Manufacturing method of electrolytic capacitor

Abstract

This method for manufacturing an electrolytic capacitor comprises: a first step for preparing an electrode group comprising an anode foil having a porous portion and a dielectric layer covering the surface of the porous portion, a cathode foil, and a separator disposed between the anode foil and the cathode foil; a second step for preparing a processing fluid including a conductive polymer; and a third step for, after controlling the anode foil and the processing fluid to mutually different temperatures, impregnating the electrode group with the processing fluid to form a solid electrolyte layer including the electrically conductive polymer in at least a part of the electrode group.

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing an electrolytic capacitor. [Background technology]

[0002] Capacitors used in electronic devices are required to have a large capacity and a small equivalent series resistance (ESR) value in the high-frequency range. Electrolytic capacitors using conductive polymers such as polythiophene are promising capacitors with a large capacity and low ESR. The capacitor element of an electrolytic capacitor is obtained, for example, by winding an anode foil and a cathode foil with a separator between them to form an electrode group, and then impregnating the electrode group with a treatment solution containing the conductive polymer.

[0003] Patent Document 1 proposes repeating a film formation process, in which a conductive polymer solution is applied to a dielectric layer of a capacitor substrate and dried to form a conductive polymer film, two or more times, and using a conductive polymer solution with a higher viscosity than the conductive polymer solution used in the first film formation process as the conductive polymer solution used in at least one of the film formation processes from the second onwards. The conductive polymer solution contains a π-conjugated conductive polymer, a polyanion, and a solvent. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-087401 Summary of the Invention [Problem to be solved by the invention]

[0005] In recent years, there has been a demand for improved performance of electrolytic capacitors. [Means for solving the problem]

[0006] One aspect of the present invention relates to a method for manufacturing an electrolytic capacitor, including: a first step of preparing an electrode group including an anode foil having a porous portion and a dielectric layer covering a surface of the porous portion, a cathode foil, and a separator disposed between the anode foil and the cathode foil; a second step of preparing a treatment solution containing a conductive polymer; and a third step of controlling the anode foil and the treatment solution to different temperatures, and then impregnating the electrode group with the treatment solution to form a solid electrolyte layer containing the conductive polymer in at least a portion of the electrode group. [Effects of the Invention]

[0007] According to the present invention, the performance of the electrolytic capacitor can be improved.

[0008] The novel features of the present invention are set forth in the appended claims, but the present invention, both in terms of structure and content, together with other objects and features of the present invention, will be better understood from the following detailed description taken in conjunction with the drawings. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a cross-sectional view schematically illustrating an example of an electrolytic capacitor according to an embodiment of the present invention. [Figure 2] FIG. 2 is a perspective view showing a part of the wound body of FIG. 1 in an expanded state. DETAILED DESCRIPTION OF THE INVENTION

[0010] The following describes examples of embodiments of electrolytic capacitors according to the present disclosure, but the present disclosure is not limited to the examples described below. In the following description, specific numerical values ​​and materials may be used as examples. However, other numerical values ​​and materials may be used as long as the effects of the present disclosure are obtained. In this specification, the term "numerical value A to numerical value B" includes numerical value A and numerical value B and can be interpreted as "numerical value A or greater and numerical value B or less." In the following description, when lower and upper limits for specific physical properties or conditions are exemplified, any of the exemplified lower limits and any of the exemplified upper limits can be arbitrarily combined, as long as the lower limit is not greater than the upper limit. When multiple materials are exemplified, one of the materials may be selected and used alone, or two or more of the materials may be used in combination.

[0011] The present disclosure also encompasses combinations of two or more features arbitrarily selected from the appended claims, i.e., two or more features arbitrarily selected from the appended claims can be combined unless a technical contradiction arises.

[0012] A method for manufacturing an electrolytic capacitor according to one embodiment of the present invention includes the steps of: preparing an electrode assembly (1), preparing a treatment solution containing a conductive polymer (2), and forming a solid electrolyte layer containing the conductive polymer on at least a portion of the electrode assembly (3). The electrode assembly includes an anode foil having a porous portion and a dielectric layer covering the surface of the porous portion, a cathode foil, and a separator disposed between the anode foil and the cathode foil.

[0013] In the third step, the anode foil and the treatment solution are controlled to different temperatures, and then the electrode assembly is impregnated with the treatment solution to form a solid electrolyte layer containing a conductive polymer in at least a portion of the electrode assembly. In the third step, the temperature difference between the anode foil and the treatment solution is used to adjust the impregnation of the treatment solution in the porous portion and the separator, thereby adjusting the amount of conductive polymer impregnated in the porous portion and the separator. This improves the performance of the electrolytic capacitor. For example, in the case of step (a-1) described below, the capacitance can be increased, and in the case of step (a-2) described below, the ESR can be reduced.

[0014] By creating a temperature difference between the anode foil and the treatment solution, a local concentration difference is generated in the treatment solution impregnated in the electrode assembly, and the amount of conductive polymer adhered to the electrode assembly can be biased. Specifically, when the temperature of the anode foil is made higher than that of the treatment solution, the concentration of the treatment solution near the porous portion of the anode foil increases, and the amount of conductive polymer filled in the porous portion can be increased. Furthermore, when the temperature of the treatment solution is made higher than that of the anode foil, the concentration of the treatment solution near the separator increases, and the amount of conductive polymer filled in the separator can be increased.

[0015] The third step includes a step (a) of controlling the anode foil and the treatment solution to different temperatures, and a step (b) of impregnating the electrode group with the treatment solution to form a solid electrolyte layer after the step (a). In the step (b), the electrode group may be impregnated with the treatment solution and then dried.

[0016] Step (a) may include step (a-1) of raising the temperature of the anode foil higher than that of the treatment solution, which allows a large amount of the treatment solution (conductive polymer) to be impregnated into the porous portion of the anode foil, thereby sufficiently coating the dielectric layer with the conductive polymer and increasing the capacitance.

[0017] In step (a-1), for example, the temperature of the anode foil may be higher than the temperature of the treatment solution by a temperature difference in the range of 50° C. to 100° C. For example, the temperature of the anode foil may be set to 80° C. to 120° C., and the temperature of the treatment solution may be set to 20° C. to 30° C. Step (a-1) may be performed, for example, by heating the anode foil and / or cooling the treatment solution.

[0018] Step (a) may include step (a-2) of increasing the temperature of the treatment solution to a temperature higher than that of the anode foil. In this case, the separator can be impregnated with a large amount of the treatment solution (conductive polymer), and many conductive paths can be formed between the anode foil and the cathode foil by the conductive polymer, thereby achieving a low ESR.

[0019] In step (a-2), for example, the temperature of the treatment solution may be higher than the temperature of the anode foil by a temperature difference in the range of 50° C. to 100° C. For example, the temperature of the anode foil may be set to -20° C. to 0° C., and the temperature of the treatment solution may be set to 30° C. to 60° C. Step (a-2) is performed, for example, by cooling the anode foil and / or heating the treatment solution.

[0020] The heating or cooling of the anode foil may be performed by heating or cooling the electrode group. The anode foil has high thermal conductivity and is easy to control the heating (cooling) temperature. On the other hand, the separator has low thermal conductivity and is less affected by heating (cooling). Therefore, by heating (cooling) the electrode group, the temperature difference between the anode foil and the treatment solution can be used to adjust the impregnation of the treatment solution in the porous portion and the separator.

[0021] The above steps (a) and (b) may be performed once or multiple times. When step (a) is performed multiple times, the temperature of the anode foil and / or the treatment solution may be changed during the multiple steps of step (a). When step (b) is performed multiple times, drying may be performed after each impregnation of the electrode group with the treatment solution.

[0022] Step (a) may include step (a-1) and step (a-2). That is, step 3 may include step 3A and step 3B, in which step 3A involves raising the temperature of the anode foil higher than that of the treatment solution, and then impregnating the electrode group with the treatment solution, and step 3B involves raising the temperature of the treatment solution higher than that of the anode foil, and then impregnating the electrode group with the treatment solution. The order of steps 3A and 3B is not limited.

[0023] In step 3A, the temperature of the anode foil may be increased by 50°C or more and 100°C or less above the temperature of the treatment liquid, and then the electrode group may be impregnated with the treatment liquid. In step 3B, the temperature of the treatment liquid may be increased by 50°C or more and 100°C or less above the temperature of the anode foil, and then the electrode group may be impregnated with the treatment liquid.

[0024] In the third step, it is preferable to perform step 3B after step 3A. In this case, it is easy to reduce ESR while increasing capacitance. The treatment liquid can diffuse into the porous portion of the anode foil through the separator. Performing step 3A, which impregnates the porous portion with a large amount of treatment liquid, first, and then performing step 3B, which impregnates the separator with a large amount of treatment liquid, allows the treatment liquid to be efficiently impregnated into both the porous portion and the separator.

[0025] In the second step, a treatment liquid A and a treatment liquid B containing a component different from that of treatment liquid A are prepared as treatment liquids, and in the third step, the electrode group is impregnated with treatment liquid A, and in the third step, the electrode group is impregnated with treatment liquid B. Treatment liquid A may contain a component capable of repairing defects in the dielectric layer or a component capable of suppressing an increase in leakage current caused by defects in the dielectric layer.

[0026] Treatment liquid A may contain conductive polymer A, and treatment liquid B may contain conductive polymer B, which has a higher conductivity than conductive polymer A. By step 3B, the separator can contain a large amount of conductive polymer B, which has a high conductivity, thereby reducing ESR. Conductive polymer B, which has a high conductivity, tends to increase leakage current, but by containing a large amount of conductive polymer A, which has a low conductivity, in the porous portion by step 3A, it is possible to limit contact of conductive polymer B, which has a high conductivity, with the porous portion, thereby suppressing an increase in leakage current.

[0027] The conductivity of the conductive polymer A is, for example, 10 S / cm or more and 200 S / cm or less, and the conductivity of the conductive polymer B is, for example, 300 S / cm or more and 500 S / cm or less.

[0028] The conductivity of the conductive polymer in the treatment solution can be determined by applying the treatment solution to a substrate, drying it to form a conductive polymer film (e.g., 10 μm to 30 μm thick), and measuring the conductivity of the film. The conductivity can be measured using a Loresta-GX and PSP probe manufactured by Nitto Seiko Analytech Co., Ltd.

[0029] (1st step) In the first step, an electrode assembly is prepared. The electrode assembly includes an anode foil having a porous portion and a dielectric layer covering the surface of the porous portion, a cathode foil, and a separator disposed between the anode foil and the cathode foil.

[0030] In the first step, a separator may be disposed between the anode foil and the cathode foil to obtain an electrode assembly. In the case of a wound capacitor, the electrode assembly (wound body) may be formed by winding the anode foil and the cathode foil with a separator interposed between them. In the case of a laminated capacitor, the electrode assembly (laminate) may be formed by folding the anode foil and the cathode foil in a zigzag pattern with a separator interposed between them.

[0031] (anode foil) The anode foil has a porous portion and a dielectric layer covering the surface of the porous portion. At least a portion of the dielectric layer of the anode foil is in contact with the conductive polymer (solid electrolyte layer). The porous portion is formed by roughening the surface of the metal foil, for example, by etching. The dielectric layer is obtained by forming an oxide film on the roughened surface of the metal foil, for example, by chemical conversion treatment.

[0032] The type of metal constituting the metal foil is not particularly limited. In terms of ease of forming a dielectric layer, examples of metals constituting the metal foil include valve metals such as aluminum, tantalum, niobium, and titanium, and alloys of valve metals. Preferred examples are aluminum and aluminum alloys.

[0033] (cathode foil) A metal foil can be used for the cathode foil. The type of metal constituting the metal foil is not particularly limited. The metal foil can be any of those exemplified for the anode foil. The surface of the metal foil may be provided with a coating of a metal (dissimilar metal) different from the metal constituting the metal foil or a non-metal. Examples of dissimilar metals and non-metals include metals such as titanium and non-metals such as carbon.

[0034] The cathode foil may be a metal foil whose surface has been roughened by etching or other treatment. That is, the cathode foil may have a porous portion on its surface. A chemical conversion coating may be provided on the roughened metal foil surface. In this case, in the third step, the cathode foil and the treatment solution may be controlled to different temperatures, and then the electrode group may be impregnated with the treatment solution. The cathode foil, together with the anode foil, may be controlled to a temperature different from that of the treatment solution by heating or cooling the electrode group. This may adjust the impregnation of the treatment solution into the porous portion of the cathode portion.

[0035] (separator) The separator may be made of, for example, a nonwoven fabric containing fibers of cellulose, polyethylene terephthalate, vinylon, or polyamide (for example, aliphatic polyamide, or aromatic polyamide such as aramid).

[0036] (2nd process) In the second step, a treatment liquid containing a conductive polymer is prepared. The treatment liquid is a dispersion (or solution) of a conductive polymer. Water is usually used as the dispersion medium (or solvent) of the treatment liquid. The treatment liquid may contain a dopant together with the conductive polymer, or may further contain components other than the conductive polymer and the dopant.

[0037] The treatment liquid can be obtained, for example, by oxidatively polymerizing a conductive polymer precursor in a dispersion medium (or solvent), which may contain a dopant. Examples of the conductive polymer precursor include a monomer that constitutes a conductive polymer and / or an oligomer in which several monomers are linked together. The conductivity of the conductive polymer can be adjusted, for example, by adjusting the polymerization conditions of the conductive polymer precursor (e.g., the type of conductive polymer precursor, oxidant, or catalyst), the type of dopant, etc.

[0038] Examples of conductive polymers include polypyrrole, polythiophene, polyfuran, polyaniline, polyacetylene, and derivatives thereof. The derivatives include polymers with polypyrrole, polythiophene, polyfuran, polyaniline, and polyacetylene as their basic skeletons. For example, polythiophene derivatives include poly(3,4-ethylenedioxythiophene). These conductive polymers may be used alone or in combination. Furthermore, the conductive polymer may be a copolymer of two or more monomers. The weight-average molecular weight of the conductive polymer is not particularly limited and may be in the range of 1,000 to 100,000, for example. A preferred example of the conductive polymer is poly(3,4-ethylenedioxythiophene) (PEDOT).

[0039] Examples of dopants include polyvinyl sulfonic acid, polystyrene sulfonic acid, polyallyl sulfonic acid, polyacrylic sulfonic acid, polymethacrylic sulfonic acid, poly(2-acrylamido-2-methylpropane sulfonic acid), polyisoprene sulfonic acid, and polyacrylic acid. These may be used alone or in combination of two or more. They may be added in the form of a salt. The dopant may exist in the electrolyte in the form of an anion in which cations (e.g., protons) are dissociated from at least a portion of the acid groups. A preferred example of the dopant is polystyrene sulfonic acid (PSS).

[0040] The weight-average molecular weight of the dopant is not particularly limited, but may be in the range of 1,000 to 100,000 in order to facilitate the formation of a homogeneous solid electrolyte layer.

[0041] The conductive polymer may be a conductive polymer doped with a dopant, or may be poly(3,4-ethylenedioxythiophene) doped with polystyrene sulfonic acid (hereinafter also referred to as PEDOT / PSS).

[0042] The concentration of the conductive polymer (e.g., PEDOT / PSS) in the treatment liquid is, for example, 1% by mass or more and 3% by mass or less. When the concentration of the conductive polymer in the treatment liquid is in the above range, the viscosity of the treatment liquid at 20°C is, for example, 10 mPa s or more and 60 mPa s or less.

[0043] (3rd step) In the third step, the anode foil and the treatment solution are controlled to different temperatures, and then the electrode group is impregnated with the treatment solution to form a solid electrolyte layer containing a conductive polymer in at least a portion of the electrode group. This results in a capacitor element. The impregnation with the treatment solution may be performed by immersing the electrode group in the treatment solution, or by dropping the treatment solution onto the electrode group. The impregnation with the treatment solution may be performed under atmospheric pressure or under reduced pressure. After impregnation with the treatment solution, the electrode group containing the treatment solution may be dried. Drying may be performed by heating (for example, 120°C to 200°C).

[0044] In the third step, the step of impregnating the electrode group with the treatment liquid may be performed multiple times, and at least one of the impregnation steps may be a step of impregnating the electrode group with the treatment liquid after controlling the anode foil and the treatment liquid to temperatures different from each other.

[0045] (Other processes) The method for manufacturing an electrolytic capacitor may include a step of impregnating a capacitor element with a liquid component, and a step of sealing a bottomed case containing the capacitor element.

[0046] (liquid component) The liquid component may be an electrolytic solution or a non-aqueous solvent. The liquid component has the role of protecting the conductive polymer. Furthermore, the inclusion of the liquid component can improve the contact between the conductive polymer and the dielectric layer, and can also improve the repairability of defects in the dielectric layer. The electrolytic solution can function as an electrolyte together with the conductive polymer.

[0047] The non-aqueous solvent may be an organic solvent or an ionic liquid. Examples of non-aqueous solvents include polyhydric alcohols such as ethylene glycol and propylene glycol, cyclic sulfones such as sulfolane (SL), lactones such as γ-butyrolactone (GBL), amides such as N-methylacetamide, N,N-dimethylformamide, and N-methyl-2-pyrrolidone, esters such as methyl acetate, carbonate compounds such as propylene carbonate, ethers such as 1,4-dioxane, ketones such as methyl ethyl ketone, and formaldehyde. The non-aqueous solvents may be used singly or in combination of two or more.

[0048] The liquid component may contain an acid component and a base component. Examples of the acid component include maleic acid, phthalic acid, benzoic acid, pyromellitic acid, and resorcylic acid. Examples of the base component include 1,2,4-trimethylimidazoline, 1,2-dimethyl-1,4,5,6-tetrahydropyrimidine, and 1-methylimidazole.

[0049] The electrolyte solution contains a non-aqueous solvent and a solute (e.g., an organic salt) dissolved therein. Examples of the non-aqueous solvent that constitutes the electrolyte solution include the examples of the non-aqueous solvents described above. Examples of the solute include inorganic salts and organic salts. An organic salt is a salt in which at least one of the anion and cation contains an organic substance. Examples of the organic salt include trimethylamine maleate, ethyldimethylamine phthalate, mono-1,2,3,4-tetramethylimidazolinium phthalate, mono-1,3-dimethyl-2-ethylimidazolinium phthalate, etc.

[0050] In order to suppress dedoping of the dopant, the pH of the liquid component may be set to less than 7, or may be set to 5 or less.

[0051] Here, Fig. 1 is a cross-sectional view that schematically shows an example of an electrolytic capacitor according to an embodiment of the present invention, and Fig. 2 is a perspective view in which a part of the wound body of Fig. 1 is developed.

[0052] Electrolytic capacitor 200 includes wound body 100 (electrode group). Wound body 100 is formed by winding anode foil 10 and cathode foil 20 with separator 30 interposed therebetween. Wound body 100 includes a conductive polymer (not shown).

[0053] One end of lead tabs 50A and 50B is connected to anode foil 10 and cathode foil 20, respectively, and lead tabs 50A and 50B are wound to form wound body 100. Lead wires 60A and 60B are connected to the other end of lead tabs 50A and 50B, respectively.

[0054] A stop tape 40 is disposed on the outer surface of the cathode foil 20 located in the outermost layer of the wound body 100, and the ends of the cathode foil 20 are fixed by the stop tape 40. When the anode foil 10 is prepared by cutting it from a large foil, the wound body 100 may be further subjected to a chemical conversion treatment in order to provide a dielectric layer on the cut surface.

[0055] The wound body 100 is housed in the bottomed case 211 so that the lead wires 60A and 60B are located on the opening side of the bottomed case 211. The bottomed case 211 can be made of a metal such as aluminum, stainless steel, copper, iron, brass, or an alloy of these metals.

[0056] A sealing member 212 is placed at the opening of a bottomed case 211 in which the wound body 100 is stored, the open end of the bottomed case 211 is crimped to the sealing member 212 and curled, and a seat plate 213 is placed at the curled portion, thereby sealing the wound body 100 within the bottomed case 211.

[0057] Sealing member 212 is formed so that lead wires 60A and 60B pass through it. Sealing member 212 may be made of any insulating material, and is preferably made of an elastic material. Among these, highly heat-resistant materials such as silicone rubber, fluororubber, butyl rubber, and isoprene rubber are preferred.

[0058] [Example] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples.

[0059] Example 1 A wound electrolytic capacitor (diameter Φ: 10 mm × length L: 12 mm) was fabricated by the following procedure.

[0060] (Preparation of anode foil) An Al foil (thickness: 100 μm) whose surface had been roughened by etching was subjected to chemical conversion treatment. Specifically, the Al foil was anodized at 150 V in an aqueous solution of ammonium adipate (concentration: 2%). In this way, a dielectric layer was formed on the surface of the Al foil, and an anode foil was obtained.

[0061] (Creating cathode foil) An Al foil (50 μm thick) whose surface had been roughened by etching was subjected to a chemical conversion treatment. Specifically, the Al foil was anodized at 3 V in an ammonium adipate aqueous solution (concentration 2%). In this way, a dielectric layer was formed on the surface of the Al foil, and a cathode foil was obtained.

[0062] (Production of wound body) An anode lead tab and a cathode lead tab, each connected to a lead wire, were connected to the prepared anode foil and cathode foil, respectively. The anode foil and cathode foil were then wound with a separator sandwiched between them, and the outer surfaces were secured with tape. In this way, a wound electrode assembly (diameter 8.5 mm, height 7.0 mm) was produced. A nonwoven fabric of aramid fiber (thickness 40 μm) was used as the separator.

[0063] (Preparation of treatment solution containing conductive polymer) The following treatment liquid A was prepared as a treatment liquid containing a conductive polymer. Note that PEDOT / PSS means PEDOT doped with PSS.

[0064] Treatment solution A: PEDOT / PSS (conductivity 100 S / cm) aqueous dispersion (concentration 2% by mass)

[0065] (Formation of solid electrolyte layer) The impregnation step with the treatment liquid containing the conductive polymer was performed once. Specifically, the temperatures of the wound body and treatment liquid A were adjusted to the temperatures shown in Table 1. The wound body was heated to 120°C, thereby setting the temperature of the anode foil at 120°C. Next, approximately 200 mg of treatment liquid A was dropped onto the wound body using a dispenser, and the wound body soaked in treatment liquid A was then left in a reduced pressure atmosphere (-90 kPa) for 5 minutes. Next, the wound body soaked in treatment liquid A was dried at 150°C for 30 minutes in an atmospheric pressure atmosphere. In this way, a solid electrolyte layer containing the conductive polymer was formed in the wound body, and a capacitor element was obtained.

[0066] (Capacitor sealing) A sealing member and a seat plate were placed in the opening of the bottomed case to seal the capacitor element. In this way, electrolytic capacitor X1 was completed. After that, an aging treatment was performed at 140°C for 1 hour while applying the rated voltage.

[0067] Comparative Example 1 In the solid electrolyte layer formation process, the wound body was impregnated with the treatment solution at room temperature. That is, the temperatures of the wound body and the treatment solution were both 25° C. Except for the above, electrolytic capacitor Y1 was fabricated in the same manner as in Example 1.

[0068] The electrolytic capacitor X1 of Example 1 and the electrolytic capacitor Y1 of Comparative Example 1 were subjected to the following evaluation 1.

[0069] [Rating 1] The initial capacitance (μF) was measured at a frequency of 120 Hz using a four-terminal LCR meter in an environment of 20° C. The evaluation results are shown in Table 1.

[0070] [Table 1]

[0071] In electrolytic capacitor X1, the porous portion of the anode foil contains a large amount of conductive polymer, and a higher capacitance was obtained than in electrolytic capacitor Y1.

[0072] Example 2 In the solid electrolyte layer forming step, the wound body and treatment solution A were adjusted to the temperatures shown in Table 2. The wound body was cooled to −10° C., thereby adjusting the temperature of the anode foil to −10° C. Except for the above, electrolytic capacitor X2 was produced in the same manner as in Example 1.

[0073] The electrolytic capacitor X2 of Example 2 and the electrolytic capacitor Y1 of Comparative Example 1 were subjected to the following evaluation 2.

[0074] [Rating 2] The initial ESR (mΩ) was measured at a frequency of 100 kHz using a four-terminal LCR meter in an environment of 20°C. The evaluation results are shown in Table 2.

[0075] [Table 2]

[0076] In electrolytic capacitor X2, the separator contains a large amount of conductive polymer, and a lower ESR was obtained than in electrolytic capacitor Y1.

[0077] Example 3 In the step of preparing a treatment liquid containing a conductive polymer, the following treatment liquid A and treatment liquid B were prepared.

[0078] Treatment solution A: PEDOT / PSS (conductivity 100 S / cm) aqueous dispersion (concentration 2% by mass)

[0079] Treatment solution B: PEDOT / PSS (conductivity 400 S / cm) aqueous dispersion (concentration 2% by mass)

[0080] In the process of forming the solid electrolyte layer, the impregnation process with a treatment liquid containing a conductive polymer was performed twice. Specifically, the following Step 3A and Step 3B were performed in this order.

[0081] (3rd A process) The temperatures of the wound body and treatment liquid A were adjusted to the temperatures shown in Table 3. Next, approximately 200 mg of treatment liquid A was dropped onto the wound body using a dispenser, and the wound body soaked in treatment liquid A was then left to stand in a reduced pressure atmosphere (-90 kPa) for 5 minutes. Next, the wound body soaked in treatment liquid A was dried at 150°C for 30 minutes under atmospheric pressure.

[0082] (3B process) Next, the wound body and treatment liquid B were adjusted to the temperatures shown in Table 3. Next, approximately 200 mg of treatment liquid B was dropped onto the wound body using a dispenser, and the wound body soaked in treatment liquid B was then left in a reduced pressure atmosphere (-90 kPa) for 5 minutes. Next, the wound body soaked in treatment liquid B was dried at 150°C for 30 minutes in an atmospheric pressure atmosphere.

[0083] Except for the above, the electrolytic capacitor X3 was produced in the same manner as in Example 1.

[0084] Comparative Example 2 In the solid electrolyte layer forming steps (steps 3A and 3B), the wound body was impregnated with the treatment solution at room temperature. That is, in steps 3A and 3B, the temperatures of the wound body and the treatment solution were both 25°C. Except for the above, electrolytic capacitor Y2 was fabricated in the same manner as in Example 3.

[0085] The electrolytic capacitor X3 of Example 3 and the electrolytic capacitor Y2 of Comparative Example 2 were subjected to the following evaluation 3.

[0086] [Rating 3] The initial capacitance (μF) and initial ESR (mΩ) were determined in the same manner as in Evaluation 1 and Evaluation 2 above. The leakage current (LC) was determined by measuring the current value (μA) when the rated voltage was applied for 1 minute in an environment of 20°C. The evaluation results are shown in Table 3.

[0087] [Table 3]

[0088] Electrolytic capacitor X3 had a higher capacitance and a lower ESR than electrolytic capacitor Y2. Electrolytic capacitor X3, which was fabricated by performing steps 3A and 3B in this order, was able to reduce both ESR and LC compared to electrolytic capacitor Y2. [Industrial Applicability]

[0089] The electrolytic capacitor obtained by the method for manufacturing an electrolytic capacitor according to the present invention can be used in applications where high performance is required.

[0090] While the present invention has been described in terms of presently preferred embodiments, such disclosure is not to be interpreted as limiting. Various changes and modifications will no doubt become apparent to those skilled in the art to which the present invention pertains upon reading the above disclosure. It is therefore intended that the appended claims be interpreted to cover all changes and modifications that do not depart from the true spirit and scope of the invention. [Explanation of symbols]

[0091] 10: Anode foil, 20: Cathode foil, 30: Separator, 40: Winding tape, 50A, 50B: Lead tabs, 60A, 60B: Lead wires, 100: Wound body, 200: Electrolytic capacitor, 211: Bottomed case, 212: Sealing member, 213: Seat plate

Claims

1. a first step of preparing an electrode group including an anode foil having a porous portion and a dielectric layer covering a surface of the porous portion, a cathode foil, and a separator disposed between the anode foil and the cathode foil; a second step of preparing a treatment liquid containing a conductive polymer; a third step of controlling the anode foil and the treatment solution to different temperatures, and then impregnating the electrode group with the treatment solution to form a solid electrolyte layer containing the conductive polymer on at least a portion of the electrode group; A method for manufacturing an electrolytic capacitor, comprising:

2. 2. The method for manufacturing an electrolytic capacitor according to claim 1, wherein in the third step, the temperature of the anode foil is made higher than the temperature of the treatment solution, and then the treatment solution is impregnated into the electrode group.

3. 3. The method for manufacturing an electrolytic capacitor according to claim 2, wherein in the third step, the temperature of the anode foil is increased by 50° C. or more and 100° C. or less than the temperature of the treatment solution, and then the treatment solution is impregnated into the electrode group.

4. 2. The method for manufacturing an electrolytic capacitor according to claim 1, wherein in the third step, the temperature of the treatment liquid is increased to be higher than the temperature of the anode foil, and then the electrode group is impregnated with the treatment liquid.

5. 5. The method for manufacturing an electrolytic capacitor according to claim 4, wherein in the third step, the temperature of the treatment solution is increased by 50° C. or more and 100° C. or less than the temperature of the anode foil, and then the electrode group is impregnated with the treatment solution.

6. The third step includes a step 3A and a step 3B, In the step 3A, the temperature of the anode foil is increased to be higher than the temperature of the treatment solution, and then the treatment solution is impregnated into the electrode group; 2 . The method for manufacturing an electrolytic capacitor according to claim 1 , wherein in the step 3B, the temperature of the treatment liquid is increased to be higher than the temperature of the anode foil, and then the electrode group is impregnated with the treatment liquid.

7. 7. The method for manufacturing an electrolytic capacitor according to claim 6, wherein in the 3A step, the temperature of the anode foil is increased by 50° C. or more and 100° C. or less than the temperature of the treatment solution, and then the treatment solution is impregnated into the electrode group.

8. 8. The method for manufacturing an electrolytic capacitor according to claim 6, wherein in the step 3B, the temperature of the treatment solution is increased by 50°C or more and 100°C or less higher than the temperature of the anode foil, and then the electrode group is impregnated with the treatment solution.

9. 9. The method for manufacturing an electrolytic capacitor according to claim 6, wherein in the third step, the third step is performed after the third step.

10. In the second step, a treatment liquid A and a treatment liquid B containing a component different from that of the treatment liquid A are prepared as the treatment liquids, In the 3A step, the electrode group is impregnated with the treatment solution A, 10. The method for manufacturing an electrolytic capacitor according to claim 6, wherein in the third step, the electrode group is impregnated with the treatment liquid B.

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