Formed foil and preparation method thereof

Abstract

The invention provides a formed foil and a preparation method thereof. The preparation method of the formed foil comprises the following steps: carrying out pretreatment on an aluminum foil, namely carrying out at least one high-temperature treatment and acid treatment on the aluminum foil; and carrying out multi-stage formation treatment on the pretreated aluminum foil. According to the invention, the hydration resistance of the formed foil can be improved, and the reliability and stability of the aluminum electrolytic capacitor can be improved.

Description

Technical Field

[0001] This disclosure relates to the field of aluminum electrolytic capacitor technology, and in particular to a method for preparing a formed foil and a formed foil obtained by the method. Background Technology

[0002] Aluminum electrolytic capacitors are widely used in various electronic products due to their excellent performance, large capacitance, low price, and ease of processing. The electrolytic foil, as a key material in aluminum electrolytic capacitors, directly affects the capacitor's performance.

[0003] The electrolyte in aluminum electrolytic capacitors typically contains a certain proportion of water to achieve higher conductivity. However, water molecules can penetrate the oxide film layer of the forming foil and undergo a hydration reaction, thereby damaging the insulating structure of the oxide film, deteriorating its dielectric properties, and consequently leading to performance degradation and a shortened lifespan of the capacitor. Therefore, the hydration resistance of the forming foil is crucial for aluminum electrolytic capacitors, and it is necessary to further improve its hydration resistance. Summary of the Invention

[0004] This disclosure provides a method for preparing electroformed foil and an electroformed foil.

[0005] This disclosure provides a method for preparing a chemically formed foil, comprising the following steps: pre-treating the aluminum foil, including at least one high-temperature treatment and acid treatment of the aluminum foil; and performing multi-stage chemical formation treatment on the pre-treated aluminum foil.

[0006] According to the method for preparing the electroformed foil disclosed herein, the aluminum foil is subjected to at least one high-temperature treatment and acid treatment, including: performing a first acid treatment on the aluminum foil using an organic acid solution; performing a first high-temperature treatment on the aluminum foil after the first acid treatment; performing a second acid treatment on the aluminum foil after the first high-temperature treatment using an inorganic acid solution; and performing a second high-temperature treatment on the aluminum foil after the second acid treatment.

[0007] According to the method for preparing the electrolytic foil disclosed herein, the organic acid solution includes one or more aqueous solutions of citric acid, tartaric acid, salicylic acid, adipic acid, azelaic acid, maleic acid, fumaric acid, and itaconic acid.

[0008] According to the method for preparing the chemically formed foil disclosed herein, the concentration of the organic acid solution is 2-10 wt%.

[0009] According to the method for preparing the electrolytic foil disclosed herein, the inorganic acid solution includes an aqueous solution of one or more of phosphoric acid or phosphate, silicic acid or silicate.

[0010] According to the method for preparing the electrolytic foil disclosed herein, the concentration of the inorganic acid solution is 0.2-1 wt%.

[0011] According to the method for preparing the electroformed foil disclosed herein, the aluminum foil that has undergone a first acid treatment is subjected to a first high-temperature treatment, which includes drying the aluminum foil that has undergone a first acid treatment at a temperature range of 300-400°C; the aluminum foil that has undergone a second acid treatment is subjected to a second high-temperature treatment, which includes drying the aluminum foil that has undergone a second acid treatment at a temperature range of 300-400°C.

[0012] According to the method for preparing the electroformed foil disclosed herein, after performing multi-stage electroformation treatment on the pretreated aluminum foil, the method further includes: performing at least one acid treatment and at least one post-treatment on the multi-stage electroformed aluminum foil using an acid treatment solution.

[0013] According to the preparation method of the formed foil disclosed herein, the acid treatment solution for acid treatment of the aluminum foil that has undergone multi-stage formed treatment is a phosphoric acid solution with a concentration of 1-10 wt%.

[0014] This disclosure also provides a chemically formed foil, which is obtained by a method for preparing chemically formed foil according to this disclosure.

[0015] The method for preparing the electroformed foil disclosed herein involves subjecting the aluminum foil to at least one high-temperature treatment and acid treatment via a pretreatment process before performing multi-stage electroformation treatment. This process can form a hydration-resistant oxide film on the surface of the aluminum foil and create better starting conditions for subsequent multi-stage electroformation treatments. This is beneficial for improving the quality of the oxide film on the surface of the aluminum foil, thereby improving the hydration resistance of the electroformed foil and enhancing the reliability and stability of aluminum electrolytic capacitors. Attached Figure Description

[0016] Figure 1 This is a flowchart of a method for preparing a low-hydration electrolytic foil according to an embodiment of the present disclosure.

[0017] Figure 2 This is a flowchart of a method for preparing a low-hydration electrolytic foil according to another embodiment of the present disclosure. Detailed Implementation

[0018] To enable those skilled in the art to better understand the technical solutions of this disclosure, the technical solutions of this disclosure will be described in detail below with reference to the accompanying drawings.

[0019] Exemplary embodiments will be described more fully below with reference to the accompanying drawings; however, these exemplary embodiments may be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will enable those skilled in the art to fully understand the scope of this disclosure.

[0020] Where there is no conflict, the various embodiments of this disclosure and the features thereof in the embodiments may be combined with each other.

[0021] As used herein, the term “and / or” includes any and all combinations of one or more related enumerated entries.

[0022] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this disclosure. As used herein, the singular forms “a” and “the” are also intended to include the plural forms unless the context clearly indicates otherwise. It will also be understood that when the terms “comprising” and / or “made of” are used in this specification, the presence of the stated feature, integral, step, operation, element, and / or component is specified, but the presence or addition of one or more other features, integrals, steps, operations, elements, components, and / or groups thereof is not excluded.

[0023] Unless otherwise specified, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art. It will also be understood that terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant art and this disclosure, and will not be interpreted as having an idealized or overly formal meaning, unless expressly so defined herein.

[0024] This disclosure provides a method for preparing electrolytic foil, referring to... Figure 1 This includes the following steps: S2. Pre-treat the aluminum foil, including at least one high-temperature treatment and acid treatment; S3. Perform multi-stage formation treatment on the pretreated aluminum foil.

[0025] During the pretreatment process, the aluminum foil undergoes at least one high-temperature treatment and acid treatment. The acid treatment cleans the aluminum foil surface, improves its surface activity, removes uneven oxide layers, and repairs defects. It also generates a hydration-resistant oxide film on the aluminum foil surface, thereby enhancing its hydration resistance. For example, treating the aluminum foil with an aqueous solution containing phosphate ions causes the aluminum ions in the oxide film to react with the phosphate ions to form aluminum phosphate. Aluminum phosphate can prevent oxygen-containing substances (such as water) from migrating into the oxide film, thus preventing the formation of porous Al(OH)3 and significantly improving the oxide film's hydration resistance and moisture resistance. High-temperature treatment of the aluminum foil can form a denser and more stable hydration-resistant oxide film on its surface. For example, it can generate a dense oxide film structure dominated by γ'-Al2O3 crystals, further enhancing the aluminum foil's hydration resistance.

[0026] Pre-treatment of aluminum foil creates better starting conditions for subsequent multi-stage formation processes. Multi-stage formation processes based on pre-treatment result in a more uniform and dense oxide film. The resulting hydration-resistant oxide film significantly improves the aluminum foil's hydration resistance, reduces leakage current, increases breakdown voltage, and enhances formation efficiency, thereby improving the reliability and stability of aluminum electrolytic capacitors.

[0027] According to one embodiment of this disclosure, referring to Figure 2 The aluminum foil undergoes at least one high-temperature treatment and acid treatment, including: S21. Perform a first acid treatment on the aluminum foil using an organic acid solution; S22. Perform a first high-temperature treatment on the aluminum foil that has undergone the first acid treatment; S23. Use an inorganic acid solution to perform a second acid treatment on the aluminum foil that has undergone the first high-temperature treatment; S24. Perform a second high-temperature treatment on the aluminum foil that has undergone the second acid treatment.

[0028] In the pretreatment process, the aluminum foil undergoes multiple acid treatments. The first acid treatment cleans the aluminum foil surface, improves its surface activity, removes uneven oxide layers, and repairs defects. The second acid treatment involves the reaction of acid radicals with aluminum to form a hydration-resistant oxide film, thereby enhancing the aluminum foil's hydration resistance. For example, treating the aluminum foil with an aqueous solution containing phosphate ions causes the aluminum ions in the oxide film to react with the phosphate ions to form aluminum phosphate. Aluminum phosphate can prevent the migration of oxygen-containing substances (such as water) into the oxide film, thus preventing the formation of porous Al(OH)3 and significantly improving the oxide film's hydration resistance and moisture resistance. Multiple high-temperature treatments of the aluminum foil can form a denser and more stable hydration-resistant oxide film on its surface. For example, a dense oxide film structure dominated by γ'-Al2O3 crystals can be generated, further enhancing the aluminum foil's hydration resistance.

[0029] According to one embodiment of this disclosure, the organic acid solution includes one or more aqueous solutions of citric acid, tartaric acid, salicylic acid, adipic acid, azelaic acid, maleic acid, fumaric acid, and itaconic acid.

[0030] According to one embodiment of this disclosure, the concentration of the organic acid solution is 2-10 wt%.

[0031] According to one embodiment of this disclosure, the inorganic acid solution includes an aqueous solution of one or more of phosphoric acid or phosphate, silicic acid or silicate.

[0032] According to one embodiment of this disclosure, the concentration of the inorganic acid solution is 0.2-1 wt%.

[0033] According to one embodiment of this disclosure, the aluminum foil that has undergone a first acid treatment is subjected to a first high-temperature treatment, including: The aluminum foil that has undergone the first acid treatment is dried at a temperature range of 300-400℃. The aluminum foil that has undergone a second acid treatment is subjected to a second high-temperature treatment, including: The aluminum foil that has undergone a second acid treatment is then dried at a temperature range of 300-400℃.

[0034] According to one embodiment of this disclosure, referring to Figure 2 The method for preparing the formed foil further includes, after subjecting the pretreated aluminum foil to multi-stage formation treatment: S4. Perform at least one acid treatment and at least one post-treatment on the aluminum foil that has undergone multi-stage formation.

[0035] The acid treatment solution used for acid treatment of aluminum foil that has undergone multi-stage formation processes can contain anions derived from one or more of phosphoric acid or phosphates, silicic acid or silicates. The concentration of anions in the aqueous solution used for the acid treatment is 1-10%.

[0036] According to one embodiment of this disclosure, the acid treatment solution is a phosphoric acid solution with a concentration of 1-10 wt%.

[0037] In this disclosure, after a multi-stage formation process, acid treatment and post-treatment can be repeated and interleaved, for example, after one acid treatment, two post-treatments are performed, followed by another acid treatment and another post-treatment.

[0038] According to one embodiment of this disclosure, after the multi-stage formation process, the acid treatment and post-treatment can be performed as follows: Acid treatment: Immerse aluminum foil in a 1-10% phosphoric acid solution at 50-80℃ for 10-15 minutes, remove and wash it, and then perform heat treatment at 400-550℃. Post-processing 1: Temperature 65-85℃, voltage 90-95% Vf, current density 30-50 mA / cm² 2 Under these conditions, aluminum foil was treated in an ammonium salt aqueous solution with a concentration of 4-6 wt% for 10-15 min; Post-processing 2: Temperature 65-85℃, voltage 90-95% Vf, current density 30-50 mA / cm² 2 Under these conditions, aluminum foil is treated in an ammonium salt aqueous solution with a concentration of 3-4 wt% for 5-10 min; Acid treatment: Immerse aluminum foil in a 1-8% phosphoric acid solution at 50-80℃ for 1-7 minutes, remove and wash it, and then perform heat treatment at 400-550℃. Post-processing 3: Temperature 65-85℃, voltage 90-95% Vf, current density 30-50 mA / cm² 2 Under these conditions, aluminum foil is treated in an aqueous solution of ammonium salt with a concentration of 1-2 wt% for 5-10 minutes.

[0039] According to one embodiment of this disclosure, the ammonium salt is one or more selected from dodecyltrimethylammonium bromide, dodecyl alcohol ether ammonium sulfate, ammonium dihydrogen phosphate, ammonium adipate, ammonium citrate, and ammonium oxalate.

[0040] According to one embodiment of this disclosure, referring to Figure 2 Before pretreatment of the aluminum foil, the following steps are also included: S1. Place the aluminum foil in pure water to react.

[0041] According to one embodiment of this disclosure, the pure water treatment involves immersing the corroded aluminum foil in deionized water at 90-95°C for 10-18 minutes.

[0042] According to one embodiment of this disclosure, the multi-stage formation process includes: at a temperature of 65-85°C and a current density of 30-50 mA / cm². 2 Under these conditions, the voltage is gradually increased in each stage of the forming solution to perform a forming process on the pretreated aluminum foil.

[0043] Generally, the formation process can be divided into 4-6 stages. For example, the following six-stage formation process can be performed.

[0044] Primary formation: at a temperature of 65-85℃, a voltage of 10-30% Vf, and a current density of 30-50 mA / cm². 2 Under the specified conditions, the formation process is carried out in a formation solution containing 5-15 wt% ammonium salt, 10-50 wt% boric acid or borate and 0.1-2 wt% organic acid for 5-10 min.

[0045] Secondary formation: at a temperature of 65-85℃, a voltage of 30-50%VF, and a current density of 30-50mA / cm². 2 Under the conditions specified, the formation process is carried out in a formation solution containing 1-10 wt% ammonium salt and 10-60 wt% boric acid or borate for 5-10 min.

[0046] Tertiary formation: at a temperature of 65-85℃, a voltage of 40-60% Vf, and a current density of 30-50 mA / cm². 2 Under the specified conditions, the formation process is carried out in a formation solution containing 5-10 wt% ammonium salt, 10-60 wt% boric acid or borate and 0.1-3 wt% organic acid for 7-15 min.

[0047] Fourth-level formation: at a temperature of 65-85℃, a voltage of 50-70% Vf, and a current density of 30-50 mA / cm². 2 Under the conditions specified, the formation process is carried out in a formation solution containing 2-15 wt% phosphate, 10-60 wt% boric acid or borate and 0.1-3 wt% organic acid for 5-10 min.

[0048] Five-stage formation: at a temperature of 65-85℃, a voltage of 85-95% Vf, and a current density of 30-50 mA / cm². 2 Under the conditions specified, the formation process is carried out in a formation solution containing 4-5% ammonium salt and 10-60 wt% boric acid or borate for 10-20 min.

[0049] Sixth-stage formation: at a temperature of 65-85℃, a voltage of 90-95% Vf, and a current density of 30-50 mA / cm². 2 Under the conditions specified, the formation process is carried out in a formation solution containing 5-7% ammonium salt and 10-60 wt% boric acid or borate for 15-20 min.

[0050] According to one embodiment of this disclosure, the method for preparing low-hydration foil includes the following steps: Preprocessing: The aluminum foil is placed in pure water at 90-95℃ for 10-18 minutes to react. After removal, soak in an organic acid solution with a temperature of 50~70℃ and a concentration of 2~7%; After cleaning, the product is dried at a temperature of 300~400℃. After removal, immerse it in a 0.2-1% phosphoric acid solution at 30-50℃; After being removed and washed, the product is dried at a temperature of 300~400℃. Primary formation: Temperature 65~85℃, time 5~10min, voltage 10~30%VF, current density 30~50mA / cm² 2 The primary formation solution consists of 5-15 wt% ammonium salt, 10-50 wt% boric acid or borate, and 0.1-2 wt% organic acid. After removal, it is washed with water. Secondary formation: Temperature 65~85℃, time 5~10min, voltage 30~50%VF, current density 30~50mA / cm² 2 The secondary formation solution consists of 1-10 wt% ammonium salt and 10-60 wt% boric acid or borate, and is washed with water after removal. Three-stage formation: temperature 65~85℃, time 7~15min, voltage 40~60%VF, current density 30~50mA / cm² 2The composition of the tertiary formation solution is as follows: 5~10wt% ammonium salt, 10~60wt% boric acid or borate, 0.1~3wt% organic acid, and then washed with water. Fourth-stage formation: Temperature 65~85℃, Time 5~10min, Voltage 50~70%VF, Current density 30~50mA / cm² 2 The composition of the fourth-stage formation solution is: 2~15wt% phosphate, 10~60wt% boric acid or borate, 0.1~3wt% organic acid, and it is washed with water after removal. Five-stage formation: 4-5% ammonium salt, 10-60 wt% boric acid or borate, temperature 65-85℃, time 10-20 min, voltage 85-95% Vf, current density 30-50 mA / cm² 2 Take it out and wash it with water; Six-stage formation: 5-7% ammonium salt, temperature 65-85℃, 10-60wt% boric acid or borate, time 15-20min, voltage 90-95% Vf, current density 30-50 mA / cm² 2 Take it out and wash it with water; Acid treatment: Immerse in a 1-10% phosphoric acid solution for 1-7 minutes at a temperature of 50-80℃, then remove, wash, and dry at a temperature of 400-550℃. Post-treatment 1: 4-6% ammonium salt, temperature 65-85℃, time 10-15 min, voltage 90-95% Vf, current density 30-50 mA / cm² 2 Take it out and wash it with water; Post-treatment 2: 3-4% ammonium salt, temperature 65-85℃, time 5-10 min, voltage 90-95% Vf, current density 30-50 mA / cm² 2 Take it out and wash it with water; Acid treatment: Immerse in a 1-8% phosphoric acid solution for 1-7 minutes at 50-80℃, then remove, wash, and dry at 400-550℃. Post-treatment 3: 1-2% ammonium salt, temperature 65-85℃, time 5-10 min, voltage 90-95% Vf, current density 30-50 mA / cm² 2 Wash and dry.

[0051] This disclosure also provides a chemically formed foil, which is obtained by a method for preparing chemically formed foil according to this disclosure.

[0052] According to one embodiment of this disclosure, a chemically formed foil is obtained according to the preparation method of the chemically formed foil of this disclosure, which has good water resistance.

[0053] To enable those skilled in the art to more clearly understand the technical solutions provided by the embodiments of this disclosure, the technical solutions provided by the embodiments of this disclosure will be described in detail below through specific embodiments: Example 1 The etched foil was reacted in pure water at 93°C for 13 minutes. After removal, it was immersed in a 2% maleic acid solution at 55°C. After cleaning, it underwent heat treatment at 400°C. Next, it was immersed in a 0.2% phosphoric acid solution at 40°C. After cleaning, it underwent heat treatment at 350°C. Finally, it underwent a primary chemical reaction: 12wt% ammonium adipate, 25wt% boric acid, and 1.3wt% citric acid at 82°C for 8 minutes, with a voltage of 30% Vf and a current density of 50 mA / cm². 2 After removal, rinse with water and proceed to secondary formation: temperature 85℃, time 5-10 min, voltage 45% Vf, current density 50 mA / cm². 2 The secondary formation solution consisted of 10 wt% ammonium salt and 20 wt% borax. After removal, it was washed with water and then proceeded to the tertiary formation stage: temperature 70℃, time 13 min, voltage 55% Vf, and current density 45 mA / cm². 2 The composition of the third-stage formation solution is: 9 wt% ammonium salt, 15 wt% boric acid, and 0.8 wt% azelaic acid. After removal, it is washed with water and then proceeds to the fourth-stage formation: temperature 83℃, time 9 min, voltage 70% Vf, and current density 40 mA / cm². 2 The fourth-stage formation solution consisted of 8 wt% ammonium tartrate, 18 wt% boric acid, and 0.7 wt% tartaric acid. After removal, it was washed with water and then proceeded to the fifth-stage formation: 4.5% ammonium citrate and 5 wt% boric acid, at a temperature of 80℃ for 10-20 minutes, a voltage of 90% Vf, and a current density of 35 mA / cm². 2 After removal, the sample is washed with water and then undergoes a six-stage formation process: 6% ammonium adipate, temperature 85℃, 40wt% sodium metaborate, time 18min, voltage 95% Vf, current density 30mA / cm². 2 After cleaning, remove and heat-treat at 400-550℃; then perform post-treatment one: 4.5% ammonium adipate, temperature 85℃, voltage 95% Vf, current density 30 mA / cm². 2 Time: 12 min; After rinsing with water, perform post-treatment two: 3.2% ammonium adipate, temperature: 85℃, voltage: 95% Vf, current density: 30 mA / cm² 2 Time: 8 min; after rinsing with water, perform heat treatment at 350-450℃; after rinsing with water, perform post-treatment three: 1.5% ammonium dihydrogen phosphate, temperature: 80℃, voltage: 95% Vf, current density: 30 mA / cm² 2 Wash for 7 minutes, then dry.

[0054] Example 2 The etched foil was reacted in pure water at 93°C for 13 minutes. After removal, it was immersed in a 2% maleic acid solution at 55°C. After cleaning, it underwent heat treatment at 400°C. Next, it was immersed in a 0.2% phosphoric acid solution at 40°C. After cleaning, it underwent heat treatment at 350°C. Finally, it underwent a primary chemical reaction: 12wt% ammonium adipate, 25wt% boric acid, and 1.3wt% citric acid at 82°C for 8 minutes, with a voltage of 30% Vf and a current density of 50 mA / cm². 2 After removal, rinse with water and proceed to secondary formation: temperature 85℃, time 5-10 min, voltage 45% Vf, current density 50 mA / cm². 2 The secondary formation solution consisted of 10 wt% ammonium salt and 20 wt% borax. After removal, it was washed with water and then proceeded to the tertiary formation stage: temperature 70℃, time 13 min, voltage 55% Vf, and current density 45 mA / cm². 2 The composition of the third-stage formation solution is: 9 wt% ammonium salt, 15 wt% boric acid, and 0.8 wt% azelaic acid. After removal, it is washed with water and then proceeds to the fourth-stage formation: temperature 83℃, time 9 min, voltage 70% Vf, and current density 40 mA / cm². 2 The fourth-stage formation solution consisted of 8 wt% ammonium tartrate, 18 wt% boric acid, and 0.7 wt% tartaric acid. After removal, it was washed with water and then proceeded to the fifth-stage formation: 4.5% ammonium citrate and 5 wt% boric acid, at a temperature of 80℃ for 10-20 minutes, a voltage of 90% Vf, and a current density of 35 mA / cm². 2 After removal, the sample is washed with water and then undergoes a six-stage formation process: 6% ammonium adipate, temperature 85℃, 40wt% sodium metaborate, time 18min, voltage 95% Vf, current density 30mA / cm². 2 After rinsing with water, perform acid treatment: immerse in a 6% phosphoric acid solution for 3 minutes at 50℃; after rinsing, perform heat treatment at 400-550℃; after rinsing with water, perform post-treatment one: 4.5% ammonium adipate at 85℃, 95% Vf voltage, and 30 mA / cm² current. 2 Time: 12 min; After rinsing with water, perform post-treatment two: 3.2% ammonium adipate, temperature: 85℃, voltage: 95% Vf, current density: 30 mA / cm² 2 Time: 8 min; after rinsing with water, perform heat treatment at 350-450℃; after rinsing with water, perform post-treatment three: 1.5% ammonium dihydrogen phosphate, temperature: 80℃, voltage: 95% Vf, current density: 30 mA / cm² 2 Wash for 7 minutes, then dry.

[0055] Example 3 The etched foil was reacted in pure water at 93°C for 13 minutes. After removal, it was immersed in a 2% maleic acid solution at 55°C. After cleaning, it underwent heat treatment at 400°C. Next, it was immersed in a 0.2% phosphoric acid solution at 40°C. After cleaning, it underwent heat treatment at 350°C. Finally, it underwent a primary chemical reaction: 12wt% ammonium adipate, 25wt% boric acid, and 1.3wt% citric acid at 82°C for 8 minutes, with a voltage of 30% Vf and a current density of 50 mA / cm². 2 After removal, rinse with water and proceed to secondary formation: temperature 85℃, time 5-10 min, voltage 45% Vf, current density 50 mA / cm². 2 The secondary formation solution consisted of 10 wt% ammonium salt and 20 wt% borax. After removal, it was washed with water and then proceeded to the tertiary formation stage: temperature 70℃, time 13 min, voltage 55% Vf, and current density 45 mA / cm². 2 The composition of the third-stage formation solution is: 9 wt% ammonium salt, 15 wt% boric acid, and 0.8 wt% azelaic acid. After removal, it is washed with water and then proceeds to the fourth-stage formation: temperature 83℃, time 9 min, voltage 70% Vf, and current density 40 mA / cm². 2 The fourth-stage formation solution consisted of 8 wt% ammonium tartrate, 18 wt% boric acid, and 0.7 wt% tartaric acid. After removal, it was washed with water and then proceeded to the fifth-stage formation: 4.5% ammonium citrate and 5 wt% boric acid, at a temperature of 80℃ for 10-20 minutes, a voltage of 90% Vf, and a current density of 35 mA / cm². 2 After removal, the sample is washed with water and then undergoes a six-stage formation process: 6% ammonium adipate, temperature 85℃, 40wt% sodium metaborate, time 18min, voltage 95% Vf, current density 30mA / cm². 2 After removal, rinse with water and undergo acid treatment: soak in a 6% phosphoric acid solution for 3 minutes at 50℃; remove, rinse, and then heat-treat at 400-550℃; remove, rinse with water, and then undergo post-treatment one: 4.5% ammonium adipate at 85℃, voltage 95% Vf, and current density 30 mA / cm². 2 Time: 12 min; After rinsing with water, perform post-treatment two: 3.2% ammonium adipate, temperature: 85℃, voltage: 95% Vf, current density: 30 mA / cm² 2 Time: 8 min; After removal and rinsing, acid treatment: Immersion in 2% phosphoric acid solution for 2 min at 70℃, then rinsed and heat-treated at 460℃; After removal and rinsing, post-treatment three: 1.5% ammonium dihydrogen phosphate, temperature: 80℃, voltage: 95% Vf, current density: 30 mA / cm² 2 Wash for 7 minutes, then dry.

[0056] Comparative Example 1: Aluminum foil with a purity of 99.9% that has been etched was treated in pure water at 96℃ for 15 minutes. After removal, it underwent a six-stage formation process. The first stage of formation consisted of 10% ammonium adipate, 30% boric acid, and 0.7% adipic acid at 80℃ for 10 minutes, with a voltage of 10% Vf-30% Vf and a current density of 30 mA / cm². 2 After washing with water, it enters the secondary formation stage: 8% ammonium adipate, 25% boric acid, temperature 80℃, time 10 min, voltage 30% Vf-50% Vf, current density 30 mA / cm². 2 After washing with water, the process proceeds to the third-stage formation stage: 10% disodium hydrogen phosphate, 35% boric acid, temperature 80℃, time 12 min, voltage 40% Vf-60% Vf, and current density 45 mA / cm². 2 After washing with water, a four-stage formation process is performed: 8% disodium hydrogen phosphate, 30% borate, temperature 80℃, time 8 min, voltage 50%-70% VF, and current density 45 mA / cm². 2 After washing with water, it enters the fifth stage of formation: 6% disodium hydrogen phosphate, 20% boric acid, temperature 85℃, time 20min, voltage 70%-90% VF, current density 30 mA / cm². 2 After washing with water, it undergoes a sixth-stage formation process: 5% disodium hydrogen phosphate, temperature 90℃, time 25 min, voltage 80%-95% VF, and current density 30 mA / cm². 2 After washing with water, perform heat treatment at 450-550℃ for 2 minutes; after removing and washing again, perform post-treatment one: 3% disodium hydrogen phosphate at 85℃ for 15 minutes, with a voltage of 80%-95% VF and a current density of 30 mA / cm². 2 After washing with water, react in a 10% phosphoric acid solution at 65℃ for 6 minutes per tank; after washing with water, perform post-treatment two: 3% disodium hydrogen phosphate, temperature 85℃, time 12 minutes, voltage 80%-95% VF, current density 30 mA / cm². 2 After washing with water, heat-treat at 400-480℃ for 1.5 min; after removing and washing again, perform post-treatment three: 3% disodium hydrogen phosphate, temperature 85℃, time 10 min, voltage 80%-95% VF, current density 30 mA / cm². 2 Wash and dry.

[0057] The performance of the formed foils prepared in Examples 1-3 and the comparative examples was tested, and the results are shown in Table 1.

[0058] Table 1 Comparison of performance parameters of chemical foil in the examples and comparative examples As can be seen from the data in Table 1, the pressure rise time after boiling the formed foil in the embodiment is significantly shorter than that in the comparative example. The shorter pressure rise time after boiling indicates that the formed foil has good hydration resistance and the stability of the capacitor is improved.

[0059] Example embodiments have been disclosed herein, and while specific terminology has been used, it is for illustrative purposes only and should be construed as such, and is not intended to be limiting. In some instances, it will be apparent to those skilled in the art that features, characteristics, and / or elements described in connection with particular embodiments may be used alone, or in combination with features, characteristics, and / or elements described in connection with other embodiments, unless otherwise expressly indicated. Therefore, those skilled in the art will understand that various changes in form and detail may be made without departing from the scope of this disclosure as set forth by the appended claims.

Claims

1. A method for preparing electrolytic foil, characterized in that, Includes the following steps: Pre-treatment of aluminum foil includes at least one high-temperature treatment and acid treatment; The pretreated aluminum foil undergoes a multi-stage formation process.

2. The method for preparing the electroformed foil according to claim 1, characterized in that, The aluminum foil undergoes at least one high-temperature treatment and acid treatment, including: The aluminum foil was first acid-treated with an organic acid solution. The aluminum foil that has undergone the first acid treatment is subjected to a first high-temperature treatment. A second acid treatment is performed on the aluminum foil that has undergone the first high-temperature treatment using an inorganic acid solution. The aluminum foil that has undergone a second acid treatment is subjected to a second high-temperature treatment.

3. The method for preparing the electroformed foil according to claim 2, characterized in that, The organic acid solution includes one or more aqueous solutions of citric acid, tartaric acid, salicylic acid, adipic acid, azelaic acid, maleic acid, fumaric acid, and itaconic acid.

4. The method for preparing the electroformed foil according to claim 3, characterized in that, The concentration of the organic acid solution is 2-10 wt%.

5. The method for preparing the electroformed foil according to claim 2, characterized in that, The inorganic acid solution includes one or more aqueous solutions of phosphoric acid or phosphates, silicic acid or silicates.

6. The method for preparing the electroformed foil according to claim 5, characterized in that, The concentration of the inorganic acid solution is 0.2-1 wt%.

7. The method for preparing the electroformed foil according to any one of claims 2 to 6, characterized in that, The aluminum foil that has undergone the first acid treatment is subjected to a first high-temperature treatment, including: The aluminum foil that has undergone the first acid treatment is dried at a temperature range of 300-400℃. The aluminum foil that has undergone a second acid treatment is subjected to a second high-temperature treatment, including: The aluminum foil that has undergone a second acid treatment is then dried at a temperature range of 300-400℃.

8. The method for preparing the electroformed foil according to any one of claims 1 to 6, characterized in that, After subjecting the pretreated aluminum foil to multi-stage formation processing, the method for preparing the formed foil further includes: The aluminum foil that has undergone multi-stage formation treatment shall be subjected to at least one acid treatment and at least one post-treatment.

9. The method for preparing the electroformed foil according to claim 8, characterized in that, The acid treatment solution for the aluminum foil that has undergone multi-stage formation is a phosphoric acid solution with a concentration of 1-10 wt%.

10. A chemically formed foil, said chemically formed foil being obtained by the method for preparing chemically formed foil according to any one of claims 1 to 9.

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