Electrolytic capacitor and method for manufacturing the same

Abstract

The electrolytic capacitor includes a capacitor element. The capacitor element includes an anode body having a dielectric layer on its surface and an electrolyte layer disposed adjacent to the dielectric layer. The electrolyte layer includes a self-doping type first conductive polymer and a non-aqueous solvent.

Description

Technical Field

[0001] The present invention relates to electrolytic capacitors and methods for manufacturing the same. Background Art

[0002] Capacitors used in electronic devices are required to have large capacity and low equivalent series resistance (ESR) values ​​in high-frequency regions. As capacitors with large capacity and low ESR, electrolytic capacitors using conductive polymers such as polypyrrole, polythiophene, polyfuran, and polyaniline are promising. Patent document 1 (International Publication No. 2012 / 117994) discloses, as a conductive polymer solution for forming a solid electrolyte layer, "a conductive polymer solution containing: a conductive polymer, a polysulfonic acid or its salt that functions as a dopant for the conductive polymer, a mixture of a polyacid and a carbon material, and a solvent" (claim 1 of patent document 1). In addition, patent document 1 discloses a solid electrolytic capacitor manufactured using the conductive polymer solution.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: International Publication No. 2012 / 117994 Summary of the invention

[0006] Problem that the invention aims to solve

[0007] Nowadays, an electrolytic capacitor having a low rate of increase in ESR over a long period of time is required. Under such circumstances, one of the objects of the present application is to provide an electrolytic capacitor having a low rate of increase in ESR over a long period of time.

[0008] Solutions for solving problems

[0009] One aspect of the present application relates to an electrolytic capacitor including a capacitor element including: an anode body having a dielectric layer on its surface; and an electrolyte layer disposed adjacent to the dielectric layer, wherein the electrolyte layer includes a self-doping first conductive polymer and a non-aqueous solvent.

[0010] Another aspect of the present application relates to a method for manufacturing an electrolytic capacitor. The method comprises: step (i) of preparing a capacitor element precursor, the capacitor element precursor comprising an anode body having a dielectric layer on its surface; step (ii) of forming a polymer layer adjacent to the dielectric layer by an impregnation treatment, the polymer layer comprising a self-doping type first conductive polymer; and step (iii) of impregnating the polymer layer with a non-aqueous solvent.

[0011] Effects of the Invention

[0012] According to the present application, an electrolytic capacitor having a low rate of increase in ESR over a long period of time can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is a cross-sectional view schematically showing an example of the electrolytic capacitor of the present application.

[0014] Figure 2 To schematically illustrate Figure 1 A diagram of a portion of an electrolytic capacitor is shown. DETAILED DESCRIPTION

[0015] Hereinafter, the embodiments of the present application will be described by way of example, but the present application is not limited to the examples described below. In the following description, specific numerical values ​​and materials are sometimes illustrated, but other numerical values ​​and materials may also be applied as long as the effects of the present application can be obtained.

[0016] (Electrolytic Capacitors)

[0017] The electrolytic capacitor of the present application includes a capacitor element. The capacitor element includes: an anode body having a dielectric layer on its surface, and an electrolyte layer disposed adjacent to the dielectric layer. The electrolyte layer includes a self-doping type first conductive polymer and a non-aqueous solvent.

[0018] The capacitor element may include: a foil-shaped anode body having a dielectric layer on the surface, a foil-shaped cathode body, a separator arranged between the anode body and the cathode body, and an electrolyte layer arranged between the anode body and the cathode body. Such a capacitor element is sometimes referred to as the "first capacitor element" below. The first capacitor element may be a winding type or a stacked type. In one example of a winding type capacitor element, a foil-shaped anode body, a foil-shaped cathode body and a separator are wound in a manner that a separator is arranged between the anode body and the cathode body. In one example of a stacked type capacitor element, a foil-shaped anode body, a foil-shaped cathode body and a separator are folded into a zigzag shape in a manner that a separator is arranged between the anode body and the cathode body.

[0019] Alternatively, the capacitor element may include: a porous anode body having a dielectric layer on the surface, a cathode layer, and an electrolyte layer disposed between the anode body and the cathode layer. Such a capacitor element is sometimes referred to as a "second capacitor element" below. In the first and second capacitor elements, the electrolyte layer is adjacent to the dielectric layer of the anode body.

[0020] The electrolyte layer may further include a second conductive polymer doped with a dopant.

[0021] The first and second conductive polymers contained in the electrolyte layer are described below. It should be noted that in this specification, the conductive polymer may be referred to as a conductive polymer.

[0022] (First conductive polymer)

[0023] The first conductive polymer is a self-doping conductive polymer. Here, the self-doping conductive polymer refers to a polymer in which a functional group that functions as a dopant is directly or indirectly bonded to the skeleton of the conductive polymer using a covalent bond. Examples of functional groups that function as dopants include anionic groups. Anionic groups are groups that have a negative charge due to dissociation of cations. Anionic groups can be at least one selected from the group consisting of sulfonic acid groups, phosphoric acid groups, phosphonic acid groups, and carboxyl groups, or can be their salts (salts with inorganic bases, salts with organic bases, etc.). A preferred example of anionic groups is a sulfonic acid group or its salt.

[0024] The amount of the functional group (eg, anionic group) functioning as a dopant may be in the range of 0.2 to 3, 0.5 to 2, or 1 per one structural unit constituting the macromolecule (polymer).

[0025] The first conductive polymer may be used alone or in combination of two or more.

[0026] Examples of the skeleton of the first conductive polymer include polypyrrole, polythiophene, polyaniline, etc. Atomic groups (such as functional groups) other than functional groups that function as dopants may be bonded to these skeletons. Examples of the first conductive polymer include polypyrroles (polypyrroles and derivatives thereof) having anionic groups, polythiophenes (polythiophene and derivatives thereof) having anionic groups, polyanilines (polyaniline and derivatives thereof) having anionic groups, etc. Among these examples, an example of a preferred anionic group is a sulfonic acid group or a salt thereof. The first conductive polymer may be a copolymer of two or more monomers.

[0027] From the perspective of suppressing the increase of ESR and the decrease of electrostatic capacitance even in a high temperature environment, the first conductive polymer may be one obtained by introducing an atomic group containing a sulfonic acid group into poly(3,4-ethylenedioxythiophene) (PEDOT). For example, the first conductive polymer may contain a structural unit represented by the following chemical formula, or may be composed of a structural unit represented by the following chemical formula.

[0028]

[0029] In the above formula, R represents an organic chain. R may be composed of a hydrocarbon chain, or may further include an ether bond, a branched alkyl group, or other substituents on the basis of the hydrocarbon chain. In the above formula, the sulfonic acid group may be made into a salt. Examples of R include (skeleton side) -CH2-O-(CH2)2-(CHCH3)-(sulfonic acid group side) and the like.

[0030] Alternatively, the first conductive polymer may be one in which an atomic group including a sulfonic acid group is introduced into polyaniline, and may be, for example, polyaniline sulfonic acid.

[0031] The weight average molecular weight of the first conductive polymer may be in the range of 1,000 to 100,000, or in the range of 1,000 to 30,000.

[0032] (Second conductive polymer)

[0033] The second conductive polymer is a polymer whose conductivity is improved by doping with a dopant. Examples of the second conductive polymer include polypyrrole, polythiophene, polyfuran, polyaniline, polyacetylene, and their derivatives. The derivatives include polymers with polypyrrole, polythiophene, polyfuran, polyaniline, and polyacetylene as basic skeletons. For example, derivatives of polythiophene include poly(3,4-ethylenedioxythiophene) and the like. The second conductive polymer can be used alone or in combination. In addition, the second conductive polymer can be a copolymer of two or more monomers. The weight average molecular weight of the second conductive polymer is not particularly limited, for example, it can be in the range of 1000 to 100000. A preferred example of the second conductive polymer is poly(3,4-ethylenedioxythiophene) (PEDOT).

[0034] Unlike the first conductive polymer, in the second conductive polymer, the functional group that functions as a dopant is not covalently bonded to the skeleton of the conductive polymer. The second conductive polymer is doped with a dopant. From the viewpoint of suppressing dedoping from the second conductive polymer, a polymer dopant is preferably used as the dopant. Examples of polymer dopants include polyvinyl sulfonic acid, polystyrene sulfonic acid, polyallyl sulfonic acid, polyacrylic acid sulfonic acid, polymethacrylic acid sulfonic acid, poly (2-acrylamide-2-methylpropane sulfonic acid), polyisoprene sulfonic acid, polyacrylic acid, etc. They can be used alone or in combination of two or more. They can be included in the electrolyte layer in the form of a salt. A preferred example of a dopant is polystyrene sulfonic acid (PSS).

[0035] The weight average molecular weight of the dopant is not particularly limited, but can be in the range of 1,000 to 100,000 from the viewpoint of easily forming a homogeneous electrolyte layer.

[0036] In the electrolytic capacitor of the present application, the dopant may be polystyrene sulfonic acid, and the second conductive polymer may be poly(3,4-ethylenedioxythiophene). That is, the electrolyte layer may include poly(3,4-ethylenedioxythiophene) doped with polystyrene sulfonic acid.

[0037] (Liquid ingredients)

[0038] The electrolyte layer of the electrolytic capacitor of the present application contains a non-aqueous solvent. The electrolyte layer may contain an electrolyte solution (non-aqueous electrolyte) containing a non-aqueous solvent and an alkaline component dissolved in the non-aqueous solvent. That is, the electrolyte layer of the electrolytic capacitor of the present application may contain a liquid component. Hereinafter, the liquid component (non-aqueous solvent or electrolyte) contained in the electrolyte layer is sometimes referred to as "liquid component (L)". It should be noted that in this specification, the liquid component (L) may be a component that is liquid at room temperature (25°C) or a component that is liquid at the temperature when the electrolytic capacitor is in use. An electrolytic capacitor having an electrolyte layer containing a liquid component (L) is sometimes referred to as a hybrid capacitor.

[0039] The non-aqueous solvent contained in the electrolyte layer may be an organic solvent or an ionic liquid. Examples of the non-aqueous solvent include polyols such as ethylene glycol and propylene glycol, cyclic sulfones such as sulfolane (SL), lactones such as γ-butyrolactone (γBL), amides such as N-methylacetamide, N,N-dimethylformamide, N-methyl-2-pyrrolidone, esters such as methyl acetate, carbonate compounds such as propylene carbonate, ethers such as 1,4-dioxane, ketones such as methyl ethyl ketone, formaldehyde, etc.

[0040] In addition, as a non-aqueous solvent, a polymer solvent can be used. Examples of polymer solvents include compounds in which at least one hydroxyl group in polyalkylene glycol, a derivative of polyalkylene glycol, or a polyol is substituted with polyalkylene glycol (including derivatives), etc. Specifically, examples of polymer solvents include polyethylene glycol (PEG), polyethylene glycol glycerol ether, polyethylene glycol diglycerol ether, polyethylene glycol sorbitol ether, polypropylene glycol, polypropylene glycol glycerol ether, polypropylene glycol diglycerol ether, polypropylene glycol sorbitol ether, polybutylene glycol, etc. Examples of polymer solvents also include copolymers of ethylene glycol-propylene glycol, copolymers of ethylene glycol-butylene glycol, copolymers of propylene glycol-butylene glycol, etc. A non-aqueous solvent can be used alone or in combination of two or more.

[0041] As described above, the electrolyte layer may contain a non-aqueous solvent and an alkali component (base) dissolved in the non-aqueous solvent. Alternatively, the electrolyte layer may contain a non-aqueous solvent and an alkali component and / or an acid component (acid) dissolved in the non-aqueous solvent.

[0042] As the acid component, polycarboxylic acids and monocarboxylic acids can be used. Examples of the polycarboxylic acids include aliphatic polycarboxylic acids ([saturated polycarboxylic acids, such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, 1,6-decanedicarboxylic acid, 5,6-decanedicarboxylic acid]; [unsaturated polycarboxylic acids, such as maleic acid, fumaric acid, itaconic acid]), aromatic polycarboxylic acids (such as phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, pyromellitic acid), and alicyclic polycarboxylic acids (such as cyclohexane-1,2-dicarboxylic acid, cyclohexene-1,2-dicarboxylic acid, etc.).

[0043] Examples of the monocarboxylic acids include aliphatic monocarboxylic acids (having 1 to 30 carbon atoms) ([saturated monocarboxylic acids, such as formic acid, acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, caproic acid, heptanoic acid, octanoic acid, nonanoic acid, lauric acid, myristic acid, stearic acid, behenic acid]; [unsaturated monocarboxylic acids, such as acrylic acid, methacrylic acid, oleic acid]), aromatic monocarboxylic acids (such as benzoic acid, cinnamic acid, naphthoic acid), and hydroxycarboxylic acids (such as salicylic acid, mandelic acid, and m-dihydroxybenzoic acid).

[0044] Among these, maleic acid, phthalic acid, benzoic acid, pyromellitic acid, and m-dihydroxybenzoic acid are thermally stable and are preferably used.

[0045] As the acid component, an inorganic acid can be used. Representative examples of inorganic acids include phosphoric acid, phosphorous acid, hypophosphorous acid, alkyl phosphates, boric acid, fluoroboric acid, tetrafluoroboric acid, hexafluorophosphoric acid, benzenesulfonic acid, naphthalenesulfonic acid, etc. In addition, a composite compound of an organic acid and an inorganic acid can be used as the acid component. Examples of such composite compounds include boron diglycolic acid, boron dioxalic acid, boron disalicylic acid, etc.

[0046] The base component may be a compound having an alkyl-substituted amidine group, for example, an imidazole compound, a benzimidazole compound, an alicyclic amidine compound (pyrimidine compound, imidazoline compound), etc. Specifically, 1,8-diazabicyclo[5,4,0]undecene-7, 1,5-diazabicyclo[4,3,0]nonene-5, 1,2-dimethylimidazolinium, 1,2,4-trimethylimidazoline, 1-methyl-2-ethyl-imidazoline, 1,4-dimethyl-2-ethylimidazoline, 1-methyl-2-heptylimidazoline, 1-methyl-2-(3'heptyl)imidazoline, 1-methyl-2-dodecylimidazoline, 1,2-dimethyl-1,4,5,6-tetrahydropyrimidine, 1-methylimidazole, and 1-methylbenzimidazole are preferred. By using these, a capacitor having excellent impedance performance can be obtained.

[0047] As the base component, a quaternary salt of a compound having an alkyl-substituted amidine group can be used. Examples of such base components include imidazole compounds, benzimidazole compounds, and alicyclic amidine compounds (pyrimidine compounds, imidazoline compounds) quaternized with an alkyl group having 1 to 11 carbon atoms or an arylalkyl group. Specifically, 1-methyl-1,8-diazabicyclo[5,4,0]undecene-7, 1-methyl-1,5-diazabicyclo[4,3,0]nonene-5, 1,2,3-trimethylimidazolinium, 1,2,3,4-tetramethylimidazolinium, 1,2-dimethyl-3-ethylimidazolinium, 1,3,4-trimethyl-2-ethylimidazolinium, 1,3-dimethyl-2-heptylimidazolinium, 1,3-dimethyl-2-(3'heptyl)imidazolinium, 1,3-dimethyl-2-dodecylimidazolinium, 1,2,3-trimethyl-1,4,5,6-tetrahydropyrimidinium, 1,3-dimethylimidazolium, 1-methyl-3-ethylimidazolium, and 1,3-dimethylbenzimidazolium are preferred. By using these, a capacitor having excellent impedance performance can be obtained.

[0048] In addition, tertiary amines can be used as base components. Examples of tertiary amines include trialkylamines (trimethylamine, dimethylethylamine, methyldiethylamine, triethylamine, dimethyln-propylamine, dimethylisopropylamine, methylethyln-propylamine, methylethylisopropylamine, diethyln-propylamine, diethylisopropylamine, tri-n-propylamine, triisopropylamine, tri-n-butylamine, tri-tert-butylamine, etc.), and phenyl-containing amines (dimethylphenylamine, methylethylphenylamine, diethylphenylamine, etc.). Among them, from the perspective of high conductivity of the electrolyte layer, trialkylamines are preferred, and at least one selected from the group consisting of trimethylamine, dimethylethylamine, methyldiethylamine, and triethylamine is more preferred. In addition, as base components, secondary amines such as dialkylamines, primary amines such as monoalkylamines, and ammonia can also be used.

[0049] The liquid component (L) may contain a salt of an acid component and an alkali component. The salt may be an inorganic salt and / or an organic salt. An organic salt is a salt in which at least one of an anion and a cation contains an organic substance. As an organic salt, for example, trimethylammonium maleate, triethylammonium borodisalicylate, ethyldimethylamine phthalate, 1,2,3,4-tetramethylimidazolinium phthalate, 1,3-dimethyl-2-ethylimidazolinium phthalate, etc. may be used.

[0050] In order to suppress dedoping of the dopant, the pH of the liquid component (L) may be set to less than 7, or may be set to 5 or less (for example, in the range of 2 to 5).

[0051] For electrolytic capacitors, it is important that the ESR is low. By using an electrolyte layer comprising a conductive polymer doped with a dopant, a low ESR can be achieved. However, the inventors of the present application have found that when using an electrolyte layer comprising a conductive polymer doped with a dopant and a liquid component (L), although the initial ESR is low, the deterioration phenomenon of the ESR increasing over time is large. The reason for this has been studied, and it can be seen that in the electrolyte layer comprising a liquid component (L), the dopant is sometimes easily dedoped. It is believed that due to this dedoping, the ESR increases over time. Therefore, compared with a solid electrolytic capacitor comprising a solid electrolyte without a liquid component (L), it is important for an electrolytic capacitor comprising a liquid component (L) to suppress the increase of the ESR over time.

[0052] The self-doping type first conductive polymer is less likely to be dedoped, so the conductivity thereof deteriorates less with time. Therefore, by including the first conductive polymer in the electrolyte layer, it is possible to suppress an increase in ESR with time.

[0053] In the electrolytic capacitor of the present application, the dopant may be a dopant containing an acidic group or a polymer dopant containing an acidic group. After conducting research, the inventors of the present application have newly discovered that when a dopant containing an acidic group is used, dedoping may occur significantly as the pH increases. Therefore, when a dopant containing an acidic group is used, it is particularly important to suppress the increase in ESR over time.

[0054] In the electrolytic capacitor of the present application using the second conductive polymer, the dopant may be a polymer dopant containing an acidic group, and the electrolyte layer may include an electrolyte containing a non-aqueous solvent and an alkaline component dissolved in the non-aqueous solvent. In this case, dedoping is easily caused by the alkaline component, so it is particularly important to suppress the increase of ESR over time. As described above, the electrolytic capacitor of the present application includes a self-doping type first conductive polymer, so it is possible to suppress the increase of ESR over time.

[0055] Examples of the base component include the above-mentioned base components. Examples of the acidic group include a sulfonic acid group, a carboxyl group, etc. A polymer dopant containing an acidic group is a polymer (polymer) in which at least a part of the structural units contain an acidic group. Examples of such a polymer dopant include the above-mentioned polymer dopant.

[0056] In the electrolytic capacitor of the present application, the amount of the alkali component in the electrolyte can be 0.1 mass % or more and 20 mass % or less. When the amount of the alkali component is 0.1 mass % or more, it is particularly important to use a self-doping type first conductive polymer. In addition, by setting the amount of the alkali component to 20 mass % or less, it is easy to dissolve the alkali component in the electrolyte.

[0057] The content of the liquid component (L) in the electrolyte layer may be in the range of 60 to 99 mass % (e.g., in the range of 70 to 95 mass %). The content of the first conductive polymer in the solid content in the electrolyte layer may be in the range of 1 to 100 mass % (e.g., in the range of 1 to 45 mass %). The total content of the second conductive polymer and the dopant in the solid content in the electrolyte layer may be in the range of 1 to 99 mass % (e.g., in the range of 55 to 99 mass %). The electrolyte layer may satisfy the relationship of (mass of the first conductive polymer): (total mass of the second conductive polymer and the dopant) = 10:90 to 45:55.

[0058] In the electrolytic capacitor of the present application, the total mass of the second conductive polymer and the dopant contained in the electrolyte layer can be greater than the mass of the first conductive polymer contained in the electrolyte layer. That is, the total content (mass %) of the second conductive polymer and the dopant in the electrolyte layer can be greater than the content (mass %) of the first conductive polymer in the electrolyte layer. Conductive polymers doped with dopants are generally more conductive than self-doped conductive polymers. Therefore, increasing the content of the second conductive polymer doped with a dopant is effective for reducing the initial ESR.

[0059] The mass W1(g) of the first conductive polymer contained in the electrolyte layer and the total mass W2(g) of the second conductive polymer and the dopant contained in the electrolyte layer may satisfy the relationship 1<W2 / W1 or the relationship 1.1≤W2 / W1≤9.

[0060] The electrolytic capacitor of the present application can satisfy the following condition (1).

[0061] (1) The electrolyte layer includes a polymer layer (conductive polymer layer) composed of a first conductive polymer and a second conductive polymer doped with a dopant, wherein the polymer layer includes: a first polymer layer formed on the dielectric layer on the surface of the anode body, and a second polymer layer formed on the first polymer layer.

[0062] The conductive polymer contained in the first polymer layer and the conductive polymer contained in the second polymer layer may be the same or different. When both the first and second polymer layers contain the second conductive polymer, the dopant contained in the first polymer layer and the dopant contained in the second polymer layer may be the same or different.

[0063] In one example, the first polymer layer is composed of the second conductive polymer doped with a dopant, and the second polymer layer is composed of the first conductive polymer. In another example, the first polymer layer is composed of the first conductive polymer, and the second polymer layer is composed of the second conductive polymer doped with a dopant.

[0064] The electrolytic capacitor of the present application can satisfy the above conditions (1) and the following conditions (2).

[0065] (2) The content rate (mass %) of the second conductive polymer in the first polymer layer is greater than the content rate (mass %) of the second conductive polymer in the second polymer layer. It should be noted that in the condition (2), "the content rate (mass %) of the second conductive polymer" can be replaced by "the total content rate (mass %) of the second conductive polymer and the dopant".

[0066] The condition (2) above can be replaced by the condition (2') that the content (mass %) of the first conductive polymer in the first polymer layer is smaller than the content (mass %) of the first conductive polymer in the second polymer layer. By using the configuration of (2) above, the proportion of the second conductive polymer in the portion close to the dielectric layer on the surface of the anode body can be increased. As a result, the initial ESR can be reduced.

[0067] The electrolytic capacitor of the present application can satisfy the following conditions (A) and (B), and can further satisfy the requirement (C).

[0068] (A) The first conductive polymer is poly(3,4-ethylenedioxythiophene) into which a sulfonic acid group is introduced, for example, the polymer described above.

[0069] (B) The second conductive polymer is poly(3,4-ethylenedioxythiophene), and the dopant doped into the second conductive polymer is polystyrene sulfonic acid.

[0070] (C) The mass W1(g) of the first conductive polymer contained in the electrolyte layer and the total mass W2(g) of the second conductive polymer and the dopant contained in the electrolyte layer satisfy the relationship 1<W2 / W1, for example, satisfy the relationship 1.1≤W2 / W1≤9.

[0071] The components of the capacitor element other than the electrolyte (anode body, cathode body, separator, etc.) are not particularly limited, and known components can be used. Examples of these components of the first capacitor element are described below.

[0072] (Anode)

[0073] The anode body can use a metal foil having a dielectric layer formed on the surface. The type of metal constituting the metal foil is not particularly limited. From the aspect of easy formation of the dielectric layer, examples of metals constituting the metal foil include metals having valve functions such as aluminum, tantalum, niobium, titanium, and alloys of metals having valve functions. A preferred example is aluminum and aluminum alloys. Usually, the surface of the anode body is roughened (made porous). The dielectric layer of the anode body is formed in the porous portion (roughened surface). The electrolyte layer is in contact with the dielectric layer of the anode body.

[0074] (Cathode)

[0075] A metal foil can be used as the cathode body. The type of metal constituting the metal foil is not particularly limited. Examples of metals constituting the metal foil include valve metals such as aluminum, tantalum, niobium, titanium, and alloys of valve metals. A preferred example is aluminum and aluminum alloys. A chemical conversion coating can be provided on the surface of the cathode body, and a coating of a metal different from the metal constituting the cathode body (dissimilar metal) or a non-metallic film can also be provided. As dissimilar metals and non-metals, for example, metals such as titanium, non-metals such as carbon, etc. can be cited.

[0076] (Spacer)

[0077] The separator can be a sheet-like object that can be impregnated with an electrolyte, for example, a sheet-like object that has insulation and can be impregnated with an electrolyte can be used. The separator can be a woven fabric, a non-woven fabric, or a porous film. Examples of materials for the separator include cellulose, polyethylene terephthalate, polybutylene terephthalate, polyphenylene sulfide, vinylon, nylon, aromatic polyamide, polyimide, polyamide-imide, polyetherimide, rayon, and glass.

[0078] An example of components of the second capacitor element other than the electrolyte layer will be described below. The second capacitor element includes a porous anode body having a dielectric layer on its surface, a cathode layer, and an electrolyte layer disposed between the anode body and the cathode layer.

[0079] The porous anode body may be, for example, a porous sintered body obtained by sintering material particles containing a valve metal. The anode body may be in the shape of a rectangular parallelepiped. Examples of valve metals include titanium (Ti), tantalum (Ta), niobium (Nb), and the like. The material particles may be formed of an alloy containing a valve metal. For example, an alloy containing a valve metal and silicon, vanadium, boron, and the like may be used. The alloy of the valve metal contains the valve metal as a main component, for example, containing more than 50 atomic % of the valve metal. In addition, material particles formed of a compound containing a valve metal and a typical element such as nitrogen may be used. The material particles may be used alone or in combination of two or more.

[0080] The anode body of the second capacitor element is porous and thus has a porous portion on the surface, and the dielectric layer is formed in the porous portion. The electrolyte layer is in contact with the dielectric layer of the anode body. The dielectric layer is formed, for example, by subjecting a sintered body serving as the anode body to a chemical conversion treatment and growing an oxide film on the surface of the sintered body.

[0081] The cathode layer has a current collecting function. The cathode layer is formed, for example, of a conductive material. The cathode layer may be a conductive layer formed in a manner covering the electrolyte layer. The cathode layer may include a carbon layer formed in a manner covering the electrolyte layer, and a metal paste layer formed on the carbon layer. The carbon layer may include a conductive carbon material such as graphite and a resin. The metal paste layer may include metal particles (e.g., silver particles) and a resin. The cathode layer can be formed by applying the above-mentioned materials, etc.

[0082] (Method for manufacturing electrolytic capacitor)

[0083] The following describes the method of the present application for manufacturing an electrolytic capacitor. The electrolytic capacitor of the present application can be manufactured using this manufacturing method. It should be noted that the matters described for the electrolytic capacitor of the present application can be applied to the following manufacturing method, so repeated descriptions are sometimes omitted. For example, the constituent elements of the capacitor element are described above, so repeated descriptions are sometimes omitted. In addition, the matters described in the following manufacturing method can be applied to the above-mentioned electrolytic capacitor.

[0084] The production method according to the present application includes step (i), step (ii), and step (iii), which are described below.

[0085] (Process (i))

[0086] Step (i) is a step of preparing a capacitor element precursor including an anode body having a dielectric layer on its surface. Step (i) may be a step of forming the capacitor element precursor by a known method.

[0087] In the case of manufacturing an electrolytic capacitor including a first capacitor element, step (i) may be a step of forming a capacitor element precursor, wherein the capacitor element precursor comprises: a foil-shaped anode body having a dielectric layer on the surface, a foil-shaped cathode body, and a separator disposed between the anode body and the cathode body. In this case, as described above, the capacitor element precursor may be a wound type or a stacked type. In the case of manufacturing an electrolytic capacitor including a second capacitor element, the capacitor element precursor may be composed of an anode body (porous anode body) having a dielectric layer on the surface, and an anode wire partially buried in the anode body.

[0088] (Step (ii))

[0089] Step (ii) is a step of forming a polymer layer including a self-doping type first conductive polymer so as to be adjacent to the dielectric layer by an impregnation treatment.

[0090] The polymer layer formed in step (ii) may include the first conductive polymer and the second conductive polymer doped with a dopant. That is, step (ii) may be a step of forming the polymer layer including the first conductive polymer and the second conductive polymer doped with a dopant so as to be adjacent to the dielectric layer by an impregnation treatment.

[0091] The impregnation treatment of step (ii) can be an impregnation treatment (x) in which a liquid (dispersion or solution. The same applies below) containing a first conductive polymer and a second conductive polymer doped with a dopant is impregnated into the capacitor element precursor. For example, the liquid can be impregnated by immersing the capacitor element precursor in the liquid. By removing (drying) the dispersion medium or solvent of the liquid impregnated into the capacitor element precursor, a polymer layer containing a first conductive polymer and a second conductive polymer doped with a dopant can be arranged adjacent to the dielectric layer. It should be noted that the impregnation treatment (x) can be performed multiple times. In this case, a drying process for removing the dispersion medium or solvent of the impregnated liquid can be performed before performing the second or subsequent impregnation treatments (x).

[0092] The liquid dispersion medium or solvent is not particularly limited, and a known dispersion medium or solvent can be used. For example, an aqueous liquid containing water can be used as the dispersion medium or solvent, or water can be used.

[0093] The ratio of the first conductive polymer and the second conductive polymer (and the dopant) in the liquid can be adjusted by adjusting their mass (content) in the liquid. For example, by making the mass (content) of the second conductive polymer (and the dopant) in the liquid greater than the mass (content) of the first conductive polymer in the liquid, the mass of the second conductive polymer (and the dopant) contained in the electrolyte layer can be greater than the mass of the first conductive polymer contained in the electrolyte layer.

[0094] The impregnation treatment of step (ii) may include: an impregnation treatment (y), in which a first liquid containing a first conductive polymer is impregnated into a capacitor element precursor; and an impregnation treatment (z), in which a second liquid containing a second conductive polymer doped with a dopant is impregnated into a capacitor element precursor. For the impregnation treatment (y) and the impregnation treatment (z), the impregnation treatment (z) may be performed first, the impregnation treatment (y) may be performed first, or both may be performed simultaneously. In a preferred example, the impregnation treatment (y) is performed after the impregnation treatment (z). It should be noted that the impregnation treatment (y) and the impregnation treatment (z) may be performed independently multiple times. In addition, a drying process for removing the dispersion medium (or solvent) of the impregnated liquid may be performed after each of the impregnation treatments (y) and (z).

[0095] Regarding the dispersion medium (or solvent) of the first and second liquids, and the impregnation method in the impregnation treatment (y) and the impregnation treatment (z), the dispersion medium (or solvent) and the impregnation method described in the impregnation treatment (x) can be applied.

[0096] In one example, the first liquid does not contain the second conductive polymer doped with a dopant, and the second liquid does not contain the first conductive polymer. However, the first liquid may contain the second conductive polymer doped with a dopant, and the second liquid may contain the first conductive polymer.

[0097] After performing any of the impregnation treatments (y) and (z), drying may be performed, and then another impregnation treatment may be performed. By doing so, a polymer layer including a first polymer layer and a second polymer layer can be formed. In addition, by adjusting the type and content of the conductive polymer (and dopant) in the first liquid, and the type and content of the conductive polymer (and dopant) in the second liquid, the type and content of the conductive polymer (and dopant) in the first polymer layer, and the type and content of the conductive polymer (and dopant) in the second polymer layer can be adjusted.

[0098] (Process (iii))

[0099] Step (iii) is a step of impregnating the polymer layer formed in step (ii) with a non-aqueous solvent. Thus, an electrolyte layer comprising a self-doped first conductive polymer and a non-aqueous solvent is formed. Step (iii) may be a step of impregnating the polymer layer formed in step (ii) with an electrolyte solution (comprising a non-aqueous solvent). That is, step (iii) may be a step of impregnating the polymer layer formed in step (ii) with a liquid component (L).

[0100] When the polymer layer formed in step (ii) includes the second conductive polymer doped with a dopant, an electrolyte layer including the self-doping first conductive polymer, the second conductive polymer doped with a dopant, and a non-aqueous solvent is formed by step (iii).

[0101] The impregnation method in step (iii) is not particularly limited, and a known method can be used. For example, the capacitor element precursor after step (ii) can be immersed in a non-aqueous solvent (or electrolyte). The non-aqueous solvent (or electrolyte) used in step (iii) can be the non-aqueous solvent (or electrolyte) described above.

[0102] In the production method of the present application, the dopant may be a polymer dopant containing an acidic group, and the step (iii) may be a step of impregnating the polymer layer with an electrolyte solution containing a non-aqueous solvent and an alkali component dissolved in the non-aqueous solvent.

[0103] Through step (iii), a first capacitor element can be obtained. Alternatively, through step (iii), an anode body and an electrolyte layer of a second capacitor element can be obtained. After step (iii), an electrolytic capacitor can be made using the components obtained in step (iii). There is no particular limitation on this step, and a known method can be used.

[0104] Hereinafter, with reference to the accompanying drawings, examples of electrolytic capacitors involved in the present application are specifically described, but the electrolytic capacitors of the present application are not limited to the following figures. The constituent elements of the electrolytic capacitor of the example described below can be applied to the above constituent elements. In addition, the constituent elements of the electrolytic capacitor of the example described below can be changed based on the above description. In addition, the matters described below can be applied to the above-mentioned embodiments. It should be noted that sometimes the same symbols are marked on the same parts and repeated descriptions are omitted.

[0105] (Implementation Method 1)

[0106] In Embodiment 1, an example of an electrolytic capacitor according to the present application is described. This electrolytic capacitor is an electrolytic capacitor including a first capacitor element. Figure 1 A cross section of an example of electrolytic capacitor 100 according to Embodiment 1 is schematically shown. Figure 2 Show that Figure 1 1 is a schematic diagram showing a portion of capacitor element 10 included in electrolytic capacitor 100 .

[0107] like Figure 1As shown, the electrolytic capacitor 100 includes: a capacitor element 10, a bottomed case 11 for accommodating the capacitor element 10, a sealing member 12 for blocking the opening of the bottomed case 11, a seat plate 13 covering the sealing member 12, leads 14A and 14B extending from the sealing member 12 and penetrating the seat plate 13, and lead tabs 15A and 15B for connecting the leads 14A and 14B to electrodes of the capacitor element 10. The capacitor element 10 is accommodated in the bottomed case 11. The opening end of the bottomed case 11 is necked inwardly, and the opening end of the bottomed case 11 is crimped in such a way that the sealing member 12 is riveted.

[0108] Reference Figure 2 The capacitor element 10 includes: a foil-shaped anode body 21 having a dielectric layer on the surface, a foil-shaped cathode body 22, and a separator 23 and an electrolyte layer (not shown) disposed therebetween. The anode body 21 and the cathode body 22 are wound with the separator 23 disposed therebetween. The outermost periphery of the wound body is fixed with a stop tape 24. It should be noted that Figure 2 The diagram shows a partially unwound state before the outermost circumference of the wound body is fixed.

[0109] Example

[0110] Hereinafter, the embodiments of the present application will be described in more detail through examples.

[0111] (Example 1)

[0112] In Example 1, a plurality of electrolytic capacitors (capacitors A1 to A7 and capacitor C1) were manufactured and evaluated. The manufacturing method and evaluation method of these capacitors are described below. It should be noted that in the description of the manufacturing method of the capacitor of the comparative example, conditions different from those of the above-mentioned steps (ii) and (iii) are sometimes used, but for the sake of convenience, they are also described as steps (ii) and (iii).

[0113] [Fabrication of capacitor A1]

[0114] The capacitor A1 is a wound electrolytic capacitor having a rated voltage of 35 V and a rated electrostatic capacitance of 270 μF. The capacitor A1 was produced according to the following procedure.

[0115] (Preparation of cathode body)

[0116] As the cathode body, Al foil (aluminum foil) having a thickness of 70 μm was used.

[0117] (Preparation of anode body)

[0118] Prepare Al foil with a thickness of 120 μm. Perform DC etching on the Al foil to roughen the surface. Next, perform chemical conversion treatment on the Al foil to form a dielectric layer (thickness: about 70 nm), thereby obtaining an anode body. The dielectric layer is formed by immersing the Al foil in an ammonium adipate solution, applying a voltage of 50 V to the Al foil, and performing chemical conversion treatment at 70°C for 30 minutes. Then, cut the anode body into a specified size, thereby preparing the anode body of capacitor A1.

[0119] (Preparation of Liquid Containing Self-doping Type First Conductive Polymer)

[0120] As a liquid containing a self-doping type first conductive polymer, the following aqueous solution was prepared.

[0121] (Liquid AL containing conductive polymer A)

[0122] An aqueous solution (liquid AL) containing poly(4-(2,3-dihydrothieno-[3,4-b][1,4]dioxan-2-ylmethoxy)-1-propanesulfonic acid) as the conductive polymer A at a concentration of 5 mass % was prepared.

[0123] (Liquid BL containing conductive polymer B)

[0124] An aqueous solution (liquid BL) containing N-substituted sulfonated polyaniline as the conductive polymer B at a concentration of 5 mass % was prepared.

[0125] (Preparation of PEDOT:PSS dispersion)

[0126] A dispersion of a second conductive polymer doped with a dopant is prepared by the following method. 3,4-ethylenedioxythiophene and polystyrene sulfonic acid as a dopant are dissolved in ion exchange water to prepare a mixed solution thereof. While stirring the obtained mixed solution, iron (III) sulfate (oxidant) dissolved in ion exchange water is added to carry out a polymerization reaction. After the reaction, the obtained reaction solution is dialyzed to remove unreacted monomers and excess oxidant to obtain a dispersion of poly(3,4-ethylenedioxythiophene) doped with about 5% by mass of polystyrene sulfonic acid (PSS). Hereinafter, poly(3,4-ethylenedioxythiophene) doped with about 5% by mass of polystyrene sulfonic acid (PSS) is sometimes referred to as "PEDOT:PSS". In addition, a dispersion in which PEDOT:PSS is dispersed is sometimes referred to as a "PEDOT:PSS dispersion". In this manner, a PEDOT:PSS dispersion having a PEDOT:PSS content of 2% by mass is prepared.

[0127] (Production of wound body (step (i)))

[0128] The anode lead connector and cathode lead connector connected with the lead are connected to the prepared anode body and cathode body respectively. Then, the anode body and the cathode body are wound in a manner of sandwiching the spacer therebetween, and the outer surface is fixed with a stop tape. The spacer uses a non-woven fabric formed of cellulose. The winding body (capacitor element precursor) is made in this way. The prepared winding body is immersed in an ammonium adipate solution, and a chemical conversion treatment is performed again at 70°C for 60 minutes while applying a voltage of 50V to the anode body, thereby forming a dielectric layer mainly on the end face of the anode body.

[0129] (Step (ii))

[0130] First, the liquid AL containing the self-doped conductive polymer A is placed in a container. Next, at room temperature in a reduced pressure atmosphere (40 kPa), the wound body is immersed in the liquid AL in the container for 15 minutes, and then the wound body is lifted from the liquid AL. In this way, the liquid AL is impregnated into the wound body. Next, in a drying furnace, the wound body is dried at 60°C for 30 minutes, and then dried at 150°C for 15 minutes. Thus, the liquid AL is dried. In this way, a polymer layer (conductive polymer layer) is formed.

[0131] (Impermeation of electrolyte)

[0132] At room temperature and atmospheric pressure, the wound body after step (iii) is impregnated with an electrolyte. As an electrolyte, a solution is used in which polyethylene glycol, γ-butyrolactone, cyclopentane sulfone and phthalic acid mono(ethyldimethylamine) (solute) are mixed in a mass ratio of polyethylene glycol: γ-butyrolactone: cyclopentane sulfone: phthalic acid mono(ethyldimethylamine) = 30:30:20:20. In this way, a capacitor element including an electrolyte layer is obtained. The capacitor element is sealed to complete an electrolytic capacitor. Then, an aging treatment is performed at 130°C for 2 hours while applying the rated voltage. In this way, capacitor A1 is obtained.

[0133] [Fabrication of capacitors A2 to A7]

[0134] Capacitors A2 to A7 are made using the same materials and conditions as capacitor A1, except that the liquid used in step (ii) is different. In the production of capacitors A2 to A7, a mixed liquid of the liquid AL containing the self-doped conductive polymer A and the PEDOT:PSS dispersion liquid is used as the liquid used in step (ii). Then, capacitors A2 to A7 are produced by changing the mass ratio of the self-doped conductive polymer contained in the mixed liquid (dispersion liquid) to the mass ratio of PEDOT:PSS. This mass ratio directly corresponds to the mass ratio of the self-doped conductive polymer and PEDOT:PSS in the formed electrolyte layer.

[0135] [Fabrication of capacitor C1]

[0136] Capacitor C1 was produced using the same materials and conditions as capacitor A1 except that the liquid used in step (ii) was different. In the production of capacitor C1, the above-mentioned PEDOT:PSS dispersion was used as the liquid used in step (ii). Therefore, the electrolyte layer of capacitor C1 contained PEDOT:PSS but did not contain a self-doping conductive polymer.

[0137] [Fabrication of capacitors B1 to B7]

[0138] Capacitors B1 to B7 were produced using the same materials and conditions as capacitors A1 to A7 except that the liquid used in step (ii) was different. In the production of capacitors B1 to B7, liquid BL was used instead of liquid AL.

[0139] (ESR measurement)

[0140] The equivalent series resistance (ESR) of the electrolytic capacitor produced as described above was measured. The ESR was measured at 20°C using a 4-terminal LCR meter. The ESR was measured at the initial value after production and at the value after the electrolytic capacitor was placed at high temperature (165°C for 500 hours). Then, as an indicator of long-term characteristics, the long-term characteristics evaluation value F was calculated using the following formula.

[0141] Long-term characteristic evaluation value F = (ESR value after high-temperature storage) / (initial ESR value)

[0142] The ratio of the mass of the self-doped conductive polymer to the mass of PEDOT:PSS in the electrolyte layer of the electrolytic capacitor is shown in Tables 1 and 2. In addition, Tables 1 and 2 show the evaluation results of the ESR of the electrolytic capacitor.

[0143] [Table 1]

[0144]

[0145] [Table 2]

[0146]

[0147] As shown in Tables 1 and 2, the evaluation value F of the capacitors A1 to A7 and B1 to B7 of the present application is small. That is, for these capacitors, the rate of increase of ESR caused by long-term high-temperature storage is small. For the electrolyte layer, when (mass of the first conductive polymer): (total mass of the second conductive polymer and the dopant) = 10:90 to 45:55, the ESR at the beginning and after high-temperature storage is low.

[0148] (Example 2)

[0149] In Example 2, a plurality of electrolytic capacitors (capacitors A8 and A9) were manufactured and evaluated. The manufacturing method and evaluation method of these capacitors are described below.

[0150] [Capacitor A8]

[0151] Capacitor A8 is manufactured using the same materials and conditions as capacitor A1 except that process (ii) is different. In process (ii) of capacitor A8, the above-mentioned impregnation treatment (z) is performed, and then the above-mentioned impregnation treatment (y) is performed. The following describes process (ii) of capacitor A8.

[0152] (Impregnation Treatment (z) and Drying Steps)

[0153] Specifically, first, the above-mentioned PEDOT:PSS dispersion is placed in a container. Next, at room temperature in a reduced pressure atmosphere (40 kPa), the wound body formed in step (i) is immersed in the dispersion in the container for 5 minutes, and then the wound body is lifted from the dispersion. In this way, the dispersion is infiltrated into the wound body. Next, in a drying oven, the wound body is dried at 60°C for 30 minutes, and then at 155°C for 15 minutes. Thus, the dispersion is dried. In this way, the first polymer layer composed of PEDOT:PSS is formed.

[0154] (Impregnation Treatment (y) and Drying Steps)

[0155] Next, the liquid AL containing the self-doping conductive polymer A is used instead of the PEDOT:PSS dispersion liquid, and the liquid AL is impregnated and dried under the same conditions as the first polymer layer. In this way, the second polymer layer composed of the self-doping conductive polymer A is formed.

[0156] Step (ii) is performed as described above. Through step (ii), an electrolyte layer including a first polymer layer (PEDOT:PSS layer) formed on the dielectric layer of the anode body and a second polymer layer (self-doped conductive polymer layer) formed on the first polymer layer is formed.

[0157] [Capacitor A9]

[0158] Capacitor A9 was manufactured using the same materials and conditions as capacitor A8, except that the order of impregnation treatment (z) and impregnation treatment (y) was reversed. That is, in step (ii) of capacitor A9, impregnation treatment (z) was performed after impregnation treatment (y). It should be noted that the drying step was performed under the same conditions as the drying step of capacitor A8.

[0159] Step (ii) is performed as described above. Through step (ii), an electrolyte layer including a first polymer layer (self-doped conductive polymer layer) formed on the dielectric layer of the anode body and a second polymer layer (PEDOT:PSS layer) formed on the first polymer layer is formed.

[0160] The ESR of the electrolytic capacitor produced as described above was measured under the same conditions as those for the electrolytic capacitor A1. The evaluation results are shown in Table 3.

[0161] [Table 3]

[0162]

[0163] As shown in Table 3, the capacitors A8 and A9 have low values ​​of ESR and evaluation value F. Comparing the capacitors A8 and A9, the evaluation value F of the capacitor A9 is lower.

[0164] Industrial Applicability

[0165] The present application can be applied to electrolytic capacitors and methods for manufacturing the same.

[0166] Description of Reference Numerals

[0167] 10 Capacitor elements

[0168] 21 Anode

[0169] 22 Cathode

[0170] 23 Spacer

[0171] 100 Electrolytic Capacitors

Claims

1. An electrolytic capacitor comprising a capacitor element, The capacitor element includes: an anode body having a dielectric layer on a surface thereof, and an electrolyte layer disposed adjacent to the dielectric layer. The electrolyte layer includes a self-doping first conductive polymer, a second conductive polymer doped with a dopant, and a non-aqueous solvent. The first conductive polymer is one or more selected from the group consisting of poly(3,4-ethylenedioxythiophene) having an atomic group containing a sulfonic acid group introduced therein and polyaniline having an atomic group containing a sulfonic acid group introduced therein. The second conductive polymer is poly(3,4-ethylenedioxythiophene), The dopant is a polymer dopant, When the mass of the first conductive polymer contained in the electrolyte layer is represented by W1 and the total mass of the second conductive polymer and the dopant contained in the electrolyte layer is represented by W2, the relationship of 1.1≤W2 / W1≤9 is satisfied.

2. The electrolytic capacitor according to claim 1, wherein: The dopant is a polymer dopant containing an acidic group. The electrolyte layer includes an electrolytic solution including the nonaqueous solvent and an alkali component dissolved in the nonaqueous solvent.

3. The electrolytic capacitor according to claim 2, wherein: The amount of the alkaline component in the electrolytic solution is 0.1 mass % or more and 20 mass % or less.

4. The electrolytic capacitor according to claim 1, wherein: The relationship 11 / 9≤W2 / W1≤9 is satisfied.

5. The electrolytic capacitor according to any one of claims 1 to 4, wherein The electrolyte layer includes a polymer layer, and the polymer layer includes the first conductive polymer and the second conductive polymer doped with the dopant. The polymer layer includes: a first polymer layer formed on the dielectric layer, and a second polymer layer formed on the first polymer layer. The content of the second conductive polymer in the first polymer layer is greater than the content of the second conductive polymer in the second polymer layer. The content of the second conductive polymer is expressed in mass %.

6. The electrolytic capacitor according to any one of claims 1 to 4, wherein The dopant is polystyrene sulfonic acid.

7. A method for manufacturing an electrolytic capacitor, comprising: Step i, preparing a capacitor element precursor, wherein the capacitor element precursor includes an anode body having a dielectric layer on the surface; Step ii, forming a polymer layer adjacent to the dielectric layer by an impregnation treatment, the polymer layer including a self-doping first conductive polymer; and Step iii, impregnating the polymer layer with a non-aqueous solvent to form an electrolyte layer, The polymer layer includes: the first conductive polymer and a second conductive polymer doped with a dopant. The first conductive polymer is one or more selected from the group consisting of poly(3,4-ethylenedioxythiophene) having an atomic group containing a sulfonic acid group introduced therein and polyaniline having an atomic group containing a sulfonic acid group introduced therein. The second conductive polymer is poly(3,4-ethylenedioxythiophene), The dopant is a polymer dopant, When the mass of the first conductive polymer contained in the electrolyte layer is represented by W1 and the total mass of the second conductive polymer and the dopant contained in the electrolyte layer is represented by W2, the relationship of 1.1≤W2 / W1≤9 is satisfied.

8. The manufacturing method according to claim 7, wherein: The dopant is a polymer dopant containing an acidic group. The step iii is a step of impregnating the polymer layer with an electrolyte solution, wherein the electrolyte solution includes the non-aqueous solvent and an alkali component dissolved in the non-aqueous solvent.

9. The manufacturing method according to claim 7 or 8, wherein: The impregnation treatment in the step ii is an impregnation treatment x of impregnating the capacitor element precursor with a liquid containing the first conductive polymer and the second conductive polymer doped with the dopant.

10. The manufacturing method according to claim 7 or 8, wherein: The impregnation treatment in step ii includes: an impregnation process y of impregnating the capacitor element precursor with a first liquid containing the first conductive polymer; and The impregnation process z is to impregnate the capacitor element precursor with a second liquid including the second conductive polymer doped with the dopant.

11. The manufacturing method according to claim 10, wherein: The impregnation treatment y is performed after the impregnation treatment z.

12. The manufacturing method according to claim 7 or 8, wherein: The dopant is polystyrene sulfonic acid.

13. The method for manufacturing an electrolytic capacitor according to claim 7, wherein: The relationship 11 / 9≤W2 / W1≤9 is satisfied.

Images