JP3163682B2 - Molten salt type electrolyte for driving electrolytic capacitor and electrolytic capacitor using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molten salt electrolyte for driving an electrolytic capacitor, which can be used in place of a conventional electrolytic solution for driving an electrolytic capacitor in which an electrolyte salt is dissolved in a solvent, and an electrolytic capacitor using the same. .

[0002]

2. Description of the Related Art Generally, a driving electrolyte having conductivity in an electrolytic capacitor substantially functions as a cathode and plays a role of extracting capacitance from a dielectric material on an anode. As the electrolytic solution, a liquid paste in which an organic acid or an inorganic acid or a salt thereof is dissolved as an electrolyte in an organic solvent such as ethylene glycol or γ-butyrolactone is used.
An electrolyte using a quaternary ammonium salt of an aromatic carboxylic acid as an electrolyte (Japanese Patent Publication No. 3-8092) and an electrolyte using a quaternary phosphonium salt of a carboxylic acid as an electrolyte (Japanese Patent Application Laid-Open No. 62-272512) ) Are known, but all of these are electrolyte solutions in which an electrolyte is dissolved in a solvent.

[0003]

However, in an electrolytic capacitor using the above-mentioned electrolytic solution, when the temperature becomes high, the organic solvent component in the electrolytic solution is vaporized and the internal pressure of the outer case is increased. It passes through the sealing body and escapes to the outside. With the decrease in the amount of the electrolyte due to the dissipation of the organic solvent, a decrease in the capacitance and an increase in the tangent (tanδ) of the loss angle occur. Had. Further, the electrolytic solution itself has a problem that, in a high temperature atmosphere, electrolyte ions react with solvent molecules, so that the electrical conductivity gradually decreases and tan δ increases. That is, in the prior art, it was extremely difficult to use the electrolytic capacitor at a temperature near the boiling point of the electrolyte solvent in principle.

[0004] The present invention solves the above-mentioned conventional problems, improves the deterioration of the electrolytic capacitor characteristics caused by using an electrolytic solution, and enables the electrolytic capacitor to be used at a higher temperature. It is an object of the present invention to provide a molten salt electrolyte for driving an electrolytic capacitor capable of improving its life and reliability, and an electrolytic capacitor using the same.

[0005]

In order to achieve the above object, a molten salt electrolyte for driving an electrolytic capacitor according to the present invention is obtained by mixing a carboxylate and a carboxylic acid in a molten state without using a solvent. It is.

Further, the electrolytic capacitor of the present invention uses a molten salt-type electrolyte obtained by mixing a carboxylate and a carboxylic acid into a molten state without using a solvent, and using this alone or together with a separator with an anode foil and a cathode foil. And a capacitor element is interposed between them.

[0007]

Since the molten salt electrolyte of the present invention does not contain volatile components such as solvent molecules, the electrolyte components permeate through the sealing body and escape to the outside even when used for a long time at a high temperature. The electrolyte ions do not react with the solvent molecules. Therefore, even if the battery is used for a long time at a high temperature, there is almost no decrease in the capacity or increase in tan δ due to the decrease in the electrolytic mass or the conductivity.

In the electrolytic capacitor using the molten salt electrolyte of the present invention, since the volatile component is not contained in the outer case, the pressure rise in the outer case is small, and as a result, the outer case is deformed. The safety valve is rarely opened.

Further, since the decomposition temperature of the molten salt electrolyte is higher than the boiling point of an organic solvent such as ethylene glycol or γ-butyrolactone, an electrolytic capacitor using this is compared with an electrolytic capacitor using a conventional electrolytic solution. , And can be used at higher temperatures.

By using a molten salt type electrolyte instead of the electrolytic solution, the upper limit of the operating temperature, life and reliability of the electrolytic capacitor can be remarkably improved.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a molten salt electrolyte for driving an electrolytic capacitor according to the present invention will be described below.

The molten salt electrolyte for driving an electrolytic capacitor according to the present invention is basically formed by mixing a carboxylate and a carboxylic acid without using a solvent so as to be in a molten state.

Examples of the acid component of the carboxylate used in the present invention and the carboxylic acid mixed therewith include polycarboxylic acid (2-4 tetravalent); aliphatic polycarboxylic acid [saturated polycarboxylic acid such as oxalic acid , Malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, 1,6-decanedicarboxylic acid, 5,6-decanedicarboxylic acid: unsaturated polycarboxylic acid such as maleic acid , Fumaric acid, icotanic acid];
Aromatic polycarboxylic acids such as phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, pyromellitic acid;
Alicyclic polycarboxylic acids such as tetrohydrophthalic acid (such as cyclohexane-1,2-dicarboxylic acid) and hexahydrophthalic acid; alkyl (1 to 3 carbon atoms) or nitro-substituted polycarboxylic acids such as cytocholane Acids, dimethylmaleic acid, nitrophthalic acid (3-nitrophthalic acid, 4-nitrophthalic acid); and sulfur-containing polycarboxylic acids such as thiopropionic acid; monocarboxylic acids; aliphatic monocarboxylic acids (1 to 30 carbon atoms) [saturated] Monocarboxylic acids such as formic acid, acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, lauric acid, myristic acid, stearic acid, behenic acid; Acrylic acid, methacrylic acid, oleic acid]; aromatic monocarboxylic acids such as ammonium Kosan, cinnamic acid, naphthoic acid;
Oxycarboxylic acids such as salicylic acid, mandelic acid, resorcylic acid are mentioned by way of example. Of these, maleic acid, citraconic acid, phthalic acid, adipic acid and benzoic acid are preferred.

As the quaternary ammonium salt in the present invention, tetraalkyl (the alkyl group has 1 to 1 carbon atoms)
2) ammonium salts such as tetramethylammonium salt, tetraethylammonium salt, tetrapropylammonium salt, tetrabutylammonium salt and methyltriethylammonium salt; aryl (phenyl etc.) trialkylammonium salts such as phenyltrimethylammonium salt and phenyltriethylammonium Salts; cycloalkyl (such as cyclohexyl) trialkylammonium salts, for example, cyclohexyltrimethylammonium salt, cyclohexyltriethylammonium salt; aralkyl (such as benzyl) trialkylammonium salts,
For example, benzyltrimethylammonium salt and benzyltriethylammonium salt are exemplified.

As the quaternary phosphonium salt in the present invention, tetraalkyl (the alkyl group has 1 to 1 carbon atoms)
2) phosphonium salts, for example, tetramethylphosphonium salts, tetraethylphosphonium salts, tetrapropylphosphonium salts, tetrabutylphosphonium salts, methyltriethylphosphonium salts; aryl (phenyl etc.) trialkylphosphonium salts, for example, phenyltrimethylphosphonium salts, phenyltriethylphosphonium salts A cycloalkyl (such as cyclohexyl) trialkyl phosphonium salt, for example, cyclohexyl trimethyl phosphonium salt, cyclohexyl triethyl phosphonium salt; and an aralkyl (such as benzyl) trialkyl phosphonium salt, such as benzyl trimethyl phosphonium salt, benzyl triethyl phosphonium salt.

[0016] As the heterocyclic carboxylates having conjugated double bonds in the present invention are pyrrole, pyridine, imidazole, and salts of these alkyl-substituted compounds with a cationic component thereof.

Specifically, a pyridinium salt;
-Methylpyridinium salt, 1-ethylpyridinium salt,
1-propylpyridinium salt, 1-butylpyridinium salt, 1,2-dimethylpyridinium salt, 1,3-dimethylpyridinium salt, 1,4-dimethylpyridinium salt,
1-methyl-2-ethylpyridinium salt imidazolium salt; for example, 1,3-dimethylimidazolium salt, 1,3-diethylimidazolium salt, 1,3
-Dipropyl imidazolium salt, 1,3-dibutyl imidazolium salt, 1-methyl-3-ethyl imidazolium salt, 1-methyl-3-propyl imidazolium salt, 1-
Methyl-3-butylimidazolium salt is exemplified.

The fused heterocyclic carboxylate having a conjugated double bond of the present invention includes quinoline, benzimidazole,
Examples thereof include diazabicycloalkenes and salts containing these alkyl-substituted compounds as a cationic component.

Specifically, a quinolinium salt;
-Methylquinolinium salt, 1-ethylquinolinium salt,
1-propylquinolinium salt, 1-butylquinolinium salt, 1,2-dimethylquinolinium salt, 1,3-dimethylquinolinium salt, 1,4-dimethylquinolinium salt,
1-methyl-2-ethylquinolinium salt Benzimidazolium salt; for example, 1,3-dimethylbenzimidazolium salt, 1,3-diethylbenzimidazolium salt, 1,3-dipropylbenzimidazolium salt, , 3-Dibutylbenzimidazolium salt, 1-methyl-3-ethylbenzimidazolium salt diazabicycloalkene salt; for example, 1,5-diazabicyclo [4,3,0] nonene-5 and 1,8-diazabicyclo [ 5,4,0] undecene-7.

The molten salt electrolyte used in the present invention is at room temperature (2
5 ° C), it is desirable to be in a liquid, gel, or jelly form, but it has electrical conductivity in any phase state and has the ability to act on a defective portion on the anode foil to form an oxide film. What is necessary is just to have.

The molten salt electrolyte used in the present invention comprises:
It is desirable that the acid component constituting the carboxylate and the carboxylic acid mixed therein have the same composition and structure, but two or more carboxylate salts and carboxylic acids having different compositions and structures may be mixed. At this time, the content of the carboxylate in the molten salt electrolyte is desirably 50 to 95% by weight. Above this range, a liquid composition at room temperature cannot be obtained, and below this range, sufficient electrical conductivity cannot be obtained.

Further, various additives such as a phosphoric acid derivative, for the purpose of preventing electrolytic corrosion, reducing leakage current, and absorbing hydrogen gas.
Nitrobenzene derivatives can be added.

The molten salt electrolyte of the present invention basically does not contain a solvent component, but may contain a trace amount of a reaction solvent, water, or the like mixed when synthesizing or purifying the electrolyte salt. Rather, mixing of water or a solvent of 1% by weight or less may be desirable because electric conductivity is improved.

Next, specific examples of the molten salt electrolyte for driving an electrolytic capacitor according to the present invention will be described. However, the present invention is not limited to these examples.

Table 1 shows Examples 1 to 11 of the present invention,
FIG. 4 shows specific electrolyte compositions of Conventional Examples 1 to 3 in which an electrolyte is dissolved in ethylene glycol or γ-butyrolactone and the phase state at normal temperature. The numbers in each example indicate the mixing ratio on a weight basis.

[0026]

[Table 1]

(Table 2) shows the results obtained by using the molten salt electrolytes of Examples 1 to 11 of the present invention shown in Table 1 and the electrolytes of Conventional Examples 1 to 3 at a rated voltage of 10 V and a capacitance of 220 μF. This shows the results of trial production of roll-up type aluminum electrolytic capacitors, applying a rated voltage to them, and performing a high-temperature load test at 125 ° C. for 2000 hours. The number of tests was 10 in each case, and the characteristics were shown by the average value of 10 electrolytic capacitors.

[0028]

[Table 2]

As is clear from Table 2, the characteristics of the capacitors of Conventional Examples 1 to 3 after 125.degree. C. for 2,000 hours show a remarkable decrease in capacity and an increase in tan .delta. However, in Examples 1 to 11 of the present invention, both the capacitance and tan δ hardly changed. As is evident from the results, the electrolytic capacitor experimentally produced using the molten salt electrolyte of the present invention shows more stable characteristics at high temperatures than the electrolytic capacitor using the conventional electrolytic solution.

(Table 3) shows a winding type having a rated voltage of 10 V-220 μF using the molten salt electrolytes of Examples 1 to 11 of the present invention shown in Table 1 and the electrolytes of Conventional Examples 1 to 3. This shows the results of trial production of aluminum electrolytic capacitors, applying a rated voltage to them, and performing a high-temperature load test at 175 ° C. for 500 hours. The number of tests was 10 in each case.
And the characteristics thereof are shown as an average value of ten electrolytic capacitors.

[0031]

[Table 3]

As can be seen from Table 3, in Conventional Examples 1 to 3, all ten valves were opened in each case. The capacitor element after the test was also evaporated to dryness. However, in Examples 1 to 11 of the present invention, normal operation was performed even at a high temperature of 175 ° C. Therefore, it is apparent that the electrolytic capacitor using the molten salt electrolyte of the present invention has a higher operating temperature upper limit than the electrolytic capacitor using the conventional electrolytic solution.

[0033]

As described above, the molten salt electrolyte for driving an electrolytic capacitor according to the present invention is obtained by mixing a carboxylate and a carboxylic acid without using a solvent to obtain a molten salt electrolyte. Since the electrolytic capacitor that uses an organic solvent does not contain volatile components such as organic solvents and water, the pressure rise in the outer case is smaller than that of an electrolytic capacitor that uses an electrolytic solution, resulting in deformation of the outer case and a safety valve. This also reduces the number of valve openings.

Further, since the molten salt electrolyte does not contain solvent molecules, the electrolyte component does not react with the solvent molecules even when exposed to a high temperature for a long time. And the increase in tan δ due to the decrease in the electric conductivity and the electric conductivity hardly occurs.

Further, since the decomposition temperature of the molten salt electrolyte is higher than the boiling point of an organic solvent such as ethylene glycol or γ-butyrolactone, an electrolytic capacitor using this is compared with an electrolytic capacitor using a conventional electrolytic solution. Thus, it is possible to remarkably improve the upper limit of the operating temperature, the service life, and the reliability of the electrolytic capacitor, for example, by enabling use at a higher temperature.

Since the molten salt electrolyte of the present invention is liquid at normal temperature, an electrolytic capacitor having good low-temperature characteristics can be obtained without significantly impairing electric conductivity in a low-temperature range. Also, since it is a liquid at normal temperature, it is possible to directly impregnate the capacitor element by the same method as the method for impregnating the electrolytic solution, and thus it is not necessary to change the impregnation method again to use the molten salt type electrolyte. Things.

Continuation of the front page (56) References JP-A-4-311019 (JP, A) JP-A-4-139712 (JP, A) JP-A-2-14506 (JP, A) JP-A-59-117209 (JP) , A) (58) Field surveyed (Int. Cl. ⁷ , DB name) H01G 9/035

Claims (7)

(57) [Claims] 1. A molten salt electrolyte for driving an electrolytic capacitor in which a carboxylate and a carboxylic acid are mixed without using a solvent to obtain a molten state. 2. The molten salt electrolyte for driving an electrolytic capacitor according to claim 1, wherein the carboxylate is a quaternary ammonium salt. 3. The molten salt electrolyte for driving an electrolytic capacitor according to claim 1, wherein the carboxylate is a quaternary phosphonium salt. 4. A complex in which the carboxylate has a conjugated double bond.
Ring cation salt or condensed complex having conjugated double bond
The molten salt electrolyte for driving an electrolytic capacitor according to claim 1, which is a salt of a ring cation . 5. The molten salt electrolyte for driving an electrolytic capacitor according to claim 1, wherein the composition of the acid component constituting the carboxylate and the carboxylic acid mixed therein are equal. 6. A carboxylate content of 50 to 95% by weight.
The molten salt electrolyte for driving an electrolytic capacitor according to claim 1. 7. A molten salt-type electrolyte obtained by mixing a carboxylate and a carboxylic acid without using a solvent and in a molten state, and being used alone or together with a separator between an anode foil and a cathode foil. An electrolytic capacitor comprising a capacitor element.