WO2023054502A1

WO2023054502A1 - Solid electrolytic capacitor

Info

Publication number: WO2023054502A1
Application number: PCT/JP2022/036243
Authority: WO
Inventors: 洙光金; 高史三浦; 尚人武島; 慎吾竹内; 健治町田; 健太佐藤; 一平中村
Original assignee: 日本ケミコン株式会社
Priority date: 2021-09-30
Filing date: 2022-09-28
Publication date: 2023-04-06
Also published as: TW202338873A; JPWO2023054502A1

Abstract

Provided is a solid electrolytic capacitor that exhibits low equivalent series resistance even at high frequencies. The solid electrolytic capacitor comprises a positive electrode foil, a negative electrode foil, and an electrolyte layer. The positive electrode foil contains a valve metal, and a dielectric oxide film is formed thereupon. The negative electrode foil contains a valve metal, and faces the positive electrode foil. The electrolyte layer contains an electrically conductive polymer and an electrolyte solution, and is interposed between the positive electrode foil and the negative electrode foil. The electrolyte solution contains an aliphatic dicarboxylic acid and a phosphoric acid compound that has a butyl group, and the phosphoric acid compound is present in the amount of 32 mmol or less per 100 g of the electrolyte solution.

Description

solid electrolytic capacitor

The present invention relates to solid electrolytic capacitors.

Solid electrolytic capacitors are equipped with valve metals such as tantalum or aluminum as anode and cathode foils. The anode foil is expanded by forming a valve metal into a sintered body or an etched foil, and has a dielectric oxide film on the expanded surface by anodization or the like. Between the anode foil and the cathode foil is interposed a solid electrolyte layer that adheres to the anode foil and acts as a true cathode.

Manganese dioxide and 7,7,8,8-tetracyanoquinodimethane (TCNQ) complexes are known as solid electrolytes. In recent years, poly(3,4-ethylenedioxythiophene) (PEDOT), which has high conductivity and excellent adhesion to dielectric oxide films, has rapidly spread as a solid electrolyte. Poly(3,4-ethylenedioxythiophene) typically exhibits high conductivity by being doped with polystyrene sulfonic acid (PSS) or having a partial structure that acts as a dopant in the molecule.

However, solid electrolytic capacitors are less effective in repairing defects in the dielectric oxide film than liquid-type electrolytic capacitors in which capacitor elements are impregnated with an electrolytic solution, and there is a risk of an increase in leakage current. Therefore, so-called hybrid-type solid electrolytic capacitors in which a solid electrolyte layer is formed on a capacitor element and the voids of the capacitor element are impregnated with an electrolytic solution are attracting attention. The electrolytic solution uses, for example, γ-butyrolactone or sulfolane as a solvent, triethylamine borodisalicylate, ethyldimethylamine phthalate, mono-1,2,3,4-tetramethylimidazolinium phthalate, and mono-1,3-dimethyl phthalate. -Contains 2-ethylimidazolinium and the like as a solute.

JP 2008-10657 A

With the digitization of electronic devices, there is a growing demand for capacitors that are small, have a large capacity, and have a low ESR (equivalent series resistance). Electrolytic capacitors have a larger capacity than film capacitors and ceramic capacitors, and solid electrolytic capacitors containing conductive polymers such as poly(3,4-ethylenedioxythiophene) (PEDOT) have conductive polymers. Since it has high conductivity, it has good ESR.

Digital equipment has come to operate in the high frequency range of several tens of kHz, and solid electrolytic capacitors are required to have low ESR even in the high frequency range. SUMMARY OF THE INVENTION The present invention has been proposed to solve the above problems, and an object of the present invention is to provide a solid electrolytic capacitor with low ESR even in a high frequency region.

In order to solve the above problems, the solid electrolytic capacitor of the present embodiment includes an anode foil containing a valve metal and having a dielectric oxide film formed thereon; a cathode foil containing a valve metal and facing the anode foil; an electrolyte layer interposed between the anode foil and the cathode foil containing a conductive polymer and an electrolytic solution, wherein the electrolytic solution contains a phosphoric acid compound having a butyl group and an aliphatic dicarboxylic acid; and the phosphoric acid compound is 32 mmol or less per 100 g of the electrolytic solution.

The amount of the phosphoric acid compound may be 8 mmol or less per 100 g of the electrolytic solution. As a result, the ESR of the solid electrolytic capacitor is greatly reduced, and the leakage current is also greatly reduced.

The phosphoric acid compound may be one or a mixture of two or more selected from the group consisting of dibutyl phosphate, tributyl phosphate, dibutyl phosphite, and tributyl phosphite.

The aliphatic dicarboxylic acid may be one or a mixture of two or more selected from the group consisting of azelaic acid, succinic acid, glutaric acid and citraconic acid.

The aliphatic dicarboxylic acid may be one or a mixture of two or more selected from the group of azelaic acid, succinic acid, and glutaric acid.

The electrolytic solution may contain one or more selected from the group of ethylene glycol, glycerin and sulfolane.

The electrolytic solution may contain ammonia.

The aliphatic dicarboxylic acid may be contained in the electrolytic solution in a molar ratio of 0.25 or more when the phosphoric acid compound is 1.

According to the present invention, the solid electrolytic capacitor has a low ESR at least in the high frequency range.

A solid electrolytic capacitor according to an embodiment of the present invention will be described below. In addition, this invention is not limited to embodiment described below.

(solid electrolytic capacitor)
A solid electrolytic capacitor is a passive element that stores and discharges electric charges by obtaining capacitance from the dielectric polarization action of a dielectric oxide film. This solid electrolytic capacitor is formed by housing a capacitor element in a case and sealing the case opening with a sealing member. A capacitor element comprises an anode foil, a cathode foil, a separator and an electrolyte layer. The anode foil and the cathode foil are wound or laminated facing each other with a separator interposed therebetween. A dielectric oxide film is formed on the surface of the anode foil. The electrolyte layer is composed of a solid electrolyte layer containing a conductive polymer and an electrolytic solution. The solid electrolyte layer is interposed between the anode foil and the cathode foil and adheres to the dielectric oxide film. The electrolytic solution impregnates the voids of the capacitor element in which the solid electrolyte layer is formed.

(electrode foil)
The anode foil and the cathode foil are long foil bodies obtained by stretching the valve action metal. Valve metals include aluminum, tantalum, niobium, niobium oxide, titanium, hafnium, zirconium, zinc, tungsten, bismuth and antimony. The purity of the anode foil is desirably 99.9% or higher, and the purity of the cathode foil is desirably about 99% or higher. Impurities such as silicon, iron, copper, magnesium and zinc may be contained.

The surface of the anode foil is enlarged as a molded body obtained by molding the powder of the valve metal, a sintered body obtained by sintering the molded body, or an etched foil obtained by etching a rolled foil. That is, the surface spreading structure consists of tunnel-like pits, spongy pits, or voids between dense particles. The expanded surface structure is typically formed by direct current or alternating current etching or alternating current etching in an acidic aqueous solution in which halogen ions such as hydrochloric acid are present, or by depositing or sintering metal particles or the like on the core. It is formed by The cathode foil may also have an enlarged surface structure by vapor deposition, sintering or etching.

The dielectric oxide film is typically an oxide film formed on the surface layer of the anode foil. For example, if the anode foil is an aluminum foil, the dielectric oxide film is aluminum oxide with an oxidized surface expansion structure. The dielectric oxide film is formed by chemical conversion treatment in which a voltage is applied to the anode foil in an aqueous solution of adipic acid, boric acid, phosphoric acid, or the like. A thin oxide film (about 1 to 10 V) may be formed on the surface layer of the cathode foil by chemical conversion treatment, if necessary.

(Electrolyte)
The electrolytic solution impregnates the voids of the capacitor element in which the solid electrolyte layer is formed. This electrolytic solution is a solution in which an anion component and a cation component are added to a solvent. The anion component and the cation component are typically a salt of an organic acid, a salt of an inorganic acid, or a salt of a complex compound of an organic acid and an inorganic acid. Added to the solvent. An acid as an anionic component and a base as a cationic component may be added separately to the solvent. Moreover, the electrolytic solution does not have to contain an anion component, a cation component, or both an anion component and a cation component in the solvent.

The electrolyte contains both a phosphoric acid compound with a butyl group and an aliphatic dicarboxylic acid. The phosphate compound has at least one butyl group. Since both the phosphate compound having a butyl group and the aliphatic dicarboxylic acid are contained in the electrolyte, even when the solid electrolytic capacitor is used in a high frequency range such as 100 kHz, low ESR is maintained for a long period of time and leakage is low. Current is maintained for a long period of time. This ESR becomes a lower value than when either of the phosphoric acid compound having a butyl group and the aliphatic dicarboxylic acid, which has a good ESR, is added to the electrolytic solution.

However, the amount of the phosphoric acid compound having a butyl group is 32 mmol or less per 100 g of the electrolyte, preferably 8 mmol or less per 100 g of the electrolyte. If it is 48 mmol or more, the ESR becomes worse than when only the phosphoric acid compound having a butyl group is contained in the electrolytic solution, and the synergistic effect of the phosphoric acid compound having a butyl group and the aliphatic dicarboxylic acid cannot be obtained. do not have. On the other hand, when it is 32 mmol or less, the ESR becomes better than when only the phosphoric acid compound having a butyl group is contained in the electrolytic solution. When it is 8 mmol or less, in addition to the low ESR, the LC (leakage current) is lower than when the electrolyte contains only the phosphoric acid compound having a butyl group and when the electrolyte contains only the aliphatic dicarboxylic acid. becomes better.

The amount of the aliphatic dicarboxylic acid to be added is not particularly limited, and a synergistic effect relating to the ESR of the phosphoric acid compound having a butyl group and the aliphatic dicarboxylic acid can be obtained. Preferably, the molar ratio of the phosphoric acid compound to 1 is 0.25 or more of the aliphatic dicarboxylic acid. At least in this range, even when the solid electrolytic capacitor is used in a high frequency range such as 100 kHz, the low ESR is maintained for a long period of time, and the LC is also good.

A phosphate compound having a butyl group is, for example, dibutyl phosphate, tributyl phosphate, dibutyl phosphite or tributyl phosphite. The electrolytic solution may contain one or more phosphoric acid compounds. Aliphatic dicarboxylic acids are for example azelaic acid, succinic acid, glutaric acid or citraconic acid. The electrolytic solution may contain one or more aliphatic dicarboxylic acids. Preferably, the aliphatic dicarboxylic acid is one or more selected from the group of azelaic acid, succinic acid or glutaric acid. Azelaic acid, succinic acid and glutaric acid worsen the ESR of solid electrolytic capacitors compared to phosphoric acid compounds having butyl groups. However, when it is contained in the electrolytic solution together with the phosphoric acid compound having a butyl group, the ESR of the solid electrolytic capacitor is improved and the ESR reduction effect is higher than when only the phosphoric acid compound having a butyl group is contained.

Even if citraconic acid, which is highly effective in reducing ESR, is used as the aliphatic dicarboxylic acid, the ESR of the solid electrolytic capacitor is higher than that of the electrolyte containing only the phosphoric acid compound having a butyl group and the electrolyte containing only citraconic acid. make good.

If both the phosphate compound having a butyl group and the aliphatic dicarboxylic acid are contained in the electrolytic solution, other kinds of anion components may be further contained as solutes. Among other anion components, organic acids include oxalic acid, succinic acid, glutaric acid, pimelic acid, suberic acid, sebacic acid, phthalic acid, isophthalic acid, terephthalic acid, maleic acid, adipic acid, benzoic acid, and toluyl. acid, enanthic acid, malonic acid, 1,6-decanedicarboxylic acid, 1,7-octanedicarboxylic acid, azelaic acid, undecanedioic acid, dodecanedioic acid, tridecanedioic acid, t-butyladipic acid, 11-vinyl-8 -Carboxylic acids such as octadecenedioic acid, resorcinic acid, phloroglucic acid, gallic acid, gentisic acid, protocatechuic acid, pyromellitic acid, trimellitic acid, and pyromellitic acid, phenols, and sulfonic acids. Examples of inorganic acids include boric acid, other phosphoric acid, other phosphorous acid, hypophosphorous acid, carbonic acid, silicic acid and the like. Compound compounds of organic acids and inorganic acids include borodisalicylic acid, borodisaliic acid, borodiglycolic acid, borodimalonic acid, borodisuccinic acid, borodiadipic acid, borodiazelaic acid, borodibenzoic acid, borodimaleic acid, borodilactic acid, borodimalic acid, boroditartaric acid, borodicitric acid, borodiphthalic acid, borodi(2-hydroxy)isobutyric acid, borodiresorucic acid, borodimethylsalicylic acid, borodinaphthoic acid, borodimandelic acid and borodi(3-hydroxy)propionic acid.

Examples of at least one salt of an organic acid, an inorganic acid, and a composite compound of an organic acid and an inorganic acid include ammonium salts, quaternary ammonium salts, quaternary amidinium salts, amine salts, sodium salts, potassium salts, and the like. be done. The quaternary ammonium ion of the quaternary ammonium salt includes tetramethylammonium, triethylmethylammonium, tetraethylammonium and the like. Quaternary amidinium salts include ethyldimethylimidazolinium, tetramethylimidazolinium, and the like. Amine salts include salts of primary, secondary and tertiary amines. Examples of primary amines include methylamine, ethylamine and propylamine; examples of secondary amines include dimethylamine, diethylamine, ethylmethylamine and dibutylamine; examples of tertiary amines include trimethylamine, triethylamine, tributylamine and ethyldimethylamine; and ethyldiisopropylamine.

The solute cationic species is preferably ammonia, an ammonium salt, or a quaternary ammonium salt. When the electrolyte contains ammonium, even when the solid electrolytic capacitor is used in a high frequency range such as 100 kHz, the ESR is maintained for a long period of time, compared to when other cationic species are contained.

The solvent for the electrolytic solution is not particularly limited, but a protic organic polar solvent or an aprotic organic polar solvent can be used. Protic organic solvents include monohydric alcohols, polyhydric alcohols and oxyalcohol compounds. Examples of monohydric alcohols include ethanol, propanol, butanol, pentanol, hexanol, cyclobutanol, cyclopentanol, cyclohexanol, and benzyl alcohol. Examples of polyhydric alcohols and oxyalcohol compounds include ethylene glycol, diethylene glycol, propylene glycol, glycerin, methyl cellosolve, ethyl cellosolve, methoxypropylene glycol, dimethoxypropanol, polyglycerin, polyethylene glycol, polyoxyethylene glycerin, polypropylene glycol, and the like. Examples include alkylene oxide adducts of polyhydric alcohols.

As aprotic organic polar solvents, sulfone-based, amide-based, lactones, cyclic amide-based, nitrile-based, sulfoxide-based, and the like may be used. Sulfone-based solvents include dimethylsulfone, ethylmethylsulfone, diethylsulfone, sulfolane, 3-methylsulfolane, 2,4-dimethylsulfolane, and the like. Examples of amides include N-methylformamide, N,N-dimethylformamide, N-ethylformamide, N,N-diethylformamide, N-methylacetamide, N,N-dimethylacetamide, N-ethylacetamide, N,N- diethylacetamide, hexamethylphosphoricamide and the like. Lactones and cyclic amides include γ-butyrolactone, γ-valerolactone, δ-valerolactone, N-methyl-2-pyrrolidone, ethylene carbonate, propylene carbonate, butylene carbonate and isobutylene carbonate. Nitrile type includes acetonitrile, 3-methoxypropionitrile, glutaronitrile and the like. The sulfoxide type includes dimethyl sulfoxide and the like.

Preferably, polyhydric alcohols such as ethylene glycol or glycerin, monohydric alcohols, or oxyalcohol compounds are contained as the solvent of the electrolytic solution or other species in the solvent. These solvents tend to cause an esterification reaction with aliphatic dicarboxylic acids. When the aliphatic dicarboxylic acid is decomposed by the esterification reaction, the acidity of the electrolytic solution is lowered, and dedoping from the conductive polymer is likely to occur. However, when the electrolytic solution contains a phosphoric acid compound having a butyl group, dedoping of the conductive polymer is suppressed, and low ESR is maintained. Sulfolane may also preferably be included as a solvent in the electrolyte or as another species in the solvent.

　Other additives can be added to the electrolyte. Additives include complex compounds of boric acid and polysaccharides (mannite, sorbitol, etc.), complex compounds of boric acid and polyhydric alcohol, boric acid esters, nitro compounds (o-nitrobenzoic acid, m-nitrobenzoic acid, acid, p-nitrobenzoic acid, o-nitrophenol, m-nitrophenol, p-nitrophenol, p-nitrobenzyl alcohol, etc.). These may be used alone or in combination of two or more.

(Solid electrolyte layer)
In the solid electrolyte layer, the conductive polymer is a self-doped conjugated polymer doped with intramolecular dopant molecules or a conjugated polymer doped with external dopant molecules. A conjugated polymer is obtained by subjecting a monomer having a π-conjugated double bond or a derivative thereof to chemical oxidation polymerization or electrolytic oxidation polymerization. A conductive polymer expresses high conductivity by performing a doping reaction on a conjugated polymer. That is, by adding a small amount of a dopant, such as an acceptor that easily accepts electrons or a donor that easily donates electrons, to the conjugated polymer, conductivity is exhibited.

As the conjugated polymer, any known one can be used without any particular limitation. Examples include polypyrrole, polythiophene, polyfuran, polyaniline, polyacetylene, polyphenylene, polyphenylenevinylene, polyacene, polythiophenevinylene and the like. These conjugated polymers may be used alone, may be used in combination of two or more types, and may be a copolymer of two or more types of monomers.

Among the above conjugated polymers, conjugated polymers obtained by polymerizing thiophene or derivatives thereof are preferable, and 3,4-ethylenedioxythiophene (that is, 2,3-dihydrothieno[3,4-b][ 1,4]dioxin), 3-alkylthiophenes, 3-alkoxythiophenes, 3-alkyl-4-alkoxythiophenes, 3,4-alkylthiophenes, 3,4-alkoxythiophenes, or conjugated high Molecules are preferred. The thiophene derivative is preferably a compound selected from thiophenes having substituents at the 3- and 4-positions, and the substituents at the 3- and 4-positions of the thiophene ring form a ring together with the carbon atoms at the 3- and 4-positions. can be An alkyl group or an alkoxy group preferably has 1 to 16 carbon atoms.

In particular, a polymer of 3,4-ethylenedioxythiophene called EDOT, that is, poly(3,4-ethylenedioxythiophene) called PEDOT is particularly preferred. Also, alkylated ethylenedioxythiophene in which an alkyl group is added to 3,4-ethylenedioxythiophene, such as methylated ethylenedioxythiophene (that is, 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. mentioned.

A known dopant can be used without any particular limitation. A dopant may be used independently and may be used in combination of 2 or more type. Also, polymers or monomers may be used. For example, dopants include polyanions, inorganic acids such as boric acid, nitric acid and phosphoric acid, acetic acid, oxalic acid, citric 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, bisoxalateborate acid, sulfonylimidic acid, dodecylbenzenesulfonic acid, propylnaphthalenesulfonic acid, butylnaphthalenesulfonic acid, etc. Organic acids are mentioned.

Polyanions are, for example, substituted or unsubstituted polyalkylenes, substituted or unsubstituted polyalkenylenes, substituted or unsubstituted polyimides, substituted or unsubstituted polyamides, substituted or unsubstituted polyesters, and have anionic groups. Examples include a polymer consisting of only units, and a polymer consisting of a structural unit having an anionic group and a structural unit having no anionic group. Specifically, polyanions include polyvinylsulfonic acid, polystyrenesulfonic acid, polyallylsulfonic acid, polyacrylsulfonic acid, polymethacrylsulfonic acid, poly(2-acrylamido-2-methylpropanesulfonic acid), and polyisoprenesulfonic acid. , polyacrylic acid, polymethacrylic acid, and polymaleic acid.

The solid electrolyte layer may contain various additives such as polyhydric alcohol in addition to the conductive polymer. Polyhydric alcohols include sorbitol, ethylene glycol, diethylene glycol, triethylene glycol, polyoxyethylene glycol, glycerin, polyglycerin, polyoxyethylene glycerin, xylitol, erythritol, mannitol, dipentaerythritol, pentaerythritol, or two of these. The above combination is mentioned. Since the polyhydric alcohol has a high boiling point, it can remain in the solid electrolyte layer even after the drying process, and effects of reducing ESR and improving withstand voltage can be obtained.

(separator)
Separators are made of cellulose such as kraft, manila hemp, esparto, hemp, rayon, and mixed paper thereof, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyester resins such as their derivatives, polytetrafluoroethylene resin, polyfluoride, etc. Polyamide resins such as vinylidene resins, vinylon resins, aliphatic polyamides, semi-aromatic polyamides, and wholly aromatic polyamides, polyimide resins, polyethylene resins, polypropylene resins, trimethylpentene resins, polyphenylene sulfide resins, acrylic resins, polyvinyl alcohol resins, etc., and these resins can be used singly or in combination.

The solid electrolytic capacitors of the examples will be described in more detail below. It should be noted that the present invention is not limited to the examples described below.

(Example 1)
A solid electrolytic capacitor of Example 1 was produced. The anode foil was an aluminum foil, which was subjected to surface enlargement by etching treatment, and was subjected to chemical conversion treatment at a chemical conversion voltage of 63.6 Vfs to form a dielectric oxide film. The surface of the cathode foil was expanded by etching, and an oxide film was formed by chemical conversion at a chemical conversion voltage of 3 Vfs. A lead wire was connected to each of the anode foil and the cathode foil, and the foil was wound with the anode foil and the cathode foil opposed to each other with a manila separator interposed therebetween. The wound body was immersed in an aqueous solution of ammonium dihydrogen phosphate for 15 minutes to perform repair formation. After that, it was dried at 105°C.

Next, the wound body was immersed in a dispersion of polyethylenedioxythiophene (PEDOT/PSS) doped with polystyrenesulfonic acid as a conductive polymer. Ethylene glycol was added to the dispersion. The wound body was dried at 110° C. for 30 minutes after being immersed in the dispersion. As a result, the conductive polymer was attached to the wound body, and the solid electrolyte layer containing the conductive polymer was impregnated with ethylene glycol.

Next, an electrolytic solution was prepared, and the wound body on which the solid electrolyte was formed was impregnated with the electrolytic solution. Ethylene glycol was used as the solvent for the electrolytic solution. Azelaic acid and dibutyl phosphate were added to the electrolytic solution so as to be 16 mmol each per 100 g of the electrolytic solution. In addition, as a cation component, ammonia was included in an amount of 16 mmol with respect to 100 g of the electrolytic solution.

The completed capacitor element was impregnated with electrolyte and inserted into a bottomed cylindrical exterior case. A sealing rubber was attached to the open end of the exterior case and sealed by caulking. Each solid electrolytic capacitor was aged by voltage application. Each of the produced solid electrolytic capacitors had a rated withstand voltage of 35 WV and a rated capacity of 270 μF.

Corresponding to this Example 1, solid electrolytic capacitors of Comparative Examples 1 and 2 were produced. The solid electrolytic capacitor of Comparative Example 1 is different from the solid electrolytic capacitor of Example 1 in that only dibutyl phosphate is added to the electrolytic solution without adding azelaic acid. Dibutyl phosphate was added so as to be 32 mmol with respect to 100 g of the electrolytic solution. The solid electrolytic capacitor of Comparative Example 2 differs from the solid electrolytic capacitor of Example 1 in that only azelaic acid is added to the electrolytic solution without adding dibutyl phosphate. Azelaic acid was added so as to be 32 mmol with respect to 100 g of the electrolytic solution. The solid electrolytic capacitors of Comparative Examples 1 and 2 are the same as those of Example 1 in all other respects, including the use of ammonia as a cation component, as well as in other configurations, manufacturing methods, manufacturing conditions, and the like.

(ESR 1)
The ESR of the solid electrolytic capacitors of Example 1 and Comparative Examples 1 and 2 was measured. The measurement frequency of ESR is 100 kHz. For ESR measurement, the solid electrolytic capacitor was exposed to a temperature environment of 160°C. Then, the ESR was measured at the timing when the elapsed time is 0 hours, which is immediately before exposure to the high temperature environment, and at the timing after 1200 hours of continuous exposure to the high temperature environment. ΔESR, which is the ratio of the ESR between the timing at zero time and the timing after 1200 hours, was also calculated. ΔESR is the percentage ratio of the ESR at timing after 1200 hours to the ESR at timing at zero time. The results are shown in Table 1 below.

(Table 1)

As shown in Table 1, the ESR of the solid electrolytic capacitor of Example 1 changes little even after being exposed to a high temperature environment of 160°C for 1200 hours, and has the smallest value. From this, it was confirmed that adding azelaic acid, which has a relatively poor ESR, to dibutyl phosphate, which has a relatively good ESR, results in a better ESR than dibutyl phosphate.

(Examples 2 to 4)
Solid electrolytic capacitors of Examples 2 to 4 were produced. The solid electrolytic capacitors of Examples 2 to 4 differ from the solid electrolytic capacitor of Example 1 in the type of phosphoric acid compound having a butyl group. Example 2 used tributyl phosphate, Example 3 used dibutyl phosphite, and Example 4 used tributyl phosphite. The solid electrolytic capacitors of Examples 2 to 4 were the same as those of Example 1 except that the type of phosphoric acid compound having a butyl group was different from that of Example 1. be.

(ESR 2)
The ESR of the solid electrolytic capacitors of Examples 2 to 4 was measured under the same conditions as in Example 1. The results are shown in Table 2 below.
(Table 2)

As shown in Table 2, the ESR of the solid electrolytic capacitors of Examples 2 to 4, like Example 1, show little change even when exposed to a high temperature environment of 160°C for 1200 hours, and the values are also small. From this, it was confirmed that the ESR of the solid electrolytic capacitor was improved even when a phosphoric acid compound having a butyl group and azelaic acid were added to the electrolytic solution, not limited to dibutyl phosphate.

(Examples 5 to 7)
Solid electrolytic capacitors of Examples 5 to 7 were produced. The solid electrolytic capacitors of Examples 5 to 7 differ from the solid electrolytic capacitor of Example 1 in the type of aliphatic dicarboxylic acid. Example 5 used succinic acid, Example 6 used glutaric acid, and Example 7 used citraconic acid. The solid electrolytic capacitors of Examples 5 to 7 were the same as those of Example 1 except that the type of aliphatic dicarboxylic acid was different from that of Example 1, and other constitutions, manufacturing methods, and manufacturing conditions.

Corresponding to Examples 5 to 7, solid electrolytic capacitors of Comparative Examples 3 to 5 were produced. The solid electrolytic capacitors of Comparative Examples 3 to 5 differ from those of Examples 5 to 7 in that the electrolytic solution does not contain a phosphoric acid compound having a butyl group. The solid electrolytic capacitors of Comparative Examples 3 to 5 were identical to those of Examples 5 to 7 in all other configurations, production methods, production conditions, etc., except for the presence or absence of the addition of a phosphoric acid compound having a butyl group. is.

(ESR 3)
The ESR of the solid electrolytic capacitors of Examples 5 to 7 and Comparative Examples 3 to 5 were measured under the same conditions as in Example 1. The results are shown in Table 3 below.
(Table 3)

As shown in Table 3, the ESR of the solid electrolytic capacitors of Examples 5 to 7 changed less than those of the corresponding Comparative Examples 3 to 5 even after exposure to a high temperature environment of 160°C for 1200 hours, and the value is small. From this, it was confirmed that the ESR of the solid electrolytic capacitor was improved not only by azelaic acid but also by adding other kinds of aliphatic dicarboxylic acid and dibutyl phosphate to the electrolytic solution. Overall, as can be seen from the results of Examples 1 to 7, the ESR of solid electrolytic capacitors is improved by containing various phosphoric acid compounds having butyl groups and various aliphatic dicarboxylic acids in the electrolytic solution. confirmed.

Moreover, as shown in Table 3, ESR is worse in Comparative Examples 3 and 4 than in Comparative Example 1. However, Examples 5 and 6, which correspond to Comparative Examples 3 and 4, have better ESR than Comparative Example 1. Combined with the results of Example 1 and Comparative Example 1, when an aliphatic dicarboxylic acid is selected from the group of azelaic acid, succinic acid, or glutaric acid, adding an aliphatic dicarboxylic acid with relatively poor ESR , it was confirmed that the ESR is better than that of a phosphoric acid compound having a butyl group, which has a relatively good ESR. Moreover, in Examples 1, 5, and 6, the ESR is much lower than in Comparative Examples 2, 3, and 4, and the ESR is better than in Example 7 as well.

Also in Example 7, the ESR is better than in Comparative Examples 1 and 5. As a result, when citraconic acid is selected as the aliphatic dicarboxylic acid, adding a phosphoric acid compound having a butyl group with relatively poor ESR results in a better ESR than citraconic acid, which has relatively good ESR. ing. That is, it was confirmed that when an aliphatic dicarboxylic acid and a phosphoric acid compound having a butyl group were added to the electrolytic solution, the ESR of the solid electrolytic capacitor became even better than the one with relatively good ESR.

(Leakage current measurement)
The LC (leakage current) of the solid electrolytic capacitors of Comparative Example 1 and Examples 1 and 5 to 7 was measured. Each solid electrolytic capacitor was left in a temperature environment of 160° C. for 2000 hours, and the leakage current after the standing was measured. The leakage current was obtained by applying a rated withstand voltage of 35 WV to each solid electrolytic capacitor and maintaining the voltage for 2 minutes.

The measurement results of LC (leakage current) of the solid electrolytic capacitors of Comparative Example 1 and Examples 1 and 5 to 7 are shown in Table 4 below.
(Table 4)

As shown in Table 4, in the solid electrolytic capacitors of Examples 1 and 5 to 7, leakage current is significantly reduced compared to the solid electrolytic capacitor of Comparative Example 1. From this, it was confirmed that adding a phosphoric acid compound having a butyl group and an aliphatic dicarboxylic acid to the electrolytic solution lowered the ESR and also reduced the leakage current.

(Examples 8 and 9)
As shown in Table 5 below, the ESR and leakage current of various solid electrolytic capacitors with different amounts of dibutyl phosphate added were measured. In Table 5, Example 8, Example 9, and Comparative Example 6 have all the same configurations, manufacturing methods, and manufacturing conditions as those of Example 1, except that the amount of dibutyl phosphate added is different from that of Example 1. Identical to 1. In addition, as shown in Table 5, the ESR was measured at the timing of 0 hours just before exposure to the temperature environment of 160° C. and the timing after 1200 hours of exposure to the high temperature environment. Leakage current was measured after 2000 hours of exposure to this high temperature environment.

(Table 5)

As shown in Comparative Examples 6 and 2 in Table 5, when 48 mmol of dibutyl phosphate, which has a relatively good ESR, was added to 100 g of the electrolytic solution, 1200 hours elapsed from the case of azelaic acid, which had a relatively poor ESR. It can be seen that the subsequent ESR is degraded. Moreover, as shown in Comparative Examples 6 and 1, when 48 mmol of dibutyl phosphate is added to 100 g of the electrolytic solution, the leakage current is significantly worse than when only dibutyl phosphate is contained in the electrolytic solution.

On the other hand, as shown in Example 9 and Comparative Example 1, even if azelaic acid, which relatively worsens the ESR, is contained, when dibutyl phosphate is 32 mmol or less per 100 g of the electrolyte, only dibutyl phosphate is contained in the electrolytic solution, the ESR after 1200 hours is better. That is, when the electrolytic solution contains an aliphatic dicarboxylic acid and a phosphoric acid compound having a butyl group, and the amount of the phosphoric acid compound having a butyl group added is 32 mmol or less per 100 g of the electrolytic solution, the ESR becomes favorable. was confirmed.

Then, as shown in Table 5, when the amount of the phosphoric acid compound having a butyl group, which has a relatively good ESR, is decreased and the ratio of the aliphatic dicarboxylic acid, which has a relatively poor ESR, is increased, the solid electrolytic capacitor It was confirmed that the ESR of Further, as shown in Example 8, when a phosphoric acid compound having a butyl group with relatively poor leakage current is mixed at a ratio of 8 mmol or less with respect to 100 g of the electrolyte, when only the aliphatic dicarboxylic acid is included in the electrolyte It was confirmed that the leakage current was improved.

(Examples 10 to 12)
Solid electrolytic capacitors of Examples 10 to 12 were produced. Further, corresponding to Examples 10 to 12, solid electrolytic capacitors of Comparative Examples 7 and 8 were produced. The solid electrolytic capacitors of Examples 10 to 12 and Comparative Examples 7 and 8 differ from the solid electrolytic capacitor of Example 1 in the amount of aliphatic dicarboxylic acid added. The solid electrolytic capacitors of Examples 10 to 12 and Comparative Examples 7 and 8 are the same as those of Example 1 in all other configurations, manufacturing methods, manufacturing conditions, and the like.

Then, the ESR and leakage current of the solid electrolytic capacitors of Examples 1, 10 to 12, and Comparative Examples 7 and 8 were measured. As shown in Table 6 below, the ESR was measured at the timing of 0 hours just before exposure to the temperature environment of 150° C. and at the timing of 2700 hours after exposure to this high temperature environment. Leakage current was measured after 2700 hours of exposure to this high temperature environment.

(Table 6)

A phosphate compound having a butyl group is dibutyl phosphate, and an aliphatic dicarboxylic acid is azelaic acid. As shown in Table 6, in Example 1, equimolar amounts of the phosphoric acid compound and azelaic acid were contained in the electrolytic solution. In Example 10, the electrolytic solution contained azelaic acid at a molar ratio of 0.75 to 1 for the phosphoric acid compound. In Example 11, the electrolytic solution contained azelaic acid at a molar ratio of 0.5 to 1 for the phosphoric acid compound. In Example 12, the electrolytic solution contained azelaic acid at a molar ratio of 0.25 to 1 for the phosphoric acid compound.

In Comparative Example 7, the electrolyte does not contain a phosphoric acid compound. In Comparative Example 8, the electrolytic solution contained no aliphatic dicarboxylic acid, and the electrolytic solution contained 0 azelaic acid when the phosphoric acid compound was taken as 1 in molar ratio.

As shown in Table 6, it was confirmed that the solid electrolytic capacitors of Examples 1, 10, 11 and 12 had good ESR regardless of the amount of the aliphatic dicarboxylic acid added. In particular, from Table 6, when the molar ratio of the phosphoric acid compound is 1, when the aliphatic dicarboxylic acid is contained in the electrolytic solution in an amount of 0.25 or more, deterioration of ESR is suppressed even when exposed to a high temperature environment, and leakage current It can be confirmed that (LC) is also lowered.

(Example 13)
A solid electrolytic capacitor of Example 13 was produced. The solid electrolytic capacitor of Example 13 differs from the solid electrolytic capacitor of Example 1 in that triethylamine was added as a cationic component. The solid electrolytic capacitor of Example 13 is the same as Example 1 in all other configurations, manufacturing methods, manufacturing conditions, and the like.

The ESR of the solid electrolytic capacitors of Examples 1 and 13 was measured. As shown in Table 7 below, the ESR was measured at time zero, which is just before exposure to the temperature environment of 150° C., and at time 260 hours after exposure to this high temperature environment.

(Table 7)

As shown in Table 7, the ESR of the solid electrolytic capacitor is good regardless of the cation species in the electrolyte, but especially when the cation species is ammonia, the ESR deteriorates at high frequencies even when exposed to a high temperature environment. was confirmed to be suppressed.

(Examples 14 to 20)
Solid electrolytic capacitors of Examples 14 to 20 were produced. Also, a solid electrolytic capacitor of Comparative Example 9 was produced. The solid electrolytic capacitors of Examples 14 to 20 and Comparative Example 9 differ from the solid electrolytic capacitor of Example 13 in the solvent type of the electrolytic solution. The solid electrolytic capacitors of Examples 14 to 20 and Comparative Example 9 are the same as those of Example 13 in all other configurations, manufacturing methods, manufacturing conditions, and the like.

Then, the ESR of the solid electrolytic capacitors of Examples 13 to 20 and Comparative Example 9 was measured. As shown in Table 8 below, the ESR was measured at the timing of 0 hours, which is just before exposure to the temperature environment of 150° C., and at the timing of 260 hours after exposure to the high temperature environment.

(Table 8)

As shown in Table 8, the solvent species in Example 13 is ethylene glycol. The solvent species in Example 14 is a mixture of ethylene glycol and glycerin. The solvent species of Example 15 is a mixed liquid of ethylene glycol and glycerin as in Example 14, but the mixing ratio is different between Example 14 and Example 15. In Example 14, ethylene glycol accounts for 90 wt% and glycerin accounts for 10 wt% in the solvent. In Example 15, ethylene glycol accounts for 40 wt% and glycerin accounts for 60 wt% in the solvent.

The solvent species in Example 16 is glycerin. The solvent species for Example 17 is sulfolane. The solvent species in Example 18 is a mixture of glycerin and polyethylene glycol with an average molecular weight of about 300. The solvent species in Example 19 is a mixture of glycerin and polyethylene glycol having an average molecular weight of about 300 as in Example 18. In Example 18, glycerin accounts for 70 wt% and polyethylene glycol represents 30 wt% in the solvent. In Example 18, the weight ratio of glycerin and polyethylene glycol in the solvent is equal.

The solvent species in Example 20 is γ-butyrolactone. The solvent type in Comparative Example 9 was γ-butyrolactone, but did not contain a phosphoric acid compound having a butyl group.

As shown in Table 8, Examples 16 to 19 had better ESR after being exposed to a high-temperature environment than Example 20. Examples 13 to 15 had better ESR at a measurement frequency of 100 kHz than Examples 16 to 19, and even better ESR when exposed to a high temperature environment.

Examples 13 to 15 are solid electrolytic capacitors containing ethylene glycol as a solvent species. Examples 16 to 19 are solid electrolytic capacitors containing glycerin or sulfolane as solvent species. This confirms that the low ESR is maintained when the electrolyte contains glycerin or sulfolane. Moreover, it was confirmed that the ESR was maintained even lower when the electrolytic solution contained ethylene glycol.

Claims

an anode foil containing a valve metal and having a dielectric oxide film formed thereon;
a cathode foil containing a valve metal and facing the anode foil;
an electrolyte layer containing a conductive polymer and an electrolytic solution and interposed between the anode foil and the cathode foil;
with
The electrolytic solution contains a phosphoric acid compound having a butyl group and an aliphatic dicarboxylic acid,
The phosphoric acid compound is 32 mmol or less per 100 g of the electrolytic solution,
A solid electrolytic capacitor characterized by:
The phosphoric acid compound is 8 mmol or less per 100 g of the electrolytic solution,
The solid electrolytic capacitor according to claim 1, characterized by:
The phosphoric acid compound is one or a mixture of two or more selected from the group consisting of dibutyl phosphate, tributyl phosphate, dibutyl phosphite, and tributyl phosphite;
3. The solid electrolytic capacitor according to claim 1 or 2, characterized by:
The aliphatic dicarboxylic acid is one or a mixture of two or more selected from the group consisting of azelaic acid, succinic acid, glutaric acid, and citraconic acid;
3. The solid electrolytic capacitor according to claim 1 or 2, characterized by:
The aliphatic dicarboxylic acid is one or a mixture of two or more selected from the group consisting of azelaic acid, succinic acid, and glutaric acid;
3. The solid electrolytic capacitor according to claim 1 or 2, characterized by:
The electrolytic solution contains one or more selected from the group consisting of ethylene glycol, glycerin and sulfolane;
3. The solid electrolytic capacitor according to claim 1 or 2, characterized by:
the electrolytic solution containing ammonia;
3. The solid electrolytic capacitor according to claim 1 or 2, characterized by:
The aliphatic dicarboxylic acid is contained in the electrolytic solution in a molar ratio of 0.25 or more when the phosphoric acid compound is 1,
3. The solid electrolytic capacitor according to claim 1 or 2, characterized by: