Electrode foil and method for producing the same and aluminum electrolytic capacitor

Abstract

The application belongs to the technical field of electrode materials, and particularly relates to an electrode foil, a preparation method thereof and an aluminum electrolytic capacitor. The preparation method of the electrode foil comprises forming a porous titanium dioxide film on the surface of an aluminum foil before pretreatment of the aluminum foil. The preparation method in the application is simple to operate and easy to control. By forming the porous titanium dioxide film on the surface of the aluminum foil before the pretreatment, the preparation of the electrode foil with uniform surface pores and consistent tunnel hole length is realized. The electrode foil prepared by the method has high capacity and good bending performance.

Description

Technical Field

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

[0002] Electrode foil is the core material of aluminum electrolytic capacitors, significantly influencing key technical indicators such as capacitance, leakage current, loss, lifespan, reliability, and size. The quality of the etching process determines the specific capacitance of the electrode foil; a higher specific capacitance means a stronger charge storage capacity, requiring less aluminum foil and resulting in a smaller capacitor size. The etching process uses high-purity electronic aluminum foil as raw material, employing chemical / electrochemical methods to etch numerous nanometer or micrometer-sized pores on its surface and interior, thereby increasing the surface area of ​​the foil and improving its specific capacitance. The uniformity of the surface pores and the consistency of the cross-sectional tunnel pores are crucial to the capacitance of the etched foil.

[0003] While there are publicly available technologies that use lasers to create temperature rise points on the surface of aluminum foil to improve the uniformity of medium- and high-voltage anode foil surfaces, this method is costly and can easily damage the aluminum foil surface if not handled properly.

[0004] Therefore, existing electrode foils and their preparation processes still need improvement. Summary of the Invention

[0005] The main objective of this invention is to provide an electrode foil, its preparation method, and an aluminum electrolytic capacitor. The preparation method provided by this invention is simple to operate and easy to control. By forming a porous titanium dioxide film on the surface of the aluminum foil before pretreatment, the electrode foil with uniform surface porosity and consistent tunnel hole length is prepared. The electrode foil prepared by the method described in this invention has high capacity and good bending performance.

[0006] To achieve the above objectives, the present invention provides the following technical solutions.

[0007] The first aspect of the present invention provides a method for preparing an electrode foil, the method comprising forming a porous titanium dioxide film on the surface of an aluminum foil before pretreatment.

[0008] In some embodiments of the present invention, forming the porous titanium dioxide film on the surface of the aluminum foil includes: preparing titanium dioxide sol using a sol-gel method, coating the titanium dioxide sol onto the surface of the aluminum foil using a dip-coating method, and forming the porous titanium dioxide film after drying.

[0009] In some embodiments of the present invention, the pore size of the porous titanium dioxide film is 100 nm to 200 nm.

[0010] In some embodiments of the present invention, the titanium dioxide sol contains a solvent and a titanium source.

[0011] In some embodiments of the present invention, the solvent includes polyethylene glycol and polyethylene.

[0012] In some embodiments of the present invention, the titanium source includes tetrabutyl titanate and titanium tetrachloride.

[0013] In some embodiments of the present invention, the mass percentage of the polyethylene glycol is 0.05% to 2% based on the total mass of the titanium source and the solvent.

[0014] In some embodiments of the present invention, the mass ratio of polyethylene glycol to polyethylene in the solvent is 1-3:1.5-9.

[0015] In some embodiments of the present invention, the mass ratio of tetrabutyl titanate to titanium tetrachloride in the titanium source is 1-3:4-8.

[0016] In some embodiments of the present invention, the temperature of the titanium dioxide sol in the lifting and impregnation method is 30°C to 60°C, and the lifting speed is 10 mm / min to 100 mm / min.

[0017] In some embodiments of the present invention, the drying temperature is 70°C to 120°C, and the drying time is 20 min to 60 min.

[0018] In some embodiments of the present invention, the pretreatment solution is a solution containing hydrochloric acid and phosphoric acid.

[0019] In some embodiments of the present invention, the pretreatment solution contains 5% to 10% hydrochloric acid and 3% to 20% phosphoric acid by mass.

[0020] In some embodiments of the present invention, the temperature of the pretreatment is 30°C to 80°C.

[0021] In some embodiments of the present invention, the pretreatment time is 1 min to 20 min.

[0022] In some embodiments of the present invention, the preparation method further includes primary hole formation and secondary hole expansion after the pretreatment.

[0023] In some embodiments of the present invention, the primary borehole is formed using an etching solution containing aluminum ions.

[0024] In some embodiments of the present invention, the mass percentage of aluminum ions in the etching solution is 2% to 10%.

[0025] In some embodiments of the present invention, the etching solution is an acidic solution containing aluminum ions.

[0026] In some embodiments of the present invention, the corrosive liquid contains hydrochloric acid and sulfuric acid.

[0027] In some embodiments of the present invention, the corrosive liquid contains 3.0% to 10.0% hydrochloric acid and 20% to 40% sulfuric acid by mass.

[0028] In some embodiments of the present invention, the temperature of the primary hair hole is 50°C to 90°C.

[0029] In some embodiments of the present invention, the time for the first-stage perforation is 10s to 60s.

[0030] In some embodiments of the present invention, the secondary pore enlargement uses an electrolyte containing aluminum ions.

[0031] In some embodiments of the present invention, the mass percentage of aluminum ions in the electrolyte is 0.5% to 4.5%.

[0032] In some embodiments of the present invention, the electrolyte is an acidic solution containing aluminum ions.

[0033] In some embodiments of the present invention, the electrolyte contains nitric acid and phosphoric acid.

[0034] In some embodiments of the present invention, the electrolyte contains 2.5% to 7.5% nitric acid and 0.02% to 0.25% phosphoric acid by mass.

[0035] In some embodiments of the present invention, the temperature of the secondary borehole expansion is 60°C to 95°C.

[0036] In some embodiments of the present invention, the current density of the secondary orifice expansion is 0.1 A / cm². 2 ~3A / cm 2 .

[0037] In some embodiments of the present invention, the effective energizing time for the secondary borehole expansion is 6 min to 30 min.

[0038] In some embodiments of the present invention, the preparation method further includes post-processing.

[0039] In some embodiments of the present invention, the post-treatment uses a solution containing nitric acid.

[0040] In some embodiments of the present invention, the mass percentage of nitric acid in the solution containing nitric acid is 3% to 10%.

[0041] In some embodiments of the present invention, the temperature of the post-processing is 60°C to 80°C.

[0042] In some embodiments of the present invention, the post-processing time is 1 min to 10 min.

[0043] In some embodiments of the present invention, the preparation method further includes removing the porous titanium dioxide film before performing the post-processing.

[0044] In some embodiments of the present invention, the porous titanium dioxide film is removed by a drying method.

[0045] In some embodiments of the present invention, the drying temperature is 50°C to 100°C.

[0046] In some embodiments of the present invention, the drying time is 20 min to 60 min.

[0047] A second aspect of the present invention provides an electrode foil, which is prepared by the preparation method described in the first aspect.

[0048] A third aspect of the present invention provides an aluminum electrolytic capacitor, the aluminum electrolytic capacitor comprising an electrode foil prepared by the preparation method described in the first aspect or the electrode foil described in the second aspect.

[0049] Compared with the prior art, the present invention achieves the following technical effects:

[0050] 1) In the preparation method of the present invention, a porous titanium dioxide film is first formed on the surface of aluminum foil, and pre-drilled holes are made. The porous holes are distributed in an orderly manner on the surface of aluminum foil, thereby obtaining an electrode foil with uniform surface etched holes, achieving uniform surface pores and consistent tunnel hole length, and improving the electrode foil capacity.

[0051] 2) In the preparation method of the present invention, the degree of thinning of the electrode foil surface is reduced by forming a porous titanium dioxide film.

[0052] 3) In the preparation method of the present invention, the formation of a controllable porous titanium dioxide film reduces the surface capacity loss of the electrode foil and increases the capacity of the electrode foil.

[0053] 4) In the preparation method of the present invention, under a certain amount of applied charge, the pore size of the titanium dioxide film can be controlled by adjusting the amount of solvent added in the sol-gel method, thereby achieving the purpose of uniform pore depth and effectively improving the bending performance of the etched foil.

[0054] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described below. Attached Figure Description

[0055] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. In the drawings:

[0056] Figure 1 This is a surface morphology diagram of the electrode foil prepared in Example 1 of the present invention;

[0057] Figure 2 This is a cross-sectional morphology diagram of the electrode foil prepared in Example 1 of the present invention;

[0058] Figure 3 This is a surface morphology diagram of the electrode foil prepared in Comparative Example 1 of the present invention;

[0059] Figure 4 This is a cross-sectional morphology diagram of the electrode foil prepared in Comparative Example 1 of the present invention. Detailed Implementation

[0060] Exemplary embodiments of the present invention will now be described in more detail with reference to specific examples. It should be understood that the present invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this invention will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

[0061] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the invention, are intended to cover non-exclusive inclusion.

[0062] In the description of the embodiments of the present invention, the technical terms "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features.

[0063] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of the invention. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0064] In the description of the embodiments of this invention, the term "and / or" is merely a description of the association relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A exists, A and B exist simultaneously, and B exists. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0065] Existing conventional preparation processes often employ pretreatment, primary pore formation, secondary electrochemical pore expansion, and post-treatment. These processes have drawbacks such as uneven distribution of surface etched holes, poor pore uniformity, increased corrosion pore size and surface co-pore formation after secondary electrochemical pore expansion, and severe thinning of the corrosion foil surface, leading to a decrease in the specific capacity of medium and high voltage anode foil and a significant reduction in its capacity.

[0066] To improve the uniformity of pit distribution and the consistency of tunnel hole length on the surface of medium- and high-voltage anode foil, some literature reports the use of lasers to create laser-induced temperature rise points on the aluminum foil. Multiple laser-induced temperature rise points are used, with two lasers symmetrically arranged on both sides of the aluminum foil, and the temperature of the generated focal points is below 600℃. This method can obtain a etched foil with a uniform pit distribution, but it requires more equipment, is more complex, and has higher costs. Furthermore, recrystallization may occur if the local temperature of the aluminum foil exceeds 300℃.

[0067] Therefore, providing a simple and reliable method to obtain electrode foils with uniform surface etched pit distribution and consistent tunnel hole length, such as medium and high voltage anode foils, plays an important role in reducing production costs and improving product performance.

[0068] The present invention provides a method for preparing an electrode foil, the method comprising forming a porous titanium dioxide film on the surface of an aluminum foil before pretreatment.

[0069] In an embodiment of the present invention, a porous titanium dioxide film is first formed on the surface of the aluminum foil before pretreatment, and the pores are pre-distributed in an orderly manner on the surface of the aluminum foil, thereby obtaining an electrode foil with uniform surface etched pore distribution and improving the electrode foil capacity.

[0070] Pre-drilled holes

[0071] In an embodiment of the present invention, pre-drilling holes is first performed on the surface of the aluminum foil. Specifically, a porous titanium dioxide film is formed on the surface of the aluminum foil. This can be understood as first forming a porous titanium dioxide film on the surface of the aluminum foil to pre-drill holes on the surface of the aluminum foil, thereby obtaining an electrode foil with uniformly distributed surface etched holes.

[0072] In an embodiment of the present invention, titanium dioxide sol is prepared by sol-gel method, and titanium dioxide sol is coated on the surface of aluminum foil by dip coating method, and a porous titanium dioxide film is formed on the surface of aluminum foil after drying.

[0073] In embodiments of the present invention, the pore size of the porous titanium dioxide film is in the range of 100 nm to 200 nm. The pore size of the porous titanium dioxide film provided by the present invention can be any value within the range formed by any two values ​​within the above-mentioned range, for example, 100 nm to 150 nm, or 150 nm to 200 nm, and so on. Exemplarily, the pore size of the porous titanium dioxide film can be one of 100 nm, 110 nm, 120 nm, 130 nm, 140 nm, 150 nm, 160 nm, 170 nm, 180 nm, 190 nm, and 200 nm, or any value satisfying the above-mentioned range.

[0074] Sol-gel method

[0075] In embodiments of the present invention, the titanium dioxide sol contains a solvent and a titanium source.

[0076] In embodiments of the present invention, the titanium source includes tetrabutyl titanate and titanium tetrachloride.

[0077] In some embodiments of the present invention, the mass ratio of tetrabutyl titanate to titanium tetrachloride in the titanium source is 1–3:4–8. The mass ratio of tetrabutyl titanate to titanium tetrachloride provided by the present invention can be any value within the range formed by any two values ​​in the above-mentioned range, for example, it can be 1:4–8, 3:4–8, 1–3:4, 1–3:8, and so on. Exemplarily, the mass ratio of tetrabutyl titanate to titanium tetrachloride can be one of 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 2:5, 2:7, 3:4, 3:5, 3:6, 3:7, 3:8, or any value satisfying the above-mentioned range.

[0078] In embodiments of the present invention, the solvent includes polyethylene glycol and polyethylene.

[0079] In some embodiments of the present invention, the mass ratio of polyethylene glycol to polyethylene in the solvent is 1–3:1.5–9. The mass ratio of polyethylene glycol to polyethylene provided by the present invention can be any value within the range formed by any two values ​​in the above-mentioned range, for example, it can be 1–3:1.5, 1–3:9, 1:1.5–9, 3:1.5–9, and so on. Exemplarily, the mass ratio of polyethylene glycol to polyethylene can be one of 1:0.5, 1:1, 1:1.5, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 2:1.5, 2:3, 2:5, 2:7, 2:9, 3:2, 3:4, 3:5, 3:7, 3:8, or any value satisfying the above-mentioned range.

[0080] In some embodiments of the present invention, the mass percentage of polyethylene glycol is 0.05% to 2% based on the total mass of the titanium source and solvent. The mass percentage of polyethylene glycol provided by the present invention can be any value within the range formed by any two values ​​within the above range, for example, it can be 0.05% to 1%, or 1% to 2%, and so on. The mass percentage of polyethylene glycol provided by the present invention can also be one of 0.05%, 0.06%, 0.08%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, 0.55%, 0.6%, 0.65%, 0.7%, 0.75%, 0.8%, 0.85%, 0.9%, 0.95%, 1%, 1.2%, 1.4%, 1.5%, 1.6%, 1.8%, 2%, or any value satisfying the above range.

[0081] It is worth mentioning that the process for preparing titanium dioxide sol using the sol-gel method in this embodiment of the invention includes hydrolysis, polycondensation, and drying and aging. First, the titanium source is dispersed in a solvent containing polyethylene glycol and polyethylene. Then, a hydrolysis reaction is performed to generate active monomers. These active monomers then polymerize to form a sol. After a period of drying and aging, the desired titanium dioxide sol is obtained. The drying and aging temperature in the sol-gel method is 50℃~100℃, and the drying and aging time is 1~4 days. Exemplarily, the drying and aging temperature in the sol-gel method can be one of 50℃, 60℃, 70℃, 80℃, 90℃, 100℃, or any value within the above range. The drying and aging time can be one of 1 day, 1.5 days, 2 days, 2.5 days, 3 days, 3.5 days, 4 days, or any value within the above range.

[0082] Lifting and dipping method

[0083] In an embodiment of the present invention, the lifting immersion method is a method of vertically immersing aluminum foil into titanium dioxide sol, then vertically lifting the aluminum foil from the titanium dioxide sol at a low speed, and allowing the attached liquid film to gel in the air.

[0084] In some embodiments of the present invention, the lifting and dipping method can also be understood as the dipping and lifting method.

[0085] In some embodiments of the present invention, the lifting speed is 10 mm / min to 100 mm / min. The lifting speed provided by the present invention can be any value within the range formed by any two values ​​in the above range, such as 10 mm / min to 40 mm / min, 40 mm / min to 70 mm / min, 70 mm / min to 100 mm / min, and so on. Exemplarily, the lifting speed in the present invention can be one of 10 mm / min, 20 mm / min, 30 mm / min, 40 mm / min, 50 mm / min, 60 mm / min, 70 mm / min, 80 mm / min, 90 mm / min, and 100 mm / min, or any value satisfying the above range.

[0086] In some embodiments of the present invention, the temperature of the titanium dioxide sol in the dip-coating method is 30°C to 60°C. The temperature of the titanium dioxide sol in the dip-coating method provided by the present invention can be any value within the range formed by any two values ​​within the above-mentioned range, for example, it can be 30°C to 45°C, or 45°C to 60°C, and so on. Exemplarily, the temperature of the titanium dioxide sol in the present invention can be one of 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, and 60°C, or any value satisfying the above-mentioned range.

[0087] In embodiments of the present invention, the drying temperature after coating the titanium dioxide sol onto the aluminum foil surface using the dip-coating method is 70℃~120℃, and the drying time is 20min~60min. The drying temperature after coating the titanium dioxide sol onto the aluminum foil surface using the dip-coating method can be any value within the range formed by any two values ​​mentioned above, such as 70℃~90℃, or 90℃~120℃, and so on. Exemplarily, the drying temperature provided by the present invention can be one of 70℃, 75℃, 80℃, 85℃, 90℃, 95℃, 100℃, 105℃, 110℃, 115℃, and 120℃, or any value satisfying the above range. The drying time after coating the titanium dioxide sol onto the aluminum foil surface using the dip-coating method can be any value within the range formed by any two values ​​mentioned above, such as 20min~40min, or 40min~60min, and so on. The drying time provided by the present invention can be one of 20 min, 30 min, 40 min, 50 min, and 60 min, or any value that meets the above range.

[0088] In an embodiment of the present invention, titanium dioxide sol is prepared by a sol-gel method. The titanium source includes tetrabutyl titanate and titanium tetrachloride. A solvent containing polyethylene glycol and polyethylene is used. Based on the total mass of the titanium source and the solvent, the mass percentage of polyethylene glycol is 0.05% to 2%. The titanium dioxide sol is coated onto the surface of an aluminum foil using a dip-coating method. After drying, a porous titanium dioxide film is formed on the surface of the aluminum foil. The temperature of the titanium dioxide sol is 30°C to 60°C, the dip-coating speed is 10 mm / min to 100 mm / min, the drying temperature is 70°C to 120°C, and the drying time is 20 min to 60 min.

[0089] Preprocessing

[0090] In an embodiment of the present invention, the aluminum foil after pre-drilling holes is pre-treated to remove grease and oxide film from the surface of the aluminum foil and increase the active sites on the surface of the aluminum foil.

[0091] In an embodiment of the present invention, the pretreatment solution used is a solution containing hydrochloric acid (HCl) and phosphoric acid (H3PO4).

[0092] In some embodiments of the present invention, the pretreatment solution contains 5% to 10% hydrochloric acid and 3% to 20% phosphoric acid by mass. Exemplarily, the mass percentage of hydrochloric acid in the pretreatment solution provided by the present invention can be one of 5%, 6%, 7%, 8%, 9%, or 10%, or any value satisfying the above range. The mass percentage of phosphoric acid in the pretreatment solution provided by the present invention can be one of 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, or 20%, or any value satisfying the above range.

[0093] In some embodiments of the present invention, the pretreatment temperature is 30°C to 80°C, which can be understood as the temperature of the pretreatment solution being 30°C to 80°C. Exemplarily, the pretreatment temperature can be one of 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, or 80°C, or any value satisfying the above range.

[0094] In some embodiments of the present invention, the preprocessing time is 1 min to 20 min. The preprocessing time provided by the present invention can be any value within the range formed by any two values ​​in the above-mentioned interval, such as 1 min to 6 min, 6 min to 12 min, 12 min to 20 min, and so on. For example, the preprocessing time can be one of 1 min, 2 min, 3 min, 4 min, 5 min, 6 min, 7 min, 8 min, 9 min, 10 min, 11 min, 12 min, 13 min, 14 min, 15 min, 16 min, 17 min, 18 min, 19 min, and 20 min, or any value that satisfies the above-mentioned range.

[0095] In an embodiment of the present invention, the aluminum foil with a porous titanium dioxide film formed on its surface is pretreated in a treatment solution containing hydrochloric acid and phosphoric acid. The pretreatment temperature is 30°C to 80°C and the time is 1 min to 20 min.

[0096] Level 1 hair hole

[0097] In an embodiment of the present invention, the pretreated aluminum foil is subjected to primary perforation.

[0098] In an embodiment of the present invention, the primary bore uses aluminum ions (Al) 3+ () corrosive liquid.

[0099] In some embodiments of the present invention, the mass percentage of aluminum ions in the etching solution is 2% to 10%. Exemplarily, the mass percentage of aluminum ions in the etching solution can be one of 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, and 10%, or any value satisfying the above range.

[0100] In some embodiments of the present invention, the etching solution is a solution containing aluminum ions (Al). 3+ An acidic solution.

[0101] In some embodiments of the present invention, the corrosive solution contains hydrochloric acid (HCl) and sulfuric acid (H2SO4).

[0102] In some embodiments of the present invention, the corrosive solution contains 3.0% to 10.0% hydrochloric acid and 20% to 40% sulfuric acid by mass. Exemplarily, the mass percentage of hydrochloric acid in the corrosive solution provided by the present invention can be one of 3.0%, 4.0%, 5.0%, 6.0%, 7.0%, 8.0%, 9.0%, and 10.0%, or any value satisfying the above range. The mass percentage of sulfuric acid in the corrosive solution provided by the present invention can be a value within the range formed by any two values ​​within the above range, for example, it can be 20% to 30%, or 30% to 40%, and so on. The mass percentage of sulfuric acid in the corrosive solution provided by the present invention can also be one of 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, or 40%, or any value that satisfies the above range.

[0103] In some embodiments of the present invention, the temperature of the primary borehole is 50°C to 90°C. This can be understood as the temperature of the etching solution used for the primary borehole can be any value within the range defined by any two values ​​mentioned above, such as 50°C to 60°C, 60°C to 80°C, 80°C to 90°C, and so on. For example, the temperature of the primary borehole can be one of 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, or 90°C, or any value satisfying the above range.

[0104] In some embodiments of the present invention, the time for primary hole generation is 10s to 60s. The time for primary hole generation provided by the present invention can be any value within the range formed by any two values ​​within the above-mentioned range, such as 10s to 30s, 30s to 60s, and so on. For example, the time for primary hole generation can be one of 10s, 15s, 20s, 25s, 30s, 40s, 50s, and 60s, or any value satisfying the above-mentioned range.

[0105] In an embodiment of the present invention, the primary borehole is formed using an etching solution containing aluminum ions, hydrochloric acid, and sulfuric acid, with the temperature of the primary borehole being 50°C to 90°C and the time being 10s to 60s.

[0106] Secondary hole enlargement

[0107] In an embodiment of the present invention, the aluminum foil that has undergone primary perforation is subjected to secondary perforation.

[0108] In an embodiment of the present invention, the secondary pore enlargement uses an electrolyte containing aluminum ions.

[0109] In embodiments of the present invention, the mass percentage of aluminum ions in the electrolyte is 0.5% to 4.5%. The mass percentage of aluminum ions in the electrolyte provided by the present invention can be any value within the range formed by any two values ​​in the above range, for example, it can be 0.5% to 3.0%, or 3.0% to 4.5%, and so on. For example, the mass percentage of aluminum ions in the electrolyte 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%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3.0%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, 4.0%, 4.1%, 4.2%, 4.3%, 4.4%, and 4.5%, or any value within the range described above.

[0110] In some embodiments of the present invention, the electrolyte is an electrolyte containing aluminum ions (Al). 3+ An acidic solution.

[0111] In some embodiments of the present invention, the electrolyte contains nitric acid (HNO3) and phosphoric acid (H3PO4).

[0112] In some embodiments of the present invention, the electrolyte contains 2.5% to 7.5% nitric acid by mass and 0.02% to 0.25% phosphoric acid by mass. Exemplarily, the mass percentage of nitric acid in the electrolyte provided by the present invention can be any value within the range formed by any two values ​​in the above-mentioned range, such as 2.5% to 4.5%, or 4.5% to 7.5%, and so on. The mass percentage of nitric acid in the electrolyte provided by the present invention can be 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3.0%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, 4.0%, 4.1%, 4.2%, 4.3%, 4.4%, 4.5%, 4.6%, 4.7%, 4.8%, 4.9%, etc. The mass percentage of phosphoric acid in the electrolyte provided by this invention can be any value within the range of any two values ​​listed above, such as 5.0%, 5.1%, 5.2%, 5.3%, 5.4%, 5.5%, 5.6%, 5.7%, 5.8%, 5.9%, 6.0%, 6.1%, 6.2%, 6.3%, 6.4%, 6.5%, 6.6%, 6.7%, 6.8%, 6.9%, 7.0%, 7.1%, 7.2%, 7.3%, 7.4%, and 7.5%. The mass percentage of nitric acid in the electrolyte provided by this invention can be one of 0.02%, 0.04%, 0.06%, 0.08%, 0.1%, 0.12%, 0.14%, 0.16%, 0.18%, 0.2%, 0.22%, 0.24%, or 0.25%, or any value within the above range.

[0113] In some embodiments of the present invention, the temperature for secondary orifice expansion is 60℃ to 95℃. The temperature for secondary orifice expansion provided by the present invention can be any value within the range formed by any two values ​​in the above range, such as 60℃ to 75℃, 75℃ to 95℃, and so on. It can be understood that the temperature of the electrolyte used for secondary orifice expansion is one of 60℃, 65℃, 70℃, 75℃, 80℃, 85℃, 90℃, and 95℃, or any value that satisfies the above range.

[0114] In some embodiments of the present invention, the current density for the secondary orifice expansion is 0.1 A / cm². 2 ~3A / cm 2 For example, the current density for secondary orifice expansion can be 0.1 A / cm². 2 0.2A / cm 2 0.5A / cm 2 0.8A / cm2 1.0A / cm 2 1.2A / cm 2 1.4A / cm 2 1.5A / cm 2 1.6A / cm 2 1.8A / cm 2 2.0A / cm 2 2.2A / cm 2 2.4A / cm 2 2.5A / cm 2 2.6A / cm 2 2.8A / cm 2 3A / cm 2 One of the above values ​​or any value that satisfies the above range.

[0115] In some embodiments of the present invention, the effective energizing time for secondary borehole reaming is 6 min to 30 min. The effective energizing time for secondary borehole reaming provided by the present invention can be any value within the range formed by any two values ​​within the above-mentioned interval, such as 6 min to 15 min, 15 min to 30 min, and so on. Exemplarily, the effective energizing time for secondary borehole reaming can be one of 6 min, 7 min, 8 min, 9 min, 10 min, 11 min, 12 min, 13 min, 14 min, 15 min, 16 min, 17 min, 18 min, 19 min, 20 min, 21 min, 22 min, 23 min, 24 min, 25 min, 26 min, 27 min, 28 min, 29 min, or 30 min, or any value satisfying the above-mentioned range.

[0116] In an embodiment of the present invention, the secondary pore-expanding stage employs an electrolyte containing aluminum ions, nitric acid, and phosphoric acid. The temperature for the secondary pore-expanding stage is 60°C to 95°C, and the current density is 0.1 A / cm². 2 ~3A / cm 2 The effective power-on time is 6 min to 30 min.

[0117] It is worth mentioning that, in the embodiments of the present invention, the aluminum foil after the secondary pore-expanding treatment can be washed with water as needed before removing the porous titanium dioxide film to remove residual acid on the surface of the aluminum foil. For example, pure water can be used to rinse the surface of the aluminum foil.

[0118] Membrane removal

[0119] In an embodiment of the present invention, the porous titanium dioxide film on the surface of the aluminum foil after secondary pore expansion is removed by drying.

[0120] In some embodiments of the present invention, the drying temperature for membrane removal is 50°C to 100°C. Exemplarily, the drying temperature for membrane removal can be one of 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, and 100°C, or any value satisfying the above range.

[0121] In some embodiments of the present invention, the drying time for membrane removal is 20 min to 60 min. Exemplarily, the drying time for membrane removal can be one of 20 min, 30 min, 40 min, 50 min, and 60 min, or any value satisfying the above range.

[0122] In an embodiment of the present invention, the porous titanium dioxide film on the surface of the aluminum foil after secondary pore expansion is removed by drying. The drying temperature is 50℃~100℃ and the drying time is 20min~60min.

[0123] Post-processing

[0124] In an embodiment of the present invention, the aluminum foil after the porous titanium dioxide film is removed is post-treated to remove residual aluminum ions on the surface of the aluminum foil through a displacement reaction.

[0125] In an embodiment of the present invention, the post-treatment uses a solution containing nitric acid.

[0126] In some embodiments of the present invention, the mass percentage of nitric acid in the solution containing nitric acid is 3% to 10%. Exemplarily, the mass percentage of nitric acid in the solution containing nitric acid can be one of 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or any value satisfying the above range.

[0127] In some embodiments of the present invention, the post-treatment temperature is 60°C to 80°C, which can be understood as the temperature of the nitric acid-containing solution used in the post-treatment being 60°C to 80°C. Exemplarily, the post-treatment temperature can be one of 60°C, 65°C, 70°C, 75°C, and 80°C, or any value satisfying the above range.

[0128] In some embodiments of the present invention, the post-processing time is 1 min to 10 min. Exemplarily, the post-processing time can be one of 1 min, 2 min, 3 min, 4 min, 5 min, 6 min, 7 min, 8 min, 9 min, and 10 min, or any value that satisfies the above range.

[0129] In some embodiments of the present invention, the post-treatment uses a solution containing nitric acid, the post-treatment temperature is 60°C to 80°C, and the post-treatment time is 1 min to 10 min.

[0130] In an embodiment of the present invention, the method for preparing the electrode foil includes forming a porous titanium dioxide film on the surface of an aluminum foil before pretreatment, and sequentially performing primary pore formation, secondary pore expansion, film removal, and post-treatment after pretreatment.

[0131] The present invention also provides an electrode foil, which is prepared by the above-described preparation method.

[0132] In embodiments of the present invention, the electrode foil can be a medium- or high-voltage anode foil.

[0133] The present invention also provides an aluminum electrolytic capacitor, which includes an electrode foil prepared by the above-described preparation method or the electrode foil described above.

[0134] Unless otherwise defined, the technical terms used in the following embodiments have the same meaning as commonly understood by those skilled in the art. Unless otherwise specified, the experimental reagents used in the following embodiments are all conventional biochemical reagents; the raw materials, instruments, and equipment used in the following embodiments can all be obtained commercially or through existing methods; unless otherwise specified, the amounts of experimental reagents used are the amounts used in conventional experimental operations; unless otherwise specified, the experimental methods are all conventional methods.

[0135] Example 1

[0136] A method for preparing an electrode foil includes the following steps:

[0137] Pre-drilled holes: Titanium dioxide sol was prepared using a titanium source of tetrabutyl titanate and titanium tetrachloride in a mass ratio of 2:5, and a solvent of polyethylene glycol and polyethylene in a mass ratio of 2:6. Based on the total mass of the titanium source and solvent, the mass percentage of polyethylene glycol was 0.05%. Titanium dioxide sol was prepared by sol-gel method, and the titanium dioxide sol was coated on the surface of aluminum foil by dip-coating method. The temperature of titanium dioxide sol was 50℃, the dip-coating speed was 80mm / min, and after drying at 100℃ for 40min, a porous titanium dioxide film with a pore size of 100nm to 200nm was formed on the surface of aluminum foil, thus realizing the pre-drilled holes on the surface of aluminum foil.

[0138] Pretreatment: The aluminum foil with titanium dioxide film formed on the surface was placed in a pretreatment solution containing hydrochloric acid and phosphoric acid at 70°C for 3 minutes. The mass percentage of hydrochloric acid in the pretreatment solution was 6.0% and the mass percentage of phosphoric acid was 8.0%.

[0139] First-stage perforation: The pretreated aluminum foil is placed in an etching solution at 72°C for perforation, and the perforation time is 20 seconds. The etching solution is an aqueous solution containing hydrochloric acid, sulfuric acid and aluminum ions, with the mass percentage of hydrochloric acid being 5.2%, the mass percentage of sulfuric acid being 25%, and the mass percentage of aluminum ions being 5.5%.

[0140] Secondary pore enlargement: The aluminum foil after primary pore enlargement is placed in an electrolyte at 73°C for pore enlargement. The electrolyte is a mixture containing nitric acid, aluminum ions, and phosphoric acid, with the nitric acid mass percentage being 5.0%, the aluminum ion mass percentage being 3.5%, and the phosphoric acid mass percentage being 0.08%. The current density for secondary pore enlargement is 0.2 A / cm². 2 The total effective power-on time is 9 minutes.

[0141] Washing and film removal: The aluminum foil after secondary pore expansion is rinsed with pure water, and then the porous titanium dioxide film on the surface of the aluminum foil is removed by drying. The drying temperature is 70℃ and the drying time is 30min.

[0142] Post-treatment: The aluminum foil after removing the porous titanium dioxide film was placed in a 4.0% nitric acid aqueous solution at 65°C for 2 min.

[0143] Example 2

[0144] A method for preparing an electrode foil includes the following steps:

[0145] The remaining operations are the same as in Example 1, except that the mass percentage of polyethylene glycol is 1%.

[0146] Example 3

[0147] A method for preparing an electrode foil includes the following steps:

[0148] The remaining operations are the same as in Example 1, except that the mass percentage of polyethylene glycol is 2%.

[0149] Example 4

[0150] A method for preparing an electrode foil includes the following steps:

[0151] The remaining operations are the same as in Example 1, except that the temperature of the titanium dioxide sol in the dip-coating method is 30°C.

[0152] Example 5

[0153] A method for preparing an electrode foil includes the following steps:

[0154] The remaining operations are the same as in Example 1, except that the temperature of the titanium dioxide sol in the dip-coating method is 45°C.

[0155] Example 6

[0156] A method for preparing an electrode foil includes the following steps:

[0157] The remaining operations are the same as in Example 1, except that the temperature of the titanium dioxide sol in the dip-coating method is 60°C.

[0158] Example 7

[0159] A method for preparing an electrode foil includes the following steps:

[0160] The remaining operations are the same as in Example 1, except that the lifting speed in the immersion lifting method is 10 mm / min.

[0161] Example 8

[0162] A method for preparing an electrode foil includes the following steps:

[0163] The remaining operations are the same as in Example 1, except that the lifting speed in the immersion lifting method is 50 mm / min.

[0164] Example 9

[0165] A method for preparing an electrode foil includes the following steps:

[0166] The remaining operations are the same as in Example 1, except that the lifting speed in the immersion lifting method is 100 mm / min.

[0167] Comparative Example 1

[0168] A method for preparing an electrode foil includes the following steps:

[0169] Pretreatment: The aluminum foil was placed in a pretreatment solution containing hydrochloric acid and phosphoric acid at 70°C for 3 minutes. The mass percentage of hydrochloric acid in the pretreatment solution was 6.0%, and the mass percentage of phosphoric acid was 8.0%.

[0170] First-stage perforation: The pretreated aluminum foil is placed in an etching solution at 72°C for perforation, and the perforation time is 20 seconds. The etching solution is an aqueous solution containing hydrochloric acid, sulfuric acid and aluminum ions, with the mass percentage of hydrochloric acid being 5.2%, the mass percentage of sulfuric acid being 25%, and the mass percentage of aluminum ions being 5.5%.

[0171] Secondary pore enlargement: The aluminum foil after primary pore enlargement is placed in an electrolyte at 73°C for pore enlargement. The electrolyte is a mixture containing nitric acid, aluminum ions, and phosphoric acid, with the nitric acid mass percentage being 5.0%, the aluminum ion mass percentage being 3.5%, and the phosphoric acid mass percentage being 0.08%. The current density for secondary pore enlargement is 0.2 A / cm². 2 The total effective power-on time is 9 minutes.

[0172] Water washing: Rinse the aluminum foil after the secondary pore expansion with pure water.

[0173] Post-treatment: The washed aluminum foil was placed in a 4.0% nitric acid aqueous solution at 65°C for 2 minutes.

[0174] Comparative Example 2

[0175] A method for preparing an electrode foil includes the following steps:

[0176] The remaining operations are the same as in Example 1, except that the mass percentage of polyethylene glycol added is 0.02%.

[0177] Comparative Example 3

[0178] A method for preparing an electrode foil includes the following steps:

[0179] The remaining operations are the same as in Example 1, except that the mass percentage of polyethylene glycol added is 3%.

[0180] Comparative Example 4

[0181] The remaining operations are the same as in Example 1, except that the mass ratio between polyethylene glycol and polyethylene is 1:10.

[0182] Comparative Example 5

[0183] The remaining operations are the same as in Example 1, except that the mass ratio of tetrabutyl titanate to titanium tetrachloride is 1:9.

[0184] Performance testing

[0185] (1) Morphological detection.

[0186] The samples prepared in the examples and comparative examples were resin-prepared and polished, and then observed under an electron microscope.

[0187] Figure 1 The image shows the surface morphology of the etched holes on the electrode foil prepared in Example 1. It can be seen that the etched holes on the electrode foil surface are evenly distributed and relatively few in number. Figure 2 The image shows the cross-sectional morphology of the etched holes in the electrode foil prepared in Example 1, which shows that the tunnel hole lengths are consistent.

[0188] Figure 3 The image shows the surface morphology of the etched holes of the electrode foil prepared in Comparative Example 1. It can be seen that the surface uniformity of the electrode foil is poor and the co-occurrence phenomenon is serious. Figure 4 The image shows the cross-sectional morphology of the etched holes in the electrode foil prepared in Comparative Example 1, which reveals poor consistency in the length of the tunnel holes.

[0189] (2) Electrode foil capacity detection.

[0190] Specific capacitance test method: The electrode foil was subjected to formation treatment at 520V in a 10% boric acid solution at 90℃. Then, a ZX8516B model electrostatic capacitance tester from Changzhou Zhixin Precision Electronics Co., Ltd. was used. The measurement accuracy was ±2%, the test frequency was 120±5Hz, and the measurement voltage was below 0.5Vrms. The bath composition was: 1000mL pure water, 80g ammonium pentaborate, and the test temperature was 30±2℃.

[0191] (3) Bending strength test.

[0192] Bending performance test method: The electrode foil size is 10mm*150mm (the punching burr should be less than 0.1mm). The YAFENG MIT-DA bending tester is used. The test conditions are: radius of curvature R1.0±0.1mm at the bending point, load 2.5±0.5N, bending angle 90±2°, bending speed 6 times / s, and distance between the upper and lower clamps 70±2mm.

[0193] The test results are detailed in Table 1.

[0194] Table 1 Summary of electrode foil performance results in the embodiments and comparative examples of the present invention

[0195]

[0196]

[0197] Combination Figure 1-4 As shown in Table 1, the method of this invention first forms a porous titanium dioxide film on the surface of the aluminum foil, resulting in an electrode foil with a specific capacitance of not less than 0.879 μf / cm². 2 The bending time should be no less than 72 times.

[0198] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for producing an electrode foil, characterized by, The process includes forming a porous titanium dioxide film on the surface of the aluminum foil before pretreatment; performing primary pore formation and secondary pore enlargement after the pretreatment; and posttreatment, removing the porous titanium dioxide film before performing the posttreatment. The pretreatment uses a solution containing hydrochloric acid and phosphoric acid; the posttreatment uses a solution containing nitric acid.

2. The method of producing an electrode foil according to claim 1, wherein The process of forming the porous titanium dioxide film on the surface of the aluminum foil includes: preparing titanium dioxide sol using a sol-gel method, coating the titanium dioxide sol onto the surface of the aluminum foil using a dip-coating method, and then drying to form the porous titanium dioxide film.

3. The method for producing an electrode foil according to claim 1, characterized by, The porous titanium dioxide membrane has a pore size of 100 nm to 200 nm.

4. The method of producing an electrode foil according to claim 2, wherein The titanium dioxide sol contains a solvent and a titanium source.

5. The method of producing an electrode foil according to claim 4, wherein The solvents include polyethylene glycol and polyethylene.

6. The method of producing an electrode foil according to claim 4, wherein The titanium source includes tetrabutyl titanate and titanium tetrachloride.

7. The method of producing an electrode foil according to claim 5, wherein Based on the total mass of the titanium source and the solvent, the mass percentage of the polyethylene glycol is 0.05% to 2%.

8. The method of producing an electrode foil according to claim 5, wherein In the solvent, the mass ratio of polyethylene glycol to polyethylene is 1~3:1.5~9.

9. The method of producing an electrode foil according to claim 6, wherein In the titanium source, the mass ratio of tetrabutyl titanate to titanium tetrachloride is 1~3:4~8.

10. The method for producing an electrode foil according to claim 2, characterized by, The temperature of the titanium dioxide sol in the dip-lifting method is 30℃~60℃, and the lifting speed is 10 mm / min~100 mm / min.

11. The method of producing an electrode foil according to claim 2, characterized by, The drying temperature is 70℃~120℃, and the drying time is 20 min~60 min.

12. The method for preparing the electrode foil as described in claim 1, characterized in that, The pretreatment solution contains 5% to 10% hydrochloric acid and 3% to 20% phosphoric acid by mass.

13. The method of producing an electrode foil according to claim 1, wherein The temperature for the pretreatment is 30℃~80℃.

14. The method of producing an electrode foil according to claim 1, wherein The preprocessing time is 1 min to 20 min.

15. The method of claim 1, wherein The primary borehole is formed using an etching solution containing aluminum ions.

16. The method of producing an electrode foil according to claim 15, wherein The mass percentage of aluminum ions in the corrosion solution is 2% to 10%.

17. The method of producing an electrode foil according to claim 15, wherein The corrosion solution is an acidic solution containing aluminum ions.

18. The method of producing an electrode foil according to claim 17, wherein The corrosive solution contains hydrochloric acid and sulfuric acid.

19. The method of producing an electrode foil according to claim 18, wherein The corrosive solution contains 3.0% to 10.0% hydrochloric acid and 20% to 40% sulfuric acid by mass.

20. The method of producing an electrode foil according to claim 1, wherein The temperature of the primary hair follicle is 50℃~90℃.

21. The method of producing an electrode foil according to claim 1, wherein The time for the first-stage perforation is 10 s to 60 s.

22. The method of producing an electrode foil according to claim 1, wherein The secondary pore enlargement uses an electrolyte containing aluminum ions.

23. The method for preparing the electrode foil as described in claim 22, characterized in that, The mass percentage of aluminum ions in the electrolyte is 0.5% to 4.5%.

24. The method for preparing the electrode foil as described in claim 22, characterized in that, The electrolyte is an acidic solution containing aluminum ions.

25. The method for preparing the electrode foil as described in claim 24, characterized in that, The electrolyte contains nitric acid and phosphoric acid.

26. The method for preparing the electrode foil as described in claim 25, characterized in that, The electrolyte contains 2.5% to 7.5% nitric acid and 0.02% to 0.25% phosphoric acid by mass.

27. The method for preparing the electrode foil as described in claim 1, characterized in that, The temperature for the secondary borehole expansion is 60℃~95℃.

28. The method for preparing the electrode foil as described in claim 1, characterized in that, The current density of the secondary reaming is 0.1 A / cm 2 ~3 A / cm 2 .

29. The method for preparing the electrode foil as described in claim 1, characterized in that, The effective energizing time for the secondary borehole expansion is 6 min to 30 min.

30. The method for preparing the electrode foil as described in claim 1, characterized in that, The mass percentage of nitric acid in the solution containing nitric acid is 3% to 10%.

31. The method for preparing the electrode foil as described in claim 1, characterized in that, The post-processing temperature is 60℃~80℃.

32. The method for preparing the electrode foil as described in claim 1, characterized in that, The post-processing time is 1 min to 10 min.

33. The method for preparing the electrode foil as described in claim 1, characterized in that, The porous titanium dioxide film was removed by a drying method.

34. The method for preparing the electrode foil as described in claim 33, characterized in that, The drying temperature is 50℃~100℃.

35. The method for preparing the electrode foil as described in claim 33, characterized in that, The drying time is 20 min to 60 min.

36. An electrode foil, characterized in that, The electrode foil is prepared by any one of the preparation methods described in claims 1-35.

37. An aluminum electrolytic capacitor, characterized in that, The aluminum electrolytic capacitor includes an electrode foil prepared by any one of the preparation methods of claims 1-35 or the electrode foil of claim 36.

Images