Electrolytic capacitors

Abstract

To provide an electrolytic capacitor that can sufficiently suppress performance degradation when used for a long period of time or when used in a high-temperature environment. [Solution] The electrolytic capacitor according to this disclosure comprises a capacitor element, a liquid component impregnated into the capacitor element, a plurality of microcapsules, and a case that houses the capacitor element, the liquid component, and the plurality of microcapsules. The capacitor element includes an anode foil having a dielectric layer, a cathode foil arranged opposite to the dielectric layer, a separator interposed between the anode foil and the cathode foil, and a conductive polymer layer interposed between the anode foil and the cathode foil and in contact with the separator. Each of the plurality of microcapsules contains a degradation prevention component, and the capsule wall of each of the plurality of microcapsules ruptures when predetermined conditions are met, releasing the degradation prevention component to the outside.

Description

[Technical Field]

[0001] This invention relates to an electrolytic capacitor. [Background technology]

[0002] An electrolytic capacitor comprises, for example, a capacitor element, a liquid component (e.g., an electrolyte) impregnated into the capacitor element, and a case that houses the capacitor element and the liquid component. Conventionally, attempts have been made to use microcapsules containing various core materials in electrolytic capacitors.

[0003] Patent Document 1 discloses a flame-retardant electrolytic capacitor comprising an anode foil having an oxide film on its surface, a cathode foil, a separator, and an electrolyte containing a solute in a solvent, characterized in that the electrolytic capacitor element contains a microencapsulated flame retardant in which a fluorine-containing phosphate ester having a specific structure is sealed within a resin that melts at 150°C or higher. In other words, Patent Document 1 discloses an electrolytic capacitor in which, when the electrolytic capacitor element burns, the microcapsules melt, thereby exhibiting the flame-retardant effect of the fluorine-containing phosphate ester and preventing the continuation of combustion through self-extinguishing action.

[0004] Patent Document 2 discloses a flame-retardant electrolytic capacitor coated with inorganic microcapsules prepared by an interfacial reaction method containing boric acid or a boric acid compound as a core material. Specifically, Patent Document 2 discloses an electrolytic capacitor that, by containing inorganic microcapsules containing boric acid or a boric acid compound with excellent self-extinguishing properties as a core material, can prevent accidents by not igniting even when an overvoltage exceeding the specifications is applied.

[0005] Patent Document 3 discloses a method for manufacturing an electrolytic capacitor, in which microcapsules containing a driving electrolyte are coated onto an anode foil, a cathode foil, and / or a spacer, these are wound or laminated to form a capacitor element, a resin casing is applied, the microcapsules in the capacitor element are dissolved by resin molding and / or heating for the application of the casing, and after the casing is applied, the driving electrolyte is impregnated inside the capacitor element. In other words, Patent Document 3 discloses a method for impregnating a capacitor element with a driving electrolyte in a way that prevents leakage when manufacturing a capacitor with a resin casing such as a chip type, by using microcapsules containing a driving electrolyte during manufacturing. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2013-243170 [Patent Document 2] Japanese Patent Application Laid-Open No. 63-199410 [Patent Document 3] Japanese Patent Application Publication No. 61-121417 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] When electrolytic capacitors are used for extended periods or in high-temperature environments, the liquid components impregnated into the capacitor element (e.g., electrolyte) may deteriorate due to oxygen contained within the case (e.g., oxygen contained in the liquid components or oxygen contained in the gas phase within the case). Furthermore, if the electrolytic capacitor contains a solid electrolyte such as a conductive polymer, the solid electrolyte may also deteriorate during use due to oxygen contained within the case. Thus, deterioration of the liquid components and / or solid electrolyte may lead to a decrease in capacitance and an increase in equivalent series resistance (ESR), resulting in a decline in the characteristics of the electrolytic capacitor.

[0008] While the aforementioned Patent Document 1 and others disclose technologies for suppressing the combustion of electrolytic capacitors even in the event of ignition using microcapsules, and technologies for ensuring that the driving electrolyte is completely impregnated into the capacitor element during manufacturing, sufficient research has not yet been conducted on how to adequately suppress the degradation of electrolytic capacitor characteristics when electrolytic capacitors are used for a long period of time or in high-temperature environments using microcapsules.

[0009] Therefore, this disclosure provides an electrolytic capacitor that can sufficiently suppress performance degradation when used for a long period of time or when used in a high-temperature environment. [Means for solving the problem]

[0010] One aspect of the present invention relates to an electrolytic capacitor. The electrolytic capacitor comprises a capacitor element, a liquid component impregnated into the capacitor element, a plurality of microcapsules, and a case housing the capacitor element, the liquid component, and the plurality of microcapsules. The capacitor element includes an anode foil having a dielectric layer, a cathode foil disposed opposite to the dielectric layer, a separator interposed between the anode foil and the cathode foil, and a conductive polymer layer interposed between the anode foil and the cathode foil and in contact with the separator. Each of the plurality of microcapsules contains a degradation prevention component, and the capsule wall of each of the plurality of microcapsules ruptures when predetermined conditions are met, releasing the degradation prevention component to the outside.

[0011] Another aspect of the present invention relates to an electrolytic capacitor. The electrolytic capacitor comprises a capacitor element, a liquid component impregnated into the capacitor element, a plurality of microcapsules, and a case housing the capacitor element, the liquid component, and the plurality of microcapsules. The capacitor element includes an anode foil having a dielectric layer, a cathode foil disposed opposite to the dielectric layer, a separator interposed between the anode foil and the cathode foil, and a conductive polymer layer interposed between the anode foil and the cathode foil and in contact with the separator. Each of the plurality of microcapsules contains a conductive polymer, and the capsule wall of each of the plurality of microcapsules ruptures when predetermined conditions are met, releasing the conductive polymer to the outside. [Effects of the Invention]

[0012] According to this disclosure, it is possible to provide an electrolytic capacitor that can sufficiently suppress performance degradation when used for a long period of time or when used in a high-temperature environment. [Brief explanation of the drawing]

[0013] [Figure 1] This is a schematic cross-sectional view of an electrolytic capacitor according to one embodiment of the present disclosure. [Figure 2] Figure 1 is a schematic diagram showing a portion of the capacitor elements of the electrolytic capacitor. [Modes for carrying out the invention]

[0014] The embodiments of this disclosure will be described below with examples, but this disclosure is not limited to the examples described below. In the following description, specific numerical values ​​and materials may be given as examples, but other numerical values, materials, etc. may be applied as long as the effects of this disclosure are obtained. Notwithstanding, known components may be applied to components of parts that are characteristic of this disclosure. In this specification, when "the range of numerical values ​​A to numerical values ​​B" is used, that range includes numerical values ​​A and B.

[0015] In the following description, when the lower limit and the upper limit of numerical values related to specific physical properties, conditions, etc. are exemplified, as long as the lower limit is not greater than the upper limit, any combination of any of the exemplified lower limits and any of the exemplified upper limits can be made. When a plurality of materials are exemplified, unless otherwise specified, one of them may be selected and used alone, or two or more of them may be used in combination.

[0016] This disclosure includes combinations of matters described in two or more claims arbitrarily selected from a plurality of claims described in the appended claims. That is, as long as no technical contradiction occurs, matters described in two or more claims arbitrarily selected from a plurality of claims described in the appended claims can be combined.

[0017] [First Embodiment] The electrolytic capacitor according to the first embodiment of the present disclosure includes a capacitor element, a liquid component impregnated in the capacitor element, a plurality of microcapsules, and a case that houses the capacitor element, the liquid component, and the plurality of microcapsules.

[0018] In the electrolytic capacitor according to the first embodiment, the capacitor element includes an anode foil having a dielectric layer, a cathode foil arranged to face the dielectric layer, a separator interposed between the anode foil and the cathode foil, and a conductive polymer layer interposed between the anode foil and the cathode foil and in contact with the separator.

[0019] In the electrolytic capacitor according to the first embodiment, each of the plurality of microcapsules encapsulates a deterioration prevention component, and the capsule wall of each of the plurality of microcapsules breaks to release the deterioration prevention component to the outside when a predetermined condition is satisfied.

[0020] Hereinafter, the configuration of the electrolytic capacitor according to the first embodiment will be described.

[0021] [Capacitor Element] As described above, the capacitor element includes an anode foil, a cathode foil, a separator, and a conductive polymer layer. The anode foil, cathode foil, separator, and conductive polymer layer will be described below.

[0022] (Anode foil) Examples of anode foils include metal foils containing at least one valve metal such as titanium, tantalum, aluminum, and niobium. The anode foil may also be a metal foil of the valve metal (for example, aluminum foil). The anode foil may contain the valve metal in the form of an alloy containing the valve metal or a compound containing the valve metal. The thickness of the anode foil may be 15 μm or more and 300 μm or less. At least one main surface of the anode foil may be roughened by etching or the like. Preferably, both main surfaces of the anode foil are roughened.

[0023] A dielectric layer is formed on at least one main surface of the anode foil. The dielectric layer may be formed by chemical conversion treatment of the anode foil. In this case, the dielectric layer may contain an oxide of the valve metal (e.g., aluminum oxide). The dielectric layer may be formed of any dielectric material other than an oxide of the valve metal, as long as it functions as a dielectric.

[0024] A dielectric layer may or may not be formed on the end face of the anode foil. However, it is preferable that a dielectric layer be formed on the end face of the anode foil. For example, in a wound capacitor element as shown in Figure 2, it is preferable that dielectric layers be formed on the upper and lower end faces of the anode foil in the wound body.

[0025] (Cathode foil) The cathode foil is not particularly limited as long as it has the function of a cathode. Examples of cathode foils include metal foil (for example, aluminum foil). The type of metal contained in the metal foil is not particularly limited. The metal may be a valve metal or an alloy containing a valve metal. The thickness of the cathode foil may be 15 μm or more and 300 μm or less. At least one main surface of the cathode foil may have an etched layer or a dielectric layer formed on it, as necessary, similar to the anode foil. That is, at least one main surface of the cathode foil may be roughened or chemically treated, as necessary.

[0026] The cathode foil may include a conductive coating layer. If the metal foil includes a valve metal, the coating layer may include at least one of carbon and a metal with a lower ionization tendency than the valve metal. This makes it easier to improve the acid resistance of the metal foil. If the metal foil includes aluminum, the coating layer may include at least one selected from the group consisting of carbon, nickel, titanium, tantalum, and zirconium. With an emphasis on low cost and low resistance, the coating layer may include at least one of nickel and titanium.

[0027] The thickness of the coating layer may be 5 nm or more, or 10 nm or more. The thickness of the coating layer may be 200 nm or less. The coating layer may be formed by depositing or sputtering the above-mentioned metal onto a metal foil. Alternatively, the coating layer may be formed by depositing a conductive carbon material onto a metal foil, or by applying a carbon paste containing a conductive carbon material. Examples of conductive carbon materials include graphite, hard carbon, soft carbon, and carbon black.

[0028] (Separator) A porous sheet can be used as the separator. Examples of porous sheets include woven fabrics, nonwoven fabrics, and microporous membranes. The thickness of the separator is not particularly limited and may be in the range of 10 μm to 300 μm. Examples of separator materials include cellulose, polyethylene terephthalate, polybutylene terephthalate, polyphenyl sulfide, vinylon, nylon, aromatic polyamide, polyimide, polyamideimide, polyetherimide, rayon, and glass.

[0029] (Conductive polymer layer) The conductive polymer layer is formed by a conductive polymer. Preferably, the conductive polymer layer is formed by conductive polymer particles. Examples of conductive polymers include polypyrrole, polythiophene, polyaniline, and their derivatives. The conductive polymer may be used alone or in combination of two or more types. The conductive polymer may also be a copolymer of two or more monomers. A derivative of a conductive polymer refers to a polymer that has a conductive polymer as its basic skeleton. For example, derivatives of polythiophene include poly(3,4-ethylenedioxythiophene).

[0030] The conductive polymer may contain a dopant. The dopant can be appropriately selected depending on the type of conductive polymer. Various known dopants may be used as dopants. Examples of dopants include naphthalene sulfonic acid, p-toluenesulfonic acid, polystyrene sulfonic acid, and salts thereof. An example of a conductive polymer is poly(3,4-ethylenedioxythiophene) (PEDOT) doped with polystyrene sulfonic acid (PSS). In the electrolytic capacitor according to the first embodiment of this disclosure, the conductive polymer layer is preferably formed of particles of poly(3,4-ethylenedioxythiophene) (PEDOT) (hereinafter also referred to as PEDOT / PSS) doped with polystyrene sulfonic acid (PSS).

[0031] It is preferable that the conductive polymer layer is in contact with the anode foil, cathode foil, and separator with a sufficiently large contact area. This allows the conductive polymer layer to form a sufficient conductive path between the anode foil and cathode foil. As a result, the equivalent series resistance (ESR) of the electrolytic capacitor can be reduced, thereby improving the reliability of the electrolytic capacitor.

[0032] The conductive polymer layer is preferably formed on at least one surface of the dielectric layer of the anode foil. It is also preferable that the conductive polymer layer is formed on the surface of the cathode foil facing the dielectric layer. The conductive polymer layer may also be formed within the voids of the separator (i.e., on the surface of the separator's constituent material surrounding the voids of the separator). This allows for the formation of a stronger conductive path between the anode foil and the cathode foil by the conductive polymer layer. The conductive polymer layer is preferably formed on at least the surface of the dielectric layer of the anode foil, more preferably on both the surface of the dielectric layer and the surface of the cathode foil, and more preferably within the voids of the separator. It is preferable that the conductive polymer layer is formed to continuously connect the surface of the dielectric layer and the surface of the cathode foil.

[0033] A conductive polymer layer can be formed, for example, by applying a polymer dispersion, in which a conductive polymer and a dopant are dispersed in a liquid medium, to a dielectric layer, and then removing at least a portion of the liquid medium. Alternatively, the conductive polymer layer may be formed by impregnating a separator with the polymer dispersion or coating a separator with the polymer dispersion, and then removing at least a portion of the liquid medium. Furthermore, the conductive polymer layer can also be formed by applying a polymerization solution containing monomers that form the constituent units of a conductive polymer and a dopant to a dielectric layer, and then chemically or electrolytically polymerizing the monomers in the dielectric layer in the presence of the dopant. For electrolytic capacitors to exhibit excellent voltage withstand characteristics, it is preferable that the conductive polymer layer be formed using a polymer dispersion.

[0034] <Case> The case houses a capacitor element, a liquid component, and a plurality of microcapsules. The case may be a bottomed case having a space for housing the capacitor element, the liquid component, and the plurality of microcapsules. The bottomed case can be manufactured, for example, by processing a metal plate into a predetermined shape. The case may be a resin exterior made using a sealing resin. Various known resins can be used as the sealing resin. The sealing resin may include a thermosetting resin. Examples of thermosetting resins include epoxy resins, phenolic resins, silicone resins, melamine resins, urea resins, alkyd resins, polyurethane resins, polyimide resins, and unsaturated polyester resins. The sealing resin may contain at least one selected from the group consisting of fillers, curing agents, polymerization initiators, and catalysts.

[0035] <Liquid component> The liquid component includes an electrolyte and / or an ionic liquid. As the electrolyte, a non-aqueous electrolyte containing a non-aqueous solvent and a solute dissolved in the non-aqueous solvent can be used. The non-aqueous solvent may be an organic solvent. For the non-aqueous solvent and solute, non-aqueous solvents and solutes used in various known electrolytic capacitors can be used. The liquid component may be a component that is liquid at room temperature (25°C), or a component that is liquid at the temperature at which the electrolytic capacitor is used.

[0036] Examples of organic solvents include glycol compounds, sulfone compounds, and lactone compounds. Examples of glycol compounds include ethylene glycol (EG), diethylene glycol (DEG), triethylene glycol (TEG), and propylene glycol (PG). Examples of sulfone compounds include sulfolane (SL), dimethyl sulfoxide (DMSO), and diethyl sulfoxide (DESO). Examples of lactone compounds include γ-butyrolactone (GBL) and γ-valerolactone (GVL).

[0037] Examples of organic solvents include carbonate compounds and monohydric or trihydric or higher alcohols. 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 monohydric or trihydric or higher alcohols include glycerin and polyglycerin. These may be used individually or in combination of two or more.

[0038] In organic solvents, if the group consisting of glycol compounds, sulfone compounds, and lactone compounds is designated as Group 1, and the group consisting of carbonate compounds and monohydric or trihydric or higher alcohols is designated as Group 2, then it is preferable that the organic solvents belonging to Group 1 make up more than 50% by mass of the organic solvent, more preferably 60% by mass or more, and more preferably 70% by mass or more. The entirety of the organic solvent may consist of organic solvents belonging to Group 1. That is, the organic solvent belonging to Group 1 may be the main solvent, and the organic solvent belonging to Group 2 may be the secondary solvent.

[0039] The liquid component preferably contains at least one organic solvent selected from the group consisting of glycol compounds, sulfone compounds, and lactone compounds. When the liquid component contains at least one of these compounds, the re-formation of the dielectric layer by the acid component contained in the liquid component can be efficiently carried out. Furthermore, the presence of a glycol compound in the liquid component allows the conductive polymer constituting the conductive polymer layer to receive protons (H) from the glycol compound. + )(Specifically, the proton (H) contained in the hydroxyl group +This allows for easy provision of a phosphate group. In other words, it improves the affinity with the conductive polymer layer. Furthermore, since sulfone compounds and lactone compounds are aprotic, the presence of at least one of the sulfone compound and lactone compound in the liquid component suppresses the reaction of the liquid component with the acid component described later (e.g., esterification reaction). In this case, even if the electrolytic capacitor is exposed to temperatures of 120°C or higher during automobile operation or to temperatures exceeding 200°C during reflow mounting, as described later, the stability of the liquid component can be improved. This helps to stabilize the characteristics of the electrolytic capacitor.

[0040] From the viewpoint of donating protons to the conductive polymer, the liquid component may contain compounds other than glycol compounds. Examples of such other compounds include glycerin and polyglycerin.

[0041] The liquid component may contain water. The water content in the liquid component may be between 0.1% by mass and 6.0% by mass, between 0.2% by mass and 4.0% by mass, or between 0.5% by mass and 2.0% by mass. Including water in the liquid component within the above ranges enhances the repairability of the dielectric layer by the liquid component. Furthermore, even if the electrolytic capacitor is exposed to temperatures above 120°C during automobile operation or above 200°C during reflow mounting, as described later, fluctuations in the equivalent series resistance (ESR) can be suppressed. Since sulfone compounds have excellent hydrolysis resistance, as described above, if the liquid component contains a sulfone compound, the hydrolysis resistance of the liquid component can be enhanced.

[0042] The liquid component contains an acid component (acid) and a base component (base) as solutes. The base component is also called a cationic component, and the acid component is also called an anionic component. The proportion of solute in the liquid component is preferably 70% by mass or less, and more preferably 50% by mass or less.

[0043] The acid component may be at least one selected from the group consisting of aromatic carboxylic acids, aliphatic carboxylic acids, and salts thereof. The aromatic carboxylic acids and aliphatic carboxylic acids may be polycarboxylic acids or monocarboxylic acids. Examples of aliphatic polycarboxylic acids include saturated polycarboxylic acids and unsaturated polycarboxylic acids. Examples of saturated polycarboxylic acids include oxalic acid, malonic acid, succinic acid, glutanoic acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebatic acid, 1,6-decanedicarboxylic acid, and 5,6-decanecarboxylic acid, while examples of unsaturated polycarboxylic acids include maleic acid, fumaric acid, and itaconic acid. Examples of aromatic polycarboxylic acids include phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, pyromellitic acid, and benzoic acid. Phthalic acid may also be o-phthalic acid. An example of an aromatic monocarboxylic acid is salicylic acid.

[0044] Examples of polycarboxylic acids include alicyclic polycarboxylic acids. Examples of alicyclic polycarboxylic acids include cyclohexane-1,2-dicarboxylic acid and cyclohexene-1,2-dicarboxylic acid.

[0045] Examples of monocarboxylic acids include aliphatic monocarboxylic acids and aromatic monocarboxylic acids. In this specification, aromatic monocarboxylic acids are a concept that includes oxycarboxylic acids. Examples of aliphatic monocarboxylic acids include saturated monocarboxylic acids and unsaturated monocarboxylic acids. Examples of saturated monocarboxylic acids include formic acid, acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, lauric acid, myristic acid, stearic acid, and behenic acid, while examples of unsaturated monocarboxylic acids include acrylic acid, methacrylic acid, and oleic acid. Examples of aromatic monocarboxylic acids include benzoic acid, cinnamic acid, and naphthoic acid. Examples of oxycarboxylic acids include salicylic acid, mandelic acid, and resorcinic acid.

[0046] As the aromatic carboxylic acid, it is preferable to use at least one selected from the group consisting of o-phthalic acid, salicylic acid, and benzoic acid. As the aliphatic carboxylic acid, it is preferable to use at least one selected from the group consisting of adipic acid, azelaic acid, and sebacic acid.

[0047] Inorganic acids may be used as the acid component. Examples of inorganic acids include phosphoric acid, phosphorous acid, hypophosphorous acid, alkyl phosphate esters, boric acid, borofluoric acid, tetrafluoroboric acid, hexafluorophosphoric acid, benzenesulfonic acid, and naphthalenesulfonic acid. Alternatively, a composite compound of an organic acid and an inorganic acid may be used as the acid component. Examples of such composite compounds include dicarboxylic acid derivatives such as borodiglycolic acid, borodisalic acid, and borodisalicylic acid.

[0048] The basic component may be a compound having an alkyl-substituted amidine group, such as imidazole compounds, benzimidazole compounds, and alicyclic amidine compounds (pyrimidine compounds, imidazoline compounds). Specifically, 1,8-diazabicyclo[5,4,0]undecene-7; 1,5-diazabicyclo[4,3,0]nonene-5; 1,2-dimethylimidazolinium; 1,2,4-trimethylimidazoline; 1-methyl-2-ethylimidazoline; 1,4-dimethyl-2-ethylimidazoline; 1-methyl-2-heptylimidazoline; 1-methyl-2-(3'heptyl)imidazoline; 1-methyl-2-dodecylimidazoline; 1,2-dimethyl-1,4,5,6-tetrahydropyrimidine; 1-methylimidazole; and 1-methylbenzimidazole are preferred. By using these methods, electrolytic capacitors can be made to have excellent impedance characteristics.

[0049] As the base component, a quaternary salt of a compound having an alkyl-substituted amidine group may be used. Examples of such base components include imidazole compounds, benzimidazole compounds, and alicyclic amidine compounds (pyrimidine compounds, imidazoline compounds) that have been quaternized with an alkyl or arylalkyl group having 1 to 11 carbon atoms. Specifically, 1-methyl-1,8-diazabicyclo[5,4,0]undecene-7; 1-methyl-1,5-diazabicyclo[4,3,0]nonene-5; 1,2,3-trimethylimidazolinium; 1,2,3,4-tetramethylimidazolinium; 1,2-dimethyl-3-ethylimidazolinium; 1,3,4-trimethyl-2-ethylimidazolinium; 1,3-dimethyl-2-heptylimidazolinium; 1,3-dimethyl-2-(3'heptyl)imidazolinium; 1,3-dimethyl-2-dodecylimidazolinium; 1,2,3-trimethyl-1,4,5,6-tetrahydropyrimidium; 1,3-dimethylimidazolium; 1-methyl-3-ethylimidazolium; and 1,3-dimethylbenzimidazolium are preferred. By using these methods, electrolytic capacitors can be made to have excellent impedance characteristics.

[0050] Tertiary amines may be used as the base component. Examples of tertiary amines include trialkylamines and phenyl group-containing amines. Examples of trialkylamines include trimethylamine, dimethylethylamine, methyldiethylamine, triethylamine, dimethyl-n-propylamine, dimethylisopropylamine, methylethyl-n-propylamine, methylethylisopropylamine, diethyl-n-propylamine, diethylisopropylamine, tri-n-propylamine, triisopropylamine, tri-n-butylamine, and tri-tert-butylamine. Examples of phenyl group-containing amines include dimethylphenylamine, methylethylphenylamine, and diethylphenylamine. From the viewpoint of increasing conductivity, it is preferable to use trialkylamines, and among trialkylamines, it is preferable to use at least one selected from the group consisting of trimethylamine, dimethylethylamine, methyldiethylamine, and triethylamine. As the base component, secondary amines such as dialkylamines, primary amines such as monoalkylamines, and ammonia may be used.

[0051] Heterocyclic amines may be used as the base component. Examples of heterocyclic amines include morpholines, and examples of morpholines include morpholine and morpholine derivatives. Specifically, examples include morpholine, N-alkylmorpholine, and N-hydroxyalkylmorpholine, and examples of N-alkylmorpholine include N-methylmorpholine, N-butylmorpholine, and 4-isobutylmorpholine. In addition, pyridine and imidazole can also be used as heterocyclic amines.

[0052] The liquid component may contain a salt of an acid component and a base component. The salt may be an inorganic salt or an organic salt. An organic salt is a salt in which at least one of the anion and cation contains an organic substance. Examples of organic salts include trimethylamine maleate, triethylamine borodisalicylate, ethyldimethylamine phthalate, mono-1,2,3,4-tetramethylimidazolinium phthalate, and mono-1,3-dimethyl-2-ethylimidazolinium phthalate. The organic salt may be an amine salt of a long-chain dibasic carboxylic acid. Examples of amine salts of long-chain dibasic carboxylic acids include diethylamine 2-butyloctanedioate (2BA).

[0053] An ionic liquid is synonymous with a molten salt (molten salt), for example, an ionic substance that is liquid at 25 °C.

[0054] Examples of cations constituting the ionic liquid include cations of nitrogen atom-containing heterocycles (imidazolium, pyrrolidinium, piperidinium, pyridinium, morpholinium, etc.), ammonium, phosphonium, sulfonium, and derivatives thereof (substituted products having substituents such as alkyl groups). The cation may be an organic cation.

[0055] Examples of anions constituting the ionic liquid include hydrogen sulfate ion (HSO4 - ), sulfate ion (SO4 2- , -SO4 - ), carboxylate anion (-COO - ), nitrate anion, sulfonate anion (-SO3 - ), and phosphonate anion (PO3 2- , -HPO3 -Examples include the above. Acids capable of generating these anions include sulfuric acid, sulfuric acid monoesters (such as methyl sulfuric acid), carboxylic acids (such as acetic acid, lactic acid, benzoic acid, and trifluoromethaneacetic acid), nitric acid, sulfonic acids (such as methanesulfonic acid, trifluoromethanesulfonic acid, and bis(trifluoromethylsulfonyl)imide anion), phosphonic acids (such as diethylphosphonic acid), and derivatives thereof (substituted products having substituents such as alkyl groups, halogenated alkyl groups, and halogen atoms). The anions may also contain a fluorine atom. Examples of fluorine atom-containing anions include the above-mentioned trifluoromethaneacetic acid, trifluoromethanesulfonic acid, bis(trifluoromethylsulfonyl)imide anion, and derivatives thereof.

[0056] Specific examples of ionic liquids include 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, 1-butyl-3-methylimidazolium trifluoromethanesulfonic acid, and 1-ethyl-3-methylimidazolium diethylphosphonic acid.

[0057] The liquid component may contain a polymer compound. Examples of polymer compounds include polyalkylene glycol, derivatives of polyalkylene glycol, and compounds in which at least one hydroxyl group of a polyhydric alcohol is substituted with polyalkylene glycol (including derivatives). Specifically, examples include polyethylene glycol (PEG), polyethylene glycol glyceryl ether, polyethylene glycol diglyceryl ether, polyethylene glycol sorbitol ether, polypropylene glycol, polypropylene glycol diglyceryl ether, polypropylene glycol sorbitol ether, and polybutylene glycol.

[0058] Polyalkylene glycol may be a copolymer (such as a random copolymer, a block copolymer, or a random block copolymer). For example, it may be a copolymer of ethylene glycol and propylene glycol, a copolymer of ethylene glycol and butylene glycol, and a copolymer of propylene glycol and butylene glycol.

[0059] The polymer compound may be a copolymer having ethylene oxide (EO) units and propylene oxide (PO) units. The copolymer includes copolymers of EO and PO (EO-PO copolymers) and their derivatives. These may be used individually or in combination of two or more. The copolymer may be crosslinked with a crosslinking agent. Examples of the derivatives include EO-PO copolymers in which the hydroxyl groups (-OH) normally present at the ends are replaced with acrylic groups (O-CO-CH=CH2) or the like. When the entire EO-PO copolymer is considered as 1 mole, the molar ratio of EO units to PO units is preferably EO:PO = 0.9:0.1 to 0.5:0.5. That is, in the EO-PO copolymer, it is preferable that the amount of EO units is equal to or greater than the amount of PO units. This makes it possible to suppress the permeation of the EO-PO copolymer contained in the liquid component from the sealing member in an electrolytic capacitor in which the capacitor element is housed in a bottomed case and the opening of the bottomed case is sealed with a sealing member (such as sealing rubber).

[0060] The weight-average molecular weight Mw of the polymer compound may be 200 or more, 300 or more, 400 or more, or 500 or more. The weight-average molecular weight Mw of the polymer compound may be 5000 or less, 4000 or less, 3000 or less, 2000 or less, or 1000 or less. Note that the weight-average molecular weight Mw of the polymer compound is a polystyrene equivalent value measured by gel permeation chromatography (GPC).

[0061] The liquid component preferably contains an antioxidant. This prevents the acidic component in the liquid component from being oxidized and degraded by oxygen contained in the case. It also prevents the conductive polymer constituting the conductive polymer layer from being oxidized and degraded by oxygen contained in the case. The antioxidant may include at least one selected from the group consisting of phenolic antioxidants, amine antioxidants, phosphorus antioxidants, sulfur-based antioxidants, and aliphatic antioxidants. Among these, phenolic antioxidants are preferred from the viewpoint of reactivity with oxygen.

[0062] The phenolic antioxidant preferably includes at least one selected from the group consisting of monophenolic antioxidants, bisphenolic antioxidants, and polyphenolic antioxidants. Among these, polyphenolic antioxidants are preferred from the viewpoint of having many functional groups that react well with oxygen.

[0063] The monophenol antioxidants preferably include 2,6-di-tert-butyl-4-methylphenol, butylhydroxyanisole, sesamol, tocopherol, tocotrienol, and p-nitrophenol. The monophenol antioxidants may also include mono, di, or tri(α-methylbenzyl)phenol, trolox, normelatonin, and ferulic acid.

[0064] The material may also contain a bisphenol-based antioxidant, preferably an anoxomer. Furthermore, it may also contain bisphenol-based antioxidants such as 2,2'-methylenebis(4-ethyl-6-tert-butylphenol), 2,2'-methylenebis(4-methyl-6-tert-butylphenol), 4,4'-butylidenebis(3-ethyl-6-tert-butylphenol), 4,4'-thiobis(3-ethyl-6-tert-butylphenol), and the butylation reaction product of p-cresol and dicyclopentadiene.

[0065] The polyphenol antioxidants preferably include 2,5-di-tert-butylhydroquinone, 2,5-di-tert-amylhydroquinone, gallic acid, propyl gallate, chlorogenic acid, catechin, epigallocatechin, epigallocatechin gallate, rosmarinic acid, genkwanin, luteolin, carnosic acid, carnosol, ursolic acid, pyrogallol, kebradic acid, hydroxytyrosol, dopamine, caffeic acid, adrenaline, noradrenaline, catechol, bouciol, hydroquinone, and resorcinol.

[0066] Furthermore, the polyphenol antioxidants may include protocatechuic acid, rutin, gnetin C, theaflavin, luteolin, resveratrol, pinosembrin, pinobanksin, 1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, and 4,4',4”-(1-methylpropanyl-3-ylidene)tris(6-tert-butyl-m-cresol).

[0067] Amine-based antioxidants include aromatic secondary amine antioxidants, benzotriazole antioxidants, benzimidazole antioxidants, and amine-ketone antioxidants.

[0068] Aromatic secondary amine antioxidants include N-phenyl-1-naphthylamine, diphenylamine antioxidants, and phenylenediamine antioxidants. Diphenylamine antioxidants include alkylated diphenylamines such as p,p'-dioctyldiphenylamine, 4,4'-bis(α,α-dimethylbenzyl)diphenylamine, and p-(p-toluenesulfonylamide)diphenylamine. Phenylenediamine antioxidants include N,N'-di-2-naphthyl-p-phenylenediamine, N-phenyl-N'-isopyropyr-p-phenylenediamine, N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine, and N-phenyl-N'-(3-methacryloyloxy-2-hydroxypropyl)-p-phenylenediamine.

[0069] Benzotriazole antioxidants include benzotriazole, etc. Benzimidazole antioxidants include benzimidazole, 2-mercapto-benzoimidazole, 2-mercaptomethyl-benzoimidazole, and imidazole dipeptides, etc.

[0070] Amine-ketone antioxidants include 2,2,4-trimethyl-1,2-dihydroquinoline polymer, 6-ethoxy-1,2-dihydro-2,2,4-trimethylquinoline, a reaction product of diphenylamine and acetone, acetylcysteine, and melatonin.

[0071] Phosphorus-based antioxidants include phosphate ester antioxidants and phosphite ester antioxidants. Examples of esters include monoalkyl esters, dialkyl esters, and trialkyl esters. Examples of phosphite ester antioxidants include tris(nonylphenyl)phosphite.

[0072] Sulfur-based antioxidants include thioether-based antioxidants, isothiocyanates, sulfites, and pyrosulfites. Thioether-based antioxidants include phenothiazines, dibenzyl disulfide, diacetyl sulfide, and dilauryl thiodipropionate.

[0073] Aliphatic antioxidants include citric acid, L-ascorbic acid, erythorbic acid, and ethylenediaminetetraacetic acid.

[0074] The antioxidant may be used alone or in combination of two or more types. The antioxidant content in the liquid component is, for example, 0.5% by mass or more and 30% by mass or less of the total liquid component. Liquid chromatography (LC), gas chromatography-mass spectrometry (GC / MS), etc., can be used for the analysis of the antioxidant.

[0075] <Microcapsules> In the electrolytic capacitor according to the first embodiment, the case houses a plurality of microcapsules. In the electrolytic capacitor according to the first embodiment, the plurality of microcapsules contain a degradation-preventing component. Specifically, the microcapsules have capsule walls, and the degradation-preventing component is contained inside the capsule walls by being enclosed within them. In other words, in the electrolytic capacitor according to the first embodiment, the core material of each of the plurality of microcapsules is a degradation-preventing component.

[0076] In the electrolytic capacitor according to the first embodiment, the degradation prevention component preferably includes at least one of an antioxidant and an acid component. The antioxidant and acid component can be those exemplified above.

[0077] The capsule walls of microcapsules can be constructed using various known organic compounds. Examples of organic compounds include gum arabic (acacia resin), epoxy resin, phenolic resin, polyphenylene sulfide resin, polyimide resin, polyaramid resin, melamine resin, polyurea resin, and polyurethane resin.

[0078] As described above, in the electrolytic capacitor according to the first embodiment, the capsule wall of each of the multiple microcapsules ruptures when predetermined conditions are met, releasing degradation-preventing components to the outside. Preferably, the predetermined conditions are that the liquid component has a pH of or above a predetermined level, or that the liquid component has a temperature of or above a predetermined level. In one example, the predetermined pH is preferably 7. Alternatively, the predetermined pH may be 5. Furthermore, in one example, the predetermined temperature of the liquid component is preferably 100°C, and in another example, it is preferably 200°C. The timing of the rupture of each of the multiple microcapsule walls can be adjusted by appropriately selecting, for example, the size of the microcapsule, the thickness of the capsule wall, and the constituent material of the capsule wall.

[0079] The liquid component typically contains acidic components such as aromatic carboxylic acids and aliphatic carboxylic acids, as described above, in order to repair defects in the dielectric layer (in other words, to regenerate the dielectric layer). If the liquid component contains an antioxidant, the oxidation of the acidic components can be prevented in the presence of the antioxidant. Furthermore, the oxidation of the conductive polymer constituting the conductive polymer layer can be prevented in the presence of the antioxidant. However, when the antioxidant contained in the liquid component is consumed and depleted, the acidic components or the conductive polymer will begin to oxidize. As a result of the oxidation and disappearance of the acidic components, the pH of the liquid component rises by the amount of the acidic components that have been lost. Therefore, when the pH of the liquid component rises above a predetermined level, the capsule walls of each of the multiple microcapsules rupture, allowing the degradation prevention components contained within the multiple microcapsules to be released to the outside.

[0080] For example, if the degradation-preventing component is an antioxidant, it can suppress further oxidation of acidic components in the liquid component. It can also suppress further oxidation of conductive polymers. Furthermore, if the degradation-preventing component is an acidic component, it can replenish the acidic components that have been lost due to oxidation. Considering the effects of the degradation-preventing component described above, it is preferable that multiple microcapsules contain at least an antioxidant. This can suppress further oxidation of acidic components and conductive polymers. It is even more preferable that multiple microcapsules contain both an antioxidant and an acidic component. This can suppress further oxidation of acidic components and conductive polymers, as well as replenish the acidic components that have been lost in the liquid component. In this case, each of the multiple microcapsules may contain both an antioxidant and an acidic component, or some of the multiple microcapsules may contain an antioxidant and the remaining microcapsules may contain an acidic component.

[0081] In electrolytic capacitors, the pH of the liquid component is usually biased towards the acidic side (for example, pH 4-6). Therefore, by setting the predetermined pH to 7, the acidic components contained in the liquid component are prevented from being excessively oxidized and lost, and the pH of the liquid component does not exceed 7. This is achieved by rupturing the capsule walls of multiple microcapsules at a more appropriate timing, thereby supplying degradation-preventing components to the liquid component.

[0082] Furthermore, electrolytic capacitors are sometimes used in various devices such as automatic braking systems, image recognition systems, and sensor-related devices for safety-related technologies related to advanced driver-assistance systems (ADAS) aimed at improving safety performance, and for realizing automobiles equipped with autonomous driving functions. In other words, electrolytic capacitors are sometimes used in automotive applications. Here, the above-mentioned devices are constructed by mounting their components at high density. Alternatively, the above-mentioned devices may be installed in high-temperature environments. Therefore, the temperature of the above-mentioned devices may rise during the operation of the automobile. In this case, the electrolytic capacitor is exposed to high temperatures, and the degradation of the liquid component is more likely to progress due to oxygen contained in the case. Also, the degradation of the conductive polymer constituting the conductive polymer layer is more likely to progress due to oxygen contained in the case. Therefore, when the liquid component reaches a certain temperature or higher, the capsule walls of each of the multiple microcapsules rupture, allowing the degradation prevention components contained in the multiple microcapsules to be released to the outside.

[0083] For example, if the degradation-preventing component is an antioxidant, it can suppress further oxidation of acidic components in the liquid component. It can also suppress further oxidation of conductive polymers. Furthermore, if the degradation-preventing component is an acidic component, it can replenish the acidic components that have been lost due to oxidation. Similarly, it is preferable that multiple microcapsules contain at least an antioxidant, and more preferably both an antioxidant and an acidic component.

[0084] Furthermore, during vehicle operation, automotive electrolytic capacitors can be exposed to temperatures exceeding 120°C. Therefore, for automotive electrolytic capacitors, the predetermined temperature of the liquid component is more preferably 100°C. This allows the capsule walls of multiple microcapsules to rupture at a more appropriate timing, preventing excessive oxidation and loss of the acidic component contained in the liquid component, and thereby supplying degradation-preventing components to the liquid component.

[0085] Furthermore, electrolytic capacitors are sometimes reflow-mounted onto circuit boards using solder. The melting point of solder (including eutectic solder of tin and lead) is usually 180°C or higher, and reflow mounting is usually performed at a temperature 40°C to 60°C higher than the melting point of the solder. Therefore, electrolytic capacitors may be exposed to temperatures exceeding 200°C during reflow mounting. When electrolytic capacitors are exposed to such high temperatures, the degradation of acidic components is more likely to progress due to oxygen and other substances contained within the case. In addition, the degradation of the conductive polymer constituting the conductive polymer layer is more likely to progress due to oxygen and other substances contained within the case. Therefore, in this case as well, when the liquid component reaches a predetermined temperature or higher, the capsule walls of each of the multiple microcapsules rupture, allowing the degradation-preventing components contained within the multiple microcapsules to be released to the outside.

[0086] Considering the above temperatures, it is more preferable that the predetermined temperature of the liquid component be 200°C during reflow mounting of electrolytic capacitors. This allows the capsule walls of multiple microcapsules to rupture at a more appropriate timing, preventing excessive oxidation and loss of the acidic component contained in the liquid component, and thereby supplying degradation-preventing components to the liquid component.

[0087] The size of the microcapsules is, for example, between 0.02 μm and 100 μm. The size of the microcapsule refers to the diameter of the circumscribed circle of the microcapsule when viewed from above. Microcapsules of the above size can also be used in the electrolytic capacitor according to the second embodiment.

[0088] Methods for encapsulating a degradation inhibitor in microcapsules include, for example, (1) chemical methods such as interfacial polymerization and in-situ polymerization, (2) physicochemical methods such as liquid drying and coacervation, and (3) mechanical methods such as dry mixing and spray drying. In the electrolytic capacitor according to the second embodiment, the conductive polymer can also be encapsulated in microcapsules by any of the above methods (1) to (3).

[0089] Multiple microcapsules can be housed in a case, for example, in the form of a dispersion (hereinafter also referred to as the first dispersion) in which multiple microcapsules are dispersed in a liquid component (first method). The first dispersion may be injected into the case after the capacitor element has been housed in the case. In this case, the first dispersion may be injected into the void formed between the capacitor element and the inner surface of the case. This allows multiple microcapsules to be placed in the void formed between the capacitor element and the inner surface of the case. By placing multiple microcapsules in the above-mentioned void, the amount of oxygen present in the void can be reduced, thereby mitigating the oxidation of the acid component contained in the liquid component caused by the air (oxygen) present in the case. Furthermore, oxidation of the conductive polymer constituting the conductive polymer layer can be mitigated. The packing rate of the multiple microcapsules in the above-mentioned void is preferably 5% by volume or more. The upper limit of the packing rate of the multiple microcapsules is, for example, 50% by volume.

[0090] Furthermore, multiple microcapsules can also be housed in a case by first impregnating a capacitor element with the first dispersion described above, and then placing this impregnated body inside the case (second method). In addition, multiple microcapsules can also be housed in a case by first attaching multiple microcapsules to at least one of the anode foil, cathode foil, and separator components, and then placing the capacitor element containing the component with the attached microcapsules inside the case (third method). In the third method, the attachment of multiple microcapsules can be carried out by coating the surface of at least one of the anode foil, cathode foil, and separator components with a second dispersion, which is obtained by dispersing multiple microcapsules in a dispersion medium, or by immersing at least one of the anode foil, cathode foil, and separator components in the second dispersion. As the dispersion medium for the first dispersion, for example, a liquid component such as an electrolyte can be used, and as the dispersion medium for the second dispersion, for example, water can be used.

[0091] Multiple microcapsules may be housed in a case by combining the first to third methods. For example, multiple microcapsules may be housed in a case by placing the impregnating material inside the case and then injecting the first dispersion into the case. That is, multiple microcapsules may be housed in a case by combining the first and second methods. In addition, in the electrolytic capacitor according to the second embodiment, multiple microcapsules can be housed in a case by any of the first to third methods described above, or by appropriately combining the first to third methods described above.

[0092] As described above, in the electrolytic capacitor according to the first embodiment, the multiple microcapsules contain degradation-preventing components, and when predetermined conditions are met, the capsule walls of each of the multiple microcapsules are ruptured, releasing the degradation-preventing components to the outside, thereby suppressing further degradation of acid components in the liquid component and further degradation of conductive polymers in the conductive polymer layer. Therefore, in the electrolytic capacitor according to the first embodiment, it is preferable that the multiple microcapsules are contained in the liquid component. That is, in the electrolytic capacitor according to the first embodiment, it is preferable to house the multiple microcapsules in the case by the first or second method described above. This allows for more sufficient suppression of further degradation of acid components and conductive polymers.

[0093] [Second Embodiment] An electrolytic capacitor according to the second embodiment of this disclosure comprises a capacitor element, a liquid component impregnated into the capacitor element, a plurality of microcapsules, and a case that houses the capacitor element, the liquid component, and the plurality of microcapsules.

[0094] In the electrolytic capacitor according to the second embodiment, each of the plurality of microcapsules contains a conductive polymer, and the capsule wall of each of the plurality of microcapsules ruptures when predetermined conditions are met, releasing the conductive polymer to the outside.

[0095] As described above, the electrolytic capacitor according to the first embodiment and the electrolytic capacitor according to the second embodiment differ in that the electrolytic capacitor according to the first embodiment is equipped with a plurality of microcapsules each containing a degradation prevention component, while the electrolytic capacitor according to the second embodiment is equipped with a plurality of microcapsules each containing a conductive polymer. The plurality of microcapsules equipped with the electrolytic capacitor according to the second embodiment will be described below.

[0096] <Microcapsules> In the electrolytic capacitor according to the second embodiment, each of the plurality of microcapsules contains a conductive polymer. Specifically, the microcapsules have a capsule wall, and the conductive polymer is contained within the capsule wall by being enclosed within it. That is, in the electrolytic capacitor according to the second embodiment, the core material of each of the plurality of microcapsules is a conductive polymer. The capsule wall can be constructed using the above-mentioned material. Furthermore, the conductive polymers exemplified above can be used.

[0097] In the electrolytic capacitor according to the second embodiment, the capsule wall of each of the multiple microcapsules ruptures when predetermined conditions are met, releasing the conductive polymer to the outside. As a result, the undegraded conductive polymer released to the outside replenishes the conductive polymer layer that has been degraded by oxygen contained in the case, thereby restoring the conductivity of the degraded conductive polymer layer. The predetermined conditions are preferably that the liquid component has a pH of or above a predetermined level, or that the liquid component has a temperature of or above a predetermined level. In one example, the predetermined pH is preferably 7. Alternatively, the predetermined pH may be 5. Furthermore, in one example, the predetermined temperature of the liquid component is preferably 100°C, and in another example, it is preferably 200°C.

[0098] In electrolytic capacitors, the pH of the liquid component is usually biased towards the acidic side (for example, pH 4-6). Therefore, by setting the predetermined pH to 7, the acidic components in the liquid component are not excessively oxidized and lost, preventing the pH of the liquid component from exceeding 7. This allows the capsule walls of multiple microcapsules to rupture at a more appropriate timing, and the conductive polymer released to the outside can restore the conductivity of the conductive polymer layer.

[0099] Furthermore, during vehicle operation, automotive electrolytic capacitors can be exposed to temperatures exceeding 120°C. Therefore, by setting the predetermined temperature of the liquid component to 100°C, the capsule walls of multiple microcapsules can be ruptured at a more appropriate timing to prevent excessive oxidation and loss of the acidic components contained in the liquid component. This allows the conductive polymer released to the outside to restore the conductivity of the conductive polymer layer.

[0100] Furthermore, during reflow soldering, electrolytic capacitors can be exposed to temperatures exceeding 200°C. Therefore, by setting the predetermined temperature of the liquid component to 200°C, the capsule walls of multiple microcapsules can be ruptured at a more appropriate timing to prevent excessive oxidation and loss of the acidic components contained in the liquid component. This allows the conductive polymer released to the outside to restore the conductivity of the conductive polymer layer.

[0101] As described above, in the electrolytic capacitor according to the second embodiment, the plurality of microcapsules contain a conductive polymer, and when predetermined conditions are met, the capsule walls of each of the plurality of microcapsules are ruptured, releasing the conductive polymer to the outside, thereby restoring the conductivity of the conductive polymer layer. The conductive polymer layer is a component of the electrolytic capacitor. Therefore, in the electrolytic capacitor according to the second embodiment, it is preferable that the plurality of microcapsules are arranged within the capacitor element. Specifically, it is preferable that the plurality of microcapsules are contained within the separator between the anode foil and the cathode foil within the capacitor element. In other words, in the electrolytic capacitor according to the second embodiment, it is preferable to house the plurality of microcapsules in a case by the second or third method described above. This allows the conductivity of the conductive polymer layer to be restored.

[0102] [Manufacturing method for electrolytic capacitors] The method for manufacturing an electrolytic capacitor according to the embodiment of this disclosure comprises an electrode foil preparation step S1, a separator preparation step S2, and a laminate formation step S3. The electrode foil preparation step S1, the separator preparation step S2, and the laminate formation step S3 will be described below.

[0103] (Electrode foil preparation process S1) The electrode foil preparation step S1 is a step of preparing an anode foil and a cathode foil having a dielectric layer. The anode foil and cathode foil can be those described above.

[0104] (Separator preparation process S2) The separator preparation step S2 is a step of preparing a separator that includes, for example, a conductive polymer and a plurality of microcapsules. The conductive polymer may form a conductive polymer layer in the separator. Each of the plurality of microcapsules may contain a degradation prevention component or a conductive polymer. When each of the plurality of microcapsules contains a degradation prevention component, the electrolytic capacitor according to the first embodiment can be obtained. Furthermore, when each of the plurality of microcapsules contains a conductive polymer, the electrolytic capacitor according to the second embodiment can be obtained.

[0105] The conductive polymer and multiple microcapsules can be incorporated into a separator by, for example, obtaining a dispersion of the conductive polymer and multiple microcapsules in a liquid medium, and then impregnating the separator with this dispersion or coating the separator with this dispersion. The separator containing the above dispersion may be dried to remove a portion of the liquid medium contained in the separator.

[0106] (Laminate formation process S3) The laminate formation step S3 is a step in which, after the separator preparation step S2, the anode foil and cathode foil are laminated with a separator in between to form a laminate. In other words, the laminate formation step S3 is a step in which the anode foil, separator, and cathode foil are laminated in that order to form a laminate.

[0107] The laminate described above may be a wound body as shown in Figure 2. Specifically, it may be a wound body in which an anode foil and a cathode foil are wound with a separator in between. Therefore, the laminate described above may have a cylindrical shape. When the laminate is a wound body, such a laminate can be formed, for example, by winding the anode foil, separator, and cathode foil, which are fed out from three rollers respectively, onto a single roller.

[0108] On the other hand, the above-mentioned laminate may be a laminate formed by stacking an anode foil, a separator, and a cathode foil in one direction. Therefore, the above-mentioned laminate may have a flat plate shape. When the laminate has a flat plate shape, such a laminate can be formed by stacking these in one direction, for example, with a separator interposed between the anode foil and the cathode foil.

[0109] As described above, a capacitor element according to the embodiment of this disclosure can be obtained by carrying out the electrode foil preparation step S1, the separator preparation step S2, and the laminate formation step S3. Then, by housing this capacitor element and a liquid component such as an electrolyte in a case, an electrolytic capacitor according to the embodiment of this disclosure can be obtained.

[0110] Furthermore, the method of housing multiple microcapsules in a case is not limited to including them in the separator during the separator preparation step S2, as described above. The housing of multiple microcapsules in a case may also be carried out by dispersing the multiple microcapsules in a liquid component and then housing this liquid component in the case. In this case, the multiple microcapsules do not need to be included in the separator during the separator preparation step S2.

[0111] The specific configuration of the electrolytic capacitor according to the embodiment of this disclosure will be described below with reference to Figures 1 and 2. Figure 1 is a schematic cross-sectional view showing an electrolytic capacitor 100 according to the embodiment of this disclosure, and Figure 2 is a schematic diagram showing a part of the capacitor element 10 included in the electrolytic capacitor 100 unfolded.

[0112] The electrolytic capacitor 100 comprises a capacitor element 10, a bottomed case 101 housing the capacitor element 10, a sealing member 102 (for example, a sealing rubber) that closes the opening of the bottomed case 101, a base plate 103 that covers the sealing member 102, a base plate 103 positioned outside the bottomed case 101 so as to cover the sealing member 102 from the opening side of the bottomed case 101, a pair of lead wires 104A and 104B that are led out from the sealing member 102 and pass through the base plate 103, and a pair of lead tabs 105A and 105B that connect each of the pair of lead wires 104A and 104B to the electrodes of the capacitor element (for example, an anode foil 11 and a cathode foil 12, which will be described later). The area near the opening end of the bottomed case 101 is drawn inward, and the opening end of the bottomed case 101 is curled so as to be crimped to the sealing member 102. In the example shown in Figure 1, lead wire 104A is connected to the electrode of the capacitor element via lead tab 105A, and lead wire 104B is connected to the electrode of the capacitor element via lead tab 105B.

[0113] In the electrolytic capacitor 100, a gap C is formed between the capacitor element 10 and the inner surface I of the bottomed case 101, and multiple microcapsules MC are arranged within the gap C. Although not shown in Figure 1, multiple microcapsules MC may also be further arranged inside the capacitor element 10. Specifically, they may be contained within the separator 13 between the anode foil 11 and the cathode foil 12 as shown in Figure 2. Alternatively, multiple microcapsules MC may be arranged only inside the capacitor element 10. Each of the multiple microcapsules MC contains a degradation prevention component. The degradation prevention component includes at least one of an antioxidant and an acid component. The antioxidant and acid component can be those exemplified above. Each of the multiple microcapsules MC also contains a conductive polymer. The conductive polymer can be those exemplified above.

[0114] The sealing member 102 is formed of an elastic material containing a rubber component. Examples of rubber components that can be used include butyl rubber (IIR), nitrile rubber (NBR), ethylene propylene rubber, ethylene propylene diene rubber (EPDM), chloroprene rubber (CR), isoprene rubber (IR), Hypalon® rubber, silicone rubber, and fluororubber. The sealing member 102 may also contain fillers such as carbon black and silica.

[0115] The capacitor element 10 is configured, for example, as a wound body as shown in Figure 2. The wound body comprises an anode foil 11 connected to a lead tab 105A, a cathode foil 12 connected to a lead tab 105B, and a separator 13. The capacitor element 10 includes a conductive polymer layer (not shown). Note that the electrolytic capacitor 100 shown in Figure 1 includes the capacitor element 10 shown in Figure 2, and is therefore referred to as a wound-type electrolytic capacitor.

[0116] The anode foil 11 and cathode foil 12 are wound together with a separator 13 interposed between them to form a wound body. The outermost circumference of this wound body is then secured by a winding stopper tape 14. Figure 2 shows the state of the wound body with a portion unfolded before the outermost circumference is secured by the winding stopper tape 14.

[0117] The electrolytic capacitor according to this disclosure only needs to have at least one capacitor element, but may also have multiple capacitor elements. The number of capacitor elements in the electrolytic capacitor is determined appropriately depending on the application.

[0118] Figures 1 and 2 illustrate wound-type electrolytic capacitors, but the electrolytic capacitors according to the embodiments of this disclosure are not limited to these, and may also be chip-type electrolytic capacitors or multilayer-type electrolytic capacitors.

[0119] (Note) The following technologies are disclosed as described above. (Technology 1) Capacitor element and A liquid component impregnated into the capacitor element, Multiple microcapsules, The device comprises the capacitor element, the liquid component, and a case for housing the plurality of microcapsules, The aforementioned capacitor element is Anode foil having a dielectric layer, A cathode foil is disposed opposite the dielectric layer, A separator interposed between the anode foil and the cathode foil, It includes a conductive polymer layer interposed between the anode foil and the cathode foil and in contact with the separator, Each of the aforementioned plurality of microcapsules contains a degradation-preventing component, Each of the capsule walls of the plurality of microcapsules ruptures when predetermined conditions are met, releasing the degradation-preventing component to the outside. Electrolytic capacitor. (Technology 2) The aforementioned degradation-preventing component comprises at least one of an antioxidant and an acid component. Electrolytic capacitor as described in Technical 1. (Technology 3) Capacitor element and A liquid component impregnated into the capacitor element, Multiple microcapsules, The device comprises the capacitor element, the liquid component, and a case for housing the plurality of microcapsules, The aforementioned capacitor element is Anode foil having a dielectric layer, A cathode foil is disposed opposite the dielectric layer, A separator interposed between the anode foil and the cathode foil, It includes a conductive polymer layer interposed between the anode foil and the cathode foil and in contact with the separator, Each of the aforementioned plurality of microcapsules contains a conductive polymer, Each of the capsule walls of the plurality of microcapsules ruptures when predetermined conditions are met, releasing the conductive polymer to the outside. Electrolytic capacitor. (Technology 4) The predetermined conditions are that the liquid component reaches a predetermined pH or higher, or that the liquid component reaches a predetermined temperature or higher. An electrolytic capacitor as described in one of the following three technical specifications. (Technology 5) The predetermined pH is 7. Electrolytic capacitor as described in Technical Section 4. (Technology 6) The aforementioned predetermined temperature is 100°C or higher. Electrolytic capacitor as described in Technical Section 4. (Technology 7) The aforementioned predetermined temperature is 200°C or higher. Electrolytic capacitor as described in Technical Section 4. (Technology 8) The plurality of microcapsules are contained within the liquid component, An electrolytic capacitor as described in one of the following technical sections: 1, 2, or 4-7. (Technology 9) The plurality of microcapsules are arranged within the capacitor element. An electrolytic capacitor as described in one of the following technical specifications (1-7). (Technology 10) A gap is formed between the capacitor element and the inner surface of the case. The plurality of microcapsules are arranged within the void. An electrolytic capacitor as described in one of the following technical sections: 1, 2, or 4-8. (Technology 11) The filling rate of the plurality of microcapsules in the aforementioned void is 5% by volume or more. Electrolytic capacitor as described in Technical 10.

[0120] Although the present invention has been described in relation to preferred embodiments at present, such disclosure should not be interpreted restrictively. Various modifications and alterations will undoubtedly become apparent to those skilled in the art in the field to which the invention pertains by reading the above disclosure. Accordingly, the appended claims should be interpreted as encompassing all modifications and alterations without departing from the true spirit and scope of the invention. [Industrial applicability]

[0121] The electrolytic capacitors relating to this disclosure can be used in applications where it is required to sufficiently suppress performance degradation when used for a long period of time or when used in a high-temperature environment. [Explanation of Symbols]

[0122] 10: Capacitor element, 11: Anode foil, 12: Cathode foil, 13: Separator, 14: Winding tape, 100: Electrolytic capacitor, 101: Bottomed case, 102: Encapsulation material, 103: Base plate, 104A, 104B: Lead wires, 105A, 105B: Lead tabs, C: Air gap, I: Inner surface, MC: Microcapsule

Claims

1. Capacitor element and A liquid component impregnated into the capacitor element, Multiple microcapsules, The device comprises the capacitor element, the liquid component, and a case for housing the plurality of microcapsules, The aforementioned capacitor element is Anode foil having a dielectric layer, A cathode foil is disposed opposite the dielectric layer, A separator interposed between the anode foil and the cathode foil, It includes a conductive polymer layer interposed between the anode foil and the cathode foil and in contact with the separator, Each of the aforementioned plurality of microcapsules contains a degradation-preventing component, Each of the capsule walls of the plurality of microcapsules ruptures when predetermined conditions are met, releasing the degradation-preventing component to the outside. Electrolytic capacitor.

2. The aforementioned degradation-preventing component includes at least one of an antioxidant and an acid component. The electrolytic capacitor according to claim 1.

3. Capacitor element and A liquid component impregnated into the capacitor element, Multiple microcapsules, The device comprises the capacitor element, the liquid component, and a case for housing the plurality of microcapsules, The aforementioned capacitor element is Anode foil having a dielectric layer, A cathode foil is disposed opposite the dielectric layer, A separator interposed between the anode foil and the cathode foil, It includes a conductive polymer layer interposed between the anode foil and the cathode foil and in contact with the separator, Each of the aforementioned plurality of microcapsules contains a conductive polymer, Each of the capsule walls of the plurality of microcapsules ruptures when predetermined conditions are met, releasing the conductive polymer to the outside. Electrolytic capacitor.

4. The predetermined conditions are that the liquid component reaches a predetermined pH or higher, or that the liquid component reaches a predetermined temperature or higher. The electrolytic capacitor according to claim 1 or 3.

5. The predetermined pH is 7. The electrolytic capacitor according to claim 4.

6. The predetermined temperature is 100°C. The electrolytic capacitor according to claim 4.

7. The predetermined temperature is 200°C. The electrolytic capacitor according to claim 4.

8. The plurality of microcapsules are contained within the liquid component, The electrolytic capacitor according to claim 1.

9. The plurality of microcapsules are arranged within the capacitor element. The electrolytic capacitor according to claim 1 or 3.

10. A gap is formed between the capacitor element and the inner surface of the case. The plurality of microcapsules are arranged within the void. The electrolytic capacitor according to claim 1.

11. The filling rate of the plurality of microcapsules in the aforementioned void is 5% by volume or more. The electrolytic capacitor according to claim 10.

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