JPH04233712A - Electrolyte for electrolytic capacitor - Google Patents

Abstract

PURPOSE:To obtain the stabilized electrolyte for driving of an electrolytic capacitor having a high specific electrical conductance at high temperature. CONSTITUTION:A capacitor element is constituted by rolling up an anode foil 1, as an aluminum anode electrode, and cathode foil 2, as an aluminum cathode electrode, by interposing a separator 3 between them, and quaternary ammonium salt of squalene acid or asymmetrical quaternary ammonium salt of squalinecic acid is used as the solute of capacitor driving electrolyte to be impregnated into the above-mentioned capacitor element.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrolytic solution for driving an electrolytic capacitor.

0002

[Prior Art] Conventional electrolytic solutions for driving electrolytic capacitors include those in which a quaternary ammonium salt of an aromatic carboxylic acid (phthalic acid, etc.) is used as a solute (Japanese Unexamined Patent Publication No. 145715/1983).
(Japanese Unexamined Patent Publication No. 145713/1983) using a quaternary ammonium salt of maleic acid as a solute; and using a quaternary ammonium salt of an aliphatic saturated monocarboxylic acid (such as formic acid) as a solute ( (Japanese Patent Application Laid-Open No. 62-226614)
, using a quaternary ammonium salt of an aliphatic saturated dicarboxylic acid (such as malonic acid) as a solute (JP-A-62-24821)
Publication No. 7), etc. are known.

0003

[Problems to be Solved by the Invention] However, those using a quaternary ammonium salt of phthalic acid as a solute have insufficient specific conductivity, and quaternary ammonium salts such as maleic acid, formic acid, and malonic acid There were problems with the solute, such as insufficient stability at high temperatures and the generation of gas.

The object of the present invention is to eliminate the above-mentioned conventional drawbacks and to provide an electrolytic solution for driving an electrolytic capacitor that has a high specific conductivity and is stable at high temperatures.

[0005]

Means for Solving the Problems In order to solve the above problems, the present invention provides an electrolytic solution for driving an electrolytic capacitor, which is characterized in that a quaternary ammonium salt of squaric acid is used as a solute.

[0006]

[Action] Squaric acid is easily ionized due to resonance stabilization, and has a small molecular weight, so it can obtain high specific conductivity.

[0007]

[Examples] Examples of the present invention will be described below.

The basis of the present invention relates to an electrolytic solution for driving an electrolytic capacitor using a quaternary ammonium salt of squaric acid as a solute.

In the present invention, as the quaternary ammonium salt, tetraalkyl (the number of carbon atoms in the alkyl group is usually 1 to 1) is used.
12) Ammonium (tetramethylammonium, tetraethylammonium, tetrapropylammonium,
Tetrabutylammonium, methyltriethylammonium, dimethyldiethylammonium, ethyltrimethylammonium, etc.), aryltrialkylammonium (phenyltrimethylammonium, etc.), cyclohexyltrialkylammonium (cyclohexyltrimethylammonium, etc.), arylalkyltrialkylammonium (benzyltrimethylammonium, etc.) ) and N,N-dialkylpiperidinium (N,
N-dimethylpiperidinium, etc.) and mixtures thereof. Among these, preferred are tetraalkylammonium salts. Particularly preferred are asymmetric (all four alkyl groups are not identical) tetraalkylammonium salts. Since asymmetric tetraalkylammonium salts have good solubility in solvents, the conductivity can be easily increased. Examples of the asymmetric tetraalkylammonium salts include methyltriethylammonium, dimethyldiethylammonium, and ethyltriethylammonium salts among the above-mentioned salts.

The molar ratio of squaric acid to quaternary ammonium is usually 0.5 to 1.
5, preferably 0.8 to 1.2.

Specific examples of the salts used in the present invention include the following. No. 1. Salt of squaric acid and methyltriethylammonium (molar ratio 1.0) Such a salt is easily synthesized, for example, by reaction with methyltriethylammonium hydroxide.

The electrolytic solution of the present invention consists of a salt and a solvent (usually an organic solvent). Examples of the organic solvent include alcohols {monohydric alcohols (methyl alcohol, ethyl alcohol, propyl alcohol, butyl alcohol, diacetone alcohol, benzyl alcohol, amino alcohol, etc.); dihydric alcohols (ethylene glycol, propylene glycol, diethylene glycol, (hexylene glycol, etc.); trihydric alcohol (glycerin, etc.)
; hexitol, etc.}, ethers {monoethers (ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, ethylene glycophenyl ether, etc.); diethers (ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, etc.)}, 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.); hexamethylphosphorylamide, etc.}, oxazolidinones (N-dimethylpropionamide, etc.);
-methyl-2-oxazolidinone), 3,5-dimethyl-2-oxazolidinone, etc.), lactones (γ-butyrolactone, α-acetyl-γ-butyrolactone, β-
butyrolactone, γ-valerolactone, etc., δ-valerolactone, etc.), nitriles (acetonitrile, acrylonitrile, etc.), dimethyl sulfoxide, sulfolane, 1,3-dimethyl-2-imidazolidinone, N-methylpyrrolidone, aromatic solvents ( toluene, xylene, etc.)
, paraffinic solvents (normal paraffin, isoparaffin, etc.), and mixtures of two or more of these. Preferably, these solvents are mainly composed of γ-butyrolactone.

The electrolytic solution of the present invention can also contain water if necessary. Its content is usually less than 10% based on the weight of the electrolyte.

In the electrolytic solution of the present invention, the content of squaric acid salt is usually 1 to 50% based on the weight of the electrolytic solution.
, preferably 10 to 40%.

The electrolytic solution of the present invention essentially consists of a salt of squaric acid and a solvent, but various additives can be added for purposes such as reducing leakage current and absorbing hydrogen gas. As additives, mention may be made of phosphoric acid derivatives, boric acid derivatives and nitro compounds.

The present invention will be further explained below with reference to specific examples, but the present invention is not limited thereto. The percentages in the examples are by weight.

Examples and Comparative Examples 1 to 4 (Table 1) The electrolyte solution of the example of the present invention and the electrolyte of the comparative example consisting of a 25% γ-butyrolactone solution of the salt (electrolyte) of the example of the present invention A solution (25% γ-butyrolactone solution) was prepared, and their specific conductivity (30°C, mS/cm) was measured at the initial stage and after heat treatment (150°C, 5 hours). In addition, the presence or absence of gas generation during heat treatment was observed. The results are shown in (Table 1).

[0018]

[Table 1]

(Note) (1) No. 1 represents the specific examples of salts in the examples of the present invention, A represents phthalic acid, B represents maleic acid, C represents formic acid, and D represents methyltriethylammonium salt of malonic acid.

(Table 2) shows examples of the present invention in (Table 1),
The initial characteristics (capacitance, loss angle tangent, leakage current, and impedance) of electrolytic capacitors using the electrolytes of Comparative Examples 1 and 2 and the impedance characteristics after a voltage application test at 125° C. for 1000 hours are shown.

[0021] The sample capacitor is 10V, 2200μF (
It is an aluminum electrolytic capacitor of φ16×32). FIG. 1 shows the configuration of the element part of this aluminum electrolytic capacitor. In FIG. 1, an anode foil 1 as an anode electrode made of aluminum and a cathode foil 2 as a cathode electrode also made of aluminum are placed with a separator 3 in between. A capacitor element is constructed by winding the capacitors so as to face each other with the capacitors interposed therebetween. Further, a lead 4 is connected to each of the anode foil 1 and the cathode foil 2 of this capacitor element. An electrolytic capacitor is constructed by impregnating a capacitor element with such a configuration with a driving electrolyte and sealing it in a case such as an aluminum case.

[0022]

[Table 2]

As is clear from Table 2, the drive electrolyte of the example of the present invention can lower the impedance compared to the comparative example, has little change even at high temperatures, and has high reliability. High electrolytic capacitors can be obtained.

[0024]

[Effects of the Invention] As described above, the electrolytic solution for driving an electrolytic capacitor of the present invention exhibits high specific conductivity and is stable even after high-temperature treatment. It is possible to reduce the loss, and moreover, the deterioration at high temperatures is improved and a longer life can be achieved.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing the structure of a capacitor element of an electrolytic capacitor using a driving electrolyte according to an embodiment of the present invention.

[Explanation of symbols]

1 Anode foil 2 Cathode foil 3 Separator 4 Drawer lead

Claims (2)

[Claims] 1. An electrolytic solution for driving an electrolytic capacitor, characterized in that a quaternary ammonium salt of squaric acid is used as a solute. 2. An electrolytic solution for driving an electrolytic capacitor, characterized in that an asymmetric quaternary ammonium salt of squaric acid is used as a solute.