Formed foil manufacturing method through pretreatment before formation

Abstract

The invention provides a method for manufacturing a formed foil pretreated before formation, which comprises the following steps of: heating a corroded aluminum foil in pure water of which the temperature is not lower than 96 DEG C for 1-5 minutes to obtain an aluminum foil subjected to first treatment; treating the aluminum foil subjected to the first treatment in an organic acid solution for 5-20 seconds to obtain an aluminum foil subjected to second treatment; heating the aluminum foil subjected to the third treatment in pure water for 1-2 minutes to obtain an aluminum foil subjected to fourth treatment; the aluminum foil obtained after fourth treatment is placed in a furnace with the temperature ranging from 450 DEG C to 500 DEG C to be treated for 3 seconds to 8 seconds, and aluminum foil obtained after fifth treatment is obtained; the aluminum foil subjected to fifth treatment is placed in pure water to be heated for 1-2 minutes, and the pretreated aluminum foil is obtained; and carrying out post-treatment on the aluminum foil subjected to six-stage formation for 5-10 minutes, and drying the aluminum foil in an atmosphere of 150 DEG C to obtain the formed foil.

Description

Technical Field

[0001] This invention relates to the field of information technology, and in particular to a method for manufacturing formed foil with pretreatment before formation. Background Technology

[0002] In modern industrial manufacturing, aluminum foil is a core material for high-performance electronic components such as capacitors, and its surface treatment technology directly affects the product's performance and lifespan. The quality of the oxide film formed on the aluminum foil surface not only affects its voltage resistance and electrochemical stability but also plays a crucial role in the reliability of the entire electronic device. Therefore, improving the uniformity and stability of aluminum foil surface treatment processes has always been a research focus of great interest in the industry.

[0003] However, current mainstream processing methods have revealed some significant shortcomings in practical applications. Many processes, when treating aluminum foil surfaces, often fail to balance the uniformity and structural stability of the oxide film, resulting in areas where the film is either too thin or too thick, thus affecting overall performance. This imbalance, especially in demanding scenarios, can easily lead to fluctuations in product performance and even premature failure.

[0004] A deeper issue lies in the fact that controlling the thickness and structure of the oxide film on the aluminum foil surface has become a core technical challenge. Uneven oxide film thickness can lead to insufficient voltage withstand capability in localized areas, while structural instability can cause film peeling or damage during long-term use. For example, in capacitor manufacturing, if the oxide film on the aluminum foil surface is too thin in some areas, it may break down under high voltage conditions; conversely, if the film is too thick or the structure is loose, it will increase internal resistance and reduce electrochemical performance. This performance contradiction caused by improper control of film thickness and structure runs through the entire process from pretreatment to final molding, becoming a technical bottleneck that urgently needs to be overcome.

[0005] Therefore, how to achieve precise control of oxide film thickness and structure during aluminum foil surface treatment, and ensure the uniformity and long-term stability of the film in different regions, has become a key issue in current research and application. Summary of the Invention

[0006] This invention provides a method for manufacturing formed foil with pretreatment before formation, mainly including:

[0007] The etched aluminum foil is heated in pure water at a temperature not lower than 96°C for 1 to 5 minutes to obtain the first-treated aluminum foil; the first-treated aluminum foil is then treated in an organic acid solution for 5 to 20 seconds to obtain the second-treated aluminum foil; the second-treated aluminum foil is then treated in a furnace at a temperature of 450 to 500°C for 3 to 8 seconds to obtain the third-treated aluminum foil; the third-treated aluminum foil is then heated in pure water for 1 to 2 minutes to obtain the fourth-treated aluminum foil; the fourth-treated aluminum foil is then placed in a furnace at a temperature of 4... The aluminum foil is treated in a furnace at 50 to 500°C for 3 to 8 seconds to obtain a fifth-treated aluminum foil; the fifth-treated aluminum foil is then heated in pure water for 1 to 2 minutes to obtain a pretreated aluminum foil; the pretreated aluminum foil is then placed in an ammonium dihydrogen phosphate solution for primary formation at a voltage of 125 volts to 625 volts for 10 to 25 minutes to obtain a first-formed aluminum foil; the first-formed aluminum foil is then placed in a mixed solution of adipic acid and citric acid for secondary formation at a voltage of 10 to 25 minutes to obtain a second-formed aluminum foil. A secondary-stage aluminum foil is obtained by applying a voltage of 125 volts to 625 volts. The secondary-stage aluminum foil is then placed in a mixed solution of ammonium adipic acid and adipic acid for tertiary-stage formation, with a formation time of 10 to 25 minutes and a formation voltage of 125 volts to 625 volts, resulting in a tertiary-stage aluminum foil. The tertiary-stage aluminum foil is then placed in the same mixed solution for quaternary-stage formation, with a formation time of 10 to 25 minutes and a formation voltage of 125 volts to 625 volts, resulting in a quaternary-stage aluminum foil. Aluminum foil is placed in a mixed solution of ammonium pentaborate and boric acid for five-stage formation, with a formation time of 10 to 25 minutes and a formation voltage of 125 volts to 625 volts, to obtain aluminum foil after five-stage formation. The aluminum foil after five-stage formation is then placed in a mixed solution of ammonium pentaborate and azelaic acid for six-stage formation, with a formation time of 10 to 25 minutes and a formation voltage of 125 volts to 625 volts, to obtain aluminum foil after six-stage formation. The aluminum foil after six-stage formation is then post-treated for 5 to 10 minutes and dried in an atmosphere at 150°C to obtain formed foil. Further, the step of heating the etched aluminum foil in pure water at a temperature not lower than 96°C for 1 to 5 minutes includes: immersing the etched aluminum foil in the pure water, wherein the pure water is deionized water, heating at a temperature of 96 to 100°C, and continuing heating for 1 to 5 minutes to obtain the first-treated aluminum foil; 3. The method according to claim 1, wherein the step of treating the first-treated aluminum foil in an organic acid solution for 5 to 20 seconds includes: immersing the first-treated aluminum foil in the organic acid solution, wherein the concentration of the organic acid solution is 0.1 to 1 mol / L, the treatment temperature is room temperature to 60°C, and continuing treatment for 5 to 20 seconds to obtain the second-treated aluminum foil; wherein the organic acid includes citric acid, and the pH value of the organic acid solution is 2 to 4; 4.The method as described in claim 1, characterized in that, the step of placing the second-treated aluminum foil in a furnace at a temperature of 450 to 500°C for 3 to 8 seconds comprises: placing the second-treated aluminum foil in the furnace, the furnace being a muffle furnace with a temperature control accuracy of ±5°C, rapidly heating it to 450 to 500°C, and continuously treating it for 3 to 8 seconds to obtain the third-treated aluminum foil; placing the third-treated aluminum foil in pure water and heating it for 1 to 2 minutes, the pure water being deionized water, the heating temperature being 90 to 100°C, the third-treated aluminum foil being immersed in the pure water and stirred to obtain the fourth-treated aluminum foil; 5. The method as described in claim 1, characterized in that, the step of pre-treating the aluminum foil... The aluminum foil is subjected to a primary formation process in an ammonium dihydrogen phosphate solution, comprising: placing the pretreated aluminum foil in the ammonium dihydrogen phosphate solution, wherein the concentration of ammonium dihydrogen phosphate is 10 to 20 g / L, and performing the primary formation process under constant current and constant voltage mode, wherein the current density is 10 to 50 mA / cm², the formation time is 10 to 25 minutes, and the formation voltage is 125 V to 625 V, to obtain the primary-formed aluminum foil; and placing the primary-formed aluminum foil in a mixed solution of adipic acid and citric acid for a secondary formation process, wherein the molar ratio of adipic acid to citric acid is 1:1 to 1:10, and performing the process under constant current and constant voltage mode, wherein the current density is 10 to 50 mA / cm², and the formation time is 10 to 25 minutes. The aluminum foil is then subjected to a secondary formation at a voltage of 125 volts to 625 volts to obtain the aluminum foil after secondary formation. The aluminum foil after secondary formation is then placed in a mixed solution of ammonium adipic acid and adipic acid for tertiary formation, wherein the molar ratio of ammonium adipic acid to adipic acid is 1:1 to 10:1, and the formation is carried out under constant current and constant voltage mode, with a current density of 10 to 50 mA per square centimeter, a formation time of 10 to 25 minutes, and a formation voltage of 125 volts to 625 volts, to obtain the aluminum foil after tertiary formation. 6. The method according to claim 1, wherein the step of placing the aluminum foil after tertiary formation in a mixed solution of ammonium adipic acid and adipic acid for quaternary formation includes: placing the aluminum foil after tertiary formation in the mixed solution of ammonium adipic acid and adipic acid... In the combined solution, the molar ratio of ammonium adipicate to adipic acid is 1:1 to 10:1. The four-stage formation is carried out under constant current and constant voltage mode, with a current density of 10 to 50 mA per square centimeter, a formation time of 10 to 25 minutes, and a formation voltage of 125 V to 625 V, to obtain the aluminum foil after the four-stage formation; 7. The method according to claim 1, wherein the post-treatment of the aluminum foil after the six-stage formation for 5 to 10 minutes includes: placing the aluminum foil after the six-stage formation in a solution containing a surfactant for the post-treatment at a temperature of 40 to 60°C for 5 to 10 minutes; and drying the aluminum foil after the post-treatment in an atmosphere at 150°C to obtain the formed foil; 8.The method as described in claim 1, characterized in that, the step of placing the fifth-stage formed aluminum foil in a mixed solution of ammonium pentaborate and azelaic acid for sixth-stage formation comprises: placing the fifth-stage formed aluminum foil in the mixed solution of ammonium pentaborate and azelaic acid, wherein the concentration ratio of ammonium pentaborate to azelaic acid is 1:1 to 1:5, performing the sixth-stage formation in a constant current and constant voltage mode, wherein the current density is 10 to 50 mA per square centimeter, the formation time is 10 to 25 minutes, and the formation voltage is 125 volts to 625 volts, thereby obtaining the sixth-stage formed aluminum foil.

[0008] The technical solutions provided by the embodiments of the present invention may include the following beneficial effects:

[0009] This invention discloses an aluminum foil formation process, addressing the challenges of uneven oxide film quality and insufficient performance stability during the formation process. Through a logically linked design of multi-stage formation and fine pretreatment, it systematically solves the problems of inconsistent surface treatment and improved voltage resistance of aluminum foil. This invention utilizes an initial high-temperature pure water treatment, organic acid solution immersion, and multiple high-temperature furnace treatments, combined with a multi-stage formation process, to gradually form a uniform and dense oxide film on the aluminum foil surface. Particularly during the formation stage, different solution ratios and a constant current / constant voltage mode are employed to ensure the thickness and structural stability of the oxide film. Furthermore, post-treatment and drying further optimize surface properties. Ultimately, this invention significantly improves the voltage resistance and electrochemical performance of aluminum foil, extends its service life, and is suitable for the manufacturing of high-performance capacitors, demonstrating excellent technical effects and application value. Attached Figure Description

[0010] Figure 1 This is a flowchart of a method for manufacturing a pre-treated electroforming foil according to the present invention. Detailed Embodiments

[0011] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0012] like Figure 1 This embodiment of a method for manufacturing formed foil with pretreatment before formation may specifically include:

[0013] S1, The etched aluminum foil is placed in pure water at a temperature not lower than 96°C and heated for 1 to 5 minutes to obtain the first-treated aluminum foil; S2, The first-treated aluminum foil is placed in an organic acid solution for 5 to 20 seconds to obtain the second-treated aluminum foil.

[0014] S3, the second-treated aluminum foil is placed in a furnace at a temperature of 450 to 500°C for 3 to 8 seconds to obtain the third-treated aluminum foil; S4, the third-treated aluminum foil is placed in pure water and heated for 1 to 2 minutes to obtain the fourth-treated aluminum foil.

[0015] S5, the aluminum foil after the fourth treatment is placed in a furnace at a temperature of 450 to 500°C for 3 to 8 seconds to obtain the aluminum foil after the fifth treatment; S6, the aluminum foil after the fifth treatment is placed in pure water and heated for 1 to 2 minutes to obtain the pretreated aluminum foil.

[0016] S7, the pretreated aluminum foil is placed in an ammonium dihydrogen phosphate solution for primary formation, the formation time is 10 to 25 minutes, and the formation voltage is 125 volts to 625 volts, to obtain the primary formed aluminum foil.

[0017] S8, the aluminum foil after primary formation is placed in a mixed solution of adipic acid and citric acid for secondary formation, the formation time is 10 to 25 minutes, and the formation voltage is 125 volts to 625 volts, to obtain the aluminum foil after secondary formation.

[0018] S9, the aluminum foil after secondary formation is placed in a mixed solution of ammonium adipic acid and adipic acid for tertiary formation, the formation time is 10 to 25 minutes, and the formation voltage is 125 volts to 625 volts, to obtain the aluminum foil after tertiary formation.

[0019] S10, the aluminum foil after the third-stage formation is placed in a mixed solution of ammonium adipic acid and adipic acid for fourth-stage formation, the formation time is 10 to 25 minutes, and the formation voltage is 125 volts to 625 volts, to obtain the aluminum foil after the fourth-stage formation.

[0020] S11, the aluminum foil after the fourth-stage formation is placed in a mixed solution of ammonium pentaborate and boric acid for the fifth-stage formation. The formation time is 10 to 25 minutes and the formation voltage is 125 volts to 625 volts to obtain the aluminum foil after the fifth-stage formation.

[0021] S12, the aluminum foil after the fifth stage of formation is placed in a mixed solution of ammonium pentaborate and azelaic acid for a sixth stage of formation. The formation time is 10 to 25 minutes and the formation voltage is 125 volts to 625 volts to obtain the aluminum foil after the sixth stage of formation.

[0022] S13, the aluminum foil after the sixth-stage formation is post-treated for 5 to 10 minutes and dried in an atmosphere at 150°C to obtain the formed foil.

[0023] S1011, the step of heating the etched aluminum foil in pure water at a temperature not lower than 96°C for 1 to 5 minutes includes: S11, immersing the etched aluminum foil in the pure water, wherein the pure water is deionized water, heating at a temperature of 96 to 100°C, and continuously heating for 1 to 5 minutes to obtain the first treated aluminum foil.

[0024] S1012, the step of placing the first treated aluminum foil in an organic acid solution for 5 to 20 seconds includes: S21, immersing the first treated aluminum foil in the organic acid solution, wherein the concentration of the organic acid solution is [missing information].

[0025] S1013, 1 to 1 mole per liter, processing temperature from room temperature to 60°C, processing for 5 to 20 seconds to obtain the second-treated aluminum foil; S22, the organic acid includes citric acid, and the pH value of the organic acid solution is 2 to 4.

[0026] S1014. The step of placing the second-treated aluminum foil in a furnace at a temperature of 450 to 500°C for 3 to 8 seconds includes: S31, placing the second-treated aluminum foil in the furnace, which is a muffle furnace with a temperature control accuracy of ±5°C, rapidly heating it to 450 to 500°C, and continuously treating it for 3 to 8 seconds to obtain the third-treated aluminum foil; S32, placing the third-treated aluminum foil in pure water and heating it for 1 to 2 minutes, wherein the pure water is deionized water and the heating temperature is 90 to 100°C, immersing the third-treated aluminum foil in the pure water and stirring it to obtain the fourth-treated aluminum foil.

[0027] S1015. The step of placing the pretreated aluminum foil in an ammonium dihydrogen phosphate solution for primary formation includes: S41, placing the pretreated aluminum foil in the ammonium dihydrogen phosphate solution, wherein the concentration of ammonium dihydrogen phosphate is 10 to 20 g / L, performing the primary formation under constant current and constant voltage mode, wherein the current density is 10 to 50 mA / cm², the formation time is 10 to 25 minutes, and the formation voltage is 125 V to 625 V, to obtain the primary-formed aluminum foil; S42, placing the primary-formed aluminum foil in a mixed solution of adipic acid and citric acid for secondary formation, wherein the molar concentration ratio of adipic acid to citric acid is... The formation process is carried out in a constant current and constant voltage mode with a current density of 10 to 50 mA per square centimeter, a formation time of 10 to 25 minutes, and a formation voltage of 125 volts to 625 volts, to obtain the aluminum foil after the second-stage formation; S43, the aluminum foil after the second-stage formation is placed in a mixed solution of ammonium adipic acid and adipic acid for tertiary formation, wherein the molar concentration ratio of ammonium adipic acid to adipic acid is 1:1 to 10:1, carried out in a constant current and constant voltage mode with a current density of 10 to 50 mA per square centimeter, a formation time of 10 to 25 minutes, and a formation voltage of 125 volts to 625 volts, to obtain the aluminum foil after the third-stage formation.

[0028] S1016. The step of placing the aluminum foil after the third-stage formation in a mixed solution of ammonium adipic acid and adipic acid for fourth-stage formation includes: S51, placing the aluminum foil after the third-stage formation in the mixed solution of ammonium adipic acid and adipic acid, wherein the molar concentration ratio of ammonium adipic acid to adipic acid is 1:1 to 10:1, performing the fourth-stage formation in a constant current and constant voltage mode, wherein the current density is 10 to 50 mA per square centimeter, the formation time is 10 to 25 minutes, and the formation voltage is 125 volts to 625 volts, to obtain the aluminum foil after the fourth-stage formation.

[0029] S1017. The step of post-processing the aluminum foil after the sixth-stage formation for 5 to 10 minutes includes: S61, placing the aluminum foil after the sixth-stage formation in a solution containing a surfactant for the post-processing at a temperature of 40 to 60°C for 5 to 10 minutes; S62, drying the aluminum foil after the post-processing in an atmosphere at 150°C to obtain the formed foil.

[0030] S1018. The step of placing the aluminum foil after the fifth-stage formation in a mixed solution of ammonium pentaborate and azelaic acid for sixth-stage formation includes: S71, placing the aluminum foil after the fifth-stage formation in the mixed solution of ammonium pentaborate and azelaic acid, wherein the concentration ratio of ammonium pentaborate to azelaic acid is 1:1 to 1:5, performing the sixth-stage formation in a constant current and constant voltage mode, wherein the current density is 10 to 50 mA per square centimeter, the formation time is 10 to 25 minutes, and the formation voltage is 125 volts to 625 volts, to obtain the aluminum foil after the sixth-stage formation.

[0031] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present invention will not describe the various possible combinations separately. Furthermore, various different embodiments of the present invention can also be arbitrarily combined, as long as they do not violate the spirit of the present invention, and should also be regarded as the content disclosed by the present invention.

Claims

1. A method for manufacturing a pre-treated electroforming foil, characterized in that, include: The etched aluminum foil is placed in pure water at a temperature not lower than 96°C and heated for 1 to 5 minutes to obtain the first-treated aluminum foil; The first-treated aluminum foil is placed in an organic acid solution for 5 to 20 seconds to obtain a second-treated aluminum foil; the second-treated aluminum foil is placed in a furnace at 450 to 500°C for 3 to 8 seconds to obtain a third-treated aluminum foil; the third-treated aluminum foil is heated in pure water for 1 to 2 minutes to obtain a fourth-treated aluminum foil; the fourth-treated aluminum foil is placed in a furnace at 450 to 500°C for 3 to 8 seconds to obtain a fifth-treated aluminum foil; the fifth-treated aluminum foil is heated in pure water for 1 to 2 minutes to obtain a pre-treated aluminum foil; the pre-treated aluminum foil is placed in an ammonium dihydrogen phosphate solution for primary formation for 10 to 25 minutes at a formation voltage of 125 volts to 625 volts to obtain a first-formed aluminum foil; the first-formed aluminum foil is placed in a mixed solution of adipic acid and citric acid for secondary formation for 10 to 25 minutes at a formation voltage of 125 volts to 625 volts to obtain a second-formed aluminum foil. The aluminum foil is then subjected to a tertiary formation process in a mixed solution of ammonium adipic acid and adipic acid for 10 to 25 minutes at a voltage of 125 to 625 volts. The tertiary aluminum foil is then subjected to a quaternary formation process in the same solution for 10 to 25 minutes at a voltage of 125 to 625 volts. Finally, the quaternary aluminum foil is subjected to a mixture of ammonium pentaborate and... A five-stage formation process is performed in a boric acid mixed solution for 10 to 25 minutes at a voltage of 125 to 625 volts to obtain a five-stage formed aluminum foil. The five-stage formed aluminum foil is then placed in a mixed solution of ammonium pentaborate and azelaic acid for a six-stage formation process for 10 to 25 minutes at a voltage of 125 to 625 volts to obtain a six-stage formed aluminum foil. The six-stage formed aluminum foil is then post-treated for 5 to 10 minutes and dried in a 150°C atmosphere to obtain a formed foil.

2. The method as described in claim 1, characterized in that, The step of heating the etched aluminum foil in pure water at a temperature not lower than 96°C for 1 to 5 minutes includes: immersing the etched aluminum foil in the pure water, wherein the pure water is deionized water, heating at a temperature of 96 to 100°C, and continuously heating for 1 to 5 minutes to obtain the first-treated aluminum foil.

3. The method as described in claim 1, characterized in that, The step of placing the first-treated aluminum foil in an organic acid solution for 5 to 20 seconds includes: immersing the first-treated aluminum foil in the organic acid solution, wherein the concentration of the organic acid solution is 0.1 to 1 mol per liter, the treatment temperature is room temperature to 60°C, and the treatment is continued for 5 to 20 seconds to obtain the second-treated aluminum foil; wherein the organic acid includes citric acid, and the pH value of the organic acid solution is 2 to 4.

4. The method as described in claim 1, characterized in that, The step of placing the second-treated aluminum foil in a furnace at a temperature of 450 to 500°C for 3 to 8 seconds includes: placing the second-treated aluminum foil in the furnace (a muffle furnace with a temperature control accuracy of ±5°C), rapidly heating it to 450 to 500°C, and continuing the treatment for 3 to 8 seconds to obtain the third-treated aluminum foil; placing the third-treated aluminum foil in pure water and heating it for 1 to 2 minutes (the pure water is deionized water with a heating temperature of 90 to 100°C), immersing the third-treated aluminum foil in the pure water and stirring it to obtain the fourth-treated aluminum foil.

5. The method as described in claim 1, characterized in that, The step of placing the pretreated aluminum foil in an ammonium dihydrogen phosphate solution for primary formation includes: placing the pretreated aluminum foil in the ammonium dihydrogen phosphate solution, wherein the concentration of ammonium dihydrogen phosphate is 10 to 20 g / L, performing the primary formation under constant current and constant voltage mode, wherein the current density is 10 to 50 mA / cm², the formation time is 10 to 25 minutes, and the formation voltage is 125 V to 625 V, to obtain the primary-formed aluminum foil; and placing the primary-formed aluminum foil in a mixed solution of adipic acid and citric acid for secondary formation, wherein the molar ratio of adipic acid to citric acid is 1:1 to... The formation process is carried out at a ratio of 1:10, under constant current and constant voltage mode, with a current density of 10 to 50 mA per square centimeter, a formation time of 10 to 25 minutes, and a formation voltage of 125 V to 625 V, to obtain the aluminum foil after the second-stage formation. The aluminum foil after the second-stage formation is then placed in a mixed solution of ammonium adipic acid and adipic acid for tertiary formation, where the molar ratio of ammonium adipic acid to adipic acid is 1:1 to 10:1, under constant current and constant voltage mode, with a current density of 10 to 50 mA per square centimeter, a formation time of 10 to 25 minutes, and a formation voltage of 125 V to 625 V, to obtain the aluminum foil after the third-stage formation.

6. The method as described in claim 1, characterized in that, The step of placing the aluminum foil after the third-stage formation in a mixed solution of ammonium adipic acid and adipic acid for fourth-stage formation includes: placing the aluminum foil after the third-stage formation in the mixed solution of ammonium adipic acid and adipic acid, wherein the molar concentration ratio of ammonium adipic acid to adipic acid is 1:1 to 10:1, performing the fourth-stage formation in a constant current and constant voltage mode, wherein the current density is 10 to 50 mA per square centimeter, the formation time is 10 to 25 minutes, and the formation voltage is 125 volts to 625 volts, to obtain the aluminum foil after the fourth-stage formation.

7. The method as described in claim 1, characterized in that, The step of post-processing the aluminum foil after the sixth-level formation for 5 to 10 minutes includes: placing the aluminum foil after the sixth-level formation in a solution containing a surfactant for post-processing at a temperature of 40 to 60°C for 5 to 10 minutes; and drying the aluminum foil after post-processing in an atmosphere at 150°C to obtain the formed foil.

8. The method as described in claim 1, characterized in that, The step of placing the aluminum foil after the fifth-stage formation in a mixed solution of ammonium pentaborate and azelaic acid for sixth-stage formation includes: placing the aluminum foil after the fifth-stage formation in the mixed solution of ammonium pentaborate and azelaic acid, wherein the concentration ratio of ammonium pentaborate to azelaic acid is 1:1 to 1:5, performing the sixth-stage formation in a constant current and constant voltage mode, wherein the current density is 10 to 50 mA per square centimeter, the formation time is 10 to 25 minutes, and the formation voltage is 125 volts to 625 volts, to obtain the aluminum foil after the sixth-stage formation.

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