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

Abstract

The present specification relates to a carbon nanotube dispersion solution, a preparation method therefor, an electrode slurry composition comprising same, an electrode comprising same, and a secondary battery comprising same, the carbon nanotube dispersion solution comprising: a carbon nanotube; a nitrile-based copolymer; an alkanolamine-based dispersant; and a cellulose-based dispersant.

Description

Carbon nanotube dispersion, method for producing the same, 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. 10-2023-0127042, filed September 22, 2023, and Korean Patent Office No. 10-2024-0027073, filed February 26, 2024, the contents of which are incorporated herein by reference.

[0002] The present specification provides a carbon nanotube dispersion, a method for producing the same, an electrode slurry composition comprising the same, an electrode comprising the same, and a secondary battery comprising 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 significantly reduces the amount of conductive material needed compared to carbon black, resulting in increased electrical capacity.

[0006] Hydrogenated nitrile butadiene rubber is widely known to be effective in dispersing carbon nanotubes in solvents. Methods utilizing various polymer dispersants are also being utilized.

[0007] However, the above method has limitations in lowering the viscosity of the dispersant, so a method that can drastically lower the viscosity is needed.

[0008] [Prior Art Literature]

[0009] [Patent Document]

[0010] (Patent Document 1) Republic of Korea Publication Patent No. 10-2016-0152219

[0011] One embodiment of the present invention provides a carbon nanotube dispersion, a method for producing the same, an electrode slurry composition comprising the same, an electrode comprising the same, and a secondary battery comprising the same.

[0012] One embodiment of the present invention comprises a carbon nanotube;

[0013] Nitrile copolymer;

[0014] Alkanolamine dispersant; and

[0015] A carbon nanotube dispersion containing a cellulose-based dispersant is provided.

[0016] In addition, one embodiment of the present invention provides an electrode slurry composition comprising the above-described carbon nanotube dispersion, electrode active material, and binder.

[0017] In addition, one embodiment of the present invention provides an electrode including an electrode active material layer formed by the electrode slurry composition described above.

[0018] In addition, one embodiment of the present invention provides a secondary battery including the above-described electrode.

[0019] A carbon nanotube dispersion according to one embodiment of the present invention has the effect of improving the dispersibility of carbon nanotubes.

[0020] Hereinafter, the specification will be described in detail.

[0021] 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.

[0022] One embodiment of the present invention provides a carbon nanotube dispersion comprising carbon nanotubes; a nitrile-based copolymer; an alkanolamine-based dispersant; and a cellulose-based dispersant.

[0023] The above carbon nanotube dispersion liquid can lower the viscosity of the dispersion liquid and induce performance improvement when applied to an electrode by including an alkanolamine-based dispersant and a cellulose-based dispersant.

[0024] NMP, a solvent used in conventional cathode manufacturing, is expensive and requires recycling. However, alkanolamine dispersants have similar boiling points to NMP, posing various challenges during recycling. Therefore, the development of a dispersion solution with superior performance while minimizing the alkanolamine dispersant content was essential.

[0025] The present inventors have discovered that when an alkanolamine-based dispersant and a cellulose-based dispersant are used together, the viscosity of the dispersion can be lowered while reducing the amount of the alkanolamine-based dispersant used, and have completed the present invention.

[0026] According to one embodiment of the present invention, a carbon nanotube dispersion comprises a nitrile copolymer. The nitrile copolymer can adsorb onto the surface of carbon nanotubes to provide physical dispersion stability. However, due to its interaction with the high surface energy of carbon nanotubes, strong van der Waals forces may be exerted, causing re-agglomeration, thereby lowering viscosity and thus reducing dispersion stability. This problem can be solved by using an alkanolamine dispersant and a cellulose dispersant together.

[0027] A carbon nanotube dispersion according to one embodiment of the present invention is characterized by including both an alkanolamine-based dispersant and a cellulose-based dispersant. A carbon nanotube dispersion according to one embodiment of the present invention includes an alkanolamine-based dispersant. The alkanolamine-based dispersant has a structure in which both a hydroxyl group (-OH) and an amine group are present in its molecular structure. The alkanolamine-based dispersant mainly adsorbs to the surface of carbon nanotubes to increase surface charge and induce electrical repulsion between carbon nanotubes. Meanwhile, the alkanolamine-based dispersant has the characteristic of simultaneously possessing hydrophilicity and hydrophobicity, and thus can contribute to mixing well with a solvent in the dispersion while interacting with carbon nanotubes. The alkanolamine-based dispersant has the characteristic of being effective in dispersing carbon nanotubes, and has the characteristic of being easy to control the characteristics by changing the number of amine groups and alkanol groups in the molecule and the number of carbon atoms contained in the alkanol groups.

[0028] According to one embodiment of the present invention, a carbon nanotube dispersion comprises a cellulose-based dispersant. The cellulose-based dispersant forms a physically stable structure surrounding the carbon nanotubes, thereby preventing aggregation between the carbon nanotubes. Furthermore, the cellulose-based dispersant forms a polymer network, thereby preventing re-aggregation of the carbon nanotubes.

[0029] In one embodiment of the present invention, the alkanolamine dispersant may contain 1 to 3 alkanol groups having 1 to 10 carbon atoms. Preferably, it may contain 1 to 2 alkanol groups having 2 to 8 carbon atoms. The alkanol group includes a hydroxyl group and an alkyl group. At this time, the hydroxyl group has the property of dissolving well in a solvent such as water by imparting hydrophilicity, and the alkyl group has the property of adsorbing to the surface of carbon nanotubes. By utilizing these properties, the alkanolamine dispersant can adsorb well to carbon nanotubes while being well mixed with a solvent, and can contribute to lowering the viscosity of the carbon nanotube dispersion.

[0030] In one embodiment of the present invention, the alkanol group may be a methanol group, an ethanol group, a propanol group, or a combination thereof.

[0031] In one embodiment of the present invention, the alkanolamine dispersant includes a first-, second-, or tertiary amine group. Preferably, it includes a first-class amine group. The amine group can be adsorbed onto the surface of carbon nanotubes to weaken the van der Waals force between the carbon nanotubes, thereby preventing the carbon nanotubes from agglomerating with each other. In addition, when the amine group is bonded to the surface of the carbon nanotubes, the surface charge increases, which can induce the formation of an electrical repulsive force between the carbon nanotubes. Through the above-described operating principle, it can contribute to further lowering the viscosity of the carbon nanotube dispersion.

[0032] In one embodiment of the present invention, the content of the alkanolamine dispersant may be 0.01 parts by weight or more and 10 parts by weight or less based on 100 parts by weight of the carbon nanotubes. Preferably, it may be 0.1 parts by weight or more and 8 parts by weight or less, 1 part by weight or more and 5 parts by weight or less, or 1.5 parts by weight or more and 3 parts by weight or less. In the above numerical range, the dispersibility of the carbon nanotubes is improved and the viscosity is maintained low. If it is lower than the above numerical range, the alkanolamine dispersant may not be sufficiently adsorbed on the surface of the carbon nanotubes, so that the aggregation phenomenon between the carbon nanotubes may not be controlled. On the other hand, if it is higher than the above numerical range, the remaining alkanolamine dispersant that was not adsorbed to the carbon nanotubes may be distributed in the solvent, which may lower the fluidity of the solvent and lower the viscosity of the dispersion.

[0033] In one embodiment of the present invention, the alkanolamine dispersant is aminoethylethanolamine, N-methylaminoethanol, aminoethoxyethanol, aminoethoxyethoxyethanol, methoxypropylamine, butoxyisopropylamine, 2-ethylhexylisopropoxyamine, ethanolpropylamine, ethylethanolamine, n-hydroxyethylmorpholine, aminopropyldiethanolamine, dimethylaminoethoxyethanol, diethanolamine, N-methyldiethanolamine, monoethanolamine, triethanolamine, 1-amino-2-propanol, 3-amino propanol, diisopropylamine, aminomethylpropanediol, N,N-dimethylaminomethylpropanediol, aminoethylpropanediol, N,N-dimethylaminoethylpropanediol, isopropylamine, 2-amino-1-butanol, aminomethylpropanol, aminodimethylpropanol, It may be one or two or more selected from the group consisting of N,N-dimethylaminomethylpropanol, isobutanolamine, diisopropanolamine, 3-amino,4-hydroxyoctane, 2-aminobutanol, tris(hydroxymethyl)aminomethane, N,N-dimethyltris(hydroxymethyl)aminomethane, hydroxypropylamine, benzylamine, hydroxyethyl amine, tris(hydroxyethyl)aminomethane, and diglycolamine.

[0034] In one embodiment of the present invention, the alkanolamine dispersant may be 2-amino-2-methyl-1-propanol or ethanolamine. ANGUS' Voltan100 or MERCK's ethanolamine may be used. Ethanolamine has short alkyl and hydroxyl groups, and thus has higher hydrophilic properties than other alkanolamine dispersants (e.g., propanolamine or butanolamine). In addition, since it can form strong hydrogen bonds, it contributes to strong adsorption onto the surface of carbon nanotubes, thereby reducing interactions between carbon nanotubes. This property can contribute to significantly lowering viscosity when using a hydrophilic solvent such as water.

[0035] In one embodiment of the present invention, the number average molecular weight (Mn) of the cellulose-based dispersant may be 5,000 or more and 50,000 or less. Preferably, it may be 8,000 or more and 50,000 or less, 10,000 or more and 45,000 or less, or 13,000 or more and 40,000 or less. Within the above numerical range, the dispersibility of carbon nanotubes can be improved, and excellent solubility in organic solvents is maintained, thereby providing excellent dispersibility of the entire dispersion. Meanwhile, when the above numerical range is satisfied, the size of the cellulose-based dispersant is controlled, so that an appropriate number of cellulose-based dispersants can be adsorbed onto the surface of the carbon nanotubes. In addition, since the polymer chains are not maintained too short, physical network formation is advantageous, so that the long-term storage stability of the dispersion can be improved. The above number average molecular weight can be measured by methods such as gel permeation chromatography (GPC), nuclear magnetic resonance spectroscopy (NMR spectroscopy), and light scattering.

[0036] In one embodiment of the present invention, the content of the cellulose-based dispersant may be 0.01 parts by weight or more and 10 parts by weight or less based on 100 parts by weight of the carbon nanotubes. Preferably, it may be 0.1 parts by weight or more and 8 parts by weight or less, 1 part by weight or more and 5 parts by weight or less, or 1.5 parts by weight or more and 3 parts by weight or less. Within the above numerical range, the dispersibility of carbon nanotubes can be improved, and the solubility in an organic solvent is excellently maintained, thereby providing an excellent effect of dispersibility of the entire dispersion. If the content is lower than the above numerical range, the cellulose-based dispersant may not be sufficiently adsorbed on the surface of the carbon nanotubes, and the aggregation phenomenon between the carbon nanotubes may not be controlled. On the other hand, if the content is higher than the above numerical range, the remaining cellulose-based dispersant that was not adsorbed to the carbon nanotubes may be distributed in the solvent, and the fluidity of the solvent may be reduced, thereby lowering the viscosity of the dispersion.

[0037] In one embodiment of the present invention, the value calculated by the following mathematical formula 1 may be 1% or more and 30% or less. Preferably, it may be 4% or more and 22% or less, 6% or more and 20% or less, or 6% or more and 13% or less. The following mathematical formula 1 explains the relationship between the contents of the alkanolamine dispersant, the nitrile copolymer, and the cellulose dispersant. The alkanolamine dispersant interacts with carbon nanotubes to contribute to lowering the viscosity of the dispersion, and its interaction with other dispersants is also important. Within the above numerical range, the viscosity of the dispersion can be significantly lowered, and a great effect can be expected even with a small amount of the alkanolamine dispersant.

[0038] [Mathematical Formula 1]

[0039] W1 / (W1+W2+W3)*100(%)

[0040] In mathematical formula 1,

[0041] W1 is the weight of the alkanolamine dispersant,

[0042] W2 is the weight of the nitrile copolymer,

[0043] W3 is the weight of the cellulose-based dispersant.

[0044] In one embodiment of the present invention, the carbon nanotube dispersion contains carbon nanotubes.

[0045] In one embodiment of the present invention, the carbon nanotube is for improving the conductivity of the electrode, and the graphite sheet has a cylindrical shape with a nano-sized diameter and has an sp2 bonding structure. At this time, the graphite sheet exhibits the characteristics of a conductor or a semiconductor depending on the angle and structure at which it is rolled. Carbon nanotubes can be classified into single-walled carbon nanotubes (SWCNT, single-walled carbon nanotube), double-walled carbon nanotubes (DWCNT, double-walled carbon nanotube), and multi-walled carbon nanotubes (MWCNT, multi-walled carbon nanotube) depending on the number of bonds forming the wall, and these carbon nanotubes can be appropriately selected depending on the use of the dispersion. In addition, the carbon nanotube may have a secondary shape formed by agglomeration or arrangement of a plurality of carbon nanotubes, for example, a bundle type carbon nanotube in which a plurality of carbon nanotubes are arranged or aligned in a bundle or rope shape in a certain direction, or an entangled type carbon nanotube in which a plurality of carbon nanotubes are entangled in a sphere or potato shape without a certain direction.

[0046] In one embodiment of the present invention, the carbon nanotube may be a multi-walled carbon nanotube. Multi-walled carbon nanotubes exhibit excellent conductivity and flexibility while also being able to be smoothly dispersed within the electrode. Furthermore, they have appropriately controlled crystallinity and include a nodal structure, thereby enhancing contact with the electrode's active material particles, thereby providing a beneficial effect in securing a conductive network.

[0047] In one embodiment of the present invention, the specific surface area (BET) of the carbon nanotube is 10 m 2 / g or more than 800 m 2 / g or less. Preferably, 20 m 2 / g or more than 700 m 2 / g or less or 50 m 2 / g or more than 500 m 2 / g or less. Within the above numerical range, the electrical conductivity of carbon nanotubes is excellent and the aggregation phenomenon can be controlled. If the above numerical range is exceeded, the van der Waals force between carbon nanotubes increases, causing aggregation, which may increase the viscosity of the dispersion and deteriorate the dispersion stability.

[0048] In one embodiment of the present invention, the average particle diameter (D50) of the carbon nanotubes may be 0.1 ㎛ to 20 ㎛, 0.5 ㎛ to 18 ㎛, 1 ㎛ to 16 ㎛, 9 ㎛ to 15 ㎛, or 9 ㎛ to 12.1 ㎛. The average particle diameter (D50) refers to a particle diameter corresponding to 50% of the cumulative number in a particle diameter distribution curve of carbon nanotubes. The average particle diameter (D50) can be measured using, for example, a laser diffraction method. Within the above range, carbon nanotubes do not aggregate with each other, and dispersibility can be improved. If it is less than the above numerical range, the particle size is too small, so that carbon nanotubes easily aggregate, which can increase the viscosity of the carbon nanotube dispersion.

[0049] In one embodiment of the present invention, the content of the carbon nanotubes may be 0.01 parts by weight or more and 10 parts by weight or less based on the total weight of the carbon nanotube dispersion. Preferably, it may be 0.1 parts by weight or more and 8 parts by weight or less, or 1 part by weight or more and 5 parts by weight or less. In the above numerical range, it is possible to prevent a decrease in the loading amount during electrode manufacturing, thereby increasing the process cost, and to prevent problems such as binder migration occurring during electrode drying, which reduces the adhesive strength, or increases the viscosity of the carbon nanotube dispersion.

[0050] In one embodiment of the present invention, the carbon nanotube dispersion contains a nitrile copolymer.

[0051] In one embodiment of the present invention, the nitrile copolymer may be a hydrogenated nitrile copolymer. Specifically, it may be a copolymer having an α,β-unsaturated nitrile-derived unit and a conjugated diene-derived unit. At this time, the conjugated diene-derived unit may be partially or completely hydrogenated. The hydrogenation method of the conjugated diene may be performed through a hydrogenation reaction known in the art, for example, a catalytic hydrogenation reaction using a catalyst system such as Rh, Ru, Pd, or Ir, and the hydrogenation rate may be controlled by controlling the amount of the catalyst, the reaction hydrogen pressure, the reaction time, etc.

[0052] The above nitrile copolymer can be produced by copolymerizing an α,β-unsaturated nitrile monomer and a conjugated diene monomer, and then hydrogenating the C=C double bonds in the copolymer. The polymerization reaction and hydrogenation process of the above monomers can be performed according to a conventional method.

[0053] As the above α,β-unsaturated nitrile monomer, for example, acrylonitrile or methacrylonitrile may be used, and one of these may be used alone or a mixture of two or more may be used.

[0054] As the above conjugated diene monomer, for example, conjugated diene monomers having 4 to 6 carbon atoms, such as 1,3-butadiene, isoprene or 2,3-methyl butadiene, can be used, and one of these alone or a mixture of two or more of these can be used.

[0055] Meanwhile, the nitrile copolymer may contain an α,β-unsaturated nitrile-derived unit: a conjugated diene-derived unit in a weight ratio of 10 to 50:50 to 90, preferably 20 to 40:60 to 80, and more preferably 25 to 40:60 to 75. When the content of each unit in the nitrile copolymer satisfies the above range, excellent dispersibility and high-temperature characteristics are exhibited. Here, the content of the α,β-unsaturated nitrile-derived unit may be measured as the median value of the quantified value by measuring the amount of nitrogen generated according to the Mill Oven Method of JIS K 6364 and converting the amount of bonding thereof from the α,β-unsaturated nitrile molecular weight, and the content of the conjugated diene-derived unit may be calculated as a value obtained by subtracting the weight of the α,β-unsaturated nitrile-derived unit from the weight of the entire copolymer.

[0056] The above nitrile copolymer may have a hydrogenation rate of 80% or more, preferably 90%, of the conjugated diene unit. This is because, when a dispersant with remaining unhydrogenated conjugated diene units is used, the reactivity with the electrolyte may increase due to the double bond in the conjugated diene, resulting in poor high-temperature properties.

[0057] The above nitrile copolymer may include a repeating unit represented by the following chemical formula 2 and a repeating unit represented by the following chemical formula 3.

[0058] [Chemical Formula 2]

[0059]

[0060] [Chemical Formula 3]

[0061]

[0062] The content of the repeating unit represented by the above chemical formula 2 may be 10 wt% to 50 wt%, preferably 20 wt% to 40 wt%, more preferably 25 wt% to 40 wt%, and the content of the repeating unit represented by the above chemical formula 3 may be 50 wt% to 90 wt%, preferably 60 wt% to 80 wt%, more preferably 60 wt% to 75 wt%.

[0063] In one embodiment of the present invention, the weight average molecular weight of the nitrile copolymer may be 10,000 g / mol or more and 100,000 g / mol or less. Preferably, it may be 20,000 g / mol or more and 100,000 g / mol or less, or 20,000 g / mol or more and 50,000 g / mol or less. When a nitrile copolymer having the above weight average molecular weight is used, the positive electrode active material can be uniformly dispersed with a small amount of dispersant, and the viscosity reduction effect of the positive electrode slurry composition is further excellent.

[0064] In one embodiment of the present invention, the content of the nitrile copolymer may be 0.1 parts by weight or more and 10 parts by weight or less based on the total weight of the carbon nanotube dispersion. Preferably, it may be 0.1 parts by weight or more and 8 parts by weight or less, or 0.2 parts by weight or more and 5 parts by weight or less. The chemical resistance and dispersion stability of the carbon nanotube dispersion are improved, and the viscosity can be prevented from increasing. The nitrile copolymer can be adsorbed to the surface of the carbon nanotubes to prevent aggregation between the carbon nanotubes. If the content is less than the above numerical range, a sufficient amount of the nitrile copolymer to be adsorbed to the surface of the carbon nanotubes is not secured, and if the content exceeds the above numerical range, the nitrile copolymer that is not adsorbed to the surface of the carbon nanotubes may form a polymer structure in the dispersion, thereby increasing the viscosity of the dispersion.

[0065] In one embodiment of the present invention, the acrylonitrile (ACN) content of the nitrile-based copolymer may be 10 wt% or more and 50 wt% or less. Preferably, it may be 15 wt% or more and 45 wt% or less, or 20 wt% or more and 38 wt% or less. Within the above numerical range, chemical resistance, mechanical strength, and flexibility may be increased. In particular, within the above numerical range, interaction with carbon nanotubes is strengthened, thereby improving the dispersibility of carbon nanotubes, thereby reducing the viscosity of the carbon nanotube dispersion. The acrylonitrile (ACN) content refers to the weight ratio of acrylonitrile groups based on 100% of the total weight of the nitrile-based copolymer. The acrylonitrile content in the carbon nanotube dispersion can be derived by calculating the presence and content of acrylonitrile groups and other functional groups using nuclear magnetic resonance analysis (NMR), four-dimensional infrared spectroscopy (FTIR), or gel permeation chromatography (GPC).

[0066] In one embodiment of the present invention, the Mooney viscosity of the nitrile copolymer at 100°C may be 15 or more and 120 or less. Preferably, it may be 18 or more and 100 or less, or 20 or more and 50 or less. Within the above numerical range, the fluidity, processability, and mechanical strength of the dispersion may be excellently maintained. The Mooney viscosity may be measured by using a Mooney viscometer to measure the resistance provided by the sample when a rotor rotates within the polymer sample at 100°C for a certain period of time. At this time, the heat distribution within the copolymer may be uniformly distributed by preheating for 1 minute, and the measurement may be performed for 4 minutes.

[0067] In one embodiment of the present invention, the carbon nanotube dispersion may include a second dispersant selected from the group consisting of a copolymer dispersant including an ionic main chain, a polyvinylpyrrolidone-based dispersant, a polyacrylic acid-based dispersant, a polyvinyl alcohol-based dispersant, a hydroxyalkyl cellulose-based dispersant, and combinations thereof.

[0068] In one embodiment of the present invention, the copolymer dispersant including the ionic main chain may include an ionic main chain and a non-ionic side chain.

[0069] In one embodiment of the present invention, the ionic main chain may include an anionic component containing one or more salts selected from the group consisting of carboxylates, phosphates, sulfonates, and sulfates; or a cationic component containing an ammonium salt. Preferably, the cationic component containing an ammonium salt may be included.

[0070] In one embodiment of the present invention, the nonionic side chain may be a hydroxy alkyl group having 1 to 10 carbon atoms.

[0071] In one embodiment of the present invention, the copolymer dispersant may be a hydroxyalkyl ammonium salt polymer. Specifically, BYK LPN 23676 may be used.

[0072] 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 3,000 cPs or less. The viscosity may be 2,500 cPs or less, 2,000 cPs or less, or 1,500 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.

[0073] In one embodiment of the present invention, the carbon nanotube dispersion is heated at 25°C and 15 sec. -1The viscosity at a shear rate of may be 900 cPs or less. The viscosity may be 500 cPs or less, 400 cPs or less, or 300 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.

[0074] 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.

[0075] In one embodiment of the present invention, the carbon nanotube dispersion may further include a solvent.

[0076] The solvent may be water, an organic solvent, or a mixture thereof. Examples of the organic solvent include amide-based polar organic solvents such as dimethylformamide (DMF), diethyl formamide, dimethyl acetamide (DMAc), and N-methyl pyrrolidone (NMP); alcohols such as methanol, ethanol, 1-propanol, 2-propanol (isopropyl alcohol), 1-butanol (n-butanol), 2-methyl-1-propanol (isobutanol), 2-butanol (sec-butanol), 1-methyl-2-propanol (tert-butanol), pentanol, hexanol, heptanol, and octanol; glycols such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, 1,3-propanediol, 1,3-butanediol, 1,5-pentanediol, or hexylene glycol; Examples thereof include polyhydric alcohols such as glycerin, trimethylolpropane, pentaerythritol, or sorbitol; glycol ethers such as 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 monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, or tetraethylene glycol monobutyl ether; ketones such as acetone, methyl ethyl ketone, methyl propyl ketone, or cyclopentanone; and esters such as ethyl acetate, γ-butyl lactone, and ε-propiolactone, and any one of these or a mixture of two or more thereof may be used, but the present invention is not limited thereto.

[0077] One embodiment of the present invention provides an electrode slurry composition comprising the above-described carbon nanotube dispersion, electrode active material, and binder.

[0078] 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 Li, Ni, or Mn.

[0079] 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.

[0080] In one embodiment of the present invention, the binder may be included in an amount of 5 wt% or less, and preferably 1 to 3 wt%, based on the total solid content in the electrode slurry composition. When the binder content satisfies the above range, excellent electrode adhesion can be achieved while minimizing an increase in electrode resistance.

[0081] 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.

[0082] 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.

[0083] 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.

[0084] 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.

[0085] In one embodiment of the present invention, the electrode may be an anode.

[0086] One embodiment of the present invention provides a secondary battery including the above-described electrode.

[0087] 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.

[0088] 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 secondary batteries. 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 nonwoven fabric, for example, a nonwoven 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.

[0089] 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.

[0090] Hereinafter, the present invention will be described in more detail through examples.

[0091] <Preparation of nitrile copolymer>

[0092] HNBR1: Acrylonitrile (ACN) content 34 wt%, Mooney viscosity at 100℃ 39

[0093] <Preparation of alkanolamine dispersant>

[0094] Dispersant B1: Voltan100 from ANGUS

[0095] Dispersant B2: Ethanolamine from MERCK

[0096] <Preparation of Cellulose Dispersant>

[0097] Dispersant C1: Cellulose acetate propionate (Mn: 15,000) from MERCK

[0098] Dispersant C2: Cellulose acetate butyrate (Mn: 12,000) from MERCK

[0099] <Preparation of carbon nanotube dispersion>

[0100] <Example 1>

[0101] Multi-walled carbon nanotubes (surface area 186 m) made of carbon nanotubes 2 / g) 3 wt%, hydrogenated nitrile butadiene rubber (HNBR1) 0.45 wt% as a nitrile copolymer, dispersant B1 0.075 wt% as an alkanolamine dispersant, C1 0.075 wt% as a cellulose dispersant, and N-methyl pyrrolidone (NMP) as a solvent were mixed to prepare a 1 kg mixture, and then stirred for 10 minutes with a stirrer, and then treated 5 times under a pressure condition of 1,200 bar using a high-pressure homogenizer to prepare a carbon nanotube dispersion. The weight of the above materials is based on the total weight of the dispersion.

[0102] <Examples 2 to 5>

[0103] A carbon nanotube dispersion was prepared by changing the composition as shown in Table 1 below.

[0104] <Comparative Examples 1 to 3>

[0105] A carbon nanotube dispersion was prepared by changing the composition as shown in Table 1 below.

[0106] <Experimental Example 1: Viscosity Measurement>

[0107] 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 .

[0108] <Experimental Example 2: Measurement of average particle size>

[0109] 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 solution was allowed to stabilize for 10 minutes before measurement. The average particle diameter (D50) based on 50% of the particle diameter distribution was calculated from the measuring device.

[0110] <Experimental Example 3: Relationship between the contents of different dispersants>

[0111] The values ​​calculated using the following mathematical formula 1 were calculated and entered in Table 1.

[0112] [Mathematical Formula 1]

[0113] W1 / (W1+W2+W3)*100(%)

[0114] In mathematical formula 1,

[0115] W1 is the weight of the alkanolamine dispersant,

[0116] W2 is the weight of the nitrile copolymer,

[0117] W3 is the weight of the cellulose-based dispersant.

[0118] ClassificationComparative Example 1Comparative Example 2Comparative Example 3Example 1Example 2Example 3Example 4Example 5Carbon nanotube weight part 33333333Nitrile copolymer typeHNBR1HNBR1HNBR1HNBR1HNBR1HNBR1HNBR1HNBR1HNBR1HNBR1weight part 0.450.450.450.450.450.420.450.45Alkanolamine typeDispersant typeB1B2-B1B1B1B1B2weight part 0.150.1500.0750.030.120.0750.075% by mass of CNT5.0%5.0%-2.5%1.0%4.0%2.5%2.5%Cellulose type Dispersant type--C1C1C1C1C2C1Part by weight000.150.0750.120.030.0750.075% by mass of CNT--5.0%2.5%4.0%1.0%2.5%2.5%Experimental example 1Viscosity (cP@2.5 / s)3,2393,4164,4391,4222,7232,0811,9361,980Viscosity (cP@15 / s)9139651196275499338409418Experimental example 2Particle size (D50, ㎛)8.57.112.311.281111.910Experimental example 3Mathematical formula 125.0%25.0%0.0%12.5%5.0%21.1%12.5%12.5%

[0119] From the above results, it was confirmed that the viscosity of the carbon nanotube dispersion was low when it contained all of a nitrile copolymer, an alkanolamine dispersant, and a cellulose dispersant (Examples 1 to 5).

[0120] On the other hand, it was confirmed that the viscosity increased when no alkanolamine-based dispersant was included (Comparative Example 3) or when no cellulose-based dispersant was included (Comparative Examples 1 and 2).

Claims

1. Carbon nanotubes; Nitrile copolymer; Alkanolamine dispersant; and A carbon nanotube dispersion containing a cellulose-based dispersant.

2. In claim 1, A carbon nanotube dispersion wherein the above alkanolamine-based dispersant contains 1 to 3 alkanol groups having 1 to 10 carbon atoms.

3. In claim 1, A carbon nanotube dispersion liquid in which the content of the alkanolamine-based dispersant is 0.01 parts by weight or more and 10 parts by weight or less based on 100 parts by weight of the carbon nanotube.

4. In claim 1, A carbon nanotube dispersion having a number average molecular weight (Mn) of the above cellulose-based dispersant of 5,000 or more and 50,000 or less.

5. In claim 1, A carbon nanotube dispersion liquid in which the content of the cellulose-based dispersant is 0.01 parts by weight or more and 10 parts by weight or less based on 100 parts by weight of the carbon nanotubes.

6. In claim 1, A carbon nanotube dispersion having a value calculated by the following mathematical formula 1 of 1% or more and 30% or less: [Mathematical Formula 1] W1 / (W1+W2+W3)*100(%) In mathematical formula 1, W1 is the weight of the alkanolamine dispersant, W2 is the weight of the nitrile copolymer, W3 is the weight of the cellulose-based dispersant.

7. In claim 1, A carbon nanotube dispersion wherein the above carbon nanotubes are multi-walled carbon nanotubes.

8. In claim 1, The specific surface area (BET) of the above carbon nanotube is 10 m 2 / g or more than 800 m 2 Carbon nanotube dispersion having a mass of / g or less.

9. In claim 1, A carbon nanotube dispersion having an average particle diameter (D50) of the above carbon nanotubes of 0.1 ㎛ or more and 20 ㎛ or less.

10. In claim 1, A carbon nanotube dispersion, wherein the content of the carbon nanotube is 0.01 parts by weight or more and 10 parts by weight or less based on the total weight of the carbon nanotube dispersion.

11. In claim 1, A carbon nanotube dispersion, wherein the content of the nitrile copolymer is 0.1 parts by weight or more and 10 parts by weight or less based on the total weight of the carbon nanotube dispersion.

12. In claim 1, A carbon nanotube dispersion having an acrylonitrile (ACN) content of 10 wt% or more and 50 wt% or less of the above nitrile copolymer.

13. In claim 1, A carbon nanotube dispersion having a Mooney viscosity of 15 to 120 at 100°C of the above nitrile copolymer.

14. In claim 1, 25℃ and 15 sec -1 A carbon nanotube dispersion having a viscosity of 3,000 cPs or less at a shear rate of .

15. An electrode slurry composition comprising a carbon nanotube dispersion according to any one of claims 1 to 14, an electrode active material, and a binder.

16. An electrode comprising an electrode active material layer formed by an electrode slurry composition according to claim 15.

17. A secondary battery comprising an electrode according to claim 16.

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