Copolymer, dispersion liquid, positive electrode slurry composition, positive electrode, and secondary battery

Abstract

The present invention relates to a copolymer, a dispersion liquid, a positive electrode slurry composition, a positive electrode, and a secondary battery. The copolymer 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 monomer units containing one or more substituted or unsubstituted aromatic or aliphatic rings and vinyl monomer units containing one or more substituted or unsubstituted aromatic or aliphatic rings; and a polar monomer unit containing one or more functional groups selected from the group consisting of a carboxyl group, a sulfonic acid group, a phosphonic acid group, a cyano group, a pyrrolidone group, an amide group, an alkylamido group, a dialkylamido group, a hydroxyl group, an epoxy group, a caprolactam group, a morpholinyl group, and an oxazolidinone group.

Description

Technical Field

[0001] This invention relates to copolymers, dispersions comprising the thereof, positive electrode slurry compositions, positive electrodes, and secondary batteries. More specifically, it relates to copolymers that can produce carbon nanotube dispersions with increased solids content and improved dispersibility, and that can produce positive electrode slurry compositions and electrodes comprising the thereof. Background Technology

[0002] Carbon materials possess unique mechanical, electrical, and thermal properties, leading to their application in various fields such as electronics, biotechnology, and medicine. In recent years, in addition to traditional carbon materials such as graphite, activated carbon, and carbon black, carbon nanomaterials such as carbon nanotubes, fullerenes, and graphene have also attracted attention.

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

[0004] However, carbon materials, especially carbon nanomaterials, tend to aggregate within a matrix due to their strong van der Waals forces. If carbon materials aggregate within a matrix, they cannot exhibit their inherent properties and may experience reduced uniformity.

[0005] Methods for dispersing carbon materials include mechanical dispersion using physical forces such as ultrasound, grinding, and high shear force; dispersion using dispersants; and dispersion based on surface modification.

[0006] However, mechanical dispersion and surface-modified dispersion are prone to damage to carbon materials, and the original properties of carbon materials (e.g., electrical conductivity, thermal conductivity, etc.) will be significantly reduced due to such damage.

[0007] Therefore, research is actively underway to utilize dispersants to disperse carbon materials. In particular, in order to effectively disperse carbon nanomaterials such as carbon nanotubes, in-depth research is being conducted on using polymeric dispersants to wrap carbon nanomaterials or on the π-π interaction between the p orbitals of the aromatic rings of polymeric dispersants and the p orbitals of carbon nanomaterials.

[0008] However, in reality, there are still not many dispersants that can effectively disperse carbon materials, especially carbon nanomaterials, while maintaining their inherent properties, and further research is needed.

[0009] Existing technical documents

[0010] Patent documents

[0011] Patent Document 1: Korean Patent Publication No. 10-2022-0141368 Summary of the Invention

[0012] The problem to be solved

[0013] The purpose of this invention is to maximize electrostatic repulsion by using a copolymer of polar monomer units and metal cations as a dispersant, thereby producing a carbon nanotube dispersion with improved dispersibility and a higher solid content, and to provide a positive electrode slurry composition, a positive electrode, and a secondary battery containing the carbon nanotube dispersion.

[0014] However, the problems to be solved by this application are not limited to those mentioned above, and those skilled in the art should be able to clearly understand other problems not mentioned based on the following description.

[0015] Methods for solving problems

[0016] One aspect of this application provides a copolymer comprising:

[0017] Acrylate monomer units containing straight-chain or branched aliphatic hydrocarbons with 5 to 22 carbon atoms;

[0018] The monomer unit selected from the group consisting of acrylate monomer units containing one or more substituted or unsubstituted aromatic or aliphatic rings and vinyl monomer units containing one or more substituted or unsubstituted aromatic or aliphatic rings; and

[0019] Contains a group selected from carboxyl (COOH), sulfonic acid (SO3H), phosphonic acid (PO3H2), cyano (CN), pyrrolidone (NC4H6O), amide, alkylamide, dialkylamide, hydroxyl, epoxy, and caprolactam (C5H) groups. 10 A polar monomer unit comprising any one or more functional groups from the group consisting of CNO, morpholino (C4H8NO), and oxazolidinone (C3H4NO2).

[0020] Another aspect of this application provides a dispersion comprising:

[0021] The above copolymer;

[0022] Solvent; and

[0023] Carbon nanotubes.

[0024] Another aspect of this application provides a positive electrode slurry composition comprising:

[0025] The above dispersion; and

[0026] Positive electrode active material.

[0027] Another aspect of this application provides a positive electrode comprising:

[0028] Current collector; and

[0029] A positive electrode active material layer is formed by coating the above-mentioned current collector with the above-mentioned positive electrode slurry composition.

[0030] Another aspect of this application provides a secondary battery comprising the aforementioned positive electrode.

[0031] Invention Effects

[0032] As described above, the copolymers of the present invention can be manufactured by selecting monomer units capable of electrostatic repulsion and selecting substituents to maximize such electrostatic repulsion during copolymer synthesis.

[0033] At this point, in order to maximize the electrostatic repulsion, the functional groups of the polar monomer units that have been ionized into anions can be replaced with cations, especially metal cations.

[0034] In addition, the dispersion of the present invention can ensure dispersibility and dispersion stability by maximizing electrostatic repulsion, and can have more solid components.

[0035] In addition, positive electrode slurry compositions, positive electrodes, and secondary batteries comprising dispersions made using copolymers of the present invention can be manufactured. Detailed Implementation

[0036] The terms or words used in this specification and claims should not be interpreted as having their usual or dictionary meanings, but should be interpreted only based on the principles that the inventors can appropriately define the concepts of the terms to best illustrate their invention, and in accordance with the meanings and concepts consistent with the technical ideas of the invention.

[0037] Therefore, the embodiments described in this specification are only one of the most preferred embodiments of the present invention and do not represent all the technical ideas of the present invention. It should be understood that there may be many equivalents and modifications that can replace these embodiments when this application is filed.

[0038] In this specification, unless the context clearly specifies otherwise, singular expressions include plural expressions. It should be understood in this specification that terms such as “comprising,” “possessing,” or “having” are intended to specify the presence of the implemented features, numbers, steps, constituent elements, or combinations thereof, and do not presuppose the presence or additional possibilities of more than one other feature, number, step, constituent element, or combination thereof.

[0039] In this specification, where various parameters are given as a list of ranges, preferred ranges, or preferred upper and lower limits, it should be understood that, regardless of whether the range is disclosed individually, all ranges formed by any pair of upper or preferred values ​​and any lower or preferred values ​​are specifically disclosed.

[0040] Where a range of values ​​is mentioned in this specification, unless otherwise described, the range is intended to include its endpoints and all integers and fractions within its range.

[0041] The scope of this invention is not intended to be limited to the specific values ​​mentioned when defining the scope.

[0042] In this specification, the terms “a to b” and “a ~ b”, which represent a range of values, are defined as ≥ a and ≤ b.

[0043] The copolymer of one aspect of the present invention may comprise:

[0044] Acrylate monomer units containing straight-chain or branched aliphatic hydrocarbons with 5 to 22 carbon atoms;

[0045] The monomer unit selected from the group consisting of acrylate monomer units containing one or more substituted or unsubstituted aromatic or aliphatic rings and vinyl monomer units containing one or more substituted or unsubstituted aromatic or aliphatic rings; and

[0046] Contains a group selected from carboxyl (COOH), sulfonic acid (SO3H), phosphonic acid (PO3H2), cyano (CN), pyrrolidone (NC4H6O), amide, alkylamide, dialkylamide, hydroxyl, epoxy, and caprolactam (C5H) groups. 10 A polar monomer unit comprising any one or more functional groups from the group consisting of CNO, morpholino (C4H8NO), and oxazolidinone (C3H4NO2).

[0047] In one embodiment, the acrylate monomer unit containing a straight-chain or branched aliphatic hydrocarbon with 5 to 22 carbon atoms can be polymerized to form: n-pentyl(meth)acrylate, n-hexyl(meth)acrylate, n-heptyl(meth)acrylate, n-octyl(meth)acrylate, 2-ethylhexyl(meth)acrylate, and (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 The following are listed: 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, isopentyl(meth)acrylate, isoheptyl(meth)acrylate, isooctyl(meth)acrylate, and isononyl(meth)acrylate.isodecyl(meth)acrylate, isoundecyl(meth)acrylate, isododecyl(meth)acrylate, isotridecyl(meth)acrylate, isotetradecyl(meth)acrylate, isopentadecyl(meth)acrylate, isocetyl(meth)acrylate, isometh... Isohexadecyl(meth)acrylate, isohexadecyl(meth)acrylate, isostearyl(meth)acrylate, isononadecyl(meth)acrylate, isoeicosyl(meth)acrylate, isoheneicosyl(meth)acrylate, isodocosyl(meth)acrylate, or combinations thereof.

[0048] At this point, the (meth)acrylate monomer unit described as an example of the acrylate monomer unit containing 5 to 22 carbon atoms in a straight-chain or branched aliphatic hydrocarbon can represent both methacrylate and acrylate.

[0049] For example, the above-described n-pentyl(meth)acrylate can refer to both n-pentyl methacrylate and n-pentyl acrylate.

[0050] For example, the acrylate monomer units containing straight-chain or branched aliphatic hydrocarbons with 5 to 22 carbon atoms can be polymerized to form stearyl acrylate.

[0051] In one embodiment, the monomer units selected from the group consisting of acrylate monomer units containing one or more substituted or unsubstituted aromatic or aliphatic rings and vinyl monomer units containing one or more substituted or unsubstituted aromatic or aliphatic rings can be polymerized to form: styrene, cyclopentyl acrylate, cyclohexyl acrylate, benzyl acrylate, benzyl methacrylate, phenyl acrylate, phenyl methacrylate, 3-phenoxybenzyl acrylate, σ-phenyl phenoxyethyl acrylate, σ-phenyl phenoxyethylmethacrylate, (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 combinations thereof.

[0052] For example, the acrylate monomer units containing one or more substituted or unsubstituted aromatic or aliphatic rings and the vinyl monomer units containing one or more substituted or unsubstituted aromatic or aliphatic rings can be polymerized from styrene to form them.

[0053] In one embodiment, the aforementioned polar monomer unit can be polymerized to form: acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, aconitic acid, vinylbenzoic acid, 2-acrylamido-2-methylpropanesulfonic acid, vinyl sulfonic acid, 4-styrenesulfonicacid, vinyl phosphonic acid, acrylonitrile, vinyl pyrrolidone, acrylamide, N-methylacylamide, 2-hydroxyethyl acrylate, 2-hydroxyethylmethacrylate, glycidyl methacrylate, or combinations thereof.

[0054] For example, the aforementioned polar monomer units can be formed by polymerizing methacrylic acid, maleic acid, 4-styrenesulfonic acid, vinyl phosphonic acid, or combinations thereof.

[0055] In one embodiment, the copolymer can be formed by polymerizing stearic acid, styrene, acrylonitrile, and methacrylic acid, or...

[0056] It is formed by polymerizing stearyl acrylate, styrene, acrylonitrile, and maleic acid, or

[0057] It is formed by polymerizing stearyl acrylate, styrene, acrylonitrile, and 4-styrenesulfonic acid, or

[0058] It is formed by polymerizing stearyl acrylate, styrene, acrylonitrile, and vinyl phosphonic acid.

[0059] In one embodiment, based on 100 mol% of the copolymer, the copolymer may comprise:

[0060] Acrylate monomer units containing 5 to 22 carbon atoms of straight-chain or branched aliphatic hydrocarbons, comprising 5 to 70 mol% or more;

[0061] The monomer units selected from the group consisting of acrylate monomer units containing one or more substituted or unsubstituted aromatic or aliphatic rings (5 mol% to 70 mol%); and vinyl monomer units containing one or more substituted or unsubstituted aromatic or aliphatic rings;

[0062] The above-mentioned substances containing 5 mol% to 50 mol% of groups selected from carboxyl (COOH), sulfonic acid (SO3H), phosphonic acid (PO3H2), cyano (CN), pyrrolidone (NC4H6O), amide, alkylamide, dialkylamide, hydroxyl, epoxy, and caprolactam (C5H) groups are present in an amount selected from carboxyl (COOH), sulfonic acid (SO3H), phosphonic acid (PO3H2), cyano (CN), pyrrolidone (NC4H6O), amide, alkylamide, dialkylamide, hydroxyl, epoxy, and caprolactam (C5H) groups. 10 A polar monomer unit comprising any one or more functional groups from the group consisting of CNO, morpholino (C4H8NO), and oxazolidinone (C3H4NO2).

[0063] For example, in the above copolymers, based on 100 mol% of the copolymer, the content of the acrylate monomer units containing linear or branched aliphatic hydrocarbons with 5 to 22 carbon atoms can be 5 mol% to 70 mol%, 10 mol% to 60 mol%, 15 mol% to 50 mol%, 20 mol% to 40 mol%, 30 mol% to 40 mol%, or 35 mol% to 45 mol%. When the content of the acrylate monomer units containing linear or branched aliphatic hydrocarbons with 5 to 22 carbon atoms is lower than the range of this application, the copolymer may have difficulty wrapping carbon nanotubes; when it is higher than the range of this application, the copolymer may be insoluble in the solvent and precipitate or separate into phases.

[0064] Furthermore, for example, in the aforementioned copolymer, based on 100 mol% of the copolymer, the content of any one or more monomer units selected from the group consisting of acrylate monomer units containing one or more substituted or unsubstituted aromatic or aliphatic rings and vinyl monomer units containing one or more substituted or unsubstituted aromatic or aliphatic rings can be 5 mol% to 70 mol% or less, 10 mol% to 60 mol% or less, 15 mol% to 50 mol% or less, 15 mol% to 40 mol% or less, 20 mol% to 40 mol% or less, or 25 mol% to 35 mol% or less. Wherein, the content of either the acrylate monomer unit or the vinyl monomer unit can be 0 mol%. When the content of any one or more monomer units in the group consisting of acrylate monomer units containing one or more substituted or unsubstituted aromatic or aliphatic rings and vinyl monomer units containing one or more substituted or unsubstituted aromatic or aliphatic rings is lower than the range of this application, the interaction between carbon nanotubes and copolymer chains may become weak and difficult to play a dispersing role; when it is higher than the range of this application, the viscosity of the dispersion may become too high.

[0065] Furthermore, for example, in the aforementioned copolymers, based on 100 mol% of the copolymer, the content of the aforementioned polar monomer units can be 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%. When the content of the aforementioned polar monomer units is below the range of this application, the copolymer may not be soluble in the solvent and may precipitate or undergo phase separation. When it is above the range of this application, the glass transition temperature may become too high, and the electrode may break due to lack of flexibility during manufacturing.

[0066] In one embodiment, the copolymer described above may be represented by the following chemical formula 1.

[0067] [Chemical Formula 1]

[0068]

[0069] In the above chemical formula 1,

[0070] R1 to R 15 They may be the same or different from each other, each independently consisting of a straight-chain or branched hydrocarbon group with 1 to 4 carbon atoms.

[0071] R'1 is a straight-chain or branched aliphatic hydrocarbon group with 5 to 22 carbon atoms.

[0072] R'2 contains one or more substituted or unsubstituted aromatic or aliphatic rings.

[0073] R'3 contains one or more substituted or unsubstituted aromatic or aliphatic rings.

[0074] R'4 is selected from cyano (CN), pyrrolidone (NC4H6O), amide, alkylamide, dialkylamide, hydroxyl, epoxy, caprolactam (C5H) 10 Any one or more of the following groups: CNO, morpholino (C4H8NO), and oxazolidinone (C3H4NO2)

[0075] R'5 is selected from one or more of the group consisting of carboxyl (COOH), sulfonic acid (SO3H) and phosphonic acid (PO3H2).

[0076] l+m+n+o+p=1, 0.05≤l≤0.70, 0.05≤m+n≤0.70, and 0.05≤o+p≤0.50.

[0077] (Where either m or n can be 0, and o can be 0.)

[0078] In one embodiment, in the above chemical formula 1, R1 to R... 15 Both can be hydrogen.

[0079] In one embodiment, R'1 in the above chemical formula 1 may include any one or more selected from the group consisting of n-pentyl, n-hexyl, n-heptyl, n-octyl, 2-ethylhexyl, n-nonyl, n-decyl, n-undecyl, lauryl, n-dodecyl, n-tridecyl, n-tetradecyl, n-pentadecayl, cetyl, n-hexadecyl, n-heptadecyl, stearyl, n-octadecyl, n-nonadecayl, n-heptadecyl, n-heptadecyl, isocetyl, isohexyl, isohexyl, isohexyl, isohexyl, isohexyl, isohexyl, isohexyl, isohexyl, isohexyl, isohexyl, isohexyl, isohexyl, and isohexyl.

[0080] For example, in the above chemical formula 1, R'1 can be n-octadecyl.

[0081] In one embodiment, in the above chemical formula 1, R'2 and R'3 may be the same as or different from each other, and each may independently comprise one or more of the group consisting of substituted or unsubstituted cyclopentyl, cyclohexyl, benzyl, phenyl, phenoxy, naphthalene, anthracene and pyrene.

[0082] For example, in the above chemical formula 1, R'2 can be benzyl, phenyl, naphthalene, or 3-phenoxybenzyl, and R'3 can be phenyl.

[0083] In one embodiment, the monomer comprising R'1 in the above-described chemical formula 1 may be, but is not limited to, a copolymer formed by polymerizing the following compounds: 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, and 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, Isopentyl(meth)acrylate, Isoheptyl(meth)acrylate, Isooctyl(meth)acrylate, Isononyl(meth)acrylateisodecyl(meth)acrylate, isoundecyl(meth)acrylate, isododecyl(meth)acrylate, isotridecyl(meth)acrylate, isotetradecyl(meth)acrylate, isopentadecyl(meth)acrylate, isocetyl(meth)acrylate, isometh... Isohexadecyl(meth)acrylate, isohexadecyl(meth)acrylate, isostearyl(meth)acrylate, isononadecyl(meth)acrylate, isoeicosyl(meth)acrylate, isoheneicosyl(meth)acrylate, isodocosyl(meth)acrylate, or combinations thereof.

[0084] For example, in the above chemical formula 1, the monomer containing R'1 can be stearyl acrylate.

[0085] In this case, the (meth)acrylate monomer unit described in the above chemical formula 1 as an example of a monomer containing R'1 can represent both methacrylate and acrylate. For example, n-pentyl(meth)acrylate described above can represent both n-pentyl methacrylate and n-pentyl acrylate.

[0086] In one embodiment, in the above-described chemical formula 1, the monomer containing R'2 may include a monomer selected from 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, (1-pyrene)2-methyl-2-propenoate, 1-naphthyl acrylate, 1-naphthyl methacrylate, and 2-naphthyl acrylate. It is any one or more of the group consisting of acrylate, 2-naphthylmethacrylate, 9-anthracene methyl acrylate and 9-anthracene methyl methacrylate.

[0087] For example, in the above chemical formula 1, the monomer containing R'2 can be any one or more selected from the group consisting of benzyl acrylate, benzyl methacrylate, phenyl acrylate, phenyl methacrylate, 1-naphthyl acrylate, 1-naphthyl methacrylate, 2-naphthyl acrylate, 2-naphthyl methacrylate, and 3-phenoxybenzyl acrylate.

[0088] In one embodiment, the monomer containing R'3 in the above chemical formula 1 can be styrene.

[0089] In one embodiment, in the above chemical formula 1, the monomer containing R'4 may include one or more selected from the group consisting of acrylonitrile, vinyl pyrrolidone, acrylamide, N-methyl acylamide, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, and glycidylmethacrylate.

[0090] For example, in the above chemical formula 1, the monomer containing R'4 can be acrylonitrile.

[0091] In one embodiment, the monomer containing R'5 in the above chemical formula 1 may comprise one or more selected from the group consisting of acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, aconitic acid, vinylbenzoic acid, 2-acrylamido-2-methylpropanesulfonic acid, vinyl sulfonic acid, 4-styrenesulfonicacid, and vinyl phosphonic acid.

[0092] For example, in the above chemical formula 1, the monomer containing R'5 can be any one or more selected from the group consisting of methacrylic acid, maleic acid, 4-styrenesulfonic acid, and vinyl phosphonic acid.

[0093] In one embodiment, the copolymer can be a random copolymer or a block copolymer, depending on the synthesis process.

[0094] In one embodiment, the number average molecular weight of the copolymer can be between 8,000 and 40,000.

[0095] For example, the number average molecular weight of the above copolymers can be 8,000 to 35,000, 8,000 to 30,000, 9,000 to 30,000, 10,000 to 30,000, or 11,000 to 30,000.

[0096] When the number average molecular weight of the copolymer is lower than the range of this application, the ability to prevent the re-aggregation of carbon materials in the dispersion may be reduced due to the increased fluidity of the copolymer. When the number average molecular weight is higher than the range of this application, the usability may be reduced due to excessive viscosity.

[0097] In one embodiment, the polar monomer unit of the copolymer is bonded to a metal cation, and the q value calculated according to Formula 1 can be more than 1.5 mol% and less than 300 mol%.

[0098] [Formula 1]

[0099] 5*a / b mol%≤q≤100*a / b mol%

[0100] (Wherein, in Formula 1 above, a is the number of functional groups that can be replaced by the metal cation in each polar monomer unit formed by polymerization, b is the number of positive charges of the metal cation, and a and b are 1 to 3.)

[0101] At this point, when a = 1 and b = 1, the value of q calculated according to Equation 1 above can be 5 mol% ≤ q ≤ 100 mol%, when a = 1 and b = 2, the value of q calculated according to Equation 1 above can be 2.5 mol% ≤ q ≤ 50 mol%, and when a = 1 and b = 3, the value of q calculated according to Equation 1 above can be 1.67 mol% ≤ q ≤ 33.3 mol%.

[0102] Furthermore, when a = 2 and b = 1, the q value calculated according to Equation 1 above can be 10 mol% ≤ q ≤ 200 mol%, when a = 2 and b = 2, the q value calculated according to Equation 1 above can be 5 mol% ≤ q ≤ 100 mol%, and when a = 2 and b = 3, the q value calculated according to Equation 1 above can be 3.33 mol% ≤ q ≤ 66.7 mol%.

[0103] Furthermore, when a = 3 and b = 1, the value of q calculated according to Equation 1 above can be 15 mol% ≤ q ≤ 300 mol%, when a = 3 and b = 2, the value of q calculated according to Equation 1 above can be 7.5 mol% ≤ q ≤ 150 mol%, and when a = 3 and b = 3, the value of q calculated according to Equation 1 above can be 5 mol% ≤ q ≤ 100 mol%.

[0104] For example, when the polar monomer unit mentioned above is acrylic acid, methacrylic acid, vinylbenzoic acid, 2-acrylamido-2-methylpropane sulfonic acid, vinyl sulfonic acid, 4-styrenesulfonic acid, etc., a is 1.

[0105] Additionally, for example, when the polar monomer unit mentioned above is maleic acid, fumaric acid, itaconic acid, vinyl phosphonic acid, etc., a is 2.

[0106] For example, when the polar monomer unit mentioned above is aconitic acid, a is 3.

[0107] In one embodiment, the metal cation can be obtained from an inorganic salt consisting of a pair of cations and anions that are capable of ionization in a solvent.

[0108] For example, the cations mentioned above can 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 zinc (Zn) ions.

[0109] At this point, when the above-mentioned cations are lithium (Li), sodium (Na), potassium (K), etc., b is 1; when the above-mentioned cations are magnesium (Mg), calcium (Ca), nickel (Ni) ions, etc., b is 2; and when the above-mentioned cations are aluminum (Al) ions, etc., b is 3.

[0110] Alternatively, for example, the anions mentioned above can be F-, Cl-, Br-, I-, O2-, S2-, or SO42-. 2- PO4 3- CO3 2- Or OH-.

[0111] The aforementioned inorganic salts can be achieved by using a combination of the aforementioned cations and anions to achieve substitution, but are not limited thereto. There are no restrictions as long as the functional groups of the aforementioned polar monomer units can be replaced with metal cations.

[0112] In one embodiment, the polar monomer units of the copolymer can be combined with metal cations.

[0113] In this case, to maximize the electrostatic repulsion, the functional groups of the polar monomer units ionized into anions can be replaced with cations, particularly metal cations. Furthermore, the copolymers described above can simultaneously contain functional groups of the aforementioned polar monomer units that are either replaced by metal cations or not.

[0114] Thus, the electrostatic repulsion is maximized, which ensures the dispersibility and dispersion stability of the dispersion made from the above copolymer, and allows it to have a higher solid content.

[0115] In one embodiment, a free radical initiator can be used when manufacturing the copolymer.

[0116] For example, the free radical initiator mentioned above can be 2,2'-azobis-2,4-dimethylvaleronitrile, but it is not limited to this. Any free radical initiator that can be used in a solvent can be used.

[0117] In one embodiment, the copolymer described above can be used for the effective dispersion of all types of carbon nanotubes, carbon black, acetylene black, graphite, etc., including single-walled carbon nanotubes, double-walled carbon nanotubes, multi-walled carbon nanotubes, and thin-walled carbon nanotubes.

[0118] Furthermore, these materials can be used in the manufacture of both the positive and negative electrodes of secondary batteries that include them.

[0119] As another aspect of this application, the dispersion may contain the aforementioned copolymer, solvent, and carbon nanotubes.

[0120] In one embodiment, the solvent may be a polar solvent, for example, it may be any one or more selected from the group consisting of N-methyl-2-pyrrolidone (NMP), N-ethyl-2-pyrrolidone (NEP), dimethylformamide (DMF), dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), γ-butyrolactone, ethyl acetate, propyl acetate, ethanol, isopropylalcohol, and deionized water.

[0121] 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 combinations thereof. The types of carbon nanotubes are not limited thereto.

[0122] In addition, based on 100% of the total weight of the dispersion, the content of the carbon nanotubes can be more than 1% and less than 10% by weight.

[0123] If the carbon nanotube content in the dispersion is lower than the range of this application, the solid content of the electrode slurry will decrease; if it is higher than the range of this application, the viscosity will be too high and it will be difficult to disperse, making it difficult to manufacture a high-quality dispersion.

[0124] On the other hand, in the above dispersion, the content of the copolymer can be 0.1 to 0.5 times the content of the carbon nanotubes.

[0125] If the content of the copolymer is lower than the range specified in this application relative to the content of the carbon nanotubes, sufficient dispersion cannot be achieved, and the carbon material cannot be effectively dispersed. Conversely, if the content of the copolymer is higher than the range specified in this application relative to the content of the carbon nanotubes, the ratio of materials inside the battery increases, and the energy density may decrease.

[0126] In one embodiment, the viscosity of the dispersion at a shear rate of 2.5 / s can be below 10,000 cps.

[0127] For example, the viscosity of the dispersion at a shear rate of 2.5 / s can be 200 cps or more and 800 cps or less, 270 cps or more and 750 cps or less, and preferably 220 cps or more and 725 cps or less.

[0128] In one embodiment, the viscosity of the dispersion after storage at a shear rate of 2.5 / s can be below 87,000 cps.

[0129] For example, the viscosity of the above dispersion after storage at a shear rate of 2.5 / s can be 3000 cps or more and 8600 cps or less, preferably 3100 cps or more and 8550 cps or less.

[0130] In one embodiment, the particle size (D50) of the carbon nanotubes dispersed in the dispersion can be 4.6 μm or less.

[0131] That is, the dispersion containing the copolymer of this application has a low particle size value (D50) of less than 4.6 μm, thus the carbon nanotubes have excellent dispersibility in the dispersion.

[0132] For example, the particle size (D50) of the carbon nanotubes dispersed in the dispersion can be 2.9 μm or more and 4.6 μm or less, 2.9 μm or more and 4.51 μm or less, or 3.05 μm or more and 4.51 μm or less, and preferably 2.94 μm or more and 4.51 μm or less.

[0133] That is, the copolymer (dispersant) of this application, with its excellent dispersing power, can reduce the particle size of carbon nanotubes in the dispersion, and produce a carbon material dispersion with uniform and fine particle size and low viscosity, thereby shortening the dispersion process.

[0134] In another aspect, the positive electrode slurry composition of the present invention may comprise the above-described dispersion and the positive electrode active material.

[0135] In one embodiment, the content of the carbon nanotubes contained in the above-mentioned positive electrode slurry composition can be 0.001 to 0.1 times the content of the above-mentioned positive electrode active material, preferably 0.003 to 0.02 times.

[0136] If the content of the carbon nanotubes contained in the above-mentioned positive electrode slurry composition is lower than the range of this application relative to the content of the above-mentioned positive electrode active material, the conductivity in the electrode active material may decrease, resulting in a decrease in output characteristics; if it is higher than the range of this application, the content of the positive electrode active material decreases, and the battery capacity may decrease.

[0137] In one embodiment, the aforementioned positive electrode active material can be any positive electrode active material that can be used in this technical field. Specific examples of such positive electrode active materials include lithium metal; lithium cobalt oxides such as LiCoO2; and Li... 1+ x Mn 2-x Lithium manganese oxides such as O4 (where x is 0 to 0.33), LiMnO3, LiMn2O3, and LiMnO2; lithium copper oxides such as Li2CuO2; vanadium oxides such as LiV3O8, V2O5, and Cu2V2O7; and LiNi 1-x M x Lithium-nickel oxides represented by O2 (where M = Co, Mn, Al, Cu, Fe, Mg, B or Ga, x = 0.01 to 0.3); LiMn 2-x M x Lithium-manganese composite oxides represented by O2 (where M = Co, Ni, Fe, Cr, Zn or Ta, x = 0.01 to 0.1) or Li2Mn3MO8 (where M = Fe, Co, Ni, Cu or Zn); Li(Ni a Co b Mn cLithium-nickel-manganese-cobalt oxides represented by O2 (where 0 < a < 1, 0 < b < 1, 0 < c < 1, a + b + c = 1); sulfur or disulfide compounds; phosphates such as LiFePO4, LiMnPO4, LiCoPO4, and LiNiPO4; Fe2(MoO4)3, etc., but not limited to these.

[0138] The content of the positive electrode active material, based on the solid content, can be 90-99% by weight. If the content of the active material is low, the battery cannot achieve high capacity. If the content of the active material is too high, the content of binders, conductive materials, etc. will be relatively reduced, and thus the electrode adhesion and conductivity may decrease.

[0139] In one embodiment, the above-described positive electrode slurry composition may further include a conductive material.

[0140] There are no particular restrictions on the conductive materials mentioned above, and they can be selected appropriately according to the type of battery and capacitor. For example, in the case of lithium-ion secondary batteries, carbon such as graphite and activated carbon can be used, while in the case of nickel-metal hydride secondary batteries, cobalt oxide can be used, and the negative electrode can be nickel powder, cobalt oxide, titanium oxide, carbon, etc.

[0141] Examples of carbon species mentioned above include acetylene black, furnace black, graphite, carbon fiber, and fullerenes.

[0142] Regarding the amount of the aforementioned conductive material used, based on 100% by weight of the electrode active material, it is typically 1 to 20% by weight, preferably 2 to 10% by weight.

[0143] Since the energy density of a secondary battery can be increased by reducing the amount of conductive material and increasing the amount of positive electrode active material, it is important to exhibit high efficiency when using the same amount of conductive material.

[0144] The smaller the conductive material used in the electrode slurry for secondary batteries and the more uniformly it is dispersed, the higher the conductivity, the lower the internal resistance of the battery, resulting in improved output characteristics and increased battery life. Conversely, if the material is large and unevenly dispersed, even using the same amount, the binding properties and conductivity will decrease, adversely affecting the battery's life and output characteristics. Furthermore, if the dispersion has low viscosity, the solid content of the slurry can be increased to improve electrode production speed.

[0145] In one embodiment, the above-described positive electrode slurry composition may further include a binder.

[0146] As the aforementioned adhesive, one or more of the following can be selected from poly(meth)acrylic acid, poly(meth)acrylamide, carboxymethyl cellulose, polyvinylidene fluoride, copolymers of polyhexafluoropropylene and polyvinylidene fluoride (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 are not limited thereto.

[0147] The content of the above-mentioned binder in the positive electrode slurry composition, based on the solid content conversion, can be more than 0.3% by weight and less than 10% by weight. Preferably, the content of the above-mentioned binder in the positive electrode slurry composition can be more than 0.7% by weight and less than 8% by weight.

[0148] When the content of the adhesive is lower than that of this application, it may be difficult to expect sufficient adhesion between the current collector and the positive electrode active material or between the positive electrode active materials. When the content of the adhesive is higher than that of this application, the adhesive will act as a resistor in the battery, and the relative content of the positive electrode active material will decrease, resulting in a decrease in battery capacity and other battery performance degradation.

[0149] In another aspect of this application, the positive electrode may include a current collector and a layer of positive electrode active material formed by coating the above-described positive electrode slurry composition.

[0150] The aforementioned positive electrode can be manufactured by (a) a step of manufacturing a positive electrode slurry composition comprising a positive electrode active material and the copolymer of the present application; and (b) a step of coating the aforementioned positive electrode slurry composition onto a positive electrode current collector and then drying it.

[0151] The above-mentioned positive electrode slurry composition can be mixed using conventional mixers, such as high-speed shear mixers and homogenizers, according to conventional methods.

[0152] Step (b) above is a step of manufacturing a positive electrode for a lithium secondary battery by coating the positive electrode slurry composition produced in step (a) onto the positive electrode current collector and then drying it.

[0153] At this time, there are no limitations on the method of coating the above-mentioned positive electrode slurry composition. For example, it can be manufactured by implementing doctor blade coating, dip coating, gravure coating, slit die coating, spin coating, comma coating, barcoating, reverse roll coating, screen coating, cap coating, etc.

[0154] After coating and drying the above-mentioned positive electrode slurry composition, a positive electrode for secondary batteries with a positive electrode active material layer can be finally manufactured.

[0155] The aforementioned current collectors can be used as long as they are conductive and do not chemically react with the electrode forming paste. Representative examples include aluminum foil and copper foil. Current collectors with a thickness between 3 and 50 micrometers can be selected.

[0156] Another aspect of this application suggests that a secondary battery may include the aforementioned positive electrode.

[0157] In one embodiment, the secondary battery may further include a separator.

[0158] The separator must be an insulator that separates the negative and positive electrodes and must provide a pathway for lithium ions to move only. Therefore, it must have good wettability with the electrolyte, and porous polymer membranes such as PE / PP or porous nonwoven fabrics are used. To prevent battery short circuits, coated separators with ceramics or other materials that enhance heat resistance and mechanical strength can be used, and these coatings can be single-layer or multi-layered.

[0159] The aforementioned diaphragm can be made of a porous substrate. Any porous substrate commonly used in electrochemical devices can be used as the aforementioned porous substrate, such as polyolefin porous membranes or nonwoven fabrics, but it is not particularly limited to these.

[0160] The aforementioned diaphragm may be a porous substrate composed of any one or a mixture of two or more of polyethylene, polypropylene, polybutene, polypentene, polyethylene terephthalate, polybutylene terephthalate, polyester, polyacetal, polyamide, polycarbonate, polyimide, polyetheretherketone, polyethersulfone, polyphenylene ether, polyphenylene sulfide, and polyethylene naphthalate.

[0161] The electrolyte of the aforementioned lithium secondary battery is a non-aqueous electrolyte containing lithium salt, consisting of lithium salt and solvent. The solvent used includes non-aqueous organic solvents, organic solid electrolytes, and inorganic solid electrolytes.

[0162] The lithium salts mentioned above are substances that are readily soluble in the aforementioned non-aqueous electrolytes. For example, LiCl, LiBr, LiI, LiClO4, LiBF4, and LiB can be used. 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 carboxylic acids, lithium 4-phenylboronic acid imide, etc.

[0163] The aforementioned non-aqueous organic solvents may include, for example, N-methyl-2-pyrrolidone, propylene carbonate, ethylene carbonate, butenyl carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, γ-butyrolactone, 1,2-dimethoxyethane, 1,2-diethoxyethane, tetrahydroxyfranc, 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, 4-methyl-1,3-dioxane, diethyl ether, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, triphosphate, trimethoxymethane, dioxolane derivatives, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ethers, methyl propionate, ethyl propionate, and other non-protic organic solvents.

[0164] As the aforementioned organic solid electrolyte, for example, polyethylene derivatives, polyethylene oxide derivatives, polypropylene oxide derivatives, phosphate polymers, polyagitationlysine, polyester sulfides, polyvinyl alcohol, polyvinylidene fluoride, polymers containing secondary dissociation groups, etc., can be used.

[0165] As the aforementioned inorganic solid electrolytes, for example, nitrides, halides, and sulfates of Li such as Li3N, LiI, Li5NI2, Li3N-LiI-LiOH, LiSiO4, LiSiO4-LiI-LiOH, Li2SiS3, Li4SiO4, Li4SiO4-LiI-LiOH, and Li3PO4-Li2S-SiS2 can be used.

[0166] In addition, non-aqueous electrolytes may contain other additives for purposes such as improving charge-discharge characteristics and flame retardancy. Examples of such additives include pyridine, triethyl phosphite, triethanolamine, cyclic ethers, ethylenediamine, n-glycine dimethyl ether, triamide hexaphosphate, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N,N-substituted imidazolides, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, aluminum trichloride, fluoroethylene carbonate (FEC), propylene sulpholone (PRS), and vinylene carbonate (VC).

[0167] In addition to the conventional winding process, the lithium secondary battery of the present invention can also undergo lamination stacking and folding processes for the separator and electrodes. Furthermore, the battery casing can be cylindrical, square, pouch-shaped, or coin-shaped, etc. Moreover, such a lithium secondary battery can be used in small or medium-to-large-sized devices such as automobiles and electronic devices.

[0168] The present invention will now be described in more detail through embodiments. However, the following embodiments are intended to illustrate the present invention more specifically, and the scope of the present invention is not limited to the following embodiments.

[0169] Examples and Comparative Examples: Preparation of Copolymers

[0170] [Example 1]

[0171] In a 5-necked flask reactor, 70 g of N-methyl pyrrolidone (NMP) was added as a solvent. Then, based on a total monomer mole percentage of 100 mol%, 40 mol% of stearyl acrylate (SA), 30 mol% of styrene (SM), 10 mol% of acrylonitrile (AN), and 20 mol% of methacrylic acid were added. A reflux condenser and thermometer were installed, nitrogen was purged, and the mixture was heated to 75°C to produce a solution. At this point, the total weight of the copolymerized monomers was set at 70 g.

[0172] Then, 0.15 g of 2,2'-azobis-2,4-dimethylvaleronitrile was dissolved in 20 g of N-methylpyrrolidone and added dropwise to the above solution over 30 minutes. After the addition was completed, the solution was kept at 75°C for 7 hours to produce the copolymer.

[0173] The inorganic salt LiOH, used to replace the functional group of methacrylic acid, was dissolved in methanol at a ratio of 100 mol% of the substituted product (methacrylic acid). The solution was then added to the reactor and stirred at 75°C for 1 hour to carry out the replacement of the functional group of methacrylic acid with the inorganic salt LiOH.

[0174] The methanol is then removed by distillation to produce a copolymer that can be used as a dispersant.

[0175] [Example 2]

[0176] The copolymer was prepared by the same method as in Example 1, except that NaOH was used instead of the inorganic salt LiOH used to replace the functional groups of methacrylic acid.

[0177] [Example 3]

[0178] The copolymer was prepared by the same method as in Example 1, except that NaCl was used instead of the inorganic salt LiOH used to replace the functional group of methacrylic acid.

[0179] [Example 4]

[0180] The copolymer was prepared by the same method as in Example 1, except that KOH was used instead of the inorganic salt LiOH used to replace the functional group of methacrylic acid.

[0181] [Example 5]

[0182] Mg(OH)2 was used to replace the inorganic salt LiOH used to replace the functional group of methacrylic acid, and the amount of Mg(OH)2 was 50 mol% relative to the substituted product (methacrylic acid). Otherwise, the copolymer was produced by the same method as in Example 1.

[0183] [Example 6]

[0184] The copolymer was prepared by using 20 mol% maleic acid instead of 20 mol% methacrylic acid, and the amount of NaOH added was 200 mol% relative to the substituted product (maleic acid). Otherwise, the copolymer was prepared by the same method as in Example 2.

[0185] [Example 7]

[0186] The copolymer was otherwise manufactured by the same method as in Example 2, except that 20 mol% of 4-styrenesulfonic acid was used instead of 20 mol% of methacrylic acid.

[0187] [Example 8]

[0188] The copolymer was prepared by replacing 20 mol% of methacrylic acid with 20 mol% of vinylphosphonic acid, and by using NaOH with an addition of 200 mol% relative to the substituted product (vinylphosphonic acid). Otherwise, the copolymer was prepared by the same method as in Example 2.

[0189] [Comparative Example 1]

[0190] The copolymer was prepared by the same method as in Example 1, except that the inorganic salt LiOH, which is used to replace the functional group of methacrylic acid, was not used.

[0191] [Comparative Example 2]

[0192] The NaOH was used at a rate of 2 mol% relative to the substituted product (methacrylic acid), and the copolymer was otherwise manufactured by the same method as in Example 2.

[0193] [Comparative Example 3]

[0194] The NaOH was used at a rate of 150 mol% relative to the substituted product (methacrylic acid), and the copolymer was otherwise manufactured by the same method as in Example 2.

[0195] [Comparative Example 4]

[0196] Hydrogenated nitrile butadiene rubber (H-NBR, product name 720H) from ZEON Corporation, a commercially available dispersant, was used instead of the dispersant manufactured in Examples 1 to 8.

[0197] Table 1 below shows the monomer content (mol%), inorganic salt, and inorganic salt input (mol%) relative to the substituted substance used to manufacture the copolymers of Examples 1 to 8 and Comparative Examples 1 to 3.

[0198] [Table 1]

[0199]

[0200] In Table 1 above, 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.

[0201] In Table 1 above, the amount of inorganic salt added relative to the substituted substance in Examples 1 to 8 (mol%) represents the total substitution amount (100*a / b mol%) in the q value calculated according to the following formula 1.

[0202] [Formula 1]

[0203] 5*a / b mol%≤q≤100*a / b mol%

[0204] In Formula 1 above, a represents the number of functional groups that can be replaced by metal cations in the polar monomer units formed by the polymerization of methacrylic acid, maleic acid, 4-styrenesulfonic acid, and vinyl phosphonic acid, as described in Table 1 above.

[0205] In Equation 1 above, b represents the number of positive charges of the inorganic salt metal cations Li, Na, K, and Mg in Table 1 above.

[0206] That is, Examples 1 to 4 and Example 7 correspond to the case where the number of functional groups that can be replaced by metal cations in the polar monomer unit formed by polymerization of methacrylic acid or 4-styrenesulfonic acid is a = 1, and the number of positive charges of the metal cations of inorganic salts is b = 1; Example 5 corresponds to the case where the number of functional groups that can be replaced by metal cations in the polar monomer unit formed by polymerization of methacrylic acid is a = 1, and the number of positive charges of the metal cations of inorganic salts is b = 2; Examples 6 and Example 8 correspond to the case where the number of functional groups that can be replaced by metal cations in the polar monomer unit formed by polymerization of maleic acid or vinylphosphonic acid is a = 2, and the number of positive charges of the metal cations of inorganic salts is b = 1.

[0207] [Manufacturing Example]

[0208] Manufacturing Examples 1 to 8, Comparative Manufacturing Examples 1 to 4: Manufacturing of Dispersions

[0209] 0.75 g of copolymers (100% solids basis) prepared in Examples 1 to 8 and Comparative Examples 1 to 4 as dispersants, 3 g of multi-walled carbon nanotubes (MWCNTs), 96.25 g of N-methylpyrrolidone, and 400 g of zirconia beads with an average diameter of 0.65 mm were added to a planetary ball mill and dispersed at 400 rpm for 60 minutes. The zirconia bead mixture was then filtered through a 40-mesh sieve to produce a dispersion with a solids content of 3.75% by weight.

[0210] Table 2 below shows the types of copolymers contained in the dispersions of Manufacturing Examples 1 to 8 and Comparative Manufacturing Examples 1 to 4.

[0211] [Table 2]

[0212]

[0213]

[0214] Manufacturing Example 9: Manufacturing of the Positive Electrode

[0215] Using a planetary centrifugal mixer (ARE-310, Thinky), 4.6 g of the dispersion prepared according to Manufacturing Examples 1 to 8, 27.3 g of the positive electrode active material (NCM622), 18 g of PVdF dissolved in N-methylpyrrolidone at 8 wt%, and 7.9 g of N-methylpyrrolidone were mixed to prepare a slurry for positive electrode formation. At this time, the solid content of the slurry was 50% by weight.

[0216] The above slurry was coated onto a 20 μm thick aluminum foil using a doctor blade. The electrode coated with the slurry was dried in an oven at 130°C for at least 12 hours, and then the density of the mixture was adjusted to 2.4 g / cc by calendering. Subsequently, vacuum drying was performed at 110°C to manufacture the positive electrode plate.

[0217] [Evaluation Example]

[0218] Evaluation Example 1: Initial viscosity, viscosity after storage, and particle size determination of the dispersion

[0219] The initial viscosity of the dispersions of Preparation Examples 1 to 8 and Comparative Preparation Examples 1 to 4 was measured at 25°C using a Haake mars rheometer. The shear rate was measured in the range of 0.01 / s to 200 / s.

[0220] The dispersions of Manufacturing Examples 1 to 8 and Comparative Manufacturing Examples 1 to 4 were stored at 60°C for 3 days, and then the viscosity after storage was measured at 25°C using a Hacker rotational rheometer. The shear rate was measured in the range of 0.01 / s to 200 / s.

[0221] The particle size of the dispersions of Manufacturing Examples 1 to 8 and Comparative Manufacturing Examples 1 to 4 was determined using the Fraunhofer diffraction model and a laser particle size analyzer (Mastersizer 3000).

[0222] The initial viscosity, storage viscosity, and particle size D50 (median) at a shear rate of 2.5 / s are shown in Table 3 below.

[0223] [Table 3]

[0224]

[0225] At this point, when comparing Manufacturing Examples 1 to 8 with Comparative Manufacturing Example 1, it can be confirmed that when carbon nanotubes (CNTs) are dispersed using copolymers of polar monomer units combined with metal cations, the initial viscosity and post-storage viscosity of the dispersion are significantly improved. This is because the functional groups of the polar monomer units, existing in anionic state, greatly improve the dispersion stability through electrostatic repulsion.

[0226] Furthermore, it can be confirmed that the dispersions of Manufacturing Examples 1 to 8 are superior in terms of initial viscosity and viscosity after storage compared to the dispersion of Comparative Manufacturing Example 4, which was manufactured using a commercially available dispersant.

[0227] On the other hand, when manufacturing example 2 is compared with comparative manufacturing example 2, it can be confirmed that if the amount of functional group of polar monomer unit replaced by metal cation is less than an appropriate range, electrostatic repulsion will not be sufficiently generated, and thus improvement in dispersibility and dispersion stability cannot be expected.

[0228] Furthermore, when manufacturing example 2 was compared with comparative manufacturing example 3, it was confirmed that even when an inorganic salt larger than the appropriate range was used, no further substitution of functional groups of polar monomer units occurred, and therefore the dispersibility and dispersion stability were not further improved.

[0229] That is, the dispersions made using the copolymers of Examples 1 to 4 and Example 7, i.e., the q values ​​calculated according to Formula 1 above for Examples 1 to 4 and Example 7, are in the range of 5 mol% ≤ q ≤ 100 mol%. The dispersions made using the copolymer of Example 5, i.e., the q values ​​calculated according to Formula 1 above for Example 5, are in the range of 2.5 mol% ≤ q ≤ 50 mol%. The dispersions made using the copolymers of Examples 6 and 8, i.e., the q values ​​calculated according to Formula 1 above for Examples 6 and 8, are in the range of 10 mol% ≤ q ≤ 200 mol%.

[0230] Therefore, Examples 1 to 8 all demonstrate that by replacing the functional groups of the polar monomer units formed by polymerizing methacrylic acid, maleic acid, 4-styrenesulfonic acid and vinylphosphonic acid with metal cations within the range of the values ​​of Formula 1 defined in this application, the initial viscosity and the viscosity after storage of the dispersion can be improved.

[0231] The scope of this invention is defined by the claims that follow rather than by the detailed description above, and all modifications or variations derived from the meaning and scope of the claims and their equivalents should be interpreted as being included within the scope of this invention.

Claims

1. A copolymer comprising: Acrylate monomer units containing straight-chain or branched aliphatic hydrocarbons with 5 to 22 carbon atoms; The monomer unit selected from the group consisting of acrylate monomer units containing one or more substituted or unsubstituted aromatic or aliphatic rings and vinyl monomer units containing one or more substituted or unsubstituted aromatic or aliphatic rings; and A polar monomer unit containing one or more functional groups selected from the group consisting of carboxyl, sulfonic acid, phosphonic acid, cyano, pyrrolidone, amide, alkylamide, dialkylamide, hydroxyl, epoxy, caprolactam, morpholino, and oxazolidinone.

2. The copolymer according to claim 1, wherein the acrylate monomer unit containing a linear or branched aliphatic hydrocarbon having 5 to 22 carbon atoms is formed by polymerizing the following compounds: (meth)pentyl acrylate, (meth)hexyl acrylate, (meth)heptyl acrylate, (meth)octyl acrylate, (meth)2-ethylhexyl acrylate, (meth)nonyl acrylate, (meth)decyl acrylate, (meth)undecyl acrylate, (meth)lauryl acrylate, (meth)dodecyl acrylate, (meth)tridecyl acrylate, (meth)tetradecyl acrylate, (meth)pentadecanyl acrylate, (meth)cetyl acrylate, (meth)cetyl acrylate, (meth)hexadecyl acrylate, (meth)heptadecyl acrylate, (meth)stearyl acrylate, (meth) Nineteen acrylate, twenty acrylate, twenty-one acrylate, twenty-two acrylate, isoamyl acrylate, isoheptyl acrylate, isooctyl acrylate, isononyl acrylate, isodecyl acrylate, isoundecyl acrylate, isotridecyl acrylate, isotetradecyl acrylate, isodecyl acrylate, isoctyl acrylate, isocetyl acrylate, isohexadecyl acrylate, isoheptadecyl acrylate, isostearyl acrylate, isononadecanyl acrylate, isocetyl acrylate, isocetyl acrylate, or combinations thereof.

3. The copolymer according to claim 1, wherein the monomer unit selected from the group consisting of acrylate monomer units containing one or more substituted or unsubstituted aromatic or aliphatic rings and vinyl monomer units containing one or more substituted or unsubstituted aromatic or aliphatic rings is formed by polymerizing the following compounds: styrene, cyclopentyl acrylate, cyclohexyl acrylate, benzyl acrylate, benzyl methacrylate, phenyl acrylate, phenyl methacrylate, 3-phenoxybenzyl acrylate, σ-phenylphenoxyethyl acrylate, σ-phenylphenoxyethyl methacrylate, (1-pyrene)2-methyl-2-acrylate, 1-naphthyl acrylate, 1-naphthyl methacrylate, 2-naphthyl acrylate, 2-naphthyl methacrylate, 9-anthracene methyl acrylate, 9-anthracene methyl methacrylate, or combinations thereof.

4. The copolymer according to claim 1, wherein the polar monomer unit is formed by polymerizing the following compounds: acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, aconitic acid, vinylbenzoic acid, 2-acrylamido-2-methylpropanesulfonic acid, vinyl sulfonic acid, 4-styrene sulfonic acid, vinylphosphonic acid, acrylonitrile, vinylpyrrolidone, acrylamide, N-methylacrylamide, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, glycidyl methacrylate, or combinations thereof.

5. The copolymer according to claim 1, comprising, based on 100 mol% of the copolymer: Acrylate monomer units containing 5 to 22 carbon atoms of straight-chain or branched aliphatic hydrocarbons, comprising 5 to 70 mol% or more; The monomer units selected from the group consisting of acrylate monomer units containing one or more substituted or unsubstituted aromatic or aliphatic rings, and vinyl monomer units containing one or more substituted or unsubstituted aromatic or aliphatic rings, comprising 5 mol% to 70 mol%; and The polar monomer unit comprising 5 mol% to 50 mol% of the above.

6. The copolymer according to claim 1, which is represented by the following chemical formula 1, Chemical Formula 1 R1 to R 15 They may be the same or different from each other, each independently consisting of hydrogen, and a straight-chain or branched hydrocarbon group having 1 to 4 carbon atoms. R'1 is a straight-chain or branched aliphatic hydrocarbon group with 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 selected from one or more of the group consisting of cyano, pyrrolidone, amide, alkylamide, dialkylamide, hydroxy, epoxy, caprolactam, morpholino, and oxazolidinone. R'5 is selected from one or more groups consisting of carboxyl, sulfonic acid, and phosphonic acid groups. l + m + n + o + p = 1, 0.05 ≤ l ≤ 0.70, 0.05 ≤ m + n ≤ 0.70, and 0.05 ≤ o + p ≤ 0.

50. in, Either m or n can be 0, and o can be 0.

7. The copolymer according to claim 6, wherein R'1 comprises any one or more selected from the group consisting of n-pentyl, n-hexyl, n-heptyl, n-octyl, 2-ethylhexyl, n-nonyl, n-decyl, n-undecyl, lauryl, n-dodecyl, n-tridecyl, n-tetradecyl, n-pentadecayl, cetyl, n-hexadecyl, n-heptadecyl, stearyl, n-octadecyl, n-nonadecayl, n-undecayl, n-undecayl, n-undecayl, isopentyl, isoheptyl, isooctyl, isononyl, isodecayl, isoundecayl, iso-undecayl, iso-tetradecyl, iso-decyl, isocetyl, iso-heptadecyl, iso-stearyl, iso-octadecyl, iso-nonadecayl, iso-undecayl, iso-undecayl, and iso-undecayl.

8. The copolymer according to claim 6, wherein R'2 and R'3 are the same or different from each other, and each independently comprises one or more of the group consisting of substituted or unsubstituted cyclopentyl, cyclohexyl, benzyl, phenyl, phenoxy, naphthyl, anthraceneyl and pyrene.

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

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

11. The copolymer according to claim 6, wherein the monomer comprising R'5 is selected from one or more of the group consisting of acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, aconitic acid, vinylbenzoic acid, 2-acrylamido-2-methylpropanesulfonic acid, vinylsulfonic acid, 4-styrenesulfonic acid and vinylphosphonic acid.

12. The copolymer according to claim 1, wherein, The polar monomer unit combines with a metal cation. The q value calculated according to Equation 1 is between 1.5 mol% and 300 mol%. Formula 1 5*a / b mol%≤q≤100*a / b mol% In Equation 1, a represents the number of functional groups in the polar monomer unit that can be substituted with the metal cation, and b represents the number of positive charges of the metal cation. a and b are 1 to 3.

13. A dispersion comprising: The copolymer of any one of claims 1 to 12; Solvent; and Carbon nanotubes.

14. A positive electrode slurry composition comprising: The dispersion of claim 13; and Positive electrode active material.

15. A positive electrode comprising: Current collector; and A positive electrode active material layer is formed by coating the current collector with the positive electrode slurry composition of claim 14.

16. A secondary battery comprising the positive electrode as described in claim 15.

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