JPH0797541B2 - Electrolytic solution for electrolytic capacitors - Google Patents

Description

The present invention relates to a non-aqueous electrolyte solution for electrolytic capacitors.

According to the present invention, it is possible to obtain an electrolytic solution for electrolytic capacitors for medium- and high-voltages (which may be simply referred to as an electrolytic solution hereinafter) for relatively high electric conductivity.

(Prior Art) In an electrolytic capacitor, an electrolytic solution for a medium- and high-voltage capacitor is conventionally one in which boric acid or anomonium borate as a solute is dissolved in an ethylene glycol solvent because a spark generation voltage can be relatively high. Came. However, since such an electrolyte is a large amount of condensed water generated by the esterification reaction between ethylene glycol and boric acid, when it is used at a temperature over 100 ° C, the package is destroyed due to the vapor pressure of water. There was a problem.

In order to improve this problem, ammonium salt of aliphatic dicarboxylic acid such as azelaic acid having 9 carbon atoms, sebacic acid having 10 carbon atoms and decanedicarboxylic acid having 12 carbon atoms, which has high spark generation voltage, is used as a solute. It has been proposed to use (JP-A-52-85356 and JP-A-58-197712).

However, these solutes have poor solubility in a solvent, and it is difficult to increase the conductivity of the electrolyte without adding water, and the dissolution precipitates at low temperatures below room temperature, degrading the low temperature characteristics of the capacitor. There was a problem.

Further, it has been proposed to improve the low temperature characteristics by using a branched aliphatic dicarboxylic acid having better solubility in a solvent than a linear aliphatic dicarboxylic acid (JP-A-56-45014). And 57-27013).

Since all of the above electrolytic solution uses a solvent mainly composed of ethylene glycol, the viscosity of the electrolytic solution is high, and the freezing point is relatively high. Poor low temperature characteristics.

(Problems to be solved by the invention) On the other hand, in order to improve the low temperature characteristics, γ-butyrolactone or N, which has a wider freezing point to boiling point range than ethylene glycol,
It is possible to use an aprotic solvent such as N-dimethylformamide and the above ammonium salt of a branched aliphatic dicarboxylic acid, but the solubility of the solute is poor and it is not practical.

(Means for Solving Problems) The present inventor has conducted extensive studies to find a method of dissolving a salt of a higher aliphatic dicarboxylic acid in an aprotic solvent, and has found that a solvent mainly containing γ-butyrolactone is used. It was found that the use of the quaternary ammonium salt of the above-mentioned acid markedly improved the solubility and showed a high electric conductivity, and completed the present invention.

That is, the present invention uses a quaternary ammonium salt of a branched aliphatic dicarboxylic acid having a total carbon number of 13 to 30 as a solute, and dissolves it in a solvent containing γ-butyrolactone as a main component and does not contain water. And an electrolytic solution for an electrolytic capacitor.

(Effect of the invention) The quaternary ammonium salt of a branched chain aliphatic dicarboxylic acid having a total carbon number of 13 to 30 used as a solute in the present invention has good solubility in γ-butyrolactone and has a relatively high conductivity. When used with a solvent having a wide range of freezing point to boiling point, it becomes an excellent electrolytic solution for medium- and high-voltage electrolytic capacitors having a wide operating temperature range.

(Detailed Description of the Invention) In the quaternary ammonium salt of a branched aliphatic dicarboxylic acid having a total carbon number of 13 to 30 used in the present invention,
The aliphatic dicarboxylic acid is a branched chain having a total carbon number of 13 to 30, specifically, 4,6-dimethyl-4
-Nonene-1,2-dicarboxylic acid, 4,6-dimethyl-1,2-
Nonanedicarboxylic acid, 1,7-dodecanedicarboxylic acid, 5
-Ethyl-1,10-decanedicarboxylic acid, 6-methyl-6
-Dodecene-1,12-dicarboxylic acid, 6-methyl-1,12-
Dodecanedicarboxylic acid, 6-ethylene-1,12-dodecanedicarboxylic acid, 6ethyl-1,12-dodecanedicarboxylic acid, 7-methyl-7-tetradecene-1,14-dicarboxylic acid, 7-methyl-1,14- Tetradecanedicarboxylic acid, 3
-Hexyl-4-decene-1,2-dicarboxylic acid, 3-hexyl-1,2-decanedicarboxylic acid, 6-ethylene-9
-Hexadecene-1,16-dicarboxylic acid, 6-ethyl-1,
16-hexadecanedicarboxylic acid, 6-phenyl-1,12-
Dodecanedicarboxylic acid, 7,12-dimethyl-7,11-octadecadiene-1,18-dicarboxylic acid, 7,12-dimethyl-1,
18-octadecanedicarboxylic acid, 6,8-diphenyl-1,1
4-tetradecane dicarboxylic acid etc. can be illustrated.

As the quaternary ammonium salt, tetraethylammonium, tetrapropylammonium, tetrabutylammonium, methyltriethylammonium, methyltripropylammonium, methyltributylammonium,
Dimethyldiethylammonium, dimethyldipropylammonium, dimethyldibutylammonium, ethyltripropylammonium, aliphatic quaternary ammonium salts such as ethyltributylammonium, N, N-dimethylpyrrolidinium, N, N-dimethylpiperidinium, N- Alicyclic quaternary ammonium salts such as methyl-N-ethylpyrrolidinium, N-methyl-N-ethylpiperidinium and N, N-pentamethylenepiperidinium, aromatic quaternary ammonium such as N-ethylpyridinium A salt can be illustrated.

As a solvent for dissolving the quaternary ammonium salt of a branched aliphatic dicarboxylic acid having a total carbon number of 13 to 30 of the present invention,
γ-butyrolactone may be mentioned. γ-Butyrolactone is used because it has low toxicity and little attack by the sealing agent of the electrolytic capacitor and mixing of halogen.

The solubility of the solute of the present invention in a solvent mainly composed of γ-butyrolactone is not more than the saturation concentration, preferably 1 to 40% by weight.
The lower the concentration, the higher the breakdown voltage can be. The molar ratio of acid to base in the dissolved salt of the electrolytic solution is usually in the range of 1: 2 to 2: 1.

The solute of the present invention can be obtained, for example, by neutralizing the above-mentioned dicarboxylic acid in water or methanol with a quaternary ammonium hydroxide aqueous solution, distilling off the solvent under reduced pressure, and vacuum drying.
The non-aqueous electrolytic solution of the present invention, the above-mentioned dicarboxylic acid and quaternary ammonium hydroxide solution is directly added to the solvent, after the neutralization reaction,
It can also be prepared by dehydration.

The non-aqueous electrolyte solution of the present invention essentially has a total carbon number of 13 to
At 30 consisting of a solvent mainly composed of a branched aliphatic carboxylic acid quaternary ammonium salt and γ-butyrolactone,
Various co-solutes such as boric acid derivatives, phosphoric acid derivatives, and nitrobenzene derivatives can be added for the purpose of improving pressure resistance, preventing electrolytic corrosion, reducing leakage current, absorbing hydrogen gas, and the like.

EXAMPLES The present invention will be described more specifically with reference to Examples and Comparative Examples below.

Example 1 5 wt% 6-ethyl-1,16 in γ-butyrolactone solvent
-Hexadecanedicarboxylic acid monotetraethylammonium was dissolved to obtain an electrolytic solution. This electrolyte has a conductivity of 2.0 mS / cm at 25 ° C, and a spark generation voltage is 3 when a constant current of 4 mA / cm ² is applied to a pair of + and-aluminum smooth foil.
It was 55V.

Examples 2 to 6 The solute concentration in Example 1 was changed to 2 (Example 2), 10 respectively.
(Example 3), 20 (Example 4), 30 (Example 5), 40
(Example 6) Table 1 shows the electric conductivity and the spark generation voltage when the weight% was set.

Example 7 20% by weight of 3-hexyl-1, in γ-butyrolactone solvent
Table 1 shows the electric conductivity and the spark generation voltage of the electrolytic solution in which the monotetraethylammonium salt of 2-decanedicarboxylic acid was dissolved.

Examples 8-9 In Example 7, instead of the monotetraethylammonium salt of 3-hexyl-1,2-decanedicarboxylic acid,
A monotetraethylammonium salt of 7,12-dimethyl-7,11-octadecadiene-1,18-dicarboxylic acid (Example 8) or 6,8-diphenyl-1,14-tetradecanedicarboxylic acid (Example 9) was used. The electric conductivity and the spark generation voltage when used are shown in Table 1.

Comparative Example 1 20 wt% 6-ethyl-1,16 in ethylene glycol solvent
Table 1 shows the electric conductivity and the spark generation voltage of the electrolytic solution in which the ammonium salt of hexadecanedicarboxylic acid was dissolved.

Comparative Example 2 5% by weight of 6-ethyl-1,16 in γ-butyrolactone solvent
-Adding ammonium salt of hexadecanedicarboxylic acid,
Although it was heated, it was not partially dissolved and was unsuitable for use as an electrolytic solution.

In Table 1, the following abbreviations are used.

GBL: γ-butyrolactone EG: ethylene glycol Example 10 The temperature change of the electric conductivity of the electrolytic solutions of Example 4 and Comparative Example 1 was measured and shown in FIG. The electrolytic solution of the present invention had a significantly improved conductivity as compared with the electrolytic solutions of Comparative Examples, and did not solidify even at -50 ° C.

[Brief description of drawings]

FIG. 1 shows the electrolytic solution of the present invention in Example 10 (Example 4).
FIG. 3 is a diagram showing a temperature change (A) in the electric conductivity of the sample and a temperature change (B) in the electrolytic solution of Comparative Example 1.

Claims (1)

[Claims] 1. A quaternary ammonium salt of a branched chain aliphatic dicarboxylic acid having a total carbon number of 13 to 30 is used as a solute, which is dissolved in a solvent containing γ-butyrolactone as a main component, and is free of water. An electrolytic solution for electrolytic capacitors.