Electrolytic capacitor and method of manufacturing electrolytic capacitor

Abstract

An electrolytic capacitor includes: an anode having a dielectric layer on a surface; a cathode; a porous insulating layer formed on at least one electrode selected from the group consisting of the anode and the cathode, and disposed between the anode and the cathode; and an electrolyte disposed in voids of the insulating layer.

Description

Technical Field

[0001] This disclosure relates to an electrolytic capacitor and a method for manufacturing an electrolytic capacitor. Background Technology

[0002] Electrolytic capacitors are known to consist of a wound body comprising an anode foil, a separator, and a cathode foil. On the other hand, electrolytic capacitors that do not use a separator have also been proposed.

[0003] In patent document 1 (Japanese Patent No. 5072857), technical solution 1 describes "a method for manufacturing an electrolytic capacitor, comprising the following steps: forming an anode member coated with a first conductive polymer layer on the surface of a first metal foil; forming a cathode member coated with a second conductive polymer layer on the surface of a second metal foil; connecting a first lead terminal to the anode member; connecting a second lead terminal to the cathode member; winding the anode member and the cathode member in such a manner that no component is separated between them; and after the winding step, forming a third conductive polymer layer by polymerization in the gap between the anode member and the cathode member."

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent No. 5072857 Summary of the Invention

[0007] One aspect of this disclosure relates to an electrolytic capacitor. The electrolytic capacitor includes a cathode and an anode having a dielectric layer on its surface. It further includes: a porous insulating layer formed on at least one electrode selected from the group consisting of the anode and the cathode, and disposed between the anode and the cathode; and an electrolyte disposed within the voids of the insulating layer.

[0008] Another aspect of this disclosure relates to a method of manufacturing an electrolytic capacitor, the electrolytic capacitor comprising a cathode and an anode having a dielectric layer on its surface. The manufacturing method includes: step (i), forming a porous insulating layer on at least one electrode selected from the group consisting of the anode and the cathode; and step (ii), stacking the anode and the cathode in such a manner that the insulating layer is disposed between the anode and the cathode. Step (a) further includes distributing an electrolyte within the voids of the insulating layer.

[0009] The effects of the invention

[0010] According to this disclosure, it is possible to obtain electrolytic capacitors with high capacitance. Attached Figure Description

[0011] Figure 1 This is a side view schematically illustrating an example of an electrolytic capacitor according to an embodiment of the present disclosure.

[0012] Figure 2 It is shown schematically. Figure 1 An exploded perspective view of an example of the capacitor elements included in the electrolytic capacitor shown.

[0013] Figure 3 This is a cross-sectional view schematically showing a portion of a stacked structure of capacitor elements.

[0014] Figure 4 This is a schematic diagram illustrating an example of electrospinning. Detailed Implementation

[0015] The following is a brief explanation of the problems in the existing technology.

[0016] In electrolytic capacitors using a diaphragm, the diaphragm needs to be thinned to achieve high capacitance. However, thinning the diaphragm makes its processing difficult, increases the risk of short circuits, and complicates the manufacturing process. On the other hand, without a diaphragm, problems arise such as reduced voltage withstand capability and decreased reliability at high temperatures.

[0017] This disclosure provides a novel electrolytic capacitor capable of achieving high capacitance.

[0018] The following examples illustrate embodiments of the present invention, 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 disclosed herein 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 and any of the illustrated upper limits can be arbitrarily combined, as long as the lower limit is not greater than the upper limit. In the following description, when examples of constituent elements or methods are listed, unless specifically stated otherwise, only one of the listed examples can be used, or multiple of the listed examples can be used simultaneously.

[0019] (Electrolytic capacitor)

[0020] Hereinafter, the electrolytic capacitor according to this embodiment will sometimes be referred to as an "electrolytic capacitor (C)". The electrolytic capacitor (C) includes a cathode, an anode having a dielectric layer on its surface, a porous insulating layer, and an electrolyte disposed within the voids of the insulating layer. The porous insulating layer is formed on at least one electrode selected from the group consisting of an anode and a cathode, and is disposed between the anode and the cathode. Hereinafter, this at least one electrode will sometimes be referred to as an "electrode (E)" or "at least one electrode (E)". Furthermore, the porous insulating layer formed on the electrode (E) will sometimes be referred to as an "insulating layer (L)".

[0021] The insulating layer (L) functions as an insulating layer in place of the diaphragm. The insulating layer (L) is formed on the electrode (E), making it easy to handle even when thin. Therefore, it can be made thinner than the diaphragm. By using a thin insulating layer (L), the electrostatic capacitance per unit volume can be increased. That is, the electrolytic capacitor (C) can have a high capacitance.

[0022] In the electrolytic capacitor of Patent Document 1, where no diaphragm is provided between the anode and cathode, a decrease in withstand voltage and a reduction in reliability are likely to occur. On the other hand, an insulating layer (L) is provided between the anode and cathode of the electrolytic capacitor (C). Therefore, in the electrolytic capacitor (C), a decrease in withstand voltage and a reduction in reliability can be suppressed.

[0023] Electrolytic capacitors (C) typically do not include a separator. However, electrolytic capacitors (C) may also include a separator. For example, an insulating layer may be formed only on one surface of the electrode (E), and the separator may be disposed on the other surface. In this specification, a separator refers to a porous insulating membrane that is treated as a component existing independently of the electrodes. Examples of separators include nonwoven fabrics and microporous membranes. The insulating layer (L) formed by depositing fibers differs from the construction of known nonwoven fabrics used as separators.

[0024] The insulating layer (L) can be attached to either the dielectric layer of the anode or the cathode. The insulating layer (L) can be attached to the dielectric layer and integrated with the anode, or it can be attached to the cathode and integrated with the cathode. Integration with the electrode (E) simplifies the processing of the insulating layer (L). Here, "integration" refers to a state where it can be processed as a single component during the manufacturing process. The insulating layer (L) can be formed only on the anode, only on the cathode, or on both the anode and cathode.

[0025] The capacitor element of an electrolytic capacitor (C) may also include a wound body formed by winding an anode and a cathode. In this case, the anode and cathode are stacked radially in the wound body. The electrolytic capacitor (C) may also include a laminate formed by stacking anodes and cathodes. For example, the capacitor element of an electrolytic capacitor (C) may include a laminated type laminate formed by stacking flat anodes and flat cathodes in one direction. For example, multiple anodes and multiple cathodes may be stacked in one direction to form a laminate. In this case, the anodes and cathodes are arranged alternately.

[0026] The region in the electrode (E) where the insulating layer (L) is formed can be selected according to the shape of the electrolytic capacitor (C). The insulating layer (L) can be formed on one or both sides of the electrode (E) depending on the shape of the capacitor element. The insulating layer (L) is usually formed on both sides of the electrode (E). The insulating layer (L) can also be formed to cover more than 90% (e.g., more than 95%) of the area of ​​both sides of the electrode (E). However, it is preferable not to form the insulating layer (L) at the locations of connecting leads, etc. Furthermore, in the electrodes (E) disposed at both ends of a laminated body, the insulating layer (L) can be formed only on the surface of the adjacent electrode side.

[0027] In capacitor elements, it is preferable that the electrode without an insulating layer (L) does not protrude further outward than the insulating layer (L). For example, it is preferable that the width (length in the short side direction) of the electrode without an insulating layer (L) is smaller than the width of the insulating layer (L). According to this structure, short circuits of the electrodes can be suppressed.

[0028] The insulating layer (L) may also contain fibers deposited on at least one electrode (E). The insulating layer (L) may consist solely of these fibers or may contain these fibers as a main component. The content of these fibers in the material constituting the insulating layer (L) may be 50% by mass or more, 80% by mass or more, 90% by mass or more, or 95% by mass or more.

[0029] The average diameter of the fibers constituting the insulating layer (L) can be 0.05 μm or more, 0.1 μm or more, 0.3 μm or more, or 0.5 μm or more, and can also be 2.0 μm or less, 1.5 μm or less, 1.0 μm or less, or 0.6 μm or less. The average diameter of the fibers can be in the range of 0.1 μm to 1.5 μm. The lower limit and / or upper limit of this range can be replaced by the aforementioned lower limit and / or upper limit, provided that the lower limit does not exceed the upper limit. By setting the average diameter of the fibers to 0.1 μm or more, a high density of the insulating layer can be achieved, and the withstand voltage performance can be improved. By setting the average diameter of the fibers to 1.5 μm or less, it is easy to form a structure composed of complexly overlapping fibers, and the withstand voltage performance of the insulating layer can be improved.

[0030] The average diameter of the fiber is calculated by taking the arithmetic mean of the diameters of 30 randomly selected fibers. The diameter of each fiber is determined by measuring the diameter at an randomly selected location. In cases where the fiber cross-section is not circular, the equivalent diameter of the circle calculated based on the area of ​​the fiber's cross-section is taken as the fiber's diameter.

[0031] There are no particular limitations on the fibers constituting the insulating layer (L). Materials that are insulating and stable within the electrolytic capacitor can be used for the fibers. The fibers can be composed of polymers. Examples of fiber materials include various insulating polymers. For example, examples of fiber materials include polyacrylonitrile, fluoropolymers (polyvinylidene fluoride, etc.), polyurethane, polyethylene oxide, polyvinyl alcohol, poly-L-lactic acid, nylon 6, polyethylene terephthalate, polystyrene, polymethyl methacrylate, polypropylene, polysulfone, polyethersulfone, polycaprolactone, polyimide, cellulose polymers, etc. Cellulose polymers include cellulose and cellulose derivatives. Examples of cellulose polymers include cellulose, alkyl cellulose, cellulose acetate, etc. The fibers constituting the insulating layer (L) can also be composed of at least one selected from the group consisting of polyacrylonitrile and polyvinylidene fluoride. Polyacrylonitrile and polyvinylidene fluoride are easily spun by electrospinning. By using these fibers, the characteristics of the electrolytic capacitor (C) can be particularly improved.

[0032] The insulating layer (L) may also contain materials other than fibers, and may be composed of materials other than fibers. Examples of insulating layers (L) composed of materials other than fibers include insulating layers formed by depositing a polymer or a composition containing a polymer onto the electrode (E). There are no particular limitations on the method of depositing the polymer onto the electrode (E). For example, a porous insulating layer (L) may also be formed by spraying a coating containing a polymer. For the polymer, polymers exemplified as fibers may also be used.

[0033] The thickness of the insulating layer (L) can be 0.5 μm or more, 3 μm or more, 5 μm or more, 10 μm or more, or 20 μm or more, or it can be less than 50 μm, 30 μm or less, 20 μm or less, or 10 μm or less. The thickness of the insulating layer (L) can also be in the range of 0.5 μm to 30 μm. The lower limit and / or upper limit of this range can be replaced with the aforementioned lower limit and / or upper limit, provided the lower limit does not exceed the upper limit. By setting the insulating layer (L) to 0.5 μm or more, the insulation withstand voltage can be increased and the leakage current reduced. By setting the insulating layer (L) to 30 μm or less, high capacity becomes particularly easy.

[0034] The insulating layer (L) is typically formed in a manner that makes its thickness as uniform as possible. The thickness of the insulating layer (L) can be determined using an image of a cross-section of the electrode (E) to which the insulating layer (L) is formed.

[0035] Both the anode and cathode can contain metal foil, or both can be metal foil. Examples of metal foil will be described later. The cathode can also contain metal foil and other layers formed on the surface of the metal foil. Examples of other layers include conductive layers made of a material different from the metal foil.

[0036] In an electrolytic capacitor (C), the anode and cathode face each other, sandwiched between an insulating layer (L). There are no particular limitations on the arrangement of the anode and cathode. The anode and cathode can be wound together. That is, the electrolytic capacitor (C) can also comprise a wound body formed by winding the anode and cathode together.

[0037] (Manufacturing method of electrolytic capacitors)

[0038] Hereinafter, the manufacturing method of this embodiment will sometimes be referred to as "manufacturing method (M)". According to manufacturing method (M), an electrolytic capacitor (C) can be manufactured. However, the electrolytic capacitor (C) can also be manufactured by methods other than manufacturing method (M). The matters described with respect to the electrolytic capacitor (C) can be applied to the manufacturing method (M), therefore repeated descriptions are sometimes omitted. The matters described with respect to the manufacturing method (M) can also be applied to the electrolytic capacitor (C).

[0039] The manufacturing method (M) is a method for manufacturing an electrolytic capacitor comprising a cathode and an anode having a dielectric layer on its surface. The manufacturing method (M) includes: step (i), forming a porous insulating layer (insulating layer (L)) on at least one electrode (electrode (E)) selected from the group consisting of an anode and a cathode; and step (ii), stacking the anode and cathode such that the insulating layer (L) is disposed between the anode and the cathode. The manufacturing method (M) further includes step (a) of distributing an electrolyte within the voids of the insulating layer (L).

[0040] (Process (i))

[0041] There is no particular limitation on the method for forming the insulating layer (L) in step (i). As described above, a porous insulating layer (L) can be formed by spraying a coating containing a polymer. Alternatively, in step (i), the insulating layer (L) can also be formed by depositing fibers onto at least one electrode (E). For example, in step (i), fibers can be deposited onto at least one electrode (E) by electrospinning. In step (i), the insulating layer (L) can also be formed by attaching it to the electrode (E). By attaching the insulating layer (L) to the electrode (E), the electrode (E) and the insulating layer (L) can be treated as an integrated component in step (ii).

[0042] When the insulating layer (L) is formed by electrospinning, the higher the conductivity of the electrode (E) surface, the easier it is to improve the adhesion of the fiber to the electrode (E). Therefore, from the viewpoint of improving the adhesion of the insulating layer (L) to the electrode (E), the cathode can also be set as the electrode (E). When the insulating layer (L) is formed by electrospinning, the fiber can be deposited on the electrode (E) by spraying the polymer solution from a nozzle. The polymer described above can be used for the polymer solution. There is no limitation on the solvent of the polymer solution, and known solvents used in electrospinning can be used depending on the type of polymer. Examples of solvents include water and organic solvents. Examples of organic solvents include alcohols, acetone, dichloromethane, dimethylformamide, dimethylacetamide, tetrahydrofuran, and dimethyl sulfoxide. A single solvent can be used, or multiple solvents can be used in combination. The polymer solution may also contain additives (e.g., known additives).

[0043] There is no limit to the concentration of the polymer solution; it can be selected based on the desired fiber composition. By changing the electrospinning process conditions (nozzle diameter, applied voltage, solvent type, polymer solution concentration, etc.), the physical properties of the resulting fiber (e.g., fiber diameter) can be altered. The polymer solution concentration can be 5% by mass or more, 10% by mass or more, or 15% by mass or more, or it can be less than 20% by mass, less than 15% by mass, or less than 10% by mass.

[0044] In process (i), an insulating layer (L) can also be formed on a large conductive sheet, and then the conductive sheet can be cut to form an electrode (E). In this case, the width of the insulating layer (L) is usually equal to the width of the electrode (E). The conductive sheet becomes an anode or cathode by cutting. Therefore, for conductive sheets, metal foil or metal foil with a dielectric layer formed can be used.

[0045] A dielectric layer is formed on the surface of the anode used in process (i). The dielectric layer can be formed by known methods (e.g., chemical conversion treatment). The surface of the anode is typically porous. The surface of the cathode can also be porous. By making their surfaces porous, the surface area of ​​the electrode can be increased. Furthermore, by making the surface of the electrode (E) porous, the adhesion of the insulating layer (L) to the electrode (E) can be improved. There is no limitation on the method of making the electrode surface porous; known methods can be used. For example, the electrode surface can be porous by etching.

[0046] (Process (ii))

[0047] There are no particular limitations on the method of stacking the anode and cathode in step (ii), and known methods can be used. In step (ii), the anode and cathode can be stacked by winding them together. Alternatively, in step (ii), flat anodes and flat cathodes can be stacked in one direction.

[0048] (Process(a))

[0049] Step (a) is the process of placing the electrolyte within the voids of the insulating layer (L). Step (a) can also be considered as the process of placing the electrolyte between the anode and cathode. By placing the electrolyte between the anode and cathode, the electrolyte is placed within the voids of the insulating layer (L).

[0050] The step (a) of placing the electrolyte within the voids of the insulating layer (L) can be performed simultaneously with the step (ii) of forming the insulating layer (L), but it is usually performed after the insulating layer (L) is formed. If the electrolyte contains a conductive polymer (solid electrolyte), the conductive polymer can also be placed within the voids of the insulating layer (L) before forming the anode and cathode windings (or laminates). In this case, the conductive polymer can be placed within the insulating layer (L) by drying the liquid containing the conductive polymer after coating it with the insulating layer (L). Then, the anode and cathode windings (or laminates) are formed.

[0051] The conductive polymer can also be disposed within the voids of the insulating layer (L) after the anode and cathode are formed by the winding (or lamination). In this case, the conductive polymer can be disposed within the insulating layer (L) by impregnating the winding (or lamination) with a liquid containing the conductive polymer and then drying it.

[0052] When the electrolyte contains an electrolyte solution, the electrolyte solution can also be placed within the voids of the insulating layer (L) after the anode and cathode are formed. For example, the electrolyte solution can also be placed within the insulating layer (L) by impregnating the winding body (or laminate) with the electrolyte solution. The impregnation of the electrolyte solution can be performed either before the winding body (or laminate) is housed in the outer casing or after the winding body (or laminate) is housed in the outer casing.

[0053] A capacitor element including an electrolyte is formed as described above. An electrolytic capacitor is then manufactured using the formed capacitor element. For example, an electrolytic capacitor is obtained by housing the capacitor element within an outer casing. There are no particular limitations on processes other than those described above; processes used in known manufacturing methods can be employed.

[0054] The following describes examples of components used in an electrolytic capacitor (C). However, the components used in an electrolytic capacitor (C) are not limited to the examples described below. There are no particular limitations on components other than those specific to an electrolytic capacitor (C), and known components may be used.

[0055] (anode)

[0056] Examples of anodes include metal foils containing at least one valve metal such as titanium, tantalum, aluminum, and niobium. The anode can also be a metal foil containing a valve metal (e.g., aluminum foil). The anode may also contain the valve metal in the form of an alloy or compound containing the valve metal. The surface of the anode can also be roughened by etching or the like. That is, the surface of the anode can also be made porous. The thickness of the anode can be 15 μm or more, 50 μm or more, or 300 μm or less, or 100 μm or less. In the case where the capacitor element is a wound element, the anode has a strip shape.

[0057] A dielectric layer is formed on the surface of the anode. The dielectric layer can also be formed by chemically converting the anode. In this case, the dielectric layer can contain an oxide of the valve metal (e.g., aluminum oxide). Furthermore, the dielectric layer can be formed from a dielectric material other than an oxide of the valve metal, as long as it functions as a dielectric.

[0058] (cathode)

[0059] For the cathode, conductive sheets or metal foils (e.g., aluminum foil) can be used. The metal constituting the foil can also be a valve metal or an alloy containing a valve metal. The surface of the cathode can be roughened by etching or the like. That is, the surface of the cathode can also be made porous. The thickness of the cathode can be 15 μm or more, 50 μm or more, or 300 μm or less, or 100 μm or less. In the case where the capacitor element is a wound element, the cathode has a strip shape.

[0060] (electrolytes)

[0061] The electrolyte is disposed between the anode and cathode (e.g., within the voids of the insulating layer (L)). A solid electrolyte (e.g., a conductive polymer) and / or a liquid electrolyte can be used. The electrolytic capacitor (C) preferably comprises a conductive polymer and a liquid electrolyte. The electrolytic capacitor (C) may also comprise a conductive polymer and a liquid component disposed between the anode and cathode. The liquid component can be either a liquid electrolyte or a non-aqueous solvent used for the liquid electrolyte. When using an insulating layer (L), using a conductive polymer and a liquid electrolyte as the electrolyte is preferred from the perspective of easily reducing ESR and achieving high reliability and high withstand voltage of the electrolytic capacitor.

[0062] Examples of conductive polymers include polypyrrole, polythiophene, polyfuran, polyaniline, polyacetylene, and their derivatives. These derivatives include polypyrrole, polythiophene, polyfuran, polyaniline, and polymers with polyacetylene as the 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. There are no particular limitations on the weight-average molecular weight of conductive polymers; for example, it can be in the range of 1,000 to 100,000. A preferred example of a conductive polymer is poly(3,4-ethylenedioxythiophene) (PEDOT).

[0063] Dopant can be incorporated into conductive polymers. From the viewpoint of suppressing dedoping from conductive polymers, polymeric dopants can be used as dopants. Examples of polymeric dopants include polyvinylsulfonic acid, polystyrene sulfonic acid, polyallyl sulfonic acid, polypropylene sulfonic acid, polymethylpropylene 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 some of them can also be added in the form of salts. A preferred example of a dopant is polystyrene sulfonic acid (PSS).

[0064] The dopant can also be polystyrene sulfonic acid, and the conductive polymer can also be poly(3,4-ethylenedioxythiophene). That is, the conductive polymer can also be poly(3,4-ethylenedioxythiophene) doped with polystyrene sulfonic acid.

[0065] When a conductive polymer is disposed between the anode and cathode, a liquid containing the conductive polymer can be used, as described above. There are no particular limitations on the liquid medium. Examples of liquid media include water, organic solvents (alcohols, ethylene glycol), and mixtures thereof. The liquid containing the conductive polymer can be a dispersion of conductive polymer particles dispersed in a liquid with water as the main component (content: 50% by mass or more).

[0066] The content of conductive polymers in liquids containing conductive polymers can be 0.5% by mass or more, or 1.0% by mass or less, or less than 4.0% by mass, less than 3.0% by mass, or less than 2.0% by mass.

[0067] There are no particular limitations on the electrolyte; any known electrolyte used in electrolytic capacitors may be used. The electrolyte may also contain a non-aqueous solvent and a solute dissolved in the non-aqueous solvent (e.g., an organic salt).

[0068] 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.

[0069] Non-aqueous solvents can include polymeric solvents. Examples of polymeric solvents include polyalkylene glycols, derivatives of polyalkylene glycols, and compounds in which at least one hydroxyl group of a polyol is replaced by a polyalkylene glycol (including its derivatives). Specifically, examples of polymeric 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 polymeric solvents also include ethylene glycol-propylene glycol copolymers, ethylene glycol-butanediol copolymers, propylene glycol-butanediol copolymers, etc. Regarding non-aqueous solvents, one or more can be used alone or in combination.

[0070] Examples of solutes include inorganic and organic salts. Organic salts are salts 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.

[0071] (Outer packaging)

[0072] The capacitor element is housed in an outer casing. There are no particular limitations on the outer casing; any known outer casing may be used.

[0073] Hereinafter, an example of the present disclosure will be specifically described with reference to the accompanying drawings. The constituent elements of the example described below can be applied to the aforementioned constituent elements. Furthermore, the constituent elements of the example described below can be modified based on the above description. Additionally, the matters to be described below can be applied to the above-described embodiments. Furthermore, in the example described below, constituent elements that are not essential to the electrolytic capacitor involved in this disclosure may be omitted.

[0074] (Implementation Method 1)

[0075] Figure 1 This is a schematic cross-sectional view of an electrolytic capacitor 100 according to an example of this embodiment. Figure 2 This is a schematic diagram showing a portion of the capacitor element 10 included in the electrolytic capacitor 100 unfolded. The electrolytic capacitor 100 is a wound-type capacitor including a wound body.

[0076] The electrolytic capacitor 100 includes: a capacitor element 10; a base housing 101 that houses the capacitor element 10; a sealing member 102 that closes the opening of the base housing 101; a base plate 103 that covers the sealing member 102; leads 104A and 104B that are led out from the sealing member 102 and pass through the base plate 103; and lead connectors 105A and 105B that connect the leads to the electrodes of the capacitor element 10. The open end of the base housing 101 is coiled inward.

[0077] Figure 2 An example of a capacitor element 10 is schematically shown. The capacitor element 10 is a wound body formed by winding an anode (anode foil) 11 and a cathode (cathode foil) 12. A porous insulating layer 21 is formed on the anode 11 and the cathode 12, or on either the anode 11 or the cathode 12. Figure 2 The diagram shows an example where an insulating layer 21 is formed on both sides of the cathode 12. The insulating layer 21 is integral with the cathode 12 and is wound together with the cathode 12. The outermost periphery of the wound body is fixed by a stop-winding tape 14. Furthermore, Figure 2 This shows a portion of the capacitor element 10 being unfolded before the outermost periphery of the winding is secured.

[0078] Figure 3 A portion of capacitor element 10 is schematically shown. Furthermore, in Figure 3 In the diagram, the anode 11, cathode 12, and insulating layer 21 are represented as flat components, but within the capacitor element 10, the anode 11, cathode 12, and insulating layer 21 are curved.

[0079] like Figure 3 As shown, the capacitor element 10 includes an anode 11, a cathode 12, an insulating layer 21 (insulating layer (L)), and an electrolyte (not shown). A dielectric layer 11a is formed on the surface of the anode 11. The insulating layer 21 and the electrolyte are disposed between the anode 11 (more specifically, the dielectric layer 11a on the surface of the anode 11) and the cathode 12. The electrolyte is disposed between the anode 11 and the cathode 12 (e.g., within the voids of the insulating layer 21). The insulating layer 21 is formed on the anode 11 and / or the cathode 12. As described above, the surfaces of the anode 11 and / or the cathode 12 can also be made porous.

[0080] There are no particular limitations on the apparatus used to perform electrospinning. Figure 4An example of an apparatus 200 for performing electrospinning is schematically shown. The apparatus 200 includes a syringe 201 with a conductive nozzle 201a and a power source 202. A polymer solution 211 is disposed within the syringe 201. A high voltage is applied between the nozzle 201a and an electrode 221 (anode or cathode) via the power source 202. Fibers 212 are formed by ejecting the polymer solution 211 from the nozzle 201a. The formed fibers 212 are deposited on the electrode 221, forming a porous insulating layer. By increasing the number of nozzles 201a, a large number of fibers 212 can be deposited simultaneously.

[0081] (Postscript)

[0082] The following technology is disclosed through the above description.

[0083] (Technology 1)

[0084] An electrolytic capacitor, comprising:

[0085] The anode has a dielectric layer on its surface;

[0086] cathode;

[0087] A porous insulating layer formed on at least one electrode selected from the group consisting of the anode and the cathode, and disposed between the anode and the cathode; and

[0088] Electrolytes are disposed within the voids of the insulating layer.

[0089] (Technology 2)

[0090] According to the electrolytic capacitor of technology 1, wherein...

[0091] The insulating layer is attached to at least one of the dielectric layer and the cathode.

[0092] (Technology 3)

[0093] According to the electrolytic capacitor of technique 1 or 2, wherein,

[0094] The insulating layer comprises fibers deposited on the at least one electrode.

[0095] (Technology 4)

[0096] According to the electrolytic capacitor of technology 3, wherein...

[0097] The average diameter of the fiber is greater than 0.1 μm and less than 1.5 μm.

[0098] (Technology 5)

[0099] According to the electrolytic capacitor described in technique 3 or 4, wherein...

[0100] The fiber contains a polymer.

[0101] (Technology 6)

[0102] According to the electrolytic capacitor of technology 3, wherein...

[0103] The fiber comprises at least one selected from the group consisting of polyacrylonitrile and polyvinylidene fluoride.

[0104] (Technology 7)

[0105] The electrolytic capacitor according to any one of techniques 1 to 6, wherein,

[0106] The thickness of the insulating layer is greater than 0.5 μm and less than 30 μm.

[0107] (Technology 8)

[0108] The electrolytic capacitor according to any one of techniques 1 to 7, wherein...

[0109] The anode and the cathode are metal foils, respectively.

[0110] (Technology 9)

[0111] The electrolytic capacitor according to any one of techniques 1 to 8, wherein...

[0112] It also includes a wound body formed by winding the anode and the cathode.

[0113] (Technology 10)

[0114] The electrolytic capacitor according to any one of techniques 1 to 8, wherein,

[0115] It also includes a laminate formed by stacking the anode and the cathode.

[0116] (Technology 11)

[0117] A method for manufacturing an electrolytic capacitor, the electrolytic capacitor comprising a cathode and an anode having a dielectric layer on its surface, the method comprising:

[0118] Step (i) involves forming a porous insulating layer on at least one electrode selected from the group consisting of the anode and the cathode; and

[0119] Step (ii) involves stacking the anode and the cathode such that the insulating layer is disposed between the anode and the cathode.

[0120] The method for manufacturing the electrolytic capacitor further includes a step (a) of distributing an electrolyte within the voids of the insulating layer.

[0121] (Technology 12)

[0122] According to the manufacturing method described in technique 11, wherein,

[0123] In step (i), the insulating layer is formed by depositing fibers onto the at least one electrode.

[0124] (Technology 13)

[0125] According to the manufacturing method described in technique 12, wherein,

[0126] In step (i), the fibers are deposited on the at least one electrode by electrospinning.

[0127] (Technology 14)

[0128] The manufacturing method according to any one of techniques 11-13, wherein,

[0129] In step (ii), the anode and the cathode are stacked by winding the anode and the cathode.

[0130] Example

[0131] The present disclosure is described in more detail below based on embodiments, but the present disclosure is not limited to the embodiments described below. In this embodiment, a plurality of electrolytic capacitors were fabricated and evaluated. In this embodiment, a parallel plate capacitor including an anode and a cathode was fabricated.

[0132] (Capacitor A1)

[0133] An electrolytic capacitor (capacitor A1) was manufactured using the following method.

[0134] (1) Prepare anode foil

[0135] The surface of the aluminum foil (thickness: 100 μm) is roughened (porosified) by etching. A dielectric layer is then formed by chemical conversion treatment of the roughened aluminum foil surface. Next, the aluminum foil with the dielectric layer formed is cut into 20 mm square pieces. In this way, an anode foil with dielectric layers formed on both sides is obtained.

[0136] (2) Prepare cathode foil

[0137] A cathode foil was obtained by etching an aluminum foil (thickness: 50 μm) to roughen its surface (make it porous). Next, electrospinning was used to deposit fibers onto the surface of the cathode foil (aluminum foil), thereby forming a porous insulating layer on the cathode foil. A solution of polyacrylonitrile was used as the polymer solution for the electrospinning process. An aprotic polar solvent was used as the solvent for the polymer solution. Using this polymer solution, a porous insulating layer (thickness: 15 μm) composed of polyacrylonitrile fibers was formed on the cathode foil. The cathode foil with the insulating layer then was cut into 22 mm square pieces. In this way, a cathode foil with an insulating layer formed on one side was obtained.

[0138] (3) Assemble electrolytic capacitors

[0139] With a solid component surface density of 0.3 mg / cm³ 2 A dispersion of a conductive polymer was drop-added to the porous insulating layer of the cathode foil. Then, the anode and cathode foils were overlapped with the insulating layer in between to form a laminate. Next, the laminate was dried at 150°C for 20 minutes, thereby distributing the conductive polymer between the anode and cathode foils. At this point, the conductive polymer is distributed within the voids of the insulating layer. For the conductive polymer, poly(3,4-ethylenedioxythiophene) (PEDOT) doped with polystyrene sulfonate (PSS) was used. Furthermore, the dispersion medium for the conductive polymer dispersion was a liquid obtained by adding 5% by mass of ethylene glycol to water.

[0140] Next, the electrolyte was incorporated into the voids of the insulating layer by impregnating the laminate. The electrolyte was prepared by dissolving 5-sulfosalicylic acid and triethylamine in ethylene glycol (solvent) at a combined concentration of 25% by mass. The equivalent ratio of 5-sulfosalicylic acid to triethylamine was 2.0. The electrolytic capacitor thus fabricated was aged to obtain a parallel-plate capacitor A1. Aging was performed by applying the rated voltage to the capacitor for 30 minutes.

[0141] Three capacitors A1 were fabricated, and their electrostatic capacitance (Cap) at 120 Hz, equivalent series resistance (ESR) at 100 kHz, and leakage current (LC) were measured. The evaluation results of the three cells were then arithmetically averaged.

[0142] (Capacitor A2)

[0143] Except for changes to the polymer solution and the thickness of the insulating layer used in the electrospinning process, capacitor A2 was fabricated using the same methods and conditions as capacitor A1. In the fabrication of capacitor A2, a solution of polyvinylidene fluoride (PVDF) was used as the polymer solution. An aprotic polar solvent was used as the solvent for the polymer solution. Using this polymer solution, a porous insulating layer (thickness: 10 μm) composed of PVDF fibers was formed on the cathode foil. Three capacitors A2 were fabricated and evaluated in the same manner as capacitor A1.

[0144] (Capacitor C1)

[0145] Capacitor C2 was manufactured using the same methods and conditions as capacitor A1, except that a diaphragm was used instead of an insulating layer. That is, in capacitor C1, no insulating layer was formed on the cathode, but a diaphragm was placed between the anode and cathode. For the diaphragm, a nonwoven fabric made of cellulose (thickness: 50 μm) was used. Three capacitors C1 were manufactured and evaluated in the same way as capacitor A1.

[0146] Table 1 shows a portion of the manufacturing conditions and evaluation results for each capacitor. The numerical values ​​of the evaluation results are the arithmetic mean of the evaluation results for the three capacitors. Furthermore, the evaluation results in Table 1 are expressed as relative values ​​with the evaluation result of capacitor C1 set to 1.00. "Insulator" in Table 1 refers to the insulator disposed between the anode and cathode. A large electrostatic capacitance is preferred, as are low ESR and leakage current.

[0147] [Table 1]

[0148]

[0149] Capacitors A1 and A2 are electrolytic capacitors (C) according to the present invention. Capacitor C1 is a comparative example. As shown in Table 1, capacitors A1 and A2 have large electrostatic capacitance, low ESR, and low leakage current. The increase in electrostatic capacitance can be attributed to the thinner insulating layer, which increases the amount of conductive polymer filling the porous material of the anode. The decrease in ESR can be attributed to the thinner insulating layer compared to the separator. When using the insulating layer for capacitors A1 and A2 to form a wound (or laminated) capacitor element, the thinner insulating layer allows for an increase in electrostatic capacitance per unit volume.

[0150] Industrial availability

[0151] This disclosure can be used in electrolytic capacitors.

[0152] Explanation of reference numerals in the attached figures

[0153] 10: Capacitor element; 11: Anode; 11a: Dielectric layer; 12: Cathode; 21: Porous insulating layer; 100: Electrolytic capacitor.

Claims

1. An electrolytic capacitor, comprising: The anode has a dielectric layer on its surface; cathode; A porous insulating layer is formed on at least one electrode selected from the group consisting of the anode and the cathode, and disposed between the anode and the cathode; as well as Electrolytes are disposed within the voids of the insulating layer.

2. The electrolytic capacitor according to claim 1, wherein, The insulating layer is attached to at least one of the dielectric layer and the cathode.

3. The electrolytic capacitor according to claim 1 or 2, wherein, The insulating layer comprises fibers deposited on the at least one electrode.

4. The electrolytic capacitor according to claim 3, wherein, The average diameter of the fiber is greater than 0.1 μm and less than 1.5 μm.

5. The electrolytic capacitor according to claim 3, wherein, The fiber contains a polymer.

6. The electrolytic capacitor according to claim 3, wherein, The fiber comprises at least one selected from the group consisting of polyacrylonitrile and polyvinylidene fluoride.

7. The electrolytic capacitor according to claim 1 or 2, wherein, The thickness of the insulating layer is greater than 0.5 μm and less than 30 μm.

8. The electrolytic capacitor according to claim 1 or 2, wherein, The anode and the cathode are metal foils, respectively.

9. The electrolytic capacitor according to claim 1 or 2, wherein, It also includes a wound body formed by winding the anode and the cathode.

10. The electrolytic capacitor according to claim 1 or 2, wherein, It also includes a laminate formed by stacking the anode and the cathode.

11. A method for manufacturing an electrolytic capacitor, the electrolytic capacitor comprising a cathode and an anode having a dielectric layer on its surface, the method comprising: Step (i) involves forming a porous insulating layer on at least one electrode selected from the group consisting of the anode and the cathode; as well as Step (ii) involves stacking the anode and the cathode such that the insulating layer is disposed between the anode and the cathode. The method for manufacturing the electrolytic capacitor further includes a step (a) of distributing an electrolyte within the voids of the insulating layer.

12. The manufacturing method according to claim 11, wherein, In step (i), the insulating layer is formed by depositing fibers onto the at least one electrode.

13. The manufacturing method according to claim 12, wherein, In step (i), the fibers are deposited on the at least one electrode by electrospinning.

14. The manufacturing method according to claim 11 or 12, wherein, In step (ii), the anode and the cathode are stacked by winding the anode and the cathode.

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