Carbon nanotube dispersion solution and preparation method therefor

Abstract

A carbon nanotube dispersion solution comprising carbon nanotubes, a dispersant and a solvent is provided. The dispersant includes a first dispersant, which includes a vinyl-based polymer comprising a halogen atom, and a second dispersant, which includes a cationic compound having a pyrazine structure. The carbon nanotube dispersion solution according to one embodiment of the present invention comprises a first dispersant and a second dispersant, and thus can significantly reduce an initial viscosity of the carbon nanotube dispersion solution and a subsequent rate of change in viscosity over time.

Description

Carbon nanotube dispersion and method for preparing the same

[0001] The present invention relates to a carbon nanotube dispersion and a method for preparing the same. Specifically, to improve the dispersibility of carbon nanotubes, the invention relates to a carbon nanotube dispersion comprising, together with carbon nanotubes, a first dispersant comprising a vinyl polymer containing a halogen atom as a dispersant, and a second dispersant comprising a cationic compound having a pyrazine structure, and a method for preparing the same.

[0002] The present application claims the benefit of priority based on Korean Patent Application No. 10-2024-0130426 filed September 26, 2024 and Korean Patent Application No. 10-2025-0137021 filed September 23, 2025, and includes all contents disclosed in the documents of said Korean patent applications as part of this specification.

[0003] With the increasing technological development and demand for mobile devices, the demand for secondary batteries as an energy source is rapidly rising. Among these secondary batteries, lithium-ion batteries, which possess high energy density and voltage, long cycle life, and low self-discharge rates, have been commercialized and are widely used. Furthermore, active research is being conducted on methods to manufacture electrodes for such high-capacity lithium-ion batteries by improving electrode density to achieve higher energy density per unit volume.

[0004] Generally, high-density electrodes are formed by molding electrode active material particles with a size of several micrometers to tens of micrometers using a high-pressure press. However, during the molding process, the particles may be deformed and the space between them may be reduced, which can easily lead to a decrease in electrolyte penetration. To solve the above problems, conductive materials with excellent electrical conductivity and strength are used during the manufacture of electrodes. Even when the conductive material is positioned between the electrode active materials and undergoes the molding process, it maintains the micropores between the active material particles, allowing the electrolyte to penetrate easily, and has excellent electrical conductivity, which can reduce resistance within the electrode. Among such conductive materials, the use of carbon nanotubes, which are fibrous carbon-based conductive materials capable of further reducing electrode resistance by forming electrical conduction paths within the electrode, is increasing.

[0005] The carbon nanotubes mentioned above are fine carbon fibers in which carbons connected by hexagonal rings form a long tube-shaped structure with a diameter of 1 μm or less. Due to the high conductivity, tensile strength, and heat resistance resulting from the unique structure of the carbon nanotubes, their application and commercialization in various fields are anticipated. For the commercialization of the carbon nanotubes as conductive materials, it is necessary to manufacture them in a dispersion state rather than in powder form. However, due to the strong agglomeration of the carbon nanotubes, it is difficult to lower the viscosity when manufactured as a dispersion, and even if the viscosity is lowered, it rises rapidly over time, posing a problem that makes it difficult to apply in actual processes.

[0006] To address these issues, methods have been proposed to disperse carbon nanotubes in a dispersion medium using mechanical dispersion treatments such as ultrasonic treatment. However, mechanical dispersion methods suffer from the problem that the carbon nanotubes aggregate as soon as the ultrasonic irradiation ends. When carbon nanotubes aggregate, the coating properties deteriorate during the process, or it becomes difficult to obtain a product with a uniform thickness.

[0007] Therefore, the relevant technical field requires a technology for manufacturing carbon nanotube dispersions with low viscosity and low rate of change of viscosity over time. The inventors completed the present invention after continuous research on additives as a solution to the aforementioned problems regarding carbon nanotube dispersions.

[0008] [Prior Art Literature]

[0009] [Patent Literature]

[0010] (Patent Document 1) Korean Published Patent Application No. 10-2023-0102774

[0011] The present invention aims to provide a carbon nanotube dispersion in which carbon nanotubes are efficiently dispersed using a first dispersant comprising a vinyl polymer containing halogen atoms and a second dispersant comprising a cationic compound having a pyrazine structure, and a method for preparing the same.

[0012] According to the first aspect of the present invention,

[0013] The present invention provides a carbon nanotube dispersion comprising carbon nanotubes, a dispersant, and a solvent, wherein the dispersant comprises a first dispersant comprising a vinyl polymer comprising halogen atoms, and a second dispersant comprising a cationic compound comprising a pyrazine structure.

[0014] In one embodiment of the present invention, the cationic compound is a compound represented by the following chemical formula 1 or 2.

[0015]

[0016] [Chemical Formula 1]

[0017]

[0018]

[0019] [Chemical Formula 2]

[0020]

[0021]

[0022] In one embodiment of the present invention, ring A and ring B are the same or different from each other and are each independently substituted or unsubstituted C6 to C20 aryl rings, or substituted or unsubstituted heteroaryl rings of 6 to 20.

[0023] In one embodiment of the present invention, R1 is selected from the group consisting of hydrogen, a substituted or unsubstituted C1 to C10 alkyl group, a substituted or unsubstituted C1 to C10 alkenyl group, a substituted or unsubstituted C6 to C20 aryl group, and a substituted or unsubstituted 6 to 20 heteroaryl group.

[0024] In one embodiment of the present invention, R2 and R3 are the same or different from each other and are each independently selected from the group consisting of hydrogen, halogen, cyano group, sulfonate group, hydroxyl group, amine group, substituted or unsubstituted C1 to C10 alkyl group, substituted or unsubstituted C1 to C10 alkenyl group, substituted or unsubstituted C1 to C10 alkoxy group, substituted or unsubstituted C6 to C20 aryl group, and substituted or unsubstituted 6 to 20 heteroaryl group.

[0025] In one embodiment of the present invention, the cationic compound is a compound represented by the following chemical formula 3.

[0026]

[0027] [Chemical Formula 3]

[0028]

[0029]

[0030] In one embodiment of the present invention, R4 is selected from the group consisting of hydrogen, a substituted or unsubstituted C1 to C10 alkyl group, a substituted or unsubstituted C1 to C10 alkenyl group, a substituted or unsubstituted C6 to C20 aryl group, and a substituted or unsubstituted 6 to 20 heteroaryl group.

[0031] In one embodiment of the present invention, R5 to R 12The groups are the same or different from each other and are each independently selected from the group consisting of hydrogen, halogen, cyano group, sulfonate group, hydroxyl group, amine group, substituted or unsubstituted C1 to C10 alkyl group, substituted or unsubstituted C1 to C10 alkenyl group, substituted or unsubstituted C1 to C10 alkoxy group, substituted or unsubstituted C6 to C20 aryl group, and substituted or unsubstituted 6 to 20 heteroaryl group.

[0032] In one embodiment of the present invention, the cationic compound comprises at least one amine group at a position capable of forming an aluminum cation through electron transfer.

[0033] In one embodiment of the present invention, the vinyl polymer is selected from the group consisting of polyvinyl fluoride, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polytetrafluoroethylene, polyethylene tetrafluoroethylene, polychlorotrifluoroethylene, polyethylene chlorotrifluoroethylene, polyvinyl chloride, and combinations thereof.

[0034] In one embodiment of the present invention, the carbon nanotubes are included in the carbon nanotube dispersion in an amount of 0.05% to 5% by weight based on the total weight of the carbon nanotube dispersion.

[0035] In one embodiment of the present invention, the first dispersant is included in the carbon nanotube dispersion in an amount of 80 to 450 parts by weight based on 100 parts by weight of carbon nanotubes.

[0036] In one embodiment of the present invention, the second dispersant is included in the carbon nanotube dispersion in an amount of 10 to 150 parts by weight based on 100 parts by weight of carbon nanotubes.

[0037] In one embodiment of the present invention, the second dispersant is included in the carbon nanotube dispersion in an amount of 10 to 90 parts by weight based on 100 parts by weight of the first dispersant.

[0038] In one embodiment of the present invention, the carbon nanotube dispersion has an initial viscosity of 10 Pa·s or less when measured at 25°C and 1 rpm.

[0039] In one embodiment of the present invention, the carbon nanotube dispersion has a viscosity increase rate of 0.1% to 18% calculated by the following mathematical formula 1.

[0040]

[0041] [Mathematical Formula 1]

[0042] Viscosity Increase Rate (%) = (BA) / A × 100

[0043]

[0044] Here, A is the initial viscosity (Pa·s) measured at 25°C and 1 rpm, and B is the viscosity (Pa·s) measured at 25°C and 1 rpm after being left for 1 week at 25°C.

[0045] In one embodiment of the present invention, the carbon nanotube is 800 m 2 / g to 5000 m 2 It has a BET specific surface area of ​​ / g.

[0046] In one embodiment of the present invention, the solvent comprises a non-aqueous polar solvent.

[0047]

[0048] According to a second aspect of the present invention,

[0049] The present invention provides a method for preparing the carbon nanotube dispersion described above.

[0050] In one embodiment of the present invention, the manufacturing method comprises: (1) a step of preparing a first mixture by mixing a first dispersant, a second dispersant, and a solvent; (2) a step of preparing a second mixture by adding carbon nanotubes to the first mixture and then mixing; and (3) a step of dispersing the second mixture.

[0051] In one embodiment of the present invention, in step (3), the second mixture is dispersed by treating it 5 to 15 times at a pressure of 5,000 psi to 30,000 psi.

[0052] A carbon nanotube dispersion according to one embodiment of the present invention can effectively disperse carbon nanotubes by using a first dispersant comprising a vinyl polymer containing halogen atoms and a second dispersant comprising a cationic compound having a pyrazine structure. The carbon nanotube dispersion exhibits a stable dispersion effect, as it has a relatively low initial viscosity and does not show a high rate of viscosity increase even after one week.

[0053] All embodiments provided according to the present invention can be achieved by the following description. It should be understood that the following description describes preferred embodiments of the present invention and that the present invention is not necessarily limited thereto.

[0054] Where measurement conditions and methods are not specifically described for the physical properties described in this specification, said physical properties are measured according to measurement conditions and methods generally used by a person skilled in the art.

[0055]

[0056] Carbon nanotube dispersion

[0057]

[0058] According to one aspect of the present invention, the present invention provides a carbon nanotube dispersion comprising carbon nanotubes, a dispersant, and a solvent. The carbon nanotubes possess high conductivity and can be utilized as conductive materials for lithium secondary batteries, but there is a problem in that they are difficult to apply in actual processes due to their difficulty in dispersion. The present invention provides a carbon nanotube dispersion with improved dispersibility of carbon nanotubes by utilizing a first dispersant comprising a vinyl polymer containing halogen atoms and a second dispersant comprising a cationic compound containing a pyrazine structure as dispersants to effectively disperse carbon nanotubes.

[0059] The carbon nanotubes mentioned above may be materials commonly used as conductive materials in the relevant technical field. The carbon nanotubes are secondary structures formed by assembling carbon nanotube units to form a bundle shape, either wholly or partially; the carbon nanotube units are graphite sheets having a cylindrical shape with a nano-sized diameter, and sp 2 It has a bonded structure. At this time, depending on the angle and structure in which the graphite plane is rolled, it may exhibit conductive or semiconductor properties. The monomers of the carbon nanotube can be 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 walls.

[0060] In this specification, "bundle type" refers to a secondary shape in the form of a bundle or rope in which a plurality of carbon nanotube units are arranged in parallel with a substantially identical orientation along the axis along the length direction of the units, or are twisted or entangled after arrangement. Additionally, "non-bundle type" or "entangled type" refers to a shape in which carbon nanotube units are entangled without a specific shape such as a bundle or rope.

[0061] The carbon nanotubes mentioned above have high conductivity, but they exhibit high aggregation due to van der Waals forces generated between the carbon nanotubes. When the conductive material aggregates, it cannot properly form a conductive path, and since a relatively larger amount of conductive material is used, the amount of active material decreases, which can actually degrade the performance of the electrode. Therefore, there have been difficulties in commercializing carbon nanotubes as conductive materials.

[0062] The carbon nanotube dispersion according to the present invention comprises a first dispersant comprising a vinyl polymer containing halogen atoms and a second dispersant comprising a cationic compound having a pyrazine structure, thereby significantly reducing the viscosity of the aqueous carbon nanotube dispersion and suppressing changes over time, so that when applied to an electrode slurry of a lithium secondary battery, high conductivity can be achieved due to the high conductivity of the carbon nanotubes.

[0063] Specifically, when the carbon nanotube dispersion according to the present invention is applied to the manufacture of an electrode slurry, the carbon nanotubes are uniformly positioned between the active materials, so that the microspace between the electrode active materials can be consistently maintained even during the manufacture of an electrode by coating, drying, and rolling the electrode slurry. In addition, since the carbon nanotubes are uniformly distributed without aggregation, a sufficient conductive path can be formed even with a small amount of carbon nanotubes.

[0064] A carbon nanotube dispersion according to one embodiment of the present invention may include one or more of single-wall, double-wall, and multi-wall carbon nanotube units as carbon nanotubes, and specifically may include single-wall carbon nanotubes. Since the single-wall carbon nanotubes have a higher specific surface area compared to double-wall and multi-wall carbon nanotubes, they can be used as a conductive material for lithium secondary batteries to help improve the performance of the battery.

[0065] According to one embodiment of the present invention, the carbon nanotube has a diameter of 0.5 nm to 10 nm. Here, the diameter refers to the largest value among the distances from any point on the outermost side of the circular cross-section of the carbon nanotube to another point. The diameter of the carbon nanotube can be measured by imaging with a scanning electron microscope. Specifically, the diameter of the carbon nanotube is 0.5 nm or more, 0.6 nm or more, 0.7 nm or more, 0.8 nm or more, 0.9 nm or more, 1 nm or more, 10 nm or less, 9 nm or less, 8 nm or less, 7 nm or less, 6 nm or less, 5 nm or less, and may be 0.5 nm to 10 nm, 0.7 nm to 7 nm, or 1 nm to 5 nm. Carbon nanotubes having a diameter within the above range can be effectively dispersed within the electrode of a lithium secondary battery to impart conductivity to the electrode.

[0066] According to one embodiment of the present invention, the carbon nanotube has a length of 1 μm to 20 μm. Here, length refers to the height of the cylindrical carbon nanotube. The length of the carbon nanotube can be measured by photographing it with a scanning electron microscope. Specifically, the length of the carbon nanotube may be 1 μm or more, 2 μm or more, 3 μm or more, 4 μm or more, 5 μm or more, 20 μm or less, 19 μm or less, 18 μm or less, 17 μm or less, 16 μm or less, 15 μm or less, or 1 μm to 20 μm, 3 μm to 18 μm, or 5 μm to 15 μm. Carbon nanotubes having a length within the above range can effectively connect components within the electrode of a lithium secondary battery to impart conductivity to the electrode.

[0067] According to one embodiment of the present invention, the carbon nanotube is 800 m 2 / g to 5,000 m 2 It has a BET specific surface area of ​​g / g. The above BET specific surface area is a specific surface area measured by the BET method; specifically, it is preferably calculated by determining the amount of nitrogen gas adsorbed at a liquid nitrogen temperature (77K) using a BEL SORP-mini II from BEL Japan. Specifically, the BET specific surface area of ​​the carbon nanotube is 800 m² 2 / g or more, 850 m 2 / g or more, 900 m 2 / g or more, 950 m 2 / g or more, 1,000 m 2 / g and 5,000 m 2 / g or less, 4,500 m 2 / g or less, 4,000 m 2 / g or less, 3,500 m 2 / g or less, 3,000 m 2 / g or less, 2,500 m 2 / g or less, 2,000 m 2 / g or less, and 800 m 2 / g to 5,000 m 2 / g, 900 m2 / g to 3,500 m 2 / g, 1,000 m 2 / g to 2,000 m 2 It can be / g. Carbon nanotubes having a BET specific surface area within the above range can effectively contact other components within the electrode of a lithium secondary battery to impart conductivity to the electrode.

[0068] According to one embodiment of the present invention, the carbon nanotubes are included in the carbon nanotube dispersion in an amount of 0.05% to 5% by weight based on the total weight of the carbon nanotube dispersion. Specifically, the content of the carbon nanotubes is 0.05% by weight or more, 0.1% by weight or more, 0.2% by weight or more, 0.3% by weight or more, 0.4% by weight or more, 0.5% by weight or more, 5% by weight or less, 4.5% by weight or less, 4% by weight or less, 3.5% by weight or less, 3% by weight or less, 2.5% by weight or less, 2% by weight or less, 1.5% by weight or less, and may be 0.05% to 5% by weight, 0.1% to 3% by weight, and 0.5% to 1.5% by weight. When carbon nanotubes in the above-described carbon nanotube dispersion are controlled within the aforementioned range, carbon nanotubes can be effectively dispersed, making it easy to apply to lithium secondary batteries.

[0069] A carbon nanotube dispersion according to one embodiment of the present invention includes a solvent as well as a first dispersant and a second dispersant to effectively disperse the carbon nanotubes described above. Since the carbon nanotube dispersion has a relatively high carbon nanotube content, it may be important to appropriately combine components other than carbon nanotubes to effectively disperse the carbon nanotubes without aggregating and to increase their utility value. On the other hand, if the carbon nanotube content is low, the solid content of the electrode slurry produced decreases during the preparation of the electrode slurry, which may cause the electrode slurry to become unnecessarily thick before drying, which may lead to a deterioration in the quality of the electrode after drying.

[0070] The above solvent basically serves to disperse carbon nanotubes, a first dispersant, and a second dispersant. Although carbon nanotubes are used as conductive materials in actual products such as lithium secondary batteries, if the carbon nanotubes are introduced into the electrode slurry in a powder state, the carbon nanotubes aggregate and cannot exhibit proper functionality within the electrode. To solve this problem, carbon nanotubes are pre-dispersed and supplied as a carbon nanotube dispersion.

[0071] The above solvent is not particularly limited as long as it can effectively disperse the carbon nanotube, the first dispersant, and the second dispersant. According to one embodiment of the present invention, the solvent comprises a non-aqueous polar solvent. The non-aqueous polar solvent comprises a nitrogen atom and, specifically, may comprise a functional group selected from the group consisting of cyano groups, amine groups, and amide groups. The above-mentioned non-aqueous polar solvent may be selected from the group consisting of, for example, dimethylformamide (DMF), acetonitrile, dimethylacetamide (DMAc), N,N-dimethylpropionamide (DMPA), N-methylformamide (NMF), formamide, N,N-diethylformamide (DEF), 2-pyrrolidone, N-methyl-2-pyrrolidone (NMP), N-ethyl-2-pyrrolidone (NEP), ε-caprolactam, benzonitrile, propionitrile, butyronitrile, and combinations thereof, but is not necessarily limited thereto.

[0072] The above-mentioned non-aqueous polar solvent may be included in an amount such that the electrode slurry composition can have an appropriate viscosity, taking into account the coating properties of the electrode slurry composition prepared using the carbon nanotube dispersion. Even if the solvent content is not specifically mentioned in this specification, the solvent content may be the result of subtracting the respective amounts of carbon nanotubes, the first dispersant, and the second dispersant from the carbon nanotube dispersion.

[0073] A carbon nanotube dispersion according to one embodiment of the present invention further includes a dispersant because the carbon nanotubes cannot be effectively dispersed using only a solvent. The dispersant may use a single substance, but may also use a combination of two or more substances. According to one embodiment of the present invention, the dispersant includes a first dispersant and a second dispersant. The first dispersant and the second dispersant may be distinguished according to their usage amounts, and the dispersant used in a larger amount among the two dispersants may be the first dispersant.

[0074] According to one embodiment of the present invention, the first dispersant comprises a vinyl polymer containing a halogen atom. The vinyl polymer refers to a polymer that undergoes addition polymerization through double bonds in an ethylene monomer, which is the basic structure. At this time, the ethylene monomer may be substituted with various functional groups, and in one embodiment of the present invention, the vinyl polymer containing a halogen atom may be in a form in which the ethylene polymer is substituted with a halogen, an alkyl halide, an aryl halide, etc. The vinyl polymer may be selected from the group consisting of, for example, polyvinyl fluoride, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polytetrafluoroethylene, polyethylene tetrafluoroethylene, polychlorotrifluoroethylene, polyethylene chlorotrifluoroethylene, polyvinyl chloride, and combinations thereof, but is not necessarily limited thereto.

[0075] The second dispersant described above may be a material capable of producing synergy in the dispersion of carbon nanotubes when used together with the first dispersant described above. According to one embodiment of the present invention, the second dispersant comprises a cationic compound having a pyrazine structure. By using the first dispersant together with the second dispersant, the dispersibility is superior compared to the case where only the first dispersant is used in the conventional manner, resulting in less particle aggregation and a lower sedimentation rate within the slurry composition.

[0076] As the second dispersant comprises a cationic compound containing a pyrazine structure, the second dispersant has a relatively low molecular weight and a small molecular size, which allows it to adsorb onto conductive materials not covered by the first dispersant, thereby exhibiting an additional dispersion effect. The pyrazine structure included in the second dispersant stably generates π-π interactions with carbon nanotubes in local regions, thereby increasing the bonding strength between the dispersant and the carbon nanotubes. Consequently, the content of excess dispersant that was not effectively adsorbed onto the carbon nanotube surface is reduced, preventing aggregation among the remaining dispersants. Furthermore, since the second dispersant contains a cationic compound, it forms electrostatic repulsion between ions within the dispersion, preventing aggregation between adjacent dispersants and enabling the 'carbon nanotube-dispersant' complex to maintain a stable dispersed state within the dispersion.

[0077] The pyrazine included in the above cationic compound is an aromatic ring compound containing two nitrogen atoms and has the following structure.

[0078]

[0079] [Pyrazine structure]

[0080]

[0081]

[0082] A cationic compound according to one embodiment of the present invention has cationic properties as one or more of the two nitrogen atoms included in the pyrazine structure are substituted with a substituent such as an alkyl or aryl. When a substituent is substituted on one nitrogen, it becomes a monovalent cationic compound, and when substituents are substituted on two nitrogen atoms, it can become a divalent cationic compound.

[0083] In defining a cationic compound according to one embodiment of the present invention, terms used in this specification may be defined as follows.

[0084] As used in this specification, the term “Cn1 to Cn2” means that the functional group has n1 to n2 carbon atoms.

[0085] As used in this specification, the term “alkyl” means a straight-chain or branched-chain saturated hydrocarbon containing one radical, and the one radical determines the bonding position as a functional group, and the bonding position is not particularly limited. Examples of the term “alkyl” include, but are not limited to, methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, t-butyl, n-pentyl, i-pentyl, and hexyl.

[0086] As used herein, the term “alkenyl” means a straight-chain or branched-chain hydrocarbon having one or more carbon-carbon double bonds and containing one radical, wherein the one radical determines the bonding site as a functional group, and the bonding site is not particularly limited. Examples of the term “alkenyl” include, but are not limited to, ethenyl and propenyl.

[0087] As used herein, the term “halogen” means fluorine (F), chlorine (Cl), bromine (Br), or iodine (I).

[0088] As used in this specification, the term “n1- to n2-membered” means that the sum of the number of carbon atoms and the number of heteroatoms is n1 to n2. While heteroatoms broadly refer to elements other than carbon, in this specification, the term “n1- to n2-membered” is used before a cyclic functional group to refer to the number of elements constituting the ring.

[0089] As used in this specification, the term “aryl” refers to an aromatic cyclic hydrocarbon having one or more rings and containing one radical, wherein the one radical determines the bonding position as a functional group, and the bonding position is not particularly limited. Examples of the term “aryl” include, but are not necessarily limited to, phenyl and naphthyl. As used in this specification, the term “aryl ring” is also used to distinguish aromatic cyclic hydrocarbons that do not contain a separate radical.

[0090] As used herein, the term “heteroaryl” refers to an aromatic cyclic hydrocarbon comprising one radical, having one or more rings, and having one or more heteroatoms within the rings; the one radical determines the bonding position as a functional group, and the bonding position is not particularly limited. The heteroatom is capable of forming a ring, and examples include O, N, S, etc. Examples of the term “heteroaryl” include, but are not necessarily limited to, pyrrolyl, furanyl, and pyrazinyl. As used herein, the term “heteroaryl ring” is also used to distinguish aromatic cyclic hydrocarbons having heteroatoms without containing a separate radical.

[0091] The term “alkoxy” as used in this specification refers to a functional group of the -ORa form in which Ra is the alkyl described above. Examples of the term “alkoxy” include, but are not limited to, methoxy, difluoromethoxy, trifluoromethoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, and t-butoxy.

[0092] As used in this specification, the term “hydroxy” refers to a functional group of the -OH form.

[0093] As used in this specification, the term “sulfonate” refers to a functional group of the -SO3H form.

[0094] As used in this specification, the term “cyano” refers to a functional group of the -CN form.

[0095] The term “amine” as used in this specification refers to a functional group of the form including -NH2, -N(R)H, -N(R)2, -L-NH2, -LN(R)H, and -LN(R)2. Here, R may be alkyl, alkenyl, aryl, heteroaryl, etc., and L may be alkylene, alkenylene, etc. The “amine” may also be named by separating it into “amino” based on the nitrogen. For example, -N(CH3)2 may be named dimethylamino.

[0096] According to one embodiment of the present invention, the cationic compound is a compound represented by the following chemical formula 1 or 2.

[0097]

[0098] [Chemical Formula 1]

[0099]

[0100]

[0101] [Chemical Formula 2]

[0102]

[0103]

[0104] In the above chemical formula 1 or 2,

[0105] Ring A and Ring B are the same or different from each other and are each independently substituted or unsubstituted C6 to C20 aryl rings, or substituted or unsubstituted 6 to 20 heteroaryl rings. Specifically, Ring A and Ring B are the same or different from each other and are each independently substituted or unsubstituted C6 to C14 or C6 to C10 aryl rings, or substituted or unsubstituted 6 to 14 or 6 to 10 heteroaryl rings. More specifically, Ring A and Ring B are the same or different from each other and are each independently substituted or unsubstituted benzene, or substituted or unsubstituted naphthalene.

[0106] R1 is selected from the group consisting of hydrogen, a substituted or unsubstituted C1 to C10 alkyl group, a substituted or unsubstituted C1 to C10 alkenyl group, a substituted or unsubstituted C6 to C20 aryl group, and a substituted or unsubstituted 6 to 20 heteroaryl group. Specifically, R1 is selected from the group consisting of a substituted or unsubstituted C1 to C8 or C1 to C4 alkyl group, a substituted or unsubstituted C1 to C8 or C1 to C4 alkenyl group, a substituted or unsubstituted C6 to C14 or C6 to C10 aryl group, or a substituted or unsubstituted 6 to 14 or 6 to 10 heteroaryl group. More specifically, R1 is a substituted or unsubstituted benzene or a substituted or unsubstituted naphthalene.

[0107] R2 and R3 are the same or different from each other and are each independently selected from the group consisting of hydrogen, halogen, cyano group, sulfonate group, hydroxyl group, amine group, substituted or unsubstituted C1 to C10 alkyl group, substituted or unsubstituted C1 to C10 alkenyl group, substituted or unsubstituted C1 to C10 alkoxy group, substituted or unsubstituted C6 to C20 aryl group, and substituted or unsubstituted 6 to 20 heteroaryl group. Specifically, R2 and R3 are the same or different from each other and are each independently selected from the group consisting of hydrogen, halogen, cyano group, sulfonate group, hydroxyl group, amine group, substituted or unsubstituted C1 to C8 or C1 to C4 alkyl group, substituted or unsubstituted C1 to C8 or C1 to C4 alkenyl group, and substituted or unsubstituted C1 to C8 or C1 to C4 alkoxy group. More specifically, R2 and R3 are the same or different from each other and are each independently selected from the group consisting of hydrogen, C1 to C4 alkyl groups, amino groups, C1 to C4 alkylamino groups, and C1 to C4 dialkylamino groups.

[0108] According to one embodiment of the present invention, the cationic compound is a compound represented by the following chemical formula 3.

[0109]

[0110] [Chemical Formula 3]

[0111]

[0112]

[0113] In the above chemical formula 3,

[0114] R4 can be defined as R1 in the above chemical formulas 1 and 2, and R5 to R 12 It can be defined as R2 and R3 in the above chemical formulas 1 and 2.

[0115] In the above chemical formulas 1 to 3, ring A and ring B and R1 to R 12 In defining the term, “substitution” means that the structure can be easily modified to the extent that it is understandable to a person skilled in the art by substituting it with a halogen, hydroxy, cyano, nitro, amino, C1 to C4 alkyl, C1 to C4 alkenyl, etc.

[0116] The above-mentioned cationic compound can be modified into various forms through electron transfer. In this case, if the cation within the pyrazine structure can easily move to another location through electron transfer, the functionality of the cationic compound in carbon nanotube dispersion can be further enhanced. According to one embodiment of the present invention, the cationic compound comprises at least one amine group at a position capable of forming an iminium cation through electron transfer. For example, Basic Red 2, a cationic compound according to one embodiment of the present invention, comprises two amine groups at a position capable of forming an iminium cation through electron transfer.

[0117]

[0118] [Example of electron transfer in Basic Red 2 structure]

[0119]

[0120]

[0121] When the above-described dispersant is used in an appropriate ratio, it can effectively disperse carbon nanotubes within a carbon nanotube dispersion while increasing the carbon nanotube content. According to one embodiment of the present invention, the dispersant is included in the carbon nanotube dispersion in an amount of 100 to 500 parts by weight based on 100 parts by weight of carbon nanotubes. Here, the content of the dispersant refers to the sum of the content of the first dispersant and the content of the second dispersant. Specifically, the content of the dispersant is 100 parts by weight or more, 110 parts by weight or more, 120 parts by weight or more, 130 parts by weight or more, 140 parts by weight or more, 150 parts by weight or more, 500 parts by weight or less, 400 parts by weight or less, 300 parts by weight or less, 290 parts by weight or less, 280 parts by weight or less, 270 parts by weight or less, 260 parts by weight or less, 250 parts by weight or less, and may be 100 parts by weight to 500 parts by weight, 130 parts by weight to 400 parts by weight, and 150 parts by weight to 300 parts by weight. By adjusting the content of the dispersant to the above-described ratio, carbon nanotubes can be effectively dispersed without excessively increasing the content of the dispersant.

[0122] According to one embodiment of the present invention, the first dispersant is included in the carbon nanotube dispersion in an amount of 80 to 450 parts by weight based on 100 parts by weight of carbon nanotubes. Specifically, the content of the first dispersant is 80 parts by weight or more, 90 parts by weight or more, 100 parts by weight or more, 110 parts by weight or more, 120 parts by weight or more, 130 parts by weight or more, 140 parts by weight or more, 150 parts by weight or more, 450 parts by weight or less, 400 parts by weight or less, 350 parts by weight or less, 300 parts by weight or less, 250 parts by weight or less, 200 parts by weight or less, and may be 80 to 450 parts by weight, 100 to 300 parts by weight, and 150 to 250 parts by weight. By adjusting the content of the first dispersant to the ratio described above, the functionality of the first dispersant can be effectively expressed when appropriately combined with the second dispersant.

[0123] According to one embodiment of the present invention, the second dispersant is included in the carbon nanotube dispersion in an amount of 10 to 150 parts by weight based on 100 parts by weight of carbon nanotubes. Specifically, the content of the first dispersant is 10 parts by weight or more, 20 parts by weight or more, 30 parts by weight or more, 40 parts by weight or more, 50 parts by weight or more, 150 parts by weight or less, 140 parts by weight or less, 130 parts by weight or less, 120 parts by weight or less, 110 parts by weight or less, 100 parts by weight or less, 10 to 150 parts by weight, 30 to 130 parts by weight, and 50 to 100 parts by weight. By adjusting the content of the second dispersant to the above-described ratio, the functionality of the second dispersant can be effectively expressed when appropriately combined with the first dispersant.

[0124] According to one embodiment of the present invention, the second dispersant is included in the carbon nanotube dispersion in an amount of 10 to 90 parts by weight based on 100 parts by weight of the first dispersant. As described above, since the naming of the first dispersant and the second dispersant is based on the content of the dispersant, the content of the first dispersant can basically be equal to or greater than the content of the second dispersant. Specifically, the content of the second dispersant may be 10 parts by weight or more, 15 parts by weight or more, 20 parts by weight or more, 25 parts by weight or more, 90 parts by weight or less, 80 parts by weight or less, 70 parts by weight or less, 60 parts by weight or less, 50 parts by weight or less, 10 to 90 parts by weight, 15 to 70 parts by weight, and 20 to 50 parts by weight. When the above-mentioned first dispersant and second dispersant are used in combination at the corresponding ratio, carbon nanotubes can be effectively dispersed relative to the same total amount of dispersant.

[0125] The carbon nanotube dispersion according to the present invention exhibits excellent dispersibility for carbon nanotubes. This dispersibility can be confirmed through the viscosity of the carbon nanotube dispersion. According to one embodiment of the present invention, the carbon nanotube dispersion has an initial viscosity of 10,000 Pa·s or less at 25°C and 1 rpm. Here, the initial viscosity refers to the value obtained by measuring the viscosity immediately after the dispersion of the mixture is completed. The specific method for measuring viscosity may follow the method described in the experimental examples below. The initial viscosity may be 10,000 Pa·s or less, 9,500 Pa·s or less, 9,000 Pa·s or less, or 8,500 Pa·s or less. Since there is a limit to how much viscosity can be lowered while including a certain amount of carbon nanotubes in the carbon nanotube dispersion, the lower limit may not be particularly important. The lower limit of the above initial viscosity may be, for example, 3.000 Pa·s or more, 3.500 Pa·s or more, 4.000 Pa·s or more, 4.500 Pa·s or more, or 5.000 Pa·s or more.

[0126] According to one embodiment of the present invention, the carbon nanotube dispersion has a viscosity increase rate of 0.1% to 18%. The viscosity increase rate is calculated by the following Equation 1.

[0127]

[0128] [Mathematical Formula 1]

[0129] Viscosity Increase Rate (%) = (BA) / A × 100

[0130]

[0131] Here, A is the initial viscosity (Pa·s) measured at 25°C and 1 rpm, and B is the viscosity (Pa·s) measured at 25°C and 1 rpm after being left at 25°C for one week. Specifically, the viscosity increase rate may be 0.1% or more, 0.5% or more, 1.0% or more, and 18% or less, 17% or less, 16% or less, or 15% or less.

[0132] As described above, the carbon nanotube dispersion according to one embodiment of the present invention not only has a low initial viscosity but also has a low rate of change in viscosity even after storage for a certain period of time, thus possessing stable dispersibility.

[0133]

[0134] Method for preparing carbon nanotube dispersion

[0135]

[0136] According to one aspect of the present invention, the present invention provides a method for preparing a carbon nanotube dispersion as described above. A method for preparing a carbon nanotube dispersion according to one embodiment of the present invention comprises: (1) a step of preparing a first mixture by mixing a first dispersant, a second dispersant, and a solvent; (2) a step of preparing a second mixture by adding carbon nanotubes to the first mixture and then mixing; and (3) a step of dispersing the second mixture.

[0137] In steps (1) and (2) above, mixing can be performed under temperature conditions where physical properties, such as the viscosity of the mixture, do not change due to the evaporation of the solvent. For example, it can be performed at a temperature of 50°C or lower, specifically between 5°C and 50°C. The mixing can be performed by an impeller, milling, etc., and the milling can be performed by a ball mill, bead mill, disc mill, or basket mill, etc., specifically by a disc mill.

[0138] Since carbon nanotubes are added in step (2) above, mixing in step (2) can be performed under harsher conditions than mixing in step (1). When milling with the disc mill, the size of the beads can be appropriately determined according to the type and amount of carbon nanotubes and the type of dispersant, and specifically, the diameter of the beads can be 0.1 mm to 5 mm, more specifically 0.5 mm to 4 mm. Also, the bead milling process can be performed at a speed of 1,000 rpm to 10,000 rpm, and more specifically at a speed of 2,000 rpm to 9,000 rpm. The mixing process can be performed according to the degree of dispersion of the carbon nanotube dispersion, and specifically, can be performed for 30 minutes to 120 minutes, and more specifically, for 60 minutes to 90 minutes.

[0139] In step (3) above, the second mixture may be carried out by a high-pressure homogenizer (high-pressure disperser). Dispersion by the high-pressure homogenizer is achieved, for example, by pressurizing the mixture with a plunger pump of the high-pressure homogenizer and pushing it through the gap of a homogenizing valve, by forces such as cavitation, shear, impact, and explosion when passing through said gap. According to one embodiment of the present invention, in step (3) above, the second mixture is dispersed by processing it 5 to 15 times, 6 to 14 times, or 7 to 13 times at a pressure of 5,000 psi to 30,000 psi, 10,000 psi to 30,000 psi, or 15,000 psi to 25,000 psi.

[0140]

[0141] Electrode Slurry Composition

[0142]

[0143] According to one aspect of the present invention, the present invention provides an electrode slurry composition for a lithium secondary battery comprising the carbon nanotube dispersion and the electrode active material. The electrode slurry composition for a lithium secondary battery may be a positive electrode slurry composition or a negative electrode slurry composition, specifically a positive electrode slurry composition. The electrode slurry composition for a lithium secondary battery may comprise a carbon nanotube dispersion, a positive electrode active material or a negative electrode active material as the electrode active material, a binder, a solvent and / or other additives as needed.

[0144] As the above-mentioned cathode active material, cathode active materials well known in the relevant 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 above-mentioned cathode active material, LiCoO2, LiNiO2, LiMn2O4, LiCoPO4, LiFePO4, and LiNi a Mn b Co c O 2　 (here, 0 <a,b,c<1) 등이 사용될 수 있으나, 이에 한정되는 것은 아니다.

[0145] The above-mentioned negative electrode active material includes natural graphite, artificial graphite, carbonaceous material; lithium-containing titanium composite oxide (LTO); metals (Me) such as Si, Sn, Li, Zn, Mg, Cd, Ce, Ni, or Fe; alloys composed of the above-mentioned metals (Me); and oxides (MeO) of the above-mentioned metals (Me). x Examples include one or more cathode active materials selected from the group consisting of metals (Me) and composites of carbon. The cathode active material may be included in an amount of 60 to 98 weight%, more preferably 70 to 98 weight%, based on the total weight of the solids excluding the solvent in the cathode slurry.

[0146] The above-mentioned binder is a component that assists in the bonding of the active material and the conductive material, as well as in the bonding to the current collector, and is typically added in an amount of 1 to 30 weight percent based on the total weight of the mixture containing the electrode active material. Examples of such binders include polyvinylidene fluoride, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene-butadiene rubber, fluororubber, and various copolymers. The carbon nanotube dispersion according to one embodiment of the present invention has excellent compatibility with the above-mentioned binder.

[0147] The above solvents include organic solvents such as N-methylpyrrolidone (NMP), dimethylformamide (DMF), acetone, and dimethylacetamide, or water, and these solvents may be used alone or in a mixture of two or more. The amount of solvent used is sufficient if it is sufficient to dissolve and disperse the electrode active material, binder, and conductive material, taking into account the coating thickness of the slurry and the manufacturing yield.

[0148] The above viscosity modifier may be carboxymethylcellulose or polyacrylic acid, and the viscosity of the electrode slurry can be controlled by adding it to facilitate the preparation of the electrode slurry and the coating process on the electrode current collector.

[0149] The above-mentioned filler is optionally used as a component to inhibit 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-based polymers such as polyethylene and polypropylene; and fibrous materials such as glass fibers and carbon fibers are used.

[0150] If the above electrode slurry composition is a composition of an anode slurry for forming an anode, the anode can be manufactured by applying the above anode slurry composition onto an anode current collector, followed by drying and rolling. Alternatively, the anode can be manufactured by casting the above anode slurry onto a separate support and then laminating the film obtained by peeling it off from the support onto the above anode current collector.

[0151] The thickness of the anode active material layer formed by the anode slurry may vary depending on the loading amount, loading speed, etc., for applying the anode slurry.

[0152] The above positive current collector generally has a thickness of 3 μm to 500 μm. Such a positive current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery. For example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. may be used. In addition, fine irregularities may be formed on the surface of the positive current collector to strengthen the bonding strength of the positive active material, and it may be used in various forms such as films, sheets, foils, nets, porous bodies, foams, and nonwoven fabrics.

[0153] In the case where the above electrode slurry composition is a composition of a cathode slurry for forming a cathode, the cathode can be manufactured by applying the composition of the cathode slurry onto a cathode current collector, followed by drying and rolling. Alternatively, the cathode can be manufactured by casting the cathode slurry onto a separate support and then laminating the film obtained by peeling it off from the support onto the cathode current collector.

[0154] The thickness of the cathode active material layer formed by the above cathode slurry may vary depending on the loading amount, loading speed, etc., for applying the cathode slurry.

[0155] The above-mentioned negative current collector generally has a thickness of 3 μm to 500 μm. Such a negative current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, and for example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface treated with carbon, nickel, titanium, silver, etc., or aluminum-cadmium alloy may be used. In addition, similar to the negative current collector, fine irregularities may be formed on the surface to strengthen the bonding strength of the negative active material, and it may be used in various forms such as films, sheets, foils, nets, porous bodies, foams, and nonwoven fabrics.

[0156]

[0157] Lithium secondary battery

[0158]

[0159] According to one aspect of the present invention, the present invention provides a lithium secondary battery comprising a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and an electrolyte, utilizing the carbon nanotube dispersion described above. Since the positive electrode and the negative electrode are identical to those described above, a detailed description is omitted.

[0160] The above separator separates the negative electrode and the positive electrode and provides a pathway for the movement of lithium ions. It can be used without special restrictions as long as it is commonly used as a separator in a lithium secondary battery, and it is particularly desirable that it has low resistance to the movement of electrolyte ions and excellent electrolyte moisture retention capacity. Specifically, a porous polymer film, such as a porous polymer film made of a polyolefin-based polymer like ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, and ethylene / methacrylate copolymer, or a laminated structure of two or more layers thereof may be used. In addition, a conventional porous nonwoven fabric, such as a nonwoven fabric made of high-melting-point glass fiber or polyethylene terephthalate fiber, may be used. To ensure heat resistance or mechanical strength, a coated separator containing ceramic components or polymer materials may be used, and it may optionally be used in a single-layer or multi-layer structure.

[0161] The above electrolyte may be an organic liquid electrolyte, an inorganic liquid electrolyte, a solid polymer electrolyte, a gel-type polymer electrolyte, a solid inorganic electrolyte, a molten inorganic electrolyte, etc., which can be used in the manufacture of a lithium secondary battery, but is not limited to these. Specifically, the above electrolyte may include an organic solvent and a lithium salt.

[0162] The above organic solvent may be used without special restrictions as long as it can serve as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, the above organic solvent may include ester-based solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether-based solvents such as dibutyl ether or tetrahydrofuran; ketone-based solvents such as cyclohexanone; and aromatic hydrocarbon-based solvents such as benzene and fluorobenzene. Carbonate-based solvents such as dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC); alcohol-based solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (where R is a straight-chain, branched, or cyclic hydrocarbon group having C2 to C20 structures and may include a double bond, a directional ring, or an ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes may be used. Among these, a carbonate-based solvent is preferred, and a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate, etc.) having high ionic conductivity and high dielectric constant that can improve the charge / discharge performance of the battery, and a low-viscosity linear carbonate-based compound (e.g., ethylmethyl carbonate, dimethyl carbonate or diethyl carbonate, etc.) is more preferred.In this case, using a mixture of cyclic carbonate and chain carbonate in a volume ratio of about 1:1 to about 1:9 can result in excellent performance of the electrolyte.

[0163] The above lithium salt can be used without special restrictions as long as it is a 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 above lithium salt may be used within the range of 0.1M to 2.0M. When the concentration of the lithium salt falls within the above range, the electrolyte has appropriate conductivity and viscosity, so it can exhibit excellent electrolyte performance and allow lithium ions to move effectively.

[0164] In addition to the above electrolyte components, the above electrolyte may further include one or more additives for the purpose of improving the lifespan characteristics of the battery, suppressing the decrease in battery capacity, and improving the discharge capacity of the battery, such as, for example, haloalkylene carbonate-based compounds such as difluoroethylene carbonate, pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylene diamine, n-glyme, triamide hexaphosphate, nitrobenzene derivative, sulfur, quinone imine dye, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxyethanol, or aluminum trichloride. In this case, the additive may be included in an amount of 0.1% to 5% by weight based on the total weight of the electrolyte.

[0165] A lithium secondary battery comprising an electrode manufactured using a carbon nanotube dispersion according to the present invention, specifically a lithium secondary battery comprising a negative electrode manufactured using a carbon nanotube dispersion, has carbon nanotubes uniformly dispersed within the negative electrode and can stably exhibit excellent discharge capacity and output characteristics by reducing the content of conductive materials such as conventional carbon black compared to cases containing such materials. As a result, it can be usefully applied in fields such as portable devices like mobile phones, laptop computers, and digital cameras, and electric vehicles such as hybrid electric vehicles (HEVs).

[0166] Accordingly, according to another embodiment of the present invention, the lithium secondary battery, the battery module including the lithium secondary battery as a unit cell, and the battery pack including the same may be provided.

[0167] The above battery module or battery pack can be used as a power source for one or more medium-to-large devices, including a power tool; an electric vehicle (EV), a hybrid electric vehicle, and a plug-in hybrid electric vehicle (PHEV); or a power storage system.

[0168]

[0169] Hereinafter, preferred embodiments are presented to aid in understanding the present invention, but the following embodiments are provided only to facilitate a better understanding of the present invention and do not limit the present invention thereto.

[0170] Example (Preparation of carbon nanotube dispersion)

[0171]

[0172] Example 1

[0173] A carbon nanotube dispersion with a total weight of 500g was prepared by the following method. A first mixture was prepared by mixing polyvinylidene fluoride (PVdF) (Solvay, Solef 5130) as the first dispersant, Basic red 2 (Sigma-Aldrich) as the second dispersant, and N-methyl-2-pyrrolidone (Daejeong Chemical Co.) as the solvent. The first mixture was prepared by installing an impeller and a container in a dissolution tank (VMA-Getzmann CV4-PLUS), adding the dispersant and solvent, and stirring at 400 rpm for 10 minutes. Single-walled carbon nanotubes (SWCNT, BET specific surface area: 1,160 m² / g, diameter: 1–2 nm, length: 5 µm or more, OCSiAl TUBALL) were added to the prepared first mixture, and a second mixture was prepared by stirring at 8,000 rpm for 60 minutes. The prepared second mixture was homogeneously dispersed 10 times at a pressure of 20,000 psi using a high-pressure disperser (Micronox PICOMAX product) to prepare a total of 500 g of carbon nanotube dispersion. The prepared carbon nanotube dispersion contained 0.8 wt% single-walled carbon nanotubes, 1.2 wt% polyvinylidene fluoride, and 0.4 wt% Basic red 2, with the remainder consisting of N-methyl-2-pyrrolidone as the solvent.

[0174]

[0175] Example 2

[0176] A total of 500g of carbon nanotube dispersion was prepared in the same manner as in Example 1, except that 1.2 wt% of polyvinylidene fluoride-hexafluoropropylene copolymer (PVdF-co-HFP) was included as the first dispersant in the prepared carbon nanotube dispersion.

[0177]

[0178] Example 3

[0179] A total of 500g of carbon nanotube dispersion was prepared in the same manner as in Example 1, except that 0.6 wt% of Basic red 2 was included as the second dispersant in the prepared carbon nanotube dispersion.

[0180]

[0181] Example 4

[0182] A total of 500g of carbon nanotube dispersion was prepared in the same manner as in Example 1, except that 1.6% by weight of polyvinylidene fluoride was included as the first dispersant in the prepared carbon nanotube dispersion.

[0183]

[0184] Example 5

[0185] A total of 500g of carbon nanotube dispersion was prepared in the same manner as in Example 1, except that 0.4 wt% of Basic red 5 (Sigma-Aldrich) was included as the second dispersant in the prepared carbon nanotube dispersion.

[0186]

[0187] Comparative Example 1

[0188] A total of 500g of carbon nanotube dispersion was prepared in the same manner as in Example 1, except that the prepared carbon nanotube dispersion contained 0.6 wt% of single-walled carbon nanotubes, contained 3 wt% of polyvinylidene fluoride-hexafluoropropylene copolymer as the first dispersant, and did not contain the second dispersant.

[0189]

[0190] Comparative Example 2

[0191] A total of 500g of carbon nanotube dispersion was prepared in the same manner as in Example 1, except that the prepared carbon nanotube dispersion contained 0.6 wt% of single-walled carbon nanotubes, 2 wt% of polyvinylidene fluoride-hexafluoropropylene copolymer as a first dispersant, and 1 wt% of polyvinylpyrrolidone (PVP) as a second dispersant.

[0192]

[0193] Comparative Example 3

[0194] A total of 500g of carbon nanotube dispersion was prepared in the same manner as in Example 1, except that the prepared carbon nanotube dispersion contained 1.5 wt% of polyvinylidene fluoride as the first dispersant and 0.1 wt% of Basic red 2 as the second dispersant.

[0195]

[0196] Comparative Example 4

[0197] A total of 500g of carbon nanotube dispersion was prepared in the same manner as in Example 1, except that the prepared carbon nanotube dispersion contained 0.8 wt% of polyvinylidene fluoride as the first dispersant and 0.8 wt% of Basic red 2 as the second dispersant.

[0198]

[0199] Comparative Example 5

[0200] A total of 500g of carbon nanotube dispersion was prepared in the same manner as in Example 1, except that the first dispersant was not included in the prepared carbon nanotube dispersion and 4% by weight of Basic red 2 was included as the second dispersant.

[0201]

[0202] Experimental Example

[0203]

[0204] Experimental Example 1 (Viscosity Evaluation)

[0205] The initial viscosity of the carbon nanotube dispersions prepared according to Examples 1 to 5 and Comparative Examples 1 to 5 was measured, and the viscosity was measured after storage for one week, and the results are shown in Tables 1 and 2 below. The viscosity was measured using a viscometer (TOKISANGYO viscometer TV-25) at a temperature of 25°C with Rotor No. 1 at 1 rpm for 3 minutes. In Table 1 below, the viscosity increase rate is calculated by the following Equation 1.

[0206]

[0207] [Mathematical Formula 1]

[0208] Viscosity Increase Rate (%) = (BA) / A × 100

[0209]

[0210] Here, A is the initial viscosity (Pa·s) measured at 25°C and 1 rpm, and B is the viscosity (Pa·s) measured at 25°C and 1 rpm after being left for 1 week at 25°C.

[0211]

[0212] Example 1 Example 2 Example 3 Example 4 Example 5 Carbon Nanotubes (WHC) 0.8 SWCNT 0.8 SWCNT 0.8 SWCNT 0.8 SWCNT 0.8 First Dispersant (WHC) 1.2 PVdF-co-HFP 1.2 PVdF 1.2 PVdF 1.6 PVdF 1.2 Second Dispersant (WHC) 20.4 Basic red 20.4 Basic red 20.6 Basic red 20.4 Basic red 50.4 Initial Viscosity (25°C, Pa·s) 6.960 6.400 7.900 8.300 7.300 Viscosity after 1 week (25°C, Pa·s) 7.900 7.200 8.800 9.100 8.500 Viscosity Growth rate (%) 1413111016

[0213]

[0214] Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Carbon Nanotubes (WH%) SWCNT 0.6 SWCNT 0.6 SWCNT 0.8 SWCNT 0.8 SWCNT 0.8 First Dispersant (WH%) PVdF-co-HFP 3 PVdF-co-HFP 2 PVdF 1.5 PVdF 0.8 Second Dispersant (WH%) PVP 1 Basic red 20.1 Basic red 20.8 Basic red 24 Initial Viscosity (25℃, Pa·s) 11.000 10.900 13.700 14.300 10.200 Viscosity After 1 Week (25℃, Pa·s) 16.400 13.000 18.200 19.300 17.800 Viscosity Growth Rate (%) 49 19 33 35 75

[0215]

[0216] According to Tables 1 and 2 above, when dispersing carbon nanotubes, polyvinylidene fluoride and polyvinylidene fluoride-hexafluoropropylene copolymer (first dispersant), which are vinyl polymers containing halogen atoms, can easily disperse carbon nanotubes when used in combination with Basic red 2 or Basic red 5 (second dispersant), which are cationic compounds containing a pyrazine structure. Referring to Examples 1 to 4 and Comparative Examples 3 and 4, when combining, if the second dispersant is adjusted to 10 to 90 parts by weight based on 100 parts by weight of the first dispersant, the dispersion effect of carbon nanotubes may be superior.

[0217]

[0218] All simple variations or modifications of the present invention fall within the scope of the present invention, and the specific scope of protection of the present invention will be clarified by the appended claims.

Claims

1. Comprising carbon nanotubes, a dispersant, and a solvent, The above dispersant is, A first dispersant comprising a vinyl polymer containing halogen atoms; and A carbon nanotube dispersion comprising a second dispersant comprising a cationic compound having a pyrazine structure.

2. In Claim 1, A carbon nanotube dispersion characterized in that the above-mentioned cationic compound is a compound represented by the following chemical formula 1 or 2: [Chemical Formula 1] [Chemical Formula 2] In the above chemical formula 1 or 2, Ring A and ring B are the same or different from each other and are each independently substituted or unsubstituted C6 to C20 aryl rings, or substituted or unsubstituted 6 to 20 heteroaryl rings, and R1 is selected from the group consisting of hydrogen, a substituted or unsubstituted C1 to C10 alkyl group, a substituted or unsubstituted C1 to C10 alkenyl group, a substituted or unsubstituted C6 to C20 aryl group, and a substituted or unsubstituted 6 to 20 heteroaryl group. R2 and R3 are the same or different from each other and are each independently selected from the group consisting of hydrogen, halogen, cyano group, sulfonate group, hydroxyl group, amine group, substituted or unsubstituted C1 to C10 alkyl group, substituted or unsubstituted C1 to C10 alkenyl group, substituted or unsubstituted C1 to C10 alkoxy group, substituted or unsubstituted C6 to C20 aryl group, and substituted or unsubstituted 6 to 20 heteroaryl group.

3. In Claim 1, A carbon nanotube dispersion characterized in that the above-mentioned cationic compound is a compound represented by the following chemical formula 3: [Chemical Formula 3] In the above chemical formula 3, R4 is selected from the group consisting of hydrogen, a substituted or unsubstituted C1 to C10 alkyl group, a substituted or unsubstituted C1 to C10 alkenyl group, a substituted or unsubstituted C6 to C20 aryl group, and a substituted or unsubstituted 6 to 20 heteroaryl group, and R5 to R 12 The groups are the same or different from each other and are each independently selected from the group consisting of hydrogen, halogen, cyano group, sulfonate group, hydroxyl group, amine group, substituted or unsubstituted C1 to C10 alkyl group, substituted or unsubstituted C1 to C10 alkenyl group, substituted or unsubstituted C1 to C10 alkoxy group, substituted or unsubstituted C6 to C20 aryl group, and substituted or unsubstituted 6 to 20 heteroaryl group.

4. In Claim 1, A carbon nanotube dispersion characterized by the above-mentioned cationic compound containing at least one amine group at a position capable of forming an aluminum cation through electron transfer.

5. In Claim 1, A carbon nanotube dispersion characterized in that the vinyl polymer is selected from the group consisting of polyvinyl fluoride, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polytetrafluoroethylene, polyethylene tetrafluoroethylene, polychlorotrifluoroethylene, polyethylene chlorotrifluoroethylene, polyvinyl chloride, and combinations thereof.

6. In Claim 1, A carbon nanotube dispersion characterized in that the carbon nanotubes are included in the carbon nanotube dispersion in an amount of 0.05% to 5% by weight based on the total weight of the carbon nanotube dispersion.

7. In Claim 1, A carbon nanotube dispersion characterized in that the first dispersant is included in an amount of 80 to 450 parts by weight based on 100 parts by weight of carbon nanotubes in the carbon nanotube dispersion.

8. In Claim 1, A carbon nanotube dispersion characterized in that the second dispersant is included in an amount of 10 to 150 parts by weight based on 100 parts by weight of carbon nanotubes in the carbon nanotube dispersion.

9. In Claim 1, A carbon nanotube dispersion characterized in that the second dispersant is included in the carbon nanotube dispersion in an amount of 10 to 90 parts by weight based on 100 parts by weight of the first dispersant.

10. In Claim 1, The carbon nanotube dispersion is characterized by having an initial viscosity of 10 Pa·s or less measured at 25℃ and 1 rpm.

11. In Claim 10, The carbon nanotube dispersion above is characterized by having a viscosity increase rate of 0.1% to 18% calculated by the following mathematical formula 1: [Mathematical Formula 1] Viscosity increase rate (%) = (BA) / A × 100 Here, A is the initial viscosity (Pa·s) measured at 25°C and 1 rpm, and B is the viscosity (Pa·s) measured at 25°C and 1 rpm after being left for 1 week at 25°C.

12. In Claim 1, The above carbon nanotube is 800 m 2 / g to 5000 m 2 A carbon nanotube dispersion characterized by having a BET specific surface area of ​​ / g.

13. In Claim 1, A carbon nanotube dispersion characterized by the above solvent comprising a non-aqueous polar solvent.

14. A method for preparing a carbon nanotube dispersion according to Claim 1, The above manufacturing method is, (1) A step of preparing a first mixture by mixing a first dispersant, a second dispersant, and a solvent; (2) A step of preparing a second mixture by adding carbon nanotubes to the first mixture and then mixing; and (3) A method for preparing a carbon nanotube dispersion comprising the step of dispersing the second mixture.

15. In Claim 14, A method for preparing a carbon nanotube dispersion, characterized in that, in step (3) above, the second mixture is dispersed by treating it 5 to 15 times at a pressure of 5,000 psi to 30,000 psi.

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