Conductor dispersion solution and method for manufacturing the same

Abstract

Provided are a conductor dispersion solution including a carbon-based conductor, a first dispersant including a vinyl-based polymer containing a nitrogen atom, a second dispersant including a primary component and an auxiliary component, and a dispersion medium, and a method for manufacturing the same. The primary component includes a cellulose-based polymer, the auxiliary component includes at least one of a lactone-based polymer and a glycol-based polymer, and by manufacturing a conductor dispersion solution simultaneously including the first dispersant and the second dispersant, a particle size reduction of dispersed particles in the dispersion solution and a viscosity reduction of the dispersion solution are induced, so that the carbon-based conductor can have a characteristic of being uniformly and effectively dispersed in the dispersion solution.

Description

Technical Field

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2024-0133644, filed on October 2, 2024, and Korean Patent Application No. 10-2025-0139581, filed on September 26, 2025, and all disclosures in the documents of the said Korean patent applications are incorporated herein by reference.

[0002] This invention relates to a conductor dispersion solution and a method for manufacturing the same. Specifically, the invention relates to a conductor dispersion solution comprising a carbon-based conductor, a first dispersant comprising a vinyl-based polymer containing nitrogen atoms, a second dispersant comprising a main component and auxiliary components, and a dispersion medium, wherein the main component comprises a cellulose-based polymer, and the auxiliary components comprise at least one of a lactone-based polymer and a diol-based polymer. Background Technology

[0003] With technological advancements and increasing demand for mobile devices, the need for secondary batteries as an energy source is rapidly growing. Among these secondary batteries, lithium-ion batteries, characterized by high energy density and voltage, long cycle life, and low self-discharge rate, have been commercialized and are widely used. Furthermore, as electrodes for such high-capacity lithium-ion batteries, methods are being actively researched to manufacture electrodes with higher energy density per unit volume by improving electrode density.

[0004] Typically, 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 deform and the space between the particles may decrease, which may make the electrolyte permeability deteriorate easily.

[0005] To address these issues, conductors with excellent conductivity and strength are used in the manufacture of the electrodes. These conductors are positioned between the electrode active materials and maintain the micropores between the active material particles even during the molding process, allowing for easy electrolyte permeation and providing excellent conductivity to reduce resistance within the electrode.

[0006] Various materials can be used as conductors, and the use of carbon black or carbon nanotubes is increasing. When conductors are added to electrode slurries in powder form, there is a problem of degraded conductivity of the manufactured electrode due to uneven dispersion of the conductors. Therefore, a method is being used to prepare a conductor dispersion solution by mixing the conductor with a dispersant and a dispersion medium, and then applying the conductor dispersion solution to the electrode slurry composition. PVP or hydrogenated nitrile butadiene rubber (HNBR) is mainly used as a dispersant.

[0007] However, a problem with conductor dispersions using only PVP or hydrogenated nitrile rubber is the inability to significantly reduce the particle size of the dispersed particles. When the particle size cannot be reduced, the viscosity increases rapidly with increasing conductor content, thus limiting the potential for increasing conductor content and consequently restricting improvements in the productivity of the conductor dispersion. Specifically, when the conductor content cannot be increased, it is difficult to increase the solids content of the cathode slurry, potentially leading to deterioration in processability during manufacturing. Furthermore, the cathode active material layer may form unevenly during the drying process when manufacturing the active material layer.

[0008] To address these issues, methods are being used to mix the conductor and dispersant using various techniques such as jetting, milling, and high-pressure homogenizers, thus increasing process time. However, this approach leads to increased process costs and time. Furthermore, in the case of such mechanical dispersion methods, a potential problem is that the conductor may aggregate once the process is complete. Additionally, even with changes to process conditions as described above, there are limitations on reducing the particle size of the dispersed particles when using only PVP or hydrogenated nitrile rubber conductor dispersion solutions.

[0009] Therefore, there is a need to develop dispersants with excellent dispersing effects, and methods to produce conductor dispersions with excellent dispersibility even when the conductor content increases by reducing the particle size of the dispersed particles and the viscosity of the dispersion solution.

[0010] [Existing Technical Documents]

[0011] [Patent Literature]

[0012] (Patent Document 1) Korean Patent Publication No. 2024-0115753 Summary of the Invention

[0013] Technical issues

[0014] One object of the present invention is to provide a conductor dispersion solution comprising a carbon-based conductor, a first dispersant comprising a vinyl-based polymer containing nitrogen atoms, a second dispersant comprising a major component and an auxiliary component, and a dispersion medium, wherein the major component comprises a cellulose-based polymer, and the auxiliary component comprises at least one of a lactone-based polymer and a diol-based polymer, the conductor dispersion solution being excellent in reducing the particle size of the dispersed particles and the viscosity of the dispersion solution, thereby having improved dispersibility.

[0015] Another object of the present invention is to provide a method for manufacturing a conductor dispersion solution.

[0016] Technical solution

[0017] A first aspect of the invention provides a conductor dispersion solution comprising: a carbon-based conductor, a first dispersant comprising a vinyl-based polymer containing nitrogen atoms, a second dispersant comprising a major component and an auxiliary component, and a dispersion medium, wherein the major component comprises a cellulose-based polymer, and the auxiliary component comprises at least one of a lactone-based polymer and a diol-based polymer.

[0018] In one embodiment of the invention, the auxiliary component comprises both a lactone-based polymer and a diol-based polymer.

[0019] In one embodiment of the invention, the second dispersant further comprises a branched aliphatic hydrocarbon containing at least one amine group and at least one hydroxyl group.

[0020] In one embodiment of the invention, based on 100 parts by weight of the conductor, the content of the first dispersant in the dispersion solution is 5 to 60 parts by weight.

[0021] In one embodiment of the invention, based on 100 parts by weight of the conductor, the content of the second dispersant in the dispersion solution is from 1 part by weight to 20 parts by weight.

[0022] In one embodiment of the invention, based on 100 parts by weight of the first dispersant, the content of the second dispersant in the dispersion solution is 10 to 40 parts by weight.

[0023] In one embodiment of the invention, the total molar ratio of cellulose-based polymer repeating units to the total molar ratio of lactone-based polymer repeating units in the second dispersant is 2:1 to 10:1, and the total molar ratio of cellulose-based polymer repeating units to the total molar ratio of diol-based polymer repeating units in the second dispersant is 2:1 to 10:1.

[0024] In one embodiment of the invention, the dispersion solution further comprises a third dispersant, said third dispersant comprising a linear aliphatic hydrocarbon containing at least one amine group and at least one hydroxyl group.

[0025] In one embodiment of the invention, based on 100 parts by weight of the conductor, the content of the third dispersant in the dispersion solution is from 1 part by weight to 60 parts by weight.

[0026] In one embodiment of the invention, based on 100 parts by weight of the first dispersant, the content of the third dispersant in the dispersion solution is from 5 parts by weight to 200 parts by weight.

[0027] In one embodiment of the invention, the span value of the particles dispersed in the conductor dispersion solution is represented by the following [Formula 1], which is 0.5 to 3.

[0028] [Formula 1]

[0029] Span = [(D 90 -D 10 )] / D 50

[0030] (Here, D) 90 D corresponds to the particle size that represents 90% of the volumetric cumulative distribution of particles dispersed in the dispersion solution. 50 For the particle size corresponding to 50% of the volumetric cumulative distribution of particles dispersed in the dispersion solution, and D 10 (This refers to the particle size that corresponds to 10% of the volumetric cumulative distribution of particles dispersed in the dispersion solution.)

[0031] In one embodiment of the invention, the dispersion medium comprises a non-aqueous polar solvent containing nitrogen atoms.

[0032] In one embodiment of the invention, the carbon-based conductor includes at least one selected from carbon nanotubes, carbon black, and combinations thereof.

[0033] A second aspect of the invention provides a method for manufacturing a conductor dispersion solution, the method comprising: (1) mixing a carbon-based conductor, a first dispersant, a second dispersant and a dispersion medium to manufacture a primary conductor dispersion solution; and (2) dispersing the primary conductor dispersion solution to manufacture a secondary conductor dispersion solution.

[0034] In one embodiment of the present invention, step (2) includes a high-pressure dispersion process.

[0035] Beneficial effects

[0036] The conductor dispersion solution according to the invention comprises: a first dispersant comprising a vinyl-based polymer containing nitrogen atoms, a second dispersant comprising a main component and an auxiliary component, and a dispersion medium, wherein the main component comprises a cellulose-based polymer, and the auxiliary component comprises at least one of a lactone-based polymer and a diol-based polymer, thereby the conductor dispersion solution having the characteristics of small particle size of dispersed particles, low viscosity of the dispersion solution, and uniform and effective dispersion of carbon-based conductors in the conductor dispersion solution.

[0037] Furthermore, when the conductor dispersion solution of the present invention is used in an electrode slurry composition, electrodes and secondary batteries with excellent capacity and cycle characteristics can be manufactured. Detailed Implementation

[0038] The invention will be described in more detail below.

[0039] Prior to this, the terms or words used in this specification and claims should not be construed as limited to their conventional or dictionary meanings, but rather should be interpreted based on the principle that the inventor can appropriately define the concepts of the terms to best describe his or her invention, in a meaning and concept consistent with the technical spirit of the invention. Therefore, the constructions described in the embodiments described in this specification are merely the most preferred embodiments of the invention and do not represent the full technical spirit of the invention. It should be understood that various equivalents and modifications may exist at the time of this application.

[0040] In this specification, unless otherwise stated, when a part “includes” a component, it means that the part may also include other components without excluding other components.

[0041] In this specification, unless otherwise expressly stated, “%” means weight.

[0042] In this specification, "D" 10 “D” 50 "and "D 90 "These refer to particle sizes corresponding to 10%, 50%, and 90% of the cumulative volume, respectively." 10 D 50 and D 90 Laser diffraction, for example, can be used for measurement. Laser diffraction typically enables the measurement of particle sizes from submicron to several millimeters, and can yield results with high reproducibility and high resolution.

[0043] In this specification, "specific surface area" is measured by the BET method (Brunauer-Emmett-Teller analysis), and specifically, it can be calculated using the amount of nitrogen adsorbed at liquid nitrogen temperature (77 K) using the BELSORP-mino II manufactured by BEL Japan.

[0044] The present invention will be described in detail below.

[0045] Conductor dispersion solution

[0046] The conductor dispersion solution according to the present invention comprises a carbon-based conductor, a dispersant, and a dispersion medium.

[0047] The conductor dispersion solution can be a conductor dispersion solution for electrode formation, and specifically, it can be a conductor dispersion solution for positive electrode formation.

[0048] The components of the conductor dispersion solution of the present invention will be described in detail below.

[0049] (1) Carbon-based conductors

[0050] According to one embodiment of the invention, the carbon-based conductor of the conductor dispersion solution is a material with excellent conductivity, and when the conductor dispersion solution is used as a component of an electrode slurry, it is used to impart conductivity to the electrode slurry.

[0051] In one embodiment of the invention, the carbon-based conductor includes at least one selected from carbon nanotubes, carbon black, and combinations thereof.

[0052] Carbon nanotubes are secondary structures formed by aggregating all or part of carbon nanotube units to form bundles. These units have a nanometer-sized diameter, resembling a cylindrical graphite sheet, and possess sp... 2 Bonded structure. At this point, depending on the angle and structure of the rolled-up graphite sheets, carbon nanotubes can exhibit conductor or semiconductor properties. Based on the number of bonds forming the walls, carbon nanotube units can be classified into single-walled carbon nanotubes (SWCNTs), double-walled carbon nanotubes (DWCNTs), and multi-walled carbon nanotubes (MWCNTs).

[0053] The carbon nanotubes according to one embodiment of the present invention may include at least one of single-walled carbon nanotubes, double-walled carbon nanotubes and multi-walled carbon nanotubes, but are not limited thereto, and may specifically include multi-walled carbon nanotubes.

[0054] In one embodiment of the invention, the carbon nanotube content in the conductor dispersion solution is from 0.5 wt% to 10 wt%. Specifically, the carbon nanotube content is 0.5 wt% or more, 1 wt% or more, 1.5 wt% or more, 2 wt% or more, 2.5 wt% or more, 3 wt% or more, 3.5 wt% or more, 4 wt% or more, or 4.5 wt% or more, and 10 wt% or less, 9.5 wt% or less, 9 wt% or less, 8.5 wt% or less, 8 wt% or less, 7.5 wt% or less, 7 wt% or less, 6.5 wt% or less, 6 wt% or less, 5.5 wt% or less, or 5 wt% or less, and can be from 0.5 wt% to 10 wt%, 2 wt% to 8 wt%, or 3 wt% to 7 wt%. When the carbon nanotube content meets the above ranges, high productivity is maintained, and the transfer and input of the electrode slurry are easy. Furthermore, since the solids content of the electrode slurry to be manufactured does not become too low, binder migration during electrode drying can be suppressed. Therefore, electrode adhesion can be improved, and the loading of the electrode active material layer can be effectively performed, enabling the manufacture of electrodes with low thickness.

[0055] (2) Dispersant

[0056] In one embodiment of the invention, the conductor dispersion solution simultaneously comprises a first dispersant and a second dispersant as dispersants for improving the dispersibility of the carbon-based conductor. The first dispersant comprises a vinyl-based polymer containing nitrogen atoms, and the second dispersant comprises a major component and an auxiliary component.

[0057] The first and second dispersants are used to increase the dispersibility of the carbon-based conductors, so that the carbon-based conductors can be uniformly dispersed without agglomerating in the dispersion solution, and in particular, they exhibit the effect of reducing the particle size of the dispersed particles and the viscosity of the dispersion solution.

[0058] The first dispersant is a vinyl-based polymer containing nitrogen atoms, and may be included without limitation, as long as it is soluble in the dispersion medium of the conductor dispersion solution according to the invention.

[0059] In one embodiment of the invention, the nitrogen-containing vinyl-based polymer comprises one selected from: polyvinylpyrrolidone, polyacrylamide hydrazide, poly-N-vinyl-5-methyl Zolpidemone, N-alkyl polyimide, N-acetyl polyimide, polyacrylamide, poly-L-lysine hydrobromide, benzyl-dodecyl-dimethylammonium chloride, polyethyleneimine, and combinations thereof.

[0060] In one embodiment of the invention, based on 100 parts by weight of the conductor, the content of the first dispersant in the dispersion solution is from 5 parts by weight to 60 parts by weight. Specifically, the content of the first dispersant is 5 parts by weight or more, 10 parts by weight or more, 15 parts by weight or more, 20 parts by weight or more, or 25 parts by weight or more, and 60 parts by weight or less, 55 parts by weight or less, 50 parts by weight or less, 45 parts by weight or less, 40 parts by weight or less, 35 parts by weight or less, or 30 parts by weight or less, and can be from 5 parts by weight to 60 parts by weight, 10 parts by weight to 50 parts by weight, or 20 parts by weight to 40 parts by weight. When the content of the first dispersant meets the above ranges, the dispersibility of the solids in the dispersion solution can be appropriately maintained, so that the viscosity of the dispersion solution can be formed to be low.

[0061] According to one embodiment of the invention, the conductor dispersion solution contains a second dispersant that simultaneously contains a major component and an auxiliary component, in order to solve the problem that the viscosity of the dispersion solution increases with increasing conductor content in conductor dispersion solutions containing only a first dispersant. Therefore, compared with conventional conductor dispersion solutions using only a first dispersant, it can exhibit the effect of less agglomeration and lower settling rate of particles in the slurry composition due to its superior dispersibility.

[0062] The main component comprises a cellulose-based polymer, and the auxiliary components comprise at least one of a lactone-based polymer and a diol-based polymer.

[0063] Cellulose-based polymers refer to cellulose-based polymers including cellulose and cellulose derivatives such as cellulose acetate; lactone-based polymers refer to polymers polymerized via a ring-opening reaction of lactones; and diol-based polymers refer to polymers polymerized via a condensation reaction of diols.

[0064] Since the second dispersant contains a cellulose-based polymer as its main component, it can interact with the carbon-based conductor through van der Waals forces or π-π interactions, and can be adsorbed onto the conductor not covered by the first dispersant to exhibit additional dispersing effects. Furthermore, the large surface area and fibrous structure of the cellulose-based polymer allow for physical interactions with the conductor, ensuring sufficient binding force between the dispersant and the conductor. This reduces the amount of excess dispersant not effectively adsorbed onto the conductor surface, preventing aggregation of residual dispersant.

[0065] Furthermore, since the second dispersant contains at least one of a lactone-based polymer and a diol-based polymer as an auxiliary component, the second dispersant can bind to the conductor through interactions similar to those of cellulose-based polymers, and appropriate interactions can be formed between the second dispersants to prevent aggregation between the dispersants, thereby allowing the "conductor-dispersant" complex to remain stably dispersed in the dispersion solution.

[0066] In one embodiment of the invention, based on 100 parts by weight of the conductor, the content of the second dispersant in the dispersion solution is from 1 part by weight to 20 parts by weight. Specifically, the content of the second dispersant is 1 part by weight or more, 3 parts by weight or more, or 5 parts by weight or more, and 20 parts by weight or less, 15 parts by weight or less, 13 parts by weight or less, 10 parts by weight or less, or 7 parts by weight or less, and can be from 1 part by weight to 20 parts by weight, 3 parts by weight to 15 parts by weight, or 3 parts by weight to 10 parts by weight. When the content of the second dispersant meets the above ranges, the interactions between the dispersant and the dispersion medium, between the dispersion medium and the conductor, and between the dispersants can be smoothly formed to exhibit an effective dispersion effect of the conductor in the dispersion solution.

[0067] In one embodiment of the invention, based on 100 parts by weight of the first dispersant, the content of the second dispersant in the dispersion solution is from 10 parts by weight to 40 parts by weight. Specifically, the content of the second dispersant is 10 parts by weight or more, 15 parts by weight or more, or 20 parts by weight or more, and 40 parts by weight or less, 35 parts by weight or less, 30 parts by weight or less, or 25 parts by weight or less, and can be from 10 parts by weight to 40 parts by weight, 15 parts by weight to 35 parts by weight, or 15 parts by weight to 30 parts by weight. When the content of the second dispersant meets the above ranges, the dispersant can be uniformly dispersed in the dispersion solution, so that the dispersion solution can exhibit low viscosity.

[0068] In one embodiment of the invention, the total molar ratio of cellulose-based polymer repeating units to lactone-based polymer repeating units in the second dispersant is 2:1 to 10:1. Specifically, the molar ratio is 2:1 or greater, 3:1 or greater, 4:1 or greater, 5:1 or greater, or 6:1 or greater, and 10:1 or less, 9:1 or less, 8:1 or less, or 7:1 or less, and can be 2:1 to 10:1, 3:1 to 9:1, or 4:1 to 8:1. When the molar ratio meets the above ranges, an interaction between the second dispersants suitable for stably maintaining the "conductor-dispersant" complex can be formed.

[0069] The total number of moles of repeating units of the cellulose-based polymer means the value obtained by adding up the total number of moles of repeating units in each of the cellulose-based polymers contained in the second dispersant, and the total number of moles of repeating units of the lactone-based polymer also means the value obtained by adding up the total number of moles of repeating units in each of the lactone-based polymers contained in the second dispersant in the same manner, and the molar ratio means the molar ratio when the lactone-based polymers are contained in the auxiliary components of the second dispersant.

[0070] In one embodiment of the invention, the total molar ratio of cellulose-based polymer repeating units to diol-based polymer repeating units in the second dispersant is 2:1 to 10:1. Specifically, the molar ratio is 2:1 or greater, 3:1 or greater, 4:1 or greater, 5:1 or greater, or 6:1 or greater, and 10:1 or less, 9:1 or less, 8:1 or less, or 7:1 or less, and can be 2:1 to 10:1, 3:1 to 9:1, or 4:1 to 8:1. When the molar ratio meets the above ranges, an interaction between the second dispersants suitable for stably maintaining the "conductor-dispersant" complex can be formed.

[0071] The total number of moles of repeating units in the diol-based polymer also refers to the value obtained by adding up the total number of moles of repeating units in each diol-based polymer contained in the second dispersant, and the molar ratio refers to the molar ratio when the diol-based polymer is contained in the auxiliary component of the second dispersant.

[0072] In one embodiment of the invention, the auxiliary component comprises both a lactone-based polymer and a diol-based polymer. When the auxiliary component comprises both a lactone-based polymer and a diol-based polymer, interactions can be formed between the dispersant and the conductor, as well as among the dispersants themselves, thereby allowing the dispersion solution to maintain a stable dispersion state.

[0073] In one embodiment of the invention, the second dispersant further comprises a branched aliphatic hydrocarbon containing at least one amine group and at least one hydroxyl group.

[0074] Branched hydrocarbons are hydrocarbons in which one or more hydrocarbon chains are substituted on the carbon atoms that make up the main chain. For example, isopentane corresponds to a branched hydrocarbon because an alkyl chain is substituted on the main chain consisting of 4 carbon atoms, and similarly, neopentane corresponds to a branched hydrocarbon because an alkyl chain is substituted on the main chain consisting of 3 carbon atoms.

[0075] Since the second dispersant also contains a branched aliphatic hydrocarbon containing at least one amine group and at least one hydroxyl group, the polymer contained in the second dispersant as both a major and auxiliary component can be uniformly mixed. Therefore, when the second dispersant is mixed in the dispersion solution, the polymer contained in the second dispersant as both a major and auxiliary component can be uniformly distributed in the dispersion solution to form a uniform interaction with the conductor, dispersant, and dispersion medium throughout the entire region of the dispersion solution. Furthermore, by including a branched hydrocarbon with lower viscosity and higher solubility in organic solvents compared to linear hydrocarbons, the solubility of the second dispersant in the dispersion medium can be increased, and the branched aliphatic hydrocarbon can also interact with the conductor, dispersant, and dispersion medium without agglomerating in the dispersion solution, thereby contributing to maintaining a stable dispersion state in the dispersion solution.

[0076] In one embodiment of the invention, based on the sum of the weights of the main component and auxiliary components in 100 parts by weight of the second dispersant, the dispersion solution contains 50 to 150 parts by weight of branched aliphatic hydrocarbons comprising at least one amine group and at least one hydroxyl group. Specifically, the hydrocarbon content is 50 parts by weight or more, 60 parts by weight or more, 70 parts by weight or more, 80 parts by weight or more, 90 parts by weight or more, or 100 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, or 110 parts by weight or less, and can be 50 to 150 parts by weight, 70 to 130 parts by weight, or 80 to 120 parts by weight. When the hydrocarbon content meets the above ranges, by interacting with the main component and auxiliary components in the second dispersant, the main component and auxiliary components in the second dispersant can be uniformly mixed, and can form ionic compounds with the main component and auxiliary components to effectively disperse the conductor and prevent aggregation in the dispersion solution, so that the dispersion solution can maintain a stable dispersion state.

[0077] In one embodiment of the invention, the branched aliphatic hydrocarbon comprising at least one amine group and at least one hydroxyl group is a C2 to C10 hydrocarbon.

[0078] In one embodiment of the invention, the branched aliphatic hydrocarbon comprising at least one amino group and at least one hydroxyl group includes a selection from the group consisting of 2-amino-2-methylprop-1-ol, 2-amino-2-methylbut-1-ol, 3-amino-2-methylprop-1-ol, 2-amino-2-methylpent-1-ol, 2-amino-2-ethylprop-1-ol, 2-amino-2-ethylbut-1-ol, 2-amino-2-methylhex-1-ol, 2-amino-2-methylhept-1-ol, 2-amino-2-ethylhex-1-ol, 2-amino-2-methyloct-1-ol, 3-amino-2-ethylpent-1-ol, 3-amino-2-methylhept-1-ol, and combinations thereof.

[0079] In one embodiment of the invention, the dispersion solution further comprises a third dispersant, said third dispersant comprising a linear aliphatic hydrocarbon containing at least one amine group and at least one hydroxyl group.

[0080] Unlike branched hydrocarbons, linear hydrocarbons are hydrocarbons in which the carbon atoms forming the main chain are not substituted with hydrocarbon chains. For example, n-pentane or n-hexane correspond to linear hydrocarbons because the main chains consisting of 5 and 6 carbon atoms, respectively, are not substituted with hydrocarbon chains. In the case of pent-2-ol, it corresponds to a linear aliphatic hydrocarbon containing a hydroxyl group because the main chain consisting of 5 carbon atoms is substituted with a hydroxyl group, without any substituted hydrocarbon chains.

[0081] By including a third dispersant having a linear aliphatic hydrocarbon containing at least one amine group and at least one hydroxyl group in the dispersion solution along with the first and second dispersants, the solubility of the first and second dispersants in the dispersion solution can be improved. Furthermore, the conductors that can bind to the first or second dispersant can form hydrogen bonds to prevent aggregation of the "conductor-dispersant" complex, and by including a linear hydrocarbon with higher thermal and mechanical stability compared to branched hydrocarbons, a stable dispersion state can be maintained in the dispersion solution even after a dispersion process such as high-pressure dispersion.

[0082] In one embodiment of the invention, based on 100 parts by weight of the conductor, the content of the third dispersant in the dispersion solution is from 1 part by weight to 60 parts by weight. Specifically, the content of the third dispersant is 1 part by weight or more, 5 parts by weight or more, 10 parts by weight or more, or 20 parts by weight or more, and 60 parts by weight or less, 50 parts by weight or less, 40 parts by weight or less, or 30 parts by weight or less, and can be from 1 part by weight to 60 parts by weight, 5 parts by weight to 50 parts by weight, or 10 parts by weight to 40 parts by weight. When the content of the third dispersant meets the above ranges, the interaction between the dispersant and the dispersion medium, the dispersion medium and the conductor, and the dispersant can be smoothly formed to exhibit an effective dispersion effect of the conductor in the dispersion solution.

[0083] In one embodiment of the invention, based on 100 parts by weight of the first dispersant, the content of the third dispersant in the dispersion solution is from 5 parts by weight to 200 parts by weight. Specifically, the content of the third dispersant is 5 parts by weight or more, 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 200 parts by weight or less, 190 parts by weight or less, 180 parts by weight or less, 170 parts by weight or less, 160 parts by weight or less, 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 from 5 parts by weight to 200 parts by weight, 20 parts by weight to 180 parts by weight, or 50 parts by weight to 150 parts by weight. When the content of the third dispersant meets the above range, the dispersant can be uniformly dispersed in the dispersion solution, so that the dispersion solution can exhibit low viscosity.

[0084] In one embodiment of the invention, the linear aliphatic hydrocarbon comprising at least one amine group and at least one hydroxyl group is a C1 to C6 hydrocarbon.

[0085] In one embodiment of the invention, the linear aliphatic hydrocarbon comprising at least one amino group and at least one hydroxyl group includes a selection from the group consisting of monoethanolamine, 3-aminopropanol, 4-aminobutanol, 5-aminopentanol, 6-aminohexanol, 3-aminoprop-2-ol, 3-aminobut-2-ol, 3-aminopentanol, 4-aminobut-2-ol, 4-aminopent-3-ol, 5-aminopent-2-ol, 5-aminohex-2-ol, 6-aminohex-3-ol, and combinations thereof.

[0086] (3) Dispersion medium

[0087] According to one embodiment of the invention, the dispersion medium of the conductor dispersion solution is a dispersion medium for dispersing carbon-based conductors and dispersants, and is used to supply the conductor dispersion solution by pre-dispersing the carbon-based conductors to prevent aggregation when the carbon-based conductors in powder form are used directly to manufacture electrode slurry compositions.

[0088] In one embodiment of the invention, the dispersion medium comprises a non-aqueous polar solvent containing nitrogen atoms.

[0089] In one embodiment of the invention, the dispersion medium comprises a non-aqueous polar solvent containing one selected from cyano, amino, and amide groups.

[0090] The dispersion medium may be, for example, selected from at least one of dimethylformamide (DMF), acetonitrile, dimethylacetamide (DMAc), N,N-dimethylpropionamide (DMPA), N-methylformamide (NMF), formamide, N,N-diethylformamide (DEF), 2-pyrrolidone, N-methyl-2-pyrrolidone (NMP), N-ethyl-2-pyrrolidone (NEP), ε-caprolactam, benzyl nitrile, propionitrile, and butyronitrile, but not limited thereto.

[0091] Considering the coatability of the electrode paste composition subsequently manufactured using a conductor dispersion solution, the dispersion medium can be included in an amount such that the electrode paste composition can have an appropriate viscosity.

[0092] (4) Conductor dispersion solution

[0093] This invention provides a conductor dispersion solution.

[0094] In one embodiment of the invention, the conductor dispersion solution comprises a carbon-based conductor, a dispersant, and a dispersion medium.

[0095] The conductor dispersion containing the above components has excellent dispersibility and reduced particle size, resulting in low viscosity of the dispersion.

[0096] In one embodiment of the invention, the D of carbon-based conductor dispersion particles in the conductor dispersion solution 10 The thickness ranges from 0.5 μm to 1.5 μm. Specifically, D 10 The micrometer size can be 0.5 μm or larger, 0.6 μm or larger, 0.7 μm or larger, 0.8 μm or larger, or 0.9 μm or larger, and 1.5 μm or smaller, 1.4 μm or smaller, 1.3 μm or smaller, 1.2 μm or smaller, 1.1 μm or smaller, or 1.0 μm or smaller, and can be from 0.5 μm to 1 μm, 0.7 μm to 1.3 μm, or 0.8 μm to 1.2 μm. When D 10 When the above range is met, the viscosity of the dispersion solution can be reduced according to the rate of increase of the conductor content in the dispersion solution.

[0097] In one embodiment of the invention, the D of carbon-based conductor dispersion particles in the conductor dispersion solution 50 The thickness ranges from 1.5 μm to 2.5 μm. Specifically, D 50The micrometer size can be 1.5 μm or larger, 1.6 μm or larger, 1.7 μm or larger, 1.8 μm or larger, 1.9 μm or larger, or 2.0 μm or larger, and 2.5 μm or smaller, 2.4 μm or smaller, 2.3 μm or smaller, 2.2 μm or smaller, or 2.1 μm or smaller, and can be from 1.5 μm to 2.5 μm, 1.6 μm to 2.4 μm, or 1.8 μm to 2.2 μm. When D 50 When the above range is met, the viscosity of the dispersion solution can be reduced according to the rate of increase of the conductor content in the dispersion solution.

[0098] In one embodiment of the invention, the D of carbon-based conductor dispersion particles in the conductor dispersion solution 90 The thickness ranges from 3 μm to 8 μm. Specifically, D 90 The micrometer size can be 3 μm or larger, 3.5 μm or larger, 4 μm or larger, or 4.5 μm or larger, and 8 μm or smaller, 7.5 μm or smaller, 7 μm or smaller, 6.5 μm or smaller, 6 μm or smaller, 5.5 μm or smaller, or 5 μm or smaller, and can be from 3 μm to 8 μm, 3 μm to 7 μm, or 3.5 μm to 5 μm. When D 90 When the above range is met, the viscosity of the dispersion solution can be reduced according to the rate of increase of the conductor content in the dispersion solution.

[0099] In one embodiment of the invention, the span value of the particles dispersed in the conductor dispersion solution, represented by the following [Formula 1], is from 0.5 to 3. Specifically, the span value is 0.5 or greater, 0.6 or greater, 0.7 or greater, 0.8 or greater, 0.9 or greater, 1 or greater, 1.1 or greater, 1.2 or greater, 1.3 or greater, 1.4 or greater, 1.5 or greater, 1.6 or greater, or 1.7 or greater, and 3 or less, 2.9 or less, 2.8 or less, 2.7 or less, 2.6 or less, 2.5 or less, 2.4 or less, 2.3 or less, 2.2 or less, 2.1 or less, 2 or less, 1.9 or less, or 1.8 or less, and can be from 0.5 to 3, 1 to 3, or 1.5 to 2.5. When the span value meets the above range, the dispersed particles in the dispersion solution can maintain a stable dispersion state.

[0100] [Formula 1]

[0101] Span = [(D 90 -D 10 )] / D 50

[0102] In one embodiment of the invention, the viscosity of the conductor dispersion solution was measured for 5 minutes at 25°C and 40 rpm using a viscometer (manufactured by Brookfield, RVDV2T, rotor No. 4) and was between 0.1 Pa∙second and 1 Pa∙second. Specifically, the viscosity is 0.1 Pa·s or greater, 0.15 Pa·s or greater, 0.2 Pa·s or greater, or 0.25 Pa·s or greater, and 1 Pa·s or less, 0.95 Pa·s or less, 0.9 Pa·s or less, 0.85 Pa·s or less, 0.8 Pa·s or less, 0.75 Pa·s or less, 0.7 Pa·s or less, 0.65 Pa·s or less, 0.6 Pa·s or less, 0.55 Pa·s or less, 0.5 Pa·s or less, 0.45 Pa·s or less, 0.4 Pa·s or less, 0.35 Pa·s or less, or 0.3 Pa·s or less, and can be from 0.1 Pa·s to 1 Pa·s, 0.1 Pa·s to 0.8 Pa·s, or 0.15 Pa·s to 0.6 Pa·s. When the viscosity meets the above range, the conductor is uniformly distributed in the dispersion solution, making the use of the dispersion solution easy when manufacturing the electrode slurry composition.

[0103] Method for manufacturing conductor dispersion solutions

[0104] This invention provides a method for manufacturing a conductor dispersion solution.

[0105] In one embodiment of the invention, the manufacturing method is a method for manufacturing a conductor dispersion solution comprising a carbon-based conductor, a dispersant, and a dispersion medium.

[0106] In one embodiment of the present invention, a method for manufacturing a conductor dispersion solution includes: (1) mixing a carbon-based conductor, a first dispersant, a second dispersant and a dispersion medium to manufacture a primary conductor dispersion solution, and (2) dispersing the primary conductor dispersion solution to manufacture a secondary conductor dispersion solution.

[0107] In step (1), firstly, the first dispersant, the second dispersant and the dispersion medium are mixed to prepare a mixed solution.

[0108] In step (1), the primary conductor dispersion solution is then prepared by mixing the conductor with the mixed solution.

[0109] In one embodiment of the invention, the mixing for preparing the primary conductor dispersion solution can be carried out using conventional mixing methods. Specifically, the mixing device may be a PD mixer, a pony mixer, a change-can mixer, a Hobert mixer, a planetary mixer, a butterfly mixer, a crusher, a homogenizer, a bead mill, a ball mill, a basket mill, a grinder, a general-purpose agitator, a transparent mixer, or a TK mixer, and may include a step of mixing at a rotational speed of 300 rpm to 10,000 rpm for 30 minutes to 7 hours.

[0110] In one embodiment of the invention, when mixing to prepare a primary conductor dispersion solution, cavitation dispersion treatment can be performed to increase the miscibility of the carbon-based conductor with the dispersion medium or the dispersibility of the conductor in the dispersion medium. Cavitation dispersion treatment is a dispersion method using shock waves generated by the collapse of vacuum bubbles in water when high energy is applied to the liquid, and this method can disperse the conductor without impairing its properties. Specifically, cavitation dispersion treatment can be performed by ultrasonication, jet milling, or shear dispersion.

[0111] In one embodiment of the invention, the step of preparing the primary conductor dispersion solution can be carried out at temperature conditions where the physical properties of the mixture, including viscosity, will not change due to the evaporation of the dispersion medium. For example, it can be carried out at 50°C or lower, more specifically, at a temperature between 5°C and 50°C.

[0112] In step (2), a secondary conductor dispersion is prepared by dispersing the primary conductor dispersion solution.

[0113] In one embodiment of the invention, the process of preparing the secondary conductor dispersion solution can be carried out by methods such as ball mills, bead mills, disc mills, basket mills, or high-pressure homogenizers, and more specifically, by grinding and dispersing methods using bead mills or high-pressure homogenizers.

[0114] In one embodiment of the invention, when grinding is performed using a disc mill or a bead mill, the size of the beads can be appropriately determined based on the type and amount of carbon nanotubes and the type of dispersant. Specifically, the diameter of the beads can be from 0.1 mm to 5 mm, more specifically, from 0.5 mm to 4 mm. Furthermore, the bead milling process can be carried out 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.

[0115] The grinding by a high-pressure homogenizer is carried out by, for example, pressurizing a mixture with a piston pump of the high-pressure homogenizer and forcing it through the gap of a homogenization valve, thereby utilizing forces such as cavitation, shear, impact, and bursting when passing through the gap.

[0116] In one embodiment of the present invention, the dispersion process can be carried out according to the degree of dispersion of the conductor dispersion solution. Specifically, it can be carried out at a pressure of 5,000 psi to 30,000 psi for 30 minutes to 120 minutes, more specifically, 60 minutes to 90 minutes, and this process can be repeated 3 to 12 times.

[0117] In one embodiment of the present invention, step (2) includes a high-pressure dispersion process.

[0118] The conductor dispersion solution according to the present invention can mean a secondary conductor dispersion solution.

[0119] Electrode slurry composition for lithium secondary batteries

[0120] The present invention also provides an electrode paste composition for a secondary battery.

[0121] In one embodiment of the present invention, the electrode paste composition for a secondary battery contains a conductor dispersion solution and an electrode active material.

[0122] In one embodiment of the present invention, the electrode paste composition for a lithium secondary battery can be a positive electrode paste composition or a negative electrode paste composition, and specifically, it can be a positive electrode paste composition.

[0123] In one embodiment of the present invention, the electrode paste composition for a lithium secondary battery can contain a conductor dispersion solution, a positive electrode active material or a negative electrode active material as the electrode active material, a binder, and optionally a solvent and / or other additives.

[0124] In one embodiment of the present invention, as the positive electrode active material, positive electrode active materials well-known in the art can be used without limitation, and for example, lithium cobalt-based oxides, lithium nickel-based oxides, lithium manganese-based oxides, lithium iron phosphate, lithium nickel manganese cobalt-based oxides, or combinations thereof can be used. Specifically, as the positive electrode active material, LiCoO2, LiNiO2, LiMn2O4, LiCoPO4, LiFePO4, and LiNi a Mn b Co c O2 (where 0 < a, b, c < 1), etc., but not limited thereto.

[0125] In one embodiment of the present invention, at least one negative electrode active material selected from the following can be used as the negative electrode active material: natural graphite, artificial graphite, and carbonaceous materials; lithium-containing titanium oxide (LTO); metal (Me) of which is Si, Sn, Li, Zn, Mg, Cd, Ce, Ni, or Fe; alloy composed of metal (Me); oxide of metal (Me) (MeO) x ); and metal (Me) and carbon composites. Based on the total weight of solids other than solvent in the negative electrode slurry, the negative electrode active material may be included in an amount of 60% to 98% by weight, more preferably 70% to 98% by weight.

[0126] In one embodiment of the invention, the binder is a component that facilitates the bonding of the active material to the conductor and 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, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene-butadiene rubber, fluororubber, and various copolymers.

[0127] In one embodiment of the 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 combination of both or more thereof. Considering the coating thickness and manufacturing yield of the slurry, the amount of solvent used is sufficient as long as it dissolves and disperses the electrode active material, binder, and conductor.

[0128] In one embodiment of the invention, the viscosity modifier may be carboxymethyl cellulose or polyacrylic acid, and by adding it, the viscosity of the electrode paste can be adjusted, thereby facilitating the manufacture of the electrode paste and the coating process on the electrode current collector.

[0129] In one embodiment of the invention, the filler is optionally used as a component to suppress electrode expansion, and there are no particular limitations as long as it is a fibrous material that does not cause chemical changes in the battery, and for example, fibrous materials such as olefin-based polymers, such as polyethylene and polypropylene; glass fibers, and carbon fibers are used.

[0130] In one embodiment of the invention, when the electrode slurry composition is a positive electrode slurry composition for forming a positive electrode, the positive electrode can be manufactured by drying and rolling after coating the positive electrode slurry composition onto the positive electrode current collector. Alternatively, the positive electrode can be manufactured by casting the positive electrode slurry onto a separate support and then laminating a film obtained by peeling it from the support onto the positive electrode current collector.

[0131] In one embodiment of the present invention, the thickness of the positive electrode active material layer formed by the positive electrode slurry can be varied according to the loading amount, loading speed, etc. of the positive electrode slurry used for coating.

[0132] In one embodiment of the invention, the thickness of the positive electrode current collector is from 3 μm to 500 μm. There are no particular limitations on such a positive electrode current collector, 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., can be used. Furthermore, the bonding force of the positive electrode active material can be enhanced by forming fine irregularities on the surface of the positive electrode current collector, and the positive electrode current collector can be used in various forms (e.g., films, sheets, foils, meshes, porous bodies, foams, and nonwoven fabrics).

[0133] In one embodiment of the invention, when the electrode slurry composition is a negative electrode slurry composition for forming a negative electrode, the negative electrode can be manufactured by drying and rolling after coating the negative electrode slurry composition onto the negative electrode current collector. Alternatively, the negative electrode can be manufactured by casting the negative electrode slurry onto a separate support and then laminating a film obtained by peeling it from the support onto the negative electrode current collector.

[0134] In one embodiment of the present invention, the thickness of the negative electrode active material layer formed by the negative electrode slurry can be varied according to the loading amount, loading speed, etc. of the negative electrode slurry used for coating.

[0135] In one embodiment of the invention, the thickness of the negative electrode current collector is from 3 μm to 500 μm. There are no particular limitations on such a negative electrode current collector, 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. Furthermore, similar to the negative electrode current collector, the bonding force of the negative electrode active material can be enhanced by forming fine irregularities on the surface, and the negative electrode current collector can be used in various forms (e.g., films, sheets, foils, meshes, porous bodies, foams, and nonwoven fabrics).

[0136] Lithium secondary batteries

[0137] This invention provides a lithium secondary battery.

[0138] In one embodiment of the present invention, the lithium secondary battery includes: the above-described positive electrode, negative electrode, a separator disposed between the positive electrode and the negative electrode, and an electrolyte. Since the positive and negative electrodes are the same as those described above, their detailed description will be omitted.

[0139] The separator separates the negative and positive electrodes and provides a channel for the movement of lithium ions. It can be used without particular limitation, as long as it is typically used as a separator in lithium secondary batteries. Particularly preferred is that it has low resistance to the movement of electrolyte ions and excellent electrolyte retention. Specifically, porous polymer membranes can be used, such as porous polymer membranes made from polyolefin-based polymers such as ethylene homopolymers, propylene homopolymers, ethylene / butene copolymers, ethylene / hexene copolymers, and ethylene / methacrylate copolymers, or laminates of two or more layers thereof. Alternatively, conventional porous nonwoven fabrics can be used, such as nonwoven fabrics made from high-melting-point glass fibers, polyethylene terephthalate fibers, etc. Furthermore, coated separators containing ceramic components or polymer materials can be used to ensure heat resistance or mechanical strength, and can optionally be used in single-layer or multi-layer structures.

[0140] 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 polymer electrolyte, a solid inorganic electrolyte, or a molten inorganic electrolyte, which can be used in the manufacture of lithium secondary batteries, but is not limited thereto. Specifically, the electrolyte may contain an organic solvent and a lithium salt.

[0141] In one embodiment of the invention, the organic solvent can be used without particular limitation, as long as it can serve as a medium through which ions participating in the electrochemical reaction of the battery can move. Specifically, as organic solvents, ester-based solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone can be used; ether-based solvents such as dibutyl ether and tetrahydrofuran; ketone-based solvents such as cyclohexanone; aromatic hydrocarbon-based solvents such as benzene and 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 ethanol and isopropanol; nitriles such as R-CN (where R is a linear, branched, or cyclic C2 to C20 hydrocarbon group and may contain double bonds, aromatic rings, or ether bonds); amides such as dimethylformamide; dioxolane, such as 1,3-dioxolane; or sulfolane. Among these, carbonate-based solvents are preferred, and mixtures of cyclic carbonates (e.g., ethylene carbonate or propylene carbonate) with high ionic conductivity and high dielectric constant, and low-viscosity linear carbonate-based compounds (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate) that can improve the charge / discharge performance of the battery are even more preferred. In this case, when the cyclic carbonate and linear carbonate are mixed and used in a volume ratio of about 1:1 to about 1:9, excellent electrolyte performance can be exhibited.

[0142] In one embodiment of the invention, lithium salts can be used without particular limitation, as long as they are compounds capable of providing lithium ions for use in lithium secondary batteries. Specifically, lithium salts can 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, etc. Preferably, lithium salts are used at concentrations in the range of 0.1 M to 2.0 M. When the concentration of the lithium salt is within this range, the electrolyte has suitable conductivity and viscosity, resulting in excellent electrolyte performance and efficient lithium ion movement.

[0143] In one embodiment of the present invention, in addition to the electrolyte components, the electrolyte may also contain, for purposes such as improving battery life characteristics, suppressing battery capacity reduction, and improving battery discharge capacity, compounds based on alkyl halogen carbonates (e.g., ethylene difluorocarbonate), pyridine, triethyl phosphite, triethanolamine, cyclic ethers, ethylenediamine, n-glycol dimethyl ether, triammonium hexaphosphate, nitrobenzene derivatives, sulfur, quinone imine dyes, and N-substituted compounds. Alzolidinedione, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxyethanol, or aluminum trichloride may be used as additives. In this case, the additive may be included in an amount from 0.1% to 5% by weight, based on the total weight of the electrolyte.

[0144] In one embodiment of the invention, the lithium secondary battery includes an electrode manufactured using a conductor dispersion solution according to the invention, specifically, a negative electrode manufactured using said conductor dispersion solution. The lithium secondary battery including an electrode manufactured using the conductor dispersion solution according to the invention (specifically, a lithium secondary battery including a negative electrode manufactured using said conductor dispersion solution) can stably exhibit excellent discharge capacity and output characteristics because the conductor is uniformly dispersed in the negative electrode, allowing for a reduction in its content. As a result, it can be usefully used in portable devices such as mobile phones, laptops, and digital cameras, as well as in electric vehicles such as hybrid electric vehicles (HEVs).

[0145] Therefore, according to another embodiment of the present invention, a lithium secondary battery, a battery module including the lithium secondary battery as a unit cell, and a battery pack including the battery module can be provided.

[0146] Battery modules or battery packs can be used as a power source for any or more of the following medium to large-sized equipment: power tools; electric vehicles, including electric vehicles (EVs), hybrid electric vehicles, and plug-in hybrid electric vehicles (PHEVs); or energy storage systems.

[0147] Invention Embodiments

[0148] Specific embodiments of the invention will be presented below. However, the embodiments described below are for illustrative purposes only and are not intended to limit the invention. Furthermore, since those skilled in the art can readily infer the invention from the description, content not described herein has been omitted.

[0149] Example

[0150] <Example 1>

[0151] (1) Preparation of primary conductor dispersion solution

[0152] 7.35 g (1.47 wt% in the dispersion) of polyvinylpyrrolidone (PVP) (manufactured by Boai NKY Pharmaceuticals, NKY® PVPK30) as the first dispersant containing a nitrogen-containing vinyl-based polymer, 1.05 g (0.21 wt% in the dispersion) of monoethanolamine (MEA) (manufactured by Duksan Pharmaceutical Co., Ltd.) as the third dispersant, and N-methyl-2-pyrrolidone (NMP) (manufactured by Daejung Chemical) as the dispersion medium. (Manufactured by Metals Co., Ltd.) A mixture was prepared to yield 472 g of a mixed solution. 21 g (4.2 wt% of the conductor dispersion) was added to the mixed solution as a carbon-based conductor with a specific surface area of ​​250 m². 2 After obtaining / g of multi-walled carbon nanotubes (MWCNTs, manufactured by LG Chem, BT1003M), the mixture was stirred at 6,000 rpm for 180 minutes using a PD mixer (manufactured by TSI, PDM-1T 1500L) to prepare a mixture.

[0153] 2.1 g (0.42 wt% in the dispersion solution) of a dispersant containing cellulose as the main component, polycaprolactone and polypropylene glycol as auxiliary components, and 2-amino-2-methylprop-1-ol was added to the mixture as a second dispersant, wherein the total molar ratio of cellulose repeating units to polycaprolactone repeating units to polypropylene glycol repeating units was 61.9:10:9.7. In order to add the second dispersant, 7 g of a solution containing 15 wt% of the polymer blend and 15 wt% of 2-amino-2-methylprop-1-ol (manufactured by BYK, LP N25542) was added and stirred at 8,000 rpm for 60 minutes in a dissolving tank (dissolver, manufactured by VMA-GETZMANN, Dispermat-CA) equipped with an impeller and container to prepare a total of 500 g of primary conductor dispersion solution.

[0154] (2) Preparation of conductor dispersion solution

[0155] The conductor dispersion was prepared by uniformly dispersing the primary conductor dispersion nine times at a pressure of 20,000 psi using a high-pressure disperser (manufactured by Micronox, PICOMAX).

[0156] <Example 2>

[0157] The conductor dispersion solution was prepared in the same manner as in Example 1, except that no third dispersant was added.

[0158] <Comparative Example 1>

[0159] The conductor dispersion solution was prepared in the same manner as in Example 1, except that 3 g of a dispersant (manufactured by BYK, ET3001) containing an ammonium salt of an acidic copolymer was used as a second dispersant.

[0160] <Comparative Example 2>

[0161] The conductor dispersion solution was prepared in the same manner as in Example 1, except that 2.1 g of a dispersant (manufactured by Sekisui, FX-08) containing a resin based on polyvinyl butyral was used as a second dispersant.

[0162] <Comparative Example 3>

[0163] The conductor dispersion solution was prepared in the same manner as in Example 1, except that 2.1 g of a dispersant containing butadiene-styrene copolymer (manufactured by Cray Valley, Ricon®) was used as a second dispersant.

[0164] <Comparative Example 4>

[0165] The conductor dispersion solution was prepared in the same manner as in Example 1, except that no second dispersant was added.

[0166] <Example 3>

[0167] A primary conductor dispersion was prepared by stirring a first dispersant, a second dispersant, a third dispersant, a dispersion medium, and a carbon-based conductor at 6,000 rpm for 180 minutes via a PD mixer (manufactured by TSI), and a conductor dispersion was prepared by uniformly dispersing the primary conductor dispersion nine times. The conductor dispersion was prepared in the same manner as in Example 1, except that 5.25 g (1.05 wt% of the first dispersant in the dispersion), 1.05 g (0.21 wt% of the second dispersant in the dispersion), and 5.25 g (1.05 wt% of the third dispersant in the dispersion) were mixed.

[0168] <Example 4>

[0169] The conductor dispersion solution was prepared in the same manner as in Example 3, except that 7.35 g (1.47 wt% of the dispersion solution) of the first dispersant, 2.1 g (0.42 wt% of the dispersion solution) of the second dispersant and 1.05 g (0.21 wt% of the dispersion solution) of the third dispersant were mixed.

[0170] <Example 5>

[0171] The conductor dispersion solution was prepared in the same manner as in Example 3, except that 6.3 g (1.26 wt% of the dispersion solution) of the first dispersant, 1.05 g (0.21 wt% of the dispersion solution) of the second dispersant and 5.25 g (1.05 wt% of the dispersion solution) of the third dispersant were mixed.

[0172] <Example 6>

[0173] The conductor dispersion solution was prepared in the same manner as in Example 3, except that 6.3 g (1.26 wt% of the dispersion solution) of the first dispersant, 1.05 g (0.21 wt% of the dispersion solution) of the second dispersant and 10.5 g (2.1 wt% of the dispersion solution) of the third dispersant were mixed.

[0174] Experimental Example

[0175] <Experimental Example 1: Particle Size Analysis>

[0176] The particle size of the dispersed particles in the conductor dispersion solutions of the Examples and Comparative Examples was analyzed by laser diffraction and is shown in [Table 1] and [Table 2]. Specifically, after the conductor dispersion solution was dispersed in a solvent, the dispersion solution immediately following dispersion was introduced into a laser diffraction particle size measurement device (manufactured by Malvern, Mastersizer 3000) to measure the difference in diffraction patterns according to particle size when the particles passed through the laser beam at 25°C, thereby calculating the particle size distribution. D was measured by examining the particle size at points where the volumetric cumulative distribution of particle size was 10%, 50%, and 90%. 10 D 50 and D 90 .

[0177] In addition, using the measured D 10 D 50 and D 90 The span values ​​for the embodiments and comparative examples were calculated using the following [Equation 1] and are then shown in [Table 1] and [Table 2].

[0178] [Formula 1]

[0179] Span = [(D 90 -D 10 )] / D 50

[0180] <Experimental Example 2: Viscosity Analysis>

[0181] The viscosity of the conductor dispersions prepared according to the examples and comparative examples was measured for 5 minutes at 25°C and 40 rpm using a viscometer (manufactured by Brookfield, RVDV2T, rotor No. 4), and the viscosity after 5 minutes is shown in Tables 1 and 2 below.

[0182] [Table 1]

[0183]

[0184] [Table 2]

[0185]

[0186] As shown in Table 1 above, as in the dispersion solutions of Examples 1 and 2, when a dispersant containing at least one of a cellulose-based polymer as the main component and a lactone-based polymer and a diol-based polymer as the auxiliary component is used as the second dispersant, it can be determined that even when a high content of conductor is contained, the dispersed particles in the dispersion solution are small and the viscosity of the dispersion solution does not have a high value.

[0187] In particular, although the dispersions of Comparative Examples 1 to 3 exhibited low span values ​​and small particle sizes comparable to those of the Examples, they showed a viscosity nearly four times higher than that of the dispersion of Example 1, and the product of span value and viscosity also showed a value nearly four times higher than that of the dispersion of Example 1. This demonstrates that the second dispersant comprising a cellulose-based polymer as the main component and at least one of a lactone-based polymer and a diol-based polymer as an auxiliary component is effective in reducing the viscosity of the dispersion and improving the dispersion effect, and is superior to commercially available conductor dispersants.

[0188] Furthermore, the fact that the dispersion solution of Comparative Example 4, which does not contain the second dispersant, not only exhibits a higher viscosity than that of Comparative Examples 1 to 3, but also shows a worse value in terms of the product of span and viscosity, demonstrates that the second dispersant must be included to produce an improvement effect in both particle size and viscosity.

[0189] Furthermore, although the dispersion solution of Example 2, which does not contain the third dispersant, exhibits a lower viscosity than the other comparative examples, the fact that the product of the span value and viscosity is slightly higher than that of Example 1 indicates that a conductor dispersion solution can be obtained more effectively when the third dispersant is included.

[0190] Based on the above [Table 2], it can be determined that by using a second dispersant comprising a cellulose-based polymer as the main component and at least one of a lactone-based polymer and a diol-based polymer as an auxiliary component, both the particle size of the dispersed particles and the viscosity of the dispersion solution were improved in all Examples 3 to 6, and in particular, it can be determined that the product of the span value and the viscosity is 1 or less, exhibiting excellent dispersion effect.

[0191] In particular, it can be seen that in Examples 3, 5 and 6 (where the content of the first dispersant is 25 parts by weight or less based on 100 parts by weight of the first dispersant), and in Examples 3 and 6 (where the content of the third dispersant is 90 parts by weight or more based on 100 parts by weight of the first dispersant), the particle size of the dispersed particles in the dispersion solution is effectively reduced, and it can be seen that the effect of reducing the particle size of the dispersed particles in the dispersion solution and the effect of reducing the viscosity of the dispersion solution occur in a balanced manner.

[0192] In addition to the contents mentioned above, Examples 3 to 6 show differences in the contents of the third dispersant based on the second dispersant, the contents of the second dispersant based on the conductor, and the contents of the second dispersant based on the first dispersant. Therefore, it can be seen that when a dispersion solution is prepared by adjusting the contents of the substances contained in the dispersion solution and the content ratio between the substances under conditions similar to those in Example 3, the effect of reducing the particle size of the dispersed particles in the dispersion solution and the effect of reducing the viscosity of the dispersion solution can be more effective.

[0193] Therefore, it can be seen that when a dispersant containing at least one of a cellulose-based polymer as the main component and a lactone-based polymer and a diol-based polymer as an auxiliary component is used as the second dispersant in the dispersion solution, it can exhibit an effect of reducing the particle size of dispersed particles and the viscosity of the dispersion solution that exceeds that of commercially available conductor dispersants. Furthermore, when a third dispersant is included and the content and ratio of each substance in the dispersion solution are close to those in Example 3, the dispersion effect of the conductor in the dispersion solution can be further improved.

[0194] While the 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 made by those skilled in the art using the basic concept of the present invention as defined in the appended claims also fall within the scope of the present invention.

Claims

1. A conductor dispersion solution, comprising: Carbon-based conductors; A first dispersant comprising a vinyl-based polymer containing nitrogen atoms; A second dispersant comprising a main component and auxiliary components; and Dispersion medium, The main component comprises a cellulose-based polymer, and The auxiliary component comprises at least one of a lactone-based polymer and a diol-based polymer.

2. The conductor dispersion solution according to claim 1, wherein: The auxiliary component comprises both the lactone-based polymer and the diol-based polymer.

3. The conductor dispersion solution according to claim 1, wherein: The second dispersant also comprises a branched aliphatic hydrocarbon containing at least one amine group and at least one hydroxyl group.

4. The conductor dispersion solution according to claim 1, wherein: Based on 100 parts by weight of the conductor, the content of the first dispersant in the dispersion solution is from 5 parts by weight to 60 parts by weight.

5. The conductor dispersion solution according to claim 1, wherein: Based on 100 parts by weight of the conductor, the content of the second dispersant in the dispersion solution is from 1 part by weight to 20 parts by weight.

6. The conductor dispersion solution according to claim 1, wherein: Based on 100 parts by weight of the first dispersant, the content of the second dispersant in the dispersion solution is from 10 parts by weight to 40 parts by weight.

7. The conductor dispersion solution according to claim 1, wherein: The total molar ratio of cellulose-based polymer repeating units to lactone-based polymer repeating units in the second dispersant is 2:1 to 10:1, and The total molar ratio of cellulose-based polymer repeating units to diol-based polymer repeating units in the second dispersant is 2:1 to 10:

1.

8. The conductor dispersion solution according to claim 1, wherein: The dispersion solution further comprises a third dispersant, which comprises a linear aliphatic hydrocarbon containing at least one amine group and at least one hydroxyl group.

9. The conductor dispersion solution according to claim 8, wherein: Based on 100 parts by weight of the conductor, the content of the third dispersant in the dispersion solution is from 1 part by weight to 60 parts by weight.

10. The conductor dispersion solution according to claim 8, wherein: Based on 100 parts by weight of the first dispersant, the content of the third dispersant in the dispersion solution is from 5 parts by weight to 200 parts by weight.

11. The conductor dispersion solution according to claim 1, wherein: The span values ​​of the particles dispersed in the conductor dispersion solution, as expressed by the following [Equation 1], are from 0.5 to 3. [Formula 1] Span = [(D 90 -D 10 )] / D 50 (where D) 90 This refers to the particle size that corresponds to 90% of the volumetric cumulative distribution of the particles dispersed in the dispersion solution. D 50 For the particle size corresponding to 50% of the volumetric cumulative distribution of the particles dispersed in the dispersion solution, and D 10 The particle size corresponds to 10% of the cumulative volume distribution of the particles dispersed in the dispersion solution.

12. The conductor dispersion solution according to claim 1, wherein: The dispersion medium includes a non-aqueous polar solvent containing nitrogen atoms.

13. The conductor dispersion solution according to claim 1, wherein: The carbon-based conductor includes at least one selected from carbon nanotubes, carbon black, and combinations thereof.

14. A method for manufacturing a conductor dispersion solution according to claim 1, the method comprising: (1) A carbon-based conductor, a first dispersant, a second dispersant, and a dispersion medium are mixed to prepare a primary conductor dispersion solution; as well as (2) The primary conductor dispersion solution is dispersed to produce a secondary conductor dispersion solution.

15. The method for producing a conductor dispersion solution according to claim 14, wherein: Step (2) includes a high-pressure dispersion process.

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