JPS63232410A - Electrolytic capacitor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electrolytic capacitor, and more particularly to an electrolytic capacitor using a novel driving electrolyte.

[Conventional technique S4] Electrolytic capacitors are made by winding an anode foil and a cathode foil made of a valve metal such as aluminum together with a separator to form a capacitor element.Generally, the capacitor element is impregnated with a driving electrolyte, and then the capacitor element is impregnated with a metal case made of aluminum or the like. The capacitor element is housed in a synthetic resin case and has a sealed structure.

Conventionally, the driving electrolyte for such electrolytic capacitors uses a polar organic solvent such as ethylene glycol as the main solvent, and dissolves therein a salt that does not corrode the metal electrodes, such as ammonium salt of saturated peroxide acid. An electrolytic solution is generally used (Japanese Patent Publication No. 13019/1983). It is also known to use a mixed solvent of γ-butyrolactone and ethylene glycol as a solvent for the electrolyte (Japanese Unexamined Patent Publication No. 7564/1983).

In the electrolyte shown, 1% to 30% of the loss angle (tan δ), which is an index of electrical resistance, is reduced.
However, in this case, the characteristics of the capacitor deteriorate at high temperatures due to corrosion of the cathode foil and transpiration of dissociated ammonia (NHa), especially changes in the tangent of the loss angle (tanδ). The problem was that it was large. In addition, as an electrolytic solution that has high conductivity (low electrical resistance) and is stable at high temperatures, the use of an electrolytic solution in which a quaternary ammonium salt of a saturated chain dicarboxylic acid is dissolved in a polar organic solvent has been disclosed in JP-A No. 59-78522. Disclosed in the official gazette. However, according to the example in the same publication, the conductivity of this electrolyte is at most 9.4 mS/cm, which is lower than the currently required water t% (12-25 mS/cm).
The problem was that it was insufficient from the point of view. Furthermore, when Y-butyrolactone and ethylene glycol are used as a mixed solvent as seen in the above-mentioned JP-A-54-7564, the viscosity of ethylene glycol increases at low temperatures, which improves the low-temperature characteristics of the capacitor. The problem was that it was small.

The present invention aims to solve these problems and provide an electrolytic capacitor that uses a driving electrolyte that has low electrical resistance (high conductivity), excellent low-temperature characteristics, and excellent high-temperature stability. purpose.

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention is characterized by using a driving electrolyte prepared by dissolving a quaternary ammonium salt of glutaric acid in a polar organic solvent. The present invention provides electrolytic capacitors.

The quaternary ammonium salts of glutaric 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;
In particular, 1 to 4 of them can be suitably used. For example, in the case of tetramethylammonium glutarate, tetraethylammonium glutarate, tetrapropylammonium glutarate, tetrabutylammonium glutarate, etc., the conductivity of the electrolytic solution This is because the strength is low and the ta opening δ of the product becomes large, which is not preferable.

The content (concentration) of the quaternary ammonium salt of glutaric acid used in the present invention in the electrolyte composition can be selected as appropriate, but considering that the resistivity is the lowest in a saturated solution state, it is 1 to 50%. The weight percentage is suitable, and in order to obtain good high temperature stability, 5 to 40 fii% is particularly suitable.

In order to solve the above problems, the polar organic solvent used in the present invention includes at least γ-butyrolactone and 3-alkyl-1,3-oxazolidin-2-one (hereinafter referred to as A,
0. ).

Here, the alkyl group includes methyl, ethyl, propyl, etc. Among them, for improving low temperature characteristics,
Methyl and ethyl are preferred. Furthermore, any polar organic solvent commonly used in electrolytic capacitors can be used as the solvent to be mixed, including amides, lactones, etc.
Gutucols, sulfur compounds or carbon salts can be preferably used. Specific examples of preferred miscible solvents include N,N-dimethylformamide, N-methylformamide, β-butyrolactone, γ-valerolactone, N
-Methylpyrrolidone, ethylene glycol, ethylene glycol monoalkyl ether, ethylene glycol dialkyl ether, dimethyl sulfoxide, propylene carbonate, ethylene cyanohydrin, etc., and these: aa may be used alone or in combination as appropriate. Il! used through.

In the present invention, in order to obtain a driving electrolyte containing a quaternary ammonium salt of glutaric acid, the quaternary ammonium salt may be added to a polar organic solvent. This quaternary ammonium salt may be produced by reacting substances that can be produced.

In the present invention, it is necessary to include water in the electrolyte because increasing the water content will increase the bulging of the case of the electrolytic capacitor due to the generation of internal gas and the corrosion of the electrode foil. For the purpose of long-term use, it is preferable that the water content be as low as possible. Therefore, depending on the purpose of use of the electrolytic capacitor, the content of water in the electrolyte composition is preferably in the range of 0.1 to 20% by weight, and 0.5 to 1% by weight.
More preferred is a weight ratio of 5% by weight.

The electrolytic capacitor of the present invention includes various types of capacitors. In a typical embodiment, an aluminum foil anode and an aluminum foil cathode separated by a suitable separator such as paper are used, and these are wound into a cylindrical shape to form a capacitor element.

This element is impregnated with a driving electrolyte. The amount of electrolyte impregnated is preferably 50 to 300 per separator.
% by weight. The element impregnated with the electrolyte is housed in a case made of corrosion-resistant metal, synthetic MIW1, or the like, and has a sealed structure.

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

After dissolving glutaric acid by mixing a 10% aqueous solution of tetraalkylammonium hydroxide (alkyl group has 1 to 3 carbon atoms) and glutaric acid to an equimolar number, water is removed using an evaporator and glutaric acid is dissolved. A quaternary ammonium salt of an acid was generated, and a predetermined amount of these salts were dissolved in a polar organic solvent as a solute to obtain the electrolyte solutions of Examples 1 to 8. The pH of the electrolytic solution was adjusted to 5-7.

Using these electrolytes, we manufactured an electrolytic capacitor (rated 10V, 1000μF) with aluminum electrodes,
A high temperature load test (rated voltage applied, 125° C., 1000 hours) was conducted to measure changes in the loss angle tangent (tan δ), and the results are shown in Table 1. In addition, Comparative Example 1 shows the case where a solute other than the quaternary ammonium salt of glutaric acid was used.
~4, an electrolytic capacitor was manufactured in the same manner as in the example, and a high temperature load test was conducted under the same conditions as in the example.
represents those in which the alkyl group is methyl and ethyl, respectively.

Table 1 Example of electrolyte composition and high temperature load test Next, Table 2 shows the low temperature characteristics of the electrolytic capacitor. The electrolytic capacitors were the same as those described above, and the number of samples was 10 each. The measurement frequency is 120Hz. ΔC/C20℃ in the table is the rate of change in capacity at 20℃, Z/Z
20°C indicates the impedance ratio with respect to 20°C.

As can be seen from Table 1, the average value for n=10, the change in the tangent of the loss angle is large in the comparative example in the high temperature load test, whereas this change can be made small in the example.

In addition, as can be seen from Table 2, the comparative example has excellent low-temperature characteristics with ΔC/C20η and Z/Z of 20°C. It is possible to provide an electrolytic capacitor with excellent high-temperature stability and a small change in the tangent of the loss angle (tan δ).

Claims (4)

[Claims] (1) An electrolytic capacitor characterized by using a driving electrolytic solution formed by dissolving a quaternary ammonium salt of glutaric acid in a polar organic solvent. (2) A driving electrolyte is used, which is obtained by dissolving a quaternary ammonium salt of glutaric acid in a polar organic solvent consisting of γ-butyrolactone and 3-alkyl-1,3-oxazolidin-2-one. An electrolytic capacitor according to claim 1. (3) The electrolytic capacitor according to claim 1, wherein the content of the quaternary ammonium salt of glutaric acid in the driving electrolyte is 1 to 50% by weight. (4) The electrolysis according to claim 1 or 2, wherein the alkyl group (R) of the quaternary ammonium represented by the general formula R_4N^+ has 1 to 10 carbon atoms. capacitor.