JP4866586B2 - Electrolytic capacitor and electrolytic capacitor manufacturing method - Google Patents

Description

  The present invention relates to an electrolytic capacitor and a method of manufacturing an electrolytic capacitor, and more particularly to a method including a step of repairing and forming a capacitor element after forming the capacitor element and before impregnating with the electrolytic solution, and an electrolytic capacitor manufactured thereby. .

  Electrolytic capacitors are characterized by having a large capacitance while being small, and are often used for low-frequency filters and bypasses. The electrolytic capacitor generally has a structure as shown in FIGS. That is, a strip-like high-purity aluminum foil is chemically or electrochemically etched to increase the surface area of the aluminum foil (surface expansion treatment), and this aluminum foil is used in a chemical conversion solution such as an ammonium borate aqueous solution. The anode electrode foil 2 formed with an oxide film layer on the surface by chemical conversion treatment and the cathode electrode foil 3 made of high-purity aluminum foil subjected only to the etching treatment through a separator 11 made of manila paper or the like To form the capacitor element 1. The 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, the anode electrode foil 2 and the cathode electrode foil 3 have lead wires 4 and 5 as electrode drawing means for drawing the anode and cathode electrodes to the outside, respectively, such as stitching and ultrasonic welding. Connected by. The lead wires 4 and 5 are composed of a round bar portion 6 made of aluminum and a connecting portion 7 that comes into contact with the bipolar electrode foils 2 and 3 provided at the tip of the round bar portion, and further to the other tip of the round bar portion 6. The external connection portion 8 made of a solderable metal is fixed by means such as welding.

  In an electrolytic capacitor, the electrolyte, cathode, and anode are all important components that have a significant effect on the characteristics, but conventionally, studies have been made on improving the characteristics of the electrolytic capacitor, focusing on improvements in the electrolyte and the cathode. I came.

Specifically, for electrolytes, it has been found that electrolytes containing tetrafluoroaluminate ions are effective in reducing impedance, thermal stability and heat resistance of electrolytic capacitors. (For example, refer to Patent Document 1).

  In addition, regarding the cathode, the problem of liquid leakage due to the natural immersion potential of the cathode electrode foil and the cathode extraction means has been pointed out, and various improved techniques have been proposed to solve this (for example, patents) References 2 and 3).

  In addition, in the electrolytic capacitor manufacturing process, the oxide film on the surface of the anode electrode foil is damaged when the lead wire is connected, or the oxide film is cracked due to mechanical stress on the electrode foil in the winding process. , There are unique problems. This damage to the oxide film can lead to deterioration of the characteristics of the electrolytic capacitor.

However, in an ordinary electrolytic capacitor, the electrolytic solution itself has a function of forming a damaged portion of the oxide film. Therefore, if the outer case is sealed and the electrolytic capacitor is assembled and then re-converted into the electrolytic solution, the electrolytic solution is damaged. Was repaired and such problems were supposed to be solved. Therefore, the anode is a conventional anode and has sufficient performance, and has not received much attention.
JP 2003-142346 A JP 2004-165206 A JP 2004-165207 A

  As the inventors proceeded with research on electrolytic capacitors in combination with the above-described electrolytic solution containing tetrafluoroaluminate ions, it has been sufficient in the past to perform re-formation after assembling the electrolytic capacitor. The repair of the oxide film on the foil surface is not always sufficient, which can lead to problems such as the occurrence of liquid leakage from the anode, and it has been found that solving this problem is useful for further improving the characteristics of electrolytic capacitors. The present invention has been completed.

  The present invention includes (1) a step of forming a capacitor element by winding an anode electrode foil provided with an anode electrode extraction means and a cathode electrode foil provided with a cathode electrode extraction means via a separator; (2) a capacitor A step of immersing the element in a chemical conversion solution and performing a repair conversion; (3) optionally a step of cleaning and drying the capacitor element; (4) a step of impregnating the capacitor element with an electrolyte; and (5) an exterior of the capacitor element. The present invention relates to a method for manufacturing an electrolytic capacitor including a step of sealing in a case and sealing an opening of an exterior case with a sealing body, and also relates to an electrolytic capacitor obtained by this manufacturing method.

  According to the manufacturing method of the present invention, an electrolytic capacitor in which liquid leakage from the anode is remarkably suppressed can be obtained. In addition, although the manufacturing method of this invention is especially effective for the electrolytic capacitor using the electrolyte solution containing a tetrafluoroaluminate ion, it is not limited to this.

  As shown in FIG. 3, the electrolytic capacitor according to the present invention includes: (1) Capacitor element formation → (2) Repair formation → (3) In some cases, cleaning and drying → (4) Electrolyte impregnation → (5) Exterior case It can be manufactured by a manufacturing process called insertion and sealing. Hereinafter, this manufacturing process will be described as an example.

(1) Capacitor element formation The method for forming the capacitor element is not particularly limited, and for example, the anode electrode foil and the cathode electrode foil can be formed by winding them through a separator. The anode electrode foil and the cathode electrode foil are respectively provided with an anode electrode extraction means and a cathode electrode extraction means.

[Anode electrode foil]
The anode electrode foil is not particularly limited. For example, after an aluminum foil having a purity of 99.9% or more is subjected to a surface expansion treatment by chemical or electrochemical etching in an acidic solution, ammonium dihydrogen phosphate or phosphorous is used as an electrolyte. Chemical conversion treatment in phosphoric acid-based chemicals containing diammonium oxyhydrogen, boric acid-based chemicals containing ammonium borate, adipic acid-based chemicals containing ammonium adipate, etc. The one formed with an aluminum oxide film layer can be used.

[Cathode electrode foil]
The cathode electrode foil is not particularly limited, and for example, a material obtained by etching an aluminum foil having a purity of 99.9% or more can be used similarly to the anode electrode foil. Moreover, the cathode electrode foil which formed the film which consists of 1 type (s) or 2 or more types of a metal nitride or a metal in part or all of the surface of a cathode electrode foil can also be used. Such a cathode electrode foil is described in, for example, Japanese Patent Application Laid-Open No. 2004-165203. Specifically, examples of the metal nitride include titanium nitride, zirconium nitride, tantalum nitride, niobium nitride, and the like. Examples of the metal include titanium, zirconium, tantalum, niobium, and the like. The thickness of the film is 0.02. -0.1 micrometer is mentioned. Furthermore, a cathode electrode foil made of aluminum having a purity of less than 99.9% containing one or more of copper, iron, manganese, tin, and titanium can be used, and in particular, a cathode lead having a purity of 99.9% or more. Preferred in combination with means. Such a cathode electrode foil is described in, for example, Japanese Patent Application Laid-Open No. 2004-165204.

[Separator]
The separator is not particularly limited, and paper such as manila paper or kraft paper can be used. Moreover, nonwoven fabrics, such as glass fiber, a polypropylene, and polyethylene, can also be used for a separator.

(Electrode extraction means)
The electrode drawing means is not particularly limited, and can be provided, for example, by connecting lead wires by a known means such as stitching or ultrasonic welding. More specifically, first, an aluminum conductor including a first portion and a second portion formed by cutting an aluminum wire material that is intermittently pressed into a predetermined size is formed, and then a chemical conversion treatment is performed. Then, an anodized film is formed on the surface. Usually, the first part is a round bar part and the second part is a connection part. Thereafter, an external connection portion made of a copper-plated steel wire (CP wire) is welded to the end face of the aluminum conductor to form a lead wire, and the second portion of the lead wire is formed on the electrode foil by stitching or It can be mechanically connected by sonic welding or the like. For the electrode drawing means, aluminum having a purity of 99.9% or more can be used. From the viewpoint of preventing liquid leakage, the electrode foil preferably has the same or higher purity than the electrode foil.

  From the viewpoint of improving the liquid leakage characteristics of the electrolytic capacitor, the cathode electrode lead-out means is provided with a ceramic coating layer and / or an insulating synthetic resin at the contact portion with the sealing body when the capacitor element is inserted into the outer case and sealed. It is preferably processed so that the layer is present. Such a cathode electrode lead-out means is described in, for example, Japanese Patent Application Laid-Open Nos. 2004-165206 and 2004-165207.

  The ceramic coating layer on the cathode electrode lead-out means is formed by, for example, discharging and coating a coating agent made of a metal alkoxide ceramic on the first portion of an aluminum conductor having an anodized film formed on the surface as described above, and then performing a heat treatment. Then, after the coating agent is discharged and coated again, it can be formed by heat treatment again.

Examples of the ceramic used for the metal alkoxide ceramic include Al ₂ O ₃ , SiO ₂ , ZrO ₂ , TiO ₂ , MgO, H ₂ BO ₃ , Cr ₂ O ₃ , BaTiO ₃ , PbTiO ₃ , and KTaO ₃ . The ceramic used here is preferably one or more selected from Al ₂ O ₃ , SiO ₂ and ZrO ₂ in view of coating characteristics, and further considering the strength. It is preferable to use a mixture of Al ₂ O ₃ and SiO ₂ .

  In forming the insulating synthetic resin layer on the cathode lead-out means, as the insulating synthetic resin material, for example, thermosetting resins such as epoxy, phenol, furan, melamine, xylene, guanamine resin, fluorine, butadiene, Thermoplastic resins such as polyamide, polyamideimide, polyarylate, polyimide, polyetherimide, polyetheretherketone, polycarbonate, polyvinyl formal, polyphenylene sulfide, liquid crystal polymer, ketone, coumarone, and MBS resin can be used. These materials may be used in combination with a coupling agent such as silane or titanate at a ratio of 10% by weight or less.

  For example, the insulating synthetic resin layer layer may be formed after the coupling agent layer is formed by applying and drying the coupling agent on the first portion of the aluminum conductor having the anodized film formed on the surface as described above, or after coupling. It can be formed by applying a coating agent made of a liquid melt of an insulating synthetic resin adjusted by heating or an appropriate solvent without applying the agent, followed by drying. Alternatively, the first portion may be formed by molding a heat-meltable synthetic resin film, and then heat-treated.

  In the present invention, it is preferable from the viewpoint of prevention of liquid leakage to perform not only the cathode drawing means but also the anode drawing means to form the ceramic coating layer or the insulating synthetic resin layer. These layers can have a thickness of 5 to 30 μm, preferably 10 to 20 μm.

(2) Restoration formation Next, the capacitor element is impregnated with a formation solution to carry out restoration formation. Thereby, cracks and damaged parts of the oxide film layer can be repaired.

[Chemical solution for restoration conversion]
There is no particular limitation on the chemical conversion liquid for restoration conversion, and a chemical conversion liquid conventionally used for chemical conversion of an anode electrode foil can be used. Specifically, as an electrolyte, phosphoric acid-based chemical conversion liquid containing ammonium dihydrogen phosphate or diammonium hydrogen phosphate, boric acid-based chemical conversion liquid including ammonium borate, adipic acid including ammonium adipate, etc. Examples of the chemical conversion liquid of the system. Especially, it is preferable to use a phosphoric acid type | system | group chemical conversion liquid from a water-resistant point. The concentration of the chemical conversion liquid can also be the concentration of the chemical conversion liquid conventionally used for chemical conversion of the anode electrode foil, for example, an aqueous solution containing 0.01 to 1% by weight of electrolyte. In addition, the chemical conversion liquid for restoration chemical conversion may be the same as or different from the chemical conversion liquid used for chemical conversion of the anode electrolytic foil of the capacitor element.

[Means for restoration formation]
The restoration conversion can be performed, for example, by impregnating a capacitor element with a conversion solution and then applying a voltage to the anode. The voltage is preferably higher than the rated voltage and lower than the anode electrode foil formation voltage. Moreover, chemical formation time can be 5 to 120 minutes, for example.

(3) Cleaning and drying The capacitor element that has been repaired and formed is optionally cleaned and dried. The means for washing and drying is not particularly limited.

(4) Electrolyte impregnation Next, the capacitor element is impregnated with the electrolytic solution.

[Electrolyte]
The electrolytic solution is not particularly limited, and an electrolytic solution used for an aluminum electrolytic capacitor can be used. In particular, the present invention is effective in combination with an electrolytic solution containing tetrafluoroaluminate ions. This is because with conventional electrolytic capacitors using an electrolytic solution containing tetrafluoroaluminate ions, re-forming after assembling the conventional electrolytic capacitor, the film is difficult to repair, and liquid leakage is also seen from the anode. is there. The reason why the oxide film is difficult to repair is not clear, but it is presumed that the electrolyte-derived component of the electrolytic solution enters the damaged portion of the anode electrode foil. The liquid leakage from the anode is considered to be caused by the fact that the aluminum portion is exposed because the anode electrode foil is damaged, and as a result, the electrode potential of the anode electrode foil in the electrolyte becomes a lower potential than the anode extraction means. It is done. In the present invention, before impregnating the capacitor element with the electrolytic solution containing tetrafluoroaluminate ions, the capacitor element is immersed in a conversion solution other than the conversion solution containing tetrafluoroaluminate ions to damage the anode electrode foil. It is presumed that by repairing by restoration conversion, the electrode potential of the anode electrode foil is prevented from becoming a lower potential than that of the anode drawing means, and thus liquid leakage is suppressed.

An electrolytic solution containing tetrafluoroaluminate is described in, for example, Japanese Patent Application Laid-Open No. 2003-142346. Specifically, it is an electrolytic solution in which tetrafluoroaluminate ions (AlF ₄ ⁻ ) are used for all or a part of the anionic components of the electrolytic solution, and among these anionic components, tetrafluoroaluminate ions are 5 to 100. An electrolytic solution that is mol% is preferable, more preferably 30 to 100 mol%, particularly preferably 50 to 100 mol%, and most preferably 100 mol%.

  The electrolytic solution may contain tetrafluoroaluminate ions in the form of a salt, and the tetrafluoroaluminate is preferably a quaternary onium salt, an amine salt, an ammonium salt, and an alkali metal. One or more selected from the group consisting of salts.

  Preferable examples of the quaternary onium salt include quaternary ammonium salts, quaternary phosphonium salts, quaternary imidazolium salts and quaternary amidinium salts.

Preferable examples of the quaternary ammonium ion of the quaternary ammonium salt include the following.
(I) Tetraalkylammonium For example, tetramethylammonium, ethyltrimethylammonium, diethyldimethylammonium, triethylmethylammonium, tetraethylammonium, trimethyl-n-propylammonium, trimethylisopropylammonium, trimethyl-n-butylammonium, trimethylisobutylammonium, trimethyl -T-butylammonium, trimethyl-n-hexylammonium, dimethyldi-n-propylammonium, dimethyldiisopropylammonium, dimethyl-n-propylisopropylammonium, methyltri-n-propylammonium, methyltriisopropylammonium, methyldi-n-propylisopropyl Ammonium, methyl-n-propyldi Isopropylammonium, triethyl-n-propylammonium, triethylisopropylammonium, triethyl-n-butylammonium, triethylisobutylammonium, triethyl-t-butylammonium, dimethyldi-n-butylammonium, dimethyldiisobutylammonium, dimethyldi-t-butylammonium, Dimethyl-n-butylethylammonium, dimethylisobutylethylammonium, dimethyl-t-butylethylammonium, dimethyl-n-butylisobutylammonium, dimethyl-n-butyl-t-butylammonium, dimethylisobutyl-t-butylammonium, diethyldi- n-propylammonium, diethyldiisopropylammonium, diethyl-n-propylisopropyl Pyrammonium, ethyltri-n-propylammonium, ethyltriisopropylammonium, ethyldi-n-propylisopropylammonium, ethyl-n-propyldiisopropylammonium, diethylmethyl-n-propylammonium, ethyldimethyl-n-propylammonium, ethylmethyldi-n -Propylammonium, diethylmethylisopropylammonium, ethyldimethylisopropylammonium, ethylmethyldiisopropylammonium, ethylmethyl-n-propylisopropylammonium, tetra-n-propylammonium, tetraisopropylammonium, n-propyltriisopropylammonium, di-n- Propyl diisopropyl ammonium, tri-n-propyl isopropyl Le ammonium, trimethyl pentyl ammonium, trimethyl hexyl ammonium, trimethyl heptyl ammonium, trimethyl octyl ammonium, trimethyl nonyl ammonium and the like. All of these have a sum of 4 to 12 carbon atoms, but those having a sum of 13 or more carbon atoms can also be used as the electrolyte, such as trimethyldecylammonium, trimethylundecylammonium, Etc.

(Ii) Aromatic substituted ammonium Examples include those having a sum of 4 to 12 carbon atoms such as trimethylphenylammonium and those having a sum of 13 or more carbon atoms such as tetraphenylammonium.

(Iii) Aliphatic cyclic ammonium Pyrrolidinium such as N, N-dimethylpyrrolidinium, N-ethyl-N-methylpyrrolidinium, N, N-diethylpyrrolidinium, N, N-tetramethylenepyrrolidinium N, N-dimethylpiperidinium, N-ethyl-N-methylpiperidinium, N, N-diethylpiperidinium, N, N-tetramethylenepiperidinium, N, N-pentamethylenepiperidinium, etc. And morpholinium such as N, N-dimethylmorpholinium, N-ethyl-N-methylmorpholinium, N, N-diethylmorpholinium. Any of these has a sum of 4 to 12 carbon atoms, but an electrolyte having a sum of 13 or more carbon atoms can also be used.

(Iv) Ions of nitrogen-containing heterocyclic aromatic compounds For example, pyridiniums such as N-methylpyridinium, N-ethylpyridinium, Nn-propylpyridinium, N-isopropylpyridinium, Nn-butylpyridinium and the like can be mentioned. . Any of these has a sum of 4 to 12 carbon atoms, but an electrolyte having a sum of 13 or more carbon atoms can also be used.

  Preferable examples of the quaternary phosphonium ion of the quaternary phosphonium salt include tetramethylphosphonium, triethylmethylphosphonium, tetraethylphosphonium and the like. Any of these has a sum of 4 to 12 carbon atoms, but an electrolyte having a sum of 13 or more carbon atoms can also be used.

  Suitable examples of the quaternary imidazolium ion of the quaternary imidazolium salt include 1,3-dimethylimidazolium, 1,2,3-trimethylimidazolium, 1-ethyl-3-methylimidazolium, 1- Ethyl-2,3-dimethylimidazolium, 1,3-diethylimidazolium, 1,2-diethyl-3-methylimidazolium, 1,3-diethyl-2-methylimidazolium, 1,2-dimethyl-3- n-propylimidazolium, 1-n-butyl-3-methylimidazolium, 1,2,4-trimethyl-3-n-propylimidazolium, 1,2,3,4-tetramethylimidazolium, 1,2 , 3,4,5-pentamethylimidazolium, 2-ethyl-1,3-dimethylimidazolium, 1,3-dimethyl-2-n-propylimidazole 1,3-dimethyl-2-n-pentylimidazolium, 1,3-dimethyl-2-n-heptylimidazolium, 1,3,4-trimethylimidazolium, 2-ethyl-1,3,4 Trimethylimidazolium, 1,3-dimethylbenzimidazolium, 1-phenyl-3-methylimidazolium, 1-benzyl-3-methylimidazolium, 1-phenyl-2,3-dimethylimidazolium, 1-benzyl-2 , 3-dimethylimidazolium, 2-phenyl-1,3-dimethylimidazolium, 2-benzyl-1,3-dimethylimidazolium, and the like. These are all quaternary imidazoliums having 4 to 12 carbon atoms.

  In addition, a quaternary imidazolium having a sum of 13 or more carbon atoms can also be used for the electrolytic solution. Preferred examples include 1,3-dimethyl-2-n-undecylimidazolium, 1, Examples include 3-dimethyl-2-n-heptadecylimidazolium. In addition, a quaternary imidazolium containing a hydroxyl group or an ether group can also be used in the electrolytic solution. As a suitable example, 2- (2′-hydroxy) ethyl-1,3-dimethylimidazolium is used. 1- (2′-hydroxy) ethyl-2,3-dimethylimidazolium, 2-ethoxymethyl-1,3-dimethylimidazolium, 1-ethoxymethyl-2,3-dimethylimidazolium and the like. .

  Preferable examples of the quaternary amidinium include 1,3-dimethylimidazolinium, 1,2,3-trimethylimidazolinium, 1-ethyl-3-methylimidazolinium, 1-ethyl-2,3- Dimethylimidazolinium, 1,3-diethylimidazolinium, 1,2-diethyl-3-methylimidazolinium, 1,3-diethyl-2-methylimidazolinium, 1,2-dimethyl-3-n- Propylimidazolinium, 1-n-butyl-3-methylimidazolinium, 1,2,4-trimethyl-3-n-propylimidazolinium, 1,2,3,4-tetramethylimidazolinium, 2 -Ethyl-1,3-dimethylimidazolinium, 1,3-dimethyl-2-n-propylimidazolinium, 1,3-dimethyl-2-n-pentylimidazoli 1,3-dimethyl-2-n-heptylimidazolinium, 1,3,4-trimethylimidazolinium, 2-ethyl-1,3,4-trimethylimidazolinium, 1-phenyl-3-methyl Imidazolinium, 1-benzyl-3-methylimidazolinium, 1-phenyl-2,3-dimethylimidazolinium, 1-benzyl-2,3-dimethylimidazolinium, 2-phenyl-1,3-dimethyl Imidazolinium such as imidazolinium and 2-benzyl-1,3-dimethylimidazolinium; 1,3-dimethyltetrahydropyrimidinium, 1,3-diethyltetrahydropyrimidinium, 1-ethyl-3-methyltetrahydro Pyrimidinium, 1,2,3-trimethyltetrahydropyrimidinium, 1,2,3-triethyltetrahi Ropyrimidinium, 1-ethyl-2,3-dimethyltetrahydropyrimidinium, 2-ethyl-1,3-dimethyltetrahydropyrimidinium, 1,2-diethyl-3-methyltetrahydropyrimidinium, 1,3-diethyl- Tetrahydro such as 2-methyltetrahydropyrimidinium, 5-methyl-1,5-diazabicyclo [4.3.0] nonenium-5, 8-methyl-1,8-diazabicyclo [5.4.0] undecenium-7 Mention may be made of pyrimidinium. These are all quaternary amidinium having 4 to 12 carbon atoms.

  In addition, a quaternary amidinium having a sum of 13 or more carbon atoms can also be used for the electrolytic solution. Preferred examples include 1,3-dimethyl-2-n-undecylimidazolinium, 1, 3-dimethyl-2-n-heptadecylimidazolinium and the like can be mentioned. Further, a quaternary amidinium containing a hydroxyl group or an ether group can also be used for the electrolytic solution, and a suitable example is 2- (2′-hydroxy) ethyl-1,3-dimethylimidazolinium. 1- (2′-hydroxy) ethyl-2,3-dimethylimidazolinium, 2-ethoxymethyl-1,3-dimethylimidazolinium, 1-ethoxymethyl-2,3-dimethylimidazolinium, etc. be able to.

In addition to the quaternary onium salt, the electrolytic solution can contain an amine salt, an ammonium salt (NH ₄ ⁺ AlF ₄ ⁻ ), and a tetrafluoroaluminate ion as an alkali metal salt.

  Preferable examples of the amine salt include trimethylamine, ethyldimethylamine, diethylmethylamine, triethylamine, pyridine, N-methylimidazole, 1,5-diazabicyclo [4.3.0] nonene-5, 1,8- And tertiary amines such as diazabicyclo [5.4.0] unden-7. In addition to the above tertiary amines, primary amines and secondary amines can be used, for example, diethylamine, diisopropylamine, isobutylamine, di-2-ethylhexylamine, pyrrolidine, piperidine, morpholine. , Hexamethyleneimine, ethylamine, n-propylamine, isopropylamine, t-butylamine, sec-butylamine, 2-ethylhexylamine, 3-methoxypropylamine, 3-ethoxypropylamine and the like. Preferable examples of the alkali metal include lithium, sodium, potassium, rubidium, cesium and the like.

  Among these cationic components, from the viewpoint of obtaining an electrolytic solution having a high electrical conductivity, a quaternary onium having a sum of 4 to 12 carbon atoms is preferable, among which tetraethylammonium, triethylmethylammonium, diethyldimethylammonium, Ethyltrimethylammonium, tetramethylammonium, N, N-dimethylpyrrolidinium, N-ethyl-N-methylpyrrolidinium, 1,3-dimethylimidazolium, 1,2,3-trimethylimidazolium, 1-ethyl- 3-methylimidazolium, 1-ethyl-2,3-dimethylimidazolium, 1,2,3,4-tetramethylimidazolium, 1,3-diethylimidazolium, 2-ethyl-1,3-dimethylimidazolium 1,3-dimethyl-2-n-propylimidazolium 1,3-dimethyl-2-n-pentylimidazolium, 1,3-dimethyl-2-n-heptylimidazolium, 1,3,4-trimethylimidazolium, 2-ethyl-1,3,4-trimethylimidazolium 1,3-dimethylbenzimidazolium, 1-phenyl-3-methylimidazolium, 1-benzyl-3-methylimidazolium, 1-phenyl-2,3-dimethylimidazolium, 1-benzyl-2,3 -Dimethylimidazolium, 2-phenyl-1,3-dimethylimidazolium, 2-benzyl-1,3-dimethylimidazolium, 1,3-dimethylimidazolinium, 1,2,3-trimethylimidazolium, 1 -Ethyl-3-methylimidazolinium, 1-ethyl-2,3-dimethylimidazolinium, 1,2,3,4 Tetramethylimidazolinium, 1,3-diethylimidazolinium, 2-ethyl-1,3-dimethylimidazolinium, 1,3-dimethyl-2-n-propylimidazolinium, 1,3-dimethyl-2 -N-pentylimidazolinium, 1,3-dimethyl-2-n-heptylimidazolinium, 1,3,4-trimethylimidazolinium, 2-ethyl-1,3,4-trimethylimidazolinium, 1 -Phenyl-3-methylimidazolinium, 1-benzyl-3-methylimidazolinium, 1-phenyl-2,3-dimethylimidazolinium, 1-benzyl-2,3-dimethylimidazolinium, 2-phenyl One or more selected from the group consisting of -1,3-dimethylimidazolinium and 2-benzyl-1,3-dimethylimidazolinium And more preferably 1-ethyl-2,3-dimethylimidazolinium and 1,2,3,4-tetramethylimidazolinium.

  The electrolyte solution may contain an anionic component other than tetrafluoroaluminate ions. Specific examples of these include, for example, fluorine-containing inorganic ions tetrafluoroborate ions, hexafluorophosphate ions, hexafluorohyphenates. Fluorine-containing inorganic ions such as acid ion, hexafluoroantimonate ion, hexafluoroniobate ion and hexafluorotantalate ion; carboxylate ions such as phthalate ion, maleate ion, salicylate ion, benzoate ion and adipate ion Sulfonic acid ions such as benzenesulfonic acid ion, toluenesulfonic acid ion, dodecylbenzenesulfonic acid ion, trifluoromethanesulfonic acid ion and perfluorobutanesulfonic acid; inorganic oxo acid ions such as boric acid ion and phosphate ion; bis Can be exemplified trifluoromethanesulfonyl) imide ion, bis (pentafluoroethane sulfonyl) imide ion, tris (trifluoromethanesulfonyl) Mechidoion, perfluoroalkyl borate ions, the perfluoroalkyl phosphate ions. As the salt, hydrogen phthalate, hydrogen maleate and the like can be used in combination. For example, when tetrafluoroaluminate, hydrogen phthalate, hydrogen maleate, etc. are used in combination, it is preferable that tetrafluoroaluminate is the main component, and the tetrafluoroaluminate is based on the total weight of the salt. It is preferably 50% by weight or more, more preferably 60% by weight or more, still more preferably 70% by weight or more, and the higher the ratio, the more preferable.

  When tetrafluoroaluminate is used for an electrolytic capacitor, it needs to have a high purity. Therefore, if necessary, the salt is used after being purified to a desired purity by recrystallization or solvent extraction.

  The concentration of tetrafluoroaluminate in the electrolytic solution is preferably 5 to 40% by weight, more preferably 10 to 35% by weight. This is because the electrical conductivity is low when the concentration is too low, and when the concentration is too high, the viscosity of the electrolytic solution increases and precipitation of salt at low temperatures is likely to occur. Generally, the withstand voltage of the electrolytic solution for electrolytic capacitors tends to increase as the concentration decreases, so that the optimum concentration can be determined according to the desired rated voltage of the capacitor. However, the electrolytic solution may be a concentrated solution containing 50% or more of a salt or a room temperature molten salt.

  The electrolytic solution preferably contains 50% by weight or more of a solvent from the viewpoint of obtaining an electrolytic solution having further excellent electrical conductivity, thermal stability, and voltage resistance. Examples of the solvent include one or more selected from the group consisting of carbonate ester, carboxylate ester, phosphate ester, nitrile, amide, sulfone, alcohol, and water. However, when used as an electrolyte, the solvent is stable over time. It is preferred to select from carbonates, carboxylic esters, phosphates, nitriles, amides, sulfones and alcohols that tend to exhibit the desired properties. When water is used as the solvent, it is preferably used as a part of the solvent in combination with other solvents.

  Specific examples of such solvents include the following. Chain carbonate (eg, chain carbonate such as dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, diphenyl carbonate, methyl phenyl carbonate), cyclic carbonate (eg, ethylene carbonate, propylene carbonate, 2,3-dimethyl ethylene carbonate) Carbonate esters such as butylene carbonate, vinylene carbonate, cyclic carbonate esters such as 2-vinylethylene carbonate); aliphatic carboxylic acid esters (for example, methyl formate, methyl acetate, methyl propionate, ethyl acetate, propyl acetate, butyl acetate, Amyl acetate, etc.), aromatic carboxylic acid esters (eg, aromatic carboxylic acid esters such as methyl benzoate and ethyl benzoate), lactones (eg, γ-butyrolactone, γ-valerolactone, δ-valerolactone, etc.), etc. Carboxylic acid ester; trimethyl phosphate, ethyl phosphate Phosphate esters such as dimethyl, diethylmethyl phosphate and triethyl phosphate; Nitriles such as acetonitrile, propionitrile, methoxypropionitrile, glutaronitrile, adiponitrile, 2-methylglutaronitrile; N-methylformamide, N- Amides such as ethylformamide, N, N-dimethylformamide, N, N-dimethylacetamide, N-methylpyrrolidinone; dimethylsulfone, ethylmethylsulfone, diethylsulfone, sulfolane, 3-methylsulfolane, 2,4-dimethylsulfolane, etc. Sulfone; Alcohol such as ethylene glycol, propylene glycol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether; ethylene glycol dimethyl ether, ethylene glycol di Ethers such as tilether, 1,4-dioxane, 1,3-dioxolane, tetrahydrofuran, 2-methyltetrahydrofuran, 2,6-dimethyltetrahydrofuran, tetrahydropyran; sulfoxides such as dimethyl sulfoxide, methylethyl sulfoxide, diethyl sulfoxide; 1,3 -Dimethyl-2-imidazolidinone, 1,3-dimethyl-3,4,5,6-tetrahydro-2 (1H) -pyrimidinone, 3-methyl-2-oxazolidinone and the like can be mentioned.

  In addition, from the viewpoint of obtaining an electrolytic solution that is more excellent in conductivity, a non-aqueous solvent having a relative dielectric constant (ε, 25 ° C.) of 25 or more can be preferably used as the solvent. A non-aqueous solvent having a flash point of 70 ° C. or higher can also be preferably used.

  From the standpoint of obtaining an electrolyte with better thermal stability, a solvent having a boiling point of 250 ° C. or higher, a melting point of −60 to 40 ° C., and a dielectric constant (ε, 25 ° C.) of 25 or higher is 25 It is preferably contained in an amount of not less than 50% by weight, more preferably not less than 40% by weight, particularly preferably not less than 50% by weight. Examples of such a solvent include sulfone, and sulfolane and 3-methylsulfolane are particularly preferable. By using such a solvent in combination with the electrolytic solution, it is possible to obtain an electrolytic capacitor with a low impedance and a high withstand voltage that guarantees an operation at an environmental temperature of 110 to 150 ° C. for 1000 hours or more.

  Further, from the viewpoint of obtaining a lower impedance electrolytic capacitor, a solvent having a boiling point of 190 ° C. or higher, lower than 250 ° C., a melting point of −60 to 40 ° C., and a dielectric constant (ε, 25 ° C.) of 25 or higher is used. The content is preferably 25% by weight or more, more preferably 40% by weight or more, and particularly preferably 50% by weight or more. Examples of such solvents include carbonic acid esters, carboxylic acid esters, phosphoric acid esters, nitriles, amides and alcohols, with γ-butyrolactone and ethylene glycol being particularly preferred. By using such a solvent in combination with the electrolytic solution, an electrolytic capacitor with extremely low impedance and high voltage can be obtained.

  As a particularly preferable electrolytic solution, from the viewpoint of thermal stability, the solvent is sulfolane, and 1-ethyl-2,3-dimethylimidazolinium tetrafluoroaluminate or 1,2,3,4-tetramethyltetrafluoroaluminate. An electrolytic solution for electrolytic capacitors in which imidazolinium is added at 5 to 40% by weight with respect to the total weight of the electrolytic solution is mentioned. From the point that a low impedance electrolytic capacitor can be obtained, the solvent is γ-butyrolactone. Yes, 1-ethyl-2,3-dimethylimidazolinium tetrafluoroaluminate or 1,2,3,4-tetramethylimidazolinium tetrafluoroaluminate is used in an amount of 5-40 with respect to the total weight of the electrolyte. Examples thereof include an electrolytic solution for electrolytic capacitors added by weight%. However, a solvent using both sulfolane and γ-butyrolactone is also preferred.

  In addition to the salt and the solvent, various additives may be used in the electrolytic solution. The purpose of adding additives to the electrolyte is diverse, including improving electrical conductivity, improving thermal stability, suppressing electrode deterioration due to hydration and dissolution, suppressing gas generation, improving withstand voltage, improving wettability, etc. Can be mentioned. Although content of an additive is not specifically limited, It is preferable that it is the range of 0.1-20 weight%, and it is more preferable that it is the range of 0.5-10 weight%.

  In addition, it is preferable to mix | blend various additives with electrolyte solution in order to further improve the liquid leakage prevention from an anode.

  As the additive, one or more compounds selected from the group consisting of phthalimides, quinolines, dioximes, nitrophenols, and amino group-containing aromatic carboxylic acids can be used. Moreover, the 1 type, or 2 or more types of compound selected from the group which consists of an aluminum complex, boric acid ester, and silicate ester can also be used. Furthermore, 1 type, or 2 or more types selected from the group which consists of a monocyclic quinone compound and a bicyclic quinone compound can also be used. One or two quinone compounds having three or more rings can also be used. These are preferably 0.1 to 5% by weight in the total weight of the electrolytic solution.

(5) Insertion / sealing into outer case The capacitor element impregnated with the electrolytic solution is inserted into the outer case, and the opening of the case is sealed. For example, it is housed in an outer case made of bottomed cylindrical aluminum, a sealing body made of butyl rubber is inserted into the opening end of the outer case, and the end of the outer case is further drawn to seal the electrolytic capacitor. Thus, an aluminum electrolytic capacitor can be obtained. It is more preferable to coat the surface of the sealing body with a resin such as a fluororesin or to attach a plate such as a phenol resin because the permeability of the solvent vapor is reduced. The electrolytic capacitor thus obtained can then be subjected to re-chemical conversion as necessary.

  The present invention will be described more specifically with reference to the following examples. The scope of the present invention is not limited by these examples, and materials, amounts used, ratios, operations, and the like in the examples can be changed as appropriate without departing from the spirit of the present invention.

[Example 1]
The electrolytic capacitor of the example was manufactured as follows.
The anode electrode foil and the cathode electrode foil were wound through a separator to form a capacitor element having a rating of 6.3 V-220 μF and an element shape (φ6.3 × 6 L).

  As a cathode electrode extraction means and an anode electrode extraction means, a lead wire comprising 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 is used. Got ready. The lead wire connecting portion and the round bar portion are made of 99.9% aluminum, and the external connecting portion is made of CP wire. These lead wires were connected to the bipolar electrode foil at the connection portion.

  As the anode electrode foil, an aluminum foil having a purity of 99.9% was etched and subjected to a surface expansion treatment, and then a chemical conversion treatment was performed to form an anodized film layer on the surface. A 9% aluminum foil etched in the same manner as the anode electrode foil was used.

  Next, the capacitor element was immersed in an aqueous solution of ammonium dihydrogen phosphate (0.5 wt%) that is a chemical conversion solution, and a voltage of 9 V was applied for 60 minutes to perform restoration conversion.

  The capacitor element after the repair conversion was washed with pure water at 90 ° C. for 30 minutes, and then dried at 100 ° C. for 2 hours.

  Thereafter, the capacitor element is impregnated with an electrolytic solution (electrolytic solution having a concentration of 25% by weight of 1-ethyl-2,3-dimethylimidazolinium tetrafluoroaluminate dissolved in γ-butyrolactone), and has a bottomed cylindrical shape. It was housed in an exterior case made of aluminum, and a sealing body made of peroxide-vulcanized butyl rubber was attached to the opening of the exterior case, and the exterior case was sealed by redrawing at the end of the exterior case and re-formed. Thereafter, an electrolytic capacitor of Example 1 was obtained.

[Comparative Example 1]
After forming the capacitor element in the same manner as in Example 1, the electrolytic capacitor of Comparative Example 1 was obtained after impregnating with the electrolytic solution without carrying out restoration conversion, inserting into the outer case, sealing, and re-forming. .

[Measurement of liquid leakage]
Moreover, about the electrolytic capacitor of Example 1 and Comparative Example 1, the liquid leak condition was measured. The measuring method is as follows. The electrolytic capacitor was allowed to stand at 85 ° C./85% RH for 500 hours and 750 hours, and then liquid leakage was determined based on EIAJ RC-2372 Appendix 2 “Criteria”. The liquid leakage corresponds to the determination of C and D of the same criterion.

  From these results, it can be seen that according to the electrolytic solution of the present invention, liquid leakage is suppressed on both the cathode side and the anode side of the electrolytic capacitor.

It is an internal sectional view showing the structure of an electrolytic capacitor. It is a disassembled perspective view which shows the structure of a capacitor | condenser element. It is a figure which shows the manufacturing process of the electrolytic capacitor by this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Capacitor element 2 Anode electrode foil 3 Cathode electrode foil 4 Lead wire for anode extraction 5 Lead wire for cathode extraction 6 Round bar portion 7 Connection portion 8 External connection portion 9 Sealing body 10 Exterior case 11 Separator

Claims (8)

(1) A capacitor element is formed by winding an anode electrode foil provided with an anode electrode extraction means, having an oxide film layer formed on the surface thereof, and a cathode electrode foil provided with a cathode electrode extraction means via a separator. Process;
(2) A step of repairing and forming an anode electrode foil in which a capacitor element is immersed in a chemical conversion solution other than a chemical conversion solution containing tetrafluoroaluminate ions and an oxide film layer is formed on the surface thereof;
(3) washing and drying the capacitor element;
(4) impregnating a capacitor element with an electrolytic solution containing tetrafluoroaluminate ions; and (5) an electrolytic capacitor including a step of sealing the capacitor element in an outer case and sealing the opening of the outer case with a sealing body. Manufacturing method.   The method for producing an electrolytic capacitor according to claim 1, wherein the chemical conversion liquid contains ammonium dihydrogen phosphate, diammonium hydrogen phosphate, ammonium borate, or ammonium adipate as an electrolyte.   The cathode electrode foil has one or more metal nitrides selected from the group consisting of titanium nitride, zirconium nitride, tantalum nitride and niobium nitride on the surface of the aluminum foil, and / or the group consisting of titanium, zirconium, tantalum and nickel. The manufacturing method of the electrolytic capacitor of Claim 1 or 2 formed by providing the 0.02-0.1 micrometer layer containing 1 or more types of the metal selected from more.   The cathode electrode foil is aluminum having a purity of less than 99.9% containing at least one selected from the group consisting of copper, iron, manganese, tin and titanium, and the cathode drawing means is aluminum having a purity of 99.9% or more. The manufacturing method of the electrolytic capacitor of Claim 1 or 2.   The method for producing an electrolytic capacitor according to any one of claims 1 to 4, wherein the cathode electrode extraction means forms a ceramic coating layer and / or an insulating synthetic resin layer at a contact portion with the sealing body.   The method for producing an electrolytic capacitor according to any one of claims 1 to 5, wherein the anode electrode lead-out means forms a ceramic coating layer and / or an insulating synthetic resin layer at a contact portion with the sealing body.   The electrolytic solution contains tetrafluoroaluminate ions in the form of one or more salts selected from the group consisting of quaternary onium salts, amine salts, ammonium salts and alkali metal salts of tetrafluoroaluminate. The manufacturing method of the electrolytic capacitor of any one of claim | item 1 -6.   The electrolytic capacitor obtained by the manufacturing method of any one of Claims 1-7.

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