阅读说明：本技术 电解电容器用电极箔、电解电容器及其制造方法 (Electrode foil for electrolytic capacitor, electrolytic capacitor and method for manufacturing same ) 是由 小川美和 栗原直美 吉村满久 于 2020-02-21 设计创作，主要内容包括：使用一种电解电容器用电极箔,其具备具有多孔质部的阳极体和覆盖构成多孔质部的金属骨架的表面的电介质层,电介质层具有第一层,该第一层包含与金属骨架中所含的第一金属不同的第二金属的氧化物,在金属骨架与第一层之间具有与第一层连续的基底层,基底层至少包含磷和碳。通过基底层至少包含磷和碳,从而可以提供能够充分降低漏电流的电解电容器用电极箔。(An electrode foil for electrolytic capacitors is used, which comprises an anode body having a porous portion and a dielectric layer covering the surface of a metal skeleton constituting the porous portion, wherein the dielectric layer has a first layer containing an oxide of a second metal different from the first metal contained in the metal skeleton, a base layer continuous with the first layer is provided between the metal skeleton and the first layer, and the base layer contains at least phosphorus and carbon. The base layer contains at least phosphorus and carbon, and thus an electrode foil for electrolytic capacitors capable of sufficiently reducing leakage current can be provided.)

1. An electrode foil for an electrolytic capacitor, comprising:

an anode body having a porous portion; and

a dielectric layer covering a surface of the metal skeleton constituting the porous portion,

the dielectric layer has a first layer containing an oxide of a second metal different from the first metal contained in the metal skeleton,

a base layer continuous with the first layer between the metal skeleton and the first layer,

the base layer includes at least phosphorus and carbon.

2. The electrode foil for electrolytic capacitors as claimed in claim 1, wherein at least a peak attributed to phosphorus and a peak attributed to carbon are observed when analyzed by glow discharge emission spectroscopy GD-OES along a depth direction of the base layer from the surface of the base layer on the first layer side.

3. The electrode foil for electrolytic capacitors as claimed in claim 1 or 2, having a second layer comprising the base layer between the metal skeleton and the first layer,

the second layer includes an oxide of the first metal and has the base layer on the first layer side.

4. The electrode foil for electrolytic capacitors as claimed in any one of claims 1 to 3, wherein, assuming that the coordination number of oxygen in the stoichiometric composition of the oxide of the second metal is X1 and the coordination number of actual oxygen in the oxide of the second metal is X2, the ratio of X2 to X1: X2/X1 is 0.9 or more.

5. The electrode foil for electrolytic capacitors as claimed in any one of claims 1 to 4, wherein the base layer further contains nitrogen, and a C-N bond is detected in electron energy loss spectroscopy (TEM-EELS).

6. The electrode foil for electrolytic capacitors as claimed in any one of claims 1 to 5, wherein the first metal comprises Al,

the second metal includes at least 1 selected from the group consisting of Ta, Nb, Ti, Si, Zr, and Hf.

7. An electrolytic capacitor, comprising:

an electrode foil for electrolytic capacitors as claimed in any one of claims 1 to 6; and

a cathode portion covering at least a portion of the dielectric layer.

8. A method for manufacturing an electrode foil for an electrolytic capacitor, comprising:

preparing an anode body having a porous portion;

bringing an alkaline solution into contact with the anode body;

heating the anode body to which the alkaline solution is attached, thereby forming a base layer on a surface of the metal skeleton constituting the porous portion; and

and forming a dielectric layer on the surface of the underlayer by a vapor phase method, the dielectric layer including a first layer containing an oxide of a second metal different from the first metal contained in the metal skeleton.

9. The method of manufacturing an electrode foil for an electrolytic capacitor according to claim 8, wherein the alkali solution is brought into contact with the anode body after the anode body is washed with the acidic solution.

10. The method of manufacturing an electrode foil for electrolytic capacitors as claimed in claim 8 or 9, wherein the alkali solution contains an organic amine compound.

11. The method for manufacturing an electrode foil for electrolytic capacitors as claimed in any one of claims 8 to 10, wherein the base layer contains at least phosphorus.

12. The method of manufacturing an electrode foil for electrolytic capacitors as claimed in claim 11, wherein the alkaline solution is caused to contain phosphorus, or a solution containing phosphorus is brought into contact with the anode body.

13. The method of manufacturing an electrode foil for electrolytic capacitors as claimed in claim 12, wherein the concentration of the phosphorus in the alkaline solution or the solution containing phosphorus is 0.01ppm to 500ppm in mass ratio.

14. The method for producing an electrode foil for electrolytic capacitors as claimed in any one of claims 8 to 13, wherein in the step of forming the undercoat layer, the anode body to which the alkaline solution has been adhered is heated at 200 to 550 ℃.

15. The method for producing an electrode foil for electrolytic capacitors as claimed in any one of claims 8 to 14, further comprising: chemically converting the anode body having the first layer, forming a second layer including an oxide of the first metal between the metal skeleton and the first layer and having the base layer on the first layer side.

16. A method for manufacturing an electrolytic capacitor, comprising:

the step of providing the method for producing an electrode foil for electrolytic capacitors according to any one of claims 8 to 15; and

and forming a cathode portion covering the dielectric layer.

Technical Field

The present invention relates to an electrode foil for an electrolytic capacitor, and a method for manufacturing the same.

Background

As the anode body of the electrolytic capacitor, for example, a metal foil containing a valve metal can be used. In order to increase the capacity of the electrolytic capacitor, the main surface of the metal foil is etched to form a porous metal portion. Then, the metal foil is subjected to chemical conversion treatment to form a layer of metal oxide (dielectric) on the surface of the porous metal portion.

On the other hand, patent document 1 teaches forming a dielectric layer on the surface of a porous metal substrate by a vapor phase method.

Documents of the prior art

Patent document

Patent document 1: international publication No. 2015/190278 pamphlet

Disclosure of Invention

Problems to be solved by the invention

However, when the metal contained in the anode element and the metal element contained in the dielectric layer are different from each other, the leakage current of the electrolytic capacitor tends to increase.

Means for solving the problems

One aspect of the present invention relates to an electrode foil for an electrolytic capacitor, including: an anode body having a porous portion; and a dielectric layer covering a surface of a metal skeleton constituting the porous portion, wherein the dielectric layer has a first layer containing an oxide of a second metal different from a first metal contained in the metal skeleton, and a base layer continuous with the first layer is provided between the metal skeleton and the first layer, and the base layer contains at least phosphorus and carbon.

Another aspect of the present invention relates to an electrolytic capacitor including the electrode foil for an electrolytic capacitor; and a cathode portion covering at least a part of the dielectric layer.

Another aspect of the present invention relates to a method for manufacturing an electrode foil for an electrolytic capacitor, including: preparing an anode body having a porous portion; bringing an alkaline solution into contact with the anode body; heating the anode body to which the alkaline solution is attached, thereby forming a base layer on a surface of the metal skeleton constituting the porous portion; and forming a dielectric layer on the surface of the underlayer by a vapor phase method, the dielectric layer including a first layer containing an oxide of a second metal different from the first metal contained in the metal skeleton.

Another aspect of the present invention relates to a method for manufacturing an electrolytic capacitor, including: a step of providing the method for manufacturing an electrode foil for an electrolytic capacitor; and forming a cathode portion covering the dielectric layer.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, it is possible to obtain an electrode foil for an electrolytic capacitor, and a method for manufacturing the same, which can sufficiently reduce a leakage current even when a metal contained in an anode body is different from a metal element contained in a dielectric layer.

Drawings

Fig. 1 is a schematic sectional view (a) showing a part of a porous portion having a dielectric layer in an enlarged manner and an enlarged view (B) of a portion surrounded by a broken line X according to an embodiment of the present invention.

Fig. 2 is a schematic sectional view (a) showing a part of a porous portion having a dielectric layer in another embodiment of the present invention in an enlarged manner and an enlarged view (B) of a portion surrounded by a broken line Y.

FIG. 3 is a schematic cross-sectional view of an electrolytic capacitor.

Fig. 4 is a perspective view schematically showing the structure of a wound body provided in an electrolytic capacitor.

Fig. 5 is a graph showing the relationship between the distance of the underlayer from the surface on the dielectric layer side and the P content in the underlayer in the example of the present invention.

Fig. 6 is a graph showing the relationship between the distance of the underlayer from the surface on the dielectric layer side and the C content in the underlayer in the example of the present invention.

Detailed Description

The electrode foil for electrolytic capacitors of the present embodiment includes: an anode body having a porous portion and a dielectric layer covering the surface of a metal skeleton constituting the porous portion. The electrolytic capacitor of the present embodiment includes a cathode portion having the electrode foil and covering the dielectric layer. Hereinafter, the anode body having the porous portion may be referred to as a metal foil having the porous portion.

The anode body is, for example, an integrated body with the core portion and the porous portion. The anode body is obtained by, for example, etching a part of a metal foil made of the first metal. Thus, the metal skeleton comprises the first metal. The porous portion is an outer portion of the metal foil that is made porous by etching, and the remaining portion that is an inner portion of the metal foil is a core portion.

The metal skeleton refers to a metal portion having a fine structure in the porous portion. The porous portion has a pit or a pore surrounded by a metal skeleton. The dielectric layer is provided so as to cover at least a part of the surface of the metal skeleton surrounding the recess or the pore.

The dielectric layer has a first layer containing an oxide of a second metal different from the first metal contained in the metal skeleton. In the case where the dielectric layer contains an oxide of a second metal different from the first metal, for example, the second metal having a high dielectric constant can be selected without being limited to the first metal. Therefore, the capacity of the electrolytic capacitor can be easily increased. Further, since the selection range of the second metal is expanded, various properties can be imparted to the dielectric layer without being restricted by the first metal.

Between the metal skeleton and the first layer, there is a base layer continuous with the first layer. The base layer corresponds to a boundary between the first layer and the metal skeleton or between the first layer and another layer. The base layer may be thin or may not have a definite layer structure. The thickness of the underlayer may be 1nm or less, for example. Here, the base layer contains at least phosphorus and carbon, or at least hydrogen and oxygen. This can provide the dielectric layer with, for example, sufficient acid resistance, and can sufficiently reduce leakage current.

When the first layer is formed as at least a part of the dielectric layer on the surface of the metal skeleton, the growth of a good first layer is promoted by providing the base layer containing a combination of phosphorus and carbon or a combination of hydrogen and oxygen. This is considered to be because the surface state of the base layer is stabilized.

Generally, a natural oxide film of the first metal is present on the surface of the metal skeleton. When an oxide of the second metal is formed on the surface of the natural oxide film of the first metal, it is difficult to form a good first layer. The reason for this is considered to be that the physical properties of the natural oxide film containing the first metal are different from those of the oxide of the second metal, and it is difficult to improve the continuity between the natural oxide film and the oxide of the second metal. In this case, defects are likely to occur in the dielectric layer, and the leakage current is likely to increase. Even when the surface of the metal skeleton is modified, the modified surface is generally unstable, and it is difficult to grow the oxide of the second metal homogeneously. In this case, when the coordination number of oxygen in the stoichiometric composition of the oxide of the second metal is X1 and the actual coordination number of oxygen in the oxide of the second metal is X2, the ratio of X2 to X1 is: X2/X1 is usually considerably less than 0.9, and may be, for example, 0.8 or less or 0.7 or less.

On the other hand, phosphorus stabilizes the surface of the modified metal skeleton. The amount of phosphorus contained in the base layer is a trace amount. Unlike the case where a large amount of phosphorus is present, carbon is also detected in the case where a trace amount of phosphorus is detected. In addition, hydrogen stabilizes unstable oxygen that is not bound to the first metal. For example-O-becomes in the state of-OH. Hydrogen is detected together with oxygen. The elements of phosphorus, carbon, hydrogen and oxygen may form compounds or groups.

The contents of each element of phosphorus, carbon, and hydrogen contained in the base layer may be all minute amounts. The phosphorus, carbon, and/or hydrogen may be present in the base layer, and for example, at least 1 selected from phosphorus, carbon, and hydrogen may be contained in the first layer.

The method of analyzing each element is not particularly limited, and the distribution or concentration of each element can be measured by analysis of a cross section of the underlying layer, the dielectric layer, or the first layer, for example, an element distribution diagram using energy dispersive X-ray spectroscopy (EDX), or analysis in the depth direction of the underlying layer, the dielectric layer, or the first layer, for example, glow discharge emission spectroscopy (GD-OES).

For example, when the base layer is analyzed by glow discharge emission spectroscopy (GD-OES) from the surface on the first layer side of the base layer in the depth direction of the base layer, if a peak attributed to any one of the elements is observed, it can be determined that the base layer contains an element corresponding to the peak. When the base layer is analyzed by glow discharge emission spectroscopy along the depth direction thereof, it is preferable that at least a peak attributed to phosphorus is observed. In addition, peaks ascribed to at least 1 selected from carbon, hydrogen and oxygen were also observed.

When the coordination number of oxygen in the stoichiometric composition of the oxide of the second metal is X1 and the actual coordination number of oxygen in the oxide of the second metal is X2, the ratio of X2 to X1: X2/X1 may be 0.9 or more, for example. In the case where growth of a good first layer is promoted, the coordination number X2 of oxygen in the oxide of the second metal is close to the coordination number X1 in the stoichiometric composition.

The base layer may further comprise nitrogen. In this case, the C-N bond can be detected in electron energy loss spectroscopy (TEM-EELS).

A second layer including a base layer may be between the metal skeleton and the first layer. The second layer contains an oxide of the first metal and has a base layer on the first layer side. The second layer can be formed by, for example, chemically converting the porous portion of the anode body. In this case, the first metal is preferably a valve-acting metal suitable for chemical conversion. The region of the second layer other than the base layer may be different in composition from the base layer. In the region other than the underlayer of the second layer, for example, the concentration of an element such as phosphorus or carbon decreases as the distance from the underlayer increases. The second layer may have a composition different from that of the base layer, for example, in that it may have a region substantially free of phosphorus.

The second layer may include a composite oxide of an oxide of the first metal and an oxide of the second metal. By forming the second layer, even if the first layer has a defect, the defect can be repaired. Therefore, the leakage current is further reduced.

The thickness T1 of the first layer and the thickness T2 of the second layer can satisfy T1 ≥ 2 XT 2, and also satisfy T1 ≥ 3 XT 2. By relatively increasing the thickness of the first layer, for example, in the case of selecting a second metal having a high dielectric constant, the capacity of the electrolytic capacitor can be significantly increased.

The first metal may comprise Al, for example. At this time, the second metal may contain, for example, at least 1 selected from Ta, Nb, Ti, Si, Zr, and Hf.

The electrode foil for electrolytic capacitors is produced, for example, by a method including at least the steps of: (i) preparing an anode body (or a metal foil) having a porous portion; (ii) forming a base layer on a surface of the metal skeleton; and (iii) forming a dielectric layer covering at least a part of the surface of the base layer. The electrolytic capacitor is produced by a method including, in addition to the above-described steps (i) to (iii), a step (iv) of forming a cathode portion covering at least a part of the dielectric layer.

Step (i)

The step (i) of preparing the metal foil (anode body) having the porous portion may be, for example, a step of etching a metal foil containing the first metal to roughen the metal foil. By roughening, a plurality of pits or fine pores are formed on the surface of the metal foil. The etching may be performed by, for example, direct current etching based on direct current or alternating current etching based on alternating current. As the etching solution for immersing the metal foil, for example, an aqueous solution containing hydrochloric acid and sulfuric acid can be used.

After the etching is completed, the anode body having the porous portion may be cleaned with an acidic solution. For example, the anode body may be washed with an aqueous solution containing sulfuric acid, nitric acid, oxalic acid, or the like to remove chlorine components. At this time, if the anode body is washed with the phosphoric acid aqueous solution, excessive phosphorus may be attached to the anode body, and the capacity of the electrolytic capacitor may be reduced.

The kind of the first metal is not particularly limited, and a valve metal such as aluminum (Al), tantalum (Ta), or niobium (Nb), or an alloy containing a valve metal can be used in order to facilitate formation of the second layer by chemical conversion. In order to form the porous portion efficiently, copper (Cu) may be contained in the metal foil. The thickness of the metal foil is not particularly limited, and is, for example, 15 μm or more and 300 μm or less.

The pore diameter of the pits or pores formed on the surface of the metal foil is not particularly limited, and may be, for example, 50nm to 2000nm from the viewpoint of increasing the surface area and forming the dielectric layer to the deep portion of the porous portion. The pore diameter is, for example, the highest frequency pore diameter of the pore distribution measured by a mercury porosimeter. The thickness of the porous portion is not particularly limited, and may be appropriately set according to the thickness of the metal foil, and for example, may be 1/10 or more and 4/10 or less of the thickness of the anode body on each surface. The thickness D of the porous portion may be determined as an average value of arbitrary 10 points in an electron micrograph of a cross section of the anode body. Hereinafter, the thickness of the dielectric layer, that is, the thickness of the first layer and the second layer may be calculated in the same manner.

Step (ii)

Next, a step of bringing an alkaline solution into contact with the anode body having the porous portion; and a step of forming a base layer on the surface of the metal skeleton constituting the porous portion by heating the anode body to which the alkaline solution has been adhered.

If the alkali solution is too basic, the metal skeleton may be damaged, and therefore, it is preferable that the alkali solution has mild basicity. It is preferable to use an organic base component rather than an inorganic base component, and for example, it is preferable to use an organic amine compound. The pH of the alkali solution is set to 8 to 14 or 8 to 13, for example. The solvent of the alkali solution preferably contains water as a main component, and 80% by mass or more of the solvent may be water.

The organic amine compound preferably exhibits water solubility and chelating ability. For example, alkanolamines may be used. The alkanolamine may have a plurality of hydroxyl groups in one molecule, for example may have 2 or 3 hydroxyl groups. More specifically, for example, monoethanolamine, diethanolamine, triethanolamine, ethylenediamine, diethylenetriamine, aminoethylethanolamine, and the like can be used.

The method of bringing the alkaline solution into contact with the anode body is not particularly limited, and for example, the anode body can be immersed in an alkaline solution, or the alkaline solution can be sprayed on the anode body. The contact time until the alkaline solution and the anode body are heated may be, for example, 10 seconds to 10 minutes.

In the step of heating the anode body to which the alkali solution is attached, for example, the anode body to which the alkali solution is attached may be heated at 200 to 550 ℃, preferably 250 to 500 ℃. In this case, the heating atmosphere may be an oxidizing atmosphere, but a non-oxidizing atmosphere is preferable in terms of forming a thin, homogeneous and stable underlayer as much as possible. The non-oxidizing atmosphere may be an atmosphere in which the mole fraction of an inert gas (e.g., a rare gas such as Ar or He, or nitrogen) exceeds 9, a reduced pressure atmosphere, or the like. In such a heating step, unstable oxygen not bonded to the first metal is hydrogenated to generate a large number of surface hydroxyl groups, thereby forming a stable underlayer.

Here, the base layer may contain phosphorus, and may further contain carbon, oxygen, hydrogen, or the like. For example, the alkaline solution may contain phosphorus, or the anode body may be contacted with an alkaline solution containing no phosphorus, and then the anode body may be contacted with a solution containing phosphorus. However, from the viewpoint of making the base layer contain an appropriate amount of phosphorus, it is preferable to make the alkali solution contain a slight amount of phosphorus.

The method of adding phosphorus to the alkaline solution or the solution containing phosphorus is not limited, and for example, a phosphorus compound may be added to the solution. Examples of the phosphorus compound include phosphoric acid, ammonium dihydrogen phosphate, phosphonic acid, and phosphinic acid. In addition, in the case where the organic alkali component is contained in the alkali solution, phosphorus and carbon may be contained in the underlayer.

From the viewpoint of improving the capacity of the electrolytic capacitor, the phosphorus concentration in the alkaline solution or the solution containing phosphorus is preferably a trace amount, and may be, for example, 0.01ppm or more, or may be 0.1ppm or more in terms of mass ratio. In order to prevent excessive phosphorus from adhering to the anode body, the phosphorus concentration in the alkaline solution or the phosphorus-containing solution is, for example, preferably 500ppm or less, and more preferably 100ppm or less, in terms of mass ratio.

Procedure (iii)

The step (iii) of forming the dielectric layer may include, for example, the steps of: a first layer containing an oxide of a second metal different from the first metal is formed on the surface of the base layer by a vapor phase method.

Examples of the second metal include Al, Ta, Nb, silicon (Si), titanium (Ti), zirconium (Zr), hafnium (Hf), and the like. These may be used alone or in combination of 2 or more. That is, the first layer may contain Al alone₂O₃、Ta₂O₅、Nb₂O₅、SiO₂、TiO₂、ZrO₂、HfO₂Etc., or 2 or more. When the first layer contains 2 or more oxides of the second metal, the 2 or more oxides may be present in a mixture or may be arranged in a layered form. From the viewpoint of increasing the capacity of the electrolytic capacitor, the oxide of the second metal preferably has a higher relative permittivity than the oxide of the first metal. In addition, from the viewpoint of improving the withstand voltage of the electrolytic capacitor, the second metal is preferably Ta, Ti, Si, or the like.

Examples of the vapor phase method include a vacuum evaporation method, a chemical evaporation method, a mist evaporation method, a sputtering method, a pulse laser Deposition method, and an Atomic Layer Deposition method (ALD method). Among them, the ALD method is excellent in that a dense dielectric layer can be formed to a deep portion of a porous portion. The thickness of the first layer is not particularly limited, and may be, for example, 0.5nm or more and 200nm or less, or 5nm or more and 100nm or less.

Fig. 1 (a) shows an example of the anode foil 10, and the anode foil 10 includes an anode body 110 which is an integrated body of a core portion 111 and a porous portion 112, and a dielectric layer 120 which covers a surface of a metal skeleton constituting the porous portion 112. Fig. 1 (a) is a schematic cross-sectional view showing a part of the porous portion 112 having only the first layer 121 as the dielectric layer 120 in an enlarged manner. Fig. 1 (B) is an enlarged view of a portion surrounded by a broken line X in fig. 1 (a). A base layer 130 is provided at the boundary between the first layer 121 and the metal skeleton.

As shown in fig. 1 (a), the porous portion 112 has a plurality of pits (or pores) P surrounded by a metal skeleton. The dielectric layer 120 (first layer 121) is provided so as to cover at least a part of the surface of the metal skeleton. The first layer 121 contains an oxide of a second metal different from the first metal contained in the metal skeleton, and its thickness is represented by T1.

The ALD method is a film formation method in which a source gas containing a second metal and an oxidizing agent are alternately supplied to a reaction chamber in which an object is placed, and a dielectric layer (first layer) containing an oxide of the second metal is formed on the surface of the object. In the ALD method, the Self-stopping (Self-limiting) action is exerted, and therefore the second metal is deposited on the surface of the object in atomic layer units. Therefore, the thickness of the first layer is controlled by setting the number of cycles of 1 cycle to supply of the raw material gas → exhaust (purge) of the raw material gas → supply of the oxidizing agent → exhaust (purge) of the oxidizing agent. That is, the ALD method can easily control the thickness of the formed dielectric layer.

The ALD method can be performed at a temperature of 100 to 400 ℃ as compared with CVD performed at a temperature of 400 to 900 ℃. That is, the ALD method is excellent in that thermal damage to the metal foil can be suppressed.

Examples of the oxidizing agent used in the ALD method include water, oxygen, and ozone. The oxidant may be supplied to the reaction chamber in the form of a plasma that uses the oxidant as a raw material.

The second metal is supplied to the reaction chamber in the form of a gas containing a precursor (precursor) of the second metal. The precursor is, for example, an organometallic compound containing a second metal, and thus the second metal is easily chemisorbed to the target. As the precursor, various organometallic compounds conventionally used in the ALD method can be used.

Examples of the precursor containing Al include trimethylaluminum ((CH)₃)₃Al), and the like. Examples of the Zr-containing precursor include bis (. eta.5-methyl-cyclopentadienyl)) Methoxymethylzirconium (Zr (CH)₃C₅H₄)₂CH₃OCH₃) Tetrakis (dimethylamido) zirconium (IV) ([ (CH)₃)₂N]₄Zr), tetrakis (ethylmethylamido) zirconium (IV) (Zr (NCH)₃C₂H₅)₄) Zirconium (IV) tert-butoxide (Zr [ OC (CH)₃)₃]₄) And the like. Examples of the Nb-containing precursor include niobium (V) ethoxide (Nb (OCH)₂CH₃)₅Tris (diethylamido) (tert-butylimide) niobium (V) (C)₁₆H₃₉N₄Nb), and the like.

Examples of the precursor containing Ta include (t-butylimide) tris (ethylmethylamino) tantalum (V) (C)₁₃H₃₃N₄Ta, TBTEMT), tantalum (V) pentaethanolate (Ta (OC)₂H₅)₅) And (tert-butylimide) tris (diethylamino) tantalum (V) ((CH)₃)₃CNTa(N(C₂H₅)₂)₃) Pentakis (dimethylamino) tantalum (V) (Ta (N (CH))₃)₂)₅) And the like.

Examples of the Nb-containing precursor include niobium (V) ethoxide (Nb (OCH)₂CH₃)₅Tris (diethylamido) (tert-butylimide) niobium (V) (C)₁₆H₃₉N₄Nb), and the like.

Examples of the precursor containing Si include N-sec-butyl (trimethylsilyl) amine (C)₇H₁₉NSi), 1, 3-diethyl-1, 1, 3, 3-tetramethyldisilazane (C)₈H₂₃NSi₂) 2, 4, 6, 8, 10-pentamethylcyclopentasiloxane ((CH)₃SiHO)₅) Pentamethyldisilane ((CH)₃)₃SiSi(CH₃)₂H) Tris (isopropoxy) silanol ([ (H)₃C)₂CHO]₃SiOH), chloropentane methyldisilane ((CH)₃)₃SiSi(CH₃)₂Cl), dichlorosilane (SiH)₂Cl₂) Tris (dimethylamino) silane (Si [ N (CH) ]₃)₂]₄) Tetraethyl silane (Si (C)₂H₅)₄) Tetramethylsilane (Si: (A), (B) and (C)CH₃)₄) Tetraethoxysilane (Si (OC)₂H₅)₄) Dodecamethylcyclohexasilane ((Si (CH))₃)₂)₆) Silicon tetrachloride (SiCl)₄) Silicon tetrabromide (SiBr)₄) And the like.

Examples of the precursor containing Ti include bis (tert-butylcyclopentadienyl) titanium (IV) dichloride (C)₁₈H₂₆C₁₂Ti), tetrakis (dimethylamino) titanium (IV) ([ (CH)₃)₂N]₄Ti, TDMAT), tetrakis (diethylamino) titanium (IV) ([ (C)₂H₅)₂N]₄Ti, tetra (ethylmethylamino) titanium (IV) (Ti [ N (C) ]₂H₅)(CH₃)]₄) And (diisopropoxy-bis (2, 2, 6, 6-tetramethyl-3, 5-heptanedionato titanium (IV) (Ti [ OCC (CH))₃)₃CHCOC(CH₃)₃]₂(OC₃H₇)₂) Titanium tetrachloride (TiCl)₄) Titanium (IV) isopropoxide (Ti [ OCH (CH) ]₃)₂]₄) Titanium (IV) ethoxide (Ti [ O (C) ]₂H₅)]₄) And the like.

Examples of the Zr-containing precursor include bis (methyl-. eta.)⁵Cyclopentadienyl) methoxymethylzirconium (Zr (CH)₃C₅H₄)₂CH₃OCH₃) Tetrakis (dimethylamido) zirconium (IV) ([ (CH)₃)₂N]₄Zr), tetrakis (ethylmethylamido) zirconium (IV) (Zr (NCH)₃C₂H₅)₄) Zirconium (IV) tert-butoxide (Zr [ OC (CH)₃)₃]₄) And the like.

As the Hf-containing precursor, for example, hafnium tetrachloride (HfCl) is exemplified₄) Tetra (dimethylamino) hafnium (Hf [ N (CH) ]₃)₂]₄) Tetra (ethylmethylamino) hafnium (Hf [ N (C) ]₂H₅)(CH₃)]₄) Tetra (diethylamino) hafnium (Hf [ N (C) ]₂H₅)₂]₄) Hafnium tert-butoxide (Hf [ OC (CH))₃)₃]₄) And the like.

The method for manufacturing the electrode foil for electrolytic capacitors may further include a step of chemically converting (anodizing) the anode body having the first layer. Thus, a second layer containing an oxide of the first metal and having a base layer on the first layer side can be formed between the metal skeleton and the first layer. The thickness T2 of the second layer can be controlled by the voltage applied to the anode body at the time of chemical conversion. The chemical conversion solution is not particularly limited, and for example, an aqueous diammonium adipate solution may be used.

In fig. 2 (a), the porous portion 112 having the first layer 121 and the second layer 122 as the dielectric layer 120 is shown in an enlarged schematic sectional view. Fig. 2 (B) is an enlarged view of a portion surrounded by a broken line Y in fig. 2 (a). In fig. 2, the same reference numerals as in fig. 1 are given to the components corresponding to fig. 1.

As shown in fig. 2 (a), the dielectric layer 120 has a second layer 122 and a first layer 121 in this order from the metal skeleton side. The thickness of the first layer 121 is indicated by T1 and the thickness of the second layer is indicated by T2. As shown in fig. 2 (B), a base layer 130 is provided at the boundary between the first layer 121 and the second layer 122. For example, when the thickness of the second layer is very small, there may be a portion where the base layer and the metal skeleton are continuous without interposing the second layer between the base layer and the metal skeleton.

According to the ALD method, a thin and uniform dielectric layer (first layer) can be formed. However, in reality, there are cases where macroscopic defects such as pinholes and fine defects such as lattice defects are present on the surface of the deep part of the pits in the porous part. When the second layer is formed, the ionized first metal diffuses into the first layer, and has an effect of repairing defects of the first layer. As a result, a dielectric layer having a uniform thickness with reduced defects such as pinholes is formed as a whole. Therefore, the capacity of the electrolytic capacitor is increased, and the natural potential of the anode body is increased, thereby improving the withstand voltage.

The thickness T2 of the second layer is not particularly limited, and may be smaller than the thickness T1 of the first layer. The thickness T2 of the second layer is, for example, 0.5nm or more and 200nm or less, or may be 5nm or more and 100nm or less.

The ratio of the thickness T1 of the first layer to the thickness T2 of the second layer is not particularly limited, and may be appropriately set according to the application, the desired effect, and the like. For example, the ratio of the thicknesses: T1/T2 may be 1 or more, 2 or more, or 5 or more.

Here, when the porous portion is divided into the first region, the second region, and the third region in the order of trisection from the metal core portion side in the thickness direction of the porous portion, the porosity P1 of the first region, the porosity P2 of the second region, and the porosity P3 of the third region may satisfy P1 < P2 < P3. That is, the porosity of the porous portion may be increased as the distance from the outer surface of the anode body is increased.

On the other hand, in the deep portion (for example, the third region) of the porous portion, the void ratio is relatively small, and the pit diameter (or pore diameter) of the etched pit is relatively small. In other words, a large number of fine pores are present in the deep part of the porous part, and a large surface area is secured. Therefore, even when the surface area in the vicinity of the outer surface of the anode body (for example, the first region) is relatively small, it is easy to secure a sufficiently large capacitance.

The porosity of the porous portion may be measured by the following method.

First, the anode body was cut so as to obtain a cross section in the thickness direction of the metal core portion and the porous portion of the anode body, and an electron micrograph of the cross section was taken. Next, the image of the cross section is binarized to distinguish the metal skeleton from the voids. Next, the image was divided into a plurality of portions (for example, 0.1 μm intervals) along a path parallel to the thickness direction of the anode body from the surface side of the anode body toward the metal core portion, and the average value of the porosity of each portion after division was calculated as the porosity. By using the calculated values, a graph showing a relationship between a distance from the surface of the anode body and a porosity can be drawn. In the first region, the second region, and the third region, the void ratios at a plurality of arbitrary positions are extracted at equal intervals, and the average value of the plurality of void ratios may be calculated as the void ratio P1, the void ratio P2, and the void ratio P3.

P2 and P3 can satisfy P2X 1.1 ≦ P3, and also satisfy P2X 1.2 ≦ P₃. In addition, P1 and P2 may satisfy P1X 1.05. ltoreq.P 2, and may also satisfy P1X 1.1. ltoreq.P 2.

For example, P1 may be 30% or more. P2 may be 40% or more, for example, or 50% or more. P3 may be 60% or more. In this case, when the dielectric layer is formed by a vapor phase method such as an atomic layer deposition method, the diffusion of the raw material gas of the dielectric layer into the deep portion of the metal porous portion is further improved. However, from the viewpoint of ensuring sufficient strength of the anode body, P3 is preferably 80% or less, P2 is preferably 70% or less, and P1 is preferably 60% or less.

Procedure (iv)

In the step (iv) of forming the cathode portion covering the dielectric layer, for example, the anode element having the dielectric layer may be impregnated with an electrolytic solution, and/or a solid electrolyte layer may be formed on the surface of the dielectric layer. In the case where both the formation of the solid electrolyte layer and the impregnation of the electrolytic solution are performed, the impregnation of the electrolytic solution may be performed after the formation of the solid electrolyte layer on the dielectric layer.

The electrolyte solution may be a nonaqueous solvent or a mixture of a nonaqueous solvent and an ionic substance (solute (e.g., organic salt)) dissolved therein. The nonaqueous solvent may be an organic solvent or an ionic liquid.

As the nonaqueous solvent, a high boiling point solvent is preferable. For example, polyhydric alcohols such as ethylene glycol and propylene glycol, cyclic sulfones such as sulfolane, lactones such as γ -butyrolactone, amides such as N-methylacetamide, N-dimethylformamide, and N-methyl-2-pyrrolidone, esters such as methyl acetate, carbonate compounds such as propylene carbonate, ethers such as 1, 4-dioxane, ketones such as methyl ethyl ketone, and formaldehyde can be used.

The organic salt is a salt in which at least one of an anion and a cation contains an organic substance. Examples of the organic salt include trimethylamine maleate, triethylamine bissalicylate, ethyldimethylamine phthalate, mono 1, 2, 3, 4-tetramethylimidazolinium phthalate, and mono 1, 3-dimethyl-2-ethylimidazolium phthalate.

The solid electrolyte layer contains, for example, a manganese compound, a conductive polymer, and the like. As the conductive polymer, polypyrrole, polythiophene, polyaniline, a derivative thereof, and the like can be used. The solid electrolyte layer containing a conductive polymer can be formed by, for example, chemically polymerizing and/or electrolytically polymerizing a raw material monomer on the dielectric layer. The solid electrolyte layer can be formed by adhering a solution in which a conductive polymer is dissolved or a dispersion in which a conductive polymer is dispersed to the dielectric layer.

In the case where the anode body having the dielectric layer is the anode foil shown in fig. 1 and 2, the roll body 100 shown in fig. 4 may be produced before the cathode portion is formed. Fig. 4 is a developed view for explaining the structure of the roll body 100.

When wound body 100 is produced, cathode foil 20 is prepared in addition to anode foil 10. As the cathode foil 20, a metal foil can be used as the anode foil 10. The type of metal constituting cathode foil 20 is not particularly limited, and valve metal such as Al, Ta, and Nb, or an alloy containing valve metal may be used. The surface of the cathode foil 20 may be roughened as necessary.

Next, anode foil 10 and cathode foil 20 are wound with spacer 30 interposed therebetween. One end of lead tab 50A or 50B is connected to anode foil 10 and cathode foil 20, respectively, and wound body 100 is configured while winding lead tabs 50A and 50B. Lead wires 60A and 60B are connected to the other ends of the lead tabs 50A and 50B, respectively.

The spacer 30 is not particularly limited, and for example, a nonwoven fabric containing cellulose, polyethylene terephthalate, vinylon, aramid fiber, or the like as a main component can be used.

Next, a tape stopper 40 is disposed on the outer surface of the cathode foil 20 positioned at the outermost layer of the wound body 100, and the end of the cathode foil 20 is fixed by the tape stopper 40. When anode foil 10 is prepared by cutting from a large piece of foil, wound body 100 may be further subjected to chemical conversion treatment in order to provide a dielectric layer on the cut surface.

The method of impregnating the roll body 100 with the electrolyte solution, the solution in which the conductive polymer is dissolved, and/or the dispersion in which the conductive polymer is dispersed is not particularly limited. For example, a method of immersing the roll body 100 in an electrolytic solution, a solution, or a dispersion contained in a container, a method of dropping the electrolytic solution, the solution, or the dispersion into the roll body 100, or the like may be used. The impregnation may be carried out under reduced pressure, for example, in an atmosphere of 10kPa to 100kPa, preferably 40kPa to 100 kPa.

Next, the roll 100 is sealed, whereby the electrolytic capacitor 200 shown in fig. 3 can be obtained. To manufacture electrolytic capacitor 200, first, wound body 100 is housed in case 211 with a bottom so that leads 60A and 60B are positioned on the opening side of case 211 with a bottom. As a material of the bottomed case 211, a metal such as aluminum, stainless steel, copper, iron, brass, or an alloy thereof can be used.

Next, the sealing member 212 formed so that the leads 60A and 60B penetrate therethrough is disposed above the wound body 100, and the wound body 100 is sealed in the bottomed case 211. The sealing member 212 may be an insulating material, and is preferably an elastomer. Among them, silicone rubber, fluororubber, ethylene-propylene rubber, hypalon rubber, butyl rubber, isoprene rubber, and the like having high heat resistance are preferable.

Next, the vicinity of the open end of the bottomed case 211 is subjected to a lateral necking process, and the open end is crimped to the sealing member 212 to be crimped. Finally, sealing is completed by disposing a seat plate 213 at the curled portion. Then, the aging treatment may be performed while applying a rated voltage.

In the above embodiment, the winding type electrolytic capacitor was explained, but the application range of the present invention is not limited to the above, and the present invention can be applied to other electrolytic capacitors, for example, a laminated type electrolytic capacitor.

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the examples.

EXAMPLE 1

In this example, an electrode foil for an aluminum electrolytic capacitor having a chemical conversion voltage of 5V was produced. Hereinafter, a specific method for manufacturing the anode foil for electrolytic capacitors will be described.

(preparation of Anode foil)

Al foil having a thickness of 120 μm was prepared. The Al foil is subjected to AC etching treatment by adding sulfuric acid to an aqueous solution of hydrochloric acid to roughen the surface and form a porous portion. Porous parts having a thickness of 40 μm are formed on both surfaces of the Al foil, and the pores of the pits have a diameter of 100 to 200 nm. Then, the Al foil having the porous portion was washed with an oxalic acid aqueous solution (oxalic acid concentration 0.01 mol/L).

Next, the Al foil having the porous portion was immersed in an alkaline aqueous solution containing monoethanolamine (monoethanolamine concentration of 0.1mol/L) for 5 minutes, and then further immersed in an aqueous solution containing a trace amount of phosphorus (phosphoric acid concentration of 50ppm) for 5 minutes. Then, the Al foil was heated in an inert atmosphere (argon atmosphere) at 300 f to form a thin base layer.

Next, tris (ethylmethylamino) tantalum (V) (C) was produced by ALD method (temperature: 200 ℃ C., precursor: (t-butylimide)₁₃H₃₃N₄Ta, TBTEMT), oxidizing agent: h₂O, pressure: 10Pa, 250 cycles), an oxide containing Ta was formed as a dielectric layer (first layer) on the surface of the Al skeleton constituting the porous portion.

Next, the Al foil was subjected to chemical conversion treatment to form a second layer containing an oxide of Al between the Al skeleton and the first layer, thereby obtaining an anode foil. The chemical conversion treatment was performed by dipping the Al foil having the first layer in an aqueous solution of diammonium adipate (diammonium adipate concentration of 10 mass%), and applying a voltage of 5V thereto. The application time after the chemical conversion voltage reached about 5V was set to 30 minutes. Then, the anode foil is cut into a predetermined shape.

As a result of the GD-OES based elemental analysis, the base layer contains phosphorus, carbon, hydrogen and oxygen, and the first layer (thickness: about 8nm) contains Ta₂O₅Ta has an oxygen coordination number of 8, and the second layer (thickness: about 2nm) contains Al₂O₃(T1 ═ 4 × T2). The underlayer is a mixed layer of Ta oxide and Al oxide.

The underlayer contains nitrogen (N) derived from monoethanolamine, and the presence of a C — N bond can be confirmed by electron energy loss spectroscopy (TEM-EELS).

The relationship of the distance (depth) of the base layer from the surface on the first layer side and the P content is shown in fig. 5. A clear peak of P was observed in fig. 5, and it was confirmed that P had a peak near the basal layer.

The relationship of the distance (depth) of the base layer from the surface on the first layer side and the C content is shown in fig. 6. In fig. 6, a peak of C was observed, and it was confirmed that the peak of C was present in the vicinity of the basal layer.

[ evaluation ]

For the obtained anode foil, the electrostatic capacity and the leakage current were measured. The leakage current was measured as the cumulative value of the leakage current flowing until 4.6V by immersing the anode foil in an aqueous solution of ammonium adipate having a concentration of 10 mass% and applying a voltage while increasing the voltage at a rate of 0.2V/sec.

As the acid resistance (degradation test), after immersion in an acidic aqueous solution at 35 ℃ for 60 minutes (degradation), the leakage current was measured by the same measurement method as described above, and the acid resistance was evaluated. The evaluation results are shown in table 1. Table 1 shows relative values when the result of comparative example 1 is 100.

Comparative example 1

An electrolytic capacitor was produced in the same manner as in example 1, except that the step of immersing the Al foil having the porous portion in an alkaline aqueous solution and the subsequent step of heating in an inert atmosphere were not performed. In the GD-OES based elemental analysis of the base layer, no substantial peaks of phosphorus, carbon and hydrogen were observed.

Comparative example 2

An electrolytic capacitor was produced in the same manner as in example 1, except that the Al foil having a porous portion was washed with an aqueous ammonium dihydrogen phosphate solution (ammonium dihydrogen phosphate concentration: 1.4g/L) instead of washing with an aqueous sulfuric acid solution, and the step of immersing the Al foil having a porous portion in an aqueous alkaline solution was not performed. In the GD-OES based elemental analysis of the base layer, a peak of phosphorus was observed, but no substantial peak of carbon was observed.

[ TABLE 1 ]

	Electrostatic capacity	Leakage current	Acid resistance
				A1	110	60	50
B1	100	100	100
				B2	95	98	95

In example 1, the capacitance was improved, the leak current was reduced, and the acid resistance was improved as compared with comparative examples 1 and 2.

Industrial applicability

According to the present invention, an electrode foil for an electrolytic capacitor, and a method for manufacturing the same, which can sufficiently reduce a leakage current, can be obtained.

Description of the reference numerals

10: anode foil, 20: cathode foil, 30: spacer, 40: tape stop, 50A, 50B: lead tab, 60A, 60B: lead, 100: roll, 110: anode body, 111: core portion, 112: porous portion, 120: dielectric layer, 121: first layer, 122: second layer, 130: base layer, 200: electrolytic capacitor, 211: bottomed case, 212: sealing member, 213: a seat board.