JP2005294593A - Electrolytic capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrolytic capacitor exhibiting good high temperature, high humidity characteristics. <P>SOLUTION: Since the capacitor element of an electrolytic capacitor is formed by a positive electrode foil and a negative electrode foil through a separator, the positive electrode foil is subjected to formation again by applying a voltage to the capacitor element in solution containing phosphoric acid ion and chelating agent, and the capacitor element is impregnated with electrolyte for electrolytic capacitor and then encased in a capacitor case, phosphoric acid ion, chelating agent and aluminium ion in formation liquid form a compound body in repair formation liquid. The compound body adheres to the cutting cross-section of the foil and formation progresses while emitting phosphorus to form an oxide film containing phosphorus. Since that film exhibits high resistance against hydration degradation, high temperature moisture resistant characteristics of the electrolytic capacitor are enhanced. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an electrolytic capacitor, and particularly relates to an electrolytic capacitor having good high temperature and high humidity characteristics.

  An aluminum electrolytic capacitor generally has the following configuration. That is, a high-purity aluminum foil formed in a strip shape is subjected to surface expansion treatment by chemical or electrochemical etching, and the surface expansion treatment is performed in a chemical conversion solution such as an ammonium borate aqueous solution. The capacitor element is formed by winding the anode foil having a dielectric film formed on the surface of the aluminum foil by the treatment and the cathode foil having the same high-purity aluminum foil subjected to surface enlargement through a separator. The capacitor element is impregnated with a driving electrolyte solution and stored in a metal bottomed cylindrical outer case. Further, a sealing body made of elastic rubber is accommodated in the opening end portion of the outer case, and the opening end portion of the outer case is sealed by drawing, and then aging is performed to constitute an aluminum electrolytic capacitor.

There are various types of driving electrolytes impregnated in the capacitor element depending on the performance of the aluminum electrolytic capacitor used. Among them, γ-butyrolactone is used as a main solvent as an electrolyte having high conductivity. As an imidazolinium cation or imidazolium cation which is a cation obtained by quaternizing a cyclic amidine compound as a cation component and a salt having an acid conjugate base as an anion component (Patent Document 1, Patent) Reference 2).

In recent years, in the in-vehicle field, electrolytic capacitors have been used in high-temperature engine rooms, and moisture resistance similar to that of semiconductors has been demanded. As countermeasures against such high temperatures, those using sulfolane and sulfolane derivatives as solvents have been proposed (Patent Documents 3 and 4).
JP-A-8-32440 JP-A-8-32441 JP 11-126732 A JP-A-11-219863

However, the temperature of the engine room has been further increased, and the demand for longer life has been increased. In the moisture resistance life test, characteristics deteriorate due to moisture inside the electrolytic capacitor and moisture entering from the outside, resulting in high temperature, high humidity, and long life. There was a problem that the request could not be satisfied.

  Therefore, the present invention has been proposed to solve such problems of the prior art, and an object of the present invention is to provide an electrolytic capacitor having good high temperature and high humidity characteristics.

  In the electrolytic capacitor of the present invention, an anode foil and a cathode foil are used to form a capacitor element via a separator, and a voltage is applied to the capacitor element in a solution containing phosphate ions and a chelating agent to re-form the anode foil. It is characterized by being impregnated with an electrolytic solution for an electrolytic capacitor and enclosing the capacitor element in a capacitor case.

  In order to solve the problems of the present invention, the present inventors have considered the following problems at a high temperature and high humidity that have not existed before. That is, the conventional method for manufacturing an electrolytic capacitor is as follows. The capacitor element formed by winding the cut anode foil and cathode foil through a separator is impregnated with an electrolytic solution, sealed in a capacitor case, and then subjected to aging. Here, the cut surface of the electrode foil and the cracked portion of the electrode foil damaged in the capacitor element forming process such as element winding (hereinafter referred to as the foil cut surface) are applied with voltage in the aging process to form an oxide film. To be repaired. That is, the oxide film formed on the foil cut surface or the like is an oxide film formed by the electrolytic solution. Here, the oxide film formed by this electrolytic solution is considered to be more vulnerable to hydration degradation than the oxide film formed by the chemical solution, and this electrolysis is not possible at high temperatures and high humidity as described above. It was considered that the hydration deterioration of the part of the oxide film formed by the liquid progressed and the characteristics deteriorated.

    Therefore, it was found that when this foil cutting or the like was subjected to chemical conversion (hereinafter referred to as restoration chemical conversion) in a chemical conversion solution after the element formation step, good results were obtained. It has also been found that when this restoration conversion is performed, good characteristics are maintained without aging after enclosing the capacitor case.

    When phosphate ion and chelating agent are included in the chemical solution for repair conversion here, phosphate ions, chelating agent, and aluminum ions in the chemical forming solution form a conjugate, and this conjugate forms on the foil cutting surface, etc. The chemical conversion proceeds while adhering to and releasing phosphorus, and an oxide film containing phosphorus is formed. This film is highly resistant to hydration deterioration, and therefore, it seems that the high temperature and humidity resistance characteristics of the electrolytic capacitor are improved.

  Further, when the water content in the electrolytic solution is 5 wt% or less, the hydration deterioration is further suppressed, and the high temperature and humidity resistance characteristics are further improved.

Phosphate ions can be contained by adding the following phosphorus compounds to the chemical conversion solution. Examples of the phosphorus compound include a phosphorus compound represented by the general formula (Formula 1), a salt thereof, a condensate thereof, or a salt of the condensate thereof.


(Wherein R ₁ and R ₂ are —H, —OH, —R ₃ , —OR ₄ : R ₃ and R ₄ are an alkyl group, an aryl group, a phenyl group, and an ether group)

Examples of these phosphoric acid-generating compounds include the following. Orthophosphoric acid, phosphorous acid, hypophosphorous acid, and salts thereof, and salts thereof include ammonium salt, aluminum salt, sodium salt, calcium salt, and potassium salt. Orthophosphoric acid and its salts decompose in aqueous solution to produce phosphate ions. Phosphorous acid, hypophosphorous acid, and salts thereof are decomposed in an aqueous solution to form phosphite ions and hypophosphite ions, which are then oxidized to phosphate ions.

In addition, phosphoric acid compounds such as ethyl phosphate, diethyl phosphate, butyl phosphate, and dibutyl phosphate, phosphonic acid compounds such as 1-hydroxyethylidene-1,1-diphosphonic acid, aminotrimethylenephosphonic acid, and phenylphosphonic acid Is mentioned. Moreover, phosphinic acid compounds, such as methylphosphinic acid and butyl phosphinate, are mentioned.

Furthermore, the following condensed phosphoric acid or salts thereof can be mentioned. A linear condensed phosphoric acid such as pyrophosphoric acid, tripolyphosphoric acid or tetrapolyphosphoric acid, a cyclic condensed phosphoric acid such as metaphosphoric acid or hexametaphosphoric acid, or such a chain or cyclic condensed phosphoric acid. . As these condensed phosphoric acid salts, ammonium salts, aluminum salts, sodium salts, calcium salts, potassium salts and the like can be used.

These are also phosphate-generating compounds that generate phosphate ions in an aqueous solution, or generate phosphite ions and hypophosphite ions, which are then oxidized to phosphate ions.

Among these, normal phosphoric acid or a salt thereof, condensed phosphoric acid, or phosphoric acid compound that easily generates phosphate ions is preferable. Furthermore, linear condensed phosphoric acid such as orthophosphoric acid, pyrophosphoric acid, tripolyphosphoric acid, or a salt thereof, which generates a large amount of phosphate ions relatively quickly with respect to the amount added, or a salt thereof is preferable. In addition to these compounds, the effect of the present invention can be obtained as long as the substance generates phosphate ions in an aqueous solution.

The following are mentioned as a chelating agent. That is, citric acid, tartaric acid, gluconic acid, malic acid, lactic acid, glycolic acid, α-hydroxybutyric acid, hydroxymalonic acid, α-methylmalic acid, α-hydroxycarboxylic acids such as dihydroxytartaric acid, γ-resorcylic acid, β- Resorcylic acid, trihydroxybenzoic acid, hydroxyphthalic acid, dihydroxyphthalic acid, phenol tricarboxylic acid, aurin tricarboxylic acid, aromatic hydroxycarboxylic acids such as eriochrome cyanine R, sulfocarboxylic acids such as sulfosalicylic acid, guanidines such as dicyandiamide, Sugars such as galactose and glucose, lignins such as lignosulfonate, ethylenediaminetetraacetic acid (EDTA), nitrilotriacetic acid (NTA), glycol etherdiaminetetraacetic acid (GEDTA), diethylenetriamine Aminopolycarboxylic acids such as acetic acid (DTPA), hydroxyethylethylenediaminetriacetic acid (HEDTA), triethylenetetraminehexaacetic acid (TTHA), or salts thereof. And as these salts, ammonium salt, aluminum salt, sodium salt, potassium salt etc. can be used.

    The following can be mentioned as electrolyte solution to be used. As the solute of the electrolytic solution, the following ammonium salts, quaternary ammonium salts, or amine salts of carboxylic acids can be used. Linear aliphatic dicarboxylic acid such as adipic acid, formic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, aromatic monocarboxylic acid such as benzoic acid, toluic acid, or dicarboxylic acid having the following side chain: Its derivatives can be used. 1,6-decanedicarboxylic acid, 5,6-decanedicarboxylic acid, 1,10-decanedicarboxylic acid, 1,7-octanedicarboxylic acid, 2,4,7,6-tetramethyl-1,10-decanedicarboxylic acid 2,4,7,9-tetramethyl-1,6-decanedicarboxylic acid, 2,4,7,6-tetramethyl-5,6-decanedicarboxylic acid, 7-methyl-7-methoxycarbonyl-1, 9-decanedicarboxylic acid and the like, and derivatives thereof include 7,9-dimethyl-7,9-dimethoxycarbonyl-1,11-dodecanedicarboxylic acid, 7,8-dimethyl-7,8-dimethoxycarbonyl-1,14. -Tetradecanedicarboxylic acid etc. can be mentioned.

  The quaternary ammonium constituting the quaternary ammonium salt includes tetraalkylammonium (tetramethylammonium, tetraethylammonium, tetrapropylammonium, tetrabutylammonium, methyltriethylammonium, dimethyldiethylammonium, etc.), pyridium (1-methylpyridium). 1-ethylpyridium, 1,3-diethylpyridium, etc.). In addition, amines constituting the amine salt include primary amines (methylamine, ethylamine, propylamine, butylamine, ethylenediamine, monoethanolamine, etc.), secondary amines (dimethylamine, diethylamine, dipropylamine, ethylmethylamine, diphenylamine). , Diethanolamine, etc.) and tertiary amines (trimethylamine, triethylamine, tributylamine, 1,8-diazabicyclo (5,4,0) -undecene-7, triethanolamine, etc.).

Furthermore, a salt containing a quaternized cyclic amidinium ion as a cation component can be used. Examples of the acid serving as the anion component of the salt include phthalic acid, isophthalic acid, terephthalic acid, maleic acid, benzoic acid, toluic acid, enanthic acid, malonic acid, and the like.

The quaternized cyclic amidinium ion serving as a cation component is a cation obtained by quaternizing a cyclic compound having an N, N, N′-substituted amidine group, and a cyclic compound having an N, N, N′-substituted amidine group Examples of the compound include the following compounds. Imidazole monocyclic compounds (1-methylimidazole, 1-phenylimidazole, 1,2-dimethylimidazole, 1-ethyl-2-methylimidazole, 1,2-dimethylimidazole, 1-ethyl-2-methylimidazole, 1,2 -Imidazole homologues such as dimethylimidazole, 1,2,4-trimethylimidazole, oxyalkyl derivatives such as 1-methyl-2-oxymethylimidazole, 1-methyl-2-oxyethylimidazole, 1-methyl-4 ( 5) Nitro derivatives such as -nitroimidazole, amino derivatives such as 1,2-dimethyl-5 (4) -aminoimidazole), benzimidazole compounds (1-methylbenzimidazole, 1-methyl-2-benzimidazole, 1 -Methyl-5 (6) -nitrobenzimidazole Etc.), compounds having a 2-imidazoline ring (1-methylimidazoline, 1,2-dimethylimidazoline, 1,2,4-trimethylimidazoline, 1-methyl-2-phenylimidazoline, 1-ethyl-2-methyl-imidazoline) 1,4-dimethyl-2-ethylimidazoline, 1-methyl-2-ethoxymethylimidazoline, etc.), compounds having a tetrahydropyrimidine ring (1-methyl-1,4,5,6-tetrahydropyrimidine, 1,2- Dimethyl-1,4,5,6-tetrahydropyrimidine, 1,5-diazabicyclo [4,3,0] nonene-5, etc.).

It is preferable to use a salt containing such a quaternized cyclic amidinium ion as a cation component because the conductivity of the electrolytic solution can be increased.

As the solvent of the electrolytic solution of the present invention, a protic polar solvent, an aprotic solvent, and a mixture thereof can be used. Protic polar solvents include monohydric alcohols (ethanol, propanol, butanol, pentanol, hexanol, cyclobutanol, cyclopentanol, cyclohexanol, benzyl alcohol, etc.), polyhydric alcohols and oxyalcohol compounds (ethylene glycol) Propylene glycol, glycerin, methyl cellosolve, ethyl cellosolve, methoxypropylene glycol, dimethoxypropanol, etc.). Examples of aprotic polar solvents include amides (N-methylformamide, N, N-dimethylformamide, N-ethylformamide, N, N-diethylformamide, N-methylacetamide, N, N-dimethylacetamide, N-ethylacetamide, N, N-diethylacetamide, hexamethylphosphoricamide, etc.), lactones (γ-butyrolactone, δ-valerolactone, γ-valerolactone, etc.), sulfolane (3-methylsulfolane, 2,4 -Dimethylsulfolane, etc.), cyclic amides (N-methyl-2-pyrrolidone, ethylene carbonate, propylene carbonate, isobutylene carbonate, etc.), nitriles (acetonitrile, etc.), oxides (dimethylsulfoxide, etc.), 2-imidazolidinones [1,3-di Rukyle-2-imidazolidinone (1,3-dimethyl-2-imidazolidinone, 1,3-diethyl-2-imidazolidinone, 1,3-di (n-propyl) -2-imidazolidinone, etc.) 1,3,4-trialkyl-2-imidazolidinone (1,3,4-trimethyl-2-imidazolidinone, etc.)] and the like.

In the electrolytic capacitor of the present invention, an anode foil and a cathode foil are used to form a capacitor element via a separator, and a voltage is applied to the capacitor element in a solution containing phosphate ions and a chelating agent to re-form the anode foil. Since the electrolytic solution for electrolytic capacitors is impregnated and this capacitor element is enclosed in a capacitor case, phosphate ions, chelating agents, and aluminum ions in the chemical conversion solution form a conjugate in the repair chemical, and this bond As the body adheres to the foil cutting surface and releases phosphorus, chemical conversion proceeds, and an oxide film containing phosphorus is formed, and this film has high resistance to hydration deterioration, so the high temperature and moisture resistance characteristics of the electrolytic capacitor are improved. .

  Next, examples of the electrolytic capacitor of the present invention will be shown.

  The anode electrode foil and the cathode electrode foil are wound through the separator 1 to form a capacitor element. Here, an anode lead lead wire and a cathode lead lead wire are connected to the anode electrode foil and the cathode electrode foil, respectively.

These lead wires are composed of a connection portion that comes into contact with the electrode foil, a round bar portion formed integrally with the connection portion, and an external connection portion fixed to the tip of the round bar portion. The connecting part and the round bar part are made of 99% aluminum, and the external connecting part is made of a copper-plated steel wire plated with solder. This lead wire is electrically connected to the bipolar electrode foil by means such as stitching or ultrasonic welding at the connection portion.

Anode electrode foil is a 99.9% pure aluminum foil chemically or electrochemically etched in an acidic solution and then subjected to a surface expansion treatment, followed by a chemical conversion treatment to form an anodic oxide film layer on the surface. Is used. The cathode electrode foil 3 is obtained by etching an aluminum foil having a purity of 99.7%. The surface of the cathode electrode foil was covered with titanium nitride. The surface of the round bar portion of the lead wire was covered with aluminum oxide.

  The formation voltage of the used anode foil is 24V. This capacitor element was repaired by applying 22 V voltage in 0.2 wt% ammonium dihydrogen phosphate, 0.1 wt% DTPA aqueous solution. In the comparative example, no restoration conversion was performed.

The capacitor element configured as described above is impregnated with an electrolytic solution for driving an aluminum electrolytic capacitor. The composition of the electrolyte used was 75 parts of γ-butyrolactone as Example 1, 25 parts of 1-ethyl-2,3-dimethylimidazolinium phthalate, 4 parts of water, 30 parts of -butyrolactone and 45 of sulfolane as Example 2. Part, 1-ethyl-2,3-dimethylimidazolinium phthalate, 25 parts, and 4 parts of water.

    Next, this capacitor element is housed in an outer case made of bottomed cylindrical aluminum, and a sealing body is attached to the opening of the outer case, and the outer case is sealed by drawing the end of the outer case. , 16W-470 μF electrolytic capacitor was formed. In the comparative example, aging was performed by applying a voltage of 18 V to the electrolytic capacitor sealed in the outer case.

    In order to evaluate the high-temperature moisture resistance characteristics of the above electrolytic capacitors, a moisture resistance test of 85 ° C./85% RH was performed. The results are shown in (Table 1).

(Table 1)

As described above, in the comparative example, the case swells after 3000 hours, but the example maintains good characteristics. That is, Examples 1 and 2, which were repaired and formed in a repairing chemical solution containing phosphate ions and a chelating agent, showed good characteristics without performing aging, and Comparative Example 1 without performing repairing was subjected to aging. Even case bulging has occurred. As described above, the effect of improving the high-temperature and high-humidity characteristics by the restoration conversion in the chemical conversion liquid containing the phosphate ion and the chelating agent of the present invention is clear.

Claims (1)

Capacitor element is formed with separator between anode foil and cathode foil, and this capacitor element is re-formed by applying voltage in a solution containing phosphate ion and chelating agent, and impregnated with electrolytic solution for electrolytic capacitor An electrolytic capacitor in which this capacitor element is enclosed in a capacitor case.