electrolytic capacitor

Abstract

To provide an electrolytic capacitor whose ESR increases at a low rate over a long period.SOLUTION: An electrolytic capacitor 100 disclosed includes a capacitor element 10. The capacitor element 10 includes an anode body 21 having a dielectric layer on its surface, and an electrolyte layer arranged adjacent to the dielectric layer. The electrolyte layer includes a self-doped first conductive polymer, and a non-aqueous solvent.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to an electrolytic capacitor and a method for manufacturing the same.

Background Art

[0002] Capacitors used in electronic devices are required to have a large capacitance and a low equivalent series resistance (ESR) value in the high-frequency region. As capacitors with a large capacitance and a 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 a salt thereof 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). Further, Patent Document 1 discloses a solid electrolytic capacitor manufactured using the conductive polymer solution.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Currently, there is a need for an electrolytic capacitor with a low ESR increase rate over a long period. In such a situation, one of the objectives of the present disclosure is to provide an electrolytic capacitor with a low ESR increase rate over a long period.

Means for Solving the Problems

[0005] One aspect of the present disclosure relates to an electrolytic capacitor. The electrolytic capacitor is an electrolytic capacitor including a capacitor element, and 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-doped type first conductive polymer and a non-aqueous solvent.

[0006] Another aspect of the present disclosure relates to a method for manufacturing an electrolytic capacitor. The manufacturing method includes: step (i) of preparing a capacitor element precursor including an anode body having a dielectric layer on its surface; step (ii) of forming a polymer layer including a self-doped type first conductive polymer adjacent to the dielectric layer by an impregnation treatment; and step (iii) of impregnating the polymer layer with a non-aqueous solvent. Still another aspect of the present disclosure is an electrolytic capacitor including a capacitor element, wherein 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-doped type first conductive polymer, a second conductive polymer doped with a polymer dopant containing an acidic group, and a non-aqueous solvent, and when the mass of the first conductive polymer contained in the electrolyte layer is W1 and the total mass of the second conductive polymer and the dopant contained in the electrolyte layer is W2, it relates to an electrolytic capacitor satisfying the relationship of 1.1 ≦ W2 / W1 ≦ 9.

Advantages of the Invention

[0007] According to the present disclosure, an electrolytic capacitor with a low ESR increase rate over a long period can be obtained.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Modes for Carrying Out the Invention

[0009] Hereinafter, embodiments of the present disclosure will be described with examples, but the present disclosure is not limited to the examples described below. In the following description, specific numerical values and materials may be exemplified, but other numerical values and materials may be applied as long as the effects of the present disclosure can be obtained.

[0010] (Electrolytic capacitor) The electrolytic capacitor of the present disclosure 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-doped type first conductive polymer and a non-aqueous solvent.

[0011] The capacitor element may include a foil-shaped anode body having a dielectric layer on its surface, a foil-shaped cathode body, a separator disposed between the anode body and the cathode body, and an electrolyte layer disposed between the anode body and the cathode body. Such a capacitor element may be referred to as a "first capacitor element" hereinafter. The first capacitor element may be of a wound type or a stacked type. In an example of a wound type capacitor element, a foil-shaped anode body, a foil-shaped cathode body, and a separator are wound such that the separator is disposed between the anode body and the cathode body. In an example of a stacked type capacitor element, a foil-shaped anode body, a foil-shaped cathode body, and a separator are folded in a zigzag manner such that the separator is disposed between the anode body and the cathode body.

[0012] Alternatively, the capacitor element may include 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. Such a capacitor element may be referred to as a "second capacitor element" hereinafter. In the first and second capacitor elements, the electrolyte layer is adjacent to the dielectric layer of the anode body.

[0013] The electrolyte layer may further include a second conductive polymer doped with a dopant.

[0014] The first and second conductive polymers contained in the electrolyte layer will be described below. In this specification, the conductive polymer may be read as a conductive polymer.

[0015] (First conductive polymer) The first conductive polymer is a self-doped type conductive polymer. Here, the self-doped type conductive polymer means a polymer in which a functional group that functions as a dopant is directly or indirectly bonded to the backbone of the conductive polymer by a covalent bond. Examples of the functional group that functions as a dopant include anionic groups. An anionic group is a group that becomes negatively charged by dissociation of a cation. The anionic group may be at least one selected from the group consisting of a sulfonic acid group, a phosphoric acid group, a phosphonic acid group, and a carboxyl group, or may be a salt thereof (a salt with an inorganic base, a salt with an organic base, etc.). A preferred example of the anionic group is a sulfonic acid group or a salt thereof.

[0016] The amount of the functional group (for example, anionic group) that functions as a dopant may be in the range of 0.2 to 3 per structural unit constituting the polymer (polymer), may be in the range of 0.5 to 2, or may be 1.

[0017] The first conductive polymer may be used alone or in combination of multiple types.

[0018] Examples of the backbone of the first conductive polymer include polypyrrole, polythiophene, polyaniline, etc. Other atomic groups (for example, functional groups) other than the functional group that functions as a dopant may be bonded to these backbones. Examples of the first conductive polymer include polypyrroles having an anionic group (polypyrrole and its derivatives), polythiophenes having an anionic group (polythiophene and its derivatives), polyanilines having an anionic group (polyaniline and its derivatives), etc. In these examples, a preferred example of the anionic group is a sulfonic acid group or a salt thereof. The first conductive polymer may be a copolymer of two or more monomers.

[0019] In terms of having a high effect of suppressing the increase in ESR and the decrease in capacitance even in a high-temperature environment, the first conductive polymer may be one in which an atomic group containing a sulfonic acid group is introduced 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.

[0020] [Chemical formula]

[0021] In the above formula, R represents an organic chain. R may be composed of a hydrocarbon chain, and in addition to the hydrocarbon chain, may contain an ether bond, a branched alkyl group, or other substituents. In the above formula, the sulfonic acid group may be in the form of a salt. Examples of R include (skeleton side)-CH2-O-(CH2)2-(CHCH3)-(sulfonic acid group side), etc.

[0022] Alternatively, the first conductive polymer may be one in which an atomic group containing a sulfonic acid group is introduced into polyaniline, for example, it may be polyaniline sulfonic acid.

[0023] The weight average molecular weight of the first conductive polymer may be in the range of 1000 to 100000, or may be in the range of 1000 to 30000.

[0024] (The second conductive polymer) 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 having polypyrrole, polythiophene, polyfuran, polyaniline, and polyacetylene as the basic skeleton. For example, derivatives of polythiophene include poly(3,4-ethylenedioxythiophene). The second conductive polymer may be used alone or in combination of two or more kinds. Also, the second conductive polymer may be a copolymer of two or more kinds of monomers. The weight average molecular weight of the second conductive polymer is not particularly limited, and may be, for example, in the range of 1000 to 100000. A preferred example of the second conductive polymer is poly(3,4-ethylenedioxythiophene) (PEDOT).

[0025] Unlike the first conductive polymer, in the second conductive polymer, a 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, it is preferable to use a polymer dopant as the dopant. Examples of the polymer dopant include polyvinylsulfonic acid, polystyrenesulfonic acid, polyallylsulfonic acid, polyacrylicsulfonic acid, polymethacrylicsulfonic acid, poly(2-acrylamido-2-methylpropanesulfonic acid), polyisoprenesulfonic acid, polyacrylic acid, and the like. These may be used alone or in combination of two or more kinds. These may be contained in the electrolyte layer in the form of a salt. A preferred example of the dopant is polystyrenesulfonic acid (PSS).

[0026] The weight average molecular weight of the dopant is not particularly limited. From the viewpoint of facilitating the formation of a homogeneous electrolyte layer, the weight average molecular weight of the dopant may be in the range of 1000 to 100000.

[0027] In the electrolytic capacitor of the present disclosure, the dopant may be polystyrene sulfonic acid, and the second conductive polymer may be poly(3,4-ethylenedioxythiophene). That is, the electrolyte layer may contain poly(3,4-ethylenedioxythiophene) doped with polystyrene sulfonic acid.

[0028] (Liquid component) The electrolyte layer of the electrolytic capacitor of the present disclosure contains a non-aqueous solvent. The electrolyte layer may contain an electrolytic solution (non-aqueous electrolytic solution) containing a non-aqueous solvent and a base component dissolved in the non-aqueous solvent. That is, the electrolyte layer of the electrolytic capacitor of the present disclosure may contain a liquid component. Hereinafter, the liquid component (non-aqueous solvent or electrolytic solution) contained in the electrolyte layer may be referred to as "liquid component (L)". 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 during use of the electrolytic capacitor. An electrolytic capacitor having an electrolyte layer containing the liquid component (L) may be called a hybrid capacitor.

[0029] 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 polyhydric alcohols 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, and 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, and formaldehyde.

[0030] Alternatively, a polymeric solvent may be used as the non-aqueous solvent. Examples of the polymeric solvent include polyalkylene glycols, derivatives of polyalkylene glycols, and compounds in which at least one of the hydroxyl groups in a polyhydric alcohol is substituted with a polyalkylene glycol (including derivatives). Specifically, examples of the polymeric solvent include polyethylene glycol (PEG), polyethylene glycol glyceryl ether, polyethylene glycol diglyceryl ether, polyethylene glycol sorbitol ether, polypropylene glycol, polypropylene glycol glyceryl ether, polypropylene glycol diglyceryl ether, polypropylene glycol sorbitol ether, polybutylene glycol, and the like. Examples of the polymeric solvent further include copolymers of ethylene glycol-propylene glycol, copolymers of ethylene glycol-butylene glycol, copolymers of propylene glycol-butylene glycol, and the like. The non-aqueous solvent may be used alone or in combination of two or more.

[0031] As described above, the electrolyte layer may contain a non-aqueous solvent and a base component (base) dissolved in the non-aqueous solvent. Further, the electrolyte layer may contain a non-aqueous solvent and a base component and / or an acid component (acid) dissolved in the non-aqueous solvent.

[0032] 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.).

[0033] Examples of the monocarboxylic acid 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, enanthic acid, caprylic acid, pelargonic 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 oxycarboxylic acids (such as salicylic acid, mandelic acid, resorcylic acid).

[0034] Among these, maleic acid, phthalic acid, benzoic acid, pyromellitic acid, and resorcylic acid are thermally stable and preferably used.

[0035] An inorganic acid may be used as the acid component. Examples of typical inorganic acids include phosphoric acid, phosphorous acid, hypophosphorous acid, alkyl phosphate esters, boric acid, fluoboric acid, tetrafluoroboric acid, hexafluorophosphoric acid, benzenesulfonic acid, naphthalenesulfonic acid, etc. Further, a composite compound of an organic acid and an inorganic acid may be used as the acid component. Examples of such composite compounds include borodiglycolic acid, boromalonic acid, borosalicylic acid, etc.

[0036] The base component may be a compound having an alkyl-substituted amidine group, and examples thereof may include imidazole compounds, benzimidazole compounds, alicyclic amidine compounds (pyrimidine compounds, imidazoline compounds), 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, 1-methylbenzimidazole are preferred. By using these, a capacitor with excellent impedance performance can be obtained.

[0037] As the base component, a quaternary salt of a compound having an alkyl-substituted amidine group may be used. Examples of such base components include imidazole compounds, benzimidazole compounds, and alicyclic amidine compounds (pyrimidine compounds, imidazoline compounds) quaternized with an alkyl group or arylalkyl group having 1 to 11 carbon atoms. Specifically, 1-methyl-1,8-diazabicyclo[5,4,0]undecene-7, 1-methyl-1,5-diazabicyclo[4,3,0]nonene-5, 1,2,3-trimethylimidazolinium, 1,2,3,4-tetramethylimidazolinium, 1,2-dimethyl-3-ethyl-imidazolinium, 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, 1,3-dimethylbenzimidazolium are preferred. By using these, a capacitor with excellent impedance performance can be obtained.

[0038] In addition, a tertiary amine may be used as the base component. Examples of the tertiary amine include trialkylamines (trimethylamine, dimethylethylamine, methyldiethylamine, triethylamine, dimethyl-n-propylamine, dimethylisopropylamine, methylethyln-propylamine, methylethylisopropylamine, diethyl-n-propylamine, diethylisopropylamine, tri-n-propylamine, triisopropylamine, tri-n-butylamine, tri-tert-butylamine, etc.), phenyl group-containing amines (dimethylphenylamine, methylethylphenylamine, diethylphenylamine, etc.). Among them, trialkylamines are preferred in terms of enhancing the conductivity of the electrolyte layer, and it is more preferable to contain at least one selected from the group consisting of trimethylamine, dimethylethylamine, methyldiethylamine, and triethylamine. Further, as the base component, a secondary amine such as a dialkylamine, a primary amine such as a monoalkylamine, or ammonia may be used.

[0039] The liquid component (L) may contain a salt of an acid component and a base component. The salt may be an inorganic salt and / or an organic salt. The organic salt is a salt in which at least one of the anion and the cation contains an organic substance. As the organic salt, for example, trimethylamine maleate, triethylamine borodisalicylate, ethyldimethylamine phthalate, mono-1,2,3,4-tetramethylimidazolinium phthalate, mono-1,3-dimethyl-2-ethylimidazolinium phthalate, etc. may be used.

[0040] In order to suppress the dedoping of the dopant, the pH of the liquid component (L) may be less than 7, and may be 5 or less (for example, in the range of 2 to 5).

[0041] In an electrolytic capacitor, it is important to have a low ESR. By using an electrolyte layer containing a conductive polymer doped with a dopant, a low ESR can be achieved. However, when using an electrolyte layer containing a conductive polymer doped with a dopant and a liquid component (L), the inventors of the present application have found that although the initial ESR is low, the degradation phenomenon in which the ESR increases with time is significant. When examining the cause, it was found that in the electrolyte layer containing the liquid component (L), the dopant may be easily dedoped. It is considered that this dedoping causes the ESR to increase with time. Therefore, compared with a solid electrolytic capacitor containing a solid electrolyte that does not contain the liquid component (L), it is important to suppress the increase in ESR over time in an electrolytic capacitor containing the liquid component (L).

[0042] Since the self-doping type of the first conductive polymer is less likely to be dedoped, the deterioration of its conductivity over time is small. Therefore, by including the first conductive polymer in the electrolyte layer, an increase in ESR over time can be suppressed.

[0043] In the electrolytic capacitor of the present disclosure, the dopant may be a dopant containing an acidic group or a polymer dopant containing an acidic group. As a result of examination, the inventors of the present application newly found that when using a dopant containing an acidic group, dedoping may occur significantly as the pH increases. Therefore, when using a dopant containing an acidic group, it is particularly important to suppress the increase in ESR over time.

[0044] In the electrolytic capacitor of the present disclosure using the second conductive polymer, the dopant may be a polymer dopant containing an acidic group, and the electrolyte layer may include an electrolytic solution containing a non-aqueous solvent and a base component dissolved in the non-aqueous solvent. In this case, since the dopant is likely to be removed by the base component, it is particularly important to suppress the increase in ESR over time. As described above, since the electrolytic capacitor of the present disclosure includes the self-doping type of the first conductive polymer, an increase in ESR over time can be suppressed.

[0045] Examples of the basic component include the basic components described above. Examples of the acidic group include a sulfonic acid group, a carboxyl group, and the like. The polymer dopant containing an acidic group is a polymer (polymer) in which at least some of the constituent units contain an acidic group. Examples of such polymer dopants include the polymer dopants described above.

[0046] In the electrolytic capacitor of the present disclosure, the amount of the basic component in the electrolytic solution may be 0.1% by mass or more and 20% by mass or less. When the amount of the basic component is 0.1% by mass or more, it becomes particularly important to use the self-doping type first conductive polymer. Further, by setting the amount of the basic component to 20% by mass or less, it becomes easy to dissolve the basic component in the electrolytic solution.

[0047] The content rate of the liquid component (L) in the electrolyte layer may be in the range of 60 to 99% by mass (for example, in the range of 70 to 95% by mass). The content rate of the first conductive polymer in the solid content in the electrolyte layer may be in the range of 1 to 100% by mass (for example, in the range of 1 to 45% by mass). The total content rate 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% by mass (for example, in the range of 55 to 99% by mass). In the electrolyte layer, the relationship of (mass of the first conductive polymer):(total mass of the second conductive polymer and the dopant) = 10:90 to 45:55 may be satisfied.

[0048] In the electrolytic capacitor of the present disclosure, the total mass of the second conductive polymer and the dopant contained in the electrolyte layer may be larger than the mass of the first conductive polymer contained in the electrolyte layer. That is, the total content rate (mass%) of the second conductive polymer and the dopant in the electrolyte layer may be larger than the content rate (mass%) of the first conductive polymer in the electrolyte layer. The conductive polymer doped with the dopant generally has higher conductivity than the self-doping type conductive polymer. Therefore, increasing the content rate of the second conductive polymer doped with the dopant is effective for reducing the initial ESR.

[0049] 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 of 1 < W2 / W1, or may satisfy the relationship of 1.1 ≦ W2 / W1 ≦ 9.

[0050] The electrolytic capacitor of the present disclosure may satisfy the following condition (1). (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. 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.

[0051] 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.

[0052] In one example, the first polymer layer is composed of a 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 a second conductive polymer doped with a dopant.

[0053] The electrolytic capacitor of the present disclosure may satisfy the above condition (1) and the following condition (2). (2) The content (mass %) of the second conductive polymer in the first polymer layer is greater than the content (mass %) of the second conductive polymer in the second polymer layer. In the condition (2), the "content (mass %) of the second conductive polymer" may be replaced with the "total content (mass %) of the second conductive polymer and the dopant".

[0054] The condition in (2) above may be replaced with the condition that (2’) the content (mass %) of the first conductive polymer in the first polymer layer is less than the content (mass %) of the first conductive polymer in the second polymer layer. According to the configuration in (2) above, the proportion of the second conductive polymer in the portion of the surface of the anode body close to the dielectric layer can be increased. As a result, it is possible to lower the initial ESR.

[0055] The electrolytic capacitor of the present disclosure may satisfy the following conditions (A) and (B), and may further satisfy the requirement of (C). (A) The first conductive polymer is poly(3,4-ethylenedioxythiophene) into which a sulfonic acid group is introduced, for example, the polymer described above. (B) The second conductive polymer is poly(3,4-ethylenedioxythiophene), and the dopant doped into the second conductive polymer is polystyrene sulfonic acid. (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 of 1 < W2 / W1, for example, satisfy the relationship of 1.1 ≦ W2 / W1 ≦ 9.

[0056] There are no particular limitations on the components (anode body, cathode body, separator, etc.) of the capacitor element other than the electrolyte, and known ones may be used. Examples of those of the first capacitor element will be described below.

[0057] (Anode body) For the anode body, a metal foil having a dielectric layer formed on its surface may be used. The type of metal constituting the metal foil is not particularly limited. From the viewpoint of easy formation of the dielectric layer, examples of the metal constituting the metal foil include valve metals such as aluminum, tantalum, niobium, and titanium, and alloys of valve metals. A preferred example is aluminum and aluminum alloys. Usually, the surface of the anode body is roughened (porous). The dielectric layer of the anode body is formed on the porous portion (roughened surface). The electrolyte layer is in contact with the dielectric layer of the anode body.

[0058] (Cathode body) For the cathode body, a metal foil may be used. The type of metal constituting the metal foil is not particularly limited. Examples of the metal constituting the metal foil include metals having a valve action, such as aluminum, tantalum, niobium, and titanium, and alloys of metals having a valve action. A preferred example is aluminum and aluminum alloys. A formation film may be provided on the surface of the cathode body, or a film of a metal (dissimilar metal) or non-metal different from the metal constituting the cathode body may be provided. Examples of the dissimilar metal or non-metal include metals such as titanium and non-metals such as carbon.

[0059] (Separator) For the separator, a sheet-like material that can be impregnated with an electrolyte can be used. For example, a sheet-like material having insulation and capable of being impregnated with an electrolyte may be used. The separator may be a woven fabric, a non-woven fabric, or a porous membrane. Examples of the material of the separator include cellulose, polyethylene terephthalate, polybutylene terephthalate, polyphenylene sulfide, vinylon, nylon, aromatic polyamide, polyimide, polyamideimide, polyetherimide, rayon, and glass.

[0060] Examples of the components other than the electrolyte layer of the second capacitor element 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.

[0061] 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 have a rectangular parallelepiped shape. Examples of valve metals include titanium (Ti), tantalum (Ta), niobium (Nb), and the like. The material particles may be made of an alloy containing a valve metal. For example, an alloy containing a valve metal and silicon, vanadium, boron, or the like may be used. The alloy of the valve metal has the valve metal as the main component and contains, for example, 50 atomic% or more of the valve metal. Also, material particles made 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 kinds.

[0062] Since the anode body of the second capacitor element is porous, it has a porous portion on the surface, and the dielectric layer is formed on 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 the sintered body serving as the anode body to a forming treatment to grow an oxide film on the surface of the sintered body.

[0063] The cathode layer has a current collecting function. The cathode layer is formed of, for example, a conductive material. The cathode layer may be a conductive layer formed so as to cover the electrolyte layer. The cathode layer may include a carbon layer formed so as to cover 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 (for example, silver particles) and a resin. The cathode layer can be formed by applying the above materials.

[0064] (Method for manufacturing an electrolytic capacitor) The method of the present disclosure for manufacturing an electrolytic capacitor will be described below. According to this manufacturing method, the electrolytic capacitor of the present disclosure can be manufactured. Note that the matters described for the electrolytic capacitor of the present disclosure can be applied to the following manufacturing method, and thus duplicate explanations may be omitted. For example, since the components of the capacitor element and the like have been described above, duplicate explanations may be omitted. Also, the matters described in the following manufacturing method can be applied to the electrolytic capacitor described above.

[0065] The manufacturing method according to the present disclosure includes step (i), step (ii), and step (iii). These will be described below.

[0066] (Step (i)) 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.

[0067] When manufacturing an electrolytic capacitor including a first capacitor element, step (i) may be a step of forming a capacitor element precursor including a foil-shaped anode body having a dielectric layer on its 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 of a wound type or a stacked type. When 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 its surface and an anode wire partially embedded in the anode body.

[0068] (Step (ii)) Step (ii) is a step of forming a polymer layer containing a self-doped type first conductive polymer adjacent to the dielectric layer by an impregnation process.

[0069] The polymer layer formed in step (ii) may contain a first conductive polymer and a second conductive polymer doped with a dopant. That is, step (ii) may be a step of forming a polymer layer containing a first conductive polymer and a second conductive polymer doped with a dopant adjacent to the dielectric layer by an impregnation process.

[0070] The impregnation treatment in step (ii) may be an impregnation treatment (x) in which a liquid (dispersion or solution; the same applies hereinafter) containing the first conductive polymer and the 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 the first conductive polymer and the second conductive polymer doped with a dopant can be disposed adjacent to the dielectric layer. Note that the impregnation treatment (x) may be performed multiple times. In that case, a drying step of removing the dispersion medium or solvent of the liquid impregnated before performing the impregnation treatment (x) for the second and subsequent times may be performed.

[0071] There is no particular limitation on the dispersion medium or solvent of the liquid, and a known dispersion medium or solvent may be used. For example, as the dispersion medium or solvent, an aqueous liquid containing water may be used, or water may be used.

[0072] By adjusting the mass (content ratio) of the first conductive polymer and the mass (content ratio) of the second conductive polymer (and dopant) in the liquid, the ratio between them in the formed electrolyte layer can be adjusted. For example, by making the mass (content ratio) of the second conductive polymer (and dopant) in the liquid larger than the mass (content ratio) of the first conductive polymer in the liquid, the mass of the second conductive polymer (and dopant) contained in the electrolyte layer can be made larger than the mass of the first conductive polymer contained in the electrolyte layer.

[0073] The impregnation treatment in step (ii) may include an impregnation treatment (y) of impregnating a capacitor element precursor with a first liquid containing a first conductive polymer, and an impregnation treatment (z) of impregnating the capacitor element precursor with a second liquid containing a second conductive polymer doped with a dopant. 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 they may be performed simultaneously. In a preferred example, the impregnation treatment (y) is performed after the impregnation treatment (z). Note that the impregnation treatment (y) and the impregnation treatment (z) may each be performed independently a plurality of times. Further, after each of the impregnation treatment (y) and the impregnation treatment (z), a drying step of removing the dispersion medium (or solvent) of the impregnated liquid may be performed.

[0074] 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) may be applied.

[0075] In one example, the first liquid does not contain a second conductive polymer doped with a dopant, and the second liquid does not contain a first conductive polymer. However, the first liquid may contain a second conductive polymer doped with a dopant, and the second liquid may contain a first conductive polymer.

[0076] Drying may be performed after performing either the impregnation treatment (y) or the impregnation treatment (z), and then the other impregnation treatment may be performed. By doing so, a polymer layer including a first polymer layer and a second polymer layer can be formed. Further, by adjusting the type and content ratio of the conductive polymer (and dopant) in the first liquid and the type and content ratio of the conductive polymer (and dopant) in the second liquid, the type and content ratio of the conductive polymer (and dopant) in the first polymer layer and the type and content ratio of the conductive polymer (and dopant) in the second polymer layer can be adjusted.

[0077] (Step (iii)) Step (iii) is a step of impregnating the polymer layer formed in step (ii) with a non-aqueous solvent. Thereby, an electrolyte layer containing a self-doped type 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 electrolytic solution (including 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).

[0078] When the polymer layer formed in step (ii) contains a second conductive polymer doped with a dopant, step (iii) forms an electrolyte layer containing a self-doped type first conductive polymer, a second conductive polymer doped with a dopant, and a non-aqueous solvent.

[0079] There is no particular limitation on the impregnation method in step (iii), and known methods may be used. For example, the capacitor element precursor that has undergone step (ii) may be immersed in a non-aqueous solvent (or an electrolytic solution). The non-aqueous solvent (or electrolytic solution) used in step (iii) may be the one described above.

[0080] In the manufacturing method of the present disclosure, the dopant may be a polymer dopant containing an acidic group, and step (iii) may be a step of impregnating the polymer layer with an electrolytic solution containing a non-aqueous solvent and a base component dissolved in the non-aqueous solvent.

[0081] A first capacitor element is obtained by step (iii). Alternatively, an anode body and an electrolyte layer of a second capacitor element are obtained by step (iii). After step (iii), an electrolytic capacitor may be manufactured using the components obtained in step (iii). There is no particular limitation on that step, and known methods can be used.

[0082] Hereinafter, an example of an electrolytic capacitor according to the present disclosure will be specifically described with reference to the drawings. However, the electrolytic capacitor of the present disclosure is not limited by the following figures. The components of the electrolytic capacitor in the example described below can apply the above-described components. Further, the components of the electrolytic capacitor in the example described below can be changed based on the above description. In addition, the matters described below may be applied to the above-described embodiments. Note that the same reference numerals may be given to the same parts, and duplicate descriptions may be omitted.

[0083] (Embodiment 1) In Embodiment 1, an example of an electrolytic capacitor according to the present disclosure will be described. This electrolytic capacitor is an electrolytic capacitor including a first capacitor element. FIG. 1 schematically shows a cross section of an example of the electrolytic capacitor 100 of Embodiment 1. FIG. 2 shows a schematic diagram of a part of the capacitor element 10 included in the electrolytic capacitor 100 shown in FIG. 1, which is developed.

[0084] As shown in FIG. 1, the electrolytic capacitor 100 includes a capacitor element 10, a bottomed case 11 that houses the capacitor element 10, a sealing member 12 that closes the opening of the bottomed case 11, a seat plate 13 that covers the sealing member 12, lead wires 14A and 14B that are led out from the sealing member 12 and penetrate the seat plate 13, and lead tabs 15A and 15B that connect the lead wires 14A and 14B to the electrodes of the capacitor element 10. The capacitor element 10 is housed in the bottomed case 11. The vicinity of the open end of the bottomed case 11 is inwardly tapered, and the open end of the bottomed case 11 is curled so as to caul the sealing member 12.

[0085] Referring to FIG. 2, the capacitor element 10 includes a foil-shaped anode body 21 having a dielectric layer on its 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 by a winding tape 24. Note that FIG. 2 shows a partially developed state before fixing the outermost periphery of the wound body.

Example

[0086] Hereinafter, embodiments of the present disclosure will be described in more detail with reference to examples.

[0087] (Example 1) 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 will be described below. In the description of the manufacturing method of the capacitors of the comparative examples, conditions different from those of the above-described steps (ii) and (iii) may be used, but for convenience, they will also be described as steps (ii) and (iii).

[0088] [Manufacture of Capacitor A1] Capacitor A1 is a wound-type electrolytic capacitor with a rated voltage of 35V and a rated capacitance of 270 μF. Capacitor A1 was manufactured by the following procedure. [[ID=

[0089] (Preparation of cathode body) For the cathode body, an Al foil (aluminum foil) with a thickness of 70 μm was used.

[0090] (Preparation of anode body) An Al foil with a thickness of 120 μm was prepared. This Al foil was subjected to DC etching treatment to roughen the surface. Next, the Al foil was subjected to formation treatment to form a dielectric layer (thickness: about 70 nm), thereby obtaining an anode body. The dielectric layer was formed by immersing the Al foil in an ammonium adipate solution and performing formation treatment at 70°C for 30 minutes while applying a voltage of 50V to the Al foil. Thereafter, the anode body was cut into a predetermined size to prepare the anode body of Capacitor A1.

[0091] (Preparation of liquid containing self-doped type first conductive polymer) As the liquid containing the self-doped type first conductive polymer, the following aqueous solution was prepared. (Liquid AL containing conductive polymer A) An aqueous solution (Liquid AL) containing poly(4-(2,3-dihydrothieno-[3,4-b][1,4]dioxin-2-ylmethoxy)-1-propanesulfonic acid) as a conductive polymer A at a concentration of 5% by mass was prepared. (Liquid BL containing a conductive polymer B) An aqueous solution (Liquid BL) containing N-substituted sulfonated polyaniline as a conductive polymer B at a concentration of 5% by mass was prepared.

[0092] (Preparation of PEDOT:PSS dispersion) A dispersion of a second conductive polymer doped with a dopant was prepared by the following method. A mixed solution was prepared by dissolving 3,4-ethylenedioxythiophene and polystyrene sulfonic acid as a dopant in ion-exchanged water. While stirring the obtained mixed solution, iron(III) sulfate (oxidizing agent) dissolved in ion-exchanged water was added to carry out a polymerization reaction. After the reaction, the obtained reaction solution was dialyzed to remove unreacted monomers and excess oxidizing agent, and a dispersion containing poly(3,4-ethylenedioxythiophene) doped with about 5% by mass of polystyrene sulfonic acid (PSS) was obtained. Hereinafter, poly(3,4-ethylenedioxythiophene) doped with about 5% by mass of polystyrene sulfonic acid (PSS) may be referred to as "PEDOT:PSS". Also, a dispersion in which PEDOT:PSS is dispersed may be referred to as "PEDOT:PSS dispersion". In this way, a PEDOT:PSS dispersion having a PEDOT:PSS content of 2% by mass was prepared.

[0093] (Production of wound body (step (i))) An anode lead tab and a cathode lead tab to which lead wires were connected were respectively connected to the prepared anode body and cathode body. Then, the anode body and the cathode body were wound with a separator interposed therebetween, and the outer surface was fixed with a winding tape. As the separator, a non-woven fabric made of cellulose was used. In this way, a wound body (precursor of a capacitor element) was produced. The produced wound body was immersed in an ammonium adipate solution, and a dielectric layer was mainly formed on the end face of the anode body by performing a secondary formation treatment at 70 °C for 60 minutes while applying a voltage of 50 V to the anode body.

[0094] (Step (ii)) First, liquid AL containing the above-mentioned self-doping conductive polymer A was placed in a container. Next, the wound body was immersed in the liquid AL in the container at room temperature in a reduced pressure atmosphere (40 kPa) for 15 minutes, and then the wound body was pulled out of the liquid AL. In this way, the wound body was impregnated with the liquid AL. Next, the wound body was dried in a drying oven at 60°C for 30 minutes, and then at 150°C for 15 minutes. In this way, the liquid AL was dried. In this way, a polymer layer (conductive polymer layer) was formed.

[0095] (Electrolyte impregnation) The wound body after step (iii) was impregnated with an electrolyte at room temperature and atmospheric pressure. The electrolyte solution was a mixture of polyethylene glycol, γ-butyrolactone, sulfolane, and mono(ethyldimethylamine) phthalate (solute) in a mass ratio of polyethylene glycol:γ-butyrolactone:sulfolane:mono(ethyldimethylamine) phthalate = 30:30:20:20. In this way, a capacitor element including an electrolyte layer was obtained. This capacitor element was sealed to complete an electrolytic capacitor. Thereafter, an aging treatment was performed at 130°C for 2 hours while applying the rated voltage. In this way, capacitor A1 was obtained.

[0096] [Making capacitors A2 to A7] Capacitors A2 to A7 were fabricated using the same materials and conditions as Capacitor A1, except for the liquid used in step (ii). In fabricating Capacitors A2 to A7, a mixture of Liquid AL containing the self-doping conductive polymer A and the PEDOT:PSS dispersion was used as the liquid used in step (ii). Capacitors A2 to A7 were fabricated by varying the mass ratio of the self-doping conductive polymer to the PEDOT:PSS contained in the mixture (dispersion). This mass ratio directly corresponds to the mass ratio of the self-doping conductive polymer to PEDOT:PSS in the electrolyte layer to be formed.

[0097] [Making capacitor C1] The capacitor C1 was fabricated using the same materials and conditions as capacitor A1, except that the liquid used in step (ii) was different. In the fabrication of capacitor C1, the above-mentioned PEDOT:PSS dispersion was used as the liquid in step (ii). Therefore, the electrolyte layer of capacitor C1 contained PEDOT:PSS but did not contain a self-doped conductive polymer.

[0098] [Fabrication of Capacitors B1 - B7] Capacitors B1 - B7 were fabricated using the same materials and conditions as capacitors A1 - A7, except that the liquid used in step (ii) was different. In the fabrication of capacitors B1 - B7, liquid BL was used instead of liquid AL.

[0099] (Measurement of ESR) The equivalent series resistance (ESR) of the electrolytic capacitors fabricated as described above was measured. The ESR was measured at 20°C using an LCR meter for four-terminal measurement. The ESR was measured for the initial value after fabrication and the value after leaving the electrolytic capacitor at a high temperature (left at 165°C for 500 hours). Then, as an index of long-term characteristics, the long-term characteristic evaluation value F was obtained by the following formula. Long-term characteristic evaluation value F = (Value of ESR after high-temperature storage) / (Initial value of ESR)

[0100] Table 1 and Table 2 show the ratio of the mass of the self-doped conductive polymer to the mass of PEDOT:PSS in the electrolyte layer of the above-mentioned electrolytic capacitors. Table 1 and Table 2 also show the evaluation results of the ESR of the above-mentioned electrolytic capacitors.

[0101] [Table 1]

[0102] [Table 2]

[0103] As shown in Table 1 and Table 2, the capacitors A1 to A7 and B1 to B7 of the present disclosure had small values of the evaluation value F. That is, in these capacitors, the rate of increase in ESR due to long-term storage at high temperature was small. In 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 was low both initially and after high-temperature storage.

[0104] (Example 2) In Example 2, a plurality of electrolytic capacitors (capacitors A8 and A9) were fabricated and evaluated. Their manufacturing method and evaluation method will be described below.

[0105] [Capacitor A8] Capacitor A8 was fabricated with the same materials and conditions as capacitor A1, except that step (ii) was different. In step (ii) of capacitor A8, after performing the above-described impregnation treatment (z), the above-described impregnation treatment (y) was performed. Step (ii) of capacitor A8 will be described below.

[0106] (Impregnation treatment (z) and drying process) Specifically, first, the above-described dispersion of PEDOT:PSS was placed in a container. Next, at room temperature in a reduced-pressure atmosphere (kPa), the wound body formed in step (i) was immersed in the dispersion in the container for 5 minutes, and then the wound body was pulled out from the dispersion. In this way, the dispersion was impregnated into the wound body. Next, in a drying furnace, the wound body was dried at 60°C for 30 minutes and then continuously dried at 155°C for 15 minutes. Thereby, the dispersion was dried. In this way, the first polymer layer composed of PEDOT:PSS was formed.

[0107] (Impregnation treatment (y) and drying process) Next, except for using the liquid AL containing the above-described self-doped conductive polymer A instead of the dispersion of PEDOT:PSS, the impregnation and drying of the liquid AL were performed under the same conditions as the formation of the first polymer layer. In this way, the second polymer layer composed of the self-doped conductive polymer A was formed.

[0108] As described above, step (ii) was performed. By 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 was formed.

[0109] [Capacitor A9] Capacitor A9 was fabricated with the same materials and conditions as Capacitor A8, except that the order of the impregnation treatment (z) and the impregnation treatment (y) was reversed. That is, in step (ii) of Capacitor A9, the impregnation treatment (z) was performed after the impregnation treatment (y). The drying process was carried out under the same conditions as the drying process of Capacitor A8.

[0110] As described above, step (ii) was performed. By 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 was formed.

[0111] For the electrolytic capacitor fabricated as described above, the ESR was measured under the same conditions as those for Electrolytic Capacitor A1. The evaluation results are shown in Table 3.

[0112] [Table 3]

[0113] As shown in Table 3, both Capacitors A8 and A9 had low values of ESR and evaluation value F. When comparing Capacitor A8 and A9, Capacitor A9 had a lower value of evaluation value F. [Industrial Applicability]

[0114] The present disclosure can be applied to electrolytic capacitors and methods for manufacturing the same. [Description of Reference Numerals]

[0115] 10 Capacitor elements 21 Anode body 22 Cathode body 23 Separator 100 Electrolytic capacitor

Claims

1. An electrolytic capacitor including 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 and a second conductive polymer doped with a polymer dopant containing an acidic group; the electrolyte layer further contains at least one compound selected from the group consisting of polyhydric alcohols, cyclic sulfones, lactones, amides, esters, carbonate compounds, ethers, ketones, polyalkylene glycols, derivatives of polyalkylene glycols, compounds in which at least one hydroxyl group in a polyhydric alcohol is substituted with a polyalkylene glycol, and compounds in which at least one hydroxyl group in a polyhydric alcohol is substituted with a derivative of a polyalkylene glycol; the polymer dopant is polystyrene sulfonic acid; the second conductive polymer is poly(3,4-ethylenedioxythiophene), an electrolytic capacitor, wherein a proportion of the total mass of the second conductive polymer and the polymer dopant to the total mass of the second conductive polymer, the polymer dopant, and the first conductive polymer contained in the electrolyte layer is 55% or more and 90% or less.

2. An electrolytic capacitor including 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 and a second conductive polymer doped with a polymer dopant containing an acidic group; the electrolyte layer further contains at least one compound selected from the group consisting of ethylene glycol, propylene glycol, sulfolane, γ-butyrolactone, N-methylacetamide, N,N-dimethylformamide, N-methyl-2-pyrrolidone, methyl acetate, propylene carbonate, 1,4-dioxane, methyl ethyl ketone, formaldehyde, polyethylene glycol, polyethylene glycol glyceryl ether, polyethylene glycol diglyceryl ether, polyethylene glycol sorbitol ether, polypropylene glycol, polypropylene glycol glyceryl ether, polypropylene glycol diglyceryl ether, polypropylene glycol sorbitol ether, polybutylene glycol, a copolymer of ethylene glycol and propylene glycol, a copolymer of ethylene glycol and butylene glycol, and a copolymer of propylene glycol and butylene glycol; the polymer dopant is polystyrene sulfonic acid; the second conductive polymer is poly(3,4-ethylenedioxythiophene), an electrolytic capacitor, wherein a proportion of the total mass of the second conductive polymer and the polymer dopant to the total mass of the second conductive polymer, the polymer dopant, and the first conductive polymer contained in the electrolyte layer is 55% or more and 90% or less.

3. An electrolytic capacitor including 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 polymer dopant containing an acidic group, and a non-aqueous solvent; the polymer dopant is polystyrene sulfonic acid; the second conductive polymer is poly(3,4-ethylenedioxythiophene), an electrolytic capacitor in which, when a mass of the first conductive polymer contained in the electrolyte layer is defined as W1 and a total mass of the second conductive polymer and the polymer dopant contained in the electrolyte layer is defined as W2, the relationship of 1.1≦W2 / W1≦9 is satisfied.

4. An electrolytic capacitor including 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 and a second conductive polymer doped with a polymer dopant containing an acidic group; the electrolyte layer further contains at least one compound selected from the group consisting of polyhydric alcohols, cyclic sulfones, lactones, amides, esters, carbonate compounds, ethers, ketones, polyalkylene glycols, derivatives of polyalkylene glycols, compounds in which at least one hydroxyl group in a polyhydric alcohol is substituted with a polyalkylene glycol, and compounds in which at least one hydroxyl group in a polyhydric alcohol is substituted with a derivative of a polyalkylene glycol; the polymer dopant is polystyrene sulfonic acid; the second conductive polymer is poly(3,4-ethylenedioxythiophene), an electrolytic capacitor in which, when a mass of the first conductive polymer contained in the electrolyte layer is defined as W1 and a total mass of the second conductive polymer and the polymer dopant contained in the electrolyte layer is defined as W2, the relationship of 1.1≦W2 / W1≦9 is satisfied.

5. An electrolytic capacitor including 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 and a second conductive polymer doped with a polymer dopant containing an acidic group; the electrolyte layer further contains at least one compound selected from the group consisting of ethylene glycol, propylene glycol, sulfolane, γ-butyrolactone, N-methylacetamide, N,N-dimethylformamide, N-methyl-2-pyrrolidone, methyl acetate, propylene carbonate, 1,4-dioxane, methyl ethyl ketone, formaldehyde, polyethylene glycol, polyethylene glycol glyceryl ether, polyethylene glycol diglyceryl ether, polyethylene glycol sorbitol ether, polypropylene glycol, polypropylene glycol glyceryl ether, polypropylene glycol diglyceryl ether, polypropylene glycol sorbitol ether, polybutylene glycol, a copolymer of ethylene glycol and propylene glycol, a copolymer of ethylene glycol and butylene glycol, and a copolymer of propylene glycol and butylene glycol; the polymer dopant is polystyrene sulfonic acid; the second conductive polymer is poly(3,4-ethylenedioxythiophene), an electrolytic capacitor in which, when a mass of the first conductive polymer contained in the electrolyte layer is defined as W1 and a total mass of the second conductive polymer and the polymer dopant contained in the electrolyte layer is defined as W2, the relationship of 1.1≦W2 / W1≦9 is satisfied.

6. An electrolytic capacitor described in any one of claims 1 to 5, wherein the proportion of the total mass of the second conductive polymer and the polymer dopant to the total mass of the second conductive polymer and the polymer dopant contained in the electrolyte layer and the first conductive polymer is 80% or less.

7. The electrolyte layer includes a polymer layer composed of the first conductive polymer and the second conductive polymer doped with the polymer 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 first polymer layer includes the first conductive polymer; 7. The electrolytic capacitor according to claim 1, wherein the second polymer layer includes the second conductive polymer doped with the polymer dopant.

8. 8. The electrolytic capacitor according to claim 1, wherein the capacitor element is formed by winding the foil-shaped anode body and foil-shaped cathode body with a separator sandwiched therebetween.

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