Electrolytic capacitor and method for manufacturing electrolytic capacitor

Abstract

An electrolytic capacitor is provided with a capacitor element having an anode foil having a dielectric layer, a cathode foil, a separator interposed between the anode foil and the cathode foil, and a conductive polymer layer interposed between the anode foil and the cathode foil and in contact with the separator. The conductive polymer layer contains a conductive polymer, a dopant, and a sugar alcohol, and the sugar alcohol is at least one type selected from xylitol and xylitol derivatives. In the conductive polymer layer, the ratio (Ms / Mp) of the mass (Ms) of the sugar alcohol to the total mass (Mp) of the conductive polymer and the dopant is from 1 to 40 (inclusive).

Description

Technical Field

[0001] This disclosure relates to electrolytic capacitors and methods for manufacturing electrolytic capacitors. Background Technology

[0002] Patent Document 1 discloses an electrolytic capacitor comprising a capacitor element, the capacitor element comprising an anode foil having a dielectric layer on its surface, a cathode foil, a separator between the anode foil and the cathode foil, a hydroxyl-containing compound, and a conductive polymer, the separator comprising synthetic fibers and cellulose fibers, the conductive polymer and the hydroxyl-containing compound being attached to the surface and interior of the separator, the hydroxyl-containing compound being at least one compound selected from sugars and polyols (excluding polymers), and the hydroxyl-containing compound being present non-uniformly in the separator.

[0003] Patent document 2 proposes "a capacitor characterized by comprising: an anode composed of a porous body of valve metal, a dielectric layer formed by oxidizing the surface of the anode, and a solid electrolyte layer formed on the surface of the dielectric layer, wherein the solid electrolyte layer comprises: a cationic conductive polymer (a), a polymer anionic salt (b) or a polymer anionic salt (b) and anionic salt (c), a binder (d) selected from polyester, polyurethane, acrylic, epoxy, polyamide, polyacrylamide and silane coupling agent, and an oxidation inhibitory component (e) comprising sugar and / or sugar alcohol, wherein the solid electrolyte layer comprises 10 to 200 parts by mass of binder (d) and 50 or more parts by mass of oxidation inhibitory component (e) relative to the total amount of conductive polymer (a) and polymer anionic salt (b), or conductive polymer (a), polymer anionic salt (b) and anionic salt (c).

[0004] Patent document 3 proposes "an electrolytic capacitor, characterized in that a solid electrolyte layer is formed in a capacitor element formed by winding an anode electrode foil and a cathode electrode foil with a separator in between, using a dispersion of a conductive polymer compound containing particles of a conductive polymer, sorbitol and a polyol, the solid electrolyte layer containing 60 to 92 wt% of the above-mentioned sorbitol and polyol, and the voids in the capacitor element in which the solid electrolyte layer is formed are filled with an electrolyte containing 5 to 20 wt% or less of ethylene glycol in a solvent, wherein the polyol is selected from at least one of glycerol, mannitol and ethylene glycol."

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2022-117355

[0008] Patent Document 2: Japanese Patent Application Publication No. 2011-171675

[0009] Patent Document 3: Japanese Patent No. 7248056 Summary of the Invention

[0010] The first aspect of this disclosure relates to an electrolytic capacitor. The electrolytic capacitor includes a capacitor element comprising: an anode foil having a dielectric layer, a cathode foil, a separator between the anode foil and the cathode foil, and a conductive polymer layer between the anode foil and the cathode foil and in contact with the separator. The conductive polymer layer comprises a conductive polymer, a dopant, and a sugar alcohol, wherein the sugar alcohol is at least one selected from xylitol and xylitol derivatives. In the conductive polymer layer, the ratio (Ms / Mp) of the mass Ms of the sugar alcohol to the total mass Mp of the conductive polymer and the dopant is 1 or more and 40 or less.

[0011] The second aspect of this disclosure relates to a method for manufacturing an electrolytic capacitor. The method comprises, in sequence: step (a), preparing an anode foil, a cathode foil, and a separator having a dielectric layer; step (b), applying a coating solution containing a conductive polymer, a dopant, and a liquid medium to at least one surface selected from the surface of the dielectric layer and the surface of the cathode foil, and to the voids of the separator; step (c), forming a conductive polymer layer in the voids of the at least one surface and the separator by removing at least a portion of the liquid medium from the coating solution; step (d), forming a capacitor element containing the conductive polymer layer by disposing the separator between the anode foil and the cathode foil; and step (e), impregnating the capacitor element with a solution containing a sugar alcohol, thereby containing the sugar alcohol in the conductive polymer layer. The sugar alcohol is at least one selected from xylitol and xylitol derivatives. In the aforementioned conductive polymer layer, the ratio (Ms / Mp) of the mass Ms of the sugar alcohol to the total mass Mp of the conductive polymer and the dopant is 1 or more and 40 or less.

[0012] A third aspect of this disclosure relates to a method for manufacturing an electrolytic capacitor. The manufacturing method sequentially includes: step (a) preparing an anode foil, a cathode foil, and a separator having a dielectric layer; step (b) applying a coating liquid containing a conductive polymer, a dopant, a sugar alcohol, and a liquid medium to at least one surface selected from the surface of the dielectric layer and the surface of the cathode foil, and to the voids of the separator; step (c) forming a conductive polymer layer in the voids of the at least one surface and the separator by removing at least a portion of the liquid medium from the coating liquid; and step (d) forming a capacitor element comprising the conductive polymer layer by disposing the separator between the anode foil and the cathode foil. The sugar alcohol is at least one selected from xylitol and xylitol derivatives. In the conductive polymer layer, the ratio (Ms / Mp) of the mass Ms of the sugar alcohol to the total mass Mp of the conductive polymer and the dopant is 1 or more and 40 or less.

[0013] According to this disclosure, it is possible to obtain an electrolytic capacitor manufacturing process and an electrolytic capacitor with suppressed sugar alcohol precipitation and excellent characteristics. Attached Figure Description

[0014] Figure 1 This is a side view schematically showing an electrolytic capacitor according to an embodiment of the present disclosure.

[0015] Figure 2 This is an exploded perspective view schematically illustrating a capacitor element according to an embodiment of the present disclosure. Detailed Implementation

[0016] The following is a brief explanation of the problems in the existing technology.

[0017] Since sugar alcohols are solids, they are dissolved in solvents and used in solution form. While this also depends on the type of solvent, sugar alcohols tend to precipitate at room temperature, and this tendency increases with the amount of sugar alcohol used. If sugar alcohols precipitate during the manufacturing process of electrolytic capacitors, it is difficult to form a well-structured conductive polymer layer. Furthermore, if sugar alcohols precipitate within the completed electrolytic capacitor, the capacitor's characteristics may be degraded.

[0018] The following examples illustrate embodiments of this disclosure, but this disclosure is not limited to the examples described below. In the following description, specific numerical values ​​and materials are sometimes illustrated, but other numerical values ​​and materials can be applied as long as the invention of this disclosure can be implemented. In this specification, the phrase "numerical value A to numerical value B" includes both numerical value A and numerical value B, and can be replaced with "numerical value A or higher and numerical value B or lower." In the following description, when lower and upper limits of numerical values ​​related to specific physical properties, conditions, etc., are illustrated, any of the illustrated lower limits can be arbitrarily combined with any of the illustrated upper limits, as long as the lower limit is not higher than the upper limit.

[0019] [Electrolytic capacitors]

[0020] The electrolytic capacitor of the first aspect of this disclosure comprises at least a capacitor element. The capacitor element comprises an anode foil having a dielectric layer, a cathode foil, a separator, and a conductive polymer layer. The separator is located between the anode foil and the cathode foil. The conductive polymer layer is located between the anode foil and the cathode foil and is in contact with the separator. Preferably, the conductive polymer layer contacts the anode foil, the cathode foil, and the separator with a sufficiently large contact area. Thus, by forming a sufficient conductive path between the anode foil and the cathode foil through the conductive polymer layer, the equivalent series resistance (ESR) of the electrolytic capacitor is reduced, and its reliability is improved.

[0021] The conductive polymer layer comprises a conductive polymer, a dopant, and a sugar alcohol. The sugar alcohol is selected from at least one of xylitol and xylitol derivatives (hereinafter collectively referred to as "xylitol compounds"). Therefore, sugar alcohols are sometimes referred to as xylitol compounds below.

[0022] Among sugar alcohols, xylitol compounds have a low melting point and excellent solubility in solvents. By using xylitol compounds, even with the use of large quantities, the precipitation of sugar alcohols in the manufacturing process and the completed electrolytic capacitors can be effectively suppressed.

[0023] Here, the use of a large amount of xylitol compound refers to the situation where the ratio (Ms / Mp) of the mass of the sugar alcohol Ms to the total mass Mp of the conductive polymer and dopant is 1 or more and 40 or less. By satisfying such conditions, the contact area between the conductive polymer layer and the anode foil, cathode foil, and separator is increased, and a sufficient conductive path based on the conductive polymer layer is formed between the anode foil and the cathode foil.

[0024] To form a better conductive path based on the conductive polymer layer between the anode foil and the cathode foil, it is preferable to set the ratio (Ms / Mp) to 2 or more, more preferably 5 or more and 20 or less, more preferably 7 or more and 20 or less, and even more preferably 10 or more and 20 or less. The higher the ratio (Ms / Mp), the more xylitol compounds are contained in the conductive polymer layer. Furthermore, except for the case where the mass content of xylitol compounds in the conductive polymer layer is excessive, a higher ratio (Ms / Mp) results in a larger contact area between the conductive polymer layer and the anode foil, cathode foil, and separator, thus enabling the formation of a sufficient conductive path based on the conductive polymer layer between the anode foil and the cathode foil.

[0025] Xylitol derivatives can be compounds obtained by esterification of a portion of the hydroxyl group of xylitol, compounds obtained by etherification of a portion of the hydroxyl group of xylitol, or compounds obtained by anionization of a portion of the hydroxyl group of xylitol to form a salt, etc. However, the chemical structures of xylitol derivatives are not limited to these. The molar mass of xylitol derivatives can be in the range of 0.9 to 2 times the molar mass of xylitol (152.15 g / mol). The chemical formula of xylitol derivatives can be based on the chemical formula of xylitol (C5H7(OH)5), for example, it can be C5H7(OH). 5-a X a (X is an atom or group other than the OH group, and 1≤a≤4). X can be a halogen atom, an OM group (M is an alkali metal atom), an OR group (R is a hydrocarbon group with 5 or fewer carbon atoms, at least one of the hydrogen atoms of which can be replaced by a hydrophilic group such as a hydroxyl group or a carboxyl group, or a halogen atom, etc.) etc. X preferably satisfies 1≤a≤3 or 1≤a≤2.

[0026] Preferably, the xylitol compound content in the conductive polymer layer is greater than the individual mass content of all other components in the conductive polymer layer. In this case, the ratio (Ms / Mp) is 1 or more, and can be 5 or more, 7 or more, or 10 or more. When the xylitol compound content in the conductive polymer layer is so high, the contact area between the conductive polymer layer and the anode foil, cathode foil, and separator can be significantly increased.

[0027] The mass content of xylitol compounds in the conductive polymer layer can be above 50% by mass and below 98% by mass, above 60% by mass and below 93% by mass, above 50% by mass and below 93% by mass, or above 80% by mass and below 93% by mass.

[0028] The conductive polymer layer is preferably formed on at least one surface selected from the surface of the dielectric layer and the surface of the cathode foil, and may also be formed within the voids of the diaphragm (i.e., the inner wall of the diaphragm's constituent material surrounding the voids of the diaphragm). This allows for the formation of a more robust conductive path based on the conductive polymer layer between the anode foil and the cathode foil. The conductive polymer layer is preferably formed at least on the surface of the dielectric layer of the anode foil, preferably on both the surface of the dielectric layer and the surface of the cathode foil, and further preferably within the voids of the diaphragm.

[0029] It may further include liquid components contained in the voids within the capacitor element. The liquid component only needs to fill at least a portion of the voids within the capacitor element. That is, the electrolytic capacitor of this disclosure can be a solid electrolytic capacitor or a solid-liquid hybrid electrolytic capacitor.

[0030] The liquid component preferably contains at least one selected from ethylene glycol, diethylene glycol, triethylene glycol, ethylene glycol condensates with a molecular weight of less than 250, glycerol, γ-butyrolactone, and sulfolane. The liquid component may be solely a solvent or an electrolyte containing an electrolyte salt.

[0031] <How to calculate the ratio (Ms / Mp)>

[0032] The ratio (Ms / Mp) of the mass Ms of the sugar alcohol (xylitol compound) to the total mass Mp of the conductive polymer and dopant can be determined, for example, by the following method.

[0033] (The case where the electrolytic capacitor does not contain liquid components)

[0034] First, the cathode foil is separated from the capacitor element. A conductive polymer layer is then attached to the cathode foil. Next, water-soluble components, including xylitol compounds, are removed from the cathode foil with the attached conductive polymer layer. The conductive polymer and dopants have different solubility in water than other water-soluble components, therefore water can be used to separate the conductive polymer and dopants from the other components.

[0035] For example, when a cathode foil is immersed in an excess of ion-exchange water to thoroughly remove water-soluble components and then dried, the dried cathode foil contains no water-soluble components (including xylitol compounds). Therefore, the mass of water-soluble components can be determined based on the dried mass of the cathode foil before and after the removal of water-soluble components.

[0036] In addition, the mass content of each component in the water-soluble components (therefore, the mass content of xylitol compounds) can be determined by various analytical methods such as gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS).

[0037] Furthermore, by performing thermal analysis on the cathode foil after the removal of water-soluble components using, for example, a differential scanning calorimeter, the mass content of the conductive polymer layer contained in the sample can be determined.

[0038] Using the above measurement results, the conductivity ratio (Ms / Mp) in the polymer layer of an electrolytic capacitor that does not contain liquid components can be determined.

[0039] (The case where the electrolytic capacitor contains liquid components)

[0040] First, the cathode foil is separated from the capacitor element, and the liquid component is also separated from the cathode foil. For example, by immersing the cathode foil in an excess of a solvent (which could be deionized water) that has an affinity for the liquid component, and then thoroughly removing the solvent and drying it, the dried cathode foil contains no liquid component. Therefore, a cathode foil with a conductive polymer layer containing no liquid component can be obtained.

[0041] Then, similar to the case where the electrolytic capacitor does not contain liquid components, the water-soluble components are removed from the cathode foil with the attached conductive polymer layer, and the sample is dried. Thermal analysis is then performed, for example, using a differential scanning calorimeter, thereby determining the mass content of the conductive polymer layer in the sample.

[0042] On the other hand, the mass content of each component in the separated liquid and water-soluble components (therefore, the mass content of xylitol compounds) can be determined by various analytical methods such as gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS).

[0043] In addition, by separating and analyzing only the liquid components, the mass content of each component in the liquid component can be determined.

[0044] Furthermore, after separating the cathode foil from the capacitor element, it is dried without cleaning, thereby allowing the determination of the mass percentage of solvent contained in the liquid component of the cathode foil. Based on this solvent mass percentage and the separately determined mass percentages of each component in the liquid component, the mass percentage of solute contained in the liquid component of the cathode foil can be calculated.

[0045] Using the above measurement results, the conductivity ratio (Ms / Mp) in the polymer layer of an electrolytic capacitor containing liquid components can be determined.

[0046] Next, examples of the constituent elements of the electrolytic capacitor of this disclosure will be further described. However, the constituent elements of the electrolytic capacitor are not limited to the following examples.

[0047] (Anode foil)

[0048] Examples of anode foils include metal foils containing at least one of the valve-acting metals such as titanium, tantalum, aluminum, and niobium. The anode foil can also be a metal foil containing a valve-acting metal (e.g., aluminum foil). The anode foil may contain the valve-acting metal in the form of an alloy or a compound containing the valve-acting metal. The thickness of the anode foil can be 15 μm or more and 300 μm or less. The surface of the anode foil can be roughened by etching or the like.

[0049] A dielectric layer is formed on the surface of the anode foil. This dielectric layer can be formed by chemically converting the anode foil. In this case, the dielectric layer may contain an oxide of the valve-acting metal (e.g., aluminum oxide). It should be noted that the dielectric layer can function as a dielectric, or it may be formed from a dielectric material other than an oxide of the valve-acting metal.

[0050] In electrolytic capacitors, a conductive polymer layer may not be formed on the end face of the anode foil. On the other hand, it is preferable to form a dielectric layer on the end face of the anode foil.

[0051] (Cathode foil)

[0052] The cathode foil only needs to function as a cathode and is not particularly limited. Examples of cathode foils include metal foils (such as aluminum foil). The type of metal is not particularly limited and can be a valve-acting metal or an alloy containing a valve-acting metal. The thickness of the cathode foil can be 15 μm or more and 300 μm or less. The surface of the cathode foil can be roughened or chemically converted as needed.

[0053] The cathode foil may include a conductive coating. When the metal foil contains a valve-acting metal, the coating may contain carbon and at least one metal with a lower ionization tendency than the valve-acting metal. This readily improves the acid resistance of the metal foil. When the metal foil contains aluminum, the coating may contain at least one selected from carbon, nickel, titanium, tantalum, and zirconium. From the perspective of cost and low resistance, the coating may contain nickel and / or titanium.

[0054] The thickness of the coating can be 5 nm or more, 10 nm or more, or less than 200 nm. The coating can be formed by vapor deposition or sputtering of the aforementioned metal onto a metal foil. Alternatively, the coating can be formed by vapor deposition of a conductive carbon material onto a metal foil, or by coating a carbon paste containing a conductive carbon material. Examples of conductive carbon materials include graphite, hard carbon, soft carbon, and carbon black.

[0055] (Diaphragm)

[0056] The diaphragm can be made of porous sheet material. Examples of porous sheet materials include woven fabrics, nonwoven fabrics, and microporous membranes. The thickness of the diaphragm is not particularly limited and can range from 10 μm to 300 μm. Examples of diaphragm materials include cellulose, polyethylene terephthalate, polybutylene terephthalate, polyphenylene sulfide, vinylon, nylon, aromatic polyamides, polyimides, polyamide-imides, polyether-imides, rayon, and glass.

[0057] (outer body)

[0058] The outer casing comprises a housing and / or a sealing resin. It is not limited to this; known housings and sealing resins may also be used. The sealing resin may comprise 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 comprise fillers, curing agents, polymerization initiators, and / or catalysts, etc.

[0059] Hereinafter, an example of the electrolytic capacitor of this disclosure will be specifically described with reference to the accompanying drawings. The aforementioned constituent elements can be applied to the constituent elements of the example described below. Furthermore, the constituent elements of the example described below can be modified based on the above description. Additionally, the matters described below can be applied to the embodiments described above. Furthermore, in one example described below, constituent elements that are not essential to the electrolytic capacitor of this disclosure can be omitted.

[0060] Figure 1 This is a schematic cross-sectional view of an electrolytic capacitor 100, illustrating an example of this embodiment. Figure 2 This is a schematic diagram obtained by unfolding a portion of the capacitor element 10 contained in the electrolytic capacitor 100.

[0061] The electrolytic capacitor 100 includes a capacitor element 10, a bottom housing 101 for housing the capacitor element 10, a sealing member 102 that blocks the opening of the bottom housing 101, a base plate 103 covering the sealing member 102, leads 104A and 104B extending from the sealing member 102 and through the base plate 103, and lead connectors 105A and 105B connecting the leads to the electrodes of the capacitor element 10. The bottom housing 101 is drawn inward near the opening end, and the opening end is rolled in a manner that tightens it against the sealing member 102.

[0062] Capacitor element 10 is, for example, as Figure 1 The wound body shown. The wound body includes an anode foil 11 connected to a lead connector 105A, a cathode foil 12 connected to a lead connector 105B, and a diaphragm 13. The capacitor element 10 (wound body) includes a conductive polymer layer (not shown).

[0063] The anode foil 11 and cathode foil 12 are wound together with a diaphragm 13 in between. The outermost periphery of the wound is secured by a winding fixing tape 14. It should be noted that... Figure 1 This indicates the unfolded state of a portion of the fixed winding before its outermost circumference.

[0064] An electrolytic capacitor may have at least one capacitor element or multiple capacitor elements. The number of capacitor elements in an electrolytic capacitor is determined by its intended use.

[0065] The electrolytic capacitor of this disclosure can be manufactured by the manufacturing method (I) of the second aspect of this disclosure or the manufacturing method (II) of the third aspect of this disclosure as described below. However, the electrolytic capacitor can also be manufactured by methods other than manufacturing methods (I) and (II).

[0066] [Method for manufacturing electrolytic capacitors (I)]

[0067] The second aspect of this disclosure relates to a method (I) for manufacturing an electrolytic capacitor. The method (I) sequentially includes: step (a), preparing an anode foil, a cathode foil, and a separator having a dielectric layer; step (b), applying a coating liquid comprising a conductive polymer, a dopant, and a liquid medium to at least one surface selected from the surface of the dielectric layer and the surface of the cathode foil, and to the voids of the separator; step (c), forming a conductive polymer layer in the voids of the at least one surface and the separator by removing at least a portion of the liquid medium from the coating liquid; step (d), forming a capacitor element comprising the conductive polymer layer by disposing the separator between the anode foil and the cathode foil; and step (e), thereby including the conductive polymer layer as a xylitol compound by impregnating the capacitor element with a solution containing a xylitol compound.

[0068] <Process (a)>

[0069] There are no particular limitations on the process for preparing the anode foil, cathode foil, and diaphragm with dielectric layers. There are also no particular limitations on the materials used for the anode foil, cathode foil, and diaphragm. The materials already described can be used as the anode foil, cathode foil, and diaphragm.

[0070] <Process (b)>

[0071] In step (b), the coating solution can be applied to the surface of the dielectric layer and the separator, or it can be applied to the surface of the cathode foil and the separator. Alternatively, the coating solution can be applied to the surface of the dielectric layer, the surface of the cathode foil, and the separator. Depending on the requirements, the coating solution is applied to the dielectric layer formed on both sides of the anode foil, and to both sides of the cathode foil. A conductive polymer layer is formed at the coated areas.

[0072] There is no limitation on the coating method; it can be performed using known methods. For example, it can be done using a coating machine, by spraying the coating liquid, or by immersing the object to be coated in the coating liquid. Examples of using a coating machine include gravure coating and die coating. In gravure coating, the coating liquid is adhered to a transfer component such as a gravure roller. After removing excess coating liquid from the transfer component, the coating liquid adhered to the transfer component is transferred to the anode foil, cathode foil, and diaphragm, respectively, thereby allowing a uniform thickness of coating liquid layer to adhere to the anode foil, cathode foil, and diaphragm. It should be noted that the method of coating the diaphragm includes methods of impregnating the diaphragm with the coating liquid. The coating liquid applied to the diaphragm penetrates into the interior of the diaphragm, forming a conductive polymer layer integrally in the thickness direction of the diaphragm. The viscosity of the coating liquid can, for example, be 10 mPa·s or more (or 100 mPa·s or more) and 200 mPa·s or less. In this case, the coating solution is easily applied to the anode foil, cathode foil, and diaphragm, and easily penetrates the diaphragm. It should be noted that the viscosity of the coating solution is determined at room temperature (20°C) using a vibratory viscometer (e.g., SEKONIC, VM-100A).

[0073] Dopants can be incorporated into conductive polymers. Dopants can be negatively charged anions, and conductive polymers can be positively charged cations. The ionized dopants and conductive polymers interact through Coulomb forces. The doped conductive polymers can be dispersed as particles in the coating solution.

[0074] The liquid medium preferably contains water. The liquid medium may contain an organic compound (hereinafter also referred to as "organic compound (C)") that does not boil at 100°C under 1 atmosphere of pressure. One or more compounds may be used as organic compound (C). Organic compound (C) may be replaced with "at least one organic compound".

[0075] In this specification, unless otherwise specified, boiling point refers to the boiling point at 1 atmosphere. Examples of organic compounds (C) include organic compounds with boiling points above 100°C. When an organic compound (C) has a boiling point, that boiling point can be above 110°C, above 150°C, or above 200°C, or below 400°C, below 300°C, below 250°C, or below 200°C. The boiling point can be in the range of 110°C to 400°C (e.g., the range of 150°C to 350°C).

[0076] In a preferred example of manufacturing method (I), the water content in the coating solution is preferably 40% by mass or more (e.g., 50% by mass or more), and after the conductive polymer layer is formed, solutions containing xylitol compounds and liquid components (e.g., electrolytes) can easily penetrate into the conductive polymer layer. When using an organic compound (C), the content of the organic compound (C) in the coating solution can be 0% by mass or more and 10% by mass or less.

[0077] Water boils and evaporates at approximately 100°C under 1 atmosphere of pressure. On the other hand, the organic compound (C) is a compound that does not boil at 100°C under 1 atmosphere of pressure. Therefore, by heating the coating liquid at a temperature above 100°C, where the organic compound (C) does not boil or decompose, water can be removed from the coating liquid, while leaving the organic compound (C) as a residue. As a result, the organic compound (C) remains in the formed conductive polymer layer. In this case, solutions or liquid components (e.g., electrolytes) containing xylitol compounds can easily penetrate into the conductive polymer layer.

[0078] <Process (c)>

[0079] In step (c), the method for removing at least a portion of the liquid medium from the coating is not limited. The removal of the liquid medium can be carried out under heating and / or reduced pressure, preferably at least under heating.

[0080] When heating is performed, it is preferable to remove a portion of the liquid medium by heating at a temperature above 100°C. Heating at a temperature above 100°C allows for rapid removal of water from the liquid medium. The heating temperature is preferably a temperature at which the organic compound (C) does not boil or decompose. If the organic compound (C) is a compound without a defined boiling point, it is preferable to perform heating at a temperature where the evaporation of the organic compound (C) is minimal and the organic compound (C) does not decompose. The heating temperature can be above 100°C, above 120°C, or above 140°C, or below 200°C or below 160°C. The heating temperature can be in the range of 100°C to 200°C. The heating time is not particularly limited, as long as it is sufficient to remove at least a portion of the liquid medium. An example heating time is in the range of 5 to 60 minutes.

[0081] When forming a conductive polymer layer on a single component, heating can be performed more than twice at a specified temperature range (e.g., 100°C to 200°C). For example, when forming a conductive polymer layer on a dielectric layer formed on both sides of an anode foil, heating can be performed after coating one side with a coating solution, followed by further heating after coating the other side with a coating solution. The same method can be applied when forming a conductive polymer layer on both sides of a cathode foil.

[0082] <Process (d)>

[0083] In step (d), after forming a conductive polymer layer on at least one of the anode foil and the cathode foil and on the separator, a separator is disposed between the anode foil and the cathode foil, thereby forming a capacitor element comprising the conductive polymer layer. This step also involves stacking the anode foil and the cathode foil with the separator in between. Therefore, the capacitor element can also be referred to as a "laminated structure".

[0084] There is no limitation on the method of forming the capacitor element (laminated body), and the capacitor element can be formed by known methods. The capacitor element can be a wound body. In this case, the wound body is formed by winding the anode foil, cathode foil, and separator in such a way that a separator is disposed between the anode foil and the cathode foil. In the wound body, the anode foil, cathode foil, and separator are stacked radially in the wound body.

[0085] A capacitor element can be formed by stacking a flat anode foil, a flat cathode foil, and a flat separator in one direction. For example, a capacitor element can also be formed by stacking multiple anode foils, multiple cathode foils, and multiple separators in one direction. In a typical example of a stack, the anode foils and cathode foils are arranged alternately, and the separator is disposed between the anode foils and cathode foils.

[0086] <Process (e)>

[0087] In step (e), a solution containing a xylitol compound (hereinafter also referred to as "xylitol solution") is impregnated into the capacitor element. This allows the conductive polymer layer to contain the xylitol compound. The solvent of the xylitol solution preferably contains at least water. Water may comprise at least 80% by mass, and more preferably 90% by mass (100%) of the solvent in the xylitol solution. Alternatively, the solvent of the xylitol solution may contain an organic solvent. Ethylene glycol, sulfolane, and γ-butyrolactone may be used as organic solvents. The mass content of the xylitol compound in the xylitol solution is preferably 10% by mass to 75% by mass, but may also be 15% by mass to 60% by mass.

[0088] There is no limitation to the method of impregnating the capacitor element with a xylitol solution. For example, the capacitor element can be infused with a xylitol compound by immersing at least a portion of the capacitor element in the xylitol solution. The steps of immersing at least a portion of the capacitor element in the xylitol solution and removing at least a portion of the solvent can be performed multiple times. The xylitol solution can be heated to 40°C to 90°C.

[0089] Following step (e), a further step can be performed to impregnate the liquid component into the voids within the capacitor element. In this case, a solid-liquid hybrid electrolytic capacitor can be obtained. The liquid component can be either a solvent or an electrolyte containing electrolyte salts.

[0090] There is no limitation to the method of permeating the liquid component into the voids within the capacitor element. For example, the liquid component can be permeated into the capacitor element by immersing at least a portion of the capacitor element in the liquid component.

[0091] According to manufacturing method (I), the ratio (Ms / Mp) of the mass Ms of the xylitol compound to the total mass Mp of the conductive polymer and the dopant can be easily controlled to be 1 or more and 40 or less, and further controlled to be 5 or more and 20 or less.

[0092] An example of a typical electrolytic capacitor includes a wound of an anode foil, a separator, and a cathode foil. Such an electrolytic capacitor includes a conductive polymer layer disposed within the wound. The conductive polymer layer is formed by impregnating the wound with a dispersion containing conductive polymers.

[0093] However, due to the high viscosity of dispersions containing conductive polymers, even when the dispersion permeates the wound, a sufficiently conductive polymer layer may not form inside the wound. Insufficient formation of the conductive polymer layer can lead to reduced initial capacity, increased equivalent series resistance (ESR), and decreased reliability. Furthermore, since sugar alcohols are solids, solutions formed by dissolving sugar alcohols in solvents have high viscosity. If the dispersion containing conductive polymers contains sugar alcohols, it becomes even more difficult to form a sufficiently conductive polymer layer inside the wound.

[0094] On the other hand, the method (I) for manufacturing an electrolytic capacitor includes steps (b) and (c), in which a coating liquid is applied to at least one surface selected from the surface of the dielectric layer of the anode foil and the surface of the cathode foil, and the coating liquid is also applied to the voids of the separator. Since the coating liquid contains conductive polymers and dopants, it can be of high viscosity. However, for example, when the coating liquid is applied to the surface of the dielectric layer or the surface of the cathode foil using a coating apparatus (coating machine), a sufficient amount of conductive polymer layer can be formed within the capacitor element. Similarly, in the method (I) for manufacturing an electrolytic capacitor, for example, when the coating liquid is applied to the surface of the separator using a coating apparatus (coating machine), a sufficient amount of conductive polymer layer can be formed within the voids of the separator (more precisely, on the inner wall formed by the separator material in a manner that surrounds the voids).

[0095] Furthermore, the xylitol compound used in step (e) of the electrolytic capacitor manufacturing method (I) has a relatively low melting point among sugar alcohols and excellent solubility in solvents, thus enabling the conductive polymer layer to contain a sufficient amount of sugar alcohol or xylitol compound. Therefore, the xylitol compound easily penetrates into the interior of the conductive polymer layer, increasing the adhesion between the conductive polymer layers formed on each component. Consequently, a strong conductive path based on the conductive polymer layer can be formed between the anode foil and the cathode foil.

[0096] The total mass Mp of the conductive polymer and dopant in the conductive polymer layer and the mass Ms of the xylitol compound can be controlled by controlling the concentration of the conductive polymer and dopant in the coating solution, as well as the concentration of the xylitol compound in the solution containing the xylitol compound.

[0097] In manufacturing method (I), the conductive polymer layer can be formed in the form of a combination of a first conductive polymer layer formed on the surface of the dielectric layer of the anode foil and / or the surface of the cathode foil and a second conductive polymer layer formed in the voids of the diaphragm.

[0098] The first and second conductive polymer layers can be composed of the same conductive polymer or contain different conductive polymers. The first and second conductive polymer layers can contain the same dopant or different dopant. The first conductive polymer layer formed on the anode foil (on the dielectric layer), the first conductive polymer layer formed on the cathode foil, and the second conductive polymer layer can be composed of the same conductive polymer or contain different conductive polymers. The first conductive polymer layer formed on the anode foil (on the dielectric layer), the first conductive polymer layer formed on the cathode foil, and the second conductive polymer layer can contain the same dopant or different dopant.

[0099] When a first conductive polymer layer is formed on the surface of the anode foil (or cathode foil), it is preferable that the first conductive polymer layer is formed on 80% or more (e.g., 90% or more) of the surface area of ​​the surface where the first conductive polymer layer is formed. The first conductive polymer layer is preferably formed on the entire surface of the electrode foil (anode foil, cathode foil) to contribute to the electrostatic capacitance of the capacitor element. The area of ​​the second conductive polymer layer formed on the separator is preferably 80% or more (e.g., 90% or more) of the area of ​​the separator, but it may also be formed on the entire separator. Here, the surface area of ​​the electrode foil (anode foil, cathode foil) refers to the area without considering surface unevenness, and can be calculated based on the shape of the electrode foil. When the first conductive polymer is formed on both sides of the electrode foil, the surface area of ​​the first conductive polymer is the sum of the areas of both sides.

[0100] The mass of the first conductive polymer layer per unit area can be 0.01 mg / cm³. 2 Above, or 0.02 mg / cm 2 The above can be 0.5 mg / cm³ 2 Below, or 0.3 mg / cm 2 The following is an example. By setting this mass to 0.1 mg / cm³. 2 The above allows for a more uniform formation of the conductive polymer layer. It should be noted that when the first conductive polymer layer is formed on both sides of the electrode foil, the mass per unit area mentioned above refers to the mass of the layer formed on only one side of the electrode foil.

[0101] The mass of the second conductive polymer layer per unit area can be 0.02 mg / cm³. 2 Above, or 0.05 mg / cm 2 The above can be 2.0 mg / cm³ 2 Below, or 1.0 mg / cm 2 The following is an example. The mass is set to 0.3 mg / cm³. 2 The above methods enable the formation of a more uniform conductive polymer layer.

[0102] The mass of the conductive polymer layer per unit area can be determined using the following method. First, prepare five samples cut from the component (electrode foil or diaphragm) before the formation of the conductive polymer layer, using a specified area, and measure the mass of these five samples. Then, prepare five samples cut from the component (electrode foil or diaphragm) with the conductive polymer layer formed, using the specified area, and measure the mass of these samples. The mass of the conductive polymer layer per unit area is determined by using the difference between the total mass of the five samples after the formation of the conductive polymer layer and the total mass of the five samples before the formation of the conductive polymer layer, along with the specified area.

[0103] The above-described process forms a capacitor element comprising a conductive polymer layer and a liquid component. Then, the capacitor element is encapsulated in an outer casing as needed. This manufactures an electrolytic capacitor. It should be noted that manufacturing method (I) may include processes other than those described above, depending on the requirements.

[0104] [Method for manufacturing electrolytic capacitors (II)]

[0105] The third aspect of this disclosure relates to a method (II) for manufacturing an electrolytic capacitor. The method comprises, sequentially: step (a), preparing an anode foil, a cathode foil, and a separator having a dielectric layer; step (b), applying a coating solution comprising a conductive polymer, a dopant, a xylitol compound, and a liquid medium to at least one surface selected from the surface of the dielectric layer and the surface of the cathode foil, and to the voids of the separator; step (c), forming a conductive polymer layer in the voids of at least one surface and the separator by removing at least a portion of the liquid medium from the coating solution; and step (d), forming a capacitor element comprising the conductive polymer layer by disposing the separator between the anode foil and the cathode foil.

[0106] That is, the difference between manufacturing method (II) and manufacturing method (I) is that the coating solution contains a xylitol compound, and therefore the step of impregnating the capacitor element with the solution containing the xylitol compound (step (d) of manufacturing method (I)) can be omitted. Other than this, the steps of manufacturing method (II) are the same as those of manufacturing method (I). However, step (d) of manufacturing method (I) can also be performed in manufacturing method (II).

[0107] According to manufacturing method (II), the ratio (Ms / Mp) of the mass Ms of the xylitol compound to the total mass Mp of the conductive polymer and the dopant can be easily controlled to be 1 or more and 40 or less, and further controlled to be 5 or more and 20 or less.

[0108] In step (b) of manufacturing method (II), a coating liquid is applied to at least one surface selected from the surface of the dielectric layer of the anode foil and the surface of the cathode foil, and the coating liquid is also applied to the voids of the diaphragm. The coating liquid contains a conductive polymer and a dopant, and also contains a xylitol compound, thus achieving a high viscosity. However, for example, when the coating liquid is applied to the surface of the dielectric layer or the surface of the cathode foil using a coating apparatus (coating machine), a sufficient amount of conductive polymer layer can be formed within the capacitor element, and the conductive polymer layer can contain a xylitol compound at any mass content. Similarly, for example, when the coating liquid is applied to the surface of the diaphragm using a coating apparatus (coating machine), a sufficient amount of conductive polymer layer can be formed within the voids of the diaphragm, and the conductive polymer layer can contain a xylitol compound at any mass content.

[0109] The total mass Mp of the conductive polymer and dopant in the conductive polymer layer, and the mass Ms of the xylitol compound, can be controlled by adjusting the concentration of these components in the coating solution. Therefore, any ratio (Ms / Mp) can be achieved.

[0110] In manufacturing method (II), if a further step is taken after step (d) to impregnate the liquid component (solvent only, or electrolyte containing electrolyte salt) into the voids within the capacitor element, a solid-liquid hybrid electrolytic capacitor can be obtained.

[0111] As described above, in manufacturing methods (I) and (II), the conductive polymer layer can be formed in the form of a combination of a first conductive polymer layer formed on the surface of the dielectric layer of the anode foil and / or the surface of the cathode foil, and a second conductive polymer layer formed within the voids of the separator. According to manufacturing methods (I) and (II), a mixed region can be formed at the boundary between the first and second conductive polymer layers, where a portion of the first conductive polymer layer and a portion of the second conductive polymer layer are mixed. This is because the conductive polymer layer contains a sufficient amount of xylitol compound, which has the effect of fusing a portion of the first conductive polymer layer with a portion of the second conductive polymer layer. In other words, the first and second conductive polymer layers can adhere to each other. Therefore, a robust conductive path based on the conductive polymer layer is formed between the anode foil and the cathode foil, reducing the ESR of the electrolytic capacitor and significantly improving its reliability.

[0112] (Applying liquid)

[0113] The coating solution will now be described in more detail. The coating solution comprises a conductive polymer, a dopant, and a liquid medium, and may also contain a xylitol compound. The liquid medium preferably comprises water, and more preferably further comprises an organic compound (C). The coating solution may contain other components as needed. As the organic compound (C), an organic compound readily soluble in water is preferred. The organic compound (C) can be a compound miscible with water.

[0114] The coating solution may contain sugar alcohols other than xylitol compounds. However, it is preferable that the majority of the sugar alcohols contained in the coating solution are xylitol compounds. Preferably, 80% or more (and further 90% or more by mass) of the sugar alcohols contained in the coating solution are xylitol compounds. Examples of sugar alcohols other than xylitol compounds include mannitol, sorbitol, erythritol, and pentaerythritol.

[0115] Examples of organic compounds (C) include compounds used as organic solvents. Examples of organic compounds (C) include polyols (excluding sugar alcohols) having two or more hydroxyl groups. Water in which organic compounds (C) are dissolved can be used as a dispersion medium for conductive polymers. In one view, the coating liquid is a dispersion of particles of a conductive polymer doped with a dopant, the dispersion medium of which can be water in which organic compounds (C) and / or xylitol compounds are dissolved.

[0116] Examples of organic compounds (C) include polyols (excluding sugar alcohols), sulfolane, γ-butyrolactone, and borate esters. Organic compound (C) may contain at least one selected from polyols, sulfolane, γ-butyrolactone, and borate esters, or may be only one of these at least one.

[0117] Examples of polyols include glycols and glycerols. Examples of glycols include ethylene glycol, diethylene glycol, triethylene glycol, polyalkylene glycols (e.g., polyethylene glycol), and polyoxyethylene-polyoxypropylene glycol (ethylene oxide-propylene oxide copolymer). Examples of glycerols include glycerol and polyglycerols.

[0118] Examples of conductive polymers include polypyrrole, polythiophene, polyfuran, polyaniline, polyacetylene, and their derivatives. These derivatives include polymers with polypyrrole, polythiophene, polyfuran, polyaniline, and polyacetylene as their basic backbone. For example, derivatives of polythiophene include poly(3,4-ethylenedioxythiophene). These conductive polymers can be used alone or in combination. Furthermore, conductive polymers can also be copolymers of two or more monomers. The weight-average molecular weight of conductive polymers is not particularly limited, and can, for example, range from 1,000 to 100,000. A preferred example of a conductive polymer is poly(3,4-ethylenedioxythiophene) (PEDOT).

[0119] Dopant is incorporated into conductive polymers. From the viewpoint of suppressing dedoping from the conductive polymer, polymeric dopant is preferred as the dopant. Examples of polymeric dopant include polyvinyl sulfonic acid, polystyrene sulfonic acid, polyallyl sulfonic acid, polypropylene sulfonic acid, polymethyl methacrylate sulfonic acid, poly(2-acrylamido-2-methylpropanesulfonic acid), polyisoprene sulfonic acid, and polyacrylic acid. They can be used alone or in combination of two or more. At least a portion of them can be added in the form of a salt. A preferred example of a dopant is polystyrene sulfonic acid (PSS).

[0120] In the electrolytic capacitor disclosed herein, the dopant can be a dopant containing acidic groups or a polymeric dopant containing acidic groups. Examples of acidic groups include sulfonic acid groups, carboxyl groups, etc. A polymeric dopant containing acidic groups is a polymer whose structural units contain acidic groups at least in part. Examples of such polymeric dopants include the aforementioned polymeric dopant.

[0121] There is no particular limitation on the weight-average molecular weight of the dopant. From the viewpoint of easily forming a homogeneous conductive polymer layer, the weight-average molecular weight of the dopant can be set in the range of 1,000 to 100,000.

[0122] The dopant can be polystyrene sulfonic acid, and the conductive polymer can be poly(3,4-ethylenedioxythiophene). That is, the conductive polymer doped with the dopant can be poly(3,4-ethylenedioxythiophene) doped with polystyrene sulfonic acid.

[0123] When using conductive polymers doped with dopants, the pH of the coating solution is preferably less than 7.0, but can also be below 6.0 or 5.0, in order to suppress dopant dedoping. The pH of the coating solution can be above 1.0 or above 2.0.

[0124] Dopant-doped conductive polymers can exist in the coating solution as particles. In the volume-based particle size distribution of these dopant-doped conductive polymer particles, the most frequent particle size can be greater than 10 nm or greater than 20 nm, or less than 1000 nm, 500 nm, 200 nm, or 100 nm. The volume-based particle size distribution can be determined using a laser diffraction / scattering particle size distribution measuring device.

[0125] The most frequent value of the particle size of the doped conductive polymer can be in the range of 20 nm to 200 nm (e.g., 20 nm to 100 nm). Furthermore, in the volumetric particle size distribution, the proportion of particles with a particle size in the range of 20 nm to 100 nm can be more than 90% of the total. Based on these ranges, it is easy to form a conductive polymer layer containing the doped conductive polymer within the pores of the components (electrode foil and separator).

[0126] The water content in the coating solution can be 40% by mass or more, 50% by mass or more, 70% by mass or more, 73% by mass or more, 78% by mass or more, 80% by mass or more, 88% by mass or more, 90% by mass or more, or 95% by mass or more. The water content can also be below 98% by mass, below 95% by mass, below 90% by mass, or below 80% by mass. The water content can fall within the ranges of 40% to 98% by mass or more, 50% to 98% by mass, 80% to 98% by mass, or 70% to 98% by mass. Within any of these ranges, the upper limit can be replaced with 95% by mass, 90% by mass, or 80% by mass.

[0127] The content of xylitol compounds and organic compounds (C) in the coating solution can be 0% by mass or more, 1.0% by mass or more, 3.0% by mass or more, 5.0% by mass or more, or 10% by mass or more. This content can be 59.5% by mass or less, 45% by mass or less, 30% by mass or less, 25% by mass or less, 20% by mass or less, 15% by mass or less, or 10% by mass or less. This content can be in the range of 1 to 59.5% by mass, 3 to 59.5% by mass, or 5 to 59.5% by mass. Within any of these ranges, the upper limit can be replaced with 45% by mass, 30% by mass, 25% by mass, 20% by mass, 15% by mass, or 10% by mass.

[0128] The total mass content of the conductive polymer and dopant in the coating solution can be 0.5% by mass or more, or 1.0% by mass or more, or 4.0% by mass or less, 3.0% by mass or less, or 2.0% by mass or less. This content can 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 can be set to 3.0% by mass or 2.0% by mass. From the perspective of excellent physical properties and long-term stability of the coating solution, and a good balance between ESR and cost of the electrolytic capacitor, this content is preferably in the range of 1.0% to 3.0%.

[0129] There is no particular limitation on the mass of the dopant contained in the coating solution, and it can be in the range of 0.1 to 5 times (e.g., 0.5 to 3 times) the mass of the conductive polymer contained in the coating solution.

[0130] The mass content of xylitol compounds in the coating solution is preferably 1 to 12 times the total mass content of conductive polymers and dopants in the coating solution, more preferably 7 to 12 times. Furthermore, considering the excellent physical properties and long-term stability of the coating solution, as well as a good balance between the ESR of the electrolytic capacitor and its cost, this content is preferably in the range of 1.0 to 3.0%.

[0131] In the coating solution, the water content, the total content of xylitol compounds and organic compounds (C), and the total content of conductive polymers and dopants can be (40-98): (1.0-59.5): (0.5-4.0), or (69.5-98): (1.0-30): (0.5-4.0).

[0132] The water content, the total content of xylitol compounds and organic compounds (C), and the total content of conductive polymers and dopants can be combined arbitrarily as long as they do not contradict each other. An example of a coating liquid can satisfy one, two, three or four conditions selected from (1) to (5) below, or it can satisfy all conditions.

[0133] (1) The water content is in the range of 50 to 98% by mass (e.g., 73 to 95% by mass), the total content of xylitol compounds and organic compounds (C) is in the range of 3 to 30% by mass (e.g., 5 to 25% by mass), and the total content of conductive polymers and dopants is in the range of 0.5 to 4.0% by mass (e.g., 1.0 to 3.0% by mass).

[0134] (2) The mass content of xylitol compounds in the coating solution is 1 to 45 times the total mass content of conductive polymers and dopants in the coating solution, and further 7 to 20 times.

[0135] (3) The organic compound (C) is a diol (e.g., ethylene glycol).

[0136] (4) The conductive polymer component includes poly(3,4-ethylenedioxythiophene) and polystyrene sulfonic acid. For example, the conductive polymer component may be composed of poly(3,4-ethylenedioxythiophene) and polystyrene sulfonic acid.

[0137] (5) The pH of the coating solution is in the range of 1.0 to 6.0 (e.g., 2.0 to 5.0).

[0138] (6) The conductive polymer doped with dopant exists in the coating liquid as particles, and in the volume-based particle size distribution of these particles, the most frequent value of the particle size is in the range of 20 nm to 1000 nm (e.g., the range of 20 nm to 200 nm, the range of 20 nm to 100 nm). In the volume-based particle size distribution, the proportion of particles with a particle size in the range of 20 nm to 1000 nm (e.g., the range of 20 nm to 200 nm, the range of 20 nm to 100 nm) in the total number of particles (volume basis) can be more than 90%.

[0139] (Liquid component)

[0140] Examples of liquid components include solvents and electrolytes. Electrolytes can be solvents containing dissolved solutes. It should be noted that, in this specification, liquid components can be components that are liquid at room temperature (25°C) or components that are liquid at the temperature at which the electrolytic capacitor is used.

[0141] The solvent used in liquid components can be an organic solvent, an ionic liquid, or a protic solvent. Examples of non-aqueous solvents include polyols 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, carbonates such as propylene carbonate, ethers such as 1,4-dioxane, ketones such as methyl ethyl ketone, and formaldehyde.

[0142] Polymer solvents can also be used as solvents. Examples of polymer solvents include polyalkylene glycols, derivatives of polyalkylene glycols, and compounds in which at least one hydroxyl group in a polyol is replaced by a polyalkylene glycol (including its derivatives). Specifically, examples of polymer solvents include polyethylene glycol (PEG), polyethylene glycol glycerol ether, polyethylene glycol diglycerol ether, polyethylene glycol sorbitol ether, polypropylene glycol, polypropylene glycol glycerol ether, polypropylene glycol diglycerol ether, polypropylene glycol sorbitol ether, polybutanediol, etc. Examples of polymer solvents also include copolymers of ethylene glycol and propylene glycol, copolymers of ethylene glycol and butanediol, copolymers of propylene glycol and butanediol, etc. Non-aqueous solvents can be used alone or in combination of two or more.

[0143] The liquid component can contain xylitol compounds as a solute. Among sugar alcohols, xylitol compounds have a low melting point and excellent solubility in solvents. By using xylitol compounds, even with the use of large quantities, the precipitation of xylitol compounds during the manufacturing process and within the completed electrolytic capacitor can be effectively suppressed.

[0144] Here, the use of a large amount of xylitol compound refers to a situation where the content of xylitol compound in the liquid component is, for example, 4% by mass or more and 70% by mass or less. Under such conditions, the xylitol compound acts on the conductive polymer layer, further increasing the contact area between the conductive polymer layer and the anode foil, cathode foil, and diaphragm, making it easier to form a sufficient conductive path based on the conductive polymer layer between the anode foil and the cathode foil.

[0145] In order to form a better conductive path based on a conductive polymer layer between the anode foil and the cathode foil, it is preferable to set the mass content of xylitol compound in the liquid component to 5% by mass or more, more preferably 7.5% by mass or more, and even more preferably 10% by mass or more or 15% by mass or more.

[0146] On the other hand, in order to more reliably suppress the precipitation of xylitol compounds, it is preferable to set the mass content of xylitol compounds in the liquid component to 50% by mass or less, more preferably 40% by mass or less, and even more preferably 30% by mass or less.

[0147] The solute may further include at least one selected from acids, bases, and electrolyte salts. In this case, in order to more reliably suppress the precipitation of xylitol compounds, the total mass content of all solutes in the liquid component is preferably 70% by mass or less, more preferably 50% by mass or less.

[0148] As acid components, both polycarboxylic acids and monocarboxylic acids can be used. Examples of the aforementioned polycarboxylic acids include aliphatic polycarboxylic acids ([saturated polycarboxylic acids, such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, octanoic acid, azelaic acid, sebacic acid, 1,6-decanedicarboxylic acid, 5,6-decanedicarboxylic acid]; [unsaturated polycarboxylic acids, such as maleic acid, fumaric acid, itaconic acid]), aromatic polycarboxylic acids (such as phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, pyromellitic acid), and alicyclic polycarboxylic acids (such as cyclohexane-1,2-dicarboxylic acid, cyclohexene-1,2-dicarboxylic acid, etc.).

[0149] Examples of the aforementioned monocarboxylic acids include aliphatic monocarboxylic acids (1 to 30 carbon atoms) ([saturated monocarboxylic acids, such as formic acid, acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, lauric acid, myristic acid, stearic acid, behenic acid]; [unsaturated monocarboxylic acids, such as acrylic acid, methacrylic acid, oleic acid]), aromatic monocarboxylic acids (such as benzoic acid, cinnamic acid, naphtholic acid), and hydroxycarboxylic acids (such as salicylic acid, mandelic acid, resorcinol acid).

[0150] Among them, maleic acid, phthalic acid, benzoic acid, pyromellitic acid, and resorcinol are heat-stable and are preferred.

[0151] Inorganic acids can be used as the acid component. Representative examples of inorganic acids include phosphoric acid, phosphorous acid, hypophosphite, alkyl phosphates, boric acid, fluoroboric acid, tetrafluoroboric acid, hexafluorophosphate, benzenesulfonic acid, and naphthalenesulfonic acid. Alternatively, complex compounds of organic and inorganic acids can also be used as the acid component. Examples of such complex compounds include borodiethylene glycol acid, borodioxalic acid, and borodisalicylic acid.

[0152] The base component can be a compound with an alkyl-substituted amidine group, such as imidazole compounds, benzimidazole compounds, alicyclic amidine compounds (pyrimidine compounds, imidazoline compounds), etc. Specifically, 1,8-diazabicyclo[5,4,0]undec-7-ene, 1,5-diazabicyclo[4,3,0]non-5-ene, 1,2-dimethylimidazolineon, 1,2,4-trimethylimidazoline, 1-methyl-2-ethylimidazoline, 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-methylimidazolium, and 1-methylbenzimidazole can be obtained. By using them, capacitors with excellent impedance performance can be obtained.

[0153] As a base component, quaternary salts of compounds having alkyl-substituted amidine groups can be used. Examples of such base components include imidazole compounds, benzimidazole compounds, and alicyclic amidine compounds (pyrimidine compounds, imidazole kinase compounds) that have been quaternized by alkyl or aryl alkyl groups having 1 to 11 carbon atoms. Specifically, 1-methyl-1,8-diazabicyclo[5,4,0]undec-7-ene, 1-methyl-1,5-diazabicyclo[4,3,0]non-5-ene, 1,2,3-trimethylimidazolinium, 1,2,3,4-tetramethylimidazolinium, 1,2-dimethyl-3-ethylimidazolinium, and 1,3,4-trimethyl-2-ethylimidazolinium are preferred. Imidazoline, 1,3-dimethyl-2-heptylimidazoline, 1,3-dimethyl-2-(3'-heptyl)imidazoline, 1,3-dimethyl-2-dodecylimidazoline, 1,2,3-trimethyl-1,4,5,6-tetrahydropyrimidine, 1,3-dimethylimidazoline, 1-methyl-3-ethylimidazoline, and 1,3-dimethylbenzimidazolium. By using these, capacitors with excellent impedance properties can be obtained.

[0154] Tertiary amines can 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-containing amines (dimethylaniline, methylethylaniline, diethylaniline, etc.). Among these, trialkylamines are preferred from the perspective of increasing conductivity, and it is more preferable that they contain at least one selected from trimethylamine, dimethylethylamine, methyldiethylamine, and triethylamine. Alternatively, secondary amines such as dialkylamines, primary amines such as monoalkylamines, and ammonia can also be used as the base component.

[0155] The liquid component may contain salts of both acidic and basic components. The salt can be inorganic and / or organic. An organic salt is a salt in which at least one of the anion and cation contains an organic compound. Examples of organic salts include trimethylamine maleate, triethylamine borosalicylate, ethyldimethylamine phthalate, mono-1,2,3,4-tetramethylimidazoline phthalate, and mono-1,3-dimethyl-2-ethylimidazoline phthalate.

[0156] To suppress dopant dedoping, the pH of the liquid component (L) can be set to less than 7.0 or 5.0, or to more than 1.0 or 2.0. This pH can be set to more than 1.0 and less than 7.0 (e.g., in the range of 2.0 to 5.0).

[0157] The liquid component preferably contains a protic solvent. By using a protic solvent, the conductive polymer layer can be particularly swollen. In addition to a protic solvent, the liquid component may also contain solvents other than protic solvents.

[0158] A protic solvent may contain at least one selected from glycols, glycerol, polyglycerol, and sugar alcohols, or it may consist of only one of these at least one compounds. A protic solvent may consist of only one compound or it may contain multiple compounds.

[0159] Postscript

[0160] The following technology has been disclosed through the above description of the embodiments.

[0161] (Technology 1)

[0162] An electrolytic capacitor includes a capacitor element comprising: an anode foil having a dielectric layer, a cathode foil, a separator between the anode foil and the cathode foil, and a conductive polymer layer between the anode foil and the cathode foil and in contact with the separator.

[0163] The aforementioned conductive polymer layer comprises conductive polymers, dopants, and sugar alcohols.

[0164] The aforementioned sugar alcohol is selected from at least one of xylitol and xylitol derivatives.

[0165] In the aforementioned conductive polymer layer, the ratio (Ms / Mp) of the mass Ms of the sugar alcohol to the total mass Mp of the conductive polymer and the dopant is 1 or more and 40 or less.

[0166] (Technology 2)

[0167] According to the electrolytic capacitor described in Technique 1, the ratio (Ms / Mp) is 5 or more and 20 or less.

[0168] (Technology 3)

[0169] According to the electrolytic capacitor described in Technique 1 or 2, the mass content of the sugar alcohol in the conductive polymer layer is greater than the mass content of all other components in the conductive polymer layer.

[0170] (Technology 4)

[0171] According to any one of the techniques 1 to 3, the mass content of the sugar alcohol in the conductive polymer layer is 50% by mass or more and 98% by mass or less.

[0172] (Technology 5)

[0173] According to any one of the techniques 1 to 4, the electrolytic capacitor wherein the conductive polymer layer is formed on at least one surface selected from the surface of the dielectric layer and the surface of the cathode foil, and is formed within the voids of the diaphragm.

[0174] (Technology 6)

[0175] The electrolytic capacitor described in any one of techniques 1 to 5 further includes a liquid component contained in the voids within the capacitor element.

[0176] (Technology 7)

[0177] According to the electrolytic capacitor described in Technique 6, the liquid component comprises at least one selected from ethylene glycol, diethylene glycol, triethylene glycol, ethylene glycol condensates with a molecular weight of less than 250, glycerol, γ-butyrolactone, and sulfolane.

[0178] (Technology 8)

[0179] A method for manufacturing an electrolytic capacitor, comprising the following steps:

[0180] Step (a): Prepare an anode foil, a cathode foil, and a diaphragm with dielectric layers;

[0181] Step (b) involves applying a coating containing a conductive polymer, a dopant, and a liquid medium to at least one surface selected from the surface of the dielectric layer and the surface of the cathode foil, as well as to the voids of the diaphragm.

[0182] Step (c) involves removing at least a portion of the liquid medium from the coating liquid, thereby forming a conductive polymer layer in the voids between the at least one surface and the diaphragm.

[0183] Step (d) involves forming a capacitor element comprising the conductive polymer layer by disposing the diaphragm between the anode foil and the cathode foil; and

[0184] In step (e), the conductive polymer layer is made to contain the sugar alcohol by impregnating the capacitor element with a solution containing sugar alcohol.

[0185] The aforementioned sugar alcohol is selected from at least one of xylitol and xylitol derivatives.

[0186] In the aforementioned conductive polymer layer, the ratio (Ms / Mp) of the mass Ms of the sugar alcohol to the total mass Mp of the conductive polymer and the dopant is 1 or more and 40 or less.

[0187] (Technology 9)

[0188] According to the manufacturing method of the electrolytic capacitor described in Technique 8, after the above-mentioned step (e), a further step is included to impregnate the liquid component into the voids within the capacitor element.

[0189] (Technology 10)

[0190] According to the manufacturing method of the electrolytic capacitor described in Technique 8 or 9, the conductive polymer layer comprises a first conductive polymer layer formed on the at least one surface and a second conductive polymer layer formed within the voids of the separator.

[0191] At the boundary between the first conductive polymer layer and the second conductive polymer layer, there exists a mixed region where a portion of the first conductive polymer layer and a portion of the second conductive polymer layer are mixed.

[0192] (Technology 11)

[0193] A method for manufacturing an electrolytic capacitor, comprising the following steps:

[0194] Step (a): Prepare an anode foil, a cathode foil, and a diaphragm with dielectric layers;

[0195] Step (b) involves applying a coating solution containing a conductive polymer, a dopant, a sugar alcohol, and a liquid medium to at least one surface selected from the surface of the dielectric layer and the surface of the cathode foil, as well as to the voids of the diaphragm.

[0196] Step (c) involves removing at least a portion of the liquid medium from the coating solution, thereby forming a conductive polymer layer within the voids of the at least one surface and the diaphragm; and

[0197] In step (d), a capacitor element comprising the conductive polymer layer is formed by disposing the diaphragm between the anode foil and the cathode foil.

[0198] The aforementioned sugar alcohol is selected from at least one of xylitol and xylitol derivatives.

[0199] In the aforementioned conductive polymer layer, the ratio (Ms / Mp) of the mass Ms of the sugar alcohol to the total mass Mp of the conductive polymer and the dopant is 1 or more and 40 or less.

[0200] (Technology 12)

[0201] According to the manufacturing method of the electrolytic capacitor described in Technique 11, after the above-mentioned step (d), a further step is included to impregnate the liquid component into the voids within the capacitor element.

[0202] (Technology 13)

[0203] According to the method for manufacturing an electrolytic capacitor as described in Technique 11 or 12, the conductive polymer layer comprises a first conductive polymer layer formed on at least one surface and a second conductive polymer layer formed within the voids of the separator.

[0204] At the boundary between the first conductive polymer layer and the second conductive polymer layer, there exists a mixed region where a portion of the first conductive polymer layer and a portion of the second conductive polymer layer are mixed.

[0205] [Example]

[0206] The present disclosure will now be described in more detail based on embodiments, but the disclosure is not limited to these embodiments. In this embodiment, a plurality of electrolytic capacitors are fabricated and evaluated using the following method.

[0207] <Capacitor A1>

[0208] Electrolytic capacitors are made using the following method.

[0209] (a) Preparation of constituent components

[0210] An aluminum foil (100 μm thick) is etched to roughen its surface. The roughened surface is then chemically converted to form a dielectric layer. This yields an anode foil with dielectric layers on both sides.

[0211] The aluminum foil (50 μm thick) was etched to roughen its surface, resulting in a cathode foil.

[0212] As a diaphragm, a nonwoven fabric (50 μm thick) is prepared. The nonwoven fabric consists of 50% by mass synthetic fibers (25% by mass polyester fiber and 25% by mass aramid fiber) and 50% by mass cellulose, containing polyacrylamide as a paper strength reinforcing agent. The density of the nonwoven fabric is 0.35 g / cm³. 3 .

[0213] (b) Preparation of coating solution

[0214] A dispersion (commercially available product) of polyvinyl dioxythiophene (PEDOT) particles doped with polystyrene sulfonic acid (PSS) is prepared in water to be used as a coating solution.

[0215] (c) Formation of a conductive polymer layer

[0216] Using a gravure coating machine, a coating solution is applied to one side of the anode foil (the surface of the dielectric layer). Then, a drying process is performed to form a conductive polymer layer on one side of the anode foil (the surface of the dielectric layer). The drying process is carried out by heating the coated anode foil at 125°C for 5 minutes. Next, a conductive polymer layer is formed on the other side of the anode foil (the surface of the dielectric layer) using the same method.

[0217] A conductive polymer layer is also formed on both sides of the cathode foil using the same method as that used for forming the anode foil. Furthermore, after coating the diaphragm with the solution, a drying process is performed using the same method as that used for forming the anode foil, thereby forming a conductive polymer layer on the diaphragm.

[0218] (d) Fabrication of capacitor components

[0219] The anode foil, cathode foil, and diaphragm are cut to specified sizes. Anode and cathode lead connectors are then attached to the anode and cathode foils. Next, the anode and cathode foils are wound together with the diaphragm in between. The ends of the outer surface of the wound are then secured with a winding retaining tape. Anode and cathode leads are attached to the ends of the lead connectors protruding from the wound. The resulting wound is then subjected to another chemical conversion treatment to form a dielectric layer on the end face of the anode foil. This yields a capacitor element.

[0220] (e) Impregnation of solutions containing sugar alcohols

[0221] Xylitol, a sugar alcohol, is dissolved in ion-exchanged water to prepare an aqueous solution containing xylitol at a specified mass content. Next, the xylitol-containing aqueous solution is impregnated into a capacitor element, thereby concentrating the conductive polymer layer with xylitol.

[0222] The mass content (CX) and ratio (Ms / Mp) of xylitol compound relative to the total mass of PEDOT doped with PSS, Mp and the mass of xylitol compound, Ms, are shown in Table 1.

[0223] (f) Electrolyte infiltration into capacitor elements

[0224] An electrolyte (liquid component) was prepared by dissolving phthalic acid and triethylamine (base component) in ethylene glycol as a solvent at a combined concentration of 25% by mass. The capacitor element was then immersed in the electrolyte for 5 minutes under reduced pressure (40 kPa). This allowed the electrolyte to permeate the capacitor element.

[0225] (g) Sealing of capacitor elements

[0226] The capacitor element impregnated with electrolyte is sealed to manufacture such a process. Figure 1 The solid-liquid hybrid electrolytic capacitor shown is then subjected to aging at 95°C for 90 minutes while a voltage is applied. This yields the electrolytic capacitor (capacitor A1).

[0227] <Capacitors A2, B1~B5>

[0228] Except for omitting the impregnation process of the sugar alcohol-containing solution described in (e) above, so that the conductive polymer layer does not contain sugar alcohol, capacitor B1 is manufactured in the same manner as capacitor A1. Furthermore, except for changing the type of sugar alcohol and the mass content of sugar alcohol in the conductive polymer layer as shown in Table 1, capacitors A2 and B2 to B5 are manufactured in the same manner as capacitor A1. It should be noted that the type and mass content of sugar alcohol in the electrolyte are varied as shown in Table 1.

[0229] (Measurement of electrostatic capacitance and ESR)

[0230] The initial capacitance and initial ESR at 100 kHz were measured using an LCR meter on the aforementioned aged electrolytic capacitors. The measurement temperature was set to 20°C. Additionally, assuming exposure to high temperatures during the reflow soldering (RF) process, the electrolytic capacitors were heated at 200°C–245°C for 70 seconds, and the post-RF ESR was measured to obtain the rate of change relative to the initial ESR (post-RF ESR / initial ESR). The measurement temperature was set to 20°C.

[0231]

[0232] Table 1 shows that by using xylitol compounds, in particular, as the sugar alcohol, electrolytic capacitors with small initial ESR and small rate of change of ESR after RF can be obtained compared with the use of other sugar alcohols.

[0233] <Capacitors A3 to A16>

[0234] Except for changing the xylitol content (CX) in the conductive polymer layer as shown in Table 2, capacitors A3 to A10 are manufactured in the same manner as capacitor A1. Furthermore, except for changing the electrolyte solvent as shown in Table 2, capacitors A11 to A16 are manufactured in the same manner as capacitor A1.

[0235] Table 2 shows the ratio of the mass of xylitol Ms in the conductive polymer layer to the total mass Mp of the conductive polymer and dopants (Ms / Mp), the mass content of xylitol in the conductive polymer layer (CX), and the types of solvents in the electrolyte.

[0236] (ESR measurement after reliability testing)

[0237] For the electrolytic capacitors after the sealing process (aging) of the capacitor elements described in (g) above, a reliability test was conducted by storing them in a constant temperature bath at 145°C for 1000 hours. The ESR of the electrolytic capacitors after the reliability test was measured. The measurement temperature was set to 20°C. The measurement results are shown in Table 2. It should be noted that in Table 2, the ESR values ​​of capacitors A4 to A16 after the reliability test are expressed as a ratio to the ESR of capacitor A3 after the reliability test.

[0238]

[0239] The results in Table 2 demonstrate that by including xylitol compounds in the conductive polymer layer at a ratio (Ms / Mp) of 1 or more and 40 or less, a solid-liquid hybrid electrolytic capacitor with a low ESR after reliability testing can be obtained. In particular, it is shown that by including xylitol compounds in the conductive polymer layer at a ratio (Ms / Mp) of 10 or more and 20 or less, a solid-liquid hybrid electrolytic capacitor with an even lower ESR after reliability testing can be obtained.

[0240] Furthermore, as a solvent in the electrolyte, among capacitors A11 using DEG, A12 using TEG, and A14 using GLC, compared to capacitor A7 using EG, solid-liquid hybrid electrolytic capacitors with lower ESR after reliability testing can be obtained.

[0241] <Capacitors A17 to A24>

[0242] Except for omitting the electrolyte impregnation process of capacitor element described in (f) above, solid electrolyte type electrolytic capacitors (capacitors A17 to A24) were manufactured using the same method as capacitor A1.

[0243] Table 1 shows the ratio of the mass Ms of xylitol in the conductive polymer layer to the total mass Mp of the conductive polymer and dopants (Ms / Mp), and the mass content of xylitol in the conductive polymer layer (CX).

[0244] (ESR measurement after reliability testing)

[0245] Perform reliability tests in the same manner as described above. Measure the ESR of the electrolytic capacitors after the reliability tests. The measurement temperature is set to 20°C. The measurement results are shown in Table 3. It should be noted that in Table 3, the ESR values ​​of capacitors A18 to A24 after the reliability tests are expressed as a ratio to the ESR of capacitor A17 after the reliability tests.

[0246] [Table 3]

[0247]

[0248] The results in Table 3 demonstrate that by including xylitol compounds in the conductive polymer layer at a ratio (Ms / Mp) of 1 or more and 40 or less, a solid electrolyte electrolytic capacitor with a low ESR after reliability testing can be obtained. In particular, it is shown that by including xylitol compounds in the conductive polymer layer at a ratio (Ms / Mp) of 10 or more and 40 or less, a solid electrolyte electrolytic capacitor with an even lower ESR after reliability testing can be obtained.

[0249] <Capacitors A25 to A28>

[0250] The liquid component was prepared by dissolving xylitol in ethylene glycol (solvent) at the mass content (CY) shown in Table 4. The capacitor element was immersed in the liquid component for 5 minutes under reduced pressure (40 kPa). This allowed the liquid component to permeate the capacitor element. In addition, capacitors A25 to A28 of the embodiments were manufactured in the same manner as capacitors A19 and A21.

[0251] Table 4 shows the ratio of the mass of xylitol Ms in the conductive polymer layer to the total mass Mp of the conductive polymer and dopants (Ms / Mp), the mass content of xylitol in the conductive polymer layer (CX), the type of solvent in the liquid component, and the mass content of xylitol in the liquid component (CY).

[0252] (ESR measurement after reliability testing)

[0253] Perform reliability testing in the same manner as described above. Measure the ESR of the electrolytic capacitors after the reliability test. The measurement temperature is set to 20°C. The measurement results are shown in Table 4. It should be noted that in Table 4, the ESR values ​​of capacitors A25 to A28 after the reliability test are expressed as a ratio to the ESR of capacitor A3 in Table 2.

[0254] [Table 4]

[0255]

[0256] The results in Table 4 show that by also including xylitol compounds in the electrolyte, a solid-liquid hybrid electrolytic capacitor with a lower ESR after reliability testing can be obtained.

[0257] The above results can be considered helpful in suppressing the precipitation of sugar alcohols in the manufacturing process and the completed electrolytic capacitor.

[0258] Industrial availability

[0259] This disclosure can be used for solid electrolyte type capacitors and solid-liquid hybrid type electrolytic capacitors.

[0260] Explanation of reference numerals in the attached figures

[0261] 10: Capacitor Components

[0262] 11: Anode foil

[0263] 12: Cathode foil

[0264] 13: Diaphragm

[0265] 14: Winding and fixing tape

[0266] 100: Electrolytic capacitor

[0267] 101: Bottom shell

[0268] 102: Sealing components

[0269] 103: Seat board

[0270] 104A, 104B: Lead wires

[0271] 105A, 105B: Lead wire connectors

Claims

1. An electrolytic capacitor comprising a capacitor element, the capacitor element having: an anode foil having a dielectric layer, a cathode foil, a separator between the anode foil and the cathode foil, and a conductive polymer layer between the anode foil and the cathode foil and in contact with the separator. The conductive polymer layer comprises a conductive polymer, a dopant, and a sugar alcohol. The sugar alcohol is selected from at least one of xylitol and xylitol derivatives. In the conductive polymer layer, the ratio of the mass Ms of the sugar alcohol to the total mass Mp of the conductive polymer and the dopant, i.e., Ms / Mp, is greater than 1 and less than 40.

2. The electrolytic capacitor according to claim 1, wherein, The ratio Ms / Mp is greater than 5 and less than 20.

3. The electrolytic capacitor according to claim 1, wherein, The mass content of the sugar alcohol in the conductive polymer layer is greater than the mass content of all other components in the conductive polymer layer.

4. The electrolytic capacitor according to claim 1, wherein, The mass content of the sugar alcohol in the conductive polymer layer is more than 50% by mass and less than 98% by mass.

5. The electrolytic capacitor according to claim 1, wherein, The conductive polymer layer is formed on at least one surface selected from the surface of the dielectric layer and the surface of the cathode foil, and is formed within the voids of the diaphragm.

6. The electrolytic capacitor according to claim 1, further comprising liquid components contained in the voids within the capacitor element.

7. The electrolytic capacitor according to claim 6, wherein, The liquid component comprises at least one selected from ethylene glycol, diethylene glycol, triethylene glycol, ethylene glycol condensates with a molecular weight of less than 250, glycerol, γ-butyrolactone, and sulfolane.

8. A method for manufacturing an electrolytic capacitor, comprising the following steps: Step (a): Prepare an anode foil, a cathode foil, and a diaphragm with dielectric layers; Step (b) involves applying a coating containing a conductive polymer, a dopant, and a liquid medium to at least one surface selected from the surface of the dielectric layer and the surface of the cathode foil, as well as to the voids of the diaphragm. Step (c) involves removing at least a portion of the liquid medium from the coating liquid, thereby forming a conductive polymer layer within the voids of the at least one surface and the diaphragm. Step (d) involves forming a capacitor element comprising the conductive polymer layer by disposing the diaphragm between the anode foil and the cathode foil; as well as Step (e) involves impregnating the capacitor element with a solution containing sugar alcohol, thereby concentrating the conductive polymer layer with the sugar alcohol. The sugar alcohol is selected from at least one of xylitol and xylitol derivatives. In the conductive polymer layer, the ratio of the mass Ms of the sugar alcohol to the total mass Mp of the conductive polymer and the dopant, i.e., Ms / Mp, is greater than 1 and less than 40.

9. The method for manufacturing an electrolytic capacitor according to claim 8, wherein, The process following step (e) further includes a step of permeating the liquid component into the voids within the capacitor element.

10. The method for manufacturing an electrolytic capacitor according to claim 8, wherein, The conductive polymer layer comprises a first conductive polymer layer formed on the at least one surface and a second conductive polymer layer formed within the voids of the membrane. At the boundary between the first conductive polymer layer and the second conductive polymer layer, there exists a mixed region where a portion of the first conductive polymer layer and a portion of the second conductive polymer layer are mixed.

11. A method for manufacturing an electrolytic capacitor, comprising the following steps: Step (a): Prepare an anode foil, a cathode foil, and a diaphragm with dielectric layers; Step (b) involves applying a coating solution containing a conductive polymer, a dopant, a sugar alcohol, and a liquid medium to at least one surface selected from the surface of the dielectric layer and the surface of the cathode foil, as well as to the voids of the diaphragm. Step (c) involves removing at least a portion of the liquid medium from the coating liquid, thereby forming a conductive polymer layer within the voids of the at least one surface and the diaphragm. as well as Step (d) involves forming a capacitor element comprising the conductive polymer layer by distributing the diaphragm between the anode foil and the cathode foil. The sugar alcohol is selected from at least one of xylitol and xylitol derivatives. In the conductive polymer layer, the ratio of the mass Ms of the sugar alcohol to the total mass Mp of the conductive polymer and the dopant, i.e., Ms / Mp, is greater than 1 and less than 40.

12. The method for manufacturing an electrolytic capacitor according to claim 11, wherein, The process following step (d) further includes a step of permeating the liquid component into the voids within the capacitor element.

13. The method for manufacturing an electrolytic capacitor according to claim 11, wherein, The conductive polymer layer comprises a first conductive polymer layer formed on the at least one surface and a second conductive polymer layer formed within the voids of the membrane. At the boundary between the first conductive polymer layer and the second conductive polymer layer, there exists a mixed region where a portion of the first conductive polymer layer and a portion of the second conductive polymer layer are mixed.

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