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

Abstract

To suppress the decrease in capacitance of an electrolytic capacitor and the increase in a leakage current.SOLUTION: An electrode foil for an electrolytic capacitor includes an anode body containing a valve metal, an intermediate layer covering at least a portion of the anode body, and a first dielectric layer covering at least a portion of the intermediate layer. The intermediate layer contains elemental zinc.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to an electrode foil for an electrolytic capacitor, an electrolytic capacitor, and a method for manufacturing an electrode foil for an electrolytic capacitor.

Background Art

[0002] The electrode foil of an electrolytic capacitor includes an anode body containing a valve action metal and a dielectric layer covering at least a part of the surface of the anode body.

[0003] Patent Document 1 discloses "an electrode foil for an electrolytic capacitor including a base material containing a valve action metal and a heterogeneous metal composite layer covering the surface of the base material, the heterogeneous metal composite layer including a mixed region in which a first metal and a second metal different from the first metal are mixed, the mixed region constituting at least 50% of the thickness direction of the heterogeneous metal composite layer, and the content ratio M1 of the first metal and the content ratio M2 of the second metal with respect to all the metals in the mixed region being each 1 atomic% or more".

[0004] Patent Document 2 discloses "a layer structure for acting as or forming at least one thin layer capacitor including a first metal layer, a dielectric layer having a thickness of about 0.03 to about 2 microns, and a second metal layer". Further, Patent Document 2 discloses that the above layer structure "further includes an adhesive layer having a specific thickness between the dielectric layer and the second metal layer", and that "the adhesive layer is zinc oxide".

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] The presence of a natural oxide film on the surface of the anode body may cause a decrease in the capacitance of the electrolytic capacitor or an increase in the leakage current.

Means for Solving the Problem

[0007] One aspect of the present disclosure relates to an electrode foil for an electrolytic capacitor, comprising an anode body containing a valve-acting metal, an intervening layer covering at least a part of the anode body, and a first dielectric layer covering at least a part of the intervening layer, wherein the intervening layer contains a zinc element.

[0008] Another aspect of the present disclosure relates to an electrolytic capacitor comprising the above electrode foil for an electrolytic capacitor and a cathode portion covering at least a part of the first dielectric layer.

[0009] Yet another aspect of the present disclosure relates to a method for manufacturing an electrode foil for an electrolytic capacitor, including a first step of preparing an anode body containing a valve-acting metal, a second step of forming an intervening layer covering at least a part of the anode body, and a third step of forming a first dielectric layer covering at least a part of the intervening layer, wherein the intervening layer contains a zinc element.

Advantages of the Invention

[0010] According to the present disclosure, it is possible to suppress a decrease in the capacitance of the electrolytic capacitor and an increase in the leakage current.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Embodiments for Carrying Out the Invention

[0012] Hereinafter, embodiments of the present disclosure will be described with examples, but the present disclosure is not limited to the examples described below. In the following description, specific numerical values and materials may be exemplified, but other numerical values and materials may be applied as long as the effects of the present disclosure can be obtained. In this specification, the description "numerical value A to numerical value B" includes numerical value A and numerical value B and can be read as "numerical value A or more and numerical value B or less". In the following description, when the lower limit and the upper limit are exemplified for numerical values such as specific physical properties and conditions, any combination of any of the exemplified lower limits and any of the exemplified upper limits can be made as long as the lower limit is not more than the upper limit. When a plurality of materials are exemplified, one of them may be selected and used alone, or two or more of them may be used in combination.

[0013] [Electrolytic capacitor electrode foil] The electrolytic capacitor electrode foil according to an embodiment of the present disclosure includes an anode body containing a valve metal, an intervening layer covering at least a part of the anode body, and a first dielectric layer covering at least a part of the intervening layer. The intervening layer contains zinc element.

[0014] When a natural oxide film containing a valve metal exists on the surface of the anode body, the capacitance expected according to the dielectric constant of the first dielectric layer cannot be obtained. In addition, the natural oxide film has low insulation and the leakage current may increase. On the other hand, in the electrolytic capacitor electrode foil according to the present disclosure, the surface of the anode body is covered with an intervening layer containing zinc element. As a result, oxygen contained in the natural oxide film on the surface of the anode body easily diffuses (dissolves) into the intervening layer, and by the diffusion (dissolution) of the oxygen contained in the natural oxide film into the intervening layer, the natural oxide film can be thinned or eliminated (the natural oxide film is removed). Therefore, it is possible to suppress a decrease in capacitance and an increase in leakage current (LC) due to the natural oxide film.

[0015] (Intervening layer) The intermediate layer is formed between the first dielectric layer and the anode body (or the second dielectric layer described later). The intermediate layer contains at least a zinc element, and may contain a valve-acting metal and / or a first metal as an oxide. The intermediate layer may be formed of, for example, a compound (such as an oxide) containing a zinc element, or may be formed by the functional group bonding to the anode foil (metal skeleton) on the surface of the anode foil (metal skeleton constituting the porous part) containing a zinc element. From the viewpoint of being easy to form by the ALD method, etc., the intermediate layer may be a layer of zinc oxide (ZnO x ). The Zn-O bond may be detected in the intermediate layer by analysis such as X-ray photoelectron spectroscopy (XPS). The thickness of the intermediate layer may be small and may not have a clear layer structure.

[0016] The thickness T0 of the intermediate layer is, for example, 5 nm or less, and preferably 0.5 nm or more and 3.0 nm or less. When the thickness T0 of the intermediate layer is 3.0 nm or less, it is easy to increase the capacitance by forming the high dielectric constant first dielectric layer. When the thickness T0 of the intermediate layer is 0.5 nm or more, the effect of removing the natural oxide film due to the formation of the intermediate layer is easily obtained.

[0017] From the viewpoint of being easy to remove the natural oxide film, the content rate of the zinc element with respect to all the elements in the intermediate layer is preferably 60% by mass or more, and more preferably 80% by mass or more. From the viewpoint of easily ensuring appropriate thicknesses of the first dielectric layer and the intermediate layer, the content rate of the zinc element with respect to all the elements in the intermediate layer may be 90% by mass or less, or may be 60% by mass or less.

[0018] (The first dielectric layer) The first dielectric layer contains an oxide of a first metal. The first dielectric layer may be a layer of the oxide of the first metal. From the perspective of increasing the capacitance, it is preferable that the oxide of the first metal has a high dielectric constant. Since the natural oxide film can be removed by the intervening layer, the large capacitance expected from the high-dielectric-constant first dielectric layer can be obtained. From the perspective of increasing the capacitance, the first metal preferably contains at least one metal A selected from the group consisting of tantalum (Ta), titanium (Ti), zirconium (Zr), niobium (Nb), and hafnium (Hf). Among them, Ti is more preferable. In the first dielectric layer, for example, Ta 2 O 5 , TiO 2 , ZrO 2 , Nb 2 O 5 , HfO 2 etc. can be included alone or in combination of two or more. When the first dielectric layer contains two or more oxides of the first metal, the two or more oxides may be mixed or each may be arranged in layers. The first metal may be a metal element different from the valve metal contained in the anode body. By the ALD method described later, a high-dielectric-constant first dielectric layer can be formed by appropriately selecting the first metal regardless of the valve metal.

[0019] The first metal may contain at least one metal B selected from the group consisting of silicon (Si) and aluminum (Al) together with the above metal A. That is, the oxide of the first metal may be a composite oxide in which the oxide of metal A and the oxide of metal B are mixed. When the oxide of metal A is likely to crystallize and tends to have a large leakage current, crystallization can be suppressed by making it a composite oxide, and the effect of suppressing the increase in leakage current can be easily obtained. When the first metal (metal A) is Ti, in particular, the effect of making it a composite oxide is remarkable. For example, the first dielectric layer is a composite oxide layer in which TiO 2 and Al 2 O 3 or SiO 2 are mixed (Ti-Al-O x or Ti-Si-O xIt is preferably a (layer). In this case, the molar ratio of Ti / Al in the composite oxide layer may be, for example, 2 or more and 6 or less. The molar ratio of Ti / Si in the composite oxide layer may be, for example, 2 or more and 6 or less. The first dielectric layer is TiO 2 and Al 2 O 3 and SiO 2 It may be a composite oxide layer in which are mixed.

[0020] The interposed layer and the first dielectric layer can be confirmed as follows. Obtain a cross-sectional image (a cross-sectional image including the porous part) near the surface of the electrode foil by a scanning electron microscope (SEM) or a transmission electron microscope (TEM). Using the image, perform elemental mapping by energy-dispersive X-ray spectroscopy (EDX) analysis to obtain maps of the valve-acting metal, zinc, and the first metal. In the elemental mapping, confirm the region where zinc is distributed along the surface of the anode body (the region where the valve-acting metal is distributed), and use it as the interposed layer. Next, confirm the region where the first metal is distributed along the surface of the anode body through the interposed layer, and use it as the first dielectric layer.

[0021] From the viewpoints of easy increase in capacitance and easy reduction of LC, it is preferable that the thickness T0 of the interposed layer is smaller than the thickness T1 of the first dielectric layer. From the same viewpoints, the ratio of the thickness T0 of the interposed layer to the thickness T1 of the first dielectric layer: T0 / T1 may be, for example, 0.5 or less, 0.3 or less, 0.15 or less, or 0.05 or less. The thickness T0 of the interposed layer is obtained by measuring the thicknesses of any 10 locations of the interposed layer confirmed by elemental mapping of the cross-section of the electrode foil described later and calculating their average value. The thickness T1 of the first dielectric layer is also obtained in the same manner as the thickness T0 of the interposed layer.

[0022] The electrode foil may further include a second dielectric layer containing an oxide of the valve metal between the anode body and the intervening layer. The second dielectric layer may be a layer of the oxide of the valve metal. The second dielectric layer can be formed by a formation treatment (a fourth step described later) of the anode body having the intervening layer and the first dielectric layer. When forming the second dielectric layer, the ionized valve metal diffuses to the first dielectric layer, and defects at the boundary between the first dielectric layer and the anode body of the first dielectric layer can be repaired, and the leakage current can be further reduced. Also, depending on the components of the first dielectric layer (for example, when the first dielectric layer is a Ti-Si-O x layer), the capacitance can also be further improved. The thickness of the second dielectric layer may be small and may not have a clear layer structure. From the perspective of increasing the capacitance, it is preferable that the thickness T2 of the second dielectric layer is smaller than the thickness T1 of the first dielectric layer. T2 / T1 may be, for example, 0.6 or less, 0.3 or less, or 0.1 or less. From the perspective of increasing the capacitance, the thickness T2 of the second dielectric layer may be, for example, 0.5 nm or less. The thickness T2 of the second dielectric layer can be obtained by EDX analysis using a cross-sectional image near the surface of the above electrode foil. The region of the metal structure constituting the anode body and the region of the second dielectric layer can be distinguished, for example, by binarization processing of the image.

[0023] For the analysis of the distribution or concentration of each element in the intervening layer and the dielectric layer, for example, energy dispersive X-ray spectroscopy (EDX), glow discharge optical emission spectroscopy (GD-OES), field emission Auger electron spectroscopy (FE-AES), etc. can be used. The dielectric layer does not substantially contain zinc element. Not substantially containing means that zinc is below the detection limit by analysis such as EDX.

[0024] FIG. 1(A) is a cross-sectional view schematically showing a main part (surface part) of an electrode foil for an electrolytic capacitor according to an embodiment of the present disclosure. FIG. 1(B) is an enlarged view of the X portion of FIG. 1(A). In the figure, P is a pit (or pore) of the porous portion 112, D is the thickness of the porous portion 112, and T1 is the thickness of the first dielectric layer 121. The electrode foil for an electrolytic capacitor according to the embodiment of the present disclosure is not limited thereto.

[0025] The anode foil 10 (electrode foil) includes an anode body 110 containing a valve action metal, an intervening layer 130 covering at least a part of the anode body 110, and a first dielectric layer 121 covering at least a part of the intervening layer 130. The intervening layer 130 contains a zinc element (for example, an oxide of zinc). The first dielectric layer 121 contains an oxide of a first metal.

[0026] The anode body 110 is a metal foil having a surface roughened by etching or the like, and has a core portion 111 and a porous portion 112. The porous portion 112 has a large number of pits P. The intervening layer 130 and the first dielectric layer 121 are formed so as to cover the outer surface of the porous portion 112 and the inner wall surface of the pits P. A second dielectric layer (not shown) may be formed between the anode body 110 and the intervening layer 130.

[0027] [Method for manufacturing an electrode foil for an electrolytic capacitor] The method for manufacturing an electrode foil for an electrolytic capacitor according to an embodiment of the present disclosure includes the following first to third steps. First step: Prepare an anode body containing a valve action metal. Second step: Form an intervening layer covering at least a part of the anode body. The intervening layer contains a zinc element. Third step: Form a first dielectric layer covering at least a part of the intervening layer.

[0028] Hereinafter, each step will be described in detail.

[0029] (First step: Preparation of the anode body) The anode body contains a valve action metal. The valve action metal preferably contains at least one selected from the group consisting of tantalum, niobium, and aluminum.

[0030] For the anode body, for example, a foil-shaped base material (metal foil) containing a valve-acting metal is used. The thickness of the metal foil is, for example, 15 μm or more and 300 μm or less. The anode body is produced, for example, by roughening the surface of the metal foil by an etching treatment or the like. The metal foil with a roughened surface includes a porous portion and a core portion continuous with the porous portion. In this case, the intermediate layer and the first dielectric layer are formed so as to cover the metal skeleton constituting the porous portion. The porous portion has a large number of pits. The most frequent pore diameter of the pits is not particularly limited, but for example, it is 50 nm or more and 2000 nm or less in that a large surface area can be easily obtained and the first dielectric layer can be easily formed up to the deep part of the pits. Note that the most frequent pore diameter of the pits is the most frequent pore diameter in the pore diameter distribution based on volume measured by a mercury porosimeter. The thickness D per side of the porous portion is not particularly limited, but from the viewpoints of ensuring a large surface area and maintaining the strength of the electrode foil, for example, it is 1 / 10 or more and 4 / 10 or less of the total thickness of the metal foil. The thickness D per side of the porous portion is obtained by measuring the thicknesses of any 10 points using a cross-sectional image of the metal foil by SEM or TEM and calculating their average value.

[0031] (Second step: Formation of intermediate layer) In the second step, it is preferable to form the intermediate layer by the Atomic Layer Deposition (ALD) method. In this case, a layer of zinc oxide can be formed as the intermediate layer. The formation of the intermediate layer by the ALD method is preferably performed while the surface of the anode body is heated to 150°C or more. In this case, by forming the intermediate layer and making the natural oxide film in a solid solution state, oxygen contained in the natural oxide film can be easily diffused into the intermediate layer, and the natural oxide film can be easily removed.

[0032] In the case of ALD method, a raw material gas containing zinc and an oxidizing agent are alternately supplied to a reaction chamber in which an object is disposed, and an intervening layer can be formed on the surface of the object. In the ALD method, since the self-limiting action functions, zinc is deposited on the surface of the object in atomic layer units. Therefore, it is easy to control the thickness T0 of the intervening layer by the number of cycles with one cycle being the supply of the raw material gas → the exhaust (purge) of the raw material gas → the supply of the oxidizing agent → the exhaust (purge) of the oxidizing agent.

[0033] Examples of the oxidizing agent include water, oxygen, ozone, etc. The oxidizing agent may be supplied to the reaction chamber as a plasma using the oxidizing agent as a raw material.

[0034] Zinc is supplied to the reaction chamber as a gas (raw material gas) of a precursor containing zinc. The precursor is, for example, an organometallic compound containing zinc, and thereby zinc is likely to chemisorb on the object. As the precursor, various organometallic compounds conventionally used in the ALD method can be used.

[0035] Examples of the precursor containing zinc include diethylzinc (Zn(C 2 H 5 ) 2 ), etc.

[0036] (Step 3: Formation of the first dielectric layer) In the third step, a first dielectric layer containing an oxide of the first metal is formed. In the third step, it is preferable to form the first dielectric layer by ALD method. In this case, the first metal can be appropriately selected regardless of the valve action metal contained in the anode body.

[0037] In the case of ALD method, a raw material gas containing a first metal and an oxidizing agent are alternately supplied to a reaction chamber in which an object is disposed, and a first dielectric layer can be formed on the surface of the object. In the ALD method, since the self-limiting action functions, the first metal is deposited on the surface of the object in atomic layer units. Therefore, it is easy to control the thickness T1 of the first dielectric layer by the number of cycles with one cycle being the supply of the raw material gas → the exhaust (purge) of the raw material gas → the supply of the oxidizing agent → the exhaust (purge) of the oxidizing agent.

[0038] Examples of the oxidizing agent include water, oxygen, ozone, etc. The oxidizing agent may be supplied to the reaction chamber as a plasma using the oxidizing agent as a raw material.

[0039] The first metal is supplied to the reaction chamber as a gas (raw material gas) of a precursor containing the first metal. The precursor is, for example, an organometallic compound containing the first metal, whereby the first metal is easily chemisorbed on the object. As the precursor, various organometallic compounds conventionally used in the ALD method can be used.

[0040] The first metal may be used alone or in combination of two or more. When two or more types of the first metal are used in combination, a precursor containing two or more types of the first metal may be used. Also, in this case, depending on the cycle, the type of precursor supplied to the reaction chamber may be changed to change the type of the first metal deposited in atomic layer units. In this case, a first dielectric layer (layer of composite oxide) in which oxides of two or more types of the first metal are mixed can be formed.

[0041] Metal A may be used as the first metal. Also, metal A and metal B may be used in combination as the first metal. In this case, a precursor containing metal A and metal B may be used. Also, in this case, depending on the cycle, the type of precursor supplied to the reaction chamber may be changed to change the metal species deposited in atomic layer units. In this case, a first dielectric layer (layer of composite oxide) in which an oxide of metal A and an oxide of metal B are mixed can be formed. In the case of the ALD method, it is easy to control the mixing ratio of the oxide of metal A and the oxide of metal B in the composite oxide layer.

[0042] Examples of the precursor containing metal A include precursors containing Ta, precursors containing Ti, precursors containing Zr, precursors containing Nb, and precursors containing Hf.

[0043] Examples of the precursor containing Ta include, for example, tris(ethylmethylamide)(t-butylamide)tantalum(V)(C 13 H 33 N 4 Ta), tantalum(V) ethoxide (Ta(OC 2 H 5 ) 5 ), tris(diethylamide)(t-butylimide)tantalum(V)((CH 3 ) 3 CNTa(N(C 2 H 5 ) 2 ) 3 ), pentakis(dimethylamino)tantalum(V)(Ta(N(CH 3 ) 2 ) 5 ), etc.

[0044] Examples of the precursor containing Ti include, for example, bis(t-butylcyclopentadienyl)titanium(IV) dichloride (C 18 H 26 Cl 2 Ti), tetrakis(dimethylamino)titanium(IV)([(CH 3 ) 2 N] 4 Ti), tetrakis(diethylamino)titanium(IV)([(C 2 H 5 ) 2 N] 4 Ti), tetrakis(ethylmethylamino)titanium(IV)(Ti[N(C 2 H 5 )(CH 3 )] 4 ), titanium(IV)(diisopropoxide-bis(2,2,6,6-tetramethyl-3,5-heptanedionate (Ti[OCC(CH 3 ) 3CHCOC(CH 3 ) 3 2 (OC 3 H 7 ) 2 )、 titanium tetrachloride (TiCl 4 )、 titanium(IV) isopropoxide (Ti[OCH(CH 3 ) 2 4 )、 titanium(IV) ethoxide (Ti[O(C 2 H 5 )] 4 ) and the like can be mentioned.

[0045] Examples of the precursor containing Zr include, for example, bis(methyl-η 5 -cyclopentadienyl)methoxymethyldizirconium (Zr(CH 3 C 5 H 4 ) 2 CH 3 OCH 3 )、 tetrakis(dimethylamide)zirconium(IV) ([(CH 3 ) 2 N] 4 Zr), tetrakis(ethylmethylamide)zirconium(IV) (Zr(NCH 3 C 2 H 5 ) 4 )、 zirconium(IV) t-butoxide (Zr[OC(CH 3 ) 3 4 ) and the like can be mentioned.

[0046] Examples of the precursor containing Nb include, for example, niobium(V) ethoxide (Nb(OCH 2 CH 3 ) 5 、 tris(diethylamide)(t-butylimide)niobium(V) (C 16 H 39 N 4 Nb) and the like can be mentioned.

[0047] Examples of the precursor containing Hf include, for example, hafnium tetrachloride (HfCl 4 ​​​)、Tetrakis(dimethylamino)hafnium (Hf[N(CH 3 ) 2 4 )、Tetrakis(ethylmethylamino)hafnium (Hf[N(C 2 H 5 )(CH 3 )] 4 )、Tetrakis(diethylamino)hafnium (Hf[N(C 2 H 5 ) 2 4 )、Hafnium tert-butoxide (Hf[OC(CH 3 ) 3 4 ) etc. can be mentioned.

[0048] Also, as the precursor containing metal B, a precursor containing Al and a precursor containing Si can be mentioned. As the precursor containing Al, for example, trimethylaluminum ((CH 3 ) 3 Al) etc. can be mentioned.

[0049] As the precursor containing Si, for example, N-sec-butyl(trimethylsilyl)amine (C 7 H 19 NSi), 1,3-diethyl-1,1,3,3-tetramethyldisilazane (C 8 H 23 NSi 2 ), 2,4,6,8,10-pentamethylcyclopentasiloxane ((CH 3 SiHO) 5 ), pentamethyldisilane ((CH 3 ) 3 SiSi(CH 3 ) 2 H), tris(dimethylamino)silane ([(CH 3 ) 2 N] 3 SiH), tris(isopropoxy)silanol ([(H 3 C) 2 CHO] 3 SiOH), chloropentamethyl disilane ((CH 3 ) 3 SiSi(CH​​​3 ) 2 Cl), dichlorosilane (SiH 2 Cl 2 ), trimethylaminosilane (Si[N(CH 3 ) 2 4 ), tetraethylsilane (Si(C 2 H 5 ) 4 ), tetramethylsilane (Si(CH 3 ) 4 ), tetraethoxysilane (Si(OC 2 H 5 ) 4 ), dodecamethylcyclohexasilane ((Si(CH 3 ) 2 ) 6 ), silicon tetrachloride (SiCl 4 ), silicon tetrabromide (SiBr 4 ) etc. can be mentioned.

[0050] (Fourth step: formation treatment) The method for manufacturing an electrode foil for an electrolytic capacitor according to an embodiment of the present disclosure may include a fourth step of subjecting an anode body having an intervening layer and a first dielectric layer to a formation treatment. By the formation treatment, a second dielectric layer (formation film) containing an oxide of the valve metal may be formed between the anode body and the intervening layer. The formation treatment is performed, for example, by immersing the anode body in a formation solution such as an ammonium adipate solution and applying a predetermined formation voltage (anodic oxidation). The thickness T2 of the second dielectric layer can be controlled by the formation voltage and the like.

[0051] [Electrolytic capacitor] An electrolytic capacitor according to an embodiment of the present disclosure includes the above electrode foil for an electrolytic capacitor and a cathode portion that covers at least a part of the first dielectric layer. The cathode portion may contain an electrolyte that covers at least a part of the first dielectric layer. The electrolyte may contain a solid electrolyte or may contain an electrolytic solution. The cathode portion may contain a solid electrolyte and a liquid component. The liquid component includes an electrolytic solution or a solvent (for example, a polyol compound).

[0052] ​The solid electrolyte contains a conductive polymer. Examples of the conductive polymer include π-conjugated polymers. Examples of the conductive polymer include polypyrrole, polythiophene, polyfuran, polyaniline, etc. The conductive polymer may be used alone, or in combination of two or more kinds, or may be a copolymer of two or more kinds of monomers. The weight average molecular weight of the conductive polymer is, for example, 1000 to 100,000.

[0053] In this specification, polypyrrole, polythiophene, polyfuran, polyaniline, etc. each mean a polymer having polypyrrole, polythiophene, polyfuran, polyaniline, etc. as a basic skeleton. Therefore, derivatives of polypyrrole, polythiophene, polyfuran, polyaniline, etc. may be included. For example, poly(3,4-ethylenedioxythiophene) (PEDOT) etc. are included in polythiophene.

[0054] The conductive polymer may be doped with a dopant. Examples of the dopant include polystyrene sulfonic acid (PSS) etc. The solid electrolyte may further contain an additive as necessary.

[0055] The electrolytic solution contains a solvent and an ionic substance (solute (for example, organic salt)) dissolved therein. The solvent may be an organic solvent or an ionic liquid. As the solvent, a high-boiling solvent is preferable. For example, polyol compounds such as ethylene glycol, sulfone compounds such as sulfolane, lactone compounds such as γ-butyrolactone, 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, etc. can be used. The solvent may be used alone or in combination of two or more kinds.

[0056] An organic salt is a salt in which at least one of the anion and the cation contains an organic substance. As the organic salt, for example, trimethylamine maleate, triethylamine borodisalicylate, ethyldimethylamine phthalate, mono-1,2,3,4-tetramethylimidazolinium phthalate, mono-1,3-dimethyl-2-ethylimidazolinium phthalate, etc. may be used. The organic salt may be used alone or in combination of two or more.

[0057] Here, FIG. 2 is a cross-sectional view schematically showing an electrolytic capacitor according to an embodiment of the present disclosure. FIG. 3 is a perspective view of a part of the wound body developed.

[0058] The wound type electrolytic capacitor 200 includes a capacitor element. The capacitor element includes a wound body 100 and an electrolyte (not shown). The wound body 100 is formed by winding an anode foil 10 and a cathode foil 20 with a separator 30 interposed therebetween. The anode foil 10 is an electrode foil for an electrolytic capacitor according to the present disclosure. In this case, the cathode portion includes the electrolyte and the cathode foil 20.

[0059] An electrolyte is interposed between the anode foil 10 and the cathode foil 20. The electrolyte adheres to the surface of the anode foil 10 (the first dielectric layer). A solid electrolyte (or a solid electrolyte and a liquid component) may be interposed between the anode foil 10 and the cathode foil 20. For example, a capacitor element can be obtained by impregnating the wound body with a treatment liquid (or an electrolytic solution) containing a conductive polymer. The impregnation may be performed under reduced pressure, for example, in an atmosphere of 10 kPa to 100 kPa.

[0060] Known materials can be used for the cathode foil and the separator. The cathode foil 20 is not particularly limited, and for example, a metal foil containing a valve metal such as tantalum, niobium, and aluminum is used. If necessary, the surface of the metal foil may be roughened, or a formation film or a coating layer may be formed on the surface of the metal foil. The coating layer may contain a metal different from the valve metal contained in the metal foil (for example, titanium), or may contain a non-metal such as carbon. The separator 30 is not particularly limited, and for example, a non-woven fabric containing fibers of cellulose, polyethylene terephthalate, vinylon, polyamide, etc. is used.

[0061] One end of each of the lead tabs 50A and 50B is connected to the anode foil 10 and the cathode foil 20, respectively, and the wound body 100 is formed while winding the lead tabs 50A and 50B. Lead wires 60A and 60B are connected to the other ends of the lead tabs 50A and 50B, respectively.

[0062] The winding tape 40 is disposed on the outer surface of the cathode foil 20 located on the outermost layer of the wound body 100, and the end of the cathode foil 20 is fixed by the winding tape 40. When the anode foil 10 is prepared by cutting a large-sized foil, a formation process may be further performed on the wound body 100 in order to provide a dielectric layer on the cut surface.

[0063] The wound body 100 is housed in the bottomed case 211 so that the lead wires 60A and 60B are located on the opening side of the bottomed case 211. As the material of the bottomed case 211, a metal such as aluminum, stainless steel, copper, iron, brass, or an alloy thereof can be used.

[0064] A sealing member 212 is disposed at the opening of the bottomed case 211 in which the wound body 100 is housed, the opening end of the bottomed case 211 is caulked to the sealing member 212 and curled, and a seat plate 213 is disposed on the curled portion, whereby the wound body 100 is sealed in the bottomed case 211.

[0065] The sealing member 212 is formed so that the lead wires 60A and 60B penetrate therethrough. The sealing member 212 may be an insulating material, and an elastic body is preferable. Among them, silicone rubber, fluororubber, ethylene propylene rubber, hypalon rubber, butyl rubber, isoprene rubber, etc. having high heat resistance are preferable.

[0066] In the above embodiment, the wound type electrolytic capacitor has been described, but the application range of the present disclosure is not limited thereto, and it can also be applied to other electrolytic capacitors, for example, multilayer type electrolytic capacitors. The cathode portion of the multilayer type electrolytic capacitor includes, for example, a solid electrolyte layer covering at least a part of the first dielectric layer, and a cathode lead-out layer covering at least a part of the solid electrolyte layer. The cathode lead-out layer has, for example, a carbon layer covering the solid electrolyte layer and a silver paste layer covering the carbon layer. The carbon layer contains, for example, carbon particles and silver. The silver paste layer contains, for example, silver particles and a binder (for example, an epoxy resin).

[0067] 《Supplementary Note》 From the description of the above embodiments, the following technologies are disclosed. (Technology 1) An anode body containing a valve-acting metal, An intervening layer covering at least a part of the anode body, A first dielectric layer covering at least a part of the intervening layer, and The intervening layer is an electrode foil for an electrolytic capacitor containing a zinc element. (Technology 2) The first dielectric layer contains an oxide of a first metal, The first metal contains titanium, and the electrode foil for an electrolytic capacitor according to Technology 1. (Technology 3) The valve-acting metal contains at least one selected from the group consisting of tantalum, niobium, and aluminum, and the electrode foil for an electrolytic capacitor according to Technology 1 or 2. (Technology 4) The thickness T0 of the intervening layer is smaller than the thickness T1 of the first dielectric layer, and the electrode foil for an electrolytic capacitor according to any one of Technologies 1 to 3. (Technology 5) The thickness T0 of the intervening layer is 0.5 nm or more and 3.0 nm or less, and the electrolytic capacitor electrode foil according to any one of Technologies 1 to 4. (Technology 6) The electrolytic capacitor electrode foil according to any one of Technologies 1 to 5, comprising a second dielectric layer containing an oxide of the valve metal between the anode body and the intervening layer. (Technology 7) The electrolytic capacitor electrode foil according to any one of Technologies 1 to 6, and an electrolytic capacitor comprising a cathode portion covering at least a part of the first dielectric layer. (Technology 8) A first step of preparing an anode body containing a valve metal, A second step of forming an intervening layer covering at least a part of the anode body, A third step of forming a first dielectric layer covering at least a part of the intervening layer, and the intervening layer contains a zinc element, and a method for manufacturing an electrolytic capacitor electrode foil. (Technology 9) The first dielectric layer contains an oxide of a first metal, the first metal contains titanium, and a method for manufacturing an electrolytic capacitor electrode foil according to Technology 8. (Technology 10) The valve metal contains at least one selected from the group consisting of tantalum, niobium, and aluminum, and a method for manufacturing an electrolytic capacitor electrode foil according to Technology 8 or 9. (Technology 11) In the second step, the intervening layer is formed by atomic layer deposition, and a method for manufacturing an electrolytic capacitor electrode foil according to any one of Technologies 8 to 10. (Technology 12) The formation of the intervening layer by atomic layer deposition is performed in a state where the surface of the anode body is heated to 150 °C or higher, and a method for manufacturing an electrolytic capacitor electrode foil according to Technology 11. (Technology 13) In the third step, the first dielectric layer is formed by atomic layer deposition, and a method for manufacturing an electrolytic capacitor electrode foil according to any one of Technologies 8 to 12. (Technology 14) The manufacturing method of the electrode foil for an electrolytic capacitor according to any one of Technologies 8 to 13, including a fourth step of forming a chemical conversion treatment on the anode body having the intervening layer and the first dielectric layer. (Technology 15) The manufacturing method of the electrode foil for an electrolytic capacitor according to Technology 14, wherein a second dielectric layer containing an oxide of the valve action metal is formed between the anode body and the intervening layer by the chemical conversion treatment.

[0068] [Examples] Hereinafter, the present disclosure will be described in more detail based on examples, but the present disclosure is not limited to the examples.

[0069] 《Example 1》 In this example, an electrode foil (anode foil) for an aluminum electrolytic capacitor was manufactured. Hereinafter, a specific manufacturing method of the anode foil will be described.

[0070] (Manufacture of Anode Foil) (First Step: Preparation of Anode Body) An Al foil with a thickness of 130 μm was prepared, and the surface of the Al foil was roughened by an etching treatment to form a porous portion (thickness per side: 50 μm, pore diameter of pits: 100 to 200 nm). In this way, an anode body was obtained.

[0071] (Second Step: Formation of Intervening Layer) By the ALD method (temperature: 150 °C, precursor: a precursor containing Zn, oxidant: O 3 , pressure: 1 Pa), a layer of zinc oxide (ZnO x ) was formed as an intervening layer on the surface of the anode body. Diethyl zinc (Zn(C 2 H 5 )) was used as the precursor containing Zn. The number of cycles was appropriately adjusted so that the thickness T0 of the intervening layer was the value shown in Table 1. 2 ) was used. The number of cycles was adjusted as appropriate so that the thickness T0 of the intervening layer was the value shown in Table 1.

[0072] (Third Step: Formation of First Dielectric Layer) By the ALD method (temperature: 150 °C, precursor: a precursor containing Ti and a precursor containing Al, oxidant: O 3, at a pressure of 1 Pa, a first dielectric layer (Ti - Al - O x layer) was formed on the surface of the intervening layer.

[0073] Tetrakis(dimethylamino)titanium(IV) was used as the precursor containing Ti, and trimethylaluminum was used as the precursor containing Al. With 6 cycles as one set, 5 cycles per set were for supplying the precursor containing Ti, and 1 cycle was for supplying the precursor containing Al. In this way, a composite oxide (Ti - Al - O 2 and Al 2 O 3 and) in which TiO x ) with a molar ratio of 5:1 was formed. The number of cycles (number of sets) was appropriately adjusted so that the thickness T1 of the first dielectric layer was the value shown in Table 1. In this way, an anode foil (anode foil A1) was obtained. Then, the anode foil was cut to a predetermined size.

[0074] The intervening layer and the first dielectric layer were confirmed by the method described above. The thickness T0 of the intervening layer and the thickness T1 of the first dielectric layer shown in Table 1 were obtained by the method described above.

[0075] 《Example 2》 By ALD method (temperature: 150 °C, precursors: precursor containing Ti and precursor containing Si, oxidant: O 3 , pressure: 1 Pa), a first dielectric layer (Ti - Si - O x layer) was formed on the surface of the intervening layer.

[0076] Tetrakis(dimethylamino)titanium(IV) was used as the precursor containing Ti, and tris(dimethylamino)silane was used as the precursor containing Si. With 6 cycles as one set, 5 cycles per set were for supplying the precursor containing Ti, and 1 cycle was for supplying the precursor containing Si. In this way, a composite oxide (Ti - Si - O 2 and SiO 2 and) in which TiO xA layer of was formed. The number of cycles (sets) was adjusted as appropriate so that the thickness T1 of the first dielectric layer was the value shown in Table 1.

[0077] An anode foil A2 was produced in the same manner as the anode foil A1 of Example 1, except as otherwise noted.

[0078] <<Comparative Example 1>> A first dielectric layer was formed on the surface of the anode body without forming an intervening layer. Specifically, the anode body was subjected to a forming treatment to form a formed film (AlO x layer) as the first dielectric layer on the surface of the anode body. An ammonium adipate solution (concentration 7% by mass, temperature 70°C) was used as the forming solution. The forming voltage was adjusted as appropriate so that the thickness T1 of the first dielectric layer (formed film) was the value shown in Table 1.

[0079] An anode foil B1 was produced in the same manner as the anode foil A1 of Example 1, except as otherwise noted.

[0080] <<Comparative Example 2>> A first dielectric layer was formed on the surface of the anode body without forming an intervening layer. By ALD method (temperature: 150°C, precursor: tetrakis(dimethylamino)titanium(IV), oxidant: O 3 , pressure: 1 Pa), a first dielectric layer (TiO x layer) was formed on the surface of the anode body. The number of cycles was adjusted as appropriate so that the thickness of the first dielectric layer was the value shown in Table 1.

[0081] An anode foil B2 was produced in the same manner as the anode foil A1 of Example 1, except as otherwise noted.

[0082] <<Comparative Example 3>> An anode foil B3 was produced in the same manner as the anode foil A1 of Example 1, except that no intervening layer was formed.

[0083] <<Comparative Example 4>> An anode foil B4 was produced in the same manner as the anode foil A2 of Example 2, except that no intervening layer was formed.

[0084] [Evaluation 1] For the anode foils A1 to A2, B1, and B3 to B4, the capacitance (frequency: 120 Hz) was measured under an environment of 20°C. The capacitance was expressed as a relative value (capacitance index) when the capacitance of the anode foil B1 in Comparative Example 1 was set to 100.

[0085] For the anode foils A1 to A2, B1 to B4, the leakage current (LC) was measured under an environment of 20°C. The leakage current was measured by immersing the anode foil in an aqueous ammonium adipate solution with a concentration of 10% by mass, applying a voltage of 2 V, and measuring the current value 180 seconds after the application. The leakage current was expressed as a relative value (LC index) when the leakage current of the anode foil B1 in Comparative Example 1 was set to 100.

[0086] The evaluation results are shown in Table 1.

[0087]

Table 1

[0088] In the anode foils A1 to A2, a large capacitance and a low LC were obtained simultaneously. In A1 to A2, with the formation of the intervening layer, the natural oxide film on the surface of the anode body became thinner (or disappeared).

[0089] In the anode foils B1 to B4, since the intervening layer was not formed, the natural oxide film on the surface of the anode body did not become thinner (or disappear). In the anode foils B1 to B4, a decrease in capacitance and / or an increase in LC were observed. In the anode foil B2 with the first dielectric layer containing a high-dielectric-constant Ti oxide, the LC increased significantly more than that in the anode foil B1 with the first dielectric layer containing an Al oxide.

[0090] 《Examples 3 to 4》 The fourth step was performed on the anode foils A1 and A2 (anode bodies having an intervening layer and a first dielectric layer on the surface) to produce anode foils A3 and A4. Specifically, a forming treatment was performed to form a forming film (AlO xA layer) was formed. An ammonium adipate solution (concentration: 7% by mass, temperature: 70°C) was used as the formation solution. The formation voltage was adjusted as appropriate so that the thickness T2 of the second dielectric layer was the value shown in Table 1.

[0091] [Evaluation 2] For the anode foils A3 to A4, the capacitance and leakage current were measured in the same manner as in Evaluation 1. The capacitance and leakage current were expressed as relative values (capacitance index and LC index) when the capacitance and leakage current of the anode foil B1 in Comparative Example 1 were each set to 100.

[0092] The evaluation results are shown in Tables 2 to 3. Table 2 also shows the results for the anode foil A1. Table 3 also shows the results for the anode foil A2.

[0093] [Table 2]

[0094] [Table 3]

[0095] As shown in Table 2, both the anode foils A1 and A3 achieved a large capacitance and a low LC at the same time, and the LC was further reduced in the anode foil A3. As shown in Table 3, both the anode foils A2 and A4 achieved a large capacitance and a low LC at the same time, and in the anode foil A4, the capacitance was further increased and the LC was further reduced. [Industrial Applicability]

[0096] The electrode foil for an electrolytic capacitor according to the present disclosure is suitably used for an electrolytic capacitor that requires a large capacitance and a low LC. [Explanation of Signs]

[0097] 10: Anode foil, 110: Anode body, 111: Core part, 112: Porous part, 121: First dielectric layer, 130: Intermediate layer, 20: Cathode foil, 30: Separator, 40: Winding tape, 60A, 60B: Lead wires, 50A, 50B: Lead tabs, 100: Wound body, 200: Electrolytic capacitor, 211: Bottomed case, 212: Sealing member, 213: Base plate

Claims

1. An anode body containing a valve-acting metal, An intervening layer covering at least a part of the anode body, A first dielectric layer covering at least a part of the intervening layer, and comprising: The intervening layer is an electrode foil for an electrolytic capacitor containing a zinc element.

2. The first dielectric layer contains an oxide of a first metal, The first metal contains titanium, and the electrode foil for an electrolytic capacitor according to claim 1.

3. The valve-acting metal contains at least one selected from the group consisting of tantalum, niobium, and aluminum, and the electrode foil for an electrolytic capacitor according to claim 1.

4. The thickness T0 of the intervening layer is smaller than the thickness T1 of the first dielectric layer, and the electrode foil for an electrolytic capacitor according to claim 1.

5. The thickness T0 of the intervening layer is 0.5 nm or more and 3.0 nm or less, and the electrolytic capacitor electrode foil according to claim 1.

6. A second dielectric layer containing an oxide of the valve-acting metal is provided between the anode body and the intervening layer, and the electrode foil for an electrolytic capacitor according to claim 1.

7. An electrolytic capacitor comprising the electrode foil for an electrolytic capacitor according to claim 1, And a cathode portion covering at least a part of the first dielectric layer.

8. A first step of preparing an anode body containing a valve-acting metal, A second step of forming an intervening layer covering at least a part of the anode body, A third step of forming a first dielectric layer covering at least a part of the intervening layer, and including: The intervening layer contains a zinc element, and a method for manufacturing an electrode foil for an electrolytic capacitor.

9. The first dielectric layer contains an oxide of a first metal, The first metal contains titanium, and the method for manufacturing an electrode foil for an electrolytic capacitor according to claim 8.

10. The valve-acting metal contains at least one selected from the group consisting of tantalum, niobium, and aluminum, and the method for manufacturing an electrode foil for an electrolytic capacitor according to claim 8.

11. In the second step, the intervening layer is formed by atomic layer deposition, and the method for manufacturing an electrode foil for an electrolytic capacitor according to claim 8.

12. The formation of the intervening layer by atomic layer deposition is performed in a state where the surface of the anode body is heated to 150 ° C or higher, and the method for manufacturing an electrode foil for an electrolytic capacitor according to claim 11.

13. In the third step, the first dielectric layer is formed by atomic layer deposition, and the method for manufacturing an electrode foil for an electrolytic capacitor according to claim 8.

14. The method for manufacturing an electrode foil for an electrolytic capacitor according to claim 8, comprising a fourth step of forming a chemical film on the anode body having the intervening layer and the first dielectric layer.

15. The method for manufacturing an electrode foil for an electrolytic capacitor according to claim 14, wherein a second dielectric layer containing an oxide of the valve action metal is formed between the anode body and the intervening layer by the chemical film formation treatment.

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