Electrode foil, preparation method thereof and aluminum electrolytic capacitor

Abstract

The invention belongs to the technical field of electrode foil formation treatment, and particularly relates to an electrode foil and a preparation method thereof and an aluminum electrolytic capacitor, the preparation method of the electrode foil comprises the steps of performing multi-stage formation treatment on a corrosion foil, the number of stages of the formation treatment is at least two, and the formation treatment at least comprises first-stage formation and second-stage formation, first heat treatment is carried out after the second-stage formation; a formation liquid used in the second-stage formation is a mixed solution containing adipate and monopotassium phosphate. According to the preparation method provided by the invention, the formation liquid used in secondary formation is the mixed solution containing adipate and monopotassium phosphate, the limitation of traditional single formation liquid is broken through, and synchronous optimization of the structure, hydration resistance and electrochemical performance of the aluminum oxide film is realized through multi-stage formation, mixed solution synergy and the synergistic effect of formation and heat treatment; meanwhile, production cost is reduced, and environmental load is relieved.

Description

Technical Field

[0001] This invention belongs to the field of electrode foil formation technology, specifically relating to an electrode foil and its preparation method, and an aluminum electrolytic capacitor. Background Technology

[0002] Traditional low-voltage electrode foil formation processes often employ a single formation solution, which leads to problems such as poor oxide film uniformity, difficulty in suppressing hydration reactions, and easy film degradation. Furthermore, frequent bath changes or the use of high-concentration phosphides not only result in large nitrogen and phosphorus emissions but also in high production costs.

[0003] In addition, traditional formation processes cannot effectively balance the high specific volume and water resistance of the oxide film during processing, and it is also difficult to reduce reaction intensity, energy consumption and oxide film stress, which limits the improvement of electrode foil performance. Summary of the Invention

[0004] The main objective of this invention is to propose an electrode foil and its preparation method, as well as an aluminum electrolytic capacitor. In the preparation method provided by this invention, the forming solution used in the secondary formation is a mixed solution containing adipate and potassium dihydrogen phosphate, which breaks through the limitations of traditional single forming solutions. Through multi-stage formation, synergistic effect of mixed solution and synergistic effect of formation and heat treatment, the structure, hydration resistance and electrochemical performance of alumina film are simultaneously optimized, while reducing production costs and reducing environmental impact.

[0005] The first aspect of the present invention provides a method for preparing an electrode foil, the method comprising performing a formation treatment on an etched foil, the formation treatment having at least two stages, the formation treatment including at least a primary formation and a secondary formation, and performing a first heat treatment after the secondary formation; the formation solution used in the secondary formation is a mixed solution containing adipate and potassium dihydrogen phosphate.

[0006] In some embodiments of the present invention, the formation voltage of the secondary formation is lower than the formation voltage of the primary formation.

[0007] In some embodiments of the present invention, the formation voltage of the secondary formation is 10% to 70% of the formation voltage of the primary formation.

[0008] In some embodiments of the present invention, the formation voltage of the primary formation is 4% to 20% of the rated voltage.

[0009] In some embodiments of the present invention, the current density of the secondary formation is less than the current density of the primary formation.

[0010] In some embodiments of the present invention, the current density of the secondary formation is 30% to 70% of the current density of the primary formation.

[0011] In some embodiments of the present invention, the current density of the primary formation is 10 mA / cm². 2 ~500mA / cm 2 .

[0012] In some embodiments of the present invention, the adipate salt has a mass percentage of 3% to 20% in the formation solution used for the secondary formation.

[0013] In some embodiments of the present invention, the mass percentage of potassium dihydrogen phosphate in the formation solution used for the secondary formation is 0.1% to 3%.

[0014] In some embodiments of the present invention, the adipic acid salt includes at least one of ammonium adipic acid and potassium adipic acid.

[0015] In some embodiments of the present invention, the solvent of the formation solution used in the secondary formation is pure water or deionized water.

[0016] In some embodiments of the present invention, the formation temperature of the secondary formation is 60°C to 90°C.

[0017] In some embodiments of the present invention, the formation time of the secondary formation is 0.5 min to 10 min.

[0018] In some embodiments of the present invention, the temperature of the first heat treatment is 380°C to 500°C.

[0019] In some embodiments of the present invention, the duration of the first heat treatment is 1 min to 5 min.

[0020] In some embodiments of the present invention, the first heat treatment is performed in an oxygen-containing atmosphere.

[0021] In some embodiments of the present invention, the formation temperature of the primary formation is 60°C to 90°C.

[0022] In some embodiments of the present invention, the formation time of the primary formation is 0.5 min to 15 min.

[0023] In some embodiments of the present invention, the solute in the formation solution used in the primary formation includes at least one of adipate and dihydrogen phosphate.

[0024] In some embodiments of the present invention, the mass percentage of the solute in the formation solution used in the primary formation is 0.1% to 20%.

[0025] In some embodiments of the present invention, the solvent of the forming solution used in the primary forming is pure water or deionized water.

[0026] In some embodiments of the present invention, the formation process has at least three stages, and the formation process further includes performing a third or more stages of formation after the first heat treatment.

[0027] In some embodiments of the present invention, the formation process has three stages, including a first-stage formation, a second-stage formation, and a third-stage formation, wherein a first heat treatment is performed after the second-stage formation, and the third-stage formation is performed after the first heat treatment.

[0028] In some embodiments of the present invention, the formation process has four stages, including primary formation, secondary formation, tertiary formation and quaternary formation, and a first heat treatment is performed after the secondary formation, the tertiary formation is performed after the first heat treatment, and the quaternary formation is performed after the tertiary formation.

[0029] In some embodiments of the present invention, the formation process has five stages, including a first-stage formation, a second-stage formation, a third-stage formation, a fourth-stage formation, and a fifth-stage formation. A first heat treatment is performed after the second-stage formation, the third-stage formation is performed after the first heat treatment, the fourth-stage formation is performed after the third-stage formation, and the fifth-stage formation is performed after the fourth-stage formation.

[0030] In some embodiments of the present invention, the formation process has six stages, including first-stage formation, second-stage formation, third-stage formation, fourth-stage formation, fifth-stage formation, and sixth-stage formation. A first heat treatment is performed after the second-stage formation, the third-stage formation is performed after the first heat treatment, the fourth-stage formation is performed after the third-stage formation, the fifth-stage formation is performed after the fourth-stage formation, and the sixth-stage formation is performed after the fifth-stage formation.

[0031] In some embodiments of the present invention, in the three-stage and above formation processes, the solute in the formation solution used in each stage of formation independently includes at least one of adipate and dihydrogen phosphate.

[0032] In some embodiments of the present invention, in the three-stage and above formation processes, the mass percentage of the solute in the formation solution used in each formation process is independently 0.1% to 20%.

[0033] In some embodiments of the present invention, in the three-stage and above formation processes, the solvent of the formation solution used in each stage of formation is independently pure water or deionized water.

[0034] In some embodiments of the present invention, in the three-stage and above formation processes, the formation temperature of each formation stage is independently 60°C to 90°C.

[0035] In some embodiments of the present invention, in the three-stage and above formation, the formation time of each formation stage is independently 0.5 min to 15 min.

[0036] In some embodiments of the present invention, in the three-stage and above formation, the current density of each formation stage is independently 10 mA / cm². 2 ~500mA / cm 2 .

[0037] In some embodiments of the present invention, in the three-stage and above formation, the formation voltage increases progressively from the third-stage formation to the final-stage formation.

[0038] In some embodiments of the present invention, the formation voltage of the three-stage formation is greater than the formation voltage of the first-stage formation.

[0039] In some embodiments of the present invention, the preparation method further includes post-processing, the post-processing including: performing at least one second heat treatment after the final formation, and / or performing at least one phosphoric acid treatment, and / or performing at least one supplementary formation.

[0040] In some embodiments of the present invention, the temperature of each of the second heat treatments is independently 380°C to 550°C.

[0041] In some embodiments of the present invention, the duration of each second heat treatment is independently 0.5 min to 10 min.

[0042] In some embodiments of the present invention, the temperature of each phosphoric acid treatment is independently 40°C to 90°C.

[0043] In some embodiments of the present invention, the duration of each phosphoric acid treatment is independently 0.5 min to 10 min.

[0044] In some embodiments of the invention, each phosphoric acid treatment uses a phosphorus-containing solution independently.

[0045] In some embodiments of the present invention, the mass percentage of phosphorus in the phosphorus-containing solution is independently 0.5% to 8%.

[0046] In some embodiments of the present invention, the temperature of each replenishment is independently 60°C to 90°C.

[0047] In some embodiments of the present invention, the time for each replenishment is independently 0.5 min to 15 min.

[0048] In some embodiments of the present invention, the solute in the treatment solution used for each replenishment independently includes at least one of adipate and dihydrogen phosphate.

[0049] In some embodiments of the present invention, the mass percentage of the solute in the treatment solution used in each replenishment process is independently 0.1% to 20%.

[0050] In some embodiments of the present invention, the current density formed each time is independently 10 mA / cm². 2 ~500mA / cm 2 .

[0051] In some embodiments of the present invention, the voltage formed by the compensation each time is greater than or equal to the rated voltage.

[0052] A second aspect of the present invention provides an electrode foil, which is prepared by the preparation method described in the first aspect.

[0053] A third aspect of the present invention provides an aluminum electrolytic capacitor, the aluminum electrolytic capacitor comprising an electrode foil prepared by the preparation method described in the first aspect or the electrode foil described in the second aspect.

[0054] In the preparation method of this invention, the secondary formation solution used is a mixed solution containing adipate and potassium dihydrogen phosphate, which breaks through the limitations of traditional single formation solutions. Through multi-stage formation, synergy of mixed solutions, and synergistic effects of formation and heat treatment, the optimization of alumina film structure, simultaneous improvement of hydration resistance and electrochemical performance are achieved. At the same time, it has environmental friendliness and cost advantages, breaking through the technical bottleneck of traditional processes.

[0055] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and in order to make the above and other objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described below. Detailed Implementation

[0056] Exemplary embodiments of the present invention will now be described in more detail with reference to specific examples. It should be understood that the present invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this invention will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

[0057] 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 is for the purpose of describing particular embodiments only and is not intended to limit the invention; the terms “comprising” and “having”, and any variations thereof, in the specification and claims of this invention are intended to cover non-exclusive inclusion.

[0058] In the description of the embodiments of the present invention, the technical terms "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features.

[0059] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of the invention. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0060] In the description of the embodiments of this invention, the term "and / or" is merely a description of the association relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A exists, A and B exist simultaneously, and B exists. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0061] In the description of the embodiments of the present invention, the term "multiple" refers to two or more (including two), similarly, "multiple groups" refers to two or more (including two groups), "multiple pieces" refers to two or more (including two pieces), and "three or more formations" (including three-level formation).

[0062] In the production of aluminum electrolytic capacitor electrode foil, the formation process is crucial to product performance. Current mainstream traditional low-voltage formation processes and some existing technical solutions have several problems that urgently need to be solved, as follows:

[0063] Defects of Traditional Low-Pressure Formation Processes: Traditional low-pressure formation processes often employ a single ammonium adipate solution for formation, with the formation voltage increasing progressively in stages. Alternatively, ammonium dihydrogen phosphate is added to the formation solution in subsequent stages (second, third, fourth, fifth, and / or sixth stages) to repair the oxide film. Since formation with a single ammonium adipate solution is insufficient to meet the high specific capacity and hydration resistance requirements of low-pressure foils, and while the introduction of ammonium dihydrogen phosphate provides some repair, performance limitations remain, failing to effectively address the performance improvement challenges posed by the sponge-like porous structure on the surface of low-pressure foils.

[0064] The existing technical solution has the following drawbacks: Chinese patent CN 103258649 B discloses a three-stage formation process with the same voltage and current density, using an adipic acid salt and / or dihydrogen phosphate solution as the electrolyte. Its limitations include: if ammonium dihydrogen phosphate is used, its decomposition at high temperatures releases NH3, which may interfere with the film formation process by altering the solution pH or generating byproducts, inducing porosity defects in the oxide film; the thermal stability of ammonium dihydrogen phosphate solution is limited, and its adaptability to high-temperature processes is weaker than that of organic acid salts; furthermore, the solution does not consider the synergistic effects of different anions (such as phosphate and adipic acid) and different current densities in the staged formation process, resulting in insufficient depth of control over the structure-performance relationship of the oxide film and making it difficult to achieve comprehensive optimization of the oxide film performance.

[0065] Problems involving single potassium salts and other salts: K + It can adsorb onto the surface of alumina to inhibit hydration reactions, and its high mobility can increase the conductivity of the solution and make the oxide film more uniform. However, using potassium salts alone as the formation solution is too costly and not conducive to large-scale applications. Sodium dihydrogen phosphate contains Na... + With Al 3+ Large size differences lead to a loose passivation layer structure; its weak acidity makes it difficult to effectively activate the passivation reaction, resulting in a low amount of aluminum phosphate generated; in subsequent heat treatment, sodium ions may also form low-melting-point compounds with aluminum oxide, reducing the thermal stability of the film and failing to meet the requirements of low-pressure foil for hydration resistance and film quality.

[0066] In summary, existing electrode foil formation processes have significant shortcomings in terms of oxide film quality improvement, solution stability control, and cost optimization. More effective technical solutions are urgently needed to overcome these bottlenecks and meet the development needs of high-performance low-pressure foils.

[0067] The first aspect of the present invention provides a method for preparing a low-voltage electrode foil. The key to this method is to perform a formation treatment on the etched foil. The formation treatment has at least two stages, that is, the formation treatment includes at least a first-stage formation and a second-stage formation, and a first heat treatment is performed after the second-stage formation. The formation solution used for the second-stage formation is a mixed solution containing adipate and potassium dihydrogen phosphate.

[0068] In embodiments of the present invention, a mixed solution synergistic passivation technique is employed. In the secondary formation stage, a mixed solution containing adipate and potassium dihydrogen phosphate is used as the formation solution. Wherein, K... + With its strong polarization ability, it adsorbs onto the surface of alumina, reducing the penetration of water molecules in the electrolyte and inhibiting the hydration reaction. The trace amounts of phosphate in potassium dihydrogen phosphate react with aluminum to form aluminum phosphate, which forms a dense passivation layer in the deep pores of the corrosion layer, increases the phosphorus-containing coating layer, significantly inhibits the hydration reaction and oxide film deterioration, and balances the improvement of oxidation efficiency and water resistance.

[0069] Meanwhile, in this embodiment of the invention, the formation process and the first heat treatment work synergistically. The primary and secondary formation processes create an extremely thin alumina film, which prevents the aluminum base on the surface of the corrosion foil from melting and collapsing due to the instantaneous high temperature of the first heat treatment, avoiding the formation of corrosion pits and ensuring the effective area. The first heat treatment after the secondary formation promotes the transformation of hydrated alumina and amorphous alumina into crystalline alumina, eliminates internal stress in the film layer, reduces cracks and defects, and forms more and more stable phosphating films, optimizing the structural stability of the oxide film, significantly improving the specific capacity and hydration resistance of the electrode foil, and reducing leakage current.

[0070] In this embodiment of the invention, nitrogen and phosphorus emissions are reduced and the service life of the bath is extended by compounding the mixed solution in the secondary formation process. Compared with the traditional process, this effectively reduces production costs and has both environmental friendliness and cost advantages.

[0071] In this embodiment of the invention, the preparation method of the electrode foil is carried out according to the following steps.

[0072] Primary formation

[0073] In an embodiment of the present invention, the etched foil is placed in a forming solution used for primary forming to perform primary forming.

[0074] In some embodiments of the present invention, the formation temperature of the primary formation is 60°C to 90°C, which can also be understood as the temperature of the formation solution used in the primary formation being 60°C to 90°C. Exemplarily, the formation temperature of the primary formation can be one of 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, and 90°C, or any value satisfying the above range.

[0075] In some embodiments of the present invention, the formation time for the first-stage formation is 0.5 min to 15 min, which can also be understood as the formation time for the first-stage formation being 0.5 min to 15 min. Exemplarily, the formation time for the first-stage formation can be one of 0.5 min, 0.8 min, 1 min, 2 min, 3 min, 4 min, 5 min, 6 min, 7 min, 8 min, 9 min, 10 min, 11 min, 12 min, 13 min, 14 min, and 15 min, or any value satisfying the above range.

[0076] In some embodiments of the present invention, the current density of the first-stage formation is 10 mA / cm². 2 ~500mA / cm 2 The current density for primary formation provided by this invention can be any value within the range of any two values ​​mentioned above, for example, it can be 10 mA / cm². 2 ~200mA / cm 2 It can also be 200mA / cm 2~500mA / cm 2 And so on. For example, in an embodiment of the present invention, the current density of the first-stage formation can also be 10 mA / cm². 2 20mA / cm 2 40mA / cm 2 50mA / cm 2 80mA / cm 2 100mA / cm 2 120mA / cm 2 150mA / cm 2 180mA / cm 2 200mA / cm 2 220mA / cm 2 250mA / cm 2 280mA / cm 2 300mA / cm 2 320mA / cm 2 350mA / cm 2 380mA / cm 2 400mA / cm 2 420mA / cm 2 450mA / cm 2 480mA / cm 2 500mA / cm 2 One of the above values ​​or any value that satisfies the above range.

[0077] In some embodiments of the present invention, the formation voltage of the first-stage formation is 4% to 20% of the rated voltage. If the formation voltage of the first-stage formation is less than 4%, the resulting oxide film is very thin and discontinuous, which cannot prevent excessive corrosion of the aluminum substrate by phosphate ions in the subsequent second-stage formation, leading to a decrease in the strength of the electrode foil. If the formation voltage of the first-stage formation is greater than 20%, the resulting oxide film is thicker, affecting the bonding of phosphate ions with aluminum in the corrosion pores during the second-stage formation process, thus weakening the hydration resistance of the electrode foil. Therefore, selecting a formation voltage of 4% to 20% of the rated voltage for the first-stage formation will not affect the formation effect of the second-stage formation. Exemplarily, the formation voltage of the first-stage formation can be one of 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, and 20% of the rated voltage, or any value satisfying the above range.

[0078] In some embodiments of the present invention, the solute in the formation solution used for primary formation includes at least one of adipate and dihydrogen phosphate.

[0079] In some embodiments of the present invention, adipic acid salt includes ammonium adipate, and the forming solution used in the primary formation can be an ammonium adipate solution.

[0080] In some embodiments of the present invention, the dihydrogen phosphate salt includes ammonium dihydrogen phosphate, and the forming solution used in the primary formation can be an ammonium dihydrogen phosphate solution.

[0081] In some embodiments of the present invention, the mass percentage of the solute in the forming solution used in the primary forming is 0.1% to 20%. Exemplarily, the mass percentage of the solute in the forming solution used in the primary forming can be one of 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 1%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, or 20%, or any value satisfying the above range.

[0082] In some embodiments of the present invention, the solvent of the forming solution used in the primary forming is pure water or deionized water.

[0083] Secondary formation

[0084] In an embodiment of the present invention, the aluminum foil after primary formation is placed in the formation solution used for secondary formation to undergo secondary formation.

[0085] In some embodiments of the present invention, the formation temperature of the secondary formation is 60°C to 90°C, which can also be understood as the temperature of the formation solution used in the secondary formation being 60°C to 90°C. Exemplarily, the formation temperature of the secondary formation can be one of 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, and 90°C, or any value satisfying the above range.

[0086] In some embodiments of the present invention, the formation time for secondary formation is 0.5 min to 10 min, which can also be understood as the secondary formation time being 0.5 min to 10 min. Exemplarily, the formation time for secondary formation can be one of 0.5 min, 0.8 min, 1 min, 2 min, 3 min, 4 min, 5 min, 6 min, 7 min, 8 min, 9 min, and 10 min, or any value satisfying the above range.

[0087] In some embodiments of the present invention, the formation voltage of the secondary formation is lower than that of the primary formation.

[0088] In some embodiments of the present invention, the formation voltage of the secondary formation is 10% to 70% of the formation voltage of the primary formation. The formation voltage of the secondary formation provided by the present invention can be any value within the range of any two values ​​described above, for example, it can be 10% to 40% of the formation voltage of the primary formation, or 40% to 70% of the formation voltage of the primary formation, and so on. Exemplarily, in embodiments of the present invention, the formation voltage of the secondary formation can be one of 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, or 70% of the formation voltage of the primary formation, or any value satisfying the above range.

[0089] In some embodiments of the present invention, the current density of secondary formation is less than that of primary formation.

[0090] In some embodiments of the present invention, the current density of the secondary formation is 30% to 70% of the current density of the primary formation. The current density of the secondary formation provided by the present invention can be any value within the range of any two values ​​described above, for example, it can be 30% to 50% of the current density of the primary formation, or 50% to 70% of the current density of the primary formation, and so on. Exemplarily, in embodiments of the present invention, the current density of the secondary formation can be one of 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, or 70% of the current density of the primary formation, or any value satisfying the above range.

[0091] In some embodiments of the present invention, the forming solution used for secondary formation is a mixed solution containing adipate and potassium dihydrogen phosphate.

[0092] In some embodiments of the present invention, the solvent of the formation solution used in the secondary formation is pure water or deionized water.

[0093] In some embodiments of the present invention, the mass percentage of potassium dihydrogen phosphate in the forming solution used for secondary formation is 0.1% to 3%. The mass percentage of potassium dihydrogen phosphate in the forming solution used for secondary formation provided by the present invention can be any value within the range of any two values ​​described above, such as 0.1% to 1.5%, 1.5% to 3%, and so on. Exemplarily, the mass percentage of potassium dihydrogen phosphate in the forming solution used for secondary formation provided by the present invention can also be one of 0.1%, 0.2%, 0.5%, 0.8%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, and 3%, or any value satisfying the above range.

[0094] In some embodiments of the present invention, the mass percentage of adipic acid salt in the forming solution used for secondary formation is 3% to 20%. The mass percentage of adipic acid salt in the forming solution used for secondary formation provided by the present invention can be any value within the range of any two values ​​described above, such as 3% to 10%, 10% to 20%, and so on. Exemplarily, the mass percentage of adipic acid salt in the forming solution used for secondary formation provided by the present invention can also be one of 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, and 20%, or any value satisfying the above range.

[0095] In some embodiments of the present invention, adipic acid salt includes at least one of ammonium adipic acid and potassium adipic acid.

[0096] In some embodiments of the present invention, the forming solution used in the secondary forming process is a mixed solution containing ammonium adipate and / or potassium adipate and potassium dihydrogen phosphate. This mixed solution exhibits good stability. In the mixed solution, ammonium adipate and / or potassium adipate provide a stable ammonium and potassium ion environment, promoting alumina film formation; the phosphate ions of potassium dihydrogen phosphate enhance hydration resistance, while the potassium ions improve the solution's conductivity. Its weak acidity matches the buffer system of ammonium adipate, maintaining a stable pH environment in the forming solution, adapting to the requirements of the forming reaction, and preventing excessive dissolution of the oxide film. Furthermore, this mixed solution is not easily decomposed at the forming temperature, and the high solubility matching of the two components prevents fluctuations in the bath concentration caused by crystallization. + It exhibits high mobility in electrolytes, can regulate the pore structure of alumina films, promote uniform deposition of aluminum phosphide, optimize formation effects, and minimize residual potassium. + It has minimal impact on film performance, can be washed away with water, and its ionic radius is similar to that of aluminum ions, which can reduce internal stress in the passivation layer and prevent film cracking. Furthermore, compared to ammonium dihydrogen phosphate, potassium dihydrogen phosphate has moderate acidity, optimal thermal stability, and balanced conductivity.

[0097] First heat treatment

[0098] In an embodiment of the present invention, the aluminum foil after the secondary formation is subjected to a first heat treatment.

[0099] In some embodiments of the present invention, the temperature of the first heat treatment is 380°C to 500°C. Exemplarily, the temperature of the first heat treatment can be one of 380°C, 400°C, 420°C, 450°C, 480°C, and 500°C, or any value satisfying the above range.

[0100] In some embodiments of the present invention, the duration of the first heat treatment is 1 min to 5 min. Exemplarily, the duration of the first heat treatment can be one of 1 min, 2 min, 3 min, 4 min, or 5 min, or any value satisfying the above range.

[0101] In some embodiments of the present invention, the first heat treatment is performed in an oxygen-containing atmosphere.

[0102] It is worth mentioning that the first heat treatment is carried out in an oxygen atmosphere, which can be understood as not isolating the air during the first heat treatment process. Since there is oxygen in the air, the aluminum foil is heat treated in an environment where the active aluminum base reacts with the gaseous oxygen to form an aluminum oxide passivation film.

[0103] Re-transformed

[0104] In embodiments of the present invention, the formation process has at least three stages. This can be understood as the formation process having three, four, five, six, or more stages. In this case, the formation process includes at least a first-stage formation, a second-stage formation, and a third-stage formation. The third-stage formation is performed after the first heat treatment. Alternatively, the formation process can be understood as including a first-stage formation, a second-stage formation, and a third-stage or higher formation after the first heat treatment. The third-stage or higher formation means that it includes a third-stage formation. Furthermore, a fourth-stage, fifth-stage, or sixth-stage formation can be performed after the third-stage formation to correspond to the number of stages of the formation process.

[0105] In some embodiments of the present invention, the formation process has three stages, including primary formation, secondary formation and tertiary formation. The first heat treatment is performed after the secondary formation, and the tertiary formation is performed after the first heat treatment. In this case, the tertiary formation can also be referred to as re-formation.

[0106] In some embodiments of the present invention, the formation process has four stages, including primary formation, secondary formation, tertiary formation and quaternary formation. The first heat treatment is performed after the secondary formation, the tertiary formation is performed after the first heat treatment, and the quaternary formation is performed after the tertiary formation. In this case, the tertiary and quaternary formations can also be collectively referred to as re-formation.

[0107] In some embodiments of the present invention, the formation process has five stages, including first-stage formation, second-stage formation, third-stage formation, fourth-stage formation, and fifth-stage formation. The first heat treatment is performed after the second-stage formation, the third-stage formation is performed after the first heat treatment, the fourth-stage formation is performed after the third-stage formation, and the fifth-stage formation is performed after the fourth-stage formation. In this case, the third-stage formation, fourth-stage formation, and fifth-stage formation can also be collectively referred to as re-formation.

[0108] In some embodiments of the present invention, the formation process has six stages, including first-stage formation, second-stage formation, third-stage formation, fourth-stage formation, fifth-stage formation, and sixth-stage formation. The first heat treatment is performed after the second-stage formation, the third-stage formation is performed after the first heat treatment, the fourth-stage formation is performed after the third-stage formation, the fifth-stage formation is performed after the fourth-stage formation, and the sixth-stage formation is performed after the fifth-stage formation. In this case, the third-stage formation, fourth-stage formation, fifth-stage formation, and sixth-stage formation can also be collectively referred to as re-formation.

[0109] In some embodiments of the present invention, in the third-level and above formation, which can also be understood as in the re-formation, the solute of the formation solution used in each stage of formation independently includes at least one of adipate and dihydrogen phosphate.

[0110] In some embodiments of the present invention, the adipate includes ammonium adipate, and in the third-level and above formation processes, the formation solution used in each formation process can be an ammonium adipate solution.

[0111] In some embodiments of the present invention, the dihydrogen phosphate salt includes ammonium dihydrogen phosphate, and in the three-stage and above formation processes, the formation solution used in each stage of formation can be an ammonium dihydrogen phosphate solution.

[0112] In some embodiments of the present invention, in three-stage and higher-stage formations, the mass percentage of solute in the forming solution used in each stage of formation is independently 0.1% to 20%. Exemplarily, the mass percentage of solute in the forming solution used in each stage of formation can be independently one of 0.1%, 0.5%, 1%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, and 20%, or any value satisfying the above range.

[0113] In some embodiments of the present invention, in three-stage and higher-stage formation, the solvent of the formation solution used in each stage of formation is independently pure water or deionized water.

[0114] In some embodiments of the present invention, the formation process has at least three stages, including at least primary, secondary, and tertiary formation. In these embodiments, a multi-stage formation process is employed. The secondary formation uses a mixed solution, while the primary and tertiary formations independently use either adipate or dihydrogen phosphate solutions. This three-stage formation method, alternating between mixed and single solutions, constructs a gradient alumina film structure. Primary formation generates an extremely thin base film layer; secondary formation utilizes low voltage and low current density to passivate and repair the base oxide film layer with a mixture of ammonium adipate and / or potassium adipate and potassium dihydrogen phosphate; tertiary formation further repairs microcracks and thickens the film layer. This graded formation and layered alumina film design ensures both high specific capacity and improved water resistance. Simultaneously, reducing the voltage and current density of the secondary formation effectively reduces the formation reaction intensity, oxide film stress, and formation energy consumption, while also effectively reducing the formation of electrode foil fringes.

[0115] In some embodiments of the present invention, in three-stage and above formation processes, the formation temperature of each formation stage is independently between 60°C and 90°C. Exemplarily, the formation temperature of each formation stage is independently one of 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, and 90°C, or any value satisfying the above range.

[0116] In some embodiments of the present invention, in three or more stages of formation, the formation time for each stage is independently 0.5 min to 15 min. Exemplarily, the formation time for each stage can be one of 0.5 min, 0.8 min, 1 min, 2 min, 3 min, 4 min, 5 min, 6 min, 7 min, 8 min, 9 min, 10 min, 11 min, 12 min, 13 min, 14 min, or 15 min, or any value satisfying the above range.

[0117] In some embodiments of the present invention, in three-stage and higher formation processes, the current density of each formation stage is independently 10 mA / cm². 2 ~500mA / cm 2 The current density of each stage provided by this invention can be any value within the range of any two values ​​mentioned above, for example, it can be 10 mA / cm². 2 ~200mA / cm 2 It can also be 200mA / cm 2 ~500mA / cm 2 And so on. For example, in this embodiment of the invention, the current density of each stage of formation can also be 10 mA / cm². 2 20mA / cm 2 40mA / cm 2 50mA / cm2 80mA / cm 2 100mA / cm 2 120mA / cm 2 150mA / cm 2 180mA / cm 2 200mA / cm 2 220mA / cm 2 250mA / cm 2 280mA / cm 2 300mA / cm 2 320mA / cm 2 350mA / cm 2 380mA / cm 2 400mA / cm 2 420mA / cm 2 450mA / cm 2 480mA / cm 2 500mA / cm 2 One of the above values ​​or any value that satisfies the above range.

[0118] In some embodiments of the present invention, in three-stage and above formation, the formation voltage increases progressively from the third-stage formation to the final-stage formation.

[0119] In some embodiments of the present invention, the formation voltage of the three-stage formation is greater than that of the first-stage formation.

[0120] In some embodiments of the present invention, in three-stage or higher formation, the voltage is stabilized at the rated voltage during the last stage of formation.

[0121] In some embodiments of the present invention, when the formation process has three stages, the formation voltage of the three-stage formation is the rated voltage.

[0122] In embodiments of the present invention, the method for preparing the electrode foil further includes post-processing, wherein the post-processing includes performing at least one second heat treatment after the final formation, and / or performing at least one phosphoric acid treatment, and / or performing at least one supplementary formation.

[0123] In some embodiments of the present invention, the second heat treatment may be performed once or multiple times, the phosphoric acid treatment may be performed once or multiple times, and the re-forming process may be performed once or multiple times. To avoid confusion and for ease of description, in the embodiments of the present invention, the heat treatments are labeled according to their order in the entire preparation method as first heat treatment, second heat treatment, third heat treatment, etc.; and in the embodiments of the present invention, the re-forming processes are labeled according to their order in the entire preparation method as first re-forming, second re-forming, etc.

[0124] In some embodiments of the present invention, the order of the second heat treatment, phosphoric acid treatment, and re-forming can be varied and can be designed according to the actual situation.

[0125] As some embodiments of the present invention, after the final formation, a second heat treatment, a first supplementary formation, a phosphoric acid treatment, a third heat treatment, and a second supplementary formation are performed in sequence.

[0126] As some embodiments of the present invention, after the final formation, phosphoric acid treatment, first supplementary formation, second heat treatment, and second supplementary formation are performed sequentially.

[0127] Second heat treatment

[0128] In embodiments of the present invention, the temperature of each second heat treatment is independently between 380°C and 550°C. Exemplarily, the temperature of each second heat treatment can be independently one of 380°C, 400°C, 420°C, 450°C, 480°C, 500°C, 520°C, and 550°C, or any value satisfying the above range.

[0129] In embodiments of the present invention, the duration of each second heat treatment is independently 0.5 min to 10 min. Exemplarily, the duration of each second heat treatment can be independently one of 0.5 min, 0.8 min, 1 min, 2 min, 3 min, 4 min, 5 min, 6 min, 7 min, 8 min, 9 min, and 10 min, or any value satisfying the above range.

[0130] Phosphoric acid treatment

[0131] In embodiments of the present invention, the temperature of each phosphoric acid treatment is independently between 40°C and 90°C. Exemplarily, the temperature of each phosphoric acid treatment can be independently one of 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, and 90°C, or any value satisfying the above range.

[0132] In embodiments of the present invention, the duration of each phosphoric acid treatment is independently 0.5 min to 10 min. The duration of each phosphoric acid treatment can be independently one of 0.5 min, 0.8 min, 1 min, 2 min, 3 min, 4 min, 5 min, 6 min, 7 min, 8 min, 9 min, and 10 min, or any value satisfying the above range.

[0133] In embodiments of the present invention, each phosphoric acid treatment uses a phosphorus-containing solution independently.

[0134] In some embodiments of the present invention, the mass percentage of phosphorus in the phosphorus-containing solution is independently 0.5% to 8%. Exemplarily, the mass percentage of phosphorus in the phosphorus-containing solution may be independently one of 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, 2.2%, 2.5%, 2.8%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, and 8%, or any value satisfying the above range.

[0135] In some embodiments of the present invention, the phosphorus-containing solution may be a phosphoric acid solution, for example, a phosphoric acid solution may be used independently for each phosphoric acid treatment.

[0136] Complementary formation

[0137] In embodiments of the present invention, the temperature of each replenishment formation is independently between 60°C and 90°C. Exemplarily, the temperature of each replenishment formation can be independently one of 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, and 90°C, or any value satisfying the above range.

[0138] In embodiments of the present invention, the time for each supplementary formation is independently 0.5 min to 15 min. Exemplarily, the time for each supplementary formation can be independently one of 0.5 min, 0.8 min, 1 min, 2 min, 3 min, 4 min, 5 min, 6 min, 7 min, 8 min, 9 min, 10 min, 11 min, 12 min, 13 min, 14 min, and 15 min, or any value satisfying the above range.

[0139] In some embodiments of the present invention, the solute in the treatment solution used for each replenishment independently includes at least one of adipate and dihydrogen phosphate.

[0140] In some embodiments of the present invention, the adipate comprises ammonium adipate, and the treatment solution used in each replenishment can be an ammonium adipate solution independently.

[0141] In some embodiments of the present invention, the dihydrogen phosphate salt includes ammonium dihydrogen phosphate, and the treatment solution used in each replenishment can be an ammonium dihydrogen phosphate solution independently.

[0142] In some embodiments of the present invention, the mass percentage of the solute in the treatment solution used in each replenishment process is independently 0.1% to 20%. Exemplarily, the mass percentage of the solute in the treatment solution used in each replenishment process can be independently one of 0.1%, 0.5%, 1%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, or any value satisfying the above range.

[0143] In some embodiments of the present invention, the solvent of the processing solution used in each replenishment is independently pure water or deionized water.

[0144] In some embodiments of the present invention, the current density formed each time is independently 10 mA / cm². 2 ~500mA / cm 2 The current density formed in each iteration of the present invention can be any value within the range of any two values ​​described above, for example, 10 mA / cm². 2 ~200mA / cm 2 It can also be 200mA / cm 2 ~500mA / cm 2 And so on. For example, in each embodiment of the invention, the current density formed during the replenishment process can also be 10 mA / cm². 2 20mA / cm 2 40mA / cm 2 50mA / cm 2 80mA / cm 2 100mA / cm 2 120mA / cm 2 150mA / cm 2 180mA / cm 2 200mA / cm 2 220mA / cm 2 250mA / cm 2 280mA / cm 2 300mA / cm 2 320mA / cm 2 350mA / cm 2 380mA / cm 2 400mA / cm 2 420mA / cm 2 450mA / cm 2 480mA / cm 2 500mA / cm 2One of the above values ​​or any value that satisfies the above range.

[0145] In some embodiments of the present invention, the voltage formed by the compensation each time is greater than or equal to the rated voltage.

[0146] In some embodiments of the present invention, the method for preparing the electrode foil includes:

[0147] Primary formation: The etched foil is placed in the formation solution used for primary formation to perform primary formation.

[0148] Secondary formation: The aluminum foil that has undergone primary formation is placed in the formation solution used for secondary formation to undergo secondary formation.

[0149] First heat treatment: The aluminum foil after the secondary formation is completed undergoes the first heat treatment.

[0150] Re-forming: The aluminum foil that has undergone the first heat treatment is subjected to three or more levels of forming.

[0151] Post-treatment: At least one second heat treatment is performed after the final formation, and / or at least one phosphoric acid treatment, and / or at least one supplementary formation.

[0152] The preparation method in this invention breaks through the limitations of traditional single formation solution. Through innovative formation process, it achieves synergistic optimization of alumina film structure, hydration resistance and electrochemical performance, while reducing production costs and environmental impact.

[0153] A second aspect of the present invention provides an electrode foil prepared by the preparation method described in the first aspect.

[0154] In some embodiments of the present invention, the electrode foil may be a low-pressure aluminum electrode foil.

[0155] A third aspect of the present invention provides an aluminum electrolytic capacitor comprising an electrode foil prepared by the preparation method described in the first aspect or the electrode foil described in the second aspect.

[0156] Unless otherwise defined, the technical terms used in the following embodiments have the same meaning as commonly understood by those skilled in the art. Unless otherwise specified, the experimental reagents used in the following embodiments are all conventional biochemical reagents; the raw materials, instruments, and equipment used in the following embodiments can all be obtained commercially or through existing methods; unless otherwise specified, the amounts of experimental reagents used are the amounts used in conventional experimental operations; unless otherwise specified, the experimental methods are conventional methods. It should be further noted that the following description is merely exemplary and not a specific limitation of the present invention.

[0157] Example 1

[0158] A method for preparing 21Vf low-voltage aluminum electrode foil, the method comprising: primary formation → secondary formation + heat treatment → re-formation and post-treatment.

[0159] Primary formation: A 120 μm thick etched foil was placed in an ammonium adipate solution (the mass percentage of ammonium adipate in the ammonium adipate solution was 15%, and the remainder was deionized water) for primary formation. The formation temperature was 85℃, the formation time was 5 min, and the current density was 20 mA / cm². 2 The conversion voltage is 15% of the rated voltage.

[0160] Secondary formation: The aluminum foil that has undergone primary formation is placed in a mixed solution (the mixed solution contains 15% potassium adipic acid by mass, 0.1% potassium dihydrogen phosphate by mass, and the remainder is deionized water) for secondary formation. The formation temperature for secondary formation is 85℃, the formation time is 5 min, the current density is 30% of the current density of primary formation, and the formation voltage is 10% of the voltage of primary formation.

[0161] First heat treatment: Under an oxygen atmosphere, the aluminum foil that has undergone secondary formation is subjected to the first heat treatment at a temperature of 380℃ for 3 minutes.

[0162] Re-formation and post-processing

[0163] Third-stage formation: The aluminum foil that has undergone the first heat treatment is placed in an ammonium adipate solution (the mass percentage of ammonium adipate in the ammonium adipate solution is 15%, and the balance is deionized water) for third-stage formation. The formation temperature for third-stage formation is 85℃, the formation time is 5 minutes, and the current density is 40 mA / cm². 2 The voltage is converted to 60% of the rated voltage.

[0164] Fourth-stage formation: The aluminum foil after the third-stage formation is placed in an ammonium adipate solution (the mass percentage of ammonium adipate in the ammonium adipate solution is 15%, and the remainder is deionized water) for fourth-stage formation. The formation temperature for the fourth-stage formation is 85℃, the formation time is 5 minutes, and the current density is 40 mA / cm². 2 The voltage is converted to 100% of the rated voltage.

[0165] Second heat treatment: After the aluminum foil has undergone four-stage formation, it is washed with water and then subjected to a second heat treatment at a temperature of 480℃ for 2 minutes.

[0166] First replenishment formation: The aluminum foil that has undergone the second heat treatment is placed in a 5% (w / w) ammonium dihydrogen phosphate solution for the first replenishment formation. The temperature of the first replenishment formation is 85℃, the time is 2 min, and the current density is 40 mA / cm². 2The voltage for the supplementary voltage is 21V.

[0167] Phosphoric acid treatment: The aluminum foil after the first repair is immersed in a phosphoric acid solution with a phosphoric acid content of 3% by mass. The phosphoric acid treatment temperature is 45℃ and the time is 4min.

[0168] Third heat treatment: After washing the aluminum foil that has undergone phosphoric acid treatment, a third heat treatment is performed at a temperature of 480℃ for 2 minutes.

[0169] Second replenishment formation: The aluminum foil that has undergone the third heat treatment is placed in a 5% (w / w) ammonium dihydrogen phosphate solution for a second replenishment formation. The temperature for the second replenishment formation is 85℃, the time is 2 min, and the current density is 40 mA / cm². 2 The voltage of the second replenishment is 21V. After washing with water and drying, a 21Vf low-voltage aluminum electrode foil is obtained.

[0170] Example 2

[0171] A method for preparing a 67Vf low-voltage aluminum electrode foil, the method comprising: primary formation → secondary formation + heat treatment → re-formation and post-treatment.

[0172] Primary formation: A 120 μm thick etched foil was placed in an ammonium adipate solution (the mass percentage of ammonium adipate in the ammonium adipate solution was 10%, and the balance was deionized water) for primary formation. The formation temperature was 60℃, the formation time was 15 min, and the current density was 300 mA / cm². 2 The voltage is converted to 20% of the rated voltage.

[0173] Secondary formation: The aluminum foil that has undergone primary formation is placed in a mixed solution (the mixed solution contains 10% ammonium adipate by mass, 1% potassium dihydrogen phosphate by mass, and the remainder is deionized water) for secondary formation. The formation temperature for secondary formation is 75℃, the formation time is 10min, the current density is 70% of the current density of primary formation, and the formation voltage is 50% of the voltage of primary formation.

[0174] First heat treatment: Under an oxygen atmosphere, the aluminum foil that has undergone secondary formation is subjected to the first heat treatment at a temperature of 500℃ for 1 minute.

[0175] Re-formation and post-processing

[0176] Third-stage formation: The aluminum foil that has undergone the first heat treatment is placed in an ammonium adipate solution (the mass percentage of ammonium adipate in the ammonium adipate solution is 10%, and the balance is deionized water) for third-stage formation. The formation temperature for third-stage formation is 75℃, the formation time is 6 minutes, and the current density is 200 mA / cm². 2The conversion voltages are 60% of the rated voltage.

[0177] Fourth-stage formation: The aluminum foil after the third-stage formation is placed in an ammonium adipate solution (the mass percentage of ammonium adipate in the ammonium adipate solution is 10%, and the remainder is deionized water) for fourth-stage formation. The formation temperature for the fourth-stage formation is 75℃, the formation time is 6 minutes, and the current density is 200 mA / cm². 2 The voltage is converted to 100% of the rated voltage.

[0178] Phosphoric acid treatment: The aluminum foil after four-stage formation is immersed in a phosphoric acid solution with a phosphoric acid content of 3% by mass. The phosphoric acid treatment temperature is 60℃ and the time is 2min.

[0179] First replenishment formation: After rinsing the phosphoric acid-treated aluminum foil with water, the foil was placed in a 5% (w / w) ammonium dihydrogen phosphate solution for the first replenishment formation. The temperature of the first replenishment formation was 75℃, the time was 2 min, and the current density was 200 mA / cm². 2 The voltage for the first repair was 67V.

[0180] Second heat treatment: After washing the aluminum foil after the first repair, a second heat treatment is performed at a temperature of 500℃ for 2 minutes.

[0181] Second Completion Formation: The aluminum foil that has undergone the second heat treatment is placed in a 5% (w / w) ammonium dihydrogen phosphate solution for a second completion formation. The temperature for the second completion formation is 75℃, the time is 2 min, and the current density is 200 mA / cm². 2 The second forming voltage is 67V, and after washing with water and drying, a 67Vf low-voltage aluminum electrode foil is obtained.

[0182] Example 3

[0183] A method for preparing a 105Vf low-voltage aluminum electrode foil, the method comprising: primary formation → secondary formation + heat treatment → re-formation and post-treatment.

[0184] Primary formation: A 120 μm thick etched foil was placed in an ammonium adipate solution (the mass percentage of ammonium adipate in the ammonium adipate solution was 20%, and the balance was deionized water) for primary formation at a temperature of 70℃ for 3 min and a current density of 500 mA / cm². 2 The voltage is converted to 10% of the rated voltage.

[0185] Secondary formation: The aluminum foil that has undergone primary formation is placed in a mixed solution (the mixed solution contains 20% ammonium adipate by mass, 3% potassium dihydrogen phosphate by mass, and the remainder is deionized water) for secondary formation. The formation temperature for secondary formation is 60℃, the formation time is 3min, the current density is 50% of the current density of primary formation, and the formation voltage is 70% of the voltage of primary formation.

[0186] First heat treatment: Under an oxygen atmosphere, the aluminum foil that has undergone secondary formation is subjected to the first heat treatment at a temperature of 480℃ for 4 minutes.

[0187] Re-formation and post-processing

[0188] Third-stage formation: The aluminum foil that has undergone the first heat treatment is placed in an ammonium adipate solution (the mass percentage of ammonium adipate in the ammonium adipate solution is 20%, and the balance is deionized water) for third-stage formation. The third-stage formation temperature is 60℃, the formation time is 5 minutes, and the current density is 500mA / cm². 2 The voltage is converted to 50% of the rated voltage.

[0189] Fourth-stage formation: The aluminum foil after the third-stage formation is placed in an ammonium adipate solution (the mass percentage of ammonium adipate in the ammonium adipate solution is 20%, and the remainder is deionized water) for fourth-stage formation. The formation temperature for the fourth-stage formation is 60℃, the formation time is 5min, and the current density is 500mA / cm². 2 The voltage is converted to 75% of the rated voltage.

[0190] Fifth-stage formation: The aluminum foil after the fourth-stage formation is placed in an ammonium adipate solution (the mass percentage of ammonium adipate in the ammonium adipate solution is 20%, and the balance is deionized water) for fifth-stage formation. The formation temperature for the fifth-stage formation is 60℃, the formation time is 5min, and the current density is 500mA / cm². 2 The voltage is converted to 100% of the rated voltage.

[0191] Second heat treatment: After the aluminum foil has undergone four-stage formation, it is washed with water and then subjected to a second heat treatment at a temperature of 520℃ for 3 minutes.

[0192] First replenishment formation: The aluminum foil that has undergone the second heat treatment is placed in a 5% (w / w) ammonium dihydrogen phosphate solution for the first replenishment formation. The temperature of the first replenishment formation is 70℃, the time is 2 min, and the current density is 500 mA / cm². 2 The voltage for the first repair was 105V.

[0193] Phosphoric acid treatment: The aluminum foil after the first repair is immersed in a phosphoric acid solution with a phosphoric acid content of 3% by mass. The phosphoric acid treatment temperature is 65℃ and the time is 4min.

[0194] Third heat treatment: After washing the aluminum foil that has undergone phosphoric acid treatment, a third heat treatment is performed at a temperature of 520℃ for 3 minutes.

[0195] Second replenishment formation: The aluminum foil that has undergone the third heat treatment is placed in a 5% (w / w) ammonium dihydrogen phosphate solution for a second replenishment formation. The temperature for the second replenishment formation is 70℃, the time is 2 min, and the current density is 500 mA / cm². 2 The second forming voltage is 105V, and after washing and drying, a 105Vf low-voltage aluminum electrode foil is obtained.

[0196] Example 4

[0197] A method for preparing a 142Vf low-voltage aluminum electrode foil, the method comprising: primary formation → secondary formation + heat treatment → re-formation and post-treatment.

[0198] Primary formation: A 120 μm thick etched foil was placed in an ammonium adipate solution (the mass percentage of ammonium adipate in the ammonium adipate solution was 5%, and the balance was deionized water) for primary formation. The primary formation temperature was 90℃, the time was 0.5 min, and the current density was 50 mA / cm². 2 The conversion voltage is 4% of the rated voltage.

[0199] Secondary formation: The aluminum foil that has undergone primary formation is placed in a mixed solution (the mixed solution contains 3% ammonium adipate by mass, 3% potassium dihydrogen phosphate by mass, and the remainder is deionized water) for secondary formation. The temperature of secondary formation is 90℃, the time is 0.5min, the current density is 40% of the current density of primary formation, and the formation voltage is 60% of the voltage of primary formation.

[0200] First heat treatment: Under an oxygen atmosphere, the aluminum foil that has undergone secondary formation is subjected to the first heat treatment at a temperature of 380℃ for 5 minutes.

[0201] Re-formation and post-processing

[0202] Third-stage formation: The aluminum foil that has undergone the first heat treatment is placed in an ammonium adipate solution (ammonium adipate mass percentage of 15%, the remainder is deionized water) for third-stage formation. The third-stage formation temperature is 75℃, the formation time is 3 minutes, and the current density is 50mA / cm². 2 The voltage is converted to 50% of the rated voltage.

[0203] Fourth-stage formation: The aluminum foil after the third-stage formation is placed in an ammonium adipate solution (the mass percentage of ammonium adipate in the ammonium adipate solution is 15%, and the remainder is deionized water) for fourth-stage formation. The formation temperature for the fourth-stage formation is 75℃, the formation time is 3 minutes, and the current density is 50 mA / cm². 2 The voltage is converted to 75% of the rated voltage.

[0204] Fifth-stage formation: The aluminum foil after the fourth-stage formation is placed in an ammonium adipate solution (the mass percentage of ammonium adipate in the ammonium adipate solution is 15%, and the balance is deionized water) for fifth-stage formation. The formation temperature for the fifth-stage formation is 75℃, the formation time is 3 minutes, and the current density is 50 mA / cm². 2 The voltage is converted to 100% of the rated voltage.

[0205] Second heat treatment: After the aluminum foil has undergone five stages of formation, it is washed with water and then subjected to a second heat treatment at a temperature of 550℃ for 2 minutes.

[0206] First replenishment formation: The aluminum foil that has undergone the second heat treatment is placed in a 5% (w / w) ammonium dihydrogen phosphate solution for the first replenishment formation. The temperature of the first replenishment formation is 75℃, the time is 2 min, and the current density is 50 mA / cm². 2 The voltage for the first repair was 142V.

[0207] Phosphoric acid treatment: The aluminum foil after the first repair is immersed in a phosphoric acid solution with a phosphoric acid content of 3% by mass. The phosphoric acid treatment temperature is 60℃ and the time is 2min.

[0208] Third heat treatment: After the aluminum foil that has undergone phosphoric acid treatment is washed with water, it is subjected to a third heat treatment at a temperature of 550℃ for 2 minutes.

[0209] Second Completion Formation: The aluminum foil that has undergone the third heat treatment is placed in a 5% (w / w) ammonium dihydrogen phosphate solution for a second completion formation. The temperature for the second completion formation is 85℃, the time is 2 min, and the current density is 50 mA / cm². 2 The second replacement voltage is 142V, and after washing and drying, a 142Vf low-voltage aluminum electrode foil is obtained.

[0210] Example 5

[0211] A method for preparing a 40Vf low-voltage aluminum electrode foil, the method comprising: primary formation → secondary formation + heat treatment → re-formation and post-treatment.

[0212] Primary formation: A 120 μm thick etched foil was placed in an ammonium adipate solution (ammonium adipate comprising 15% by mass, with the remainder being deionized water) for primary formation. The primary formation temperature was 85 °C, the time was 5 min, and the current density was 20 mA / cm². 2 The first-stage conversion voltage is 15% of the rated voltage.

[0213] Secondary formation: The aluminum foil that has undergone primary formation is placed in a mixed solution (the mixed solution contains 15% potassium adipic acid by mass, 0.1% potassium dihydrogen phosphate by mass, and the remainder is deionized water) for secondary formation. The formation temperature for secondary formation is 85℃, the time is 5min, the current density is 30% of the current density of primary formation, and the formation voltage is 10% of the voltage of primary formation.

[0214] First heat treatment: Under an oxygen atmosphere, the aluminum foil that has undergone secondary formation is subjected to the first heat treatment at a temperature of 400℃ for 3 minutes.

[0215] Re-formation and post-processing

[0216] Third-stage formation: The aluminum foil that has undergone the first heat treatment is placed in an ammonium adipate solution (the mass percentage of ammonium adipate in the ammonium adipate solution is 15%, and the balance is deionized water) for third-stage formation. The formation temperature for third-stage formation is 85℃, the formation time is 5 minutes, and the current density is 80 mA / cm². 2 The voltage is converted to 100% of the rated voltage.

[0217] Second heat treatment: After the aluminum foil has undergone three-stage formation, it is washed with water and then subjected to a second heat treatment at a temperature of 480℃ for 2 minutes.

[0218] First replenishment formation: The aluminum foil that has undergone the second heat treatment is placed in a 5% (w / w) ammonium dihydrogen phosphate solution for the first replenishment formation. The temperature of the first replenishment formation is 85℃, the time is 2 min, and the current density is 80 mA / cm². 2 The voltage for the supplementary voltage is 40V.

[0219] Phosphoric acid treatment: The aluminum foil after the first repair is immersed in a phosphoric acid solution with a phosphoric acid content of 3% by mass. The phosphoric acid treatment temperature is 45℃ and the time is 4min.

[0220] Third heat treatment: After washing the aluminum foil that has undergone phosphoric acid treatment, a third heat treatment is performed at a temperature of 480℃ for 2 minutes.

[0221] Second Completion Formation: The aluminum foil that has undergone the third heat treatment is placed in a 5% (w / w) ammonium dihydrogen phosphate solution for a second completion formation. The temperature for the second completion formation is 85℃, the time is 2 min, and the current density is 80 mA / cm². 2 The second replacement voltage is 40V, and after washing with water and drying, a 40Vf low-voltage aluminum electrode foil is obtained.

[0222] Comparative Example 1

[0223] A method for preparing a 105Vf low-voltage aluminum electrode foil, the only difference between this method and Example 3 is that the secondary formation solution in Comparative Example 1 does not contain potassium dihydrogen phosphate, as detailed below:

[0224] Secondary formation: The aluminum foil that has undergone primary formation is placed in an ammonium adipate solution (the mass percentage of ammonium adipate in the ammonium adipate solution is 20%, and the remainder is deionized water) for secondary formation. The formation temperature of secondary formation is 60℃, the formation time is 3min, the current density is 50% of the current density of primary formation, and the formation voltage is 70% of the voltage of primary formation.

[0225] Comparative Example 2

[0226] A method for preparing a 105Vf low-voltage aluminum electrode foil, the only difference between this method and Example 3 is that in Comparative Example 2, after the completion of the secondary formation, the first heat treatment is not performed, but the re-formation and post-treatment are performed directly.

[0227] Comparative Example 3

[0228] A method for preparing a 105Vf low-voltage aluminum electrode foil, which differs from Example 3 only in the current density and formation voltage of the secondary formation in Comparative Example 3, as detailed below:

[0229] Secondary formation: The aluminum foil that has undergone primary formation is placed in a mixed solution (the mixed solution contains 20% ammonium adipate by mass, 3% potassium dihydrogen phosphate by mass, and the remainder is deionized water) for secondary formation. The formation temperature for secondary formation is 60℃, the formation time is 3 minutes, and the current density is 500 mA / cm². 2 The voltage is converted to 40% of the rated voltage.

[0230] Comparative Example 4

[0231] A method for preparing a 105Vf low-voltage aluminum electrode foil, which differs from Example 3 only in that the first-stage, second-stage, third-stage, fourth-stage, and fifth-stage formations in Comparative Example 4 all use a formation solution containing only one solute, and the first heat treatment is performed after the fifth-stage formation, as detailed below:

[0232] Primary formation: A 120 μm thick etched foil was placed in an ammonium adipate solution (the mass percentage of ammonium adipate in the ammonium adipate solution was 20%, and the balance was deionized water) for primary formation. The formation temperature was 70℃, the formation time was 3 min, and the current density was 500 mA / cm². 2 The first-stage conversion voltage is 10% of the rated voltage.

[0233] Secondary formation: The aluminum foil after primary formation is placed in an ammonium adipate solution (the mass percentage of ammonium adipate in the ammonium adipate solution is 20%, and the balance is deionized water) for secondary formation. The formation temperature for secondary formation is 70℃, the formation time is 3 minutes, and the current density is 500 mA / cm². 2 The secondary formation voltage is 30% of the rated voltage.

[0234] Tertiary formation: The aluminum foil that has undergone secondary formation is placed in an ammonium adipate solution (the mass percentage of ammonium adipate in the ammonium adipate solution is 20%, and the remainder is deionized water) for tertiary formation. The formation temperature for tertiary formation is 60℃, the formation time is 5min, and the current density is 500mA / cm². 2 The third-stage formation voltage is 50% of the rated voltage.

[0235] Fourth-stage formation: The aluminum foil that has undergone third-stage formation is placed in an ammonium adipate solution (the mass percentage of ammonium adipate in the ammonium adipate solution is 20%, and the remainder is deionized water) for fourth-stage formation. The formation temperature for fourth-stage formation is 60℃, the formation time is 5min, and the current density is 500mA / cm². 2 The fourth-level formation voltage is 75% of the rated voltage.

[0236] Fifth-stage formation: The aluminum foil that has undergone fourth-stage formation is placed in an ammonium adipate solution (the mass percentage of ammonium adipate in the ammonium adipate solution is 20%, and the balance is deionized water) for fifth-stage formation. The formation temperature for fifth-stage formation is 60℃, the formation time is 5 min, and the current density is 500 mA / cm². 2 The fifth-level formation voltage is 100% of the rated voltage.

[0237] First heat treatment: After washing with water, the aluminum foil is subjected to the first heat treatment at a temperature of 520℃ for 3 minutes.

[0238] First replenishment formation: The aluminum foil that has undergone the first heat treatment is placed in a 5% (w / w) ammonium dihydrogen phosphate solution for the first replenishment formation. The temperature of the first replenishment formation is 70℃, the time is 2 min, and the current density is 500 mA / cm². 2 The voltage for the first repair was 105V.

[0239] Phosphoric acid treatment: The aluminum foil after the first repair is immersed in a phosphoric acid solution with a phosphoric acid content of 3% by mass. The phosphoric acid treatment temperature is 65℃ and the time is 4min.

[0240] Second heat treatment: After the aluminum foil that has undergone phosphoric acid treatment is washed with water, it is subjected to a second heat treatment at a temperature of 520℃ for 3 minutes.

[0241] Second Completion Formation: The aluminum foil that has undergone the second heat treatment is placed in a 5% (w / w) ammonium dihydrogen phosphate solution for a second completion formation. The temperature for the second completion formation is 70℃, the time is 2 min, and the current density is 500 mA / cm². 2 The second forming voltage is 105V, and after washing and drying, a 105Vf low-voltage aluminum electrode foil is obtained.

[0242] Performance testing

[0243] Specific capacitance and hydration resistance of Tr60 were tested according to the standard test method SJ / T 11140-2022, the national standard for electrode foil for aluminum electrolytic capacitors.

[0244] Leakage current test method: First, according to the requirements of SJ / T 11140-2022 standard regarding withstand voltage and boost time tests, cut the sample into an effective size of 1cm × 5cm; then, complete the withstand voltage test according to the withstand voltage test procedure specified in the standard; subsequently, in the same bath environment as the withstand voltage test, set the boost current to 1mA and the test voltage to 90%Vf for testing; after continuously energizing for 10 minutes, the current value measured at this time is the leakage current value of the sample.

[0245] This can be understood as the leakage current being the magnitude of the leakage current after the withstand voltage test is completed and the voltage is continuously applied for 10 minutes at 90% Vf.

[0246] In this invention, the electrode foils prepared in the above embodiments and comparative examples were tested, and the test results are detailed in Table 1.

[0247] Table 1. Summary of performance test results of the electrode foils prepared in the examples and comparative examples.

[0248]

[0249] As can be seen from the data in Table 1, the electrode foil preparation method of the present invention can improve specific volume and enhance hydration resistance.

[0250] This invention achieves the optimization of alumina film structure and the simultaneous improvement of hydration resistance and electrochemical performance through the organic combination of multi-stage formation, mixed solution synergistic passivation, mixed solution stability control, and the synergistic effect of formation and heat treatment. It also has environmental friendliness and cost advantages, breaking through the technical bottlenecks of traditional processes.

[0251] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for preparing an electrode foil, characterized in that, The preparation method includes: performing a formation treatment on the etched foil, wherein the formation treatment has at least two stages, the formation treatment includes at least a first-stage formation and a second-stage formation, and performing a first heat treatment after the second-stage formation; The formation solution used in the secondary formation is a mixed solution containing adipate and potassium dihydrogen phosphate.

2. The method for preparing the electrode foil as described in claim 1, characterized in that, The formation voltage of the secondary formation is less than the formation voltage of the primary formation; Preferably, the formation voltage of the secondary formation is 10% to 70% of the formation voltage of the primary formation; Preferably, the formation voltage of the first-stage formation is 4% to 20% of the rated voltage; Preferably, the current density of the secondary formation is less than the current density of the primary formation; Preferably, the current density of the secondary formation is 30% to 70% of the current density of the primary formation; Preferably, the current density of the first-stage formation is 10 mA / cm². 2 ~500mA / cm 2 .

3. The method for preparing the electrode foil as described in claim 1, characterized in that, In the formation solution used in the secondary formation, the mass percentage of the adipic acid salt is 3% to 20%; and / or, the mass percentage of the potassium dihydrogen phosphate is 0.1% to 3%. Preferably, the adipic acid salt includes at least one of ammonium adipic acid and potassium adipic acid; Preferably, the solvent of the forming solution used in the secondary forming is pure water or deionized water; Preferably, the formation temperature of the secondary formation is 60℃~90℃; and / or, the formation time of the secondary formation is 0.5min~10min.

4. The method for preparing the electrode foil as described in claim 1, characterized in that, The temperature of the first heat treatment is 380℃~500℃; and / or the time of the first heat treatment is 1min~5min; Preferably, the first heat treatment is performed in an oxygen-containing atmosphere.

5. The method for preparing the electrode foil as described in claim 1, characterized in that, The formation temperature of the primary formation is 60℃~90℃; and / or, the formation time of the primary formation is 0.5min~15min; Preferably, the solute in the formation solution used in the primary formation includes at least one of adipate and dihydrogen phosphate; Preferably, the mass percentage of the solute in the formation solution used in the primary formation is 0.1% to 20%; Preferably, the solvent of the forming solution used in the primary forming process is pure water or deionized water.

6. The method for preparing the electrode foil as described in claim 1, characterized in that, The formation process has at least three stages, and the formation process further includes: performing three or more stages of formation after the first heat treatment; Optionally, the formation process has three stages, including primary formation, secondary formation and tertiary formation, and a first heat treatment is performed after the secondary formation, and the tertiary formation is performed after the first heat treatment; Optionally, the formation process has four stages, including primary formation, secondary formation, tertiary formation and quaternary formation, and a first heat treatment is performed after the secondary formation, the tertiary formation is performed after the first heat treatment, and the quaternary formation is performed after the tertiary formation. Optionally, the formation process has 5 stages, including first-stage formation, second-stage formation, third-stage formation, fourth-stage formation and fifth-stage formation, and a first heat treatment is performed after the second-stage formation, the third-stage formation is performed after the first heat treatment, the fourth-stage formation is performed after the third-stage formation, and the fifth-stage formation is performed after the fourth-stage formation. Optionally, the formation process has six stages, including first-stage formation, second-stage formation, third-stage formation, fourth-stage formation, fifth-stage formation, and sixth-stage formation. A first heat treatment is performed after the second-stage formation, the third-stage formation is performed after the first heat treatment, the fourth-stage formation is performed after the third-stage formation, the fifth-stage formation is performed after the fourth-stage formation, and the sixth-stage formation is performed after the fifth-stage formation.

7. The method for preparing the electrode foil as described in claim 6, characterized in that, In the three-stage and above formation processes, the solute in the formation solution used in each stage of formation independently includes at least one of adipate and dihydrogen phosphate. Preferably, in the three-stage and above formation processes, the mass percentage of solute in the formation solution used in each stage of formation is independently 0.1% to 20%; Preferably, in the three-stage and above formation processes, the solvent of the formation solution used in each stage of formation is independently pure water or deionized water; Preferably, in the three-stage and above formation processes, the formation temperature of each stage is independently 60°C to 90°C; and / or, the formation time of each stage is independently 0.5 min to 15 min. Preferably, in the three-stage and above formation processes, the current density of each formation stage is independently 10 mA / cm². 2 ~500mA / cm 2 ; Preferably, in the three-stage and above formation, the formation voltage increases progressively from the third-stage formation to the final-stage formation; Preferably, the formation voltage of the three-stage formation is greater than the formation voltage of the first-stage formation.

8. The method for preparing the electrode foil according to any one of claims 6 to 7, characterized in that, The preparation method further includes post-processing, which includes: performing at least one second heat treatment after the final formation, and / or performing at least one phosphoric acid treatment, and / or performing at least one supplementary formation; Preferably, the temperature of each second heat treatment is independently 380°C to 550°C, and / or the time of each second heat treatment is independently 0.5 min to 10 min; Preferably, the temperature of each phosphoric acid treatment is independently 40°C to 90°C; and / or the time of each phosphoric acid treatment is independently 0.5 min to 10 min. Preferably, each phosphoric acid treatment uses a phosphorus-containing solution independently; preferably, the mass percentage of phosphorus in the phosphorus-containing solution is independently 0.5% to 8%. Preferably, the temperature of each replenishment formation is independently 60°C to 90°C; and / or the time of each replenishment formation is independently 0.5 min to 15 min. Preferably, the solute in the treatment solution used in each replenishment process independently includes at least one of adipate and dihydrogen phosphate; Preferably, the mass percentage of the solute in the treatment solution used in each replenishment process is independently 0.1% to 20%; Preferably, the current density formed in each replenishment is independently 10 mA / cm². 2 ~500mA / cm 2 ; Preferably, the voltage formed by each compensation is greater than or equal to the rated voltage.

9. An electrode foil, characterized in that, The electrode foil is prepared by any one of claims 1 to 8.

10. An aluminum electrolytic capacitor, characterized in that, The aluminum electrolytic capacitor includes an electrode foil prepared by any one of claims 1 to 8 or an electrode foil as described in claim 9.

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