Manufacturing method of a high-voltage and high-capacity electrode foil without boric acid system

Abstract

The invention discloses a manufacturing method of a high-voltage and high-capacity electrode foil without a boric acid system. The etched foil is impregnated in pure water at a temperature above 95°C for 8 to 12 minutes; pre-treatment, primary formation, secondary formation, tertiary formation, first depolarization treatment, quaternary formation, quinary formation, second depolarization treatment, first formation at the sixth stage, third depolarization treatment, second formation at the sixth stage, fourth depolarization treatment, third formation at the sixth stage, ultrasonic cleaning, heat treatment, fourth formation at the sixth stage. Advantages: By screening non-boric acid series chemicals for the formation of the electrode foil, the screened chemicals include inorganic chemicals and organic chemicals; and the formation process of the electrode foil is redesigned, and pre-treatment and multi-stage intermediate treatments are added. The structure of the oxide film is optimized through the added intermediate treatment process, the defects in the oxide film are reduced, and the formed electrode foil has a high capacity, low leakage current, and good stability, and can replace the traditional inorganic acid or organic acid process.

Description

Technical Field:

[0001] The present invention relates to the technical field of electrode foil production, and particularly relates to a manufacturing method of a high-voltage and high-capacity electrode foil without a boric acid system. Background Art:

[0002] The manufacturing process of electrode foils for aluminum electrolytic capacitors is generally divided into two categories. One is the inorganic acid process mainly using inorganic acids, and the main inorganic acid used is boric acid. The formed aluminum foil by this process has the advantages of low leakage current and small capacity attenuation, but its capacity is low and the bending strength is poor, which is suitable for making large-size, long-life, and high-stability aluminum electrolytic capacitors. The other is the organic acid process mainly using organic acids, mainly using adipic acid, citric acid, azelaic acid, sebacic acid and their salts as forming agents. When all organic acids are used for forming, the formed aluminum foil has the advantages of high capacity and good bending strength, but there are many defects in the formed oxide film, resulting in large leakage current and large capacity attenuation of the formed aluminum foil. In order to improve the disadvantages of large leakage current and large capacity attenuation, a small amount of boric acid is still used in the forming process.

[0003] In recent years, international and domestic environmental management agencies and environmental protection organizations have become stricter in the control of various environmental management substances, and more and more substances are involved; boric acid, as a substance with potential hazards to the human body, has also been included in the control system; on June 11, 2010, the European Chemicals Agency (ECHA) officially included boric acid in the list of substances of very high concern (SVHC) under REACH regulations. According to the REACH regulations, for products exported to the European Union, if the boric acid content exceeds 0.1%, it is necessary to notify the European Chemicals Agency; the standard of boric acid in the waste water discharged in the European Union is <2.4 ppm; in 2015, the Ministry of Environmental Protection included borate in the list of "highly polluting and high environmental risk" products; and it is required that the content of boric acid in irrigation water does not exceed 3 ppm.

[0004] However, whether it is the traditional inorganic acid forming process or the organic acid forming process, the boric acid content in the discharged waste water far exceeds the above control standards; at present, although research is being carried out on the recovery technology of boric acid in the electrode foil forming solution, on the one hand, the recovery technology is not yet mature, and on the other hand, to meet the discharge standards, a very high treatment cost needs to be paid.

[0005] In addition, in Chinese Patent Application No. 202111252557.0, titled "A Forming Method of an Electrode Foil", a manufacturing method of a forming process using ammonium citrate, azelaic acid and ammonium azelate is disclosed. The ammonium citrate, azelaic acid and ammonium azelate used in this forming method all belong to organic acid series agents. When all organic acids are used for forming, there are many defects in the formed oxide film, resulting in large leakage current, large capacity attenuation and poor water hydration resistance of the formed aluminum foil. Summary of the Invention:

[0006] The object of the present invention is to provide a manufacturing method for a high-voltage and high-capacity electrode foil without a boric acid system, which can effectively eliminate the use of boric acid during the formation process and fundamentally solve the problems of boric acid pollution and subsequent treatment.

[0007] The present invention is implemented by the following technical solutions: A manufacturing method for a high-voltage and high-capacity electrode foil without a boric acid system, which includes the following steps:

[0008] (1) Immerse the etched foil in pure water at a temperature above 95 °C for 8 to 12 minutes;

[0009] (2) Pretreatment:

[0010] Place the etched foil after immersion in pure water into a 0.1 to 1.0 wt% fumaric acid solution and soak it;

[0011] (3) Primary formation:

[0012] After the etched foil undergoes pretreatment and is washed with pure water, place it in a 0.1 to 1.0 wt% ammonium dihydrogen phosphate solution for primary formation;

[0013] (4) Secondary formation:

[0014] Place the aluminum foil after primary formation in a 0.1 to 0.8 wt% ammonium dihydrogen phosphate solution for secondary formation;

[0015] (5) Tertiary formation:

[0016] Place the aluminum foil after secondary formation in a 0.1 to 0.6 wt% ammonium dihydrogen phosphate solution for tertiary formation;

[0017] (6) First depolarization treatment:

[0018] Place the aluminum foil after tertiary formation in a 0.1 to 1.0 mol / L phosphoric acid solution at 50 to 70 °C for depolarization treatment for 5 to 10 minutes;

[0019] (7) Fourth formation:

[0020] Place the aluminum foil after the first depolarization treatment in a 0.05 to 0.3 wt% azelaic acid and 0.05 to 0.2 wt% ammonium sebacate solution at 75 to 90 °C for fourth formation;

[0021] (8) Fifth formation:

[0022] Place the aluminum foil after fourth formation in a 0.05 to 0.3 wt% azelaic acid and 0.05 to 0.2 wt% ammonium sebacate solution at 75 to 90 °C for fifth formation;

[0023] (9) Second depolarization treatment:

[0024] Then, place the aluminum foil in a 0.2 - 1.0 mol / L phosphoric acid solution at 50 - 70 °C for another 5 - 10 minutes for depolarization treatment;

[0025] (10) First six - stage formation:

[0026] Place the aluminum foil after the secondary depolarization treatment in a solution of 0.05 - 0.3 wt% azelaic acid and 0.05 - 0.2 wt% ammonium sebacate at 75 - 90 °C for the first six - stage formation;

[0027] (11) Tertiary depolarization treatment:

[0028] Place the aluminum foil after the first six - stage formation treatment in a 0.2 - 1.0 mol / L phosphoric acid solution at 50 - 70 °C for depolarization treatment for 5 - 10 minutes;

[0029] (12) Second six - stage formation:

[0030] Place the aluminum foil after the tertiary depolarization treatment in a solution of 0.05 - 0.3 wt% azelaic acid and 0.05 - 0.2 wt% ammonium sebacate at 75 - 90 °C for the second six - stage formation;

[0031] (13) Quaternary depolarization treatment

[0032] Place the aluminum foil after the second six - stage formation treatment in a 0.5 - 1.5 mol / L phosphoric acid solution at 50 - 70 °C for depolarization treatment for 10 - 15 minutes;

[0033] (14) Third six - stage formation:

[0034] Place the aluminum foil after the quaternary depolarization treatment in a solution of 0.02 - 0.2 wt% azelaic acid and 0.02 - 0.2 wt% ammonium sebacate at 75 - 90 °C for the third six - stage formation;

[0035] (15) Ultrasonic cleaning:

[0036] After washing the aluminum foil after the third six - stage formation treatment with pure water, place it in pure water at 40 - 60 °C for ultrasonic cleaning for 1 - 5 minutes;

[0037] (16) Heat treatment:

[0038] Place the ultrasonic - cleaned aluminum foil in a roasting furnace at 300 - 500 °C for heat treatment for 2 - 5 minutes;

[0039] (17) Fourth six - stage formation:

[0040] The heat-treated aluminum foil is placed in a solution of 0.02 - 0.2 wt% azelaic acid and 0.02 - 0.2 wt% ammonium sebacate at 75 - 90 °C for six-stage four-time formation;

[0041] (18) After washing the aluminum foil after six-stage four-time formation repair treatment, it is placed in a 0.05 - 0.3 mol / L ammonium dihydrogen phosphate solution at 50 - 70 °C for 10 - 15 minutes;

[0042] (19) After washing the aluminum foil treated with ammonium dihydrogen phosphate solution, it is dried at 200 - 300 °C for 2 - 3 minutes to obtain the final formed foil.

[0043] Further, in step (2), the soaking time is 1 - 5 minutes and the soaking temperature is 65 °C - 75 °C.

[0044] Further, in step (3), the temperature of the ammonium dihydrogen phosphate solution is 75 - 90 °C, the formation voltage is 100 ± 20 VF, and the constant voltage formation time is 5 - 10 minutes.

[0045] Further, in step (4), the temperature of the ammonium dihydrogen phosphate solution is 75 - 90 °C, the formation voltage is 200 ± 20 VF, and the constant voltage formation time is 5 - 10 minutes.

[0046] Further, in step (5), the temperature of the ammonium dihydrogen phosphate solution is 75 - 90 °C, the formation voltage is 300 ± 20 VF, and the constant voltage formation time is 5 - 10 minutes.

[0047] Further, in step (7), the formation voltage is 400 ± 20 VF, and the constant voltage formation time is 5 - 10 minutes.

[0048] Further, in step (8), the formation voltage is 480 ± 20 VF, and the constant voltage formation time is 10 - 20 minutes.

[0049] Further, in step (10), the formation voltage is 550 ± 10 VF, and the constant voltage formation time is 20 - 30 minutes.

[0050] Further, in steps (12), (14) and (17), the formation voltage is 550 ± 10 VF, and the constant voltage formation time is 10 - 20 minutes.

[0051] Advantages of the present invention: In the present invention, non-boric acid series chemicals are screened for the formation of electrode foils. The screened chemicals include inorganic chemicals and organic chemicals. The formation process of the electrode foil is redesigned. During the formation process, non-boric acid series inorganic chemicals and organic chemicals are used simultaneously, and pretreatment and multi-stage intermediate treatment are added. The structure of the oxide film is optimized through the added intermediate treatment process, the defects in the oxide film are reduced, and the formed electrode foil has high capacitance, low leakage current, high bending strength, and good stability, and can replace the traditional inorganic acid or organic acid process.

[0052] Compared with the prior art, the advantages of the present invention are as follows: In the front-stage formation, an ammonium dihydrogen phosphate solution is used as the reagent. When the formation is carried out using the ammonium dihydrogen phosphate solution, there are fewer internal defects in the formed oxide film, and since the aluminum phosphate structure is doped in the oxide film, the water resistance of the formed aluminum foil oxide film is greatly improved. On the other hand, in this solution, the number of formation stages is increased to six during the formation, and the number of depolarization treatments is increased. Through multi-stage formation, the oxide film formed in each stage will not be too thick, and then through multi-stage depolarization treatment, the defects in the oxide film are easily exposed, and the defects in the oxide film are repaired through repair formation, and finally the purpose of gradually reducing the defects in the oxide film is achieved. Therefore, the present invention has the characteristics of not using boric acid at all during the formation process, and the formed aluminum foil for formation has low leakage current, small capacity attenuation, and high water resistance. Description of the drawings:

[0053] Figure 1 It is a scanning electron microscope image of the formed aluminum foil obtained in Example 1.

[0054] Figure 2 It is a scanning electron microscope image of the formed aluminum foil obtained in Comparative Example 1. Specific implementation manners:

[0055] The technical solutions in the embodiments of the present invention will be described clearly and completely below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0056] Example 1: A manufacturing method of a high-voltage and high-capacity electrode foil without boric acid system, which includes the following steps:

[0057] (1) Immerse the etched foil in pure water at a temperature above 95 °C for 11 minutes;

[0058] A hydrated alumina film is pre-formed on the surface of the etched foil, which is beneficial to saving the power consumption of the subsequent formation process.

[0059] (2) Pretreatment:

[0060] The aluminum foil impregnated with high-temperature pure water is placed in a 0.5 wt% fumaric acid solution at 70 °C and soaked for 3 minutes;

[0061] As an organic substance, fumaric acid adheres to the surface of the aluminum foil and plays an effective protective role, which can slow down the erosion of the formation solution on the foil surface during the subsequent formation process, thus contributing to improving the formation capacity.

[0062] (3) Primary formation:

[0063] After being washed with pure water, the pre-treated aluminum foil is placed in a 0.6 wt% ammonium dihydrogen phosphate solution at 85 °C for primary formation. The formation voltage is 100 VF, and the constant voltage formation time is 8 minutes;

[0064] (4) Secondary formation:

[0065] The aluminum foil after primary formation is placed in a 0.4 wt% ammonium dihydrogen phosphate solution at 85 °C for secondary formation. The formation voltage is 200 VF, and the constant voltage formation time is 8 minutes;

[0066] (5) Tertiary formation:

[0067] The aluminum foil after secondary formation is placed in a 0.3 wt% ammonium dihydrogen phosphate solution at 85 °C for tertiary formation. The formation voltage is 300 VF, and the constant voltage formation time is 8 minutes;

[0068] After successive primary, secondary, and tertiary formations, an oxide film gradually forms on the surface of the aluminum foil.

[0069] (6) First depolarization treatment:

[0070] The aluminum foil after tertiary formation is placed in a 0.5 mol / L phosphoric acid solution at 60 °C for depolarization treatment for 7 minutes;

[0071] After the previous primary, secondary, and tertiary formations, a certain thickness of oxide film has formed on the aluminum foil. Through the surface treatment of the oxide film with phosphoric acid solution, small defects in the oxide film are exposed, facilitating the formation of oxide film at these small defect sites through subsequent formation processes, making the oxide film on the aluminum foil denser and more complete in structure.

[0072] (7) Quaternary formation:

[0073] The aluminum foil after first depolarization treatment is placed in a solution containing 0.15 wt% azelaic acid and 0.15 wt% ammonium sebacate at 85 °C for quaternary formation. The formation voltage is 400 VF, and the constant voltage formation time is 8 minutes;

[0074] Through quaternary formation, the aluminum foil continues to form an oxide film, and during the process of forming the oxide film, the small defects exposed by the phosphoric acid treatment in step (6) are compensated.

[0075] (8) Fifth-stage conversion:

[0076] The aluminum foil that has undergone four-stage conversion is placed in a solution of 0.15 wt% azelaic acid and 0.15 wt% ammonium sebacate at 85°C for fifth-stage conversion. The conversion voltage is 480 VF, and the constant-voltage conversion time is 16 minutes. Through the fifth-stage conversion, an oxide film is continuously formed on the aluminum foil.

[0077] (9) Secondary depolarization treatment:

[0078] Then, the aluminum foil is placed in a 0.5 mol / L phosphoric acid solution at 60°C for another 7 minutes of depolarization treatment.

[0079] Through the treatment with the phosphoric acid solution, the surface of the oxide film is redissolved, exposing the small defects in the oxide film, which facilitates the formation of an oxide film at these small defect sites during the subsequent conversion process, making the oxide film denser and the structure more complete.

[0080] (10) Sixth-stage primary conversion:

[0081] The aluminum foil that has undergone secondary depolarization treatment is placed in a solution of 0.12 wt% azelaic acid and 0.12 wt% ammonium sebacate at 85°C for sixth-stage primary conversion. The conversion voltage is 550 VF, and the constant-voltage conversion time is 25 minutes.

[0082] The sixth-stage primary conversion continues to form an oxide film on the surface of the aluminum foil and compensates for the small defects exposed by the phosphoric acid treatment during the formation of the oxide film.

[0083] (11) Tertiary depolarization treatment:

[0084] The aluminum foil after the sixth-stage primary conversion is placed in a 0.5 mol / L phosphoric acid solution at 60°C for 7 minutes of depolarization treatment.

[0085] Through the treatment with the phosphoric acid solution, the surface of the oxide film is further dissolved, exposing the small defects in the oxide film, which facilitates the formation of an oxide film at these small defect sites during the subsequent conversion process, making the oxide film denser and the structure more complete.

[0086] (12) Sixth-stage secondary conversion:

[0087] The aluminum foil that has undergone tertiary depolarization treatment is placed in a solution of 0.12 wt% azelaic acid and 0.12 wt% ammonium sebacate at 85°C for sixth-stage secondary conversion. The conversion voltage is 550 VF, and the constant-voltage conversion time is 16 minutes.

[0088] The sixth-stage secondary conversion compensates for the small defects exposed by the tertiary depolarization treatment.

[0089] (13) Quaternary depolarization treatment

[0090] The aluminum foil after being secondary-formed at the sixth level is placed in a 0.5 mol / L phosphoric acid solution at 60 °C for 14 minutes of depolarization treatment;

[0091] Through the treatment with the phosphoric acid solution, the surface of the oxide film is redissolved to expose the tiny defects in the oxide film, facilitating the formation of an oxide film at these small defect sites during the subsequent forming process, making the oxide film denser and more complete in structure.

[0092] (14) Tertiary forming at the sixth level:

[0093] The aluminum foil after being depolarized four times is placed in a solution of 0.12 wt% azelaic acid and 0.12 wt% ammonium sebacate at 85 °C for tertiary forming at the sixth level, with a forming voltage of 550 VF and a constant voltage forming time of 16 minutes; The tertiary forming at the sixth level compensates for the small defects exposed by the four depolarization treatments.

[0094] (15) Ultrasonic cleaning:

[0095] After the aluminum foil after being formed at the sixth level three times is washed with pure water, it is placed in pure water at 50 °C for ultrasonic cleaning for 3 minutes;

[0096] The main purpose of ultrasonic cleaning the aluminum foil is to clean the residual azelaic acid and ammonium sebacate organic substances in the pores of the aluminum foil, avoiding the combustion of organic substances during subsequent high-temperature heat treatment and damaging the already formed oxide film.

[0097] (16) Heat treatment:

[0098] The aluminum foil after ultrasonic cleaning is placed in a roasting furnace at 400 °C for 4 minutes of heat treatment;

[0099] Through heat treatment, the oxide film is further dehydrated, and defects in the oxide film are exposed during the dehydration process.

[0100] (17) Quaternary forming at the sixth level:

[0101] The aluminum foil after heat treatment is placed in a solution of 0.12 wt% azelaic acid and 0.12 wt% ammonium sebacate at 85 °C for quaternary forming at the sixth level, with a forming voltage of 550 VF and a constant voltage forming time of 16 minutes; The quaternary forming at the sixth level compensates for the small defects exposed by the heat treatment.

[0102] (18) After the aluminum foil after being repaired by quaternary forming at the sixth level is washed, it is placed in a 0.15 mol / L ammonium dihydrogen phosphate solution at 60 °C for 13 minutes of treatment;

[0103] After being treated in the ammonium dihydrogen phosphate solution, a thin aluminum phosphate film is formed on the surface of the aluminum foil, and the water-insolubility of the aluminum phosphate film is used to improve the water resistance of the aluminum foil.

[0104] After washing the aluminum foil treated with ammonium dihydrogen phosphate solution, it is dried at 250 °C for 3 minutes to obtain the final electrode foil.

[0105] Example 2: A manufacturing method of a high-voltage and high-capacity electrode foil without boric acid system, which includes the following steps:

[0106] (1) Immerse the etched foil in pure water above 95 °C for 8 minutes;

[0107] (2) Pretreatment:

[0108] Place the aluminum foil impregnated with high-temperature pure water in a 1wt% fumaric acid solution at 70 °C and soak for 2 minutes;

[0109] (3) Primary formation:

[0110] After washing the pretreated aluminum foil with pure water, place it in a 1.0wt% ammonium dihydrogen phosphate solution at 85 °C for primary formation, the formation voltage is 100 VF, and the constant voltage formation time is 8 minutes;

[0111] (4) Secondary formation:

[0112] Place the aluminum foil after primary formation in a 0.8wt% ammonium dihydrogen phosphate solution at 85 °C for secondary formation, the formation voltage is 200 VF, and the constant voltage formation time is 8 minutes;

[0113] (5) Tertiary formation:

[0114] Place the aluminum foil after secondary formation in a 0.6wt% ammonium dihydrogen phosphate solution at 85 °C for tertiary formation, the formation voltage is 300 VF, and the constant voltage formation time is 8 minutes;

[0115] (6) First depolarization treatment:

[0116] Place the aluminum foil after tertiary formation in a 1 mol / L phosphoric acid solution at 60 °C for depolarization treatment for 5 minutes;

[0117] (7) Quaternary formation:

[0118] Place the aluminum foil after the first depolarization treatment in a solution of 0.3wt% azelaic acid and 0.2wt% ammonium sebacate at 85 °C for quaternary formation, the formation voltage is 400 VF, and the constant voltage formation time is 8 minutes;

[0119] (8) Quinary formation:

[0120] Place the aluminum foil after quaternary formation in a solution of 0.3wt% azelaic acid and 0.2wt% ammonium sebacate at 85 °C for quinary formation, the formation voltage is 480 VF, and the constant voltage formation time is 16 minutes.

[0121] (9) Secondary depolarization treatment:

[0122] Then place the aluminum foil in a 1 mol / L phosphoric acid solution at 60 °C for secondary depolarization treatment for another 5 minutes;

[0123] (10) First six-stage formation:

[0124] Place the aluminum foil after secondary depolarization treatment in a solution of 0.25 wt% azelaic acid and 0.2 wt% ammonium sebacate at 85 °C for the first six-stage formation. The formation voltage is 550 VF, and the constant voltage formation time is 30 minutes;

[0125] (11) Tertiary depolarization treatment:

[0126] Place the aluminum foil after the first six-stage formation in a 1 mol / L phosphoric acid solution at 60 °C for depolarization treatment for 5 minutes;

[0127] (12) Second six-stage formation:

[0128] Place the aluminum foil after tertiary depolarization treatment in a solution of 0.3 wt% azelaic acid and 0.2 wt% ammonium sebacate at 85 °C for the second six-stage formation. The formation voltage is 550 VF, and the constant voltage formation time is 16 minutes;

[0129] (13) Quaternary depolarization treatment

[0130] Place the aluminum foil after the second six-stage formation in a 1 mol / L phosphoric acid solution at 60 °C for depolarization treatment for 10 minutes;

[0131] (14) Third six-stage formation:

[0132] Place the aluminum foil after quaternary depolarization treatment in a solution of 0.2 wt% azelaic acid and 0.2 wt% ammonium sebacate at 85 °C for the third six-stage formation. The formation voltage is 550 VF, and the constant voltage formation time is 16 minutes; The third six-stage formation compensates for the small defects exposed by the quaternary depolarization treatment.

[0133] (15) Ultrasonic cleaning:

[0134] After washing the aluminum foil after the third six-stage formation with pure water, place it in pure water at 50 °C for ultrasonic cleaning for 5 minutes;

[0135] (16) Heat treatment:

[0136] Place the aluminum foil after ultrasonic cleaning in a roasting furnace at 500 °C for heat treatment for 4 minutes;

[0137] (17) Fourth six-stage formation:

[0138] The heat-treated aluminum foil is placed in a 0.2 wt% azelaic acid and 0.2 wt% ammonium sebacate solution at 85 °C for six-stage four-time formation. The formation voltage is 550 VF, and the constant voltage formation time is 16 minutes.

[0139] (18) After washing the aluminum foil after six-stage four-time formation repair treatment, it is placed in a 0.3 mol / L ammonium dihydrogen phosphate solution at 60 °C for 15 minutes.

[0140] (19) After washing the aluminum foil treated with ammonium dihydrogen phosphate solution, it is dried at 300 °C for 3 minutes to obtain the final electrode foil.

[0141] Comparative Example 1:

[0142] This example provides a method for preparing formed aluminum foil using a conventional boric acid process, including the following steps:

[0143] (1) Immerse the etched foil in pure water above 95 °C for 11 minutes.

[0144] (2) First-stage formation:

[0145] The aluminum foil after immersion in high-temperature pure water is placed in a solution of 0.6 wt% ammonium adipate and 2 wt% boric acid at 85 °C for first-stage formation. The formation voltage is 120 VF, and the constant voltage formation time is 10 minutes.

[0146] (3) Second-stage formation:

[0147] The aluminum foil after first-stage formation is placed in a solution of 0.4 wt% ammonium adipate and 2 wt% boric acid at 85 °C for second-stage formation. The formation voltage is 250 VF, and the constant voltage formation time is 10 minutes.

[0148] (4) Third-stage formation:

[0149] The aluminum foil after second-stage formation is placed in a solution of 5 wt% boric acid and 0.2 wt% ammonium pentaborate at 85 °C for third-stage formation. The formation voltage is 350 VF, and the constant voltage formation time is 10 minutes.

[0150] (5) Fourth-stage formation:

[0151] The aluminum foil after third-stage formation is placed in a solution of 5 wt% boric acid and 0.1 wt% ammonium pentaborate at 85 °C for fourth-stage formation. The formation voltage is 450 VF, and the constant voltage formation time is 18 minutes.

[0152] (6) Fifth-stage first formation:

[0153] The aluminum foil after fourth-stage formation is placed in a solution of 5 wt% boric acid and 0.1 wt% ammonium pentaborate at 85 °C for fifth-stage first formation. The formation voltage is 550 VF, and the constant voltage formation time is 26 minutes.

[0154] (7) Primary heat treatment:

[0155] Place the aluminum foil that has undergone five - stage primary formation into a roasting furnace at 480 °C and conduct heat treatment for 5 minutes;

[0156] (8) Five - stage secondary formation:

[0157] Place the aluminum foil that has undergone primary heat treatment into a solution of 5wt% boric acid and 0.1wt% ammonium pentaborate at 85 °C for five - stage secondary formation. The formation voltage is 550 VF and the constant - voltage formation time is 18 minutes;

[0158] (9) Primary depolarization treatment

[0159] Place the aluminum foil after five - stage secondary formation treatment into a 0.5 mol / L phosphoric acid solution at 60 °C for depolarization treatment for 18 minutes;

[0160] (10) Five - stage tertiary formation:

[0161] Place the aluminum foil after primary depolarization treatment into a solution of 5wt% boric acid and 0.1wt% ammonium pentaborate at 85 °C for five - stage tertiary formation. The formation voltage is 550 VF and the constant - voltage formation time is 18 minutes;

[0162] (11) Secondary heat treatment:

[0163] Place the aluminum foil after five - stage tertiary formation into a roasting furnace at 450 °C and conduct heat treatment for 5 minutes;

[0164] (12) Five - stage quaternary formation:

[0165] Place the aluminum foil after secondary heat treatment into a solution of 5wt% boric acid and 0.1wt% ammonium pentaborate at 85 °C for five - stage tertiary formation. The formation voltage is 550 VF and the constant - voltage formation time is 18 minutes;

[0166] (13) After washing the aluminum foil after five - stage quaternary formation repair treatment, place it into a 0.15 mol / L ammonium dihydrogen phosphate solution at 60 °C for treatment for 15 minutes;

[0167] (14) After washing the aluminum foil after treatment with ammonium dihydrogen phosphate solution, dry it at 250 °C for 3 minutes to obtain the final electrode foil.

[0168] Comparative Example 2:

[0169] This example provides a method for preparing formed aluminum foil using only organic acid treatment, including the following steps:

[0170] (1) Immerse the etched foil in pure water at a temperature above 95 °C for 11 minutes;

[0171] (2) Primary formation:

[0172] The aluminum foil impregnated with high-temperature pure water is placed in a 0.6 wt% ammonium adipate solution at 85°C for primary formation. The formation voltage is 120 VF, and the constant voltage formation time is 10 minutes.

[0173] (3) Secondary formation:

[0174] The aluminum foil after primary formation is placed in a 0.6 wt% ammonium adipate solution at 85°C for secondary formation. The formation voltage is 250 VF, and the constant voltage formation time is 10 minutes.

[0175] (4) Tertiary formation:

[0176] The aluminum foil after secondary formation is placed in a solution of 0.3 wt% azelaic acid and 0.2 wt% ammonium sebacate at 85°C for tertiary formation. The formation voltage is 350 VF, and the constant voltage formation time is 10 minutes.

[0177] (5) Quaternary formation:

[0178] The aluminum foil after tertiary formation is placed in a solution of 0.2 wt% azelaic acid and 0.15 wt% ammonium sebacate at 85°C for quaternary formation. The formation voltage is 450 VF, and the constant voltage formation time is 18 minutes.

[0179] (6) Fifth-stage primary formation:

[0180] The aluminum foil after quaternary formation is placed in a solution of 0.2 wt% azelaic acid and 0.15 wt% ammonium sebacate at 85°C for quaternary formation. The formation voltage is 550 VF, and the constant voltage formation time is 26 minutes.

[0181] (7) First heat treatment:

[0182] The aluminum foil after fifth-stage primary formation is placed in a roasting furnace at 400°C for heat treatment for 5 minutes.

[0183] (8) Fifth-stage secondary formation:

[0184] The aluminum foil after first heat treatment is placed in a solution of 0.2 wt% azelaic acid and 0.15 wt% ammonium sebacate at 85°C for formation. The formation voltage is 550 VF, and the constant voltage formation time is 18 minutes.

[0185] (9) First depolarization treatment

[0186] The aluminum foil after fifth-stage secondary formation is placed in a 0.5 mol / L phosphoric acid solution at 60°C for depolarization treatment for 15 minutes.

[0187] (10) Fifth-stage tertiary formation:

[0188] The aluminum foil that has undergone a single depolarization treatment is subjected to formation in a solution of 0.2 wt% azelaic acid and 0.15 wt% ammonium sebacate at 85°C. The formation voltage is 550 VF, and the constant voltage formation time is 18 minutes.

[0189] (11) Secondary heat treatment:

[0190] The aluminum foil that has undergone five-stage three-time formation is placed in a roasting furnace at 400°C and heat-treated for 5 minutes.

[0191] (12) Five-stage four-time formation:

[0192] The aluminum foil that has undergone secondary heat treatment is subjected to formation in a solution of 0.2 wt% azelaic acid and 0.15 wt% ammonium sebacate at 85°C. The formation voltage is 550 VF, and the constant voltage formation time is 18 minutes.

[0193] (13) After washing the aluminum foil that has undergone five-stage four-time formation repair treatment, it is placed in a 0.15 mol / L ammonium dihydrogen phosphate solution at 60°C and treated for 15 minutes.

[0194] (14) After washing the aluminum foil that has been treated with ammonium dihydrogen phosphate solution, it is dried at 200°C for 3 minutes to obtain the final electrode foil.

[0195] In the present invention, non-boric acid series chemicals are screened for the formation of electrode foils. The screened chemicals include inorganic and organic chemicals. The formation process of the electrode foil is redesigned. During the formation process, non-boric acid-based inorganic and organic chemicals are used simultaneously, and pretreatment and multi-stage intermediate treatment are added. The structure of the oxide film is optimized through the added intermediate treatment process, and the defects in the oxide film are reduced. The formed electrode foil has high capacitance, low leakage current, high bending strength, and good stability, and can replace the traditional inorganic or organic acid process.

[0196] Compared with the prior art, the advantages of the present invention are that in the front-stage formation, ammonium dihydrogen phosphate solution is used as the reagent. When using ammonium dihydrogen phosphate solution for formation, there are fewer internal defects in the formed oxide film, and due to the doping of aluminum phosphate structure in the oxide film, the water resistance of the formed aluminum foil oxide film is greatly improved. On the other hand, in this solution, the number of formation stages is increased to six, and the number of depolarization treatments is increased. Through multi-stage formation, the oxide film formed in each stage will not be too thick, and then through multi-stage depolarization treatment, the defects in the oxide film are easily exposed, and the defects in the oxide film are repaired through repair formation, ultimately achieving the purpose of gradually reducing the defects in the oxide film. Therefore, the present invention has the characteristics of not using boric acid at all during the formation process, and the formed aluminum foil has low leakage current, small capacity attenuation, and high water resistance.

[0197] Various parameters of the formed aluminum foils obtained in Example 1, Example 2, Comparative Example 1, and Comparative Example 2 were tested according to EIAJ RC-2364A. The test parameters are listed in Table 1, where Vt represents the withstand voltage of the product; Cap represents the capacity; LC represents the leakage current; Tr120 represents the withstand voltage rise time of the product after being boiled in boiling water for 120 minutes; and Bend represents the flexural strength.

[0198] Table 1 Comparison of parameters of aluminum foil formed by different forming processes

[0199]

[0200] By comparing Example 1 and Example 2 with Comparative Example 1 in Table 1, it can be concluded that the capacity of the electrode foil produced by the present invention is greater than that of the electrode foil produced by the boric acid process; compared with the electrode foil produced by the boric acid process, the electrode foil produced by the present invention has low leakage current, good hydration stability, high flexural strength, and good overall stability.

[0201] By comparing Example 1 and Example 2 with Comparative Example 2 in Table 1, it can be concluded that the capacity of the electrode foil produced by the present invention is similar to that of the electrode foil produced by the organic acid process; compared with the electrode foil produced by the organic acid process, the electrode foil produced by the present invention has low leakage current, good hydration stability, and good overall stability.

[0202] The performance parameters of capacitors made from the electrode foil produced by the present invention are compared with those made from the electrode foil produced by the boric acid process and the electrode foil produced by the organic acid process. The data are shown in Table 2:

[0203] Table 2: Comparison of performance parameters of capacitors

[0204]

[0205]

[0206] By comparison in Table 2, it can be concluded that, compared with the electrode foil produced using the boric acid process, the capacitor prepared using the electrode foil of the present invention has a larger Cap (capacitance), lower LC (leakage current), DF (loss tangent), and ESR (impedance), and has better overall performance.

[0207] By comparison in Table 2, it can be concluded that, compared with the electrode foil produced using the organic acid process, the capacitor prepared using the electrode foil of the present invention has a smaller Cap (capacitance) change rate, lower LC (leakage current), DF (loss tangent), and ESR (impedance), and has better overall performance.

[0208] like Figure 1 and Figure 2As shown, the internal and external structures of the oxide film of the formed foil obtained in Example 1 are uniform, and there are fewer feathery structures on the surface of the oxide film; while for the formed foil obtained in Comparative Example 1, the oxide film shows a loose interior and a dense exterior, and there are more feathery structures on the surface of the oxide film; thus, it is proved from the microscopic structure of the product oxide film that the formed foil of the present invention has more excellent and stable properties.

[0209] The foregoing are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A manufacturing method of a high-voltage and high-capacity electrode foil without a boric acid system, characterized in that, It includes the following steps: (1) Immerse the etched foil in pure water at a temperature above 95°C for 8 - 12 minutes; (2) Pretreatment: Immerse the etched foil after immersion in pure water in a 0.1 - 1.0 wt% fumaric acid solution; (3) Primary formation: After being washed with pure water, the etched foil pretreated is placed in a 0.1 - 1.0 wt% ammonium dihydrogen phosphate solution for primary formation, and the formation voltage is 100 ± 20 VF; (4) Secondary formation: Place the aluminum foil after primary formation in a 0.1 - 0.8 wt% ammonium dihydrogen phosphate solution for secondary formation, and the formation voltage is 200 ± 20 VF; (5) Tertiary formation: Place the aluminum foil after secondary formation in a 0.1 - 0.6 wt% ammonium dihydrogen phosphate solution for tertiary formation, and the formation voltage is 300 ± 20 VF; (6) First depolarization treatment: Place the aluminum foil after tertiary formation in a 0.1 - 1.0 mol / L phosphoric acid solution at 50 - 70°C for depolarization treatment for 5 - 10 minutes; (7) Quaternary formation: Place the aluminum foil after the first depolarization treatment in a solution containing 0.05 - 0.3 wt% azelaic acid and 0.05 - 0.2 wt% ammonium sebacate at 75 - 90°C for quaternary formation, and the formation voltage is 400 ± 20 VF; (8) Quinary formation: Place the aluminum foil after quaternary formation in a solution containing 0.05 - 0.3 wt% azelaic acid and 0.05 - 0.2 wt% ammonium sebacate at 75 - 90°C for quinary formation, and the formation voltage is 480 ± 20 VF; (9) Second depolarization treatment: Then place the aluminum foil in a 0.2 - 1.0 mol / L phosphoric acid solution at 50 - 70°C for depolarization treatment for 5 - 10 minutes again; (10) First hexavalent formation: Place the aluminum foil after the second depolarization treatment in a solution containing 0.05 - 0.3 wt% azelaic acid and 0.05 - 0.2 wt% ammonium sebacate at 75 - 90°C for first hexavalent formation, and the formation voltage is 550 ± 10 VF; (11) Third depolarization treatment: Place the aluminum foil after the first hexavalent formation treatment in a 0.2 - 1.0 mol / L phosphoric acid solution at 50 - 70°C for depolarization treatment for 5 - 10 minutes; (12) Second hexavalent formation: Place the aluminum foil after the third depolarization treatment in a solution containing 0.05 - 0.3 wt% azelaic acid and 0.05 - 0.2 wt% ammonium sebacate at 75 - 90°C for second hexavalent formation, and the formation voltage is 550 ± 10 VF; (13) Fourth depolarization treatment Place the aluminum foil after the second hexavalent formation treatment in a 0.5 - 1.5 mol / L phosphoric acid solution at 50 - 70°C for depolarization treatment for 10 - 15 minutes; (14) Third hexavalent formation: Place the aluminum foil after the fourth depolarization treatment in a solution containing 0.02 - 0.2 wt% azelaic acid and 0.02 - 0.2 wt% ammonium sebacate at 75 - 90°C for third hexavalent formation, and the formation voltage is 550 ± 10 VF; (15) Ultrasonic cleaning: After being washed with pure water, the aluminum foil after the third hexavalent formation treatment is placed in pure water at 40 - 60°C for ultrasonic cleaning for 1 - 5 minutes; (16) Heat treatment: Place the ultrasonically cleaned aluminum foil in a roasting furnace at 300 - 500 °C and heat-treat for 2 - 5 minutes; (17) Six-stage four-time formation: Place the heat-treated aluminum foil in a 0.02 - 0.2 wt% azelaic acid and 0.02 - 0.2 wt% ammonium sebacate solution at 75 - 90 °C for six-stage four-time formation, and the formation voltage is 550 ± 10 VF; (18) After washing the aluminum foil after six-stage four-time formation repair treatment, place it in a 0.05 - 0.3 mol / L ammonium dihydrogen phosphate solution at 50 - 70 °C and treat for 10 - 15 minutes; (19) After washing the aluminum foil treated with ammonium dihydrogen phosphate solution, dry it at 200 - 300 °C for 2 - 3 minutes to obtain the final formed foil.

2. The manufacturing method of a high-voltage and high-capacity electrode foil without a boric acid system according to claim 1, characterized in that In step (2), the soaking time is 1 - 5 minutes and the soaking temperature is 65 °C - 75 °C.

3. The manufacturing method of a high-voltage and high-capacity electrode foil in a boric acid-free system according to claim 1, characterized in that, In step (3), the temperature of the ammonium dihydrogen phosphate solution is 75 °C - 90 °C and the constant-voltage formation time is 5 - 10 minutes.

4. The manufacturing method of a high-voltage and high-capacity electrode foil without boric acid system according to claim 1, characterized in that, In step (4), the temperature of the ammonium dihydrogen phosphate solution is 75 °C - 90 °C and the constant-voltage formation time is 5 - 10 minutes.

5. The manufacturing method of a high-voltage and high-capacity electrode foil without a boric acid system according to claim 1, characterized in that, In step (5), the temperature of the ammonium dihydrogen phosphate solution is 75 °C - 90 °C and the constant-voltage formation time is 5 - 10 minutes.

6. The manufacturing method of a high-voltage and high-capacity electrode foil without boric acid system according to claim 1, characterized in that In step (7), the constant-voltage formation time is 5 - 10 minutes.

7. The manufacturing method of a high-voltage and high-capacity electrode foil without boric acid system according to claim 1, characterized in that, In step (8), the constant-voltage formation time is 10 - 20 minutes.

8. The manufacturing method of a high-voltage and high-capacity electrode foil without boric acid system according to claim 1, characterized in that In step (10), the constant-voltage formation time is 20 - 30 minutes.

9. The manufacturing method of a high-voltage and high-capacity electrode foil without boric acid system according to claim 1, characterized in that, In steps (12), (14) and (17), the constant-voltage formation time is 10 - 20 minutes.

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