Electrolytic capacitor and manufacturing method

Abstract

To provide an electrolytic capacitor and a manufacturing method that can maintain low ESR while utilizing conductive polymers and flexible crystals.SOLUTION: An electrolytic capacitor comprises an electrolytic layer between a pair of electrodes. The electrolytic layer includes conductive polymers obtained by depositing a conductive polymer solution containing conductive polymers and neutralizing agents and flexible crystals, and the electrolytic layer does not contain metal ions derived from the neutralizing agents. A manufacturing method for the electrolytic capacitor has an electrolytic layer formation step of impregnating and drying the conductive polymer solution in which a conductive polymer is dispersed or dissolved between the pair of electrodes, and the conductive polymer solution does not contain metal ions.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 use valve metals such as tantalum or aluminum as anode and cathode foils. The anode foil is enlarged by forming a powder sintered layer made of valve metal powder on the foil surface, or by etching the foil itself. The enlarged surface has a dielectric coating. An electrolyte is interposed between the anode and cathode foils. The electrolyte is in close contact with the uneven surface of the anode foil and functions as the true cathode.

[0003] Capacitors are used in a variety of applications. In all applications, there is a growing demand for higher capacitance. In this regard, electrolytic capacitors have the advantage that the specific surface area can be increased by expanding the surface area of the anode foil, making it easier to achieve a higher capacitance than other types of capacitors, such as film capacitors. Among such electrolytic capacitors, electrolytic capacitors using solid electrolytes as the electrolyte are widely used (see, for example, Patent Document 1). Because electrolytic capacitors use highly conductive solid electrolytes, they are small in size, have large capacitance, and also have low equivalent series resistance (low ESR). In addition to their small size, large capacitance, and low ESR, electrolytic capacitors also have other characteristics, such as being easily fabricated into chips and being suitable for surface mounting, making them essential for miniaturizing, improving functionality, and reducing the cost of electronic devices.

[0004] Known examples of solid electrolytes include manganese dioxide and 7,7,8,8-tetracyanoquinodimethane (TCNQ) complexes. In recent years, conductive polymers have rapidly become popular as solid electrolytes. Conductive polymers are derived from monomers with π-conjugated double bonds, such as poly(3,4-ethylenedioxythiophene) (PEDOT). PEDOT has a slow reaction rate and excellent adhesion to dielectric films. Conductive polymers use acid compounds such as polyanions as dopants, and the monomer molecules contain substructures that act as dopants, resulting in high conductivity and promoting low ESR in electrolytic capacitors.

[0005] However, electrolytic capacitors using solid electrolytes as the electrolyte have poor repair properties for defects in the dielectric film, which can lead to increased leakage current. Therefore, a so-called hybrid-type electrolytic capacitor has been proposed, in which a solid electrolyte layer is formed on a capacitor element in which an anode foil and a cathode foil are arranged facing each other with a separator interposed therebetween, and the voids in the capacitor element are impregnated with an ionic liquid (see, for example, Patent Document 2). Ionic liquids are salts that melt and remain in a liquid state at room temperature. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] International Publication No. 2007 / 091656 [Patent Document 2] International Publication No. 2014 / 050071 Summary of the Invention [Problem to be solved by the invention]

[0007] However, even solid electrolytes are required to suppress leakage current. Therefore, the inventors are considering filling the electrolyte layer with plastic crystals. Plastic crystals, also known as plastic crystals, have both ordered and disordered orientations and can be considered as a material that exists between a liquid and a solid within the target temperature range for use of electrolytic capacitors.

[0008] However, as a result of intensive research by the inventors, it was confirmed that when a conductive polymer and a plastic crystal are used in combination, there are cases where the low ESR, which is an advantage of electrolytic capacitors that use a solid electrolyte as the electrolyte, is significantly impaired. It is generally pointed out that plastic crystals have an ionic conductivity that is orders of magnitude lower than that of conductive polymers, but it was confirmed that when a conductive polymer and a plastic crystal are used in combination, the increase in ESR exceeds the effect of the ionic conductivity of the plastic crystal.

[0009] The present invention has been proposed to solve the above problems, and its object is to provide an electrolytic capacitor that can maintain a low ESR while using a conductive polymer and a plastic crystal, and a manufacturing method thereof. [Means for solving the problem]

[0010] In order to solve the above problem, the electrolytic capacitor of this embodiment is an electrolytic capacitor having an electrolyte layer between a pair of electrodes, wherein the electrolyte layer contains a conductive polymer and a plastic crystal, and the electrolyte layer does not contain metal ions.

[0011] As a result of intensive research by the inventors, it was confirmed that the ESR of an electrolytic capacitor increases when a conductive polymer and a plastic crystal are used in combination and when the electrolyte layer contains metal ions. When metal ions smaller than the cationic components of the plastic crystal are present in the electrolyte layer, a cation exchange reaction occurs between the cationic components of the plastic crystal and the metal ions, liberating the cationic components of the plastic crystal. The liberated cationic components of the plastic crystal promote the de-doping reaction of the conductive polymer, increasing the ESR of the electrolytic capacitor. Therefore, if the electrolyte layer contains a conductive polymer and a plastic crystal but does not contain metal ions, the ESR of the electrolytic capacitor can be maintained low.

[0012] The metal ions may be alkali metal ions.

[0013] The electrolyte layer may be formed from a conductive polymer liquid in which a conductive polymer is dispersed or dissolved, the metal ions are derived from a neutralizing agent contained in the conductive polymer liquid, and the electrolyte layer may be free of the metal ions derived from the neutralizing agent contained in the conductive polymer liquid.

[0014] The conductive polymer liquid may contain no metal ions and may contain a non-metallic compound.

[0015] In order to solve the above-described problems, the method for manufacturing an electrolytic capacitor according to the present embodiment includes an electrolyte layer formation step of impregnating a conductive polymer liquid, in which a conductive polymer is dispersed or dissolved, between a pair of electrodes and drying the impregnated conductive polymer liquid, and the conductive polymer liquid does not contain metal ions.

[0016] The conductive polymer liquid may contain a neutralizing agent, and the neutralizing agent may be a non-metallic compound that does not contain the metal ions. [Effects of the Invention]

[0017] According to the present invention, it is possible to suppress deterioration of the ESR of an electrolytic capacitor. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a graph showing the relationship between the ESR change rate (ΔESR) of each electrolytic capacitor and the elapsed time. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to the embodiments described below.

[0020] (Overall composition) An electrolytic capacitor is a passive device that obtains capacitance through the dielectric polarization of a dielectric film and stores and discharges electric charge. An electrolytic capacitor has a pair of electrodes and an electrolyte layer sandwiched between the electrodes. One electrode is an anode body with a dielectric film formed on its surface, and the other electrode is a cathode body.

[0021] The capacitor element may be a wound type in which anode bodies and cathode bodies are alternately stacked with a separator sandwiched therebetween and wound, or a stacked type in which anode bodies and cathode bodies are alternately stacked with a separator sandwiched therebetween.The capacitor element may also be a flat plate type in which an electrolyte layer is formed on an individual anode body, and then a carbon layer and a silver layer that will become the cathode body are formed on the electrolyte layer.

[0022] The electrolyte layer is interposed between the anode body and the cathode body. In other words, the anode body and the cathode body are arranged opposite each other with the electrolyte layer sandwiched between them. The electrolyte layer contains a conductive polymer. The conductive polymer is in close contact with the dielectric film of the anode body and is arranged so as to be continuous between the dielectric film and the cathode body, creating a conductive path and functioning as a true cathode. This electrolyte layer contains a conductive polymer and plastic crystals.

[0023] Conductive polymers are self-doped conjugated polymers doped with intramolecular dopant molecules, or conjugated polymers doped with external dopant molecules. Conjugated polymers are obtained by chemical oxidative polymerization or electrolytic oxidative polymerization of monomers or their derivatives having π-conjugated double bonds. The dopant or external dopant molecule acts as an acceptor that readily accepts electrons into the conjugated polymer, or as a donor that readily donates electrons, which allows the conductive polymer to exhibit high conductivity.

[0024] Plastic crystals, also known as plastic crystals, have an ordered arrangement and a disordered orientation. That is, plastic crystals have a three-dimensional crystal lattice structure in which anions and cations are regularly arranged, while these anions and cations have rotational disorder. The types of anion and cation components that make up plastic crystals are not particularly limited as long as they are solid, not ionic liquid, within the target temperature range in which the electrolytic capacitor is used.

[0025] The electrolyte layer contains cationic components added separately from the plastic crystals. These cationic components are non-metallic ions. In other words, the electrolyte layer does not contain metal ions such as alkali metals. When metal ions smaller than the cationic components of the plastic crystals are present in the electrolyte layer, a cation exchange reaction occurs between the cationic components of the plastic crystals and the metal ions, liberating the cationic components of the plastic crystals. The liberated cationic components of the plastic crystals promote the dedoping reaction of the conductive polymer, increasing the ESR of the electrolytic capacitor. Therefore, the cationic components contained in the electrolyte layer are non-metallic ions, which suppress the liberation of the cationic components of the plastic crystals and suppress the increase in ESR of the electrolytic capacitor. Therefore, in this invention, "no metal ions" refers to the absence of metal ions in an amount sufficient to increase the ESR of the electrolytic capacitor due to the dedoping reaction of the conductive polymer caused by the cationic components of the plastic crystals liberated by the cation exchange reaction with the metal ions. In other words, if the metal ions contained in the neutralizer are at an impurity level (e.g., 350 ppm or less) that does not increase the ESR of the electrolytic capacitor due to the dedoping reaction of the conductive polymer, the metal ions derived from the neutralizer may be contained and do not fall under the non-containment aspect of the present invention.

[0026] Here, the conductive polymer can be formed in the electrolyte layer by various methods. For example, the conductive polymer is formed in the electrolyte layer by impregnating a conductive polymer solution, which is dispersed or dissolved in a dispersion medium or solvent, between a pair of electrodes in a polymer deposition process and then drying the dispersion medium or solvent. The dopant of the conductive polymer is highly acidic. Therefore, a neutralizing agent is added to the conductive polymer solution.

[0027] The neutralizing agent is an ion-dissociating salt that generates cationic components in the conductive polymer liquid. The cationic components derived from the neutralizing agent neutralize the dopant, inhibiting corrosion of the dielectric film and increasing adhesion between the electrolyte layer and the dielectric film. To convert the cationic components in the electrolyte layer into non-metallic ions, a non-metallic compound that does not generate metal ions such as alkali metal ions is used as the neutralizing agent in the conductive polymer liquid.

[0028] Examples of cationic components added separately from the plastic crystals include ammonium ions, water-soluble alkylamines such as ethylamine and diethylamine, water-soluble arylamines such as aniline and benzylamine, and water-soluble heterocyclic amines such as pyridine and imidazole. It is preferable to add a neutralizing agent that generates cationic components of these non-metallic ions to the conductive polymer liquid.

[0029] On the other hand, examples of ion dissociative salts that generate metal ions to be excluded include hydroxides of alkali metals or alkaline earth metals such as sodium hydroxide and calcium hydroxide, carbonates of alkali metals or alkaline earth metals such as sodium carbonate and calcium carbonate, alkoxides of alkali metals or alkaline earth metals such as sodium methoxide and calcium methoxide, etc. Neutralizing agents that generate cations of these metal ions are not added to the conductive polymer solution when a conductive polymer and a plastic crystal are used in combination.

[0030] (anode body) In such electrolytic capacitors, the anode body is a foil made of a valve metal. In wound electrolytic capacitors, it is a long strip of elongated valve metal, while in laminated electrolytic capacitors or flat-plate electrolytic capacitors, it is a flat plate made of valve metal. Valve metals include aluminum, tantalum, niobium, niobium oxide, titanium, hafnium, zirconium, zinc, tungsten, bismuth, and antimony. The purity of the anode body is preferably 99.9% or higher, but impurities such as silicon, iron, copper, magnesium, and zinc may be present.

[0031] A surface-expanding layer is formed on one or both sides of the anode body. The surface-expanding layer can be an etched layer formed by etching a foil, a sintered layer formed by sintering valve metal powder, or a vapor-deposited layer formed by vapor-depositing valve metal particles onto a foil. That is, the surface-expanding layer has a porous structure consisting of tunnel-like pits, spongy pits, or voids between densely packed powder or particles.

[0032] 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 enlarged by passing a direct current in an acidic aqueous solution, such as nitric acid. The surface-enlarging layer having spongy etching pits is a sponge-like layer with fine voids extending in a space-like pattern. These spongy etching pits are formed by passing an alternating current in an acidic aqueous solution containing halogen ions, such as hydrochloric acid.

[0033] The sintered layer is produced by obtaining a powder of a valve action metal of the same or different type as the foil 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 the foil, 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. The vapor deposition layer is produced by, for example, a resistance heating vapor deposition method or an electron beam heating vapor deposition method. This vapor deposition layer is formed by heating and evaporating a valve action metal of the same or different type as the foil by resistance heat or electron beam energy, and depositing the vapor of the valve action metal particles on the surface of the foil.

[0034] The dielectric coating is formed on one or both sides of the anode body on which the surface-expanding layer is formed. The dielectric coating is typically an oxide coating formed on the surface layer of the anode body. If the anode body is made of aluminum, it is an aluminum oxide layer formed by oxidizing the surface of the surface-expanding layer. In the chemical conversion treatment to form the dielectric coating, a voltage is applied to the anode body in a chemical conversion solution until a desired withstand voltage is achieved. The chemical conversion solution is a solution free of halogen ions, such as a phosphoric acid-based chemical conversion solution such as ammonium dihydrogen phosphate, a boric acid-based chemical conversion solution such as ammonium borate, or an adipic acid-based chemical conversion solution such as ammonium adipate.

[0035] An anode lead is connected to the anode body and extends outside the capacitor element. The capacitor element is an assembly of the anode body, cathode body, electrolyte layer, and separator. The anode lead is connected to the anode body by stitching, cold welding, ultrasonic welding, laser welding, or the like.

[0036] (cathode body) In the case of a wound-type electrolytic capacitor, the cathode body is preferably a foil made of a valve metal and stretched. The purity of the cathode body is preferably 99% or higher. A surface-expanding layer is formed on the cathode body, just like on the anode body. Plain foil without a surface-expanding layer may also be used as the cathode body. The cathode body may have a natural oxide film or a thin oxide film (about 1 to 10 V) formed by chemical conversion treatment. The natural oxide film is formed by the cathode body reacting with oxygen in the air. Furthermore, a layer made of metal nitride, metal carbide, or metal carbonitride may be formed on the cathode body by vapor deposition, or a carbon-containing layer may be formed on the surface.

[0037] Alternatively, in the case of a stacked electrolytic capacitor, the cathode body is preferably a laminate of a metal layer and a carbon layer. The carbon layer of the cathode body is disposed facing the anode body. The carbon layer is formed by applying a paste onto the electrolyte layer after the electrolyte layer is formed on the anode body, and then curing the paste by heating. The metal layer is, for example, a silver layer, and is formed by applying a paste onto the carbon layer and then curing the paste by heating.

[0038] A cathode lead is connected to the cathode body and is drawn out of the capacitor element by stitching, cold welding, ultrasonic welding, laser welding, or the like.

[0039] (electrolyte layer) (conductive polymer) As the conjugated polymer, any known polymer can be used without any particular limitation. Examples include polypyrrole, polythiophene, polyfuran, polyaniline, polyacetylene, polyphenylene, polyphenylene vinylene, polyacene, polythiophene vinylene, etc. These conjugated polymers may be used alone or in combination of two or more types, or may even be a copolymer of two or more types of monomers.

[0040] Among the above conjugated polymers, preferred are conjugated polymers obtained by polymerizing thiophene or its derivatives, and preferred are conjugated polymers obtained by polymerizing 3,4-ethylenedioxythiophene (i.e., 2,3-dihydrothieno[3,4-b][1,4]dioxin), 3-alkylthiophene, 3-alkoxythiophene, 3-alkyl-4-alkoxythiophene, 3,4-alkylthiophene, 3,4-alkoxythiophene, or derivatives thereof. The thiophene derivative is preferably a compound selected from thiophenes having substituents at the 3rd and 4th positions, and the substituents at the 3rd and 4th positions of the thiophene ring may form a ring together with the carbon atoms at the 3rd and 4th positions. The alkyl group or alkoxy group preferably has 1 to 16 carbon atoms.

[0041] In particular, a polymer of 3,4-ethylenedioxythiophene, known as EDOT, i.e., poly(3,4-ethylenedioxythiophene), known as PEDOT, is particularly preferred. A substituent may be added to 3,4-ethylenedioxythiophene. For example, alkylated ethylenedioxythiophene, in which an alkyl group having 1 to 5 carbon atoms is added as a substituent, may be used. Examples of alkylated ethylenedioxythiophene include methylated ethylenedioxythiophene (i.e., 2-methyl-2,3-dihydro-thieno[3,4-b][1,4]dioxin), ethylated ethylenedioxythiophene (i.e., 2-ethyl-2,3-dihydro-thieno[3,4-b][1,4]dioxin), butylated ethylenedioxythiophene (i.e., 2-butyl-2,3-dihydro-thieno[3,4-b][1,4]dioxin), and 2-alkyl-3,4-ethylenedioxythiophene.

[0042] Any known dopant can be used without any particular limitation. A single dopant may be used, or two or more dopants may be used in combination. Furthermore, a polymer or a monomer may be used. Examples of dopants include inorganic acids such as polyanions, boric acid, nitric acid, and phosphoric acid, and organic acids such as acetic acid, oxalic acid, citric acid, tartaric acid, squaric acid, rhodizonic acid, croconic acid, salicylic acid, p-toluenesulfonic acid, 1,2-dihydroxy-3,5-benzenedisulfonic acid, methanesulfonic acid, trifluoromethanesulfonic acid, borodisalicylic acid, bisoxalateborate acid, sulfonylimide acid, dodecylbenzenesulfonic acid, propylnaphthalenesulfonic acid, and butylnaphthalenesulfonic acid.

[0043] Examples of polyanions include substituted or unsubstituted polyalkylenes, substituted or unsubstituted polyalkenylenes, substituted or unsubstituted polyimides, substituted or unsubstituted polyamides, and substituted or unsubstituted polyesters, and include polymers consisting only of structural units having anionic groups, and polymers consisting of structural units having anionic groups and structural units not having anionic groups.Specific examples of polyanions include polyvinyl sulfonic acid, polystyrene sulfonic acid, polyallylsulfonic acid, polyacrylic sulfonic acid, polymethacrylic acid, poly(2-acrylamido-2-methylpropanesulfonic acid), polyisoprene sulfonic acid, polyacrylic acid, polymethacrylic acid, and polymaleic acid.

[0044] This conductive polymer is produced by chemical oxidative polymerization or electrolytic oxidative polymerization. In chemical oxidative polymerization, a solution containing a monomer that will become the monomer unit of the conductive polymer is mixed with an oxidizing agent to cause a polymerization reaction. The oxidizing agent may be any known compound that releases a dopant. Examples of the oxidizing agent include trivalent iron salts such as iron(III) p-toluenesulfonate, iron(III) naphthalenesulfonate, and iron(III) anthraquinonesulfonate, and peroxodisulfates such as peroxodisulfate, ammonium peroxodisulfate, and sodium peroxodisulfate. A single compound may be used, or two or more compounds may be used. The polymerization temperature is not strictly limited, but is generally in the range of 10 to 200°C. The polymerization time is generally in the range of 10 minutes to 30 hours.

[0045] In electrolytic oxidation polymerization, a monomer that will become a monomer unit of a conductive polymer is mixed with a supporting electrolyte and polymerized by a constant potential method, a constant current method, or a potential sweep method. The supporting electrolyte includes at least one compound selected from the group consisting of borodisalicylic acid and borodisalicylic acid salts. Examples of the salt include alkali metal salts such as lithium salt, sodium salt, and potassium salt; alkylammonium salts such as ammonium salt, ethylammonium salt, and butylammonium salt; dialkylammonium salts such as diethylammonium salt and dibutylammonium salt; trialkylammonium salts such as triethylammonium salt and tributylammonium salt; and tetraalkylammonium salts such as tetraethylammonium salt and tetrabutylammonium salt.

[0046] In the case of the constant potential method, a potential of 1.0 to 1.5 V relative to the reference electrode is suitable, and in the case of the constant current method, a potential of 1 to 10,000 μA / cm 2 In the case of a potential sweep method, it is preferable to sweep the potential in the range of 0 to 1.5 V with respect to the reference electrode at a rate of 5 to 200 mV / sec. There is no strict limit to the polymerization temperature, but it is generally in the range of 10 to 60°C. The polymerization time is generally in the range of 10 minutes to 30 hours.

[0047] In chemical oxidation polymerization or electrolytic oxidation polymerization, the solvent to which the monomer, oxidizing agent, or supporting electrolyte is added can be any solvent that can dissolve the desired amount of monomer and supporting electrolyte and does not adversely affect the electrolytic oxidation polymerization. Examples of suitable solvents include water, methanol, ethanol, isopropanol, butanol, ethylene glycol, acetonitrile, butyronitrile, acetone, methyl ethyl ketone, tetrahydrofuran, 1,4-dioxane, γ-butyrolactone, methyl acetate, ethyl acetate, methyl benzoate, ethyl benzoate, ethylene carbonate, propylene carbonate, nitromethane, nitrobenzene, sulfolane, and dimethyl sulfolane. These solvents may be used alone or in combination.

[0048] The conductive polymer is formed in the electrolytic capacitor by immersing an object to which the conductive polymer is to be attached in a solution of a monomer that will become a monomer unit of the conductive polymer and an oxidizing agent or a supporting electrolyte, and generating the conductive polymer through a polymerization reaction. The object to be attached includes at least an anode body. In addition to the anode body, one or both of the cathode body and the separator may also be used as the object to which the conductive polymer is to be attached. Alternatively, a capacitor element, which is an assembly incorporating an anode body, a cathode body, and a separator, may be used as the object to be attached, and immersed in a solution of a monomer that will become a monomer unit of the conductive polymer and an oxidizing agent or a supporting electrolyte, and generating a polymerization reaction.

[0049] Alternatively, the conductive polymer may be formed in the electrolytic capacitor by an impregnation method in which a conductive polymer liquid in which particles or powder of the conductive polymer are dispersed or dissolved is impregnated into an object to be attached. The conductive polymer liquid is prepared by purifying the solution after chemical oxidation polymerization or electrolytic oxidation polymerization by ultrafiltration, cation exchange, anion exchange, or the like to remove residual monomers and impurities, and dispersing the resultant in the solution.

[0050] The solvent for the conductive polymer solution may be any solvent that disperses or dissolves the conductive polymer, and is preferably water or a mixture of water and an organic solvent. Examples of the organic solvent include polar solvents, alcohols, esters, hydrocarbons, carbonate compounds, ether compounds, chain ethers, heterocyclic compounds, and nitrile compounds.

[0051] Examples of polar solvents include N-methyl-2-pyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, and dimethyl sulfoxide. Examples of alcohols include methanol, ethanol, propanol, and butanol. Examples of esters include ethyl acetate, propyl acetate, and butyl acetate. Examples of hydrocarbons include hexane, heptane, benzene, toluene, and xylene. Examples of carbonate compounds include ethylene carbonate and propylene carbonate. Examples of ether compounds include dioxane and diethyl ether. Examples of linear ethers include ethylene glycol dialkyl ether, propylene glycol dialkyl ether, polyethylene glycol dialkyl ether, and polypropylene glycol dialkyl ether. Examples of heterocyclic compounds include 3-methyl-2-oxazolidinone. Examples of nitrile compounds include acetonitrile, glutarodinitrile, methoxyacetonitrile, propionitrile, and benzonitrile.

[0052] The conductive polymer liquid contains a nonmetallic cationic component as a neutralizer, and may also contain polyhydric alcohols and various additives as needed. Examples of polyhydric alcohols include sorbitol, ethylene glycol, diethylene glycol, triethylene glycol, polyoxyethylene glycol, glycerin, polyoxyethyleneglycerin, xylitol, erythritol, mannitol, dipentaerythritol, pentaerythritol, and combinations of two or more of these. Because polyhydric alcohols have a high boiling point, they remain in the electrolyte layer even after the conductive polymer liquid is impregnated into the substrate and dried, thereby reducing the ESR and improving the withstand voltage of the electrolytic capacitor. Examples of additives include organic binders, surfactants, dispersants, antifoaming agents, coupling agents, antioxidants, and ultraviolet absorbers.

[0053] After the conductive polymer liquid has been impregnated into the object to be attached, the solvent is removed by a drying process. The temperature environment in the drying process is, for example, 40°C or higher and 200°C or lower, and the drying time is, for example, in the range of 3 minutes to 180 minutes. The drying process may be repeated multiple times. Drying may be performed in a reduced pressure environment, for example, by reducing the pressure to 5 kPa to 100 kPa. The drying process may be divided into a preliminary drying process and a main drying process. In addition to immersion, the conductive polymer liquid may be applied by drop coating or spray coating.

[0054] (flexible crystal) The plastic crystal may be an ionic organic substance having a solid-solid transition point, ionic conductivity, and a melting point lower than room temperature. Furthermore, the solid-solid transition point is located lower than the operating temperature range of the electrolytic capacitor, and the melting point is located higher than the operating temperature range of the electrolytic capacitor. The operating temperature range of the electrolytic capacitor is from -40°C to 150°C when it is intended for outdoor use, such as in a vehicle.

[0055] The solid-solid phase transition point is an endothermic peak that occurs below the melting point during the temperature rise process in differential scanning calorimetry (DSC), i.e., a peak where the heat flow per unit weight is negative. Below this solid-solid phase transition point, the material has a regular crystalline structure with regular molecular orientation and center of gravity. Above this solid-solid phase transition point and below the melting point, the material is in a plastic crystalline phase. The plastic crystalline phase transitions to a plastic crystalline phase at room temperature. Therefore, this electrolytic capacitor operates while maintaining the ionic organic material, which has a melting point higher than room temperature and a solid-solid phase transition point lower than room temperature, in a plastic crystalline state.

[0056] Examples of anion components constituting the plastic crystal include various amide anions, tris(trifluoromethanesulfonyl)methanide anions, various phosphate anions, various borate anions, various sulfone-based anions, and tetrafluoroaluminate anions.

[0057] In the various amide anions, two hydrogen atoms of the NH anion are substituted with perfluoroalkylsulfonyl groups, fluorosulfonyl groups, or both. The various amide anions include, for example, linear anions, such as various bis(perfluoroalkylsulfonyl)amide anions, bis(fluorosulfonyl)amide anions, and various N-(fluorosulfonyl)-N-(perfluoroalkylsulfonyl)amide anions represented by the following chemical formula (1).

[0058] (chemical 1) TIFF2025121317000002.tif30161In chemical formula (1), n and m are integers of 0 or more, and the number of carbon atoms may be any number.

[0059] In the chemical formula (1), if n and m are 1 or more, the anion is a bis(perfluoroalkylsulfonyl)amide anion. Specific examples of the bis(perfluoroalkylsulfonyl)amide anion include the bis(trifluoromethanesulfonyl)amide anion (TFSA anion) represented by the following chemical formula (2) and the bis(pentafluoroethylsulfonyl)amide anion (BETA anion) represented by the following chemical formula (3).

[0060] (Case 2) TIFF2025121317000003.tif37161

[0061] (3) TIFF2025121317000004.tif38161

[0062] Specific examples of the bis(perfluoroalkylsulfonyl)amide anion include (pentafluoroethylsulfonyl)trifluoromethanesulfonylamide anion, which is represented by the following chemical formula (4) in which n is 1 and m is 2 in the chemical formula (1).

[0063] (C4) TIFF2025121317000005.tif41161

[0064] In chemical formula (1), a group having 0 carbon atoms is a fluorosulfonyl group, and when n and m are 0, the anion is a bis(fluorosulfonyl)amide anion (FSA anion) represented by the following chemical formula (5).

[0065] (C5) TIFF2025121317000006.tif37161

[0066] In the chemical formula (1), when n is 0 and m is 1 or more, the anion is an N-(fluorosulfonyl)-N-(perfluoroalkylsulfonyl)amide anion represented by the following chemical formula (6). Specific examples of the N-(fluorosulfonyl)-N-(perfluoroalkylsulfonyl)amide anion include the N-(fluorosulfonyl)-N-(trifluoromethanesulfonyl)amide anion represented by the following chemical formula (7) when m is 1, and the N-(fluorosulfonyl)-N-(pentafluoroethylsulfonyl)amide anion represented by the following chemical formula (8) when m is 2.

[0067] (6) TIFF2025121317000007.tif35161

[0068] (7) TIFF2025121317000008.tif41161

[0069] (C8) TIFF2025121317000009.tif41161

[0070] The various amide anions also include a (perfluoroalkylsulfonyl)fluoroacetamide anion, which is represented by the following chemical formula (9) and in which two hydrogen atoms of the NH2 anion are substituted with a perfluoroalkylsulfonyl group and a fluoroacetyl group. (9) TIFF2025121317000010.tif41164In chemical formula (9), n is an integer of 0 or more, and the number of carbon atoms may be any number.

[0071] Furthermore, various amide anions include, for example, five-membered and six-membered heterocyclic rings, such as N,N-hexafluoro-1,3-disulfonylamide anion (CFSA anion) represented by the following chemical formula (10) and N,N-pentafluoro-1,3-disulfonylamide anion represented by the following chemical formula (11).

[0072] (C10) TIFF2025121317000011.tif56161

[0073] (Chem.11) TIFF2025121317000012.tif51161

[0074] The tris(trifluoromethanesulfonyl)methanide anion (TFSM anion) is represented by the following chemical formula (12). (C12) TIFF2025121317000013.tif64161

[0075] The various phosphate anions are hexafluorophosphate anions (PF6 anions) represented by the following chemical formula (13), or various perfluoroalkylphosphate anions represented by the following chemical formula (14), in which some of the fluorine atoms of PF6 are substituted with fluoroalkyl groups.

[0076] (C13) TIFF2025121317000014.tif38161

[0077] (C14) TIFF2025121317000015.tif38161In chemical formula (14), q is an integer of 1 or more, and the number of carbon atoms may be any number.

[0078] Specifically, tris(pentafluoroethyl)trifluorophosphate anion (FAP anion) represented by the following chemical formula (15) can be mentioned. (C15) TIFF2025121317000016.tif48161

[0079] Examples of the various borate anions include tetrafluoroborate anion (BF4 anion) represented by the following chemical formula (16), and various perfluoroalkylborate anions represented by the following chemical formula (17) in which some of the fluorine atoms in the BF4 anion are substituted with fluoroalkyl groups. Specific examples of the various perfluoroalkylborate anions include mono(fluoroalkyl)trifluoroborate anion and bis(fluoroalkyl)fluoroborate anion.

[0080] (C16) TIFF2025121317000017.tif39161

[0081] (C17) TIFF2025121317000018.tif39161In the formula, s is an integer of 0 or more, t is an integer of 1 or more, and the number of carbon atoms may be any number.

[0082] Furthermore, the various borate anions further include a borate anion represented by the following chemical formula (18). (C18) TIFF2025121317000019.tif29161In the formula, R1 and R2 are each independently a ketone group, or R1 and R2 are carbon atoms in a common six-membered aromatic ring.In the formula, R3 and R4 are each independently a ketone group, or R3 and R4 are carbon atoms in a common six-membered aromatic ring.

[0083] In the chemical formula (18), when R1, R2, R3, and R4 are all ketone groups, the anion is a bis(oxalato)borate (BoB) anion represented by the following chemical formula (19). (C19) TIFF2025121317000020.tif42161

[0084] Furthermore, in chemical formula (18), if R1 and R2 are carbon atoms that form a common six-membered aromatic ring, and R3 and R4 are carbon atoms that form a common six-membered aromatic ring, then the anion is a bis(pyrocatecholato)borate anion represented by the following chemical formula (20). (20) TIFF2025121317000021.tif29161

[0085] Furthermore, the various borate anions further include a borate anion represented by the following chemical formula (21). (21) TIFF2025121317000022.tif32161In the formula, R1 to R6 are each independently a ketone group or a methylene group. Alternatively, in the formula, either R1 or R3 is a ketone group or a methylene group, and the other combination of R1 and R2 or the other combination of R2 and R3 is a carbon atom of a common six-membered aromatic ring. In the formula, either R4 or R6 is a ketone group or a methylene group, and the other combination of R4 and R5 or the other combination of R5 and R6 is a carbon atom of a common six-membered aromatic ring. The aromatic six-membered ring may have one or four methyl groups, or the aromatic six-membered ring may be part of a polycyclic aromatic ring having two or more aromatic rings, such as a naphthalene ring.

[0086] In the chemical formula (21), if R1 and R6 are ketone groups, R2 and R3 are carbon atoms that form a common six-membered aromatic ring, and R4 and R5 are carbon atoms that form a common six-membered aromatic ring, the anion is a bis(salicylato)borate anion (BScB anion) represented by the following chemical formula (22). (22) TIFF2025121317000023.tif55161

[0087] In the chemical formula (21), when R1 and R6 are ketone groups, R2 and R3 are carbon atoms constituting a common six-membered aromatic ring, R4 and R5 are carbon atoms constituting a common six-membered aromatic ring, and both aromatic six-membered rings each have four methyl groups, the resulting anion is bis(tetramethylsalicylato)borate, as represented by the following chemical formula (23). (23) TIFF2025121317000024.tif58161

[0088] In the chemical formula (21), when R1 and R6 are ketone groups, R2 and R3 are carbon atoms constituting a common six-membered aromatic ring, R4 and R5 are carbon atoms constituting a common six-membered aromatic ring, and both aromatic six-membered rings each have one methyl group, the resulting anion is a bis(methylsalicylate)borate anion (BmScB anion) represented by the following chemical formula (24). (24) TIFF2025121317000025.tif48161

[0089] In the chemical formula (21), when R1 and R6 are ketone groups, R2 and R3 are carbon atoms forming a common naphthalene ring, and R4 and R5 are carbon atoms forming a common naphthalene ring, the anion is a bis(1-hydroxy-2-naphtholato)borate anion represented by the following chemical formula (25), a bis(2-hydroxy-1-naphtholato)borate anion (BhNB anion) represented by the following chemical formula (26), or a bis(3-hydroxy-2-naphtholato)borate anion represented by the following chemical formula (27).

[0090] (25) TIFF2025121317000026.tif68161

[0091] (C26) TIFF2025121317000027.tif38161

[0092] (27) TIFF2025121317000028.tif54161

[0093] Examples of various sulfone-based anions include alkylsulfonate anions represented by the following chemical formula (28), various perfluoroalkylsulfonate anions represented by the following chemical formula (29), and p-toluenesulfonate anions represented by the following chemical formula (30).

[0094] (28) TIFF2025121317000029.tif7161In chemical formula (28), x is an integer of 1 or more and 4 or less.

[0095] (C29) TIFF2025121317000030.tif7161In chemical formula (29), y is an integer of 1 or more and 4 or less.

[0096] Specifically, various perfluoroalkylsulfonate anions include a trifluoromethanesulfonate anion in which y is 1 in the above chemical formula (29), a pentafluoroethylsulfonate anion in which y is 2 in the above chemical formula (29), a heptafluoropropanesulfonate anion in which y is 3 in the above chemical formula (29), and a nonafluorobutanesulfonate anion in which y is 4 in the above chemical formula (29).

[0097] (30) TIFF2025121317000031.tif28161

[0098] The tetrafluoroaluminate anion is represented by the following formula (31). (31) TIFF2025121317000032.tif39161

[0099] Examples of cationic components constituting the plastic crystal include various quaternary ammonium cations, various pyrrolidinium cations, various piperidinium cations, various imidazolium cations, various phosphonium cations, and various trialkylsulfonyl cations.

[0100] Examples of the quaternary ammonium cation include tetraalkylammonium cations represented by the following chemical formula (32) and substituted with a linear alkyl group, regardless of the number of carbon atoms. (C32) TIFF2025121317000033.tif47161In the formula, a, b, c, and d are integers of 1 or more, and the number of carbon atoms may be any number.

[0101] In the above chemical formula (32), when a, b, c, and d are 2, it is a tetraethylammonium cation (TEA cation) represented by the following chemical formula (33). (33) TIFF2025121317000034.tif38165

[0102] In the above chemical formula (32), when a, b, and c are 2 and d is 1, it is a triethylmethylammonium cation (TEMA cation) represented by the following chemical formula (34). (34) TIFF2025121317000035.tif38161

[0103] In the above chemical formula (32), when a, b, and c are 1, d is 2, and one of the hydrogen atoms of the ethyl group is substituted with a hydroxy group to form a hydroxyethyl group, the resulting cation is a choline cation (CHL cation) represented by the following chemical formula (35). (35) TIFF2025121317000036.tif32161

[0104] Furthermore, examples of the quaternary ammonium cation include a pyrrolidinium cation represented by the following chemical formula (36), which is a five-membered ring to which a methyl group, an ethyl group, or an isopropyl group is bonded. (36) TIFF2025121317000037.tif46161In the formula, R1 and R2 are methyl groups, ethyl groups, or isopropyl groups.

[0105] Specific examples of the five-membered ring pyrrolidinium cation generalized by the above chemical formula (36) include, for example, the N-ethyl-N-methylpyrrolidinium cation (P12 cation) represented by the following chemical formula (37), the N-isopropyl-N-methylpyrrolidinium cation (P13iso cation) represented by the following chemical formula (38), and the N,N-diethylpyrrolidinium cation (P22 cation) represented by the following chemical formula (39).

[0106] (37) TIFF2025121317000038.tif49161

[0107] (38) TIFF2025121317000039.tif52161

[0108] (39) TIFF2025121317000040.tif48161

[0109] Furthermore, examples of the quaternary ammonium include spiro-type pyrrolidinium cations (SBP cations) represented by the following chemical formula (40). (40) TIFF2025121317000041.tif52161

[0110] Various piperidinium cations are represented by the following chemical formula (41), and examples thereof include piperidinium cations in which a methyl group, an ethyl group, or an isopropyl group is a six-membered ring. (C41) TIFF2025121317000042.tif41161In the formula, R3 and R4 are methyl groups, ethyl groups, or isopropyl groups.

[0111] A specific example of the six-membered ring piperidinium cation generalized by the above chemical formula (41) is, for example, the 1-ethyl-1-methylpiperidinium cation represented by the following chemical formula (42), in which R1 is a methyl group and R2 is an ethyl group. (C42) TIFF2025121317000043.tif36161

[0112] The various imidazolium cations are 1,3-dialkylimidazolium or 1,2,3-trialkylimidazolium cations represented by the following chemical formula (43). (C43) TIFF2025121317000044.tif46161In the formula, h and i are integers between 1 and 3, and j is 0 or 1.

[0113] In chemical formula (43), when j is 0, and h and i are 1, the compound is a 1,3-dimethylimidazolium cation (DMI cation) represented by the following chemical formula (44). The 2-position of this DMI cation may be substituted with a methyl group. (C44) TIFF2025121317000045.tif30161

[0114] In chemical formula (43), when j is 0, h is 1, and i is 2, the cation is a 1-ethyl-3-methylimidazolium cation (EMI cation) represented by the following chemical formula (45). The 2-position of this EMI cation may be substituted with a methyl group. (C45) TIFF2025121317000046.tif30161

[0115] In chemical formula (43), when j is 0, h is 1, and i is 3, it is a 1-methyl-3-propylimidazolium cation (MPI cation) represented by the following chemical formula (46). The 2-position of this MPI cation may be substituted with a methyl group. (C46) TIFF2025121317000047.tif30161

[0116] The various phosphonium cations are represented by the following chemical formula (47), and examples thereof include tetraalkylphosphonium cations substituted with a linear alkyl group, regardless of the number of carbon atoms. Examples of the tetraalkylphosphonium cations include tetraethylphosphonium cations (TEP cations). (C47) TIFF2025121317000048.tif47161In the formula, e, f, g, and h are integers of 1 or more, and the number of carbon atoms may be any number.

[0117] Examples of various trialkylsulfonyl cations include the trimethylsulfonium cation represented by the following chemical formula (48), in which all hydrogen atoms of the sulfonium are substituted with methyl groups. (C48) TIFF2025121317000049.tif38161

[0118] Two or more types of plastic crystals may be included in the electrolyte layer. When two or more types of plastic crystals are included, plastic crystals of the same anion type may be included in the electrolyte layer, plastic crystals of the same cation type may be included in the electrolyte layer, or plastic crystals with different anion and cation components may be included in the electrolyte layer. The blending ratio of different plastic crystals in the electrolyte layer may be equimolar or may be different.

[0119] Plastic crystals can be produced, for example, by the following manufacturing method, but various other methods can also be used. Specifically, alkali metal salts of the anion components that make up the plastic crystals and halogenated cation components are each dissolved in a solvent. Examples of alkali metals include Na, K, Li, and Cs. Examples of halogens include F, Cl, Br, and I. Water is preferred as the solvent. An ion exchange reaction is carried out by gradually adding a solution of the metal salt of the anion to the solution of the halogenated cation. An equimolar amount of the solution of the metal salt of the anion is added to the solution of the halogenated cation, and the mixture is stirred.

[0120] At this time, ion exchange produces plastic crystals and alkali metal halides. When an organic solvent such as dichloromethane is mixed and allowed to stand, the mixture separates into an aqueous layer and an organic solvent layer. The alkali metal halides are removed by removing the aqueous layer. This operation can be repeated multiple times. After removing the alkali metal halides, the organic solvent such as dichloromethane is evaporated to obtain plastic crystals.

[0121] The plastic crystals are dissolved in a solvent in which the plastic crystals are soluble. The solvent is preferably a polar solvent. Examples of polar solvents include acetonitrile, propylene carbonate, γ-butyrolactone, dimethyl carbonate, ethyl methyl carbonate, ethylene carbonate, sulfolane, acetone, methanol, ethanol, isopropyl alcohol, and mixtures thereof. These polar solvents efficiently dissolve the plastic crystals, resulting in excellent productivity of the electrolyte layer.

[0122] The object to which the electrolyte layer is to be attached is then impregnated with a solution of plastic crystals. After impregnation with the solution of plastic crystals, the object is left in a temperature environment at which the solvent volatilizes, such as at 100°C, to volatilize the solvent by drying, and then left in a temperature environment at 150°C, etc., to volatilize any remaining moisture. This allows plastic crystals to be formed on the object to be attached.

[0123] The plastic crystal may be doped with an ionic salt that serves as an electrolyte. The ionic salt may be a salt of an organic acid, a salt of an inorganic acid, or a salt of a complex compound of an organic acid and an inorganic acid, and may be used alone or in combination of two or more.

[0124] Examples of organic acids 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, undecanedioic acid, dodecanedioic acid, and tridecanedioic acid, as well as phenols and sulfonic acids. Examples of inorganic acids include boric acid including tetrafluoroborate, phosphoric acid, phosphorous acid, hypophosphorous acid, carbonic acid, and silicic acid. Examples of composite compounds of organic and inorganic acids include borodisalicylic acid, borodioxalic acid, and borodiglycolic acid.

[0125] Examples of the salts of these organic acids, inorganic acids, and at least one salt of a complex compound of an organic acid and an inorganic acid include ammonium salts, quaternary ammonium salts, quaternized amidinium salts, amine salts, sodium salts, and potassium salts. Examples of the quaternary ammonium ions of the quaternary ammonium salts include tetramethylammonium, triethylmethylammonium, and tetraethylammonium. Examples of the quaternized amidiniums include ethyldimethylimidazolinium and tetramethylimidazolinium. Examples of the amines of the amine salts include primary amines, secondary amines, and tertiary amines. Examples of primary amines include methylamine, ethylamine, and propylamine. Examples of secondary amines include dimethylamine, diethylamine, ethylmethylamine, and dibutylamine. Examples of tertiary amines include trimethylamine, triethylamine, tripropylamine, tributylamine, ethyldimethylamine, and ethyldiisopropylamine.

[0126] (separator) A separator may be provided between the anode body and the cathode body to separate the anode body and the cathode body and to maintain the electrolyte layer between the anode body and the cathode body in order to prevent short-circuiting between the anode body and the cathode body. If the shape of the electrolyte layer can be maintained by itself and the cathode body can be separated by the electrolyte layer, the separator can be eliminated from the electrolytic capacitor.

[0127] Examples of separators include cellulose papers such as kraft, Manila hemp, esparto, hemp, and rayon, and mixed papers 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.

[0128] (Method of manufacturing electrolytic capacitors) (wound type) An example of the assembly process for a wound-type electrolytic capacitor is shown below. First, a surface-expanding layer is formed on one or both sides of the valve metal foil on the anode side, and a dielectric film is formed on the surface-expanding layer by chemical conversion treatment. If necessary, a surface-expanding layer is also formed on one or both sides of the valve metal foil on the cathode side, and an oxide film is formed on the surface. An anode lead and a cathode lead are connected to the anode body and the cathode body, respectively.

[0129] Long anode and cathode bodies are wound with a separator interposed therebetween to produce a cylindrical wound body. The separator is overlapped so that one end protrudes beyond one end of the anode and cathode bodies. The protruding separator is wound first so that the core of the wound body is aligned with the short sides of the anode and cathode bodies to produce a winding core. Then, the anode and cathode bodies are wound by rolling up the long sides of the anode and cathode bodies using the winding core as a winding shaft.

[0130] After the winding, a repair chemical conversion step is 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, and to repair defects in the dielectric film formed on the anode body caused by physical stress such as winding.

[0131] In the repair anodization process, the wound body is immersed in an anodization solution and a voltage is applied. Examples of anodization solutions include phosphoric acid-based anodization solutions such as ammonium dihydrogen phosphate, boric acid-based anodization solutions such as ammonium borate, adipic acid-based anodization solutions such as ammonium adipate, and an anodization solution containing a mixture of boric acid and dicarboxylic acid such as citric acid. The repair anodization voltage is preferably 0.1 to 1.2 times the anodization voltage of the anode body. The voltage application method during repair anodization can be appropriately selected from methods such as applying a constant voltage from the start of repair anodization or increasing the applied voltage stepwise at regular intervals.

[0132] Next, the process moves to the electrolyte layer formation process, where an electrolyte layer is formed between the anode body and the cathode body. The electrolyte layer formation process is broadly divided into a polymer attachment process and a plastic crystal attachment process. In the polymer attachment process, a conductive polymer is attached between the anode body and the cathode body, and in the plastic crystal attachment process, a plastic crystal is attached between the anode body and the cathode body.

[0133] In the polymer application process using a conductive polymer liquid, the wound body is immersed in the conductive polymer liquid to impregnate the wound body with the conductive polymer liquid. A conductive polymer and a neutralizer for ion-dissociating salts composed of non-metallic cationic components are added to the conductive polymer liquid. To promote the impregnation of the wound body with the conductive polymer liquid, a decompression treatment or a pressurization treatment may be performed as necessary. The impregnation process may be repeated multiple times. After the wound body is impregnated with the conductive polymer liquid, a drying process is performed to remove the solvent from the conductive polymer liquid.

[0134] Next, in the plastic crystal attachment step, the roll is immersed in a solution of plastic crystals to impregnate the roll. To promote the impregnation of the roll with the plastic crystal solution, a decompression treatment or a pressurization treatment may be performed as necessary. The impregnation step may be repeated multiple times. After the roll is impregnated with the plastic crystal solution, the solvent is removed by a drying step.

[0135] In this example, the conductive polymer is first attached to the wound body, followed by the plastic crystal, but it is also possible to attach the plastic crystal first and then the conductive polymer. However, from the perspective of forming a conductive path between the anode body and the cathode body, it is preferable to attach the conductive polymer first. By attaching the conductive polymer first, an electrolyte layer including the plastic crystal and the conductive polymer layer can be formed uniformly, resulting in good capacitance characteristics and good ESR characteristics.

[0136] The conductive polymer and the plastic crystal may be attached to the anode body, and then the anode body and the cathode body may be wound facing each other with a separator interposed therebetween. Alternatively, the conductive polymer and the plastic crystal may be attached to the anode body, the cathode body, the separator, or both, and then the anode body and the cathode body may be wound facing each other with a separator interposed therebetween.

[0137] The capacitor element is housed in an outer case that is closed at one end and open at the other, and the capacitor element is sealed in the outer case with a sealing body. The sealing body is made of, for example, rubber or a laminate of rubber and a hard substrate. Examples of rubber include ethylene propylene rubber and butyl rubber. The sealing body is attached by crimping the open end of the outer case. After the capacitor element is sealed in the outer case, 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 coating layer, etc.

[0138] In addition to being housed in an exterior case with one end closed and the other end open, the capacitor element may be sealed with a laminate film or molded with resin. Examples of the molding resin include heat-resistant resin and insulating resin. The molding resin may be formed into a thin film using techniques such as dip coating and printing. Furthermore, a flat-plate capacitor element may not require an exterior case.

[0139] (Laminated type) An example of the assembly process for a laminated type electrolytic capacitor is shown below. First, a surface-expanding layer is formed on the surface of the valve metal foil that serves as the anode body. Next, the foil with the surface-expanding layer is subjected to a chemical conversion treatment in a chemical conversion solution to form a dielectric film on the surface of the valve metal foil. An insulating resist layer is printed and dried on the area that will later become the anode terminal, excluding the area that will become the anode. In other words, the insulating resist layer is printed so that an electrolyte layer does not form on the area that will become the anode terminal.

[0140] After printing the insulating resist layer, the process moves to the conductive polymer deposition process. The deposition of the conductive polymer can be performed by any of the following methods: immersing the foil in a conductive polymer solution; or applying the conductive polymer solution to the foil surface by ejection or printing, thereby depositing the conductive polymer so as to cover the dielectric film. A conductive polymer, diethylene glycol, and a compound containing an ethylene oxide group are added to the conductive polymer solution. Alternatively, a conductive polymer, diethylene glycol, a compound containing an ethylene oxide group, and a crosslinking agent are added to the conductive polymer solution. After the solvent of the conductive polymer solution is removed by drying, the process moves to the plastic crystal deposition process, where the foil is immersed in a solution of plastic crystals to further deposit the plastic crystals. The solvent of the plastic crystals is then removed by drying. An electrolyte layer is formed by this deposition of the conductive polymer and the plastic crystals.

[0141] Next, a carbon paste is printed on the electrolyte layer using a screen printer or the like and dried. This drying process forms a carbon layer on the electrolyte layer. Furthermore, a metal paste such as silver paste is printed on the carbon layer and dried. This drying process forms a silver layer on the carbon layer. These carbon and silver layers correspond to the cathode body of the electrolytic capacitor.

[0142] After the cathode body is formed, the insulating resist layer is peeled off. The insulating resist layer may be peeled off by laser irradiation or mechanical peeling using a jig. The exposed portion is plated to complete the anode terminal.

[0143] The capacitor element thus fabricated is covered with, for example, a laminate film, or is sealed by molding, dip coating, or printing with a resin such as a heat-resistant resin or an insulating resin. [Example]

[0144] The electrolytic capacitor will be described in more detail below based on examples, but the present invention is not limited to the following examples.

[0145] The electrolytic capacitor of Example 1 was fabricated as follows. First, a pair of electrodes was fabricated using aluminum foil. Both electrode foils were subjected to an etching process to enlarge the surface. One electrode was used as an anode body, and its surface was enlarged by AC etching to form a surface-enlarged layer. In the anode body surface-enlargement process, an AC current was passed through the aluminum foil in an aqueous solution containing hydrochloric acid to form spongy pits. In the cathode body surface-enlargement process, an AC current was passed through the aluminum foil in an aqueous solution containing hydrochloric acid to form spongy etching pits.

[0146] For the anode body, a dielectric film was formed on the foil surface by chemical conversion treatment. In the chemical conversion treatment process, aluminum foil with a surface expansion layer was treated in an ammonium adipate solution to form a 63.6V dielectric film on the aluminum foil surface. For the cathode body, a 3V dielectric film was formed on aluminum foil with a surface expansion layer.

[0147] Lead wires were connected to each of the anode and cathode bodies, and the anode and cathode foils were wound facing each other with a manila paper separator in between. The wound body had a diameter of 6.3 mm and a height of 5.8 mm. The wound body was repaired by passing a voltage of 58 V and a current density of 2 mA through an ammonium dihydrogen phosphate aqueous solution.

[0148] The wound body was first impregnated with a conductive polymer dispersion in which a conductive polymer was dispersed in a dispersion medium as a conductive polymer solution. The conductive polymer dispersion was a dispersion of poly(3,4-ethylenedioxythiophene) (PEDOT / PSS) doped with polystyrene sulfonic acid (PSS). PEDOT / PSS was added at a rate of 2 wt% relative to the entire conductive polymer dispersion. A neutralizing agent was also added to the conductive polymer dispersion at a rate of 1 wt% relative to the entire conductive polymer dispersion, and the pH was adjusted to 4.0. Ammonia water was added as the neutralizing agent for Example 1. In the conductive polymer dispersion to which ammonia water was added, ammonium ions (NH4 + ) occurs.

[0149] The wound body was impregnated with the conductive polymer dispersion for 5 minutes at room temperature and in a reduced pressure environment of -0.3 MPa. This impregnation process was performed twice in total. After the wound body was removed from the conductive polymer dispersion, it was left to stand at room temperature for 10 minutes and then in a temperature environment of 110°C for 30 minutes to dry the wound body. As a result, an electrolyte layer containing a conductive polymer was formed on the anode body, cathode body, and separator of the wound body.

[0150] Next, a plastic crystal was attached between the anode and cathode bodies in addition to the conductive polymer. The plastic crystal was P12BScB. That is, the plastic crystal contained P12 cations and BScB anions in a 1:1 molar ratio. The P12 cation was an N-ethyl-N-methylpyrrolidinium cation represented by chemical formula (30). The BScB anion was a bis(salicylate)borate anion represented by chemical formula (22).

[0151] The plastic crystals were added to acetonitrile at a ratio of 50 wt% to the total solution. 90 μL of this acetonitrile solution was dropped onto the wound body, impregnating the wound body with the acetonitrile solution. The amount of acetonitrile impregnated per wound body was 70 mg.

[0152] After the impregnation, the wound body was left to stand in an argon atmosphere at 45°C for 2 hours, then in an argon atmosphere at 60°C for 2 hours, then in an argon atmosphere at 80°C for 2 hours, and finally in an argon atmosphere at 100°C for 12 hours to dry the acetonitrile solution, thereby forming an electrolyte layer containing a conductive polymer and plastic crystals.

[0153] The capacitor element of Example 1 was housed in an outer case, and the opening of the outer case was sealed with a sealant. The sealant and the outer case were tightly attached by crimping. The electrolytic capacitor of Example 1 was then subjected to an aging treatment by applying a voltage of 40.25 V for 1 hour in a temperature environment of 105°C. As a result, electrolytic capacitors with a diameter of 6.3 mm, a height of 5.8 mm, a rated voltage of 35 WV, and a rating of 47 μF were fabricated.

[0154] (Comparative Example 1, etc.) Furthermore, electrolytic capacitors of Comparative Example 1, Reference Example 1, and Reference Example 2 were fabricated. As shown in Table 1 below, Example 1, Comparative Example 1, Reference Example 1, and Reference Example 2 differ in the neutralizing agent added to the conductive polymer dispersion and the presence or absence of plastic crystals. The configurations and compositions, as well as the manufacturing methods and manufacturing conditions, of the other electrolytic capacitors of Comparative Example 1, Reference Example 1, and Reference Example 2 are the same as those of Example 1.

[0155] (Table 1) TIFF2025121317000050.tif71161

[0156] As shown in Table 1 above, in Example 1, an electrolyte layer is formed using a conductive polymer dispersion to which ammonia water, which generates ammonium ions through ionic dissociation, is added as a neutralizing agent. In contrast, in Comparative Example 1, an electrolyte layer is formed using a conductive polymer dispersion to which sodium hydroxide, which generates sodium ions through ionic dissociation, is added as a neutralizing agent. The pH of the conductive polymer dispersion is adjusted to 4.0 using ammonia water and sodium hydroxide. Here, the ammonium ions are non-metallic ions, and the sodium ions are metallic ions. The electrolyte layers of Example 1 and Comparative Example 1 are also formed by using the same plastic crystals.

[0157] In Reference Example 1, the electrolyte layer is formed using a conductive polymer dispersion liquid to which the same neutralizing agent as in Example 1 has been added. In Reference Example 2, the electrolyte layer is formed using a conductive polymer dispersion liquid to which the same neutralizing agent as in Comparative Example 1 has been added. However, in Reference Examples 1 and 2, the electrolyte layer is formed only from the conductive polymer and does not include plastic crystals.

[0158] The electrolytic capacitors of Example 1, Comparative Example 1, Reference Example 1, and Reference Example 2 were continuously exposed to a temperature environment of 170°C, and the equivalent series resistance (ESR) was measured at each elapsed time. The ESR was measured at 20°C using an LCR meter (manufactured by NF Corporation, model number ZM2376). The ESR measurement frequency was 100 kHz, and the AC current level was a sine wave of 1.0 Vms.

[0159] The change in ESR over time when the electrolytic capacitors of Example 1, Comparative Example 1, Reference Example 1, and Reference Example 2 were exposed to a temperature environment of 170°C is shown in Fig. 1. Fig. 1 is a graph showing the relationship between the ESR change rate (ΔESR) and the elapsed time for the electrolytic capacitors of Example 1, Comparative Example 1, Reference Example 1, and Reference Example 2.

[0160] As shown in Figure 1, Reference Example 1 and Reference Example 2, which do not contain plastic crystals in the electrolyte layer, have the same ESR change rate. In other words, it was confirmed that when the electrolyte layer does not contain plastic crystals, the ESR change rate of the electrolytic capacitor is the same whether the electrolyte layer contains metal ions or does not contain metal ions but instead contains non-metal ions.

[0161] On the other hand, the rate of change in ESR is significantly different between Example 1, which contains plastic crystals in the electrolyte layer, and Comparative Example 1. Comparative Example 1 contains metal ions, namely sodium ions, in the electrolyte layer. In Comparative Example 1, which contains plastic crystals and metal ions in the electrolyte layer, the change in ESR is significantly larger than in Reference Examples 1 and 2, and the ESR of the electrolytic capacitor is deteriorated.

[0162] In contrast, Example 1 does not contain metal ions, such as sodium ions, in the electrolyte layer, but instead contains non-metal ions, such as ammonium ions. This electrolyte layer contains plastic crystals, but does not contain metal ions. Example 1, which contains ammonium ions, maintains an ESR of the electrolytic capacitor at a level equal to or better than that of Reference Examples 1 and 2.

[0163] In this way, it was confirmed that an electrolytic capacitor whose electrolyte layer contains a conductive polymer and plastic crystals but does not contain metal ions can suppress deterioration of the ESR of the electrolytic capacitor even if it contains plastic crystals.

Claims

1. An electrolytic capacitor having an electrolyte layer between a pair of electrodes, the electrolyte layer includes a conductive polymer and a plastic crystal; the electrolyte layer does not contain metal ions; An electrolytic capacitor characterized by:

2. the metal ion is an alkali metal; 2. The electrolytic capacitor according to claim 1,

3. the electrolyte layer is formed from a conductive polymer liquid in which a conductive polymer is dispersed or dissolved, the metal ions are derived from a neutralizing agent contained in the conductive polymer liquid, the electrolyte layer does not contain the metal ions derived from the neutralizing agent contained in the conductive polymer liquid; 2. The electrolytic capacitor according to claim 1,

4. the conductive polymer liquid does not contain the metal ions but contains a non-metallic compound; 4. The electrolytic capacitor according to claim 3,

5. a polymer adhesion step of impregnating a pair of electrodes with a conductive polymer liquid in which a conductive polymer is dispersed or dissolved, and then drying the liquid; the conductive polymer liquid does not contain metal ions; A method for manufacturing an electrolytic capacitor, comprising:

6. the conductive polymer liquid contains a neutralizing agent, the neutralizing agent is a non-metallic compound that does not contain the metal ions; 6. The method for manufacturing an electrolytic capacitor according to claim 5,

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