JPH0471328B2 - - 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 An electrolytic solution serving as an electrolyte layer is brought into contact with the electrode, and a current collecting electrode, usually called a cathode, is arranged. 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. This had the drawback of increasing vapor pressure, causing damage to the sealing part and deterioration of life due to evaporation of the electrolyte, and the inability 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, as disclosed in Japanese Patent Application No. 61-61835,
- The present inventors have proposed a method using a quaternary ammonium salt of an enol-type acid of a diketone as a solute, and a method using a carboxylate of a pyridinium compound as a solute, as in Japanese Patent Application No. 62-51886. However, the present inventor further found that a solute having a cation of quaternary ammonium of a pyridine derivative and an anion of 1,3-diketone is suitable for the purpose of the present invention as a solute that provides such high conductivity. This is what I found. [Means for solving the problem] The electrolytic solution of the present invention has the general formula: (wherein R ₁ is an alkyl group, alkenyl group or aryl group having 1 to 6 carbon atoms, R ₂ and R ₃ are an alkyl group or aryl group having 1 to 6 carbon atoms, m+n is 0 to 5), The quaternary ammonium of a pyridine derivative is used as a cation, and the general formula is (wherein R ₄ and R ₅ are an alkyl group or an aryl group having 1 to 6 carbon atoms, R ₆ is hydrogen, an alkyl group or an aryl group having 1 to 6 carbon atoms),
This electrolytic solution is characterized by containing a solute having an enol-type acid of 1,3-diketone as an anion. 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,
N-methyl-2-ethyl-6-methylpyridinium, N-methyl-2-allylpyridinium, N-
Examples include quaternary ammonium pyridine derivatives such as methyl-2-allyl-6-methylpyridinium. Next, specific examples of 1,3-diketone compounds on the anion side (the numbers in brackets represent an indicating formula) are acetylacetone [CH ₃ COCH ₂ COCH ₃ ],
Benzoylacetone [CH ₃ COCH ₂ COC ₆ H ₅ ], Dibenzoylmethane [C ₆ H ₅ COCH ₂ COC ₆ H ₅ ], Di-
tert-butyl-acetylacetone [(CH ₃ ) ₃ CCOCH ₂ COC(CH ₃ ) ₃ ], 3-methyl-
2,4-pentadione [CH ₃ COCH (CH ₃ )
COCH ₃ ] etc. An electrolytic solution is obtained by dissolving in a solvent a solute containing a combination of a quaternary ammonium cation obtained from these pyridine derivatives and an anion consisting of an enol type acid of 1,3-diketone. Note that the pyridine derivatives and 1,3-diketones 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 aprotic solvents, protic solvents, or mixed solvents thereof can be used. . 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, acetylacetonate 15 γ-butyrolactone 77 ethylene glycol 8 (conductivity) 9.2ms Invention example 2 (composition) N-ethylpyridinium, 3-methyl-2,4 -Pentanedionate 15 N,N-dimethylformamide 77 Ethylene glycol 8 (Conductivity) 13.6ms Invention Example 3 (Composition) N-Methyl-α-picolinium, acetylacetonate 15 N-Methylformamide 85 (Conductivity) 18.6ms Invention example 4 (Composition) N-methyl-β-picolinium, benzoylacetonate 15 Acetonitrile 60 γ-butyrolactone 25 (Conductivity) 15.2ms Invention example 5 (Composition) N-methyl-2,6- Rutidinium, acetylacetonate 15 N-methylformamide 60 N,N-dimethylformamide 25 (Conductivity) 14.2ms Invention example 6 (Composition) N-Methyl-2,5-lutidinium, di-tert
-Butylacetylacetonate 15 Acetonitrile 45 N,N-dimethylformamide 40 (Conductivity) 16.1ms Comparative example (Composition) Ammonium adipate 12 Ethylene glycol 78 Water 10 (Conductivity) 6.7ms As shown in the above results, this It can be seen that the electrolyte of the invention exhibits higher conductivity than the conventional electrolyte. Next, electrolytic capacitors were manufactured using these electrolytes and their characteristics were compared. The manufactured electrolytic capacitor used aluminum foil as an anode and a cathode, and rolled it overlappingly with separator paper in between to form a cylindrical capacitor element, which was then impregnated with the electrolytic solution of each example and stored in an external 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) after 1000 hours of applying the rated voltage at 110℃, the tangent of the loss angle (tanδ),
It shows the leakage current value (LC) (2 minute value).
Each value is the average value of 10 products.

〔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 (wherein R ₁ is an alkyl group, alkenyl group or aryl group having 1 to 6 carbon atoms, R ₂ and R ₃ are an alkyl group or aryl group having 1 to 6 carbon atoms, m+n is 0 to 5), Using quaternary ammonium of a pyridine derivative as a cation, the general formula (wherein R ₄ and R ₅ are an alkyl group or an aryl group having 1 to 6 carbon atoms, R ₆ is hydrogen, an alkyl group or an aryl group having 1 to 6 carbon atoms),
An electrolytic solution for an electrolytic capacitor, characterized in that it contains a solute having an enol-type acid of 1,3-diketone as an anion.