Electrode foil, preparation method thereof and aluminum electrolytic capacitor

Abstract

The invention belongs to the technical field of electrode materials, and particularly relates to an electrode foil and a preparation method thereof and an aluminum electrolytic capacitor, the preparation method of the electrode foil comprises the step of carrying out soaking pretreatment on a corrosion foil before formation treatment, and the soaking pretreatment adopts a pretreatment solution containing rare earth nitrate. The corrosion foil is subjected to soaking pretreatment by adopting the pretreatment liquid containing the rare earth nitrate before the formation treatment, so that the effects of shortening the formation reaction time, reducing the energy consumption in the formation process, improving the capacity of the formed foil and reducing the leakage current are achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrode materials, and particularly relates to an electrode foil, a preparation method thereof, and an aluminum electrolytic capacitor. Background Art

[0002] Aluminum electrolytic capacitors are widely used in electronic products and devices due to their low price, high withstand voltage value, large specific capacitance, etc. The forming foil is an important component of an aluminum electrolytic capacitor. It is a material formed by first expanding the surface area of a specially made high-purity aluminum foil through electrochemical or chemical corrosion to form a etched foil, and then forming a dielectric layer of an oxide film that can withstand a specific voltage on the surface of the etched foil through an electrochemical (anodic oxidation) process.

[0003] The forming foil industry is a high-energy-consuming industry, and the electricity cost accounts for about 70% of the production cost of high-voltage forming foils. How to control the electricity consumption during the forming process has great practical significance for reducing the production cost of enterprises and increasing enterprise profits. In addition, the quality of the oxide film of the forming foil is related to the electrical properties of the forming foil and the performance of the aluminum electrolytic capacitor, and directly affects the specifications, lifespan, etc. of the aluminum electrolytic capacitor products.

[0004] Therefore, the quality of the existing oxide film and the electrical properties of the forming foil still need to be improved. Summary of the Invention

[0005] The purpose of the present invention is to provide an electrode foil, a preparation method thereof, and an aluminum electrolytic capacitor. The preparation method in the present invention realizes the effects of shortening the forming reaction time, reducing the energy consumption during the forming process, increasing the capacitance of the forming foil, and reducing the leakage current by soaking and pre-treating the etched foil with a pre-treatment solution containing rare earth nitrate before the forming treatment.

[0006] The first aspect of the present invention provides a preparation method of an electrode foil. The preparation method includes soaking and pre-treating the etched foil with a pre-treatment solution containing rare earth nitrate before the forming treatment.

[0007] In some embodiments of the present invention, the rare earth nitrate is a nitrate containing at least one of the rare earth elements cerium, lanthanum, and yttrium.

[0008] In some embodiments of the present invention, the concentration of the rare earth nitrate in the pre-treatment solution is 4 g / L to 8 g / L.

[0009] In some embodiments of the present invention, the solvent of the pre-treatment solution is pure water or deionized water.

[0010] In some embodiments of the present invention, the rare earth nitrate is cerium nitrate.

[0011] In some embodiments of the present invention, the time of the immersion pretreatment is 2 min to 10 min.

[0012] In some embodiments of the present invention, during the immersion pretreatment, the temperature of the pretreatment liquid is 20°C to 30°C.

[0013] In some embodiments of the present invention, the etched foil is an etched aluminum foil.

[0014] In some embodiments of the present invention, the preparation method further includes performing a boiling water treatment on the etched foil before the immersion pretreatment.

[0015] In some embodiments of the present invention, the temperature of the boiling water treatment is ≥95°C.

[0016] In some embodiments of the present invention, the time of the boiling water treatment is 8 min to 12 min.

[0017] In some embodiments of the present invention, the number of levels of the formation treatment is selected from 1 to 4 levels, and the formation liquid used for each level of formation independently includes one or more of boric acid, ammonium adipate, and citric acid.

[0018] In some embodiments of the present invention, the solvent of the formation liquid is pure water or deionized water.

[0019] In some embodiments of the present invention, in the formation liquid used for each level of formation, the mass percentage of boric acid is independently 2% to 10%.

[0020] In some embodiments of the present invention, in the formation liquid used for each level of formation, the mass percentage of citric acid is independently 0.2% to 2%.

[0021] In some embodiments of the present invention, in the formation liquid used for each level of formation, the mass percentage of ammonium adipate is independently 0.5% to 2%.

[0022] In some embodiments of the present invention, the formation temperature for each level of formation is independently 70°C to 90°C.

[0023] In some embodiments of the present invention, in each level of formation, the formation voltage increases step by step from the first level of formation to the last level of formation.

[0024] In some embodiments of the present invention, in each level of formation, the constant voltage time increases step by step from the first level of formation to the last level of formation.

[0025] In some embodiments of the present invention, the number of stages of the forming treatment is 1 stage, and the forming treatment is primary forming; or the number of stages of the forming treatment is 2 stages, and the forming treatment is successively primary forming and secondary forming; or the number of stages of the forming treatment is 3 stages, and the forming treatment is successively primary forming, secondary forming and tertiary forming; or the number of stages of the forming treatment is 4 stages, and the forming treatment is successively primary forming, secondary forming, tertiary forming and quaternary forming.

[0026] In some embodiments of the present invention, the forming voltage of the primary forming is 170V - 190V.

[0027] In some embodiments of the present invention, the forming voltage of the secondary forming is 350V - 370V.

[0028] In some embodiments of the present invention, the forming voltage of the tertiary forming is 500V - 520V.

[0029] In some embodiments of the present invention, the forming voltage of the quaternary forming is 570V - 590V.

[0030] In some embodiments of the present invention, the constant voltage time of the primary forming is 240s - 360s.

[0031] In some embodiments of the present invention, the constant voltage time of the secondary forming is 400s - 500s.

[0032] In some embodiments of the present invention, the constant voltage time of the tertiary forming is 550s - 650s.

[0033] In some embodiments of the present invention, the constant voltage time of the quaternary forming is 900s - 1200s.

[0034] In some embodiments of the present invention, the preparation method further includes performing multiple heat treatments and multiple replenishment formations after the forming treatment.

[0035] In some embodiments of the present invention, the temperature of each heat treatment is independently 520°C - 580°C.

[0036] In some embodiments of the present invention, the time of each heat treatment is independently 100s - 200s.

[0037] In some embodiments of the present invention, the replenishment formation liquid used for each replenishment formation independently includes at least one of boric acid and ammonium pentaborate.

[0038] In some embodiments of the present invention, the solvent of the replenishment formation liquid used for each replenishment formation is pure water or deionized water.

[0039] In some embodiments of the present invention, the voltage formed during each replenishment is independently 570V to 590V.

[0040] In some embodiments of the present invention, the constant voltage time formed during each replenishment is independently 400s to 500s.

[0041] In some embodiments of the present invention, the temperature formed during each replenishment is independently 70°C to 90°C.

[0042] In some embodiments of the present invention, in the replenishment liquid used for each replenishment, the mass percentage of boric acid is independently 2% to 10%.

[0043] In some embodiments of the present invention, in the replenishment liquid used for each replenishment, the mass percentage of ammonium pentaborate is independently 0.5% to 2%.

[0044] In some embodiments of the present invention, the preparation method further includes performing a depolarization treatment after the formation treatment.

[0045] In some embodiments of the present invention, the depolarization treatment uses a depolarization treatment liquid containing phosphoric acid.

[0046] In some embodiments of the present invention, the solvent of the depolarization treatment liquid used for the depolarization treatment is pure water or deionized water.

[0047] In some embodiments of the present invention, the temperature of the depolarization treatment is 60°C to 70°C.

[0048] In some embodiments of the present invention, the time of the depolarization treatment is 120s to 600s.

[0049] In some embodiments of the present invention, in the depolarization treatment liquid, the mass percentage of phosphoric acid is 6% to 8%.

[0050] In some embodiments of the present invention, the preparation method further includes performing a stabilization treatment after the formation treatment.

[0051] In some embodiments of the present invention, the stabilization treatment uses a stabilization treatment liquid containing ammonium dihydrogen phosphate.

[0052] In some embodiments of the present invention, the solvent of the stabilization treatment liquid used for the stabilization treatment is pure water or deionized water.

[0053] In some embodiments of the present invention, the temperature of the stabilization treatment is 50°C to 60°C.

[0054] In some embodiments of the present invention, the time of the stabilization treatment is 60s to 360s.

[0055] In some embodiments of the present invention, in the stabilization treatment solution, the mass percentage of ammonium dihydrogen phosphate is 0.5% - 3%.

[0056] The second aspect of the present invention also provides an electrode foil, which is prepared by the preparation method described in the first aspect.

[0057] The third aspect of the present invention also provides an aluminum electrolytic capacitor, which includes an electrode foil prepared by the preparation method described in the first aspect or the electrode foil described in the second aspect.

[0058] In the present invention, by using a pretreatment solution containing rare earth nitrate to soak and pretreat the etched foil before the formation treatment, the effects of shortening the formation reaction time, reducing the energy consumption during the formation process, increasing the capacitance of the formed foil, and reducing the leakage current are achieved, which has unexpected technical effects.

[0059] In the present invention, after the etched foil is soaked in the pretreatment solution containing rare earth nitrate, local microcells will be formed on the surface of the etched foil. Al will dissolve at the microanode of the microcell, and O2 will be reduced at the microcathode, making the concentration of OH - increase in the microcathode region, and the local pH value at the interface rises and tends to be alkaline, so that insoluble hydroxides (Ce(OH)3, La(OH)3 or Y(OH)3) are formed and attached to the surface of the etched foil. These rare earth metals have higher valence states and relatively positive standard redox potentials, and play a role similar to that of a catalyst during the anodic oxidation process. After the etched foil is soaked and treated in the pretreatment solution containing rare earth nitrate, it can promote the formation of the surface oxide film, improve the rate of the formation reaction, and shorten the time required to reach the set voltage, which has unexpected technical effects.

[0060] In the present invention, anodic oxidation is a process in which the formation of the oxide film and the dissolution of the oxide film coexist. After soaking and treating with the pretreatment solution containing rare earth nitrate, the corrosion resistance of the etched foil can be improved, the dissolution of the oxide film during the formation process of the etched foil can be hindered, and more energy can be used for the growth of the oxide film. After soaking in the pretreatment solution containing rare earth nitrate, the anodic surface reaction during the formation process can be accelerated, the adsorption of bubbles on the electrode surface and the voltage drop can be reduced, the time to reach the set voltage can be shortened, and thus the power consumption during the formation process can be reduced, which has unexpected technical effects.

[0061] In the present invention, after soaking and pretreating with the pretreatment solution containing rare earth nitrate, Ce(OH)3, La(OH)3 or Y(OH)3 attached to the surface of the etched foil and citric acid HCit in the electrolyte solution produce a synergistic effect during the anodic oxidation process to form complexes [Ce(HCit)2] - [La(HCit)2]- or [Y(HCit)2] - These generated complex ions, due to their relatively large volume, mainly adhere to the outer surface of the oxide film. This not only reduces the defects on the surface of the oxide film but also decreases the dissolution of the oxide film during the phosphoric acid treatment process, increases the compactness of the oxide film, improves the overall dielectric properties of the film layer, thereby enhancing the capacitance of the etched foil and achieving unexpected technical effects.

[0062] In the present invention, the magnitude of the leakage current is mainly related to the quality of the oxide film. After soaking and pre-treating with a pre-treatment solution containing rare earth nitrate and then performing anodic oxidation treatment, the rare earth nitrate in the pre-treatment solution and citric acid in the electrolyte synergistically generate complexes that adhere to the film layer, reducing the defect positions of the oxide film and improving the structure and properties of the oxide film, thereby reducing the leakage current of the etched foil and achieving unexpected technical effects.

[0063] The above description is only an overview of the technical solution of the present invention. In order to understand the technical means of the present invention more clearly, it can be implemented according to the content of the specification. Moreover, in order to make the above and other objects, features, and advantages of the present invention more obvious and understandable, the specific embodiments of the present invention are specifically described below. Specific Embodiments

[0064] The exemplary embodiments of the present invention will be described in more detail below. It should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art.

[0065] It should be understood that the terms used herein are for the purpose of describing specific exemplary embodiments only and are not intended to be limiting. Unless otherwise clearly specified in the context, the singular forms "a", "an", and "the" as used herein may also include the plural forms. The terms "comprising", "including", "containing", and "having" are inclusive and thus specify the presence of the stated features, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and / or combinations thereof. The method steps, processes, and operations described herein are not to be construed as necessarily requiring them to be performed in the specific order described or illustrated, unless the execution order is clearly stated. It should also be understood that additional or alternative steps may be used.

[0066] In the description of the embodiments of the present invention, technical terms such as "first" and "second" are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity, specific order or primary-secondary relationship of the indicated technical features. In the description of the embodiments of the present invention, the meaning of "a plurality of" is more than two, unless otherwise specifically defined.

[0067] Reference to "embodiment" in this text means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the present invention. The phrase appears in various places in the specification and does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0068] In the description of the embodiments of the present invention, the term "and / or" is merely a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this text generally represents an "or" relationship between the associated objects before and after.

[0069] In the description of the embodiments of the present invention, the term "a plurality of" means more than two (including two). Similarly, "a plurality of groups" means more than two groups (including two groups), and "a plurality of sheets" means more than two sheets (including two sheets).

[0070] In the description of the embodiments of the present invention, unless otherwise clearly specified and limited, technical terms such as "installation", "connection", "connection", "fixation" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or integrated; it can also be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and can be the communication inside two components or the interaction relationship between two components. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present invention can be understood according to specific situations.

[0071] The first aspect of the present invention provides a method for preparing an electrode foil. The key to this electrode foil preparation method is that it includes soaking and pre-treating the etched foil before formation treatment, and the soaking and pre-treatment uses a pre-treatment solution containing rare earth nitrate.

[0072] In the embodiments of the present invention, by soaking and pre-treating the etched foil with a pre-treatment solution containing rare earth nitrate before formation treatment, the effects of shortening the formation reaction time, reducing the energy consumption during the formation process, increasing the capacitance of the formed foil, and reducing the leakage current can be achieved.

[0073] In an embodiment of the present invention, after the etched foil is immersed in a pretreatment solution containing rare earth nitrate, such as cerium nitrate solution, local microcells will be formed on the surface of the etched foil. Aluminum dissolution occurs at the microanode of the microcell, and oxygen reduction occurs at the microcathode, increasing the concentration of OH - in the microcathode region, and the local pH value at the interface rises and tends to be alkaline, causing the formation of insoluble hydroxide Ce(OH)3 to adhere to the surface of the etched foil. These rare earth metals have relatively high valence states and relatively positive standard oxidation-reduction potentials, and play a role similar to that of a catalyst during the anodic oxidation process. In the embodiment of the present invention, after the etched foil is immersed and treated in a pretreatment solution containing rare earth nitrate, it can promote the formation of the surface oxide film, increase the rate of the formation reaction, and shorten the time required to reach the set voltage.

[0074] In an embodiment of the present invention, anodic oxidation is a process in which oxide film formation and oxide film dissolution coexist. After immersion treatment with a pretreatment solution containing rare earth nitrate, such as cerium nitrate solution, the corrosion resistance of the etched foil can be improved, hindering the dissolution of the oxide film during the formation process, and enabling more energy to be used for the growth of the oxide film. After immersion in a pretreatment solution containing rare earth nitrate, it can accelerate the anodic surface reaction during the formation process, reduce the adsorption of bubbles on the electrode surface and the voltage drop, shorten the time to reach the set voltage, and thus reduce the power consumption during the formation process.

[0075] In an embodiment of the present invention, after immersion pretreatment with a pretreatment solution containing rare earth nitrate, such as cerium nitrate solution, Ce(OH)3 attached to the surface of the etched foil and citric acid HCit in the electrolyte produce a synergistic effect during the anodic oxidation process to form a complex [Ce(HCit)2] - . These generated complex ions, due to their relatively large volume, mainly adhere to the outer surface of the oxide film. This not only reduces the defects on the surface of the oxide film but also reduces the dissolution of the oxide film during the phosphoric acid treatment process, increases the compactness of the oxide film, improves the overall dielectric properties of the film layer, and thus increases the capacitance of the formed foil.

[0076] In an embodiment of the present invention, the magnitude of the leakage current is mainly related to the quality of the oxide film. After immersion pretreatment with a pretreatment solution containing rare earth nitrate, such as cerium nitrate solution, and then anodic oxidation treatment, rare earth nitrate in the pretreatment solution, such as cerium nitrate, and citric acid in the electrolyte synergistically form a complex that adheres to the film layer, reducing the defect positions of the oxide film and improving the structure and performance of the oxide film, thereby reducing the leakage current of the formed foil.

[0077] Boiling water treatment

[0078] In an embodiment of the present invention, the etched foil is subjected to boiling water treatment before immersion pretreatment.

[0079] In some embodiments of the present invention, the temperature of the boiling water treatment is ≥95°C. Exemplarily, the temperature of the boiling water treatment can be one of 95°C, 96°C, 97°C, 98°C, 99°C, 100°C or any value satisfying the above range.

[0080] In some embodiments of the present invention, the time of the boiling water treatment is 8 min to 12 min. Exemplarily, the time of the boiling water treatment can be one of 8 min, 9 min, 10 min, 11 min, 12 min or any value satisfying the above range.

[0081] As some embodiments of the present invention, the etched foil is placed in pure water at ≥95°C and boiled for 8 min to 12 min.

[0082] Soaking pretreatment

[0083] In an embodiment of the present invention, the etched foil after the boiling water treatment is placed in a pretreatment solution for soaking pretreatment.

[0084] In some embodiments of the present invention, the soaking pretreatment uses a pretreatment solution containing rare earth nitrate.

[0085] In some embodiments of the present invention, the rare earth nitrate is a nitrate containing at least one of the rare earth elements cerium, lanthanum, and yttrium. For example, it can be cerium nitrate (Ce(NO3)3), lanthanum nitrate (La(NO3)3), or yttrium nitrate (Y(NO3)3).

[0086] In some embodiments of the present invention, the concentration of rare earth nitrate in the pretreatment solution is 4 g / L to 8 g / L. Exemplarily, the concentration of rare earth nitrate in the pretreatment solution can be one of 4 g / L, 5 g / L, 6 g / L, 7 g / L, 8 g / L or any value satisfying the above range.

[0087] In some embodiments of the present invention, the solvent of the pretreatment solution is pure water or deionized water.

[0088] In some embodiments of the present invention, the rare earth nitrate is cerium nitrate.

[0089] In some embodiments of the present invention, the time of the soaking pretreatment is 2 min to 10 min. Exemplarily, the time of the soaking pretreatment can be one of 2 min, 3 min, 4 min, 5 min, 6 min, 7 min, 8 min, 9 min, 10 min or any value satisfying the above range.

[0090] In some embodiments of the present invention, the temperature of the immersion pretreatment, which can also be understood as the temperature of the pretreatment liquid during the immersion pretreatment, is 20°C to 30°C. Exemplarily, the temperature of the pretreatment liquid can be one of 20°C, 21°C, 22°C, 23°C, 24°C, 25°C, 26°C, 27°C, 28°C, 29°C, 30°C or any value satisfying the above range.

[0091] In some embodiments of the present invention, the etched foil is an etched aluminum foil.

[0092] In an embodiment of the present invention, the etched foil after immersion pretreatment is subjected to formation treatment, and the formation treatment includes multi-stage formation.

[0093] In some embodiments of the present invention, the number of stages of the formation treatment can be four; however, the number of stages of the formation treatment of the present invention includes but is not limited to four.

[0094] In some embodiments of the present invention, the number of stages of the formation treatment is selected from 1 to 4 stages.

[0095] In an embodiment of the present invention, the formation liquid used in each stage of formation independently includes one or more of boric acid, ammonium adipate, and citric acid.

[0096] In an embodiment of the present invention, the solvent of the formation liquid used in each stage of formation is pure water or deionized water.

[0097] In an embodiment of the present invention, in the formation liquid used in each stage of formation, the mass percentage of boric acid is independently 2% to 10%. Exemplarily, in the formation liquid used in each stage of formation, the mass percentage of boric acid is independently one of 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10% or any value satisfying the above range.

[0098] In an embodiment of the present invention, in the formation liquid used in each stage of formation, the mass percentage of citric acid is independently 0.2% to 2%. Exemplarily, in the formation liquid used in each stage of formation, the mass percentage of citric acid is independently one of 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2% or any value satisfying the above range.

[0099] In the embodiments of the present invention, in the formation solution used for each stage of formation, the mass percentage of ammonium adipate is independently 0.5% to 2%. Exemplarily, in the formation solution used for each stage of formation, the mass percentage of ammonium adipate is independently one of 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2% or any value satisfying the above range.

[0100] In the embodiments of the present invention, the formation temperature for each stage of formation is independently 70°C to 90°C. Exemplarily, the formation temperature for each stage of formation is independently one of 70°C, 75°C, 80°C, 85°C, 90°C or any value satisfying the above range.

[0101] In the embodiments of the present invention, in each stage of formation, the formation voltage increases step by step from the first stage of formation to the last stage of formation.

[0102] In the embodiments of the present invention, in each stage of formation, the constant voltage time increases step by step from the first stage of formation to the last stage of formation.

[0103] In some embodiments of the present invention, the number of stages of formation treatment is 1 stage, and the formation treatment is the first stage of formation; or the number of stages of formation treatment is 2 stages, and the formation treatments are the first stage of formation and the second stage of formation in sequence; or the number of stages of formation treatment is 3 stages, and the formation treatments are the first stage of formation, the second stage of formation, and the third stage of formation in sequence; or the number of stages of formation treatment is 4 stages, and the formation treatments are the first stage of formation, the second stage of formation, the third stage of formation, and the fourth stage of formation in sequence.

[0104] The first stage of formation

[0105] In the embodiments of the present invention, the etched foil after immersion pretreatment is rinsed clean with pure water and then put into the prepared first-stage formation solution for the first stage of formation.

[0106] In some embodiments of the present invention, the first-stage formation solution contains boric acid with a mass percentage of 2% to 10%, citric acid with a mass percentage of 0.2% to 2%, and ammonium adipate with a mass percentage of 0.5% to 2%.

[0107] Exemplarily, the first-stage formation solution contains boric acid with a mass percentage of 6%, citric acid with a mass percentage of 0.8%, and ammonium adipate with a mass percentage of 1%.

[0108] In the embodiments of the present invention, the solvent of the first-stage formation solution is pure water or deionized water.

[0109] In some embodiments of the present invention, the formation voltage for the first-stage formation is 170V to 190V. Exemplarily, the formation voltage for the first-stage formation can be one of 170V, 180V, 190V or any value satisfying the above range.

[0110] In some embodiments of the present invention, the constant voltage time for the first-stage formation is 240s to 360s. Exemplarily, the constant voltage time for the first-stage formation can be one of 240s, 250s, 260s, 270s, 280s, 290s, 300s, 310s, 320s, 330s, 340s, 350s, 360s or any value satisfying the above range.

[0111] In some embodiments of the present invention, the temperature for the first-stage formation is 70°C to 90°C. Exemplarily, the temperature for the first-stage formation can be one of 70°C, 75°C, 80°C, 85°C, 90°C or any value satisfying the above range.

[0112] In some embodiments of the present invention, the etched foil after immersion pretreatment is rinsed clean with pure water and then put into the prepared first-stage formation solution for first-stage formation. The temperature for the first-stage formation is 70°C to 90°C, the formation voltage is 170V to 190V, the constant voltage time is 240s to 360s, and the first-stage formation solution contains boric acid with a mass percentage of 2% to 10%, citric acid with a mass percentage of 0.2% to 2%, and ammonium adipate with a mass percentage of 0.5% to 2%.

[0113] Second-stage formation

[0114] In an embodiment of the present invention, the etched foil after the first-stage formation is rinsed clean with pure water and then put into the prepared second-stage formation solution for second-stage formation.

[0115] In some embodiments of the present invention, the second-stage formation solution contains boric acid with a mass percentage of 2% to 10% and citric acid with a mass percentage of 0.2% to 2%.

[0116] Exemplarily, the second-stage formation solution contains boric acid with a mass percentage of 6% and citric acid with a mass percentage of 0.6%.

[0117] In an embodiment of the present invention, the solvent of the second-stage formation solution is pure water or deionized water.

[0118] In some embodiments of the present invention, the formation voltage for the second-stage formation is 350V to 370V. Exemplarily, the formation voltage for the second-stage formation can be one of 350V, 360V, 370V or any value satisfying the above range.

[0119] In some embodiments of the present invention, the constant voltage time for secondary formation is 400 s to 500 s. Exemplarily, the constant voltage time for secondary formation can be one of 400 s, 410 s, 420 s, 430 s, 440 s, 450 s, 460 s, 470 s, 480 s, 490 s, 500 s or any value satisfying the above range.

[0120] In some embodiments of the present invention, the temperature for secondary formation is 70 °C to 90 °C. Exemplarily, the temperature for secondary formation can be one of 70 °C, 75 °C, 80 °C, 85 °C, 90 °C or any value satisfying the above range.

[0121] In some embodiments of the present invention, the etched foil after primary formation is rinsed clean with pure water and then put into the prepared secondary formation solution for secondary formation. The temperature for secondary formation is 70 °C to 90 °C, the formation voltage is 350 V to 370 V, the constant voltage time is 400 s to 500 s, and the secondary formation solution contains boric acid with a mass percentage of 2% to 10% and citric acid with a mass percentage of 0.2% to 2%.

[0122] Tertiary formation

[0123] In an embodiment of the present invention, the etched foil after secondary formation is rinsed clean with pure water and then put into the prepared tertiary formation solution for tertiary formation.

[0124] In some embodiments of the present invention, the tertiary formation solution contains boric acid with a mass percentage of 2% to 10% and citric acid with a mass percentage of 0.2% to 2%.

[0125] Exemplarily, the tertiary formation solution contains boric acid with a mass percentage of 6% and citric acid with a mass percentage of 0.4%.

[0126] In an embodiment of the present invention, the solvent of the tertiary formation solution is pure water or deionized water.

[0127] In some embodiments of the present invention, the formation voltage for tertiary formation is 500 V to 520 V. Exemplarily, the formation voltage for tertiary formation can be one of 500 V, 510 V, 520 V or any value satisfying the above range.

[0128] In some embodiments of the present invention, the constant voltage time for tertiary formation is 550 s to 650 s. Exemplarily, the constant voltage time for tertiary formation can be one of 550 s, 560 s, 570 s, 580 s, 590 s, 600 s, 610 s, 620 s, 630 s, 640 s, 650 s or any value satisfying the above range.

[0129] In some embodiments of the present invention, the temperature of the tertiary formation is 70°C to 90°C. Exemplarily, the temperature of the tertiary formation can be one of 70°C, 75°C, 80°C, 85°C, 90°C or any value satisfying the above range.

[0130] In some embodiments of the present invention, the etched foil after secondary formation is rinsed clean with pure water and then put into the prepared tertiary formation solution for tertiary formation. The temperature of the tertiary formation is 70°C to 90°C, the formation voltage is 500V to 520V, the constant voltage time is 550s to 650s, and the tertiary formation solution contains boric acid with a mass percentage of 2% to 10% and citric acid with a mass percentage of 0.2% to 2%.

[0131] Quaternary formation

[0132] In an embodiment of the present invention, the etched foil after tertiary formation is rinsed clean with pure water and then put into the prepared quaternary formation solution for quaternary formation.

[0133] In some embodiments of the present invention, the quaternary formation solution contains boric acid with a mass percentage of 2% to 10% and citric acid with a mass percentage of 0.2% to 2%.

[0134] In an embodiment of the present invention, the solvent of the quaternary formation solution is pure water or deionized water.

[0135] In some embodiments of the present invention, the formation voltage of the quaternary formation is 570V to 590V. Exemplarily, the formation voltage of the quaternary formation can be one of 570V, 580V, 590V or any value satisfying the above range.

[0136] In some embodiments of the present invention, the constant voltage time of the quaternary formation is 900s to 1200s. Exemplarily, the constant voltage time of the quaternary formation can be one of 900s, 1000s, 1100s, 1200s or any value satisfying the above range.

[0137] In some embodiments of the present invention, the temperature of the quaternary formation is 70°C to 90°C. Exemplarily, the temperature of the quaternary formation can be one of 70°C, 75°C, 80°C, 85°C, 90°C or any value satisfying the above range.

[0138] In some embodiments of the present invention, the etched foil after tertiary formation is rinsed clean with pure water and then put into the prepared quaternary formation solution for quaternary formation. The temperature of the quaternary formation is 70°C to 90°C, the formation voltage is 570V to 590V, the constant voltage time is 900s to 1200s, and the quaternary formation solution contains boric acid with a mass percentage of 2% to 10% and citric acid with a mass percentage of 0.2% to 2%.

[0139] In an embodiment of the present invention, the preparation method of the present invention further includes performing multiple heat treatments and multiple replenishment formations on the etched foil after formation treatment.

[0140] In some embodiments of the present invention, the number of heat treatments can be two; however, the number of heat treatments of the present invention includes but is not limited to two.

[0141] In some embodiments of the present invention, one replenishment formation is performed on the etched foil after each heat treatment.

[0142] In some embodiments of the present invention, the temperature of each heat treatment is independently 520°C to 580°C. Exemplarily, the temperature of each heat treatment is independently one of 520°C, 530°C, 540°C, 550°C, 560°C, 570°C, 580°C or any value satisfying the above range.

[0143] In some embodiments of the present invention, the time of each heat treatment is independently 100 s to 200 s. Exemplarily, the time of each heat treatment is independently one of 100 s, 110 s, 120 s, 130 s, 140 s, 150 s, 160 s, 170 s, 180 s, 190 s, 200 s or any value satisfying the above range.

[0144] In some embodiments of the present invention, the number of replenishment formations can be three; however, the number of replenishment formations of the present invention includes but is not limited to three.

[0145] In some embodiments of the present invention, the replenishment formation liquid used for each replenishment formation independently includes at least one of boric acid and ammonium pentaborate.

[0146] In some embodiments of the present invention, the solvent of the replenishment formation liquid used for each replenishment formation is pure water or deionized water.

[0147] In some embodiments of the present invention, in the replenishing solution used for each replenishing formation, the mass percentage of boric acid is independently 2% to 10%, and / or, in the replenishing solution used for each replenishing formation, the mass percentage of ammonium pentaborate is independently 0.5% to 2%. Exemplarily, in the replenishing solution used for each replenishing formation, the mass percentage of boric acid can independently be one of 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10% or any value satisfying the above range; and / or, in the replenishing solution used for each replenishing formation, the mass percentage of ammonium pentaborate can independently be one of 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2% or any value satisfying the above range.

[0148] In some embodiments of the present invention, the voltage for each replenishing formation is independently 570V to 590V. Exemplarily, the voltage for each replenishing formation can independently be one of 570V, 580V, 590V or any value satisfying the above range.

[0149] In some embodiments of the present invention, the constant voltage time for each replenishing formation is independently 400s to 500s. Exemplarily, the constant voltage time for each replenishing formation can independently be one of 400s, 410s, 420s, 430s, 440s, 450s, 460s, 470s, 480s, 490s, 500s or any value satisfying the above range.

[0150] In some embodiments of the present invention, the temperature for each replenishing formation is independently 70°C to 90°C. Exemplarily, the temperature for each replenishing formation can independently be one of 70°C, 75°C, 80°C, 85°C, 90°C or any value satisfying the above range.

[0151] In an embodiment of the present invention, the preparation method of the present invention further includes a depolarization treatment and a stabilization treatment.

[0152] In some embodiments of the present invention, the etched foil after the first replenishing formation is subjected to a depolarization treatment.

[0153] In some embodiments of the present invention, the etched foil after the depolarization treatment is subjected to a second replenishing formation.

[0154] In some embodiments of the present invention, the etched foil after the last replenishing formation is subjected to a stabilization treatment.

[0155] In some embodiments of the present invention, the preparation method of the present invention includes the following preparation processes: boiling treatment → soaking pretreatment → first formation → second formation → third formation → fourth formation → first heat treatment → first supplementary formation → depolarization treatment → second supplementary formation → second heat treatment → third supplementary formation → stabilization treatment.

[0156] First heat treatment

[0157] In an embodiment of the present invention, the etched foil after the last-stage formation is rinsed clean with pure water and then subjected to the first heat treatment.

[0158] In some embodiments of the present invention, the temperature of the first heat treatment is 520°C to 580°C. Exemplarily, the temperature of the first heat treatment can be one of 520°C, 530°C, 540°C, 550°C, 560°C, 570°C, 580°C or any value within the above range.

[0159] In some embodiments of the present invention, the time of the first heat treatment is 100s to 200s. Exemplarily, the time of the first heat treatment can be one of 100s, 110s, 120s, 130s, 140s, 150s, 160s, 170s, 180s, 190s, 200s or any value within the above range.

[0160] First supplementary formation

[0161] In an embodiment of the present invention, the etched foil after the first heat treatment is rinsed clean with pure water and then put into the prepared first supplementary formation solution for the first supplementary formation.

[0162] In some embodiments of the present invention, the supplementary formation solution used for the first supplementary formation contains boric acid with a mass percentage of 2% to 10% and ammonium pentaborate with a mass percentage of 0.5% to 2%. Exemplarily, the mass percentage of boric acid in the supplementary formation solution used for the first supplementary formation can be one of 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10% or any value within the above range. The mass percentage of ammonium pentaborate in the supplementary formation solution used for the first supplementary formation can be one of 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2% or any value within the above range.

[0163] In some embodiments of the present invention, the solvent of the supplementary formation solution used for the first supplementary formation is pure water or deionized water.

[0164] In some embodiments of the present invention, the voltage formed by the first replenishment is 570V - 590V. Exemplarily, the voltage formed by the first replenishment can be one of 570V, 580V, 590V or any value satisfying the above range.

[0165] In some embodiments of the present invention, the constant voltage time for the first replenishment is 400s - 500s. Exemplarily, the constant voltage time for the first replenishment can be one of 400s, 410s, 420s, 430s, 440s, 450s, 460s, 470s, 480s, 490s, 500s or any value satisfying the above range.

[0166] In some embodiments of the present invention, the temperature for the first replenishment is 70°C - 90°C. Exemplarily, the temperature for the first replenishment can be one of 70°C, 75°C, 80°C, 85°C, 90°C or any value satisfying the above range.

[0167] Depolarization treatment

[0168] In an embodiment of the present invention, the etched foil after the first replenishment is rinsed clean with pure water and then subjected to depolarization treatment in the prepared depolarization treatment solution.

[0169] In some embodiments of the present invention, the depolarization treatment uses a depolarization treatment solution containing phosphoric acid.

[0170] In some embodiments of the present invention, in the depolarization treatment solution, the mass percentage of phosphoric acid is 6% - 8%. Exemplarily, in the depolarization treatment solution, the mass percentage of phosphoric acid can be one of 6%, 7%, 8% or any value satisfying the above range.

[0171] In some embodiments of the present invention, the solvent of the depolarization treatment solution used for the depolarization treatment is pure water or deionized water.

[0172] In some embodiments of the present invention, the temperature of the depolarization treatment is 60°C - 70°C, which can also be understood as the temperature of the depolarization treatment solution is 60°C - 70°C. Exemplarily, the temperature of the depolarization treatment can be one of 60°C, 65°C, 70°C or any value satisfying the above range.

[0173] In some embodiments of the present invention, the time for depolarization treatment is 120 s to 600 s. Exemplarily, the time for depolarization treatment can be one of 120 s, 150 s, 160 s, 180 s, 200 s, 220 s, 250 s, 260 s, 280 s, 300 s, 320 s, 350 s, 360 s, 380 s, 400 s, 420 s, 450 s, 460 s, 480 s, 500 s, 520 s, 550 s, 560 s, 580 s, 600 s or any value satisfying the above range.

[0174] Second replenishment formation

[0175] In an embodiment of the present invention, the etched foil after depolarization treatment is rinsed clean with pure water and then put into the configured second replenishment formation solution for second replenishment formation.

[0176] In some embodiments of the present invention, the replenishment formation solution used for second replenishment formation contains boric acid with a mass percentage of 2% to 10% and ammonium pentaborate with a mass percentage of 0.5% to 2%. Exemplarily, the mass percentage of boric acid can be one of 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10% or any value satisfying the above range; the mass percentage of ammonium pentaborate can be one of 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2% or any value satisfying the above range.

[0177] In some embodiments of the present invention, the solvent of the replenishment formation solution used for second replenishment formation is pure water or deionized water.

[0178] In some embodiments of the present invention, the voltage for second replenishment formation is 570 V to 590 V. Exemplarily, the voltage for second replenishment formation can be one of 570 V, 580 V, 590 V or any value satisfying the above range.

[0179] In some embodiments of the present invention, the constant voltage time for second replenishment formation is 400 s to 500 s. Exemplarily, the constant voltage time for second replenishment formation can be one of 400 s, 410 s, 420 s, 430 s, 440 s, 450 s, 460 s, 470 s, 480 s, 490 s, 500 s or any value satisfying the above range.

[0180] In some embodiments of the present invention, the temperature for second replenishment formation is 70 °C to 90 °C. Exemplarily, the temperature for second replenishment formation can be one of 70 °C, 75 °C, 80 °C, 85 °C, 90 °C or any value satisfying the above range.

[0181] Second heat treatment

[0182] In an embodiment of the present invention, the etched foil after the second repair forming is rinsed clean with pure water and then subjected to the second heat treatment.

[0183] In some embodiments of the present invention, the temperature of the second heat treatment is 520°C to 580°C. Exemplarily, the temperature of the second heat treatment can be one of 520°C, 530°C, 540°C, 550°C, 560°C, 570°C, 580°C or any value satisfying the above range.

[0184] In some embodiments of the present invention, the time of the second heat treatment is 100s to 200s. Exemplarily, the time of the second heat treatment can be one of 100s, 110s, 120s, 130s, 140s, 150s, 160s, 170s, 180s, 190s, 200s or any value satisfying the above range.

[0185] Third repair forming

[0186] In an embodiment of the present invention, the etched foil after the second heat treatment is rinsed clean with pure water and then placed in the configured third repair forming solution for the third repair forming.

[0187] In some embodiments of the present invention, the repair forming solution used for the third repair forming contains boric acid with a mass percentage of 2% to 10% and ammonium pentaborate with a mass percentage of 0.5% to 2%. Exemplarily, the mass percentage of boric acid can be one of 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10% or any value satisfying the above range; the mass percentage of ammonium pentaborate can be one of 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2% or any value satisfying the above range.

[0188] In some embodiments of the present invention, the solvent of the repair forming solution used for the third repair forming is pure water or deionized water.

[0189] In some embodiments of the present invention, the voltage of the third repair forming is 570V to 590V. Exemplarily, the voltage of the third repair forming can be one of 570V, 580V, 590V or any value satisfying the above range.

[0190] In some embodiments of the present invention, the constant pressure time for the third replenishment forming is 400 s to 500 s. Exemplarily, the constant pressure time for the third replenishment forming can be one of 400 s, 410 s, 420 s, 430 s, 440 s, 450 s, 460 s, 470 s, 480 s, 490 s, 500 s or any value satisfying the above range.

[0191] In some embodiments of the present invention, the temperature for the third replenishment forming is 70 °C to 90 °C. Exemplarily, the temperature for the third replenishment forming can be one of 70 °C, 75 °C, 80 °C, 85 °C, 90 °C or any value satisfying the above range.

[0192] Stabilization treatment

[0193] In an embodiment of the present invention, the etched foil after the last replenishment forming is rinsed clean with pure water and then subjected to stabilization treatment in a configured stabilization treatment solution.

[0194] In some embodiments of the present invention, the stabilization treatment uses a stabilization treatment solution containing ammonium dihydrogen phosphate.

[0195] In some embodiments of the present invention, in the stabilization treatment solution, the mass percentage of ammonium dihydrogen phosphate is 0.5% to 3%. Exemplarily, the mass percentage of ammonium dihydrogen phosphate can be one of 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3% or any value satisfying the above range.

[0196] In some embodiments of the present invention, the solvent of the stabilization treatment solution used for the stabilization treatment is pure water or deionized water.

[0197] In some embodiments of the present invention, the temperature of the stabilization treatment is 50 °C to 60 °C. Exemplarily, the temperature of the stabilization treatment can be one of 50 °C, 55 °C, 60 °C or any value satisfying the above range.

[0198] In some embodiments of the present invention, the time of the stabilization treatment is 60 s to 360 s. Exemplarily, the time of the stabilization treatment can be one of 60 s, 80 s, 90 s, 100 s, 120 s, 150 s, 160 s, 180 s, 200 s, 220 s, 250 s, 260 s, 280 s, 300 s, 320 s, 350 s, 360 s or any value satisfying the above range.

[0199] In an embodiment of the present invention, the present invention provides a method for preparing an electrode foil:

[0200] Water boiling: Put the foil into pure water at ≥95°C and boil for 8 min to 12 min.

[0201] Immersion pretreatment: Put the foil after water boiling into the prepared pretreatment solution for immersion pretreatment, at a temperature of 20°C to 30°C for 2 min to 10 min.

[0202] Primary formation: Rinse the foil after immersion pretreatment with pure water, and put it into the prepared primary formation solution for primary formation. The formation voltage is 170V to 190V, the constant voltage time is 240s to 360s, and the temperature is 70°C to 90°C.

[0203] Secondary formation: Rinse the foil after primary formation with pure water, and put it into the prepared secondary formation solution for secondary formation. The formation voltage is 350V to 370V, the constant voltage time is 400s to 500s, and the temperature is 70°C to 90°C.

[0204] Tertiary formation: Rinse the foil after secondary formation with pure water, and put it into the prepared tertiary formation solution for tertiary formation. The formation voltage is 500V to 520V, the constant voltage time is 550s to 650s, and the temperature is 70°C to 90°C.

[0205] Quaternary formation: Rinse the foil after tertiary formation with pure water, and put it into the prepared quaternary formation solution for quaternary formation. The formation voltage is 570V to 590V, the constant voltage time is 900s to 1200s, and the temperature is 70°C to 90°C.

[0206] First heat treatment: Rinse the foil after quaternary formation with pure water, and perform heat treatment at 520°C to 580°C for 100s to 200s.

[0207] First repair formation: Rinse the foil after the first heat treatment with pure water, and put it into the prepared first repair formation solution for first repair formation. The repair formation voltage is 570V to 590V, the constant voltage time is 400s to 500s, and the temperature is 70°C to 90°C.

[0208] Depolarization treatment: Rinse the foil after the first repair formation with pure water, and put it into the prepared depolarization treatment solution for depolarization treatment, at a temperature of 60°C to 70°C for 120s to 600s.

[0209] Second replenishment formation: Rinse the depolarized foil thoroughly with pure water, and place it in the prepared second replenishment formation solution for second replenishment formation. The voltage for the second replenishment formation is 570V - 590V, the constant voltage time is 400s - 500s, and the temperature is 70°C - 90°C.

[0210] Second heat treatment: Rinse the foil after the second replenishment formation thoroughly with pure water, and perform heat treatment at 520°C - 580°C for 100s - 200s.

[0211] Third replenishment formation: Rinse the foil after the second heat treatment thoroughly with pure water, and place it in the prepared third replenishment formation solution for third replenishment formation. The voltage for the third replenishment formation is 570V - 590V, the constant voltage time is 400s - 500s, and the temperature is 70°C - 90°C.

[0212] Stabilization treatment: Rinse the foil after the third replenishment formation thoroughly with pure water, and place it in the prepared stabilization treatment solution for depolarization treatment. The temperature is 50°C - 60°C, and the time is 60s - 360s.

[0213] The second aspect of the present invention provides an electrode foil, which is characterized by being prepared by the preparation method described in the first aspect.

[0214] In some embodiments of the present invention, the electrode foil can be a high-voltage forming foil.

[0215] The third aspect of the present invention provides an aluminum electrolytic capacitor, which includes the electrode foil prepared by the preparation method described in the first aspect or the electrode foil described in the second aspect.

[0216] Unless otherwise defined, the technical terms used in the following embodiments have the same meanings as commonly understood by those skilled in the art to which the present invention belongs. The experimental reagents used in the following embodiments are all conventional biochemical reagents unless otherwise specified; the raw materials, instruments, and equipment used in the following embodiments can all be obtained through market purchase or by existing methods; the dosages of the experimental reagents are all the dosages of the reagents in conventional experimental operations unless otherwise specified; the experimental methods are all conventional methods unless otherwise specified. It should be further noted that the following description is only exemplary and not a specific limitation of the present invention.

[0217] It is worth mentioning that in the embodiments and comparative examples of the present invention, foil sheets of the same specification are selected, high-voltage etched foils (99.99% Al) are used, and they are cut into foil sheets of 100mm × 100mm.

[0218] Example 1

[0219] An electrode foil, and its preparation method includes: the cut foil → boiled in water for 10 min → soaked and pretreated in a 4 g / L Ce(NO3)3 solution at a temperature of 25 °C for 5 min → first stage formation → second stage formation → third stage formation → fourth stage formation → first heat treatment → first supplementary formation → depolarization treatment → second supplementary formation → second heat treatment → third supplementary formation → stabilization treatment.

[0220] The specific preparation process is as follows:

[0221] Put the cut foil into pure water at >95 °C and boil for 10 min.

[0222] Put the foil after boiling treatment into a 4 g / L Ce(NO3)3 aqueous solution at 25 °C for soaking pretreatment for 5 min.

[0223] Rinse the foil after soaking pretreatment with pure water, and put it into the first stage formation solution (first stage formation solution: the mass percentage of boric acid is 6%, the mass percentage of citric acid is 0.8%, the mass percentage of ammonium adipate is 1%, and the balance is deionized water) for first stage formation. The formation voltage is 180 V, the constant voltage time is 300 s, and the temperature is 85 °C.

[0224] Rinse the foil after first stage formation with pure water, and put it into the second stage formation solution (second stage formation solution: the mass percentage of boric acid is 6%, the mass percentage of citric acid is 0.6%, and the balance is deionized water) for second stage formation. The formation voltage is 360 V, the constant voltage time is 450 s, and the temperature is 85 °C.

[0225] Rinse the foil after second stage formation with pure water, and put it into the third stage formation solution (third stage formation solution: the mass percentage of boric acid is 6%, the mass percentage of citric acid is 0.4%, and the balance is deionized water) for third stage formation. The formation voltage is 510 V, the constant voltage time is 600 s, and the temperature is 85 °C.

[0226] Rinse the foil after third stage formation with pure water, and put it into the fourth stage formation solution (fourth stage formation solution: the mass percentage of boric acid is 6%, the mass percentage of citric acid is 0.2%, and the balance is deionized water) for fourth stage formation. The formation voltage is 580 V, the constant voltage time is 1000 s, and the temperature is 85 °C.

[0227] Rinse the foil after fourth stage formation with pure water, and conduct the first heat treatment at 550 °C for 120 s.

[0228] The foil after the first heat treatment is rinsed thoroughly with pure water and then put into the first replenishing formation solution (the first replenishing formation solution: the mass percentage of boric acid is 8%, the mass percentage of ammonium pentaborate is 1%, and the balance is deionized water) for the first replenishing formation. The replenishing formation voltage is 580 V, the constant voltage time is 450 s, and the temperature is 85°C.

[0229] The foil after the first replenishing formation is rinsed thoroughly with pure water and then put into an aqueous solution of phosphoric acid with a mass percentage of 7% for depolarization treatment. The temperature is 65°C and the time is 400 s.

[0230] The foil after depolarization treatment is rinsed thoroughly with pure water and then put into the second replenishing formation solution (the second replenishing formation solution: the mass percentage of boric acid is 8%, the mass percentage of ammonium pentaborate is 1%, and the balance is deionized water) for the second replenishing formation. The second replenishing formation voltage is 580 V, the constant voltage time is 450 s, and the temperature is 85°C.

[0231] The foil after the second replenishing formation is rinsed thoroughly with pure water and then subjected to a second heat treatment at 550°C for 120 s.

[0232] The foil after the second heat treatment is rinsed thoroughly with pure water and then put into the third replenishing formation solution (the third replenishing formation solution: the mass percentage of boric acid is 8%, the mass percentage of ammonium pentaborate is 1%, and the balance is deionized water) for the third replenishing formation. The third replenishing formation voltage is 580 V, the constant voltage time is 450 s, and the temperature is 85°C.

[0233] The foil after the third replenishing formation is rinsed thoroughly with pure water and then put into an aqueous solution of ammonium dihydrogen phosphate with a mass percentage of 2% for stabilization treatment. The temperature is 55°C and the time is 120 s.

[0234] Example 2

[0235] An electrode foil, the preparation method of which refers to Example 1. The difference from Example 1 is only that the pretreatment solution used in the immersion pretreatment is an aqueous solution of 6 g / L Ce(NO3)3.

[0236] Example 3

[0237] An electrode foil, the preparation method of which refers to Example 1. The difference from Example 1 is only that the pretreatment solution used in the immersion pretreatment is an aqueous solution of 8 g / L Ce(NO3)3.

[0238] Comparative Example 1

[0239] An electrode foil, the preparation method of which refers to Example 1. The difference from Example 1 is only that the pretreatment solution used in the immersion pretreatment is pure water.

[0240] Comparative Example 2

[0241] An electrode foil, the preparation method of which refers to Example 1. The difference between it and Example 1 is only that the pretreatment solution used in the immersion pretreatment is an 8 g / L KNO3 aqueous solution.

[0242] Performance test

[0243] 1. Shortening reaction time test:

[0244] The formation of the etched foil by anodic oxidation is a process of first constant current and then constant voltage. By comparing the time from the start of the reaction to the voltage rising to the set voltage, the speed of the reaction during the voltage rise process of the formed foil can be judged.

[0245] The present invention has counted the time required for each stage of formation to reach the set voltage after immersion pretreatment in cerium nitrate solutions with different concentrations, and the results are shown in Table 1.

[0246] Table 1 Statistics of the time required for each stage of formation of the foil in the examples and comparative examples to reach the preset voltage

[0247]

[0248]

[0249] As can be seen from Table 1, after immersion pretreatment with cerium nitrate solution, the time for the first four stages of formation to reach the set voltage is significantly shortened. This shows that the introduction of rare earth element Ce affects the reaction process of formation, accelerates the anodic oxidation rate, and shortens the voltage rise time. And since the voltage in the post-formation stage is the same as that in the four-stage formation stage, the influence on the reaction process in the subsequent post-formation stage is not significant.

[0250] 2. Energy consumption test:

[0251] The total electricity consumption of the foils in different examples and comparative examples during the formation process was counted, and the results are shown in detail in Table 2.

[0252] 3. Capacity test:

[0253] The capacity is the electrostatic capacity per unit area of the formed foil after withstand voltage test. The value of it reflects the strength of the charge storage ability of the formed foil. The higher the capacity value, the better (except for special specifications), and the results are shown in detail in Table 2.

[0254] 4. Leakage current test:

[0255] Simulating the usage scenario of an aluminum electrolytic capacitor, a 5-hour leakage current test was carried out on the formed foils in different examples and comparative examples. By detecting the magnitude of the leakage current, the quality of the oxide film was identified, and the results are shown in detail in Table 2.

[0256] Table 2 Summary of the performance of the foils in the examples and comparative examples

[0257]

[0258] Note: The rate of change refers to the percentage change compared to Comparative Example 1.

[0259] As can be seen from Table 2, the power consumption during the forming process of the etched foil pretreated by immersion in cerium nitrate is significantly reduced, and the higher the cerium nitrate concentration, the greater the reduction in power consumption. When the cerium nitrate concentration reaches 8 g / L, the power consumption is reduced by about 6%.

[0260] At the same time, after the etched foil is pretreated by immersion in cerium nitrate, the capacitance of the formed foil increases with the increase of the cerium nitrate concentration.

[0261] The leakage current gradually decreases with the increase of the cerium nitrate concentration. When the cerium nitrate concentration is low, the reduction amplitude of the leakage current is small. When the cerium nitrate concentration is 4 g / L, the minimum value of the leakage current is reduced by 17.6%. When the cerium nitrate concentration is 8 g / L, the minimum value of the leakage current is reduced by 35.3%.

[0262] 5. Test of the voltage rise time (Tr), breakdown voltage (Vt) and voltage rise time after hydration resistance treatment (Tr60):

[0263] According to the standard in the "Group Standard of China Electronic Components Association T / CECA22-2017 Electrode Foil for Aluminum Electrolytic Capacitors", the voltage rise time, breakdown voltage and hydration resistance of the formed foil are detected. The voltage rise time refers to the time required to raise the voltage of the formed foil to 90% of the rated forming voltage (Vf) of the formed foil at a specified current. The shorter the voltage rise time, the better the quality of the oxide film. The breakdown voltage refers to the voltage value maintained at 180 s starting from the voltage rise time. The higher the voltage value, the better. The results are shown in Table 3.

[0264] Table 3 Voltage rise time, breakdown voltage and hydration resistance data of the foil in the examples and comparative examples

[0265] Group Tr / s Vt / V Tr60 / s Example 1 142 604.7 17 Example 2 125 604.8 17 Example 3 125 603.7 15 Comparative Example 1 140 603.1 21 Comparative Example 2 138 603.5 20

[0266] As can be seen from Table 3, the breakdown voltage Vt of the formed foil after immersion in cerium nitrate does not change significantly. In addition, the voltage rise time Tr60 after hydration resistance treatment is also significantly shortened, indicating that the hydration resistance of the formed foil is improved to a certain extent after immersion in cerium nitrate. The improvement of the hydration resistance is because the complex [Ce(HCit)2] - on the surface of the formed foil hinders the contact time between alumina and water, slowing down the progress of alumina turning into hydrated aluminum oxide and becoming ineffective, so the hydration resistance of the formed foil is improved to a certain extent.

[0267] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing an electrode foil, characterized in that, The preparation method includes pre-soaking the etched foil before formation treatment, and the pre-soaking is carried out using a pre-treatment solution containing rare earth nitrate.

2. The method for preparing an electrode foil according to claim 1, characterized in that, The rare earth nitrate is a nitrate containing at least one of rare earth elements cerium, lanthanum, and yttrium; and / or, The concentration of rare earth nitrate in the pre-treatment solution is 4 g / L to 8 g / L; Preferably, the rare earth nitrate is cerium nitrate.

3. The method for preparing an electrode foil according to claim 1, wherein, The time of the pre-soaking is 2 min to 10 min; and / or, During the pre-soaking, the temperature of the pre-treatment solution is 20°C to 30°C; and / or, The etched foil is an etched aluminum foil.

4. The preparation method of the electrode foil according to claim 1, characterized in that, The preparation method further includes boiling the etched foil before the pre-soaking; Preferably, the temperature of the boiling is ≥95°C; and / or, the time of the boiling is 8 min to 12 min.

5. The method for preparing an electrode foil according to claim 1, characterized in that, The number of stages of the formation treatment is selected from 1 to 4 stages, and the formation solution used in each stage independently includes one or more of boric acid, ammonium adipate, and citric acid; Preferably, the solvent of the formation solution used in each stage is pure water or deionized water; Preferably, in the formation solution used in each stage, the mass percentage of boric acid is independently 2% to 10%; and / or, in the formation solution used in each stage, the mass percentage of citric acid is independently 0.2% to 2%; and / or, in the formation solution used in each stage, the mass percentage of ammonium adipate is independently 0.5% to 2%; Preferably, the formation temperature of each stage is independently 70°C to 90°C; and / or, In each stage of formation, the formation voltage increases step by step from the first stage of formation to the last stage of formation; and / or, In each stage of formation, the constant voltage time increases step by step from the first stage of formation to the last stage of formation; and / or, The number of stages of the formation treatment is 1 stage, and the formation treatment is the first-stage formation; or the number of stages of the formation treatment is 2 stages, and the formation treatment is the first-stage formation and the second-stage formation in sequence; or the number of stages of the formation treatment is 3 stages, and the formation treatment is the first-stage formation, the second-stage formation, and the third-stage formation in sequence; or the number of stages of the formation treatment is 4 stages, and the formation treatment is the first-stage formation, the second-stage formation, the third-stage formation, and the fourth-stage formation in sequence; Preferably, the formation voltage of the first-stage formation is 170 V to 190 V; and / or, the formation voltage of the second-stage formation is 350 V to 370 V; and / or, the formation voltage of the third-stage formation is 500 V to 520 V; and / or, the formation voltage of the fourth-stage formation is 570 V to 590 V; Preferably, the constant voltage time of the first-stage formation is 240 s to 360 s; and / or, the constant voltage time of the second-stage formation is 400 s to 500 s; and / or, the constant voltage time of the third-stage formation is 550 s to 650 s; and / or, the constant voltage time of the fourth-stage formation is 900 s to 1200 s.

6. The method for preparing an electrode foil according to any one of claims 1 to 5, characterized in that, The preparation method further includes performing multiple heat treatments and multiple post-formations after the formation treatment; Preferably, the temperature of each heat treatment is independently 520°C to 580°C, and the time of each heat treatment is independently 100 s to 200 s; Preferably, the replenishing liquid used for each replenishing formation independently includes at least one of boric acid and ammonium pentaborate; and / or, The voltage of each replenishing formation is independently 570 V to 590 V, the constant voltage time of each replenishing formation is independently 400 s to 500 s, and the temperature of each replenishing formation is independently 70°C to 90°C; Preferably, in the replenishing liquid used for each replenishing formation, the mass percentage of boric acid is independently 2% to 10%; and / or, in the replenishing liquid used for each replenishing formation, the mass percentage of ammonium pentaborate is independently 0.5% to 2%.

7. The method for preparing an electrode foil according to claim 1, wherein, The preparation method further includes a depolarization treatment after the forming treatment; Preferably, the depolarization treatment uses a depolarization treatment liquid containing phosphoric acid; and / or, The temperature of the depolarization treatment is 60°C to 70°C; and / or, The time of the depolarization treatment is 120 s to 600 s; Preferably, in the depolarization treatment liquid, the mass percentage of phosphoric acid is 6% to 8%.

8. The method for preparing an electrode foil according to claim 1, wherein, The preparation method further includes a stabilization treatment after the forming treatment; Preferably, the stabilization treatment uses a stabilization treatment liquid containing ammonium dihydrogen phosphate; and / or, The temperature of the stabilization treatment is 50°C to 60°C; and / or, The time of the stabilization treatment is 60 s to 360 s; Preferably, in the stabilization treatment liquid, the mass percentage of ammonium dihydrogen phosphate is 0.5% to 3%.

9. An electrode foil, characterized in that, The electrode foil is prepared by the preparation method according to 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 the preparation method according to any one of claims 1 to 8 or the electrode foil according to claim 9.

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