Aluminum foil and method for producing the same

Abstract

This disclosure provides aluminum foil and its preparation method. The preparation method includes: electrochemically etching the aluminum foil to create pores; performing a first chemical etching on the aluminum foil in a first etching solution containing benzotriazole; performing a second chemical etching on the aluminum foil in a second etching solution containing polyethylene glycol; and performing a third chemical etching on the aluminum foil in a third etching solution containing benzotriazole and polyethylene glycol. This disclosure achieves pure chemical pore enlargement by adding benzotriazole (BTA) and polyethylene glycol to form a composite corrosion inhibitor system. The composite slow-release system of this disclosure allows the overall tunnel pore diameter to be moderately increased while maintaining good axial elongation.

Description

Technical Field

[0001] This disclosure relates to the field of capacitors, and in particular to aluminum foil and methods for its preparation. Background Technology

[0002] Pure chemical etching is gradually replacing some electrode foil products in medium and high voltage ranges due to its low power consumption and minimal environmental impact. These electrode foil products typically do not require high capacity, but demand specific strength and thickness characteristics. Hydrochloric acid chemical etching expands the pores, eliminating the influence of current and thus significantly improving the overall uniformity of the product. While reducing the thickness of the etched foil, the capacity decreases slightly, but the strength remains unchanged. Therefore, they are gradually emerging in products below 650V.

[0003] The chemical etching process for high-voltage aluminum anode foil typically employs an electrochemical pore formation—pure chemical pore expansion—formation treatment approach. In the pure chemical etching process, polystyrene sulfonate (PSSA) is usually used as a corrosion inhibitor. PSSA is typically a chain polymer with a molecular weight of 100,000+, making it difficult to maintain stability in acidic solutions. During the addition of acid, under energized conditions, it usually maintains its stability through a process of decomposition followed by polymerization. Therefore, for pure chemical etching pore expansion that completely eliminates current (eliminating the electrochemical migration and adsorption protection process), its protective mechanism is insufficient. Product capacity is positively correlated with PSSA, but excessive addition of PSSA can lead to a decrease in tunnel pore size, resulting in pores smaller than 0.99 micrometers. This makes them prone to clogging during the formation process, affecting the specific charge conversion (CV) efficiency. Summary of the Invention

[0004] The present disclosure provides a method for preparing aluminum foil, comprising: electrochemically etching the aluminum foil to create pores; performing a first chemical etching on the aluminum foil in a first etching solution containing benzotriazole; performing a second chemical etching on the aluminum foil in a second etching solution containing polyethylene glycol; and performing a third chemical etching on the aluminum foil in a third etching solution containing benzotriazole and polyethylene glycol.

[0005] In some embodiments, the first etchant, the second etchant, and the third etchant all include acid and Al. 3+ The concentrations of acid in the first, second, and third corrosive solutions are each independently between 1 mol / L and 2 mol / L. Al 3+ The concentrations of each acid are independently between 0.2 mol / L and 0.8 mol / L, and the acids include HCl.

[0006] In some embodiments, the concentrations of benzotriazole in the first and third etchants are each independently from 0.1 g / L to 0.3 g / L.

[0007] In some embodiments, the first chemical corrosion includes corrosion at a temperature of 65°C to 75°C for 1 to 3 minutes.

[0008] In some embodiments, the concentration of polyethylene glycol in the second and third etching solutions is independently from 0.3 g / L to 0.8 g / L, and the polyethylene glycol includes at least one of polyethylene glycol 200, polyethylene glycol 300, polyethylene glycol 400, polyethylene glycol 600 and polyethylene glycol 1000.

[0009] In some embodiments, the second chemical corrosion includes corrosion at a temperature of 65°C to 75°C for 3 to 7 minutes.

[0010] In some embodiments, the third chemical corrosion includes corrosion at a temperature of 75°C to 85°C for 3 to 7 minutes.

[0011] In some embodiments, electrochemical etching for pitting includes: in a solution containing HCl, H2SO4, and Al 3+ In a mixed acidic solution, pulsed DC etching was performed, repeated three to five times. The concentration of HCl in the mixed acidic solution was 0.6 mol / L to 1.2 mol / L, the concentration of H₂SO₄ was 3 mol / L to 3.6 mol / L, and the concentration of Al... 3+ The concentration was from 0.1 mol / L to 0.5 mol / L, and the pulsed DC etching included a rate of 2 A / cm. 2 Up to 3A / cm 2 The initial current density etching was performed from 0.3 s to 0.8 s at 0.5 A / cm. 2 Up to 1A / cm 2 The mid-section was etched with a current of 6 to 11 seconds, and at a current of 0.12 A / cm. 2 Up to 0.3A / cm 2 The end current is etched for 3 to 7 seconds.

[0012] In some embodiments, the preparation method further includes: alkaline washing of the aluminum foil before electrochemical etching to create pores; and acid washing, drying, and formation treatment of the aluminum foil after the third chemical etching.

[0013] Another embodiment of this disclosure provides an aluminum foil, which is an aluminum foil obtained according to any of the above preparation methods.

[0014] This disclosure achieves purely chemical pore enlargement by adding a composite corrosion inhibitor system composed of benzotriazole (BTA) and polyethylene glycol. This composite corrosion inhibitor system exhibits a preferential protection effect during the pore enlargement process—that is, it preferentially covers the high-energy region around the pore opening, slowing down the lateral expansion rate, thereby relatively promoting the downward and longitudinal development of the corrosive fluid along the original tunnel direction. This dynamic balance allows the overall tunnel pore to maintain good axial extension capacity while moderately increasing in diameter. Attached Figure Description

[0015] Figure 1 A schematic flowchart of a method for preparing aluminum foil according to some embodiments is shown.

[0016] Figure 2 A scanning electron microscope image of a comparative aluminum foil is shown.

[0017] Figure 3 A scanning electron microscope image of the aluminum foil of an embodiment is shown.

[0018] Figure 4 The number of holes of corresponding sizes in the aluminum foils of the embodiments and comparative examples is shown as a comparison. Detailed Implementation

[0019] To enable those skilled in the art to better understand the technical solutions of this disclosure, the technical solutions of this disclosure will be described in detail below with reference to the accompanying drawings.

[0020] Exemplary embodiments will be described more fully below with reference to the accompanying drawings; however, these exemplary embodiments may be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will enable those skilled in the art to fully understand the scope of this disclosure.

[0021] Where there is no conflict, the various embodiments of this disclosure and the features thereof in the embodiments may be combined with each other.

[0022] As used herein, the term “and / or” includes any and all combinations of one or more related enumerated entries.

[0023] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this disclosure. As used herein, the singular forms “a” and “the” are also intended to include the plural forms unless the context clearly indicates otherwise. It will also be understood that when the terms “comprising” and / or “made of” are used in this specification, the presence of the stated feature, integral, step, operation, element, and / or component is specified, but the presence or addition of one or more other features, integrals, steps, operations, elements, components, and / or groups thereof is not excluded.

[0024] Unless otherwise specified, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art. It will also be understood that terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant art and this disclosure, and will not be interpreted as having an idealized or overly formal meaning, unless expressly so defined herein.

[0025] This disclosure proposes a novel pure chemical etching pathway that retains electrochemical etching in the pore formation stage to ensure initial pore density, while completely abandoning external current in the pore enlargement stage and instead using a etching solution containing a specific corrosion inhibitor for pure chemical pore enlargement.

[0026] This disclosure uses an acid (e.g., HCl) solution as the basic pore-expanding medium, and simultaneously adds benzotriazole (BTA) and polyethylene glycol (e.g., PEG-600) to form a composite corrosion inhibitor system, achieving purely chemical pore expansion. Unlike the single-mechanism action of commonly used hydrochloric acid pore-expanding corrosion inhibitors such as polystyrene sulfonate, benzotriazole, as an organic corrosion inhibitor, can selectively adsorb onto the active sites of the oxide composite film on the aluminum substrate surface (regions with relatively high copper impurity content), forming a dense protective film and inhibiting non-directional lateral corrosion; while polyethylene glycol (e.g., PEG-600) regulates interfacial tension through physical adsorption, enhances the film-forming stability of BTA, and synergistically inhibits excessive corrosion at the pore edge.

[0027] Furthermore, this composite corrosion inhibitor system exhibits a "selective protection" effect during the borehole enlargement process—that is, it preferentially covers the high-energy region around the borehole opening, slowing down the lateral expansion rate, thereby relatively promoting the downward and vertical development of the corrosive fluid along the original tunnel direction. This dynamic balance allows the overall tunnel borehole to maintain good axial extension capacity while its diameter is moderately increased, resulting in a higher depth-to-width ratio and a more unobstructed borehole structure.

[0028] like Figure 1 As shown, the preparation method of this disclosure includes step S101, which involves electrochemically etching aluminum foil to create pores. By performing electrochemical etching to create pores, the initial pore density can be ensured.

[0029] In some embodiments, the preparation method of this disclosure includes step S102, which involves performing a first chemical etching on an aluminum foil in a first etching solution containing benzotriazole (BTA). BTA forms a preliminary film during the chemical etching process, suppresses stray corrosion, and directionally guides the longitudinal extension of the pores, creating conditions for subsequent PEG filling of the film gaps and synergistic protection.

[0030] In some embodiments, the preparation method of this disclosure includes step S103, performing a second chemical etching on the aluminum foil in a second etching solution with added polyethylene glycol. PEG is extruded into the gaps of the protective film formed by BTA to form a stable, dense composite corrosion inhibitor film.

[0031] In some embodiments, the preparation method of this disclosure includes step S104, performing a third chemical etching on the aluminum foil in a third etching solution containing benzotriazole and polyethylene glycol. Through the synergistic effect of benzotriazole and polyethylene glycol, the overall tunnel hole maintains good axial elongation capacity while moderately increasing in diameter, resulting in a higher aspect ratio and a more unobstructed pore structure.

[0032] This disclosure achieves purely chemical pore enlargement by adding a composite corrosion inhibitor system composed of benzotriazole (BTA) and polyethylene glycol. This composite corrosion inhibitor system exhibits a preferential protection effect during the pore enlargement process—that is, it preferentially covers the high-energy region around the pore opening, slowing down the lateral expansion rate, thereby relatively promoting the downward and longitudinal development of the corrosive fluid along the original tunnel direction. This dynamic balance allows the overall tunnel pore to maintain good axial extension capacity while moderately increasing in diameter.

[0033] In some embodiments, the first etchant, the second etchant, and the third etchant all include acid and Al. 3+ The concentrations of acid in the first, second, and third corrosive solutions are each independently between 1 mol / L and 2 mol / L. Al 3+ The concentrations of each acid independently range from 0.2 mol / L to 0.8 mol / L, including HCl. The H+ of the acids... + It can drive the anodic dissolution reaction of aluminum and is the driving force for the corrosion reaction. Cl - It has strong penetrating power and can destroy the natural oxide film (Al2O3) on the aluminum surface, inducing local pitting corrosion and providing starting sites for the formation of subsequent tunnel holes. 3+ It helps to inhibit excessive aluminum dissolution, stabilize the corrosion interface, improve pore uniformity, and participate in BTA film formation, enhancing the corrosion inhibition effect. In some embodiments, the concentrations of acid in the first, second, and third etching solutions are each independently 1 mol / L, 1.2 mol / L, 1.4 mol / L, 1.6 mol / L, 1.8 mol / L, 2 mol / L, or any suitable value between them. If the acid concentration is too low, the corrosion rate is too slow, and the pores cannot expand sufficiently; Cl - The drawbacks include difficulty in initiating pitting corrosion and low pore density. If the acid concentration is too high, corrosion becomes excessively severe, easily leading to thinning of the pore walls or even perforation, exacerbating lateral corrosion, resulting in a rough surface and disordered pore distribution. In some embodiments, Al in the first, second, and third etchants... 3+ The concentrations of each are independently 0.2 mol / L, 0.4 mol / L, 0.6 mol / L, 0.8 mol / L, or any suitable value between them. If Al 3+If the concentration of Al is too low, the corrosion inhibition will be insufficient, the corrosion rate will be too fast, the BTA film will be incomplete, and the pore structure will be easily out of control; if Al 3+ If the concentration is too high, the corrosion rate will be too slow, and the pores will not expand sufficiently; the solution viscosity will increase, and mass transfer will be hindered; AlCl3·6H2O crystals may precipitate, contaminating the surface.

[0034] In some embodiments, the concentrations of benzotriazole in the first and third etching solutions are each independently from 0.1 g / L to 0.3 g / L. The nitrogen atom in the BTA molecule can react with Al³⁺. + Alternatively, coordination bonds can form on the aluminum metal surface, generating a hydrophobic, dense [Al–BTA] polymer film. This film preferentially adsorbs in highly active regions (such as pore edges, impurity-rich areas, grain boundaries, etc.), inhibiting excessive dissolution at these sites, thereby suppressing lateral corrosion (preventing lateral expansion of pores), guiding corrosion to deepen along the electric field direction (improving aspect ratio), and enhancing pore distribution uniformity. In some embodiments, the concentrations of benzotriazole in the first and third etching solutions are independently 0.1 g / L, 0.1 g / L, 0.3 g / L, or any suitable value between them. If the concentration of benzotriazole is too low, the adsorbed film is discontinuous and has low coverage, failing to effectively inhibit the rapid dissolution of highly active sites, leading to pore enlargement, rough pore walls, severe lateral corrosion, decreased aspect ratio, uneven pore distribution, and increased risk of local perforation. If the concentration of benzotriazole is too high, the surface will be excessively passivated, the corrosion rate will decrease significantly, the pore expansion will be hindered, the pore depth will be insufficient, and the film layer will be too thick, which may block the pore opening, hinder mass transfer, and even lead to "false pores" or a decrease in pore density.

[0035] In some embodiments, the first chemical etching includes etching at a temperature of 65°C to 75°C for 1 to 3 minutes. In some embodiments, the temperature of the first chemical etching is 65°C, 67°C, 69°C, 71°C, 73°C, 75°C, or any suitable value between them. If the temperature is too low, the initial expansion of the channel is insufficient, the tunnel is not effectively opened, and subsequent depth development is difficult, resulting in a low specific volume. If the temperature is too high, over-etching is likely to occur, the hole wall becomes thinner, the orifice enlarges, lateral corrosion intensifies, the depth-to-width ratio decreases, and even local perforation or surface peeling may occur. In some embodiments, the time of the first chemical etching is 1 minute, 2 minutes, 3 minutes, or any suitable value between them. If the time is too short, the hole channel may not be effectively enlarged, resulting in insufficient hole depth and low specific volume. If the time is too long, the orifice is excessively enlarged ("trumpet effect"), and the number of branching or stray holes in the channel increases.

[0036] In some embodiments, the concentrations of polyethylene glycol (PEG) in the second and third etching solutions are each independently from 0.3 g / L to 0.8 g / L, and the PEG includes at least one of PEG 200, PEG 300, PEG 400, PEG 600, and PEG 1000. PEG molecules have long chains and strong hydrophilicity, allowing them to adsorb onto the aluminum surface and the inner walls of pores, especially embedding themselves in the gaps between the initially formed BTA film layers, filling defects and forming a denser BTA / PEG composite protective film. In some embodiments, the PEG is PEG 600. In some embodiments, the concentrations of PEG in the second and third etching solutions are each independently 0.3 g / L, 0.4 g / L, 0.5 g / L, 0.6 g / L, 0.7 g / L, 0.8 g / L, or any suitable value between them. If the concentration of polyethylene glycol is too low, it may not be able to effectively fill the gaps in the BTA film, resulting in a discontinuous composite film, reduced corrosion inhibition, insufficient lateral corrosion suppression, and pores that appear as "funnel mouths" or branched shapes. If the concentration of polyethylene glycol is too high, the solution viscosity will be too high, mass transfer will be hindered, PEG will accumulate excessively at the pore opening, blocking the pore inlet, and making it difficult for the corrosive solution to enter the bottom of the pore.

[0037] In some embodiments, the second chemical etching includes etching at a temperature of 65°C to 75°C for 3 to 7 minutes. In some embodiments, the temperature of the second chemical etching is 65°C, 67°C, 69°C, 71°C, 73°C, 75°C, or any suitable value between them. If the temperature is too low, PEG may not be effectively squeezed into the gaps of the protective film formed by BTA, resulting in an insufficiently dense and complete film; if the temperature is too high, excessive PEG deposition is likely to occur. In some embodiments, the time of the second chemical etching is 3 minutes, 4 minutes, 5 minutes, 6 minutes, 7 minutes, or any suitable value between them. If the time is too short, the film formed will not be sufficiently dense and complete; if the time is too long, excessive etching of the orifice is likely to occur.

[0038] In some embodiments, the third chemical etching includes etching at a temperature of 75°C to 85°C for 3 to 7 minutes. In some embodiments, the temperature of the third chemical etching is 75°C, 77°C, 79°C, 81°C, 83°C, 85°C, or any suitable value between them. If the temperature is too low, the orifice passivation is insufficient, leaving active sites on the surface, resulting in high leakage current in subsequent formation, a loose film, and poor protection. If the temperature is too high, the orifice enlarges, the aspect ratio decreases, the film carbonizes or desorbs, the specific capacitance decreases, and the pressure resistance and dispersion deteriorate. In some embodiments, the time of the second chemical etching is 3 minutes, 4 minutes, 5 minutes, 6 minutes, 7 minutes, or any suitable value between them. If the time is too short, the passivation is incomplete, the electrical properties fluctuate greatly, and self-corrosion may occur during storage. If the time is too long, the effective pore density decreases, and the equivalent series resistance (ESR) increases.

[0039] In some embodiments, electrochemical etching for pitting includes: in a solution containing HCl, H2SO4, and Al 3+ In a mixed acidic solution, pulsed DC etching is performed, repeated three to five times. In some embodiments, the concentration of HCl in the mixed acidic solution is 0.6 mol / L to 1.2 mol / L, the concentration of H2SO4 is 3 mol / L to 3.6 mol / L, and the concentration of Al is... 3+ The concentration was from 0.1 mol / L to 0.5 mol / L, and the pulsed DC etching included a rate of 2 A / cm. 2 Up to 3A / cm 2 The initial current density etching was performed from 0.3 s to 0.8 s at 0.5 A / cm. 2 Up to 1A / cm 2 The mid-section was etched with a current of 6 to 11 seconds, and at a current of 0.12 A / cm. 2 Up to 0.3A / cm 2 The end current is etched for 3 to 7 seconds. Through electrochemical etching, pores are formed, creating main tunnels perpendicular to the aluminum foil surface.

[0040] In some embodiments, the preparation method further includes: alkaline washing of the aluminum foil before electrochemical etching to create pores. In some embodiments, aluminum foil with a thickness of 135 μm to 145 μm is immersed in a sodium hydroxide solution with a concentration of 0.02 mol / L to 0.5 mol / L at 50°C to 80°C for 3 to 5 minutes, followed by washing with pure water. Alkaline washing can remove the natural oxide film and organic contaminants on the surface of the aluminum foil, achieving uniform activation and providing a clean substrate with consistent reactivity for subsequent electrochemical etching. In some embodiments, after the third chemical etching, the aluminum foil is subjected to acid washing, drying, and formation treatment. In some embodiments, the foil is washed in a dilute nitric acid solution of 0.1 mol / L to 0.2 mol / L at 60°C to 80°C for 1 to 3 minutes, then washed in a dilute sulfuric acid solution of 0.1 mol / L to 0.2 mol / L at 60°C to 80°C for 1 to 3 minutes, followed by rinsing with pure water for 5 to 8 minutes. Afterward, it is dried at 270°C to 400°C. Afterwards, a chemical formation process is performed to obtain the finished etched aluminum foil.

[0041] To better understand this disclosure, specific embodiments are described below.

[0042] Comparative example: S1. Select 135μm thick aluminum foil, soak it in 55℃ sodium hydroxide (0.5 mol / L) solution for 3 min, and then wash it with pure water.

[0043] S2. The product obtained in S1 was subjected to HCl (0.9 mol / L), H2SO4 (3.3 mol / L), and Al... 3+ Pulsed DC etching was performed in a (0.3 mol / L) mixed acidic solution (initial current density 2.5 A / cm). 2 The duration is 0.5s, and the mid-section current is 0.75A / cm. 2 The duration was 8 seconds, and the terminal current was 0.15 A / cm. 2 Repeat five times (lasting 5 seconds) to form the main tunnel perpendicular to the aluminum foil surface.

[0044] S3. The product obtained in S2 is placed in HCl (1.5 mol / L) and Al. 3+ The solution was 0.5 mol / L, and PSSA (0.16 g / L) was added. The solution was then etched at 78 °C for 2 min.

[0045] S4. The product obtained in S3 was placed in HCl (1.5 mol / L) and Al 3+ The solution was added to a 0.5 mol / L solution, and PSSA (0.16 g / L) was added. The solution was then etched at 78 °C for 15 min, with a corrosion rate of 0.01 A / cm during the etching process. 2 Corrosion under constant DC current for 60 seconds.

[0046] S5. The product obtained in S4 was washed in dilute nitric acid solution (0.15 mol / L) at 65°C for 2 min, then washed in dilute sulfuric acid solution (0.15 mol / L) at 65°C for 2 min, rinsed with pure water for 5 min, and dried at 300°C.

[0047] S6. The product obtained in S5 is subjected to a formation process to obtain the finished etched foil.

[0048] Example: S1. Select 135μm thick aluminum foil, soak it in 55℃ sodium hydroxide (0.5mol / L) solution for 3min, and then wash it with pure water.

[0049] S2. The product obtained in S1 was subjected to HCl (0.9 mol / L), H2SO4 (3.3 mol / L), and Al... 3+ Pulsed DC etching was performed in a 0.3 mol / L mixed acidic solution (initial current density 2.5 A / cm²). 2 The duration is 0.5s, and the mid-section current is 0.75A / cm. 2 The duration was 8 seconds, and the terminal current was 0.15 A / cm. 2 Repeat five times (lasting 5 seconds) to form the main tunnel perpendicular to the aluminum foil surface.

[0050] S3. The product obtained in S2 is placed in HCl (1.5 mol / L) and Al. 3+ The sample was placed in a 0.5 mol / L solution and BTA (0.16 g / L) was added. The sample was then etched at 70 °C for 2 min.

[0051] S4. The product obtained in S3 is placed in HCl (1.5 mol / L) and Al. 3+ Add PEG600 (0.5 g / L) to a 0.5 mol / L solution and let it stand at 70℃ for 5 min.

[0052] S5. The product obtained in S4 is placed in HCl (1.5 mol / L) and Al. 3+ Add BTA (0.16 g / L) and PEG600 (0.5 g / L) to a 0.5 mol / L solution and let stand at 80 °C for 5 min.

[0053] S6. The product obtained in S5 was washed in dilute nitric acid solution (0.15 mol / L) at 65°C for 2 min, then washed in dilute sulfuric acid solution (0.15 mol / L) at 65°C for 2 min, rinsed with pure water for 5 min, and dried at 300°C.

[0054] S7. The product obtained in S6 is subjected to a formation process to obtain the finished etched foil.

[0055] Figure 2 A scanning electron microscope image of a comparative aluminum foil is shown. Figure 3 A scanning electron microscope (SEM) image of the aluminum foil from an embodiment is shown. Figure 2 and Figure 3 It can be seen that the number of effective macropores (e.g., pores with a diameter of 0.65 μm to 1.2 μm) in the aluminum foil of the embodiment is significantly higher than the number of effective macropores in the aluminum foil of the comparative example.

[0056] Figure 4 The diagram shows a comparison of the number of holes of corresponding sizes in the aluminum foil of the embodiments and comparative examples, where the blue lines represent the embodiments and the gray lines represent the comparative examples. Figure 4 It can also be seen that the number of effective macropores in the aluminum foil of the embodiment is significantly higher than that in the aluminum foil of the comparative example.

[0057] Example embodiments have been disclosed herein, and while specific terminology has been used, it is for illustrative purposes only and should be construed as such, and is not intended to be limiting. In some instances, it will be apparent to those skilled in the art that features, characteristics, and / or elements described in connection with particular embodiments may be used alone, or in combination with features, characteristics, and / or elements described in connection with other embodiments, unless otherwise expressly indicated. Therefore, those skilled in the art will understand that various changes in form and detail may be made without departing from the scope of this disclosure as set forth by the appended claims.

Claims

1. A method for preparing aluminum foil, characterized in that, include: Electrochemical etching is used to create pores in aluminum foil; The aluminum foil was subjected to a first chemical etching in a first etching solution containing benzotriazole; The aluminum foil is subjected to a second chemical etching in a second etching solution containing polyethylene glycol; The aluminum foil is subjected to a third chemical etching in a third etching solution containing benzotriazole and polyethylene glycol.

2. The preparation method according to claim 1, characterized in that, The first, second, and third corrosive solutions all contain acid and Al. 3+ The concentration of the acid in the first, second, and third corrosive solutions is independently 1 mol / L to 2 mol / L, Al 3+ The concentrations of each acid are independently from 0.2 mol / L to 0.8 mol / L, and the acid includes HCl.

3. The preparation method according to claim 1, characterized in that, The concentrations of benzotriazole in the first and third corrosive solutions are each independently between 0.1 g / L and 0.3 g / L.

4. The preparation method according to claim 1 or 3, characterized in that, The first chemical corrosion includes corrosion at a temperature of 65°C to 75°C for 1 to 3 minutes.

5. The preparation method according to claim 1, characterized in that, The concentration of polyethylene glycol in the second and third etching solutions is independently from 0.3 g / L to 0.8 g / L, and the polyethylene glycol includes at least one of polyethylene glycol 200, polyethylene glycol 300, polyethylene glycol 400, polyethylene glycol 600 and polyethylene glycol 1000.

6. The preparation method according to claim 1 or 5, characterized in that, The second chemical corrosion involves corrosion at a temperature of 65°C to 75°C for 3 to 7 minutes.

7. The preparation method according to any one of claims 1, 3, or 5, characterized in that, The third chemical corrosion involves corrosion at a temperature of 75°C to 85°C for 3 to 7 minutes.

8. The preparation method according to claim 1, characterized in that, The electrochemical corrosion pitting includes: In a container containing HCl, H2SO4 and Al 3+ In a mixed acidic solution, pulsed DC etching is performed, repeated three to five times. The concentration of HCl in the mixed acidic solution is 0.6 mol / L to 1.2 mol / L, the concentration of H₂SO₄ is 3 mol / L to 3.6 mol / L, and the concentration of Al is... 3+ The concentration is from 0.1 mol / L to 0.5 mol / L, and the pulsed DC etching includes a frequency of 2 A / cm. 2 Up to 3A / cm 2 The initial current density etching was performed from 0.3 s to 0.8 s at 0.5 A / cm. 2 Up to 1A / cm 2 The mid-section was etched with a current of 6 to 11 seconds, and at a current of 0.12 A / cm. 2 Up to 0.3A / cm 2 The end current is etched for 3 to 7 seconds.

9. The preparation method according to claim 1, characterized in that, Also includes: Before performing the electrochemical etching to create pores, the aluminum foil is subjected to alkaline washing; Following the third chemical etching, the aluminum foil is subjected to pickling, drying, and chemical formation treatment.

10. An aluminum foil, characterized in that, The aluminum foil is the aluminum foil obtained by the preparation method according to any one of claims 1 to 9.

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