Carbon nanotube dispersion solution, electrode slurry composition comprising same, electrode comprising same, and secondary battery comprising same

Abstract

The present specification relates to a carbon nanotube dispersion solution, an electrode slurry composition comprising same, an electrode comprising same, and a secondary battery comprising same, the solution including: carbon nanotubes; a first dispersant comprising a polyvinyl butyral resin in which the content of a repeating unit containing a hydroxyl group is 15 to 30 wt%; a second dispersant comprising an amine group or an imine group; and an alcohol-based solvent.

Description

Carbon nanotube dispersion, electrode slurry composition containing the same, electrode containing the same, and secondary battery containing the same

[0001] This application claims the benefit of the filing dates of Korean Patent Office No. 10-2024-0027662, filed February 27, 2024, Korean Patent Office No. 10-2024-0027663, filed February 27, 2024, and Korean Patent Office No. 10-2025-0021752, filed February 19, 2025, the contents of which are incorporated herein by reference.

[0002] The present specification relates to a carbon nanotube dispersion, an electrode slurry composition containing the same, an electrode containing the same, and a secondary battery containing the same.

[0003] Secondary batteries are batteries that can be used repeatedly through a discharge process in which chemical energy is converted into electrical energy and a charge process in the reverse direction. Secondary batteries are composed of a positive electrode, a negative electrode, an electrolyte, and a separator. The positive and negative electrodes are generally composed of an electrode current collector and an electrode active material layer formed on the electrode current collector. The electrode active material layer is manufactured by applying an electrode slurry composition containing an electrode active material, a conductive material, a binder, etc., onto the electrode current collector, drying it, and then rolling it.

[0004] Conductive agents are used to improve the conductivity of electrode active materials. Conventionally, dot-shaped conductive agents, such as carbon black, were primarily used. However, dot-shaped conductive agents do not significantly improve electrical conductivity, requiring excessive use to achieve sufficient effects. This, in turn, reduces the electrode active material content and lowers battery capacity.

[0005] To address these issues, active efforts are being made to apply highly conductive carbon nanotubes (CNTs) as conductive materials. Because CNTs can achieve high conductivity even in small quantities, their use allows for a significant reduction in conductive material content compared to carbon black, resulting in increased electrical capacity.

[0006] As carbon nanotubes are increasingly utilized as conductive materials in secondary batteries, attempts have been made to disperse them in solvents like water or NMP. However, relatively little research has been done on dispersing them in organic solvents other than water or NMP. To create antistatic coatings using carbon nanotubes or to coat the surfaces of secondary battery active materials with them, a dispersion solution containing carbon nanotubes dispersed in a highly volatile solvent is required.

[0007] One embodiment of the present invention provides a carbon nanotube dispersion, an electrode slurry composition containing the same, an electrode containing the same, and a secondary battery containing the same.

[0008] One embodiment of the present invention comprises a carbon nanotube;

[0009] A first dispersant comprising a polyvinyl butyral resin having a content of repeating units containing hydroxyl groups of 15 wt% or more and 30 wt% or less;

[0010] A second dispersant comprising an amine group or an imine group; and

[0011] A carbon nanotube dispersion containing an alcohol-based solvent is provided.

[0012] One embodiment of the present invention provides an electrode slurry composition comprising the above-described carbon nanotube dispersion, electrode active material, and binder.

[0013] One embodiment of the present invention provides an electrode including an electrode active material layer formed by the electrode slurry composition described above.

[0014] One embodiment of the present invention provides a secondary battery including the above-described electrode.

[0015] The carbon nanotube dispersion of the present invention has the effect of improving the dispersibility of carbon nanotubes.

[0016] Hereinafter, the specification will be described in detail.

[0017] A carbon nanotube dispersion according to one embodiment of the present invention refers to a dispersion containing carbon nanotubes. Specifically, it refers to a dispersion in which carbon nanotubes are dispersed and do not aggregate with each other.

[0018] In this specification, the "content of repeating units" refers to the mass ratio of the repeating units based on the total weight of the material. For example, a polyvinyl butyral resin having a content of repeating units containing hydroxyl groups of 15 wt% means that the mass ratio of repeating units containing hydroxyl groups is 15 wt% based on the total weight of the polyvinyl butyral resin.

[0019] In this specification, the 'weight ratio of chemical formula x' means the mass ratio of the chemical formula x based on the total weight of the substance. An explanation of the above definition will be provided later.

[0020] One embodiment of the present invention provides a carbon nanotube dispersion comprising: carbon nanotubes; a first dispersant including a polyvinyl butyral resin having a content of repeating units containing hydroxyl groups of 15 wt% or more and 30 wt% or less; a second dispersant including an amine group or an imine group; and an alcoholic solvent. The carbon nanotube dispersion has an effect of improving the dispersibility of carbon nanotubes in the dispersion. Specifically, the hydroxyl group of the first dispersant can prevent the carbon nanotubes from agglomerating by interacting with the surface of the carbon nanotubes, and the second dispersant can improve the dispersion stability of the carbon nanotubes by performing a surface-active action. In addition, the first dispersant and the second dispersant have a characteristic of being well dissolved in an alcoholic solvent, and thus can improve the dispersibility of carbon nanotubes in an alcoholic solvent.

[0021] According to one embodiment of the present invention, a carbon nanotube dispersion comprises a first dispersant comprising a polyvinyl butyral resin having a content of repeating units containing hydroxyl groups of 15 wt% or more and 30 wt% or less. Specifically, the content may be 16 wt% or more, 17 wt% or more, 18 wt% or more, 28 wt% or less, 26 wt% or less, 24 wt% or less, or 22 wt% or less. More specifically, the content may be 16 wt% or more and 28 wt% or less, 17 wt% or more and 24 wt% or less, or 18 wt% or more and 21 wt% or less. Within the above numerical range, the first dispersant effectively interacts with the carbon nanotubes and maintains excellent miscibility with an alcohol-based solvent, thereby lowering the viscosity of the dispersion and improving dispersion stability. The content of the repeating unit containing the above hydroxyl group may refer to the weight of the repeating unit containing the hydroxyl group based on the total weight of the polyvinyl butyral resin.

[0022] A carbon nanotube dispersion according to one embodiment of the present invention comprises a second dispersant containing an amine group or an imine group. The functional group of the amine group or imine group has the effect of maintaining the dispersed state of the carbon nanotubes within the dispersion.

[0023] A carbon nanotube dispersion according to one embodiment of the present invention comprises an alcohol-based solvent. The alcohol-based solvent is environmentally friendly compared to volatile organic compounds such as NMP and has the advantage of a simple drying process.

[0024] In one embodiment of the present invention, the first dispersant may include a first unit represented by the following chemical formula 1, a second unit represented by the following chemical formula 2, and a third unit represented by the following chemical formula 3. The first unit represented by the following chemical formula 1 may be a butyral-containing repeating unit, the second unit represented by the following chemical formula 2 may be an acetyl group-containing repeating unit, and the third unit represented by the following chemical formula 3 may correspond to the above-described hydroxyl group-containing repeating unit.

[0025] [Chemical Formula 1]

[0026]

[0027] [Chemical Formula 2]

[0028]

[0029] [Chemical Formula 3]

[0030]

[0031] In chemical formulas 1 to 3,

[0032] R1 is a butyl group,

[0033] l is a weight ratio of 0.5 or more and 0.9 or less in chemical formula 1,

[0034] m is a weight ratio of chemical formula 2, which is 0.001 or more and 0.1 or less,

[0035] n is a weight ratio of chemical formula 3, which is 0.15 or more and 0.3 or less.

[0036] In this specification, the 'weight ratio of chemical formula x' means the total mass ratio of the repeating unit represented by the chemical formula x when the total weight of the material is 1. The first dispersant may include at least two repetitions of each of the first unit, the second unit, and the third unit. In this case, the number of repetitions of the repeating unit may be expressed as the weight ratio of each repeating unit based on the total weight of the first dispersant.

[0037] For example, if the first dispersant includes a first unit represented by Chemical Formula 1, a second unit represented by Chemical Formula 2, and a third unit represented by Chemical Formula 3, and l is 0.7, m is 0.1, and n is 0.2, the total mass ratio (l) of the repeating unit represented by Chemical Formula 1 may be 70%, the total mass ratio (m) of the repeating unit represented by Chemical Formula 2 may be 10%, and the total mass ratio (n) of the repeating unit represented by Chemical Formula 3 may be 20%. At this time, l+m+n, which means the total mass of the first unit represented by Chemical Formula 1, the second unit represented by Chemical Formula 2, and the third unit represented by Chemical Formula 3, may be 1.

[0038] In one embodiment of the present invention, the m may be 0.001 or more and 0.1 or less, 0.005 or more and 0.06 or less, or 0.01 or more and 0.04 or less. Within the above numerical range, the viscosity of the dispersion can be reduced.

[0039] In one embodiment of the present invention, n may be 0.16 or more, 0.17 or more, 0.18 or more, and 0.28 or less, 0.26 or less, 0.24 or less, or 0.22 or less. More specifically, it may be 0.16 or more and 0.28 or less, 0.17 or more and 0.24 or less, or 0.18 or more and 0.21 or less. In the above numerical range, the first dispersant effectively interacts with the carbon nanotubes and maintains excellent miscibility with the alcohol-based solvent, thereby lowering the viscosity of the dispersion and improving dispersion stability.

[0040] In one embodiment of the present invention, the weight average molecular weight of the first dispersant may be 10,000 g / mol or more and 100,000 g / mol or less. Preferably, it may be 11,000 g / mol or more, 12,000 g / mol or more, 13,000 g / mol or more, 14,000 g / mol or more, 90,000 g / mol or less, 80,000 g / mol or less, 70,000 g / mol or less, or 50,000 g / mol or less. More preferably, it may be 15,000 g / mol or more and 50,000 g / mol or less, or 30,000 g / mol or more and 40,000 g / mol or less. In the above numerical range, the solubility or miscibility of the first dispersant in an alcohol-based solvent is increased, and the carbon nanotubes are effectively prevented from agglomerating with each other, thereby further reducing the viscosity of the carbon nanotube dispersion. The weight average molecular weight of the first dispersant can be measured by gel permeation chromatography (GPC).

[0041] In one embodiment of the present invention, the second dispersant includes an alkanolamine-based dispersant or an alkylene imine-based dispersant.

[0042] The above alkanolamine dispersant refers to a dispersant that includes both a hydroxyl group and an amino group in an alkane skeleton, and the above alkylene imine dispersant refers to a dispersant that includes an imine group or an amine group in an alkylene skeleton. At this time, it includes both a hydrophobic portion by an alkane skeleton or an alkylene skeleton and a hydrophilic portion by a hydroxyl group or an amino group. That is, the hydrophobic portion can induce interaction with the first dispersant described above, and the hydrophilic portion has the effect of high solubility in an alcohol solvent. By the above-mentioned operating principle, there is an effect of effectively preventing carbon nanotubes from agglomerating with each other, thereby lowering the viscosity of a carbon nanotube dispersion.

[0043] In one embodiment of the present invention, the alkanolamine dispersant may be monoethanol amine, monoisopropanol amine, 2-amino-2-methyl-1-propanol, 2-methylaminoethanol, 3-aminopropanol amine, or a combination thereof. Preferably, 2-amino-2-methyl-1-propanol may be used.

[0044] In one embodiment of the present invention, the alkylene imine dispersant may be a polyalkylene imine dispersant. The amine group within the imine group of the alkylene imine dispersant has an unshared electron pair, thereby exhibiting excellent bonding strength with the carbon nanotubes within the dispersion. Furthermore, the amine group exhibits excellent affinity for alcohol-based solvents, thereby enhancing the dispersibility of the carbon nanotube dispersion.

[0045] In one embodiment of the present invention, the alkylene imine dispersant may include a C2 to C4 alkylene group.

[0046] In one embodiment of the present invention, the alkylene imine dispersant is alkylene imine (-(CH2) n It is an amine polymer with NH-) as a repeating unit, and can be a straight-chain polymer or a branched-chain polymer.

[0047] In one embodiment of the present invention, the alkylene imine dispersant may be polyethyleneimine.

[0048] In one embodiment of the present invention, the weight average molecular weight of the alkylene imine dispersant may be 300 g / mol or more and 2,000 g / mol or less. Preferably, it may be 500 g / mol or more and 1,500 g / mol or less, or 600 g / mol or more and 1,000 g / mol or less. Within the above numerical range, the alkylene imine dispersant has excellent affinity with carbon nanotubes and the solvent, thereby improving the dispersibility of the dispersion.

[0049] In one embodiment of the present invention, the content of the first dispersant may be 10 parts by weight or more and 400 parts by weight or less based on 100 parts by weight of the carbon nanotubes. Preferably, it may be 15 parts by weight or more, 20 parts by weight or more, 30 parts by weight or more, 40 parts by weight or more, or 70 parts by weight or more, and may be 350 parts by weight or less, 320 parts by weight or less, 290 parts by weight or less, or 280 parts by weight or less. When the above numerical range is satisfied, the carbon nanotubes can be uniformly dispersed, and the viscosity of the dispersion can be maintained low.

[0050] In one embodiment of the present invention, the content of the second dispersant may be 1 part by weight or more and 90 parts by weight or less based on 100 parts by weight of the carbon nanotubes. Preferably, it may be 2 parts by weight or more, 3 parts by weight or more, 4 parts by weight or more, or 5 parts by weight or more, and may be 80 parts by weight or less, 60 parts by weight or less, 50 parts by weight or less, or 40 parts by weight or less. When the above numerical range is satisfied, the carbon nanotubes can be uniformly dispersed, and the viscosity of the dispersion can be maintained low.

[0051] In one embodiment of the present invention, the content of the second dispersant may be 1 part by weight or more and 50 parts by weight or less based on 100 parts by weight of the first dispersant. Preferably, it may be 2 parts by weight or more, 4 parts by weight or more, 8 parts by weight or more, or 10 parts by weight or more, and may be 45 parts by weight or less, 40 parts by weight or less, 30 parts by weight or less, or 26 parts by weight or less. When the above numerical range is satisfied, carbon nanotubes can be uniformly dispersed, and the viscosity of the dispersion can be maintained low.

[0052] In one embodiment of the present invention, the total content of the first dispersant and the second dispersant may be 15 parts by weight or more and 400 parts by weight or less based on 100 parts by weight of the carbon nanotubes. Preferably, it may be 20 parts by weight or more, 30 parts by weight or more, 50 parts by weight or more, or 90 parts by weight or more, and may be 380 parts by weight or less, 360 parts by weight or less, 340 parts by weight or less, or 310 parts by weight or less. When the above numerical range is satisfied, the carbon nanotubes can be uniformly dispersed, and the viscosity of the dispersion can be maintained low.

[0053] In one embodiment of the present invention, the carbon nanotube dispersion may include a third dispersant having an amide group.

[0054] In one embodiment of the present invention, the third dispersant may include at least one selected from the group consisting of polyvinylpyrrolidone, polyester amide, polycarboxylic amide, polyamido amine, thioamido amine, and water soluble nylon.

[0055] In one embodiment of the present invention, the carbon nanotube may include a single-walled carbon nanotube, a multi-walled carbon nanotube, or a combination thereof.

[0056] A carbon nanotube dispersion according to one embodiment of the present invention comprises single-walled carbon nanotubes. The single-walled carbon nanotubes refer to carbon nanotubes having one bond forming a wall, and exhibit excellent electrical conductivity.

[0057] A carbon nanotube dispersion according to one embodiment of the present invention comprises multi-walled carbon nanotubes. The multi-walled carbon nanotubes have excellent strength and rigidity and excellent elongation, making them suitable for use in high-performance batteries.

[0058] In one embodiment of the present invention, the specific surface area (BET) of the carbon nanotube is 10 m 2 / g or more 1,200 m 2 / g or less. Specifically, the surface area ranges of the single-walled carbon nanotube and the multi-walled carbon nanotube may be different.

[0059] In one embodiment of the present invention, the specific surface area (BET) of the single-walled carbon nanotube is 750 m 2 / g or more. Preferably, 800 m 2 / g or more, 900 m 2 / g or more or 1,000 m 2 / g or more. The upper limit is not specifically limited, but 2,000 m 2 / g or less 1,800 m 2 / g or less or 1,500 m 2 / g or less. In the above numerical range, the aggregation phenomenon of carbon nanotubes can be controlled and the electrical conductivity can be improved.

[0060] In one embodiment of the present invention, the specific surface area (BET) of the multi-walled carbon nanotube is 10 m 2 / g or more than 900 m 2 / g or less. Preferably, 50 m 2 / g or more, 100 m 2 / g or more or 150 m 2 / g or more. The upper limit is not specifically limited, but 800 m 2 / g or less 750 m 2 / g or less or 700 m 2 / g or less. In the above numerical range, the aggregation phenomenon of carbon nanotubes can be controlled and the electrical conductivity can be improved.

[0061] In one embodiment of the present invention, the content of the carbon nanotubes may be 0.01 wt% or more and 10 wt% or less based on the total weight of the carbon nanotube dispersion. Preferably, it may be 0.1 wt% or more and 8 wt% or less. When the above numerical range is satisfied, the loading amount is increased during electrode manufacturing, thereby reducing the process cost, binder migration is prevented from occurring during electrode drying, and the viscosity of the carbon nanotube dispersion can be maintained low.

[0062] In one embodiment of the present invention, the first average particle diameter (D50) and the second average particle diameter (D90) of the carbon nanotubes may each be 0.5 μm or more and 60 μm or less. The average particle diameter (Dx) refers to a particle diameter corresponding to x% of the cumulative number of particles in a particle diameter distribution curve of the carbon nanotubes. The average particle diameter (Dx) can be measured, for example, using a laser diffraction method.

[0063] In one embodiment of the present invention, the first average particle diameter (D50) of the single-walled carbon nanotube may be 0.5 μm or more and 30 μm or less. Preferably, it may be 1 μm or more, 2 μm or more, 3 μm or more, 4 μm or more, 5 μm or more, 6 μm or more, 7 μm or more, or 8 μm or more, and may be 28 μm or less, 26 μm or less, 24 μm or less, 22 μm or less, 20 μm or less, 18 μm or less, 16 μm or less, or 15 μm or less.

[0064] In one embodiment of the present invention, the second average particle diameter (D90) of the single-walled carbon nanotube may be 1 μm or more and 55 μm or less. Preferably, it may be 5 μm or more, 10 μm or more, 15 μm or more, 20 μm or more, 25 μm or more, or 30 μm or more, and may be 53 μm or less, 51 μm or less, 49 μm or less, or 47 μm or less.

[0065] In one embodiment of the present invention, the first average particle diameter (D50) of the multi-walled carbon nanotube may be 0.5 µm or more and 30 µm or less. Preferably, it may be 0.8 µm or more, 1 µm or more, 1.2 µm or more, 1.4 µm or more, and may be 25 µm or less, 20 µm or less, 15 µm or less, 10 µm or less, 6 µm or less, 5 µm or less, or 4 µm or less.

[0066] In one embodiment of the present invention, the second average particle diameter (D90) of the multi-walled carbon nanotube may be 1 µm or more and 60 µm or less. Preferably, it may be 1.5 µm or more, 2 µm or more, 2.5 µm or more, 3 µm or more, 3.5 µm or more, or 4 µm or less, 30 µm or less, 20 µm or less, or 16 µm or less.

[0067] When the above-described average particle diameter (D50, D90) conditions are satisfied, particle agglomeration can be reduced.

[0068] In one embodiment of the present invention, the alcohol solvent may be methanol, ethanol, propanol, isopropanol, butanol, isobutanol, s-butanol, t-butanol, pentanol, isopentanol, hexanol, or a combination thereof. Preferably, ethanol or isopropanol may be used.

[0069] In one embodiment of the present invention, the carbon nanotube dispersion is heated at 25°C and 2.5 sec. -1 The viscosity at a shear rate of may be 5,000 cPs or less. The viscosity may be 3,000 cPs or less, 2,800 cPs or less, 2,500 cPs or less, or 2,400 cPs or less. Considering the purpose of the present invention, the lower the viscosity, the better, so the lower limit is not particularly limited, but may be 1 cPs or more, 3 cPs or more, or 5 cPs or more. When the viscosity range is satisfied, the carbon nanotubes of the carbon nanotube dispersion do not aggregate with each other, and the processability is improved when used in electrode manufacturing.

[0070] In one embodiment of the present invention, the carbon nanotube dispersion is heated at 25°C and 15 sec. -1 The viscosity at a shear rate of may be 1,500 cPs or less. The viscosity may be 800 cPs or less, 700 cPs or less, or 600 cPs or less. Considering the purpose of the present invention, the lower the viscosity, the better, so the lower limit is not particularly limited, but may be 1 cPs or more, 3 cPs or more, or 5 cPs or more. When the viscosity range is satisfied, the carbon nanotubes of the carbon nanotube dispersion do not aggregate with each other, and the processability is improved when used in electrode manufacturing.

[0071] The viscosity of the above carbon nanotube dispersion can be measured by a method commonly used in the field to which this technology belongs. For example, using a Brookfield DVNextCP Rheometer, the measurement temperature is 25°C and the time is 2.5 sec. -1 or 15 sec -1 It can be measured at the shear rate of . For more accurate measurement, the manufactured carbon nanotube dispersion can be stored at 25℃ for one week and then measured.

[0072] One embodiment of the present invention provides an electrode slurry composition comprising the above-described carbon nanotube dispersion, electrode active material, and binder.

[0073] In one embodiment of the present invention, the electrode active material may be a cathode active material. The cathode active material is not particularly limited as long as it is a cathode material that can be generally used, such as nickel cobalt manganese (NCM), lithium manganese iron phosphate (LMFP), or lithium iron phosphate (LFP).

[0074] In one embodiment of the present invention, the binder is used to secure adhesion between active materials or between the active materials and the current collector, and general binders used in the relevant technical field can be used, and the type thereof is not particularly limited. Examples of the binder include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber (SBR), fluororubber, or various copolymers thereof, and one type alone or a mixture of two or more types thereof may be used.

[0075] In one embodiment of the present invention, the binder may be included in an amount of 5 wt% or less based on the total solid content in the electrode slurry composition, and preferably in an amount of 1 wt% or more and 3 wt% or less. When the binder content satisfies the above range, excellent electrode adhesion can be achieved while minimizing an increase in electrode resistance.

[0076] In one embodiment of the present invention, the electrode slurry composition may additionally include additives such as a viscosity modifier, a filler, etc., as needed.

[0077] One embodiment of the present invention provides an electrode comprising an electrode active material layer formed by the electrode slurry composition described above. Specifically, the electrode can be manufactured by applying the electrode slurry composition of the present invention described above and drying it to form an electrode active material layer. More specifically, the electrode active material layer can be formed by applying the electrode slurry composition on an electrode current collector and then drying it, or by applying the electrode slurry composition on a separate support and then peeling it from the support, and laminating the obtained film on an electrode current collector. If necessary, a rolling process can be additionally performed after forming the electrode active material layer through the above method. At this time, the drying and rolling can be performed under appropriate conditions in consideration of the physical properties of the electrode to be finally manufactured, and is not particularly limited.

[0078] In one embodiment of the present invention, the electrode current collector is not particularly limited as long as it is a material that is conductive and does not cause a chemical change in the battery, and for example, copper, stainless steel, aluminum, nickel, titanium, alloys thereof, those surface-treated with carbon, nickel, titanium, silver, etc., or calcined carbon, etc. can be used.

[0079] In one embodiment of the present invention, the electrode current collector may typically have a thickness of 3 μm to 500 μm, and may form fine irregularities on the surface of the current collector to enhance the bonding strength of the electrode active material. In addition, the electrode current collector may be used in various forms, such as a film, sheet, foil, net, porous body, foam, or non-woven fabric.

[0080] In one embodiment of the present invention, the electrode may be a cathode.

[0081] One embodiment of the present invention provides a secondary battery including the above-described electrode.

[0082] One embodiment of the present invention provides a lithium secondary battery comprising a positive electrode; a negative electrode; and a separator and an electrolyte provided between the positive electrode and the negative electrode, wherein at least one of the positive electrode and the negative electrode is the electrode described above.

[0083] In one embodiment of the present invention, the separator separates the negative electrode and the positive electrode and provides a passage for lithium ions, and can be used without any particular limitation as long as it is commonly used as a separator in a secondary battery. Specifically, the separator may be a porous polymer film, for example, a porous polymer film made of a polyolefin polymer such as ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, and ethylene / methacrylate copolymer, or a laminated structure of two or more layers thereof. In addition, a conventional porous non-woven fabric, for example, a non-woven fabric made of high-melting-point glass fiber, polyethylene terephthalate fiber, etc. may also be used. In addition, a coated separator containing a ceramic component or a polymer material to secure heat resistance or mechanical strength may be used, and may optionally be used in a single-layer or multi-layer structure.

[0084] In one embodiment of the present invention, the electrolyte may include, but is not limited to, 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. that can be used in the manufacture of a lithium secondary battery.

[0085] Hereinafter, the present invention will be described in more detail through examples.

[0086] Preparation of carbon nanotubes

[0087] CNT1: Single-walled carbon nanotube, manufactured by OCSiAl, product name TUBALL 01RW03, specific surface area >800 m 2 / g)

[0088] CNT2: Multi-walled carbon nanotube, manufactured by JEIO, product name 6A, specific surface area 643 m 2 / g, average diameter of unit body 5~7nm

[0089] CNT3: Multi-walled carbon nanotube, manufactured by LG CHEM, product name BT1003M, specific surface area 186 m 2 / g, average diameter of unit cell 13 nm

[0090] <Preparation of the first dispersion agent>

[0091] PVB1: Polyvinyl butyral resin (manufactured by Kuraray, product name B30H, PVOH: 18–21 wt%, PVAc: 1–4 wt%, weight average molecular weight: 30,000–40,000 g / mol)

[0092] PVB2: Polyvinyl butyral resin (manufactured by Kuraray, product name B20H, PVOH: 18–21 wt%, PVAc: 1–4 wt%, weight average molecular weight: 15,000–30,000 g / mol)

[0093] PVB3: Polyvinyl butyral resin (manufactured by Kuraray, product name B30HH, PVOH: 11–14 wt%, PVAc: 1–4 wt%, weight average molecular weight: 30,000–40,000 g / mol)

[0094] PVB4: Polyvinyl butyral resin (manufactured by EASTMAN, product name B-98, PVOH: 18–20 wt%, PVAc: 0–2.5 wt%, weight average molecular weight: 40,000–70,000 g / mol)

[0095] PVOH: Content of repeating units containing hydroxyl groups

[0096] PVAc: Content of repeating units containing acetate groups

[0097] <Preparation of the second dispersion agent>

[0098] AMP: Alkanolamine dispersant (manufactured by MERCK, 2-amino-2-methyl-1-propanol)

[0099] PEI800: Polyalkylene dispersant (manufactured by MERCK, polyethyleneimine, weight average molecular weight 800 g / mol)

[0100] K15: Polyvinyl pyrrolidone resin (manufactured by Sigma-Aldrich)

[0101] <Preparation of solvent>

[0102] EtOH: ethanol

[0103] IPA: Isopropyl alcohol (isopropanol)

[0104] NMP: N-methyl pyrrolidone

[0105] <Preparation of carbon nanotube dispersion>

[0106] <Example 1>

[0107] A 1 kg mixture was prepared by mixing 0.4 wt% of carbon nanotubes CNT1, 0.72 wt% of PVB1 as a first dispersant, 0.08 wt% of AMP as a second dispersant, and EtOH as a solvent. A carbon nanotube dispersion was prepared by stirring with a stirrer and high-pressure treatment with a high-pressure homogenizer. The weight of the above materials is based on the total weight of the dispersion.

[0108] <Examples 2 to 16 and Comparative Examples 1 to 8>

[0109] A carbon nanotube dispersion was prepared by changing the composition as shown in Table 1 below.

[0110] <Experimental Example 1: Viscosity Measurement>

[0111] Brookfield's DVNextCP Rheometer was used, at a temperature of 25℃ and 2.5 sec. -1 shear rate of 15 sec or -1 was measured at the shear rate of .

[0112] <Experimental Example 2: Measurement of average particle size>

[0113] The laser diffraction method was used, and a commercially available laser diffraction particle size measuring device (Malvern Mastersizer3000) was used. Before measurement, the carbon nanotube dispersions of the examples and comparative examples were sufficiently diluted so that the carbon nanotube concentration was 0.05 wt% or less, and then the measurement was performed after stabilizing for 10 minutes. The average particle diameter at 50% of the particle diameter distribution (D50) and the average particle diameter at 90% of the particle diameter distribution (D90) were calculated from the measuring device.

[0114] Classification Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 CNT type CNT1 CNT1 CNT1 CNT1 CNT1 CNT1 CNT1 CNT1 CNT1 Content 0.40.40.40.40.40.40.2 First dispersant type PVB1 PVB1 PVB2 PVB4 PVB1 PVB1 PVB1 PVB1 Content 0.72 1.08 1.08 1.08 1.08 0.96 1.08 0.54 Second dispersant type AMPAMPAMPAMPPEI800 AMPAMPAMP Content 0.08 0.120.120.120.120.120.120.06 Third Dispersant type-----K15--Content-----0.12--Solvent typeEtOHEtOHEtOHEtOHEtOHIPAEtOHViscosity (cPs)2.5 / s2,1232,2032,2041,8111,6562,1231,85315915 / s54854756151247254847874Particle size (㎛)D5011.51111.79.59.113.914.38.2D9040.239.538.33640.241.246.833.8

[0115] Classification Example 9 Example 10 Example 11 Example 12 Example 13 Example 14 Example 15 Example 16 CNT type CNT2 CNT2 CNT2 CNT2 CNT2 CNT2 CNT2 CNT3 Content 1 ... Dispersant type AMPAMPAMPAMPAMPPEI800AMPAMPContent 0.050.20.40.20.20.40.20.18Solvent type EtOHEtOHEtOHEtOHEtOHEtOHIPAEtOHViscosity (cPs) 2.5 / s6441,0442711,5929401,4561,5172,36815 / s22835097481108143116153Particle size (㎛) D501.72.51.91.72.51.63.71.4 D908.414.97.76.19.911.315.84

[0116] ClassificationComparative Example 1Comparative Example 2Comparative Example 3Comparative Example 4Comparative Example 5Comparative Example 6Comparative Example 7Comparative Example 8CNT typeCNT1CNT1CNT1CNT1CNT2CNT2CNT2CNT2Content0.40.40.40.41 ... Dispersant type K15 Content 1.08 Solvent type EtOHEtOHEtOHEtOHEtOHEtOHEtOHNMP Viscosity (cPs) 2.5 / s 26, 71112, 97411, 88911, 4134, 4335, 2185, 7124, 67815 / s 5, 6692, 7863, 2622, 0801, 3591, 2221, 008954 Particle size (㎛) D 5 0 2 1.4 2.2 2.4 2.9 4.5 5.3 2.0 7.1 1.2 1.1 2.6 D 9 0 5 7.6 5.8 6.4 9.2 2.7 5.6 4.9 3.0 5.3 9.4

[0117] In the above Tables 1 to 3, 'content (based on dispersion)' is the content based on 100 parts by weight of dispersion. From the above results, it was confirmed that the viscosity of the dispersion of the example did not increase significantly.

[0118] On the other hand, it was confirmed that the viscosity increased when the first dispersant or the second dispersant was not included (Comparative Examples 1, 2 and 4 to 6).

[0119] Meanwhile, it was confirmed that the viscosity increased when the content of repeating units containing hydroxyl groups included in the polyvinyl butyral resin, which is the first dispersant, was less than 15 wt% (Comparative Examples 3 and 7).

[0120] In addition, it was confirmed that when NMP, rather than an alcohol-based solvent, was used as a solvent, the dispersant was not properly dissolved and the viscosity increased (Comparative Example 8).

Claims

1. Carbon nanotubes; A first dispersant comprising a polyvinyl butyral resin having a content of repeating units containing hydroxyl groups of 15 wt% or more and 30 wt% or less; A second dispersant comprising an amine group or an imine group; and A carbon nanotube dispersion containing an alcohol-based solvent.

2. In claim 1, A carbon nanotube dispersion comprising a first unit represented by the following chemical formula 1, a second unit represented by the following chemical formula 2, and a third unit represented by the following chemical formula 3: [Chemical Formula 1] [Chemical Formula 2] [Chemical Formula 3] In chemical formulas 1 to 3, R1 is a butyl group, l is a weight ratio of 0.5 or more and 0.9 or less in chemical formula 1, m is a weight ratio of chemical formula 2, which is 0.001 or more and 0.1 or less, n is a weight ratio of chemical formula 3, which is 0.15 or more and 0.3 or less.

3. In claim 1, A carbon nanotube dispersion having a weight average molecular weight of the first dispersant of 10,000 g / mol or more and 100,000 g / mol or less.

4. In claim 1, A carbon nanotube dispersion liquid wherein the second dispersant comprises an alkanolamine-based dispersant or an alkylene imine-based dispersant.

5. In claim 1, A carbon nanotube dispersion liquid in which the content of the first dispersant is 10 parts by weight or more and 400 parts by weight or less based on 100 parts by weight of the carbon nanotube.

6. In claim 1, A carbon nanotube dispersion liquid in which the content of the second dispersant is 1 part by weight or more and 50 parts by weight or less based on 100 parts by weight of the first dispersant.

7. In claim 1, A carbon nanotube dispersion liquid, wherein the total content of the first dispersant and the second dispersant is 15 parts by weight or more and 400 parts by weight or less based on 100 parts by weight of the carbon nanotube.

8. In claim 1, A carbon nanotube dispersion comprising the above carbon nanotubes, single-walled carbon nanotubes, multi-walled carbon nanotubes, or a combination thereof.

9. In claim 1, The specific surface area (BET) of the above carbon nanotube is 10 m 2 / g or more 1,200 m 2 Carbon nanotube dispersion having a mass of / g or less.

10. In claim 1, A carbon nanotube dispersion, wherein the first average particle diameter (D50) and the second average particle diameter (D90) of the carbon nanotubes are each 0.5 ㎛ or more and 60 ㎛ or less.

11. In claim 1, A carbon nanotube dispersion having a content of the carbon nanotubes of 0.01 wt% or more and 10 wt% or less based on the total weight of the carbon nanotube dispersion.

12. In claim 1, 25℃ and 2.5 sec -1 A carbon nanotube dispersion having a viscosity of 5,000 cPs or less at a shear rate of .

13. An electrode slurry composition comprising a carbon nanotube dispersion according to any one of claims 1 to 12, an electrode active material, and a binder.

14. An electrode comprising an electrode active material layer formed by an electrode slurry composition according to claim 13.

15. A secondary battery comprising an electrode according to claim 14.

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