Capacitor and method of manufacturing the same

Abstract

To realize a capacitor capable of reducing the number of short-circuits and a rate of short-circuits even if a CV value becomes large.SOLUTION: A capacitor element (2) comprises an anode foil (4), a cathode foil (6), a first separator (8) adjacent to the anode foil, and a second separator (10) adjacent to the cathode foil. A relationship between an air permeability resistance [s / 100 mL] of the first separator and the second separator is the first separator<the second separator, and the relationship between the air permeability [μm / (Pa s)] of the first separator and the second separator is the first separator>the second separator. Thus, even if a CV value increases, it is possible to provide a capacitor in which the number of occurrences of short-circuiting and a rate of occurrence of short-circuiting are reduced.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a capacitor such as an aluminum electrolytic capacitor, and to a capacitor including a separator in a capacitor element, and to a method for manufacturing the same. [Background technology]

[0002] In a capacitor, the separator is placed between the anode foil and the cathode foil, and its functions include insulating the anode foil and cathode foil (preventing voltage and short circuits) and retaining the electrolyte between the anode foil and the cathode foil.

[0003] For a capacitor element equipped with this separator, it has been disclosed that the separator is a combination of a multi-layer paper having a low-density layer and a high-density layer from the anode foil side, and a single-layer paper having a density intermediate between the low-density layer and the high-density layer of this multi-layer paper (for example, Patent Document 1).

[0004] It has been disclosed that the separator includes, from the anode foil side, a first multi-layer paper having a low-density layer and a high-density layer, and a second multi-layer paper having a low-density layer and a high-density layer (for example, Patent Document 2).

[0005] It has been disclosed that a separator with a double structure, with a high density on the inside and a low density on the outside, is interposed between electrode foils, and burrs occurring on the electrode foil are made to protrude to the low density side adjacent to the electrode foil (for example, Patent Document 3).

[0006] Thus, in the past, attention has been focused on the density of the separator as a way to improve voltage resistance and prevent short circuits when an overvoltage occurs. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-66696 [Patent Document 2] Japanese Patent Application Laid-Open No. 2009-64959 [Patent Document 3] Japanese Patent Application Laid-Open No. 2000-150307 Summary of the Invention [Problem to be solved by the invention]

[0008] Meanwhile, capacitors are required to have, firstly, improved overvoltage characteristics and voltage resistance characteristics, and secondly, smaller size and higher capacity.

[0009] Regarding the first improvement of overvoltage characteristics and withstand voltage characteristics, the JIS standard stipulates that no short circuit occurs when an overvoltage of 1.15 to 1.25 times the rated voltage is applied. Even capacitors that meet this standard may be subjected to an overvoltage of about 1.5 times the rated voltage depending on the usage environment, and it is required that no short circuit occurs even in such cases.

[0010] The second goal, miniaturization and high capacity, is to achieve miniaturization and high capacity while maintaining the necessary voltage resistance. To achieve miniaturization and high capacity, it is necessary to increase the capacity per unit area of ​​the anode foil.

[0011] Therefore, the possibility of short circuits has increased for capacitors that have improved overvoltage characteristics and voltage resistance characteristics, as well as achieved miniaturization and high capacity. This led the inventors of the present disclosure to discover that the index (hereinafter referred to as the "CV value") obtained by multiplying the capacitance (C) per unit area of ​​the anode foil by the voltage resistance (V) of the anode foil tends to increase, and that the higher this CV value, the higher the incidence of short circuits.

[0012] It is believed that the cause of such short circuits is that gas generated from the surface of the anode foil due to the application of an overvoltage accumulates within the capacitor element, and the accumulated gas presses the anode foil in a direction perpendicular to the foil surface, that is, toward the outside or center of the capacitor element, causing damage to the anode foil.In other words, it is essential to vent the gas generated in the anode foil to the outside of the capacitor element as quickly as possible, but this gas venting problem cannot be solved by selecting or changing the density of the separator.

[0013] Therefore, an object of the present disclosure is to realize a capacitor that can reduce the number and rate of occurrence of short circuits even if the CV value increases. [Means for solving the problem]

[0014] To achieve the above object, according to one aspect of a capacitor of the present disclosure, there is provided a capacitor element including an anode foil, a cathode foil, a first separator adjacent to the anode foil, and a second separator adjacent to the cathode foil, The magnitude relationship between the air permeation resistances [s / 100 mL] of the first separator and the second separator is The first separator < the second separator Or, the magnitude relationship between the air permeabilities [μm / (Pa s)] of the first separator and the second separator is The first separator>the second separator is.

[0015] In this capacitor, the anode foil has a capacitance per unit area [μF / cm 2 The index obtained by multiplying [V] by the withstand voltage [V] may exceed 336.1, and more preferably exceed 384.4.

[0016] In this capacitor, the first separator may be mainly made of natural fiber or may contain natural fiber.

[0017] In this capacitor, the cathode foil may include a carbon layer.

[0018] In order to achieve the above object, according to one aspect of the method for manufacturing a capacitor of the present disclosure, the magnitude relationship between the air permeation resistances [s / 100 mL] of a first separator adjacent to an anode foil and a second separator adjacent to a cathode foil is as follows: The first separator < the second separator or the magnitude relationship between the air permeabilities [μm / (Pa s)] of the first separator and the second separator is The first separator>the second separator and includes a step of stacking the anode foil, the first separator adjacent to the anode foil, the cathode foil, and the second separator adjacent to the cathode foil to form a capacitor element. [Effects of the Invention]

[0019] According to the present disclosure, any of the following effects can be obtained. (1) It is possible to provide a capacitor that reduces the number and rate of short circuits even when the CV value is large.

[0020] (2) With regard to the air permeability resistance or air permeability, which is directly related to gas discharge, the magnitude relationship between the air permeability resistance [s / 100 mL] of the first separator and the second separator is the first separator<the second separator, or the magnitude relationship between the air permeability [μm / (Pa s)] of the first separator and the second separator is the first separator>the second separator. Therefore, gas is efficiently discharged from the first separator side, which has a lower air permeability or a higher air permeability, to the outside of the capacitor element. This reduces the number and rate of short circuits even if the CV value increases.

[0021] (3) The first separator and the second separator can be selected using the air resistance or air permeability, which directly indicates the ease of gas permeation, as an index, and short circuits in the capacitor element can be prevented with a high degree of accuracy compared to the conventional method of selecting a separator that relies on density.

[0022] (4) The CV value can be increased, enabling a small size, high capacity, and high voltage resistance. [Brief explanation of the drawings]

[0023] [Figure 1] FIG. 1A shows a capacitor element according to one embodiment, and FIGS. 1B and 1C show examples of an anode foil, a cathode foil, a first separator, and a second separator. DETAILED DESCRIPTION OF THE INVENTION

[0024] The capacitor and its manufacturing method of the present disclosure selects a separator material based on the magnitude (high / low) relationship between the air resistance and air permeability of the paper to improve gas discharge to the outside of the capacitor element, thereby achieving advantages such as a reduction in the number and rate of short circuits even if the CV value increases. The air resistance and air permeability used in the present disclosure are as follows.

[0025] <Air resistance and air permeability of paper> Air resistance is the air resistance that indicates the ease with which air passes through, and is specified by the time it takes for air to pass through paper. In other words, air resistance is the time it takes for 100 mL of air to pass through the separator. Air resistance is measured using the Gurley method in accordance with the JIS standard (JIS P8117:2009 "Paper and paperboard - Air permeability and air resistance test method (intermediate range) - Gurley method"). A gasket with an inner diameter of 28.6 mm is used to measure this air resistance. For items with an air resistance of 1 s / 100 mL or less, measurements are taken using a gasket with an inner diameter of 6 mm, and the value is converted to the value measured with an inner diameter of 28.6 mm. Specifically, the value obtained with an inner diameter of 6 mm is multiplied by 6. 2 / 28.6 2 For example, if you use this conversion formula to convert the air resistance of 5.8 [s / 100mL] obtained for an inner diameter of 28.6 [mm] to an inner diameter of 6 [mm], you will get an air resistance of 132 [s / 100mL].

[0026] Furthermore, according to the JIS standard (JIS P8117:2009 "Paper and paperboard - Test methods for air permeability and air resistance (intermediate range) - Gurley method"), the air permeability [μm / (Pa·s)] is calculated using the ISO air permeability formula 1. Therefore, in this disclosure, "air permeability" refers to the ISO air permeability (hereinafter simply referred to as "air permeability"). P=135.3 / t (Formula 1) Where, P: ISO air permeability [μm / (Pa·s)] t: Average time (s) for 100 mL of air to pass through Here, by substituting the air resistance value (s / 100mL) for t, the air permeability (μm / (Pa s)) of the paper can be calculated. Therefore, the air permeability of paper is the average flow rate of air that permeates in the thickness direction of the paper, that is, the average flow rate of air per unit area, unit pressure difference, and unit time.

[0027] <One embodiment> Fig. 1A shows one embodiment of a capacitor and a manufacturing method thereof according to the present disclosure. Fig. 1B and Fig. 1C show an anode foil, a cathode foil, a first separator, and a second separator in a capacitor element. The configurations shown in Fig. 1A, B, and C are merely examples, and the present disclosure is not limited to such configurations.

[0028] This capacitor element 2 is an example of a capacitor disclosed herein. This capacitor element 2 is formed by stacking and winding an anode foil 4, a cathode foil 6, first separators 8-1 and 8-2 (hereinafter simply referred to as "separators 8-1 and 8-2" or "separator 8"), and second separators 10-1 and 10-2 (hereinafter simply referred to as "separators 10-1 and 10-2" or "separator 10") into a cylindrical shape. This capacitor element 2 is impregnated with an electrolyte (not shown).

[0029] <Anode foil 4> The anode foil 4 is formed by subjecting a base foil made of a valve metal to a surface expansion treatment and forming a dielectric oxide film. Valve metals include aluminum, tantalum, niobium, titanium, hafnium, zirconium, zinc, tungsten, bismuth, antimony, etc., and any of these is selected as the base material and formed into the base foil.

[0030] Surface expansion is a process for expanding the surface of the base foil, and a surface expansion layer is formed by surface expansion processes such as etching and sputtering. For example, etching involves immersing the base foil in an acidic aqueous solution containing halogen ions, such as hydrochloric acid, and passing a direct current (DC etching), an alternating current (AC etching), or both (AC-DC etching) to form a porous surface expansion layer on the base foil, such as a concave-convex, tunnel-shaped pore, or spongy pore. This surface expansion layer may contain countless pits as well as pores that penetrate the base foil (such as through-pits). In other words, advanced etching is used to increase the capacitance of the capacitor element 2.

[0031] As another surface-expanding treatment, instead of etching, metal particles may be vapor-deposited or sintered on the base foil, or metal particles may be vapor-deposited or sintered on the etched base foil to form a surface-expanding layer on the base foil.

[0032] After the surface-expanding treatment, a dielectric oxide film is formed on the surface of the surface-expanding layer of the base foil by chemical conversion treatment, thereby forming the anode foil 4.

[0033] <Cathode foil 6> The cathode foil 6 is a substrate foil made of the same valve metal as the anode foil 4, but with its surface expanded. The substrate foil is formed from a material selected from the valve metals described above. The etching process for the substrate foil is similar to that for the anode foil 4, and therefore will not be described here. An oxide film is formed on the surface-expanded layer of the cathode foil 6. This oxide film may be intentionally formed or may be naturally occurring (a natural oxide film). The oxide film is formed by chemical conversion treatment in which a voltage is applied in a solution free of halogen ions, such as an aqueous solution of adipic acid or boric acid, and is a thin oxide film of approximately 1 to 10 V. The natural oxide film is a thin oxide film formed by the reaction of the cathode foil with oxygen in the air.

[0034] The cathode foil 6 may be a carbon foil in which a carbon layer is laminated on a base foil. The carbon layer is laminated on one side or both sides of the base foil that has been subjected to surface expansion treatment. In other words, the carbon layer penetrates the etching layer and engages with the base foil, strengthening the base foil in addition to functioning as a cathode. This carbon layer may be composed of, for example, a carbon material as the main material, and additives such as a binder and a dispersing material.

[0035] The carbon material may be activated carbon, carbon black, carbon nanohorn, amorphous carbon, natural graphite, artificial graphite, graphitized ketjen black, mesoporous carbon, fibrous carbon, etc. Activated carbon may be produced from, for example, natural plant tissue such as coconut husk, synthetic resin such as phenol, or fossil fuel-derived material such as coal, coke, or pitch.

[0036] Carbon black includes ketjen black, acetylene black, channel black, thermal black, etc. Fibrous carbon includes carbon nanotubes, carbon nanofibers, etc. Carbon nanotubes may be single-walled carbon nanotubes, which have one graphene sheet, or multi-walled carbon nanotubes (MWCNTs), which have two or more graphene sheets rolled coaxially to form multiple tube walls.

[0037] The binder may be a resin binder such as styrene butadiene rubber, polyvinylidene fluoride, or polytetrafluoroethylene, and is bonded to the carbon material. The dispersing agent may be, for example, sodium carboxymethyl cellulose.

[0038] <Separators 8-1, 8-2> The separators 8-1 and 8-2 are disposed adjacent to the anode foil 4, and each separator 8-1 and 8-2 is made of an insulating material (insulating paper) having the same physical properties. This insulating paper may contain other separator materials (hereinafter simply referred to as "separator materials") such as kraft, Manila hemp, esparto, hemp, rayon, cellulose, mixtures of these materials, cotton linter, and non-wood pulp.

[0039] In this embodiment, separator 8-1 is disposed adjacent to (for example, in contact with) one surface of anode foil 4, and separator 8-2 is disposed adjacent to (for example, in contact with) the other surface of anode foil 4. The width of separators 8-1 and 8-2 is set larger than the width of anode foil 4, thereby insulating them from cathode foil 6. The insulating material is preferably a separator material whose main material is natural fiber, such as kraft, Manila hemp, esparto, hemp, cellulose, or a mixture of these. In other words, separator materials containing natural fiber are preferred for separators 8 and 10.

[0040] <Separators 10-1, 10-2> Separators 10-1 and 10-2 are disposed adjacent to cathode foil 6 and are made of insulating paper having the same physical properties. The insulating paper may be made of the same separator material as separators 8-1 and 8-2, such as kraft, Manila hemp, esparto, hemp, rayon, cellulose, a mixture of these materials, cotton linter, or non-wood pulp.

[0041] In this embodiment, separator 10-1 is disposed adjacent to one surface of cathode foil 6, and separator 10-2 is disposed adjacent to the other surface of cathode foil 6. The width of separators 10-1 and 10-2 is set larger than the width of cathode foil 6, thereby insulating them from anode foil 4.

[0042] The electrolyte used may be, for example, an electrolytic solution containing ethylene glycol as a main solvent. In addition to this electrolytic solution, a gel electrolyte may also be used, or a so-called hybrid electrolyte may be used that includes a solid electrolyte containing a conductive polymer in addition to the electrolytic solution.

[0043] <Physical properties of separators 8-1, 8-2, 10-1, and 10-2> Regarding the physical properties of the separators 8-1, 8-2, 10-1, and 10-2, the magnitude relationship of the air permeation resistance between the separators 8-1 and 8-2 and the separators 10-1 and 10-2 is as follows: First separators 8-1, 8-2 < Second separators 10-1, 10-2 Or, the magnitude relationship between the air permeabilities of the separators 8-1 and 8-2 and the separators 10-1 and 10-2 is First separators 8-1, 8-2>Second separators 10-1, 10-2 is. The air resistance or air permeability of the separators 8-1, 8-2 and the separators 10-1, 10-2 may be set with reference to Example 1 or experimental results described later.

[0044] Due to these physical properties, separators 8-1 and 8-2 have better gas permeability than separators 10-1 and 10-2, and gas generated on the anode foil 4 side is efficiently discharged from separators 8-1 and 8-2 to the outside of capacitor element 2.

[0045] <Method of manufacturing capacitor element 2> This method for manufacturing capacitor element 2 is an example of a method for manufacturing a capacitor according to the present disclosure. This manufacturing method includes a process for forming capacitor element 2, a process for impregnating with an electrolyte, a process for attaching a sealing plate and connecting terminals, and a process for sealing, crimping, and aging. The process for forming capacitor element 2 includes a process for forming anode foil 4, a process for forming cathode foil 6, a process for forming first separator 8, a process for forming second separator 10, and a process for forming capacitor element 2. Each process will be described in detail below.

[0046] Anode foil 4 formation process: As described above, a surface-expanding layer is formed on the base foil used for the anode foil 4 by etching or other surface-expanding process, and then a dielectric oxide film is formed on this surface-expanding layer, and the anode foil 4 is cut to the required dimensions to conform to the specifications of the capacitor element 2.

[0047] Formation process of cathode foil 6: As described above, a surface-expanding layer is formed on the base foil used for the cathode foil 6 by surface-expanding treatment such as etching, and then an oxide film is formed on the cathode foil 6 including this surface-expanding layer as needed, and the cathode foil 6 is cut to the required dimensions for the cathode foil 6 that conforms to the specifications of the capacitor element 2. When carbon foil is used for the cathode foil 6, the carbon foil as the cathode foil 6 is formed into a cathode foil 6 that conforms to the specifications of the capacitor element 2.

[0048] This formation step is necessary when using carbon foil for the cathode foil 6. A slurry is required to form the carbon layer. This slurry is formed, for example, by adding the aforementioned carbon material, binder, and dispersant to a diluent and mixing them using a dispersion process such as a mixer, jet mixing (jet collision), ultracentrifugation, or ultrasonic treatment. Examples of diluents that can be used include alcohols, hydrocarbon solvents, aromatic solvents, amide solvents, water, and mixtures of these. Examples of alcohols that can be used include methanol, ethanol, and 2-propanol. Examples of amide solvents that can be used include N-methyl-2-pyrrolidone (NMP) and N,N-dimethylformamide (DMF).

[0049] In the carbon foil forming process, a slurry is applied to the substrate foil, and the solvent is evaporated from the slurry to form a carbon layer on the substrate foil. By pressing the substrate foil together with this carbon layer, the carbon material is forced into the pores of the surface-expanding layer of the substrate foil, or the carbon material is deformed along the surface-expanding layer. This improves the adhesion between the substrate foil and the carbon layer, and enhances the fixation of the carbon layer to the substrate foil.

[0050] Formation process of separators 8-1 and 8-2: Separator materials are selected from those already described. In this case, with reference to the following Examples, Comparative Examples, and Reference Examples, separator materials with lower air resistance than separators 10-1 and 10-2 are selected for separators 8-1 and 8-2, or separator materials with higher air permeability than separators 10-1 and 10-2 are selected. Separators 8-1 and 8-2 are then cut into shapes that meet the specifications of capacitor element 2.

[0051] Formation process of separators 10-1 and 10-2: Separator materials are selected from those already described. In this case, separator materials having higher air resistance than separators 8-1 and 8-2 or lower air permeability than separators 8-1 and 8-2 are selected with reference to the following examples, comparative examples, and reference examples. Separators 10-1 and 10-2 are then cut into shapes that conform to the specifications of capacitor element 2.

[0052] Formation process of capacitor element 2: In this formation process, as shown in A in Figure 1, if capacitor element 2 is a wound element, separators 8-1 and 8-2 are placed adjacent to the front and back surfaces of anode foil 4, and separators 10-1 and 10-2 are placed adjacent to the front and back surfaces of cathode foil 6, and these are then stacked and wound into a cylindrical shape. In this case, the winding core of capacitor element 2 is formed with either or both of separators 8-1 and 8-2 and separators 10-1 and 10-2, or cathode foil 6, or both cathode foil 6 and a separator. Then, either separators 8-1 and 8-2 or separators 10-1 and 10-2 may be wound around the outer periphery of capacitor element 2.

[0053] Although not shown, it goes without saying that an anode tab is electrically connected to the anode foil 4 and a cathode tab is electrically connected to the cathode foil 6 in advance by a process such as stitching, ultrasonic welding, cold pressure welding, or laser welding.

[0054] Electrolyte Impregnation Step: The capacitor element 2 is impregnated with an electrolyte. As described above, this electrolyte may be, for example, an electrolyte containing ethylene glycol as the main solvent. Alternatively, a gel electrolyte or a so-called hybrid electrolyte that includes an electrolyte and a solid electrolyte containing a conductive polymer may be used.

[0055] Sealing plate attachment and terminal connection process: The anode tab of the capacitor element 2 is connected to the anode terminal of the sealing plate, and the cathode tab is connected to the cathode terminal. The sealing plate is a sealing member for the exterior case that encloses the capacitor element 2 and also a terminal holding member.

[0056] The sealing plate is made of an insulating material, such as a laminate formed by layering a rubber material on a paper phenolic resin and then hot-pressing the laminate to form a sealing shape for the outer case. The sealing plate is secured by rivet-shaped anode and cathode terminals that penetrate through it. In the sealing plate, the rubber layer made of a rubber material and the resin layer made of paper phenolic resin both perform the functions of insulation and sealing the outer case, while the resin layer reinforces the rubber layer and supports the anode and cathode terminals.

[0057] Encapsulating, crimping, and aging process: The exterior case that houses the capacitor element 2 is made of, for example, a valve metal material, similar to the anode foil 4 and cathode foil 6 of the capacitor element 2. The exterior case is made of, for example, aluminum. This exterior case is equipped with a safety valve for releasing gas emitted from the capacitor element 2 into the outside air.

[0058] If the capacitor element 2 is cylindrical, as shown in Figure 1, the outer case is formed into a cylindrical shape with a bottom that can accommodate the capacitor element 2. First, the anode tab and cathode tab led out from the capacitor element 2 after it has been impregnated with the electrolyte are connected to the anode terminal and cathode terminal held by the sealing plate, respectively, to integrate the capacitor element 2 and the sealing plate. This sealing plate integrated with the capacitor element 2 is then inserted into the outer case. The opening of the outer case is curled, and a crimping process is performed to secure the sealing plate. The case then undergoes an aging process, completing the capacitor as a product.

[0059] <Effects of the embodiment> According to this embodiment, one of the following effects can be obtained. (1) With regard to the air resistance or air permeability, which is directly related to gas discharge, the magnitude relationship of the air resistance between separators 8-1, 8-2 and separators 10-1, 10-2 is separators 8-1, 8-2 < separators 10-1, 10-2, or the magnitude relationship of the air permeability is separators 8-1, 8-2 > separators 10-1, 10-2. By placing separators 8-1, 8-2 adjacent to anode foil 4, which generates gas, gas discharge to the outside of capacitor element 2 is improved, and even if the CV value increases, short-circuiting of capacitor element 2 can be reduced.

[0060] (2) Even if the CV value increases, the number and rate of capacitor short circuits can be reduced.

[0061] (3) The separator materials for separators 8-1, 8-2 and separators 10-1, 10-2 can be selected using the air permeability or air resistance, which directly indicates the ease of gas permeation, and this can reduce capacitor short circuits compared to the selection of separator materials that were previously dependent on density.

[0062] (4) The separator materials used for the separators 8-1, 8-2 and the separators 10-1, 10-2 can be selected based on their air resistance or air permeability, which is closely related to the air permeability, eliminating the need to select separator materials that emphasize density as in the past.

[0063] (5) The CV value can be increased, allowing for a smaller size and higher capacity, as well as increased rated voltage and withstand voltage.

[0064] (6) Anode foil 4 is sandwiched between separator 8-1 and separator 8-2, cathode foil 6 is sandwiched between separator 10-1 and separator 10-2, and separators 8-1 and 10-2 or separators 8-2 and 10-1 are sandwiched between anode foil 4 and cathode foil 6 by lamination, thereby forming insulating separation layers and ventilation layers with different air resistance or air permeability, and improving gas discharge performance. [Example]

[0065] Hereinafter, a capacitor and a manufacturing method thereof according to examples will be described in detail, but the present disclosure is not limited to the contents of the following examples.

[0066] In this example, capacitors shown in Examples 1 to 5 and Comparative Examples 1, 2, and 4 were fabricated. The capacitors shown in Examples 1 to 5 and Comparative Examples 1, 2, and 4 had a rated voltage of 400 V, a diameter of 30 mm, and a height of 35 mm. Strip-shaped aluminum foil was used as the base foil for the anode foil 4 and the cathode foil 6.

[0067] For anode foil 4, the base foil was subjected to a DC etching process to form a surface-expanding layer consisting of tunnel-shaped etching pits. In the DC etching process, a DC current was passed through the aluminum foil in an aqueous solution containing hydrochloric acid to form pits, and then a DC current was passed through the aluminum foil in an aqueous solution containing nitric acid to expand the pits. The aluminum foil was then immersed in an aqueous boric acid solution for chemical conversion, forming a dielectric oxide film on the surface. This resulted in anode foil 4 with a CV value of 401.9, calculated by multiplying the capacitance per unit area by the withstand voltage. The capacitance per unit area and withstand voltage of anode foil 4 were measured in accordance with the Japan Electronics and Information Technology Industries Association (EIAJ) RC-2364A test method for electrode foils for aluminum electrolytic capacitors.

[0068] The base foil of the cathode foil 6 was subjected to AC etching to form a surface-expanding layer consisting of spongy etching pits. The base foil with the surface-expanding layer thus formed was then subjected to a chemical conversion treatment to form an oxide film on the surface of the surface-expanding layer. In the chemical conversion treatment, chlorine that had adhered during the AC etching was removed using a phosphoric acid aqueous solution, and then a voltage was applied to the base foil in an ammonium dihydrogen phosphate aqueous solution to obtain the cathode foil 6.

[0069] As described above, the first separator 8 and the second separator 10 are formed from separator materials selected based on their air resistance or air permeability. The first separator 8 is adjacent to the anode foil 4, while the second separator 10 is adjacent to the cathode foil 6, and these are then overlapped and wound to produce the capacitor element 2. The capacitor element 2 is impregnated with an electrolyte solution. For example, an electrolyte solution containing ethylene glycol as a solvent and ethylamine azelaate as a solute is used.

[0070] Anode and cathode tabs were individually connected to the anode foil 4 and cathode foil 6 by cold welding. Aluminum strip terminals were used for the anode and cathode tabs, and each anode and cathode tab was connected to an external terminal on the sealing plate. The capacitor element 2 thus integrated with the sealing plate was placed in an exterior case and sealed with the sealing plate of this exterior case. After this sealing, the capacitor was subjected to an aging treatment.

[0071] Furthermore, capacitors shown in Example 6 and Comparative Example 3 were fabricated. The capacitors of Example 6 and Comparative Example 3 differ from Examples 1 to 5 and Comparative Examples 1, 2, and 4 in that the cathode foil 6 has a carbon layer formed on a base foil. Except for this difference in the cathode foil 6, the anode foil 4, cathode foil 6, and, for example, the first separator 8 and second separator 10 in the capacitors of Examples 1 to 5 and Comparative Examples 1, 2, and 4 have the same configurations and compositions, and the same manufacturing methods and manufacturing conditions.

[0072] For the cathode foil 6 shown in Example 6 and Comparative Example 3, the base foil was subjected to AC etching to form a surface-expanding layer consisting of spongy etching pits on both sides of the foil. After the formation of this surface-expanding layer, the base foil was subjected to a chemical conversion treatment to form an oxide film on the surface of the surface-expanding layer. In the chemical conversion treatment, chlorine adhering during the AC etching process was removed using a phosphoric acid aqueous solution, and then a voltage was applied to the base foil in an ammonium dihydrogen phosphate aqueous solution. Furthermore, the carbon layer laminated on the base foil contained carbon black as a carbon material. To form this carbon layer, a slurry was prepared by mixing and kneading carbon black powder, a styrene butadiene rubber binder, and a carboxymethyl cellulose ammonium aqueous solution as a dispersant-containing aqueous solution. This slurry was uniformly applied to the base foil. The slurry was heated and dried to volatilize the solvent, and then pressed. In the press processing, the base foil with the slurry laminated thereon was sandwiched between press rollers, and a linear pressure of 5.38 kN / cm was applied to fix the carbon layer to the base foil, producing cathode foil 6.

[0073] The capacitor shown in Reference Example 1 was fabricated. The capacitor according to Reference Example 1 differs from the capacitors according to Examples 1 to 5 and Comparative Examples 1, 2, and 4 in that the CV value of the anode foil 4 is different. Except for the difference in the anode foil 4, the capacitors according to Examples 1 to 5 and Comparative Examples 1, 2, and 4 have the same structure and composition, and are manufactured using the same manufacturing method and conditions.

[0074] For the anode foil 4 used in the capacitor shown in Reference Example 1, the conditions for the chemical conversion treatment and etching were adjusted to obtain an anode foil 4 with a CV value, calculated by multiplying the capacitance per unit area by the withstand voltage, of 336.1.

[0075] Furthermore, a capacitor shown in Reference Example 2 was fabricated. The capacitor shown in Reference Example 2 differs from Examples 1 to 5 and Comparative Examples 1, 2, and 4 in that the CV value of the anode foil 4 is different. Except for this difference in the anode foil, the capacitors of Examples 1 to 5 and Comparative Examples 1, 2, and 4 have the same structure and composition, and are also fabricated using the same manufacturing method and conditions.

[0076] For the anode foil 4 used in the capacitor shown in Reference Example 2, the conditions for chemical conversion treatment and etching were adjusted to form an anode foil 4 with a CV value, calculated by multiplying the capacitance per unit area by the withstand voltage, of 384.4.

[0077] The separators 8 and 10 used in the capacitors shown in each of the Examples, Comparative Examples, and Reference Examples were selected from separators S1 to S9 shown in Table 1.

[0078] [Table 1]

[0079] The air resistance and air permeability of paper have already been described, so a detailed explanation will be omitted. In this disclosure, the air resistance was measured using a Gurley densometer (manufactured by Toyo Seiki Seisakusho, Ltd.). In Table 1, an air resistance of 20,000 [s / 100 mL] indicates that no air permeated even after 20,000 [seconds] of measurement.

[0080] Here, rayon, which is the main material of separators S5 and S9, is a chemical fiber, while the main material of the other separators is a natural fiber.

[0081] The anode foil 4, cathode foil 6, and separators 8 and 10 used in each of the Examples, Comparative Examples, and Reference Examples are shown in Table 2. In Table 2, Table 2-1 shows the anode foil 4, cathode foil 6, and separator 8 for the Examples, Comparative Examples, and Reference Examples, Table 2-2 shows the separator 10 for the Examples, Comparative Examples, and Reference Examples, and Table 2-3 shows the comparison of air permeation resistance, air permeability, and density for the Examples, Comparative Examples, and Reference Examples. In Table 2-3, ">" and "<" are inequality signs indicating a magnitude relationship, and "=" is an equality sign indicating no magnitude relationship, identical, or nearly identical (the same applies to Tables 3 and 4).

[0082] [Table 2]

[0083] In the examples, comparative examples, and reference examples of the present disclosure, the number and rate of occurrence of short circuits were confirmed for each of the following cases, and the significance or advantages of making the air permeability resistance of separator 8 smaller than that of separator 10 and making the air permeability larger than that of separator 10 were verified.

[0084] (1) When the air resistance or air permeability of the separators 8 and 10 is the same: Comparative Example 1, Comparative Example 3 (Table 2) and (Table 3)

[0085] (2) Separator 8 has a lower air resistance than separator 10, a higher air permeability than separator 10, and is mainly made of chemical fiber: Comparative Example 2 (Table 2) and (Table 3)

[0086] (3) When the air resistance of separator 8 is smaller than that of separator 10 and the air permeability is larger than that of separator 10: Examples 1 to 6 (Table 2) and (Table 3)

[0087] (4) When a plurality of anode foils (4-1, 4-2, 4-3) having the same air resistance or air permeability but different CV values ​​were used for the separators 8 and 10, and the density of the separator 8 was made lower than that of the separator 10: Reference Example 1, Reference Example 2, and Comparative Example 4 (Table 2) and (4)

[0088] <Test Method> A current of 10 A and 600 V (1.5 times the rated voltage) was applied to the capacitors of Examples 1 to 6, Comparative Examples 1 to 4, and Reference Examples 1 and 2, and a further voltage was applied to allow current to flow for 1 minute after the capacitor safety valves were opened, and it was confirmed whether or not a short circuit had occurred.

[0089] The occurrence of a short circuit was determined based on whether the following three criteria were met. (1) One minute after the safety valve opens, is there a voltage drop of more than half (300V or more) of the applied voltage (600V)? (2) Whether or not a short circuit noise occurs (3) Whether the safety valve is in an open state one minute after opening

[0090] If none of (1) to (3) occurred, the test was judged as "no short circuit," and if any of (1) to (3) occurred, the test was judged as "short circuit."

[0091] <Examples 1 to 6, Comparative Examples 1 to 3> The test results of Comparative Examples 1 to 3 and Examples 1 to 6 are shown in Table 3.

[0092] [Table 3]

[0093] For Comparative Example 1, the magnitude relationship of air resistance is "20,000 [s / 100 mL] = 20,000 [s / 100 mL]," and the magnitude relationship of air permeability is "0.01 [μm / (Pa·s)] = 0.01 [μm / (Pa·s)]." In this case, the number of short circuits in Comparative Example 1 was 3 / 5, and the short circuit rate was 60%. From Comparative Example 1, it can be seen that if the magnitude relationship of air resistance and air permeability is not related to the present disclosure, it will not contribute to reducing the number or rate of short circuits.

[0094] In Comparative Example 2, the magnitude relationship of the air permeation resistance was 5.08 [s / 100 mL] < 7.96 [s / 100 mL], i.e., separators 8-1 and 8-2 < separators 10-1 and 10-2. The magnitude relationship of the air permeability was 26.63 [μm / (Pa·s)] > 17.00 [μm / (Pa·s)], i.e., separators 8-1 and 8-2 > separators 10-1 and 10-2. In this case, the number of short circuits in Comparative Example 2 was 5 / 5, and the short circuit ratio was 100%. Comparative Example 2 demonstrates that even if the magnitude relationship of the air permeation resistance and air permeability is in accordance with the present disclosure, when the separator is primarily made of chemical fiber, this does not contribute to a reduction in the number or rate of short circuits.

[0095] For Comparative Example 3, the magnitude relationship of the air resistance is 20,000 [s / 100 mL] = 20,000 [s / 100 mL], and the magnitude relationship of the air permeability is 0.01 [μm / (Pa s)] = 0.01 [μm / (Pa s)]. In this case, the number of short circuits in Comparative Example 3 was 4 / 10, and the short circuit ratio was 40%.

[0096] In contrast, in Example 1, the magnitude relationship of air permeation resistance was "0.77 [s / 100 mL] < 20,000 [s / 100 mL]", separators 8-1 and 8-2 < separators 10-1 and 10-2. The magnitude relationship of air permeability was "175.71 [μm / (Pa·s)] > 0.01 [μm / (Pa·s)]", separators 8-1 and 8-2 > separators 10-1 and 10-2. In Example 1, the number of short circuits was 0 / 10, and the short circuit ratio was 0%.

[0097] In Example 2, the magnitude relationship of the air permeation resistance was "0.77 [s / 100 mL] < 20,000 [s / 100 mL]", i.e., separators 8-1 and 8-2 < separators 10-1 and 10-2. The magnitude relationship of the air permeability was "175.71 [μm / (Pa·s)] > 0.01 [μm / (Pa·s)]", i.e., separators 8-1 and 8-2 > separators 10-1 and 10-2. In Example 2, the number of short circuits was 0 / 10, and the short circuit ratio was 0%.

[0098] In Example 3, the magnitude relationship of the air permeation resistance was "1.37 [s / 100 mL] < 20,000 [s / 100 mL]", separators 8-1 and 8-2 < separators 10-1 and 10-2. The magnitude relationship of the air permeability was "98.76 [μm / (Pa·s)] > 0.01 [μm / (Pa·s)]", separators 8-1 and 8-2 > separators 10-1 and 10-2. In Example 3, the number of short circuits was 0 / 10, and the short circuit ratio was 0%.

[0099] In Example 4, the magnitude relationship of the air permeation resistance was "1.37 [s / 100 mL] < 20,000 [s / 100 mL]", separators 8-1 and 8-2 < separators 10-1 and 10-2. The magnitude relationship of the air permeability was "98.76 [μm / (Pa·s)] > 0.01 [μm / (Pa·s)]", separators 8-1 and 8-2 > separators 10-1 and 10-2. In Example 4, the number of short circuits was 1 / 10, and the short circuit ratio was 10%.

[0100] In Example 5, the magnitude relationship of the air permeation resistance was "0.77 [s / 100 mL] < 20,000 [s / 100 mL]", separators 8-1 and 8-2 < separators 10-1 and 10-2. The magnitude relationship of the air permeability was "175.71 [μm / (Pa·s)] > 0.01 [μm / (Pa·s)]", separators 8-1 and 8-2 > separators 10-1 and 10-2. In Example 5, the number of short circuits was 0 / 10, and the short circuit ratio was 0%.

[0101] In Example 6, the magnitude relationship of the air permeation resistance was "0.77 [s / 100 mL] < 20,000 [s / 100 mL]", separators 8-1 and 8-2 < separators 10-1 and 10-2. The magnitude relationship of the air permeability was "175.71 [μm / (Pa·s)] > 0.01 [μm / (Pa·s)]", separators 8-1 and 8-2 > separators 10-1 and 10-2. In Example 6, the number of short circuits was 0 / 10, and the short circuit ratio was 0%.

[0102] <Reference Examples 1 and 2, Comparative Example 4> The test results of Reference Examples 1 and 2 and Comparative Example 4 are shown in Table 4.

[0103] [Table 4]

[0104] In Reference Examples 1 and 2 and Comparative Example 4, the relationships between air resistance, air permeability, and density were set in common for anode foils (4-1, 4-2, 4-3) with different CV values.

[0105] The number of shorts in Reference Example 1 was 0 / 10 and the short ratio was 0%; the number of shorts in Reference Example 2 was 3 / 10 and the short ratio was 30%; and the number of shorts in Comparative Example 4 was 5 / 5 and the short ratio was 100%.

[0106] In Reference Examples 1 and 2 and Comparative Example 4, when the density of separator 8 was set to be lower than that of separator 10, it was found that the number of short circuits and the short circuit ratio increased as the CV value increased, regardless of the density. In other words, it was confirmed that the number of short circuits and the short circuit ratio increased depending on the CV value. It was also found that, as the CV value increased, the number of short circuits and the short circuit ratio could not be reduced even by changing the density. In other words, the present disclosure is a technology that is recognized as being superior to capacitors using anode foils 4 with a large CV value, specifically, anode foils 4 with a CV value of 384.4 or more, and its superiority was recognized to be significant in capacitors using anode foils with a CV value of 401.9 or more.

[0107] <Effects of the Example> From the above experimental results, one of the following effects can be inferred. (1) It was confirmed that, with respect to the air permeability resistance of the separators 8 and 10, if the air permeability resistance of the separator 8 is made smaller than that of the separator 10, or, with respect to the air permeability of the separators 8 and 10, if the air permeability of the separator 8 is made larger than that of the separator 10, the occurrence of short circuits can be suppressed or eliminated even if the CV value is large.

[0108] (2) In the capacitor element 2, gas is efficiently released to the outside of the capacitor element 2 from the separator 8 side with low air resistance or the separator 8 side with high air permeability, thereby reducing the number and rate of short circuits.

[0109] (3) The CV value can be increased, enabling the realization of a small, high-capacity capacitor element.

[0110] Other Embodiments The present disclosure includes the following embodiments. (1) Tables 1, 2, and 3 show examples of paper types for the separators 8 and 10 used in the experiments, but the present disclosure is not limited to these paper types.

[0111] (2) Although the capacitor element is exemplified as a wound element as shown in FIG. 1, the element configuration is not limited to a wound element, and may be a non-wound laminated element.

[0112] (3) Although the capacitor element shown has the anode foil 4 sandwiched between separators 8-1 and 8-2 and the cathode foil 6 sandwiched between separators 10-1 and 10-2, the separator 8 disposed on at least one side adjacent to the anode foil 4 may have a smaller air permeability resistance than the separator 10 adjacent to the cathode foil 6, or the separator 8 may have a larger air permeability than the separator 10.

[0113] As explained above, the most preferred embodiments of the present disclosure have been described, but the present disclosure is not limited to the above description. It goes without saying that various modifications and changes are possible for those skilled in the art based on the gist of the claims and the disclosure in the specification. It goes without saying that such modifications and changes are included in the scope of the present disclosure. [Industrial Applicability]

[0114] According to the capacitor and manufacturing method thereof of the present disclosure, if the air permeability resistance of separator 8 and separator 10 is such that separator 8 < separator 10, or if the air permeability of separator 8 and separator 10 is such that separator 8 > separator 10, then even if the CV value increases, gas release from the capacitor element will be improved, the number and rate of short circuits will be reduced, and a small, high-capacity capacitor can be provided, which is beneficial. [Explanation of symbols]

[0115] 2 Capacitor elements 4 Anode foil 6 cathode foil 8-1, 8-2 First separator 10-1, 10-2 Second separator

Claims

1. an anode foil and a cathode foil; a first separator adjacent to the anode foil; a second separator adjacent to the cathode foil; a capacitor element having The magnitude relationship between the air permeation resistance [s / 100 mL] of the first separator and the air permeation resistance [s / 100 mL] of the second separator is The first separator < the second separator Or, the magnitude relationship between the air permeabilities [μm / (Pa s)] of the first separator and the second separator is The first separator > the second separator That is, a capacitor.

2. The anode foil has a capacitance per unit area [μF / cm 2 2. The capacitor according to claim 1, wherein an index obtained by multiplying [V] by the breakdown voltage [V] exceeds 336.1, and more preferably exceeds 384.

4.

3. The capacitor according to claim 1 or 2, wherein the first separator is mainly made of natural fibers or contains natural fibers.

4. The capacitor of claim 1 or 2, wherein the cathode foil includes a carbon layer.

5. The magnitude relationship between the air permeation resistances [s / 100 mL] of the first separator adjacent to the anode foil and the second separator adjacent to the cathode foil is The first separator < the second separator Or, the magnitude relationship between the air permeabilities [μm / (Pa s)] of the first separator and the second separator is The first separator > the second separator and forming a capacitor element by stacking the anode foil, the first separator adjacent to the anode foil, the cathode foil, and the second separator adjacent to the cathode foil.

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