Carbon filler dispersant, composition containing carbon filler, and nonaqueous-electrolyte secondary battery

Abstract

Provided is a carbon filler dispersant which inhibits carbon fillers from aggregating and improves the dispersibility. Specifically, the carbon filler dispersant is a polyester represented by any of general formulae (1-1), (1-2) and (1-3) (in the general formulae (1-1), (1-2) and (1-3), G is a C2-20 aliphatic diol residue, A is a C4-18 aromatic dicarboxylic acid residue, X is a C1-20 monocarboxylic acid residue, Y is a C1-30 monohydric alcohol residue, and n indicates the number of repetitions).

Description

Carbon filler dispersant, carbon filler-containing composition, and nonaqueous electrolyte secondary battery

[0001] The present invention relates to a carbon filler dispersant, a carbon filler-containing composition, and a nonaqueous electrolyte secondary battery.

[0002] In recent years, the introduction of electric vehicles has progressed rapidly in countries around the world in order to reduce carbon dioxide emissions. Electric vehicles are powered by lithium-ion batteries (LiBs), and the performance of the LiB determines the driving distance of the electric vehicle. Since the LiB accounts for a large portion of the capacity of the electric vehicle, there is a demand for LiBs with higher capacity and smaller size.

[0003] An LiB is a laminate of a positive electrode sheet, a separator, and a negative electrode sheet, and the positive electrode sheet and negative electrode sheet are composed of an active material, a conductive material, and a binder resin. The performance of an LiB is highly dependent on the performance of the active material, and increasing the amount of active material in the electrode is effective in increasing the capacity of an LiB. For this reason, there is a demand to reduce the amount of conductive material and binder resin used.

[0004] The conductive material serves to connect the active material particles to form conductive paths within the electrode sheet, and generally comprises carbon fillers such as carbon black and carbon nanotubes.

[0005] Patent Document 1 discloses a dispersant that improves the dispersibility of a conductive material, and proposes increasing the amount of active material by improving the dispersibility of the conductive material.

[0006] Japanese Patent Application Laid-Open No. 2022-42965

[0007] Carbon filler, a conductive material, is difficult to disperse due to its large specific surface area, and tends to form coarse aggregates. The dispersant disclosed in Patent Document 1 reduces the viscosity of a dispersion containing the carbon filler, apparently improving dispersibility. However, coarse aggregates of the carbon filler were observed in the dispersion, and the effect was not considered sufficient.

[0008] The present invention provides a carbon filler dispersant that suppresses the aggregation of carbon fillers and improves dispersibility. Another object of the present invention is to provide a carbon filler-containing composition that suppresses the aggregation of carbon fillers and improves dispersibility.

[0009] As a result of intensive research to solve the above problems, the present inventors have found that a polyester having a specific structure can suppress the aggregation of carbon fillers and increase the dispersibility of the carbon fillers, thereby completing the present invention.

[0010] That is, the present invention relates to the following carbon filler dispersants, etc.: 1. A carbon filler dispersant which is a polyester represented by the following general formula (1-1), (1-2) or (1-3). (In the general formulae (1-1), (1-2), and (1-3), G is an aliphatic diol residue having 2 to 20 carbon atoms, A is an aromatic dicarboxylic acid residue having 4 to 18 carbon atoms, X is a monocarboxylic acid residue having 1 to 20 carbon atoms, Y is a monoalcohol residue having 1 to 30 carbon atoms, and n represents the number of repetitions.) 2. The carbon filler dispersant according to 1, wherein A contains one or more selected from a phthalic acid residue, an isophthalic acid residue, a terephthalic acid residue, and a naphthalenedicarboxylic acid residue. 3. The carbon filler dispersant according to 1 or 2, wherein G is an aliphatic diol residue having a branched structure and having 3 to 20 carbon atoms. 4. The carbon filler dispersant according to any one of 1 to 3, wherein the polyester is an amorphous polyester. 5. The carbon filler dispersant according to any one of 1 to 4, wherein the polyester has a number average molecular weight in the range of 400 to 10,000. 6. The carbon filler dispersion according to any one of 1 to 5, wherein the carbon filler is one or more selected from graphite, carbon black, carbon nanotubes, graphene, and graphene oxide. 7. A carbon filler dispersion containing a carbon filler, the carbon filler dispersion according to any one of 1 to 6, and a dispersion medium. 8. The carbon filler dispersion according to 7, wherein the carbon filler is one or more selected from graphite, carbon black, carbon nanotubes, graphene, and graphene oxide. 9. A lithium secondary battery electrode containing a carbon filler, the carbon filler dispersion according to any one of 1 to 6, and an electrode active material. 10. A lithium secondary battery having the lithium secondary battery electrode according to 9.

[0011] According to the present invention, it is possible to provide a carbon filler dispersant that improves the dispersibility of a carbon filler, and a carbon filler-containing composition in which the dispersibility of a carbon filler is improved.

[0012] An embodiment of the present invention will be described below. The present invention is not limited to the following embodiment, and can be carried out by making appropriate modifications within the scope that does not impair the effects of the present invention. The compounds in this specification may be derived from fossil resources or biological resources.

[0013] [Carbon filler dispersant] The carbon filler dispersant of the present invention is a polyester represented by the following general formula (1-1), (1-2) or (1-3): Hereinafter, the polyester that is the carbon filler dispersant of the present invention may be referred to as the "polyester of the present invention."

[0014] (In the general formulae (1-1), (1-2), and (1-3), G represents an aliphatic diol residue having 2 to 20 carbon atoms, A represents an aromatic dicarboxylic acid residue having 4 to 18 carbon atoms, X represents a monocarboxylic acid residue having 1 to 20 carbon atoms, Y represents a monoalcohol residue having 1 to 30 carbon atoms, and n represents the number of repeating units.)

[0015] It is presumed that the aromatic dicarboxylic acid residue moiety of the polyester of the present invention has an increased affinity with the carbon filler due to π-π interactions, enabling it to be adsorbed to the carbon filler. It is considered that the polyester of the present invention adsorbed to the carbon filler can suppress aggregation of the carbon filler and disperse it due to the compatibility of the moiety other than the aromatic dicarboxylic acid residue with the matrix resin.

[0016] In the present invention, the terms "diol residue" and "alcohol residue" refer to the organic group remaining after removing the hydroxyl group from a diol or alcohol. In the present invention, the term "carboxylic acid residue" refers to the organic group remaining after removing the carboxyl group from a carboxylic acid. The number of carbon atoms in the carboxylic acid residue does not include the carbon atoms in the carboxyl group.

[0017] The aliphatic chain of the aliphatic diol residue of G having 2 to 20 carbon atoms may be linear or branched, and may contain an alicyclic structure and / or an ether bond. In addition, the aliphatic chain of the aliphatic diol residue of G may be a saturated aliphatic chain or an unsaturated aliphatic chain having a carbon-carbon unsaturated bond.

[0018] The aliphatic diol residue G having 2 to 20 carbon atoms is preferably an aliphatic diol residue having a branched structure having 3 to 20 carbon atoms, and more preferably a diol represented by the following general formula (G-1). (In the general formula (G-1), p is an integer of 1 or more, q is an integer of 0 or more, r is an integer of 1 or more, R is a hydrogen atom or an alkyl group having 1 or more carbon atoms, at least one of the r R is an alkyl group having 1 or more carbon atoms, and the total number of carbon atoms of p, q, r, and R is an integer of 3 to 20.)

[0019] Examples of the aliphatic diol residue having 2 to 20 carbon atoms for G include an ethylene glycol residue, a 1,2-propylene glycol residue, a 1,3-propanediol residue, a 1,2-butanediol residue, a 1,3-butanediol residue, a 2-methyl-1,3-propanediol residue, a 1,4-butanediol residue, a 1,5-pentanediol residue, a 2,2-dimethyl-1,3-propanediol (neopentyl glycol) residue, a 2,2-diethyl-1,3-propanediol (3,3-dimethylolpentane) residue, a 2-methyl-1,3-propanediol (neopentyl glycol) residue, a 2,2-diethyl-1,3-propanediol (3,3-dimethylolpentane) residue, a 2-methyl-1,3-propanediol (neopentyl glycol) residue, a 2-methyl ... Examples of the alkyl group include n-butyl-2-ethyl-1,3-propanediol (3,3-dimethylolheptane) residue, 3-methyl-1,5-pentanediol residue, 1,6-hexanediol residue, 2,2,4-trimethyl-1,3-pentanediol residue, 2-ethyl-1,3-hexanediol residue, 2-methyl-1,8-octanediol residue, 1,9-nonanediol residue, 1,10-decanediol residue, 1,12-dodecanediol residue, 1,2-tetradecanediol residue, and 1,2-dodecanediol residue.

[0020] The aliphatic diol residue having 2 to 20 carbon atoms for G may contain an alicyclic structure, and examples of the aliphatic diol residue having 2 to 20 carbon atoms containing an alicyclic structure include a 1,3-cyclopentanediol residue, a 1,2-cyclohexanediol residue, a 1,3-cyclohexanediol residue, a 1,4-cyclohexanediol residue, a 1,2-cyclohexanedimethanol residue, and a 1,4-cyclohexanedimethanol residue.

[0021] The aliphatic diol residue having 2 to 20 carbon atoms for G may contain an ether bond (—O—), and examples of the aliphatic diol residue having 2 to 20 carbon atoms and containing an ether bond include a diethylene glycol residue, a triethylene glycol residue, a tetraethylene glycol residue, a dipropylene glycol residue, and a tripropylene glycol residue.

[0022] G is preferably an aliphatic diol residue having 2 to 14 carbon atoms, and more preferably an ethylene glycol residue, a diethylene glycol residue, a 1,2-propylene glycol residue, a 1,6-hexanediol residue, a 3-methyl-1,5-pentanediol residue, a 1,4-butanediol residue, a 1,3-butanediol residue, a 1,2-tetradecanediol residue, or a 1,2-dodecanediol residue.

[0023] The aromatic dicarboxylic acid residue of A having 4 to 18 carbon atoms is a residue of a dicarboxylic acid in which two carboxyl groups are substituted on an aromatic ring, and the aromatic ring may further be substituted with a substituent (for example, an alkyl group having 1 to 6 carbon atoms).

[0024] Examples of the aromatic dicarboxylic acid residue having 4 to 18 carbon atoms for A include 2,5-furandicarboxylic acid, phthalic acid residue, isophthalic acid residue, terephthalic acid residue, 1,4-naphthalenedicarboxylic acid residue, 1,5-naphthalenedicarboxylic acid residue, 2,3-naphthalenedicarboxylic acid residue, 2,6-naphthalenedicarboxylic acid residue, 4,4'-biphenyldicarboxylic acid, 1,5-anthracenedicarboxylic acid, 2,3-anthracenedicarboxylic acid residue, and 9,10-anthracenedicarboxylic acid.

[0025] In the present specification, the term "aromatic dicarboxylic acid residue" also includes those in which an aromatic ring is further substituted with a substituent (for example, an alkyl group having 1 to 6 carbon atoms). For example, the term "terephthalic acid residue" also includes a dimethyl terephthalate residue, and the term "2,6-naphthalenedicarboxylic acid residue" also includes a dimethyl 2,6-naphthalenedicarboxylate residue.

[0026] The aromatic dicarboxylic acid residue having 6 to 18 carbon atoms for A preferably includes at least one selected from the group consisting of a phthalic acid residue, an isophthalic acid residue, a terephthalic acid residue, and a naphthalenedicarboxylic acid residue. The phthalic acid residue, the isophthalic acid residue, the terephthalic acid residue, and the naphthalenedicarboxylic acid residue have high affinity with the carbon filler, and are expected to have a high dispersing effect.

[0027] The monocarboxylic acid residue having 1 to 20 carbon atoms for X may be, for example, either an aliphatic monocarboxylic acid residue having 1 to 20 carbon atoms or an aromatic monocarboxylic acid residue having 1 to 20 carbon atoms, and is preferably an aliphatic monocarboxylic acid residue having 1 to 20 carbon atoms.

[0028] When X is a residue of an aliphatic monocarboxylic acid having 1 to 20 carbon atoms, the aliphatic chain of the residue of the aliphatic monocarboxylic acid having 1 to 20 carbon atoms may be linear or branched, and may contain an alicyclic structure and / or an ether bond. Furthermore, the aliphatic chain of the residue of the aliphatic monocarboxylic acid having 1 to 20 carbon atoms may be a saturated aliphatic chain or an unsaturated aliphatic chain having a carbon-carbon unsaturated bond.

[0029] Examples of the monocarboxylic acid residue having 1 to 20 carbon atoms for X include acetic acid residue, propionic acid residue, butanoic acid residue, hexanoic acid residue, octanoic acid residue, octylic acid residue, benzoic acid residue, dimethylbenzoic acid residue, trimethylbenzoic acid residue, tetramethylbenzoic acid residue, ethylbenzoic acid residue, propylbenzoic acid residue, butylbenzoic acid residue, cumic acid residue, para-tert-butylbenzoic acid residue, orthotoluic acid residue, meta-toluic acid residue, para-toluic acid residue, ethoxybenzoic acid residue, propoxybenzoic acid residue, and anisic acid residue.

[0030] The monoalcohol residue having 1 to 30 carbon atoms for Y may be, for example, either an aliphatic monoalcohol residue having 1 to 30 carbon atoms or an aromatic monoalcohol residue having 6 to 30 carbon atoms, and is preferably an aliphatic monoalcohol residue having 1 to 30 carbon atoms.

[0031] When Y is a residue of an aliphatic monoalcohol having 1 to 30 carbon atoms, the aliphatic chain of the aliphatic monoalcohol residue having 1 to 30 carbon atoms may be linear or branched, and may contain an alicyclic structure and / or an ether bond. In addition, the aliphatic chain of the aliphatic monoalcohol residue having 1 to 30 carbon atoms may be a saturated aliphatic chain or an unsaturated aliphatic chain having a carbon-carbon unsaturated bond.

[0032] The monoalcohol residue having 1 to 30 carbon atoms represented by Y is preferably an alkyl alcohol residue having 1 to 10 carbon atoms or an alcohol residue of a polyalkylene glycol monoalkyl ether having 5 to 30 carbon atoms.

[0033] Examples of the alkyl alcohol residue having 1 to 10 carbon atoms represented by Y include a methanol residue, ethanol residue, propanol residue, butanol residue, pentanol residue, hexanol residue, cyclohexanol residue, heptanol residue, octanol residue, nonanol residue, and decanol residue.

[0034] Examples of the alcohol residue of a polyalkylene glycol alkyl ether having 5 to 30 carbon atoms represented by Y include alcohol residues of polyethylene glycol alkyl ethers such as diethylene glycol monomethyl ether and triethylene glycol monomethyl ether; polypropylene glycol alkyl ethers such as polypropylene glycol monomethyl ether and polypropylene glycol monoethyl ether; and (polyethylene glycol-polypropylene glycol) monoalkyl ethers.

[0035] The average value of the repeat number of n is preferably in the range of 0.1 to 20, more preferably in the range of 0.2 to 15, and more preferably in the range of 0.5 to 10. The average value of the repeat number of n can be calculated from the number average molecular weight of the polyester of the present invention.

[0036] The number average molecular weight (Mn) of the polyester of the present invention has a lower limit of, for example, 300 or more, 400 or more, or 450 or more, and an upper limit of, for example, 20,000 or less, 10,000 or less, 8,000 or less, 5,000 or less, or 3,000 or less. The number average molecular weight (Mn) of the polyester of the present invention is, for example, in the range of 300 to 20,000, preferably 400 to 10,000, and more preferably 450 to 8,000. The number average molecular weight (Mn) is a value calculated in terms of polystyrene based on gel permeation chromatography (GPC) measurement, and is measured by the method described in the Examples.

[0037] The acid value of the polyester of the present invention has a lower limit of, for example, 0.001 mgKOH / g or more, 0.01 mgKOH / g or more, 0.1 mgKOH / g or more, or 1 mgKOH / g or more, and an upper limit of, for example, 10 mgKOH / g or less, 5 mgKOH / g or less, 3 mgKOH / g or less, or 1 mgKOH / g or less. The acid value of the polyester of the present invention is, for example, in the range of 0.001 to 3 mgKOH / g. The acid value of the polyester is confirmed by the method described in the Examples.

[0038] The hydroxyl value of the polyester of the present invention is, for example, in the range of 0.1 to 400 mgKOH / g, preferably in the range of 0.1 to 200 mgKOH / g, and more preferably in the range of 0.1 to 100 KOH / g. The hydroxyl value of the polyester is confirmed by the method described in the examples.

[0039] The polyester of the present invention is preferably an amorphous polyester. Here, "amorphous" means that the polyester does not show a clear endothermic peak in differential scanning calorimetry (DSC). Specifically, a polyester that does not show a clear endothermic peak when subjected to the differential scanning calorimetry described in the Examples is an amorphous polyester. When the polyester is amorphous, the polyester is more easily dissolved in a matrix resin and a solvent, allowing for uniform adsorption to the carbon filler surface, thereby improving dispersibility.

[0040] The polyester of the present invention may be any polyester that satisfies the above general formula (1-1), (1-2) or (1-3), and may be used as a mixture of two or more polyesters having different structures.

[0041] The polyester of the present invention can be obtained using reaction raw materials containing an aliphatic diol, an aromatic dicarboxylic acid, a monoalcohol and / or a monocarboxylic acid (however, monoalcohol and / or monocarboxylic acid are not required for the production of the polyester represented by general formula (1-3). The monoalcohol and / or monocarboxylic acid are optional components). Here, the reaction raw materials mean raw materials that constitute the polyester of the present invention, and do not include solvents or catalysts that do not constitute the polyester. The method for producing the polyester of the present invention is not particularly limited, and the polyester can be produced by known methods, or by the production method described below.

[0042] The reaction raw materials for the polyester of the present invention may contain an aliphatic diol, an aromatic dicarboxylic acid, a monoalcohol, and / or a monocarboxylic acid, and may also contain other raw materials. The reaction raw materials for the polyester of the present invention preferably contain an aliphatic diol, an aromatic dicarboxylic acid, a monoalcohol, and / or a monocarboxylic acid in an amount of 90 mass% or more based on the total amount of the reaction raw materials, and more preferably consist of only an aliphatic diol, an aromatic dicarboxylic acid, a monoalcohol, and / or a monocarboxylic acid.

[0043] The aliphatic diol used in the production of the polyester of the present invention is an aliphatic diol corresponding to the aliphatic diol residue of G having 2 to 20 carbon atoms, and the aliphatic diol used may be used alone or in combination of two or more. The aromatic dicarboxylic acid used in the production of the polyester of the present invention is an aromatic dicarboxylic acid corresponding to the aromatic dicarboxylic acid residue of A having 6 to 18 carbon atoms, and the aromatic dicarboxylic acid used may be used alone or in combination of two or more. The monocarboxylic acid used in the production of the polyester of the present invention is a monocarboxylic acid corresponding to the monocarboxylic acid residue of X having 1 to 20 carbon atoms, and the monocarboxylic acid used may be used alone or in combination of two or more. The monoalcohol used in the production of the polyester of the present invention is a monoalcohol corresponding to the monoalcohol residue of Y having 1 to 30 carbon atoms, and the monoalcohol used may be used alone or in combination of two or more.

[0044] Hydrogenated vegetable oil fatty acids may be used as the monocarboxylic acid used in producing the polyester of the present invention. Examples of such hydrogenated vegetable oil fatty acids include hydrogenated coconut oil fatty acids, hydrogenated palm kernel oil fatty acids, hydrogenated palm oil fatty acids, hydrogenated olive oil fatty acids, hydrogenated castor oil fatty acids, and hydrogenated rapeseed oil fatty acids. These are obtained by hydrolyzing and hydrogenating oils obtained from coconut, palm kernel, palm, olive, castor, and rapeseed, respectively, and are all mixtures of two or more long-chain aliphatic monocarboxylic acids including an aliphatic monocarboxylic acid having 8 to 21 carbon atoms. The monocarboxylic acid used in producing the polyester of the present invention may be the above-mentioned vegetable oil fatty acids that have not been hydrogenated, as long as the effects of the present invention are not impaired. Furthermore, the vegetable oil fatty acids are not limited to those mentioned above.

[0045] When the polyester of the present invention is a polyester obtained by reacting an aliphatic diol, an aromatic dicarboxylic acid, and a hydrogenated vegetable oil fatty acid as reaction raw materials, the resulting polyester is a mixture of two or more polyesters represented by the general formula (1-1).

[0046] The aliphatic diol, aromatic dicarboxylic acid, monoalcohol, and monocarboxylic acid used in the production of the polyester of the present invention can all be used as derivatives thereof. Examples of such derivatives include esters, acid chlorides, acid anhydrides, and cyclic esters. For example, since an epoxy compound undergoes ring-opening to form a diol when reacted with a carboxylic acid, an aliphatic epoxy compound may be used as a derivative of the aliphatic diol used as a reaction raw material in the present invention.

[0047] The polyester represented by the general formula (1-1) can be produced, for example, by charging an aliphatic diol, an aromatic dicarboxylic acid, and a monocarboxylic acid all at once and reacting them in such a way that the equivalent weight of the carboxyl groups is greater than the equivalent weight of the hydroxyl groups. Alternatively, the polyester represented by the general formula (1-1) can be produced, for example, by reacting an aliphatic diol and an aromatic dicarboxylic acid in any equivalent ratio, and then reacting the terminal hydroxyl groups of the resulting polyester with a monocarboxylic acid to cap the hydroxyl groups with a carboxylic acid residue.

[0048] The polyester represented by the general formula (1-2) can be produced, for example, by charging an aliphatic diol, an aromatic dicarboxylic acid, and a monoalcohol all at once and reacting them in such a way that the equivalent weight of the carboxyl group is greater than the equivalent weight of the hydroxyl group. Alternatively, the polyester represented by the general formula (1-2) can be produced, for example, by reacting an aliphatic diol and an aromatic dicarboxylic acid in any equivalent ratio, and then reacting the terminal of the resulting polyester with a monoalcohol.

[0049] The polyester represented by the general formula (1-3) can be produced, for example, by charging an aliphatic diol and an aromatic dicarboxylic acid all at once and reacting them in such a way that the equivalent weight of the hydroxyl group is greater than the equivalent weight of the carboxyl group. Alternatively, the polyester represented by the general formula (1-3) can also be produced, for example, by reacting an aliphatic diol and an aromatic dicarboxylic acid in any equivalent ratio, and then reacting the terminal of the resulting polyester with an aliphatic diol.

[0050] In the production of the polyester of the present invention, the reaction of the raw materials may be carried out as an esterification reaction, for example, in the presence of an esterification catalyst at a temperature of 170 to 250° C. for 10 to 25 hours. The conditions of the esterification reaction, such as the temperature and time, are not particularly limited and may be set appropriately.

[0051] Examples of the esterification catalyst include titanium-based catalysts such as tetraisopropyl titanate and tetrabutyl titanate; zinc-based catalysts such as zinc acetate; tin-based catalysts such as tin octoate and dibutyltin oxide; and organic sulfonic acid-based catalysts such as p-toluenesulfonic acid.

[0052] The amount of the esterification catalyst used may be appropriately determined, but is usually in the range of 0.0001 to 0.1 parts by mass per 100 parts by mass of the total amount of the reaction raw materials.

[0053] [Carbon filler dispersion] The carbon filler dispersion of the present invention contains a carbon filler, the carbon filler dispersant of the present invention, and a dispersion medium. The electrode-forming composition described below is usually prepared by adding various components to the carbon filler dispersion. Each component contained in the carbon filler dispersion of the present invention will be described below.

[0054] (Carbon Filler) The carbon filler contained in the carbon filler dispersion of the present invention is not particularly limited, and examples thereof include graphite, carbon black (acetylene black, furnace black, hollow carbon black, channel black, thermal black, ketjen black, etc.), carbon nanotubes (single-walled carbon nanotubes, multi-walled carbon nanotubes, etc.), graphene, graphene oxide, etc. The carbon fillers may be used alone or in combination of two or more.

[0055] The particle size, fiber length, fiber diameter, and other shapes of the carbon filler are not particularly limited and may be adjusted appropriately depending on the intended use. For example, carbon nanotubes include single-walled carbon nanotubes in which one surface of graphite is wrapped in one layer, and multi-walled carbon nanotubes in which graphite is wrapped in two or more layers, and both can be used. In addition, the surface treatment state of the carbon filler is not particularly limited, and the surface may be modified with, for example, saturated fatty acid depending on the intended use.

[0056] The content of the carbon filler is not particularly limited, but is preferably in the range of 0.01 to 15.0 mass%, 0.1 to 10.0 mass%, 0.2 to 8.0 mass%, 1.0 to 6.0 mass%, or 2.0 to 5.0 mass% relative to the total amount of the dispersion, in that order.

[0057] The content of the carbon filler dispersant of the present invention is not particularly limited, but is, for example, in the range of 0.01 to 50 parts by mass, preferably 0.1 to 40 parts by mass, and more preferably 1 to 30 parts by mass of the carbon filler dispersant per 100 parts by mass of the carbon filler.

[0058] (Dispersion medium) The dispersion medium contained in the carbon filler dispersion of the present invention is not particularly limited as long as it can disperse the carbon filler, and organic solvents such as aromatic solvents, alcohol solvents, polyhydric alcohol solvents, glycol ether solvents, ester solvents, amine / amide solvents, heterocyclic solvents, and sulfone solvents, as well as water (purified water, distilled water, pure water, ultrapure water, etc.) can be used.

[0059] Examples of aromatic solvents that can be used include benzyl alcohol, ethylene glycol monophenyl ether, ethylene glycol monobenzyl ether, propylene glycol monophenyl ether, diethylene glycol monophenyl ether, ethylene glycol monophenyl ether, propylene glycol monophenyl ether, alkylsulfonic acid phenyl ester, butyl phthalate, ethylhexyl phthalate, tridecyl phthalate, ethylhexyl trimellitate, diethylene glycol dibenzoate, and dipropylene glycol dibenzoate.

[0060] Examples of alcohol solvents that can be used include ethanol, n-propanol, isopropanol, n-butanol, isobutanol, tert-butyl alcohol, 1-pentanol, isoamyl alcohol, sec-amyl alcohol, 3-pentanol, tert-amyl alcohol, n-hexanol, methyl amyl alcohol, 2-ethylbutanol, n-heptanol, 2-heptanol, 3-heptanol, n-octanol, 2-octanol, 2-ethylhexanol, 3,5,5-trimethylhexanol, nonanol, n-decanol, undecanol, n-decanol, trimethylnonyl alcohol, tetradecanol, heptadecanol, cyclohexanol, and 2-methylcyclohexanol.

[0061] Examples of polyhydric alcohol solvents that can be used include ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, butylene glycol, hexanediol, pentanediol, glycerin, hexanetriol, thiodiglycol, 3-methyl-1,3-butanediol, triethylene glycol, dipropylene glycol, 1,3-propanediol, 1,3-butanediol, 1,5-pentanediol, hexylene glycol, and octylene glycol.

[0062] Examples of glycol ether solvents include methyl isopropyl ether, ethyl ether, ethyl propyl ether, ethyl butyl ether, isopropyl ether, butyl ether, hexyl ether, 2-ethylhexyl ether, ethylene glycol monohexyl ether, ethylene glycol mono-2-ethylbutyl ether, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, tetraethylene glycol monobutyl ether, 3-methyl-3-methoxy-1-butanol, 3-methoxy-1-butanol, propyl Examples of the ethylene glycol monomethyl ether that can be used include ethylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, propylene glycol tertiary butyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol monopropyl ether, dipropylene glycol monobutyl ether, tripropylene glycol monomethyl ether, tripropylene glycol monobutyl ether, tetrapropylene glycol monobutyl ether, ethylene glycol monomethyl ether acetate, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, and triethylene glycol monobutyl ether.

[0063] Examples of ester solvents include propylene glycol methyl ether acetate, propylene glycol diacetate, 3-methyl-3-methoxybutyl acetate, propylene glycol ethyl ether acetate, ethylene glycol ethyl ether acetate, butyl formate, isobutyl formate, isoamyl formate, propyl acetate, butyl acetate, isopropyl acetate, isobutyl acetate, isoamyl acetate, methyl propionate, ethyl propionate, propyl propionate, isobutyl propionate, isoamyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, butyl butyrate, methyl isobutyrate, ethyl isobutyrate, and propion isobutyrate. Examples of the surfactant that can be used include pyridine, methyl valerate, ethyl valerate, propyl valerate, methyl isovalerate, ethyl isovalerate, propyl isovalerate, methyl trimethylacetate, ethyl trimethylacetate, propyl trimethylacetate, methyl caproate, ethyl caproate, propyl caproate, methyl caprylate, ethyl caprylate, propyl caprylate, methyl laurate, ethyl laurate, methyl oleate, ethyl oleate, caprylic acid triglyceride, tributyl acetate citrate, octyl oxystearate, propylene glycol monoricinoleate, methyl 2-hydroxyisobutyrate, and 3-methoxybutyl acetate.

[0064] Examples of amine / amide solvents include amines such as ethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, morpholine, N-ethylmorpholine, ethylenediamine, diethylenediamine, triethylenetetramine, tetraethylenepentamine, polyethyleneimine, pentamethyldiethylenetriamine, and tetramethylpropylenediamine, as well as N-methyl-2-pyrrolidone (NMP), N-ethyl-2-pyrrolidone (NEP), N,N-dimethylformamide, N,N-dimethylacetamide, N,N-diethylacetamide, and N-methylcaprolactam. Examples of heterocyclic solvents include cyclohexylpyrrolidone, 2-oxazolidone, 1,3-dimethyl-2-imidazolidinone, and γ-butyrolactone. Examples of sulfone solvents include dimethyl sulfoxide, hexamethylphosphorotriamide, and sulfolane.

[0065] The carbon nanotube dispersion of the present invention may further contain additives according to its intended use, such as thickeners, anti-settling agents, wetting agents, emulsifiers, anti-sagging agents, antifoaming agents, leveling agents, plasticizers, anti-mold and anti-algae agents, and antibacterial agents.

[0066] The carbon nanotube dispersion of the present invention can be prepared by dispersing the above components using a known dispersing device. Examples of the dispersing device include mixers commonly used for pigment dispersion, such as a Disper, a Homomixer, a rotation-revolution mixer, a Henschel mixer, and a planetary mixer, (high-pressure) homogenizers, paint conditioners, colloid mills, media-type dispersers such as a bead mill, a cone mill, a ball mill, a sand mill, an attritor, a pearl mill, and a Coball mill, media-less dispersers such as a wet jet mill and a thin film rotary high-speed mixer, and other roll mills.

[0067] [Electrode-forming composition] The carbon filler dispersant of the present invention can improve the dispersibility of the carbon filler used as a conductive material, so that the function as a conductive material can be maintained even when the amount of carbon filler used is reduced. Therefore, an electrode-forming composition containing the carbon filler dispersant of the present invention can increase the amount of electrode active material used, and can improve the battery performance of the resulting battery.

[0068] The content of the carbon filler dispersant in the electrode-forming composition of the present invention is not particularly limited, but is, for example, in the range of 0.01 to 50 parts by mass of the carbon filler dispersant of the present invention per 100 parts by mass of the carbon filler, preferably in the range of 0.1 to 40 parts by mass of the carbon filler dispersant of the present invention per 100 parts by mass of the carbon filler, and more preferably in the range of 1 to 30 parts by mass of the carbon filler dispersant of the present invention per 100 parts by mass of the carbon filler. Each component contained in the electrode-forming composition of the present invention will now be described.

[0069] (Carbon Filler) The carbon filler contained in the electrode-forming composition of the present invention is the same as the carbon filler contained in the carbon filler-containing dispersion described above.

[0070] The content of the carbon filler is not particularly limited, but is, for example, 0.1 to 30 parts by mass, preferably 0.1 to 20 parts by mass, more preferably 1 to 20 parts by mass, and even more preferably 1 to 15 parts by mass relative to 100 parts by mass of the electrode active material.

[0071] (Electrode Active Material) Electrode active materials are classified into positive electrode active materials used for positive electrodes and negative electrode active materials used for negative electrodes based on their electromotive force.

[0072] Examples of the positive electrode active material include lithium-containing composite oxides, lithium-containing oxides, transition metal oxides, transition metal sulfides, and conductive polymers.

[0073] The lithium-containing composite oxide serving as the positive electrode active material may be a composite oxide of lithium and one or more elements selected from the group consisting of Co, Mn, Fe, Cu, Ti, Mg, Ca, Al, W, Mo, Nb, Zn, Sn, Zr, Ga, V, B, and Si. Specific examples of the lithium-containing composite oxide include LiNi ０．３３ Co ０．３３ Mn ０．３３ O ２ , LiNi ０．５ Co ０．３ Mn ０．２ O ２ , LiNi ０．５ Co ０．２ Mn ０．３ O ２ , LiNi ０．６ Co ０．２ Mn ０．２ O ２ , LiNi ０．８ Co ０．１ Mn ０．１ O ２ , LiNi ０．８ Co ０．１５ Al ０．０５ O ２ etc.

[0074] The lithium-containing oxide used as the positive electrode active material is LiNiO ２ , LiCoO ２ , LiMnO ２ , LiMn ２ O ４ , LiNiO ２ Lithium-containing oxides such as LiFePO ４ , LiMnPO ４ and the like.

[0075] The transition metal oxide used as the positive electrode active material is MnO ２ , V ２ O ５ Examples of transition metal sulfides that are positive electrode active materials include MoS ２ , TiS ２ etc.

[0076] Examples of conductive polymers that are positive electrode active materials include polyaniline, polythiophene, polypyrrole, polyacetylene, polyacene, dimercaptothiadiazole, and polyaniline composites.

[0077] The positive electrode active material may be used alone or in combination of two or more.

[0078] Examples of the negative electrode active material include carbon materials, chalcogen compounds (for example, oxides and sulfides), nitrides, metals, and alloys, and materials that can be doped and dedoped with lithium ions at a lower potential than the positive electrode can be used.

[0079] Examples of the carbon material that is the negative electrode active material include graphite such as natural graphite and artificial graphite, cokes, carbon black, carbon fiber, and baked organic polymer compounds.

[0080] The oxide that is the negative electrode active material is SiO ２ oxides of silicon represented by the formula SiOx (where x is a positive real number), such as SiO; SnO ２ tin oxides represented by the formula SnOx (where x is a positive real number), such as SnO; ４ Ti ５ O １２ , LiVO ２ Examples of metal composite oxides containing lithium and titanium include those mentioned above.

[0081] Examples of the metal or alloy that is the negative electrode active material include elemental metals such as lithium metal, silicon metal, and tin metal, as well as alloys containing these metals.

[0082] Among the negative electrode active materials, carbon materials containing graphite as a main component, such as natural graphite or artificial graphite, are preferably used. The reasons for this include the fact that the potential of the negative electrode hardly changes from an uncharged state to a fully charged state during charging (good potential flatness), that the average discharge potential is low, and that the capacity retention rate after repeated charge and discharge is high (good cycle characteristics). The shape of the carbon material may be, for example, flakes like natural graphite, spherical like mesocarbon microbeads, fibrous like graphitized carbon fiber, or aggregates of fine powder.

[0083] The negative electrode active material may be used alone or in combination of two or more.

[0084] (Binder Resin) The electrode-forming composition may contain a binder resin, and a thermoplastic resin can be used as the binder resin. Specific examples of the thermoplastic resin include polyimide resin, fluororesin such as polyvinylidene fluoride and polytetrafluoroethylene, polyolefin resin such as polyethylene and polypropylene, carboxymethylene cellulose, and styrene-butadiene rubber.

[0085] [Electrode for Lithium Secondary Battery] The electrode-forming composition of the present invention can be applied to a current collector and dried to form an electrode for a lithium secondary battery. The material and shape of the current collector are not particularly limited, and examples of the material for the current collector include metals and alloys such as aluminum, copper, nickel, titanium, and stainless steel. Furthermore, while flat foils are generally used as the shape of the current collector, those with a roughened surface, perforated foils, and mesh-shaped current collectors can also be used.

[0086] The method for applying the electrode-forming composition onto the current collector is not particularly limited, and any known method can be used. Specific examples include die coating, dip coating, roll coating, doctor coating, knife coating, spray coating, gravure coating, screen printing, and electrostatic painting. The drying method can be, but is not limited to, standing to dry, a blower dryer, a hot air dryer, an infrared heater, or a far-infrared heater.

[0087] [Lithium Secondary Battery] The lithium secondary battery of the present invention is a battery comprising the lithium secondary battery electrode of the present invention, and is preferably a battery comprising the lithium secondary battery electrode of the present invention as a positive electrode.

[0088] The lithium secondary battery of the present invention may be any battery in which at least one electrode contains a carbon filler and the carbon filler dispersion of the present invention, and may be in the form of a lithium ion secondary battery in which the electrolyte is liquid and a separator is provided, an all-solid-state secondary battery in which the electrolyte is solid, or a semi-solid secondary battery in which the electrolyte is both solid and liquid.

[0089] The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0090] In the examples of the present application, the acid value and hydroxyl value were evaluated by the following methods. [Method for measuring acid value] Measured by a method conforming to JIS K0070-1992. [Method for measuring hydroxyl value] Measured by a method conforming to JIS K0070-1992.

[0091] In the examples of the present application, the number average molecular weight of the polyester is a value calculated as polystyrene based on GPC measurement, and the measurement conditions are as follows. [GPC measurement conditions] Measurement apparatus: High-speed GPC apparatus "HLC-8320GPC" manufactured by Tosoh Corporation Column: "TSK GURDCOLUMN SuperHZ-L" manufactured by Tosoh Corporation + "TSK gel SuperHZM-M" manufactured by Tosoh Corporation + "TSK gel SuperHZM-M" manufactured by Tosoh Corporation + "TSK gel SuperHZ-2000" manufactured by Tosoh Corporation + "TSK gel SuperHZ-2000" manufactured by Tosoh Corporation Detector: RI (differential refractometer) Data processing: "EcoSEC Data Analysis Version 1.07" manufactured by Tosoh Corporation Column temperature: 40°C Developing solvent: tetrahydrofuran Flow rate: 0.35 mL / min Measurement sample: 7.5 mg of sample was dissolved in 10 ml of tetrahydrofuran, and the resulting solution was filtered through a microfilter to prepare the measurement sample. Sample injection amount: 20 μl Standard sample: The following monodisperse polystyrene with known molecular weight was used in accordance with the measurement manual for the "HLC-8320GPC".

[0092] (Monodisperse polystyrene) "A-300" manufactured by Tosoh Corporation "A-500" manufactured by Tosoh Corporation "A-1000" manufactured by Tosoh Corporation "A-2500" manufactured by Tosoh Corporation "A-5000" manufactured by Tosoh Corporation "F-1" manufactured by Tosoh Corporation "F-2" manufactured by Tosoh Corporation "F-4" manufactured by Tosoh Corporation "F-10" manufactured by Tosoh Corporation "F-20" manufactured by Tosoh Corporation "F-40" manufactured by Tosoh Corporation "F-80" manufactured by Tosoh Corporation "F-128" manufactured by Tosoh Corporation "F-288" manufactured by Tosoh Corporation

[0093] Whether a polyester is crystalline or amorphous was confirmed by carrying out differential scanning calorimetry under the following conditions. Specifically, in the second heating cycle described below, if an endothermic peak indicating the melting of a clear crystalline component was observed, it was judged to be crystalline, and if no endothermic peak was observed, it was judged to be amorphous. [Differential scanning calorimetry conditions] Measurement device: DSC3+ manufactured by Mettler Toledo K.K. Data processing: STARe Software Measurement conditions: (1) Heating from 25°C to 300°C (10°C / min): first heating cycle (2) Cooling from 300°C to 25°C (10°C / min): cooling (3) Holding at 25°C for 5 minutes (4) Heating from 25°C to 300°C (10°C / min): second heating cycle

[0094] (Synthesis Example 1: Synthesis of Dispersant A) A 3-liter four-neck flask equipped with a thermometer, a stirrer, and a reflux condenser was charged with 476 g of propylene glycol as the glycol component, 554 g of dimethyl terephthalate as the dicarboxylic acid component, 817 g of para-toluic acid as the monocarboxylic acid component, and 0.11 g of tetraisopropyl titanate as the catalyst, and the mixture was heated stepwise over 5 hours to 230 ° C. while stirring under a nitrogen stream, and then subjected to a condensation reaction for 12 hours at 230 ° C. After the reaction, unreacted raw materials and low-volatile components were removed at 195 ° C. under reduced pressure to obtain a polyester dispersant A.

[0095] The resulting Dispersant A was a viscous liquid at room temperature, and had an acid value of 0.19 mg KOH / g, a hydroxyl value of 11 mg KOH / g, and a number average molecular weight of 450. Furthermore, no clear endothermic peak was observed in differential scanning calorimetry, confirming that Dispersant A was an amorphous polyester.

[0096] Synthesis Example 2: Synthesis of Dispersant B A 0.3-liter stainless steel flask equipped with a thermometer, a stirrer, and a reflux condenser was charged with 129 g of dimethyl 2,6-naphthalenedicarboxylate as the dicarboxylic acid component, 95 g of terephthalic acid, 98 g of propylene glycol and 9 g of ethylene glycol as glycol components, and 0.01 g of tetraisopropyl titanate as a catalyst, and the mixture was heated stepwise over 2 hours to 200°C while stirring under a nitrogen stream. Once the temperature reached 200°C, a condensation reaction was carried out for 40 hours. After the reaction, unreacted raw materials and low-volatile components were removed at 160°C under reduced pressure, yielding Dispersant B, a polyester.

[0097] The resulting Dispersant B was solid at room temperature and had an acid value of 0.60 mg KOH / g, a hydroxyl value of 109 mg KOH / g, and a number average molecular weight of 1,400. Furthermore, no clear endothermic peak was observed in differential scanning calorimetry, confirming that Dispersant B was an amorphous polyester.

[0098] (Synthesis Example 3: Synthesis of Dispersant C) A 3-liter four-neck flask equipped with a thermometer, a stirrer, and a reflux condenser was charged with 512 g of propylene glycol as the glycol component, 971 g of dimethyl terephthalate as the dicarboxylic acid component, and 0.08 g of tetraisopropyl titanate as the catalyst, and the mixture was heated stepwise over 5 hours to 220 ° C. while stirring under a nitrogen stream. Once the temperature reached 220 ° C., a condensation reaction was carried out for 6 hours. After the reaction, the condensation reaction was carried out at 220 ° C. under reduced pressure for an additional 2 hours, and unreacted raw materials and low-volatile components were removed to obtain a polyester dispersant C.

[0099] The resulting Dispersant C was solid at room temperature and had an acid value of 1.1 mgKOH / g, a hydroxyl value of 67 mgKOH / g, and a number average molecular weight of 1,500. Furthermore, differential scanning calorimetry analysis did not reveal any clear endothermic peak, confirming that Dispersant C was an amorphous polyester.

[0100] Synthesis Example 4 Synthesis of Dispersant D A 3-liter four-neck flask equipped with a thermometer, a stirrer, and a reflux condenser was charged with 409 g of ethylene glycol as the glycol component, 741 g of phthalic anhydride as the dicarboxylic acid component, and 0.07 g of tetraisopropyl titanate as a catalyst, and the mixture was heated stepwise over 5 hours to 220° C. with stirring under a nitrogen stream. Once the temperature reached 220° C., a condensation reaction was carried out for 6 hours. After the reaction, the condensation reaction was carried out at 220° C. under reduced pressure for an additional 2 hours, and unreacted raw materials and low-volatile components were removed to obtain Dispersant D, a polyester.

[0101] The resulting Dispersant D was solid at room temperature and had an acid value of 0.26 mg KOH / g, a hydroxyl value of 35 mg KOH / g, and a number average molecular weight of 1,670. Furthermore, no clear endothermic peak was observed in differential scanning calorimetry, confirming that Dispersant D was an amorphous polyester.

[0102] Synthesis Example 5 Synthesis of Dispersant E A 1-liter four-neck flask equipped with a thermometer, a stirrer, and a reflux condenser was charged with 307 g of propylene glycol as the glycol component, 498 g of isophthalic acid as the dicarboxylic acid component, and 0.05 g of tetraisopropyl titanate as a catalyst, and the mixture was heated stepwise over 10 hours to 230° C. with stirring under a nitrogen stream. Once the temperature reached 230° C., a condensation reaction was carried out for 7 hours. After the reaction, the condensation reaction was carried out at 230° C. under reduced pressure for an additional 3 hours, and unreacted raw materials and low-volatile components were removed to obtain Dispersant E, a polyester.

[0103] The resulting Dispersant E was solid at room temperature and had an acid value of 0.89 mg KOH / g, a hydroxyl value of 70 mg KOH / g, and a number average molecular weight of 1,920. Furthermore, differential scanning calorimetry analysis did not reveal any clear endothermic peak, confirming that Dispersant E was an amorphous polyester.

[0104] (Synthesis Example 6: Synthesis of Dispersant F) A 2-liter four-neck flask equipped with a thermometer, a stirrer, and a reflux condenser was charged with 486 g of propylene glycol and 21 g of ethylene glycol as glycol components, 831 g of terephthalic acid as a dicarboxylic acid component, and 0.08 g of tetraisopropyl titanate as a catalyst, and the mixture was heated stepwise over 64 hours to 235°C while stirring under a nitrogen stream. Once the temperature reached 230°C, a condensation reaction was carried out for 8 hours. After the reaction, the condensation reaction was carried out at 235°C under reduced pressure for an additional 2 hours, and unreacted raw materials and low-volatile components were removed to obtain a polyester dispersant F.

[0105] The resulting Dispersant F was solid at room temperature and had an acid value of 1.05 mg KOH / g, a hydroxyl value of 42 mg KOH / g, and a number average molecular weight of 3,690. Furthermore, differential scanning calorimetry analysis did not reveal any clear endothermic peak, confirming that Dispersant F was an amorphous polyester.

[0106] Synthesis Example 7 Synthesis of Dispersant G A 2-liter four-neck flask equipped with a thermometer, a stirrer, and a reflux condenser was charged with 361 g of 2-methyl-1,3-propanediol as the glycol component, 498 g of terephthalic acid as the dicarboxylic acid component, and 0.05 g of tetraisopropyl titanate as a catalyst, and the temperature was raised stepwise over 26 hours to 225°C while stirring under a nitrogen stream, and once the temperature reached 225°C, a condensation reaction was carried out for 2 hours. After the reaction, the condensation reaction was carried out at 225°C under reduced pressure for an additional 4 hours, and unreacted raw materials and low-volatile components were removed to obtain Dispersant G, a polyester.

[0107] The resulting Dispersant G was solid at room temperature and had an acid value of 0.82 mg KOH / g, a hydroxyl value of 36 mg KOH / g, and a number average molecular weight of 7930. Furthermore, differential scanning calorimetry analysis did not reveal any clear endothermic peak, confirming that Dispersant G was an amorphous polyester.

[0108] Synthesis Example 8 Synthesis of Dispersant H A 3-liter four-neck flask equipped with a thermometer, a stirrer, and a reflux condenser was charged with 347 g of neopentyl glycol as the glycol component, 415 g of terephthalic acid as the dicarboxylic acid component, and 0.05 g of tetraisopropyl titanate as a catalyst, and the mixture was heated stepwise over 33 hours to 230°C while stirring under a nitrogen stream. Once the temperature reached 230°C, a condensation reaction was carried out for 8 hours. After the reaction, the condensation reaction was carried out at 230°C under reduced pressure for an additional 1 hour, and unreacted raw materials and low-volatile components were removed to obtain Dispersant H, a polyester.

[0109] The resulting Dispersant H was solid at room temperature and had an acid value of 0.95 mg KOH / g, a hydroxyl value of 71 mg KOH / g, and a number average molecular weight of 2,100. Furthermore, no clear endothermic peak was observed in differential scanning calorimetry, confirming that Dispersant H was an amorphous polyester.

[0110] Synthesis Example 9 Synthesis of Dispersant I A 3-liter four-neck flask equipped with a thermometer, a stirrer, and a reflux condenser was charged with 325 g of propylene glycol as the glycol component, 733 g of dimethyl 2,6-naphthalenedicarboxylate as the dicarboxylic acid component, and 0.06 g of tetraisopropyl titanate as a catalyst, and the temperature was raised stepwise over 25 hours to 220°C while stirring under a nitrogen stream. Once the temperature reached 220°C, a condensation reaction was carried out for 36 hours. After the reaction, the condensation reaction was carried out at 220°C under reduced pressure for an additional 2 hours, and unreacted raw materials and low-volatile components were removed to obtain Dispersant I, a polyester.

[0111] The resulting Dispersant I was solid at room temperature and had an acid value of 0.74 mg KOH / g, a hydroxyl value of 85 mg KOH / g, and a number average molecular weight of 1,810. Furthermore, no clear endothermic peak was observed in differential scanning calorimetry, confirming that Dispersant I was an amorphous polyester.

[0112] (Synthesis Comparative Example 1: Synthesis of Dispersant A') A 2-liter four-neck flask equipped with a thermometer, a stirrer, and a reflux condenser was charged with 2,456 g of adipic acid as the dicarboxylic acid component, 676 g of 1,4-butanediol as the glycol component, 782 g of neopentyl glycol, 260 g of isononyl alcohol as the monoalcohol component, and 0.13 g of tetraisopropyl titanate as the catalyst. The mixture was gradually heated to 220°C over 5 hours with stirring under a nitrogen stream, and once it reached 220°C, a condensation reaction was carried out for 19 hours. After the reaction, unreacted raw materials and low-volatile components were removed under reduced pressure at 200°C to obtain Dispersant A', a polyester. The resulting Dispersant A' was solid at room temperature and had an acid value of 34 mgKOH / g, a hydroxyl value of 1 mgKOH / g, and a number average molecular weight of 1,400.

[0113] (Examples 1-6 and Comparative Examples 1-3: Preparation and Evaluation of Carbon Filler-Containing Compositions) Ketjen black ("EC300J" manufactured by Lion Specialty Chemicals Co., Ltd., primary particle size: 39.5 nm) was used as the carbon filler, N-methylpyrrolidone (NMP) was used as the solvent, and the dispersant and glass beads (φ0.1 mm) used as the dispersion medium were placed in a 100 mL plastic bottle in the amounts shown in Table 1. This plastic bottle was set in a paint shaker (manufactured by Toyo Seiki Seisakusho), and the mixture in the plastic bottle was subjected to a dispersion treatment at room temperature for 30 minutes at a speed of 750 times per minute. The dispersed mixture was passed through a 300-mesh wire screen to filter out the glass beads, yielding a carbon dispersion.

[0114] The particle size distribution of Ketjen black in the obtained carbon dispersion was evaluated using histogram analysis with a dynamic light scattering particle size distribution analyzer ("ELSZ-2000" manufactured by Otsuka Electronics Co., Ltd.) The D10, D50, and D90 obtained from the histogram analysis are shown in Table 1.

[0115]

[0116] In Table 1, dispersant B' in Comparative Example 3 is a known dispersant, hydrogenated nitrile rubber ("Therban 3446" manufactured by ARLANXEO).

[0117] As can be seen from the results in Table 1, it can be confirmed that the use of the dispersants of the synthesis examples effectively suppresses the aggregation of Ketjen Black. On the other hand, with the dispersants A' and B' of the comparative examples, the particle size increased significantly at D90, confirming the formation of coarse aggregates.

[0118] Examples 7-10 and Comparative Examples 4-5: Preparation and Evaluation of Carbon Filler-Containing Compositions Carbon dispersions were prepared in the same manner as in Examples 1-6 and Comparative Examples 1-3, except that multi-walled carbon nanotubes (K-Nanos 300T manufactured by Kumho Petrochemical, diameter: 10-15 nm, length: 60-90 μm) were used as the carbon filler and the dispersion treatment was carried out for 120 minutes, and the particle size distribution of the multi-walled carbon nanotubes in the carbon dispersions was evaluated. The results are shown in Table 2.

[0119]

[0120] As can be seen from the results in Table 2, it can be confirmed that the use of the dispersants of the synthesis examples effectively suppresses the aggregation of multi-walled carbon nanotubes.

Claims

1. A carbon filler dispersant which is an amorphous polyester represented by the following general formula (1-1) or (1-2): 【Chemistry 1】 (In the general formulas (1-1) and (1-2), G is an aliphatic diol residue having 2 to 20 carbon atoms; A is a residue of an aromatic dicarboxylic acid having 4 to 18 carbon atoms; X is a monocarboxylic acid residue having 1 to 20 carbon atoms; Y is a monoalcohol residue having 1 to 30 carbon atoms; n represents the number of repetitions.)

2. A carbon filler dispersant which is a polyester represented by the following general formula (1-3): 【Chemistry 1】 (In the general formula (1-3), G is an aliphatic diol residue having 2 to 20 carbon atoms; A is a residue of an aromatic dicarboxylic acid having 4 to 18 carbon atoms; n represents the number of repetitions.)

3. A carbon filler dispersant as described in claim 2, wherein the polyester is an amorphous polyester.

4. 3. The carbon filler dispersant according to claim 1, wherein A comprises at least one selected from the group consisting of a phthalic acid residue, an isophthalic acid residue, a terephthalic acid residue and a naphthalenedicarboxylic acid residue.

5. 3. The carbon filler dispersant according to claim 1, wherein G is a residue of an aliphatic diol having a branched structure and having 3 to 20 carbon atoms.

6. A carbon filler dispersant as described in claim 1 or 2, wherein the acid value of the polyester is 0.01 mg KOH / g or more and 10 mg KOH / g or less.

7. A carbon filler dispersant as described in claim 1 or 2, wherein the hydroxyl value of the polyester is in the range of 0.1 to 400 mg KOH / g.

8. 3. The carbon filler dispersant according to claim 1, wherein the number average molecular weight of the polyester is in the range of 400 to 10,000.

9. The carbon filler dispersion according to claim 1 or 2, wherein the carbon filler is at least one selected from the group consisting of graphite, carbon black, carbon nanotubes, graphene, and graphene oxide.

10. A carbon filler dispersion comprising a carbon filler, the carbon filler dispersant according to claim 1 or 2, and a dispersion medium.

11. The carbon filler dispersion according to claim 10, wherein the carbon filler is at least one selected from the group consisting of graphite, carbon black, carbon nanotubes, graphene, and graphene oxide.

12. 3. An electrode for a lithium secondary battery comprising a carbon filler, the carbon filler dispersion according to claim 1 or 2, and an electrode active material.

13. A lithium secondary battery comprising the electrode for lithium secondary batteries according to claim 12.

Images