Method for manufacturing an electrode foil

Abstract

The application provides a preparation method of an electrode foil, comprising the following steps: providing an unformed foil, wherein the unformed foil comprises an aluminum foil substrate and an aluminum powder sintering layer which is combined on at least one surface of the aluminum foil substrate; sequentially performing primary formation, secondary formation, tertiary formation, quaternary formation and quinary formation on the unformed foil; wherein the formation solution of the primary formation, the secondary formation and the tertiary formation is an aqueous solution containing boric acid, citric acid and citrate or azelaic acid and azelaic acid salt, adipic acid and adipic acid salt; and the formation solution of the quaternary formation and the quinary formation is an aqueous solution containing boric acid and ammonium carbonate or ammonium pentaborate. The electrode foil prepared by the preparation method has a high specific capacity.

Description

Technical Field

[0001] This invention relates to the field of electrode foil technology, and in particular to a method for preparing electrode foil. Background Technology

[0002] Currently, most low, medium, and high voltage aluminum electrolytic capacitors use etched foil as the anode foil. However, high voltage etched foil has the following disadvantages: the pits formed on the etched foil are relatively large, thus affecting the surface area of ​​the anode foil; at the same time, the etching process requires the use of low-concentration aqueous solutions such as hydrochloric acid, sulfuric acid, and nitric acid, which have strong environmental destructive capabilities, requiring significant waste acid treatment costs; moreover, the residual acid on the anode foil also affects production costs and the capacitor manufacturing process.

[0003] To address this, a method was proposed to laminate a sintered layer of aluminum powder onto the surface of an aluminum substrate, forming an electrode foil with a porous aluminum powder sintered layer, thus replacing the etching foil. This electrode foil with an aluminum powder sintered layer does not require etching treatment with hydrochloric acid or similar substances, resulting in less environmental impact and lower cost. Furthermore, it can form a sufficiently thick porous layer, creating an intricately mixed structure with voids, thus exhibiting a larger electrostatic capacitance compared to the etched foil.

[0004] Currently, aluminum powder is typically bonded to aluminum foil using sintering or hot extrusion to obtain electrode foils with a porous aluminum powder sintered layer. However, there are few reports on the formation techniques and processes for such electrode foils. These electrode foils differ fundamentally from traditionally etched foils, and their formation processes are also different. Therefore, improving the formation process of these electrode foils to enhance their performance, such as increasing specific capacity, improving hydration properties, and reducing leakage current, has become a research hotspot in this field. Summary of the Invention

[0005] Therefore, it is necessary to provide a method for preparing an electrode foil that can improve the specific capacity of the electrode foil.

[0006] According to one aspect of the present invention, a method for preparing an electrode foil is provided, comprising the following steps:

[0007] Provides an unformed foil, the unformed foil comprising an aluminum foil substrate and an aluminum powder sintered layer disposed on at least one surface of the aluminum foil substrate; and

[0008] The unformed foil is subjected to first-stage formation, second-stage formation, third-stage formation, fourth-stage formation, and fifth-stage formation processes in sequence;

[0009] The solvent for the formation solutions used in the primary, secondary, and tertiary formations is water, and the solutes include boric acid, citric acid and citrate or azelaic acid and azelate, adipic acid and adipicate; the solvent for the formation solutions used in the quaternary and quinary formations is water, and the solutes include boric acid and ammonium salts.

[0010] In some embodiments, in the forming solution used for the primary formation, the mass concentration of boric acid is 0.3%–3%, the mass concentration of citric acid and citrate or azelaic acid and azelaic acid is 0.05%–0.8%, and the mass concentration of adipic acid and adipic acid is 0.05%–0.8%; the temperature of the primary formation is 80–95°C, and the current density is 30–60 mA / cm². 2 The applied voltage is 30%–35% Vf, and the formation time is 8–18 min.

[0011] In some embodiments, in the forming solution used for the secondary formation, the mass concentration of boric acid is 0.3%–3%, the mass concentration of citric acid and citrate or azelaic acid and azelaic acid is 0.03%–0.6%, and the mass concentration of adipic acid and adipic acid is 0.03%–0.6%; the temperature of the secondary formation is 80–95°C, and the current density is 30–60 mA / cm². 2 The applied voltage is 60%–70% Vf, and the formation time is 8–18 min.

[0012] In some embodiments, in the forming solution used for the tertiary formation, the mass concentration of boric acid is 0.5%–5%, the mass concentration of citric acid and citrate or azelaic acid and azelaic acid is 0.02%–0.5%, and the mass concentration of adipic acid and adipic acid is 0.02%–0.5%; the temperature of the tertiary formation is 80–95°C, and the current density is 25–55 mA / cm². 2 The applied voltage is 85%–95% Vf, and the formation time is 8–18 min.

[0013] In some embodiments, in the forming solution used for the fourth-stage formation, the mass concentration of boric acid is 1% to 10%, and the mass concentration of ammonium salt is 0.05% to 0.5%; the temperature of the fourth-stage formation is 80 to 95°C, and the current density is 10 to 40 mA / cm². 2 The applied voltage is 95%–110% Vf, and the formation time is 12–27 min.

[0014] In some embodiments, the five-stage formation includes a first five-stage formation, a second five-stage formation, a third five-stage formation, and a fourth five-stage formation performed sequentially.

[0015] In some embodiments, in the forming solution used for the fifth-stage first formation, the mass concentration of boric acid is 1% to 10%, and the mass concentration of ammonium salt is 0.03% to 0.3%; the temperature of the fifth-stage first formation is 80 to 95°C, and the current density is 15 to 40 mA / cm². 2 The applied voltage is 110%–130% Vf, and the formation time is 25–35 min.

[0016] In some embodiments, in the forming solution used for the fifth-stage second formation, the mass concentration of boric acid is 1% to 10%, and the mass concentration of ammonium salt is 0.01% to 0.3%; the temperature of the fifth-stage second formation is 80 to 95°C, and the current density is 1 to 15 mA / cm². 2 The applied voltage is 110%–130% Vf, and the formation time is 8–18 min.

[0017] In some embodiments, in the forming solution used for the fifth-stage third formation, the mass concentration of boric acid is 1% to 10%, and the mass concentration of ammonium salt is 0.03% to 0.3%; the temperature of the fifth-stage third formation is 80 to 95°C, and the current density is 1 to 15 mA / cm². 2 The applied voltage is 110%–130% Vf, and the formation time is 8–18 min.

[0018] In some embodiments, in the forming solution used for the fifth-stage fourth formation, the mass concentration of boric acid is 1% to 10%, and the mass concentration of ammonium salt is 0.01% to 0.3%; the temperature of the fifth-stage third formation is 40 to 80°C, and the current density is 1 to 15 mA / cm². 2 The applied voltage is 110%–130% Vf, and the formation time is 0.5–5 min.

[0019] In some embodiments, after the first five-stage formation and before the second five-stage formation, the preparation method further includes the following steps:

[0020] The unformed foil is subjected to a first heat treatment at 400–550°C for 1–3 minutes; and

[0021] The unformed foil after the first heat treatment is subjected to a first phosphoric acid treatment at 55-75°C for 2-8 minutes in a phosphoric acid solution with a mass concentration of 4%-8%.

[0022] In some embodiments, after the fifth-stage second formation and before the fifth-stage third formation, the preparation method further includes the following steps:

[0023] The unformed foil is subjected to a second heat treatment at 400–550°C for 1–3 minutes; and

[0024] The unformed foil after the second heat treatment is subjected to a second phosphoric acid treatment in a phosphoric acid solution with a mass concentration of 4% to 8% at 55 to 75°C for 2 to 8 minutes.

[0025] In some embodiments, after the fifth-stage third formation and before the fifth-stage fourth formation, the preparation method further includes the following steps:

[0026] The unformed foil is subjected to a third heat treatment at 400–550°C for 1–3 minutes.

[0027] In some embodiments, after the fifth-stage fourth formation, the preparation method further includes the following steps:

[0028] The unformed foil was subjected to a third phosphoric acid treatment at 25–45°C for 2–8 minutes in a phosphoric acid solution with a mass concentration of 0.1%–1%.

[0029] In some embodiments, the preparation method further includes the following steps prior to primary formation of the unformed foil:

[0030] The unformed foil is placed in a first pretreatment solution for a first pretreatment; the first pretreatment solution is water or nitric acid with a mass concentration of 0.5% to 3%; the temperature of the water in the first pretreatment is 80 to 98°C, the temperature of the nitric acid is 50 to 80°C, and the treatment time of the first pretreatment is 1 to 5 minutes; and

[0031] The unformed foil after the first pretreatment is placed in a second pretreatment solution for a second pretreatment; the second pretreatment solution is water, the treatment temperature of the second pretreatment is 90-98°C, and the treatment time is 5-20 min.

[0032] In some embodiments, after the tertiary formation and before the quaternary formation, the preparation method further includes the following steps:

[0033] The unformed foil is placed in a feeding bath for feeding treatment. The feeding bath is a mixed solution containing 2% to 7% adipic acid and adipic acid salt or citric acid and citrate, and 0.1% to 1% borax by mass concentration. The feeding treatment temperature is 15 to 45°C, the voltage is 15 to 35V, the current is 650 to 1550A, and the treatment time is 8 to 18 minutes.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] By sequentially performing primary, secondary, tertiary, quaternary, and quinary formation processes on the unformed foil, with the primary, secondary, and tertiary formation solutions using aqueous solutions containing boric acid, citric acid, and citrate, or azelaic acid and azelate, or adipic acid and adipicate; and the quaternary and quinary formation solutions using aqueous solutions containing boric acid and ammonium carbonate or ammonium pentaborate, this preparation method can effectively improve the specific capacity of the electrode foil.

[0036] By performing a two-stage pretreatment on the unformed foil after sintering before formation, residual substances such as carbon in the sintered layer can be effectively removed, reducing the leakage current of the electrode foil.

[0037] By incorporating multiple heat treatment and phosphoric acid treatment steps into the multi-stage formation process, the density of the oxide film on the surface of aluminum particles in the electrode foil can be increased, thereby enhancing the hydration resistance of the electrode foil and reducing hydration and leakage current. Detailed Implementation

[0038] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0039] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to limit the invention. Unless otherwise specifically stated, all raw materials, reagents, instruments, and equipment used in this invention are commercially available or can be prepared by existing methods.

[0040] Some embodiments of the present invention provide a method for preparing an electrode foil, the method comprising the following steps S1 to S20:

[0041] Step S1: Prepare the slurry

[0042] Aluminum powder, dispersant, and binder are mixed in a certain proportion, and the mixed slurry is homogenized to obtain the finished slurry.

[0043] In some embodiments, the weight ratio of aluminum powder, dispersant, and binder is (40-60):(34-60):(0-6). The prepared slurry is homogenized at a speed of 1000-2000 r / min for 1-2 h to obtain the finished slurry.

[0044] In some embodiments, the average particle size D of the aluminum powder 50 The aluminum powder has a purity greater than 99.9% in the range of 1 to 6 μm.

[0045] In some embodiments, the dispersant includes one or more of ethanol, terpineol, acetone, toluene, dibutyl phthalate, tributyl citrate, diethylene glycol butyl ether, and diffusion pump oil.

[0046] In some embodiments, the binder includes one or more of ethyl cellulose, methyl cellulose, acrylic resin, and epoxy resin.

[0047] Step S2: Coating

[0048] The finished slurry prepared in step S1 is coated onto at least one surface of an aluminum foil substrate with a thickness of 10-60 μm, and then dried to obtain the finished dried foil.

[0049] In some embodiments, the finished slurry is applied to at least one surface of the aluminum foil substrate using transfer coating, extrusion coating, or comma-shaped scraping.

[0050] In some embodiments, the finished paste is first coated on the front side of the aluminum foil substrate and then dried in air at 50°C, 100°C, 150°C, 200°C, 250°C and 300°C in sequence, with each drying process taking 2 minutes; then the finished paste is coated on the back side of the aluminum foil substrate and then dried in air at 50°C, 100°C, 150°C, 200°C, 250°C and 300°C in sequence, with each drying process taking 2 minutes, to obtain the finished dried foil.

[0051] In some embodiments, the thickness of the single-sided paste layer on the aluminum foil substrate after drying is 10–60 μm.

[0052] Step S3: Sintering

[0053] The dried foil obtained in step S2 is placed in a vacuum furnace and degreased for 1 to 2 hours under vacuum conditions and a temperature of 300 to 400°C. Then, it is sintered for 1 to 12 hours at a temperature of 560 to 650°C to obtain an unformed foil.

[0054] Step S4: First preprocessing

[0055] The unformed foil obtained in step S3 is treated in pure water at a temperature of 80–98°C, or in nitric acid at a temperature of 50–80°C and a mass concentration of 0.5%–3% for 1–5 minutes.

[0056] Thus, by performing a first pretreatment on the unformed foil obtained after sintering before formation, residual substances such as carbon elemental substances between aluminum particles in the sintered layer during the foil sintering process can be removed, which helps to reduce the leakage current of the electrode foil.

[0057] Step S5: Second preprocessing

[0058] The unformed foil after step S4 is treated in pure water at a temperature of 90–98°C for 5–20 minutes. This second pretreatment further removes residual material between aluminum particles in the sintered layer.

[0059] Step S6: Primary Formation

[0060] The unformed foil after step S5 is subjected to primary formation treatment in the primary formation solution.

[0061] In some embodiments, the primary formation solution is an aqueous solution containing 0.3% to 3% boric acid, 0.05% to 0.8% citric acid and citrate or azelaic acid and azelate, and 0.05% to 0.8% adipic acid and adipicate.

[0062] It is understood that the primary formation solution can be an aqueous solution containing boric acid, citric acid and citrate, adipic acid and adipic acid salt; or it can be an aqueous solution containing boric acid, azelaic acid and azelaic acid salt, adipic acid and adipic acid salt. Among them, citric acid and citrate, azelaic acid and azelaic acid salt, and adipic acid and adipic acid salt are all added as a whole after forming a mixture of acid and corresponding salt in a 1:2 weight ratio.

[0063] In some embodiments, the primary formation process is performed at a temperature of 80–95°C and a current density of 30–60 mA / cm². 2 The applied voltage is 30%–35% vf (vf represents the maximum voltage that the electrode foil can withstand), and the formation time is 8–18 min.

[0064] Therefore, citric acid and citrate, azelaic acid and azelate, and adipic acid and adipicate in the primary formation solution can improve the specific capacity of the electrode foil.

[0065] Step S7: Secondary formation

[0066] The foil that has undergone the primary formation process in step S6 is then subjected to a secondary formation process in a secondary formation solution.

[0067] In some embodiments, the secondary formation solution is an aqueous solution containing 0.3% to 3% boric acid, 0.03% to 0.6% citric acid and citrate or azelaic acid and azelate, and 0.03% to 0.6% adipic acid and adipicate.

[0068] It is understandable that the secondary formation solution can be an aqueous solution containing boric acid, citric acid and citrate, adipic acid and adipic acid salt; or it can be an aqueous solution containing boric acid, azelaic acid and azelaic acid salt, adipic acid and adipic acid salt.

[0069] In some embodiments, the secondary formation process is performed at a temperature of 80–95°C and a current density of 30–60 mA / cm². 2 The applied voltage is 60%–70% Vf, and the formation time is 8–18 min.

[0070] Step S8: Tertiary Formation

[0071] The foil, after undergoing the secondary formation process in step S7, is then subjected to a tertiary formation process in a tertiary formation solution.

[0072] In some embodiments, the tertiary formation solution is an aqueous solution containing 0.5% to 5% boric acid, 0.02% to 0.5% citric acid and citrate or azelaic acid and azelate, and 0.02% to 0.5% adipic acid and adipicate.

[0073] It is understandable that the tertiary formation solution can be an aqueous solution containing boric acid, citric acid and citrate, adipic acid and adipic acid salt; or it can be an aqueous solution containing boric acid, azelaic acid and azelaic acid salt, adipic acid and adipic acid salt. Among them, citric acid and citrate, azelaic acid and azelaic acid salt, and adipic acid and adipic acid salt are all added as a whole after forming a mixture of acid and corresponding salt in a 1:2 weight ratio.

[0074] In some embodiments, the secondary formation process is performed at a temperature of 80–95°C and a current density of 25–55 mA / cm². 2 The applied voltage is 85%–95% Vf, and the formation time is 8–18 min.

[0075] Step S9: Power Feeding Process

[0076] The foil, after undergoing the three-stage formation process in step S8, is subjected to electro-energizing treatment in the electro-energizing tank.

[0077] In some embodiments, the power supply solution is a mixed solution containing 2% to 7% by mass of adipic acid and adipic acid salt or citric acid and citrate, and 0.1% to 1% by mass of borax.

[0078] It is understood that the electrolyte solution can be a mixed solution containing adipic acid and adipic acid salt, and borax; or it can be a mixed solution containing citric acid and citrate, and borax.

[0079] In some embodiments, the power supply temperature is 15–45°C, the voltage is 15–35V, the current is 650–1550A, and the processing time is 8–18 minutes.

[0080] Thus, by using a mixed solution of adipic acid and adipic acid salt or citric acid and citrate salt, and borax to perform liquid feeding treatment on the foil after tertiary formation, the specific capacity of the electrode foil can be further improved.

[0081] Step S10: Quadruple formation

[0082] The foil after the feeding treatment in step S9 is subjected to a fourth-stage formation treatment in a fourth-stage formation solution.

[0083] In some embodiments, the fourth-stage formation solution is an aqueous solution containing 1% to 10% boric acid and 0.05% to 0.5% ammonium carbonate or ammonium pentaborate by mass.

[0084] It is understandable that the fourth-stage formation solution can be an aqueous solution containing boric acid and ammonium carbonate; or it can be an aqueous solution containing boric acid and ammonium pentaborate.

[0085] In some embodiments, the temperature of the fourth-stage formation process is 80–95°C, and the current density is 10–40 mA / cm². 2 The applied voltage is 95%–110% Vf, and the formation time is 12–27 min.

[0086] Step S11: First transformation of level 5

[0087] The foil that has undergone the fourth-stage formation process in step S10 is then subjected to the fifth-stage first-stage formation process in the fifth-stage first-stage formation solution.

[0088] In some embodiments, the fifth-stage first formation solution is an aqueous solution containing 1% to 10% boric acid and 0.03% to 0.3% ammonium carbonate or ammonium pentaborate by mass.

[0089] It is understandable that the first reaction solution in the fifth stage can be an aqueous solution containing boric acid and ammonium carbonate; or it can be an aqueous solution containing boric acid and ammonium pentaborate.

[0090] In some embodiments, the temperature of the first five-stage formation process is 80–95°C, and the current density is 15–40 mA / cm². 2 The applied voltage is 110%–130% Vf, and the formation time is 25–35 min.

[0091] Step S12: First heat treatment

[0092] The foil after step S11 is heat-treated at 400-550℃ for 1-3 minutes.

[0093] Step S13: Primary phosphoric acid treatment

[0094] The foils treated in step S12 are then treated in a phosphoric acid solution at 55–75°C with a mass concentration of 4%–8% for 2–8 minutes.

[0095] By subjecting the foil after the first formation process of the fifth stage to the first heat treatment and the first phosphoric acid treatment, the oxide film on the surface of aluminum particles in the sintered layer can be repaired and optimized, the density of the oxide film can be improved, thereby improving the hydration resistance of the electrode foil and reducing the hydration and leakage current of the electrode foil product.

[0096] Step S14: Level 5 Second Transformation

[0097] The foil processed in step S13 is subjected to a fifth-stage second formation process in the fifth-stage second formation solution.

[0098] In some embodiments, the fifth-stage secondary formation solution is an aqueous solution containing 1% to 10% boric acid and 0.01% to 0.3% ammonium carbonate or ammonium pentaborate by mass.

[0099] It is understandable that the fifth-stage second-stage reaction solution can be an aqueous solution containing boric acid and ammonium carbonate; or it can be an aqueous solution containing boric acid and ammonium pentaborate.

[0100] In some embodiments, the temperature of the fifth-stage second formation process is 80–95°C, and the current density is 1–15 mA / cm². 2 The applied voltage is 110%–130% Vf, and the formation time is 8–18 min.

[0101] Step S15: Second heat treatment

[0102] The foil after step S14 is heat-treated at 400-550°C for 1-3 minutes.

[0103] Step S16: Treatment with diphosphate

[0104] The foil treated in step S15 is then treated in a phosphoric acid solution with a mass concentration of 4%–8% at 55–75°C for 2–8 minutes. By subjecting the foil after the fifth-stage second formation treatment to the above-mentioned second heat treatment and second phosphoric acid treatment, the density of the oxide film on the surface of the aluminum particles can be further improved, the hydration resistance of the electrode foil can be further improved, and the hydration and leakage current of the electrode foil product can be reduced.

[0105] Step S17: Level 5, Third Transformation

[0106] The foil processed in step S16 is subjected to a fifth-stage third-stage formation process in a fifth-stage third-stage formation solution.

[0107] In some embodiments, the fifth-stage third formation solution is an aqueous solution containing 1% to 10% boric acid and 0.03% to 0.3% ammonium carbonate or ammonium pentaborate by mass.

[0108] It is understandable that the fifth-stage third-stage reaction solution can be an aqueous solution containing boric acid and ammonium carbonate; or it can be an aqueous solution containing boric acid and ammonium pentaborate.

[0109] In some embodiments, the temperature of the fifth-stage third formation process is 80–95°C, and the current density is 1–15 mA / cm². 2 The applied voltage is 110%–130% Vf, and the formation time is 8–18 min.

[0110] Step S18: Third heat treatment

[0111] The foil after step S17 is heat-treated at 400-550°C for 1-3 minutes.

[0112] Step S19: Level 5, Fourth Transformation

[0113] The foil processed in step S18 is subjected to a fifth-level fourth-stage formation process in the fifth-level fourth-stage formation solution.

[0114] In some embodiments, the fifth-stage fourth-stage formation solution is an aqueous solution containing 1% to 10% boric acid and 0.01% to 0.3% ammonium carbonate or ammonium pentaborate by mass.

[0115] It is understandable that the fourth reaction solution in the fifth stage can be an aqueous solution containing boric acid and ammonium carbonate; or it can be an aqueous solution containing boric acid and ammonium pentaborate.

[0116] In some embodiments, the temperature of the fifth-stage fourth formation process is 40–80°C, and the current density is 1–15 mA / cm². 2 The applied voltage is 110%–130% Vf, and the formation time is 0.5–5 min.

[0117] Step S20: Treatment with tertiary phosphoric acid

[0118] The foil treated in step S19 is then treated in a 0.1%–1% phosphoric acid solution at 25–45°C for 2–8 minutes; the foil is then removed and dried. Further repair of the oxide film on the surface of the aluminum particles is then performed.

[0119] This invention significantly improves the specific capacity of the electrode foil by performing five-stage formation in specific formation solutions, feeding tank solutions, and phosphoric acid treatment solutions, combined with three heat treatments and three-stage phosphoric acid treatments. It also increases the density of the oxide film on the surface of aluminum particles in the sintered layer and improves the hydration resistance of the electrode foil, thereby reducing the hydration and leakage current of the electrode foil product.

[0120] The present invention will be further described below with reference to specific embodiments and comparative examples, but these should not be construed as limiting the scope of protection of the present invention.

[0121] Example 1:

[0122] (1) Preparation without foil formation

[0123] Tributyl citrate was used as a dispersant, acrylic resin as a binder, and the average particle size D was used. 50 The aluminum powder has a particle size of 3μm. A slurry was prepared by mixing aluminum powder, tributyl citrate, and acrylic resin in a weight ratio of 40:57:3. The slurry was homogenized at 1700 rpm for 10 min to obtain the final product.

[0124] A 30μm thick film layer was prepared on the front side of a 30μm thick substrate foil (aluminum foil substrate) using a stainless steel scraper. The film was then dried in air at 50℃, 100℃, 150℃, 200℃, 250℃, and 300℃, with each drying step lasting 2 minutes. A slurry was then coated on the back side of the substrate foil and dried in air at 50℃, 100℃, 150℃, 200℃, 250℃, and 300℃, with each drying step lasting 2 minutes, to obtain the finished dried foil.

[0125] The dried foil was placed in a vacuum furnace, evacuated, and kept at 400℃ for 1 hour and then at 640℃ for 2 hours. This yielded an unformed foil (sintered foil).

[0126] (2) Formation process

[0127] First pretreatment: The unformed foil was treated in pure water at 90°C for 2 minutes.

[0128] Second pretreatment: The unformed foil after the first pretreatment is treated in pure water at 95°C for 15 minutes.

[0129] Primary formation: The foil, after the second pretreatment, undergoes primary formation in an aqueous solution containing 2% boric acid, 0.4% citric acid and citrate, and 0.3% adipic acid and adipic acid salt. The primary formation temperature is 85℃, and the current density is 55 mA / cm². 2 The applied voltage was 30% Vf, and the formation time was 10 min.

[0130] Secondary formation: The foil after primary formation is subjected to secondary formation treatment in an aqueous solution containing 2% boric acid, 0.3% citric acid and citrate, and 0.3% adipic acid and adipic acid salt. The temperature of the secondary formation treatment is 85℃, and the current density is 50mA / cm². 2 The applied voltage was 60% Vf, and the formation time was 10 min.

[0131] Tertiary formation: The foil, after secondary formation, undergoes a tertiary formation treatment in an aqueous solution containing 4% boric acid, 0.25% citric acid and citrate, and 0.25% adipic acid and adipic acid salt. The tertiary formation treatment temperature is 85℃, and the current density is 40 mA / cm². 2 The applied voltage was 90% Vf, and the formation time was 12 min.

[0132] Liquid electrostatic treatment: The tertiary formed foil was electrostatically treated in a mixed solution of 4% adipic acid and adipic acid salt and 0.2% borax. The electrostatic treatment temperature was 30℃, the voltage was 20V, the current was 1500A, and the treatment time was 12min.

[0133] Fourth-stage formation: The foil, after liquid-fed treatment, undergoes a fourth-stage formation process in an aqueous solution containing 5% boric acid and 0.3% ammonium pentaborate. The fourth-stage formation process is carried out at a temperature of 85℃ and a current density of 35 mA / cm². 2 The applied voltage was 100% Vf, and the formation time was 15 min.

[0134] The fifth-stage first formation: The foil, after the fourth-stage formation, undergoes a fifth-stage first formation treatment in an aqueous solution containing 8% boric acid and 0.2% ammonium pentaborate. The fifth-stage first formation temperature is 85℃, and the current density is 25mA / cm². 2 The applied voltage was 120% Vf, and the formation time was 30 min.

[0135] First heat treatment: The foil sheet after the first five-stage formation is subjected to high-temperature heat treatment at 450℃ for 2 minutes.

[0136] First phosphoric acid treatment: The foil after the first heat treatment is treated in a phosphoric acid solution with a mass concentration of 6% at 60°C for 7 minutes.

[0137] Fifth-stage second formation: The foil treated with the first phosphoric acid is subjected to a fifth-stage second formation treatment in an aqueous solution containing 8% boric acid and 0.2% ammonium pentaborate. The temperature of the fifth-stage second formation treatment is 85℃, and the current density is 13mA / cm². 2The applied voltage was 120% Vf, and the formation time was 10 min.

[0138] Second heat treatment: The foil that has undergone the second formation of the fifth stage is subjected to a second heat treatment at 450°C for 2 minutes.

[0139] Second phosphoric acid treatment: The foil after the second heat treatment is treated in a phosphoric acid solution with a mass concentration of 5% at 60°C for 7 minutes.

[0140] Fifth-stage third formation: The foil treated with the second phosphoric acid is subjected to a fifth-stage third formation treatment in an aqueous solution containing 8% boric acid and 0.2% ammonium pentaborate. The temperature of the fifth-stage third formation treatment is 85℃, and the current density is 10 mA / cm². 2 The applied voltage was 120% Vf, and the formation time was 10 min.

[0141] Third heat treatment: The foil after the fifth stage of third formation is heat treated at 450℃ for 2 minutes.

[0142] Fifth-stage fourth formation: The foil, after the third heat treatment, undergoes a fifth-stage fourth formation treatment in an aqueous solution containing 8% boric acid and 0.2% ammonium pentaborate. The temperature for the fifth-stage fourth formation treatment is 60℃, and the current density is 8 mA / cm². 2 The applied voltage was 120% Vf, and the formation time was 2 min.

[0143] Third phosphoric acid treatment: The foil, after undergoing the fifth-stage fourth formation, was treated in a 0.2% phosphoric acid solution at 30°C for 2 minutes, then removed and dried to obtain the electrode foil. The properties of the prepared electrode foil are shown in Table 1.

[0144] Example 2:

[0145] (1) Preparation without foil formation

[0146] Tributyl citrate was used as a dispersant, acrylic resin as a binder, and the average particle size D was used. 50 The aluminum powder has a particle size of 3μm. A slurry was prepared by mixing aluminum powder, tributyl citrate, and acrylic resin in a weight ratio of 40:57:3. The slurry was homogenized at 1700 rpm for 10 min to obtain the final product.

[0147] A 30μm thick film layer was prepared on the front side of a 30μm thick substrate foil using a stainless steel doctor blade. The film was then dried in air at 50℃, 100℃, 150℃, 200℃, 250℃, and 300℃, with each drying step lasting 2 minutes. A slurry was then coated on the back side of the substrate foil and dried in air at 50℃, 100℃, 150℃, 200℃, 250℃, and 300℃, with each drying step lasting 2 minutes, to obtain the finished dried foil.

[0148] The dried foil was placed in a vacuum furnace, evacuated, and kept at 400℃ for 1 hour and then at 640℃ for 2 hours. This yielded an unformed foil (sintered foil).

[0149] (2) Formation process

[0150] First pretreatment: The unformed foil was treated in nitric acid at 60°C and 1% by mass for 3 minutes.

[0151] Second pretreatment: The unformed foil after the first pretreatment is treated in pure water at 98°C for 20 minutes.

[0152] Primary formation: The foil that has undergone the second pretreatment is subjected to primary formation treatment in an aqueous solution containing 1% boric acid, 0.5% azelaic acid and azelate, and 0.5% adipic acid and adipicate. The temperature of the primary formation treatment is 90℃, and the current density is 50mA / cm². 2 The applied voltage was 35% Vf, and the formation time was 15 min.

[0153] Secondary formation: The foil after primary formation is subjected to secondary formation treatment in an aqueous solution containing 1% boric acid, 0.4% azelaic acid and azelate, and 0.4% adipic acid and adipicate. The temperature of the secondary formation treatment is 90℃, and the current density is 45mA / cm². 2 The applied voltage was 65% Vf, and the formation time was 15 min.

[0154] Tertiary formation: The foil, after secondary formation, undergoes a tertiary formation treatment in an aqueous solution containing 3% boric acid, 0.3% azelaic acid and azelate, and 0.3% adipic acid and adipicate. The tertiary formation treatment temperature is 90℃, and the current density is 35 mA / cm². 2 The applied voltage was 85% Vf, and the formation time was 15 min.

[0155] Liquid electrostatic treatment: The foil after tertiary formation was electrostatically treated in a mixed solution of 4% citric acid and citrate and 0.3% borax. The electrostatic treatment temperature was 35℃, the voltage was 25V, the current was 1550A, and the formation time was 15min.

[0156] Quaternary formation: The foil, after liquid-fed treatment, undergoes a four-stage formation process in an aqueous solution containing 6% boric acid and 0.25% ammonium carbonate. The temperature for the four-stage formation process is 90℃, and the current density is 30 mA / cm². 2 The applied voltage was 105% Vf, and the formation time was 15 min.

[0157] The fifth-stage first formation: The foil, after the fourth-stage formation, undergoes a fifth-stage first formation treatment in an aqueous solution containing 7% boric acid and 0.2% ammonium carbonate. The fifth-stage first formation temperature is 90℃, and the current density is 20 mA / cm². 2 The applied voltage was 115% Vf, and the formation time was 35 min.

[0158] First heat treatment: The foil sheet after the first five-stage formation is subjected to high-temperature heat treatment at 550℃ for 2 minutes.

[0159] First phosphoric acid treatment: The foil after the first heat treatment is treated in a 5% phosphoric acid solution at 65°C for 5 minutes.

[0160] Fifth-stage second formation: The foil treated with the first phosphoric acid is subjected to a fifth-stage second formation treatment in an aqueous solution containing 7% boric acid and 0.2% ammonium carbonate. The temperature of the fifth-stage second formation treatment is 90℃, and the current density is 12 mA / cm². 2 The applied voltage was 115% Vf, and the formation time was 15 min.

[0161] Second heat treatment: The foil that has undergone the second formation of the fifth stage is subjected to a second heat treatment at 550°C for 2 minutes.

[0162] Second phosphoric acid treatment: The foil after the second heat treatment is treated in a phosphoric acid solution with a mass concentration of 4% at 65°C for 5 minutes.

[0163] Fifth-stage third formation: The foil treated with the second phosphoric acid is subjected to a fifth-stage third formation treatment in an aqueous solution containing 7% boric acid and 0.2% ammonium carbonate. The fifth-stage third formation treatment is performed at a temperature of 90℃ and a current density of 8 mA / cm². 2 The applied voltage was 115% Vf, and the formation time was 15 min.

[0164] Third heat treatment: The foil sheet after the fifth stage of third formation is heat treated at 550℃ for 2 minutes.

[0165] Fifth-stage fourth formation: The foil, after the third heat treatment, undergoes a fifth-stage fourth formation treatment in an aqueous solution containing 7% boric acid and 0.2% ammonium carbonate. The temperature for the fifth-stage fourth formation treatment is 70℃, and the current density is 5 mA / cm². 2 The applied voltage was 115% Vf, and the formation time was 3 min.

[0166] Third phosphoric acid treatment: The foil, after undergoing the fifth-stage fourth formation, was treated in a 0.3% phosphoric acid solution at 35°C for 1 minute, then removed and dried to obtain the electrode foil. The properties of the prepared electrode foil are shown in Table 1.

[0167] Example 3:

[0168] (1) Preparation without foil formation

[0169] Tributyl citrate was used as a dispersant, acrylic resin as a binder, and the average particle size D was used. 50 The aluminum powder has a particle size of 2μm. A slurry was prepared by mixing aluminum powder, tributyl citrate, and acrylic resin in a weight ratio of 45:52:3. The slurry was homogenized at 1700 rpm for 10 min to obtain the final slurry.

[0170] A 30μm thick film layer was prepared on the front side of a 30μm thick substrate foil using a stainless steel doctor blade. The film was then dried in air at 50℃, 100℃, 150℃, 200℃, 250℃, and 300℃, with each drying step lasting 2 minutes. A slurry was then coated on the back side of the substrate foil and dried in air at 50℃, 100℃, 150℃, 200℃, 250℃, and 300℃, with each drying step lasting 2 minutes, to obtain the finished dried foil.

[0171] The dried foil was placed in a vacuum furnace, evacuated, and kept at 400℃ for 1 hour, then at 640℃ for 2 hours. This resulted in the formation of an unformed foil.

[0172] (2) Formation process

[0173] First pretreatment: The unformed foil was treated in nitric acid at 55°C and 2% by mass for 2 minutes.

[0174] Second pretreatment: The unformed foil after the first pretreatment is treated in pure water at 92°C for 10 minutes.

[0175] Primary formation: The foil that has undergone the second pretreatment is subjected to primary formation treatment in an aqueous solution containing 3% boric acid, 0.8% azelaic acid and azelate, and 0.8% adipic acid and adipicate. The temperature of the primary formation treatment is 95℃, and the current density is 45mA / cm². 2 The applied voltage was 35% Vf, and the formation time was 15 min.

[0176] Secondary formation: The foil after primary formation is subjected to secondary formation treatment in an aqueous solution containing 3% boric acid, 0.5% azelaic acid and azelate, and 0.5% adipic acid and adipicate. The temperature of the secondary formation treatment is 95℃, and the current density is 45mA / cm². 2 The applied voltage was 65% Vf, and the formation time was 15 min.

[0177] Tertiary formation: The foil, after secondary formation, undergoes a tertiary formation treatment in an aqueous solution containing 5% boric acid, 0.5% azelaic acid and azelate, and 0.5% adipic acid and adipicate. The tertiary formation treatment temperature is 90℃, and the current density is 35 mA / cm². 2 The applied voltage was 85% Vf, and the formation time was 15 min.

[0178] Liquid electrostatic treatment: The foil after tertiary formation was electrostatically treated in a mixed solution of 4% citric acid and citrate and 0.3% borax. The electrostatic treatment temperature was 35℃, the voltage was 25V, the current was 1550A, and the formation time was 15min.

[0179] Fourth-stage formation: The foil, after liquid-fed treatment, undergoes a fourth-stage formation process in an aqueous solution containing 4% boric acid and 0.2% ammonium carbonate. The fourth-stage formation process is carried out at a temperature of 90℃ and a current density of 30 mA / cm². 2 The applied voltage was 105% Vf, and the formation time was 15 min.

[0180] The fifth-stage first formation: The foil, after the fourth-stage formation, undergoes a fifth-stage first formation treatment in an aqueous solution containing 6% boric acid and 0.1% ammonium carbonate. The fifth-stage first formation temperature is 90℃, and the current density is 20 mA / cm². 2 The applied voltage was 115% Vf, and the formation time was 35 min.

[0181] First heat treatment: The foil sheet after the first five-stage formation is subjected to high-temperature heat treatment at 550℃ for 2 minutes.

[0182] First phosphoric acid treatment: The foil after the first heat treatment is treated in a 5% phosphoric acid solution at 65°C for 5 minutes.

[0183] Fifth-stage second formation: The foil treated with the first phosphoric acid is subjected to a fifth-stage second formation treatment in an aqueous solution containing 6% boric acid and 0.1% ammonium carbonate. The temperature of the fifth-stage second formation treatment is 90℃, and the current density is 12 mA / cm². 2 The applied voltage was 115% Vf, and the formation time was 15 min.

[0184] Second heat treatment: The foil that has undergone the second formation of the fifth stage is subjected to a second heat treatment at 550°C for 2 minutes.

[0185] Second phosphoric acid treatment: The foil after the second heat treatment is treated in a phosphoric acid solution with a mass concentration of 4% at 65°C for 5 minutes.

[0186] Fifth-stage third formation: The foil treated with the second phosphoric acid is subjected to a fifth-stage third formation treatment in an aqueous solution containing 6% boric acid and 0.1% ammonium carbonate. The fifth-stage third formation treatment is performed at a temperature of 90℃ and a current density of 8 mA / cm². 2 The applied voltage was 115% Vf, and the formation time was 15 min.

[0187] Third heat treatment: The foil sheet after the fifth stage of third formation is heat treated at 550℃ for 2 minutes.

[0188] Fifth-stage fourth formation: The foil, after the third heat treatment, undergoes a fifth-stage fourth formation treatment in an aqueous solution containing 6% boric acid and 0.1% ammonium carbonate. The temperature for the fifth-stage fourth formation treatment is 70℃, and the current density is 5 mA / cm². 2 The applied voltage was 115% Vf, and the formation time was 3 min.

[0189] Third phosphoric acid treatment: The foil, after undergoing the fifth-stage fourth formation, was treated in a 0.3% phosphoric acid solution at 35°C for 1 minute, then removed and dried to obtain the electrode foil. The properties of the prepared electrode foil are shown in Table 1.

[0190] Example 4:

[0191] (1) Preparation without foil formation

[0192] Tributyl citrate was used as a dispersant, acrylic resin as a binder, and the average particle size D was used. 50The aluminum powder has a particle size of 5μm. A slurry was prepared by mixing aluminum powder, tributyl citrate, and acrylic resin in a weight ratio of 50:47:3. The slurry was homogenized at 1700 rpm for 10 min to obtain the final product.

[0193] A 30μm thick film layer was prepared on the front side of a 30μm thick substrate foil using a stainless steel doctor blade. The film was then dried in air at 50℃, 100℃, 150℃, 200℃, 250℃, and 300℃, with each drying step lasting 2 minutes. A slurry was then coated on the back side of the substrate foil and dried in air at 50℃, 100℃, 150℃, 200℃, 250℃, and 300℃, with each drying step lasting 2 minutes, to obtain the finished dried foil.

[0194] The dried foil was placed in a vacuum furnace, evacuated, and kept at 400℃ for 1 hour, then at 640℃ for 2 hours. This resulted in the formation of an unformed foil.

[0195] (2) Formation process

[0196] First pretreatment: The unformed foil was treated in pure water at 85°C for 2 minutes.

[0197] Second pretreatment: The unformed foil after the first pretreatment is treated in pure water at 92°C for 13 minutes.

[0198] Primary formation: The foil, after the second pretreatment, undergoes primary formation in an aqueous solution containing 3% boric acid, 0.8% citric acid and citrate, and 0.8% adipic acid and adipic acid salt. The primary formation temperature is 95℃, and the current density is 45 mA / cm². 2 The applied voltage was 35% Vf, and the formation time was 15 min.

[0199] Secondary formation: The foil after primary formation is subjected to secondary formation treatment in an aqueous solution containing 3% boric acid, 0.5% citric acid and citrate, and 0.5% adipic acid and adipic acid salt. The temperature of the secondary formation treatment is 95℃, and the current density is 45mA / cm². 2 The applied voltage was 65% Vf, and the formation time was 15 min.

[0200] Tertiary formation: The foil, after secondary formation, undergoes a tertiary formation treatment in an aqueous solution containing 5% boric acid, 0.5% citric acid and citrate, and 0.5% adipic acid and adipic acid salt. The tertiary formation treatment temperature is 90℃, and the current density is 35 mA / cm². 2 The applied voltage was 85% Vf, and the formation time was 15 min.

[0201] Liquid electrostatic treatment: The foil after tertiary formation was electrostatically treated in a mixed solution of 4% citric acid and citrate and 0.3% borax. The electrostatic treatment temperature was 35℃, the voltage was 25V, the current was 1550A, and the formation time was 15min.

[0202] Fourth-stage formation: The foil, after liquid-fed treatment, undergoes a fourth-stage formation process in an aqueous solution containing 4% boric acid and 0.2% ammonium pentaborate. The fourth-stage formation process is carried out at a temperature of 90℃ and a current density of 30 mA / cm². 2 The applied voltage was 105% Vf, and the formation time was 15 min.

[0203] The fifth-stage first formation: The foil, after the fourth-stage formation, undergoes a fifth-stage first formation treatment in an aqueous solution containing 6% boric acid and 0.1% ammonium pentaborate. The fifth-stage first formation temperature is 90℃, and the current density is 20 mA / cm². 2 The applied voltage was 115% Vf, and the formation time was 35 min.

[0204] First heat treatment: The foil sheet after the first five-stage formation is subjected to high-temperature heat treatment at 550℃ for 2 minutes.

[0205] First phosphoric acid treatment: The foil after the first heat treatment is treated in a 5% phosphoric acid solution at 65°C for 5 minutes.

[0206] Fifth-stage second formation: The foil treated with the first phosphoric acid is subjected to a fifth-stage second formation treatment in an aqueous solution containing 6% boric acid and 0.1% ammonium pentaborate. The temperature of the fifth-stage second formation treatment is 90℃, and the current density is 12mA / cm². 2 The applied voltage was 115% Vf, and the formation time was 15 min.

[0207] Second heat treatment: The foil that has undergone the second formation of the fifth stage is subjected to a second heat treatment at 550°C for 2 minutes.

[0208] Second phosphoric acid treatment: The foil after the second heat treatment is treated in a phosphoric acid solution with a mass concentration of 4% at 65°C for 5 minutes.

[0209] Fifth-stage third formation: The foil treated with the second phosphoric acid is subjected to a fifth-stage third formation treatment in an aqueous solution containing 6% boric acid and 0.1% ammonium pentaborate. The fifth-stage third formation treatment is performed at a temperature of 90℃ and a current density of 8 mA / cm². 2 The applied voltage was 115% Vf, and the formation time was 15 min.

[0210] Third heat treatment: The foil sheet after the fifth stage of third formation is heat treated at 550℃ for 2 minutes.

[0211] Fifth-stage fourth formation: The foil, after the third heat treatment, undergoes a fifth-stage fourth formation treatment in an aqueous solution containing 6% boric acid and 0.1% ammonium pentaborate. The temperature for the fifth-stage fourth formation treatment is 70℃, and the current density is 5 mA / cm². 2 The applied voltage was 115% Vf, and the formation time was 3 min.

[0212] Third phosphoric acid treatment: The foil, after undergoing the fifth-stage fourth formation, was treated in a 0.3% phosphoric acid solution at 35°C for 1 minute, then removed and dried to obtain the electrode foil. The properties of the prepared electrode foil are shown in Table 1.

[0213] Comparative Example 1:

[0214] The foil not formed in Example 1 was formed in a 100 g / L boric acid solution to 520 V and held at a constant voltage for 30 min. It was then left to stand in the forming solution without electricity for 2 min, and finally laminated in the forming solution for 10 min. This yielded the anode foil (electrode foil) for electrolytic capacitors. The properties of the prepared electrode foil are shown in Table 1.

[0215] Comparative Example 2:

[0216] Tributyl citrate was used as a dispersant, acrylic resin as a binder, and the average particle size D was used. 50 The aluminum powder has a particle size of 5 μm. A slurry was prepared by mixing aluminum powder, tributyl citrate, and acrylic resin in a weight ratio of 40:57:3. The slurry was homogenized at 1700 r / min for 10 min to obtain the finished slurry.

[0217] A 50 μm thick film layer was prepared on the front side of a 30 μm thick substrate foil using a stainless steel doctor blade. The film was then dried in air at 50°C, 100°C, 150°C, 200°C, 250°C, and 300°C, with each drying step lasting 2 minutes. A slurry was then coated on the back side of the substrate foil and dried in air at 50°C, 100°C, 150°C, 200°C, 250°C, and 300°C, with each drying step lasting 2 minutes, to obtain the finished dried foil.

[0218] The dried foil was placed in a vacuum furnace, evacuated, and kept at 400℃ for 1 hour, then at 640℃ for 2 hours. This resulted in the formation of an unformed foil.

[0219] The unformed foil was formed in a 100 g / L boric acid solution to 520 V, held at a constant voltage for 25 min, placed in air at 550 °C for 2 min, and then laminated in the forming solution for 5 min. This yielded the anode foil (electrode foil) for electrolytic capacitors. The properties of the prepared electrode foil are shown in Table 1.

[0220] Comparative Example 3:

[0221] The unformed foil from Example 1 was used for the formation process.

[0222] First preprocessing: None.

[0223] Second pretreatment: The unformed foil after the first pretreatment is treated in pure water at 95°C for 15 minutes.

[0224] Primary formation: The foil, after the second pretreatment, undergoes primary formation in an aqueous solution containing 2% boric acid, 0.4% citric acid and citrate, and 0.3% adipic acid and adipic acid salt. The primary formation temperature is 85℃, and the current density is 55 mA / cm². 2 The applied voltage was 30% Vf, and the formation time was 10 min.

[0225] Secondary formation: The foil after primary formation is subjected to secondary formation treatment in an aqueous solution containing 2% boric acid, 0.3% citric acid and citrate, and 0.3% adipic acid and adipic acid salt. The temperature of the secondary formation treatment is 85℃, and the current density is 50mA / cm². 2 The applied voltage was 60% Vf, and the formation time was 10 min.

[0226] Tertiary formation: The foil, after secondary formation, undergoes a tertiary formation treatment in an aqueous solution containing 4% boric acid, 0.25% citric acid and citrate, and 0.25% adipic acid and adipic acid salt. The tertiary formation treatment temperature is 85℃, and the current density is 40 mA / cm². 2 The applied voltage was 90% Vf, and the formation time was 12 min.

[0227] Liquid electrostatic treatment: The tertiary formed foil was electrostatically treated in a mixed solution of 4% adipic acid and adipic acid salt and 0.2% borax. The electrostatic treatment temperature was 30℃, the voltage was 20V, the current was 1500A, and the treatment time was 12min.

[0228] Fourth-stage formation: The foil, after liquid-fed treatment, undergoes a fourth-stage formation process in an aqueous solution containing 5% boric acid and 0.3% ammonium pentaborate. The fourth-stage formation process is carried out at a temperature of 85℃ and a current density of 35 mA / cm².2 The applied voltage was 100% Vf, and the formation time was 15 min.

[0229] The fifth-stage first formation: The foil, after the fourth-stage formation, undergoes a fifth-stage first formation treatment in an aqueous solution containing 8% boric acid and 0.2% ammonium pentaborate. The fifth-stage first formation temperature is 85℃, and the current density is 25mA / cm². 2 The applied voltage was 120% Vf, and the formation time was 30 min.

[0230] First heat treatment: The foil sheet after the first five-stage formation is subjected to high-temperature heat treatment at 450℃ for 2 minutes.

[0231] First phosphoric acid treatment: The foil after the first heat treatment is treated in a phosphoric acid solution with a mass concentration of 6% at 60°C for 7 minutes.

[0232] Fifth-stage second formation: The foil treated with the first phosphoric acid is subjected to a fifth-stage second formation treatment in an aqueous solution containing 8% boric acid and 0.2% ammonium pentaborate. The temperature of the fifth-stage second formation treatment is 85℃, and the current density is 13mA / cm². 2 The applied voltage was 120% Vf, and the formation time was 10 min.

[0233] Second heat treatment: The foil that has undergone the second formation of the fifth stage is subjected to a second heat treatment at 450°C for 2 minutes.

[0234] Second phosphoric acid treatment: The foil after the second heat treatment is treated in a phosphoric acid solution with a mass concentration of 5% at 60°C for 7 minutes.

[0235] Fifth-stage third formation: The foil treated with the second phosphoric acid is subjected to a fifth-stage third formation treatment in an aqueous solution containing 8% boric acid and 0.2% ammonium pentaborate. The temperature of the fifth-stage third formation treatment is 85℃, and the current density is 10 mA / cm². 2 The applied voltage was 120% Vf, and the formation time was 10 min.

[0236] Third heat treatment: The foil after the fifth stage of third formation is heat treated at 450℃ for 2 minutes.

[0237] Fifth-stage fourth formation: The foil, after the third heat treatment, undergoes a fifth-stage fourth formation treatment in an aqueous solution containing 8% boric acid and 0.2% ammonium pentaborate. The temperature for the fifth-stage fourth formation treatment is 60℃, and the current density is 8 mA / cm². 2 The applied voltage was 120% Vf, and the formation time was 2 min.

[0238] Third phosphoric acid treatment: The foil, after undergoing the fifth-stage fourth formation, was treated in a 0.2% phosphoric acid solution at 30°C for 2 minutes, then removed and dried to obtain the electrode foil. The properties of the prepared electrode foil are shown in Table 1.

[0239] Comparative Example 4:

[0240] The unformed foil from Example 1 was used for the formation process.

[0241] First pretreatment: The unformed foil was treated in nitric acid at 60°C and 1% by mass for 3 minutes.

[0242] Second pretreatment: The unformed foil after the first pretreatment is treated in pure water at 95°C for 15 minutes.

[0243] Primary formation: The foil, after the second pretreatment, undergoes primary formation in an aqueous solution containing 2% boric acid, 0.3% adipic acid, and adipic acid salt. The primary formation temperature is 85℃, and the current density is 55 mA / cm². 2 The applied voltage was 30% Vf, and the formation time was 10 min.

[0244] Secondary formation: The foil after primary formation is subjected to secondary formation treatment in an aqueous solution containing 2% boric acid, 0.3% adipic acid, and adipic acid salt. The temperature of the secondary formation treatment is 85℃, and the current density is 50mA / cm². 2 The applied voltage was 60% Vf, and the formation time was 10 min.

[0245] Tertiary formation: The foil, after secondary formation, undergoes a tertiary formation treatment in an aqueous solution containing 4% boric acid, 0.25% adipic acid, and adipic acid salt. The tertiary formation treatment temperature is 85℃, and the current density is 40 mA / cm². 2 The applied voltage was 90% Vf, and the formation time was 12 min.

[0246] Liquid electrostatic treatment: The tertiary formed foil was electrostatically treated in a mixed solution of 4% adipic acid and adipic acid salt and 0.2% borax. The electrostatic treatment temperature was 30℃, the voltage was 20V, the current was 1500A, and the treatment time was 12min.

[0247] Fourth-stage formation: The foil, after liquid-fed treatment, undergoes a fourth-stage formation process in an aqueous solution containing 5% boric acid and 0.3% ammonium pentaborate. The fourth-stage formation process is carried out at a temperature of 85℃ and a current density of 35 mA / cm². 2 The applied voltage was 100% Vf, and the formation time was 15 min.

[0248] The fifth-stage first formation: The foil, after the fourth-stage formation, undergoes a fifth-stage first formation treatment in an aqueous solution containing 8% boric acid and 0.2% ammonium pentaborate. The fifth-stage first formation temperature is 85℃, and the current density is 25mA / cm². 2 The applied voltage was 120% Vf, and the formation time was 30 min.

[0249] First heat treatment: The foil sheet after the first five-stage formation is subjected to high-temperature heat treatment at 450℃ for 2 minutes.

[0250] First phosphoric acid treatment: The foil after the first heat treatment is treated in a phosphoric acid solution with a mass concentration of 6% at 60°C for 7 minutes.

[0251] Fifth-stage second formation: The foil treated with the first phosphoric acid is subjected to a fifth-stage second formation treatment in an aqueous solution containing 8% boric acid and 0.2% ammonium pentaborate. The temperature of the fifth-stage second formation treatment is 85℃, and the current density is 13mA / cm². 2 The applied voltage was 120% Vf, and the formation time was 10 min.

[0252] Second heat treatment: The foil that has undergone the second formation of the fifth stage is subjected to a second heat treatment at 450°C for 2 minutes.

[0253] Second phosphoric acid treatment: The foil after the second heat treatment is treated in a phosphoric acid solution with a mass concentration of 5% at 60°C for 7 minutes.

[0254] Fifth-stage third formation: The foil treated with the second phosphoric acid is subjected to a fifth-stage third formation treatment in an aqueous solution containing 8% boric acid and 0.2% ammonium pentaborate. The temperature of the fifth-stage third formation treatment is 85℃, and the current density is 10 mA / cm². 2 The applied voltage was 120% Vf, and the formation time was 10 min.

[0255] Third heat treatment: The foil after the fifth stage of third formation is heat treated at 450℃ for 2 minutes.

[0256] Fifth-stage fourth formation: The foil, after the third heat treatment, undergoes a fifth-stage fourth formation treatment in an aqueous solution containing 8% boric acid and 0.2% ammonium pentaborate. The temperature for the fifth-stage fourth formation treatment is 60℃, and the current density is 8 mA / cm². 2 The applied voltage was 120% Vf, and the formation time was 2 min.

[0257] Third phosphoric acid treatment: The foil, after undergoing the fifth-stage fourth formation, was treated in a 0.2% phosphoric acid solution at 30°C for 2 minutes, then removed and dried to obtain the electrode foil. The properties of the prepared electrode foil are shown in Table 1.

[0258] Comparative Example 5:

[0259] The unformed foil from Example 1 was used for the formation process.

[0260] First pretreatment: The unformed foil was treated in pure water at 85°C for 2 minutes.

[0261] Second pretreatment: The unformed foil after the first pretreatment is treated in pure water at 95°C for 15 minutes.

[0262] Primary formation: The foil, after the second pretreatment, undergoes primary formation in an aqueous solution containing 2% boric acid, 0.4% azelaic acid and azelate, and 0.3% adipic acid and adipicate. The primary formation temperature is 85℃, and the current density is 55 mA / cm². 2 The applied voltage was 30% Vf, and the formation time was 10 min.

[0263] Secondary formation: The foil after primary formation is subjected to secondary formation treatment in an aqueous solution containing 2% boric acid, 0.3% azelaic acid and azelate, and 0.3% adipic acid and adipicate. The temperature of the secondary formation treatment is 85℃, and the current density is 50mA / cm². 2 The applied voltage was 60% Vf, and the formation time was 10 min.

[0264] Tertiary formation: The foil, after secondary formation, undergoes a tertiary formation treatment in an aqueous solution containing 4% boric acid, 0.25% azelaic acid and azelate, and 0.25% adipic acid and adipicate. The tertiary formation treatment temperature is 85℃, and the current density is 40 mA / cm². 2 The applied voltage was 90% Vf, and the formation time was 12 min.

[0265] Liquid electrostatic treatment: The tertiary formed foil was electrostatically treated in a mixed solution of 4% adipic acid and adipic acid salt and 0.2% borax. The electrostatic treatment temperature was 30℃, the voltage was 20V, the current was 1500A, and the treatment time was 12min.

[0266] Fourth-stage formation: The foil, after liquid-fed treatment, undergoes a fourth-stage formation process in an aqueous solution containing 5% boric acid and 0.3% ammonium pentaborate. The fourth-stage formation process is carried out at a temperature of 85℃ and a current density of 35 mA / cm².2 The applied voltage was 100% Vf, and the formation time was 15 min.

[0267] The fifth-stage first formation: The foil, after the fourth-stage formation, undergoes a fifth-stage first formation treatment in an aqueous solution containing 8% boric acid and 0.2% ammonium pentaborate. The fifth-stage first formation temperature is 85℃, and the current density is 25mA / cm². 2 The applied voltage was 120% Vf, and the formation time was 30 min.

[0268] First heat treatment: The foil sheet after the first five-stage formation is subjected to high-temperature heat treatment at 450℃ for 2 minutes.

[0269] Fifth-stage second formation: The foil treated with the first phosphoric acid is subjected to a fifth-stage second formation treatment in an aqueous solution containing 8% boric acid and 0.2% ammonium pentaborate. The temperature of the fifth-stage second formation treatment is 85℃, and the current density is 13mA / cm². 2 The applied voltage was 120% Vf, and the formation time was 10 min.

[0270] Second heat treatment: The foil that has undergone the second formation of the fifth stage is subjected to a second heat treatment at 450°C for 2 minutes.

[0271] First phosphoric acid treatment: The foil after the second heat treatment is treated in a 5% phosphoric acid solution at 60°C for 7 minutes.

[0272] Fifth-stage third formation: The foil treated with the second phosphoric acid is subjected to a fifth-stage third formation treatment in an aqueous solution containing 8% boric acid and 0.2% ammonium pentaborate. The temperature of the fifth-stage third formation treatment is 85℃, and the current density is 10 mA / cm². 2 The applied voltage was 120% Vf, and the formation time was 10 min.

[0273] Third heat treatment: The foil after the fifth stage of third formation is heat treated at 450℃ for 2 minutes.

[0274] Fifth-stage fourth formation: The foil, after the third heat treatment, undergoes a fifth-stage fourth formation treatment in an aqueous solution containing 8% boric acid and 0.2% ammonium pentaborate. The temperature for the fifth-stage fourth formation treatment is 60℃, and the current density is 8 mA / cm². 2 The applied voltage was 120% Vf, and the formation time was 2 min.

[0275] Second phosphoric acid treatment: The foil, after undergoing the fourth formation in five stages, was treated in a 0.2% phosphoric acid solution at 30°C for 2 minutes, then removed and dried to obtain the electrode foil. The properties of the prepared electrode foil are shown in Table 1.

[0276] Table 1 Performance indicators of the electrode foils in each embodiment and comparative example

[0277]

[0278] Where Vt(V): is the withstand voltage value; Cap(μF / cm) 2 ): Specific capacity; Tr60(s): Hydration pressure rise time, i.e., the pressure rise time tested after the aluminum foil has been boiled in boiling water for 1 hour; LC(mA / 5cm) 2 ): This represents leakage current. Vt, Tr, and LC are all tested using a TV tester; Cap is tested using an LCR digital bridge.

[0279] As shown in Table 1, the present invention improves the specific capacity of the electrode foil by adding organic acids and their corresponding salts, such as citric acid and citrate, azelaic acid and azelate, and adipic acid and adipicate, to the forming solutions of the first, second, and third forming processes. By setting a first pretreatment step, residual substances in the foil sintering process can be effectively removed, which helps to reduce the leakage current of the electrode foil and facilitates the formation of a better water-aluminum film in the second boiling reaction. By adding multiple heat treatments and phosphoric acid treatments in the later forming stages (such as the fifth forming stage), the hydration pressure rise time and leakage current of the electrode foil can be effectively reduced.

[0280] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0281] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for preparing an electrode foil, characterized in that, Includes the following steps: Provides an unformed foil, the unformed foil comprising an aluminum foil substrate and an aluminum powder sintered layer disposed on at least one surface of the aluminum foil substrate; and The unformed foil is subjected to first-stage formation, second-stage formation, third-stage formation, power feeding treatment, fourth-stage formation, and fifth-stage formation treatment in sequence; The solvent for the formation solutions used in the first-stage, second-stage, and third-stage formations is water, and the solutes include boric acid, citric acid and citrate, or azelaic acid and azelate, adipic acid and adipicate; the solvent for the formation solutions used in the fourth-stage and fifth-stage formations is water, and the solutes include boric acid and ammonium salts; the feed tank solution for the power feeding treatment includes adipic acid and adipicate, or citric acid and citrate, and borax; The five-stage formation process includes, in sequence, a first-stage formation, a first-stage heat treatment, a first-stage phosphoric acid treatment, a second-stage formation, a second-stage heat treatment, a second-stage phosphoric acid treatment, a third-stage formation, a third-stage heat treatment, a fourth-stage formation, and a third-stage phosphoric acid treatment. The first heat treatment is performed at a temperature of 400-550℃ for 1-3 minutes; the first phosphoric acid treatment uses a phosphoric acid solution with a mass concentration of 4%-8%, a temperature of 55-75℃, and a treatment time of 2-8 minutes; the second heat treatment is performed at a temperature of 400-550℃ for 1-3 minutes; the second phosphoric acid treatment uses a phosphoric acid solution with a mass concentration of 4%-8%, a temperature of 55-75℃, and a treatment time of 2-8 minutes; the third heat treatment is performed at a temperature of 400-550℃ for 1-3 minutes; the third phosphoric acid treatment uses a phosphoric acid solution with a mass concentration of 0.1%-1%, a temperature of 25-45℃, and a treatment time of 2-8 minutes.

2. The method for preparing the electrode foil according to claim 1, characterized in that, In the forming solution used in the primary formation, the mass concentration of boric acid is 0.3%~3%, the mass concentration of citric acid and citrate or azelaic acid and azelaic acid is 0.05%~0.8%, and the mass concentration of adipic acid and adipic acid is 0.05%~0.8%; the temperature of the primary formation is 80~95℃, and the current density is 30~60 mA / cm². 2 The applied voltage is 30%~35% Vf, and the formation time is 8~18 min.

3. The method for preparing the electrode foil according to claim 1, characterized in that, In the formation solution used for the secondary formation, the mass concentration of boric acid is 0.3%~3%, the mass concentration of citric acid and citrate or azelaic acid and azelaic acid is 0.03%~0.6%, and the mass concentration of adipic acid and adipic acid is 0.03%~0.6%; the temperature of the secondary formation is 80~95℃, and the current density is 30~60mA / cm. 2 The applied voltage is 60%~70% Vf, and the formation time is 8~18 min.

4. The method for preparing the electrode foil according to claim 1, characterized in that, In the forming solution used in the three-stage formation, the mass concentration of boric acid is 0.5%~5%, the mass concentration of citric acid and citrate or azelaic acid and azelaic acid is 0.02%~0.5%, and the mass concentration of adipic acid and adipic acid is 0.02%~0.5%; the temperature of the three-stage formation is 80~95℃, and the current density is 25~55mA / cm. 2 The applied voltage is 85%~95% Vf, and the formation time is 8~18 min.

5. The method for preparing the electrode foil according to claim 1, characterized in that, In the formation solution of the fourth-stage formation, the mass concentration of boric acid is 1%~10%, and the mass concentration of ammonium salt is 0.05%~0.5%; the temperature of the fourth-stage formation is 80~95℃, and the current density is 10~40 mA / cm². 2 The applied voltage is 95%~110% Vf, and the formation time is 12~27 min.

6. The method for preparing the electrode foil according to claim 1, characterized in that, In the forming solution used for the first stage of the fifth-stage formation, the mass concentration of boric acid is 1%~10%, and the mass concentration of ammonium salt is 0.03%~0.3%; the temperature of the first stage of the fifth-stage formation is 80~95℃, and the current density is 15~40mA / cm². 2 The applied voltage is 110%~130% Vf, and the formation time is 25~35 min.

7. The method for preparing the electrode foil according to claim 1, characterized in that, In the forming solution used in the fifth-stage second formation, the mass concentration of boric acid is 1%~10%, and the mass concentration of ammonium salt is 0.01%~0.3%; the temperature of the fifth-stage second formation is 80~95℃, and the current density is 1~15mA / cm². 2 The applied voltage is 110%~130% Vf, and the formation time is 8~18 min.

8. The method for preparing the electrode foil according to claim 1, characterized in that, In the forming solution used in the fifth-stage third formation, the mass concentration of boric acid is 1%~10%, and the mass concentration of ammonium salt is 0.03%~0.3%; the temperature of the fifth-stage third formation is 80~95℃, and the current density is 1~15mA / cm². 2 The applied voltage is 110%~130% Vf, and the formation time is 8~18 min.

9. The method for preparing the electrode foil according to claim 1, characterized in that, In the forming solution used in the fifth-stage fourth formation, the mass concentration of boric acid is 1%~10%, and the mass concentration of ammonium salt is 0.01%~0.3%; the temperature of the fifth-stage third formation is 40~80℃, and the current density is 1~15mA / cm. 2 The applied voltage is 110%~130% Vf, and the formation time is 0.5~5 min.

10. The method for preparing the electrode foil according to any one of claims 1 to 9, characterized in that, Before performing primary formation on the unformed foil, the preparation method further includes the following steps: The unformed foil is placed in a first pretreatment solution for a first pretreatment; the first pretreatment solution is water or nitric acid with a mass concentration of 0.5% to 3%; the temperature of the water in the first pretreatment is 80 to 98°C, the temperature of the nitric acid is 50 to 80°C, and the treatment time of the first pretreatment is 1 to 5 minutes. as well as The unformed foil after the first pretreatment is placed in a second pretreatment solution for a second pretreatment; the second pretreatment solution is water, the treatment temperature of the second pretreatment is 90~98℃, and the treatment time is 5~20min.

11. The method for preparing the electrode foil according to any one of claims 1 to 9, characterized in that, The power supply process includes the following steps: The unformed foil is placed in a feeding bath for feeding treatment. The feeding bath is a mixed solution containing 2%~7% adipic acid and adipic acid salt or citric acid and citrate, and 0.1%~1% borax. The feeding treatment temperature is 15~45℃, the voltage is 15~35V, the current is 650~1550A, and the treatment time is 8~18min.

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