JPH01319922A - Electrolytic-capacitor driving electrolyte - Google Patents

Abstract

PURPOSE:To obtain an electrolytic-capacitor driving electrolyte having high conductivity by dissolving the quarternary ammonium salt of maleic acid into mixed solvent of gamma-butyrolactone and acetonitrile. CONSTITUTION:The quarternary ammonium salt of maleic acid is dissolved into mixed solvent of gamma-butyrolactone and acetonitrile. As the quaternary ammonium salt of the maleic acid, a material wherein the number of carbons in the alkyl group of the quaternary ammonium expressed by a general formula R4N<+> is 1-10, especially 1-4, can be adequately used. For example, tetramethylammonium maleate, tetrabutylammonium maleate and the like are used. Thus, an electrolytic-capacitor driving electrolyte having high conductivity is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electrolytic solution for driving an electrolytic capacitor.

[Conventional technology]

With the expansion of the electronic equipment industry, the market for power supplies, which can be said to be the core of equipment, is rapidly expanding, and switching power supplies, which are small, lightweight, highly reliable, and highly efficient, have become mainstream. Also, the switching frequency is 100 to 50
0 kHz, and with this, aluminum electrolytic capacitors used in switching power supplies have become important issues, such as miniaturization and weight reduction, as well as improvement of high frequency characteristics, longer life, and higher reliability.

An aluminum electrolytic capacitor has a structure in which an anode foil and a cathode foil made of aluminum are wound around each other with a separator in between, the capacitor element is impregnated with a driving electrolyte, and the capacitor element is assembled into an aluminum case together with a sealing body and sealed. In order to address the above-mentioned problems and reduce the impedance of electrolytic capacitors, especially in the high frequency range, driving electrolytes with higher conductivity have been developed (for example, see Japanese Patent Application Laid-Open No. 145713/1983). ).

[Problems to be Solved by the Invention] JP-A-62-145713 discloses an electrolytic solution for driving an aluminum electrolytic capacitor in which a quaternary ammonium salt of maleic acid is dissolved in γ-butyrolactone. In this electrolyte, when tetramethylammonium maleate is 25 wt% and γ-butyrolactone is 75 wt%, the conductivity at 25°C is 13.7 m
S/cm. Furthermore, when an aluminum electrolytic capacitor with a rating of 25 V and 1000 μF was manufactured using this electrolyte, the impedance at 100 kHz was 19.1 mΩ.

Although an electrolytic solution in which quaternary ammonium maleate is dissolved in γ-butyrolactone has a somewhat higher conductivity than conventional electrolytic solutions, it does not fully satisfy the demand for low impedance in electrolytic capacitors. Therefore, it is desired to develop an electrolytic solution with even higher conductivity.

[Means for Solving the Problems] The present invention provides an electrolytic solution for driving an electrolytic capacitor that has even higher conductivity.

The present invention achieves the above object by dissolving a quaternary ammonium salt of maleic acid in a mixed solvent of γ-butyrolactone and acetonitrile.

First, in Figure 1, tetraethylammonium maleate 2
This shows the change in the conductivity of the electrolytic solution with respect to the mixed solvent ratio of γ-butyrolactone and acetonitrile at 5 wt%. When the amount of acetonitrile increases to 20 wt% and 40 wt%, the conductivity increases. However, 60wt%, 70wt%
%, the increase in conductivity becomes small, and at 100 wt%, the solute no longer dissolves, and the conductivity decreases rapidly.

Next, the boiling point of the mixed solvent is shown in Figure 2.6 In the electrolytic solution according to the present invention, since the boiling point of acetonitrile is low, γ-butyrolactone is used as a mixed solvent in an aluminum electrolytic capacitor for 105°C and acetonitrile is preferably 6=4 or more.

The quaternary ammonium salts of maleic acid used in the present invention include quaternary ammonium salts represented by the general formula R4N'' in which the alkyl group (R) has 1 to 10 carbon atoms;
Particularly preferred are 1 to 4 of them, and examples thereof include tetramethylammonium maleate, tetraethylammonium maleate, tetrapropylammonium maleate, and tetrabutylammonium maleate.

[Examples] The present invention will be described below based on Examples and Comparative Examples.

Examples 1 to 3 were prepared by dissolving a quaternary ammonium salt of maleic acid in a mixed solvent. Using these electrolytes, an aluminum electrolytic capacitor with a rating of 25 V and 1000 μF was manufactured. In addition, a comparative example was prepared by dissolving a quaternary ammonium salt of maleic acid in a sole solvent of γ-butyrolactone.

The conductivity of the electrolyte at 25° C. and the impedance of the electrolytic capacitor at 100 kHz were measured, and the results are shown in Table 1.

Table 1 [Effects of the Invention] According to the present invention described above, it is possible to provide a high conductivity electrolyte solution for driving an electrolytic capacitor and a low impedance electrolytic capacitor.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing electrical conductivity versus mixed solvent ratio according to the present invention, and FIG. 2 is a diagram showing boiling point versus mixed solvent ratio. Figure 1

Claims (2)

[Claims] (1) An electrolytic solution for driving an electrolytic capacitor, which is obtained by dissolving a quaternary ammonium salt of maleic acid in a mixed solvent of γ-butyrolactone and acetonitrile. (2) The electrolytic solution for driving an electrolytic capacitor according to claim 1, wherein the quaternary ammonium salt of maleic acid is tetramethylammonium maleate or tetraethylammonium maleate.