JPH0748458B2 - Electrolytic solution for driving electrolytic capacitors - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an electrolytic solution for driving an electrolytic capacitor, and more particularly to an electrolytic solution for driving an electrolytic capacitor, which has improved spark generation voltage and improved stability at high temperatures. Regarding

(Prior Art) In general, as an electrolytic solution for driving an electrolytic capacitor (hereinafter abbreviated as an electrolytic solution), ethylene glycol sugar is used as a main solvent and ammonium salt of an organic acid such as ammonium adipate is used as a main solute. Has been done.

Recently, an electrolytic solution in which γ-butyrolactone is used as a main solvent and amine salts of organic acids such as phthalic acid and maleic acid are dissolved has been developed for the purpose of improving low temperature characteristics and life characteristics at high temperatures. However, in this type of electrolytic solution, the spark generation voltage is generally as low as 80 to 90 V, so there is a problem that it cannot be used in a 100 WV electrolytic capacitor.

Recently, 1 to 5 wt% of heteropoly acid was added to the above electrolyte.
An electrolytic solution in which the spark generation voltage is increased by adding it is known (JP-A-62-114207).

(Problems to be Solved by the Invention) However, the above-described conventional electrolytic solution has the following problems.

That is, since heteropolyacids such as phosphotungstic acid and silicotungstic acid are expensive, the addition of 1 wt% or more increases the price of the electrolytic solution itself. Further, according to the experiments of the present inventors, it was found that even in the electrolyte solution to which the heteropolyacid was added, a sufficient spark generation voltage could not be obtained for use in a 100 WV capacitor, and the stability at high temperature was lacking. .

The present invention has been made in view of the above points, without increasing the cost of the electrolytic solution, sufficiently high spark generation voltage,
Moreover, it aims at providing the electrolyte solution which has high temperature stability.

(Means for Solving the Problem) The present invention provides an electrolytic solution containing γ-butyrolactone as a main solvent and an amine salt of an organic acid as a main solute, and (A) phosphoric acid or phosphorous acid or their 0.1-1 wt% of at least one salt, (B) 1-5 wt% of boric acid or its salt, and (C) 0.1-2 wt% of polysaccharides such as mannitol and sorbit.
%, (D) Phosphotungstic acid, silicotungstic acid, or a salt thereof is added in an amount of 0.1 to 1 wt%.

The solvent can be applied to an electrolytic solution containing γ-butyrolactone as a main solvent, but particularly a mixed solvent having a ratio of γ-butyrolactone and ethylene glycol of 70:30 to 95: 5 exerts a remarkable effect.

As the organic acid, one kind or a combination of two or more kinds of carboxylic acids such as benzoic acid, phthalic acid, salicylic acid and maleic acid is particularly preferable.

(Function) Generally, an electrolytic solution containing γ-butyrolactone as a main solvent and an amine salt of an organic acid as a main solute has a spark generation voltage of 100 V or less. If 1 wt% or more of heteropolyacid is added to increase the spark generation voltage, the spark generation voltage rises, but the stability is poor and puncture failure occurs in the life test at high temperature. Further, since the heteropolyacid is expensive, adding 1 wt% or more increases the cost of the electrolytic solution.

In the present invention, pay particular attention to phosphotungstic acid and silicotungstic acid among heteropolyacids, and by combining these acids or salts thereof with phosphoric acid or phosphorous acid or salts thereof, the heteropolyacid is 1 wt% or more. It was possible to achieve the same spark generation voltage as when added alone. Phosphoric acid and phosphorous acid are very cheap in price,
Since the addition amount of phosphotungstic acid or silicotungstic acid can be 1 wt% or less, the cost is low. still,
When phosphoric acid or phosphorous acid is added alone, the spark generation voltage is not expensive and therefore phosphoric acid or phosphorous acid cooperates with phosphotungstic acid or silicotungstic acid to generate sparks. It is thought to increase the voltage.

However, the stability at high temperature could not be obtained only by adding phosphoric acid or phosphorous acid, but by adding boric acid or its salt, and polysaccharides, the oxide film was destroyed during the spark generation. Was suppressed, and the stability of the electrolyte at high temperature was significantly improved while maintaining a high spark generation voltage.

The heteropolyacids that can be used in the present invention are only phosphotungstic acid and silicotungstic acid, and other phosphomolybdic acid and silicomolybdic acid, for example, cause punctures in the high temperature load test, and also discolor by reacting with the lead wire. It cannot be used because it does.

(Example) Table 1 shows the composition, the specific resistance, and the spark generation voltage for the conventional example, Comparative examples 1 to 4, and Examples 1 to 3. As is clear from Table 1, the spark generation voltage increased to around 150 V except for the conventional example.

FIG. 1 shows a comparison of 100 for Comparative Examples 1 and 2 and Example 1.
The results of measuring the spark generation voltage at ℃ are shown. Comparative Example 1,
In No. 2, it can be seen that after the voltage once rises, the voltage changes with a very large amplitude, and the low part reaches about 60V. On the other hand, in Example 1, the voltage is extremely stable even after reaching the spark generation voltage.

FIG. 2 shows the results of measuring the amplitude of the voltage change after reaching the spark generation voltage during the measurement of the spark generation voltage by changing the amounts of boric acid and mannite added in the same composition of the electrolytic solution as in Example 1. . It can be seen that it becomes very stable when the amount of boric acid is 1 wt% or more. It is sufficient if the amount of polysaccharide such as mannitol added to boric acid is about 1/5, and if it is less than that, the voltage stabilizing effect is reduced, and if it is more than that, the effect is not increased so much.

FIG. 3 shows the spark generation voltage when changing the addition amount of phosphotungstic acid in Comparative Examples 1 and 2 and Example 1. Compared to Comparative Example 1 in which the additive was phosphotungstic acid alone, in Comparative Example 2 and Example 1 in which phosphoric acid was added, the spark generation voltage can be improved with an extremely small amount of phosphotungstic acid.

That is, as is clear from the figure, the spark generation voltage starts to rise from a small addition amount of phosphotungstic acid of about 0.1 wt% and becomes saturated at about 1 wt%. Compared to Comparative Example 1, the increase curve of the spark generation voltage can be shifted to the side where the amount of phosphotungstic acid added is smaller. Therefore, if the amount of phosphotungstic acid added is small, a spark generation voltage equal to or higher than the conventional one can be achieved, and the cost can be reduced.

Table 2 shows the electrolytic capacitors (100V 470μF) produced by using the electrolytic solution having the composition shown in Table 1 at 105 ° C 2000
The result of having carried out the time load test is shown.

As is clear from Table 2, in Comparative Examples 1, 2 and 3, the spark generation voltage could be increased, but the stability at high temperature was inferior. Further, as can be seen from Comparative Example 4, even if the heteropolyacid is phosphomolybdic acid, the spark generation voltage can be increased, but the stability at high temperature is lacking. On the other hand, the electrolytic solutions of Examples 1, 2, and 3 had extremely stable characteristics at high temperatures.

(Effect of the Invention) According to the present invention, by adding phosphoric acid or phosphorous acid or a salt thereof together with phosphotungstic acid or silicotungstic acid or a salt thereof, phosphotungstic acid or silicotungstic acid or a salt thereof is added. The spark generation voltage starts to rise from a small addition amount of about 0.1 wt% and can be saturated with a sufficiently high spark generation voltage with an addition amount of about 1 wt%. That is, by adding phosphoric acid or phosphorous acid or a salt thereof, the increase curve of the spark generation voltage shifts the addition amount of phosphotungstic acid or silicotungstic acid or a salt thereof to a smaller side than in the conventional case. It is possible to reduce the amount of expensive phosphotungstic acid etc. added,
Moreover, it is possible to achieve a spark generation voltage equal to or higher than that of the conventional one, and at the same time reduce the cost, and at the same time, add an electrolytic solution for driving an electrolytic capacitor whose stability at high temperature is remarkably improved by adding boric acid and polysaccharides such as mannite. Can be provided.

[Brief description of drawings]

FIG. 1 is a diagram showing the stability of the spark generation voltage at 100 ° C., and FIG. 2 is a diagram showing the relationship between the addition amounts of boric acid and mannite and the voltage stability after reaching the spark generation voltage. The figure shows the relationship between the amount of phosphotungstic acid added and the spark generation voltage.

Claims (1)

[Claims] 1. An electrolytic solution containing γ-butyrolactone as a main solvent and an amine salt of an organic acid as a main solute. 0.1-1 wt%, (B) 1-5 wt% boric acid or a salt thereof, (C) 0.1-2 wt% polysaccharides such as mannitol and sorbit
%, (D) Phosphotungstic acid, silicotungstic acid, or a salt thereof is added in an amount of 0.1 to 1 wt%.