JPH05217806A - Electrolytic solution of electrolytic capacitor - Google Patents

Abstract

PURPOSE:To improve the mixture composition of an electrolytic solution, to lower the resistivity of an electrolytic capacitor and to enhance the reliability of the electrolytic capacitor. CONSTITUTION:The electrolytic solution is constituted in the following manner: gamma-butyrolactone is used as a main solvent; the tetraethylammonium salt or the tetraethylsulfonium salt of phthalic acid is dissolved; in addition, polysaccharides such as mannitol, sorbitol or the like is dissolved; and 5 to 30g of the tetraethylammonium salt or the tetraethylsulfonium salt of phthalic acid exists to 100g of a mixed solvent.

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 electrolytic capacitors.

[0002]

2. Description of the Related Art Conventionally, as an electrolytic solution for a low-voltage electrolytic capacitor, an electrolytic solution in which ethylene glycol is used as a main solvent and adipic acid salt is dissolved has been widely used. In order to cope with the trend toward higher reliability and higher reliability, an electrolytic solution in which tetramethylammonium salt of phthalic acid is dissolved is generally used with γ-butyrolactone as a main solvent.

[0003]

DISCLOSURE OF INVENTION Problems to be Solved by the Invention As an electrolytic solution for an electrolytic capacitor, γ-butyrolactone in which tetramethylammonium salt of phthalic acid is dissolved is limited to 90 Ω · cm from the solubility limit. Although it was studied to further reduce the specific resistance by adding a small amount of water, the reliability was high in the high temperature atmosphere by itself, but the reliability was extremely high due to the increase of the water content in the electrolyte by several percent. Since it causes a decrease in sex, fundamental measures were needed.

[0004]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems and prevents deterioration of reliability even when water is mixed in an electrolytic solution. That is, the electrolytic solution is characterized by dissolving tetraethylammonium salt or tetraethylphosphonium salt of phthalic acid with γ-butyrolactone as a main solvent. In addition, mannite,
An electrolytic solution for an electrolytic capacitor, which is characterized in that a polysaccharide such as sorbit is dissolved.

[0005]

[Function] When water is mixed in an electrolyte solution using a tetramethylammonium salt, the cathode foil undergoes a hydration reaction, resulting in an extremely low reliability. However, in the case of a tetraethylammonium salt, Tetraethylammonium ions are strongly adsorbed on the surface of the cathode foil to form a protective film layer, so that the hydration reaction of the cathode foil is unlikely to occur and the reliability is not deteriorated. Furthermore, since polysaccharides such as mannitol and sorbit are adsorbed on the surface of the electrode foil to form a thin water-resistant film, the hydration reaction of the cathode foil is unlikely to occur and the reliability is not deteriorated.

[0006]

EXAMPLES Examples of the present invention will be described below. Table 1 shows comparative examples of the composition, the specific resistance and the spark generation voltage of the electrolytic solution of the present invention and the conventional electrolytic solution. In addition, Table 1
Medium electrolyte solution sample symbols A and B are conventional examples, C, D, E, F,
G, H, I, J and K are examples of the present invention, and GBL is γ
-Indicates butyrolactone. Table 2 shows the results of a high temperature load test performed for 2000 hours in an atmosphere of 105 ° C. using an electrolytic capacitor having a rating of 25 V and 3300 μF, which was prototyped using the electrolytic solution shown in Table 1.

[0007]

[Table 1]

[0008]

[Table 2]

As is clear from Table 2, the electrolytic capacitors using the electrolytic solutions of sample symbols C, D, E, F, G, H, I, J and K according to the present invention are exposed to a high temperature atmosphere for a long time. In the test in the above, all the characteristics are satisfactory. If the tetraethylammonium salt or tetraethylphosphonium salt of phthalic acid is less than 5 g with respect to 100 g of the mixed solvent, the effect of the present invention cannot be obtained, and if it exceeds 30 g, solute precipitation is observed. Further, with respect to polysaccharides such as mannitol and sorbit, the effect of the invention cannot be obtained when the amount is less than 0.1 g per 100 g of the mixed solvent, and solute precipitation is observed when the amount exceeds 3 g.

[0010]

As described above, the electrolytic solution characterized by dissolving the tetraethylammonium salt or the tetraethylphosphonium salt of phthalic acid with γ-butyrolactone as the main solvent is a polysaccharide such as mannitol or sorbit. The electrolytic solution characterized by having a low specific resistance has high reliability even in a high temperature atmosphere and has great industrial and practical value.

Claims (4)

[Claims] 1. An electrolytic solution for an electrolytic capacitor, characterized in that tetraethylammonium salt or tetraethylphosphonium salt of phthalic acid is dissolved with γ-butyrolactone as a main solvent. 2. The electrolytic solution for an electrolytic capacitor according to claim 1, wherein the tetraethylammonium salt or tetraethylphosphonium salt of phthalic acid is present in an amount of 5 to 30 g per 100 g of the mixed solvent. 3. Mannite, containing γ-butyrolactone as a main solvent, into a solution in which a tetraethylammonium salt or a tetraethylphosphonium salt of phthalic acid is dissolved,
An electrolytic solution for an electrolytic capacitor according to claim 1, wherein a polysaccharide such as sorbit is dissolved. 4. The electrolytic solution of the electrolytic capacitor according to claim 1, wherein the polysaccharide such as mannitol and sorbit is present in an amount of 0.1 to 3 g per 100 g of the mixed solvent.