JP4737352B2 - Electrode foil for electrolytic capacitor, method for producing the same, and electrolytic capacitor using the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electrode foil for an electrolytic capacitor, a method for producing the same, and an electrolytic capacitor using the same.
[0002]
[Prior art]
The electrolytic capacitor generally has the following configuration. That is, a high-purity aluminum foil formed in a band shape is chemically or electrochemically etched to expand the surface, and the expanded aluminum foil is subjected to chemical conversion in a chemical conversion solution such as an aqueous ammonium borate solution. By doing so, a capacitor element is formed by winding an anode foil in which an oxide film layer is formed on the surface of the aluminum foil and a cathode foil obtained by enlarging the same high-purity aluminum foil 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 to constitute an electrolytic capacitor.
[0003]
In addition, as an electrolytic solution impregnated in a capacitor element of a small-sized, low-pressure electrolytic capacitor, conventionally, an ethylene glycol as a main solvent and an ammonium salt such as adipic acid or benzoic acid as a solute, or γ Known are those having butyrolactone as a main solvent and quaternized cyclic amidinium salts such as phthalic acid and maleic acid as solutes.
[0004]
[Problems to be solved by the invention]
However, if such an electrolytic capacitor is left unattended, there is a problem that the electrostatic capacity decreases, the leakage current characteristics deteriorate, and the safety valve may be opened. The neglected characteristics, which are characteristics after a long period of time, greatly affect the reliability of the electrolytic capacitor.
[0005]
Therefore, analysis of an electrolytic capacitor that had deteriorated after standing for a long time revealed that the pH of the electrolytic solution was high and that a solute anion component adhered to the surface of the electrode foil. From this, the aluminum on the surface of the electrode foil reacts with the solute anion component and adheres to the electrode foil, and further, the aluminum dissolves into a hydroxide or the like, and a part of the aluminum reacts with the solute anion component. Hydrogen gas is generated. It was clarified that this reaction was repeated, the pH increased, leading to deterioration of the electrode foil and valve opening.
[0006]
By the way, it is well known that phosphoric acid is effective in preventing such deterioration of the electrode foil, but it is not sufficient. This is because even if this phosphoric acid is added to the electrolytic solution, the added phosphoric acid forms a complex with the aluminum in the electrolytic solution and adheres to the electrode foil, and the phosphoric acid disappears from the electrolytic solution. Is. Furthermore, when there is too much addition amount, there also exists a problem that a leakage current will increase. However, the characteristics of the electrolytic capacitor are kept good while an appropriate amount of phosphate ions remains. These facts have been clarified, and the present invention has been made in accordance with the present invention, and an object thereof is to provide an electrode foil for an electrolytic capacitor having good leaving characteristics, a manufacturing method thereof, and an electrolytic capacitor using the same.
[0007]
[Means for Solving the Problems]
The electrode foil for an electrolytic capacitor of the present invention creates a solution comprising a chelating agent, a compound that generates phosphate ions in a solvent, and a metal or metal compound, and completes the chelation reaction and the phosphate ion binding reaction. It is characterized in that a conjugate formed by binding phosphate ions to a water-soluble metal complex produced by the above-mentioned method is attached.
[0008]
And the manufacturing method of the electrode foil for electrolytic capacitors of this invention produces the solution which consists of a chelating agent, the compound which produces | generates a phosphate ion in a solvent, and a metal or a metal compound, Chelation reaction and phosphoric acid After completing the ion binding reaction to produce a conjugate in which phosphate ions are bound to a water-soluble metal complex, this conjugate is attached to the electrode foil.
[0009]
Here, the compound that generates a phosphate ion in the solvent is a phosphorus compound represented by the general formula (Chemical Formula 2), a salt thereof, a condensate thereof, or a salt of the condensate. To do.
[0010]
The electrolytic capacitor of the present invention is characterized by using the above electrode foil for an electrolytic capacitor.
[0011]
In the electrode foil for an electrolytic capacitor, the metal complex is an aluminum complex, and the metal or the metal compound is aluminum or an aluminum compound in the manufacturing method thereof.
[Chemical 2]
(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)
[0012]
DETAILED DESCRIPTION OF THE INVENTION
The electrode foil for electrolytic capacitors of the present invention has a bonded body in which phosphate ions are bonded to a water-soluble metal complex. And in the electrolytic capacitor using the electrode foil for electrolytic capacitors of the present invention, a bonded body (hereinafter referred to as a water-soluble bonded body) in which phosphate ions are bonded to a water-soluble metal complex immediately after production is contained in the electrolytic solution. Phosphate ions are gradually released, and phosphate ions in the electrolytic solution are maintained at an appropriate amount for a long period of time. And in the electrolytic capacitor using this electrode foil for electrolytic capacitors, leaving characteristics become favorable by the phosphate ion hold | maintained in this appropriate quantity.
[0013]
This water-soluble conjugate can be obtained by dissolving a chelating agent, a metal or a metal compound, and a compound that generates phosphate ions in a solvent in a solvent. In this solution, the chelating agent and the metal ion dissolved in the solvent form a complex, and the phosphate ion binds to the complex to form a water-soluble conjugate. And this bonded body is attached to electrode foil, and the electrode foil for electrolytic capacitors of this invention is manufactured. Moreover, the solvent used here should just be a solvent which melt | dissolves a chelating agent, a metal or a metal compound, and the compound which produces | generates a phosphate ion in a solvent, Especially, water, ethylene glycol, (gamma) -butyrolactone, etc. are preferable.
[0014]
The following are mentioned as a chelating agent used for this invention. 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, phenoltricarboxylic acid, aurintricarboxylic acid, aromatic hydroxycarboxylic acids such as eriochrome cyanine R, sulfocarboxylic acids such as sulfosalicylic acid, tannins such as tannic acid , Guanidines such as dicyandiamide, saccharides such as galactose and glucose, lignins such as lignosulfonate, and ethylenediaminetetraacetic acid (EDTA), nitrilotriacetic acid (NTA), glycol etherdiaminetetraacetic acid (GEDTA) ), Aminopolycarboxylic acids such as diethylenetriaminepentaacetic acid (DTPA), hydroxyethylethylenediaminetriacetic acid (HEDTA), triethylenetetraminehexaacetic acid (TTHA), or salts thereof. Among these, tannic acid, gluconic acid, DTPA, GEDTA, and TTHA are preferable. And as these salts, ammonium salt, aluminum salt, sodium salt, potassium salt etc. can be used. Two or more of these chelating agents may be used.
[0015]
As the metal, a metal that forms a complex with a chelating agent, such as aluminum, iron, copper, nickel, manganese, zinc, calcium, magnesium, barium, lead, titanium, niobium, and tantalum can be used. Moreover, as a metal compound, the compound which produces | generates a metal ion in a solvent, such as metal salts, such as an oxide, a hydroxide, a chloride, and a sulfate, carbonate, can be used.
[0016]
And the compound (henceforth a phosphoric acid production | generation compound) which produces | generates a phosphate ion in aqueous solution is added. Examples of the phosphoric acid-generating compound include a phosphorus compound represented by the general formula (Formula 2), a salt thereof, a condensate thereof, or a salt of the condensate.
[0017]
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 salt decompose in aqueous solution to produce phosphate ions. In addition, phosphorous acid, hypophosphorous acid, and salts thereof are decomposed in an aqueous solution to generate phosphite ions and hypophosphite ions, and then oxidized to phosphate ions.
[0018]
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.
[0019]
Furthermore, the following condensed phosphoric acid or salts thereof can be mentioned. Linear condensed phosphoric acid such as pyrophosphoric acid, tripolyphosphoric acid and tetrapolyphosphoric acid, cyclic condensed phosphoric acid such as metaphosphoric acid and hexametaphosphoric acid, or such chain and cyclic condensed phosphoric acid are combined. . And as a salt of these condensed phosphoric acids, ammonium salt, aluminum salt, sodium salt, calcium salt, potassium salt etc. can be used.
[0020]
These are also phosphate-forming compounds that generate phosphate ions in an aqueous solution, or generate phosphite ions and hypophosphite ions, which are then oxidized to phosphate ions.
[0021]
Among these, normal phosphoric acid or a salt thereof, condensed phosphoric acid, or a phosphoric acid compound that easily generates phosphate ions is preferable. Further, normal condensed phosphoric acid, pyrophosphoric acid, tripolyphosphoric acid or the like that produces a large amount of phosphate ions relatively quickly with respect to the amount added, or a salt thereof is preferable. In addition, the effect of this invention can be acquired if it is a substance which produces a phosphate ion in aqueous solution other than these compounds.
[0022]
Here, normally, when the solvent of the electrolytic capacitor electrolyte solution contains water, the electrode foil deteriorates remarkably, but in this case as well, an appropriate amount of phosphate ions is released from the water-soluble binder. The leaving characteristics of the electrolytic capacitor of the invention are good. Furthermore, when a solvent mainly composed of water is used, the standing characteristics are not deteriorated, and by using such a solvent, the specific resistance of the electrolytic solution for the electrolytic capacitor can be reduced. The impedance can be reduced.
[0023]
The electrolytic capacitor using the electrode foil of the present invention described above has good standing characteristics, that is, characteristics after a long-term load and no-load test.
[0024]
The present invention will be described below. The electrode foil for an electrolytic capacitor of the present invention has a bonded body in which phosphate ions are bonded to a water-soluble metal complex. Can be kept in quantity. That is, phosphate ions in the electrolyte solution decrease by reacting with aluminum eluted from the electrode foil, but with this decrease, the water-soluble binder releases phosphate ions, and the phosphate ions in the electrolyte solution It acts to keep the ions in the proper amount. The proper amount of phosphate ions suppresses dissolution of aluminum and generation of aluminum hydroxide and the like, thereby suppressing deterioration of the electrode foil, thereby improving the leaving characteristics of the electrolytic capacitor.
[0025]
That is, simply adding phosphate ions to the electrolytic solution causes the phosphate ions to react with aluminum and disappear from the electrolytic solution, so that the standing characteristics deteriorate. In addition, when added in a large amount, the leakage current characteristics further deteriorate. However, in the electrolytic capacitor of the present invention, an appropriate amount of phosphate ions is present in the electrolytic solution without disappearing even after a long period of time, and it is possible to maintain good leaving characteristics and leakage current characteristics. Good without deterioration.
[0026]
The following experiment revealed these things. The electrolytic capacitor of the present invention was disassembled, and the electrolytic solution impregnated in the capacitor element was washed and removed. Thereafter, an electrolytic capacitor was produced by impregnating the capacitor element with an electrolyte solution not containing phosphate ions, and the electrolytic capacitor had good standing characteristics. And the phosphate ion was detected from the electrolyte solution of this electrolytic capacitor, and aluminum was hardly detected. That is, the water-soluble binder attached to the electrode foil releases phosphate ions into the electrolyte solution that does not contain phosphate ions, and after that, by maintaining a certain amount of phosphate ions properly for a long time, The characteristics are improved. Further, even when the electrolytic capacitor thus prepared was subjected to the above operation several times, phosphate ions were detected from the electrolytic solution, and the leaving characteristics of the electrolytic capacitor were good. In addition, when the metal complex of the present invention is not water-soluble, that is, hardly soluble or insoluble, it is considered that the phosphate ion in the electrolytic solution as in the present invention does not have an action of maintaining an appropriate amount. The effect cannot be obtained. Moreover, although the aluminum electrolytic capacitor has been described, the same applies to other electrolytic capacitors such as a tantalum electrolytic capacitor.
[0027]
As described above, the water-soluble conjugate used in the present invention has a characteristic of releasing phosphate ions. Here, the number of phosphate ions that can be bonded to the complex varies depending on the coordination number of the chelating agent and the metal, but it is preferable that an appropriate number of phosphate ions be bonded to obtain desired characteristics. That is, if the phosphate ion bound to the water-soluble conjugate is not appropriate, the number of phosphate ions that can be released during standing is reduced, and a desired effect cannot be obtained. Therefore, as in the present invention, a solution of a chelating agent, a phosphate-generating compound, and a metal or metal compound is prepared, and a conjugate in which phosphate ions are bound to a water-soluble metal complex is generated in this solution. As a result, the chelation reaction and the phosphate ion binding reaction can be completed, and a water-soluble conjugate having an appropriate number of phosphate ions bound thereto can be obtained. And the electrode foil for electrolytic capacitors of this invention can be manufactured by adhering this coupling body to electrode foil.
[0028]
Furthermore, it has been found that when a chelating agent is added to the electrolyte to produce a water soluble conjugate in the electrolyte, the chelating agent will dissolve the electrode foil. However, in the electrode foil for an electrolytic capacitor according to the present invention, the water-soluble binder after the chelation reaction is attached, so that this binder does not dissolve the electrode foil.
[0029]
And it turned out that pH of the electrolytic solution of the electrolytic capacitor of the present invention does not increase and is maintained at 5 to 7 (measured by diluting 50 times as an aqueous solution). This is because the dissolution of the electrode foil is suppressed by the phosphate ions held in the electrolytic solution, and therefore, the anion component of the electrolyte is suppressed from reacting with the electrode foil, and the increase in pH is suppressed. I think that the.
[0030]
【Example】
Examples will be described in detail below. The capacitor element is formed by winding an anode foil and a cathode foil through a separator. The anode electrode foil was obtained by subjecting an aluminum foil of 99.9% purity to chemical or electrochemical etching in an acidic solution to enlarge the surface, followed by chemical conversion treatment in an aqueous solution of ammonium adipate. What formed the oxide film layer is used. As the cathode foil, a foil obtained by etching an aluminum foil having a purity of 99.9% and expanding the surface was used.
[0031]
The capacitor element configured as described above is impregnated with an electrolytic solution for driving an aluminum electrolytic capacitor. The capacitor element impregnated with this electrolytic solution is housed in an outer case made of bottomed cylindrical aluminum, a butyl rubber sealing body is inserted into the opening end of the outer case, and the end of the outer case is drawn. By doing so, the aluminum electrolytic capacitor is sealed.
[0032]
The electrode foil used here was prepared as follows. First, a chelating agent, a metal compound and ammonium dihydrogen phosphate shown in (Table 1) were added to 10 parts of water to complete the chelation reaction and the phosphate ion binding reaction, thereby preparing a water-soluble conjugate. As Comparative Example 1, an aqueous solution in which 0.2 part of aluminum hydroxide and 1 part of ammonium dihydrogen phosphate were added to 10 parts of water was prepared. Next, the electrolytic capacitor electrode foil was immersed in the aqueous solution of the water-soluble binder, and then dried to adhere the water-soluble binder, thereby forming the electrolytic capacitor electrode foil of the present invention. And the electrolytic capacitor was created using this electrode foil. And the electrolytic capacitor was created using the electrolyte solution shown in (Table 2). As a conventional example, an electrolytic solution of 75 parts of γ-butyrolactone and 25 parts of ethyldimethylimidazolinium phthalate was used. The specific resistance was 81 Ωcm.
[0033]
A high temperature life test of the aluminum electrolytic capacitor configured as described above was performed. The rating of the aluminum electrolytic capacitor is 6.3 WV-5600 μF. The test conditions are 105 ° C., rated voltage load, no load, and 1000 hours. And the capacitor | condenser after a test was decomposed | disassembled, the electrode foil was immersed in the buffer solution of pH7 or more, it heated, the phosphate ion was extracted, and the density | concentration was measured. In addition, the measurement lower limit of phosphate ion concentration is 1 ppm. The respective results are shown in (Table 3) to (Table 4). The initial characteristics of the conventional example were a capacitance of 5660 μF, tan δ of 0.101, and a leakage current of 13 μA.
[0034]
[Table 1]
(Note) TaA: Tannic acid [CAS: 1401-55-4]
GluA: Gluconic acid
DTPA: Diethylenetriamine hexaacetic acid
AlOH: Aluminum hydroxide
FeSO: Ferric sulfate
NiSO: Nickel sulfate
CaCO: Calcium carbonate
2PA: ammonium dihydrogen phosphate [0035]
[Table 2]
(Note) EG: Ethylene glycol
AAd: Ammonium adipate [0036]
[Table 3]
(Note) Cap: Capacitance (μF), tan δ: Tangent of dielectric loss,
LC: leakage current (μA), ΔCap: capacitance change rate (%)
Phosphoric acid: Phosphoric acid concentration (ppm)
[0037]
[Table 4]
[0038]
As can be seen from (Table 3) and (Table 4), the phosphoric acid concentration after 1000 hours in the examples was 4 to 12 ppm under the respective test conditions, and the standing characteristics at 105 ° C. were also good.
[0039]
In comparison with Comparative Examples 2 and 3, in which only diammonium hydrogen phosphate was added, 50 ppm and 10000 ppm of diammonium hydrogen phosphate were added to the electrolytic solution, respectively. Phosphate radicals are not detected from the electrolyte when the valve is opened. This indicates that the phosphate ions in the electrolyte solution have disappeared. The initial leakage current of Comparative Example 3 to which 1 part of diammonium hydrogen phosphate was added is high.
[0040]
Furthermore, even in Comparative Example 1 using aluminum hydroxide and diammonium hydrogen phosphate, the valve was opened, and further, the phosphate group was not detected from the electrolyte at the time when the valve was opened. You can see the combined effect.
[0041]
Moreover, about the electrolytic capacitor which added only the chelating agent to electrolyte solution, when the film voltage of electrode foil was measured, the film voltage was falling. This indicates that the oxide film of the electrode foil was dissolved by the chelating agent. On the other hand, in the examples, such a decrease in the coating voltage is not observed. Furthermore, the initial leakage current is also good. This indicates that the aqueous solution of the water-soluble conjugate prepared in advance does not contain a chelating agent and excess phosphoric acid, and the chelation reaction and the phosphate ion binding reaction are complete.
[0042]
【The invention's effect】
As described above, in the present invention, a solution comprising a chelating agent, a compound that generates phosphate ions in a solvent, and a metal or a metal compound is prepared, and the chelation reaction and the phosphate ion binding reaction are completed. As a result, the conjugate of phosphate ions bound to a water-soluble metal complex is attached to the electrode foil for electrolytic capacitors. By suppressing deterioration of the electrode foil after being left, it is possible to provide an electrode foil for an electrolytic capacitor having good leaving characteristics, a method for producing the same, and an electrolytic capacitor using the same.

Claims (6)

A water-soluble metal complex produced by creating a solution consisting of a chelating agent, a compound that generates phosphate ions in a solvent, and a metal or metal compound, and completing the chelation reaction and the phosphate ion binding reaction. Electrode capacitor electrode foil, to which a conjugate of phosphate ions is attached. Create a solution consisting of a chelating agent, a compound that generates phosphate ions in a solvent, and a metal or metal compound, complete the chelation reaction and the phosphate ion binding reaction, and then add phosphorus to the water-soluble metal complex. A method for producing an electrode foil for an electrolytic capacitor, comprising: generating a combined body in which acid ions are combined; and attaching the combined body to the electrode foil. 3. The electrolytic capacitor according to claim 2, wherein the compound that generates phosphate ions in the solvent is a phosphorus compound represented by the general formula (Chemical Formula 1), a salt thereof, a condensate thereof, or a salt of the condensate. Of manufacturing electrode foil for use.
(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) An electrolytic capacitor using the electrode foil for an electrolytic capacitor according to claim 1. The electrode foil for an electrolytic capacitor according to claim 1, wherein the metal complex is an aluminum complex. The method for producing an electrode foil for an electrolytic capacitor according to claim 2, wherein the metal or the metal compound is aluminum or an aluminum compound.