JP2672128B2 - Electrolyte for electrolytic capacitors - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a mono- or di-N, N-dialktetrahydroxazinium compound salt of an alkyldicarboxylic acid as an electrolyte in a solvent mainly composed of an aprotic solvent. The present invention relates to an electrolytic solution for electrolytic capacitors contained as.

(Conventional technology) Electrolytic capacitors use a valve metal having an insulating oxide film formed on the surface of aluminum or tantalum as an anode electrode, use the oxide film layer as a dielectric, and apply the oxide film layer to the surface of the oxide film layer. It is configured such that an electrolytic solution serving as an electrolyte layer is brought into contact with the battery, and an electrode for current collection usually called a cathode is arranged.

As described above, the electrolytic solution for the electrolytic capacitor directly contacts the dielectric layer and acts as a true cathode. That is, the electrolytic solution is interposed between the dielectric layer of the electrolytic capacitor and the collector cathode, and the resistance of the electrolytic solution is inserted in series with the electrolytic capacitor. Therefore, the characteristic is a major factor affecting the characteristics of the electrolytic capacitor. For example, when the conductivity of the electrolytic solution is low, there is a disadvantage that the equivalent series resistance inside the electrolytic capacitor is increased and the high-frequency characteristics and the loss characteristics are deteriorated. From such a background, an electrolyte having a high conductivity is required, and as a conventionally known high conductivity electrolyte, an organic acid such as adipic acid or a salt thereof is dissolved in a glycol or an alcohol such as ethylene glycol. Things are used mainstream for normal use.

(Problems to be Solved by the Invention) With the recent increase in the range of use of electronic devices, demands for improving and improving the performance of electrolytic capacitors have increased, and the conductivity of current electrolytic solutions cannot be said to be sufficient. In particular, in the case of the current electrolytic solution, when the desired electric conductivity cannot be obtained, or when using an electrolyte having low solubility, it is attempted to intentionally add water to improve the electric conductivity. .

However, recently, in the use situation of electrolytic capacitors that require long-term use at high temperature exceeding conventional products, the presence of moisture in the electrolyte causes deterioration of the dielectric film layer and internal vapor of the electrolytic capacitor. When the pressure is increased, the sealing portion is damaged and the life of the electrolyte is deteriorated due to evaporation of the electrolytic solution, and there is a disadvantage that stable characteristics cannot be maintained for a long period of time.

Therefore, an object of the present invention is to provide a substantially non-aqueous, high-conductivity electrolytic solution mainly composed of an aprotic solvent, thereby improving the electric characteristics of an electrolytic capacitor and extending the stable characteristics. It is to improve the reliability of the electrolytic capacitor by maintaining the period.

(Means for Solving the Problems) The inventors of the present invention have conducted diligent research on an electrolyte which is a substantially non-aqueous electrolytic solution containing an aprotic solvent as a main component and which gives high conductivity. Alternatively, the present invention has been achieved by finding that a di-N, N-dialkyltetrahydrooxazinium compound salt has a high solubility in an aprotic solvent, a high dissociation degree, and a high conductivity.

That is, the electrolytic solution for an electrolytic capacitor according to the present invention has a general formula: (Wherein, m + n = 4, m = 2-4, n = 2-0, R ₁ and R ₂ may be the same or different alkyl groups having 1 to 6 carbon atoms,
R ₃ and R ₄ may be the same or different and each may be a hydrogen atom, an alkoxy group having 1 to 6 carbon atoms, or an alkyl group having 1 to 6 carbon atoms, y is an integer of 2 or 3, and R is a hydrogen atom or carbon. In an alkyl group having 1 to 10 atoms, all R are not hydrogen atoms, and X represents a hydrogen atom or the same group as the N, N-dialkyltetrahydrooxazinium compound group shown in the formula). Alkyldicarboxylic acid compound mono or di-N,
It is characterized by containing an N-dialkyltetrahydrooxazinium compound salt as an electrolyte.

Examples of aprotic solvents used include: (1) N-methylformamide, N, N
-Dimethylformamide, N-ethylformamide, N,
N-diethylformamide, N-methylacetamide,
N, N-dimethylacetamide, N-ethylacetamide, N, N-diethylacetamide, hexamethylphosphoramide, (2) Dimethylsulfoxide as oxide system (3) Acetonitrile as nitrile system, (4) Cyclic ester, as amide system Typical examples are γ-butyrolactone, N-methyl-2-pyrrolidone, ethylene carbonate, propylene carbonate, and the like.

The polyhydric alcohol compound targeted by the present invention is preferably a dihydric alcohol compound or a monoalkyl ether of a dihydric alcohol compound, the dihydric alcohol compound is ethylene glycol, and the dihydric alcohol monoalkyl ether compound is methylcellosolve or It is an ethyl cellosolve.

The weight ratio of the polyhydric alcohol compound to the aprotic solvent is (100-50) :( 0-50), and 100% of the aprotic solvent is appropriate, but up to about 50% of the polyhydric alcohol compound is substantially It is possible to avoid deterioration of the product and use it as appropriate.

The alkyl dicarboxylic acid compound targeted by the present invention is an alkyl succinic acid compound and an alkyl glutaric acid compound, and as the alkyl succinic acid compound, methyl succinic acid, 2,2-dimethyl succinic acid, 2,3-dimethyl succinic acid, Tetramethyl succinic acid, ethyl succinic acid, 2,2-diethyl succinic acid, propyl succinic acid, etc., and alkyl glutaric acid compounds include 2-methyl glutaric acid,
-Methylglutaric acid, 3,3-dimethylglutaric acid, 3-
Examples thereof include methyl-3-ethylglutaric acid and 3,3-diethylglutaric acid, but are not limited thereto.

The N, N-dialkyltetrahydrooxazinium compound that is the object of the present invention is represented by the following structural formula.

The tetrahydrooxazine compound used as a raw material for synthesizing the N, N-dialkyltetrahydrooxazinium compound used in the present invention is, for example, tetrahydro-1,4-oxazine (morpholine), which is industrially produced by dehydration and ring closure of diethanolamine with sulfuric acid or the like. Manufactured and available on the market,
This can be N-methylated with an alkyl halide, for example, methyl iodide, by a conventional method to obtain the corresponding N, N-dimethylmorpholinium iodide. This is desalted with deiodine for anion exchange using electrodialysis using an ion exchange membrane to obtain a purified N, N-dimethylmorpholinium hydroxide aqueous solution suitable for use in the electrolytic capacitor of the present invention. obtain. A desired alkyldicarboxylic acid compound or the like is added to this aqueous solution in an amount of 1/2 mol, a neutralization reaction is performed, and the alkyldicarboxylic acid mono- or di-N, N- is evaporated to dryness under reduced pressure.
A dimethylmorpholinium salt can be obtained. Also 1,
3-Oxazine or 1,2-Oxazine is described, for example, in N. King: Journal Chemical Society 1942, 43rd.
It can be suitably synthesized by the method described on page 2, for example, 1,2-oxazine can be synthesized as follows using ethyl hydroxamate and 1,4-dibromobutane as raw materials: The electrolytic solution for the electrolytic capacitor according to the present invention is generally,
It can be obtained by adding and dissolving a desired alkyldicarboxylic acid mono- or di-N, N-dialkyltetrahydrooxazinium compound salt in a solvent in which a polyhydric alcohol compound or a monoalkyl ether compound thereof is mixed with an aprotic solvent as needed.

(Examples) Hereinafter, with respect to Examples of the electrolytic solution for an electrolytic capacitor according to the present invention, various aprotic solvents of alkyldicarboxylic acid mono- or di-N, N-dialkyltetrahydrooxazinium compound salts or ethylene glycol or Methyl cellosolve (ethylene glycol monomethyl ether)
Table 1 shows the electric conductivity of the 20 wt% solution of the above at 30 ° C. As a comparative example, a conventional standard electrolyte solution (78% by weight of ethylene glycol, 10% of water, 12% of diammonium adipate) is shown.

As can be seen from the above results, the electrolytic solution of the present invention has higher conductivity than the conventional one.

Next, electrolytic capacitors were manufactured using the electrolytic solutions of Examples 1 to 10 and Comparative Example, and their characteristics were compared.

The manufactured electrolytic capacitor was formed by using an aluminum foil as an anode and a cathode, and overlapping and winding a separator paper therebetween to form a cylindrical capacitor element, and impregnating the electrolytic solution of each of the examples and comparative examples. It is housed in an outer case and sealed.

All use the same capacitor element and rated voltage
The 16V rated capacity is 180 μF.

Table 2 shows the initial values of these electrolytic capacitors as well as 110
Capacitance value (μF), loss tangent (tan δ) and leakage current (μA) 1000 hours after application of low voltage at ℃
(Binary value).

As is clear from the results of this test, since the conductivity of the electrolytic solution of the present invention is high, the loss compared to the conventional one, that is,
The value of tan δ decreases.

Further, since it does not essentially contain water, even when placed in a high temperature load state, there is no abnormal appearance or a decrease in capacitance due to an increase in internal pressure, and even when comparing the initial value and the characteristic value after 1000 hours, Things change very little.

(Effect of the Invention) The electrolytic capacitor using the electrolytic solution according to the present invention can maintain a low loss value and stable characteristics even when used for a long time at a high temperature. It can be used for power supply devices such as switching regulators, and various electric devices that are used at high temperatures for a long period of time.

Claims (7)

(57) [Claims] [1] A solvent comprising an aprotic solvent as a main component and a general formula: (Wherein, m + n = 4, m = 2-4, n = 2-0, R ₁ and R ₂ may be the same or different alkyl groups having 1 to 6 carbon atoms,
R ₃ and R ₄ may be the same or different and each may be a hydrogen atom, an alkoxy group having 1 to 6 carbon atoms, or an alkyl group having 1 to 6 carbon atoms, y is an integer of 2 or 3, and R is a hydrogen atom or carbon. In an alkyl group having 1 to 10 atoms, all R are not hydrogen atoms, and X represents a hydrogen atom or the same group as the N, N-dialkyltetrahydrooxazinium compound group shown in the formula). Alkyldicarboxylic acid compound mono or di-N,
An electrolytic solution for an electrolytic capacitor, which contains an N-dialkyltetrahydrooxazinium compound salt as an electrolyte. 2. A solvent mainly comprising an aprotic solvent comprises 100 to 50 parts by weight of an aprotic solvent and 0 to 50 parts of a polyhydric alcohol compound.
2. The electrolytic solution for an electrolytic capacitor according to claim 1, comprising: parts by weight. 3. The aprotic solvent is N-methylformamide.
N, N-dimethylformamide, N-ethylformamide, N, N-diethylformamide, N-methylacetamide, N, N-dimethylacetamide N-ethylacetamide, N, N-diethylacetamide, γ-butyrolactone, N-methyl- 2-pyrrolidone, ethylene carbonate, propylene carbonate, dimethyl sulfoxide,
The electrolytic solution for an electrolytic capacitor according to claim 1 or 2, which is selected from the group of acetonitrile or a mixture thereof. 4. The electrolytic solution for an electrolytic capacitor according to claim 2, wherein the polyhydric alcohol compound is a dihydric alcohol compound or a monoalkyl ether of the dihydric alcohol compound. 5. The electrolytic solution for an electrolytic capacitor according to claim 2, wherein the dihydric alcohol compound is ethylene glycol, and the dihydric alcohol monoalkyl ether compound is methylcellosolve or ethylcellosolve. 6. An N, N-dialkyltetrahydrooxazinium compound is N, N-dimethylmorpholinium, N, N-diethylmorpholinium, N, N-diethyltetrahydro-1,2.
-Oxazinium, N, N-dimethyl-2-methoxymorpholinium, N, N-dimethyl-2,5-dimethylmorpholinium, N, N-dimethyltetrahydro-1,3-oxazinium. Electrolytic solution for electrolytic capacitors. 7. The electrolytic solution for an electrolytic capacitor according to claim 1, wherein the alkyldicarboxylic acid compound is an alkylsuccinic acid compound or an alkylglutaric acid compound.