of R23 to R27 is a moiety that is bonded to a nitrogen atom that is not bonded to Ar1 among the two nitrogen atoms of the azo group to which Ar1 is bonded among the two azo groups of Chemical Formula 1, R28 to R32 are the same or different and each independently represent hydrogen; deuterium; halogen; cyano group; sulfonate group; hydroxyl group; amine group; nitro group; substituted or unsubstituted C1 to C5 alkyl group; substituted or unsubstituted C1 to C5 alkoxy group; or a moiety that is bonded to a nitrogen atom that is not bonded to Ar2 among the two nitrogen atoms of the azo group to which Ar2 is bonded among the two azo groups in Chemical Formula 1, and any one of R28 to R32 is a moiety that is bonded to a nitrogen atom that is not bonded to Ar2 among the two nitrogen atoms of the azo group to which Ar2 is bonded among the two azo groups in Chemical Formula 1, Z is a single bond; a substituted or unsubstituted C2-C10 alkenylene group; or a substituted or unsubstituted C2-C10 alkynylene group.

[0106] In one embodiment of the present invention, R15 to R18 of Chemical Formula 4 may contain at least one sulfonate group and one hydroxyl group, excluding the site where the nitrogen atom not connected to Ar1 is bonded to one of the two nitrogen atoms of the azo group to which Ar1 is bonded, among the two azo groups of Chemical Formula 1; and R19 to R22 of Chemical Formula 4 may contain at least one sulfonate group and one hydroxyl group, excluding the site where the nitrogen atom not connected to Ar2 is bonded to one of the two nitrogen atoms of the azo group to which Ar2 is bonded, among the two azo groups of Chemical Formula 1.

[0107] In one embodiment of the present invention, R23 to R27 of Chemical Formula 5 may contain at least one sulfonate group, excluding a site connected to a nitrogen atom not connected to Ar1 among the two nitrogen atoms of the azo group to which Ar1 is linked among the two azo groups of Chemical Formula 1, and R28 to R32 of Chemical Formula 5 may contain at least one sulfonate group, excluding a site connected to a nitrogen atom not connected to Ar2 among the two nitrogen atoms of the azo group to which Ar2 is linked among the two azo groups of Chemical Formula 1.

[0108] In one embodiment of the present invention, R23 to R27 in Chemical Formula 5 may contain at least one substituted or unsubstituted C1-C3 alkyl group; or a substituted or unsubstituted C1-C3 alkoxy group, excluding a site connected to a nitrogen atom not connected to Ar1 among the two nitrogen atoms of the azo group to which Ar1 is linked among the two azo groups in Chemical Formula 1; and R28 to R32 in Chemical Formula 5 may contain at least one substituted or unsubstituted C1-C3 alkyl group; or a substituted or unsubstituted C1-C3 alkoxy group, excluding a site connected to a nitrogen atom not connected to Ar2 among the two nitrogen atoms of the azo group to which Ar2 is linked among the two azo groups in Chemical Formula 1.

[0109] In one embodiment of the present invention, R23 to R27 in Chemical Formula 5 may contain at least one substituted or unsubstituted methyl group or a substituted or unsubstituted methoxy group, except for the site connected to the nitrogen atom not connected to Ar1 among the two nitrogen atoms of the azo group to which Ar1 is linked among the two azo groups in Chemical Formula 1, and R28 to R32 in Chemical Formula 5 may contain at least one substituted or unsubstituted methyl group or a substituted or unsubstituted methoxy group, except for the site connected to the nitrogen atom not connected to Ar2 among the two nitrogen atoms of the azo group to which Ar2 is linked among the two azo groups in Chemical Formula 1.

[0110] In one embodiment of the present invention, the second dispersant may include a compound represented by any one of the following Formulas 1-1a to 1-1d.

[0111] [ka]

[0112] In the above chemical formula 1-1a, R1 to R5, R7 to R11, and R13 to R18 are the same as or different from one another and each independently represent hydrogen, deuterium, a halogen, a cyano group, a sulfonate group, a hydroxyl group, an amine group, or a nitro group; [ka]

[0113] In the above chemical formula 1-1b, R1 to R7 and R9 to R15 are the same or different and each independently represent hydrogen, deuterium, a halogen, a cyano group, a sulfonate group, a hydroxyl group, an amine 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, or a substituted or unsubstituted C6 to C20 aryl group, and at least one of R1 to R7 is a sulfonate group, and at least one of R9 to R15 is a sulfonate group; [ka]

[0114] In the above chemical formula 1-1c, R1 to R5 and R7 to R11 are the same or different and each independently represent 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, wherein at least one of R1 to R5 is a hydroxyl group and at least one of R7 to R11 is a hydroxyl group; R13 to R20 are the same or different and each independently represent 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, and at least one of R13 to R16 is a sulfonate group, and at least one of R17 to R20 is a sulfonate group; [ka]

[0115] In the above chemical formula 1-1d, R1 to R7 and R9 to R15 are the same or different and each independently represent hydrogen; deuterium; halogen; cyano group; sulfonate group; hydroxyl group; amine group; or nitro group; R17 to R20 and R22 to R25 are the same or different and each independently represent hydrogen, deuterium, a halogen, a cyano group, a sulfonate group, a hydroxyl group, an amine group, a nitro group, a substituted or unsubstituted C1 to C5 alkyl group, or a substituted or unsubstituted C1 to C5 alkoxy group.

[0116] In one embodiment of the present invention, R1 to R5 and R7 to R11 in the above formula 1-1a may be the same or different, and may each independently represent hydrogen, halogen, a sulfonate group, or a hydroxyl group.

[0117] In one embodiment of the present invention, R13 to R18 in the above formula 1-1a may be the same or different, and may each independently represent a hydrogen atom, a sulfonate group, or a hydroxyl group.

[0118] In one embodiment of the present invention, when the second dispersant is a compound represented by Chemical Formula 1-1a, it may contain a compound represented by the following Chemical Formula 6 (SulfoChlorophenol S).

[0119] [ka]

[0120] In a carbon nanotube dispersion according to one embodiment of the present invention, the compound represented by formula 1-1a contained in the second dispersant contains at least one hydroxyl group, thereby forming hydrogen bonds with the solvent in the dispersion, thereby enabling the ``carbon nanotube-dispersant'' complex to maintain a stable dispersion state in the solvent.

[0121] In addition, in a carbon nanotube dispersion according to one embodiment of the present invention, the compound represented by Chemical Formula 1-1a contained in the second dispersant contains at least one sulfonate group, and thus the dispersant is ionized when dissolved in the solvent, forming electrostatic repulsion between the sulfonate anions, preventing aggregation between adjacent dispersants and allowing the "carbon nanotube-dispersant" combination to maintain a stable dispersion state in the solvent.

[0122] In one embodiment of the present invention, R1 to R7 in Chemical Formula 1-1b may be the same or different and each independently represent hydrogen, a sulfonate group, or a hydroxyl group, and at least one of R1 to R7 may be a sulfonate group. In one embodiment of the present invention, R9 to R15 in Chemical Formula 1-1b may be the same or different and each independently represent hydrogen, a sulfonate group, or a hydroxyl group, and at least one of R9 to R15 may be a sulfonate group.

[0123] In one embodiment of the present invention, when the second dispersant is a compound represented by Chemical Formula 1-1b, it may be one or more selected from the group consisting of Direct Red 28, Direct Red 2, Direct Red 7, Direct Red 46, and Direct Red 56, and is not limited to the above type as long as it is a substituted azo compound that contains at least two sulfonate groups in the molecule and can enhance the dispersibility of carbon nanotubes.

[0124] In one embodiment of the present invention, when the second dispersant is a compound represented by Formula 1-1b, it may further include at least two amine groups.

[0125] When the second dispersant is a compound represented by Chemical Formula 1-1b, it further contains at least two amine groups, which form hydrogen bonds with the solvent, allowing the carbon nanotube-dispersant complex to maintain a stable dispersion state in the solvent. Furthermore, the hydrogen bond interaction between the nitrogen atom contained in the first dispersant and the amine group of the second dispersant is appropriately balanced, thereby further improving the effect of reducing the viscosity of the carbon nanotube dispersion and suppressing viscosity increase over time.

[0126] In one embodiment of the present invention, R1 to R5 in the above formula 1-1c may be the same or different and each independently represent a hydrogen atom or a hydroxyl group, and at least one of R1 to R5 may be a hydroxyl group.

[0127] In one embodiment of the present invention, R7 to R11 in the above formula 1-1c may be the same or different and each independently represent a hydrogen atom or a hydroxyl group, and at least one of R7 to R11 may be a hydroxyl group.

[0128] In one embodiment of the present invention, R13 to R16 in Formula 1-1c may be the same or different and each independently represent a hydrogen atom or a sulfonate group, and at least one of R13 to R16 may be a sulfonate group.

[0129] In one embodiment of the present invention, R17 to R20 in Formula 1-1c may be the same or different and each independently represent a hydrogen atom or a sulfonate group, and at least one of R17 to R20 may be a sulfonate group.

[0130] In one embodiment of the present invention, when the second dispersant is a compound represented by Chemical Formula 1-1c, a specific example thereof is Direct Yellow 4 as shown in Chemical Formula 7 below. However, the substituted azo compound is not limited to the above type as long as it contains at least two sulfonate groups and two or more hydroxyl groups in the molecule and can enhance the dispersibility of carbon nanotubes.

[0131] [ka]

[0132] In one embodiment of the present invention, R1 to R7 in Formula 1-1d may be the same or different and each independently represent a hydrogen atom, a sulfonate group, a hydroxyl group, or an amine group, and R1 to R7 may include at least one hydroxyl group and two or more sulfonate groups.

[0133] In one embodiment of the present invention, R9 to R15 in Formula 1-1d may be the same or different and each independently represent a hydrogen atom, a sulfonate group, a hydroxyl group, or an amine group, and R9 to R15 may include at least one hydroxyl group and two or more sulfonate groups.

[0134] In one embodiment of the present invention, R17 to R20 in the above formula 1-1d may be the same or different, and each independently may be hydrogen or a substituted or unsubstituted C1 to C5 alkyl group.

[0135] In one embodiment of the present invention, R22 to R25 in the above formula 1-1d may be the same or different, and each independently may be hydrogen or a substituted or unsubstituted C1 to C5 alkyl group.

[0136] In one embodiment of the present invention, when the second dispersant is a compound represented by Formula 1-1d, the second dispersant may be one or more selected from the group consisting of Direct Blue 1, Direct Blue 14, Direct Blue 15, and Direct Blue 53.

[0137] In a carbon nanotube dispersion according to one embodiment of the present invention, the compound represented by chemical formula 1-1d contained in the second dispersant contains at least one hydroxyl group, thereby forming hydrogen bonds with the solvent in the dispersion, thereby enabling the ``carbon nanotube-dispersant'' complex to maintain a stable dispersion state in the solvent.

[0138] In addition, in a carbon nanotube dispersion according to one embodiment of the present invention, the compound represented by chemical formula 1-1d contained in the second dispersant contains two or more sulfonate groups, and thus the dispersant is ionized when dissolved in the solvent, forming electrostatic repulsion between the sulfonate anions, preventing aggregation between adjacent dispersants and enabling the ``carbon nanotube-dispersant'' complex to maintain a stable dispersion state in the solvent.

[0139] If the carbon nanotube dispersion does not contain the second dispersant according to the present invention, there may be an increase in areas where the surface of the carbon nanotubes is not sufficiently covered by the dispersant, which may result in an excessively strong bonding force between the carbon nanotubes, causing aggregation between the carbon nanotubes and resulting in a high viscosity of the dispersion.

[0140] Furthermore, if the second dispersant contains, for example, three or more aromatic rings in its molecular structure, the molecules may form a linear, angular, or dense structure, which is unfavorable for the surface adsorption of small-diameter carbon nanotubes, especially single-walled carbon nanotubes. Furthermore, strong π-π interactions occur between unadsorbed dispersants, which deepens the aggregation of the dispersants, resulting in a high viscosity dispersion, which may increase significantly over time.

[0141] In one embodiment of the present invention, the second dispersant may be included in an amount of 0.001 to 9 parts by weight based on 100 parts by weight of the carbon nanotube dispersion liquid, for example, 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 Above, 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 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, 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.

[0142] If the content of the second dispersant is less than 0.001 parts by weight based on 100 parts by weight of the carbon nanotube dispersion, an effective dispersion effect may not be exhibited, resulting in a problem that the viscosity of the dispersion may not be low and the viscosity may increase over time. If the content of the second dispersant exceeds 9 parts by weight, the content of the second dispersant is too high, which may cause problems as the viscosity of the dispersion may increase due to the promotion of aggregation of solids in the dispersion.

[0143] 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 more, 100:15 or more, 100:17.65 or more, 100:20 or more, 100:25 or more, 100:30 or more, 100:33.33 or more, 100:35 or more, 100:40 or more, 100:45 or more, 100:50 or more, or 100:55 or more. 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.

[0144] When the first dispersant and the second dispersant are contained in the carbon nanotube dispersion in the above weight ratio, the carbon nanotubes are uniformly dispersed in the carbon nanotube dispersion, and the viscosity can be maintained at a constant level over time along with a low viscosity.

[0145] (3) Solvent The solvent of the carbon nanotube dispersion liquid 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 linearly disperse the powdered carbon nanotubes and supply them to the carbon nanotube dispersion liquid to prevent them from agglomerating when they are immediately used to prepare an electrode slurry composition.

[0146] The solvent can dissolve or disperse the carbon nanotubes, the first dispersant, and the second dispersant to a certain level or more. The aqueous solvent may be, for example, water, and may be included in an amount that allows the electrode slurry composition to have an appropriate viscosity in consideration of the coatability of the electrode slurry composition to be prepared using the carbon nanotube dispersion liquid.

[0147] In one embodiment of the carbon nanotube dispersion according to the present invention, the first dispersant and the second dispersant enable the carbon nanotubes to be uniformly dispersed in the solvent, thereby reducing the average particle size distribution of the dispersed particles contained in the dispersion, for example, the composite of the carbon nanotubes and each dispersant.

[0148] The average particle size distribution (D 50 ) may be, for example, 0.5 to 10 μm, 1 to 10 μm, 1 to 8 μm, or preferably 1 to 5 μm.

[0149] The carbon nanotube dispersion of the present invention containing the above-mentioned components has excellent dispersibility, a low viscosity of the dispersion, and a small degree of viscosity increase over time.

[0150] The carbon nanotube dispersion may have an initial viscosity of 1 to 8 Pa·s measured at 25°C and 1 rpm using a viscometer (TOKI SANGYO, viscometer TV-25, Rotor Code01), for example, 1 Pa·s or more, 1.1 Pa·s or more, 1.2 Pa·s or more, 1.3 Pa·s or more, 1.4 Pa·s or more, 1.5 Pa·s or more, 1.6 Pa·s or more, 1.7 Pa·s or more, 1.8 Pa·s or more, 1.9 Pa·s or more, 2 Pa·s or more, 2.1 Pa·s or more, or 2.2 Pa·s or more. , 2.3 Pa s or more, 2.4 Pa s or more, 2.5 Pa s or more, 2.6 Pa s or more, 2.7 Pa s or more, 2.8 Pa s or more, 2.9 Pa s or more, 3 Pa s or more, 3.1 Pa s or more Above, 3.2 Pa s or more, 3.3 Pa s or more, 3.4 Pa s or more, 3.5 Pa s or more, 3.6 Pa s or more, 3.7 Pa s or more, 3.8 Pa s or more, 3.9 Pa s or more, 4 Pa ​​s or more, 4.1Pa·s or more, 4.2Pa·s or more, 4.3Pa·s or more, 4.4Pa·s or more, 4.5Pa·s or more, 4.6Pa·s or more, 4.7Pa·s or more, 4.8Pa·s or more, 4.9Pa·s or more, 5Pa·s or more, 5.1Pa·s or more, 5.2Pa·s or more, 5.3Pa·s or more, 5.4Pa·s or more or 5.5Pa·s or more, and may be 10Pa·s or less, 9.9Pa·s or less. s or less, 9.8Pa·s or less, 9.7Pa·s or less, 9.6Pa·s or less, 9.5Pa·s or less, 9.4Pa·s or less, 9.3Pa·s or less, 9.2Pa·s or less, 9.1Pa·s or less, 9Pa·s or less, 8.9Pa·s or less, 8.8Pa·s or less, 8.7Pa·s or less, 8.6Pa·s or less, 8.5Pa·s or less, 8.4Pa·s or less, 8.3Pa·s or less, 8.2Pa·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.The initial viscosity of the carbon nanotube dispersion may be 7 Pa·s or less, or 5.6 Pa·s or less. When the carbon nanotube dispersion has an initial viscosity within this range, it can be used to more smoothly prepare an electrode slurry, and the electrode slurry containing the carbon nanotube dispersion can have an appropriate viscosity for forming an electrode.

[0151] Furthermore, when the carbon nanotube dispersion is left at 25°C for one week, the viscosity increase rate calculated by the following formula (1) may be 0.1% to 15% or less, specifically 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.

[0152] [Formula 1] Viscosity increase rate (%) = {(viscosity measured after leaving at 25°C for 1 week - initial viscosity) / initial viscosity} x 100 At this time, the viscosity after standing for one week and the initial viscosity were measured at 25°C and 1 rpm.

[0153] Method for producing carbon nanotube dispersion Hereinafter, a method for producing a carbon nanotube dispersion liquid according to an embodiment of the present invention will be described.

[0154] The method for producing a carbon nanotube dispersion according to the present invention includes: (1) mixing carbon nanotubes, a first dispersant containing nitrogen atoms, a second dispersant containing a compound represented by the following Chemical Formula 1, and a solvent to produce a primary dispersion of carbon nanotubes; and (2) dispersing the primary dispersion of carbon nanotubes to produce a secondary dispersion of carbon nanotubes.

[0155] [ka]

[0156] In the above Chemical Formula 1, 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.

[0157] In step (1), a primary dispersion of carbon nanotubes is prepared by mixing carbon nanotubes, a first dispersant containing nitrogen atoms, a second dispersant containing a compound represented by the following Formula 1, and a solvent. The step of preparing the primary dispersion of carbon nanotubes is performed by a wetting process in which each component is uniformly mixed.

[0158] The carbon nanotubes, the first dispersant containing nitrogen atoms, the second dispersant containing a compound represented by the following Chemical Formula 1, and the solvent used in the method for producing the carbon nanotube dispersion are as described above, and therefore will not be described in detail below.

[0159] The mixing for preparing the primary dispersion of carbon nanotubes may be carried out using a conventional mixing method, specifically, a mixing device such as a pony mixer, a change-can mixer, a Hobert mixer, a pulley mixer, a butterfly mixer, a stone mill, a homogenizer, a bead mill, a ball mill, a basket mill, an attrition mill, a universal mixer, a clear mixer, or a TK mixer, and may include a mixing step at a rotation speed of 300 to 5,000 rpm for 30 minutes to 7 hours.

[0160] In addition, during mixing to prepare the primary dispersion of carbon nanotubes, a cavitation dispersion process may be performed to improve the mixability of the carbon nanotubes with the solvent or the dispersibility of the carbon nanotubes in the solvent. The cavitation dispersion process is a dispersion process that uses shock waves generated by the bursting of vacuum bubbles generated in water when high energy is applied to the liquid, and this process allows for dispersion of carbon nanotubes without damaging their properties. Specifically, the cavitation dispersion process may be performed using ultrasound, a jet mill, or shear dispersion.

[0161] The step of preparing the primary dispersion of carbon nanotubes may be carried out under temperature conditions that do not cause changes in the physical properties of the mixture, such as viscosity, due to evaporation of the solvent, for example, at a temperature of 50°C or less, more specifically, 5°C to 50°C.

[0162] In step (2), the primary dispersion of carbon nanotubes is dispersed to prepare a secondary dispersion of carbon nanotubes.

[0163] The process of preparing the secondary dispersion of carbon nanotubes may be performed using a method such as a ball mill, a bead mill, a disc mill, a basket mill, or a high-pressure homogenizer, and more specifically, may be performed using a dispersion method using a high-pressure homogenizer.

[0164] Dispersion by the high-pressure disperser is carried out by, for example, pressing the mixture with a plunger pump of the high-pressure disperser and forcing it through a gap in a dispersing valve, and by forces such as cavitation, shear, impact, and explosion when passing through the gap.

[0165] The dispersion process may be carried out according to the degree of dispersion of the carbon nanotube dispersion liquid. Specifically, it may be carried out under a pressure of 5,000 to 30,000 psi for 30 to 120 minutes, more specifically 60 to 90 minutes, and the above process can be repeated 1 to 10 times.

[0166] The carbon nanotube dispersion liquid according to the present invention may mean a secondary dispersion liquid of the carbon nanotubes.

[0167] Electrode slurry composition for lithium secondary battery In addition, the present invention provides an electrode slurry composition for a lithium secondary battery including the carbon nanotube dispersion liquid and an electrode active material.

[0168] The electrode slurry composition for the lithium secondary battery may be a positive electrode slurry composition or a negative electrode slurry composition, specifically, it may be a negative electrode slurry composition.

[0169] The electrode slurry composition for the lithium secondary battery may include the carbon nanotube dispersion liquid, 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 required.

[0170] As the positive electrode active material, well-known positive electrode active materials in the technical field may be used without limitation. For example, lithium cobalt-based oxides, lithium nickel-based oxides, lithium manganese-based oxides, lithium iron phosphate, lithium nickel manganese cobalt-based oxides or combinations thereof may be used. Specifically, as the positive electrode active material, LiCoO2, LiNiO2, LiMn2O4, LiCoPO4, LiFePO4 and LiNiaMnbCocO2 (where 0 < a, b, c < 1) etc. may be used, but it is not limited thereto.

[0171] Examples of the negative electrode active material include natural graphite, artificial graphite, and carbonaceous materials; lithium-containing titanium composite oxide (LTO); metals (Me) such as Si, Sn, Li, Zn, Mg, Cd, Ce, Ni, and Fe; alloys composed of the metals (Me); and oxides of the metals (MeO x and a composite of the metal (Me) with carbon. The negative electrode active material may be included in the negative electrode slurry in an amount of 60 to 98 wt %, more preferably 70 to 98 wt %, based on the total weight of solids excluding the solvent.

[0172] The binder is a component that aids in binding the active material and conductive material, etc., and binding them to the current collector, and is typically added in an amount of 1 to 30 wt% based on the total weight of the mixture including the electrode active material. Examples of such binders include polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene propylene diene terpolymer (EPDM), sulfonated EPDM, styrene butadiene rubber, fluororubber, and various copolymers.

[0173] The solvent may be an organic solvent such as N-methylpyrrolidone (NMP), dimethylformamide (DMF), acetone, or dimethylacetamide, or water, and these solvents may be used alone or in combination. The amount of solvent used should be sufficient to dissolve and disperse the electrode active material, binder, and conductive material, taking into consideration the coating thickness of the slurry and the production yield.

[0174] The viscosity adjuster may be carboxymethyl cellulose or polyacrylic acid, and the addition thereof may adjust the viscosity of the electrode slurry to facilitate the preparation of the electrode slurry and the coating process on the electrode current collector.

[0175] The filler is selectively used as a component to suppress the expansion of the electrode, and is not particularly limited as long as it is a fibrous material that does not cause chemical changes in the battery. For example, olivine polymers such as polyethylene and polypropylene; glass fiber, carbon fiber, and other fibrous materials are used.

[0176] When the electrode slurry composition is a positive electrode slurry composition for forming a positive electrode, the positive electrode can be manufactured by coating the positive electrode slurry composition on a positive electrode current collector, drying, and rolling the composition, or by casting the positive electrode slurry on a separate support, peeling it off from the support, and laminating the resulting film on the positive electrode current collector.

[0177] The thickness of the positive electrode active material layer formed by the positive electrode slurry varies depending on the loading amount and loading speed for applying the positive electrode slurry.

[0178] The positive electrode current collector generally has a thickness of 3 μm to 500 μm. There are no particular limitations on the positive electrode current collector, as long as it has high conductivity and does not cause chemical changes in the battery. For example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel whose surface has been treated with carbon, nickel, titanium, silver, or the like may be used. Furthermore, the surface of the positive electrode current collector may be provided with fine irregularities to strengthen the bonding strength of the positive electrode active material, and the positive electrode current collector may be used in various forms, such as a film, sheet, foil, net, porous material, foam, or nonwoven fabric.

[0179] When the electrode slurry composition is a negative electrode slurry composition for forming a negative electrode, the negative electrode can be manufactured by coating the negative electrode slurry composition on a negative electrode current collector, drying and rolling the composition, or by casting the negative electrode slurry on a separate support, peeling it off from the support, and laminating the resulting film on the negative electrode current collector.

[0180] The thickness of the negative electrode active material layer formed by the negative electrode slurry varies depending on the loading amount and loading speed for applying the negative electrode slurry.

[0181] The negative electrode current collector generally has a thickness of 3 μm to 500 μm. Such a negative electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, and examples of such a negative electrode current collector include copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surfaces treated with carbon, nickel, titanium, silver, etc., and aluminum-cadmium alloys. Similarly to the negative electrode current collector, the surface may be formed with fine irregularities to strengthen the binding strength of the negative electrode active material, and the negative electrode current collector may be used in various forms such as a film, sheet, foil, net, porous material, foam, or nonwoven fabric.

[0182] Lithium secondary battery The lithium secondary battery includes a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and an electrolyte. The positive electrode and the negative electrode are the same as those described above, and therefore, detailed description thereof will be omitted.

[0183] The separator separates the negative electrode and the positive electrode and provides a path for lithium ions to move. Any separator commonly used in lithium secondary batteries can be used without any particular limitations. In particular, a separator that exhibits low resistance to ion movement in the electrolyte and excellent humidification of the electrolyte is preferred. Specifically, a porous polymer film, such as a porous polymer film made of a polyolefin-based polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, or an ethylene / methacrylate copolymer, or a laminate structure of two or more layers thereof, can be used. Conventional porous nonwoven fabrics, such as nonwoven fabrics made of high-melting-point glass fibers or polyethylene terephthalate fibers, can also be used. To ensure heat resistance or mechanical strength, a separator coated with a ceramic component or a polymer material can be used, and it can be used in a single-layer or multi-layer structure.

[0184] The electrolyte may be, but is not limited to, an organic liquid electrolyte, an inorganic liquid electrolyte, a solid polymer electrolyte, a gel polymer electrolyte, a solid inorganic electrolyte, a molten inorganic electrolyte, etc. that can be used in manufacturing a lithium secondary battery. Specifically, the electrolyte may include an organic solvent and a lithium salt.

[0185] The organic solvent may be any solvent that can act as a medium through which ions involved in the electrochemical reaction of the battery can move. Specific examples of the organic solvent include ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether solvents such as dibutyl ether and tetrahydrofuran; ketone solvents such as cyclohexanone; aromatic hydrocarbon solvents such as benzene and fluorobenzene; dimethylcarbonate (DMC), diethylcarbonate (DEC), methylethylcarbonate (MEC), ethylmethylcarbonate (EMC), ethylene carbonate (EC), and propylene carbonate. Examples of suitable solvents include carbonate-based solvents such as ethylene carbonate (PC), alcohol-based solvents such as ethanol and isopropyl alcohol, nitriles such as R-CN (where R is a C2-C20 linear, branched, or cyclic hydrocarbon group that may contain a double-bonded aromatic ring or an ether bond), amides such as dimethylformamide, dioxolanes such as 1,3-dioxolane, and sulfolanes. Among these, carbonate-based solvents are preferred, and mixtures of cyclic carbonates (e.g., ethylene carbonate or propylene carbonate) with low viscosity linear carbonate compounds (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate) are more preferred, as they have high ionic conductivity and a high dielectric constant, which can improve the charge / discharge performance of batteries. In this case, the cyclic carbonate and chain carbonate should be mixed in a volume ratio of about 1:1 to about 1:9 to achieve excellent electrolyte performance.

[0186] The lithium salt may be any compound capable of providing lithium ions used in lithium secondary batteries. Specifically, the lithium salt may 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 within a range of 0.1M to 2.0M. When the lithium salt concentration is within this range, the electrolyte has appropriate conductivity and viscosity, resulting in excellent electrolyte performance and efficient lithium ion migration.

[0187] In addition to the electrolyte components, the electrolyte may further contain one or more additives, such as haloalkylene carbonate compounds (e.g., difluoroethylene carbonate), pyridine, triethyl phosphite, triethanolamine, cyclic ethers, ethylenediamine, n-glyme, hexaphosphoric acid triamide, nitrobenzene derivatives, sulfur, quinoneimine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, or aluminum trichloride, for the purpose of improving battery life characteristics, suppressing battery capacity reduction, and improving battery discharge capacity. In this case, the additives may be contained in an amount of 0.1 wt % to 5 wt % based on the total weight of the electrolyte.

[0188] A lithium secondary battery including an electrode prepared using the carbon nanotube dispersion according to the present invention, specifically, a lithium secondary battery including an anode prepared using the carbon nanotube dispersion, has carbon nanotubes uniformly dispersed in the anode, and can reduce the amount of a conductive material, such as carbon black, compared to conventional batteries that include such a conductive material. This allows the battery to stably exhibit excellent discharge capacity and output characteristics. As a result, the battery is useful in portable devices such as mobile phones, laptops, and digital cameras, and electric vehicles such as hybrid electric vehicles (HEVs).

[0189] Accordingly, according to another embodiment of the present invention, there are provided the lithium secondary battery, a battery module including the lithium secondary battery as a unit cell, and a battery pack including the same.

[0190] The battery module or battery pack may be used as a power source for one or more medium- to large-sized devices in a power tool; an electric vehicle (EV), a hybrid electric vehicle, and an electric vehicle (PHEV), including a plug-in hybrid electric vehicle; or a power storage system. DETAILED DESCRIPTION OF THE INVENTION

[0191] Specific examples of the present invention will be presented below. However, the following examples are merely intended to specifically illustrate and explain the present invention, and are not intended to limit the present invention. Furthermore, details not described herein can be easily inferred by those skilled in the art, and therefore, a detailed description thereof will be omitted.

[0192] Example Example 1a (1) 5.625 g of polyvinylpyrrolidone (PVP) (PVP K15, manufactured by Zhangzhou Huafu Chemical Co., Ltd.) as a first dispersant containing nitrogen atoms (1.125 parts by weight relative to 100 parts by weight of the total carbon nanotube dispersion), 1.875 g of sulfochlorophenol S sodium calcium salt (manufactured by Sigma-Aldrich Co., Ltd.) as a second dispersant containing a compound represented by Chemical Formula 1 (0.375 parts by weight relative to 100 parts by weight of the total carbon nanotube dispersion), and 487.5 g of water as a solvent were mixed to prepare 495 g of a mixed solution, which was then placed in a dissolver (Dispermat-CA, manufactured by VMA-GETZMANN Co., Ltd.) equipped with an impeller and a container, and stirred at 400 rpm for 10 minutes.

[0193] The mixture has a specific surface area of ​​1,160 m 2 / g, average particle size (D 50 ) 5.0 g (1.0 part by weight per 100 parts by weight of the total carbon nanotube dispersion) of 5 μm single-walled carbon nanotubes (SWCNT, TUBALL, manufactured by OCSiAl) was further added and stirred at 8,000 rpm for 60 minutes to produce a total of 500 g of a primary dispersion of carbon nanotubes.

[0194] (3) The primary dispersion of carbon nanotubes was homogenously dispersed seven times using a high-pressure disperser (PICOMAX, manufactured by Micronox) at a pressure of 20,000 psi to prepare a secondary dispersion of carbon nanotubes.

[0195] Example 2a A carbon nanotube dispersion was prepared in the same manner as in Example 1a, except that the content of the first dispersant was 5.0 g (1.0 part by weight based on 100 parts by weight of the total carbon nanotube dispersion) and the content of the second dispersant was 2.5 g (0.5 part by weight based on 100 parts by weight of the total carbon nanotube dispersion).

[0196] Example 3a A carbon nanotube dispersion was prepared in the same manner as in Example 1a, except that the content of the first dispersant was 3.375 g (0.675 parts by weight relative to 100 parts by weight of the total carbon nanotube dispersion), the content of the second dispersant was 1.125 g (0.225 parts by weight relative to 100 parts by weight of the total carbon nanotube dispersion), and the content of carbon nanotubes was 3.0 g (0.6 parts by weight relative to 100 parts by weight of the total carbon nanotube dispersion).

[0197] Example 1b (1) 4.5 g (0.9 parts by weight per 100 parts by weight of the total carbon nanotube dispersion) of polyvinylpyrrolidone (PVP) (PVP K15, manufactured by Zhangzhou Huafu Chemical Co., Ltd.) as a first dispersant, which is a polymer dispersant containing nitrogen atoms, 1.5 g (0.3 parts by weight per 100 parts by weight of the total carbon nanotube dispersion) of Direct Red 28 (manufactured by Sigma Aldrich Co., Ltd.) as a second dispersant containing a compound containing at least two azo groups and two or more sulfonate groups, and 490 g of water as a solvent were mixed to prepare 496 g of a mixed solution, which was then placed in a dissolver (Dispermat-CA, manufactured by VMA-GETZMANN Co., Ltd.) equipped with an impeller and a container, and stirred at 400 rpm for 10 minutes.

[0198] The mixture has a specific surface area of ​​1,160 m 2 / g, average particle size (D 50 ) 4.0 g (0.8 parts by weight relative to 100 parts by weight of the total carbon nanotube dispersion) of 5 μm single-walled carbon nanotubes (SWCNT, TUBALL, manufactured by OCSiAl) was further added and stirred at 8,000 rpm for 60 minutes to produce a total of 500 g of a primary dispersion of carbon nanotubes.

[0199] (2) The carbon nanotube primary dispersion was homogenously dispersed seven times using a high-pressure disperser (PICOMAX, manufactured by Micronox) at a pressure of 14,000 psi to prepare a carbon nanotube dispersion.

[0200] Example 2b A carbon nanotube dispersion was prepared in the same manner as in Example 1b, except that the carbon nanotube content was 1.0 parts by weight relative to 100 parts by weight of the total carbon nanotube dispersion, the first dispersant content was 1.125 parts by weight relative to 100 parts by weight of the total carbon nanotube dispersion, and the second dispersant content was 0.375 parts by weight relative to 100 parts by weight of the total carbon nanotube dispersion.

[0201] Example 3b A carbon nanotube dispersion was prepared in the same manner as in Example 1b, except that the carbon nanotube content was 1.0 parts by weight relative to 100 parts by weight of the total carbon nanotube dispersion, the first dispersant content was 1.2 parts by weight relative to 100 parts by weight of the total carbon nanotube dispersion, and the second dispersant content was 0.3 parts by weight relative to 100 parts by weight of the total carbon nanotube dispersion.

[0202] Example 4b A carbon nanotube dispersion was prepared in the same manner as in Example 1b, except that the carbon nanotube content was 1.0 part by weight relative to 100 parts by weight of the total carbon nanotube dispersion, the first dispersant content was 1.0 part by weight relative to 100 parts by weight of the total carbon nanotube dispersion, and the second dispersant content was 0.5 part by weight relative to 100 parts by weight of the total carbon nanotube dispersion.

[0203] Example 5b A carbon nanotube dispersion was prepared in the same manner as in Example 1b, except that 1.5 g (0.3 parts by weight relative to 100 parts by weight of the total carbon nanotube dispersion) of Direct Red 7 (Sigma-Aldrich) was used instead of Direct Red 28 as the second dispersant.

[0204] Example 1c (1) 4.5 g (0.9 parts by weight per 100 parts by weight of the total carbon nanotube dispersion) of polyvinylpyrrolidone K15 (PVP K15) (PVP K15, manufactured by Zhangzhou Huafu Chemical Co., Ltd.) as a first dispersant, which is a polymer dispersant containing nitrogen atoms; 1.5 g (0.3 parts by weight per 100 parts by weight of the total carbon nanotube dispersion) of Direct Yellow 4 (manufactured by Sigma Aldrich Co., Ltd.) as a second dispersant containing a compound containing at least two azo groups, two sulfonate groups, and two hydroxyl groups; and 490 g of water as a solvent were mixed to prepare 496 g of a mixed solution, which was then placed in a dissolver (Dispermat-CA, manufactured by VMA-GETZMANN Co., Ltd.) equipped with an impeller and a container, and stirred at 400 rpm for 10 minutes.

[0205] The mixture has a specific surface area of ​​1,160 m 2 4.0 g (0.8 parts by weight per 100 parts by weight of the total carbon nanotube dispersion) of single-walled carbon nanotubes (SWCNT, TUBALL, manufactured by OCSiAl) with an average particle size (D50) of 5 μm was further added and stirred at 8,000 rpm for 60 minutes to produce a total of 500 g of a primary dispersion of carbon nanotubes.

[0206] (2) The carbon nanotube primary dispersion was homogenously dispersed seven times using a high-pressure disperser (PICOMAX, manufactured by Micronox) at a pressure of 14,000 psi to prepare a carbon nanotube dispersion.

[0207] Example 2c A carbon nanotube dispersion was prepared in the same manner as in Example 1c, except that the content of the first dispersant was 0.96 parts by weight based on 100 parts by weight of the total carbon nanotube dispersion, and the content of the second dispersant was 0.24 parts by weight based on 100 parts by weight of the total carbon nanotube dispersion.

[0208] Example 3c A carbon nanotube dispersion was prepared in the same manner as in Example 1c, except that the content of the first dispersant was 0.8 parts by weight based on 100 parts by weight of the total carbon nanotube dispersion, and the content of the second dispersant was 0.4 parts by weight based on 100 parts by weight of the total carbon nanotube dispersion.

[0209] Example 4c A carbon nanotube dispersion was prepared in the same manner as in Example 1c, except that the content of the first dispersant was 1.0 part by weight based on 100 parts by weight of the total carbon nanotube dispersion, and the content of the second dispersant was 0.8 part by weight based on 100 parts by weight of the total carbon nanotube dispersion.

[0210] Example 5c A carbon nanotube dispersion was prepared in the same manner as in Example 1c, except that the content of the first dispersant was 2.4 parts by weight based on 100 parts by weight of the total carbon nanotube dispersion, and the content of the second dispersant was 1.2 parts by weight based on 100 parts by weight of the total carbon nanotube dispersion.

[0211] Example 1d (1) 4.5 g of polyvinylpyrrolidone (PVP) (PVP K15, manufactured by Zhangzhou Huafu Chemical Co., Ltd.) as a first dispersant containing nitrogen atoms (0.9 parts by weight relative to 100 parts by weight of the total carbon nanotube dispersion), 1.5 g of Direct Blue 53 (manufactured by Sigma Aldrich Co., Ltd.) as a second dispersant containing a compound represented by Chemical Formula 1 (0.3 parts by weight relative to 100 parts by weight of the total carbon nanotube dispersion), and 490 g of water as a solvent were mixed to prepare 496 g of a mixed solution, which was then placed in a dissolver (Dispermat-CA, manufactured by VMA-GETZMANN Co., Ltd.) equipped with an impeller and a container, and stirred at 400 rpm for 10 minutes.

[0212] The mixture has a specific surface area of ​​1,160 m 2 / g, average particle size (D 50) 4.0 g (0.8 parts by weight relative to 100 parts by weight of the total carbon nanotube dispersion) of 5 μm single-walled carbon nanotubes (SWCNT, TUBALL, manufactured by OCSiAl) was further added and stirred at 8,000 rpm for 60 minutes to produce a total of 500 g of a primary dispersion of carbon nanotubes.

[0213] (3) The primary dispersion of carbon nanotubes was homogenously dispersed seven times using a high-pressure disperser (PICOMAX, manufactured by Micronox) at a pressure of 14,000 psi to prepare a secondary dispersion of carbon nanotubes.

[0214] Example 2d In Example 1d, the carbon nanotube dispersion was prepared in the same manner as in Example 1d, except that the content of the first dispersant was 4.8 g (0.96 parts by weight based on 100 parts by weight of the total carbon nanotube dispersion) and the content of the second dispersant was 1.2 g (0.24 parts by weight based on 100 parts by weight of the total carbon nanotube dispersion).

[0215] Example 3d In Example 1d, the carbon nanotube dispersion was prepared in the same manner as in Example 1d, except that the content of the first dispersant was 4.0 g (0.8 parts by weight based on 100 parts by weight of the total carbon nanotube dispersion) and the content of the second dispersant was 2.0 g (0.4 parts by weight based on 100 parts by weight of the total carbon nanotube dispersion).

[0216] Comparative Example 1a The carbon nanotube dispersion liquid was prepared in the same manner as in Example 1a, except that the second dispersant was not added.

[0217] Comparative example 2a In Example 1a, 3.0 g (0.6 parts by weight relative to 100 parts by weight of the total carbon nanotube dispersion liquid) of the first dispersant was added, and 4.5 g (0.9 parts by weight relative to 100 parts by weight of the total carbon nanotube dispersion liquid) of the first dispersant was added. The carbon nanotube dispersion liquid was prepared in the same manner as in Example 1a, except that no second dispersant was added.

[0218] Comparative example 3a A carbon nanotube dispersion was prepared in the same manner as in Example 1a, except that the content of the first dispersant was 7.275 g (1.455 parts by weight based on 100 parts by weight of the total carbon nanotube dispersion) and the content of the second dispersant was 0.225 g (0.045 parts by weight based on 100 parts by weight of the total carbon nanotube dispersion).

[0219] Comparative example 4a A carbon nanotube dispersion was prepared in the same manner as in Example 1a, except that the first dispersant was not added and the content of the second dispersant was set to 7.5 g (1.5 parts by weight relative to a total of 100 parts by weight of the carbon nanotube dispersion).

[0220] Comparative example 5a A carbon nanotube dispersion was prepared in the same manner as in Example 1a, except that the content of the first dispersant was 0.225 g (0.045 parts by weight relative to 100 parts by weight of the total carbon nanotube dispersion) and the content of the second dispersant was 7.275 g (1.455 parts by weight relative to 100 parts by weight of the total carbon nanotube dispersion).

[0221] Comparative Example 6a A carbon nanotube dispersion was prepared in the same manner as in Example 1a, except that in Example 3a, the second dispersant was changed to 1.125 g of tristyrylphenol ethoxylate (0.225 parts by weight relative to 100 parts by weight of the total carbon nanotube dispersion) instead of sulfochlorophenol S sodium calcium salt.

[0222] Comparative example 7a A carbon nanotube dispersion was prepared in the same manner as in Example 1a, except that in Example 3a, 1.125 g of styrene-maleic acid copolymer was used (0.225 parts by weight relative to 100 parts by weight of the total carbon nanotube dispersion) instead of Sulfochlorophenol S sodium calcium salt as the second dispersant.

[0223] Comparative example 1b In Example 1b, the carbon nanotube content was 1.0 parts by weight relative to 100 parts by weight of the total carbon nanotube dispersion, the first dispersant content was 1.125 parts by weight relative to 100 parts by weight of the total carbon nanotube dispersion, and no second dispersant was added. A carbon nanotube dispersion was prepared in the same manner as in Example 1b.

[0224] Comparative Example 2b A carbon nanotube dispersion was prepared in the same manner as in Example 1b, except that the carbon nanotube content was 1.0 part by weight relative to 100 parts by weight of the total carbon nanotube dispersion, the first dispersant content was 0.75 parts by weight relative to 100 parts by weight of the total carbon nanotube dispersion, and the second dispersant content was 0.75 parts by weight relative to 100 parts by weight of the total carbon nanotube dispersion.

[0225] Comparative example 3b A carbon nanotube dispersion was prepared in the same manner as in Example 1b, except that the carbon nanotube content was 1.0 part by weight relative to 100 parts by weight of the total carbon nanotube dispersion, the first dispersant content was 1.4 parts by weight relative to 100 parts by weight of the total carbon nanotube dispersion, and the second dispersant content was 0.1 parts by weight relative to 100 parts by weight of the total carbon nanotube dispersion.

[0226] Comparative example 4b A carbon nanotube dispersion was prepared in the same manner as in Example 1b, except that the first dispersant was not added and the content of the second dispersant was set to 1.2 parts by weight based on a total of 100 parts by weight of the carbon nanotube dispersion.

[0227] Comparative Example 5b A carbon nanotube dispersion was prepared in the same manner as in Example 1b, except that the carbon nanotube content was 0.6 parts by weight based on 100 parts by weight of the total carbon nanotube dispersion, the first dispersant content was 0.675 parts by weight based on 100 parts by weight of the total carbon nanotube dispersion, and the second dispersant, tristyrylphenol ethoxylate instead of Direct Red 28, was 0.225 parts by weight based on 100 parts by weight of the total carbon nanotube dispersion.

[0228] Comparative Example 6b A carbon nanotube dispersion was prepared in the same manner as in Example 1b, except that the content of carbon nanotubes in Example 1b was 0.6 parts by weight based on 100 parts by weight of the total carbon nanotube dispersion, the content of the first dispersant was 0.675 parts by weight based on 100 parts by weight of the total carbon nanotube dispersion, and the content of styrene-maleic acid copolymer instead of Direct Red 28 as the second dispersant was 0.225 parts by weight based on 100 parts by weight of the total carbon nanotube dispersion.

[0229] Comparative example 1c In Example 1c, the carbon nanotube dispersion was prepared in the same manner as in Example 1c, except that 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.

[0230] Comparative Example 2c A carbon nanotube dispersion was prepared in the same manner as in Example 1c, except that the content of the first dispersant was 0.6 parts by weight based on 100 parts by weight of the total carbon nanotube dispersion, and the content of the second dispersant was 0.6 parts by weight based on 100 parts by weight of the total carbon nanotube dispersion.

[0231] Comparative example 3c A carbon nanotube dispersion was prepared in the same manner as in Example 1c, except that the content of the first dispersant was 1.12 parts by weight based on 100 parts by weight of the total carbon nanotube dispersion, and the content of the second dispersant was 0.08 parts by weight based on 100 parts by weight of the total carbon nanotube dispersion.

[0232] Comparative Example 4c A carbon nanotube dispersion was prepared in the same manner as in Example 1c, except that the first dispersant was not added and the content of the second dispersant was set to 1.2 parts by weight based on a total of 100 parts by weight of the carbon nanotube dispersion.

[0233] Comparative Example 5c A carbon nanotube dispersion was prepared in the same manner as in Example 1c, except that the carbon nanotube content was 0.6 parts by weight based on 100 parts by weight of the total carbon nanotube dispersion, the first dispersant content was 0.675 parts by weight based on 100 parts by weight of the total carbon nanotube dispersion, and the second dispersant, tristyrylphenol ethoxylate instead of Direct Yellow 4, was 0.225 parts by weight based on 100 parts by weight of the total carbon nanotube dispersion.

[0234] Comparative Example 6c A carbon nanotube dispersion was prepared in the same manner as in Example 1c, except that the carbon nanotube content was 0.6 parts by weight relative to 100 parts by weight of the total carbon nanotube dispersion, the first dispersant content was 0.675 parts by weight relative to 100 parts by weight of the total carbon nanotube dispersion, and the second dispersant was a styrene-maleic acid copolymer instead of Direct Yellow 4, and the second dispersant was a styrene-maleic acid copolymer ...

[0235] Comparative Example 1d In Example 1d, the carbon nanotube dispersion was prepared in the same manner as in Example 1d, except that 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.

[0236] Comparative example 2d In Example 1d, the carbon nanotube dispersion was prepared in the same manner as in Example 1d, except that the content of the first dispersant was 3.0 g (0.6 parts by weight based on 100 parts by weight of the total carbon nanotube dispersion) and the content of the second dispersant was 3.0 g (0.6 parts by weight based on 100 parts by weight of the total carbon nanotube dispersion).

[0237] Comparative example 3d In Example 1d, the carbon nanotube dispersion was prepared in the same manner as in Example 1d, except that the content of the first dispersant was 5.6 g (1.12 parts by weight based on 100 parts by weight of the total carbon nanotube dispersion) and the content of the second dispersant was 0.4 g (0.08 parts by weight based on 100 parts by weight of the total carbon nanotube dispersion).

[0238] Comparative example 4d In Example 1d, the carbon nanotube dispersion was prepared in the same manner as in Example 1d, except that the second dispersant was added in an amount of 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.

[0239] Comparative Example 5d In Example 3d, the carbon nanotube dispersion was prepared in the same manner as in Example 1d, except that the content of the first dispersant was 3.375 g (0.675 parts by weight based on 100 parts by weight of the total carbon nanotube dispersion), and the content of the second dispersant was 1.125 g (0.225 parts by weight based on 100 parts by weight of the total carbon nanotube dispersion) of tristyrylphenol ethoxylate instead of Direct Blue 53 (Sigma Aldrich).

[0240] Comparative Example 6d In Example 3d, the carbon nanotube dispersion was prepared in the same manner as in Example 1d, except that the content of the first dispersant was 3.375 g (0.675 parts by weight based on 100 parts by weight of the total carbon nanotube dispersion), and the second dispersant was 1.125 g (0.225 parts by weight based on 100 parts by weight of the total carbon nanotube dispersion) of styrene-maleic acid copolymer instead of Direct Blue 53 (Sigma-Aldrich).

[0241] Experimental example The viscosity of the carbon nanotube dispersions of Examples 1a to 3a and Comparative Examples 1a to 7a was measured, and the viscosity was measured again after leaving them at 25° C. for one week. The results are shown in Table 1 below.

[0242] The viscosity of the carbon nanotube dispersions of Examples 1b to 5b and Comparative Examples 1b to 6b was measured, and the viscosity was measured again after leaving them at 25° C. for one week. The results are shown in Table 2 below.

[0243] The viscosity of the carbon nanotube dispersions of Examples 1c to 5c and Comparative Examples 1c to 6c was measured, and the viscosity was measured again after leaving them at 25° C. for one week. The results are shown in Table 3 below.

[0244] The viscosity of the carbon nanotube dispersions of Examples 1d to 3d and Comparative Examples 1d to 6d was measured, and the viscosity was measured again after leaving them at 25° C. for one week. The results are shown in Table 4 below.

[0245] The viscosity was measured at 25°C and 1 rpm using a viscometer (TOKI SANGYO, viscometer TV-25, Rotor Code 01).

[0246] [Table 1A]

[0247] [Table 1B]

[0248] Referring to Table 1, compared to 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 Sulfochlorophenol S sodium calcium salt, which is the compound represented by Chemical Formula 1 of the present invention, as the second dispersant, have a lower initial viscosity immediately after dispersing carbon nanotubes in an aqueous solvent, and in particular, it can be seen that the increase in viscosity of the carbon nanotube dispersion over time is very effectively suppressed.

[0249] In the case of the carbon nanotube dispersion of Comparative Example 2a, the carbon nanotube content was reduced compared to the carbon nanotube dispersion of Comparative Example 1a, and the initial viscosity immediately after dispersing the carbon nanotubes in the aqueous solvent and the viscosity of the dispersion after one week were reduced compared to the carbon nanotube dispersion of Comparative Example 1a.However, as with the carbon nanotube dispersion of Comparative Example 1a, it can be seen that, compared to Examples 1a to 3a, the dispersion does not contain a second dispersant containing the compound represented by Chemical Formula 1 of the present invention, and therefore does not exhibit the effect of suppressing the increase in viscosity of the dispersion over time.

[0250] In the case of the carbon nanotube dispersion of Comparative Example 3a, the second dispersant, which is a compound represented by Chemical Formula 1 according to the present invention, is contained in an amount less than a certain amount, and therefore the initial viscosity immediately after dispersing the carbon nanotubes in the aqueous solvent is high.

[0251] In the case of the carbon nanotube dispersions of Comparative Examples 4a and 5a, compared to the carbon nanotube dispersions of Examples 1a to 3a, the carbon nanotubes could not be completely dispersed in the aqueous solvent because they did not contain the first dispersant (Comparative Example 4a) or contained less than a certain amount of the first dispersant (Comparative Example 5a), which resulted in aggregation of the dispersion and made it impossible to measure the viscosity.

[0252] In the case of the carbon nanotube dispersions of Comparative Examples 6a and 7a, compared to the carbon nanotube dispersions of Examples 1a to 3a, the compound represented by Chemical Formula 1 according to the present invention is not used as a second dispersant, and therefore the initial viscosity immediately after dispersing the carbon nanotubes in the aqueous solvent is high, and the effect of suppressing the increase in viscosity of the carbon nanotube dispersion over time is not exhibited.

[0253] [Table 2A]

[0254] [Table 2B]

[0255] Referring to Table 2, compared to the carbon nanotube dispersion of Comparative Example 1b, which contains only polyvinylpyrrolidone as the first dispersant, the carbon nanotube dispersions of Examples 1b to 5b, which contain a first dispersant and a second dispersant containing Direct Red 28, a compound containing at least two azo groups and two or more sulfonate groups, have a lower initial viscosity immediately after dispersing the carbon nanotubes in the aqueous solvent, and in particular, it can be seen that the increase in viscosity of the carbon nanotube dispersion over time is very effectively suppressed.

[0256] In the case of the carbon nanotube dispersions of Comparative Examples 2b and 3b, the carbon nanotube dispersion contained a first dispersant and a second dispersant, and the initial viscosity immediately after dispersion was lower than in Comparative Example 1b. However, the weight ratio of the first dispersant to the second dispersant in the carbon nanotube dispersion exceeded 100:90, resulting in strong electrostatic repulsion between the second dispersant containing at least two sulfonate groups (Comparative Example 2b), or the weight ratio of the second dispersant was less than 100:10, preventing smooth interaction between the second dispersant, carbon nanotubes, and dispersant. As a result, the stable dispersion state of the carbon nanotube dispersion was not maintained, and the effect of suppressing the increase in viscosity of the dispersion over time was not achieved (Comparative Examples 2b and 3b).

[0257] In the case of the carbon nanotube dispersion of Comparative Example 4b, unlike the carbon nanotube dispersions of Examples 1b to 5b, it does not contain the first dispersant, and the carbon nanotube dispersion contains more than 145 parts by weight of the second dispersant based on 100 parts by weight of carbon nanotubes.This results in strong electrostatic repulsion between the second dispersants, making it impossible to maintain a stable dispersion state of the carbon nanotube dispersion, resulting in aggregation of the dispersion and not achieving the effect of suppressing the increase in viscosity of the dispersion over time.

[0258] In the case of the carbon nanotube dispersions of Comparative Examples 5b and 6b, by not using a substance containing a compound containing at least two azo groups and two or more sulfonate groups as in Examples 1b to 5b as the second dispersant, the initial viscosity immediately after dispersing the carbon nanotubes in the aqueous solvent is high (Comparative Example 5b), and it can be seen that the effect of suppressing the increase in viscosity of the carbon nanotube dispersion over time is not exhibited (Comparative Examples 5b and 6b).

[0259] [Table 3A]

[0260] [Table 3B]

[0261] Referring to Table 3, compared to the carbon nanotube dispersion of Comparative Example 1c, which contains only polyvinylpyrrolidone as the first dispersant, the carbon nanotube dispersions of Examples 1c to 5c, which contain a first dispersant and a second dispersant containing Direct Yellow 4, a compound containing at least two azo groups, two sulfonate groups, and two or more hydroxyl groups, have a lower initial viscosity immediately after dispersing the carbon nanotubes in the aqueous solvent, and in particular, it can be seen that the increase in viscosity of the carbon nanotube dispersion over time is very effectively suppressed.

[0262] In the case of the carbon nanotube dispersions of Comparative Examples 2c and 3c, the carbon nanotube dispersion contained a first dispersant and a second dispersant, and the initial viscosity immediately after dispersion was lower than in Comparative Example 1c. However, the weight ratio of the first dispersant to the second dispersant in the carbon nanotube dispersion exceeded 100:90, resulting in strong electrostatic repulsion between the second dispersant, which contains at least two sulfonate groups and a hydroxyl group, and the hydrogen bonds formed between the dispersant and the solvent (Comparative Example 2c). Alternatively, the weight ratio of the second dispersant was less than 100:10, preventing smooth interaction between the second dispersant, the carbon nanotubes, and the dispersant. As a result, the carbon nanotube dispersion was not able to maintain a stable dispersion state, and the effect of suppressing the increase in viscosity of the dispersion over time was not achieved (Comparative Examples 2c and 3c).

[0263] In the case of the carbon nanotube dispersion of Comparative Example 4c, unlike the carbon nanotube dispersions of Examples 1c to 5c, it does not contain a first dispersant, and therefore the carbon nanotube dispersion contains more than 150 parts by weight of a second dispersant based on 100 parts by weight of carbon nanotubes.As a result, electrostatic repulsion between the second dispersants and strong hydrogen bonds are formed between the dispersant and between the dispersant and the solvent, making it impossible to maintain a stable dispersion state of the carbon nanotube dispersion, resulting in aggregation of the dispersion and not achieving the effect of suppressing the increase in viscosity of the dispersion over time.

[0264] In the case of the carbon nanotube dispersions of Comparative Examples 5c and 6c, by not using a substance containing a compound containing at least two azo groups, two or more sulfonate groups, and two or more hydroxyl groups as the second dispersant in Examples 1c to 5c, the initial viscosity immediately after dispersing the carbon nanotubes in the aqueous solvent is high (Comparative Example 5c), and it can be seen that the effect of suppressing the increase in viscosity of the carbon nanotube dispersion over time is not exhibited (Comparative Examples 5c and 6c).

[0265] [Table 4A]

[0266] [Table 4B]

[0267] Referring to Table 4, compared to the carbon nanotube dispersion of Comparative Example 1d containing only polyvinylpyrrolidone as the first dispersant, the carbon nanotube dispersions of Examples 1d to 3d containing the first dispersant and Direct Blue 53, a compound represented by Chemical Formula 1 of the present invention, as the second dispersant, have lower initial viscosities immediately after dispersing carbon nanotubes in an aqueous solvent, and in particular, it can be seen that the increase in viscosity of the carbon nanotube dispersion over time is very effectively suppressed.

[0268] In the case of the carbon nanotube dispersions of Comparative Examples 2d and 3d, the second dispersant is contained in excess (Comparative Example 2d) or in an amount less than a certain level (Comparative Example 3d) compared to the carbon nanotube dispersions of Examples 1d to 3d, which means that the initial viscosity immediately after dispersing the carbon nanotubes in the aqueous solvent is high and the effect of suppressing the increase in viscosity of the dispersion over time is not exhibited.

[0269] In the case of the carbon nanotube dispersion of Comparative Example 4d, it can be confirmed that, compared to the carbon nanotube dispersions of Examples 1d to 3d, the carbon nanotube dispersion does not contain the first dispersant, which causes a problem of the viscosity of the carbon nanotube dispersion rapidly increasing over time.

[0270] In the case of the carbon nanotube dispersions of Comparative Examples 5d and 6d, compared to the carbon nanotube dispersions of Examples 1d to 3d, the compound represented by Chemical Formula 1 according to the present invention is not used as a second dispersant, and therefore the initial viscosity immediately after dispersing the carbon nanotubes in the aqueous solvent is high, and the effect of suppressing the increase in viscosity of the carbon nanotube dispersion over time is not exhibited.

[0271] Therefore, it was confirmed that the carbon nanotube dispersion liquid in which carbon nanotubes are dispersed in an aqueous solvent contains a first dispersant containing a nitrogen atom and a second dispersant containing the compound represented by Chemical Formula 1 according to the present invention, and that the carbon nanotube dispersion liquid exhibits low viscosity and suppresses viscosity increase over time only when the first dispersant and the second dispersant are contained in a certain weight ratio.

[0272] Although the preferred embodiments of the present invention have been described in detail above, 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 following claims also fall within the scope of the present invention.

Claims

1. carbon nanotubes; a first dispersant containing a nitrogen atom; A second dispersant comprising a compound represented by the following Chemical Formula 1: containing a solvent, Carbon nanotube dispersion: 【Chemistry 1】 In the above Chemical Formula 1, Ar1 and Ar2 each independently represent a substituted or unsubstituted C6 to C30 aryl group; L1 is a substituted or unsubstituted C6 to C30 arylene group.

2. Ar1 and Ar2 in Chemical Formula 1 are each represented by the following Chemical Formula 2 or Chemical Formula 3: The carbon nanotube dispersion according to claim 1: 【Chemistry 2】 【Transformation 3】 In the above Chemical Formula 2, R1 to R8 are the same or different and each independently represent hydrogen, deuterium, a halogen, a cyano group, a sulfonate group, a hydroxyl group, an amine group, a nitro group, a substituted or unsubstituted C1 to C10 alkyl group, a substituted or unsubstituted C1 to C10 alkoxy group, or a moiety connecting to Chemical Formula 1, and any one of R1 to R8 is a moiety connecting to the azo group of Chemical Formula 1, In the above Chemical Formula 3, R9 to R14 are the same or different and each independently represent hydrogen, deuterium, a halogen, a cyano group, a sulfonate group, a hydroxyl group, an amine group, a nitro group, a substituted or unsubstituted C1 to C10 alkyl group, a substituted or unsubstituted C1 to C10 alkoxy group, or a moiety connecting to Chemical Formula 1, and any one of R9 to R14 is a moiety connecting to the azo group in Chemical Formula 1.

3. L1 in Chemical Formula 1 is represented by the following Chemical Formula 4 or Chemical Formula 5: The carbon nanotube dispersion according to claim 1: 【Chemistry 4】 【Transformation 5】 In the above Chemical Formula 4, R15 to R18 are the same or different and each independently represent hydrogen; deuterium; halogen; cyano group; sulfonate group; hydroxyl group; amine group; nitro group; or a moiety connecting to Chemical Formula 1, wherein any one of R15 to R18 is a moiety connecting to the nitrogen atom not connected to Ar1 among the two nitrogen atoms of the azo group to which Ar1 is linked among the two azo groups in Chemical Formula 1; R19 to R22 are the same or different and each independently represent hydrogen; deuterium; halogen; cyano group; sulfonate group; hydroxyl group; amine group; nitro group; or a moiety connecting to Chemical Formula 1, wherein any one of R19 to R22 is a moiety connecting to the nitrogen atom not connected to Ar2 among the two nitrogen atoms of the azo group to which Ar2 is linked among the two azo groups in Chemical Formula 1; In the above Chemical Formula 5, R23 to R27 are the same or different, and each independently represents hydrogen; deuterium; a halogen; a cyano group; a sulfonate group; a hydroxyl group; an amine group; a nitro group; a substituted or unsubstituted C1 to C5 alkyl group; a substituted or unsubstituted C1 to C5 alkoxy group; or a site that is bonded to a nitrogen atom that is not bonded to Ar1 among the two nitrogen atoms of the azo group to which Ar1 is bonded among the two azo groups of Chemical Formula 1, and any one of R23 to R27 is a site that is bonded to a nitrogen atom that is not bonded to Ar1 among the two nitrogen atoms of the azo group to which Ar1 is bonded among the two azo groups of Chemical Formula 1, R28 to R32 are the same or different, and each independently represent hydrogen; deuterium; a halogen; a cyano group; a sulfonate group; a hydroxyl group; an amine group; a nitro group; a substituted or unsubstituted C1 to C5 alkyl group; a substituted or unsubstituted C1 to C5 alkoxy group; or a site that is bonded to a nitrogen atom that is not bonded to Ar2 among the two nitrogen atoms of the azo group to which Ar2 is bonded among the two azo groups of Chemical Formula 1, and any one of R28 to R32 is a site that is bonded to a nitrogen atom that is not bonded to Ar2 among the two nitrogen atoms of the azo group to which Ar2 is bonded among the two azo groups of Chemical Formula 1, Z is a single bond; a substituted or unsubstituted C2-C10 alkenylene group; or a substituted or unsubstituted C2-C10 alkynylene group.

4. The second dispersant includes a compound represented by any one of the following formulas 1-1a to 1-1d: The carbon nanotube dispersion according to claim 1: 【Transformation 6】 In the above chemical formula 1-1a, R1 to R5, R7 to R11, and R13 to R18 are the same or different and each independently represent hydrogen, deuterium, a halogen, a cyano group, a sulfonate group, a hydroxyl group, an amine group, or a nitro group; 【Transformation 7】 In the above chemical formula 1-1b, R1 to R7 and R9 to R15 are the same or different and each independently represent hydrogen, deuterium, a halogen, a cyano group, a sulfonate group, a hydroxyl group, an amine 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, or a substituted or unsubstituted C6 to C20 aryl group, and at least one of R1 to R7 is a sulfonate group, and at least one of R9 to R15 is a sulfonate group; 【Transformation 8】 In the above chemical formula 1-1c, R1 to R5 and R7 to R11 are the same or different and each independently represent 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, wherein at least one of R1 to R5 is a hydroxyl group and at least one of R7 to R11 is a hydroxyl group; R13 to R20 are the same or different and each independently represent 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, and at least one of R13 to R16 is a sulfonate group, and at least one of R17 to R20 is a sulfonate group; 【Chemistry 9】 In the above chemical formula 1-1d, R1 to R7 and R9 to R15 are the same or different and each independently represent hydrogen; deuterium; halogen; cyano group; sulfonate group; hydroxyl group; amine group; or nitro group; R17 to R20 and R22 to R25 are the same or different and each independently represent hydrogen, deuterium, a halogen, a cyano group, a sulfonate group, a hydroxyl group, an amine 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 contains 0.05 to 5 parts by weight of carbon nanotubes based on 100 parts by weight of the carbon nanotube dispersion. The carbon nanotube dispersion liquid according to claim 1 .

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

7. The first dispersant may be selected from the group consisting of polyvinylpyrrolidone, polyacrylic acid hydrazide, poly-N-vinyl-5-methoxazolidon, N-alkyl polyimine, N-acetyl polyimine, polyacrylamide, poly-L-lysine hydrobromide, and benzyl-dodecyl-dimethylammonium chloride. chloride), and polyethyleneimine, The carbon nanotube dispersion liquid according to claim 1 .

8. The carbon nanotube dispersion liquid contains 0.01 to 10 parts by weight of the first dispersant based on 100 parts by weight of the carbon nanotube dispersion liquid. The carbon nanotube dispersion liquid according to claim 1 .

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

10. The first dispersant and the second dispersant are contained in a weight ratio of 100:10 to 100:

90. The carbon nanotube dispersion liquid according to claim 1 .

11. The carbon nanotube dispersion has an initial viscosity of 1 to 10 Pa s measured at 25°C and 1 rpm. The carbon nanotube dispersion liquid according to claim 1 .

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

13. (1) preparing a primary dispersion of carbon nanotubes by mixing carbon nanotubes, a first dispersant containing nitrogen atoms, a second dispersant containing a compound represented by Formula 1 below, and a solvent; and (2) dispersing the primary dispersion of carbon nanotubes to prepare a secondary dispersion of carbon nanotubes; The method for producing the carbon nanotube dispersion liquid according to claim 1, comprising: 【Chemistry 10】 In the above Chemical Formula 1, Ar1 and Ar2 each independently represent a substituted or unsubstituted C6 to C30 aryl group; L1 is a substituted or unsubstituted C6 to C30 arylene group.

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