JPH01214007A - Electrolyte for driving electrolytic capacitor - Google Patents

Abstract

PURPOSE:To enhance a conductivity value, to improve a frequency-impedance characteristic and a life characteristic at a high temperature, to enable enduring a wide-range operating temperature and to improve a working environment by using an electrolyte where a quaternary ammonium salt of a specific hydroxycarboxylic acid bas been dissolved in a mixed solvent of a non-protone- based solvent and a protone-based solvent. CONSTITUTION:An electrolyte where a quaternary ammonium salt of a hydroxycarboxylic acid whose total number of carbon is 4 or less and which has an adjacent carboxylic group and an adjacent oxy group has been dissolved as a solute in a mixed solvent of a non-protone-based solvent and a protone- based solvent is used. As said non-protone-based solvent, e.g., gamma-butyrolactone, N,N'-dimethylformamide or the like is used singly or in the form of a mixture; as the protone-based solvent, e.g., ethylene glycol, diethylene glycol, methyl cellosolve or the like is used singly or in the form of a mixture. As said quaternary ammonium salt, e.g., lactic acid tetramethyl ammonium, glycollic acid tetramethyl ammonium or the like is used.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to an electrolytic solution for driving electrolytic capacitors, and particularly to an electrolytic solution that improves conductivity, significantly improves frequency-impedance characteristics, and can be used over a wide range of temperatures. The present invention provides an electrolytic solution for driving a low-voltage electrolytic capacitor that has significantly improved durability and life characteristics, and also has a significantly improved working environment.

[Prior Art] Conventionally, the driving electrolyte for high-performance low-voltage aluminum electrolytic capacitors has mainly been r-butyrolactone, with some ethylene glycol, ethylene glycol methyl ether, or N,N'-dimethyl. Electrolytes are known in which tolumethylamine or triethylamine salts of maleic acid, phthalic acid, etc. are used as solutes in a mixed solvent containing formamide, etc.;
There are problems with stability under high temperatures, and phthalates have problems with specific gravity conductivity (and their salts, trimethylamine and triethylamine, are difficult to work with due to their odor and toxicity. However, it was not always possible to use it with a satisfactory punishment.

[Problems to be Solved by the Present Invention] The purpose of the present invention is to solve the problems of the prior art, improve the conductivity, improve the frequency-impedance characteristics of the capacitor, and make it capable of withstanding a wide range of operating temperatures. The purpose is to improve the working environment by improving the life characteristics under high temperatures.

[Means for Solving the Problems] and [Operations] The inventors of the present invention have made strenuous efforts to improve the conductivity of electrolytes and the stability in high-temperature scorching. The total number of carbon atoms is 4 in the mixed solvent with the system solvent.
Below, carboxyl group and oxy group (hydroxyl group)
It was discovered that an electrolytic solution for driving an electrolytic capacitor obtained by dissolving a quaternary ammonium salt of an oxycarboxylic acid with adjacent oxycarboxylic acids is excellent as an electrolytic solution, exhibits high conductivity, and has excellent thermal stability. Based on this heading, we have completed the present invention.

Since the solute of the present invention has a carboxyl group and an oxy group adjacent to each other, when it is made into a quaternary ammonium salt, -
11° of the OH group becomes easily ionized, forming a shared electron pair with -COO- and -〇-, and associates with many polar solvents,
Forms a solvate.

For example, in the case of glycolic acid, the following solvate is formed.

(However, n is the number of additions, R is a quaternary ammonium salt forming group) Therefore, it dissolves in many polar solvents and exhibits excellent conductivity.Furthermore, since the number of carbon atoms is 4 or less, the molecular diameter is small.
The ion migration speed was fast, and the conductivity was further improved.

Examples of the aprotic solvent used in the electrolyte of the present invention include "-butyrolactone, N-methyl-2-pyrrolidone,
r-valerolactone, ethylene carbonate, propylene carbonate, butylene carbonate, sulfolane,
Cyclic ester solvents such as 1,3-dimethyl-1,2-imidazolysine, N,N'-dimethylformamide, N-
Examples include amide solvents such as methylformamide and N,N'-dimethylacetamide, and cyclic ether solvents such as tetrahydrofuran, 2-methyltetrahydrofuran, and 1,3-dioxolane, or mixtures thereof.

Examples of the protic solvent include polyhydric alcohol solvents such as ethylene glycol, diethylene glycol, and glycerin, polyhydric alcohol monoether solvents such as methyl cellosolve and ethyl cellosolve, and water alone or in mixtures thereof.

The quaternary ammonium salt used in the present invention has the general formula %. The total number of carbon atoms is 4 or less.

R is a group that forms a quaternary ammonium salt by ionic bonding with the oxycarboxylic acid, an example of which is a hydrocarbon residue,
Specific examples thereof include alkyl groups and aryl groups.

Examples of oxycarboxylic acids having 4 or less carbon atoms and in which a carboxylic acid group and a (hydro)oxy group are adjacent to each other include glycolic acid, lactic acid, malic acid, etc. alone or a mixture thereof; Examples of the quaternary ammonium salt as a salt include tetramethylammonium, tetraethylammonium, N,N-dimethylpyrrolidium, etc. alone or a mixture thereof.

The oxycarboxylic acid used as the solute in the present invention has low solubility in the above-mentioned aprotic solvents, but its solubility can be greatly increased by adding even a small amount of the above-mentioned protic solvents. . or,
The electrical conductivity of the electrolytic solution prepared in this way was very high, showing very good results, and since the quaternary ammonium salt was used, there was no odor, and the workability was significantly improved.

In the present invention, the ratio of the solute and the mixed solvent to the former/latter = 5 to 30 wt%/70 to 95 wt% exhibits good properties as an electrolytic solution in the above-mentioned applications,
It can have a favorable effect on improving conductivity, improving frequency-impedance characteristics, expanding the operating temperature range, and improving life characteristics.

Further, the ratio of the aprotic solvent to the protic solvent is the former/latter=99 to 25 wt%/1 to 75 wt%.

[Example] The present invention will be further explained below by giving examples of the present invention and comparing them with conventional products.

5 1-2 and 1-3 Quaternary ammonium of oxycarboxylic acid (total carbon number = 4 or less) shown in Tables 1 and 2 was dissolved in an aprotic/protic mixed solvent to form an electrolytic solution. The electrical conductivity was investigated.

The results are shown in Tables 1 and 2.

Example 1 Table 1 Changes in electrical conductivity when 2% tetramethylammonium lactate was used as a solute and dissolved in various mixed solvents.

C GBL:DMF (◆EG5%) Example 2゜Table 2: Changes in electrical conductivity when 12%-tetramethylammonium glycolate was used as a solute and dissolved in various mixed solvents.

In the symbols listed above, GBL: r-Buchiyu)
EG: ethylene glycol, MG: methyl cellosolve, DMF: N,N'-dimethylformamide.

Next, various solutes were set to 17%, (GBL75:MG
25) When dissolved in the mixed solvent to form an electrolyte,
The electrical conductivity of the comparative product shown in Table 3 and the above-mentioned product of the present invention was compared. The results are shown in Table 3.

No. 2 As shown above, it can be seen that the embodiment according to the present invention has higher electric power and superior characteristics compared to the conventional product.

Next, the rated voltage of the electrolyte according to the present invention! 6V capacity jit
The capacitor characteristics when a driving electrolyte is prepared by impregnating an electrolytic capacitor element of 1 O00u F will be explained.

In addition, the capacitor characteristics of a different product for comparison are also shown. (In each case, the electrolyte compositions in Table 1 and 3 were used.) Table 4 shows the initial characteristics of the above-mentioned sample electrolytic capacitor.

In addition, the following Table 5 shows that the sample electrolytic capacitor was applied with the rated voltage (16 volts) at a high temperature of 105°C, and
This shows the characteristics when a time life test was conducted.

Table 5 As is clear from the results shown in Tables 4 and 5, all of the examples according to the present invention exhibit good capacitor characteristics with lower series resistance and frequency-impedance characteristics than with conventional products.

In addition, even after 1000 hours have passed at a high temperature of 105°C, the product of the present invention maintains most of its initial electrical characteristics, showing excellent stability. [Effects of the Invention] According to the present invention, , it is possible to supply an electrolytic solution for driving an electrolytic capacitor that has excellent conductivity, can withstand a wide range of operating temperatures, and has significantly improved thermal stability, and as shown in the examples,
The electrolytic capacitor impregnated with the electrolytic solution of the present invention has excellent electrolytic properties such as low resistance loss and high frequency - low impedance, and can be used for a long period of time even at a high temperature of 105°C. Therefore, it is possible to maintain stable characteristics, and contributes to improving the electrical characteristics of low-voltage single-piece capacitors. There is a V kimono for α-gisa-ta.

Claims (1)

[Claims] It is characterized by being formed by dissolving, as a solute, a quaternary ammonium salt of an oxycarboxylic acid having a total number of carbon atoms of 4 or less and in which a carboxyl group and an oxy group are adjacent to each other in a mixed solvent of an aprotic solvent and a protic solvent. Electrolyte for driving electrolytic capacitors.