JPH02158117A - Electrolyte for electrolytic capacitor - Google Patents

Abstract

PURPOSE:To enable a stable property to be maintained for a long period by making solvent mainly composed of nonproton solvent, as an electrolyte for electrolytic capacitor, contain mono or di-N-alkyl-1-azabiciclo [m, n, 0] alkanium compound salt of specific aliphatic unsaturated dicarboxylic acid compound as an electrolyte. CONSTITUTION:Solvent mainly composed of aproton solvent contains mono- or di-N-alkyl-1-azabiciclo [m, n, 0] alkanium compound salt of aliphatic saturated dicarboxylic acid compound shown by the formula as an electrolyte. And as the aproton solvent, N-methylformamide, dimethylsulfoxide, etc., are cited. And further for a polyhydric alcohol compound, dihydric alcohol compound or monoalkyl ether of dihydric alcohol compound is suitable, and as the dihydric alcohol compound ethylene glycol is preferable and as dihydric alcohol monoalkyl ether compound methyl cellosolve or ethyl cellosolve is preferable. Also, as the aliphatic unsaturated dicarboxylic acid, malonic acid, succinic acid, etc., exist.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an electrolytic solution used in an electrolytic capacitor, and particularly to an electrolytic solution whose main solvent is an aprotic solvent.

[Conventional technology]

Electrolytic capacitors use a valve metal such as aluminum or tantalum on the surface of which an insulating oxide film is formed, and use the oxide film layer as a dielectric, and an electrolyte layer on the surface of the oxide film layer. by contacting an electrolytic solution of
Furthermore, a current collecting electrode, usually called a cathode, is arranged.

As described above, the electrolyte for an electrolytic capacitor comes into direct contact with the dielectric and acts as a true cathode. That is, the electrolytic solution is interposed between the dielectric layer and the current collecting cathode of the electrolytic capacitor, and the resistance of the electrolytic solution is inserted in series with the electrolytic capacitor.

Therefore, the characteristics of the electrolyte are a major factor that influences the characteristics of electrolytic capacitors. For example, if the conductivity of the electrolytic solution is low, the equivalent series resistance inside the electrolytic capacitor increases, resulting in poor high frequency characteristics and loss characteristics.

Conventionally, organic acids such as adipic acid or their salts dissolved in glycols such as ethylene glycol or alcohols have been used as electrolytes with high conductivity in order to improve high frequency characteristics, loss characteristics, etc. There is.

[Problem to be solved by the invention]

However, as the range of use of electronic devices has increased in recent years, there has been a growing demand for improvements in the performance of electrolytic capacitors, and the current conductivity of electrolytes is no longer sufficient. Especially in the case of current electrolytes, when the desired conductivity cannot be obtained or when an electrolyte with low solubility is used, water is intentionally added to improve the conductivity. .

However, in recent years, electrolytic capacitors are required to be used for long periods of time in a wider temperature environment than conventional products, and the presence of moisture in the electrolyte can cause deterioration of the dielectric film layer and decrease the internal vapor pressure of the electrolytic capacitor. This results in abnormal rise in temperature, damage to the sealing body, and deterioration of life due to evaporation of the electrolyte, making it difficult to maintain stable characteristics over a long period of time.

An object of the present invention is to improve the electrical characteristics of electrolytic capacitors and maintain stable characteristics for a long period of time by providing a substantially non-aqueous high conductivity electrolytic solution containing an aprotic solvent as a main component. The aim is to improve the reliability of electrolytic capacitors.

[Means to solve the problem]

This invention can be used as an electrolytic solution for electrolytic capacitors (1)
In a solvent mainly consisting of an aprotic solvent, a compound of the general formula:
0 alkylene group, X represents a hydrogen atom or the same group as the N-alkyl-1-azabicyclo(m, n, O)alkanium compound group shown in the formula). It is characterized by containing -N-alkyl-1-azabicyclo(m,n,0)alkanium compound salt as an electrolyte.

In addition, the aprotic solvent used is (1)
Amides include N-methylformamide, N,N-dimethylformamide, N-ethylformamide, N,N
-diethylformamide, N-methylacetamide, N
, N-dimethylacetamide, N-ethylacetamide, N,N-diethylacetamide, hexamethylphosphoric amide, (2) dimethyl sulfoxide as an oxide system, (3)
Representative examples of the nitrile type include acetonitrile, (4) cyclic esters, and examples of the amide type include T-butyrolactone, N-methyl-2-pyrrolidone, ethylene carbonate, propylene carbonate, and the like.

Furthermore, the polyhydric alcohol compound that is the subject of the present invention is
Dihydric alcohol compounds or monoalkyl ethers of dihydric alcohol compounds are preferred, where the dihydric alcohol compound is ethylene glycol and the dihydric alcohol monoalkyl ether compound is methylcellosolve or ethylcellosolve.

The weight ratio of the polyhydric alcohol compound to the aprotic solvent is (100-50): (0-50),
An aprotic solvent of 100x is suitable, but up to about 50% polyhydric alcohol compound may be used as appropriate without substantial product deterioration.

Further, specific examples of aliphatic saturated dicarboxylic acids include malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, corkic acid, azelaic acid, sebacic acid, undecanoic acid, dodecanoic acid, brassic acid, and tetradecanoic acid. , pentadecanoic acid, tabucinic acid, heptadecanniic acid, octadecanoic acid, nonadecanniic acid, icosanniic acid, heneicosanniic acid, docosanniic acid, and the like.

Furthermore, N-alkyl-1-azabicyclo (m, n, O
) A typical example of the alkanium compound is shown by the following structural formula.

(1) When m=n=3 N-alkylpyrocodinium bar (2) m=4. When n.3, N-alkylpyrrolidinium (3) When m=n=4, N-alkylpyrrolidinium Mono- or di-N-alkyl l-azabicycloCm,n,0)alkanium used in the present invention 1-azabicyclo (m, n, 0), which is a raw material for compound synthesis
Alkanium compounds, such as pyrrolizidine, F, S
orm, J, brandejs, Co11ecti
on Czechoslov.

Chem, Commun, Volume 12, No. 4
It is produced by the following reaction described on page 44 (1947).

When this is N-methylated with an alkyl halide such as methyl iodide in a conventional manner, N-methylpyrrolizidinium iodide can be obtained. This is subjected to electrodialysis using an ion exchange membrane, followed by deiodination and desalting to perform anion exchange to obtain an aqueous solution of N-methylpyrrolizidinium hydroxide. Equimolar or 1/2 mole of the desired aliphatic saturated dicarboxylic acid compound is added to this aqueous solution, a neutralization reaction is carried out, and the N-
Methylvirolizidinium salts can be obtained.

The electrolytic solution for an electrolytic capacitor according to the present invention is prepared by adding a mono- or di-hydrocarbon compound of a desired aliphatic saturated dicarboxylic acid to a solvent prepared by mixing an aprotic solvent with a polyhydric alcohol compound or its monoalkyl ether compound as required. -N
-Alkyl-1-azabicyclo(m,n,0)alkanium compound salt is added and dissolved.

〔Example〕

Hereinafter, examples of the electrolytic solution for electrolytic capacitors according to the present invention will be explained using mono- or di-N-alkyl-1-azabicyclo(m, n, O) aliphatic saturated dicarboxylic acid compounds.
Table 1 shows the electrical conductivities of various aprotic solvents of alkanium compound salts or solutions of these and ethylene glycol.

Note that a standard electrolytic solution is shown as a conventional example.

＼ As can be seen from the results in Table 1 and above, the electrolytic solution of the present invention exhibits higher conductivity than the conventional electrolytic solution.

Next, ten electrolytic capacitors were manufactured using the electrolytes of Examples 1 to 10 and Comparative Example, and their characteristics were compared.

The manufactured electrolytic capacitors were made by using aluminum foil as an anode and a cathode, and rolling the foil overlappingly with separator paper in between to form a cylindrical capacitor element, which was impregnated with the electrolyte of each example and comparative example. It is stored in an external case and sealed.

Both use the same capacitor element, and have a rated voltage of 16 V and a rated capacity of 180 μF.

Table 2 shows the initial values of these electrolytic capacitors and 85°
C represents the capacitance value (CAP; μF), the tangent of the loss angle (tan δ), and the leakage current (C: μA) as a biminute value after 100 hours have elapsed after applying the rated voltage.

It is understood that appearance abnormalities and capacitance reduction rates due to increased internal pressure under loaded conditions are extremely rare.

〔Effect of the invention〕

The electrolytic capacitor using the electrolyte according to the present invention has a low loss value and can maintain stable characteristics for a long time even in a wide range of temperature environments, so it is used at high frequencies and is required to have high efficiency. It can be used in power supplies such as switching regulators and various electrical devices that are used at high temperatures for long periods of time.

Claims (1)

[Claims] (1) General formula: ▲Mathematical formula, chemical formula, table, etc. in a solvent mainly composed of aprotic solvent▼ (In the formula, m = 3 to 6, n = 3 to 6, R is a carbon atom of 1 to 6
R_1 is an alkylene group having 1 to 20 carbon atoms, X is a hydrogen atom or the same group as the N-alkyl-1-azabicyclo[m,n,O]alkanium compound group shown in the formula) mono- or di-N-alkyl-1-azabicyclo[m
, n, O] An electrolytic solution for an electrolytic capacitor containing an alkanium compound salt as an electrolyte.