Electrolytic capacitor and production method for electrolytic capacitor

Abstract

An electrolytic capacitor according to the present invention includes a laminate and a liquid component impregnated into the laminate. The laminate includes: a positive electrode foil that has a dielectric layer on the surface thereof; a separator that is layered on the positive electrode foil; a negative electrode foil; and a conductive polymer layer that is formed on the surface of the dielectric layer and in voids in the separator. The positive electrode foil and the separator are bonded together by the conductive polymer layer.

Description

Electrolytic capacitor and method for manufacturing the same

[0001] The present disclosure relates to electrolytic capacitors and methods for manufacturing electrolytic capacitors.

[0002] Known electrolytic capacitors include those that include a wound assembly of an anode foil, a separator, and a cathode foil. One example of such an electrolytic capacitor includes a conductive polymer layer disposed within the wound assembly. The conductive polymer layer can be formed by impregnating the wound assembly with a dispersion liquid containing a conductive polymer. Various proposals have been made for electrolytic capacitors that include a conductive polymer layer.

[0003] Claim 1 of Patent Document 1 (Japanese Patent No. 6911910) describes, "An electrolytic capacitor comprising a capacitor element formed by winding an anode electrode foil and a cathode electrode foil with a separator interposed therebetween, the capacitor element comprising a solid electrolyte layer using a conductive polymer compound dispersion containing conductive polymer particles and sorbitol or sorbitol and a polyhydric alcohol, the solid electrolyte layer containing 60 to 92 wt % of the sorbitol or sorbitol and a polyhydric alcohol, and the voids in the capacitor element on which the solid electrolyte layer is formed being filled with an electrolytic solution containing 10 wt % or more of ethylene glycol in a solvent."

[0004] Claim 1 of Patent Document 2 (JP 2019-516241 A) describes, "A capacitor including a processing element, the processing element including: an anode including a dielectric on a surface and an anode conductive polymer layer on the surface of the dielectric; a cathode including a cathode conductive polymer layer; a conductive separator between the anode and the cathode; an anode lead in electrical contact with the anode; and a cathode lead in electrical contact with the cathode."

[0005] Claim 1 of Patent Document 3 (WO 2021 / 125182) describes a hybrid electrolytic capacitor comprising: a cathode having a cathode substrate made of a valve metal, an oxide layer made of an oxide of the valve metal provided on the surface of the cathode substrate, an inorganic conductive layer containing an inorganic conductive material provided on the surface of the oxide layer, and an organic conductive layer containing a conductive polymer provided on the surface of the inorganic conductive layer; an anode having an anode substrate made of a valve metal and a dielectric layer made of an oxide of the valve metal constituting the anode substrate provided on the surface of the anode substrate; and a composite electrolyte layer having a solid electrolyte layer provided between the organic conductive layer of the cathode and the dielectric layer of the anode and containing conductive polymer particles in contact with them, and an electrolytic solution filled between the conductive polymer particles in the solid electrolyte layer.

[0006] Japanese Patent No. 6911910 Special Publication No. 2019-516241 International Publication No. 2021 / 125182

[0007] One aspect of the present disclosure relates to an electrolytic capacitor including a laminate and a liquid component impregnated in the laminate. The laminate includes an anode foil having a dielectric layer on its surface, a separator laminated on the anode foil, a cathode foil, and a conductive polymer layer formed on the surface of the dielectric layer and in voids in the separator. The anode foil and the separator are bonded together by the conductive polymer layer.

[0008] Another aspect of the present disclosure relates to a method for manufacturing an electrolytic capacitor, the method including: a preparation step of preparing an anode foil having a dielectric layer on a surface thereof; a laminate sheet formation step of forming a laminate sheet including the anode foil, a separator bonded to the anode foil, and a conductive polymer layer; a first laminate formation step of cutting the laminate sheet to a first width to form a first laminate including the anode foil, the separator, and the conductive polymer layer; and a second laminate formation step of stacking the first laminate and a cathode foil having a second width such that the separator is disposed between the anode foil and the cathode foil to form a second laminate. The laminate sheet forming step includes: a coating liquid applying step of applying a coating liquid containing a conductive polymer and a liquid medium to the surface of the dielectric layer and into the voids of the separator while the anode foil and the separator are superimposed on each other; and a liquid medium removing step of removing at least a part of the liquid medium from the coating liquid to form the conductive polymer layer on the surface of the dielectric layer and in the voids of the separator and to bond the anode foil and the separator together to form the laminate sheet.

[0009] According to the present disclosure, an electrolytic capacitor containing a liquid component and a conductive polymer layer and having a low ESR can be obtained.

[0010] FIG. 1 is a side view schematically illustrating an example of an electrolytic capacitor according to an embodiment of the present disclosure. FIG. 2 is an exploded perspective view schematically illustrating an example of a capacitor element according to an embodiment of the present disclosure. FIG. 3A is a cross-sectional view schematically illustrating one step of an example of a method for forming a second laminate (capacitor element). FIG. 3B is a cross-sectional view schematically illustrating one step following FIG. 3A. FIG. 3C is a cross-sectional view schematically illustrating one step following FIG. 3B. FIG. 4 schematically illustrates a peel strength measuring device.

[0011] The problems in the prior art will be briefly described below.

[0012] Because the dispersion containing the conductive polymer has high viscosity, even if the dispersion is impregnated into the wound body, a sufficient conductive polymer layer may not be formed inside the wound body. Insufficient formation of the conductive polymer layer may cause an increase in equivalent series resistance (ESR).

[0013] Furthermore, when a conductive polymer layer formed on a separator is used, it is important to improve the adhesion between the conductive polymer layer and the anode foil. Poor adhesion between the conductive polymer layer and the anode foil increases the ESR of the electrolytic capacitor and reduces the reliability of the electrolytic capacitor.

[0014] There has been a long-standing demand for reducing the ESR of electrolytic capacitors. The present disclosure provides an electrolytic capacitor that includes a liquid component and a conductive polymer layer and that can reduce the ESR.

[0015] Hereinafter, embodiments of the present invention will be described using examples, but the present invention is not limited to the examples described below. In the following description, specific numerical values ​​and materials may be exemplified, but other numerical values ​​and other materials may be applied as long as the invention according to the present disclosure can be implemented. In this specification, the expression "numerical value A to numerical value B" includes numerical value A and numerical value B and can be read as "numerical value A or more and numerical value B or less." In the following description, when lower and upper limits of numerical values ​​related to 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 equal to or greater than the upper limit.

[0016] (Method for Manufacturing Electrolytic Capacitor) The manufacturing method according to this embodiment may be referred to as "manufacturing method (M)" below. The manufacturing method (M) includes a preparation step, a laminate sheet forming step, a first laminate forming step, and a second laminate forming step, in this order. The manufacturing method (M) may also include an impregnation step after the second laminate forming step. These steps will be described later.

[0017] Conventionally, wound electrolytic capacitors having a conductive polymer layer disposed between an anode foil and a cathode foil have been manufactured by impregnating a wound capacitor element with an aqueous dispersion of a conductive polymer. However, this method has limitations on the aqueous dispersion that can be impregnated into the wound body, making it difficult to form a sufficient amount of conductive polymer layer. In contrast, manufacturing method (M) easily forms a sufficient amount of conductive polymer layer because the conductive polymer layer is formed before forming the wound body. Furthermore, manufacturing method (M) forms a conductive polymer layer, thereby bonding the anode foil and the separator together to form a laminate. The laminate and the cathode foil are then used to form the wound body. Therefore, misalignment between the anode foil and the separator is less likely to occur, making it easy to manufacture a highly reliable laminate.

[0018] (Preparation Step) The preparation step is a step of preparing an anode foil having a dielectric layer on its surface. The anode foil having a dielectric layer on its surface may be a commercially available product, or may be formed by forming a dielectric layer on the surface of a metal foil (anode foil). The dielectric layer may be formed by a known method. For example, the dielectric layer may be formed by oxidizing the surface of the metal foil (anode foil).

[0019] (Laminate Sheet Forming Process) The laminate sheet forming process is a process for forming a laminate sheet including an anode foil, a separator bonded to the anode foil, and a conductive polymer layer. The laminate sheet forming process includes a coating liquid application process and a liquid medium removal process. The obtained laminate sheet is cut to the width to be used in the capacitor element in the subsequent first laminate forming process. Therefore, the widths of the anode foil and separator used in the laminate sheet forming process are larger than the widths of the anode foil and separator in the capacitor element. In the laminate sheet forming process, the separator is bonded to at least one side of the anode foil, for example, to both sides of the anode foil. When a separator is bonded to both sides of the anode foil, the separator may be bonded to both sides of the anode foil simultaneously, or a separator may be bonded to one side of the anode foil and then another separator may be bonded to the other side.

[0020] The coating liquid application step is a step of applying a coating liquid containing a conductive polymer and a liquid medium to the surface of the dielectric layer (the dielectric layer on the surface of the anode foil) and into the voids of the separator while the anode foil and the separator are superimposed. The liquid medium removal step is a step of removing at least a portion of the liquid medium from the coating liquid to form a conductive polymer layer on the surface of the dielectric layer and in the voids of the separator, and then bonding the anode foil and the separator together to form a laminated sheet. Examples of conductive polymers will be described later.

[0021] The liquid medium is not particularly limited, and any liquid medium that can be used to form a polymer layer can be used. Examples of the liquid medium include water, organic solvents (e.g., alcohol), and mixtures thereof. The coating liquid may be a dispersion in which conductive polymer particles are dispersed in water.

[0022] The liquid medium may contain water and an organic compound that does not boil at 100°C under 1 atmosphere (101,325 Pa). Hereinafter, this organic compound may be referred to as "organic compound (C)." The organic compound (C) may be one type of compound or may be composed of multiple types of compounds.

[0023] The method for applying the coating liquid is not limited and may be a known method. For example, a coater may be used, the coating liquid may be sprayed, or the substrate may be immersed in the coating liquid. Examples of methods using a coater include gravure coating and die coating. In one example of gravure coating, the coating liquid is first applied to a transfer member (such as a gravure roll), and then excess coating liquid is removed from the transfer member. Next, the coating liquid applied to the transfer member is transferred to a predetermined member (anode foil, cathode foil, or separator), thereby allowing a layer of coating liquid with a uniform thickness to be applied to the member. The viscosity of the coating liquid may be, for example, 10 mPa·s or more (e.g., 100 mPa·s or more) and 200 mPa·s or less. In this case, the coating liquid is easily applied to the anode foil, cathode foil, and separator, and is easily impregnated into the separator. The viscosity of the coating liquid is measured at room temperature (20°C) using a vibration viscometer (for example, VM-100A, manufactured by Sekonic Corporation). Methods for applying the coating liquid to the separator include a method in which the separator is impregnated with the coating liquid. The coating liquid applied to the separator permeates into the separator and reaches the dielectric layer on the surface of the anode foil. As a result, a conductive polymer layer is formed on the surface of the dielectric layer and throughout the entire thickness of the separator. The formation of the conductive polymer layer significantly improves the adhesion between the anode foil (more specifically, the dielectric layer on the surface of the anode foil) and the separator.

[0024] The method for removing at least a portion of the liquid medium from the coating liquid is not particularly limited, and can be performed by heating, etc. When the coating liquid contains an organic compound (C), heating may be performed so that the organic compound (C) remains in the polymer layer. For example, when the coating liquid contains the organic compound (C) and water (liquid medium), heating the coating liquid at a temperature at which the organic compound (C) does not boil or decompose and at a temperature of 100°C or higher can remove water from the coating liquid while allowing the organic compound (C) to remain in the polymer layer. The heating temperature may be 100°C or higher, 120°C or higher, or 140°C or higher, and may be 200°C or lower, or 160°C or lower. The heating temperature may be in the range of 100°C to 200°C. The heating time is not particularly limited, as long as it is a time that allows appropriate removal of a portion of the liquid medium. An example heating time is in the range of 5 to 60 minutes.

[0025] By leaving the organic compound (C) in the conductive polymer layer, it is possible to reduce the shrinkage of the conductive polymer layer when the liquid medium is removed from the coating liquid. As a result, in the subsequent impregnation step, a liquid component (e.g., an electrolyte solution) can easily penetrate into the conductive polymer layer. As a result, the liquid component's function of forming a dielectric layer (oxide film) can be more easily exerted, and leakage current can be reduced.

[0026] In a preferred example of production method (M), the water content in the coating liquid is 40 mass % or more (e.g., 50 mass % or more), and the liquid medium of the applied coating liquid is removed so that the mass of the organic compound (C) in the conductive polymer layer is greater than the mass of water in the conductive polymer layer. When the water content in the coating liquid is high, the conductive polymer layer is more likely to be impregnated with an electrolytic solution after formation.

[0027] (First Laminate Forming Step) The first laminate forming step is a step of forming a first laminate including an anode foil, a separator, and a conductive polymer layer by cutting the laminate sheet to a first width. The width W0 of the laminate sheet may be at least twice the first width W1 of the first laminate. When the width W0 is at least twice the first width W1, multiple first laminates can be formed from the laminate sheet by cutting the laminate sheet. The method of cutting the laminate sheet is not limited, and known methods may be used. For example, the laminate sheet may be cut using a slitter used to cut metal foil. The width of the separator and the width of the anode foil are each substantially the same as the first width W1 of the first laminate. In this specification, width refers to the length in a direction perpendicular to the longitudinal direction. Furthermore, the width of the members (first laminate and cathode foil) used to form the wound body refers to the length in a direction parallel to the winding axis of the wound body.

[0028] The first width W1 is not limited and may be selected depending on the type and application of the electrolytic capacitor. The first width W1 may be 2.0 mm or more, or 5.0 mm or more, or may be 20 mm or less, or 12 mm or less.

[0029] When the laminated sheet is cut, the cut surfaces of the anode foil are exposed. It is preferable to form a dielectric layer on the exposed cut surfaces by subsequent chemical conversion treatment. In the first laminate, the separator is bonded to one or both sides of the anode foil.

[0030] (Second Laminate Forming Step) The second laminate forming step is a step of forming a second laminate by stacking the first laminate and a cathode foil having a second width such that a separator is disposed between the anode foil and the cathode foil. The width W2 (second width W2) of the cathode foil may be smaller than the first width W1 of the first laminate. In this case, in the second laminate forming step, the first laminate and the cathode foil are stacked such that the widthwise edge of the cathode foil is positioned inside the widthwise edge of the first laminate. That is, the first laminate and the cathode foil are positioned such that neither of the two widthwise edge of the cathode foil is positioned between the two widthwise edge of the first laminate without contacting the two widthwise edge of the first laminate. As a result, short-circuiting between the anode foil and the cathode foil can be suppressed.

[0031] The method for forming the laminate is not limited, and the laminate may be formed by a known method. The laminate may be a wound body. In this case, in the laminate formation step, the wound body may be formed by winding an anode foil, a cathode foil, and a separator such that the separator is disposed between the anode foil and the cathode foil. In the wound body, the anode foil, the cathode foil, and the separator are stacked in the radial direction of the wound body.

[0032] The stack may be formed by stacking flat anode foils, flat cathode foils, and flat separators in one direction. For example, a stack may be formed by stacking a plurality of anode foils, a plurality of cathode foils, and a plurality of separators in one direction. In a typical example of such a stack, the anode foils and the cathode foils are alternately arranged, and the separators are arranged between the anode foils and the cathode foils.

[0033] The difference (W1-W2) between the first width W1 of the first laminate and the second width W2 of the cathode foil may be 0.5 mm or more, or 1.0 mm or more, or may be 2.0 mm or less, 1.5 mm or less, or 1.2 mm or less. The difference (W1-W2) may be in the range of 0.5 mm to 1.2 mm. By making the difference (W1-W2) 0.5 mm or more, short circuits and the like can be particularly suppressed. By making the difference (W1-W2) 1.0 mm or less, a decrease in capacitance can be suppressed.

[0034] (Impregnation Step) The manufacturing method (M) may further include an impregnation step after the second laminate formation step. The impregnation step is a step of impregnating the second laminate with a liquid component. Hereinafter, the liquid component may be referred to as the "liquid component (LC)." The method of impregnating the laminate with the liquid component (LC) is not limited. For example, the laminate may be impregnated with the liquid component (LC) by immersing at least a portion of the laminate in the liquid component (LC). The liquid component (LC) may be an electrolyte solution.

[0035] The liquid component (LC) may contain at least one selected from the group consisting of ethylene glycol, diethylene glycol, triethylene glycol, ethylene glycol condensates having a molecular weight of 250 or less, glycerin, γ-butyrolactone, and sulfolane. When the liquid component (LC) contains one of these compounds, the withstand voltage of the capacitor can be increased.

[0036] In this manner, a capacitor element impregnated with the liquid component (LC) is obtained. Thereafter, other steps may be performed as necessary. For example, a step of encapsulating the capacitor element impregnated with the liquid component (LC) in an exterior body may be performed.

[0037] The manufacturing method (M) may include a liquid application step and a removal step, in this order, after the second laminate formation step and before the impregnation step. The liquid application step is a step of impregnating the laminate with a liquid (hereinafter sometimes referred to as "liquid (L)"). The removal step is a step of removing at least a portion of the liquid (L) impregnated into the second laminate. The liquid (L) may be a liquid containing water as a main component and an organic compound (C) that does not boil at 100°C under 1 atmosphere. In this case, the removal step may be a step of removing a portion of the liquid impregnated into the laminate so that the mass of the organic compound (C) in the laminate is greater than the mass of water in the laminate. Alternatively, the liquid (L) may be a liquid containing an organic solvent.

[0038] The liquid used in the liquid application step may be a liquid obtained by removing the conductive polymer component from the coating liquid used in the laminate sheet formation step. The impregnation with the liquid in the liquid application step may be performed by the method exemplified for the coating liquid application step in the laminate sheet formation step. The removal of the liquid in the removal step may be performed by the method exemplified for the liquid medium removal step in the laminate sheet formation step. By performing the liquid application step and the removal step, the adhesion between the conductive polymer layer and the cathode foil can be improved.

[0039] When the cathode foil is made solely of metal foil (e.g., aluminum foil), an oxide layer forms on the surface of the metal foil, generating capacitance in the cathode foil as well. As a result, the combined capacitance of the anode foil and the cathode foil may result in a problem of a decrease in the capacitance of the entire capacitor. Covering the surface of the metal foil with an inorganic layer or the like can prevent this problem from occurring. In other words, forming an inorganic layer can enhance the capacitance of the anode foil alone. On the other hand, poor adhesion between the conductive polymer layer and the inorganic layer increases the ESR. By performing the liquid application process, it is possible to improve the adhesion between the conductive polymer layer and the inorganic layer.

[0040] Because inorganic layers tend to repel water, conventional methods for forming a conductive polymer layer by impregnating a laminate (capacitor element) with an aqueous dispersion of a conductive polymer make it difficult for the conductive polymer to penetrate between the inorganic layer of the cathode foil and the anode foil in the laminate. This makes it difficult to form a uniform conductive polymer layer on the separator placed between the cathode foil and the anode foil, resulting in an increase in ESR. In manufacturing method (M), a laminate (capacitor element) is formed using a separator on which a conductive polymer layer has already been formed. This prevents the conductive polymer from becoming unevenly distributed within the separator.

[0041] The surface density of the conductive polymer layer is 0.05 mg / cm ２ Above, 0.1mg / cm ２ or more, or 0.3 mg / cm ２ or more, and may be 1.0 mg / cm ２ or less than 0.5 mg / cm ２For example, the surface density of the conductive polymer layer may be 0.05 mg / cm or less. ２ 1.0 mg / cm or more ２ or less. This configuration allows for an electrolytic capacitor with particularly low ESR to be obtained. Here, the areal density refers to the mass per unit area. The areal density of the conductive polymer layer can be controlled by the concentration of the conductive polymer in the coating liquid and the amount of coating.

[0042] The areal density of the conductive polymer layer can be determined by the following method. First, five samples with a predetermined area are cut out of the anode foil and separator before the laminate sheet is formed, and the masses of the five samples are measured. Five samples with the predetermined area are also cut out of the laminate sheet on which the conductive polymer layer has been formed, and the masses of the five samples are measured. The areal density of the conductive polymer layer is determined using the predetermined area and the difference between the total mass of the five samples after the conductive polymer layer has been formed and the total mass of the five samples before the conductive polymer layer has been formed.

[0043] In the electrolytic capacitor produced by production method (M), the cathode foil may have an inorganic layer on the surface thereof, and the conductive polymer layer may be in close contact with the inorganic layer.

[0044] The peel strength between the anode foil and the separator may be 1.0 N / cm or more, 2.0 N / cm or more, or 2.9 N / cm or more. There is no particular upper limit to the peel strength. The peel strength can be measured by the method described in the Examples.

[0045] (Electrolytic Capacitor) The electrolytic capacitor according to this embodiment may be referred to as the "electrolytic capacitor (E)" below. The electrolytic capacitor (E) may be manufactured by the manufacturing method (M) described above. The matters described for the manufacturing method (M) may be applied to the electrolytic capacitor (E), and therefore, redundant explanations may be omitted. The matters described for the electrolytic capacitor (E) may also be applied to the manufacturing method (M).

[0046] The electrolytic capacitor (E) includes a laminate and a liquid component impregnated in the laminate. The laminate includes an anode foil having a dielectric layer on its surface, a separator laminated on the anode foil, a cathode foil, and a conductive polymer layer formed on the surface of the dielectric layer and in the voids of the separator. The anode foil and the separator are bonded together by the conductive polymer layer. The width of the cathode foil (second width W2) may be smaller than the width of the anode foil (first width W1). The width of the separator is substantially the same as the first width W1 of the anode foil.

[0047] The electrolytic capacitor (E) can provide the effects described in the manufacturing method (M). For example, the configuration of the electrolytic capacitor (E) can reduce the ESR.

[0048] In the electrolytic capacitor (E), the surface density of the conductive polymer layer may be in the above range. For example, the surface density of the conductive polymer layer may be 0.05 mg / cm ２ 1.0 mg / cm or more ２ It may be the following:

[0049] In the electrolytic capacitor (E), the cathode foil may have an inorganic layer on the surface thereof. In this case, it is preferable that the conductive polymer layer is in close contact with the inorganic layer.

[0050] As described above, the peel strength between the anode foil and the separator may be 1.0 N / cm or more. As described above, the laminate may be a wound body or a laminate other than a wound body.

[0051] Examples of materials and components used in the manufacturing method (M) and the electrolytic capacitor (E) are described below, but the materials and components used in the manufacturing method (M) and the electrolytic capacitor (E) are not limited to the examples described below.

[0052] In this specification, the term "conductive polymer component" may be used. When a conductive polymer is not doped with a dopant, the conductive polymer component consists of the conductive polymer. When a conductive polymer is doped with a dopant, the conductive polymer component consists of the conductive polymer and the dopant.

[0053] (Coating Liquid) The coating liquid used in the polymer layer forming step may contain a conductive polymer and water. The conductive polymer (conductive polymer component) may be contained in the coating liquid in the form of particles. The coating liquid may be an aqueous dispersion of the conductive polymer (conductive polymer component).

[0054] The coating liquid may contain other components (for example, an organic compound (C)). The organic compound (C) may contain at least one selected from the group consisting of polyhydric alcohols, sulfolane, γ-butyrolactone, and boric acid esters, or may consist of at least one such compound. The organic compound (C) may contain at least one selected from the group consisting of glycols, glycerins, sugar alcohols, sulfolane, γ-butyrolactone, and boric acid esters, or may consist of at least one such compound.

[0055] Examples of polyhydric alcohols include glycols, glycerins, and sugar alcohols. Examples of glycols include ethylene glycol, diethylene glycol, triethylene glycol, polyalkylene glycol (e.g., polyethylene glycol), polyoxyethylene polyoxypropylene glycol (ethylene oxide-propylene oxide copolymer), etc. Examples of glycerins include glycerin and polyglycerin. Examples of sugar alcohols include mannitol, xylitol, sorbitol, erythritol, and pentaerythritol.

[0056] Examples of conductive polymers include polypyrrole, polythiophene, polyfuran, polyaniline, polyacetylene, and derivatives thereof. These 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. One preferred example of a conductive polymer is poly(3,4-ethylenedioxythiophene) (PEDOT).

[0057] The conductive polymer may be doped with a dopant. From the viewpoint of suppressing dedoping from the conductive polymer, it is preferable to use a polymer dopant as the dopant. Examples of polymer dopants include polyvinyl sulfonic acid, polystyrene sulfonic acid, polyallylsulfonic acid, polyacrylic sulfonic acid, polymethacrylic sulfonic acid, poly(2-acrylamido-2-methylpropanesulfonic acid), polyisoprene sulfonic acid, polyacrylic acid, and the like. These may be used alone or in combination of two or more. At least a portion of these may be added in the form of a salt. A preferred example of the dopant is polystyrene sulfonic acid (PSS).

[0058] The dopant may be polystyrene sulfonic acid, and the conductive polymer may be poly(3,4-ethylenedioxythiophene). That is, the conductive polymer component may be poly(3,4-ethylenedioxythiophene) doped with polystyrene sulfonic acid.

[0059] When a conductive polymer doped with a dopant is used, the pH of the coating liquid is preferably less than 7.0, and may be 6.0 or less or 5.0 or less, in order to suppress dedoping of the dopant. The pH of the coating liquid may be 1.0 or more, or 2.0 or more.

[0060] The water content in the coating liquid may be 40% by mass or more, 50% by mass or more, 80% by mass or more, 90% by mass or more, or 95% by mass or more, and may be 98% by mass or less, 95% by mass or less, 90% by mass or less, or 80% by mass or less.

[0061] The content of the organic compound (C) in the coating liquid may be 1.0% by mass or more, 3.0% by mass or more, 5.0% by mass or more, or 10% by mass or more. It may be 30% by mass or less, 20% by mass or less, 15% by mass or less, or 10% by mass or less. The content of the conductive polymer component in the coating liquid may be 0.5% by mass or more or 1.0% by mass or more, and may be 4.0% by mass or less, 3.0% by mass or less, or 2.0% by mass or less. The content may be in the range of 0.5 to 4.0% by mass or 1.0 to 4.0% by mass. Within any of these ranges, the upper limit may be 3.0% by mass or 2.0% by mass. In terms of excellent physical properties and stability over time of the coating liquid, and a good balance between the ESR of the electrolytic capacitor and cost, the content is preferably in the range of 1.0 to 3.0%. When the coating liquid contains a dopant, the mass of the dopant is included in the mass of the conductive polymer component.

[0062] There are no particular limitations on the mass of the dopant contained in the coating liquid, and it may be in the range of 0.1 to 5 times (for example, in the range of 0.5 to 3 times) the mass of the conductive polymer contained in the coating liquid.

[0063] In the coating liquid, the ratio of water content:organic compound (C) content:conductive polymer component content may be 40 to 98:1.0 to 59.5:0.5 to 4.0, or the ratio of water content:organic compound (C) content:conductive polymer component content may be 69.5 to 98:1.0 to 30:0.5 to 4.0.

[0064] (Liquid Component (LC)) Examples of the liquid component (LC) used in the impregnation step include a non-aqueous solvent and an electrolytic solution. The electrolytic solution may be an electrolytic solution containing a non-aqueous solvent and a solute dissolved in the non-aqueous solvent. In this specification, the liquid component (LC) may be a component that is liquid at room temperature (25°C) or a component that is liquid at the temperature at which the electrolytic capacitor is used.

[0065] The non-aqueous solvent used in the liquid component (LC) may be an organic solvent, an ionic liquid, or a protic solvent. Examples of the non-aqueous solvent include polyhydric alcohols such as ethylene glycol and propylene glycol, cyclic sulfones such as sulfolane (SL), lactones such as γ-butyrolactone (γBL), 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.

[0066] Furthermore, a polymer solvent may be used as the non-aqueous solvent. Examples of polymer solvents include polyalkylene glycol, polyalkylene glycol derivatives, and compounds in which at least one hydroxyl group in a polyhydric alcohol has been substituted with polyalkylene glycol (including derivatives). Specific examples of polymer solvents include polyethylene glycol (PEG), polyethylene glycol glyceryl ether, polyethylene glycol diglyceryl ether, polyethylene glycol sorbitol ether, polypropylene glycol, polypropylene glycol glyceryl ether, polypropylene glycol diglyceryl ether, polypropylene glycol sorbitol ether, and polybutylene glycol. Further examples of polymer solvents include ethylene glycol-propylene glycol copolymers, ethylene glycol-butylene glycol copolymers, and propylene glycol-butylene glycol copolymers. One type of non-aqueous solvent may be used alone, or two or more types may be used in combination.

[0067] The liquid component (LC) may include a non-aqueous solvent and a base component (base) dissolved in the non-aqueous solvent. Alternatively, the liquid component (LC) may include a non-aqueous solvent and a base component and / or an acid component (acid) dissolved in the non-aqueous solvent.

[0068] The acid component can be a polycarboxylic acid or a monocarboxylic acid. Examples of the polycarboxylic acid include aliphatic polycarboxylic acids (saturated polycarboxylic acids such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, 1,6-decanedicarboxylic acid, and 5,6-decanedicarboxylic acid; unsaturated polycarboxylic acids such as maleic acid, fumaric acid, and itaconic acid), aromatic polycarboxylic acids (phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, and pyromellitic acid), and alicyclic polycarboxylic acids (cyclohexane-1,2-dicarboxylic acid and cyclohexene-1,2-dicarboxylic acid).

[0069] Examples of the monocarboxylic acid include aliphatic monocarboxylic acids (having 1 to 30 carbon atoms) ([saturated monocarboxylic acids such as formic acid, acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, lauric acid, myristic acid, stearic acid, and behenic acid]; [unsaturated monocarboxylic acids such as acrylic acid, methacrylic acid, and oleic acid]), aromatic monocarboxylic acids (such as benzoic acid, cinnamic acid, and naphthoic acid), and oxycarboxylic acids (such as salicylic acid, mandelic acid, and resorcylic acid).

[0070] Among these, maleic acid, phthalic acid, benzoic acid, pyromellitic acid, and resorcylic acid are thermally stable and are therefore preferably used.

[0071] An inorganic acid may be used as the acid component. Typical examples of inorganic acids include phosphoric acid, phosphorous acid, hypophosphorous acid, alkyl phosphate esters, boric acid, fluoroboric acid, tetrafluoroboric acid, hexafluorophosphoric acid, benzenesulfonic acid, and naphthalenesulfonic acid. Alternatively, a composite compound of an organic acid and an inorganic acid may be used as the acid component. Examples of such composite compounds include borodiglycolic acid, borodisalic acid, and borodisalicylic acid.

[0072] The base component may be a compound having an alkyl-substituted amidine group, such as an imidazole compound, a benzimidazole compound, or an alicyclic amidine compound (a pyrimidine compound, an imidazoline compound). Specifically, 1,8-diazabicyclo[5,4,0]undecene-7, 1,5-diazabicyclo[4,3,0]nonene-5, 1,2-dimethylimidazolinium, 1,2,4-trimethylimidazoline, 1-methyl-2-ethyl-imidazoline, 1,4-dimethyl-2-ethylimidazoline, 1-methyl-2-heptylimidazoline, 1-methyl-2-(3'heptyl)imidazoline, 1-methyl-2-dodecylimidazoline, 1,2-dimethyl-1,4,5,6-tetrahydropyrimidine, 1-methylimidazole, or 1-methylbenzimidazole is preferred. By using these, a capacitor with excellent impedance performance can be obtained.

[0073] The base component may be a quaternary salt of a compound having an alkyl-substituted amidine group. Examples of such base components include imidazole compounds, benzimidazole compounds, and alicyclic amidine compounds (pyrimidine compounds, imidazoline compounds) quaternized with an alkyl group or arylalkyl group having 1 to 11 carbon atoms. Specifically, 1-methyl-1,8-diazabicyclo[5,4,0]undecene-7, 1-methyl-1,5-diazabicyclo[4,3,0]nonene-5, 1,2,3-trimethylimidazolinium, 1,2,3,4-tetramethylimidazolinium, 1,2-dimethyl-3-ethyl-imidazolinium, 1,3,4-trimethyl-2-ethylimidazolinium, 1,3-dimethyl-2-heptylimidazolinium, 1,3-dimethyl-2-(3'heptyl)imidazolinium, 1,3-dimethyl-2-dodecylimidazolinium, 1,2,3-trimethyl-1,4,5,6-tetrahydropyrimidium, 1,3-dimethylimidazolium, 1-methyl-3-ethylimidazolium, 1,3-dimethylbenzimidazolium is preferred. By using these, a capacitor with excellent impedance performance can be obtained.

[0074] Tertiary amines may also be used as the base component. Examples of tertiary amines include trialkylamines (trimethylamine, dimethylethylamine, methyldiethylamine, triethylamine, dimethyl-n-propylamine, dimethylisopropylamine, methylethyl-n-propylamine, methylethylisopropylamine, diethyl-n-propylamine, diethylisopropylamine, tri-n-propylamine, triisopropylamine, tri-n-butylamine, tri-tert-butylamine, etc.), and phenyl group-containing amines (dimethylphenylamine, methylethylphenylamine, diethylphenylamine, etc.). Among these, trialkylamines are preferred in terms of increasing conductivity, and it is more preferable to use at least one selected from the group consisting of trimethylamine, dimethylethylamine, methyldiethylamine, and triethylamine. Furthermore, secondary amines such as dialkylamines, primary amines such as monoalkylamines, and ammonia may also be used as the base component.

[0075] The liquid component (LC) may contain a salt of an acid component and a base component. The salt may be an inorganic salt and / or an organic salt. An organic salt is a salt in which at least one of the anion and the cation contains an organic substance. Examples of organic salts that may be used include trimethylamine maleate, triethylamine borodisalicylate, ethyldimethylamine phthalate, mono-1,2,3,4-tetramethylimidazolinium phthalate, and mono-1,3-dimethyl-2-ethylimidazolinium phthalate.

[0076] To prevent the dopant from being dedoped, the pH of the liquid component (LC) may be less than 7.0 or 5.0 or less, or may be 1.0 or more, or 2.0 or more. The pH may be 1.0 or more and less than 7.0 (for example, in the range of 2.0 to 5.0).

[0077] The liquid component (LC) preferably contains a protic solvent. By using a protic solvent, it is possible to particularly swell the conductive polymer layer. The liquid component (LC) may contain, in addition to the protic solvent, a solvent other than the protic solvent.

[0078] The protic solvent may include at least one selected from the group consisting of glycols, glycerin, polyglycerin, and sugar alcohols, and may be composed of only one type of compound or may include multiple types of compounds.

[0079] The organic compound (C) and the liquid component (LC) may contain the same compound, for example, they may contain the same polyhydric alcohol, the same glycol (e.g., ethylene glycol), or the same sugar alcohol.

[0080] (Liquid (L)) The liquid (L) may be a liquid containing the organic compound (C) and water. In this case, it is preferable to impregnate the laminate with the liquid (L) and then remove water from the laminate under conditions in which the organic compound (C) remains in the laminate. The organic compound (C) may be at least one selected from the group consisting of mannitol, mannitol derivatives, xylitol, and xylitol derivatives.

[0081] The liquid (L) may contain at least one substance (hereinafter, sometimes referred to as "substance X") selected from the group consisting of sugar, sugar alcohol, epoxy resin, and polyvinyl alcohol. By containing substance X in the liquid (L), the adhesion between the conductive polymer layer and the cathode foil can be improved. The content of substance X in the liquid (L) may be in the range of 10% by mass to 70% by mass (for example, in the range of 30% by mass to 50% by mass).

[0082] The sugar alcohol may include at least one selected from the group consisting of mannitol, mannitol derivatives, xylitol, and xylitol derivatives, or may be at least one of these. Substance X may be at least one selected from the group consisting of mannitol, mannitol derivatives, xylitol, and xylitol derivatives. Mannitol, mannitol derivatives, xylitol, and xylitol derivatives have the effect of acting as an adhesive to bond the conductive polymer layer and the cathode foil together. Examples of xylitol derivatives include compounds in which some of the hydroxyl groups of xylitol are esterified, compounds in which some of the hydroxyl groups of xylitol are etherified, and compounds in which some of the hydroxyl groups of xylitol are anionized to form a salt. Examples of mannitol derivatives include compounds in which some of the hydroxyl groups of mannitol are esterified, compounds in which some of the hydroxyl groups of mannitol are etherified, and compounds in which some of the hydroxyl groups of mannitol are anionized to form a salt.

[0083] The organic solvent contained in the liquid (L) may contain at least one selected from the group consisting of ethylene glycol, diethylene glycol, triethylene glycol, and polyethylene glycol, or may be the at least one selected from the group consisting of ethylene glycol, diethylene glycol, triethylene glycol, and polyethylene glycol. By containing the organic solvent in the liquid (L), the adhesion between the conductive polymer layer and the cathode foil can be improved, and the ESR can be reduced.

[0084] A preferred example of the liquid (L) is a liquid in which xylitol is contained in at least one organic solvent selected from the group consisting of triethylene glycol and polyethylene glycol.

[0085] (Anode Foil) Examples of the anode foil include metal foils containing at least one valve metal such as titanium, tantalum, aluminum, and niobium, and may be metal foils of valve metals (e.g., aluminum foil). The anode foil may contain the valve metal in the form of an alloy containing the valve metal or a compound containing the valve metal. The thickness of the anode foil may be 15 μm or more and 300 μm or less. The surface of the anode foil may be roughened by etching or the like.

[0086] A dielectric layer is formed on the surface of the anode foil. The dielectric layer may be formed by chemically treating the anode foil. In this case, the dielectric layer may contain an oxide of a valve metal (e.g., aluminum oxide). Note that the dielectric layer may be formed of any dielectric other than an oxide of a valve metal as long as it functions as a dielectric.

[0087] In an electrolytic capacitor, the end surface of the anode foil does not necessarily have to be provided with a conductive polymer layer, but it is preferable that the end surface of the anode foil has a dielectric layer formed thereon.

[0088] (Cathode foil) The cathode foil includes a metal foil (e.g., aluminum foil). The metal constituting the metal foil may be a valve metal or an alloy containing a valve metal. The surface of the metal foil may be roughened by etching or the like. The thickness of the cathode foil may be 15 μm or more and 300 μm or less. A conductive polymer layer may be formed on the surface of the cathode foil. The conductive polymer layer can be formed by the same method as the methods described in the coating liquid application step and the liquid medium removal step above.

[0089] As described above, the cathode foil may have an inorganic layer on its surface. A commercially available cathode foil having an inorganic layer on its surface may be used, or the cathode foil may be formed by forming an inorganic layer on the surface of a metal foil (cathode foil). The inorganic layer may be formed by a known method. For example, the inorganic layer may be formed by a vacuum deposition method or the like. Alternatively, the inorganic layer may be formed by applying a paste containing at least one selected from the group consisting of carbon (particularly a conductive carbon material), titanium, and nickel onto the metal foil (cathode foil) and then drying the paste. The deposition amount of the inorganic layer is 50 mg / m. ２ ~300 mg / m ２ range (e.g., 70 mg / m ２ ~200 mg / m ２The inorganic layer may be a carbon layer having a carbon content of 50% by mass or more. Examples of carbon (particularly conductive carbon materials) contained in the inorganic layer include graphite, hard carbon, soft carbon, and carbon black. When the inorganic layer contains titanium, it may be a layer on which titanium is vapor-deposited, or a layer formed of titanium oxide particles. The inorganic layer may be a carbon layer. The carbon layer may be a layer containing carbon, and may have a carbon content of 50% by mass or more. In this specification, the term "inorganic layer" may be replaced with "carbon layer".

[0090] The cathode foil may include a metal foil, an inorganic layer, and a titanium-containing layer disposed between the inorganic layer and the metal foil. An example of a cathode foil has a laminated structure of inorganic layer / titanium-containing layer / metal foil (e.g., aluminum foil) / titanium-containing layer / inorganic layer. The titanium-containing layer may contain at least one selected from the group consisting of titanium and titanium compounds. Examples of titanium compounds include titanium nitride, titanium oxide, titanium aluminum alloy, and titanium carbonate. The titanium-containing layer may be formed by any known method without any particular limitation. For example, the titanium-containing layer may be formed by physical vapor deposition such as vacuum deposition or sputtering. The coating weight of the titanium-containing layer may be 200 mg / m. ２ ~500 mg / m ２ range (e.g., 250 mg / m ２ ~400 mg / m ２ The range may be within .

[0091] (Separator) A porous sheet can be used as the separator. Examples of porous sheets include woven fabric, nonwoven fabric, and microporous membrane. The thickness of the separator is not particularly limited and may be in the range of 10 to 300 μm. Examples of separator materials include cellulose, polyethylene terephthalate, polybutylene terephthalate, polyphenylene sulfide, vinylon, nylon, aromatic polyamide, polyimide, polyamideimide, polyetherimide, rayon, and glass.

[0092] (Exterior Body) The laminate and the liquid component (LC) are housed in an exterior body. The exterior body includes a case and / or a sealing resin. There is no limitation thereto, and known cases and sealing resins may be used. The sealing resin may include a thermosetting resin. Examples of thermosetting resins include epoxy resins, phenolic resins, silicone resins, melamine resins, urea resins, alkyd resins, polyurethanes, polyimides, unsaturated polyesters, etc. The sealing resin may include a filler, a curing agent, a polymerization initiator, and / or a catalyst, etc.

[0093] An example of the present disclosure will be specifically described below with reference to the drawings. The components described above can be applied to the components of the example described below. Furthermore, the components of the example described below can be modified based on the above description. Furthermore, the matters described below may be applied to the above-described embodiment. Furthermore, in the example described below, components that are not essential for the electrolytic capacitor of the present disclosure may be omitted.

[0094] Fig. 1 is a cross-sectional view schematically illustrating an example of an electrolytic capacitor 100 according to this embodiment. Fig. 2 is a schematic view showing a portion of a capacitor element 10 included in the electrolytic capacitor 100 in an exploded view.

[0095] Electrolytic capacitor 100 includes capacitor element 10, bottomed case 101 that houses capacitor element 10, sealing member 102 that closes the opening of bottomed case 101, seat plate 103 that covers sealing member 102, lead wires 104A and 104B that extend from sealing member 102 and pass through seat plate 103, and lead tabs 105A and 105B that connect the lead wires to electrodes of capacitor element 10. The vicinity of the open end of bottomed case 101 is drawn inward, and the open end is curled so as to be crimped to sealing member 102.

[0096] Capacitor element 10 is, for example, a wound body as shown in FIG. 1 . The wound body includes an anode foil connected to lead tab 105A, a cathode foil 12 connected to lead tab 105B, and a separator 13. Capacitor element 10 (wound body) includes a conductive polymer layer (not shown). The conductive polymer layer may include an organic compound (C). Electrolytic capacitor 100 includes a liquid component (LC) (e.g., an electrolyte solution) impregnated in capacitor element 10.

[0097] Capacitor element 10 is formed by winding a strip-shaped first laminate 11y having a first width W1 and a strip-shaped cathode foil 12 having a second width W2. First laminate 11y includes an anode foil, a separator bonded to the anode foil, and a conductive polymer layer. First laminate 11y and cathode foil 12 are wound such that separator 13 is disposed between the anode foil and cathode foil 12. The outermost periphery of the wound body is fixed with stop tape 14. Note that FIG. 2 shows the wound body in a partially unfolded state before the outermost periphery is secured.

[0098] The electrolytic capacitor may have at least one capacitor element, or may have a plurality of capacitor elements, and the number of capacitor elements included in the electrolytic capacitor may be determined depending on the application.

[0099] An example of a method for forming a second laminate (capacitor element) is shown in the cross-sectional views of FIGS. 3A to 3C. First, as shown in FIG. 3A, an anode foil 11a and a separator 13a are superimposed. Note that a dielectric layer (not shown) is formed on the surfaces (both sides) of the anode foil 11a. Next, the above-described coating liquid application step and liquid medium removal step are performed to form a laminate sheet 11x shown in FIG. 3B. The laminate sheet 11x includes an anode foil 11a and a separator 13b having a conductive polymer layer formed in its voids. The conductive polymer layer is integrally formed on the surface of the dielectric layer and in the voids of the separator. As a result, the anode foil 11a and the separator 13b are bonded together. Similarly, the above-described coating liquid application step and liquid medium removal step are performed on the surface of the anode foil 11a opposite to the surface to which the separator 13b is bonded, thereby bonding the anode foil 11a and the separator 13b together.

[0100] Next, as shown in FIG. 3C , a laminate sheet 11x, in which separators 13b are bonded to both sides of an anode foil 11a, is cut to a first width W1 to form a first laminate 11y including the anode foil 11, a conductive polymer layer, and separators 13 (13b). Next, a second laminate is obtained by stacking the first laminate 11y and a cathode foil 12 having a second width W2. For example, as shown in FIG. 2 , the first laminate 11y and the cathode foil 12 may be wound together.

[0101] (Additional Note) The above description discloses the following techniques.

[0102] (Technology 1) An electrolytic capacitor including a laminate and a liquid component impregnated in the laminate, wherein the laminate includes: an anode foil having a dielectric layer on a surface thereof; a separator laminated on the anode foil; a cathode foil; and a conductive polymer layer formed on the surface of the dielectric layer and in voids in the separator, and the anode foil and the separator are bonded together by the conductive polymer layer.

[0103] (Technology 2) The electrolytic capacitor according to Technology 1, wherein the width of the cathode foil is smaller than the width of the anode foil.

[0104] (Technology 3) The surface density of the conductive polymer layer is 0.05 mg / cm ２ 1.0mg / cm or more ２ The electrolytic capacitor according to Technology 1 or 2, which is as follows:

[0105] (Technology 4) The electrolytic capacitor according to any one of Technologies 1 to 3, wherein the cathode foil has an inorganic layer on a surface thereof, and the conductive polymer layer is in close contact with the inorganic layer.

[0106] (Technology 5) The electrolytic capacitor according to any one of Technologies 1 to 4, wherein the peel strength between the anode foil and the separator is 1.0 N / cm or more.

[0107] (Technology 6) The electrolytic capacitor according to any one of Technologies 1 to 5, wherein the width of the anode foil and the width of the separator are the same.

[0108] (Technology 7) The electrolytic capacitor according to any one of Technologies 1 to 6, wherein the laminate is a wound body.

[0109] (Technology 8) A method for manufacturing an electrolytic capacitor, comprising: a preparation step of preparing an anode foil having a dielectric layer on a surface thereof; a laminate sheet formation step of forming a laminate sheet including the anode foil, a separator bonded to the anode foil, and a conductive polymer layer; a first laminate formation step of cutting the laminate sheet to a first width to form a first laminate including the anode foil, the separator, and the conductive polymer layer; and a second laminate formation step of stacking the first laminate and a cathode foil having a second width such that the separator is disposed between the anode foil and the cathode foil to form a second laminate, wherein the laminate sheet formation step comprises: a coating liquid application step of applying a coating liquid containing a conductive polymer and a liquid medium to the surface of the dielectric layer and into voids in the separator while the anode foil and the separator are superimposed; a liquid medium removing step of removing at least a part of the liquid medium from the coating liquid to form the conductive polymer layer on the surface of the dielectric layer and in the voids of the separator, and also to bond the anode foil and the separator together to form the laminated sheet.

[0110] (Technology 9) The method for manufacturing an electrolytic capacitor according to Technology 8, wherein the second width of the cathode foil is smaller than the first width of the first laminate.

[0111] (Technology 10) The surface density of the conductive polymer layer is 0.05 mg / cm ２ 1.0mg / cm or more ２ The method for manufacturing an electrolytic capacitor according to Technology 8 or 9, which is as follows:

[0112] (Technology 11) The method for manufacturing an electrolytic capacitor according to any one of Techniques 8 to 10, wherein the cathode foil has an inorganic layer on a surface thereof, and the conductive polymer layer is in close contact with the inorganic layer.

[0113] (Technology 12) The method for manufacturing an electrolytic capacitor according to any one of Technologies 8 to 11, wherein the peel strength between the anode foil and the separator is 1.0 N / cm or more.

[0114] (Technology 13) The method for manufacturing an electrolytic capacitor according to any one of Technologies 8 to 12, wherein the second laminate is a wound body.

[0115] The present disclosure will be described in more detail below based on examples, but the present disclosure is not limited to these examples. In these examples, a plurality of electrolytic capacitors were fabricated and evaluated by the following method.

[0116] (Capacitor A1) An electrolytic capacitor (capacitor A1) was produced by the following method.

[0117] (a) Preparation of Components Aluminum foil (thickness: 100 μm) was subjected to an etching treatment to roughen the surface of the aluminum foil. The roughened aluminum foil surface was subjected to a chemical conversion treatment to form a dielectric layer. In this way, an anode foil with a dielectric layer formed on both sides was obtained. Carbon layers were formed on both sides of aluminum foil (thickness: 50 μm) that would become a cathode foil. The carbon layers were formed by vacuum deposition.

[0118] A nonwoven fabric (50 μm thick) made of polyester fiber, aramid fiber, and cellulose was prepared as a separator.

[0119] (b) Formation of Laminated Sheet As a coating liquid, a dispersion liquid (commercially available) in which particles of polyethylenedioxythiophene (PEDOT) doped with polystyrene sulfonic acid (PSS) were dispersed in water was prepared.

[0120] Next, with the anode foil and separator stacked, a coating liquid was applied to the separator, thereby applying the coating liquid to the surface of the dielectric layer of the anode foil and into the voids in the separator. Next, the anode foil and separator coated with the coating liquid were heated at 125°C for 5 minutes to remove the liquid medium from the applied coating liquid. This heating formed a conductive polymer layer on the surface of the dielectric layer and in the voids in the separator, and also bonded the anode foil and separator together. In this example, separators were bonded to both sides of the anode foil. In this manner, a laminate sheet was obtained.

[0121] (c) Formation of a First Laminate and a Second Laminate Next, the laminate sheet was cut to form a first laminate having a first width W1 (10 mm). Next, the first laminate and a cathode foil having a second width W2 (9 mm) were wound together so that a separator was disposed between the anode foil and the cathode foil, thereby forming a wound body (second laminate). At this time, the end of the outer surface of the wound body was fixed with a winding tape. Note that, before forming the wound body, an anode lead tab was connected to the anode foil, and a cathode lead tab was connected to the cathode foil.

[0122] Next, an anode lead wire and a cathode lead wire were connected to the ends of the lead tabs protruding from the wound body, respectively. The wound body was again subjected to chemical conversion treatment to form a dielectric layer on the end surface of the anode foil. In this way, a capacitor element was obtained.

[0123] (d) Impregnation with Liquid Component An electrolyte solution (liquid component) was prepared by dissolving o-phthalic acid and triethylamine (base component) in ethylene glycol (solvent) at a total concentration of 25% by mass. The capacitor element was immersed in the electrolyte solution for 5 minutes in a reduced pressure atmosphere (40 kPa). This allowed the capacitor element (laminate) to be impregnated with the electrolyte.

[0124] (e) Sealing of Capacitor Element The capacitor element impregnated with the electrolytic solution was sealed to produce an electrolytic capacitor as shown in Fig. 1. Then, aging was performed at 95°C for 90 minutes while applying a voltage. In this way, an electrolytic capacitor (Capacitor A1) was produced.

[0125] (Capacitor C1) An electrolytic capacitor (capacitor C1) was fabricated using the same method and conditions as those for fabricating capacitor A1, except for the different methods for forming the conductive polymer layer and the wound body. The conductive polymer layer formed on the dielectric layer on the surface of the anode foil was formed by applying the coating liquid used in capacitor A1 to the dielectric layer and then drying it. The conductive polymer layer formed in the voids in the separator was formed by applying the coating liquid used in capacitor A1 to the separator and then drying it. That is, in fabricating capacitor C1, the conductive polymer layer on the dielectric layer and the conductive polymer layer in the separator were formed separately, and the anode foil and the separator were not bonded together.

[0126] The wound body was formed by winding an anode foil with a conductive polymer layer formed thereon, a cathode foil with a conductive polymer layer formed thereon, and a separator so that the separator was disposed between the anode foil and the cathode foil. The sizes of these components were the same as those of the components used in capacitor A1. After the wound body was formed, capacitor C1 was fabricated using the same method and conditions as those for capacitor A1.

[0127] (Evaluation) The equivalent series resistance (ESR) of the fabricated electrolytic capacitor was measured. The fabricated electrolytic capacitor was also disassembled, and the peel strength between the anode foil (more specifically, the dielectric layer on the surface of the anode foil) and the separator was measured by the following method.

[0128] (1) Measurement of Peel Strength In this example, first, the electrolytic capacitor was disassembled, and the wound body (capacitor element 10) was removed. Next, the anode foil 11 was pulled from the outer periphery of the wound body, and a portion of the anode foil 11 was peeled off from the wound body, separating the anode foil 11 from the separator 13 that was in close contact with the anode foil 11.

[0129] The schematic configuration of the measuring device 20 used to measure the peel strength is shown in FIG. 4. The measuring device is preferably designed to perform tests in accordance with JIS C0806-3:2014. The measuring device 20 includes a feed sheet 21, feed rollers 22, and a recovery device 23. The outer peripheral surface of the peeled anode foil 11 is fixed to the feed sheet 21 by a fixture 24. The feed sheet 21 is fed in a first direction by the feed rollers 22. The recovery device 23 recovers the cathode foil 12 and separator 13 from which the anode foil 11 has been peeled, pulling them in a second direction opposite to the first direction. The recovery device 23 has a take-up roller that winds up the cathode foil 12 and separator 13. The feed speed of the anode foil 11 by the feed rollers 22 and the take-up speed of the cathode foil 12 and separator 13 by the recovery device 23 are controlled to prevent the position of the capacitor element 10 from moving during measurement.

[0130] The peeled portion of anode foil 11 was fixed to a feed sheet, and cathode foil 12 and separator 13 from which anode foil 11 had been peeled were set in recovery device 23. An embossed tape high-speed peel strength tester (PTS-5000K) manufactured by EPI Co., Ltd. was used as the measurement device.

[0131] In this example, the anode foil 11, cathode foil 12, and separator 13 were pulled in the measuring device 20 so that the angle between the direction in which the anode foil 11 fixed to the feed sheet 21 was pulled and the direction in which the cathode foil 12 and separator 13 were pulled by the recovery device 23 was approximately 175°. The anode foil 11 and separator 13 were pulled for 60 seconds so that the anode foil 11 and separator 13 were continuously peeled off at a constant speed (160 mm / min). The pulling force on the cathode foil 12 was measured at sampling intervals of 0.01 seconds. The average of the measured pulling forces on the cathode foil 12 was defined as the peel strength.

[0132] The evaluation results are shown in Table 1.

[0133]

[0134] Capacitor A1 is an electrolytic capacitor (E) according to the present disclosure manufactured by manufacturing method (M). Capacitor C1 is a comparative example. As shown in Table 1, capacitor A1 had a high peel strength between the anode foil and the separator and a low ESR.

[0135] The present disclosure can be used for electrolytic capacitors.

[0136] 10: Capacitor element (second laminate) 11: Anode foil 11a: Anode foil 11x: Laminated sheet 11y: First laminate 12: Cathode foil 13, 13a, 13b: Separator 100: Electrolytic capacitor

Claims

1. An electrolytic capacitor comprising a laminate and a liquid component impregnated in the laminate, wherein the laminate comprises: an anode foil having a dielectric layer on a surface thereof; a separator laminated on the anode foil; a cathode foil; and a conductive polymer layer formed on the surface of the dielectric layer and in voids in the separator, wherein the anode foil and the separator are bonded together by the conductive polymer layer.

2. The electrolytic capacitor of claim 1, wherein the width of said cathode foil is smaller than the width of said anode foil.

3. The surface density of the conductive polymer layer is 0.05 mg / cm ２ 1.0mg / cm or more ２ 2. The electrolytic capacitor of claim 1, wherein:

4. The electrolytic capacitor according to claim 1, wherein the cathode foil has an inorganic layer on a surface thereof, and the conductive polymer layer is in close contact with the inorganic layer.

5. The electrolytic capacitor according to claim 1, wherein the peel strength between the anode foil and the separator is 1.0 N / cm or more.

6. The electrolytic capacitor of claim 1, wherein the width of said anode foil and the width of said separator are the same.

7. The electrolytic capacitor of claim 1, wherein the laminate is a wound body.

8. A method for manufacturing an electrolytic capacitor, comprising: a preparation step of preparing an anode foil having a dielectric layer on a surface thereof; a laminate sheet formation step of forming a laminate sheet including the anode foil, a separator bonded to the anode foil, and a conductive polymer layer; a first laminate formation step of cutting the laminate sheet to a first width to form a first laminate including the anode foil, the separator, and the conductive polymer layer; and a second laminate formation step of laminating the first laminate and a cathode foil having a second width such that the separator is disposed between the anode foil and the cathode foil to form a second laminate, the laminate sheet formation step comprising: a coating liquid application step of applying a coating liquid containing a conductive polymer and a liquid medium to the surface of the dielectric layer and into voids in the separator while the anode foil and the separator are superimposed; a liquid medium removing step of removing at least a part of the liquid medium from the coating liquid to form the conductive polymer layer on the surface of the dielectric layer and in the voids of the separator, and also to form the laminate sheet by bonding the anode foil and the separator together.

9. The method for producing an electrolytic capacitor according to claim 8, wherein the second width of the cathode foil is smaller than the first width of the first laminate.

10. The surface density of the conductive polymer layer is 0.05 mg / cm ２ 1.0mg / cm or more ２ The method for producing an electrolytic capacitor according to claim 8, wherein:

11. The method for producing an electrolytic capacitor according to claim 8, wherein the cathode foil has an inorganic layer on a surface thereof, and the conductive polymer layer is in close contact with the inorganic layer.

12. The method for producing an electrolytic capacitor according to claim 8, wherein the peel strength between the anode foil and the separator is 1.0 N / cm or more.

13. The method for producing an electrolytic capacitor according to claim 8, wherein the second laminate is a wound body.

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