Conductive pigment paste, laminated material paste, and electrode for lithium ion battery

Abstract

The object of this invention is to provide a conductive pigment paste and a multilayer material paste that exhibit excellent pigment dispersibility and storage stability even at high pigment concentrations, and to provide an electrode for lithium-ion batteries with excellent performance in various aspects (such as battery performance). As a solution, a conductive pigment paste is provided, comprising a pigment dispersion resin (A), a conductive pigment (B), a solvent (C), a fluororesin (D), and a highly polar, low molecular weight component (E). The pigment dispersion resin (A) has at least one polar functional group selected from the group consisting of amide, imide, hydroxyl, carboxyl, sulfonic acid, phosphate, silanol, cyano, and pyrrolidone groups, and the concentration of the polar functional group in the pigment dispersion resin (A) is 0.3 mmol / g or more and 23 mmol / g or less. The conductive pigment (B) contains carbon nanotubes (B1), and the highly polar, low molecular weight component (E) contains an amine compound (E1).

Description

Technical Field

[0001] This invention relates to a conductive pigment paste and a multilayer material paste that exhibit excellent pigment dispersibility and storage stability even at high pigment concentrations, as well as an electrode for lithium-ion batteries coated with the multilayer material paste. Background Technology

[0002] Traditionally, paste-like pigment dispersions, formed by dispersing pigments in a mixture of pigment dispersion resins and solvents, have been widely used in various fields. In these fields, there is an increasing demand for improved pigment dispersibility, storage stability, coatability, conductivity, processability, and solvent resistance. Therefore, pigment dispersion resins and pigment pastes with excellent pigment dispersibility and superior storage stability, preventing reagglomeration of pigment particles in the resulting dispersion, are being developed.

[0003] When designing pigment pastes, it is important to produce pigment pastes with a high concentration and uniform dispersion of a small amount of pigment dispersion resin, in order to prevent the pigment dispersion resin from adversely affecting the performance of the final products such as electrodes, or to reduce the amount of solvent and pigment dispersion resin used and the energy used during drying. Furthermore, it is also important that the pigment paste can be stored without changing its texture over a long period.

[0004] In this case, Patent Document 1 describes a carbon nanotube dispersion comprising bundled carbon nanotubes, a dispersion medium, and a polyvinyl butyral resin with a weight-average molecular weight exceeding 50,000, wherein the dispersed particle size of the bundled carbon nanotubes is 3–10 μm in the particle size distribution D50.

[0005] However, although the electrode slurry containing the above-mentioned carbon nanotube dispersion, electrode active material and binder resin has good initial dispersibility and viscosity, its long-term storage performance is sometimes insufficient.

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent Publication No. 2018-535284 Summary of the Invention

[0009] The problem the invention aims to solve

[0010] The problem to be solved by the present invention is to provide a conductive pigment paste and a multilayer material paste that have excellent pigment dispersibility even at high pigment concentrations and have appropriate viscosity (low viscosity), excellent storage stability, and an electrode for lithium-ion batteries with excellent performance (such as battery performance).

[0011] Technical solution

[0012] The inventors conducted in-depth research to solve the above problems and found that the above problems could be solved by the following conductive pigment paste, thus completing the present invention. The conductive pigment paste contains a pigment dispersion resin (A), a conductive pigment (B), a solvent (C), a fluororesin (D), and a high polarity low molecular weight component (E). The pigment dispersion resin (A) has at least one polar functional group selected from the group consisting of amide, imide, hydroxyl, carboxyl, sulfonic acid, phosphoric acid, silanol, cyano, and pyrrolidone groups. The concentration of the polar functional group of the pigment dispersion resin (A) is 0.3 mmol / g or more and 23 mmol / g or less. The conductive pigment (B) contains carbon nanotubes (B1), and the high polarity low molecular weight component (E) contains an amine compound (E1).

[0013] Specifically, the present invention provides the following conductive pigment paste, multilayer material paste, and electrode for lithium-ion batteries.

[0014] [Item 1] A conductive pigment paste comprising a pigment dispersion resin (A), a conductive pigment (B), a solvent (C), a fluororesin (D), and a high-polarity low molecular weight component (E), wherein the pigment dispersion resin (A) has at least one polar functional group selected from the group consisting of amide, imide, hydroxyl, carboxyl, sulfonic acid, phosphoric acid, silanol, cyano, and pyrrolidone, and the concentration of the polar functional group of the pigment dispersion resin (A) is ≥0.3 mmol / g and ≤23 mmol / g, the conductive pigment (B) contains carbon nanotubes (B1), and the high-polarity low molecular weight component (E) contains an amine compound (E1).

[0015] [Item 2] According to the conductive pigment paste of Item 1, wherein, based on 100% by mass of the solid content of the conductive pigment (B), the content of the amine compound (E1) is 12% by mass or more and 500% by mass or less.

[0016] [Item 3] The conductive pigment paste according to item 1 or 2, wherein the amount of acidic groups in the carbon nanotubes (B1) is 0.01 mmol / g or more and 0.5 mmol / g or less.

[0017] [Item 4] The conductive pigment paste according to any one of items 1 to 3, wherein the median diameter (D50) of the carbon nanotubes (B1) is 10 μm or more and 250 μm or less.

[0018] [Item 5] The conductive pigment paste according to any one of items 1 to 4, wherein the BET specific surface area of ​​carbon nanotubes (B1) is 100 m². 2 / g or more and 800m 2 Below / g, in the Raman spectrum of carbon nanotubes (B1), 1560cm-1 Above and 1600cm -1 Let the maximum peak intensity within the following range be defined as G, and set 1310 cm⁻¹ as the maximum peak intensity. -1 Above and 1350cm -1 The maximum peak intensity is set to D within the following range, where the G / D ratio is above 0.1 and below 5.0.

[0019] [Item 6] The conductive pigment paste according to any one of items 1 to 4, wherein the water content of the solvent (C) is 1% by mass or less, and the amine compound content is 1% by mass or less.

[0020] [Item 7] The conductive pigment paste according to any one of items 1 to 6, wherein the weight-average molecular weight of the amine compound (E1) is less than 1000.

[0021] [Item 8] The conductive pigment paste according to any one of items 1 to 7, wherein the amine value of the amine compound (E1) is 105 mg KOH / g or more and 1000 mg KOH / g or less.

[0022] [Item 9] The conductive pigment paste according to any one of items 1 to 8, wherein the solvent (C) is N-methyl-2-pyrrolidone.

[0023] [Item 10] The conductive pigment paste according to any one of items 1 to 9, wherein the conductive pigment (B) further contains acetylene black.

[0024] [Item 11] A multilayer material paste, which is prepared by combining a conductive pigment paste as described in any one of items 1 to 10 with an electrode active material (F).

[0025] [Item 12] A multilayer material paste comprising a pigment dispersion resin (A), a conductive pigment (B), a solvent (C), a fluororesin (D), a high-polarity low molecular weight component (E), and an electrode active material (F), wherein the pigment dispersion resin (A) has at least one polar functional group selected from the group consisting of amide, imide, hydroxyl, carboxyl, sulfonic acid, phosphoric acid, silanol, cyano, and pyrrolidone, and the concentration of the polar functional group of the pigment dispersion resin (A) is ≥0.3 mmol / g and ≤23 mmol / g, the conductive pigment (B) contains carbon nanotubes (B1), and the high-polarity low molecular weight component (E) contains an amine compound (E1).

[0026] [Item 13] An electrode for a lithium-ion battery, which is obtained using the multilayer material paste described in Item 11 or 12.

[0027] Beneficial effects

[0028] The conductive pigment paste and multilayer material paste of the present invention exhibit excellent pigment dispersibility and appropriate viscosity (low viscosity) even at high pigment concentrations, excellent storage stability, and excellent conductivity of the coating film. Furthermore, the lithium-ion battery electrode obtained by coating the multilayer material paste exhibits excellent performance in various aspects (battery performance, etc.). Detailed Implementation

[0029] The following describes in detail the methods for carrying out the present invention.

[0030] It should be noted that the present invention is not limited to the following embodiments, but should be understood to include various modifications implemented within the scope of the present invention without changing the spirit of the invention.

[0031] In this invention, "specific surface area" refers to the BET specific surface area measured by nitrogen adsorption method.

[0032] In this invention, a conductive pigment paste with a suitable dispersion state is first prepared. Then, to obtain an electrode for lithium-ion batteries that meets various performance requirements, electrode active materials and other components are added to the conductive pigment paste to manufacture a multilayer material paste.

[0033] [Conductive Pigment Paste]

[0034] The conductive pigment paste of the present invention comprises a pigment dispersion resin (A), a conductive pigment (B), a solvent (C), a fluororesin (D), and a high polarity low molecular weight component (E). The pigment dispersion resin (A) has at least one polar functional group selected from the group consisting of amide, imide, hydroxyl, carboxyl, sulfonic acid, phosphoric acid, silanol, cyano, and pyrrolidone groups. The concentration of the polar functional group of the pigment dispersion resin (A) is 0.3 mmol / g or more and 23 mmol / g or less. The conductive pigment (B) contains carbon nanotubes (B1), and the high polarity low molecular weight component (E) contains an amine compound (E1).

[0035] Pigment dispersion resin (A)

[0036] The pigment dispersion resin (A) described above has at least one polar functional group selected from the group consisting of amide, imide, hydroxyl, carboxyl, sulfonic acid, phosphoric acid, silanol, cyano, and pyrrolidone groups, and the concentration of the polar functional group in the pigment dispersion resin (A) is 0.3 mmol / g or more and 23 mmol / g or less. Furthermore, the acid groups described above can also form salts.

[0037] As for the type of resin, there are no particular limitations as long as it is not a fluoropolymer (D) described later. Examples include: acrylic resins, polyester resins, epoxy resins, polyether resins, alkyd resins, urethane resins, polyvinyl alcohol, polyvinyl acetal, polyvinylpyrrolidone, polyvinyl acetate, silicone resins, polycarbonate resins, chlorinated resins, and their composite resins. These resins can be used alone or in combination of two or more.

[0038] From the viewpoints of pigment dispersibility, storage stability, and finishability, the pigment dispersion resin (A) preferably contains a vinyl (co)polymer (A1) obtained by polymerizing or copolymerizing monomers containing polymerizable unsaturated groups of formula (1). It should be noted that the term "(co)polymer" in this invention refers to both polymers formed by polymerizing one monomer and copolymers formed by copolymerizing two or more monomers.

[0039] C(-R)²=C(-R)²……Equation (1)

[0040] [In the above formulas, R can be chosen to be the same or different, and can be a hydrogen atom or an organic group.]

[0041] As the aforementioned vinyl (co)polymer (A1), it is preferable that its structure contains the structural unit represented by "-CH2-CH(-X)-" (where X is an active hydrogen group or an organic group containing an active hydrogen group). Examples of the aforementioned vinyl (co)polymer (A1) include, for example, vinyl (co)polymers containing hydroxyl groups, vinyl (co)polymers containing carboxyl groups, vinyl (co)polymers containing amide groups, vinyl (co)polymers containing sulfonic acid groups, vinyl (co)polymers containing phosphate groups, and vinyl (co)polymers containing pyrrolidone groups. These (co)polymers can be used alone or in combination of two or more.

[0042] Examples of hydroxyl-containing vinyl (co)polymers include, for example, poly(meth)acrylate hydroxyethyl ester, polyvinyl alcohol, vinyl alcohol-vinyl fatty acid ester copolymer, vinyl alcohol-ethylene copolymer, vinyl alcohol-(N-vinylformamide) copolymer, and copolymers of (meth)acrylate hydroxyethyl ester with other polymerizable unsaturated monomers. The vinyl alcohol unit in the (co)polymer may also be obtained by hydrolyzing the vinyl fatty acid ester unit after (co)polymerization.

[0043] Examples of carboxyl-containing vinyl (co)polymers include, for example, polymers of (meth)acrylic acid or copolymers of poly(meth)acrylic acid with other polymerizable unsaturated monomers.

[0044] Examples of vinyl (co)polymers containing amide groups include, for example, polymers of (meth)acrylamide or copolymers of (meth)acrylamide with other polymerizable unsaturated monomers.

[0045] Examples of vinyl (co)polymers containing sulfonic acid groups include, for example, polymers of allyl sulfonic acid or styrene sulfonic acid, copolymers of allyl sulfonic acid and / or styrene sulfonic acid with other polymerizable unsaturated monomers.

[0046] Examples of phosphate-containing vinyl (co)polymers include, for example, polymers of (meth)acryloyloxyalkyl acid phosphates or copolymers of (meth)acryloyloxyalkyl acid phosphates with other polymerizable unsaturated monomers.

[0047] In addition to the structural unit "-CH2-CH(-X)-" shown above, the aforementioned vinyl (co)polymer (A1) may also include, as needed, the following structural units derived from monomers containing polymerizable unsaturated groups capable of copolymerization. Examples of monomers containing polymerizable unsaturated groups capable of copolymerization include: vinyl formate, vinyl acetate, vinyl propionate, isopropylene acetate, vinyl valerate, vinyl octanoate, vinyl decanoate, vinyl laurate, vinyl stearate, vinyl benzoate, vinyl neodecanoate, vinyl pivalate, and other carboxylic acid vinyl ester monomers; olefins such as ethylene, propylene, and butene; aromatic vinyl groups such as styrene and α-methylstyrene; methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and dimethyl fumarate. Monomers such as methyl ester, dimethyl maleate, diethyl maleate, and diisopropyl itaconic acid; vinyl ether monomers such as methyl vinyl ether, n-propyl vinyl ether, isobutyl vinyl ether, and dodecyl vinyl ether; halogenated vinyl monomers or vinylidene monomers such as vinyl chloride, vinylidene chloride, vinyl fluoride, and vinylidene fluoride; allyl compounds such as allyl acetate and allyl chloride; monomers containing quaternary ammonium groups such as 3-(meth)acrylamidopropyltrimethylammonium chloride; and vinyltrimethoxysilane, N-vinylformamide, (meth)acrylamide, and N-ethylene-2-pyrrolidone. These monomers can be used alone or in combination of two or more.

[0048] From the viewpoints of pigment dispersibility, storage stability and compatibility with solvents, the concentration of polar functional groups in the pigment dispersion resin (A) is generally 0.3 mmol / g or more, preferably 9 mmol / g or more, and generally preferably 23 mmol / g or less.

[0049] The polymerization method of the aforementioned vinyl (co)polymer (A1) can be used by polymerization methods known per se, such as solution polymerization, but not limited thereto; bulk polymerization, emulsion polymerization, suspension polymerization, etc., are also possible. In the case of solution polymerization, it can be continuous polymerization or batch polymerization; the monomer can be added all at once, in batches, or continuously or intermittently.

[0050] There are no particular limitations on the polymerization initiators used in solution polymerization. Specifically, for example, the following azo compounds can be used: azobisisobutyronitrile, azobis-2,4-dimethylpentanonitrile, azobis(4-methoxy-2,4-dimethylpentanonitrile); peroxides such as acetyl peroxide, benzoyl peroxide, lauroyl peroxide, acetylcyclohexyl peroxide, and 2,4,4-trimethylpentyl-2-peroxyphenoxyacetate; percarbonate compounds such as diisopropyl peroxide, di-2-ethylhexyl peroxide, and diethoxyethyl peroxide; perester compounds such as tert-butyl peroxyneodecanate, α-cumyl peroxyneodecanate, and tert-butyl peroxyneodecanate; and well-known free radical polymerization initiators such as azobisdimethylpentanonitrile and azobismethoxypentanonitrile.

[0051] There is no particular limitation on the polymerization reaction temperature; it can usually be set within a range of approximately 30°C to 200°C.

[0052] The degree of polymerization of the vinyl (co)polymer (A1) that can be obtained as described above is, for example, 100 or more, preferably 150 or more, for example, 4000 or less, preferably 3000 or less, and more preferably 700 or less.

[0053] Furthermore, the weight-average molecular weight is, for example, 1,000 or more, preferably 2,000 or more, more preferably 7,000 or more, for example, 2,000,000 or less, preferably 1,000,000 or less, and more preferably 500,000 or less.

[0054] The weight-average molecular weight of the modified epoxy resin of the present invention is typically 500 or more, preferably 1000 or more, more preferably 1500 or more, and typically 50000 or less, preferably 20000 or less, more preferably 10000 or less, from the viewpoint of processability and corrosion resistance.

[0055] It should be noted that, unless otherwise specified, the weight-average molecular weight in this instruction manual is calculated by converting the retention time (retention capacity) determined by gel permeation chromatography (GPC) into the molecular weight of polystyrene using the retention time (retention capacity) of a standard polystyrene with a known molecular weight, measured under the same conditions. Specifically, the "HLC8120GPC" (manufactured by Tosoh, trade name) can be used as the gel permeation chromatography column, and the four columns "TSKgel G-4000HXL", "TSKgel G-3000HXL", "TSKgel G-2500HXL", and "TSKgel G-2000HXL" (all manufactured by Tosoh, trade names) can be used as the chromatographic column, with the following conditions: mobile phase tetrahydrofuran, measurement temperature 40°C, flow rate 1 mL / min, and detector RI.

[0056] The aforementioned vinyl (co)polymer (A1) can be prepared into a solid or a resin solution replaced with any solvent by solvent removal and / or solvent displacement after synthesis.

[0057] Solvent removal can be carried out by heating under normal pressure or under reduced pressure. As a solvent displacement method, a displacement solvent can be added at any stage before, during, or after solvent removal.

[0058] (Content of pigment dispersion resin (A))

[0059] Based on the total solid content of the conductive pigment paste, the solid content of the pigment dispersion resin (A) is, for example, 0.1% by mass or more, preferably 1% by mass or more, more preferably 3% by mass or more, for example, 40% by mass or less, preferably 20% by mass or less, more preferably 15% by mass or less.

[0060] Furthermore, based on the content of conductive pigment (B), the solid content of pigment dispersion resin (A) is, for example, 0.1% by mass or more, preferably 1% by mass or more, more preferably 5% by mass or more, for example, 50% by mass or less, preferably 40% by mass or less, more preferably 30% by mass or less.

[0061] Conductive pigment (B)

[0062] The aforementioned conductive pigment (B) contains carbon nanotubes (B1).

[0063] The conductive pigment (B) may further contain other conductive pigments (B2) besides carbon nanotubes (B1).

[0064] The content of carbon nanotubes (B1) in the conductive pigment (B) is based on 100% by mass of conductive pigment (B), for example, 50% by mass or more, preferably 75% by mass or more, and more preferably 95% by mass or more.

[0065] (Carbon nanotubes (B1))

[0066] As carbon nanotubes (B1), single-walled carbon nanotubes or multi-walled carbon nanotubes can be used alone or in combination. In particular, considering the relationship between viscosity, conductivity and cost, multi-walled carbon nanotubes are preferred.

[0067] The average outer diameter of the carbon nanotube (B1) is, for example, 1 nm or more, preferably 3 nm or more, more preferably 5 nm or more, for example, 30 nm or less, preferably 28 nm or less, more preferably 25 nm or less.

[0068] The average length of the carbon nanotubes (B1) is, for example, 0.1 μm or more, preferably 1 μm or more, more preferably 5 μm or more, for example, 100 μm or less, preferably 80 μm or less, more preferably 60 μm or less.

[0069] The BET specific surface area of ​​carbon nanotubes (B1), considering the relationship between viscosity and conductivity, is typically 100 m². 2 / g or more, preferably 130m 2 / g or more, preferably 160m 2 / g or above, typically 800m 2 / g or less, preferably 600m 2 / g or less, more preferably 400m 2 / g or less.

[0070] From the viewpoint of dispersibility and storage, the amount of acidic groups in the aforementioned carbon nanotubes (B1) is typically 0.01 mmol / g or more, preferably 0.01 mmol / g or more, typically 1.0 mmol / g or less, preferably 0.5 mmol / g or less, more preferably 0.2 mmol / g or less, and even more preferably 0.1 mmol / g or less. If the amount of acidic groups is 0.01 mmol / g or more, the dispersibility becomes good; furthermore, if the amount of acidic groups is 1.0 mmol / g or less, the storage properties become good.

[0071] The aforementioned acidic groups can be imparted by the following acid treatment of carbon nanotubes.

[0072] <Acid Treatment Methods>

[0073] As for the acid treatment method, there are no particular limitations as long as the acid can come into contact with the carbon nanotubes; however, it is preferable to immerse the carbon nanotubes in an acid treatment solution (an aqueous solution of acid). The acid contained in the acid treatment solution is not particularly limited; examples include nitric acid, sulfuric acid, and hydrochloric acid. One or more of these acids can be used alone or in combination. Nitric acid and sulfuric acid are preferred.

[0074] The amount of acidic groups in carbon nanotubes can be adjusted according to the concentration, temperature, and treatment time of the acid treatment solution.

[0075] After acid treatment, the remaining acid components adhering to the surface can be removed by the cleaning method described later, resulting in acid-treated carbon nanotubes.

[0076] There are no particular limitations on the method for cleaning acid-treated carbon nanotubes, but washing with water is preferred. For example, carbon nanotubes can be recovered from acid-treated carbon nanotubes by known methods such as filtration, followed by washing with water. After the above cleaning, if necessary, the water adhering to the surface can be removed by drying, etc., to obtain acid-treated carbon nanotubes.

[0077] Furthermore, the median diameter (D50), used as a volume conversion of carbon nanotubes (B1), is typically 10 μm or more, preferably 15 μm or more, more preferably 20 μm or more, and typically 250 μm or less, preferably 200 μm or less, more preferably 150 μm or less, when measured using the method described in the examples. Here, the median diameter (D50) can be determined by irradiating the carbon nanotube particles with a laser and converting the diameter of the carbon nanotubes to a spherical shape based on the scattered light. A larger median diameter (D50) means that more carbon nanotube aggregates exist, resulting in poorer dispersion. When the median diameter (D50) is greater than 250 μm, the likelihood of carbon nanotube aggregates in the electrode increases, and the overall conductivity of the electrode becomes uneven. On the other hand, when the median diameter (D50) is less than 10 μm, the fiber length becomes shorter, resulting in insufficient conductive paths and reduced conductivity. Carbon nanotubes can be uniformly dispersed within the electrode while maintaining conductivity when the median diameter (D50) is greater than 10 μm and less than 250 μm.

[0078] Furthermore, in the Raman spectrum of the aforementioned carbon nanotubes (B1), the 1560 cm⁻¹... -1 Above and 1600cm -1 Let the maximum peak intensity within the following range be defined as G, and set 1310 cm⁻¹ as the maximum peak intensity. -1 Above and 1350cm -1 The G / D ratio when the maximum peak intensity is set to D within the following range is typically 0.1 or more, preferably 0.4 or more, more preferably 0.6 or more, typically 5.0 or less, preferably 3.0 or less, and more preferably 1.0 or less.

[0079] Here, if the G / D ratio is in the range of 0.1 or higher and 5.0 or lower, the carbon surface has fewer defects and crystal interfaces, and the conductivity is more likely to be higher, so it is preferred.

[0080] (Other conductive pigments (B2))

[0081] Other conductive pigments (B2) besides carbon nanotubes (B1) may include, for example, at least one conductive carbon selected from the group consisting of acetylene black, Ketjen black, furnace black, pyrolysis black, graphene, and graphite. Preferably, it is selected from one or more of the group consisting of acetylene black, Ketjen black, furnace black, and pyrolysis black; more preferably, it is selected from one or more of the group consisting of acetylene black and Ketjen black; and even more preferably, it is selected from one or more of acetylene black.

[0082] The average primary particle size of other conductive pigments (B2) is, for example, 10 nm or more, preferably 20 nm or more, for example, 80 nm or less, and preferably 70 nm or less. Here, the average primary particle size refers to the average particle size of the primary particles obtained by simply averaging the diameters of 100 particles, calculating the projected area of ​​each of 100 particles (assuming the area is equal to that of a circle) when observing conductive carbon (B2) with an electron microscope. It should be noted that when the pigment is in an agglomerated state, the calculation is performed using the primary particles constituting the agglomerated particles.

[0083] There is no particular limitation on the BET specific surface area of ​​conductive carbon (B2). Considering the relationship between viscosity and conductivity, for example, 1 m² / s² is acceptable. 2 / g or more, preferably 10m 2 / g or more, preferably 20m 2 / g or more, for example, 500m 2 / g or less, preferably 250m 2 / g or less, more preferably 200m 2 / g or less.

[0084] There is no particular limitation on the oil absorption of dibutyl phthalate (DBP) of conductive carbon (B2). Considering the relationship between pigment dispersibility and conductivity, it is preferably 60 ml / 100g or more, more preferably 150 ml / 100g or more, and preferably 1000 ml / 100g or less, more preferably 800 ml / 100g or less.

[0085] (Content of conductive pigment (B))

[0086] From the viewpoint of conductivity and pigment dispersibility, based on the total solid content of the conductive pigment paste, the solid content of the conductive pigment (B) is, for example, 10.0% by mass or more, preferably 30.0% by mass or more, more preferably 40.0% by mass or more, for example, 99.0% by mass or less, preferably 80.0% by mass or less, more preferably 60.0% by mass or less.

[0087] Solvent (C)

[0088] The solvent (C) mentioned above can preferably be water, various organic solvents, etc.

[0089] Specifically, examples include: hydrocarbon solvents such as n-butane, n-hexane, n-heptane, n-octane, cyclopentane, cyclohexane, and cyclobutane; aromatic solvents such as toluene and xylene; ketone solvents such as methyl isobutyl ketone; ether solvents such as n-butyl ether, dioxane, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, and diethylene glycol; ester solvents such as ethyl acetate, n-butyl acetate, isobutyl acetate, ethylene glycol monomethyl ether acetate, and butyl carbitol acetate; ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone, and diisobutyl ketone; alcohol solvents such as ethanol, isopropanol, n-butanol, sec-butanol, and isobutanol; and amide solvents such as Equamide (an amide solvent manufactured by Idemitsu Kosan Co., Ltd., trade name), N,N-dimethylformamide, N,N-dimethylacetamide, N-methylformamide, N-methylacetamide, N-methylpropionamide, and N-methyl-2-pyrrolidone.

[0090] The preferred solvent is an amide-based solvent, and more preferably N-methyl-2-pyrrolidone. These solvents can be used alone or in combination of two or more.

[0091] Furthermore, from the viewpoint of ensuring pigment dispersibility of the conductive pigment paste and preventing deterioration or hydrolysis of the resin components, it is preferable that it is substantially water-free. Here, "substantially water-free" means that, based on the total amount of the conductive pigment paste, the water content is typically 1% by mass or less, preferably 0.5% by mass or less, and particularly preferably 0.1% by mass or less.

[0092] In this invention, the water content of the conductive pigment paste can be determined by Karl Fischer electrostatic titration. Specifically, a Karl Fischer moisture meter (manufactured by Kyoto Electronics Co., Ltd., trade name "MKC-610") can be used, with the set temperature of the water vaporization device (manufactured by Kyoto Electronics Co., Ltd., trade name "ADP-611") set to 130°C for measurement.

[0093] When using amide compounds (solvents) such as N-methyl-2-pyrrolidone, amine components are sometimes contained as impurities. In the conductive pigment paste of the present invention, the viscosity or thickening tendency of each batch may vary due to the amine components as such impurities.

[0094] Furthermore, when the conductive pigment paste of the present invention is used to form an electrode layer by the method described later, the evaporation of solvents and the like leaves no residue. To reduce waste, promote environmental friendliness, and / or reduce raw material costs, it is preferable to recover and reuse the evaporating solvent. That is, it is preferable to use recycled solvent (C). This recycled solvent (recycled product) also contains the amine compounds (E1) originally present in the conductive pigment paste of the present invention. Similarly, the viscosity or thickening tendency of each batch of conductive pigment paste may vary. Furthermore, amine compounds often have a strong odor.

[0095] Therefore, it is preferable to manage / adjust the amine compound content in the solvent (C) used as a recycled product to a certain amount or less. The amine compound content is usually less than 1% by mass, preferably less than 0.5% by mass, and particularly preferably less than 0.1% by mass.

[0096] It should be noted that the above-mentioned "using recycled material as solvent (C)" means that the solvent (C) used in the conductive pigment paste of the present invention contains 10% by mass or more (preferably 20% by mass or more) of recycled material.

[0097] Based on the total amount of conductive pigment paste, the content of solvent (C) in the conductive pigment paste is, for example, 40% by mass or more, preferably 60% by mass or more, more preferably 80% by mass or more, for example, 99% by mass or less, preferably 98% by mass or less, more preferably 97% by mass or less.

[0098] Furthermore, from the viewpoint of resin solubility, the solubility parameter δA of the pigment dispersion resin (A) and the solubility parameter δC of the solvent (C) are preferably in a relationship of |δA-δC|<2.0. More preferably, the solubility parameter δC of the solvent (C) itself is, for example, 10.0 or more, more preferably 10.5 or more, for example, 12.0 or less, more preferably 11.5 or less.

[0099] The solubility parameters of the resin are obtained by numerical quantification using turbidity measurement methods known to those skilled in the art. Specifically, they can be calculated according to the formula of KWSUH and JMCORBETT (Journal of Applied Polymer Science, 12, 2359, 1968).

[0100] The solubility parameter of the solvent can be determined according to the method described in J. Brandrup and E. Himmergut's "Polymer Handbook" VII Solubility Parameter Values, pp. 519-559 (John Wiley & Sons, third edition, published in 1989).

[0101] When two or more solvents (C) are combined as a mixed solvent, the solubility parameter of the mixed solvent can be determined experimentally. Alternatively, as a simple method, it can be determined by summing the products of the mole fractions of each liquid solvent and the solubility parameter.

[0102] It should be noted that, in this invention, the unit of solubility parameter is "(cal / cm³)". 3 ) 1 / 2 ".

[0103] Fluoropolymer (D)

[0104] The aforementioned fluororesin (D) is a resin intended to form a film for electrode layers.

[0105] As a fluoropolymer (D), polyvinylidene fluoride (PVDF) is particularly preferred, and one or more of them can be used alone or in combination.

[0106] Fluoropolymer (D) may be contained during pigment dispersion or may be added after pigment dispersion. From the viewpoint of adhesion to the substrate, enhanced film properties, and solvent resistance, the weight-average molecular weight of the fluoropolymer (D) is, for example, 100,000 or more, preferably 500,000 or more, more preferably 650,000 or more, for example, 3,000,000 or less, and preferably 2,000,000 or less.

[0107] Based on the solid content of the conductive pigment paste, the content of fluororesin (D) is, for example, 10.0% by mass or more, preferably 30.0% by mass or more, more preferably 40.0% by mass or more, for example, 99.0% by mass or less, preferably 80.0% by mass or less, more preferably 60.0% by mass or less.

[0108] Highly polar, low molecular weight components (E)

[0109] From the viewpoint of improving the wettability and / or storage stability of conductive pigments, the above-mentioned high polarity low molecular weight component (E) contains an amine compound (E1).

[0110] The content of amine compound (E1) in the above-mentioned high polarity low molecular weight component (E) is based on 100% by mass of the high polarity low molecular weight component (E), for example, 50% by mass or more, preferably 75% by mass or more, and more preferably 95% by mass or more.

[0111] Examples of the amine compounds (E1) mentioned above include, for example, ammonia, primary amines, secondary amines, tertiary amines, etc.

[0112] Examples of primary amines include: ethylamine, n-propylamine, sec-propylamine, n-butylamine, sec-butylamine, isobutylamine, tert-butylamine, pentanamine, hexylamine, heptamine, octylamine, decylamine, laurylamine, myristamine, 1,2-dimethylhexylamine, 3-pentanamine, 2-ethylhexylamine, allylamine, aminoethanol, 1-aminopropanol, 2-aminopropanol, aminobutanol, aminopentanol, aminohexanol, 3-ethoxypropylamine, 3-propoxypropylamine, 3-isopropoxypropylamine, 3-butoxypropylamine, 3-isobutoxypropylamine, 3-(2-ethylhexoxy)propylamine, aminocyclopentane, aminocyclohexane, aminonorbornene, aminomethylcyclohexane, aminobenzene, benzylamine, phenethylamine, α-phenylethylamine, naphthylamine, furfurylamine, and other monoprimary amines.Ethylenediamine, 1,2-diaminopropane, 1,3-diaminopropane, 1,2-diaminobutane, 1,3-diaminobutane, 1,4-diaminobutane, 1,5-diaminopentane, 1,6-diaminohexane, 1,7-diaminoheptane, 1,8-diaminooctane, dimethylaminopropylamine, diethylaminopropylamine, bis-(3-aminopropyl)ether, 1,2-bis-(3-aminopropoxy)ethane, 1,3-bis-(3-aminopropoxy)-2,2'-dimethylpropane, aminoethylethanolamine, 1,2-diaminocyclohexane, 1,3-diaminocyclohexane, 1,4 - Diaminocyclohexane, 1,3-Diaminomethylcyclohexane, 1,4-Diaminomethylcyclohexane, 1,3-Diaminoethylcyclohexane, 1,4-Diaminoethylcyclohexane, 1,3-Diaminopropylcyclohexane, 1,4-Diaminopropylcyclohexane, hydrogenated 4,4'-diaminodiphenylmethane, 2-aminopiperidine, 4-aminopiperidine, 2-aminomethylpiperidine, 4-aminomethylpiperidine, 2-aminoethylpiperidine, 4-aminoethylpiperidine, N-aminoethylpiperidine, N-aminopropylpiperidine, N-aminoethylmorpholine, N-aminopropylmorpholine, isophorone diamine, menthane diamine 1,4-Diaminopropylpiperazine, o-phenylenediamine, m-phenylenediamine, p-phenylenediamine, 2,4-toluenediamine, 2,6-toluenediamine, 2,4-toluenediamine, m-aminobenzylamine, 4-chloro-o-phenylenediamine, tetrachloro-p-phenylenediamine, 4-methoxy-6-methyl-m-phenylenediamine, m-phenylenediamine, p-phenylenediamine, 1,5-naphthylenediamine, 2,6-naphthylenediamine, benzidine, 4,4'-bis(o-toluidine), bianisidine, 4,4'-diaminodiphenylmethane, 2,2-(4,4'-diaminodiphenyl)propane, 4,4'-diaminodiphenyl ether, 4,4'-thiodiphenylamine, 4 ,4'-Diaminodiphenyl sulfone, 4,4'-Diaminodimethyl sulfone, methylene bis(o-chloroaniline), 3,9-bis(3-aminopropyl)2,4,8,10-tetraoxaspiro[5,5]undecane, diethylenetriamine, iminodipropylamine, methyliminodipropylamine, bis(hexamethylene)triamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, N-aminoethylpiperazine, N-aminopropylpiperazine, 1,4-bis(aminoethylpiperazine), 1,4-bis(aminopropylpiperazine), 2,6-diaminopyridine, bis(3,4-diaminophenyl)sulfone, and other primary amines, etc.

[0113] Examples of secondary amines include, for example: diethylamine, dipropylamine, di-n-butylamine, di-sec-butylamine, diisobutylamine, di-n-pentylamine, di-3-pentylamine, dihexylamine, dioctylamine, di(2-ethylhexyl)amine, methylhexylamine, diallylamine, pyrrolidine, piperidine, 2,4-dimethylpiperidine, 2,6-dimethylpiperidine, 3,5-dimethylpiperidine, diphenylamine, N-methylaniline, N-ethylaniline, dibenzylamine, methyl Mono-secondary amines such as benzylamine, dinaphthylamine, pyrrole, indoline, indole, and morpholine; N,N'-dimethylethylenediamine, N,N'-dimethyl-1,2-diaminopropane, N,N'-dimethyl-1,3-diaminopropane, N,N'-dimethyl-1,2-diaminobutane, N,N'-dimethyl-1,3-diaminobutane, N,N'-dimethyl-1,4-diaminobutane, and N,N'-dimethyl... -1,5-Diaminopentane, N,N'-Dimethyl-1,6-Diaminohexane, N,N'-Dimethyl-1,7-Diaminoheptane, N,N'-Diethylethylenediamine, N,N'-Diethyl-1,2-Diaminopropane, N,N'-Diethyl-1,3-Diaminopropane, N,N'-Diethyl-1,2-Diaminobutane, N,N'-Diethyl-1,3-Diaminobutane, N, N'-Diethyl-1,4-Diaminobutane, N,N'-Diethyl-1,6-Diaminohexane, piperazine, 2-methylpiperazine, 2,5-dimethylpiperazine, 2,6-dimethylpiperazine, high-piperazine, 1,1-di-(4-piperidinyl)methane, 1,2-di-(4-piperidinyl)ethane, 1,3-di-(4-piperidinyl)propane, 1,4-di-(4-piperidinyl)butane, and other polyamines.

[0114] Examples of tertiary amines include: trimethylamine, triethylamine, tri-n-propylamine, triisopropylamine, tri-1,2-dimethylpropylamine, tri-3-methoxypropylamine, tri-n-butylamine, triisobutylamine, tri-sec-butylamine, tripentylamine, tri-3-pentylamine, tri-n-hexylamine, tri-n-octylamine, tri-2-ethylhexylamine, tri-dodecylaminoamine, laurylamine, dicyclohexylethylamine, cyclohexyldiethylamine, tricyclohexylamine, N,N-dimethylhexylamine, N-methyldihexylamine, N,N-dimethylcyclohexylamine, N-methyldicyclohexylamine, N,N-diethylethanolamine, N,N-dimethylethanolamine, N-ethyldiethanolamine, triethanolamine, tribenzylamine, N,N-dimethylbenzylamine, diethylbenzylamine, triphenylamine, N,N-dimethylamino-p-cresol, N,N-dimethylaminomethylphenol, 2-( Monotertiary amines such as N,N-dimethylaminomethyl)phenol, N,N-dimethylaniline, N,N-diethylaniline, pyridine, quinoline, N-methylmorpholine, N-methylpiperidine, 2-(2-dimethylaminoethoxy)-4-methyl-1,3,2-dioxane, 2-methylpyridine, 3-methylpyridine, and 4-methylpyridine; polytertiary amines such as tetramethylethylenediamine, pyrazine, N,N'-dimethylpiperazine, N,N'-bis((2-hydroxy)propyl)piperazine, hexamethylenetetramine, N,N,N',N'-tetramethyl-1,3-butylamine, 2-dimethylamino-2-hydroxypropane, diethylaminoethanol, N,N,N-tris(3-dimethylaminopropyl)amine, 2,4,6-tris(N,N-dimethylaminomethyl)phenol, and heptamethylisobisguanidine.

[0115] They can be used individually or in combination with two or more.

[0116] Preferably, it does not contain acid groups, hydroxyl groups or other functional groups, is a primary amine compound, and is more preferably a monovalent amine compound (monoamine).

[0117] Examples of amine compounds (E1) include aliphatic amines, alicyclic amines, and aromatic amines, all of which can be used preferably, with aromatic amines being the most preferred.

[0118] Preferably, no amine compounds remain on the dried electrode layer; therefore, the weight-average molecular weight of the amine compound (E1) is preferably less than 1000, more preferably 800 or less, even more preferably 500 or less, and particularly preferably 350 or less. Furthermore, for the same reason, the boiling point of the amine compound is preferably 400°C or less, more preferably 300°C or less, and even more preferably 200°C or less.

[0119] Furthermore, the amine value of the amine compound (E1) is generally 5 mg KOH / g or more, preferably 50 mg KOH / g or more, more preferably 105 mg KOH / g or more, and generally within the range of 1000 mg KOH / g or less.

[0120] As other highly polar, low molecular weight components, they can be used in combination with amine compounds (E1), for example, one or more acidic, highly polar, low molecular weight components selected from organic and inorganic acids. Additionally, one or more basic, highly polar, low molecular weight components selected from organic and inorganic bases can be used.

[0121] Examples of organic acids include organic carboxylic acids (formic acid, acetic acid, propionic acid, benzoic acid, phthalic acid, etc.) and organic sulfonic acids (benzenesulfonic acid, etc.). Examples of inorganic acids include hydrochloric acid, sulfuric acid, nitric acid, and phosphoric acid.

[0122] As organic bases, base components other than amine compounds can be listed; as inorganic bases, for example, metal hydroxides (sodium hydroxide, potassium hydroxide, etc.) can be listed.

[0123] The content of the aforementioned high polarity low molecular weight component (E) is based on 100% by mass of the solid content of the conductive pigment paste, for example, 1% by mass or more, preferably 10% by mass or more, more preferably 40% by mass or more, for example, 600% by mass or less, preferably 500% by mass or less, more preferably 200% by mass or less, and even more preferably 150% by mass or less.

[0124] Furthermore, based on 100% by mass of the solid content of the conductive pigment (B), the lower limit is, for example, 1% by mass or more, preferably 12% by mass or more, more preferably 40% by mass or more, and even more preferably 80% by mass or more. The upper limit is, for example, 1000% by mass or less, preferably 500% by mass or less, more preferably 350% by mass or less, and even more preferably 300% by mass or less.

[0125] Highly polar, low molecular weight components (E) [especially amine compounds (E1)] often have strong odors, which can sometimes worsen the working environment during compounding and drying. Furthermore, they are generally expensive, thus increasing costs. Therefore, it is necessary to set the required minimum content.

[0126] Furthermore, the ratio of solvent (C) to high polarity low molecular weight component (E), measured by mass ratio of solvent (C) to high polarity low molecular weight component (E), is preferably in the range of 100 / 0.1 to 100 / 10, more preferably in the range of 100 / 0.5 to 100 / 8, more preferably in the range of 100 / 1 to 100 / 6, and even more preferably in the range of 100 / 1.5 to 100 / 4.

[0127] Furthermore, the content of the high polarity low molecular weight component (E) relative to the content of the conductive pigment (B) is set as α (parts by mass), and the BET specific surface area of ​​the conductive pigment (B) is set as β (m²). 2In the case of / g), the value of X in the following formula (1) is generally 5 or more, preferably 10 or more, more preferably 40 or more, even more preferably 60 or more, generally 2500 or less, preferably 1000 or less, more preferably 500 or less, even more preferably 300 or less.

[0128] X = α / β × 300……Equation (1)

[0129] It was found that if the value of X is within this range, the highly polar, low molecular weight component (E) can be sufficiently wetted on the surface of the conductive pigment (B), which can improve the dispersibility (including viscosity) and storage stability (including inhibiting thickening) of the conductive pigment (B).

[0130] If the value of X is higher than the upper limit range mentioned above, then the content of high polarity low molecular weight component (E) relative to the surface area of ​​the conductive pigment (B) is excessive (odor, increased cost), and if the value of X is lower than the lower limit range mentioned above, then the content of high polarity low molecular weight component (E) relative to the surface area of ​​the conductive pigment (B) is insufficient.

[0131] Other ingredients

[0132] As the conductive pigment paste of the present invention, in addition to containing the above-mentioned components (A), (B), (C), (D) and (E), it may also contain other components as needed.

[0133] Other components include, for example, resins other than pigment dispersion resin (A) and fluororesin (D), neutralizers, defoamers, preservatives, rust inhibitors, plasticizers, and pigments other than conductive pigments (B).

[0134] Pigments other than conductive pigments (B) include, for example: white pigments such as titanium dioxide and zinc oxide; blue pigments such as cyanine blue and indigo blue; green pigments such as cyan green and verdigris; organic red pigments such as azo dyes, quinacridone dyes, and iron oxide red; organic yellow pigments such as benzimidazolone dyes, isoindolineone dyes, isoindoline dyes, and quinophthalone dyes; and yellow pigments such as titanium yellow and chrome yellow. These pigments can be used alone or in combination of two or more. These pigments other than conductive pigments (B) can be used for purposes such as color adjustment and enhancing the physical properties of the film without significantly impairing conductivity. They can also be dispersed simultaneously with pigment dispersion resin (A) and conductive pigment (B). Alternatively, pigment dispersion resin (A) and conductive pigment (B) can be dispersed to form a paste and then mixed as pigments or pigment pastes.

[0135] The content of pigments other than the conductive pigment (B) mentioned above, based on all pigments in the conductive pigment paste, is preferably 10% by mass or less, more preferably 5% by mass or less, even more preferably 1% by mass or less, and particularly preferably substantially non-existent.

[0136] As for the viscosity of the aforementioned conductive pigment paste, considering factors such as pigment dispersibility and storage stability, a shear rate of 2s is considered. -1 The viscosity is, for example, less than 5000 mPa·s, preferably less than 2500 mPa·s, more preferably less than 1000 mPa·s, for example, 10 mPa·s or more, preferably 50 mPa·s or more, and more preferably 100 mPa·s or more.

[0137] Viscosity can be measured, for example, using a cone-plate viscometer (manufactured by HAAKE, trade name "Mars2", 35mm in diameter, 2° inclined cone plate).

[0138] The conductive pigment paste of the present invention can be prepared by uniformly mixing and dispersing the above-mentioned components, for example, using the following conventionally known dispersers: paint mixer, sand mill, ball mill, pebble mill, LMZ mill, DCP pearl mill, planetary ball mill, homogenizer, twin-shaft mixer, thin film gyratory high-speed mixer (manufactured by Filmix, trade name "CLEARMIX", etc.).

[0139] [(Lithium-ion battery electrode) Multilayer material paste]

[0140] This invention provides a multilayer material paste, which is formed by further combining an electrode active material (F) with the above-mentioned conductive pigment paste. This multilayer material paste is preferably used in positive or negative electrode applications for lithium-ion batteries, and more preferably in positive electrode applications.

[0141] Furthermore, as a second embodiment of the multilayer material paste of the present invention, the manufacturing method (the mixing order of each component) is not particularly limited as long as the following embodiment is adopted: that is, the multilayer material paste contains a pigment dispersion resin (A), a conductive pigment (B), a solvent (C), a fluororesin (D), a high polarity low molecular weight component (E), and an electrode active substance (F), wherein the pigment dispersion resin (A) has at least one polar functional group selected from the group consisting of amide group, imide group, hydroxyl group, carboxyl group, sulfonic acid group, phosphoric acid group, silanol group, and cyano group, and the concentration of the polar functional group of the pigment dispersion resin (A) is 0.3 mmol / g or more and 23 mmol / g or less, the conductive pigment (B) contains carbon nanotubes (B1), and the high polarity low molecular weight component (E) contains an amine compound (E1).

[0142] Electrode active material (F)

[0143] Examples of electrode active materials (F) include: lithium nickel oxide (LiNiO2), lithium manganese oxide (LiMn2O4), lithium cobalt oxide (LiCoO2), and LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 Lithium composite oxides such as O2; lithium iron phosphate (LiFePO4); sodium composite oxides; potassium composite oxides, etc. These electrode active materials (F) can be used alone or in combination of two or more. Electrode active materials containing lithium iron phosphate are inexpensive, have good cycle characteristics and energy density, and are therefore preferred.

[0144] The particle size of the electrode active material is typically 0.5 μm or larger, preferably 10.5 μm or larger, typically 30 μm or smaller, and preferably 20 μm or smaller.

[0145] The solid content of electrode active material (F) in the solid component of the lithium-ion battery electrode multilayer material paste of the present invention is usually 70% by mass or more, preferably 80% by mass or more and less than 100% by mass, which is preferred from the perspective of battery capacity, battery resistance and other aspects.

[0146] If the aforementioned electrode active material (F) is contained in the multilayer material paste, it may sometimes become viscous during storage. This is because the electrode active material (F) has alkali metal hydroxides (e.g., LiOH, KOH, NaOH, etc.) derived from the raw materials on its particle surface, and thus aggregates (becomes viscous) due to the conductive pigment (B) with an acidic surface. Therefore, by containing a certain amount or more of a high-polarity, low-molecular-weight component (E) [especially amine compounds (E1)], the viscous thickening during storage of the multilayer material paste can be suppressed.

[0147] Preparation method of multilayer material paste

[0148] The multilayer material paste of the present invention can be obtained by first preparing the above-mentioned conductive pigment paste and then combining it with at least one electrode active substance (F).

[0149] Furthermore, the multilayer material paste of the present invention can also be prepared by mixing the above-mentioned components (A), (B), (C), (D), (E) and electrode active material (F).

[0150] The solid content of pigment dispersion resin (A) in the solid component of the multilayer material paste of the present invention is usually 0.01% by mass or more, preferably 0.02% by mass or more, usually 20% by mass or less, preferably 10% by mass or less, which is preferred from the perspective of battery performance, paste viscosity and other aspects.

[0151] In the multilayer material paste of the present invention, from the viewpoint of storage stability (inhibition of thickening) of the multilayer material paste, it contains a highly polar low molecular weight component (E), and as the highly polar low molecular weight component (E), it contains at least one amine compound (E1).

[0152] From the viewpoint that contacting (wetting) the highly polar, low molecular weight component (E) with the conductive pigment (B) and then mixing the electrode active material (F) thereby mitigating the aggregation of the conductive pigment (B) and the electrode active material (F), the preferred order includes first mixing the conductive pigment (B) with the highly polar, low molecular weight component (E).

[0153] In the multilayer material paste of the present invention, based on 100% by mass of the solid content of the conductive pigment (B), the preferred lower limit of the content of the high polarity low molecular weight component (E) is typically 1% by mass or more, preferably 10% by mass or more, more preferably 40% by mass or more, and even more preferably 80% by mass or more, from the viewpoint of storage stability (inhibition of thickening) of the multilayer material paste. As an upper limit, from the viewpoint of the residual amount of component (E) in the electrode film, it is typically 500% by mass or less, preferably 400% by mass or less, more preferably 350% by mass or less, and even more preferably 300% by mass or less.

[0154] The solid content of the conductive pigment (B) in the solid component of the multilayer material paste of the present invention is generally 0.01% by mass or more, preferably 0.05% by mass or more, more preferably 0.1% by mass or more, generally 30% by mass or less, preferably 20% by mass or less, more preferably 15% by mass or less, which is preferred from the perspective of battery performance. Furthermore, the content of the solvent (C) in the multilayer material paste of the present invention is generally 1% by mass or more, preferably 5% by mass or more, more preferably 10% by mass or more, generally 70% by mass or less, preferably 60% by mass or less, more preferably 50% by mass or less, which is preferred from the perspective of electrode drying efficiency and paste viscosity.

[0155] [Lithium-ion battery electrodes]

[0156] Methods for fabricating lithium-ion battery electrodes

[0157] As described above, the electrode cladding material layer (also known as the electrode layer or cladding material layer) of a lithium-ion secondary battery can be manufactured by coating the core material of the positive or negative electrode with a cladding material paste and then drying it, with the positive electrode being particularly preferred.

[0158] In addition, the conductive pigment paste of the present invention can be used not only as a paste for a multilayer material, but also as a base coating between the electrode core and the multilayer material.

[0159] The coating method for the multilayer material paste for lithium-ion battery electrodes can be performed using methods known to them, such as those employing a die-coating machine. The coating amount of the multilayer material paste for lithium-ion battery electrodes is not particularly limited, and can be set such that the thickness of the dried multilayer material layer is, for example, 0.04 mm or more, preferably 0.06 mm or more, for example, 0.30 mm or less, and preferably 0.24 mm or less. The temperature for the drying process can be appropriately set, for example, 80°C or more, preferably 100°C or more, for example, 200°C or less, and preferably 180°C or less. The drying time can be appropriately set, for example, 5 seconds or more, for example, 120 seconds or less, and preferably 60 seconds or less.

[0160] In the above drying process, all or part of the solvent (C) and the highly polar low molecular weight component (E) evaporate. However, as mentioned above, in order to reduce waste, be environmentally friendly and / or reduce costs, it is preferable to recycle / reuse the volatile components (C) and (E).

[0161] The present invention will be described in more detail below with reference to specific embodiments, but the present invention is not limited to these specific embodiments.

[0162] Example

[0163] [Manufacturing of Pigment Dispersion Resins]

[0164] Manufacturing Example 1: Sulfonic Acid Modified Polyvinyl Alcohol Resin

[0165] In a reaction vessel equipped with a thermometer, reflux cooling pipe, nitrogen inlet pipe, and stirrer, copolymerization was carried out at approximately 60°C using 97 parts by mass of vinyl acetate and 3.0 parts by mass of sodium allyl sulfonate as polymerizable monomers, methanol as solvent, and azobisisobutyronitrile as polymerization initiator. Unreacted monomers were then removed under reduced pressure to obtain a resin solution. Next, a saponification reaction was carried out with a methanol solution containing sodium hydroxide. After thorough washing, the solution was dried using a hot air dryer. Finally, a sulfonic acid-modified polyvinyl alcohol resin with a weight-average molecular weight of 17,000, a polar functional group concentration of 18.1 mmol / g, and a saponification degree of 90 mol% was obtained.

[0166] [Manufacturing of conductive pigment pastes and multilayer material pastes]

[0167] Example 1A

[0168] 40 parts of sulfonic acid modified polyvinyl alcohol resin (40 parts solid component) obtained in Manufacturing Example 1, 200 parts of carbon nanotubes (CNT1), 180 parts of KF POLYMER W#7300 (manufactured by KUREHA, trade name, polyvinylidene fluoride, weight average molecular weight 1 million), 9380 parts of N-methyl-2-pyrrolidone (NMP1) and 200 parts of benzylamine were mixed and dispersed in a ball mill for 5 hours to produce a conductive pigment paste (A-1).

[0169] Example 1B

[0170] Relative to 100 parts of the above conductive pigment paste (A-1), active material particles (formula LiNi) were mixed using a disperser. 0.5 Mn 1.5 The lithium nickel manganese oxide particles with a spinel structure shown in O4 have an average particle size of 6 μm and a BET specific surface area of ​​0.7 m². 2 900 parts of / g) were used to manufacture a multilayer material paste (B-1).

[0171] Examples 2A to 20A, Comparative Examples 1A to 2A

[0172] Using the formulations in Tables 1 and 2 below, except that conductive pigment pastes (A-2) to (A-22) of Examples 2A to 20A and Comparative Examples 1A to 2A were obtained in the same manner as in Example 1A.

[0173] Examples 2B-20B and Comparative Examples 1B-2B

[0174] Using the formulations in Table 3 below, except that, the multilayer material pastes (B-2) to (B-22) of Examples 2B to 20B and Comparative Examples 1B to 2B were obtained in the same manner as in Example 1B.

[0175] [Table 1]

[0176]

[0177]

[0178] [Table 2]

[0179]

[0180]

[0181] [Table 3]

[0182]

[0183]

[0184] It should be noted that the details of each component in Tables 1 and 2 above are shown in Tables 4 to 6 below.

[0185] <Pigment Dispersion Resin (A)>

[0186] [Table 4]

[0187]

[0188]

[0189] <Carbon Nanotubes (B)>

[0190] [Table 5]

[0191]

[0192] CNT1 through CNT6 are all multi-walled carbon nanotubes.

[0193] It should be noted that the median diameter (D50), G / D ratio, and amount of acidic groups in Table 5 above were determined by the following method.

[0194] <Median diameter (D50)>

[0195] The median diameter (D50) was determined using a laser diffraction / scattering particle size distribution measuring device “LA-960” (manufactured by HORIBA Corporation, trade name) and the procedure described below.

[0196] [Preparation of Aqueous Dispersion Media]

[0197] Add 0.10 g of F10MC (manufactured by Nippon Paper Corporation, trade name, sodium carboxymethyl cellulose (hereinafter also referred to as CMCNa)) to 100 mL of distilled water and stir at room temperature for more than 24 hours to dissolve it, thus preparing an aqueous dispersion medium of 0.1% by mass of CMCNa.

[0198] [Preparation of CMCNa aqueous solution]

[0199] Add 2.0 g of F10MC (manufactured by Nippon Paper Corporation, trade name: sodium carboxymethyl cellulose) to 100 mL of distilled water and stir at room temperature for more than 24 hours to dissolve it, thus preparing an aqueous solution of CMCNa 2.0% by mass.

[0200] [Pretreatment before assay]

[0201] 6.0 mg of carbon nanotubes were weighed into a vial, and 6.0 g of the aforementioned aqueous dispersion medium was added. An ultrasonic homogenizer (Microtec "SmurtNR-50") was used in the pretreatment process. After confirming that the chip was not degraded, adjustments were made to ensure the chip was immersed at least 10 mm above the surface of the sample liquid. The TIME SET (irradiation time) was set to 40 seconds, the POW SET to 50%, and the STARTPOW to 50% (output 50%). Homogenization was achieved through ultrasonic irradiation with constant output power to prepare the carbon nanotube aqueous dispersion.

[0202] [Measurement]

[0203] Using the aforementioned carbon nanotube aqueous dispersion, the proportion and median diameter (D50) of dispersed carbon nanotube particles smaller than 1 μm were determined according to the following method.

[0204] The optical model of the LS13 320 universal liquid module was set with refractive indices of 1.520 for carbon nanotubes and 1.333 for water. After cleaning the module, approximately 1.0 mL of CMCNa aqueous solution was added.

[0205] Offset measurement, optical axis adjustment, and background measurement were performed at 50% pump speed. Then, the prepared carbon nanotube aqueous dispersion was added to a particle size analyzer at a relative concentration of 8–12% (representing the percentage of light scattered to the outside of the beam due to particles) or a PIDS of 40%–55%. The dispersion was then subjected to ultrasonic irradiation at 78W for 2 minutes using an accessory device of the particle size analyzer (pretreatment). After 30 seconds of circulation to remove air bubbles, particle size distribution was measured. A graph of volume % versus particle size was obtained, and the proportion of dispersed particles smaller than 1 μm and the median diameter (D50) were determined.

[0206] For the measurement, three samples were collected from different locations for each carbon nanotube sample to determine the particle size distribution. The proportion of dispersed particles smaller than 1 μm and the median diameter (D50) were determined by averaging these samples.

[0207] <G / D ratio of carbon nanotubes>

[0208] Regarding the Raman spectrum of carbon nanotubes, the carbon nanotubes were placed on a Raman microscope (manufactured by Horiba Manufacturing Co., Ltd., trade name "XploRA") and measurements were performed using a laser wavelength of 532 nm. Within the obtained peak, the 1560 cm⁻¹ peak was observed in the spectrum. -1 Above 1600cm -1 Let the maximum peak intensity within the following range be defined as G, and set 1310 cm⁻¹ as the maximum peak intensity. -1 Above ~ 1350cm-1 The G / D ratio of carbon nanotubes is defined as the maximum peak intensity within the following range when D is taken as the G / D ratio.

[0209] <Amount of acidic groups in carbon nanotubes (CNTs)>

[0210] 2 g of CNTs were accurately weighed and immersed in 50 ml of a 0.01 M benzylamine / n-methylpyrrolidone solution, and dispersed using an ultrasonic irradiation machine for 1 hour. The solution was then centrifuged, and the supernatant was filtered. The amount of acidic groups (mmol / g) per g of CNTs was determined by potentiometric titration of the residual benzylamine in the filtrate with 0.1 M hydrochloric acid.

[0211] <Amine compounds (E1)>

[0212] [Table 6]

[0213]

[0214] Solvent (C)

[0215] The moisture content and amine content of the solvents used were determined.

[0216] Moisture and amine content were determined using a Karl Fischer moisture meter (Kyoto Electronics Co., Ltd., trade name "MKC-610") and ion chromatography.

[0217] NMP1: N-methyl-2-pyrrolidone, SP value 11.1, moisture content 0.1% by mass, amine content 0% by mass.

[0218] NMP2: N-methyl-2-pyrrolidone, SP value 11.1, moisture content 1.2% by mass, amine content 0% by mass.

[0219] PGMME: SP value 10.4, moisture content 0.1% by mass, amine content 0% by mass.

[0220] <Evaluation Experiment>

[0221] Evaluation tests were conducted on the conductive pigment paste and multilayer material paste obtained in the above examples and comparative examples. As an evaluation, D was deemed unqualified. Even with just one unqualified evaluation result, the conductive pigment paste was still deemed unqualified. The evaluation results are shown in Tables 1 and 2.

[0222] <Dispersion>

[0223] The dispersibility of the obtained conductive pigment paste was evaluated using a grain gauge according to the following criteria, based on the dispersibility test of JIS K-5600-2-5.

[0224] A: The pigment is dispersed at a density of less than 10 μm. The dispersibility is excellent.

[0225] B: The pigment is dispersed at a size greater than 10 μm and less than 20 μm. The dispersibility is slightly good.

[0226] C: The pigment is dispersed at a size greater than 20 μm, but aggregates cannot be visually identified. Dispersibility is slightly poor.

[0227] D: Agglomerates were visually confirmed. Dispersibility is very poor.

[0228] <Initial viscosity>

[0229] The obtained multilayer material paste was tested using a cone-plate viscometer (HAAKE, trade name "Mars2", 35mm diameter, 2° inclined cone plate) at a shear rate of 2.0 sec. -1 The viscosity was measured and evaluated according to the following criteria.

[0230] A: Viscosity less than 10 Pa·s.

[0231] B: Viscosity is above 10 Pa·s and less than 20 Pa·s.

[0232] C: Viscosity greater than 20 Pa·s and less than 50 Pa·s.

[0233] D: Viscosity above 50 Pa·s.

[0234] <Storage Stability>

[0235] The obtained multilayer material paste was stored at 50°C for two weeks, and the initial viscosity was compared with the viscosity after storage. Viscosity was measured using a cone-plate viscometer (HAAKE, trade name "Mars2", 35mm diameter, 2° inclined cone plate) at a shear rate of 2.0 s⁻¹. -1 Measurements were performed, the viscosity increase rate was calculated using the following formula, and the storage stability was evaluated based on the following criteria.

[0236] Viscosity increase rate (%) = Viscosity after storage (mPa·s) / Initial viscosity (mPa·s) × 100 - 100

[0237] S: Viscosity increase rate (%) after storage is less than 10%.

[0238] A: The viscosity increase rate (%) after storage is greater than 10% and less than 20%.

[0239] B: The viscosity increase rate (%) after storage is greater than 20% and less than 50%.

[0240] C: The viscosity increase rate (%) after storage is greater than 50% and less than 200%.

[0241] D: The viscosity increase rate (%) after storage is greater than 200% (or gelation makes it impossible to measure).

[0242] <Volume resistivity (conductivity)>

[0243] The conductive pigment pastes obtained in Examples 1A, 7A, 8A, and 9A were further subjected to volume resistivity determination. In the volume resistivity determination, a 5% by mass solution of polyvinylidene fluoride (manufactured by KUREHA, trade name "KFPOLYMER W#7300", solvent: N-methyl-2-pyrrolidone) was used as a binder.

[0244] The conductive pigment paste and KF POLYMER W#7300 solution were measured in a ratio of 5:100, where the mass of the conductive pigment (B) in the obtained conductive pigment paste was equal to the mass of the solid components of the pigment dispersion resin (A) and KF POLYMER W#7300 in the conductive pigment paste. The mixture was then mixed for 2 minutes using an ultrasonic homogenizer to obtain the test sample.

[0245] The test sample was coated onto a glass plate (2 mm × 100 mm × 150 mm) using a doctor blade method and dried at 80 °C for 60 minutes to form a coating film. The film thickness was measured, and the resistance was measured using an ASP probe (Mitsubishi Chemical Analytech, trade name "MCP-TP03P") and a resistivity meter (Mitsubishi Chemical Analytech, trade name "Loresta-GP MCP-T610"). The volume resistivity was calculated by multiplying the resistance value by the resistivity correction factor (RCF) 4.532 and the film thickness. The volume resistivity was evaluated according to the following criteria.

[0246] A: Volume resistivity is less than 7 Ω·cm, and conductivity is good.

[0247] B: Volume resistivity is above 7 Ω·cm and less than 15 Ω·cm, and conductivity is average.

[0248] D: Volume resistivity is above 15 Ω·cm, poor conductivity.

[0249] As an evaluation result, the conductive pigment pastes obtained in Examples 1A and 7A are designated as "A", and the conductive pigment pastes obtained in Examples 8A and 9A are designated as "B".

[0250] [Manufacturing of battery electrode layers]

[0251] Application Examples 1-20

[0252] The weight per unit area of ​​a strip of aluminum foil (positive current collector) with an average thickness of 15 μm is 10 mg / cm² on both sides. 2 (Based on solid composition) The multilayer material paste obtained in Examples 1B to 20B was coated into a strip by roller coating and dried (drying temperature 180°C, 10 minutes) to form the positive electrode layer. The positive electrode active material layer (positive electrode layer) supported on the positive electrode current collector was calendered using a roller press to adjust its properties.

[0253] The residual solvent content of the obtained electrode layer is less than 1%, making it an electrode layer with good machinability.

Claims

1. A conductive pigment paste, said conductive pigment paste comprising a pigment dispersion resin (A), a conductive pigment (B), a solvent (C), a fluoropolymer (D), and a highly polar, low molecular weight component (E), wherein, The pigment dispersion resin (A) has at least one polar functional group selected from the group consisting of amide, imide, hydroxyl, carboxyl, sulfonic acid, phosphoric acid, silanol, cyano, and pyrrolidone groups, and the concentration of the polar functional group in the pigment dispersion resin (A) is 0.3 mmol / g or more and 23 mmol / g or less. The conductive pigment (B) contains carbon nanotubes (B1). The highly polar, low molecular weight component (E) contains amine compounds (E1). The amount of acidic groups in the carbon nanotubes (B1) is greater than 0.01 mmol / g and less than 0.5 mmol / g. The amount of acidic groups in the carbon nanotubes (B1) is determined by the following method: the carbon nanotubes (B1) are immersed in a benzylamine / dispersion medium solution for dispersion treatment, followed by centrifugation. The supernatant is filtered, and the amount of acidic groups per gram of carbon nanotubes (B1) is determined by potentiometric titration of the residual benzylamine in the filtrate with hydrochloric acid. Let α be the content of the high polarity low molecular weight component (E) relative to 100 parts by mass of conductive pigment (B), and let β be the BET specific surface area of ​​conductive pigment (B). 2 In the case of / g, the value of X in the following formula (1) is 60 or more and 300 or less. X = α / β × 300……Equation (1).

2. The conductive pigment paste according to claim 1, wherein, Based on 100% by mass of the solid content of the conductive pigment (B), the content of the amine compound (E1) is 12% by mass or more and 500% by mass or less.

3. The conductive pigment paste according to claim 1 or 2, wherein, The median diameter (D50) of carbon nanotubes (B1) based on volume conversion is greater than 10µm and less than 250µm.

4. The conductive pigment paste according to claim 1 or 2, wherein, The BET specific surface area of ​​carbon nanotubes (B1) is 100 m². 2 / g or more and 800m 2 / g or less In the Raman spectrum of carbon nanotubes (B1), the 1560 cm⁻¹... -1 Above and 1600cm -1 Let the maximum peak intensity within the following range be defined as G, and set 1310 cm⁻¹ as the maximum peak intensity. -1 Above and 1350cm -1 The maximum peak intensity is set to D within the following range, where the G / D ratio is above 0.1 and below 5.

0.

5. The conductive pigment paste according to claim 1 or 2, wherein, The solvent (C) has a water content of less than 1% by mass and an amine compound content of less than 1% by mass.

6. The conductive pigment paste according to claim 1 or 2, wherein, The weight-average molecular weight of amine compounds (E1) is less than 1000.

7. The conductive pigment paste according to claim 1 or 2, wherein, The amine value of the amine compound (E1) is above 105 mg KOH / g and below 1000 mg KOH / g.

8. The conductive pigment paste according to claim 1 or 2, wherein, The solvent (C) is N-methyl-2-pyrrolidone.

9. The conductive pigment paste according to claim 1 or 2, wherein, The conductive pigment (B) further contains acetylene black.

10. A multilayer material paste, wherein the multilayer material paste is formed by combining the conductive pigment paste as described in claim 1 with an electrode active material (F).

11. A multilayer material paste, said multilayer material paste comprising a pigment dispersion resin (A), a conductive pigment (B), a solvent (C), a fluororesin (D), a highly polar low molecular weight component (E), and an electrode active substance (F), wherein, The pigment dispersion resin (A) has at least one polar functional group selected from the group consisting of amide, imide, hydroxyl, carboxyl, sulfonic acid, phosphoric acid, silanol, cyano, and pyrrolidone groups, and the concentration of the polar functional group in the pigment dispersion resin (A) is 0.3 mmol / g or more and 23 mmol / g or less. The conductive pigment (B) contains carbon nanotubes (B1). The highly polar, low molecular weight component (E) contains amine compounds (E1). The amount of acidic groups in the carbon nanotubes (B1) is greater than 0.01 mmol / g and less than 0.5 mmol / g. The amount of acidic groups in the carbon nanotubes (B1) is determined by the following method: the carbon nanotubes (B1) are immersed in a benzylamine / dispersion medium solution for dispersion treatment, followed by centrifugation. The supernatant is filtered, and the amount of acidic groups per gram of carbon nanotubes (B1) is determined by potentiometric titration of the residual benzylamine in the filtrate with hydrochloric acid. Let α be the content of the high polarity low molecular weight component (E) relative to 100 parts by mass of conductive pigment (B), and let β be the BET specific surface area of ​​conductive pigment (B). 2 In the case of / g, the value of X in the following formula (1) is 60 or more and 300 or less. X = α / β × 300……Equation (1).

12. An electrode for a lithium-ion battery, said electrode being obtained using a multilayer material paste as described in claim 10 or 11.

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