JPH0381291B2 - - 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. 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 pyrrolidinium compound or a piperidinium compound as a solute, as in Japanese Patent Application No. 62-51885. However, the present inventor further proposed in the present invention that a solute that provides such high conductivity is a solute that has a cation of quaternary ammonium of a pyrrolidine derivative or a piperidine derivative and an anion of 1,3-diketone. It has been found that it is suitable for the purpose of [Means for solving the problem] The electrolytic solution of the present invention has the general formula: (wherein, R ₁ and R ₂ are alkyl groups having 1 to 6 carbon atoms or phenyl groups, R ₃ is hydrogen, alkyl groups having 1 to 6 carbon atoms, and n is 4 or 5), a pyrrolidine derivative or piperidine The quaternary ammonium 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),
The 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 or a phenyl group is bonded to the nitrogen atom of the pyrrolidine derivative or piperidine derivative to form a covalent 4-valent cation, and the nitrogen of the pyrrolidine or piperidine ring is a quaternary ammonium. The one that takes the form of is used. Examples of pyrrolidine derivatives include N-methyl-pyrrolidine N-methyl-2-methylpyrrolidine N-methyl-3-methylpyrrolidine and so on. Regarding piperidine derivatives, N-methyl-piperidine N-methyl-2-pipecoline N-methyl-3-pipecoline N-methyl-4-pipecoline N-ethyl-piperidine Examples include derivatives such as. Next, specific example compound names of 1,3-diketones on the anion side (the numbers in parentheses represent an indicative formula) are as follows: acetylacetone [CH ₃ COCHCOHCH ₃ ], benzoylacetone [CH ₃ COCHCOHC ₆ H ₅ ], Dibenzoylmethane [C ₆ H ₅ COCHCOHC ₆ H ₅ ], di-tert-butyl-acetylacetone [(CH ₃ ) ₃ CCOCHCOHC
( _CH3 ) ₃ ], 3-methyl-2,4-pentadione [ _CH3COC ( _CH3 ) _COHCH3 ], and the like. A quaternary ammonium cation obtained from these pyrrolidine derivatives or piperidine derivatives,
An electrolytic solution is obtained by dissolving a solute in combination with an anion consisting of an enol type acid of 1,3-diketone in a solvent. Note that the pyrrolidine derivatives, piperidine derivatives, and 1,3-diketones are not limited to those exemplified above. Furthermore, the solvents that can be used in this invention are:
There is no particular limitation as long as it is a nonaqueous 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, exylene glycol, phenyl glycol, glycerin, methyl cellosolve, and 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. improves. 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 the cation and anion of the present invention in a solute solvent in combination, 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 % by weight, and electrical conductivity is ms (milliSiemens)/cm・30
It is ℃. Present invention example 1 (Composition) N,N-dimethylpyrrolidium, acetylacetonate 15 γ-butyrolactone 77 Ethylene glycol 8 (Conductivity) 8.7ms Present invention example 2 (Composition) N,N-dimethyl-2-methylpyrrolidium nium,
3-Methyl-2,4-pentanedionate 15 N,N-dimethylformamide 77 Ethylene glycol 8 (Conductivity) 13.0ms Invention example 3 (Composition) N,N-dimethylpiperidinium, benzoylacetonate 15 N- Methylformamide 85 (Conductivity) 18.0ms Invention Example 4 (Composition) N,N-dimethyl-2-pipecorinium, diphenylacetylacetonate 15 Acetonitrile 60 γ-butyrolactone 25 (Conductivity) 14.3ms Invention Example 5 (Composition) ) N,N-diethylpiperidinium, di-tert-
Butylacetylacetonate 15 N-methylformamide 60 N,N-dimethylformamide 25 (Conductivity) 13.7ms Comparative example (Composition) Ammonium adipate 12 Ethylene glycol 78 Water 10 (Conductivity) 6.7ms As shown in the above results, It can be seen that the electrolytic solution of the present invention exhibits higher conductivity than the conventional electrolytic solution. 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) after 1000 hours of applying the rated voltage at 110℃, the tangent of the loss angle (tanδ),
It represents the leakage current value (LC) (2-minute value). Note that these measured values are for product 10 in all examples.
is the average of individual measurements.

[Table] As is clear from the results of this test, since the electrolytic solution of the present invention has a high conductivity, the loss, that is, the tan δ value, is lower than that of the conventional electrolytic solution. In addition, since it essentially does not contain water, there is no appearance abnormality or decrease in capacitance due to increased internal pressure even when placed under high-temperature load conditions, and a comparison of initial values and characteristic values after 1000 hours shows that this invention Things change very little. [Effects 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 for a long time at high temperatures, so it can be used at high frequencies. Moreover, it can exhibit excellent characteristics when used in power supplies such as switching regulators that require high efficiency, and various electrical devices that are used at high temperatures for long periods of time.

Claims (1)

[Claims] 1. General formula (wherein R ₁ and R ₂ are alkyl groups having 1 to 6 carbon atoms or phenyl groups, R ₃ is hydrogen or an alkyl group having 1 to 6 carbon atoms, and n is 4 or 5), a pyrrolidine derivative or piperidine Using the derivative quaternary ammonium 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.