JPH0254515A - Electrolyte solution for electrolytic capacitor - Google Patents

Abstract

PURPOSE:To maintain a low loss value and stable characteristics even with use thereof at a high temperature for a long period of time by containing as the electrolyte a mono- or di-spiro-ammonium compound salt of a specific alkyl malonic acid compound in a solvent chiefly comprising an aprotic solvent. CONSTITUTION:The title electrolyte solution for electrolytic capacitor contains as the electrolyte a mono- or di-spiro-ammonium compound salt of an alkyl malonic acid compound of a general formula (I) (in the formula, (n) is a 4-8 integer, (m) a 3-6 integer, R1 and R2 hydrogen atom or an alkyl group of 1-10 carbon atoms, and X the same group as the spiro-ammonium group in the formula.) in a solvent chiefly comprising an aprotic solvent. The salt of the alkyl malonic acid compound with the mono- or di-spiro-ammonium compound has high solubility to aprotic solvent and high dissociation and is therefore given high conductivity.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to an electrolytic capacitor containing a salt of a mono- or di-spiroammonium compound of an alkyl malonic acid compound as an electrolyte in a solvent mainly consisting of an aprotic solvent. The present invention relates to electrolytes for use in industrial applications.

(Prior art) An electrolytic capacitor uses a valve metal such as aluminum or tantalum on the surface of which an insulating oxide film is formed as an anode electrode, the oxide film layer is used as a dielectric, and the surface of the oxide film layer is It is constructed by bringing an electrolytic solution, which forms an electrolyte layer, into contact with it, and further arranging a current collecting electrode, usually called a cathode.

The electrolyte for an electrolytic capacitor comes into direct contact with the dielectric layer, as described above, 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, its characteristics become 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. From this background, electrolytes with high conductivity have been selected, and as the conventionally known electrolytes with high conductivity,
Organic acids such as adipic acid or their salts dissolved in glycols such as ethylene glycol or alcohols are mainly used for ordinary purposes.

(Problems to be Solved by the Invention) 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 electrical conductivity of electrolytes is not 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 achieve the same conductivity. There is.

However, in recent years, when electrolytic capacitors are used for long periods of time at higher temperatures than conventional products, the presence of moisture in the electrolyte can cause deterioration of the dielectric film layer and internal steam of the electrolytic capacitor. This increases the pressure, leading to damage to the sealing part and evaporation of the electrolyte, which shortens its lifespan, and has the disadvantage that stable characteristics cannot be maintained over a long period of time.

Therefore, an object of the present invention is to provide a substantially non-aqueous highly conductive electrolytic solution containing an aprotic solvent as a main ingredient, thereby improving the Ts air characteristics of an electrolytic capacitor and maintaining stable characteristics for a long time. The purpose is to improve the reliability of electrolytic capacitors by maintaining them for a long period of time.

(Means for Solving the Problems) As a result of extensive research into an electrolyte that is a substantially non-aqueous electrolyte containing an aprotic solvent and that provides high conductivity, the present inventors have discovered an alkylmalonic acid compound. The present invention was achieved based on the discovery that a salt of the above with a mono- or di-spiroammonium compound has high solubility in an aprotic solvent, has a high degree of dissociation, and imparts high electrical conductivity.

That is, the electrolytic solution for an electrolytic capacitor according to the present invention has a general formula: (where n is an integer of 4 to 8, mist is an integer of 3 to 6, R1,
R1 is a hydrogen atom or an alkyl group having 1 to 10 carbon atoms,
It is characterized in that it contains a mono- or di-spiroammonium compound salt of an alkylmalonic acid compound (X represents a hydrogen atom or the same molecule as the spiroammonium molecule shown in the formula) as an electrolyte.

Solvents mainly composed of aprotic solvents are aprotic solvents 10
It consists of 0 to 50 parts by weight and 0 to 50 parts by weight of a polyhydric alcohol compound.

The aprotic solvents used include (1) amide N-methylformamide, N,N-dimethylformamide, N-ethylformamide, N,N-diethylformamide, N-methylacetamide, N,N-dimethylacetamide; , N-ethylacetamide, N,N-diethylacetamide, hexamethylphosphoric amide (2) Oxide-based dimethyl sulfoxide (3) Nitrile-based acetonitrile (4) Cyclic ester, amide-based γ-butyrolactone, tomethyl-2-pyrrolidone, ethylene Representative examples include carbonate, fluoropylene carbonate, etc., but the present invention is not limited thereto.

The target polyhydric alcohol compound of the present invention is preferably a dihydric alcohol compound or a monoalkyl ether of a dihydric alcohol compound, and the dihydric alcohol compound is ethylene glycol, and the dihydric alcohol monoalkyl ether compound is preferably a dihydric alcohol compound or a monoalkyl ether of a dihydric alcohol compound. Methyl cellosolve or ethyl cellosolve.

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

The alkylmalonic acid compounds targeted by the present invention include methylmalonic acid, ethylmalonic acid,
Propylmalonic acid, inpropylmalonic acid, butylmalonic acid, isobutylmalonic acid, nibutylmalonic acid, tert-butylmalonic acid, pentylmalonic acid, etc., dialkylmalon Qlt, dimethylmalonic acid, ethylmethylmalonic acid, diethylmalonic acid. , ethylpropylmalonic acid, ciflobylmalonic acid, propylmethylmalonic acid, methylpentylmalonic acid, etc., but are not limited to these.

The spiroammonium acid compound is ■, 1°-spiro[
azetidine 1.1'-piviveridinium].

Spiroammonium compounds can be synthesized by the method described in J. V. Brown, Berichna 6, Vol. 49, p. 466 (1916). For example, pyrrolidine is reacted with 1,4-dibromobutane to form 1,1-bromide. Spirobipyrrolidinium can be obtained.

An aqueous solution of 1,1°-subirobipyrrolidinium hydroxide can be synthesized by electrodialyzing the obtained 1,1°-spiropipyrrolidinium bromide using an ion exchange membrane to perform anion exchange.

Adding a desired aliphatic unsaturated dicarboxylic acid compound to the obtained aqueous solution of 1.1'-subirobipyrrolidinium hydroxide,
After the neutralization reaction, water is removed by drying under reduced pressure (thereby, a 1,1°-spiropipyrrolidinium salt of an aliphatic unsaturated dicarboxylic acid compound can be obtained).

The electrolytic solution for an electrolytic capacitor according to the present invention is generally prepared by adding an equivalent amount of a spiroammonium compound salt of a desired alkylmalonic acid compound to a solvent prepared by mixing an aprotic solvent with a polyhydric alfur compound or its monoalkyl ether compound as required. Alternatively, it can be obtained by adding and dissolving 2 equivalents.

Writer (Example) Examples of the electrolytic solution for electrolytic capacitors according to the present invention will be described below using various aprotic solvents of spiroammonium compound salts of various alkylmalonic acid compounds or ethylene glycol or methyl cellulose. 15.2 for (ethylene glycol/methyl ether)
Table 1 shows the electrical conductivity of the 011r solution. As a comparative example, a conventional standard electrolyte (ethylene glycol = + -
Lua 8tf It%, water 10%, ammonium adipate 12%).

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

Next, 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 a separator paper in between to form a cylindrical capacitor element, which was impregnated with the electrolytic solution 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 16V and a rated capacity of 180 μF.

Table 2 shows the initial values of these electrolytic capacitors and 85℃
Capacitance value (μF), tangent of loss angle (tan δ), and leakage current (μ^) after 1000 hours have passed after applying the rated voltage at
(dichotomous value).

As is clear from the results of this test, the electrolyte of the present invention has a high conductivity, so the loss, i.e., t, is lower than that of the conventional one.
The value of anδ becomes low.

In addition, since it essentially does not contain water, there will be no abnormal appearance or decrease in capacitance due to increased internal pressure even when placed under high temperature load conditions.
Even when comparing the initial values and the characteristic values after 1000 hours, there is very little change in the properties of the present invention.

(Effects of the Invention) The electrolytic capacitor using the electrolyte according to the present invention has a low loss value and can maintain stable characteristics even when used at high temperatures for long periods of time, so it can be used at high frequencies and requires high efficiency. It can be used in power supply devices such as switching regulators, which are used for a long period of time, and various electrical devices that are used at high temperatures for long periods of time.

Claims (7)

[Claims] (1) General formulas in solvents that are mainly aprotic solvents: ▲Mathematical formulas, chemical formulas, tables, etc.▼ (In the formula, n is an integer from 4 to 8, m is an integer from 3 to 6, R_1
, R_2 is a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, x is a hydrogen atom or the same group as the spiroammonium group shown in the formula) Mono- or di-spiroammonium compounds of alkylmalonic acid compounds An electrolytic solution for electrolytic capacitors that contains salt as an electrolyte. (2) The solvent mainly composed of an aprotic solvent contains 100 to 50 parts by weight of an aprotic solvent and 0 to 5 parts by weight of a polyhydric alcohol compound.
The electrolytic solution for an electrolytic capacitor according to claim 1, comprising 0 parts by weight. (3) The aprotic solvent is N-methylformamide, N
, N-dimethylformamide, N-ethylformamide, N,N-diethylformamide, N-methylacetamide, N,N-dimethylacetamide, N-ethylacetamide, N,N-diethylacetamide, γ-butyrolactone, N-methyl- The electrolytic solution for an electrolytic capacitor according to claim 1 or 2, which is selected from the group of 2-pyrrolidone, ethylene carbonate, propylene carbonate, dimethyl sulfoxide, acetonitrile, or a mixture thereof. (4) The electrolytic solution for an electrolytic capacitor according to claim 2, wherein the polyhydric alcohol compound is a dihydric alcohol compound or a monoalkyl ether of a dihydric alcohol compound. (5) The electrolytic solution for an electrolytic capacitor according to claim 2, wherein the dihydric alcohol compound is ethylene glycol and the dihydric alcohol monoalkyl ether compound is methyl cellosolve or ethyl cellosolve. (6) The electrolytic solution for an electrolytic capacitor according to claim 1, wherein the alkylmalonic acid compound is ethylmalonic acid, dimethylmalonic acid, or diethylmalonic acid. (7) The spiroammonium compound is 1,1'-spirobipyrrolidinium, spiro[piperidine-1,1'-pyrrolidinium], 1,1'-spirobipiperidinium or 1,1-spirobipyrrolidinium The electrolytic solution for an electrolytic capacitor according to claim 1.