Conductive material dispersion liquid, electrode, and lithium secondary battery

Abstract

The present invention relates to a conductive material dispersion comprising single-walled carbon nanotube (SWCNT) clusters, in which the SWCNT clusters have a number average length of 0.8 [mu] m to 8.0 [mu] m, and SWCNT clusters having a length greater than 10 [mu] m account for 15% or less of the total number, SWCNT clusters having a number average diameter of 5 nm to 30 nm, and SWCNT clusters having a diameter greater than 30 nm account for 15% or less of the total number, and the length and diameter of the SWCNT clusters are measured using an atomic force microscope (AFM), and the present invention relates to an electrode comprising the SWCNT clusters, which can ensure excellent conductivity even in a small amount due to excellent dispersibility and satisfactory generation of a conductive network, which can be easily produced due to low viscosity of a dispersion liquid, which has excellent processability. And when the conductive material dispersion liquid is applied to an electrode, the performance of the battery is improved.

Description

Technical Field

[0001] The present invention relates to a conductive material dispersion liquid including SWCNT clusters having finite length and diameter characteristics, and an electrode and a lithium secondary battery using the dispersion liquid. Background Art

[0002] Due to the rapid increase in the use of fossil fuels, the demand for the use of alternative energy or clean energy is increasing, and as a part of this, the most actively conducted research field is the field of power generation and storage using electrochemical reactions.

[0003] At present, a representative example of an electrochemical element using electrochemical energy may be a secondary battery, and increasingly, its use field is expanding. Recently, with the technological development and increase in demand for portable devices such as portable computers, mobile phones, and cameras, the demand for secondary batteries as power sources is rapidly increasing, and among secondary batteries, many studies have been conducted on lithium secondary batteries having high energy density (i.e., having high capacity), and lithium secondary batteries have also been commercialized and widely used.

[0004] The electrodes of secondary batteries include an electrode active material, a conductive material, and a binder. In order to improve the conductivity of the electrode, carbon nanotubes can be used as a conductive material, and in particular, when carbon nanotubes with a large specific surface area are used, the effect of improving conductivity is excellent even in a small amount.

[0005] When single-walled carbon nanotubes (SWCNTs) are used as carbon nanotubes, the resistance of the electrode can be further reduced, and due to their relatively large specific surface area, conductivity is easily ensured even in small amounts. In order to uniformly distribute the SWCNTs in the electrode, a conductive material dispersion containing the SWCNTs is pre-formed, and then the conductive material dispersion is used to prepare an electrode slurry during electrode preparation.

[0006] However, single-walled carbon nanotubes have the following problems: the improvement of battery performance varies significantly depending on dispersibility and intrinsic properties, and also have the following problems: the expected dispersibility based on the value measured from the conductive material dispersion does not directly correlate with the distribution in the electrode, resulting in differences in evaluation.

[0007] Therefore, in order to use single-walled carbon nanotubes as conductive materials for electrodes, it is necessary to study conductive material dispersions that have excellent properties in the form of dispersions and whose properties can be reflected in electrodes. Therefore, the performance of electrodes can be intuitively predicted by evaluating the dispersions. Summary of the Invention

[0008] Technical issues

[0009] An object of the present invention is to provide a conductive material dispersion liquid in which single-walled carbon nanotube (SWCNT) clusters, which are aggregates of single-walled carbon nanotubes having relatively small length and small diameter, are used, the proportion of SWCNT clusters having large length and large diameter being minimized, and SWCNT clusters characterized by having a wide distribution of number average length and number average diameter are used among the SWCNT clusters having relatively small length and small diameter, thereby achieving excellent dispersibility, low viscosity, and excellent processability.

[0010] Another object of the present invention is to provide an electrode which, when a conductive material dispersion is applied to the electrode, has excellent resistance characteristics due to a well-produced conductive network.

[0011] Another object of the present invention is to provide a lithium secondary battery including an electrode having excellent conductivity and retention performance and thus having low resistance, excellent output, and improved lifespan.

[0012] Technical Solution

[0013] [1] An embodiment of the present invention provides a conductive material dispersion including single-walled carbon nanotube (SWCNT) clusters, wherein the SWCNT clusters have a number average length of 0.8 μm to 8.0 μm, and SWCNT clusters having a length greater than 10 μm account for 15% or less of the total number, the SWCNT clusters have a number average diameter of 5 nm to 25 nm, and SWCNT clusters having a diameter greater than 30 nm account for 15% or less of the total number, and the length and diameter of the SWCNT clusters are measured using an atomic force microscope (AFM).

[0014] [2] In the above [1], the SWCNT cluster may have a number average length of 1.0 μm to 6.0 μm.

[0015] [3] In the above [1] and / or [2], in the SWCNT cluster, single-walled carbon nanotubes having a number average length greater than 10 μm may account for 10% or less of the total.

[0016] [4] In at least one of the above [1] to [3], the SWCNT cluster may have a number average diameter of 7 nm to 20 nm.

[0017] [5] In at least one of the above [1] to [4], SWCNT clusters having a diameter greater than 30 nm may account for 10% or less of the total.

[0018] [6] In at least one of the above [1] to [5], the conductive material dispersion further includes a dispersant, and the dispersant may include one or more selected from the group consisting of polyacrylate, polyvinylidene fluoride (PVDF), polyvinylpyrrolidone (PVP), polyvinyl alcohol (Polyvinylalchol), polyacrylamide (Polyacrylamide), polyethylene oxide (Polyethyleneoxide), carboxymethyl cellulose (CMC), and diisopropylamine (DIPA).

[0019] [7] In the above [6], the SWCNT cluster may be included in an amount of 0.2 to 3.5 parts by weight, and the dispersant may be included in an amount of 0.2 to 7.0 parts by weight, based on 100 parts by weight of the conductive material dispersion.

[0020] [8] Another embodiment of the present invention provides an electrode comprising an electrode active material layer, the electrode active material layer comprising an electrode active material disposed on a current collector, single-walled carbon nanotube (SWCNT) clusters, and a binder, wherein the SWCNT clusters have a number average length of 0.8 μm to 8.0 μm, and SWCNT clusters having a length greater than 10 μm account for 15% or less of the total number, the SWCNT clusters have a number average diameter of 5 nm to 30 nm, and SWCNT clusters having a diameter greater than 30 nm account for 15% or less of the total number, and the length and diameter of the SWCNT clusters are measured using an atomic force microscope (AFM).

[0021] [9] In the above [8], the electrode active material may be a positive electrode active material, and the positive electrode active material may include one or more selected from the group consisting of lithium nickel ternary oxide, lithium-rich manganese-based oxide, lithium iron-based phosphate, lithium nickel oxide, lithium cobalt oxide, and lithium manganese oxide.

[0022]

[10] In the above [8] and / or [9], the electrode active material may be a negative electrode active material, and the negative electrode active material may include one or more selected from the group consisting of carbon-based particles, silicon-based particles, and carbon-silicon-based composite particles.

[0023]

[11] In at least one of the above [8] to

[10] , the electrode may further include a dot-shaped conductive material, and the dot-shaped conductive material may include carbon black.

[0024]

[12] Another embodiment of the present invention provides a lithium secondary battery having a structure in which a positive electrode, a separator, and a negative electrode are stacked in this order, and at least one of the positive electrode and the negative electrode is the aforementioned electrode.

[0025] Beneficial effects

[0026] The conductive material dispersion according to the present invention may include SWCNT clusters having unique length and diameter characteristics and thus may have excellent dispersibility and low viscosity, and due to small change in viscosity over time, storage stability may be excellent and thus processability may be improved.

[0027] Therefore, by applying SWCNT clusters with the above-mentioned properties to electrode slurries, phase stability of the slurry can be achieved. Due to their excellent dispersibility, conductivity can be fully ensured even in small amounts, enabling the realization of electrodes with excellent resistance properties. Furthermore, as described above, by applying electrodes with excellent resistance properties, the output of lithium secondary batteries can be improved, and not only a good conductive network is generated, but also excellent performance is maintained, thereby contributing to improved lifespan of lithium secondary batteries. DETAILED DESCRIPTION

[0028] It is to be understood that the words or terms used in the specification and claims should not be interpreted as the meanings defined in commonly used dictionaries, and it is to be further understood that, based on the principle that the inventor can appropriately define the meanings of words or terms to best interpret the present invention, the words or terms should be interpreted as having a meaning consistent with their meaning in the context of the relevant art and the technical idea of ​​the present invention.

[0029] It will also be understood that when used in this specification, the terms "comprising", "providing", "having", etc. specify the presence of stated features, integers, steps, elements, or a combination thereof, but do not preclude the presence or addition of one or more other features, integers, steps, elements, or a combination thereof.

[0030] In this specification, the cumulative volume average particle size D 50 and D 90 D can be defined as the particle size corresponding to the 50% and 90% cumulative volume in the particle size distribution curve. D can be measured using, for example, a laser diffraction method. 50 and D 90 Laser diffraction can generally measure particle sizes ranging from submicron to several millimeters, and can obtain highly reproducible and resolvable results.

[0031] In the present specification, the ratio of the number average length to the length greater than 10 μm and the ratio of the number average diameter to the diameter greater than 30 nm of the carbon nanotubes can be derived from the number cumulative length and diameter distribution obtained by calculating the lengths and diameters of 400 or more carbon nanotubes from images measured at 20 μm×20 μm, 15 μm×15 and / or 10 μm×10 μm using an atomic force microscope (Atomic Force Microscopy, AFM) (Asylum Research, Cypher ES AFM System) at a set point of 0.4 V and a scan rate of 1.5 Hz in AC air topography mode (tapping mode).

[0032] In this specification, a cluster may refer to a form of aggregation in which a plurality of units are bonded to each other, and a single-walled carbon nanotube (SWCNT) cluster may refer to an aggregate or cohesion in the form of fibers in which a plurality of SWCNT units are bonded to each other.

[0033] Hereinafter, the present invention will be described in detail.

[0034] In this specification, the conductive material dispersion, the electrode, and the lithium secondary battery may each include one or more of technical characteristics and / or technical components to be described below, and the technical characteristics and / or technical components may have various types of combinations.

[0035] Conductive material dispersion

[0036] The conductive material dispersion according to an embodiment of the present invention includes single-walled carbon nanotube (SWCNT) clusters, and the SWCNT clusters have a number average length of 0.8 μm to 8.0 μm, and SWCNT clusters having a length greater than 10 μm account for 15% or less of the total number, and the SWCNT clusters have a number average diameter of 5 nm to 25 nm, and SWCNT clusters having a diameter greater than 30 nm account for 15% or less of the total number, and the length and diameter of the SWCNT clusters are measured using an atomic force microscope (AFM).

[0037] (1) Single-walled carbon nanotubes

[0038] Carbon nanotubes (CNTs) consist of cylindrical graphite sheets with nanometer-sized diameters and an sp2-bonded structure. Depending on the angle and structure of the rolled graphite sheets, they exhibit either conductive or semiconducting properties. Depending on the number of walls formed by the bonds, CNTs can be categorized as single-walled carbon nanotubes (SWCNTs), double-walled carbon nanotubes (DWCNTs), and multi-walled carbon nanotubes (MWCNTs).

[0039] According to an embodiment of the present invention, the conductive material dispersion includes SWCNT clusters that are aggregates of single-walled carbon nanotubes (SWCNTs). Since single-walled carbon nanotubes have a larger specific surface area than multi-walled carbon nanotubes, electrical conductivity can be fully ensured even when added in small amounts, and therefore, the reduction in electrode resistance can be greatly increased. However, in the case of single-walled carbon nanotubes, excellent length characteristics are required in order to maximize the advantage of easily ensuring electrical conductivity using only a small amount. However, length characteristics are not easy to measure accurately, and the expected level of electrical conductivity improvement is usually not reflected in this way. In addition, despite having excellent length characteristics, if excessive, there is a problem that the viscosity of the dispersion and even the viscosity of the slurry may be affected.

[0040] Therefore, the present inventors provide a conductive material dispersion including SWCNT clusters having limited length and diameter and unique characteristics, in which excellent dispersibility can be ensured without increasing the viscosity of the dispersion and the ability to form a conductive path in an electrode can be intuitively predicted by measured values.

[0041] According to an embodiment of the present invention, the SWCNT clusters included in the conductive material dispersion are characterized by having a number average length of 0.8 μm to 8.0 μm, and include SWCNT clusters having a length greater than 10 μm in a proportion of less than 15% of the total number, and the ratio of the number average length of the SWCNT clusters to the number of SWCNT clusters having a length greater than 10 μm can be derived from the number distribution obtained by measurement using the previously described atomic force microscope.

[0042] SWCNT clusters having a number average length satisfying an appropriate level within the range of 0.8 μm to 8.0 μm may be characterized by excluding SWCNT clusters having a large length greater than 10 μm. In addition, SWCNT clusters may be characterized by being able to well maintain the resulting conductive network despite volume expansion of the electrode during charge and discharge cycles within the range satisfying the number average length.

[0043] According to an embodiment of the present invention, the number average length of the SWCNT cluster may be 0.8 μm to 8.0 μm, preferably 0.9 μm or more, 1.0 μm or more, 1.1 μm or more, 1.2 μm or more, 1.3 μm or more, 1.4 μm or more, or 1.5 μm or more, and 7.8 μm or less, 7.5 μm or less, 7.0 μm or less, 6.5 μm or less, 6.0 μm or less, 5.5 μm or less, 5.0 μm or less, 4.5 μm or less, or 4.0 μm or less. When the number average length is less than 0.8 μm, the length may be too short to easily maintain the connection path of the conductive network due to the volume change of the electrode caused by charging and discharging. In addition, when the number average length is greater than 8.0 μm, the viscosity of the dispersion may increase, the number of SWCNT clusters per unit weight may decrease, and the distribution in the electrode may become uneven.

[0044] Furthermore, according to embodiments of the present invention, the SWCNT clusters may be characterized in that SWCNT clusters having a length greater than 10 μm account for 15% or less of the total number, and preferably, 13% or less, 11% or less, 10% or less, or 9% or less. Once the proportion of SWCNT clusters having a length greater than 10 μm exceeds 15%, the viscosity of the dispersion may not be controlled, and even if the dispersion conditions are controlled to achieve uniform dispersion, the likelihood of viscosity variations becoming more severe over time may rapidly increase. Furthermore, the greater the number of SWCNT clusters having a longer length, the more difficult it is to achieve uniform distribution in the electrode. Furthermore, since there is a high probability that the predicted fixed conductivity measured on the dispersion liquid will not be intuitively reflected in the electrode state, it is necessary to precisely control the number of SWCNT clusters having a length greater than 10 μm.

[0045] According to an embodiment of the present invention, the SWCNT clusters included in the conductive material dispersion may be characterized in that the number average diameter is 7 nm to 20 nm, and the SWCNT clusters having a diameter greater than 30 nm account for 10% or less of the total number, and the ratio of the number average diameter of the SWCNT clusters to the number of SWCNT clusters having a diameter greater than 30 nm may be derived from the number distribution obtained by the atomic force microscopy measurement described previously.

[0046] The SWCNT clusters having a number average diameter at an appropriate level satisfying the range of 7 nm to 20 nm may be characterized by excluding excessive inclusion of SWCNT clusters having a large diameter greater than 30 nm, and in addition, the SWCNT clusters may be characterized by being able to well maintain the generated conductive network despite the volume expansion of the electrode during charge and discharge cycles within the range satisfying the number average diameter.

[0047] According to an embodiment of the present invention, the number average diameter of the SWCNT cluster may be 7 nm to 20 nm, preferably 8 nm or more, 9 nm or more, 10 nm or more, 11 nm or more, or 12 μm or more, and 19 nm or less, 18 nm or less, 17 nm or less, 16 nm or less, or 15 nm or less. When the number average diameter is less than 7 nm, the diameter is too small, so that the SWCNT cluster may be easily damaged during charging and discharging, and short circuit problems may occur due to volume expansion, etc., making it difficult to maintain a conductive network connection path. In addition, when the number average diameter is greater than 20 nm, the viscosity of the dispersion increases and the number of SWCNT clusters per unit weight decreases, and due to improper dispersion, a problem of uneven distribution in the electrode may occur, which may act as an element that hinders lithium ion mobility when bound to the surface of the active material.

[0048] According to embodiments of the present invention, SWCNT clusters may be characterized in that SWCNT clusters having a length greater than 30 nm account for 10% or less of the total number, and preferably, 9% or less, 8% or less, or 7% or less. Once the proportion of SWCNT clusters having a diameter greater than 30 nm exceeds 10%, the viscosity of the dispersion may not be controlled, and even if the dispersion conditions are controlled to achieve uniform dispersion, the likelihood of viscosity variation becoming more severe over time may rapidly increase. Furthermore, the greater the number of SWCNT clusters having large diameters, the more difficult it is to achieve uniform distribution in the electrode. Furthermore, due to the high likelihood of acting as an element that hinders lithium ion mobility as described above, the number of SWCNT clusters having a diameter greater than 30 nm needs to be precisely controlled.

[0049] Generally, in the case of a conductive material dispersion including carbon nanotubes, the cumulative volume average particle size (D 50 and / or D 90 ) is used to predict the formation and uniform distribution of conductive paths in the electrode, but the particle size distribution in this state of the dispersion may not reflect the length and diameter of the actual carbon nanotubes or their aggregates, so that the performance of the electrode may vary even when the same particle size distribution is applied. However, the length and diameter characteristics obtained by accumulating the length and diameter distribution by the number of atomic force microscope images according to an embodiment of the present invention can have basically the same dispersion state and conductive network formation in the electrode, which can more effectively and intuitively act on the improvement of electrode performance.

[0050] According to an embodiment of the present invention, based on 100 parts by weight of the conductive material dispersion, the SWCNT cluster can be included in an amount of 0.2 to 3.5 parts by weight, and in particular, can be included in an amount of 0.2 to 3.0 parts by weight. When the amount falls within the above range, the transfer and input of the electrode slurry are easy while maintaining high productivity. In addition, since the solid content of the electrode slurry to be prepared is not too low, the occurrence of binder migration can be suppressed when the electrode is dried. Therefore, the adhesion of the electrode can be improved, and the compaction (packing) of the electrode active material layer can be effectively carried out, so that an electrode with a small thickness can be prepared.

[0051] (2) Dispersant

[0052] The conductive material dispersion according to an embodiment of the present invention may further include a dispersant, and the dispersant may include one or more selected from the group consisting of polyacrylate, polyvinylidene fluoride (PVDF), polyvinylpyrrolidone (PVP), polyvinyl alcohol (PVA), polyacrylamide (PVA), polyethylene oxide (PEO), hydrogenated nitrile copolymer, cellulose-based compound, and diisopropylamine (DIPA). Here, the hydrogenated nitrile copolymer may be hydrogenated acrylonitrile-butadiene rubber, and the cellulose-based compound may be carboxymethyl cellulose (CMC) or hydroxyethyl cellulose (HEC).

[0053] In addition, the dispersant may be included in an amount of 0.2 to 7.0 parts by weight, particularly 0.2 to 6.0 parts by weight, and more particularly 0.3 to 5.0 parts by weight, based on 100 parts by weight of the conductive material dispersion. When the amount falls within the above range, the carbon-based conductive material can be smoothly dispersed in the conductive material dispersion, and the energy density of the electrode to be prepared can be improved, and the resistance can be reduced.

[0054] (3) Solvent

[0055] According to an embodiment of the present invention, the conductive material dispersion may further include a solvent, which may include water or an organic solvent, and the organic solvent may include any one or two or more heteroatoms selected from the group consisting of nitrogen atoms (N) and oxygen atoms having unshared electron pairs.

[0056] In particular, the organic solvent may be an amide-based polar organic solvent, including dimethylformamide (DMF), diethylformamide, dimethylacetamide (DMAc), N-methylpyrrolidone (NMP), etc.; an alcohol, including methanol, ethanol, 1-propanol, 2-propanol (isopropanol), 1-butanol (n-butanol), 2-methyl-1-propanol (isobutanol), 2-butanol (sec-butanol), 1-methyl-2-propanol (tert-butanol), pentanol, hexanol, heptanol, or octanol; a diol, including ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, 1,3-propylene glycol, 1,3-butanediol, 1,5-pentanediol, or hexanediol. Glycols; polyols including glycerol, trimethylolpropane, pentaerythritol, or sorbitol; glycol ethers including ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, triethylene glycol monomethyl ether, tetraethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monoethyl ether, triethylene glycol monoethyl ether, tetraethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, or tetraethylene glycol monobutyl ether; ketones including acetone, methyl ethyl ketone, methyl propyl ketone, or cyclopentanone; and esters including ethyl acetate, γ-butyrolactone, and ε-propiolactone, and any one of them or a mixture of two or more of them can be used. N-methylpyrrolidone (NMP) is particularly preferred in view of compatibility with the electrode slurry.

[0057] (4) Others

[0058] According to an embodiment of the present invention, the solids content of the conductive material dispersion can be included in an amount of 0.3% to 7.0% by weight, particularly 0.4% to 5.0% by weight, and more particularly 0.5% to 3.5% by weight. When the content falls within this range, the viscosity of the conductive material dispersion can be maintained at a low level, and the conductive material dispersion can also be effectively dispersed. In this case, the solids can guide the SWCNT clusters and dispersant contained in the conductive material dispersion.

[0059] The conductive material dispersion of the present invention comprising the above components can be prepared by mixing SWCNT clusters, a dispersant, and a solvent. In this case, mixing can be performed by a general mixing method, in particular by using a mixing instrument such as a homogenizer, a bead mill, a ball mill, a basket mill, a grinder, a universal stirrer, a transparent mixer, a spike mill, or a TK mixer, and the order in which the components are mixed is not particularly limited. That is, the conductive material dispersion according to the present invention can be formed by adding single-walled carbon nanotubes (for example, in a large bundle state in a micro unit) to a solvent, then adding a dispersant and mixing, or by first adding a dispersant to a solvent and then mixing the single-walled carbon nanotube bundles. It can also be formed by adding the single-walled carbon nanotube bundles and a dispersant together to a solvent and then mixing.

[0060] During the mixing process, a cavitation dispersion process can also be performed to increase the dispersibility of the single-walled carbon nanotube bundles. This cavitation dispersion process uses shock waves generated by the collapse of vacuum bubbles in water when high energy is applied to the liquid. This method allows the single-walled carbon nanotubes to be dispersed within the SWCNT clusters without compromising their properties. Specifically, the cavitation dispersion process can be performed using ultrasonic waves, jet milling, or shear dispersion.

[0061] According to an embodiment of the present invention, the conductive material dispersion may further include a dot-shaped conductive material. The conductive material that may be further included may have properties different from those of the previously described SWCNT clusters, and preferably, the shape properties may be different from each other. In the case of including a conductive material having similar shape properties (for example, a linear conductive material such as multi-walled carbon nanotubes or carbon nanofibers), the formation of a conductive network using the previously described properties of the SWCNT clusters may be affected.

[0062] For example, the dot-shaped conductive material may include carbon black, and the carbon black may include one or more selected from the group consisting of acetylene black, Kejten black, channel black, furnace black, lamp black, and thermal black.

[0063] electrode

[0064] Another embodiment of the present invention provides an electrode, wherein an electrode active material layer including an electrode active material, single-walled carbon nanotube (SWCNT) clusters, and a binder is disposed on a current collector, the SWCNT clusters having a number average length of 0.8 μm to 8.0 μm, and SWCNT clusters having a length greater than 10 μm account for 15% or less of the total number, the SWCNT clusters having a number average diameter of 5 nm to 30 nm, and SWCNT clusters having a diameter greater than 30 nm account for 15% or less of the total number, and the length and diameter of the SWCNT clusters are measured using an atomic force microscope (AFM).

[0065] At this time, as described above, the SWCNT cluster is a SWCNT cluster contained in the conductive material dispersion according to the present invention, and since the content thereof is the same as above, the detailed description will be omitted, and other components will be described below.

[0066] According to an embodiment of the present invention, the electrode active material may be a positive electrode active material, the electrode may be a positive electrode, and the positive electrode may include a positive electrode collector and a positive electrode active material layer formed on the positive electrode collector and including the positive electrode active material.

[0067] In the positive electrode, the positive electrode current collector is not particularly limited as long as it does not cause chemical changes in the relevant battery and has conductivity. 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 as the positive electrode current collector.

[0068] The positive electrode current collector may generally have a thickness of 3 μm to 500 μm, and may preferably have a thickness of 300 μm or less, 200 μm or less, 100 μm or less, or 80 μm or less. The current collector may also have microscopic random bodies on its surface to enhance the binding force with the positive electrode active material. For example, the current collector may be used in various forms including films, sheets, foils, nets, porous bodies, foams, non-woven fibrous bodies, and the like.

[0069] The positive electrode active material may be a commonly used positive electrode active material. In particular, the positive electrode active material may include a layered compound including lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), or a compound substituted with one or more transition metals; lithium iron oxide such as LiFe3O4; 1+c1 Mn 2-c1 Lithium manganese oxides represented by chemical formulas such as LiMnO4 (0≤c1≤0.33), LiMnO3, LiMn2O3, and LiMnO2; lithium copper oxides (Li2CuO2); vanadium oxides including LiV3O8, V2O5, Cu2V2O7, etc.; Ni-rich layered lithium nickel oxides or those represented by chemical formulas LiNi 1-c2 M c2 Lithium nickel ternary oxide represented by O2 (wherein M is at least one selected from the group consisting of Co, Mn, Al, Cu, Fe, Mg, B, and Ga, and satisfies 0.01≤c2≤0.3); ... 2-c3 M c3 Lithium manganese composite oxide represented by Li2Mn3MO8 (wherein M is at least one selected from the group consisting of Co, Ni, Fe, Cr, Zn, and Ta, and satisfies 0.01≤c3≤0.1) or Li2Mn3MO8 (wherein M is at least one selected from the group consisting of Fe, Co, Ni, Cu, and Zn); and LiMn2O4 in which some Li is replaced by alkaline earth metal ions, but embodiments of the present invention are not limited thereto. The positive electrode may also be Li metal.

[0070] Preferably, the positive electrode active material may include one or more selected from the group consisting of lithium nickel ternary oxide, lithium-rich manganese-based oxide, lithium iron-based phosphate, lithium nickel oxide, lithium cobalt oxide, and lithium manganese oxide.

[0071] The positive active material layer may include a positive conductive material and a positive binder together with the previously described positive active material.

[0072] At this time, as the positive electrode conductive material, the conductive material dispersion described previously can be applied, and in addition to the conductive material dispersion, any conductive material that provides conductivity to the electrode can be further included and can be used without particular limitation as long as it does not cause chemical changes in the battery and conducts electrons.

[0073] Specific examples may be graphite, such as natural graphite or artificial graphite; carbon black, including acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, etc.; fibrous carbon materials, including carbon nanotubes, carbon nanofibers, carbon fibers, etc.; metal powders or fibers, including copper, nickel, aluminum, silver, etc.; conductive whiskers, including zinc oxide, potassium titanate, etc.; conductive metal oxides, such as titanium oxide; or conductive polymers, such as polyphenylene derivatives, and any one of them may be used alone or as a mixture of two or more thereof.

[0074] In addition, the positive electrode binder can be used to improve the adhesion between the positive electrode active material particles and the adhesion between the positive electrode active material and the positive electrode current collector. Specific examples may include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, or various copolymers thereof, and any one of them may be used alone or as a mixture of two or more thereof.

[0075] According to an embodiment of the present invention, the electrode active material may be a negative electrode active material, the electrode may be a negative electrode, and the negative electrode may include a negative electrode collector and a negative electrode active material layer formed on the negative electrode collector and including the negative electrode active material.

[0076] The negative electrode current collector is not particularly limited as long as it does not cause chemical changes to the battery and has high conductivity, and for example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, or copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., aluminum-cadmium alloy, etc. can be used.

[0077] The negative electrode current collector may generally have a thickness of 3 μm to 500 μm, and may preferably have a thickness of 300 μm or less, 200 μm or less, 100 μm or less, or 80 μm or less. The current collector may also have microscopic random bodies on its surface to enhance the binding force with the negative electrode active material. For example, the negative electrode current collector may be used in various forms including films, sheets, foils, nets, porous bodies, foams, non-woven fiber bodies, and the like.

[0078] Compounds that can reversibly intercalate and deintercalate lithium can be used as negative electrode active materials. Specific examples can be carbon-based materials, including artificial graphite, natural graphite, graphitized carbon fibers, amorphous carbon, etc.; (semi-)metal-based compounds that can be alloyed with lithium, including Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloys, Sn alloys, or Al alloys; (semi-)metal oxides that can be doped or dedoped with lithium, such as SiOv (0<v≤2), SnO2, vanadium oxide, and lithium vanadium oxide; or composite materials comprising metal-based compounds and carbon-based materials, such as Si-C composite materials or Sn-C composite materials, and any one of them or a mixture of two or more of them can be used. In addition, metallic lithium thin films can also be used as negative electrode active materials. In addition, for carbon materials, low-crystalline carbon, high-crystalline carbon, etc. can be used. Representative examples of low-crystalline carbon include soft carbon and hard carbon, and representative examples of high-crystalline carbon include non-shaped, plate-shaped, flaky, spherical, or fibrous natural graphite or artificial graphite, Kish graphite, pyrolytic carbon, mesophase pitch based carbon fiber, meso-carbon microbeads, mesophase pitches, high-temperature calcined carbon such as petroleum or coal tar pitch derived cokes, and the like.

[0079] For example, the negative electrode active material may include one or more selected from the group consisting of carbon-based particles, silicon-based particles, and carbon-silicon-based composite particles. In addition, the negative electrode active material may preferably include a silicon-based active material, and for example, Si particles, SiOv (0 < v ≤ 2), or Si-C composite materials.

[0080] Based on the total solid content in the negative electrode slurry, the negative electrode active material may be contained in an amount of 70% to 99% by weight, 75% by weight or more, 80% by weight or more, 85% by weight or more, 90% by weight or more, or 95% by weight or more, and 99.0% by weight or less, 98.5% by weight or less, 98.0% by weight or less, or 97.5% by weight or less. When the amount of the negative electrode active material falls within the above range, excellent energy density, electrode adhesion, and electrical conductivity can be achieved.

[0081] The binder is used to ensure the bonding force between the electrode active materials or between the electrode active material and the current collector, and the binder commonly used in the related art can be used, and the type is not particularly limited. The example of the binder can include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile (polyacrylonitrile), carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber or its various copolymers, and any one can be used alone or a mixture of two or more thereof.

[0082] Based on the total solid content in the negative electrode slurry, the binder may be contained in an amount of 10.0 wt % or less, preferably 0.5 wt % or more, 1.0 wt % or more, 1.5 wt % or more, or 2.0 wt % or more, and in an amount of 9.0 wt % or less, 8.0 wt % or less, 7.0 wt % or less, or 5.0 wt % or less. When the binder content falls within the above range, excellent electrode adhesion can be achieved while minimizing the increase in electrode resistance.

[0083] At this time, as the negative electrode conductive material, the conductive material dispersion described previously can be applied, and in addition to the conductive material dispersion, any conductive material that provides conductivity to the electrode can be further included and can be used without particular limitation as long as it does not cause chemical changes in the battery and conducts electrons.

[0084] Specific examples may be graphite, such as natural graphite or artificial graphite; carbon black, including acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, etc.; fibrous carbon materials, including carbon nanotubes, carbon nanofibers, carbon fibers, etc.; metal powders or fibers, including copper, nickel, aluminum, silver, etc.; conductive whiskers, including zinc oxide, potassium titanate, etc.; conductive metal oxides, such as titanium oxide; or conductive polymers, such as polyphenylene derivatives, and any one of them may be used alone or as a mixture of two or more thereof.

[0085] Meanwhile, the electrode active material layer may be formed by applying an electrode slurry in which an electrode active material, a binder, and a conductive material dispersion including SWCNT clusters are dispersed in a solvent on a current collector, followed by drying and performing a rolling process.

[0086] In particular, the electrode active material layer can be formed by applying the electrode slurry to the electrode collector and then drying it, or by applying the electrode slurry to a separate support and then laminating the film separated from the support onto the electrode collector. If necessary, a rolling process can be further performed after the electrode active material layer is formed by the above method. At this time, taking into account the properties of the electrode to be finally prepared, drying and rolling can be performed under appropriate conditions and are not particularly limited.

[0087] The electrode slurry may further include a solvent for adjusting the viscosity, etc. as needed. In this case, the solvent may be water, an organic solvent, or a mixture thereof. The organic solvent may be, for example, an amide-based polar organic solvent, including dimethylformamide (DMF), diethylformamide, dimethylacetamide (DMAc), N-methylpyrrolidone (NMP), etc.; alcohols include methanol, ethanol, 1-propanol, 2-propanol (isopropanol), 1-butanol (n-butanol), 2-methyl-1-propanol (isobutanol), 2-butanol (sec-butanol), 1-methyl-2-propanol (tert-butanol), pentanol, hexanol, heptanol, or octanol; glycols include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, 1,3-propylene glycol, 1,3-butanediol, 1,5-pentanediol, or hexanediol; polyols include The glycol ethers include ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, triethylene glycol monomethyl ether, tetraethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monoethyl ether, triethylene glycol monoethyl ether, tetraethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, or tetraethylene glycol monobutyl ether; ketones include acetone, methyl ethyl ketone, methyl propyl ketone, or cyclopentanone; and esters include ethyl acetate, γ-butyrolactone, and ε-propiolactone, and any one of them or a mixture of two or more of them may be used, but embodiments of the present invention are not limited thereto.

[0088] The solvent may be contained in an amount that allows the electrode slurry to have a solid content of 40% to 85% by weight, and preferably 50% to 80% by weight. When the amount falls within the above range, binder migration can be suppressed, so that electrode adhesion can be improved, and the drying temperature can be reduced, so that the coating quality can be improved, and the coating speed can be increased, thereby improving productivity.

[0089] lithium secondary batteries

[0090] The lithium secondary battery according to another embodiment of the present invention has a structure in which a positive electrode, a separator, and a negative electrode are stacked in sequence, and at least one of the positive electrode and the negative electrode is the aforementioned electrode. In particular, the lithium secondary battery according to the present invention may include a positive electrode, a negative electrode, and a separator provided between the positive electrode and the negative electrode, and an electrolyte, in which case the positive electrode and the negative electrode are the same as those described above.

[0091] Hereinafter, only the other components will be described.

[0092] According to an embodiment of the present invention, the separator separates the negative electrode and the positive electrode and provides a mobile path for lithium ions, and any separator can be used without particular limitation, as long as it is used as the separator in a general secondary battery. In particular, as a separator, a porous polymer film can be used, for example, a porous polymer film prepared by a polyolefin-based polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, and an ethylene / methacrylate copolymer, or a laminated structure with two or more layers thereof. In addition, common porous nonwoven fabrics can also be used, for example, a nonwoven fabric made of glass fiber, polyethylene terephthalate fiber, etc. with a high melting point. In addition, a coating separator including a ceramic component or a polymeric material can also be used to ensure heat resistance or mechanical strength, and can be selectively used in a single layer or multilayer structure.

[0093] According to an embodiment of the present invention, the electrolyte may include organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, molten inorganic electrolytes, etc. that can be used to prepare lithium secondary batteries, and the types are not limited thereto.

[0094] In particular, the electrolyte may include a non-aqueous organic solvent and a lithium salt.

[0095] As the non-aqueous organic solvent, an aprotic organic solvent can be used, for example, N-methyl-2-pyrrolidone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, γ-butyrolactone, 1,2-dimethoxyethane, tetrahydroxyfuran, 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, triester phosphate, trimethoxymethane, dioxolane derivatives, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ether, methyl propionate, ethyl propionate, etc.

[0096] In particular, among carbonate organic solvents, ethylene carbonate and propylene carbonate, which are cyclic carbonates, have high viscosity and high dielectric constant and dissociate lithium salts well, and therefore can be preferably used, and if low-viscosity, low-dielectric-constant linear carbonates such as dimethyl carbonate and diethyl carbonate are mixed in cyclic carbonates in an appropriate proportion, an electrolyte with high conductivity can be provided, which can be more preferably used.

[0097] A lithium salt may be used as the metal salt, and the lithium salt may be a material suitable for dissolving in a non-aqueous electrolyte solution, and for example, the negative ion of the lithium salt may include a material selected from the group consisting of F - 、Cl - , 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 - One or more of the groups.

[0098] In addition to the electrolyte components, at least one additive, for example, a halogenated alkylene carbonate-based compound such as ethylene difluorocarbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ether, ethylenediamine, glyme, hexaphosphoric acid amide, nitrobenzene derivatives, sulfur, quinoneimine dye, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxyethanol, or aluminum trichloride, may be further included in the electrolyte in order to improve the life characteristics of the battery, suppress the reduction in battery capacity, and improve the discharge capacity of the battery.

[0099] Example

[0100] Hereinafter, examples of the present invention will be described in detail so that those skilled in the art can easily implement the present invention. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein.

[0101] Examples 1a-4a and Comparative Examples 1a-9a: Conductive Material Dispersion

[0102] 1 part by weight of single-walled carbon nanotube bundles, 1 part by weight of polyvinylpyrrolidone (PVP, K15, Zhangzhou Huafu) as a dispersant, and 200 parts by weight of N-methylpyrrolidone were mixed, and then subjected to a first mixing for 180 minutes using a mixer (BTM-50, disper 1000 rpm / anchor 100 rpm). The mixed mixture was subjected to a high-pressure homogenizer (NG-20K, Genizer) to obtain a conductive material dispersion by varying the number of cycles. The obtained conductive material dispersions were subjected to a second mixing at different mixing ratios (weight ratios) as shown in Table 1 below, thereby obtaining dispersions containing SWCNT clusters each having a solids content of 1% by weight.

[0103] [Table 1]

[0104]

[0105] * Relative values ​​of the pressure applied to each are shown based on the pressure in Example 1 being 100.

[0106] Experimental Example 1: Measurement of length and particle size

[0107] The conductive material dispersions according to the examples and comparative examples were diluted in water, and 50 μl of the diluted solution was dropped onto the surface of freshly cleaved mica, followed by vacuum drying to prepare samples. The prepared samples were photographed using an atomic force microscope (AFM) (Asylum Research, Cypher ES AFM System) under the following conditions.

[0108] -Measurement mode: AC air topography mode (tapping mode)

[0109] -Measurement conditions: 0.4V set point and 1.5Hz scan rate

[0110] -Measured image size: measured at 20μm×20μm, 15μm×15 and 10μm×10μm magnifications

[0111] -Probe: AC160TS (n-type doped Si, reflective Al coating, f0 300kHz, k 26N / m)

[0112] By measuring the AFM images obtained under the above conditions, the lengths and diameters of at least 100 SWCNT clusters were measured (using an image processing program) to obtain a length distribution, from which the number average length and diameter, the proportion of the number of SWCNT clusters having a length greater than 10 μm, and the proportion of the number of SWCNT clusters having a diameter greater than 30 nm were derived.

[0113] To measure the average particle size D in the cumulative volume 50 (μm) and D 90 (μm), the conductive material dispersion is introduced into a laser diffraction particle size measuring instrument (Mastersizer 2000 of Malvern), irradiated with ultrasonic waves of about 28 kHz at an output of 60 W, and then a cumulative volume particle size distribution diagram is obtained, and then the particle size corresponding to 50% in the cumulative volume is calculated.

[0114] [Table 2]

[0115]

[0116] Referring to Table 2 above, it can be seen that even if the average particle size D in the cumulative volume 50 and D 90 have similar values ​​in the dispersed liquid, but the lengths of the SWCNT clusters substantially contained in the electrode are different.

[0117] Examples 1b to 4b and Comparative Examples 1b to 9b

[0118] The average particle size (D 50 ) 5 μm pure Si particles, a granular conductive material (SFG6L), a conductive material dispersion prepared according to each of Examples 1a to 4a and Comparative Examples 1a to 9a (based on solid content weight), and an aqueous binder were mixed at a weight ratio of 80:9.6:0.8:9.6, and water was used as a solvent to prepare a negative electrode slurry with a solid content of 30%. Here, the aqueous binder is a polymer in which acrylamide, acrylic acid, and acrylonitrile are used in a weight ratio of 60:30:10 and polymerized (ammonium persulfate polymerization initiator, at 75°C, and a polymerization reaction for 8 hours).

[0119] The negative electrode slurry was applied onto one side of a copper foil having a thickness of 18 μm so that the thickness of the active material layer became 50 μm, and then dried to prepare a negative electrode.

[0120] Experimental Example 2: Evaluation of coating processability and life characteristics

[0121] A porous polyethylene separator was disposed between the negative electrode and the positive electrode according to each of Examples 1b to 4b and Comparative Examples 1b to 9b above to prepare an electrode assembly, and the electrode assembly was positioned within a case, and then an electrolyte solution was injected therein to prepare a lithium secondary battery.

[0122] At this time, LiPF6 having a concentration of 1 M was dissolved in an organic solvent including ethylene carbonate / ethyl methyl carbonate / diethyl carbonate at a volume ratio of 3:4:4 to prepare an electrolyte solution, and a positive electrode was prepared as follows.

[0123] LiNi 0.6 Co 0.1 Mn 0.3 O2, polyvinylidene fluoride, and carbon black were added in a weight ratio of 95:3:2, and N-methylpyrrolidone (NMP) was further added to prepare a positive electrode slurry with a solid content of 70.1 wt%, and then the positive electrode slurry was applied to an Al thin film collector with a thickness of 20 μm, and then dried at 130°C and pressed to prepare a positive electrode.

[0124] The lithium secondary battery was charged to 4.2 V at a C rate of 0.1 C and then discharged to 2.5 V to perform a formation process.

[0125] After each lithium secondary battery was charged to 4.25 V with 0.2 C in CCCV mode (1 / 20 C cutoff), when charged to 4.25 V with 0.33 C constant current at 45° C. and then discharged to 2.5 V with 0.33 C constant current was called 1 cycle, 100 charge and discharge cycles were performed on each lithium secondary battery, and the charge and discharge capacities were measured, and the capacity retention rate was calculated as follows.

[0126] Capacity retention (%)=(discharge capacity after 100 cycles) / (discharge capacity after 1 cycle)×100.

[0127] When the negative electrode slurry was applied to the copper foil, whether stains occurred on the electrode surface, whether pinholes occurred, and whether filter clogging occurred in the slurry circulation pump were observed, and if any one problem occurred, it was marked with X, and if no problem occurred, it was marked with O to evaluate the coating processability.

[0128] [Table 3]

[0129] negative electrode Capacity retention rate (%) Electrode coating quality Example 1b 82 O Example 2b 85 O Example 3b 86 O Example 4b 85 O Comparative Example 1b 62 O Comparative Example 2b 68 O Comparative Example 3b 75 X Comparative Example 4b 72 O Comparative Example 5b 70 O Comparative Example 6b 71 O Comparative Example 7b 77 O Comparative Example 8b 72 X Comparative Example 9b 65 O

[0130] Referring to Table 3 above, it can be seen that when the negative electrodes according to Examples 1b to 4b were used, no problems occurred during the coating process, and the capacity retention was also excellent. However, it can be seen that when the negative electrodes according to Comparative Examples 1b and 2b were used, the capacity retention was about 20% lower than that of the Examples. This is probably due to performance differences that cannot be distinguished by the particle size distribution of the conductive material dispersion.

[0131] In particular, the results of Comparative Examples 1b and 2b show that even though the particle size on the dispersion is considered to be an appropriate size, the substantial length of the SWCNT clusters is too small to properly form a conductive path, indicating that improved performance can be achieved by utilizing the characteristics of the conductive material dispersion according to the present invention.

[0132] Besides, it can be seen that when the negative electrode according to Comparative Example 3b is applied, SWCNT clusters having a large length exist in excess, and the number average length is large, causing problems during coating.

[0133] Furthermore, it can be seen that when the negative electrode according to Comparative Example 4b is used, the particle size characteristics on the dispersion are not much different from those of the examples, as the length characteristics are satisfactory. However, the SWCNT clusters have a large number average diameter compared to their length. This may not cause dispersion problems, but since the diameter is relatively large compared to the length, a conductive network cannot be well formed in the electrode as a whole, resulting in low capacity retention. It can be seen that Comparative Examples 5b and 6b show similar results to the above-mentioned Comparative Example 4b due to the relatively excessive presence of SWCNT clusters with large diameters.

[0134] In addition, when the negative electrode according to Comparative Example 7b is applied, the number of SWCNT clusters having a large length is small, but due to the difference in number average length, the possibility of problems occurring in dispersion is expected to be high compared to the case of applying the negative electrode according to Example 4b, and it can be seen that the capacity retention rate is also about 10% lower.

[0135] In Comparative Example 8b, it can be seen that due to the excessive presence of large SWCNT clusters, similar to the case of using the negative electrode according to Comparative Example 3b, dispersion problems occurred, leading to coating processability problems. When using the negative electrode according to Comparative Example 9b, considering the very poor capacity retention, it is expected that the length is small and the diameter is also small, making it impossible to properly form a conductive network.

Claims

1. A conductive material dispersion comprising: Single-walled carbon nanotube (SWCNT) clusters, wherein the SWCNT clusters have a number average length of 0.8 μm to 8.0 μm, The SWCNT clusters having a length greater than 10 μm account for 15% or less of the total number of the SWCNT clusters, The SWCNT clusters have a number average diameter of 5 nm to 25 nm, The SWCNT clusters having a diameter greater than 30 nm account for 15% or less of the total number of the SWCNT clusters, and The length and diameter of the SWCNT clusters were measured using atomic force microscopy. 2 . The conductive material dispersion according to claim 1 , wherein the SWCNT clusters have a number average length of 1.0 μm to 6.0 μm. 3 . The conductive material dispersion according to claim 1 , wherein the SWCNT clusters having a length greater than 10 μm account for 10% or less of the total number of the SWCNT clusters. The conductive material dispersion according to claim 1 , wherein the SWCNT clusters have a number average diameter of 7 nm to 20 nm. 5 . The conductive material dispersion according to claim 1 , wherein the SWCNT clusters having a diameter greater than 30 nm account for 10% or less of the total number of the SWCNT clusters.

6. The conductive material dispersion according to claim 1, wherein the conductive material dispersion further comprises a dispersant, and The dispersant includes one or more selected from the group consisting of polyacrylate, polyvinylidene fluoride, polyvinyl pyrrolidone, polyvinyl alcohol, polyacrylamide, polyethylene oxide, carboxymethyl cellulose, and diisopropylamine.

7. The conductive material dispersion according to claim 6, wherein Based on 100 parts by weight of the conductive material dispersion, The SWCNT clusters are included in an amount of 0.2 to 3.5 parts by weight, and The dispersant is included in an amount of 0.2 to 7.0 parts by weight.

8. An electrode comprising an electrode active material layer, the electrode active material layer comprising an electrode active material, single-walled carbon nanotube (SWCNT) clusters, and a binder, the electrode active material layer being disposed on a current collector, wherein the SWCNT clusters have a number average length of 0.8 μm to 8.0 μm, The SWCNT clusters having a length greater than 10 μm account for 15% or less of the total number of the SWCNT clusters, The SWCNT clusters have a number average diameter of 5 nm to 30 nm, The SWCNT clusters having a diameter greater than 30 nm account for 15% or less of the total number of the SWCNT clusters, and The length and diameter of the SWCNT clusters were measured using atomic force microscopy.

9. The electrode according to claim 8, wherein the electrode active material is a positive electrode active material, and The positive electrode active material includes one or more selected from the group consisting of lithium nickel ternary oxide, lithium-rich manganese-based oxide, lithium iron-based phosphate, lithium nickel oxide, lithium cobalt oxide, and lithium manganese oxide.

10. The electrode according to claim 8, wherein the electrode active material is a negative electrode active material, and The negative electrode active material includes one or more selected from the group consisting of carbon-based particles, silicon-based particles, and carbon-silicon-based composite particles.

11. The electrode according to claim 8, wherein the electrode further comprises a dot-shaped conductive material, and The dot-shaped conductive material includes carbon black. 12 . A lithium secondary battery having a structure in which a positive electrode, a separator, and a negative electrode are stacked in this order, wherein at least one of the positive electrode and the negative electrode is the electrode according to claim 8 .

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