Method for functionalizing carbon nanotubes, self-dispersible functionalized carbon nanotubes, and battery electrode material comprising same

Abstract

The disclosed method for functionalizing carbon nanotubes comprises a step of oxidizing the carbon nanotubes by providing potassium monopersulfate and magnesium sulfate to the carbon nanotubes. Accordingly, the present invention functionalizes the carbon nanotubes while minimizing damage or cutting, thereby preventing degradation of electrical properties of the carbon nanotubes during the functionalization process. In addition, this method can provide self-dispersible carbon nanotubes.

Description

Functionalization method of carbon nanotubes, carbon nanotubes functionalized to have self-dispersibility, and electrode material for a battery including the same

[0001] The present invention relates to carbon nanotubes. More specifically, the present invention relates to a method for functionalizing carbon nanotubes, carbon nanotubes functionalized to have self-dispersibility, and electrode materials for batteries containing the same.

[0002] Carbon nanotubes (CNTs) are materials in which carbon atoms are linked by sp2 bonds to form a hexagonal honeycomb-shaped planar structure, and are formed into a tube shape overall. They are highly anisotropic and have high electrical conductivity comparable to metals due to the overlap of π electrons present on the outer wall.

[0003] Carbon nanotubes are being studied for application in various fields due to their excellent physical and electrical properties. However, the strong van der Waals forces between carbon nanotube molecules cause them to readily agglomerate. Consequently, their solubility in water and organic solvents is low, and this low solubility and dispersibility limit their application.

[0004] To improve the dispersibility of carbon nanotubes, functionalizing them with substances such as strong acids is known. However, this method can cause structural damage to carbon nanotubes, reducing electrical properties such as conductivity. Furthermore, shortened carbon nanotubes are more prone to agglomeration.

[0005] When carbon nanotubes are dispersed in polar solvents using a dispersant, the residual dispersant after solvent removal can degrade their performance as electronic materials and battery stability. Furthermore, dry electrode manufacturing methods have recently been developed to improve battery performance and streamline the process. However, carbon nanotubes currently used in batteries can only be manufactured using wet electrode methods due to the use of dispersants. Therefore, carbon nanotubes used in dry electrodes must possess self-dispersibility, which means they do not require dispersants.

[0006] One object of the present invention is to provide a method for functionalizing carbon nanotubes that can improve the dispersibility of carbon nanotubes without deteriorating electrical properties.

[0007] Another object of the present invention is to provide a carbon nanotube functionalized to have self-dispersibility.

[0008] Another object of the present invention is to provide an electrode material for a battery including the carbon nanotube.

[0009] However, the problem to be solved by the present invention is not limited to the problem mentioned above, and may be expanded in various ways without departing from the spirit and scope of the present invention.

[0010] A method for functionalizing a carbon nanotube according to exemplary embodiments of the present invention for achieving the above-described object of the present invention includes a step of providing potassium monopersulfate and magnesium sulfate to the carbon nanotube to oxidize the carbon nanotube.

[0011] According to one embodiment, the content of the potassium monopersulfate is 0.5 to 15 parts by weight based on 1 part by weight of the carbon nanotube, and the content of the magnesium sulfate is 0.02 to 0.7 parts by weight based on 1 part by weight of the carbon nanotube.

[0012] According to one embodiment, the step of oxidizing the carbon nanotubes is performed in a solution containing a nonionic surfactant.

[0013] In one embodiment, the nonionic surfactant comprises a mixture of a hydrocarbon alcohol ethoxylated agent and a nonionic fluorosurfactant.

[0014] According to one embodiment, the hydrocarbon alcohol ethoxylated compound is a secondary alcohol ethoxylated compound represented by the following chemical formula 1.

[0015] <Chemical Formula 1>

[0016]

[0017] In chemical formula 1, n+m is a natural number from 2 to 8, and p is a natural number from 3 to 10.

[0018] According to one embodiment, the nonionic fluorine surfactant is represented by the following chemical formula 2:

[0019] <Chemical Formula 2>

[0020]

[0021] In chemical formula 2, a is a natural number from 4 to 6, and b is a natural number from 10 to 15.

[0022] According to one embodiment, the content of the mixture of the hydrocarbon alcohol ethoxylated and the nonionic fluorine surfactant is 0.01 to 5 parts by weight based on 1 part by weight of the carbon nanotube.

[0023] According to one embodiment, the content of the potassium monopersulfate is 1 to 5 parts by weight relative to 1 part by weight of the carbon nanotube, the content of the magnesium sulfate is 0.02 to 0.3 parts by weight relative to 1 part by weight of the carbon nanotube, and the content of the mixture of the hydrocarbon-based alcohol ethoxylated and the nonionic fluorine-based surfactant is 0.1 to 1 part by weight relative to 1 part by weight of the carbon nanotube.

[0024] Carbon nanotubes according to exemplary embodiments of the present invention have functional groups bonded to the surface via ester bonds derived from hydrocarbon alcohol ethoxylated and / or nonionic fluorosurfactants.

[0025] According to one embodiment, the functional group is represented by the following chemical formulas 3 and 4.

[0026] <Chemical Formula 3>

[0027]

[0028] In chemical formula 3, n+m is a natural number from 2 to 8, p is a natural number from 3 to 10, and * is a covalent bond bonded to a carbon nanotube.

[0029] <Chemical Formula 4>

[0030]

[0031] In chemical formula 2, a is a natural number from 4 to 6, b is a natural number from 10 to 15, and * is a covalent bond bonded to a carbon nanotube.

[0032] An electrode material for a battery according to exemplary embodiments of the present invention includes an electrode active material, a binder, and a conductive material, wherein the conductive material includes a carbon nanotube having a first functional group derived from a hydrocarbon-based alcohol ethoxylated group and bonded to the surface via an ester bond, and a second functional group derived from a nonionic fluorine surfactant and bonded to the surface via an ester bond.

[0033] As described above, according to exemplary embodiments of the present invention, by functionalizing carbon nanotubes while minimizing damage or breakage, it is possible to prevent deterioration of the electrical properties of carbon nanotubes during the functionalization process. Furthermore, by providing carbon nanotubes capable of self-dispersion (dispersion without a dispersant), the performance of battery electrodes utilizing such carbon nanotubes can be improved, and a carbon nanotube conductive material usable in the manufacture of dry electrodes can be provided.

[0034] FIG. 1 and FIG. 2 are diagrams schematically illustrating a functionalization process of carbon nanotubes according to one embodiment of the present invention.

[0035] Figure 3 is a graph showing the rate characteristics of battery cells manufactured using carbon nanotubes of Example 1, Example 2, and Comparative Example.

[0036] Hereinafter, with reference to the attached drawings, the functionalization method of carbon nanotubes, functionalized carbon nanotubes, and electrode materials according to embodiments of the present invention will be described in detail. The present invention can be modified in various ways and can take various forms, and thus specific embodiments will be illustrated and described in detail in the text. However, this is not intended to limit the present invention to a specific disclosed form, but should be understood to include all modifications, equivalents, and substitutes included in the spirit and technical scope of the present invention. In the attached drawings, the dimensions of structures are illustrated larger than actual dimensions to ensure clarity of the present invention.

[0037] The terminology used in this application is only used to describe specific embodiments and is not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly indicates otherwise. In this application, it should be understood that the terms "comprise" or "have" indicate the presence of a feature, number, step, operation, component, or combination thereof described in the specification, but do not preclude the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, or combinations thereof.

[0038] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Terms defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and shall not be interpreted in an idealized or overly formal sense unless explicitly defined herein.

[0039] Functionalization method of carbon nanotubes

[0040] A method for functionalizing a carbon nanotube according to one embodiment of the present invention includes a step of oxidizing the carbon nanotube.

[0041] The carbon nanotube has a structure in which hexagonal ring structures formed by sp2 bonds of carbons are continuous on a plane, and has an overall tube shape. For example, the diameter of the carbon nanotube may be 1 nm to 100 nm, and the length may be 1 μm to 1,000 μm. However, the embodiments of the present invention are not limited thereto, and the carbon nanotube may have various diameters and lengths that are not limited thereto.

[0042] The carbon nanotubes may have various known structures. For example, the carbon nanotubes may include single-walled carbon nanotubes, double-walled carbon nanotubes, multi-walled carbon nanotubes, thin-walled carbon nanotubes, rope carbon nanotubes, or combinations thereof.

[0043] In one embodiment, potassium persulfate and magnesium salts may be used to oxidize the carbon nanotubes. Specifically, potassium monopersulfate (KHSO5, PMPS) and magnesium sulfate (MgSO4, MGS) may be used to oxidize the carbon nanotubes.

[0044] In conventional techniques, sulfuric acid, nitric acid, or mixtures thereof have been used to oxidize carbon nanotubes. Oxidation using these strong acids, due to ionic reactions, can damage the carbon nanotube structure and degrade electrical properties. The potassium monopersulfate used in the present invention is a weakly acidic substance that can oxidize carbon nanotubes through a relatively stable radical reaction. Therefore, the reaction rate can be easily controlled, and structural damage to the carbon nanotubes can be prevented or minimized.

[0045] Magnesium ions (Mg) generated from magnesium sulfate 2+ ) can increase the efficiency of the oxidation reaction by promoting the introduction of hydrophilic functional groups and improving the dispersibility of carbon nanotubes during the oxidation reaction process by acting as a catalyst in the oxidation process of carbon nanotubes.

[0046] According to one embodiment, the content of the potassium monopersulfate may be 0.5 to 15 parts by weight, preferably 0.5 to 10 parts by weight, and more preferably 1 to 5 parts by weight, relative to 1 part by weight of the carbon nanotube. The content of the magnesium sulfate may be 0.01 to 1 part by weight, preferably 0.02 to 0.7 parts by weight, and more preferably 0.02 to 0.3 parts by weight, relative to 1 part by weight of the carbon nanotube.

[0047] In one embodiment, the oxidation of the carbon nanotubes may be carried out under conditions containing a surfactant. A nonionic surfactant may be used as the surfactant. For example, an ethoxylated compound may be used as the surfactant.

[0048] In one embodiment, the surfactant may include a combination of different materials. Specifically, the surfactant may include a hydrocarbon-based alcohol ethoxylated agent and a non-ionic fluorosurfactant. The non-ionic fluorosurfactant may include an ethoxylated non-ionic fluorosurfactant (fluorinated ethoxylated agent or fluorinated polyether ethoxylated agent).

[0049] Nonionic fluorosurfactants can lower the static surface tension of ultrapure water at room temperature, for example, to levels of 17 to 20 dynes / cm. However, the dynamic surface tension (DST) does not decrease within a short period of time, within 100 ms, due to the influence of the fluorine-containing molecular structure.

[0050] According to one embodiment of the present invention, by mixing a hydrocarbon alcohol ethoxylated compound with low dynamic surface tension, the surface tension at the interface of carbon nanotube particles can be rapidly reduced. Accordingly, by rapidly lowering the surface tension at the interface of carbon nanotubes in the early stages of the oxidation process, the particles are dispersed, allowing the oxidizing agent to widely and rapidly access the surface of the carbon nanotubes. Consequently, the oxidation efficiency of carbon nanotubes can be increased.

[0051] In addition, the surfactant can improve dispersibility by preventing re-agglomeration of functional groups formed on the surface of carbon nanotubes by bonding to the surface of carbon nanotubes through van der Waals forces or forming covalent bonds.

[0052] According to one embodiment, the hydrocarbon alcohol ethoxylated product may be a secondary alcohol ethoxylated product represented by the following chemical formula 1.

[0053] <Chemical Formula 1>

[0054]

[0055] In chemical formula 1, n+m is a natural number from 2 to 8, and p is a natural number from 3 to 10.

[0056] According to one embodiment, the nonionic fluorine surfactant may be a compound having a perfluorinated structure and a hydroxyl group, as represented by the following chemical formula 2.

[0057] <Chemical Formula 2>

[0058]

[0059] In chemical formula 2, a is a natural number from 4 to 6, and b is a natural number from 10 to 15.

[0060] A nonionic surfactant mixture having the above structure can easily form covalent bonds on the surface of carbon nanotubes by significantly lowering the surface tension of the perfluorinated structure, for example, to 20 dynes / cm or less, and can reduce aggregation of carbon nanotube particles through the branched structure of the hydrocarbon alcohol ethoxylated group and the bulky perfluorinated structure of the fluorinated surfactant.

[0061] In one embodiment, the content of the nonionic surfactant (the sum of the hydrocarbon alcohol ethoxylated agent and the nonionic fluorosurfactant) may be 0.01 to 5 parts by weight, preferably 0.01 to 1.5 parts by weight, and more preferably 0.1 to 1 part by weight, relative to 1 part by weight of the carbon nanotube. For example, the weight ratio of the hydrocarbon alcohol ethoxylated agent and the nonionic fluorosurfactant may be 3:1 to 1:3.

[0062] If the content of the above nonionic surfactant is too low, the dispersibility of the carbon nanotubes may be reduced, and if it is too high, the nonionic surfactant and magnesium sulfate may form micelles, reducing the effect of reducing surface tension.

[0063] FIG. 1 and FIG. 2 are diagrams schematically illustrating a functionalization process of carbon nanotubes according to one embodiment of the present invention.

[0064] Referring to FIG. 1, carbon nanotubes can be oxidized by an oxidizing agent and functionalized, and as shown, carboxyl groups and / or hydroxyl groups can be formed on the surface.

[0065] According to one embodiment, the nonionic surfactant can be bonded to the surface of the carbon nanotube through a covalent bond.

[0066] Referring to FIG. 2, carbon nanotubes can be functionalized by being oxidized by an oxidizing agent to have at least carboxyl groups, and at least some of the carboxyl groups can additionally react to form ester bonds.

[0067] Even if nonionic surfactants have reactive functional groups (e.g., hydroxyl groups), they do not react with the carboxyl groups of carbon nanotubes in mild environments. However, according to the present invention, an acidic environment is formed during the oxidation process of carbon nanotubes, and as surface tension is significantly reduced by the fluorinated surfactant, the hydroxyl groups of the nonionic surfactant react with the carboxyl groups on the surface of the carbon nanotubes, allowing them to bind to the surface of the carbon nanotubes through ester bonds.

[0068] For example, the hydroxyl group of the surfactant of Chemical Formula 1 and / or the hydroxyl group of the surfactant of Chemical Formula 2 may react with the carboxyl group of the carbon nanotube to form a functionalized carbon nanotube as shown in FIG. 2. For example, the functionalized group derived from the hydrocarbon-based alcohol ethoxylated agent may be referred to as a first functionalized group, and the functionalized group derived from the nonionic fluorine-based surfactant may be referred to as a second functionalized group. The functionalized carbon nanotube according to an embodiment of the present invention may have a first functionalized group, a second functionalized group, or both a first functionalized group and a second functionalized group.

[0069] The functionalized carbon nanotubes described above can form secondary shapes by agglomerating or arranging multiple carbon nanotubes. For example, multiple carbon nanotubes can be arranged or aligned in a certain direction to form bundle-type particles in the form of bundles or ropes, or entangled-type particles in the form of spheres or potatoes that are entangled without a certain direction.

[0070] After oxidizing (functionalizing) the above carbon nanotubes, the carbon nanotubes can be washed to remove residual components (oxidizing agent, surfactant, etc.).

[0071] According to embodiments of the present invention, by functionalizing carbon nanotubes while minimizing damage or breakage, it is possible to prevent deterioration of the electrical properties of carbon nanotubes during the functionalization process. Furthermore, by providing carbon nanotubes capable of self-dispersion (dispersion without a dispersant), the performance of battery electrodes utilizing such carbon nanotubes can be improved, and a carbon nanotube conductive material usable in the manufacture of dry electrodes can be provided.

[0072] Cathode materials for batteries containing carbon nanotubes

[0073] A cathode material for a battery according to one embodiment of the present invention includes a cathode active material, a binder, and a conductive material. For example, the cathode material may be a slurry-type composition.

[0074] As the above positive electrode active material, a compound capable of reversible intercalation and deintercalation of lithium (lithiated intercalation compound) can be used, and positive electrode active materials used in the relevant technical field can be used without limitation.

[0075] For example, the positive electrode active material may include a lithium composite metal oxide containing lithium and one or more metals such as cobalt, manganese, nickel or aluminum. More specifically, the lithium composite metal oxide may include a lithium-manganese oxide (e.g., LiMnO2, LiMn2O, etc.), a lithium-cobalt oxide (e.g., LiCoO2, etc.), a lithium-nickel oxide (e.g., LiNiO2, etc.), a lithium-nickel-manganese oxide (e.g., LiNi 1-Y1 Mn Y1 O2 (here, 0 <Y1<1), LiNi Z1 Mn 2-Z1 O4 (wherein, 0<Z1<2) etc.), lithium-nickel-cobalt oxides (e.g., LiNi 1-Y2 Co Y2 O2 (here, 0 <Y2<1) 등), 리튬-망간-코발트계 산화물(예를 들면, LiCo 1-Y3 Mn Y3O2 (here, 0 <Y3<1), LiMn 2-Z2 Co Z2 O4 (wherein, 0<Z2<2) etc.), lithium-nickel-cobalt-manganese oxides (e.g., Li(Ni P1 Co Q1 Mn R1 )O2(wherein, 0<P1<1, 0<Q1<1, 0<R1<1, P1+Q1+R1=1) or Li(Ni P2 Co Q2 Mn R2 )O4 (wherein, 0<P2<2, 0<Q2<2, 0<R2<2, P2+Q2+R2=2) etc.), or lithium-nickel-cobalt-manganese-other metal(M) oxide (e.g., Li(Ni P3 Co Q3 Mn R3 M S )O2 (wherein, M is selected from the group consisting of Al, Cu, Fe, V, Cr, Ti, Zr, Zn, Ta, Nb, Mg, B, W, and Mo, and P3, Q3, R3, and S are atomic fractions of independent elements, 0<P3<1, 0<Q3<1, 0<R3<1, 0<S<1, P+Q+R+S=1), etc.), and any one or two or more compounds thereof may be included. However, embodiments of the present invention are not limited thereto, and the positive electrode active material may include lithium iron phosphate (LiFePO4).

[0076] For example, the content of the positive electrode active material may be 90 to 99 wt% of the total solid content (100%), and preferably 94 to 99 wt%.

[0077] The above binder is for adhesion between positive electrode active material particles and adhesion to the current collector, and binders used in the relevant technical field can be used without limitation.

[0078] For example, the binder may include polyvinylidene fluoride (PVDF), tetrafluoroethylene (PTFE), vinylidene fluoride-hexafluoropropylene copolymer (VDF-HFP Copolymer), vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer (VDF-HFP-TFE Copolymer), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated-EPDM, styrene butadiene rubber (SBR), fluoroelastomers, or various copolymers thereof, and one of these may be used alone or a mixture of two or more thereof may be used.

[0079] For example, the content of the binder may be 1 to 5 wt% of the total solids.

[0080] The above-mentioned cathode material may further include a solvent (dispersing medium) for mixing and dispersing the above-mentioned components. The solvent may be a solvent commonly used in the art, and examples thereof include N-methylpyrrolidone (NMP), dimethyl sulfoxide (DMSO), isopropyl alcohol, acetone, or water. One of these may be used alone, or a mixture of two or more may be used. The amount of the solvent used may be determined in consideration of the dispersion and viscosity of the above-mentioned components. For example, the above-mentioned cathode material may include a solvent such that the solid content concentration is 60 wt% to 80 wt%.

[0081] In one embodiment, the cathode material may be a slurry that does not contain a solvent, but embodiments of the present invention are not limited thereto. For example, the cathode material may have a composition that is substantially solvent-free or has minimal solvent content for a dry process.

[0082] The above conductive material may include the functionalized carbon nanotubes described above. However, embodiments of the present invention are not limited thereto and may further include other conductive materials, such as carbon black, graphene, graphite, and conductive fibers.

[0083] For example, the content of the above-mentioned conductive agent may be 0.1 to 5 wt% of the total solids, and preferably, 0.1 to 2 wt%.

[0084] Cathode materials for batteries containing carbon nanotubes

[0085] A negative electrode material for a battery according to one embodiment of the present invention includes a negative electrode active material, a binder, and a conductive material. For example, the negative electrode material may be a slurry composition.

[0086] In one embodiment, the negative active material may include graphite. The graphite may include at least one of artificial graphite or natural graphite.

[0087] In one embodiment, the negative active material may include a silicon-based active material. The silicon-based active material may include silicon particles, silicon oxide including lithium silicate, silicon carbide (SiC), a silicon oxide-carbon composite, a silicon-silicon oxide-carbon composite, or a combination thereof.

[0088] In one embodiment, the negative active material may include a combination of graphite and silicon-based active materials.

[0089] For example, the content of the negative active material may be 2 to 95 wt%, 70 to 99 wt%, or 90 to 99 wt% of the total solids.

[0090] The binder may be the same materials as those described for the positive electrode material. For example, the binder content may be 1 to 5 wt% of the total solids.

[0091] The above-mentioned negative electrode material may further include a solvent (dispersing medium) for mixing and dispersing the above-mentioned components. The solvent may be the same materials as those described for the above-mentioned positive electrode material.

[0092] The above-described conductive material may include the functionalized carbon nanotubes described above. However, embodiments of the present invention are not limited thereto and may further include other conductive materials such as carbon black, graphene, graphite, etc.

[0093] For example, the content of the above-mentioned conductive agent may be 0.1 to 5 wt% of the total solids, and preferably, 0.01 to 1 wt%.

[0094] Hereinafter, the method for functionalizing carbon nanotubes of the present invention and its effects will be examined through specific examples.

[0095] Functionalization of carbon nanotubes

[0096] According to the composition (unit: parts by weight) in Table 1 below, carbon nanotubes (NC7000TM, Nanocyl SA) and additives were added to ultrapure water (DI water), stirred at room temperature for 2 hours, placed in a depressurizing device, washed with DI water, filtered, and washed repeatedly until the filtrate became pH neutral. The treated carbon nanotubes were dried. As a surfactant, UHWA FA-5431 (emulsifying solution) containing hydrocarbon alcohol ethoxylated of Chemical Formula 1 and nonionic fluorine surfactant of Chemical Formula 2 in a weight ratio of 1:3 to 3:1 was used.

[0097] <Table 1 (unit: parts by weight)>

[0098]

[0099] particle size analysis experiment

[0100] The carbon nanotube powder obtained in Example 1, Example 2 and Comparative Example was dispersed in NMP at 0.0001 wt%, and subjected to bath sonication for 15 minutes. The particle size was measured and shown in Table 2 below.

[0101] Table 2

[0102]

[0103] Referring to Table 2, it was confirmed that the carbon nanotubes of the examples of the present invention had smaller average particle sizes and deviations than the carbon nanotubes of the comparative examples. This indicates that the dispersibility of the carbon nanotubes was improved through examples 1 and 2. Furthermore, in the case of example 1, which added magnesium sulfate, it was confirmed that the average particle size and deviations were further reduced.

[0104] Resistance measurement experiment

[0105] The carbon nanotube powder (CNT) obtained in Example 1, Example 2 and Comparative Example was mixed with the positive electrode active material (NMC811) and binder (PVdF) at a mass ratio of 97:1:2 (NMC811:CNT:PVdF) to prepare a slurry having a solid content of 63 wt%, and the mixture was coated and dried on a current collector (aluminum foil) under the following conditions to form an electrode, and then the interfacial resistance at five different locations was measured, and the average value and standard deviation are shown in Table 3.

[0106] * Mass loading: 17 ± 1 mg cm -2

[0107] * Electrode density: 2.7 ±0.1 g cm -3

[0108] Table 3

[0109]

[0110] Referring to Table 3, it was confirmed that the electrodes manufactured using the examples of the present invention had significantly lower resistance and deviation than the electrodes manufactured using the comparative examples. This demonstrates that electrodes with excellent performance can be manufactured using the carbon nanotubes obtained in Examples 1 and 2. Furthermore, in the case of Example 1, which added magnesium sulfate, it was confirmed that the resistance and deviation were further reduced.

[0111] Rate capability comparison experiment

[0112] According to the following conditions, a battery cell was manufactured using the electrodes obtained in the resistance measurement experiment, and the rate characteristics were measured, which are shown in Table 4 and Fig. 3 below.

[0113] * Voltage window: 3.0-4.3V

[0114] *Charge mode: CC / CV mode (cut-off current 0.05C)

[0115] * Discharge mode: CC mode

[0116] * Cycle test: 0.2C / xC (1C=200 mA g-1)

[0117] * Electrolyte type: 1M LiPF6 EC (ethylene carbonate) / EMC (ethyl methyl carbonate) (3:7 v / v) + 10 wt% FEC (fluoroethylene carbonate) + 2 wt% VC (vinylene carbonate)

[0118] <Table 4 (Unit: mAh / gram of NMC811)>

[0119]

[0120] Referring to FIG. 3 and Table 4, it was confirmed that the batteries manufactured using the examples of the present invention had much better rate characteristics than the batteries manufactured using the comparative examples. This demonstrates that it is possible to manufacture batteries with superior performance using the carbon nanotubes obtained in Examples 1 and 2. Furthermore, it was confirmed that the rate characteristics of Example 1, which added magnesium sulfate, further increased.

[0121] Although the present invention has been described with reference to exemplary embodiments thereof as described above, it will be understood by those skilled in the art that various modifications and changes may be made to the present invention without departing from the spirit and scope of the present invention as set forth in the claims below.

[0122] Carbon nanotubes according to exemplary embodiments of the present invention can be used in the manufacture of various electrical and electronic devices that can utilize carbon nanotubes, such as anodes and cathodes of secondary batteries, electrodes of hydrogen fuel cells and water electrolysis, and transparent electrodes.

Claims

1. A method for functionalizing a carbon nanotube, comprising the step of providing potassium monopersulfate and magnesium sulfate to the carbon nanotube to oxidize the carbon nanotube.

2. A method for functionalizing carbon nanotubes, characterized in that in paragraph 1, the content of the potassium monopersulfate is 0.5 to 15 parts by weight based on 1 part by weight of the carbon nanotubes, and the content of the magnesium sulfate is 0.02 to 0.7 parts by weight based on 1 part by weight of the carbon nanotubes.

3. A method for functionalizing carbon nanotubes, characterized in that the step of oxidizing the carbon nanotubes in the first paragraph is performed in a solution containing a nonionic surfactant.

4. A method for functionalizing carbon nanotubes, characterized in that in the third paragraph, the nonionic surfactant comprises a mixture of a hydrocarbon alcohol ethoxylated agent and a nonionic fluorine surfactant.

5. A method for functionalizing a carbon nanotube, characterized in that in the fourth paragraph, the hydrocarbon-based alcohol ethoxylated product is a secondary alcohol ethoxylated product represented by the following chemical formula 1. <Chemical Formula 1> (In chemical formula 1, n+m is a natural number from 2 to 8, and p is a natural number from 3 to 10.) 6. A method for functionalizing carbon nanotubes, characterized in that in paragraph 4, the nonionic fluorine surfactant is represented by the following chemical formula 2. <Chemical Formula 2> (In chemical formula 2, a is a natural number from 4 to 6, and b is a natural number from 10 to 15.) 7. A method for functionalizing carbon nanotubes, characterized in that in paragraph 4, the content of the mixture of the hydrocarbon-based alcohol ethoxylated agent and the nonionic fluorine surfactant is 0.01 to 5 parts by weight based on 1 part by weight of the carbon nanotube.

8. A method for functionalizing carbon nanotubes, characterized in that in paragraph 4, the content of the potassium monopersulfate is 1 to 5 parts by weight relative to 1 part by weight of the carbon nanotubes, the content of the magnesium sulfate is 0.02 to 0.3 parts by weight relative to 1 part by weight of the carbon nanotubes, and the content of the mixture of the hydrocarbon-based alcohol ethoxylated agent and the nonionic fluorine surfactant is 0.1 to 1 part by weight relative to 1 part by weight of the carbon nanotubes.

9. A method for functionalizing a carbon nanotube, characterized in that in the first paragraph, the carbon nanotube comprises at least one selected from the group consisting of a single-walled carbon nanotube, a double-walled carbon nanotube, a multi-walled carbon nanotube, a thin-walled carbon nanotube, and a rope carbon nanotube.

10. A carbon nanotube having a functional group bonded to the surface through an ester bond derived from a hydrocarbon alcohol ethoxylated group.

11. A carbon nanotube according to claim 10, wherein the functional group is represented by the following chemical formula 3. <Chemical Formula 3> (In chemical formula 3, n+m is a natural number from 2 to 8, p is a natural number from 3 to 10, and * is a covalent bond bonded to a carbon nanotube.) 12. A carbon nanotube having a functional group bonded to the surface via an ester bond derived from a nonionic fluorine surfactant.

13. A carbon nanotube according to claim 12, wherein the functional group is represented by the following chemical formula 4. <Chemical Formula 4> (In chemical formula 4, a is a natural number from 4 to 6, b is a natural number from 10 to 15, and * is a covalent bond bonded to a carbon nanotube.) 14. Electrode active material; binder; and Includes challenges, The above-mentioned conductive material is an electrode material for a battery comprising a carbon nanotube having a first functional group derived from a hydrocarbon-based alcohol ethoxylated group and bonded to the surface via an ester bond, and a second functional group derived from a nonionic fluorine surfactant and bonded to the surface via an ester bond.

15. An electrode material for a battery, characterized in that the electrode active material in claim 14 includes a positive electrode active material.

16. An electrode material for a battery, characterized in that the electrode active material in claim 14 includes a negative electrode active material.

17. In the 14th paragraph, the binder is characterized in that it includes at least one selected from the group consisting of polyvinylidene fluoride (PVDF), tetrafluoroethylene (PTFE), vinylidene fluoride-hexafluoropropylene copolymer (VDF-HFP Copolymer), vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer (VDF-HFP-TFE Copolymer, polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated-EPDM, styrene butadiene rubber (SBR), and fluoroelastomer.

18. An electrode material for a battery, characterized in that in claim 14, the first functional group is represented by the following chemical formula 3, and the second functional group is represented by the following chemical formula 4. <Chemical Formula 3> (In chemical formula 3, n+m is a natural number from 2 to 8, p is a natural number from 3 to 10, and * is a covalent bond bonded to a carbon nanotube.) <Chemical Formula 4> (In chemical formula 4, a is a natural number from 4 to 6, b is a natural number from 10 to 15, and * is a covalent bond bonded to a carbon nanotube.)

Images