Dispersive agent, conductive composition, slurry composition for forming anode and lithium secondary battery including the same

Abstract

The dispersant according to the exemplary embodiments comprises a polycyclic aromatic functional group; and any one of a polyethylene glycol group, a sulfonate group, and a pyrrolidinium group. A conductive composition with improved dispersion uniformity can be prepared using the dispersant.

Description

Technology Field

[0001] The present invention relates to a dispersant, a conductive composition containing the same, a slurry composition for forming a negative electrode, and a lithium secondary battery. More specifically, it relates to a conductive composition containing a nonionic dispersant or an ionic dispersant. Background Technology

[0003] Recently, the utilization of carbon-based materials has been increasing as conductive structural materials, such as electrodes or antistatic materials included in various information electronic devices, display devices, and batteries. Carbon-based materials encompass carbon allotropes, and examples of such allotropes include plate-shaped graphene, graphite (a stack of graphene), spherical fullerene, elongated cylindrical carbon nanotubes (CNT), amorphous carbon, and diamond. The aforementioned carbon allotropes possess different bonding forms and geometric structures, and accordingly, exhibit different mechanical, electrical, and chemical properties.

[0004] Among the carbon allotropes mentioned above, carbon nanotubes have a structure in which graphene sheets are rolled into a cylinder, and depending on the number of stacked walls, they can be classified into single-walled carbon nanotubes (SWCNT), few-walled carbon nanotubes (FWCNT), and multi-walled carbon nanotubes (MWCNT).

[0005] Carbon nanotubes are attracting attention as alternative materials to existing conductive materials because they possess excellent electrical conductivity, thermal conductivity, and mechanical properties. Carbon nanotubes can be manufactured in the form of slurries, pastes, inks, etc., for use as conductive materials. However, it is not easy to ensure uniform dispersion of carbon nanotubes due to the high surface area at the nanoscale, for example, due to agglomeration caused by van der Waals forces.

[0006] For example, Korean Patent Publication No. 2016-0107030 attempts to disperse carbon allotropes using ultrasound and the application of shear force, but in this case, while instantaneous dispersibility can be secured, there are limitations in suppressing re-aggregation. Prior art literature

[0008] Korean Patent Publication No. 2016-0107030 The problem to be solved

[0009] One objective of the present invention is to provide a dispersant that improves the uniformity of dispersion of carbon allotropes.

[0010] One objective of the present invention is to provide a conductive composition comprising the above-mentioned dispersant.

[0011] One objective of the present invention is to provide a slurry composition for forming a negative electrode of a lithium secondary battery comprising the conductive composition.

[0012] One objective of the present invention is to provide a negative electrode for a lithium secondary battery manufactured using the above-described negative electrode forming slurry composition, and a lithium secondary battery comprising the above-described negative electrode. means of solving the problem

[0014] The dispersant according to exemplary embodiments comprises a polycyclic aromatic functional group; and any one of a polyethylene glycol group, a sulfonate group, and a pyrrolidinium group.

[0015] In some embodiments, the polycyclic aromatic functional group may include a pyrene group or a carbazole group.

[0016] In some embodiments, the dispersant may include a compound having a structure represented by the following chemical formula 1.

[0017] [Chemical Formula 1]

[0018]

[0019] In the above chemical formula 1, R 1 is a pyrene group or a carbazole group, and R 2 is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and L 1 is a single bond or an alkylene group having 1 to 5 carbon atoms, and n can be an integer from 0 to 100.

[0020] In some embodiments, the dispersant may include a compound having a structure represented by the following chemical formula 2 or chemical formula 3.

[0021] [Chemical Formula 2]

[0022]

[0023] In the above chemical formula 2, R 3 is a pyrene group or a carbazole group, and L 2 is an alkoxylene group having 1 to 10 carbon atoms or an alkylene group having 1 to 10 carbon atoms, and M + It can be an alkali metal cation.

[0024] [Chemical Formula 3]

[0025]

[0026] In the above chemical formula 3, R 4 is a pyrene group or a carbazole group, and L 3 is an alkoxylene group having 1 to 10 carbon atoms or an alkylene group having 1 to 10 carbon atoms, and X - It can be a halogen ion.

[0027] A conductive composition according to exemplary embodiments comprises at least one carbon allotrope selected from the group consisting of carbon nanotubes, graphene, graphite, carbon black, and fullerene; a dispersant comprising a polycyclic aromatic functional group and any one of a polyethylene glycol group, a sulfonate group, and a pyrrolidinium group; and a dispersion medium.

[0028] In some embodiments, the dispersant may be adsorbed onto the surface of the carbon allotrope.

[0029] In some embodiments, the dispersion medium comprises water or a hydrophilic organic solvent, and the polycyclic aromatic functional group may comprise a pyrene group or a carbazole group.

[0030] In some embodiments, the content of the dispersant may be 1 to 50 parts by weight per 100 parts by weight of the carbon allotrope.

[0031] In some embodiments, the dispersant may include a compound having a structure represented by any one of Formulas 1 to 3.

[0032] A slurry composition for forming a cathode according to exemplary embodiments comprises a cathode active material, the conductive composition, a binder, and a solvent.

[0033] In some embodiments, the binder may comprise at least one selected from the group consisting of polytetrafluoroethylene, carboxymethyl cellulose, vinylidene fluoride / hexafluoropropylene copolymer, polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, polyacrylate, poly(styrene-butadiene) copolymer, alginate, and polydopamine.

[0034] In some embodiments, the composition may comprise 70 to 98 parts by weight of the negative electrode active material, 0.1 to 15 parts by weight of the conductive composition, and 1 to 20 parts by weight of the binder, based on 100 parts by weight of the total solid content of the negative electrode active material, the conductive composition, and the binder.

[0035] In some embodiments, the conductive composition can be used as a negative electrode material for a lithium secondary battery.

[0036] A negative electrode for a lithium secondary battery according to exemplary embodiments comprises a current collector and a negative electrode active material layer located on the current collector, and the negative electrode active material layer may be formed from a slurry composition for forming the negative electrode.

[0037] A lithium secondary battery according to exemplary embodiments includes a positive electrode and a negative electrode facing the positive electrode. Effects of the invention

[0039] The dispersant according to the embodiments of the present invention includes a polycyclic aromatic functional group along with a functional group of any one of a polyethylene glycol group, a sulfonate group, and a pyrrolidinium group, so it simultaneously has a hydrophobic π-domain and a hydrophilic region.

[0040] Therefore, since it has strong interactions with carbon allotropes, it can effectively prevent aggregation between carbon allotropes and disperse carbon allotropes more uniformly.

[0041] In addition, the dispersant may include, for example, hydrophilic groups such as hydroxyl groups, or cations and anions. Accordingly, carbon allotropes can be effectively dispersed even in water or hydrophilic solvents.

[0042] In addition, the above-mentioned dispersant can be mixed with carbon allotropes to form compositions such as inks, pastes, and polymer resin composites. The above-mentioned dispersant can suppress the decrease in dispersibility and the increase in viscosity caused by the re-aggregation of carbon allotropes. By using the above-mentioned composition, for example, a negative electrode for a secondary battery having improved electrical characteristics and uniformity can be manufactured. Specific details for implementing the invention

[0044] According to embodiments of the present invention, a dispersant comprising a polycyclic aromatic functional group; and any one of a polyethylene glycol group, a sulfonate group, and a pyrrolidinium group; and a conductive composition comprising the same are provided.

[0045] In addition, embodiments of the present invention provide a slurry composition for forming a cathode comprising the conductive composition, and a cathode and a lithium secondary battery manufactured using the slurry composition.

[0046] Hereinafter, embodiments of the present invention will be described in more detail. However, this is not intended to limit the present invention to specific disclosed forms, and it should be understood that it includes all modifications, equivalents, and substitutions that fall within the spirit and scope of the present invention.

[0048] Dispersant

[0049] The dispersant according to the embodiments of the present invention can be utilized for the uniform dispersion of various carbon allotropes such as carbon nanotubes, graphene, graphite, carbon black, and fullerene, and in one embodiment, can be effectively applied as a dispersant for carbon nanotubes.

[0050] Carbon nanotubes comprise a repeating structure of aromatic hexagonal rings and may include, for example, multiwalled carbon nanotubes and / or singlewalled carbon nanotubes. The dispersant according to the embodiments of the present invention can be used universally for the dispersion of all types of carbon nanotubes, for example, and is not limited to use for a specific type of carbon nanotube.

[0051] The dispersant according to exemplary embodiments may include a polycyclic aromatic functional group; and any one of a polyethylene glycol group, a sulfonate group, and a pyrrolidinium group.

[0052] For example, the above dispersant includes a polycyclic aromatic functional group along with any one of a polyethylene glycol group, a sulfonate group, and a pyrrolidinium group, so it can simultaneously have a hydrophobic π-domain and a hydrophilic region.

[0053] For example, the polycyclic aromatic functional group may refer to an aromatic hydrocarbon functional group or an aromatic heterocyclic functional group in which two or more aromatic rings, for example, benzene rings, are bonded or included within a single compound structure. Additionally, the polycyclic aromatic functional group may have one or more oxygen-containing functional groups, such as hydroxyl groups, bonded to the aromatic rings.

[0054] In some embodiments, the polycyclic aromatic functional group may include a pyrene group or a carbazole group. Since polycyclic aromatic functional groups such as the pyrene group and the carbazole group form π-π bonds with carbon allotropes such as carbon nanotubes, they can effectively disperse the carbon allotropes.

[0055] For example, the sulfonate group may be a sulfonate salt, and the pyrrolidinium group may be a pyrrolidinium salt.

[0056] In some embodiments, the dispersant may include a compound having a structure represented by the following chemical formula 1.

[0057] [Chemical Formula 1]

[0058]

[0059] In the above chemical formula 1, R 1 is a pyrene group or a carbazole group, and R 2 is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and L 1 is a single bond or an alkylene group having 1 to 5 carbon atoms, and n can be an integer from 0 to 100.

[0060] For example, R 1 It can be a pyrene group and a carbazole group, and R 2 can be a hydrogen atom or a carbon-1 to carbon-3 alkyl group, a hydrogen atom or a carbon-1 to carbon-2 alkyl group, or a methyl group.

[0061] For example, L 1 It may be a single bond or an alkylene group having 1 to 4 carbon atoms, a single bond or an alkylene group having 1 to 3 carbon atoms, or a single bond or a methylene group.

[0062] For example, n may be an integer from 0 to 80, an integer from 0 to 60, an integer from 0 to 40, an integer from 0 to 20, an integer from 0 to 10, or an integer from 1 to 5.

[0063] For example, the above-mentioned dispersant includes a hydrophilic group such as a hydroxyl group, and can effectively disperse carbon allotropes even in water or a hydrophilic solvent.

[0064] In some embodiments, the dispersant may include a compound having a structure represented by the following formula 1-1 or formula 1-2.

[0065] [Chemical Formula 1-1]

[0066]

[0067] [Chemical Formula 1-2]

[0068]

[0069] In some embodiments, the dispersant may include a compound having a structure represented by the following chemical formula 2 or chemical formula 3.

[0070] [Chemical Formula 2]

[0071]

[0072] In the above chemical formula 2, R 3 is a pyrene group or a carbazole group, and L 2 is an alkoxylene group having 1 to 10 carbon atoms or an alkylene group having 1 to 10 carbon atoms, and M + It can be an alkali metal cation.

[0073] For example, R 3 It can be a pyrene group or a carbazole group.

[0074] For example, L 2 It may be an alkoxylene group having 1 to 8 carbon atoms or an alkylene group having 1 to 8 carbon atoms, an alkoxylene group having 1 to 6 carbon atoms or an alkylene group having 1 to 6 carbon atoms, an alkoxylene group having 1 to 4 carbon atoms or an alkylene group having 1 to 4 carbon atoms, or an alkoxylene group having 1 to 3 carbon atoms or an alkylene group having 1 to 3 carbon atoms, and preferably a propoxylene group.

[0075] For example, M + It can be a sodium cation, a potassium cation, etc., and preferably a potassium cation.

[0076] [Chemical Formula 3]

[0077]

[0078] In the above chemical formula 3, R 4 is a pyrene group or a carbazole group, and L 3 is an alkoxylene group having 1 to 10 carbon atoms or an alkylene group having 1 to 10 carbon atoms, and X - It can be a halogen ion.

[0079] For example, R 4 It can be a pyrene group or a carbazole group.

[0080] For example, L 3 ...is an alkoxylene group having 1 to 8 carbon atoms or an alkylene group having 1 to 8 carbon atoms, an alkoxylene group having 1 to 6 carbon atoms or an alkylene group having 1 to 6 carbon atoms, or L 2 It may be an alkoxylene group having 1 to 4 carbon atoms or an alkylene group having 1 to 4 carbon atoms, and preferably may be a butoxylene group or a butylene group.

[0081] For example, X - is a fluoride ion (F - ), chloride ions (Cl - ) or bromide ions (Br - It can be ) and preferably can be a bromide ion.

[0082] In some embodiments, the dispersant may include a compound having a structure represented by the following formula 2-1, formula 3-1, or formula 3-2.

[0083] [Chemical Formula 2-1]

[0084]

[0085] [Chemical Formula 3-1]

[0086]

[0087] [Chemical Formula 3-2]

[0088]

[0089] In one embodiment, the dispersant may have a hydrophobic π-domain formed by aromatic rings, along with a hydrophilic region formed by oxygen-containing functional groups, cations, and anions.

[0090] For example, the hydrophobic π-domain can have π-π interactions with the surface of a carbon allotrope, such as a carbon nanotube, in which carbon-carbon bonds are formed, and the hydrophilic region can improve dispersion stability through hydrogen bonding and polar-polar interactions with water, which is the dispersion solvent.

[0091] Accordingly, the dispersant is present between the powder or particles constituting each carbon allotrope, thereby effectively preventing aggregation between the carbon allotropes and dispersing the carbon allotropes more uniformly. For example, the dispersant may be adsorbed onto the surface of each particle of the carbon allotrope through the aforementioned π-π interaction.

[0093] Conductive composition

[0094] According to embodiments of the present invention, a conductive composition comprising the above-described dispersant is provided.

[0095] In one embodiment, the conductive composition may include a carbon allotrope such as a carbon nanotube, the dispersant, and a dispersion medium.

[0096] For example, the carbon allotrope may include at least one selected from the group consisting of carbon nanotubes, graphene, graphite, carbon black, and fullerene.

[0097] In some embodiments, the dispersion medium may include water or a hydrophilic organic solvent.

[0098] Specifically, the dispersion medium is not particularly limited as long as the dispersant can be dissolved therein. For example, N-methylpyrrolidone (NMP), dimethylformamide (DMF), dimethyl sulfoxide (DMSO), N,N-dimethylacetamide (DMAC), N-cyclohexylpyrrolidone (CHP), 1,3-dimethylpyrimidinone (DMPU), hexane, benzene, toluene, tetrahydrilfuran (THF), and alcohol-based solvents (e.g., C1 to C1 such as ethanol, butanol, isopropanol, pentanol, etc.). 10 Organic solvents such as alcohol can be used.

[0099] Both hydrophilic organic solvents and hydrophobic organic solvents may be used as dispersion media of the dispersant according to exemplary embodiments without special limitations.

[0100] In some embodiments, when the dispersant contains hydroxyl groups or cations and anions, water may be used as the dispersion medium. When water is used, environmental pollution problems caused by the generation of oil vapor can be avoided, and economic efficiency can be improved.

[0101] The conductive composition described above may be prepared in a liquid form, such as a paste or ink. A paste may refer to a fluid that is relatively viscous yet fluid, formed by mixing solid particles with a liquid substance such as water or an organic solvent. In the paste, the solid particles may not be completely dissolved in the liquid substance, and the solid particles may be visible to the naked eye during coating or dilution. The ink may contain a coloring fluid that has relatively lower viscosity and particle size within the liquid substance compared to the paste. Therefore, the interface of the particles may not be visible to the naked eye during coating or dilution.

[0102] In one embodiment, the conductive composition may be prepared in the form of an ink in which a carbon allotrope is substantially transparently dissolved in the liquid dispersion medium. Meanwhile, to improve the particle size and particle uniformity of the carbon allotrope in the ink, the carbon allotrope (or the aforementioned raw material byproduct or residue) may be milled or ground using a ball mill, a homogenizer, a high-pressure homogenizer, etc.

[0103] In one embodiment, the conductive composition may be prepared in the form of a paste, for example, by increasing the content of carbon allotropes and / or adding a thickener. For example, cellulose-based materials such as carboxymethyl cellulose (CMC), hydroxypropylmethyl cellulose, and methyl cellulose may be used as the thickener.

[0104] In one embodiment, the conductive composition may be prepared in a powder state comprising a carbon allotrope in a powder or particle state and a dispersant present on the surface of the powder or particle of the carbon allotrope. For example, the dispersant may be adsorbed onto the surface of the carbon allotrope by the aforementioned π-π interaction, etc.

[0105] In some embodiments, the carbon allotrope may comprise about 10% to 90% by weight of carbon black and about 10% to 90% by weight of one or more selected from graphene and carbon nanotubes, but the content range may be appropriately adjusted considering electrical properties or the type of battery.

[0106] In one embodiment, the carbon allotrope may be composed of carbon nanotubes.

[0107] In some embodiments, the content of the dispersant may be 1 to 50 parts by weight per 100 parts by weight of the carbon allotrope.

[0108] For example, the content of the dispersant may be 3 to 40 parts by weight, 5 to 30 parts by weight, or 5 to 15 parts by weight, based on 100 parts by weight of the carbon allotrope. Within the above range, the carbon allotrope can be dispersed more uniformly without the physical properties of the electrode formed from the conductive composition deteriorating.

[0109] The conductive composition of the above-described embodiment can be used to form electrodes of various batteries, for example, it can be included in an electrode slurry composition of a lithium secondary battery and used to form electrodes such as a positive electrode or a negative electrode of a lithium secondary battery.

[0110] For example, as the above-described dispersant is adsorbed on the surface of each particle of a carbon allotrope, the conductive composition can exhibit excellent redispersibility against various polar solvents or aqueous solvents, particularly aqueous solvents used in the manufacture of negative electrodes for lithium secondary batteries, as well as NMP used in the manufacture of positive electrodes.

[0111] In some embodiments, the conductive composition may be prepared by dissolving a carbon allotrope and a dispersant in a dispersion medium and irradiating with ultrasound. For example, carbon nanotubes and a dispersant may be dissolved in water and ultrasonically treated for 0.5 to 1.5 hours, after which the conductive composition in powder form may be recovered and dried.

[0112] The above recovery can be performed by methods such as centrifugation, vacuum filtration, or pressure filtration, and the above drying can be performed by methods such as vacuum drying at a temperature of about 30°C to 90°C.

[0114] <Slurry composition for cathode formation>

[0115] According to embodiments of the present invention, a slurry composition for forming a cathode comprising the conductive composition described above is provided.

[0116] In one embodiment, the slurry composition may include a negative electrode active material, the conductive composition, a binder, and a solvent.

[0117] For example, the above negative electrode active material is lithium metal or lithium alloy; coke, artificial graphite, natural graphite, combustible organic polymer compound, carbon fiber, Si, SiO x Any lithium or alloy thereof, carbon-based or silicon-based materials, etc., which have been known to be usable as negative electrode active materials for lithium secondary batteries, such as Sn or SnO2, can be used without any particular restrictions.

[0118] In some embodiments, the binder may comprise at least one selected from the group consisting of polytetrafluoroethylene, carboxymethyl cellulose, vinylidene fluoride / hexafluoropropylene copolymer, polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, polyacrylate, poly(styrene-butadiene) copolymer, alginate, and polydopamine.

[0119] In some embodiments, the solvent may comprise at least one selected from the group consisting of water, N-methylpyrrolidone, acetone, tetrahydrofuran, and decane.

[0120] In some embodiments, the composition may comprise 70 to 98 parts by weight of the negative electrode active material, 0.1 to 15 parts by weight of the conductive composition, and 1 to 20 parts by weight of the binder, based on 100 parts by weight of the total solid content of the negative electrode active material, the conductive composition, and the binder.

[0121] Within the above range, a cathode and a battery can be manufactured that contain carbon allotropes in a uniformly dispersed state at a high content and exhibit improved electrical characteristics.

[0122] Embodiments of the present invention provide a lithium secondary battery or a negative electrode for a lithium secondary battery manufactured from a slurry composition comprising the conductive composition described above.

[0123] The above conductive composition can be used as an electrode material for a cathode.

[0124] In some embodiments, the cathode may include a current collector and a cathode active material layer, and the slurry composition may be applied, for example, onto the current collector to form the cathode active material layer. As described above, the dispersibility of the carbon allotrope is significantly improved by the dispersant, so that uniform and excellent electrical characteristics can be realized across the entire cathode region.

[0125] The above-mentioned cathode current collector may include, for example, stainless steel, nickel, aluminum, copper, titanium, or alloys thereof; or aluminum, copper, or stainless steel, etc., surface-treated with carbon, nickel, titanium, silver, etc., and preferably may include copper or a copper alloy.

[0126] The material of the binder or electrode current collector described above may include materials known in the art, and the scope of the present invention is not limited by the materials described above.

[0127] In some embodiments, the lithium secondary battery may include a positive electrode and a negative electrode for the lithium secondary battery described above.

[0128] For example, the decrease in dispersibility and increase in viscosity caused by the re-aggregation of carbon allotropes can be suppressed by the above-mentioned dispersant, and the lithium secondary battery may contain a high content of carbon allotropes uniformly dispersed in the negative electrode, and the electrical characteristics and uniformity of the negative electrode may be improved.

[0129] Hereinafter, experimental examples including preferred embodiments and comparative examples are presented to aid in understanding the present invention; however, these embodiments are merely illustrative of the present invention and are not intended to limit the appended claims. It is obvious to those skilled in the art that various changes and modifications to the embodiments are possible within the scope and spirit of the present invention, and that such variations and modifications fall within the scope of the appended claims.

[0131] Examples and Comparative Examples

[0132] Example 1

[0133]

[0134] 12.8g of K2CO3 was added to a solution in which 21.8g (0.1mol) of pyrenol and 28.6g (0.1mol) of a PEG-based nitrate compound were dissolved in 200g of DMF, and the mixture was stirred at 100℃ for 24 hours.

[0135] It was confirmed by TLC that no pyrenol remained in the above stirred solution, and it was cooled to room temperature. The cooled stirred solution was added to 1 L of water to produce a precipitate, and then filtered and dried to obtain dispersant I having a structure represented by the following chemical formula 1-1.

[0136] 0.0032g of the obtained dispersant I and 0.0541g of carbon nanotubes were dissolved in 108.2g of water, which is a solvent, and ultrasonically irradiated for 60 minutes to prepare a conductive composition.

[0137] A slurry composition for forming a cathode was prepared by mixing the manufactured conductive composition, artificial graphite, and carboxymethyl cellulose with water in a weight ratio of 15:80:5.

[0138] [Chemical Formula 1-1]

[0139]

[0141] Example 2

[0142]

[0143] A dispersant II having a structure represented by the following chemical formula 1-2 was obtained by the same method as in Example 1, except that 16.7 g (0.1 mol) of carbazole was used instead of 21.8 g of pyrenol.

[0144] Subsequently, a conductive composition and a slurry composition for forming a cathode were prepared using the same method as in Example 1.

[0145] [Chemical Formula 1-2]

[0146]

[0148] Example 3

[0149]

[0150] Bromobutoxypyrene was prepared by adding K2CO3 to a solution in which pyrenol and dibromobutane were dissolved in DMF, a solvent, and stirring at 100°C for 24 hours.

[0151] A solution of 35.3 g (0.1 mol) of prepared bromobutoxypyrene and 8.5 g (0.1 mol) of methylpyrrolidine dissolved in 300 g of acetonitrile was heated and refluxed for 12 hours, cooled to room temperature, and then subjected to vacuum distillation to remove the solvent, thereby obtaining dispersant III having a structure represented by the following chemical formula 3-1.

[0152] [Chemical Formula 3-1]

[0153]

[0154] Subsequently, a conductive composition and a slurry composition for forming a cathode were prepared using the same method as in Example 1.

[0156] Example 4

[0157]

[0158] Bromobutylcarbazole was obtained through the same method as in Example 3 above, except that carbazole and dibromobutane were used instead of pyrenol and dibromobutane.

[0159] Subsequently, a dispersant IV having a structure represented by the following chemical formula 3-2, a conductive composition, and a cathode-forming slurry composition were prepared using the same method as in Example 3, except that bromobutylcarbazole was used instead of bromobutoxypyrene.

[0160] [Chemical Formula 3-2]

[0161]

[0163] Example 5

[0164]

[0165] 5.6g of KOH was added to a solution in which 21.8g (0.1mol) of pyrenol and 12.2g (0.1mol) of propanesulfone were dissolved in 100g of acetonitrile solvent, and the mixture was stirred at 50℃ for 2 hours.

[0166] The acetonitrile solvent was removed from the above stirred solution by vacuum distillation to obtain 37g of dispersant V having a structure represented by the following chemical formula 2-1.

[0167] Subsequently, a conductive composition and a slurry composition for forming a cathode were prepared using the same method as in Example 1.

[0168] [Chemical Formula 2-1]

[0169]

[0171] Comparative Example 1

[0172] A conductive composition and a cathode-forming slurry composition were prepared using the same method as in Example 1, except that isophthalic acid was used as the dispersant instead of the above-mentioned dispersant.

[0174] Comparative Example 2

[0175] A conductive composition and a cathode-forming slurry composition were prepared using the same method as in Example 1, except that polyacrylic acid was used as the dispersant instead of the above-mentioned dispersant.

[0177] Experimental Example

[0178] (1) Check for dispersion

[0179] The conductive compositions according to the examples and comparative examples were stirred for about 1 minute, and then the dispersion state was checked visually. The dispersed carbon allotrope solution was diluted 500 times with the same solvent, and the dispersion state was observed visually.

[0180] The evaluation criteria are as follows, and the evaluation results are shown in Table 1 below.

[0181] <Dispersion Evaluation Criteria>

[0182] Transparent: Completely dissolved and transparent state

[0183] Precipitation: A state in which carbon allotropes form precipitates.

[0184] Translucent: A state in which small particles are suspended but are not completely transparent.

[0186] (2) Viscosity measurement

[0187] The viscosity of the cathode-forming slurry compositions according to the examples and comparative examples was measured at 25°C and 1 rpm using a viscometer, and the results are shown in Table 1 below.

[0189] Dispersant Distributed state Viscosity (Pa·s) Example 1 Dispersant I transparency 26 Example 2 Dispersant II transparency 22 Example 3 Dispersant III transparency 21 Example 4 Dispersant IV transparency 24 Example 5 Dispersant V transparency 27 Comparative Example 1 isophthalic acid precipitation 13 Comparative Example 2 polyacrylic acid translucent 74

[0190] Referring to Table 1, the conductive compositions of the embodiments containing the dispersant of the present invention were transparent and had good dispersion, while the viscosity of the slurry composition prepared using the conductive composition was low.

[0191] However, the conductive composition of Comparative Example 1, which does not contain the above-mentioned dispersant, had a low solubility of the dispersant and precipitated.

[0192] In addition, the conductive composition of Comparative Example 2, which does not contain the above-mentioned dispersant, was translucent, so the dispersion state deteriorated, and the viscosity of the slurry composition prepared from the above-mentioned conductive composition was high.

Claims

Claim 1 A dispersant comprising a polycyclic aromatic functional group; and either one of a sulfonate group and a pyrrolidinium group. Claim 2 In claim 1, the polycyclic aromatic functional group is a pyrene group or a dispersant containing a carbazole group. Claim 3 delete Claim 4 The dispersant of claim 1, comprising a compound having a structure represented by the following formula 2 or formula 3: [Formula 2] (In the above chemical formula 2, R 3 is a pyrene group or a carbazole group, and L 2 is an alkoxylene group having 1 to 10 carbon atoms or an alkylene group having 1 to 10 carbon atoms, and M + is an alkali metal cation)[Chemical Formula 3] (In the above chemical formula 3, R 4 is a pyrene group or a carbazole group, and L 3 is an alkoxylene group having 1 to 10 carbon atoms or an alkylene group having 1 to 10 carbon atoms, and X - is a halogen ion). Claim 5 A conductive composition comprising: at least one carbon allotrope selected from the group consisting of carbon nanotubes, graphene, graphite, carbon black, and fullerene; a dispersant comprising a polycyclic aromatic functional group and either a sulfonate group or a pyrrolidinium group; and a dispersion medium. Claim 6 In claim 5, the conductive composition, wherein the dispersant is adsorbed onto the surface of the carbon allotrope. Claim 7 A conductive composition according to claim 5, wherein the dispersion medium comprises water or a hydrophilic organic solvent, and the polycyclic aromatic functional group comprises a pyrene group or a carbazole group. Claim 8 A conductive composition according to claim 5, wherein the content of the dispersant is 1 to 50 parts by weight per 100 parts by weight of the carbon allotrope. Claim 9 A conductive composition according to claim 5, wherein the dispersant comprises a compound having a structure represented by either Chemical Formula 2 or Chemical Formula 3: [Chemical Formula 2] (In the above chemical formula 2, R 3 is a pyrene group or a carbazole group, and L 2 is an alkoxylene group having 1 to 10 carbon atoms or an alkylene group having 1 to 10 carbon atoms, and M + is an alkali metal cation)[Chemical Formula 3] (In the above chemical formula 3, R 4 is a pyrene group or a carbazole group, and L 3 is an alkoxylene group having 1 to 10 carbon atoms or an alkylene group having 1 to 10 carbon atoms, and X - is a halogen ion). Claim 10 A slurry composition for forming a cathode, comprising a cathode active material, a conductive composition according to claim 5, a binder, and a solvent. Claim 11 A cathode-forming slurry composition according to claim 10, wherein the binder comprises at least one selected from the group consisting of polytetrafluoroethylene, carboxymethyl cellulose, vinylidene fluoride / hexafluoropropylene copolymer, polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, polyacrylate, poly(styrene-butadiene) copolymer, alginate, and polydopamine. Claim 12 A slurry composition for forming a cathode according to claim 10, comprising 70 to 98 parts by weight of a cathode active material, 0.1 to 15 parts by weight of a conductive composition, and 1 to 20 parts by weight of a binder, based on a total solid content of 100 parts by weight of the sum of the cathode active material, the conductive composition, and the binder. Claim 13 A negative electrode for a lithium secondary battery comprising: a current collector; and a negative electrode active material layer located on the current collector, wherein the negative electrode active material layer is formed from a slurry composition for forming a negative electrode according to claim 10. Claim 14 A lithium secondary battery comprising: a positive electrode; and a negative electrode for a lithium secondary battery according to claim 13 facing the positive electrode.

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