Copolymer, dispersion liquid prepared using same, positive electrode for secondary battery prepared using dispersion liquid, and secondary battery including positive electrode

Abstract

To provide a positive electrode slurry composition using a copolymer having a polar monomer unit bonded to a metal cation as a dispersant to maximize electrostatic repulsion, thereby producing a carbon nanotube dispersion having higher solid content and improved dispersibility, and to provide a positive electrode and a secondary battery using the same.SOLUTION: A copolymer comprising an acrylate-based monomer unit comprising a linear or branched aliphatic hydrocarbon having 5 to 22 carbon atoms, an acrylate-based monomer unit comprising an aromatic or aliphatic ring, and a polar monomer unit comprising a functional group selected from the group consisting of a carboxylic acid, a sulfonic acid, a phosphonic acid, a cyano, a pyrrolidone, an amide, an alkylamide, and the like; And a positive electrode for a secondary battery prepared using the dispersion liquid, and a secondary battery including the positive electrode.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a copolymer, a dispersion containing the copolymer, a cathode slurry composition, a cathode, and a secondary battery, and more specifically, to a copolymer that can be used to prepare a carbon nanotube dispersion having improved dispersibility and a higher solid content, and a cathode slurry composition and an electrode containing the copolymer. [Background technology]

[0002] Carbon materials have unique mechanical, electrical, and thermal properties, and are therefore used in a variety of fields, including electronics, biotechnology, and medicine. Recently, in addition to conventional carbon materials such as graphite, activated carbon, and carbon black, carbon nanomaterials such as carbon nanotubes, fullerenes, and graphene have been attracting attention.

[0003] On the other hand, in order to use carbon materials efficiently, they must be effectively dispersed in matrices of various materials.

[0004] However, carbon materials, especially carbon nanomaterials, tend to aggregate within the matrix due to strong van der Waals forces, which can lead to problems such as a loss of inherent properties and reduced uniformity.

[0005] Methods for dispersing carbon materials include mechanical dispersion, which utilizes physical forces such as ultrasound, milling, and high shear force; dispersion using a dispersant; and dispersion through surface modification.

[0006] However, mechanical dispersion and dispersion by surface modification are likely to damage the carbon material, which can lead to a significant decrease in the inherent properties of the carbon material (e.g., electrical conductivity, thermal conductivity, etc.).

[0007] Therefore, the dispersion of carbon materials using dispersants is being actively researched. In particular, in order to efficiently disperse carbon nanomaterials such as carbon nanotubes, intensive research is being conducted on wrapping carbon nanomaterials with polymer dispersants or utilizing π-π interactions between the p orbitals of the aromatic rings of polymer dispersants and the p orbitals of carbon nanomaterials.

[0008] However, there are still not many dispersants that can efficiently disperse carbon materials, especially carbon nanomaterials, while maintaining their inherent properties, and there is a need for research into this. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Republic of Korea Patent Publication No. 10-2022-0141368 Summary of the Invention [Problem to be solved by the invention]

[0010] The present invention provides a carbon nanotube dispersion having a higher solid content and improved dispersibility by using a copolymer in which a polar monomer unit is bonded to a metal cation as a dispersant to maximize electrostatic repulsion, and also provides a positive electrode slurry composition, a positive electrode, and a secondary battery containing the same. The purpose is to:

[0011] However, the problems to be solved by the present application are not limited to those mentioned above, and other problems not mentioned will be clearly understood by those skilled in the art from the following description. [Means for solving the problem]

[0012] One aspect of the present application is an acrylate-based monomer unit containing a linear or branched aliphatic hydrocarbon having 5 to 22 carbon atoms; one or more monomer units selected from the group consisting of acrylate-based monomer units containing one or more substituted or unsubstituted aromatic or aliphatic rings and vinyl-based monomer units containing one or more substituted or unsubstituted aromatic or aliphatic rings; Carboxylic acid (COOH), sulfonic acid (SO3H), phosphonic acid (PO3H2), cyano (CN), pyrrolidone (NC4H6O), amide, alkylamide, dialkylamide, alcohol, epoxy group, caprolactam (C5H 10 a polar monomer unit containing one or more functional groups selected from the group consisting of morpholine (C4H8NO) and oxazolidone (C3H4NO2), A copolymer is provided.

[0013] Another aspect of the present application is The copolymer; A solvent; carbon nanotubes, A dispersion is provided.

[0014] Yet another aspect of the present application is the dispersion; a positive electrode active material; A positive electrode slurry composition is provided.

[0015] Yet another aspect of the present application is A current collector; a positive electrode active material layer formed by applying the positive electrode slurry composition onto the current collector, Provide the positive electrode.

[0016] Yet another aspect of the present application is The positive electrode includes A secondary battery is provided. [Effects of the Invention]

[0017] As described above, the copolymer of the present invention can be prepared by selecting a monomer unit capable of exhibiting electrostatic repulsion during copolymer synthesis and selecting a substituent to maximize this.

[0018] In this case, in order to maximize the electrostatic repulsion, the functional groups of the polar monomer units that have been ionized to anions can be substituted with cations, particularly metal cations.

[0019] Furthermore, the dispersion of the present invention can ensure dispersibility and dispersion stability by maximizing electrostatic repulsion, and can have a higher solid content.

[0020] In addition, a positive electrode slurry composition, a positive electrode, and a secondary battery containing a dispersion prepared using the copolymer of the present invention can be produced. DETAILED DESCRIPTION OF THE INVENTION

[0021] The terms and words used in this specification and claims should not be interpreted in a limited way to their ordinary or dictionary meanings, but should be interpreted in a way that is consistent with the technical idea of ​​the present invention, in accordance with the principle that the inventor can appropriately define the concept of the term in order to best describe his or her invention.

[0022] Therefore, it should be understood that the configuration of the embodiment described in this specification is merely one of the most preferred embodiments of the present invention and does not represent the entire technical idea of ​​the present invention, and that there may be various equivalents and modifications that can replace them at the time of this application.

[0023] In this specification, the singular includes the plural unless the context clearly indicates otherwise. It should be understood that in this specification, the terms "comprise," "comprise," or "have" are intended to specify the presence of embodied features, numbers, steps, components, or combinations thereof, but do not preclude the possibility of the presence or addition of one or more other features, numbers, steps, components, or combinations thereof.

[0024] Where various parameters are given herein as ranges, preferred ranges or lists of upper and lower preferred values, it should be understood that all ranges formed by any pair of any upper range limit or preferred value, and any lower range limit or preferred value, are specifically disclosed, regardless of whether ranges are otherwise disclosed.

[0025] Where a range of numerical values ​​is recited herein, unless otherwise stated, the range is intended to include the endpoints thereof, and all integers and fractions within the range. It is not intended that the scope of the invention be limited to the specific values ​​recited when defining a range.

[0026] In this specification, the terms "from" and "to" in "from a to b" and "a to b" that indicate a numerical range are defined as ≧a and ≦b. The copolymer according to one embodiment of the present invention comprises an acrylate monomer unit containing a linear or branched aliphatic hydrocarbon having 5 to 22 carbon atoms, one or more monomer units selected from the group consisting of acrylate-based monomer units containing one or more substituted or unsubstituted aromatic or aliphatic rings and vinyl-based monomer units containing one or more substituted or unsubstituted aromatic or aliphatic rings; Carboxylic acid (COOH), sulfonic acid (SO3H), phosphonic acid (PO3H2), cyano (CN), pyrrolidone (NC4H6O), amide, alkylamide, dialkylamide, alcohol, epoxy group, caprolactam (C5H 10 and polar monomer units containing one or more functional groups selected from the group consisting of morpholine (C4H8NO) and oxazolidone (C3H4NO2).

[0027] In one embodiment, the acrylate-based monomer unit containing a linear or branched aliphatic hydrocarbon having 5 to 22 carbon atoms is n-pentyl(meth)acrylate, n-hexyl(meth)acrylate, n-heptyl(meth)acrylate, n-octyl(meth)acrylate, 2-ethylhexyl(meth)acrylate, n-nonyl(meth)acrylate, or the like. n-nonyl(meth)acrylate, n-decyl(meth)acrylate, n-undecyl(meth)acrylate, lauryl(meth)acrylate, n-dodecyl(meth)acrylate, n-tridecyl(meth)acrylate, n-tetradecyl(meth)acrylate n-tetradecyl(meth)acrylate, n-pentadecyl(meth)acrylate, cetyl(meth)acrylate, n-hexadecyl(meth)acrylate, n-heptadecyl(meth)acrylate, stearyl(meth)acrylate, n-nonadecyl(meth)acrylate, n-eicosyl(meth)acrylate, n-heneicosyl(meth)acrylate, n-dococyl(meth)acrylate, iso-pentyl(meth)acrylate, iso-heptyl(meth)acrylate -heptyl(meth)acrylate, iso-octyl(meth)acrylate, iso-nonyl(meth)acrylate, iso-decyl(meth)acrylate, iso-undecyl(meth)acrylate, iso-dodecyl(meth)acrylate,iso-tridecyl(meth)acrylate, iso-tetradecyl(meth)acrylate, iso-pentadecyl(meth)acrylate, iso-cetyl(meth)acrylate, iso-hexadecyl(meth)acrylate, iso-heptadecyl(meth)acrylate The copolymer may be formed by polymerizing iso-stearyl(meth)acrylate, iso-stearyl(meth)acrylate, iso-nonadecyl(meth)acrylate, iso-eicosyl(meth)acrylate, iso-heneicosyl(meth)acrylate, iso-docosyl(meth)acrylate, or combinations thereof.

[0028] In this regard, the (meth)acrylate-based monomer unit described as an example of the acrylate-based monomer unit containing the linear or branched aliphatic hydrocarbon having 5 to 22 carbon atoms may represent both methacrylate and acrylate.

[0029] For example, the above-mentioned n-pentyl(meth)acrylate can represent both n-pentyl methacrylate and n-pentyl acrylate.

[0030] For example, the acrylate-based monomer unit containing a linear or branched aliphatic hydrocarbon having 5 to 22 carbon atoms may be formed by polymerizing stearyl acrylate.

[0031] In one embodiment, the at least one monomer unit selected from the group consisting of acrylate-based monomer units containing one or more substituted or unsubstituted aromatic or aliphatic rings and vinyl-based monomer units containing one or more substituted or unsubstituted aromatic or aliphatic rings is selected from the group consisting of styrene, cyclopentyl acrylate, cyclohexyl acrylate, benzyl acrylate, benzyl methacrylate, phenyl acrylate, phenyl methacrylate, 3-phenoxybenzyl acrylate, σ-phenyl phenoxy ethyl acrylate, σ-phenyl phenoxy ethyl methacrylate, The polymerizable monomer may be formed from 1-pyrene 2-methyl-2-propenoate, 1-naphthyl acrylate, 1-naphthyl methacrylate, 2-naphthyl acrylate, 2-naphthyl methacrylate, 9-anthracene methyl acrylate, 9-anthracene methyl methacrylate, or a combination thereof.

[0032] For example, the acrylate-based monomer unit containing one or more substituted or unsubstituted aromatic or aliphatic rings and the vinyl-based monomer unit containing one or more substituted or unsubstituted aromatic or aliphatic rings may be formed by polymerizing styrene.

[0033] In one embodiment, the polar monomer unit is selected from the group consisting of acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, aconitic acid, vinylbenzoic acid, 2-acrylamido-2-methylpropane sulfonic acid, vinyl sulfonic acid, 4-styrenesulfonic acid, vinyl phosphonic acid, acrylonitrile, vinyl pyrrolidone, acrylamide, N-methyl acylamide, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, and the like. The polymer may be formed by polymerizing glycidyl methacrylate, glycidyl methacrylate, or a combination thereof.

[0034] For example, the polar monomer unit may be formed by polymerizing methacrylic acid, maleic acid, 4-styrenesulfonic acid, vinylphosphonic acid, or a combination thereof.

[0035] In one embodiment, the copolymer is formed by polymerizing stearyl acrylate, styrene, acrylonitrile, and methacrylic acid, or

[0036] It is formed by the polymerization of stearyl acrylate, styrene, acrylonitrile, and maleic acid, It is formed by the polymerization of stearyl acrylate, styrene, acrylonitrile, and 4-styrenesulfonic acid, It may be formed by polymerizing stearyl acrylate, styrene, acrylonitrile, and vinyl phosphonic acid.

[0037] In one embodiment, the copolymer comprises, based on 100 mol % of the copolymer: acrylate-based monomer units containing 5 mol % or more and 70 mol % or less of the linear or branched aliphatic hydrocarbon having 5 to 22 carbon atoms; one or more monomer units selected from the group consisting of 5 mol % or more and 70 mol % or less of the substituted or unsubstituted acrylate-based monomer units containing one or more aromatic or aliphatic rings, and substituted or unsubstituted vinyl-based monomer units containing one or more aromatic or aliphatic rings, 5 mol% or more and 50 mol% or less of the above carboxylic acids (COOH), sulfonic acids (SO3H), phosphonic acids (PO3H2), cyano (CN), pyrrolidone (NC4H6O), amides, alkylamides, dialkylamides, alcohols, epoxy groups, caprolactam (C5H 10and one or more monomer units selected from the group consisting of polar monomer units containing one or more functional groups selected from the group consisting of morpholine (C4H8NO) and oxazolidone (C3H4NO2).

[0038] For example, the copolymer may contain, based on 100 mol % of the copolymer, 5 mol % to 70 mol % to 10 mol % to 60 mol % to 15 mol % to 50 mol % to 20 mol % to 40 mol % to 30 mol % to 40 mol % or 35 mol % to 45 mol % of the acrylate-based monomer unit containing a linear or branched aliphatic hydrocarbon having 5 to 22 carbon atoms. If the content of the acrylate-based monomer unit containing a linear or branched aliphatic hydrocarbon having 5 to 22 carbon atoms is below the range of the present application, the copolymer may have difficulty wrapping carbon nanotubes. If the content exceeds the range of the present application, the copolymer may not dissolve in a solvent and may precipitate or phase separation may occur.

[0039] Furthermore, for example, the copolymer may contain, based on 100 mol% of the copolymer, one or more monomer units selected from the group consisting of acrylate-based monomer units containing one or more substituted or unsubstituted aromatic or aliphatic rings and vinyl-based monomer units containing one or more substituted or unsubstituted aromatic or aliphatic rings, in an amount of 5 mol% or more, 70 mol% or less, 10 mol% or more, 60 mol% or less, 15 mol% or more, 50 mol% or less, 15 mol% or more, 40 mol% or less, 20 mol% or more, 40 mol% or less, or 25 mol% or more, 35 mol% or less. However, either one of the content of the acrylate-based monomer units and the content of the vinyl-based monomer units may be 0 mol%. The acrylate-based monomer units containing one or more substituted or unsubstituted aromatic or aliphatic rings and vinyl-based monomer units containing one or more substituted or unsubstituted aromatic or aliphatic rings may be 0 mol%. If the content of any one or more monomer units selected from the group consisting of monomer units is below the range of the present application, the interaction between the carbon nanotubes and the copolymer chains may be weak, making it difficult for them to function as a dispersant. If the content of any one or more monomer units selected from the group consisting of monomer units is above the range of the present application, the viscosity of the dispersion may become excessively high.

[0040] For example, the copolymer may contain the polar monomer unit in an amount of 5 mol% to 50 mol%, 5 mol% to 40 mol%, 5 mol% to 30 mol%, 5 mol% to 25 mol%, 5 mol% to 20 mol%, or 10 mol% to 20 mol%, based on 100 mol% of the copolymer. If the content of the polar monomer unit is below the range specified in the present application, the copolymer may not dissolve in a solvent and may precipitate or phase separation may occur. If the content exceeds the range specified in the present application, the glass transition temperature may become too high, and the electrode may not be flexible and may crack when manufactured.

[0041] In one embodiment, the copolymer may be represented by the following Formula 1: [ka] In the above Chemical Formula 1, R1~R 15 are the same or different and each independently represents hydrogen or a linear or branched hydrocarbon having 1 to 4 carbon atoms; R'1 is a linear or branched aliphatic hydrocarbon having 5 to 22 carbon atoms; R'2 contains one or more substituted or unsubstituted aromatic or aliphatic rings; R'3 contains one or more substituted or unsubstituted aromatic or aliphatic rings; R'4 is cyano (CN), pyrrolidone (NC4H6O), amide, alkylamide, dialkylamide, alcohol, epoxy group, caprolactam (C5H 10 one or more selected from the group consisting of morpholine (C4H8NO) and oxazolidone (C3H4NO2); R'5 is at least one selected from the group consisting of carboxylic acid (COOH), sulfonic acid (SO3H), and phosphonic acid (PO3H2); l+m+n+o+p=1, 0.05≦l≦0.70, 0.05≦m+n≦0.70, and 0.05≦o+p≦0.50. (However, either m or n may be 0, and o may be 0.)

[0042] In one embodiment, in Chemical Formula 1, R to R 15 may all be hydrogen.

[0043] In one embodiment, in Chemical Formula 1, R'1 is n-pentyl, n-hexyl, n-heptyl, n-octyl, 2-ethylhexyl, n-nonyl, n-decyl, n-undecyl, lauryl, n-dodecyl, n-tridecyl, n-tetradecyl, n-pentadecyl, cetyl, n-hexadecyl, n-heptadecyl, stearyl, n-octadecyl, n-nonadecyl, n-eicosyl, n-heneicosyl, n-docosyl, iso-pentyl, iso-heptyl, iso-octyl, iso-nonyl, iso-decyl, iso-undecyl, iso-dodecyl, iso-tridecyl, iso-tetradecyl, iso-pentadecyl, iso-cetyl, iso-hexadecyl, iso-heptadecyl, iso-stearyl, The alkyl group may include any one or more selected from the group consisting of iso-octadecyl, iso-nonadecyl, iso-eicosyl, iso-heneicosyl, and iso-docosyl.

[0044] For example, in the above Chemical Formula 1, R'1 may be n-octadecyl.

[0045] In one embodiment, in Formula 1, R'2 and R'3 may be the same or different and each independently may comprise one or more groups selected from the group consisting of substituted or unsubstituted cyclopentyl, cyclohexyl, benzyl, phenyl, phenoxy, naphthalene, anthracene, and pyrene.

[0046] For example, in the above Chemical Formula 1, R'2 may be benzyl, phenyl, naphthalene, or a 3-phenoxybenzyl group, and R'3 may be a phenyl group.

[0047] In one embodiment, the monomer containing R'1 in Chemical Formula 1 is n-pentyl(meth)acrylate, n-hexyl(meth)acrylate, n-heptyl(meth)acrylate, n-octyl(meth)acrylate, 2-ethylhexyl(meth)acrylate, n -nonyl(meth)acrylate, n-decyl(meth)acrylate, n-undecyl(meth)acrylate, lauryl(meth)acrylate, n-dodecyl(meth)acrylate, n-tridecyl(meth)acrylate , n-tetradecyl(meth)acrylate, n-pentadecyl(meth)acrylate, cetyl(meth)acrylate, n-hexadecyl(meth)acrylate, n-heptadecyl(meth)acrylate, stearyl(meth)acrylate aryl(meth)acrylate, n-nonadecyl(meth)acrylate, n-eicosyl(meth)acrylate, n-heneicosyl(meth)acrylate, n-dococyl(meth)acrylate, iso-pentyl(meth)acrylate,isoheptyl(meth)acrylate, iso-octyl(meth)acrylate, iso-nonyl(meth)acrylate, iso-decyl(meth)acrylate, iso-undecyl(meth)acrylate, iso-dodecyl(meth)acrylate, iso, -Iso-tridecyl(meth)acrylate, iso-tetradecyl(meth)acrylate, iso-pentadecyl(meth)acrylate, iso-cetyl(meth)acrylate, iso-hexadecyl(meth)acrylate, iso-heptadecyl(meth)acrylate The copolymer may be, but is not limited to, a copolymer formed by polymerizing iso-stearyl(meth)acrylate, iso-nonadecyl(meth)acrylate, iso-eicosyl(meth)acrylate, iso-heneicosyl(meth)acrylate, iso-docosyl(meth)acrylate, or a combination thereof.

[0048] For example, in Formula 1, the monomer containing R'1 may be stearyl acrylate.

[0049] In this case, the (meth)acrylate-based monomer unit described as an example of the monomer containing R'1 in Formula 1 above can represent both methacrylate and acrylate. For example, the above-described n-pentyl(meth)acrylate can represent both n-pentyl methacrylate and n-pentyl acrylate.

[0050] In one embodiment, the monomer containing R'2 in Formula 1 is cyclopentyl acrylate, cyclohexyl acrylate, benzyl acrylate, benzyl methacrylate, phenyl acrylate, phenyl methacrylate, 3-phenoxybenzyl acrylate, σ-phenylphenoxyethyl acrylate, σ-phenylphenoxyethyl methacrylate. The compound may include any one or more selected from the group consisting of (1-pyrene)2-methyl-2-propenoate, 1-naphthyl acrylate, 1-naphthyl methacrylate, 2-naphthyl acrylate, 2-naphthyl methacrylate, 9-anthracene methyl acrylate, and 9-anthracene methyl methacrylate.

[0051] For example, in Formula 1, the monomer containing R'2 is benzyl acrylate, benzyl methacrylate, phenyl acrylate, phenyl methacrylate, 1-naphthyl acrylate, The acrylate may be any one or more selected from the group consisting of 1-naphthyl acrylate, 1-naphthyl methacrylate, 2-naphthyl acrylate, 2-naphthyl methacrylate, and 3-phenoxy benzyl acrylate.

[0052] In one embodiment, the monomer containing R'3 in Formula 1 may be styrene.

[0053] In one embodiment, the monomer containing R'4 in Formula 1 may include at least one selected from the group consisting of acrylonitrile, vinyl pyrrolidone, acrylamide, N-methyl acrylamide, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, and glycidyl methacrylate.

[0054] For example, in the above formula 1, the monomer containing R'4 may be acrylonitrile.

[0055] In one embodiment, the monomer including R'5 in Chemical Formula 1 may include at least one selected from the group consisting of acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, aconitic acid, vinylbenzoic acid, 2-acrylamido-2-methylpropane sulfonic acid, vinyl sulfonic acid, 4-styrenesulfonic acid, and vinyl phosphonic acid.

[0056] For example, in Formula 1, the monomer containing R'5 may be at least one selected from the group consisting of methacrylic acid, maleic acid, 4-styrenesulfonic acid, and vinyl phosphonic acid.

[0057] In one embodiment, the copolymer may be a random copolymer or a block copolymer depending on the synthesis process.

[0058] In one embodiment, the number average molecular weight of the copolymer may be 8,000 or more and 40,000 or less.

[0059] For example, the number average molecular weight of the copolymer may be 8,000 or more and 35,000 or less, 8,000 or more and 30,000 or less, 9,000 or more and 30,000 or less, 10,000 or more and 30,000 or less, or 11,000 or more and 30,000 or less.

[0060] If the number average molecular weight of the copolymer is below the range of the present invention, the fluidity of the copolymer is high. If the number average molecular weight exceeds the range of the present application, the viscosity may become too high and the usability may decrease.

[0061] In one embodiment, the copolymer may have the polar monomer unit bonded to a metal cation, and the q value calculated by the following Equation 1 may be 1.5 mol % or more and 300 mol % or less.

[0062] [Formula 1] 5×a / bmol%≦q≦100×a / bmol% (In the formula 1, a is the number of functional groups capable of substituting for the metal cation per polar monomer forming the polar monomer unit by polymerization, b is the number of positive charges on the metal cation, and a and b are each 1 to 3.)

[0063] In this case, when a=1 and b=1, the q value calculated by the formula 1 may be 5 mol%≦q≦100 mol%, when a=1 and b=2, the q value calculated by the formula 1 may be 2.5 mol%≦q≦50 mol%, and when a=1 and b=3, the q value calculated by the formula 1 may be 1.67 mol%≦q≦33.3 mol%.

[0064] Furthermore, when a=2 and b=1, the q value calculated by the formula 1 may be 10 mol%≦q≦200 mol%, when a=2 and b=2, the q value calculated by the formula 1 may be 5 mol%≦q≦100 mol%, and when a=2 and b=3, the q value calculated by the formula 1 may be 3.33 mol%≦q≦66.7 mol%.

[0065] In addition, when a=3 and b=1, the q value calculated by the formula 1 may be 15 mol%≦q≦300 mol%, when a=3 and b=2, the q value calculated by the formula 1 may be 7.5 mol%≦q≦150 mol%, and when a=3 and b=3, the q value calculated by the formula 1 may be 5 mol%≦q≦100 mol%.

[0066] For example, when the polar monomer unit is acrylic acid, methacrylic acid, vinylbenzoic acid, 2-acrylamido-2-methylpropane sulfonic acid, vinyl sulfonic acid, 4-styrenesulfonic acid, or the like, a is 1.

[0067] Furthermore, for example, when the polar monomer unit is maleic acid, fumaric acid, itaconic acid, vinyl phosphonic acid, or the like, a is 2.

[0068] For example, when the polar monomer unit is aconitic acid, a is 3.

[0069] In one embodiment, the metal cation is derived from an inorganic salt that pairs an ionizable cation and anion in the solvent.

[0070] For example, the cations may be lithium (Li), sodium (Na), magnesium (Mg), potassium (K), calcium (Ca), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), aluminum (Al), or the like. It may be aluminum (Al) or zinc (Zn).

[0071] In this case, when the cation is lithium (Li), sodium (Na), potassium (K), etc., b is 1; when the cation is magnesium (Mg), calcium (Ca), nickel (Ni), etc., b is 2; and when the cation is aluminum (Al), etc., b is 3.

[0072] Also, for example, the anion is F - , Cl - , Br - , I - , O 2- , S 2- , SO4 2- , PO4 3- , CO3 2- or OH - may be.

[0073] The inorganic salt may be a combination of the cation and anion for substitution, but is not limited thereto, as long as the functional group of the polar monomer unit can be substituted with a metal cation.

[0074] In one embodiment, the copolymer is such that the polar monomer units are capable of binding with metal cations.

[0075] In this case, to maximize the electrostatic repulsion, the functional group of the polar monomer unit that has been ionized to an anion may be substituted with a cation, particularly with a metal cation, and the copolymer may include both the functional group of the polar monomer unit substituted with a metal cation and the functional group not substituted.

[0076] As a result, electrostatic repulsion is maximized, and the dispersion prepared using the copolymer can ensure dispersibility and dispersion stability, and can have a higher solid content.

[0077] In one embodiment, a radical initiator may be used when preparing the copolymer.

[0078] For example, the radical initiator may be 2,2'-azobis-2,4-dimethyl valeronitrile, but is not limited thereto, and any radical initiator that can be used in a solvent may be used.

[0079] In one embodiment, the copolymer can be used to efficiently disperse all types of carbon nanotubes, including single-walled carbon nanotubes, double-walled carbon nanotubes, multi-walled carbon nanotubes, and thin-walled carbon nanotubes, as well as carbon black, acetylene black, and graphite.

[0080] In addition, the present invention can be applied to the manufacture of positive and negative electrodes of secondary batteries including the above.

[0081] A dispersion liquid, which is another aspect of the present application, can contain the copolymer, a solvent, and carbon nanotubes.

[0082] In one embodiment, the solvent may be a polar solvent, such as N-methyl-2-pyrrolidone (NMP), N-ethyl-2-pyrrolidone (NEP), dimethylformamide (DMF), dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), γ-butyrolactone, ethyl acetate, propyl acetate, ethanol, or isopropyl alcohol. The solvent may be any one or more selected from the group consisting of isopropyl alcohol and deionized water.

[0083] In one embodiment, the carbon nanotubes contained in the dispersion may be single-walled carbon nanotubes, double-walled carbon nanotubes, multi-walled carbon nanotubes, thin-walled carbon nanotubes, or a combination thereof. The type of carbon nanotubes is not limited thereto.

[0084] Furthermore, the carbon nanotubes may be contained in an amount of 1 wt % or more and 10 wt % or less, based on the total weight of the dispersion being 100 wt %.

[0085] If the carbon nanotube content in the dispersion is below the range of the present application, the solid content of the electrode slurry will be low, and if it exceeds the range of the present application, the viscosity will be too high and dispersion will not be performed well, which may make it difficult to produce a high-quality dispersion.

[0086] On the other hand, the content of the copolymer in the dispersion may be 0.1 to 0.5 times the content of the carbon nanotubes.

[0087] If the ratio of the copolymer content to the carbon nanotube content is below the range of the present application, a sufficient dispersion effect cannot be obtained and the carbon material cannot be dispersed efficiently, and if the ratio of the copolymer content to the carbon nanotube content is above the range of the present application, the ratio of the internal material of the battery may increase, resulting in a decrease in energy density.

[0088] In one embodiment, the dispersion may have a viscosity of 10,000 cps or less at a shear rate of 2.5 / s.

[0089] For example, the viscosity of the dispersion at a shear rate of 2.5 / s may be 200 cps or more and 800 cps or less, 270 cps or more and 750 cps or less, preferably 220 cps or more and 725 cps or less.

[0090] In one embodiment, the dispersion may have a viscosity of 87000 cps or less after storage at a shear rate of 2.5 / s.

[0091] For example, the viscosity of the dispersion after storage at a shear rate of 2.5 / s may be 3000 cps or more and 8600 cps or less, preferably 3100 cps or more and 8550 cps or less.

[0092] In one embodiment, the particle size (D50) of the carbon nanotubes dispersed in the dispersion liquid may be 4.6 μm or less.

[0093] That is, the dispersion containing the copolymer of the present invention has a low particle size value (D50) of 4.6 μm or less, and therefore has excellent dispersibility of carbon nanotubes in the dispersion.

[0094] For example, the particle size (D50) of the carbon nanotubes dispersed in the dispersion may be 2.9 μm or more and 4.6 μm or less, 2.9 μm or more and 4.51 μm or less, 3.05 μm or more and 4.51 μm or less, preferably 2.94 μm or more and 4.51 μm or less.

[0095] That is, the copolymer (dispersant) of the present application can reduce the particle size of carbon nanotubes in the dispersion liquid based on its excellent dispersing power, thereby producing a carbon material dispersion liquid with uniform and dense particle size and low viscosity, thereby shortening the dispersion process time.

[0096] A positive electrode slurry composition according to another aspect of the present invention may include the dispersion and a positive electrode active material.

[0097] In one embodiment, the content of the carbon nanotubes in the positive electrode slurry composition may be 0.001 to 0.1 times, and preferably 0.003 to 0.02 times, the content of the positive electrode active material.

[0098] If the content of the carbon nanotubes contained in the positive electrode slurry composition relative to the content of the positive electrode active material is below the range of the present application, the conductivity of the electrode active material may decrease, resulting in a decrease in output characteristics. If the content of the carbon nanotubes exceeds the range of the present application, the content of the positive electrode active material may decrease, resulting in a decrease in battery capacity.

[0099] In one embodiment, the positive electrode active material may be any positive electrode active material available in the art. Specific examples of such positive electrode active materials include lithium metal; lithium cobalt-based oxides such as LiCoO; Li 1+x Mn 2-x O4 (where x is 0 to 0.33), lithium manganese oxides such as LiMnO3, LiMn2O3, and LiMnO2; lithium copper oxides such as Li2CuO2; vanadium oxides such as LiV3O8, V2O5, and Cu2V2O7; LiNi 1-x M xLithium nickel-based oxide represented by O2 (where M = Co, Mn, Al, Cu, Fe, Mg, B or Ga and x = 0.01 to 0.3); LiMn 2-x M x Lithium manganese composite oxide represented by O2 (where M = Co, Ni, Fe, Cr, Zn or Ta and x = 0.01 to 0.1) or Li2Mn3MO8 (where M = Fe, Co, Ni, Cu or Zn); Li(Ni a Co b Mn c )O2 (where 0 < a < 1, 0 < b < 1, 0 < c < 1, and a + b + c = 1); sulfur or disulfide compounds; phosphates such as LiFePO4, LiMnPO4, LiCoPO4, LiNiPO4; Fe2(MoO4)3, etc., but not limited thereto.

[0100] The positive electrode active material may be contained in an amount of 90 to 99% by weight based on the solid content. If the content of the active material is low, the battery cannot achieve a high capacity. If the content of the active material is excessively high, the contents of the binder, conductive material, etc. will be relatively reduced, so the electrode adhesion, conductivity, etc. may decrease.

[0101] In one embodiment, the positive electrode slurry composition may additionally contain a conductive material.

[0102] The conductive material is not particularly limited and can be appropriately selected according to the types of batteries and capacitors. For example, in the case of a lithium ion secondary battery, carbon such as graphite and activated carbon is used. In the case of a nickel hydrogen secondary battery, cobalt oxide can be used, and for the negative electrode, nickel powder, cobalt oxide, titanium oxide, carbon, etc. can be used.

[0103] Examples of the carbon include acetylene black, furnace black, graphite, carbon fiber, and fullerenes.

[0104] The amount of the conductive material used is usually 1 to 20% by weight, preferably 2 to 10% by weight, based on 100% by weight of the electrode active material.

[0105] The lower the content of the conductive material and the higher the content of the positive electrode active material, the more the energy density of the secondary battery can be improved. Therefore, it is important to achieve high efficiency even when using the same amount of conductive material. It is essential.

[0106] The smaller and more uniformly dispersed the conductive material used in secondary battery electrode slurry, the higher the conductive efficiency, reducing resistance within the battery and improving output and life characteristics. Larger and unevenly dispersed particles, even when used in the same amount, result in poor binding properties and conductivity, adversely affecting the battery's life and output characteristics. Furthermore, a low viscosity dispersion can increase the solids content of the slurry and improve electrode production speed.

[0107] In one embodiment, the positive electrode slurry composition may additionally include a binder.

[0108] The binder may be any one or more selected from the group consisting of poly(meth)acrylic acid, poly(meth)acrylamide, carboxymethyl cellulose, polyvinylidene fluoride, polyhexafluoropropylene-polyvinylidene fluoride copolymer (P(VdF / HFP)), poly(vinyl acetate), polyvinyl alcohol, polyethylene oxide, polyvinylpyrrolidone, alkylated polyethylene oxide, polyvinyl ether, poly(methyl methacrylate), poly(ethyl acrylate), polytetrafluoroethylene, polyvinyl chloride, polyacrylonitrile, polyvinylpyridine, styrene-butadiene rubber, acrylonitrile-butadiene rubber, and copolymers thereof, but is not limited to these.

[0109] The content of the binder in the positive electrode slurry composition may be 0.3 wt % or more and 10 wt % or less, calculated on a solid content basis, and preferably 0.7 wt % or more and 8 wt % or less.

[0110] If the content of the binder is below the range of the present application, it may be difficult to expect sufficient binding strength between the current collector and the positive electrode active material or between the positive electrode active materials themselves. If the content of the binder is above the range of the present application, the binder may act as a resistor within the battery, reducing the relative content of the positive electrode active material and decreasing battery capacity, thereby deteriorating battery performance.

[0111] A positive electrode according to yet another aspect of the present application may include a current collector and a positive electrode active material layer formed by applying the positive electrode slurry composition.

[0112] The positive electrode can be manufactured by (a) preparing a positive electrode slurry composition containing a positive electrode active material and the copolymer of the present application, and (b) applying the positive electrode slurry composition onto a positive electrode current collector and then drying the applied composition.

[0113] The positive electrode slurry composition can be mixed by a conventional mixer, such as a high-speed shear mixer or a homogenizer, using a conventional method.

[0114] The step (b) is a step of applying the positive electrode slurry composition prepared in the step (a) onto a positive electrode current collector and then drying it to prepare a positive electrode for a lithium secondary battery.

[0115] At this time, the method of applying the positive electrode slurry composition is not limited, and examples thereof include doctor blade coating, dip coating, gravure coating, slit die coating, spin coating, comma coating, bar coating, reverse roll coating, and screen coating. The coating method can be applied by en coating, cap coating, etc.

[0116] The positive electrode slurry composition is applied and then dried to finally manufacture a positive electrode for a secondary battery having a positive electrode active material layer formed thereon.

[0117] Any current collector can be used as long as it is conductive and does not chemically react with the electrode-forming slurry. Typical examples include aluminum foil and copper foil. A current collector with a thickness of 3 to 50 micrometers can be selected and used.

[0118] A secondary battery according to yet another aspect of the present application can include the positive electrode.

[0119] In one embodiment, the secondary battery may further include a separator.

[0120] The separator must be an insulator that can separate the negative and positive electrodes and provide a path through which only lithium ions can move. To achieve this, it must have good wettability with the electrolyte, and is made of porous polymer films such as PE / PP or porous nonwoven fabrics. To prevent short circuits in the battery, a coated separator coated with ceramic or other materials that enhance heat resistance and mechanical strength can be used, and it can be coated in a single layer or multiple layers.

[0121] The separator may be made of a porous substrate. The porous substrate may be any porous substrate commonly used in electrochemical devices, such as, but not limited to, a polyolefin-based porous membrane or nonwoven fabric.

[0122] The separation membrane may be a porous substrate made of any one selected from the group consisting of polyethylene, polypropylene, polybutylene, polypentene, polyethylene terephthalate, polybutylene terephthalate, polyester, polyacetal, polyamide, polycarbonate, polyimide, polyether ether ketone, polyether sulfone, polyphenylene oxide, polyphenylene sulfide, and polyethylene naphthalate, or a mixture of two or more thereof.

[0123] The electrolyte of the lithium secondary battery is a non-aqueous electrolyte containing a lithium salt, and is composed of a lithium salt and a solvent. The solvent may be a non-aqueous organic solvent, an organic solid electrolyte, or an inorganic solid electrolyte.

[0124] The lithium salt is a substance that is easily dissolved in the non-aqueous electrolyte solution, and examples thereof include LiCl, LiBr, LiI, LiClO4, LiBF4, and LiB 10 Cl 10 , LiPF6, LiAsF6, LiSbF6, LiAlCl4, LiSCN, LiC4BO8, LiCF3CO2, LiCH3SO3, LiCF3SO3, LiN(SO2CF3)2, LiN(SO2F)2, LiN(SO2C2F5)2, LiC4F9SO3, LiC(CF3SO2)3, (CF3SO2)·2NLi, lithium chloroborane, lower aliphatic lithium carboxylates, and lithium 4-phenylborate imide can be used.

[0125] Examples of the non-aqueous organic solvent include N-methyl-2-pyrrolidone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, gamma-butyrolactone, 1,2-dimethoxyethane, 1,2-diethoxyethane, tetrahydroxyfuran, 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, 4-methyl-1,3-dioxene, diethyl ether, formamide, dimethylformamide, dioxane, Aprotic organic solvents such as benzene, acetonitrile, nitromethane, methyl formate, methyl acetate, phosphate triester, trimethoxymethane, dioxolane derivatives, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ether, methyl propionate, and ethyl propionate can be used.

[0126] Examples of the organic solid electrolyte that can be used include polyethylene derivatives, polyethylene oxide derivatives, polypropylene oxide derivatives, phosphate ester polymers, polyagitation lysine, polyester sulfide, polyvinyl alcohol, polyvinylidene fluoride, and polymers containing secondary dissociating groups.

[0127] Examples of the inorganic solid electrolyte that can be used include nitrides, halides, and sulfates of Li, such as LiN, LiI, LiNI, LiN-LiI-LiOH, LiSiO, LiSiO-LiI-LiOH, LiSiS, LiSiO, LiSiO-LiI-LiOH, and LiPO-LiS-SiS.

[0128] The non-aqueous electrolyte may further contain other additives for the purpose of improving charge / discharge characteristics, flame retardancy, etc. Examples of the additives include pyridine, triethyl phosphite, triethanolamine, cyclic ether, ethylenediamine, n-glyme, hexaphosphoric acid triamide, nitrobenzene derivatives, sulfur, quinoneimine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, aluminum trichloride, fluoroethylene carbonate (FEC), propene sultone (PRS), vinylene carbonate (VC), etc.

[0129] The lithium secondary battery according to the present invention can be manufactured by laminating and stacking the separator and electrodes and by folding them, in addition to the conventional winding process. The battery case may be cylindrical, prismatic, pouch-shaped, or coin-shaped. The lithium secondary battery can be used in small, medium-sized, and large-sized models of automobiles and electronic devices.

[0130] The present invention will be described in more detail with reference to the following examples. However, the following examples are provided to more specifically explain the present invention, and the scope of the present invention is not limited to the following examples.

[0131] Examples and Comparative Examples: Preparation of Copolymers [Example 1] 70 g of N-methylpyrrolidone (NMP) was placed in a five-neck flask reactor as a solvent, and 40 mol % of stearyl acrylate (SA), 30 mol % of styrene (SM), 10 mol % of acrylonitrile (AN), and 20 mol % of methacrylic acid (based on 100 mol % of the total moles of the monomers to be copolymerized) were added. A reflux condenser and a thermometer were then attached, and the temperature was raised to 75°C while purging with nitrogen to produce a solution. The total weight of the monomers to be copolymerized was 70 g.

[0132] Then, 0.15 g of 2,2'-azobis-2,4-dimethyl valeronitrile was dissolved in 20 g of N-methylpyrrolidone and added dropwise to the solution for 30 minutes. After the addition was completed, the temperature was maintained at 75°C for 7 hours to produce a copolymer.

[0133] The inorganic salt LiOH used to replace the functional group of methacrylic acid was dissolved in methanol, with the amount of LiOH added being 100 mol% relative to the substance to be replaced (methacrylic acid), and then added to a reactor. The mixture was stirred at 75°C for 1 hour to allow the replacement of the functional group of methacrylic acid with the inorganic salt LiOH to proceed.

[0134] Thereafter, the methanol was distilled off to produce a copolymer to be used as a dispersant.

[0135] [Example 2] A copolymer was produced in the same manner as in Example 1, except that NaOH was used instead of LiOH as the inorganic salt used to substitute the functional group of methacrylic acid.

[0136] [Example 3] A copolymer was produced in the same manner as in Example 1, except that NaCl was used instead of the inorganic salt LiOH used to substitute the functional group of methacrylic acid.

[0137] [Example 4] A copolymer was produced in the same manner as in Example 1, except that KOH was used instead of LiOH as the inorganic salt used to substitute the functional group of methacrylic acid.

[0138] [Example 5] A copolymer was produced in the same manner as in Example 1, except that Mg(OH) was used instead of the inorganic salt LiOH used to substitute the functional groups of methacrylic acid, and the amount of Mg(OH) was set to 50 mol% relative to the substance to be substituted (methacrylic acid).

[0139] [Example 6] A copolymer was produced in the same manner as in Example 2, except that 20 mol % of maleic acid was used instead of 20 mol % of methacrylic acid, and the amount of NaOH added relative to the substituted substance (maleic acid) was 200 mol %.

[0140] [Example 7] A copolymer was produced in the same manner as in Example 2, except that 20 mol % of 4-styrenesulfonic acid was used instead of 20 mol % of methacrylic acid.

[0141] [Example 8] A copolymer was produced in the same manner as in Example 2, except that 20 mol % of vinyl phosphonic acid was used instead of 20 mol % of methacrylic acid, and the amount of NaOH added relative to the substituted substance (vinyl phosphonic acid) was 200 mol %.

[0142] [Comparative Example 1] A copolymer was produced in the same manner as in Example 1, except that the inorganic salt LiOH used for substituting the functional group of methacrylic acid was not used.

[0143] Comparative Example 2 A copolymer was produced in the same manner as in Example 2, except that the amount of NaOH added relative to the substance to be substituted (methacrylic acid) was 2 mol %.

[0144] Comparative Example 3 A copolymer was produced in the same manner as in Example 2, except that the amount of NaOH added relative to the substance to be substituted (methacrylic acid) was 150 mol %.

[0145] Comparative Example 4 Instead of the dispersants produced in Examples 1 to 8, a commercial dispersant, hydrogenated nitrile butadiene rubber (H-NBR, product name 720H) from ZEON was used.

[0146] Table 1 below shows the content (mol%) of the monomers used to prepare the copolymers of Examples 1 to 8 and Comparative Examples 1 to 3, the inorganic salts, and the amounts (mol%) of the inorganic salts added relative to the substituted materials.

[0147] [Table 1]

[0148] In Table 1, SA represents stearyl acrylate, SM represents styrene, AN represents acrylonitrile, MAA represents methacrylic acid, MA represents maleic acid, SSA represents 4-styrenesulfonic acid, and VPA represents vinyl phosphonic acid.

[0149] In Table 1, the amount (mol%) of inorganic salt added relative to the substituted substance in Examples 1 to 8 indicates the total substitution (100×a / b mol%) of the q value calculated by the following formula 1.

[0150] [Formula 1] 5×a / bmol%≦q≦100×a / bmol% In the formula 1, a represents the number of functional groups replaceable with metal cations in the polar monomer units formed by polymerizing methacrylic acid, maleic acid, 4-styrenesulfonic acid, and vinylphosphonic acid in Table 1. In the formula 1, b is the number of positive charges of the metal cations Li, Na, K and Mg of the inorganic salt in Table 1.

[0151] That is, Examples 1 to 4 and Example 7 correspond to the case where the number of functional groups replaceable with the metal cations of the polar monomer unit formed by polymerization of methacrylic acid or 4-styrenesulfonic acid is 1, and the number of positive charges of the metal cations of the inorganic salt is 1; Example 5 corresponds to the case where the number of functional groups replaceable with the metal cations of the polar monomer unit formed by polymerization of methacrylic acid is 1, and the number of positive charges of the metal cations of the inorganic salt is 2; and Examples 6 and 8 correspond to the case where the number of functional groups replaceable with the metal cations of the polar monomer unit formed by polymerization of maleic acid or vinylphosphonic acid is 2, and the number of positive charges of the metal cations of the inorganic salt is 1.

[0152] [Manufacturing example] Production Examples 1 to 8 and Comparative Production Examples 1 to 4: Production of Dispersions As a dispersant, 0.75 g (based on 100% solid content) of each of the copolymers prepared in Examples 1 to 8 and Comparative Examples 1 to 4, 3 g of multi-walled carbon nanotubes (MWCNT), 96.25 g of N-methylpyrrolidone, and 400 g of zirconia beads with an average diameter of 0.65 mm were placed in a planetary ball mill and dispersed at 400 rpm for 60 minutes. The zirconia bead mixture was filtered through a 40 mesh to prepare a dispersion with a solid content of 3.75 wt %.

[0153] Table 2 below shows the types of copolymers contained in the dispersions of Production Examples 1 to 8 and Comparative Production Examples 1 to 4.

[0154] [Table 2]

[0155] Manufacturing Example 9: Manufacturing of Positive Electrode 4.6 g of the dispersion prepared in Preparation Examples 1 to 8, 27.3 g of a positive electrode active material (NCM622), 18 g of PVdF dissolved in N-methyl pyrrolidone at 8 wt %, and 7.9 g of N-methyl pyrrolidone were mixed in a planetary centrifugal mixer (ARE-310, Thinky) to prepare a slurry for forming a positive electrode, and the solid content of the slurry was 50 wt %. The slurry was applied to a 20 μm thick aluminum foil using a doctor blade. The electrode with the applied slurry was dried in an oven at 130°C for 12 hours or more and rolled to adjust the composite density to 2.4 g / cc. Then, vacuum drying was carried out at 110°C to prepare a positive electrode plate.

[0156] [Evaluation example] Evaluation example 1: Measurement of initial viscosity of dispersion, viscosity after storage, and particle size The initial viscosity of the dispersions of Production Examples 1 to 8 and Comparative Production Examples 1 to 4 was measured with a Haake Mars rheometer at 25° C. The shear rate was measured in the range of 0.01 / s to 200 / s.

[0157] The dispersions of Production Examples 1 to 8 and Comparative Production Examples 1 to 4 were stored at 60°C for 3 days, and the viscosity after storage was measured using a Haake Mars rheometer at 25°C. The shear rate was measured in the range of 0.01 / s to 200 / s.

[0158] The particle sizes of the dispersions of Production Examples 1 to 8 and Comparative Production Examples 1 to 4 were measured with a Mastersizer 3000 using a Fraunhofer diffraction model.

[0159] The initial viscosity at a shear rate of 2.5 / s, viscosity after storage and particle size D50 (median value) are shown in Table 3 below.

[0160] [Table 3]

[0161] At this time, when comparing Preparation Examples 1 to 8 with Comparative Preparation Example 1, when carbon nanotubes (CNTs) are dispersed using a copolymer in which polar monomer units are bonded to metal cations, the dispersion It was confirmed that the initial viscosity and viscosity after storage were significantly improved. This is because the functional groups of the polar monomer units, which exist in an anionic state, significantly improve dispersion stability through electrostatic repulsion.

[0162] It was also confirmed that the dispersions of Production Examples 1 to 8 were superior in terms of initial viscosity and viscosity after storage compared to the dispersion produced using the commercial dispersant of Comparative Production Example 4.

[0163] On the other hand, when comparing Preparation Example 2 with Comparative Preparation Example 2, it was confirmed that if the amount of the functional group of the polar monomer unit substituted with the metal cation is smaller than the appropriate range, the electrostatic repulsion force cannot be generated sufficiently, and improvements in dispersibility and dispersion stability cannot be expected.

[0164] In addition, when comparing Preparation Example 2 with Comparative Preparation Example 3, it was confirmed that even when an inorganic salt in an amount greater than the appropriate range was used, the functional groups of the polar monomer units were not further substituted, and therefore, no further improvement in dispersibility or dispersion stability was achieved.

[0165] That is, in Production Examples 1 to 4 and Production Example 7, which are dispersions produced using the copolymers of Examples 1 to 4 and Example 7, the q value calculated by the above formula 1 is in the range of 5 mol%≦q≦100 mol%, in Production Example 5, which is a dispersion produced using the copolymer of Example 5, the q value calculated by the above formula 1 is in the range of 2.5 mol%≦q≦50 mol%, and in Production Examples 6 and 8, which are dispersions produced using the copolymers of Examples 6 and 8, the q value calculated by the above formula 1 is in the range of 10 mol%≦q≦200 mol%.

[0166] Therefore, in all of Examples 1 to 8, it was confirmed that the initial viscosity and viscosity after storage of the dispersion can be improved by substituting the functional group of the polar monomer unit formed by polymerization of methacrylic acid, maleic acid, 4-styrenesulfonic acid, and vinylphosphonic acid with a metal cation within the value range of Equation 1 defined herein.

[0167] The scope of the present invention is indicated by the claims that follow rather than by the above detailed description, and all modifications and variations that fall within the meaning and scope of the claims and their equivalents should be interpreted as being included within the scope of the present invention.

Claims

1. an acrylate-based monomer unit containing a linear or branched aliphatic hydrocarbon having 5 to 22 carbon atoms; one or more monomer units selected from the group consisting of acrylate-based monomer units containing one or more substituted or unsubstituted aromatic or aliphatic rings and vinyl-based monomer units containing one or more substituted or unsubstituted aromatic or aliphatic rings; Carboxylic acid (COOH), sulfonic acid (SO ３ H), phosphonic acid (PO ３ H ２ ), cyano (CN), pyrrolidone (NC ４ H ６ O), amide, alkylamide, dialkylamide, alcohol, epoxy group, caprolactam (C ５ H １０ CNO), morpholine (C ４ H ８ NO), and oxazolidones (C ３ H ４ NO ２ and a polar monomer unit containing one or more functional groups selected from the group consisting of Copolymer.

2. The acrylate-based monomer unit containing a linear or branched aliphatic hydrocarbon having 5 to 22 carbon atoms includes n-pentyl(meth)acrylate, n-hexyl(meth)acrylate, n-heptyl(meth)acrylate, n-octyl(meth)acrylate, 2-ethylhexyl(meth)acrylate, and 2-ethylhexyl(meth)acrylate. acrylate), n-nonyl(meth)acrylate, n-decyl(meth)acrylate, n-undecyl(meth)acrylate, lauryl(meth)acrylate, n-dodecyl(meth)acrylate, n-tridecyl(meth)acrylate acrylate), n-tetradecyl(meth)acrylate, n-pentadecyl(meth)acrylate, cetyl(meth)acrylate, n-hexadecyl(meth)acrylate, n-heptadecyl(meth)acrylate, stearyl(meth)acrylate stearyl(meth)acrylate), n-nonadecyl(meth)acrylate, n-eicosyl(meth)acrylate, n-heneicosyl(meth)acrylate, n-dococyl(meth)acrylate, iso-pentyl(meth)acrylate,iso-heptyl(meth)acrylate, iso-octyl(meth)acrylate, iso-nonyl(meth)acrylate, iso-decyl(meth)acrylate, iso-undecyl(meth)acrylate, iso-dode iso-dodecyl(meth)acrylate, iso-tridecyl(meth)acrylate, iso-tetradecyl(meth)acrylate, iso-pentadecyl(meth)acrylate, iso-cetyl(meth)acrylate, ate), iso-hexadecyl(meth)acrylate, iso-heptadecyl(meth)acrylate, iso-stearyl(meth)acrylate, iso-nonadecyl(meth)acrylate iso-eicosyl(meth)acrylate, iso-heneicosyl(meth)acrylate, iso-docosyl(meth)acrylate, or a combination thereof; The copolymer of claim 1.

3. At least one monomer unit selected from the group consisting of acrylate-based monomer units containing one or more substituted or unsubstituted aromatic or aliphatic rings and vinyl-based monomer units containing one or more substituted or unsubstituted aromatic or aliphatic rings is / are styrene, cyclopentyl acrylate, cyclohexyl acrylate, benzyl acrylate, benzyl methacrylate, phenyl acrylate, acrylate), phenyl methacrylate, 3-phenoxybenzyl acrylate, σ-phenylphenoxyethyl acrylate, σ-phenylphenoxyethyl methacrylate, (1-pyrene)2-methyl-2-propenoate, 1-naphthyl acrylate, 1-naphthyl methacrylate methacrylate), 2-naphthyl acrylate, 2-naphthyl methacrylate, 9-anthracene methyl acrylate, 9-anthracene methyl methacrylate, or a combination thereof, The copolymer of claim 1.

4. The polar monomer unit may be acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, aconitic acid, vinylbenzoic acid, 2-acrylamido-2-methylpropane sulfonic acid, vinyl sulfonic acid, 4-styrenesulfonic acid, vinylphosphonic acid, or the like. acid), acrylonitrile, vinylpyrrolidone, acrylamide, N-methylacrylamide, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, glycidyl methacrylate, or a combination thereof, The copolymer of claim 1.

5. Based on 100 mol% of the copolymer, an acrylate-based monomer unit containing 5 mol % or more and 70 mol % or less of the linear or branched aliphatic hydrocarbon having 5 to 22 carbon atoms; one or more monomer units selected from the group consisting of 5 mol % or more and 70 mol % or less of the substituted or unsubstituted acrylate-based monomer units containing one or more aromatic or aliphatic rings, and vinyl-based monomer units containing one or more substituted or unsubstituted aromatic or aliphatic rings; and 5 mol% or more and 50 mol% or less of the polar monomer units, The copolymer of claim 1.

6. Represented by the following chemical formula 1: The copolymer of claim 1. 【Chemistry 1】 R １ ~R １５ are the same or different and each independently represents hydrogen or a linear or branched hydrocarbon having 1 to 4 carbon atoms; R' １ is a linear or branched aliphatic hydrocarbon having 5 to 22 carbon atoms, R' ２ contains one or more substituted or unsubstituted aromatic or aliphatic rings, R' ３ contains one or more substituted or unsubstituted aromatic or aliphatic rings, R' ４ are cyano (CN), pyrrolidone (NC ４ H ６ O), amide, alkylamide, dialkylamide, alcohol, epoxy group, caprolactam (C ５ H １０ CNO), morpholine (C ４ H ８ NO), and oxazolidones (C ３ H ４ NO ２ ) any one or more selected from the group consisting of R' ５ is a carboxylic acid (COOH), a sulfonic acid (SO ３ H), and phosphonic acid (PO ３ H ２ ) any one or more selected from the group consisting of l+m+n+o+p=1, 0.05≦l≦0.70, 0.05≦m+n≦0.70, and 0.05≦o+p≦0.

50. (However, either m or n may be 0, and o may be 0.)

7. R' １ is n-pentyl, n-hexyl, n-heptyl, n-octyl, 2-ethylhexyl, n-nonyl, n-decyl, n-undecyl, lauryl, n-dodecyl, n-tridecyl, n-tetradecyl, n-pentadecyl, cetyl, n-hexadecyl, n-heptadecyl, stearyl, n-octadecyl, n-nonadecyl, n-eicosyl, n-heneicosyl, n-docosyl, iso-pentyl, iso-heptyl, iso-octyl the alkyl esters include any one or more selected from the group consisting of isobutyl, iso-nonyl, iso-decyl, iso-undecyl, iso-dodecyl, iso-tridecyl, iso-tetradecyl, iso-pentadecyl, iso-cetyl, iso-hexadecyl, iso-heptadecyl, iso-stearyl, iso-octadecyl, iso-nonadecyl, iso-eicosyl, iso-heneicosyl, and iso-docosyl; The copolymer according to claim 6.

8. R' ２ and R' ３ are the same or different, and each independently includes one or more selected from the group consisting of substituted or unsubstituted cyclopentyl, cyclohexyl, benzyl, phenyl, phenoxy, naphthalene, anthracene, and pyrene; The copolymer according to claim 6.

9. R' ２ The monomers containing the above are cyclopentyl acrylate, cyclohexyl acrylate, benzyl acrylate, benzyl methacrylate, phenyl acrylate, phenyl methacrylate, 3-phenoxybenzyl acrylate, σ-phenylphenoxyethyl acrylate, σ-phenylphenoxyethyl methacrylate, methacrylate), (1-pyrene)2-methyl-2-propenoate, 1-naphthyl acrylate, 1-naphthyl methacrylate, 2-naphthyl acrylate, 2-naphthyl methacrylate, 9-anthracene methyl acrylate, and 9-anthracene methyl methacrylate. one or more selected from the group consisting of R' ３ The monomer containing is styrene. The copolymer according to claim 6.

10. R' ４ The monomer containing is at least one selected from the group consisting of acrylonitrile, vinylpyrrolidone, acrylamide, N-methylacrylamide, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, and glycidyl methacrylate; The copolymer according to claim 6.

11. R' ５ The monomers containing acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, aconitic acid, vinylbenzoic acid, 2-acrylamido-2-methylpropane sulfonic acid, vinyl sulfonic acid, 4-styrenesulfonic acid, and vinylphosphonic acid. acid), The copolymer according to claim 6.

12. the polar monomer unit binds to a metal cation; The q value calculated by the following formula 1 is 1.5 mol% or more and 300 mol% or less. The copolymer of claim 1. [Formula 1] 5×a / bmol%≦q≦100×a / bmol% (wherein, in the formula 1, a is the number of functional groups in the polar monomer unit that can be substituted with the metal cation, and b is the number of positive charges on the metal cation, a and b are 1 to 3.

13. The copolymer according to any one of claims 1 to 12, A solvent; carbon nanotubes, dispersion liquid.

14. The dispersion of claim 13; a positive electrode active material; Positive electrode slurry composition.

15. A current collector; a positive electrode active material layer formed by applying the positive electrode slurry composition according to claim 14 onto the current collector; Positive electrode.

16. The positive electrode according to claim 15, Secondary battery.

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