Electrode foil, power storage device, and method for manufacturing same

Abstract

The purpose of the present invention is to suppress a decrease in the withstand voltage of a foil due to cutting or the like, and to repair a defective portion of an oxide coating film generated on the foil due to cutting or the like after formation of a power storage element, thereby improving the withstand voltage of the power storage element or power storage device. A manufacturing method according to one aspect of the present application comprises: a step for performing a surface expansion treatment on a foil formed from a valve metal; a step for forming an oxide film layer (26) on the foil subjected to the surface expansion treatment; a step for cutting the foil on which the oxide coating layer is formed; and a step in which a resin layer having a withstand voltage equal to or higher than that of the oxide coating layer is formed on the cut surface of the foil.

Description

Technical Field

[0001] The present application relates to, for example, an electrode foil including an insulating film layer such as an oxide film layer, a power storage device, and a method for manufacturing the same. Background Art

[0002] In a solid electrolytic capacitor as an example of a power storage device, an amorphous film is formed as an oxide film formed on an electrode foil, and a capacitor is formed using the electrode foil (for example, Patent Document 1).

[0003] Prior Art Documents

[0004] Patent Documents

[0005] Patent Document 1: WO2022 / 044932 Gazette Summary of the Invention

[0006] Problems to be Solved by the Invention

[0007] The withstand voltage of a solid electrolytic capacitor depends on the lowest withstand voltage determined by the oxide film formed on the electrode foil. Even if the withstand voltage of the oxide film formed on the surface of the electrode foil is increased, in the case where there is a voltage region lower than the withstand voltage region, the effect of increasing the withstand voltage of the oxide film formed on the surface of the electrode foil cannot be reflected in the product withstand voltage of the solid electrolytic capacitor.

[0008] Generally, in the process of forming a capacitor element, a foil having an oxide film is cut into a predetermined shape. Therefore, the base metal of the foil is exposed on the cut surface generated by cutting. Therefore, in the manufacturing process of a solid electrolytic capacitor, in order to form a film on the exposed base metal and prevent electrical contact between the base metal, that is, the base foil exposed from the electrode foil, and the solid electrolyte, an element formation process of formation treatment is necessary.

[0009] However, regarding a solid electrolytic capacitor having an oxide film on an electrode foil, Figure 5 The withstand voltage of a solid electrolytic capacitor manufactured in such a manner that the solid electrolyte does not come into contact with the cut surface of the electrode foil is illustrated. The withstand voltage with respect to the film formation voltage is plotted (black dots), with the film formation voltage of the electrode foil on the horizontal axis and the withstand voltage of the solid electrolytic capacitor on the vertical axis.

[0010] According to this illustration, for a solid electrolytic capacitor formed in such a way that the solid electrolyte does not contact the cut surface of the electrode foil, in a high voltage region where the breakdown voltage of the oxide film formed through the element formation process is at a limit value of about 450 V or more, the breakdown voltage of the solid electrolytic capacitor also increases depending on the film formation voltage of the electrode foil. On the other hand, in a solid electrolytic capacitor where an oxide film is formed on the cut surface of the electrode foil through the element formation process, even if the breakdown voltage of the oxide film exceeds 450 [V], the breakdown voltage of the solid electrolytic capacitor remains at about 450 [V]. This indicates that the limit value of the breakdown voltage of the oxide film formed in the element formation process becomes the limit of the breakdown voltage of the solid electrolytic capacitor.

[0011] That is, if the breakdown voltage of the oxide film on the surface of the electrode foil is compared with the breakdown voltage of the film formed on the cut surface of the electrode foil in the element formation process (hereinafter referred to as the element formation film), the relationship of breakdown voltage of oxide film > breakdown voltage of element formation film is satisfied. From this relationship, it can be understood that the breakdown voltage of the solid electrolytic capacitor depends on the breakdown voltage of the element formation film.

[0012] The inventors of the present application have obtained the following insight: the breakdown voltage of the capacitor element or the final product depends on the breakdown voltage of the foil. Therefore, the method of treating the base metal part exposed on the cut surface of the foil due to cutting is the reason for reducing the breakdown voltage of the foil, and further becomes the reason for reducing the breakdown voltage of not only the capacitor element but also the product.

[0013] Therefore, in view of the above problems and insights, an object of the present application is to, for example, suppress the reduction of the breakdown voltage of the foil caused by the defective part of the oxide film generated due to cutting or the like.

[0014] In addition, another object of the present application is to, for example, repair the defective part of the oxide film generated on the foil due to cutting or the like after the formation of the power storage element, and improve the breakdown voltage of the power storage element or the power storage device.

[0015] Means for Solving the Problem

[0016] According to one aspect of the method for manufacturing an electrode foil of the present application, it includes: a step of performing a surface expansion treatment on a foil formed of a valve metal; a step of forming an oxide film layer on the foil after the surface expansion treatment; a step of cutting the foil formed with the oxide film layer; and a step of forming a resin layer having a breakdown voltage equal to or higher than that of the oxide film layer on the cut surface of the foil.

[0017] In this method for manufacturing an electrode foil, the step of forming the resin layer may include a forming step based on electrophoretic deposition.

[0018] In the method for manufacturing the electrode foil, after forming the electrophoretic electrodeposition film, it may further include a step of forming an oxide film through a repair forming process.

[0019] According to one aspect of the method for manufacturing an electrical storage device of the present application, including the above-mentioned method for manufacturing the electrode foil, it further includes: a step of forming an electrical storage element using the electrode foil; and a step of forming a conductive polymer layer on the electrical storage element.

[0020] In the method for manufacturing the electrical storage device, it may further include a step of performing repair forming on the electrical storage element to form an oxide film on the foil.

[0021] According to one aspect of the electrode foil of the present application, it includes: a foil formed of a valve metal, a surface expansion treatment layer formed on the foil, an oxide film layer formed on the surface expansion treatment layer, and a resin layer formed on at least the cut surface of the foil. The resin layer is formed such that the base metal portion exposed on the cut surface is thick and gradually thins towards the foil surface.

[0022] According to one aspect of the electrical storage device of the present application, it includes an electrical storage element using the electrode foil, and the electrical storage element includes a conductive polymer layer.

[0023] Advantages of the Invention

[0024] According to the present application, any of the following advantages can be obtained.

[0025] (1) According to the method for manufacturing the electrode foil of the present application, by using the insulating film layer to repair at least the cut surface of the foil, it is possible to prevent a decrease in the breakdown voltage of the foil depending on the cut surface of the foil, and it is possible to manufacture an electrode foil with a high breakdown voltage achieved.

[0026] (2) According to the method for manufacturing the electrical storage device of the present application, by repairing the cut surface of the foil at the manufacturing stage of the electrode foil, it is possible to make the breakdown voltage of the electrical storage device highly resistant to voltage. In addition, even in the case of using an electrode foil with a defect portion in the oxide film layer, since the defect portion of the oxide film layer is repaired after forming the electrical storage element, it is also possible to make the breakdown voltage of the electrical storage device highly resistant to voltage.

[0027] (3) According to the electrode foil of the present application, during the manufacturing process, an insulating film layer having a breakdown voltage equal to or higher than that of the oxide film layer is formed on the cut surface of the foil generated on the foil, and the breakdown voltage of the entire electrode foil is highly resistant to voltage. Therefore, it is possible to highly resistant to voltage the breakdown voltage of the element using the electrode foil.

[0028] (4) According to the electrical storage device of the present application, since an electrode foil with a defect portion repaired at the manufacturing stage of the electrode foil is used, it is possible to make the breakdown voltage highly resistant to voltage. Description of the Drawings

[0029] Figure 1 Figure A shows the manufacturing process of the energy storage element. Figure 1 Figure B shows a perspective view of the energy storage element.

[0030] Figure 2 Figure shows the experimental results of Example 1, Example 2, Comparative Example 6, Comparative Example 7, Comparative Example 9 and Comparative Example 11.

[0031] Figure 3 Figure A shows a cross-sectional view of the cut surface of the foil. Figure 3 Figure B shows a cross-sectional view of the cut surface of the foil after electrophoretic deposition treatment.

[0032] Figure 4 Figure is used to illustrate the state before the reformation treatment of the foil after electrophoretic deposition treatment.

[0033] Figure 5 Figure shows the breakdown voltage of the solid electrolytic capacitor with respect to the film formation voltage of the electrode foil. Detailed implementation mode

[0034] [First implementation mode]

[0035] The manufacturing process of the energy storage device of the first implementation mode is an example of the electrode foil, energy storage device and their manufacturing methods of the present application.

[0036] The manufacturing process of the energy storage device includes the formation of valve metal foil (hereinafter simply referred to as "foil"), surface expansion treatment, formation of an oxide film layer, cutting of the foil, repair of the cut surface of the cut foil, formation of the energy storage element, etc. In this manufacturing process, the process from the formation of the foil to the repair of the cut surface of the foil is an example of the manufacturing method of the electrode foil of the present application, and the foil generated in this manufacturing process is an example of the electrode foil of the present application.

[0037] In the formation of the foil, valve metal is used as a raw material to form the foil. The form of the foil is, for example, plate-shaped or strip-shaped according to the form of the energy storage device and the energy storage element.

[0038] The foil is subjected to a surface area enlargement treatment to increase its surface area. This surface area enlargement treatment is carried out, for example, by chemical etching or the like, and a surface area enlargement treatment layer is formed on the foil. This chemical etching involves immersing the foil in a formation solution and performing an etching treatment on the surface of the foil. In order to increase the capacitance, irregularities are formed on the surface of the foil to expand the surface area of the foil. The irregular surface, for example, has a porous structure. The irregular surface is formed by direct current etching using direct current, by alternating current etching using alternating current, or by vapor depositing or sintering metal particles on the valve metal foil. For example, in direct current etching or alternating current etching, the valve metal foil is immersed in an acidic aqueous solution containing halogen ions such as hydrochloric acid, and a direct current or alternating current is passed through the valve metal foil in this acidic aqueous solution to make the surface of the metal into an irregular surface and expand its surface area.

[0039] Next, an oxide film layer is formed on the foil that has been surface area enlarged by the surface area enlargement treatment to produce a base foil. As the oxide film layer, an amorphous (non-crystalline) amorphous oxide film layer is formed through the amorphization treatment of the oxide film layer. This oxide film layer has high toughness and corrosion resistance.

[0040] The foil formed with the oxide film layer is cut, and a cutting process (i.e., a cutting-out process) for cutting out a foil of a specified shape is performed. The foil formed with the oxide film layer is formed from an arbitrary shape into a shaped foil piece required for the components of the energy storage device.

[0041] When the cutting process is performed on the foil after the oxide film layer is formed, a cutting surface is formed on the foil of the specified shape obtained from the prototype foil. At this cutting surface, the base metal portion of the foil is exposed. This base metal portion is a valve metal and is the part that has not undergone the surface area enlargement treatment and is not covered by the oxide film layer. Even if the cutting surface of the foil is formed with an oxide film layer, as described above, it is the part with the lowest breakdown voltage, and as a result, it becomes the cause of the reduction in the breakdown voltage of the foil.

[0042] The cutting surface of the cut foil is repaired. For example, an electrophoretic deposition process is performed to form an insulating film layer on the cutting surface of the foil to produce an electrode foil. The base metal portion is covered at least by this insulating film layer. This insulating film layer can be a resin layer with insulating properties. It is preferable to form an insulating film layer with a breakdown voltage equal to or higher than that of the oxide film layer. That is, if the insulating film layer formed through repair or regeneration has a breakdown voltage equal to or higher than that of the existing oxide film layer, the dependence of the breakdown voltage of the foil on the breakdown voltage of the oxide film layer formed on the cutting surface of the foil can be improved.

[0043] The foil after repairing the cutting surface of the foil (i.e., the foil with an insulating film layer formed on the cutting surface of the foil) is used to form components. The components are energy storage components such as solid electrolytic capacitor components. The energy storage component, for example, has a sandwich structure in which the electrode foil on the anode side and the electrode foil on the cathode side face each other with a spacer in between. The capacitance of the energy storage device depends on this facing area.

[0044] The electricity storage element is impregnated with an electrolyte to form an electrolytic capacitor element. As the electrolyte, a solid electrolyte is used. The solid electrolyte contains a conductive polymer. The conductive polymer is a conjugated polymer doped with an acid component as a dopant. The conjugated polymer is obtained by chemically oxidative polymerization or electrolytic oxidative polymerization of a monomer having a π-conjugated double bond or a derivative thereof. By performing a doping reaction on the conjugated polymer, the conductive polymer exhibits high conductivity. As the conjugated polymer, known conjugated polymers can be used without particular limitation. For example, as the conjugated polymer, poly(3,4-ethylenedioxythiophene) (PEDOT) doped with polystyrene sulfonic acid (PSS) is typically cited. The dopant formed from an acid can be a known dopant without particular limitation. For example, inorganic acids such as boric acid, nitric acid, and phosphoric acid; organic acids such as acetic acid, oxalic acid, citric acid, ascot acid, tartaric acid, squaric acid, rhodizonic acid, croconic acid, salicylic acid, p-toluenesulfonic acid, 1,2-dihydroxy-3,5-benzenedisulfonic acid, methanesulfonic acid, trifluoromethanesulfonic acid, borodisalicylate, bis(oxalato)borate, sulfimide acid, dodecylbenzenesulfonic acid, propylnaphthalenesulfonic acid, and butylnaphthalenesulfonic acid can be cited. In addition, as the dopant, polyanions can be used, and as the polyanions, polyvinylsulfonic acid, polystyrenesulfonic acid, polyallylsulfonic acid, polyacrylic acid sulfonic acid, polymethacrylic acid sulfonic acid, poly(2-acrylamide-2-methylpropanesulfonic acid), polyisoprenesulfonic acid, polyacrylic acid, polymethacrylic acid, and polymaleic acid can be cited. The dopants can be used alone or in combination of two or more. In addition, polymers or monomers can also be used. In addition, as the electrolyte, in addition to the solid electrolyte, an electrolytic solution can also be used in parallel.

[0045] <Effects of the First Embodiment>

[0046] According to this first embodiment, any of the following effects can be obtained.

[0047] (1) After forming an oxide film layer on the foil, by cutting the foil or the like, the base metal portion of the foil where the oxide film layer is not formed is exposed on the cut surface of the foil. On this base metal portion, an insulating film layer is formed by a repair treatment after cutting. Thereby, the reduction in withstand voltage caused by the cut surface of the foil can be improved. Therefore, an electrode foil with increased withstand voltage can be manufactured.

[0048] (2) It is beneficial because it can repair the cut surface of the foil caused by cutting, so it can improve the freedom of cutting the foil, and can freely form the foil according to the shape and equipment of the prototype foil.

[0049] (3) The repair of the cut surface of the foil can be carried out by electrophoretic electrodeposition, chemical conversion treatment, etc., and this repair can be carried out in the manufacturing process of the electrode foil.

[0050] (4) It is possible to repair the cut surface of the foil through the repair treatment, improve the reduction of the withstand voltage caused by the base metal part exposed on the cut surface of the foil, and manufacture an electrode foil with increased withstand voltage.

[0051] (5) It is possible to improve the reduction of the withstand voltage caused by the base metal part exposed on the cut surface of the foil, manufacture a power storage device such as a fixed electrolytic capacitor using an electrode foil with increased withstand voltage, and contribute to the manufacture of a power storage device with excellent electrical characteristics and no deviation in withstand voltage.

[0052] <Mechanism for improving the withstand voltage of the foil based on the repair of the cut surface of the foil>

[0053] As described above, on the foil, after the surface expansion treatment, an oxide film layer is formed on the foil surface. This oxide film layer is damaged due to cutting, and the base metal part of the foil without the oxide film layer is exposed on the cut surface of the foil. For example, an insulating film layer is formed on this base metal part to repair the cut surface of the foil, and it can be repaired to have the same withstand voltage as the original oxide film layer of the foil.

[0054] It is sufficient to use an insulator to cover the base metal part of the foil. This insulating film layer can be a resin layer with insulating properties, for example, an insulating film layer with a withstand voltage equal to or higher than that of the oxide film layer is formed. The insulating film layer covering the base metal part can achieve a withstand voltage equal to or higher than that of the existing oxide film layer. Therefore, it is possible to improve the withstand voltage of the defective part of the oxide film layer, and the withstand voltage of the entire foil can be increased by repairing this defective part.

[0055] [Second Embodiment]

[0056] The manufacturing process of this power storage device includes foil formation, surface expansion treatment, oxide film layer formation, foil cutting, first repair of repairing the cut surface of the foil, second repair of repairing the oxide film layer, element formation, etc. In this manufacturing process, the process from foil formation to oxide film layer repair is an example of the manufacturing method of the electrode foil of this application, and the foil generated in this manufacturing process is an example of the electrode foil of this application.

[0057] The foil formation, surface expansion treatment, oxide film layer formation, and foil cutting are the same as those in the first embodiment, so their descriptions are omitted.

[0058] Similar to the first embodiment, as the first repair of the cut surface of the repaired foil, a repair process or a regeneration process of the cut surface of the foil is performed. In this second embodiment, for example, an electrophoretic electrodeposition process is performed on the cut foil to form an insulating film layer on the cut surface of the foil. Therefore, the first repair for repairing the cut surface of the foil is the same as the repair of the cut surface of the foil in the first embodiment.

[0059] After the process of the first repair for repairing the cut surface of the foil, as a supplementary process to the first repair, a second repair for repairing the oxidized film layer is performed. In the second embodiment, the process of repairing the cut surface of the foil is carried out in two stages through the first repair for repairing the cut surface of the foil and the second repair different from the first repair. That is, for example, the first repair is performed by an electrophoretic electrodeposition process, and the second repair for repairing the defective parts remaining in the oxidized film layer is performed by a chemical conversion process, for example.

[0060] The formed element is formed using the foil after the second repair. The formation of this element is the same as that in the first embodiment, so its description is omitted.

[0061] <Effects of the Second Embodiment>

[0062] According to this second embodiment, any of the following effects can be obtained.

[0063] (1) Since the same first repair for repairing the cut surface of the foil as in the first embodiment is performed, the cut surface of the foil is repaired by this first repair, and the same effects as in the first embodiment are obtained.

[0064] (2) For example, in the first repair based on electrophoretic electrodeposition, when there are defective parts remaining in the oxidized film layer, if, after the first repair, the defective parts are repaired by the second repair based on a chemical conversion process, for example, the process of the first repair is supplemented by the second repair, and the repair accuracy of the defective parts can be improved.

[0065] <Mechanism of Improving Dielectric Strength by Chemical Conversion Treatment after Electrophoretic Electrodeposition Treatment>

[0066] If an electrophoretic electrodeposition process is performed, for example, in the process of the first repair, and a chemical conversion process is performed in the process of the second repair, the repair effect of the chemical conversion process is superimposed on the repair effect based on electrophoretic electrodeposition. That is, the effects brought about by the re - repair of the oxidized film layer are superimposed, and the improvement of the dielectric strength of the oxidized film layer can be achieved. Therefore, the repair accuracy of the defective parts of the oxidized film layer is improved, and as a result, the high dielectric strength of the foil is realized.

[0067] <Advantages of Re - repair of Oxidized Film Layer by Chemical Conversion Treatment after Electrophoretic Electrodeposition Treatment>

[0068] a) It is possible to repair the defective part of the oxide film layer by chemical conversion treatment, and the treatment time of the first repair based on electrophoretic electrodeposition treatment can be shortened.

[0069] b) If the supplementary treatment based on chemical conversion is taken as a premise, the electrophoretic electrodeposition treatment and the chemical conversion treatment can share the repair function, the treatment time of the electrophoretic electrodeposition can be shortened, and as a result, the repair treatment time can be shortened.

[0070] <Advantages of the pretreatment of electrophoretic electrodeposition treatment>

[0071] If electrophoretic electrodeposition is performed on the exposed part of the base metal part generated on the foil by cutting, the insulating film layer can grow rapidly, and an insulating film layer covering the exposed part can be formed. That is, the withstand voltage of the cut surface of the foil is improved by this pretreatment.

[0072] [Third Embodiment]

[0073] The manufacturing process of the energy storage device includes foil formation, surface expansion treatment, oxide film layer formation, foil cutting, element formation, oxide film layer repair, etc. In this manufacturing process, the process from foil formation to foil cutting plus the process of repairing the cut surface of the foil and the generated foil is an example of the electrode foil and its manufacturing process of the present application.

[0074] The formation of the foil, the surface expansion treatment, the formation of the oxide film layer, the cutting of the foil, and the formation of the element are the same as those in the first embodiment, so their descriptions are omitted.

[0075] In the first embodiment and the second embodiment, the repair of the cut surface of the foil is performed before element formation, but in the third embodiment, the repair of the cut surface of the foil is performed by electrophoretic electrodeposition treatment after element formation.

[0076] <Effects of the Third Embodiment>

[0077] According to this third embodiment, any of the following effects can be obtained.

[0078] (1) It is possible to first form the element and repair the defective part existing on the cut surface of the foil after element formation.

[0079] (2) Since the repair treatment is performed on the energy storage element as an intermediate product, it is possible to quickly transfer from foil manufacturing to element formation. After the repair treatment at the element stage, the effect of improving the withstand voltage can be confirmed after element formation.

[0080] Examples

[0081] The examples include Examples 1 to 3 and Comparative examples 1 to 11 for comparison. In this application, the term "comparative" means comparison with Examples 1 to 3. The term "comparative" does not indicate whether it belongs to the invention involved in the claims.

[0082] <Example 1>

[0083] The manufacturing process of Example 1 includes the formation of an amorphous oxide film layer, cutting out of the foil, electrophoretic electrodeposition treatment, formation of elements, etc.

[0084] The formation of the amorphous oxide film layer is carried out after the formation of the foil using the substrate (the aforementioned valve metal) and the surface expansion treatment of the foil. This amorphous oxide film layer is an example of the oxide film layer of this application and is generated by subjecting the oxide film layer formed on the foil to an amorphization treatment.

[0085] The foil is formed of valve metal. On this foil, after the surface is etched for surface expansion treatment, an amorphous oxide film layer is formed. This amorphous oxide film layer is an example of the oxide film layer of this application. The formation process of this amorphous oxide film layer includes the formation process of a porous film layer and a forming process.

[0086] For example, the foil is immersed in an oxalic acid aqueous solution maintained at a certain temperature of 25 [°C], and anodic oxidation is carried out using a constant current. Through this anodic oxidation, a porous film layer is formed on the surface of the foil.

[0087] The foil on which the porous film layer is formed is, for example, immersed in a boric acid aqueous solution maintained at a certain temperature of 85 [°C], and in this boric acid aqueous solution, a certain current density of 25 [mA / cm 2 is applied to conduct forming. In this forming, after the forming voltage reaches a specified value (for example, 700 [V]), it is maintained ( = held) for a certain time, for example, 10 minutes. Thereby, an amorphous oxide film layer (hereinafter simply referred to as "oxide film layer" or "amorphous oxide film layer") can be formed inside the porous film layer of the foil. This oxide film layer is an example of the oxide film layer of this application.

[0088] The cutting out of the foil on which the amorphous oxide film layer is formed is an example of the cutting of the foil of this application. In this process, the foil of the shape required for the power storage element is cut out from the base foil. Through this cutting out, the foil is formed into a specified shape from the base foil, but the cutting out also exposes the base metal (substrate, valve metal) from the cutting surface of the foil. That is, there is no oxide film layer on the base metal part exposed on this cutting surface.

[0089] In Example 1, as a cutting mechanism for cutting out a foil piece from a foil formed with an amorphous oxide film layer, a laser processing machine is used, for example. As described above, in the cut surface of the foil piece cut out from the foil by laser processing, the base metal part (valve metal) of the base material is exposed due to the cutting. As Figure 1 shown, the foil piece has, for example, a square anode part and a lead part (anode lead part 14) protruding from one side of the anode part. This anode part is an example of a functional part that functions as an anode of a power storage element. One side of this anode part is 1.0 [cm]. The width of the lead part is narrower than one side of the anode part. In Example 1, the width of the lead part is 0.5 [cm].

[0090] Next, electrophoresis is performed on the foil cut into the shape required for the power storage element. The electrophoresis is an example of the repair of the cut surface of the foil in the first embodiment. Through the electrophoresis, a resin, which is an insulator serving as an insulating film layer, is formed on the cut surface of the foil by electrophoresis, and the cut surface of the foil is repaired with the resin. The electrophoresis is carried out using an electrophoresis apparatus. This electrophoresis apparatus includes, for example, a processing container formed of a conductive metal such as stainless steel (SUS). A resin dispersion is filled in this processing container. This resin dispersion is a processing liquid in which a resin is dispersed in a solvent. The resin dispersion is set to such an extent that the entire square anode part and most of the lead part are immersed in the processing container.

[0091] In the foil piece and the processing container, with the foil piece side as the anode and the processing container side as the cathode, a DC power supply and a voltmeter are connected via a switch. The DC power supply applies a certain DC voltage, for example, 100 [V], to the foil piece set as the anode and the processing container set as the cathode and filled with the resin dispersion, constituting a driving source for the electrophoresis process for the foil piece. And the processing time of the electrophoresis is limited by a timer provided in the electrophoresis apparatus. In Example 1, the electrophoresis is carried out for a certain time of 120 [seconds], and the resin is electrodeposited on the cut surface of the foil of the foil piece. The foil piece after the electrophoresis process is taken out from the resin dispersion, and the resin dispersion is removed by washing. After washing, the foil piece is dried. This drying is carried out by placing it at a certain temperature, for example, 60 [°C], for a certain time, for example, 10 [minutes]. After drying, the foil piece is heated to perform a crosslinking process on the electrophoresis film. This heating is carried out at a certain temperature, for example, 180 [°C], for a certain time, for example, 40 [minutes].

[0092] The element is formed using the foil on which the electrophoresis has been carried out. The formation of the element is the same as that in the first embodiment. Specifically, the element is formed through the following processes.

[0093] Figure 1A shows an example of the formation process of the energy storage element 2. This formation process is an example of the electrode foil, energy storage device, and their manufacturing methods of the present application.

[0094] This energy storage element 2 includes, for example, one anode foil 4, two cathode foils 6, and a spacer 8, and is also attached with two support plates 10 and 12. The anode foil 4 uses the foil sheet that has undergone the above treatment. On this anode foil 4, an anode lead portion 14 is formed with respect to the square anode portion.

[0095] The cathode foil 6 uses the foil with the same shape as the anode foil 4. On this cathode foil 6, a cathode portion opposite to the anode portion is formed, and a cathode lead portion 16 is formed. This cathode portion is a functional portion that functions as the cathode of the energy storage element 2.

[0096] The spacer 8 is, for example, a sheet formed of a regenerated cellulose-based material, and is processed into a zigzag shape in units of, for example, a square spacer portion larger than the anode portion of the anode foil 4. The spacer 8 is formed, for example, using a regenerated cellulose-based material as a strip-shaped sheet that covers the width of the anode portion of the anode foil 4. Therefore, the energy storage element 2 is formed such that two cathode foils 6 are disposed opposite to each other with the zigzag spacer 8 interposed therebetween on the front and back sides of one anode foil 4.

[0097] After the energy storage element 2 is formed, a conductive polymer layer is formed on the anode foil 4 and the cathode foil 6. The formation process of this conductive polymer layer includes the infiltration of a resin dispersion liquid and the drying of the energy storage element 2. This resin dispersion liquid is obtained by dispersing PEDOT fine particles and polystyrene sulfonic acid in an aqueous solution containing 5% ethylene glycol. The PEDOT fine particles are an example of the conductive polymer of the present application. As the infiltration conditions, for example, a certain infiltration time, such as 5 [minutes], is set under a reduced pressure of 50 [kPa] to infiltrate the dispersion liquid into the energy storage element 2. After infiltrating the dispersion liquid, the energy storage element 2 is dried. As the drying conditions, for example, the energy storage element 2 is placed at a certain temperature of 110 [°C], and the energy storage element 2 is dried within a certain drying time, such as within 30 [minutes].

[0098] Figure 1 B shows the energy storage element 2 disposed on the support plates 10 and 12. The support plates 10 and 12 can use a tough insulating material, such as a sliding glass plate. In this energy storage element 2, two cathode foils 6 are disposed with respect to one anode foil 4 with the spacer 8 interposed therebetween, and are held between the support plates 10 and 12. The support plates 10 and 12 are an example of the support members that hold the energy storage element 2, and the support plates 10 and 12 are, for example, firmly held by clips 18.

[0099] <Example 2>

[0100] The difference between Example 2 and Example 1 is that a repair forming treatment is carried out after the electrophoretic electrodeposition treatment. That is, except for carrying out the repair forming treatment after the electrophoretic electrodeposition treatment, the manufacturing process of the anode foil and the forming process of the element in Example 2 are the same as those in Example 1. In addition, the conditions of the electrophoretic electrodeposition treatment in Example 2 are the same as those in Example 1, so their descriptions are omitted. The electrophoretic electrodeposition treatment corresponds to the first repair of the cut surface of the repair foil in the second embodiment, and the repair forming treatment corresponds to the second repair of the oxide film layer in the second embodiment. That is, the defective part of the oxide film layer is repaired through two-stage treatments of electrophoretic electrodeposition treatment and repair forming treatment.

[0101] <Repair (repair forming) of amorphous oxide film layer>

[0102] The repair of this amorphous oxide film layer is carried out through a repair forming treatment. This repair forming treatment is a treatment in which the foil is energized in an aqueous boric acid solution. In this treatment, the foil is immersed in an aqueous boric acid solution at a certain temperature, for example, 85 [°C], and the foil is energized at a current density of 0.4 [mA / cm 2 . When the specified voltage, for example, 630 [V] is reached, the voltage of 630 [V] is maintained for a certain time, for example, 10 [minutes]. Thereby, the defective part of the oxide film layer is repaired. In this way, the repair of the amorphous oxide film layer is carried out through two-stage treatments of electrophoretic electrodeposition treatment and repair forming treatment after the electrophoretic electrodeposition treatment, so the repair accuracy of the defective part generated in the amorphous oxide film layer can be improved.

[0103] <Example 3>

[0104] This Example 3 corresponds to the third embodiment. As described above, an electrophoretic electrodeposition treatment is carried out after the formation of the power storage element 2, and a conductive polymer layer is formed on the anode foil 4 of the power storage element 2. Thereby, the defective part generated in the oxide film layer of the anode foil 4 of the power storage element 2 can also be repaired at the formation stage of the power storage element 2.

[0105] <Comparative Example 1>

[0106] The difference between Comparative Example 1 and Example 2 is that the repair forming treatment is carried out before the electrophoretic electrodeposition treatment. That is, except for carrying out the electrophoretic electrodeposition treatment after the repair forming treatment, Comparative Example 1 is manufactured in the same manner as Example 2 for the processes until the foil is cut out and the processes after the element forming process. In addition, the conditions of the electrophoretic electrodeposition treatment and the repair forming treatment are also the same as those in Example 2, so their descriptions are omitted.

[0107] <Comparative Example 2>

[0108] The difference between Comparative Example 2 and Example 2 is that the foil is cut out before the amorphous oxide film layer is formed. That is, Comparative Example 2 is prepared in the same manner as Example 2 after the foil is cut out and the amorphous oxide film layer is formed on the foil. In addition, the conditions of each process are the same as those of Example 2, so their description is omitted.

[0109] The formation of the amorphous oxide film layer is the same process as that of the amorphous oxide film layer in Example 1, but it is considered that the amorphous oxide film layer is formed uniformly on the entire foil, including the cut surface of the cut foil. Since the amorphous oxide film layer is formed after the foil is cut, it is possible that the amorphous oxide film layer is not completely formed on the cut surface generated by the cutting of the foil. This is also a defective portion of the oxide film layer, which causes the withstand voltage of the foil to decrease.

[0110] <Comparative Example 3>

[0111] Comparative Example 3 is different from Comparative Example 1 in that the foil is cut out before the amorphous oxide film layer is formed. That is, Comparative Example 3 is manufactured in the same manner as Comparative Example 1 after the process of forming the amorphous oxide film layer on the foil piece cut out from the foil, specifically, the process of performing the repair chemical formation treatment and the subsequent processes. In addition, the conditions of each process are the same as those of Comparative Example 1, so their description is omitted.

[0112] <Comparative Example 4>

[0113] Comparative Example 4 has the same process sequence and conditions of each process as those of Comparative Example 3 except that the repair chemical conversion treatment is omitted, and thus the description thereof is omitted.

[0114] <Comparative Example 5>

[0115] In Comparative Example 5, an end face resist treatment (Japanese: End face resist treatment) was performed instead of the electrophoretic electrodeposition treatment in Example 2. In addition, when performing the end face resist treatment, in order to ensure the printing width (0.1 [cm]) of the resist resin covering the cut surface of the foil, the length of one side was set to 1.2 [cm]. Except for the size of the foil and the end face resist treatment instead of the electrophoretic electrodeposition treatment, the process sequence and the conditions of each process are the same as those in Example 2, so their description is omitted.

[0116] <Edge Resist Treatment>

[0117] The end face resist treatment is a treatment for insulating the exposed base metal portion of the cut foil, such as the cut surface of the foil, by covering the cut foil with a solder resist resin. The end face resist treatment includes a printing step, a first drying step, and a second drying step.

[0118] The printing process is a process of printing a solder resist resin on the cut surface of the foil. For this printing, for example, a screen printing machine is used, and a certain width of the foil, for example, a width of 0.1 [cm], is used as the printing portion, and the solder resist resin is printed on this printing portion. That is, the solder resist resin covers the cut surface and extends to the foil surface adjacent to the cut surface, improving the covering strength of the solder resist resin layer.

[0119] The first drying process is a process of drying one side of the solder resist resin layer formed on the foil. In this process, the solder resist resin layer and the foil are heated at a certain heating temperature, for example, 150 [°C], for a certain drying time, for example, 10 [minutes], to dry the solder resist resin. Then, the second drying process is carried out. The second drying process is a process of drying the other side of the solder resist resin layer. In this process, the other side of the solder resist resin layer and the foil are similarly heated at a certain heating temperature, for example, 150 [°C], for a certain drying time longer than that for one side, for example, 30 [minutes], to dry the solder resist resin. Thus, the solder resist resin layer is fixed to the end face of the foil as an end face resist layer.

[0120] <Comparative Example 6>

[0121] In Comparative Example 6, an end face resist treatment was performed instead of the electrophoretic electrodeposition treatment in Comparative Example 1. In addition, when performing the end face resist treatment, in order to ensure the printing width (0.1 [cm]) of the resist resin covering the cut surface of the foil, the length of one side was set to 1.2 [cm]. Except for the size of the foil and performing the end face resist treatment instead of the electrophoretic electrodeposition treatment, the process sequence and the conditions of each process are the same as those in Comparative Example 1, so their descriptions are omitted.

[0122] <Comparative Example 7>

[0123] Comparative Example 7 is the same as Comparative Example 5 in terms of the process sequence and the conditions of each process except that the repair formation treatment is omitted from Comparative Example 5, so their descriptions are omitted.

[0124] <Comparative Example 8>

[0125] In Comparative Example 8, an end face resist treatment was performed instead of the electrophoretic electrodeposition treatment in Comparative Example 2. In addition, when performing the end face resist treatment, in order to ensure the printing width (0.1 [cm]) of the resist resin covering the cut surface of the foil, the length of one side was set to 1.2 [cm]. Except for the size of the foil and performing the end face resist treatment instead of the electrophoretic electrodeposition treatment, the process sequence and the conditions of each process are the same as those in Comparative Example 2, so their descriptions are omitted.

[0126] <Comparative Example 9>

[0127] Comparative Example 9 is the same as Comparative Example 1 in terms of the process sequence and the conditions of each process, except that the electrophoretic electrodeposition treatment is omitted from Comparative Example 1. Therefore, the description thereof is omitted.

[0128] <Comparative Example 10>

[0129] Comparative Example 10 is the same as Comparative Example 1 in terms of the process sequence and the conditions of each process, except that the reformation chemical conversion treatment and the electrophoretic electrodeposition treatment are omitted from Comparative Example 1. Therefore, the description thereof is omitted.

[0130] After forming the amorphous oxide film layer in Comparative Example 10, the cutting out of the foil and the formation of the element were carried out. In this Comparative Example 10, the cut surface of the foil formed by the cutting out of the foil was in an unrepaired state.

[0131] <Comparative Example 11>

[0132] Comparative Example 11 is the same as Comparative Example 2 in terms of the process sequence and the conditions of each process, except that the electrophoretic electrodeposition treatment and the reformation chemical conversion treatment are omitted from Comparative Example 2. Therefore, the description thereof is omitted.

[0133] After the cutting out of the foil in Comparative Example 11, the formation of the amorphous oxide film layer was carried out, and the formation of the element was carried out. In this Comparative Example 11, an amorphous oxide film layer was formed on the cut surface generated by the cutting out of the foil by the formation of the amorphous oxide film layer.

[0134] <Production Results of the Storage Elements 2 of Examples 1 and 2 and Comparative Examples 1 to 11>

[0135] In Example 1, after cutting out the foil formed with the amorphous film, an insulating film layer was formed on the cut surface of the foil by electrophoretic electrodeposition to produce the storage element 2.

[0136] In Example 2, after cutting out the foil formed with the amorphous film, an insulating film layer was formed on the cut surface of the foil by electrophoretic electrodeposition, and then the reformation chemical conversion treatment was carried out to produce the storage element 2.

[0137] In Comparative Example 1, the cut surface of the foil formed with the amorphous film was reformed and chemically converted, and an attempt was made to perform electrophoretic electrodeposition on the reformed and chemically converted film, but an electrophoretic electrodeposition film could not be formed.

[0138] In Comparative Example 2, after forming an amorphous film on the foil cut out from the foil on which the amorphous film was not formed, electrophoretic electrodeposition treatment was carried out, and then reformation chemical conversion was carried out. An electrophoretic electrodeposition film could not be formed in Comparative Example 2.

[0139] In Comparative Example 3, after forming an amorphous film on the foil cut out from the foil on which the amorphous film was not formed, reformation chemical conversion was carried out, and after this chemical conversion treatment, electrophoretic electrodeposition treatment was carried out. An electrophoretic electrodeposition film could not be formed in Comparative Example 3 either.

[0140] In Comparative Example 4, after forming an amorphous film on a foil piece cut from a foil on which no amorphous film had been formed, an electrophoretic electrodeposition treatment was attempted. An electrophoretic electrodeposition film could not be formed in Comparative Example 4 either.

[0141] In Comparative Example 5, a foil piece was cut from a foil on which an amorphous film had been formed, an end face resist treatment was performed on the cut surface thereof, and then a repair formation treatment was performed. In Comparative Example 5, due to deformation of the anode portion or the like, it was not applicable to the power storage element 2.

[0142] In Comparative Example 6, after performing a repair formation on the cut surface of the foil piece, it was covered with an end face resist to form the power storage element 2. In Comparative Example 6, since an end face resist was laminated on the oxide film layer obtained by the repair formation, it could function as a capacitor.

[0143] In Comparative Example 7, the cut surface of the foil piece was covered with an end face resist to form the power storage element 2. The cut surface of the foil was insulated by the end face resist. Comparative Example 7 could function as a capacitor.

[0144] In Comparative Example 8, a foil piece was cut from a foil on which no amorphous film had been formed, an amorphous film was formed thereon, an end face resist treatment was performed on the cut surface thereof, and then a repair formation treatment was performed. In this Comparative Example 8, due to deformation of the anode portion or the like, it was not applicable to the power storage element 2.

[0145] In Comparative Example 9, a repair formation treatment was performed on the cut surface of the foil piece to form the power storage element 2. Comparative Example 9 could function as a capacitor.

[0146] In Comparative Example 10, a foil piece was cut from the foil after forming the amorphous film to form the power storage element 2. At the cut surface of the foil piece, the base metal portion was in an exposed state. In this Comparative Example 10, since a short circuit was formed between the base metal portion and the cathode, it did not function as a capacitor.

[0147] In Comparative Example 11, a foil piece was cut from a foil on which no amorphous film had been formed, a formation treatment of an amorphous film was performed on the foil piece to form the power storage element 2. Comparative Example 11 could function as a capacitor.

[0148] <Experimental results of the power storage element 2 of Examples 1 and 2 and Comparative Examples 1 to 11>

[0149] Figure 2 The measurement results of the withstand voltage of the power storage element 2 of Examples 1 and 2 and Comparative Examples 6, 7, 9, and 11 are shown.

[0150] The withstand voltages of Examples 1 and 2 and Comparative Examples 6, 7, 9, and 11 could be measured, and the withstand voltages of the other Comparative Examples 1 to 5, 8, and 10 could not be measured.

[0151] In Example 1, a breakdown voltage of 575 [V] was obtained. In Example 2, a breakdown voltage of 671 [V] was obtained. In Comparative Example 6, a breakdown voltage of 609 [V] was obtained. In Comparative Example 7, a breakdown voltage of 586 [V] was obtained. In Comparative Example 9, a breakdown voltage of 514 [V] was obtained. In Comparative Example 11, a breakdown voltage of 484 [V] was obtained.

[0152] When comparing the breakdown voltage of Example 1 with that of Example 2, the breakdown voltage of Example 2 is higher than that of Example 1. This is because, after the foil was cut out in Example 1, only electrophoretic electrodeposition was performed. In contrast, in Example 2, after the electrophoretic electrodeposition in Example 1, a repair formation treatment was carried out. Therefore, it can be presumed that through the repair formation treatment, the defective parts were further repaired and the breakdown voltage was increased.

[0153] When comparing the breakdown voltage of Example 1 with that of Comparative Example 9, the breakdown voltage of Example 1 is higher than that of Comparative Example 9. In Example 1, after the foil was cut out, electrophoretic electrodeposition was performed. In contrast, in Comparative Example 9, after the foil was cut out, a repair formation treatment was carried out. The difference between the two lies in whether the repair treatment is electrophoretic electrodeposition or repair formation treatment. Therefore, it can be presumed that electrophoretic electrodeposition is the main reason for increasing the breakdown voltage of the energy storage element 2. That is, in Comparative Example 9, only repair formation was carried out, so the breakdown voltage was low.

[0154] <Repair of the cut surface of the foil based on electrophoretic electrodeposition and the breakdown voltage of the energy storage element 2>

[0155] An oxide film layer was formed on the foil before cutting out the foil after the surface expansion treatment.

[0156] As described above, after the oxide film layer was formed, the foil was cut by laser irradiation.

[0157] On the cut surface generated by cutting out the foil, the laminated state of the oxide film layer, the etching layer, and the base metal part is exposed from the outer surface side of the foil. In this cut surface, the etching layer is formed on the surface expansion part of the valve metal foil and has the same conductivity as the base metal part. Here, the base metal part refers to the metal part that has not been etched. The oxide film layer is an amorphous oxide film layer formed on the surface of the etching layer, and the etching layer is a roughened layer formed by performing a surface expansion treatment on the base metal part. The base metal part is the valve metal part as the base material.

[0158] As described above, the repair of this cut surface uses a film formation method based on electrophoretic electrodeposition. As described above, this electrophoretic electrodeposition means immersing the foil in a resin dispersion liquid, and by means of a potential difference, the resin in the resin dispersion liquid is deposited (electrodeposited) on the base metal part 22 to form a resin layer.

[0159] Figure 3 A shows an enlarged view of the cut surface 20 of the foil before electrophoretic electrodeposition. This enlarged view is a sketch of an electron micrograph. On this cut surface 20, etching layers 24 are formed on both the front and back sides of the base metal portion 22, and an oxide film layer 26 is formed on the outer surface side of each etching layer 24.

[0160] Figure 3 B shows an enlarged view of the cut surface 20 of the foil after electrophoretic electrodeposition. This enlarged view is also a sketch of an electron micrograph. An electrophoretic electrodeposition film 28 formed by electrophoretic electrodeposition is formed on the exposed surface of the base metal portion 22. This electrophoretic electrodeposition film 28 is a resin layer or insulating layer that covers the base metal portion 22 and the etching layer 24 by electrophoretic electrodeposition.

[0161] This electrophoretic electrodeposition film 28 is the insulating film layer of the present application, and is an insulating film layer formed such that the film thickness is thicker in the base metal portion 22 and gradually thins toward the foil surface side.

[0162] In the process of repairing (film forming) the cut surface of the foil using this electrophoretic electrodeposition film 28, it includes precipitation of resin, electrolysis, adhesion of resin, and improvement of the withstand voltage of the foil.

[0163] If the anode of a DC power supply is connected to the foil immersed in the resin dispersion liquid, the cathode is connected to the treatment container filled with the resin dispersion liquid, and a specified voltage is applied, electrophoresis occurs in the resin of the resin dispersion liquid. This resin precipitates in the resin dispersion liquid due to the decrease in pH.

[0164] In the case where the base material of the valve metal is, for example, aluminum (Al), if aluminum is anodized, the water in the resin dispersion liquid undergoes electrolysis, and at the part where electrolysis occurs, the hydrogen ion index (pH) decreases. That is, the reactions shown in the following chemical reaction formulas (1) and (2) occur.

[0165] Electrolysis of water: 2H2O → 4H + + O2↑ + 4e - …(1)

[0166] Anodization of Al: Al 3+ + 3H2O → Al2O3 + 6H + + 6e - …(2)

[0167] The current is concentrated in the base metal portion 22 of the foil, and the resin precipitated in the resin dispersion liquid adheres thereto.

[0168] Resin adheres to the portion where the oxide film layer 26 is not formed. That is, the resin adheres to the base metal portion 22 exposed on the cut surface 20, and an electrophoretic electrodeposition film 28 is formed by film formation based on this resin, and the cut surface of the foil is repaired. Thus, the breakdown voltage of the foil is increased by the resin coating film.

[0169] <Combined use of electrophoretic electrodeposition treatment and repair chemical conversion treatment>

[0170] In Example 2, for the foil used in the power storage element 2, after the electrophoretic electrodeposition treatment, a repair chemical conversion treatment is performed, and the repair of the cut surface of the foil is performed by a two-stage treatment of electrophoretic electrodeposition treatment and repair chemical conversion treatment.

[0171] Figure 4 It shows an enlarged cross-section of the foil after the electrophoretic electrodeposition treatment and before the repair chemical conversion treatment. In this Figure 4 , the same reference numerals are assigned to the same parts as Figure 3 the same.

[0172] In the cross-section of this foil, an etching layer 24 is formed across the base metal portion 22, and an oxide film layer 26 is formed on the outer surface of the etching layer 24. The uneven shape of the etching layer 24 schematically shows numerous etching pits. An electrophoretic electrodeposition film 28 formed by electrophoretic electrodeposition treatment is formed on the base metal portion 22 of this foil. That is, the exposed portion of the base metal portion 22 of the foil causes a decrease in the breakdown voltage of the foil. Therefore, the electrophoretic electrodeposition film 28 is formed, and insulation is achieved by the aforementioned resin, eliminating the cause of the decrease in the breakdown voltage of the foil.

[0173] An oxide film layer 26 is formed on the surface of the etching layer 24, but a plurality of defect portions are generated in this oxide film layer 26. This defect portion not only refers to a state where the valve metal aluminum is exposed without the oxide film layer 26, but also refers to a case where the thickness is thinner than other oxide film layers 26. This defect portion represents a minute defect. In this minute defect, the portion where current flows in the resin dispersion liquid is small, so resin cannot adhere during electrophoretic electrodeposition. If such minute defect portions remain, they become the cause of the decrease in the breakdown voltage of the oxide film layer 26, and become the cause of the decrease in the breakdown voltage of the foil and even the power storage element 2.

[0174] When the repair chemical conversion treatment is performed on the foil after the electrophoretic electrodeposition treatment, the chemical conversion liquid penetrates into the defect portions, so a repair chemical conversion film based on the chemical conversion liquid is formed, and the defect portions are repaired using this repair chemical conversion film.

[0175] In the electrophoretic electrodeposition film 28, pores (bubbles) may be generated in the electrophoretic electrodeposition film 28 due to oxygen generated during the formation of the electrophoretic electrodeposition film 28. The remaining of these pores is not preferable for maintaining the breakdown voltage.

[0176] If the foil after electrophoretic electrodeposition is immersed in a repair formation solution, the repair formation solution penetrates into the electrophoretic electrodeposition film 28, passes through the pores to reach the base metal portion 22 of the foil, and a repair formation film is formed on the base metal portion 22 opposite to the pores. Thereby, the withstand voltage of the foil after electrophoretic electrodeposition can be further improved.

[0177] In this way, after the withstand voltage of the defective portion of the oxide film layer 26 is improved by using the electrophoretic electrodeposition film 28 in the electrophoretic electrodeposition process, the defective portion that was not completely repaired in the electrophoretic electrodeposition process can be repaired by the repair formation film. That is, the cause of the decrease in withstand voltage can be eliminated in the two-stage repair process, and the withstand voltage of the power storage element 2 can be improved.

[0178] <Repair of the oxide film layer only by repair formation (Comparative Example 9) and withstand voltage>

[0179] In Comparative Example 9, a foil was cut out from a foil having an amorphous oxide film layer, and the cut surface was subjected to a repair formation treatment to produce a power storage element 2. The withstand voltage of this power storage element 2 is lower than that of Example 1. The reason for the low withstand voltage in Comparative Example 9 is that it is difficult to form an oxide film layer based on repair formation on the base metal portion 22 exposed on the cut surface.

[0180] The withstand voltage of the oxide film layer formed by repair formation based on the base metal portion 22 is lower than the withstand voltage of the oxide film layer formed by repair formation of the defective portion of the oxide film (the withstand voltage of the oxide film assumed according to repair formation). Since the withstand voltage of the power storage element 2 depends on the withstand voltage of the oxide film on each end face, even if the oxide film layer is repaired by repair formation, its withstand voltage cannot be improved by this repair of the oxide film layer.

[0181] <Reasons why it is difficult to form an oxide film layer based on repair formation on the base metal portion 22>

[0182] a) On the cut surface of the foil, a pretreatment layer that serves as a base for forming a high-quality film with few defects cannot be formed as in the usual pretreatment before formation. Therefore, it is difficult to form an oxide film with few defects.

[0183] b) Processing damage and surface oxides during cutting adhere to the cut surface of the foil, and it is not easy to form a high-quality oxide film layer without defects due to factors such as impurities and burrs. When there are impurities on the cut surface of the foil, more current leaks from the oxide film. In addition, when there are burrs on the cut surface of the foil, even if an oxide film layer is formed on the burrs, depending on the shape of the burrs, defects may be generated due to stress concentration in the oxide film layer. Therefore, it is difficult to form a high-quality oxide film layer.

[0184] <Electrophoretic electrodeposition treatment after repair formation (Comparative Example 1 or 4)>

[0185] In the prior repair formation process, an oxide film layer is formed on the base metal portion exposed on the cut surface of the foil. Here, as described above, the oxide film layer formed on the base metal portion exposed on the cut surface of the foil is an insulating substance. Therefore, the base metal portion on which the oxide film layer is formed has a higher insulation property due to the oxide film layer and becomes a state where current hardly flows. Therefore, even if electrophoretic deposition is attempted after the repair formation process, the migration of the resin is hindered and the resin does not adhere to the base metal portion.

[0186] <Effects of the Embodiment>

[0187] According to the embodiment of the present application, any of the following effects can be obtained.

[0188] (1) The base metal portion 22 exposed at least on the cut surface of the foil can be repaired by the resin layer as the insulating film layer, and a decrease in withstand voltage depending on the oxide film layer of the base metal portion 22 can be prevented. Therefore, an electrode foil with a higher withstand voltage can be manufactured.

[0189] (2) The cut surface of the foil is repaired at the manufacturing stage of the foil, so that the withstand voltage of the power storage device can be increased. In addition, even in the case of using an electrode foil with a defective portion in the oxide film layer, since the defective portion of the oxide film layer is repaired after the power storage element 2 is formed, the withstand voltage of the power storage device can be increased in the same way.

[0190] (3) A film layer having a withstand voltage equal to or higher than that of the oxide film layer is formed at least on the defective portion of the oxide film layer generated on the foil during manufacturing, and the withstand voltage of the entire electrode foil is increased, so that the withstand voltage of the element using the electrode foil can be increased.

[0191] (4) Since an electrode foil in which the defective portion is repaired at the manufacturing stage of the electrode foil is used, the withstand voltage can be increased.

[0192] [Other Embodiments]

[0193] (1) Regarding the treatment of the conductive polymer described above, poly(3,4-ethylenedioxythiophene) (PEDOT) doped with polystyrenesulfonic acid (PSS) is particularly preferred. The solid electrolyte is formed by impregnating a capacitor element in a dispersion obtained by dispersing the solid electrolyte in a solvent and drying it. The anode foil, the cathode foil, and the spacer can be respectively impregnated in the dispersion before assembly, or treatment such as drop coating or spraying can be performed.

[0194] (2) For the infiltration treatment of the electrolyte into the power storage element, the electrolyte can be infiltrated into the power storage element on which the solid electrolyte layer is formed.

[0195] (3) Repair of the oxide film layer after electrophoretic electrodeposition treatment in the state of a foil, but it is also possible to perform repair formation in the state of an element before forming the solid electrolyte layer in the element formation treatment. Thus, the oxide film layer damaged in the element formation process can also be repaired simultaneously.

[0196] As described above, the most preferred embodiments of the present application and the like have been described. The technology of the present application is not limited to the above description. Based on the gist of the invention described in the claims or disclosed in the specification, those skilled in the art can make various modifications and changes. Such modifications and changes are of course included within the scope of the present application.

[0197] Industrial Applicability

[0198] According to the electrode foil, the power storage device, and the manufacturing method thereof of the present application, the base metal part exposed on the cut surface of the foil is covered with an insulating film layer, so that the withstand voltage of the electrode foil, the power storage element, or the power storage device can be improved, which helps to improve the reliability of the power storage device and is useful.

[0199] Description of Reference Numerals

[0200] 2: Power storage element

[0201] 4: Anode foil

[0202] 6: Cathode foil

[0203] 8: Spacer

[0204] 10, 12: Support plate

[0205] 14: Anode lead part

[0206] 16: Cathode lead part

[0207] 18: Clip

[0208] 20: Cut surface

[0209] 22: Base metal part

[0210] 24: Etched layer

[0211] 26: Oxide film layer

[0212] 28: Electrophoretic electrodeposition film

Claims

1. A method for manufacturing an electrode foil, comprising: a step of performing a surface expansion treatment on a foil made of a valve metal; a step of forming an oxide film layer on the foil that has undergone the surface expansion treatment; a step of cutting the foil on which the oxide film layer is formed; and a step of forming a resin layer having a breakdown voltage equal to or higher than that of the oxide film layer on the cut surface of the foil.

2. The method for manufacturing an electrode foil according to claim 1, wherein the step of forming the resin layer includes a forming step based on electrophoretic deposition.

3. The method for manufacturing an electrode foil according to claim 1 or 2, comprising: a step of forming an oxide film by a reformation forming treatment after forming an electrophoretic deposition film.

4. A method for manufacturing a power storage device, comprising the method for manufacturing an electrode foil according to claim 1 or 2, and the method for manufacturing the power storage device further includes: a step of forming a power storage element using the electrode foil; and a step of forming a conductive polymer layer on the power storage element.

5. The method for manufacturing a power storage device according to claim 4, comprising: performing a reformation forming treatment on the power storage element and forming an oxide film on the foil.

6. An electrode foil, comprising: a foil made of a valve metal, a surface expansion treatment layer formed on the foil, an oxide film layer formed on the surface expansion treatment layer, and a resin layer formed on at least the cut surface of the foil, wherein the resin layer is formed to be thick at the base metal part exposed on the cut surface and gradually thinner toward the foil surface.

7. A power storage device, comprising a power storage element using the electrode foil according to claim 6, and the power storage element includes a conductive polymer layer.

Images