Chemical conversion foil and method for producing the same

Abstract

The present disclosure provides a chemical conversion foil and a preparation method thereof. The preparation method of the chemical conversion foil comprises the following steps: pre-treating an aluminum foil, including subjecting the aluminum foil to at least one high-temperature treatment and acid treatment; and subjecting the pre-treated aluminum foil to multi-stage chemical conversion treatment. The present disclosure can improve the hydration resistance of the chemical conversion foil, and is conducive to improving the reliability and stability of an aluminum electrolytic capacitor.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the technical field of aluminum electrolytic capacitor, in particular to a preparation method of formation foil and a formation foil prepared by the preparation method. BACKGROUND

[0002] Aluminum electrolytic capacitor is widely used in various electronic products due to its excellent performance, large capacity, low price, and easy processing. The performance of formation foil, as a key material of aluminum electrolytic capacitor, directly affects the effect of the capacitor.

[0003] The electrolyte of aluminum electrolytic capacitor usually contains a certain proportion of water to obtain higher conductivity. However, water molecules will invade the oxide film layer of the formation foil and undergo hydration reaction with it, thereby destroying the insulating layer structure of the oxide film, making the dielectric properties of the oxide film worse, and further leading to the degradation of various performances of the capacitor and the shortening of the service life. Therefore, the hydration resistance of the formation foil is crucial to the aluminum electrolytic capacitor, and it is necessary to further improve the hydration resistance of the formation foil. SUMMARY

[0004] The present disclosure provides a preparation method of formation foil and a formation foil.

[0005] The present disclosure provides a preparation method of formation foil, comprising the following steps: pretreating an aluminum foil, including at least one high-temperature treatment and acid treatment of the aluminum foil; and performing multi-stage formation treatment on the aluminum foil after the pretreatment.

[0006] According to the preparation method of the formation foil of the present disclosure, the at least one high-temperature treatment and acid treatment of the aluminum foil comprises: using an organic acid solution to perform first acid treatment on the aluminum foil; performing first high-temperature treatment on the aluminum foil after the first acid treatment; using an inorganic acid solution to perform second acid treatment on the aluminum foil after the first high-temperature treatment; and performing second high-temperature treatment on the aluminum foil after the second acid treatment.

[0007] According to the preparation method of the formation foil of the present disclosure, the organic acid solution comprises an aqueous solution of one or more of citric acid, tartaric acid, salicylic acid, adipic acid, azelaic acid, maleic acid, fumaric acid, and itaconic acid.

[0008] According to the preparation method of the formation foil of the present disclosure, the concentration of the organic acid solution is 2-10wt%.

[0009] According to the preparation method of the formation foil of the present disclosure, the inorganic acid solution comprises an aqueous solution of one or more of phosphoric acid or phosphoric acid salt, and silicic acid or silicic acid salt.

[0010] According to the preparation method of the formation foil of the present disclosure, the concentration of the inorganic acid solution is 0.2-1wt%.

[0011] The preparation method of the formation foil according to the present disclosure, wherein the first high-temperature treatment of the aluminum foil after the first acid treatment comprises: drying treatment of the aluminum foil after the first acid treatment, the temperature range being 300-400℃; the second high-temperature treatment of the aluminum foil after the second acid treatment comprises: drying treatment of the aluminum foil after the second acid treatment, the temperature range being 300-400℃.

[0012] The preparation method of the formation foil according to the present disclosure, wherein after the multi-stage formation treatment of the aluminum foil, the preparation method of the formation foil further comprises: at least one acid treatment and at least one post-treatment of the aluminum foil after the multi-stage formation treatment using the acid treatment solution.

[0013] The preparation method of the formation foil according to the present disclosure, wherein the acid treatment solution for the acid treatment of the aluminum foil after the multi-stage formation treatment is a phosphoric acid solution, the concentration being 1-10wt%.

[0014] The present disclosure further provides a formation foil obtained by the preparation method of the formation foil according to the present disclosure.

[0015] The preparation method of the formation foil provided by the present disclosure, before the multi-stage formation treatment of the aluminum foil, at least one high-temperature treatment and acid treatment of the aluminum foil through the pretreatment process can form a layer of hydration-resistant oxide film on the surface of the aluminum foil, and can also create better starting conditions for the subsequent multi-stage formation treatment, which is conducive to improving the quality of the oxide film on the surface of the aluminum foil, thereby improving the hydration resistance of the formation foil and the reliability and stability of the aluminum electrolytic capacitor. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 Flowchart of the preparation method of the low-hydration formation foil according to one embodiment of the present disclosure.

[0017] Figure 2 Flowchart of the preparation method of the low-hydration formation foil according to another embodiment of the present disclosure. DETAILED DESCRIPTION

[0018] In order for those skilled in the art to better understand the technical solutions of the present disclosure, the technical solutions of the present disclosure will be described in detail below with reference to the accompanying drawings.

[0019] In the following, example embodiments will be described more fully with reference to the accompanying drawings, in which example embodiments can be embodied in different forms and should not be construed as being limited to the embodiments set forth herein. Rather, the purpose of the embodiments is to make the present disclosure thorough and complete, and to fully convey the scope of the present disclosure to those skilled in the art.

[0020] In the case of no conflict, the embodiments of the present disclosure and the features in the embodiments can be combined with each other.

[0021] As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0022] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present disclosure. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and / or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0023] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and the present disclosure, and will not be interpreted in an overly literal or overly formal sense unless expressly so defined herein.

[0024] The present disclosure provides a preparation method of a formation foil, referring to Figure 1 , comprising the following steps:

[0025] S2, pretreating the aluminum foil, including at least one high-temperature treatment and acid treatment on the aluminum foil;

[0026] S3, performing multi-stage formation treatment on the pretreated aluminum foil.

[0027] In the pretreatment process, at least one high-temperature treatment and acid treatment are performed on the aluminum foil, wherein the acid treatment can clean the surface of the aluminum foil, improve the surface activity of the aluminum foil, remove uneven oxide layers, and repair defects, and can also generate a hydration-resistant oxide film on the surface of the aluminum foil, thereby improving the hydration resistance of the aluminum foil. For example, a water solution containing phosphate ions is used to treat the aluminum foil, so that aluminum ions in the oxide film react with phosphate ions to generate aluminum phosphate, which can hinder the migration of oxygen-containing substances (such as water) into the oxide film, thereby preventing the formation of porous Al(OH)3, thereby significantly improving the hydration resistance and moisture resistance of the oxide film. High-temperature treatment of the aluminum foil can form a more dense and stable hydration-resistant oxide film on the surface of the aluminum foil, for example, a dense oxide film structure mainly in the form of γ'-Al2O3 crystals can be generated, thereby improving the hydration resistance of the aluminum foil.

[0028] By pretreating the aluminum foil, better starting conditions can be created for subsequent multi-stage formation processing. On the basis of pretreating the aluminum foil, multi-stage formation processing can be performed, which can make the oxide film more uniform and more dense, the generated hydration-resistant oxide film can greatly improve the hydration resistance of the aluminum foil, and can also reduce the leakage current, improve the breakdown voltage, and improve the formation efficiency, thereby facilitating the improvement of the reliability and stability of the aluminum electrolytic capacitor.

[0029] According to one embodiment of the present disclosure, referring to Figure 2 The at least one high-temperature treatment and acid treatment of the aluminum foil includes:

[0030] S21, performing first acid treatment on the aluminum foil using an organic acid solution;

[0031] S22, performing first high-temperature treatment on the aluminum foil subjected to the first acid treatment;

[0032] S23, performing second acid treatment on the aluminum foil subjected to the first high-temperature treatment using an inorganic acid solution;

[0033] S24, performing second high-temperature treatment on the aluminum foil subjected to the second acid treatment.

[0034] In the pretreatment process, the aluminum foil is subjected to multiple acid treatments. The first acid treatment can clean the surface of the aluminum foil, improve the surface activity of the aluminum foil, remove uneven oxide layers, and repair defects. The second acid treatment generates a hydration-resistant oxide film from the acid radical and aluminum, thereby improving the hydration resistance of the aluminum foil. For example, the aluminum foil is treated using an aqueous solution containing phosphate ions, so that aluminum ions in the oxide film react with phosphate ions to generate aluminum phosphate. Aluminum phosphate can hinder the migration of oxygen-containing substances (such as water) into the oxide film, thereby preventing the formation of porous Al(OH)3, thereby significantly improving the hydration resistance and moisture resistance of the oxide film. Multiple high-temperature treatments of the aluminum foil can form a more dense and stable hydration-resistant oxide film on the surface of the aluminum foil. For example, a dense oxide film structure with γ'-Al2O3 as the main crystalline phase can be generated, thereby improving the hydration resistance of the aluminum foil.

[0035] According to one embodiment of the present disclosure, the organic acid solution includes an aqueous solution of one or more of citric acid, tartaric acid, salicylic acid, adipic acid, azelaic acid, maleic acid, fumaric acid, and itaconic acid.

[0036] According to one embodiment of the present disclosure, the concentration of the organic acid solution is 2-10 wt%.

[0037] According to one embodiment of the present disclosure, the inorganic acid solution includes an aqueous solution of one or more of phosphoric acid or a phosphoric acid salt, and silicic acid or a silicic acid salt.

[0038] According to one embodiment of the present disclosure, the concentration of the inorganic acid solution is 0.2-1wt%.

[0039] According to one embodiment of the present disclosure, the first high-temperature treatment of the aluminum foil after the first acid treatment comprises:

[0040] The aluminum foil after the first acid treatment is subjected to a drying treatment at a temperature of 300-400℃;

[0041] The second high-temperature treatment of the aluminum foil after the second acid treatment comprises:

[0042] The aluminum foil after the second acid treatment is subjected to a drying treatment at a temperature of 300-400℃.

[0043] According to one embodiment of the present disclosure, with reference to Figure 2 After the multi-stage chemical treatment of the pretreated aluminum foil, the method for preparing the chemical-treated foil further comprises:

[0044] S4, at least one acid treatment and at least one post-treatment are performed on the aluminum foil after the multi-stage chemical treatment.

[0045] The acid anion in the acid treatment solution for the acid treatment of the aluminum foil after the multi-stage chemical treatment can come from one or more of phosphoric acid or phosphates, silicic acid or silicates. The concentration of the acid anion in the aqueous solution for the acid treatment is 1-10%.

[0046] According to one embodiment of the present disclosure, the acid treatment solution is a phosphoric acid solution with a concentration of 1-10wt%.

[0047] In the present disclosure, after the multi-stage chemical treatment, the acid treatment and the post-treatment can be repeatedly performed in a cross manner, for example, after one acid treatment, two post-treatments are performed, and then one acid treatment and one post-treatment are performed.

[0048] According to one embodiment of the present disclosure, after the multi-stage chemical treatment, the acid treatment and the post-treatment can be performed in the following manner:

[0049] The acid treatment: the aluminum foil is soaked in a phosphoric acid solution with a concentration of 1-10% at a temperature of 50-80℃ for 10-15min, and then washed and subjected to a heat treatment at a temperature of 400-550℃;

[0050] The post-treatment one: the aluminum foil is treated in an aqueous ammonium salt solution with a concentration of 4-6wt% under the conditions of a temperature of 65-85℃, a voltage of 90-95%vf, a current density of 30-50mA / cm 2 for 10-15min;

[0051] Post-treatment two: treating the aluminum foil in an aqueous ammonium salt solution with a concentration of 3-4 wt% at a temperature of 65-85 °C, a voltage of 90-95% vf, and a current density of 30-50 mA / cm 2 for 5-10 min.

[0052] Acid treatment: immersing the aluminum foil in a phosphoric acid solution with a concentration of 1-8% at a temperature of 50-80 °C for 1-7 min, washing, and then heat treating at a temperature of 400-550 °C.

[0053] Post-treatment three: treating the aluminum foil in an aqueous ammonium salt solution with a concentration of 1-2 wt% at a temperature of 65-85 °C, a voltage of 90-95% vf, and a current density of 30-50 mA / cm 2 for 5-10 min.

[0054] According to one embodiment of the present disclosure, the ammonium salt is one or more of dodecyltrimethylammonium bromide, dodecyl alcohol ether ammonium sulfate, ammonium dihydrogen phosphate, ammonium adipate, ammonium citrate, and ammonium oxalate.

[0055] According to one embodiment of the present disclosure, before the aluminum foil is subjected to the pre-treatment, the method further comprises: Figure 2

[0056] S1, reacting the aluminum foil in pure water.

[0057] According to one embodiment of the present disclosure, the pure water treatment is reacting the corroded aluminum foil in deionized water at a temperature of 90-95 °C for 10-18 min.

[0058] According to one embodiment of the present disclosure, the multi-stage formation treatment comprises gradually increasing the voltage in each stage of the formation solution to form the aluminum foil subjected to the pre-treatment at a temperature of 65-85 °C and a current density of 30-50 mA / cm 2 .

[0059] Generally, the formation treatment can be divided into 4-6 stages. For example, the following six-stage formation treatment can be performed.

[0060] First-stage formation: forming the aluminum foil subjected to the pre-treatment in a formation solution containing 5-15 wt% ammonium salt, 10-50 wt% boric acid or boric acid salt, and 0.1-2 wt% organic acid at a temperature of 65-85 °C, a voltage of 10-30% vf, and a current density of 30-50 mA / cm 2 for 5-10 min.

[0061] Second-stage formation: forming the aluminum foil subjected to the pre-treatment in a formation solution containing 5-15 wt% ammonium salt, 10-50 wt% boric acid or boric acid salt, and 0.1-2 wt% organic acid at a temperature of 65-85 °C, a voltage of 30-50% vf, and a current density of 30-50 mA / cm 2 ​under the conditions of 65-85°C temperature, voltage 40-60%vf, current density 30-50 mA / cm

[0062] tertiary formation: under the conditions of 65-85°C temperature, voltage 40-60%vf, current density 30-50 mA / cm 2 under the conditions of 65-85°C temperature, voltage 40-60%vf, current density 30-50 mA / cm

[0063] quaternary formation: under the conditions of 65-85°C temperature, voltage 50-70%vf, current density 30-50 mA / cm 2 under the conditions of 65-85°C temperature, voltage 40-60%vf, current density 30-50 mA / cm

[0064] quinary formation: under the conditions of 65-85°C temperature, voltage 85-95%vf, current density 30-50 mA / cm 2 under the conditions of 65-85°C temperature, voltage 40-60%vf, current density 30-50 mA / cm

[0065] quinary formation: under the conditions of 65-85°C temperature, voltage 85-95%vf, current density 30-50 mA / cm 2 under the conditions of 65-85°C temperature, voltage 40-60%vf, current density 30-50 mA / cm

[0066] According to one embodiment of the present disclosure, the preparation method of the low-water formation foil comprises the following steps:

[0067] pretreatment:

[0068] Put the aluminum foil into pure water at 90-95°C for reaction, time 10-18 min;

[0069] After taking out, soak in an organic acid solution with a concentration of 2-7% and a temperature of 50-70°C;

[0070] After taking out and washing, perform drying treatment at a temperature of 300-400°C;

[0071] After taking out, soak in a phosphoric acid solution with a concentration of 0.2-1% and a temperature of 30-50°C;

[0072] After taking out and washing, perform drying treatment at a temperature of 300-400°C;

[0073] Primary formation: temperature 65~85℃, time 5~10min, voltage 10~30%vf, current density 30~50mA / cm 2 ; the composition of the primary formation solution: 5~15wt% ammonium salt, 10~50wt% boric acid or borate, 0.1~2wt% organic acid, water washing after taking out;

[0074] Secondary formation: temperature 65~85℃, time 5~10min, voltage 30~50%vf, current density 30~50mA / cm 2 ; the composition of the secondary formation solution: 1~10wt% ammonium salt, 10~60wt% boric acid or borate, water washing after taking out;

[0075] Tertiary formation: temperature 65~85℃, time 7~15min, voltage 40~60%vf, current density 30~50mA / cm 2 ; the composition of the tertiary formation solution: 5~10wt% ammonium salt, 10~60wt% boric acid or borate, 0.1~3wt% organic acid, water washing after taking out;

[0076] Quaternary formation: temperature 65~85℃, time 5~10min, voltage 50~70%vf, current density 30~50mA / cm 2 ; the composition of the quaternary formation solution: 2~15wt% phosphate, 10~60wt% boric acid or borate, 0.1~3wt% organic acid, water washing after taking out;

[0077] Quinary formation: 4~5% ammonium salt, 10~60wt% boric acid or borate, temperature 65~85℃, time 10~20min, voltage 85~95%vf, current density 30~50mA / cm 2 , water washing after taking out;

[0078] Sextuple formation: 5~7% ammonium salt, temperature 65~85℃, 10~60wt% boric acid or borate, time 15~20min, voltage 90~95%vf, current density 30~50mA / cm 2 , water washing after taking out;

[0079] Acid treatment: soaking in a phosphoric acid solution with a concentration of 1~10%, time 1~7min, temperature 50-80℃, drying treatment after taking out and washing;

[0080] Post-treatment I: 4~6% ammonium salt, temperature 65~85℃, time 10~15min, voltage 90~95%vf, current density 30~50mA / cm 2 , water washing after taking out;

[0081] Post-treatment two: 3-4% ammonium salt, temperature 65-85℃, time 5-10min, voltage 90-95% vf, current density 30-50mA / cm 2 , and then washed with water;

[0082] Acid treatment: soaking in a phosphoric acid solution with a concentration of 1-8%, time 1-7min, temperature 50-80℃, and then washed and dried at a temperature of 400-550℃;

[0083] Post-treatment three: 1-2% ammonium salt, temperature 65-85℃, time 5-10min, voltage 90-95% vf, current density 30-50mA / cm 2 , and then washed with water and dried.

[0084] The present disclosure also provides a chemical conversion foil obtained by the method for preparing a chemical conversion foil according to the present disclosure.

[0085] According to one embodiment of the present disclosure, the chemical conversion foil obtained by the method for preparing a chemical conversion foil according to the present disclosure has good water resistance.

[0086] In order for those skilled in the art to more clearly understand the technical solutions provided by the embodiments of the present disclosure, the technical solutions provided by the embodiments of the present disclosure are described in detail below through specific examples:

[0087] Example 1

[0088] The etching foil was placed in pure water at 93℃ for reaction for 13min, then placed in a maleic acid solution at a temperature of 55℃ and a concentration of 2% for soaking, washed after taking out, and then heat treated at a temperature of 400℃; then placed in a phosphoric acid solution at a temperature of 40℃ and a concentration of 0.2% for soaking, washed after taking out, and then heat treated at a temperature of 350℃; then placed in a first chemical conversion: 12wt% ammonium adipate, 25wt% boric acid, 1.3wt% citric acid, temperature 82℃, time 8min, voltage 30% vf, current density 50mA / cm 2 ; washed with water after taking out, and then placed in a second chemical conversion: temperature 85℃, time 5-10min, voltage 45% vf, current density 50mA / cm 2 ; the composition of the second chemical conversion solution was: 10wt% ammonium salt, 20wt% borax; washed with water after taking out, and then placed in a third chemical conversion: temperature 70℃, time 13min, voltage 55% vf, current density 45mA / cm 2 ; the composition of the third chemical conversion solution was: 9wt% ammonium salt, 15wt% boric acid, 0.8wt% azelaic acid; washed with water after taking out, and then placed in a fourth chemical conversion: temperature 83℃, time 9min, voltage 70% vf, current density 40mA / cm 2; the composition of the fourth stage of chemical conversion liquid is: 8wt% ammonium tartrate, 18wt% boric acid, 0.7wt% tartaric acid; after taking out, water washing is carried out to enter the fifth stage of chemical conversion: 4.5% ammonium citrate, 5wt% boric acid, temperature 80℃, time 10-20min, voltage 90%vf, current density 35mA / cm 2 ; after taking out, water washing is carried out to enter the sixth stage of chemical conversion: 6% ammonium adipate, temperature 85℃, 40wt% sodium metaborate, time 18min, voltage 95%vf, current density 30mA / cm 2 ; after taking out and washing, heat treatment is carried out, temperature 400-550℃; after taking out, post-treatment one is carried out: 4.5% ammonium adipate, temperature 85℃, voltage 95%vf, current density 30mA / cm 2 time 12min; after taking out and water washing, post-treatment two is carried out: 3.2% ammonium adipate, temperature 85℃, voltage 95%vf, current density 30mA / cm 2 time 8min; after taking out and water washing, heat treatment is carried out, temperature 350-450℃; after taking out and water washing, post-treatment three is carried out: 1.5% ammonium dihydrogen phosphate, temperature 80℃, voltage 95%vf, current density 30mA / cm 2 , time 7min, water washing and drying.

[0089] Example 2

[0090] The etching foil is put into pure water of 93℃ to react, time 13min, after taking out, it is put into a maleic acid solution of 55℃ and 2% concentration to soak, after taking out and washing, heat treatment is carried out, temperature 400℃; after taking out, it is put into a phosphoric acid solution of 40℃ and 0.2% concentration to soak, after taking out and washing, heat treatment is carried out, temperature 350℃; after taking out, it enters the first stage of chemical conversion: 12wt% ammonium adipate, 25wt% boric acid, 1.3wt% citric acid, temperature 82℃, time 8min, voltage 30%vf, current density 50mA / cm 2 ; after taking out, water washing is carried out to enter the second stage of chemical conversion: temperature 85℃, time 5-10min, voltage 45%vf, current density 50mA / cm 2 ; the composition of the second stage of chemical conversion liquid is: 10wt% ammonium salt, 20wt% borax; after taking out, water washing is carried out to enter the third stage of chemical conversion: temperature 70℃, time 13min, voltage 55%vf, current density 45mA / cm 2 ; the composition of the third stage of chemical conversion liquid is: 9wt% ammonium salt, 15wt% boric acid, 0.8wt% azelaic acid; after taking out, water washing is carried out to enter the fourth stage of chemical conversion: temperature 83℃, time 9min, voltage 70%vf, current density 40mA / cm 2; the composition of the fourth stage of formation: 8wt% ammonium tartrate, 18wt% boric acid, 0.7wt% tartaric acid; after taking out, water washing, entering the fifth stage of formation: 4.5% ammonium citrate, 5wt% boric acid, temperature 80°C, time 10-20min, voltage 90%vf, current density 35mA / cm 2 ; after taking out, water washing, entering the sixth stage of formation: 6% ammonium adipate, temperature 85°C, 40wt% sodium metaborate, time 18min, voltage 95%vf, current density 30mA / cm 2 ; after taking out, water washing, acid treatment: soaking in 6% phosphoric acid solution, time 3min, temperature 50°C; after taking out, washing, heat treatment, temperature 400-550°C; after taking out, water washing, post-treatment one: 4.5% ammonium adipate, temperature 85°C, voltage 95%vf, current density 30mA / cm 2 time 12min; after taking out, water washing, post-treatment two: 3.2% ammonium adipate, temperature 85°C, voltage 95%vf, current density 30mA / cm 2 time 8min; after taking out, water washing, heat treatment, temperature 350-450°C; after taking out, water washing, post-treatment three: 1.5% ammonium dihydrogen phosphate, temperature 80°C, voltage 95%vf, current density 30mA / cm 2 , time 7min, water washing, drying.

[0091] Example 3

[0092] The etching foil is put into pure water of 93°C to react, time 13min, after taking out, put into 2% maleic acid solution of temperature 55°C to soak, after taking out, washing, heat treatment, temperature 400°C; after taking out, put into 0.2% phosphoric acid solution of temperature 40°C to soak, after taking out, washing, heat treatment, temperature 350°C; after taking out, entering the first stage of formation: 12wt% ammonium adipate, 25wt% boric acid, 1.3wt% citric acid, temperature 82°C, time 8min, voltage 30%vf, current density 50mA / cm 2 ; after taking out, water washing, entering the second stage of formation: temperature 85°C, time 5-10min, voltage 45%vf, current density 50mA / cm 2 ; the composition of the second stage of formation: 10wt% ammonium salt, 20wt% borax; after taking out, water washing, entering the third stage of formation: temperature 70°C, time 13min, voltage 55%vf, current density 45mA / cm 2 ; the composition of the third stage of formation: 9wt% ammonium salt, 15wt% boric acid, 0.8wt% azelaic acid; after taking out, water washing, entering the fourth stage of formation: temperature 83°C, time 9min, voltage 70%vf, current density 40mA / cm 2; the composition of the fourth stage of chemical conversion liquid is: 8wt% ammonium tartrate, 18wt% boric acid, 0.7wt% tartaric acid; after taking out, water washing is carried out to enter the fifth stage of chemical conversion: 4.5% ammonium citrate, 5wt% boric acid, temperature 80°C, time 10-20min, voltage 90%vf, current density 35mA / cm 2 ; after taking out, water washing is carried out to enter the sixth stage of chemical conversion: 6% ammonium adipate, temperature 85°C, 40wt% sodium metaborate, time 18min, voltage 95%vf, current density 30mA / cm 2 ; after taking out, water washing is carried out to enter the sixth stage of chemical conversion: 6% ammonium adipate, temperature 85°C, 40wt% sodium metaborate, time 18min, voltage 95%vf, current density 30mA / cm 2 ; after taking out, water washing is carried out to enter the sixth stage of chemical conversion: 6% ammonium adipate, temperature 85°C, 40wt% sodium metaborate, time 18min, voltage 95%vf, current density 30mA / cm 2 ; after taking out, water washing is carried out to enter the sixth stage of chemical conversion: 6% ammonium adipate, temperature 85°C, 40wt% sodium metaborate, time 18min, voltage 95%vf, current density 30mA / cm 2 ; after taking out, water washing is carried out to enter the sixth stage of chemical conversion: 6% ammonium adipate, temperature 85°C, 40wt% sodium metaborate, time 18min, voltage 95%vf, current density 30mA / cm

[0093] Comparative Example 1

[0094] The purity of the aluminum foil is 99.9% and is subjected to corrosion, and is treated in 96°C pure water for 15min, and after taking out, the sixth stage of chemical conversion is carried out. The first stage of chemical conversion: 10% ammonium adipate, 30% boric acid, 0.7% adipic acid, temperature 80°C, time 10min, voltage 10%vf-30%vf, current density 30mA / cm 2 ; after water washing, the second stage of chemical conversion is entered: 8% ammonium adipate, 25% boric acid, temperature 80°C, time 10min, voltage 30%vf-50%vf, current density 30mA / cm 2 ; after water washing, the third stage of chemical conversion is entered: 10% disodium hydrogen phosphate, 35% boric acid, temperature 80°C, time 12min, voltage 40%vf-60%vf, current density 45mA / cm 2 ; after water washing, the fourth stage of chemical conversion is carried out: 8% disodium hydrogen phosphate, 30% boric acid, temperature 80°C, time 8min, voltage 50%vf-70%vf, current density 45mA / cm 2; after water washing, into five-stage chemical conversion: 6% disodium hydrogen phosphate, 20% boric acid, temperature 85°C, time 20min, voltage 70% vf-90% vf, current density 30mA / cm 2 ; after water washing, into six-stage chemical conversion: 5% disodium hydrogen phosphate, temperature 90°C, time 25min, voltage 80% vf-95% vf, current density 30mA / cm 2 ; after water washing, heat treatment at 450-550°C for 2min; after water washing, post-treatment one: 3% disodium hydrogen phosphate, temperature 85°C, time 15min, voltage 80% vf-95% vf, current density 30mA / cm 2 ; after water washing, reaction in 10% phosphoric acid solution at 65°C for 6min; after water washing, post-treatment two: 3% disodium hydrogen phosphate, temperature 85°C, time 12min, voltage 80% vf-95% vf, current density 30mA / cm 2 ; after water washing, heat treatment at 400-480°C for 1.5min; after water washing, post-treatment three: 3% disodium hydrogen phosphate, temperature 85°C, time 10min, voltage 80% vf-95% vf, current density 30mA / cm 2 , after water washing, drying.

[0095] The chemical conversion foils prepared in Examples 1-3 and Comparative Examples were subjected to performance tests, and the results are shown in Table 1.

[0096] Table 1 Comparison of performance parameters of chemical conversion foils in Examples and Comparative Examples

[0097]

[0098] According to the data in Table 1, it can be seen that the pressure rising time after boiling of the chemical conversion foils in the Examples is significantly shortened compared with the Comparative Examples, and the short pressure rising time after boiling indicates that the chemical conversion foils have good hydration resistance and improved capacitor stability.

[0099] Example embodiments have been disclosed herein and, although the use of specific terms is exemplified throughout this specification, they are used in an illustrative sense and should not be construed as limiting. In some instances, certain features, characteristics or elements of the embodiments have been presented singly for ease of description. It will be appreciated, however, that the features, characteristics or elements can be combined together or separated, unless otherwise specified. Therefore, although the present disclosure has been described in some detail with specific reference to certain embodiments thereof, it is not intended to limit the scope of the present disclosure to the embodiments specifically described. Rather, it is contemplated to include all embodiments that fall within the spirit and scope of the present disclosure as defined by the appended claims.

Claims

1. A method for preparing electrolytic foil, characterized in that, Includes the following steps: Pre-treatment of aluminum foil includes at least one high-temperature treatment and acid treatment; The pretreated aluminum foil undergoes a multi-stage formation process; The aluminum foil undergoes at least one high-temperature treatment and acid treatment, including: The aluminum foil was first acid-treated with an organic acid solution. The aluminum foil that has undergone the first acid treatment is subjected to a first high-temperature treatment, wherein the temperature range of the first high-temperature treatment is 300-400℃; A second acid treatment is performed on the aluminum foil that has undergone the first high-temperature treatment using an inorganic acid solution. The aluminum foil that has undergone a second acid treatment is subjected to a second high-temperature treatment, with the temperature range of the second high-temperature treatment being 300-400℃.

2. The method for preparing the electroformed foil according to claim 1, characterized in that, The organic acid solution includes one or more aqueous solutions of citric acid, tartaric acid, salicylic acid, adipic acid, azelaic acid, maleic acid, fumaric acid, and itaconic acid.

3. The method for preparing the electroformed foil according to claim 2, characterized in that, The concentration of the organic acid solution is 2-10 wt%.

4. The method for preparing the electroformed foil according to claim 1, characterized in that, The inorganic acid solution includes one or more aqueous solutions of phosphoric acid or phosphates, silicic acid or silicates.

5. The method for preparing the electroformed foil according to claim 4, characterized in that, The concentration of the inorganic acid solution is 0.2-1 wt%.

6. The method for preparing the electroformed foil according to any one of claims 1 to 5, characterized in that, The aluminum foil that has undergone the first acid treatment is subjected to a first high-temperature treatment, including: The aluminum foil that has undergone the first acid treatment is dried at a temperature range of 300-400℃. The aluminum foil that has undergone a second acid treatment is subjected to a second high-temperature treatment, including: The aluminum foil that has undergone a second acid treatment is then dried at a temperature range of 300-400℃.

7. The method for preparing the electroformed foil according to any one of claims 1 to 5, characterized in that, After subjecting the pretreated aluminum foil to multi-stage formation processing, the method for preparing the formed foil further includes: The aluminum foil that has undergone multi-stage formation treatment shall be subjected to at least one acid treatment and at least one post-treatment.

8. The method for preparing the electroformed foil according to claim 7, characterized in that, The acid treatment solution for the aluminum foil that has undergone multi-stage formation is a phosphoric acid solution with a concentration of 1-10 wt%.

9. A chemically formed foil, said chemically formed foil being obtained by the method for preparing chemically formed foil according to any one of claims 1 to 8.

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