Electrolytic capacitors

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. This specification discloses the following: (Technology 1) An electrolytic capacitor including a capacitor element, The capacitor element includes an anode having a dielectric layer on its surface and an electrolyte layer disposed adjacent to the dielectric layer. The electrolyte layer comprises a self-doped first conductive polymer and a second conductive polymer doped with a polymer dopant containing an acidic group. The electrolyte layer further comprises 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, and 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 the ratio of the total mass of the second conductive polymer and the polymer dopant, and the total mass of the first conductive polymer, to the total mass of the second conductive polymer and the polymer dopant contained in the electrolyte layer is 55% or more and 90% or less. (Technology 2) An electrolytic capacitor including a capacitor element, The capacitor element includes an anode having a dielectric layer on its surface and an electrolyte layer disposed adjacent to the dielectric layer. The electrolyte layer comprises a self-doped first conductive polymer and a second conductive polymer doped with a polymer dopant containing an acidic group. The electrolyte layer further comprises 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, copolymer of ethylene glycol and propylene glycol, copolymer of ethylene 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 the ratio of the total mass of the second conductive polymer and the polymer dopant, and the total mass of the first conductive polymer, to the total mass of the second conductive polymer and the polymer dopant contained in the electrolyte layer is 55% or more and 90% or less. (Technology 3) An electrolytic capacitor including a capacitor element, The capacitor element includes an anode having a dielectric layer on its surface and an electrolyte layer disposed adjacent to the dielectric layer. The electrolyte layer comprises a self-doped 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 that satisfies the relationship 1.1 ≤ W2 / W1 ≤ 9, where W1 is the mass of the first conductive polymer contained in the electrolyte layer, and W2 is the total mass of the second conductive polymer and the polymer dopant contained in the electrolyte layer. (Technology 4) <000​​​​​​​​​​​​​​​ An electrolytic capacitor including a capacitor element, The capacitor element includes an anode having a dielectric layer on its surface and an electrolyte layer disposed adjacent to the dielectric layer. The electrolyte layer comprises a self-doped first conductive polymer and a second conductive polymer doped with a polymer dopant containing an acidic group. The electrolyte layer further comprises 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, copolymer of ethylene glycol and propylene glycol, copolymer of ethylene glycol and butylene glycol, The polymer dopant is polystyrene sulfonic acid. The second conductive polymer is poly(3,4-ethylenedioxythiophene), An electrolytic capacitor that satisfies the relationship 1.1 ≤ W2 / W1 ≤ 9, where W1 is the mass of the first conductive polymer contained in the electrolyte layer, and W2 is the total mass of the second conductive polymer and the polymer dopant contained in the electrolyte layer. (Technology 6) The electrolytic capacitor according to any one of the technologies 1 to 5, wherein the ratio of the total mass of the second conductive polymer and the polymer dopant, and the total mass of the first conductive polymer, to the total mass of the second conductive polymer and the polymer dopant contained in the electrolyte layer is 80% or less. (Technology 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 comprises the first conductive polymer, The electrolytic capacitor according to any one of the art 1 to 6, wherein the second polymer layer comprises the second conductive polymer doped with the polymer dopant. (Technology 8) The capacitor element is an electrolytic capacitor according to any one of the technologies 1 to 7, wherein a foil-shaped anode and a foil-shaped cathode are wound with a separator in between.

[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, 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 this disclosure, an electrolytic capacitor with a low rate of ESR increase over a long period of time can be obtained. [Brief explanation of the drawing]

[0008] [Figure 1] This is a schematic cross-sectional view showing an example of an electrolytic capacitor of the present disclosure. [Figure 2] This diagram schematically shows a portion of the electrolytic capacitor shown in Figure 1. [Modes for carrying out the invention]

[0009] The following describes embodiments of the present disclosure with examples, but the present disclosure is not limited to the examples described below. While specific numerical values ​​and materials may be given as examples in the following description, other numerical values ​​and materials may be applied as long as the effects of the present disclosure are achieved.

[0010] (Electrolytic capacitor) The electrolytic capacitor of this disclosure includes a capacitor element. The capacitor element includes an anode having a dielectric layer on its surface and an electrolyte layer disposed adjacent to the dielectric layer. The electrolyte layer includes a self-doped first conductive polymer and a non-aqueous solvent.

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

[0012] Alternatively, the capacitor element may include a porous anode having a dielectric layer on its surface, a cathode layer, and an electrolyte layer disposed between the anode and the cathode layer. Such a capacitor element may be referred to as the "second capacitor element" below. In the first and second capacitor elements, the electrolyte layer is adjacent to the dielectric layer of the anode.

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

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

[0015] (First conductive polymer) The first conductive polymer is a self-doped conductive polymer. Here, a self-doped conductive polymer means a polymer in which functional groups that function as dopants are directly or indirectly bonded to the conductive polymer skeleton by covalent bonds. Examples of functional groups that function as dopants include anionic groups. Anionic groups are groups that acquire a negative charge when a cation dissociates. Anionic groups may be at least one selected from the group consisting of sulfonic acid groups, phosphate groups, phosphonic acid groups, and carboxyl groups, or they may be salts thereof (salts with inorganic bases, salts with organic bases, etc.). A preferred example of anionic groups is a sulfonic acid group or a salt thereof.

[0016] The amount of functional groups (e.g., anionic groups) that function as dopants may be in the range of 0.2 to 3, 0.5 to 2, or 1 per constituent unit of the polymer.

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

[0018] Examples of the skeleton of the first conductive polymer include polypyrrole, polythiophene, and polyaniline. These skeletons may have atomic groups other than functional groups that function as dopants (e.g., functional groups) bonded to them. Examples of the first conductive polymer include polypyrroles having anionic groups (polypyrrole and its derivatives), polythiophenes having anionic groups (polythiophene and its derivatives), and polyanilines having anionic groups (polyaniline and its derivatives). In these examples, a preferred example of anionic group is a sulfonic acid group or a salt thereof. The first conductive polymer may also be a copolymer of two or more monomers.

[0019] In terms of its high effectiveness in suppressing the increase in ESR and decrease in capacitance even in high-temperature environments, the first conductive polymer may be poly(3,4-ethylenedioxythiophene) (PEDOT) into which an atomic group containing a sulfonic acid group has been introduced. For example, the first conductive polymer may contain the constituent units shown in the following chemical formula, or may consist of the constituent units shown in the following chemical formula.

[0020] [ka]

[0021] In the above formula, R represents an organic chain. R may consist of a hydrocarbon chain, and in addition to the hydrocarbon chain, it may also include ether bonds, branched alkyl groups, and other substituents. In the above formula, the sulfonic acid group may be a salt. Examples of R include (skeleton side)-CH2-O-(CH2)2-(CHCH3)-(sulfonic acid group side).

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

[0023] 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.

[0024] (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. These derivatives include polymers with 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 multiple types. The second conductive polymer may also be a copolymer of two or more monomers. The weight-average molecular weight of the second conductive polymer is not particularly limited and may be in the range of, for example, 1,000 to 100,000. A preferred example of the second conductive polymer is poly(3,4-ethylenedioxythiophene) (PEDOT).

[0025] Unlike the first conductive polymer, the second conductive polymer does not have functional groups that function as dopants covalently bonded to the backbone 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 polymer dopants include polyvinyl sulfonic acid, polystyrene sulfonic acid, polyallyl sulfonic acid, polyacryl sulfonic acid, polymethacrylate sulfonic acid, poly(2-acrylamido-2-methylpropane sulfonic acid), polyisoprene sulfonic acid, and polyacrylic acid. These may be used individually or in combination of two or more. These may also be included in the electrolyte layer in the form of salts. A preferred example of a dopant is polystyrene sulfonic 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 1,000 to 100,000.

[0027] In the electrolytic capacitor of this 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 this disclosure contains a non-aqueous solvent. The electrolyte layer may also contain an electrolyte (non-aqueous electrolyte) comprising a non-aqueous solvent and a basic component dissolved in the non-aqueous solvent. That is, the electrolyte layer of the electrolytic capacitor of this disclosure may contain a liquid component. Hereinafter, the liquid component (non-aqueous solvent or electrolyte) contained in the electrolyte layer may be referred to as "liquid component (L)". In this specification, liquid component (L) may be a component that is liquid at room temperature (25°C) or a component that is liquid at the temperature at which the electrolytic capacitor is used. An electrolytic capacitor having an electrolyte layer containing 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 non-aqueous solvents 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] Furthermore, polymeric solvents may be used as non-aqueous solvents. Examples of polymeric solvents include polyalkylene glycols, derivatives of polyalkylene glycols, and compounds in which at least one hydroxyl group in a polyhydric alcohol is substituted with polyalkylene glycol (including derivatives). Specifically, examples of polymeric solvents 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, and polybutylene glycol. Examples of polymeric solvents further include ethylene glycol-propylene glycol copolymers, ethylene glycol-butylene glycol copolymers, and propylene glycol-butylene glycol copolymers. Non-aqueous solvents may be used individually or as a mixture of two or more.

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

[0032] Polycarboxylic acids and monocarboxylic acids can be used as the acid component. Examples of the above polycarboxylic acids include aliphatic polycarboxylic acids ([saturated polycarboxylic acids, e.g., oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebatic acid, 1,6-decanedicarboxylic acid, 5,6-decanedicarboxylic acid]; [unsaturated polycarboxylic acids, e.g., maleic acid, fumaric acid, eicotanoic acid]), aromatic polycarboxylic acids (e.g., phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, pyromellitic acid), and alicyclic polycarboxylic acids (e.g., cyclohexane-1,2-dicarboxylic acid, cyclohexene-1,2-dicarboxylic acid, etc.).

[0033] Examples of the monocarboxylic acids mentioned above include aliphatic monocarboxylic acids (1 to 30 carbon atoms) ([saturated monocarboxylic acids, e.g., 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, e.g., acrylic acid, methacrylic acid, oleic acid]), aromatic monocarboxylic acids (e.g., benzoic acid, cinnamic acid, naphthoic acid), and oxycarboxylic acids (e.g., salicylic acid, mandelic acid, resorcinic acid).

[0034] Among these, maleic acid, phthalic acid, benzoic acid, pyromellitic acid, and resorcinic acid are thermally stable and are therefore preferred.

[0035] Inorganic acids may be used as the acid component. Typical examples of inorganic acids include phosphoric acid, phosphorous acid, hypophosphorous acid, alkyl phosphate esters, boric acid, borofluoric acid, tetrafluoroboric acid, hexafluorophosphoric acid, benzenesulfonic acid, and naphthalenesulfonic acid. In addition, composite compounds of organic and inorganic acids may be used as the acid component. Examples of such composite compounds include borodiglycolic acid, borodioxalic acid, and borodisalicylic acid.

[0036] The basic component may be a compound having an alkyl-substituted amidine group, for example, an imidazole compound, a benzimidazole compound, or an alicyclic amidine compound (pyrimidine compound, imidazoline compound). Specifically, 1,8-diazabicyclo[5,4,0]undecene-7, 1,5-diazabicyclo[4,3,0]nonene-5, 1,2-dimethylimidazolinium, 1,2,4-trimethylimidazoline, 1-methyl-2-ethylimidazoline, 1,4-dimethyl-2-ethylimidazoline, 1-methyl-2-heptylimidazoline, 1-methyl-2-(3'heptyl)imidazoline, 1-methyl-2-dodecylimidazoline, 1,2-dimethyl-1,4,5,6-tetrahydropyrimidine, 1-methylimidazole, and 1-methylbenzimidazole are preferred. By using these, 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) that have been quaternized with an alkyl or arylalkyl group having 1 to 11 carbon atoms. Specifically, 1-methyl-1,8-diazabicyclo[5,4,0]undecene-7, 1-methyl-1,5-diazabicyclo[4,3,0]nonene-5, 1,2,3-trimethylimidazolinium, 1,2,3,4-tetramethylimidazolinium, 1,2-dimethyl-3-ethylimidazolinium, 1,3,4-trimethyl-2-ethylimidazolinium, 1,3-dimethyl-2-heptylimidazolinium, 1,3-dimethyl-2-(3'heptyl)imidazolinium, 1,3-dimethyl-2-dodecylimidazolinium, 1,2,3-trimethyl-1,4,5,6-tetrahydropyrimidium, 1,3-dimethylimidazolium, 1-methyl-3-ethylimidazolium, and 1,3-dimethylbenzimidazolium are preferred. By using these, a capacitor with excellent impedance performance can be obtained.

[0038] Furthermore, tertiary amines may be used as the base component. Examples of tertiary amines include trialkylamines (trimethylamine, dimethylethylamine, methyldiethylamine, triethylamine, dimethyl-n-propylamine, dimethylisopropylamine, methylethyl-n-propylamine, methylethylisopropylamine, diethyl-n-propylamine, diethylisopropylamine, tri-n-propylamine, triisopropylamine, tri-n-butylamine, tri-tert-butylamine, etc.) and phenyl group-containing amines (dimethylphenylamine, methylethylphenylamine, diethylphenylamine, etc.). Among these, trialkylamines are preferred in that they increase the conductivity of the electrolyte layer, and it is more preferable to include at least one selected from the group consisting of trimethylamine, dimethylethylamine, methyldiethylamine, and triethylamine. Furthermore, secondary amines such as dialkylamines, primary amines such as monoalkylamines, and ammonia may be used as the base component.

[0039] The liquid component (L) may contain a salt of an acidic component and a basic 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 the anion and cation is an organic substance. Examples of organic salts include trimethylamine maleate, triethylamine borodisalicylate, ethyldimethylamine phthalate, mono-1,2,3,4-tetramethylimidazolinium phthalate, and mono-1,3-dimethyl-2-ethylimidazolinium phthalate.

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

[0041] In electrolytic capacitors, a low ESR is important. Low ESR can be achieved by using an electrolyte layer containing a dopant-doped conductive polymer. However, the inventors of this invention have found that when an electrolyte layer containing a dopant-doped conductive polymer and a liquid component (L) is used, although the initial ESR is low, there is a significant degradation phenomenon in which the ESR increases over time. Upon investigating the cause, it was found that in electrolyte layers containing a liquid component (L), the dopant may be easily dedoped. This dedoping is thought to cause the ESR to increase over time. Therefore, compared to solid electrolytic capacitors containing a solid electrolyte without a liquid component (L), it is important to suppress the time-dependent increase in ESR in electrolytic capacitors containing a liquid component (L).

[0042] The self-doped first conductive polymer is less prone to dedoping, resulting in less degradation of its conductivity over time. Therefore, by including the first conductive polymer in the electrolyte layer, the increase in ESR over time can be suppressed.

[0043] In the electrolytic capacitor of this disclosure, the dopant may be a dopant containing an acidic group, or a polymer dopant containing an acidic group. Through investigation, the inventors of this application have newly discovered that when a dopant containing an acidic group is used, dedoping may occur significantly as the pH increases. Therefore, when using a dopant containing an acidic group, it is particularly important to suppress the time-dependent increase in ESR.

[0044] In the electrolytic capacitor of this disclosure using a second conductive polymer, the dopant may be a polymer dopant containing an acidic group, and the electrolyte layer may contain an electrolyte solution containing a non-aqueous solvent and a basic component dissolved in the non-aqueous solvent. In this case, de-dopanting is likely to occur due to the basic component, so it is particularly important to suppress the rise in ESR over time. As described above, since the electrolytic capacitor of this disclosure contains a self-doped first conductive polymer, the rise in ESR over time can be suppressed.

[0045] Examples of basic components include the basic components mentioned above. Examples of acidic groups include sulfonic acid groups and carboxyl groups. A polymer dopant containing an acidic group is a polymer in which at least some of the constituent units contain an acidic group. Examples of such polymer dopants include the polymer dopants mentioned above.

[0046] In the electrolytic capacitor of this disclosure, the amount of basic components in the electrolyte may be 0.1% by mass or more and 20% by mass or less. When the amount of basic components is 0.1% by mass or more, it is particularly important to use a self-doped first conductive polymer. Furthermore, by setting the amount of basic components to 20% by mass or less, it becomes easier to dissolve the basic components in the electrolyte.

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

[0048] In the electrolytic capacitor of this disclosure, the total mass of the second conductive polymer and dopant contained in the electrolyte layer may 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 dopant in the electrolyte layer may be greater than the content (mass%) of the first conductive polymer in the electrolyte layer. Dopant-doped conductive polymers generally have higher conductivity than self-doped conductive polymers. Therefore, increasing the content of the dopant-doped second conductive polymer is effective in 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 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. In the condition (2), the "content rate (mass %) of the second conductive polymer" may be replaced with the "total content rate (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 smaller than the content (mass %) of the first conductive polymer in the second polymer layer. According to the configuration in (2) above, the ratio 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] [[ID=I3]] 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 metals having a valve action such as aluminum, tantalum, niobium, titanium, etc., and alloys of metals having a valve action. 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] (Cathole body) A metal foil may be used for the cathode. The type of metal constituting the metal foil is not particularly limited. Examples of metals constituting the metal foil include valve-forming metals and alloys of valve-forming metals such as aluminum, tantalum, niobium, and titanium. A preferred example is aluminum and aluminum alloys. The surface of the cathode may be provided with a chemical conversion coating, or a coating of a different metal (dissimilar metal) or a nonmetal. Examples of dissimilar metals or nonmetals include metals such as titanium and nonmetals such as carbon.

[0059] (Separator) The separator can be a sheet-like material that can be impregnated with an electrolyte; for example, a sheet-like material that is insulating and can be impregnated with an electrolyte may be used. The separator may be a woven fabric, a nonwoven fabric, or a porous membrane. Examples of separator materials include cellulose, polyethylene terephthalate, polybutylene terephthalate, polyphenylene sulfide, vinylon, nylon, aromatic polyamide, polyimide, polyamide-imide, polyetherimide, rayon, and glass.

[0060] Examples of components other than the electrolyte layer of the second capacitor element are described below. The second capacitor element includes a porous anode having a dielectric layer on its surface, a cathode layer, and an electrolyte layer disposed between the anode and the cathode layer.

[0061] The porous anode may be, for example, a porous sintered body obtained by sintering material particles containing a valve metal. The anode may have a rectangular parallelepiped shape. Examples of valve metals include titanium (Ti), tantalum (Ta), and niobium (Nb). The material particles may consist of an alloy containing a valve metal. For example, an alloy containing a valve metal and silicon, vanadium, boron, etc., may be used. The valve metal alloy has a valve metal as its main component, for example, containing 50 atomic percent or more of the valve metal. Alternatively, material particles consisting of a compound containing a valve metal and a typical element such as nitrogen may be used. The material particles may be used individually or in mixtures of two or more types.

[0062] The anode of the second capacitor element is porous, and therefore has a porous portion on its surface, with the dielectric layer formed in this porous portion. The electrolyte layer is in contact with the dielectric layer of the anode. The dielectric layer is formed, for example, by chemical conversion treatment of the sintered body that will become the anode, and by growing 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 also be a conductive layer formed to cover the electrolyte layer. The cathode layer may include a carbon layer formed 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 (e.g., silver particles) and a resin. The cathode layer can be formed by coating the above materials.

[0064] (Manufacturing method for electrolytic capacitors) The method for manufacturing electrolytic capacitors according to this disclosure is described below. According to this manufacturing method, electrolytic capacitors according to this disclosure can be manufactured. Note that the matters described regarding the electrolytic capacitors according to this disclosure are applicable to the following manufacturing method, and therefore, redundant explanations may be omitted. For example, the components of the capacitor element have been described above, so redundant explanations may be omitted. Furthermore, the matters described in the following manufacturing method are applicable to the electrolytic capacitors described above.

[0065] The manufacturing method relating to this disclosure includes steps (i), (ii), and (iii), which are described below.

[0066] (Step (i)) Step (i) is a step of preparing a capacitor element precursor including an anode having a dielectric layer on its surface. Step (i) may also be a step of forming a 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 that includes a foil-shaped anode having a dielectric layer on its surface, a foil-shaped cathode, and a separator disposed between the anode and the cathode. In this case, as described above, the capacitor element precursor may be of the wound type or the laminated type. When manufacturing an electrolytic capacitor including a second capacitor element, the capacitor element precursor may consist of an anode having a dielectric layer on its surface (a porous anode) and an anode wire, part of which is embedded in the anode.

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

[0069] The polymer layer formed in step (ii) may include 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 the first conductive polymer and the second conductive polymer doped with a dopant adjacent to the dielectric layer by impregnation treatment.

[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 a first conductive polymer and a second conductive polymer doped with a dopant is impregnated into the capacitor element precursor. For example, the capacitor element precursor can be impregnated by immersing it in the liquid. By removing (drying) the dispersion medium or solvent of the liquid impregnated into the capacitor element precursor, the polymer layer containing the first conductive polymer and the second conductive polymer doped with a dopant can be arranged adjacent to the dielectric layer. The impregnation treatment (x) may be performed multiple times. In that case, a drying step to remove the dispersion medium or solvent of the impregnated liquid may be performed before the second and subsequent impregnation treatments (x).

[0071] There are no particular limitations on the liquid dispersion medium or solvent, and known dispersion mediums or solvents may be used. For example, an aqueous liquid containing water may be used as the dispersion medium or solvent, or water may be used.

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

[0073] The impregnation treatment in step (ii) may include an impregnation treatment (y) in which a first liquid containing a first conductive polymer is impregnated into the capacitor element precursor, and an impregnation treatment (z) in which a second liquid containing a dopant-doped second conductive polymer is impregnated into the capacitor element precursor. The impregnation treatments (y) and (z) may be performed with impregnation treatment (z) first, or with impregnation treatment (y) first, or simultaneously. In a preferred example, impregnation treatment (y) is performed after impregnation treatment (z). The impregnation treatments (y) and (z) may each be performed independently multiple times. Furthermore, a drying step may be performed after each of the impregnation treatments (y) and (z) to remove the dispersion medium (or solvent) of the impregnated liquid.

[0074] For the first and second liquid dispersion media (or solvents), and the impregnation methods in impregnation treatment (y) and impregnation treatment (z), the dispersion media (or solvent) and impregnation methods described in impregnation treatment (x) may be applied.

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

[0076] The impregnation treatment (y) and impregnation treatment (z) may be performed, followed by drying, and then the other impregnation treatment may be performed. By doing so, a polymer layer containing a first polymer layer and a second polymer layer can be formed. Furthermore, by adjusting the type and content of conductive polymer (and dopant) in the first liquid and the type and content of conductive polymer (and dopant) in the second liquid, the type and content of conductive polymer (and dopant) in the first polymer layer and the type and content of 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. This forms an electrolyte layer containing a self-doped first conductive polymer and a non-aqueous solvent. Step (iii) may also be a step of impregnating the polymer layer formed in step (ii) with an electrolyte (containing a non-aqueous solvent). That is, step (iii) may also be a step of impregnating the polymer layer formed in step (ii) with a liquid component (L).

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

[0079] There are no particular limitations on the impregnation method in step (iii), and known methods may be used. For example, the capacitor element precursor that has gone through step (ii) may be immersed in a non-aqueous solvent (or electrolyte). The non-aqueous solvent (or electrolyte) used in step (iii) can be one of those 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 electrolyte containing a non-aqueous solvent and a basic component dissolved in the non-aqueous solvent.

[0081] Step (iii) yields a first capacitor element. Alternatively, step (iii) yields the anode and electrolyte layer of a second capacitor element. After step (iii), an electrolytic capacitor can be fabricated using the components obtained in step (iii). There are no particular limitations on this process, and known methods can be used.

[0082] In the following, an example of an electrolytic capacitor relating to this disclosure will be specifically described with reference to the drawings, but the electrolytic capacitor of this disclosure is not limited to the drawings below. The components of the example electrolytic capacitor described below can be the components described above. Furthermore, the components of the example electrolytic capacitor described below can be modified based on the above description. In addition, the matters described below may be applied to the above embodiments. Note that the same reference numerals may be used for similar parts, and redundant explanations may be omitted.

[0083] (Embodiment 1) Embodiment 1 describes an example of an electrolytic capacitor according to the present disclosure. This electrolytic capacitor is an electrolytic capacitor that includes a first capacitor element. Figure 1 schematically shows a cross-section of an example of the electrolytic capacitor 100 of Embodiment 1. Figure 2 shows a schematic diagram of a part of the capacitor element 10 included in the electrolytic capacitor 100 shown in Figure 1.

[0084] As shown in Figure 1, the electrolytic capacitor 100 includes a capacitor element 10, a bottomed case 11 housing the capacitor element 10, a sealing member 12 closing the opening of the bottomed case 11, a base plate 13 covering the sealing member 12, lead wires 14A and 14B extending from the sealing member 12 and passing through the base plate 13, and lead tabs 15A and 15B connecting 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 area near the opening end of the bottomed case 11 is tapered inward, and the opening end of the bottomed case 11 is curled to crimp the sealing member 12.

[0085] Referring to Figure 2, the capacitor element 10 includes a foil-shaped anode 21 having a dielectric layer on its surface, a foil-shaped cathode 22, and a separator 23 and an electrolyte layer (not shown) placed between them. The anode 21 and cathode 22 are wound with the separator 23 placed between them. The outermost circumference of the winding is secured by a winding stopper tape 24. Note that Figure 2 shows the winding in a partially unfolded state before the outermost circumference is secured. [Examples]

[0086] The embodiments of this disclosure will be described in more detail below with reference to examples.

[0087] (Example 1) In Example 1, several electrolytic capacitors (capacitors A1 to A7 and capacitor C1) were fabricated and evaluated. The manufacturing method and evaluation method for these capacitors are described below. In the description of the manufacturing method for the comparative example capacitors, conditions different from those in steps (ii) and (iii) described above may be used, but for convenience, these will also be described as steps (ii) and (iii).

[0088] [Fabrication of Capacitor A1] Capacitor A1 is a wound-type electrolytic capacitor with a rated voltage of 35V and a rated capacitance of 270μF. Capacitor A1 was fabricated using the following procedure.

[0089] (Preparation of the cathode) A 70 μm thick aluminum foil was used as the cathode.

[0090] (Preparation of the anode) A 120 μm thick aluminum foil was prepared. The surface of this aluminum foil was roughened by DC etching. Next, a dielectric layer (thickness: approximately 70 nm) was formed by chemical conversion treatment of the aluminum foil to obtain the anode. The dielectric layer was formed by immersing the aluminum foil in an ammonium adipate solution and performing chemical conversion treatment at 70°C for 30 minutes while applying a voltage of 50 V to the aluminum foil. After that, the anode was cut to a predetermined size to prepare the anode for capacitor A1.

[0091] (Preparation of a liquid containing a self-doped first conductive polymer) The following aqueous solutions were prepared as liquids containing a self-doped first conductive polymer. (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 conductive polymer A at a concentration of 5% by mass was prepared. (Liquid BL containing conductive polymer B) An aqueous solution (liquid BL) containing 5% by mass of N-substituted sulfonated polyaniline as conductive polymer B was prepared.

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

[0093] (Fabrication of the wound body (step (i))) Anode lead tabs and cathode lead tabs, each with connected lead wires, were attached to the prepared anode and cathode bodies, respectively. The anode and cathode bodies were then wound together with a separator in between, and the outer surface was secured with winding tape. A nonwoven fabric made of cellulose was used as the separator. In this way, a wound body (capacitor element precursor) was fabricated. The fabricated wound body was immersed in an ammonium adipate solution, and a conversion treatment was 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.

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

[0095] (Impregnation with electrolyte solution) The wound material that had undergone step (iii) was impregnated with an electrolyte at room temperature under atmospheric pressure. As the electrolyte, a solution was used which 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 containing an electrolyte layer was obtained. This capacitor element was sealed to complete the electrolytic capacitor. After that, 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 that the liquid used in process (ii) was different. In the fabrication of capacitors A2 to A7, a mixture of liquid AL containing the above-mentioned self-doped conductive polymer A and the above-mentioned PEDOT:PSS dispersion was used as the liquid in process (ii). Capacitors A2 to A7 were then fabricated by changing the ratio of the mass of the self-doped conductive polymer to the mass of PEDOT:PSS contained in the mixture (dispersion). This mass ratio directly corresponds to the mass ratio of the self-doped conductive polymer to PEDOT:PSS in the formed electrolyte layer.

[0097] [Fabrication of Capacitor C1] Capacitor C1 was fabricated using the same materials and conditions as capacitor A1, except that the liquid used in process (ii) was different. In the fabrication of capacitor C1, the above-mentioned PEDOT:PSS dispersion was used as the liquid in process (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 to B7] Capacitors B1 to B7 were manufactured using the same materials and conditions as capacitors A1 to A7, except that the liquid used in process (ii) was different. Liquid BL was used instead of liquid AL in the manufacture of capacitors B1 to B7.

[0099] (ESR measurement) The equivalent series resistance (ESR) of the electrolytic capacitors fabricated as described above was measured. The ESR was measured using a 4-terminal LCR meter in an environment of 20°C. The ESR was measured both initially after fabrication and after the electrolytic capacitors were left at a high temperature (165°C for 500 hours). Then, as an indicator of long-term characteristics, the long-term characteristic evaluation value F was calculated using the following formula. Long-term characteristic evaluation value F = (ESR value after high-temperature storage) / (initial ESR value)

[0100] Tables 1 and 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 electrolytic capacitor described above. Tables 1 and 2 also show the ESR evaluation results for the electrolytic capacitor described above.

[0101] [Table 1]

[0102] [Table 2]

[0103] As shown in Tables 1 and 2, capacitors A1-A7 and B1-B7 of this disclosure had small evaluation values ​​F. That is, these capacitors showed a small increase in ESR due to prolonged exposure to high temperatures. In the electrolyte layer, when (mass of first conductive polymer):(total mass of second conductive polymer and dopant) = 10:90 to 45:55, the ESR was low both initially and after exposure to high temperatures.

[0104] (Example 2) In Example 2, several electrolytic capacitors (capacitors A8 and A9) were fabricated and evaluated. The manufacturing method and evaluation method for these capacitors are described below.

[0105] [Capacitor A8] Capacitor A8 was manufactured using the same materials and conditions as capacitor A1, except that process (ii) was different. In process (ii) of capacitor A8, the impregnation treatment (z) described above was performed, followed by the impregnation treatment (y) described above. Process (ii) of capacitor A8 is described below.

[0106] (Impregnation treatment (z) and drying process) Specifically, first, the PEDOT:PSS dispersion was placed in a container. Next, in a reduced-pressure atmosphere (40 kPa) at room temperature, the coiled body formed in step (i) was immersed in the dispersion in the container for 5 minutes, and then the coiled body was removed from the dispersion. In this way, the dispersion was impregnated into the coiled body. Next, the coiled body was dried in a drying oven at 60°C for 30 minutes, and then at 155°C for 15 minutes. This dried the dispersion. In this way, a first polymer layer composed of PEDOT:PSS was formed.

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

[0108] Step (ii) was carried out as described above. Step (ii) formed an electrolyte layer including a first polymer layer (PEDOT:PSS layer) formed on the dielectric layer of the anode and a second polymer layer (self-doped conductive polymer layer) formed on the first polymer layer.

[0109] [Capacitor A9] 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 process (ii) of capacitor A9, impregnation treatment (y) was performed followed by impregnation treatment (z). The drying process was carried out under the same conditions as the drying process for capacitor A8.

[0110] Step (ii) was carried out as described above. Step (ii) formed an electrolyte layer including a first polymer layer (self-doped conductive polymer layer) formed on the dielectric layer of the anode and a second polymer layer (PEDOT:PSS layer) formed on the first polymer layer.

[0111] The electrolytic capacitors fabricated as described above were subjected to ESR measurements under the same conditions as 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 ESR and evaluation value F. Comparing capacitors A8 and A9, capacitor A9 had a lower evaluation value F. [Industrial applicability]

[0114] This disclosure can be used for electrolytic capacitors and methods for manufacturing the same. [Explanation of Symbols]

[0115] 10 Capacitor element 21 Anode 22 Cathode Body 23 Separator 100 electrolytic capacitors

Claims

1. An electrolytic capacitor including a capacitor element, The capacitor element includes an anode having a dielectric layer on its surface and an electrolyte layer disposed adjacent to the dielectric layer. The electrolyte layer comprises a first self-doped conductive polymer and a second conductive polymer doped with a polymer dopant containing an acidic group. The electrolyte layer further comprises 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 the ratio of the total mass of the second conductive polymer and the polymer dopant, and the total mass of the first conductive polymer, to the total mass of the second conductive polymer and the polymer dopant 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 having a dielectric layer on its surface and an electrolyte layer disposed adjacent to the dielectric layer. The electrolyte layer comprises a first self-doped conductive polymer and a second conductive polymer doped with a polymer dopant containing an acidic group. The electrolyte layer further comprises 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, copolymer of ethylene glycol and propylene glycol, copolymer of ethylene 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 the ratio of the total mass of the second conductive polymer and the polymer dopant, and the total mass of the first conductive polymer, to the total mass of the second conductive polymer and the polymer dopant 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 having a dielectric layer on its surface and an electrolyte layer disposed adjacent to the dielectric layer. The electrolyte layer comprises a self-doped 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 that satisfies the relationship 1.1 ≤ W2 / W1 ≤ 9, where W1 is the mass of the first conductive polymer contained in the electrolyte layer, and W2 is the total mass of the second conductive polymer and the polymer dopant contained in the electrolyte layer.

4. An electrolytic capacitor including a capacitor element, The capacitor element includes an anode having a dielectric layer on its surface and an electrolyte layer disposed adjacent to the dielectric layer. The electrolyte layer comprises a first self-doped conductive polymer and a second conductive polymer doped with a polymer dopant containing an acidic group. The electrolyte layer further comprises 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 that satisfies the relationship 1.1 ≤ W2 / W1 ≤ 9, where W1 is the mass of the first conductive polymer contained in the electrolyte layer, and W2 is the total mass of the second conductive polymer and the polymer dopant contained in the electrolyte layer.

5. An electrolytic capacitor including a capacitor element, The capacitor element includes an anode having a dielectric layer on its surface and an electrolyte layer disposed adjacent to the dielectric layer. The electrolyte layer comprises a first self-doped conductive polymer and a second conductive polymer doped with a polymer dopant containing an acidic group. The electrolyte layer further comprises 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, copolymer of ethylene glycol and propylene glycol, copolymer of ethylene glycol and butylene glycol, The polymer dopant is polystyrene sulfonic acid. The second conductive polymer is poly(3,4-ethylenedioxythiophene), An electrolytic capacitor that satisfies the relationship 1.1 ≤ W2 / W1 ≤ 9, where W1 is the mass of the first conductive polymer contained in the electrolyte layer, and W2 is the total mass of the second conductive polymer and the polymer dopant contained in the electrolyte layer.

6. The electrolytic capacitor according to any one of claims 1 to 5, wherein the ratio of the total mass of the second conductive polymer and the polymer dopant and the total mass of the first conductive polymer to the total mass of the second conductive polymer and the polymer dopant contained in the electrolyte layer 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 comprises the first conductive polymer, The electrolytic capacitor according to any one of claims 1 to 6, wherein the second polymer layer comprises the second conductive polymer doped with the polymer dopant.

8. The electrolytic capacitor according to any one of claims 1 to 7, wherein the capacitor element is formed by winding a foil-shaped anode and a foil-shaped cathode with a separator in between.

Images