Electrolytic capacitor

Abstract

The electrolytic capacitor of the present disclosure is provided with a capacitor element and a liquid component, the capacitor element is provided with an anode foil, a cathode foil, a separator between them, and a conductive polymer layer in contact with the separator, an etching layer is formed on the anode foil, the etching layer has a dielectric layer, the etching layer sequentially has a first etching area and a second etching area from the surface of the anode foil to the center part, the first etching area contains a plurality of first fine holes arranged in series in each direction of the thickness direction and the plane direction, the second etching area contains a plurality of second fine holes extending in a tunnel shape along the thickness direction, the average pore diameter of the first fine hole is smaller than the average pore diameter of the second fine hole, the conductive polymer layer is formed in the first etching area, and the second etching area is impregnated with the liquid component.

Description

Technical Field

[0001] This invention relates to electrolytic capacitors. More specifically, this invention relates to electrolytic capacitors having a liquid component and a conductive polymer layer. Background Technology

[0002] Conventionally, it is known that in electrolytic capacitors, the equivalent series resistance (ESR) is reduced by replacing the liquid component (electrolyte, etc.) with a conductive polymer layer (solid electrolyte layer) formed of a conductive polymer (for example, Patent Document 1 below). In electrolytic capacitors, an etched layer is typically formed on the surface portion of the anode substrate, and a dielectric oxide film is formed on this etched layer. Furthermore, the conductive polymer layer is formed on the dielectric oxide film.

[0003] Patent Document 1 describes a method of forming an etched layer by stacking two etched regions with different structures in the thickness direction. Specifically, the etched layer is described as having a first region, which is a sponge-like structure composed of multiple cubic pits, and a second region, which is composed of multiple tunnel pits extending along the thickness direction, sequentially extending from the surface of the anode substrate toward the center. Furthermore, Patent Document 1 describes how, by forming the etched layer as described above, an electrolytic capacitor that can ensure high electrostatic capacitance and reduce equivalent series resistance (ESR) can be obtained.

[0004] As electrolytic capacitors, hybrid electrolytic capacitors possessing both a liquid component and a conductive polymer layer are also known (e.g., Patent Document 2 below). Hybrid electrolytic capacitors have the advantages of reducing the equivalent series resistance (ESR) through the conductive polymer layer and improving the repairability of the dielectric oxide film through the liquid component.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 6-168855

[0008] Patent Document 2: Japanese Patent Application Publication No. 2017-69390 Summary of the Invention

[0009] The problem that the invention aims to solve

[0010] In hybrid electrolytic capacitors, an anode body (anode foil) with an etched layer formed on its surface is commonly used. Furthermore, in hybrid electrolytic capacitors, it is desirable to balance ensuring high capacitance and reducing equivalent series resistance (ESR) through the configuration of the etched layer; however, research in this area is insufficient. In other words, the configuration of an etched layer that appropriately balances ensuring high capacitance and reducing equivalent series resistance (ESR) using both liquid components and conductive polymer layers has not been adequately studied.

[0011] Therefore, this disclosure provides an electrolytic capacitor having both a conductive polymer layer and a liquid component, and is able to ensure high electrostatic capacitance and reduce equivalent series resistance (ESR).

[0012] Methods for solving problems

[0013] One aspect of the present invention relates to an electrolytic capacitor comprising a capacitor element and a liquid component, the capacitor element comprising: an anode foil; a cathode foil disposed opposite to the anode foil; a separator disposed between the anode foil and the cathode foil; and a conductive polymer layer disposed between the anode foil and the cathode foil and in contact with the separator, wherein an etched layer is formed in the anode foil from the surface toward the center, the etched layer having a dielectric layer, the etched layer having a first etched region and a second etched region sequentially from the surface of the anode foil toward the center, the first etched region comprising a plurality of first pores arranged continuously in both the thickness direction and the planar direction, the second etched region comprising a plurality of second pores extending in a tunnel-like manner along the thickness direction, the average pore diameter of the first pores being smaller than the average pore diameter of the second pores, the conductive polymer layer being formed in the first etched region, and the liquid component being impregnated in at least the second etched region.

[0014] Invention Effects

[0015] According to this disclosure, an electrolytic capacitor can be provided that has both a conductive polymer layer and a liquid component, and can simultaneously ensure high electrostatic capacitance and reduce equivalent series resistance (ESR). Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the cross-section of the anode foil.

[0017] Figure 2 It is equivalent to Figure 1 Electron microscope image of part A.

[0018] Figure 3 This is a cross-sectional schematic diagram of an electrolytic capacitor according to one embodiment of the present disclosure.

[0019] Figure 4 It is Figure 3 A schematic diagram showing a portion of the capacitor elements of an electrolytic capacitor. Detailed Implementation

[0020] The following description illustrates embodiments of this disclosure by way of example, but this disclosure is not limited to the examples described below. In the following description, specific numerical values ​​and materials are sometimes illustrated, but other numerical values, materials, etc., can also be applied as long as the effects of this disclosure are achieved. It should be noted that known constituent elements can also be applied to the constituent elements of the characteristic portions of this disclosure. In this specification, when referred to as the "range of numerical value A to numerical value B," this range includes both numerical value A and numerical value B.

[0021] In the following description, when lower and upper limits of values ​​related to specific physical properties, conditions, etc. are given, any of the given lower limits can be combined with any of the given upper limits as long as the lower limit is not above the upper limit. When multiple materials are given, unless otherwise specified, one of them can be used alone or in combination.

[0022] Furthermore, this disclosure includes a combination of matters described in any two or more claimed technical solutions selected from the plurality of claimed technical solutions described in the appended scope of protection. That is, as long as no technical contradiction arises, a combination of matters described in any two or more claimed technical solutions selected from the plurality of claimed technical solutions described in the appended scope of protection is permissible.

[0023] Electrolytic capacitors

[0024] The electrolytic capacitor of this disclosure is an electrolytic capacitor comprising a capacitor element and a liquid component. In the electrolytic capacitor of this disclosure, the capacitor element comprises: an anode foil; a cathode foil disposed opposite to the anode foil; a separator disposed between the anode foil and the cathode foil; and a conductive polymer layer disposed between the anode foil and the cathode foil and in contact with the separator. In the electrolytic capacitor of this disclosure, an etched layer is formed in the anode foil from the surface toward the center, and the etched layer has a dielectric layer. In the electrolytic capacitor of this disclosure, the etched layer comprises a first etched region and a second etched region sequentially from the surface of the anode foil toward the center. The first etched region includes a plurality of first micropores arranged continuously in both the thickness direction and the planar direction, and the second etched region includes a plurality of second micropores extending in a tunnel-like manner along the thickness direction. The first micropores are micropores with an aspect ratio (length / width) of 0.5 or more and 2 or less, and the second micropores are micropores with an aspect ratio (length / width) of 15 or more and 100 or less. The aspect ratio of the pores can be obtained by cross-sectional observation of the etched layer of the anode foil. Cross-sectional observation can be performed, for example, using a scanning electron microscope (SEM) at a magnification of 100x to 500x to observe the cross-section of the anode foil (more specifically, the cross-section of the etched layer of the anode foil). It should be noted that the cross-section is along the thickness direction of the anode foil. The anode foil can be an anode foil removed from a disassembled electrolytic capacitor. Alternatively, the cross-section of the anode foil can be obtained using a section polishing machine (CP). In the electrolytic capacitor of the embodiments of this disclosure, the average pore diameter of the first pore is smaller than the average pore diameter of the second pore. In the electrolytic capacitor of the embodiments of this disclosure, a conductive polymer layer is formed in the first etched region, and at least the second etched region is impregnated with liquid components.

[0025] As described above, the electrolytic capacitor of this embodiment includes a liquid component. The liquid component is contained within the voids of the capacitor element. The liquid component only needs to fill at least a portion of the voids within the capacitor element. Preferably, the liquid component is impregnated inside the etched layer. Preferably, the liquid component primarily impregnates into the second etched region. By primarily impregnating the second etched region, the liquid component can fully penetrate into each of the plurality of tunnel-shaped second pores formed within the second etched region. Therefore, capacitance can be sufficiently drawn out from the interior of the second etched region, and a sufficient conductive path can be formed via the liquid component. Furthermore, as described later, a conductive path is formed between the first etched region, the separator, and the cathode foil by a conductive polymer layer. Therefore, as described above, by fully penetrating the interior of the second etched region, a more sufficient conductive path can be formed between the etched layer and the cathode foil via the liquid component and the conductive polymer layer. As a result, the electrolytic capacitor of this embodiment has a low equivalent series resistance (ESR) and exhibits high electrostatic capacitance.

[0026] Liquid components can be impregnated in the first etching region. When the total mass of the liquid components impregnated into the etched layer is set to 100%, in the second etching region, it is preferable to impregnate with 70% by mass or more of liquid components, more preferably 80% by mass or more, and even more preferably 90% by mass or more. In the second etching region, it is preferable to impregnate with 99% by mass or less, or 97% by mass or less, or 95% by mass or less, or even 93% by mass or less. In the first etching region, it is preferable to impregnate with 30% by mass or less of liquid components, more preferably 20% by mass or less, and even more preferably 10% by mass or less. In the first etching region, it is preferable to impregnate with 1% by mass or more of liquid components, or 3% by mass or more, or 5% by mass or more, or even 7% by mass or more. The impregnation ratio of liquid components in the first etching region and the impregnation ratio of liquid components in the second etching region can be determined by energy-dispersive X-ray spectroscopy (EDX). For example, a scanning electron microscope (SEM) can be used to observe a cross-section of the etched layer along its thickness direction. Using the SEM image of this cross-section, the infiltration ratio of the liquid component in the first etched region and the infiltration ratio of the liquid component in the second etched region can be determined by EDX. That is, it can be determined by SEM-EDX. Cross-sectional observation of the etched layer based on SEM can be performed in the same manner as described above.

[0027] The following shows the preferred determination conditions for SEM-EDX analysis.

[0028] Measurement apparatus (SEM): Hitachi SU8220 (Field Emission Scanning Electron Microscope)

[0029] Measurement apparatus (EDX): BRUKER XFlash5060FQ / XFlash6 combined system

[0030] Accelerating voltage: 5kV

[0031] Emission: 25μm

[0032] Probe current: High

[0033] Condensing lens: 1.0

[0034] <Liquid Components>

[0035] The liquid component includes a non-aqueous solvent and an electrolyte. As the electrolyte, a non-aqueous electrolyte containing a non-aqueous solvent and a solute dissolved in that non-aqueous solvent can be used. The non-aqueous solvent and solute can be those used in various known electrolytic capacitors. The liquid component can be liquid at room temperature (25°C) or at the temperature at which the electrolytic capacitor is used.

[0036] Non-aqueous solvents can be organic solvents or ionic liquids.

[0037] Examples of organic solvents include glycol compounds, sulfone compounds, and lactone compounds. Examples of glycol compounds include ethylene glycol (EG), diethylene glycol (DEG), triethylene glycol (TEG), and propylene glycol (PG). Examples of sulfone compounds include sulfolane (SL), dimethyl sulfoxide (DMSO), and diethyl sulfoxide (DESO). Examples of lactone compounds include γ-butyrolactone (GBL) and γ-valerolactone (GVL).

[0038] Examples of organic solvents include carbonate compounds and alcohols with one or more nucleotides. Examples of carbonate compounds include dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (EMC), ethylene carbonate (EC), propylene carbonate (PC), and fluoroethylene carbonate (FEC). Examples of alcohols with one or more nucleotides include glycerol and polyglycerol. They can be used individually or in combination of two or more.

[0039] In organic solvents, when Group 1 consists of diol compounds, sulfone compounds, and lactone compounds, and Group 2 consists of carbonate compounds and mono- or tri- or more alcohols, it is preferable that the organic solvent contains more than 50% by mass of organic solvents belonging to Group 1, more preferably more than 60% by mass of organic solvents belonging to Group 1, and most preferably more than 70% by mass of organic solvents belonging to Group 1. The organic solvent may be entirely composed of organic solvents belonging to Group 1. That is, organic solvents belonging to Group 1 may be the main solvent, and organic solvents belonging to Group 2 may be secondary solvents.

[0040] The liquid component preferably contains at least one organic solvent selected from diol compounds, sulfone compounds, and lactone compounds. If the liquid component contains at least one of these compounds, the re-chemical transformation of the dielectric layer based on the acid component contained in the liquid component can be carried out efficiently. Furthermore, by including a diol compound in the liquid component, protons (H+) from the diol compound can be readily supplied to the conductive polymer constituting the conductive polymer layer. ＋ (Specifically, the protons (H) contained in the hydroxyl group) ＋This makes it particularly easy for the conductive polymer layer to swell. By including a sulfone compound in the liquid component, the liquid component exhibits high resistance to acidic and alkaline components. By including a lactone compound in the liquid component, the electrolytic capacitor can exhibit excellent dielectric properties. Furthermore, glycol compounds, sulfone compounds, and lactone compounds generally have high boiling points (specifically, boiling points above 180°C). Therefore, if the liquid component contains these compounds, the liquid component is less likely to volatilize even when the electrolytic capacitor is used at high temperatures (e.g., at 145°C). As a glycol compound, ethylene glycol (EG) is preferred; as a sulfone compound, sulfolane (SL) is preferred; and as a lactone compound, γ-butyrolactone is preferred.

[0041] When the liquid component contains at least one organic solvent selected from diol compounds, sulfone compounds, and lactone compounds, the proportion of diol compounds in the liquid component is preferably 40% by mass or more and 80% by mass or less, the proportion of sulfone compounds in the liquid component is preferably 20% by mass or more and 60% by mass or less, and the proportion of lactone compounds in the liquid component is preferably 40% by mass or more and 80% by mass or less. By including diol compounds, sulfone compounds, and lactone compounds within the above-mentioned numerical ranges, the re-chemical conversion of the dielectric layer based on the acid component contained in the liquid component can be carried out more effectively. In addition, the proton supply to conductive polymers can be further improved, and the resistance of the liquid component to acid and alkali components can be further improved. Furthermore, excellent dielectric properties can be achieved by electrolytic capacitors.

[0042] From the perspective of supplying protons to conductive polymers, the liquid component can contain compounds other than glycol compounds. Examples of such other compounds include glycerol and polyglycerol.

[0043] The liquid component may contain water. The water content in the liquid component can be 0.1% by mass or more and 6.0% by mass or less, or 0.2% by mass or more and 4.0% by mass or less, or 0.5% by mass or more and 2.0% by mass or less. By including water in the liquid component within the ranges described above, the repairability of the dielectric layer based on the liquid component can be improved. Furthermore, when using electrolytic capacitors at high temperatures (e.g., at 145°C), fluctuations in the equivalent series resistance (ESR) can be suppressed. It should be noted that sulfone compounds have excellent hydrolysis resistance; therefore, as described above, the hydrolysis resistance of the liquid component can be improved when a sulfone compound is included in the liquid component.

[0044] The solute may include at least one of an acidic component (acid) and a basic component (base). When the liquid component contains a solute, the proportion of the solute in the liquid component is preferably 70% by mass or less, more preferably 50% by mass or less.

[0045] As acid components, polycarboxylic acids and monocarboxylic acids can be used. Examples of polycarboxylic acids include aliphatic polycarboxylic acids, aromatic polycarboxylic acids, and alicyclic polycarboxylic acids. Examples of aliphatic polycarboxylic acids include saturated and unsaturated polycarboxylic acids. Examples of saturated polycarboxylic acids include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, octanoic acid, azelaic acid, sebacic acid, 1,6-decanedicarboxylic acid, and 5,6-decanedicarboxylic acid. Examples of unsaturated polycarboxylic acids include maleic acid, fumaric acid, and itaconic acid. Examples of aromatic polycarboxylic acids include phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, and pyromellitic acid. Examples of alicyclic polycarboxylic acids include cyclohexane-1,2-dicarboxylic acid and cyclohexene-1,2-dicarboxylic acid.

[0046] Examples of monocarboxylic acids include aliphatic monocarboxylic acids, aromatic monocarboxylic acids, and hydroxycarboxylic acids. Examples of aliphatic monocarboxylic acids include saturated and unsaturated monocarboxylic acids. Examples of saturated monocarboxylic acids include formic acid, acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, lauric acid, myristic acid, stearic acid, and behenic acid. Examples of unsaturated monocarboxylic acids include acrylic acid, methacrylic acid, and oleic acid. Examples of aromatic monocarboxylic acids include benzoic acid, cinnamic acid, and naphtholic acid. Examples of hydroxycarboxylic acids include salicylic acid, mandelic acid, and resorcinolic acid.

[0047] Inorganic acids can be used as the acid component. Examples of inorganic acids include phosphoric acid, phosphorous acid, hypophosphite, alkyl phosphates, boric acid, fluoroboric acid, tetrafluoroboric acid, hexafluorophosphate, benzenesulfonic acid, and naphthalenesulfonic acid. Alternatively, complex compounds of organic and inorganic acids can be used as the acid component. Examples of such complex compounds include dicarboxylic acid derivatives such as borodiethylene glycol acid, borodioxalic acid, and borodisalicylic acid.

[0048] The base component can be a compound with an alkyl-substituted amidine group, such as imidazole compounds, benzimidazole compounds, alicyclic amidine compounds (pyrimidine compounds, imidazoline compounds), etc. Specifically, 1,8-diazabicyclo[5,4,0]undec-7-ene; 1,5-diazabicyclo[4,3,0]non-5-ene; 1,2-dimethylimidazolineon; 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-methylimidazolium; 1-methylbenzimidazole. By using these compounds, the impedance characteristics of the electrolytic capacitor can be made excellent.

[0049] As the base component, quaternary salts of compounds having alkyl-substituted amidine groups can be used. Examples of such base components include imidazole compounds, benzimidazole compounds, and alicyclic amidine compounds (pyrimidine compounds, imidazole kinase compounds) that have been quaternized by alkyl or aryl alkyl groups having 1 to 11 carbon atoms. Specifically, 1-methyl-1,8-diazabicyclo[5,4,0]undec-7-ene; 1-methyl-1,5-diazabicyclo[4,3,0]non-5-ene; 1,2,3-trimethylimidazolinium; 1,2,3,4-tetramethylimidazolinium; 1,2-dimethyl-3-ethylimidazolinium; 1,3,4-trimethyl-2-ethylimidazolinium; Imidazoline indium; 1,3-dimethyl-2-heptylimidazoline indium; 1,3-dimethyl-2-(3'-heptyl)imidazoline indium, 1,3-dimethyl-2-dodecylimidazoline indium; 1,2,3-trimethyl-1,4,5,6-tetrahydropyrimidine indium; 1,3-dimethylimidazoline indium; 1-methyl-3-ethylimidazoline indium; 1,3-dimethylbenzimidazolium indium. Using these compounds can also improve the impedance characteristics of electrolytic capacitors.

[0050] Tertiary amines can be used as the base component. Examples of tertiary amines include trialkylamines and phenyl-containing amines. Examples of trialkylamines include trimethylamine, dimethylethylamine, methyldiethylamine, triethylamine, dimethyl-n-propylamine, dimethylisopropylamine, methylethyl-n-propylamine, methylethylisopropylamine, diethyl-n-propylamine, diethylisopropylamine, tri-n-propylamine, triisopropylamine, tri-n-butylamine, and tri-tert-butylamine. Examples of phenyl-containing amines include dimethylaniline, methylethylaniline, and diethylaniline. From the viewpoint of improving conductivity, trialkylamines are preferred, and among trialkylamines, at least one selected from trimethylamine, dimethylethylamine, methyldiethylamine, and triethylamine is preferred. As the base component, secondary amines such as dialkylamines, primary amines such as monoalkylamines, and ammonia can be used.

[0051] Heterocyclic amines can be used as the base component. Examples of heterocyclic amines include morpholines, and examples of morpholines include morpholines and morpholine derivatives. Specifically, examples include morpholines, N-alkylmorpholines, and N-hydroxyalkylmorpholines. Examples of N-alkylmorpholines include N-methylmorpholine, N-butylmorpholine, and 4-isobutylmorpholine.

[0052] The liquid component can contain salts that are both acidic and basic. Salts can be inorganic or organic. Organic salts are those in which at least one of the anion and cation contains an organic compound. Examples of organic salts include trimethylamine maleate, triethylamine borosalicylate, ethyldimethylamine phthalate, mono-1,2,3,4-tetramethylimidazoline phthalate, and mono-1,3-dimethyl-2-ethylimidazoline phthalate. Organic salts can also be amine salts of long-chain dicarboxylic acids. An example of an amine salt of a long-chain dicarboxylic acid is diethylamine 2-butyloctanoate (2BA).

[0053] Ionic liquids and molten salts (molten salts) have the same meaning; for example, ionic substances that are liquid at 25°C.

[0054] Examples of cations constituting ionic liquids include nitrogen-containing heterocyclic cations (imidazolium, pyrrolidineium, piperidinium, pyridinium, morpholinium, etc.), ammonium, phosphonium, sulfonium, and their derivatives (substitutes with alkyl or other substituents). Cations can be organic cations.

[0055] Examples of anions that constitute ionic liquids include the hydrogen sulfate ion (HSO4). - ), sulfate ions (SO4) 2- -SO4 - ), carboxylate anion (-COO) - ), nitrate anion, sulfonate anion (-SO3), - ), phosphonate anion (PO3) 2- -HPO3 - Examples of acids capable of generating these anions include sulfuric acid, monosulfate (methyl sulfate, etc.), carboxylic acids (acetic acid, lactic acid, benzoic acid, trifluoromethaneacetic acid, etc.), nitric acid, sulfonic acid (methanesulfonic acid, trifluoromethanesulfonic acid, bis(trifluoromethanesulfonyl)imine anion, etc.), phosphonic acid (diethylphosphonic acid, etc.), or their derivatives (substitutes having alkyl, haloalkyl, halogen atoms, etc.). The anion may contain a fluorine atom. Examples of fluorine-containing anions include the aforementioned trifluoromethaneacetic acid, trifluoromethanesulfonic acid, bis(trifluoromethanesulfonyl)imine anion, and their derivatives.

[0056] Specific examples of ionic liquids include 1-butyl-3-methylimidazolium hydrogen sulfate, 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, 1-butyl-3-methylimidazolium trifluoromethanesulfonic acid, and 1-ethyl-3-methylimidazolium diethylphosphonic acid.

[0057] Liquid components may contain polymeric compounds. Examples of polymeric compounds include polyalkylene glycols, derivatives of polyalkylene glycols, and compounds in which at least one hydroxyl group of a polyol is replaced by a polyalkylene glycol (including its derivatives). Specifically, examples include polyethylene glycol (PEG), polyethylene glycol glycerol ether, polyethylene glycol diglycerol ether, polyethylene glycol sorbitol ether, polypropylene glycol, polypropylene glycol diglycerol ether, polypropylene glycol sorbitol ether, and polybutylene glycol.

[0058] Polyalkylene glycols can be copolymers (random copolymers, block copolymers, or random block copolymers, etc.). For example, they can be copolymers of ethylene glycol and propylene glycol, copolymers of ethylene glycol and butanediol, or copolymers of propylene glycol and butanediol.

[0059] The polymeric compound can be a copolymer having ethylene oxide (EO) units and propylene oxide (PO) units. The copolymers mentioned above include copolymers of EO and PO (EO-PO copolymers) and their derivatives. They can be used individually or in combination of two or more. The copolymers can be crosslinked using a crosslinking agent. Examples of such derivatives include those obtained by replacing the hydroxyl groups (-OH) typically present at the ends of the EO-PO copolymer with acryloyl groups (O-CO-CH=CH2). When the total amount of the EO-PO copolymer is 1 mole, the molar ratio of EO units to PO units is preferably EO:PO = 0.9:0.1 to 0.5:0.5. That is, the EO-PO copolymer preferably contains an amount of EO units equal to or greater than the amount of PO units. Therefore, in an electrolytic capacitor where the capacitor element is housed in a bottom casing and the opening of the bottom casing is sealed by a sealing member (sealing rubber, etc.), the permeation of the EO-PO copolymer contained in the liquid component through the sealing member can be suppressed.

[0060] In the electrolytic capacitor of the embodiments of this disclosure, the mass-average molecular weight Mw of the polymer compound can be 200 or more, 300 or more, 400 or more, or 500 or more. The mass-average molecular weight Mw of the polymer compound can be 5000 or less, 4000 or less, 3000 or less, 2000 or less, or 1000 or less.

[0061] The mass-average molecular weight (Mw) of the polymer is a polystyrene equivalent determined by gel permeation chromatography (GPC). It should be noted that GPC determination is typically performed using a polystyrene gel column and a water / methanol (8 / 2 v / v) mobile phase.

[0062] For example, the determination based on GPC can be performed as follows: using a column consisting of two connected Shodex OHpak SB804HQ and SB8025HQ columns, using 50 mM NaNO3 aqueous solution as the eluent, using an RI detector, and setting the column temperature to 40 °C, the eluent flow rate to 0.7 mL / min, and the analysis time to 40 min.

[0063] In the electrolytic capacitor of the embodiments of this disclosure, the liquid component preferably comprises a polymer compound, a sulfone compound, and an amine salt of a long-chain dicarboxylic acid. The polymer compound preferably comprises a polyalkylene glycol, and more preferably polyethylene glycol (PEG). The sulfone compound preferably comprises sulfolane (SL). The amine salt of the long-chain dicarboxylic acid preferably comprises diethylamine 2-butyloctanoate (2BA). When the liquid component comprises a polymer compound, a sulfone compound, and an amine salt of a long-chain dicarboxylic acid, the proportion of the polymer compound is preferably 20% by mass or more and 60% by mass or less, more preferably 40% by mass or more and 50% by mass or less. The proportion of the sulfone compound is preferably 20% by mass or more and 60% by mass or less, more preferably 40% by mass or more and 50% by mass or less. The proportion of the amine salt of the long-chain dicarboxylic acid is preferably 5% by mass or more and 30% by mass or less, more preferably 10% by mass or more and 20% by mass or less. By including polymeric compounds, sulfone compounds, and amine salts of long-chain dicarboxylic acids in the liquid component within the range described above, a conductive pathway via the liquid component can be more fully formed inside the second etched region.

[0064] <Capacitor Components>

[0065] As described above, the electrolytic capacitor of the present disclosure includes a capacitor element in addition to the liquid component. The capacitor element includes: an anode foil, a cathode foil arranged opposite to the anode foil, a separator between the anode foil and the cathode foil, and a conductive polymer layer between the anode foil and the cathode foil and in contact with the separator.

[0066] (Anode foil)

[0067] Examples of anode foils include metal foils containing at least one valve-acting metal such as titanium, tantalum, aluminum, and niobium. The anode foil may also be a metal foil containing a valve-acting metal (e.g., aluminum foil). The anode foil may contain the valve-acting metal in the form of an alloy or a compound containing the valve-acting metal. The thickness of the anode foil may be 15 μm or more and 300 μm or less.

[0068] As described above, in the electrolytic capacitor of the embodiments of this disclosure, an etched layer is formed on the anode foil from the surface toward the center. Hereinafter, reference will be made to... Figure 1 and 2 An explanation is given for the anode foil with an etched layer. Figure 1 This is a schematic diagram of the cross-section of the anode foil 11. Figure 2 It is equivalent to Figure 1 Electron micrograph of the etched layer in part A. It should be noted that... Figure 1 In the process, the size and shape of each component may not be consistent with the actual object.

[0069] like Figure 1 As shown, the anode foil 11 has two etched layers 11b formed from each of its two surfaces (two main surfaces) toward the center, and a foil core 11a between the two etched layers 11b. Each of the etched layers 11b from each of the two surfaces (two main surfaces) of the anode foil 11 toward the center has a first etched region 11b1 and a second etched region 11b2. The first etched region 11b1 contains a plurality of first micropores 11b11 continuously arranged in both the thickness and planar directions, and the second etched region 11b2 contains a plurality of second micropores 11b21 extending in a tunnel-like manner along the thickness direction. It should be noted that the foil core 11a is the remaining portion of the metal foil (e.g., aluminum foil) after etching the valve-acting metal. The first etched region 11b1 is configured, for example, as a sponge. Adjacent first micropores 11b11 in the thickness and planar directions of the first etched region 11b1 may or may not be connected to each other. That is, adjacent first apertures 11b11 may or may not be connected to each other. Multiple second apertures 11b21 may penetrate the second etched region 11b2 in the thickness direction.

[0070] The first etched region 11b1 can be formed, for example, by applying a direct current to a metal foil (e.g., aluminum foil) containing chloride ions in a solution containing chloride ions. That is, the first etched region can be formed by direct current electrolysis. The second etched region 11b2 can be formed, for example, by applying an alternating current to a metal foil containing chloride and sulfate ions in which the first etched region is formed. That is, the second etched region can be formed by alternating current electrolysis. Direct current electrolysis and alternating current electrolysis can be carried out by appropriately selecting various known conditions.

[0071] In the electrolytic capacitor of the embodiments of this disclosure, a dielectric layer (not shown) is formed on the etched layer 11b. That is, the etched layer 11b has a dielectric layer. The dielectric layer may be formed by chemical conversion treatment of the anode foil 11. In this case, the chemical conversion film formed by the chemical conversion treatment becomes the dielectric layer. The chemical conversion treatment may be performed by applying a predetermined chemical conversion voltage to the anode foil 11 while immersing it in an acidic solution (hereinafter also referred to as chemical conversion liquid), or by heat-treating the anode foil 11 at a predetermined temperature while immersing it in the chemical conversion liquid. In addition, as described above, when the dielectric layer is formed by chemical conversion treatment, the dielectric layer (chemical conversion film) may contain an oxide of the valve-acting metal (e.g., aluminum oxide). It should be noted that the dielectric layer only needs to function as a dielectric, and may also be formed of a dielectric other than an oxide of the valve-acting metal. The dielectric layer may be formed in at least the first etch region 11b1 of the first etch region 11b1 and the second etch region 11b2 constituting the etch layer 11b. Alternatively, the dielectric layer may be formed in both the first etch region 11b1 and the second etch region 11b2.

[0072] In electrolytic capacitors, the end face (side face) of the anode foil 11 may not have a conductive polymer layer formed. On the other hand, it is preferable that a dielectric layer is formed on the end face (side face) of the anode foil 11. (Refer to a wound-type electrolytic capacitor...) Figure 3 and 4 When using ) as an example for explanation, in Figure 4 In the wound capacitor element 10 shown, although a conductive polymer layer is formed in the circumferential direction, it is also possible not to form a conductive polymer layer on the upper end face and the lower end face.

[0073] In the electrolytic capacitor of the embodiments of this disclosure, the average pore diameter P of the first pore 11b11 is important. d1 The average pore diameter P is smaller than that of the second pore 11b21. d2 By making the average pore diameter P d1 and average pore diameter P d2By satisfying this relationship, when a conductive polymer layer is formed on the surface of the dielectric layer formed on the etched layer using conductive polymer particles, it is possible to suppress the conductive polymer particles from passing through the first pore 11b11 to the second etched region 11b2. Therefore, it is easy to selectively form a conductive polymer layer on the surface of the dielectric layer formed in the first etched region 11b1. Furthermore, even if conductive polymer particles pass through the first pore 11b11 and enter the interior of the second pore 11b21, the second pore 11b21 can be prevented from being blocked by conductive polymer particles due to its large diameter. Therefore, after the conductive polymer layer is formed, even if liquid components are impregnated in the etched layer 11b, the liquid components can be sufficiently introduced into the interior of the second pore 11b21. That is, the liquid components can be sufficiently retained in the second etched region 11b2. It should be noted that the average pore diameter P... d1 and P d2 The pore diameter can be determined by measuring the pore diameter distribution of the first etched region 11b1 and the second etched region 11b2 using a mercury porosimeter. Specifically, the average pore diameter is calculated as the pore diameter (mode diameter) corresponding to the peak (the largest peak when multiple peaks exist) in the measured pore distribution curve (vertical axis: log differential pore volume, horizontal axis: pore diameter). The average pore diameter P is then calculated. d1 The average pore diameter P can be determined from the pore distribution curve of the first etched region 11b1. d2 The pore distribution curve of the second etched region 11b2 can be used. For example, the AutoPore V series manufactured by Micromeritics can be used as the measuring device.

[0074] The ratio (L2 / L1) of the thickness L2 of the second etched region 11b2 to the thickness L1 of the first etched region 11b1 is preferably 5 or more, more preferably 8 or more, and more preferably 12 or more. L2 / L1 is preferably 20 or less, more preferably 18 or less, and more preferably 16 or less. By setting L2 / L1 to the range described above, a more sufficient conductive path can be formed between the etched layer and the cathode foil via the liquid component and the conductive polymer layer. As a result, the electrolytic capacitor of this embodiment exhibits a higher electrostatic capacitance. The thicknesses L1 and L2 can be measured by observing a cross-section along the thickness direction of the anode foil using a scanning electron microscope (SEM). The cross-sectional observation of the anode foil using SEM can be performed in the same manner as described above. Regarding L2, five locations in the cross-section of the anode foil where the second aperture penetrates the second etched region 11b2 from top to bottom can be selected, and the length of each location can be measured. The arithmetic mean of the measured values ​​at the five locations is then calculated. Regarding L1, the length from the surface of the anode foil to the upper end of the second etched region 11b2 can be measured at any five locations along the cross-section of the anode foil, and the obtained measurements can be calculated by arithmetic averaging. It should be noted that L2 / L1 can be adjusted by varying the magnitude of the etching current or the length of the etching time.

[0075] The average pore diameter P of the first pore 11b11 d1 Preferably, the pore size is 0.1 μm or more, more preferably 0.2 μm or more, and even more preferably 0.3 μm or more. Average pore diameter P d1 Preferably, the micrometer diameter is 1.0 μm or less, more preferably 0.8 μm or less, and even more preferably 0.5 μm or less. Furthermore, the average pore diameter P of the second micropore 11b21... d2 Preferably, the pore size is 0.2 μm or more, more preferably 0.4 μm or more, and even more preferably 0.6 μm or more. Average pore diameter P d2 Preferably, the particle size is 1.2 μm or less, more preferably 1.0 μm or less, and even more preferably 0.8 μm or less. Conductive polymer particles typically have an average particle size D of 0.1 μm (100 nm) to 0.5 μm (500 nm). cp Therefore, if the average pore diameter P d1 and average pore diameter P d2 With such a range, it is easier to selectively form a conductive polymer layer on the surface of the dielectric layer formed in the first etched region 11b1. Furthermore, it is possible to more effectively suppress the clogging of the second pore 11b21 by conductive polymer particles.

[0076] (Cathode foil)

[0077] There are no particular limitations on the cathode foil as long as it functions as a cathode. Examples of cathode foils include metal foils (e.g., aluminum foil). The type of metal contained in the metal foil is not particularly limited. The metal can be a valve-acting metal or an alloy containing a valve-acting metal. The thickness of the cathode foil can be 15 μm or more and 300 μm or less. The surface of the cathode foil can be formed with an etched layer, similar to that of the anode foil, or with a dielectric layer, as needed. That is, the surface of the cathode foil can be roughened or chemically converted as needed.

[0078] The cathode foil may include a conductive coating. When the metal foil contains a valve-acting metal, the coating may contain at least one of carbon and a metal with a lower ionization tendency than the valve-acting metal. This readily improves the acid resistance of the metal foil. When the metal foil contains aluminum, the coating may contain at least one selected from carbon, nickel, titanium, tantalum, and zirconium. From the viewpoint of prioritizing low cost and low resistance, the coating may contain at least one of nickel and titanium.

[0079] The thickness of the coating layer can be 5 nm or more, or 10 nm or more. The thickness of the coating layer can be less than 200 nm. The coating layer can be formed by vapor deposition or sputtering the aforementioned metal onto a metal foil. Alternatively, the coating layer can be formed by vapor deposition of a conductive carbon material onto a metal foil, or by coating a carbon paste containing a conductive carbon material onto a metal foil. Examples of conductive carbon materials include graphite, hard carbon, soft carbon, and carbon black.

[0080] (Diaphragm)

[0081] The diaphragm can be made of porous sheet. Examples of porous sheets include woven fabrics, nonwoven fabrics, and microporous membranes. The thickness of the diaphragm is not particularly limited and can range from 10 μm to 300 μm. Examples of materials used for the diaphragm include cellulose, polyethylene terephthalate, polybutylene terephthalate, polyphenylene sulfide, vinylon, nylon, aromatic polyamides, polyimides, polyamide-imides, polyether-imides, rayon, and glass.

[0082] (Conductive polymer layer)

[0083] The conductive polymer layer is formed of a conductive polymer. In the electrolytic capacitor of the embodiments of this disclosure, the conductive polymer layer is preferably formed of conductive polymer particles. Examples of conductive polymers include polypyrrole, polythiophene, polyaniline, and their derivatives. A single conductive polymer can be used alone, or two or more can be used in combination. The conductive polymer can also be a copolymer of two or more monomers. It should be noted that derivatives of conductive polymers refer to polymers with a conductive polymer as their basic backbone. For example, derivatives of polythiophene include poly(3,4-ethylenedioxythiophene).

[0084] The conductive polymer may contain dopants. The dopants can be appropriately selected depending on the type of conductive polymer. Various known dopants can be used as dopants. Examples of dopants include naphthalenesulfonic acid, p-toluenesulfonic acid, polystyrenesulfonic acid, and their salts. As an example of a conductive polymer, poly(3,4-ethylenedioxythiophene) (PEDOT) doped with polystyrenesulfonic acid (PSS) can be cited. In the electrolytic capacitor of the embodiments of this disclosure, the conductive polymer layer is preferably formed from particles of poly(3,4-ethylenedioxythiophene) (PEDOT) (hereinafter also referred to as PEDOT / PSS) doped with polystyrenesulfonic acid (PSS).

[0085] The conductive polymer layer preferably contacts the anode foil 11, cathode foil, and separator with a sufficiently large contact area. This creates a sufficient conductive path between the anode foil 11 and the cathode foil through the conductive polymer layer. As a result, the equivalent series resistance (ESR) of the electrolytic capacitor can be reduced, thus improving the reliability of the electrolytic capacitor.

[0086] The conductive polymer layer is preferably formed on at least one of the surfaces of the dielectric layer of the anode foil 11 and the cathode foil. The conductive polymer layer may also be formed within the voids of the separator (i.e., on the surface of the constituent material of the separator surrounding the voids). This allows for a more robust conductive path based on the conductive polymer layer to be formed between the anode foil 11 and the cathode foil. The conductive polymer layer is preferably formed at least on the surface of the dielectric layer of the anode foil 11, more preferably on both the surface of the dielectric layer and the surface of the cathode foil, and further within the voids of the separator. Preferably, a conductive polymer layer is formed to continuously connect the surface of the dielectric layer to the surface of the cathode foil.

[0087] When the conductive polymer layer is formed by conductive polymer particles, the average particle size D of the conductive polymer particles is... cp Preferably, the diameter P of the second fine hole 11b21, which extends in a tunnel-like manner along the thickness direction in the second etched region 11b2, is larger than the average pore diameter P. d2 That is, D cp With P d2 Preferred to satisfy D cp >P d2The relationship is such that when a conductive polymer layer is formed on the dielectric layer of the anode foil 11, the entry of conductive polymer particles into the interior of the second pore 11b21 can be suppressed. This prevents the formation of a conductive polymer layer in a state of excessive intrusion into the interior of the anode foil 11, thus preventing insufficient contact between the conductive polymer layer and the cathode foil. As a result, a conductive polymer layer can be formed, ensuring a more sufficient contact area between the anode foil 11, the cathode foil, and the separator. That is, by forming a more sufficient conductive path between the anode foil 11 and the cathode foil through the conductive polymer layer, the equivalent series resistance (ESR) of the electrolytic capacitor can be reduced more effectively. Consequently, the reliability of the electrolytic capacitor can be improved. It should be noted that the average particle size D... cp The particle size distribution is determined by the volumetric reference of the conductive polymer particles. The volumetric reference particle size distribution of the conductive polymer particles is measured using a particle size distribution measuring device based on dynamic light scattering. For example, the DLS-8000 light scattering photometer manufactured by Otsuka Electronics Co., Ltd. can be used as a particle size distribution measuring device based on dynamic light scattering.

[0088] It should be noted that in the determination of the particle size distribution of conductive polymer particles based on volume, a dispersion containing conductive polymer particles can be used. The dispersion can be prepared, for example, by using a dispersant to disperse the conductive polymer particles in a liquid dispersion medium. As the dispersion medium, for example, an organic medium that is liquid at room temperature (e.g., 20°C to 35°C) can be used. The type and concentration of the dispersant, the type of dispersion medium, and the concentration of conductive polymer particles in the dispersion can be selected within a range suitable for preparing a dispersion suitable for particle size distribution determination.

[0089] The following is for reference Figure 3 and 4 The specific configuration of an electrolytic capacitor according to one embodiment of the present disclosure will be described. Figure 3 This is a schematic cross-sectional view of an electrolytic capacitor 100 according to one embodiment of the present disclosure. Figure 4 This is a schematic diagram showing a portion of the capacitor element 10 contained in the electrolytic capacitor 100 after it has been unfolded.

[0090] The electrolytic capacitor 100 includes: a capacitor element 10, a bottomed housing 101 housing the capacitor element 10, a sealing member 102 (e.g., sealing rubber) blocking the opening of the bottomed housing 101, a base plate 103 covering the sealing member 102, a base plate 103 disposed outside the bottomed housing 101 such that it covers the sealing member 102 from the opening side of the bottomed housing 101, a pair of leads 104A, 104B extending from the sealing member 102 and passing through the base plate 103, and a pair of lead connectors 105A, 105B connecting the pair of leads 104A, 104B to the electrodes of the capacitor element (e.g., the anode foil 11 and cathode foil 12 described later), respectively. A deep drawing process is performed near the opening end of the bottomed housing 101 in an inwardly recessed manner, and a coiling process is performed at the opening end of the bottomed housing 101 such that it is tightly fitted to the sealing member 102. It should be noted that... Figure 3 In the example shown, lead 104A is connected to the electrode of the capacitor element via lead connector 105A, and lead 104B is connected to the electrode of the capacitor element via lead connector 105B.

[0091] The sealing member 102 is formed of an elastic member containing a rubber component. As the rubber component, butyl rubber (IIR), nitrile rubber (NBR), ethylene propylene rubber, ethylene propylene diene monomer (EPDM), chloroprene rubber (CR), isoprene rubber (IR), Hypalon rubber, silicone rubber, fluororubber, etc., can be used. The sealing member 102 may contain fillers such as carbon black and silica.

[0092] Capacitor element 10 is configured, for example, as follows: Figure 4 The wound body shown. The wound body includes an anode foil 11 connected to lead connector 105A, a cathode foil 12 connected to lead connector 105B, and a separator 13. The capacitor element 10 includes a conductive polymer layer (not shown). It should be noted that... Figure 3 The electrolytic capacitor 100 shown includes Figure 4 The capacitor element 10 shown is therefore called a wound electrolytic capacitor.

[0093] The anode foil 11 and the cathode foil 12 are wound together with a diaphragm 13 sandwiched between them to form a wound body. Furthermore, the outermost periphery of this wound body is fixed by a winding fixing tape 14. It should be noted that... Figure 4 This indicates the state of the coiled body before the outermost part was fixed by the winding fixing tape 14.

[0094] The electrolytic capacitor disclosed herein may have at least one capacitor element, or may have multiple capacitor elements. The number of capacitor elements in the electrolytic capacitor is appropriately determined according to the application.

[0095] exist Figure 3and 4 The present invention describes a wound electrolytic capacitor, but the electrolytic capacitor of the present invention is not limited to this, and may be a chip-type electrolytic capacitor or a stacked electrolytic capacitor.

[0096] [Manufacturing Method of Electrolytic Capacitors]

[0097] An example of a method for manufacturing an electrolytic capacitor according to an embodiment of the present disclosure includes: (a) a step of preparing an etched layer having an etched layer including a first etched region and a second etched region, and an anode foil, a cathode foil, and a separator having a dielectric layer formed thereon; (b) a step of depositing a polymer dispersion formed by dispersing a conductive polymer and a dopant in a liquid medium onto the surface of at least one of the dielectric layer and the cathode foil and into the voids of the separator; (c) a step of forming a conductive polymer layer into the voids of the aforementioned surface and the separator by removing at least a portion of the liquid medium from the polymer dispersion; (d) a step of forming a capacitor element by distributing a separator between the anode foil and the cathode foil; and (e) a step of filling the voids within the capacitor element with a liquid component. In the method for manufacturing an electrolytic capacitor according to an embodiment of the present disclosure, steps (a) to (e) are preferably performed sequentially.

[0098] <(a) Process>

[0099] In the process of preparing the anode foil, the etched layer including the first etched region and the second etched region, as well as the dielectric layer, can be formed as described above. The process of preparing the cathode foil and the separator is not particularly limited. The materials of the cathode foil and the separator are also not particularly limited. The cathode foil and separator described above can be used as the cathode foil and the separator.

[0100] <(b) Process>

[0101] In step (b), a polymer dispersion can be applied to the surface of the dielectric layer and the separator, or to the surface of the cathode foil and the separator. Alternatively, a polymer dispersion can be applied to the surface of the dielectric layer, the surface of the cathode foil, and the separator. It should be noted that when a dielectric layer is formed on both sides of the anode foil, the polymer dispersion can be applied to the surface of the dielectric layer formed on both sides of the dielectric layer. Furthermore, the polymer dispersion can be applied to both sides of the cathode foil. A conductive polymer layer is formed at the site where the polymer dispersion is applied.

[0102] One method for applying a polymer dispersion is coating. Coating can be carried out by various known methods. Examples of coating include coating using a coating machine, spray-based coating, and coating in which the object to be coated is immersed in the polymer dispersion. Examples of coating using a coating machine include gravure coating and die coating. It should be noted that water is a liquid medium, for example.

[0103] <(c) Process>

[0104] In step (c), the method for removing at least a portion of the liquid medium from the polymer dispersion is not particularly limited. The removal of the liquid medium is preferably carried out at least by heating. The removal of the liquid medium can be carried out by heating under reduced pressure. It should be noted that, when the liquid medium is water, the removal of the liquid medium is preferably carried out by heating the liquid medium to above 100°C.

[0105] It should be noted that, in electrolytic capacitors, Figure 3 In the case of the wound-type electrolytic capacitor 100 shown, the polymer dispersion is impregnated to... Figure 4 After constructing a capacitor element 10 in the form of a wound body as shown, the capacitor element 10 is heated at a specified temperature, thereby forming a conductive polymer layer.

[0106] <(d) Process>

[0107] In step (d), after forming a conductive polymer layer on the surface of at least one of the dielectric layer and the cathode foil and on the separator, a separator is disposed between the anode foil and the cathode foil, thereby forming a capacitor element (specifically, a capacitor element comprising a conductive polymer layer). This step is also a step of stacking the anode foil and the cathode foil with the separator in between.

[0108] There are no particular limitations on the method of forming capacitor elements. Capacitor elements can be formed using various well-known methods. Figure 4 A wound body as shown. In Figure 4 In the winding shown, the anode foil, cathode foil, and diaphragm are stacked radially on the winding.

[0109] A capacitor element can be formed by stacking flat anode foil, flat cathode foil, and flat separator in one direction. For example, a capacitor element can be formed by stacking multiple anode foils, multiple cathode foils, and multiple separators in one direction. An electrolytic capacitor containing such a stacked capacitor element is called a stacked electrolytic capacitor. In a typical example of a stack, anode foils and cathode foils are arranged alternately, with a separator disposed between the anode foils and cathode foils.

[0110] <(e) Process>

[0111] There is no particular limitation on the method of filling the voids within a capacitor element with a liquid component. For example, the liquid component can be filled into the voids within the capacitor element by permeating at least a portion of the capacitor element.

[0112] As described above, by performing steps (a) to (e), a capacitor element comprising a conductive polymer layer and a liquid component is formed. Then, as needed, the capacitor element is encapsulated in an outer casing (housing). This manufactures an electrolytic capacitor according to an embodiment of the present disclosure.

[0113] It should be noted that the above description illustrates an example of forming a conductive polymer layer on the surface of at least one of the dielectric layer and the cathode foil and on the separator before the anode foil and cathode foil are stacked with the separator in between. However, the examples of forming a conductive polymer layer are not limited to this. The conductive polymer layer can be formed after the anode foil and cathode foil are stacked with the separator in between. For example, a conductive polymer layer can be formed on the surface of at least one of the dielectric layer and the cathode foil and on the separator by immersing the wound body, which is formed by stacking the anode foil and the cathode foil with the separator in between, after obtaining the wound body.

[0114] (Postscript)

[0115] Based on the above description, the following technologies were disclosed.

[0116] (Technology 1)

[0117] An electrolytic capacitor comprising a capacitor element and a liquid component,

[0118] The above-mentioned capacitor element includes:

[0119] Anode foil;

[0120] A cathode foil, which is arranged opposite to the aforementioned anode foil;

[0121] A diaphragm, which is located between the anode foil and the cathode foil; and

[0122] A conductive polymer layer is disposed between the anode foil and the cathode foil and is in contact with the diaphragm.

[0123] An etched layer is formed in the anode foil from the surface toward the center, and this etched layer has a dielectric layer.

[0124] The aforementioned etched layer comprises a first etched region and a second etched region sequentially from the surface of the anode foil toward its center. The first etched region includes a plurality of first micropores arranged continuously in both the thickness and planar directions. The second etched region includes a plurality of second micropores extending in a tunnel-like manner along the thickness direction.

[0125] The average diameter of the first pore is smaller than the average diameter of the second pore.

[0126] The aforementioned conductive polymer layer is formed in the first etched region.

[0127] The liquid components described above are impregnated in at least the second etched area.

[0128] (Technology 2)

[0129] According to the electrolytic capacitor described in Technology 1, the aforementioned conductive polymer layer is formed of conductive polymer particles.

[0130] The average particle size of the aforementioned conductive polymer particles is larger than the average pore diameter of the aforementioned second pore.

[0131] (Technology 3)

[0132] According to the electrolytic capacitor described in technique 1 or 2, the ratio (L2 / L1) of the thickness L2 of the second etched region to the thickness L1 of the first etched region is 5 or more and 20 or less.

[0133] (Technology 4)

[0134] According to any one of the techniques 1 to 3, the electrolytic capacitor wherein the average diameter of the first pore is 0.1 μm or more and 1.0 μm or less.

[0135] (Technology 5)

[0136] According to any one of the techniques 1 to 3, the electrolytic capacitor wherein the average diameter of the second pore is 0.2 μm or more and 1.2 μm or less.

[0137] (Technology 6)

[0138] According to any one of the techniques 1 to 3, the average diameter of the first pore is 0.1 μm or more and 1.0 μm or less.

[0139] The average diameter of the second pore is above 0.1 μm and below 1.2 μm.

[0140] (Technology 7)

[0141] According to any one of the techniques 1 to 6, the electrolytic capacitor contains at least one solvent selected from lactone compounds, sulfone compounds, glycol compounds and polyalkylene glycols.

[0142] Preferred embodiments of the present invention have been described, but such disclosure is not intended to be limiting. Various modifications and alterations will be readily apparent to those skilled in the art upon reading the foregoing disclosure. Therefore, the scope of the appended claims should be interpreted as including all modifications and alterations without departing from the true spirit and scope of the invention.

[0143] Example

[0144] The present disclosure is described in detail below based on embodiments and comparative examples, but the present disclosure is not limited to the following embodiments.

[0145] [Example 1]

[0146] (A) Preparation of constituent components

[0147] (A-1) Anode foil

[0148] An aluminum foil (6 mm wide × 195 mm long × 120 μm thick) is prepared, with a first etched region and a second etched region sequentially formed from both surfaces toward the center. Chemical conversion treatment is applied to both surfaces of the aluminum foil to form a dielectric layer. This yields an anode foil with dielectric layers formed on both surfaces. It should be noted that the average pore diameter P of the first pore contained in the first etched region... d1 The average pore diameter P of the second pore contained in the second etched region is 0.3 μm. d2 It is 0.6 μm. That is, the average pore diameter P of the first pore is... d1 The average pore diameter P is smaller than that of the second pore. d2 The average pore diameter P of the first pore d1 And the average pore diameter P of the second pore d2 The measurements were performed according to the method described in the above embodiments. Furthermore, the thickness L1 of the first etched region was 2.5 μm, and the thickness L2 of the second etched region was 38 μm. That is, the ratio (L2 / L1) of the thickness L2 of the second etched region to the thickness L1 of the first etched region was 15.2. The thicknesses L1 of the first etched region and L2 of the second etched region were measured according to the method described in the above embodiments.

[0149] (A-2) Cathode foil

[0150] Etching was performed on both surfaces of an aluminum foil (50 μm thick) to obtain a cathode foil with roughened surfaces.

[0151] (A-3) Diaphragm

[0152] As a diaphragm, a nonwoven fabric (50 μm thick) is prepared. The nonwoven fabric consists of 50% by mass synthetic fibers (25% by mass polyester fiber and 25% by mass aramid fiber) and 50% by mass cellulose, containing polyacrylamide as a paper strength reinforcing agent. The density of the nonwoven fabric is 0.35 g / cm³. 3 .

[0153] (B) Preparation of polymeric dispersions

[0154] 3,4-ethylenedioxythiophene and poly(4-styrenesulfonic acid) (PSS, mass-average molecular weight Mw 100,000, dopant) were dissolved in ion-exchanged water to prepare a mixed solution. Next, while stirring the mixed solution, oxidants (ferric sulfate (III) and ammonium persulfate) dissolved in ion-exchanged water were added to the mixed solution to carry out a polymerization reaction. After the polymerization reaction, the resulting reaction solution was dialyzed to remove unreacted monomers and excess oxidant. Thus, PSS-doped poly(3,4-ethylenedioxythiophene) (PEDOT / PSS) was obtained as a polymer dispersion. In the polymer dispersion, the average particle size D of the PEDOT / PSS particles, which are conductive polymer particles, is... cp The average particle size D of the PEDOT / PSS particles is 0.8 μm. cp The average pore diameter P of the second pore contained in the second etched region is greater than that of the second pore. d2 It should be noted that the average particle size D cp The measurement was performed according to the method described in the above embodiments.

[0155] (C) Fabrication of the wound body

[0156] The anode foil, cathode foil, and diaphragm are each cut to specified planar dimensions. An anode lead connector is connected to the anode foil, and a cathode lead connector is connected to the cathode foil. Next, the anode and cathode foils are wound together with the diaphragm in between to obtain a wound body. The ends of the outer surface of the wound body are then secured with a winding fixing tape. An anode lead is connected to the end of the anode lead connector, and a cathode lead is connected to the end of the cathode lead connector. The wound body is then subjected to another chemical conversion treatment to form a dielectric layer on the end face of the anode foil. Specifically, in… Figure 4 A dielectric layer is formed on the upper and lower end faces of the winding body as shown.

[0157] (D) Formation of conductive polymer layer

[0158] In a reduced pressure atmosphere (40 kPa), the wound body is immersed in a polymer dispersion contained in a specified container for 5 minutes, and then the wound body is lifted out of the polymer dispersion. Next, the wound body impregnated with the polymer dispersion is dried in a drying oven at 150°C for 20 minutes to form a conductive polymer layer in such a way as to coat at least a portion of the dielectric layer, thus obtaining a capacitor element.

[0159] (E) Infiltration of liquid components

[0160] An electrolyte (liquid component) containing polyethylene glycol (PEG), sulfolane (SL), and diethylamine 2-butyloctanoate (2BA) in a ratio of PEG:SL:2BA = 45:40:15 was prepared. The capacitor element was then immersed in the electrolyte for 5 minutes under reduced pressure (40 kPa). This allowed the electrolyte to permeate the capacitor element.

[0161] (F) Sealing of capacitor elements

[0162] The capacitor element, impregnated with electrolyte, is sealed to manufacture... Figure 3 An electrolytic capacitor as shown was then produced. A voltage was applied while an aging treatment was performed at 95°C for 90 minutes. This yielded the electrolytic capacitor of Example 1. It should be noted that an elastic material containing butyl rubber as the rubber component was used as the sealing member for sealing the capacitor element. It should be noted that 40 electrolytic capacitors were manufactured. The same applies to the following examples.

[0163] [Example 2]

[0164] In polymer dispersions, besides ensuring the average particle size D of PEDPT / PSS particles, which are conductive polymer particles, cp In addition to being 0.5 μm, that is, except for making the average particle size D of PETDOT / PSS particles... cp The average pore diameter P of the second pore contained in the second etched region is smaller than that of the second pore. d2 In addition, the electrolytic capacitor of Example 2 was obtained by operating in the same manner as in Example 1. It should be noted that in Example 2, the average particle size D... cp The measurements were also performed according to the methods described in the above embodiments.

[0165] [Comparative Example 1]

[0166] As the anode foil, an aluminum foil (6 mm wide × 195 mm long × 120 μm thick) with only a second etched region extending from both surfaces towards the center was used. Otherwise, the procedure was the same as in Example 1, and the electrolytic capacitor of Comparative Example 1 was obtained. It should be noted that the average pore diameter P of the second pore contained within the second etched region... d2The thickness L2 of the second etched region is 40 μm, and the thickness L2 of the second etched region is 0.6 μm. The average pore diameter P of the second etched region is... d2 The thickness L2 of the second etched region was measured according to the method described in the above embodiments.

[0167] [Comparative Example 2]

[0168] Except for preventing the liquid components (electrolyte) from seeping into the capacitor element, the electrolytic capacitor of Comparative Example 2 was obtained by operating in the same manner as in Example 1.

[0169] [Comparative Example 3]

[0170] Except for preventing the liquid components (electrolyte) from seeping into the capacitor element, the electrolytic capacitor of Comparative Example 3 was obtained by operating in the same manner as in Example 2.

[0171] For each example of an electrolytic capacitor, the composition of the etched layer of the anode foil and the average particle size D of the conductive polymer particles are considered. cp The average pore diameter P of the second pore d2 The size relationships and the presence or absence of electrolyte infiltration are shown in Table 1 below.

[0172]

[0173] <Evaluation>

[0174] Initial electrostatic capacitance

[0175] For each of the 20 electrolytic capacitors, the initial electrostatic capacitance (in μF) was measured at 20°C and 120Hz. The initial electrostatic capacitance was measured using an LCR meter. Then, the arithmetic mean of the measured values ​​was calculated to obtain the average initial capacitance (average capacitance). The results are shown in Table 2 below.

[0176] • Equivalent series resistance (ESR)

[0177] The equivalent series resistance (ESR) of 20 electrolytic capacitors for each example was measured. The ESR was measured using an LCR meter as a resistance value at 100 kHz. The average ESR was then calculated by arithmetic averaging of the measured values. The results are shown in Table 2 below.

[0178]

[0179] As shown in Table 2, the electrolytic capacitors of Examples 1 and 2 can ensure a high electrostatic capacitance of 9.6 μF, and further reduce the equivalent series resistance (ESR) (Example 1: 30 mΩ, Example 2: 36 mΩ). This is particularly evident in the average particle size D of the PEDOT / PSS particles.cp The average pore diameter P of the second pore contained in the second etched region is greater than that of the second pore. d2 In Example 1, it is evident that the equivalent series resistance (ESR) becomes lower. In contrast, while a high electrostatic capacitance of 9.6 μF is ensured in the electrolytic capacitor of Comparative Example 1, the equivalent series resistance (ESR) becomes a high value of 50 mΩ. Furthermore, while the equivalent series resistance (ESR) can be reduced in the electrolytic capacitors of Comparative Examples 2 and 3 (Comparative Example 2: 30 mΩ, Comparative Example 3: 35 mΩ), sufficient electrostatic capacitance cannot be ensured (Comparative Example 2: 6.2 μF, Comparative Example 3: 8.4 μF). It should be noted that the maximum electrostatic capacitance (capacitance in water) of the electrolytic capacitors in each example is 10 μF; therefore, it is evident that in the electrolytic capacitors of Examples 1 and 2, an electrostatic capacitance of 95% or more of the maximum electrostatic capacitance is achieved.

[0180] Industrial availability

[0181] The electrolytic capacitor disclosed herein can be used in applications requiring both high electrostatic capacitance and reduced equivalent series resistance.

[0182] Explanation of reference numerals in the attached figures

[0183] 10: Capacitor Components

[0184] 11: Anode foil

[0185] 11a: Foil core, 11b: Etched layer, 11b1: First etched area, 11b2: Second etched area, 11b11: First micro-hole, 11b21: Second micro-hole

[0186] 12: Cathode foil

[0187] 13: Diaphragm

[0188] 14: Winding and fixing tape

[0189] 100: Electrolytic capacitor

[0190] 101: Bottom shell

[0191] 102: Sealing components

[0192] 103: Seat board

[0193] 104A, 104B: Lead wires

[0194] 105A, 105B: Lead wire connectors

Claims

1. An electrolytic capacitor comprising a capacitor element and a liquid component, The capacitor element comprises: Anode foil; A cathode foil, which is arranged opposite to the anode foil; A diaphragm, which is located between the anode foil and the cathode foil; and A conductive polymer layer is disposed between the anode foil and the cathode foil and is in contact with the diaphragm. An etched layer is formed in the anode foil from the surface toward the center, and this etched layer has a dielectric layer. The etched layer comprises a first etched region and a second etched region sequentially from the surface of the anode foil toward the center. The first etched region includes a plurality of first micropores arranged continuously in both the thickness and planar directions. The second etched region includes a plurality of second micropores extending in a tunnel-like manner along the thickness direction. The average diameter of the first pore is smaller than the average diameter of the second pore. The conductive polymer layer is formed in the first etched region. The liquid component is impregnated in at least the second etched region.

2. The electrolytic capacitor according to claim 1, wherein, The conductive polymer layer is formed from conductive polymer particles. The average particle size of the conductive polymer particles is greater than the average pore diameter of the second pore.

3. The electrolytic capacitor according to claim 1 or 2, wherein, The ratio of the thickness L2 of the second etched region to the thickness L1 of the first etched region, i.e., L2 / L1, is 5 or more and 20 or less.

4. The electrolytic capacitor according to claim 1 or 2, wherein, The average diameter of the first pore is greater than 0.1 μm and less than 1.0 μm.

5. The electrolytic capacitor according to claim 1 or 2, wherein, The average diameter of the second pore is greater than 0.2 μm and less than 1.2 μm.

6. The electrolytic capacitor according to claim 1 or 2, wherein, The average diameter of the first pore is greater than 0.1 μm and less than 1.0 μm. The average diameter of the second pore is greater than 0.2 μm and less than 1.2 μm.

7. The electrolytic capacitor according to claim 1 or 2, wherein, The liquid component comprises at least one solvent selected from lactone compounds, sulfone compounds, glycol compounds, and polyalkylene glycols.

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