JP3487911B2 - Electrolyte for driving electrolytic capacitors - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improved electrolyte for driving an electrolytic capacitor, and more particularly to an electrolyte for driving an electrolytic capacitor (hereinafter, simply referred to as "electrolyte") which has long-term stability of life characteristics at high temperature. It is a thing.

[0002]

2. Description of the Related Art An electrolytic solution is present between an anode and a cathode in an electrolytic capacitor and serves as a conductive medium, and the characteristics of the electrolytic solution are a major factor that influences the characteristics of the electrolytic capacitor. Among them, the electrolytic solution of the electrolytic capacitor used in a wide temperature range must have the following excellent properties. (1) High boiling point and low vapor pressure at high temperature. (2) Viscosity does not increase even at low temperature, and conductivity is high. (3) The freezing point is low. (4) The spark voltage is as high as possible. (5) Good ability to form an anodized film. (6) Corrosion does not particularly occur without damaging the electrolytic capacitor portion including the dielectric. (7) The characteristics are stable even when left at high temperature for a long time.

As a low-voltage electrolytic solution for a conventional electrolytic capacitor, a solvent prepared by adding ammonium benzoate and ammonium adipate to a solvent prepared by mixing ethylene glycol and water has been used.

[0004]

This electrolytic solution satisfies the above items (1) to (6), but (7)
There was a problem with respect to the stability of the characteristics under high temperature. That is, since the boiling point of water is as low as 100 ° C., the solvent is easily volatilized at the time of use at high temperature, and the organic acid ammonium used as a solute is decomposed at high temperature and dissipated as ammonia gas, resulting in a ratio of the electrolyte solution. Increased resistance,
The tangent (tan δ) of the loss angle of the electrolytic capacitor increases.

The present invention solves the above problems,
Capacitance change and ta of electrolytic capacitor under high temperature
An object of the present invention is to provide an electrolytic solution for driving an electrolytic capacitor, which can improve the change in nδ.

[0006]

In order to achieve the above object, the electrolytic solution of the present invention comprises a solvent in which ethylene glycol or ethylene glycol and γ-butyrolactone are mixed, potassium benzoate and potassium formate, and other additives. It is a product added and dissolved.

Instead of conventional water as a solvent, the boiling point is 20
By mixing γ-butyrolactone as high as 3 ° C with ethylene glycol, the volatilization of the electrolytic solution is suppressed and the temperature is kept at 105
It is possible to obtain heat resistance at a high temperature of ℃ to 125 ℃.

Among the organic acid salts, the potassium salt of benzoic acid, which is stable at high temperature, is used as the solute, whereby the decomposition of solute and the generation of gas can be prevented.

Further, an electrolytic solution containing only one kind of potassium benzoate, which is an organic acid potassium, has not only a high specific resistance value but also a high pH and a low chemical conversion property, and therefore the dissociation degree is considerably high among the potassium salts. Add potassium formate to reduce the specific resistance of the electrolyte and add one of formic acid, adipic acid, succinic acid and benzoic acid to add p.
Lowers the H value and improves chemical conversion.

Further, a small amount of phosphorous acid is added to stabilize the anodized film.

That is, according to the present invention, a solvent mainly comprising ethylene glycol or a solvent obtained by mixing 0.1 to 30.0% by weight of γ-butyrolactone with ethylene glycol is added to 1.0 to 10.0% by weight of potassium benzoate. And 1.0 to 10.0% by weight of potassium formate, and 0.3 to 1 of any one of formic acid, adipic acid, succinic acid and benzoic acid.
This is an electrolytic solution for driving an electrolytic capacitor in which 3.0% by weight and 0.1 to 0.3% by weight of phosphorous acid are dissolved.

[0012]

Since the solvent used in the present invention has a high boiling point, volatilization of the electrolytic solution at high temperatures can be suppressed. Also, potassium benzoate used as a solute stabilizes the long-term life characteristics of electrolytic capacitors at high temperatures.
It is considered that the action is due to the stability of the benzene nucleus forming potassium benzoate at high temperature. In addition, ammonium salts of organic acids decompose at high temperatures,
While it dissipates as ammonia gas, potassium salts of organic acids do not cause this, and stable life characteristics can be obtained at high temperatures. The amount of potassium formate is 1.0% by weight
If it is less than 1, the specific resistance value of the electrolyte cannot be lowered sufficiently, and 1
If it exceeds 0.0% by weight, the spark voltage of the electrolytic solution decreases. When the amount of potassium benzoate is less than 1.0% by weight, the stability at high temperature is lowered, and when it exceeds 10.0% by weight, the conductivity at low temperature is deteriorated. Further, if the addition amount of any one of the four kinds of acids of formic acid, adipic acid, succinic acid and benzoic acid is less than 0.3% by weight, the effect of promoting the chemical conversion is small and the chemical conversion ability is improved. If it exceeds 3.0% by weight, the conductivity at low temperature deteriorates.
Further, if the addition amount of phosphorous acid is less than 0.1% by weight, the stabilizing effect of the anodized film is small, and if it exceeds 0.3% by weight, the high temperature life test characteristics deteriorate. Regarding the solvent, the low-temperature characteristics can be further improved by adding γ-butyrolactone in an amount of 0.1% by weight or more, but its content is 30.
When it exceeds 0% by weight, the high temperature life test characteristics are deteriorated.
Moreover, when γ-butyrolactone is not added, an electrolytic capacitor having more stable high temperature life characteristics can be obtained.

[0013]

EXAMPLES Examples of the present invention will be described below. Table 1 shows the compositions of the electrolytic solution of the present invention and the conventional electrolytic solution, the specific resistance,
Comparative examples of pH and spark generation voltage will be shown. 1-2, electrolyte solutions of the present invention, sample numbers 14 and 17
And the conventional electrolyte sample No. 1 were used, rated 10V, 47
The results obtained by producing an electrolytic capacitor of 0 μF and a rating of 50 V and 33 μF and performing a high temperature load life test (125 ° C. rated voltage application) are shown. Fig. 1 is a high temperature load life test characteristic diagram of an electrolytic capacitor rated at 10V and 470µF. Fig. 2 is a high temperature load life test characteristic diagram of an electrolytic capacitor rated at 50V and 33µF. In each figure, (a) shows leakage current and (b) shows.
Represents the tangent (tan δ) of the loss angle, and (c) represents the change with time of the capacitance change rate. Further, in the figure, a and b are electrolytic capacitors using the electrolytic solution sample numbers 14 and 17 of the present invention, and c is an electrolytic capacitor using the conventional electrolytic solution sample number 1. As is clear from FIGS. 1 and 2, the electrolytic capacitor (a, b) using the electrolytic solution of the present invention has a capacitance change and tan δ at high temperature as compared with the electrolytic capacitor (c) using the conventional electrolytic solution. The changes have been greatly improved.

[0014]

[Table 1]

[0015]

As described above, the electrolytic solution of the present invention uses potassium benzoate which is stable at high temperature, and the potassium formate used in combination does not decompose at high temperature. Since the boiling point of the organic solvent used is high, the volatilization of the electrolytic solution is less likely to occur, and the change in capacitance and change in tan δ of the electrolytic capacitor at high temperature can be improved.

[Brief description of drawings]

FIG. 1 High temperature load life test characteristic diagram of electrolytic capacitor rated at 10V and 470μF

FIG. 2 High temperature load life test characteristic diagram of electrolytic capacitor rated 50V, 33μF

Claims (2)

(57) [Claims] 1. A solvent comprising ethylene glycol as a main component, containing 1.0 to 10.0% by weight of potassium benzoate and 1.0 to 10.0% by weight of potassium formate, and containing formic acid, adipic acid, succinic acid and benzoic acid. Any one of 0.3 ~
An electrolytic solution for driving an electrolytic capacitor, wherein 3.0% by weight and 0.1 to 0.3% by weight of phosphorous acid are dissolved. 2. γ-butyrolactone as a solvent is 0.1
The electrolytic solution for driving an electrolytic capacitor according to claim 1, wherein the electrolytic solution is added in an amount of about 30.0% by weight.