JP2011211146A - Electrolytic solution for electrolytic capacitor, and electrolytic capacitor using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrolytic solution for an electrolytic capacitor, striking a balance between the high conductivity and the high spark voltage; and to provide an electrolytic capacitor using the electrolytic solution.SOLUTION: The electrolytic solution for the electrolytic capacitor is provided which contains an electrolyte (E) comprising a complex anion (C) having at least one hydroxy group and an ammonium cation (D), the complex anion being a complex anion (B) of a borate anion expressed by general formula (1) and a carboxylic acid compound (A), and an organic solvent (F). Preferably, the carboxylic acid compound (A) has 6 to 20 C, and the ammonium cation (D) is an amidinium cation or tertiary ammonium cation.

Description

  The present invention relates to an electrolytic solution used for an electrolytic capacitor and an electrolytic capacitor using the electrolytic solution.

  In recent years, with the space saving and high temperature of the surrounding environment where capacitors are used, when the conductivity is high and the spark voltage is high, that is, it is difficult to destroy the aluminum conversion coating of the electrode, and the aluminum conversion coating has a defect, There is a demand for an electrolytic solution that is excellent in film repairing ability to repair this, and that has low characteristic deterioration at high temperatures. On the other hand, an electrolytic solution using boric acid has been proposed. For example, an electrolytic solution (for example, Patent Document 1) containing ethylene glycol as a main solvent and containing boric acid, an organic acid, or a salt thereof is known.

JP2000-182896

An electrolytic solution containing boric acid, an organic acid or a salt thereof using ethylene glycol as a main solvent in the prior art is an anion of boric acid and an ethylene glycol esterified product. For this reason, the effect of improving the spark voltage is reduced, and the viscosity of the electrolyte is increased due to esterification, and the conductivity is also lowered. When the solvent is water, borate anions are formed, but there is a drawback that the electrode foil is hydrated and the capacitance is lowered.

An electrolyte whose anion is a borate anion is esterified in a protic solvent in the same manner as ethylene glycol, and the effect of improving the spark voltage is reduced, and an aprotic solvent has poor solubility and a limited amount of addition. .

That is, the present invention seeks to solve the problems associated with the prior art as described above, and provides an electrolytic solution for an electrolytic capacitor that achieves both high conductivity and high spark voltage, and an electrolytic capacitor using the electrolytic solution. Is to provide.

As a result of intensive studies to solve the above problems, the present inventors have arrived at the present invention. That is, the present invention is a complex anion (B) of a borate anion represented by the general formula (1) and a carboxylic acid compound (A), which has at least one hydroxyl group and an ammonium cation ( An electrolytic solution for an aluminum electrolytic capacitor containing an electrolyte (E) composed of D) and an organic solvent (F); an electrolytic capacitor using the electrolytic solution.

  The electrolytic capacitor using the electrolytic solution of the present invention can increase the spark voltage while maintaining high electrical conductivity.

The electrolytic solution of the present invention is characterized by containing an electrolyte (E).
The electrolyte (E) is a complex anion (B) of a borate anion and a carboxylic acid compound (A), and is a salt composed of a complex anion (C) having at least one hydroxyl group and an ammonium cation (D). .
The carboxylic acid compound (A) is a compound having a carboxyl group, and preferably has 6 to 20 carbon atoms. The complex anion (B) with such a carboxylic acid compound can increase the spark voltage while maintaining high electrical conductivity.

The complex anion (C) is a monovalent anion presumed that one molecule, two molecules or three molecules of the carboxylic acid compound (A) form a complex with respect to one molecule of borate anion. Since the complex anion (C) has one or more hydroxyl groups of the borate anion, the complex anion (C) has a carrier effect of the hydroxyl anion and plays a role in promoting the repair reaction of the aluminum chemical conversion film. In other words, the aluminum chemical conversion film is usually repaired by hydroxyl anions generated by electrolysis of water, but in the electrolyte solution of the present invention, in addition to hydroxyl anions generated by water electrolysis, there are hydroxyl groups of complex anions. It is considered that the repair voltage is high and the spark voltage is high. Moreover, since the complex is formed, the solubility of the electrolyte (E) in the organic solvent (F) is high. As a result, the spark voltage of the electrolytic solution for an aluminum electrolytic capacitor containing the electrolyte (E) increases. Moreover, since the effect is high, it is possible to increase the spark voltage while maintaining high electrical conductivity.

The carboxylic acid compound (A) is a compound having a carboxyl group, and preferably has 6 to 20 carbon atoms. For example, the following are exemplified.
(1) Aliphatic polycarboxylic acids (such as adipic acid, pimelic acid, speric acid, azelaic acid, sebacic acid, 1,10-decanedicarboxylic acid, 1,6-decanedicarboxylic acid).
(2) Aromatic polycarboxylic acids (phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, pyromellitic acid, etc.).
(3) S-containing polycarboxylic acid (such as thiodibropionic acid).
(4) Oxycarboxylic acid: (salicylic acid, mandelic acid, etc.).
(5) Aliphatic monocarboxylic acids (such as caproic acid, enanthic acid, caprylic acid, pelargonic acid, lauric acid, myristic acid, stearic acid, behenic acid).
(6) Unsaturated monocarboxylic acid (such as oleic acid).
(7) Aromatic monocarboxylic acids (benzoic acid, cinnamic acid, naphthoic acid, etc.).
Among these, (1) aliphatic polycarboxylic acid is more preferable, and aliphatic dicarboxylic acid is more preferable.

In the present invention, the ammonium cation (D) includes amidinium cation, quaternary ammonium cation, tertiary ammonium cation, secondary ammonium cation, primary ammonium cation, ammonium cation (NH ₄ ⁺ ) and the like. included. The ammonium cation (D) may be used alone or in combination of two or more.

Examples of the amidinium cation include a cyclic amidinium cation (1) imidazolinium cation and (2) imidazolium cation (3) diazabicycloalkenium cation.

(1) Imidazolinium cation 1,2,3,4-tetramethylimidazolinium, 1,3,4-trimethyl-2-ethylimidazolinium, 1,3-dimethyl-2,4-diethylimidazolinium 1,2-dimethyl-3,4-diethylimidazolinium, 1-methyl-2,3,4-triethylimidazolinium, 1,2,3,4-tetraethylimidazolinium, 1,2,3- Trimethylimidazolinium, 1,3-dimethyl-2-ethylimidazolinium, 1-ethyl-2,3-dimethylimidazolinium, 1,2,3-triethylimidazolinium, 4-cyano-1,2, 3-trimethylimidazolinium, 3-cyanomethyl-1,2-dimethylimidazolinium, 2-cyanomethyl-1,3-dimethylimidazolinium, 4-acetate Til-1,2,3-trimethylimidazolinium, 3-acetylmethyl-1,2-dimethylimidazolinium, 4-methylcarbooxymethyl-1,2,3-trimethylimidazolinium, 3-methylcarbooxy Methyl-1,2-dimethylimidazolinium, 4-methoxy-1,2,3-trimethylimidazolinium, 3-methoxymethyl-1,2-dimethylimidazolinium, 4-formyl-1,2,3- Trimethylimidazolinium, 3-formylmethyl-1,2-dimethylimidazolinium, 3-hydroxyethyl-1,2-dimethylimidazolinium, 4-hydroxymethyl-1,2,3-trimethylimidazolinium, 2 -Hydroxyethyl-1,3-dimethylimidazolinium and the like.

(2) Imidazolium cation 1,3-dimethylimidazolium, 1,3-diethylimidazolium, 1-ethyl-3-methylimidazolium, 1,2,3-trimethylimidazolium, 1,2,3,4- Tetramethylimidazolium, 1,3-dimethyl-2-ethylimidazolium, 1-ethyl-2,3-dimethyl-imidazolium, 1,2,3-triethylimidazolium, 1,2,3,4-tetraethylimidazolium Lithium, 1,3-dimethyl-2-phenylimidazolium, 1,3-dimethyl-2-benzylimidazolium, 1-benzyl-2,3-dimethyl-imidazolium, 4-cyano-1,2,3-trimethyl Imidazolium, 3-cyanomethyl-1,2-dimethylimidazolium, 2-cyanomethyl-1,3-dimethyl-imidazole Zorium, 4-acetyl-1,2,3-trimethylimidazolium, 3-acetylmethyl-1,2-dimethylimidazolium, 4-methylcarbooxymethyl-1,2,3-trimethylimidazolium, 3-methylcarbo Oxymethyl-1,2-dimethylimidazolium, 4-methoxy-1,2,3-trimethylimidazolium, 3-methoxymethyl-1,2-dimethylimidazolium, 4-formyl-1,2,3-trimethylimidazolium Rium, 3-formylmethyl-1,2-dimethylimidazolium, 3-hydroxyethyl-1,2-dimethylimidazolium, 4-hydroxymethyl-1,2,3-trimethylimidazolium, 2-hydroxyethyl-1, 3-dimethylimidazolium and the like.

(3) Diazabicycloalkenium cation 1,4-diazabicyclo [3,2,0] -4-heptanium, 1,4-diazabicyclo [3,3,0] -4-octenium, 1,7-diazabicyclo [4 , 3,0] -6-nonenium, 1,8-diazabicyclo [5,3,0] -7-decenium, 1,9-diazabicyclo [6,3,0] -8-undecenium, 1,5-diazabicyclo [ 4,2,0] -5-octenium, 1,5-diazabicyclo [4,3,0] -5-nonenium, 1,5-diazabicyclo [4,4,0] -5-decenium, 1,8-diazabicyclo [5,4,0] -7-undecenium, 1,9-diazabicyclo [6,4,0] -8-dodecenium.

As the quaternary ammonium cation, a tetraalkylammonium cation having an alkyl group having 1 to 4 carbon atoms which may be linked to each other to form a ring {tetramethylammonium, tetraethylammonium, ethyltrimethylammonium, triethylmethylammonium, N, N-dimethylpyrrolidinium, N, N-dimethylpiperidinium, spirobipyrrolidinium, etc.}.
As the tertiary ammonium cation, a trialkylammonium cation having a C 1-4 alkyl group which may be linked to each other to form a ring {triethylammonium, diethylmethylammonium, ethyldimethylammonium, trimethylammonium, N-methyl Pyrrolidinium, N-methylpiperidinium, etc.} and the like.
Examples of the secondary ammonium cation include dialkylammonium cations {diethylammonium, methylethylammonium, dimethylammonium, pyrrolidinium, piperidinium, etc.} having a C1-4 alkyl group that may be linked to each other to form a ring. It is done.
Examples of the primary ammonium cation include monoalkylammonium cations having an alkyl group having 1 to 4 carbon atoms {such as ethylammonium and methylammonium}.

  Among the cations (D), an amidinium cation or a tertiary ammonium cation is preferable from the viewpoint of the temporal stability of conductivity. Among the amidinium cations, a cyclic amidinium cation is preferable, (1) an imidazolinium cation and (2) an imidazolium cation, and more preferably 1,2,3,4-tetramethylimidazoli. And a 1-ethyl-2,3-dimethylimidazolium cation, a 1-ethyl-3-methylimidazolium cation, and a 1-ethyl-2,3-dimethylimidazolium cation. Among the tertiary ammonium cations, preferred are trialkylammonium cations having an alkyl group having 1 to 4 carbon atoms which may be linked to each other to form a ring, more preferably a triethylammonium cation or an ethyldimethylammonium cation. .

The electrolyte (E) was synthesized by mixing boric acid and a carboxylic acid compound (A) with ammonium salt {monomethyl carbonate, hydroxide salt, etc.} and water, and having a pressure of 0.01 kPa to 10 kPa at 20 ° C to 120 ° C. A method of dissolving in an organic solvent (F) at 10 ° C. to 70 ° C. after dehydration under reduced pressure is preferable. The number of moles of the carboxyl group of the carboxylic acid compound (A) [(number of moles of the carboxylic acid compound (A)) × (number of carboxyl groups per molecule)] of 3 moles or less of 1 mole of boric acid Thus, the complex anion (B) can be a complex anion (C) having at least one hydroxyl group.
The number of hydroxyl groups per mole of the complex anion (C) can be calculated from the integrated value of the peaks derived from the ¹ H-NMR and ¹¹ B-NMR B—OH structures of the electrolyte (E).

The electrolyte (E) is dissolved in the organic solvent (F) to obtain the electrolytic solution of the present invention.
The organic solvent (F) is preferably an aprotic organic solvent (H) or an aprotic organic solvent (H) containing an alcohol (I) from the viewpoint of the temporal stability of conductivity. (I) is preferably contained in (F) in an amount of 0 to 40 wt% (hereinafter sometimes referred to as wt%), more preferably 0 to 10 wt%.
An organic solvent (F) is illustrated below, for example, and can also use 2 or more types together.
The content of the electrolyte (E) in the electrolytic solution is preferably 1 to 30 wt%, more preferably 2 to 20 wt%, based on the total weight of the electrolyte (E) and the organic solvent (F).
The alcohols (I) are exemplified below, for example.
Monohydric alcohol: monohydric alcohol having 1 to 6 carbon atoms (methyl alcohol, ethyl alcohol, propyl alcohol, butyl alcohol, diacetone alcohol, furfuryl alcohol, etc.), monohydric alcohol having 7 or more carbon atoms (benzyl alcohol, octanol, etc.) )
Dihydric alcohol: C1-C6 dihydric alcohol (ethylene glycol, propylene glycol, diethylene glycol, hexylene glycol, etc.), C7 or more dihydric alcohol (octylene glycol, etc.)
A trihydric alcohol; a trihydric alcohol having 3 to 6 carbon atoms (such as glycerin),
Tetravalent to hexavalent or higher alcohols; C 4-6 tetravalent to hexavalent or higher alcohols (such as hexitol).
As alcohol (I), a polyhydric alcohol is preferable, and ethylene glycol or glycerin is particularly preferable.

Examples of the aprotic organic solvent (H) include those exemplified below.
(1) Ethers;
Monoether (tetrahydrofuran, 3-methyltetrahydrofuran, etc.), diether (ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, etc.), etc.

(2) Amides;
Formamides (N-methylformamide, N, N-dimethylformamide, N-ethylformamide, N, N-diethylformamide, etc.), acetamides (N-methylacetamide, N, N-dimethylacetamide, N-ethylacetamide, N , N-diethylacetamide), propionamides (N, N-dimethylpropionamide, etc.), hexamethylphosphorylamide, etc.

(3) oxazolidinones;
N-methyl-2-oxazolidinone, 3,5-dimethyl-2-oxazolidinone, and the like.

(4) Lactones;
γ-butyrolactone, α-acetyl-γ-butyrolactone, β-butyrolactone, γ-valerolactone, δ-valerolactone, and the like.

(5) Nitriles;
Acetonitrile, acrylonitrile, etc.

(6) carbonates;
Ethylene carbonate, propylene carbonate, etc.

(7) Other organic solvents;
Dimethyl sulfoxide, sulfolane, 1,3-dimethyl-2-imidazolidinone, N-methylpyrrolidone, aromatic solvents (toluene, xylene, etc.), paraffinic solvents (normal paraffin, isoparaffin), etc.

Among these organic solvents, the aprotic organic solvent (H) is preferably γ-butyrolactone, sulfolane, or a mixed solvent of γ-butyrolactone and sulfolane, particularly γ-butyrolactone and sulfolane from the viewpoint of solubility and low toxicity. The mixed solvent is preferable.

  The electrolytic solution of the present invention preferably further contains water. When water is contained, the chemical property of the capacitor member {aluminum oxide foil or the like as the anode foil} {the property of forming an oxide film and repairing it if there is a defect portion on the surface of the anode foil} can be improved. On the other hand, when there is much content of water, vapor pressure will become high and it will become impossible to use at high temperature. Therefore, when water is contained, the content of water is preferably 0.01 to 10 wt%, more preferably 0.1 to 0.1% based on the total weight of the electrolyte (C) and the aprotic solvent (A). 5 wt%, particularly preferably 1 to 5 wt%.

As for moisture, JIS K0113: 2005 “8. Karl Fischer titration method, 8.1 volumetric titration method” {corresponding international standard ISO760: 1978; the disclosure content disclosed therein is incorporated into the present application by reference. } Is measured in accordance with.

As the electrolyte in the electrolytic solution, an electrolyte component other than the electrolyte (E) may be used in combination. The cation of the electrolyte (G) to be used in combination is preferably an ammonium cation (D), and as the anion, various organic acid and / or inorganic acid anions (J) that are usually used in an electrolytic solution can be used. The anion may be used alone or in combination of two or more.
The electrolyte (G) is preferably 0 to 1000 wt%, more preferably 5 to 500 wt%, based on the weight of the electrolyte (E).

Examples of the organic acid and inorganic acid include the following (1) to (6).
(1) Carboxylic acids / C2-C15 divalent to tetravalent polycarboxylic acids: aliphatic polycarboxylic acids [saturated polycarboxylic acids (oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, Speric acid, azelaic acid, sebacic acid, 1,10-decanedicarboxylic acid, 1,6-decanedicarboxylic acid, etc.), unsaturated polycarboxylic acid (maleic acid, fumaric acid, itaconic acid, etc.)], aromatic polycarboxylic acid [Phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, pyromellitic acid, etc.], S-containing polycarboxylic acids [thiodibropionic acid, etc.].
C2-C20 oxycarboxylic acid: aliphatic oxycarboxylic acid [glycolic acid, lactic acid, tartaric acid, castor oil fatty acid, etc.]; aromatic oxycarboxylic acid [salicylic acid, mandelic acid, etc.].
C1-C30 monocarboxylic acid: aliphatic monocarboxylic acid [saturated monocarboxylic acid (formic acid, acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, uraryl Acid, myristic acid, stearic acid, behenic acid, etc.), unsaturated monocarboxylic acids (acrylic acid, methacrylic acid, crotonic acid, oleic acid, etc.)]; aromatic monocarboxylic acids [benzoic acid, cinnamic acid, naphthoic acid, etc. ].

(2) Phosphate ester anion Here, the phosphate ester anion means a monoalkyl phosphate ester and a dialkyl phosphate ester, and the phosphate ester anion has 1 to 15 carbon atoms in total.
Mono and dimethyl phosphate, mono and diethyl phosphate, mono and diisopropyl phosphate, mono and dibutyl phosphate, mono and di- (2-ethylhexyl) phosphate, mono and diisodecyl phosphate, and the like.

(3) Phenols and monohydric phenols (including phenols and naphthols): Phenol, alkyl (C1-15) phenols (cresol, xylenol, ethylphenol, n- or isopropylphenol, isododecylphenol, etc.) , Methoxyphenols (eugenol, guaiacol, etc.), α-naphthol, β-naphthol, cyclohexylphenol, etc .;
Polyhydric phenol: catechol, resorcin, pyrogallol, phloroglucin, bisphenol A, bisphenol F, bisphenol S, etc.

(4) Sulfonic acid / alkyl (C1-15) benzenesulfonic acid (p-toluenesulfonic acid, nonylbenzenesulfonic acid, dodecylbenzenesulfonic acid, etc.), sulfosalicylic acid, methanesulfonic acid, trifluoromethanesulfonic acid, etc. .

(5) Inorganic acid / phosphoric acid, boron tetrafluoride, perchloric acid, hexafluorophosphoric acid, hexafluoroantimonic acid, hexafluoroarsenic acid, etc.

(6) Others: Imide anions such as methanesulfonyl imide imide, and methide anions such as methanesulfonyl methoxide trifluoride.
Preferred as the anion (J) of the electrolyte (G) are (1) carboxylic acids, (2) phosphate ester anions (J1) (mono and dialkyl phosphate anions having 1 to 15 carbon atoms). Yes, the phosphate ester anion (J1) is more preferable, and the diethyl phosphate ester and the dibutyl phosphate anion are particularly preferable. It is preferable to use an electrolyte (G) composed of these anions together in that the effect of increasing the temporal stability of the conductivity at high temperatures is achieved.

  The pH of the electrolytic solution of the present invention is usually 3 to 12, preferably 4 to 11. When producing the electrolyte (A), conditions are selected so that the pH of the electrolytic solution is within this range. The pH of the electrolytic solution is an analytical value of 25 ° C. of the electrolytic solution stock solution.

  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 nitro compounds (for example, o-nitrobenzoic acid, p-nitrobenzoic acid, m-nitrobenzoic acid, o-nitrophenol, p-nitrophenol, etc.). The addition amount is preferably 5 wt% or less, particularly preferably 0.1 to 2 wt%, based on the weight of the electrolytic solution, from the viewpoint of specific conductivity and solubility in the electrolytic solution.

  The electrolytic solution of the present invention is suitable for an aluminum electrolytic capacitor. The aluminum electrolytic capacitor is not particularly limited. For example, it is a scraped electrolytic capacitor, and a separator is interposed between an anode (aluminum oxide foil) in which aluminum oxide is formed on the anode surface and a cathode aluminum foil. For example, a capacitor formed by winding is used. A separator is impregnated with the electrolytic solution of the present invention as a driving electrolytic solution, housed in a bottomed cylindrical aluminum case together with a positive electrode, and then the aluminum case opening is sealed with a sealing rubber to form an electrolytic capacitor. Can do.

  Next, specific examples of the present invention will be described, but the present invention is not limited thereto.

<Production Example 1>
By adding 2,4-dimethylimidazoline (0.1 mol) dropwise to a methanol solution (74 wt%) of dimethyl carbonate (0.2 mol) and stirring at 120 ° C. for 15 hours, 1,2,3,4- A methanol solution of tetramethylimidazolinium methyl carbonate salt was obtained. Boric acid (manufactured by Kanto Chemical Co., Inc.) (0.1 mol) and sebacic acid (A-1) (0.1 mol) were dissolved in water (1 mol) and heated at 90 ° C. for 1 hour. Further, a methanol solution of 1,2,3,4-tetramethylimidazolinium methyl carbonate salt (0.1 mol) was added, and the mixture was stirred for 1 hour to cause a salt exchange reaction. Further, methanol and water are distilled off at 100 ° C. under a reduced pressure of 1.0 kPa or less, and the electrolyte (E-1) {1,2,3,4-tetramethylimidazolinium borate sebacate complex Anion}.

<Production Example 2>
By adding 1-ethylimidazole (0.1 mol) dropwise to a methanol solution (74 wt%) of dimethyl carbonate (0.1 mol) and stirring at 130 ° C. for 70 hours, 1-ethyl-3-methylimidazolium. A methanol solution of methyl carbonate salt was obtained.
Boric acid (manufactured by Kanto Chemical Co., Inc.) (0.1 mol) and adipic acid (A-2) (0.04 mol) were dissolved in water (1 mol) and heated at 90 ° C. for 1 hour. Further, a methanol solution of 1-ethyl-3-methylimidazolium methyl carbonate salt (0.1 mol) was added, and the mixture was stirred for 1 hour to cause a salt exchange reaction. Further, methanol and water are distilled off at 100 ° C. under a reduced pressure of 1.0 kPa or less to obtain an electrolyte (E-2) {1-ethyl-3-methylimidazolium / borate adipate complex anion}. It was.

<Production Example 3>
Boric acid (manufactured by Kanto Chemical Co., Inc.) (0.1 mol) was dissolved in water (1 mol), sebacic acid (A-1) (0.1 mol) was added, and the mixture was heated at 90 ° C. for 1 hour. Further, an aqueous solution (50 wt%) of triethylamine (0.1 mol) was added, and the mixture was stirred for 1 hour to cause a salt exchange reaction. Furthermore, water was distilled off at a reduced pressure of 1.0 kPa or less and 100 ° C. to obtain an electrolyte (E-3) {triethylammonium borate sebacate complex anion}.

<Production Example 4>
Boric acid (manufactured by Kanto Chemical Co., Inc.) (0.1 mol) was dissolved in water (1 mol), adipic acid (A-2) (0.04 mol) was added, and the mixture was heated at 90 ° C. for 1 hour. Further, an aqueous solution (60 wt%) of ethyldimethylamine (0.1 mol) was added, and the mixture was stirred for 1 hour to cause a salt exchange reaction. Furthermore, water was distilled off at a reduced pressure of 1.0 kPa or less and 100 ° C. to obtain an electrolyte (E-4) {ethyldimethylammonium borate adipate complex anion}.

<Production Example 5>
Triethyl phosphate (0.1 mol) is added to a methanol solution of 1-ethyl-3-methylimidazolium methyl carbonate salt (0.1 mol), water (0.3 mol) is added, and the mixture is stirred at 100 ° C. for 100 hours. Thus, triethyl phosphate was hydrolyzed and a salt exchange reaction was performed to obtain a methanol solution of 1-ethyl-3-methylimidazolium · diethyl phosphate monoanion. The above solution was heated at a reduced pressure of 1.0 kPa or less at 50 ° C. until the distillation of methanol disappeared, the methanol was distilled off, the temperature was raised from 50 ° C. to 100 ° C., and the mixture was heated for 30 minutes to monomethyl carbonate By distilling off (HOCO2CH3), methanol and carbon dioxide, an electrolyte (G-1) {1-ethyl-3-methylimidazolium diethylphosphate monoanion} was obtained.

<Production Example 6>
Triethyl phosphate (0.1 mol), triethylamine (0.1 mol), and water (0.3 mol) are placed in a pressure vessel and reacted at 100 ° C. for 100 hours to hydrolyze triethyl phosphate and undergo a salt exchange reaction. And a methanol solution of triethylammonium diethyl phosphate monoanion was obtained. The above solution was heated at a reduced pressure of 1.0 kPa or less at 50 ° C. until the distillation of methanol disappeared, and after the methanol was distilled off, the temperature was raised from 50 ° C. to 100 ° C. and heated for 30 minutes to volatilize components. Was distilled off to obtain an electrolyte (G-2) {triethylammonium · diethyl phosphate ester monoanion}.

<Production Example 7>
Triethyl phosphate (0.1 mol), ethyldimethylamine (0.1 mol), and water (0.3 mol) are placed in a pressure vessel and reacted at 100 ° C. for 100 hours to hydrolyze triethyl phosphate and salt. Exchange reaction was performed to obtain a methanol solution of ethyldimethylammonium diethylphosphate monoanion. The above solution was heated at a reduced pressure of 1.0 kPa or less at 50 ° C. until the distillation of methanol disappeared, and after the methanol was distilled off, the temperature was raised from 50 ° C. to 100 ° C. and heated for 30 minutes to volatilize components. Was distilled off to obtain an electrolyte (G-3) {ethyldimethylammonium diethylphosphate monoanion}.

<Example 1>
6 g of the electrolyte (E-1) was dissolved in 30 g of γ-butyrolactone (F-1) and 64 g of sulfolane (F-2) to obtain the electrolytic solution of the present invention. Further water was added to adjust the water content to 1.5%.

<Example 2>
3 g of the electrolyte (E-1) and 3 g of the electrolyte (G-1) were dissolved in 94 g of γ-butyrolactone (F-1) to obtain the electrolytic solution of the present invention. Further water was added to adjust the water content to 1.5%.

<Example 3>
3 g of electrolyte (E-2) and 3 g of electrolyte (G-1) were dissolved in 30 g of γ-butyrolactone (F-1) and 64 g of sulfolane (F-2) to obtain the electrolyte solution of the present invention. Further water was added to adjust the water content to 1.5%.

<Example 4>
By dissolving 12.0 g of the electrolyte (E-3) in 88 g of γ-butyrolactone (F-1), an electrolytic solution of the present invention was obtained. Further water was added to adjust the water content to 1.5%.

<Example 5>
The electrolyte solution of the present invention is prepared by dissolving 3.5 g of electrolyte (E-3) and 8.5 g of electrolyte (G-2) in 34 g of γ-butyrolactone (F-1) and 54 g of sulfolane (F-2). Got. Further water was added to adjust the water content to 1.5%.

<Example 6>
By dissolving 2.5 g of electrolyte (E-4) and 7.0 g of electrolyte (G-3) in 35 g of γ-butyrolactone (F-1), 55 g of sulfolane (F-2) and 0.5 g of glycerin, The electrolytic solution of the present invention was obtained. Further water was added to adjust the water content to 1.5%.

<Example 7>
An electrolytic solution of the present invention was obtained by dissolving 3.5 g of the electrolyte (E-3) and 8.5 g of the electrolyte (G-2) in 88 g of dimethylformamide. Further water was added to adjust the water content to 1.5%.

<Comparative Example 1>
3.4 g (34 mmol) of triethylamine, 2.1 g (34 mmol) of boric acid and 2.9 g (34 mmol) of ethylene glycol were mixed and dissolved in 90 g of γ-butyrolactone (E-1) to obtain the electrolytic solution of the present invention. . The water content was adjusted to 1.5%. An electrolytic solution of Comparative Example 1 was obtained.

<Comparative example 2>
5 g of electrolyte {ammonium / adipic acid} was dissolved in 95 g of ethylene glycol, and 2 g of boric acid was further added to obtain an electrolytic solution of Comparative Example 2.

  Using the electrolytic solutions obtained in Examples 1 to 7 and Comparative Examples 1 and 2, spark voltage and specific conductivity were measured by the following methods and listed in Table 1.

Spark voltage: A 10 cm ² chemical conversion etching aluminum foil for high voltage was used for the anode and a 10 cm ² plain aluminum foil was used for the cathode, and the spark voltage of the electrolyte was measured at 25 ° C. when a constant current method (2 mA) was applied. .

Specific conductivity: Specific conductivity at 30 ° C. was measured using a conductivity meter CM-40S manufactured by Toa Denpa Kogyo Co., Ltd.

  As is clear from Table 1, in the electrolyte solutions of the present invention (Examples 1 to 7), the specific conductivity of the electrolyte solution at 30 ° C. was high, and the spark voltage could be increased.

By using the electrolytic solution of the present invention, it is possible to provide an electrolytic solution for electrolytic capacitors that has both high electrical conductivity and high spark voltage, and an electrolytic capacitor using the electrolytic solution. Therefore, the market value of the electrolytic solution of the present invention is very large as the withstand voltage of the power source used in the market is increasing.

Claims (7)

An electrolyte comprising a complex anion (B) of a borate anion represented by the general formula (1) and a carboxylic acid compound (A) and having a complex anion (C) having at least one hydroxyl group and an ammonium cation (D) ( E) and an electrolytic solution for electrolytic capacitors containing an organic solvent (F).

The electrolytic solution according to claim 1, wherein the carboxylic acid compound (A) has 6 to 20 carbon atoms. The electrolytic solution according to claim 1 or 2, wherein the ammonium cation (D) is an amidinium cation. The electrolytic solution according to claim 1 or 2, wherein the ammonium cation (D) is a tertiary ammonium cation. The electrolyte solution of any one of Claims 1-4 containing electrolyte (G) which consists of electrolyte (E), phosphate ester anion (J1), and ammonium cation (D) as electrolyte. The electrolyte solution according to any one of claims 1 to 5, wherein the organic solvent (F) is an aprotic organic solvent (H) which may contain an alcohol (I). The electrolytic capacitor formed using the electrolyte solution of any one of Claims 1-6.