KR101997054B1 - Carbon nanotube dispersed solution and method for preparing the same - Google Patents

Carbon nanotube dispersed solution and method for preparing the same Download PDF

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KR101997054B1
KR101997054B1 KR1020150137099A KR20150137099A KR101997054B1 KR 101997054 B1 KR101997054 B1 KR 101997054B1 KR 1020150137099 A KR1020150137099 A KR 1020150137099A KR 20150137099 A KR20150137099 A KR 20150137099A KR 101997054 B1 KR101997054 B1 KR 101997054B1
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carbon nanotube
polyvinyl butyral
butyral resin
electrode
dispersion
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KR20170037454A (en
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유흥식
강경연
설종헌
이종원
김동현
권계민
우지희
김예린
조동현
최상훈
최현
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주식회사 엘지화학
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    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00Electrodes
    • H01M4/02Electrodes composed of or comprising active material
    • H01M4/62Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624Electric conductive fillers
    • H01M4/625Carbon or graphite
    • CCHEMISTRY; METALLURGY
    • C01INORGANIC CHEMISTRY
    • C01BNON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00Carbon; Compounds thereof
    • C01B32/15Nano-sized carbon materials
    • C01B32/158Carbon nanotubes
    • C01B32/168After-treatment
    • C01B32/174Derivatisation; Solubilisation; Dispersion in solvents
    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00Secondary cells; Manufacture thereof
    • H01M10/05Accumulators with non-aqueous electrolyte
    • H01M10/052Li-accumulators
    • H01M10/0525Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00Electrodes
    • H01M4/02Electrodes composed of or comprising active material
    • H01M4/13Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00Electrodes
    • H01M4/02Electrodes composed of or comprising active material
    • H01M4/62Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/621Binders
    • H01M4/622Binders being polymers
    • CCHEMISTRY; METALLURGY
    • C01INORGANIC CHEMISTRY
    • C01PINDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00Particle morphology
    • C01P2004/51Particles with a specific particle size distribution
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02EREDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00Enabling technologies or technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10Energy storage
    • Y02E60/12Battery technologies with an indirect contribution to GHG emissions mitigation
    • Y02E60/122Lithium-ion batteries

Abstract

The present invention relates to an entangled carbon nanotube; Dispersion media; And a polyvinyl butyral resin having a weight average molecular weight of more than 50,000, a method for producing the same, an electrode slurry and an electrode manufacturing method using the same, an electrode and a secondary battery using the carbon nanotube dispersion, .

Description

TECHNICAL FIELD [0001] The present invention relates to a carbon nanotube dispersion and a method for manufacturing the carbon nanotube dispersion.

The present invention relates to a carbon nanotube dispersion in which carbon nanotubes are uniformly dispersed in a dispersion medium, a method for producing the same, an electrode slurry and an electrode using the carbon nanotube dispersion, .

Background Art Fine carbon materials such as carbon black, ketjen black, fullerene, graphene, and carbon nanotubes have been widely used in fields such as electronics and energy fields due to their electrical properties and thermal conductivity. Particularly, carbon nanotubes, which are one kind of fine carbon fibers, are tubular carbon having a diameter of 1 μm or less and are expected to be applied and practically used in various fields due to their high conductivity, tensile strength and heat resistance due to their specific structure.

However, despite the availability of such carbon nanotubes, the use of carbon nanotubes is limited due to their low solubility and dispersibility. That is, carbon nanotubes can not stably disperse in an aqueous solution due to a strong van der Waals attractive force between them, and coagulation phenomenon occurs.

Various attempts have been made to solve these problems. Specifically, a method of dispersing carbon nanotubes in a dispersion medium through a mechanical dispersion treatment such as an ultrasonic treatment has been proposed. However, in this method, the dispersibility during the irradiation of the ultrasonic wave is excellent, but when the ultrasonic irradiation is finished, aggregation of the carbon nanotubes starts and aggregation occurs when the concentration of the carbon nanotubes increases.

In addition, a method of dispersing and stabilizing carbon nanotubes by using various dispersants has been proposed. For example, an anionic surfactant such as sodium dodecylsulfonate or sodium dodecylbenzenesulfonate, or a nonionic surfactant such as Triton (R) -X-100, -2-pyrrolidone (hereinafter referred to as NMP) to disperse the carbon nanotubes. A method of dispersing carbon nanotubes in water or a dispersion medium of NMP using a polymer dispersant such as polyvinylpyrrolidone (hereinafter referred to as PVP) or a cellulose derivative as a water-soluble polymer has been proposed instead of a surfactant. However, these methods also have a problem in that when the fine carbon fibers are dispersed in the dispersion medium at a high concentration, the handling becomes difficult due to an increase in viscosity.

Accordingly, in order to expand the use of the carbon nanotubes, it is important to prepare a dispersion in which the carbon nanotubes are uniformly dispersed in the dispersion medium.

Japanese Patent Application Laid-Open No. 2005-075661 (published on March 24, 2005)

One embodiment of the present application provides a carbon nanotube dispersion having improved dispersibility. Other embodiments of the present invention relate to a method for producing the carbon nanotube dispersion, a method for manufacturing an electrode slurry and an electrode using the carbon nanotube dispersion, an electrode manufactured by the method, and a battery including the same.

One embodiment of the present application includes an entangled carbon nanotube, a dispersion medium, and a polyvinyl butyral resin having a weight average molecular weight of more than 50,000, wherein the particle size distribution of the entangled carbon nanotubes has a particle size distribution D 50 of 2 to 5 Lt; RTI ID = 0.0 > g / m. ≪ / RTI >

According to another embodiment of the present application, the weight average molecular weight of the polyvinyl butyral resin is 150,000 or more.

According to another embodiment of the present application, the content of the repeating unit containing a hydroxyl group in the polyvinyl butyral resin is at least 15% by weight.

According to another embodiment of the present application, the carbon nanotube dispersion comprises a first polyvinyl butyral resin having a weight average molecular weight of more than 50,000; And a second polyvinyl butyral resin having a weight average molecular weight smaller than that of the first polyvinyl butyral resin. Here, the second polyvinyl butyral resin may have a weight average molecular weight of 50,000 or less as long as the weight average molecular weight is smaller than that of the first polyvinyl butyral resin, but may be 50,000 or less.

According to another embodiment of the present application, the carbon nanotube dispersion includes a carbon nanotube composite into which the polyvinyl butyral resin is introduced on the surface of the entangled carbon nanotube.

According to another embodiment of the present application, the dispersed particle size of the entangled carbon nanotubes is such that D 50 of the particle size distribution is 2 to 5 탆, D 10 is 0.5 to 1.5 탆, and D 90 is 6 to 10 탆 . Here, the particle size distribution D 50 can be defined as the particle size on the basis of 50% of the particle size distribution. The dispersion particle size of the carbon nanotubes can be measured using a laser diffraction method, for example. More specifically, the carbon nanotubes dispersed solution was introduced into a commercially available laser diffraction particle size analyzer (for example, Malvern MS300) to determine the average particle size (D 50 ) Can be calculated. D 10 and D 90 mean the particle size at 10% and 90% of the particle size distribution, respectively.

Another embodiment of the present application provides a method for manufacturing a carbon nanotube dispersion, which comprises mixing an entangled carbon nanotube, a dispersion medium, and a polyvinyl butyral resin having a weight average molecular weight of more than 50,000.

Another embodiment of the present application provides a method of manufacturing an electrode slurry comprising mixing the carbon nanotube dispersion, an electrode active material and a binder resin.

Another embodiment of the present application relates to a method of manufacturing an electrode slurry, comprising: preparing an electrode slurry by mixing the carbon nanotube dispersion, an electrode active material, and a binder resin; And forming an electrode using the electrode slurry.

Another embodiment of the present application provides an electrode slurry comprising the carbon nanotube dispersion, an electrode active material, and a binder resin.

Another embodiment of the present application provides an electrode manufactured using an electrode slurry including the carbon nanotube dispersion, an electrode active material, and a binder resin, and a secondary battery including the electrode. The fact that the electrode is manufactured using the electrode slurry means that the electrode slurry, the dried product thereof, or a cured product thereof.

The carbon nanotube dispersion according to the embodiments of the present application is a polyvinyl butyral resin containing a hydroxyl group as a polar group and a butyral group as a polar group together with an entangled carbon nanotube, It is advantageous to allow the carbon nanotubes and the dispersion medium to be mixed with each other. Further, by using the above-mentioned polyvinyl butyral resin, it is possible to solve the problem that the adhesive force of the electrode, which is caused by not dispersing the conductive material, is low. Accordingly, the carbon nanotube dispersion according to the embodiments described herein can disperse the carbon nanotubes uniformly in the dispersion medium, and can disperse and contain the carbon nanotubes at a high concentration without fear of increasing the viscosity of the dispersion. .

Hereinafter, the present invention will be described in detail in order to facilitate understanding of the present invention.

The terms and words used in the present specification and claims should not be construed as limited to ordinary or dictionary terms and the inventor may appropriately define the concept of the term in order to best describe its invention It should be construed as meaning and concept consistent with the technical idea of the present invention.

The carbon nanotube dispersion according to one embodiment of the present application comprises an entangled carbon nanotube, a dispersion medium, and a polyvinyl butyral resin having a weight average molecular weight of more than 50,000, wherein the particle size distribution of the entangled carbon nanotubes has a particle diameter distribution And D 50 is 2 to 5 탆. When the weight average molecular weight of the polyvinyl butyral resin is large, the dispersibility of the carbon nanotubes can be improved more than when the same amount of the low molecular weight polyvinyl butyral resin is used.

According to another embodiment of the present application, the weight average molecular weight of the polyvinyl butyral resin is 150,000 or more.

According to another embodiment of the present application, the weight average molecular weight of the polyvinyl butyral resin is 200,000 or more.

According to another embodiment of the present application, the weight average molecular weight of the polyvinyl butyral resin is 350,000 or less.

The weight average molecular weight of the polyvinyl butyral resin is measured using GPC (Gel Permeation Chromatography) under the following conditions. In the molecular weight measurement, DMF is used as a solvent. In the dispersion state, the molecular weight of the supernatant can be measured by centrifugation. In the electrode and the cell state, the electrode can be scratched and the molecular weight can be measured by extracting the polyvinyl butyral resin using THF.

- Column: Polar Gel M + L

Solvent: DMF (0.45 μm filtered) containing 0.05 M LiBr salt,

- Flow rate: 1.0 ml / min

- Injection volume: 100 μL (0.45 μm filtered)

- Measurement time: 30 min

- Detection device: Waters RI detector

According to another embodiment of the present application, the content of the repeating unit containing a hydroxyl group in the polyvinyl butyral resin is at least 15% by weight.

According to another embodiment of the present application, the content of the repeating unit containing a hydroxyl group in the polyvinyl butyral resin is 20% by weight or more.

According to another embodiment of the present application, the content of the repeating unit containing a hydroxyl group in the polyvinyl butyral resin is 35% by weight or less.

When the hydroxyl group content of the polyvinyl butyral resin is high, the mixing energy of the carbon nanotube dispersion increases and the stability of the battery state can be improved. The content of the hydroxyl group-containing repeating unit of the polyvinyl butyral resin can be measured by NMR. Generally, polyvinyl butyral resins are prepared in water, and when the hydroxyl content is high, the polyvinyl butyral resin melts in water and blocks the process line. As a result, smooth production was difficult, and polyvinyl butyral resin having a high content of a hydroxyl group-containing repeating unit was hardly mass-produced. However, in the present invention, it has been found that when the content of the repeating unit containing a hydroxyl group is as high as described above, it can be usefully used in a carbon nanotube dispersion.

The content of the acetyl group-containing repeating unit in the polyvinyl butyral resin is 5% by weight or less. When the acetal group is present in the polyvinyl butyral resin, dispersion can be inhibited due to viscosity increase. Therefore, the acetal group-containing repeating unit is preferably 5 wt% or less and as small as possible. The acetal group-containing repeating unit can be measured through NMR.

According to another embodiment of the present application, the carbon nanotube dispersion comprises a first polyvinyl butyral resin having a weight average molecular weight of more than 50,000; And a second polyvinyl butyral resin having a weight average molecular weight smaller than that of the first polyvinyl butyral resin. When two or more kinds of polyvinyl butyral resins having different molecular weights are used, the PDI can be widened, for example, from 3 to 7. As a result, it is possible to improve the dispersibility by the low molecular weight resin and to improve the adhesion by the high molecular weight resin. PDI can also be measured using Gel Permeation Chromatography (GPC). After the weight average molecular weight (Mw) and the number average molecular weight (Mn) are determined by the above method, the molecular weight distribution (PDI) can be calculated from the weight average molecular weight / number average molecular weight (Mw / Mn).

Here, the second polyvinyl butyral resin may have a weight average molecular weight of 50,000 or less as long as the weight average molecular weight is smaller than that of the first polyvinyl butyral resin, but may be 50,000 or less. When a polyvinyl butyral resin having a weight average molecular weight of 50,000 or less is used, the dispersibility of the carbon nanotubes can be improved by lowering the viscosity. By using a polyvinyl butyral resin having a weight average molecular weight of more than 50,000, Flexibility can be increased. Specifically, in the process of dispersing carbon nanotubes, a polyvinyl butyral resin having a low molecular weight is firstly dispersed using a bead mill or a dispersing machine to obtain a carbon nanotube dispersed solution by a polyvinyl butyral resin having a low molecular weight It is possible to exhibit an effect of lowering the viscosity and improving the dispersibility. Subsequently, the polyvinyl butyral resin having a high molecular weight is mixed by using a mixer, whereby the flexibility of the battery can be improved by the polyvinyl butyral resin having a high molecular weight.

According to one example, as the second polyvinyl butyral resin, a polyvinyl butyral resin having a weight average molecular weight of from 1 to 50,000 can be used. When the weight average molecular weight of the second resin is 1,000 or more, it is possible to prevent the deterioration of final physical properties (flexibility reduction and the like). When the weight average molecular weight is less than 50,000, the viscosity can be prevented from increasing and the dispersibility can be improved.

According to one example, as the polyvinyl butyral resin, a resin containing a butyral-containing unit represented by the following formula (1), an acetyl group-containing unit represented by the following formula (2) and a hydroxyl group containing unit represented by the following formula (3) may be used.

[Chemical Formula 1]

Figure 112015094105391-pat00001

In Formula 1, R is an alkyl group having 1 to 20 carbon atoms. The R may be an alkyl group having 1 to 5 carbon atoms, specifically an alkyl group having 1 to 3 carbon atoms.

(2)

Figure 112015094105391-pat00002

(3)

Figure 112015094105391-pat00003

As the polyvinyl butyral resin, various commercially available products and synthetic products may be used alone or in combination of two or more kinds as long as the content of the repeating units and the weight average molecular weight are satisfied. The hydroxyl group may be adjusted by a chemical modification method such as acylation or urethanization.

According to another embodiment of the present application, the carbon nanotube dispersion includes a carbon nanotube composite into which the polyvinyl butyral resin is introduced on the surface of the entangled carbon nanotube.

The dispersed particle size of the entangled carbon nanotubes is such that D 50 of the particle diameter distribution is 2 to 5 탆, D 10 is 0.5 to 1.5 탆, and D 90 is 6 to 10 탆. Here, the dispersed particle diameter of the carbon nanotubes means the particle diameter of the secondary particles formed by aggregating the primary particles of the carbon nanotubes. Such a dispersed particle size can be measured by a laser diffraction particle size analysis method.

The entangled type refers to a secondary shape of a sphere or potato form in which a plurality of carbon nanotubes are entangled without directionality. According to an example, the diameter of the entangled carbon nanotubes is 10 to 30 nm. Diameters of carbon nanotubes can be measured by SEM. For reference, the bundle type refers to a secondary shape in the form of a bundle or a rope in which a plurality of carbon nanotubes are arranged or aligned in a predetermined direction.

The carbon nanotubes referred to in the present specification are graphite sheets having a nano-sized diameter cylinder shape and have an sp2 bond structure. At this time, the characteristic of the conductor or the semiconductor is shown according to the angle and the structure of the graphite surface. The carbon nanotubes can be classified into single walled carbon nanotubes (SWCNTs), double walled carbon nanotubes (DWCNTs) and multiwalled carbon nanotubes (MWCNTs, multi -walled carbon nanotubes, and these carbon nanotubes can be appropriately selected depending on the use of the dispersion. Specifically, the single-walled carbon nanotube has a metallic characteristic and a semiconductor characteristic and can exhibit a variety of electrical, chemical, physical and optical characteristics. Therefore, it is suitable for the use of the carbon nanotube dispersion for the purpose of finely integrating the device can do.

In the carbon nanotube dispersion according to an embodiment of the present invention, the carbon nanotubes may include one or more of the single wall, double wall, and multiwall carbon nanotubes described above.

The entangled carbon nanotubes may have a BET specific surface area of 180 to 260 m 2 / g. By having the BET specific surface area as described above, it is possible to exhibit better dispersibility when used in combination with the above-mentioned polyvinyl butyral resin.

In the present invention, the specific surface area of the entangled carbon nanotube is measured by the BET method. Specifically, the specific surface area of the entangled carbon nanotube is calculated from the adsorption amount of nitrogen gas under the liquid nitrogen temperature (77K) using BEL Japan's BELSORP-mino II can do.

The entangled carbon nanotubes can be produced by a conventional method such as an arc discharge method, a laser evaporation method, a chemical vapor deposition method, or the like, and commercially available ones can be used.

According to one embodiment, the entangled carbon nanotubes in the dispersion are contained in an amount of 1 to 10% by weight based on the entire dispersion (100% by weight), the polyvinyl butyral resin is contained in an amount of 10 to 50% by weight based on 100 parts by weight of the entangled carbon nanotubes . When the content of the carbon nanotubes is 1 wt% or more, the solid content of the slurry takes a certain amount or more during the preparation of the electrode slurry, which is advantageous for the electrode coating. Although it is advantageous in terms of fairness to increase the content of carbon nanotubes, the content of 10 wt% or less prevents the viscosity of the dispersion from becoming too high, and thus it is easy to manufacture the dispersion apparatus.

According to one embodiment of the present application, the dispersion medium may be an organic solvent containing one or two or more hetero atoms selected from the group consisting of nitrogen atoms (N) and oxygen atoms (O) having a non-covalent electron pair.

Specifically, the dispersion medium may be an amide-based polar organic solvent such as dimethylformamide (DMF), diethylformamide, dimethylacetamide (DMAc) or N-methylpyrrolidone (NMP); Propanol (isobutanol), 2-butanol (sec-butanol), 1-methyl -2-propanol (tert-butanol), pentanol, hexanol, heptanol or octanol; Glycols such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, 1,3-propanediol, 1,3-butanediol, 1,5-pentanediol, or hexylene glycol; Polyhydric alcohols such as glycerin, trimethylol propane, pentaerythritol, or sorbitol; Ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, triethylene glycol monomethyl ether, tetraethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monoethyl ether, triethylene glycol monoethyl ether, tetraethylene glycol Glycol ethers such as monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, and tetraethylene glycol monobutyl ether; Ketones such as acetone, methyl ethyl ketone, methyl propyl ketone, or cyclopentanone; And esters such as ethyl acetate,? -Butyllactone, and? -Propiolactone. Any one or a mixture of two or more of them may be used.

In particular, N-methyl-2-pyrrolidone is an organic compound having a five-membered ring structure including a lactam structure, and belongs to an aprotic polar solvent such as dimethylformamide, dimethylacetamide, dimethylsulfoxide and the like. In order to have high solubility, it is used as a solvent for various materials especially in the field of polymer chemistry. Therefore, it is preferable to use N-methyl-2-pyrrolidone.

The content of the entangled carbon nanotubes, the dispersion medium, and the polyvinyl butyral resin may be appropriately determined depending on the use of the dispersion.

According to one embodiment, the polyvinyl butyral resin may be included in an amount of 10 to 50 parts by weight based on 100 parts by weight of the entangled carbon nanotubes for uniform dispersion of the carbon nanotubes in the dispersion. If the content of the polyvinyl butyral resin is less than 10 parts by weight, it is difficult to uniformly disperse the carbon nanotubes in the dispersion. If the content of the polyvinyl butyral resin exceeds 50 parts by weight, the viscosity of the dispersion may increase.

According to one embodiment, the content of the total solute including the entangled carbon nanotube and the polyvinyl butyral resin may be 1 to 15 wt%, and the content of the dispersion medium may be 85 to 99 wt%. In addition, the content of the Entangled carbon nanotube in the total solute may be 50 to 90% by weight, and the content of the polyvinyl butyral resin may be 10 to 50% by weight. In this range, the entangled carbon nanotubes can be uniformly dispersed in the solvent.

According to another embodiment of the present application, the viscosity of the carbon nanotube dispersion may be 1-120 Pa.s, for example 50-160 Pa.s, preferably 50-150 Pa.s. The viscosity of the dispersion can be measured with a Haake rheometer, specifically at Shear viscosity of 1.2 / s.

The carbon nanotube dispersion according to the above-described embodiment can be produced by a manufacturing method including mixing an entangled carbon nanotube, a dispersion medium and the above-mentioned polyvinyl butyral resin. For example, the carbon nanotube dispersion may be prepared by adding an entangled carbon nanotube to a dispersion medium in which a polyvinyl butyral resin is dissolved, or by adding an entangled carbon nanotube to a dispersion medium and then dissolving the polyvinyl butyral resin, And can be prepared by adding and mixing the entangled carbon nanotubes and the polyvinyl butyral resin together.

According to an example, a step (step 1) of preparing a carbon nanotube slurry by mixing an entangled carbon nanotube and a dispersion medium; And mixing the carbon nanotube slurry with a polyvinyl butyral resin (step 2).

Each step will be described in detail below.

Step 1 for preparing the carbon nanotube dispersion is a step for preparing carbon nanotube slurry by mixing the entangled carbon nanotubes and the dispersion medium. At this time, the types and amounts of the entangled carbon nanotubes and the dispersion medium are the same as those described above.

The entangled carbon nanotube and the dispersion medium may be mixed using a mixing apparatus such as a conventional mixing method, specifically, a homogenizer, a bead mill, a ball mill, a basket mill, an impact stirrer, a universal stirrer, a clear mixer or a TK mixer . ≪ / RTI >

In mixing the entangled carbon nanotubes with the dispersion medium, a cavitation dispersion treatment may be performed to enhance the mixing property of the entangled carbon nanotubes with the dispersion medium or the dispersibility of the entangled carbon nanotubes in the dispersion medium. The cavitation dispersion treatment is a dispersion treatment method using a shock wave generated by rupture of vacuum bubbles formed in water when high energy is applied to a liquid. The cavitation dispersion treatment is a method of dispersing the entangled carbon nanotubes . Specifically, the cavitation dispersion treatment may be performed by ultrasonic wave, jet mill, or shear dispersion treatment.

The dispersion treatment may be suitably performed depending on the amount of the entangled carbon nanotubes and the kind of the dispersant.

Specifically, when performing the ultrasonic treatment, the frequency is in the range of 10 kHz to 150 kHz, the amplitude is in the range of 5 to 100 탆, and the irradiation time may be 1 to 300 min. As the ultrasonic wave generating device for performing the ultrasonic wave processing process, for example, an ultrasonic homogenizer may be used. When performing the jet mill treatment, the pressure may be 20 MPa to 250 MPa, and may be performed a plurality of times, more specifically, two or more times. As the jet mill dispersing apparatus, a high pressure wet jet mill or the like can be used.

The temperature during the cavitation dispersion treatment step is not particularly limited, but may be performed at a temperature at which there is no fear of viscosity change of the dispersion due to evaporation of the dispersion medium. Specifically at a temperature of 50 DEG C or less, more specifically 15 to 50 DEG C. [

Step 2 for preparing a carbon nanotube dispersion according to an embodiment of the present invention is a step of mixing the polyvinyl butyral resin with the carbon nanotube slurry prepared in step 1 above. At this time, the kind and amount of the polyvinyl butyral resin are the same as those described above.

The mixing step may be performed by a conventional mixing or dispersing method, and specifically concretely, a milling (milling) process such as a ball mill, a bead mill, a basket mill, ) Method, or a homogenizer, a bead mill, a ball mill, a basket mill, an impact mill, a universal stirrer, a clear mixer or a TK mixer. More specifically, it can be performed by a milling method using a bead mill. At this time, the size of the bead mill may be suitably determined according to the kind and amount of the entangled carbon nanotubes and the type of the polyvinyl butyral resin, and specifically, the diameter of the bead mill may be 0.5 to 2 mm.

According to the above-described production method, the entangled carbon nanotubes can be uniformly dispersed in a dispersion medium.

Specifically, in the carbon nanotube dispersion according to the embodiments of the present invention, the polyvinyl butyral resin is introduced to the surface of the carbon nanotubes through physical or chemical bonding to the surface of the carbon nanobut, Dispersant complexes. The dispersed particle size of the entangled carbon nanotubes is such that D 50 of the particle diameter distribution is 2 to 5 탆, D 10 is 0.5 to 1.5 탆, and D 90 is 6 to 10 탆. Accordingly, the carbon nanotube dispersion according to the present invention can exhibit more excellent electrical, thermal and mechanical characteristics due to the uniform dispersion of the entangled carbon nanotubes, and the workability can be improved by maintaining the low viscosity, Is possible.

Another embodiment of the present application provides a method of manufacturing an electrode slurry comprising mixing the carbon nanotube dispersion, an electrode active material and a binder resin.

Another embodiment of the present application relates to a method of manufacturing an electrode slurry, comprising: preparing an electrode slurry by mixing the carbon nanotube dispersion, an electrode active material and a binder resin; And forming an electrode using the electrode slurry.

The electrode slurry and the method of manufacturing the electrode and the material such as the electrode active material, the binder resin, and the like can be used as those known in the art. For example, PVDF or the like may be used as the binder resin. The binder resin such as PVDF in the electrode slurry is used for bonding the metal thin film and the electrode active material, while the polyvinyl butyral resin in the carbon nanotube dispersion is for dispersing the carbon nanotubes before being mixed with the electrode active material. Since the binder resin in the electrode slurry to which the electrode active material is already added can not disperse the carbon nanotubes, the binder resin in the electrode slurry and the polyvinyl butyral resin in the carbon nanotube dispersion are distinguished.

The step of forming the electrode may be performed by applying the slurry to the current collector and drying or curing the slurry as necessary.

Another embodiment of the present application provides an electrode slurry comprising the carbon nanotube dispersion, an electrode active material, and a binder resin.

Another embodiment of the present application provides an electrode manufactured using an electrode slurry including the carbon nanotube dispersion, an electrode active material, and a binder resin, and a secondary battery including the electrode. The fact that the electrode is manufactured using the electrode slurry means that the electrode slurry, the dried product thereof, or a cured product thereof.

The secondary battery includes an anode, a cathode, and an electrolyte, and at least one of an anode and a cathode may be manufactured by an electrode slurry including the carbon nanotube dispersion. The battery may further include a separator provided between the anode and the cathode, if necessary.

The secondary battery may be a lithium ion secondary battery.

Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily carry out the present invention. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

Example  1 to 6 and Comparative Example  1 to 5

Entangled carbon nanotubes having a unit diameter of 10-30 nm and a BET of 200 m 2 / g and a polyvinyl butyral resin of the following Table 1 were mixed in the N-methylpyrrolidone (NMP) solvent in the amounts shown in Table 2 Carbon nanotube dispersions were prepared. The weight% in Table 1 is based on 100% by weight of the polyvinyl butyral resin, and the weight% in Table 2 is based on 100% by weight of the carbon nanotube dispersion. At this time, a beads mill was used. The dispersed particle diameter and viscosity of the prepared dispersion were measured and are shown in Table 3 below.

To prepare an electrode slurry (solid content: 100 parts by weight), the carbon nanotube dispersion prepared above was mixed with 97.3 parts by weight of a three-component cathode active material and 1.5 parts by weight of a PVdF binder. The carbon nanotube and the polyvinyl butyral resin were present in an amount of 1 part by weight and 0.2 part by weight, respectively. Subsequently, the electrode slurry was coated on the aluminum current collector and rolled by a roll press to produce a positive electrode plate (compound density of 3.3 g / cc).

On the other hand, an anode slurry containing 97.3 parts by weight of an anode active material, 0.7 parts by weight of a conductive material, 1 part by weight of a thickener (CMC) and 1 part by weight of a binder (SBR) was applied to a copper current collector, cc. < / RTI >

Monocells were prepared by using the positive electrode and negative electrode to which the dispersion prepared above was applied. Specifically, a polyethylene separator was inserted between the negative electrode plate and the positive electrode plate, inserted into a battery case, and then an electrolyte was injected to assemble the battery. At this time, a mixed solution of ethylene carbonate, ethyl methyl carbonate and diethyl carbonate (1/2/1 by volume) in which 1.0 M LiPF 6 was dissolved was used as the electrolyte solution.

Adhesive strength measurement

For the measurement of the adhesive strength, the anode plate (before the preparation of the battery) prepared above was cut to the same size of 15 mm × 150 mm and fixed on the slide glass. Then, the anode plate was stripped from the current collector and the 180 degree peel strength was measured. The evaluation was made by measuring the peel strengths of 5 or more and calculating the average value. The results of adhesion measurement are shown in Table 3 below.

Monocell evaluation

The battery prepared above was charged and discharged at a temperature of 1.0 C / 1.0 C three times, and the SOC was set based on the final discharge capacity. A 10-second resistance was measured by applying a discharge pulse from SOC50 to 6.5C.

Polyvinyl butyral resin
(wt%)
Molecular weight (DMF)
PVB
(Formula 1)
PVAc
(2)
PVA
(Formula 3)
MW
(X1,000 g / mol)
PDI
Example 1 68.3 0.9 30.8 270 3.8 Example 2 75.0 1.2 23.8 350 3.2 Example 3 74.1 2.3 23.6 160 3.6 Example 4 * 73.5 1.8 24.7 190 6.3 Example 4 (1) * 75.0 1.2 23.8 350 3.2 Example 4 (2) * 72 2.5 25.5 57 2.7 Example 5 ** 74.6 1.8 23.7 250 4.4 Example 5 (1) ** 75.0 1.2 23.8 350 3.2 Example 5 (2) ** 74.1 2.3 23.6 160 3.6 Example 6 82.6 2.4 14.9 180 3.4 Comparative Example 1 unused Comparative Example 2 Commercial dispersant AFCONA 4570 Comparative Example 3 78.0 2.5 19.5 37 2.7 Comparative Example 4 68.3 0.9 30.8 270 3.8 Comparative Example 5 68.3 0.9 30.8 270 3.8 * The content and the molecular weight of the constituent unit in Example 4 were such that when the polyvinyl butyral resin of Example 4 (1) and the polyvinyl butyral resin of Example 4 (2) were used together, the whole of the carbon nanotube dispersion It is a standard value.

** The content and the molecular weight of the constituent unit in Example 5 were such that when the polyvinyl butyral resin of Example 5 (1) and the polyvinyl butyral resin of Example 5 (2) were used together, the total amount of the carbon nanotube dispersion As shown in Fig.

CNT type Dispersion Composition (wt%) CNT Polyvinyl butyral resin The dispersion medium (NMP) Example 1 Entangled 5 One 94 Example 2 Entangled 5 One 94 Example 3 Entangled 5 One 94 Example 4 Entangled 5 One 94 Example 5 Entangled 5 One 94 Example 6 Entangled 5 One 94 Comparative Example 1 Entangled 2 0 98 Comparative Example 2 Entangled 5 One 94 Comparative Example 3 Entangled 5 One 94 Comparative Example 4 Bundled 5 One 94 Comparative Example 5 Entangled 5 One 94

Dispersion property Electrode adhesion Battery performance (DC-IR (ohm)) Dispersed particle diameter (占 퐉) Viscosity (@ 1.2 / s) D 10 D 50 D 90 Pa.s gf / cm 6.5 C, 25 degrees
Discharge SOC 50
Example 1 0.69 2.94 6.58 110.0 32 1.313 Example 2 0.76 3.12 6.85 130.0 30 1.308 Example 3 0.82 3.37 7.47 118.0 26 1.367 Example 4 0.68 2.87 6.28 103.0 24 1.355 Example 5 0.93 3.59 7.88 127.0 29 1.325 Example 6 1.35 4.22 9.02 155.0 13 1.632 Comparative Example 1 No CNT coating available (no dispersion liquid) Comparative Example 2 No CNT coating available (no dispersion liquid) Comparative Example 3 2.30 7.06 14.60 150.0 8 CELL can not be manufactured due to adhesion problem Comparative Example 4 No CNT coating available (no dispersion liquid) Comparative Example 5 2.75 10.50 27.40 170.0 Electrode coating failure occurred

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, And falls within the scope of the invention.

Claims (13)

  1. Entangled carbon nanotubes; Dispersion media; And a polyvinyl butyral resin having a weight average molecular weight of more than 50,000, wherein the entangled carbon nanotubes have a particle size distribution D 50 of 2 to 5 탆, D 10 of 0.5 to 1.5 탆, and D 90 6 to 10 [micro] m.
  2. The carbon nanotube dispersion according to claim 1, wherein the polyvinyl butyral resin has a weight average molecular weight of 150,000 or more.
  3. The carbon nanotube dispersion according to claim 1, wherein the polyvinyl butyral resin has a weight average molecular weight of 200,000 or more.
  4. The carbon nanotube dispersion according to claim 1, wherein the content of the hydroxyl group-containing repeating unit in the polyvinyl butyral resin is 15% by weight or more.
  5. The carbon nanotube dispersion according to claim 1, wherein the content of the hydroxyl group-containing repeating unit in the polyvinyl butyral resin is 20 wt% or more.
  6. [2] The method of claim 1, wherein the polyvinyl butyral resin comprises a first polyvinyl butyral resin having a weight average molecular weight of more than 50,000; And a second polyvinyl butyral resin having a weight average molecular weight smaller than that of the first polyvinyl butyral resin.
  7. delete
  8. A method for producing a carbon nanotube dispersion liquid according to any one of claims 1 to 6, comprising mixing an entangled carbon nanotube and a polyvinyl butyral resin having a weight average molecular weight of more than 50,000.
  9. A method for producing an electrode slurry, which comprises mixing the carbon nanotube dispersion liquid of any one of claims 1 to 6, an electrode active material, and a binder resin.
  10. Preparing an electrode slurry by mixing the carbon nanotube dispersion liquid, the electrode active material and the binder resin according to any one of claims 1 to 6; And forming an electrode using the electrode slurry.
  11. An electrode slurry comprising the carbon nanotube dispersion liquid according to any one of claims 1 to 6, an electrode active material, and a binder resin.
  12. An electrode manufactured using the electrode slurry comprising the carbon nanotube dispersion liquid, the electrode active material, and the binder resin according to any one of claims 1 to 6.
  13. A secondary battery comprising an electrode according to claim 12.
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