Capacitor and method for manufacturing the same

Abstract

To provide, for example, a separator suited to a capacitor that includes cathode foil on which a carbon layer is formed, and a capacitor including the separator.SOLUTION: A capacitor (2) includes anode foil (12), cathode foil (14), and a separator (16) disposed between the anode foil and the cathode foil. The cathode foil includes a carbon layer (20), and the separator is in contact with the carbon layer and has a density [symbol: ρ, unit: g / cm3] that satisfies the following formula: ρ≥4.0×10-3×WPA, where WPA represents the amount of carbon per square centimeter of the separator [unit: μg / cm2].SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This disclosure relates to a capacitor including a cathode foil on which a carbon layer is formed. and the manufacturing method thereof Regarding. [Background technology]

[0002] An electrolytic capacitor includes an anode foil, a cathode foil, and a separator placed between the anode and cathode foils, and is capable of storing electricity. In such an electrolytic capacitor, it is known that a carbon layer is formed on the cathode foil (for example, Patent Document 1). The carbon layer has the effect of increasing the capacitance of the cathode foil, for example. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2006-80111 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] Incidentally, in capacitors such as electrolytic capacitors, it is necessary to prevent short circuits between the anode foil and the cathode foil. If a large amount of carbon detaches from the cathode foil, there is a concern that it will adversely affect the insulating function of the separator. Patent Document 1 does not disclose or suggest such a problem, and the configuration disclosed in Patent Document 1 cannot solve such a problem.

[0005] Therefore, the present disclosure aims to provide a separator suitable for a capacitor including, for example, a cathode foil having a carbon layer formed on it, or a capacitor including this separator. [Means for solving the problem]

[0006] To achieve the above object, according to a first aspect of the present disclosure, a capacitor includes an anode foil, a cathode foil, and a separator disposed between the anode foil and the cathode foil. The cathode foil includes a carbon layer, and the separator contacts the carbon layer and is detached from the carbon layer. and adhere to the separator contains carbon, and the separator has a density [symbol: ρ, unit: g / cm 3 , and the attached conduction resistance value of the separator containing carbon is 100 MΩ or more. ρ ≥ 4.0 × 10 -3 ×WPA Here, WPA is the Amount of carbon deposits on carbon or set adhesion amount [unit: μg / cm 2 per 1 square centimeter of the separator.

[0008] In the above capacitor, the Record carbon may be attached only to the cathode side surface. Contact with cathode foil

[0009] In the above capacitor, the Record carbon may be disposed over the entire cathode side surface or may be partially disposed on the cathode side surface. In the above capacitor, the carbon detached from the carbon layer may consist only of carbon black. 。 To achieve the above object, according to a second aspect of the present disclosure, a method for manufacturing a capacitor includes a step of manufacturing an anode foil, a step of forming a carbon layer on a valve action metal foil to manufacture a cathode foil, and setting an adhesion amount of detached carbon detached from the carbon layer to a separator, and setting a density [symbol: ρ, unit: g / cm 3 of the separator so as to satisfy the following formula from the set adhesion amount: ρ ≥ 4.0 × 10 -3 ×WPA Here, WPA is the set adhesion amount [unit: μg / cm 2 per 1 square centimeter of the separator. A step of manufacturing a separator having the set density, and a step of disposing the separator between the anode foil and the cathode foil. In the method of manufacturing the capacitor, the conduction resistance of the separator having the set density may be 100 MΩ or more. The method of manufacturing the capacitor may further include a step of adding a carbon material, a binder, and a dispersant as main materials to a diluent, and mixing the carbon material, the binder, the dispersant, and the diluent by dispersion treatment to form a slurry, and a step of applying the slurry to the valve-action metal foil, drying the slurry, and then pressing the slurry. The carbon layer may be formed by the formation, application, drying, and pressing of the slurry. In the method of manufacturing the capacitor, the carbon material may be only carbon black.

Advantages of the Invention

[0010] According to the above aspect of the present disclosure, the following effects can be obtained.

[0011] Since the separator has a density of 4.0×10 -3 ×WPA or more, it is possible to provide a large short-circuit suppression effect between the electrodes of a capacitor including a cathode foil having a carbon layer in various types and a wide range of thicknesses of the separator. The separator has a different effect of suppressing the decrease in insulation due to the attached carbon and is suitable for a capacitor including a cathode foil having a carbon layer.

Brief Description of the Drawings

[0012] [Figure 1] It is a diagram showing an example of a capacitor according to an embodiment. [Figure 2] It is a diagram showing an experimental sample and the measurement of conduction resistance. [Figure 3] It is a table of the conduction resistance values of the experimental samples. [Figure 4] It is a graph of the conduction resistance values of the experimental samples. [Figure 5] This table shows the sheet resistance and sheet resistance difference of experimental separators with carbon deposits. [Figure 6] This is a graph showing the sheet resistance difference of experimental separators with carbon deposits. [Modes for carrying out the invention]

[0013] Figure 1 shows an example of a capacitor according to an embodiment. In Figure 1, the capacitor's outer casing, sealing member, and electrolyte are omitted. Figure 1B is an enlarged view of the area IB shown in Figure 1A. The configuration shown in Figure 1 is an example, and the technology of this disclosure is not limited to such a configuration.

[0014] Capacitor 2 is an example of an electronic component, such as an electrolytic capacitor. Capacitor 2 includes a capacitor element 4, terminal leads 6, an outer casing, and a sealing member. The terminal leads 6 are connected to the capacitor element 4 and protrude from one end face of the capacitor element 4. Parts of the capacitor element 4 and terminal leads 6 are inserted into the outer casing. A sealing member is placed in the opening of the outer casing to seal the inside of the outer casing. In other words, parts of the capacitor element 4 and terminal leads 6 are sealed inside the outer casing. The terminal leads 6 pass through through holes in the sealing member and protrude from the sealing member.

[0015] The capacitor element 4 includes an anode foil 12, a cathode foil 14, a separator 16, and an electrolyte. The anode foil 12 and cathode foil 14 are each connected to different terminal leads 6. The anode foil 12, cathode foil 14, and separator 16 are stacked and wound together to form a wound element, such that the separator 16 is positioned between the anode foil 12 and cathode foil 14. This wound element forms the capacitor element 4. The voids within the capacitor element 4 and the separator 16 are filled with an electrolyte. The electrolyte may be an electrolyte solution or a gel electrolyte, may contain both an electrolyte solution and a gel electrolyte, or may contain both an electrolyte solution or a gel electrolyte and a solid electrolyte. The solid electrolyte may include, for example, a conductive polymer.

[0016] The anode foil 12 constitutes the anode electrode of the capacitor 2. The anode foil 12 is a valve-acting metal foil, such as tantalum foil or aluminum foil, and is, for example, in the form of a strip. The surface of the anode foil 12 has irregularities formed, for example by etching, and also contains a dielectric oxide film formed, for example by chemical conversion treatment. The irregularities formed by etching have, for example, a porous structure.

[0017] The cathode foil 14 constitutes the cathode electrode of the capacitor 2. The cathode foil 14 is, for example, a strip-shaped foil and includes a main foil 18 and a carbon layer 20. The main foil 18 is, for example, a valve-acting metal foil such as aluminum foil, tantalum foil, niobium foil, titanium foil, hafnium foil, zirconium foil, zinc foil, tungsten foil, bismuth foil, or antimony foil. The surface of the main foil 18 has irregularities formed, for example, by etching, thereby increasing the surface area of ​​the main foil 18. The surface of the main foil 18 may include, for example, tunnel-shaped or spongy etching pits, and these tunnel-shaped or spongy etching pits may form irregularities.

[0018] The carbon layer 20 is arranged on both sides of the main foil 18, for example. The carbon layer 20 may be arranged on only one side of the main foil 18. The carbon layer 20 is in close contact with the irregularities of the main foil 18. In other words, the carbon layer 20 is arranged on the outside of the main foil 18, and the cathode foil 14 has a two-layer structure consisting of the main foil 18 and the carbon layer 20, or a three-layer structure in which the carbon layer 20 is arranged on both sides of the main foil 18. The carbon layer 20 contains a carbon material as its main material, and further contains a binder and a dispersant as additives.

[0019] The carbon material is, for example, spherical carbon. Each spherical carbon acts as an active material. Therefore, the carbon layer 20 contains an electrically double-layer active material layer made of spherical carbon, which increases the capacitance of the cathode foil 14.

[0020] Spherical carbon includes carbon blacks such as Ketjenblack, acetylene black, channel black, and thermal black.

[0021] The carbon material may be a mixture containing the spherical carbon and graphite described. The graphite may be, for example, natural graphite, artificial graphite, or graphitized Ketjenblack, and may have shapes such as flake, scale-like, lumpy, earthy, spherical, or flaky. The graphite is preferably in the form of flakes or flaky particles, and the aspect ratio of the short axis to the long axis of the graphite is preferably in the range of 1:5 to 1:100. With the flake or flaky graphite having the aspect ratio described above, for example, spherical carbon can be pressed into etching pits, and a portion of the carbon layer 20 can be formed inside the etching pits. As a result, the carbon layer 20 can adhere firmly to the main foil 18 due to the anchoring effect.

[0022] When the average particle size of the graphite is between 6 μm and 10 μm, effects such as suppressing the decrease in capacitance due to high-temperature environmental loads can be obtained. Furthermore, when the average particle size of the graphite is 6 μm or less, the capacitance of capacitor 2 can be increased while suppressing the decrease in capacitance due to high-temperature environmental loads. In addition, when the average particle size of the graphite is 6 μm or less, it becomes easier to retain the graphite within the carbon layer 20, and the amount of binder added can be reduced. By reducing the amount of binder added, the proportion of carbon material increases. Therefore, the electrical resistance of the cathode foil 14 can be reduced, and the equivalent series resistance (ESR) of capacitor 2 can be reduced. Note that the average particle size values ​​described are based on the median diameter, also known as D50.

[0023] When the carbon material is a mixture of graphite and spherical carbon, in order to obtain the combined effect of graphite and spherical carbon, the mass ratio of graphite to the mixture of graphite and spherical carbon [mass of graphite / (mass of graphite + mass of spherical carbon)] is, for example, in the range of 25% to 90%.

[0024] The binder is, for example, styrene-butadiene rubber, polyvinylidene fluoride, or polytetrafluoroethylene, which binds the graphite to the spherical carbon. The dispersant is, for example, sodium carboxymethylcellulose. The carbon layer 20 is made, for example, from an aqueous solution in which spherical carbon is dispersed. The dispersant can disperse the spherical carbon in the aqueous solution.

[0025] Separator 16 is disposed between the anode foil 12 and the cathode foil 14 to prevent a short circuit between the anode foil 12 and the cathode foil 14. Separator 16 contacts the anode foil 12 and the carbon layer 20 of the cathode foil 14. Separator 16 is an insulating material and includes separator members such as kraft, manila hemp, esparto, hemp, rayon, cellulose, and mixtures thereof.

[0026] Separator 16 is preferably a kraft-based separator 16. The kraft-based separator 16 is a separator 16 composed only of kraft, a separator 16 having a kraft content of more than, for example, 50% by mass, or a multi-layer separator 16 including a kraft layer composed only of kraft or having a kraft content of more than, for example, 50% by mass and a non-kraft layer composed of a material other than kraft. From the results of the first experiment shown below, the kraft-based separator 16 with carbon attached has a smaller reduction in conduction resistance and higher insulation than other separators 16 with carbon attached. Therefore, in the capacitor 2 including the cathode foil 14 on which the carbon layer 20 is formed, the kraft-based separator 16 is considered to have a greater effect of suppressing short circuits than other separators 16.

[0027] Separator 16 has a density [symbol: ρ, unit: g / cm 3 that satisfies the following formula (1). ρ ≧ 4.0×10 -3 ×WPA ···(1) Here, WPA is the amount of carbon per square centimeter of the separator [unit: μg / cm 2 . WPA is, for example, the set amount of carbon deposition set at the design stage of the capacitor 2. For example, when designing a capacitor 2 that has sufficient insulation between electrodes even when 100 μg / cm 2 of carbon adheres to the separator 16, WPA is set to, for example, 100 μg / cm 2 and the density of the separator 16 is 0.4 g / cm from the following formula (2). 3The settings will be as described above. ρ≧4.0×10 -3 ×100 = 0.4 ... (2) If the density of separator 16 satisfies equation (1), then, as shown in the results of the second experiment below, a significant short-circuit suppression effect between electrodes can be expected for various types and a wide range of thicknesses of separator 16. In other words, if WPA satisfies equation (3) below, then a significant short-circuit suppression effect between electrodes can be expected for various types and a wide range of thicknesses of separator 16. WPA ≤ 250ρ ···(3) Furthermore, in order to standardize the units of mass, WPA uses the unit "g / cm³". 2 When expressed by '', equations (1) and (3) become equations (4) and (5), respectively. ρ≧4.0×10 3 ×WPA ···(4) WPA ≤ 2.5 × 10 -4 ×ρ ···(5) WPA may be the previously described set amount of carbon deposits in the design phase of capacitor 2, or it may be the actual amount of carbon deposits in capacitor 2, or an amount greater than the actual amount of carbon deposits.

[0028] The terminal leads 6 are formed of, for example, a highly conductive metal. One terminal lead 6 is the anode-side terminal and is connected to the anode foil 12 by, for example, cold pressure welding or stitch connection. The other terminal lead 6 is the cathode-side terminal and is connected to the cathode foil 14 by, for example, cold pressure welding or stitch connection.

[0029] The sealing member is made of, for example, insulating rubber. The sealing member has through holes at positions corresponding to the terminal leads 6. The terminal leads 6 of the capacitor element 4 pass through the through holes in the sealing member and are exposed to the outside of the capacitor 2.

[0030] The outer casing is, for example, a cylindrical aluminum case with a bottom. [Capacitor manufacturing process]

[0031] The manufacturing process for capacitor 2 is an example of a method for manufacturing a capacitor according to the present disclosure, and includes, for example, a process for manufacturing an anode foil 12, a process for manufacturing a cathode foil 14, a process for manufacturing a separator 16, a process for manufacturing a capacitor element 4, and a process for encapsulating the capacitor element 4.

[0032] In the process of manufacturing the anode foil 12, the surface of a valve metal foil, such as tantalum foil or aluminum foil, is etched to form irregularities on the surface of the valve metal foil. After the etching process, the valve metal foil is subjected to a chemical conversion treatment to form a dielectric oxide film on the surface of the valve metal foil. The valve metal foil is etched, for example, by applying an electric current to a valve metal foil immersed in an aqueous chloride solution such as hydrochloric acid or sodium chloride. The applied current may be direct current or alternating current. The valve metal foil is chemically converted, for example, by applying a voltage to a valve metal foil immersed in an electrolyte solution containing a solution such as ammonium borate, ammonium borate, ammonium phosphate, or ammonium adipate. The converted valve metal foil is cut to manufacture the anode foil 12.

[0033] In the process of manufacturing the cathode foil 14, the surface of a valve-acting metal foil such as aluminum foil, tantalum foil, niobium foil, titanium foil, hafnium foil, zirconium foil, zinc foil, tungsten foil, bismuth foil, or antimony foil is etched to create irregularities on the surface of the valve-acting metal foil. The etching on the cathode foil 14 side may be the same as or different from the etching on the anode foil 12 side. A carbon layer 20 is formed on the valve-acting metal foil after the etching process, and the valve-acting metal foil with the carbon layer 20 formed on it is cut to manufacture the cathode foil 14.

[0034] The carbon layer 20 is prepared as follows: The carbon material, binder, and dispersant described above are added to the diluent and mixed by a dispersion treatment such as a mixer, jet mixing, ultracentrifugation, or ultrasonic treatment to form a slurry. The binder is added in the amount necessary for bonding the carbon material, for example, and the dispersant is added in the amount necessary for dispersing the carbon material, for example. Therefore, the amount of binder and dispersant added is minuscule compared to the amount of carbon material added. When graphite is used as the carbon material, the graphite may be crushed using a grinder such as a bead mill or ball mill to adjust the average particle size of the graphite before adding it to the diluent.

[0035] Diluents include, for example, alcohols, hydrocarbon solvents, aromatic solvents, amide solvents, water, and mixtures thereof. Alcohols include, for example, methanol, ethanol, or 2-propanol. Amide solvents include, for example, N-methyl-2-pyrrolidone (NMP) or N,N-dimethylformamide (DMF).

[0036] The slurry is applied to the valve metal foil after etching. After the slurry dries, it is pressed. The pressing aligns the carbon material. If the carbon material contains graphite, the pressing aligns the graphite and deforms it to conform to the irregularities of the valve metal foil. Also, when the graphite is pressed against the irregularities, spherical carbon is pushed into the pores of the valve metal foil. As a result, the slurry adheres closely to the valve metal foil, and a carbon layer 20 that adheres closely to the main foil 18 is obtained.

[0037] In the process of manufacturing the separator 16, the separator material described is cut to produce the separator 16.

[0038] Furthermore, during the design phase of the capacitor 2, a maximum or permissible amount of detached carbon to detach from the carbon layer 20 may be set, and the aforementioned set adhesion amount may be set from this maximum or permissible amount, and the density of the separator 16 may be set from the set adhesion amount and the formula (1) described above. Then, in the manufacturing process of the separator 16, a separator 16 having the set density may be manufactured.

[0039] In the process of fabricating the capacitor element 4, terminal leads 6 are connected to the anode foil 12 and cathode foil 14, respectively. A first separator 16 is placed between the anode foil 12 and cathode foil 14, and a second separator 16 is placed outside either the anode foil 12 or the cathode foil 14. The capacitor element 4 is fabricated by winding the anode foil 12, cathode foil 14, and the first and second separators 16.

[0040] In the capacitor element 4 encapsulation process, the capacitor element 4, which has been impregnated with an electrolyte such as an electrolyte solution, is inserted into the outer casing, and then a sealing member is attached to the opening of the outer casing to manufacture the capacitor 2. [First experimental example]

[0041] In the first experiment, the conductivity resistance of the experimental separator 32 (Figure 2) to which carbon 26 was attached was confirmed. Carbon 26 is a substitute for the detached carbon that falls off from the carbon layer 20.

[0042] To prepare the experimental separator 32 to which carbon 26 is attached, prepare slurries 1 to 10 having the solid content concentrations shown in Table 1. The components of slurries 1 to 10 are as follows: Carbon: Carbon black powder Binder: Styrene-butadiene rubber Dispersant: Sodium carboxymethylcellulose aqueous solution Diluent: Pure water The amounts of binder and dispersant added are sufficiently small compared to the amount of carbon added. Therefore, the amount of solids in slurries 1 to 10 can be considered equal to the amount of carbon. [Table 1]

[0043] 10 μL (microliters) of any of the slurries 1 to 10 is evenly dropped onto a 1 cm square surface of the experimental separator 32, and the experimental separator 32 and the slurry are heated to 80°C to obtain the experimental separator 32 with carbon 26 attached. The experimental separator 32 is one of the separators S1 to S18 (manufactured by Nippon Kodo Paper Industry Co., Ltd.) shown in Table 2. Since the solid content concentration of slurries 1 to 10 is low, the specific gravity of slurries 1 to 10 can be considered to be equal to that of water. Therefore, the amount of carbon attached CA when 10 μL of each slurry 1 to 10 is dropped onto the separator can be considered to be the amount shown in Table 1. [Table 2] The materials used for the separators are as follows: Separators S1~S6: Craft Separator S7: (High-density side) Kraft papermaking (Low-density side) Cotton linter and hemp blended paper Separator S8: Mixed paper made from Manila hemp and esparto. Separator S9: Manila hemp Separators S10~S13: Mixed paper made from Manila hemp and esparto. Separator S14: Mixed paper made from nylon fibers and fibrillated acrylic fibers. Separator S15~S18: Special rayon Furthermore, polyvinyl alcohol (PVA) is coated on the kraft paper of separator S7 and on the anode foil-facing surface of the mixed paper of separator S14.

[0044] Figure 2 shows an example of measuring conductivity resistance. In Figure 2, the use of clips for fixing is omitted.

[0045] An experimental separator 32 with carbon 26 attached is placed between two copper foils 34 from above and below, the experimental separator 32 and copper foils 34 are sandwiched between two glass slides 36, and the glass slides 36 are secured with clips to obtain the experimental sample 38. The experimental separator 32 protrudes to the outside of at least one of the copper foils 34 so that the two copper foils 34 do not come into direct contact with each other.

[0046] An insulation resistance meter is connected to the two copper foils 34 to measure the resistance (conductivity resistance) of the experimental sample 38. In the portion where only the experimental separator 32 is placed between the copper foils 34, the resistance value is outside the measurement range, for example, 500 MΩ (megaohms) or more. Therefore, by measuring the resistance value of the experimental sample 38, the effect of carbon 26 on the insulating properties of the separator can be understood.

[0047] Figure 3 shows a table of the conduction resistance values ​​of the experimental samples. Figures 4A and 4B show graphs of the conduction resistance values ​​of the experimental samples. Figure 4A shows the conduction resistance values ​​of experimental sample 38 including each separator S1 and S8, and Figure 4B shows the conduction resistance values ​​of experimental sample 38 including each separator S2 and S9. In Figure 3, "OR" is an abbreviation for "out of range," indicating that the conduction resistance value exceeds 500 MΩ and is outside the measurement range. Also in Figure 3, for example, 1 MΩ and 100 MΩ are represented as "1.00. E+06" and "1.00. E+08," respectively.

[0048] In the first experiment, as shown in the table in Figure 3, it was found that separators S2 to S7 (kraft paper) had high conductivity resistance. 3 Excluding the results for the thin (30 μm) separator S1 and the thickest separator S18, only the Kraft-based separators S2-S7 showed a concentration of 0 to 125 μg / cm². 2 It was found that in the range of carbon deposition amount CA, the conductive resistance values ​​were all "OR" (outside the measurement range), i.e., over 500 MΩ. In the kraft-type separators S2 to S7, it is thought that the carbon powder does not permeate from the front to the back of the separator, and therefore the insulating properties are not reduced.

[0049] In Figure 4A, separators S1 and S8 have different materials and a thickness of 30 μm (density: 0.5 g / cm³). 3 ) were compared, and in Figure 4B, separators S2 and S9 (density: 0.5 g / cm³) have different separator materials and a thickness of 60 μm. 3 The following are being compared. From the graph shown in Figure 4A, it can be seen that at a thickness of 30 μm, the conductive resistance values ​​of separator S1 (kraft paper) and separator S8 (Manila paper) are similar overall, although there is a slight difference. No significant difference was observed between separator S1 and separator S8. However, from the graph shown in Figure 4B, at a thickness of 60 μm and 37.5 μg / cm², 2 At the carbon deposition amounts CA described above, it can be seen that separator S2 (kraft paper) has a higher conductivity resistance than separator S9 (Manila paper). In particular, separator S2 (kraft paper) has a conductivity resistance of 125 μg / cm³. 2 The carbon deposition amount CA below is "OR" (outside the measurement range), indicating a significant effect. In the first experiment, it was found that the Kraft-type separator has superior insulating properties compared to the Manila-type separator.

[0050] Manila paper, 0.5 g / cm² 3 In terms of density, separator S9 (thickness: 60 μm) was found to have a generally higher conductivity resistance than separator S2 (thickness: 30 μm). It is thought that the thickness of the separator affects the conductivity resistance.

[0051] Kraft paper, 0.5 g / cm² 3 At the given density, the conductivity resistance of separator S1 (thickness: 30 μm) decreased significantly with increasing carbon deposition CA, while the conductivity resistance of separator S2 (thickness: 60 μm) hardly decreased. In the case of the thin separator S1, it is thought that pinholes in the separator affect the conductivity resistance.

[0052] The following experimental results were obtained from the first experiment. Craft-type separators: In separators with greater thickness and density, the conductive resistance does not decrease easily. In other words, the effect of pinholes is less, and carbon 26 does not permeate easily. In separators with less thickness and density, the conductive resistance drops sharply. In other words, carbon 26 permeates easily due to the effect of pinholes. Manila-type separators: Carbon 26 becomes less permeable in proportion to or approximately proportion to thickness and density. The phenomenon of a sudden drop in conductivity resistance is not observed when the thickness or density falls below a certain value.

[0053] The separator has the same density (0.5 g / cm³). 3 When the separators have the same thickness (30 μm), both Kraft-type and Manila-type separators exhibit similar levels of conductivity resistance. However, when the separators have the same density (0.5 g / cm³), the conductivity resistance decreases to a similar degree. 3 When having the same thickness (60 μm), Kraft-type separators have a higher conductivity resistance than Manila-type separators. Therefore, according to the first experiment, a significant short-circuit suppression effect between electrodes can be expected by using Kraft-type separators 16 in capacitor 2 containing a carbon layer 20. [Example of the second experiment]

[0054] In the second experiment, to confirm the preferred range of density for separator 16, the sheet resistance difference of experimental separator 32 with carbon 26 attached, as described in the first experiment, was checked. The experimental separator 32 with carbon 26 attached was the same as in the first experiment, so its description is omitted.

[0055] The sheet resistance (surface resistivity) of the first and second surfaces of the experimental separator 32 to which carbon 26 is attached is measured, and the difference in sheet resistance (hereinafter referred to as "sheet resistance difference") is determined. Here, the first surface is the surface to which the slurry is applied and carbon 26 is attached, and the second surface is the surface opposite to the first surface.

[0056] The sheet resistance of the first surface is measured at the center of carbon 26 using the following resistivity meter (4). SearchThe measurement is taken by pressing the needle probe against the surface. The sheet resistance of the second surface is measured using the following resistivity meter at the location corresponding to the center as described above. Search Measurement is performed by pressing a needle probe against the surface. resistivity meter Measuring instrument: Loresta GP Model: MCP-T600 Measurable range: 100 MΩ / sq. or less

[0057] Figure 5 shows a table of sheet resistance and sheet resistance difference for experimental separators with carbon deposits. Figure 6 shows a graph of the sheet resistance difference for experimental separators with carbon deposits. Figures 5 and 6 show the experimental results for each separator S2, S3, S4, S6, S7, S10, S11, S12, and S14.

[0058] In the second experiment, the carbon deposition amount CA was 100 μg / cm³. 2 In that case, 0.4 g / cm³ 3 It was found that the sheet resistance difference was similarly high for separators S2, S3, S4, S6, S7, S11, and S12, which have the densities mentioned above. In the second experiment, the carbon deposition amount CA was 125 μg / cm³. 2 In that case, 0.5 g / cm³ 3 It was found that the sheet resistance difference was equally high in separators S2, S3, S4, S6, and S7 having the densities described above. According to the second experiment, at the densities shown in equations (1) and (4) described above, the sheet resistance difference of experimental separator 32 was at its maximum or nearly maximum, and a capacitor with excellent short-circuit suppression can be obtained regardless of the separator classification or thickness.

[0059] According to the above embodiment, for example, the following effects can be obtained.

[0060] (1) The kraft-type separator 16 can provide a greater short-circuit suppression effect than separators 16 of other paper types having the same density and thickness as the kraft-type separator 16. Therefore, the kraft-type separator 16 has the unique effect of suppressing the decrease in insulation due to carbon adhering to the separator, making it more suitable than other separators 16 for capacitors 2 that include cathode foil 14 on which a carbon layer 20 is formed.

[0061] (2) Separator 16 is 4.0 × 10 -3 When the separator 16 has a density of ×WPA or higher, it can provide a significant short-circuit suppression effect between the electrodes of the capacitor 2 in a range of various types and thicknesses. A separator 16 with such density has the unique effect of suppressing the decrease in insulation due to carbon adhering to the separator, and is suitable for a capacitor 2 that includes a cathode foil 14 on which a carbon layer 20 is formed.

[0062] The features and variations of the embodiments described above are listed below.

[0063] (1) In the above embodiment, the capacitor element 4 is a wound element. However, the capacitor element 4 may also be a laminated element in which a plurality of flat anode foils, cathode foils and separators are stacked.

[0064] (2) The materials of the anode foil 12, cathode foil 14, separator 16, outer case, sealing member, and electrolyte are not limited to those described in the above embodiment. These materials may be other materials used in aluminum electrolytic capacitors or similar capacitors. For example, a capacitor element may be formed by winding a separator between an anode foil and a cathode body, with aluminum tab-shaped lead terminals ultrasonically connected. A phenolic laminate with external terminals attached may be used as the sealing member, or the lead terminals led out from the capacitor element may be connected to the external terminals of the sealing member after the electrolyte has been impregnated into the capacitor element, or the capacitor element and sealing member may be inserted into an outer case and sealed with the sealing member. Furthermore, the material of the carbon layer 20 is not limited to those described in the above embodiment. The material forming the carbon layer 20 may be any conductive material.

[0065] (3) The separator 16 may include members other than the separator members described. The separator 16 may include, for example, detached carbon that separates from the cathode foil 14 on the cathode-side surface that contacts the cathode foil 14. The separator 16 described above can maintain its insulating function even if carbon 26 such as detached carbon is attached to it. Furthermore, from the first experiment described above, the amount of carbon attached CA was 37.5 μg / cm³. 2 If the value is less than 37.5 μg / cm³, it can be seen that the conductivity resistance of all 38 experimental samples will be 100 MΩ or higher. In other words, the carbon deposition amount CA is 37.5 μg / cm³. 2 If the value is less than this, the effect of the separator 16 on the function of the capacitor 2 can be reduced. The detached carbon may be distributed over the entire cathode-side surface or partially on the cathode-side surface.

[0066] The amount of carbon adhering to the separator 16 can be determined, for example, by the following method: The separator 16 removed from the capacitor 2 is washed, for example, with ethanol to remove the electrolyte from the separator 16. The separator 16 from which the electrolyte has been removed is dried. The dried separator 16 is thermally analyzed using an existing analytical method, such as thermogravimetric analysis (TGA) or thermogravimetric differential thermal analysis (TG-DTA), to determine the amount (weight or mass) of carbon 26 adhering to it. By dividing the obtained weight or mass by the analyzed area of ​​the separator 16, the amount of carbon per square centimeter of the separator can be determined.

[0067] As explained above, the most preferred embodiments of this disclosure have been described, but this disclosure is not limited to the above description, and it goes without saying that various modifications and changes can be made by those skilled in the art based on the gist of the invention described in the claims or disclosed in the specification, and such modifications and changes are included in the scope of this disclosure. [Industrial applicability]

[0068] The technology disclosed herein can be used for insulating electrodes containing conductive materials such as carbon, and is therefore useful. [Explanation of Symbols]

[0069] 2 Capacitors 4 Capacitor elements 6-terminal lead 12 Anode foil 14 Cathode foil 16 Separators 18 Main body foil 20 Carbon Layer

Claims

1. A capacitor comprising an anode foil, a cathode foil, and a separator disposed between the anode foil and the cathode foil, The cathode foil includes a carbon layer, The separator contains carbon that has come into contact with the carbon layer and has detached from the carbon layer and adhered to the separator. The separator has a density that satisfies the following equation [symbol: ρ, unit: g / cm³]. 3 A capacitor having the following characteristics: the conductive resistance of the separator containing the attached carbon is 100 MΩ or more. ρ≧4.0×10 -3 ×WPA Here, WPA is the amount of carbon deposited or set amount of carbon per square centimeter of separator [unit: μg / cm]. 2 ]

2. The capacitor according to claim 1, characterized in that the carbon is attached only to the cathode-side surface that contacts the cathode foil.

3. The capacitor according to claim 2, characterized in that the carbon is arranged over the entire cathode-side surface or partially on the cathode-side surface.

4. The capacitor according to claim 1, wherein the carbon that detaches from the carbon layer consists only of carbon black.

5. A method for manufacturing a capacitor, The process of manufacturing anode foil, The process involves forming a carbon layer on a valve-acting metal foil to produce a cathode foil, The amount of detached carbon that separates from the carbon layer and adheres to the separator is set, and the density of the separator [symbol: ρ, unit: g / cm³] is set from the set amount of adhesion to satisfy the following equation. 3 The process of setting ] and ρ≧4.0×10 -3 ×WPA Here, WPA is the set amount of adhesion per square centimeter of separator [unit: μg / cm]. 2 ] A step of manufacturing a separator having the set density, A step of placing the separator between the anode foil and the cathode foil, A method for manufacturing a capacitor, comprising the following features.

6. The method for manufacturing a capacitor according to claim 5, wherein the conductive resistance of the separator having the set density is 100 MΩ or more.

7. A step of adding a carbon material as the main material, a binder, and a dispersant to a diluent, and mixing the carbon material, the binder, the dispersant, and the diluent by a dispersion process to form a slurry, The steps include applying the slurry to the valve-acting metal foil, drying the slurry, and then pressing the slurry. Furthermore, The method for manufacturing a capacitor according to claim 5, wherein the carbon layer is formed by forming the slurry, applying it, drying it, and pressing it.

8. The method for manufacturing a capacitor according to claim 7, wherein the carbon material is carbon black only.

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