Electrolytic capacitor and electrolytic solution used for same

Abstract

This electrolytic solution is used in an electrolytic capacitor provided with a capacitor element containing a conductive polymer. The electrolytic solution contains an organic solvent, a first acid, and a base component. The first acid is an ether group-containing carboxylic acid including a carboxy group, a hydrocarbon moiety, and a linking group that links the carboxy group and the hydrocarbon moiety and includes an oxyalkylene moiety or a poly(oxyalkylene) moiety.

Description

Electrolytic capacitors and the electrolytes used therein Cross-reference of related applications

[0001] This disclosure claims priority with respect to Japanese Patent Application No. 2024-191009, filed with the Japan Patent Office on 30 October 2024, and the entirety of the said patent application is incorporated herein by reference.

[0002] This disclosure relates to an electrolytic capacitor and an electrolyte used therein.

[0003] Electrolytic capacitors are considered promising as small, high-capacity capacitors with low ESR (equivalent series resistance). These capacitors comprise an anode with a dielectric layer, a conductive polymer covering at least a portion of the dielectric layer, and an electrolyte. The conductive polymer includes, for example, a conjugated polymer and a dopant. As the electrolyte, a solution obtained by dissolving a solute in an organic solvent is used.

[0004] As solutes, salts of acidic and basic components are used. As acidic components, aliphatic carboxylic acids and aromatic carboxylic acids are used.

[0005] Patent Document 1 proposes an electrolyte containing a polycarboxylic acid compound having an ether group represented by a specific formula.

[0006] Patent document 2 proposes an electrolyte for electrolytic capacitors containing a dicarboxylic acid and / or a salt thereof having an ether group represented by a specific formula.

[0007] Patent Document 3 proposes an electrolyte for aluminum electrolytic capacitors containing an electrolyte (A), an aprotic solvent (B), and an ether carboxylic acid and / or a salt thereof represented by a specific formula (C).

[0008] International Publication No. 2015 / 147321, Japanese Patent Publication No. 2004-071727, Japanese Patent Publication No. 2012-209433

[0009] The first aspect of this disclosure relates to an electrolyte used in an electrolytic capacitor comprising a capacitor element containing a conductive polymer, wherein the electrolyte comprises an organic solvent, a first acid, and a basic component, and the first acid is an ether group-containing carboxylic acid comprising a carboxyl group, a hydrocarbon moiety, and a linking group that links the carboxyl group and the hydrocarbon moiety and includes an oxyalkylene moiety or a poly(oxyalkylene) moiety.

[0010] A second aspect of this disclosure relates to an electrolytic capacitor comprising a capacitor element and the above-mentioned electrolyte, wherein the capacitor element comprises an anode having a dielectric layer on its surface and a conductive polymer covering a portion of the dielectric layer.

[0011] According to this disclosure, an electrolyte useful for ensuring high voltage resistance and high heat resistance in an electrolytic capacitor containing a conductive polymer can be provided.

[0012] This is a schematic cross-sectional view of an electrolytic capacitor according to one embodiment of the present disclosure. This is a schematic diagram showing a portion of the capacitor element of the electrolytic capacitor shown in Figure 1 in an unfolded view.

[0013] Novel features of the present invention are described in the appended claims, but the present invention, both in terms of structure and content, and in conjunction with other objects and features of the present invention, will be better understood by the following detailed description in conjunction with the drawings.

[0014] In electrolytic capacitors using conductive polymers, the conductive polymer may degrade under high-temperature conditions, leading to a decrease in conductivity. If the electrolytic capacitor contains an electrolyte, the properties of the electrolyte can accelerate the degradation of the conductive polymer, potentially resulting in insufficient heat resistance. Furthermore, depending on the application, electrolytic capacitors may require high voltage resistance.

[0015] In electrolytic capacitors containing conductive polymers, the conductivity of the conductive polymer significantly affects the ESR. When an electrolytic capacitor contains an electrolyte, the conductivity of the conductive polymer is greatly influenced by the electrolyte. For example, in high-temperature environments, conductive polymers are prone to degradation, and the degradation of the electrolyte further accelerates the degradation of the conductive polymer. When conductive polymers degrade, their conductivity decreases not only due to a decrease in the conductivity of the polymer itself, but also due to a decrease in adhesion to the dielectric layer and adhesion within the conductive polymer layer. As a result, the ESR of the electrolytic capacitor increases significantly. On the other hand, in aluminum electrolytic capacitors, conductive polymers are not used, so the electrical connections of the electrolyte and components affect the ESR. Thus, the mechanism of ESR fluctuation in electrolytic capacitors is completely different depending on the presence or absence of conductive polymers. Therefore, generally speaking, using the electrolyte of an aluminum electrolytic capacitor directly in an electrolytic capacitor containing conductive polymers does not necessarily guarantee the same effects as those expected in an aluminum electrolytic capacitor. In particular, in high-temperature environments, while the increase in ESR may not be a significant problem when the voltage applied to the electrolytic capacitor is low, the ESR may increase noticeably when the applied voltage becomes high (for example, above 100V).

[0016] Electrolytes generally contain acidic components such as carboxylic acids. Among carboxylic acids, aliphatic carboxylic acids tend to denature more easily in the electrolyte and have lower heat resistance compared to aromatic carboxylic acids. Therefore, to ensure high heat resistance in electrolytic capacitors, it is generally advantageous to use aromatic carboxylic acids rather than aliphatic carboxylic acids.

[0017] Technical (1) In view of the above, the electrolyte of the present disclosure is used in an electrolytic capacitor comprising a capacitor element containing a conductive polymer. The electrolyte comprises an organic solvent, a first acid, and a basic component. The first acid is an ether group-containing carboxylic acid comprising a carboxyl group, a hydrocarbon moiety, and a linking group that links the carboxyl group and the hydrocarbon moiety and includes an oxyalkylene moiety or a poly(oxyalkylene) moiety.

[0018] By using the first acid, relatively high voltage resistance can be ensured, as well as high heat resistance. More specifically, first, the carboxyl group is bonded to the oxyalkylene or polyoxyalkylene moiety, which provides high voltage resistance to the electrolyte, thus ensuring high voltage resistance to the electrolytic capacitor. The hydrocarbon moiety and linking group suppress the deactivation of the carboxyl group, maintaining high conductivity of the electrolyte and suppressing the rise in pH of the electrolyte. Maintaining a low pH of the electrolyte suppresses dedoping when the electrolytic capacitor is exposed to high-temperature environments or used repeatedly for long periods, thus maintaining high conductivity of the conductive polymer. As a result, the rise in ESR is suppressed. Thus, by using the electrolyte of this disclosure, high heat resistance can be obtained when combined with an electrolytic capacitor using a conductive polymer, even though an aliphatic first acid is used. In particular, even when the voltage applied to the electrolytic capacitor is high (for example, 100V or more) in a high-temperature environment, the increase in ESR can be suppressed. In addition, because the high performance of the electrolyte is maintained even when the electrolytic capacitor is exposed to a high-temperature environment, the film repairability of the dielectric layer covering the surface of the anode is enhanced, and high voltage resistance can be maintained for a long period of time.

[0019] Technology (2) In Technology (1) above, the hydrocarbon moiety may be a linear or branched aliphatic hydrocarbon moiety, or an aromatic hydrocarbon moiety. By using such a first acid, it is easier to obtain higher heat resistance while ensuring high voltage resistance of the electrolytic capacitor. Furthermore, such a first acid is relatively easy to synthesize and obtain.

[0020] Technology (3) In Technology (1) or Technology (2) described above, the hydrocarbon moiety may be a linear or branched aliphatic hydrocarbon moiety having 4 to 20 carbon atoms. Using the first acid having such a hydrocarbon moiety makes it easier to suppress the deactivation of the carboxyl group and to obtain higher heat resistance.

[0021] Technology (4) In any one of the above technologies (1) to (3), the hydrocarbon moiety may be a linear or branched aliphatic hydrocarbon moiety having 6 to 20 carbon atoms. When using the first acid having such a hydrocarbon moiety, higher heat resistance is more easily obtained. In particular, an increase in ESR when a high voltage (for example, a voltage of 100 V or more and 140 V or less) is applied in a high-temperature environment is further suppressed.

[0022] Technology (5) In any one of the above technologies (1) to (4), the linking group may be a -(O-R １ )- group or a -(O-R ｎ１ )-O-R ２ )- group. Here, R ｎ２ and R ３ are each an alkylene group having 1 to 4 carbon atoms, R １ is an alkylene group, and n1 and n2 are each an integer of 1 or more. The linking group is bonded to the hydrocarbon moiety via an oxygen atom O, and is bonded to the carboxy group via the alkylene group R ２ or the alkylene group R ３ . When the linking group has such a structure, higher breakdown voltage resistance is more easily obtained. １ or the alkylene group R ３

[0023] Technology (6) In the above technology (5), n1 may be an integer of 2 or more. In this case, the breakdown voltage resistance can be further increased.

[0024] Technology (7) In the above technology (5), the carbon number of the alkylene group R ３ may be 1 or more and 4 or less. In this case, the synthesis and availability of the first acid are relatively easy. Also, higher breakdown voltage resistance is more easily obtained.

[0025] Technology (8) In any one of the above technologies (1) to (7), the organic solvent may contain an aprotic polar solvent and a protic polar solvent. By the electrolyte containing such a solvent, higher conductivity of the electrolyte and the conductive polymer can be obtained.

[0026] Technology (9) The present disclosure also includes an electrolytic capacitor using the above electrolytic solution. The electrolytic capacitor of the present disclosure includes a capacitor element and an electrolytic solution according to any one of the above technologies (1) to (8). The capacitor element includes an anode body having a dielectric layer on its surface and a conductive polymer covering a part of the dielectric layer.

[0027] Hereinafter, the electrolytic solution and electrolytic capacitor of the present disclosure, including the above technologies (1) to (9), will be described more specifically with reference to the drawings as necessary. In a technically consistent range, at least one of the above technologies (1) to (9) may be combined with at least one of the elements described below. Note that each figure is shown schematically, and the ratios of dimensions (e.g., thickness) of each component member are different from the actual ones.

[0028] [Electrolytic Solution] The electrolytic solution of the present disclosure is used for an electrolytic capacitor including a capacitor element containing a conductive polymer. The electrolytic solution includes an organic solvent, an acid component, and a base component. As the acid component, at least a first acid is used. The acid component may further include a second acid different from the first acid in addition to the first acid as necessary. Further, the electrolytic solution may further include an additive.

[0029] (Acid Component) (First Acid) The first acid includes a carboxy group, a hydrocarbon moiety, and a linking group connecting them. The linking group includes an oxyalkylene moiety or a poly(oxyalkylene) moiety. Therefore, the first acid may be referred to as an ether group-containing carboxylic acid. The first acid has one carboxy group and is also referred to as an ether group-containing monocarboxylic acid.

[0030] In the electrolytic solution, the carboxy group of the first acid may be in a free state, an anion state, or a salt state. In the electrolytic capacitor, in addition to the above states, the carboxy group of the first acid may interact or complex with a component (e.g., a conductive polymer) included in the electrolytic capacitor. In this specification, all these states may be referred to as a carboxy group.

[0031] The hydrocarbon moiety may be aliphatic, alicyclic, or aromatic. From the viewpoint of more easily suppressing the deactivation of the carboxyl group, the hydrocarbon moiety is preferably an aliphatic hydrocarbon moiety or an aromatic hydrocarbon moiety. Furthermore, first acids having these hydrocarbon moieties are relatively easy to synthesize and obtain. The hydrocarbon moiety may be a hydrocarbon group, or a hydrocarbon group having a substituent (sometimes referred to as a first substituent).

[0032] Examples of aliphatic hydrocarbon groups constituting the aliphatic hydrocarbon moiety include alkyl groups, alkenyl groups, and dienyl groups. Examples of alkyl groups include methyl, ethyl, propyl, iso-propyl, butyl, tert-butyl, hexyl, 2-ethylhexyl, decyl, lauryl, myristyl, hexadecyl, and stearyl groups. Examples of alkenyl groups include vinyl, allyl, hexenyl, octenyl, and oleyl groups. Examples of dienyl groups include the monovalent group corresponding to butadiene and isoprene, and the linolyl group. The aliphatic hydrocarbon moiety may be linear or branched. The number of carbon atoms in the aliphatic hydrocarbon moiety or aliphatic hydrocarbon group may be 1 to 26, 1 to 20, 1 to 10, or 1 to 6. In the case of alkenyl groups, the lower limit of these ranges for the number of carbon atoms is 2. In the case of a dienyl group, the lower limit of the above range of carbon atoms is 3. The number of carbon atoms in the aliphatic hydrocarbon moiety or aliphatic hydrocarbon group may have a lower limit of 4 within the above range of carbon atoms. From the viewpoint of further suppressing the deactivation of the carboxyl group, a linear or branched aliphatic hydrocarbon moiety or aliphatic hydrocarbon group having 4 to 20 carbon atoms (preferably 6 to 20) is preferred.

[0033] Examples of alicyclic hydrocarbon groups constituting the alicyclic hydrocarbon moiety include cycloalkyl groups (such as cyclopentyl, cyclohexyl, and cyclooctyl groups), cycloalkenyl groups (such as cyclohexenyl and cyclooctenyl groups), cycloalkadienyl groups (such as cyclopentadienyl and cyclohexadienyl groups), and bridging or condensed alicyclic hydrocarbon groups (such as dicyclopentadienyl and the monovalent group corresponding to indene). The number of carbon atoms in the alicyclic hydrocarbon moiety or alicyclic hydrocarbon group may be 4 to 20, 5 to 14, or 5 to 10.

[0034] Examples of aromatic hydrocarbon groups constituting the aromatic hydrocarbon moiety include phenyl groups, naphthyl groups, and biphenyl groups. The number of carbon atoms in the aromatic hydrocarbon moiety or aromatic hydrocarbon group may be 5 to 20, or 6 to 14.

[0035] Examples of the first substituent include aliphatic hydrocarbon groups, halogen atoms (fluorine atoms, chlorine atoms, bromine atoms, etc.), hydroxyl groups, hydroxyalkyl groups, and alkoxy groups (for example, methoxy groups, ethoxy groups, propoxy groups, butoxy groups, tert-butoxy groups, etc., with alkoxy groups having 1 to 6 or 1 to 4 carbon atoms). Examples of aliphatic hydrocarbon groups include alkyl groups or alkenyl groups, which are exemplified as aliphatic hydrocarbon groups constituting the aliphatic hydrocarbon moiety. The number of carbon atoms in the first substituent aliphatic hydrocarbon group (alkyl group, alkenyl group) may be 1 to 10, 1 to 6, or 1 to 4. In the case of an alkenyl group, the lower limit of this range of carbon atoms is 2. Examples of hydroxyalkyl groups include hydroxymethyl groups, hydroxyethyl groups, and 3-hydroxypropyl groups. The number of carbon atoms in the hydroxyalkyl group is selected from the same range as the number of carbon atoms in the aliphatic hydrocarbon groups described above. Among these, the aliphatic hydrocarbon group and the hydroxyalkyl group may be the first substituent of a hydrocarbon group constituting the alicyclic hydrocarbon moiety or the aromatic hydrocarbon moiety. The aliphatic hydrocarbon group, hydroxyalkyl group, and alkoxy group as the first substituent may be linear or branched. The hydrocarbon moiety may also preferably not have a hydroxyl group. The first substituent may be any atom or group other than a hydroxyl group from the first substituents exemplified above.

[0036] The hydrocarbon moiety may have one first substituent, or two or more first substituents. It is also preferable that it does not have any first substituents. The number of first substituents is selected, for example, depending on the number of carbon atoms in the hydrocarbon moiety or hydrocarbon group. The number of first substituents may be, for example, three or less.

[0037] The linking group connects the carboxyl group to the hydrocarbon moiety. The linking group includes an oxyalkylene moiety or a poly(oxyalkylene) moiety. The poly(oxyalkylene) moiety has two or more oxyalkylene units. In the poly(oxyalkylene) moiety, at least two oxyalkylene units may be the same, or all oxyalkylene units may be different. The poly(oxyalkylene) moiety may be, for example, a poly(oxyethylene) moiety or an oxyethylene-oxypropylene-oxyethylene moiety.

[0038] In the oxyalkylene moiety and the poly(oxyalkylene) moiety, the number of carbon atoms in the alkylene group of the oxyalkylene unit may be 1 to 4, 1 to 3, or 2 or 3. The alkylene group may be linear or branched. Examples of oxyalkylene units include oxyethylene units, oxypropylene units, oxytrimethylene units, and oxybutylene units. The poly(oxyalkylene) moiety may have one of these oxyalkylene units or two or more. In the poly(oxyalkylene) moiety, the number of repeating oxyalkylene units may be 2 to 20, or 2 to 10. Depending on the solvent and the type of hydrocarbon moiety, etc., from the viewpoint of easy dissolution or miscibility in the solvent, the number of repeating oxyalkylene units is preferably 4 to 20, more preferably 4 to 16, and even more preferably 6 to 12.

[0039] The linking group is, for example, -(O-R １ ) ｎ１ -Base or -(O-R) ２ ) ｎ２ -O-R ３ It can be represented by - groups. The linking group is bonded to the hydrocarbon moiety via an oxygen atom O, and the alkylene group R １ or alkylene group R ３ It is bonded to the carboxyl group via [a specific link / mechanism].

[0040] In the above linking group, O-R １ O-R ２ or O-R ３Each part corresponds to an oxyalkylene group or oxyalkylene unit of the oxyalkylene moiety or poly(oxyalkylene) moiety. Alkylene group R １ ~R ３ Each of these may be linear or branched. Alkylene group R １ ~R ３ The number of carbon atoms in each of these is selected, for example, from the range of carbon atoms in the alkylene group of the oxyalkylene unit described above. For example, R １ ~R ３ Each of these atoms may have between 1 and 4 carbon atoms.

[0041] n1 and n2 are integers of 1 or greater, and may also be integers of 2 or greater. When n1 or n2 is 2 or greater, higher dielectric strength is obtained, deactivation of carboxyl groups is more easily suppressed, and the increase in ESR is further suppressed. In addition, higher film repairability of the dielectric layer is obtained, and high dielectric strength is maintained for a long period of time. The upper limits of n1 and n2 can be selected, for example, from the upper limits of the number of repetitions of the oxyalkylene units described above. When n1 is 2 or greater, R １ At least two of them may be the same, and all of them may be different. ２ and R ３ They may be the same or different. If n2 is 2 or greater, R ２ At least two of them may be the same, and they may all be different.

[0042] The linking group may have substituents (sometimes referred to as secondary substituents). Examples of secondary substituents include alicyclic hydrocarbon groups (such as cyclopentyl and cyclohexyl groups), aromatic hydrocarbon groups (such as phenyl groups), halogen atoms (such as the halogen atoms exemplified for the first substituent), hydroxyl groups, and alkoxy groups (such as the alkoxy groups exemplified for the first substituent). The linking group may have one secondary substituent or two or more. The number of secondary substituents can be selected according to the chain length of the linking group and may be four or less. The secondary substituents may be bonded to the main chain or to the side chain of the linking group.

[0043] Preferred first acids include, for example, ether group-containing carboxylic acids represented by the following formula (I) and ether group-containing carboxylic acids represented by the following formula (II).

[0044]

[0045] In equations (I) and (II), R ４ R corresponds to a hydrocarbon moiety (or hydrocarbon group), and is preferably an aliphatic hydrocarbon moiety (or aliphatic hydrocarbon group). Ar is preferably an aromatic hydrocarbon moiety (or aromatic hydrocarbon group). １ ~R ３ n1 and n2 are the same as described above. R １ ~R ３ Each of these is preferably an alkylene group having 1 to 4 carbon atoms. n1 is preferably 2 or less, but may be 1.

[0046] The electrolyte may contain one type of primary acid, or a combination of two or more types.

[0047] The concentration of the first acid in the electrolyte may be 1% by mass or more and 20% by mass or less, 3% by mass or more and 15% by mass or less, or 4% by mass or more and 12% by mass or less. When the concentration of the first acid is within these ranges, higher dielectric strength and higher heat resistance are easily obtained.

[0048] The electrolyte may contain a secondary acid other than the primary acid as an acid component, in addition to the primary acid. The proportion of the primary acid in the acid component may be 25% by mass or more, 30% by mass or more, 50% by mass or more, or 70% by mass or more. The proportion of the primary acid in the acid component is 100% by mass or less. When the proportion of the primary acid is 25% by mass or more, or 30% by mass or more, it is easier to obtain even higher dielectric strength.

[0049] (Secondary Acids) Examples of acids other than primary acids (secondary acids) include carboxylic acid compounds other than primary acids, acids having carbonyloxy bonds other than carboxylic acids (such as oxocarbonic acid and meldrumic acid) or their coordination compounds, phenolic compounds (such as picric acid, p-nitrophenol, pyrogallol, and catechol) or their coordination compounds, sulfur-containing acids (such as sulfuric acid, sulfonic acid (such as aromatic sulfonic acid), oxyaromatic sulfonic acid (such as phenol-4-sulfonic acid)), compounds having sulfonyliimide bonds, boron-containing acids (such as boric acid, halide boric acid (such as tetrafluoroboric acid), or partial esters thereof), phosphorus-containing acids (such as phosphoric acid, halide phosphoric acid (such as hexafluorophosphate), phosphonic acid, phosphinic acid, or partial esters thereof), and nitrogen-containing acids (such as nitric acid and nitrite).

[0050] Examples of carboxylic acid compounds include carboxylic acids other than the first acid (aliphatic carboxylic acids, aromatic carboxylic acids, etc.), carboxylic acid anhydrides, and coordination compounds of carboxylic acids. Examples of aliphatic carboxylic acids include aliphatic polycarboxylic acids (aliphatic polycarboxylic acids with 4 to 12 (or 10 or less) carbon atoms, such as adipic acid, azelaic acid, 1,7-octanedicarboxylic acid, and sebacic acid). Examples of aromatic carboxylic acids include aromatic hydroxy acids (benzoic acid, salicylic acid, etc.), aromatic polycarboxylic acids (phthalic acid, pyromellitic acid, etc.), and sulfo-aromatic carboxylic acids (m-sulfobenzoic acid, 4-sulfophthalic acid, 5-sulfosalicylic acid, etc.). Carboxylic acids other than the first acid also include ether-containing polycarboxylic acids (dicarboxylic acids, tricarboxylic acids, tetracarboxylic acids, etc.) which contain a carboxyl group, a hydrocarbon moiety, and a linking group that connects them, and have a carboxyl group in at least one of the hydrocarbon moiety and the linking group.

[0051] Examples of compounds containing a sulfonylimide bond include saccharin, 1,2-benzenedisulfonamide, cyclohexafluoropropane-1,3-bis(sulfonyl)imide, 4-methyl-N-[(4-methylphenyl)sulfonyl]benzenesulfonamide, dibenzenesulfonamide, trifluoromethanesulfonanilide, N-[(4-methylphenyl)sulfonyl]acetamide, benzenesulfonanilide, and N,N'-diphenylsulfamide.

[0052] Examples of the coordination compounds mentioned above include those comprising at least one central atom selected from the group consisting of boron, aluminum, and silicon, to which a carboxylic acid, an acid having a carbonyloxy bond, or a phenolic compound is bonded. Specific examples of coordination compounds include borodisalicylic acid, borodisuoic acid, borodiglycolic acid, borodigallic acid, borodicatechol, and borodipyrogallol.

[0053] The acid component may contain one secondary acid, or a combination of two or more. Among the secondary acids, ether group-containing polycarboxylic acids, aliphatic polycarboxylic acids, aromatic carboxylic acids (phthalic acid, salicylic acid, benzoic acid, etc.), and the above coordination compounds (borodisalicylic acid, borodisuoic acid, borodiglycolic acid, etc.) are preferred, and among these, adipic acid, phthalic acid, salicylic acid, borodisalicylic acid, etc. are preferred.

[0054] In the electrolyte, the acidic groups of the secondary acid (carboxyl groups, sulfonic acid groups, phosphate groups, phosphonic acid groups, phenolic hydroxyl groups, etc.) may exist in any of the following forms: free form, salt form, anionic form, or form interacting with (compounding with) a conductive polymer. Each of the acidic groups of the secondary acid encompasses all of these forms.

[0055] (Basic component) The presence of a basic component in the electrolyte increases the dissociability of the acid component, making it easier for acidic groups such as carboxyl groups to act on the conductive polymer. Therefore, it is easier to obtain higher conductivity from the conductive polymer.

[0056] Examples of basic components include ammonia, amines (specifically, primary amines, secondary amines, and tertiary amines), quaternary ammonium compounds, and amidinium compounds. The electrolyte may contain one of these basic components or a combination of two or more.

[0057] The amine may be aliphatic, aromatic, or heterocyclic. Examples of amines include dialkylamines (such as diethylamine), trialkylamines (such as trimethylamine, ethyldimethylamine, triethylamine (TEA), tri-n-butylamine (TBA), dimethyl-n-octylamine (DMOA), and dimethyldecylamine (DMDA)), alkylenediamines (such as ethylenediamine), aromatic amines (such as aniline), and heterocyclic amines (such as pyrrolidine, imidazole compounds (such as imidazole (Imd), 1,2,3,4-tetramethylimidazolinium), pyridine (Pyr), 4-dimethylaminopyridine, and diazabicycloundecene (DBU)). Both aromatic amines and heterocyclic amines may be monocyclic or polycyclic (such as fused rings or cross-linked rings). Examples of quaternary ammonium compounds include amidine compounds (including imidazole compounds).

[0058] The electrolyte may contain basic components in free form, in cation form, or in salt form. All of these forms are sometimes collectively referred to as basic components.

[0059] The equivalent ratio of the first acid to the base component (= first acid / base component) may be 0.5 or more and 10 or less, or 1.0 or more and 9.0 or less. The first acid / base component (equivalent ratio) is preferably 1.5 or more and 10 or less, more preferably 2.0 or more and 10 or less (or 3.0 or more and 10 or less), and even more preferably 1.5 or more and 9.0 or less (or 2.0 or more and 9.0 or less). The first acid / base component (equivalent ratio) may be 5.0 or more and 9.0 or less, or 6.0 or more and 9.0 or less. In these cases, a high degree of dissociation of the first acid can be ensured, and electrode corrosion can be suppressed. Furthermore, it is easier to ensure higher dielectric strength.

[0060] The equivalent ratio of the first acid to the base component is (total number of carboxyl groups per molecule of the first acid) / (OH groups that can be generated per molecule of the base component). － This is the ratio of the total number of moles.

[0061] The equivalent ratio of the acid component to the base component (= acid component / base component) may be 0.5 or more and 15 or less, 1.0 or more and 12 or less, or 3.0 or more and 10 or less. The equivalent ratio of the acid component / base component may be selected from the above numerical range described for the equivalent ratio of the first acid / base component.

[0062] The equivalent ratio of the acid component to the base component is (total number of acid groups per molecule of acid component) / (OH groups that can be generated per molecule of base component). － This is the ratio of the total number of moles.

[0063] (Organic solvents) Non-aqueous solvents are examples of organic solvents included in the electrolyte. It is preferable to use at least a polar solvent as the organic solvent. Polar solvents include aprotic polar solvents and protic polar solvents. Examples of such organic solvents include sulfone compounds, lactone compounds, carbonate compounds, and alcohol compounds. The electrolyte may contain one of these organic solvents, or a combination of two or more.

[0064] Among aprotic polar solvents, sulfone compounds include cyclic sulfone compounds (such as sulfolane (SL)) and sulfoxide compounds (such as dimethyl sulfoxide and diethyl sulfoxide). Lactone compounds include γ-butyrolactone (GBL) and γ-valerolactone. Carbonate compounds include linear carbonates (such as dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate) and cyclic carbonates (such as ethylene carbonate, propylene carbonate, and fluoroethylene carbonate).

[0065] Alcohol compounds, which are protic polar solvents, include monohydric alcohols and polyhydric alcohols. Examples of polyhydric alcohols include glycol compounds (alkylene glycols (ethylene glycol (EG), propylene glycol, etc.), polyalkylene glycols (polyethylene glycol (PEG), polypropylene glycol, etc.)), glycerol compounds (glycerol, polyglycerol, etc.), sugar alcohol compounds, or alkylene oxide adducts thereof (ethylene oxide adducts, polyethylene oxide adducts, etc.).

[0066] From the viewpoint of easily obtaining higher conductivity of the electrolyte and conductive polymer, the organic solvent may include a protic polar solvent and an aprotic polar solvent. As the protic polar solvent, at least one selected from the group consisting of glycol compounds and polyalkylene glycols (such as PEG) may be used. When at least polyalkylene glycols (such as PEG) are used as the protic polar solvent, higher heat resistance can be obtained, which is preferable. From the viewpoint of easily obtaining higher dielectric strength, the aprotic polar solvent may include a sulfone compound (such as a cyclic sulfone compound like SL).

[0067] From the viewpoint of easily obtaining higher heat resistance and dielectric strength, the ratio of aprotic polar solvent to the total organic solvent may be 30% by mass or more and 80% by mass or less, or 50% by mass or more and 75% by mass or less. From the viewpoint of easily ensuring high dielectric strength and even higher heat resistance, the ratio of polyalkylene glycol to the total organic solvent may be 5% by mass or more and 50% by mass or less, or 10% by mass or more and 40% by mass or less.

[0068] [Electrolytic Capacitors] The components of an electrolytic capacitor other than the electrolyte will be explained in more detail below.

[0069] (Capacitor element) The capacitor element includes an anode having a dielectric layer on its surface and a conductive polymer covering at least a portion of the dielectric layer. The conductive polymer constitutes at least a portion of the cathode of the capacitor element. The cathode may further include a cathode extraction layer (such as a cathode foil).

[0070] (Anode) The anode may include a valve metal, an alloy containing a valve metal, and a compound containing a valve metal. These materials may be used individually or in combination of two or more. As valve metals, aluminum, tantalum, niobium, and titanium are preferred, for example.

[0071] An anode foil is preferred as the anode body. Preferably, the anode body has a porous portion with pores in at least its surface layer. Other anode bodies include porous sintered bodies or porous molded bodies of particles containing valve metal.

[0072] An anode foil having a porous portion can be obtained, for example, by roughening the surface of a substrate containing a valve-acting metal (such as a foil-shaped or plate-shaped substrate). Surface roughening may be carried out by etching (for example, electrolytic etching or chemical etching).

[0073] (Dielectric layer) The dielectric layer is formed, for example, by anodizing the valve metal on the surface of the anode. Anodizing is carried out, for example, by chemical conversion treatment. The dielectric layer is formed, for example, to cover at least a portion of the surface of the anode.

[0074] The dielectric layer includes, for example, an oxide of the valve metal. For example, when tantalum is used as the valve metal, the dielectric layer is Ta ２ O ５ It includes. When aluminum is used as the valve metal, the dielectric layer is Al ２ O ３ This includes [the specified element]. However, the dielectric layer is not limited to this; any material that functions as a dielectric is acceptable.

[0075] The dielectric layer is typically formed on the surface of the anode. When the dielectric layer is formed on the surface of a porous portion of the anode, it forms along the inner walls of the pores in the porous portion or the depressions (pits) on the anode surface.

[0076] (Conductive Polymer) The conductive polymer includes, for example, a conjugated polymer and a dopant. The conductive polymer covers at least a portion of the dielectric layer. This embodiment includes cases where the conductive polymer is in contact with at least a portion of the dielectric layer. If the capacitor element includes an anode foil and a cathode foil, the conductive polymer may be interposed between these foils. In this case, the conductive polymer may be impregnated into a separator interposed between the anode foil and the cathode foil. The conductive polymer may be in contact with at least a portion of the cathode foil in addition to at least a portion of the dielectric layer. The conductive polymer may constitute a layer. The conductive polymer is sometimes called a solid electrolyte. The conductive polymer constitutes at least a portion of the cathode body in an electrolytic capacitor. The conductive polymer may further contain additives as needed.

[0077] (Conjugated Polymers) Examples of conjugated polymers include known conjugated polymers used in electrolytic capacitors, such as π-conjugated polymers. Examples of conjugated polymers include polymers with polypyrrole, polythiophene, polyaniline, polyfuran, polyacetylene, polyphenylene, polyphenylenevinylene, polyacene, and polythiophenevinylene as their basic skeleton. The above polymers only need to contain at least one monomer unit that constitutes the basic skeleton. The above polymers also include homopolymers, copolymers of two or more monomers, and derivatives thereof (such as substituted products having substituents). For example, polythiophene also includes poly(3,4-ethylenedioxythiophene) (PEDOT).

[0078] Conjugated polymers may be used individually or in combination of two or more types.

[0079] The weight-average molecular weight (Mw) of the conjugated polymer is not particularly limited, and is, for example, between 1,000 and 1,000,000.

[0080] In this specification, weight-average molecular weight (Mw) is a polysaccharide-converted value measured by gel permeation chromatography (GPC). GPC is typically performed using a polyhydroxymethacrylate gel column and an aqueous sodium nitrate solution as the mobile phase.

[0081] (Dopants) Examples of dopants include relatively low-molecular-weight anions and high-molecular-weight anions. Examples of anions include sulfate ions, nitrate ions, phosphate ions, borate ions, organic sulfonate ions, and carboxylate ions. Compounds that produce these anions are used as dopants. Examples of dopants that produce sulfonate ions include aromatic sulfonic acid compounds (such as p-toluenesulfonic acid and naphthalenesulfonic acid). Aromatic sulfonic acid compounds may have, for example, at least one selected from the group consisting of a carboxyl group and a hydroxyl group.

[0082] Examples of polymer anions include polyvinyl sulfonic acid, polystyrene sulfonic acid (PSS), polyallyl sulfonic acid, polyacrylic sulfonic acid, polymethacrylate sulfonic acid, poly(2-acrylamido-2-methylpropanesulfonic acid), polyisoprene sulfonic acid, polyester sulfonic acid (such as aromatic polyester sulfonic acid), phenol sulfonic acid novolac resin, and polyacrylic acid. The polymer anion may be a polymer of a single monomer, a copolymer of two or more monomers, or a substituted product having substituents. Among these, polyanions derived from polystyrene sulfonic acid are preferred.

[0083] However, these dopants are merely examples and are not limited to them. A single dopant may be used alone, or two or more may be used in combination.

[0084] The conductive polymer may be formed, for example, by performing at least one of chemical polymerization and / or electropolymerization of a conjugated polymer precursor on a dielectric layer in the presence of a dopant. Alternatively, a conductive polymer (e.g., a layer of conductive polymer) may be formed by contacting a dielectric layer with a solution in which the conductive polymer is dissolved or a dispersion in which the conductive polymer is dispersed. The conductive polymer used in these solutions or dispersions can be obtained by polymerizing a conjugated polymer precursor in the presence of a dopant. Examples of conjugated polymer precursors include raw material monomers for conjugated polymers, oligomers and prepolymers in which multiple molecular chains of raw material monomers are linked together. One type of precursor may be used, or two or more types may be used in combination.

[0085] The Dopant's Mw is not particularly limited and may be between 1,000 and 1,000,000.

[0086] The amount of dopant contained in the conductive polymer may be 10 parts by mass or more and 1000 parts by mass or 20 parts by mass or more and 500 parts by mass per 100 parts by mass of the conjugated polymer.

[0087] (Cathode Extraction Layer) The cathode extraction layer comprises, for example, a first layer covering at least a portion of a conductive polymer. The cathode extraction layer may also comprise a first layer and a second layer covering the first layer. Examples of the first layer include a layer containing conductive particles and a metal foil (cathode foil). Examples of conductive particles include at least one selected from conductive carbon and metal powder. For example, the cathode extraction layer may be composed of a layer containing conductive carbon (such as graphite) as the first layer (also referred to as a carbon layer) and a layer containing metal powder or a metal foil as the second layer. When a metal foil is used as the first layer, the cathode extraction layer may be composed of this metal foil. The cathode extraction layer can be formed by known methods depending on the layer configuration.

[0088] A second layer containing metal powder can be formed, for example, by laminating a composition containing metal powder onto the surface of the first layer. Examples of such a second layer include a metal particle-containing layer (such as a silver particle-containing layer) formed using a composition containing metal particles such as silver particles and a resin (binder resin). As the resin, a thermosetting resin such as an imide resin or epoxy resin may be used, or a thermoplastic resin may be used.

[0089] When using metal foil as the first layer, the type of metal is not particularly limited, but it is preferable to use valve metals such as aluminum, tantalum, or niobium, or alloys containing valve metals. The surface of the metal foil may be roughened as needed. The surface of the metal foil may be coated with a chemical conversion film, or a coating of a metal different from the metal constituting the metal foil (dissimilar metal) or a nonmetal. Examples of dissimilar metals or nonmetals include metals such as titanium and nonmetals such as carbon (conductive carbon, etc.).

[0090] The above-mentioned dissimilar metal or nonmetal (for example, conductive carbon) coating may be used as the first layer, and the above-mentioned metal foil may be used as the second layer.

[0091] (Separator) A separator may be placed between the cathode (cathode foil, etc.) and the anode (anode foil, etc.). The separator is not particularly limited, and for example, nonwoven fabrics containing fibers of cellulose, polyethylene terephthalate, vinylon, or polyamide (e.g., aliphatic polyamide, aromatic polyamide such as aramid) may be used.

[0092] If the capacitor element includes a separator, the conductive polymer may be impregnated into the separator. The conductive polymer may be interposed between the anode (such as an anode foil) and the cathode (such as a cathode foil), and may be in contact with at least a portion of the dielectric layer and at least a portion of the cathode.

[0093] (Other) Electrolytic capacitors may be wound type, chip type, or multilayer type. Electrolytic capacitors have at least one capacitor element. Electrolytic capacitors may have multiple capacitor elements. For example, an electrolytic capacitor may have a multilayer structure of two or more capacitor elements, or it may have two or more wound type capacitor elements. The configuration or number of capacitor elements may be selected depending on the type or application of the electrolytic capacitor.

[0094] In a capacitor element, one end of the cathode lead is electrically connected to the cathode lead-out layer. One end of the anode lead is electrically connected to the anode body. The other end of the anode lead and the other end of the cathode lead are led out from the outer casing or case, respectively. The other ends of each lead exposed from the outer casing or case are used for soldering to the substrate on which the electrolytic capacitor is to be mounted. Each lead may be a lead wire or a lead frame.

[0095] The electrolyte of this disclosure can be used in electrolytic capacitors, such as hybrid electrolytic capacitors. The electrolytic capacitors of this disclosure have high voltage resistance and high heat resistance. Therefore, the electrolytic capacitors of this disclosure are particularly suitable for a variety of applications where high voltage resistance, high reliability, or long lifespan are required. However, the applications of electrolytic capacitors are not limited to these.

[0096] Figure 1 is a schematic cross-sectional view of an electrolytic capacitor according to one embodiment of the present disclosure, and Figure 2 is a schematic diagram showing a part of the capacitor element relating to the electrolytic capacitor unfolded. However, the electrolytic capacitor of the present disclosure is not limited to the following embodiments. Furthermore, the components of the following embodiments may be arbitrarily combined with at least one of the above technologies (1) to (8) relating to the electrolytic capacitor of the present disclosure, or at least one of the above technologies (1) to (8) and the components described above.

[0097] An electrolytic capacitor comprises, for example, a capacitor element 10, a bottomed case 101, a sealing member 102 that closes the opening of the bottomed case 101, a base plate 103 that covers the sealing member 102, lead wires 104A, 104B, and lead tabs 105A, 105B. The bottomed case 101 houses the capacitor element 10 and an electrolyte (not shown). The area near the opening end of the bottomed case 101 is tapered inward, and the opening end is curled so as to be crimped to the sealing member 102. The lead wires 104A and 104B are led out from the sealing member 102 and pass through the base plate 103. The lead tabs 105A and 105B connect the lead wires 104A and 104B to the electrodes of the capacitor element 10, respectively.

[0098] The capacitor element 10 is, for example, a wound body as shown in Figure 2. The wound body comprises an anode foil 11 connected to a lead tab 105A, a cathode foil 12 connected to a lead tab 105B, and a separator 13. The anode foil 11 and the cathode foil 12 are wound around the separator 13. The outermost circumference of the wound body is secured by a winding stopper tape 14. Note that Figure 2 shows the state in which a portion of the wound body is unfolded before securing the outermost circumference.

[0099] In the capacitor element 10, a dielectric layer (not shown) is formed on at least a portion of the surface of the anode foil 11. A separator 13 and a conductive polymer (not shown) are interposed between the anode foil 11 and the cathode foil 12. The conductive polymer is in contact with at least a portion of the dielectric layer. The conductive polymer is also in contact with at least a portion of the cathode foil 12. The conductive polymer and the separator are impregnated with an electrolyte. As the electrolyte, the electrolyte described herein, which contains an organic solvent, a first acid, and a basic component, is used.

[0100] [Examples] The electrolyte and electrolytic capacitor according to the present disclosure will be described in detail below based on examples and comparative examples. However, the electrolyte and electrolytic capacitor according to the present disclosure are not limited to the following examples. The components described in the following examples may be combined with the conceptual description above, which includes at least one of the technologies (1) to (7).

[0101] 《Production Example 1》 Under a nitrogen atmosphere, a methanol solution containing sodium methoxide at a concentration of 28% by mass was added to polyoxyethylene octyl ether having an average number of moles of ethylene oxide added of 7. At this time, the proportions of polyoxyethylene octyl ether and sodium methoxide were adjusted to 1 mol:1 mol. The resulting mixture was distilled at 80°C and atmospheric pressure, and then further distilled under reduced pressure to completely remove methanol. Potassium tertoxide (0.1 mol) and sodium monochloroacetate (1.2 mol) were added to the resulting residue. The resulting mixture was heated at 110°C with stirring for 3 hours and then allowed to cool. The reaction mixture was washed with a 7% by mass aqueous sulfuric acid solution. The organic phase was washed with distilled water. The organic phase after washing was removed and concentrated under reduced pressure. In this way, the first acid represented by the following formula (A1) was produced.

[0102]

[0103] <Production Example 2> Instead of polyoxyethylene octyl ether with an average number of moles of ethylene oxide added of 7, polyoxyethylene octyl ether with an average number of moles of ethylene oxide added of 4 was used. Except for this, the first acid represented by the following formula (A2) was produced using the same procedure as in Production Example 1.

[0104]

[0105] <Production Example 3> Instead of polyoxyethylene octyl ether, which has an average number of moles of ethylene oxide added of 7, polyoxyethylene isotridecyl ether, which also has an average number of moles of ethylene oxide added of 7, was used. Aside from this, the first acid represented by the following formula (A3) was produced using the same procedure as in Production Example 1.

[0106]

[0107] Examples 1-11 and Comparative Examples 1-2: Wound-wound electrolytic capacitors (electrolytic capacitor I with a rated voltage of 25V and a rated capacitance of 330μF, and electrolytic capacitor II with a rated voltage of 125V and a rated capacitance of 18μF) were fabricated and evaluated using the following procedure.

[0108] (Preparation of the anode) A 100 μm thick aluminum foil was etched to roughen its surface. Then, a dielectric layer was formed on the surface of the aluminum foil by chemical conversion treatment. The chemical conversion treatment was performed by immersing the aluminum foil in an ammonium adipate solution and applying a voltage to it. After that, the aluminum foil was cut to a size of 8 mm x 120 mm to prepare the anode.

[0109] (Preparation of the cathode) A 50 μm thick aluminum foil was etched to roughen its surface. Then, the aluminum foil was cut to a size of 8 mm x 120 mm to prepare the cathode.

[0110] (Fabrication of the wound body) Anode lead tabs and cathode lead tabs were connected to the anode and cathode bodies, and the anode and cathode bodies were wound together with paper separators, winding the lead tabs as they were wound. Anode lead wires and cathode lead wires were connected to the ends of each lead tab protruding from the wound body. Then, the fabricated wound body was subjected to another chemical conversion treatment to form a dielectric layer on the cut end of the anode body. Next, the ends of the outer surface of the wound body were fixed with winding tape to fabricate the wound body.

[0111] (Preparation of polymer dispersion containing conductive polymer) 3,4-ethylenedioxythiophene and the polymer dopant poly(4-styrenesulfonic acid) (PSS, Mw 100,000) were dissolved in deionized water to prepare a mixed solution. While stirring the mixed solution, an oxidizing agent (ferrous sulfate and ammonium persulfate) 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 polymer dispersion containing PSS-doped poly(3,4-ethylenedioxythiophene) (PEDOT / PSS) as the conductive polymer was obtained. The Mw of the polymer dopant is the value measured under the conditions described above.

[0112] (Coating of the dielectric layer with conductive polymer) The wound body was immersed in a polymer dispersion contained in a predetermined container for 5 minutes in a reduced-pressure atmosphere (40 kPa), and then the wound body was removed from the polymer dispersion. Next, the wound body impregnated with the polymer dispersion was dried in a drying oven at 150°C for 20 minutes, and at least a portion of the dielectric layer was coated with a conductive polymer. A capacitor element was formed in this way. However, in Comparative Examples 8 to 10, the capacitor element was formed without performing this step of coating the dielectric layer with a conductive polymer.

[0113] (Impregnation of electrolyte) As the solvent for the electrolyte, a mixture obtained by mixing EG, PEG (number average molecular weight Mn: 300), and SL in a volume ratio of EG:PEG:SL = 1:1:1 was used. The electrolyte was prepared by dissolving the acid and base components shown in Table 1 or Table 2 in this mixture. The total concentration of the first and second acids in the electrolyte was set to 4% by mass to 12% by mass. Tables 1 and 2 also show the equivalent ratio of the first acid to the base component. For comparative examples in Table 1 or Table 2, the equivalent ratio of the second acid to the base component is shown in parentheses in the column for the equivalent ratio of the first acid to the base component. As the acid component, in the examples, the first acids (A1) to (A3) produced in Production Examples 1 to 3, or the first acid (A4) or (A5) below were used. In Example 6, the first acid (A1) and the second acid, adipic acid (AA), were used as the acid component. In Example 6, the proportion of the primary acid in the acidic component was 33% by mass. In Comparative Examples 1 and 2, nonanoic acid and benzoic acid, which are secondary acids, were used, respectively.

[0114] (A4): (2-butoxyethoxy)acetic acid represented by the following formula (A4) (A5): 2-phenoxypropionic acid represented by the following formula (A5)

[0115]

[0116] The basic components used were triethylamine (TEA), dimethyldecylamine (DMDA), imidazole (Imd), pyridine (Pyr), or diazabicycloundecene (DBU).

[0117] (Assembly of electrolytic capacitors) The capacitor elements were immersed in the electrolyte and placed in a reduced pressure atmosphere (40 kPa) for 5 minutes to allow the electrolyte to penetrate the capacitor elements.

[0118] A capacitor element impregnated with electrolyte was housed in a bottomed case, with the lead wires positioned on the opening side of the bottomed case. A sealing member, formed to allow the lead wires to pass through, was placed above the capacitor element. Then, a drawing process was performed near the opening end of the bottomed case, and the opening end was further curled to create a tight seal with the sealing member. In this way, the capacitor element and electrolyte were sealed inside the bottomed case. By placing a base plate on the curled portion, an electrolytic capacitor as shown in Figure 1 was completed. For each example, a total of 40 electrolytic capacitors I and a total of 20 electrolytic capacitors II were manufactured. The manufactured electrolytic capacitors were subjected to an aging process at 130°C for 2 hours while applying the rated voltage.

[0119] [Evaluation] The electrolytic capacitors fabricated as described above were evaluated according to the following (1) and (2).

[0120] (1) ESR values ​​were measured for electrolytic capacitors I and II after ESR aging treatment using an LCR meter at a frequency of 100 kHz in an environment of 20°C. The average value of the measured values ​​for 40 electrolytic capacitors I and 20 electrolytic capacitors II (initial ESR value: r0 (Ω)) was then calculated.

[0121] After determining r0, accelerated tests were performed on electrolytic capacitors I under the following conditions 1 and 2, and on electrolytic capacitors II under the following condition 3. Condition 1 (No-load accelerated test): 20 of the 40 electrolytic capacitors I were left standing at 145°C for 750 hours. Condition 2 (25V load accelerated test): The remaining 20 electrolytic capacitors I from the no-load accelerated test were subjected to a rated voltage (25V) at 145°C for 750 hours. Condition 3 (125V load accelerated test): A voltage of 125V was applied to 20 electrolytic capacitors II at 145°C for 750 hours.

[0122] For each electrolytic capacitor I and II after each accelerated test, the average ESR value (r1 (Ω)) after the accelerated test was calculated in the same manner as for the initial ESR value.

[0123] Using the obtained values ​​of r0 and r1, the ESR change (ΔESR) was calculated using the following formula: ΔESR = r1 / r0

[0124] (2) Withstand Voltage Characteristics The withstand voltage characteristics were measured using the following procedure. First, a sample of electrolytic capacitor for evaluating the withstand voltage characteristics was prepared in accordance with the example or comparative example. More specifically, a 120 μm thick aluminum foil was treated by applying a voltage of 630 V while immersed in an ammonium adipate solution, and then cut to a size of 14 mm in length and 110 mm in width. In this way, an anode foil (anode body) having a dielectric layer was prepared. A 22 μm thick aluminum foil was treated by applying a voltage of 2 V while immersed in an ammonium adipate solution, and then cut to a size of 14 mm in length and 135 mm in width. In this way, a cathode foil (cathode body) having a dielectric layer was prepared. The obtained anode foil and cathode foil having a dielectric layer were used. Except for these, a total of five electrolytic capacitors were prepared using the same procedure as in the example or comparative example, and then subjected to aging treatment.

[0125] An electrolytic capacitor was placed in a constant temperature bath set to 145°C, and a DC current was applied to the electrolytic capacitor by connecting the leads to a power supply. At this time, the current density per unit area was 3 mA / cm² relative to the area of ​​the anode foil (the area of ​​the projected shape when the anode foil is projected in the thickness direction). ２ The applied DC current was adjusted to achieve the following result. This caused voltage fluctuations, such as increases and decreases in the electrolytic capacitor's voltage. During this time, when the voltage increase of the electrolytic capacitor subsided and several points of voltage decrease appeared, the voltage at the second point was measured. This voltage was measured for five electrolytic capacitors, and the average value was calculated. This average value was used as an indicator of the voltage withstand characteristic. The table shows the relative values ​​when the value of the capacitor in Comparative Example 1 is set to 100. A larger value indicates better voltage withstand characteristics and superior performance of the electrolytic capacitor.

[0126] The evaluation results for each electrolytic capacitor are shown in Table 1 or Table 2. In Tables 1 and 2, E1 to E11 are Examples 1 to 11, and C1 to C2 are Comparative Examples 1 and 2.

[0127]

[0128] As shown in Table 1, the increase in ESR was suppressed in the examples compared to the comparative example, even after the no-load accelerated test and the 25V and 100V load accelerated tests. In the 125V load accelerated test, the electrolytic capacitor of Comparative Example 2 was deemed undetectable (ND) because the internal pressure increased during the test and the safety valve opened. In addition, relatively high withstand voltage was obtained in the examples. From the viewpoint of ensuring even higher withstand voltage, it is preferable that the hydrocarbon part of the first acid is an aliphatic hydrocarbon part. From the viewpoint of further suppressing the increase in ESR after the 125V load accelerated test, it is preferable that the hydrocarbon part of the first acid is an aliphatic hydrocarbon part or an aromatic hydrocarbon part with 6 or more carbon atoms (for example, 6 to 20).

[0129]

[0130] As shown in Table 2, even when using the first and second acids, the high effectiveness of the first acid is ensured (comparison between E1 and E6). Furthermore, high dielectric strength was obtained even when using base components other than TEA, and the rise in ESR was suppressed after both the no-load accelerated test and the 25V and 100V load accelerated tests.

[0131] Although the present invention has been described in relation to preferred embodiments at present, such disclosure should not be interpreted restrictively. Various modifications and alterations will undoubtedly become apparent to those skilled in the art in the field to which the invention pertains by reading the above disclosure. Accordingly, the appended claims should be interpreted as encompassing all modifications and alterations without departing from the true spirit and scope of the invention.

[0132] 100: Electrolytic capacitor 101: Bottomed case 102: Sealing material 103: Base plate 104A, 104B: Lead wires 105A, 105B: Lead tabs 10: Capacitor element 11: Anode foil 12: Cathode foil 13: Separator 14: Winding tape

Claims

1. An electrolyte for use in an electrolytic capacitor comprising a capacitor element containing a conductive polymer, wherein the electrolyte comprises an organic solvent, a first acid, and a basic component, and the first acid is an ether group-containing carboxylic acid comprising a carboxyl group, a hydrocarbon moiety, and a linking group that connects the carboxyl group and the hydrocarbon moiety and includes an oxyalkylene moiety or a poly(oxyalkylene) moiety.

2. The electrolyte according to claim 1, wherein the hydrocarbon moiety is a linear or branched aliphatic hydrocarbon moiety, or an aromatic hydrocarbon moiety.

3. The electrolyte according to claim 1, wherein the hydrocarbon moiety is a linear or branched aliphatic hydrocarbon moiety having 4 to 20 carbon atoms.

4. The electrolyte according to claim 1, wherein the hydrocarbon moiety is a linear or branched aliphatic hydrocarbon moiety having 6 to 20 carbon atoms.

5. The linking group is -(O-R １ ). ｎ１ - group or -(O-R ２ ). ｎ２ -O-R ３ - group, and R １ and R ２ are each an alkylene group having 1 to 4 carbon atoms, R ３ is an alkylene group, n1 and n2 are each an integer of 1 or more, the linking group is bonded to the hydrocarbon moiety via an oxygen atom O, and is bonded to the carboxy group via the alkylene group R １ or the alkylene group R ３ . The electrolytic solution according to any one of claims 1 to 4.

6. The electrolyte according to claim 5, wherein n1 is an integer of 2 or more.

7. The alkylene group R ３ The electrolyte according to claim 5, wherein the number of carbon atoms is 1 or more and 4 or less.

8. The electrolyte according to any one of claims 1 to 4, wherein the organic solvent comprises a non-protic polar solvent and a protic polar solvent.

9. An electrolytic capacitor comprising a capacitor element and an electrolyte according to any one of claims 1 to 4, wherein the capacitor element comprises an anode having a dielectric layer on its surface and a conductive polymer covering a portion of the dielectric layer.

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