Electrolytic capacitors

Abstract

This invention provides an electrolytic capacitor in which electrolyte evaporation is suppressed even at high temperatures. The electrolytic capacitor includes: a capacitor element having an anode foil, a cathode foil, and an electrolyte; a housing housing the capacitor element; and a sealing body sealing the housing. The sealing body comprises butyl rubber, and the electrolyte contains at least 60 wt% glycerol, diglycerol, or both.

Description

[Technical Field]

[0001] The present invention relates to an electrolytic capacitor that obtains electrostatic capacitance and performs charge storage and discharge by means of the dielectric polarization effect of the dielectric film. [Previous Technology]

[0002] Electrolytic capacitors utilizing valve-acting metals such as tantalum or aluminum expand the dielectric by forming the valve-acting metal, which serves as the anode-side opposing electrode, into a sintered body or etched foil shape, thereby achieving a small size and large capacitance. In this type of electrolytic capacitor, to ensure close contact between the dielectric oxide film of the anode and the opposing electrode, the gaps are filled using an electrolyte.

[0003] The electrolyte is in direct contact with the dielectric oxide film and acts as the true cathode, while also repairing the dielectric film. However, over time, the electrolyte will evaporate and leak out of the electrolytic capacitor. Therefore, the electrolytic capacitor faces the risk of drying out, its electrostatic capacitance decreases over time, and it eventually reaches the end of its lifespan.

[0004] The capacitor element is housed in a bottomed outer casing. A sealing body is used to seal the opening of the outer casing, thereby sealing the electrolyte impregnated in the capacitor element to suppress the evaporation and diffusion of the electrolyte, thus achieving a longer lifespan. However, the electrolyte is not completely sealed inside the casing, but gradually evaporates to the outside of the electrolytic capacitor through the sealing body.

[0005] Therefore, the use of high-boiling-point solvents in electrolytes has been proposed (see, for example, Patent Document 1). Known high-boiling-point solvents include γ-butyrolactone (boiling point 203°C), butanediol (boiling point 230°C), cyclobutane (boiling point 285°C), ethylene glycol (boiling point 198°C), and polyethylene glycol (boiling point 244°C). [Prior Art Documents] [Patent Documents]

[0006] [Patent Document 1] International Publication No. 2013 / 094462 [Summary of the Invention]

[0007] [Problem to be Solved by the Invention] In recent years, electrolytic capacitors, such as those used in automotive applications, have been required to maintain good performance under high-temperature environments, such as 170°C. Specifically, electrolytic capacitors are required to maintain a certain level of electrostatic capacitance for a long period of time, even under high-temperature environments. On the other hand, the inventors have confirmed that even when the electrolyte is composed of a high-solvent medium with a boiling point exceeding 170°C, the evaporation of the electrolyte cannot be suppressed under such high-temperature environments, and the electrolytic capacitor is prone to drying out.

[0008] This invention was proposed to solve the aforementioned problems, and its object is to provide an electrolytic capacitor in which electrolyte evaporation is suppressed even under high-temperature conditions. [Means for Solving the Problem]

[0009] In order to solve the aforementioned problem, the electrolytic capacitor of this embodiment includes: a capacitor element having an anode foil, a cathode foil, an electrolyte and a solid electrolyte layer; a housing for housing the capacitor element; and a sealing body for sealing the housing, the sealing body comprising butyl rubber, and the electrolyte containing 60 wt% or more of glycerol, diglycerol or both in the solvent of the electrolyte.

[0010] In this way, even if the electrolytic capacitor is exposed to a high temperature environment such as 170°C, the evaporation of the electrolyte is suppressed, and a certain electrostatic capacitance can be maintained for a long time.

[0011] Here, ethylene propylene rubber is used as the sealing body. Compared to butyl rubber, ethylene propylene rubber has higher heat resistance and is therefore less prone to cracking at high temperatures, but it has high electrolyte permeability. Therefore, even when using solvents with high boiling points, including glycerol or diglycerol, electrolyte evaporation cannot be suppressed at high temperatures. On the other hand, compared to ethylene propylene rubber, butyl rubber has low electrolyte permeability. However, even if the sealing body contains butyl rubber, when using solvents other than glycerol or diglycerol, including polyglycerol having the same glycerol backbone as glycerol or diglycerol, the sealing body will crack at high temperatures, and electrolyte evaporation cannot be suppressed.

[0012] Thus, the inventors and others conducted diligent research and obtained the following insight: that the combination and composition of the sealing body and the electrolyte solvent have a greater impact on the evaporation of the electrolyte than the boiling point of the solvent in the electrolyte and the permeability and ease of breakage of the sealing body. This insight led to the completion of the present invention.

[0013] The sealing body may further contain ethylene propylene rubber. If butyl rubber is contained, the evaporation inhibition effect of the electrolyte can still be achieved even if the sealing body contains ethylene propylene rubber. The weight ratio of the butyl rubber (A) to the ethylene propylene rubber (B) can be expressed by the following (Formula 1). That is, the butyl rubber may contain more than 10 wt% relative to the total amount of the elastomer. (Formula 1) A / (A+B)×100≧10

[0014] The electrolyte may further comprise ethylene glycol, polyethylene glycol, or both. In addition to glycerol or diglycerol, when using ethylene glycol or polyethylene glycol as the electrolyte solvent, compared to using γ-butyrolactone or cyclobutane as the electrolyte solvent, a lower concentration of glycerol or diglycerol can achieve the same degree of electrolyte evaporation inhibition effect, further enhancing the electrolyte evaporation inhibition effect, or the concentration of glycerol or diglycerol can be reduced. In particular, when ethylene glycol is used in conjunction, a lower concentration of glycerol or diglycerol can achieve the same degree of electrolyte evaporation inhibition effect.

[0015] Furthermore, by including a solid electrolyte layer in the capacitor element, the viscosity of glycerol or diglycerol is high and the resistivity is high, but the resistivity of the electrolytic capacitor can be reduced.

[0016] The solid electrolyte layer may contain a liquid compound with a boiling point of 150°C or higher and having hydroxyl groups.

[0017] The liquid compound may be ethylene glycol.

[0018] The electrolyte may contain one or more of the group selected from 1,6-decanedicarboxylic acid, azelaic acid, adipic acid, phthalic acid and benzoic acid.

[0019] The electrolyte may contain ammonia. [Effects of the Invention]

[0020] According to the present invention, the evaporation of electrolyte is suppressed in high temperature environments such as 170°C, thereby achieving a long lifespan that can maintain a certain electrostatic capacitance for a long time.

Implementation Method

[0021] Hereinafter, a solid electrolytic capacitor according to an embodiment of the present invention will be described. However, the present invention is not limited to the embodiments described below.

[0022] An electrolytic capacitor is a passive component that stores and discharges charge through electrostatic capacitance. The electrolytic capacitor has a capacitor element, a housing, and a sealing body. The housing is the outer casing that houses the capacitor element. The sealing body is installed on the opening of the housing by riveting and seals the opening. The capacitor element includes an anode foil, a cathode foil, a separator, and an electrolyte. The anode foil and cathode foil are separated by the separator. A dielectric oxide film is formed on the surface of the anode foil. As the electrolyte, the electrolytic capacitor has an electrolyte liquid and a solid electrolyte layer. The solid electrolyte layer is located between the anode foil and the cathode foil and is in close contact with the dielectric oxide film. The electrolyte liquid fills the voids in the capacitor element.

[0023] In the electrolytic capacitor, the sealing body is an elastomer mainly composed of an elastomer, or a laminate formed by synthesizing a resin plate or metal plate into the elastic volume layer. As an elastomer, the sealing body comprises isobutylene isoprene rubber, also known as butyl rubber. Furthermore, the electrolyte may be a solution of an ionic salt that dissociates into anionic and cationic components, and the solvent of the electrolyte may be glycerol, diglycerol, or both.

[0024] If the sealing body contains butyl rubber and the electrolyte solvent is glycerol, diglycerol, or both, then even if the electrolytic capacitor is exposed to high-temperature environments such as 170°C for a long time, the electrolyte is not easily evaporated from the sealing body to the outside, and the sealing body is also not easily ruptured. Therefore, the electrolyte will remain inside the electrolytic capacitor for a long time, maintaining a high electrostatic capacitance for a long period of time, thereby achieving an electrolytic capacitor with a long service life.

[0025] However, if the polyglycerol is a dimer, even when combined with a sealing body containing butyl rubber, the sealing body will crack under prolonged high-temperature conditions. Furthermore, even if glycerol, diglycerol, or both are used in the electrolyte solvent, they must account for at least 60 wt% of the total solvent volume. If they are less than 60 wt%, the sealing body will crack under prolonged high-temperature conditions, even if the sealing body contains butyl rubber and the electrolyte solvent is glycerol, diglycerol, or both.

[0026] When adding glycerol, diglycerol, or a type other than these two as the electrolyte solvent, ethylene glycol, polyethylene glycol, or a combination thereof is preferred. For example, compared to adding a solvent other than ethylene glycol or polyethylene glycol such as γ-butyrolactone or cyclobutane, the evaporation of the electrolyte from the butyl rubber-containing sealing body can be reduced, and the life of the electrolytic capacitor can be extended. In particular, when adding glycerol, diglycerol, or a type other than these two, ethylene glycol and polyethylene glycol can reduce the overall viscosity of the electrolyte and reduce the specific resistance, which is therefore preferred. Ethylene glycol, polyethylene glycol, or a combination thereof can be used without limitation in the amount added, for example, it can be set to 40 wt% or less or 20 wt% or less of the total amount of the solvent.

[0027] Here, the solid electrolyte layer contains a conductive polymer, which, together with the electrolyte, functions as the true cathode of the electrolytic capacitor and counteracts the high specific resistance caused by the high viscosity of glycerol and diglycerol, thus reducing the internal resistance of the electrolytic capacitor. Furthermore, if dedoping occurs in the conductive polymer, the conductivity of the solid electrolyte layer decreases, weakening its effect on eliminating the specific resistance of glycerol and diglycerol. However, since glycerol and diglycerol have low ion diffusivity, the dedoping reaction is suppressed. Therefore, in the electrolytic capacitor, a solid electrolyte layer is used in conjunction with the electrolyte.

[0028] The electrolyte may contain one or more of the group selected from 1,6-decanedicarboxylic acid, azelaic acid, adipic acid, phthalic acid, and benzoic acid. If the electrolyte contains glycerol, diglycerol, or both, and one or more of the group selected from 1,6-decanedicarboxylic acid, azelaic acid, adipic acid, phthalic acid, and benzoic acid, the expansion of the shell after reflux is significantly suppressed.

[0029] Furthermore, the electrolyte may contain ammonia. If the electrolyte contains glycerol, diglycerol, or both, as well as ammonia, the dedoping of the conductive polymer is further suppressed, and the increase in the equivalent series resistance (ESR) of the electrolytic capacitor is suppressed. Therefore, it is easy to make the amount of glycerol, diglycerol, or both 60 wt% or more relative to the total amount of the electrolyte solvent.

[0030] In the above-mentioned electrolytic capacitor, the butyl rubber contained in the sealing body is manufactured by vulcanization. Examples of vulcanization methods include resin vulcanization, sulfur vulcanization, and quinone vulcanization. Examples of vulcanizing agents include alkylphenol formaldehyde resins, quinones, and sulfur. In addition, examples of crosslinking accelerators include zinc oxide, magnesium oxide, lead peroxide, dibenzothiazole, disulfides, 1,2-polybutadiene, triallyl cyanurate, metal salts of methacrylic acid and acrylic acid, and N,N'-m-phenylenediamine stearate.

[0031] If butyl rubber is used in the sealing body and the electrolyte solvent contains glycerol, diglycerol, or both, ethylene propylene rubber may also be included as another elastomer to exert an anti-evaporation effect on the electrolyte. However, butyl rubber is preferably added at 10 wt% or more relative to the total elastomer content. More preferably, butyl rubber comprises 90 wt% or more relative to the total elastomer content. If the butyl rubber content is less than this, electrolyte will remain in the electrolytic capacitor for a long time.

[0032] That is, the weight of butyl rubber (A) and ethylene propylene rubber (B) generally satisfies A / (A+B)×100≧10, as described in Formula 1. In other words, the weight ratio of butyl rubber (A) to ethylene propylene rubber (B) is A:B=10:90, or it contains more butyl rubber than this weight ratio.

[0033] In the case of using butyl rubber and ethylene propylene rubber together, the elastomer is preferably manufactured by resin vulcanization with alkylphenol formaldehyde resin or the like. In the case of using butyl rubber and ethylene propylene rubber together, resin vulcanization provides the best evaporation inhibition effect for the electrolyte. This is achieved by adding a resin vulcanizing agent to the mixture after mixing butyl rubber and ethylene propylene rubber, and then crosslinking the butyl rubber and ethylene propylene rubber using resin vulcanization.

[0034] In addition to butyl rubber, the elastomer containing butyl rubber may also contain carbon and inorganic fillers. Adding carbon and inorganic fillers reduces the likelihood of cracking in the butyl rubber and inhibits its softening. Examples of inorganic fillers include talc, mica, silica, kaolin, titanium dioxide, alumina, and mixtures thereof; preferably, talc or mica with a flattened shape. Inorganic fillers with a flattened shape promote crosslinking and are suitable for adjusting the crosslinking density.

[0035] The housing sealed by the sealing body is made of aluminum, an aluminum alloy containing aluminum or manganese, or stainless steel, and is, for example, a cylindrical body with a bottom and an open end. The sealing body is flattened by riveting, bending the opening of the housing inward to form a tight seal with the inner circumferential surface of the housing.

[0036] In a capacitor element housed within a casing, the anode foil and cathode foil are long foils made of a valve-acting metal. Valve-acting metals include aluminum, tantalum, niobium, niobium oxide, titanium, hafnium, zirconium, zinc, tungsten, bismuth, and antimony. Regarding purity, the anode foil ideally has a purity of 99.9% or higher, and the cathode foil ideally has a purity of approximately 99% or higher, but may also contain impurities such as silicon, iron, copper, magnesium, and zinc.

[0037] The anode foil, as a sintered body formed by sintering powder of valve-acting metal, or an etched foil formed by etching an extended foil, has an expanded surface. The expanded surface structure includes tunnel-like pits, sponge-like pits, or dense inter-powder voids. Typically, the expanded surface structure is formed by applying direct current or alternating current etching or alternating current etching in an acidic aqueous solution containing halide ions, such as hydrochloric acid, or by core evaporation or sintering of metal particles. The cathode foil can also have an expanded surface structure through evaporation, sintering, or etching.

[0038] The dielectric oxide film is typically an oxide film formed on the surface of the anode foil. If the anode foil is made of aluminum, it is aluminum oxide formed by oxidizing the porous structural regions. This dielectric oxide film is formed by a chemical conversion treatment involving voltage application in an aqueous solution of adipic acid, boric acid, or phosphoric acid. Alternatively, a thin dielectric oxide film (approximately 1 V to 10 V) can be formed on the surface of the cathode foil by chemical conversion treatment as needed. Furthermore, the cathode foil can also be made by forming a layer containing metal nitrides, metal carbides, or metal carbonitrides through vapor deposition, or by having a carbon-containing surface.

[0039] The partition can be made of cellulose and blends thereof, such as kraft paper, Manila hemp, esparto, hemp, and rayon; polyester resins such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, and their derivatives; polytetrafluoroethylene resins; polyvinylidene fluoride resins; vinylon resins; polyamide resins such as aliphatic polyamide, semi-aromatic polyamide, and fully aromatic polyamide; polyimide resins; polyethylene resin; polypropylene resin; trimethylpentene resin; polyphenylene sulfide resin; acrylic resin; polyvinyl alcohol resin, etc., and these resins can be used alone or in combination.

[0040] The solid electrolyte layer is formed by immersing a structure having the above-mentioned anode foil, cathode foil and separator in a dispersion of conductive polymer and then drying it. The anode foil, cathode foil and separator can be immersed in the dispersion before assembly, or they can be applied by drop coating or spray coating.

[0041] Conductive polymers are self-doped conjugated polymers doped with intramolecular dopants or with external dopants. Conjugated polymers are obtained by chemical oxidative polymerization or electrolytic oxidative polymerization of monomers or their derivatives having π-conjugated double bonds. Known conjugated polymers can be used without particular limitation. Examples include: polypyrrole, polythiophene, polyfuran, polyaniline, polyacetylene, polyphenylene vinylene, polyacene, polythiophene vinylene, etc. These conjugated polymers can be used alone, or in combination of two or more, and further, as copolymers of two or more monomers.

[0042] Among the said conjugated polymers, it is preferred to be a conjugated polymer formed by polymerization of thiophene or its derivatives, preferably 3,4-epethyldioxothiophene (i.e., 2,3-dihydrothiophene[3,4-b][1,4]dioxin), 3-alkylthiophene, 3-alkoxythiophene, 3-alkyl-4-alkoxythiophene, 3,4-alkylthiophene, 3,4-alkoxythiophene or its derivatives. As a thiophene derivative, it is preferred to be a compound selected from thiophenes having substituents at the 3 and 4 positions, wherein the substituents at the 3 and 4 positions of the thiophene ring can form a ring together with the carbons at the 3 and 4 positions. The number of carbon atoms in the alkyl or alkoxy group is preferably 1 to 16, especially preferably a polymer of 3,4-ethylenedioxythiophene called EDOT (3,4-ethylenedioxythiophene), i.e., poly(3,4-ethylenedioxythiophene) called PEDOT (poly(3,4-ethylenedioxythiophene)). Alternatively, it can be an alkylated ethylenedioxythiophene with an alkyl group added to 3,4-ethylenedioxythiophene, for example: methylated ethylenedioxythiophene (i.e., 2-methyl-2,3-dihydro-thieno[3,4-b][1,4]dioxin), ethylated ethylenedioxythiophene (i.e., 2-ethyl-2,3-dihydro-thieno[3,4-b][1,4]dioxin), etc.

[0043] Dopants can be any known type without particular limitation. Examples include: inorganic acids such as boric acid, nitric acid, and phosphoric acid; and organic acids such as acetic acid, oxalic acid, citric acid, ascorbic acid, tartaric acid, squaric acid, rhodizonic acid, croconic acid, salicylic acid, p-toluenesulfonic acid, 1,2-dihydroxy-3,5-benzenedisulfonic acid, methanesulfonic acid, trifluoromethanesulfonic acid, borodisalicylic acid, bis(oxalato)borate acid, sulfonyl amide, dodecylbenzenesulfonic acid, propylnaphthalenesulfonic acid, and butylnaphthalenesulfonic acid. Additionally, as polyanionic agents, examples include: polyvinyl sulfonic acid, polystyrene sulfonic acid, polyallyl sulfonic acid, polyacrylic acid sulfonic acid, polymethacrylic acid sulfonic acid, poly(2-acrylamide-2-methylpropanesulfonic acid), polyisoprene sulfonic acid, polyacrylic acid, polymethacrylic acid, and polymaleic acid.

[0044] In addition to the conductive polymer, the solid electrolyte layer may also contain a polar solvent with a boiling point of 150°C or higher. Examples of such polar solvents include ethylene glycol, diethylene glycol, triethylene glycol, polyoxyethylene glycol, glycerol, diglycerol, polyglycerol, dimethyl sulfoxide, dimethylformamide, N-methyl-2-pyrrolidone, or combinations of two or more of these. These polar solvents, through changes in the higher-order structure of the conductive polymer and the reorientation of the polymer chain's crystal structure, can improve carrier mobility and enhance the conductivity of the conductive polymer.

[0045] Among these polar solvents, liquid compounds with a boiling point of 150°C or higher and containing hydroxyl groups are preferred due to the further enhancement of the conductivity of the conductive polymer. Preferably, the liquid compound is ethylene glycol, diethylene glycol, triethylene glycol, polyoxyethylene glycol, glycerol, or polyglycerol.

[0046] In addition, compounds with a boiling point of 150°C or higher and containing hydroxyl groups include sorbitol, pentaerythritol, mannitol, xylitol, heptahydrate, or combinations of two or more of these. These compounds improve the chemical conversion processability of dielectric oxide films and enhance voltage resistance.

[0047] As anionic components of the electrolyte, organic acids, inorganic acids, or complexes of organic and inorganic acids can be listed. Examples of organic acids include: oxalic acid, succinic acid, glutaric acid, pimelic acid, octanoic acid, sebacic acid, phthalic acid, isophthalic acid, terephthalic acid, maleic acid, adipic acid, benzoic acid, toluic acid, enanthic acid, malonic acid, 1,6-decanedicarboxylic acid, 1,7-octanedicarboxylic acid, azelaic acid, resorcinolic acid, 2,4,6-trihydroxybenzoic acid, gallic acid, gentisic acid, protocatechuic acid, pyrocatechuic acid, trimellitic acid, pyromellitic acid, and other carboxylic acids, phenols, and sulfonic acids. In addition, examples of inorganic acids include: boric acid, phosphoric acid, phosphorous acid, hypophosphorous acid, carbonic acid, and silicic acid. Examples of complex compounds of organic and inorganic acids include: borosilicate, borosilicate oxalic acid, borosilicate diglycolic acid, borosilicate dimalonic acid, borosilicate disuccinic acid, borosilicate diadipic acid, borosilicate diazelic acid, borosilicate dibenzoic acid, borosilicate dimaleic acid, borosilicate dilactic acid, borosilicate dimalic acid, borosilicate ditartaric acid, borosilicate dicitric acid, borosilicate diphthalic acid, borosilicate di(2-hydroxy)isobutyric acid, borosilicate diresorcinic acid, borosilicate dimethylsalicylic acid, borosilicate dinaphtholic acid, borosilicate dimandelic acid, and borosilicate di(3-hydroxy)propionic acid.

[0048] Preferably, one or more of the anionic components are selected from the group consisting of 1,6-decanedicarboxylic acid, azelaic acid, adipic acid, phthalic acid, and benzoic acid. If these anionic components are included, the expansion of the electrolytic capacitor casing can be suppressed, for example, at ultra-high temperatures such as the peak temperature of 260°C during the reflow step when installing the electrolytic capacitor.

[0049] As a cationic component of the electrolyte, in addition to ammonium containing ammonia, cations generated from ammonium salts, quaternary ammonium salts, quaternary amidine salts, amine salts, sodium salts, potassium salts, etc., can also be listed. Quaternary ammonium ions, such as tetramethylammonium, triethylmethylammonium, tetraethylammonium, etc., can be listed as quaternary amidine salts. Ethyldimethylimidazolium, tetramethylimidazolium, etc., can be listed as quaternary amidine salts. Amine salts, such as salts of primary amines, secondary amines, and tertiary amines, can be listed. Primary amines, such as methylamine, ethylamine, propylamine, etc., can be listed as secondary amines, such as dimethylamine, diethylamine, ethylmethylamine, dibutylamine, etc., can be listed as tertiary amines, such as trimethylamine, triethylamine, tributylamine, ethyldimethylamine, ethyldiisopropylamine, etc.

[0050] Furthermore, other additives may also be added to the liquid. Examples of additives include complexes of boric acid and polysaccharides (mannitol, sorbitol, etc.), complexes of boric acid and polyols, borate esters, nitro compounds (o-nitrobenzoic acid, m-nitrobenzoic acid, p-nitrobenzoic acid, o-nitrophenol, m-nitrophenol, p-nitrophenol, p-nitrobenzyl alcohol, etc.), and phosphate esters. These may be used alone or in combination of two or more.

[0051] Furthermore, the electrolyte may not contain ionicly dissociable salts or additives that dissociate into anionic and cationic components, but may consist only of glycerol, diglycerol, both of these, or these combined with ethylene glycol. [Example]

[0052] Hereinafter, the electrolytic capacitor of the present invention will be described in detail based on embodiments. Furthermore, the present invention is not limited to the following embodiments. Comparative Examples 1 to 9, and Examples 1 and 2, were fabricated with different combinations of the elastomer used in the sealing body and the electrolyte solvent. These solid electrolytic capacitors are common except for the elastomer used in the sealing body and the electrolyte solvent, and are fabricated in the following manner.

[0053] That is, the anode foil is aluminum foil, which is enlarged by etching and forms a dielectric oxide film by chemical conversion. Similarly, the cathode foil is also aluminum foil, which is enlarged by etching and forms an oxide film by chemical conversion. The same anode and cathode foils are used in a fully electrolytic capacitor, and leads are connected to each, with Manila-type separators separating the anode and cathode foils as they are wound facing each other. The capacitor element undergoes a repair chemical conversion by immersing it in an aqueous solution of ammonium dihydrogen phosphate of the same concentration for 10 minutes.

[0054] Next, a dispersion of polyvinyl dioxythiophene (PEDOT / polystyrene sulfonic acid (PSS)) doped with the same product and used as a conductive polymer is prepared, and the capacitor element is impregnated with the dispersion. The capacitor element is then lifted out and dried at 150°C for 30 minutes. In this way, a solid electrolyte is formed on the capacitor element.

[0055] Ammonium azelate was added as an ion-dissociating salt to the solvents corresponding to those in the embodiments and comparative examples. Ammonium azelate was added at a ratio of 0.16 mol to 1 kg of electrolyte. A capacitor element having a solid electrolyte was immersed in the electrolyte, with 150 mg of electrolyte contained within the capacitor element. The capacitor element was then housed in an aluminum casing of the same size and shape.

[0056] A sealing body containing only an elastomer, corresponding to those in each embodiment and comparative example, is installed at the open end of the aluminum casing, and sealed by riveting under the same pressure. The lead wire from the capacitor element is first led out from the sealing body to energize the solid electrolytic capacitor. The solid electrolytic capacitor has a diameter of 10 mm, a height of 10 mm, and a rated voltage of 35 WV and 270 μF.

[0057] In Comparative Examples 1 to 9, and Examples 1 and 2, the types of elastomers used in the sealing bodies and the types of electrolyte solvents used are shown in Table 1 below. Furthermore, the butyl rubber used as the elastomer is ordinary butyl. In Comparative Example 9, polyethylene glycol with an average molecular weight of 300 was used. (Table 1) Types of sealing bodies electrolyte solvent Comparative Example 1 Ethylene propylene rubber glycerin Comparative Example 2 Butyl rubber Ethylene glycol Comparative Example 3 Butyl rubber diethylene glycol Comparative Example 4 Butyl rubber Triethylene glycol Comparative Example 5 Butyl rubber Propylene glycol Comparative Example 6 Butyl rubber Polyglycerol Comparative Example 7 Butyl rubber Pentylene glycol Comparative Example 8 Butyl rubber Ethylhexanediol Comparative Example 9 Butyl rubber polyethylene glycol Example 1 Butyl rubber glycerin Example 2 Butyl rubber diglycerides

[0058] The solid electrolytic capacitors of Comparative Examples 1 to 9, as well as Examples 1 and 2, were exposed to a high-temperature environment of 170°C. Then, the electrostatic capacitance (Cap), equivalent series resistance (ESR), and electrolyte evaporation were measured before exposure to the high-temperature environment, after 1000 hours of exposure to the high-temperature environment, and after 2000 hours of exposure to the high-temperature environment. The state of the sealed body was also observed visually.

[0059] The measurement results and visual results at each time point are shown in Table 2 below. (Table 2) Types of sealing bodies electrolyte solvent Early stage 170℃, 1000 h 170℃, 2000 h Cap (μF) ESR (Ω) Cap (μF) ESR (Ω) ΔWt (mg) The state of the sealed body Cap (μF) ESR (Ω) ΔWt (mg) The state of the sealed body Comparative Example 1 Ethylene propylene rubber glycerin 254 0.012 182 0.017 -73 No change 0 312 -150 No change Comparative Example 2 Butyl rubber Ethylene glycol 260 0.011 240 0.014 -64 No change 0 121 -150 Observed rupture Comparative Example 3 Butyl rubber diethylene glycol 256 0.012 199 0.015 -71 No change 0 302 -150 Observed rupture Comparative Example 4 Butyl rubber Triethylene glycol 255 0.012 198 0.016 -62 No change 0 212 -150 Observed rupture Comparative Example 5 Butyl rubber Propylene glycol 245 0.015 190 0.021 -102 No change 0 319 -150 Observed rupture Comparative Example 6 Butyl rubber Polyglycerol 241 0.017 179 0.024 -28 No change 0 56 -150 Observed rupture Comparative Example 7 Butyl rubber Pentylene glycol 252 0.012 158 0.017 -98 No change 0 111 -150 Observed rupture Comparative Example 8 Butyl rubber Ethylhexanediol 250 0.012 171 0.019 -98 No change 0 263 -150 Observed rupture Comparative Example 9 Butyl rubber polyethylene glycol 254 0.012 217 0.017 -45 No change 0 96 -150 Observed rupture Example 1 Butyl rubber glycerin 254 0.012 236 0.015 -26 No change 227 0.016 -54 No change Example 2 Butyl rubber diglycerides 253 0.012 214 0.016 -28 No change 208 0.018 -60 No change

[0060] As shown in Table 2, after being exposed to a high-temperature environment of 170°C for 2000 hours, the solid electrolytic capacitor of Comparative Example 1 lost all of its electrolyte, and its electrostatic capacitance was zero. Comparative Example 1 included a sealing body formed of ethylene propylene rubber, which did not rupture. That is, it was confirmed that all of the electrolyte in the sealing body formed of ethylene propylene rubber evaporated to the outside through the sealing body.

[0061] Furthermore, after exposure to a high-temperature environment of 170°C for 2000 hours, the solid electrolytic capacitors of Comparative Examples 2 to 9 also lost all of their electrolyte, resulting in zero electrostatic capacitance. Comparative Examples 2 to 9 included a sealing body formed of butyl rubber, which did not rupture. That is, it was confirmed that rupture occurred in the sealing body formed of butyl rubber, and that evaporation to the outside was caused by the rupture.

[0062] On the other hand, even after exposure to a high temperature of 170°C for 2000 hours, the solid electrolytic capacitors of Examples 1 and 2 still retained a large amount of electrolyte, thus maintaining high electrostatic capacitance. The solid electrolytic capacitors of Examples 1 and 2 included a sealing body made of butyl rubber, the same as that of Comparative Examples 2 to 9. However, unlike Comparative Examples 2 to 9, the solid electrolytic capacitors of Examples 1 and 2 used glycerol or diglycerol as the electrolyte solvent. As a result, unlike Comparative Examples 2 to 9, the sealing body of the solid electrolytic capacitors of Examples 1 and 2 did not crack.

[0063] Thus, if the sealing body contains butyl rubber and the electrolyte solvent is glycerol or diglycerol, the sealing body will not crack even when exposed to a high temperature environment of 170°C. Furthermore, the sealing body is low permeability, thus confirming that a lot of electrolyte will remain in the solid electrolytic capacitor to maintain electrostatic capacitance and thereby achieve a long lifespan.

[0064] Next, solid electrolytic capacitors of Comparative Example 10 and Examples 3 to 9 were prepared. In Comparative Example 10 and Examples 3 to 9, butyl rubber was used as the sealing body, and glycerol or diglycerol was used as the electrolyte solvent. In Comparative Example 10 and Examples 3 to 9, in addition to glycerol or diglycerol, ethylene glycol was added as the electrolyte solvent, and the proportion of glycerol or diglycerol in the solvent was different.

[0065] In Comparative Example 10 and Examples 3 to 9, the solvents of the electrolytes and the content of each solvent are shown in Table 3 below. (Table 3) Type 1 solvent Second type of solvent type content type content Comparative Example 10 glycerin 50 Ethylene glycol 50 Example 3 60 40 Example 4 70 30 Example 5 80 20 Example 6 90 10 Example 7 97 3 Example 8 diglycerides 60 40 Example 9 97 3

[0066] The solid electrolytic capacitors of Comparative Example 10 and Examples 3 to 9 were exposed to a high temperature environment of 170°C. Then, the electrostatic capacitance (Cap), equivalent series resistance (ESR), and electrolyte evaporation were measured before exposure to the high temperature environment, after 1000 hours of exposure to the high temperature environment, and after 2000 hours of exposure to the high temperature environment, and the state of the sealed body was observed visually.

[0067] The measurement results and visual results at each time point are shown in Table 4 below. In the table, the percentage of the solvent contained in parentheses after the solvent name indicates the total amount of solvent. (Table 4) Solvent and content (wt%) of electrolyte Early stage 170℃, 1000 h 170℃, 2000 h Cap (μF) ESR (Ω) Cap (μF) ESR (Ω) ΔWt (mg) The state of the sealed body Cap (μF) ESR (Ω) ΔWt (mg) The state of the sealed body Comparative Example 10 Glycerin (50) Ethylene glycol (50) 256 0.011 239 0.015 -47 No change twenty two 1.2 -150 Observed rupture Example 3 Glycerin (60) Ethylene glycol (40) 254 0.011 239 0.015 -42 No change 218 0.016 -84 No change Example 4 Glycerin (70) Ethylene glycol (30) 254 0.011 238 0.014 -36 No change 222 0.016 -68 No change Example 5 Glycerin (80) Ethylene glycol (20) 254 0.012 238 0.014 -33 No change 225 0.016 -61 No change Example 6 Glycerin (90) Ethylene glycol (10) 254 0.012 237 0.015 -29 No change 226 0.016 -57 No change Example 7 Glycerin (97) Ethylene glycol (3) 254 0.012 236 0.016 -27 No change 227 0.016 -56 No change Example 8 Glycerin (60) Ethylene glycol (40) 253 0.012 214 0.016 -48 No change 208 0.018 -90 No change Example 9 diglycerides (97) Ethylene glycol (3) 253 0.012 215 0.016 -30 No change 208 0.018 -64 No change

[0068] As shown in Table 4, the solid electrolytic capacitor of Comparative Example 10 was exposed to a high temperature environment of 170°C for 2000 hours, resulting in the seal breaking, all the electrolyte evaporating, and the electrostatic capacitance decreasing sharply to zero. On the other hand, the solid electrolytic capacitors of Examples 3 to 9, even when exposed to a high temperature environment of 170°C for 2000 hours, did not have their seals broken, a large amount of electrolyte remained, and the electrostatic capacitance was well maintained.

[0069] As shown in Table 4, in the solid electrolytic capacitor of Comparative Example 10, although glycerol was included in the electrolyte, the total amount of glycerol relative to the solvent in the electrolyte was 50 wt%. On the other hand, in the solid electrolytic capacitors of Examples 3 to 9, in which the seal did not break, the total amount of glycerol or diglycerol relative to the solvent in the electrolyte was 60 wt% or more.

[0070] Accordingly, in general, it was confirmed in Examples 1 to 9 that if the sealing body contains butyl rubber, contains glycerol, diglycerol or both as the electrolyte solvent, and the total amount of glycerol, diglycerol or both relative to the electrolyte solvent is more than 60 wt%, then even if exposed to high temperature environment for a long time, the sealing body will not crack and can maintain good electrostatic capacitance, thereby achieving a long life of solid electrolytic capacitor.

[0071] Next, solid electrolytic capacitors of Examples 10 and 11 were manufactured. In Examples 10 and 11, butyl rubber was used as the sealing body, and glycerol or diglycerol was used as the electrolyte solvent. Unlike Examples 4 and 5, which added ethylene glycol as the electrolyte solvent in addition to glycerol or diglycerol, γ-butyrolactone or cyclobutane was added as the electrolyte solvent in Examples 10 and 11.

[0072] In Examples 10 and 11, the solvents of the electrolytes and the content of each solvent are shown in Table 5 below. Examples 4 and 5 are also described in Table 5 below. (Table 5) Type 1 solvent Second type of solvent type content type content Example 10 glycerin 75 γ-Butyrolactone 25 Example 11 75 Cyclobutrazol 25 Example 4 70 Ethylene glycol 30 Example 5 80 20

[0073] The solid electrolytic capacitors of Examples 10 and 11 were exposed to a high temperature environment of 170°C. Then, the electrostatic capacitance (Cap), equivalent series resistance (ESR), and electrolyte evaporation were measured before exposure to the high temperature environment, after 1000 hours of exposure to the high temperature environment, and after 2000 hours of exposure to the high temperature environment, and the state of the sealed body was observed visually.

[0074] The measurement results and visual results at each time point are shown in Table 6 below. In the table, the percentage of the solvent contained in parentheses after the solvent name indicates the total amount of solvent. (Table 6) Solvent and content (wt%) of electrolyte Early stage 170℃, 1000 h 170℃, 2000 h Cap (μF) ESR (Ω) Cap (μF) ESR (Ω) ΔWt (mg) The state of the sealed body Cap (μF) ESR (Ω) ΔWt (mg) The state of the sealed body Example 10 Glycerin (75) γ-Butyrolactone (25) 257 0.012 219 0.016 -62 No change 216 0.017 -70 No change Example 11 Glycerin (75) Cyclobutrazol (25) 258 0.012 238 0.016 -40 No change 222 0.017 -78 No change Example 4 Glycerin (70) Ethylene glycol (30) 254 0.011 238 0.014 -36 No change 222 0.016 -68 No change Example 5 Glycerin (80) Ethylene glycol (20) 254 0.012 238 0.014 -33 No change 225 0.016 -61 No change

[0075] As shown in Table 6, compared with Examples 10 and 11, the solid electrolytic capacitors of Examples 4 or 5 exhibited less electrolyte evaporation after being exposed to a high-temperature environment of 170°C for 2000 hours. In particular, in Example 4, compared with Examples 10 and 11, the content of glycerol was lower, resulting in less electrolyte evaporation. This confirms that when ethylene glycol is used as the electrolyte solvent in addition to glycerol, diglycerol, or both, the evaporation suppression effect of the electrolyte is enhanced. Therefore, the content of glycerol or diglycerol can be reduced, thereby achieving a further extended lifespan for the solid electrolytic capacitor.

[0076] Next, solid electrolytic capacitors of Comparative Example 11 and Examples 12 to 18 were manufactured. The electrolytes of Comparative Example 11 and Examples 12 to 18 had different solvents and solutes. Except for the different solvents and solutes in the electrolytes, Comparative Example 11 and Examples 12 to 18 were manufactured using the same manufacturing method and the same manufacturing conditions as Examples 1 and 2, and had the same structure.

[0077] In Comparative Example 11, the solid electrolytic capacitor used ethylene glycol as the electrolyte solvent, and triethylamine salicylate was added to 1 kg of electrolyte at a ratio of 0.66 mol. In Examples 12 to 18, the solid electrolytic capacitors used glycerol as the electrolyte solvent.

[0078] Furthermore, the solute added to 1 kg of electrolyte at a ratio of 0.66 mol was triethylamine salicylate in Example 12, triethylamine phthalate in Example 13, triethylamine benzoate in Example 14, triethylamine maleate in Example 15, triethylamine azelaic acid in Example 16, triethylamine adipate in Example 17, and triethylamine 1,6-decanedicarboxylic acid in Example 18.

[0079] The solid electrolytic capacitors of Comparative Example 11 and Examples 12 to 18 were subjected to a total of four reflow steps. The height of the solid electrolytic capacitors before and after the four reflow steps was measured, and the change was calculated. In the reflow step, the solid electrolytic capacitors were placed in the reflow tank and heated to a peak temperature of 260°C.

[0080] The changes in Comparative Example 11 and Examples 12 to 18 are shown in Table 7 below. (Table 7) solvent solute Changes after reflux (four times) (mm) Comparative Example 11 Ethylene glycol salicylic acid Triethylamine 0.26 Example 12 glycerin salicylic acid Triethylamine 0.21 Example 13 glycerin Phthalic acid Triethylamine 0.08 Example 14 glycerin benzoic acid Triethylamine 0.10 Example 15 glycerin Maleic acid Triethylamine 0.21 Example 16 glycerin azelaic acid Triethylamine 0.07 Example 17 glycerin adipic acid Triethylamine 0.10 Example 18 glycerin 1,6-Decanedicarboxylic acid Triethylamine 0.04

[0081] As shown in Table 7, the solid electrolytic capacitors of Examples 12 to 18, which used glycerol as the electrolyte solvent, showed less variation compared to the solid electrolytic capacitor of Comparative Example 11, thus suppressing the expansion of the casing after reflow. Furthermore, the solid electrolytic capacitors of Examples 13, 14, 16, 17, and 18, which used phthalic acid, benzoic acid, azelaic acid, adipic acid, or 1,6-decanedicarboxylic acid as the anionic component of the electrolyte, showed less than half the expansion of the casing after reflow compared to the solid electrolytic capacitors of Examples 12 and 15.

[0082] Next, solid electrolytic capacitors of Comparative Example 12, Example 19, and Example 20 were manufactured. The electrolytes of Comparative Example 12, Example 19, and Example 20 used different solvents and solutes. Except for the different solvents and solutes in the electrolytes, Comparative Example 12, Example 19, and Example 20 were manufactured using the same manufacturing method and the same manufacturing conditions as Example 1 and Example 2, and had the same structure.

[0083] The solid electrolytic capacitor of Comparative Example 12 used ethylene glycol as the electrolyte solvent, and triethylamine azelate was added to 1 kg of electrolyte at a ratio of 0.66 mol. The solid electrolytic capacitor of Example 19 used 60 wt% glycerol and 40 wt% ethylene glycol as the electrolyte solvent, and ammonium azelate was added to 1 kg of electrolyte at a ratio of 0.66 mol. The solid electrolytic capacitor of Example 20 used glycerol as the electrolyte solvent, and ammonium azelate was added to 1 kg of electrolyte at a ratio of 0.66 mol.

[0084] The solid electrolytic capacitor of Example 16, which used glycerol as the electrolyte solvent and triethylamine azelate as the electrolyte solute, and the solid electrolytic capacitors of Comparative Example 12, Example 19, and Example 20, were subjected to four reflow steps. The equivalent series resistance (ESR) before the reflow step and the equivalent series resistance (ESR) after the four reflow steps were then measured. In the reflow step, the solid electrolytic capacitor was placed in a reflow tank and heated to a peak temperature of 260°C.

[0085] The equivalent series resistances of Comparative Example 12, Example 16, Example 19, and Example 20 are shown in Table 8 below. In the table, the values ​​in parentheses after the solvent name indicate the percentage of the solvent contained in the total amount. (Table 8) solvent solute Before reflux ESR (Ω) After reflux ESR (Ω) Comparative Example 12 Ethylene glycol azelaic acid Triethylamine 0.011 2.1 Example 16 glycerin azelaic acid Triethylamine 0.011 0.72 Example 19 Glycerin (60) Ethylene glycol (40) azelaic acid ammonium 0.011 0.028 Example 20 glycerin azelaic acid ammonium 0.011 0.025

[0086] As shown in Table 8, the solid electrolytic capacitors of Examples 16, 19, and 20 have lower equivalent series resistance (ESR) after reflux compared to the solid electrolytic capacitor of Comparative Example 12. This confirms that when glycerol, diglycerol, or both are used as solvents and in combination with a solid electrolyte, the specific resistance elimination effect and dedoping suppression effect of glycerol or diglycerol can be utilized, and the equivalent series resistance of the solid electrolytic capacitor can be maintained at a low level even when exposed to high-temperature environments.

[0087] As shown in Table 8, the solid electrolytic capacitors of Examples 19 and 20 exhibited lower equivalent series resistance (ESR) after reflow compared to the solid electrolytic capacitor of Example 16. This confirms that when glycerol, diglycerol, or both are used as solvents and ammonia is included in the electrolyte, dedoping is less likely to occur, and the equivalent series resistance of the solid electrolytic capacitor can be maintained at a lower level even when exposed to high temperatures.

[0088] Next, solid electrolytic capacitors of Examples 21 to 26 were manufactured. In Examples 21 to 26, except for the ratio of glycerol in the elastomer to the electrolyte solvent, they were manufactured using the same manufacturing method and the same manufacturing conditions as in Example 3, and had the same structure.

[0089] In the solid electrolytic capacitors of Examples 21 to 26, the elastomer used for the sealing body is a mixture of butyl rubber and ethylene propylene rubber. Uncured butyl rubber and uncured ethylene propylene rubber are mixed at various mixing ratios specified in Examples 21 to 26, and then alkylphenol formaldehyde resin is used to perform resin curing while heating and pressurizing. In this way, the butyl rubber and ethylene propylene rubber are crosslinked by resin curing.

[0090] Furthermore, in the solid electrolytic capacitors of Examples 21 to 26, the solvent for the electrolyte is a mixture of glycerol and ethylene glycol. Glycerol is added in various mixing ratios specified in Examples 21 to 26.

[0091] In Examples 21 to 26, the weight ratios of various elastomers and the contents of various solvents in the electrolytes are shown in Table 9 below. (Table 9) Types of sealing bodies electrolyte solvent Type 1 solvent Second type of solvent Butyl rubber Ethylene propylene rubber type content type content Example 3 100 0 glycerin 60 Ethylene glycol 40 Example 21 90 10 60 40 Example 22 70 30 60 40 Example 23 50 50 60 40 Example 24 30 70 80 20 Example 25 10 90 80 20 Example 26 10 90 100 0 Comparative Example 1 0 100 100 0

[0092] Table 9 also describes Example 3, in which the elastomer is only butyl rubber, and Comparative Example 1, in which the elastomer is only ethylene propylene rubber. In Examples 21 to 25, Example 3, and Comparative Example 1, the amount of butyl rubber varies with respect to the total elastomer from 100 wt% to 0 wt% in intervals of 10 wt% or 20 wt%. In other words, in Examples 21 to 25 and Examples 3 and Comparative Example 1, the amount of ethylene propylene rubber varies with respect to the total elastomer from 100 wt% to 0 wt% in intervals of 10 wt% or 20 wt%.

[0093] Additionally, as shown in Table 9, for Examples 3 and 21 to 23, the glycerol content was 60 wt% relative to the total solvent. In Examples 24 and 25, the glycerol content was 80 wt% relative to the total solvent. The solvent in Example 26 and Comparative Example 1 consisted only of glycerol.

[0094] The solid electrolytic capacitors of Examples 21 to 26 were exposed to a high temperature environment of 170°C. Then, the electrostatic capacitance (Cap), equivalent series resistance (ESR), and electrolyte evaporation were measured before exposure to the high temperature environment, after 1000 hours of exposure to the high temperature environment, and after 2000 hours of exposure to the high temperature environment, and the state of the sealed body was observed visually.

[0095] The measurement results and visual results at each time point in Examples 21 to 26, together with those of Example 3 and Comparative Example 1, are shown in Table 10 below. (Table 10) Types of sealing bodies electrolyte solvent Early stage 170℃, 1000 h 170℃, 2000 h Type 1 solvent Second type of solvent Butyl rubber Ethylene propylene rubber type content type content Cap (μF) ESR (Ω) Cap (μF) ESR (Ω) ΔWt (mg) The state of the sealed body Cap (μF) ESR (Ω) ΔWt (mg) The state of the sealed body Example 3 100 0 glycerin 60 Ethylene glycol 40 254 0.011 239 0.015 -42 No change 218 0.016 -84 No change Example 21 90 10 60 40 254 0.011 231 0.015 -48 No change 215 0.016 -95 No change Example 22 70 30 60 40 254 0.011 226 0.015 -61 No change 209 0.016 -123 No change Example 23 50 50 60 40 254 0.011 222 0.015 -70 No change 206 0.016 -137 No change Example 24 30 70 80 20 254 0.012 229 0.015 -52 No change 213 0.016 -103 No change Example 25 10 90 80 20 254 0.012 224 0.015 -65 No change 208 0.016 -125 No change Example 26 10 90 100 0 254 0.012 243 0.015 -37 No change 213 0.016 -98 No change Comparative Example 1 0 100 100 0 254 0.012 182 0.017 -73 No change 0 312 -150 No change

[0096] As shown in Table 10, in the solid electrolytic capacitors of Examples 21 to 26, the amount of electrolyte detached ΔWt (mg) after exposure to a high temperature environment of 170°C for 2000 hours is less than 150 mg. The electrolyte content in the solid electrolytic capacitor is 150 mg. That is, even after exposure to a high temperature environment of 170°C for 2000 hours, electrolyte remains in the solid electrolytic capacitors of Examples 21 to 26, and the deterioration of the electrostatic capacitance Cap or equivalent series resistance ESR is suppressed.

[0097] Thus, it is confirmed that even if the sealing body contains ethylene propylene rubber, if it also contains butyl rubber, and the electrolyte contains glycerol at a concentration of more than 60 wt% relative to the total solvent, the electrolyte will remain in the solid electrolytic capacitor, thereby achieving a longer lifespan.

[0098] In addition, as shown in Examples 25 and 26, it was confirmed that if the content of butyl rubber is 10 wt% or more relative to the elastomer as a whole, the deterioration of electrostatic capacitance Cap or equivalent series resistance ESR is also suppressed, depending on the content of glycerol.

[0099] Next, solid electrolytic capacitors of Examples 27 and 28 were manufactured. In Examples 27 and 28, butyl rubber was used as the sealing body, and glycerol or diglycerol was used as the electrolyte solvent. Unlike Example 3, where ethylene glycol was added as the electrolyte solvent in addition to glycerol or diglycerol, in Example 27, polyethylene glycol was added as the electrolyte solvent in addition to glycerol or diglycerol. Example 28 differs from Example 3 in that polyethylene glycol with an average molecular weight of 300 and ethylene glycol were added as the electrolyte solvent in addition to glycerol or diglycerol.

[0100] In Examples 27 and 28, the solvents of the electrolytes and the content of each solvent are shown in Table 11 below. Example 3 is also described in Table 11 below. (Table 11) Type 1 solvent Second type of solvent The third type of solvent type content type content type content Example 3 glycerin 60 Ethylene glycol 40 none Example 27 60 polyethylene glycol 40 Example 28 60 polyethylene glycol 20 Ethylene glycol 20

[0101] The solid electrolytic capacitors of Examples 27 and 28 were exposed to a high temperature environment of 170°C. Then, the electrostatic capacitance (Cap), equivalent series resistance (ESR), and electrolyte evaporation were measured before exposure to the high temperature environment, after 1000 hours of exposure to the high temperature environment, and after 2000 hours of exposure to the high temperature environment, and the state of the sealed body was observed visually.

[0102] The measurement results and visual results at each time point are shown in Table 12 below. In the table, the percentage of the solvent contained in parentheses after the solvent name is the numerical value. (Table 12) Solvent and content (wt%) of electrolyte Early stage 170℃, 1000 h 170℃, 2000 h Cap (μF) ESR (Ω) Cap (μF) ESR (Ω) ΔWt (mg) The state of the sealed body Cap (μF) ESR (Ω) ΔWt (mg) The state of the sealed body Example 3 Glycerin (60) Ethylene glycol (40) 254 0.011 239 0.015 -42 No change 218 0.016 -84 No change Example 27 Glycerin (60) Polyethylene glycol (40) 254 0.012 236 0.017 -31 No change 201 0.018 -87 No change Example 28 Glycerin (60) Polyethylene glycol (20) Ethylene glycol (20) 254 0.012 236 0.016 -36 No change 208 0.017 -85 No change

[0103] As shown in Table 12, the evaporation of the electrolyte in the solid electrolytic capacitors of Examples 27 and 28 after being exposed to a high-temperature environment of 170°C for 2000 hours was as low as that in Example 3. This confirms that even when polyethylene glycol is used as the electrolyte solvent in addition to glycerol, diglycerol, or both, the evaporation suppression effect of the electrolyte is increased. Therefore, the content of glycerol or diglycerol can be reduced, thereby achieving a further increase in the lifespan of the solid electrolytic capacitor.

[0104] Next, solid electrolytic capacitors of Examples 29 to 32 were fabricated. In Examples 29 to 32, butyl rubber was used as the sealing body, and glycerol or diglycerol was used as the electrolyte solvent. In Examples 29 to 32, as shown in Table 13 below, other solvents besides glycerol or diglycerol were added. (Table 13) Type 1 solvent Second type of solvent The third type of solvent type content type content type content Example 29 glycerin 75 Ethylene glycol 15 γ-Butyrolactone 10 Example 30 75 Ethylene glycol 15 Cyclobutrazol 10 Example 31 75 Cyclobutrazol 15 γ-Butyrolactone 10 Example 32 75 Cyclobutrazol 15 polyethylene glycol 10

[0105] The solid electrolytic capacitors of Examples 29 to 32 were exposed to a high temperature environment of 170°C. Then, the electrostatic capacitance (Cap), equivalent series resistance (ESR), and electrolyte evaporation were measured before exposure to the high temperature environment, after 1000 hours of exposure to the high temperature environment, and after 2000 hours of exposure to the high temperature environment, and the state of the sealed body was observed visually.

[0106] The measurement results and visual results at each time point are shown in Table 14 below. In the table, the parentheses after the solvent name indicate the percentage of the solvent contained in the total amount. (Table 14) Solvent and content (wt%) of electrolyte Early stage 170℃, 1000 h 170℃, 2000 h Cap (μF) ESR (Ω) Cap (μF) ESR (Ω) ΔWt (mg) The state of the sealed body Cap (μF) ESR (Ω) ΔWt (mg) The state of the sealed body Example 29 Glycerin (75) Ethylene glycol (15) γ-Butyrolactone (10) 257 0.012 231 0.016 -48 No change 223 0.017 -78 No change Example 30 Glycerin (75) Ethylene glycol (15) Cyclobutrazol (10) 258 0.012 234 0.016 -36 No change 225 0.017 -70 No change Example 31 Glycerin (75) Cyclobutrazol (15) γ-Butyrolactone (10) 257 0.012 226 0.016 -52 No change 220 0.017 -74 No change Example 32 Glycerin (75) Cyclobutrazol (15) Polyethylene glycol (10) 257 0.012 232 0.016 -35 No change 224 0.017 -76 No change

[0107] As shown in Table 14, in Examples 29 to 32, since the solvent contained glycerol or diglycerol at a proportion of 60 wt% or more, even if multiple solvents such as ethylene glycol, polyethylene glycol, γ-butyrolactone, or cyclobutane were added, the electrolyte would not completely evaporate, and the seal would not rupture. Therefore, it was confirmed that by containing glycerol or diglycerol at a proportion of 60 wt% or more in the solvent, even if one or more other solvents were added, an electrolyte evaporation inhibition effect could be obtained.

Claims

1. An electrolytic capacitor, characterized in that it comprises: A capacitor element having an anode foil, a cathode foil, an electrolyte, and a solid electrolyte layer; Housing that houses the capacitor element; The enclosure includes a sealing body for sealing the shell, the sealing body comprising butyl rubber, and the electrolyte comprising more than 60 wt% of glycerol, diglycerol, or both.

2. The electrolytic capacitor as claimed in claim 1, wherein, The sealing body further comprises ethylene propylene rubber.

3. The electrolytic capacitor as claimed in claim 2, wherein, The weight ratio of the butyl rubber (A) to the ethylene propylene rubber (B) is expressed by the following formula 1: Formula 1 A / (A+B)×100≧10.

4. The electrolytic capacitor as described in any one of claims 1 to 3, wherein, The electrolyte further comprises ethylene glycol, polyethylene glycol, or both.

5. The electrolytic capacitor as described in any one of claims 1 to 3, wherein, The solid electrolyte layer contains a liquid compound with a boiling point above 150°C and hydroxyl groups.

6. The electrolytic capacitor as claimed in claim 5, wherein, The liquid compound is ethylene glycol.

7. The electrolytic capacitor as described in any one of claims 1 to 3, wherein, The electrolyte contains one or more of the group consisting of 1,6-decanedicarboxylic acid, azelaic acid, adipic acid, phthalic acid, and benzoic acid.

8. The electrolytic capacitor as described in any one of claims 1 to 3, wherein, The electrolyte contains ammonia.