Electrolytic capacitor and production method for electrolytic capacitor

Abstract

An electrolytic capacitor according to the present invention includes a laminate and a liquid component impregnated into the laminate. The laminate includes: a positive electrode foil that has a dielectric layer on the surface thereof; a negative electrode foil; a separator; a first conductive polymer layer that is retained on the separator; and a second conductive polymer layer that is formed on the dielectric layer. The first conductive polymer layer contains a first conductive polymer, a polyvinyl alcohol polymer, and a boric acid compound. The second conductive polymer layer contains a second conductive polymer. The boric acid compound is at least one boric acid compound selected from the group consisting of boric acid and borate compounds. The polyvinyl alcohol polymer in the first conductive polymer layer is at least partially crosslinked.

Description

Electrolytic capacitor and method for manufacturing the same

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

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

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

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

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

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

[0007] One aspect of the present disclosure relates to an electrolytic capacitor including a laminate and a liquid component impregnated in the laminate. The laminate includes an anode foil having a dielectric layer on its surface, a cathode foil, a separator, a first conductive polymer layer supported by the separator, and a second conductive polymer layer formed on the dielectric layer. The first conductive polymer layer contains a first conductive polymer, a polyvinyl alcohol-based polymer, and a boric acid-based compound. The second conductive polymer layer contains a second conductive polymer. The boric acid-based compound is at least one boric acid-based compound selected from the group consisting of boric acid and boric acid compounds. At least a portion of the polyvinyl alcohol-based polymer in the first conductive polymer layer is crosslinked.

[0008] Another aspect of the present disclosure relates to a method for manufacturing an electrolytic capacitor. The method includes a preparation step of preparing an anode foil having a dielectric layer on its surface, a first polymer layer formation step of forming a first conductive polymer layer containing a first conductive polymer and a polyvinyl alcohol-based polymer in voids of a separator, a second polymer layer formation step of forming a second conductive polymer layer on the dielectric layer, a laminate formation step of stacking the anode foil, cathode foil, and separator so that the separator is disposed between the anode foil and the cathode foil to form a laminate containing the first conductive polymer layer and the second conductive polymer layer, an impregnation step of impregnating the laminate with a liquid component containing at least one boric acid-based compound selected from the group consisting of boric acid and boric acid compounds, and a crosslinking step of heating the liquid-impregnated laminate to a temperature of 85°C or higher. In the crosslinking step, at least a portion of the polyvinyl alcohol-based polymer in the first conductive polymer layer is crosslinked by the at least one boric acid-based compound.

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

[0010] 1 is a side view schematically illustrating an example of an electrolytic capacitor according to an embodiment of the present disclosure, and FIG. 2 is an exploded perspective view schematically illustrating an example of a capacitor element according to an embodiment of the present disclosure.

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

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

[0013] There has been a long-standing demand for reducing the ESR of electrolytic capacitors. The present disclosure provides an electrolytic capacitor that includes a liquid component and a conductive polymer layer and that can reduce the ESR.

[0014] Hereinafter, embodiments of the present invention will be described using examples, but the present invention is not limited to the examples described below. In the following description, specific numerical values ​​and materials may be exemplified, but other numerical values ​​and other materials may be applied as long as the invention according to the present disclosure can be implemented. In this specification, the expression "numerical value A to numerical value B" includes numerical value A and numerical value B and can be read as "numerical value A or more and numerical value B or less." In the following description, when lower and upper limits of numerical values ​​related to specific physical properties or conditions are exemplified, any of the exemplified lower limits and any of the exemplified upper limits can be arbitrarily combined as long as the lower limit is not equal to or greater than the upper limit.

[0015] (Method for Manufacturing Electrolytic Capacitor) The manufacturing method according to this embodiment may be referred to as "manufacturing method (M)" below. The manufacturing method (M) includes, in this order, a preparation step, a polymer layer forming step (a first polymer layer forming step, a second polymer layer forming step), a laminate forming step, an impregnation step, and a crosslinking step. The first polymer layer forming step and the second polymer layer forming step may be performed in any order, and either step may be performed first. These steps will be described later.

[0016] As described below, in manufacturing method (M), the polyvinyl alcohol-based polymer contained in the conductive polymer layer is crosslinked with a boric acid-based compound. This improves adhesion between the anode foil and the separator and between the cathode foil and the separator, thereby reducing the ESR of the electrolytic capacitor. Furthermore, the ability to retain the electrolyte in the conductive polymer layer is improved, improving the repairability of the dielectric layer and increasing the withstand voltage of the electrolytic capacitor. Furthermore, during long-term use, loss of the electrolyte due to volatilization can be suppressed, thereby extending the life of the electrolytic capacitor.

[0017] (Preparation Step) The preparation step is a step of preparing an anode foil having a dielectric layer on its surface. The anode foil having a dielectric layer on its surface may be a commercially available product, or may be formed by forming a dielectric layer on the surface of a metal foil (anode foil). The dielectric layer may be formed by a known method. For example, the dielectric layer may be formed by oxidizing the surface of the metal foil (anode foil).

[0018] (First Polymer Layer Forming Step) The first polymer layer forming step is a step of forming a first conductive polymer layer containing a first conductive polymer and a polyvinyl alcohol-based polymer in the voids of the separator. The first polymer layer forming step may include a first coating liquid applying step of applying a first coating liquid containing the first conductive polymer, the polyvinyl alcohol-based polymer, and a first liquid medium to the voids of the separator, and 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.

[0019] Polyvinyl alcohol polymers are -CH ２ It is a polymer containing CH(OH)- (hereinafter sometimes referred to as "vinyl alcohol unit") as a structural unit. The proportion of vinyl alcohol units in all structural units may be 40 mol% or more, 60 mol% or more, or 80 mol% or more. Examples of structural units other than vinyl alcohol units include vinyl acetate units. The total proportion of vinyl alcohol units and vinyl acetate units in all structural units may be 60 mol% or more, or 80 mol% or more.

[0020] Examples of polyvinyl alcohol-based polymers include polyvinyl alcohol and polyvinyl alcohol derivatives. The polyvinyl alcohol-based polymer may be a polymer obtained by saponifying a vinyl acetate polymer. Alternatively, the polyvinyl alcohol-based polymer may be a polymer obtained by saponifying a copolymer of vinyl acetate and another monomer.

[0021] The weight average molecular weight of the polyvinyl alcohol polymer may be in the range of 500 to 3500 (for example, in the range of 1000 to 2000).

[0022] The concentration of the polyvinyl alcohol-based polymer in the first coating liquid may be in the range of 0.01% by mass to 3.0% by mass (e.g., 0.05% by mass to 0.5% by mass). In the first coating liquid, the ratio Wp / Wc of the mass of the polyvinyl alcohol-based polymer Wp to the mass of the first conductive polymer Wc may be 0.01 or more, and may be in the range of 0.01 to 3.0 (e.g., 0.05 to 0.5). That is, in the first conductive polymer layer, the ratio (Wp / Wc) of the mass of the polyvinyl alcohol-based polymer Wp to the mass of the first conductive polymer Wc may be 0.01 or more, and may be in the range of 0.01 to 3.0 (e.g., 0.05 to 0.5).

[0023] (Second Polymer Layer Forming Step) The second polymer layer forming step is a step of forming a second conductive polymer layer on the surface of the dielectric layer. The second polymer layer forming step may include a second coating liquid applying step of applying a second coating liquid containing a second conductive polymer and a second liquid medium to the surface of the dielectric layer (the dielectric layer on the surface of the anode foil), and a second liquid medium removing step of removing at least a portion of the second liquid medium from the second coating liquid to form the second conductive polymer layer on the surface of the dielectric layer.

[0024] The second coating liquid may or may not contain a polyvinyl alcohol-based polymer. The first conductive polymer and the second conductive polymer may be the same or different. The first liquid medium and the second liquid medium may be the same or different. The first coating liquid and the second coating liquid may be the same or different.

[0025] The conductive polymers (first conductive polymer, second conductive polymer) may be dispersed in the coating liquid (first coating liquid, second coating liquid) in the form of particles. Examples of conductive polymers will be described later.

[0026] In the first coating liquid, the ratio of the mass Wp of the polyvinyl alcohol-based polymer to the mass Wc of the first conductive polymer (Wp / Wc) may be 0.01 or more, 0.05 or more, or 0.1 or more, or may be 3.0 or less, or 0.5 or less. By setting the ratio Wp / Wc to 0.01 or more, it is possible to ensure a sufficient amount of the polyvinyl alcohol-based polymer crosslinked by reaction with the boric acid-based compound while maintaining the stability of the coating liquid.

[0027] The liquid medium (first liquid medium, second liquid medium) is not particularly limited, and any liquid medium that can be used to form a polymer layer can be used. Examples of the liquid medium include water, organic solvents (e.g., alcohols), and mixtures thereof.

[0028] The liquid medium may contain water and an organic compound that does not boil at 100°C under 1 atmosphere (101,325 Pa). Hereinafter, this organic compound may be referred to as "organic compound (C)." The organic compound (C) may be one type of compound or may be composed of multiple types of compounds.

[0029] The method for applying the coating liquids (first coating liquid, second coating liquid) is not limited and may be a known method. For example, a coater may be used, the coating liquid may be sprayed, or the substrate may be immersed in the coating liquid. Examples of methods using a coater include gravure coating and die coating. In one example of gravure coating, the coating liquid is first applied to a transfer member (such as a gravure roll), and then excess coating liquid is removed from the transfer member. Next, the coating liquid applied to the transfer member is transferred to a predetermined member (anode foil, cathode foil, or separator), thereby allowing a layer of coating liquid with a uniform thickness to be applied to the member. The viscosity of the coating liquid may be, for example, 10 mPa·s or more (e.g., 100 mPa·s or more) and 200 mPa·s or less. In this case, the coating liquid can be easily applied to the anode foil, cathode foil, and separator, and easily impregnated into the separator. The viscosity of the coating liquid is measured at room temperature (20° C.) using a vibration viscometer (for example, VM-100A manufactured by Sekonic Corporation).

[0030] The method for removing at least a portion of the liquid medium from the coating liquid is not particularly limited, and can be performed by heating, etc. When the coating liquid contains an organic compound (C), heating may be performed so that the organic compound (C) remains in the polymer layer. For example, when the coating liquid contains the organic compound (C) and water (liquid medium), heating the coating liquid at a temperature at which the organic compound (C) does not boil or decompose and at a temperature of 100°C or higher can remove water from the coating liquid while allowing the organic compound (C) to remain in the polymer layer. The heating temperature may be 100°C or higher, 120°C or higher, or 140°C or higher, and may be 200°C or lower, or 160°C or lower. The heating temperature may be in the range of 100°C to 200°C. The heating time is not particularly limited, as long as it is a time that allows appropriate removal of a portion of the liquid medium. An example heating time is in the range of 5 to 60 minutes.

[0031] By leaving the organic compound (C) in the conductive polymer layer (first conductive polymer layer, second conductive polymer layer), it is possible to reduce the shrinkage of the conductive polymer layer when the liquid medium is removed from the coating liquid. As a result, in the subsequent impregnation step, a liquid component (e.g., an electrolyte solution) can easily penetrate into the conductive polymer layer. As a result, the liquid component's function of forming a dielectric layer (oxide film) can be more easily exerted, and leakage current can be reduced.

[0032] In a preferred example of production method (M), the water content in the coating liquid is 40 mass % or more (e.g., 50 mass % or more), and the liquid medium of the applied coating liquid is removed so that the mass of the organic compound (C) in the conductive polymer layer is greater than the mass of water in the conductive polymer layer. When the water content in the coating liquid is high, the conductive polymer layer is more likely to be impregnated with an electrolytic solution after formation.

[0033] (Laminate Forming Step) The laminate forming step is a step of forming a laminate including a first conductive polymer layer and a second conductive polymer layer by stacking an anode foil, a cathode foil, and a separator such that the separator is disposed between the anode foil and the cathode foil.

[0034] The method for forming the laminate is not particularly limited, and the laminate may be formed by a known method. The laminate may be a wound body. In this case, in the laminate formation step, the wound body may be formed by winding an anode foil, a cathode foil, and a separator such that the separator is disposed between the anode foil and the cathode foil. In the wound body, the anode foil, the cathode foil, and the separator are stacked in the radial direction of the wound body.

[0035] The stack may be formed by stacking flat anode foils, flat cathode foils, and flat separators in one direction. For example, a stack may be formed by stacking a plurality of anode foils, a plurality of cathode foils, and a plurality of separators in one direction. In a typical example of such a stack, the anode foils and the cathode foils are alternately arranged, and the separators are arranged between the anode foils and the cathode foils.

[0036] (Impregnation Step) The impregnation step is a step of impregnating the laminate with a liquid component containing at least one boric acid compound selected from the group consisting of boric acid and boric acid compounds. Hereinafter, this liquid component may be referred to as the "liquid component (LC)." The method for impregnating the laminate with the liquid component (LC) is not limited. For example, the laminate may be impregnated with the liquid component (LC) by immersing at least a portion of the laminate in the liquid component (LC). The liquid component (LC) may be an electrolyte solution.

[0037] Examples of boric acid compounds include boric acid and borate salts. Examples of borate salts include ammonium salts of boric acid (such as ammonium borate), sodium salts of boric acid (such as sodium tetraborate), and potassium salts of boric acid. The boric acid compound may be at least one selected from the group consisting of boric acid, ammonium salts of boric acid, sodium salts of boric acid, and potassium salts of boric acid.

[0038] The concentration of the boric acid compound in the liquid component (LC) may be in the range of 0.5% by mass to 5.0% by mass (for example, in the range of 1.5% by mass to 3.5% by mass).

[0039] The liquid component (LC) may further 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. The inclusion of these compounds in the liquid component (LC) can increase the withstand voltage of the capacitor. Furthermore, loss of the electrolyte due to volatilization during long-term use can be suppressed, thereby extending the life of the electrolytic capacitor.

[0040] (Crosslinking Step) The crosslinking step is a step of heating the laminate impregnated with the liquid component (LC) to a temperature of 85°C or higher. In the crosslinking step, at least a portion of the polyvinyl alcohol-based polymer in the first conductive polymer layer is crosslinked by the at least one boric acid-based compound. That is, the crosslinking step is a step of crosslinking the polyvinyl alcohol-based polymer in the first conductive polymer layer by the boric acid-based compound by heating the laminate impregnated with the liquid component (LC) to a temperature of 85°C or higher. When the second conductive polymer layer contains a polyvinyl alcohol-based polymer, the polyvinyl alcohol-based polymer in the second conductive polymer layer is also crosslinked by the boric acid-based compound. By crosslinking the polyvinyl alcohol-based polymer in the conductive polymer layer, the above-mentioned effects can be obtained.

[0041] The heating temperature of the laminate in the crosslinking step is 85° C. or higher, and may be 100° C. or higher, or 105° C. or higher. The heating temperature may be 180° C. or lower, 160° C. or lower, or 135° C. or lower. The heating time of the laminate in the crosslinking step varies depending on the heating temperature, but may be in the range of 30 to 180 minutes (for example, in the range of 60 to 90 minutes).

[0042] Heating the laminate in the crosslinking process can promote reoxidation of the anode foil surface. That is, it is possible to oxidize areas of the anode foil surface where the oxide film is insufficient. As a result, leakage current and the like can be reduced. In addition, in the crosslinking process, the anode foil may be re-oxidized by applying a voltage between the anode foil and the cathode foil. Alternatively, the anode foil may be re-oxidized separately from the crosslinking process.

[0043] In this manner, a capacitor element is obtained. Thereafter, other processes may be performed as necessary. For example, a process of encapsulating the capacitor element impregnated with the liquid component (LC) in an exterior body may be performed. A crosslinking process may be performed after the process of encapsulating the capacitor element impregnated with the liquid component (LC) in an exterior body.

[0044] The manufacturing method (M) may include a liquid application step and a removal step, in this order, after the laminate formation step and before the impregnation step. The liquid application step is a step of impregnating the laminate with a liquid (hereinafter sometimes referred to as "liquid (L)"). The removal step is a step of removing at least a portion of the liquid (L) impregnated into the laminate. The liquid (L) may be a liquid containing water as a main component and an organic compound (C) that does not boil at 100°C under 1 atmosphere. In this case, the removal step may be a step of removing a portion of the liquid (L) impregnated into the laminate so that the mass of the organic compound (C) in the laminate is greater than the mass of water in the laminate. The liquid (L) may be a liquid containing an organic solvent.

[0045] The liquid (L) used in the liquid application step may be a liquid obtained by removing the conductive polymer component from the second coating liquid used in the second polymer layer formation step. The impregnation with the liquid in the liquid application step may be performed by the method exemplified for the coating liquid application step in the polymer layer formation step. The removal of the liquid in the removal step may be performed by the method exemplified for the liquid medium removal step in the polymer layer formation step. By performing the liquid application step and the removal step, the adhesion between the first conductive polymer layer and the second conductive polymer layer, and the adhesion between the first conductive polymer layer and the cathode foil can be improved. Note that a conductive polymer layer containing a polyvinyl alcohol-based polymer crosslinked in the crosslinking step has sufficient adhesiveness, and therefore the adhesion between the first conductive polymer layer and the second conductive polymer layer, and the adhesion between the first conductive polymer layer and the cathode foil can be improved. Therefore, the liquid application step is not essential.

[0046] In the electrolytic capacitor produced by production method (M), the cathode foil may have an inorganic layer on the surface thereof, and the conductive polymer layer may be in close contact with the inorganic layer.

[0047] When the cathode foil is made solely of a metal foil (e.g., aluminum foil), an oxide layer forms on the surface of the metal foil, generating capacitance in the cathode foil as well. As a result, the combined capacitance of the anode foil and the cathode foil may result in a problem of a decrease in the capacitance of the entire capacitor. Covering the surface of the metal foil with an inorganic layer or the like can prevent this problem. In other words, forming an inorganic layer allows only the capacitance of the anode foil to be extracted. On the other hand, poor adhesion between the conductive polymer layer and the inorganic layer increases the ESR. By performing the liquid application process, it is possible to increase the adhesion between the first conductive polymer layer and the inorganic layer.

[0048] Because inorganic layers tend to repel water, conventional methods for forming a conductive polymer layer by impregnating a laminate (capacitor element) with an aqueous dispersion of a conductive polymer make it difficult for the conductive polymer to penetrate between the inorganic layer of the cathode foil and the anode foil in the laminate. This prevents the conductive polymer layer from being uniformly formed on the separator disposed between the cathode foil and the anode foil, resulting in an increase in ESR. In manufacturing method (M), a laminate (capacitor element) is formed using a separator on which a first conductive polymer layer has been formed in advance. This prevents the first conductive polymer from being unevenly distributed within the separator.

[0049] The surface density of the conductive polymer layers (first conductive polymer layer, second conductive polymer layer) is 0.05 mg / cm ２ Above, 0.1mg / cm ２ or more, or 0.3 mg / cm ２ or more, and may be 1.0 mg / cm ２ or less than 0.5 mg / cm ２ For example, the surface density of the conductive polymer layer may be 0.05 mg / cm or less. ２ 1.0 mg / cm or more ２or less. This configuration allows for an electrolytic capacitor with particularly low ESR to be obtained. The areal density refers to the mass per unit area. When second conductive polymer layers are formed on both sides of the anode foil, the areal density of the second conductive polymer layer refers to the areal density of one second conductive polymer layer formed on one side of the anode foil. The areal density of the conductive polymer layer can be controlled by the concentration of the conductive polymer in the coating liquid or the amount of the coating liquid applied.

[0050] The areal density of the first conductive polymer layer can be determined by the following method. First, five samples are prepared by cutting out a separator having a predetermined area before the first conductive polymer layer is formed, and the masses of the five samples are measured. Five samples are also prepared by cutting out a separator having the first conductive polymer layer formed thereon, and the masses of the five samples are measured. The areal density of the first conductive polymer layer is determined by using the predetermined area and the difference between the total mass of the five samples after the first conductive polymer layer is formed and the total mass of the five samples before the first conductive polymer layer is formed. The areal density of the second conductive polymer layer can also be determined by a similar method.

[0051] (Electrolytic Capacitor) The electrolytic capacitor according to this embodiment may be referred to as the "electrolytic capacitor (E)" below. The electrolytic capacitor (E) may be manufactured by the manufacturing method (M) described above. The matters described for the manufacturing method (M) may be applied to the electrolytic capacitor (E), and therefore, redundant explanations may be omitted. The matters described for the electrolytic capacitor (E) may also be applied to the manufacturing method (M).

[0052] The electrolytic capacitor (E) includes a laminate and a liquid component impregnated in the laminate. The laminate includes an anode foil having a dielectric layer on its surface, a cathode foil, a separator, a first conductive polymer layer supported by the separator, and a second conductive polymer layer formed on the dielectric layer. The first conductive polymer layer includes a first conductive polymer, a polyvinyl alcohol-based polymer, and a boric acid-based compound. The second conductive polymer layer includes a second conductive polymer. The boric acid-based compound is at least one boric acid-based compound selected from the group consisting of boric acid and boric acid compounds. At least a portion of the polyvinyl alcohol-based polymer in the first conductive polymer layer is crosslinked.

[0053] The electrolytic capacitor (E) can provide the effects described in the manufacturing method (M). For example, the configuration of the electrolytic capacitor (E) can reduce the ESR.

[0054] In the first conductive polymer layer of the electrolytic capacitor (E), the ratio (Wp / Wc) of the mass Wp of the polyvinyl alcohol-based polymer to the mass Wc of the first conductive polymer may be within the above-mentioned range, for example, the ratio (Wp / Wc) may be 0.2 or more.

[0055] In the electrolytic capacitor (E), the cathode foil may have an inorganic layer on its surface. In this case, it is preferable that the first conductive polymer layer is in close contact with the inorganic layer.

[0056] The liquid component (LC) of the electrolytic capacitor (E) may further contain 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.

[0057] As described above, the laminate may be a wound body or a laminate other than a wound body.

[0058] Examples of materials and components used in the manufacturing method (M) and the electrolytic capacitor (E) are described below, but the materials and components used in the manufacturing method (M) and the electrolytic capacitor (E) are not limited to the examples described below.

[0059] In this specification, the term "conductive polymer component" may be used. When a conductive polymer is not doped with a dopant, the conductive polymer component consists of the conductive polymer. When a conductive polymer is doped with a dopant, the conductive polymer component consists of the conductive polymer and the dopant.

[0060] (Coating Liquid (First Coating Liquid, Second Coating Liquid)) The coating liquids (first coating liquid, second coating liquid) used in the polymer layer forming step may contain a conductive polymer and water. The conductive polymer (conductive polymer component) may be contained in the coating liquid in the form of particles. The coating liquid may be an aqueous dispersion of the conductive polymer (conductive polymer component).

[0061] The coating liquid may contain other components (for example, an organic compound (C)). The organic compound (C) may contain at least one selected from the group consisting of polyhydric alcohols, sulfolane, γ-butyrolactone, and boric acid esters, or may consist of at least one such compound. The organic compound (C) may contain at least one selected from the group consisting of glycols, glycerins, sugar alcohols, sulfolane, γ-butyrolactone, and boric acid esters, or may consist of at least one such compound.

[0062] Examples of polyhydric alcohols include glycols, glycerins, and sugar alcohols. Examples of glycols include ethylene glycol, diethylene glycol, triethylene glycol, polyalkylene glycol (e.g., polyethylene glycol), polyoxyethylene polyoxypropylene glycol (ethylene oxide-propylene oxide copolymer), etc. Examples of glycerins include glycerin and polyglycerin. Examples of sugar alcohols include mannitol, xylitol, sorbitol, erythritol, and pentaerythritol.

[0063] Examples of conductive polymers include polypyrrole, polythiophene, polyfuran, polyaniline, polyacetylene, and derivatives thereof. These derivatives include polymers with polypyrrole, polythiophene, polyfuran, polyaniline, and polyacetylene as their basic skeletons. For example, polythiophene derivatives include poly(3,4-ethylenedioxythiophene). These conductive polymers may be used alone or in combination. Furthermore, the conductive polymer may be a copolymer of two or more monomers. The weight-average molecular weight of the conductive polymer is not particularly limited and may be in the range of 1,000 to 100,000, for example. One preferred example of a conductive polymer is poly(3,4-ethylenedioxythiophene) (PEDOT).

[0064] The conductive polymer may be doped with a dopant. From the viewpoint of suppressing dedoping from the conductive polymer, it is preferable to use a polymer dopant as the dopant. Examples of polymer dopants include polyvinyl sulfonic acid, polystyrene sulfonic acid, polyallylsulfonic acid, polyacrylic sulfonic acid, polymethacrylic sulfonic acid, poly(2-acrylamido-2-methylpropanesulfonic acid), polyisoprene sulfonic acid, polyacrylic acid, and the like. These may be used alone or in combination of two or more. At least a portion of these may be added in the form of a salt. A preferred example of the dopant is polystyrene sulfonic acid (PSS).

[0065] The dopant may be polystyrene sulfonic acid, and the conductive polymer may be poly(3,4-ethylenedioxythiophene). That is, the conductive polymer component may be poly(3,4-ethylenedioxythiophene) doped with polystyrene sulfonic acid.

[0066] When a conductive polymer doped with a dopant is used, the pH of the coating liquid is preferably less than 7.0, and may be 6.0 or less or 5.0 or less, in order to suppress dedoping of the dopant. The pH of the coating liquid may be 1.0 or more, or 2.0 or more.

[0067] The water content in the coating liquid may be 40% by mass or more, 50% by mass or more, 80% by mass or more, 90% by mass or more, or 95% by mass or more, and may be 98% by mass or less, 95% by mass or less, 90% by mass or less, or 80% by mass or less.

[0068] The content of the organic compound (C) in the coating liquid may be 1.0% by mass or more, 3.0% by mass or more, 5.0% by mass or more, or 10% by mass or more. It may be 30% by mass or less, 20% by mass or less, 15% by mass or less, or 10% by mass or less. The content of the conductive polymer component in the coating liquid may be 0.5% by mass or more or 1.0% by mass or more, and may be 4.0% by mass or less, 3.0% by mass or less, or 2.0% by mass or less. The content may be in the range of 0.5 to 4.0% by mass or 1.0 to 4.0% by mass. Within any of these ranges, the upper limit may be 3.0% by mass or 2.0% by mass. In terms of excellent physical properties and stability over time of the coating liquid, and a good balance between the ESR of the electrolytic capacitor and cost, the content is preferably in the range of 1.0 to 3.0%. When the coating liquid contains a dopant, the mass of the dopant is included in the mass of the conductive polymer component.

[0069] There are no particular limitations on the mass of the dopant contained in the coating liquid, and it may be in the range of 0.1 to 5 times (for example, in the range of 0.5 to 3 times) the mass of the conductive polymer contained in the coating liquid.

[0070] There are no particular limitations on the mass of the dopant contained in the coating liquid, and it may be in the range of 0.1 to 5 times (for example, in the range of 0.5 to 3 times) the mass of the conductive polymer contained in the coating liquid.

[0071] In the coating liquid, the ratio of water content:organic compound (C) content:conductive polymer component content may be 40 to 98:1.0 to 59.5:0.5 to 4.0, or the ratio of water content:organic compound (C) content:conductive polymer component content may be 69.5 to 98:1.0 to 30:0.5 to 4.0.

[0072] (Liquid Component (LC)) Examples of the liquid component (LC) used in the impregnation step include a non-aqueous solvent and an electrolytic solution. The electrolytic solution may be an electrolytic solution containing a non-aqueous solvent and a solute dissolved in the non-aqueous solvent. In this specification, the liquid component (LC) may be a component that is liquid at room temperature (25°C) or a component that is liquid at the temperature at which the electrolytic capacitor is used.

[0073] The non-aqueous solvent used in the liquid component (LC) may be an organic solvent, an ionic liquid, or a protic solvent. Examples of the non-aqueous solvent include polyhydric alcohols such as ethylene glycol and propylene glycol, cyclic sulfones such as sulfolane (SL), lactones such as γ-butyrolactone (γBL), amides such as N-methylacetamide, N,N-dimethylformamide, and N-methyl-2-pyrrolidone, esters such as methyl acetate, carbonate compounds such as propylene carbonate, ethers such as 1,4-dioxane, ketones such as methyl ethyl ketone, and formaldehyde.

[0074] Furthermore, a polymer solvent may be used as the non-aqueous solvent. Examples of polymer solvents include polyalkylene glycol, polyalkylene glycol derivatives, and compounds in which at least one hydroxyl group in a polyhydric alcohol has been substituted with polyalkylene glycol (including derivatives). Specific examples of polymer solvents include polyethylene glycol (PEG), polyethylene glycol glyceryl ether, polyethylene glycol diglyceryl ether, polyethylene glycol sorbitol ether, polypropylene glycol, polypropylene glycol glyceryl ether, polypropylene glycol diglyceryl ether, polypropylene glycol sorbitol ether, and polybutylene glycol. Further examples of polymer solvents include ethylene glycol-propylene glycol copolymers, ethylene glycol-butylene glycol copolymers, and propylene glycol-butylene glycol copolymers. One type of non-aqueous solvent may be used alone, or two or more types may be used in combination.

[0075] The liquid component (LC) may include a non-aqueous solvent and a base component (base) dissolved in the non-aqueous solvent. Alternatively, the liquid component (LC) may include a non-aqueous solvent and a base component and / or an acid component (acid) dissolved in the non-aqueous solvent.

[0076] The acid component can be a polycarboxylic acid or a monocarboxylic acid. Examples of the polycarboxylic acid include aliphatic polycarboxylic acids (saturated polycarboxylic acids such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, 1,6-decanedicarboxylic acid, and 5,6-decanedicarboxylic acid; unsaturated polycarboxylic acids such as maleic acid, fumaric acid, and itaconic acid), aromatic polycarboxylic acids (phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, and pyromellitic acid), and alicyclic polycarboxylic acids (cyclohexane-1,2-dicarboxylic acid and cyclohexene-1,2-dicarboxylic acid).

[0077] Examples of the monocarboxylic acid include aliphatic monocarboxylic acids (having 1 to 30 carbon atoms) ([saturated monocarboxylic acids such as formic acid, acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, lauric acid, myristic acid, stearic acid, and behenic acid]; [unsaturated monocarboxylic acids such as acrylic acid, methacrylic acid, and oleic acid]), aromatic monocarboxylic acids (such as benzoic acid, cinnamic acid, and naphthoic acid), and oxycarboxylic acids (such as salicylic acid, mandelic acid, and resorcylic acid).

[0078] Among these, maleic acid, phthalic acid, benzoic acid, pyromellitic acid, and resorcylic acid are thermally stable and are therefore preferably used.

[0079] An inorganic acid may be used as the acid component. Typical examples of inorganic acids include phosphoric acid, phosphorous acid, hypophosphorous acid, alkyl phosphate esters, boric acid, fluoroboric acid, tetrafluoroboric acid, hexafluorophosphoric acid, benzenesulfonic acid, and naphthalenesulfonic acid. Alternatively, a composite compound of an organic acid and an inorganic acid may be used as the acid component. Examples of such composite compounds include borodiglycolic acid, borodisalic acid, and borodisalicylic acid.

[0080] The base component may be a compound having an alkyl-substituted amidine group, such as an imidazole compound, a benzimidazole compound, or an alicyclic amidine compound (a pyrimidine compound, an imidazoline compound). Specifically, 1,8-diazabicyclo[5,4,0]undecene-7, 1,5-diazabicyclo[4,3,0]nonene-5, 1,2-dimethylimidazolinium, 1,2,4-trimethylimidazoline, 1-methyl-2-ethyl-imidazoline, 1,4-dimethyl-2-ethylimidazoline, 1-methyl-2-heptylimidazoline, 1-methyl-2-(3'heptyl)imidazoline, 1-methyl-2-dodecylimidazoline, 1,2-dimethyl-1,4,5,6-tetrahydropyrimidine, 1-methylimidazole, or 1-methylbenzimidazole is preferred. By using these, a capacitor with excellent impedance performance can be obtained.

[0081] The base component may be a quaternary salt of a compound having an alkyl-substituted amidine group. Examples of such base components include imidazole compounds, benzimidazole compounds, and alicyclic amidine compounds (pyrimidine compounds, imidazoline compounds) quaternized with an alkyl group or arylalkyl group having 1 to 11 carbon atoms. Specifically, 1-methyl-1,8-diazabicyclo[5,4,0]undecene-7, 1-methyl-1,5-diazabicyclo[4,3,0]nonene-5, 1,2,3-trimethylimidazolinium, 1,2,3,4-tetramethylimidazolinium, 1,2-dimethyl-3-ethyl-imidazolinium, 1,3,4-trimethyl-2-ethylimidazolinium, 1,3-dimethyl-2-heptylimidazolinium, 1,3-dimethyl-2-(3'heptyl)imidazolinium, 1,3-dimethyl-2-dodecylimidazolinium, 1,2,3-trimethyl-1,4,5,6-tetrahydropyrimidium, 1,3-dimethylimidazolium, 1-methyl-3-ethylimidazolium, 1,3-dimethylbenzimidazolium is preferred. By using these, a capacitor with excellent impedance performance can be obtained.

[0082] Tertiary amines may also be used as the base component. Examples of tertiary amines include trialkylamines (trimethylamine, dimethylethylamine, methyldiethylamine, triethylamine, dimethyl-n-propylamine, dimethylisopropylamine, methylethyl-n-propylamine, methylethylisopropylamine, diethyl-n-propylamine, diethylisopropylamine, tri-n-propylamine, triisopropylamine, tri-n-butylamine, tri-tert-butylamine, etc.), and phenyl group-containing amines (dimethylphenylamine, methylethylphenylamine, diethylphenylamine, etc.). Among these, trialkylamines are preferred in terms of increasing conductivity, and it is more preferable to use at least one selected from the group consisting of trimethylamine, dimethylethylamine, methyldiethylamine, and triethylamine. Furthermore, secondary amines such as dialkylamines, primary amines such as monoalkylamines, and ammonia may also be used as the base component.

[0083] 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.

[0084] To prevent the dopant from being dedoped, the pH of the liquid component (LC) may be less than 7.0 or 5.0 or less, or may be 1.0 or more, or 2.0 or more. The pH may be 1.0 or more and less than 7.0 (for example, in the range of 2.0 to 5.0).

[0085] The liquid component (LC) preferably contains a protic solvent. By using a protic solvent, it is possible to improve the adhesion of the conductive polymer layer. The liquid component (LC) may contain, in addition to the protic solvent, a solvent other than the protic solvent.

[0086] The protic solvent may include at least one selected from the group consisting of glycols, glycerin, polyglycerin, and sugar alcohols, and may be composed of only one type of compound or may include multiple types of compounds.

[0087] The organic compound (C) and the liquid component (LC) may contain the same compound, for example, they may contain the same polyhydric alcohol, the same glycol (e.g., ethylene glycol), or the same sugar alcohol.

[0088] (Liquid (L)) The liquid (L) may be a liquid containing the organic compound (C) and water. In this case, it is preferable to impregnate the laminate with the liquid (L) and then remove water from the laminate under conditions in which the organic compound (C) remains in the laminate. The organic compound (C) may be at least one selected from the group consisting of mannitol, mannitol derivatives, xylitol, and xylitol derivatives.

[0089] The liquid (L) may contain at least one substance (hereinafter, sometimes referred to as "substance X") selected from the group consisting of sugar, sugar alcohol, epoxy resin, and polyvinyl alcohol. By containing substance X in the liquid (L), the adhesion between the conductive polymer layer and the cathode foil can be improved. The content of substance X in the liquid (L) may be in the range of 10% by mass to 70% by mass (for example, in the range of 30% by mass to 50% by mass).

[0090] The sugar alcohol may include at least one selected from the group consisting of mannitol, mannitol derivatives, xylitol, and xylitol derivatives, or may be at least one of these. Substance X may be at least one selected from the group consisting of mannitol, mannitol derivatives, xylitol, and xylitol derivatives. Mannitol, mannitol derivatives, xylitol, and xylitol derivatives have the effect of acting as an adhesive to bond the conductive polymer layer and the cathode foil. 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. 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.

[0091] The organic solvent contained in the liquid (L) may contain at least one selected from the group consisting of ethylene glycol, diethylene glycol, triethylene glycol, and polyethylene glycol, or may be the at least one selected from the group consisting of ethylene glycol, diethylene glycol, triethylene glycol, and polyethylene glycol. By containing such an organic solvent in the liquid (L), the electrical conductivity of the conductive polymer layer can be increased.

[0092] A preferred example of the liquid (L) is a liquid in which xylitol is contained in at least one organic solvent selected from the group consisting of triethylene glycol and polyethylene glycol.

[0093] (Anode Foil) Examples of the anode foil include metal foils containing at least one valve metal such as titanium, tantalum, aluminum, and niobium, and may be metal foils of valve metals (e.g., aluminum foil). The anode foil may contain the valve metal in the form of an alloy containing the valve metal or a compound containing the valve metal. The thickness of the anode foil may be 15 μm or more and 300 μm or less. The surface of the anode foil may be roughened by etching or the like.

[0094] A dielectric layer is formed on the surface of the anode foil. The dielectric layer may be formed by chemically treating the anode foil. In this case, the dielectric layer may contain an oxide of a valve metal (e.g., aluminum oxide). Note that the dielectric layer may be formed of any dielectric other than an oxide of a valve metal as long as it functions as a dielectric.

[0095] In an electrolytic capacitor, the end surface of the anode foil does not necessarily have to be provided with a conductive polymer layer, but it is preferable that the end surface of the anode foil has a dielectric layer formed thereon.

[0096] (Cathode foil) The cathode foil includes a metal foil (e.g., aluminum foil). The metal constituting the metal foil may be a valve metal or an alloy containing a valve metal. The surface of the metal foil may be roughened by etching or the like. The thickness of the cathode foil may be 15 μm or more and 300 μm or less. A conductive polymer layer may be formed on the surface of the cathode foil by the above-mentioned method.

[0097] As described above, the cathode foil may have an inorganic layer on its surface. A commercially available cathode foil having an inorganic layer on its surface may be used, or the inorganic layer may be formed by forming the inorganic layer on the surface of a metal foil (cathode foil). The inorganic layer may be formed by a known method. For example, the inorganic layer may be formed by a vacuum deposition method or the like. Alternatively, the inorganic layer may be formed by applying a paste containing one selected from the group consisting of carbon (particularly a conductive carbon material), titanium, and nickel onto the metal foil (cathode foil) and then drying the paste. The deposition amount of the inorganic layer is 50 mg / m. ２ ~300 mg / m ２ range (e.g., 70 mg / m ２ ~200 mg / m ２The inorganic layer may be a carbon layer having a carbon content of 50% by mass or more. Examples of carbon (particularly conductive carbon materials) contained in the inorganic layer include graphite, hard carbon, soft carbon, and carbon black. When the inorganic layer contains titanium, it may be a layer on which titanium is vapor-deposited, or a layer formed of titanium oxide particles. The inorganic layer may be a carbon layer. The carbon layer may be a layer containing carbon, and may have a carbon content of 50% by mass or more. In this specification, the term "inorganic layer" may be replaced with "carbon layer".

[0098] The cathode foil may include a metal foil, an inorganic layer, and a titanium-containing layer disposed between the inorganic layer and the metal foil. An example of a cathode foil has a laminated structure of inorganic layer / titanium-containing layer / metal foil (e.g., aluminum foil) / titanium-containing layer / inorganic layer. The titanium-containing layer may contain at least one selected from the group consisting of titanium and titanium compounds. Examples of titanium compounds include titanium nitride, titanium oxide, titanium aluminum alloy, and titanium carbonate. The titanium-containing layer may be formed by any known method without any particular limitation. For example, the titanium-containing layer may be formed by physical vapor deposition such as vacuum deposition or sputtering. The coating weight of the titanium-containing layer may be 200 mg / m. ２ ~500 mg / m ２ range (e.g., 250 mg / m ２ ~400 mg / m ２ The range may be within .

[0099] (Separator) A porous sheet can be used as the separator. Examples of porous sheets include woven fabric, nonwoven fabric, and microporous membrane. The thickness of the separator is not particularly limited and may be in the range of 10 to 300 μm. Examples of separator materials include cellulose, polyethylene terephthalate, polybutylene terephthalate, polyphenylene sulfide, vinylon, nylon, aromatic polyamide, polyimide, polyamideimide, polyetherimide, rayon, and glass.

[0100] (Exterior Body) The laminate and the liquid component (LC) are housed in an exterior body. The exterior body includes a case and / or a sealing resin. There is no limitation thereto, and known cases and sealing resins may be used. The sealing resin may include a thermosetting resin. Examples of thermosetting resins include epoxy resins, phenolic resins, silicone resins, melamine resins, urea resins, alkyd resins, polyurethanes, polyimides, unsaturated polyesters, etc. The sealing resin may include a filler, a curing agent, a polymerization initiator, and / or a catalyst, etc.

[0101] An example of the present disclosure will be specifically described below with reference to the drawings. The components described above can be applied to the components of the example described below. Furthermore, the components of the example described below can be modified based on the above description. Furthermore, the matters described below may be applied to the above-described embodiment. Furthermore, in the example described below, components that are not essential for the electrolytic capacitor of the present disclosure may be omitted.

[0102] Fig. 1 is a cross-sectional view schematically illustrating an example of an electrolytic capacitor 100 according to this embodiment. Fig. 2 is a schematic view showing a portion of a capacitor element 10 included in the electrolytic capacitor 100 in an exploded view.

[0103] Electrolytic capacitor 100 includes capacitor element 10, bottomed case 101 that houses capacitor element 10, sealing member 102 that closes the opening of bottomed case 101, seat plate 103 that covers sealing member 102, lead wires 104A and 104B that extend from sealing member 102 and pass through seat plate 103, and lead tabs 105A and 105B that connect the lead wires to electrodes of capacitor element 10. The vicinity of the open end of bottomed case 101 is drawn inward, and the open end is curled so as to be crimped to sealing member 102.

[0104] Capacitor element 10 is, for example, a wound body as shown in FIG. 1 . The wound body includes anode foil 11 connected to lead tab 105A, cathode foil 12 connected to lead tab 105B, and separator 13. Capacitor element 10 (wound body) includes a conductive polymer layer (not shown). The conductive polymer layer may include an organic compound (C). Electrolytic capacitor 100 includes a liquid component (LC) (e.g., an electrolyte solution) impregnated in capacitor element 10.

[0105] The anode foil 11 and the cathode foil 12 are wound with a separator 13 interposed therebetween. The outermost periphery of the wound body is fixed with a stop tape 14. Note that Fig. 2 shows a partially unfolded state of the wound body before the outermost periphery is fixed.

[0106] The electrolytic capacitor may have at least one capacitor element, or may have a plurality of capacitor elements, and the number of capacitor elements included in the electrolytic capacitor may be determined depending on the application.

[0107] (Additional Note) The above description discloses the following techniques.

[0108] (Technology 1) An electrolytic capacitor including a laminate and a liquid component impregnated in the laminate, wherein the laminate includes: an anode foil having a dielectric layer on a surface thereof; a cathode foil; a separator; a first conductive polymer layer held by the separator; and a second conductive polymer layer formed on the dielectric layer, wherein the first conductive polymer layer contains a first conductive polymer, a polyvinyl alcohol-based polymer, and a boric acid-based compound, the second conductive polymer layer contains a second conductive polymer, the boric acid-based compound is at least one boric acid-based compound selected from the group consisting of boric acid and boric acid compounds, and at least a portion of the polyvinyl alcohol-based polymer in the first conductive polymer layer is crosslinked.

[0109] (Technology 2) The electrolytic capacitor according to Technology 1, wherein in the first conductive polymer layer, a ratio (Wp / Wc) of a mass Wp of the polyvinyl alcohol-based polymer to a mass Wc of the first conductive polymer is 0.01 or more.

[0110] (Technology 3) The electrolytic capacitor according to Technology 1 or 2, wherein the cathode foil has an inorganic layer on a surface thereof, and the first conductive polymer layer is in close contact with the inorganic layer.

[0111] (Technology 4) The electrolytic capacitor according to any one of Technologies 1 to 3, wherein the liquid component further contains at least one selected from the group consisting of ethylene glycol, diethylene glycol, triethylene glycol, an ethylene glycol condensate having a molecular weight of 250 or less, glycerin, γ-butyrolactone, and sulfolane.

[0112] (Technology 5) The electrolytic capacitor according to any one of Technologies 1 to 4, wherein the laminate is a wound body.

[0113] a first polymer layer forming step of forming a first conductive polymer layer in voids of a separator, the first conductive polymer layer including a first conductive polymer and a polyvinyl alcohol-based polymer; a second polymer layer forming step of forming a second conductive polymer layer on the surface of the dielectric layer; a laminate forming step of forming a laminate including the first conductive polymer layer and the second conductive polymer layer by stacking the anode foil, cathode foil, and separator such that the separator is disposed between the anode foil and the cathode foil; an impregnation step of impregnating the laminate with a liquid component containing at least one boric acid-based compound selected from the group consisting of boric acid and boric acid compounds; and a crosslinking step of heating the laminate impregnated with the liquid component to a temperature of 85°C or higher, wherein in the crosslinking step, at least a portion of the polyvinyl alcohol-based polymer in the first conductive polymer layer is crosslinked by the at least one boric acid-based compound.

[0114] (Technology 7) The method for manufacturing an electrolytic capacitor according to Technology 6, wherein in the first conductive polymer layer, a ratio (Wp / Wc) of a mass Wp of the polyvinyl alcohol-based polymer to a mass Wc of the first conductive polymer is 0.01 or more.

[0115] (Technology 8) The method for manufacturing an electrolytic capacitor according to Technology 6 or 7, wherein the cathode foil has an inorganic layer on a surface thereof, and the first conductive polymer layer is in close contact with the inorganic layer.

[0116] (Technology 9) The method for producing an electrolytic capacitor according to any one of Techniques 6 to 8, wherein the liquid component further 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.

[0117] (Technology 10) The method for manufacturing an electrolytic capacitor according to any one of Technologies 6 to 9, wherein the laminate is a wound body.

[0118] The present disclosure will be described in more detail below based on examples, but the present disclosure is not limited to these examples. In these examples, a plurality of electrolytic capacitors were fabricated and evaluated by the following method.

[0119] (Capacitor A1) An electrolytic capacitor (capacitor A1) was produced by the following method.

[0120] (a) Preparation of Components Aluminum foil (thickness: 100 μm) was subjected to an etching treatment to roughen the surface of the aluminum foil. The roughened aluminum foil surface was subjected to a chemical conversion treatment to form a dielectric layer. In this way, an anode foil with a dielectric layer formed on both sides was obtained. Carbon layers were formed on both sides of aluminum foil (thickness: 50 μm) that would become a cathode foil. The carbon layers were formed by vacuum deposition.

[0121] A nonwoven fabric (50 μm thick) made of polyester fiber, aramid fiber, and cellulose was prepared as a separator.

[0122] (b) Formation of a Conductive Polymer Layer A dispersion (commercially available) of polystyrene sulfonic acid (PSS)-doped polyethylenedioxythiophene (PEDOT) particles dispersed in water was prepared. Polyvinyl alcohol and water were added to this dispersion to obtain a coating solution. The concentration of the conductive polymer component in the coating solution was 1.8% by mass, and the concentration of polyvinyl alcohol in the coating solution was 0.6% by mass.

[0123] Next, using a gravure coater, the coating liquid was applied to one side of the anode foil (surface of the dielectric layer). A drying process was then performed to form a second conductive polymer layer on one side of the anode foil (surface of the dielectric layer). The drying process was performed by heating the anode foil with the coating liquid applied thereto at 125°C for 5 minutes. Next, a second conductive polymer layer was formed on the other side of the anode foil (surface of the dielectric layer) in the same manner. A first conductive polymer layer was formed on the separator by applying the coating liquid to the separator and then performing a drying process.

[0124] (c) Formation of Wound Body (Laminate) The anode foil, cathode foil, and separator were each cut to a predetermined size. An anode lead tab and a cathode lead tab were connected to the anode foil and the cathode foil, respectively. Next, the anode foil and the cathode foil were wound with the separator interposed therebetween. At this time, the ends of the outer surface of the wound body were fixed with winding tape. An anode lead wire and a cathode lead wire were connected to the ends of each lead tab protruding from the wound body, respectively. The obtained wound body was again subjected to chemical conversion treatment, and a dielectric layer was formed on the end surface of the anode foil. In this way, a capacitor element was obtained.

[0125] (d) Impregnation with Liquid Component An electrolyte solution (liquid component) was prepared by dissolving o-phthalic acid and triethylamine (base component) in ethylene glycol (solvent) at a total concentration of 25% by mass, and then adding ammonium borate. The concentration of ammonium borate in the electrolyte solution was 2.5% by mass. The capacitor element was immersed in the electrolyte solution for 5 minutes in a reduced pressure atmosphere (40 kPa). This allowed the capacitor element (laminate) to be impregnated with the electrolyte.

[0126] (e) Capacitor Element Sealing and Crosslinking Process The capacitor element impregnated with the electrolyte was sealed to assemble an electrolytic capacitor as shown in FIG. 1 . The electrolytic capacitor including the capacitor element (laminate) was then heated at 105°C for 60 minutes while applying a voltage between the anode foil and the cathode foil. This process crosslinked the polyvinyl alcohol in the conductive polymer layer with ammonium borate. This process also reconstituted the anode foil. In this manner, an electrolytic capacitor (Capacitor A1) was produced.

[0127] (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 polyvinyl alcohol was not added to the coating liquid for forming the conductive polymer layer.

[0128] (Capacitor C2) An electrolytic capacitor (capacitor C2) was produced in the same manner and under the same conditions as those for producing capacitor A1, except that ammonium borate was not added to the electrolytic solution.

[0129] (Capacitor C3) An electrolytic capacitor (Capacitor C3) was produced in the same manner and under the same conditions as those for producing Capacitor A1, except that polyvinyl alcohol was not added to the coating liquid for forming the conductive polymer layer and ammonium borate was not added to the electrolytic solution.

[0130] (Evaluation) The equivalent series resistance (ESR) and withstand voltage of the produced electrolytic capacitors were measured. The evaluation results are shown in Table 1. A low ESR is preferable, and a high withstand voltage is preferable.

[0131]

[0132] Capacitor A1 is an electrolytic capacitor (E) according to the present disclosure manufactured by manufacturing method (M). Capacitors C1 to C3 are comparative examples. As shown in Table 1, capacitor A1 had a low ESR and a high withstand voltage.

[0133] The present disclosure can be used for electrolytic capacitors.

[0134] 10: Capacitor element 11: Anode foil 12: Cathode foil 13: Separator 100: Electrolytic capacitor

Claims

1. An electrolytic capacitor comprising a laminate and a liquid component impregnated into the laminate, The laminated body is Anode foil having a dielectric layer on its surface, Cathode foil and Separator and, The first conductive polymer layer held in the separator, The dielectric layer comprises a second conductive polymer layer formed on the dielectric layer, The first conductive polymer layer contains a first conductive polymer, a polyvinyl alcohol-based polymer, and a boric acid-based compound. The second conductive polymer layer contains the second conductive polymer, The boric acid compound is at least one boric acid compound selected from the group consisting of boric acid and boric acid compounds. An electrolytic capacitor in which at least a portion of the polyvinyl alcohol-based polymer in the first conductive polymer layer is crosslinked.

2. The electrolytic capacitor according to claim 1, wherein in the first conductive polymer layer, the ratio of the mass Wp of the polyvinyl alcohol-based polymer to the mass Wc of the first conductive polymer (Wp / Wc) is 0.01 or more.

3. The cathode foil has an inorganic layer on its surface, The electrolytic capacitor according to claim 1, wherein the first conductive polymer layer is in close contact with the inorganic layer.

4. The electrolytic capacitor according to claim 1, 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.

5. The electrolytic capacitor according to claim 1, wherein the laminate is a wound body.

6. A method for manufacturing an electrolytic capacitor, A preparation step for preparing an anode foil having a dielectric layer on its surface, A first polymer layer formation step involves forming a first conductive polymer layer containing a first conductive polymer and a polyvinyl alcohol-based polymer within the void of the separator, A second polymer layer formation step in which a second conductive polymer layer is formed on the surface of the dielectric layer, A laminate formation step of forming a laminate including a first conductive polymer layer and a second conductive polymer layer by laminating the anode foil, cathode foil and separator such that the separator is positioned between the anode foil and the cathode foil, An impregnation step in which the laminate is impregnated with a liquid component containing at least one boric acid-based compound selected from the group consisting of boric acid and boric acid compounds, The process includes a crosslinking step of heating the laminate impregnated with the liquid component to a temperature of 85°C or higher, A method for manufacturing an electrolytic capacitor, wherein in the crosslinking step, at least a portion of the polyvinyl alcohol-based polymer in the first conductive polymer layer is crosslinked with at least one boric acid-based compound.

7. The method for manufacturing an electrolytic capacitor according to claim 6, wherein in the first conductive polymer layer, the ratio of the mass Wp of the polyvinyl alcohol-based polymer to the mass Wc of the first conductive polymer (Wp / Wc) is 0.01 or more.

8. The cathode foil has an inorganic layer on its surface, The method for manufacturing an electrolytic capacitor according to claim 6, wherein the first conductive polymer layer is in close contact with the inorganic layer.

9. The method for manufacturing an electrolytic capacitor according to claim 6, wherein the liquid component further 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.

10. The method for manufacturing an electrolytic capacitor according to claim 6, wherein the laminate is a wound body.