Electrolytic capacitor and manufacturing method

Abstract

To prevent a change in the characteristics of an electrolytic capacitor by preventing dissolution of an oxide film of a cathode body.SOLUTION: An electrolytic capacitor comprises: an anode body in which a dielectric film is formed on a foil surface including valve action metal as a base material; a cathode body that faces the anode body; and an electrolytic solution that is interposed between the anode body and the cathode body. The cathode body has a foil that includes the valve action metal as a base material, an oxide film that is formed on the surface of the foil, and a carbon layer that is laminated on the oxide film and contains carbon material. The electrolytic solution includes a solvent, a solute, and inorganic oxide colloidal particles.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an electrolytic capacitor and a manufacturing method thereof. [Background technology]

[0002] Electrolytic capacitors have valve metals such as tantalum or aluminum as anode and cathode bodies. The anode body is enlarged by shaping the valve metal into a sintered body or etched foil, and a dielectric film is formed on the enlarged surface. An electrolyte is interposed between the anode and cathode bodies. The electrolyte is in close contact with the uneven surface of the anode body and functions as a true cathode.

[0003] The electrolyte is present between the dielectric film of the anode body and the cathode body. Therefore, the electrical conductivity and temperature characteristics of the electrolyte have a significant effect on the electrical characteristics of the electrolytic capacitor, such as impedance, dielectric loss (tanδ), and equivalent series resistance (ESR). In addition, the electrolyte has chemical conversion properties that repair deteriorated or damaged parts of the dielectric film formed on the anode body, which affects the leakage current (LC) and life characteristics of the electrolytic capacitor.

[0004] Therefore, an electrolyte with at least high electrical conductivity is appropriate for electrolytic capacitors, but increasing the electrical conductivity of the electrolyte tends to reduce the spark voltage, which may impair the voltage resistance characteristics of the electrolytic capacitor.From a safety standpoint, it is desirable for the electrolytic capacitor to have a high voltage resistance so as not to cause a short circuit or fire, even under harsh conditions such as when an abnormal voltage exceeding the rated voltage is applied to the electrolytic capacitor.

[0005] Therefore, in order to improve the withstand voltage while maintaining high electrical conductivity, attempts have been made to add various inorganic oxide colloidal particles to the electrolyte (see Patent Document 1). The inorganic oxide colloidal particles are typically silica colloidal particles, but other materials such as zirconia, titania, aluminosilicate, and aluminosilicate-coated silica have also been proposed.

[0006] However, in an electrolyte solution containing inorganic oxide colloidal particles, precipitation or aggregation of the inorganic oxide colloidal particles occurs over time, which may cause gelation of the electrolyte solution. Therefore, inorganic oxide colloidal particles whose surfaces are modified with an organic substance have been proposed in order to suppress gelation or precipitation of the inorganic oxide colloidal particles (see, for example, Patent Document 2). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 1-232713 [Patent Document 2] Japanese Patent Application Publication No. 10-241999 Summary of the Invention [Problem to be solved by the invention]

[0008] Electrolytic capacitors may contain moisture. In addition to being intentionally contained in the electrolyte, moisture may also be mixed in during the manufacturing process of electrolytic capacitors. The valve metal of the cathode body deteriorates due to hydration reactions. Deterioration of the valve metal of the cathode body causes, for example, a decrease in the capacitance of the electrolytic capacitor.

[0009] Therefore, it has been known to form an oxide film on the surface of the cathode foil to protect the valve metal, which is the base material of the foil, from moisture. However, it has been confirmed that when the electrolyte contains inorganic oxide colloidal particles surface-modified with an organic substance, the oxide film formed on the cathode foil dissolves. When the oxide film on the cathode body dissolves, the valve metal is exposed, and deterioration due to hydration is inevitable.

[0010] The present invention has been proposed to solve the above problems, and its object is to suppress changes in the characteristics of an electrolytic capacitor by suppressing dissolution of the oxide film on the cathode body. [Means for solving the problem]

[0011] In order to achieve the above object, the electrolytic capacitor according to the present embodiment includes an anode body having a foil based on a valve metal and a dielectric film formed on the surface thereof, a cathode body facing the anode body, and an electrolyte interposed between the anode body and the cathode body, wherein the cathode body has a foil based on a valve metal, an oxide film formed on the surface of the foil, and a carbon layer laminated on the oxide film and containing a carbon material, and the electrolyte includes a solvent, a solute, and inorganic oxide colloidal particles.

[0012] The inorganic oxide colloidal particles may be silica.

[0013] The inorganic oxide colloidal particles may be surface-modified with an organic substance.

[0014] The inorganic oxide colloidal particles surface-modified with an organic substance may be contained in an amount of 4.5 wt % to 17 wt % of the total amount of the electrolyte solution.

[0015] The capacitor may further include a capacitor element having the anode body, the cathode body, and the electrolytic solution, and an exterior that seals the capacitor element, wherein the exterior contains 2 wt % or more and 9.5 wt % or less of water with respect to the total amount of the electrolytic solution.

[0016] The solute may be contained in an amount of 5 wt % to 25 wt % of the total amount of the electrolyte.

[0017] The capacitor may further include a capacitor element having the anode body, the cathode body, and the electrolyte solution, and an exterior that seals the capacitor element, wherein the inorganic oxide colloidal particles are surface-modified with an organic substance having an epoxy group, a ureido group, or a methacryl group, the carbon material has a lactone group, a carboxyl anhydride group, or both on its surface, the inorganic oxide colloidal particles surface-modified with the organic substance account for 4.5 wt % to 17 wt % of the total amount of the electrolyte solution, and the exterior contains water in an amount of 2 wt % to 9.5 wt % of the total amount of the electrolyte solution.

[0018] In order to achieve the above object, the method for manufacturing an electrolytic capacitor according to the present embodiment includes an anode body-forming step of forming a dielectric film on a foil surface of a valve metal substrate; a cathode body-forming step of laminating a carbon layer containing a carbon material on a valve metal substrate having an oxide film on its surface; an element-forming step of stacking the anode body and the cathode body with a separator interposed therebetween; and an electrolyte solution impregnation step of impregnating the element with an electrolyte solution, the electrolyte solution containing a solvent, a solute, and inorganic oxide colloidal particles. [Effects of the Invention]

[0019] According to the present invention, the dissolution of the oxide film on the cathode body is suppressed, and therefore, changes in the characteristics of the electrolytic capacitor can be suppressed. [Brief explanation of the drawings]

[0020] [Figure 1] 1 is a graph showing the relationship between the content of inorganic oxide colloidal particles surface-modified with an organic substance and ΔCap. [Figure 2] 1 is a graph showing the relationship between the moisture content and ΔCap. DETAILED DESCRIPTION OF THE INVENTION

[0021] DETAILED DESCRIPTION OF THE INVENTION An electrolytic capacitor and a manufacturing method thereof according to an embodiment of the present invention will be described below. However, the present invention is not limited to the following embodiment.

[0022] (Overall composition) An electrolytic capacitor is a passive element that obtains capacitance through the dielectric polarization of a dielectric film and stores and discharges electric charge. An electrolytic capacitor includes an anode body and a cathode body, each with a dielectric film formed on its surface. The anode body and the cathode body are arranged opposite each other. An electrolyte is filled between the dielectric film of the anode body and the cathode body. The electrolyte is in close contact with the dielectric film, forming a true cathode. The anode body and the cathode body are arranged opposite each other with a separator interposed between them. The separator prevents shorting between the anode body and the cathode body and retains the electrolyte.

[0023] (electrode body) The anode and cathode are foils made of valve metals such as aluminum, tantalum, niobium, niobium oxide, titanium, hafnium, zirconium, zinc, tungsten, bismuth, and antimony. The purity of the anode is preferably about 99.9% or higher, and that of the cathode is preferably about 99% or higher, but impurities such as silicon, iron, copper, magnesium, and zinc may be present.

[0024] The anode and cathode bodies have their surfaces enlarged as formed foils made from valve metal powder, sintered foils made by sintering formed foils, etched foils made from rolled foils that have been etched, or sintered or vapor-deposited foils made by forming valve metal powder on the surface of rolled foil and then sintering or vapor-depositing the powder. That is, the surface-enlarged layer is made up of tunnel-like pits, spongy pits, or voids between densely packed powder particles.

[0025] The tunnel-shaped etching pits are holes dug in the foil thickness direction. These tunnel-shaped etching pits are typically formed by passing a direct current in an acidic aqueous solution containing halogen ions, such as hydrochloric acid. The tunnel-shaped etching pits are further expanded by passing a direct current in an acidic aqueous solution, such as nitric acid. The spongy etching pits turn the surface-expanding layer into a sponge-like layer with fine, interconnected voids. These spongy etching pits are formed by passing an alternating current in an acidic aqueous solution containing halogen ions, such as hydrochloric acid.

[0026] Sintered foils are produced by obtaining a powder of a valve action metal of the same or different type as the foil body by a milling method, atomization method, melt spinning method, rotating disk method, rotating electrode method, etc., forming a paste with a binder or solvent, applying it to a foil body, drying it, and heating and sintering it in a vacuum or reducing atmosphere, etc. The atomization method may be any of water atomization method, gas atomization method, and water gas atomization method. Vapor-deposited foils are produced, for example, by resistance heating vapor deposition method or electron beam heating vapor deposition method. This vapor-deposited foil is produced by heating and vaporizing a valve action metal of the same or different type as the foil body by resistance heat or electron beam energy, and depositing the vapor of valve action metal particles on the surface of the foil body to form a film.

[0027] The dielectric film is typically an oxide film formed on the surface of the anode body. If the anode body is made of aluminum, it is an aluminum oxide layer formed by oxidizing the porous structure. An oxide film is also formed on the foil surface of the cathode body. The oxide film on the cathode body is formed intentionally or naturally. This dielectric film and oxide film are formed by chemical conversion treatment in which a voltage is applied in a solution free of halogen ions, such as an acid such as ammonium borate, ammonium phosphate, or ammonium adipate, or an aqueous solution of such an acid. The oxide film intentionally formed on the foil surface of the cathode body is preferably thin, approximately 1 to 10 Vfs. The natural oxide film is formed by the cathode foil reacting with oxygen in the air.

[0028] The cathode body has a carbon layer in addition to the foil body. The carbon layer is laminated on the cathode foil and is in close contact with the surface-expanding layer, covering the oxide film on the surface of the cathode foil. The carbon layer is laminated on one or both sides of the cathode foil and is located as the outermost layer of the cathode body. The carbon layer contains a carbon material. In addition to the carbon material, the carbon layer may also contain a metal such as titanium, or a metal nitride or metal carbide such as titanium nitride, titanium carbide, or aluminum carbide. Multiple carbon layers may be laminated.

[0029] The carbon material may be fibrous carbon, carbon powder, or a mixture thereof. It may also be fibrous carbon or carbon powder that has been subjected to a porous treatment, such as an activation treatment or an opening treatment to form pores. Examples of carbon powder include activated carbon derived from natural plant tissues such as coconut husks, synthetic resins such as phenols, and fossil fuels such as coal, coke, and pitch; carbon blacks such as ketjen black, acetylene black, and channel black; carbon nanohorns; amorphous carbon; natural graphite; artificial graphite; graphitized ketjen black; and mesoporous carbon. Examples of fibrous carbon include carbon nanotubes and carbon nanofibers. Carbon nanotubes may be single-walled carbon nanotubes, which have a single graphene sheet, or multi-walled carbon nanotubes (MWCNTs), which have two or more graphene sheets coaxially rolled together to form multiple tube walls.

[0030] Methods for forming a carbon layer on a cathode foil include vacuum deposition, sputtering, ion plating, CVD, coating, electrolytic plating, and electroless plating. In the coating method, a carbon material is dispersed in a dispersion solvent to prepare a slurry, which is then coated on the cathode foil by a slurry casting method, doctor blade method, spray atomization method, or the like, and dried. In the deposition method, the carbon material is evaporated by heating with electrical current in a vacuum, or by irradiating the carbon material with an electron beam in a vacuum, forming a film of the carbon material on the cathode foil. In the sputtering method, a target made of a carbon material and the cathode foil are placed in a vacuum chamber, and an inert gas is introduced into the vacuum chamber and a voltage is applied, causing the plasma-generated inert gas to collide with the target, and carbon material particles knocked out from the target are deposited on the cathode foil.

[0031] The cathode foil and the carbon layer are preferably pressed together. The pressing process presses the carbon material of the carbon layer against the surface-expanding layer, compressing and deforming the entire surface of the cathode foil. Furthermore, the densely porosified regions of the surface-expanding layer are significantly compressed and deformed. This deforms the surface of the cathode foil, creating undulating irregularities at the interface between the surface-expanding layer and the carbon layer. Simultaneously with the appearance of the irregularities, the surface-expanding layer and the carbon layer are also in close contact with each other. This makes it more difficult for the electrolyte to penetrate the interface between the carbon layer and the surface-expanding layer of the cathode body. Alternatively, the pressing process may allow the carbon material of the carbon layer to penetrate the oxide film and contact the cathode foil, thereby reducing the connection resistance between the carbon layer and the cathode foil. Alternatively, a press roller heated to a temperature above the softening temperature of the binder contained in the carbon layer may be used. This increases the fluidity of the carbon material, making it easier for the carbon material to penetrate into the surface-expanding layer.

[0032] (electrolyte) The electrolyte solution is a mixed solution in which a solute is dissolved in a solvent and an additive is added to the solvent. As the additive, at least inorganic oxide colloidal particles surface-modified with an organic substance (hereinafter also referred to as organically modified colloidal particles) are added to the electrolyte solution. Alternatively, at least inorganic oxide colloidal particles may be added to the electrolyte solution as the additive.

[0033] Examples of inorganic oxide colloidal particles include silica, alumina, titania, zirconia, antimony oxide, aluminosilicate, silica zirconia, titania zirconia, silica coated with aluminosilicate, silica coated with silica zirconia, etc., or mixtures thereof. Among these inorganic oxide colloidal particles, silica, aluminosilicate, or silica coated with aluminosilicate is particularly preferred from the viewpoints of ease of silylation treatment, stability of colloidal particles, and improvement in withstand voltage.

[0034] However, the organically modified colloidal particles are preferably 4.5 wt% or more and 17 wt% or less relative to the electrolyte. If the content is 4.5 wt% or more, the effect of the organically modified colloidal particles in improving the withstand voltage is better. On the other hand, if the content is 17 wt% or less, the specific resistance of the electrolyte decreases. Furthermore, the average particle diameter of the organically modified colloidal particles is preferably 5 nm or more and 50 nm or less. If the average particle diameter is 5 nm or more, the rate of change in withstand voltage after a heat resistance test is small. If the average particle diameter is 50 nm or less, the initial withstand voltage is high.

[0035] The organic substance that modifies the surface of the inorganic oxide colloidal particles is substituted with the surface hydroxyl groups of the inorganic oxide colloidal particles to suppress the aggregation of the inorganic oxide colloidal particles, and is, for example, a silylating agent, a silane coupling agent, a titanate-based coupling agent, an aluminum-based coupling agent, alcohols, latex, and various other polymer compounds. The silylating agent or silane coupling agent is represented by the following general formula (Chemical Formula 1). [ka] [In the formula, X1 is an alkyl group, alkenyl group, aryl group, or aralkyl group having 1 to 20 carbon atoms, and is a hydrocarbon group (-R) in which some of the hydrogen atoms may be substituted with a carboxyl group, ester group, amide group, cyano group, ketone group, formyl group, ether group, hydroxyl group, amino group, mercapto group, sulfide group, sulfoxide group, sulfone group, isocyanate group, ureido group, or epoxy group. X2 to X4 are an acetoxy group, an alkoxy group or alkyl group having 1 to 5 carbon atoms, and at least two of X2 to X4 are alkoxy groups.]

[0036] Specific examples of X1 include alkyl groups such as a methyl group, ethyl group, propyl group, butyl group, decyl group, and octadecyl group; alkenyl groups such as a vinyl group and allyl group; aryl groups such as a phenyl group, naphthyl group, and styryl group; aralkyl groups such as a benzyl group and phenethyl group; oxyhydrocarbon groups such as a methoxy group, ethoxy group, propoxy group, butoxy group, vinyloxy group, phenoxy group, and benzyloxy group; and a hydroxyl group. Examples of substituents include acrylic groups such as 3-methacryloxypropyl and 3-acryloxypropyl; epoxy groups such as 3-glycidoxypropyl and 2-(3,4-epoxycyclohexyl)ethyl; amino groups such as 3-aminopropyl, N-phenyl-3-aminopropyl, and N-2-(aminoethyl)-3-aminopropyl; mercapto groups such as 3-mercaptopropyl; isocyanate groups such as 3-isocyanatopropyl; and ureido groups such as 3-ureidopropyl. Specific examples of X2 to X4 include alkoxy groups such as methoxy, ethoxy, propoxy, and butoxy; alkyl groups such as methyl, ethyl, propyl, butyl, decyl, and octadecyl; and acetoxy, where at least two of X2 to X4 are alkoxy groups.

[0037] Among these combinations, methyltrimethoxysilane, methyltriethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, diphenyldimethoxysilane, diphenyldiethoxysilane, isobutyltrimethoxysilane, isobutyltriethoxysilane, decyltrimethoxysilane, decyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 2-(3,4-epoxycyclohexyl)ethyl Preferred are aryltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane, 3-ureidopropyltrialkoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, N-phenyl-3-aminopropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, 3-isocyanatepropyltriethoxysilane, and p-styryltrimethoxysilane.

[0038] Specific examples of titanate coupling agents include isopropyl triisostearoyl titanate, isopropyl tridodecylbenzenesulfonyl titanate, isopropyl tris(dioctylpyrophosphate)titanate, tetraisopropyl bis(dioctylphosphite)titanate, tetraoctyl bis(ditridecylphosphite)titanate, tetra(2,2-diallyloxymethyl-1-butyl)bis(ditridecyl)phosphite titanate, bis(dioctylpyrophosphate)oxyacetate titanate, isopropyl trioctanoyl titanate, isopropyl dimethacryloyl isostearoyl titanate, isopropyl tri(dioctylphosphate)titanate, isopropyl tricumylphenyl titanate, and isopropyl tri(N-aminoethylaminoethyl)titanate.

[0039] Specific examples of aluminum-based coupling agents include aluminum ethyl acetoacetate diisopropylate, aluminum tris(ethyl acetoacetate), aluminum tris(acetylacetonate), aluminum bis(ethyl acetoacetate) monoacetylacetonate, etc. Specific examples of alcohols include methanol, ethanol, n-propanol, iso-propanol, n-butanol, amyl alcohol, 4-methyl-2-pentanol, n-heptanol, n-octanol, 2-ethylhexanol, nonanol, decanol, tridecanol, 2-methoxyethanol, 2-ethoxyethanol, 2-butoxyethanol, 3-methoxybutanol, 3-methyl-3-methoxybutanol, polyvinyl alcohol, etc.

[0040] The organic substances used for surface modification, such as silylating agents, silane coupling agents, titanate coupling agents, aluminum coupling agents, alcohols, and various polymer compounds, can be used alone or in combination.

[0041] Here, exposure of the oxide film of the cathode body to the organically modified colloid particles affects the dissolution of the oxide film. Although this is speculation and not limited to this mechanism, it is believed that the dissolution of the oxide film of the cathode body is due to the following reason: Namely, hydroxyl groups remain on the surface of the organically modified colloid particles. The hydroxyl groups on the surface of the organically modified colloid particles attract moisture in the electrolyte. Therefore, when organically modified colloid particles are present near the oxide film of the cathode body, moisture attracted by the hydroxyl groups on the surface of the organically modified colloid particles easily approaches the oxide film of the cathode body, dissolving the oxide film, passing through the oxide film and reaching the valve metal, causing hydration degradation of the valve metal.

[0042] However, in the cathode body, the oxide film is covered with a carbon layer. Furthermore, compounds with hydrophilic groups, such as hydroxyl groups, have difficulty approaching the carbon layer. Therefore, moisture is less likely to reach the oxide film. This leads to the prevention of dissolution of the oxide film on the cathode body, the prevention of deterioration of the valve metal of the cathode body, and the reduction of capacitance change in the electrolytic capacitor.

[0043] Furthermore, it is believed that the surface-modifying groups of hydrophilic groups are likely to adsorb to the functional groups of the carbon material, and that the organically modified colloidal particles are likely to be present in the vicinity of the cathode body. Among the surface-modifying groups, mercapto groups are also likely to adsorb to the carbon material itself. On the other hand, epoxy groups, ureido groups, and methacryl groups are less likely to adsorb to the carbon material itself, and compared to, for example, amino groups, they are less likely to adsorb to the functional groups of carbon, or the degree of adsorption is weaker. Therefore, when the surface-modifying groups of the organically modified colloidal particles are epoxy groups, ureido groups, or methacryl groups, the proportion of organically modified colloidal particles approaching the carbon layer can be reduced, and further, the protective effect of the oxide film can be enhanced.

[0044] Particularly preferred are organically modified colloidal particles having a ureido group or a methacryl group as the surface modifying group. Hydroxyl groups are relatively unlikely to be generated from the ureido group or the methacryl group. Therefore, the number of hydroxyl groups that attract moisture is unlikely to increase on the organically modified colloidal particles, thereby suppressing the ability of the organically modified colloidal particles to attract moisture.

[0045] In contrast, the carbon material contained in the carbon layer preferably has lactone groups, carboxylic anhydride groups, or both on the surface. The lactone groups and carboxylic anhydride groups hydrophobize the surface of the carbon layer, making it even more inaccessible to the organically modified colloidal particles.

[0046] The thickness of the carbon layer is preferably 0.1 μm or more and 10 μm or less per side of the foil. If it is 0.1 μm or more, the organically modified colloidal particles are particularly unlikely to permeate the carbon layer, resulting in a better protective effect for the oxide film. If it is 10 μm or less, the connection resistance with the external terminal is low and the product capacity is better. The average particle size of the primary particles of the carbon material is preferably 100 nm or less. If it is 100 nm or less, there are fewer voids between the carbon particles that make up the carbon layer, making it more difficult for the organically modified colloidal particles to permeate the carbon layer, resulting in a better protective effect for the oxide film.

[0047] The solvent of the electrolyte solution used with the organically modified colloidal particles may be either a protic organic polar solvent or an aprotic organic polar solvent. Representative examples of protic organic polar solvents include monohydric alcohols, polyhydric alcohols, and oxyalcohol compounds. Representative examples of aprotic organic polar solvents include sulfones, amides, lactones, cyclic amides, and nitriles.

[0048] Examples of monohydric alcohols include ethanol, propanol, butanol, pentanol, hexanol, cyclobutanol, cyclopentanol, cyclohexanol, benzyl alcohol, etc. Examples of polyhydric alcohols and oxyalcohol compounds include ethylene glycol, propylene glycol, glycerin, methyl cellosolve, ethyl cellosolve, methoxypropylene glycol, dimethoxypropanol, etc.

[0049] Examples of sulfones include dimethyl sulfone, ethyl methyl sulfone, diethyl sulfone, sulfolane, 3-methyl sulfolane, and 2,4-dimethyl sulfolane. Examples of amides include N-methylformamide, N,N-dimethylformamide, N-ethylformamide, N,N-diethylformamide, N-methylacetamide, N,N-dimethylacetamide, N-ethylacetamide, N,N-diethylacetamide, and hexamethylphosphoric amide. Examples of lactones and cyclic amides include γ-butyrolactone, γ-valerolactone, δ-valerolactone, N-methyl-2-pyrrolidone, ethylene carbonate, propylene carbonate, butylene carbonate, and isobutylene carbonate. Examples of nitriles include acetonitrile, 3-methoxypropionitrile, and glutaronitrile.

[0050] The solute contained in the electrolytic solution includes anionic and cationic components, and is typically an organic acid or its salt, an inorganic acid or its salt, or a salt of a complex compound of an organic acid and an inorganic acid, and is used alone or in combination of two or more. The anions and cations may be added to the electrolytic solution in the form of ionically dissociable salts, or an acid that becomes an anion and a base that becomes a cation may be added to the electrolytic solution separately as solute components. The anions and cations may each be used alone or in combination of two or more.

[0051] Examples of organic acids that serve as anionic solutes include carboxylic acids such as oxalic acid, succinic acid, glutaric acid, pimelic acid, suberic acid, sebacic acid, phthalic acid, isophthalic acid, terephthalic acid, maleic acid, adipic acid, benzoic acid, toluic acid, enanthic acid, malonic acid, 1,6-decanedicarboxylic acid, 1,7-octanedicarboxylic acid, azelaic acid, resorcylic acid, phloroglucinic acid, gallic acid, gentisic acid, protocatechuic acid, pyrocatechuic acid, trimellitic acid, pyromellitic acid, undecanedioic acid, dodecanedioic acid, tridecanedioic acid, t-butyladipic acid, and 11-vinyl-8-octadecenedioic acid, as well as phenols and sulfonic acids.

[0052] Examples of inorganic acids include boric acid, phosphoric acid, phosphorous acid, hypophosphorous acid, carbonic acid, silicic acid, etc. Examples of composite compounds of organic acids and inorganic acids include borodisalicylic acid, borodioxalic acid, borodiglycolic acid, borodimalonic acid, borodisuccinic acid, borodiadipic acid, borodiazelaic acid, borodibenzoic acid, borodimaleic acid, borodilactic acid, borodimalic acid, boroditartaric acid, borodicitric acid, borodiphthalic acid, borodi(2-hydroxy)isobutyric acid, borodiresorcylic acid, borodimethylsalicylic acid, borodinaphthoic acid, borodimandelic acid, and borodi(3-hydroxy)propionic acid, etc.

[0053] Examples of the cationic component include ammonium, quaternary ammonium, quaternized amidinium, amine, sodium, potassium, etc. Examples of the quaternary ammonium include tetramethylammonium, triethylmethylammonium, tetraethylammonium, etc. Examples of the quaternized amidinium include ethyldimethylimidazolinium, tetramethylimidazolinium, etc. Examples of the amine include primary amine, secondary amine, and tertiary amine. Examples of the primary amine include methylamine, ethylamine, propylamine, etc. Examples of the secondary amine include dimethylamine, diethylamine, ethylmethylamine, dibutylamine, etc. Examples of the tertiary amine include trimethylamine, triethylamine, tributylamine, ethyldimethylamine, ethyldiisopropylamine, etc.

[0054] The solute concentration, calculated as salt, is preferably 5 wt% to 25 wt% of the electrolyte. If the solute concentration is less than 5 wt%, the defect repair effect on the dielectric film and the oxide film of the cathode body is weakened. If the solute concentration is more than 25 wt%, the effect of improving voltage resistance due to the organically modified colloidal particles is weakened relative to the effect of reducing spark voltage due to high electrical conductivity.

[0055] (separator) Examples of materials for the separator include cellulose papers such as kraft, Manila hemp, esparto, hemp, and rayon, and mixtures thereof; polyester-based resins such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, and derivatives thereof; polytetrafluoroethylene-based resins, polyvinylidene fluoride-based resins, vinylon-based resins; polyamide-based resins such as aliphatic polyamides, semi-aromatic polyamides, and wholly aromatic polyamides; polyimide-based resins, polyethylene resins, polypropylene resins, trimethylpentene resins, polyphenylene sulfide resins, acrylic resins, and polyvinyl alcohol resins. These resins can be used alone or in combination.

[0056] (Manufacturing method) (wound type) An example of a manufacturing method for an electrolytic capacitor is as follows. First, in the anode formation process, a surface-expanding layer is formed on one or both sides of the anode foil, and a dielectric film is formed on the surface-expanding layer by chemical conversion treatment. In the cathode formation process, a surface-expanding layer is also formed on one or both sides of the cathode foil as needed, and an oxide film is formed on the surface, or a natural oxide film is left. Next, in the cathode formation process, the process moves to the carbon layer lamination process, where a carbon layer containing a carbon material is laminated on the cathode foil.

[0057] The anode body and the cathode body are connected to respective external terminals. The external terminals are electrically and mechanically connected to the anode body and the cathode body by stitch connection, cold welding, ultrasonic welding, laser welding, etc. The external terminals are conductors that protrude from the element and electrically connect the electrolytic capacitor to the mounting board.

[0058] Electrolytic capacitors include wound and stacked types. In wound electrolytic capacitors, the anode body, cathode body, and separator are long, and wound capacitor elements are wound bodies. In wound electrolytic capacitors, the anode body and cathode body are stacked with the separator interposed in the element formation process. The separator is stacked so that one end protrudes beyond one end of the anode body and cathode body. A core is created by starting to wind the protruding separator first so that the core of the wound body is aligned with the short sides of the anode body and cathode body. Then, the anode body and cathode body are wound by rolling up the long sides of the anode body and cathode body using the core as a winding axis. The wound body is then formed into a cylindrical shape by spirally winding the stack of the anode body, cathode body, and separator multiple times.

[0059] In a stacked electrolytic capacitor, the anode body, cathode body, and separator have a flat plate shape. In a stacked electrolytic capacitor, flat plate-shaped anode bodies and cathode bodies are stacked with separators interposed therebetween in an element formation process.

[0060] After the element formation step, a repair chemical conversion step may be provided to repair bare metal portions of the valve metal exposed when the anode body and the cathode body are cut to a desired width, or defects formed in the dielectric film of the anode body and the oxide film of the cathode body due to physical stress. In the repair chemical conversion step, the wound body or the laminate is immersed in a chemical conversion solution and a voltage is applied.

[0061] Examples of chemical conversion solutions include phosphoric acid-based conversion solutions such as ammonium dihydrogen phosphate, boric acid-based conversion solutions such as ammonium borate, adipic acid-based conversion solutions such as ammonium adipate, and conversion solutions that combine boric acid and dicarboxylic acids such as citric acid. The repair conversion voltage is preferably 0.1 to 1.2 times the conversion voltage applied to the anode body. The voltage application method during repair conversion can be selected from a variety of methods, including applying a constant voltage from the start of repair conversion or gradually increasing the applied voltage at regular intervals.

[0062] The impregnation step then proceeds to immersing the wound body or laminate in an electrolyte solution to impregnate the voids with the electrolyte solution. A depressurization or pressurization process may be performed as necessary to impregnate the electrolyte solution into smaller voids. The electrolyte impregnation step may be repeated multiple times. For example, the pressure inside the wound body or laminate may be reduced, and the electrolyte solution may be injected into the element while pressurizing the electrolyte solution.

[0063] The capacitor element produced after the impregnation process is packaged in an exterior packaging. The exterior packaging includes a case with one end closed and the other open, and a sealing body. The capacitor element is housed in the case, and the opening of the case is sealed with the sealing body. The opening of the case is bent inward by a crimping process, crushing it and sealing the sealing body tightly. After the capacitor element is sealed, the electrolytic capacitor undergoes an aging process to complete its production. In the aging process, a DC voltage is applied to the electrolytic capacitor to repair defects in the dielectric film, etc.

[0064] The exterior may be a laminate film, or may be a resin such as a heat-resistant resin or an insulating resin, which may be molded around the capacitor element or formed into a thin film by a method such as dip coating or printing.

[0065] During the manufacturing process of this electrolytic capacitor, moisture can get inside. Alternatively, moisture may be used as a solvent in the electrolyte to repair the dielectric film. The moisture content within the electrolytic capacitor is preferably 2 wt% or more and 9.5 wt% or less, based on the electrolyte. A moisture content of less than 2 wt% reduces the risk of dissolving the oxide film on the cathode body and deteriorating the valve metal, but reduces the efficiency of repairing defects in the dielectric film. Furthermore, if the moisture content is 9.5 wt% or less, the carbon layer effectively blocks the approach of moisture attracted by the organically modified colloidal particles. [Example]

[0066] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0067] Example 1 The electrolytic capacitor of Example 1 was fabricated as follows. First, in the anode formation process and cathode formation process, a pair of electrodes was fabricated using aluminum foil. Both aluminum foils were subjected to an etching process to enlarge the surface, forming a surface-enlarged layer. In the anode formation process, a DC etching process was performed to form a surface-enlarged layer consisting of tunnel-shaped etching pits. In the cathode formation process, an AC etching process was performed to form a surface-enlarged layer consisting of spongy etching pits.

[0068] The aluminum foil that would become the anode body was chemically treated to form a dielectric film on the foil surface. In the chemical treatment process, the aluminum foil with a surface-expanding layer formed thereon was subjected to chemical treatment, and a dielectric film was formed on the surface of the aluminum foil with a chemical voltage of 650V. In addition, for the cathode body, an oxide film of 1V was formed on the aluminum foil with a surface-expanding layer formed thereon. Furthermore, in the cathode formation process, the process moved to the carbon layer lamination process, where a carbon layer containing carbon material was laminated on the cathode foil.

[0069] The cathode body was a laminate of aluminum foil and a carbon layer. For the carbon layer, a slurry was prepared by mixing and kneading carbon black, a binder made of styrene butadiene rubber (SBR), and an aqueous solution of carboxymethyl cellulose sodium (CMC-Na) as a dispersant.

[0070] This slurry was uniformly applied to an aluminum foil. The slurry was then heated and dried to volatilize the solvent. The cathode body was then pressed. In the pressing process, the cathode body was sandwiched between press rollers and a linear pressure of 5 kN / cm was applied to fix the carbon layer onto the aluminum foil. The linear pressure was applied using a press machine manufactured by Takumi Giken Co., Ltd. The diameter of the press rollers was 180 mm, the pressing width was 130 mm, and the cathode body was transported once at 3 m / min. The thickness of the carbon layer on the aluminum foil was 2 μm.

[0071] Lead wires were attached to each of the anode body and cathode body by stitch connection. Next, the device was formed by winding the anode body and cathode body facing each other with a cellulose-based double layer paper interposed therebetween as a separator.

[0072] The process then moved on to the electrolyte impregnation process, where the wound body was impregnated with the electrolyte. The electrolyte consisted of 8.5 wt% water, 75.5 wt% ethylene glycol, 6 wt% azelaic acid, 2 wt% p-nitrobenzyl alcohol, 6 wt% organically modified colloidal particles, and 2 wt% dimethylamine. The organically modified colloidal particles were organically modified silica, whose surface was modified with 3-glycidoxypropyltrimethoxysilane.

[0073] The wound body was immersed in the electrolyte at room temperature, the pressure of the wound body was reduced to 0.002 MPa, and the electrolyte was pressurized to 0.2 MPa, and the electrolyte was impregnated into the wound body every 60 minutes. The electrolyte impregnation process was carried out twice in total.

[0074] The capacitor element, consisting of this anode body, cathode body, separator, and electrolyte, was housed in an aluminum outer case with one end closed and the other open, and a sealing body was press-fitted into the opening of the outer case and crimped to seal it in place.The electrolytic capacitor was then subjected to an aging process in which a voltage of 475 V was applied for two hours in a temperature environment of 85°C.

[0075] The moisture content in the electrolytic capacitor of Example 1 was 9 wt % based on the electrolyte solution. The moisture content in the electrolytic capacitor was measured as follows: The fabricated capacitor was disassembled, and the electrolyte solution was separated from the element using a tabletop centrifuge (KUBOTA, S700T) at 3000 rpm for 15 min. The moisture content of the separated electrolyte solution was measured using a Karl Fischer moisture content meter (NITTOSEIKO ANALYTECH) by coulometric titration based on the electrolyte solution in the electrolytic capacitor.

[0076] (Comparative Example 1) Next, an electrolytic capacitor of Comparative Example 1 was produced. The cathode body of Comparative Example 1 did not have a carbon layer formed thereon. Except for the fact that a carbon layer was not formed, the electrolytic capacitor of Comparative Example 1 was produced with the same configuration, composition, manufacturing method, and manufacturing conditions as the electrolytic capacitor of Example 1, and the electrolytic solution contained silica, the surface of which was modified with 3-glycidoxypropyltrimethoxysilane, as organically modified colloidal particles. The moisture content in the electrolytic capacitor of Comparative Example 1 was 9.1 wt % based on the electrolyte solution.

[0077] (Foil capacity test) Two electrolytic capacitors each of Example 1 and Comparative Example 1 were prepared, and one set was left in an environment of 20° C. for 6000 hours. The other set was left in an environment of 105° C. for 6000 hours. After being left for 6000 hours, the electrolytic capacitors were disassembled, and the foil capacitance of the cathode body was measured.

[0078] The volume of the cathode body is 5cm from the cathode body. 2 A test piece was cut out and immersed in a capacitance measurement solution in a glass measurement tank using a platinum plate as the counter electrode, and measurements were taken using a capacitance meter. The capacitance measurement solution was an aqueous solution of ammonium adipate at 30°C, and the capacitance meter was an LCR meter. The measurement conditions were an effective value of 1 Vrms and a measurement frequency of 120 Hz.

[0079] The rate of change in cathode foil capacity was calculated from the measured foil capacity. The rate of change in cathode foil capacity is the percentage of the foil capacity when left at 105°C to the foil capacity when left at 20°C. In other words, the formula for calculating the rate of change in cathode foil capacity, ΔCap (%), is: 105 The foil capacity when left at 20°C is C 20 This gives the following:

[0080] ΔCap=(C 105 / C 20 ) x 100

[0081] The change rates ΔCap (%) of the cathode foil capacitance in Example 1 and Comparative Example 1 are shown in Table 1 below.

[0082] (Table 1) TIFF2025125536000003.tif31156

[0083] As shown in Table 1, the foil capacitance of the cathode body of the electrolytic capacitor of Example 1 is almost unchanged compared to Comparative Example 1. The cathode body of the electrolytic capacitor of Example 1 is not deteriorated even in a temperature environment of 105°C. Specifically, it can be seen that the oxide film of the cathode body is hardly dissolved.

[0084] The difference between Example 1 and Comparative Example 1 is the presence or absence of a carbon layer in the cathode body. Therefore, it was confirmed that even if organically modified colloidal particles are contained in the electrolyte solution, dissolution of the oxide film on the cathode body and changes in the capacitance characteristics of the electrolytic capacitor can be suppressed as long as a carbon layer is laminated on the foil of the cathode body.

[0085] Example 2 A cathode body and an electrolyte solution included in the electrolytic capacitor of Example 2 were prepared. This cathode body and electrolyte solution were the same as the cathode body and electrolyte solution included in the electrolytic capacitor of Example 1, and were prepared by the same manufacturing method and manufacturing steps as in Example 1. Furthermore, a cathode body and an electrolyte solution included in the electrolytic capacitor of Comparative Example 2 were prepared. This cathode body and electrolyte solution were the same as the cathode body and electrolyte solution included in the electrolytic capacitor of Comparative Example 1, and were prepared by the same manufacturing method and manufacturing steps as in Comparative Example 1.

[0086] That is, the cathode body of Example 2 is a laminate in which a carbon layer is laminated on aluminum foil having a surface-expanding layer made of spongy etching pits and a 1V oxide film formed by chemical conversion treatment, and the carbon material contained in the carbon layer is carbon black. The cathode body was subjected to press processing. The composition of the electrolyte was 8.5 wt% water, 75.5 wt% ethylene glycol, 6 wt% azelaic acid, 2 wt% p-nitrobenzyl alcohol, 6 wt% organically modified colloidal particles, and 2 wt% dimethylamine. The organically modified colloidal particles were organically modified silica, and the surface of the organically modified silica was modified with 3-glycidoxypropyltrimethoxysilane.

[0087] The cathode body of Comparative Example 2 does not have a carbon layer formed thereon. Except for the fact that the carbon layer is not formed thereon, the cathode body of Comparative Example 2 has the same configuration, composition, and is produced by the same manufacturing method and under the same manufacturing conditions as the electrolytic capacitor of Example 2. The electrolytic solution of Comparative Example 2 has the same composition and composition ratio as the electrolytic solution of Example 2, and is prepared by the same manufacturing method and under the same manufacturing conditions.

[0088] (Foil capacity test) The cathode elements of Example 2 and Comparative Example 2 were placed in vials containing the electrolytes of Example 2 and Comparative Example 2 and sealed. 12 g of the electrolyte was poured into the vials. The moisture content in the vials was 8.7 wt % based on the electrolyte in both Example 2 and Comparative Example 2. As in Example 1 and Comparative Example 1, the moisture content was measured by coulometric titration using a Karl Fischer moisture meter (manufactured by NITTOSEIKO ANALYTECH).

[0089] Two vials each of Example 2 and Comparative Example 2 were prepared, and the vials of Example 2 and Comparative Example 2 were left in a temperature environment of 85°C for two hours, corresponding to the aging process of Example 1 and Comparative Example 1. Next, of the two prepared vials, one of Example 2 and Comparative Example 2 was left in a temperature environment of 20°C for 118 hours. The other set was left in a 105°C environment for 120 hours.

[0090] Then, the cathode bodies were removed from the respective vials, and the foil capacity of each cathode body was measured using the same measurement method and conditions as in Example 1 and Comparative Example 1. The rate of change in cathode body foil capacity was calculated from each measured foil capacity. The rate of change ΔCap (%) in cathode body foil capacity is the percentage of the foil capacity when left at 105°C relative to the foil capacity when left at 20°C.

[0091] The change rates ΔCap (%) of the cathode foil capacitance in Example 2 and Comparative Example 2 are shown in Table 2 below.

[0092] (Table 2) TIFF2025125536000004.tif31156

[0093] As shown in Table 2 above, even when the cathode body was sealed in a vial containing an electrolytic solution, similar to the results of the foil capacitance of the cathode bodies obtained by disassembling the electrolytic capacitors of Comparative Example 1 and Example 1, the combination of the cathode body and electrolyte of Example 2 had a higher rate of change ΔCap (%) in foil capacitance compared to Comparative Example 1. That is, similar to the results of Example 1 and Comparative Example 1, the cathode body of Example 2 did not deteriorate even in a temperature environment of 105°C. Specifically, this shows that there was almost no dissolution of the oxide film on the cathode body.

[0094] (Examples 3 to 8) The cathode bodies and electrolyte solutions included in the electrolytic capacitors of Examples 3 to 8 were prepared as follows. The cathode bodies of Examples 3 to 8 were prepared by the same manufacturing method and under the same manufacturing conditions as the cathode bodies of Examples 1 and 2, and had the same configuration. That is, the cathode bodies of Examples 3 to 8 were laminated bodies in which a carbon layer was laminated on aluminum foil having a 1V oxide film formed by chemical conversion treatment on a surface-expanding layer made of spongy etching pits, and the carbon material contained in the carbon layer was carbon black. The cathode bodies were subjected to press working.

[0095] The electrolyte solutions of Examples 3 to 8 each contained 8.5 wt% water, 6 wt% azelaic acid, 2 wt% p-nitrobenzyl alcohol, and 2 wt% dimethylamine based on the total amount of the electrolyte. Furthermore, the electrolyte solutions of Examples 3 to 8 contained organically modified colloidal particles, which were organically modified silica whose surface was modified with 3-glycidoxypropyltrimethoxysilane, and ethylene glycol. The electrolyte solutions of Examples 3 to 8 contained different amounts of organically modified colloidal particles. The difference in the content of the organically modified colloidal particles was adjusted by the amount of ethylene glycol.

[0096] The electrolyte solution of Example 3 contains 4 wt% of organically modified colloidal particles relative to the total amount of the electrolyte solution. The electrolyte solution of Example 4 contains 4.5 wt% of organically modified colloidal particles relative to the total amount of the electrolyte solution. The electrolyte solution of Example 5 contains 5 wt% of organically modified colloidal particles relative to the total amount of the electrolyte solution. The electrolyte solution of Example 6 contains 9 wt% of organically modified colloidal particles relative to the total amount of the electrolyte solution. The electrolyte solution of Example 7 contains 12 wt% of organically modified colloidal particles relative to the total amount of the electrolyte solution. The electrolyte solution of Example 8 contains 17 wt% of organically modified colloidal particles relative to the total amount of the electrolyte solution.

[0097] The cathode elements of Examples 3 to 8 were placed in vials containing the electrolytes of Examples 3 to 8 and sealed. 12 g of the electrolyte was poured into the vials. As in Examples 1 and 2, the moisture content in the vials of Examples 3 to 8 was measured by coulometric titration using a Karl Fischer moisture content meter (manufactured by NITTOSEIKO ANALYTECH) and found to be as follows:

[0098] That is, the moisture content in the vial of Example 3 was 9.4 wt% based on the electrolyte solution. The moisture content in the vial of Example 4 was 9.3 wt% based on the electrolyte solution. The moisture content in the vial of Example 5 was 9.1 wt% based on the electrolyte solution. The moisture content in the vial of Example 6 was 8.7 wt% based on the electrolyte solution. The moisture content in the vial of Example 7 was 8.9 wt% based on the electrolyte solution. The moisture content in the vial of Example 8 was 9.1 wt% based on the electrolyte solution.

[0099] (Foil capacity test) A foil capacity test was conducted for Examples 3 to 8. The test method and conditions for the foil capacity test were the same as those for Example 2 and Comparative Example 2. The change rate ΔCap (%) of the cathode body foil capacity for Examples 2 to 8 is shown in Table 3 below. Furthermore, based on Table 3 below, a graph was created showing the relationship between the content of organically modified colloidal particles and ΔCap, as shown in Figure 1.

[0100] (Table 3) TIFF2025125536000005.tif82156

[0101] 1, the ΔCap was particularly good in Examples 2 and 4 to 8. That is, it was confirmed that when the content of organically modified colloidal particles was 4.5 wt % or more relative to the total amount of the electrolyte, dissolution of the oxide film on the cathode body was particularly suppressed even in a temperature environment of 105°C, and characteristic changes in the capacitance of the electrolytic capacitor could be particularly suppressed.

[0102] Examples 9 to 14 The cathode bodies and electrolyte solutions provided in the electrolytic capacitors of Examples 9 to 14 were prepared as follows. The cathode bodies of Examples 9 to 14 were prepared by the same manufacturing method and under the same manufacturing conditions as the cathode bodies of Examples 1 to 8, and had the same configuration. That is, the cathode bodies of Examples 9 to 14 were laminated bodies in which a carbon layer was laminated on aluminum foil having a 1V oxide film formed by chemical conversion treatment on a surface-expanding layer made of spongy etching pits, and the carbon material contained in the carbon layer was carbon black. The cathode bodies were subjected to press working.

[0103] The electrolyte compositions of Examples 9 to 14 contained 6 wt% azelaic acid, 2 wt% p-nitrobenzyl alcohol, 6 wt% organically modified colloidal particles, and 2 wt% dimethylamine relative to the total amount of the electrolyte. The organically modified colloidal particles were organically modified silica, the surface of which was modified with 3-glycidoxypropyltrimethoxysilane. Furthermore, the electrolyte compositions of Examples 9 to 14 contained water and ethylene glycol. The electrolytes of Examples 9 to 14 contained different amounts of water. The differences in water content were adjusted with ethylene glycol.

[0104] The electrolyte of Example 9 contains 2.0 wt% of water based on the total amount of the electrolyte. The electrolyte of Example 10 contains 6.0 wt% of water based on the total amount of the electrolyte. The electrolyte of Example 11 contains 7.0 wt% of water based on the total amount of the electrolyte. The electrolyte of Example 12 contains 8.5 wt% of water based on the total amount of the electrolyte. The electrolyte of Example 13 contains 15.0 wt% of water based on the total amount of the electrolyte. The electrolyte of Example 14 contains 30.0 wt% of water based on the total amount of the electrolyte.

[0105] The cathode elements of Examples 9 to 14 were placed in vials containing the electrolytes of Examples 9 to 14 and sealed. 12 g of the electrolyte was poured into the vials. As in Examples 1 to 8, the moisture content in the vials of Examples 9 to 14 was measured by coulometric titration using a Karl Fischer moisture content meter (manufactured by NITTOSEIKO ANALYTECH) and found to be as follows:

[0106] That is, the water content in the vial of Example 9 was 2.5 wt% based on the electrolyte solution. The water content in the vial of Example 10 was 6.3 wt% based on the electrolyte solution. The water content in the vial of Example 11 was 7.4 wt% based on the electrolyte solution. The water content in the vial of Example 12 was 8.7 wt% based on the electrolyte solution. The water content in the vial of Example 13 was 15.2 wt% based on the electrolyte solution. The water content in the vial of Example 14 was 30.2 wt% based on the electrolyte solution.

[0107] (Foil capacity test) A foil capacity test was conducted for Examples 9 to 14. The test method and conditions for the foil capacity test were the same as those for Example 2 and Comparative Example 2. The change rates ΔCap (%) of the cathode body foil capacity for Examples 9 to 14 are shown in Table 4 below. Also, based on Table 4 below, a graph was created showing the relationship between the measured moisture content and ΔCap, as shown in FIG.

[0108] (Table 4) TIFF2025125536000006.tif71156

[0109] As shown in Table 4 and Figure 2, Examples 9 to 12 have particularly good ΔCap. That is, it was confirmed that when the amount of water in the electrolytic capacitor is 9.5 wt% or less based on the electrolyte, the carbon layer effectively blocks the approach of water attracted by the organically modified colloidal particles.

[0110] Examples 15 to 22 The cathode bodies and electrolyte solutions provided in the electrolytic capacitors of Examples 15 to 22 were prepared as follows. The cathode bodies of Examples 15 to 22 were prepared by the same manufacturing method and under the same manufacturing conditions as the cathode bodies of Examples 1 to 14, and had the same configuration. That is, the cathode bodies of Examples 15 to 22 were laminated bodies in which a carbon layer was laminated on aluminum foil having a 1V oxide film formed by chemical conversion treatment on a surface-expanding layer made of spongy etching pits, and the carbon material contained in the carbon layer was carbon black. The cathode bodies were subjected to press working.

[0111] The compositions and composition ratios of the electrolyte solutions in Examples 15 to 22, except for the type of organically modified colloidal particles, were the same as those of Example 2. That is, the electrolyte solutions contained 8.5 wt% water, 75.5 wt% ethylene glycol, 6 wt% azelaic acid, 2 wt% p-nitrobenzyl alcohol, 6 wt% organically modified colloidal particles, and 2 wt% dimethylamine relative to the total volume of the electrolyte.

[0112] The organically modified colloidal particles of Example 2 were organically modified silica in which the silica surface was modified with 3-glycidoxypropyltrimethoxysilane. In contrast, the organically modified colloidal particles of Example 15 were organically modified silica in which the silica surface was modified with 3-glycidoxypropylmethyldiethoxysilane. The organically modified colloidal particles of Example 16 were organically modified silica in which the silica surface was modified with N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane. The organically modified colloidal particles of Example 17 were organically modified silica in which the silica surface was modified with 3-methacryloxypropyltriethoxysilane. The organically modified colloidal particles of Example 18 were organically modified silica in which the silica surface was modified with vinyltrimethoxysilane.

[0113] The organically modified colloidal particles of Example 19 are organically modified silica whose surface is modified with 3-acryloxypropyltrimethoxysilane. The organically modified colloidal particles of Example 20 are organically modified silica whose surface is modified with tris(3-(trimethoxysilyl)propyl)isocyanurate. The organically modified colloidal particles of Example 21 are organically modified silica whose surface is modified with 3-isocyanatepropyltriethoxysilane. The organically modified colloidal particles of Example 22 are organically modified silica whose surface is modified with 8-glycidoxyoctyltrimethoxysilane.

[0114] The cathode elements of Examples 15 to 22 were placed in vials containing the electrolytes of Examples 15 to 22 and sealed. 12 g of the electrolyte was poured into the vials. As in Examples 1 to 8, the moisture content in the vials of Examples 15 to 22 was measured by coulometric titration using a Karl Fischer moisture content meter (manufactured by NITTOSEIKO ANALYTECH), and the results were as follows:

[0115] That is, the water content in the vial of Example 15 was 8.7 wt% based on the electrolyte solution. The water content in the vial of Example 16 was 8.7 wt% based on the electrolyte solution. The water content in the vial of Example 17 was 9.0 wt% based on the electrolyte solution. The water content in the vial of Example 18 was 8.4 wt% based on the electrolyte solution. The water content in the vial of Example 19 was 8.6 wt% based on the electrolyte solution. The water content in the vial of Example 20 was 9.1 wt% based on the electrolyte solution. The water content in the vial of Example 21 was 8.7 wt% based on the electrolyte solution. The water content in the vial of Example 22 was 8.8 wt% based on the electrolyte solution.

[0116] (Foil capacity test) A foil capacity test was conducted for Examples 15 to 22. The test method and conditions for the foil capacity test were the same as those for Example 2 and Comparative Example 2. The change rates ΔCap (%) of the cathode body foil capacity for Examples 15 to 22 are shown in Table 5 below, along with that for Example 2. Table 5 below lists organic substances that modify the surface of silica as types of organically modified colloidal particles.

[0117] (Table 5) TIFF2025125536000007.tif101167

[0118] As shown in Table 5 above, it was confirmed that the carbon layer can prevent various organically modified colloidal particles that attract moisture from approaching the oxide film on the cathode body, thereby inhibiting the dissolution of the oxide film on the cathode body, inhibiting deterioration of the valve metal of the cathode body, and reducing changes in the capacitance of the electrolytic capacitor.

Claims

1. an anode body having a dielectric coating formed on the surface of a foil made of a valve metal as a base material; a cathode body facing the anode body; an electrolyte interposed between the anode body and the cathode body; Equipped with the cathode body includes a foil having a valve metal as a base material, an oxide film formed on a surface of the foil, and a carbon layer laminated on the oxide film and containing a carbon material; the electrolyte solution comprises a solvent, a solute, and inorganic oxide colloidal particles; An electrolytic capacitor characterized by:

2. the inorganic oxide colloidal particles are silica; 2. The electrolytic capacitor according to claim 1,

3. the inorganic oxide colloidal particles are surface-modified with an organic substance; 2. The electrolytic capacitor according to claim 1,

4. the inorganic oxide colloidal particles surface-modified with an organic substance are contained in an amount of 4.5 wt % or more and 17 wt % or less based on the total amount of the electrolyte; 4. The electrolytic capacitor according to claim 3,

5. a capacitor element having the anode body, the cathode body, and the electrolyte; an exterior that seals the capacitor element; Further provided with The exterior contains water in an amount of 2 wt % or more and 9.5 wt % or less with respect to the total amount of the electrolyte; 2. The electrolytic capacitor according to claim 1,

6. The solute is contained in an amount of 5 wt % or more and 25 wt % or less based on the total amount of the electrolyte; 2. The electrolytic capacitor according to claim 1,

7. a capacitor element having the anode body, the cathode body, and the electrolyte; an exterior that seals the capacitor element; Further provided with the inorganic oxide colloidal particles are surface-modified with an organic substance having an epoxy group, a ureido group, or a methacryl group; the carbon material has a lactone group, a carboxylic anhydride group, or both on its surface; the inorganic oxide colloidal particles surface-modified with an organic substance are contained in an amount of 4.5 wt % or more and 17 wt % or less based on the total amount of the electrolyte; The exterior contains water in an amount of 2 wt % or more and 9.5 wt % or less with respect to the total amount of the electrolyte; 4. The electrolytic capacitor according to claim 3,

8. an anode body forming step of forming a dielectric film on a foil surface of a valve metal substrate; a cathode body forming step of laminating a carbon layer containing a carbon material on a valve metal substrate having an oxide film on its surface; an element forming step of stacking the anode body and the cathode body with a separator interposed therebetween; an electrolyte impregnation step of impregnating the element with an electrolyte; the electrolyte solution comprises a solvent, a solute, and inorganic oxide colloidal particles; A method for manufacturing an electrolytic capacitor, comprising:

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