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, a preparation method thereof and an aluminum electrolytic capacitor. The preparation method comprises the following steps: carrying out formation treatment, hydration treatment and first heat treatment on an aluminum foil; the formation treatment at least comprises first-stage formation and second-stage formation; the hydration treatment comprises hydration pre-treatment and hydration post-treatment; the preparation method comprises the following steps: carrying out hydration pretreatment on an aluminum foil, then carrying out formation treatment, and carrying out hydration post-treatment and first heat treatment after any stage of formation treatment. According to the preparation method of the electrode foil, the dielectric property of the electrode foil can be improved while the energy consumption can be effectively reduced.

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] Aluminum electrolytic capacitors are widely used in many electronic fields due to their excellent dielectric properties, such as high capacitance, high withstand voltage, and high energy density. The electrode foil is the core of an aluminum electrolytic capacitor; its quality determines the specific capacitance and operating voltage, directly influencing the capacitor's performance. However, the traditional anodizing process in electrode foil production requires high voltage (e.g., above 700 V) to form the dielectric oxide layer. During this process, Al... 3+ and O 2- Ion migration requires overcoming high potential barriers, resulting in high energy consumption, significant Joule heating, and a high proportion of additional energy loss. As a result, the cost of electricity in the industry has become a major factor restricting the development of the electrolytic capacitor industry.

[0003] In the field of aluminum electrolytic capacitor electrode foil preparation, existing mainstream methods for reducing electricity costs include electrolyte system innovation, intelligent control of multi-stage formation processes, and high-frequency pulse power supplies. However, these methods still have many shortcomings, which restrict their widespread application in the industry. Electrolyte systems are currently mainly developing towards low impedance, such as using non-aqueous electrolytes and other organic solvents. However, non-aqueous solvents are prone to leaving harmful impurities, leading to increased oxide film defect rates and significant environmental risks (difficulty in recycling some low-impedance electrolytes, and additional wastewater treatment costs). Intelligent control of multi-stage formation processes requires stringent data accumulation and precise voltage / temperature adjustment, resulting in high yield fluctuation risks and long payback periods, making it difficult for small and medium-sized enterprises to achieve effective energy savings in a short period. High-frequency pulse power supply equipment upgrades are costly, hindering industrial application.

[0004] In summary, existing processes suffer from numerous significant drawbacks, including oxide film degradation, high equipment upgrade costs, complex process control, insufficient material compatibility, and environmental hazards, resulting in persistently high electricity costs. There is an urgent need for a simple and universal electrode foil production method that can reduce costs while simultaneously improving performance. Summary of the Invention

[0005] The present invention aims to provide an electrode foil and its preparation method, as well as an aluminum electrolytic capacitor. The electrode foil preparation method provided by the present invention combines hydration treatment and heat treatment in the traditional multi-stage formation process, which can effectively reduce energy consumption while improving the dielectric properties of the electrode foil.

[0006] In a first aspect, the present invention provides a method for preparing an electrode foil, the method comprising: performing a formation treatment, a hydration treatment, and a first heat treatment on the aluminum foil; The formation process includes at least primary formation and secondary formation; The hydration treatment includes pre-hydration treatment and post-hydration treatment; The preparation method includes: performing a pre-hydration treatment on the aluminum foil followed by a formation treatment, and performing a post-hydration treatment and a first heat treatment after any first-stage formation treatment.

[0007] According to some embodiments of the present invention, the method for preparing the electrode foil provided by the present invention may further include the following auxiliary technical features: In some embodiments, the pre-hydration treatment includes placing the aluminum foil in boiling water for 600-720 seconds. Specifically, the pre-hydration treatment includes placing the aluminum foil in boiling water for any value within the range of 600-720 seconds, 610-620-700 seconds, 603-640-650-660-670-680-690-700-710-720 seconds.

[0008] In some embodiments, the formation process further includes tertiary formation.

[0009] In some embodiments, the formation process further includes tertiary and quaternary formation.

[0010] In some embodiments, the forming solution of the forming process includes one or more of boric acid and citric acid.

[0011] In some embodiments, the forming solution of the forming process includes boric acid and citric acid.

[0012] In some embodiments, the forming solution for the forming treatment is a mixed aqueous solution of boric acid and citric acid.

[0013] In some embodiments, the boric acid in the forming solution of the forming treatment has a mass percentage of 2%-10%. Specifically, the mass percentage of boric acid in the forming solution of the forming treatment is any value within the range of 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or 2%-10%.

[0014] In some embodiments, the citric acid in the formation solution of the formation treatment has a mass percentage of 0.2%-2%. Specifically, the citric acid in the formation solution of the formation treatment has a mass percentage of 0.2%, 0.4%, 0.6%, 0.8%, 1.0%, 1.2%, 1.4%, 1.6%, 1.8%, 2%, or any value within the range of 0.2%-2%.

[0015] In some embodiments, the formation voltage of the first-stage formation is 170V-190V. Specifically, the formation voltage of the first-stage formation is any value within the range of 170V, 175V, 180V, 185V, 190V, or 170V-190V.

[0016] In some embodiments, the constant pressure time for the first-stage formation is 240s-360s. Specifically, the constant pressure time for the first-stage formation is any value within the range of 240s, 250s, 260s, 270s, 280s, 290s, 300s, 310s, 320s, 330s, 340s, 350s, 360s, or 240s-360s.

[0017] In some embodiments, the primary formation temperature is 70°C-90°C. Specifically, the primary formation temperature is any value within the range of 70°C, 75°C, 80°C, 85°C, 90°C, or 70°C-90°C. In this invention, the primary formation temperature can be understood as the temperature of the primary formation solution (i.e., the primary formation liquid).

[0018] In some embodiments, the formation voltage of the secondary formation is 350V-370V. Specifically, the formation voltage of the secondary formation is any value within the range of 350V, 355V, 360V, 365V, 370V, or 350V-370V.

[0019] In some embodiments, the constant pressure time for the secondary formation is 400s-500s. Specifically, the constant pressure time for the secondary formation is any value within the range of 400s, 410s, 420s, 430s, 440s, 450s, 460s, 470s, 480s, 490s, 500s, or 400s-500s.

[0020] In some embodiments, the secondary formation temperature is 70°C-90°C. Specifically, the secondary formation temperature is any value within the range of 70°C, 75°C, 80°C, 85°C, 90°C, or 70°C-90°C. In this invention, the secondary formation temperature can be understood as the temperature of the secondary formation solution (i.e., the secondary formation liquid).

[0021] In some embodiments, the formation voltage of the three-stage formation is 500V-520V. Specifically, the formation voltage of the three-stage formation is any value within the range of 500V, 505V, 510V, 515V, 520V, or 500V-520V.

[0022] In some embodiments, the constant pressure time for the three-stage formation is 550s-650s. Specifically, the constant pressure time for the three-stage formation is any value within the range of 550s, 560s, 570s, 580s, 590s, 600s, 610s, 620s, 630s, 640s, 650s, or 550s-650s.

[0023] In some embodiments, the tertiary formation temperature is 70°C-90°C. Specifically, the tertiary formation temperature is any value within the range of 70°C, 75°C, 80°C, 85°C, 90°C, or 70°C-90°C. In this invention, the tertiary formation temperature can be understood as the temperature of the tertiary formation solution (i.e., the tertiary formation liquid).

[0024] In some embodiments, the formation voltage of the four-stage formation is 570V-590V. Specifically, the formation voltage of the four-stage formation is any value within the range of 570V, 570V, 580V, 585V, 590V, or 570V-590V.

[0025] In some embodiments, the constant pressure time of the four-stage formation is 900-1200s. Specifically, the constant pressure time of the four-stage formation is any value within the range of 900s, 950s, 1000s, 1050s, 1100s, 1150s, 1200s, or 900-1200s.

[0026] In some embodiments, the temperature of the fourth-stage formation is 70-90°C. Specifically, the temperature of the fourth-stage formation is any value within the range of 70°C, 75°C, 80°C, 85°C, 90°C, or 70-90°C. In this invention, the temperature of the fourth-stage formation can be understood as the temperature of the fourth-stage formation solution (i.e., the fourth-stage formation liquid).

[0027] In this invention, hydration post-treatment can be performed after any of the first-stage, second-stage, third-stage, and fourth-stage formations.

[0028] In some embodiments, the post-hydration treatment includes placing the aluminum foil after any first-stage formation treatment in boiling water for 360s-720s. Specifically, the post-hydration treatment includes placing the aluminum foil after any first-stage formation treatment in boiling water for any value within the range of 360s, 400s, 450s, 500s, 550s, 600s, 650s, 700s, 720s, or 360s-720s.

[0029] In some embodiments, a first heat treatment is performed after the hydration post-treatment.

[0030] In some embodiments, the temperature of the first heat treatment is 210°C-300°C. Specifically, the temperature of the first heat treatment is any value within the range of 210°C, 220°C, 230°C, 240°C, 250°C, 260°C, 270°C, 280°C, 290°C, 300°C, or 210°C-300°C.

[0031] In some embodiments, the duration of the first heat treatment is 300s-1800s. Specifically, the duration of the first heat treatment is any value within the range of 300s, 400s, 500s, 600s, 700s, 800s, 900s, 1000s, 1100s, 1200s, 1300s, 1400s, 1500s, 1600s, 1700s, 1800s, or 300s-1800s.

[0032] In some embodiments, the preparation method includes: performing a pre-hydration treatment on the aluminum foil followed by primary formation, a post-hydration treatment, and a first heat treatment, and then performing secondary formation; optionally, performing tertiary formation after the secondary formation; optionally, performing tertiary and quaternary formations after the secondary formation.

[0033] In some embodiments, the preparation method includes: performing a hydration pretreatment on the aluminum foil followed by primary formation and secondary formation, and performing a hydration posttreatment and a first heat treatment after the secondary formation; optionally, performing tertiary formation after the first heat treatment; optionally, performing tertiary and quaternary formation after the first heat treatment.

[0034] In some embodiments, the preparation method includes: performing a hydration pretreatment on the aluminum foil followed by primary formation, secondary formation, and tertiary formation; performing a hydration posttreatment and a first heat treatment after the tertiary formation; optionally, performing a quaternary formation after the first heat treatment.

[0035] In some embodiments, the preparation method includes: performing a pre-hydration treatment on the aluminum foil followed by primary formation, secondary formation, tertiary formation, and quaternary formation, and then performing a post-hydration treatment and a first heat treatment after the quaternary formation.

[0036] In some embodiments, the preparation method includes: depolarization treatment, repair formation treatment, and stabilization treatment.

[0037] In some implementations, the depolarization process includes: a first depolarization process; In some implementations, the depolarization process includes: a first depolarization process and a second depolarization process; In some embodiments, the treatment solution for the first depolarization treatment is an aqueous solution of phosphoric acid.

[0038] In some embodiments, the mass percentage of phosphoric acid in the treatment solution of the first depolarization treatment is 4%-6%. Specifically, the mass percentage of phosphoric acid in the treatment solution of the first depolarization treatment is any value within the range of 4%, 4.5%, 5%, 5.5%, 6%, or 4%-6%.

[0039] In some embodiments, the temperature of the first depolarization treatment is 40°C-60°C. Specifically, the temperature of the first depolarization treatment is any value within the range of 40°C, 45°C, 50°C, 55°C, 60°C, or 40°C-60°C. In this invention, the temperature of the first depolarization treatment can be understood as the temperature of the treatment solution used in the first depolarization treatment.

[0040] In some implementations, the duration of the first depolarization process is 120s-240s. Specifically, the duration of the first depolarization process is any value within the range of 120s, 140s, 160s, 180s, 200s, 220s, 240s, or 120s-240s.

[0041] In some embodiments, the treatment solution for the second depolarization treatment is an aqueous phosphoric acid solution.

[0042] In some embodiments, the mass percentage of phosphoric acid in the treatment solution of the second depolarization treatment is 6%-8%. Specifically, the mass percentage of phosphoric acid in the treatment solution of the second depolarization treatment is any value within the range of 6%, 6.5%, 7%, 7.5%, 8%, or 6%-8%.

[0043] In some embodiments, the temperature of the second depolarization treatment is 60°C-70°C. Specifically, the temperature of the second depolarization treatment is any value within the range of 60°C, 65°C, 70°C, or 60°C-70°C. In this invention, the temperature of the second depolarization treatment can be understood as the temperature of the treatment solution used in the second depolarization treatment.

[0044] In some implementations, the duration of the second depolarization process is 120s-600s. Specifically, the duration of the second depolarization process is any value within the range of 120s, 150s, 200s, 250s, 300s, 350s, 400s, 450s, 500s, 550s, 600s, or 120s-600s.

[0045] In some embodiments, the repair formation process includes: a first repair formation process.

[0046] In some embodiments, the repair formation process includes: a first repair formation process and a second repair formation process.

[0047] In some embodiments, the repair formation process includes: a first repair formation process, a second repair formation process, and a third repair formation process.

[0048] In some embodiments, the treatment solutions for the first, second, and third repair formation treatments are each independently an aqueous solution of boric acid.

[0049] In some embodiments, the mass percentage of boric acid in the treatment solutions of the first, second, and third remedial formation treatments is independently 2%-10%. Specifically, the mass percentage of boric acid in the treatment solutions of the first, second, and third remedial formation treatments is independently 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or any value within the range of 2%-10%.

[0050] In some embodiments, the formation voltages of the first, second, and third repair formation processes are each independently between 570V and 590V. Specifically, the formation voltages of the first, second, and third repair formation processes are each independently any value within the range of 270V, 275V, 580V, 585V, 590V, or 570V-590V.

[0051] In some embodiments, the constant pressure time for the first, second, and third repair formation processes is independently 400s-500s. Specifically, the constant pressure time for the first, second, and third repair formation processes is independently any value within the range of 400s, 410s, 420s, 430s, 440s, 450s, 460s, 470s, 480s, 490s, 500s, or 400s-500s.

[0052] In some embodiments, the temperatures of the first, second, and third repair formation processes are each independently between 70°C and 90°C. Specifically, the temperatures of the first, second, and third repair formation processes are each independently 70°C, 75°C, 80°C, 85°C, 90°C, or any value within the range of 70°C to 90°C. In this invention, the temperature of the first repair formation process can be understood as the temperature of the treatment solution used in the first repair formation process; the temperature of the second repair formation process can be understood as the temperature of the treatment solution used in the second repair formation process; and the temperature of the third repair formation process can be understood as the temperature of the treatment solution used in the third repair formation process.

[0053] In some embodiments, the stabilization treatment solution is an aqueous solution of ammonium dihydrogen phosphate.

[0054] In some embodiments, the mass percentage of ammonium dihydrogen phosphate in the stabilization treatment solution is 0.5%-3%. Specifically, the mass percentage of ammonium dihydrogen phosphate in the stabilization treatment solution is any value within the range of 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, or 0.5%-3%.

[0055] In some embodiments, the stabilization treatment temperature is 50°C-70°C. Specifically, the stabilization treatment temperature is any value within the range of 50°C, 55°C, 60°C, 65°C, 70°C, or 50°C-70°C.

[0056] In some embodiments, the stabilization treatment time is 60s-240s. Specifically, the stabilization treatment time is any value within the range of 60s, 70s, 80s, 90s, 100s, 110s, 120s, 130s, 140s, 150s, 160s, 170s, 180s, 190s, 200s, 210s, 220s, 230s, 240s, or 60s-240s.

[0057] In some embodiments, the preparation method further includes a second heat treatment.

[0058] In some embodiments, the preparation method further includes a second heat treatment and a third heat treatment.

[0059] In some embodiments, the temperatures of the second and third heat treatments are each independently between 520°C and 580°C. Specifically, the temperatures of the second and third heat treatments are each independently any value within the range of 520°C, 530°C, 540°C, 550°C, 560°C, 570°C, 580°C, or 520°C-580°C.

[0060] In some embodiments, the duration of the second and third heat treatments is independently between 100s and 240s. Specifically, the duration of the second and third heat treatments is independently any value within the range of 100s, 110s, 120s, 130s, 140s, 150s, 160s, 170s, 180s, 190s, 200s, 210s, 220s, 230s, 240s, or 100s-240s.

[0061] In some embodiments, the preparation method includes washing the aluminum foil with water before performing any of the treatments.

[0062] In some embodiments, the aluminum foil is an etched foil.

[0063] In some embodiments, the preparation method further includes washing with water after stabilization treatment and then drying.

[0064] In some embodiments, the drying temperature is 90°C-180°C. Specifically, the drying temperature is any value within the range of 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, 180°C, or 90°C-180°C.

[0065] In some embodiments, the drying time is 150s-240s. Specifically, the drying time is any value within the range of 150s, 160s, 170s, 180s, 190s, 200s, 210s, 220s, 230s, 240s, or 150s-240s.

[0066] In a second aspect, the present invention provides an electrode foil, which is prepared by the preparation method described in the first aspect.

[0067] Thirdly, 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.

[0068] The beneficial effects of this invention are as follows: This invention forms an alumina dielectric layer through a formation process (i.e., anodizing). Following any stage of the formation process, a post-hydration treatment induces uniformly distributed nanopores within the alumina dielectric layer generated after anodizing. These nanopores disperse the electric field intensity, preventing localized current concentration and thus increasing the breakdown voltage of the alumina dielectric layer. This structure reduces the high-voltage requirement during subsequent anodizing, enabling subsequent oxide film growth (including the formation process after hydration and depolarization) to achieve a high-quality, high-voltage dielectric layer with less energy, significantly reducing energy consumption. Furthermore, the post-hydration treatment thickens the porous boehmite layer on the outer side of the alumina dielectric layer. This thicker layer not only facilitates its subsequent conversion into the alumina dielectric layer with less energy consumption but also, to some extent, hinders the intrusion of impurity ions from the solution into the dielectric layer, further improving dielectric properties. The purpose of heat treatment is to transform the porous pseudo-thin boehm layer on the outer layer of the alumina dielectric layer into an alumina dielectric layer without affecting the nanopores, thereby reducing leakage current.

[0069] This invention introduces hydration treatment combined with heat treatment after the formation process, which introduces uniformly distributed nanopores into the alumina dielectric layer. By controlling the nanopores to optimize the current distribution, the breakdown voltage is improved to reduce the energy required for subsequent alumina dielectric layer growth, thereby reducing energy consumption while improving dielectric performance. It also has environmental friendliness and cost advantages.

[0070] Terminology Explanation In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0071] The terms “room temperature” or “normal temperature” refer to ambient temperature, which is approximately 10°C to approximately 35°C, approximately 10°C to approximately 30°C, or approximately 20°C to 30°C, or approximately 25°C.

[0072] The term "wt%" indicates a percentage by mass.

[0073] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0074] In the following content, all figures disclosed herein, whether or not they use the words "approximately" or "about," are approximate values. The value of each figure may vary by 1%, 2%, 5%, 7%, 8%, 10%, 15%, or 20%. Whenever a figure with a value of N is disclosed, any figure with a value of N+ / -1%, N+ / -2%, N+ / -3%, N+ / -5%, N+ / -7%, N+ / -8%, N+ / -10%, N+ / -15%, or N+ / -20% will be explicitly disclosed, where "+ / -" indicates addition or subtraction.

[0075] Specific Implementation Scheme The following description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

[0076] The preparation method of the electrode foil of the present invention includes the following steps: hydration pretreatment - primary formation - hydration posttreatment - first heat treatment - secondary formation - tertiary formation - quaternary formation - first depolarization treatment - second heat treatment - first repair formation - second depolarization treatment - second repair formation - third heat treatment - third repair formation - stabilization treatment - drying; Alternatively, the preparation method of the electrode foil includes the following steps: hydration pretreatment - primary formation - secondary formation - hydration posttreatment - first heat treatment - tertiary formation - quaternary formation - first depolarization treatment - second heat treatment - first repair formation - second depolarization treatment - second repair formation - third heat treatment - third repair formation - stabilization treatment - drying; Alternatively, the preparation method of the electrode foil includes the following steps: hydration pretreatment - primary formation - secondary formation - tertiary formation - hydration posttreatment - first heat treatment - quaternary formation - first depolarization treatment - second heat treatment - first repair formation - second depolarization treatment - second repair formation - third heat treatment - third repair formation - stabilization treatment - drying; Alternatively, the preparation method of the electrode foil includes the following steps: pre-hydration treatment - primary formation - secondary formation - tertiary formation - quaternary formation - post-hydration treatment - first heat treatment - first depolarization treatment - second heat treatment - first repair formation - second depolarization treatment - second repair formation - third heat treatment - third repair formation - stabilization treatment - drying.

[0077] For example, the method for preparing the electrode foil of the present invention can be specifically explained as including the following steps: S1 hydration pretreatment: Place the etched foil in boiling water for 600s-720s.

[0078] S2 Primary Formation: After the etched foil has undergone hydration pretreatment, it is washed with water and then placed in the primary formation solution (the primary formation solution is a mixed aqueous solution of boric acid and citric acid, wherein the mass percentage of boric acid is 2%-10% and the mass percentage of citric acid is 0.2%-2%) for primary formation. The formation voltage of primary formation is 170V-190V, the constant voltage time of primary formation is 240s-360s, and the temperature of primary formation is 70℃-90℃.

[0079] S3 post-hydration treatment: After washing the etched foil that has undergone primary formation with water, place it in boiling water for 360s-720s.

[0080] S4 First heat treatment: After the hydrated corrosion foil is cleaned with water, it is placed in an environment of 210℃-300℃ for 300s-1800s.

[0081] S5 Secondary Formation: After the etched foil has undergone the first heat treatment, it is cleaned with water and then placed in a secondary formation solution (a mixed aqueous solution of boric acid and citric acid, wherein the mass percentage of boric acid is 2%-10% and the mass percentage of citric acid is 0.2%-2%) for secondary formation. The formation voltage for secondary formation is 350V-370V, the constant voltage time for secondary formation is 400s-500s, and the temperature for secondary formation is 70℃-90℃.

[0082] S6 Three-stage formation: After cleaning the etched foil that has undergone two-stage formation with water, it is placed in a three-stage formation solution (the three-stage formation solution is a mixed aqueous solution of boric acid and citric acid, wherein the mass percentage of boric acid is 2%-10% and the mass percentage of citric acid is 0.2%-2%) for three-stage formation. The formation voltage of the three-stage formation is 500V-520V, the constant voltage time of the three-stage formation is 550s-650s, and the temperature of the three-stage formation is 70℃-90℃.

[0083] S7 Quadruple Formation: After the etched foil has undergone tertiary formation, it is washed with water and then placed in a quaternary formation solution (a mixed aqueous solution of boric acid and citric acid, wherein the mass percentage of boric acid is 2%-10% and the mass percentage of citric acid is 0.2%-2%) for quaternary formation. The formation voltage for quaternary formation is 570V-590V, the constant voltage time for quaternary formation is 900s-1200s, and the temperature for quaternary formation is 70℃-90℃.

[0084] S8 First Depolarization Treatment: After the etched foil after the fourth-stage formation is washed with water, it is placed in the treatment solution for the first depolarization treatment (the treatment solution for the first depolarization treatment is an aqueous solution of phosphoric acid, in which the mass percentage of phosphoric acid is 4%-6%). The temperature of the first depolarization treatment is 40℃-60℃, and the time of the first depolarization treatment is 120s-240s.

[0085] S9 Second Heat Treatment: After cleaning the etched foil after the first depolarization treatment with water, place it in an environment of 520℃-580℃ for 100s-240s.

[0086] S10 First Repair Formation: After cleaning the etched foil after the first heat treatment with water, place it in the treatment solution for the first repair formation treatment (the treatment solution for the first repair formation treatment is a boric acid aqueous solution, in which the mass percentage of boric acid is 2%-10%) for repair formation. The formation voltage for the first repair formation is 570V-590V, the constant voltage time for the first repair formation is 400s-500s, and the temperature for the first repair formation is 70℃-90℃.

[0087] S11 Second Depolarization Treatment: After cleaning the etched foil after the first repair formation with water, place it in the treatment solution for the second depolarization treatment (the treatment solution for the second depolarization treatment is an aqueous solution of phosphoric acid, in which the mass percentage of phosphoric acid is 6%-8%). The temperature of the second depolarization treatment is 60℃-70℃, and the time of the second depolarization treatment is 120s-600s.

[0088] S12 Second Repair Formation: After cleaning the etched foil after the second depolarization treatment with water, it is placed in the treatment solution for the second repair formation treatment (the treatment solution for the second repair formation treatment is a boric acid aqueous solution, in which the mass percentage of boric acid is 2%-10%) for repair formation. The formation voltage for the second repair formation is 570V-590V, the constant voltage time for the second repair formation is 400s-500s, and the temperature for the second repair formation is 70℃-90℃.

[0089] S13 Third heat treatment: After cleaning the etched foil after the second repair formation with water, place it in an environment of 520℃-580℃ for 100s-240s.

[0090] S14 Third Repair Formation: After cleaning the etched foil after the second heat treatment with water, it is placed in the treatment solution for the third repair formation treatment (the treatment solution for the third repair formation treatment is a boric acid aqueous solution, in which the mass percentage of boric acid is 2%-10%) for repair formation. The formation voltage for the third repair formation is 570V-590V, the constant voltage time for the third repair formation is 400s-500s, and the temperature for the third repair formation is 70℃-90℃.

[0091] S15 Stabilization Treatment: After cleaning the etched foil after the third repair formation with water, place it in the stabilization treatment solution (the stabilization treatment solution is an aqueous solution of ammonium dihydrogen phosphate, in which the mass percentage of ammonium dihydrogen phosphate is 0.5%-3%). The stabilization treatment temperature is 50℃-70℃, and the stabilization treatment time is 60s-240s.

[0092] S16 Drying: After the stabilization treatment, the etched foil is washed with water and then dried at 90℃-180℃ for 150s-240s to obtain the electrode foil.

[0093] The embodiments of the present invention will be described in detail below with reference to specific examples. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of the invention. Where specific conditions are not specified in the examples, the conditions described in the instruction manual, conventional conditions, or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0094] Example 1 S1 hydration pretreatment: Place the etched foil in boiling water for 720 seconds.

[0095] S2 Primary Formation: After the etched foil has undergone hydration pretreatment, it is washed with water and then placed in the primary formation solution (the primary formation solution is a mixed aqueous solution of boric acid and citric acid, wherein the mass percentage of boric acid is 6% and the mass percentage of citric acid is 0.8%) for primary formation. The formation voltage of the primary formation is 180V, the constant voltage time of the primary formation is 300s, and the temperature of the primary formation is 85℃.

[0096] S3 post-hydration treatment: After washing the etched foil that has undergone primary formation with water, place it in boiling water for 600 seconds.

[0097] S4 First heat treatment: After the hydrated corrosion foil is cleaned with water, it is placed in an environment of 260℃ for 600s.

[0098] S5 Secondary Formation: After the etched foil has undergone the first heat treatment, it is cleaned with water and then placed in a secondary formation solution (a mixed aqueous solution of boric acid and citric acid, wherein the mass percentage of boric acid is 6% and the mass percentage of citric acid is 0.6%) for secondary formation. The formation voltage for secondary formation is 360V, the constant voltage time for secondary formation is 450s, and the temperature for secondary formation is 85℃.

[0099] S6 Three-stage formation: After cleaning the etched foil that has undergone two-stage formation with water, it is placed in a three-stage formation solution (the three-stage formation solution is a mixed aqueous solution of boric acid and citric acid, wherein the mass percentage of boric acid is 6% and the mass percentage of citric acid is 0.4%) for three-stage formation. The formation voltage of the three-stage formation is 510V, the constant voltage time of the three-stage formation is 600s, and the temperature of the three-stage formation is 85℃.

[0100] S7 Quadruple Formation: After the etched foil has undergone tertiary formation, it is washed with water and then placed in a quaternary formation solution (a mixed aqueous solution of boric acid and citric acid, wherein the mass percentage of boric acid is 6% and the mass percentage of citric acid is 0.2%) for quaternary formation. The formation voltage for quaternary formation is 580V, the constant voltage time for quaternary formation is 1000s, and the temperature for quaternary formation is 85℃.

[0101] S8 First Depolarization Treatment: After the etched foil after the fourth-stage formation is washed with water, it is placed in the treatment solution for the first depolarization treatment (the treatment solution for the first depolarization treatment is an aqueous solution of phosphoric acid, in which the mass percentage of phosphoric acid is 5%). The temperature of the first depolarization treatment is 45℃ and the time of the first depolarization treatment is 180s.

[0102] S9 Second Heat Treatment: After the first depolarization treatment, the etched foil is washed with water and placed in an environment of 550℃ for 120s.

[0103] S10 First Repair Formation: After cleaning the etched foil after the first heat treatment with water, it is placed in the treatment solution for the first repair formation treatment (the treatment solution for the first repair formation treatment is a boric acid aqueous solution, in which the mass percentage of boric acid is 8%) for repair formation. The first repair formation voltage is 580V, the first repair formation constant voltage time is 450s, and the first repair formation temperature is 85℃.

[0104] S11 Second Depolarization Treatment: After the corrosion foil after the first repair formation is cleaned with water, it is placed in the treatment solution for the second depolarization treatment (the treatment solution for the second depolarization treatment is an aqueous solution of phosphoric acid, in which the mass percentage of phosphoric acid is 7%). The temperature of the second depolarization treatment is 65℃ and the time of the second depolarization treatment is 360s.

[0105] S12 Second Repair Formation: After the etched foil after the second depolarization treatment is cleaned with water, it is placed in the treatment solution for the second repair formation treatment (the treatment solution for the second repair formation treatment is a boric acid aqueous solution, in which the mass percentage of boric acid is 8%) for repair formation. The formation voltage for the second repair formation is 580V, the constant voltage time for the second repair formation is 450s, and the temperature for the second repair formation is 85℃.

[0106] S13 Third heat treatment: After cleaning the etched foil after the second repair formation with water, place it in an environment of 550℃ for 120s.

[0107] S14 Third Repair Formation: After cleaning the etched foil after the second heat treatment with water, it is placed in the treatment solution for the third repair formation treatment (the treatment solution for the third repair formation treatment is a boric acid aqueous solution, in which the mass percentage of boric acid is 8%) for repair formation. The formation voltage for the third repair formation is 580V, the constant voltage time for the third repair formation is 450s, and the temperature for the third repair formation is 85℃.

[0108] S15 Stabilization Treatment: After the corrosion foil after the third repair formation is cleaned with water, it is placed in the stabilization treatment solution (the stabilization treatment solution is an aqueous solution of ammonium dihydrogen phosphate, in which the mass percentage of ammonium dihydrogen phosphate is 2%). The stabilization treatment temperature is 60℃ and the stabilization treatment time is 120s.

[0109] S16 Drying: After the stabilization treatment, the etched foil is washed with water and then dried at 120°C for 180 seconds to obtain the electrode foil.

[0110] Example 2 The difference between Example 2 and Example 1 is that the post-hydration treatment and the first heat treatment are carried out after the second-stage formation, while the other conditions are the same as in Example 1.

[0111] Example 3 The difference between Example 3 and Example 1 is that the post-hydration treatment and the first heat treatment are carried out after the third-stage formation, while the other conditions are the same as in Example 1.

[0112] Example 4 The difference between Example 4 and Example 1 is that the post-hydration treatment and the first heat treatment are carried out after the fourth-stage formation, while the other conditions remain the same as in Example 1.

[0113] Example 5 The difference between Example 5 and Example 2 is that in the post-hydration treatment step, the etched foil after secondary formation is washed with water and then placed in boiling water for 720 seconds, while the other conditions are the same as in Example 2.

[0114] Example 6 The difference between Example 6 and Example 2 is that in the first heat treatment step, the etched foil after hydration treatment is washed with water and then placed in an environment of 300°C for 600 seconds. The remaining conditions are the same as in Example 2.

[0115] Example 7 The difference between Example 7 and Example 2 is that in the first heat treatment step, the etched foil after hydration treatment was washed with water and then placed in an environment of 260°C for 1800 seconds. The remaining conditions were the same as in Example 2.

[0116] Comparative Example 1 (post-hydration treatment without hydration and first heat treatment) No post-hydration treatment or first heat treatment was performed; all other conditions remained the same as in Example 2.

[0117] Comparative Example 2 (without first heat treatment) No first heat treatment was performed after hydration, and the remaining conditions were the same as in Example 2.

[0118] Comparative Example 3 (without post-hydration treatment) No post-hydration treatment was performed, and all other conditions remained the same as in Example 2.

[0119] Comparative Example 4 (first undergoing hydration post-treatment and first heat treatment, then undergoing formation treatment) The electrode foil is prepared as follows: pre-hydration treatment - post-hydration treatment - first heat treatment - primary formation - secondary formation - tertiary formation - quaternary formation - first depolarization treatment - second heat treatment - first repair formation - second depolarization treatment - second repair formation - third heat treatment - third repair formation - stabilization treatment - drying; The remaining conditions are the same as in Example 2.

[0120] Comparative Example 5 (the post-hydration treatment and the first heat treatment were carried out separately) The electrode foil is prepared as follows: pre-hydration treatment - primary formation - post-hydration treatment - secondary formation - first heat treatment - tertiary formation - quaternary formation - first depolarization treatment - second heat treatment - first repair formation - second depolarization treatment - second repair formation - third heat treatment - third repair formation - stabilization treatment - drying; The remaining conditions are the same as in Example 2.

[0121] Comparative Example 6 (first heat treatment, then hydration post-treatment) The electrode foil is prepared as follows: pre-hydration treatment - primary formation - secondary formation - first heat treatment - post-hydration treatment - tertiary formation - quaternary formation - first depolarization treatment - second heat treatment - first repair formation - second depolarization treatment - second repair formation - third heat treatment - third repair formation - stabilization treatment - drying; The remaining conditions are the same as in Example 2.

[0122] Test data The electrode foils obtained in Examples 1-7 and Comparative Examples 1-6 were tested for various parameters according to the test standard SJ / T 11140-2022 "Electrode Foil for Aluminum Electrolytic Capacitors"; among which, Vt(Vf): is the withstand voltage value; Cap(μF / cm 2 ): This refers to the specific capacity; Tr60(s): is the hydration pressure rise time, which is the pressure rise time tested after the aluminum foil is boiled in boiling water for 1 hour; Energy (kWh / m 2 ): The amount of electricity consumed per square meter when converted to a withstand voltage of 600V; LC(μA / cm 2 ): This represents leakage current.

[0123] Vt, Tr, and LC were all tested using a TV tester; Cap was tested using an LCR digital bridge; and the charge was tested using a TS680 small-sample formation process analyzer. The results are shown in Table 1.

[0124] Table 1

[0125] The capacity comparison is calculated as follows: (Specific capacity of the embodiment or comparative example - Specific capacity of comparative example 1) / Specific capacity of comparative example 1 × 100%; The energy consumption comparison is calculated as follows: (Electricity consumed by the example or comparative example - Electricity consumed by comparative example 1) / Electricity consumed by comparative example 1 × 100%.

[0126] Analysis of the data in Table 1 shows that: Compared with Comparative Example 1, Examples 1-7 show that by adding a process combining "hydration post-treatment + first heat treatment" during the formation process, significant improvements in energy consumption and capacity were achieved without increasing leakage current LC and hydration boost time Tr60. This is because the hydration post-treatment after any formation process induces the formation of uniformly distributed nanopores in the alumina dielectric layer.

[0127] Compared with Comparative Examples 2 and 3, Comparative Example 2 only had a post-hydration treatment without a first heat treatment, which led to a significant increase in leakage current. Comparative Example 3 only had a first heat treatment without a post-hydration treatment, which resulted in no increase in capacity or reduction in energy consumption. This is because the introduction of nanopores requires a first heat treatment to thin the outer porous pseudo-thin boehmite layer and convert it into an alumina dielectric layer, thereby reducing leakage current.

[0128] Compared with Comparative Example 4, Example 2, which performed "post-hydration treatment + first heat treatment" before the formation treatment, failed to improve capacity and reduce energy consumption. This is because performing post-hydration treatment before the formation treatment is equivalent to extending the pre-hydration treatment time. The excessively long pre-hydration treatment time causes the generated hydrated alumina to clog the pores, resulting in capacity decay. Only after a layer of crystalline alumina is generated after the formation treatment can energy consumption be effectively reduced and capacity improved.

[0129] Compared with Comparative Examples 5 and 6, in Example 2, after adjusting the order of post-hydration treatment and the first heat treatment, the leakage current increased significantly. This was because the thickened porous pseudo-thin boehmite layer on the outer layer was not treated in time, which led to an increase in defects during subsequent formation treatment and thus increased leakage current.

[0130] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0131] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for preparing an electrode foil, characterized in that, The preparation method includes: chemical formation treatment, hydration treatment and first heat treatment of aluminum foil; The formation process includes at least primary formation and secondary formation; The hydration treatment includes pre-hydration treatment and post-hydration treatment; The preparation method includes: performing a pre-hydration treatment on the aluminum foil followed by a formation treatment, and performing a post-hydration treatment and a first heat treatment after any first-stage formation treatment.

2. The preparation method according to claim 1, characterized in that, The hydration pretreatment includes placing the aluminum foil in boiling water for 600-720 seconds.

3. The preparation method according to any one of claims 1 or 2, characterized in that, The formation process also includes three-stage formation; Optionally, the formation process further includes tertiary formation and quaternary formation; Optionally, the forming solution of the forming treatment includes one or more of boric acid and citric acid; Optionally, the forming solution for the forming treatment is a mixed aqueous solution of boric acid and citric acid; Optionally, the boric acid in the formation solution of the formation treatment has a mass percentage of 2%-10%; Optionally, the citric acid in the formation solution of the formation treatment has a mass percentage of 0.2%-2%; Optionally, the formation voltage of the first-stage formation is 170V-190V; Optionally, the constant pressure time for the first-stage formation is 240s-360s; Optionally, the temperature of the primary formation is 70℃-90℃; Optionally, the formation voltage of the secondary formation is 350V-370V; Optionally, the constant pressure time for the secondary formation is 400s-500s; Optionally, the temperature of the secondary formation is 70℃-90℃; Optionally, the formation voltage of the three-stage formation is 500V-520V; Optionally, the constant pressure time for the three-stage formation is 550s-650s; Optionally, the temperature of the tertiary formation is 70℃-90℃; Optionally, the formation voltage of the four-stage formation is 570V-590V; Optionally, the constant pressure time for the four-stage formation is 900-1200 s; Optionally, the temperature of the fourth-stage formation is 70-90°C.

4. The preparation method according to any one of claims 1-3, characterized in that, The post-hydration treatment includes placing aluminum foil that has undergone any first-stage formation treatment in boiling water for 360s-720s.

5. The preparation method according to any one of claims 1-4, characterized in that, The first heat treatment is performed after the hydration post-treatment. Optionally, the temperature of the first heat treatment is 210℃-300℃; Optionally, the duration of the first heat treatment is 300s-1800s.

6. The preparation method according to any one of claims 1-5, characterized in that, The preparation method includes: performing a hydration pretreatment on the aluminum foil, followed by a primary formation, a post-hydration treatment, and a first heat treatment, and then a secondary formation; optionally, performing a tertiary formation after the secondary formation; optionally, performing a tertiary and quaternary formation after the secondary formation. And / or, The preparation method includes: performing a hydration pretreatment on the aluminum foil, followed by primary formation and secondary formation, and then performing a hydration posttreatment and a first heat treatment after the secondary formation; optionally, performing a tertiary formation after the first heat treatment; optionally, performing a tertiary formation and a quaternary formation after the first heat treatment. And / or, The preparation method includes: performing a hydration pretreatment on the aluminum foil, followed by primary formation, secondary formation and tertiary formation, and performing a hydration posttreatment and a first heat treatment after the tertiary formation; optionally, performing a quaternary formation after the first heat treatment. And / or, The preparation method includes: performing a hydration pretreatment on the aluminum foil, followed by primary formation, secondary formation, tertiary formation and quaternary formation, and then performing a hydration posttreatment and a first heat treatment after the quaternary formation.

7. The preparation method according to any one of claims 1-6, characterized in that, The preparation method includes: depolarization treatment, repair formation treatment, and stabilization treatment; Optionally, the depolarization process includes: a first depolarization process; Optionally, the depolarization process includes: a first depolarization process and a second depolarization process; Optionally, the treatment solution for the first depolarization treatment is an aqueous phosphoric acid solution; Optionally, the mass percentage of phosphoric acid in the treatment solution of the first depolarization treatment is 4%-6%; Optionally, the temperature of the first depolarization treatment is 40℃-60℃; Optionally, the duration of the first depolarization process is 120s-240s; Optionally, the treatment solution for the second depolarization treatment is an aqueous phosphoric acid solution; Optionally, the mass percentage of phosphoric acid in the treatment solution of the second depolarization treatment is 6%-8%; Optionally, the temperature of the second depolarization treatment is 60℃-70℃; Optionally, the second depolarization process takes 120s-600s; Optionally, the repair formation process includes: a first repair formation process; Optionally, the repair formation process includes: a first repair formation process and a second repair formation process; Optionally, the repair formation process includes: a first repair formation process, a second repair formation process, and a third repair formation process; Optionally, the treatment solutions for the first repair formation treatment, the second repair formation treatment, and the third repair formation treatment are each independently an aqueous solution of boric acid; Optionally, the mass percentage of boric acid in the treatment solutions of the first, second, and third remediation treatments is independently 2%-10%; Optionally, the formation voltages of the first repair formation treatment, the second repair formation treatment, and the third repair formation treatment are each independently 570V-590V; Optionally, the constant pressure time for the first repair formation treatment, the second repair formation treatment, and the third repair formation treatment is each independently 400s-500s; Optionally, the temperatures of the first repair formation treatment, the second repair formation treatment, and the third repair formation treatment are each independently 70°C-90°C; Optionally, the stabilization treatment solution is an aqueous solution of ammonium dihydrogen phosphate; Optionally, the mass percentage of ammonium dihydrogen phosphate in the stabilization treatment solution is 0.5%-3%; Optionally, the stabilization treatment temperature is 50℃-70℃; Optionally, the stabilization treatment time is 60s-240s; Optionally, the preparation method further includes a second heat treatment; Optionally, the preparation method further includes a second heat treatment and a third heat treatment; Optionally, the temperatures of the second and third heat treatments are each independently 520°C-580°C; Optionally, the duration of the second and third heat treatments is independently 100s-240s.

8. The preparation method according to any one of claims 1-6, characterized in that, The preparation method includes: washing the aluminum foil with water before performing any of the treatments; Optionally, the aluminum foil is an etched foil; Optionally, the preparation method further includes washing with water after stabilization treatment and then drying. Optionally, the drying temperature is 90℃-180℃; Optionally, the drying process takes 150s-240s.

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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