JP2810674B2 - Electrolyte for electrolytic capacitors - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for preparing a salt of a cycloalkene (dioxy) (di- or tri-one) compound and a tetraalkylammonium compound in a solvent mainly composed of an aprotic solvent. The present invention relates to an electrolytic solution for an electrolytic capacitor contained as an electrolyte.

(Conventional technology) Electrolytic capacitors use a valve metal having an insulating oxide film formed on the surface of aluminum or tantalum as an anode electrode, use the oxide film layer as a dielectric, and apply the oxide film layer to the surface of the oxide film layer. It is configured such that an electrolytic solution serving as an electrolyte layer is brought into contact with the battery, and an electrode for current collection usually called a cathode is arranged.

As described above, the electrolytic solution for the electrolytic capacitor directly contacts the dielectric layer and acts as a true cathode. That is, the electrolytic solution is interposed between the dielectric layer of the electrolytic capacitor and the collector cathode, and the resistance of the electrolytic solution is inserted in series with the electrolytic capacitor. Therefore, the characteristic is a major factor affecting the characteristics of the electrolytic capacitor. For example, when the electrolyticity of the electrolytic solution is low, there is a disadvantage that the equivalent series resistance inside the electrolytic capacitor is increased, and high-frequency characteristics and loss characteristics are deteriorated. Against this background, highly conductive electrolytes have been sought, and as a conventionally known highly conductive electrolyte, an organic acid such as adipic acid or its ammonium salt is dissolved in glycols such as ethylene glycol or alcohols. The mainstream is used for ordinary purposes.

(Problems to be Solved by the Invention) With the recent increase in the range of use of electronic devices, demands for improving and improving the performance of electrolytic capacitors have increased, and the conductivity of current electrolytic solutions cannot be said to be sufficient. In particular, in the case of the current electrolytic solution, when the desired electric conductivity cannot be obtained, or when using an electrolyte having low solubility, it is attempted to intentionally add water to improve the electric conductivity. .

However, recently, in the use situation of electrolytic capacitors that require long-term use at a higher temperature than conventional products, the presence of moisture in the electrolyte causes deterioration of the dielectric film layer and vapor pressure inside the electrolytic capacitor. And the service life is deteriorated due to breakage of the sealing portion and evaporation of the electrolytic solution, and there is a disadvantage that stable characteristics cannot be maintained for a long period of time.

Therefore, an object of the present invention is to provide a substantially non-aqueous, high-conductivity electrolytic solution mainly composed of an aprotic solvent, thereby improving the electric characteristics of an electrolytic capacitor and extending the stable characteristics. It is to improve the reliability of the electrolytic capacitor by maintaining the period.

(Means for Solving the Problems) The inventors of the present invention have conducted intensive studies on an electrolyte which is a substantially non-aqueous electrolyte mainly composed of an aprotic solvent and which gives high conductivity, and as a result, cycloalkene (dioxin) ) It has been found that a salt of a (di- or tri-one) compound and a tetraalkylammonium compound has high solubility in an aprotic solvent, has a high dissociation degree and imparts high conductivity, and has reached the present invention. .

That is, the electrolytic solution for an electrolytic capacitor according to the present invention has a general formula in a solvent mainly containing an aprotic solvent. (Wherein R ₁ , R ₂ , R ₃ and R ₄ are C ₁ -C ₆ alkyl groups,
Each may be the same or different, x is an integer of 2 or 3, A represents a hydrogen atom or the same group as the tetraalkylammonium compound group shown in the formula), and a cycloalkene (diquin) (di or tri-one) compound And a salt of a tetraalkylammonium compound as an electrolyte.

Solvents mainly composed of aprotic solvents are referred to as aprotic solvents.
It consists of a mixed solvent with 50 parts by weight or less of a polyhydric alcohol compound.

Examples of the aprotic solvent used include: (1) amide N-methylformamide, N, N-dimethylformamide, N-ethylformamide, N, N-diethylformamide, N-methylacetamide, N, N-dimethylacetamide, N-ethylacetamide, N, N-diethylacetamide, hexamethylphosphoramide (2) oxide dimethyl sulfoxide (3) nitrile acetonitrile (4) cyclic ester, amide γ-butyrolactone, N-methyl-2-pyrrolidone,
Representative examples include, but are not limited to, ethylene carbonate and propylene carbonate.

The polyhydric alcohol compound targeted by 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 monoalkyl ether compound is methylcellosolve or It is an ethyl cellosolve.

As the solvent, mainly aprotic solvent,
A mixed solvent of an aprotic solvent and a polyhydric alcohol compound can also be used. The weight ratio of the polyhydric alcohol compound to the aprotic solvent is 50 parts by weight or less, but up to about 50 parts by weight of the polyhydric alcohol compound can substantially avoid product deterioration and may be used as appropriate.

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

Compound (I) is described in S. Cohen et al .: Journal American Chemical Society, Vol. 81, p. 3480 (19
According to the method described in 59), compound (II) can be prepared as described in R. Nikkusu et al .: Berichte, Vol. 18, p. 499 (1885): R. Malakowskii et al .: Berichte, Vol. 71, p. It can be prepared by the method described.

Examples of the tetraalkylammonium compound targeted in the present invention include tetramethylammonium, tetraethylammonium, tetrapropylammonium, tetrabutylammonium, dimethyldiethylammonium, trimethylisopropylammonium, trimethylethylammonium, diethyldibutylammonium, tributylmethylammonium and the like. Can be illustrated.

1 mol of the desired cycloalkene (dioxy) (di- or tri-one) compound is added to a 1 mol or 2 mol aqueous solution of the desired tetraalkylammonium compound, neutralized, and then dried under reduced pressure to remove water. A salt of an alkene (dioxy) (di or tri-one) compound and a tetraalkyl ammonium compound can be obtained.

The electrolytic solution for the electrolytic capacitor according to the present invention is generally,
A salt of a desired cycloalkene (dioxy) (di- or tri-one) compound and a tetraalkylammonium compound is added to a solvent obtained by mixing a polyhydric alcohol compound or a monoalkyl ether compound thereof with an aprotic solvent as necessary. Is added and dissolved in the amount obtained.

EXAMPLES Hereinafter, examples of the electrolytic solution for an electrolytic capacitor according to the present invention will be described with reference to a cycloalkene (dioxy) (di or tri-one) compound (that is, dioxycyclobutadiene quinone or croconic acid) and a tetraalkylammonium compound. Table 1 shows the conductivity of a 20% by weight solution of a salt of the above with various aprotic solvents and / or methylcellosolve (ethylene glycol monomethyl ether). As a comparative example, a conventional standard electrolyte (78% by weight of ethylene glycol, 10% of water, and 12% of diammonium adipate) is shown.

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

Next, electrolytic capacitors were manufactured using the electrolytic solutions of Examples 1 to 8 and Comparative Example, and their characteristics were compared.

The manufactured electrolytic capacitors were made by using aluminum foil as the anode and cathode, and wrapping them over each other with separator paper sandwiched between them to form cylindrical capacitor elements. It is housed in a case and sealed.

All use the same capacitor element and rated voltage
The 16V rated capacity is 180 μF.

Table 2 shows the initial values of these electrolytic capacitors as well as 110
Capacitance value (μF), tangent of loss angle (tan δ), leakage current (μA) after 1000 hours from application of rated voltage at ℃
(Binary value).

As is clear from the results of this test, since the conductivity of the electrolytic solution of the present invention is high, the loss compared to the conventional one, that is,
The value of tan δ decreases.

In addition, even if it is placed in a high temperature load state without essentially containing water, there is no appearance abnormality or decrease in capacitance due to internal pressure rise,
Even in the comparison between the initial value and the characteristic value after 1000 hours, the one of the present invention has very little change.

(Effect of the Invention) An electrolytic capacitor using the electrolytic solution according to the present invention can maintain stable characteristics even when used for a long time at a high temperature with a low loss value, so that it is used at a high frequency and high efficiency is required. The present invention can be used for a power supply device such as a switching regulator, and various electric devices used at a high temperature for a long time.

Claims (7)

(57) [Claims] [1] A solvent comprising an aprotic solvent as a main component and a general formula: (Wherein R ₁ , R ₂ , R ₃ and R ₄ are C ₁ -C ₆ alkyl groups,
Each may be the same or different, x represents an integer of 2 or 3, A represents a hydrogen atom or the same group as the tetraalkylammonium group shown in the formula), cycloalkene (dioxy)
An electrolytic solution for an electrolytic capacitor, comprising a salt of a (di- or tri-one) compound and a tetraalkylammonium compound as an electrolyte. 2. The electrolytic solution for an electrolytic capacitor according to claim 1, wherein the solvent mainly composed of an aprotic solvent comprises a mixed solvent of an aprotic solvent and 50 parts by weight or less of a polyhydric alcohol compound. 3. An aprotic solvent comprising N-methylformamide, N, N-dimethylformamide, N-ethylformamide, N, N-diethylformamide, N-methylacetamide, N, N-dimethylacetamide, N-ethylacetamide, The electrolysis according to claim 1 or 2, wherein the electrolysis is selected from the group consisting of N, N-diethylacetamide, γ-butyrolactone, N-methyl-2-pyrrolidone, ethylene carbonate, propylene carbonate, dimethyl sulfoxide, acetonitrile, and a mixture thereof. Electrolyte for capacitors. 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 the 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 methylcellosolve or ethylcellosolve. 6. The electrolytic solution according to claim 1, wherein the cycloalkene (dioxy) (dione) compound is dioxycyclobutadienequinone and the cycloalkene (dioxy) (trione) compound is croconic acid. 7. The electrolytic solution according to claim 1, wherein the tetraalkylammonium compound is tetramethylammonium, tetraethylammonium and triethylmethylammonium.