Pretreatment agent for hybrid electrolytic capacitor manufacturing, and hybrid electrolytic capacitor manufacturing method

Abstract

The present invention provides a pretreatment agent for hybrid electrolytic capacitor manufacturing that is for manufacturing a hybrid electrolytic capacitor with a superior ESR characteristic, as well as a hybrid electrolytic capacitor manufacturing method using said pretreatment agent, by providing a pretreatment agent for hybrid electrolytic capacitor manufacturing that is for treating an anode foil which has a dielectric oxide film and will constitute a hybrid electrolytic capacitor, said pretreatment agent being characterized in that a carbohydrate compound is dissolved in a solvent including one or more types of solvents selected from the group consisting of water, ethanol, methanol, and isopropyl alcohol, and the included quantity thereof is 0.001-25 mass%, as well as a hybrid electrolytic capacitor manufacturing method using said pretreatment agent.

Description

Pretreatment agent for manufacturing hybrid electrolytic capacitors and method for manufacturing hybrid electrolytic capacitors

[0001] The present invention relates to a pretreatment agent for producing a hybrid electrolytic capacitor and a method for producing a hybrid electrolytic capacitor using the pretreatment agent. More specifically, the present invention relates to a pretreatment agent for producing a hybrid electrolytic capacitor, the pretreatment agent being used to produce a hybrid electrolytic capacitor including an anode foil and a cathode foil having a dielectric oxide film, a separator disposed between the anode foil and the cathode foil, and an electrolytic solution and conductive polymer as an electrolyte, the pretreatment agent comprising a carbohydrate compound dissolved in a solvent containing one or more solvents selected from the group consisting of water, ethanol, methanol, and isopropyl alcohol, and the method for producing a hybrid electrolytic capacitor.

[0002] Electrolytic capacitors can be broadly divided into those that use a liquid electrolyte and those that use a solid electrolyte. Liquid electrolyte electrolytic capacitors typically use an organic acid, inorganic acid, or their salt dissolved in an organic solvent as the electrolyte. On the other hand, solid electrolyte capacitors typically use a solid electrolyte layer containing a conductive polymer that functions as a cathode formed on an anode metal with a dielectric oxide film. Hybrid electrolytic capacitors that combine the features of both types also exist. With the recent increase in the operating voltages of automotive electrical power supplies and digital home appliances, hybrid electrolytic capacitors are required to have low equivalent series resistance (ESR).

[0003] As an example of a hybrid electrolytic capacitor, as disclosed in Patent Document 1, an electrolytic capacitor is known that includes a dispersion impregnation step in which a capacitor element formed by winding an anode foil having a dielectric film and an opposing cathode foil with a separator interposed therebetween is impregnated with a dispersion containing conductive solid particles or powder and a solvent, a drying step in which the solvent is evaporated after the dispersion impregnation step to form a conductive solid layer on the surface of the dielectric film, and an electrolyte impregnation step in which an electrolyte is impregnated into the gaps in the conductive solid layer. However, such hybrid electrolytic capacitors have been insufficient in terms of the ESR characteristics that are currently required.

[0004] To reduce ESR, studies are being conducted to determine whether methods used in conventional solid electrolytic capacitors can be applied to hybrid electrolytic capacitors. For example, Patent Document 2 (see below) discloses a solid electrolytic capacitor that includes, as a solid electrolyte, a conductive composition containing a conductive polymer (A) that satisfies the following condition (i): Condition (i): When a conductive polymer solution containing 1% by mass of the conductive polymer relative to the total mass of the conductive polymer solution is used, and the volume average particle diameter of the smallest particle distribution, including the peak showing the smallest particle diameter, among one or more peaks obtained when the particle distribution is measured by dynamic light scattering is less than 26 nm; and Condition (ii): Condition (ii): The pH of a 1 mol / L aqueous solution is 9.0 or less. In this case, sugars such as methyl cellulose and pullulan may be used as the water-soluble compound. Adding the water-soluble compound during the formation of the conductive polymer layer has been shown to reduce the ESR change rate and improve the capacitance appearance rate during a moisture resistance test. Therefore, when a conductive composition containing a water-soluble compound, particularly a sugar, is used as a solid electrolyte layer in a hybrid electrolytic capacitor, the ESR increases, resulting in a problem of reduced performance of the hybrid electrolytic capacitor.

[0005] JP 2008-010657 A International Publication No. 2014 / 061502

[0006] Therefore, the present invention provides a pretreatment agent for producing a hybrid electrolytic capacitor having excellent ESR characteristics, and a method for producing a hybrid electrolytic capacitor using the pretreatment agent.

[0007] As a result of intensive research to solve the above-mentioned problems, the present inventors have found that the above-mentioned problems can be solved by using a pretreatment agent for producing a hybrid electrolytic capacitor, which is prepared by dissolving a carbohydrate compound in a solvent containing one or more selected from the group consisting of water, ethanol, methanol, and isopropyl alcohol, in an amount of 0.001 to 25 mass %, to treat an anode foil having a dielectric oxide film that constitutes a hybrid electrolytic capacitor, and have thereby completed the present invention.

[0008] That is, the present invention provides the following [1] to

[10] . [1] A pretreatment agent for producing a hybrid electrolytic capacitor, for treating an anode foil having a dielectric oxide film that constitutes a hybrid electrolytic capacitor, characterized in that a carbohydrate compound is dissolved in a solvent containing one or more compounds selected from the group consisting of water, ethanol, methanol, and isopropyl alcohol, and the content of the carbohydrate compound is 0.001 to 25 mass%. [2] The pretreatment agent for producing a hybrid electrolytic capacitor according to [1], further containing an ionic electrolyte. [3] The pretreatment agent for producing a hybrid electrolytic capacitor according to [1], wherein the carbohydrate compound is one or more compounds selected from the group consisting of pullulan, glucose, trehalose, sucrose, dextran, starch, methylcellulose, and carrageenan. [4] The pretreatment agent for producing a hybrid electrolytic capacitor according to [1], wherein the carbohydrate compound is any one compound selected from the group consisting of glucose, trehalose, and sucrose, and the content of the carbohydrate compound is 10 to 25 mass%. [5] The pretreatment agent for producing a hybrid electrolytic capacitor according to [1], wherein the saccharide compound is any one selected from the group consisting of pullulan, dextran, and starch, and the content thereof is 0.1 to 5 mass%. [6] The pretreatment agent for producing a hybrid electrolytic capacitor according to [1], wherein the saccharide compound is methylcellulose or carrageenan, and the content thereof is 0.001 to 0.01 mass%. [7] The pretreatment agent for producing a hybrid electrolytic capacitor according to any one of [2] to [6], wherein an ionic electrolyte is contained in an amount of 10 to 50 parts by mass per 100 parts by mass of the saccharide compound. [8] The pretreatment agent for producing a hybrid electrolytic capacitor according to any one of [2] to [7], wherein the ionic electrolyte is an electrolyte salt composed of a nitrogen-containing cation having an unshared electron pair and an anion selected from a phosphate compound, a carboxylate compound, and a borate compound.[9] A method for producing a hybrid electrolytic capacitor, comprising treating an anode foil having a dielectric oxide film that constitutes a hybrid electrolytic capacitor with any one of the pretreatment agents for producing a hybrid electrolytic capacitor according to [1] to [8].

[10] A method for producing a hybrid electrolytic capacitor, comprising: a dispersion impregnation step of impregnating a capacitor element, which is formed by winding an anode foil having a dielectric oxide film formed thereon and a counter cathode foil with a separator interposed therebetween, with a dispersion containing conductive solid particles or powder and a solvent; a drying step of evaporating the solvent after the dispersion impregnation step to form a conductive solid layer on the surface of the dielectric oxide film; and an electrolyte impregnation step of impregnating gaps in the conductive solid layer with an electrolyte, the method further comprising: a pretreatment agent impregnation step of impregnating the capacitor element with any one of the pretreatment agents for producing a hybrid electrolytic capacitor according to [1] to [8] before forming the conductive solid layer; and a drying step of evaporating the solvent of the pretreatment agent for producing a hybrid electrolytic capacitor after the pretreatment agent impregnation step to retain the carbohydrate compound on the surface of the dielectric oxide film.

[0009] By using the pretreatment agent for producing a hybrid electrolytic capacitor of the present invention, a hybrid electrolytic capacitor having excellent ESR characteristics can be produced.

[0010] The pretreatment agent for producing a hybrid electrolytic capacitor of the present invention (hereinafter referred to as "the pretreatment agent of the present invention") is used to treat an anode foil having a dielectric oxide film that constitutes a hybrid electrolytic capacitor, and comprises a carbohydrate compound dissolved in a solvent containing one or more selected from the group consisting of water, ethanol, methanol, and isopropyl alcohol, the content of which is 0.001 to 25 mass %.

[0011] [Pretreatment Agent for Hybrid Electrolytic Capacitor Production] First, the pretreatment agent of the present invention will be described. Examples of carbohydrate compounds contained in the pretreatment agent of the present invention include glucose, cellulose, fructose, galactose, sucrose and its derivatives, maltose, lactose, sorbitol, xylitol, lactitol, agar, pullulan, methylcellulose, xanthan gum, guar gum, maltodextrin, dextran, starch, inulin, β-cyclodextrin, and carrageenan. Preferred carbohydrate compounds are pullulan, glucose, trehalose, sucrose, dextran, starch, methylcellulose, and carrageenan. These carbohydrate compounds can be used alone or in combination of two or more.

[0012] The content of the carbohydrate compound in the pretreatment agent is 0.001 to 25% by mass (hereinafter simply referred to as "%"), but preferably 10 to 25% if the carbohydrate compound is one selected from the group consisting of glucose, trehalose, and sucrose, 0.1 to 5% if the carbohydrate compound is one selected from the group consisting of pullulan, dextran, and starch, and 0.001 to 0.01% if the carbohydrate compound is methylcellulose or carrageenan. By setting the content within these ranges, the ESR reduction effect can be further achieved when the hybrid electrolytic capacitor is made.

[0013] The pretreatment agent further contains a solvent. The solvent is one or more selected from the group consisting of water, ethanol, methanol, and isopropyl alcohol. Among these solvents, water is preferred.

[0014] The pretreatment agent preferably further contains an ionic electrolyte. The ionic electrolyte is not particularly limited as long as it is one that is typically used in electrolytic capacitors, but for example, an electrolyte having a nitrogen-containing cation with an unshared electron pair and an anion selected from a phosphate compound, a carboxylate compound, and a borate compound is preferred.

[0015] Examples of electrolytes having a nitrogen-containing cation with an unshared electron pair and an anion selected from phosphate compounds, carboxylate compounds, and borate compounds include compounds represented by the following general formulas (1) to (5) or ammonium salts. These electrolytes can be synthesized by well-known methods, or commercially available products can be used.

[0016]

[0017] In general formulas (1) to (5), the group R １ ~R ２５ are each independently a hydrogen atom, an alkyl group having 1 to 18 carbon atoms, an alkoxy group having 1 to 18 carbon atoms, or a hydroxyl group, and may be the same or different; R １ ~R ２５ Adjacent groups among X may be linked to form an alkylene group having 2 to 6 carbon atoms. － is a carboxylate compound anion, a borate compound anion, or a phosphate compound anion.

[0018] Specific examples of the cation moiety of the compound represented by general formula (1) include ammonium cations; quaternary ammonium cations such as tetramethylammonium cation, tetraethylammonium cation, tetrapropylammonium cation, tetraisopropylammonium cation, tetrabutylammonium cation, trimethylethylammonium cation, triethylmethylammonium cation, dimethyldiethylammonium cation, dimethylethylmethoxyethylammonium cation, dimethylethylmethoxymethylammonium cation, dimethylethylethoxyethylammonium cation, trimethylpropylammonium cation, dimethylethylpropylammonium cation, triethylpropylammonium cation, spiro-(1,1')-bipyrrolidinium cation, piperidine-1-spiro-1'-pyrrolidinium cation, and spiro-(1,1')-bipiperidinium cation; trimethylamine cation, triethylamine cation, tripropylamine cation, triisopropylamine cation, tributylamine cation, and diethylmethylamine. cation, tertiary ammonium cations such as dimethylethylamine cation, diethylmethoxyamine cation, dimethylmethoxyamine cation, dimethylethoxyamine cation, diethylethoxyamine cation, methylethylmethoxyamine cation, N-methylpyrrolidine cation, N-ethylpyrrolidine cation, N-propylpyrrolidine cation, N-isopropylpyrrolidine cation, N-butylpyrrolidine cation, N-methylpiperidine cation, N-ethylpiperidine cation, N-propylpiperidine cation, N-isopropylpiperidine cation, and N-butylpiperidine cation; and secondary ammonium cations such as dimethylamine cation, diethylamine cation, diisopropylamine cation, dipropylamine cation, dibutylamine cation, methylethylamine cation, methylpropylamine cation, methylisopropylamine cation, methylbutylamine cation, ethylisopropylamine cation, ethylpropylamine cation, ethylbutylamine cation, isopropylbutylamine cation, and pyrrolidine cation.

[0019] Specific examples of the cation moiety of the compound represented by general formula (2) include tetramethylimidazolium cation, tetraethylimidazolium cation, tetrapropylimidazolium cation, tetraisopropylimidazolium cation, tetrabutylimidazolium cation, 1,3-dimethylimidazolium cation, 1,3-diethylimidazolium cation, 1,3-dipropylimidazolium cation, 1,3-diisopropylimidazolium cation, 1,3-dibutylimidazolium cation, and 1-methyl-3-ethylimidazolium cation. Examples thereof include 1-ethyl-3-methylimidazolium cation, 1-butyl-3-methylimidazolium cation, 1-butyl-3-ethylimidazolium cation, 1,2,3-trimethylimidazolium cation, 1,2,3-triethylimidazolium cation, 1,2,3-tripropylimidazolium cation, 1,2,3-triisopropylimidazolium cation, 1,2,3-tributylimidazolium cation, 1,3-dimethyl-2-ethylimidazolium cation, and 1,2-dimethyl-3-ethylimidazolium cation.

[0020] Specific examples of the cation moiety of the compound represented by general formula (3) include tetramethylimidazolinium cation, tetraethylimidazolinium cation, tetrapropylimidazolinium cation, tetraisopropylimidazolinium cation, tetrabutylimidazolinium cation, 1,3,4-trimethyl-2-ethylimidazolinium cation, 1,3-dimethyl-2,4-diethylimidazolinium cation, 1,2-dimethyl-3,4-diethylimidazolinium cation, 1- Methyl-2,3,4-triethylimidazolinium cation, 1,2,3-trimethylimidazolinium cation, 1,2,3-triethylimidazolinium cation, 1,2,3-tripropylimidazolinium cation, 1,2,3-triisopropylimidazolinium cation, 1,2,3-tributylimidazolinium cation, 1,3-dimethyl-2-ethylimidazolinium cation, 1-ethyl-2,3-dimethylimidazolinium cation, 4-cyano-1,2,3-trimethylimidazolinium cation, methylimidazolinium cation, 3-cyanomethyl-1,2-dimethylimidazolinium cation, 2-cyanomethyl-1,3-dimethylimidazolinium cation, 4-acetyl-1,2,3-trimethylimidazolinium cation, 3-acetylmethyl-1,2-dimethylimidazolinium cation, 4-methylcarboxymethyl-1,2,3-trimethylimidazolinium cation, 3-methylcarboxymethyl-1,2-dimethylimidazolinium cation, 4-methoxy-1, Examples include 2,3-trimethylimidazolinium cation, 3-methoxymethyl-1,2-dimethylimidazolinium cation, 4-formyl-1,2,3-trimethylimidazolinium cation, 3-formylmethyl-1,2-dimethylimidazolinium cation, 3-hydroxyethyl-1,2-dimethylimidazolinium cation, 4-hydroxymethyl-1,2,3-trimethylimidazolinium cation, and 2-hydroxyethyl-1,3-dimethylimidazolinium cation.

[0021] Specific examples of the cation moiety of the compound represented by general formula (4) include tetramethylpyrazolium cation, tetraethylpyrazolium cation, tetrapropylpyrazolium cation, tetraisopropylpyrazolium cation, tetrabutylpyrazolium cation, 1,2-dimethylpyrazolium cation, 1-methyl-2-ethylpyrazolium cation, 1,2-diethylpyrazolium cation, 1,2-dipropylpyrazolium cation, 1,2-dibutylpyrazolium cation, 1-methyl-2-propylpyrazolium cation, 1-methyl-2-butylpyrazolium cation, 1-methyl-2-hexylpyrazolium cation, 1-methyl-2-octylpyrazolium cation, 1-methyl-2-dodecylpyrazolium cation, 1,2,3-trimethyl ... Examples of the methylpyrazolium cation include methylpyrazolium cation, 1,2,3-triethylpyrazolium cation, 1,2,3-tripropylpyrazolium cation, 1,2,3-triisopropylpyrazolium cation, 1,2,3-tributylpyrazolium cation, 1-ethyl-2,3,5-trimethylpyrazolium cation, 1-ethyl-3-methoxy-2,5-dimethylpyrazolium cation, 3-phenyl-1,2,5-trimethylpyrazolium cation, 3-methoxy-5-phenyl-1-ethyl-2-ethylpyrazolium cation, 1,2-tetramethylene-3,5-dimethylpyrazolium cation, 1,2-tetramethylene-3-phenyl-5-methylpyrazolium cation, and 1,2-tetramethylene-3-methoxy-5-methylpyrazolium cation.

[0022] Specific examples of the cation moiety of the compound represented by general formula (5) include N-methylpyridinium cation, N-ethylpyridinium cation, N-propylpyridinium cation, N-isopropylpyridinium cation, N-butylpyridinium cation, N-hexylpyridinium cation, N-octylpyridinium cation, N-dodecylpyridinium cation, N-methyl-3-methylpyridinium cation, N-ethyl-3-methylpyridinium cation, N-propyl-3-methylpyridinium cation, N-butyl-3-methylpyridinium cation, N-butyl-4-methylpyridinium cation, and N-butyl-4-ethylpyridinium cation.

[0023] Anion X in combination with the above cation －is a carboxylic acid compound anion, a boric acid compound anion, or a phosphate compound anion. The carboxylic acid compound anion is an anion of an organic carboxylic acid such as an aromatic carboxylic acid or an aliphatic carboxylic acid, and the organic carboxylic acid may have a substituent.Specific examples thereof include aromatic carboxylic acid anions such as phthalate anion, salicylate anion, isophthalate anion, terephthalate anion, trimellitate anion, pyromellitate anion, benzoate anion, resorcylate anion, cinnamate anion, naphthoate anion, and mandelate anion; oxalate anion, malonate anion, succinate anion, glutarate anion, adipate anion, pimelate anion, suberate anion, azelaate anion, sebacate anion, undecanedioic acid anion, and dodecanedioic acid anion. Anions, tridecanedioic acid anion, tetradecanedioic acid anion, pentadecanedioic acid anion, hexadecanedioic acid anion, 3-tert-butyl adipate anion, methyl malonate anion, ethyl malonate anion, propyl malonate anion, butyl malonate anion, pentyl malonate anion, hexyl malonate anion, dimethyl malonate anion, diethyl malonate anion, methyl propyl malonate anion, methyl butyl malonate anion, ethyl propyl malonate anion, dipropyl malonate anion, methyl Succinate, ethylsuccinate, 2,2-dimethylsuccinate, 2,3-dimethylsuccinate, 2-methylglutarate, 3-methylglutarate, 3-methyl-3-ethylglutarate, 3,3-diethylglutarate, 3,3-dimethylglutarate, 3-methyladipic acid, 1,6-decanedicarboxylic acid, 5,6-decanedicarboxylic acid, formate, acetate, propionate, butyrate, isobutyrate, valerate Examples of such anions include saturated carboxylic acid anions such as caproate anion, enanthate anion, caprylate anion, pelargonate anion, laurate anion, myristate anion, stearate anion, behenate anion, undecanoate anion, itaconate anion, tartarate anion, glycolate anion, lactate anion, and pyruvate anion, and aliphatic carboxylic acid anions containing unsaturated carboxylic acids such as maleate anion, fumarate anion, acrylate anion, methacrylate anion, and oleate anion. These anions can be used alone or in combination of two or more.

[0024] Examples of the boric acid compound anion include borate anion, borodiazelaic acid anion, borodisalicylic acid anion, borodiglycolic acid anion, borodilactic acid anion, and borodisoxalic acid anion.

[0025] Examples of the phosphate compound anion include phosphate anion, dimethyl phosphate anion, diethyl phosphate anion, dipropyl phosphate anion, diisopropyl phosphate anion, dibutyl phosphate anion, dihexyl phosphate anion, methyl phosphate anion, ethyl phosphate anion, propyl phosphate anion, isopropyl phosphate anion, butyl phosphate anion, hexyl phosphate anion, 2-ethylhexyl phosphate anion, dioctyl phosphate anion, octyl phosphate anion, lauryl phosphate anion, butoxyethyl phosphate anion, isotridecyl phosphate anion, oleyl phosphate anion, tetracosyl phosphate anion, ethylene glycol phosphate anion, and 2-hydroxyethyl methacrylate phosphate anion.

[0026] Specific examples of ammonium salts include monoammonium phosphate, diammonium phosphate, ammonium oxalate, ammonium formate, ammonium benzoate, ammonium adipate, ammonium borate, ammonium polyphosphate, etc. Among these, monoammonium phosphate, diammonium phosphate, ammonium oxalate, ammonium formate, ammonium benzoate, ammonium adipate, and ammonium borate are preferred, and particularly preferably, monoammonium phosphate, diammonium phosphate, ammonium benzoate, ammonium adipate, and ammonium oxalate are preferably used.

[0027] The content of the ionic electrolyte in the pretreatment agent is not particularly limited, but preferably contains 0.4 to 500,000 parts by mass of the ionic electrolyte per 100 parts by mass of the carbohydrate compound, and particularly preferably contains 10 to 50 parts by mass of the ionic electrolyte per 100 parts by mass of the carbohydrate compound.

[0028] The pretreatment agent may contain an appropriate amount of a water-soluble polymer other than the sugar compound as an additive, provided that the effect of the present invention is not impaired.

[0029] The pretreatment agent of the present invention can be produced by mixing the components with a solvent.

[0030] The pretreatment agent of the present invention may be used to treat an anode foil having a dielectric oxide film that constitutes a hybrid electrolytic capacitor in a method for manufacturing a hybrid electrolytic capacitor. The method for treating an anode foil having a dielectric oxide film with the pretreatment agent of the present invention is not particularly limited, but the pretreatment agent may be applied, sprayed, impregnated, or the like to the anode foil having a dielectric oxide film, and then dried or the like to retain the carbohydrate compound in the anode foil having a dielectric oxide film. When the anode foil having a dielectric oxide film is incorporated into a capacitor element, the entire capacitor element may be treated, and in this case, the carbohydrate compound will be retained in the capacitor element.

[0031] Specific examples of methods for producing hybrid electrolytic capacitors using the pretreatment agent of the present invention include a dispersion impregnation step of impregnating a capacitor element formed by winding an anode foil having a dielectric oxide film formed thereon and a counter cathode foil with a separator interposed therebetween, with a dispersion containing conductive solid particles or powder and a solvent; a drying step of evaporating the solvent after the dispersion impregnation step to form a conductive solid layer on the surface of the dielectric oxide film; and an electrolyte impregnation step of impregnating gaps in the conductive solid layer with an electrolyte; and a pretreatment agent impregnation step of impregnating the capacitor element with the pretreatment agent of the present invention before forming the conductive solid layer; and a drying step of evaporating the solvent of the pretreatment agent for producing hybrid electrolytic capacitors after the pretreatment agent impregnation step to retain the carbohydrate compound on the surface of the dielectric oxide film.

[0032] In other words, the manufacturing method of the present invention is as follows: A capacitor element is formed by winding an anode foil having a dielectric oxide film formed thereon and an counter cathode foil with a separator interposed therebetween, and the manufacturing method includes at least the following steps: (a) a pretreatment agent impregnation step of impregnating a capacitor element with a pretreatment agent for use in hybrid electrolytic capacitor production; (b) a drying step of evaporating the solvent of the pretreatment agent after the pretreatment agent impregnation step to retain a carbohydrate compound on the surface of the dielectric oxide film; (c) a dispersion impregnation step of impregnating the capacitor element with a dispersion containing conductive solid particles or powder and a solvent; (d) a drying step of evaporating the solvent after the dispersion impregnation step to form a conductive solid layer on the surface of the dielectric film; and (e) an electrolyte impregnation step of impregnating gaps in the conductive solid layer with an electrolyte.

[0033] [Anode Metal Having Dielectric Oxide Film Formed Thereon] Examples of anode metals include aluminum, tantalum, niobium, and titanium. The anode metal may be in the form of a sintered body obtained by sintering fine particles, or in the form of a foil or plate that has been roughened by etching or the like. Among these anode metals, aluminum foil that has been roughened by etching or the like is particularly suitable because it is easy to achieve the effects of the present invention.

[0034] A dielectric oxide film can be formed on the surface of an anode metal by subjecting the anode metal to a known chemical conversion treatment. For example, a dielectric oxide film can be formed on the anode metal by anodizing in an aqueous solution of diammonium adipate or the like.

[0035] [Capacitor Element] A lead terminal is attached to the anode, and a lead terminal is also attached to an opposing cathode foil made of aluminum foil. The anode and cathode with lead terminals are then placed opposite each other with a separator interposed between them and wound together to produce a capacitor element.

[0036] [(a) Pretreatment Agent Impregnation Step, (b) Drying Step for Retaining Carbohydrate Compounds on the Surface of the Dielectric Oxide Film] The method for retaining carbohydrate compounds on the anode metal on which a dielectric oxide film has been formed using the pretreatment agent is not particularly limited. However, the carbohydrate compounds can be retained on the anode metal on which a dielectric oxide film has been formed by contacting the pretreatment agent with the capacitor element and then drying to partially remove the solvent. Any contact method may be used, but a preferred method is to immerse the capacitor element in the pretreatment agent of the present invention. Furthermore, the term "retaining carbohydrate compounds" as used herein refers to a state in which carbohydrate compounds are supported on part or all of the surface of the dielectric oxide film on the anode metal on which a dielectric oxide film has been formed, or a state in which a carbohydrate compound layer is formed on part or all of the surface of the dielectric oxide film.

[0037] The process of immersing the capacitor element in the pretreatment agent, removing it, and then drying it may be repeated multiple times.

[0038] The drying may be carried out by any method, from natural drying at room temperature to heat drying, but it is preferable to dry by heating at 80° C. or higher.

[0039] A more specific example of the process is a process in which a capacitor element is immersed in the pretreatment agent for producing a hybrid electrolytic capacitor of the present invention for 30 seconds, and then dried at 125° C. for 30 minutes.

[0040] After the above steps (a) and (b) are performed, (c) a conductive solid dispersion impregnation step and (d) a drying step for forming a conductive solid layer are then performed.

[0041] [Dispersion Impregnation Liquid] First, the dispersion impregnation liquid used in the conductive solid dispersion impregnation step will be described. The dispersion impregnation liquid is a suspension in which conductive solid particles or powder are dispersed and stabilized in a solvent. The particle size of the dispersed conductive solid particles or powder is preferably such that the conductive solid particles or powder do not penetrate into defects in the dielectric film in the subsequent conductive solid dispersion impregnation step, and the concentration of the conductive solid in the dispersion impregnation liquid is preferably 0.5 to 10%. The dispersion impregnation liquid can be prepared by either dispersing a conductive polymer in a solvent or polymerizing a monomer, which is a precursor of the conductive polymer, in the solvent to synthesize the conductive polymer and obtain a dispersion containing the conductive polymer. In the latter case, it is preferable to perform washing, purification, filtration, or the like to remove unreacted monomers and impurities after the polymerization reaction.

[0042] The conductive polymer used in the step of forming the solid electrolyte layer is preferably a polymer doped with a dopant. The monomer compound used to produce the polymer is not particularly limited, and examples thereof include pyrroles, thiophenes, and anilines. However, due to their excellent conductivity, thiophene compounds represented by the following general formula (6) are more preferred.

[0043] General formula (6)

[0044] In the above general formula (6), R ２６ represents a hydrogen atom or a linear or branched alkyl group having 1 to 6 carbon atoms, and each Y, which may be the same or different, represents an oxygen atom or a sulfur atom.

[0045] Specific examples of the thiophene compound represented by the general formula (6) include 3,4-ethylenedioxythiophene, methyl-3,4-ethylenedioxythiophene, ethyl-3,4-ethylenedioxythiophene, propyl-3,4-ethylenedioxythiophene, 3,4-propylenedioxythiophene, methyl-3,4-propylenedioxythiophene, ethyl-3,4-propylenedioxythiophene, propyl-3,4-propylenedioxythiophene, 3,4-ethylenedithiathiophene, methyl-3,4-ethylenedithiathiophene, ethyl-3,4-ethylenedithiathiophene, propyl-3,4-ethylenedithiathiophene, 3,4-propylenedithiathiophene, methyl-3,4-propylenedithiathiophene, ethyl-3,4-propylenedithiathiophene, and propyl-3,4-propylenedithiathiophene.

[0046] Among these, 3,4-ethylenedioxythiophene (EDOT), methyl-3,4-ethylenedioxythiophene, and ethyl-3,4-ethylenedioxythiophene are particularly preferred because they have excellent electrical properties in hybrid electrolytic capacitors.

[0047] The conductive polymer can be obtained by chemical oxidative polymerization of a monomer compound such as a thiophene compound represented by the general formula (6) in the presence of the dopant. As the oxidizing agent for chemical oxidative polymerization, a known oxidizing agent such as iron(III) paratoluenesulfonate can be used.

[0048] The dopant may have a functional group that can cause chemical oxidation doping of the polymer, and preferred examples thereof include a sulfate ester group, a phosphate ester group, a phosphate group, a carboxyl group, a sulfo group, etc. Among these, from the viewpoint of doping effect, the sulfate ester group, the carboxyl group, and the sulfo group are more preferred, and the sulfo group is particularly preferred.

[0049] Examples of the dopant include halogen ions such as iodine, bromine, and chlorine; halide ions such as hexafluorophosphorus, hexafluoroarsenic, hexafluoroantimony, tetrafluoroboron, and perchloric acid; alkyl-substituted organic sulfonate ions such as methanesulfonic acid and dodecylsulfonic acid; cyclic sulfonate ions such as camphorsulfonic acid ion; alkyl-substituted or unsubstituted benzene mono- or disulfonate ions such as benzenesulfonic acid, paratoluenesulfonic acid, dodecylbenzenesulfonic acid, and benzenedisulfonic acid; 2-naphthalenesulfonic acid; 1,7-naphthalenesulfonic acid; Examples of suitable ions include alkyl-substituted or unsubstituted naphthalenesulfonic acids ions substituted with one to four sulfonic acid groups such as sulfonic acid, anthracenesulfonic acid ions, anthraquinonesulfonic acid ions, alkyl-substituted or unsubstituted biphenylsulfonic acid ions such as alkylbiphenylsulfonic acids and biphenyldisulfonic acids, polymeric sulfonic acid ions such as polystyrenesulfonic acid and naphthalenesulfonic acid-formaldehyde condensates, heteropolyacid ions such as molybdophosphoric acid, tungstophosphoric acid, and tungstomolybdophosphoric acid, methoxybenzenesulfonic acid, ethoxybenzenesulfonic acid, and xylenesulfonic acid. Among these, at least one selected from polystyrenesulfonic acid, benzenesulfonic acid, paratoluenesulfonic acid, methoxybenzenesulfonic acid, ethoxybenzenesulfonic acid, and xylenesulfonic acid is more preferred, with polystyrenesulfonic acid (PSS) being particularly preferred.

[0050] The solvent in which the conductive polymer is dispersed is not particularly limited, but it is preferable to use a solvent in which the conductive solid has extremely low solubility or does not dissolve the conductive solid, and water is preferred.

[0051] A commercially available product can be used as the dispersion impregnation liquid. When a commercially available product is used, for example, a PEDOT / PSS aqueous dispersion (manufactured by ALDRICH, PEDOT / PSS 1.1% in H ２ The following (c) conductive solid dispersion impregnation step can be carried out using a conductive solid dispersion (e.g., 0.0, SURFACTANT-FREE, HIGH-CONDUCTIVITY GRADE).

[0052] [(c) Dispersion Impregnation Step, (d) Drying Step for Forming a Conductive Solid Layer on the Surface of the Dielectric Film] Next, the conductive solid dispersion impregnation step will be described. A capacitor element, consisting of an anode foil with a dielectric film formed thereon and a counter cathode foil wound together with a separator interposed therebetween, is impregnated with the above-described carbohydrate compound and then impregnated with a dispersion impregnation solution containing the above-described conductive solid particles or powder and a solvent. Any method may be used for impregnating and attaching the conductive solid particles, but a preferred method is to immerse the capacitor element in an aqueous dispersion of a conductive polymer, followed by drying to allow the particles to penetrate into the interior of the element. For example, a preferred dispersion impregnation solution is one in which a mixture of fine particles of poly(3,4-ethylenedioxythiophene) (PEDOT) and a solid dopant composed of polystyrene sulfonic acid (PSS) is dispersed in water as a solvent.

[0053] The anode metal carrying the carbohydrate compound may be immersed in a mixed solution containing the above-mentioned monomer compound and dopant, and then pulled out and dried. This process may be repeated several times.

[0054] The drying may be any method from natural drying at room temperature to heat drying. When the conductive polymer dispersion impregnation liquid contains a high-boiling organic solvent, it is preferable to dry the conductive polymer dispersion by heating to 150° C. or higher.

[0055] A more specific example of the process is a process in which the capacitor element is immersed in the dispersion impregnation liquid for 30 seconds, and then dried at 155° C. for 30 minutes.

[0056] [(e) Electrolyte Impregnation Step] After preparing a capacitor element in which a solid electrolyte layer is formed on the anode metal supporting the carbohydrate compound in the above step, the capacitor element is housed in a metal or other exterior case, and the voids within the capacitor element are impregnated with an electrolyte. This allows the electrolyte to penetrate into the gaps in the conductive solid layer formed on the dielectric film, as well as into the gaps in the conductive solid layer if a conductive solid layer is also formed on the surface of the separator and counter cathode foil. By not only forming a conductive solid layer but also impregnating the conductive solid layer with an electrolyte, the capacitance can be increased and the ESR can be reduced. That is, the electrolyte not only covers the surface of the dielectric film where the conductive solid layer is not formed, but also penetrates into defects present in the dielectric film, thereby repairing such defects. The electrolyte can penetrate into defects present in the dielectric film because a conductive solid layer is not formed within the defects.

[0057] Here, the electrolytic solution may contain a conventionally known organic solvent, such as a protic polar solvent or an aprotic polar solvent, and may be used alone or in combination of two or more kinds.

[0058] Examples of protic polar solvents include monohydric alcohols (methanol, ethanol, propanol, butanol, pentanol, hexanol, cyclobutanol, cyclopentanol, cyclohexanol, and benzyl alcohol), polyhydric alcohols, and oxyalcohol compounds (ethylene glycol, propylene glycol, glycerin, methyl cellosolve, ethyl cellosolve, methoxypropylene glycol, and dimethoxypropanol).

[0059] Aprotic polar solvents include γ-butyrolactone, γ-valerolactone, amides (N-methylformamide, N,N-dimethylformamide, N-ethylformamide, N,N-diethylformamide, N-methylacetamide, N,N-dimethylacetamide, N-ethylacetamide, N,N-diethylacetamide, hexamethylphosphoric amide), sulfolanes (sulfolane, 3-methylsulfolane, 2,4-dimethylsulfolane), chain sulfones (dimethylsulfone, ethylmethylsulfone, ethylisopropylsulfone), and cyclic amides. Examples of the alkyl acrylates include alkyl acrylates (N-methyl-2-pyrrolidone), carbonates (ethylene carbonate, propylene carbonate, isobutylene carbonate), nitriles (acetonitrile), sulfoxides (dimethyl sulfoxide), and 2-imidazolidinones (1,3-dialkyl-2-imidazolidinone, (1,3-dimethyl-2-imidazolidinone, 1,3-diethyl-2-imidazolidinone, 1,3-di(n-propyl)-2-imidazolidinone), 1,3,4-trialkyl-2-imidazolidinone (1,3,4-trimethyl-2-imidazolidinone)).

[0060] When used in an electrolyte solution for a hybrid electrolytic capacitor, γ-butyrolactone or sulfolane is preferably used as the main solvent. The amount of water contained in the electrolyte solution for a hybrid electrolytic capacitor is not particularly limited, but is preferably 0.1 to 30%, more preferably 0.5 to 20%. By adjusting the amount of water to this range, good electrical conductivity can be obtained.

[0061] In the electrolyte impregnation step, the capacitor element having the above-mentioned conductive solid layer formed thereon is impregnated with an electrolyte, but the impregnation method is not particularly limited and any conventionally known method can be used. Among them, the method of immersing the capacitor element in an electrolyte contained in a container is preferably used because the operation is relatively easy.

[0062] The hybrid electrolytic capacitor can be assembled by a known method. After the above steps, the assembly is sealed with epoxy resin, rubber, or the like, and aged by applying a voltage to obtain a hybrid electrolytic capacitor.

[0063] [Additives] The electrolyte solution for the hybrid electrolytic capacitor of the present invention may contain additives to the extent that the effects of the present invention are not impaired. Examples of additives include phosphate compounds such as tributyl phosphate, dibutyl phosphite, tributyl phosphite, and ammonium phosphate, nitro compounds such as o-nitrobenzoic acid, m-nitrobenzoic acid, p-nitrobenzoic acid, o-nitrophenol, m-nitrophenol, and p-nitrophenol, boron compounds such as polyethylene glycol, polyvinyl alcohol, boric acid, mannite, complex compounds of boric acid with mannite, sorbitol, and the like, and complex compounds of boric acid with polyhydric alcohols such as ethylene glycol and glycerin, amine compounds, and triazoles.

[0064] [Hybrid Electrolytic Capacitor] The hybrid electrolytic capacitor produced by the method of the present invention has a capacitor element formed by winding an anode metal foil having a dielectric oxide film and an opposing cathode foil with a separator interposed therebetween, in which a carbohydrate compound is held in the capacitor element and a solid electrolyte containing a conductive polymer is formed thereon, and the capacitor element is housed in an exterior case together with the hybrid electrolytic capacitor electrolyte.

[0065] The hybrid electrolytic capacitor has excellent ESR characteristics and little adverse effect on other capacitor characteristics. In the hybrid electrolytic capacitor of the present invention, it is preferable that the conductive polymer layer is substantially not dissolved in the electrolyte solution in the capacitor. Note that the phrase "the conductive polymer dissolves" here refers not only to the dissolution of the conductive polymer itself, but also to the dissolution of dissociated or decomposed products of the conductive polymer, and the dissolution of the complex formed by the conductive polymer with a component in the electrolyte solution. From the perspective of the lifespan of the hybrid electrolytic capacitor, it is preferable that the conductive polymer does not dissolve.

[0066] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. In the examples, "parts" means "parts by mass" and "%" means "% by mass".

[0067] (Example 1) (1) Capacitor Element: An aluminum anode foil measuring 7 × 100 mm was prepared as the anode metal, and was wound with a cathode foil facing each other via a separator paper. Leads were attached to the anode foil and cathode foil, respectively, to obtain a capacitor element. The aluminum anode foil had been subjected to a chemical conversion treatment in advance to form a dielectric oxide film. The obtained element had a rated voltage of 35 V and a rated capacitance of 120 μF.

[0068] (2) Pretreatment Agent for Hybrid Electrolytic Capacitor Production Two parts by mass of pullulan as a saccharide compound was diluted with 98 parts by mass of water to obtain a pretreatment agent for hybrid electrolytic capacitor production.

[0069] (3) Dispersion Impregnation Liquid As the dispersion impregnation liquid, a commercially available PEDOT / PSS aqueous dispersion (manufactured by ALDRICH, PEDOT / PSS 1.1% in H ２ 0, SURFACTANT-FREE, HIGH-CONDUCTIVITY GRADE) was used.

[0070] (4) Electrolyte Solution 4 parts by mass of dimethylethylammonium hydrogen phthalate was dissolved in 96 parts by mass of γ-butyrolactone to obtain an electrolyte solution.

[0071] (a) Pretreatment agent impregnation step: The capacitor element obtained in (1) was immersed in the pretreatment agent obtained in (2) for 30 seconds, and the element was slowly removed. (b) Drying step: Retaining the carbohydrate compound on the surface of the dielectric oxide film: The capacitor element subjected to step (a) was dried with air at 125°C for 30 minutes to retain the carbohydrate compound on the anode metal on which the dielectric oxide film was formed. (c) Dispersion impregnation step: The capacitor element subjected to step (b) was immersed in the PEDOT / PSS aqueous dispersion described in (3) for 30 seconds, and the element was slowly removed. (d) Drying step: Forming a conductive solid layer on the surface of the dielectric film: The capacitor element subjected to step (c) was dried with air at 155°C for 30 minutes to form a conductive solid layer. (e) Electrolyte Impregnation Step: After the capacitor element subjected to step (c) was impregnated with the electrolyte obtained in (4), it was housed in a cylindrical aluminum exterior case with a bottom. A butyl rubber sealing body having through holes for leading out lead wires was inserted into the open end of the exterior case, and the end of the exterior case was further crimped to seal it. After that, a voltage of 35 V was applied for aging, thereby obtaining a hybrid electrolytic capacitor.

[0072] Examples 2 to 25, Comparative Examples 2 to 6 Hybrid electrolytic capacitors were obtained in the same manner as in Example 1, except that the pretreatment agent used in Example 1 was replaced with the saccharide compounds and ionic electrolytes listed in Table 1, which were diluted with water to a predetermined content.

[0073] The types and contents of the carbohydrate compounds and ionic electrolytes used in Examples 1 to 25 and Comparative Examples 2 to 6 are shown in Table 1.

[0074]

[0075] Comparative Example 1 A hybrid electrolytic capacitor was obtained by performing steps (c), (d) and (e) instead of steps (a) and (b) described in Example 1.

[0076] Comparative Example 7 A hybrid electrolytic capacitor was obtained in the same manner as in Example 1, except that a pretreatment agent was used that was produced by diluting 2 parts by mass of polyvinyl alcohol instead of the saccharide compound and 1 part by mass of monoammonium phosphate as the ionic electrolyte with 97 parts by mass of water.

[0077] Comparative Example 8: Two parts by weight of pullulan as a saccharide compound and one part by weight of monoammonium phosphate as an ionic electrolyte were diluted with 97 parts by weight of water to obtain a solution. After steps (c) and (d) were performed without performing steps (a) and (b) described in Example 1, a capacitor element was immersed in the solution for 30 seconds and then slowly removed. After drying with air at 125°C for 30 minutes, step (e) was performed to obtain a hybrid electrolytic capacitor.

[0078] (Comparative Example 9) 1.5 parts by mass of pullulan and 0.7 parts by mass of glycerin were added to the PEDOT / PSS aqueous dispersion described in (3) above as the dispersion impregnation solution to obtain a solution. Without carrying out steps (a) and (b) described in Example 1, a capacitor element was immersed in the solution for 30 seconds and then slowly removed. After air drying at 155°C for 30 minutes, step (e) was carried out to obtain a hybrid electrolytic capacitor.

[0079] Test Example 1 Evaluation of Hybrid Electrolytic Capacitors The equivalent series resistance (ESR) at 100 kHz was measured for the hybrid electrolytic capacitors obtained in Examples 1 to 25 and Comparative Examples 1 to 9 using a Precision LCR Meter E4980A manufactured by Agilent Technologies, Inc. The measurement results are shown in Table 2.

[0080]

[0081] As shown in Table 2, a hybrid electrolytic capacitor with reduced ESR was obtained in Example 1 compared to Comparative Example 1. Comparing Example 1 with Examples 2 to 8, the ESR was further reduced when the pretreatment agent of the present invention contained an ionic electrolyte. Furthermore, Examples 2 to 9, 12, 14, 17 to 19, and 25, which contained 10 to 50 parts by mass of ionic electrolyte per 100 parts by mass of the saccharide compound, showed even further reduced ESR.

[0082] On the other hand, in Comparative Examples 2 and 7, although the ESR was reduced, the effect was smaller than in Examples 1 to 25, and in Comparative Examples 3 to 6 and 8 to 9, no reduction effect was observed.

[0083] The pretreatment agent and manufacturing method of the present invention can be used in the manufacture of hybrid electrolytic capacitors.

Claims

1. A pretreatment agent for manufacturing a hybrid electrolytic capacitor, for treating an anode foil having a dielectric oxide film that constitutes a hybrid electrolytic capacitor, characterized in that a carbohydrate compound is dissolved in a solvent containing one or more selected from the group consisting of water, ethanol, methanol, and isopropyl alcohol, and the content of the carbohydrate compound is 0.001 to 25 mass%.

2. The pretreatment agent for producing a hybrid electrolytic capacitor according to claim 1, further comprising an ionic electrolyte.

3. The pretreatment agent for producing a hybrid electrolytic capacitor according to claim 1, wherein the carbohydrate compound comprises one or more compounds selected from the group consisting of pullulan, glucose, trehalose, sucrose, dextran, starch, methylcellulose, and carrageenan.

4. The pretreatment agent for producing a hybrid electrolytic capacitor according to claim 1, wherein the carbohydrate compound is any one selected from the group consisting of glucose, trehalose, and sucrose, and the content thereof is 10 to 25 mass%.

5. The pretreatment agent for producing hybrid electrolytic capacitors according to claim 1, wherein the carbohydrate compound is any one selected from the group consisting of pullulan, dextran, and starch, and the content thereof is 0.1 to 5 mass%.

6. The pretreatment agent for producing a hybrid electrolytic capacitor according to claim 1, wherein the carbohydrate compound is methyl cellulose or carrageenan, and the content thereof is 0.001 to 0.01% by mass.

7. The pretreatment agent for producing a hybrid electrolytic capacitor according to claim 2, which contains 10 to 50 parts by mass of an ionic electrolyte per 100 parts by mass of the carbohydrate compound.

8. The pretreatment agent for producing a hybrid electrolytic capacitor according to claim 2, wherein the ionic electrolyte is an electrolyte salt comprising a nitrogen-containing cation having an unshared electron pair and an anion selected from a phosphate compound, a carboxylate compound, and a borate compound.

9. A method for producing a hybrid electrolytic capacitor, comprising treating an anode foil having a dielectric oxide film that constitutes the hybrid electrolytic capacitor with a pretreatment agent for producing a hybrid electrolytic capacitor according to any one of claims 1 to 8.

10. A method for producing a hybrid electrolytic capacitor, comprising: a dispersion impregnation step of impregnating a capacitor element, which is formed by winding an anode foil having a dielectric oxide film formed thereon and an opposing cathode foil with a separator interposed therebetween, with a dispersion containing conductive solid particles or powder and a solvent; a drying step of evaporating the solvent after the dispersion impregnation step to form a conductive solid layer on the surface of the dielectric oxide film; and an electrolyte impregnation step of impregnating gaps in the conductive solid layer with an electrolyte; and the method for producing a hybrid electrolytic capacitor, further comprising: a pretreatment agent impregnation step of impregnating the capacitor element with a pretreatment agent for producing a hybrid electrolytic capacitor according to any one of claims 1 to 8 before forming the conductive solid layer; and a drying step of evaporating the solvent of the pretreatment agent for producing a hybrid electrolytic capacitor after the pretreatment agent impregnation step to retain the carbohydrate compound on the surface of the dielectric oxide film.

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