Electrolytic capacitor and its manufacturing method

Abstract

This electrolytic capacitor includes a positive electrode body (21), a dielectric layer which is formed on the positive electrode body (21), a negative electrode body (22), and a separator (23) and electrolyte which are arranged between the dielectric layer and the negative electrode body (22). At least part of the separator (23) is covered by a metal oxide having conductivity.

Description

[Technical Field]

[0001] The present disclosure relates to electrolytic capacitors and methods for manufacturing the same. [Background technology]

[0002] Electrolytic capacitors are used in a variety of fields. In recent years, electrolytic capacitors have been required to have high reliability, and in particular, to be less susceptible to deterioration at high temperatures.

[0003] Patent Document 1 (WO 2015 / 033566) discloses "an electricity storage device comprising: an anode body, a cathode body facing the anode body, a separator that includes a separator substrate and a conductive polymer coated on the separator substrate and is interposed between the anode body and the cathode body; and an electrolyte solution impregnated into the electricity storage element, wherein the separator has a first surface layer that includes a first surface facing the anode body and a second surface layer that includes a second surface facing the cathode body, the first surface layer having a first region where the conductive polymer is not coated, and the second surface layer having a second region where the conductive polymer is coated."

[0004] Patent Document 2 (JP 2007-149733 A) discloses "a wound electrolytic capacitor comprising an anode foil, a separator, and a cathode material, characterized in that the cathode material is a separator having a conductive thin film formed on one side thereof." Patent Document 2 also states that "In the present invention, a conductive thin film is formed on one side of the separator, which functions as both a separator and a cathode, making the conventional cathode foil unnecessary, and the configuration of anode foil, separator, cathode foil, and separator can be changed to a configuration of anode foil, separator, and one-sided conductive separator, thereby reducing the thickness per winding. This makes it possible to achieve a smaller size than conventional wound electrolytic capacitors." [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2015 / 033566 [Patent Document 2] Japanese Patent Application Laid-Open No. 2007-149733 Summary of the Invention [Problem to be solved by the invention]

[0006] Currently, there is a demand for electrolytic capacitors whose characteristics do not deteriorate much even at high temperatures. In particular, there is a demand for electrolytic capacitors whose equivalent series resistance (ESR) does not increase much even at high temperatures. In this situation, one of the objects of the present disclosure is to provide an electrolytic capacitor whose characteristics do not deteriorate much even at high temperatures. [Means for solving the problem]

[0007] One aspect of the present disclosure relates to an electrolytic capacitor including an anode body, a dielectric layer formed on the anode body, a cathode body, a separator and an electrolyte disposed between the dielectric layer and the cathode body, and at least a portion of the separator is coated with an electrically conductive metal oxide.

[0008] Another aspect of the present disclosure relates to a method for manufacturing an electrolytic capacitor including an anode body, a dielectric layer formed on the anode body, a cathode body, a separator, and an electrolyte, the method including step (i) of forming a capacitor element by disposing the anode body, the cathode body, the separator, and the electrolyte such that the separator and the electrolyte are disposed between the dielectric layer and the cathode body, and at least a portion of the separator is coated with a conductive metal oxide. [Effects of the Invention]

[0009] According to the present disclosure, an electrolytic capacitor can be obtained that exhibits little deterioration in characteristics even at high temperatures. The novel features of the present invention are set forth in the appended claims, but the present invention, both in terms of structure and content, together with other objects and features of the present invention, will be better understood from the following detailed description taken in conjunction with the drawings. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a cross-sectional view schematically illustrating an example of an electrolytic capacitor according to the present disclosure. [Figure 2] FIG. 2 is a diagram schematically illustrating a part of the electrolytic capacitor shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0011] Examples of embodiments according to the present disclosure are described below. Note that in the following description, examples of embodiments of the present disclosure are given, but the present disclosure is not limited to the examples described below. In the following description, specific numerical values ​​and materials may be used as examples, but other numerical values ​​and other materials may be used as long as the effects of the present disclosure are obtained. In this specification, when a "range between numerical value A and numerical value B" is mentioned, the range includes numerical value A and numerical value B.

[0012] (electrolytic capacitor) The electrolytic capacitor according to this embodiment includes an anode body, a dielectric layer formed on the anode body, a cathode body, and a separator and electrolyte disposed between the dielectric layer and the cathode body. At least a portion of the separator is coated with a conductive metal oxide. Hereinafter, the metal oxide may be referred to as "metal oxide (M)."

[0013] As a result of further investigation, the present inventors have newly discovered that the use of a separator coated with a metal oxide (M) makes it possible to obtain an electrolytic capacitor that exhibits less degradation at high temperatures. The present disclosure is based on this new finding. Among conductive metal oxides (M), there are some, such as indium tin oxide, that exhibit higher conductivity than the conductive polymers described below. Furthermore, metal oxides (M) have high heat resistance and exhibit less degradation of conductivity due to heat. Therefore, the use of a separator coated with a metal oxide (M) makes it possible to obtain an electrolytic capacitor that exhibits less degradation at high temperatures (for example, an increase in ESR).

[0014] Furthermore, by coating the separator with a metal oxide (M), the strength and heat resistance of the separator can be increased. Therefore, the electrolytic capacitor of the present disclosure can prevent the plate gap between the anode body and the cathode body from narrowing due to thermal deterioration of the separator. As a result, it is possible to prevent deterioration of characteristics due to heat (such as a decrease in breakdown voltage and an increase in leakage current).

[0015] The metal oxide (M) may be attached to the separator in a particulate state or in a layered state.

[0016] The metal oxide (M) includes an oxide of at least one element selected from the group consisting of indium, tin, antimony, and zinc. Examples of the metal oxide (M) include indium tin oxide (ITO), zinc oxide (ZnO), antimony-doped tin oxide (ATO), etc.

[0017] The separator may contain or consist of synthetic fibers. Synthetic fibers are preferred because they have high heat resistance. Synthetic fibers are also preferred because they have high resistance in the process of forming the metal oxide (M). Examples of synthetic fiber materials include polyethylene terephthalate, polybutylene terephthalate, polyphenylene sulfide, vinylon, nylon, aromatic polyamide (aramid), polyimide, polyamideimide, polyetherimide, etc. Among these, aromatic polyamide and nylon are preferred because they have high heat resistance. Alternatively, the separator may contain or consist of natural fibers. Examples of natural fiber materials include cellulose, etc.

[0018] The air permeability (air resistance) of the separator may be in the range of 1.0 to 200 seconds / 100 mL (e.g., 1.5 to 100 seconds / 100 mL). By setting the air permeability in this range, the metal oxide (M) can be more uniformly formed on the fiber surface inside the separator, thereby increasing the conductivity inside the separator. Here, the air permeability can be measured, for example, using a type B tester (Gurley densometer) in accordance with Section 21.2, "Air Permeability Method B (Gurley Test Method)," as specified in JIS C2300.

[0019] The density of the separator may be substantially uniform throughout the separator or may vary depending on the location of the separator. For example, the density of the portion of the separator facing the anode body may be different from the density of the portion of the separator facing the cathode body. In one example, the density of the portion of the separator facing the anode body is higher than the density of the portion of the separator facing the cathode body. In another example, the density of the portion of the separator facing the anode body is lower than the density of the portion of the separator facing the cathode body. Here, high density can be interpreted as low porosity, and low density can be interpreted as high porosity. The lower the density of the portion, the more easily the metal oxide (M) penetrates into the separator when it is formed.

[0020] The separator having different densities depending on the location may be formed by a known method, or a commercially available separator may be used.

[0021] The electrolyte may contain an electrolytic solution and a conductive polymer. With this configuration, the conductive polymer can further reduce the electrical resistance between the anode body and the cathode body. Examples of the electrolytic solution and the conductive polymer will be described later.

[0022] Alternatively, the electrolyte may be composed of an electrolytic solution without including a conductive polymer. The electrolytic capacitor according to the present disclosure uses a separator coated with a conductive metal oxide (M). Therefore, the electrolytic capacitor according to the present disclosure can achieve good characteristics (e.g., low ESR) even without a conductive polymer. When a conductive polymer is used, it is usually necessary to use an electrolyte solution that is less susceptible to dedoping in order to avoid dedoping from the conductive polymer. On the other hand, when a conductive polymer is not used, there are fewer restrictions on the electrolyte solution. For example, when a conductive polymer is not used, it becomes easier to use an electrolyte solution with a pH close to neutral or an electrolyte salt with a high concentration.

[0023] When the electrolyte is composed of an electrolytic solution that does not contain a conductive polymer, it is possible to use a separator with a low porosity (a high-density separator) that is difficult to impregnate with the conductive polymer. By using a separator with a low porosity, the metal oxide (M) can be formed more uniformly on the fiber surface inside the separator, thereby increasing the conductivity inside the separator. The porosity of a separator with a low porosity may be in the range of 20% to 80% (for example, in the range of 40% to 70%).

[0024] The cathode body preferably contains a metal foil. Examples of metal foils will be described later. When the cathode body contains a metal foil, it is possible to reduce the ESR and increase the capacity. In the electrolytic capacitor of the present disclosure, at least a portion of the separator is coated with a metal oxide (M), which particularly reduces the contact resistance between the separator and the cathode body (or, from another perspective, the contact resistance between the electrolyte and the cathode body).

[0025] A conductive layer containing at least one element selected from the group consisting of carbon, titanium, and nickel may be formed on the surface of the cathode body facing the separator. This configuration can improve adhesion between the separator and the cathode body, particularly reducing the contact resistance between them. As a result, the ESR can be reduced. These conductive layers may be formed using a paste containing particles of these materials (e.g., graphite particles or metal particles), or may be formed by a dry process (such as vapor deposition or sputtering).

[0026] The amount of metal oxide (M) covering the portion of the separator facing the cathode body may be greater than the amount of metal oxide (M) covering the portion of the separator facing the anode body. This configuration can particularly reduce the contact resistance between the separator and the cathode body.

[0027] The amount of metal oxide (M) coating the separator may be approximately uniform in the thickness direction of the separator, or may be approximately uniform across the entire separator. By coating the entire separator with metal oxide (M), ESR and the like can be particularly reduced.

[0028] Examples of components of the electrolytic capacitor are described below, but the components of the electrolytic capacitor according to the present disclosure are not limited to the following examples.

[0029] (anode body) The anode body may be a metal foil having a dielectric layer formed on its surface. The type of metal constituting the metal foil is not particularly limited. Because the dielectric layer can be easily formed, examples of metals constituting the metal foil include valve metals such as aluminum, tantalum, niobium, and titanium, and alloys of valve metals. Preferred examples are aluminum and aluminum alloys. The surface of the anode body is usually roughened (porous). In this case, a dielectric layer is formed on at least a portion of the surface of the porous portion (roughened surface). The electrolyte is in contact with the dielectric layer.

[0030] (cathode body) The cathode body may be made of a metal foil. The type of metal constituting the metal foil is not particularly limited. Examples of metals constituting the metal foil include valve-acting metals such as aluminum, tantalum, niobium, and titanium, and alloys of valve-acting metals. Preferred examples are aluminum and aluminum alloys. The surface of the cathode body may be provided with a chemical conversion coating, or may be provided with a coating of a metal (dissimilar metal) or a nonmetal different from the metal constituting the cathode body. Examples of dissimilar metals and nonmetals include metals such as titanium and nonmetals such as carbon.

[0031] (separator) The separator may be a sheet-like material that can be impregnated with an electrolyte. For example, a sheet-like material that has insulating properties and can be impregnated with an electrolyte may be used. The separator may be a woven fabric, a nonwoven fabric, or a porous membrane. In any case, the separator has voids. Examples of separator materials include cellulose, polyethylene terephthalate, polybutylene terephthalate, polyphenylene sulfide, vinylon, nylon, aromatic polyamide, polyimide, polyamideimide, polyetherimide, rayon, and glass.

[0032] (electrolyte) The electrolyte of the electrolytic capacitor of the present disclosure typically contains a nonaqueous solvent. The electrolyte may contain an electrolytic solution (nonaqueous electrolytic solution) containing a nonaqueous solvent and a base component dissolved in the nonaqueous solvent, or may be composed of such an electrolytic solution. That is, the electrolyte of the electrolytic capacitor of the present disclosure may contain a liquid component. Hereinafter, the liquid component (nonaqueous solvent or electrolytic solution) contained in the electrolyte may be referred to as the "liquid component (L)." In this specification, the liquid component (L) may be a component that is liquid at room temperature (25°C) or at the temperature at which the electrolytic capacitor is used.

[0033] The non-aqueous solvent contained in the electrolyte may be an organic solvent or an ionic liquid. Examples of the non-aqueous solvent include polyhydric alcohols such as ethylene glycol and propylene glycol, cyclic sulfones such as sulfolane (SL), lactones such as γ-butyrolactone (γBL), amides such as N-methylacetamide, N,N-dimethylformamide, and N-methyl-2-pyrrolidone, esters such as methyl acetate, carbonate compounds such as propylene carbonate, ethers such as 1,4-dioxane, ketones such as methyl ethyl ketone, and formaldehyde.

[0034] Furthermore, a polymer solvent may be used as the non-aqueous solvent. Examples of polymer solvents include polyalkylene glycol, polyalkylene glycol derivatives, and compounds in which at least one hydroxyl group in a polyhydric alcohol has been substituted with polyalkylene glycol (including derivatives). Specific examples of polymer solvents include polyethylene glycol (PEG), polyethylene glycol glyceryl ether, polyethylene glycol diglyceryl ether, polyethylene glycol sorbitol ether, polypropylene glycol, polypropylene glycol glyceryl ether, polypropylene glycol diglyceryl ether, polypropylene glycol sorbitol ether, and polybutylene glycol. Further examples of polymer solvents include ethylene glycol-propylene glycol copolymer, ethylene glycol-butylene glycol copolymer, and propylene glycol-butylene glycol copolymer. One type of non-aqueous solvent may be used alone, or two or more types may be used in combination.

[0035] As described above, the electrolyte may include a non-aqueous solvent and a basic component (base) dissolved in the non-aqueous solvent. Alternatively, the electrolyte may include a non-aqueous solvent and a basic component and / or an acid component (acid) dissolved in the non-aqueous solvent.

[0036] The acid component can be a polycarboxylic acid or a monocarboxylic acid. Examples of the polycarboxylic acid include aliphatic polycarboxylic acids (saturated polycarboxylic acids such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, 1,6-decanedicarboxylic acid, and 5,6-decanedicarboxylic acid; unsaturated polycarboxylic acids such as maleic acid, fumaric acid, and icosanoic acid), aromatic polycarboxylic acids (phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, and pyromellitic acid), and alicyclic polycarboxylic acids (cyclohexane-1,2-dicarboxylic acid and cyclohexene-1,2-dicarboxylic acid).

[0037] Examples of the monocarboxylic acid include aliphatic monocarboxylic acids (having 1 to 30 carbon atoms) ([saturated monocarboxylic acids such as formic acid, acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, lauric acid, myristic acid, stearic acid, and behenic acid]; [unsaturated monocarboxylic acids such as acrylic acid, methacrylic acid, and oleic acid]), aromatic monocarboxylic acids (such as benzoic acid, cinnamic acid, and naphthoic acid), and oxycarboxylic acids (such as salicylic acid, mandelic acid, and resorcylic acid).

[0038] Among these, maleic acid, phthalic acid, benzoic acid, pyromellitic acid, and resorcylic acid are thermally stable and are therefore preferably used.

[0039] The acid component may be an inorganic acid and / or an organic acid. Typical examples of inorganic acids include phosphoric acid, phosphorous acid, hypophosphorous acid, boric acid, fluoroboric acid, tetrafluoroboric acid, and hexafluorophosphoric acid. Typical examples of organic acids include alkanesulfonic acids such as methanesulfonic acid, alkanolsulfonic acids such as phenolsulfonic acid and cresolsulfonic acid, benzenesulfonic acid, naphthalenesulfonic acid, alkyl phosphate esters, benzenesulfonic acid, and naphthalenesulfonic acid. Alternatively, a composite compound of an organic acid and an inorganic acid may be used as the acid component. Examples of such a composite compound include borodiglycolic acid, borodisalic acid, and borodisalicylic acid.

[0040] The base component may be a compound having an alkyl-substituted amidine group, such as an imidazole compound, a benzimidazole compound, or an alicyclic amidine compound (a pyrimidine compound, an imidazoline compound). Specifically, 1,8-diazabicyclo[5,4,0]undecene-7, 1,5-diazabicyclo[4,3,0]nonene-5, 1,2-dimethylimidazolinium, 1,2,4-trimethylimidazoline, 1-methyl-2-ethyl-imidazoline, 1,4-dimethyl-2-ethylimidazoline, 1-methyl-2-heptylimidazoline, 1-methyl-2-(3'heptyl)imidazoline, 1-methyl-2-dodecylimidazoline, 1,2-dimethyl-1,4,5,6-tetrahydropyrimidine, 1-methylimidazole, or 1-methylbenzimidazole is preferred. By using these, a capacitor with excellent impedance performance can be obtained.

[0041] The base component may be a quaternary salt of a compound having an alkyl-substituted amidine group. Examples of such base components include imidazole compounds, benzimidazole compounds, and alicyclic amidine compounds (pyrimidine compounds, imidazoline compounds) quaternized with an alkyl group or arylalkyl group having 1 to 11 carbon atoms. Specifically, 1-methyl-1,8-diazabicyclo[5,4,0]undecene-7, 1-methyl-1,5-diazabicyclo[4,3,0]nonene-5, 1,2,3-trimethylimidazolinium, 1,2,3,4-tetramethylimidazolinium, 1,2-dimethyl-3-ethyl-imidazolinium, 1,3,4-trimethyl-2-ethylimidazolinium, 1,3-dimethyl-2-heptylimidazolinium, 1,3-dimethyl-2-(3'heptyl)imidazolinium, 1,3-dimethyl-2-dodecylimidazolinium, 1,2,3-trimethyl-1,4,5,6-tetrahydropyrimidium, 1,3-dimethylimidazolium, 1-methyl-3-ethylimidazolium, and 1,3-dimethylbenzimidazolium are preferred. By using these, a capacitor with excellent impedance performance can be obtained.

[0042] Tertiary amines may also be used as the base component. Examples of tertiary amines include trialkylamines (trimethylamine, dimethylethylamine, methyldiethylamine, triethylamine, dimethyl-n-propylamine, dimethylisopropylamine, methylethyl-n-propylamine, methylethylisopropylamine, diethyl-n-propylamine, diethylisopropylamine, tri-n-propylamine, triisopropylamine, tri-n-butylamine, tri-tert-butylamine, etc.), and phenyl group-containing amines (dimethylphenylamine, methylethylphenylamine, diethylphenylamine, etc.). Among these, trialkylamines are preferred in terms of increasing the conductivity of the electrolyte, and it is more preferable to use at least one selected from the group consisting of trimethylamine, dimethylethylamine, methyldiethylamine, and triethylamine. Secondary amines such as dialkylamines, primary amines such as monoalkylamines, and ammonia may also be used as the base component.

[0043] The liquid component (L) may contain a salt of an acid component and a base component. The salt may be an inorganic salt and / or an organic salt. An organic salt is a salt in which at least one of the anion and the cation contains an organic substance. Examples of organic salts that may be used include trimethylamine maleate, triethylamine borodisalicylate, ethyldimethylamine phthalate, mono-1,2,3,4-tetramethylimidazolinium phthalate, and mono-1,3-dimethyl-2-ethylimidazolinium phthalate.

[0044] In the electrolytic capacitor of the present disclosure, the amount of the base component in the electrolyte may be 0.1% by mass or more and 20% by mass or less. When the amount of the base component is 0.1% by mass or more, it is particularly important to use conductive particles. Furthermore, by setting the amount of the base component to 20% by mass or less, it becomes easier to dissolve the base component in the electrolyte.

[0045] A low ESR is important for electrolytic capacitors. A low ESR can be achieved by using an electrolyte containing a conductive polymer doped with a dopant. However, when an electrolyte containing a conductive polymer doped with a dopant and a liquid component (L) is used, the initial ESR is low, but the ESR may increase over time. To suppress such an increase in ESR, an electrolyte that does not contain a conductive polymer may be used. Alternatively, an electrolyte solution that is less likely to cause de-dopantization may be used. To achieve these, it is preferable to use a separator coated with a metal oxide (M).

[0046] The electrolyte may contain a conductive polymer in addition to the liquid component (L) (e.g., an electrolyte solution). Examples of conductive polymers include polypyrrole, polythiophene, polyfuran, polyaniline, polyacetylene, and derivatives thereof. Such derivatives include polymers having polypyrrole, polythiophene, polyfuran, polyaniline, and polyacetylene as their basic skeletons. For example, a polythiophene derivative includes poly(3,4-ethylenedioxythiophene). These conductive polymers may be used alone or in combination. The conductive polymer may also be a copolymer of two or more monomers. The weight-average molecular weight of the conductive polymer is not particularly limited and may be, for example, in the range of 1,000 to 100,000. A preferred example of the conductive polymer is poly(3,4-ethylenedioxythiophene) (PEDOT).

[0047] The conductive polymer may be doped with a dopant. From the viewpoint of suppressing dedoping from the conductive polymer, it is preferable to use a polymer dopant as the dopant. Examples of polymer dopants include polyvinyl sulfonic acid, polystyrene sulfonic acid, polyallyl sulfonic acid, polyacrylic sulfonic acid, polymethacrylic sulfonic acid, poly(2-acrylamido-2-methylpropane sulfonic acid), polyisoprene sulfonic acid, polyacrylic acid, etc. These may be used alone or in combination of two or more. These may be contained in the electrolyte in the form of a salt. A preferred example of the dopant is polystyrene sulfonic acid (PSS).

[0048] In the electrolytic capacitor of the present disclosure, the dopant may be a dopant containing an acidic group or a polymeric dopant containing an acidic group. Examples of the acidic group include a sulfonic acid group and a carboxyl group. The polymeric dopant containing an acidic group is a polymer in which at least some of the constituent units contain an acidic group. Examples of such polymeric dopants include the polymeric dopants described above.

[0049] The weight-average molecular weight of the dopant is not particularly limited, but may be in the range of 1,000 to 100,000 in order to facilitate the formation of a homogeneous electrolyte.

[0050] In the electrolytic capacitor of the present disclosure, the dopant may be polystyrene sulfonic acid, and the conductive polymer may be poly(3,4-ethylenedioxythiophene). That is, the electrolyte may include poly(3,4-ethylenedioxythiophene) doped with polystyrene sulfonic acid.

[0051] When a conductive polymer doped with a dopant is used, the pH of the liquid component (L) may be less than 7, or may be 5 or less (for example, in the range of 2 to 4.5) in order to prevent the dopant from being dedoped.

[0052] (Method of manufacturing electrolytic capacitors) A method of the present disclosure for manufacturing an electrolytic capacitor is described below. This manufacturing method allows the electrolytic capacitor of the present disclosure to be manufactured. The details of the electrolytic capacitor of the present disclosure are applicable to the manufacturing method described below, and therefore, redundant descriptions may be omitted. For example, the components of the capacitor element have been described above, and therefore, redundant descriptions may be omitted. Furthermore, the details of the manufacturing method described below are applicable to the electrolytic capacitor described above.

[0053] A manufacturing method according to the present disclosure is a method for manufacturing an electrolytic capacitor including an anode body, a dielectric layer formed on the anode body, a cathode body, a separator, and an electrolyte. The manufacturing method includes step (i) of forming a capacitor element by arranging the anode body, the cathode body, the separator, and the electrolyte such that the separator and the electrolyte are disposed between the dielectric layer and the cathode body. As described above, at least a portion of the separator is coated with a conductive metal oxide (M).

[0054] Step (i) is not particularly limited, and a known method may be applied. An example of step (i) may include step (ia) of arranging an anode body, a cathode body, and a separator such that the separator is disposed between the dielectric layer and the cathode body, and step (ib) of impregnating the separator with an electrolyte. In step (ib), the electrolyte is disposed between the dielectric layer and the cathode body. An example of step (ia) is performed by stacking or winding a foil-shaped anode body, a foil-shaped cathode body, and a separator such that the separator is disposed between the anode body on which the dielectric layer is formed and the cathode body. That is, the capacitor element may be a stacked type or a wound type.

[0055] Step (ib) may be performed by immersing the structure (such as a laminate or a wound structure) formed in step (ia) in an electrolyte (e.g., an electrolytic solution). When the electrolyte contains a conductive polymer (and a dopant as needed), step (ib) may be performed by immersing the structure formed in step (ia) in a dispersion liquid in which the conductive polymer (and a dopant as needed) is dispersed. The dispersion medium for the dispersion liquid is not particularly limited, and a known dispersion medium may be used. For example, an aqueous liquid containing water or water may be used as the dispersion medium. The immersion step (the impregnation step of step (ib)) may be performed once or multiple times. A heat treatment step may be performed after the immersion step.

[0056] After the separator is impregnated with the conductive polymer, a step of impregnating the separator with the liquid component (L) may be carried out. The impregnation method is not particularly limited, and a known method may be used. For example, a structure (such as a laminate or a wound body) in which the conductive polymer is disposed may be immersed in a non-aqueous solvent (or an electrolytic solution).

[0057] The manufacturing method according to the present disclosure may include, in this order, steps (a) and (b) before step (i). Step (a) is a step of coating at least a portion of a sheet that will become a separator after cutting with a metal oxide (M). Step (b) is a step of cutting the sheet to form a separator.

[0058] There are no particular limitations on step (a), and known methods may be used. For example, a dry process (such as sputtering or vapor deposition) or a wet process (a process using a treatment liquid) may be used. Since both dry and wet processes are known as methods for forming indium tin oxide, zinc oxide, and antimony-doped tin oxide, these methods may also be used. When at least a portion of the separator is coated with a metal oxide (M) by a dry process, it is easy to make the amount of metal oxide (M) attached to one side of the separator greater than the amount of metal oxide (M) attached to the other side of the separator.

[0059] Examples of wet processes include gravure coating, slot die coating, bank coating, inkjet coating, and immersion coating. By using a wet process, it is possible to coat the entire separator with the metal oxide (M). In a preferred example, the entire separator is coated with the metal oxide (M) with a substantially uniform coating amount. On the other hand, by using a separator with different porosity (density) depending on the part, it is possible to unevenly distribute the metal oxide (M) even with a wet process.

[0060] The production method according to the present disclosure may include a step of crystallizing the metal oxide (M) after step (a) (e.g., between steps (a) and (b)). Crystallizing the metal oxide (M) (e.g., indium tin oxide) can increase the electrical conductivity of the metal oxide (M). Crystallization can be carried out, for example, by heat-treating the sheet coated with the metal oxide (M) in step (a). The conditions for the heat treatment are selected depending on the type of metal oxide (M). For example, when the metal oxide (M) is indium tin oxide, the heat treatment may be carried out at a temperature in the range of 150 to 300°C for 1 to 60 minutes.

[0061] In step (a), at least a portion of the sheet may be coated with the metal oxide (M) between the sheet-feeding roll and the sheet-winding roll. This configuration allows the metal oxide (M) to be efficiently attached to the sheet. A so-called roll-to-roll method can be applied to this method. In this case, the coating with the metal oxide (M) may be performed by a dry process or a wet process. In the dry process, the coating with the metal oxide (M) is usually performed in a decompression chamber. In this case, the sheet-feeding roll and the sheet-winding roll may be placed in a decompression chamber.

[0062] The capacitor element formed in step (i) is optionally connected to leads, sealed with a sealing resin, or enclosed in a case, thereby completing the production of an electrolytic capacitor.

[0063] Examples of electrolytic capacitors according to the present disclosure will be described in detail below with reference to the drawings, but the electrolytic capacitors of the present disclosure are not limited to the drawings. The components described above can be applied to the components of the example electrolytic capacitor described below. Furthermore, the components of the example electrolytic capacitor described below can be modified based on the above description. Furthermore, the matters described below may be applied to the above-described embodiments.

[0064] (Embodiment 1) In embodiment 1, an example of an electrolytic capacitor according to the present disclosure will be described. This electrolytic capacitor is an electrolytic capacitor including a first capacitor element. Fig. 1 schematically shows a cross section of an example of an electrolytic capacitor 100 according to embodiment 1. Fig. 2 shows a schematic view of a portion of a capacitor element 10 included in the electrolytic capacitor 100 shown in Fig. 1, in which the capacitor element 10 is partially expanded.

[0065] 1, electrolytic capacitor 100 includes capacitor element 10, bottomed case 11 that houses capacitor element 10, sealing member 12 that closes the opening of bottomed case 11, seat plate 13 that covers sealing member 12, lead wires 14A and 14B that extend from sealing member 12 and pass through seat plate 13, and lead tabs 15A and 15B that connect lead wires 14A and 14B to electrodes of capacitor element 10. Capacitor element 10 is housed in bottomed case 11. The vicinity of the open end of bottomed case 11 is drawn inward, and the open end of bottomed case 11 is curled so as to crimp sealing member 12.

[0066] Referring to Fig. 2, capacitor element 10 includes a foil-shaped anode body 21 having a dielectric layer (not shown) formed on its surface, a foil-shaped cathode body 22, and a separator 23 and an electrolyte (not shown) disposed therebetween. Anode body 21 and cathode body 22 are wound with separator 23 disposed therebetween. The outermost periphery of the wound body is fixed with a stop tape 24. Note that Fig. 2 shows a partially unfolded state of the wound body before the outermost periphery is fixed. As described above, at least a portion of separator 23 is coated with a metal oxide (M). [Industrial Applicability]

[0067] The present disclosure can be used for an electrolytic capacitor and a manufacturing method thereof. While the present invention has been described in terms of presently preferred embodiments, such disclosure is not to be interpreted as limiting. Various changes and modifications will no doubt become apparent to those skilled in the art to which the present invention pertains upon reading the above disclosure. It is therefore intended that the appended claims be interpreted to cover all changes and modifications that do not depart from the true spirit and scope of the invention. [Explanation of symbols]

[0068] 10 Capacitor element 21 Anode body 22 Cathode body 23 Separator 100 electrolytic capacitors

Claims

1. an anode body; a dielectric layer formed on the anode body; a cathode body; a separator and an electrolyte disposed between the dielectric layer and the cathode body, At least a portion of the separator is coated with a conductive metal oxide, The electrolytic capacitor, wherein the metal oxide comprises an oxide of at least one element selected from the group consisting of indium, tin, antimony, and zinc.

2. an anode body; a dielectric layer formed on the anode body; a cathode body; a separator and an electrolyte disposed between the dielectric layer and the cathode body, At least a portion of the separator is coated with a conductive metal oxide, an amount of the metal oxide covering a portion of the separator facing the cathode body is greater than an amount of the metal oxide covering a portion of the separator facing the anode body.

3. 3. The electrolytic capacitor of claim 1, wherein the separator comprises synthetic fibers.

4. 4. The electrolytic capacitor according to claim 1, wherein the electrolyte contains an electrolytic solution and a conductive polymer.

5. 5. The electrolytic capacitor according to claim 1, wherein the cathode body comprises a metal foil.

6. 6. The electrolytic capacitor according to claim 1, wherein a conductive layer containing at least one element selected from the group consisting of carbon, titanium, and nickel is formed on a surface of the cathode body facing the separator.

7. A method for manufacturing an electrolytic capacitor including an anode body, a dielectric layer formed on the anode body, a cathode body, a separator, and an electrolyte, the method comprising: (i) forming a capacitor element by disposing the anode body, the cathode body, the separator, and the electrolyte such that the separator and the electrolyte are disposed between the dielectric layer and the cathode body; At least a portion of the separator is coated with a conductive metal oxide, Before the step (i), a step (a) of coating at least a portion of a sheet to be cut into the separator with the metal oxide; and (b) cutting the sheet to form the separator.

8. The method according to claim 7 , further comprising the step of crystallizing the metal oxide after the step (a).

9. In the step (a), The method according to claim 7 or 8, wherein at least a portion of the sheet is coated with the metal oxide between a roll that delivers the sheet and a roll that takes up the sheet.

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