JPH02123721A - Electrolyte for electrolytic capacitor - Google Patents

Abstract

PURPOSE:To maintain stable characteristics of an electrolytic capacitor for a long period by adding salts of a specified cycloalkene (dioxy) (di- or tri-one) compound and a heterocyclic compound incorporating N,N-dialkyl as electrolyte into a solvent wherein an aprotic solvent is a main material. CONSTITUTION:As electrolyte, salts of cycloalkene (dioxy) (di- or tri-one) compound expressed by the formula I and a heterocylic compound incorporating N,N-dialkyl are added into a solvent wherein an aprotic solvent is a main material. In the expression I: R1-R4 represent alkyl groups of C1-C6 independently; (y) represents and integer in the range of 2-8 so that (y) pieces of methylene groups or their substituents can be the same different; (x) represents an integer of 2 or 3; and A represents a hydrogen atom or the same group as the heterocyclic compound group incorporating N,N-dialkyl. Thus, an electrolytic capacitor characterized by low loss value and by which the stable characteristics can be maintained even if the capacitor is used for a long time period at high temperature is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention is directed to the use of a cycloalkene (dioxy) (di or trione) compound and an N
, relates to an electrolytic solution for an electrolytic capacitor containing a salt with an N-dialkyl-containing heterocyclic compound as an electrolyte.

(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.

As described above, the electrolytic solution for an electrolytic capacitor comes into direct contact with the dielectric layer and acts as a true cathode. That is, the electrolytic solution is interposed between the dielectric layer and the i-electrode of the electrolytic capacitor, and the resistance bones of the electrolytic solution are inserted in series into 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 identified, and conventionally known electrolytes with high conductivity include organic acids such as adipic acid or their ammonium salts dissolved in glycols such as ethylene glycol or alcohols. These are the ones that are mainly used for normal purposes.

(Problems to be Solved by the Invention) Due to the recent increase in the scope of use of electronic devices, there is a growing demand for improvements in the performance of electrolytic capacitors, and the current conductivity of electrolytes is not sufficient. Particularly 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, 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 Problems) As a result of extensive 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 cycloalkenes (dioxy ) (di or trione) compound and a N,N-dialkyl-containing heterocyclic compound has high solubility in aprotic solvents, has a high degree of dissociation, and has achieved the present invention by discovering that it imparts high conductivity. This is what I did.

That is, the electrolytic solution for electrolytic capacitors according to the present invention has a general formula (in the formula, R, , R,
, R,, R, are independently C+-Cm alkyl groups, y is an integer of 2 to 8, and y methylene groups or their substituents may be the same or different, and X is an integer of 2 or 3. , ^ represents a hydrogen atom or the same group as the N,N-dialkyl-containing heterocyclic compound group shown in the formula) cycloalkene (dioxy) (di or trione) compound and N,N-dialkyl-containing heterocyclic compound It is characterized by containing a salt with a compound 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; , toethylacetamide, N, todiethylacetamide, hexamethylphosphoric amide (2) oxide type dimethyl sulfoxide (3) nitrile type acetonitrile (4) cyclic ester, amide type γ-butyrolactone, N-methyl-2-pyrrolidone, ethylene Representative examples include carbonate, propylene carbonate, etc., but the present invention is not limited thereto.

The polyhydric alcohol compound that is the object 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 glyfur, and the dihydric alcohol monoalkyl ether compound is methyl cellosolve. Or ethyl cellosolve.

The weight ratio of the polyhydric alcohol compound to the aprotic solvent is (100-50): (0-50), and 100% of the aprotic solvent is suitable, but up to about 50% of the polyhydric alcohol compound is substantially To avoid product deterioration,
May be used as appropriate.

The cycloalkene (dioxy) (di or trione) compounds that are the object of the present invention include 3,4-dioxy-3-cyclobutene-1,2-dione (commonly known as dioxycyclobutadienequinone) (formula I below) and .5-dioxy-4-
It is cyclopentene-1,2,3-trione (commonly known as croconic acid) (formula 2 below).

Compounds (■) are S., Cohen et al.: Journal of the American Chemical Society, Vol. 81.

Compound (n) was prepared by the method described in R. Nikucchi et al.: Berichte, Vol. 18, p. 3480 (1959).

Page 499 (1885): R. Malakovsky et al.
It can be prepared by the method described in Berichte, Vol. 71, p. 2241 (1938).

Examples of N,N-dialkyl-containing heterocyclic compounds targeted by the present invention include a 3-membered ring compound N,N-dimethylaziridinium, or a 4-membered ring compound N,N-dimethylaziridinium; The compound tomethyl-N-ethylazetidinium, N,N-diethyl-3-methylazetidinium, or N,N-dimethyl-3-ethylazetidinium, the 5-membered ring compound N,N-diethylpyrrolidium nium,
N,N-diethyl-2,3-dimethylpyrrolidinium,
or N,N-dimethyl-2-methyl-3-ethylpyrrolidinium, 6-membered ring compound N,N-diethylpiperidinium, N,N-dimethyl-2,4-dimethylpiperidinium, or N, Examples include N-dimethyl-2,6-diethylpiperidinium.

Add 1 mole of the desired cycloalkene (dioxy) (di or trione) compound to an aqueous solution of 1 or 2 moles of the hydroxide of the N,N-dialkyl-containing heterocyclic compound, perform a neutralization reaction, and then dry under reduced pressure. The cycloalkene (dioxy) (di or trione) compound and N
, a salt with an It-dialkyl-containing heterocyclic compound can be obtained.

The electrolytic solution for an electrolytic capacitor according to the present invention is prepared by adding a desired cycloalkene (dioxy) (di- or trione) to a solvent prepared by mixing an aprotic solvent with a polyhydric alcohol compound or its monoalkyl ether compound as required. It is obtained by adding and dissolving a salt of the compound and an N,N-dialkyl-containing heterocyclic compound in an amount that provides the desired electrical conductivity.

(Example) Examples of the electrolytic solution for electrolytic capacitors according to the present invention will be described below, containing a cycloalkene (dioxy) (di- or trione) compound (i.e., dioxycyclobutadienequinone or croconic acid) and N, N-dialkyl. Table 1 shows the conductivities of 20% by weight solutions of salts with heterocyclic compounds in various aprotic solvents or with methylcellosolve (ethylene glyfur monomethyl ether).

As a comparative example, a conventional standard electrolytic solution (78% by weight of ethylene glycol, 10% of water, 12% of diammonium adipate) is shown.

(Continued from Table 1) 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 1
The 6V rated capacity ffi is 180μF.

Table 2 shows the initial values of these electrolytic capacitors as well as 100
It shows the capacitance value (μF), tangent of loss angle (tan δ), leakage current (μ included) (2-minute value) after 1000 hours after applying the rated voltage at °C.

As is clear from the results of this test, since the electrolytic solution of the present invention has a high conductivity, the loss, that is, t
The value of anδ becomes low.

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.

(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 even when used at high temperatures for a long time, 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 (7)

[Claims] (1) General formulas in a solvent mainly composed of aprotic solvents: ▲Mathematical formulas, chemical formulas, tables, etc.▼ (In the formula, R_1, R_2, R_3, R_4 are independently C
_1 to C_■ alkyl group, y is an integer of 2 to 8, and y
The methylene groups or their substituents may be the same or different, x is an integer of 2 or 3, and A represents a hydrogen atom or the same group as the N,N-dialkyl-containing heterocyclic compound group shown in the formula. ) An electrolytic solution for an electrolytic capacitor containing a salt of a cycloalkene (dioxy) (di- or trione) compound and an N,N-dialkyl-containing heterocyclic compound 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, dimethyl sulfoxide,
The electrolytic solution for an electrolytic capacitor according to claim 1 or 2, which is selected from the group of 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 cycloalkene (dioxy) (dione) compound is dioxycyclobutadienequinone and the cycloalkene (dioxy) (trione) compound is croconic acid. (7) N,N-dialkyl-containing heterocyclic compound is N,N
2. The electrolytic solution for an electrolytic capacitor according to claim 1, which is -dimethylpyrrolidinium, N,N-diethylpyrrolidinium, N,N-dimethylpiperidinium, or N,N-diethylpiperidinium.