Electrolyte for electrolytic capacitors, electrolytic capacitors using the said electrolyte, and hybrid electrolytic capacitors

Abstract

Provided is an electrolyte that has high initial conductivity, little change over time, and causes less corrosion of capacitor members. Also provided are an aluminum electrolytic capacitor and a hybrid electrolytic capacitor that use the electrolyte and have low initial ESR and little change over time. This electrolyte for an electrolytic capacitor includes an acid component (A), a base component (B), and an organic solvent (C). The acid component (A) includes an acid component (A1) and / or an acid component (A2) that are represented by a specified formula. The total acid component (A1) and acid component (A2) content is at least 50% by mass of the mass of the acid component (A). The base component (B) includes at least one type of component selected from the group consisting of ammonium, a primary amine (B1), a secondary amine (B2), and a tertiary amine (B3).

Description

Technical Field

[0001] The present invention relates to an electrolytic solution for an electrolytic capacitor, an electrolytic capacitor using the electrolytic solution, and a hybrid electrolytic capacitor.

Background Art

[0002] From the viewpoint of preventing the dry-up of the electrolytic solution, there are electrolytic capacitors and hybrid aluminum electrolytic capacitors that use an electrolytic solution having a low sealing rubber permeability and using a polyhydric alcohol such as ethylene glycol, which is a high-boiling solvent, as a solvent. In such electrolytic capacitors, problems include a decrease in the conductivity of the electrolytic solution due to an esterification reaction between the polyhydric alcohol and the carboxylic acid, which is an electrolyte, at high temperatures, and deterioration of the conductive polymer accompanying an increase in pH.

[0003] Therefore, in order to solve this problem, in Patent Document 1, an electrolytic solution containing a carboxylic acid and a compound having a structure in which a linear alkyl group having 3 or more carbon atoms is bonded to one of the carbon atoms of the ketone group and a branched alkyl group is bonded to the other is proposed. In Patent Document 2, an electrolytic solution using a salt of phosphonic acid or phosphinic acid anion and 1,2,3,4-tetramethylimidazolinium as an electrolyte is proposed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, the electrolyte using the ketone group-containing compound described in Patent Document 1 is not sufficient as a solution because it cannot completely inhibit esterification. Furthermore, the electrolyte using phosphonic acid or phosphinate anion and 1,2,3,4-tetramethylimidazolinium salt described in Patent Document 2 has the problem that the aluminum oxide, which is the anode foil of the electrolytic capacitor, is not adequately protected, and the aluminum oxide corrodes due to the electrolyte when stored at high temperatures for a long period of time.

[0006] One aspect of the present invention aims to provide an electrolyte that has high initial conductivity, small changes over time, and reduced corrosion of capacitor components. Another aspect of the present invention aims to provide an electrolytic capacitor and a hybrid electrolytic capacitor using the above-mentioned electrolyte that have low initial ESR (equivalent series resistance) and small changes over time. [Means for solving the problem]

[0007] The inventors of this invention arrived at this present invention as a result of their research in order to achieve the above objectives.

[0008] In other words, one aspect of the present invention is an electrolyte for an electrolytic capacitor comprising an acid component (A), a basic component (B), and an organic solvent (C), The acid component (A) comprises the acid component (A1) represented by the following general formula (1) and / or the acid component (A2) represented by the following general formula (2). The sum of the content of acid component (A1) and the content of acid component (A2) is 50% by weight or more based on the weight of acid component (A), The basic component (B) is an electrolyte for electrolytic capacitors containing at least one component selected from the group consisting of ammonium, primary amine (B1), secondary amine (B2), and tertiary amine (B3). Another aspect of the present invention is an electrolytic capacitor and a hybrid electrolytic capacitor using the electrolyte. [ka] [In formula (1), X represents a hydrocarbon group having 3 to 20 carbon atoms that may have a hydroxyl group, and Y represents a hydrogen atom, a hydrocarbon group having 1 to 10 carbon atoms that may have a hydroxyl group, or a residue obtained by removing one hydrogen atom from the hydroxyl group of a polyalkylene glycol.] [ka] [In equation (2), the two Zs each independently represent a hydrocarbon group having 1 to 6 carbon atoms.] [Effects of the Invention]

[0009] According to one aspect of the present invention, an electrolyte with high initial conductivity, minimal change over time, and reduced corrosion of capacitor components can be provided. According to another aspect of the present invention, an electrolytic capacitor and a hybrid electrolytic capacitor using the electrolyte with low initial ESR and minimal change over time can be provided. [Modes for carrying out the invention]

[0010] <Acid component> The acid component (A) contained in the electrolyte according to one embodiment of the present invention includes the acid component (A1) represented by the general formula (1) and / or the acid component (A2) represented by the general formula (2).

[0011] In the acid component (A1) mentioned above, the number of carbon atoms in X is 3 to 20, preferably 4 to 8, and particularly preferably 6, from the viewpoint of conductivity and aluminum corrosivity. Y is a hydrogen atom, a hydrocarbon group having 1 to 10 carbon atoms which may have a hydroxyl group, or a residue obtained by removing one hydrogen atom from the hydroxyl group of a polyalkylene glycol, and is preferably a hydrogen atom from the viewpoint of conductivity and aluminum corrosivity.

[0012] Examples of the acid component (A1) include (n-propyl)phosphonic acid, (iso-propyl)phosphonic acid, (n-butyl)phosphonic acid, (iso-butyl)phosphonic acid, (tert-butyl)phosphonic acid, pentylphosphonic acid, hexylphosphonic acid, phenylphosphonic acid, (4-hydroxyphenyl)phosphonic acid, heptylphosphonic acid, octylphosphonic acid (such as n-octylphosphonic acid), n-eicosanphosphonic acid, dehydration condensate of phenylphosphonic acid and methanol, dehydration condensate of phenylphosphonic acid and ethanol, dehydration condensate of phenylphosphonic acid and ethylene glycol, dehydration condensate of phenylphosphonic acid and glycerin, and dehydration condensate of phenylphosphonic acid and polyethylene glycol. Examples of polyethylene glycol that undergoes dehydration condensation with phenylphosphonic acid include diethylene glycol, triethylene glycol, tetraethylene glycol, pentaethylene glycol, hexaethylene glycol, and heptaethylene glycol.

[0013] The acid component (A1) may be one type or two or more types in combination.

[0014] In the acid component (A2) mentioned above, the two Zs each independently represent a hydrocarbon group having 1 to 6 carbon atoms. The number of carbon atoms in Z is preferably 2 to 6, and particularly preferably 4 to 6, from the viewpoint of conductivity and aluminum corrosion resistance.

[0015] Examples of the acid component (A2) include dimethylphosphinic acid, diethylphosphinic acid, di(n-propyl)phosphinic acid, di(iso-propyl)phosphinic acid, di(n-butyl)phosphinic acid, di(iso-butyl)phosphinic acid, di(tert-butyl)phosphinic acid, dipentylphosphinic acid, dihexylphosphinic acid, diphenylphosphinic acid, methylethylphosphinic acid, methyl(n-propyl)phosphinic acid, methyl(iso-propyl)phosphinic acid, methyl(n-butyl)phosphinic acid, methyl(iso-butyl)phosphinic acid, methyl(tert-butyl)phosphinic acid, methylpentylphosphinic acid, methylhexylphosphinic acid, methylheptylphosphinic acid, methyloctylphosphinic acid, ethyl(n-propyl)phosphinic acid, ethyl(iso-propyl)phosphinic acid, ethyl(n-butyl)phosphinic acid, ethyl(iso-butyl)phosphinic acid, ethyl(tert-butyl)phosphinic acid, ethylpentylphosphinic acid anion, ethylhexylphosphinic acid, and the like.

[0016] The acid component (A2) may be used alone or in combination of two or more.

[0017] Among the acid components (A), from the viewpoints of conductivity and aluminum corrosiveness, the acid component (A1) is preferred, and more preferably one or more selected from the group consisting of (n-butyl)phosphonic acid, (iso-butyl)phosphonic acid, (tert-butyl)phosphonic acid, pentylphosphonic acid, hexylphosphonic acid, phenylphosphonic acid, (4-hydroxyphenyl)phosphonic acid, heptylphosphonic acid, and octylphosphonic acid, and particularly preferably phenylphosphonic acid.

[0018] The acid component (A) in one embodiment of the present invention may also include an acid component (A3) other than the acid components (A1) and (A2). Examples of the acid component (A3) include carboxylic acids, phosphonic acids and phosphinic acids other than the acid component (A1), sulfonic acids, and the like.

[0019] Examples of the carboxylic acid include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, 2-methylazelaic acid, sebacic acid, 1,5-octanedicarboxylic acid, 4,5-octanedicarboxylic acid, 1,9-nonanedicarboxylic acid, 1,10-decanedicarboxylic acid, 1,6-decanedicarboxylic acid, 5,6-decanedicarboxylic acid, benzoic acid, phthalic acid, isophthalic acid, terephthalic acid, and the like.

[0020] Examples of the phosphonic acid and phosphinic acid other than the acid component (A1) include methylphosphonic acid, ethylphosphonic acid, n-heneicosanephosphonic acid, hypophosphorous acid, diheptylphosphinic acid, dioctylphosphinic acid, dinonylphosphinic acid, and the like.

[0021] Examples of the sulfonic acid include alkylsulfonic acid (such as methylsulfonic acid and ethylsulfonic acid), benzenesulfonic acid, and alkylbenzenesulfonic acid (such as toluenesulfonic acid and dodecylbenzenesulfonic acid), and the like.

[0022] [[ID=eleven]] The total content of the acid component (A1) and the acid component (A2) is 50% by weight or more based on the weight of the acid component (A), preferably 80% by weight or more, more preferably 95% by weight or more, and particularly preferably 100% by weight from the viewpoint of stability over time.

[0023] The content of the acid component (A) in one embodiment of the present invention is preferably 1 to 20% by weight, more preferably 3 to 17% by weight based on the weight of the electrolytic solution for an electrolytic capacitor from the viewpoint of pH adjustment of the solution.

[0024] The base component (B) in one embodiment of the present invention contains at least one component selected from the group consisting of ammonium, primary amine (B1), secondary amine (B2), and tertiary amine (B3). [[ID=2|1]]

[0025] Examples of the primary amine (B1) include methylamine, ethylamine, propylamine, isopropylamine, cyclohexylamine, and the like.

[0026] Examples of secondary amines (B2) include dimethylamine, diethylamine, methylethylamine, methylpropylamine, methylisopropylamine, morpholine, N-methyl-N-[2-(N'-methylamino)propyl]acetamide, N-methyl-N-[2-(N'-methylamino)-1-methylethyl]acetamide, N-ethyl-N-[2-(N'-methylamino)ethyl]acetamide, N-methyl-N-[2-(N'-methylamino)ethyl]acetamide, N-methyl-N-[2-(N'-ethylamino)propyl]acetamide, N-ethyl-N-[2-(N'-methylamino)-1-methylethyl]acetamide, N-methyl-N-[2-(N'-methylamino)ethyl]propionamide, and N-methyl-N-[2-(N'-methylamino)ethyl]propionamide.

[0027] Examples of tertiary amines (B3) include trimethylamine, triethylamine, dimethylethylamine, dimethylpropylamine, dimethylisopropylamine, triethanolamine, pyridine, 4-methylmorpholine, 4-ethylmorpholine, 4-(2-hydroxyethyl)morpholine, 4-(2-hydroxypropyl)morpholine, ethylene oxide adducts of cyclohexylamine, and propylene oxide adducts of cyclohexylamine.

[0028] The total content of ammonium, primary amine (B1), secondary amine (B2), and tertiary amine (B3) is preferably 0.01 to 15% by weight, and more preferably 1 to 10% by weight, based on the weight of the electrolyte for the electrolytic capacitor, from the viewpoint of preventing corrosion of the aluminum foil.

[0029] The basic component (B) may include basic components (B4) other than ammonium, primary amines (B1), secondary amines (B2), and tertiary amines (B3). Examples of basic components (B4) include quaternary ammonium and amidinium.

[0030] Examples of quaternary ammonium compounds include tetramethylammonium, ethyltrimethylammonium, diethyldimethylammonium, triethylmethylammonium, and tetraethylammonium.

[0031] Examples of amidinium include imidazolinium, cations in which the hydrogen atoms of imidazolinium are replaced with alkyl groups (such as 1,2,3,4-tetramethylimidazolinium, 1,3,4-trimethyl-2-ethylimidazolinium, 1,3-dimethyl-2,4-diethylimidazolinium, and 1,2-dimethyl-3,4-diethylimidazolinium), imidazolium, and cations in which the hydrogen atoms of imidazolium are replaced with alkyl groups (such as 1,3-dimethylimidazolium, 1,3-diethylimidazolium, 1-ethyl-3-methylimidazolium, and 1,2,3-trimethylimidazolium).

[0032] The base component (B) may contain two or more of these base components.

[0033] Of these basic components (B), from the viewpoint of thermal stability, one or more are preferably selected from the group consisting of secondary amines (B2) and tertiary amines (B3), and more preferably tertiary amines (B3).

[0034] In one embodiment of the present invention, the content of the basic component (B) is preferably 0.1 to 15% by weight, and more preferably 1 to 10% by weight, based on the weight of the electrolyte for the electrolytic capacitor, from the viewpoint of adjusting the pH of the electrolyte.

[0035] <organic solvents> In one embodiment of the present invention, the organic solvent (C) preferably contains at least one component selected from polyhydric alcohols, sulfone compounds, lactone compounds, and carbonate compounds.

[0036] Examples of polyhydric alcohols include alkylene glycols, glycerin components, and sugar alcohols.

[0037] Examples of alkylene glycols include ethylene glycol, propylene glycol, and polyalkylene glycols having a repeating alkylene oxide structure. Examples of alkylene oxides include ethylene oxide, propylene oxide, trimethylene oxide, and butylene oxide. Polyalkylene glycols may contain one alkylene oxide unit or two or more alkylene oxide units. Examples of polyalkylene glycols include polyethylene glycols (diethylene glycol, triethylene glycol, tetraethylene glycol, pentaethylene glycol, hexaethylene glycol, heptaethylene glycol, octaethylene glycol, etc.).

[0038] Examples of glycerin components include glycerin, alkylene oxide adducts of glycerin, polyglycerin, and alkylene oxide adducts of polyglycerin.

[0039] Examples of sugar alcohols include tetriitol, pentitol, mannitol, sorbitol, heptitol, and octitol.

[0040] Examples of sulfone compounds include sulfolanes, dimethyl sulfoxides, and diethyl sulfoxides.

[0041] Examples of lactone compounds include γ-butyrolactone and γ-valerolactone.

[0042] Examples of carbonate compounds include dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, ethylene carbonate, propylene carbonate, and fluoroethylene carbonate.

[0043] Organic solvent (C) may contain two or more of these organic solvents.

[0044] Of these organic solvents (C), polyhydric alcohols are preferred from the viewpoint of preventing the electrolyte from drying up, more preferably alkylene glycols, glycerin components, and sugar alcohols, particularly preferably alkylene glycols and glycerin, and most preferably ethylene glycol.

[0045] When the organic solvent (C) contains a polyhydric alcohol, the polyhydric alcohol content is preferably 50% by weight or more, more preferably 90% by weight or more, and particularly preferably 100% by weight, based on the weight of the organic solvent (C), from the viewpoint of suppressing the drying up of the electrolyte.

[0046] In one embodiment of the present invention, the content of the organic solvent (C) is preferably 50 to 98% by weight, and more preferably 70 to 96% by weight, based on the weight of the electrolyte for the electrolytic capacitor, from the viewpoint of the viscosity of the electrolyte.

[0047] <Moisture> The electrolyte for the electrolytic capacitor according to one embodiment of the present invention may contain water or not, as necessary. If water is included, the water content is preferably 10% by weight or less, more preferably 5% by weight or less, and particularly preferably 0.3% by weight or less, based on the weight of the electrolyte for the electrolytic capacitor, from the viewpoint of preventing the capacitor from swelling.

[0048] The electrolyte for the electrolytic capacitor according to one embodiment of the present invention may contain various additives commonly used in electrolytes, as needed. Examples of such additives include boric acid derivatives (e.g., boric acid, complex compounds of boric acid and polysaccharides [mannitol, sorbitol, etc.], complex compounds of boric acid and polyhydric alcohols [ethylene glycol, glycerin, etc.]), nitro compounds (e.g., o-nitrobenzoic acid, p-nitrobenzoic acid, m-nitrobenzoic acid, o-nitrophenol, p-nitrophenol, etc.). The amount added is preferably 5% by weight or less, and particularly preferably 2% by weight or less, based on the total weight of the acid component (A), the base component (B), and the organic solvent (C), from the viewpoint of conductivity and solubility in the electrolyte.

[0049] The electrolyte for electrolytic capacitors according to one embodiment of the present invention is suitable for use in electrolytic capacitors and hybrid electrolytic capacitors.

[0050] An electrolytic capacitor according to one embodiment of the present invention comprises a capacitor element, a pair of lead wires, and an outer casing. Each of the pair of lead wires is connected to the capacitor element. The outer casing encloses the capacitor element, with the other ends of the lead wires leading out to the outside.

[0051] The outer casing consists of a cylindrical case and a sealing body. The case houses a capacitor element impregnated with electrolyte, and a pair of lead wires are inserted through the through-holes in the sealing body. The outer casing is sealed by compressing these wires in a drawn section on the outer surface of the case.

[0052] A capacitor element in one embodiment of the present invention has an anode foil having a dielectric layer on its surface. The anode foil is formed by roughening an aluminum foil by etching and then chemically treating its surface with an anodic oxide film, which is a dielectric.

[0053] A capacitor element also has a cathode foil and a separator in addition to the anode foil. The capacitor element is formed by stacking and winding the anode foil, cathode foil, and separator.

[0054] As described above, electrolyte enters the capacitor element, and an electrolytic capacitor is fabricated.

[0055] A hybrid electrolytic capacitor according to one embodiment of the present invention is formed from a capacitor element having a dielectric layer of an anode foil and a layer of solid electrolyte in contact with the dielectric layer. This solid electrolyte is, for example, a conductive polymer such as polythiophene and its derivatives (such as poly-3,4-ethylenedioxythiophene and polypyrrole).

[0056] From the viewpoint of reducing ESR at high temperatures, the solid electrolyte is preferably poly3,4-ethylenedioxythiophene.

[0057] This conductive polymer incorporates dopants, which play a role in exhibiting conductivity. Typical dopants include acids such as p-toluenesulfonic acid and polystyrenesulfonic acid.

[0058] A hybrid electrolytic capacitor according to one embodiment of the present invention comprises a capacitor element, a pair of lead wires, and an outer casing. Each of the pair of lead wires is connected to the capacitor element. The outer casing encloses the capacitor element, with the other ends of the lead wires leading out to the outside.

[0059] The outer casing consists of a cylindrical case and a sealing body. The case houses a capacitor element impregnated with electrolyte, and a pair of lead wires are inserted through the through-holes in the sealing body. The outer casing is sealed by compressing these wires in a drawn section on the outer surface of the case.

[0060] A hybrid electrolytic capacitor according to one embodiment of the present invention comprises an anode foil having a dielectric layer on its surface and a layer of solid electrolyte in contact with the dielectric layer of the anode foil.

[0061] The anode foil is formed by roughening an aluminum foil through an etching process, and then chemically treating its surface with an anodic oxide film, which is a dielectric material.

[0062] A capacitor element also has a cathode foil and a separator in addition to the anode foil. The capacitor element is formed by stacking and winding the anode foil, cathode foil, and separator. Then, a layer of solid electrolyte containing a conductive polymer is created between the anode foil and the cathode foil. Methods for creating the solid electrolyte layer include impregnating the conductive polymer in a conductive polymer solution and then drying it, or electrolytic polymerization of the conductive polymer.

[0063] As described above, electrolyte fills the gaps in the solid electrolyte formed within the capacitor element, thereby creating a hybrid electrolytic capacitor.

[0064] <Other> The present invention may include the following configurations. <1> An electrolyte for electrolytic capacitors comprising an acid component (A), a basic component (B), and an organic solvent (C), The acid component (A) comprises the acid component (A1) represented by the following general formula (1) and / or the acid component (A2) represented by the following general formula (2). The total content of acid component (A1) and acid component (A2) is 50% by weight or more based on the weight of acid component (A). The electrolyte for electrolytic capacitors comprises the base component (B) which includes at least one component selected from the group consisting of ammonium, primary amine (B1), secondary amine (B2), and tertiary amine (B3). [ka] [In formula (1), X represents a hydrocarbon group having 3 to 20 carbon atoms that may have a hydroxyl group, and Y represents a hydrogen atom, a hydrocarbon group having 1 to 10 carbon atoms that may have a hydroxyl group, or a residue obtained by removing one hydrogen atom from the hydroxyl group of a polyalkylene glycol.] [ka] [In equation (2), the two Zs each independently represent a hydrocarbon group having 1 to 6 carbon atoms.] <2> The organic solvent (C) comprises at least one component selected from the group consisting of polyhydric alcohols, sulfone compounds, lactone compounds, and carbonate compounds. <1> The electrolyte for electrolytic capacitors described above. <3> The organic solvent (C) contains a polyhydric alcohol <1> or <2> The electrolyte for electrolytic capacitors described above. <4> It contains no water, or if it contains water, the water content is 10% by weight or less based on the weight of the electrolyte for the electrolytic capacitor. <1> ~ <3> Electrolyte for electrolytic capacitors as described in any of the following. <5> The content of the acid component (A) is 1 to 20% by weight based on the weight of the electrolyte for the electrolytic capacitor. <1> ~ <4> Electrolyte for electrolytic capacitors as described in any of the following. <6> The aforementioned acid component (A) is acid component (A1), <1> ~ <5> Electrolyte for electrolytic capacitors as described in any of the following. <7> The aforementioned base component (B) includes one selected from the group consisting of secondary amines (B2) and tertiary amines (B3). <1> ~ <6> Electrolyte for electrolytic capacitors as described in any of the following. <8> The content of the aforementioned base component (B) is 0.1 to 15% by weight, based on the weight of the electrolyte for the electrolytic capacitor. <1> ~ <7> Electrolyte for electrolytic capacitors as described in any of the following. <9> The content of the aforementioned organic solvent (C) is 50 to 98% by weight, based on the weight of the electrolyte for the electrolytic capacitor. <1> ~ <8> The electrolyte for electrolytic capacitors described above. <10> <1> ~ <9> An electrolytic capacitor containing the electrolyte for electrolytic capacitors as described in any of the following. <11> <1> ~ <9> A hybrid electrolytic capacitor comprising an electrolyte solution and a solid electrolyte layer as described in any of the following. [Examples]

[0065] The present invention will be described below in detail based on examples and comparative examples, but the present invention is not limited to the following examples.

[0066] <Preparation of electrolyte for electrolytic capacitors> <Examples 1-22 (EL1-EL22) and Comparative Examples 1-9 (R1-R9)> Acid component (A), base component (B), organic solvent (C), and water as needed were mixed in the proportions (parts by weight) shown in Table 1 to prepare electrolytes EL1 to EL22 for electrolytic capacitors and comparative electrolytes R1 to R9. [Table 1] TIFF0007848800000006.tif155170

[0067] Using electrolytic capacitor electrolytes EL1 to EL22 and comparative electrolytes R1 to R9, the corrosion of the foil, the change in the pH of the electrolyte, the initial conductivity, and the conductivity after being left at high temperatures were evaluated using the following method, and the results are shown in Table 2.

[0068] [Etching of foil] 2cm 2 Untreated aluminum foil was completely impregnated in an electrolyte solution, and the electrolyte solution was maintained in a sealed container at 145°C for 2000 hours. The presence or absence of corrosion of the aluminum foil was visually observed and evaluated on the following four-point scale. An evaluation of ◎ or ○ indicates that corrosion has been reduced, and ◎ indicates that corrosion has been particularly reduced.

[0069] ◎: No corrosion ○: Slight discoloration is visible on a part of the edge of the foil. △: Corrosion is visible on most of the edges of the foil. ×: Corrosion is visible throughout.

[0070] [Evaluation: pH measurement] The pH (P1) of the electrolyte solution within one hour of preparation was measured at 25°C using a pH meter F-53 manufactured by Horiba Advanced Technology Co., Ltd. P1 was defined as the initial pH of the electrolyte solution.

[0071] Next, the electrolyte was held at 145°C for 2000 hours, and pH(P2) was measured at 25°C using the same procedure as for measuring pH(P1). P2 was defined as the pH of the electrolyte after holding at 145°C. The difference in pH was calculated as P2-P1.

[0072] [Evaluation: Measurement of electrical conductivity] The conductivity (initial conductivity) of the electrolyte solution within one hour of preparation was measured at a 30°C environment using a CM-40S conductivity meter manufactured by Toa Denpa Kogyo Co., Ltd.

[0073] Next, the solution was held at 145°C for 2000 hours, and the conductivity (conductivity after high-temperature storage) was measured in a 30°C environment using the same procedure as for the initial conductivity. The ratio of the conductivity of the electrolyte after being held at 145°C to the initial conductivity (conductivity after high-temperature storage / initial conductivity) was calculated.

[0074] [Table 2]

[0075] <Fabrication of electrolytic capacitors> <Examples 23-44 (Electrolytic Capacitors CA1-CA22) and Comparative Examples 10-18 (Electrolytic Capacitors CR1-CR9 for Comparison)> Using the electrolyte solution for electrolytic capacitors described above, an electrolytic capacitor is manufactured using the following procedure.

[0076] (1) The anode foil, cathode foil, and separator, each having a dielectric layer of aluminum oxide film on its surface, are cut to a certain width and length. Then, lead wires are connected to the anode and cathode by crimping.

[0077] (2) Roll it up into a cylindrical shape. Then secure the outer circumference with insulating tape to complete the capacitor element. Next, thread the sealing rubber and lead wires through and mount it.

[0078] (3) The electrolytic capacitors were then impregnated with the electrolytes described above (EL1~EL22, R1~R9), placed in cases, and crimped to complete the electrolytic capacitors.

[0079] Using electrolytic capacitors CA1-CA22 and CR1-CR9, we evaluated swelling after high-temperature storage, initial ESR, and ESR after high-temperature storage using the following method, and the results are shown in Table 3.

[0080] [Evaluation: Measurement of swelling after being left at high temperatures] Electrolytic capacitors were held at 250°C for 3 minutes, and the swelling of the electrolytic capacitors after holding was visually observed and evaluated in the following two stages. If the evaluation is ○, it can be said that the change over time is small.

[0081] ○: No swelling ×: Swelling is visible [Evaluation: Measurement of ESR] Under 20°C conditions, the ESR (initial ESR) of electrolytic capacitors at a frequency of 100kHz was measured using a 4-terminal LCR meter within one hour of fabrication.

[0082] Next, the electrolytic capacitor was held at 145°C with the rated voltage applied for 2000 hours. After that, the ESR (ESR after high-temperature storage) was measured in a 20°C environment using the same procedure as for the initial ESR. The ratio of the ESR of the electrolytic capacitor after being held at 145°C to the initial ESR (ESR after high-temperature storage / initial ESR) was calculated.

[0083] [Table 3]

[0084] <Fabrication of Hybrid Electrolytic Capacitors> <Examples 45-66 (Hybrid electrolytic capacitors HA1-HA22) and Comparative Examples 19-27 (Comparative electrolytic capacitors HR1-HR9)> Using the electrolyte solution for electrolytic capacitors described above, a hybrid electrolytic capacitor is manufactured according to the following procedure.

[0085] (1) The anode foil, cathode foil, and separator, each having a dielectric layer of aluminum oxide film on its surface, are cut to a certain width and length. Then, lead wires are connected to the anode and cathode by crimping.

[0086] (2) Roll it up into a cylindrical shape. Then secure the outer circumference with insulating tape to complete the capacitor element. Next, thread the sealing rubber and lead wires through and mount it.

[0087] (3) A solid electrolyte layer made of poly-3,4-ethylenedioxidethiophene (PEDOT) as a conductive polymer is formed on the capacitor element. Specifically, the capacitor element is impregnated with a dispersion of PEDOT in an aqueous solution, and then the capacitor element is dried in a constant temperature bath at 120°C for 1 hour. Polystyrene sulfonic acid is used as the dopant.

[0088] (4) The above electrolytes (EL1 to EL22, R1 to R9) were impregnated into the capacitor elements, placed in the cases, and crimped to complete the capacitors. In all examples and comparative examples, PEDOT was used for the solid electrolyte layer.

[0089] Using hybrid electrolytic capacitors HA1-HA22 and HR1-HR9, we evaluated swelling after high-temperature storage, initial ESR, and ESR after high-temperature storage using the following method, and the results are shown in Table 4.

[0090] [Evaluation: Measurement of swelling after being left at high temperatures] A hybrid electrolytic capacitor was held at 250°C for 3 minutes, and the swelling of the hybrid electrolytic capacitor after holding was visually observed and evaluated in the following two stages. If the evaluation is ○, it can be said that the change over time is small.

[0091] ○: No swelling ×: Swelling is visible [Evaluation: Measurement of ESR] Under 20°C conditions, the ESR (initial ESR) of hybrid electrolytic capacitors at a frequency of 100kHz was measured using a 4-terminal LCR meter within one hour of fabrication.

[0092] Next, the hybrid electrolytic capacitor was held for 2000 hours while applying the rated voltage at 145°C. After that, the ESR (ESR after high-temperature storage) was measured in a 20°C environment using the same procedure as for the initial ESR. As the rate of increase in ESR, the ratio of the ESR of the hybrid electrolytic capacitor after being held at 145°C to the initial value (ESR after high-temperature storage / initial ESR) was calculated.

[0093] [Table 4]

[0094] As shown in Table 2, the electrolytes of Examples 1 to 22 according to one embodiment of the present invention exhibit high initial conductivity and excellent performance, reduced corrosion (either no corrosion of the foil or only slight discoloration on a part of the foil's edge), and small changes in pH and conductivity even after being left at high temperatures.

[0095] On the other hand, the electrolytes in Comparative Examples 1 to 5 showed significant foil corrosion. The electrolytes in Comparative Examples 6 and 7 had low initial conductivity. The electrolytes in Comparative Examples 8 and 9 showed large changes in pH and conductivity after being left at high temperatures. Thus, none of the comparative examples' electrolytes satisfied all the requirements of high initial conductivity, reduced corrosion, and high stability.

[0096] Furthermore, as shown in Tables 3 and 4, the electrolytic capacitors and hybrid electrolytic capacitors of Examples 23 to 66 according to one embodiment of the present invention have low and excellent ESR, and the change in ESR is small even after being left at high temperatures.

[0097] On the other hand, the electrolytic capacitors of Comparative Examples 10-14 and 17-18, as well as the hybrid electrolytic capacitors of Comparative Examples 19-23 and 26-27, showed a large change in ESR after being left at high temperatures. The electrolytic capacitors of Comparative Examples 15-16 and the hybrid electrolytic capacitors of Comparative Examples 24-25 had high initial ESRs. Thus, none of the comparative examples' electrolytic capacitors or hybrid electrolytic capacitors achieved a low ESR with minimal change over time. [Industrial applicability]

[0098] By using the electrolyte according to one embodiment of the present invention, it is possible to realize an electrolyte with high initial conductivity, minimal change over time, and reduced corrosion of capacitor components. Furthermore, electrolytic capacitors and hybrid electrolytic capacitors with low initial ESR and minimal change over time can also be realized. Therefore, as the lifespan of power supplies used in the market increases, the market value of the electrolyte of this invention is very high. The electrolyte according to one embodiment of the present invention is particularly useful for electrolytic capacitors and hybrid electrolytic capacitors for automotive electrical power supplies and digital home appliances.

Claims

1. An electrolyte for electrolytic capacitors comprising an acid component (A), a basic component (B), and an organic solvent (C), The acid component (A) comprises the acid component (A1) represented by the following general formula (1) and / or the acid component (A2) represented by the following general formula (2). The total content of the acid component (A1) and the acid component (A2) is 50% by weight or more, based on the weight of the acid component (A). The electrolyte for electrolytic capacitors comprises the base component (B) which includes at least one component selected from the group consisting of ammonium, primary amine (B1), secondary amine (B2), and tertiary amine (B3). 【Chemistry 1】 [In formula (1), X represents a hydrocarbon group having 3 to 20 carbon atoms which may have a hydroxyl group, and Y represents a hydrogen atom, a hydrocarbon group having 1 to 10 carbon atoms which may have a hydroxyl group, or a residue obtained by removing one hydrogen atom from the hydroxyl group of a polyalkylene glycol.] 【Chemistry 2】 [In formula (2), the two Zs each independently represent a hydrocarbon group having 1 to 6 carbon atoms.]

2. The electrolyte for electrolytic capacitors according to claim 1, wherein the organic solvent (C) comprises at least one component selected from the group consisting of polyhydric alcohols, sulfone compounds, lactone compounds, and carbonate compounds.

3. The electrolyte for electrolytic capacitors according to claim 1, wherein the organic solvent (C) contains a polyhydric alcohol.

4. The electrolyte for electrolytic capacitors according to claim 1, wherein it contains no water, or if it contains water, the water content is 10% by weight or less based on the weight of the electrolyte for electrolytic capacitors.

5. The electrolyte for electrolytic capacitors according to claim 1, wherein the content of the acid component (A) is 1 to 20% by weight based on the weight of the electrolyte for electrolytic capacitors.

6. The electrolyte for electrolytic capacitors according to claim 1, wherein the acid component (A) is acid component (A1).

7. The electrolyte for electrolytic capacitors according to claim 1, wherein the base component (B) includes one selected from the group consisting of secondary amines (B2) and tertiary amines (B3).

8. The electrolyte for electrolytic capacitors according to claim 1, wherein the content of the base component (B) is 0.1 to 15% by weight based on the weight of the electrolyte for electrolytic capacitors.

9. The electrolyte for electrolytic capacitors according to claim 1, wherein the content of the organic solvent (C) is 50 to 98% by weight based on the weight of the electrolyte for electrolytic capacitors.

10. An electrolytic capacitor comprising the electrolyte for electrolytic capacitors according to any one of claims 1 to 9.

11. A hybrid electrolytic capacitor comprising an electrolyte for electrolytic capacitors and a solid electrolyte layer according to any one of claims 1 to 9.

Images