JP7573380B2 - Method for manufacturing anode for capacitor and method for manufacturing capacitor - Google Patents

Description

The present invention relates to a method for manufacturing a capacitor anode having a solid electrolyte layer containing a π-conjugated conductive polymer, and a method for manufacturing a capacitor.

A capacitor is known in which a solid electrolyte layer formed from a conductive polymer dispersion liquid containing poly(3,4-ethylenedioxythiophene) and polystyrenesulfonic acid is placed between a dielectric layer and a cathode in order to reduce the equivalent series resistance of the capacitor (for example, Patent Document 1).

JP 2014-67949 A

Conventional capacitors manufactured using conductive polymer dispersions are required to have a reduced equivalent series resistance.
The present invention provides a method for producing a capacitor having a reduced equivalent series resistance as compared to the conventional method, and a method for producing a capacitor anode for use in the capacitor.

[1] A method for producing an anode for a capacitor, comprising: a separation step of obtaining a mixed solution by mixing an aqueous conductive polymer dispersion containing a conductive complex containing a π-conjugated conductive polymer and a polyanion with an organic solvent, precipitating a highly conductive complex in the mixed solution, and separating the precipitated highly conductive complex; a preparation step of obtaining an aqueous highly conductive complex dispersion by mixing an aqueous dispersion medium with the highly conductive complex; and a lamination step of applying the aqueous highly conductive complex dispersion to a dielectric layer obtained by oxidizing the surface of an anode made of a porous valve metal, and drying the applied solution to form a solid electrolyte layer on the surface of the dielectric layer.
[2] The method for producing an anode for a capacitor according to [1], further comprising adding one or more kinds of alkaline compounds to the highly conductive composite aqueous dispersion.
[3] The method for producing an anode for a capacitor according to [1] or [2], further comprising adding one or more compounds having two or more hydroxyl groups to the highly conductive composite aqueous dispersion.
[4] The method for producing an anode for a capacitor according to any one of [1] to [3], wherein a content of the organic solvent in the mixed solution is 50 mass % or more with respect to a total mass of the mixed solution.
[5] The method for producing an anode for a capacitor according to any one of [1] to [4], wherein the organic solvent includes at least one of a ketone-based solvent and an alcohol-based solvent.
[6] The method for producing an anode for a capacitor according to [5], wherein the organic solvent contains a ketone-based solvent, and the ketone-based solvent contains methyl ethyl ketone.
[7] The method for producing an anode for a capacitor according to [5], wherein the organic solvent contains an alcohol-based solvent, and the alcohol-based solvent contains methanol.
[8] The method for producing an anode for a capacitor according to any one of [1] to [4], wherein the organic solvent contains methyl ethyl ketone and methanol.
[9] The method for producing an anode for a capacitor according to any one of [1] to [8], wherein the conductive complex contains at least one of poly(3,4-ethylenedioxythiophene) and polystyrenesulfonic acid.
[10] A method for producing a capacitor, comprising the steps of obtaining a capacitor anode by the production method according to any one of [1] to [9], and assembling a capacitor comprising the capacitor anode and a cathode.

Capacitors obtained by the manufacturing method of the present invention have a lower equivalent series resistance than conventional capacitors, which contributes to improving the performance of electronic devices.

This invention is believed to contribute to SDG Goal 12, "Responsible Consumption and Production."

FIG. 2 is a cross-sectional view illustrating one embodiment of a capacitor.

<<Method for manufacturing anode for capacitor>>
The first aspect of the present invention includes a separation step, a preparation step, and a layering step.
The separation step is a step of obtaining a mixed liquid by mixing an aqueous conductive polymer dispersion containing a conductive complex including a π-conjugated conductive polymer and a polyanion with an organic solvent, precipitating a highly conductive complex in the mixed liquid, and separating out the precipitated highly conductive complex.
The preparation step is a step of obtaining an aqueous dispersion of the highly conductive complex by mixing an aqueous dispersion medium with the highly conductive complex.
The lamination process is a process in which the highly conductive composite aqueous dispersion is applied to a dielectric layer formed by oxidizing the surface of an anode made of a porous valve metal, and then dried to form a solid electrolyte layer on the surface of the dielectric layer.
Each step will be described below.

<Isolation process>
[Conductive polymer aqueous dispersion]
The conductive polymer aqueous dispersion used as a material in this embodiment contains a conductive complex containing a π-conjugated conductive polymer and a polyanion, and water. This aqueous dispersion may contain an organic solvent to the extent that the conductive complex is in a dispersed state in the liquid.

The polyanion is doped into the π-conjugated conductive polymer to form a conductive complex having electrical conductivity. In the polyanion, only some of the anionic groups are doped into the π-conjugated conductive polymer, and there are excess anionic groups that are not involved in the doping. Since the excess anionic groups are hydrophilic groups, the conductive complex has dispersibility in water.

In the conductive polymer aqueous dispersion used in this embodiment, the conductive complex is in a dispersed state. The dispersed state and precipitated state can be easily distinguished by visual inspection. The dispersion liquid in the dispersed state has high transparency, and no solid floating matter is found in the dispersion liquid. On the other hand, the liquid in the precipitated state has low transparency, and solid floating matter is observed in the liquid. Usually, the conductive complex in the dispersed state does not easily precipitate, and precipitation is unlikely to occur even if the liquid is left to stand for, for example, 12 hours. On the other hand, the floating matter in the precipitated state liquid is likely to settle, and precipitation is likely to occur when the liquid is left to stand for, for example, about 12 hours.

When the conductive polymer aqueous dispersion used in this embodiment is passed through a filter with a retention particle size of 7 μm, the conductive complex in a dispersed state passes through the filter together with the dispersion medium, while the conductive complex in a precipitated state can be captured by the filter.
Here, the retention particle size of the filter paper is a measure of the coarseness of the mesh, and is determined from the leaking particle size when barium sulfate or the like is naturally filtered as specified in JIS P 3801 [filter paper (for chemical analysis)].

(π-conjugated conductive polymer)
The π-conjugated conductive polymer may be an organic polymer whose main chain is composed of a π-conjugated system, and examples thereof include polypyrrole-based conductive polymers, polythiophene-based conductive polymers, polyacetylene-based conductive polymers, polyphenylene-based conductive polymers, polyphenylenevinylene-based conductive polymers, polyaniline-based conductive polymers, polyacene-based conductive polymers, polythiophenevinylene-based conductive polymers, and copolymers thereof. From the viewpoint of stability in air, polypyrrole-based conductive polymers, polythiophenes, and polyaniline-based conductive polymers are preferred, and from the viewpoint of transparency, polythiophene-based conductive polymers are more preferred.

Examples of polythiophene-based conductive polymers include polythiophene, poly(3-methylthiophene), poly(3-ethylthiophene), poly(3-propylthiophene), poly(3-butylthiophene), poly(3-hexylthiophene), poly(3-heptylthiophene), poly(3-octylthiophene), poly(3-decylthiophene), poly(3-dodecylthiophene), poly(3-octadecylthiophene), poly(3-bromothiophene), poly(3-chlorothiophene), and poly(3-iodothiophene). thiophene), poly(3-cyanothiophene), poly(3-phenylthiophene), poly(3,4-dimethylthiophene), poly(3,4-dibutylthiophene), poly(3-hydroxythiophene), poly(3-methoxythiophene), poly(3-ethoxythiophene), poly(3-butoxythiophene), poly(3-hexyloxythiophene), poly(3-heptyloxythiophene), poly(3-octyloxythiophene), poly(3-decyloxythiophene), poly(3-dodecyloxythiophene), oxythiophene), poly(3-octadecyloxythiophene), poly(3,4-dihydroxythiophene), poly(3,4-dimethoxythiophene), poly(3,4-diethoxythiophene), poly(3,4-dipropoxythiophene), poly(3,4-dibutoxythiophene), poly(3,4-dihexyloxythiophene), poly(3,4-diheptyloxythiophene), poly(3,4-dioctyloxythiophene), poly(3,4-didecyloxythiophene), poly(3,4-di dodecyloxythiophene), poly(3,4-ethylenedioxythiophene), poly(3,4-propylenedioxythiophene), poly(3,4-butylenedioxythiophene), poly(3-methyl-4-methoxythiophene), poly(3-methyl-4-ethoxythiophene), poly(3-carboxythiophene), poly(3-methyl-4-carboxythiophene), poly(3-methyl-4-carboxyethylthiophene), and poly(3-methyl-4-carboxybutylthiophene).
Examples of polypyrrole-based conductive polymers include polypyrrole, poly(N-methylpyrrole), poly(3-methylpyrrole), poly(3-ethylpyrrole), poly(3-n-propylpyrrole), poly(3-butylpyrrole), poly(3-octylpyrrole), poly(3-decylpyrrole), poly(3-dodecylpyrrole), poly(3,4-dimethylpyrrole), poly(3,4-dibutylpyrrole), poly(3-carboxypyrrole), poly(3-methyl-4-carboxypyrrole), poly(3-methyl-4-carboxyethylpyrrole), poly(3-methyl-4-carboxybutylpyrrole), poly(3-hydroxypyrrole), poly(3-methoxypyrrole), poly(3-ethoxypyrrole), poly(3-butoxypyrrole), poly(3-hexyloxypyrrole), and poly(3-methyl-4-hexyloxypyrrole).
Examples of polyaniline-based conductive polymers include polyaniline, poly(2-methylaniline), poly(3-isobutylaniline), poly(2-anilinesulfonic acid), and poly(3-anilinesulfonic acid).
Among these π-conjugated conductive polymers, poly(3,4-ethylenedioxythiophene) is particularly preferable from the viewpoints of conductivity, transparency, and heat resistance.
The conductive composite may contain one type of π-conjugated conductive polymer, or two or more types of polymers.

(Polyanion)
A polyanion is a polymer having two or more monomer units each having an anionic group in the molecule. The anionic group of the polyanion functions as a dopant for a π-conjugated conductive polymer, thereby improving the conductivity of the π-conjugated conductive polymer.
The anion group of the polyanion is preferably a sulfo group or a carboxy group.
Specific examples of such polyanions include polymers having a sulfo group, such as polystyrene sulfonic acid, polyvinyl sulfonic acid, polyallyl sulfonic acid, polyacrylic acid esters having a sulfo group, polymethacrylic acid esters having a sulfo group (e.g., poly(4-sulfobutyl methacrylate, polysulfoethyl methacrylate, polymethacryloyloxybenzenesulfonic acid), poly(2-acrylamido-2-methylpropanesulfonic acid), and polyisoprene sulfonic acid; and polymers having a carboxy group, such as polyvinyl carboxylic acid, polystyrene carboxylic acid, polyallyl carboxylic acid, polyacrylic acid, polymethacrylic acid, poly(2-acrylamido-2-methylpropanecarboxylic acid), and polyisoprene carboxylic acid. The polyanion may be a homopolymer in which a single monomer is polymerized, or a copolymer in which two or more monomers are polymerized.
Among these polyanions, polymers having a sulfo group are preferred, and polystyrene sulfonic acid is more preferred, since they can provide higher electrical conductivity.
The polyanions may be used alone or in combination of two or more kinds.
The mass average molecular weight of the polyanion is preferably from 20,000 to 1,000,000, and more preferably from 100,000 to 500,000. The mass average molecular weight is the average molecular weight based on mass measured by gel permeation chromatography and calculated in terms of polystyrene.

The content of the polyanion in the conductive complex is preferably in the range of 1 to 1000 parts by mass, more preferably 10 to 700 parts by mass, and even more preferably 100 to 500 parts by mass, per 100 parts by mass of the π-conjugated conductive polymer. If the content of the polyanion is equal to or greater than the lower limit, the doping effect on the π-conjugated conductive polymer tends to be stronger, and the conductivity becomes higher. On the other hand, if the content of the polyanion is equal to or less than the upper limit, the π-conjugated conductive polymer can be sufficiently contained, so that sufficient conductivity can be ensured.

[Method of producing conductive polymer aqueous dispersion]
A conductive polymer aqueous dispersion in which a conductive complex containing a π-conjugated conductive polymer and a polyanion is dispersed in an aqueous dispersion medium can be obtained, for example, by chemically oxidizing and polymerizing a monomer that forms a π-conjugated conductive polymer in an aqueous solution of a polyanion. Alternatively, a commercially available conductive polymer aqueous dispersion may be used.

The chemical oxidative polymerization can be carried out using a known catalyst and oxidizing agent. Examples of catalysts include transition metal compounds such as ferric chloride, ferric sulfate, ferric nitrate, and cupric chloride. Examples of oxidizing agents include persulfates such as ammonium persulfate, sodium persulfate, and potassium persulfate. The oxidizing agent can return the reduced catalyst to its original oxidized state.

The content of the conductive complex contained in the conductive polymer aqueous dispersion of this embodiment is, for example, preferably 0.1 mass % or more and 20 mass % or less, more preferably 0.5 mass % or more and 10 mass % or less, and more preferably 1.0 mass % or more and 5.0 mass % or less, relative to the total mass of the aqueous dispersion.
When the content is equal to or greater than the lower limit of the above range, the highly conductive composite is easily precipitated after the addition of the organic solvent. When the content is equal to or less than the upper limit of the above range, the dispersibility of the conductive composite in the conductive polymer aqueous dispersion is increased, so that unintended aggregation during storage of the conductive polymer aqueous dispersion can be prevented, and the quality of the highly conductive composite precipitated after the addition of the organic solvent can be made uniform.

The conductive polymer aqueous dispersion used in this embodiment may contain an organic solvent within the range in which the conductive composite is in a dispersed state. The content of the organic solvent is preferably as small as possible, and more preferably substantially absent, and is, for example, preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 1% by mass or less, based on the total mass of the aqueous dispersion.
The organic solvent that may be contained in the conductive polymer aqueous dispersion used in this embodiment is preferably one that is highly miscible with water, and examples thereof include the alcohol-based solvents described below.
In this specification, the term "conductive polymer aqueous dispersion" is a term that clearly indicates that the dispersion medium contains water and does not substantially contain an organic solvent.

[Preparation of Mixture]
Examples of methods for mixing a conductive polymer aqueous dispersion with an organic solvent to obtain a mixed solution include a method of adding an organic solvent to a conductive polymer aqueous dispersion, and a method of adding a conductive polymer aqueous dispersion to an organic solvent. A preferred embodiment includes a method of gradually adding an organic solvent while stirring the conductive polymer aqueous dispersion. This addition method can prevent a localized sudden increase in the organic solvent concentration in the conductive polymer aqueous dispersion, and can gently precipitate the highly conductive composite. If the organic solvent concentration increases suddenly, a non-uniform aggregate of the highly conductive composite may occur.

The content of the organic solvent contained in the mixed liquid is preferably 50% by mass or more and less than 100% by mass, more preferably 55% by mass or more and 90% by mass or less, still more preferably 60% by mass or more and 85% by mass or less, and particularly preferably 65% by mass or more and 80% by mass or less, based on the total mass of the mixed liquid. Here, the content of the organic solvent is the amount including the organic solvent contained in the conductive polymer aqueous dispersion before mixing.
When the content is at least the lower limit of the above range, precipitation of the highly conductive composite becomes easier, and the yield of the conductive composite is improved.
When it is equal to or less than the upper limit of the above range, the amount of the conductive polymer aqueous dispersion contained in the mixed liquid can be relatively increased, and therefore the amount of the highly conductive complex to be separated can be increased.

When the conductive polymer aqueous dispersion is mixed with an organic solvent and the resulting mixture is allowed to stand, the appearance of the mixture may indicate that the water and the organic solvent are completely compatible with each other or that they are separated from each other. However, from the viewpoint of facilitating the precipitation of the highly conductive composite, it is preferable that they are fully compatible with each other.

(Organic Solvent)
The organic solvent constituting the mixed solution of this embodiment is preferably a water-soluble organic solvent. Here, the water-soluble organic solvent is an organic solvent that dissolves in an amount of 1 g or more in 100 g of water at a temperature of 20° C.
Examples of the water-soluble organic solvent include alcohol-based solvents, ketone-based solvents, and ester-based solvents.
Examples of the alcohol solvent include methanol, ethanol, isopropanol, n-butanol, t-butanol, and allyl alcohol.
Examples of the ketone solvent include methyl ethyl ketone, methyl propyl ketone, methyl butyl ketone, methyl isopropyl ketone, methyl isobutyl ketone, methyl amyl ketone, diethyl ketone, diisopropyl ketone, acetone, and diacetone alcohol.
Examples of the ester solvent include methyl acetate, ethyl acetate, propyl acetate, and butyl acetate.
The organic solvents may be used alone or in combination of two or more kinds.

The organic solvent constituting the mixed solution of this embodiment preferably contains at least one of a ketone-based solvent and an alcohol-based solvent.
The ketone solvent preferably contains methyl ethyl ketone.
As the alcohol-based solvent, methanol or isopropanol is preferred.
When the above-mentioned suitable organic solvent is contained, the highly conductive composite can be more easily precipitated in the mixed liquid, and the yield can be further improved.

In the mixed solution of this embodiment, methyl ethyl ketone is preferably contained in combination with methanol or isopropanol. In this case, the content of methanol or isopropanol per 100 parts by mass of methyl ethyl ketone is preferably 1 part by mass or more and 100 parts by mass or less, more preferably 3 parts by mass or more and 50 parts by mass or less, and even more preferably 6 parts by mass or more and 20 parts by mass or less.
When the above-mentioned suitable combination of organic solvents is contained, the highly conductive composite can be more easily precipitated in the mixed solution, and the yield can be further improved.
When the organic solvent is contained in the above-mentioned preferred range, the highly conductive composite can be more easily precipitated in the mixed liquid, and the yield can be further improved.

In the mixed solution of this embodiment, isopropanol is preferably contained in combination with methyl acetate or ethyl acetate. In this case, the content of methyl acetate or ethyl acetate per 100 parts by mass of isopropanol is preferably 10 parts by mass or more and 300 parts by mass or less, more preferably 30 parts by mass or more and 200 parts by mass or less, and even more preferably 60 parts by mass or more and 100 parts by mass or less.
When the above-mentioned suitable combination of organic solvents is contained, the highly conductive composite can be more easily precipitated in the mixed solution, and the yield can be further improved.
When the organic solvent is contained in the above-mentioned preferred range, the highly conductive composite can be more easily precipitated in the mixed liquid, and the yield can be further improved.

In the mixed solution of this embodiment, it is preferable that methyl ethyl ketone, isopropanol, and methyl acetate or ethyl acetate are combined. In this case, the content of methyl acetate or ethyl acetate relative to 100 parts by mass of isopropanol is preferably 10 parts by mass or more and 300 parts by mass or less, more preferably 30 parts by mass or more and 200 parts by mass or less, and even more preferably 60 parts by mass or more and 100 parts by mass or less. And, the content of methyl ethyl ketone relative to 100 parts by mass of isopropanol is preferably 100 parts by mass or more and 3000 parts by mass or less, more preferably 200 parts by mass or more and 2000 parts by mass or less, and even more preferably 500 parts by mass or more and 1000 parts by mass or less.
When the above-mentioned suitable combination of organic solvents is contained, the highly conductive composite can be more easily precipitated in the mixed solution, and the yield can be further improved.
When the organic solvent is contained in the above-mentioned preferred range, the highly conductive composite can be more easily precipitated in the mixed liquid, and the yield can be further improved.

In the mixed solution of this embodiment, the content of an acid or base other than the polyanion is preferably 0.1 mass % or less, more preferably 0.01 mass % or less, and most preferably substantially none, relative to the total mass of the mixed solution.
Examples of the acid include inorganic acids such as hydrochloric acid and sulfuric acid, and organic acids such as paratoluenesulfonic acid and naphthalenesulfonic acid.
Examples of the base include inorganic bases such as sodium hydroxide and sodium carbonate, and organic bases such as trioctylamine and octylamine.
The above-mentioned acids or bases may be a cause of preventing the highly conductive complex from precipitating in the mixed solution of this embodiment.

[Precipitation of Highly Conductive Composite]
The method for precipitating the highly conductive composite in the prepared mixed solution is not particularly limited, and the highly conductive composite can be precipitated by simply leaving the mixed solution to stand. Moreover, it is not necessary to leave the mixed solution to stand completely, and the highly conductive composite can be precipitated while being gently stirred.

When precipitating the highly conductive complex in the mixed solution, it is preferable to heat the mixed solution. The heating temperature is preferably 40° C. or higher, more preferably 50° C. or higher and 100° C. or lower, and even more preferably 60° C. or higher and 80° C. or lower. The heating time at the above suitable heating temperature can be, for example, 1 hour or higher and 10 hours or lower.
When the mixed liquid is heated, the highly conductive complex can be easily precipitated in the mixed liquid, and the yield of the conductive complex can be improved.

[Isolation of Highly Conductive Composite]
The method for separating (recovering) the highly conductive composite precipitated in the mixed liquid is not particularly limited, and examples thereof include filtration, decantation, centrifugation, drying under reduced pressure, freeze drying, spray drying, and the like.
Among these, filtration or decantation is preferred because it is easy to separate the highly conductive composite from components other than the highly conductive composite contained in the mixed liquid. Here, filtration is an operation in which the highly conductive composite is captured in a filter through which the mixed liquid has been passed. Decantation is an operation in which the precipitated highly conductive composite is allowed to settle and the supernatant liquid is removed.
When separating by filtration, it is necessary to deal with clogging of the filter, so separating by decantation is easier. In addition, since the solid matter of the highly conductive complex is compressed on the filter by the filtration pressure, the highly conductive complex separated by filtration tends to be harder than when separated by decantation. Since the highly conductive complex obtained by decantation is obtained in a relatively soft powder state, it can be easily dispersed in a dispersion medium later. Therefore, separating the highly conductive complex by decantation is more preferable.

The separated highly conductive composite is preferably washed with an organic solvent that does not easily dissolve the highly conductive composite. Specifically, for example, the organic solvent may be poured onto the filter that has captured the highly conductive composite, or the organic solvent may be added to the highly conductive composite remaining at the bottom of the container after decantation, and the mixture may be stirred, and then separated again by decantation or the like.
The organic solvent and the like adhering to the separated highly conductive composite are removed by drying, whereby a dried highly conductive composite can be obtained.

<Preparation process>
In this step, the highly conductive composite obtained in the previous step is mixed with an aqueous dispersion medium containing water to obtain an aqueous dispersion of the highly conductive composite.
The highly conductive composite has high dispersibility in water, and therefore can be easily dispersed in an aqueous dispersion medium containing water.
The highly conductive composite used in this embodiment may be dried and stored after being obtained in the fractionation step, or may be used immediately without storage.

The aqueous dispersion medium of this embodiment may contain an organic solvent. The organic solvent is preferably a water-soluble organic solvent. Here, the water-soluble organic solvent is an organic solvent that dissolves in an amount of 1 g or more per 100 g of water at a temperature of 20° C.
Examples of the water-soluble organic solvent include alcohol-based solvents, ketone-based solvents, and ester-based solvents, and alcohol-based solvents are preferred. Specific examples of the water-soluble organic solvent are the same as those described in the first embodiment, and therefore will not be repeated here.

The water content of the aqueous dispersion medium of this embodiment can be, for example, 5% by mass or more and 100% by mass or less, preferably 50% by mass or more and 100% by mass or less, and more preferably 70% by mass or more and 100% by mass or less.

In this embodiment, the method for mixing the highly conductive composite with the aqueous dispersion medium is not particularly limited, and examples thereof include (1) a method in which an aqueous dispersion medium is added to the highly conductive composite and the mixture is stirred, and (2) a method in which water is added to the highly conductive composite to obtain an aqueous dispersion of the highly conductive composite, and then an organic solvent is further added as necessary and the mixture is stirred.
Since the highly conductive composite has very high dispersibility in water, method (2) is preferred from the viewpoint of preventing the highly conductive composite from agglomerating to increase in particle size.

After mixing the highly conductive composite with the aqueous dispersion medium, the mixture may be stirred to carry out a dispersion treatment. The stirring method is not particularly limited, and may be a low shear stirring method such as a stirrer, or may be a high shear stirring method using a dispersing machine (homogenizer, etc.).

In the highly conductive composite aqueous dispersion of this embodiment, the particle size distribution of the dispersed highly conductive composite is not particularly limited, but is preferably 300 nm or less, more preferably 250 nm or less, and even more preferably 200 nm or less. Since the highly conductive composite contains a polymer, the lower limit is 1 nm or more as a guideline, taking into account the molecular radius of the polymer.
The smaller the particle size distribution, the more the ESR of a capacitor having a solid electrolyte layer formed by applying the highly conductive composite aqueous dispersion of this embodiment can be reduced.
The particle size distribution herein is a value obtained by measuring the cumulant average particle size by dynamic light scattering.

The content of the highly conductive complex relative to the total mass of the highly conductive complex aqueous dispersion of this embodiment is, for example, preferably 0.1 mass % or more and 20 mass % or less, more preferably 0.5 mass % or more and 10 mass % or less, and even more preferably 1.0 mass % or more and 5.0 mass % or less.
When the content is within the above range, the highly conductive composite can be dispersed more stably.

[Compounds having two or more hydroxy groups]
It is preferable to add one or more compounds having two or more hydroxyl groups (hereinafter, sometimes referred to as polyol compounds) to the highly conductive composite aqueous dispersion of this embodiment. By including a polyol compound, the ESR of a capacitor produced using the highly conductive composite aqueous dispersion of this embodiment can be further reduced.

Specific examples of the polyol compound include polyhydric aliphatic alcohols such as ethylene glycol, diethylene glycol, propylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, glycerin, isoprene glycol, dimethylolpropionic acid, 1,5-pentanediol, 1,6-hexanediol, 1,9-nonanediol, neopentyl glycol, trimethylolethane, trimethylolpropane, pentaerythritol, dipentaerythritol, thiodiethanol, glucose, sorbitol, tartaric acid, glucaric acid, and glutaconic acid;
Polymeric alcohols such as cellulose, polysaccharides, and sugar alcohols;
1,4-dihydroxybenzene, 1,3-dihydroxybenzene, 2,3-dihydroxy-1-pentadecylbenzene, 2,4-dihydroxyacetophenone, 2,5-dihydroxyacetophenone, 2,4-dihydroxybenzophenone, 2,6-dihydroxybenzophenone, 3,4-dihydroxybenzophenone, 3,5-dihydroxybenzophenone, 2,4'-dihydroxydiphenylsulfone, 2,2',5,5'-tetrahydroxydiphenylsulfone, 3,3',5,5'-tetramethyl-4,4'-dihydroxydiphenyl sulfone, hydroxyquinone carboxylic acid and its salts, 2,3-dihydroxybenzoic acid, 2,4-dihydroxybenzoic acid, 2,5-dihydroxybenzoic acid, 2,6-dihydroxybenzoic acid, 3,5-dihydroxybenzoic acid, 1,4-hydroquinonesulfonic acid and its salts, 4,5-hydroxybenzene-1,3-disulfonic acid and its salts, 1,5-dihydroxynaphthalene, 1,6-dihydroxynaphthalene, 2,6-dihydroxynaphthalene, 2,7-dihydroxynaphthalene, 2,3-dihydroxynaphthalene, 1,5-dihydroxynaphthalene Phthalene-2,6-dicarboxylic acid, 1,6-dihydroxynaphthalene-2,5-dicarboxylic acid, 1,5-dihydroxynaphthoic acid, 1,4-dihydroxy-2-naphthoic acid phenyl ester, 4,5-dihydroxynaphthalene-2,7-disulfonic acid and its salts, 1,8-dihydroxy-3,6-naphthalenedisulfonic acid and its salts, 6,7-dihydroxy-2-naphthalenesulfonic acid and its salts, 1,2,3-trihydroxybenzene (pyrogallol), 1,2,4-trihydroxybenzene, 5-methyl-1,2,3-trihydroxy Examples of the aromatic compounds include benzene, 5-ethyl-1,2,3-trihydroxybenzene, 5-propyl-1,2,3-trihydroxybenzene, trihydroxybenzoic acid, trihydroxyacetophenone, trihydroxybenzophenone, trihydroxybenzaldehyde, trihydroxyanthraquinone, 2,4,6-trihydroxybenzene, tetrahydroxy-p-benzoquinone, tetrahydroxyanthraquinone, methyl gallate, and ethyl gallate; and potassium hydroquinone sulfonate.

Among the above specific examples, polyhydric aliphatic alcohols are preferred, and glycols such as ethylene glycol are particularly preferred, from the viewpoint of further reducing the ESR of the capacitor produced using the highly conductive composite aqueous dispersion of this embodiment.

The content of the polyol compound added to the highly conductive composite aqueous dispersion of this embodiment is preferably 10 parts by mass or more and 10,000 parts by mass or less, more preferably 50 parts by mass or more and 1,000 parts by mass or less, and even more preferably 100 parts by mass or more and 500 parts by mass or less, relative to 100 parts by mass of the highly conductive composite. The content of the polyol compound added to the highly conductive composite aqueous dispersion of this embodiment is preferably 0.1% by mass or more and 20% by mass or less, more preferably 0.5% by mass or more and 10% by mass or less, and even more preferably 1% by mass or more and 7% by mass or less, relative to the total mass of the highly conductive composite aqueous dispersion.
When the content is within the above preferred range, the ESR of a capacitor produced using the highly conductive composite aqueous dispersion of this embodiment can be further reduced.

[Alkaline compounds]
It is preferable to add one or more kinds of alkaline compounds to the highly conductive composite aqueous dispersion of this embodiment. By containing an alkaline compound, the ESR of the capacitor produced using the highly conductive composite aqueous dispersion of this embodiment can be further reduced. The alkaline compound is preferably one that does not fall under the category of the polyol compound.

Specific examples of alkaline compounds include inorganic alkaline compounds, amine compounds, and nitrogen-containing aromatic cyclic compounds.

Examples of inorganic alkaline compounds include sodium hydroxide, potassium hydroxide, calcium hydroxide, ammonia, sodium bicarbonate, potassium bicarbonate, and ammonium bicarbonate.

The amine compound may be any of a primary amine, a secondary amine, a tertiary amine, and a quaternary ammonium salt.
The amine compound may have a substituent selected from a linear or branched alkyl group having from 2 to 12 carbon atoms, an aryl group having from 6 to 12 carbon atoms, an aralkyl group having from 7 to 12 carbon atoms, an alkylene group having from 2 to 12 carbon atoms, an arylene group having from 6 to 12 carbon atoms, an aralkylene group having from 7 to 12 carbon atoms, and an oxyalkylene group having from 2 to 12 carbon atoms.
Specific examples of the primary amine include aniline, toluidine, benzylamine, and ethanolamine.
Specific examples of the secondary amine include diethanolamine, dimethylamine, diethylamine, dipropylamine, diphenylamine, dibenzylamine, and dinaphthylamine.
Specific examples of the tertiary amine include triethanolamine, trimethylamine, triethylamine, tripropylamine, tributylamine, trioctylamine, triphenylamine, tribenzylamine, and trinaphthylamine.
Specific examples of the quaternary ammonium salt include tetramethylammonium salt, tetraethylammonium salt, tetrapropylammonium salt, tetraphenylammonium salt, tetrabenzylammonium salt, tetranaphthylammonium salt, etc. Examples of the anion that is paired with ammonium include hydroxide ion.

Examples of nitrogen-containing aromatic cyclic compounds (aromatic compounds in which at least one nitrogen atom forms a ring structure) include pyrrole, imidazole, 2-methylimidazole, 2-propylimidazole, N-methylimidazole, N-propylimidazole, N-butylimidazole, 1-(2-hydroxyethyl)imidazole, 2-ethyl-4-methylimidazole, 1,2-dimethylimidazole, 1-benzyl-2-methylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 2-phenyl-4,5-dihydroxymethylimidazole, 1-acetylimidazole, 2-aminobenzimidazole, 2-amino-1-methylbenzimidazole, 2-hydroxybenzimidazole, 2-(2-pyridyl)benzimidazole, and pyridine.

Among the above specific examples, from the viewpoint of further reducing the ESR of the capacitor produced using the highly conductive composite aqueous dispersion of this embodiment, nitrogen-containing aromatic cyclic compounds are preferred, and imidazoles are particularly preferred.

The content of the alkali compound added to the highly conductive composite aqueous dispersion of this embodiment is preferably 0.1 parts by mass or more and 1000 parts by mass or less, more preferably 1 part by mass or more and 100 parts by mass or less, even more preferably 2 parts by mass or more and 50 parts by mass or less, and particularly preferably 5 parts by mass or more and 10 parts by mass or less, relative to 100 parts by mass of the highly conductive composite. The content of the alkali compound added to the highly conductive composite aqueous dispersion of this embodiment is preferably 0.01% by mass or more and 2% by mass or less, more preferably 0.05% by mass or more and 0.5% by mass or less, and even more preferably 0.1% by mass or more and 0.3% by mass or less, relative to the total mass of the highly conductive composite aqueous dispersion.
When the content is within the above preferred range, the ESR of a capacitor produced using the highly conductive composite aqueous dispersion of this embodiment can be further reduced.

(Other additives)
The highly conductive composite aqueous dispersion of this embodiment may contain other additives.
The additives are not particularly limited as long as the effects of the present invention can be obtained, and examples thereof include surfactants, inorganic conductive agents, antifoaming agents, coupling agents, antioxidants, ultraviolet absorbers, etc. However, the additives are other than the π-conjugated conductive polymers, polyanions, organic solvents, polyol compounds, and alkali compounds.
The surfactant may be a nonionic, anionic or cationic surfactant, with the nonionic surfactant being preferred from the standpoint of storage stability. A polymer surfactant such as polyvinylpyrrolidone may also be added.
Examples of the inorganic conductive agent include metal ions, conductive carbon, etc. Metal ions can be generated by dissolving a metal salt in water.
The antifoaming agent includes silicone resin, polydimethylsiloxane, silicone oil, and the like.
The coupling agent may be a silane coupling agent having a vinyl group or an amino group.
Examples of the ultraviolet absorber include benzotriazole-based ultraviolet absorbers, benzophenone-based ultraviolet absorbers, salicylate-based ultraviolet absorbers, cyanoacrylate-based ultraviolet absorbers, oxanilide-based ultraviolet absorbers, hindered amine-based ultraviolet absorbers, and benzoate-based ultraviolet absorbers.
When the above-mentioned highly conductive composite aqueous dispersion contains the above-mentioned additives, the content ratio thereof is appropriately determined depending on the type of additive, and can be, for example, in the range of 0.001 parts by mass or more and 5 parts by mass or less per 100 parts by mass of the highly conductive composite.

<Lamination process>
Examples of the valve metal constituting the anode used as a material in this embodiment include aluminum, tantalum, niobium, titanium, hafnium, zirconium, zinc, tungsten, bismuth, and antimony. Among these, aluminum, tantalum, and niobium are preferred. Specific examples of the anode include an aluminum foil that has been etched to increase its surface area and then oxidized, and a tantalum particle or niobium particle sintered body that has been oxidized to form a pellet. The anode thus treated is a porous body with unevenness formed on the surface.

The dielectric layer formed on the surface of the anode is a layer formed by oxidizing the surface of the anode. The dielectric layer has a surface profile conforming to the surface of the anode, and is preferably a porous layer with projections and recesses.
The dielectric layer can be formed by oxidizing the surface of an anode made of a valve metal, for example, by anodizing the surface of the anode in an electrolyte for chemical conversion treatment, such as an aqueous solution of ammonium adipate, an aqueous solution of ammonium borate, or an aqueous solution of ammonium phosphate.

Examples of methods for applying the highly conductive composite aqueous dispersion to the surface of an anode having a dielectric layer include immersion (dip coating), comma coating, reverse coating, lip coating, microgravure coating, etc. Among these, immersion is preferred from the viewpoint of ease of application between an anode and a cathode in an electrode element in which the electrodes are arranged opposite each other.
The highly conductive composite aqueous dispersion used in this embodiment has excellent dispersibility of the highly conductive composite, and therefore has excellent coatability onto the anode.

Methods for drying the highly conductive composite aqueous dispersion applied to the surface of the anode include, for example, natural drying at room temperature, hot air drying, far-infrared drying, etc.

A solid electrolyte layer containing a highly conductive composite can be formed by applying an aqueous dispersion of the highly conductive composite to at least a portion of the surface of the dielectric layer of the anode and drying the applied solution. The formed solid electrolyte layer covers at least a portion of the surface of the dielectric layer, and may cover the entire surface of the dielectric layer.
The thickness of the solid electrolyte layer may be constant or may not be constant, and may be, for example, 1 μm or more and 100 μm or less.

The above steps result in a capacitor anode that includes a porous valve metal body (anode body), a dielectric layer formed by oxidizing the surface of the anode, and a solid electrolyte layer containing a highly conductive composite laminated on the surface of the dielectric layer.

<Capacitor manufacturing method>
A second aspect of the present invention is a method for producing a capacitor, comprising the steps of obtaining a capacitor anode by the production method of the first aspect, and assembling a capacitor comprising the capacitor anode and a cathode.

The cathode used in this embodiment may be a known capacitor cathode, such as a metal foil such as aluminum foil, or a conductive layer containing conductive particles such as carbon or silver.

In the capacitor produced in this embodiment, it is preferable that the anode and the cathode are disposed facing each other, and the above-mentioned dielectric layer and solid electrolyte layer are disposed between the anode and the cathode.
Before forming the solid electrolyte layer in the first embodiment, an electrode element may be prepared in advance by placing the anode with the dielectric layer side facing the cathode. The electrode element may be immersed in a highly conductive composite aqueous dispersion to form a solid electrolyte layer between the dielectric layer of the anode and the cathode. The solid electrolyte layer preferably fills the space between the anode and the cathode.

In the electrode element, a separator may be placed between the dielectric layer of the anode and the cathode. The separator may be placed before the formation of the solid electrolyte layer when the electrode element is produced, or may be placed when the anode and cathode on which the solid electrolyte layer has been formed are arranged to face each other. Alternatively, the separator may be used as a base material and impregnated with a paste containing conductive particles, and the separator and cathode integrated together may be placed against the anode. The separator is particularly useful when manufacturing a wound capacitor.

Examples of separators include sheets (including nonwoven fabrics) made of cellulose, polyvinyl alcohol, polyester, polyethylene, polystyrene, polypropylene, polyimide, polyamide, polyvinylidene fluoride, etc., and nonwoven fabrics made of glass fibers.

An example of the configuration of a capacitor manufactured in this embodiment is shown in FIG. 1. The capacitor 10 comprises an anode 11 made of a porous body of a valve metal, a dielectric layer 12 made of an oxide of the valve metal, a solid electrolyte layer 14 formed on the surface of the dielectric layer 12, and a cathode 13 provided on the outermost side. The cathode 13 is provided on the opposite side to the anode 11, with the dielectric layer 12 and the solid electrolyte layer 14 sandwiched therebetween. In this embodiment, the solid electrolyte layer 14 is formed on the surface of the dielectric layer 12. The solid electrolyte layer 14 covers at least a portion of the surface of the dielectric layer 12.

The solid electrolyte layer of the capacitor produced in this embodiment may contain an electrolyte solution prepared by dissolving an electrolyte in a solvent for the electrolyte solution. The higher the electrical conductivity of the electrolyte solution, the more preferable.
Examples of the solvent for the electrolyte solution include alcohol-based solvents such as ethylene glycol, diethylene glycol, propylene glycol, 1,4-butanediol, and glycerin; lactone-based solvents such as γ-butyrolactone, γ-valerolactone, and δ-valerolactone; amide-based solvents such as N-methylformamide, N,N-dimethylformamide, N-methylacetamide, and N-methylpyrrolidinone; nitrile-based solvents such as acetonitrile and 3-methoxypropionitrile; and water.
Examples of the electrolyte include organic acids such as adipic acid, glutaric acid, succinic acid, benzoic acid, isophthalic acid, phthalic acid, terephthalic acid, maleic acid, toluic acid, enanthic acid, malonic acid, formic acid, decanedicarboxylic acids such as 1,6-decanedicarboxylic acid and 5,6-decanedicarboxylic acid, octanedicarboxylic acids such as 1,7-octanedicarboxylic acid, azelaic acid, and sebacic acid; or boric acid, polyhydric alcohol complex compounds of boric acid obtained from boric acid and polyhydric alcohol; inorganic acids such as phosphoric acid, carbonic acid, and silicic acid as anion components, and primary amines (methylamine, ethylamine, propylamine, butylamine, etc.). and the like), secondary amines (dimethylamine, diethylamine, dipropylamine, methylethylamine, diphenylamine, etc.), tertiary amines (trimethylamine, triethylamine, tripropylamine, triphenylamine, 1,8-diazabicyclo(5,4,0)-undecene-7, etc.), tetraalkylammoniums (tetramethylammonium, tetraethylammonium, tetrapropylammonium, tetrabutylammonium, methyltriethylammonium, dimethyldiethylammonium, etc.), etc., as cationic components.

<Action and effect>
According to the present invention, 90 to 100 parts by mass of the highly conductive composite can be recovered as a precipitate for every 100 parts by mass of the conductive composite contained in the mixed liquid. It is presumed that the reason why the highly conductive composite precipitates in the mixed liquid containing the organic solvent in the separation step is that the highly conductive composite is difficult to dissolve in the organic solvent.
Surprisingly, when an anode having a solid electrolyte layer containing a highly conductive composite is used, a capacitor having a lower equivalent series resistance (ESR) can be formed than when an anode containing a conventional conductive composite (a conductive composite contained in a raw material aqueous dispersion of a conductive polymer) is used (see Examples and Comparative Examples described later).
Although the details of the mechanism by which this effect is achieved are not yet clear, the highly conductive complex is separated from the excess polyanion contained in the raw material by precipitation from the dispersion liquid of the raw material. Therefore, it is considered that the amount of excess polyanion and impurities contained in the highly conductive complex is smaller than that of the conventional conductive complex. When the amount of excess polyanion is reduced, the acidity is weakened, so that the erosion of the oxide film of the anode of the capacitor is suppressed, and as a result, the ESR is reduced (previously, the ESR was increased due to the erosion of the oxide film). In addition, the highly conductive complex may differ from the conventional conductive complex not only in chemical composition but also in physicochemical properties (e.g., particle size), and this difference may affect the ESR.

(Production Example 1) Synthesis of polystyrene sulfonic acid 206 g of sodium styrene sulfonate was dissolved in 1000 ml of ion-exchanged water, and while stirring at 80° C., 1.14 g of an oxidizing agent solution of ammonium persulfate previously dissolved in 10 ml of water was added dropwise over 20 minutes, and the solution was stirred for 12 hours.
1000ml of sulfuric acid diluted to 10% by mass was added to the obtained sodium polystyrene sulfonate-containing solution, and about 1000ml of the solvent was removed from the polystyrene sulfonic acid-containing solution by ultrafiltration. Next, 2000ml of ion-exchanged water was added to the remaining liquid, and about 2000ml of the solvent was removed by ultrafiltration to wash the polystyrene sulfonic acid with water. This water washing operation was repeated three times.
Water in the resulting solution was removed under reduced pressure to obtain colorless solid polystyrene sulfonic acid.

(Production Example 2) Synthesis of conductive polymer aqueous dispersion 14.2 g of 3,4-ethylenedioxythiophene and a solution in which 36.7 g of polystyrene sulfonic acid was dissolved in 2000 ml of ion-exchanged water were mixed at 20°C.
The resulting mixed solution was kept at 20° C., and while stirring, 29.64 g of ammonium persulfate and 8.0 g of an oxidation catalyst solution of ferric sulfate dissolved in 200 ml of ion-exchanged water were slowly added, and the mixture was reacted with stirring for 3 hours.
To the resulting reaction solution, 2000 ml of ion-exchanged water was added, and about 2000 ml of the solvent was removed by ultrafiltration. This operation was repeated three times.
Then, 200 ml of sulfuric acid diluted to 10% by mass and 2000 ml of ion-exchanged water were added to the obtained solution, and about 2000 ml of the solvent was removed by ultrafiltration. 2000 ml of ion-exchanged water was added to the remaining liquid, and about 2000 ml of the solution was removed by ultrafiltration. This operation was repeated three times.
Further, 2000 ml of ion-exchanged water was added to the obtained solution, and about 2000 ml of the solvent was removed by ultrafiltration. This operation was repeated five times to obtain a 1.2% aqueous dispersion of polystyrenesulfonic acid-doped poly(3,4-ethylenedioxythiophene) (PEDOT-PSS). The content of PSS relative to the PEDOT-PSS solid content was 75% by mass.
The pH of the above PEDOT-PSS aqueous dispersion was 1.98 at 25°C.

(Production Example 3)
An anode lead terminal was connected to the etched aluminum foil (anode foil), and then a voltage of 130 V was applied in a 10 mass % aqueous solution of ammonium adipate to perform chemical conversion (oxidation treatment), thereby forming dielectric layers on both sides of the aluminum foil, thereby obtaining an anode foil.
Next, opposing aluminum cathode foils with cathode lead terminals welded to both sides of the anode foil were laminated via a cellulose separator, and the resultant was rolled up into a cylindrical shape to obtain a capacitor element (electrode element).

Example 1
A mixture of 400 g of the PEDOT-PSS aqueous dispersion of Production Example 2, 60.0 g of methanol, and 800 g of methyl ethyl ketone was stirred at 60° C. for 4 hours. Next, the mixture was left to stand, and the highly conductive complex composed of PEDOT-PSS precipitated in the mixture was filtered out, to which 200 g of water was added and mixed. After removing the organic solvent contained therein using an evaporator, further water was added and dispersed using a high-pressure homogenizer to obtain 240 g of an aqueous dispersion containing the highly conductive complex. The solid content and pH of the obtained highly conductive complex aqueous dispersion were measured, and found to be 1.4% by mass and pH 2.24 (25° C.), respectively.

Next, the capacitor element obtained in Production Example 3 was immersed in the aqueous dispersion of the highly conductive composite obtained above under reduced pressure, and then dried once for 30 minutes using a hot air dryer at 125° C. to form a solid electrolyte layer containing the highly conductive composite on the surface of the dielectric layer.
Next, the capacitor element on which the solid electrolyte layer was formed was loaded into an aluminum case and sealed with a sealing rubber to obtain a capacitor.

Example 2
Diethylene glycol was added to the highly conductive composite aqueous dispersion obtained in Example 1 so as to be 5% by mass. This resulted in a highly conductive composite aqueous dispersion containing 357 parts by mass of diethylene glycol per 100 parts by mass of the highly conductive composite. Aside from using this, a capacitor was obtained in the same manner as in Example 1.

Example 3
Imidazole was added to the highly conductive composite aqueous dispersion obtained in Example 1 so as to be 0.1 mass %. This resulted in a highly conductive composite aqueous dispersion (pH 2.53 (25°C)) containing 7.14 parts by mass of imidazole per 100 parts by mass of the highly conductive composite. A capacitor was obtained in the same manner as in Example 1, except for using this.

Example 4
Imidazole was added to the highly conductive composite aqueous dispersion obtained in Example 1 so as to be 0.1 mass % and diethylene glycol was added to be 5 mass %. This resulted in a highly conductive composite aqueous dispersion containing 7.14 parts by mass of imidazole and 357 parts by mass of diethylene glycol per 100 parts by mass of the highly conductive composite. A capacitor was obtained in the same manner as in Example 1, except for using this.

Example 5
Imidazole was added to the highly conductive composite aqueous dispersion obtained in Example 1 so as to be 0.2 mass %. This resulted in a highly conductive composite aqueous dispersion (pH 3.78 (25°C)) containing 14.3 parts by mass of imidazole per 100 parts by mass of the highly conductive composite. A capacitor was obtained in the same manner as in Example 1, except for using this.

Example 6
Imidazole was added to the highly conductive composite aqueous dispersion obtained in Example 1 so as to be 0.2 mass % and diethylene glycol was added to be 5 mass %. This resulted in a highly conductive composite aqueous dispersion containing 14.3 parts by mass of imidazole and 357 parts by mass of diethylene glycol per 100 parts by mass of the highly conductive composite. A capacitor was obtained in the same manner as in Example 1, except for using this.

(Comparative Example 1)
A capacitor was obtained in the same manner as in Example 1, except that the PEDOT-PSS aqueous dispersion obtained in Production Example 2 was used instead of the highly conductive complex aqueous dispersion.

(Comparative Example 2)
A capacitor was obtained in the same manner as in Example 1, except that an aqueous dispersion in which diethylene glycol was added to the PEDOT-PSS aqueous dispersion obtained in Production Example 2 so as to be 5% by mass was used instead of the highly conductive composite aqueous dispersion.

(Comparative Example 3)
Instead of the highly conductive composite aqueous dispersion, imidazole was added to the PEDOT-PSS aqueous dispersion obtained in Production Example 2 so that the amount of imidazole was 0.15% by mass. This resulted in an aqueous dispersion (pH 2.27 (25° C.)) containing 12.5 parts by mass of imidazole per 100 parts by mass of PEDOT-PSS. A capacitor was obtained in the same manner as in Example 1, except for using this aqueous dispersion.

(Comparative Example 4)
Instead of the highly conductive composite aqueous dispersion, 0.15% by mass of imidazole and 5% by mass of diethylene glycol were added to the PEDOT-PSS aqueous dispersion obtained in Production Example 2. This resulted in an aqueous dispersion containing 12.5 parts by mass of imidazole and 417 parts by mass of diethylene glycol per 100 parts by mass of PEDOT-PSS. A capacitor was obtained in the same manner as in Example 1, except for using this aqueous dispersion.

(Comparative Example 5)
Instead of the highly conductive composite aqueous dispersion, imidazole was added to the PEDOT-PSS aqueous dispersion obtained in Production Example 2 so that the amount of imidazole was 0.25% by mass. This resulted in an aqueous dispersion (pH 3.99 (25° C.)) containing 20.8 parts by mass of imidazole per 100 parts by mass of PEDOT-PSS. A capacitor was obtained in the same manner as in Example 1, except for using this aqueous dispersion.

(Comparative Example 6)
Instead of the highly conductive composite aqueous dispersion, 0.25% by mass of imidazole and 5% by mass of diethylene glycol were added to the PEDOT-PSS aqueous dispersion obtained in Production Example 2. This resulted in an aqueous dispersion containing 20.8 parts by mass of imidazole and 417 parts by mass of diethylene glycol per 100 parts by mass of PEDOT-PSS. A capacitor was obtained in the same manner as in Example 1, except for using this aqueous dispersion.

[Evaluation: Capacitance/Equivalent Series Resistance]
The capacitance (Cap.) at 120 Hz and the equivalent series resistance (ESR) at 100 kHz of each capacitor were measured using an LCR meter ZM2376 (manufactured by NF Corporation). The measurement results are shown in Table 1.

It is clear from the results in Table 1 that the ESR of the examples according to the present invention is lower than that of the comparative examples. In addition, the capacitance of the examples is generally larger than that of the comparative examples, and it is therefore suitable for applications requiring large capacitance.
The ESR of Comparative Examples 4 and 6 is relatively low, but this is largely due to the combined use of imidazole and diethylene glycol. The ESR of Examples 4 and 6, which contain the same amounts of imidazole and diethylene glycol as Comparative Examples 4 and 6 and use a highly conductive composite aqueous dispersion, is lower than the ESR of Comparative Examples 4 and 6.

10 Capacitor 11 Anode 12 Dielectric layer 13 Cathode 14 Solid electrolyte layer

Claims (10)

a separation step of obtaining a mixed solution by mixing an aqueous dispersion of a conductive polymer containing a conductive complex containing a π-conjugated conductive polymer and a polyanion with an organic solvent containing a ketone-based solvent , heating the mixed solution at 40° C. or higher and 100° C. or lower to precipitate a highly conductive complex in the mixed solution, and separating out the precipitated highly conductive complex that is dispersible only in water ;
A preparation step of obtaining an aqueous dispersion of the highly conductive composite by mixing an aqueous dispersion medium with the highly conductive composite;
a lamination step of applying the aqueous dispersion of the highly conductive composite to a dielectric layer formed by oxidizing the surface of an anode made of a porous valve metal body, and drying the applied solution to form a solid electrolyte layer on the surface of the dielectric layer;
A method for producing an anode for a capacitor, comprising: The method for producing a capacitor anode according to claim 1, wherein one or more alkaline compounds are added to the highly conductive composite aqueous dispersion. The method for producing an anode for a capacitor according to claim 1 or 2, wherein one or more compounds having two or more hydroxyl groups are added to the highly conductive composite aqueous dispersion. The method for manufacturing an anode for a capacitor according to any one of claims 1 to 3, wherein the content of the organic solvent in the mixed solution is 50 mass% or more with respect to the total mass of the mixed solution. 5. The method for producing an anode for a capacitor according to claim 1, wherein the organic solvent further comprises an alcohol-based solvent . The method for producing a capacitor anode according to claim 5, wherein the organic solvent includes a ketone-based solvent, and the ketone-based solvent includes methyl ethyl ketone. The method for producing an anode for a capacitor according to claim 5, wherein the organic solvent includes an alcohol-based solvent, and the alcohol-based solvent includes methanol. The method for manufacturing a capacitor anode according to any one of claims 1 to 4, wherein the organic solvent includes methyl ethyl ketone and methanol. The method for producing a capacitor anode according to any one of claims 1 to 8, wherein the conductive complex contains at least one of poly(3,4-ethylenedioxythiophene) and polystyrenesulfonic acid. A method for manufacturing a capacitor, comprising the steps of obtaining a capacitor anode by the manufacturing method described in any one of claims 1 to 9, and assembling a capacitor including the capacitor anode and a cathode.

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