A low leakage anode foil formation process prepared by ultra-low temperature treatment
By using liquid nitrogen cryogenic treatment technology to expose and repair internal defects in the oxide film during the anode foil formation process, the problem of increased leakage current in the high-temperature formation process was solved, and anode foil with low leakage current and long life was prepared.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- XINJIANG JOINWORLD CO LTD
- Filing Date
- 2022-03-31
- Publication Date
- 2026-06-26
AI Technical Summary
Existing high-temperature anode foil formation processes expose internal defects in the oxide film while promoting the nucleation and growth of crystalline alumina within the oxide film, increasing the crystallinity of the oxide film, which leads to increased leakage current and makes it difficult to further reduce it.
Using liquid nitrogen cryogenic treatment technology, aluminum foil is treated with liquid nitrogen after five-stage formation. By utilizing the difference in thermal expansion coefficients between the oxide film and the aluminum substrate, shrinkage cracks are generated to expose internal defects, which are then repaired and filled in boric acid solution to prepare anode foil with high amorphousness and low defect content.
It significantly reduces leakage current by 40%, extends the service life of the anode foil, while minimizing capacity loss and improving the density and self-repair capability of the oxide film.
Smart Images
Figure CN116936261B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of aluminum anode foil technology, specifically to a process for preparing low-leakage anode foil using ultra-low temperature processing. Background Technology
[0002] With the development of aluminum electrolytic capacitors, not only is high capacitance required for the anode foil, but its service life is also increasingly demanding, as leakage current is closely related to product lifespan. Traditional formation processes typically involve high-temperature boiling followed by boric acid or organic acid-based pre-formation, oven heat treatment, phosphoric acid depolarization, boric acid repair, post-treatment, and drying. Since the application of water-boiling energy-saving technology in the last century, oven heat treatment has been used in the anode foil industry. The hydrated film grown in water undergoes continuous dehydration and transformation during the later formation process, eventually forming a dielectric film. This transformation process does not consume additional electrical energy, thus saving power. However, the dehydration of the hydrated film is accompanied by significant volume shrinkage, creating numerous porosity defects within the oxide film. Without repair, this will significantly increase the leakage current of the anode foil. After developing oven heat treatment technology, JCC in Japan has reduced the leakage current of water-boiling energy-saving foil by 90%, meeting the application requirements of capacitors. Oven heat treatment utilizes the difference in thermal expansion coefficients between the oxide film and the aluminum substrate to generate thermal expansion cracks, fully exposing internal porosity defects. These defects are then filled during the formation repair process, reducing internal defects in the oxide film and lowering leakage current. Furthermore, high-temperature heat treatment further enhances the crystallinity of the oxide film, increasing the dielectric constant and thus increasing capacitance. However, this new crystallization process creates tiny pores within the oxide film, making further exposure and repair difficult, thus limiting existing techniques for reducing leakage current. Nowadays, many capacitor products have higher requirements for leakage current, and amorphous oxide films, with their high uniformity, low defect content, and better self-healing capabilities, have gained significant advantages.
[0003] Application number CN202110491685.4 discloses a forming foil for long-life aluminum electrolytic capacitors and its preparation process. The technology involves anodizing a high-voltage etched foil in a phosphoric acid aqueous solution at low temperature to form a pre-oxide film. Based on this pre-oxide film, a low-temperature, low-concentration sodium hydroxide solution is used for low-current forming. By increasing the content of the amorphous oxide film on the aluminum foil surface, i.e., the amorphous oxide film, a long-life aluminum electrolytic capacitor anode foil is prepared. This technology uses phosphoric acid, sodium hydroxide, and other raw materials to prepare a high-amorphous oxide film through low-temperature, low-current forming. Compared to existing anode foil forming processes, the anodizing efficiency is strictly limited by the low current, and the preparation time is extended. Furthermore, this process does not use water-boiling energy-saving technology, potentially increasing power consumption by more than 20% compared to existing industry processes.
[0004] Application number CN201710102991.8 discloses a formation method for reducing electrode foil leakage current. In this method, after the first three stages of formation, a specific solution (complexing reagent) is used to treat the aluminum ions in the hydrated alumina film, complexing them and modifying the hydrated alumina to inhibit excessive formation of the hydrated alumina film. Simultaneously, applying current under acidic conditions promotes the transformation of the hydrated alumina film into a dense, porous alumina film, reducing the hydrated alumina content from two aspects, improving the oxide film quality, and reducing the leakage current of the formed foil. This technology improves the final quality of the oxide film and reduces leakage current by modifying the hydrated film on the oxide film surface during the anodic oxidation process. However, compared with the preparation of amorphous oxide films, its effect on improving the leakage current of the anode foil is limited. Furthermore, the anode foil needs to be thoroughly cleaned before and after each immersion and electrolysis treatment to avoid contamination of the solutions at each stage, making the preparation process relatively complex and requiring a large amount of water. Summary of the Invention
[0005] In existing high-pressure anode foil formation technologies, oven heat treatment, while exposing internal defects in the oxide film, inevitably promotes the nucleation and growth of crystalline alumina within the oxide film, thus increasing the overall crystallinity of the oxide film. The present invention aims to provide a cryogenic process for preparing low-leakage anode foil. This process utilizes liquid nitrogen cryogenic treatment, taking advantage of the difference in thermal expansion coefficients between the oxide film and the aluminum substrate. Under cryogenic conditions, shrinkage cracks are generated, fully exposing internal defects in the oxide film. Simultaneously, it fails to provide energy for the nucleation and growth of crystalline alumina, thus not increasing the crystallinity of the oxide film. Ultimately, this process produces anode foil with high amorphousness and low defect content.
[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:
[0007] A cryogenic forming process for preparing low-leakage anode foil involves subjecting the etched foil to a five-stage forming process and liquid nitrogen treatment to obtain an anode foil with a final voltage (VF) specification. VF refers to the final voltage of the formed product, determined according to actual product requirements. The process specifically includes the following steps:
[0008] (1) Primary Formation: The etched foil, after being subjected to high-temperature boiling treatment, is placed in a primary formation solution for primary formation treatment. The primary formation solution consists of: adipic acid 0.8-1.6 g / L, citric acid 1.8-2.8 g / L, ammonium adipic acid 1.5-3 g / L, and the remainder being water. The primary formation treatment time is 8-12 min, the treatment temperature is 75-95℃, and the current density is 80 mA / cm². 2 The conversion voltage is 20-25% × Vf;
[0009] (2) Secondary Formation: The aluminum foil after primary formation is placed in a secondary formation solution for secondary formation treatment. The secondary formation solution consists of: adipic acid 0.5-1 g / L, boric acid 10-30 g / L, ammonium adipic acid 1-2 g / L, and the remainder is water. The secondary formation treatment time is 8-12 min, the treatment temperature is 75-95℃, and the current density is 80 mA / cm². 2 The conversion voltage is 45-51% × Vf;
[0010] (3) Tertiary Formation: The aluminum foil after secondary formation is placed in a tertiary formation solution for tertiary formation treatment. The composition of the tertiary formation solution is: ammonium pentaborate 1.5-3.5 g / L, boric acid 40-60 g / L, and the remainder is water. The tertiary formation treatment time is 8-12 min, the treatment temperature is 75-95℃, and the current density is 80 mA / cm². 2 The voltage is converted to 71-78% × Vf;
[0011] (4) Quaternary Formation: The aluminum foil after tertiary formation is placed in a quaternary formation solution for quaternary formation treatment. The quaternary formation solution consists of: ammonium pentaborate 1-2 g / L, boric acid 40-60 g / L, and the remainder is water. The quaternary formation treatment time is 8-12 min, the treatment temperature is 75-95℃, and the current density is 80 mA / cm². 2 The conversion voltage is 88-93% × Vf;
[0012] (5) Fifth-stage formation: The aluminum foil after the fourth-stage formation is placed in a fifth-stage formation solution for fifth-stage formation treatment. The fifth-stage formation solution consists of: ammonium pentaborate 0.5-1.5 g / L, boric acid 40-60 g / L, and the remainder is water. The fifth-stage formation treatment time is 8-12 min, the treatment temperature is 75-95℃, and the current density is 80 mA / cm². 2 , which is converted into voltage vf;
[0013] (6) First liquid nitrogen treatment: After the aluminum foil after the fifth-level formation treatment is pre-dried, it is then subjected to a first liquid nitrogen treatment. The temperature of the first liquid nitrogen treatment is -150 to -196℃, and the treatment time is 1-3 min.
[0014] (7) The aluminum foil after being treated with liquid nitrogen is subjected to a first repair treatment, a mid-treatment and a second repair treatment in sequence;
[0015] (8) After the aluminum foil is pre-dried after step (7), it is then subjected to a second liquid nitrogen treatment. The temperature of the second liquid nitrogen treatment is -150 to -196℃ and the treatment time is 1-3 min.
[0016] (9) After the aluminum foil is treated with liquid nitrogen twice, it is then subjected to three repair treatments, post-treatments and drying to obtain an anode foil with a specification of 530V.
[0017] In step (1) above, the high-temperature boiling treatment involves immersing the patient in pure water at 95°C or above (with an electrical conductivity of less than 5 μs / cm) for 5-15 minutes.
[0018] In steps (6) and (8) above, the pre-drying treatment is to dry the foil surface at a temperature of 70-80℃.
[0019] In step (7) above, the primary repair treatment involves using a primary repair solution to repair the oxide film. The primary repair solution consists of: 0.5-1.5 g / L ammonium pentaborate, 40-60 g / L boric acid, and the remainder is water. The primary repair treatment time is 8-12 min, the treatment temperature is 75-95℃, and the current density is 80 mA / cm². 2 The voltage is vf.
[0020] In step (7) above, the intermediate treatment is carried out in a phosphoric acid aqueous solution with a concentration of 60-80 g / L, for a treatment time of 3-4.5 min, and at a temperature of 55-75℃.
[0021] In step (7) above, the secondary repair treatment involves using a secondary repair solution to repair the oxide film. The secondary repair solution consists of: ammonium pentaborate 0.5-1.5 g / L, boric acid 40-60 g / L, and the remainder is water. The secondary repair treatment time is 8-12 min, the treatment temperature is 75-95℃, and the current density is 80 mA / cm². 2 The voltage is vf.
[0022] In step (9) above, the three-stage repair treatment involves using a three-stage repair solution to repair the oxide film. The three-stage repair solution consists of: ammonium pentaborate 0.5-1.5 g / L, boric acid 40-60 g / L, and the remainder is water. The three-stage repair treatment time is 8-12 min, the treatment temperature is 75-95℃, and the current density is 80 mA / cm². 2 The voltage is vf.
[0023] In step (9) above, the post-treatment involves immersing the sample in an aqueous solution of ammonium dihydrogen phosphate with a concentration of 6-9 g / L for 2-3 minutes at a treatment temperature of 30-60°C.
[0024] In step (9) above, the drying temperature of the drying process is 150-300℃ and the processing time is 2-3 minutes.
[0025] The design mechanism and beneficial effects of this invention are as follows:
[0026] 1. This invention aims to reduce the leakage current of the anode foil in aluminum electrolytic capacitors and extend the service life of the anode aluminum foil. By introducing liquid nitrogen cryogenic treatment technology in the formation and repair stage to replace the original oven, a high amorphous oxide film is prepared on the surface of the aluminum corrosion foil, reducing the defect content in the oxide film, giving it higher density, and improving its self-repair capability, thereby significantly reducing the leakage current of the anode foil and extending its service life.
[0027] 2. This invention introduces liquid nitrogen cryogenic treatment to replace the existing oven heat treatment, based on the existing anode foil formation process. Utilizing the difference in thermal expansion coefficients between the oxide film and the aluminum substrate, shrinkage cracks are generated under liquid nitrogen cryogenic treatment, fully exposing internal defects in the oxide film. Simultaneously, this does not increase the crystallinity of the oxide film, ultimately producing an anode foil with high amorphousness and low defect content, with minimal capacity loss.
[0028] 3. This invention utilizes a widely adopted energy-saving technology in the industry: high-temperature boiling of the aluminum etched foil before formation treatment. The hydrated film grown during boiling undergoes continuous dehydration and transformation during the later formation process, eventually forming a dielectric film. This transformation process does not consume additional electrical energy, thus saving power. However, the dehydration process of the hydrated film is accompanied by significant volume shrinkage, generating numerous porosity defects within the oxide film. If left untreated, this will significantly increase the leakage current of the anode foil, leading to the development of oven heat treatment. After developing oven heat treatment technology, Japan's JCC reduced the leakage current of the boiled foil by 90%, meeting the requirements for capacitor applications. Through heat treatment, the difference in thermal expansion coefficients between the oxide film and the aluminum substrate generates thermal expansion cracks, fully exposing internal porosity defects for repair and filling during the repair process. Oven heat treatment also promotes further dehydration and crystallization of the amorphous oxide film and residual hydrated film, increasing the dielectric constant of the oxide film and thus improving capacity. However, the crystallization process creates tiny pores within the oxide film, making further exposure and repair difficult. Amorphous oxide films, on the other hand, exhibit higher uniformity and consistency, lower internal defect content, and are denser than crystalline oxide films. Furthermore, amorphous alumina demonstrates greater self-healing ability in capacitors than crystalline alumina. Therefore, using the technology provided by this invention, anode foils with high amorphousness and low defect content can be prepared with minimal capacity loss.
[0029] 4. This invention is highly operable and significantly reduces leakage current. By using liquid nitrogen cryogenic treatment instead of oven heat treatment, the crystallinity and defect content of the anode foil oxide film produced by existing formation processes are reduced, effectively lowering the leakage current of the anode foil and improving its self-repair capability, while minimizing capacity loss. Compared with conventional formation methods (0.030 mA / cm²), this invention significantly reduces leakage current. 2 Compared to the previous method, this method can reduce leakage current by 40% (0.018 mA / cm). 2 ). Attached Figure Description
[0030] Figure 1The leakage current detection results of the anode foils prepared in Example 1 and Comparative Examples 1-2 are shown in the 24-hour test results. Detailed Implementation
[0031] The present invention will now be described in detail and specifically through specific embodiments to provide a better understanding of the invention. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and operating procedures; however, the scope of protection of the present invention is not limited to the following embodiments.
[0032] This invention provides a cryogenic process for preparing low-leakage anode foil. After a five-stage formation process, the process uses liquid nitrogen cryogenic treatment technology to replace the existing oven heat treatment technology. The liquid nitrogen cryogenic treatment can generate shrinkage cracks by utilizing the difference in thermal expansion coefficients between the oxide film and the aluminum substrate without significantly affecting the crystallinity of the oxide film. This fully exposes the internal defects of the oxide film, which is beneficial for repair and filling in boric acid solution. This results in an anode foil product with high amorphousness and low defect content, reducing the leakage current of the anode foil and improving its service life.
[0033] Example 1:
[0034] This embodiment describes a cryogenic fabrication process for preparing low-leakage anode foil. This process is applied at 520V and 0.840μF / cm. 2 After undergoing five-stage formation treatment and liquid nitrogen treatment, 530V specification anode foil is obtained from the etched foil; the specific process is as follows:
[0035] 1. High-temperature water boiling treatment: Immerse in pure water at 95℃ or above (conductivity less than 5μs / cm) for 12 minutes.
[0036] 2. Primary Formation: Anodizing is performed using a primary formation solution. The primary formation solution consists of 0.8 g / L adipic acid, 2.1 g / L citric acid, 2.4 g / L ammonium adipate, and the remainder is water. The treatment time is 9 min, the treatment temperature is 90℃, and the current density is 80 mA / cm². 2 Voltage 120V.
[0037] 3. Secondary Formation: Anodizing is performed using a secondary formation solution. The secondary formation solution consists of 1 g / L adipic acid, 10 g / L boric acid, 0.8 g / L ammonium adipate, and the remainder is water. The treatment time is 10 min, the treatment temperature is 90℃, and the current density is 80 mA / cm². 2 Voltage 270V.
[0038] 4. Three-stage formation: Anodizing is performed using a three-stage formation solution; the three-stage formation solution consists of 2.4 g / L ammonium pentaborate, 45 g / L boric acid, and the remainder is water; the treatment time is 9 min, the treatment temperature is 90℃, and the current density is 80 mA / cm². 2 Voltage 400V.
[0039] 5. Quaternary Formation: Anodizing is performed using a quaternary formation solution. The quaternary formation solution consists of 1.6 g / L ammonium pentaborate, 45 g / L boric acid, and the remainder is water. The treatment time is 9 min, the treatment temperature is 90℃, and the current density is 80 mA / cm². 2 Voltage 490V.
[0040] 6. Five-stage formation: Anodizing is performed using a five-stage formation solution; the five-stage formation solution consists of 1 g / L ammonium pentaborate, 45 g / L boric acid, and the remainder is water; the treatment time is 12 min, the treatment temperature is 90℃, and the current density is 80 mA / cm². 2 Voltage 530V.
[0041] 7. Pre-drying treatment: Dry the foil surface at a temperature of 80℃.
[0042] 8. Single liquid nitrogen treatment: treatment temperature is -196℃, treatment time is 2.5min.
[0043] 9. Primary Repair Treatment: The oxide film is repaired using a primary repair solution. The primary repair solution consists of 1 g / L ammonium pentaborate, 45 g / L boric acid, and the remainder is water. The treatment time is 9 minutes, the treatment temperature is 90℃, and the current density is 80 mA / cm². 2 Voltage 530V.
[0044] 10. Medium treatment: 65 g / L phosphoric acid aqueous solution, treatment time 4 min, temperature 65℃.
[0045] 11. Secondary Repair Treatment: The oxide film is repaired using a secondary repair solution. The secondary repair solution consists of 1 g / L ammonium pentaborate, 45 g / L boric acid, and the remainder is water. The treatment time is 9 minutes, the treatment temperature is 90℃, and the current density is 80 mA / cm². 2 Voltage 530V.
[0046] 12. Pre-drying treatment: Dry the foil surface at a temperature of 80℃.
[0047] 13. Secondary liquid nitrogen treatment: The treatment temperature is -196℃ and the treatment time is 2.5 min.
[0048] 14. Three-stage repair treatment: The oxide film is repaired using a three-stage repair solution. The solution consists of 1 g / L ammonium pentaborate, 45 g / L boric acid, and the remainder is water. The treatment time is 9 minutes, the treatment temperature is 90℃, and the current density is 80 mA / cm². 2 Voltage 530V.
[0049] 15. Post-treatment: Immerse in a 6 g / L ammonium dihydrogen phosphate aqueous solution for 2 min at a treatment temperature of 45℃.
[0050] 16. Drying: Drying temperature 200℃, processing time 2min.
[0051] The above steps can be used to prepare an anode foil with a specification of 530V.
[0052] Anodizing at a formation voltage of 530V resulted in a foil capacitance of 0.794 μF / cm². 2 Withstand voltage is 531V, and 24-hour leakage current is 0.018mA / cm. 2 .
[0053] Comparative Example 1:
[0054] The difference from Example 1 is that the first liquid nitrogen treatment is replaced by a first roasting furnace: heat treatment temperature 470℃, time 1.5min. The second liquid nitrogen treatment is replaced by a second roasting furnace: heat treatment temperature 370℃, time 1.5min. The rest of the process is the same as in Example 1.
[0055] The foil prepared using this example has a capacitance of 0.822 μF / cm². 2 Withstand voltage is 534V, and 24-hour leakage current is 0.030mA / cm. 2 .
[0056] Comparative Example 2:
[0057] The difference from Example 1 is that the primary and secondary liquid nitrogen treatment processes are cancelled, while the rest of the process is the same as in Example 1.
[0058] The foil prepared using this example has a capacitance of 0.795 μF / cm². 2 Withstand voltage is 530V, and 24-hour leakage current is 0.051mA / cm. 2 .
[0059] The performance parameters of the anode foils prepared in Example 1 and Comparative Examples 1-2 are shown in Table 1 and... Figure 1 .
[0060] Table 1: Performance parameters of the anode foils prepared in Example 1 and Comparative Examples 1-2.
[0061]
[0062] According to Example 1 and Comparative Examples 1-2:
[0063] Comparing Example 1 with Comparative Example 1, it was found that the leakage current of the anode foil prepared by liquid nitrogen cryogenic treatment was reduced by 40% compared with that prepared by traditional oven heat treatment. In particular, the initial leakage current rebound peak disappeared, and the overall leakage current was significantly reduced, while the capacity loss was less than 4%, showing good application prospects. Comparing Example 1 with Comparative Example 2, it was found that if oven heat treatment or liquid nitrogen cryogenic treatment was not used to expose the internal defects of the oxide film, the capacity was similar to that of Example 1, but the leakage current increased significantly, by about 70% compared with Comparative Example 1, making it unusable.
Claims
1. A process for preparing low-leakage anode foil using ultra-low temperature processing, characterized in that: This process involves performing a five-stage formation treatment and liquid nitrogen treatment on the etched foil to obtain an anode foil with a final voltage (VF) specification. The process includes the following steps: (1) Primary formation: The etched foil after high-temperature boiling treatment is placed in a primary formation solution for primary formation treatment. The primary formation solution consists of: adipic acid 0.8-1.6 g / L, citric acid 1.8-2.8 g / L, ammonium adipic acid 1.5-3 g / L, and the remainder is water. The primary formation treatment time is 8-12 min, the treatment temperature is 75-95℃, and the current density is 80 mA / cm. 2 The conversion voltage is 20-25% × Vf; (2) Secondary formation: The aluminum foil after primary formation is placed in a secondary formation solution for secondary formation treatment. The composition of the secondary formation solution is: adipic acid 0.5-1 g / L, boric acid 10-30 g / L, ammonium adipic acid 1-2 g / L, and the remainder is water. The treatment time for secondary formation is 8-12 min, the treatment temperature is 75-95℃, and the current density is 80 mA / cm². 2 The conversion voltage is 45-51% × Vf; (3) Tertiary Formation: The aluminum foil after secondary formation is placed in a tertiary formation solution for tertiary formation treatment. The composition of the tertiary formation solution is: ammonium pentaborate 1.5-3.5 g / L, boric acid 40-60 g / L, and the remainder is water. The treatment time for tertiary formation is 8-12 min, the treatment temperature is 75-95℃, and the current density is 80 mA / cm. 2 The conversion voltage is 71-78% × Vf; (4) Quaternary Formation: The aluminum foil after tertiary formation is placed in a quaternary formation solution for quaternary formation treatment. The quaternary formation solution consists of: ammonium pentaborate 1-2 g / L, boric acid 40-60 g / L, and the remainder is water. The quaternary formation treatment time is 8-12 min, the treatment temperature is 75-95℃, and the current density is 80 mA / cm². 2 The conversion voltage is 88-93% × Vf; (5) Fifth-stage formation: The aluminum foil after the fourth-stage formation is placed in a fifth-stage formation solution for fifth-stage formation treatment. The fifth-stage formation solution consists of: ammonium pentaborate 0.5-1.5 g / L, boric acid 40-60 g / L, and the remainder is water. The fifth-stage formation treatment time is 8-12 min, the treatment temperature is 75-95℃, and the current density is 80 mA / cm. 2 , which is converted into voltage vf; (6) First liquid nitrogen treatment: After the aluminum foil after the fifth-level formation treatment is pre-dried, it is then subjected to a liquid nitrogen treatment. The temperature of the first liquid nitrogen treatment is -150 to -196℃, and the treatment time is 1-3 min. (7) The aluminum foil after being treated with liquid nitrogen is subjected to a first repair treatment, a second treatment and a second repair treatment in sequence; (8) After the aluminum foil is pre-dried after step (7), it is then subjected to a second liquid nitrogen treatment. The temperature of the second liquid nitrogen treatment is -150 to -196℃ and the treatment time is 1-3 min. (9) After the aluminum foil is treated with liquid nitrogen twice, it is subjected to three repair treatments, post-treatments and drying in sequence to obtain an anode foil with a specification of 530V.
2. The cryogenic processing method for preparing low-leakage anode foil according to claim 1, characterized in that: In step (1), the high-temperature boiling treatment involves immersing the patient in pure water at a temperature above 95°C with a conductivity of less than 5 μs / cm for 5-15 minutes.
3. The cryogenic processing method for preparing low-leakage anode foil according to claim 1, characterized in that: In steps (6) and (8), the pre-drying treatment is to dry the foil surface at a temperature of 70-80°C.
4. The cryogenic processing method for preparing low-leakage anode foil according to claim 1, characterized in that: In step (7), the primary repair treatment involves using a primary repair solution to repair the oxide film. The primary repair solution consists of: 0.5-1.5 g / L ammonium pentaborate, 40-60 g / L boric acid, and the remainder is water. The primary repair treatment time is 8-12 min, the treatment temperature is 75-95℃, and the current density is 80 mA / cm². 2 The voltage is vf.
5. The cryogenic processing method for preparing low-leakage anode foil according to claim 1, characterized in that: In step (7), the intermediate treatment is carried out in a phosphoric acid aqueous solution with a concentration of 60-80 g / L for 3-4.5 min at a temperature of 55-75 °C.
6. The cryogenic processing method for preparing low-leakage anode foil according to claim 1, characterized in that: In step (7), the secondary repair treatment involves using a secondary repair solution to repair the oxide film. The secondary repair solution consists of: ammonium pentaborate 0.5-1.5 g / L, boric acid 40-60 g / L, and the remainder is water. The secondary repair treatment time is 8-12 min, the treatment temperature is 75-95℃, and the current density is 80 mA / cm². 2 The voltage is vf.
7. The cryogenic processing method for preparing low-leakage anode foil according to claim 1, characterized in that: In step (9), the three-stage repair treatment involves using a three-stage repair solution to repair the oxide film. The composition of the three-stage repair solution is: ammonium pentaborate 0.5-1.5 g / L, boric acid 40-60 g / L, and the remainder is water. The three-stage repair treatment time is 8-12 min, the treatment temperature is 75-95℃, and the current density is 80 mA / cm². 2 The voltage is vf.
8. The cryogenic processing method for preparing low-leakage anode foil according to claim 1, characterized in that: In step (9), the post-treatment involves immersing the sample in an aqueous solution of ammonium dihydrogen phosphate with a concentration of 6-9 g / L for 2-3 minutes at a treatment temperature of 30-60°C.
9. The cryogenic processing method for preparing low-leakage anode foil according to claim 1, characterized in that: In step (9), the drying temperature of the drying process is 150-300℃ and the processing time is 2-3 min.