Conductive material dispersion and preparation method therefor

Abstract

Provided are a conductive material dispersion and a preparation method therefor, the conductive material dispersion comprising: a carbon-based conductive material; a first dispersant comprising a vinyl-based polymer containing an aromatic halogen atom; a second dispersant comprising a cationic compound including a thiazine structure; and a dispersion medium. Through the preparation of the conductive material dispersion comprising the first dispersant and the second dispersant together, the carbon-based conductive material is uniformly and effectively dispersed in the dispersion, so that the conductive material dispersion can exhibit a relatively low viscosity and show a small change in viscosity over time.

Description

Conductive material dispersion and method for manufacturing the same

[0001] The present application claims the benefit of priority based on Korean Patent Application No. 10-2024-0125403 filed September 13, 2024 and Korean Patent Application No. 10-2025-0129592 filed September 11, 2025, and includes all contents disclosed in the documents of said Korean patent applications as part of the specification.

[0002] The present invention relates to a conductive material dispersion and a method for preparing the same. Specifically, the invention relates to a conductive material dispersion comprising a first dispersant comprising a vinyl polymer containing halogen atoms and a second dispersant comprising a cationic compound containing a thiazine structure, and a method for preparing the same.

[0003] With the increasing technological development and demand for mobile devices, the demand for secondary batteries as an energy source is rapidly rising. Among these secondary batteries, lithium-ion batteries, which possess high energy density and voltage, long cycle life, and low self-discharge rates, have been commercialized and are widely used. Furthermore, active research is being conducted on methods to manufacture electrodes for such high-capacity lithium-ion batteries by improving electrode density to achieve higher energy density per unit volume.

[0004] Generally, high-density electrodes are formed by molding electrode active material particles with a size of several µm to tens of µm using a high-pressure press. During the molding process, the particles may be deformed and the space between the particles may be reduced, which can easily lead to a decrease in electrolyte permeability.

[0005] To solve the above problems, a conductive material having excellent electrical conductivity and strength is used during the manufacture of the electrode. Even when the conductive material is positioned between the electrode active materials and undergoes a molding process, it maintains the micropores between the active material particles, allowing the electrolyte to penetrate easily, and its excellent electrical conductivity can reduce resistance within the electrode.

[0006] Various materials can be used as the conductive material, and among them, the use of carbon black or carbon nanotubes is increasing. When the conductive material is introduced into the electrode slurry in powder form, the conductive material is not uniformly dispersed, which leads to a problem of reduced conductivity of the manufactured electrode. In particular, carbon nanotubes, which are a type of fine carbon fiber, are expected to be applied and commercialized in various fields due to their high conductivity, tensile strength, and heat resistance; however, due to their high specific surface area, they have low dispersibility and aggregation phenomena caused by strong van der Waals forces between them.

[0007] To solve these problems, various methods such as jets, mills, and high-pressure homogenizers are used to mix conductive materials and dispersants, and to increase the process time. However, these methods lead to problems such as increased process costs and longer process times. In addition, with such mechanical dispersion methods, a problem may occur where the conductive material aggregates as soon as the process is finished.

[0008] Accordingly, there is a need to develop a method capable of producing a dispersant with excellent dispersion effects and a conductive material dispersion with excellent dispersibility by improving the dispersibility of the conductive material, effectively reducing the viscosity of the dispersion, and suppressing the increase in viscosity over time.

[0009] [Prior Art Literature]

[0010] [Patent Literature]

[0011] (Patent Document 1) Japanese Patent Publication No. 2003-535185

[0012] The objective of the present invention is to provide a conductive material dispersion with improved dispersibility, comprising a carbon-based conductive material, a first dispersant comprising a vinyl-based polymer containing a halogen atom, a second dispersant comprising a cationic compound containing a thiazine structure, and a dispersion medium, wherein the viscosity of the dispersion and the decrease in viscosity increase over time are excellent.

[0013] Another objective of the present invention is to provide a method for manufacturing the conductive material dispersion.

[0014] The first aspect of the present invention provides a conductive material dispersion comprising a carbon-based conductive material, a first dispersant comprising a vinyl-based polymer comprising a halogen atom, a second dispersant comprising a cationic compound comprising a thiazine structure, and a dispersion medium.

[0015] In one embodiment of the present invention, the cationic compound is represented by any one of the following chemical formulas 1 and 2.

[0016] [Chemical Formula 1]

[0017]

[0018] [Chemical Formula 2]

[0019]

[0020] In the above chemical formulas 1 and 2, ring A and ring B are the same or different from each other and are each independently selected from the group consisting of a substituted or unsubstituted C6 to C20 aryl group and a substituted or unsubstituted C6 to C20 heteroaryl group; R1 and R2 are the same or different from each other and are each independently hydrogen; halogen; cyano group; sulfonate group; hydroxyl group; amine group; substituted or unsubstituted C1 to C10 alkyl group; substituted or unsubstituted C2 to C10 alkenyl group; substituted or unsubstituted C2 to C10 alkynyl group; substituted or unsubstituted C1 to C10 alkoxy group; substituted or unsubstituted C6 to C20 aryl group; substituted or unsubstituted C1 to C10 alkylamine group; substituted or unsubstituted C2 to C10 alkenylamine group; substituted or unsubstituted C2 to C10 alkynylamine group; and selected from the group consisting of substituted or unsubstituted C6 to C20 arylamine groups.

[0021] In one embodiment of the present invention, the cationic compound is represented by the following chemical formula 3.

[0022] [Chemical Formula 3]

[0023]

[0024] In the above chemical formula 3, R3 to R 10 The groups are the same or different from each other and are each independently selected from the group consisting of hydrogen; halogen; cyano group; sulfonate group; hydroxyl group; amine group; substituted or unsubstituted C1 to C10 alkyl group; substituted or unsubstituted C2 to C10 alkenyl group; substituted or unsubstituted C2 to C10 alkynyl group; substituted or unsubstituted C1 to C10 alkoxy group; substituted or unsubstituted C6 to C20 aryl group; substituted or unsubstituted C1 to C10 alkylamine group; substituted or unsubstituted C2 to C10 alkenylamine group; substituted or unsubstituted C2 to C10 alkynylamine group; and substituted or unsubstituted C6 to C20 arylamine group.

[0025] In one embodiment of the present invention, the compound represented by either of the formulas 1 and 2 comprises at least one amine group, wherein the amine group is substituted at a position where the positive charge located at the sulfur (S) atom in the structural formula representing the resonance structure of the compound can be located at the nitrogen atom of the amine group.

[0026] In one embodiment of the present invention, the content of the conductive material in the dispersion is 0.05 weight% to 5 weight% based on the total weight of the dispersion.

[0027] In one embodiment of the present invention, the content of the first dispersant in the dispersion is 80 to 450 parts by weight based on 100 parts by weight of the conductive material.

[0028] In one embodiment of the present invention, the content of the second dispersant in the dispersion is 10 to 150 parts by weight based on 100 parts by weight of the conductive material.

[0029] In one embodiment of the present invention, the content of the second dispersant in the dispersion is 10 to 90 parts by weight based on 100 parts by weight of the first dispersant.

[0030] In one embodiment of the present invention, the conductive material dispersion has an initial viscosity of 1 Pa·s to 12 Pa·s measured at 25°C and 1 rpm.

[0031] In one embodiment of the present invention, the conductive material dispersion has a viscosity increase rate of 0.1% to 18% as represented by the following formula (1).

[0032] [Equation 1]

[0033] Viscosity increase rate (%) = [ { P - Q} / Q} ] × 100.

[0034] Here, P is the viscosity (Pa·s) measured after leaving for one week at 25°C, and Q is the initial viscosity (Pa·s), and both P and Q are measured at 25°C and 1 rpm.

[0035] In one embodiment of the present invention, the conductive material comprises a material selected from the group consisting of carbon nanotubes, carbon black, and combinations thereof.

[0036] In one embodiment of the present invention, the vinyl polymer containing the halogen atom is selected from the group consisting of polyvinyl fluoride, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polytetrafluoroethylene, polyethylene tetrafluoroethylene, polychlorotrifluoroethylene, polyethylene chlorotrifluoroethylene, polyvinyl chloride, and combinations thereof.

[0037] In one embodiment of the present invention, the dispersion medium comprises a non-aqueous polar solvent.

[0038] A second aspect of the present invention provides a method for preparing a conductive material dispersion, comprising the steps of: (1) preparing a primary conductive material dispersion by mixing a carbon-based conductive material, a first dispersant, a second dispersant, and a dispersion medium; and (2) preparing a secondary conductive material dispersion by dispersing the primary conductive material dispersion.

[0039] In one embodiment of the present invention, step (2) includes a high-pressure dispersion process.

[0040] The conductive material dispersion according to the present invention comprises a first dispersant comprising a vinyl polymer containing halogen atoms and a second dispersant comprising a cationic compound having a thiazine structure, so that the carbon-based conductive material is uniformly and effectively dispersed within the conductive material dispersion, and the conductive material dispersion exhibits a relatively low viscosity and has the characteristic of having a small change in viscosity over time.

[0041] Furthermore, if the conductive material dispersion of the present invention is used in an electrode slurry composition, an electrode and a secondary battery having excellent capacity and cycle characteristics can be manufactured.

[0042] The present invention will be described in more detail below.

[0043] Prior to this, terms and words used in this specification and claims should not be interpreted as being limited to their ordinary or dictionary meanings, but should be interpreted in a meaning and concept consistent with the technical spirit of the invention, based on the principle that the inventor can appropriately define the concept of the terms to best describe his invention. Accordingly, the configurations described in the embodiments described in this specification are merely one preferred embodiment of the invention and do not represent all of the technical spirit of the invention; therefore, it should be understood that various equivalents and modifications capable of replacing them may exist at the time of filing this application.

[0044] In this specification, when a part is described as "comprising" a certain component, this means that, unless specifically stated otherwise, it does not exclude other components but may include additional components.

[0045] In this specification, the term "substitution" means that a hydrogen atom bonded to a carbon atom of a compound is replaced with another substituent, and the substitution site is not limited to the site where the hydrogen atom is substituted, that is, any site where a substituent can be substituted. In addition, when two or more substitutions occur, the two or more substituents may be identical or different from each other.

[0046] In this specification, "substituted or unsubstituted" means hydrogen; halogen; cyano group; sulfonate group; hydroxyl group; amine group; C1 to C10 straight-chain or branched-chain alkyl group; C2 to C10 straight-chain or branched-chain alkenyl group; C2 to C10 straight-chain or branched-chain alkynyl group; C3 to C10 monocyclic or polycyclic cycloalkyl group; C6 to C20 monocyclic or polycyclic aryl group; C2 to C20 monocyclic or polycyclic heteroaryl group; C2 to C10 monocyclic or polycyclic heterocycloalkyl group; and C1 to C10 alkylamine group; C2 to C10 alkenylamine group; C2 to C10 alkynylamine group; C6 to C20 monocyclic or polycyclic arylamine group; It means being substituted or unsubstituted with one or more substituents selected from the group consisting of C2 to C20 monocyclic or polycyclic heteroarylamine groups, or being substituted or unsubstituted with two or more substituents selected from the exemplified substituents connected to each other.

[0047] In this specification, "Cn1 to Cn2" means that the functional group has n1 to n2 carbon atoms.

[0048] In this specification, "alkyl" means a straight-chain or branched-chain saturated hydrocarbon containing one radical, and the one radical determines the bonding position as a functional group, and the bonding position is not particularly limited. Examples of the term "alkyl" include, but are not limited to, methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, t-butyl, n-pentyl, i-pentyl, and hexyl.

[0049] In this specification, "alkenyl" means a straight-chain or branched-chain hydrocarbon having one or more carbon-carbon double bonds and containing one radical, wherein the one radical determines the bonding site as a functional group, and the bonding site is not particularly limited. Examples of the term "alkenyl" include, but are not limited to, ethenyl and propenyl.

[0050] In this specification, "alkynyl" means a straight-chain or branched-chain hydrocarbon having one or more carbon-carbon triple bonds and containing one radical, wherein the one radical determines the bonding site as a functional group, and the bonding site is not particularly limited. Examples of the term "alkynyl" include, but are not limited to, ethinyl and propynyl.

[0051] In this specification, "halogen" means fluorine (F), chlorine (Cl), bromine (Br), or iodine (I).

[0052] In this specification, "aryl" means an aromatic cyclic hydrocarbon having one or more rings and containing one radical, wherein the one radical determines the bonding position as a functional group, and the bonding position is not particularly limited. Examples of the term "aryl" include phenyl and naphthyl, but are not necessarily limited thereto. As used in this specification, the term "aryl ring" is also used to distinguish aromatic cyclic hydrocarbons that do not contain a separate radical.

[0053] In this specification, "heteroaryl" refers to an aromatic cyclic hydrocarbon comprising one radical, having one or more rings, and having one or more heteroatoms within the rings, wherein the one radical determines the bonding position as a functional group, and the bonding position is not particularly limited. The heteroatoms are capable of forming a ring, and examples include O, N, S, etc. Examples of the term "heteroaryl" include, but are not necessarily limited to, pyrrolyl, furanyl, and pyrazinyl. As used in this specification, the term "heteroaryl ring" is also used to distinguish aromatic cyclic hydrocarbons having heteroatoms without containing separate radicals.

[0054] In this specification, "alkoxy" means a functional group of the -ORa type in which Ra is the alkyl described above. Examples of the term "alkoxy" include, but are not limited to, methoxy, difluoromethoxy, trifluoromethoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, and t-butoxy.

[0055] In this specification, "hydroxyl" means a functional group of the -OH form.

[0056] In this specification, "sulfonate" means a functional group of the -SO3H form.

[0057] In this specification, "cyano" means a functional group of the -CN form.

[0058] In this specification, "amine" means a functional group of the form including -NH2, -N(R)H, -N(R)2, -L-NH2, -LN(R)H, and -LN(R)2. Here, R may be alkyl, alkenyl, alkynyl, aryl, heteroaryl, etc., and L may be alkylene, alkenylene, alkynylene, etc.

[0059] In this specification, "%" means weight percent unless otherwise explicitly indicated.

[0060] In this specification, "specific surface area" is measured by the BET method (Brunauer-Emmett-Teller Analysis), and specifically, can be calculated from the amount of nitrogen gas adsorbed at liquid nitrogen temperature (77K) using BELSORP-mino II of BEL Japan.

[0061]

[0062] The present invention will be described in detail below.

[0063]

[0064] Dispersed conductive material

[0065] The conductive material dispersion according to the present invention comprises a carbon-based conductive material, a dispersant, and a dispersion medium.

[0066] The above conductive material dispersion may be a conductive material dispersion for forming an electrode, and specifically, may be a conductive material dispersion for forming an anode.

[0067] Hereinafter, each component of the conductive material dispersion of the present invention will be described in detail.

[0068]

[0069] (1) Carbon-based conductive material

[0070] In one embodiment of the present invention, the carbon-based conductive material comprises carbon nanotubes.

[0071] The above carbon nanotube is a secondary structure formed by assembling carbon nanotube units to form a bundle shape, either wholly or partially, wherein the carbon nanotube units have a graphite sheet having a cylindrical shape with a nano-sized diameter, and sp 2It has a bonded structure. At this time, depending on the angle and structure in which the graphite plane is rolled, it can exhibit conductive or semiconductor properties. The carbon nanotube monomers can be classified into single-walled carbon nanotubes (SWCNT), double-walled carbon nanotubes (DWCNT), and multi-walled carbon nanotubes (MWCNT) depending on the number of bonds forming the walls.

[0072] A carbon nanotube according to one embodiment of the present invention may include one or more of single-walled, double-walled, and multi-walled carbon nanotubes, but is not limited thereto, and specifically may include a single-walled carbon nanotube.

[0073] In one embodiment of the present invention, the average diameter of the carbon nanotube is 0.6 nm to 10 nm. Specifically, the average diameter is 0.8 nm or more, 0.9 nm or more, 1.0 nm or more, 1.1 nm or more, 1.2 nm or more, 1.3 nm or more, 1.4 nm or more, 1.5 nm or more, 1.6 nm or more, 1.7 nm or more, 1.8 nm or more, or 1.9 nm or more, and 3.0 nm or less, 2.9 nm or less, 2.8 nm or less, 2.7 nm or less, 2.6 nm or less, 2.5 nm or less, 2.4 nm or less, 2.3 nm or less, 2.2 nm or less, 2.1 nm or less, or 2.0 nm or less, and may be 0.6 nm to 10 nm, 0.8 nm to 5 nm, or 0.8 nm to 3 nm.

[0074] In one embodiment of the present invention, the carbon nanotube has an average length of 0.5 μm to 20 μm. Specifically, the average length may be 5 μm or more, 7 μm or more, 9 μm or more, 11 μm or more, or 13 μm or more, 20 μm or less, 18 μm or less, 16 μm or less, or 14 μm or less, and may be 0.5 μm to 20 μm, 1 μm to 20 μm, or 5 μm to 20 μm.

[0075] If the average diameter and average length of the carbon nanotubes satisfy the above ranges, it is effective for reducing the viscosity of the dispersion and improving storage stability, and excellent cycle characteristics can be achieved even when applied as an electrode active material. In this case, the average diameter of the carbon nanotubes can be measured by photographing the carbon nanotube powder with a scanning electron microscope, and the average length of the carbon nanotubes can be measured by photographing the carbon nanotube dispersion with a scanning electron microscope.

[0076] In one embodiment of the present invention, the BET specific surface area of ​​the carbon nanotube is 400 m² 2 It is greater than / g. Specifically, the above specific surface area is 400 m² 2 / g or more, 500 m 2 / g or more, 600 m 2 / g or more, 700 m 2 / g or more, 800 m 2 / g or more, 900 m 2 / g or more, 1,000 m 2 / g or more, 1,100 m 2 / g or more, 1,200 m 2 / g or more, 1,300 m 2 / g or more or 1,400 m 2 / g Lee Sang-ah, 2,000 m 2 / g or less, 1,900 m 2 / g or less, 1,800 m 2 / g or less, 1,700 m 2 / g or less, 1,600 m 2 / g or less or 1,500 m 2 / g or less, and 400 m 2 / g to 5,000 m 2 / g, 800 m 2 / g to 3,000 m 2 / g or 800 m 2 / g to 2,000 m 2 It can be / g. As described above, using carbon nanotubes with a high BET specific surface area allows for excellent formation of a conductive network between electrode active materials, thereby improving the cycle characteristics of the secondary battery.

[0077] In one embodiment of the present invention, the content of the conductive material in the dispersion is 0.05 wt% to 5 wt% based on the total weight of the dispersion. Specifically, the content of the conductive material is 0.05 wt% or more, 0.1 wt% or more, 0.2 wt% or more, 0.3 wt% or more, 0.4 wt% or more, 0.5 wt% or more, 0.6 wt% or more, 0.7 wt% or more, 0.8 wt% or more, 0.9 wt% or more, 1 wt% or more, 1.5 wt% or more, 2 wt% or more, or 2.5 wt% or more, 5 wt% or less, 4.5 wt% or less, 4 wt% or less, 3.5 wt% or less, or 3 wt% or less, and may be 0.05 wt% to 5 wt%, 0.2 wt% to 3 wt%, or 0.5 wt% to 2 wt%. When the content of the conductive material satisfies the above range, high productivity is maintained while the transfer and input of the electrode slurry are easy. In addition, since the solid content of the manufactured electrode slurry does not become excessively low, binder migration during electrode drying can be suppressed. Accordingly, electrode adhesion can be improved, and packing of the electrode active material layer can be effectively achieved, allowing for the manufacture of a low-thickness electrode.

[0078] In one embodiment of the present invention, the carbon-based conductive material comprises one or more selected from the group consisting of carbon nanotubes; carbon black; and combinations thereof.

[0079] A conductive material dispersion according to one embodiment of the present invention can have a relatively high conductive material content because the conductive material can be uniformly dispersed. When a conductive material dispersion with a low conductive material content is used in the manufacture of an electrode slurry, the solid content of the manufactured electrode slurry decreases, and the thickness (wetting thickness) before applying and drying the electrode slurry becomes thicker. Consequently, the rolling rate measured after subsequent drying and rolling processes increases, leading to a larger difference in the thickness ratio before and after drying and rolling. As such, if the rolling rate increases, the compositions inside the slurry, including the positive electrode active material, may be damaged during the process, and problems such as a decrease in battery performance may occur.

[0080]

[0081] (2) Dispersant

[0082] In one embodiment of the present invention, the conductive material dispersion comprises a first dispersant comprising a vinyl polymer containing a halogen atom as a dispersant and a second dispersant comprising a cationic compound having a thiazine structure as a dispersant to improve the dispersibility of the carbon-based conductive material.

[0083] The first and second dispersants mentioned above play a role in increasing the dispersibility of the carbon-based conductive material so that the carbon-based conductive material can be evenly dispersed without aggregating within the dispersion, and in particular, exhibit an effect of suppressing changes in the viscosity of the carbon nanotube dispersion over time.

[0084]

[0085] The first dispersant above may be included without limitation as long as it is a vinyl polymer containing halogen atoms that can be dissolved in the dispersion medium in the conductive material dispersion solution according to the present invention.

[0086] In one embodiment of the present invention, the vinyl polymer containing the halogen atom comprises being selected from the group consisting of polyvinyl fluoride, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polytetrafluoroethylene, polyethylene tetrafluoroethylene, polychlorotrifluoroethylene, polyethylene chlorotrifluoroethylene, polyvinyl chloride, and combinations thereof.

[0087] In one embodiment of the present invention, the content of the first dispersant in the dispersion is 80 to 450 parts by weight based on 100 parts by weight of the conductive material. Specifically, the content of the first dispersant may be 80 parts by weight or more, 100 parts by weight or more, 150 parts by weight or more, or 200 parts by weight or more, 450 parts by weight or less, 400 parts by weight or less, 350 parts by weight or less, 300 parts by weight or less, or 250 parts by weight or less, and may be 80 to 450 parts by weight, 80 to 300 parts by weight, or 100 to 200 parts by weight. When the content of the first dispersant satisfies the above range, the dispersibility of the solid in the dispersion is suitably maintained, and the viscosity of the dispersion can be formed at a low level.

[0088]

[0089] A conductive material dispersion according to one embodiment of the present invention includes a second dispersant comprising a cationic compound having a thiazine structure to solve the problem in which the viscosity of the dispersion increases as the conductive material content increases in a conductive material dispersion containing only the first dispersant. Accordingly, compared to a conventional conductive material dispersion using only the first dispersant, it has superior dispersibility, which can result in less clumping of particles in the slurry composition and a smaller sedimentation rate.

[0090] As the second dispersant comprises a cationic compound containing a thiazine structure, the second dispersant has a relatively low molecular weight and a small molecular size, which allows it to adsorb onto conductive materials that were not encapsulated by the first dispersant and exhibit an additional dispersion effect. The thiazine structure included in the cationic compound stably generates π-π interactions with the conductive material, particularly carbon nanotubes, in local regions, thereby sufficiently strengthening the bonding force between the dispersant and the conductive material. This reduces the content of excess dispersant that was not effectively adsorbed onto the surface of the conductive material, thereby preventing aggregation among the remaining dispersants. Furthermore, since the second dispersant contains a cationic compound, it forms electrostatic repulsion between ions within the dispersion, preventing aggregation between adjacent dispersants and enabling the 'conductive material-dispersant' combination to maintain a stable dispersed state within the dispersion.

[0091] In one embodiment of the present invention, the cationic compound comprises one to four thiazine structures within its molecular structure. Specifically, the thiazine structures may be one to four, one to three, one to two, or one. When the number of thiazine structures within the compound structure satisfies the above range, π-π interactions suitable for dispersion of conductive materials are formed, thereby reducing the viscosity of the dispersion and the increase in viscosity over time.

[0092] In one embodiment of the present invention, the cationic compound is monovalent to tetravalent cation. Specifically, the compound may be monovalent to tetravalent, monovalent to trivalent, monovalent to divalent, or monovalent cation. When the above range is satisfied, the second dispersant containing the compound can be evenly mixed in the dispersion, and the 'conductive material-dispersant' conjugate can be maintained in a stable dispersed state in the dispersion.

[0093] In one embodiment of the present invention, the content of the second dispersant in the dispersion is 10 to 150 parts by weight based on 100 parts by weight of the conductive material. Specifically, the content of the second dispersant is 10 parts by weight or more, 20 parts by weight or more, 30 parts by weight or more, 40 parts by weight or more, 50 parts by weight or more, 60 parts by weight or more, or 70 parts by weight or more, and 150 parts by weight or less, 140 parts by weight or less, 130 parts by weight or less, 120 parts by weight or less, 110 parts by weight or less, 100 parts by weight or less, 90 parts by weight or less, or 80 parts by weight or less, and may be 10 to 150 parts by weight, 30 to 120 parts by weight, or 30 to 100 parts by weight. When the content of the second dispersant satisfies the above range, interactions between the dispersant and the dispersion medium, and between the dispersion medium, the conductive material, and the dispersant are smoothly formed, thereby enabling an effective dispersion effect of the conductive material within the dispersion solution.

[0094] In one embodiment of the present invention, the content of the second dispersant in the dispersion is 10 to 90 parts by weight based on 100 parts by weight of the first dispersant. Specifically, the content of the second dispersant is 10 parts by weight or more, 20 parts by weight or more, 30 parts by weight or more, 40 parts by weight or more, or 50 parts by weight or more, 90 parts by weight or less, 80 parts by weight or less, 70 parts by weight or less, or 60 parts by weight or less, and may be 10 to 90 parts by weight, 10 to 80 parts by weight, or 30 to 80 parts by weight. When the content of the second dispersant satisfies the above range, the dispersant is uniformly dispersed in the dispersion, and the viscosity can be maintained at a constant level over time along with low viscosity.

[0095] In one embodiment of the present invention, the cationic compound comprising a thiazine structure of the second dispersant further comprises at least one amine group.

[0096]

[0097] In one embodiment of the present invention, the cationic compound is represented by any one of the following chemical formulas 1 and 2.

[0098] [Chemical Formula 1]

[0099]

[0100] [Chemical Formula 2]

[0101]

[0102] In the above chemical formulas 1 and 2, the A ring and the B ring are the same or different from each other and are each selected from the group consisting of a C6 to C20 aryl group that is independently substituted or unsubstituted and a C6 to C20 heteroaryl group that is substituted or unsubstituted.

[0103] In one embodiment of the present invention, the A ring and the B ring are the same or different from each other and are each selected from the group consisting of a C6 to C10 aryl group that is independently substituted or unsubstituted and a C6 to C10 heteroaryl group that is substituted or unsubstituted.

[0104] In one embodiment of the present invention, the A ring and the B ring are the same or different from each other and are each independently substituted or unsubstituted C6 to C10 aryl groups.

[0105] In one embodiment of the present invention, the A ring and the B ring are the same or different from each other and are each independently substituted or unsubstituted C6 aryl groups.

[0106] In the above chemical formulas 1 and 2, R1 and R2 are the same or different from each other and are each independently selected from the group consisting of hydrogen; halogen; cyano group; sulfonate group; hydroxyl group; amine group; substituted or unsubstituted C1 to C10 alkyl group; substituted or unsubstituted C2 to C10 alkenyl group; substituted or unsubstituted C2 to C10 alkynyl group; substituted or unsubstituted C1 to C10 alkoxy group; substituted or unsubstituted C6 to C20 aryl group; substituted or unsubstituted C1 to C10 alkylamine group; substituted or unsubstituted C2 to C10 alkenylamine group; substituted or unsubstituted C2 to C10 alkynylamine group; and substituted or unsubstituted C6 to C20 arylamine group.

[0107] In one embodiment of the present invention, R1 and R2 are the same or different from each other and are each independently selected from the group consisting of hydrogen; cyano group; hydroxyl group; amine group; substituted or unsubstituted C1 to C10 alkyl group; substituted or unsubstituted C2 to C10 alkenyl group; substituted or unsubstituted C2 to C10 alkynyl group; substituted or unsubstituted C6 to C20 aryl group; substituted or unsubstituted C1 to C10 alkylamine group; substituted or unsubstituted C2 to C10 alkenylamine group; substituted or unsubstituted C2 to C10 alkynylamine group; and substituted or unsubstituted C6 to C20 arylamine group.

[0108] In one embodiment of the present invention, R1 and R2 are the same or different from each other and are each independently selected from the group consisting of hydrogen; an amine group; a substituted or unsubstituted C1 to C10 alkyl group; a substituted or unsubstituted C2 to C10 alkenyl group; a substituted or unsubstituted C2 to C10 alkynyl group; a substituted or unsubstituted C6 to C10 aryl group; a substituted or unsubstituted C1 to C10 alkylamine group; a substituted or unsubstituted C2 to C10 alkenylamine group; a substituted or unsubstituted C2 to C10 alkynylamine group; and a substituted or unsubstituted C6 to C10 arylamine group.

[0109] In one embodiment of the present invention, R1 and R2 are the same or different from each other and are each independently selected from the group consisting of hydrogen; an amine group; a substituted or unsubstituted C1 to C10 alkyl group; and a substituted or unsubstituted C1 to C10 alkylamine group.

[0110] In one embodiment of the present invention, the compound represented by either of the formulas 1 and 2 comprises at least one amine group, wherein the amine group is substituted at a position where the positive charge located at the sulfur (S) atom in the structural formula representing the resonance structure of the compound can be located at the nitrogen atom of the amine group.

[0111] For example, the compound represented by chemical formula (A) corresponding to chemical formula 1 below can have its resonance structure expressed in addition to chemical formula (A) as well as in the structural formula of chemical formula (B), and the amine group represented in chemical formula (A) is substituted with a positive charge located on the sulfur (S) atom as in chemical formula (B) at a position where it can be located on the nitrogen atom of the amine group.

[0112]

[0113] Likewise, the compound represented by chemical formula (C) corresponding to chemical formula 1 below can have its resonance structure expressed by the structural formula of chemical formula (D) in addition to chemical formula (C), and the amine group represented in chemical formula (C) is substituted with a positive charge located on the sulfur (S) atom in chemical formula (D) at a position where it can be located on the nitrogen atom of the amine group.

[0114]

[0115] The above amine group is not limited to cases where a positive charge located on a sulfur (S) atom is substituted at a position where it can be located on a nitrogen atom of the amine group as described above, and may be an amine group substituted on a C1 to C10 alkyl group; a C2 to C10 alkenyl group; a C2 to C10 alkynyl group; or a C6 to C20 aryl group as in the above formula (A), or may be a substituted or unsubstituted C1 to C10 alkylamine group; a substituted or unsubstituted C2 to C10 alkenylamine group; a substituted or unsubstituted C2 to C10 alkynylamine group; or a substituted or unsubstituted C6 to C20 arylamine group as in the above formula (D).

[0116]

[0117] In one embodiment of the present invention, the cationic compound is represented by the following chemical formula 3.

[0118] [Chemical Formula 3]

[0119]

[0120] In the above chemical formula 3, R3 to R 10The groups are the same or different from each other and are each independently selected from the group consisting of hydrogen; halogen; cyano group; sulfonate group; hydroxyl group; amine group; substituted or unsubstituted C1 to C10 alkyl group; substituted or unsubstituted C2 to C10 alkenyl group; substituted or unsubstituted C2 to C10 alkynyl group; substituted or unsubstituted C1 to C10 alkoxy group; substituted or unsubstituted C6 to C20 aryl group; substituted or unsubstituted C1 to C10 alkylamine group; substituted or unsubstituted C2 to C10 alkenylamine group; substituted or unsubstituted C2 to C10 alkynylamine group; and substituted or unsubstituted C6 to C20 arylamine group.

[0121] In one embodiment of the present invention, the R3 to R 10 The groups are the same or different from each other and are each independently selected from the group consisting of hydrogen; cyano group; hydroxyl group; amine group; substituted or unsubstituted C1 to C10 alkyl group; substituted or unsubstituted C2 to C10 alkenyl group; substituted or unsubstituted C2 to C10 alkynyl group; substituted or unsubstituted C6 to C20 aryl group; substituted or unsubstituted C1 to C10 alkylamine group; substituted or unsubstituted C2 to C10 alkenylamine group; substituted or unsubstituted C2 to C10 alkynylamine group; and substituted or unsubstituted C6 to C20 arylamine group.

[0122] In one embodiment of the present invention, the R3 to R 10The groups are the same or different from each other and are each independently selected from the group consisting of hydrogen; an amine group; a substituted or unsubstituted C1 to C10 alkyl group; a substituted or unsubstituted C2 to C10 alkenyl group; a substituted or unsubstituted C2 to C10 alkynyl group; a substituted or unsubstituted C6 to C10 aryl group; a substituted or unsubstituted C1 to C10 alkylamine group; a substituted or unsubstituted C2 to C10 alkenylamine group; a substituted or unsubstituted C2 to C10 alkynylamine group; and a substituted or unsubstituted C6 to C10 arylamine group.

[0123] In one embodiment of the present invention, the R3 to R 10 The groups are the same or different from each other and are each independently selected from the group consisting of hydrogen; an amine group; a substituted or unsubstituted C1 to C10 alkyl group; and a substituted or unsubstituted C1 to C10 alkylamine group.

[0124] In one embodiment of the present invention, the compound represented by the chemical formula 3 comprises at least one amine group, wherein the amine group is substituted at a position where the positive charge located at the sulfur (S) atom in the structural formula representing the resonance structure of the compound can be located at the nitrogen atom of the amine group.

[0125] The above amine group is not limited to cases where a positive charge located on a sulfur (S) atom as described above is substituted at a position where it can be located on a nitrogen atom of the amine group, and may be an amine group substituted on a C1 to C10 alkyl group; a C2 to C10 alkenyl group; a C2 to C10 alkynyl group; or a C6 to C20 aryl group, or may be a substituted or unsubstituted C1 to C10 alkylamine group; a substituted or unsubstituted C2 to C10 alkenylamine group; a substituted or unsubstituted C2 to C10 alkynylamine group; or a substituted or unsubstituted C6 to C20 arylamine group.

[0126]

[0127] In one embodiment of the present invention, the cationic compound may be selected from the group consisting of, for example, basic blue 9, basic blue 17, basic blue 24, azure A, azure B, azure C, Janus green B, and combinations thereof, but is not limited thereto as long as it is a compound having cationic properties that includes a thiazine structure in its molecular structure and can improve the dispersibility of the conductive material.

[0128]

[0129] (3) Dispersion medium

[0130] The dispersion medium of the conductive material dispersion liquid according to one embodiment of the present invention is a dispersion medium for dispersing the carbon-based conductive material and the dispersant, and is used to supply the conductive material dispersion liquid by pre-dispersing it to prevent aggregation when the carbon-based conductive material in powder form is used directly in the preparation of the electrode slurry composition.

[0131] The above dispersion medium is capable of dissolving or dispersing the conductive material, the first dispersant, and the second dispersant to a certain level or higher.

[0132] In one embodiment of the present invention, the dispersion medium comprises a non-aqueous polar solvent.

[0133] In one embodiment of the present invention, the dispersion medium comprises a non-aqueous polar solvent containing nitrogen atoms.

[0134] In one embodiment of the present invention, the dispersion medium comprises a non-aqueous polar solvent selected from the group consisting of cyano groups, amine groups, and amide groups.

[0135] The above dispersion medium may be, for example, one or more selected from the group consisting of dimethylformamide (DMF), acetonitrile, dimethylacetamide (DMAc), N,N-dimethylpropionamide (DMPA), N-methylformamide (NMF), formamide, N,N-diethylformamide (DEF), 2-pyrrolidone, N-methyl2-pyrrolidone (NMP), N-ethyl-2-pyrrolidone (NEP), ε-caprolactam, benzonitrile, propionitrile, and butyronitrile, but is not limited thereto.

[0136] The above dispersion medium may be included in an amount such that the electrode slurry composition can have an appropriate viscosity, taking into account the coating properties of the electrode slurry composition subsequently manufactured using the above conductive material dispersion.

[0137]

[0138] (4) Conductive material dispersion

[0139] The present invention provides a conductive material dispersion.

[0140] In one embodiment of the present invention, the conductive material dispersion comprises the carbon-based conductive material, the dispersant, and the dispersion medium.

[0141] The conductive material dispersion of the present invention, comprising the above-mentioned components, has excellent dispersibility, resulting in low viscosity and suppression of viscosity increase over time.

[0142] In one embodiment of the present invention, the conductive material dispersion has an initial viscosity of 1 Pa·s to 12 Pa·s measured at 25°C and 1 rpm using a viscometer (TOKI SANGYO, viscometer TV-25, Rotor Code 01). Specifically, the viscosity is 1 Pa·s or more, 2 Pa·s or more, 3 Pa·s or more, 4 Pa·s or more, 5 Pa·s or more, 6 Pa·s or more, 6.5 Pa·s or more, 7 Pa·s or more, 8 Pa·s or more, or 9 Pa·s or more, 12 Pa·s or less, 11.5 Pa·s or less, 11 Pa·s or less, or 10 Pa·s or less, and may be 1 Pa·s to 12 Pa·s, 5 Pa·s to 12 Pa·s, or 6 Pa·s to 12 Pa·s. When the above viscosity satisfies the above range, the conductive material in the dispersion is evenly distributed, making it easy to use the dispersion when preparing an electrode slurry composition.

[0143] In one embodiment of the present invention, when the conductive material dispersion is left at 25°C for one week, the viscosity increase rate represented by the following formula (1) is 0.1% to 18%. Specifically, the viscosity increase rate is 0.1% or more, 0.5% or more, 1% or more, 2% or more, 3% or more, 4% or more, 5% or more, 6% or more, 7% or more, 8% or more, 9% or more, 10% or more, 11% or more, or 12% or more, and 18% or less, 17% or less, 16% or less, 15% or less, 14% or less, or 13% or less, and may be 0.1% to 18%, 3% to 18%, or 5% to 15%. When the viscosity increase rate satisfies the above range, the conductive material can maintain a stable dispersion state within the dispersion.

[0144] [Equation 1]

[0145] Viscosity increase rate (%) = [ { P - Q} / Q} ] × 100

[0146] Here, P is the viscosity (Pa·s) measured after leaving for one week at 25°C, and Q is the initial viscosity (Pa·s), and both P and Q are measured at 25°C and 1 rpm.

[0147]

[0148] Method for preparing a conductive material dispersion

[0149] The present invention provides a method for manufacturing a conductive material dispersion.

[0150] In one embodiment of the present invention, the manufacturing method is a method for manufacturing the conductive material dispersion described above.

[0151] In one embodiment of the present invention, the method for preparing the conductive material dispersion comprises: (1) a step of preparing a primary conductive material dispersion by mixing a carbon-based conductive material, a first dispersant, a second dispersant, and a dispersion medium; and (2) a step of preparing a secondary conductive material dispersion by dispersing the primary conductive material dispersion.

[0152] In step (1), a mixture is prepared by first mixing a first dispersant, a second dispersant, and a dispersion medium.

[0153] In step (1), a primary dispersion of conductive material is prepared by going through the step of mixing a conductive material into the above mixture.

[0154] In one embodiment of the present invention, mixing for preparing the primary dispersion of the conductive material can be performed using a conventional mixing method, specifically using a mixing device such as a Pony mixer, Change-can mixer, Hobert mixer, Planetary mixer, Butterfly mixer, Stone mill, Homogenizer, Beads mill, Ball mill, Basket mill, Attrition mill, Universal stirrer, Clear mixer, or TK mixer, and may include the step of mixing for 30 minutes to 7 hours at a rotational speed of 300 rpm to 10,000 rpm.

[0155] In one embodiment of the present invention, cavitation dispersion treatment may be performed to improve the miscibility of the carbon-based conductive material and the dispersion medium, or the dispersibility of the conductive material in the dispersion medium, when mixing to prepare the primary dispersion of the conductive material. The cavitation dispersion treatment is a dispersion treatment method that utilizes shock waves generated by the rupture of vacuum bubbles formed in water when high energy is applied to the liquid, and the conductive material can be dispersed without damaging its properties by this method. Specifically, the cavitation dispersion treatment may be performed by ultrasonic, jet mill, or shear dispersion treatment.

[0156] In one embodiment of the present invention, the step of preparing the primary dispersion of the conductive material may be performed under temperature conditions in which physical properties, such as the viscosity of the mixture, do not change due to the evaporation of the dispersion medium. For example, it may be performed at a temperature of 50°C or lower, more specifically at a temperature of 5°C to 50°C.

[0157] In step (2), the first dispersion of the conductive material is dispersed to produce a second dispersion of the conductive material.

[0158] In one embodiment of the present invention, the process of preparing the secondary dispersion of the conductive material may be carried out by a method such as a ball mill, a bead mill, a disc mill or a basket mill, or a high-pressure homogenizer. More specifically, it may be carried out by a dispersion method using a bead mill or a high-pressure homogenizer.

[0159] In one embodiment of the present invention, when milling by the disc mill or bead mill, the size of the bead can be appropriately determined according to the type and amount of carbon nanotubes and the type of dispersant. Specifically, the diameter of the bead may be 0.1 mm to 5 mm, more specifically 0.5 mm to 4 mm. In addition, the bead milling process may be performed at a speed of 1,000 rpm to 10,000 rpm, and more specifically at a speed of 2,000 rpm to 9,000 rpm.

[0160] Milling by the high-pressure homogenizer is achieved by pressurizing the mixture with, for example, the plunger pump of the high-pressure homogenizer and pushing it through the gap of the homogenizing valve, thereby utilizing forces such as cavitation, shear, impact, and explosion as it passes through the gap.

[0161] In one embodiment of the present invention, the dispersion process may be performed according to the degree of dispersion of the conductive material dispersion liquid. Specifically, it may be performed for 30 minutes to 120 minutes, more specifically 60 minutes to 90 minutes, under a pressure of 5,000 psi to 30,000 psi, and the process may be repeated 1 to 10 times.

[0162] In one embodiment of the present invention, step (2) includes a high-pressure dispersion process.

[0163] In one embodiment of the present invention, the conductive material dispersion refers to the conductive material secondary dispersion.

[0164]

[0165] Electrode slurry composition for lithium secondary batteries

[0166] The present invention also provides an electrode slurry composition for a secondary battery.

[0167] In one embodiment of the present invention, the electrode slurry composition for a secondary battery comprises the conductive material dispersion and the electrode active material.

[0168] In one embodiment of the present invention, the electrode slurry composition for a lithium secondary battery may be an anode slurry composition or a cathode slurry composition, and specifically may be an anode slurry composition.

[0169] In one embodiment of the present invention, the electrode slurry composition for a lithium secondary battery may include the conductive material dispersion, a positive electrode active material or a negative electrode active material as an electrode active material, a binder, and, if necessary, a solvent and / or other additives.

[0170] In one embodiment of the present invention, the cathode active material may be any cathode active material well known in the art without limitation, such as lithium cobalt-based oxide, lithium nickel-based oxide, lithium manganese-based oxide, lithium iron phosphate, lithium nickel manganese cobalt-based oxide, or combinations thereof. Specifically, the cathode active material may be LiCoO2, LiNiO2, LiMn2O4, LiCoPO4, LiFePO4, and LiNi a Mn b Co c O 2　 (Here, 0 < a, b, c < 1) etc. may be used, but are not limited thereto.

[0171] In one embodiment of the present invention, the negative electrode active material comprises natural graphite, artificial graphite, carbonaceous material; lithium-containing titanium composite oxide (LTO); metals (Me) which are Si, Sn, Li, Zn, Mg, Cd, Ce, Ni, or Fe; alloys composed of said metals (Me); and oxides (MeO) of said metals (Me). xExamples include one or more cathode active materials selected from the group consisting of the metal (Me) and a composite of carbon. The cathode active material may be included in an amount of 60% to 98% by weight, more preferably 70% to 98% by weight, based on the total weight of the solids excluding the solvent in the cathode slurry.

[0172] In one embodiment of the present invention, the binder is a component that assists in the bonding of the active material and the conductive material and the bonding to the current collector, and is typically added in an amount of 1% to 30% by weight based on the total weight of the mixture containing the electrode active material. Examples of such binders include polyvinylidene fluoride, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene-butadiene rubber, fluororubber, and various copolymers.

[0173] In one embodiment of the present invention, the solvent may be an organic solvent such as N-methylpyrrolidone (NMP), dimethylformamide (DMF), acetone, or dimethylacetamide, or water, and these solvents may be used alone or in a mixture of two or more. The amount of solvent used is sufficient if it is sufficient to dissolve and disperse the electrode active material, binder, and conductive material, taking into account the coating thickness of the slurry and the manufacturing yield.

[0174] In one embodiment of the present invention, the viscosity modifier may be carboxymethylcellulose or polyacrylic acid, and the viscosity of the electrode slurry may be controlled by adding it so that the preparation of the electrode slurry and the coating process on the electrode current collector are facilitated.

[0175] In one embodiment of the present invention, the filler is optionally used as a component that inhibits the expansion of the electrode, and is not particularly limited as long as it is a fibrous material that does not cause chemical changes in the battery, for example, olefin-based polymers such as polyethylene and polypropylene; and fibrous materials such as glass fibers and carbon fibers are used.

[0176] In one embodiment of the present invention, when the electrode slurry composition is a composition of an anode slurry for forming an anode, the anode may be manufactured by applying the anode slurry composition onto an anode current collector, followed by drying and rolling. Alternatively, the anode may be manufactured by casting the anode slurry onto a separate support and then laminating the film obtained by peeling off from the support onto the anode current collector.

[0177] In one embodiment of the present invention, the thickness of the anode active material layer formed by the anode slurry may vary depending on the loading amount, loading speed, etc., for applying the anode slurry.

[0178] In one embodiment of the present invention, the positive current collector has a thickness of 3 μm to 500 μm. Such a positive current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery. For example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. may be used. In addition, fine irregularities may be formed on the surface of the positive current collector to strengthen the bonding strength of the positive active material, and it may be used in various forms such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc.

[0179] In one embodiment of the present invention, when the electrode slurry composition is a composition of a cathode slurry for forming a cathode, the cathode can be manufactured by applying the composition of the cathode slurry onto a cathode current collector, followed by drying and rolling. Alternatively, the cathode can be manufactured by casting the cathode slurry onto a separate support and then laminating the film obtained by peeling off from the support onto the cathode current collector.

[0180] In one embodiment of the present invention, the thickness of the cathode active material layer formed by the cathode slurry may vary depending on the loading amount, loading speed, etc., for applying the cathode slurry.

[0181] In one embodiment of the present invention, the negative current collector has a thickness of 3 μm to 500 μm. Such a negative current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, and for example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface treated with carbon, nickel, titanium, silver, etc., or aluminum-cadmium alloy may be used. In addition, similar to the negative current collector, fine irregularities may be formed on the surface to strengthen the bonding strength of the negative active material, and it may be used in various forms such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc.

[0182]

[0183] lithium secondary battery

[0184] The present invention provides a lithium secondary battery.

[0185] In one embodiment of the present invention, a lithium secondary battery comprises the anode and cathode described above, a separator disposed between the anode and cathode, and an electrolyte. Since the anode and cathode are identical to those described above, a detailed description is omitted.

[0186] The above separator separates the negative electrode and the positive electrode and provides a pathway for the movement of lithium ions. It can be used without special restrictions as long as it is commonly used as a separator in a lithium secondary battery, and it is particularly desirable that it has low resistance to the movement of electrolyte ions and excellent electrolyte wettability. Specifically, a porous polymer film, such as a porous polymer film made of a polyolefin-based polymer like ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, and ethylene / methacrylate copolymer, or a laminated structure of two or more layers thereof may be used. In addition, a conventional porous nonwoven fabric, such as a nonwoven fabric made of high-melting-point glass fiber or polyethylene terephthalate fiber, may be used. Furthermore, a coated separator containing ceramic components or polymer materials may be used to ensure heat resistance or mechanical strength, and it may optionally be used in a single-layer or multi-layer structure.

[0187] In one embodiment of the present invention, the electrolyte may be an organic liquid electrolyte, an inorganic liquid electrolyte, a solid polymer electrolyte, a gel-type polymer electrolyte, a solid inorganic electrolyte, a molten inorganic electrolyte, etc., which are usable in the manufacture of a lithium secondary battery, but are not limited thereto. Specifically, the electrolyte may include an organic solvent and a lithium salt.

[0188] In one embodiment of the present invention, the organic solvent may be used without particular limitation as long as it can serve as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, the organic solvent may be an ester-based solvent such as methyl acetate, ethyl acetate, γ-butyrolactone, or ε-caprolactone; an ether-based solvent such as dibutyl ether or tetrahydrofuran; a ketone-based solvent such as cyclohexanone; or an aromatic hydrocarbon-based solvent such as benzene or fluorobenzene. Carbonate-based solvents such as dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC); alcohol-based solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (where R is a straight-chain, branched, or cyclic hydrocarbon group having C2 to C20 structures and may include a double bond, a directional ring, or an ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes may be used. Among these, a carbonate-based solvent is preferred, and a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate, etc.) having high ionic conductivity and high dielectric constant that can improve the charge / discharge performance of the battery, and a low-viscosity linear carbonate-based compound (e.g., ethylmethyl carbonate, dimethyl carbonate or diethyl carbonate, etc.) is more preferred.In this case, using a mixture of cyclic carbonate and chain carbonate in a volume ratio of about 1:1 to about 1:9 can result in excellent performance of the electrolyte.

[0189] In one embodiment of the present invention, the lithium salt can be used without special limitations as long as it is a compound capable of providing lithium ions used in a lithium secondary battery. Specifically, the lithium salt may be LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, or LiB(C2O4)2. It is preferable to use the lithium salt within the range of 0.1 M to 2.0 M. When the concentration of the lithium salt falls within the above range, the electrolyte has appropriate conductivity and viscosity, so it can exhibit excellent electrolyte performance and allow lithium ions to move effectively.

[0190] In one embodiment of the present invention, in addition to the electrolyte components, the electrolyte may further include one or more additives for the purpose of improving the lifespan characteristics of the battery, suppressing the decrease in battery capacity, and improving the discharge capacity of the battery, such as, for example, a haloalkylene carbonate-based compound such as difluoroethylene carbonate, pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylene diamine, n-glyme, triamide hexaphosphate, nitrobenzene derivative, sulfur, quinone imine dye, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxyethanol, or aluminum trichloride. In this case, the additive may be included in an amount of 0.1% to 5% by weight based on the total weight of the electrolyte.

[0191] In one embodiment of the present invention, a lithium secondary battery comprises an electrode manufactured using a conductive material dispersion according to the present invention, specifically a negative electrode manufactured using a conductive material dispersion. Since the conductive material is uniformly dispersed within the positive electrode, the content of the conductive material can be reduced, thereby enabling stable excellent discharge capacity and output characteristics. As a result, it can be usefully applied in fields such as portable devices like mobile phones, laptop computers, and digital cameras, and electric vehicles like hybrid electric vehicles (HEVs).

[0192] Accordingly, according to another embodiment of the present invention, the lithium secondary battery, the battery module including the lithium secondary battery as a unit cell, and the battery pack including the same may be provided.

[0193] The above battery module or battery pack can be used as a power source for one or more medium-to-large devices, including a power tool; an electric vehicle (EV), a hybrid electric vehicle, and a plug-in hybrid electric vehicle (PHEV); or a power storage system.

[0194] Specific embodiments of the present invention are presented below. However, the embodiments described below are merely for the purpose of specifically illustrating or explaining the present invention and do not limit the present invention. Furthermore, details not described herein can be sufficiently technically inferred by a person skilled in the art, so their description is omitted.

[0195]

[0196] Examples

[0197]

[0198] <Example 1>

[0199] (1) Preparation of primary dispersion of conductive material

[0200] A mixed solution of 496 g is prepared by mixing 6.0 g of polyvinylidene fluoride (PVdF) (Solvay, Solef 5130) as a first dispersant containing a vinyl polymer containing a halogen atom (1.2 wt% in the dispersion), 2.0 g of Basic Blue 9 (Sigma-Aldrich, 0.4 wt% in the dispersion) as a second dispersant containing a cationic compound containing a thiazine structure, and 488 g of N-methyl-2-pyrrolidone (NMP) (Daejeong Chemical Co., Ltd.) as a dispersion medium. This solution is then introduced into a dissolver (VMA-GETZMANN, Dispermat-CA) equipped with an impeller and a container, and mixed by stirring at 400 rpm for 10 minutes.

[0201] A conductive material with a specific surface area of ​​1,160 m² is used in the above mixture. 2 4.0 g of single-walled carbon nanotubes (SWCNT, manufactured by OCSiAl, TUBALL) with a weight of 0.8 wt% in the dispersion are additionally added and stirred at 8,000 rpm for 60 minutes to prepare a total of 500 g of primary dispersion of conductive material.

[0202] (2) Preparation of conductive material dispersion

[0203] The above primary dispersion of the conductive material was homogeneously dispersed 10 times at a pressure of 20,000 psi using a high-pressure disperser (Micronox, PICOMAX) to prepare a dispersion of the conductive material.

[0204]

[0205] <Example 2>

[0206] A conductive material dispersion was prepared in the same manner as in Example 1, except that polyvinylidene fluoride-hexafluoropropylene copolymer (PVdF-co-HFP) (Arkema, Ultraflex B) was mixed as the first dispersant.

[0207]

[0208] <Example 3>

[0209] A conductive material dispersion was prepared in the same manner as in Example 1, except that the second dispersant was mixed at 0.6 wt%.

[0210]

[0211] <Example 4>

[0212] A conductive material dispersion was prepared in the same manner as in Example 1, except that the first dispersant was mixed at 1.6% by weight.

[0213]

[0214] <Example 5>

[0215] A conductive material dispersion was prepared in the same manner as in Example 1, except that the second dispersant was mixed at 0.8 wt%.

[0216]

[0217] <Example 6>

[0218] A conductive material dispersion was prepared in the same manner as in Example 1, except that Basic Blue 17 (manufactured by Sigma-Aldrich) was used as the second dispersant.

[0219]

[0220] <Example 7>

[0221] A conductive material dispersion was prepared in the same manner as in Example 1, except that Azul A (Azure A, manufactured by Sigma-Aldrich) was used as the second dispersant.

[0222]

[0223] <Comparative Example 1>

[0224] A conductive material dispersion was prepared in the same manner as in Example 1, except that 0.6 wt% of the conductive material and 3 wt% of polyvinylidene fluoride-hexafluoropropylene copolymer (PVdF-co-HFP) was mixed as the first dispersant and the second dispersant was not added.

[0225]

[0226] <Comparative Example 2>

[0227] A conductive material dispersion was prepared in the same manner as Comparative Example 1, except that the first dispersant was mixed at 2% by weight and polyvinylpyrrolidone (PVP) was mixed at 1% by weight as the second dispersant.

[0228]

[0229] <Comparative Example 3>

[0230] A conductive material dispersion was prepared in the same manner as in Example 1, except that the first dispersant was mixed at 1.5 wt% and the second dispersant at 0.1 wt%.

[0231]

[0232] <Comparative Example 4>

[0233] A conductive material dispersion was prepared in the same manner as in Example 1, except that the first dispersant was mixed at 0.8 wt% and the second dispersant at 0.8 wt%.

[0234]

[0235] <Comparative Example 5>

[0236] A conductive material dispersion was prepared in the same manner as in Example 1, except that the first dispersant was not included, and the conductive material was mixed at 0.6 wt% and the second dispersant at 3 wt%.

[0237]

[0238] <Comparative Example 6>

[0239] A conductive material dispersion was prepared in the same manner as in Example 1, except that water was mixed as the dispersion medium.

[0240]

[0241] Experimental Example

[0242] The viscosity of the conductive material dispersion prepared according to the above examples and comparative examples was measured using a viscometer (TOKI SANGYO, viscometer TV-25, Rotor Code 01) to determine the initial viscosity at 25°C and 1 rpm. After leaving the above examples and comparative examples at 25°C for one week, the viscosity was measured again using the same method, and the initial viscosity and the viscosity after one week are shown in [Table 1] below.

[0243] The viscosity increase rate was calculated using the following equation (1).

[0244] [Equation 1]

[0245] Viscosity increase rate (%) = [ { P - Q} / Q} ] × 100.

[0246] Here, P is the viscosity (Pa·s) measured after leaving for one week at 25°C, and Q is the initial viscosity (Pa·s), and both P and Q are measured at 25°C and 1 rpm.

[0247]

[0248] Content of Second Dispersant (Based on 100 parts by weight of First Dispersant) Initial Viscosity (Pa·s) Viscosity After 1 Week (Pa·s) Viscosity Increase Rate (%) Example 1 339.4 10.8 15 Example 2 338.0 9.0 13 Example 3 508.7 9.5 9 Example 4 259.8 11.0 12 Example 5 678.8 9.9 13 Example 6 338.5 9.8 15 Example 7 339.1 10.4 14 Comparative Example 1 - 11.0 16.4 49 Comparative Example 2 5010.9 13.0 19 Comparative Example 3 6.7 12.8 16.7 30 Comparative Example 4 1001 3.3 17.1 29 Comparative Example 5 - 10.0 18.2 2 Comparative Example 633 Unmeasurable Unmeasurable-

[0249]

[0250] As shown in [Table 1] above, it can be confirmed that the dispersions of Examples 1 to 7, which include a first dispersant containing a vinyl polymer containing a halogen atom and a second dispersant containing a cationic compound containing a thiazine structure within the conductive material dispersion, exhibit low initial viscosity.

[0251] In particular, in the case of Comparative Example 1, which does not include the second dispersant; Comparative Example 2, which includes the second dispersant that does not include a cationic compound containing a thiazine structure; and Comparative Example 5, which does not include the first dispersant, the initial viscosity does not show a high value, but it can be confirmed that the viscosity increase of the dispersions of Examples 1 to 7 over time is very effectively suppressed through the fact that the viscosity increase rate of the dispersions increased compared to the dispersions of Examples 1 to 7.

[0252] In addition, in the case of the dispersions of Comparative Examples 3 and 4, which include a first dispersant containing a vinyl polymer containing halogen atoms and a second dispersant containing a cationic compound containing a thiazine structure within the conductive material dispersion, but in which the content of the second dispersant deviates from the range of 10 to 90 parts by weight relative to 100 parts by weight of the first dispersant, it can be confirmed that they exhibit higher initial viscosity and viscosity increase rates compared to the dispersions of Examples 1 to 7, in which the weight ratio satisfies the range of 10 to 90 parts by weight.

[0253] In the case of Comparative Example 6, which used an aqueous solvent, the dispersion exhibited a viscosity that was unsuitable for use in slurries, etc., to the extent that it was impossible to measure.

[0254] Therefore, it can be seen that the conductive material can be effectively dispersed by including a first dispersant containing a vinyl polymer containing halogen atoms and a second dispersant containing a cationic compound containing a thiazine structure in the dispersion so that the dispersion exhibits a low initial viscosity and the increase in viscosity over time can be suppressed, and that the above effects can be further improved when the content of the second dispersant satisfies the range of 10 to 90 parts by weight relative to 100 parts by weight of the first dispersant. In addition, it can be seen that the above dispersion effect can be effectively exhibited when a non-aqueous solvent is mixed as the dispersion medium.

[0255]

[0256] Although preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements by those skilled in the art using the basic concept of the present invention as defined in the following claims also fall within the scope of the present invention.

Claims

1. Carbon-based conductive material; A first dispersant comprising a vinyl polymer containing halogen atoms; A second dispersant comprising a cationic compound having a thiazine structure; and including a dispersion medium, Dispersed challenge material.

2. In Claim 1, The above-mentioned cationic compound is represented by either one of the following chemical formulas 1 and 2, Conductive material dispersion: [Chemical Formula 1] [Chemical Formula 2] In the above chemical formulas 1 and 2, Ring A and ring B are the same or different from each other and are each selected from the group consisting of independently substituted or unsubstituted C6 to C20 aryl groups and substituted or unsubstituted C6 to C20 heteroaryl groups, and R1 and R2 are the same or different from each other and are each independently selected from the group consisting of hydrogen; halogen; cyano group; sulfonate group; hydroxyl group; amine group; substituted or unsubstituted C1 to C10 alkyl group; substituted or unsubstituted C2 to C10 alkenyl group; substituted or unsubstituted C2 to C10 alkynyl group; substituted or unsubstituted C1 to C10 alkoxy group; substituted or unsubstituted C6 to C20 aryl group; substituted or unsubstituted C1 to C10 alkylamine group; substituted or unsubstituted C2 to C10 alkenylamine group; substituted or unsubstituted C2 to C10 alkynylamine group; and substituted or unsubstituted C6 to C20 arylamine group.

3. In Claim 1, The above cationic compound is represented by the following chemical formula 3, Conductive material dispersion: [Chemical Formula 3] In the above chemical formula 3, R3 to R 10 The groups are the same or different from each other and are each independently selected from the group consisting of hydrogen; halogen; cyano group; sulfonate group; hydroxyl group; amine group; substituted or unsubstituted C1 to C10 alkyl group; substituted or unsubstituted C2 to C10 alkenyl group; substituted or unsubstituted C2 to C10 alkynyl group; substituted or unsubstituted C1 to C10 alkoxy group; substituted or unsubstituted C6 to C20 aryl group; substituted or unsubstituted C1 to C10 alkylamine group; substituted or unsubstituted C2 to C10 alkenylamine group; substituted or unsubstituted C2 to C10 alkynylamine group; and substituted or unsubstituted C6 to C20 arylamine group.

4. In Claim 2, The compound represented by either of the above chemical formulas 1 and 2 comprises at least one amine group, and The above amine group is such that, in the structural formula representing the resonance structure of the compound, the positive charge located on the sulfur (S) atom is substituted at a position where it can be located on the nitrogen atom of the amine group. Dispersed challenge material.

5. In Claim 1, The conductive material content in the dispersion is 0.05% to 5% by weight based on the total weight of the dispersion. Dispersed challenge material.

6. In Claim 1, The content of the first dispersant in the dispersion is 80 to 450 parts by weight based on 100 parts by weight of the conductive material, Dispersed challenge material.

7. In Claim 1, The content of the second dispersant in the dispersion is 10 to 150 parts by weight based on 100 parts by weight of the conductive material. Dispersed challenge material.

8. In Claim 1, The content of the second dispersant in the dispersion is 10 to 90 parts by weight based on 100 parts by weight of the first dispersant, Dispersed challenge material.

9. In Claim 1, The above conductive material dispersion has an initial viscosity of 1 Pa·s to 12 Pa·s measured at 25℃ and 1 rpm, Dispersed challenge material.

10. In Claim 1, The above conductive material dispersion has a viscosity increase rate of 0.1% to 18% as represented by the following formula (1), Dispersed challenge material. [Equation 1] Viscosity increase rate (%) = [ { P - Q} / Q} ] × 100 (Here, P is the viscosity (Pa·s) measured after standing at 25°C for one week, and Q is the initial viscosity (Pa·s); both P and Q were measured at 25°C and 1 rpm.) 11. In Claim 1, The above conductive material comprises a material selected from the group consisting of carbon nanotubes, carbon black, and combinations thereof. Dispersed challenge material.

12. In Claim 1, The vinyl polymer containing the halogen atom is selected from the group consisting of polyvinyl fluoride, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polytetrafluoroethylene, polyethylene tetrafluoroethylene, polychlorotrifluoroethylene, polyethylene chlorotrifluoroethylene, polyvinyl chloride, and combinations thereof. Dispersed challenge material.

13. In Claim 1, The above dispersion medium comprises a non-aqueous polar solvent, Dispersed challenge material.

14. A method for manufacturing a conductive material dispersion, (1) A step of preparing a primary dispersion of a conductive material by mixing a carbon-based conductive material, a first dispersant, a second dispersant, and a dispersion medium; and (2) A step of preparing a secondary dispersion of conductive material by dispersing the primary dispersion of conductive material; A method for manufacturing a conductive material dispersion according to claim 1, comprising 15. In Claim 14, The above (2) step includes a high-pressure dispersion process, Method for preparing a conductive material dispersion.

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