Electrolytic capacitor and method for producing electrolytic capacitor

Abstract

This electrolytic capacitor comprises a multilayer body and a liquid component with which the multilayer body is impregnated. The multilayer body includes: an anode foil that has a dielectric layer on the surface thereof; a cathode foil that has an inorganic layer on the surface thereof; a separator; and a first conductive polymer layer that is held by the separator. The first conductive polymer layer contains a first conductive polymer. The ratio of the area of the first conductive polymer layer to the area of the surface of the separator is 80% or more. The first conductive polymer layer, which is held by the separator, is in close contact with the inorganic 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 (JP 2022-144278 A) describes a "solid electrolytic capacitor comprising: a capacitor element formed by opposing an anode foil and a cathode body; a conductive polymer layer formed by impregnating the capacitor element with a dispersion containing conductive polymer particles or powder and a solvent; and an electrolyte impregnated into the capacitor element, wherein the cathode body is made of a valve metal and has a cathode foil with a surface expansion layer formed on its surface; and a carbon layer laminated on the surface expansion layer and in contact with the conductive polymer layer on the side opposite the surface expansion layer, wherein the amount of conductive polymer particles or powder contained in the surface expansion layer is less than the amount of conductive polymer particles or powder contained in the surface layer side of the carbon layer facing the conductive polymer layer."

[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 Application Publication No. 2022-144278 Japanese Patent Application 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 cathode foil having an inorganic layer on its surface, a separator, and a first conductive polymer layer supported by the separator. The first conductive polymer layer contains a first conductive polymer, and the ratio of the area of ​​the first conductive polymer layer to the area of ​​the separator is 80% or more. The first conductive polymer layer supported by the separator is in close contact with the inorganic layer.

[0008] Another aspect of the present disclosure relates to a method for manufacturing an electrolytic capacitor. The method includes a preparation step of preparing an anode foil having a dielectric layer on its surface and a cathode foil having an inorganic layer on its surface, a first polymer layer formation step of forming a first conductive polymer layer in voids of a separator, a laminate formation step of forming a laminate including the anode foil, the cathode foil, and the separator disposed between the anode foil and the cathode foil, and a bonding step of adhering the first conductive polymer layer to the inorganic layer by impregnating the laminate with a liquid containing an organic solvent. The first polymer layer formation step includes a first coating liquid application step of applying a first coating liquid containing a first conductive polymer and a first liquid medium to the voids of the separator, and a first liquid medium removal step of removing at least a portion of the first liquid medium from the first coating liquid to form the first conductive polymer layer in the voids of the separator.

[0009] According to the present disclosure, an electrolytic capacitor containing a liquid component and a conductive polymer layer and having a low equivalent series resistance (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. 3 is a schematic diagram illustrating an example of 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 reduce the resistance between the conductive polymer layer and the cathode foil, since high resistance between the conductive polymer layer and the cathode foil increases ESR.

[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 polymer layer forming step (first polymer layer forming step), a laminate forming step, and a bonding step. The polymer layer forming step, laminate forming step, and bonding step are performed in this order. The preparation step is performed before the laminate forming step. The preparation step may also be performed before the polymer layer forming step. A cathode foil having an inorganic layer on its surface may be prepared after the polymer layer forming step. Furthermore, an impregnation step may also be included after the bonding step. Each step is described below.

[0017] (Preparation Step) The preparation step is a step of preparing an anode foil having a dielectric layer on its surface and a cathode foil having an inorganic layer on its surface. The inorganic layer is a layer containing at least one selected from the group consisting of carbon, titanium, and nickel, and may be a layer consisting of the at least one type.

[0018] The anode foil having a dielectric layer on its surface may be commercially available, or may be formed by forming a dielectric layer on the surface of a metal foil (anode foil). The cathode foil having an inorganic layer on its surface may be commercially available, or may be formed by forming an inorganic layer on the surface of a metal foil (cathode foil). The dielectric layer and inorganic layer may be formed by known methods. For example, the dielectric layer may be formed by oxidizing the surface of the metal foil (anode foil). The inorganic layer may be formed by vacuum deposition or the like. Alternatively, the inorganic layer may be formed by applying a paste containing 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 it. 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 ２ The inorganic layer may be a layer formed by vapor deposition of titanium or a layer formed using titanium oxide particles. The inorganic layer may be a layer formed by vapor deposition of nickel. 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 mass % or more. In this specification, the term "inorganic layer" may be replaced with "carbon layer".

[0019] 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 .

[0020] (Polymer layer forming step) The polymer layer forming step includes a first polymer layer forming step of forming a first conductive polymer layer in the voids of the separator. The polymer layer forming step may further include a second polymer layer forming step of forming a second conductive polymer layer on the surface of the dielectric layer (the dielectric layer formed on the surface of the anode foil). The first polymer layer forming step and the second polymer layer forming step may be performed in either order, or may be performed simultaneously.

[0021] The first polymer layer forming step includes a first coating liquid applying step of applying a first coating liquid containing a first conductive polymer and a first liquid medium to the voids of the separator, and a first liquid medium removing step of forming a first conductive polymer layer in the voids of the separator by removing at least a portion of the first liquid medium from the first coating liquid. The second polymer layer forming step includes a second coating liquid applying step of applying a second coating liquid containing a second conductive polymer and a second liquid medium to the surface of the dielectric layer (the dielectric layer formed on the surface of the anode foil), and a second liquid medium removing step of forming a second conductive polymer layer on the surface of the dielectric layer by removing at least a portion of the second liquid medium from the second coating liquid. The second conductive polymer layer is usually formed on both sides of the anode foil.

[0022] The first conductive polymer and the second conductive polymer may be the same or different. The first conductive polymer and the second conductive polymer may each be contained in the coating liquid in the form of particles. Examples of conductive polymers will be described later.

[0023] 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 first coating liquid and / or the second coating liquid may be a dispersion in which conductive polymer particles are dispersed in water.

[0024] The first liquid medium and / or the second 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.

[0025] The method for applying the coating liquid is not limited and may be any 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 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 forming a layer of coating liquid with a uniform thickness on the member. Methods for applying the coating liquid to a separator include impregnating the separator with the coating liquid. The coating liquid applied to the separator penetrates into the separator, forming a conductive polymer layer across the entire thickness of the separator. 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 can be easily applied to the anode foil, cathode foil, and separator, and can easily be impregnated into the separator. The viscosity of the coating liquid can be measured at room temperature (20°C) using a vibration viscometer (for example, VM-100A, manufactured by Sekonic Corporation).

[0026] 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.

[0027] By leaving the organic compound (C) in the conductive polymer layer, shrinkage of the conductive polymer layer when the liquid medium is removed from the coating liquid can be reduced. As a result, in the subsequent adhesion step and impregnation step, a liquid containing an organic solvent or a liquid component (e.g., an electrolyte solution) can easily penetrate into the conductive polymer layer. As a result, in the adhesion step, adhesion between the first conductive polymer layer and the inorganic layer and adhesion between the first conductive polymer layer and the second conductive polymer layer can be improved. Furthermore, the function of the liquid component to form a dielectric layer (oxide film) can be more easily exerted, thereby reducing leakage current.

[0028] 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.

[0029] In the first polymer layer formation step of production method (M), the first conductive polymer layer is preferably formed so that the ratio of the area of ​​the first conductive polymer layer to the surface of the separator (hereinafter, sometimes referred to as "ratio R") is 80% or more. By setting the ratio R to 80% or more, the ESR can be particularly reduced. Furthermore, by setting the ratio R to 80% or more, the adhesion between the first conductive polymer layer and the inorganic layer of the cathode foil can be particularly improved. The ratio R is preferably 90% or more, more preferably 95% or more, and particularly preferably 98% or more. By increasing the ratio R, the ESR can be further reduced.

[0030] The ratio R is the ratio of the area of ​​the first conductive polymer layer occupying the surface of the separator to the area of ​​the separator calculated from the size of the separator. The ratio R can be calculated by acquiring an image of the surface of the separator on which the first conductive polymer layer is formed and processing the image. Since the color of the first conductive polymer layer is usually different from the color of the separator, the area of ​​the region on which the first conductive polymer layer is formed can be calculated by binarizing the image of the surface of the separator on which the first conductive polymer layer is formed. The ratio R can then be calculated from the area Sp of the region on which the first conductive polymer layer is formed and the area Ss of the separator. The ratio R can be calculated using the following formula:

[0031] Ratio R (%) = (Sp / Ss) × 100 The surface density of the first 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 ２ Below, 1.0mg / cm ２ or less, or 0.5 mg / cm ２ For example, the surface density of the first conductive polymer layer may be 0.05 mg / cm or less. ２ 1.0 mg / cm or more ２ According to this configuration, an electrolytic capacitor having a particularly low ESR can be obtained. Note that the areal density refers to the mass per unit area.

[0032] The surface density of the second 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 ２ Below, 1.0mg / cm ２ or less, or 0.5 mg / cm ２ When the second conductive polymer layer is formed on both sides of the anode foil, the surface density of the second conductive polymer layer means the surface density of one second conductive polymer layer formed on one side of the anode foil.

[0033] The areal density of the first conductive polymer layer can be determined by the following method. First, five samples are prepared by cutting out a separator having a predetermined area before the first conductive polymer layer is formed, and the masses of the five samples are measured. Five samples are also prepared by cutting out a separator having the first conductive polymer layer formed thereon, and the masses of the five samples are measured. The areal density of the first conductive polymer layer is determined using the predetermined area and the difference between the total mass of the five samples after the first conductive polymer layer is formed and the total mass of the five samples before the first conductive polymer layer is formed.

[0034] The ratio R can be changed by adjusting the viscosity of the coating liquid when applying a coating liquid containing a conductive polymer using a coater or the like. The surface density of the conductive polymer layer can be controlled by the viscosity of the coating liquid. Alternatively, the surface density of the conductive polymer may be controlled by the concentration or coating amount of the conductive polymer in the coating liquid. The viscosity of the coating liquid can be controlled by a condensation method or by using a thickener.

[0035] (Laminate Forming Step) The laminate forming step is a step of forming a laminate including an anode foil, a cathode foil, and a separator disposed between the anode foil and the cathode foil. The laminate forming step may be a step of forming a laminate including a first conductive polymer layer and a second conductive polymer layer by laminating the anode foil, the cathode foil, and the separator such that the separator is disposed between the anode foil and the cathode foil and the first conductive polymer layer faces the inorganic layer.

[0036] 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.

[0037] 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.

[0038] (Adhesion Step) The adhesion step is a step of adhering the first conductive polymer layer to the inorganic layer by impregnating the laminate with a liquid containing an organic solvent (hereinafter, may be referred to as "liquid (L)"). At least a portion of the liquid (L) impregnated into the laminate is removed from the laminate after the adhesion step. The method for removing the liquid (L) is not limited, and heating or the like may be used. The adhesion step also improves the adhesion between the first conductive polymer layer formed on the separator and the second conductive polymer layer formed on the dielectric layer.

[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 reduces the overall capacitance of the capacitor. Covering the surface of the metal foil with an inorganic layer or the like can prevent this problem. That is, the formation of an inorganic layer allows only the capacitance of the anode foil to be extracted. On the other hand, because inorganic layers are water-repellent, 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 prevents the conductive polymer from being uniformly formed 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 first conductive polymer layer has already been formed. This prevents the conductive polymer from being unevenly distributed within the separator. Furthermore, by performing the adhesion process using a liquid (L) containing an organic solvent, the conductive polymer adheres to the inorganic layer without being repelled by the inorganic layer. For example, when a carbon layer is used as the inorganic layer, the conductive polymer becomes entangled with the carbon. This allows for strong bonding between the first conductive polymer layer and the inorganic layer, reducing the resistance between them. As a result, an electrolytic capacitor with low ESR can be manufactured.

[0040] 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 xylitol and xylitol derivatives.

[0041] 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), it is possible to improve the adhesion between the conductive polymer layer and the inorganic layer of the cathode foil. 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).

[0042] 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 inorganic layer of the cathode foil. 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.

[0043] 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 such an organic solvent in the liquid (L), the electrical conductivity of the conductive polymer layer can be increased.

[0044] 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.

[0045] (Impregnation Step) The manufacturing method (M) may include an impregnation step after the adhesion step. The impregnation step is a step of impregnating the 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.

[0046] 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.

[0047] In this manner, a capacitor element (e.g., a capacitor element impregnated with a liquid component (LC)) is obtained. Thereafter, other steps may be performed as necessary. For example, a step of encapsulating the capacitor element in an exterior body may be performed.

[0048] The adhesion step and the impregnation step may be performed simultaneously. In this case, the liquid (L) is added to the liquid component (LC) to impregnate the laminate, and then a portion of the liquid (L) is removed. However, it is preferable to perform the adhesion step and the impregnation step separately, because this ensures that the first conductive polymer layer and the inorganic layer are adhered to each other in the adhesion step.

[0049] (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).

[0050] The electrolytic capacitor (E) includes a laminate and a liquid component (liquid component (LC)) impregnated in the laminate. The laminate includes an anode foil having a dielectric layer on its surface, a cathode foil having an inorganic layer on its surface, a separator, a first conductive polymer layer held by the separator, and a second conductive polymer layer formed on the dielectric layer. The first conductive polymer layer contains a first conductive polymer. The second conductive polymer layer contains a second conductive polymer. The ratio R of the area of ​​the first conductive polymer layer to the surface area of ​​the separator is 80% or more. The first conductive polymer layer held by the separator is in close contact with the inorganic layer.

[0051] 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.

[0052] The surface density of the first conductive polymer layer may be in the range described above. For example, the surface density of the first conductive polymer layer may be 0.05 mg / cm ２ 1.0 mg / cm or more ２ It may be the following:

[0053] The first conductive polymer layer may contain at least one selected from the group consisting of sugars, sugar alcohols, epoxy resins, and polyvinyl alcohols. The sugar alcohols may include at least one selected from the group consisting of xylitol and xylitol derivatives.

[0054] 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. The titanium-containing layer may contain at least one selected from the group consisting of titanium and titanium compounds.

[0055] As described above, the laminate may be a wound body, or may be a laminate other than a wound body.

[0056] The peel strength between the cathode foil and the separator may be 0.5 N / cm or more, or 1.0 N / cm or more. There is no particular upper limit to the peel strength. The peel strength can be measured by a method described in the Examples. The peel strength between the cathode foil and the separator can be increased by performing a bonding step.

[0057] 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.

[0058] 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.

[0059] (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). 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 be at least one of these. 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 be at least one of these.

[0060] 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.

[0061] 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).

[0062] 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).

[0063] 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.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] 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. When the coating liquid contains a dopant, the mass of the dopant is included in the mass of the conductive polymer component.

[0068] 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.

[0069] 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.

[0070] (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.

[0071] 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.

[0072] 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.

[0073] 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.

[0074] 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).

[0075] 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).

[0076] Among these, maleic acid, phthalic acid, benzoic acid, pyromellitic acid, and resorcylic acid are thermally stable and are therefore preferably used.

[0077] 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.

[0078] 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.

[0079] 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.

[0080] 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.

[0081] 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.

[0082] 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).

[0083] 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.

[0084] 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.

[0085] 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.

[0086] (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.

[0087] 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.

[0088] 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.

[0089] (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.

[0090] As described above, the cathode foil includes a coating layer on its surface. The coating layer is usually formed on both sides of the cathode foil. The coating layer includes at least an inorganic layer disposed on its outermost surface. The coating layer may consist of only the inorganic layer, or may include the inorganic layer and another layer (e.g., a titanium-containing layer).

[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 anode foil 11 connected to lead tab 105A, cathode foil 12 connected to lead tab 105B, and 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 strip-shaped anode foil 11 and strip-shaped cathode foil 12 with separator 13 interposed therebetween. 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 fixed.

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

[0100] (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 cathode foil having an inorganic layer on a surface thereof, a separator, and a first conductive polymer layer held by the separator, wherein the first conductive polymer layer contains a first conductive polymer, the ratio of the area of ​​the first conductive polymer layer to the area of ​​the surface of the separator is 80% or more, and the first conductive polymer layer held by the separator is in close contact with the inorganic layer.

[0101] (Technology 2) The surface density of the first conductive polymer layer is 0.05 mg / cm ２ 1.0mg / cm or more ２ The electrolytic capacitor according to Technology 1 is as follows:

[0102] (Technology 3) The electrolytic capacitor according to Technology 1 or 2, wherein the first conductive polymer layer contains at least one selected from the group consisting of sugar, sugar alcohol, epoxy resin, and polyvinyl alcohol.

[0103] (Technology 4) The electrolytic capacitor according to Technology 3, wherein the sugar alcohol includes at least one selected from the group consisting of mannitol, mannitol derivatives, xylitol, and xylitol derivatives.

[0104] (Technology 5) The electrolytic capacitor according to any one of Technologies 1 to 4, wherein the inorganic layer contains at least one selected from the group consisting of carbon, titanium, and nickel.

[0105] (Technology 6) The electrolytic capacitor according to any one of Technologies 1 to 5, wherein the laminate is a wound body.

[0106] (Technology 7) A method for manufacturing an electrolytic capacitor, comprising: a preparation step of preparing an anode foil having a dielectric layer on its surface and a cathode foil having an inorganic layer on its surface; a first polymer layer formation step of forming a first conductive polymer layer in voids of a separator; a laminate formation step of forming a laminate including the anode foil, the cathode foil, and a separator disposed between the anode foil and the cathode foil; and a bonding step of adhering the first conductive polymer layer to the inorganic layer by impregnating the laminate with a liquid containing an organic solvent, wherein the first polymer layer formation step comprises: a first coating liquid application step of applying a first coating liquid containing a first conductive polymer and a first liquid medium to the voids of the separator; and a first liquid medium removal step of removing at least a portion of the first liquid medium from the first coating liquid to form the first conductive polymer layer in the voids of the separator.

[0107] (Technology 8) The surface density of the first 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 7 is as follows.

[0108] (Technology 9) The method for producing an electrolytic capacitor according to Technology 7 or 8, wherein the liquid contains at least one selected from the group consisting of sugar, sugar alcohol, epoxy resin, and polyvinyl alcohol.

[0109] (Technology 10) The method for producing an electrolytic capacitor according to Technology 9, wherein the sugar alcohol includes at least one selected from the group consisting of mannitol, mannitol derivatives, xylitol, and xylitol derivatives.

[0110] (Technology 11) The method for producing an electrolytic capacitor according to any one of Techniques 7 to 10, wherein the organic solvent contains at least one selected from the group consisting of ethylene glycol, diethylene glycol, triethylene glycol, and polyethylene glycol.

[0111] (Technology 12) The method for producing an electrolytic capacitor according to any one of Techniques 7 to 11, further comprising an impregnation step of impregnating the laminate with a liquid component, wherein the liquid component contains at least one selected from the group consisting of ethylene glycol, diethylene glycol, triethylene glycol, an ethylene glycol condensate having a molecular weight of 250 or less, glycerin, γ-butyrolactone, and sulfolane.

[0112] (Technology 13) The method for producing an electrolytic capacitor according to any one of Techniques 7 to 12, wherein the inorganic layer contains at least one selected from the group consisting of carbon, titanium, and nickel.

[0113] (Technology 14) The method for manufacturing an electrolytic capacitor according to any one of Technologies 7 to 13, wherein the laminate is a wound body.

[0114] 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 produced and evaluated by the following method.

[0115] (Capacitor A1) An electrolytic capacitor (capacitor A1) was produced by the following method.

[0116] (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 surface of the aluminum foil 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.

[0117] A nonwoven fabric (50 μm thick) made of polyester fiber, aramid fiber, and cellulose was prepared as a separator.

[0118] (b) Formation of a Conductive Polymer Layer A dispersion (commercially available) of polystyrene sulfonic acid (PSS)-doped polyethylenedioxythiophene (PEDOT) particles dispersed in water was prepared as a coating liquid. Next, the coating liquid was applied to one side of the anode foil (surface of the dielectric layer) using a gravure coater. A drying process was then performed to form a conductive polymer layer on one side of the anode foil (surface of the dielectric layer). The drying process was performed by heating the anode foil coated with the coating liquid at 125°C for 5 minutes. Next, a conductive polymer layer was formed on the other side of the anode foil (surface of the dielectric layer) in the same manner. A conductive polymer layer was formed on the separator by applying the coating liquid to the separator and then drying it.

[0119] (c) Formation of Wound Body (Laminate) The anode foil, cathode foil, and separator were each cut to a predetermined size. An anode lead tab and a cathode lead tab were connected to the anode foil and the cathode foil, respectively. Next, the anode foil and the cathode foil were wound with the separator interposed therebetween. At this time, the ends of the outer surface of the wound body were fixed with winding tape. An anode lead wire and a cathode lead wire were connected to the ends of each lead tab protruding from the wound body, respectively. The obtained wound body was again subjected to chemical conversion treatment, and a dielectric layer was formed on the end surface of the anode foil. In this way, a capacitor element was obtained.

[0120] (d) Adhesion Step First, liquid (L) was prepared. A solution containing polyethylene glycol was used as liquid (L). The concentration of polyethylene glycol was 10% by mass. Next, the wound body was impregnated with liquid (L), and then the wound body was dried by heating. In this way, the carbon layer (cathode foil) and the first conductive polymer layer were adhered to each other, and the first conductive polymer layer and the second conductive polymer layer were adhered to each other.

[0121] (e) 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.

[0122] (f) 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.

[0123] (Capacitor C1) An electrolytic capacitor (capacitor C1) was produced in the same manner and under the same conditions as those for producing capacitor A1, except that the adhesion step was not performed.

[0124] (Evaluation) The equivalent series resistance (ESR) of the fabricated electrolytic capacitor was measured. The fabricated electrolytic capacitor was disassembled, and the peel strength between the carbon layer of the cathode foil and the separator was measured using the following method. Furthermore, the ratio R of the area of ​​the first conductive polymer layer to the surface of the separator was measured using the following method.

[0125] (1) Measurement of Peel Strength In this example, the electrolytic capacitor was first disassembled, and the wound body (capacitor element 10) was removed. Next, the anode foil was pulled from the outer periphery of the wound body, and a portion of the anode foil was peeled off from the wound body. Because the adhesion between the dielectric layer on the surface of the anode foil and the separator was stronger than the adhesion between the cathode foil and the separator, the separator on the inner side of the peeled anode foil was peeled off from the inner cathode foil while remaining in close contact with the anode foil.

[0126] Next, the peeled portion of laminate 11A (a laminate of anode foil and separator) and portion 12A of the cathode foil from which laminate 11A was peeled were each set in a peel strength measuring device, an embossed tape high-speed peel strength tester (PTS-5000K) manufactured by EPI Co., Ltd.

[0127] FIG. 3 shows a schematic configuration of an example of a measuring device 20 used to measure peel strength. The measuring device is preferably designed to perform a test in accordance with JIS (Japanese Industrial Standards) 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 laminate 11A is fixed to the feed sheet 21 by a fixing jig 24. The feed sheet 21 is fed in a first direction by the feed rollers 22. The recovery device 23 recovers the portion 12A of the cathode foil 12 while pulling it 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. The feed speed of the laminate 11A (anode foil 11 and separator 13) by the feed rollers 22 and the take-up speed of the cathode foil 12 by the recovery device 23 are controlled to prevent the position of the capacitor element 10 from moving during measurement.

[0128] In this example, the laminate 11A and the cathode foil 12 were pulled in the measuring device 20 so that the angle between the direction in which the laminate 11A (anode foil 11 and separator 13) fixed to the feed sheet 21 was pulled and the direction in which the cathode foil 12 was pulled by the recovery device 23 was approximately 175°. The laminate 11A and the cathode foil 12 were pulled for 60 seconds so that the cathode foil 12 and the separator 13 were continuously peeled off at a constant speed (160 mm / min). The force pulling the cathode foil 12 at this time was measured at sampling intervals of 0.01 seconds. The average value of the measured forces pulling the cathode foil 12 was taken as the peel strength.

[0129] (2) Measurement of Ratio R The capacitor elements of capacitors A1 and C1 were disassembled, and their respective separators were removed. Separators without a conductive polymer layer were also prepared for comparison. Samples measuring 2 cm x 5 cm were cut from each separator and evaluated. Specifically, the separators of capacitors A1 and C1, and the separators themselves were lined up and scanned with a scanner to obtain images.

[0130] Next, the captured image was binarized using image analysis software (Adobe Photoshop (registered trademark)). At this time, the binarization was performed so that the image of the separator alone was used as a reference and the area where the conductive polymer was attached was recognized as black. From the binarized image, the ratio R of capacitor A1 and the ratio R of capacitor C1 were calculated.

[0131] The evaluation results are shown in Table 1.

[0132]

[0133] 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, which had a high ratio R, had a high peel strength between the cathode foil and the separator and a low ESR.

[0134] The present disclosure can be used for electrolytic capacitors.

[0135] 10: Capacitor element 11: Anode foil 12: Cathode foil 13: Separator 14: Winding tape 100: Electrolytic capacitor 101: Bottomed case 102: Sealing member 103: Seat plate 104A, 104B: Lead wire 105A, 105B: Lead tab

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 cathode foil having an inorganic layer on a surface thereof, a separator, and a first conductive polymer layer held by the separator, wherein the first conductive polymer layer contains a first conductive polymer, a ratio of an area of ​​the first conductive polymer layer to an area of ​​the surface of the separator is 80% or more, and the first conductive polymer layer held by the separator is in close contact with the inorganic layer.

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

3. The electrolytic capacitor according to claim 1, wherein the first conductive polymer layer contains at least one selected from the group consisting of sugar, sugar alcohol, epoxy resin, and polyvinyl alcohol.

4. The electrolytic capacitor according to claim 3, wherein the sugar alcohol includes at least one selected from the group consisting of mannitol, mannitol derivatives, xylitol, and xylitol derivatives.

5. The electrolytic capacitor according to claim 1, wherein the inorganic layer contains at least one selected from the group consisting of carbon, titanium, and nickel.

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

7. A method for manufacturing an electrolytic capacitor, comprising: a preparation step of preparing an anode foil having a dielectric layer on its surface and a cathode foil having an inorganic layer on its surface; a first polymer layer formation step of forming a first conductive polymer layer in a gap of a separator; a laminate formation step of forming a laminate including the anode foil, the cathode foil, and the separator disposed between the anode foil and the cathode foil; and a bonding step of bonding the first conductive polymer layer to the inorganic layer by impregnating the laminate with a liquid containing an organic solvent, wherein the first polymer layer formation step comprises: a first coating liquid application step of applying a first coating liquid containing a first conductive polymer and a first liquid medium to the gap of the separator; and a first liquid medium removal step of removing at least a part of the first liquid medium from the first coating liquid to form the first conductive polymer layer in the gap of the separator.

8. The surface density of the first 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 7, wherein:

9. The method for producing an electrolytic capacitor according to claim 7, wherein the liquid contains at least one selected from the group consisting of sugar, sugar alcohol, epoxy resin, and polyvinyl alcohol.

10. The method for producing an electrolytic capacitor according to claim 9, wherein the sugar alcohol includes at least one selected from the group consisting of mannitol, mannitol derivatives, xylitol, and xylitol derivatives.

11. The method for producing an electrolytic capacitor according to claim 7, wherein the organic solvent contains at least one selected from the group consisting of ethylene glycol, diethylene glycol, triethylene glycol, and polyethylene glycol.

12. The method for producing an electrolytic capacitor according to claim 7, further comprising an impregnation step of impregnating the laminate with a liquid component, the liquid component containing 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.

13. The method for producing an electrolytic capacitor according to claim 7, wherein the inorganic layer contains at least one selected from the group consisting of carbon, titanium, and nickel.

14. The method for producing an electrolytic capacitor according to claim 7, wherein the laminate is a wound body.