JP2005093595A - Electrolyte for electrolytic capacitor, and electrolytic capacitor using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrolyte having high specific conductivity and high thermal resistance, and to provide an electrolytic capacitor having low impedance and high thermal resistance. <P>SOLUTION: The electrolyte (E) for an electrolytic capacitor which is formed of an electrolyte (A) composed of tetrafluoroborate of tertiary monoamine (a1) expressed by a general formula (1), and the electrolytic capacitor using the electrolyte are used. In the general formula (1), R<SB>1</SB>, R<SB>2</SB>, and R<SB>3</SB>are a hydrocarbon group which may have a hydroxyl group, cyano group, carbonyl group, formyl group, group having an ester bond, or group having an ether bond, with the total number of carbons being not less than 1 nor more than 3. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an electrolytic solution for electrolytic capacitors, and more particularly to an electrolytic solution for electrolytic capacitors having high specific conductivity, and an electrolytic capacitor using the electrolytic solution.

Conventionally, in order to improve the energy loss and low impedance characteristics of electrolytic capacitors, development of electrolytic solutions with high specific conductivity has been actively conducted. On the other hand, there is a demand for an electrolytic solution for an electrolytic capacitor that is excellent in thermal stability as the temperature around the set position of the electrolytic capacitor such as the periphery of an automobile engine increases. As an electrolytic solution having high specific conductivity and excellent heat resistance, an electrolytic solution in which a quaternary onium salt of tetrafluoroaluminic acid (for example, Patent Document 1) is dissolved in an aprotic solvent such as γ-butyrolactone has been proposed. ing.
JP 2003-142346 A

However, an electrolytic solution in which a quaternary onium salt of tetrafluoroaluminic acid is dissolved in an aprotic solvent such as γ-butyrolactone is excellent in heat resistance but is not necessarily sufficient in specific conductivity.
That is, an object of the present invention is to provide an electrolytic solution having both high specific conductivity and high heat resistance, and an electrolytic capacitor having both low impedance and high heat resistance.

［式中、Ｒ₁、Ｒ₂およびＲ₃は、水酸基、シアノ基、カルボニル基、フォルミル基、エステル結合を有する基、又はエーテル結合を有する基を有していてもよい炭化水素基であって、炭素の合計数が１以上３以下である。］ As a result of intensive studies to solve the above problems, the present inventors have found that a quaternary ammonium or quaternary amidinium as a cation exhibits higher specific conductivity than a tertiary monoamine. It has been found that an electrolytic solution using a salt of a combination of a class monoamine and tetrafluoroboric acid as an electrolyte has a high specific conductivity that has not been achieved so far. Further, the inventors have found that an electrolytic capacitor using this electrolytic solution has low impedance and high heat resistance, and have reached the present invention.
That is, the present invention provides an electrolytic solution (E) for an electrolytic capacitor using an electrolyte (A) composed of a salt of tetrafluoroboric acid (a2) of a tertiary monoamine (a1) represented by the following general formula (1), and the use thereof It was an electrolytic capacitor.

[Wherein R ₁ , R ₂ and R ₃ are a hydrocarbon group optionally having a hydroxyl group, a cyano group, a carbonyl group, a formyl group, a group having an ester bond, or a group having an ether bond. The total number of carbons is 1 or more and 3 or less. ]

  The electrolytic solution for electrolytic capacitors of the present invention has excellent heat resistance and high unprecedented specific conductivity. In addition, an electrolytic capacitor using the present electrolytic solution exhibits excellent heat resistance and exhibits excellent low-impedance characteristics that have not existed before.

  In the present invention, examples of the tertiary monoamine (a1) include compounds represented by the general formula (1). The (a1) may be a mixture of two or more.

R ₁ , R ₂ and R ₃ in the general formula (1) are linear or branched alkyl groups such as methyl group, ethyl group, propyl group and isopropyl group; hydroxyalkyl groups such as hydroxymethyl group and hydroxyethyl group A cyanoalkyl group such as a cyanomethyl group and a cyanoethyl group; an alkoxyalkyl group such as a methoxymethyl group and a methoxyethyl group; an acetylalkyl group such as an acetylmethyl group; a methylcarbooxyalkyl group such as a methylcarbooxymethyl group; For example, a formylmethyl group, a formylethyl group, etc. are mentioned.
Of these, preferred are methyl, ethyl, propyl, isopropyl, hydroxymethyl, cyanomethyl, methoxymethyl, acetylmethyl, methylcarbooxymethyl and formylmethyl, and particularly preferred are , Methyl group and ethyl group. When at least one of R ₁ , R ₂ and R ₃ is a different group, it is particularly preferable because it exhibits a higher specific conductivity. When R ₁ , R ₂ and R ₃ are different groups, that is, when _one of R ₁ , R ₂ and R ₃ is different and the other two are the same, or R ₁ , R ₂ and Either of R ₃ is different.

Specific examples of the tertiary monoamine (a1) include the following compounds.
(1) R ₁ , R ₂ and R ₃ are hydrocarbon groups Trimethylamine, triethylamine, N, N-dimethylethylamine, N, N-dimethylpropylamine, N, N-dimethylisopropylamine, N, N-diethyl Methylamine, N, N, N-methylethylpropylamine, N, N, N-methylethylisopropylamine, N, N-dipropylmethylamine, N, N-diisopropylmethylamine and the like.

(2) In which at least one of R ₁ , R ₂ and R ₃ is a hydrocarbon group having a formyl group N, N-dimethylformylmethylamine, N, N-dimethylformylethylamine, N, N-diethylformylmethylamine N, N-diethylformylethylamine and the like.

(3) A hydrocarbon group in which at least one of R ₁ , R ₂ and R ₃ has a group having an ester bond N, N-dimethylmethoxycarbonylmethylamine, N, N-diethylmethoxycarbonylmethylamine and the like.

(4) At least one of R ₁ , R ₂ and R ₃ is a hydrocarbon group having a cyano group N, N-dimethylcyanomethylamine, N, N-dimethylcyanoethylamine, N, N-diethylcyanomethylamine N, N-diethylcyanoethylamine and the like.

(5) At least one of R ₁ , R ₂ and R ₃ is a hydrocarbon group having an ether bond N, N-dimethylmethoxymethylamine, N, N-dimethylmethoxyethylamine, N, N-diethylmethoxymethylamine N, N-diethylmethoxyethylamine and the like.

(6) At least one of R ₁ , R ₂ and R ₃ is a hydrocarbon group having a carbonyl group N, N-dimethylacetylmethylamine, N, N-diethylacetylmethylamine and the like.

(7) At least one of R ₁ , R ₂ and R ₃ is a hydrocarbon group having a hydroxyl group N, N-dimethylhydroxymethylamine, N, N-dimethylhydroxyethylamine, N, N-diethylhydroxymethylamine, N, N-diethylhydroxyethylamine and the like.

  Of these, N, N-dimethylethylamine, N, N-dimethylpropylamine, N, N-dimethylisopropylamine, N, N-methyldiethylamine, N, N-dipropylmethylamine, N, N-diisopropyl are preferred. Methylamine, more preferably N, N-dimethylethylamine and N, N-methyldiethylamine, and particularly preferably N, N-dimethylethylamine.

  In the electrolyte (A), the molar ratio of the tertiary monoamine (a1) constituting the electrolyte to the tetrafluoroboric acid has the highest specific conductivity, and little hydrogen fluoride is generated due to decomposition of the tetrafluoroboric acid. The molar ratio is preferably 0.99 or more, more preferably 1.00 or more, preferably 1.20 or less, more preferably 1.05 or less, and most preferably 1.03 or less.

  The molar ratio between the tertiary monoamine (a1) and tetrafluoroboric acid is determined by adding a known amount of a standard substance containing H and F atoms to the electrolyte, and the H-NMR peak integration ratio and F-NMR peak of the standard substance. It can be quantified by comparing the integral ratio, the H-NMR peak integral ratio of the tertiary monoamine, and the F-NMR peak integral ratio of the tetrafluoroboric acid. An example of the standard substance is 4'-fluoroacetophenone.

Weight of electrolyte solution of hydrogen fluoride (hereinafter referred to as HF) and fluorine ions (hereinafter abbreviated as F ⁻ ), which are impurities mixed in the production process of tetrafluoroboric acid in the electrolyte (A) of the present invention The total weight content based on is preferably 0.1% by weight or less, more preferably 0.01% by weight or less, because it causes swelling of the electrolytic capacitor or corrosion of the anodized film.

HF and F ^- content in preparing the electrolytic solution is reduced to such a small amount of, for example, a method of using a high purity raw material for the electrolyte, advance recrystallization and solvent extraction of the electrolyte salt to be used For example, there is a method of purification. Solvents used for recrystallization and solvent extraction include alcohols such as methanol, ethanol, n-propanol and isopropanol; ketones such as acetone, methyl ethyl ketone, diethyl ketone and methyl isobutyl ketone; diethyl ether and ethyl n-propyl ether. And ethers such as ethyl isopropyl ether, di-n-propyl ether, diisopropyl ether, n-propyl-isopropyl ether, dimethoxyethanemethoxyethoxyethane, diethoxyethane, and the like. These may be used alone or in combination of two or more. The amount of solvent used in the purification depends on the type of the solvent used, which is an impurity HF and F ^- dissolved, and since it is less loss of the electrolyte salt, the normal electrolyte salt 0.5-10 Within the double weight range is preferred. In addition, the said solvent extraction in this invention shall mean the method of adding a solvent to the electrolyte containing an impurity, and isolate | separating and refine | purifying the oil-like or gum-like electrolyte which precipitates from an impurity.

HF and F ^- total content of the F-NMR measurement of the electrolyte, HF and F ^- can be quantified by comparing the F-NMR peak integration ratio of the tetrafluoroborate.

  The reason why the total weight content based on the weight of the electrolyte of sulfuric acid and sulfate ions, which are impurities mixed in the production process of tetrafluoroboric acid in the electrolyte (A) of the present invention, causes corrosion of the anodic oxide film. To 100 ppm or less, more preferably 10 ppm or less.

In order to produce an electrolyte with such a small amount of sulfuric acid and sulfate ion content, for example, a method of using a high-purity electrolyte raw material, a recrystallization and solvent extraction of the electrolyte salt to be used in advance. For example, there is a method of purification. Examples of the solvent used for recrystallization and solvent extraction include the same solvents as those used for reducing HF and F ⁻ . The amount of the solvent used for the purification depends on the kind of the solvent used, but it dissolves the sulfuric acid and sulfate ions, which are impurities, and the loss of the electrolyte salt is small. Within the double weight range is preferred.

  The contents of sulfuric acid and sulfate can be quantified by a general measurement method such as barium sulfate turbidimetry described in Item 396, “Inorganic Applied Colorimetric Analysis” (edited by Inorganic Applied Colorimetric Analysis Editorial Committee).

  The reason why the total weight content based on the weight of the electrolytic solution of hydrofluoric acid, which is an impurity mixed in the production process of tetrafluoroboric acid in the electrolyte (A) of the present invention, causes corrosion of the anodic oxide film. To 0.1 wt% or less, more preferably 0.01 wt% or less.

In order to produce an electrolytic solution in which the content of silicofluoric acid is reduced to such a small amount, for example, a method of using a high-purity electrolyte raw material, an electrolyte salt to be used is recrystallized and a solvent in advance. There is a method of purification by extraction or the like. Examples of the solvent used for recrystallization and solvent extraction include the same solvents as those used for reducing HF and F ⁻ . The amount of the solvent used for the purification depends on the type of the solvent used, but it is usually 0.5 to 10% with respect to the electrolyte salt because it dissolves the hydrosilicofluoric acid which is an impurity and there is little loss of the electrolyte salt. Within the double weight range is preferred.

The content of silicofluoric acid can be quantified by the following method. 1 g of a sample is accurately measured in a 50 ml polyethylene flask, water is added to the marked line, and the mixture is shaken well. Then, the wavelength is 251.611 nm by ICP-AES (high frequency inductively coupled plasma emission spectroscopy, hydrofluoric acid system). Si is detected by the following calculation method.
Silicohydrofluoric acid (salt) content = Si content × 5.130 × 50

In the electrolyte (A) of the present invention, a hydrolyzate of tetrafluoroboric acid ([BF _n (OH) _4-n ] ⁻ (n is 1 to 3), which is an impurity mixed in the tetrafluoroboric acid production process. The total weight content based on the weight of the electrolyte of natural number) and boric acid) is 0.5% by weight or less, more preferably 0.1% by weight or less, because it causes a decrease in conductivity.

In order to produce an electrolytic solution in which the content of the hydrolyzate of tetrafluoroboric acid is reduced to such a small amount, for example, a method of using a high-purity electrolyte raw material, or an electrolyte salt to be used in advance is re-used. There are methods of purification by crystal and solvent extraction. Examples of the solvent used for recrystallization and solvent extraction include the same solvents as those used for reducing HF and F ⁻ . The amount of solvent used for purification depends on the type of solvent used, but it is usually 0% relative to the electrolyte salt because it dissolves the hydrolyzate of tetrafluoroboric acid, which is an impurity, and the loss of the electrolyte salt is small. Within the range of 5 to 10 times the weight is preferable.

  The content of the hydrolyzate of tetrafluoroboric acid can be quantified by ion chromatography.

The electrolytic solution of the present invention is preferably composed of a solution of the electrolyte (A) and the organic solvent (D). Specific examples of the organic solvent (D) are as follows, and two or more kinds can be used in combination.
(1) Alcohols Monohydric alcohols (methyl alcohol, ethyl alcohol, propyl alcohol, butyl alcohol, diacetone alcohol, benzyl alcohol, amino alcohol, furfuryl alcohol, etc.), dihydric alcohols (ethylene glycol, propylene glycol, diethylene glycol, Xylene glycol, etc.), trihydric alcohol (eg, glycerin), tetravalent or higher alcohol (eg, hexitol), etc .;
(2) Ethers Monoethers (ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, ethylene glycol monophenyl ether, tetrahydrofuran, 3-methyltetrahydrofuran, etc.), diethers (ethylene glycol dimethyl ether, ethylene Glycol diethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, etc.);
(3) Amides Formamides (N-methylformamide, N, N-dimethylformamide, N-ethylformamide, N, N-diethylformamide, etc.), acetamides (N-methylacetamide, N, N-dimethylacetamide, N -Ethylacetamide, N, N-diethylacetamide, etc.), propionamides (N, N-dimethylpropionamide, etc.), pyrrolidones (N-methylpyrrolidone, N-ethylpyrrolidone, etc.), hexamethylphosphorylamide, etc .;
(4) Oxazolidinones N-methyl-2-oxazolidinone, 3,5-dimethyl-2-oxazolidinone, etc .;
(5) Lactones γ-butyrolactone, α-acetyl-γ-butyrolactone, β-butyrolactone, γ-valerolactone, δ-valerolactone, etc .;
(6) Nitriles Acetonitrile, propionitrile, butyronitrile, acrylonitrile, methacrylonitrile, benzonitrile, etc .;
(7) Carbonates Ethylene carbonate, propion carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, etc .;
(8) Sulfoxides Dimethyl sulfoxide, sulfolane, 3-methyl sulfolane, 2,4-dimethyl sulfolane, etc .;
(9) Other organic solvents 1,3-dimethyl-2-imidazolidinone, N-methylpyrrolidone, aromatic solvents (such as toluene and xylene), paraffinic solvents (such as normal paraffin and isoparaffin), and the like.

Among these, γ-butyrolactone, sulfolane, 3-methylsulfolane, 2,4-dimethylsulfolane, N-methyl-2-oxazolidinone, acetonitrile, ethylene glycol, and N, N-dimethylformamide are more preferable. Those are γ-butyrolactone, sulfolane, and ethylene glycol, and particularly preferred is a mixed solvent in which γ-butyrolactone and sulfolane are used in combination.
The weight ratio of γ-butyrolactone in the mixed solvent is preferably 30% by weight or more, particularly preferably 40% by weight or more because the specific conductivity is high, and is preferably 40% by weight or more, because it is possible to suppress transpiration from the sealing rubber. % By weight or less is preferable, and 70% by weight or less is particularly preferable.

  The content of the electrolyte (A) in the electrolytic solution for an electrolytic capacitor of the present invention is preferably 5% by weight or more, more preferably 10% by weight based on the weight of the electrolytic solution from the viewpoint of electrical conductivity and solubility in the electrolytic solution solvent. It is above, Preferably it is 70 weight% or less, More preferably, it is 40 weight% or less.

  If necessary, various additives usually used in the electrolytic solution can be added to the electrolytic solution of the present invention. Examples of the additive include phosphoric acid derivatives (for example, phosphoric acid, phosphoric acid esters, etc.), boric acid derivatives (for example, boric acid, complex compounds of boric acid and polysaccharides [mannit, sorbit, etc.], boric acid and Complex compounds with polyhydric alcohols (ethylene glycol, glycerin, etc.), nitro compounds (for example, o-nitrobenzoic acid, p-nitrobenzoic acid, m-nitrobenzoic acid, o-nitrophenol, p-nitrophenol, etc.) ) And the like. The addition amount is preferably 20% by weight or less, more preferably 10% by weight or less, and preferably 0.1% by weight with respect to the electrolyte (A) from the viewpoint of specific conductivity and solubility in the electrolyte solution solvent. More preferably, it is 1% by weight or more.

  In the electrolytic solution in the present invention, the water content of the electrolytic solution is preferably 1% by weight or less, more preferably 0.1% by weight or less, because gas generation due to hydrolysis causes remarkable problems such as swelling of the capacitor. Considering the repair ability of the anodized film, it is preferably 0.0001% by weight or more, and more preferably 0.01% by weight or more.

  The electrolytic solution in the present invention is used for an electrolytic capacitor. The electrolytic capacitor is not particularly limited. For example, an aluminum oxide foil and a cathode aluminum foil are wound on the surface with a separator interposed therebetween, and impregnated with the electrolytic solution of the present invention, and stored in a bottomed cylindrical aluminum case. Then, a wound aluminum electrolytic capacitor configured by sealing the opening of the aluminum case with a sealing agent is preferable.

  Next, specific examples of the present invention will be described, but the present invention is not limited thereto. Hereinafter, “%” represents “% by weight”.

A Teflon round bottom flask was charged with 209 g of a 42% aqueous solution of tetrafluoroboric acid, 73 g of N, N-dimethylethylamine was added dropwise at 20 ° C. with stirring, and the mixture was stirred for 30 minutes after completion of the addition. Water was removed at 110 ° C./5 mmHg to obtain 160 g of tetrafluoroborate salt of N, N-dimethylethylamine. 200 g of methanol was added to this, heated and dissolved at 60 ° C., and then filtered while hot. The filtrate was cooled to 0 ° C., and the precipitated crystals were filtered. This was washed with ethanol at −25 ° C. and then dried under reduced pressure to obtain purified N, N-dimethylethylamine tetrafluoroborate. This was dissolved in γ-butyrolactone to prepare an electrolyte solution having a concentration of 25%.
From the measurement results of F-NMR and H-NMR, the molar ratio of N, N-dimethylethylamine and tetrafluoroboric acid is 1.00: 1.00, based on the weight of the electrolyte solution of hydrogen fluoride and fluorine ions. The total weight content was 0.00%.
The content of sulfuric acid and sulfate by barium sulfate nephelometry is 1 ppm, the content of hydrofluoric acid and its salt by ICP-AES measurement is 0.00%, and the hydrolyzate of tetrafluoroboric acid by ion chromatography The content rate was 0.01%. Moreover, the water | moisture content was 0.03% as a result of the water | moisture content measurement by a Karl Fischer method.

Example 1 except that N, N-diethylmethylamine tetrafluoroborate was used as the solute
An electrolyte solution was prepared in the same manner as described above.
From the measurement results of F-NMR and H-NMR, the molar ratio of N, N-diethylmethylamine and tetrafluoroboric acid is 1.00: 1.00, and the weight of the electrolyte solution of hydrogen fluoride and fluorine ions is The total weight content based was 0.01%.
The content of sulfuric acid and sulfate by barium sulfate turbidimetry is 1 ppm, the content of hydrofluoric acid and its salt by ICP-AES measurement is 0.00%, and the hydrolyzate of tetrafluoroboric acid by ion chromatography The content rate was 0.01%. In addition, as a result of moisture measurement by the Karl Fischer method, the moisture content was 0.05%.

Comparative Example 1
200 g of 1,2,3,4-tetramethylimidazolinium tetrafluoroaluminate was added to 900 ml of methanol and dissolved to perform solvent extraction. It cooled to 0 degreeC and the educt was obtained in the lower layer. This was dried under reduced pressure to obtain purified 1,2,3,4-tetramethylimidazolinium tetrafluoroaluminate. This was dissolved in γ-butyrolactone to prepare an electrolyte solution having a concentration of 25%.
From the measurement results of F-NMR and H-NMR, the total weight content based on the weight of the electrolyte solution of hydrogen fluoride and fluorine ions was 0.0%.
The content of sulfuric acid and sulfate by barium sulfate turbidimetry is 1 ppm, the content of hydrofluoric acid and its salt by ICP-AES measurement is 0.00%, and the hydrolyzate of tetrafluoroboric acid by ion chromatography The content rate was 0.01%. Moreover, the water | moisture content was 0.08% as a result of the water | moisture content measurement by a Karl Fischer method.

Comparative Example 2
An electrolyte solution was prepared in the same manner as in Comparative Example 1 except that 1,2,3,4-tetramethylimidazolinium tetrafluoroborate was used as the solute.
From the measurement results of F-NMR and H-NMR, the total weight content based on the weight of the electrolyte solution of hydrogen fluoride was 0.01%.
The content of sulfuric acid and sulfate by barium sulfate turbidimetry is 1 ppm, the content of hydrofluoric acid and its salt by ICP-AES measurement is 0.00%, and the hydrolyzate of tetrafluoroboric acid by ion chromatography The content rate was 0.01%. Moreover, the water | moisture content was 0.03% as a result of the water | moisture content measurement by a Karl Fischer method.

  With respect to the electrolytic solutions of Examples 1 and 2 and Comparative Examples 1 and 2 of the present invention, the initial specific conductivity and the rate of change in specific conductivity at 30 ° C. were measured by the following methods. The results are shown in Table 1.

<Initial specific conductivity at 30 ° C.>
The initial specific conductivity at 30 ° C. of the electrolyte was measured using a specific conductivity measuring device (manufactured by Toa Denpa Kogyo Co., Ltd .: CM-40S).

<Change rate of specific conductivity>
The rate of change in specific conductivity at 30 ° C. after conducting a heat test at 125 ° C. for 50 hours in a sealed glass ampoule, ie, [{(initial specific conductivity before heat test) − (after heat test) Specific conductivity)} / (initial specific conductivity before the heat resistance test)] × 100 (unit: “%”).

  As is clear from Table 1, the electrolytic solutions of Examples 1 and 2 have higher specific conductivity and excellent heat resistance than the electrolytic solutions of Comparative Examples 1 and 2.

  Using the electrolytic solution of Example 1, an aluminum electrolytic capacitor was produced by the following method.

  Using the electrolytic solution of Example 2, an aluminum electrolytic capacitor was produced by the following method.

Method for Producing Aluminum Electrolytic Capacitor The electrolytic solution of Example and Comparative Example was impregnated into a take-up type aluminum electrolytic capacitor element having a constant voltage of 6.3 V and a capacitance of 1000 μF, and the capacitor element was put into an outer case of φ10 × 12.5L. After sealing, the opening of the outer case was curled together with the sealing material, and then aging was performed to produce the electrolytic capacitor of the present invention.

Comparative Examples 3-4
Similarly, electrolytic capacitors were produced using the electrolytic solutions of Comparative Examples 1 and 2.

Using the produced electrolytic capacitor, the initial impedance at 20 ° C. and 100 kHz, and the impedance, impedance change rate and appearance change after 125 ° C. × 500 hr no-load test were evaluated, and the results are shown in Table 2.
The impedance change rate is a value obtained by [{(impedance after no-load test) − (initial impedance before no-load test)} / (initial impedance before no-load test)] × 100 (the unit is “%”). It is.

  As is clear from Table 2, the capacitors of Examples 3 to 4 have a lower impedance than the capacitors of Comparative Examples 3 to 4. Moreover, it is as excellent in heat resistance as compared with the rate of change in impedance of the capacitors of Comparative Examples 3 to 4.

An electrolytic capacitor using this electrolytic solution is most suitable for use as a control unit control circuit for automobiles and a control circuit for high performance AV equipment.

Claims (14)

An electrolytic solution (E) for an electrolytic capacitor comprising an electrolyte (A) comprising a tetrafluoroborate of a tertiary monoamine (a1) represented by the following general formula (1).

[Wherein R ₁ , R ₂ and R ₃ are a hydrocarbon group optionally having a hydroxyl group, a cyano group, a carbonyl group, a formyl group, a group having an ester bond, or a group having an ether bond. The total number of carbons is 1 or more and 3 or less. ] The electrolytic solution according to claim 1, comprising the electrolyte (A) and an organic solvent (D). The electrolytic solution according to claim 1 or 2, wherein at least one of R ₁ , R ₂ and R ₃ of the tertiary monoamine (a1) represented by the general formula (1) is a different group. The tertiary monoamine (a1) is at least one selected from the group consisting of N, N-dimethylethylamine, N, N-dimethylpropylamine, N, N-dimethylisopropylamine and N, N-diethylmethylamine. The electrolyte solution in any one of Claims 1-3. The electrolytic solution according to any one of claims 1 to 4, wherein the tertiary monoamine (a1) is N, N-dimethylethylamine. The electrolyte according to any one of claims 1 to 5, wherein in the electrolyte (A), a molar ratio of the tertiary monoamine (a1) constituting the electrolyte to the tetrafluoroboric acid is 0.99 or more and 1.20 or less. liquid. The total weight content based on the weight of the electrolyte solution (E) of hydrogen fluoride and fluorine ions contained in the electrolyte (A) is 0.1% by weight or less. Electrolyte. The total weight content based on the weight of the electrolyte solution (E) of sulfuric acid and sulfate contained in the electrolyte (A) is 100 ppm or less. The electrolyte solution according to any one of claims 1 to 7 The total weight content based on the weight of the electrolyte solution (E) of hydrofluoric acid and its salt contained in the electrolyte (A) is 0.1% by weight or less. The electrolyte described The total weight content of the hydrolyzate of tetrafluoroboric acid contained in the electrolyte (A) based on the weight of the electrolyte solution (E) is 0.5% by weight or less. The electrolyte solution in any one of -9. The electrolyte solution according to any one of claims 1 to 10, wherein the organic solvent (D) is at least one selected from the group consisting of γ-butyrolactone, sulfolane, and ethylene glycol. The organic solvent (D) is a mixed solvent composed of γ-butyrolactone and sulfolane, and the weight ratio of γ-butyrolactone in the mixed solvent is 30 wt% or more and 80 wt% or less. Electrolyte. The electrolytic solution according to claim 1, wherein the water content is 1% by weight or less. An electrolytic capacitor comprising the electrolytic solution according to claim 1.