Electrolytic capacitors

Abstract

An electrolytic capacitor which comprises a capacitor element, a liquid component, a case which contains the capacitor element and the liquid component, and a sealing member which seals the case, wherein: the capacitor element is provided with a porous sintered body that has a dielectric layer, a negative electrode foil that is arranged so as to face at least a part of the porous sintered body, and a conductive polymer that covers at least a part of the surface of the dielectric layer, while being in contact with the negative electrode foil; and the liquid component is filled into a void of the capacitor element.

Description

Technical Field

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[0001] The present invention relates to an electrolytic capacitor comprising a conductive polymer and a liquid component.

Background Art

[0002] In recent years, with the miniaturization and weight reduction of electronic devices, there has been a demand for small and high-capacity capacitors for high frequencies. As such capacitors, the development of solid electrolytic capacitors with a small equivalent series resistance (ESR) and excellent frequency characteristics has been underway. A solid electrolytic capacitor includes an anode body, a dielectric layer formed on the surface of the anode body, a solid electrolyte layer formed on the surface of the dielectric layer, and a cathode layer formed on the solid electrolyte layer. As the anode body, a porous sintered body obtained by sintering valve action metal particles such as tantalum, niobium, and titanium is used (Patent Document 1).

[0003] On the other hand, a wet electrolytic capacitor or a wet electrolytic condenser using a sintered body for the anode body (Patent Documents 2 to 4) has been proposed. Patent Document 2 describes that an electrochemically active cathode material is disposed on at least a part of the casing, and the electrochemically active cathode material can be a conductive polymer.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0005] From the perspective of reducing the leakage current of electrolytic capacitors, it is desirable to impregnate the voids in the porous sintered body with a liquid component to facilitate the self-healing of the dielectric layer. However, when conductive polymers and liquid components are used in combination, it is difficult to obtain good capacitor characteristics with conventional structures such as the one proposed in Patent Document 1. Patent Document 2 proposes attaching an electrochemically active cathode material to the cathode substrate, but it is difficult to obtain a low-resistance electrolytic capacitor with such a configuration. [Means for solving the problem]

[0006] Book One aspect of the invention Electrolytic capacitors related to It includes a capacitor element, a liquid component, a case for housing the capacitor element and the liquid component, and a sealing member for sealing the case. nothing. The capacitor element comprises a porous sintered body having a dielectric layer, a cathode foil disposed facing at least a portion of the porous sintered body, and a conductive polymer covering at least a portion of the surface of the dielectric layer and in contact with the cathode foil. Do it. Before Capacitor element inside void However, with the aforementioned liquid component Impregnated ru. [Effects of the Invention]

[0007] According to the electrolytic capacitor of this disclosure, good capacitor characteristics can be achieved. [Brief explanation of the drawing]

[0008] [Figure 1] This is a cross-sectional view of an electrolytic capacitor according to one embodiment of the present invention. [Figure 2] This is a perspective view of a porous sintered body comprising an electrolytic capacitor according to the same embodiment. [Figure 3] This is a front view of a capacitor element provided in an electrolytic capacitor according to the same embodiment. [Figure 4] This is a front view of a capacitor element according to another embodiment of the present invention. [Modes for carrying out the invention]

[0009] The electrolytic capacitor according to this embodiment includes a capacitor element, a liquid component, a case for housing the capacitor element and the liquid component, and a sealing member for sealing the case. The capacitor element comprises a porous sintered body having a dielectric layer, a cathode foil disposed so as to face at least a portion of the porous sintered body, and a conductive polymer covering at least a portion of the surface of the dielectric layer and in contact with the cathode foil. .Ko Electron element inside Voids (especially voids found in porous sintered bodies) It is a liquid component. It is impregnated.

[0010] The liquid component enhances the self-healing ability of the dielectric layer, thereby reducing leakage current. The conductive polymer contributes to reducing the equivalent series resistance (ESR). Using these components together is a necessary condition for achieving improved capacitor characteristics compared to conventional designs.

[0011] Furthermore, in the above configuration, the conductive polymer covers at least a portion of the surface of the dielectric layer and is in contact with the cathode foil, thus forming a conductive path that electrically connects the dielectric layer and the cathode foil. The formation of such a conductive path by the conductive polymer facilitates current extraction, making it possible to achieve good capacitor characteristics.

[0012] A separator may be interposed between the dielectric layer and the cathode foil. The conductive polymer, when compounded with the separator, forms a robust conductive path that electrically connects the dielectric layer and the cathode foil together with the separator. This facilitates current extraction and enables the achievement of better capacitor characteristics.

[0013] The conductive polymer includes, for example, a π-conjugated conductive polymer and a primary sulfonic acid. The primary sulfonic acid functions as a dopant for the conductive polymer. The primary sulfonic acid may also be included in the conductive polymer in an anionic state.

[0014] The dielectric layer may contain at least one oxide selected from the group consisting of tantalum, niobium, titanium, aluminum, silicon, and tungsten (hereinafter also referred to as oxide A). Such a dielectric layer has high corrosion resistance and is suitable for an electrolytic capacitor containing a liquid component. Oxide A may be the main component of the dielectric layer. Here, the main component means a component that occupies 50% by mass or more (more preferably 80% by mass or more) of the whole. That is, 50% by mass or more of the dielectric layer may be composed of oxide A. % That is, 50% by mass or more of the dielectric layer may be composed of oxide A.

[0015] It is known that the dopant contained in the conductive polymer causes a dedoping phenomenon in which it gradually escapes into the liquid component. As a result, the conductive polymer deteriorates and the ESR of the electrolytic capacitor gradually increases. To suppress the dedoping phenomenon, it is effective to include an acid component in the liquid component.

[0016] The liquid component may contain a second sulfonic acid. The second sulfonic acid in the liquid component has the effect of suppressing the dedoping phenomenon of the first sulfonic acid from the conductive polymer 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 at the site of the dedoping trace, so that the ESR is less likely to increase.

[0017] [[ID=~14]] Sulfonic acid is more stable than an acid component (for example, carboxylic acid) showing weak acidity. Further, the self-repairing ability of the dielectric layer is remarkably enhanced by sulfonic acid. Therefore, by including the second sulfonic acid in the liquid component, the ESR of the electrolytic capacitor can be kept low even at high temperatures. can be achieved.

[0018] When the liquid component contains the second sulfonic acid, generally, the corrosion of the dielectric layer may be promoted by the strongly acidic liquid component. On the other hand, by using a material excellent in corrosion resistance such as tantalum, niobium, titanium, tungsten, etc. for the dielectric layer, the corrosion of the dielectric layer can be suppressed while suppressing the dedoping phenomenon. As a result, the effect of suppressing the increase in leakage current and ESR is further improved.

[0019] It is desirable that the first sulfonic acid contained in the conductive polymer does not move significantly within the conductive polymer and is less likely to cause dedoping. On the other hand, it is desirable that the first sulfonic acid included in the liquid component does not excessively increase the viscosity of the liquid component, dissociates easily within the liquid component, and generates anions that move easily within the liquid component. For these reasons, it is desirable that the molecular weight of the second sulfonic acid is smaller than that of the first sulfonic acid. In this case, the second sulfonic acid, which has a smaller molecular weight than the first sulfonic acid, can easily penetrate the dedoping site of the first sulfonic acid, and redoping proceeds smoothly.

[0020] The cathode foil may be a metal foil. From the viewpoint of suppressing corrosiveness caused by liquid components, the cathode foil may also be an alloy foil with a valve metal as the main component. Here, the main component is the component that accounts for 50% or more (more preferably 80% or more) of the total. Examples of valve metals include tantalum, niobium, aluminum, and titanium. Examples of other elements contained in an alloy with a valve metal as the main component include silicon, vanadium, boron, and nitrogen. An alloy is formed by adding such elements to the valve metal that is the main component.

[0021] Specifically, the cathode foil is preferably aluminum foil (including alloy foil with aluminum as the main component). Aluminum foil is less expensive than other valve metals, and when used as a cathode material, it has sufficient corrosion resistance even in strongly acidic liquid components (e.g., pH 4.5 or lower, or 3.8 or lower, or 3.6 or lower). Furthermore, aluminum foil is easy to process by etching, blasting, and other surface treatments, and is softer than tantalum foil or titanium foil, making it easy to process such as winding. In addition, as a metal foil, a chromium alloy or stainless steel that can form a passivation film on its surface may be used, from the viewpoint of suppressing corrosion by liquid components.

[0022] A conductive layer may be formed on the surface of the cathode foil. The conductive layer may include, for example, at least one selected from the group consisting of titanium, nickel, and carbon. Among these, a conductive layer containing carbon is inexpensive and has excellent conductivity. This improves the ability to draw current through the cathode foil and suppresses a reduction in the overall composite capacitance including the cathode foil.

[0023] The liquid component may include an alkylene glycol compound. The alkylene glycol compound penetrates the conductive polymer and helps to arrange its alignment. Therefore, using a polyalkylene glycol compound improves the density of the conductive polymer covering at least a portion of the dielectric layer's surface. As a result, even when much of the dielectric layer's surface is covered with the conductive polymer, the voids in the porous sintered body are less likely to be blocked by the conductive polymer, and the liquid component can more easily penetrate into the voids deep within the sintered body. Therefore, a sufficient effect in suppressing leakage current can be expected.

[0024] Alkylene glycol compounds readily penetrate conductive polymers, and therefore also enhance the self-healing ability of the dielectric layer by its liquid components.

[0025] Examples of alkylene glycol compounds include ethylene glycol and propylene glycol. Examples include various alkylene glycols, polyethylene glycols such as diethylene glycol and triethylene glycol, and glycerin compounds such as glycerin and polyglycerin. The alkylene glycol compound may be, for example, 10% or more by mass and 95% or less by mass of the liquid component.

[0026] The capacitor element may have an anode terminal electrically connected to a porous sintered body. A portion of the anode terminal may be extended to the outside of the case by passing through the sealing member. This allows for the provision of an external anode terminal without compromising sealing performance.

[0027] The capacitor element may have a cathode terminal electrically connected to the cathode foil. In this case, a portion of the cathode terminal may be extended through the sealing member to the outside of the case. This allows for the provision of an external cathode terminal without compromising sealing performance. If the case is conductive, the cathode foil and the case may be electrically connected, and the case itself may be used as the external cathode terminal.

[0028] For the sealing member, for example, an insulating member with rubber elasticity may be used. This makes it easy to provide external terminals for the anode and cathode without compromising sealing performance. Furthermore, insulating members with rubber elasticity offer excellent sealing performance among sealing members and are inexpensive.

[0029] The case may be a metal container. The metal used to form the metal container is not particularly limited, but aluminum is preferred because it is inexpensive and has excellent workability. Therefore, it is preferable that the case be made of aluminum (including alloys with aluminum as the main component).

[0030] The shape of the porous sintered body is not particularly limited, but from the viewpoint of improving the reliability of sealing by the sealing member, a cylindrical shape is desirable. In this case, a bottomed cylindrical case with an opening can be used as the case. Furthermore, a cylindrical or disc-shaped insulating member that closes the opening of the case can be used as the sealing member that seals the case. In this case, the pressure applied to the sealing member from the opening end of the case is made uniform, which makes it easier to improve the reliability of sealing by the sealing member. When the liquid component is strongly acidic, improving the reliability of sealing is important.

[0031] The voids in the porous sintered body are preferably fine. On the other hand, the conductive polymer is located deep within the porous sintered body (especially Porous sintered body It is desirable that the dielectric layer also covers the surface near the center. , many Even to the deep parts of the porous sintered body (especially near the center) Liquid components Impregnation is preferable.

[0032] To achieve a more desirable state, the mass of the liquid component contained in the electrolytic capacitor may be set to 1% or more and 200% or less of the mass of the conductive polymer.

[0033] Furthermore, in order to achieve a more desirable state, the volume of the liquid component impregnated into the porous sintered body is adjusted to the volume of the voids in the porous sintered body. all It may be between 5% and 99.9% of the volume.

[0034] The constituent elements will be described in more detail below. (Porous sintered body (anode)) A porous sintered body is, for example, a porous sintered body obtained by sintering particles of a corrosion-resistant metal. The corrosion-resistant metal is preferably at least one selected from the group consisting of tantalum, niobium, titanium, and tungsten. The corrosion-resistant metal may also be an alloy. For example, an alloy containing the corrosion-resistant metal and silicon, vanadium, boron, etc., may be used. The alloy of the corrosion-resistant metal preferably contains 50 atomic percent or more of the corrosion-resistant metal.

[0035] (Dielectric layer) The dielectric layer preferably contains at least one oxide A selected from the group consisting of tantalum, niobium, titanium, aluminum, silicon, and tungsten, due to its high corrosion resistance. Oxide A is an alloy of corrosion-resistant metals. oxides It may also be a compound containing a corrosion-resistant metal and a typical element such as nitrogen as the dielectric layer. oxides You may also use [this].

[0036] The dielectric layer is formed, for example, by immersing the anode in a chemical conversion solution and anodizing the surface of the anode, or by heating the anode in an oxygen-containing atmosphere.

[0037] The porosity of the porous sintered body may be, for example, 45% or more and 75% or less. Porosity refers to the proportion of voids in the porous sintered body. In the process of forming an electrolytic capacitor, dielectric layers, conductive polymers, liquid components, etc., are formed or filled into the porous sintered body. However, the above porosity does not take into account these formed or filled materials (dielectric layers, conductive polymers, liquid components, etc.), and the areas where dielectric layers, conductive polymers, liquid components, etc. are formed or filled are also considered as voids.

[0038] (conductive polymer) The conductive polymer may include, for example, a π-conjugated conductive polymer and a dopant (such as a primary sulfonic acid). The conductive polymer may be formed by applying a solution containing the raw material monomers of the π-conjugated conductive polymer and the dopant to a dielectric layer and then chemically polymerizing or electrolytically polymerizing it in place. However, a pre-synthesized conductive polymer may be applied to the dielectric layer in order to obtain excellent dielectric strength characteristics. For example, a liquid polymer dispersion containing a conductive polymer and a primary sulfonic acid (particularly a polymeric sulfonic acid) may be impregnated into the dielectric layer, the conductive polymer may be attached to the dielectric layer so as to cover at least a portion of the dielectric layer, and then the conductive polymer may be dried.

[0039] The concentration of the conductive polymer in the polymer dispersion is preferably 0.5 to 10% by mass. Furthermore, the average particle size D50 of the conductive polymer is preferably, for example, 0.01 to 0.5 μm. Here, the average particle size D50 is the median diameter in the volume particle size distribution determined by a particle size distribution analyzer using dynamic light scattering.

[0040] <π-conjugated conductive polymer> The π-conjugated conductive polymer is preferably polypyrrole, polythiophene, or polyaniline. In this specification, polypyrrole, polythiophene, and polyaniline refer to polymers that have polypyrrole, polythiophene, or polyaniline as their basic skeleton, respectively. Therefore, derivatives of polypyrrole, polythiophene, and polyaniline may also be included. For example, polythiophene includes its derivative poly(3,4-ethylenedioxythiophene) (PEDOT). These may be used individually, in combination of two or more, or as copolymers of two or more monomers. The weight-average molecular weight of the conductive polymer is not particularly limited, but is, for example, 1,000 to 200,000.

[0041] <First sulfonic acid> As the primary sulfonic acid, aliphatic sulfonic acid, aromatic sulfonic acid, high molecular weight sulfonic acid, etc., can be used. Among these, high molecular weight sulfonic acid is most preferred because it readily undergoes re-doping of the low molecular weight secondary sulfonic acid and is less prone to de-doping.

[0042] Aliphatic sulfonic acids include methanesulfonic acid, ethanesulfonic acid, propanesulfonic acid, isopropylsulfonic acid, butanesulfonic acid, isobutylsulfonic acid, t-butylsulfonic acid, pentanesulfonic acid, isopentylsulfonic acid, hexanesulfonic acid, nonanesulfonic acid, decanesulfonic acid, undecanesulfonic acid, dodecanesulfonic acid, tridecanesulfonic acid, tetradecanesulfonic acid, n-octylsulfonic acid, cetylsulfonic acid, Examples include monovalent saturated aliphatic sulfonic acids such as 10-camphasulfonic acid; monounsaturated aliphatic sulfonic acids such as ethylenesulfonic acid and 1-propene-1-sulfonic acid; and polyvalent aliphatic sulfonic acids such as methionic acid, 1,1-ethanedisulfonic acid, 1,2-ethanedisulfonic acid, 1,1-propanedisulfonic acid, 1,3-propanedisulfonic acid, and polyvinylsulfonic acid, with aliphatic sulfonic acids having 1 to 30 carbon atoms being preferred.

[0043] Aromatic sulfonic acids include monovalent aromatic sulfonic acids such as benzenesulfonic acid, p-toluenesulfonic acid, o-toluenesulfonic acid, m-toluenesulfonic acid, o-xylene-4-sulfonic acid, m-xylene-4-sulfonic acid, 4-ethylbenzenesulfonic acid, 4-propylbenzenesulfonic acid, 4-butylbenzenesulfonic acid, 4-dodecylbenzenesulfonic acid, 4-octylbenzenesulfonic acid, 2-methyl-5-isopropylbenzenesulfonic acid, 2-naphthalenesulfonic acid, butylnaphthalenesulfonic acid, t-butylnaphthalenesulfonic acid, 2,4,5-trichlorobenzenesulfonic acid, benzylsulfonic acid, and phenylethanesulfonic acid; m-benzenedisulfonic acid, 1,4-naphthalenedisulfonic acid, 1,5-naphthalenedisulfonic acid, 1,6-naphthalenedisulfonic acid, 2,6-naphthalenedisulfonic acid, 2,7-naphthalenedisulfonic acid, and 1,3,6-naphthalentris. Polyhydric aromatic sulfonic acids such as sulfonic acid and sulfonated polystyrene; 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 Oxy-aromatic sulfonic acids such as hydroxytoluene-4-sulfonic acid, pyrocatechin-4-sulfonic acid, veratrol-4-sulfonic acid, resorcinol-4-sulfonic acid, 2-oxy-1-methoxybenzene-4-sulfonic acid, 1,2-dioxybenzene-3,5-disulfonic acid, resorcinol-4,6-disulfonic acid, hydroquinone sulfonic acid, hydroquinone-2,5-disulfonic acid, and 1,2,3-trioxybenzene-4-sulfonic acid;Sulfo-aromatic carboxylic acids such as o-sulfobenzoic acid, m-sulfobenzoic acid, p-sulfobenzoic acid, 2,4-disulfobenzoic acid, 3-sulfophthalic acid, 3,5-disulfophthalic acid, 4-sulfoisofalic 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-sulfoterephthalic acid, 5-sulfosalicylic acid, and 3-oxy-4-sulfobenzoic acid; thio-aromatic sulfonic acids such as thiophenolsulfonic acid, thioanisole-4-sulfonic acid, and thiophenetol-4-sulfonic acid; ;be Examples of aromatic sulfonic acids with other functional groups include 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, anthraquinone-1-sulfonic acid, anthraquinone-1,5-disulfonic acid, anthraquinone-1,8-disulfonic acid, anthraquinone-2,6-disulfonic acid, and 2-methylanthraquinone-1-sulfonic acid, with aromatic sulfonic acids having 6 to 30 carbon atoms being preferred.

[0044] Examples of high-molecular-weight sulfonic acids include polyvinyl sulfonic acid, polystyrene sulfonic acid, polyallyl sulfonic acid, polyacrylic sulfonic acid, polymethacrylic sulfonic acid, poly(2-acrylamido-2-methylpropane sulfonic acid), and polyisoprene sulfonic acid. These may be used individually or in combination of two or more. They may also be homopolymers or copolymers of two or more monomers. Among these, polystyrene sulfonic acid (PSS) is preferred. The weight-average molecular weight of the high-molecular-weight sulfonic acid is not particularly limited, but is preferably, for example, 1,000 to 1,000,000, as it facilitates the formation of a homogeneous solid electrolyte layer.

[0045] (Liquid component) The liquid component may consist of a solvent alone, or it may consist of a solvent and a solute. Preferably, the solute contains at least an acid component that dissociates or ionizes in the solvent. In addition to the acid component, the liquid component may also contain a basic component, a salt, etc. For example, the acid component may include sulfonic acid (de-sulfonic acid).

[0046] <Second sulfonic acid> As the secondary sulfonic acid, the sulfonic acids listed as the primary sulfonic acid can be used. Among these, aliphatic sulfonic acids having 1 to 30 carbon atoms and aromatic sulfonic acids having 6 to 30 carbon atoms are preferred. Among aliphatic sulfonic acids, monovalent saturated aliphatic sulfonic acids (e.g., hexanesulfonic acid, 10-camphorsulfonic acid) are preferred. Among aromatic sulfonic acids, 5-sulfosalicylic acid, p-toluenesulfonic acid, and 2-naphthalenesulfonic acid are preferred.

[0047] The secondary sulfonic acid may have a third acidic group other than a sulfo group. Examples of third acidic groups include hydroxyl groups and carboxyl groups. If the secondary sulfonic acid is an aromatic sulfonic acid, it may have a phenolic hydroxyl group as the third acidic group. Examples of such aromatic sulfonic acids include oxyaromatic sulfonic acids (e.g., phenol-2-sulfonic acid) and sulfoaromatic carboxylic acids (e.g., p-sulfobenzoic acid, 3-sulfophthalic acid, 5-sulfosalicylic acid).

[0048] From the perspective of suppressing the dedoping of primary sulfonic acid from conductive polymers and enhancing the self-healing ability of the dielectric layer, In the liquid component Disulfonic acid concentration teeth 、0 .01 mass% or more, 50 mass% or less That is This is preferable. The concentration of the 2-sulfonic acid contained in the liquid component is more preferably 5 to 50% by mass, more preferably 10 to 35% by mass, and particularly preferably 10 to 20% by mass.

[0049] The molecular weight of the secondary sulfonic acid is preferably smaller than that of the primary sulfonic acid. The molecular weight of the secondary sulfonic acid is, for example, 90 or more and 2000 or less, and preferably 90 or more and 500 or less.

[0050] The pH of the liquid component 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 liquid component is 4.5 or less, the degradation of the conductive polymer is further suppressed. The pH is preferably -2 or higher, and more preferably -1 or higher. The above pH is measured using a measuring device with a glass electrode for measuring the pH of an aqueous solution (for example, LAQUA manufactured by Horiba, Ltd.). pH This value is measured by Meter F-71.

[0051] From the viewpoint of enhancing the effect of stabilizing ESR, the liquid component may have a tertiary acid group other than a sulfo group and may also 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 these, the tertiary acid component is preferably an acid that exhibits weak acidity. Examples of tertiary acid components include carboxylic acids, boric acid, and phosphonic acid. Among these, carboxylic acids are preferred. The concentration of carboxylic acid contained in the electrolyte is preferably 5 to 50% by mass, and more preferably 10 to 30% by mass, in that the carboxylic acid is easily dissociated.

[0052] The carboxylic acid preferably includes an aromatic compound (aromatic dicarboxylic acid) having two or more carboxyl groups. The carboxyl groups of aromatic dicarboxylic acids are stable and do not easily cause side reactions. Therefore, they exhibit an effect of stabilizing conductive polymers over a long period of time. Among these, at least one selected from the group consisting of o-phthalic acid and pyromellitic acid is preferred as the aromatic dicarboxylic acid.

[0053] The liquid component may contain a basic component. The basic component neutralizes at least a portion of the acid component. Therefore, it is possible to increase the concentration of the acid component while suppressing corrosion of the anode by the acid component. From the viewpoint of effectively suppressing the dedoping of the primary sulfonic acid from the conductive polymer, it is preferable that the acid component is in an equivalent ratio excess to the basic component. For example, the equivalent ratio of the acid component to the basic component is preferably 1.0 to 30. Furthermore, the concentration of the basic component contained in the liquid component is preferably 0.1 to 20% by mass, and more preferably 3 to 10% by mass.

[0054] The basic 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. Of these, at least one selected from the group consisting of primary amines, secondary amines, and tertiary amines is preferred. Using primary to tertiary amines enhances the effect of long-term stabilization of the ESR. As each amine, aliphatic amines, aromatic amines, heterocyclic amines, etc., can be used. Among these, aliphatic amines with a molecular weight of 72 to 102 are preferred due to their high degree of dissociation.

[0055] Examples of primary to tertiary amines include methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, ethylenediamine, N,N-diisopropylethylamine, tetramethylethylenediamine, hexamethylenediamine, spermidine, spermine, amantadine, aniline, phenethylamine, toluidine, pyrrolidine, piperidine, piperazine, morpholine, imidazole, pyridine, pyridazine, pyrimidine, pyrazine, 4-dimethylaminopyridine, and others. These may be used individually or in combination of two or more. Among these, tertiary amines are preferred, with triethylamine and monoethyldimethylamine being particularly preferred. As for quaternary ammonium compounds, diethyldimethylammonium salts are preferred, and as for amidine compounds, cyclic amidine salts such as 1,2,3,4-tetramethylimidazolinium salt are preferred.

[0056] The solvent may include glycol compounds, sulfone compounds, lactone compounds, carbonate compounds, and monovalent or trivalent or higher alcohols. Examples of glycol compounds include alkylene glycol compounds such as ethylene glycol (EG), propylene glycol (PG), and polyethylene glycol (PEG), as well as diethylene glycol and triethylene glycol. Examples of sulfone compounds include sulfolane, dimethyl sulfoxide, and diethyl sulfoxide. Examples of lactone compounds include γ-butyrolactone and γ-valerolactone. Examples of carbonate compounds include dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), propylene carbonate (PC), and fluoroethylene carbonate (FEC). Examples of alcohols include glycerin and polyglycerin. These may be used individually or in combination.

[0057] In particular, the solvent preferably contains at least one selected from the group consisting of γ-butyrolactone, sulfolane, and ethylene glycol (hereinafter referred to as the main solvent). The proportion of the main solvent contained in the solvent is preferably 50% by mass or more, more preferably 60% by mass or more, and even more preferably 70% by mass or more.

[0058] The sealing member preferably has rubber elasticity due to the inclusion of a polymer component. Furthermore, the sealing member preferably has appropriate hardness due to the inclusion of inorganic particles. Suitable polymer components include butyl rubber, ethylene propylene rubber, isoprene rubber, silicone rubber, and fluororubber. ,nine Examples include rosulfonated polyethylene rubber. Examples of inorganic particles include talc, kaolin, and silica. From the viewpoint of suppressing deterioration by the liquid component, the ratio of polymer components in the sealing member is, for example, 60% by mass or less, and preferably 10% by mass or more. Furthermore, if the liquid component contains 2-sulfonic acid, the ratio of polymer components in the sealing member is preferably 50% by mass or less.

[0059] The present invention will be described more specifically below based on embodiments. However, the following embodiments are not intended to limit the present invention.

[0060] (Electrolytic capacitor) An electrolytic capacitor according to one embodiment of the present invention will be described with reference to Figures 1 to 4, but is not limited thereto. Figure 1 is a cross-sectional view of an electrolytic capacitor according to one embodiment of the present invention. Figure 2 is a perspective view of a porous sintered body provided in the electrolytic capacitor according to the present embodiment. Figure 3 is a front view of a capacitor element provided in the electrolytic capacitor according to the present embodiment.

[0061] The electrolytic capacitor 100 comprises a capacitor element 10, a liquid component (not shown), and an outer casing that houses them. The outer casing comprises a bottomed cylindrical case 20 with an opening, and a cylindrical or disc-shaped sealing member 30 that closes the opening of the case 20. The sealing member 30 is made of an insulating material with rubber elasticity. The end of the cylindrical case 20 near the opening is drawn inward, and this end is curled so that it is crimped to the outer surface of the sealing member 30. The case 20 is a metal container (for example, made of aluminum) and is conductive.

[0062] The capacitor element 10 comprises a cylindrical porous sintered body 11 (i.e., anode) having a dielectric layer, a cathode foil 12 positioned opposite the circumferential surface of the cylindrical porous sintered body 11, and a separator 13 interposed between the porous sintered body 11 and the cathode foil 12. As the separator 13, for example, woven fabric, nonwoven fabric, or microporous membrane can be used. For the fibers of the woven or nonwoven fabric, cellulose, polyethylene terephthalate, vinylon, polyamide, etc. can be used. For the material of the microporous membrane, for example, polyolefin can be used.

[0063] One end of the anode wire 11W is embedded in the porous sintered body 11. The other end of the anode wire 11W is planted from one end face of the cylindrical porous sintered body 11 to form the anode terminal 11T. The anode terminal 11T is pulled out through the sealing member 30 to the outside of the case 20. On the other hand, one end of the cathode lead 12L is connected to the cathode foil 12 by welding or the like. The other end of the cathode lead 12L is connected to the inner bottom surface of the metal container case 20 by welding or the like. Therefore, the case 20 is also used as the cathode terminal 20T.

[0064] Figure 4 is a perspective view of a capacitor element 10A according to another embodiment. In the capacitor element 10A, the other end of the cathode lead 12L connected to the cathode foil 12 is led out toward the same side as the anode terminal 11T. In this case, a wire-shaped cathode terminal (not shown) that penetrates the sealing member 30 may be provided separately, and a part of the cathode terminal may be exposed from the sealing member 30 so as to face the inside of the case 20, and the other end of the cathode lead 12L may be electrically connected to the exposed portion. This makes it possible to place both the anode terminal 11T and the cathode terminal on the opening side of the case 20.

[0065] Although not shown in the diagram, the conductive polymer is arranged to cover at least a portion of the surface of the dielectric layer and to be in contact with the cathode foil 12. Here, a sufficient amount of conductive polymer is also attached to the separator 13 interposed between the dielectric layer and the cathode foil 12, forming a conductive path between the dielectric layer and the cathode foil 12. In other words, the conductive polymer uses the separator 13 to form a strong conductive path that electrically connects the dielectric layer and the cathode foil 12.

[0066] Furthermore, the liquid component is impregnated into the voids of the porous sintered body 11 provided by the capacitor element 10. By controlling (a) the ratio of the mass of the liquid component to the mass of the conductive polymer contained in the case, (b) the ratio of the volume of the liquid component impregnated in the porous sintered body 11 to the volume of the voids in the porous sintered body 11, and (c) the mass of the dry conductive polymer impregnated in the porous sintered body 11 per unit volume of the voids in the porous sintered body 11, the liquid component can be impregnated deep into the porous sintered body (especially near the center).

[0067] The anode wire 11W is made of a conductive material. The material of the anode wire 11W is not particularly limited; for example, tantalum( Ta ) , niobium( Nb ) , titanium( Ti ) , tungsten( W ) Examples include aluminum and aluminum alloys. The materials constituting the porous sintered body 11 and the anode wire 11W may be the same or different. The cross-sectional shape of the anode wire 11W is not particularly limited and may include circular, a flattened circular shape (a shape consisting of parallel straight lines and two curves connecting the ends of these lines; hereinafter referred to as track shape), elliptical, rectangular, polygonal, etc. The diameter of the anode wire 11W (the major axis in the case of track shape and elliptical) is also not particularly limited, but for example, it may be 0.1 mm to 1.0 mm.

[0068] The porous sintered body 11 is manufactured, for example, by pressurizing a powder of corrosion-resistant metal particles into a cylindrical shape so that one end of the anode wire 11W is embedded in it, and then sintering it.

[0069] ≪Manufacturing Method for Electrolytic Capacitors≫ Below, an example of a manufacturing method for an electrolytic capacitor according to this embodiment will be described step by step. (i) Process of producing a porous sintered body Corrosion-resistant metal particles and an anode wire 11W are placed in a mold having a cylindrical cavity such that one end of the anode wire 11W is embedded in the corrosion-resistant metal particles. After the particles are pressure-molded, a porous sintered body is obtained by sintering in a vacuum, which is cylindrical in shape with an anode terminal 11T protruding from one end face. Binders such as camphor and polyacrylic carbonate may be mixed into the corrosion-resistant metal particles as needed.

[0070] (ii) Process of forming a dielectric layer A dielectric layer is formed on the surface of the porous sintered body 11. Specifically, the porous sintered body 11 is immersed in a chemical tank filled with an electrolytic aqueous solution (for example, an aqueous phosphoric acid solution), and the anode terminal 11T is connected to an external electrode to perform anodic oxidation, thereby forming a film of corrosion-resistant metal oxide (dielectric layer) on the surface of the porous sintered body 11. As the electrolytic aqueous solution, not only an aqueous phosphoric acid solution but also nitric acid, acetic acid, sulfuric acid, etc., can be used.

[0071] (iii) Process for forming the solid electrolyte layer Next, a conductive polymer is attached to the surface of the dielectric layer to form a solid electrolyte layer containing the conductive polymer. The conductive polymer may be produced in situ by chemical polymerization or electrolytic polymerization using a polymerization solution and attached to the dielectric layer. The polymerization solution is a solution containing monomers or oligomers, dopants (e.g., primary sulfonic acid), etc. In the case of chemical polymerization, an oxidizing agent is added to the polymerization solution. Alternatively, a pre-synthesized conductive polymer may be attached to the dielectric layer to form the solid electrolyte layer.

[0072] Monomers and oligomers that can be used include pyrrole, aniline, thiophene, and their derivatives. As dopants, for example, primary sulfonic acids can be used. As primary sulfonic acids, high molecular weight sulfonic acids, as mentioned above, are preferred because they easily suppress the dedoping phenomenon, but the material is not limited to these.

[0073] It is preferable to use a polymer dispersion as the pre-synthesized conductive polymer. The polymer dispersion comprises a liquid dispersion medium and a conductive polymer dispersed in the dispersion medium, and usually also contains a dopant. A simple and preferred method for applying the polymer dispersion to the surface of the dielectric layer is, for example, to impregnate a porous sintered body 11 having a dielectric layer with the polymer dispersion and then dry it. It is desirable that the polymer dispersion contains a primary sulfonic acid as a dopant along with the conductive polymer. For example, a polymer dispersion (PEDOT / PSS) containing PEDOT as the conductive polymer and PSS as the primary sulfonic acid is preferred.

[0074] The steps of applying the polymer dispersion to the surface of the dielectric layer and the drying step may be repeated two or more times. By performing these steps multiple times, the coverage of the conductive polymer on the dielectric layer can be increased.

[0075] (iv) Assembly process of capacitor elements A separator 13 is wrapped around the circumferential surface of a porous sintered body 11, which has a conductive polymer attached to the surface of a dielectric layer (a solid electrolyte layer is formed), at least once. Then, a cathode foil 12 is wrapped around the circumferential surface of the porous sintered body 11 via the separator 13. This yields a capacitor element 10.

[0076] (v) Conductive path formation process The capacitor element 10, which has a cathode foil 12 and a separator 13, is again coated with a conductive polymer. This fills a portion of the space between the cathode foil 12 and the dielectric layer with the conductive polymer. When using a separator 13, the conductive polymer adheres easily to the separator 13, making it easier to fill the space between the cathode foil 12 and the dielectric layer with the conductive polymer. In this case, it is also preferable to use a polymer dispersion. The steps of applying the polymer dispersion to the capacitor element 10 and the drying step may be repeated two or more times. By performing these steps multiple times, a stronger conductive path can be formed.

[0077] (vi) Impregnation process of liquid components First, the anode terminal 11T of the capacitor element with a conductive path is inserted through a through hole provided in the sealing member 30, and the cathode lead 12L is connected to a predetermined cathode terminal or case. Then, for example, a liquid component containing secondary sulfonic acid is impregnated into the capacitor element.

[0078] (vii) Assembly process of electrolytic capacitors A cylindrical electrolytic capacitor is completed by housing a capacitor element impregnated with a liquid component in a metal case having an opening, and crimping the end of the case near the opening to a sealing member 30. After that, an aging process may be performed while applying the rated voltage.

[0079] [Examples] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples.

[0080] Example 1 An electrolytic capacitor with a rated voltage of 35V and a rated capacitance of 47μF was fabricated according to the following procedure.

[0081] (i) Process of producing a porous sintered body As the valve-acting metal, tantalum metal particles with an average primary particle size D50 of approximately 0.1 μm and an average secondary particle diameter of approximately 0.2 μm were used. Using this tantalum metal powder and an anode wire made of tantalum, a porous sintered body in which a portion of the anode wire was embedded was obtained according to the method described above.

[0082] (ii) Process of forming a dielectric layer The anode body was immersed in a chemical conversion tank filled with an electrolytic phosphoric acid solution, and the anode terminal (exposed part of the anode wire) was connected to an external electrode. Then, by performing anodizing, tantalum oxide was formed on the surface of the porous sintered body. Ta 2 O 5) A uniform dielectric layer was formed. Anodizing was performed using a 0.02 mass% phosphoric acid aqueous solution at a conversion voltage of 63 V.

[0083] (iii) Process for forming the solid electrolyte layer A mixed solution was prepared by dissolving 3,4-ethylenedioxythiophene and polystyrene sulfonic acid (PSS, weight-average molecular weight 100,000), a high molecular weight sulfonic acid (primary sulfonic acid), in deionized water. Iron(III) sulfate (oxidizing agent) was added to the mixed solution while stirring, and the weight was reduced. The reaction was carried out. Subsequently, the reaction solution was dialyzed to remove unreacted monomers and oxidizing agents, yielding a polymeric dispersion containing polyethylene dioxythiophene (PEDOT / PSS) doped with approximately 5% by mass of PSS.

[0084] A porous sintered body was immersed in a polymer dispersion for 5 minutes in a reduced-pressure atmosphere (40 kPa), and then the porous sintered body was removed from the polymer dispersion. Next, the porous sintered body impregnated with the polymer dispersion was dried in a drying oven at 150°C for 20 minutes to form a solid electrolyte layer that covers at least a portion of the dielectric layer.

[0085] (iv) Assembly process of capacitor elements A carbon layer was formed by applying carbon paste (a mixture mainly composed of colloidal graphite and water) to the inner surface of a 30 μm thick aluminum foil, thereby creating a cathode foil with a carbon layer.

[0086] A capacitor element was obtained by wrapping a separator around the circumferential surface of a porous sintered body in which a solid electrolyte layer was formed on the surface of a dielectric layer, and then wrapping a cathode foil having a carbon layer around the circumferential surface of the porous sintered body via the separator.

[0087] (v) Conductive path formation process A capacitor element having cathode foil and separator is again subjected to the same high-frequency treatment as in (iii) above. The capacitor elements were immersed in the polymer dispersion for 5 minutes, and then removed from the polymer dispersion. Next, the capacitor elements were dried in a 150°C drying oven for 20 minutes, filling a portion of the space between the cathode foil and the dielectric layer with conductive polymer.

[0088] (vi) Impregnation process of liquid components The anode terminal of the capacitor element with a conductive path was inserted through a through-hole provided in a predetermined sealing member, and the cathode lead was connected to the case. Then, the following liquid components were poured into the case, and the capacitor element was immersed in the liquid components for 5 minutes in a reduced pressure atmosphere (40 kPa).

[0089] The liquid component was prepared by dissolving 5-sulfosalicylic acid (a divalent acid component) as the defulfonic acid and triethylamine as the base component in ethylene glycol (EG) as the solvent, at a total concentration of 25% by mass. The equivalent ratio of 5-sulfosalicylic acid to triethylamine was set to 2.0.

[0090] (vii) Assembly process of electrolytic capacitors A capacitor element impregnated with a liquid component was housed in an aluminum case with an opening, and the edges near the opening of the case were sealed with a butyl rubber sealing material to complete a cylindrical electrolytic capacitor (A1). Subsequently, it was aged for 90 minutes at 95°C while applying 44V.

[0091] <Rating> For capacitor A1, the capacitance, ESR (X0), and leakage current (LC) (Y0) at 35V were measured after aging. In addition, to evaluate long-term reliability, it was held at 145°C for 2000 hours while applying the rated voltage. After that, by measuring ESR(X) and LC(Y) at 35V... The increase rate of ESR (ΔESR) and the increase rate of LC (ΔLC) were examined. ΔESR is expressed as the ratio of ESR(X) after holding at 145°C to the initial value (X0) (X / X0 × 100%). ΔLC is expressed as the ratio of LC(Y) after holding at 145°C to the initial value (Y0) (Y / Y0 × 100%). The results are shown in Table 1. 。

[0092] Comparative Example 1 Electrolytic capacitor B1 was fabricated and evaluated in the same manner as in Example 1, except that the conductive path formation process was omitted.

[0093] Comparative Example 2 Electrolytic capacitor B2 was manufactured and evaluated in the same manner as in Example 1, except that, in the assembly process of the electrolytic capacitor, an aluminum case with an opening and a butyl rubber sealing member were not used, and the outer casing was formed using epoxy resin.

[0094] Comparative Example 3 Electrolytic capacitor B3 was manufactured and evaluated in the same manner as in Comparative Example 1, except that the liquid component impregnation process was omitted.

[0095] [Table 1]

[0096] From Table 1, the electrolytic capacitor A1 in Example 1 has a small initial ESR. initial LC is small, and ΔESR and ΔLC after holding at 145°C are also suppressed to a small extent. On the other hand, in the electrolytic capacitor B1 of Comparative Example 1, the initial ESR is big Furthermore, in Comparative Example 2, the electrolytic capacitor B2 loses liquid components through the resin-based outer casing, thus failing to suppress the degradation of the solid electrolyte layer, resulting in an increase in ΔESR and insufficient repair of the dielectric layer. Δ LC is increasing. Furthermore, the electrolytic capacitor B3 of Comparative Example 3 does not contain liquid components. initial The LC is large, and the degradation of the solid electrolyte layer cannot be suppressed, resulting in a significant increase in ΔESR. [Industrial applicability]

[0097] The present invention can be applied to so-called hybrid electrolytic capacitors, which comprise a conductive polymer and a liquid component (or electrolyte). [Explanation of Symbols]

[0098] 10: Capacitor element 10A: Capacitor element 11: Porous sintered body 11W: Anode wire 11T: Anode terminal 12: Cathode foil 12L: Cathode Lead 13: Separator 20 (20T): Cylindrical case (cathode terminal) 30: Sealing member 100: Electrolytic capacitor

Claims

1. It includes a capacitor element, a liquid component, a case for housing the capacitor element and the liquid component, and a sealing member for sealing the case. The aforementioned capacitor element is A porous sintered body having a dielectric layer, A cathode foil is disposed so as to face at least a portion of the porous sintered body, The device comprises a conductive polymer that is impregnated into the voids in the porous sintered body, covers at least a portion of the surface of the dielectric layer, and contacts the cathode foil to form a conductive path that electrically connects the dielectric layer and the cathode foil, The liquid component is impregnated into the void within the capacitor element. The porous sintered body has a shape that includes a circumferential surface around which the cathode foil is wrapped, The cathode foil is wrapped around the circumferential surface of the porous sintered body and faces at least a portion of the porous sintered body. A separator made of a woven fabric, nonwoven fabric, or microporous membrane is interposed between the porous body and the cathode foil. An electrolytic capacitor in which the conductive polymer is impregnated into the voids of the separator to form the conductive path that electrically connects the dielectric layer and the cathode foil.

2. The electrolytic capacitor according to claim 1, wherein the porous sintered body is cylindrical having the circumferential surface.

3. The dielectric layer comprises an oxide of at least one metal selected from the group consisting of tantalum, niobium, titanium, aluminum, silicon, and tungsten. The electrolytic capacitor according to claim 1 or 2, wherein the cathode foil is a foil mainly composed of a valve metal.

4. The electrolytic capacitor according to any one of claims 1 to 3, wherein the cathode foil further comprises a conductive layer formed on the surface of the cathode foil, comprising at least one selected from the group consisting of titanium, nickel, and carbon.

5. The electrolytic capacitor according to any one of claims 1 to 4, wherein the liquid component comprises an alkylene glycol compound.

6. The conductive polymer comprises a π-conjugated conductive polymer and a primary sulfonic acid. The electrolytic capacitor according to any one of claims 1 to 5, wherein the liquid component comprises a secondary sulfonic acid.

7. The capacitor element has an anode terminal electrically connected to the porous sintered body, The electrolytic capacitor according to any one of claims 1 to 6, wherein the anode terminal is extended through the sealing member to the outside of the case.

8. The capacitor element further has a cathode terminal electrically connected to the cathode foil, The electrolytic capacitor according to any one of claims 1 to 7, wherein the cathode terminal is extended through the sealing member to the outside of the case.

9. The electrolytic capacitor according to any one of claims 1 to 8, wherein the sealing member includes an insulating member having rubber elasticity.

10. The electrolytic capacitor according to any one of claims 1 to 9, wherein the case is a metal container.

11. A method for manufacturing an electrolytic capacitor, comprising a capacitor element, a liquid component, a case for housing the capacitor element and the liquid component, and a sealing member for sealing the case, A step of preparing a porous sintered body having a dielectric layer, The process involves winding a separator and a cathode foil onto the porous sintered body in layers. A step of manufacturing a capacitor element having a conductive path that electrically connects the dielectric layer and the cathode foil by impregnating the voids in the porous sintered body and the voids in the separator with a conductive polymer and adhering the conductive polymer to the cathode foil, The process includes impregnating the void within the capacitor element with the liquid component, In the step of preparing the porous sintered body, the porous sintered body having a shape that includes a circumferential surface around which the cathode foil is wrapped is prepared, In the process of manufacturing the capacitor element having the conductive path, (1) After impregnating the first voids in the porous sintered body with the first conductive polymer, (2) A separator made of woven fabric, nonwoven fabric or microporous film and a cathode foil are wrapped around the circumferential surface of the porous sintered body impregnated with the first conductive polymer, (3) A method for manufacturing an electrolytic capacitor, comprising impregnating the second void in the separator with a second conductive polymer and attaching the second conductive polymer to the cathode foil to produce the capacitor element having the conductive path.

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