Medium-high voltage formed foil, method of making the same, and aluminum electrolytic capacitor

Abstract

The application discloses a kind of medium-high voltage formation foil and its preparation method, aluminum electrolytic capacitor, comprising the following steps: foil piece is placed in vacuum plasma equipment processing set time, vacuum plasma equipment is connected with oxygen, or argon and oxygen mixed gas, foil piece is transferred from vacuum plasma equipment to first organic solvent tank and soaked for a certain time, and the boiling point of first organic solvent is lower than 60 DEG C;Formation treatment.According to the technical scheme provided in the embodiment of the application, by pretreating the etching foil, the carbon content on the surface of the etching foil is reduced or cleared to zero by using the synergistic effect of physical cracking and chemical cleaning, to improve the surface activity and cleanliness of the etching foil material.Meanwhile, the pretreatment step completely removes carbon residues, avoids impurity decomposition from polluting the formation tank, prolongs the service life of the tank solution, and the etching foil material with high surface activity and cleanliness can improve the current efficiency of the anodization process and the uniformity of the oxide film.

Description

Technical Field

[0001] This invention generally relates to the field of capacitors, specifically to aluminum electrolytic capacitors, and more particularly to medium and high voltage electrolytic foils and their preparation methods, and aluminum electrolytic capacitors. Background Technology

[0002] In recent years, aluminum electrolytic capacitors, as fundamental electronic components, have expanded their applications from traditional electronics to emerging industries such as new energy. With technological advancements, industry demands for their performance continue to rise, with miniaturization and the development of high-capacitance anode foil remaining core research directions in this field.

[0003] In aluminum electrolytic capacitors, the dielectric layer of the anode foil is made by anodizing the etched foil to produce aluminum oxide. Therefore, the quality of the aluminum oxide determines the lifespan of the electrode foil and the capacitor. Excessive carbon impurities within the aluminum oxide dielectric layer on the anode foil surface can lead to various performance degradation issues. As a conductive material, carbon can form microscopic conductive channels, significantly increasing leakage current. This not only exacerbates capacitor heating and accelerates electrolyte drying but also shortens lifespan and may even cause short-circuit risks. Simultaneously, carbon impurities disrupt the density of the aluminum oxide layer, weakening its dielectric strength and reducing its withstand voltage, making it prone to localized breakdown under high voltage or pulsed conditions. Furthermore, the introduction of carbon increases dielectric loss (increases the loss tangent tanδ), leading to increased energy loss and significant temperature rise in high-frequency applications, further affecting efficiency and stability.

[0004] Furthermore, structurally, carbon can interfere with the uniform film formation of alumina, resulting in porous or unevenly thick defect layers. This reduces corrosion resistance and accelerates electrolyte erosion, leading to localized corrosion failure after long-term use. The combined effect of these problems significantly shortens capacitor lifespan, causing capacitance decay and an increase in equivalent series resistance (ESR), making it difficult to meet the high reliability requirements of industrial power supplies, new energy vehicles, and other fields. Summary of the Invention

[0005] In view of the above-mentioned defects or deficiencies in the prior art, it is desirable to provide a medium-high voltage electrolytic foil and its preparation method, as well as an aluminum electrolytic capacitor.

[0006] Firstly, a method for preparing medium- and high-voltage electrolytic foil is provided, comprising the following steps:

[0007] First pretreatment: The etched foil is placed in a vacuum plasma device for a set time, and the vacuum plasma device is purged with oxygen or a mixture of argon and oxygen.

[0008] Second pretreatment: The foil is transferred from the vacuum plasma equipment to a first organic solvent bath and immersed for a certain period of time. The boiling point of the first organic solvent is below 60°C.

[0009] Chemical formation process: The pretreated etched foil is subjected to a multi-stage chemical formation process to form a formed foil sheet.

[0010] As an feasible method, post-processing involves placing the formed foil in the vacuum plasma equipment for a set time, then transferring the formed foil to a second organic solvent bath for immersion for a certain time; followed by drying to form a medium-high pressure formed foil.

[0011] The vacuum plasma device is purged with oxygen or a mixture of argon and oxygen, and the second organic solvent has a boiling point below 60°C.

[0012] As a possible implementation, the first organic solvent is one of acetone, diethyl ether, dichloromethane, tetrahydrofuran, and cyclohexane;

[0013] The second organic solvent is one of acetone, diethyl ether, dichloromethane, tetrahydrofuran, and cyclohexane.

[0014] As an example, the vacuum plasma device has a power of 100-1000W and a processing time of 5-25 minutes.

[0015] As an feasible method, the pre-treated etched foil and the post-treated medium-high pressure etched foil are placed in an oven at 50-60°C for 5-20 minutes.

[0016] As one possible implementation, the formation process includes:

[0017] Pre-treatment: The pre-treated etched foil is placed in pure water for the first hydration treatment;

[0018] Primary formation: The pre-formed etched foil is placed in a mixed solution of 0.5-5 g / L ammonium adipate and 2-10 g / L ammonium citrate, and the current density is 30-70 mA / cm². 2 Under a voltage of 120-190V, the process takes 10-25 minutes.

[0019] Secondary formation: The etched foil that has undergone primary formation is placed in a mixed aqueous solution of 0.3-2.5 g / L ammonium adipate and 2-10 g / L ammonium citrate, and the current density is 30-70 mA / cm². 2 Under a voltage of 280-380V, the process takes 10-25 minutes.

[0020] Third-stage formation: The etched foil after second-stage formation is placed in a mixed solution of 2-6% boric acid and 2-10 g / L ammonium pentaborate, at a current density of 30-70 mA / cm². 2 Under a voltage of 400-590V, the process takes 10-25 minutes.

[0021] Fourth-stage formation: The etched foil after third-stage formation is placed in a mixed solution of 2-6% boric acid and 2-10 g / L ammonia pentaborate, at a current density of 30-70 mA / cm². 2 Under a voltage of 500-700V, the process takes 10-25 minutes.

[0022] As feasible methods, the following also include:

[0023] Repair Formation: The etched foil after the fourth-stage formation is annealed in an air atmosphere at a temperature of 350-600℃ for 1-5 minutes. Then, the annealed foil is placed in the mixed solution of the above four-stage formation processes at a current density of 30-70 mA / cm². 2 Repair formation is carried out under a voltage of 500-700V for 10-25 minutes.

[0024] Repeat the steps above.

[0025] As an feasible approach, the etched foil is dried before post-processing.

[0026] Secondly, a medium-high voltage forming foil is provided, which is prepared by the above-mentioned medium-high voltage forming foil preparation method.

[0027] Thirdly, an aluminum electrolytic capacitor is provided, comprising a medium-high voltage formed foil prepared by the above-described medium-high voltage formed foil preparation method, or the above-described medium-high voltage formed foil.

[0028] According to the technical solution provided in this application, by pretreating the etched foil, the carbon content on the surface of the etched foil is reduced or eliminated through the synergistic effect of physical pyrolysis and chemical cleaning, thereby improving the surface activity and cleanliness of the etched foil. Simultaneously, this pretreatment step thoroughly removes carbon residue, preventing contamination of the formation tank by impurities and extending the service life of the tank solution. Furthermore, the etched foil with higher surface activity and cleanliness can improve the current efficiency and oxide film uniformity of the anodizing process. Attached Figure Description

[0029] Other features, objects, and advantages of this application will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0030] Figure 1 This is a flowchart of the preparation method of the high-voltage electroplating foil in this embodiment. Detailed Implementation

[0031] The present application will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, only the parts relevant to the invention are shown in the accompanying drawings.

[0032] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0033] Please refer to Figure 1 This embodiment provides a method for preparing medium- and high-voltage electroplating foil, including the following steps:

[0034] S10: First pretreatment: The etched foil is placed in a vacuum plasma device for a set time, and the vacuum plasma device is purged with oxygen or a mixture of argon and oxygen.

[0035] S20: Second pretreatment: The foil is transferred from the vacuum plasma equipment to a first organic solvent bath for immersion for a certain period of time, wherein the boiling point of the first organic solvent is below 60°C;

[0036] Chemical formation process: The pretreated etched foil is subjected to a multi-stage chemical formation process to form a formed foil sheet.

[0037] In the manufacturing process of the anode foil for aluminum electrolytic capacitors, metallic aluminum foil is provided and etched to form etched foil. This etched foil is then subjected to a formation process to form medium- and high-voltage formed foil. During the production of the etched foil, to improve the uniformity and stability of the corrosion structure on the aluminum foil surface, polymeric corrosion inhibitors such as polyacrylic acid, polyvinyl alcohol, and sodium polystyrene sulfonate are typically added. These polymeric substances need to be thoroughly removed in subsequent cleaning processes. If the removal is incomplete, the polymeric substances will adsorb into the micro-pores or surface defects of the aluminum foil. During the subsequent high-temperature formation process, due to pyrolysis and carbonization, they eventually embed into the interstitial spaces of the alumina dielectric layer as amorphous carbon or graphitized carbon. The carbon residue left behind not only damages the chemical purity of the dielectric layer, but its conductivity also induces local electric field distortion, reducing breakdown voltage and exacerbating leakage current. Simultaneously, interface defects between carbon and alumina grain boundaries accelerate electrolyte penetration corrosion, ultimately leading to capacitor capacity decay and decreased reliability. Furthermore, unwashed long-chain carbon impurities are prone to pyrolysis in the high-temperature and high-pressure environment of subsequent formation processes, resulting in electrolyte contamination and accelerated electrolyte aging.

[0038] Therefore, this embodiment pre-treats the etched foil by using the synergistic effect of physical pyrolysis and chemical cleaning to reduce or eliminate the carbon content on the surface of the etched foil, thereby improving the surface activity and cleanliness of the etched foil. Simultaneously, this pre-treatment step thoroughly removes carbon residue, preventing impurities from decomposing and contaminating the formation tank, thus extending the service life of the tank solution. Furthermore, the etched foil with higher surface activity and cleanliness can improve the current efficiency and oxide film uniformity of the anodizing process.

[0039] First, in this embodiment, the etched foil is cleaned using plasma cleaning technology for a first pretreatment. High-energy particles generated by ionized oxygen bombard the surface of the etched foil at a microscopic level, precisely breaking the C / C bonds in long-chain polymers and fracturing them into short-chain fragments. Then, the foil leaving the vacuum plasma equipment is cleaned with a first organic solvent for a second pretreatment. The first organic solvent selectively dissolves and removes short-chain residues through intermolecular forces. These two pretreatments fundamentally remove carbon residues from the surface of the etched foil, reducing the risk of failure of the manufactured aluminum foil and thus improving its lifespan.

[0040] The first organic solvent used in the above embodiment is a solvent with a boiling point below 60°C. After soaking in the organic solvent, the organic solvent on the surface of the foil can be removed by heating, which can effectively avoid the adverse effects of the organic solvent residue on the subsequent formation process.

[0041] The etched foil, after two pretreatments, undergoes a formation process, which includes:

[0042] S30: Pre-treatment: The pre-treated etched foil is placed in pure water for the first hydration treatment;

[0043] S40: Primary Formation: The pre-formed etched foil is placed in a mixed solution of 0.5-5 g / L ammonium adipate and 2-10 g / L ammonium citrate, at a current density of 30-70 mA / cm². 2 Under a voltage of 120-190V, the process takes 10-25 minutes.

[0044] S50: Secondary Formation: The etched foil that has undergone primary formation is placed in a mixed aqueous solution of 0.3-2.5 g / L ammonium adipate and 2-10 g / L ammonium citrate, and the current density is 30-70 mA / cm². 2 Under a voltage of 280-380V, the process takes 10-25 minutes.

[0045] S60: Tertiary Formation: The etched foil after secondary formation is placed in a mixed solution of 2-6% boric acid and 2-10 g / L ammonium pentaborate, at a current density of 30-70 mA / cm².2 Under a voltage of 400-590V, the process takes 10-25 minutes.

[0046] S70: Quaternary Formation: The etched foil after tertiary formation is placed in a mixed solution of 2-6% boric acid and 2-10 g / L ammonia pentaborate, at a current density of 30-70 mA / cm². 2 Under a voltage of 500-700V, the process takes 10-25 minutes.

[0047] In this embodiment, the etched foil undergoes a four-stage formation process, in which an organic electrolyte system is used, such as ammonium adipate and sodium citrate, as solvents for formation treatment. These organic substances act as buffers or complexing agents to adjust the pH value of the electrolyte or promote the dense growth of the alumina film.

[0048] After the fourth-stage formation is completed, S80 repair formation is required. The etched foil after the fourth-stage formation is annealed in an air atmosphere at a temperature of 350-600℃ for 1-5 minutes. Then, the annealed etched foil is placed in the mixed solution of the above four-stage formation and repair formation is performed under the conditions of a current density of 30-70mA / cm2 and a voltage of 500-700V for 10-25 minutes.

[0049] Repeat the steps above.

[0050] In the above-mentioned repair formation process, the annealing and formation processes need to be repeated. After completion, the foil needs to be dried, preferably at 150-350°C for 3-5 minutes.

[0051] Because an organic electrolyte system is used in the above-mentioned formation process, this solvent system also introduces carbon impurities. Electrochemical decomposition may occur when voltage is applied, and unreacted organic molecules remain in the pores of the alumina dielectric layer. During subsequent repair formation processes, these molecules further carbonize under high-temperature aging conditions, forming nanoscale carbon particles or clusters. These carbon residues not only degrade the chemical purity of the dielectric layer, but their conductivity also induces local electric field distortion, reducing breakdown voltage and exacerbating leakage current. Simultaneously, interface defects between carbon and alumina grain boundaries accelerate electrolyte penetration and corrosion, ultimately leading to capacitor capacitance decay and decreased reliability. Therefore, this embodiment reduces carbon contamination of the dielectric layer by post-processing the formed foil.

[0052] Optional steps include:

[0053] S90: Post-processing: The formed foil is placed in the vacuum plasma equipment for a set time, and then the formed foil is transferred to the second organic solvent bath for a certain time; then it is dried to form a medium-high pressure formed foil;

[0054] The vacuum plasma device is purged with oxygen or a mixture of argon and oxygen, and the second organic solvent has a boiling point below 60°C.

[0055] Since the carbon impurities generated during the formation process are nanoscale carbon particles or clusters, they are removed using vacuum plasma equipment and organic solvent immersion. By employing the synergistic effect of physical pyrolysis and chemical cleaning, the carbon content on the foil surface is reduced or eliminated. First, high-energy particles generated by ionized oxygen bombard the corrosion foil surface at the microscopic level, precisely breaking the C / C / CH bonds in long-chain polymers and fracturing them into short-chain fragments. Then, a second organic solvent is used to clean the foil leaving the vacuum plasma equipment, performing a second pretreatment. This second organic solvent selectively dissolves and removes short-chain residues through intermolecular forces. By using a treatment method equivalent to the pretreatment for carbon impurity removal, not only are problems such as increased leakage current, decreased withstand voltage, and accelerated dielectric aging caused by carbon impurities damaging the density of the alumina dielectric layer are avoided, but the risk of carbon particles embedding in the dielectric layer weakening its self-healing properties and causing irreversible local breakdown is also reduced. Ultimately, when using this formed foil in aluminum electrolytic capacitors, leakage current is reduced, withstand voltage stability is improved, and the overall lifespan of the capacitor is extended.

[0056] Furthermore, the second organic solvent used in the above post-treatment steps is also a solvent with a boiling point below 60°C, which facilitates the removal of the second organic solvent.

[0057] In the above embodiments, both the first and second organic solvents can be one of acetone, diethyl ether, dichloromethane, tetrahydrofuran, and cyclohexane. The power of the vacuum plasma equipment is 100-1000W, and the processing time in the vacuum plasma equipment is 5-25 minutes.

[0058] Therefore, both the pre-treated etched foil and the post-treated medium- and high-pressure formed foil require continuous low-temperature heating to evaporate the organic solvents and avoid the adverse effects of residual organic solvents. Preferably, the foil sheets are placed in an oven at 50-60°C for 5-20 minutes.

[0059] In the above embodiments, carbon impurities on the etched foil are first treated through pretreatment. High-energy plasma particles are used, and by precisely controlling the energy, they act only on long-chain polymeric impurities on the surface, avoiding mechanical or chemical damage to the micron-level porous structure of the etched foil and fully preserving its high specific surface area characteristics, providing an ideal substrate morphology for subsequent formation processes. Compared with traditional acid pickling processes, this technology is more environmentally friendly and can precisely control the cleaning depth.

[0060] The following are four sets of embodiments and comparative examples:

[0061] Example 1: A method for preparing long-life, medium-high voltage forming foil for aluminum electrolytic capacitors is provided. The method includes the following steps:

[0062] S1: Pretreatment of etched foil: The etched foil is placed in a vacuum plasma device, oxygen is introduced, and it is treated at 1000W power for 5 minutes. Then it is transferred to a cyclohexane washing tank, soaked for 10 minutes, and finally placed in a 60-degree oven for 20 minutes.

[0063] S2: Pre-treatment: The pre-treated etched foil is placed in pure water at 95°C for the first hydration treatment for 8 minutes.

[0064] S3: Primary formation. The pre-formed etched foil is placed in a mixed solution of 4.8 g / L ammonium adipate and 8.9 g / L ammonium citrate at 88°C, and formed for 15 min under the conditions of a current density of 50 mA / cm2 and a voltage of 170 V.

[0065] S4: Secondary formation. The foil that has undergone primary formation is placed in a mixed aqueous solution of 2.3 g / L ammonium adipate and 6.5 g / L ammonium citrate at 88°C and formed for 15 min under the conditions of a current density of 50 mA / cm2 and a voltage of 340 V.

[0066] S5: Third-stage formation. The foil after the second-stage formation is placed in a mixed solution of 5% boric acid and 8.5 g / L ammonia pentaborate at 88°C, with a current density of 50 mA / cm2 and a voltage of 550 V, and formed for 15 min.

[0067] S6: Fourth-stage formation. The foil after the third-stage formation is placed in a mixed solution of 2.5% boric acid and 3.5 g / L ammonia pentaborate at 88°C, and the formation is carried out for 25 min under the conditions of a current density of 50 mA / cm2 and a voltage of 625 V.

[0068] S7: Repair Formation. The foil is annealed in an air atmosphere at 450°C for 1 minute. The annealed foil is then placed in a four-stage formation bath at 88°C under conditions of 50 mA / cm² current and 625 V for 25 minutes. This annealing and formation process is repeated. Finally, the resulting foil is dried at 320°C for 3 minutes.

[0069] S8: Post-treatment: The formed foil is placed in a vacuum plasma device, and an oxygen-mixed gas is introduced. It is treated at 1000W power for 10 minutes. Then it is transferred to a cyclohexane washing tank, soaked for 15 minutes, and finally placed in a 60-degree oven for 20 minutes.

[0070] Comparative Example 1: S2-S7 operations in Example 1.

[0071] Example 2: A method for preparing long-life, medium-high voltage forming foil for aluminum electrolytic capacitors is provided, the method comprising the following steps:

[0072] S1: Pre-treatment of etched foil. The foil is placed in a vacuum plasma device and purged with an argon / oxygen mixture at a flow rate ratio of 15:85 for 25 minutes at 150W. It is then transferred to a tetrahydrofuran washing tank, soaked for 5 minutes, and finally placed in a 60°C oven for 18 minutes.

[0073] S2: Pre-treatment: The pre-treated etched foil is placed in pure water at 90°C for the first hydration treatment for 15 minutes.

[0074] S3: Primary formation. The pre-formed etched foil is placed in a mixed solution of 1.5 g / L ammonium adipate and 2.5 g / L ammonium citrate at 82°C and formed for 12 min under the conditions of a current density of 35 mA / cm2 and a voltage of 125 V.

[0075] S4: Secondary formation. The foil that has undergone primary formation is placed in a mixed aqueous solution of 0.8 g / L ammonium adipate and 2.5 g / L ammonium citrate at 82°C and formed for 12 min under the conditions of current density of 35 mA / cm2 and voltage of 295 V.

[0076] S5: Third-stage formation. The foil after the second-stage formation is placed in a mixed solution of 3.5% boric acid and 2.6 g / L ammonium pentaborate at 82°C, with a current density of 35 mA / cm2 and a voltage of 420 V, and formed for 12 min.

[0077] S6: Fourth-stage formation. The foil after the third-stage formation is placed in a mixed solution of 2.5% boric acid and 2.6 g / L ammonia pentaborate at 82°C, and the formation is carried out for 12 min under the conditions of a current density of 350 mA / cm2 and a voltage of 515 V.

[0078] S7 Repair Formation: The foil is annealed in an air atmosphere at 400°C for 3 minutes. The annealed foil is then placed in a four-stage formation bath at 82°C under conditions of 35 mA / cm² current and 515 V for 12 minutes. This annealing and formation process is repeated. Finally, the resulting foil is dried at 200°C for 5 minutes.

[0079] S8: Post-treatment. The formed foil is placed in a vacuum plasma apparatus and argon / oxygen mixed gas is introduced at a flow rate ratio of 15:85. It is treated at 150W power for 25 minutes. Then it is transferred to a tetrahydrofuran washing tank and soaked for 15 minutes. Finally, it is placed in a 60°C oven for 15 minutes.

[0080] Comparative Example 2: S2-S7 operations in Example 2.

[0081] Example 3: A method for preparing long-life, medium-high voltage forming foil for aluminum electrolytic capacitors is provided, the method comprising the following steps:

[0082] S1: Pre-treatment of etched foil. The foil is placed in a vacuum plasma device and treated with oxygen and argon / oxygen mixed gas at 350W for 15 minutes. Then it is transferred to an ether washing tank and soaked for 15 minutes, and finally placed in a 60-degree oven for 20 minutes.

[0083] S2: Pre-treatment: The pre-treated etched foil is placed in pure water at 98°C for the first hydration treatment for 6 minutes.

[0084] S3: Primary formation. The pre-formed etched foil is placed in a mixed solution of 4.2 g / L ammonium adipate and 6.5 g / L ammonium citrate at 77°C, and formed for 20 min under the conditions of a current density of 55 mA / cm2 and a voltage of 180 V.

[0085] S4: Secondary formation. The foil that has undergone primary formation is placed in a mixed aqueous solution of 2.1 g / L ammonium adipate and 6.0 g / L ammonium citrate at 77°C and formed for 20 min under the conditions of current density of 55 mA / cm2 and voltage of 300 V.

[0086] S5: Three-stage formation. The foil after the second-stage formation is placed in a mixed solution of 3.8% boric acid and 6.5 g / L ammonium pentaborate and formed for 20 min at 77°C, current density of 55 mA / cm2 and voltage of 480 V.

[0087] S6: Fourth-stage formation. The foil after the third-stage formation is placed in a mixed solution of 2.4% boric acid and 6.5 g / L ammonia pentaborate at 77°C, and the formation is carried out for 20 min under the conditions of a current density of 55 mA / cm2 and a voltage of 610 V.

[0088] S7: Repair Formation. The foil is annealed in an air atmosphere at 500°C for 3 minutes. The annealed foil is then placed in a four-stage formation bath at 77°C under conditions of 55 mA / cm² current and 610 V for 20 minutes. This annealing and formation process is repeated. Finally, the resulting foil is dried at 280°C for 5 minutes.

[0089] S8: Post-treatment: The formed foil is placed in a vacuum plasma device, oxygen is introduced, and it is treated at 350W for 15 minutes. Then it is transferred to an ether washing tank, soaked for 15 minutes, and finally placed in a 60-degree oven for 20 minutes.

[0090] Comparative Example 3: S2-S7 operations in Example 3.

[0091] Example 4: A method for preparing long-life, medium-high voltage forming foil for aluminum electrolytic capacitors is provided, the method comprising the following steps:

[0092] S1: Pre-treatment of etched foil. The foil is placed in a vacuum plasma device, oxygen is introduced, and it is treated at 565W for 12 minutes. Then it is transferred to a dichloromethane washing tank, soaked for 8 minutes, and finally placed in a 60-degree oven for 8 minutes.

[0093] S2: Pre-treatment: The pre-treated etched foil is placed in pure water at 90°C for the first hydration treatment for 15 minutes.

[0094] S3: Primary formation. The pre-formed etched foil is placed in a mixed solution of 2.1 g / L ammonium adipate and 3.8 g / L ammonium citrate at 80°C, and formed for 20 min under the conditions of a current density of 65 mA / cm2 and a voltage of 170 V.

[0095] S4: Secondary formation. The foil that has undergone primary formation is placed in a mixed aqueous solution of 1.7 g / L ammonium adipate and 3.8 g / L ammonium citrate at 80 °C and formed for 20 min under the conditions of a current density of 65 mA / cm2 and a voltage of 320 V.

[0096] S5: Third-stage formation. The foil after the second-stage formation is placed in a mixed solution of 4.5% boric acid and 8.5 g / L ammonium pentaborate and formed for 20 min at 80°C, current density of 65 mA / cm2 and voltage of 520 V.

[0097] S6: Fourth-stage formation. The foil after the third-stage formation is placed in a mixed solution of 2.8% boric acid and 8.5 g / L ammonia pentaborate at 80°C, and the formation is carried out for 20 min under the conditions of a current density of 65 mA / cm2 and a voltage of 630 V.

[0098] S7: Repair Formation. The foil is annealed in an air atmosphere at 420°C for 5 minutes. The annealed foil is then placed in a four-stage formation bath at 80°C under conditions of 65 mA / cm² current and 630 V for 20 minutes. This annealing and formation process is repeated. Finally, the resulting foil is dried at 325°C for 4 minutes.

[0099] S8: Post-treatment: The formed foil is placed in a vacuum plasma device, oxygen is introduced, and it is treated at 565W for 12 minutes. Then it is transferred to a dichloromethane washing tank, soaked for 8 minutes, and finally placed in a 60-degree oven for 8 minutes.

[0100] Comparative Example 4: S2-S7 operations in Example 4.

[0101] test:

[0102] The formed foils prepared in the above embodiments and comparative examples were subjected to specific capacity testing, withstand voltage testing, and carbon residue testing. The results are as follows:

[0103]

[0104] The test results from the examples and comparative examples show that the method provided in this disclosure effectively reduces carbon residue in the formed foil while maintaining stable withstand voltage and specific capacity.

[0105] It should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer" used above to indicate orientation or positional relationships are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention; the directional terms "inner" and "outer" refer to the inside or outside relative to the outline of each component itself. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include one or more of that feature.

[0106] For ease of description, spatial relative terms such as "above," "on top of," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation beyond the orientation of the device as described in the figures. For example, if the device in the figures were inverted, a device described as "above" or "on top of" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways, rotated 90 degrees, or in other orientations, and the spatial relative descriptions used herein will be interpreted accordingly.

[0107] The above description is merely a preferred embodiment of this application and an explanation of the technical principles employed. Those skilled in the art should understand that the scope of the invention involved in this application is not limited to technical solutions formed by specific combinations of the above-described technical features, but should also cover other technical solutions formed by arbitrary combinations of the above-described technical features or their equivalents without departing from the inventive concept. For example, technical solutions formed by substituting the above features with (but not limited to) technical features with similar functions disclosed in this application.

Claims

1. A method of producing a medium-high voltage formed foil, characterized by, The method comprises the steps of: First pretreatment: placing the etching foil in a vacuum plasma device for a set time, for bombarding the etching foil surface at a micro level by high-energy particles generated by ionized oxygen, and cracking long-chain polymers into short-chain fragments, wherein the vacuum plasma device is supplied with oxygen or a mixture of argon and oxygen, Second pretreatment: transferring the foil from the vacuum plasma device to a first organic solvent tank for a certain time, for dissolving and removing the short-chain fragments, wherein the first organic solvent has a boiling point lower than 60℃, and the first organic solvent is one of acetone, diethyl ether, dichloromethane, tetrahydrofuran, and cyclohexane; Chemical treatment: performing multi-stage chemical treatment on the pretreated etching foil to form a chemically treated foil.

2. The method of claim 1, wherein the high pressure formation of the foil is performed at a temperature of 20°C to 100°C. The method further comprises the steps of: Post-treatment: placing the chemically treated foil in the vacuum plasma device for a set time, and then transferring the chemically treated foil to a second organic solvent tank for a certain time; and then drying to form a medium-high voltage chemical etching foil; wherein the vacuum plasma device is supplied with oxygen or a mixture of argon and oxygen, and the second organic solvent has a boiling point lower than 60℃.

3. The method for preparing a medium-high voltage chemical etching foil according to claim 2, wherein: the second organic solvent is one of acetone, diethyl ether, dichloromethane, tetrahydrofuran, and cyclohexane.

4. The method of claim 2, wherein the high pressure formation of the foil is performed at a temperature of 20 to 100 °C. The power of the vacuum plasma device is 100-1000W, and the treatment time in the vacuum plasma device is 5-25 minutes.

5. The method of claim 2, wherein the high pressure formation of the foil is performed at a temperature of 20°C to 100°C. The second pretreated etching foil and the post-treated medium-high voltage chemical etching foil are placed in an oven at 50-60℃ for 5-20 minutes.

6. The method of claim 1, wherein the high pressure formation of the foil is performed at a temperature of 20°C to 100°C. The chemical treatment comprises: Pre-chemical treatment: placing the pretreated etching foil in pure water for a first hydration treatment; Primary formation: the etching foil after pre-formation is placed in a mixed solution of 0.5-5 g / L ammonium adipate and 2-10 g / L ammonium citrate, and is formed for 10-25 min under the conditions of current density of 30-70 mA / cm 2 , voltage of 120-190 V. Secondary formation: the etching foil after the first formation is put into a mixed aqueous solution of 0.3-2.5 g / L ammonium adipate and 2-10 g / L ammonium citrate, and is formed for 10-25 min under the conditions of a current density of 30-70 mA / cm 2 , a voltage of 280-380 V. tertiary formation: the secondary formed etching foil is placed in a mixed solution of 2-6% boric acid and 2-10 g / L ammonium pentaborate, and formed for 10-25 min under the conditions of current density of 30-70 mA / cm 2 , voltage of 400-590 V. Quaternary formation: after the third level of the formation of the etching foil in 2-6% boric acid, 2-10g / L five boric acid ammonia mixed solution, under the condition of current density is 30-70mA / cm 2 , voltage is 500-700V, the formation of 10-25min.

7. The method of claim 6, wherein the high pressure formation of the foil is performed at a temperature of 20°C to 100°C. The method further comprises: Repairing chemical formation: the etching foil after the fourth chemical formation is annealed, the annealing atmosphere is air atmosphere, the temperature is 350-600℃, the time is 1-5min, then the annealed etching foil is placed in the mixed solution of the above fourth chemical formation, and the repairing chemical formation is carried out under the condition that the current density is 30-70mA / cm 2 , the voltage is 500-700V, and the chemical formation time is 10-25min. repeating the above steps.

8. The method of claim 2, wherein the high pressure formation of the foil is performed at a temperature of 20°C to 100°C. Before the post-treatment of the etching foil, the etching foil is subjected to a drying treatment.

9. A medium-high voltage formation foil, characterized in that, The medium-high voltage chemical etching foil is prepared by the method for preparing a medium-high voltage chemical etching foil according to any one of claims 1-8.

10. An aluminum electrolytic capacitor characterized by comprising: The medium-high voltage chemical etching foil is prepared by the method for preparing a medium-high voltage chemical etching foil according to any one of claims 1-8, or the medium-high voltage chemical etching foil according to claim 9.

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