WO2025028067A1 - Electrolytic capacitor and method for producing electrolytic capacitor - Google Patents

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

This disclosure relates to electrolytic capacitors and methods for manufacturing electrolytic capacitors.

A known electrolytic capacitor is one that includes a wound body of an anode foil, a separator, and a cathode foil. One example of such an electrolytic capacitor includes a conductive polymer layer disposed in the wound body. The conductive polymer layer can be formed by impregnating the wound body with a dispersion liquid that contains a conductive polymer. Various proposals have been made in the past regarding electrolytic capacitors that include a conductive polymer layer.

Patent document 1 (JP Patent Publication 2022-144278 A) describes in claim 1, "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 a dispersion containing conductive polymer particles or powder and a solvent, and an electrolyte impregnated into the capacitor element, the cathode body being made of a valve metal, a cathode foil having 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 opposite side to the surface expansion layer, the amount of the conductive polymer particles or powder contained in the surface expansion layer being less than the amount of the conductive polymer particles or powder contained in the surface layer side of the carbon layer facing the conductive polymer layer."

Claim 1 of Patent Document 2 (JP Patent Publication No. 2019-516241) 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."

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; 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 electrolyte filled between the conductive polymer particles in the solid electrolyte layer.

JP 2022-144278 A Special Publication No. 2019-516241 International Publication No. 2021/125182

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 held 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 surface of the separator is 80% or more. The first conductive polymer layer held by the separator is in close contact with the inorganic layer.

Another aspect of the present disclosure relates to a method for manufacturing an electrolytic capacitor. The manufacturing 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 the 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 an adhesion 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 into the gap of the separator, and a first liquid medium removal step of forming the first conductive polymer layer in the gap of the separator by removing at least a part of the first liquid medium from the first coating liquid.

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.

FIG. 1 is a side view illustrating a schematic diagram of an example of an electrolytic capacitor according to an embodiment of the present disclosure. FIG. 2 is an exploded perspective view illustrating a schematic diagram of an example of a capacitor element according to an embodiment of the present disclosure. FIG. 3 is a schematic diagram showing an example of a peel strength measuring device.

The following is a brief explanation of the problems with the conventional technology.

Since the dispersion liquid containing the conductive polymer has a high viscosity, even if the dispersion liquid is impregnated into the wound body, it may not be possible to form a sufficient conductive polymer layer inside the wound body. Insufficient formation of the conductive polymer layer can cause an increase in equivalent series resistance (ESR).

Furthermore, when using a conductive polymer layer formed on a separator, it is important to reduce the resistance between the conductive polymer layer and the cathode. If the resistance between the conductive polymer layer and the cathode foil is high, the ESR increases.

There has long been a need to reduce the ESR of electrolytic capacitors. This disclosure provides an electrolytic capacitor that contains a liquid component and a conductive polymer layer and can reduce the ESR.

Below, examples of embodiments according to the present invention are described, 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 this 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 numerical values for specific physical properties or conditions are exemplified as lower and upper limits, any of the exemplified lower limits can be arbitrarily combined with any of the exemplified upper limits, as long as the lower limit is not equal to or greater than the upper limit.

(Method of 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, the laminate forming step, and the bonding step are performed in this order. The preparation step is performed before the laminate forming step. The preparation step may be performed before the polymer layer forming step. The cathode foil having an inorganic layer on its surface may be prepared after the polymer layer forming step. Also, an impregnation step may be included after the bonding step. Each step will be described below.

(Preparation process)
The preparation step is a step of preparing an anode foil having a dielectric layer on a surface thereof and a cathode foil having an inorganic layer on a surface thereof. 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.

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 cathode foil having an inorganic layer on its surface may be a commercially available product, or may be formed by forming an inorganic layer on the surface of a metal foil (cathode foil). The dielectric layer and the inorganic 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). 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 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 amount of the inorganic layer may be in the range of 50 mg/m ² to 300 mg/m ² (for example, in the range of 70 mg/m ² to 200 mg/m ² ). Examples of the conductive carbon material contained in the inorganic layer include graphite, hard carbon, soft carbon, carbon black, and the like. The inorganic layer may be a layer formed by vapor deposition of titanium, or may be 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".

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 the 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, titanium carbonate, and the like. The method of forming the titanium-containing layer is not limited, and the layer may be formed by a known method. For example, the titanium-containing layer may be formed by a physical vapor deposition method such as a vacuum deposition method or a sputtering method. The deposition amount of the titanium-containing layer may be in the range of 200 mg/m ² to 500 mg/m ² (e.g., in the range of 250 mg/m ² to 400 mg/m ² ).

(Polymer layer formation process)
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.

The first polymer layer forming process includes a first coating liquid applying process of applying a first coating liquid containing a first conductive polymer and a first liquid medium into the voids of the separator, and a first liquid medium removing process of forming a first conductive polymer layer in the voids of the separator by removing at least a part of the first liquid medium from the first coating liquid. The second polymer layer forming process includes a second coating liquid applying process of applying a second coating liquid containing a second conductive polymer and a second liquid medium onto the surface of the dielectric layer (the dielectric layer formed on the surface of the anode foil), and a second liquid medium removing process of forming a second conductive polymer layer on the surface of the dielectric layer by removing at least a part 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.

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.

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 liquid media include water, organic solvents (e.g., alcohol), and mixed solvents thereof. The first coating liquid and/or the second coating liquid may be a dispersion liquid in which conductive polymer particles are dispersed in water.

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

The method of applying the coating liquid is not limited, and may be applied by a known method. For example, a method using a coater may be used, the coating liquid may be sprayed, or the object to be coated may be immersed in the coating liquid. Examples of methods using a coater include gravure coating and die coating. In one example of the gravure coating method, 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 specified member (anode foil, cathode foil, or separator), so that a layer of the coating liquid with a uniform thickness can be applied to the member. Note that the method of applying the coating liquid to the separator includes a method of impregnating the separator with the coating liquid. The coating liquid applied to the separator permeates the inside of the separator, and a conductive polymer layer can be formed over the entire thickness of the separator. The viscosity of the coating liquid may be, for example, 10 mPa·s or more (for example, 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 is measured at room temperature (20°C) using a vibration viscometer (for example, VM-100A, manufactured by Sekonic Corporation).

The method of removing at least a part of the liquid medium from the coating liquid is not particularly limited, and can be performed by heating or the like. 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 an organic compound (C) and water (liquid medium), it is possible to remove water from the coating liquid while leaving the organic compound (C) in the polymer layer by 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. 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. There is no particular limit to the heating time, and it may be a time that allows a part of the liquid medium to be appropriately removed. An example of the heating time is in the range of 5 to 60 minutes.

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 adhesion step and impregnation step, liquids containing organic solvents and liquid components (e.g., electrolyte solutions) can easily penetrate into the conductive polymer layer. As a result, in the adhesion step, it is possible to improve the adhesion between the first conductive polymer layer and the inorganic layer, and between the first conductive polymer layer and the second conductive polymer layer. In addition, the function of the liquid component to form a dielectric layer (oxide film) is easily exerted, and leakage current is reduced.

In a preferred example of manufacturing 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. If the water content in the coating liquid is high, the conductive polymer layer is more easily impregnated with the electrolyte after the conductive polymer layer is formed.

In the first polymer layer formation step of manufacturing method (M), it is preferable to form the first conductive polymer layer 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 making the ratio R 80% or more, the ESR can be particularly reduced. Furthermore, by making the ratio R 80% or more, the adhesion between the first conductive polymer layer and the inorganic layer of the cathode foil can be particularly increased. 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.

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.

Ratio R (%) = (Sp/Ss) x 100
The surface density of the first conductive polymer layer may be 0.05 mg/cm2 or ^more , 0.1 mg/ ^cm2 or more, or 0.3 mg/cm2 or ^more , and may be 5.0 mg/cm2 or ^less , 1.0 mg/cm2 ^or less, or 0.5 mg/ ^cm2 or less. For example, the surface density of the first conductive polymer layer may be 0.05 mg/cm2 or ^more and 1.0 mg/cm2 ^{or less} . With this configuration, an electrolytic capacitor with a particularly low ESR is obtained. The surface density means the mass per unit area.

The areal density of the second conductive polymer layer may be 0.05 mg/cm2 or ^more , 0.1 mg/ ^cm2 or more, or 0.3 mg/cm2 or ^more , and may be 5.0 mg/cm2 or ^less , 1.0 mg/cm2 ^or less, or 0.5 mg/ ^cm2 or less. When the second conductive polymer layer is formed on both sides of the anode foil, the areal density of the second conductive polymer layer means the areal density of one second conductive polymer layer formed on one side of the anode foil.

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 specified area from the separator before the first conductive polymer layer is formed, and the mass of the five samples is measured. In addition, five samples are prepared by cutting out the separator on which the first conductive polymer layer is formed, and the mass of the samples is measured. The areal density of the first conductive polymer layer is determined using the specified 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.

The ratio R can be changed by adjusting the viscosity of the coating liquid when applying the coating liquid containing the conductive polymer with 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 of the conductive polymer in the coating liquid or the amount applied. The viscosity of the coating liquid can be controlled by a condensation method or by using a thickener.

(Laminate formation process)
The laminate formation 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 formation 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.

There is no limitation on the method for forming the laminate, and the laminate may be formed by a known method. The laminate may be a wound body. In this case, in the laminate formation process, the wound body may be formed by winding the anode foil, the cathode foil, and the separator so 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.

The laminate may be formed by stacking flat anode foils, flat cathode foils, and flat separators in one direction. For example, a laminate may be formed by stacking multiple anode foils, multiple cathode foils, and multiple separators in one direction. In a typical example of such a laminate, the anode foils and cathode foils are arranged alternately, and the separator is arranged between the anode foils and the cathode foils.

(Adhesion process)
The adhesion step is a step of impregnating the laminate with a liquid containing an organic solvent (hereinafter, sometimes referred to as "liquid (L)"), thereby adhering the first conductive polymer layer to the inorganic layer. At least a part 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. In the adhesion step, the adhesion between the first conductive polymer layer formed on the separator and the second conductive polymer layer formed on the dielectric layer is also improved.

When the cathode foil is made of only a metal foil (e.g., aluminum foil), an oxide layer is formed on the surface of the metal foil, and capacitance is also generated in the cathode foil. As a result, the capacitance of the anode foil and the capacitance of the cathode foil are combined to create a problem that the capacitance of the entire capacitor decreases. By covering the surface of the metal foil with an inorganic layer, etc., such a problem can be prevented. In other words, by forming an inorganic layer, it is possible to draw out only the capacitance of the anode foil. On the other hand, since the inorganic layer easily repels water, in the conventional method of forming a conductive polymer layer by impregnating a laminate (capacitor element) with an aqueous dispersion of a conductive polymer, the conductive polymer is difficult to enter between the inorganic layer of the cathode foil and the anode foil in the laminate, so that the conductive polymer layer cannot be formed uniformly on the separator placed between the cathode foil and the anode foil, resulting in an increase in ESR. In the manufacturing method (M), a laminate (capacitor element) is formed using a separator on which a first conductive polymer layer has been formed in advance. Therefore, it is possible to prevent the conductive polymer from being biased 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. Therefore, the first conductive polymer layer and the inorganic layer can be firmly bonded, and the resistance between them can be reduced. As a result, an electrolytic capacitor with a low ESR can be manufactured.

The liquid (L) may be a liquid containing the organic compound (C) described above and water. In this case, it is preferable to impregnate the laminate with the liquid (L) and then remove the 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.

The liquid (L) may contain at least one selected from the group consisting of sugar, sugar alcohol, epoxy resin, and polyvinyl alcohol (hereinafter, sometimes referred to as "substance X"). By containing substance X in the liquid (L), the adhesion between the conductive polymer layer and the inorganic layer of the cathode foil can be increased. 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).

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 the above. The 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 adhering 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.

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 at least one of the organic solvents. By containing these in the liquid (L), the electrical conductivity of the conductive polymer layer can be increased.

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

(Impregnation process)
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. The liquid component may be referred to as a "liquid component (LC)" below. 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 part of the laminate in the liquid component (LC). The liquid component (LC) may be an electrolyte solution.

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. By including these compounds in the liquid component (LC), the withstand voltage of the capacitor can be increased.

In this manner, a capacitor element (e.g., a capacitor element impregnated with a liquid component (LC)) is obtained. Thereafter, other processes are carried out as necessary. For example, a process of encapsulating the capacitor element in an exterior body may be carried out.

The adhesion step and the impregnation step may be carried out simultaneously. In this case, the liquid (L) is added to the liquid component (LC) to impregnate the laminate, and a part of the liquid (L) is then removed. However, it is preferable to carry out the adhesion step and the impregnation step separately, since this ensures that the first conductive polymer layer and the inorganic layer are adhered to each other in the adhesion step.

(Electrolytic capacitor)
The electrolytic capacitor according to this embodiment may be referred to as "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, duplicated explanations may be omitted. The matters described for the electrolytic capacitor (E) may also be applied to the manufacturing method (M).

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 area of the surface of the separator is 80% or more. The first conductive polymer layer held by the separator is in close contact with the inorganic layer.

The electrolytic capacitor (E) provides the effects described in the manufacturing method (M). For example, the configuration of the electrolytic capacitor (E) makes it possible to reduce the ESR.

The areal density of the first conductive polymer layer may be in the range described above. For example, the areal density of the first conductive polymer layer may be 0.05 mg/cm2 ^or more and 1.0 mg/ ^cm2 or less.

The first conductive polymer layer may contain at least one selected from the group consisting of sugar, sugar alcohol, epoxy resin, and polyvinyl alcohol. The sugar alcohol may include at least one selected from the group consisting of xylitol and xylitol derivatives.

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.

As mentioned above, the laminate may be a wound body, or it may be a laminate other than a wound body.

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 the method described in the examples. The peel strength between the cathode foil and the separator can be increased by performing an adhesion process.

Below, examples of materials and components used in the manufacturing method (M) and electrolytic capacitor (E) are described. However, the materials and components used in the manufacturing method (M) and electrolytic capacitor (E) are not limited to the examples described below.

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

(Coating Fluid)
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 a 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 the organic compounds. 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 the organic compounds.

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

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

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, polyallyl sulfonic acid, polyacryl sulfonic acid, polymethacryl sulfonic acid, poly(2-acrylamido-2-methylpropane sulfonic 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 a dopant is polystyrene sulfonic acid (PSS).

The dopant may be polystyrenesulfonic 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 polystyrenesulfonic acid.

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

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. The water content may be 98% by mass or less, 95% by mass or less, 90% by mass or less, or 80% by mass or less.

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

The content of the conductive polymer component in the coating liquid may be 0.5 mass% or more, or 1.0 mass% or more, and may be 4.0 mass% or less, 3.0 mass% or less, or 2.0 mass% or less. In addition, if the coating liquid contains a dopant, the mass of the dopant is included in the mass of the conductive polymer component.

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 (e.g., 0.5 to 3 times) the mass of the conductive polymer contained in the coating liquid.

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

(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 when the electrolytic capacitor is used.

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

Furthermore, a polymer solvent may be used as the non-aqueous solvent. Examples of polymer solvents include polyalkylene glycol, derivatives of polyalkylene glycol, and compounds in which at least one hydroxyl group in a polyhydric alcohol is replaced with polyalkylene glycol (including derivatives). Specifically, 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. Examples of polymer solvents further include ethylene glycol-propylene glycol copolymers, ethylene glycol-butylene glycol copolymers, and propylene glycol-butylene glycol copolymers. The non-aqueous solvent may be used alone or in a mixture of two or more.

The liquid component (LC) may include a non-aqueous solvent and a base component (base) dissolved in the non-aqueous solvent. The liquid component (LC) may also include a non-aqueous solvent and a base component and/or an acid component (acid) dissolved in the non-aqueous solvent.

As the acid component, polycarboxylic acids and monocarboxylic acids can be used. Examples of the polycarboxylic acids 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, 5,6-decanedicarboxylic acid; unsaturated polycarboxylic acids such as maleic acid, fumaric acid, itaconic acid), aromatic polycarboxylic acids (phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, pyromellitic acid), and alicyclic polycarboxylic acids (cyclohexane-1,2-dicarboxylic acid, cyclohexene-1,2-dicarboxylic acid, etc.).

Examples of the monocarboxylic acids include aliphatic monocarboxylic acids (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, behenic acid]; [unsaturated monocarboxylic acids, such as acrylic acid, methacrylic acid, oleic acid]), aromatic monocarboxylic acids (such as benzoic acid, cinnamic acid, naphthoic acid), and oxycarboxylic acids (such as salicylic acid, mandelic acid, resorcylic acid).

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

Inorganic acids may be used as the acid component. Representative examples of inorganic acids include phosphoric acid, phosphorous acid, hypophosphorous acid, alkyl phosphate esters, boric acid, boric fluoride, tetrafluoroboric acid, hexafluorophosphoric acid, benzenesulfonic acid, and naphthalenesulfonic acid. In addition, composite compounds of organic acids and inorganic acids may be used as the acid component. Examples of such composite compounds include borodiglycolic acid, borodioxalic acid, and borodisalicylic acid.

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 (pyrimidine compound, 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-heptyl imidazoline, 1-methyl-2-(3'heptyl)imidazoline, 1-methyl-2-dodecyl imidazoline, 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.

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) that are 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, and 1,3-dimethylbenzimidazolium are preferred. By using these, a capacitor with excellent impedance performance can be obtained.

Also, a tertiary amine may 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 electrical conductivity, and it is more preferred to include at least one selected from the group consisting of trimethylamine, dimethylethylamine, methyldiethylamine, and triethylamine. Also, secondary amines such as dialkylamines, primary amines such as monoalkylamines, and ammonia may be used as the base component.

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.

To suppress de-doping of the dopant, the pH of the liquid component (LC) may be less than 7.0 or less than 5.0, or may be greater than 1.0, or greater than 2.0. The pH may be greater than 1.0 and less than 7.0 (e.g., in the range of 2.0 to 5.0).

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

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

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 glycols (such as ethylene glycol), or the same sugar alcohol.

(anode foil)
Examples of the anode foil include metal foils containing at least one of valve metals such as titanium, tantalum, aluminum, and niobium, and may be metal foils of valve metals (e.g., aluminum foils). 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.

A dielectric layer is formed on the surface of the anode foil. The dielectric layer may be formed by subjecting the anode foil to a chemical conversion treatment. 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.

In an electrolytic capacitor, a conductive polymer layer does not need to be formed on the end surface of the anode foil. However, it is preferable that a dielectric layer is formed on the end surface of the anode foil.

(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.

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 an inorganic layer, or may include an inorganic layer and another layer (e.g., a titanium-containing layer).

(Separator)
A porous sheet can be used for the separator. Examples of the porous sheet 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 the material of the separator include cellulose, polyethylene terephthalate, polybutylene terephthalate, polyphenylene sulfide, vinylon, nylon, aromatic polyamide, polyimide, polyamideimide, polyetherimide, rayon, glass, and the like.

(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 a known case and sealing resin may be used. The sealing resin may include a thermosetting resin. Examples of the thermosetting resin include an epoxy resin, a phenolic resin, a silicone resin, a melamine resin, a urea resin, an alkyd resin, a polyurethane, a polyimide, an unsaturated polyester, and the like. The sealing resin may include a filler, a curing agent, a polymerization initiator, and/or a catalyst, and the like.

Below, an example of the present disclosure will be specifically described 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 embodiment. Furthermore, in the example described below, components that are not essential to the electrolytic capacitor of the present disclosure may be omitted.

FIG. 1 is a cross-sectional view showing an example of an electrolytic capacitor 100 according to this embodiment. FIG. 2 is a schematic diagram showing an exploded view of a portion of a capacitor element 10 included in the electrolytic capacitor 100.

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

Capacitor element 10 is, for example, a wound body as shown in FIG. 1. The wound body includes an anode foil 11 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) impregnated in capacitor element 10.

The capacitor element 10 is formed by winding a strip-shaped anode foil 11 and a strip-shaped cathode foil 12 with a separator 13 between them. The outermost circumference of the wound body is fixed with a stop tape 14. Note that Figure 2 shows the wound body in a partially unfolded state before the outermost circumference is fixed.

An electrolytic capacitor may have at least one capacitor element, but may also have multiple capacitor elements. The number of capacitor elements included in an electrolytic capacitor may be determined according to the application.

(Additional Note)
Based on the above description, the following techniques are disclosed.

(Technique 1)
An electrolytic capacitor comprising a laminate and a liquid component impregnated in the laminate,
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;
a first conductive polymer layer supported by the separator;
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 a surface of the separator is 80% or more;
the first conductive polymer layer held by the separator is in close contact with the inorganic layer.

(Technique 2)
The electrolytic capacitor according to claim 1, wherein the surface density of the first conductive polymer layer is 0.05 mg/cm ² or more and 1.0 mg/cm ² or less.

(Technique 3)
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.

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

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

(Technique 6)
The electrolytic capacitor according to any one of Techniques 1 to 5, wherein the laminate is a wound body.

(Technique 7)
A method for manufacturing an electrolytic capacitor, comprising the steps of:
A preparation step of preparing an anode foil having a dielectric layer on a surface thereof and a cathode foil having an inorganic layer on a surface thereof;
a first polymer layer forming step of forming a first conductive polymer layer in the voids of the 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;
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;
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 into the voids of the separator;
a first liquid medium removing 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.

(Technique 8)
The method for producing an electrolytic capacitor according to claim 7, wherein the surface density of the first conductive polymer layer is 0.05 mg/cm ² or more and 1.0 mg/cm ² or less.

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

(Technique 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.

(Technique 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.

(Technique 12)
The method further includes an impregnation step of impregnating the laminate with a liquid component,
The method for producing an electrolytic capacitor according to any one of techniques 7 to 11, 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.

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

(Technique 14)
The method for producing an electrolytic capacitor according to any one of Techniques 7 to 13, wherein the laminate is a wound body.

The present disclosure will be described in more detail below based on examples, but the present disclosure is not limited to the examples. In these examples, multiple electrolytic capacitors were produced and evaluated by the following method.

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

(a) Preparation of components An aluminum foil (thickness 100 μm) was etched to roughen the surface of the aluminum foil. The roughened surface of the aluminum foil was chemically treated to form a dielectric layer. In this way, an anode foil with a dielectric layer formed on both sides was obtained. A carbon layer was formed on both sides of an aluminum foil (thickness 50 μm) that would become a cathode foil. The carbon layer was formed by vacuum deposition.

A nonwoven fabric (thickness 50 μm) was prepared as a separator. The nonwoven fabric used was made of polyester fiber, aramid fiber, and cellulose.

(b) Formation of a conductive polymer layer As a coating liquid, a dispersion liquid (commercial product) in which particles of polyethylenedioxythiophene (PEDOT) doped with polystyrene sulfonic acid (PSS) were dispersed in water was prepared. Next, the coating liquid was applied to one side (surface of the dielectric layer) of the anode foil using a gravure coater. Then, a drying process was performed to form a conductive polymer layer on one side (surface of the dielectric layer) of the anode foil. 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 (surface of the dielectric layer) of the anode foil in the same manner. A conductive polymer layer was formed on the separator by applying the coating liquid to the separator and then performing a drying process.

(c) Formation of a wound body (laminate) The anode foil, cathode foil, and separator were each cut to a predetermined size. The anode lead tab and cathode lead tab were connected to the anode foil and cathode foil, respectively. Next, the anode foil and cathode foil were wound with the separator interposed therebetween. At that time, the ends of the outer surface of the wound body were fixed with a winding stop tape. The anode lead wire and 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 a chemical conversion treatment to form a dielectric layer on the end surface of the anode foil. In this manner, a capacitor element was obtained.

(d) Adhesion step First, liquid (L) was prepared. For liquid (L), an aqueous solution containing polyethylene glycol was used. The concentration of polyethylene glycol was 10 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.

(e) Impregnation of 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 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 solution.

(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 for 90 minutes at 95°C while applying a voltage. In this manner, an electrolytic capacitor (capacitor A1) was produced.

(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.

(evaluation)
The equivalent series resistance (ESR) of the produced electrolytic capacitor was measured. The produced electrolytic capacitor was disassembled, and the peel strength between the carbon layer of the cathode foil and the separator was measured by the following method. Furthermore, the ratio R of the area of the first conductive polymer layer to the surface of the separator was measured by the following method.

(1) Measurement of peel strength In this example, first, the electrolytic capacitor was disassembled and the wound body (capacitor element 10) was taken out. Next, the anode foil was pulled from the outer periphery of the wound body, and a part of the anode foil was peeled off from the wound body. Since the adhesion between the dielectric layer on the surface of the anode foil and the separator is 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 still in close contact with the anode foil.

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

The schematic configuration of an example of a measuring device 20 used to measure the peel strength is shown in FIG. 3. The measuring device is preferably designed to perform a test conforming to JIS (Japanese Industrial Standards) C0806-3:2014. The measuring device 20 includes a feed sheet 21, a feed roller 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 roller 22. The recovery device 23 recovers the above-mentioned 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 winding roller that winds up the cathode foil 12. The feed speed of the laminate 11A (anode foil 11 and separator 13) by the feed roller 22 and the winding speed of the cathode foil 12 by the recovery device 23 are controlled so that the position of the capacitor element 10 does not move during measurement.

In this embodiment, the laminate 11A and the cathode foil 12 were pulled 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 in the measuring device 20 and the direction in which the cathode foil 12 was pulled by the recovery device 23 was approximately 175°. At this time, 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.

(2) Measurement of the ratio R The capacitor elements of the capacitors A1 and C1 were disassembled, and the respective separators were taken out. In addition, for comparison, a separator without a conductive polymer layer was prepared. A sample of 2 cm x 5 cm was cut out from each separator and evaluated. Specifically, the separator of the capacitor A1, the separator of the capacitor C1, and the separator alone were lined up and scanned with a scanner to obtain images of them.

Then, the captured image was binarized using image analysis software (Adobe Photoshop (registered trademark)). At this time, 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 proportion R of capacitor A1 and the proportion R of capacitor C1 were calculated.

The evaluation results are shown in Table 1.

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 has a high ratio R, had a high peel strength between the cathode foil and the separator and a low ESR.

This disclosure can be used in electrolytic capacitors.

10: Capacitor element 11: Anode foil 12: Cathode foil 13: Separator 14: Stop tape 100: Electrolytic capacitor 101: Bottomed case 102: Sealing member 103: Seat plate 104A, 104B: Lead wires 105A, 105B: Lead tabs

Claims (14)

An electrolytic capacitor comprising a laminate and a liquid component impregnated in the laminate,
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;
a first conductive polymer layer supported by the separator;
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 a surface of the separator is 80% or more;
the first conductive polymer layer held by the separator is in close contact with the inorganic layer. 2. The electrolytic capacitor according to claim 1, wherein the first conductive polymer layer has an areal density of 0.05 mg/ ^cm2 or more and 1.0 mg/ ^cm2 or less. The electrolytic capacitor of 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. 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. 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. The electrolytic capacitor of claim 1, wherein the laminate is a wound body. A method for manufacturing an electrolytic capacitor, comprising the steps of:
A preparation step of preparing an anode foil having a dielectric layer on a surface thereof and a cathode foil having an inorganic layer on a surface thereof;
a first polymer layer forming step of forming a first conductive polymer layer in the voids of the 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;
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;
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 into the voids of the separator;
a first liquid medium removing 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 voids of the separator. 8. The method for producing an electrolytic capacitor according to claim 7, wherein the first conductive polymer layer has an areal density of 0.05 mg/ ^cm2 or more and 1.0 mg/ ^cm2 or less. The method for manufacturing 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. 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. 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. The method further includes an impregnation step of impregnating the laminate with a liquid component,
8. The method for producing an electrolytic capacitor according to claim 7, 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. The method for manufacturing 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. The method for manufacturing an electrolytic capacitor according to claim 7, wherein the laminate is a wound body.

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