Carbon nanotube dispersion and method for producing the same

Abstract

The present invention relates to a carbon nanotube dispersion comprising carbon nanotubes, a first dispersant containing nitrogen atoms, a second dispersant containing a substituted benzopyran compound, and a solvent, wherein the substituted benzopyran compound contained in the second dispersant contains at least three hydroxy groups, and a method for producing the same.

Description

[Technical Field]

[0001] This application claims the benefit of priority under Korean Patent Application No. 10-2023-0092200 dated July 17, 2023, and Korean Patent Application No. 10-2024-0077181 dated June 13, 2024, and incorporates all the contents disclosed in the relevant Korean patent applications as part of this specification.

[0002] This 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, the demand for rechargeable batteries as an energy source is surging. Among these rechargeable batteries, lithium-ion batteries, which have high energy density and voltage, long cycle life, and low self-discharge rates, have been commercialized and are widely used. Furthermore, research is actively being conducted on methods to improve electrode density and manufacture electrodes with even higher energy density per unit volume for such high-capacity lithium-ion batteries.

[0004] Generally, high-density electrodes are formed by molding electrode active material particles, which have a size of several micrometers to tens of micrometers, using high-pressure pressing. However, during the molding process, the particles may deform, and the space between the particles may decrease, which can easily reduce the permeability of the electrolyte.

[0005] To solve the aforementioned problems, conductive materials with excellent electrical conductivity and strength are used in the manufacture of electrodes. These conductive materials are positioned between the electrode active materials, and even during the molding process, they maintain fine pores between the active material particles, allowing the electrolyte to easily penetrate, resulting in excellent electrical conductivity and reduced resistance within the electrode. Among such conductive materials, the use of carbon nanotubes, which are fibrous carbon-based conductive materials that can further reduce electrode resistance by forming electrical conductive paths within the electrode, is increasing.

[0006] Carbon nanotubes, a type of fine carbon fiber, are tubular carbon fibers with a diameter of 1 μm or less. Due to their unique structure, they possess high conductivity, tensile strength, and heat resistance, making them promising for application and practical use in various fields. However, carbon nanotubes have a high specific surface area, which leads to poor dispersibility due to strong van der Waals forces between them, resulting in aggregation.

[0007] To address these issues, methods have been proposed to disperse carbon nanotubes in a dispersion medium through mechanical dispersion processes such as ultrasonic treatment. However, mechanical dispersion methods have problems such as the carbon nanotubes aggregating as soon as ultrasonic irradiation ends, or aggregating again over time after dispersion.

[0008] Therefore, there is a need to develop a method for producing a carbon nanotube dispersion that has improved dispersibility, low viscosity, and suppressed viscosity increase over time. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] China Patent Publication No. 110128784 (August 16, 2019) [Overview of the project] [Problems that the invention aims to solve]

[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 substituted benzopyran compound, and a solvent, wherein the substituted benzopyran compound contained in the second dispersant contains at least three hydroxyl groups, exhibiting excellent dispersibility, low viscosity of the dispersion, low particle size of the dispersed particles, and minimal change in viscosity over time.

[0011] Another object of the present invention is to provide an electrode slurry composition for a lithium secondary battery containing the carbon nanotube dispersion liquid.

[0012] Another object of the present invention is to provide a method for producing the carbon nanotube dispersion liquid.

Means for Solving the Problems

[0013] One embodiment of the present invention includes carbon nanotubes, a first dispersant containing nitrogen atoms, a second dispersant containing a substituted benzopyran-based compound, and a solvent, and the substituted benzopyran-based compound contained in the second dispersant contains at least three or more hydroxy groups, and provides a carbon nanotube dispersion liquid.

[0014] The second dispersant may contain a compound represented by the following Chemical Formula 1.

[0015]

Chemical Formula

[0016] In the Chemical Formula 1,

Chemical Formula

[0017]

Chemical Formula

[0018] In the aforementioned chemical formula 2, B1 to B5 are either identical or different to each other, and each is independently a hydrogen; deuterium; halogen; cyano group; hydroxyl group; carboxyl group; substituted or unsubstituted C1-C10 alkyl group; substituted or unsubstituted C2-C10 alkenyl group; substituted or unsubstituted C2-C10 alkynyl group; substituted or unsubstituted C1-C10 alkoxy group; substituted or unsubstituted C3-C10 cycloalkyl group; or substituted or unsubstituted C2-C10 heterocycloalkyl group. Among A1 to A6 of Chemical Formula 1, the substituent not represented in Chemical Formula 2, and among B1 to B5 of Chemical Formula 2, at least three are hydroxyl groups.

[0019] The second dispersant may contain a compound represented by any one of the following chemical formulas 3 to 5.

[0020] [ka]

[0021] In the aforementioned chemical formulas 3 to 5, A1-A5 and B1-B5 are either identical or different from each other, and each is independently a hydrogen; deuterium; halogen; cyano group; hydroxyl group; carboxyl group; substituted or unsubstituted C1-C10 alkyl group; substituted or unsubstituted C2-C10 alkenyl group; substituted or unsubstituted C2-C10 alkynyl group; substituted or unsubstituted C1-C10 alkoxy group; substituted or unsubstituted C3-C10 cycloalkyl group; or substituted or unsubstituted C2-C10 heterocycloalkyl group. At least three of the A1-A5 and B1-B5 groups in the aforementioned chemical formula 1 are hydroxyl groups.

[0022] The second dispersant may be one or more selected from the group consisting of luteolin, quercetin, kaempferol, myricetin, fisetin, morin, hesperetin, naringenin, and eriodictyol.

[0023] The BET specific surface area of ​​the carbon nanotube is 800 to 2,000 m². 2 / g is also acceptable.

[0024] The carbon nanotube dispersion may contain 25 to 450 parts by weight of the first dispersant based on 100 parts by weight of the carbon nanotube.

[0025] The carbon nanotube dispersion may contain 5 to 250 parts by weight of the second dispersant based on 100 parts by weight of the carbon nanotube.

[0026] The first dispersant may be one or more selected from the group consisting of polyvinylpyrrolidone, polyacrylic acid hydrazide, poly-N-vinyl-5-methoxazolidon, N-alkyl polyimine, N-acetyl polyimine, polyacrylamide, poly-L-lysine hydrobromide, benzyl-dodecyl-dimethylammonium chloride, and polyethyleneimine.

[0027] The first and second dispersants may be present in a weight ratio of 100:10 to 100:90.

[0028] The carbon nanotube dispersion may have an initial viscosity of 1 to 10 Pa·s, as measured at 25°C and 1 rpm.

[0029] The carbon nanotube dispersion may have a viscosity increase rate of 15% or less, as represented by the following formula (1).

[0030] [Formula 1] Viscosity increase rate (%) = {(Viscosity measured after being left at 25°C for one week - initial viscosity) / initial viscosity} × 100

[0031] Another embodiment of the present invention provides a method for producing a carbon nanotube dispersion, comprising the steps of (1) mixing carbon nanotubes, a first dispersant containing nitrogen atoms, a second dispersant containing a substituted benzopyran compound having at least three hydroxyl groups, 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.

[0032] Another embodiment of the present invention provides an electrode slurry composition for a lithium secondary battery comprising the carbon nanotube dispersion and the electrode active material. [Effects of the Invention]

[0033] The carbon nanotube dispersion according to the present invention, by using a first dispersant containing nitrogen atoms together with a second dispersant containing a substituted benzopyran compound containing at least three hydroxyl groups, exhibits a small change in viscosity over time and relatively low viscosity despite using carbon nanotubes with a large specific surface area, and has the characteristic of having a small particle size due to the uniform and effective dispersion of carbon nanotubes.

[0034] Furthermore, by using the carbon nanotube dispersion of the present invention in an electrode slurry composition, electrodes and secondary batteries with excellent capacity characteristics and cycle characteristics can be manufactured. [Modes for carrying out the invention]

[0035] The following describes examples of the embodiment of the present invention in detail. Prior to this, the terms and words used in this specification and claims should not be interpreted in a limited manner in their usual or dictionary sense, but rather in a sense and concept that is consistent with the technical idea of ​​the present invention, in accordance with the principle that inventors can appropriately define the concepts of terms in order to best describe their invention. Accordingly, it should be understood that the configurations described in the examples described herein are merely the most preferred embodiments of the present invention and do not represent the entire technical idea of ​​the present invention, and that there may be various equivalents and modifications that can be substituted for them at the time of filing this application.

[0036] In this specification, the term "substitution" means that a hydrogen atom bonded to a carbon atom of a compound is replaced by another substituent, and the position of substitution is not limited to any position where a hydrogen atom can be substituted, i.e., any position where a substituent can be substituted, and if two or more substituents are substituted, the two or more substituents may be identical or different.

[0037] In this specification, “substituted or unsubstituted” means that a molecule is substituted or unsubstituted with one or more substituents selected from the group consisting of deuterium; cyano groups; linear or branched alkyl groups C1-C60; linear or branched alkenyl groups C2-C60; linear or branched alkynyl groups C2-C60; monocyclic or polycyclic cycloalkyl groups C3-C60; monocyclic or polycyclic heterocycloalkyl groups C2-C60; monocyclic or polycyclic aryl groups C6-C60; monocyclic or polycyclic heteroaryl groups C2-C60; -SiRR'R''; -P(=O)RR'; alkylamine groups C1-C20; monocyclic or polycyclic arylamine groups C6-C60; and monocyclic or polycyclic heteroarylamine groups C2-C60, or that a molecule is substituted or unsubstituted with substituents in which two or more substituents selected from the above-described substituents are linked.

[0038] Throughout this specification, when a part of a section "includes" a component, this means, unless otherwise stated, that it does not exclude other components, but rather that other components may be included.

[0039] Throughout this specification, "%" means weight percent unless otherwise explicitly indicated.

[0040] In this specification, the average particle size "D 50 " refers to a particle size corresponding to a volume accumulation of 50%. 50 This can be measured, for example, using the laser diffraction method. The laser diffraction method generally allows for the measurement of particle sizes ranging from the submicron region to several millimeters, and yields results with high reproducibility and high resolution.

[0041] In this specification, "specific surface area" is measured by the BET method (Brunauer-Emmett-Teller Analysis), and specifically, it is calculated from the amount of nitrogen gas adsorbed at liquid nitrogen temperature (77K) using BELSORP-mino II from BEL Japan.

[0042] 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 a substituted benzopyran compound having at least three hydroxyl groups, and a solvent. The components of the carbon nanotube dispersion according to the present invention will be described in detail below.

[0043] (1) Carbon nanotubes The term "carbon nanotube" as used in this invention refers to a secondary structure formed by the aggregation of carbon nanotube units so as a whole or partially as a bundle type, wherein the carbon nanotube units have a graphite sheet with a cylindrical shape of nanoscale diameter, and sp 2 It has a bonding structure. In this case, depending on the angle and structure in which the graphite surface is wound, it can exhibit conductive or semiconductor properties. Carbon nanotube units are classified into single-walled carbon nanotubes (SWCNTs), double-walled carbon nanotubes (DWCNTs), and multi-walled carbon nanotubes (MWCNTs) according to the number of bonds forming the wall.

[0044] In this invention, the term "bundle type" refers to a secondary shape in which multiple carbon nanotube units are arranged in a bundle or rope form, unless otherwise specified, in which the longitudinal axes of the units are substantially aligned in the same orientation, or are twisted or tangled after being arranged. The term "non-bundle type" or "entangled type" refers to a form in which the carbon nanotube units do not have a fixed shape such as a bundle or rope form, but are tangled.

[0045] Carbon nanotubes have high conductivity, but they also have high cohesiveness due to van der Waals forces that occur between them. When conductive materials aggregate, they cannot properly form conductive pathways, requiring relatively more conductive material and reducing the amount of active material, which can actually degrade electrode performance. Therefore, there have been difficulties in commercializing carbon nanotubes as conductive materials.

[0046] The carbon nanotube dispersion according to the present invention contains a first dispersant containing nitrogen atoms and a second dispersant containing a substituted benzopyran compound containing at least three hydroxyl groups. This significantly reduces the initial viscosity of the carbon nanotube dispersion and suppresses changes in viscosity over time. When applied to an electrode slurry for a lithium secondary battery, it exhibits high conductivity due to the high conductivity of the carbon nanotubes.

[0047] Therefore, when the carbon nanotube dispersion according to the present invention is applied to the production of an electrode slurry, the carbon nanotubes are uniformly positioned between the active materials, and the fine spaces between the electrode active materials can be maintained at a constant level even during the process of manufacturing electrodes by rolling after coating and drying the electrode slurry. Furthermore, the carbon nanotubes do not aggregate and are uniformly distributed, so that conductive pathways can be sufficiently formed even with a small amount of carbon nanotubes.

[0048] A carbon nanotube dispersion according to one embodiment of the present invention may contain one or more single-walled, double-walled, and multi-walled carbon nanotubes, but is not limited thereto; specifically, it may contain single-walled carbon nanotubes. Since single-walled or double-walled carbon nanotubes have a higher specific surface area than multi-walled carbon nanotubes, they are more effective in improving cycle characteristics when applied to secondary batteries.

[0049] 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, more preferably 0.8 to 3 nm, and 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, and 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.

[0050] Furthermore, the carbon nanotubes may have an average length of 0.5 to 20 μm, preferably 1 to 20 μm, more preferably 5 to 20 μm, and may also be 5 μm or more, 7 μm or more, 9 μm or more, 11 μm or more, or 13 μm or more, and may be 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 excellent cycle characteristics can be realized when the electrode active material is applied. 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.

[0051] The carbon nanotubes may be present in an amount of 0.1 to 5% by weight, preferably 0.1 to 3% by weight, more preferably 0.5 to 2% by weight, based on the total weight of the carbon nanotube dispersion, and may be present in amounts of 0.1% or more by weight, 0.3% or more by weight, 0.5% or more by weight, 0.6% or more by weight, 0.7% or more by weight, 0.9% or more by weight, 1.0% by weight, 1.1% or more by weight, or 1.3% or more by weight, and may be present in amounts of 2% or less by weight, 1.8% or less by weight, 1.6% or less by weight, or 1.4% or less by weight. When the carbon nanotube content satisfies the above range, the effect of improving the viscosity of the dispersion and the effect of improving the secondary battery cycle characteristics are excellent.

[0052] The BET specific surface area of the carbon nanotube is 800 m 2 / g or more, preferably 800 m 2 / g to 5,000 m 2 / g, more preferably 800 m 2 / g to 2,000 m 2 / g may be used, and 800 m 2 / g or more, 900 m 2 / g or more, 1,000 m 2 / g or more, 1,100 m 2 / g or more, 1,160 m 2 / g or more, 1,200 m 2 / g or more, 1,300 m 2 / g or more or 1,400 m 2 / g or more may be used, and 2,000 m 2 / g or less, 1,900 m 2 / g or less, 1,800 m 2 / g or less, 1,700 m 2 / g or less, 1,600 m 2 / g or less or 1,500 m 2 / g or less may be used. By using the carbon nanotube having a high BET specific surface area as described above, it is excellent in forming a conductive network among the electrode active materials, and the cycle characteristics of the secondary battery can be improved.

[0053] In the carbon nanotube dispersion according to an embodiment of the present invention, the carbon nanotubes can be uniformly dispersed, so that it can have a relatively high content of carbon nanotubes. When a carbon nanotube dispersion having a low content of carbon nanotubes is used for the production of an electrode slurry, the solid content of the produced electrode slurry decreases, and the thickness (wet thickness) before applying and drying the electrode slurry becomes thick, and the rolling rate measured after subsequent drying and rolling treatments becomes high, and the difference in the ratio of the thickness before and after drying and rolling becomes large. Thus, when the rolling rate becomes high, the composition inside the slurry including the positive electrode active material may be damaged during the process, and there may occur a problem that the battery performance deteriorates due to this.

[0054] (2) First dispersant and second dispersant The carbon nanotube dispersion according to the present invention comprises a first dispersant containing nitrogen atoms to improve the dispersibility of the carbon nanotubes, together with a second dispersant containing a substituted benzopyran compound having at least three or more hydroxyl groups.

[0055] In the carbon nanotube dispersion, the first dispersant containing nitrogen atoms and the second dispersant containing a substituted benzopyran compound with at least three hydroxyl groups play a role in increasing the dispersibility of carbon nanotubes so that they are uniformly dispersed without aggregation in the dispersion, and in particular, they have the effect of suppressing changes in the viscosity of the carbon nanotube dispersion over time.

[0056] In a carbon nanotube dispersion according to one specific example of the present invention, the first dispersant containing nitrogen atoms may be dissolved in an aqueous solvent as described later, and may be one or more selected from the group consisting of polyvinylpyrrolidone, polyacrylic acid hydrazide, poly-N-vinyl-5-methoxazolidon, N-alkyl polyimine, N-acetyl polyimine, polyacrylamide, poly-L-lysine hydrobromide, benzyl-dodecyl-dimethylammonium chloride, and polyethyleneimine, and preferably polyvinylpyrrolidone can be used. A carbon nanotube dispersion according to one specific example of the present invention can exhibit viscosity improvement and viscosity change suppression effects by containing the first dispersant containing nitrogen atoms.

[0057] In one specific example of the present invention, the carbon nanotube dispersion can contain 25 to 450 parts by weight of the first dispersant based on 100 parts by weight of the carbon nanotube, for example, 25 parts by weight or more, 30 parts by weight or more, 35 parts by weight or more, 40 parts by weight or more, 45 parts by weight or more, 50 parts by weight or more, 55 parts by weight or more, 60 parts by weight or more, 65 parts by weight or more, 70 parts by weight or more, 75 parts by weight or more, 80 parts by weight or more, 85 parts by weight or more, 90 parts by weight or more, 95 parts by weight or more, 100 parts by weight or more, 105 parts by weight 110 parts by weight or more, 112.5 parts by weight or more, 115 parts by weight or more, 120 parts by weight or more, 125 parts by weight or more, 127.5 parts by weight or more, or 130 parts by weight or more, and 450 parts by weight or less, 445 parts by weight or less, 440 parts by weight or less, 435 parts by weight Parts by weight or less, 430 parts by weight or less, 425 parts by weight or less, 420 parts by weight or less, 415 parts by weight or less, 410 parts by weight or less, 405 parts by weight or less, 400 parts by weight or less, 395 parts by weight or less, 390 parts by weight or less, 385 parts by weight or less, 380 parts by weight or less, 375 parts by weight or less Bottom, 370 parts by weight or less, 365 parts by weight or less, 360 parts by weight or less, 355 parts by weight or less, 350 parts by weight or less, 345 parts by weight or less, 340 parts by weight or less, 335 parts by weight or less, 330 parts by weight or less, 325 parts by weight or less, 320 parts by weight or less, 315 parts by weight or less, 310 parts by weight or less, 305 parts by weight or less, 300 parts by weight or less, 295 parts by weight or less, 290 parts by weight or less, 285 parts by weight or less, 280 parts by weight or less, 275 parts by weight or less, 270 parts by weight or less, 265 parts by weight or less, 260 parts by weight or less, 255 parts by weight or less, 250 It may be less than or equal to parts by weight, 245 parts by weight or less, 240 parts by weight or less, 235 parts by weight or less, 230 parts by weight or less, 225 parts by weight or less, 220 parts by weight or less, 215 parts by weight or less, 210 parts by weight or less, 205 parts by weight or less, 200 parts by weight or less, 195 parts by weight or less, 190 parts by weight or less, 185 parts by weight or less, 180 parts by weight or less, 175 parts by weight or less, 170 parts by weight or less, 165 parts by weight or less, 160 parts by weight or less, 155 parts by weight or less, 150 parts by weight or less, 145 parts by weight or less, 140 parts by weight or less, or 135 parts by weight or less.

[0058] If the content of the first dispersant is less than 25 parts by weight based on 100 parts by weight of carbon nanotubes, the insufficient dispersant content will result in insufficient dispersion, leading to a problem where the viscosity of the dispersion is low and increases over time. If the content exceeds 450 parts by weight, the excessive content of the first dispersant will promote aggregation between solid particles in the dispersion, resulting in a problem where the viscosity of the dispersion is high.

[0059] Furthermore, in an embodiment of the present invention, the carbon nanotube dispersion contains only the first dispersant, and in order to solve the problem that the viscosity of the dispersion increases along with the carbon nanotube content, a second dispersant containing a substituted benzopyran compound with at least three hydroxyl groups is included together with the first dispersant. As a result, compared to conventional carbon nanotube dispersions using only a dispersant, the particles of the slurry composition are less likely to clump together, and the sedimentation velocity is reduced.

[0060] The substituted benzopyran compound contained in the second dispersant contains at least three hydroxyl groups, which allows the second dispersant to have a relatively low molecular weight and small molecular size, enabling it to adsorb onto the surface of carbon nanotubes that the first dispersant containing nitrogen atoms could not enclose, thereby exhibiting an additional dispersion effect. Furthermore, the benzopyran structure contained in the second dispersant stably generates π-π interactions with the carbon nanotubes in local regions, ensuring sufficient bonding strength between the dispersant and the carbon nanotubes, reducing the content of remaining dispersant that was not effectively adsorbed onto the carbon nanotube surface, and preventing aggregation of the remaining dispersant. In addition, the substituted benzopyran compound contained in the second dispersant, with at least three hydroxyl groups, forms hydrogen bonds with the solvent in the dispersion, allowing the "carbon nanotube-dispersant" conjugate to maintain a stable dispersed state in the solvent.

[0061] If the carbon nanotube dispersion does not contain the second dispersant according to the present invention, the area where the surface of the carbon nanotubes is not sufficiently covered by the dispersant may increase. As a result, a stronger-than-appropriate bonding force may be generated between the carbon nanotubes, and as a result of aggregation between the carbon nanotubes, the viscosity of the dispersion may be increased.

[0062] Furthermore, if the second dispersant contains, for example, three or more aromatic rings in its molecular structure, the molecules form linearly angular or densely packed structures, which is unfavorable for surface adsorption of small-diameter carbon nanotubes, especially single-walled carbon nanotubes. In addition, strong π-π interactions occur between unadsorbed dispersants, deepening the aggregation of the dispersants and resulting in a high viscosity of the dispersion, which can lead to a significant increase in the viscosity of the dispersion over time.

[0063] Furthermore, if the substituted benzopyran compound contained in the second dispersant contains more than six hydroxyl groups, such as tannic acid or epigallocatechin gallate (EGCG), when this is applied to a carbon nanotube dispersion together with the first dispersant containing nitrogen atoms, very strong hydrogen bonds may form between the dispersants, resulting in the formation of a hydrogel or insoluble conjugate, which can lead to a problem of excessively high viscosity in the dispersion.

[0064] To effectively demonstrate the aforementioned properties, the substituted benzopyran compounds included in the second dispersant may be excluded if they contain three or more aromatic rings in their molecular structure or if they have more than six hydroxyl groups.

[0065] In one specific example of the present invention, the second dispersant may include a compound represented by the following chemical formula 1.

[0066] [ka]

[0067] In the aforementioned chemical formula 1, [ka] is by single or double bond; A1 to A6 are either identical or different from each other, and each is independently of hydrogen; deuterium; halogen; cyano group; hydroxyl group; carboxyl group; substituted or unsubstituted C1-C10 alkyl group; substituted or unsubstituted C2-C10 alkenyl group; substituted or unsubstituted C2-C10 alkynyl group; substituted or unsubstituted C1-C10 alkoxy group; substituted or unsubstituted C3-C10 cycloalkyl group; substituted or unsubstituted C2-C10 heterocycloalkyl group; or substituents represented by the following chemical formula 2, with at least one of A1 to A6 being represented by the following chemical formula 2.

[0068] [ka]

[0069] In the aforementioned chemical formula 2, B1 to B5 are either identical or different to each other, and each is independently a hydrogen; deuterium; halogen; cyano group; hydroxyl group; carboxyl group; substituted or unsubstituted C1-C10 alkyl group; substituted or unsubstituted C2-C10 alkenyl group; substituted or unsubstituted C2-C10 alkynyl group; substituted or unsubstituted C1-C10 alkoxy group; substituted or unsubstituted C3-C10 cycloalkyl group; or substituted or unsubstituted C2-C10 heterocycloalkyl group. Among A1 to A6 of Chemical Formula 1, the substituent not represented in Chemical Formula 2, and among B1 to B5 of Chemical Formula 2, at least three are hydroxyl groups.

[0070] The second dispersant contains a substituted benzopyran compound having a benzene ring represented by chemical formula 2 in the core of a benzopyran represented by chemical formula 1, and at least three substituents of the substituted benzopyran compound are substituted with hydroxyl groups. This ensures that the π-π interaction between the carbon nanotubes and the aromatic ring of the second dispersant, and the hydrogen bonding interaction between the nitrogen atoms in the first dispersant and the hydroxyl groups of the second dispersant are in proper balance within the dispersion. This further improves the effect of suppressing viscosity decrease and viscosity increase over time in the carbon nanotube dispersion.

[0071] In the aforementioned chemical formula 1, A1 to A6 are either identical or different from each other, and each is independently of a hydrogen atom, deuterium, halogen, cyano group, hydroxyl group, carboxyl group, substituted or unsubstituted C1-C5 alkyl group, substituted or unsubstituted C2-C5 alkenyl group, substituted or unsubstituted C2-C5 alkynyl group, substituted or unsubstituted C1-C5 alkoxy group, substituted or unsubstituted C3-C5 cycloalkyl group, substituted or unsubstituted C2-C5 heterocycloalkyl group, or substituent represented by the aforementioned chemical formula 2, wherein at least one of A1 to A6 is represented by the aforementioned chemical formula 2. In the aforementioned chemical formula 2, B1 to B5 may be the same as or different from each other, and each may independently be hydrogen; deuterium; halogen; cyano group; hydroxyl group; carboxyl group; substituted or unsubstituted C1-C5 alkyl group; substituted or unsubstituted C2-C5 alkenyl group; substituted or unsubstituted C2-C5 alkynyl group; substituted or unsubstituted C1-C5 alkoxy group; substituted or unsubstituted C3-C5 cycloalkyl group; or substituted or unsubstituted C2-C5 heterocycloalkyl group, wherein at least three of the substituents among A1 to A6 of the aforementioned chemical formula 1 that are not represented in the aforementioned chemical formula 2, and at least three of the B1 to B5 of the aforementioned chemical formula 2, may be hydroxyl groups.

[0072] In the aforementioned chemical formula 1, A1 to A6 are either identical or different, and each is independently a hydrogen atom; a deuterium atom; a hydroxyl group; a substituted or unsubstituted C1 to C5 alkoxy group; or a substituent represented by the aforementioned chemical formula 2, wherein at least one of A1 to A6 is represented by the aforementioned chemical formula 2. In the aforementioned chemical formula 2, B1 to B5 may be the same or different from each other, and each may independently be hydrogen; deuterium; a hydroxyl group; or a substituted or unsubstituted C1 to C5 alkoxy group, and at least three of the substituents among A1 to A6 of the aforementioned chemical formula 1 that are not represented in the aforementioned chemical formula 2, and at least three of the B1 to B5 of the aforementioned chemical formula 2 may be hydroxyl groups.

[0073] In the above chemical formula 1, at least two of A1 to A6 may be hydroxyl groups.

[0074] In the above chemical formula 2, at least one of B1 to B5 may be a hydroxyl group.

[0075] In one specific example of the present invention, the second dispersant may contain a compound represented by any one of the following chemical formulas 3 to 5.

[0076] [ka]

[0077] In the aforementioned chemical formulas 3 to 5, A1-A5 and B1-B5 are either identical or different from each other, and each is independently a hydrogen; deuterium; halogen; cyano group; hydroxyl group; carboxyl group; substituted or unsubstituted C1-C10 alkyl group; substituted or unsubstituted C2-C10 alkenyl group; substituted or unsubstituted C2-C10 alkynyl group; substituted or unsubstituted C1-C10 alkoxy group; substituted or unsubstituted C3-C10 cycloalkyl group; or substituted or unsubstituted C2-C10 heterocycloalkyl group. At least three of the A1-A5 and B1-B5 groups in the aforementioned chemical formula 1 are hydroxyl groups.

[0078] In the above chemical formulas 3 to 5, A1 to A5 and B1 to B5 are either identical or different from each other, and each is independently a hydrogen group; a deuterium group; a halogen group; a cyano group; a hydroxyl group; a carboxyl group; a substituted or unsubstituted C1 to C5 alkyl group; a substituted or unsubstituted C2 to C5 alkenyl group; a substituted or unsubstituted C2 to C5 alkynyl group; a substituted or unsubstituted C1 to C5 alkoxy group; a substituted or unsubstituted C3 to C5 cycloalkyl group; or a substituted or unsubstituted C2 to C5 heterocycloalkyl group, and at least three of A1 to A5 and B1 to B5 in the above chemical formula 1 may be hydroxyl groups.

[0079] In the above chemical formulas 3 to 5, A1 to A5 and B1 to B5 are either identical or different from each other, and each is independently a hydrogen; deuterium; a hydroxyl group; or a substituted or unsubstituted C1 to C5 alkoxy group, and at least three of A1 to A5 and B1 to B5 in the above chemical formula 1 may be hydroxyl groups.

[0080] In the above chemical formulas 3 to 5, at least two of A1 to A5 may be hydroxyl groups, and at least one of B1 to B5 may be a hydroxyl group.

[0081] In one specific example of the present invention, the second dispersant may be one or more selected from the group consisting of luteolin, quercetin, kaempferol, myricetin, fisetin, morin, hesperetin, naringenin, and eriodictyol, as shown in Table 1 below. It is not limited to the above types, as long as it is a substituted benzopyran compound that contains at least three hydroxyl groups in its molecule and can enhance the dispersibility of carbon nanotubes.

[0082] [Table 1A]

[0083] [Table 1B]

[0084] In one specific example of the present invention, the carbon nanotube dispersion can contain 5 to 250 parts by weight of the second dispersant based on 100 parts by weight of the carbon nanotube, for example, 5 parts by weight or more, 10 parts by weight or more, 15 parts by weight or more, 20 parts by weight or more, 22.5 parts by weight or more, 25 parts by weight or more, 30 parts by weight or more, 35 parts by weight or more, 37.5 parts by weight or more, 40 parts by weight or more, 45 parts by weight or more, 50 parts by weight or more, 55 parts by weight or more, or 60 parts by weight or more, and may also be 250 parts by weight or less, 245 parts by weight or less, 240 parts by weight or less, 235 parts by weight or less, 230 parts by weight or less, 225 parts by weight or less, 220 parts by weight or less, 215 parts by weight or less It may be less than or equal to parts by weight, 210 parts by weight or less, 205 parts by weight or less, 200 parts by weight or less, 195 parts by weight or less, 190 parts by weight or less, 185 parts by weight or less, 180 parts by weight or less, 175 parts by weight or less, 170 parts by weight or less, 165 parts by weight or less, 160 parts by weight or less, 155 parts by weight or less, 150 parts by weight or less, 145 parts by weight or less, 140 parts by weight or less, 135 parts by weight or less, 130 parts by weight or less, 125 parts by weight or less, 120 parts by weight or less, 115 parts by weight or less, 110 parts by weight or less, 105 parts by weight or less, 100 parts by weight or less, 95 parts by weight or less, 90 parts by weight or less, 85 parts by weight or less, 80 parts by weight or less, 75 parts by weight or less, 70 parts by weight or less, or 65 parts by weight or less.

[0085] If the content of the second dispersant is less than 5 parts by weight based on 100 parts by weight of carbon nanotubes, the first and second dispersants cannot sufficiently form hydrogen bonds, resulting in an ineffective dispersion effect. Consequently, the viscosity of the dispersion may be low and not formed, and there is a problem of viscosity increasing over time. If it exceeds 250 parts by weight, the excessive content of the second dispersant promotes aggregation of solid components in the dispersion, and there is a problem as long as the viscosity of the dispersion is high.

[0086] In one specific example of the present invention, the first dispersant and the second dispersant of the carbon nanotube dispersion may be included in a weight ratio of 100:10 to 100:90. For example, the ratio of the second dispersant to the first 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 second dispersant to the first 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.

[0087] When the first and second dispersants are contained in the carbon nanotube dispersion in the aforementioned 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.

[0088] (3) Solvent The solvent in the carbon nanotube dispersion according to one embodiment of the present invention is a dispersion medium for dispersing the carbon nanotubes, the first dispersant, and the second dispersant. When carbon nanotubes in powder form are used immediately in the production of an electrode slurry composition, the solvent is used to linearly disperse them and supply them to the carbon nanotube dispersion in order to prevent aggregation.

[0089] The solvent can dissolve or disperse the carbon nanotubes, the first dispersant, and the second dispersant to a certain level or higher. The aqueous solvent may be, for example, water, and the aqueous solvent may be included in a content such that the electrode slurry composition can have an appropriate viscosity, in view of the coating properties of the electrode slurry composition subsequently produced using the carbon nanotube dispersion.

[0090] In one embodiment of the present invention, the carbon nanotube dispersion can reduce the average particle size distribution of dispersed particles contained in the dispersion, such as composites of carbon nanotubes and each dispersant, by uniformly dispersing the carbon nanotubes in the solvent using the first and second dispersants as described above.

[0091] The average particle size distribution (D) of the dispersed particles contained in the aforementioned dispersion. 50 The particle size may be, for example, 0.5 to 10 μm, 1 to 10 μm, 1 to 8 μm, preferably 1 to 5 μm.

[0092] The carbon nanotube dispersion of the present invention, containing the components described above, exhibits excellent dispersibility, low viscosity, and minimal viscosity increase over time.

[0093] The carbon nanotube dispersion may have an initial viscosity of 1 to 10 Pa.s, measured at 25°C and 1 rpm using a viscometer (TOKISANGYO Corporation, viscometer TV-25, Rotor Code 01). For example, it may be 1 Pa.s or more, 2 Pa.s or more, 2.5 Pa.s or more, 3 Pa.s or more, 4 Pa.s or more, or 5 Pa.s or more, or it may be 10 Pa.s or less, 9.8 Pa.s or less, 9.5 Pa.s or less, 9 Pa.s or less, 8.5 Pa.s or less, 8 Pa.s or less, 7.5 Pa.s or less, 7 Pa.s or less, 6.5 Pa.s or less, or 6 Pa.s or less. When the carbon nanotube dispersion has an initial viscosity within the above range, it can be used to manufacture an electrode slurry more smoothly, and the electrode slurry containing the carbon nanotube dispersion can have an appropriate viscosity for electrode formation.

[0094] 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 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% 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, 6.5% 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.

[0095] [Formula 1] Viscosity increase rate (%) = {(Viscosity measured after being left at 25°C for one week - initial viscosity) / initial viscosity} × 100

[0096] At this time, the viscosity after being left for one week and the initial viscosity were measured at 25°C and 1 rpm.

[0097] Method for producing a carbon nanotube dispersion The following describes a method for producing a carbon nanotube dispersion.

[0098] The method for producing a conductive material dispersion according to the present invention includes (1) the step of mixing carbon nanotubes, a first dispersant containing nitrogen atoms, a second dispersant containing a substituted benzopyran compound containing at least three hydroxyl groups, and a solvent to produce a primary dispersion of carbon nanotubes; and (2) the step of dispersing the primary dispersion of carbon nanotubes to produce a secondary dispersion of carbon nanotubes.

[0099] 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 substituted benzopyran compound with at least three hydroxyl groups, and a solvent. The step of preparing the primary dispersion of carbon nanotubes is carried out in a wetting step in which each component is uniformly mixed.

[0100] The mixing for producing the primary dispersion of carbon nanotubes can be carried out using conventional mixing methods, specifically using mixing equipment such as a pony mixer, change-can mixer, Hobert mixer, pullenetri mixer, butterfly mixer, stone mill, homogenizer, bead mill, ball mill, basket mill, attrition mill, universal stirrer, clear mixer, or TK mixer, and may include a step of mixing at a rotational speed of 300 to 5,000 rpm for 30 minutes to 7 hours.

[0101] Furthermore, when mixing to produce the primary dispersion of carbon nanotubes, cavitation dispersion treatment may be performed to improve the miscibility between the carbon nanotubes and the solvent, or the dispersibility of the carbon nanotubes in the solvent. The cavitation dispersion treatment is a dispersion method that utilizes shock waves generated when vacuum bubbles formed in water burst when high energy is applied to the liquid, and this method can disperse carbon nanotubes without damaging their properties. Specifically, the cavitation dispersion treatment may be performed by ultrasound, jet milling, or shear dispersion treatment.

[0102] The production step of the primary dispersion of carbon nanotubes may be carried out under temperature conditions in which the physical properties of the mixture, such as viscosity, do not change due to the evaporation of the aqueous solvent. For example, it may be carried out at a temperature of 50°C or lower, or more specifically, between 5°C and 50°C.

[0103] The specific details of the carbon nanotubes, the first dispersant containing nitrogen atoms, the second dispersant containing a substituted benzopyran compound with at least three hydroxyl groups, and the solvent in the method for producing the carbon nanotube dispersion are as described above, and therefore, a detailed explanation will be omitted below.

[0104] In step (2), the primary dispersion of carbon nanotubes is dispersed to produce a secondary dispersion of carbon nanotubes.

[0105] The stirring step may be carried out by methods such as a ball mill, bead mill, disc mill, basket mill, or high-pressure homogenizer, and more specifically, by a milling method using a disc mill or high-pressure homogenizer.

[0106] During milling with the aforementioned disc mill, the size of the beads can be appropriately determined by the type and amount of carbon nanotubes and the type of dispersant. Specifically, the diameter of the beads may be 0.1 mm to 5 mm, or more specifically, 0.5 mm to 4 mm. Furthermore, the bead milling process may be carried out at a speed of 2,000 rpm to 10,000 rpm, or more specifically, at a speed of 5,000 rpm to 9,000 rpm.

[0107] The milling by the high-pressure homogenizer is performed, for example, by pressing the mixture with the plunger pump of the high-pressure homogenizer and pushing it through the gap of the homogenization valve, thereby being carried out by forces such as cavitation, shear, impact, and explosion as it passes through the gap.

[0108] The dispersion step may be carried out depending on the degree of dispersion of the carbon nanotube dispersion, and more specifically, it may be carried out under a pressure of 5,000 to 30,000 psi for 30 to 120 minutes, or more specifically, for 60 to 90 minutes, and the process can be repeated 1 to 10 times.

[0109] The carbon nanotube dispersion according to the present invention may also mean a secondary dispersion of the carbon nanotubes.

[0110] Electrode slurry composition for lithium secondary battery In addition, the present invention provides an electrode slurry composition for a lithium secondary battery containing the carbon nanotube dispersion liquid and an electrode active material.

[0111] 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.

[0112] The electrode slurry composition for the lithium secondary battery may contain 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.

[0113] As the positive electrode active material, a positive electrode active material well known in the art may be used without limitation. For example, lithium cobalt-based oxide, lithium nickel-based oxide, lithium manganese-based oxide, lithium iron phosphate, lithium nickel manganese cobalt-based oxide or a combination thereof 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.

[0114] As the negative electrode active material, natural graphite, artificial graphite, carbonaceous material; lithium-containing titanium composite oxide (LTO), Si, Sn, Li, Zn, Mg, Cd, Ce, Ni or Fe metals (Me); alloys composed of the metals (Me); oxides (MeO) of the metals (Me) x ); and one or more negative electrode active materials selected from the group consisting of composites of the metals (Me) and carbon can be mentioned. The negative electrode active material may be contained at 60 to 98% by weight, more preferably 70 to 98% by weight, based on the total weight of the solid matter excluding the solvent in the negative electrode slurry.

[0115] The aforementioned binder is typically added at a concentration of 1 to 30% by weight relative to the total weight of the mixture containing the electrode active material, as it is a component that aids in the bonding of the active material to conductive materials and to the current collector. Examples of such binders include polyvinylidene fluoride, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene propylene dienterpolymer (EPDM), sulfonated EPDM, styrene-butadiene rubber, fluororubber, and various copolymers.

[0116] The solvent may be an organic solvent such as N-methylpyrrolidone (NMP), dimethylformamide (DMF), acetone, or dimethylacetamide, or water. These solvents can be used individually or in mixtures of two or more. The amount of solvent used should be sufficient to dissolve and disperse the electrode active material, binder, and conductive material, taking into consideration the thickness of the slurry coating and the production yield.

[0117] The viscosity modifier may be carboxymethylcellulose or polyacrylic acid, and by adding it, the viscosity of the electrode slurry can be adjusted so that the manufacturing of the electrode slurry and the coating process on the electrode current collector are facilitated.

[0118] The filler is used selectively as a component to suppress electrode swelling 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; and fibrous materials such as glass fibers and carbon fibers can be used.

[0119] If the electrode slurry composition is a composition for a positive electrode slurry to form a positive electrode, the positive electrode can be manufactured by applying the positive electrode slurry composition onto a positive electrode current collector, followed by drying and rolling. Alternatively, the positive electrode slurry can be cast separately onto a support, and the resulting film, obtained by peeling it off the support, can be laminated onto the positive electrode current collector.

[0120] 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.

[0121] The positive electrode current collector generally has a thickness of 3 μm to 500 μm. Such a positive electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes to the battery. For example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel with a surface treatment of carbon, nickel, titanium, silver, etc. may be used. Furthermore, fine irregularities can be formed on the surface of the positive electrode current collector to strengthen the bonding force of the positive electrode active material, and it may be used in various forms such as film, sheet, foil, net, porous material, foam, nonwoven fabric.

[0122] If the electrode slurry composition is a negative electrode slurry composition for forming a negative electrode, the negative electrode can be manufactured by applying the negative electrode slurry composition onto a negative electrode current collector, followed by drying and rolling. Alternatively, the negative electrode slurry can be cast separately onto a support, and the resulting film, obtained by peeling it off the support, can be laminated onto the negative electrode current collector.

[0123] 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.

[0124] 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 to the battery, and may be made of materials such as copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., or aluminum-cadmium alloy. In addition, similar to the negative electrode current collector, fine irregularities can be formed on the surface to strengthen the bonding force of the negative electrode active material, and it may be used in various forms such as film, sheet, foil, net, porous material, foam, or nonwoven fabric.

[0125] Lithium-ion rechargeable battery A lithium secondary battery includes a positive electrode, a negative electrode, a separator membrane placed between the positive and negative electrodes, and an electrolyte. Since the positive and negative electrodes are the same as described above, a detailed explanation is omitted.

[0126] The separation membrane separates the negative and positive electrodes and provides a pathway for lithium ions to move. It can be used without particular limitations as long as it is a membrane typically used in lithium secondary batteries. Particularly preferred is one that exhibits low resistance to ion movement of the electrolyte and has excellent moisture-retaining capacity for the electrolyte. Specifically, porous polymer films, such as polyolefin polymers like ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, and ethylene / methacrylate copolymer, or laminated structures of two or more layers thereof, can be used. Alternatively, ordinary porous nonwoven fabrics, such as nonwoven fabrics made of high-melting-point glass fibers or polyethylene terephthalate fibers, can also be used. Furthermore, coated separation membranes containing ceramic components or polymeric substances can be used to ensure heat resistance or mechanical strength, and can be selectively used in single-layer or multi-layer structures.

[0127] 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, or a molten inorganic electrolyte that can be used in the manufacture of lithium secondary batteries. Specifically, the electrolyte may contain an organic solvent and a lithium salt.

[0128] The organic solvent can be any solvent that can act as a medium through which ions involved in the electrochemical reaction of the battery can move, without any particular limitations. Specifically, the organic solvents include ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether solvents such as dibutyl ether or tetrahydrofuran; ketone solvents such as cyclohexanone; aromatic hydrocarbon solvents such as benzene and fluorobenzene; dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), and propylene carbonate (propylene Carbonate solvents such as carbonate (PC); alcoholic solvents such as ethanol and isopropyl alcohol; nitriles such as R-CN (where R is a linear, branched, or cyclic hydrocarbon group of C2-C20, and may include a double-bonded aromatic ring or ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes may be used. Among these, carbonate solvents are preferred, and a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate) having high ionic conductivity and high dielectric constant that can improve the charge and discharge performance of the battery, and a low-viscosity linear carbonate compound (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate) is more preferred. In this case, the electrolyte performance is best demonstrated when the cyclic carbonate and the linear carbonate are mixed in a volume ratio of about 1:1 to about 1:9.

[0129] The lithium salt may be any compound capable of providing lithium ions for use in lithium secondary batteries, without any particular limitations. 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, etc. The concentration of the lithium salt should preferably be within the range of 0.1M to 2.0M. If the concentration of the lithium salt falls within this range, the electrolyte will have appropriate conductivity and viscosity, exhibiting excellent electrolyte performance and allowing lithium ions to move effectively.

[0130] In addition to the components of the electrolyte, the electrolyte may further contain one or more additives for the purpose of improving battery life characteristics, suppressing the decrease in battery capacity, and improving battery discharge capacity, such as haloalkylene carbonate compounds like difluoroethylene carbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ethers, ethylenediamine, n-glyme, hexaphosphate triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salts, pyrrole, 2-methoxyethanol, or aluminum trichloride. In this case, the additive may be present in an amount of 0.1% to 5% by weight relative to the total weight of the electrolyte.

[0131] A lithium secondary battery containing an electrode manufactured using the carbon nanotube dispersion according to the present invention, specifically a lithium secondary battery containing a negative electrode manufactured using the carbon nanotube dispersion, has carbon nanotubes uniformly dispersed within the negative electrode. Compared to conventional batteries containing conductive materials such as carbon black, the content of such materials can be reduced, and it can stably exhibit superior discharge capacity and output characteristics. As a result, it can be usefully used in portable devices such as mobile phones, laptop computers, and digital cameras, as well as in electric vehicles such as hybrid electric vehicles (HEVs).

[0132] Accordingly, according to another embodiment of the present invention, a lithium secondary battery, a battery module containing the lithium secondary battery as a unit cell, and a battery pack containing the same are provided.

[0133] The battery module or battery pack may be used as a power source for one or more medium-to-large devices in a power tool; an electric vehicle (EV), a hybrid electric vehicle, or a plug-in hybrid electric vehicle (PHEV); or a power storage system.

[0134] The following describes specific embodiments of the present invention. However, these embodiments are merely for illustrative purposes and to explain the present invention, and do not limit it. Furthermore, any matters not described herein can be sufficiently inferred by technical analogy by those skilled in the art, and therefore their explanations are omitted.

[0135] Examples Example 1 (1) 5.625 g of polyvinylpyrrolidone (PVP, manufactured by Zhangzhou Huafu Chemical) as a first dispersant containing nitrogen atoms (1.125% by weight relative to 100 parts by weight of the total carbon nanotube dispersion), 1.875 g of luteolin (manufactured by INDOFINE Chemical) as a second dispersant containing a substituted benzopyran compound with at least three hydroxyl groups (0.375% by weight relative to 100 parts by weight of the total carbon nanotube dispersion), and 487.5 g of water as a solvent are mixed to produce 495 g of a mixed solution. This is then placed in a dissolver (Dispermat-CA, manufactured by VMA-GETZMANN) equipped with an impeller and container, and mixed by stirring at 400 rpm for 10 minutes.

[0136] (2) The above mixture has a specific surface area of ​​1,160 m 2 / g, average particle size (D 50 5.0 g of 5 μm single-walled carbon nanotubes (SWCNT, TUBALL, manufactured by OCSiAl) (1.0 wt% relative to 100 wt parts of the total carbon nanotube dispersion) is added, and the mixture is stirred at 8,000 rpm for 60 minutes to produce a total of 500 g of primary dispersion of carbon nanotubes.

[0137] (3) The primary dispersion of carbon nanotubes was homogenized seven times using a high-pressure disperser (PICOMAX, manufactured by Micronox) at a pressure of 20,000 psi to produce a secondary dispersion of carbon nanotubes.

[0138] Example 2 A carbon nanotube dispersion was produced in the same manner as in Example 1, except that the content of the first dispersant was 1.000% by weight relative to 100 parts by weight of the total carbon nanotube dispersion, and the content of the second dispersant was 0.5% by weight relative to 100 parts by weight of the total carbon nanotube dispersion.

[0139] Example 3 A carbon nanotube dispersion was prepared in the same manner as in Example 1, except that the carbon nanotube content was 0.6% by weight relative to 100 parts by weight of the total carbon nanotube dispersion, the first dispersant content was 0.675% by weight relative to 100 parts by weight of the total carbon nanotube dispersion, and the second dispersant content was 0.225% by weight relative to 100 parts by weight of the total carbon nanotube dispersion.

[0140] Example 4 In the same manner as in Example 1, a carbon nanotube dispersion was prepared, except that the content of the second dispersant was set to 0.113% by weight relative to 100 parts by weight of the total carbon nanotube dispersion.

[0141] Example 5 A carbon nanotube dispersion was prepared in the same manner as in Example 1, except that the content of the first dispersant was 2,500% by weight relative to 100 parts by weight of the total carbon nanotube dispersion, and the content of the second dispersant was 2,250% by weight relative to 100 parts by weight of the total carbon nanotube dispersion.

[0142] Example 6 A carbon nanotube dispersion was prepared in the same manner as in Example 1, except that 1.875 g of quercetin (manufactured by INDOFINE Chemical) (0.375% by weight relative to 100 parts by weight of the total carbon nanotube dispersion) was used instead of luteolin as a second dispersant containing a substituted benzopyran compound with at least three hydroxyl groups.

[0143] Example 7 A carbon nanotube dispersion was prepared in the same manner as in Example 1, except that 1.875 g of myricetin (manufactured by INDOFINE Chemical Co., Ltd.) (0.375% by weight relative to 100 parts by weight of the total carbon nanotube dispersion) was used instead of luteolin as a second dispersant containing a substituted benzopyran compound with at least three hydroxyl groups.

[0144] Comparative Example 1 A carbon nanotube dispersion was prepared in the same manner as in Example 1, except that the second dispersant was not added.

[0145] Comparative Example 2 In Example 1, a carbon nanotube dispersion was prepared in the same manner as in Example 1, except that the carbon nanotube content was 0.6% by weight relative to 100 parts by weight of the total carbon nanotube dispersion, the first dispersant content was 0.900% by weight relative to 100 parts by weight of the total carbon nanotube dispersion, and the second dispersant was not added.

[0146] Comparative Example 3 In Example 1, the carbon nanotube dispersion was prepared in the same manner as in Example 1, except that the second dispersant was added at a content of 1,500% by weight relative to 100 parts by weight of the total carbon nanotube dispersion, and the first dispersant was not added.

[0147] Comparative Example 4 A carbon nanotube dispersion was prepared in the same manner as in Example 1, except that the carbon nanotubes were added at a concentration of 0.6% by weight relative to 100 parts by weight of the total carbon nanotube dispersion, the content of the first dispersant was 0.675% by weight relative to 100 parts by weight of the total carbon nanotube dispersion, and tristyrylphenol ethoxylate was used as the second dispersant instead of luteolin at a concentration of 0.225% by weight relative to 100 parts by weight of the total carbon nanotube dispersion.

[0148] Comparative Example 5 A carbon nanotube dispersion was prepared in the same manner as in Example 1, except that the carbon nanotubes were added at a concentration of 0.6% by weight relative to 100 parts by weight of the total carbon nanotube dispersion, the content of the first dispersant was 0.675% by weight relative to 100 parts by weight of the total carbon nanotube dispersion, and styrene maleic acid copolymer was used as the second dispersant instead of luteolin at a concentration of 0.225% by weight relative to 100 parts by weight of the total carbon nanotube dispersion.

[0149] Comparative Example 6 A carbon nanotube dispersion was prepared in the same manner as in Example 1, except that luteolin was added as the second dispersant at a concentration of 0.375% by weight relative to 100 parts by weight of the total carbon nanotube tannate dispersion.

[0150] Comparative Example 7 A carbon nanotube dispersion was prepared in the same manner as in Example 1, except that epigallocatechin gallate was added as a second dispersant in the same amount as in Example 1, at a concentration of 0.375% by weight relative to 100 parts by weight of the total carbon nanotube dispersion.

[0151] Comparative Example 8 A carbon nanotube dispersion was produced in the same manner as in Example 1, except that the content of the first dispersant was 0.250% by weight relative to 100 parts by weight of the total carbon nanotube dispersion, and the content of the second dispersant was 0.025% by weight relative to 100 parts by weight of the total carbon nanotube dispersion.

[0152] Comparative Example 9 A carbon nanotube dispersion was prepared in the same manner as in Example 1, except that the content of the first dispersant was 3.056% by weight relative to 100 parts by weight of the total carbon nanotube dispersion, and the content of the second dispersant was 2.750% by weight relative to 100 parts by weight of the total carbon nanotube dispersion.

[0153] Comparative Example 10 A carbon nanotube dispersion was prepared in the same manner as in Example 1, except that the content of the first dispersant was 2,600% by weight relative to 100 parts by weight of the total carbon nanotube dispersion, and the content of the second dispersant was 2,600% by weight relative to 100 parts by weight of the total carbon nanotube dispersion.

[0154] Experimental example The viscosity of the carbon nanotube dispersions of Examples 1-7 and Comparative Examples 1-10 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.

[0155] Viscosity was measured at 25°C and 1 rpm using a viscometer (TOKI SANGYO, viscometer TV-25, Rotor Code 01).

[0156] [Table 2A]

[0157] [Table 2B]

[0158] Referring to Table 2 above, it can be confirmed that, compared to the carbon nanotube dispersion of Comparative Example 1, which contains only polyvinylpyrrolidone as the first dispersant, the carbon nanotube dispersions of Examples 1 to 7, which contain the first dispersant and a second dispersant containing a substituted benzopyran compound with at least three hydroxyl groups in specific concentrations, have a lower initial viscosity immediately after the carbon nanotubes are dispersed in an aqueous solvent, and in particular, the increase in viscosity of the carbon nanotube dispersion over time is very effectively suppressed.

[0159] In the case of the carbon nanotube dispersion of Comparative Example 2, the carbon nanotube content was reduced compared to the carbon nanotube dispersion of Comparative Example 1, and the initial viscosity immediately after dispersing the carbon nanotubes in the aqueous solvent was also reduced compared to the carbon nanotube dispersion of Comparative Example 1. However, similar to the carbon nanotube dispersion of Comparative Example 1, the absence of a second dispersant containing a substituted benzopyran compound with at least three hydroxyl groups compared to Examples 1-3 meant that the effect of suppressing the increase in viscosity of the dispersion over time was not observed.

[0160] In the case of the carbon nanotube dispersion of Comparative Example 3, the absence of the first dispersant compared to the carbon nanotube dispersions of Examples 1-3 prevented complete dispersion of the carbon nanotubes in the aqueous solvent, resulting in aggregation of the dispersion and making viscosity measurement impossible.

[0161] In the case of the carbon nanotube dispersions of Comparative Examples 4 and 5, by not using a substance that does not contain a substituted benzopyran compound containing at least three or more hydroxyl groups as a second dispersant compared to the carbon nanotube dispersions of Examples 1 to 3, the initial viscosity immediately after dispersing the carbon nanotubes in the aqueous solvent is high (Comparative Example 4), and the effect of suppressing the increase in viscosity of the carbon nanotube dispersion over time is not observed (Comparative Examples 4 and 5).

[0162] In the case of the carbon nanotube dispersions of Comparative Examples 6 and 7, compared to the carbon nanotube dispersions of Examples 1 to 3, the compound used as the second dispersant contained more than six hydroxyl groups. As a result of these excess hydroxyl groups, hydrogen bonding with the first dispersant and solvent was excessively generated, leading to deeper hydrogel formation. Consequently, the initial viscosity immediately after dispersion of carbon nanotubes was high, and the effect of suppressing the viscosity increase of the carbon nanotube dispersion over time was not observed.

[0163] In the case of the carbon nanotube dispersion of Comparative Example 8, compared to the carbon nanotube dispersions of Examples 1 to 3, the inclusion of the second dispersant below a certain content range prevented complete dispersion of the carbon nanotubes in the aqueous solvent, resulting in aggregation of the dispersion and making viscosity measurement impossible.

[0164] In the case of the carbon nanotube dispersion of Comparative Example 9, it can be seen that, compared to the carbon nanotube dispersions of Examples 1 to 3, the excessive presence of the second dispersant results in a high initial viscosity immediately after the carbon nanotubes are dispersed in the aqueous solvent, and the effect of suppressing the increase in viscosity of the carbon nanotube dispersion over time is not observed.

[0165] In the case of the carbon nanotube dispersion of Comparative Example 10, it can be seen that, compared to the carbon nanotube dispersions of Examples 1 to 3, the content of the first and second dispersants does not meet a certain ratio, resulting in a high initial viscosity immediately after dispersing the carbon nanotubes in the aqueous solvent, and the effect of suppressing the increase in viscosity of the carbon nanotube dispersion over time is not exhibited.

[0166] Therefore, it was confirmed that the carbon nanotube dispersion, obtained by dispersing carbon nanotubes in an aqueous solvent, exhibits low viscosity and suppresses viscosity increase over time only when it contains a first dispersant and a second dispersant containing nitrogen atoms, and the second dispersant contains a substituted benzopyran compound containing at least three hydroxyl groups in a certain weight ratio.

[0167] Although 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 by those skilled in the art that utilize the basic concepts of the present invention as defined in the following claims also fall within the scope of the present invention.

Claims

1. Carbon nanotubes; A first dispersant containing nitrogen atoms; A second dispersant containing a substituted benzopyran compound; and Containing a solvent, The substituted benzopyran compound contained in the second dispersant contains at least three hydroxyl groups. Carbon nanotube dispersion.

2. The second dispersant contains a compound represented by the following chemical formula 1. Carbon nanotube dispersion according to claim 1: 【Chemistry 1】 In the aforementioned chemical formula 1, 【Chemistry 2】 is by single or double bond; A1 to A6 are either identical or different from each other, and each is independently of a hydrogen; deuterium; halogen; cyano group; hydroxyl group; carboxyl group; substituted or unsubstituted C1-C10 alkyl group; substituted or unsubstituted C2-C10 alkenyl group; substituted or unsubstituted C2-C10 alkynyl group; substituted or unsubstituted C1-C10 alkoxy group; substituted or unsubstituted C3-C10 cycloalkyl group; substituted or unsubstituted C2-C10 heterocycloalkyl group; or substituent represented by the following chemical formula 2, wherein at least one of A1 to A6 is represented by the following chemical formula 2. 【Transformation 3】 In the aforementioned chemical formula 2, B1 to B5 are either identical or different to each other, and each is independently a hydrogen; deuterium; halogen; cyano group; hydroxyl group; carboxyl group; substituted or unsubstituted C1-C10 alkyl group; substituted or unsubstituted C2-C10 alkenyl group; substituted or unsubstituted C2-C10 alkynyl group; substituted or unsubstituted C1-C10 alkoxy group; substituted or unsubstituted C3-C10 cycloalkyl group; or substituted or unsubstituted C2-C10 heterocycloalkyl group. Among A1 to A6 of the aforementioned chemical formula 1, the substituent not represented in the aforementioned chemical formula 2, and among B1 to B5 of the aforementioned chemical formula 2, at least three are hydroxyl groups.

3. The second dispersant contains a compound represented by any one of the following chemical formulas 3 to 5. Carbon nanotube dispersion according to claim 1: 【Chemistry 4】 In the aforementioned chemical formulas 3 to 5, A1-A5 and B1-B5 are either identical or different to each other, and each is independently a hydrogen; deuterium; halogen; cyano group; hydroxyl group; carboxyl group; substituted or unsubstituted C1-C10 alkyl group; substituted or unsubstituted C2-C10 alkenyl group; substituted or unsubstituted C2-C10 alkynyl group; substituted or unsubstituted C1-C10 alkoxy group; substituted or unsubstituted C3-C10 cycloalkyl group; or substituted or unsubstituted C2-C10 heterocycloalkyl group. At least three of the A1-A5 and B1-B5 groups in the aforementioned chemical formula 1 are hydroxyl groups.

4. The second dispersant is one or more selected from the group consisting of luteolin, quercetin, kaempferol, myricetin, fisetin, morin, hesperetin, naringenin, and eriodictyol. A carbon nanotube dispersion according to claim 1.

5. The BET specific surface area of ​​the carbon nanotube is 800 to 2,000 m². ２ / g is A carbon nanotube dispersion according to claim 1.

6. The carbon nanotube dispersion contains 25 to 450 parts by weight of the first dispersant based on 100 parts by weight of the carbon nanotube. A carbon nanotube dispersion according to claim 1.

7. The carbon nanotube dispersion contains 5 to 250 parts by weight of the second dispersant based on 100 parts by weight of the carbon nanotube. A carbon nanotube dispersion according to claim 1.

8. The first dispersant is polyvinylpyrrolidone, polyacrylate hydrazide, poly-N-vinyl-5-methoxazolidon, N-alkyl polyimine, N-acetyl polyimine, polyacrylamide, poly-L-lysine hydrobromide, benzyl-dodecyl-dimethylammonium chloride It is one or more substances selected from the group consisting of chloride and polyethyleneimine. A carbon nanotube dispersion according to claim 1.

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

90. A carbon nanotube dispersion according to claim 1.

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

11. The carbon nanotube dispersion has a viscosity increase rate of 15% or less, as expressed by the following formula (1). Carbon nanotube dispersion according to claim 1: [Formula 1] Viscosity increase rate (%) = {(Viscosity measured after being left at 25°C for one week - initial viscosity) / initial viscosity} × 100.

12. (1) A step of preparing a primary dispersion of carbon nanotubes by mixing carbon nanotubes, a first dispersant containing nitrogen atoms, a second dispersant containing a substituted benzopyran compound having at least three or more hydroxyl groups, and a solvent; and (2) A step of producing a secondary dispersion of carbon nanotubes by dispersing the primary dispersion of carbon nanotubes, A method for producing a carbon nanotube dispersion according to claim 1, including the method described in claim 1.

13. An electrode slurry composition for lithium secondary batteries comprising the carbon nanotube dispersion and electrode active material described in claim 1.

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