JPH097895A - Electrolyte for driving electrolytic capacitor - Google Patents

Abstract

PURPOSE: To obtain electrolyte which is high in relative conductivity and thermal stability and possessed of solute that is hardly separated out at low temperatures by a method wherein a specific amount of 1,3-dimethyl-2-imidazolidinone is added to electrolyte. CONSTITUTION: Electrolyte comprises carboxylates of diazabicycloalkenes represented by a formula (where m denotes an integer of 2 to 11, n is an integer of 2 to 6, and each ring may be possessed of a lower alkyl substituting group) as solute and γ-butyrolactone as main solvent. 1 to 25% or so by weight of 1,3-dimethyl-2-imidazolidinone is added to the above electrolyte. The molar ratio of diazabicycloalkene to carboxylic acid is set to 1:0.5 to 1:1.2. By this setup, electrolyte is high in solubility even at low temperatures, relative conductivity, and thermal stability.

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 driving an aluminum electrolytic capacitor, and more particularly to prevention of precipitation of an electrolyte at a low temperature and extension of the service life of the electrolytic solution.

[0002]

2. Description of the Related Art Conventionally, as an electrolytic solution for electrolytic capacitors, etc., a solvent containing γ-butyrolactone and a solute of a salt of diazabicycloalkene (Japanese Patent Publication No. 3-79856).
No.) are known. However, in the case where the above-mentioned salt is used as a solute, the solute is precipitated at a low temperature, so that it is not possible to obtain a solute concentration that can obtain a sufficient specific electric conductivity. An example in which a polyhydric alcohol such as ethylene glycol is added to prevent the precipitation of such a solute (Japanese Patent Laid-Open No. 01-103).
819).

[0003]

However, when a polyhydric alcohol such as ethylene glycol is added, there is a drawback that the change in specific conductivity with time becomes large and the characteristics of the electrolytic solution are deteriorated. Therefore, the present inventors have arrived at the present invention as a result of extensive studies to obtain an electrolytic solution that exhibits high specific electric conductivity, is thermally stable, and does not precipitate solute even at low temperatures.

[0004]

Means for Solving the Problems That is, the present invention provides an electrolytic solution containing a carboxylate of a diazabicycloalkene represented by the following general formula (1) as a solute and γ-butyrolactone as a main solvent: An electrolytic capacitor driving electrolytic solution is characterized in that 1 to 25% by weight of 1,3-dimethyl-2-imidazolidinone is added to this electrolytic solution. General formula

Embedded image In the formula, m is 2 to 11 and n is 2 to 6, and any ring may have a lower alkyl substituent.

Examples of diazabicycloalkenes represented by the general formula (1) include those described in JP-B-46-37503.

Of these, preferred are 1,5-
Diazabicyclo [4,3,0] nonene-5 and 1,8
-Diazabicyclo [5,4,0] undecene-7.

As the carboxylic acid constituting the salt of diazabicycloalkene, polycarboxylic acid (polycarboxylic acid having a valence of 2 to 4) {aliphatic polycarboxylic acid [saturated polycarboxylic acid (oxalic acid, malonic acid, amber Acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, etc.); unsaturated polycarboxylic acids (maleic acid,
Fumaric acid, itaconic acid, etc.)]; Aromatic polycarboxylic acid [phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, pyromellitic acid, etc.]; Aliphatic oxycarboxylic acid [glycolic acid, lactic acid, tartaric acid, etc.]; Group oxycarboxylic acids [salicylic acid, mandelic acid, etc.]; S-containing polycarboxylic acids [thiodipropionic acid, etc.] and monocarboxylic acids {C1-30 aliphatic monocarboxylic acids [saturated monocarboxylic acids (formic acid, acetic acid, propione Acid, butyric acid, isobutyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, berargonic acid, lauric acid, myristic acid, stearic acid, behenic acid, etc .; unsaturated monocarboxylic acids (acrylic acid, methacrylic acid, oleic acid) Etc.]]; Aromatic monocarboxylic acid [benzoic acid, cinnamic acid, naphthoic acid, etc.]
}, Etc.

Among these, aromatic polycarboxylic acids are preferable, and among these, phthalic acid is particularly preferable.

In the carboxylic acid salt of diazabicycloalkene, the molar ratio of diazabicycloalkene to carboxylic acid is usually 1: 0.5 to 1: 1.2, preferably 1: 0.8 to It is 1: 1.1.

Such salts include, for example, phthalic acid and 1,
It is easily synthesized by mixing 5-diazabicyclo [4,3,0] nonene-5 under appropriate conditions and performing a neutralization reaction.

The solvent which can be used in the electrolytic solution of the present invention is γ-butyrolactone, and a γ-butyrolactone is mixed with a sub-solvent for the purpose of increasing the initial specific conductivity and improving compatibility with the electrodes and the separator. be able to. Examples of the auxiliary solvent that can be mixed include alcohols [monohydric alcohols (propyl alcohol, butyl alcohol, amyl alcohol, etc.) and polyhydric alcohols (ethylene glycol, propylene glycol, glycerin, etc.)], ethers [ethylene glycol monoethyl Ether, ethylene glycol monobutyl ether, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether and the like]; amides [N-methylformamide, N, N-dimethylformamide, N, N
-Diethylformamide and N, N-diethylacetamide and the like]; sulfoxides [dimethylsulfoxide and the like]; oxazolidines [3-methyloxazolidin-2-one and 3-ethyloxazolidin-2-one and the like] and two or more thereof. A mixture can be given.

The amount of auxiliary solvent mixed with γ-butyrolactone is usually less than 50% by weight, based on the weight of the total solvent,
It is preferably less than 20% by weight.

The content of the carboxylic acid salt of diazabicycloalkene in the electrolytic solution of the present invention is usually 5 to 40% by weight, preferably 10 to 30% by weight, based on the weight of the electrolytic solution. Outside of this range, the specific conductivity remarkably decreases in all cases.

1,3-dimethyl-2-added to the electrolytic solution
The amount of imidazolidinone is usually 1 to 25% by weight, preferably 5 to 20% by weight, based on the weight of the electrolytic solution. If the amount of 1,3-dimethyl-2-imidazolidinone added is less than 1% by weight, there is no effect in preventing solute precipitation, and if it exceeds 25% by weight, the specific electric conductivity decreases.

The electrolytic solution of the present invention may contain water, if desired. Its content is usually less than 10% based on the weight of the electrolyte. When the water content is 10% or more, gas generation becomes large and the characteristics of the electrolytic capacitor are significantly deteriorated.

If desired, the electrolytic solution of the present invention may be mixed with various additives. Examples of additives include phosphoric acid derivatives, boric acid derivatives, and nitro compounds.

The carboxylic acid salt of diazabicycloalkene is a white powder, but the one to which a solvent is added is a colorless to yellow liquid, and the content of the carboxylic acid salt of diazabicycloalkene is the electrolytic solution. 5-40% by weight, based on the weight of
It is preferable that the crystals do not precipitate within the range.

A method of using the electrolytic solution of the present invention in an aluminum electrolytic capacitor is described in US Pat. No. 4,432,6.
The method described in No. 12 can be exemplified.

[0019]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto. The abbreviations shown below represent the following compounds. PA / DBN: phthalic acid mono-1,5-diazabicyclo [4,3,0] nonene-5 salt GBL: γ-butyrolactone DMI: 1,3-dimethyl-2-imidazolidinone EG: ethylene glycol

Example 1 PA / DBN was dissolved in a mixed solvent of 93 parts of GBL and 7 parts of DMI until a saturated concentration was reached. Conventional Example 1 PA / DBN was dissolved in a mixed solvent of 81 parts of GBL and 19 parts of EG until a saturated concentration was reached. Conventional Example 2 PA.DBN was dissolved in 100 parts of GBL until reaching a saturated concentration. FIG. 1 shows the correlation of the saturation concentration with respect to each temperature in Example 1 and Conventional Examples 1 and 2.

[0021]

[Figure 1]

As is apparent from FIG. 1, the first embodiment of the present invention
The electrolytic solution of No. 2 is -25 compared with the electrolytic solutions of Conventional Examples 1 and 2.
It has a high saturation concentration at a temperature of -25 ° C and a saturation concentration of 20 wt% or more even at -20 ° C.

Next, the initial and post-heat treatment of the electrolytic solution compositions of Example 2 of the present invention and Conventional Examples 3 and 4 shown in Table 1 (at 150 ° C.,
The specific electric conductivity (30 ° C., mS / cm) for 10 hours was measured.

[0024]

[Table 1]

As is clear from Table 1, Example 2 of the present invention
The electrolytic solution of No. 3 has a higher specific electric conductivity and a smaller change in the specific electric conductivity than the electrolytic solutions of Conventional Examples 3 and 4.

[0026]

As described above, the electrolytic solution of the present invention has a high saturation concentration and a high specific electric conductivity even at a low temperature,
It is also thermally stable. When the electrolytic solution of the present invention is used for an electrolytic capacitor, it is possible to obtain a long-life and highly reliable electrolytic capacitor with low loss and stable electrical characteristics even at high temperatures, which is of great industrial value.

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[Procedure amendment]

[Submission date] November 6, 1995

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Brief description of drawings

[Correction method] Added

[Correction contents]

[Brief description of drawings]

FIG. 1 shows the relationship between temperature and saturation concentration in Example 1, Conventional Example 1 and Conventional Example 2.

Claims (3)

[Claims] 1. An electrolytic solution containing a dicarboxylic acid salt of a diazabicycloalkene represented by the following general formula (1) as a solute and γ-butyrolactone as a main solvent. 1-2 dimethyl-2-imidazolidinone
An electrolytic solution for driving an electrolytic capacitor, characterized in that 5% by weight is added. General formula In the formula, m is 2 to 11 and n is 2 to 6, and any ring may have a lower alkyl substituent. 2. The electrolytic solution according to claim 1, wherein the carboxylic acid salt of diazabicycloalkene is a salt of an aromatic polycarboxylic acid. 3. The electrolytic solution according to claim 1, wherein the molar ratio of the diazabicycloalkene and the carboxylic acid is 1: 0.5 to 1: 1.2.