JPH11135365A - Electrolytic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent liquid leakage of an electrolytic capacitor and improve its lifetime characteristic by forming a ceramic coating layer on a contacting portion of its cathode draw-out means with a sealing body thereof. SOLUTION: Cutting aluminum wires which have been subjected to intermittent press workings, aluminum conductors comprising respective round bar potions 6 and flat portions 7 are produced. Thereafter, forming an anode oxidation coating on the surface of one of the aluminum conductors by a chemical conversion treatment, an external connection portion 8 is welded to the end surface of this aluminum conductor to form a lead wires 4 and 5. Then, discharging a coating agent made of a metal-alkoxide-based ceramics on the round bar portion 6 of the aluminum conductor acting as a cathode drawing-out means, it is subjected to a coating and heating treatment and is once gain subjected to the coating and heat treatment by discharging the coating agent on its portion 6. As result, forming a ceramic coating layer on contacting portion of the cathode drawing-out means with the sealing body, the liquid leakage of an electrolytic capacitor is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrolytic capacitor, and more particularly to an electrolytic capacitor using a quaternary cyclic amidinium ion as a cation component as an electrolytic solution.

[0002]

2. Description of the Related Art An electrolytic capacitor generally has a structure as shown in FIG. That is, the strip-like high-purity aluminum foil is chemically or electrochemically etched to enlarge the aluminum foil surface, and the aluminum foil is subjected to a chemical conversion treatment in a chemical conversion solution such as an ammonium borate aqueous solution. An anode electrode foil 2 having an oxide film layer formed on the surface thereof and a cathode electrode foil 3 made of a high-purity aluminum foil subjected to only an etching treatment are wound through a separator 11 made of manila paper or the like to form a capacitor. An element 1 is formed. And this capacitor element 1
Is impregnated with an electrolytic solution for driving an electrolytic capacitor, and then stored in a bottomed cylindrical outer case 10 made of aluminum or the like. A sealing body 9 made of elastic rubber is attached to the opening of the outer case 10, and the outer case 10 is sealed by drawing.

As shown in FIG. 2, a lead wire 4 serving as a cathode lead means and a lead wire serving as an anode lead means are provided on an anode electrode foil 2 and a cathode electrode foil 3, respectively, for leading both electrodes to the outside. 5 are connected by means such as stitching and ultrasonic welding. Each lead wire 4, 5
It comprises a round bar portion 6 made of aluminum, a flat portion 7 in contact with the bipolar electrode foils 2 and 3, and an external connection portion 8 made of a solderable metal fixed to the tip of the round bar portion 6 by welding or the like. ing.

In such an electrolytic capacitor, generally, a contact portion of the lead wire 5 with the sealing member, that is, an electrochemical reaction between the electrolytic solution interposed in the insertion portion 12 and the round bar portion 6 of the lead wire 5 causes There is a tendency for bleeding to occur. Therefore, usually, a means for preventing the liquid from flowing out is formed by forming a chemical conversion film on the round bar portion 6.

Various electrolytic solutions for driving an electrolytic capacitor impregnated in the capacitor element 1 are known depending on the performance of the electrolytic capacitor to be used. Among them, γ-butyrolactone is used as a main solvent. A tetraalkylammonium ion as a solute as a cation component,
There is a so-called quaternary ammonium salt in which a conjugate base of an acid is used as an anionic component.

[0006]

The electrolytic solution using the quaternary ammonium salt has the characteristics of low electric resistance and excellent thermal stability, but has a conversion coating on the round bar. Even when the formed lead wire is used, there is a tendency that the electrolyte is easily discharged. For this reason, although the stability of the electrolytic solution itself using a quaternary ammonium salt or the like is high, since the electrolytic solution is discharged, the electric characteristics such as a decrease in the capacitance of the electrolytic capacitor are deteriorated, and as a result, the electrolytic solution is deteriorated. There is a disadvantage that the life of the capacitor is short.

[0007] Recently, an international application, PCT / JP94
As shown in US Pat. No./02028, attempts have been made to prevent the electrolyte from escaping by using a quaternized cyclic amidinium salt instead of a quaternary ammonium salt. This quaternized cyclic amidinium salt can considerably suppress the leaching of the electrolytic solution as compared with the case where a conventional quaternary ammonium salt is used, but is still practically usable under both loaded and unloaded conditions. Not enough level.

An object of the present invention is to remedy this drawback, and it is an object of the present invention to prevent effusion of an electrolytic capacitor using a quaternized cyclic amidinium salt or the like and to improve the life characteristics.

[0009]

A capacitor element formed by winding an anode electrode foil provided with anode extraction means and a cathode electrode foil provided with cathode extraction means via a separator is provided with a cyclic amidine compound. Impregnated with an electrolytic solution containing a grade salt, and accommodating the capacitor element in a cylindrical outer case with a bottom, and closing the opening end of the outer case with a sealing body. A ceramic coating layer is formed on a portion in contact with the sealing body.

Further, the cathode extracting means includes an aluminum conductor having a round bar portion and a flat portion, and the ceramic coating layer is formed on the round bar portion before a capacitor manufacturing process.

Further, the ceramic coating layer comprises:
It is characterized by being formed using a coating agent composed of a metal alkoxide-based ceramic using one or two or more selected from Al ₂ O ₃ , SiO ₂ and ZrO ₂ .

Further, the anode extraction means includes a round bar portion made of aluminum and a flat connecting portion, and an insulating layer made of aluminum oxide covers at least substantially the entire surface of the round bar portion. I have.

Further, the electrolyte is characterized in that it contains an oxidizing agent.

The oxidizing agent is a nitro compound.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of an aluminum electrolytic capacitor has the same structure as that of the prior art, as shown in FIGS. The capacitor element 1 is formed by winding an anode foil 2 and a cathode foil 3 with a separator 8 interposed therebetween. As shown in FIG. 2, lead wires 4 and 5 are connected to the anode foil 2 and the cathode foil 3, respectively. These lead wires 4 and 5 are made of aluminum and include a flat portion 7 connected to each foil, a round bar portion 6 continuous with the flat portion 7, and an external connection portion 8 connected to the round bar portion 6. I have. The electrode foils 2 and 3 and the flat portion 7 are mechanically connected by a stitch method, ultrasonic welding, or the like.

The anode foil 2 is formed by chemically or electrochemically etching an aluminum foil having a purity of 99% or more in an acidic solution to expand the surface, and then forming the aluminum foil in an aqueous solution of ammonium borate or ammonium adipate. And use an anodic oxide film layer formed on the surface.

The cathode foil 3 is obtained by etching an aluminum foil having a purity of 99% or more in the same manner as the anode foil 2. Here, similarly to the anode foil 2, a chemical conversion treatment of 1 to 2V may be performed.

In the present invention, when producing the electrode lead-out means, first, an aluminum wire rod formed by cutting an intermittently pressed aluminum wire into a predetermined size and having a round bar portion 6 and a flat portion 7 is formed. A conductor is formed, and then a chemical conversion treatment is performed to form an anodic oxide film on the surface. Then, on the end face of this aluminum conductor,
The external connection portion 8 made of a CP wire is welded to form a lead wire 4,
5 is constituted.

Here, the aluminum conductor serving as the cathode extraction means is coated with ceramics.
That is, a coating agent composed of a metal alkoxide ceramic is discharged and coated on the round bar portion 6 of the aluminum conductor having the anodic oxide film formed on the surface as described above,
Thereafter, a heat treatment is performed, and then the coating agent is discharged and coated again. Then, a heat treatment is performed again to form a coating layer on the aluminum conductor.

The ceramics used for the metal alkoxy ceramics include Al ₂ O ₃ , SiO ₂ , Zr
O ₂ , TiO ₂ , MgO, H ₂ BO ₃ , Cr ₂ O ₃ , B
aTiO ₃ , PbTiO ₃ , KTaO _{3 and the} like. The ceramics used here are Al ₂ O ₃ , SiO ₂ ,
One or two or more selected from ZrO ₂ is preferable, and further considering strength, Al ₂ O ₃ ,
It is preferable to use a mixture consisting of SiO ₂ .

As a coating method, a round bar 6
Is also immersed in a coating agent for coating. That is, the aluminum conductor is immersed in the coating agent, then heat-treated, then immersed again in the coating agent, and then heat-treated again to form a coating layer on the aluminum conductor. Thereafter, the flat portion 7 is immersed in a methanol solution, the coating layer is removed by ultrasonic waves or the like, and the ceramic coating layer is left only on the round bar portion 6. However,
In this method, the adjustment at the time of removing the coating layer is not easy, and in order to form the coating layer on the round bar portion with high accuracy, the above-described method using discharge and coating is more preferable.

The flat portions 7 of the lead wires 4 and 5 prepared as described above are mechanically connected to the electrode foils 2 and 3 by a stitch method, ultrasonic welding, or the like. Here, the lead wire 5 is connected to the cathode foil 3
There is also a method of performing ceramic coating after connecting to the substrate, but in consideration of coating accuracy, it is preferable to form the ceramic coating layer in advance before the capacitor manufacturing process. Further, in order to obtain a sufficient liquid leakage prevention effect, the lead wire 5 must be formed at least on the round bar portion 6.

The capacitor element 1 configured as described above
Is impregnated with an electrolytic solution for driving an electrolytic capacitor. As the electrolytic solution, an electrolytic solution in which a salt containing γ-butyrolactone or ethylene glycol as a main solvent, a conjugate base of an acid as an anionic component, and a quaternized cyclic amidinium as a cationic component was dissolved was used.

Examples of the acid serving as the anion component include phthalic acid, isophthalic acid, terephthalic acid, maleic acid, benzoic acid, toluic acid, enanthic acid, and malonic acid.

The quaternized cyclic amidinium ion serving as the cation component is a cation obtained by quaternizing a cyclic compound having an N, N, N'-substituted amidine group.
Examples of the cyclic compound having an N′-substituted amidine group include the following compounds. Imidazole monocyclic compound (1-
Methylimidazole, 1-phenylimidazole, 1,
Imidazole homologs such as 2-dimethylimidazole, 1-ethyl-2-methylimidazole, 1,2-dimethylimidazole, 1-ethyl-2-methylimidazole, 1,2-dimethylimidazole, 1,2,4-trimethylimidazole Oxyalkyl derivatives such as 1-methyl-2-oxymethylimidazole, 1-methyl-2-oxyethylimidazole, nitro derivatives such as 1-methyl-4 (5) -nitroimidazole, and 1,2-dimethyl-
Amino derivatives such as 5 (4) -aminoimidazole, etc.),
Benzimidazole compounds (such as 1-methylbenzimidazole, 1-methyl-2-benzimidazole, 1-methyl-5 (6) -nitrobenzimidazole), and 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 and the like, and compounds having a tetrahydropyrimidine ring (1-methyl-1,4,5,5)
6-tetrahydropyrimidine, 1,2-dimethyl-1,
4,5,6-tetrahydropyrimidine, 1,5-diazabicyclo [4,3,0] nonene-5 and the like.

The electrolyte solution may contain an oxidizing agent. As the oxidizing agent, nitro compounds such as nitrobenzoic acids, nitroanisole, nitrophenol and nitronaphthol can be used.

The capacitor element 1 impregnated with the electrolytic solution as described above is housed in a bottomed cylindrical outer case 10 made of aluminum, and a round bar portion 6 and a connecting portion 7 are formed at the open end of the outer case 10. The sealing of the electrolytic capacitor is performed by inserting a sealing member 9 made of butyl rubber having a through hole to be led out, and by caulking the end of the outer case 10.

The above electrolytic capacitor of the present invention has a very good bleeding characteristic. The reason is presumed to be as follows.

It has been found that such an electrolytic solution is discharged by the electrochemical action of an electrolytic solution using quaternary ammonium. That is, in a general electrolytic capacitor, a leakage current occurs between the anode electrode foil 2 and the cathode electrode foil 3 when a DC voltage is applied due to damage of an oxide film formed on the anode electrode foil 2 or the like. The occurrence of such a leakage current causes a reduction reaction of dissolved oxygen or hydrogen ions on the cathode side, and increases the concentration of hydroxide ions at the interface between the cathode side electrode and the electrolyte. This occurs in both the cathode electrode foil 3 and the lead wire 5 for drawing out the cathode.
, An increase in hydroxide ion concentration in the vicinity of, that is, an increase in basicity. With the increase in the basicity, the sealing body 9 in contact with the lead wire 5 is damaged, and the adhesion between the lead wire 5 and the sealing body 9 is impaired. It is believed that the hydroxide solution leaked out.

That is, as shown in FIG. 3, the leakage current of the electrolytic capacitor is the sum of the current I ₂ flowing through the cathode electrode foil 3 and the current I ₁ flowing through the cathode lead wire 5 in the cathode portion. I have. Normally, the natural potential E ₁ of the cathode lead wire 5 is equal to the natural potential E _{2 of the} cathode electrode foil 3.
When the cathode side undergoes cathodic polarization in a DC load state, a current first flows through the lead wire 5 to cause a reduction reaction of dissolved oxygen or hydrogen ions. Then, a current that cannot be processed by the reduction reaction of the dissolved oxygen or hydrogen ions on the lead wire 5 flows through the cathode electrode foil 3, and the reduction reaction on the cathode electrode foil 3 occurs. The active surface area of the cathode electrode foil 3 is larger than the active surface area of the lead wire 5, and the polarization resistance of the cathode electrode foil 3 is smaller than the polarization resistance of the lead wire 4. Therefore, the potential E _T becomes the rated value I _T of the leakage current of the electrolytic capacitor, although the direction of current I ₂ flowing in the cathode electrode foil 3 is large, a state in which current I ₁ also leads 5 are flowing. Therefore, in the DC load state, a state in which a current also flows through the lead wire 5 continues, and a reduction reaction of dissolved oxygen or hydrogen ions always occurs on the surface of the lead wire 5, and the generated basic hydroxide ion causes deterioration of sealing accuracy. Is causing. The above facts indicate that the initial pH value is actually about 7, but the pH value is 10 to 15 at the time of use.
It has been confirmed by rising to the extent.

The behavior of the electrolytic solution at the interface between the electrode foil and the lead wire can similarly occur in an electrolytic solution containing no quaternary ammonium salt. For example, when a tertiary ammonium salt is used, It is considered that there was no generation of the basic salt itself, or that the generated cation had high volatility, and thus no inconvenience such as liquoring occurred.

As described above, in the electrolytic capacitor using the electrolytic solution containing a quaternary ammonium salt, the natural potential of the lead wire 5 for drawing out the cathode is more noble than the natural potential of the cathode electrode foil 3, so that the DC load At times, the cathode current is concentrated on the lead wire 5, and the generated basic hydroxide ion causes deterioration of sealing accuracy.

Further, in the case of an electrolytic solution in which a quaternized amidinium salt is dissolved, such hydroxide ions generated by the reduction reaction of dissolved oxygen or hydrogen ions react with the quaternized amidinium and disappear. It was thought that bleeding could be prevented. However, it was found that when the pH value at the interface between the cathode-side electrode and the electrolytic solution was 12 or less, the reaction between hydroxide ions and quaternized amidinium did not completely proceed, and hydroxide ions remained. Thus, although liquor is improved over quaternary ammonium salts, it cannot be completely suppressed.

On the other hand, in the present invention, since the ceramic coating layer is formed on the contact portion of the lead wire with the sealing member, that is, on the round bar portion, no current flows through the round bar portion. Therefore, a basic hydroxide is not generated in the vicinity of the round bar portion, so that an adverse effect on the sealing body and the like can be prevented.

When the battery is left unloaded, the conventional electrolytic capacitor has a natural immersion potential E as described above.
₁ shows a more noble potential than the spontaneous immersion potential E ₂ of the cathode foil, so that a local battery is composed of a cathode lead wire and a cathode foil, and a reduction reaction of dissolved oxygen or hydrogen ions is formed on the lead wire side. Occur. As a result, hydroxide ions are generated, and the sealing accuracy is deteriorated.

However, in the present invention, since the ceramic coating layer is formed on the contact portion of the lead wire with the sealing member, that is, on the round bar portion, at least the gap between the round bar portion of the lead wire and the cathode foil is formed. Thus, a local battery is not formed, and hydroxide ions are not generated in the vicinity of the round bar portion. Therefore, the precision of adhesion between the lead wire and the sealing rubber is not deteriorated and liquid is not caused.

Further, when the cathode lead and the anode lead come into contact with each other when no load is left, if the anode lead is more noble than the cathode foil, a local battery is constituted by the anode lead and the cathode foil. As a result, a reduction reaction of dissolved oxygen or hydrogen ions occurs on the anode lead side. As a result, hydroxide ions are generated, and the sealing accuracy is deteriorated. Therefore, the anode lead wire includes a round bar portion made of aluminum and a flat connection portion so that the anode lead wire is more base than the cathode foil, and the insulating layer made of aluminum oxide has at least substantially the entire surface of the round bar portion. Is preferably covered. Similar effects can be obtained by forming a ceramic coating layer on the round bar portion of the anode lead wire, as in the round bar portion of the cathode lead wire.

Further, when the electrolyte contains an oxidizing agent,
The oxidizing agent acts as a depolarizer natural immersion potential of the cathode foil, the natural immersion potential E ₂ moves toward the noble. As a result, the current flowing through the cathode tab is reduced, and the generation of hydroxide ions can be suppressed, so that the adverse effect on the sealing body can be further suppressed. That is, in the present invention, even when the ceramic coating layer formed on the round bar portion is damaged during the production of the capacitor or the like and a slight current flows to the cathode tab, the generation of the hydroxide ion of the oxidizing agent is suppressed. The liquid can be prevented from flowing out by the suppressing action. In addition, due to the effect of the oxidizing agent, the same effect can be obtained even when the cathode lead wire and the anode lead wire come into contact with each other when no load is left.

For the reasons described above, it is considered that in the present invention, liquid discharge is prevented under both load and no load.

[0040]

Next, the present invention will be described with reference to embodiments. Since the structure of the electrolytic capacitor is the same as that of the related art, it will be described with reference to FIGS. The capacitor element 1 is formed by winding an anode electrode foil 2 and a cathode electrode foil 3 with a separator 11 interposed therebetween. As shown in FIG. 2, the anode electrode foil 2 and the cathode electrode foil 3 have a lead wire 4 for leading the anode,
Lead wires 5 for drawing out the cathode are connected to each other.

An aluminum conductor comprising a flat portion 7 made of 99% aluminum and in contact with the electrode foil and a round bar portion 6 integrally formed with the flat portion 7 is formed. Next, an aluminum oxide film is formed on the surface of the aluminum conductor by a chemical conversion treatment. The end face of this round bar 6
The lead wires 8 are welded to form the lead wires 4 and 5.

Then, a ceramic coating layer is formed on the surface of the round bar portion 6 of the aluminum conductor used for the cathode extracting means. This ceramic coating layer
A coating agent composed of a metal alkoxide-based ceramic using one or two or more selected from Al ₂ O ₃ , SiO ₂ and ZrO ₂ as components is discharged to the round bar portion 6, and 1
After heat treatment at 80 ° C. for 10 seconds, and then discharging the coating agent again, heat treatment again at 180 ° C. for 10 seconds,
Further, a heat treatment is performed at 180 ° C. for 20 minutes.

The lead wires 4 and 5 are electrically connected to the bipolar electrode foils 2 and 3 at the connection portions 7 by means such as stitching and ultrasonic welding.

The anode electrode foil 2 is obtained by chemically or electrochemically etching an aluminum foil having a purity of 99.9% in an acidic solution and expanding the surface thereof, and then performing a chemical conversion treatment in an aqueous solution of ammonium adipate. An anodic oxide film layer is formed on the surface.

The cathode electrode foil 3 is formed by etching an aluminum foil having a purity of 99.9% in the same manner as the anode electrode foil 2.
A material subjected to a chemical conversion treatment of 1 V is used.

The capacitor element 1 configured as described above
Is impregnated with an electrolytic solution for driving an electrolytic capacitor. As an electrolyte, γ-butyrolactone (75 parts) was used as a solvent,
As a solute, a solution in which a quaternary salt of a cyclic amidine compound (25 parts) was dissolved was used.

The capacitor element 1 impregnated with the electrolytic solution as described above is housed in an outer case 10 made of aluminum having a bottomed cylindrical shape, and a sealing body 9 is attached to the opening of the outer case 10. Is subjected to a drawing process to seal the outer case 10. The sealing body 9 is made of an elastic rubber such as butyl rubber, for example, and has through holes for leading the lead wires 4 and 5, respectively.

The electrolytic capacitor configured as described above,
As a conventional example, an electrolytic capacitor in which a ceramic coating layer was not formed on a lead wire was compared. condition is,
A rated voltage of 35 V was applied at 105 ° C. for 2,000 hours, and then a determination was made as to whether or not the electrolytic solution was discharged. The results are shown in (Table 1) and (Table 2). In addition, it was left at 105 ° C. for 2,000 hours, and similarly, it was determined whether or not the electrolytic solution had been discharged. The results are shown in (Table 3) and (Table 4).

[0049]

[Table 1]

[0050]

[Table 2]

[0051]

[Table 3]

[0052]

[Table 4]

As apparent from Tables 1 to 4,
In both cases of loading and no loading, no leaching occurred in the present invention, regardless of which quaternary salt of cyclic amidine was used as the solute of the electrolytic solution.

Next, the Al ₂ O ₃ and Si
In an electrolytic capacitor using a coating agent composed of a metal alkoxide ceramic using O ₂ as a component, a microcrack was formed on the ceramic coating layer by pressing with a pointed instrument to prepare a capacitor. Then, using the electrolytic solution and the electrolytic solution obtained by adding 1 part of paranitrobenzoic acid to the electrolytic solution, a humidity resistance test for 5000 hours under the condition of 85 ° C./85% RH and 35 V load together with the conventional capacitor. Was carried out to determine whether or not the electrolyte was discharged. The results are shown in (Table 5).

[0055]

[Table 5]

As is evident from Table 5, the electrolytic capacitor to which paranitrobenzoic acid was not added bleeds, but the electrolytic capacitor to which paranitrobenzoic acid was added did not bleed. It turns out that there is a prevention effect.

[0057]

According to the present invention, in an electrolytic capacitor using an electrolytic solution containing a quaternary salt of a cyclic amidine compound, a ceramic coating layer is provided on a contact portion of a cathode extraction means with a sealing member, particularly on a round bar portion. Because it is forming
No current flows through the cathode extraction means, and no basic hydroxide is generated at the contact portion of the cathode extraction means with the sealing member. Further, an insulating layer made of aluminum oxide is formed on the anode extraction means, so that the potential of the cathode foil can be made superior. Also, by adding an oxidizing agent to the electrolyte,
The generation of hydroxide can be suppressed. Therefore,
In both loaded and unloaded conditions, in an electrolytic capacitor using a quaternary salt of a cyclic amidine compound as a solute of the electrolytic solution, it is possible to prevent the liquid from the cathode extracting means or the anode extracting means, and to prevent the electrolytic solution from being discharged. The decrease in capacitance due to the decrease is prevented, so that the life of the electrolytic capacitor can be extended and the reliability can be increased.

[Brief description of the drawings]

FIG. 1 is an internal sectional view showing a structure of an electrolytic capacitor.

FIG. 2 is an exploded perspective view showing the structure of the capacitor element.

FIG. 3 is a graph showing cathode polarization resistance at a cathode portion of an electrolytic capacitor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Capacitor element 2 Anode electrode foil 3 Cathode electrode foil 4 Lead wire for anode drawing 5 Lead wire for cathode drawing 6 Round bar part 7 Flat part 8 External connection part 9 Sealing body 10 Outer case 11 Separator 12 Insertion part

──────────────────────────────────────────────────続 き Continued on front page (51) Int.Cl. ⁶ Identification code FI H01G 9/10 C

Claims (6)

[Claims] 1. An anode electrode foil provided with anode extraction means,
A capacitor element formed by winding a cathode electrode foil provided with a cathode extraction means and a separator through a separator is impregnated with an electrolytic solution containing a quaternary salt of a cyclic amidine compound, and the capacitor element is formed into a bottomed cylindrical casing. In an electrolytic capacitor that is housed in a case and the opening end of the outer case is sealed with a sealing body, a ceramic coating layer is formed on a contact portion of the cathode extraction means with the sealing body. Electrolytic capacitor. 2. The method according to claim 1, wherein the cathode extraction means includes an aluminum conductor including a round bar portion and a flat portion, and the ceramic coating layer is formed on the round bar portion in advance of a capacitor manufacturing process. Electrolytic capacitor. 3. The ceramic coating layer is made of Al _2
2. The electrolytic capacitor according to claim 1, wherein the electrolytic capacitor is formed using a coating agent composed of a metal alkoxide ceramic using one or two or more selected from O ₃ , SiO ₂ and ZrO ₂ . 4. The anode extraction means includes a round bar portion made of aluminum and a flat connection portion, and an insulating layer made of aluminum oxide covers at least substantially the entire surface of the round bar portion. Electrolytic capacitors. 5. The electrolytic capacitor according to claim 1, wherein the electrolytic solution contains an oxidizing agent. 6. The electrolytic capacitor according to claim 5, wherein the oxidizing agent is a nitro compound.