Method for manufacturing electrolytic capacitor and electrolytic capacitor

Abstract

The present invention provides a method for manufacturing an electrolytic capacitor and an electrolytic capacitor, the method comprising a first step, a second step, and a third step. In the first step, a capacitor element is formed, comprising an anode body having a dielectric layer formed on its surface, a cathode body, and a separator disposed between the anode body and the cathode body. In the second step, a treatment liquid containing an acid component and an alkaline component is impregnated into the capacitor element. In the third step, while a portion of the treatment liquid remains in the capacitor element after the second step, a conductive polymer dispersion is impregnated into the capacitor element, the conductive polymer dispersion being obtained by dispersing conductive polymer particles containing polyanions in a solvent. The pH of the treatment liquid is higher than the pH of the conductive polymer dispersion.

Description

[0001] This application is a divisional application. The application number of the parent application is 201910902466.3, the application date is September 23, 2019, and the invention title is: Method for manufacturing electrolytic capacitor and electrolytic capacitor Technical Field

[0002] The present invention generally relates to a method for manufacturing an electrolytic capacitor and an electrolytic capacitor. Specifically, the present invention relates to a method for manufacturing an electrolytic capacitor and an electrolytic capacitor, comprising the steps of forming a capacitor element and impregnating the capacitor element with a conductive polymer dispersion. Background Art

[0003] Patent Document 1 discloses a method for manufacturing a solid electrolytic capacitor. In the method, polystyrene sulfonic acid is applied to a capacitor element consisting of an anode foil and a cathode foil wound with a separator interposed therebetween. The element is then impregnated with a conductive polymer dispersion and dried to form a solid electrolyte layer. Subsequently, the gaps within the capacitor element are filled with an electrolyte solution.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2017-37950

[0007] Problems to be solved by the invention

[0008] In the production method of Patent Document 1, the conductive polymer dispersion cannot be sufficiently impregnated into the interior of the capacitor element, and therefore the conductive polymer may not be sufficiently attached to the separator. Summary of the Invention

[0009] An object of the present invention is to provide a method for producing an electrolytic capacitor and an electrolytic capacitor that facilitates impregnation of a conductive polymer dispersion into a capacitor element.

[0010] The first embodiment of the present invention comprises a method for manufacturing an electrolytic capacitor comprising a first step, a second step, and a third step. In the first step, a capacitor element is formed, comprising an anode having a dielectric layer formed on its surface, a cathode, and a separator disposed between the anode and cathode. In the second step, a treatment liquid containing an acid component and an alkaline component is impregnated into the capacitor element. In the third step, after the second step, while a portion of the treatment liquid remains in the capacitor element, the capacitor element is impregnated with a conductive polymer dispersion, the conductive polymer dispersion being obtained by dispersing conductive polymer particles containing polyanions in a solvent. The pH of the treatment liquid is higher than that of the conductive polymer dispersion.

[0011] The second embodiment of the present invention comprises a method for manufacturing an electrolytic capacitor comprising a first step, a second step, and a third step. In the first step, a capacitor element is formed, comprising an anode body having a dielectric layer formed on its surface, a cathode body, and a separator disposed between the anode body and the cathode body. In the second step, the capacitor element is impregnated with a treatment solution containing boric acid as an acid component and an alkaline component. In the third step, after the second step, the capacitor element is impregnated with a conductive polymer dispersion obtained by dispersing conductive polymer particles containing polyanions in a solvent.

[0012] A third embodiment of the present invention provides an electrolytic capacitor comprising an anode having a dielectric layer formed on its surface, a cathode, and a separator disposed between the anode and cathode. The capacitor element contains conductive polymer particles containing polyanions, and boric acid is present on the surface of the separator.

[0013] In the method for producing an electrolytic capacitor according to one embodiment of the present invention, the conductive polymer dispersion can be easily impregnated into the interior of the capacitor element. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a schematic cross-sectional view showing an example of an electrolytic capacitor according to an embodiment of the present invention.

[0015] Figure 2 This is a schematic perspective view of a capacitor element included in an electrolytic capacitor according to an embodiment of the present invention, with part of the capacitor element expanded.

[0016] Figure 3 This is a schematic enlarged view showing a state in which a solid electrolyte is formed between an anode body and a cathode body in a capacitor element according to an embodiment of the present invention. DETAILED DESCRIPTION

[0017] 1. Summary

[0018] The method for manufacturing an electrolytic capacitor 1 according to one embodiment of the present invention comprises a first step, a second step, and a third step. In the first step, a capacitor element 10 is formed, which includes an anode body 21 having a dielectric layer 210 formed on its surface, a cathode body 22, and a separator 23 provided between the anode body 21 and the cathode body 22 (see Figure 2 In the second step, the capacitor element 10 is impregnated with a treatment liquid containing an acid component and an alkali component. In the third step, after the second step, a portion of the treatment liquid remains in the capacitor element 10, and the capacitor element 10 is impregnated with a conductive polymer dispersion obtained by dispersing fine particles of a conductive polymer 250 containing a polyanion in a solvent (see Figure 3 ). The pH of the treatment liquid is higher than the pH of the conductive polymer dispersion.

[0019] The method for manufacturing an electrolytic capacitor 1 according to one embodiment of the present invention comprises a first step, a second step, and a third step. In the first step, a capacitor element 10 is formed, which includes an anode body 21 having a dielectric layer 210 formed on its surface, a cathode body 22, and a separator 23 provided between the anode body 21 and the cathode body 22 (see Figure 2 In the second step, the capacitor element 10 is impregnated with a treatment solution containing boric acid as an acid component and an alkali component. In the third step, after the second step, a portion of the treatment solution remains in the capacitor element 10, and the capacitor element 10 is impregnated with a conductive polymer dispersion obtained by dispersing fine particles of a conductive polymer 250 containing a polyanion in a solvent (see Figure 3 ).

[0020] In this embodiment, the conductive polymer dispersion is easily impregnated into capacitor element 10 by the acid component and the alkaline component in the treatment liquid.

[0021] Furthermore, by setting the pH of the treatment liquid higher than the pH of the conductive polymer dispersion, the conductive polymer dispersion can be easily impregnated into capacitor element 10 .

[0022] Furthermore, by using boric acid as the acid component of the treatment liquid, the conductive polymer dispersion can be easily impregnated into capacitor element 10 .

[0023] Therefore, according to the method for manufacturing electrolytic capacitor 1 of the present embodiment, the conductive polymer dispersion can be easily impregnated into capacitor element 10 , thereby increasing the amount of conductive polymer 250 attached to separator 23 .

[0024] 2. Details

[0025] 2-1. Electrolytic capacitors

[0026] Hereinafter, the configuration of the electrolytic capacitor 1 according to the present embodiment will be described in detail.

[0027] like Figure 1 As shown, electrolytic capacitor 1 includes capacitor element 10, bottomed case 11, sealing member 12, seat plate 13, leads 14A, 14B, and lead tabs 15A, 15B.

[0028] (1) Shell with bottom

[0029] Bottomed case 11 is configured to accommodate capacitor element 10. Specifically, bottomed case 11 is a cylindrical member with a closed bottom and an open top. Therefore, capacitor element 10 can be inserted into bottomed case 11 through the opening. Bottomed case 11 is made of, for example, one or more materials selected from aluminum, stainless steel, copper, iron, brass, and alloys thereof.

[0030] (2) Sealing components and seat plates

[0031] The opening of the bottomed housing 11 is sealed with a sealing member 12. Sealing member 12 is made of a rubber material such as EPT (ethylene-propylene terpolymer) or IIR (isobutylene-isoprene rubber), or a resin material such as epoxy resin. Sealing member 12 has a pair of through-holes. The area near the open end of the bottomed housing 11 is drawn inward and then crimped, thereby riveting sealing member 12. Furthermore, sealing member 12 is covered by a seat plate 13. Sealing plate 13 is made of, for example, an electrically insulating resin material.

[0032] (3) Leads and lead connectors

[0033] A pair of lead wires 14A and 14B are drawn out from through-holes in sealing member 12 and pass through seat plate 13. A pair of lead tabs 15A and 15B are embedded in sealing member 12. Lead tab 15A electrically connects lead wire 14A to the electrode (anode body 21) of capacitor element 10. Furthermore, lead tab 15B electrically connects lead wire 14B to the electrode (cathode body 22) of capacitor element 10.

[0034] (4) Capacitor elements

[0035] Hereinafter, capacitor element 10 housed in bottomed case 11 will be described in detail.

[0036] like Figure 2 As shown, capacitor element 10 of this embodiment is a wound body. Figure 2 The winding shown shows the Figure 1 The electrolytic capacitor 1 shown is in a state where capacitor element 10 is removed and partially expanded.

[0037] The capacitor element 10 includes an anode body 21, a cathode body 22, and a separator 23. Figure 2 As shown, lead tab 15A is electrically connected to anode body 21, and lead tab 15B is electrically connected to cathode body 22. Therefore, anode body 21 is electrically connected to lead 14A via lead tab 15A, and cathode body 22 is electrically connected to lead 14B via lead tab 15B.

[0038] Separator 23 is provided between anode body 21 and cathode body 22. Anode body 21, cathode body 22, and separator 23 are wound in this state. Separator 23 may be, for example, a nonwoven fabric containing cellulose fiber, kraft paper, polyethylene terephthalate, polyphenylene sulfide, nylon, aromatic polyamide, polyimide, polyamideimide, polyetherimide, rayon, glass, vinylon, or aramid fiber. In this embodiment, separator 23 preferably contains cellulose fiber. The outermost periphery of capacitor element 10 is secured with winding fixing tape 24.

[0039] In capacitor element 10, solid electrolyte 25 is formed between anode body 21 and cathode body 22. A schematic enlarged view showing this state is shown in FIG. Figure 3 In. Figure 3 As shown, the spacer 23 holds the solid electrolyte 25 .

[0040] (4-1) Anode

[0041] like Figure 3 As shown, anode body 21 includes a metal foil and a dielectric layer 210 formed on the surface of the metal foil. That is, capacitor element 10 includes anode body 21 with dielectric layer 210 formed on the surface.

[0042] The surface of the metal foil is roughened. This increases the surface area of ​​the metal foil and the area of ​​the dielectric layer 210 formed on the surface of the metal foil. The roughening method is not particularly limited; for example, etching can be used. The material of the metal foil is not particularly limited; for example, valve metals such as aluminum, tantalum, niobium, or titanium, or alloys containing valve metals, are preferably used.

[0043] Dielectric layer 210 is formed by subjecting the surface of the metal foil to a chemical conversion treatment. This chemical conversion treatment forms an oxide film on the surface of the metal foil, which serves as dielectric layer 210. For example, the chemical conversion treatment can be performed by applying a voltage to the metal foil while the metal foil is immersed in a treatment solution. The treatment solution is not particularly limited; for example, an ammonium adipate solution can be used.

[0044] (4-2) Cathode

[0045] The cathode body 22 may be made of the same metal foil as that used in the manufacture of the anode body 21. The surface of the cathode body 22 may be roughened. The cathode body 22 may have a layer containing titanium or carbon formed on its surface.

[0046] (4-3) Solid Electrolyte

[0047] like Figure 3As shown, solid electrolyte 25 is in contact with dielectric layer 210 and is sandwiched between anode body 21 and cathode body 22. Solid electrolyte 25 is a porous material having fine voids inside. Solid electrolyte 25 can be formed by impregnating capacitor element 10 with a polymer dispersion containing a solvent and fine particles of conductive polymer 250 dispersed in the solvent, and allowing the solvent to evaporate from capacitor element 10. In other words, fine particles of conductive polymer 250 are contained in capacitor element 10. Conductive polymer 250 adheres to at least a portion of the surface of dielectric layer 210, and adheres to at least a portion of the surface of separator 23 and cathode body 22.

[0048] In this embodiment, boric acid is preferably present on the surface of separator 23. This boric acid can improve the permeability of separator 23 with the conductive polymer dispersion. Consequently, the amount of conductive polymer 250 adhering to separator 23 can be increased. Furthermore, the permeability of capacitor element 10 with electrolyte 26 can be improved. It should be noted that the boric acid present on the surface of separator 23 can cover the surface of the fibers of separator 23 or adhere to the surface of separator 23 in the form of islands.

[0049] As the above-mentioned solvent, a volatile liquid component can be used. As the volatile liquid component, for example, water, a non-aqueous solvent, or a mixture of water and a non-aqueous solvent can be used. As the non-aqueous solvent, a protic solvent or an aprotic solvent can be used. Protic solvents can include, for example, at least one of alcohols and ethers. Alcohols can include, for example, one or more selected from methanol, ethanol, propanol, butanol, ethylene glycol, and propylene glycol. Ethers can include, for example, at least one selected from formaldehyde and 1,4-dioxane. Aprotic solvents can include, for example, one or more selected from amides, esters, and ketones. Amides can include, for example, one or more selected from N-methylacetamide, N,N-dimethylformamide, and N-methyl-2-pyrrolidone. Esters can include, for example, methyl acetate. Ketones can include, for example, methyl ethyl ketone.

[0050] The conductive polymer 250 preferably includes one or more components selected from polypyrrole, polythiophene, polyaniline and their derivatives. For example, among the derivatives of polythiophene, poly (3,4-ethylenedioxythiophene) (PEDOT) and the like are included. The conductive polymer 250 may include a homopolymer or a copolymer. The weight average molecular weight of the conductive polymer 250 is not particularly limited, for example, it is greater than 1000 and less than 100000. The average particle size of the microparticles of the conductive polymer 250 is not particularly limited, for example, it is preferably greater than 50nm and less than 1000nm, more preferably greater than 100nm and less than 500nm. The average particle size used in this specification refers to the average value of the particle size of the particles and / or agglomerates constituting the particle size distribution peak. It should be noted that in the particle size distribution measurement based on the dynamic light scattering method, when at least a part of the particles of the conductive polymer to be measured agglomerate in the medium to form agglomerates, the particle size of the agglomerate is measured for the agglomerate. The average particle size of the particle size distribution peak can be obtained from particle size distribution measurement based on a dynamic light scattering method.

[0051] The conductive polymer 250 of this embodiment includes a polyanion. The polyanion functions as a dopant. This dopant imparts conductivity to the conductive polymer 250. For example, the polyanion is a polymeric sulfonic acid. In this case, the dopant is less likely to leave the conductive polymer 250 than when the dopant includes a monomolecular acid component, especially at high temperatures.

[0052] The polymer sulfonic acid may include, for example, one or more selected from polyvinylsulfonic acid, polystyrenesulfonic acid, polyallylsulfonic acid, polyacryloylsulfonic acid, polymethacryloylsulfonic acid, poly(2-acrylamide-2-methylpropanesulfonic acid), and polyisoprenesulfonic acid.

[0053] The polyanion preferably contains polystyrenesulfonic acid. In this case, it is believed that conductive polymer 250 is bound to the side chains of polystyrenesulfonic acid in a dispersed, island-like manner. Therefore, the dopant is less likely to leave conductive polymer 250, especially at high temperatures.

[0054] (4-4) Electrolyte

[0055] Capacitor element 10 is impregnated with electrolyte 26 . Specifically, electrolyte 26 enters into the plurality of gaps in solid electrolyte 25 . Therefore, electrolyte 26 is in contact with dielectric layer 210 and solid electrolyte 25 .

[0056] Electrolyte 26 contains a solvent and an acid component (corresponding to a second acid component described below). The acid component's oxidizing action repairs defects in dielectric layer 210. Specifically, dielectric layer 210 is formed by oxidizing the exposed portion of the metal foil of anode body 21.

[0057] The solvent may contain, for example, one or more components selected from the group consisting of diol compounds, sulfone compounds, lactone compounds, carbonate compounds, alcohols, and polyols.

[0058] The diol compound may include, for example, one or more selected from ethylene glycol (EG), diethylene glycol, triethylene glycol, propylene glycol, polyethylene glycol (PEG), and polyalkylene glycol.

[0059] The sulfone compound may contain, for example, one or more components selected from sulfolane, 3-methylsulfolane, dimethyl sulfoxide, and diethyl sulfoxide.

[0060] The lactone compound may include, for example, one or more selected from the group consisting of γ-butyrolactone, β-butyrolactone, α-valerolactone, and γ-valerolactone.

[0061] The carbonate compound may include, for example, one or more components selected from dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), propylene carbonate (PC), and fluoroethylene carbonate (FEC).

[0062] The alcohol may include one or more selected from the group consisting of methanol, ethanol, propanol, butanol, cyclobutanol, cyclohexanol, methyl cellosolve, and ethyl cellosolve.

[0063] The solvent preferably contains a glycol compound, particularly preferably ethylene glycol or propylene glycol. In this case, the solvent can be prevented from evaporating and passing through the gap between bottomed case 11 and sealing member 12 or sealing member 12 itself, thereby reducing the solvent in electrolyte 26.

[0064] The solvent may contain a polyol having three or more hydroxyl groups, and preferably contains at least one of glycerol and polyglycerol. In this case, the reduction of the solvent in the electrolyte 26 is easily suppressed, and the electrolyte 26 is easily maintained around the conductive polymer 250.

[0065] The acid component preferably contains an organic acid. For example, the organic acid may contain one or more selected from phthalic acid, isophthalic acid, terephthalic acid, maleic acid, adipic acid, benzoic acid, toluic acid, heptanoic acid, malonic acid, 1,6-decanedicarboxylic acid, 1,7-octanedicarboxylic acid, azelaic acid, salicylic acid, oxalic acid, and glycolic acid.

[0066] The acid component may include an inorganic acid. For example, the inorganic acid may include one or more selected from the group consisting of boric acid, phosphoric acid, phosphorous acid, hypophosphorous acid, boric acid ester, phosphoric acid ester, carbonic acid, and silicic acid.

[0067] It is also preferable that the acid component contains, for example, a complex acid compound of the above-mentioned organic acid and inorganic acid. The complex acid compound preferably contains one or more selected from borodisalicylic acid, borodiglycolic acid, and borodioxalic acid.

[0068] Alternatively, a polymeric acid component may be used as the acid component. The polymeric acid component may include, for example, one or more selected from the group consisting of polyacrylic acid, polymethacrylic acid, polyvinylsulfonic acid, polystyrenesulfonic acid, polyallylsulfonic acid, polyacryloylsulfonic acid, polymethacryloylsulfonic acid, poly(2-acrylamide-2-methylpropanesulfonic acid), and polyisoprenesulfonic acid.

[0069] The electrolytic capacitor 1 may generate heat due to the flow of ripple current. In this case, a complex acid compound or a polymer acid component is preferred because of its excellent thermal stability.

[0070] The electrolyte 26 may contain components other than the solvent and the acid component. For example, the electrolyte 26 may contain an alkali component (equivalent to the second alkali component described below). In this case, at least a portion of the acid component can be neutralized, and while increasing the concentration of the acid component, corrosion of the electrode caused by the acid component can be suppressed.

[0071] In the electrolyte 26, the equivalent ratio of the acid component is preferably greater than the equivalent ratio of the alkaline component. This effectively suppresses dedoping. The equivalent ratio of the acid component to the alkaline component is preferably 1.0 to 30. Furthermore, the concentration of the alkaline component in the liquid component is preferably 0.1% by mass or more and 20% by mass or less, and more preferably 3% by mass or more and 10% by mass or less.

[0072] The alkaline component preferably includes one or more components selected from primary amine compounds, secondary amine compounds, tertiary amine compounds, ammonium compounds, quaternary ammonium compounds, and amidine compounds. These components have high heat resistance and can suppress the degradation of the electrolyte 26 caused by heat. Examples of these components include methylamine, dimethylamine, trimethylamine, dimethylethylamine, ethylamine, diethylamine, triethylamine, ethylenediamine, N,N-diisopropylethylamine, tetramethylethylenediamine, hexamethylenediamine, spermidine, spermine, adamantane, aniline, phenylethylamine, toluidine, pyrrolidine, piperidine, piperazine, morpholine, imidazole, pyridine, pyridazine, pyrimidine, pyrazine, 4-dimethylaminopyridine, ammonium, diethyldimethylammonium, 1,2,3-trimethylimidazolinium, 1,2,3,4-tetramethylimidazolinium, 1,3-dimethyl-2-ethylimidazolinium, 1,3,4-trimethyl-2-ethylimidazolinium, and 1,3-dimethyl-2-heptylimidazolium salt. The base component may contain one or more of these components.

[0073] The electrolyte solution 26 may contain a solvent, an acid component, components other than the alkaline component, additives, and the like.

[0074] The pH of the electrolyte 26 is preferably 4 or less, more preferably 3.8 or less, and even more preferably 3.6 or less. Setting the pH of the electrolyte 26 to 4 or less makes it easier to suppress dedoping. The lower limit of the pH of the electrolyte 26 is not particularly limited, but is, for example, 2.0 or greater.

[0075] 2-2. Method for Manufacturing Electrolytic Capacitors

[0076] An example of a method for manufacturing the electrolytic capacitor 1 according to the present embodiment will be described below step by step. The method for manufacturing the electrolytic capacitor 1 according to the present embodiment includes a first step, a second step, a third step, and further includes a fourth step and a fifth step.

[0077] (1) First process

[0078] In the first step, capacitor element 10 is fabricated, comprising anode body 21 having dielectric layer 210 formed on its surface, cathode body 22, and separator 23 provided between anode body 21 and cathode body 22. In the first step, preferably, anode body 21, cathode body 22, and capacitor element 10 are fabricated.

[0079] (1-1) Preparation of anode body

[0080] A metal foil is prepared as a raw material of the anode body 21. Specifically, the anode body 21 can be produced by cutting a large roll-shaped metal plate.

[0081] The surface of the metal foil is roughened to form a plurality of fine concavo-convex patterns on the surface of the metal foil. The surface of the metal foil can be roughened, for example, by etching the metal foil. As the etching process, direct current electrolysis or alternating current electrolysis can be used, for example.

[0082] Then, a dielectric layer 210 is formed on the surface of the roughened metal foil. The method for forming the dielectric layer 210 is not particularly limited, and for example, it can be formed by subjecting the metal foil to a chemical conversion treatment. In the chemical conversion treatment, for example, the roughened metal foil is immersed in a chemical conversion liquid such as an ammonium adipate solution, and then heated or a voltage is applied. Thus, an anode body 21 having a dielectric layer 210 formed on the surface is obtained. The lead 14A is electrically connected to the anode body 21. The method for connecting the anode body 21 and the lead 14A is not particularly limited, and for example, riveting or ultrasonic welding can be used. In the present embodiment, the anode body 21 and the lead 14A are electrically connected via the lead connector 15A.

[0083] (1-2) Preparation of cathode body

[0084] The cathode body 22 can be produced from a metal foil by the same method as the anode body 21. Specifically, the cathode body 22 can be produced by cutting a large roll-shaped metal plate.

[0085] Lead 14B is electrically connected to cathode body 22. The method for connecting cathode body 22 and lead 14B is not particularly limited, and for example, caulking or ultrasonic welding can be used. In this embodiment, cathode body 22 and lead 14B are electrically connected via lead tab 15B.

[0086] If necessary, the surface of the cathode body 22 may be roughened, or an oxide film or a conductive layer including titanium, carbon, or the like may be formed on the surface of the cathode body 22 .

[0087] (1-3) Fabrication of capacitor elements

[0088] Using the above-mentioned anode body 21, cathode body 22 and separator 23, a Figure 2 Specifically, the anode body 21, the separator 23, and the cathode body 22 are stacked in sequence and wound in a concentric circle, thereby producing a wound body. The end of the cathode body 22 located at the outermost layer of the wound body is fixed by the winding fixing tape 24. In this way, Figure 2 Next, lead wires 14A and 14B taken out from anode body 21 and cathode body 22 are pulled out from the through holes of sealing member 12, and sealing member 12 is disposed.

[0089] (2) Second process

[0090] In the second step, capacitor element 10 produced in the first step is impregnated with a treatment solution containing an acid component and an alkaline component. In this specification, to distinguish the acid component and alkaline component contained in the electrolyte solution used in the fourth step (described later) from the acid component and alkaline component contained in the treatment solution used in the second step, the acid component and alkaline component contained in the treatment solution are referred to as the first acid component and the first alkaline component, respectively. Furthermore, the acid component and alkaline component contained in the electrolyte solution are referred to as the second acid component and the second alkaline component, respectively.

[0091] The first acid component is a component that reacts with hydroxyl groups present on the surface of the spacer 23, and includes, for example, one or more components selected from boric acid, phosphoric acid, adipic acid, citric acid, malonic acid, and tartaric acid. The first acid component reacts with the hydroxyl groups on the surface of the spacer 23, thereby modifying the surface of the spacer 23.

[0092] The first alkali component is a component that can introduce protons. The protons combine the hydroxyl groups on the surface of the spacer 23 with the acidic functional groups such as the sulfonic groups possessed by the polyanions of the conductive polymer. The first alkali component, for example, contains ammonium. The hydroxyl groups on the surface of the spacer 23 and the acidic functional groups possessed by the polyanions of the conductive polymer are considered to be combined by protons. By utilizing the first alkali component to introduce the protons, the interaction between the surface of the spacer 23 and the polyanions of the conductive polymer can be weakened. By weakening this interaction, the conductive polymer dispersion can be suppressed from staying near the end faces 101 and 102 of the capacitor element 10, making it easy for the conductive polymer dispersion to be impregnated into the inside of the capacitor element 10. Thus, in the capacitor element 10, the particles of the conductive polymer 250 can be configured to the inside of the capacitor element 10 (the surface of the fibers of the spacer 23 leaving the end faces 101 and 102, the surface of the dielectric layer 210, the surface of the cathode body 22) through the spacer 23. It should be noted that the first acid component and the first alkaline component may also be ionized in the treatment liquid.

[0093] Boric acid, as the first acid component, is preferred because it is less likely to cause the conductive polymer 250 particles in the conductive polymer dispersion to aggregate and less likely to increase the viscosity of the conductive polymer dispersion. If the conductive polymer 250 particles in the conductive polymer dispersion aggregate or the viscosity of the conductive polymer dispersion increases, the conductive polymer dispersion will be less likely to penetrate into capacitor element 10.

[0094] Furthermore, in this embodiment, by impregnating capacitor element 10 with a treatment solution containing boric acid as a first acid component and a first alkaline component, boric acid can be attached to separator 23. Since boric acid is hygroscopic, the boric acid attached to separator 23 can absorb moisture within separator 23, thereby increasing the space within separator 23 for impregnation with the conductive polymer dispersion. Consequently, the permeability of separator 23 with the conductive polymer dispersion is improved, and the permeability of capacitor element 10 with the conductive polymer dispersion is also improved.

[0095] The first acid component and the first alkaline component in the treatment liquid are preferably formed by dissolving a salt of the first acid component and the first alkaline component in the treatment liquid. For example, the boric acid in the treatment liquid is preferably derived from a boric acid compound in the form of a hydrate. That is, the treatment liquid is preferably a solution obtained by dissolving a boric acid compound, and the boric acid compound is preferably a hydrate. Since the boric acid compound dissolves in the treatment liquid to generate boric acid, this boric acid can be used to modify the surface of spacer 23. Furthermore, the boric acid can be attached to spacer 23, thereby improving the permeability of the conductive polymer dispersion into spacer 23 and, in turn, improving the permeability of the conductive polymer dispersion into capacitor element 10.

[0096] In addition, it is preferred that after the second step, before the capacitor element 10 is impregnated with the conductive polymer dispersion (before the third step), a portion of the first acid component in the treatment solution remains in the capacitor element 10, and preferably a portion of the first alkali component in the treatment solution remains. When the conductive polymer dispersion is impregnated into the capacitor element 10, the first acid component remaining in the capacitor element 10 dissolves again, thereby making it easier for the conductive polymer dispersion to penetrate into the interior of the capacitor element 10. For example, when the first acid component is boric acid, boric acid is present on the surface of the fibers of the spacer 23. The boric acid dissolves again in the conductive polymer dispersion, thereby making it easier for the conductive polymer dispersion to penetrate into the interior of the capacitor element 10. In addition, the first alkali component remaining in the capacitor element 10 can also be used to improve the permeability of the conductive polymer dispersion into the interior of the capacitor element 10. The remaining amount of the first acid component and the remaining amount of the first alkali component are affected by the drying conditions (temperature and time) when drying after impregnation of the capacitor element 10 with the treatment solution, and the concentrations of the first acid component and the first alkali component in the treatment solution. It should be noted that the remaining first acid component may include a reaction product between the first acid component and other components, and the remaining first base component may include a reaction product between the first base component and other components.

[0097] Furthermore, depending on the type of first alkaline component remaining in capacitor element 10, the presence of the first alkaline component in capacitor element 10 may reduce the conductivity of the conductive polymer, thereby increasing the ESR of electrolytic capacitor 1. In this regard, when ammonium is used as the first alkaline component, the conductivity of the conductive polymer is less likely to decrease. This is believed to be because ammonium is highly volatile, making it less likely for ammonium to remain in capacitor element 10. Therefore, in this embodiment, ammonium is preferably used as the first alkaline component.

[0098] In addition, the boric acid compound is preferably ammonium borate. Specifically, it is preferably a hydrate of ammonium borate. Examples of the hydrate of ammonium borate include ammonium tetraborate tetrahydrate ((NH4)2B4O7·4H2O), ammonium pentaborate octahydrate ((NH4) 20 ·5B2O3·8H2O), etc., with ammonium pentaborate octahydrate being particularly preferred. When the boric acid compound is ammonium borate, while the boric acid improves the permeability of the conductive polymer dispersion into separator 23, the ammonium as the first alkaline component can suppress the increase in the viscosity of the conductive polymer dispersion, allowing the conductive polymer dispersion to penetrate into capacitor element 10.

[0099] The content of the boric acid compound in the treatment liquid is preferably 0.1% by weight or more and 5.0% by weight or less. In this case, by setting the content of the boric acid compound in the treatment liquid to 0.1% by weight or more, the conductive polymer dispersion can be sufficiently impregnated into the spacer 23. By setting the content of the boric acid compound in the treatment liquid to 5.0% by weight or less, the first alkaline component remaining in the capacitor element 10 can be reduced, and the reduction in the conductivity of the conductive polymer can be suppressed.

[0100] In the present embodiment, the pH of the treatment liquid is higher than the pH of the conductive polymer dispersion. In this case, the first alkali component contained in the treatment liquid can be effectively utilized to introduce protons. In addition, by pre-infiltrating the treatment liquid having a pH higher than that of the conductive polymer dispersion into the capacitor element 10, even if the conductive polymer dispersion has a pH lower than that of the treatment liquid, the wettability of the spacer 23 and the foil (anode body 21 and cathode body 22) can be improved. This effect can be considered to be because the surface potential of the particles of the conductive polymer 250 is a value close to zero, which can suppress the interference of the conductive polymer 250, the spacer 23 and the foil. As a result, it is easy to infiltrate the conductive polymer dispersion into the inside of the capacitor element 10, and the amount of the conductive polymer 250 attached to the spacer 23 can be increased.

[0101] The pH of the treatment liquid is preferably 6 or higher. In this case, the conductive polymer dispersion is particularly easily impregnated into separator 23, and the conductive polymer dispersion is particularly easily impregnated into the interior of capacitor element 10. The pH of the treatment liquid is more preferably 7.0 or higher. The upper limit of the pH of the treatment liquid is not particularly limited, but is preferably 9.5 or lower, and more preferably 9.0 or lower.

[0102] The temperature of the treatment liquid is preferably 45°C or lower, more preferably 35°C or lower. In this case, evaporation of the first alkaline component contained in the treatment liquid can be suppressed. This can suppress changes in the pH of the treatment liquid, allowing the first alkaline component to effectively introduce protons. In particular, when the first alkaline component is ammonium, ammonium evaporation is easily suppressed, making it easier to suppress changes in the pH of the treatment liquid.

[0103] In the second step, a voltage can be applied between anode body 21 and cathode body 22 while capacitor element 10 is immersed in the treatment liquid. In this case, dielectric layer 210 can be formed on the cross section of anode body 21 located at end faces 101 and 102 of capacitor element 10, as well as on the portion where dielectric layer 210 is not formed and anode body 21 is exposed. Subsequently, capacitor element 10 may or may not be cleaned. When cleaning capacitor element 10, it is preferably performed so that some treatment liquid remains in capacitor element 10.

[0104] In the second step, it is preferred that the capacitor element 10 be dried after the treatment liquid is impregnated into the capacitor element 10. As described above, it is preferred that the first acid component and the first alkaline component in the treatment liquid remain in the capacitor element 10, so the drying temperature of the capacitor element 10 is preferably a temperature at which the first acid component and the first alkaline component can remain. In addition, the drying time of the capacitor element 10 is preferably a time at which the first acid component and the first alkaline component can remain. In addition, it is preferred that the water in the capacitor element be evaporated when the conductive polymer dispersion is impregnated into the capacitor element 10, so the drying temperature of the capacitor element 10 is preferably at least a temperature at which the water can evaporate.

[0105] (3) The third process

[0106] In the third step, a conductive polymer dispersion is impregnated into capacitor element 10 while a portion of the treatment liquid remains in capacitor element 10. This conductive polymer dispersion comprises a solvent and fine particles of conductive polymer 250 dispersed in the solvent. In the third step, solid electrolyte 25 comprising conductive polymer 250 is formed on the surface of dielectric layer 210, and solid electrolyte 25 is also attached to the surface of separator 23 and the surface of cathode body 22.

[0107] In the above-mentioned second process, the treatment solution containing the first acid component and the first alkali component is infiltrated into the capacitor element 10, thereby making it easy to infiltrate the conductive polymer dispersion into the interior of the capacitor element 10 in the third process. Specifically, the surface of the spacer 23 is modified by utilizing the first acid component in the treatment solution. In addition, the first acid component attached to the surface of the spacer 23 is dissolved again in the conductive polymer dispersion, thereby improving the impregnation property of the conductive polymer dispersion. In addition, the first alkali component in the treatment solution is utilized to introduce protons to weaken the interaction between the surface of the spacer 23 and the polyanion. As a result, the conductive polymer dispersion is not easy to stay near the end faces 101 and 102 of the capacitor element 10, but is easy to infiltrate into the interior of the capacitor element 10, and is also easy to infiltrate into the gap inside the winding body.

[0108] Especially when the first acid component is boric acid, as in this embodiment, it is preferable that boric acid adhere to the surface of the fibers of spacer 23 immediately before the third step begins. Specifically, it is believed that by drying the capacitor element 10 impregnated with the treatment liquid, crystallized boric acid adheres to spacer 23. It is believed that the boric acid absorbs moisture from spacer 23, expanding the space within spacer 23 that can be impregnated with the conductive polymer dispersion. In this case, spacer 23 preferably includes cellulose fibers. Cellulose fibers contain a relatively high amount of moisture among fibers that can be used as spacer 23, making it easier to utilize the improved permeability of the conductive polymer dispersion using boric acid. Furthermore, by redissolving boric acid in the conductive polymer dispersion, the permeability of the conductive polymer dispersion is improved. As a result, the conductive polymer dispersion easily permeates the interior of capacitor element 10, increasing the amount of conductive polymer 250 adhering to spacer 23.

[0109] In addition, in the present embodiment, by making the pH of the treatment liquid higher than the pH of the conductive polymer dispersion, the first alkaline component can be effectively utilized to introduce protons, thereby making it easy to infiltrate the conductive polymer dispersion into the interior of the capacitor element 10 and also into the gaps inside the wound body. In addition, even for a conductive polymer dispersion with a low pH, the wettability to the separator 23 and the foil (anode body 21 and cathode body 22) can be improved. Specifically, the pH of the conductive polymer dispersion can also be 5 or less. Even in this case, it is easy to infiltrate the conductive polymer dispersion into the interior of the capacitor element 10 and also into the gaps inside the wound body.

[0110] Furthermore, in this embodiment, as described above, the conductive polymer dispersion can be easily impregnated into the interior of capacitor element 10, thereby increasing the amount of conductive polymer 250 attached to spacer 23. This can reduce the ESR of electrolytic capacitor 1. Furthermore, even when electrolytic capacitor 1 is used while a ripple current is flowing through it, causing heat generation, the ESR of electrolytic capacitor 1 is unlikely to increase or the capacitance to decrease, thereby achieving a long life of electrolytic capacitor 1.

[0111] The step of impregnating capacitor element 10 with the conductive polymer dispersion may be repeated two or more times. In this case, the amount of solid electrolyte 25 in contact with dielectric layer 210 can be increased.

[0112] (4) The fourth process

[0113] In the fourth step, capacitor element 10 impregnated with the conductive polymer dispersion is impregnated with electrolyte 26. Specifically, the method for manufacturing electrolytic capacitor 1 of this embodiment includes, after the third step, a fourth step of impregnating capacitor element 10 with electrolyte 26. This allows electrolyte 26 to penetrate into the fine gaps within solid electrolyte 25. Furthermore, electrolyte 26 is in contact with dielectric layer 210 and solid electrolyte 25. Furthermore, by impregnating capacitor element 10 with the treatment solution, electrolyte 26 also easily penetrates the interior of capacitor element 10 and the gaps within the wound body.

[0114] Furthermore, it is preferable to volatilize the first alkaline component before impregnating the capacitor element 10 with the electrolyte 26. That is, the method for manufacturing the electrolytic capacitor 1 of this embodiment preferably includes a step of volatilizing the first alkaline component after the third step and before the fourth step. In this case, it is possible to suppress a decrease in the conductivity of the conductive polymer due to the first alkaline component remaining in the electrolyte 26. Specifically, after impregnating the capacitor element 10 with the conductive polymer dispersion (the third step) and before impregnating the capacitor element 10 with the electrolyte 26, the capacitor element 10 is dried, thereby volatilizing the first alkaline component.

[0115] In the present embodiment, capacitor element 10 is impregnated with the treatment liquid in the second step, thereby facilitating the impregnation of capacitor element 10 with the electrolyte.

[0116] (5) Fifth process

[0117] In the fifth step, after the fourth step, capacitor element 10 is sealed in bottomed case 11, completing electrolytic capacitor 1. Specifically, capacitor element 10 is housed in bottomed case 11 with leads 14A and 14B positioned on the opening side of bottomed case 11. Sealing member 12, formed to allow leads 14A and 14B to penetrate, is positioned above capacitor element 10, sealing capacitor element 10 within bottomed case 11. Subsequently, the area near the open end of bottomed case 11 is drawn, and then the open end is curled, with seat plate 13 positioned within the curled portion.

[0118] Using these processes, we can obtain Figure 1 The electrolytic capacitor 1 shown in FIG. Thereafter, an aging treatment can be performed while applying the rated voltage.

[0119] 2-3. Applications of electrolytic capacitors

[0120] The use of the electrolytic capacitor 1 is not particularly limited. The electrolytic capacitor 1 can be used, for example, in a substrate or switching power supply of an ECU (engine control unit) of a car. As the car, it is mainly envisioned to be an electric car or a hybrid car, but it can also be a gasoline engine car or a diesel engine car. In addition, the electrolytic capacitor 1 can also be used in, for example, two-wheeled vehicles (including electric motorcycles), airplanes, ships, unmanned aircraft, etc. In addition, the electrolytic capacitor 1 can also be used in a power supply device of a CPU (Central Processing Unit) of a server device, a computer device, a home game console, etc. In addition, the electrolytic capacitor 1 can also be used in, for example, a power supply device of an FPGA (Field-Programmable Gate Array) of communication equipment and industrial equipment, and a power supply device of a GPU (Graphics Processing Unit) of a drawing board, etc. The use of the electrolytic capacitor 1 is not limited to them and can be used in multiple fields.

[0121] 2-4. Modification

[0122] The configuration of the electrolytic capacitor 1 is not limited to that of the above-described embodiment.

[0123] For example, capacitor element 10 may be a chip type using a metal sintered body as the anode body instead of a wound body, or a laminate type using a metal plate as the anode body.

[0124] For example, electrolytic capacitor 1 may not contain electrolyte 26. That is, capacitor element 10 may not be impregnated with electrolyte 26. In this case, electrolytic capacitor 1 is a so-called solid electrolytic capacitor. Furthermore, if electrolytic capacitor 1 does not contain electrolyte 26, the method for manufacturing electrolytic capacitor 1 may not include the step (fourth step) of impregnating capacitor element 10 with electrolyte 26.

[0125] [Example]

[0126] Hereinafter, the method for manufacturing the electrolytic capacitor 1 according to the present embodiment will be described in further detail based on examples. However, the method for manufacturing the electrolytic capacitor 1 is not limited to the contents of the following examples.

[0127] Examples 1 to 8, Comparative Examples 1 and 2

[0128] Hereinafter, methods for manufacturing the electrolytic capacitors of Examples 1 to 8 and Comparative Examples 1 and 2 will be described in detail.

[0129] (Preparation of anode body)

[0130] A 100μm thick aluminum foil was etched to roughen its surface. A dielectric layer was then formed on the surface of the aluminum foil using a chemical conversion treatment. The chemical conversion treatment was performed by immersing the aluminum foil in an ammonium adipate solution and applying a voltage of 45V. The aluminum foil was then cut into a 9mm x 220mm square to prepare an anode body.

[0131] (Preparation of cathode body)

[0132] A 50 μm thick aluminum foil was etched to roughen its surface, and then cut into a size of 9 mm in length and 230 mm in width to prepare a cathode body.

[0133] (Production of wound body)

[0134] Anode and cathode lead tabs are connected to the anode and cathode bodies, and the anode and cathode bodies are wound with separators interposed therebetween while the lead tabs are wound in. Anode and cathode leads are connected to the ends of the lead tabs protruding from the wound body.

[0135] (Preparation of treatment solution)

[0136] A treatment liquid containing the first acid component, the first alkaline component, and water shown in Table 1 was prepared. The first acid component and the first alkaline component in the treatment liquid were mixed in the form of a salt of the first acid component and the first alkaline component at the ratio shown in Table 1. The pH of the treatment liquid was the value shown in Table 1.

[0137] (Immersion in treatment liquid)

[0138] The wound body was immersed in a treatment liquid stored in a predetermined container at a temperature of 35° C., thereby allowing the treatment liquid to permeate the wound body.

[0139] (Drying of wound body)

[0140] The wound body, removed from the treatment liquid, is dried at 105°C for 1 hour. This allows the first acid component contained in the treatment liquid to remain in the wound body while the first base component contained in the treatment liquid is volatilized from the wound body. Furthermore, the outer ends of the wound body are secured with a winding securing tape.

[0141] (Preparation of Polymer Dispersion)

[0142] 3,4-ethylenedioxythiophene and polystyrenesulfonic acid (PSS, weight-average molecular weight 100,000) as a polymer dopant were mixed in ion-exchanged water (liquid component) to prepare a mixed solution. While stirring the mixed solution, iron (III) sulfate (oxidant) dissolved in the ion-exchanged water was added to allow polymerization to proceed. After the reaction, the resulting reaction solution was dialyzed to remove unreacted monomers and excess oxidant, yielding a polymer dispersion containing approximately 5% by mass of poly(3,4-ethylenedioxythiophene) doped with PSS (PEDOT / PSS). The pH of this polymer dispersion was adjusted to the values ​​shown in Table 1.

[0143] (Formation of Solid Electrolyte Layer)

[0144] In a reduced pressure atmosphere (40 kPa), the wound body was immersed in the polymer dispersion contained in a predetermined container for 5 minutes, after which it was removed from the polymer dispersion. The wound body, impregnated with the polymer dispersion, was then dried in a drying oven at 150°C for 20 minutes to form a solid electrolyte layer covering at least a portion of the dielectric layer.

[0145] (Preparation of Electrolyte)

[0146] Ethylene glycol and sulfolane were used as the solvents for the electrolyte. Phthalic acid was used as the acid component (second acid component) of the solute. Triethylamine was used as the base component (second base component) of the solute. An electrolyte was prepared using the above solvents and solutes.

[0147] The electrolyte used was a solution containing phthalic acid and triethylamine as solutes dissolved in a solvent containing ethylene glycol and sulfolane at a mass ratio of 1:1. The concentrations of the phthalic acid component and the triethylamine component in the electrolyte were 20% by mass and 5% by mass, respectively.

[0148] (Impermeation of electrolyte)

[0149] The capacitor element was immersed in the electrolyte solution in a reduced pressure atmosphere (40 kPa) for 5 minutes to allow the capacitor element to be impregnated with the electrolyte solution.

[0150] (Sealing of capacitor elements)

[0151] The capacitor element impregnated with electrolyte is sealed to complete the electrolytic capacitor. Specifically, the capacitor element is housed in the bottomed shell in such a manner that the lead wire is located on the open side of the bottomed shell, and a sealing member (an elastic material containing butyl rubber as a rubber component) formed in such a manner that the lead wire passes through is arranged above the capacitor element, and the capacitor element is sealed in the bottomed shell. Thereafter, a drawing process is performed near the open end of the bottomed shell, and then the open end is curled, and a seat plate is arranged on the curled portion, thereby completing the process as shown in FIG. Figure 1The electrolytic capacitor shown was then aged at 100°C for 2 hours while applying a voltage of 32 V.

[0152] [evaluate]

[0153] (1) Determination of initial ESR

[0154] The ESR value (initial ESR value) (mΩ) of the electrolytic capacitor at a frequency of 100 kHz was measured using a four-terminal LCR meter in an environment of 20° C. The results are shown in Table 2.

[0155] (2) Determination of initial electrostatic capacitance

[0156] The electrolytic capacitor's capacitance (initial capacitance) (μF) at a frequency of 120 kHz was measured using a four-terminal LCR meter in an environment of 20° C. The results are shown in Table 2.

[0157] (3) Reliability

[0158] To evaluate reliability, the rated voltage (25V) was applied to the electrolytic capacitor at 145°C for 1000 hours (reliability test). The ESR value (mΩ) and capacitance (μF) were then measured using the same method as above. The results are shown in Table 2. The capacitance after the reliability test is expressed as the capacitance change rate (%) [100 × (initial capacitance - capacitance after reliability test) / (initial capacitance)].

[0159] [Table 1]

[0160]

[0161] [Table 2]

[0162]

[0163] In the electrolytic capacitors of Examples 1 to 8, since the wound body is impregnated with a treatment solution containing a first acid component and a first alkaline component, and the pH of the treatment solution is higher than that of the polymer dispersion, the initial ESR can be reduced, the initial capacitance can be increased, and changes in ESR and capacitance after reliability evaluation can be suppressed, compared to the electrolytic capacitors of Comparative Examples 1 and 2, in which the wound body is impregnated with a treatment solution having a pH lower than that of the polymer dispersion. This is believed to be because the electrolytic capacitors of Examples 1 to 8 facilitate the impregnation of the conductive polymer dispersion into the interior of the capacitor element, compared to the electrolytic capacitors of Comparative Examples 1 and 2, thereby increasing the amount of conductive polymer adhering to the separator.

[0164] Furthermore, in the electrolytic capacitors of Examples 1, 2, and 4-7, since the wound body was impregnated with a treatment solution containing boric acid as the first acid component, the initial ESR was lowered, the initial capacitance was increased, and changes in ESR and capacitance after reliability evaluation were suppressed, compared to the electrolytic capacitors of Comparative Examples 1 and 2, in which the wound body was impregnated with a treatment solution that did not contain boric acid as the first acid component. This is believed to be because the electrolytic capacitors of Examples 1, 2, and 4-7 facilitated the impregnation of the conductive polymer dispersion into the interior of the capacitor element compared to the electrolytic capacitors of Comparative Examples 1 and 2, thereby increasing the amount of conductive polymer adhering to the separator.

[0165] (Summarize)

[0166] The manufacturing method of the electrolytic capacitor (1) of the first embodiment includes a first step, a second step, and a third step. In the first step, a capacitor element (10) is formed, which includes an anode body (21) having a dielectric layer (210) formed on the surface, a cathode body (22), and a separator (23) provided between the anode body (21) and the cathode body (22). In the second step, a treatment liquid containing an acid component and an alkali component is impregnated into the capacitor element (10). In the third step, a conductive polymer dispersion is impregnated into the capacitor element (10) in a state where a portion of the treatment liquid remains in the capacitor element (10) after the second step. The conductive polymer dispersion is obtained by dispersing fine particles of a conductive polymer (250) containing a polyanion in a solvent. The pH of the treatment liquid is higher than the pH of the conductive polymer dispersion.

[0167] In this case, the acid and alkali components in the treatment liquid facilitate the infiltration of the conductive polymer dispersion into the interior of the capacitor element (10). In addition, by making the pH of the treatment liquid higher than the pH of the conductive polymer dispersion, the conductive polymer dispersion also facilitates the infiltration of the capacitor element (10). Therefore, the amount of conductive polymer (250) attached to the spacer (23) can be increased.

[0168] The second method for manufacturing an electrolytic capacitor (1) includes a first step, a second step, and a third step. In the first step, a capacitor element (10) is formed, which includes an anode body (21) having a dielectric layer (210) formed on its surface, a cathode body (22), and a separator (23) provided between the anode body (21) and the cathode body (22). In the second step, a treatment liquid containing boric acid as an acid component and an alkali component is impregnated into the capacitor element (10). In the third step, in a state where a portion of the treatment liquid remains in the capacitor element (10) after the second step, a conductive polymer dispersion is impregnated into the capacitor element (10), wherein the conductive polymer dispersion is obtained by dispersing fine particles of a conductive polymer (250) containing a polyanion in a solvent.

[0169] In this case, the conductive polymer dispersion is easily infiltrated into the interior of the capacitor element (10) by utilizing the acid component and the alkaline component in the treatment liquid. In addition, by using boric acid as the acid component of the treatment liquid, the conductive polymer dispersion is also easily infiltrated into the interior of the capacitor element (10). Therefore, the amount of the conductive polymer (250) attached to the spacer (23) can be increased.

[0170] A third aspect of the method for manufacturing an electrolytic capacitor (1) is characterized in that, in the first or second aspect, the pH of the treatment liquid is 6 or higher.

[0171] In this case, it is particularly easy to impregnate the separator (23) with the conductive polymer dispersion, and it is particularly easy to impregnate the interior of the capacitor element (10) with the conductive polymer dispersion.

[0172] A fourth aspect of the method for producing an electrolytic capacitor (1) is a method according to any one of the first to third aspects, wherein the pH of the conductive polymer dispersion is 5 or less.

[0173] Even in this case, the conductive polymer dispersion can be easily impregnated into the interior of the capacitor element (10).

[0174] A fifth aspect of the method for manufacturing an electrolytic capacitor (1) is a method according to any one of the first to fourth aspects, wherein the temperature of the treatment liquid is 45°C or lower.

[0175] In this case, the evaporation of the alkaline component contained in the treatment liquid can be suppressed. This can suppress changes in the pH of the treatment liquid, and the alkaline component can be effectively used to introduce protons. In particular, when the alkaline component is ammonium, the evaporation of ammonium is easily suppressed, and changes in the pH of the treatment liquid are easily suppressed.

[0176] A sixth aspect of the method for manufacturing an electrolytic capacitor (1) is provided in any one of the first to fifth aspects, wherein the treatment liquid is a solution in which a boric acid compound is dissolved, and the boric acid compound is a hydrate.

[0177] In this case, the surface of the spacer (23) can be modified with boric acid. In addition, the boric acid can be attached to the surface of the spacer (23). Therefore, the permeability of the conductive polymer dispersion into the spacer (23) is improved, making it easier to permeate the capacitor element (10) with the conductive polymer dispersion.

[0178] A seventh aspect of the method for producing an electrolytic capacitor (1) is the sixth aspect, wherein the boric acid compound is ammonium borate.

[0179] In this case, the use of boric acid improves the permeability of the conductive polymer dispersion into the spacer (23) while making it difficult to increase the viscosity of the conductive polymer dispersion. In addition, the conductive polymer dispersion is easily impregnated into the interior of the capacitor element (10), and the use of ammonium does not easily reduce the conductivity of the conductive polymer.

[0180] An eighth aspect of the method for producing an electrolytic capacitor (1) is the sixth or seventh aspect, wherein the content of the boric acid compound in the treatment liquid is 0.1 wt% or more and 5.0 wt% or less.

[0181] In this case, the permeability of the conductive polymer dispersion into the separator (23) can be effectively improved.

[0182] A ninth aspect of the method for manufacturing an electrolytic capacitor (1) is that in any one of the sixth to eighth aspects, immediately before the third step is started, a portion to which boric acid is attached exists on the surface of the fiber of the separator (23).

[0183] In this case, it is believed that by using boric acid to absorb moisture in the spacer (23), the space in the spacer (23) that can be impregnated with the conductive polymer dispersion is expanded. In addition, by redissolving the boric acid in the conductive polymer dispersion, the impregnation property of the conductive polymer dispersion is improved. As a result, the conductive polymer dispersion is easily impregnated into the interior of the capacitor element (10), and the amount of conductive polymer (250) attached to the spacer (23) can be increased.

[0184] A tenth embodiment of the method for manufacturing an electrolytic capacitor (1) is provided in any one of the first to eighth embodiments, wherein after the third step, the method further comprises a fourth step of impregnating the capacitor element (10) with an electrolyte solution.

[0185] In this case, the electrolyte (26) can be impregnated into the fine gaps in the solid electrolyte (25). In addition, the electrolyte (26) is in contact with the dielectric layer (210) and the solid electrolyte (25). In addition, by impregnating the capacitor element (10) with the treatment liquid, the electrolyte (26) can be easily impregnated into the interior of the capacitor element (10).

[0186] The method for manufacturing an electrolytic capacitor (1) according to an eleventh aspect is the method according to the tenth aspect, further comprising a step of volatilizing the alkaline component after the third step and before the fourth step.

[0187] In this case, it is possible to suppress a decrease in the conductivity of the conductive polymer due to the alkali component.

[0188] A twelfth embodiment of the method for manufacturing an electrolytic capacitor (1) is characterized in that, in any one of the first to eleventh embodiments, the separator (23) contains cellulose fibers.

[0189] In this case, since the cellulose fibers contain a large amount of water, the improvement in the impregnation property of the conductive polymer dispersion by boric acid is more easily exhibited.

[0190] The electrolytic capacitor (1) of the thirteenth embodiment comprises a capacitor element (10) including an anode body (21) having a dielectric layer (210) formed on its surface, a cathode body (22), and a separator (23) provided between the anode body (21) and the cathode body (22). The capacitor element (10) contains fine particles of a conductive polymer (250) containing a polyanion, and boric acid is present on the surface of the separator (23).

[0191] In this case, the use of boric acid can improve the permeability of the conductive polymer dispersion into the separator (23), thereby increasing the coverage of the conductive polymer (250) on the separator (23). In addition, the permeability of the electrolyte (26) into the capacitor element (10) is also improved.

[0192] The electrolytic capacitor (1) of the fourteenth embodiment is the electrolytic capacitor (1) of the thirteenth embodiment, wherein the separator (23) contains cellulose fibers.

[0193] In this case, the improvement in the impregnation property of the conductive polymer dispersion by boric acid is more easily exhibited.

[0194] The electrolytic capacitor (1) of the fifteenth aspect is the one according to the thirteenth or fourteenth aspect, wherein the capacitor element (10) is impregnated with an electrolyte solution.

[0195] In this case, the electrolyte solution (26) can be impregnated into the fine gaps in the solid electrolyte (25). In addition, the electrolyte solution (26) is in contact with the dielectric layer (210) and the solid electrolyte (25).

[0196] Explanation of symbols

[0197] 1 Electrolytic capacitor, 10 Capacitor element, 21 Anode, 210 Dielectric layer, 22 Cathode, 23 Separator, 25 Solid electrolyte, 250 Conductive polymer, 26 Electrolyte

Claims

1. A method for manufacturing an electrolytic capacitor, comprising: A first step is to form a capacitor element including an anode body having a dielectric layer formed on its surface, a cathode body, and a separator provided between the anode body and the cathode body; A second step comprises: impregnating the capacitor element with a treatment solution containing boric acid as an acid component and an alkaline component, and then drying the capacitor element at a temperature at which at least water evaporates while the acid component and the alkaline component remain in the treatment solution, thereby causing crystallized boric acid to adhere to the surface of the fibers of the separator in the capacitor element; as well as The third step is to impregnate the capacitor element with a conductive polymer dispersion after the second step while the crystallized boric acid remains on the surface of the fiber of the spacer in the capacitor element, wherein the conductive polymer dispersion is obtained by dispersing conductive polymer particles containing polyanions in a solvent.

2. The method for manufacturing an electrolytic capacitor according to claim 1, wherein: The pH of the treatment liquid is 6 or higher.

3. The method for manufacturing an electrolytic capacitor according to claim 1 or 2, wherein: The conductive polymer dispersion has a pH of 5 or less.

4. The method for manufacturing an electrolytic capacitor according to claim 1 or 2, wherein: The temperature of the treatment liquid is below 45°C.

5. The method for manufacturing an electrolytic capacitor according to claim 1 or 2, wherein: The treatment liquid is a solution in which a boric acid compound is dissolved, and the boric acid compound is a hydrate.

6. The method for manufacturing an electrolytic capacitor according to claim 5, wherein: The boric acid compound is ammonium borate.

7. The method for manufacturing an electrolytic capacitor according to claim 5, wherein: The content of the boric acid compound in the treatment liquid is 0.1 wt % or more and 5.0 wt % or less.

8. The method for manufacturing an electrolytic capacitor according to claim 5, wherein: Immediately before the third step, boric acid is deposited on the surface of the fibers of the spacer.

9. The method for manufacturing an electrolytic capacitor according to claim 1 or 2, wherein: After the third step, a fourth step of impregnating the capacitor element with an electrolyte solution is performed.

10. The method for manufacturing an electrolytic capacitor according to claim 9, wherein: The method includes a step of volatilizing the alkali component after the third step and before the fourth step.

11. The method for manufacturing an electrolytic capacitor according to claim 1 or 2, wherein: The spacer comprises cellulose fibers.

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