Conductive material dispersion solution, electrode manufactured using same, and lithium secondary battery

Abstract

Disclosed in the present invention are a conductive material dispersion solution, an electrode manufactured using the conductive material dispersion solution, and a secondary battery. The conductive material dispersion solution comprises single-walled carbon nanotubes, a fluorine-based polymer and an organic solvent, wherein the dispersion index (D), which reflects the characteristics of unsaturated functional groups in a polymer and a comonomer or saturated functional groups, of the fluorine-based polymer is 0.10-0.90, and the conductive material dispersion solution containing the fluorine-based polymer has a low viscosity and has fewer agglomerated particles in a dispersed state, thereby having excellent dispersibility, and exhibits less change in viscosity over time, thereby having excellent storage stability.

Description

Conductive dispersion, electrodes manufactured using the same, and lithium secondary batteries The present invention relates to a conductive dispersion comprising a fluorinated polymer and single-walled carbon nanotubes, wherein the dispersion index, defined by factors affecting dispersibility, satisfies a specific value, and an electrode and a lithium secondary battery to which the dispersion is applied. Due to the rapid increase in fossil fuel use, the demand for alternative or clean energy is increasing, and as part of this, the most actively researched field is power generation and storage using electrochemical reactions. Secondary batteries are a prime example of electrochemical devices that utilize this electrochemical energy, and their applications are expanding. With the recent technological development and increasing demand for portable devices such as laptops, mobile phones, and cameras, the demand for secondary batteries as an energy source has rapidly increased. Among these secondary batteries, lithium secondary batteries, which boast high energy density and high capacity, have been extensively studied and are now commercialized and widely used. Secondary battery electrodes include electrode active materials, conductive agents, and binders. Carbon nanotubes can be used as conductive agents to improve electrode conductivity. Especially when using materials with a large specific surface area, even small amounts can significantly improve conductivity. Meanwhile, when single-walled carbon nanotubes are used instead of multi-walled carbon nanotubes, the resistance of the electrode can be further reduced, and since the specific surface area is relatively large, conductivity can be easily secured with only a small amount. In order for the single-walled carbon nanotubes to be uniformly distributed within the electrode, a conductive dispersion liquid in which the single-walled carbon nanotubes are dispersed is first formed during the manufacture of the electrode, and then an electrode slurry is manufactured using the conductive dispersion liquid. A high-pressure homogenizer is used to prepare the above-described conductive dispersion. Specifically, within the high-pressure homogenizer, a pre-mixed solution containing bundle-shaped single-walled carbon nanotubes, a dispersant, and a dispersion medium is passed through a nozzle having a diameter of 80 μm to 800 μm under a high pressure of 100 bar to 2,500 bar, thereby applying a shear force to the bundle-shaped single-walled carbon nanotubes, thereby causing dispersion of the bundle-shaped single-walled carbon nanotubes. Meanwhile, in a pre-mixed state of a solution containing bundled single-walled carbon nanotubes, a dispersant, and a dispersion medium, the bundled carbon nanotubes in the solution must be effectively debundled by the dispersant to enable a dispersion process using a high-pressure homogenizer, and ultimately, a conductive dispersion solution in which single-walled carbon nanotubes are uniformly dispersed can be produced. Conversely, if the debundling is not smooth during the pre-mixing, phase separation occurs between the bundled carbon nanotubes and the dispersion medium in the solution, so that the nozzle of the high-pressure homogenizer is blocked by the bundled carbon nanotubes, making the dispersion process using the high-pressure homogenizer impossible. To address these dispersibility issues, conventional methods involve incorporating a dispersant, such as hydrogenated nitrile butadiene rubber, into the conductive material dispersion. However, this problem becomes more pronounced when using carbon nanotubes with large surface areas, such as single-walled carbon nanotubes, and their high viscosity causes various problems. Therefore, research is needed to develop conductive material dispersions that can improve the dispersibility of single-walled carbon nanotubes. One object of the present invention is to provide a conductive dispersion having a controlled dispersion index by applying a dispersant having a controlled weight average molecular weight and content of functional groups to achieve excellent dispersibility and storage stability while having a low content of large-sized carbon nanotubes. In addition, it is intended to provide a conductive dispersion liquid containing a modified polysiloxane-based material capable of further maximizing the dispersibility of the above-mentioned excellent dispersibility dispersion liquid. Another object of the present invention is to provide an electrode and a secondary battery manufactured using the conductive dispersion. [1] According to one embodiment of the present invention, a conductive dispersion is provided, which comprises a single-walled carbon nanotube and a fluorine-based polymer, wherein the fluorine-based polymer has a dispersion index (D) of 0.10 to 0.90, as defined by the following equation 1. [Formula 1] D = [10 6 (1+W u )] / [M w (1+W s )(1+M H )] In the above equation 1, Mw is a unit of the weight average molecular weight (g / mol) of the fluorinated polymer, and W u is the weight fraction of unsaturated functional group units in fluorinated polymers, and W s is the weight fraction of saturated residual compound units in the fluorinated polymer, and M H is the number of moles of heteroatoms in the saturated residual compound unit, wherein the saturated residual compound unit is at least one selected from among saturated functional group units and comonomer units. [2] In the above [1], the conductive dispersion may further include a modified polysiloxane-based material. [3] In the above [2], the modified polysiloxane material may have a molecular weight of 4,000 g / mol to 8,000 g / mol. [4] In at least one of the above [2] and / or [3], the modified polysiloxane-based material may include polydialkyl siloxane, and the alkyl may have 1 to 5 carbon atoms. [5] In at least one of the above [1] to [4], the fluorinated polymer may be polyvinylidene fluoride. [6] In at least one of the above [1] to [5], the unsaturated functional group of the fluorine-based polymer may include a carboxyl group. [7] In at least one of the above [1] to [6], the saturated functional group may include an alkoxy group having 1 to 5 carbon atoms, and the comonomer unit may include a hexafluoropropylene unit. [8] In at least one of the above [1] to [7], the unsaturated functional group of the fluorine-based polymer may be included in an amount of 0.01 wt% to 1.0 wt% based on the total weight of the polymer. [9] In at least one of the above [1] to [8], the saturated residual compound unit of the fluorine-based polymer may be included in an amount of 0.01 wt% to 5.0 wt% based on the total weight of the polymer.

[0010] In at least one of the above [1] to [9], the fluorinated polymer may have a weight average molecular weight of 1,000,000 g / mol to 2,000,000 g / mol.

[0011] According to another embodiment of the present invention, an electrode is provided, which comprises an electrode active material, a single-walled carbon nanotube, and a fluorinated polymer, wherein the fluorinated polymer has a dispersion index (D) of 0.10 to 0.90, as represented by the following formula 1. [Formula 1] D = [10 6 (1+W u )] / [M w (1+W s )(1+M H )] In the above equation 1, Mw is a unit of the weight average molecular weight (g / mol) of the fluorinated polymer, and W uis the weight fraction of unsaturated functional group units in fluorinated polymers, and W s is the weight fraction of saturated residual compound units in the fluorinated polymer, and M H is the number of moles of heteroatoms in the saturated residual compound unit, wherein the saturated residual compound unit is at least one selected from among saturated functional group units and comonomer units.

[0012] According to another embodiment of the present invention, a lithium secondary battery is provided having a structure in which electrodes and separators are alternately laminated, wherein the electrodes are the electrodes described above. The conductive dispersion according to the present invention has excellent dispersibility due to a low content of large-sized carbon nanotubes and low viscosity by controlling the dispersion index defined from the relationship between factors affecting dispersibility in a fluorinated polymer included as a dispersant, and excellent storage stability due to a small change in viscosity over time. In addition, by including the conductive dispersion in the electrode slurry, the phase stability of the slurry can be improved, and sufficient conductivity can be secured even with a small amount of carbon nanotubes, thereby realizing a high energy density electrode. Furthermore, high-power batteries can be realized because the resistance can be improved even when the content of the conductive material in the slurry is reduced due to excellent dispersibility. Terms or words used in this specification and claims should not be interpreted as limited to their usual or dictionary meanings, but should be interpreted as meanings and concepts that conform to the technical idea of ​​the present invention, based on the principle that the inventor can appropriately define the concept of the term to explain his or her own invention in the best way. In this specification, the terms “comprise,” “include,” or “have” are intended to specify the presence of a feature, number, step, component, or combination thereof, but do not exclude the presence or addition of one or more other features, numbers, steps, components, or combinations thereof. In this specification, the “specific surface area” is measured by the BET method, and can be specifically calculated from the nitrogen gas adsorption amount at liquid nitrogen temperature (77 K) using BELSORP-mino II of BEL Japan. In this specification D 10 , D 50 and D 90 In the particle size distribution curve of silver particles, the particle sizes corresponding to 50% and 90% of the volume accumulation can be defined, respectively. The above D 50 and D 90 For example, it can be measured using the laser diffraction method. The laser diffraction method can generally measure particle diameters from the submicron range to several mm, and can obtain results with high reproducibility and high resolution. In this specification, "weight average molecular weight (Mw)" refers to a conversion value for standard polystyrene measured by gel permeation chromatography (GPC). Specifically, the weight average molecular weight is a value converted from a value measured under the following conditions using GPC, and standard polystyrene of the Agilent system was used to prepare a calibration curve. <Measurement conditions> Measuring instrument: Agilent GPC (Agulent 1200 series, USA) Column: PL Mixed B 2 connections Column temperature: 40℃ Eluent: Tetrohydrofuran Flow rate: 1.0 mL / min Concentration: ~ 1 mg / mL (100 μL injection) Hereinafter, the present invention will be described in detail. In this specification, each of the conductive dispersion, the electrode, and the lithium secondary battery includes at least one of the technical features and / or technical configurations described below, and these technical features and / or technical configurations can be combined in various ways. Dispersion of challenge agent A conductive dispersion according to one embodiment of the present invention comprises single-walled carbon nanotubes and a fluorinated polymer, wherein the fluorinated polymer has a dispersion index (D) of 0.10 to 0.90, as defined by the following equation 1. [Formula 1] D = [10 6 (1+W u )] / [M w (1+W s )(1+M H )] In the above equation 1, Mw is a unit of the weight average molecular weight (g / mol) of the fluorinated polymer, and W u is the weight fraction of unsaturated functional groups in the fluorinated polymer, and W s is the weight fraction of saturated residual compound units in the fluorinated polymer, and M H is the number of moles of heteroatoms in the saturated residual compound unit, wherein the saturated residual compound unit is at least one selected from among saturated functional group units and comonomer units. (1) Single-walled carbon nanotubes Carbon nanotubes are graphite sheets that have a cylindrical shape with a nano-sized diameter and an sp2 bonding structure. Depending on the angle and structure at which the graphite sheets are rolled, they exhibit the properties of conductors or semiconductors. Carbon nanotubes can be classified into single-walled carbon nanotubes (SWCNTs), double-walled carbon nanotubes (DWCNTs), and multi-walled carbon nanotubes (MWCNTs) depending on the number of bonds forming the wall. According to one embodiment of the present invention, the conductive dispersion comprises single-walled carbon nanotubes. Since single-walled carbon nanotubes have a larger specific surface area than multi-walled carbon nanotubes, even with a small amount added, sufficient conductivity can be secured, thereby significantly increasing the reduction in electrode resistance. D of the above single-walled carbon nanotube 50 The D of the single-walled carbon nanotube may be 2 ㎛ to 8 ㎛, specifically 3 ㎛ or more, or 4 ㎛ or more, and also 7 ㎛ or less, or 6 ㎛ or less. 90 The diameter may be 10 ㎛ to 30 ㎛, specifically 12 ㎛ or more, 14 ㎛ or more, 16 ㎛ or more, or 18 ㎛ or more, and may also be 28 ㎛ or less, 26 ㎛ or less, 24 ㎛ or less, or 22 ㎛. Satisfying the above range means that the bundled carbon nanotubes used as a raw material are effectively dispersed and present in the conductive material dispersion, and thus, the improvement of electrode and battery resistance is effective. The carbon nanotubes may be included in an amount of 0.4 to 2.0 parts by weight based on 100 parts by weight of the conductive dispersion, specifically, 0.5 parts by weight or more, 0.6 parts by weight or more, 0.7 parts by weight or more, or 0.8 parts by weight or more, and further, 1.7 parts by weight or less, 1.5 parts by weight or less, 1.3 parts by weight or less, or 1.2 parts by weight or less. When the above range is satisfied, high productivity is maintained while the transport and injection of the electrode slurry are easy. In addition, since the solid content of the electrode slurry being manufactured is not excessively low, binder migration can be suppressed during electrode drying. Accordingly, electrode adhesion can be improved, and the packing of the electrode active material layer is effectively performed, so that an electrode with a low thickness can be manufactured. (2) Fluorine polymer A conductive dispersion according to one embodiment of the present invention comprises a fluorinated polymer, and the fluorinated polymer is characterized in that it satisfies a dispersion index (D) defined by the following equation 1 of 0.10 to 0.90. [Formula 1] D = [10 6 (1+W u )] / [M w (1+W s )(1+M H )] In the above equation 1, Mw is a unit of the weight average molecular weight (g / mol) of the fluorinated polymer, and W u is the weight fraction of unsaturated functional groups in the fluorinated polymer, and W s is the weight fraction of saturated residual compound units in the fluorinated polymer, and M H is the number of moles of heteroatoms in the saturated residual compound unit, wherein the saturated residual compound unit is at least one selected from among saturated functional group units and comonomer units. In the case of the above dispersion index, the relationship between factors that can affect the dispersion of single-walled carbon nanotubes by using a fluorinated polymer as a dispersant was established, and the weight average molecular weight of the fluorinated polymer, the content of unsaturated functional groups in the fluorinated polymer, and the content of saturated residual compound units were taken into consideration. How well a polymer used as a dispersant can disperse single-walled carbon nanotubes may depend on how the polar and non-polar moieties present in the dispersant polymer interact with the non-polar carbon nanotubes and the polar organic solvent. The above dispersion index reflects the weight fraction of unsaturated functional groups with a high degree of polarity in the fluorinated polymer, while also reflecting the weight fraction of saturated residual compound units that are polar but whose degree is relatively small compared to the unsaturated functional groups. In addition, in the case of saturated residual compound units, the number of moles of heteroatoms (e.g., F, N, P, or O) included in the unit also has an effect, and is balanced with the effect of unsaturated functional groups. It is difficult to accurately determine the degree of dispersion of single-walled carbon nanotubes with these factors alone, and it may be necessary to reflect the influence of the polymer itself rather than the units within the polymer. For example, the weight-average molecular weight is reflected as a factor to reflect the influence due to steric hindrance or the overall size of the molecule. The dispersion index derived in this way can be seen as an index that can more accurately determine how well single-walled carbon nanotubes can be dispersed, and the dispersion index is characterized by being 0.10 to 0.90. The dispersion index may preferably be 0.11 or more, 0.12 or more, or 0.13 or more, and may also be 0.85 or less, 0.80 or less, 0.75 or less, 0.70 or less, or 0.68 or less, and most preferably 0.14 to 0.67. The above dispersion index reflects various factors, and a smaller value can provide a conductive dispersion with excellent dispersibility. However, if it is less than 0.10, the weight average molecular weight is too large compared to the content of unsaturated functional groups, so there is a concern that the contribution to the dispersion of carbon nanotubes due to the attractive force between the polymers may be small, and since the influence of the saturated residual compound unit becomes greater than the influence of the unsaturated functional group, there is a concern that even if the viscosity of the dispersion is lowered, large-sized lumps may be generated in the dispersion. If the above dispersion index is greater than 0.90, it is difficult to consider that the carbon nanotubes are properly dispersed, and there is a problem that the viscosity is high and the content of large-sized particles also increases. The above fluorinated polymer may be at least one polymer selected from the group consisting of polyvinylidene fluoride (PVDF), polyperfluoroalkoxy (PFA), polytetrafluoroethylene (PTFE), and copolymers thereof copolymerized with a comonomer, and preferably polyvinylidene fluoride. When the polyvinylidene fluoride is applied to disperse single-walled carbon nanotubes, it has excellent affinity with the organic solvent used, enabling formation of a polymer solution, and thus has the advantage of excellent processability. The above fluorinated polymer may contain a carboxyl group as an unsaturated functional group, and the unsaturated functional group may be included in an amount of 0.01 wt% to 1.00 wt% based on the total weight of the polymer, preferably 0.02 wt% or more, 0.03 wt% or more, or 0.05 wt% or more, and may be included in an amount of 0.90 wt% or less, 0.80 wt% or less, preferably 0.75 wt% or less. The unsaturated functional group is a major factor that imparts polar properties, and it may be desirable to control the content appropriately in order to contribute to the dispersion of single-walled carbon nanotubes. The above fluorine-based polymer may include a saturated residual compound unit, and the saturated residual compound unit may refer to a saturated functional group and / or a comonomer unit. In the present invention, the term "saturated residual compound unit" may refer to a compound unit remaining except for a main monomer unit and an unsaturated functional group. Among these saturated residual compound units, the saturated functional group may include an alkoxy group having 1 to 5 carbon atoms, and the comonomer unit may include at least one selected from the group consisting of a hexafluoropropylene unit and a chlorotrifluoroethylene unit. In the case of the above saturated residual compound unit, it may be included in an amount of 0.01 wt% to 5.0 wt% based on the total weight of the polymer, preferably 0.02 wt% or more, 0.03 wt% or more, and further 4.0 wt% or less, 3.0 wt% or less, or 2.5 wt% or less. Furthermore, the mole number of heteroatoms included in the saturated residual compound unit may be 1 to 6, and this is considered together with the content of the saturated residual compound unit so that the influence of the saturated residual compound unit on dispersibility is proportionally reflected depending on how much of the highly electronegative heteroatom is included. The above fluorinated polymer may have a weight average molecular weight of 1,000,000 g / mol to 2,000,000 g / mol. It may be desirable to control the weight average molecular weight so that it is neither too small nor too large, thereby controlling the dispersion index to be satisfied within the above range. In the conductive dispersion, the fluorine-based polymer may be included in an amount of 0.5 to 6.0 parts by weight based on 100 parts by weight of the conductive dispersion, specifically 0.8 parts by weight or more, 1.0 parts by weight or more, 1.5 parts by weight or more, 2.0 parts by weight or more, or 2.4 parts by weight or more, and further 5.0 parts by weight or less, 4.0 parts by weight or less, 3.0 parts by weight or less, or 2.6 parts by weight or less. When the above range is satisfied, the carbon-based conductive material can be smoothly dispersed in the conductive dispersion, and the energy density of the electrode to be manufactured can be improved and the resistance can be reduced. The above-mentioned conductive dispersion may further include a dispersant in addition to the fluorinated polymer, and may include, for example, a hydrogenated nitrile-based copolymer. The hydrogenated nitrile-based copolymer may be a copolymer including an α,β-unsaturated nitrile-derived structural unit and a hydrogenated conjugated diene-derived structural unit, or a copolymer including an α,β-unsaturated nitrile-derived structural unit, a conjugated diene-derived structural unit, and a hydrogenated conjugated diene-derived structural unit. The hydrogenated nitrile-based copolymer may be a hydrogenated nitrile-butadiene rubber, and specifically, a hydrogenated acrylonitrile-butadiene rubber, and more specifically, a partially hydrogenated acrylonitrile-butadiene rubber. (3) Modified polysiloxane material The conductive dispersion according to one embodiment of the present invention may further include a modified polysiloxane-based material. The modified polysiloxane-based material may have a molecular weight of 4,000 g / mol to 8,000 g / mol, and preferably 4,500 g / mol to 7,500 g / mol. The above-mentioned modified polysiloxane-based material may be affected by the dispersion index of the aforementioned fluorinated polymer. When added together with a fluorinated polymer whose dispersion index does not fall within the range of 0.10 to 0.90, a viscosity reduction effect may be expected, but the content of large particles may increase, which may cause a problem of deterioration in dispersibility. However, when added together with a fluorinated polymer that satisfies the dispersion index, a viscosity reduction effect can be expected without deterioration in dispersibility, so the effect of adding the modified polysiloxane-based material can be maximized. Therefore, it is preferable to additionally add the modified polysiloxane-based material to reduce viscosity by taking the dispersion index into consideration. Among the above-mentioned modified polysiloxane-based materials, the polysiloxane-based portion may include dialkyl siloxane as a monomer unit, and in the case of the dialkyl siloxane, the alkyl may have 1 to 5 carbon atoms. For example, polydimethyl siloxane, polymethylethyl siloxane, polymethylpropyl siloxane, etc. may be applied to the polysiloxane-based portion. Preferably, the modified polysiloxane material may be a polyether-modified polysiloxane material modified by a polyether-modified material, in which case the polyether-modified material may be modified in a form in which the polyether-modified material is bonded to the alkyl group. The polyether-modified material may include a homopolymer such as polyethylene glycol, propoxylated polyethylene glycol, polypropylene glycol, or ethoxylated polypropylene glycol; a random copolymer thereof; or a block copolymer thereof. The above polyether-modified polysiloxane-based material may be, for example, in the form of a block copolymer of a polyether-based material and a polysiloxane-based material. The above modified polysiloxane-based material may be in the form where a polyether-based material is distributed on one side and a polysiloxane-based material is distributed on the other side, and these two materials are connected by a covalent bond. For example, the weight ratio of the polysiloxane-based material and the polyether-based material of the modified polysiloxane-based material may be about 95:5 to 5:95, preferably 70:30 to 10:90, 60:40 to 10:90, 50:50 to 10:90, 40:60 to 10:90, and more preferably 30:70 to 10:90. The above-mentioned modified polysiloxane material has both polar and nonpolar portions within the molecule due to modification as described above, and thus can more actively interact with the fluorinated polymer and the conductive material, and can further improve dispersibility. In particular, it can have a great influence on the dispersibility index through interaction with the functional group portion of the fluorinated polymer, and thus a significant synergistic effect can be expected. (4) Organic solvent The above organic solvent may be an organic solvent containing one or more heteroatoms selected from the group consisting of nitrogen atoms (N) and oxygen atoms (O) having unshared electron pairs. Specifically, the organic solvent may be an amide-based polar organic solvent such as dimethylformamide (DMF), diethyl formamide, dimethyl acetamide (DMAc), or N-methyl pyrrolidone (NMP); an alcohol such as methanol, ethanol, 1-propanol, 2-propanol (isopropyl alcohol), 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 glycol such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, 1,3-propanediol, 1,3-butanediol, 1,5-pentanediol, or hexylene glycol; Examples thereof include polyhydric alcohols such as glycerin, trimethylolpropane, pentaerythritol, or sorbitol; glycol ethers such as 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 such as acetone, methyl ethyl ketone, methyl propyl ketone, or cyclopentanone; and esters such as ethyl acetate, γ-butyl lactone, and ε-propiolactone, and any one of these or a mixture of two or more thereof may be used. Considering compatibility with electrode slurry, N-methyl pyrrolidone (NMP) is particularly preferred. In the conductive dispersion, the solid content of the conductive dispersion may be 1 wt% to 10 wt%, specifically 2 wt% to 8 wt%, and more specifically 3.5 wt% to 5.5 wt%. When the above range is satisfied, the viscosity of the conductive dispersion can be maintained at a low level, while the conductive dispersion can be effectively dispersed. Here, the solid content may refer to single-walled carbon nanotubes and fluorine-based polymers included in the conductive dispersion. The conductive dispersion may be prepared by mixing single-walled carbon nanotubes, a fluorinated polymer, and an organic solvent. At this time, the mixing may be performed using a conventional mixing method, specifically, a mixing device such as a homogenizer, a bead mill, a ball mill, a basket mill, an attrition mill, a universal stirrer, a clear mixer, a spike mill, or a TK mixer, and the order of mixing each component is not particularly limited. That is, the conductive dispersion according to the present invention may be prepared by a method of adding single-walled carbon nanotubes to an organic solvent and then adding a fluorinated polymer and mixing them, or by a method of first adding a fluorinated polymer to an organic solvent and then mixing the single-walled carbon nanotubes, or by a method of adding single-walled carbon nanotubes and a fluorinated polymer together to an organic solvent and then mixing them. Meanwhile, cavitation dispersion treatment may be performed during the above mixing process to enhance the dispersibility of single-walled carbon nanotubes. The cavitation dispersion treatment is a dispersion treatment method that utilizes shock waves generated by the rupture of vacuum bubbles formed in water when high energy is applied to the liquid. This method enables dispersion without damaging the properties of single-walled carbon nanotubes. Specifically, the cavitation dispersion treatment may be performed using ultrasonic waves, a jet mill, or shear dispersion treatment. electrode An electrode according to another embodiment of the present invention comprises an electrode active material, a single-walled carbon nanotube, and a fluorinated polymer, wherein the dispersion index of the fluorinated polymer is as described above. The electrode may include a current collector and an electrode active material layer disposed on the current collector, and the electrode active material layer may include an electrode active material, a single-walled carbon nanotube, and a fluorine-based polymer. The electrode active material layer may be formed from an electrode slurry composition comprising an electrode active material, a conductive material dispersion, and a binder. Specifically, the electrode includes an electrode current collector and an electrode active material layer formed on the electrode current collector, and the electrode active material layer may be formed from an electrode slurry composition comprising an electrode active material, a conductive material dispersion, and a binder. At this time, the conductive dispersion is the conductive dispersion according to the present invention described above. Since the details of the conductive dispersion are the same as those described above, a detailed description will be omitted, and the remaining components will be described below. The electrode current collector is not particularly limited as long as it is a material that is conductive and does not cause a chemical change in the battery, and for example, copper, stainless steel, aluminum, nickel, titanium, alloys thereof, those surface-treated with carbon, nickel, titanium, silver, etc., or calcined carbon, etc. can be used. The electrode current collector may typically have a thickness of 3 μm to 500 μm, and may have fine irregularities formed on the surface of the current collector to enhance the bonding strength of the negative electrode active material. In addition, the electrode current collector may be used in various forms, such as a film, sheet, foil, net, porous body, foam, or non-woven fabric. Meanwhile, the electrode active material (a) included in the electrode active material layer may be a positive electrode active material or a negative electrode active material generally used in the relevant technical field, and its type is not particularly limited. For example, as a cathode active material, a lithium oxide containing lithium and one or more metals such as cobalt, manganese, nickel or aluminum can be used. More specifically, the lithium oxide is a lithium-manganese oxide (e.g., LiMnO2, LiMn2O, etc.), a lithium-cobalt oxide (e.g., LiCoO2, etc.), a lithium-nickel oxide (e.g., LiNiO2, etc.), a lithium-nickel-manganese oxide (e.g., LiNi 1-Y1 Mn Y1 O2 (here, 0 <Y1<1), LiNi Z1 Mn 2-Z1 O4 (wherein, 0<Z1<2) etc.), lithium-nickel-cobalt oxides (e.g., LiNi 1-Y2 Co Y2 O2 (here, 0 <Y2<1) 등), 리튬-망간-코발트계 산화물(예를 들면, LiCo 1-Y3 Mn Y3 O2 (here, 0 <Y3<1), LiMn 2-Z2 Co Z2 O4 (wherein, 0<Z2<2) etc.), lithium-nickel-cobalt-manganese oxides (e.g., Li(Ni P1 Co Q1 Mn R1 )O2(wherein, 0<P1<1, 0<Q1<1, 0<R1<1, P1+Q1+R1=1) or Li(Ni P2 Co Q2 Mn R2 )O4 (wherein, 0<P2<2, 0<Q2<2, 0<R2<2, P2+Q2+R2=2) etc.), or lithium-nickel-cobalt-manganese-other metal(M) oxide (e.g., Li(Ni P3 Co Q3 Mn R3 M 1 S )O2(here, M 1is selected from the group consisting of Al, Cu, Fe, V, Cr, Ti, Zr, Zn, Ta, Nb, Mg, B, W and Mo, and P3, Q3, R3 and S are atomic fractions of independent elements, such that 0<P3<1, 0<Q3<1, 0<R3<1, 0<S<1, P3+Q3+R3+S=1), etc.), and one or more compounds of these may be included. Meanwhile, as negative active materials, for example, carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; metallic compounds capable of alloying with lithium such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloy, Sn alloy, or Al alloy; SiO v (0 <v<2), SnO2, 바나듐 산화물, 리튬 바나듐 산화물과 같이 리튬을 도프 및 탈도프할 수 있는 금속산화물; 또는 Si-C 복합체 또는 Sn-C 복합체과 같이 상기 금속질 화합물과 탄소질 재료를 포함하는 복합물 등을 들 수 있으며, 이들 중 어느 하나 또는 둘 이상의 혼합물이 사용될 수 있다. 또한, 상기 음극활물질로서 금속 리튬 박막이 사용될 수도 있다. 또, 탄소재료는 저결정 탄소 및 고결정성 탄소 등이 모두 사용될 수 있다. The electrode active material may be included in an amount of 90 wt% to 99 wt%, preferably 95 wt% to 99 wt%, based on the total solid content in the electrode slurry composition. When the content of the electrode active material satisfies the above range, excellent energy density, electrode adhesion, and electrical conductivity can be achieved. The above binder is intended to secure adhesion between electrode active materials or between electrode active materials and a current collector, and general binders used in the relevant technical field can be used, and the type thereof is not particularly limited. Examples of the binder 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 one of these may be used alone or a mixture of two or more thereof. The above binder may be included in an amount of 5 wt% or less, and preferably 1 wt% to 3 wt%, based on the total solid content in the electrode slurry composition. When the binder content satisfies the above range, excellent electrode adhesion can be achieved while minimizing an increase in electrode resistance. Meanwhile, the electrode slurry composition may further include a solvent, if necessary, for viscosity control, etc. In this case, the solvent may be water, an organic solvent, or a mixture thereof. Examples of the organic solvent include amide-based polar organic solvents such as dimethylformamide (DMF), diethyl formamide, dimethyl acetamide (DMAc), N-methyl pyrrolidone (NMP); alcohols such as methanol, ethanol, 1-propanol, 2-propanol (isopropyl alcohol), 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 such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, 1,3-propanediol, 1,3-butanediol, 1,5-pentanediol, or hexylene glycol; polyhydric alcohols such as glycerin, trimethylolpropane, pentaerythritol, or sorbitol; glycol ethers such as 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; Examples thereof include ketones such as acetone, methyl ethyl ketone, methyl propyl ketone, or cyclopentanone; esters such as ethyl acetate, γ-butyl lactone, and ε-propiolactone; and any one or a mixture of two or more of these may be used, but is not limited thereto. The solvent may be included in an amount such that the solid content in the electrode slurry is 60 wt% to 85 wt%, preferably 65 wt% to 80 wt%. When the above range is satisfied, binder migration can be suppressed, thereby improving electrode adhesion, the drying temperature can be lowered, thereby improving coatability, and the coating speed can be increased, thereby improving productivity. The electrode according to the present invention can be manufactured by applying an electrode slurry composition containing the above components and drying it to form an electrode active material layer. Specifically, the electrode active material layer can be formed by applying the electrode slurry on an electrode current collector and then drying it, or by applying the electrode slurry on a separate support and then peeling it from the support to obtain a film and laminating it on an electrode current collector. If necessary, a rolling process can be additionally performed after the electrode active material layer is formed through the above method. At this time, the drying and rolling can be performed under appropriate conditions considering the physical properties of the electrode to be manufactured, and there are no particular limitations. lithium secondary battery According to another embodiment of the present invention, a lithium secondary battery has a structure in which electrodes and separators are alternately laminated, wherein the electrodes include the electrodes described above. Specifically, the secondary battery according to the present invention may include a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte. In this case, the positive electrode may be an electrode according to the embodiment described above. Since the electrode according to the present invention has been described above, a detailed description will be omitted, and only the remaining components will be described below. The above separator separates the negative electrode and the positive electrode and provides a passage for lithium ions. Any separator commonly used in secondary batteries can be used without any particular restrictions. Specifically, the separator may be a porous polymer film, for example, a porous polymer film made of a polyolefin 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 of two or more layers thereof. In addition, a conventional porous non-woven fabric, for example, a non-woven fabric made of high-melting-point glass fiber, polyethylene terephthalate fiber, etc. may also be used. In addition, a coated separator containing a ceramic component or a polymer material to secure heat resistance or mechanical strength may be used, and may optionally be used in a single-layer or multi-layer structure. Examples of the electrolyte include, but are not limited to, organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, and molten inorganic electrolytes that can be used in the manufacture of lithium secondary batteries. Specifically, the electrolyte may include a non-aqueous organic solvent and a metal salt. As the above non-aqueous organic solvent, for example, an aprotic organic solvent such as N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, gamma-butyrolactone, 1,2-dimethoxyethane, tetrahydroxyfuran, 2-methyl tetrahydrofuran, dimethylsulfoxide, 1,3-dioxolan, formamide, dimethylformamide, dioxolan, acetonitrile, nitromethane, methyl formate, methyl acetate, triester phosphate, trimethoxy methane, dioxolan derivatives, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ethers, methyl pyrropionate, ethyl propionate, etc. can be used. there is. In particular, among the above carbonate-based organic solvents, ethylene carbonate and propylene carbonate, which are cyclic carbonates, are high-viscosity organic solvents with high dielectric constants and thus can be preferably used because they easily dissociate lithium salts. In addition, when low-viscosity, low-dielectric constant linear carbonates such as dimethyl carbonate and diethyl carbonate are mixed and used in an appropriate ratio with these cyclic carbonates, an electrolyte with high electrical conductivity can be produced, so that they can be used even more preferably. The metal salt may be a lithium salt, and the lithium salt is a substance that is easily dissolved in the non-aqueous electrolyte, for example, the anion of the lithium salt is 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 selected from the group consisting of may be used. In addition to the electrolyte components, the electrolyte may further include one or more additives, such as, for example, a haloalkylene carbonate compound such as difluoroethylene carbonate, pyridine, triethylphosphite, triethanolamine, a cyclic ether, ethylene diamine, n-glyme, hexaphosphoric acid triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, or aluminum trichloride, for the purpose of improving the life characteristics of the battery, suppressing battery capacity decrease, and improving the discharge capacity of the battery. Example Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement them. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein. Examples 1-1 to 1-3 and Comparative Examples 1-1 to 1-3 As shown in Table 1 below, 2.0 parts by weight of polyvinylidene fluoride (PVDF), 1.0 parts by weight of single-walled carbon nanotubes (Tuball, OcSiAl), and 97 parts by weight of N-methyl pyrrolidone were mixed, and then mixed for 180 minutes using a mixer (BTM-50, disper 1000 rpm / anchor 100 rpm). The mixed mixture was stirred for 30 minutes using a high-pressure homogenizer (Micronox, Picomax MN230A, pressure: 1,500 bar) to obtain a conductive dispersion, respectively. M W (g / mol x10 6)Main monomer unit (weight fraction)Unsaturated functional group (weight fraction)Saturable residual compound unit (weight fraction)Dispersion indexSaturated functional groupMonomer unitNumber of heteroatom molesExample 1-11.50.9950.0050000.67Example 1-21.00.9980.00150.0005010.50Example 1-31.00.9700.00500.02560.14Comparative example 1-11.00.9950.0050001.01Comparative example 1-20.91.00000001.11Comparative example 1-32.00.9000.0200.0860.067 Experimental Example 1: Particle Size Analysis The particle size of each conductive dispersion of examples and comparative examples was analyzed using laser diffraction and is shown in Table 2. Specifically, after dispersing the conductive dispersion in a solvent, it was introduced into a laser diffraction particle size measuring device (Malvern, Mastersizer 3000) and the particle size distribution was calculated by measuring the difference in diffraction pattern according to particle size when the particles passed through the laser beam. The particle size at the points where the volume cumulative distribution according to particle size was 10%, 50%, and 90% was confirmed, and D 10 , D 50 and D 90 was measured. Experimental Example 2: Viscosity Analysis (Immediately After Preparation of the Dispersion) The viscosity of the conductive dispersions manufactured by the above examples and comparative examples was measured at 25°C and 12 rpm using a viscometer (Brookfield, viscometer DV2T, LV), and is shown in Table 2. Experimental Example 3: Confirmation of Viscosity Increase during Long-Term Storage For the conductive dispersions manufactured by the examples and comparative examples, the viscosity increase rate (%) was confirmed according to the following formula. Viscosity increase rate (%) = {(Viscosity of conductive dispersion measured after 4 weeks of storage at 25℃ - Viscosity of conductive dispersion immediately after manufacturing) / Viscosity of conductive dispersion immediately after manufacturing} Х100 Particle viscosity (cp)Viscosity after 4 weeks of storage (cp)Viscosity increase rate (%)D 10 (㎛)D 50 (㎛)D 90 (㎛)Example 1-11.399.6636.26,0906,6088.5Example 1-21.4811.1037.47,6208,54212.1Example 1-32.0513.8043.65,9406,60511.2Comparative Example 1-12.7015.0048.59,60011,06015.2Comparative Example 1-21.9913.3045.99,12010,96020.2Comparative Example 1-33.0017.1051.212,05014,58021.0 Referring to Table 1 above, in the case of Examples 1-1 to 1-3 where the dispersion index is in the range of 0.1 to 0.9, the viscosity is low and the change over time is small, and the average particle size at 90% accumulation by volume is relatively small compared to the comparative examples. Experimental Example 4: Evaluation of the addition of modified polysiloxane-based materials In the conductive dispersions of Examples 1-1 to 1-3 and Comparative Examples 1-1 to 1-3, instead of 2.0 parts by weight of polyvinylidene fluoride as a dispersant, 0.5 parts by weight of a modified polysiloxane-based material having a molecular weight of 6,000 g / mol (modified by combining about 0.15 parts by weight of polydimethylsiloxane (PDMS) and about 0.85 parts by weight of polyethylene glycol) and 1.5 parts by weight of polyvinylidene fluoride were added to prepare conductive dispersions of Examples 2-1 to 2-3 and Comparative Examples 2-1 to 2-3, and the viscosity and particle size characteristics were evaluated in the same manner as in Experimental Examples 1 to 3, and the results are shown in Table 3 below. Particle viscosity (cp)Viscosity after 4 weeks of storage (cp)Viscosity increase rate (%)D 10 (㎛)D 50 (㎛)D 90(㎛)Example 2-11.5112.439.65,9106,56011.2Example 2-21.6011.742.04,8005,42413.1Example 2-31.6017.141.04,7505,37013.0Comparative Example 2-11.8614.357.17,1408,21115.1Comparative Example 2-21.5814.055.07,3208,20012.1Comparative Example 2-31.5314.054.07,0007,80011.5 Referring to Table 3 above, it can be confirmed through Examples 2-1 to 2-3 that when a modified polysiloxane-based material was added to Examples 1-1 to 1-3 having a dispersion index of 0.10 to 0.90, there was an effect of lowering viscosity, and it can be seen that this effect also appeared in Comparative Examples 2-1 to 2-3 when added to Comparative Examples 1-1 to 1-3 that did not satisfy the dispersion index. However, in the case of comparative examples 2-1 to 2-3, D 90 It can be confirmed that this has increased significantly, and through this, it can be seen that in cases where the dispersion index is not satisfied, adding a modified polysiloxane-based material may have a negative effect on the dispersibility.

Claims

1. Contains single-walled carbon nanotubes and fluorine-based polymers, The above fluorinated polymer is a conductive dispersion having a dispersion index (D) of 0.10 to 0.90, as defined by the following formula 1: [Formula 1] D = [10 6 (1+W u )] / [M w (1+W s )(1+M H )] In the above equation 1, Mw is the unitless number of the weight average molecular weight (g / mol) of the fluorinated polymer, and W u is the weight fraction of unsaturated functional group units in fluorinated polymers, and W s is the weight fraction of saturated residual compound units in the fluorinated polymer, and M H is the number of moles of heteroatoms in the saturated residual compound unit, wherein the saturated residual compound unit is at least one selected from among saturated functional group units and comonomer units.

2. In claim 1, The conductive dispersion further comprises a modified polysiloxane-based material.

3. In claim 2, The above modified polysiloxane material is a conductive dispersion having a molecular weight of 4,000 g / mol to 8,000 g / mol.

4. In claim 2, The above modified polysiloxane material contains polydialkyl siloxane, The above alkyl has 1 to 5 carbon atoms, and is a conductive dispersion.

5. In claim 1, The above fluorinated polymer is a conductive dispersion liquid of polyvinylidene fluoride.

6. In claim 1, A conductive dispersion in which the unsaturated functional group of the above fluorinated polymer includes a carboxyl group.

7. In claim 1, The above saturated functional group includes an alkoxy group having 1 to 5 carbon atoms, A conductive dispersion, wherein the above monomer unit comprises at least one selected from the group consisting of hexafluoropropylene units and chlorotrifluoroethylene.

8. In claim 1, A conductive dispersion, wherein the unsaturated functional group of the fluorine-based polymer is contained in an amount of 0.01 wt% to 1.0 wt% based on the total weight of the polymer.

9. In claim 1, A conductive dispersion, wherein the saturated residual compound unit of the above fluorine-based polymer is contained in an amount of 0.01 wt% to 5.0 wt% based on the total weight of the polymer.

10. In claim 1, The above fluorinated polymer is a conductive dispersion having a weight average molecular weight of 1,000,000 g / mol to 2,000,000 g / mol.

11. Contains electrode active materials, single-walled carbon nanotubes and fluorine-based polymers. The above fluorinated polymer has a dispersion index (D) of 0.05 to 0.95, represented by the following formula 1: [Formula 1] D = [10 6 (1+W u )] / [M w (1+W s )(1+M H )] In the above equation 1, Mw is the unitless number of the weight average molecular weight (g / mol) of the fluorinated polymer, and W u is the weight fraction of unsaturated functional group units in fluorinated polymers, and W s is the weight fraction of saturated residual compound units in the fluorinated polymer, and M H is the number of moles of heteroatoms in the saturated residual compound unit, wherein the saturated residual compound unit is at least one selected from among saturated functional group units and comonomer units.

12. It has a structure in which electrodes and separators are alternately laminated. A lithium secondary battery, wherein the electrode is the electrode of claim 11.