Electrolytic capacitor and method for manufacturing same

Abstract

This electrolytic capacitor comprises: a positive electrode body that has a porous portion, at least part of the surface of said porous portion being covered by a dielectric layer; and a solid electrolyte layer that covers at least part of the dielectric layer. The solid electrolyte layer contains an elemental-sulfur-containing electrically conductive polymer. The elemental-sulfur-containing electrically conductive polymer is filled into at least some of the voids of the porous portion. A count S5 of the elemental sulfur detected by an electron beam microanalyzer, at a point where the depth from the principal surface of the porous portion is 5 μm, is 12500 or greater.

Description

Electrolytic capacitor and its manufacturing method CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This disclosure claims the benefit of priority to Japanese Patent Application No. 2024-052417, filed on March 27, 2024 in the Japan Patent Office, the entire contents of which are incorporated herein by reference.

[0002] The present disclosure relates to electrolytic capacitors and methods for manufacturing the same.

[0003] Patent Document 1 proposes a method for manufacturing an electrolytic capacitor, comprising: a first step of preparing a capacitor element body having an anode with a dielectric oxide film, a cathode, and a separator disposed between the anode and the cathode; a second step of preparing a mixed solution in which a first conductive polymer is dispersed in a solvent and a second conductive polymer is dissolved in the solvent; and a third step of impregnating the capacitor element body with the mixed solution and then heat-treating the mixed solution to form a conductive polymer layer in the voids of the capacitor element body, wherein the concentration of the first conductive polymer in the mixed solution is not more than five times the concentration of the second conductive polymer.

[0004] Japanese Patent Application Laid-Open No. 2022-161723

[0005] The electrolytic capacitor includes an anode body having a porous portion at least part of whose surface is covered with a dielectric layer, and a solid electrolyte layer covering at least part of the dielectric layer. The solid electrolyte layer contains a conductive polymer. The conductive polymer penetrates into some of the voids in the porous portion.

[0006] However, it is difficult to fill the deep voids in the porous portion with a conductive polymer, and there is room for improvement in terms of increasing the capacitance and durability of electrolytic capacitors.

[0007] One aspect of the present disclosure relates to an electrolytic capacitor comprising: an anode body having a porous portion at least a portion of a surface of which is covered with a dielectric layer; and a solid electrolyte layer covering at least a portion of the dielectric layer, wherein the solid electrolyte layer contains a conductive polymer containing elemental sulfur, and the conductive polymer containing elemental sulfur fills at least a portion of voids in the porous portion, and wherein a count number S5 of the elemental sulfur detected by an electron beam microanalyzer at a point 5 μm deep from a main surface of the porous portion is 12,500 or more.

[0008] Another aspect of the present disclosure relates to an electrolytic capacitor comprising: an anode body having a porous portion at least a portion of a surface of which is covered with a dielectric layer; and a solid electrolyte layer covering at least a portion of the dielectric layer, wherein the solid electrolyte layer contains a conductive polymer containing elemental sulfur, and the conductive polymer containing elemental sulfur fills at least a portion of voids in the porous portion, and wherein a ratio (S5 / S1) of a count number S5 of the elemental sulfur detected by an electron probe microanalyzer at a point 5 μm deep from a main surface of the porous portion to a count number S1 of the elemental sulfur detected by the electron probe microanalyzer at a point 1 μm deep from the main surface of the porous portion is 0.15 or greater.

[0009] Yet another aspect of the present disclosure relates to a method for manufacturing an electrolytic capacitor, the method comprising: preparing an anode body having a porous portion at least a portion of a surface of which is covered with a dielectric layer; and forming a solid electrolyte layer covering at least a portion of the dielectric layer, wherein the solid electrolyte layer contains a conductive polymer containing elemental sulfur, and the conductive polymer containing elemental sulfur fills at least a portion of voids in the porous portion, and a ratio (S5 / S1) of a count number S5 of the elemental sulfur detected by an electron probe microanalyzer at a point 5 μm deep from a main surface of the porous portion to a count number S1 of the elemental sulfur detected by the electron probe microanalyzer at a point 1 μm deep from the main surface of the porous portion is 0.15 or more.

[0010] According to the present disclosure, the capacitance and durability of an electrolytic capacitor can be improved.

[0011] 1 is a schematic cross-sectional view of an electrolytic capacitor according to an embodiment of the present disclosure, and is a diagram showing the relationship between the depth from the main surface of a porous portion of an anode body of an electrolytic capacitor according to an embodiment of the present disclosure and the number of counts of sulfur (S) detected by an electron probe microanalyzer.

[0012] The novel features of the present invention are set forth in the appended claims, but the present invention, both in terms of structure and content, together with other objects and features of the present invention, will be better understood from the following detailed description taken in conjunction with the drawings.

[0013] Hereinafter, embodiments of the present disclosure will be described using examples, but the present disclosure is not limited to the examples described below. In the following description, specific numerical values, materials, etc. may be exemplified, but other numerical values, materials, etc. may be applied as long as the effects of the present disclosure are obtained. Note that components other than those characteristic of the present disclosure may be components of known capacitors. In this specification, when a "range from numerical value A to numerical value B" is mentioned, the range includes numerical value A and numerical value B. When multiple materials are exemplified, one may be selected from the materials and used alone, or two or more may be used in combination.

[0014] The present disclosure also encompasses combinations of two or more features arbitrarily selected from the appended claims, i.e., two or more features arbitrarily selected from the appended claims can be combined unless a technical contradiction arises.

[0015] The "electrolytic capacitor" according to the present disclosure is a "solid electrolytic capacitor" that includes a conductive polymer as a solid electrolyte, and may further include a liquid. An "electrolytic capacitor" that includes a liquid may also be called a "solid-liquid electrolytic capacitor" or a "(solid-liquid) hybrid electrolytic capacitor." The term "capacitor" may be read as "capacitor."

[0016] The electrolytic capacitor according to the present disclosure includes an anode body having a porous portion at least partially covered with a dielectric layer, and a solid electrolyte layer covering at least a portion of the dielectric layer. The smallest unit of a structure including such an anode body, dielectric layer, and solid electrolyte layer is also referred to as a capacitor element. That is, the electrolytic capacitor includes at least one capacitor element.

[0017] The form of the capacitor element is not particularly limited. The capacitor element may include an anode portion and a cathode portion. The anode body constitutes the anode portion. The solid electrolyte layer constitutes the cathode portion. The cathode portion may include a cathode extraction layer.

[0018] The solid electrolyte layer may have a first portion and a second portion, the first portion being a portion filling the voids of the porous portion, and the second portion being a portion extending beyond the main surface of the porous portion.

[0019] In the electrolytic capacitor according to the present disclosure, the solid electrolyte layer includes a conductive polymer containing elemental sulfur. The conductive polymer containing elemental sulfur (hereinafter also referred to as an "S-containing conductive polymer") fills at least a portion of the voids in the porous portion to form a first portion. Here, the solid electrolyte layer satisfies at least one of the following conditions (A) and (B):

[0020] Condition (A): The count number S5 of sulfur elements detected by an electron probe microanalyzer (ie, EPMA) at a point 5 μm deep from the main surface of the porous portion is 12,500 or more.

[0021] The count number S5 may be 15,000 or more. In the case of a conventional electrolytic capacitor, the count number S5 is usually 11,000 or less.

[0022] Condition (B): The ratio (S5 / S1) of the count number S5 of sulfur elements detected by EPMA at a point 5 μm deep from the main surface of the porous portion to the count number S1 of sulfur elements detected by EPMA at a point 1 μm deep from the main surface of the porous portion is 0.15 or more.

[0023] The S5 / S1 ratio may be 0.18 or more. In the case of conventional electrolytic capacitors, the S5 / S1 ratio of elemental sulfur is usually 0.14 or less.

[0024] The sulfur element detected by EPMA reflects the amount of S-containing conductive polymer present in the first portion of the solid electrolyte layer. Satisfying at least one of conditions (A) and (B) means that a necessary and sufficient amount of S-containing conductive polymer is distributed in the voids of the porous portion. Satisfying at least one of conditions (A) and (B) improves both the capacity achievement rate and durability of the electrolytic capacitor.

[0025] The capacity achievement rate of the electrolytic capacitor is the ratio of the capacitance after the formation of the solid electrolyte layer to the capacitance of the anode body (capacitance before the formation of the solid electrolyte layer) when a rated voltage of 120 Hz is applied in an aqueous solution of ammonium adipate with a concentration of 15% by mass.

[0026] The durability of an electrolytic capacitor can be evaluated by its charge / discharge characteristics and heat resistance durability. The charge / discharge characteristics can be evaluated by the change in capacitance (ΔCap) of the electrolytic capacitor before and after 10,000 cycles of charge / discharge (ON (rated voltage applied) / OFF = 1 second / 1 second). The heat resistance durability can be evaluated by the equivalent series resistance (ESR) of the electrolytic capacitor after high-temperature storage (145°C for 500 hours).

[0027] Hereinafter, a method for determining the number of sulfur elements counted by EPMA at a point at an arbitrary depth of N μm from the main surface of the porous portion will be described.

[0028] (1) Preparation of a Capacitor Element Cross Section First, a capacitor element or product to be measured is prepared. Next, the capacitor element or product is cut perpendicular to its main surface to form a cross section of the porous portion (hereinafter referred to as a "cross-section sample"). In the case of a capacitor element, a thermosetting resin may be filled and cured. For example, a cross-section sample is obtained by ion milling, FIB (focused ion beam), wet polishing, or the like. However, since wet polishing may leach water-soluble sulfur-containing compounds, ion milling is preferred. In the cross-section sample, the metal skeleton constituting the porous portion, the dielectric layer covering at least a portion of its surface, and the conductive polymer constituting the solid electrolyte layer are observed.

[0029] (2) Photographing the cross-section sample using a scanning electron microscope (SEM) Next, the cross-section sample is observed using an SEM at a magnification of approximately 500 to 1500 times, which allows the metal skeleton constituting the porous portion, the dielectric layer covering at least a portion of its surface, and the conductive polymer constituting the solid electrolyte layer to be observed in their entirety.

[0030] (3) Elemental Analysis While observing the SEM image, the area for elemental analysis by EPMA is determined. A 100 μm × 80 μm area is set so as to include the metal skeleton constituting the porous portion, the dielectric layer covering at least a portion of its surface, and the entire conductive polymer constituting the solid electrolyte layer, and line analysis is performed.

[0031] (4) Analysis Conditions An example of SEM-EPMA measurement conditions is as follows: An ion milling device, ArBlade (registered trademark) 5000, manufactured by Hitachi High-Tech Corporation, is used as the processing device. The processing conditions are an acceleration voltage of 6 kV and a discharge voltage of 1.5 kV.

[0032] The measurement device used was an EPMA-8050G manufactured by Shimadzu Corporation. The acceleration voltage during analysis was 8 kV, and the SEM acceleration voltage was 15 kV. The electron beam current was 5 nA, the analysis area was 80 μm, the integration time was 20 s / point, and the measurement pitch was 1 μm.

[0033] In particular, when condition (B) is satisfied, it is believed that not only is a sufficient amount of S-containing conductive polymer filled deep in the voids, but also that the amount of conductive polymer present in the porous portion changes in a gradient close to ideal in the depth direction from the main surface, thereby further improving the capacity and durability.

[0034] Furthermore, if the same amount of conductive polymer is present deep in the voids as near the surface, although the capacity will improve, other disadvantages may arise, such as an increase in leakage current or a decrease in heat resistance and durability.

[0035] The electrolytic capacitor according to the present disclosure may further satisfy the following condition (C).

[0036] Condition (C): The ratio (S10 / S5) of the count numbers S10 and S5 of sulfur elements detected by EPMA at a point 10 μm deep from the main surface of the porous portion is 0.3 or more.

[0037] The S10 / S5 ratio may be 0.40 or more. In this case, it is considered that the amount of conductive polymer present in the porous portion changes in the depth direction from the main surface of the porous portion with a gradient that is closer to the ideal.

[0038] On the other hand, the ratio of S10 to S5 (S10 / S5) may be 0.5 or less, 0.47 or less, or 0.4 or less. In this case, S5 is sufficiently large to ensure high capacity, and the amount of conductive polymer present deep in the voids is appropriately limited. Therefore, leakage current is suppressed and the balance between capacity and durability is improved.

[0039] The S-containing conductive polymer may include a self-doping conductive polymer (hereinafter also referred to as "conductive polymer A"). The self-doping conductive polymer (conductive polymer A) is soluble in a liquid medium and therefore easily penetrates deep into the voids of the porous portion.

[0040] A self-doping conductive polymer refers to a polymer in which a functional group functioning as a dopant is directly or indirectly covalently bonded to the backbone of the conductive polymer. Examples of functional groups functioning as dopants include anionic groups. Anionic groups are groups that acquire a negative charge upon dissociation of a cation. The anionic group may be at least one selected from the group consisting of a sulfonic acid group, a phosphoric acid group, a phosphonic acid group, and a carboxyl group, or may be a salt thereof (e.g., a salt with an inorganic base or a salt with an organic base). A preferred example of the anionic group is a sulfonic acid group or a salt thereof.

[0041] The amount of functional groups (e.g., anionic groups) that function as dopants may be in the range of 0.2 to 3, 0.5 to 2, 0.5 to 1, 1, or less than 1 per structural unit (monomer unit) of the conductive polymer.

[0042] The conductive polymer A may be used alone or in combination of two or more kinds.

[0043] Examples of the skeleton of the conductive polymer A include polypyrrole, polythiophene, polyaniline, etc. These skeletons may have atomic groups (e.g., functional groups) other than the functional group that functions as a dopant bonded to them. Examples of the conductive polymer A include polypyrroles having anionic groups (polypyrrole and its derivatives), polythiophenes having anionic groups (polythiophene and its derivatives), and polyanilines having anionic groups (polyaniline and its derivatives). In these examples, an example of a preferred anionic group is a sulfonic acid group or a salt thereof. The conductive polymer A may also be a copolymer of two or more monomers.

[0044] Conductive polymer A may be a conductive polymer in which an atomic group containing a sulfonic acid group is introduced into poly(3,4-ethylenedioxythiophene) (PEDOT), which has relatively high durability. For example, conductive polymer A may contain or consist of the following structural units:

[0045]

[0046] In the above formula, R represents an organic chain. R may be composed of a hydrocarbon chain, or may contain an ether bond, a branched alkyl group, or other substituents in addition to the hydrocarbon chain. In the above formula, the sulfonic acid group may be converted into a salt. Examples of R include (skeleton side) -CH ２ -O-(CH ２ ) ２ - (CHCH ３ )-(sulfonic acid group side), etc.

[0047] An example of the monomer unit of the conductive polymer A is shown below.

[0048]

[0049] The content of the conductive polymer A in the S-containing conductive polymer is, for example, 15% by mass or more and 60% by mass or less, or may be 15% by mass or more and 45% by mass or less, or may be 15% by mass or more and 30% by mass or less.

[0050] The S-containing conductive polymer may further include a non-self-doping conductive polymer (hereinafter also referred to as "conductive polymer B"). The non-self-doping conductive polymer (conductive polymer B) is a polymer whose conductivity is improved by doping with a dopant.

[0051] Conductive polymer B has a greater effect of improving the durability of the solid electrolyte layer than conductive polymer A. From the viewpoint of improving the balance between capacity and durability, it is preferable that the S-containing conductive polymer contains both conductive polymer A and conductive polymer B.

[0052] Below, as a typical example, a case where conductive polymer A and conductive polymer B are used as S-containing conductive polymers will be mainly described. The explanation using conductive polymer A and conductive polymer B is suitable for understanding the technical significance of the present disclosure. However, the present disclosure is not limited to the case where conductive polymer A and conductive polymer B are used.

[0053] The non-self-doping conductive polymer (conductive polymer B) has superior durability compared to the self-doping conductive polymer A. However, since the non-self-doping conductive polymer (conductive polymer B) is in the form of particles dispersed in a liquid medium, it is difficult for it to penetrate deep into the voids of the porous portion. On the other hand, the conductive polymer B can play a role in controlling the degree to which both the conductive polymer A and the conductive polymer B penetrate deep into the voids.

[0054] When conductive polymer A and conductive polymer B are mixed and the mixture is impregnated into the voids of a porous portion, it is difficult to penetrate sufficient amounts of conductive polymer A and conductive polymer B deep into the voids using only this method. It is necessary to control various physical properties, including the composition of the mixture of conductive polymer A and conductive polymer B. It is also necessary to verify the physical properties of the porous portion filled with conductive polymers A and B, as well as the capacity achievement rate and durability of the electrolytic capacitor.

[0055] Conductive polymer B is also preferred in that it has high conductivity. By using a mixture of conductive polymer A and conductive polymer B, an electrolytic capacitor having high conductivity and an excellent balance between capacity and durability can be obtained.

[0056] The conductivity of the conductive polymer B may be 0.003 S / cm or more and 0.3 S / cm or less, or may be 0.01 S / cm to 0.1 S / cm.

[0057] The conductivity of conductive polymer B can be determined by applying a dispersion of conductive polymer B to a flat insulating substrate to form a solid electrolyte layer and measuring the conductivity of the solid electrolyte layer. For example, an aqueous dispersion of conductive polymer B is applied to a flat insulating substrate, dried at 60°C for 10 minutes, and then dried at 200°C for 30 minutes, and the conductivity is measured. The conductivity of the solid electrolyte layer can be measured using a Loresta GX and PSP probe manufactured by Nitto Seiko Analytech Co., Ltd.

[0058] In a mixture of conductive polymer A and conductive polymer B, the content of conductive polymer A relative to the total amount of conductive polymer A and conductive polymer B is, for example, 15% by mass or more and 60% by mass or less, or may be 15% by mass or more and 45% by mass or less, or may be 15% by mass or more and 30% by mass or less.

[0059] The conductive polymer B may be a polymer material containing a conjugated polymer and a polymer anion.

[0060] Examples of conjugated polymers include polypyrrole, polythiophene, polyfuran, polyaniline, polyacetylene, and derivatives thereof. Such derivatives include polymers having polypyrrole, polythiophene, polyfuran, polyaniline, and polyacetylene as their basic skeletons. For example, a derivative of polythiophene includes poly(3,4-ethylenedioxythiophene). A preferred example of a conjugated polymer is poly(3,4-ethylenedioxythiophene) (PEDOT).

[0061] The conjugated polymer may be used alone or in combination of two or more kinds. The conjugated polymer may also be a copolymer of two or more kinds of monomers.

[0062] The weight average molecular weight of the conjugated polymer is not particularly limited, and may be in the range of 1,000 to 100,000, for example.

[0063] In a non-self-doping conductive polymer (conductive polymer B), a functional group that functions as a dopant is not covalently bonded to the backbone of a conjugated polymer. In conductive polymer B, a dopant is doped into the conjugated polymer. From the viewpoint of suppressing dedoping from conductive polymer B, it is preferable to use a polymer dopant (polymer anion) as the dopant. That is, conductive polymer B preferably contains a conjugated polymer and a polymer anion.

[0064] 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, and polyacrylic acid. These may be used alone or in combination of two or more. These may be contained in the electrolyte layer in the form of a salt. A preferred example of the polymer dopant is polystyrene sulfonic acid (PSS).

[0065] The weight-average molecular weight of the polymer dopant is not particularly limited and may be, for example, in the range of 1,000 to 100,000. The weight-average molecular weight of the polymer dopant may be 1,000 or more and 70,000 or less.

[0066] When the conductive polymer B is dispersed in a liquid medium in the form of particles, the average particle size of the conductive polymer B may be 100 nm or more and 500 μm or less, and preferably 100 nm or more and 500 nm or less. A conductive polymer B having an average particle size in this range is particularly suitable for controlling S5 and the S1 / S5 ratio. The average particle size is the median diameter in a volume particle size distribution measured with a particle size measuring device using dynamic light scattering.

[0067] When a mixture of conductive polymer A and conductive polymer B is used, the viscosity of the liquid composition containing conductive polymer A and conductive polymer B, measured at 20°C using a rotational B-type viscometer, may be, for example, 5 mPa·s or more and 30 mPa·s or less. A liquid composition having a viscosity in this range is particularly suitable for controlling the S5 and S1 / S5 ratios. The viscosity of the liquid composition is measured, for example, using a B-type viscometer (DV-2T) manufactured by Eiko Seiki Co., Ltd. at a measurement speed of 60 rpm. If the viscosity measured at 20°C is within the range of 1.0 to 10.0 mPa·s, a ULA spindle (diameter 25.13 mm) may be used, and if the viscosity measured at 20°C is within the range of 10.1 to 100.0 mPa·s, an LV-1 spindle (diameter 18.84 mm) may be used.

[0068] The configuration of an example of an electrolytic capacitor according to the present disclosure will be described in more detail below. [Electrolytic Capacitor] The capacitor element included in the electrolytic capacitor includes an anode portion and a cathode portion. The cathode portion includes a solid electrolyte layer. The solid electrolytic capacitor and capacitor element according to the present disclosure are characterized primarily by the solid electrolyte layer, and therefore the other components are not particularly limited. Components used in known electrolytic capacitors may be applied to each component.

[0069] (Capacitor Element) The anode part of the capacitor element includes an anode body, a dielectric layer formed on at least a portion of the surface of the anode body, and a cathode part formed on at least a portion of the surface of the dielectric layer.

[0070] (Anode body) The anode body is formed of a conductive material. The anode body may be a sheet-shaped anode foil, or may be a molded body or sintered body of metal particles. The anode foil has a core and a porous part continuous with the core. The sintered body may itself be a porous part.

[0071] The average pore diameter (average pit diameter) of the porous portion is, for example, 100 nm to 1000 nm, or may be 100 nm to 200 nm. A porous portion having an average pore diameter in this range is particularly suitable for controlling S5 and the S1 / S5 ratio.

[0072] The average pore diameter of the porous portion is determined by measuring the pore diameter distribution of the porous portion using a mercury porosimeter. Specifically, the pore diameter (mode diameter) corresponding to the apex of a peak (the largest peak if multiple peaks exist) that appears on the pore diameter distribution curve (vertical axis: log differential pore volume, horizontal axis: pore diameter) obtained by the measurement is determined as the average pore diameter. For example, an AutoPore V series manufactured by Micromeritics is used as the measuring device. From such a pore diameter distribution curve, a pore diameter distribution in the pore diameter range of less than 2000 nm can be obtained.

[0073] The conductive material constituting the anode body may include a valve metal, an alloy containing a valve metal, a compound containing a valve metal, etc. The anode body may include one of these materials or a combination of two or more of them. Preferred examples of the valve metal include aluminum, tantalum, niobium, and titanium.

[0074] The anode body has a porous portion at least on the surface layer thereof. The porous portion of the anode body has many fine voids. Due to this porous portion, the anode body has a finely uneven shape.

[0075] An anode body having a porous portion on its surface can be obtained, for example, by roughening the surface of a substrate containing a valve metal. The roughening may be performed, for example, by etching (electrolytic etching, chemical etching, etc.). Such an anode body (anode foil) has, for example, a core and porous portions formed integrally with the core on both surfaces of the core. The substrate containing a valve metal may be in the form of a sheet, such as a metal foil or a plate-like substrate.

[0076] The anode body may be a sintered body or a compact of particles containing a valve metal. The compact and sintered body are porous and may be a rectangular parallelepiped, a cube, or a similar shape. The sintered body may be, for example, a sintered body of particles containing tantalum.

[0077] The anode body may have an anode lead portion including a first end and a cathode formation portion including a second end opposite the first end. A cathode portion including a solid electrolyte layer is formed on the surface of the cathode formation portion of the anode body. The anode lead portion is used, for example, for electrical connection with an external electrode on the anode side. An anode lead terminal may be connected to the anode lead portion.

[0078] (Anode Wire) When the anode body is a porous sintered body or a molded body, the anode portion may include an anode wire. The anode wire may be a metal wire. Examples of materials for the anode wire include the valve metals described above, copper, or copper alloys. A portion of the anode wire is embedded in the anode body, and the remaining portion protrudes outward from the end face of the anode body. The end of the anode wire protruding outward corresponds to the first end, and the end of the anode body opposite the first end corresponds to the second end.

[0079] (Dielectric Layer) The dielectric layer is formed so as to cover at least a portion of the surface of the anode body or the porous portion. The dielectric layer can be formed by a known method. The dielectric layer may be formed by oxidizing a valve metal on the surface of the anode body or the porous portion by chemical conversion treatment or the like. The dielectric layer has a fine uneven shape that conforms to the surface shape of the porous portion.

[0080] The dielectric layer contains an oxide of the valve metal. For example, when tantalum is used as the valve metal, the dielectric layer contains Ta. ２ O ５ When aluminum is used as the valve metal, the dielectric layer is Al ２ O ３ The dielectric layer is not limited to these examples, but may be any layer that functions as a dielectric.

[0081] (Cathode portion) The cathode portion includes at least a solid electrolyte layer covering at least a portion of the dielectric layer. The solid electrolyte layer is formed on the second end side of the anode body (in other words, the cathode-forming portion) via the dielectric layer. The cathode portion typically includes a solid electrolyte layer covering at least a portion of the dielectric layer and a cathode extraction layer covering at least a portion of the solid electrolyte layer.

[0082] (Solid Electrolyte Layer) In the capacitor element, the solid electrolyte layer is formed so as to cover at least a portion of the dielectric layer. In the anode body having the dielectric layer, the solid electrolyte layer may have a first portion filling the voids of the porous portion and a second portion protruding from the main surface of the anode body having the dielectric layer. As described above, the first portion may include both a self-doping conductive polymer and a non-self-doping conductive polymer.

[0083] (Method for Manufacturing Electrolytic Capacitor) A method for manufacturing an electrolytic capacitor according to the present disclosure includes a step (step (1)) of preparing an anode body having a porous portion at least a portion of the surface of which is covered with a dielectric layer, and a step (step (2)) of forming a solid electrolyte layer that covers at least a portion of the dielectric layer.

[0084] In step (1), an anode body having a porous portion is prepared. The anode body is prepared, for example, by roughening the surface of a metal foil to form a porous portion. The roughening step may include an etching step of etching the metal foil. By roughening the surface, a porous portion having a plurality of pits or pores is formed on the surface side of the metal foil. At the same time, a metal core portion integral with the porous portion is formed in the inner portion of the metal foil.

[0085] The etching may be performed by, for example, DC etching using a direct current or AC etching using an alternating current. In this case, the etching conditions may be controlled so that the average pore diameter (average pit diameter) of the porous portion is, for example, from 100 nm to 1000 nm, preferably from 100 nm to 200 nm.

[0086] The solid electrolyte layer formed in step (2) contains a conductive polymer containing elemental sulfur (S-containing conductive polymer). The S-containing conductive polymer fills at least a portion of the voids in the porous portion. The solid electrolyte layer is formed to satisfy at least one of the above conditions (A) and (B). That is, the count number S5 of elemental sulfur detected by EPMA at a point 5 μm deep from the main surface of the porous portion is 12,500 or more, or the S5 / S1 ratio is 0.15 or more.

[0087] The step (2) of forming the solid electrolyte layer includes, for example, a step of preparing a liquid composition containing a liquid medium and an S-containing conductive polymer dispersed in the liquid medium, and a step of impregnating the porous portion of the anode body with the liquid composition.

[0088] The liquid medium may be, for example, water, an organic solvent, or a mixture thereof, with water being preferred.

[0089] As described above, the liquid composition may contain a self-doping conductive polymer (conductive polymer A) and a non-self-doping conductive polymer (conductive polymer B). The conductive polymer A has relatively flexible polymer chains, and the positions of functional groups such as anionic groups are random. The conductive polymer A has low orientation of the polymer chains and low crystallinity. Therefore, it is more easily dissolved in a liquid medium than the conductive polymer B. Therefore, it is easily impregnated with high permeability into the deep voids of the porous portion. On the other hand, the conductive polymer B has the effect of suppressing excessive penetration of the conductive polymer A into the deep voids of the porous portion.

[0090] The content of the conductive polymer A in the total of the conductive polymer A and the conductive polymer B may be 15% by mass or more and 60% by mass or less.

[0091] When the average pore size of the porous portion of the anode body is 100 nm or more and 1000 nm or less, the average particle size of the conductive polymer B contained in the liquid composition is preferably 100 nm or more and 200 nm or less, which makes it easier to suitably control S5 and the S1 / S5 ratio.

[0092] The viscosity of the liquid composition measured at 20° C. with a rotational viscometer is preferably, for example, 5 mPa·s to 30 mPa·s, inclusive. In this case, it is easy to suitably control S5 and the S1 / S5 ratio.

[0093] In the step (2) of forming the solid electrolyte layer, for example, the step of applying the liquid composition to the dielectric layer and then drying it may be repeated one or more times.

[0094] The concentration of the conductive polymer A in the liquid composition may be, for example, 0.5% by mass or more and 5% by mass or less, or 1% by mass or more and 3% by mass or less.

[0095] The concentration of the conductive polymer B in the liquid composition may be, for example, 0.5% by mass or more and 5% by mass or less, or 1% by mass or more and 3% by mass or less.

[0096] At least a first portion of the solid electrolyte layer is formed by the above process. Thereafter, for example, a treatment liquid containing a non-self-doping conductive polymer (conductive polymer B) may be used to form a second portion covering at least a part of the first portion so as to extend beyond the main surface of the porous portion. More specifically, the second portion may be formed by applying a treatment liquid containing conductive polymer B to an anode body having a dielectric layer. If necessary, application of the treatment liquid to the anode body and drying may be repeated two or more times.

[0097] The concentration of the conductive polymer B in the treatment liquid may be 0.5% by mass or more and 5% by mass or less, or may be 1% by mass or more and 3% by mass or less.

[0098] (Cathode Extraction Layer) The cathode extraction layer may include, for example, at least a first extraction layer in contact with the solid electrolyte layer and covering at least a portion of the solid electrolyte layer, and a second extraction layer covering at least a portion of the first extraction layer.

[0099] Examples of the first extraction layer include a layer containing conductive particles and metal foil. Examples of the conductive particles include at least one selected from conductive carbon and metal powder. The cathode part (more specifically, the cathode extraction layer) may include a layer containing metal powder. The cathode extraction layer may be composed of, for example, a layer containing conductive carbon (carbon layer) as the first extraction layer and a layer containing metal powder or metal foil as the second extraction layer.

[0100] When the cathode extraction layer includes a layer containing metal foil or metal powder, the entire cathode extraction layer may be composed of a layer containing metal foil or metal powder, or at least one of the first extraction layer and the second extraction layer may be composed of a layer containing metal powder.

[0101] Examples of conductive carbon include graphite (artificial graphite, natural graphite, etc.).

[0102] The second lead layer containing metal powder can be formed, for example, by laminating a composition containing metal powder on the surface of the first lead layer. The second lead layer can be formed, for example, using a paste containing metal powder and a resin binder. While a thermoplastic resin can be used as the resin binder, a thermosetting resin such as an imide resin or an epoxy resin is preferred.

[0103] From the viewpoint of easily achieving high conductivity in the second leader layer, silver-containing particles may be used as the metal powder. Examples of silver-containing particles include silver particles and silver alloy particles. The second leader layer may contain one type of silver-containing particle or a combination of two or more types. The silver particles may contain a small amount of impurities.

[0104] When a metal foil is used as the first lead layer, the type of metal is not particularly limited. It is preferable to use a valve metal (aluminum, tantalum, niobium, etc.) or an alloy containing a valve metal as the metal foil. If necessary, the surface of the metal foil may be roughened. The surface of the metal foil may be provided with a chemical conversion coating, or may be provided with a coating of a metal (dissimilar metal) or a nonmetal different from the metal constituting the metal foil. Examples of dissimilar metals and nonmetals include metals such as titanium and nonmetals such as carbon (e.g., conductive carbon).

[0105] The coating of the dissimilar metal or non-metal (for example, conductive carbon) may serve as a first lead layer, and the metal foil may serve as a second lead layer.

[0106] (Other) The electrolytic capacitor includes at least one capacitor element. The electrolytic capacitor may be a wound type, and may be either a chip type or a stacked type. For example, the electrolytic capacitor may include multiple stacked capacitor elements. The electrolytic capacitor may also include two or more wound capacitor elements. The configuration of the capacitor element may be selected depending on the type of electrolytic capacitor.

[0107] When a metal foil is used for the cathode extraction layer, a separator may be disposed between the metal foil and the anode foil serving as the anode body. The separator is not particularly limited, and may be, for example, a nonwoven fabric containing fibers of cellulose, polyethylene terephthalate, vinylon, or polyamide (e.g., aliphatic polyamide, aromatic polyamide such as aramid).

[0108] In the capacitor element, one end of a cathode lead terminal may be electrically connected to the cathode extraction layer. The cathode lead terminal may be bonded to the cathode extraction layer via a conductive adhesive applied to the cathode extraction layer, for example. One end of an anode lead terminal may be electrically connected to the anode extraction portion of the anode body. The other end of the anode lead terminal and the other end of the cathode lead terminal are each led out of the resin exterior body or the case.

[0109] The other end of each terminal exposed from the resin exterior body or case is used for soldering to a substrate on which the electrolytic capacitor is to be mounted, etc. In addition to the case where the lead terminals are drawn out, at least one end face of the anode part and the cathode part may be exposed from the outer surface of the sealing body and electrically connected to an external electrode.

[0110] The capacitor element is sealed using a resin outer casing or case. For example, the capacitor element and the resin material of the outer casing (e.g., uncured thermosetting resin and filler) may be placed in a mold, and the capacitor element may be sealed in the resin outer casing by transfer molding, compression molding, or the like. At this time, the other end portions of the anode lead terminal and the cathode lead terminal connected to the anode lead drawn from the capacitor element are exposed from the mold. Alternatively, the capacitor element may be housed in a bottomed case so that the other end portions of the anode lead terminal and the cathode lead terminal are positioned on the opening side of the bottomed case, and the opening of the bottomed case may be sealed with a sealant to form an electrolytic capacitor. The leads may be wire-shaped or frame-shaped (e.g., lead frame).

[0111] FIG. 1 is a cross-sectional schematic diagram of an electrolytic capacitor according to an embodiment of the present disclosure. The electrolytic capacitor 1 includes a capacitor element 11, a resin outer casing 12 that seals the capacitor element 11, and an anode terminal 13 and a cathode terminal 14 that are exposed to the exterior of the resin outer casing 12. The capacitor element 11 includes an anode body 2, a dielectric layer 3 that covers the second end of the anode body 2, and a cathode portion 15 that covers the dielectric layer 3. The portion of the anode body 2 where the cathode portion 15 (particularly the solid electrolyte layer 4) is formed is the cathode-forming portion, and the portion where the cathode portion 15 is not formed is the anode lead portion. The anode terminal 13 is electrically connected to the anode lead portion of the anode body 2. The cathode terminal 14 is electrically connected to the cathode portion 15. The resin outer casing 12 has a substantially rectangular parallelepiped outer shape, and therefore the solid electrolytic capacitor 1 also has a substantially rectangular parallelepiped outer shape.

[0112] The anode body 2 and the cathode section 15 face each other with the dielectric layer 3 interposed therebetween. The cathode section 15 has a solid electrolyte layer 4 covering the dielectric layer 3, and a cathode extraction layer 5 covering the solid electrolyte layer 4. The cathode extraction layer 5 in the illustrated example has a two-layer structure and has a carbon layer 5a in contact with the solid electrolyte layer 4 and a metal particle-containing layer 5b covering the surface of the carbon layer 5a.

[0113] An insulating separator 16 is formed in a region of the anode lead portion of the anode body 2 that protrudes from the cathode portion 15 on the cathode portion 15 side so as to cover the surface of the anode body 2 in a band shape, thereby restricting contact between the cathode portion 15 and the anode body 2. A first end (anode lead portion) of the anode body 2 that protrudes from the cathode portion 15 is electrically connected to one end 13a of the anode terminal 13 by welding or the like. Meanwhile, the cathode lead layer 5 formed on the outermost layer of the cathode portion 15 is electrically connected to one end 14a of the cathode terminal 14 via a conductive adhesive 17 (e.g., a mixture of a thermosetting resin and metal particles). The other end 13b of the anode terminal 13 and the other end 14b of the cathode terminal 14 are each drawn from different side surfaces of the resin exterior package 12 and extend in an exposed state to one of the main flat surfaces (the bottom surface in FIG. 1 ). The exposed portions of the terminals on this flat surface are used for soldering to a substrate (not shown) on which the solid electrolytic capacitor 1 is to be mounted.

[0114] Dielectric layer 3 is formed on part of the surface of the conductive material that constitutes anode body 2. Specifically, dielectric layer 3 can be formed by anodizing the surface of the conductive material that constitutes anode body 2. Thus, dielectric layer 3 is formed along the surface of anode body 2 (including the inner wall surfaces of holes and depressions on the inner surface).

[0115] (Additional Notes) The above description discloses the following techniques: (Technology 1) An electrolytic capacitor comprising: an anode body having a porous portion at least a portion of the surface of which is covered with a dielectric layer; and a solid electrolyte layer covering at least a portion of the dielectric layer, wherein the solid electrolyte layer contains a conductive polymer containing elemental sulfur, and the conductive polymer containing elemental sulfur fills at least a portion of the voids in the porous portion, and wherein a count number S5 of the elemental sulfur detected by an electron probe microanalyzer at a point 5 μm deep from a main surface of the porous portion is 12,500 or more. (Technology 2) An electrolytic capacitor comprising: an anode body having a porous portion at least a portion of whose surface is covered with a dielectric layer; and a solid electrolyte layer covering at least a portion of the dielectric layer, wherein the solid electrolyte layer contains a conductive polymer containing elemental sulfur, and the conductive polymer containing elemental sulfur fills at least a portion of the voids of the porous portion, and wherein a ratio (S5 / S1) of a count number S5 of the elemental sulfur detected by an electron beam microanalyzer at a point 5 μm deep from a main surface of the porous portion to a count number S1 of the elemental sulfur detected by an electron beam microanalyzer at a point 1 μm deep from the main surface of the porous portion is 0.15 or more. (Technology 3) An electrolytic capacitor according to Technology 1 or 2, wherein a ratio (S10 / S5) of a count number S10 of the elemental sulfur detected by an electron beam microanalyzer at a point 10 μm deep from the main surface of the porous portion to the S5 is 0.3 or more. (Technology 4) The electrolytic capacitor according to Technology 3, wherein the ratio of S10 to S5 (S10 / S5) is 0.5 or less. (Technology 5) The electrolytic capacitor according to any one of Technology 1 to 4, wherein the conductive polymer containing elemental sulfur includes a self-doping conductive polymer. (Technology 6) The electrolytic capacitor according to Technology 5, wherein the content of the self-doping conductive polymer in the conductive polymer containing elemental sulfur is 15 mass% or more and 60 mass% or less. (Technology 7) The electrolytic capacitor according to Technology 5 or 6, wherein the conductive polymer containing elemental sulfur further includes a non-self-doping conductive polymer. (Technology 8) The electrolytic capacitor according to Technology 7, wherein the non-self-doping conductive polymer includes a conjugated polymer and a polymer anion.(Technology 9) The electrolytic capacitor according to any one of Technologies 1 to 8, wherein the conductivity of the non-self-doping conductive polymer is 0.003 S / cm or more and 0.3 S / cm or less. (Technology 10) The electrolytic capacitor according to any one of Technologies 1 to 9, wherein the average pore diameter of the porous portion is 100 nm or more and 1000 nm or less. (Technology 11) A method for manufacturing an electrolytic capacitor, comprising the steps of: preparing an anode body having a porous portion at least a portion of whose surface is covered with a dielectric layer; and forming a solid electrolyte layer covering at least a portion of the dielectric layer, wherein the solid electrolyte layer contains a conductive polymer containing elemental sulfur, and the conductive polymer containing elemental sulfur fills at least a portion of the voids of the porous portion, and a ratio (S5 / S1) of a count number S5 of the elemental sulfur detected by an electron probe microanalyzer at a point 5 μm deep from a main surface of the porous portion to a count number S1 of the elemental sulfur detected by an electron probe microanalyzer at a point 1 μm deep from the main surface of the porous portion is 0.15 or more. (Technology 12) A method for manufacturing an electrolytic capacitor according to Technology 11, wherein the step of forming a solid electrolyte layer comprises the steps of: preparing a liquid composition containing a liquid medium and the conductive polymer containing elemental sulfur dispersed in the liquid medium; and impregnating the porous portion of the anode body with the liquid composition. (Technology 13) The method for producing an electrolytic capacitor according to Technology 12, wherein the viscosity of the liquid composition measured at 20°C with a rotational viscometer is 5 mPa·s or more and 30 mPa·s or less. (Technology 14) The method for producing an electrolytic capacitor according to Technology 12 or 13, wherein the liquid composition contains a self-doping conductive polymer and a non-self-doping conductive polymer. (Technology 15) The method for producing an electrolytic capacitor according to Technology 14, wherein the content of the self-doping conductive polymer in the total of the self-doping conductive polymer and the non-self-doping conductive polymer is 15 mass% or more and 60 mass% or less.

[0116] EXAMPLES The present invention will be specifically described below based on examples and comparative examples, but the present invention is not limited to the following examples.

[0117] Example 1 A capacitor element was fabricated in the following manner, and its characteristics were evaluated.

[0118] (1) Preparation of an anode body having a dielectric layer An anode body having a core and porous portions formed on both sides of the core was prepared by roughening both surfaces of an aluminum foil (thickness: 100 μm) as a substrate by etching. The average pore diameter of the porous portions was 150 nm.

[0119] (2) Step of Forming Dielectric Layer The anode body was immersed in a chemical conversion solution, and a direct current voltage of 70 V was applied for 20 minutes to form a dielectric layer containing aluminum oxide.

[0120] (3) Step of Forming Solid Electrolyte Layer (3-1) Preparation of Liquid Composition The following self-doping conductive polymer (Conductive Polymer A) and non-self-doping conductive polymer (Conductive Polymer B) were prepared as S-containing conductive polymers.

[0121] <Conductive Polymer A> An aqueous solution of conductive polymer A composed of the following monomer units was prepared.

[0122]

[0123] Conductive Polymer B: An aqueous dispersion of poly(3,4-ethylenedioxythiophene) (PEDOT) doped with polystyrene sulfonic acid (PSS), i.e., PEDOT / PSS, was prepared. The average particle size of the PEDOT / PSS measured by the method described above was 150 nm.

[0124] Conductive polymer A and conductive polymer B were mixed to prepare a liquid composition containing water as a liquid medium and an S-containing conductive polymer dispersed in water. The content of the S-containing conductive polymer in the liquid composition was 30 mass %. The mass content (Cs) of conductive polymer A in the total of conductive polymer A and conductive polymer B was the content shown in Table 1.

[0125] The viscosity of the liquid composition measured at 20°C under the above-mentioned conditions using a vibration viscometer is shown in Table 1. Table 1 also shows the conductivity B of a solid electrolyte layer formed by applying an aqueous dispersion of conductive polymer B to a flat insulating substrate, drying at 60°C for 10 minutes, and then drying at 200°C for 30 minutes.

[0126] (3-2) Impregnation with Liquid Composition and Drying The liquid composition was placed in a container. Next, the anode body having the dielectric layer was immersed in the liquid composition in the container for 1 minute at room temperature under atmospheric pressure. Thereafter, the anode body was removed from the liquid composition and dried in a drying furnace at 120°C for 10 to 30 minutes, thereby filling the voids in the porous portion of the anode body with the S-containing conductive polymer and forming a solid electrolyte layer.

[0127] (4) Cathode Extraction Layer Formation Step The anode body obtained in (3) above was immersed in a dispersion liquid in which graphite particles were dispersed in water, removed from the dispersion liquid, and then dried to form a carbon layer 5a on the surface of the solid electrolyte layer. The drying was performed at 130 to 180°C for 10 to 30 minutes.

[0128] Next, a silver paste containing silver particles and a binder resin (epoxy resin) was applied to the surface of carbon layer 5a, and the binder resin was cured by heating at 150 to 200°C for 10 to 60 minutes, thereby forming metal particle-containing layer 5b. In this way, cathode extraction layer 5 composed of carbon layer 5a and metal particle-containing layer 5b was formed. Capacitor element 11 was produced in the above manner.

[0129] (5) Assembly of Electrolytic Capacitor Cathode extraction layer 5 of capacitor element 11 obtained in (4) above was joined to one end 14a of cathode terminal 14 with conductive adhesive 17. The anode extraction portion of anode body 2 protruding from capacitor element 11 was joined to one end 13a of anode terminal 13 by laser welding. In this manner, electrolytic capacitor E1 of Example 1 was completed. Resin sealing was not performed.

[0130] Examples 2 to 4, Comparative Examples 1 to 4 Electrolytic capacitors E2 to E4 of Examples 2 to 4 and electrolytic capacitors R1 to R4 of Comparative Examples 1 to 4 were completed in the same manner as in Example 1, except that the mass content (Cs) of conductive polymer A in the total of conductive polymer A and conductive polymer B, the viscosity of the liquid composition (or the molecular weight of each conductive polymer), and the conductivity B of the solid electrolyte layer were changed.

[0131] (6) Evaluation (6-1) Capacity Achievement Rate The anode body before the formation of the solid electrolyte layer was immersed in an aqueous solution of ammonium adipate with a concentration of 15% by mass, and the capacitance (C100) was determined when a rated voltage of 120 Hz was applied. Thereafter, a solid electrolyte layer was formed on the anode body, a cathode extraction layer was formed, and the capacitance (Cn) was determined when a rated voltage of 120 Hz was applied using an LCR meter. The ratio of Cn to C100 was determined as the capacity achievement rate (Cr). The results are shown in Table 1.

[0132] (6-2) Charge / Discharge Characteristics The electrolytic capacitor was charged and discharged 10,000 times (ON (rated voltage applied) / OFF = 1 second / 1 second), and the ratio (ΔCap) of the difference (C0-C10,000) between the capacitance of the electrolytic capacitor before the charge / discharge cycle (C0) and the capacitance of the electrolytic capacitor after the charge / discharge cycle (C10,000) to C0 was calculated. The results are shown in Table 1.

[0133] (6-3) Heat Resistance Durability The electrolytic capacitors were stored at 145° C., and the equivalent series resistance (ESR) was measured after 500 hours. The results are shown in Table 1.

[0134]

[0135] Figure 2 shows the relationship between the depth from the main surface of the porous portion of the anode body of electrolytic capacitors E1 and R1 and the sulfur (S) counts detected by an electron probe microanalyzer. For E1, the count S5 is a large value exceeding 12,500, and the S5 / S1 ratio is greater than 0.15. On the other hand, for R1, the count S5 is less than 12,500, and the S5 / S1 ratio is less than 0.15. These differences are thought to be the cause of the differences in the capacitance achievement rate and durability of the electrolytic capacitors.

[0136] While the present invention has been described in terms of presently preferred embodiments, such disclosure is not to be interpreted as limiting. Various changes and modifications will no doubt become apparent to those skilled in the art to which the present invention pertains upon reading the above disclosure. It is therefore intended that the appended claims be interpreted to cover all changes and modifications that do not depart from the true spirit and scope of the invention.

[0137] The electrolytic capacitor according to the present disclosure is suitable for applications requiring high reliability.

[0138] DESCRIPTION OF SYMBOLS 1: Electrolytic capacitor 2: Anode body 3: Dielectric layer 4: Solid electrolyte layer 5: Cathode extraction layer 5a: Carbon layer 5b: Metal particle-containing layer 11: Capacitor element 12: Resin exterior body 13: Anode terminal 13a: One end of anode terminal 13b: Other end of anode terminal 14: Cathode terminal 14a: One end of cathode terminal 14b: Other end of cathode terminal 15: Cathode portion 16: Separation portion 17: Conductive adhesive

Claims

1. An electrolytic capacitor comprising: an anode body having a porous portion at least a portion of whose surface is covered with a dielectric layer; and a solid electrolyte layer covering at least a portion of the dielectric layer, wherein the solid electrolyte layer contains a conductive polymer containing elemental sulfur, and the conductive polymer containing elemental sulfur fills at least a portion of the voids in the porous portion, and wherein a count number S5 of the elemental sulfur detected by an electron beam microanalyzer at a point 5 μm deep from a main surface of the porous portion is 12,500 or more.

2. An electrolytic capacitor comprising: an anode body having a porous portion at least a portion of whose surface is covered with a dielectric layer; and a solid electrolyte layer covering at least a portion of the dielectric layer, wherein the solid electrolyte layer contains a conductive polymer containing elemental sulfur, and the conductive polymer containing elemental sulfur fills at least a portion of the voids of the porous portion, and wherein the ratio (S5 / S1) of the count number S5 of the elemental sulfur detected by an electron beam microanalyzer at a point 5 μm deep from the main surface of the porous portion to the count number S1 of the elemental sulfur detected by the electron beam microanalyzer at a point 1 μm deep from the main surface of the porous portion is 0.15 or more.

3. The electrolytic capacitor according to claim 1 or 2, wherein the ratio (S10 / S5) of the count number S10 of the sulfur element detected by an electron beam microanalyzer at a point 10 μm deep from the main surface of the porous portion to the count number S5 is 0.3 or more.

4. The electrolytic capacitor according to claim 3, wherein the ratio of S10 to S5 (S10 / S5) is 0.5 or less.

5. The electrolytic capacitor according to claim 1 or 2, wherein the conductive polymer containing elemental sulfur includes a self-doped conductive polymer.

6. The electrolytic capacitor according to claim 5, wherein the content of the self-doped conductive polymer in the conductive polymer containing elemental sulfur is 15% by mass or more and 60% by mass or less.

7. The electrolytic capacitor according to claim 5, wherein the conductive polymer containing elemental sulfur further comprises a non-self-doping conductive polymer.

8. The electrolytic capacitor according to claim 7, wherein the non-self-doping conductive polymer comprises a conjugated polymer and a polymer anion.

9. The electrolytic capacitor according to claim 1 or 2, wherein the conductivity of the non-self-doping conductive polymer is 0.003 S / cm or more and 0.3 S / cm or less.

10. The electrolytic capacitor according to claim 1 or 2, wherein the average pore diameter of the porous portion is 100 nm or more and 1000 nm or less.

11. A method for manufacturing an electrolytic capacitor, comprising the steps of: preparing an anode body having a porous portion at least a portion of the surface of which is covered with a dielectric layer; and forming a solid electrolyte layer covering at least a portion of the dielectric layer, wherein the solid electrolyte layer contains a conductive polymer containing elemental sulfur, and the conductive polymer containing elemental sulfur fills at least a portion of the voids in the porous portion, and wherein the ratio (S5 / S1) of the count number S5 of the elemental sulfur detected by an electron beam microanalyzer at a point 5 μm deep from the main surface of the porous portion to the count number S1 of the elemental sulfur detected by the electron beam microanalyzer at a point 1 μm deep from the main surface of the porous portion is 0.15 or more.

12. The method for manufacturing an electrolytic capacitor according to claim 11, wherein the step of forming a solid electrolyte layer comprises the steps of: preparing a liquid composition containing a liquid medium and a conductive polymer containing elemental sulfur dispersed in the liquid medium; and impregnating the porous portion of the anode body with the liquid composition.

13. The method for producing an electrolytic capacitor according to claim 12, wherein the viscosity of the liquid composition measured at 20° C. using a rotational B-type viscometer is 5 mPa·s or more and 30 mPa·s or less.

14. The method for producing an electrolytic capacitor according to claim 12 or 13, wherein the liquid composition comprises a self-doping conductive polymer and a non-self-doping conductive polymer.

15. A method for producing an electrolytic capacitor according to claim 14, wherein the content of the self-doping conductive polymer in the total of the self-doping conductive polymer and the non-self-doping conductive polymer is 15% by mass or more and 60% by mass or less.

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