Conductive material dispersed solution, slurry composition for electrode comprising the same, and lithium secondary battery comprising the same

Abstract

A conductive material dispersion according to the embodiments of the present disclosure comprises a conductive material comprising carbon nanotubes; a first dispersant comprising a cellulose-based polymer; and a second dispersant comprising a polyethylene oxide-based polymer. The dispersibility of the conductive material dispersion comprising the first dispersant and the second dispersant together can be improved, and the resistance characteristics of a secondary battery can be improved.

Description

Technology Field

[0001] The present disclosure relates to a conductive material dispersion, an electrode slurry containing the same, and a secondary battery. Background Technology

[0003] Rechargeable batteries are batteries capable of repeated charging and discharging, and with the advancement of the information and communication and display industries, they are widely applied as power sources for portable electronic communication devices such as camcorders, mobile phones, and laptop PCs. Furthermore, recently, battery packs containing rechargeable batteries are being developed and applied as power sources for eco-friendly vehicles, such as hybrid cars.

[0004] Examples of secondary batteries include lithium-ion batteries, nickel-cadmium batteries, and nickel-hydrogen batteries; among these, active research and development is being conducted on lithium-ion batteries due to their high operating voltage and energy density per unit weight, as well as their advantages in charging speed and weight reduction.

[0005] The electrode for a secondary battery may include a conductive material, which can provide conductivity between electrode active material particles and reduce resistance within the electrode. As the conductive material, point conductive materials such as carbon black and / or linear conductive materials such as carbon nanotubes may be used. For example, an electrode slurry may be prepared by mixing electrode active material particles and a conductive material, and an electrode for a secondary battery may be prepared from the electrode slurry.

[0006] However, it is difficult for conductive materials to be uniformly dispersed in the electrode slurry, which can lead to intensified aggregation between electrode active material particles and reduce the conductivity of the electrode. In addition, the viscosity of the electrode slurry increases, which increases the manufacturing time and can lower process efficiency. Therefore, research and development are required to improve the dispersibility of conductive materials. The problem to be solved

[0008] One objective of the present disclosure is to provide a conductive material dispersion having improved dispersibility.

[0009] One objective of the present disclosure is to provide an electrode slurry having improved dispersibility.

[0010] One objective of the present disclosure is to provide a lithium secondary battery having improved electrochemical characteristics. means of solving the problem

[0012] A conductive material dispersion according to embodiments of the present disclosure comprises a conductive material comprising carbon nanotubes; a first dispersant comprising a cellulose-based polymer; and a second dispersant comprising a polyethylene oxide-based polymer.

[0013] According to exemplary embodiments, the content of the conductive material may be 0.2% to 8.0% by weight of the total weight of the conductive material dispersion.

[0014] According to exemplary embodiments, the content of the first dispersant may be 50 to 400 parts by weight per 100 parts by weight of the conductive material.

[0015] According to exemplary embodiments, the content of the second dispersant may be 10 to 100 parts by weight per 100 parts by weight of the conductive material.

[0016] According to exemplary embodiments, the weight ratio of the second dispersant to the first dispersant included in the conductive material dispersion may be 0.05 to 0.5.

[0017] According to exemplary embodiments, the weight-average molecular weight (MW) of the first dispersant may be 75,000 to 400,000.

[0018] According to exemplary embodiments, the average value of the number of hydroxyl groups substituted by alkyl or acyl groups among the three hydroxyl groups per glucose unit of the cellulose-based polymer of the first dispersant may be 0.5 to 1.0.

[0019] According to exemplary embodiments, the second dispersant may comprise polyethylene oxide, or a copolymer of polyethylene oxide and polypropylene oxide.

[0020] According to exemplary embodiments, the second dispersant may include an ethylene oxide repeating unit and a repeating unit represented by the following chemical formula 1.

[0021] [Chemical Formula 1]

[0022]

[0023] According to exemplary embodiments, the second dispersant may include one or more of the polymers represented by the following chemical formulas 2 to 4.

[0024] [Chemical Formula 2]

[0025]

[0026] [Chemical Formula 3]

[0027]

[0028] [Chemical Formula 4]

[0029]

[0030] In Chemical Formula 2, a is an integer from 5 to 500. In Chemical Formula 3, R1 is an alkyl group or alkylene group having 1 to 5 carbon atoms, and b, c, and d are each integers from 5 to 150. In Chemical Formula 4, R2 and R3 are each independently an alkyl group or alkylene group having 1 to 5 carbon atoms, and e, f, and g are each integers from 5 to 150.

[0031] According to exemplary embodiments, the weight-average molecular weight (MW) of the second dispersant may be 500 to 30,000.

[0032] According to exemplary embodiments, the viscosity change rate of the conductive material dispersion may be 15% or less.

[0033] According to exemplary embodiments, an aqueous solvent may be further included.

[0034] The electrode slurry according to exemplary embodiments includes a conductive material dispersion according to the embodiments described above.

[0035] A lithium secondary battery according to exemplary embodiments includes an electrode for a lithium secondary battery comprising an electrode active material layer formed from an electrode slurry according to the embodiments described above; and a counter electrode facing the electrode for the lithium secondary battery. Effects of the invention

[0037] According to embodiments of the present disclosure, a conductive material dispersion comprises a first dispersant comprising a cellulose-based polymer and a second dispersant comprising a polyethylene oxide-based polymer. The dispersibility of the conductive material dispersion can be improved by the first dispersant and the second dispersant, and an electrode having low sheet resistance can be formed. Additionally, the aggregation of the conductive materials is suppressed by the dispersants, thereby improving storage stability.

[0038] According to exemplary embodiments, the content of the first dispersant and the second dispersant can be controlled within a predetermined range. Accordingly, the dispersibility and storage stability of the conductive material dispersion can be further improved. Brief explanation of the drawing

[0040] FIGS. 1 and FIGS. 2 are a schematic plan view and a cross-sectional view, respectively, showing a lithium secondary battery according to exemplary embodiments. Specific details for implementing the invention

[0041] According to embodiments of the present disclosure, a conductive material dispersion comprising a conductive material and a dispersant is provided. According to embodiments of the present disclosure, an electrode slurry comprising a conductive material dispersion is provided. According to embodiments of the present disclosure, a lithium secondary battery comprising an electrode active material layer formed from the electrode slurry described above is provided.

[0042] Lithium secondary batteries according to the embodiments of the present disclosure can be widely applied in green technology fields such as electric vehicles, battery charging stations, and other applications utilizing batteries, such as solar power generation and wind power generation. Furthermore, lithium secondary batteries according to the embodiments of the present disclosure can be used in eco-friendly electric vehicles, hybrid vehicles, etc., to prevent climate change by suppressing air pollution and greenhouse gas emissions.

[0043] Hereinafter, embodiments of the present disclosure will be described in detail.

[0044] If there are isomers of a compound represented by the chemical formula used in the present disclosure, the compound represented by said chemical formula includes the isomers.

[0045] As used in this disclosure, the term "X-based polymer" may refer to a polymer comprising an X compound and a derivative of the X compound. For example, the X compound may be included as a major repeating unit. For example, the X compound may be included as part of a copolymer. For example, a cellulose-based polymer may refer to a polymer comprising cellulose.

[0046] A conductive material dispersion according to the embodiments of the present disclosure comprises a conductive material comprising carbon nanotubes. The conductive material dispersion comprises a first dispersant comprising a cellulose-based polymer and a second dispersant comprising a polyethylene oxide-based polymer.

[0047] Carbon nanotubes can refer to polymeric carbon allotropes formed by carbon atoms interconnected in a hexagonal honeycomb structure with an sp2 bonding structure. Carbon nanotubes can take the form of cylinders with nano-sized diameters.

[0048] Carbon nanotubes possess high electrical conductivity and mechanical strength. Carbon nanotubes can be positioned between electrode active materials, thereby preventing the closure of micropores between the materials during the pressurization and molding processes for electrode formation. Consequently, the electrolyte can easily penetrate into the electrode, and the internal resistance of the electrode active material layer can be reduced.

[0049] In some embodiments, the carbon nanotube may include one or more of single-walled carbon nanotubes (SWCNT), double-walled carbon nanotubes (DWCNT), and multi-walled carbon nanotubes (MWCNT).

[0050] In one embodiment, the carbon nanotube may include a single-walled carbon nanotube.

[0051] In the case of single-walled carbon nanotubes, the surface area capable of bonding with the first dispersant containing a cellulose-based polymer and the second dispersant containing a polyethylene oxide-based polymer, as described below, is high, so the dispersibility of the conductive material dispersion can be further improved.

[0052] In one embodiment, the average length of the carbon nanotube may be 0.1 μm to 100 μm, 0.1 μm to 500 μm, or 1 μm to 10 μm. The length of the carbon nanotube may be the length along the major axis of the carbon nanotube. The average length may refer to the average value of lengths measured in the carbon nanotube powder.

[0053] In one embodiment, the outer diameter of the carbon nanotube may be 1 nm to 15 nm, 1 nm to 10 nm, 1 nm to 7 nm, 1.1 nm to 5 nm, 1.2 nm to 4 nm, 1.5 nm to 3 nm, 1.6 nm to 2.5 nm, or 1.8 nm to 2.1 nm.

[0054] In one embodiment, the inner diameter of the carbon nanotube may be 0.1 nm to 5 nm, 0.3 nm to 4 nm, 0.5 nm to 3 nm, 0.8 nm to 2.5 nm, 1.0 nm to 2.2 nm, 1.1 nm to 2.0 nm, or 1.2 nm to 1.5 nm.

[0055] The outer diameter and inner diameter of the carbon nanotube represent the average values ​​of the outer and inner diameters measured in the carbon nanotube powder, respectively.

[0056] Carbon nanotubes within the above length and diameter ranges may have increased bonding strength with the dispersants described below, thereby further improving the dispersibility of the conductive material dispersion.

[0057] According to exemplary embodiments, the content of the conductive material containing carbon nanotubes may be 0.20 wt% or more, 0.22 wt% or more, 0.24 wt% or more, 0.25 wt% or more, 0.27 wt% or more, 0.28 wt% or more, 0.29 wt% or more, or 0.30 wt% or more of the total weight of the conductive material dispersion.

[0058] According to exemplary embodiments, the content of the conductive material containing carbon nanotubes may be 8.0 wt% or less, 7.5 wt% or less, 7.2 wt% or less, 7.0 wt% or less, 6.8 wt% or less, 6.5 wt% or less, 6.2 wt% or less, 6.0 wt% or less, 5.5 wt% or less, or 5.0 wt% or less of the total weight of the conductive material dispersion.

[0059] For example, the content of the conductive material containing carbon nanotubes may be 0.2% to 8.0% by weight, 0.22% to 7.5% by weight, 0.24% to 7.2% by weight, 0.25% to 7.0% by weight, 0.28% to 6.0% by weight, 0.29% to 5.5% by weight, or 0.30% to 5.0% by weight of the total weight of the conductive material dispersion.

[0060] Within the above content range, the energy density of the secondary battery can be increased by increasing the content of the electrode active material, and improved electrical conductivity can be maintained.

[0061] In one embodiment, the conductive material may be included in the form of powder.

[0062] Carbon nanotubes possess a high specific surface area and a long aspect ratio, and can exhibit strong cohesive forces due to surface binding energy and strong van der Waals forces. Consequently, carbon nanotubes may aggregate within a solvent, and the low dispersibility of carbon nanotubes can increase the viscosity of the conductive material dispersion.

[0063] However, according to exemplary embodiments, the dispersibility of carbon nanotubes can be improved by including a cellulose-based polymer in the conductive material dispersion.

[0064] According to exemplary embodiments, the first dispersant comprises a cellulose-based polymer.

[0065] The above-mentioned cellulose-based polymer may include units derived from cellulose. For example, the above-mentioned cellulose-based polymer may include carboxymethyl cellulose (CMC), hydroxyethyl cellulose, hydroxypropyl cellulose, methyl cellulose, diacetyl cellulose, carboxyethyl cellulose, etc.

[0066] For example, the above-mentioned cellulose-based polymer can adsorb a conductive material containing carbon nanotubes as a main dispersant, and can disperse the conductive material by reducing the cohesive force between them through the electrostatic repulsion force via the polar functional groups of the cellulose-based polymer.

[0067] In one embodiment, the first dispersant may include carboxymethyl cellulose.

[0068] The polymer chain of the first dispersant containing carboxymethyl cellulose can more efficiently adsorb carbon nanotubes through hydrophobic bonding.

[0069] According to exemplary embodiments, the weight-average molecular weight (MW) of the first dispersant may be 75,000 or more, 80,000 or more, 85,000 or more, 90,000 or more, 95,000 or more, or 100,000 or more.

[0070] According to exemplary embodiments, the weight-average molecular weight (MW) of the first dispersant may be 400,000 or less, 390,000 or less, 380,000 or less, 370,000 or less, 360,000 or less, 350,000 or less, 340,000 or less, or 330,000 or less.

[0071] For example, the weight-average molecular weight may be a value calculated in polystyrene equivalent based on the measurement results of a gel permeation chromatograph (GPC).

[0072] According to exemplary embodiments, the viscosity of the first dispersant may be 100 cP or more, 200 cP or more, 300 cP or more, 400 cP or more, 500 cP or more, or 600 cP or more.

[0073] According to exemplary embodiments, the viscosity of the first dispersant may be 4,000 cP or less, 3,500 cP or less, 3,200 cP or less, 3,000 cP or less, 2,800 cP or less, or 2,500 cP or less.

[0074] For example, the viscosity of the first dispersant may be 100 cP to 4,000 cP, 200 cP to 3,500 cP, 300 cP to 3,200 cP, 400 cP to 3,000 cP, 500 cP to 2,800 cP, or 600 cP to 2,500 cP.

[0075] The above viscosity may represent a value measured in an aqueous solution state. For example, an aqueous solution containing 2 wt% of a first dispersant of the total weight of the aqueous solution at a shear rate of 96.2 s -1 The viscosity measured at may be included in the above range.

[0076] The polymer chain of the first dispersant having a weight-average molecular weight and / or viscosity within the above range has high compatibility with the diameter and length of carbon nanotubes, so the adsorption efficiency can be improved.

[0077] According to exemplary embodiments, the degree of substitution of the first dispersant may be 0.5 or more, 0.55 or more, 0.60 or more, 0.65 or more, 0.68 or more, or 0.70 or more.

[0078] According to exemplary embodiments, the degree of substitution of the first dispersant may be 1.0 or less, 0.98 or less, 0.96 or less, 0.94 or less, 0.92 or less, or 0.90 or less.

[0079] For example, the degree of substitution of the first dispersant may be 0.5 to 1.0, 0.55 to 0.98, 0.60 to 0.96, 0.65 to 0.94, 0.68 to 0.92, or 0.70 to 0.90.

[0080] The above "degree of substitution (DS)" may refer to the degree to which the hydroxyl groups of the glucose units of cellulose are substituted by alkyl groups, acyl groups, etc. For example, the degree of substitution may be calculated as the average value of the number of hydroxyl groups substituted with alkyl or acyl groups among three hydroxyl groups per glucose unit. For example, the degree of substitution may be measured according to methods known in the art.

[0081] According to exemplary embodiments, the content of the first dispersant may be 50 parts by weight or more, 60 parts by weight or more, 65 parts by weight or more, 70 parts by weight or more, 72 parts by weight or more, or 75 parts by weight or more, with respect to 100 parts by weight of the conductive material.

[0082] According to exemplary embodiments, the content of the first dispersant may be 400 parts by weight or less, 380 parts by weight or less, 350 parts by weight or less, 330 parts by weight or less, 320 parts by weight or less, or 300 parts by weight or less, with respect to 100 parts by weight of the conductive material.

[0083] For example, the content of the first dispersant may be 50 to 400 parts by weight, 60 to 380 parts by weight, 65 to 350 parts by weight, 70 to 330 parts by weight, or 75 to 300 parts by weight, based on 100 parts by weight of the conductive material.

[0084] Within the above range, the increase in viscosity is suppressed to improve the flowability of the conductive material dispersion and enhance the dispersibility of the conductive material. Consequently, the penetration rate of the electrolyte is improved due to the securing of space between the electrode active materials, thereby improving the electrical conductivity characteristics of the secondary battery.

[0085] According to exemplary embodiments, the second dispersant comprises a polyethylene oxide-based polymer.

[0086] The above polyethylene oxide-based polymer may include polyethylene oxide-derived units. For example, the above polyethylene oxide-based polymer may include a polymer and / or copolymer that includes ethylene oxide repeating units as a part.

[0087] For example, the polyethylene oxide-based polymer can serve as an auxiliary dispersant, allowing micelles formed by the polyethylene oxide-based polymer to be formed on the surface of carbon nanotubes dispersed by the cellulose-based polymer. Through these micelles, intermolecular interactions involving carbon nanotubes can be reduced and steric hindrance increased, thereby enabling the dispersed state to be maintained stably.

[0088] According to exemplary embodiments, the second dispersant may comprise polyethylene oxide, or a copolymer of polyethylene oxide and polypropylene oxide.

[0089] Polyethylene oxide can form hydrogen bonds with the solvent contained in the dispersion, and as a result, dispersion stability can be improved.

[0090] According to exemplary embodiments, the second dispersant may further include a repeating unit represented by the following chemical formula 1.

[0091] [Chemical Formula 1]

[0092]

[0093] For example, the repeating unit represented by Chemical Formula 1 can form block copolymers, random copolymers, alternating copolymers, graft copolymers, etc. together with ethylene oxide repeating units.

[0094] According to exemplary embodiments, the repeating unit represented by Formula 1 can form a block copolymer together with an ethylene oxide repeating unit. A certain interaction between the conductive material and the solvent can occur through the block copolymer, and accordingly, repeatability can occur.

[0095] The copolymer of polyethylene oxide and polypropylene oxide contains both hydrophilic and hydrophobic portions, enabling it to form hydrophobic interactions with the conductive material and hydrophilic interactions with the solvent. Accordingly, the distance between the conductive materials is secured, allowing the dispersed state to be stably maintained.

[0096] According to exemplary embodiments, the second dispersant may include an ethylene oxide repeating unit at the terminal end. Accordingly, binding with the solvent is possible, and stability in the solvent can be improved.

[0097] In one embodiment, the second dispersant may include a polymer represented by the following chemical formula 2.

[0098] [Chemical Formula 2]

[0099]

[0100] In Chemical Formula 2, a is an integer from 5 to 500.

[0101] In one embodiment, a may be 50 to 500, 80 to 450, or 100 to 400.

[0102] Within the above range, a certain chain length of the second dispersant can be secured, and accordingly, aggregation between conductive materials can be suppressed.

[0103] In some embodiments, the second dispersant may include a polymer represented by the following chemical formula 3.

[0104] [Chemical Formula 3]

[0105]

[0106] In Chemical Formula 3, R1 is an alkyl group or an alkylene group having 1 to 5 carbon atoms, and b, c, and d are each integers from 5 to 150.

[0107] In one embodiment, the second dispersant may include a polymer represented by the following chemical formula 3-1.

[0108] [Chemical Formula 3-1]

[0109]

[0110] In Chemical Formula 3-1, b, c, and d are each integers from 5 to 150.

[0111] In one embodiment, b and d may each be 30 to 150, 50 to 140, or 60 to 130.

[0112] In the above range, the length of the hydrophilic portion of the terminal part of the second dispersant can be maintained within a predetermined range, and accordingly, dispersibility can be further improved.

[0113] In one embodiment, c may be 20 to 150, 25 to 120, or 30 to 90. Within the above range, the distance between the hydrophobic portion and the hydrophilic portion is secured, thereby improving the dispersion stability of the conductive material dispersion.

[0114] In some embodiments, the second dispersant may include a polymer represented by the following chemical formula 4.

[0115] [Chemical Formula 4]

[0116]

[0117] In Chemical Formula 4, R2 and R3 are each independently an alkyl group or an alkylene group having 1 to 5 carbon atoms, and e, f and g are each integers from 5 to 150.

[0118] In one embodiment, the second dispersant may include a polymer represented by the following chemical formula 4-1 or the following chemical formula 4-2.

[0119] [Chemical Formula 4-1]

[0120]

[0121] In Chemical Formula 4-1, e, f, and g are each integers from 5 to 150.

[0122] In one embodiment, e and g in Formula 4-1 may each be 20 to 150, 25 to 120, or 30 to 90.

[0123] In one embodiment, f in Formula 4-1 may be 30 to 150, 50 to 140, or 60 to 130.

[0124] Within the above range, the distance between the hydrophobic and hydrophilic parts of the second dispersant is secured, thereby improving the dispersion stability of the conductive material dispersion.

[0125] In some embodiments, the second dispersant may include a polysorbate-based polymer.

[0126] For example, the above polysorbate-based polymer may include polysorbate 20 (sorbitan monolaurate), polysorbate 21 (PEG-4 sorbitan monolaurate), polysorbate 40 (PEG-20 sorbitan monopalmitate), polysorbate 60 (PEG-20 sorbitan monostearate), polysorbate 61 (PEG-4 sorbitan monosterate), polysorbate 65 (PEG-20 sorbitan tristearate), polysorbate 80 (PEG-80 sorbitan monooleate), etc.

[0127] According to exemplary embodiments, the weight-average molecular weight (MW) of the second dispersant may be 500 or more, 700 or more, 1,000 or more, 1,500 or more, 2,000 or more, 3,000 or more, or 5,000 or more.

[0128] According to exemplary embodiments, the weight-average molecular weight (MW) of the second dispersant may be 30,000 or less, 28,000 or less, 25,000 or less, 22,000 or less, or 20,000 or less, or 18,000 or less.

[0129] For example, the weight-average molecular weight (MW) of the second dispersant may be 500 to 30,000, 700 to 28,000, 1,000 to 25,000, 1,500 to 22,000, 2,000 to 20,000, or 5,000 to 18,000.

[0130] For example, the weight-average molecular weight may be a value calculated in polystyrene equivalent based on the measurement results of a gel permeation chromatograph (GPC).

[0131] A second dispersant having a weight-average molecular weight within the above range can be distributed between the first dispersant and carbon nanotubes to form steric hindrance, and accordingly, the dispersion stability of the conductive material dispersion can be further improved.

[0132] According to exemplary embodiments, the content of the second dispersant may be 10 parts by weight or more, 11 parts by weight or more, 11.5 parts by weight or more, 12 parts by weight or more, or 12.5 parts by weight or more, with respect to 100 parts by weight of the conductive material.

[0133] According to exemplary embodiments, the content of the second dispersant may be 100 parts by weight or less, 90 parts by weight or less, 80 parts by weight or less, 75 parts by weight or less, 72 parts by weight or less, or 70 parts by weight or less, with respect to 100 parts by weight of the conductive material.

[0134] For example, the content of the second dispersant may be 10 to 100 parts by weight, 11 to 90 parts by weight, 11.5 to 80 parts by weight, 12 to 75 parts by weight, or 12.5 to 70 parts by weight, based on 100 parts by weight of the conductive material.

[0135] Within the above range, the second dispersant can be evenly distributed, and accordingly, dispersion stability due to steric hindrance can be further improved. Therefore, the storage stability of the conductive material dispersion can be improved.

[0136] According to exemplary embodiments, the weight ratio of the second dispersant to the first dispersant may be 0.05 or more, 0.055 or more, 0.06 or more, 0.065 or more, 0.07 or more, 0.075 or more, or 0.08 or more.

[0137] According to exemplary embodiments, the weight ratio of the second dispersant to the first dispersant may be 0.50 or less, 0.45 or less, 0.42 or less, 0.40 or less, 0.38 or less, 0.37 or less, 0.36 or less, or 0.35 or less.

[0138] For example, the weight ratio of the second dispersant to the first dispersant may be 0.05 to 0.50, 0.055 to 0.45, 0.06 to 0.42, 0.07 to 0.40, 0.075 to 0.37, or 0.08 to 0.35.

[0139] Within the above range, dispersibility can be improved while suppressing the increase in viscosity caused by the first dispersant. The degree of dispersion of the conductive material can be further improved.

[0140] According to exemplary embodiments, the conductive material dispersion may include a solvent. For example, the solvent may include an aqueous solvent or a non-aqueous solvent.

[0141] According to exemplary embodiments, the solvent may include an aqueous solvent. For example, the aqueous solvent may include a polar aqueous solvent such as water, an aqueous acid solution, or an aqueous base solution.

[0142] The above-mentioned aqueous solvent may include water as a main component. For example, the water content in the aqueous solvent may be 80% by weight or more, 90% by weight or more, or 95% by weight or more. The above-mentioned aqueous solvent may be substantially composed of water.

[0143] The above aqueous solvent can interact with the above second dispersant through hydrogen bonding, thereby improving stability within the solvent.

[0144] In exemplary embodiments, the conductive material dispersion may be prepared by mixing the conductive material, the first dispersant described above, the second dispersant, and a solvent. For example, the conductive material, the first dispersant, and the second dispersant may be added to a solvent, and a mixture may be prepared by performing rotation, vibration, sliding, rolling, lifting, ultrasonic treatment, etc.

[0145] In one embodiment, a dispersion process for the mixture may be additionally performed. For example, the mixture may be uniformly mixed and dispersed using a mixer, a disperser, a high-pressure disperser, a nano-high-pressure disperser, an ultrasonic disperser, etc.

[0146] In one embodiment, mixing and dispersion may be performed together. For example, the conductive material, the first dispersant, the second dispersant, and the solvent may be dispersed while being uniformly mixed.

[0147] In one embodiment, the first dispersant and the second dispersant may be introduced sequentially.

[0148] After adsorbing carbon nanotubes with the first dispersant, steric hindrance can be formed by the second dispersant to more efficiently improve dispersibility.

[0149] According to exemplary embodiments, the conductive material dispersion may include particles dispersed by the first and second dispersants described above.

[0150] According to exemplary embodiments, the average particle size (D50) of the dispersed particles may be 10 µm to 100 µm, 20 µm to 80 µm, 30 µm to 70 µm, or 40 µm to 60 µm.

[0151] The average particle size (D50) of the dispersed particles above may represent the average particle size of the particles included in the conductive material dispersion solution during manufacturing. For example, when manufactured in the form of an electrode or a film for electrode resistance evaluation, the average of the dispersed particles may be smaller than the particle size above.

[0152] According to exemplary embodiments, the average particle size (D50) of the dispersed particles included in the electrode may be 0.1 μm or more, 0.5 μm or more, 0.8 μm or more, 1.0 μm or more, 1.2 μm or more, or 1.5 μm or more.

[0153] According to exemplary embodiments, the average particle size (D50) of the dispersed particles included in the electrode may be 5 μm or less, 4.8 μm or less, 4.5 μm or less, 4.2 μm or less, 4.0 μm or less, 3.8 μm or less, 3.6 μm or less, or 3.5 μm or less.

[0154] For example, the average particle size (D50) of the dispersed particles included in the electrode may be 0.1㎛ to 5㎛, 0.5㎛ to 4.8㎛, 0.8㎛ to 4.5㎛, 1.0㎛ to 3.8㎛, 1.2㎛ to 3.6㎛, or 1.5㎛ to 3.5㎛.

[0155] A conductive material dispersion containing particles having an average particle size within the above range can improve the penetration rate of the electrolyte by securing pores between the electrode active materials.

[0156] The average particle size of the dispersed particles included in the electrode can be controlled by the average particle size of the dispersed particles included in the conductive material dispersion. For example, if the average particle size of the dispersed particles included in the conductive material dispersion is 60 μm or less, the average particle size of the dispersed particles included in the electrode may be 3 μm or less.

[0157] The above average particle size (D50) can represent the particle size at the 50% and 99.9% points of the volumetric particle size distribution based on the volumetric particle size distribution derived by the laser diffraction method.

[0158] According to exemplary embodiments, the viscosity of the conductive material dispersion may be 750 cP or less, 700 cP or less, 670 cP or less, 650 cP or less, 630 cP or less, 620 cP or less, or 600 cP or less.

[0159] The lower limit of the above conductive material dispersion is not limited, but, for example, it may be 10 cP or more, 50 cP or more, 100 cP or more, 150 cP or more, or 200 cP or more.

[0160] An electrode with low sheet resistance can be formed through an electrode slurry containing a conductive material dispersion having a viscosity within the above range.

[0161] The above viscosity can be measured according to methods known in the art, and, for example, can represent a value measured using a viscometer.

[0162] According to exemplary embodiments, the viscosity change rate of the conductive material dispersion may be 15% or less, 12% or less, 10% or less, 8% or less, 6% or less, or 5% or less.

[0163] The lower limit of the viscosity change rate of the above conductive material dispersion is not limited, but, for example, it may be 0.1% or more, 0.2% or more, 0.3% or more, 0.4% or more, or 0.5% or more.

[0164] The above viscosity change rate can represent a value calculated according to the following Equation 1.

[0165] [Equation 1]

[0166] (Initial viscosity of conductive material dispersion - Viscosity of conductive material dispersion after 1 week of storage at high temperature (50℃)) / Initial viscosity of conductive material dispersion × 100

[0167] Long-term storage stability of the conductive material dispersion having the above viscosity change rate can be ensured.

[0168] The electrode slurry according to the embodiments of the present disclosure may include the conductive material dispersion described above.

[0169] For example, an electrode slurry can be prepared by mixing and stirring an electrode active material in a solvent and adding the conductive material dispersion described above. For example, an electrode slurry can also be prepared by adding and mixing an electrode active material into the conductive material dispersion. For example, the electrode slurry may comprise 90% to 97% by weight of the electrode active material, 0.1% to 1% by weight of the conductive material dispersion, and the remainder being a binder, based on the total weight. For example, the content of the binder may be 2.5% to 9% by weight.

[0170] The solvent in the electrode slurry may include an aqueous solvent such as water, an aqueous hydrochloric acid solution, or an aqueous sodium hydroxide solution, or a non-aqueous solvent such as N-methyl-2-pyrrolidone (NMP), dimethylformamide, dimethylacetamide, N,N-dimethylaminopropylamine, ethylene oxide, or tetrahydrofuran.

[0171] The above electrode active material may be a positive electrode active material or a negative electrode active material.

[0172] As an example of the above-mentioned positive electrode active material, it may include one or more compounds selected from lithium iron phosphate-based compounds, lithium cobalt-based oxides, lithium manganese-based oxides, lithium nickel-based oxides, or lithium composite oxides. For example, the above-mentioned positive electrode active material may include layered compounds such as lithium cobalt oxide (LiCoO2) or lithium nickel oxide (LiNiO2), or lithium manganese oxides such as LiMnO3, LiMn2O3, and LiMnO2; lithium copper oxide (Li2CuO2); LiV3O8, LiFe3O4, V2O 5　 It may include vanadium oxide such as Cu2VO7, lithium iron phosphate oxide such as LiFePO4, etc.

[0173] In one embodiment, the positive active material may include a compound represented by the following chemical formula 5.

[0174] [Chemical Formula 5]

[0175] Li a Ni b M 1-b O2

[0176] In Chemical Formula 5, 0.95≤a≤1.08, b≥0.5, and M can be at least one element among Na, Mg, Ca, Y, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Co, Fe, Cu, Ag, Zn, B, Al, Ga, C, Si, Sn, Ba, and Zr.

[0177] In one embodiment, the positive electrode active material comprises nickel (Ni) and may further comprise at least one of cobalt (Co) or manganese (Mn). For example, a nickel-cobalt-manganese (NCM) based lithium oxide may be used as the positive electrode active material.

[0178] For example, nickel (Ni) can be provided as a metal associated with the capacity of lithium secondary batteries. While a higher nickel content can improve the capacity and output of lithium secondary batteries, an excessive increase in nickel content can reduce lifespan and be disadvantageous in terms of mechanical and electrical stability.

[0179] In one embodiment, the conductivity or resistance of the lithium secondary battery can be improved by cobalt (Co), and the mechanical and electrical stability of the lithium secondary battery can be improved by manganese (Mn).

[0180] The chemical structure represented by Chemical Formula 5 represents the bonding relationships included within the lattice structure or crystal structure of the positive electrode active material and does not exclude other additional elements. For example, M can be provided as the main active element of the positive electrode active material. Chemical Formula 5 is provided to express the bonding relationships of the main active element and should be understood as encompassing the introduction and substitution of additional elements.

[0181] In one embodiment, auxiliary elements may be further included to enhance the chemical stability of the cathode active material or the crystal structure by adding to the main active element. The auxiliary elements may be incorporated together within the crystal structure to form bonds, and in this case, it should be understood that they are also included within the range of the chemical structure represented by Chemical Formula 5.

[0182] The above-mentioned negative electrode active material may be any material known in the art capable of absorbing and extracting lithium ions without special limitations. For example, carbon-based materials such as crystalline carbon, amorphous carbon, carbon composites, carbon fibers; lithium alloys; silicon or tin, etc. may be used.

[0183] Examples of the above-mentioned amorphous carbon include hard carbon, coke, mesocarbon microbeads (MCMB) calcined at 1500°C or lower, and mesophase pitch-based carbon fiber (MPCF). Examples of the above-mentioned crystalline carbon include graphite-based carbon such as natural graphite, graphitized coke, graphitized MCMB, and graphitized MPCF. Elements included in the above-mentioned lithium alloy include aluminum, zinc, bismuth, cadmium, antimony, silicon, lead, tin, gallium, or indium.

[0184] In one embodiment, the electrode slurry may further include a binder.

[0185] The above binder may include water-based binders such as styrene-butadiene rubber (SBR); and non-water-based binders such as vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidenefluoride (PVDF), polyacrylonitrile, polymethylmethacrylate, and nitrile butadiene rubber.

[0186] In one embodiment, when the electrode slurry contains a positive electrode active material, the binder may contain a PVDF-based binder. In one embodiment, when the electrode slurry contains a negative electrode active material, the binder may contain, for example, an aqueous binder for compatibility with a carbon-based active material.

[0187] In one embodiment, the electrode slurry may further include a thickening agent such as carboxymethyl cellulose (CMC).

[0188] FIGS. 1 and FIGS. 2 are schematic plan and cross-sectional views, respectively, illustrating a lithium secondary battery according to exemplary embodiments. However, this is merely illustrative and the present disclosure is not limited to the specific embodiments described illustratively.

[0189] Referring to FIGS. 1 and 2, a lithium secondary battery may include a positive electrode (100) and a negative electrode (130) facing the positive electrode (100). One of the positive electrode (100) and the negative electrode (130) is an electrode for a lithium secondary battery comprising an electrode active material layer formed from the electrode slurry described above, and the other may be a counter electrode.

[0190] The positive electrode (100) may include a positive electrode current collector (105) and a positive electrode active material layer (110) formed on at least one surface of the positive electrode current collector (105). For example, the positive electrode (100) can be manufactured by coating a positive electrode slurry on at least one surface of the positive electrode current collector (105), followed by drying and rolling.

[0191] The positive current collector (105) may include stainless steel, nickel, aluminum, titanium, or an alloy thereof. The positive current collector (105) may also include aluminum or stainless steel surface-treated with carbon, nickel, titanium, or silver.

[0192] The cathode (130) may include a cathode current collector (125) and a cathode active material layer (120) formed on at least one surface of the cathode current collector (125).

[0193] The negative current collector (125) may include, for example, gold, stainless steel, nickel, aluminum, titanium, copper, or an alloy thereof, and may include, for example, copper or a copper alloy.

[0194] In one embodiment, the electrode for the lithium secondary battery may be a positive electrode, and the counter electrode may be a negative electrode. In one embodiment, the electrode for the lithium secondary battery may be a negative electrode, and the counter electrode may be a positive electrode.

[0195] In one embodiment, the counter electrode may include a carbon-based conductive material such as graphite, carbon black, graphene, carbon nanotubes, etc., and / or a metal-based conductive material such as tin, tin oxide, titanium oxide, LaSrCoO3, LaSrMnO3, etc., as a conductive material.

[0196] In some embodiments, a separator (140) may be interposed between the anode (100) and the cathode (130). The separator (140) may comprise a porous polymer film made of a polyolefin-based polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, an ethylene / methacrylate copolymer, etc. The separator may also comprise a nonwoven fabric formed of high-melting-point glass fibers, polyethylene terephthalate fibers, etc.

[0197] According to exemplary embodiments, an electrode assembly (150) may be formed by repeating an anode (100), a cathode (130), and a separator (140). In some embodiments, the electrode assembly (150) may be winding, stacking, z-folding, or stack-folding.

[0198] An electrode assembly (150) can be housed within a case (160) to define a lithium secondary battery. The lithium secondary battery can be manufactured in a cylindrical, prismatic, pouch, or coin shape, for example, using a can.

[0199] Electrode tabs (positive tabs and negative tabs) may protrude from the positive current collector (105) and negative current collector (125) belonging to each electrode cell and extend to one side of the case (160). The electrode tabs may be fused together with the one side of the case (160) to form electrode leads (positive lead (107) and negative lead (127)) that extend or are exposed to the outside of the case (160).

[0200] According to exemplary embodiments, an electrolyte may be accommodated in a case (160) together with an electrode assembly (150). A non-aqueous electrolyte may be used as the electrolyte.

[0201] The non-aqueous electrolyte may include a lithium salt as an electrolyte and an organic solvent. The lithium salt is, for example, Li + X - It is expressed as and the anion (X) of the above lithium salt - As F - , Cl - , Br - , I - , NO3 - , N(CN)2 - , BF4 - , ClO4 - , PF6 - , (CF3)2PF4 - , (CF3)3PF3 - , (CF3)4PF2 - , (CF3)5PF - , (CF3)6P - , CF3SO3 - , CF3CF2SO3 - , (CF3SO2)2N - , (FSO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , (SF5)3C - , (CF3SO2)3C - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN - and (CF3CF2SO2)2N - Examples of the back can be given.

[0202] Examples of the above organic solvents may include propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethylmethyl carbonate (EMC), methylpropyl carbonate, dipropyl carbonate, dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, vinylene carbonate, sulfolane, gamma-butyrolactone, propylene sulfite, and tetrahydrofuran. These may be used individually or in combination of two or more.

[0203] In the following, embodiments of the present disclosure are further described with reference to specific experimental examples. The embodiments and comparative examples included in the experimental examples are merely illustrative of the present disclosure and are not intended to limit the appended claims. It is obvious to those skilled in the art that various changes and modifications to the embodiments are possible within the scope and spirit of the present disclosure, and that such variations and modifications fall within the scope of the appended claims.

[0205] Examples and Comparative Examples

[0206] (1) Preparation of conductive material dispersion

[0207] (Preparation Method A) Carbon nanotubes (SWCNT, length: 5–15 μm), carboxymethyl cellulose sodium salt (MW: 250,000 Da) as a first dispersant, and polyethylene oxide (PEO, MW: 6,000 Da) as a second dispersant were mixed in distilled water (H2O) solvent in the amounts shown in Table 1 below. A lab-scale conductive material dispersion was prepared by mixing using a high-shear mixer at a speed of 8,000 rpm for 3 hours.

[0208] (Preparation Method B) A commercial conductive material dispersion was prepared for a dispersant composition that showed a performance improvement effect in a lab-scale conductive material dispersion. Specifically, carbon nanotubes (SWCNT, length: 5 μm or more), carboxymethyl cellulose sodium salt (MW: 250,000 Da) as a first dispersant, and polyethylene oxide (PEO, MW: 6,000 Da) as a second dispersant were mixed in distilled water (H2O) solvent at the amounts shown in Table 1 below. After mixing at a speed of 3,000 rpm for 20 hours using a reverse-scrapping mixer, the dispersion was prepared by mixing at 60 Hz for 20 passes using a high-pressure homogenizer (bead mill).

[0209] Conductive material dispersions were prepared by changing the carbon nanotube, the first dispersant, and the second dispersant according to Table 1 below. In the case where the first dispersant in Table 1 below contains A-2, a conductive material dispersion was prepared by mixing at a speed of 8,000 rpm for 3 hours.

[0210] division carbon nanotubes First dispersant Second dispersant Content (weight%) type Content (weight%) type Content (weight%) Example 1 0.4 A-1 0.6 B-1 0.1 Example 2 0.4 A-1 0.6 B-1 0.2 Example 3 0.4 A-1 0.6 B-1 0.05 Example 4 0.4 A-1 0.6 B-1 0.01 Example 5 0.4 A-1 0.6 B-2 0.1 Example 6 0.4 A-1 0.6 B-3 0.1 Example 7 0.4 A-1 0.6 B-4 0.1 Example 8 0.4 A-1 0.6 B-4 0.05 Example 9 0.4 A-1 0.6 B-4 0.01 Example 10 0.4 A-1 0.6 B-5 0.1 Example 11 0.4 A-1 1.2 B-1 0.1 Example 12 0.4 A-1 0.3 B-1 0.1 Example 13 0.4 A-2 0.6 B-1 0.1 Example 14 0.4 A-2 0.6 B-4 0.1 Example 15 0.4 A-3 0.6 B-1 0.1 Example 16 0.4 A-4 0.6 B-1 0.1 Example 17 0.4 A-5 0.6 B-1 0.1 Comparative Example 1 0.4 A-1 0.6 - - Comparative Example 2 0.4 A-1 0.4 - - Comparative Example 3 0.4 A-2 0.6 - - Comparative Example 4 0.4 A-1 0.6 B-6 0.1 Comparative Example 5 0.4 A-1 0.6 B-7 0.1 Comparative Example 6 0.4 - - B-1 0.6 Comparative Example 7 0.4 - - B-4 0.6

[0211] The specific compounds in Table 1 above are as follows. A-1: ​​Carboxymethyl cellulose, MW: 250,000, Degree of substitution: 0.7

[0212] A-2: Carboxymethyl cellulose, MW: 110,000, Degree of substitution: 0.85

[0213] A-3: Carboxymethyl cellulose, MW: 600,000, Degree of substitution: 0.7

[0214] A-4: Carboxymethyl cellulose, MW: 250,000, Degree of substitution: 1.2

[0215] A-5: Carboxymethyl cellulose, MW: 250,000, Degree of substitution: 0.4

[0216] B-1: Polyethylene oxide, MW: 6,000

[0217] B-2: Polyethylene oxide, MW: 400

[0218] B-3: Polyethylene oxide, MW: 50,000

[0219] B-4: Pluronic F-127, MW: 12,500

[0220] B-5: Pluronic 10R5, MW: 2,000

[0221] B-6: SDBS(Sodium dodecylbenzene sulfonate), MW: 348

[0222] B-7: CTAB (Cetrimonium bromide), MW: 365

[0224] (2) Preparation of cathode slurry and preparation of film for electrode resistance evaluation

[0225] Cathode active material (SiOx, 0 <x<2) 96.3 중량부, 제1 바인더로서 카르복시 메틸셀룰로오스 1.5 중량부, 및 제2 바인더로서 스티렌-부타디엔 고무 2.0 중량부를 물(H2O) 용매에 첨가하였다. 믹서(Thinky 사, ARE-310)를 이용하여 1,000rpm으로 10분 동안 혼합하였다. 음극 활물질 및 바인더를 포함하는 슬러리에 실시예들 및 비교예들에서 제조된 도전재 분산액 0.25 중량부를 첨가하였다. 이 후, 믹서를 이용하여 1,000rpm으로 10분 동안 혼합하여 음극 활물질 슬러리를 얻었다. 음극 활물질 슬러리의 총 고형분은 90wt% 내지 98wt% 였다.

[0226] The cathode active material slurry was applied onto a PET substrate (thickness: 50 μm) using an applicator. Afterwards, 100 using an electric oven A cathode film for measuring sheet resistance with an average thickness of 100㎛ to 130㎛ (excluding PET substrate thickness) was obtained by drying for 1 hour.

[0228] Experimental Example

[0229] (1) Analysis of particle size in the conductive material dispersion

[0230] The particle size of the particles contained in the conductive material dispersion prepared according to the above examples and comparative examples was analyzed. Specifically, the conductive material dispersion was diluted 2,000 times using an aqueous solution (H2O). The particle size was calculated by measuring the difference in diffraction patterns according to particle size using a laser diffraction particle size analyzer (HORIBA LA-950V2) for the diluted conductive material dispersion solution. Dmin was measured as the smallest particle size in the measured volume-based particle size distribution curve, D50 was measured by calculating the particle diameter at the points where the volume fraction was 50% and 99.9%, and the particle size was evaluated according to the following criteria.

[0231] <Particle Size Evaluation Criteria>

[0232] ◎: Less than 60 µm based on D50 standard

[0233] ○: D50 standard 60 µm or more and less than 80 µm

[0234] △: 80 µm or more and less than 120 µm based on D50

[0235] ×: 120 µm or more based on D50 standard

[0237] (2) Measurement of viscosity of conductive material dispersion

[0238] The viscosity of the conductive material dispersions prepared according to the above examples and comparative examples was measured. Viscosity was measured using a rheometer (Antonparr equipment, equipped with Standard measuring system CC27 / T200 / SS Cylinder type, 25.0 ℃), with a shear rate of 96.2 s⁻¹. -1 It was verified based on .

[0240] (3) Electrode resistance evaluation

[0241] The electrode resistance of the cathode was measured according to the measuring equipment and conditions using the electrode resistance measuring film prepared according to the above examples and comparative examples.

[0242] Sheet resistance was measured on 6 points of the cathode film using equipment (Nitto Seiko Analytech, LORESTA-GX, MCP-T700) and the average value was calculated. The electrode resistance was calculated by multiplying the measured sheet resistance value by the film thickness.

[0244] (4) Storage stability evaluation

[0245] Storage stability was evaluated by calculating the change in Rheometer viscosity during the storage period through high-temperature acceleration experiments of the conductive material dispersions prepared in the examples and comparative examples.

[0246] For the conductive material dispersions prepared in the examples and comparative examples, the initial Rheometer viscosity was measured within 3 days after preparation.

[0247] After storing the conductive material dispersions prepared in the examples and comparative examples at a high temperature (50°C) for one week, the viscosity was measured using the same method as the initial viscosity measurement. The degree of change (viscosity change rate) between the initial viscosity and the viscosity measured after one week of high-temperature storage was calculated, and storage stability was evaluated according to the following criteria.

[0248] The viscosity change rate was calculated as shown in Equation 1 below.

[0249] [Equation 1]

[0250] Viscosity change rate (%) = (Initial viscosity of conductive material dispersion - Viscosity of conductive material dispersion after 1 week of high-temperature storage) / Initial viscosity of conductive material dispersion × 100

[0251] Storage Stability Evaluation Criteria

[0252] ◎: Viscosity change rate 5% or less

[0253] ○: Viscosity change rate exceeding 5% and 15% or less

[0254] △: Viscosity change rate exceeding 15% and 30% or less

[0255] ×: Viscosity change rate exceeding 30%

[0257] The measurement results of the particle size, viscosity, electrode resistance, and storage stability of the cathode slurry in the above conductive material dispersion are shown in Table 2 below.

[0258] division manufacturing method Entry to the island Viscosity (cP) of the dispersion Electrode resistance (Ω / cm) Storage stability Example 1 A ◎ 580 1.1 ◎ Example 2 A ◎ 550 1.5 ◎ Example 3 A ◎ 680 1.0 ◎ Example 4 A △ 750 0.85 ○ Example 5 A ○ 630 1.1 ○ Example 6 A △ 520 1.3 ○ Example 7 A ◎ 590 1.1 ◎ Example 8 A ○ 680 0.98 ◎ Example 9 A △ 720 0.86 △ Example 10 A ◎ 560 1.2 ○ Example 11 A ○ 750 1.3 ○ Example 12 A ○ 580 1.4 ○ Example 13 A ◎ 470 1.1 ◎ Example 14 A ◎ 460 1.1 ◎ Example 15 A △ 910 1.6 ◎ Example 16 A ○ 480 1.3 △ Example 17 A ○ 810 1.3 △ Comparative Example 1 A △ 820 0.75 △ Comparative Example 2 A △ 760 0.73 × Comparative Example 3 A ◎ 520 0.71 × Comparative Example 4 A × 680 2.4 × Comparative Example 5 A × 650 2.6 × Comparative Example 6 A ○ 380 3.5 △ Comparative Example 7 A ○ 400 3.8 × Example 1 B 3 μm 365 1.2 ◎ Comparative Example 1 B 15 μm 770 1.4 △

[0259] Referring to Table 2, it was confirmed that the particle size and viscosity of the particles in the conductive material dispersion according to the examples were reduced, thereby improving dispersibility. In addition, storage stability was improved by reducing the rate of change in viscosity, and the electrode resistance of the cathode prepared with the cathode slurry composition containing the conductive material dispersion was reduced. According to the comparative examples, it was confirmed that the particle size of the particles in the conductive material dispersion increased, and the viscosity of the anode slurry composition increased, causing the conductive materials to aggregate. In addition, storage stability was low due to the high rate of change in viscosity, and the electrode resistance of the cathode prepared with the cathode slurry composition containing the conductive material dispersion increased.

[0260] When comparing the commercially available conductive material dispersion prepared according to Method B, the conductive material dispersion according to the example has low particle size, viscosity, and viscosity change rate, and the electrode resistance of the cathode prepared therefrom was reduced. However, the conductive material dispersion according to the comparative example has high particle size, viscosity, and viscosity change rate, and the electrode resistance of the cathode prepared therefrom was increased. Accordingly, the compatibility of the conductive material dispersions according to the examples was confirmed.

[0261] In Example 4, where the content of the second dispersant was relatively low, the particle size increased relatively, and the viscosity of the conductive material dispersion increased relatively.

[0262] In Example 6, where the molecular weight of the second dispersant was relatively high, the particle size increased relatively and the electrode resistance increased.

[0263] In Example 9, where a different type of second dispersant was used but the content was relatively low, the particle size increased relatively. In addition, the viscosity of the conductive material dispersion increased relatively, and the storage stability decreased relatively.

[0264] In Example 15, where the molecular weight of the first dispersant was relatively high, the particle size increased relatively. In addition, the viscosity of the conductive material dispersion increased, and the electrode resistance increased.

[0265] In Example 16, which used a first dispersant with a relatively high degree of substitution, the storage stability of the conductive material dispersion was relatively reduced.

[0266] In Example 17, which used a first dispersant with a relatively low degree of substitution, the viscosity of the conductive material dispersion increased and storage stability was relatively reduced. Explanation of the symbols

[0268] 100: Anode 105: Anode current collector 107: Anode Lead 110: Anode Active Material Layer 120: Cathode active material layer 125: Cathode current collector 127: Cathode Lead 130: Cathode 140: Separator 150: Electrode assembly 160: Case

Claims

Claim 1 A conductive material dispersion comprising: a conductive material including carbon nanotubes; a first dispersant; and a second dispersant, wherein the first dispersant is a cellulose-based polymer and the second dispersant is a polyethylene oxide-based polymer, and the weight ratio of the second dispersant to the first dispersant included in the conductive material dispersion is 0.05 to 0.

5. Claim 2 A conductive material dispersion according to claim 1, wherein the content of the conductive material is 0.2% to 8.0% by weight of the total weight of the conductive material dispersion. Claim 3 A conductive material dispersion according to claim 1, wherein the content of the first dispersant is 50 to 400 parts by weight per 100 parts by weight of the conductive material. Claim 4 A conductive material dispersion according to claim 1, wherein the content of the second dispersant is 10 to 100 parts by weight per 100 parts by weight of the conductive material. Claim 5 delete Claim 6 A conductive material dispersion according to claim 1, wherein the weight-average molecular weight (MW) of the first dispersant is 75,000 to 400,000. Claim 7 A conductive dispersion according to claim 1, wherein the average value of the number of hydroxyl groups substituted by an alkyl group or an acyl group among three hydroxyl groups per glucose unit of the cellulose-based polymer of the first dispersant is 0.5 to 1.

0. Claim 8 A conductive material dispersion according to claim 1, wherein the second dispersant comprises polyethylene oxide, or a copolymer of polyethylene oxide and polypropylene oxide. Claim 9 The conductive material dispersion of claim 1, wherein the second dispersant comprises an ethylene oxide repeating unit and a repeating unit represented by the following chemical formula 1: [Chemical Formula 1] . Claim 10 The conductive material dispersion of claim 1, wherein the second dispersant comprises one or more polymers represented by the following chemical formulas 2 to 4: [Chemical Formula 2] [Chemical Formula 3] [Chemical Formula 4] (In Chemical Formula 2, a is an integer from 5 to 500; in Chemical Formula 3, R1 is an alkyl group or alkylene group having 1 to 5 carbon atoms, b, c, and d are each integers from 5 to 150; in Chemical Formula 4, R2 and R3 are each independently an alkyl group or alkylene group having 1 to 5 carbon atoms, and e, f, and g are each integers from 5 to 150). Claim 11 A conductive material dispersion according to claim 1, wherein the weight-average molecular weight (MW) of the second dispersant is 500 to 30,000. Claim 12 A conductive material dispersion according to claim 1, wherein the viscosity change rate is 15% or less. Claim 13 A conductive material dispersion according to claim 1, further comprising an aqueous solvent. Claim 14 An electrode slurry comprising a conductive material dispersion according to claim 1. Claim 15 An electrode for a lithium secondary battery comprising an electrode active material layer formed from an electrode slurry according to claim 14; and a lithium secondary battery comprising a counter electrode facing the electrode for the lithium secondary battery.

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