JP7054859B2 - Electrolytic capacitor - Google Patents

Description

The present invention relates to an electrolytic capacitor having a solid electrolyte layer and an electrolytic solution.

As a small-sized, large-capacity capacitor with low ESR (equivalent series resistance), it includes an anode having a dielectric layer, a solid electrolyte layer formed to cover at least a part of the dielectric layer, and an electrolytic solution. Electrolyte capacitors are seen as promising.

For the solid electrolyte layer, a π-conjugated conductive polymer to which a dopant is added is used. Dopants are known to cause a dedoping phenomenon that gradually escapes into the electrolytic solution. This causes deterioration of the conductive polymer over time, and the ESR of the electrolytic capacitor gradually increases. Therefore, in Patent Document 1, the electrolytic solution contains an acid component.

Japanese Unexamined Patent Publication No. 2006-108650

The acid component in the electrolytic solution has an effect of suppressing the dedoping phenomenon from the conductive polymer and improving the self-repairing property of the dielectric layer. On the other hand, the acid component may corrode the dielectric layer and even the anode. When the dielectric layer is corroded, the leakage current increases.

In view of the above, one aspect of the present invention includes an anode having a dielectric layer, a solid electrolyte layer in contact with the dielectric layer, and an electrolytic solution, and the solid electrolyte layer is π-conjugated conductive. The dielectric layer comprises a polymer and a first sulfonic acid, the dielectric layer comprises at least one oxide selected from the group consisting of tantalum, niobium, titanium and tungsten, and the electrolyte is a solvent and an acid. Containing a component, said acid component relates to an electrolytic capacitor containing a second sulfonic acid.

According to the present invention, it is possible to provide an electrolytic capacitor having a small leakage current and a low ESR.

It is sectional drawing of the electrolytic capacitor which concerns on one Embodiment of this invention.

The electrolytic capacitor according to the present embodiment includes an anode having a dielectric layer, a solid electrolyte layer in contact with the dielectric layer, and an electrolytic solution. The dielectric layer contains at least one oxide selected from the group consisting of tantalum, niobium, titanium and tungsten. The solid electrolyte layer contains a π-conjugated conductive polymer (hereinafter, also simply referred to as a conductive polymer) and a first sulfonic acid. The electrolytic solution contains a solvent and an acid component, and the acid component contains a second sulfonic acid.

The first sulfonic acid functions as a dopant of the conductive polymer. The first sulfonic acid may be contained in the solid electrolyte layer in the form of an anion. On the other hand, the second sulfonic acid in the electrolytic solution has an effect of suppressing the dedoping phenomenon of the first sulfonic acid from the solid electrolyte layer and stabilizing the conductivity of the conductive polymer. Further, even when the first sulfonic acid is dedoped from the conductive polymer, the second sulfonic acid is redoped into the site of the dedoped trace, so that the ESR is unlikely to increase. The carboxylic acid in the electrolytic solution does not have such a redoping effect. Furthermore, the second sulfonic acid is more stable than the acid component showing weak acidity. In addition, the second sulfonic acid improves the self-healing performance of the dielectric layer. Therefore, by including the second sulfonic acid in the electrolytic solution, the ESR of the electrolytic capacitor can be maintained low even at a high temperature.

On the other hand, since sulfonic acid is a strong acid, it easily corrodes the dielectric layer and the anode. Therefore, the dielectric layer is impregnated with at least one oxide selected from the group consisting of tantalum, niobium, titanium and tungsten. Among the valve acting metals, tantalum, niobium, titanium and tungsten have excellent corrosion resistance. By suppressing the corrosion of the dielectric layer by using a valve acting metal having excellent corrosion resistance (hereinafter, may be referred to as a corrosion resistant metal), the above-mentioned action of the second sulfonic acid is maximized. Ru. As a result, the effect of suppressing the increase in leakage current and ESR is further improved.

It is desirable that the acid component to be dissolved in the electrolytic solution does not excessively increase the viscosity of the electrolytic solution, and easily dissociates in the electrolytic solution to generate an anion that easily moves in the solvent. On the other hand, it is desirable that the first sulfonic acid contained in the solid electrolyte layer does not move significantly inside the solid electrolyte layer, and the dedoping phenomenon is unlikely to occur. From the above, it is desirable that the molecular weight of the second sulfonic acid is smaller than the molecular weight of the first sulfonic acid. At this time, the second sulfonic acid having a molecular weight smaller than that of the first sulfonic acid easily invades the site of the dedoped trace of the first sulfonic acid, and the redoped proceeds smoothly.

(Dielectric layer)
The dielectric layer contains at least one oxide selected from the group consisting of corrosion resistant metals of tantalum (Ta), niobium (Nb), titanium (Ti) and tungsten (W). The oxide may be an oxide of an alloy of corrosion resistant metals. For example, an alloy containing a corrosion resistant metal and silicon, vanadium, boron and the like can be used. Further, a compound containing a corrosion resistant metal and a typical element such as nitrogen may be used. The corrosion-resistant metal alloy preferably contains a corrosion-resistant metal as a main component and contains 50 atomic% or more of the corrosion-resistant metal.

(Anode)
The anode body also preferably contains at least one of the above corrosion resistant metals, and may be an alloy as described above. The anode is, for example, a porous sintered body obtained by sintering particles of corrosion-resistant metal.

In this case, the dielectric layer containing the oxide of the corrosion-resistant metal is, for example, a method of immersing an anode body containing at least one of the corrosion-resistant metals in a chemical conversion solution to anodize the surface of the anode body. , The anode is formed by a method of heating in an atmosphere containing oxygen.

(First sulfonic acid)
As the first sulfonic acid, aliphatic sulfonic acid, aromatic sulfonic acid, high molecular weight sulfonic acid and the like can be used. Among them, the high molecular weight sulfonic acid is most preferable because the redoping of the low molecular weight second sulfonic acid is easy to proceed and the dedoping phenomenon is unlikely to occur.

Examples of the aliphatic sulfonic acid include methanesulfonic acid, ethanesulfonic acid, propanesulfonic acid, isopropylsulfonic acid, butanesulfonic acid, isobutylsulfonic acid, t-butylsulfonic acid, pentansulfonic acid, isopentylsulfonic acid, and hexanesulfonic acid. Monovalent saturated aliphatic sulfonic acids such as nonane sulfonic acid, decane sulfonic acid, undecane sulfonic acid, dodecane sulfonic acid, tridecane sulfonic acid, tetradecane sulfonic acid, n-octyl sulfonic acid, cetyl sulfonic acid, 10-kanfa sulfonic acid; Monovalent unsaturated aliphatic sulfonic acids such as ethylene sulfonic acid and 1-propen-1-sulfonic acid; methionic acid, 1,1-ethanedisulfonic acid, 1,2-ethanedisulfonic acid, 1,1-propanedisulfonic acid, Examples thereof include polyvalent aliphatic sulfonic acids such as 1,3-propanedisulfonic acid and polyvinylsulfonic acid, and aliphatic sulfonic acids having 1 to 30 carbon atoms are preferable.

Examples of the aromatic sulfonic acid include benzenesulfonic acid, p-toluenesulfonic acid, o-toluenesulfonic acid, m-toluenesulfonic acid, o-xylene-4-sulfonic acid, m-xylene-4-sulfonic acid, and 4-ethylbenzene. Sulfonic acid, 4-propylbenzenesulfonic acid, 4-butylbenzenesulfonic acid, 4-dodecylbenzenesulfonic acid, 4-octylbenzenesulfonic acid, 2-methyl-5-isopropylbenzenesulfonic acid, 2-naphthalenesulfonic acid, butylnaphthalene Monovalent aromatic sulfonic acids such as sulfonic acid, t-butylnaphthalene sulfonic acid, 2,4,5-trichlorobenzenesulfonic acid, benzylsulfonic acid, phenylethanesulfonic acid; m-benzenedisulfonic acid, 1,4-naphthalenedisulfonic acid Acids, 1,5-naphthalenedisulfonic acid, 1,6-naphthalenedisulfonic acid, 2,6-naphthalenedisulfonic acid, 2,7-naphthalenedisulfonic acid, 1,3,6-naphthalentrisulfonic acid, sulfonated polystyrene, etc. Polyvalent aromatic sulfonic acid; phenol-2-sulfonic acid, phenol-3-sulfonic acid, phenol-4-sulfonic acid, anisole-o-sulfonic acid, anisole-m-sulfonic acid, phenetol-o-sulfonic acid, phenetol -M-Sulfonic acid, phenol-2,4-disulfonic acid, phenol-2,4,6-trisulfonic acid, anisole-2,4-disulfonic acid, phenetol-2,5-disulfonic acid, 2-oxytoluene- 4-Sulfonic Acid, Pyrocatechin-4-Sulfonic Acid, Veratrol-4-Sulfonic Acid, Resolcin-4-Sulfonic Acid, 2-oxy-1-methoxybenzene-4-Sulfonic Acid, 1,2-Dioxybenzene-3 , 5-disulfonic acid, resorcin-4,6-disulfonic acid, hydroquinonesulfonic acid, hydroquinone-2,5-disulfonic acid, 1,2,3-trioxybenzene-4-sulfonic acid and other oxyaromatic sulfonic acids; o-sulfobenzoic acid, m-sulfobenzoic acid, p-sulfobenzoic acid, 2,4-disulfobenzoic acid, 3-sulfophthalic acid, 3,5-disulfophthalic acid, 4-sulfoisophthalic acid, 2-sulfoterephthalic acid, 2-Methyl-4-sulfobenzoic acid, 2-methyl-3,5-disulfobenzoic acid, 4-propyl-3-sulfobenzoic acid, 2,4,6-trimethyl-3-sulfobenzoic acid, 2-methyl- 5-Sulfonterephthalic acid, 5-sulfosalicylic acid, 3-oxy-4-sulfo Sulfonic aromatic carboxylic acids such as benzoic acid; thioaromatic sulfonic acids such as thiophenol sulfonic acid, thioanisole-4-sulfonic acid, thiophenetol-4-sulfonic acid; 0-benzaldehyde-o-sulfonic acid, benzaldehyde- 2,4-Disulfonic acid, acetophenone-o-sulfonic acid, acetophenone-2,4-disulfonic acid, benzophenone-o-sulfonic acid, benzophenone-3,3'-disulfonic acid, 4-aminophenol-3-sulfonic acid, Other functional groups such as anthraquinone-1-sulfonic acid, anthraquinone-1,5-disulfonic acid, anthraquinone-1,8-disulfonic acid, anthraquinone-2,6-disulfonic acid, 2-methylanthraquinone-1-sulfonic acid. Examples thereof include aromatic sulfonic acids having 6 to 30 carbon atoms, and aromatic sulfonic acids having 6 to 30 carbon atoms are preferable.

Examples of the high molecular weight sulfonic acid include polyvinyl sulfonic acid, polystyrene sulfonic acid, polyallyl sulfonic acid, polyacrylic sulfonic acid, polymethacrylic sulfonic acid, poly (2-acrylamide-2-methylpropanesulfonic acid), and polyisoprene sulfonic acid. Be done. These may be used alone or in combination of two or more. Further, these may be homopolymers or copolymers of two or more kinds of monomers. Of these, polystyrene sulfonic acid (PSS) is preferable. The weight average molecular weight of the polymer sulfonic acid is not particularly limited, but is preferably 1000 to 100,000, for example, in that a homogeneous solid electrolyte layer can be easily formed.

(Second sulfonic acid)
As the second sulfonic acid, the sulfonic acid listed as the first sulfonic acid can be used. Among them, an aliphatic sulfonic acid having 1 to 30 carbon atoms and an aromatic sulfonic acid having 6 to 30 carbon atoms are preferable. Among the aliphatic sulfonic acids, monovalent saturated aliphatic sulfonic acid (for example, hexane sulfonic acid, 10-camphor sulfonic acid) is preferable. Among the aromatic sulfonic acids, 5-sulfosalicylic acid, p-toluenesulfonic acid and 2-naphthalenesulfonic acid are preferable.

The second sulfonic acid may have a tertiary acidic group other than the sulfo group. Examples of the third acidic group include a hydroxy group and a carboxy group. When the second sulfonic acid is an aromatic sulfonic acid, it may have a phenolic hydroxy group as a tertiary acidic group. Examples of such aromatic sulfonic acid include oxyaromatic sulfonic acid (for example, phenol-2-sulfonic acid) and sulfoaromatic carboxylic acid (for example, p-sulfobenzoic acid, 3-sulfophthalic acid, 5-sulfosalicylic acid). Can be mentioned.

From the viewpoint of suppressing the dedoping of the first sulfonic acid from the solid electrolyte layer and enhancing the self-repairing performance of the dielectric layer, the second sulfonic acid is 0.01% by mass or more and 50% by mass in the electrolytic solution. It is preferably contained below. The concentration of the second sulfonic acid contained in the electrolytic solution is more preferably 5 to 50% by mass, more preferably 10 to 35% by mass, and particularly preferably 10 to 20% by mass.

It is desirable that the molecular weight of the second sulfonic acid is smaller than the molecular weight of the first sulfonic acid. The molecular weight of the second sulfonic acid is, for example, 90 or more and 2000 or less, preferably 90 or more and 500 or less.

(Electrolytic solution)
The electrolytic solution contains a solvent and an acid component.
The pH of the electrolytic solution is preferably 4.5 or less, more preferably 3.8 or less, and even more preferably 3.6 or less. When the pH of the electrolytic solution is 4.5 or less, the deterioration of the conductive polymer is further suppressed. The pH is preferably −2 or higher, more preferably -1 or higher. The pH is a value measured by a measuring device using a glass electrode for measuring the pH of the aqueous solution (for example, LAQUA pH Meter F-71 manufactured by HORIBA, Ltd.).

From the viewpoint of enhancing the effect of stabilizing ESR, the electrolytic solution may have a tertiary acid group other than the sulfo group and may contain a tertiary acid component different from the secondary sulfonic acid. The tertiary acid component is, for example, an acid other than sulfuric acid and sulfonic acid. Among them, the tertiary acid component is preferably an acid component showing weak acidity. Examples of the tertiary acid component include carboxylic acid, boric acid, phosphonic acid and the like. Of these, carboxylic acid is preferable. The concentration of the carboxylic acid contained in the electrolytic solution is preferably 5 to 50% by mass, more preferably 10 to 30% by mass, because the carboxylic acid can be easily dissociated.

The carboxylic acid preferably contains an aromatic compound (aromatic dicarboxylic acid) having two or more carboxyl groups. The carboxyl group of the aromatic dicarboxylic acid is stable and it is difficult for side reactions to proceed. Therefore, the effect of stabilizing the conductive polymer is exhibited for a long period of time. Among them, as the aromatic dicarboxylic acid, at least one selected from the group consisting of o-phthalic acid and pyromellitic acid is preferable.

The electrolytic solution may contain a basic component. The base component neutralizes at least a portion of the acid component. Therefore, it is possible to suppress the corrosion of the electrode due to the acid component while increasing the concentration of the acid component. From the viewpoint of effectively suppressing the dedoping of the first sulfonic acid from the solid electrolyte layer, the acid component is preferably in excess of the base component in an equivalent ratio. For example, the equivalent ratio of the acid component to the base component is preferably 1.0 to 30. The concentration of the base component contained in the electrolytic solution is preferably 0.1 to 20% by mass, more preferably 3 to 10% by mass.

The base component is preferably at least one selected from the group consisting of ammonia, primary amines, secondary amines, tertiary amines, quaternary ammonium compounds and amidinium compounds. Among them, at least one selected from the group consisting of primary amines, secondary amines and tertiary amines is preferable. By using the primary to tertiary amines, the effect of stabilizing ESR in the long term is enhanced. As each amine, an aliphatic amine, an aromatic amine, a heterocyclic amine and the like can be used. Of these, aliphatic amines having a molecular weight of 72 to 102 are preferable because they have a high degree of dissociation.

Examples of the primary to tertiary amines include methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, ethylenediamine, N, N-diisopropylethylamine, tetramethylethylenediamine, hexamethylenediamine, spermidin, spermin, amantazine, and aniline. Examples thereof include phenethylamine, toluidine, pyrrolidine, piperidine, piperazine, morpholine, imidazole, pyridine, pyridazine, pyrimidine, pyrazine, 4-dimethylaminopyridine and the like. These may be used alone or in combination of two or more. Of these, tertiary amines are preferable, and triethylamine and monoethyldimethylamine are particularly preferable. The quaternary ammonium compound is preferably a diethyldimethylammonium salt or the like, and the amidine compound is preferably a cyclic amidine salt such as 1,2,3,4-tetramethylimidazolinium salt.

The solvent can include a glycol compound, a sulfone compound, a lactone compound, a carbonate compound, a monohydric or trihydric or higher alcohol, and the like. As the glycol compound, ethylene glycol (EG), diethylene glycol, triethylene glycol, propylene glycol, polyethylene glycol (PEG) and the like can be used. As the sulfone compound, sulfolane, dimethyl sulfoxide, diethyl sulfoxide and the like can be used. As the lactone compound, γ-butyrolactone, γ-valerolactone and the like can be used. As the carbonate compound, dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), propylene carbonate (PC), fluoroethylene carbonate (FEC) and the like can be used. As the alcohol, for example, glycerin can be used. These may be used alone or in combination of two or more.

Among them, the solvent preferably contains at least one selected from the group consisting of γ-butyrolactone, sulfolane and ethylene glycol (hereinafter, main solvent). The ratio of the main solvent contained in the solvent is preferably 50% by mass or more, more preferably 60% by mass or more, and further preferably 70% by mass or more.

The solid electrolyte layer may be formed by applying a solution containing a monomer and a dopant composed of the first sulfonic acid to the dielectric layer and chemically polymerizing or electrolytically polymerizing the solid electrolyte layer on the spot. However, since excellent withstand voltage characteristics can be expected, it is preferable to form a solid electrolyte layer by a method of applying a conductive polymer to the dielectric layer. That is, the solid electrolyte layer is made by impregnating the dielectric layer with a polymer dispersion containing a liquid component, a conductive polymer dispersed in the liquid component, and a first sulfonic acid (particularly, a polymer sulfonic acid). It is preferably formed by forming a film covering at least a part of the body layer and then volatilizing a liquid component from the film.

The concentration of the conductive polymer contained in the polymer dispersion is preferably 0.5 to 10% by mass. Further, the average particle size D50 of the conductive polymer is preferably 0.01 to 0.5 μm, for example. Here, the average particle size D50 is the median diameter in the volume particle size distribution obtained by the particle size distribution measuring device by the dynamic light scattering method.

The π-conjugated conductive polymer is preferably polypyrrole, polythiophene, polyaniline or the like. In addition, in this specification, polypyrrole, polythiophene, polyaniline and the like mean a polymer having polypyrrole, polythiophene, polyaniline and the like as a basic skeleton, respectively. Therefore, polypyrrole, polythiophene, polyaniline and the like may also contain their respective derivatives. For example, polythiophene includes its derivative, poly (3,4-ethylenedioxythiophene) (PEDOT) and the like. These may be used alone or in combination of two or more kinds, or may be a copolymer of two or more kinds of monomers. The weight average molecular weight of the conductive polymer is not particularly limited, but is, for example, 1000 to 100,000.

Hereinafter, the present invention will be described in more detail based on the embodiments. However, the following embodiments do not limit the present invention.

<Electrolytic capacitor>
The electrolytic capacitor according to the embodiment of the present invention will be described with reference to FIG. 1, but the present invention is not limited thereto. FIG. 1 is a schematic cross-sectional view of the electrolytic capacitor 20 according to the present embodiment.

The electrolytic capacitor 20 is electrically connected to the anode portion 6 and the capacitor element 10 having the anode portion 6 and the cathode portion 7, the exterior case 11 accommodating the capacitor element 10 together with the electrolytic solution, and one from the exterior case 11. It includes an anode lead terminal 13 whose portion is exposed, and a cathode lead terminal 14 which is electrically connected to the cathode portion 7 and whose part is exposed from the outer case 11. The anode portion 6 has an anode body 1 having a dielectric layer 3 and an anode wire 2. The cathode portion 7 has a solid electrolyte layer 4 formed on the dielectric layer 3 and a cathode layer 5 covering the surface of the solid electrolyte layer 4.

<Capacitor element>
The capacitor element 10 according to this embodiment will be described in detail.
(Anode part)
The anode portion 6 has an anode body 1 and an anode wire 2 extending from one surface of the anode body 1 and electrically connected to the anode lead terminal 13. A dielectric layer 3 is formed on the surface of the anode body 1. The dielectric layer 3 contains an oxide of a corrosion resistant metal.

The anode wire 2 is made of a conductive material. The material of the anode wire 2 is not particularly limited, and examples thereof include Ta, Nb, Ti, W, copper, aluminum, and an aluminum alloy. The materials constituting the anode body 1 and the anode wire 2 may be of the same type or different types. The anode wire 2 has a first portion 2a embedded in the anode body 1 from one surface of the anode body 1 and a second portion 2b extending from the one surface of the anode body 1. The cross-sectional shape of the anode wire 2 is not particularly limited, and is a circle or a shape like a crushed circle (a shape consisting of straight lines parallel to each other and two curves connecting the ends of these straight lines. Hereinafter referred to as a track shape. ), Oval, rectangular, polygon, etc. The diameter of the anode wire 2 (major diameter in the case of a track type and an elliptical shape) is also not particularly limited, but is, for example, 0.1 mm to 1.0 mm.

The anode portion 6 is manufactured, for example, by embedding the first portion 2a in the powder of corrosion-resistant metal particles, pressure-molding it into a rectangular parallelepiped shape, and sintering it. As a result, the second portion 2b of the anode wire 2 is pulled out from one surface of the anode body 1 so as to be planted. The second portion 2b is joined to the anode lead terminal 13 by welding or the like, and the anode wire 2 and the anode lead terminal 13 are electrically connected to each other. The welding method is not particularly limited, and examples thereof include resistance welding and laser welding.

(Cathode)
The cathode portion 7 has a solid electrolyte layer 4 formed on the dielectric layer 3 and a cathode layer 5 covering the solid electrolyte layer 4. A solid electrolyte layer is formed by adhering a π-conjugated conductive polymer and a first sulfonic acid to at least a part of the surface of the dielectric layer 3. The solid electrolyte layer 4 may be formed so as to cover at least a part of the dielectric layer 3.

The cathode layer 5 has, for example, a carbon layer formed so as to cover the solid electrolyte layer 4 and a metal paste layer formed on the surface of the carbon layer. The carbon layer contains a conductive carbon material such as graphite and a resin. The metal paste layer contains, for example, metal particles (eg, silver) and a resin. The configuration of the cathode layer 5 is not limited to this configuration. The cathode layer 5 may be configured as long as it has a current collecting function.

<Anode lead terminal>
The anode lead terminal 13 is electrically connected to the anode body 1 via the second portion 2b of the anode wire 2. The anode lead terminal 13 may be bonded to the second portion 2b of the anode wire 2 by a conductive adhesive or solder, or may be bonded to the anode wire 2 by resistance welding or laser welding.

The material of the anode lead terminal 13 is not particularly limited as long as it is electrochemically and chemically stable and has conductivity, and may be metal or non-metal. Among them, when the anode lead terminal 13 comes into contact with the electrolytic solution, the material of the anode lead terminal 13 is preferably a metal having corrosion resistance to the electrolytic solution. Alternatively, an insulating coating layer (for example, an oxide film or an insulating resin layer) may be formed on the surface of the anode lead terminal 13 in contact with the electrolytic solution. The shape is not particularly limited.

<Cathode lead terminal>
The cathode lead terminal 14 is electrically connected to the cathode portion 7. One end of the cathode lead terminal 14 is joined to the cathode layer 5 via, for example, a conductive adhesive 8. The other end of the cathode lead terminal 14 is led out from one surface of the outer case 11.

The material of the cathode lead terminal 14 is also not particularly limited as long as it is electrochemically and chemically stable and has conductivity, and may be metal or non-metal. Among them, when the cathode lead terminal 14 comes into contact with the electrolytic solution, the material of the cathode lead terminal 14 is preferably a metal having corrosion resistance to the electrolytic solution. Alternatively, an insulating coating layer (for example, an oxide film or an insulating resin layer) may be formed on the surface of the cathode lead terminal 14 which is in contact with the electrolytic solution and is not coated with the conductive adhesive 8. ..

<Exterior case>
The outer case 11 houses the capacitor element 10 and the electrolytic solution. As the material of the outer case 11, a metal such as aluminum, stainless steel, copper, iron, or brass, an alloy thereof, or a resin material can be used. An insulating sealing member 12 is arranged between the outer case 11 and the second portion 2b of the anode wire 2 to seal the outer case 11. Similarly, a sealing member (not shown) may be arranged between the outer case 11 and the cathode lead terminal 14.

When a metal component is contained in the outer case 11 or the portion of each lead terminal that comes into contact with the electrolytic solution, it is preferable to adjust the pH of the electrolytic solution to a region where the metal component does not dissolve. For example, when the metal component contained in the outer case 11 and each lead terminal is aluminum, it is preferable to adjust the pH of the electrolytic solution to 2 or more.

≪Manufacturing method of electrolytic capacitors≫
Hereinafter, an example of a method for manufacturing an electrolytic capacitor according to this embodiment will be described for each process.
(I) Step of manufacturing the anode portion The corrosion-resistant metal particles and the anode wire 2 were placed in a mold so that the first portion 2a of the anode wire 2 was embedded in the corrosion-resistant metal particles, and molded by pressure. Later, by sintering in vacuum, an anode portion in which a part of the anode wire 2 is planted is produced. The pressure during molding is not particularly limited. If necessary, the particles of the corrosion-resistant metal may be mixed with a binder such as polyacrylic carbonate.

(Ii) Step of forming the dielectric layer The dielectric layer 3 is formed on the surface of the anode body 1. Specifically, the anode 1 is immersed in a chemical bath filled with an electrolytic aqueous solution (for example, a phosphoric acid aqueous solution), and the second portion 2b of the anode wire 2 is connected to the anode body of the chemical tank for anodizing. By performing the above, the dielectric layer 3 made of an oxide film of a corrosion-resistant metal can be formed on the surface of the anode body 1. The electrolytic aqueous solution is not limited to the phosphoric acid aqueous solution, and nitric acid, acetic acid, sulfuric acid and the like can be used.

(Iii) Forming Step of Solid Electrolyte Layer Next, a solid electrolyte layer 4 containing a π-conjugated conductive polymer and a first sulfonic acid is formed on the surface of the dielectric layer 3. At this time, the solid electrolyte layer 4 may be formed by adhering the conductive polymer produced by chemical polymerization or electrolytic polymerization to the dielectric layer 3 on the spot using a polymerization solution. The polymerization liquid is a solution containing a monomer or an oligomer, a first sulfonic acid as a dopant, and the like. In the case of chemical polymerization, an oxidizing agent is added to the polymerization solution. Further, the conductive polymer synthesized in advance may be adhered to the dielectric layer 3 to form the solid electrolyte layer 4.

As the monomer and oligomer, pyrrole, aniline, thiophene, derivatives thereof and the like are used. As the dopant, the first sulfonic acid is used. As the first sulfonic acid, the above-mentioned high molecular weight sulfonic acid is preferable, but is not limited to this, because it is easy to suppress the dedoping phenomenon.

As the conductive polymer synthesized in advance, it is preferable to use a polymer dispersion. The polymer dispersion contains a liquid component and a conductive polymer dispersed in the liquid component, and usually also contains a dopant. As a method of applying the polymer dispersion to the surface of the dielectric layer 3, for example, a method of impregnating the polymer dispersion with the anode 1 and drying the polymer dispersion is simple and preferable. It is desirable that the polymer dispersion contains the first sulfonic acid as a dopant together with the conductive polymer. For example, a polymer dispersion (PEDOT / PSS) containing PEDOT as the conductive polymer and PSS as the first sulfonic acid is preferable.

The step of applying the polymer dispersion to the surface of the dielectric layer 3 and the step of drying the anode 1 may be repeated twice or more. By performing these steps a plurality of times, the coverage of the solid electrolyte layer 4 with respect to the dielectric layer 3 can be increased.

(Iv) Step of Forming Cathode Layer By sequentially applying carbon paste and silver paste to the surface of the solid electrolyte layer 4, the cathode layer 5 composed of the carbon layer and the silver paste layer can be formed. As a result, the capacitor element 10 is obtained. The configuration of the cathode layer 5 is not limited to this, and any configuration may be used as long as it has a current collecting function. Further, depending on the current collecting structure of the cathode, the cathode layer 5 may not be provided.

(V) Step of impregnating the solid electrolyte layer with the electrolytic solution The solid electrolyte layer 4 is impregnated with the electrolytic solution. The method of impregnating the solid electrolyte layer 4 with the electrolytic solution is not particularly limited. When the solid electrolyte layer 4 is impregnated with the electrolytic solution after the cathode layer 5 is formed, it is preferable to form the cathode layer 5 so that the solid electrolyte layer 4 is partially exposed (not shown in FIG. 1).

(Vi) Bonding step of anode lead terminal One end of the anode wire 2 to be planted from the anode body 1 is joined to the anode lead terminal 13 by laser welding, resistance welding, or the like.

(Vii) Bonding Step of Cathode Lead Terminal The cathode lead terminal 14 is joined to the cathode layer 5 via the conductive adhesive material 8.

(Viii) Capacitor element sealing step The capacitor element 10 impregnated with the electrolytic solution and bonded to each lead terminal is housed in the outer case 11. At this time, a part of the anode lead terminal 13 and the cathode lead terminal 14 is led out from the outer case 11, respectively. After that, the aging process may be performed while applying the rated voltage.

In the above embodiment, an electrolytic capacitor using a sintered body containing a corrosion resistant metal as an anode has been described, but the scope of application of the present invention is not limited to the above, and includes other electrolytic capacitors, for example, a corrosion resistant metal. It can also be applied to a wound type electrolytic capacitor using a metal foil as an anode and a laminated type electrolytic capacitor using a metal plate containing a corrosion resistant metal as an anode.

[Example]
Hereinafter, the present invention will be described in more detail based on Examples, but the present invention is not limited to Examples.

<< Example 1 >>
An electrolytic capacitor with a rated voltage of 35 V and a rated capacitance of 30 μF was manufactured in the following manner.

(Preparation of anode part)
As the valve acting metal, tantalum metal particles having an average particle size D50 of the primary particles of about 0.1 μm and an average particle size of the secondary particles of about 0.2 μm were used. Using this anode wire composed of tantalum metal powder and tantalum, an anode body in which a part (first part) of the anode wire was embedded was obtained according to the above method.

(Formation of dielectric layer)
A part of the second part of the anode and the anode wire was immersed in the chemical bath filled with the phosphoric acid aqueous solution which is the electrolytic aqueous solution, and the other part of the second part was connected to the anode body of the chemical tank. Then, by anodizing, tantalum pentoxide (Ta ₂ O ₅ ) is applied to the surface of the anode (the surface of the porous sintered body including the inner wall surface of the hole) and the surface of a part of the second part of the anode wire. A uniform dielectric layer was formed. Anodization was carried out using a 0.02 mass% phosphoric acid aqueous solution at a chemical conversion voltage of 60 V.

(Preparation of polymer dispersion)
A mixed solution was prepared by dissolving 3,4-ethylenedioxythiophene and polystyrene sulfonic acid (PSS, weight average molecular weight 100,000) which is a high molecular weight sulfonic acid (first sulfonic acid) in ion-exchanged water. Iron (III) sulfate (oxidizing agent) was added while stirring the mixed solution, and the polymerization reaction was carried out. Then, the reaction solution was dialyzed to remove unreacted monomers and oxidizing agents to obtain a polymer dispersion containing polyethylene dioxythiophene (PEDOT / PSS) doped with about 5% by mass of PSS.

(Formation of solid electrolyte layer)
The anode portion was immersed in the polymer dispersion for 5 minutes in a reduced pressure atmosphere (40 kPa), and then the anode portion was pulled up from the polymer dispersion. Next, the anode portion impregnated with the polymer dispersion was dried in a drying oven at 150 ° C. for 20 minutes to form a solid electrolyte layer covering at least a part of the dielectric layer.

(Formation of cathode layer)
A carbon layer was formed by applying a carbon paste to the surface of the solid electrolyte layer. Next, a silver paste layer was formed by applying a silver paste to the surface of the carbon layer. In this way, a cathode layer composed of a carbon layer and a silver paste layer was formed to obtain a capacitor element. At this time, a carbon layer and a silver paste layer were provided so that a part of the surface of the solid electrolyte layer was exposed from the cathode layer.

(Immersion of electrolyte)
Ethylene glycol (EG) was prepared as a solvent. An electrolytic solution was prepared by dissolving 5-sulfosalicylic acid (divalent acid component) as a second sulfonic acid in EG and triethylamine as a base component at a total concentration of 25% by mass. The equivalent ratio of 5-sulfosalicylic acid to triethylamine was 2.0. The capacitor element was immersed in the electrolytic solution for 5 minutes in a reduced pressure atmosphere (40 kPa).

(Seal of capacitor element)
A capacitor element impregnated with an electrolytic solution was housed in an outer case and sealed to complete an electrolytic capacitor (A1) as shown in FIG. Then, while applying the rated voltage, aging was performed at 95 ° C. for 90 minutes.

<Evaluation>
For the capacitor A1, the capacitance after aging, ESR, and leakage current (LC) at 35 V were measured. The results are shown in Table 1. Table 1 shows the relative evaluation results when the result of Comparative Example 1 is 1.

<< Examples 2 to 5 >>
Electrolytic capacitors A2 to A5 were prepared in the same manner as in Example 1 except that the equivalent ratio of the acid component and the base component was changed without changing the concentration of the acid component and the pH was set as shown in Table 1. Evaluated in the same way. The results are shown in Table 1.

<< Comparative Example 1 >>
An electrolytic capacitor B1 was prepared and evaluated in the same manner as in Example 1 except that phthalic acid was used instead of 5-sulfosalicylic acid without changing the equivalent ratio of the acid component and the base component.

<< Examples 6 to 8 >>
Example 1 and the same except that the pH was adjusted as shown in Table 2 by changing the concentration of the second sulfonic acid and the concentration of the base component in the electrolytic solution without changing the equivalent ratio of the second sulfonic acid to the base component. In the same manner, electrolytic capacitors A6 to A8 were prepared and evaluated in the same manner. The results are shown in Table 2. Table 2 also shows the evaluation results of the electrolytic capacitor A3 for convenience.

<< Examples 9 to 13 >>
The pH was set as shown in Table 3 by changing the equivalent ratio of the acid component to the base component without changing the concentration of the acid component, and the acid component shown in Table 3 was used instead of 5-sulfosalicylic acid. Electrolytic capacitors A9 to A13 were produced in the same manner as in Example 1 and evaluated in the same manner. The results are shown in Table 3. However, in the electrolytic capacitor A12, amidine was used as the base component instead of triethylamine.

The present invention can be applied to a so-called hybrid type electrolytic capacitor including a solid electrolyte layer covering at least a part of the dielectric layer and an electrolytic solution.

20: Electrolytic capacitor 10: Condenser element 1: Anode body 2: Anode wire 2a: First part 2b: Second part 3: Dielectric layer 4: Solid electrolyte layer 5: Cathode layer 6: Anode part 7: Cathode part 8: Conductive Sexual adhesive 11: Exterior case 12: Sealing member 13: Anode lead terminal 14: Cathode lead terminal

Claims (17)

An anode having a dielectric layer, a solid electrolyte layer in contact with the dielectric layer, and an electrolytic solution are provided.
The solid electrolyte layer contains a π-conjugated conductive polymer and a first sulfonic acid.
The dielectric layer contains at least one oxide selected from the group consisting of tantalum, niobium, titanium and tungsten.
The electrolytic solution contains a solvent and an acid component, and contains a solvent and an acid component.
The acid component contains a second sulfonic acid.
The acid component is an electrolytic capacitor having a tertiary acid group other than the sulfo group and containing a tertiary acid component different from the second sulfonic acid . The electrolytic capacitor according to claim 1, wherein the tertiary acid component contains a carboxylic acid. The electrolytic capacitor according to claim 1 or 2 , wherein the anode contains at least one metal selected from the group consisting of tantalum, niobium, titanium and tungsten. The electrolytic capacitor according to claim 3 , wherein the anode is a sintered body of the metal particles. The electrolytic capacitor according to any one of claims 1 to 4 , wherein the second sulfonic acid is contained in the electrolytic solution at a concentration of 0.01% by mass or more and 50% by mass or less. The electrolytic capacitor according to any one of claims 1 to 5 , wherein the second sulfonic acid has a molecular weight of 90 or more and 500 or less. The electrolysis according to any one of claims 1 to 6 , wherein the second sulfonic acid is at least one selected from the group consisting of camphasulfonic acid, sulfosalicylic acid, p-toluenesulfonic acid and naphthalenesulfonic acid. Condenser. The electrolytic capacitor according to any one of claims 1 to 7 , wherein the pH of the electrolytic solution is 4.5 or less. The electrolytic capacitor according to any one of claims 1 to 8 , wherein the second sulfonic acid has a tertiary acidic group other than the sulfo group. The electrolytic capacitor according to any one of claims 1 to 9 , wherein the second sulfonic acid has a smaller molecular weight than the first sulfonic acid. The electrolytic capacitor according to any one of claims 1 to 10 , wherein the electrolytic solution contains a base component and contains the acid component in an equivalent ratio to an excess of the base component. The electrolysis according to claim 11 , wherein the base component is at least one selected from the group consisting of ammonia, a primary amine, a secondary amine, a tertiary amine, a quaternary ammonium compound and an amidinium compound. Condenser. The electrolytic capacitor according to any one of claims 1 to 12 , wherein the first sulfonic acid contains polystyrene sulfonic acid. The electrolytic capacitor according to any one of claims 1 to 13 , wherein the second sulfonic acid contains an aromatic sulfonic acid. The electrolytic capacitor according to claim 14 , wherein the aromatic sulfonic acid has a hydroxy group or a carboxy group in addition to a sulfo group. The electrolytic capacitor according to any one of claims 1 to 15 , wherein the solvent contains at least one selected from the group consisting of γ-butyrolactone, sulfolane and ethylene glycol. The electrolytic capacitor according to any one of claims 1 to 16 , wherein the π-conjugated conductive polymer is at least one of polythiophene and a derivative thereof.

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