JP3168594B2 - 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 an electrolyte for driving an electrolytic capacitor and an electrolytic capacitor using the same. , Significantly improving the reliability.

[0002]

2. Description of the Related Art Generally, as shown in FIG. 1, an electrolytic capacitor is formed by forming a dielectric oxide film by anodic oxidation on the surface of a valve metal such as an aluminum foil to form an anode foil. These are laminated or wound with a separator such as electrolytic paper interposed therebetween, and impregnated with a driving electrolyte to form a capacitor element 1, and a lead wire 2 drawn out of the capacitor element 1 is sealed with a sealing body 3. , The capacitor element 1 is housed in a metal outer case 4, and then the opening end of the outer case 4 is curled with respect to the sealing body 3 to seal. .

[0003] A driving electrolyte having electrical conductivity substantially acts as a cathode and plays a role of extracting capacitance from a dielectric material on an anode. As the electrolyte, a liquid paste obtained by dissolving an organic acid, an inorganic acid, or a salt thereof in an organic solvent such as ethylene glycol or γ-butyrolactone as an electrolyte is used, and a quaternary aromatic carboxylic acid (phthalic acid, etc.) is used. An electrolyte using an ammonium salt as a solute (see JP-A-62-145716), and an electrolyte using a quaternary ammonium salt of maleic acid (see JP-A-62-1).
No. 45713), an electrolyte using a quaternary ammonium salt of an aliphatic saturated monocarboxylic acid (formic acid or the like) as a solute (see JP-A-62-226614), an aliphatic saturated dicarboxylic acid (malonic acid or the like) An electrolyte solution using a quaternary ammonium salt as a solute (see JP-A-62-248217) and an electrolyte solution using a phosphonium salt of a carboxylic acid as a solute (see JP-A-62-272512) are known. However, these are all "electrolyte solutions" in which an electrolyte is dissolved in a solvent.

[0004]

However, in the electrolytic capacitor constructed as described above, since the electrolytic solution is used, when the temperature becomes high, the organic solvent component in the electrolytic solution is vaporized and the internal pressure of the outer case 4 is reduced. And the solvent vapor eventually passes through the sealing body 3 and escapes to the outside. Therefore, when the electrolytic capacitor is used in a high-temperature atmosphere for a long period of time, the outer case 4 is deformed due to an increase in the internal pressure, and finally the safety valve is operated and the valve is opened. In addition, with the decrease in the amount of the electrolytic solution due to the dissipation of the organic solvent, a decrease in the capacitance and an increase in the tangent (tan δ) of the loss angle occur. Was. In addition, the electrolyte itself reacts with the solvent ions in a high-temperature atmosphere, so that the electrical conductivity gradually decreases,
There was also a disadvantage that tan δ increased.

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.

SUMMARY OF THE INVENTION The present invention solves the above-mentioned conventional problems, improves the deterioration of capacitor characteristics caused by using an electrolytic solution, and makes it possible to use electrolytic capacitors at higher temperatures. Another object of the present invention is to provide a molten salt electrolyte for driving an electrolytic capacitor and an electrolytic capacitor using the same, which can improve the life and reliability thereof.

[0007]

In order to solve the above-mentioned problems, a molten salt electrolyte for driving an electrolytic capacitor according to the present invention comprises:
In this case, only the electrolyte salt is melted without using a solvent.

Further, the electrolytic capacitor of the present invention uses a molten salt type electrolyte in which only an electrolyte salt is melted without using a solvent, and is used alone or together with a separator between an anode foil and a cathode foil to form a capacitor element. It is what constituted.

[0009]

The electrolytic capacitor using the above-mentioned molten salt electrolyte of the present invention does not contain volatile components such as organic solvents and water. Therefore, the pressure rise in the outer case is higher than that of the electrolytic capacitor using the electrolytic solution. As a result, deformation of the outer case and opening of the safety valve are reduced.

[0010] Further, since the molten salt electrolyte does not contain solvent molecules, even if it is exposed to a high temperature atmosphere for a long time, the components permeate through the sealing body and escape to the outside, or the electrolyte ions are removed from other components (solvent). Molecules). Therefore,
Even when used at a high temperature, a decrease in capacity and an increase in tan δ due to a decrease in electrolytic mass and a decrease in electric conductivity hardly occur.

Further, since the decomposition temperature of the molten salt electrolyte salt 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 can be used at a higher temperature.

Therefore, by using the molten salt type electrolyte instead of the electrolytic solution in this way, it is possible to remarkably improve the operating temperature upper limit, life and reliability of the electrolytic capacitor.

[0013]

Embodiments of the present invention will be described below.

The molten salt electrolyte for driving an electrolytic capacitor according to the present invention is based on the fact that only an electrolyte salt is melted without using a solvent.
Any material may be used as long as it is liquid at normal temperature (25 ° C.), has electrical conductivity, and has the ability to act on a defective portion on the anode foil to form an oxide film.

The acid of the electrolyte salt used in the present invention includes boric acid, phosphoric acid, sulfonic acid, tungstic acid, molybdic acid, carboxylic acid and derivatives thereof. Preferred among these are carboxylic acids, examples of which are polycarboxylic acids (2-4 tetravalent); aliphatic polycarboxylic acids [saturated polycarboxylic acids 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 acid 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), hexahydrophthalic acid; alkyls of these polycarboxylic acids (C 1-3) or nitro-substituted products such as cytocholanoic acid, dimethylmaleic acid, nitrophthalic acid (3-nitrophthalic acid, 4-nitrophthalic acid; and sulfur-containing polycarboxylic acids such as thiopropionic acid; monocarboxylic acid; and fats) Group monocarboxylic acids (C 1-3
0) [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: unsaturated Monocarboxylic acids such as acrylic acid, methacrylic acid, oleic acid];
Examples include aromatic monocarboxylic acids, such as benzoic acid, cinnamic acid, naphthoic acid; oxycarboxylic acids, such as salicylic acid, mandelic acid, resorcylic acid; and mixtures of two or more thereof. Of these, more preferred are polycarboxylic acids, and particularly preferred are maleic acid, phthalic acid, adipic acid, benzoic acid, 1,6-decanedicarboxylic acid, and 5,6-decanedicarboxylic acid.

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, methyltriethylammonium salt, methyltripropylammonium salt, methyltributylammonium salt, dimethyldiethylammonium salt, dimethyldipropylammonium Salt, dimethyldibutylammonium salt, trimethylethylammonium salt, trimethylpropylammonium salt, trimethylbutylammonium salt, ethyltripropylammonium salt, ethyltributylammonium salt, diethyldipropylammonium salt, diethyldibutylammonium salt, triethylpropylammonium salt, triethyl Butyl ammonium salt, propyl tributyl ammonium salt, Propyldibutylammonium salt, tripropylbutylammonium salt; aryl (phenyl etc.) trialkylammonium salt such as phenyltrimethylammonium salt, phenyltriethylammonium salt; cycloalkyl (cyclohexyl etc.) trialkylammonium salt such as cyclohexyltrimethylammonium salt, cyclohexyl Aralkyl (such as benzyl) trialkylammonium salts such as benzyltrimethylammonium salt, benzyltriethylammonium salt; and N, N
-Dialkylpiperidinium salts such as N, N-dimethylpiperidinium salt, N, N-diethylpiperidinium salt; and mixtures of two or more thereof. Among these, preferred are tetraalkylammonium salts, and particularly preferred are tetramethylammonium salts, tetraethylammonium salts, methyltriethylammonium salts, and ethyltrimethylammonium salts.

The quaternary phosphonium salt in the present invention includes tetraalkyl (the alkyl group has 1 to 1 carbon atoms).
2) Phosphonium salts, for example, tetramethylphosphonium salt, tetraethylphosphonium salt, tetrapropylphosphonium salt, tetrabutylphosphonium salt, methyltriethylphosphonium salt, methyltripropylphosphonium salt, methyltributylphosphonium salt, dimethyldiethylphosphonium salt, dimethyldipropylphosphonium Salt, dimethyldibutylphosphonium salt, trimethylethylphosphonium salt, trimethylpropylphosphonium salt, trimethylbutylphosphonium salt, ethyltripropylphosphonium salt, ethyltributylphosphonium salt, diethyldipropylphosphonium salt, diethyldibutylphosphonium salt, triethylpropylphosphonium salt, triethyl Butylphosphonium salt, propyltributylphosphonium salt, Propyldibutylphosphonium salt, tripropylbutylphosphonium salt; aryl (phenyl etc.) trialkylphosphonium salt such as phenyltrimethylphosphonium salt, phenyltriethylphosphonium salt; cycloalkyl (cyclohexyl etc.) trialkylphosphonium salt such as cyclohexyltrimethylphosphonium salt, cyclohexyl Aralkyl (such as benzyl) trialkylphosphonium salts such as benzyltrimethylphosphonium salt, benzyltriethylphosphonium salt; and N, N
-Dialkyl phosphoranium salts such as N, N-dimethyl phosphoranium salt, N, N-diethyl phosphoranium salt; and mixtures of two or more of these. Of these, preferred are tetraalkylphosphonium salts, and particularly preferred are tetramethylphosphonium salts, tetraethylphosphonium salts, methyltriethylphosphonium salts, and ethyltrimethylphosphonium salts.

Further preferred as electrolyte salts are alkyl ammonium dicarboxylates and alkyl phosphonium dicarboxylates, and particularly preferred are tetramethyl ammonium maleate, tetraethyl phosphonium maleate, tetramethyl ammonium phthalate, and the like. Tetraethylphosphonium phthalate, Tetramethylammonium adipate, Tetraethylphosphonium adipate, Tetramethylammonium 1,6-decanedicarboxylate, Tetraethylphosphonium 1,6-decanedicarboxylate, Tetra-5,6-decanedicarboxylate Methylammonium salt and tetraethylphosphonium 5,6-decanedicarboxylate.

Among these, two or more kinds of electrolytes may be mixed and used at an arbitrary ratio. Preferably, they are mixed in a eutectic composition or a eutectic composition.

In the molten salt electrolyte, a trace amount of a reaction solvent, water, or the like mixed when synthesizing or purifying the electrolyte salt may be present. 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, but the present invention is not limited to these examples.

Table 1 shows specific electrolyte compositions of Examples 1 to 7 of the present invention and Conventional Examples 1 to 3 in which an electrolyte was dissolved in ethylene glycol or γ-butyrolactone. The numbers in each example of the solvent and the electrolyte are mixing ratios.

[0023]

[Table 1]

Table 2 shows a rated voltage of 10 V and a capacitance of 220 μm using the molten salt electrolytes of Examples 1 to 7 of the present invention shown in Table 1 and the electrolytes of Conventional Examples 1 to 3.
5 shows the results of trial production of a roll-up type aluminum electrolytic capacitor of F, applying a rated voltage to them, and performing a high-temperature load test at 125 ° C. for 2,000 hours. The number of tests was 10 in each case, and the characteristics were 10
The average value of the capacitors was shown.

[0025]

[Table 2]

As is evident from Table 2, in the conventional examples 1 to 3, the temperature was 125 ° C.
In the characteristics after 0 hour, the capacity is significantly reduced and the tan δ is significantly increased, but in Examples 1 to 7, both the capacity and tan δ hardly change. As evident from this result,
The electrolytic capacitor produced by using the molten salt electrolyte of the present invention exhibits more stable characteristics at high temperatures than a capacitor using a conventional electrolytic solution.

Table 3 shows a rated voltage of 10 V and a capacitance of 220 μm using the molten salt electrolytes of Examples 1 to 7 of the present invention shown in Table 1 and the electrolytes of Conventional Examples 1 to 3.
5 shows the results of trial production of a roll-up type aluminum electrolytic capacitor F, applying a rated voltage thereto, and performing a high-temperature load test at 200 ° C. for 500 hours. The number of tests was 10 in each case, and the characteristics were 10
The average value of the capacitors was shown.

[0028]

[Table 3]

As is clear from Table 3, in Conventional Examples 1 to 3, all ten valves were opened, and the capacitor elements after the test were also evaporated to dryness. Are normally operated even in a high-temperature atmosphere such as 200 ° C., therefore, the electrolytic capacitor using the molten salt electrolyte of the present invention has a higher operating temperature than the electrolytic capacitor using the conventional electrolytic solution. Is clearly higher.

[0030]

As described above, the molten salt electrolyte for driving an electrolytic capacitor of the present invention uses only an electrolyte salt without using a solvent.
Since the electrolytic capacitor using the molten salt type electrolyte does not contain a volatile component such as an organic solvent or water, the electrolytic capacitor using the electrolytic solution in the outer case is compared with the electrolytic capacitor using the electrolytic solution. The pressure rise is small, and as a result, the deformation of the outer case and the opening of the safety valve are also reduced.

Further, since the molten salt electrolyte does not contain solvent molecules, even if it is exposed to a high temperature atmosphere for a long time, the component permeates through the sealing body and escapes to the outside, or the electrolyte ion is removed by another component (solvent). Molecules), and therefore, even when used at a high temperature, there is almost no occurrence of a decrease in capacity or an increase in tan δ due to a decrease in electrolytic mass or a decrease in electric conductivity.

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

[Brief description of the drawings]

FIG. 1 is a sectional view showing a conventional electrolytic capacitor.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01G 9/035 H01G 9/028

Claims (10)

(57) [Claims] 1. A molten salt electrolyte for driving an electrolytic capacitor, wherein only an electrolyte salt is melted without using a solvent. 2. The method according to claim 1, wherein the electrolyte salt is a carboxylic acid salt.
A molten salt electrolyte for driving an electrolytic capacitor according to the above. 3. A carboxylic acid salt comprising a dicarboxylic acid monovalent-1.
The molten salt electrolyte for driving an electrolytic capacitor according to claim 2, which is a monovalent salt or a divalent to monovalent salt. 4. The molten salt electrolyte for driving an electrolytic capacitor according to claim 1, wherein the electrolyte salt is a quaternary ammonium salt. 5. The molten salt electrolyte for driving an electrolytic capacitor according to claim 4, wherein the quaternary ammonium salt is an alkyl ammonium salt. 6. The molten salt electrolyte for driving an electrolytic capacitor according to claim 1, wherein the electrolyte salt is a quaternary phosphonium salt. 7. The molten salt electrolyte for driving an electrolytic capacitor according to claim 6, wherein the quaternary phosphonium salt is an alkyl phosphonium salt. 8. The molten salt electrolyte for driving an electrolytic capacitor according to claim 1, wherein two or more kinds of electrolyte salts having different compositions and structures are mixed at an arbitrary ratio. 9. The molten salt electrolyte for driving an electrolytic capacitor according to claim 8, wherein two or more kinds of electrolyte salts having different compositions and structures are mixed in a eutectic composition or a eutectic composition. 10. A method of melting only an electrolyte salt without using a solvent.
An electrolytic capacitor characterized in that a capacitor element is constituted by using a molten salt type electrolyte alone or together with a separator between an anode foil and a cathode foil.