JPH0269918A - Electrolyte for electrolytic capacitor - Google Patents

Abstract

PURPOSE:To improve the electric characteristics and reliability of an electrolytic capacitor by incorporating specific compound salt in a predetermined solvent as electrolyte. CONSTITUTION:When an N-alkyl-1-azabicyclo[m,n,p]arcanium compound salt of fatty saturated monocarboxylic acid represented by a formula I is contained in a solvent containing as a main gradient nonproton solvent as electrolyte, it becomes an electrolyte containing the nonproton solvent as a main ingredient and having substantially nonaqueous high conductivity. Accordingly, when this electrolyte is used, its characteristics are stabilized even at the time of use for a long period of time at a high temperature with low loss to enhance its electric characteristics to obtain an electrolytic capacitor having stable characteristics to be maintained for a long period of time with high reliability. In the formula, m, n: 2 or 3, p: 1, 2 or 3, R1: 30-0C alkyl group, and R2: 6-0C alkyl group.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention is directed to a solution containing an N-alkyl-■azabicycloalkanium compound salt of an aliphatic saturated monocarboxylic acid as an electrolyte in a solvent mainly consisting of an aprotic solvent. This invention relates to an electrolytic solution for electrolytic capacitors.

(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 is in 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 electrolytic solution has a low amount of conductive dust, it increases the equivalent series resistance inside the electrolytic capacitor, resulting in poor high frequency characteristics and loss characteristics. From this background, electrolytes with high conductive dust have been selected, and as electrolytes with high conductive dust,
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) Due to the recent increase in the scope of use of electronic devices, there has been an increasing demand for improvements in the performance of electrolytic capacitors, and the current conductive dust in electrolytes is not sufficient. Especially in the case of current electrolytes, when the desired conductive dust cannot be obtained or when an electrolyte with low solubility is used, water is intentionally added to improve the conductive dust. .

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 improve the electrical characteristics of electrolytic capacitors and to maintain stable characteristics for a long time by providing a substantially non-aqueous highly conductive electrolytic solution containing an aprotic solvent as a main component. The purpose is to improve the reliability of electrolytic capacitors by maintaining them for a long period of time.

(Means for Solving the Problem) As a result of intensive research into an electrolyte that is a substantially non-aqueous electrolyte mainly composed of an aprotic solvent and provides high conductivity, the present inventors have discovered that an aliphatic saturated electrolyte The present invention was achieved by discovering that N-alkyl-1-azabicycloalkanium compound salts of carboxylic acids have high solubility in aprotic solvents, have a high degree of dissociation, and impart high electrical conductivity.

That is, the electrolytic solution for an electrolytic capacitor according to the present invention has a general formula (where m is 2 or 3, n is 2 or 3, p is 1, 2 or 3, R1 represents an alkyl group having 30 or less carbon atoms, and R2 represents an alkyl group having 6 or less carbon atoms.
n+ p]Alkanium compound salt as an electrolyte.

The aprotic solvents used include (1) N-methylformamide, N-methylformamide as an amide type;
, N-dimethylformamide, N-ethylformamide, N,N-diethylformamide, N-methylacetamide, N,N-dimethylacetamide, N-ethylacetamide, N,N-diethylacetamide, hexamethylphosphoric amide, (2) Representative examples include dimethyl sulfoxide as an oxide type, (3) acetonitrile as a nitrile type, and (4) γ-butyrolactone, N-methyl-2-pyrrolidone, ethylene carbonate, propylene carbonate, and the like as cyclic esters and amide types.

The polyhydric alcohol compound that is the subject of the present invention is preferably a dihydric alcohol compound or a monoalkyl ether of a dihydric alcohol compound, the dihydric alcohol compound is ethylene glycol, and the dihydric alcohol mono/alkyl ether compound is methyl cellulose. Solv or Ethyl Cell Solv.

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 aliphatic saturated monocarboxylic acid compounds targeted by the present invention include formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, undecanoic acid, lauric acid, tridecanoic acid, Myristic acid, pentadecanoic acid, valmitic acid, heptadecanoic acid, stearic acid, nonadecanoic acid, araxic acid, i-nobutyric acid, invaleric acid, incapric acid, ethylbutyric acid, methylvaleric acid, incaprylic acid, propylvalerate, ethylcaprone acid, incapric acid, tsherculostearic acid,
Pivalic acid, 2,2-dimethylbutanoic acid, 2,2-dimethylpentanoic acid, 2,2-dimethylhexanoic acid, 2,2-
Dimethylhebutanoic acid, 2.2-dimethyloctanoic acid, 2
-Methyl-2-ethylbutanoic acid, 2-methyl-2-ethylpenconic acid, 2-methyl-2-propylhexanoic acid, 2
-methyl-2-furohylhebutanoic acid and the like, but are not limited thereto.

Representative examples of N-alkyl-niazabicycloalkanium compounds are: N-alkyl-・bovine nuclidinium N-alkyl-
・Azabicyclo[2,2,11 to butanium N-alkyl-1-azabicyclo[3,2,2] /nanium N-alkyl]-azabicyclo[3,3,I]nonanium■-Al-Cow Ru 1-Azabicyclo[3 ,2,I]octanium N-alkyl-1-azabicycloalkanium compounds, for example,
Volume 32, page 83 (1937), He et al.: Berichte No. 7
Vol. 2, p. 1319 (1939), the tripromide-ammonia method described in C1^, Grove et al.
Alternatively, N-alkyl-1-azabicycloalkane is synthesized by a double alkylation method, and then N-alkylated with an alkyl halide in a conventional manner to obtain the corresponding N-alkyl halide-azabicycloalkanium compound. You can get it. This is electrodialyzed using an ion exchange membrane to perform anion exchange and desalination to form hydroxylated N-
An aqueous solution of an alkyl-1-azabinchloroalkanium compound is obtained. Equimolar moles of the desired aliphatic saturated monocarboxylic acid are added to the obtained N-alkyl-1-azabicycloalkanium compound aqueous solution, a neutralization reaction is carried out, and the aliphatic saturated monocarboxylic acid is evaporated to dryness under reduced pressure. mono-N-alkyl-
It is possible to obtain a 1-azabicycloalkanium salt.

The electrolytic solution for an electrolytic capacitor according to the present invention is generally prepared by mixing an aprotic solvent with a polyhydric alcohol compound or its monoalkyl ether compound as required, and adding a desired N-alkyl-saturated aliphatic monocarboxylic acid. Obtained by adding and dissolving 1-azabicycloalkanium salt.

(Example) The following describes examples of the electrolyte solution for electrolytic capacitors according to the present invention.N-alkyl-1- of aliphatic saturated monocarphonic acid
2 for various aprotic solvents of azabicycloalkanium compound salts or this and ethylene glycol or methylcellolph (ethylene glycol monomethyl ether)
The electrical conductivity of the 0% by weight solution is shown in Table 1. As a comparative example, a conventional standard electrolytic solution (78% by weight of ethylene glycol, 10% of water, 412% of diammonium adipate) is shown.

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), leakage current (μA) after 1000 hours have passed after applying the rated voltage at C
) (dichotomous value).

Two authors (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 It can be used in power supplies such as switching regulators that require efficiency, and in various electrical devices that are used at high temperatures for long periods of time.

Patent Applicant: Nippon Chemi-Con Co., Ltd. As is clear from the results of this test, the electrolytic solution of the present invention has a high level of conductive dust, so the loss, that is, the value of tan δ, is lower than that of the conventional electrolyte.

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

Claims (7)

[Claims] (1) General formulas in solvents that are mainly aprotic solvents: ▲Mathematical formulas, chemical formulas, tables, etc.▼ (In the formula, m is 2 or 3, n is 2 or 3, p is 1, 2 or 3, R_1 is an alkyl group having 30 or less carbon atoms, R_2
represents an alkyl group having up to 6 carbon atoms) N-alkyl-1-azabicyclo[
An electrolytic solution for an electrolytic capacitor containing an alkanium compound salt as an electrolyte. (2) A solvent mainly composed of an aprotic solvent is 100 to 50 parts by weight of an aprotic solvent and 0 to 50 parts by weight of a polyhydric alcohol compound.
The electrolytic solution for an electrolytic capacitor according to claim 1, comprising 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-2-pyrrolidone, ethylene carbonate, propylene carbonate, The electrolytic solution for an electrolytic capacitor according to claim 1 or 2, which is selected from the group of 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) N-alkyl-1-azabicyclo[m,n,p]
Alkanium compounds include N-ethylquinuclidinium, N
The electrolytic solution for an electrolytic capacitor according to claim 1, which is -methylquinuclidium or N-ethyl-1-azabicyclo[3,3,1]nonanium. (7) The electrolytic solution for an electrolytic capacitor according to claim 1, wherein the aliphatic saturated monocarboxylic acid compound is acetic acid, pivalic acid, enanthic acid, or propionic acid.