Electrode foil for electrolytic capacitor, electrolytic capacitor, method for manufacturing electrode foil for electrolytic capacitor, and method for manufacturing electrolytic capacitor

Abstract

The electrode foil for an electrolytic capacitor of the present application has an anode body having a porous portion and a core portion continuous with the porous portion, and a dielectric layer covering the surface of a metal skeleton constituting the porous portion. Between the metal skeleton constituting the porous portion and the dielectric layer, there is an interface layer containing a first element. The first element is at least one selected from the group consisting of sulfur, nitrogen, and phosphorus.

Description

Technical Field

[0001] This invention relates to electrode foil for electrolytic capacitors, electrolytic capacitors, a method for manufacturing electrode foil for electrolytic capacitors, and a method for manufacturing electrolytic capacitors. Background Technology

[0002] The electrode foil of the electrolytic capacitor includes an anode body with porous portions on its surface. The anode body, for example, uses a metal foil containing a valve-acting metal, and the porous portions are formed by etching the metal foil, thereby increasing the capacitance of the electrolytic capacitor. Furthermore, the electrode foil includes a dielectric layer covering the porous portions. For example, Patent Document 1 proposes forming the dielectric layer using a vapor-phase method.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: International Publication No. 2017 / 26247 Summary of the Invention

[0006] The problem that the invention aims to solve

[0007] In electrolytic capacitors where the surface of the dielectric layer is covered by a conductive polymer compound, leakage current can easily increase if defects are generated in the dielectric layer.

[0008] Methods for solving problems

[0009] One aspect of the present invention relates to an electrode foil for an electrolytic capacitor, comprising an anode body and a dielectric layer, the anode body having a porous portion and a core portion continuous with the porous portion, the dielectric layer covering the surface of a metal skeleton constituting the porous portion, and an interface layer comprising a first element being provided between the metal skeleton and the dielectric layer, the first element being at least one selected from sulfur, nitrogen and phosphorus.

[0010] Another aspect of the present invention relates to an electrolytic capacitor comprising a capacitor element having an electrode foil for an electrolytic capacitor and a conductive polymer compound covering at least a portion of the dielectric layer.

[0011] Another aspect of the present invention relates to a method for manufacturing an electrode foil for an electrolytic capacitor, comprising: a first step of preparing an anode body having a porous portion and a core continuous with the porous portion; a second step of forming an interface layer covering the surface of a metal skeleton constituting the porous portion and including a first element; and a third step of forming a dielectric layer continuous with the interface layer, wherein the first element is at least one selected from sulfur, nitrogen, and phosphorus.

[0012] Another aspect of the present invention relates to a method for manufacturing an electrolytic capacitor, comprising: a step of the method for manufacturing electrode foil for an electrolytic capacitor as described above, and a fourth step of covering at least a portion of the dielectric layer with a conductive polymer compound.

[0013] Invention Effects

[0014] According to the present invention, the increase in leakage current of electrolytic capacitors can be suppressed.

[0015] Novel features of the invention are set forth in the appended claims; however, the invention, in both its composition and content, together with its other objects and features, can be more fully understood from the following detailed description taken in conjunction with the accompanying drawings. Attached Figure Description

[0016] Figure 1 This is a schematic cross-sectional view showing the essential parts of an electrode foil according to one embodiment of the present invention.

[0017] Figure 2 yes Figure 1 An enlarged view of the portion enclosed by the dashed line X.

[0018] Figure 3 This is a schematic cross-sectional view showing the essential parts of an electrode foil according to another embodiment of the present invention.

[0019] Figure 4 yes Figure 2 An enlarged view of the portion enclosed by the dashed line Y.

[0020] Figure 5 This is a schematic cross-sectional view showing an example of an anode body with tunnel-shaped pits.

[0021] Figure 6 This is a schematic cross-sectional view showing another example of an anode body with tunnel-shaped pits.

[0022] Figure 7 This is a schematic cross-sectional view showing another example of an anode body with tunnel-shaped pits.

[0023] Figure 8 This is a schematic cross-sectional view showing an example of an anode body having a porous portion with a main pit and small pits.

[0024] Figure 9 This is a schematic cross-sectional view showing an example of an anode body having a porous portion with a main recess and branch recesses.

[0025] Figure 10 This is a schematic cross-sectional view of an electrolytic capacitor.

[0026] Figure 11 It is a three-dimensional diagram schematically representing the structure of the winding body of an electrolytic capacitor. Detailed Implementation

[0027] An electrode foil for an electrolytic capacitor according to one embodiment of the present invention comprises: an anode body having a porous portion and a core continuous with the porous portion, and a dielectric layer covering the surface of a metal skeleton constituting the porous portion. Hereinafter, the anode body having the porous portion will also be referred to as a metal foil having the porous portion.

[0028] An interface layer containing a first element is provided between the metal framework constituting the porous portion and the dielectric layer. The first element is selected from at least one of sulfur, nitrogen, and phosphorus.

[0029] By setting the aforementioned interface layer, leakage current can be significantly reduced, thereby improving the reliability of the electrolytic capacitor. This can be presumably because, when repairing defects in the dielectric layer, the use of an interface layer containing the first element creates a high-quality film containing more amorphous components and less prone to leakage current.

[0030] In medium- and high-voltage electrolytic capacitors, leakage current is particularly prone to increase due to defects in the dielectric layer. Therefore, the leakage current reduction effect achieved by providing the aforementioned interface layer can be significantly obtained. The electrode foil used in medium- and high-voltage electrolytic capacitors has a withstand voltage of, for example, 30V or more, preferably 120V or more, more preferably 160V or more, and even more preferably 200V or more.

[0031] Sulfur and phosphorus, as the first element mentioned above, are advantageous in terms of their ease of forming amorphous forms. Nitrogen, as the first element mentioned above, is advantageous in terms of its ability to suppress crystallization.

[0032] The interface layer can be thin or lack a clear layer structure. It can be thin enough to identify a region where the first element is located between the dielectric layer and the metal framework. In other words, if the first element is detected in a small region between the dielectric layer and the metal framework using analysis methods such as EDX, GD-OES, and FE-AES (described later), an interface layer can be considered to have formed. The thickness of the interface layer can be, for example, less than 10 nm, or greater than 0.1 nm but less than 5 nm. The thickness of the interface layer is the average thickness of any 10 points in a cross-sectional image of the porous portion of the electrode foil obtained using a scanning electron microscope (SEM) along the thickness direction.

[0033] From the viewpoint of easily and sufficiently reducing leakage current, the content of the first element in the interface layer relative to all elements is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and even more preferably 0.5% by mass or more. From the viewpoint of easily ensuring the dielectric layer and interface layer with an appropriate thickness, the content of the first element can be 0.01% by mass or more and 10% by mass or less, or 0.50% by mass or more and 5% by mass or less.

[0034] In analyzing the distribution or concentration of elements in the interface layer and dielectric layer, methods such as energy-dispersive X-ray spectroscopy (EDX), glow discharge luminescence analysis (GD-OES), and electric field emission Auger electron spectroscopy (FE-AES) can be used. For example, when performing GD-OES analysis on the interface layer from the surface of the first layer side along its depth direction, if a peak belonging to the first element is observed, it can be determined that the interface layer contains the first element corresponding to that peak.

[0035] The anode body comprises a first metal, and the dielectric layer has a first layer of an oxide comprising a second metal. The second metal may be the same as or different from the first metal. Between the metal framework constituting the porous portion and the first layer, there exists an interface layer continuous with the first layer. The interface layer may exist at the boundary between the first layer and the metal framework, or at the boundary between the first layer and other layers covering the metal framework (e.g., a portion of the second layer described later).

[0036] The interface layer contains at least a first element and may also contain a first metal and / or a second metal in the form of an oxide. The interface layer may be formed, for example, from an insulating compound containing the first element (oxide, etc.), or by making the functional groups bonded to the metal framework on the surface of the metal framework contain the first element.

[0037] When the second metal differs from the first metal, a second metal with a relatively high permittivity can be selected without being limited by the first metal, making it easier to increase the capacitance of the electrolytic capacitor. Furthermore, because the range of choices for the second metal is broadened, it is easier to impart a wide variety of properties to the dielectric layer without being limited by the first metal. The first metal may contain Al. The second metal may contain at least one selected from Ta, Nb, Ti, Si, Zr, and Hf.

[0038] When the first layer contains oxides of two or more second metals, the two or more oxides can be mixed or arranged in layers. The first layer may contain a composite oxide containing two or more metals. From the viewpoint of increasing the capacitance of the electrolytic capacitor, it is preferable that the oxide of the second metal has a higher relative permittivity than the oxide of the first metal. Furthermore, from the viewpoint of improving the voltage withstand capability of the electrolytic capacitor, the second metal is preferably Ta, Ti, Si, etc.

[0039] Here, Figure 1 This is a schematic cross-sectional view showing an example of an electrode foil. Figure 1 This refers to a portion of a porous section that has a dielectric layer. Figure 2 yes Figure 1 An enlarged view of the portion enclosed by the dashed line X.

[0040] like Figure 1 As shown, the anode foil 10 includes an anode body 110 that is an integral part of a core portion 111 and a porous portion 112, and a dielectric layer 120 (first layer 121) covering the surface of the metal skeleton constituting the porous portion 112. The porous portion 112 has a plurality of tunnel-shaped pits P surrounded by the metal skeleton. The dielectric layer 120 is configured to cover at least a portion of the surface of the metal skeleton. The first layer 121 contains an oxide of a second metal and has a thickness T1. An interface layer 130 is provided at the boundary between the first layer 121 and the metal skeleton. Figure 1 In this context, D represents the thickness of the porous portion. In the case of medium- to high-voltage electrolytic capacitors, the thickness T1 of the first layer 121 is, for example, 40 nm or more and 200 nm or less.

[0041] (Level 2)

[0042] The electrode foil may have a second layer containing the first metal between the metal skeleton and the first layer. In this case, the dielectric layer has both the first and second layers. The second layer is formed by the formation process of the anode body, and defects in the first layer can be repaired accordingly. The second layer may contain an oxide of the first metal, an oxide of the second metal, or a composite oxide of the first and second metals.

[0043] The second layer, formed by forming an anode body having a first layer and an interface layer on its surface, has at least a region containing a first element (interface layer) on the side of the first layer. When the thickness of the second layer is small, the entire second layer can be a region containing the first element (interface layer). With the formation process (formation of the second layer), a high-quality film with low crystallinity and low defect incidence is easily formed in the region containing the first element. This further reduces leakage current. When forming the second layer using a formation process, the first metal is preferably a valve-acting metal suitable for formation.

[0044] The thickness T2 of the second layer is not particularly limited, but it can be less than the thickness T1 of the first layer. By relatively increasing the thickness of the first layer, for example, by selecting a second metal with a high dielectric constant, the capacitance of the electrolytic capacitor can be significantly improved. The thickness T2 of the second layer can be, for example, 0.5 nm or more and 200 nm or less, or 5 nm or more and 100 nm or less.

[0045] The ratio of the thickness T1 of the first layer to the thickness T2 of the second layer is not particularly limited, and can be appropriately set according to the application and the desired effect. For example, the thickness ratio T1 / T2 can be greater than 1, greater than 2, or greater than 5.

[0046] Here, Figure 3 This is a schematic cross-sectional view showing another example of an electrode foil. Figure 3 This refers to a portion of a porous section on a surface that has a dielectric layer. Figure 4 yes Figure 3 An enlarged view of the portion enclosed by the dashed line Y. Figure 3 In China, for the sake of Figure 1 Corresponding constituent elements and usage Figure 1 The same symbol, for the same... Figure 1 The repeated elements are omitted from the description. Figure 4 In China, for the sake of Figure 2 Corresponding constituent elements and usage Figure 2 The same symbol, for the same... Figure 2 The repeated elements are omitted from the description.

[0047] like Figure 3 As shown, the dielectric layer 120 has a second layer 122 and a first layer 121 sequentially from the metal skeleton side of the porous portion. The first layer 121 has a thickness T1, and the second layer has a thickness T2. Figure 4 As shown, the second layer 122 has a region (interface layer 130) containing the first element on the side of the first layer 121. When the thickness of the second layer is very small, the entire second layer can be a region (interface layer) containing the first element.

[0048] (Anode)

[0049] The anode body is, for example, an integral part of the core and the porous portion. The anode body can be obtained, for example, by etching a portion of a metal foil containing the first metal. The porous portion is the outer part of the metal foil that has been porousened by etching, and the remaining portion, which is the inner part of the metal foil, is the core.

[0050] The term "metal skeleton" refers to a metal portion with a fine structure within a porous section. The porous section has pits or pores surrounded by the metal skeleton. A dielectric layer is configured to cover at least a portion of the surface of the metal skeleton surrounding the pits or pores.

[0051] The thickness of the porous portion is not particularly limited, and can be appropriately selected according to the application of the electrolytic capacitor and the required withstand voltage. The thickness D of the porous portion can be, for example, 10 μm or more and 160 μm or less, or 50 μm or more and 160 μm or less. Furthermore, the thickness D of the porous portion can be, for example, set to 1 / 10 or more and 5 / 10 or less of the thickness of the anode body on each side. The thickness D of the porous portion can be obtained by obtaining a SEM image of a cross-section of the porous portion of the anode body (electrode foil) in the thickness direction and calculating the average thickness at any 10 points. The thicknesses of the dielectric layers, i.e., the thickness T1 of the first layer and the thickness T2 of the second layer, are also calculated in the same way below.

[0052] The porous portion has multiple pits (pores). The shape of the pits can be tunnel-like. Examples of tunnel-like pit shapes include columnar (e.g., cylindrical, square columnar, etc.), conical (e.g., conical, square pyramidal, etc.), and frustum-shaped (e.g., frustum-shaped, square pyramidal, etc.). The shapes of the multiple tunnel-like pits contained in the porous portion can be the same or different from each other. The length direction of the tunnel-like pit is parallel to the axis of the cylinder when the pit is cylindrical, and parallel to the straight line passing through the center of the circle passing through the top and bottom surfaces of the frustum when the pit is frustum-shaped. In the case of tunnel-like pits, it is easy to form an interface layer on the walls of the pits. In addition, it is easy to form a dielectric layer (first layer) with a thickness of, for example, 20 nm or more and 300 nm or less from the surface side to the core side (deep part of the pit) of the porous portion. It is easy to form a film covering the walls of the pits using the ALD method. The walls of the pit can be easily covered with a conductive polymer compound or a combination of a conductive polymer compound and a liquid component, extending all the way to the depth of the pit. Low-resistance, high-heat-dissipation, and high-strength electrode foils are readily obtained. Furthermore, the pit shape can be sponge-like.

[0053] From the viewpoint of increasing the surface area and forming a dielectric layer extending to the depth of the porous portion (pit), the average diameter of the pit (pore diameter) can be set to, for example, 50 nm or more and 2100 nm or less. When the average diameter of the pit is 200 nm or more, in the second step described later (the step of impregnating the anode body with a first processing solution containing the first element), it is easy to adhere the first processing solution containing the first element to the walls of the pit. Furthermore, in the fourth step described later (the step of impregnating the electrode foil with a second processing solution containing a conductive polymer compound), it is easy to cover the walls of the pit with a conductive polymer compound or a combination of a conductive polymer compound and a liquid component.

[0054] The average diameter of the tunnel-like pits can be 170 nm or more and 2100 nm or less, or 200 nm or more and 2100 nm or less, or 500 nm or more and 1500 nm or less. When the average diameter of the tunnel-like pits is within the above range, it is easy to form a relatively thick dielectric layer up to the depth of the porous portion (pit), making it easy to obtain electrode foil suitable for medium and high voltage electrolytic capacitors. Furthermore, the average diameter of the sponge-like pits can be 50 nm or more and 500 nm or less, or 80 nm or more and 300 nm or less.

[0055] It should be noted that the average diameter of the pit is the highest frequency pore diameter in the pore diameter distribution of the volume reference measured using a mercury porosimeter. In the case of tunnel-shaped pits, the average diameter of the pit can be obtained by measuring the pore diameter at any 10 points using an SEM image of the thickness-direction cross-section of the porous portion of the electrode foil (anode body), and calculating their average value.

[0056] The tunnel-like pit includes at least a main pit extending from the surface side of the porous portion to the core side. Using the main pit, a dielectric layer can be easily formed up to the core side of the porous portion, facilitating the infiltration of conductive polymer compounds and liquid components. The main pit can extend along the thickness direction of the porous portion (perpendicular to the surface of the porous portion) or it can extend obliquely relative to the thickness direction of the porous portion. In a cross-section of the porous portion of the anode body along the thickness direction, the angle (acute angle) formed by the length direction of the main pit and the thickness direction of the porous portion can be less than 80°, less than 45°, less than 30°, or less than 15°.

[0057] Compared to the surface side of the porous portion, the diameter of the main recess on the core side can be larger or smaller. Therefore, in the thickness direction cross-section of the porous portion of the anode body, the wall of the main recess can be inclined relative to the length direction of the main recess. In this case, it is easy to impregnate the recess with a conductive polymer compound or a conductive polymer compound and liquid components. In this case, the shape of the main recess is, for example, conical or frustum-shaped. Furthermore, in this case, the inclination angle of the main recess (length direction) relative to the thickness direction of the porous portion is preferably 15° or less. When the length direction of the main recess is approximately aligned with the thickness direction of the porous portion, the inclination angle of the wall of the main recess relative to the length direction of the main recess is approximately the same as the inclination angle of the wall of the main recess relative to the thickness direction of the porous portion. In the above-described case, the angle (acute angle) of inclination of the wall of the main pit relative to the length direction of the main pit is preferably 0.01° or more and 3° or less, more preferably 0.1° or more and 2.8° or less, even more preferably 0.1° or more and 2.5° or less, and particularly preferably 0.2° or more and 2.2° or less. The angle of inclination of the wall of the main pit can be adjusted, for example, by using the crystal orientation of the metal foil, etching processing conditions (e.g., type of etching solution (acid), current density, liquid temperature, etching time, etc.).

[0058] The angle formed by the wall of the main pit and its length direction can be determined by measuring the angle of any 10 main pits using an SEM image of the cross-section of the porous portion of the electrode foil (anode body) along the thickness direction, and then calculating their average value. The angle formed by the length direction of the main pit (the direction in which the main pit extends) and the thickness direction of the porous portion can be determined in the same way.

[0059] The anode body can have a first main surface and a second main surface opposite to the first main surface. The porous portion can have a first porous portion on the side of the first main surface and a second porous portion on the side of the second main surface. The main recess can have a first recess within the first porous portion and a second recess within the second porous portion. At least a portion of the first recess can extend further from the first porous portion toward the second porous portion. In this case, it is easy to form a dielectric layer up to the depth of the recess, conductive polymers and liquid components can easily penetrate, and the surface area of ​​the anode body is increased, which is advantageous from the perspective of improving electrostatic capacitance.

[0060] Furthermore, at least a portion of the first pit can be extended further from the first porous portion toward the second porous portion and connected to at least a portion of the second pit. The proportion (number ratio) of the first pit connected to the second pit relative to all the first pits is, for example, 5% or more, or 5% or more and 20% or less. When the feed gas is supplied to the anode body (porous portion) using the ALD method, the feed gas that has entered the pit from one side of the first and second main surfaces can move into the pit on the other side of the first and second main surfaces. As a result, the feed gas can easily diffuse to the depth of the first and second pits. In addition, unwanted components in the feed gas that have entered the pit from one side of the first and second main surfaces can easily be discharged to the outside from the pit on the other side of the first and second main surfaces. As a result, a uniform film can easily be formed on the surface of the first and second pits in a short time. When supplying raw material gas into the pit using the ALD method, the pressure rise within the pit is suppressed. Smooth supply of the raw material gas facilitates the formation of a dense film (dielectric layer), which is beneficial for reducing the leakage current of the electrolytic capacitor. Furthermore, when venting the raw material gas from the pit using the ALD method, the gas is also vented smoothly, preventing the accumulation of excessive raw material gas components in the dielectric layer. This shortens venting time and increases productivity. During the manufacture of electrolytic capacitors, the pressure rise within the pit can be suppressed during the permeation of conductive polymer compounds and liquid components into the pit, allowing for smooth permeation and contributing to a reduction in leakage current and ESR of the electrolytic capacitor.

[0061] Here, Figure 5 This is a schematic cross-sectional view showing an example of an anode body. Figure 5 This represents a cross-section along the thickness direction of the porous portion of the anode body.

[0062] like Figure 5 As shown, the anode body 300 has a porous portion 310 and a core portion 320 connected to the porous portion 310. The anode body 300 has a first main surface 301 and a second main surface 302 opposite to the first main surface 301. The porous portion 310 has a first porous portion 311 provided on the side of the first main surface 301 and a second porous portion 312 provided on the side of the second main surface 302. The first porous portion 311 has a tunnel-shaped first recess 331, and the second porous portion 312 has a tunnel-shaped second recess 332. The first recess 331 and the second recess 332 are main recesses.

[0063] Compared to the first main surface 301 side of the first porous portion 311, the diameter of the first recess 331 on the core portion 320 side is smaller. Consequently, the wall of the first recess 331 is inclined relative to the thickness direction of the first porous portion 311 (the direction perpendicular to the first main surface 301). The first recess 331 is frustoconical, and its length direction is approximately aligned with the thickness direction of the first porous portion.

[0064] Compared to the second main surface 302 side of the second porous portion 312, the diameter of the second recess 332 on the core portion 320 side is smaller. Consequently, the wall of the second recess 332 is inclined relative to the thickness direction of the second porous portion 312 (the direction perpendicular to the second main surface 302). The second recess 332 is frustoconical, and its length direction is approximately aligned with the thickness direction of the second porous portion 312.

[0065] In a cross-section along the thickness direction of the porous portion 310 of the anode body 300, the angle formed by the wall of the first recess 331 and the thickness direction of the first porous portion 311 ( Figure 5 Angle θ in 3A For example, it can be 0.01° or more and 2.8° or less, or it can be 0.1° or more and 2.8° or less. In the cross-section of the porous portion 310 of the anode body 300 in the thickness direction, the angle formed by the wall of the second recess 332 and the thickness direction of the second porous portion 312 ( Figure 5 Angle θ in 3B For example, it can be above 0.01° and below 2.8°, or it can be above 0.1° and below 2.8°.

[0066] exist Figure 5 In the case of an anode body, it is more advantageous from a strength perspective. In addition, since the diameter of the pit is large on the main surface side (pit opening side) of the porous part, it is easier for conductive polymer compounds or conductive polymer compounds and liquid components to penetrate into the porous part, which is beneficial to reducing the ESR of the electrolytic capacitor.

[0067] Figure 5 The first and second pits are truncated cones, but they can also be truncated square pyramids, cones, or square pyramids. Figure 5 The length directions of the first and second recesses are generally aligned with the thickness directions of the first and second porous portions, but they may also be slightly inclined relative to the thickness directions of the first and second porous portions within a range of 15° or less. The first and second recesses may also have small recesses and / or branch recesses, as described later.

[0068] Here, Figure 6 This is a schematic cross-sectional view showing another example of an anode body. Figure 6 This represents a cross-section along the thickness direction of the porous portion of the anode body. Figure 6In China, for the sake of Figure 5 Corresponding constituent elements and usage Figure 5 The same symbol, for the same... Figure 5 The repeated elements are omitted from the description.

[0069] Figure 6 In the anode body 400 shown, the first porous portion 311 has a tunnel-shaped first recess 431, and the second porous portion 312 has a tunnel-shaped second recess 432. The first recess 431 and the second recess 432 are main recesses. Compared with the first main surface 301 side of the first porous portion 311, the diameter of the first recess 431 on the core portion 320 side is larger. As a result, the wall surface of the first recess 431 is inclined relative to the thickness direction of the first porous portion 311 (the direction perpendicular to the first main surface 301). The first recess 431 is frustoconical, and the length direction of the first recess 431 is approximately aligned with the thickness direction of the first porous portion 311.

[0070] Compared to the second main surface 302 side of the second porous portion 312, the diameter of the second recess 432 on the core portion 320 side is larger. Consequently, the wall of the second recess 432 is inclined relative to the thickness direction of the second porous portion 312 (the direction perpendicular to the second main surface 302). The second recess 432 is frustoconical, and its length direction is approximately aligned with the thickness direction of the second porous portion 312.

[0071] In a cross-section along the thickness direction of the porous portion 310 of the anode body 400, the angle formed by the wall of the first recess 431 and the thickness direction of the first porous portion 311 ( Figure 6 Angle θ in 4A For example, it can be 0.01° or more and 2.2° or less, or it can be 0.1° or more and 2.2° or less. In the cross-section of the porous portion 310 of the anode body 400 in the thickness direction, the angle formed by the wall of the second recess 432 and the thickness direction of the second porous portion 312 ( Figure 6 Angle θ in 4B For example, it can be above 0.01° and below 2.2°, or it can be above 0.1° and below 2.2°.

[0072] Figure 6 Since the anode body can be manufactured by etching the substrate while suppressing the dissolution of the substrate surface, it is advantageous in terms of improving the electrostatic capacitance of the electrode foil and increasing the capacitance of the electrolytic capacitor.

[0073] Figure 6 The first and second pits are truncated cones, but they can also be truncated square cones. Figure 6The length directions of the first and second recesses are generally aligned with the thickness directions of the first and second porous portions, but they may also be slightly inclined relative to the thickness directions of the first and second porous portions within a range of 15° or less. The first and second recesses may also have small recesses and / or branch recesses, as described later.

[0074] Here, Figure 7 This is a schematic cross-sectional view showing another example of an anode body. Figure 7 This represents a cross-section along the thickness direction of the porous portion of the anode body. Figure 7 In China, for the sake of Figure 5 Corresponding constituent elements and usage Figure 5 The same symbol, for the same... Figure 5 The repeated elements are omitted from the description.

[0075] Figure 7 In the anode body 500 shown, a portion of the first recess 331 extends further from the first porous portion 311 toward the second porous portion 412, and has a third recess 533 penetrating the core portion 320, connected to a portion of the second recess 332. The proportion (number ratio) of the first recess having the third recess 533 to all first recesses can, for example, be more than 5% and less than 20%.

[0076] Figures 5-7 In the middle, the first pit and the second pit have the same shape, however, the first pit and the second pit can also have different shapes. Figure 7 The first and second pits shown are related to Figure 5 The first and second pits shown have the same shape, however the shape is not limited to this.

[0077] The tunnel-like pits may also include small pits in the surface region of the porous portion. The small pits are shorter than the main pits, and the length ratio of the small pits to the main pits is 0.7 or less, or even 0.6 or less. The aforementioned surface region of the porous portion refers to a region with a depth of 10 μm or less from the surface of the porous portion. Small pits are pits that exist only in this region with a depth of 10 μm or less from the surface of the porous portion. The surface region of the porous portion is, for example, a region with a thickness of 20% or less of the thickness of the porous portion, and the thickness of the porous portion is, for example, 50 μm or more. Small pits are sometimes formed due to the rolling process of the metal foil. In this case, small pits with a large tilt angle relative to the thickness direction of the porous portion may be formed. By including small pits, the surface area of ​​the anode body is further increased, and the electrostatic capacitance can be further improved. Small pits may or may not be connected to the main pits. From the viewpoint of ensuring the strength of the anode body, it is preferable that the proportion of small pits is small compared to the main pits, and the number of small pits is preferably more than 5% and less than 20% of the number of main pits.

[0078] The length of the main pit is the average length of any 20 main pits obtained using an SEM image of the porous portion of the electrode foil (anode) in the thickness direction. The length of the minor pit is the average length of any 10 minor pits existing in a region at a depth of less than 10 μm from the surface of the porous portion, obtained using an SEM image of the porous portion of the electrode foil (anode) in the thickness direction.

[0079] Compared to the main pit, the smaller pits can have a larger tilt angle relative to the thickness direction of the porous section. With a large tilt angle, smaller pits with larger length dimensions can exist in the surface region of the porous section, making it easier to increase the surface area of ​​the anode body and further improve the electrostatic capacitance.

[0080] In the cross-section of the porous portion of the anode body in the thickness direction, the angle (acute angle) formed by the length direction of the small pit and the thickness direction of the porous portion can be greater than 5° and less than 88°, greater than 10° and less than 85°, greater than 45° and less than 85°, or greater than 50° and less than 85°.

[0081] The angle (acute angle) formed by the length direction of the small pit and the thickness direction of the porous part can be obtained by the following operation: using an SEM image of the cross-section of the porous part of the electrode foil (anode body) in the thickness direction, measuring the above angle for any 10 small pits, and calculating their average value.

[0082] The tunnel-shaped recess may further include branch recesses that branch off from and extend from the main recess. By including branch recesses, the surface area of ​​the anode body is further increased, thereby further improving the capacitance. Furthermore, from the viewpoint of ensuring the strength of the anode body, in the cross-section of the porous portion of the anode body along the thickness direction, the angle formed by the length direction of the main recess and the length direction of the branch recess can be 70° or more and 110° or less, or 80° or more and 100° or less. The branch recesses, for example, have a length of 5% or more and 25% or less of the length of the main recess.

[0083] The angle formed by the length direction of the main pit and the length direction of the branch pits can be obtained by the following operation: using an SEM image of the cross-section of the porous part of the electrode foil (anode body) in the thickness direction, measuring the above angle for any 10 branch pits, and calculating their average value.

[0084] Here, Figure 8 This is a schematic cross-sectional view showing an example of an anode body having a porous portion with a main pit and small pits. Figure 8 This represents a cross-section along the thickness direction of the porous portion of the anode body.

[0085] The anode body 600 has a porous portion 610 and a core portion 620 continuous with the porous portion 610. The anode body 600 has a first main surface 601 and a second main surface 602 opposite to the first main surface 601. The porous portion 610 has a first porous portion 611 located on the side of the first main surface 601 and a second porous portion 612 located on the side of the second main surface 602, which separates the core portion 620. The first porous portion 611 has a tunnel-shaped first recess 631, and the second porous portion 612 has a tunnel-shaped second recess 632.

[0086] like Figure 8 As shown, the first recess 631 includes a main recess 631a and a small recess 631b. The small recess 631b exists in the surface region of the first porous portion 611 (the region with a depth of less than 10 μm from the main surface 601 of the first porous portion 611) and has a length of less than 70% of the length of the main recess 631a. The second recess 632 includes a main recess 632a and a small recess 632b. The small recess 632b exists in the surface region of the second porous portion 612 (the region with a depth of less than 10 μm from the main surface 602 of the second porous portion 612) and has a length of less than 70% of the length of the main recess 632a.

[0087] In a cross-section along the thickness direction of the porous portion 610 of the anode body 600, the angle formed by the length direction of the main recess 631a and the thickness direction of the first porous portion 611 (the direction perpendicular to the first main surface 601) is ( Figure 8 Angle θ in 6A For example, it is 45° or less. In the cross-section of the porous portion 610 of the anode body 600 in the thickness direction, the angle formed by the length direction of the main recess 632a and the thickness direction of the second porous portion 612 (the direction perpendicular to the second main surface 602) is ( Figure 8 Angle θ in 6B For example, below 45°.

[0088] In a cross-section along the thickness direction of the porous portion 610 of the anode body 600, the angle formed by the length direction of the small pit 631b and the thickness direction of the first porous portion 611 ( Figure 8 Angle θ in 6C The angle can be greater than 30° and less than 88°, or greater than 45° and less than 85°. In the cross-section of the porous portion 610 of the anode body 600 along the thickness direction, the angle formed by the length direction of the small pit 632b and the thickness direction of the second porous portion 612 ( Figure 8 Angle θ in 6D () can be above 30° and below 88°, or above 45° and below 85°. Figure 8 The first and second pits are cylindrical, but the shape of the pits is not limited to this, and can also be square columnar, etc.

[0089] Here, Figure 9 This is a schematic cross-sectional view showing an example of an anode body having a main recess and branch recesses. Figure 9 This represents a cross-section along the thickness direction of the porous portion of the anode body. Figure 9 In China, for the sake of Figure 8 Corresponding constituent elements and usage Figure 8 The same symbol, for the same... Figure 8 The repeated elements are omitted from the description.

[0090] like Figure 9 As shown, in the anode body 700, the first porous portion 611 has a tunnel-shaped first recess 731, and the second porous portion 612 has a tunnel-shaped second recess 732. The first recess 731 includes a main recess 731a and branch recesses 731b that branch off from and extend from the main recess 731a. The second recess 732 includes a main recess 732a and branch recesses 731b that branch off from and extend from the main recess 731a.

[0091] In a cross-section along the thickness direction of the porous portion 610 of the anode body 700, the length direction of the main recess 731a is approximately aligned with the thickness direction of the first porous portion 611 (the direction perpendicular to the first main surface 601). In a cross-section along the thickness direction of the porous portion 610 of the anode body 700, the length direction of the main recess 732a is approximately aligned with the thickness direction of the second porous portion 612 (the direction perpendicular to the second main surface 602). The main recess (length direction) may be slightly inclined relative to the thickness direction of the porous portion within a range of 15° or less.

[0092] In the cross-section along the thickness direction of the porous portion 610 of the anode body 700, the angle formed by the length direction of the main recess 731a and the length direction of the branch recess 731b ( Figure 9 Angle θ in 7A For example, the angle is 70° or more and 110° or less, preferably 85° or more and 95° or less. In the cross-section of the porous portion 610 of the anode body 700 in the thickness direction, the angle formed by the length direction of the main recess 732a and the length direction of the branch recess 732b ( Figure 9 Angle θ in 7B For example, the angle is 70° or higher and 110° or lower, preferably 85° or higher and 95° or lower. Figure 9 The first and second pits are cylindrical, but the shape of the pits is not limited to this, and can also be square columnar, etc.

[0093] Electrolytic capacitors

[0094] An electrolytic capacitor according to one embodiment of the present invention includes a capacitor element. The capacitor element includes the electrode foil for an electrolytic capacitor described above and a conductive polymer compound covering at least a portion of a dielectric layer. A cathode body may also be disposed facing the electrode foil (porous portion) for the electrolytic capacitor described above. In this case, it is sufficient to sandwich the conductive polymer compound between the electrode foil (porous portion) and the cathode body. With this arrangement, the cathode portion can be constructed using the conductive polymer compound and the cathode body.

[0095] (Conductive polymer compound)

[0096] Examples of conductive polymers include π-conjugated polymers. Other examples include polypyrrole, polythiophene, polyfuran, polyaniline, polyacetylene, polyphenylene, polyphenylene vinylidene, polyphenylene oxide, and polythiophene vinylidene. These can be used alone, in combination of two or more monomers, or as copolymers of two or more monomers. The weight-average molecular weight of conductive polymers is, for example, 1000 to 100000.

[0097] It should be noted that in this specification, polypyrrole, polythiophene, polyfuran, and polyaniline refer to polymers with polypyrrole, polythiophene, polyfuran, and polyaniline as their basic backbones, respectively. Therefore, polypyrrole, polythiophene, polyfuran, and polyaniline may also contain their respective derivatives. For example, polythiophene may include poly(3,4-ethylenedioxythiophene).

[0098] Conductive polymers can be doped with dopants. The dopants can be polyanions. Specific examples of polyanions include polyvinylsulfonic acid, polystyrene sulfonic acid, polyallyl sulfonic acid, polyacrylamide sulfonic acid, polymethacrylamide 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. Furthermore, they can be polymers of a single monomer or copolymers of two or more monomers. Polyanions derived from polystyrene sulfonic acid are preferred.

[0099] For example, at least a portion of the surface of the dielectric layer is covered by a solid electrolyte layer comprising at least a conductive polymer compound. The solid electrolyte layer may contain dopants in addition to the conductive polymer compound. In an electrolytic capacitor, the conductive polymer compound (solid electrolyte layer) forms part of the cathode portion together with the cathode body. The solid electrolyte layer may also contain additives as needed.

[0100] (Liquid component)

[0101] Electrolytic capacitors can have capacitor elements and a liquid component. The liquid component is in contact with the dielectric layer (first layer) directly or through a conductive polymer compound. The liquid component only needs to exist together with the conductive polymer compound between the anode (dielectric layer) and the cathode.

[0102] The liquid component can be a non-aqueous solvent or an electrolyte containing a non-aqueous solvent and dissolved ionic substances (solutes, such as organic salts). The non-aqueous solvent can be an organic solvent or an ionic liquid. When the electrolyte is impregnated into the porous portion, the electrolyte is used to repair defects in the dielectric layer. At this time, due to the presence of an interface layer containing the first element, a high-quality film is easily formed. As a result, leakage current is further reduced.

[0103] As a non-aqueous solvent, a high-boiling-point solvent is preferred. For example, polyol compounds, cyclic sulfone compounds such as sulfolane, lactone compounds such as γ-butyrolactone, amide compounds such as N-methylacetamide, N,N-dimethylformamide, and N-methyl-2-pyrrolidone, ester compounds such as methyl acetate, carbonate compounds such as propylene carbonate, ether compounds such as 1,4-dioxane, ketone compounds such as methyl ethyl ketone, and formaldehyde can be used.

[0104] The liquid component preferably contains a polyol compound. Within the polyol compound, the conductive polymer is readily dispersed in a good state, easily penetrating into the pits and thus readily covering the pit walls with the conductive polymer. This, in turn, improves the contact between the dielectric layer and the conductive polymer.

[0105] The polyol compound preferably includes at least one selected from diol compounds and glycerol compounds (hereinafter also referred to as diol compounds, etc.). When the liquid component includes diol compounds, the conductive polymer compound is more likely to swell, the orientation of the conductive polymer compound is improved, the conductivity of the conductive polymer compound (solid electrolyte layer) is improved, and the ESR is more easily reduced. In addition, the high boiling point of diol compounds, etc., also suppresses permeation from the sealing part of the electrolytic capacitor to the outside, suppresses the reduction of film repair function caused by the reduction of solvent, and suppresses the reduction of voltage withstand capability.

[0106] Glycol compounds include alkylene glycols, polyalkylene glycols, etc. The weight-average molecular weight of polyalkylene glycols is, for example, 100 or more and 3000 or less, or 100 or more and 2000 or less. The weight-average molecular weight of polyethylene glycol is, for example, 100 or more and 600 or less, or 100 or more and 400 or less. Specifically, examples include ethylene glycol, propylene glycol, butanediol, hexanediol, diethylene glycol, triethylene glycol, etc. Among glycol compounds, ethylene glycol is preferred from the perspective of low viscosity and easy solubility of acidic and alkaline components. Furthermore, ethylene glycol is preferred because of its high thermal conductivity and excellent heat dissipation, which improves its heat resistance.

[0107] Glycerol compounds include glycerol, polyglycerol, and their derivatives. Examples of derivatives of glycerol or polyglycerol include esters in which at least a portion of the hydroxyl groups of glycerol or polyglycerol are esterified, and alkylene oxide adducts of glycerol or polyglycerol.

[0108] Polyglycerol contains repeating structures of glycerol units. The number of repeating glycerol units in polyglycerol is, for example, 2 or more and 20 or less, or 2 or more and 12 or less, or 2 or more and 10 or less, or 2 or more and 6 or less. Examples of polyglycerol include diglycerol and triglycerol. The weight-average molecular weight of polyglycerol is preferably, for example, 200 or more and 3000 or less, more preferably 300 or more and 800 or less.

[0109] Liquid components can contain both acidic (anionic) and basic (cationic) components. Salts (solutes) can be formed from these acidic and basic components. Acidic components contribute to the skin's repair function. Examples of acidic components include organic carboxylic acids and inorganic acids. Examples of inorganic acids include phosphoric acid, boric acid, and sulfuric acid.

[0110] Organic carboxylic acid compounds may include at least one selected from aromatic carboxylic acid compounds and aliphatic carboxylic acid compounds.

[0111] Aliphatic carboxylic acid compounds include saturated and unsaturated aliphatic carboxylic acids. Examples of saturated aliphatic carboxylic acids include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, 1,6-decanedicarboxylic acid, 1,7-octanedicarboxylic acid, formic acid, acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, lauric acid, myristic acid, stearic acid, and behenic acid. Examples of unsaturated aliphatic carboxylic acids include acrylic acid, methacrylic acid, maleic acid, fumaric acid, and oleic acid. Aliphatic carboxylic acid compounds can be used alone or in combination of two or more.

[0112] Aromatic carboxylic acid compounds include, for example, phthalic acid (ortho-form), isophthalic acid (meta-form), terephthalic acid (para-form), benzoic acid, salicylic acid, trimellitic acid, and pyromellitic acid. Aromatic carboxylic acid compounds can be used alone or in combination of two or more.

[0113] From the perspective of improving the skin repair function and thermal stability, the organic carboxylic acid compound preferably includes at least one selected from benzoic acid, azelaic acid, sebacic acid, 1,6-decanedicarboxylic acid and 1,7-octanedicarboxylic acid.

[0114] Examples of base components include primary to tertiary amine compounds. Examples of amine compounds include monoalkylamines such as ethylamine, dialkylamines such as diethylamine, and trialkylamines such as triethylamine. Additionally, compounds with alkyl-substituted amidine groups, such as imidazole compounds (including quaternary ammonium compounds), can be used as base components.

[0115] An organic salt is a salt in which at least one of the anion and cation contains an organic compound. Examples of organic salts include trimethylamine maleate, triethylamine borosilicate, ethyldimethylamine phthalate, mono-1,2,3,4-tetramethylimidazoline phthalate, and mono-1,3-dimethyl-2-ethylimidazoline phthalate.

[0116] The liquid component preferably contains more acidic components than the alkaline component. The acidic component lowers the pH of the electrolyte from the initial stage, inhibiting the dedoping of dopants from the conductive polymer. By containing more acidic components than the alkaline component, the dedoping of dopants from the conductive polymer (deterioration of the solid electrolyte) can be suppressed. Furthermore, the acidic component contributes to the film repair function of the liquid component; for this reason, it is also preferable to contain more acidic components than the alkaline component.

[0117] From the viewpoint of suppressing the dedoping of dopants from conductive polymers (suppressing the degradation of solid electrolyte layers) and improving the film repair function, the molar ratio of acid component to alkali component (acid component / alkali component) is, for example, 1.1 or more, preferably 1.5 or more, and more preferably 1.5 or more and 10 or less.

[0118] From the perspective of suppressing the dedoping of dopants from conductive polymers, the pH of the liquid component can be below 6, or above 1 and below 5.

[0119] (Cathode)

[0120] The cathode can be made of metal foil. There are no particular limitations on the type of metal, but valve-acting metals such as aluminum, tantalum, and niobium, or alloys containing valve-acting metals, are preferred. The surface of the metal foil can be roughened as needed. A metallization film or a film of a different metal (dissimilar metal) or non-metal can be applied to the surface of the metal foil. Examples of dissimilar metals or non-metals include metals such as titanium and non-metals such as carbon.

[0121] (spacer)

[0122] When using metal foil as the cathode, a spacer can be disposed between the metal foil and the anode. There are no particular limitations on the spacer; for example, a nonwoven fabric containing fibers such as cellulose, polyethylene terephthalate, vinylon, or polyamides (e.g., aliphatic polyamides, aramids, and other aromatic polyamides) can be used.

[0123] (other)

[0124] An electrolytic capacitor may have at least one capacitor element or multiple capacitor elements. The number of capacitor elements in an electrolytic capacitor is determined by its intended use.

[0125] [Manufacturing method of electrode foil for electrolytic capacitors]

[0126] A method for manufacturing electrode foil for electrolytic capacitors includes a first step of preparing an anode body having a porous portion and a core continuous with the porous portion. The method further includes a second step of forming an interface layer covering the surface of a metal framework constituting the porous portion, and a third step of forming a dielectric layer continuous with the interface layer. The interface layer includes a first element, which is at least one selected from sulfur, nitrogen, and phosphorus.

[0127] (Step 1)

[0128] In the first step, for example, the metal foil containing the first metal is roughened by etching. Roughening creates multiple pits or pores on the surface of the metal foil. The metal foil is then immersed in an etching solution (acidic solution) for etching. For example, etching can be performed using direct current etching or alternating current etching.

[0129] The type of the first metal is not particularly limited. From the perspective of ease of formation of the second layer using chemical conversion, valve-acting metals such as aluminum (Al), tantalum (Ta), and niobium (Nb), or alloys containing valve-acting metals, can be used. Additionally, to effectively form porous portions, copper (Cu) can be included in the metal foil. The thickness of the metal foil is not particularly limited, for example, it can be 15 μm or more and 300 μm or less.

[0130] (Step 2)

[0131] In the second step, the anode body can be impregnated with the first processing solution containing the first element. For example, the anode body can be immersed in the first processing solution, or the first processing solution can be sprayed onto the anode body. From the viewpoint of improving productivity, the second step can be performed during the first step.

[0132] The first treatment solution is, for example, an aqueous solution containing the first element. The aqueous solution can be an alkaline solution. From the viewpoint of suppressing damage to the metal framework, the alkaline solution is preferably weakly alkaline. The pH of the alkaline solution is, for example, set to 8-13. The solvent of the alkaline solution preferably contains water as the main component, or water may constitute 80% or more of the solvent by mass. Furthermore, when the treatment time using the first treatment solution is a short period of 5 minutes or less, the aqueous solution containing the first element can be an acidic solution. In the case of an acidic solution, from the viewpoint of suppressing damage to the metal framework, the acidic solution preferably contains 0.2% or more of aluminum ions by mass.

[0133] The first treatment solution is, for example, an aqueous solution of a compound containing the first element. Examples of compounds containing sulfur include sulfuric acid. Examples of compounds containing nitrogen include nitric acid. Examples of compounds containing phosphorus include phosphoric acid, ammonium dihydrogen phosphate, phosphonic acid, and hypophosphonic acid.

[0134] From the viewpoint of improving the capacitance of electrolytic capacitors, the content of the first element in the first treatment solution is preferably trace, for example, it can be 0.01 ppm or more and 500 ppm or less, or 0.1 ppm or more and 100 ppm or less. Furthermore, when the first treatment solution is an acidic aqueous solution and the process of impregnating the anode body with the first treatment solution is performed for a short time, the content of the compound containing the first element in the first treatment solution can be 0.1% by mass or more and 10% by mass or less, or 0.5% by mass or more and 5% by mass or less.

[0135] In the second step, the anode body coated with the first treatment solution can be dried or heated. The temperature for heating is, for example, 200°C or higher and 550°C or lower, preferably 250°C or higher and 500°C or lower. The heating atmosphere can be an oxidizing atmosphere; however, from the viewpoint of forming a thin, uniform, and stable interface layer, a non-oxidizing atmosphere is preferred. A non-oxidizing atmosphere is simply an atmosphere with a molar fraction of inactive gases (such as Ar, He, or nitrogen) greater than 90%, or a reduced-pressure atmosphere. Through heating, unstable oxygen not bonded to the first metal is hydrogenated, generating more surface hydroxyl groups, thus forming a stable interface layer.

[0136] (Step 3)

[0137] In the third step, a vapor phase method can be used to form the dielectric layer. When forming a thick dielectric layer, a liquid phase method such as the sol-gel method can be used. Examples of vapor phase methods include vacuum evaporation, chemical vapor deposition, droplet evaporation, sputtering, pulsed laser deposition, and atomic layer deposition (ALD). Among these, ALD is superior because it can form a dense dielectric layer deep into the porous structure. The thickness of the first layer is not particularly limited, but it can be, for example, 0.5 nm or more and 250 nm or less, or 5 nm or more and 100 nm or less.

[0138] The Alternating Layer Deposition (ALD) method is a film-forming method in which a feed gas containing a second metal and an oxidant are alternately supplied to a reaction chamber containing the target material, forming a dielectric layer (first layer) containing an oxide of the second metal on the surface of the target material. In the ALD method, due to the self-limiting effect, the second metal is deposited on the surface of the target material in atomic layer units. Therefore, the thickness of the first layer can be controlled by using the cycle number as one cycle of feed gas supply → feed gas exhaust (purging) → oxidant supply → oxidant exhaust (purging). In other words, the ALD method allows for easy control of the thickness of the formed dielectric layer.

[0139] It should be noted that, unlike CVD, which is typically performed at temperatures between 400 and 900°C, ALD can be performed at temperatures between 100 and 400°C. That is, ALD can suppress thermal damage to the metal foil, which is an advantage in this respect.

[0140] Examples of oxidants used in the ALD process include water, oxygen, and ozone. The oxidant can be supplied to the reaction chamber in the form of plasma, with the oxidant as a feedstock.

[0141] The second metal is supplied to the reaction chamber in the form of a gas containing a precursor of the second metal. The precursor is, for example, an organometallic compound containing the second metal, thereby facilitating the chemisorption of the second metal onto the target material. Various organometallic compounds conventionally used in the ALD process can be used as precursors.

[0142] Examples of precursors containing Al include trimethylaluminum ((CH3)3Al).

[0143] Examples of Zr-containing precursors include bis(methyl-n5-cyclopentadienyl)methoxymethylzirconium (Zr(CH3C5H4)2CH3OCH3), tetra(dimethylamide)zirconium(IV) ([(CH3)2N]4Zr), tetra(ethylmethylamide)zirconium(IV) (Zr(NCH3C2H5)4), and tert-butanolzirconium(IV) (Zr[OC(CH3)3]4).

[0144] Examples of precursors containing Ta include (tert-butylimide)tri(ethylmethylamino)tantalum(V)(C) 13 H 33 N4Ta, TBTEMT), pentaethanol tantalum (V) (Ta(OC2H5)5), (tert-butylimide)tris(diethylamino)tantalum (V) ((CH3)3CNTa(N(C2H5)2)3), penta(dimethylamino)tantalum (V) (Ta(N(CH3)2)5), etc.

[0145] Examples of precursors containing Nb include niobium ethanol (V) (Nb(OCH2CH3)5, and tris(diethylamide) (tert-butylimide) niobium (V) (C 16 H 39 (N4Nb), etc.

[0146] Examples of precursors containing Si include N-sec-butyl(trimethylsilyl)amine (C7H). 19 NSi), 1,3-diethyl-1,1,3,3-tetramethyldisilazane (C8H) 23 NSi2), 2,4,6,8,10-pentamethylcyclopentasiloxane ((CH3SiHO)5), pentamethyldisilane ((CH3)3SiSi(CH3)2H), tris(isopropoxy)silanol ([(H3C)2CHO]3SiOH), chloropentanemethyldisilane ((CH3)3SiSi(CH3)2Cl), dichlorosilane (SiH2Cl2), tris(dimethylamino)silane (Si[N(CH3)2]4), tetraethylsilane (Si(C2H5)4), tetramethylsilane (Si(CH3)4), tetraethoxysilane (Si(OC2H5)4), dodecylmethylcyclohexasilane ((Si(CH3)2)6), silicon tetrachloride (SiCl4), silicon tetrabromide (SiBr4), etc.

[0147] Examples of Ti-containing precursors include bis(tert-butylcyclopentadienyl)titanium(IV) dichloride (C 18 H 26 C l2Ti, tetra(dimethylamino)titanium(IV) ([(CH3)2N]4Ti, TDMAT), tetra(diethylamino)titanium(IV) ([(C2H5)2N]4Ti), tetra(ethylmethylamino)titanium(IV) (Ti[N(C2H5)(CH3)]4), diisopropoxybis(2,2,6,6-tetramethyl-3,5-heptanoic acid)titanium(IV) (Ti[OCC(CH3)3CHCOC(CH3)3]2(OC3H7)2), titanium tetrachloride (TiCl4), titanium isopropoxide (IV) (Ti[OCH(CH3)2]4), titanium ethoxide (IV) (Ti[O(C2H5)]4), etc.

[0148] Examples of precursors containing Hf include hafnium tetrachloride (HfCl4), tetra(dimethylamino)hafnium (Hf[N(CH3)2]4), tetra(ethylmethylamino)hafnium (Hf[N(C2H5)(CH3)]4), tetra(diethylamino)hafnium (Hf[N(C2H5)2]4), and tert-butanol hafnium (Hf[OC(CH3)3]4).

[0149] (Process a)

[0150] The third step may further include step a, which involves forming (anodic oxidation) the anode body having an interface layer and a first layer on its surface. This forms a second layer between the metal framework and the first layer. The thickness T2 of the second layer can be controlled by the voltage applied to the anode body during forming. The forming solution is not particularly limited; for example, an aqueous solution of diammonium adipic acid can be used. In this case, the first metal is preferably a valve-acting metal suitable for forming.

[0151] According to the ALD method, a thin and uniform dielectric layer (first layer) can be formed. However, in reality, macroscopic defects such as pinholes and microscopic defects such as lattice defects sometimes exist deep within the pits of the porous portion. During the formation of the second layer, the ionized first metal diffuses into the first layer, which helps to repair the defects of the first layer. As a result, a dielectric layer with uniform thickness and reduced defects such as pinholes is formed as a whole. Consequently, the capacitance of the electrolytic capacitor increases, the natural potential of the anode increases, and the withstand voltage is improved.

[0152] [Manufacturing method of electrolytic capacitors]

[0153] A method for manufacturing an electrolytic capacitor according to one embodiment of the present invention includes a method for manufacturing an electrode foil for an electrolytic capacitor (steps 1 to 3) and a fourth step of covering at least a portion of a dielectric layer with a conductive polymer compound. The manufacturing method may further include a step of arranging a cathode body facing the electrode foil for the electrolytic capacitor. In this case, it is sufficient to sandwich the conductive polymer compound between the electrode foil and the cathode body. With this arrangement, the cathode portion can be constructed using the conductive polymer compound and the cathode body.

[0154] (Step 4)

[0155] In the fourth step, a second processing solution containing a conductive polymer compound can be impregnated into the electrode foil. The second processing solution can be adhered to the dielectric layer to form a solid electrolyte layer. The second processing solution can be a solution of the conductive polymer compound or a dispersion of the conductive polymer compound. Preferably, the second processing solution contains a conductive polymer compound and the aforementioned liquid component. In this case, the surface of the dielectric layer can be covered with the solid electrolyte layer (conductive polymer compound), and the liquid component can impregnate the anode body (porous portion). When the liquid component contains a polyol compound, the conductive polymer compound is well dispersed in the second processing solution, easily penetrating into the pits and easily covering the walls of the pits with the conductive polymer compound.

[0156] In an anode having a dielectric layer, such as... Figure 1 , 3 In the case of the anode foil shown, it is possible to fabricate a foil such as the one shown before forming the cathode portion. Figure 11 The coil 100 shown. Figure 11 This is a unfolded diagram used to illustrate the structure of the wound body 100.

[0157] In fabricating the wound body 100, in addition to preparing the anode foil 10, a cathode foil 20 is also prepared. The cathode foil 20 can be made of metal foil in the same way as the anode foil 10. There are no particular limitations on the type of metal constituting the cathode foil 20; valve-acting metals such as Al, Ta, and Nb, or alloys containing valve-acting metals, can be used. The surface of the cathode foil 20 can be roughened as needed.

[0158] Then, the anode foil 10 and the cathode foil 20 are wound together with a spacer 30 in between. A lead connector 50A or 50B is connected to one end of the anode foil 10 and the cathode foil 20, respectively, and a winding body 100 is formed while the lead connectors 50A and 50B are wound in. Leads 60A and 60B are connected to the other ends of the lead connectors 50A and 50B, respectively.

[0159] The spacer 30 is not particularly limited, and for example, a nonwoven fabric with cellulose, polyethylene terephthalate, vinylon, aramid fiber, etc. as the main components can be used.

[0160] Then, a winding fixing tape 40 is placed on the outer surface of the outermost cathode foil 20 located in the winding body 100, and the end of the cathode foil 20 is fixed with the winding fixing tape 40. It should be noted that when the anode foil 10 is prepared by cutting from a large-sized foil, in order to provide a dielectric layer on the cut surface, the winding body 100 can be further processed by chemical formation. At this time, a second layer can be formed.

[0161] The second processing solution described above is then applied to the wound body 100. The method is not particularly limited; for example, the wound body 100 can be immersed in the second processing solution contained in a container, or the second processing solution can be added dropwise to the wound body 100. The impregnation can be performed under reduced pressure, for example, an atmosphere of 10 kPa to 100 kPa, preferably 40 kPa to 100 kPa.

[0162] Then, the wound body 100 is sealed, thereby obtaining the following: Figure 10 The electrolytic capacitor 200 is shown. In manufacturing the electrolytic capacitor 200, firstly, the wound body 100 is housed within the bottomed housing 211 such that the leads 60A and 60B are located on the open side of the bottomed housing 211. The bottomed housing 211 can be made of metals such as aluminum, stainless steel, copper, iron, or brass, or alloys thereof.

[0163] Then, a sealing member 212, formed in such a way that leads 60A and 60B pass through, is disposed above the wound body 100 to seal the wound body 100 within the bottomed outer casing 211. The sealing member 212 may be made of an insulating material, preferably an elastomer. Preferably, it is made of heat-resistant materials such as silicone rubber, fluororubber, ethylene propylene rubber, Hypalon rubber, butyl rubber, or isoprene rubber.

[0164] Then, a necking process is performed near the opening end of the bottomed outer casing 211, and the opening end is riveted to the sealing member 212 and then rolled. Finally, a seat plate 213 is placed on the rolled portion, thereby completing the seal. Subsequently, an aging treatment is performed while the rated voltage is applied.

[0165] The above embodiments describe a wound electrolytic capacitor; however, the application scope of the present invention is not limited to the above scope, and it can also be applied to other electrolytic capacitors, such as stacked electrolytic capacitors.

[0166] Industrial availability

[0167] According to the present invention, it is possible to obtain an electrode foil for an electrolytic capacitor, an electrolytic capacitor, and a method for manufacturing the same, which can sufficiently reduce leakage current.

[0168] While the invention has been described with respect to preferred embodiments, this disclosure should not be interpreted as restrictive. Various modifications and alterations will be readily apparent to those skilled in the art upon reading the foregoing disclosure. Therefore, the scope of the appended claims should be interpreted as encompassing all modifications and alterations without departing from the true spirit and scope of the invention.

[0169] Explanation of reference numerals in the attached figures

[0170] 10 Anode foil, 20 Cathode foil, 30 Spacer, 40 Winding and fixing tape, 50A, 50B Lead connectors, 60A, 60B Leads, 100 Winding body, 110 Anode body, 111 Core material, 112 Porous part, 120 Dielectric layer, 121 First layer, 122 Second layer, 130 Interface layer, 200 Electrolytic capacitor, 211 Bottomed housing, 212 Sealing member, 213 Base plate, 300, 400, 500, 600, 700 Anode body, 301, 601 First main surface, 302, 602 Second main surface, 310, 610 Porous part, 311, 611 First porous part, 312, 612 Second porous part, 320, 620 Core: 331, 431, 631, 731 - First recess; 332, 432, 632, 732 - Second recess; 533 - Third recess; 631a, 632a, 731a, 732a - Main recess; 631b, 632b - Small recess; 731b, 732b - Branch recess.

Claims

1. An electrode foil for an electrolytic capacitor, comprising: An anode body having a porous portion and a core continuous with said porous portion, and A dielectric layer covering the surface of the metal skeleton constituting the porous portion. An interface layer containing a first element is provided between the metal skeleton and the dielectric layer. The first element is selected from at least one of sulfur, nitrogen, and phosphorus. The first element in the interface layer has a content of 0.50% by mass or more relative to all elements.

2. The electrode foil for an electrolytic capacitor according to claim 1, wherein, The porous portion has multiple tunnel-shaped pits.

3. The electrode foil for an electrolytic capacitor according to claim 2, wherein, The average diameter of the pit is above 170 nm and below 2100 nm.

4. The electrode foil for an electrolytic capacitor according to claim 2, wherein, The pit includes at least a main pit extending from the surface side of the porous portion toward the core side.

5. The electrode foil for an electrolytic capacitor according to claim 4, wherein, The diameter of the main recess is smaller on the core side compared to the surface side of the porous portion.

6. The electrode foil for an electrolytic capacitor according to claim 4, wherein, The diameter of the main recess is larger on the core side than on the surface side of the porous portion.

7. The electrode foil for an electrolytic capacitor according to claim 4, wherein, In a cross-section along the thickness direction of the porous portion of the anode body, the wall of the main recess is inclined relative to the length direction of the main recess.

8. The electrode foil for an electrolytic capacitor according to claim 7, wherein, The wall of the main recess is inclined at an angle of more than 0.01° and less than 3° relative to the length direction of the main recess.

9. The electrode foil for an electrolytic capacitor according to any one of claims 4 to 8, wherein, The anode body has a first principal surface and a second principal surface on the side opposite to the first principal surface. The porous portion has a first porous portion disposed on one side of the first main surface and a second porous portion disposed on one side of the second main surface. The main recess has a first recess within the first porous portion and a second recess within the second porous portion. At least a portion of the first pit extends further from the first porous portion toward the second porous portion.

10. The electrode foil for an electrolytic capacitor according to claim 9, wherein, At least a portion of the first pit is connected to at least a portion of the second pit.

11. The electrode foil for an electrolytic capacitor according to any one of claims 4 to 8, wherein, In the cross-section of the porous portion of the anode body along the thickness direction, the angle formed by the length direction of the main recess and the thickness direction of the porous portion is 45° or less.

12. The electrode foil for an electrolytic capacitor according to any one of claims 4 to 8, wherein, The pit includes smaller pits in the surface area of ​​the porous portion, which have a length of less than 70% of the length of the main pit.

13. The electrode foil for an electrolytic capacitor according to claim 12, wherein, In the cross-section of the porous portion of the anode body along the thickness direction, the angle formed by the length direction of the small pit and the thickness direction of the porous portion is greater than 45° and less than 88°.

14. The electrode foil for an electrolytic capacitor according to any one of claims 4 to 8, wherein, The pit includes branch pits that branch off from and extend from the main pit. In the thickness direction cross-section of the porous portion of the anode body, the angle formed by the length direction of the main recess and the length direction of the branch recess is 70° or more and 110° or less.

15. The electrode foil for an electrolytic capacitor according to claim 1 or 2, wherein, The metal skeleton includes a first metal. The first metal contains Al. The dielectric layer comprises an oxide of a second metal. The second metal comprises at least one selected from Ta, Nb, Ti, Si, Zr, and Hf.

16. An electrolytic capacitor, It contains capacitor elements. The capacitor element comprises an electrode foil for an electrolytic capacitor as described in any one of claims 1 to 15 and a conductive polymer compound covering at least a portion of the dielectric layer.

17. The electrolytic capacitor according to claim 16, comprising the capacitor element and the liquid component.

18. The electrolytic capacitor according to claim 17, wherein, The liquid component contains polyol compounds.

19. A method for manufacturing electrode foil for an electrolytic capacitor, comprising: The first step is to prepare an anode body having a porous portion and a core continuous with said porous portion. The second step of forming an interface layer comprising the first element covering the surface of the metal skeleton constituting the porous portion, and the third step of forming an interface layer comprising the first element. The third step involves forming a dielectric layer continuous with the interface layer. The first element is selected from at least one of sulfur, nitrogen, and phosphorus. The first element in the interface layer has a content of 0.50% by mass or more relative to all elements.

20. The method for manufacturing electrode foil for an electrolytic capacitor according to claim 19, wherein, In the second step, a first treatment solution containing the first element is impregnated into the anode body.

21. The method for manufacturing electrode foil for an electrolytic capacitor according to claim 19, wherein, In the third step, the dielectric layer is formed using atomic layer stacking.

22. The method for manufacturing electrode foil for an electrolytic capacitor according to any one of claims 19 to 21, wherein, The metal skeleton includes a first metal. The first metal contains Al. The dielectric layer comprises an oxide of a second metal. The second metal comprises at least one selected from Ta, Nb, Ti, Si, Zr, and Hf.

23. A method for manufacturing an electrolytic capacitor, comprising: The method comprising the steps of manufacturing electrode foil for an electrolytic capacitor as described in any one of claims 19 to 22, and The fourth step involves covering at least a portion of the dielectric layer with a conductive polymer compound.

24. The method for manufacturing an electrolytic capacitor according to claim 23, wherein, In the fourth step, a second treatment solution containing the conductive polymer compound is impregnated into the electrode foil.

25. The method for manufacturing an electrolytic capacitor according to claim 24, wherein, The second treatment solution contains polyol compounds.

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