JPH04311021A - Electrolyte for driving electrolytic capacitor - Google Patents

Abstract

PURPOSE:To provide an electrolytic capacitor driving electrolyte with which spark-generating voltage can be increased sufficiently without lowering conductivity. CONSTITUTION:A superfine particle inorganic compound is dispersed in a solvent which is mainly composed of ethylene glycol, and an electrolytic capacitor driving electrolyte is prepared by adding one of hexitols and boric acid or both of them and dissolving them.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrolytic solution for driving an electrolytic capacitor, and more specifically, to an electrolytic solution for driving an aluminum electrolytic capacitor.

0002

BACKGROUND OF THE INVENTION Conventional electrolytic solutions for aluminum electrolytic capacitors include an electrolytic solution prepared by dissolving boric acid or ammonium borate as an electrolyte in ethylene glycol because the spark generation voltage can be made relatively high.

However, in such an electrolytic solution, a large amount of water is contained in the electrolytic solution due to crystallization water directly released from boric acid and condensed water produced by the esterification reaction between ethylene glycol and boric acid. If this electrolyte is used in an aluminum electrolytic capacitor that is heated to over 100℃, the water in the electrolyte will evaporate into water vapor, which will increase the internal pressure inside the aluminum electrolytic capacitor package and destroy it. There was a problem with letting it happen. In order to solve these problems, organic carboxylic acids such as adipic acid or benzoic acid or their salts, which have a very slow esterification reaction with ethylene glycol, were considered as electrolytes, but in this case, the necessary Formation/discharge characteristics during high constant current formation (hereinafter referred to as
The drawback was that it was not possible to obtain a spark generation voltage. In order to solve this drawback, there is an example of adding polyoxyethylene dicarboxylic acid to the electrolytic solution to improve the spark generation voltage, as disclosed in Japanese Patent Application Laid-Open No. 176218/1983. As an example, there is Japanese Patent Application Laid-open No. 12717/1983. Furthermore, Japanese Patent Publication No. 2-57328 discloses an example in which bismuth oxide, which is a metal oxide, is contained in an electrolytic solution.

0004

[Problems to be Solved by the Invention] However, polyoxyethylene dicarboxylic acid, which is an additive for improving the spark generation voltage, has the disadvantage of lowering the specific conductivity and increasing the loss of electrolytic capacitors. be. In addition, the size of the ceramic powder is 5 μm to 50 μm.
Although some methods are known, they are difficult to disperse, and their effect on spark generation voltage is not clear. moreover,
The bismuth oxide known from Japanese Patent Publication No. 2-57328 has the disadvantage that it is difficult to disperse and readily precipitates, and its effect on improving the spark generation voltage has not been clarified.

The present invention solves the above-mentioned conventional problems, and aims to provide an electrolytic solution for driving an electrolytic capacitor that can sufficiently increase the spark generation voltage without reducing the specific conductivity. It is something.

[0006]

[Means for Solving the Problems] In order to solve the above problems, the electrolytic solution for driving an electrolytic capacitor of the present invention is prepared by dispersing an ultrafine inorganic compound in a solvent mainly composed of ethylene glycol, and containing hexites and boric acid. Either one or both of these are added and dissolved.

[0007]

[Operation] The electrolytic solution for driving an electrolytic capacitor of the present invention described above is prepared by dispersing an ultrafine particle inorganic compound in a solvent mainly composed of ethylene glycol, and adding either or both of hexites and boric acid to dissolve it. I did it,
Since the ultrafine inorganic compound is charged in the electrolytic solution and becomes colloidal, it can be uniformly dispersed in the electrolytic solution. In addition, when an oxide film is formed, the ultrafine inorganic compound adsorbs and aggregates to fill in the defective parts of the oxide film, making it possible to produce an oxide film with fewer defects.This makes it possible to increase the spark generation voltage, and In addition to this, by adding one or both of hexites and boric acid, the surface of the anodic oxide film is covered with the hexites, thereby making it possible to further increase the spark generation voltage.

[0008]

[Examples] Examples of the present invention will be described below.

The basic principle of the electrolytic solution for driving an electrolytic capacitor of the present invention is to disperse an ultrafine inorganic compound in a solvent mainly composed of ethylene glycol, and to dissolve it by adding one or both of hexites and boric acid. As the ultrafine inorganic compound, metal oxides, metal nitrides, or metal carbides are preferable.

[0010]Usually, ultrafine inorganic compounds are electrically charged in an electrolytic solution and are dispersed in the form of a colloid, but some particles may be difficult to disperse depending on the pH of the solution or the type of inorganic compound. In that case, dispersion can be achieved by using an appropriate surfactant or performing surface treatment.

Examples of metal oxides include basic oxides (SiO2, TiO2, Y2O3, Al2O3, Fe
2O3, HfO2, Ga2O3, In2O3, SnO2
, Bi2O3, etc.); acidic oxides (Ta2O5, GeO2
, SeO2, Sb2O3, TeO2, WO3, Nb2O
5 etc.); composite oxides (SiO2-Al2O3, SiO2
-MgO, SiO2-CaO, SiO2-SrO, Si
O2-BaO, SiO2-ZrO2, etc.). Among these, SiO2 and TiO2 are preferred.

Examples of metal nitrides include TiN, S
i3N2, AlN, TaN, Zr3N4, NbN, Zr
An example is N. Among these, preferred is Ti
It is one type or a mixture of two or more types of N, Si3N2, AlN, and Zr3N4.

[0013] As the metal carbide, SiC, TiC, M
Examples include o2C and WC. Among these, preferred is one type or a mixture of two types of SiC and TiC.

[0014] Furthermore, the same effect can be obtained even when the ultrafine particle inorganic compound is dispersed in other solvents. Usable solvents include, for example, alcohols {monohydric alcohols (methyl alcohol, ethyl alcohol, propyl alcohol, butyl alcohol, , diacetone alcohol, benzyl alcohol, amino alcohol, etc.); dihydric alcohols (ethylene glycol, propylene glycol, diethylene glycol, hexylene glycol, etc.); trihydric alcohols (glycerin, etc.); hexitol, etc.}, ethers {monoether (ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, ethylene glycol phenyl ether, etc.); diethers (ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, etc.)}, amides {formamides (N- Methylformamide, N,N-dimethylformamide, N-ethylformamide, N,N-diethylformamide, etc.); Acetamides (N-methylacetamide, N,N-dimethylacetamide, N-ethylacetamide, N,N-diethylacetamide) etc);
Propionamides (N,N-dimethylpropionamide, etc.); Hexamethylphosphorylamide, etc.}, Oxazolidinones (N-methyl-2-oxazolidinone, 3,
5-dimethyl-2-oxasolidinone, etc.), lactones (γ-butyrolactone, α-acetyl-γ-butyrolactone, β-butyrolactone, γ-valerolactone, δ-
valerolactone, etc.), nitriles (acetonitrile, acrylonitrile, etc.), dimethyl sulfoxide, sulfolane, 1,3-dimethyl-2-imidazolidinone, N-methylpyrrolidone, aromatic solvents (toluene, xylene, etc.)
, paraffinic solvents (normal paraffin, isoparaffin, etc.), and mixtures of two or more thereof. Among these, preferred are solvents mainly containing γ-butyrolactone and ethylene glycol.

The solute may be an inorganic acid, an organic acid, or a salt thereof, such as boric acid, azelaic acid, adipic acid, glutaric acid, phthalic acid, maleic acid, benzoic acid, butyloctanedioic acid or a salt thereof. One or more of these may be mentioned as the main solute.

[0016] As the above acid salts, ammonium salts, amine salts, and quaternary ammonium salts can be used.

The amount of the ultrafine inorganic compound to be dispersed is 0.1 to 30%, preferably 1 to 30%, based on the electrolyte.
It is 20%. This has no effect below 0.1%,
Moreover, if it exceeds 30%, agglomeration tends to occur.

[0018] Furthermore, the smaller the particle size, the better;
Although it can be dispersed from about μm, in this case, it is preferable that it is 100 nm or less.

Although hexites and boric acid may be added alone, it is preferable to add both of them because of better solubility.

Next, specific embodiments of the present invention will be explained. (Table 1) shows specific electrolyte compositions of conventional examples 1, 2, 3, and 4 and examples 1, 2, 3, 4, 5, 6, 7, 8, and 9 of the present invention, and each of these examples. This figure shows the measurement results of specific conductivity and spark generation voltage at 30°C.

The ultrafine anhydrous silica, which is a metal oxide constituting the ultrafine inorganic compound used in Examples 1, 3, 4, 8, and 9 of the present invention, was obtained by chlorinating ferrosilicon to form silicon tetrachloride. Thereafter, the product obtained by purification and hydrolysis in an oxygen and hydrogen flame was mechanically stirred and dispersed.

[0022] Further, ultrafine titanium oxide, which is a metal oxide constituting the ultrafine inorganic compound used in Examples 2, 5, 6, and 7 of the present invention, is obtained by oxidizing titanium tetrachloride vapor with oxygen in the gas phase. The resulting mixture was mechanically stirred and dispersed.

[0023]

[Table 1]

[0024]

[Table 2]

As is clear from these (Tables 1) and (Table 2), Examples 1, 3, 4, 8, 9
and Examples 2 and 5 of the present invention in which titanium oxide was dispersed,
The electrolytic solutions No. 6 and 7 can increase the spark generation voltage without lowering the specific conductivity compared to the electrolytic solutions of Conventional Examples 1, 2, 3, and 4.

(Table 3) shows the conventional examples 1 and 3 and the embodiments 1 and 4 of the present invention among the electrolytes shown in (Table 1) and (Table 2).
This figure shows the results of a high-temperature ripple test conducted at a temperature of 105° C. for 1000 hours on 20 electrolytic capacitors each using electrolytes of No. 5 and No. 5. Among these electrolytic capacitors, the electrolytic capacitors using the electrolytes of Conventional Example 1 and Example 1 of the present invention have a rating of 330V1500μF, and the aging of the products was performed by applying a voltage of 380V for 4 hours, and a ripple test was performed. The condition is 4.23A. Further, the rating of the electrolytic capacitors using the electrolytes of Conventional Example 3 and Examples 4 and 5 of the present invention is 400V270μF, and the aging of the product was performed by applying a voltage of 450V for 4 hours.
And the ripple test condition is 1.1A.

[0027]

[Table 3]

As is clear from this (Table 3), the electrolytic capacitors using the electrolytes of Examples 1, 4, and 5 of the present invention have higher performance than the electrolytic capacitors using the electrolytes of Conventional Examples 1 and 3. Therefore, the capacitance change is small after conducting a high temperature ripple test for 1000 hours at a temperature of 105°C.
A highly reliable electrolytic capacitor can be obtained.

(Table 4) shows the conventional examples 1 and 3 shown in (Table 3).
For electrolytic capacitors using the electrolytic solution of Example 1, 4, and 5 of the present invention, the short circuit occurrence rate of the product was determined when a high-temperature ripple superimposition test was conducted at a temperature of 105°C for 1000 hours. This is what is shown.

[0030]

[Table 4]

As is clear from this (Table 4), the electrolytic solutions of Examples 1 to 9 of the present invention are all characterized by a higher spark generation voltage than the electrolytic solutions of conventional examples 1 to 4. While the electrolytic capacitors using the electrolytes of Conventional Examples 1 and 3 caused a short circuit during the high-temperature ripple superposition test, the electrolytic capacitors using the electrolytes of Examples 1, 4, and 5 of the present invention Therefore, it is possible to obtain an electrolytic solution for driving an electrolytic capacitor that has excellent short-circuit properties without causing short-circuits during the high-temperature ripple superposition test.

FIG. 1 shows a comparison of the formation and discharge characteristics during constant current formation between the electrolytic solution for driving an electrolytic capacitor in Example 4 of the present invention and the electrolytic solution for driving an electrolytic capacitor in Conventional Example 2. As is clear from Example 1, the characteristics of Example 4 of the present invention are significantly superior to those of Conventional Example 2.

[0033]

Effects of the Invention As described above, the electrolytic solution for driving an electrolytic capacitor of the present invention has an ultrafine particle inorganic compound dispersed in a solvent mainly composed of ethylene glycol, and one or both of hexites and boric acid. When added and dissolved, the ultrafine inorganic compound is charged in the electrolytic solution and becomes colloidal, so it can be uniformly dispersed in the electrolytic solution. In addition, when an oxide film is formed, the ultrafine inorganic compound adsorbs and aggregates to fill in the defective parts of the oxide film, making it possible to produce an oxide film with fewer defects.This makes it possible to increase the spark generation voltage, and In addition to this, by adding one or both of hexites and boric acid, the surface of the anodic oxide film is covered with the hexites, thereby making it possible to further increase the spark generation voltage.

Therefore, compared to conventional electrolytes, the spark generation voltage can be increased without lowering the specific conductivity, and high conductivity electrolytes can be used in a high voltage range. This makes it possible to provide low-loss electrolytic capacitors.

[Brief explanation of the drawing]

FIG. 1 is a characteristic diagram showing a comparison of the formation and discharge characteristics during constant current formation of the electrolytic solution for driving an electrolytic capacitor in Example 4 of the present invention and the electrolytic solution for driving an electrolytic capacitor in Conventional Example 2.

Claims (9)

[Claims] Claim 1: A solvent mainly composed of ethylene glycol,
An electrolytic solution for driving an electrolytic capacitor in which an ultrafine inorganic compound is dispersed and one or both of hexites and boric acid is added and dissolved. 2. The electrolytic solution for driving an electrolytic capacitor according to claim 1, wherein the ultrafine inorganic compound is a metal oxide. 3. The electrolytic solution for driving an electrolytic capacitor according to claim 1, wherein the ultrafine inorganic compound is a metal nitride. 4. The electrolytic solution for driving an electrolytic capacitor according to claim 1, wherein the ultrafine inorganic compound is a metal carbide. 5. The electrolytic solution for driving an electrolytic capacitor according to claim 2, wherein the metal oxide is SiO2 and TiO2 alone or in a mixture. [Claim 6] The metal nitride is TiN, Si3N2, AIN.
4. The electrolytic solution for driving an electrolytic capacitor according to claim 3, which is one type or a mixture of two or more types selected from , TaN, NbN, and Zr3N4. 7. The electrolytic solution for driving an electrolytic capacitor according to claim 4, wherein the metal carbide is SiC and TiC alone or in a mixture. Claim 8: The size of the ultrafine inorganic compound is 100 nm.
The electrolytic solution for driving an electrolytic capacitor according to claim 4, which is as follows. [Claim 9] Hexites include mannitol, sorbitol,
The electrolytic solution for driving an electrolytic capacitor according to claim 1, which is dulcit, xylitol, or pentaerythritol.