JPH0471329B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] This invention relates to improvement of electrolyte solutions for electrolytic capacitors. [Prior Art] Electrolytic capacitors use a valve metal such as aluminum or tantalum on the surface of which an insulating oxide film is formed for the anode electrode.The oxide film layer is used as a dielectric, and the surface of this oxide film layer is It is constructed by bringing an electrolytic solution which forms an electrolyte layer into contact with the electrode, and further arranging a current collecting electrode, which is usually called a cathode. As described above, the electrolytic solution for an electrolytic capacitor comes into direct contact with the dielectric layer and acts as a true cathode, so its properties are a major factor influencing the properties of the electrolytic capacitor. The electrolyte is interposed between the dielectric layer of the electrolytic capacitor and the collector cathode, and the resistance of the electrolyte is inserted in series with the electrolytic capacitor, so if the conductivity of the electrolyte is low, By increasing the equivalent series resistance inside the electrolytic capacitor,
It has the disadvantage of poor high frequency characteristics and loss characteristics. Against this background, there is a demand for electrolytes with high conductivity, and conventionally, electrolytes with high conductivity have been prepared by dissolving organic acids such as adipic acid or their salts in glycols such as ethylene glycol or alcohols. something is being used. Incidentally, in recent years, electrolytic capacitors with increasingly sophisticated electrical characteristics have been required, and the current conductivity of the electrolytic solution is not sufficient. Particularly in the case of current electrolytes, when the desired conductivity cannot be obtained or when a solute with low solubility is used, water is intentionally added to improve the conductivity. However, in recent years, when electrolytic capacitors are used for long periods of time at high temperatures exceeding 100°C, the presence of moisture in the electrolyte can cause deterioration of the dielectric film layer and the inside of the electrolytic capacitor. The drawback was that it increased the vapor pressure, leading to damage to the sealing part and deterioration of life due to evaporation of the electrolyte, making it impossible to maintain stable characteristics over a long period of time. [Problems to be Solved by the Invention] The present invention improves the above-mentioned drawbacks of conventional electrolytes. By obtaining a non-aqueous electrolyte that provides high conductivity, the present invention improves the electrical performance of electrolytic capacitors. The objective is to improve the reliability of electrolytic capacitors by improving their physical characteristics and maintaining stable characteristics for a long period of time. As such a non-aqueous electrolyte with high conductivity, for example, a cyclic β electrolyte as disclosed in Japanese Patent Application No. 61-65331,
- those using quaternary ammonium salts of dicarbonyl compounds as solutes, and as in Japanese Patent Application No. 1986-51886,
The present inventors have proposed a method using a carboxylate of a pyridinium compound as a solute;
The present inventor further discovered that a solute having a cation of quaternary ammonium of a pyridine derivative and an anion of a cyclic β-dicarbonyl compound is suitable for the purpose of the present invention as a solute that provides such high conductivity. It is. [Means for solving the problem] The electrolytic solution of the present invention has the general formula: (In the formula, R ₁ is an alkyl group having 1 to 6 carbon atoms,
alkenyl group or aryl group, R ₂ and R ₃ are alkyl groups or aryl groups having 1 to 6 carbon atoms, l
+m is expressed as 0 to 5). Using quaternary ammonium of a pyridine derivative as a cation, the general formula (wherein, R ₄ is hydrogen or an alkyl group having 1 to 6 carbon atoms, and n is 2 to 5). It is a liquid. On the cation side of the solute of this invention, an alkyl group, alkenyl group, or aryl group is bonded to the nitrogen atom of the pyridine compound to form a covalent 4-valent cation, and the nitrogen of the pyridine ring is a quaternary ammonium. Those that have taken shape are used. To give specific examples of pyridine derivatives, first, pyridinium compounds include N-methylpyridinium, N-ethylpyridinium, N-
Examples include allylpyridinium, N-isopropenylpyridinium, and N-benzylpyridinium. Picolinium compounds include N-methylpicolinium, N-ethylpicolinium, N-allylpicolinium, N-isopropenylpicolinium, and N-benzylpicolinium. Examples of rutidinium compounds include N-methylrutidinium, N-ethylrutidinium, N-allylrutidinium, N-isopropenylrutidinium, and N-benzylrutidinium. Furthermore, pyridinium compounds in which R ₂ and R ₃ are changed include N-methyl-2-ethylpyridinium,
Examples include quaternary ammonium pyridine derivatives such as N-methyl-2-ethyl-6-methylpyridinium, N-methyl-2allylpyridinium, and N-methyl-2-allyl-6-methylpyridinium. On the other hand, specific examples of cyclic β-dicarbonyl compounds on the anion side include 1,3-cyclopentanedione. 2-methyl-1,3-cyclopentanedione 1,3-cyclohexanedione 2-methylcyclohexane-1,3-dione 5,5-dimethyl-1,3-cyclohexanedione etc. can be given. An electrolytic solution is obtained by dissolving in a solvent a solute in which a quaternary ammonium cation obtained from these pyridine derivatives and an anion of an enol type acid of a β-dicarbonyl compound are combined. Note that the pyridine derivative and the β-dicarbonyl compound are not limited to those exemplified above. Further, the solvent that can be used in this invention is not particularly limited as long as it is a non-aqueous solvent that does not substantially contain water, and various non-pronto solvents, pronto solvents, or mixed solvents thereof may be used. can. Examples of solvents that can be used in this invention include N-methylformamide, N,N-dimethylformamide, N-ethylformamide, N,N
- Acid amides such as diethylformamide, N-methylacetamide, N,N-dimethylacetamide, N-ethylacetamide, N,N-diethylacetamide, lactones such as γ-butyrolactone and γ-valerolactone, ethylene carbonate, butylene carbonate, carbonates such as propylene carbonate, polyhydric alcohols such as ethylene glycol, diethylene glycol, propylene glycol, hexylene glycol, phenyl glycol, glycerin, methyl cellosolve, and further N-methyl-2-pyrrolidone, dimethyl sulfoxide, Various solvents such as acetonitrile can be mentioned. Note that these solvents are not limited to the use of only one type, and may be a mixture of two or more types. The selection of the solvent may be determined in consideration of the solubility of the solute used, the operating temperature range, etc. [Function] The electrolytic solution in which the solute of the present invention is dissolved has higher conductivity than conventional ones, so when used in an electrolytic capacitor, the resistance inside the electrolytic capacitor is reduced, and electrical properties such as loss reduction are improved. will improve. Furthermore, since it essentially does not contain water, there is no risk of generating water vapor when used at high temperatures. [Example] The present invention will be described below based on Examples. First, as an example of the present invention, an electrolytic solution was prepared by dissolving a solute containing a combination of a cation and an anion according to the present invention in a solvent, and its conductivity was examined. As a conventional example, a comparison was made with an ammonium adipate-ethylene glycol electrolyte that has conventionally shown high conductivity. The composition and conductivity are shown below. All composition ratios are weight %, and electrical conductivity is ms (millisiemens)/cm at 30°C.
It is. Invention example 1 (composition) N-methylpyridinium, 1,3-cyclopentanedionate 15 γ-butyrolactone 77 ethylene glycol 8 (conductivity) 7.4ms Invention example 2 (composition) N-ethylpyridinium, 2- Methyl-1,3
-Cyclopentanedionate 15 N,N-dimethylformamide 77 Ethylene glycol 8 (Conductivity) 13.3ms Invention example 3 (Composition) N-methyl-α-picolinium, 1,3-cyclohexanedioate 15 N-methylformamide 85 (Conductivity) 12.1ms Invention Example 4 (Composition) N-methyl-2,6-lutidinium, 2-methylcyclohexane-1,3-dionate 15 Acetonitrile 60 γ-butyrolactone 25 (Conductivity) 15.4ms Invention Example 5 (Composition) N-methyl-3,5-lutidinium, 5,5-
Dimethyl-1,3-cyclohexanedioate
15 N-methylformamide 60 N,N-dimethylformamide 25 (Conductivity) 11.2ms Comparative example (Composition) Ammonium adipate 12 Ethylene glycol 78 Water 10 (Conductivity) 6.7ms As shown in the above results, the results of this invention It can be seen that the electrolyte exhibits higher conductivity than conventional electrolytes. Next, electrolytic capacitors were manufactured using these electrolytes and their characteristics were compared. The manufactured electrolytic capacitors used aluminum foil for the anode and cathode, and rolled them overlappingly with separator paper in between to form a cylindrical capacitor element.The electrolytic solution of each example was impregnated into the capacitor element, which was then stored in an exterior case. and sealed. Both use the same capacitor element,
It has a rated voltage of 16V and a rated capacity of 180μF. The table below shows the initial values of these electrolytic capacitors, the capacitance value (CAP), tangent of loss angle (tanδ), leakage current value (LC) after 1000 hours of applying the rated voltage at 110℃. The average value of 10 products each.

〔Effect of the invention〕

As described above, the electrolytic capacitor using the electrolyte of the present invention has a low loss value and can maintain stable characteristics even when used at high temperatures for long periods of time, so it is used at high frequencies and requires high efficiency. It exhibits excellent characteristics when used in power supply devices such as switching regulators, which are used for a long period of time, and various electrical devices that are used at high temperatures for long periods of time.

Claims (1)

[Claims] 1. General formula (In the formula, R ₁ is an alkyl group having 1 to 6 carbon atoms,
alkenyl group or aryl group, R ₂ and R ₃ are alkyl groups or aryl groups having 1 to 6 carbon atoms, l
+m is a cation of quaternary ammonium of a pyridine derivative represented by 0 to 5), and the general formula (wherein, R ₄ is hydrogen or an alkyl group having 1 to 6 carbon atoms, and n is 2 to 5). Electrolyte for capacitors.