A method for reaming corrosion of an ultra-high voltage corrosion foil

Abstract

The present invention discloses a method for reaming corrosion of ultra-high voltage corrosion foil. The method comprises the following steps: pretreatment, primary pore-forming corrosion treatment, secondary reaming corrosion treatment and post-treatment; in the secondary reaming corrosion treatment, a reaming corrosion additive is used to perform secondary reaming corrosion treatment on the aluminum foil after the primary pore-forming corrosion treatment; the reaming corrosion additive is selected from one or two of copper nitrate solution or silver nitrate solution, and the addition amount of the reaming corrosion additive is 0.1-500 mg / L. The reaming corrosion method can preferably improve the pore size and the pore size uniformity of the corrosion foil, and solve the problems of small and uneven pores of the ultra-high voltage corrosion foil and easy blockage after formation, resulting in low specific capacitance.

Description

Technical Field

[0001] The present invention belongs to the technical field of aluminum electrolytic capacitors, and more specifically, relates to a method for expanding holes and corroding a super-high voltage corrosion foil. Background Art

[0002] In aluminum electrolytic capacitors, the anode foil is an important component. Currently, the whole machine electronic devices are developing towards miniaturization, integration, and low-profile, which requires aluminum electrolytic capacitors to have a high capacitance, and thus requires the anode foil, which is the core material of aluminum electrolytic capacitors, to have a high specific capacitance. At the same time, with the development of fields such as new energy charging piles, inverters, frequency converters, and 5G base station power supplies, aluminum electrolytic capacitors are also developing towards high voltage. In some of these fields, the working voltage of aluminum electrolytic capacitors is above 500V, which makes the anode foil in aluminum electrolytic capacitors need to withstand an ultra-high withstand voltage of above 750V to avoid failure.

[0003] The anode foil in aluminum electrolytic capacitors is formed by subjecting the corrosion foil for aluminum electrolytic capacitors to anodic oxidation (also known as forming treatment), and a pressure-resistant dielectric oxide film with a certain thickness is formed on the surface of the corrosion foil, which is the anode foil of the aluminum electrolytic capacitor. The realization of the ultra-high withstand voltage anode foil is closely related to the control of parameters such as the pore size and pore depth of the corrosion foil. If the aperture of the corrosion pits on the surface of the corrosion foil is too small, the oxide film generated during the forming process will fill the entire corrosion pit, preventing the working electrolyte from entering the corrosion pit, and thus unable to achieve the effective surface expansion effect and the requirements of ultra-high withstand voltage.

[0004] Currently, the general technological process for surface expansion and corrosion of the corrosion foil of aluminum electrolytic capacitors generally includes the following steps: pretreatment → primary corrosion → secondary corrosion → post-treatment. Pretreatment refers to various physical and chemical treatments on the aluminum foil before electro-corrosion, including acid-base treatment, surface oxidation, deposition of inert metals, and other measures. Primary corrosion is mainly to form initial corrosion pits with a certain distribution, depth, and aperture on the surface of the aluminum foil, commonly known as pore formation or pore distribution. Secondary corrosion is mainly to further enlarge and deepen the initial corrosion pits formed during primary corrosion without forming new corrosion pits, commonly known as hole expansion.

[0005] Patent CN 108538600 A discloses a method for mixed acid hole expansion and corrosion of medium-high voltage anode foils in aluminum electrolysis, which includes secondary hole expansion corrosion and tertiary hole expansion corrosion. In the secondary hole expansion corrosion, hydrochloric acid or nitric acid solution, or a mixed solution of hydrochloric acid and nitric acid is used for hole expansion corrosion, and a corrosion inhibitor with a mass percentage of 1.0 - 1.25% is added. This method makes full use of the respective characteristics of hydrochloric acid and nitric acid for common hole expansion, and can make up for the deficiencies of single acid hole expansion corrosion. However, this method is only for the preparation of medium-high voltage anode foils, and the pore size of the prepared corrosion foil is difficult to meet the requirements of super-high voltage (above 750V) anode foils, and the improvement degree of its specific capacitance is also limited.

[0006] At present, for ultra-high voltage anode foils, the holes in the etched foils need to be large enough without causing hole collapse or hole merging. However, the pore diameters of existing medium-high voltage aluminum foils are difficult to meet the requirements and it is difficult to achieve the requirements of high capacitance and energy conservation. Therefore, how to provide a pore-expanding etching treatment method that can increase the hole size of the etched foil and improve the capacitance of the anode foil has become a technical problem that urgently needs to be solved. Summary of the Invention

[0007] In view of the above existing technical problems, the primary object of the present invention is to provide a pore-expanding etching method for ultra-high voltage etched foils. The pore-expanding etching method can preferably increase the pore diameter size and the pore diameter uniformity of the etched foil, and thereby preferably improve the capacitance of the etched foil.

[0008] The second object of the present invention is to provide an ultra-high voltage etched foil obtained by the pore-expanding etching method for ultra-high voltage etched foils.

[0009] The third object of the present invention is to provide an ultra-high voltage anode foil.

[0010] To achieve the above objects, the present invention is realized through the following technical solutions:

[0011] A pore-expanding etching method for ultra-high voltage etched foils includes the following steps: pretreatment, primary pore-forming etching treatment, secondary pore-expanding etching treatment, and post-treatment; in the secondary pore-expanding etching treatment, a pore-expanding etching additive is used to perform secondary pore-expanding etching treatment on the aluminum foil after the primary pore-forming etching treatment; the pore-expanding etching additive is selected from one or two of copper nitrate solution or silver nitrate solution, and the addition amount of the pore-expanding etching additive is 0.1 - 500 mg / L.

[0012] In the secondary pore-expanding etching treatment of the present invention, a nitric acid solution containing copper ions and / or silver ions is added as a pore-expanding etching aid. The addition of copper ions and / or silver ions can greatly improve the reaction kinetics and reaction efficiency between the pore-expanding etching solution and the aluminum foil, and thereby improve the inner pore diameter and pore depth during the pore-expanding etching of the aluminum foil, resulting in a significant improvement in the specific capacitance and performance of the etched foil. The inventors further found during the R & D and exploration process that the addition amount of the pore-expanding etching additive is also extremely important. Below this addition amount, the etching effect is not obvious, while above this addition amount, it will cause adverse results such as hole merging or hole collapse of the etched foil, thereby reducing the specific capacitance of the etched foil. In addition, with the improvement of the reaction kinetics and reaction efficiency, under the same amount of applied electricity, the reaction time of the pore-expanding etching is shortened, the electricity application efficiency is improved, the amount of applied electricity is reduced, and the reaction cost is lowered. The present invention solves the problems of small and uneven holes in ultra-high voltage etched foils and the problem of low specific capacitance caused by easy blockage after formation of ultra-high voltage etched foils.

[0013] Preferably, the addition amount of the reaming corrosion additive is 100 to 500 mg / L; more preferably, the addition amount of the reaming corrosion additive is 100 to 300 mg / L. Most preferably, the addition amount of the reaming corrosion additive is 200 mg / L.

[0014] Preferably, the secondary reaming corrosion treatment is as follows: putting the aluminum foil that has undergone the primary pore-forming corrosion treatment into the reaming corrosion additive and the reaming corrosion solution for secondary reaming corrosion treatment, and then cleaning; the reaming corrosion solution is a mixed solution of nitric acid and aluminum nitrate.

[0015] Preferably, in the reaming corrosion solution, the concentration of nitric acid is 2 to 9 wt%, and the concentration of aluminum nitrate is 0.1 to 2.0 wt%. More preferably, the concentration of nitric acid is 5 to 8 wt%, and the concentration of aluminum nitrate is 0.5 to 1.0 wt%. Most preferably, the concentration of nitric acid is 6 wt%, and the concentration of aluminum nitrate is 0.8 wt%. The reaming corrosion solution is an aqueous mixed solution of nitric acid and aluminum nitrate.

[0016] Preferably, in the secondary reaming corrosion treatment, the temperature is controlled at 60 to 80 °C. More preferably, the temperature is controlled at 75 °C.

[0017] Preferably, in the secondary reaming corrosion treatment, the current density is controlled at 0.05 to 0.13 A / cm 2 , and the power-on time is 360 to 500 s. More preferably, the current density is controlled at 0.08 to 0.12 A / cm 2 , and the power-on time is 400 to 450 s; most preferably, the current density is 1.2 A / cm 2 , and the power-on time is 420 s.

[0018] More preferably, the reaming corrosion additive is a mixed solution of a copper nitrate solution and a silver nitrate solution. The dosage of the reaming corrosion additive is based on the amount of the solvent used in the secondary reaming corrosion treatment. More specifically, it is based on the volume of the reaming corrosion solution used in the secondary reaming corrosion treatment, that is, 0.1 to 500 mg of the reaming corrosion additive is used for every 1 L of the reaming corrosion solution.

[0019] In one of the embodiments, a method for reaming corrosion of an ultra-high voltage corrosion foil includes the following steps:

[0020] S1. Pretreatment: soaking the aluminum foil in a phosphoric acid solution, cleaning, and obtaining a pretreated aluminum foil;

[0021] S2. Primary pore-forming corrosion treatment: putting the pretreated aluminum foil into the electrolyte, applying electricity for primary pore-forming corrosion treatment, cleaning, and obtaining a primary pore-forming corrosion aluminum foil; the electrolyte is a mixed solution of hydrochloric acid, sulfuric acid and aluminum trichloride;

[0022] S3. Secondary reaming corrosion treatment: The primary pore-forming corrosion aluminum foil is put into a reaming corrosion additive and a reaming corrosion solution for secondary reaming corrosion treatment, and then cleaned to obtain the secondary reaming corrosion aluminum foil;

[0023] S4. Post-treatment: The secondary reaming corrosion aluminum foil is soaked in a nitric acid solution, cleaned, and dried to obtain the ultra-high voltage corrosion foil.

[0024] Preferably, the concentration of hydrochloric acid is 1-10 wt%, the concentration of sulfuric acid is 35-60 wt%, and the concentration of aluminum trichloride is 0.5-2.0 wt%. Further preferably, the concentration of hydrochloric acid is 3-8 wt%, the concentration of sulfuric acid is 40-50 wt%, and the concentration of aluminum trichloride is 0.8-1.5 wt%. Most preferably, the concentration of hydrochloric acid is 5 wt%, the concentration of sulfuric acid is 40 wt%, and the concentration of aluminum trichloride is 1.0 wt%. An appropriate amount of aluminum ions can control the migration rate of aluminum ions in the tunnel holes and ensure the effective growth of the holes. The lack of aluminum trichloride is not conducive to the growth of the holes, while too much aluminum trichloride will inhibit the reaction rate. Specifically, the electrolyte is an aqueous solution of hydrochloric acid, sulfuric acid and aluminum trichloride.

[0025] Preferably, in step S2, during the primary pore-forming corrosion treatment, the temperature is controlled at 68-85 °C. Further preferably, the temperature is controlled at 70-75 °C; most preferably, the temperature is controlled at 70 °C.

[0026] Preferably, in step S2, the current density of the primary pore-forming corrosion treatment is 0.3-1.0 A / cm 2 , and the power-on time is 60-300 s. Further preferably, the current density of the primary pore-forming corrosion treatment is 0.4-0.6 A / cm 2 , and the power-on time is 160-200 s; most preferably, the current density of the primary pore-forming corrosion treatment is 0.5 A / cm 2 , and the power-on time is 180 s.

[0027] Preferably, in the pre-treatment, the phosphoric acid solution is an aqueous solution of phosphoric acid, and the concentration of phosphoric acid in the aqueous phosphoric acid solution is 1-20 wt%. Further preferably, the concentration of phosphoric acid in the aqueous phosphoric acid solution is 3-8 wt%. The purpose of the pre-treatment is to improve the surface state of the aluminum foil, fully expose the active points on the aluminum foil surface, improve the density and uniformity of the corrosion holes during the electro-erosion of the aluminum foil, and reduce the adverse effects of the differences in the purity and rolling process of the aluminum foil on the electro-erosion process.

[0028] Preferably, in the pre-treatment, the temperature during soaking is 50-70 °C; the soaking time is 60-180 s.

[0029] Preferably, in the post-treatment, the nitric acid solution is an aqueous nitric acid solution, and the concentration of nitric acid in the aqueous nitric acid solution is 3-7 wt%.

[0030] Preferably, in the post-treatment, the temperature of the soaking is 50-80 °C; the soaking time is 60-240 s. The function of the post-treatment is to remove the residual metal impurities on the surface of the aluminum foil and the acid radical anions in the etching holes, etc., and lay a foundation for the subsequent formation treatment to prepare an anodic aluminum foil with a high-performance anodic oxidation film as the dielectric layer.

[0031] Preferably, in the pre-treatment, the first-stage pore-opening corrosion, the second-stage pore-expanding corrosion and the post-treatment, the aluminum foil after each step of treatment is cleaned with deionized water at room temperature.

[0032] Preferably, the drying temperature is 100-110 °C.

[0033] Furthermore, the present invention claims to protect a super-high voltage etched foil obtained by a pore-expanding corrosion method for a super-high voltage etched foil.

[0034] Furthermore, the present invention claims to protect a super-high voltage anodic foil, and the super-high voltage etched foil is subjected to a formation treatment to obtain the super-high voltage anodic foil.

[0035] Furthermore, the formation treatment includes a first formation treatment and a second formation treatment performed in sequence. The conditions of the first formation treatment are: in a boric acid aqueous solution of 65-75 g / L, the temperature is 88-92 °C, and the current density is 4-6 A / dm 2 , and the formation voltage Vfe = 850 V.

[0036] The conditions of the second formation treatment are: baking the sheet at 500 °C for 2 min, in a boric acid aqueous solution of 65-75 g / L, the temperature is 88-92 °C, and the current is 4-6 A / dm 2 , and the formation voltage Vfe = 850 V.

[0037] Compared with the prior art, the technical effect of the present invention is that: in the second-stage pore-expanding corrosion treatment of the present invention, a nitric acid solution containing copper ions and / or silver ions is added as a pore-expanding corrosion aid, which greatly improves the reaction kinetics and reaction efficiency between the pore-expanding corrosion solution and the aluminum foil, and further improves the inner diameter and depth of the pores during the pore-expanding corrosion of the aluminum foil, so that the specific capacitance and performance of the etched foil are significantly improved. In addition, with the improvement of the reaction kinetics and reaction efficiency, under the same amount of applied electricity, the reaction time of the pore-expanding corrosion is shortened, the power supply efficiency is improved, the amount of applied electricity is reduced, and the reaction cost is reduced. The present invention solves the problems of small and uneven holes in the super-high voltage etched foil, and solves the problem of low specific capacitance caused by easy blockage after the formation of the super-high voltage etched foil. Description of the Drawings

[0038] Figure 1 SEM image of the ultra-high pressure etched foil prepared in Example 1.

[0039] Figure 2 SEM image of the ultra-high pressure etched foil prepared in Example 3.

[0040] Figure 3 SEM image of the ultra-high pressure etched foil prepared in Comparative Example 1. Detailed implementation manners

[0041] The present invention will be further described below in conjunction with the accompanying drawings of the specification and specific embodiments, but the embodiments do not impose any form of limitation on the present invention. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the technical field.

[0042] Example 1 A method for expanding holes and etching an ultra-high pressure etched foil

[0043] (1) Pretreatment: Immerse the aluminum foil in a 6wt% H3PO4 solution at 60°C for 120 s, and then wash it clean with deionized water;

[0044] (2) Primary hole-opening etching treatment: Place the aluminum foil after the above pretreatment in an electrolyte at 70°C containing 5wt% hydrochloric acid, 40wt% sulfuric acid, and 1.0wt% aluminum trichloride, and apply electricity for primary hole-opening etching treatment. The current density is 0.5 A / cm 2 , the power-on time is 180 s, and then the aluminum foil is washed with deionized water at normal temperature;

[0045] (3) Secondary hole-expanding etching treatment: Place the aluminum foil after the primary hole-opening etching treatment in a hole-expanding etching solution at 75°C containing 6wt% nitric acid and 0.8wt% aluminum nitrate, add a hole-expanding etching additive (silver nitrate solution, and the addition amount of the silver nitrate solution (based on the hole-expanding etching solution) is 5 mg / L), and apply electricity for secondary hole-expanding etching treatment. The current density is 0.1 A / cm 2 , the power-on time is 420 s, and then the aluminum foil is washed with deionized water at normal temperature;

[0046] (4) Post-treatment: Immerse the aluminum foil after the secondary hole-expanding etching treatment in a 5wt% nitric acid aqueous solution at 70°C for 180 s, wash the aluminum foil with deionized water at normal temperature, and dry it at 105°C to obtain the ultra-high pressure etched foil.

[0047] Example 2 A method for expanding holes and etching an ultra-high pressure etched foil

[0048] (1) Pretreatment: Immerse the aluminum foil in a 6wt% H3PO4 solution at 60°C for 120 s, and then wash it clean with deionized water;

[0049] (2) Primary pore-forming corrosion treatment: The aluminum foil after the above pretreatment is placed in an electrolytic solution containing 5 wt% hydrochloric acid, 40 wt% sulfuric acid, and 1.0 wt% aluminum trichloride at 70 °C, and an electric current is applied for primary pore-forming corrosion treatment. The current density is 0.5 A / cm 2 , and the electrolysis time is 180 s. Subsequently, the aluminum foil is washed with deionized water at room temperature;

[0050] (3) Secondary pore-expanding corrosion treatment: The aluminum foil after the primary pore-forming corrosion treatment is placed in a pore-expanding corrosion solution containing 6 wt% nitric acid and 0.8 wt% aluminum nitrate at 75 °C, and a pore-expanding corrosion additive (silver nitrate solution, and the addition amount of the silver nitrate solution (based on the pore-expanding corrosion solution) is 0.1 mg / L) is added, and an electric current is applied for secondary pore-expanding corrosion treatment. The current density is 0.1 A / cm 2 , and the electrolysis time is 420 s. Subsequently, the aluminum foil is washed with deionized water at room temperature;

[0051] (4) Post-treatment: The aluminum foil after the secondary pore-expanding corrosion treatment is first immersed in an aqueous solution containing 5 wt% nitric acid at 70 °C for 180 s, and the aluminum foil is washed with deionized water at room temperature and dried at 105 °C to obtain a super-high-voltage corrosion foil.

[0052] Example 3 A method for pore-expanding corrosion of a super-high-voltage corrosion foil

[0053] (1) Pretreatment: The aluminum foil is immersed in a 6 wt% H3PO4 solution at 60 °C for 120 s and then cleaned with deionized water;

[0054] (2) Primary pore-forming corrosion: The aluminum foil after the above pretreatment is placed in an electrolytic solution containing 5 wt% hydrochloric acid, 40 wt% sulfuric acid, and 1.0 wt% aluminum trichloride at 70 °C, and an electric current is applied for primary pore-forming corrosion treatment. The current density is 0.5 A / cm 2 , and the electrolysis time is 180 s. Subsequently, the aluminum foil is washed with deionized water at room temperature;

[0055] (3) Secondary pore-expanding corrosion: The aluminum foil after the primary pore-forming corrosion treatment is placed in a pore-expanding corrosion solution containing 6 wt% nitric acid and 0.8 wt% aluminum nitrate at 75 °C, and a pore-expanding corrosion additive (silver nitrate solution, and the addition amount of the silver nitrate solution (based on the pore-expanding corrosion solution) is 500 mg / L) is added, and an electric current is applied for secondary pore-expanding corrosion treatment. The current density is 0.1 A / cm 2 , and the electrolysis time is 300 s. Subsequently, the aluminum foil is washed with deionized water at room temperature;

[0056] (4) Post-treatment: The aluminum foil after the secondary reaming and etching treatment is first immersed in an aqueous solution containing 5 wt% nitric acid at 70 °C for 180 s, and then the aluminum foil is washed with deionized water at room temperature and dried at 105 °C to obtain the ultra-high voltage etched foil.

[0057] Example 4 A method for reaming and etching of ultra-high voltage etched foil

[0058] (1) Pretreatment: The aluminum foil is immersed in a 6 wt% H3PO4 solution at 60 °C for 120 s and then cleaned with deionized water.

[0059] (2) Primary pore-forming etching: The aluminum foil after the above pretreatment is placed in an electrolyte solution containing 5 wt% hydrochloric acid, 40 wt% sulfuric acid, and 1 wt% aluminum trichloride at 70 °C and electrolyzed for primary pore-forming etching. The current density is 0.5 A / cm 2 , and the electrolysis time is 180 s. Subsequently, the aluminum foil is washed with deionized water at room temperature.

[0060] (3) Secondary reaming and etching: The aluminum foil after the primary pore-forming etching treatment is placed in a reaming and etching solution containing 6 wt% nitric acid and 0.8 wt% aluminum nitrate at 75 °C, and a reaming and etching additive (copper nitrate solution, the addition amount of the copper nitrate solution (based on the reaming and etching solution) is 5 mg / L) is added, and electrolyzed for secondary reaming and etching. The current density is 0.1 A / cm 2 , and the electrolysis time is 420 s. Subsequently, the aluminum foil is washed with deionized water at room temperature.

[0061] (4) Post-treatment: The aluminum foil after the secondary reaming and etching treatment is first immersed in an aqueous solution containing 5 wt% nitric acid at 70 °C for 180 s, and then the aluminum foil is washed with deionized water at room temperature and dried at 105 °C to obtain the ultra-high voltage etched foil.

[0062] Example 5 A method for reaming and etching of ultra-high voltage etched foil

[0063] (1) Pretreatment: The aluminum foil is immersed in a 6 wt% H3PO4 solution at 60 °C for 120 s and then cleaned with deionized water.

[0064] (2) Primary pore-forming etching: The aluminum foil after the above pretreatment is placed in an electrolyte solution containing 5 wt% hydrochloric acid, 40 wt% sulfuric acid, and 1 wt% aluminum trichloride at 70 °C and electrolyzed for primary pore-forming etching. The current density is 0.5 A / cm 2 , and the electrolysis time is 180 s. Subsequently, the aluminum foil is washed with deionized water at room temperature.

[0065] (3) Secondary reaming corrosion: Place the aluminum foil that has undergone the first-stage pore-forming corrosion treatment above in a reaming corrosion solution at 75 °C containing 6 wt% nitric acid and 0.8 wt% aluminum nitrate. Add a reaming corrosion additive (silver nitrate solution and copper nitrate solution, and the addition amounts of the silver nitrate solution and copper nitrate solution are respectively (based on the reaming corrosion solution) 2.5 mg / L), apply electricity for secondary reaming corrosion treatment, and the current density is 0.1 A / cm 2 , the electricity application time is 360 s, and then the aluminum foil is washed with deionized water at room temperature;

[0066] (4) Post-treatment: Immerse the aluminum foil after secondary reaming corrosion treatment in an aqueous solution containing 5 wt% nitric acid at 70 °C for 180 s, wash the aluminum foil with deionized water at room temperature, and dry it at 105 °C to obtain the ultra-high voltage etched foil.

[0067] Example 6 A method for reaming corrosion of ultra-high voltage etched foil

[0068] (1) Pretreatment: Immerse the aluminum foil in a 6 wt% H3PO4 solution at 60 °C for 120 s, and then wash it clean with deionized water;

[0069] (2) First-stage pore-forming corrosion treatment: Place the aluminum foil after the above pretreatment in an electrolytic solution at 70 °C containing 5 wt% hydrochloric acid, 40 wt% sulfuric acid, and 1.0 wt% aluminum trichloride, apply electricity for first-stage pore-forming corrosion treatment, and the current density is 0.5 A / cm 2 , the electricity application time is 180 s, and then the aluminum foil is washed with deionized water at room temperature;

[0070] (3) Secondary reaming corrosion treatment: Place the aluminum foil that has undergone the first-stage pore-forming corrosion treatment above in a reaming corrosion solution at 75 °C containing 6 wt% nitric acid and 0.8 wt% aluminum nitrate. Add a reaming corrosion additive (silver nitrate solution, and the addition amount of the silver nitrate solution (based on the reaming corrosion solution) is 200 mg / L), apply electricity for secondary reaming corrosion treatment, and the current density is 0.1 A / cm 2 , the electricity application time is 420 s, and then the aluminum foil is washed with deionized water at room temperature;

[0071] (4) Post-treatment: Immerse the aluminum foil after secondary reaming corrosion treatment in an aqueous solution containing 5 wt% nitric acid at 70 °C for 180 s, wash the aluminum foil with deionized water at room temperature, and dry it at 105 °C to obtain the ultra-high voltage etched foil.

[0072] Comparative Example 1:

[0073] (1) Pretreatment: Immerse the aluminum foil in a 6 wt% H3PO4 solution at 60 °C for 120 s, and then wash it clean with deionized water;

[0074] (2) Primary pore-forming corrosion: The pretreated aluminum foil is placed in an electrolyte solution at 70 °C containing 5 wt% hydrochloric acid, 40 wt% sulfuric acid, and 1 wt% aluminum chloride, and electrochemically treated for primary pore-forming corrosion. The current density is 0.5 A / cm 2 , and the electrolysis time is 180 s. Subsequently, the aluminum foil is washed with deionized water at room temperature;

[0075] (3) Secondary pore-expanding corrosion: The aluminum foil that has undergone primary pore-forming corrosion is placed in a pore-expanding corrosion solution at 75 °C containing 6 wt% nitric acid and 0.8 wt% aluminum nitrate, and electrochemically treated for secondary pore-expanding corrosion. The current density is 0.1 A / cm 2 , and the electrolysis time is 300 s. Subsequently, the aluminum foil is washed with deionized water at room temperature;

[0076] (4) Post-treatment: The aluminum foil after secondary pore-expanding corrosion is first immersed in an aqueous solution containing 5 wt% nitric acid at 70 °C for 180 s, washed with deionized water at room temperature, and dried at 105 °C to obtain an ultra-high voltage etched foil.

[0077] Comparative Example 2:

[0078] The difference between this comparative example and Example 1 is that in step (3), the pore-expanding corrosion additive used is a sodium nitrate solution.

[0079] Comparative Example 3:

[0080] The difference between this comparative example and Example 1 is that in step (3), the pore-expanding corrosion additive used is a potassium nitrate solution.

[0081] Comparative Example 4:

[0082] The difference between this comparative example and Example 1 is that in step (3), the addition amount of silver nitrate solution (based on the pore-expanding corrosion solution) is 600 mg / L.

[0083] Test Example

[0084] Detection method: The ultra-high voltage etched foils prepared in the above examples and comparative examples are treated under the following conditions: 70 g / L boric acid aqueous solution, temperature 90 °C, current density 5 A / dm 2 , at a formation voltage Vfe = 850 V, to obtain sample formation 1. Sample formation 1 is calcined at 500 °C for 2 min, and then treated under the following conditions: 70 g / L boric acid aqueous solution, temperature 90 °C, current 5 A / dm 2, the formation voltage Vfe = 850V, and the obtained small sample formation 2 is the ultra-high voltage anode foil. The obtained ultra-high voltage anode foil is tested for voltage and capacitance using the TS2612 high-voltage formation foil time-voltage tester and the LCR digital bridge. The test results are shown in Table 1 below.

[0085] The scanning electron microscope was used to analyze the pore size and morphology of the ultra-high voltage etched foils prepared in each example and comparative example. The test results are shown in Table 1 below. The SEM image of the ultra-high voltage etched foil prepared in Example 1 is as Figure 1 shown. The SEM image of the ultra-high voltage etched foil prepared in Example 3 is as Figure 2 shown. The SEM image of the ultra-high voltage etched foil prepared in Comparative Example 1 is as Figure 3 shown.

[0086] Table 1

[0087]

[0088]

[0089] Note: The proportion of the number of pores within the pore size range of each of the above examples and comparative examples in all the pore sizes of the etched foil is ≥ 80%, and the average value of the pore size of the etched foil is close to the arithmetic mean of the numerical values at both ends of the above pore size.

[0090] From the above data, it can be seen that in Example 1, the pore size range of the ultra-high voltage etched foil is 1.0 - 1.3 μm, and its capacitance at a formation voltage of 850 Vf can reach 0.318. In Comparative Example 1, the pore size range of the ultra-high voltage etched foil prepared without using the pore-expanding corrosion additive is 0.7 - 0.9 μm, and its capacitance at a formation voltage of 850 Vf is 0.290. Compared with Comparative Example 1, the pore size of the ultra-high voltage etched foil prepared in Example 1 increased by 44%; at a formation voltage of 850 Vf, the capacitance increased by 9.7%. In addition, from Figure 1 and Figure 3 it can be seen that the pores and pore sizes of the etched foil prepared in Example 1 are more uniform.

[0091] Example 3 is the example with the silver nitrate solution addition amount of 500 mg / L. From its data and Figure 2 it can be seen that compared with Example 1, the addition amount of silver nitrate in Example 3 increased, and the corresponding Figure 2 size of the pores in the etched foil also increased to a certain extent. However, due to the increase in the addition amount of silver nitrate, the appearance of pore coalescence in the etched foil was caused to a certain extent. Therefore, compared with Example 1, although the addition amount of silver nitrate increased, its capacitance at 850 Vf decreased slightly.

[0092] Example 5 is an example in which copper nitrate solution and silver nitrate solution are simultaneously used as additives for reaming corrosion. From the data, it can be seen that, compared with Example 1, the range of pore sizes of the ultra-high pressure etched foil has increased to a certain extent, and the capacitance has increased by nearly 4%. Therefore, the combined use of copper nitrate solution and silver nitrate solution can exhibit a synergistic effect. Compared with Comparative Example 1, the capacitance in Example 5 has increased by nearly 14%.

[0093] Example 6 is an example in which the addition amount of silver nitrate solution is 200 mg / L. The ultra-high pressure etched foil prepared in Example 6 has a 43.75% increase in pore size and a 19% increase in capacitance compared with Comparative Example 1.

[0094] In Comparative Examples 2 and 3, other metal nitrate solutions (sodium nitrate and potassium nitrate solutions) are used, and their capacitance and pore size are similar to those in Comparative Example 1. It can be seen that other types of metal nitrate salts cannot increase the reaction driving force and reaction efficiency between the reaming corrosion solution and the aluminum foil, and cannot play a role in increasing the pore size and capacitance of the aluminum foil.

[0095] Comparative Example 4 is a comparative example in which the addition amount of silver nitrate solution is 600 mg / L. From the data, it can be seen that when the dosage of the reaming corrosion additive exceeds a specific range, although the pore size of the etched foil has increased significantly, these pores are the result of over-corrosion caused by pore merging or pore collapse of the etched foil. Due to the collapse and merging of the pores, the capacitance of the final anode foil also decreases.

[0096] The foregoing examples are illustrative and are used to explain some features of the method of the present invention. The appended claims are intended to claim the broadest scope possible, and the examples presented herein are supported by the applicant's actual test results. Therefore, the applicant's intention is that the appended claims should not be limited by the selection of examples that illustrate the features of the present invention. Some of the numerical ranges used in the claims also include sub-ranges within them, and variations within these ranges should also be interpreted as being covered by the appended claims whenever possible.

Claims

1. A method for reaming corrosion of an ultra-high pressure corrosion foil, characterized in that, It includes the following steps: S1. Pretreatment: After soaking the aluminum foil in a phosphoric acid solution, it is washed to obtain a pretreated aluminum foil; S2. Primary pore-forming corrosion treatment: The pretreated aluminum foil is placed in an electrolyte, and electricity is applied for primary pore-forming corrosion treatment, followed by washing to obtain a primary pore-forming corrosion aluminum foil; the electrolyte is a mixed solution of hydrochloric acid, sulfuric acid, and aluminum trichloride; S3. Secondary pore-expanding corrosion treatment: The primary pore-forming corrosion aluminum foil is placed in a pore-expanding corrosion additive and a pore-expanding corrosion solution for secondary pore-expanding corrosion treatment, followed by washing to obtain a secondary pore-expanding corrosion aluminum foil; S4. Post-treatment: The secondary pore-expanding corrosion aluminum foil is soaked in a nitric acid solution, washed, and dried to obtain the ultra-high voltage corrosion foil; The reaming corrosion additive is selected from one or two of copper nitrate solution or silver nitrate solution, and the addition amount of the reaming corrosion additive is 0.1-500 mg / L; the reaming corrosion solution is a mixed solution of nitric acid and aluminum nitrate; in the reaming corrosion solution, the concentration of nitric acid is 2-9 wt%, and the concentration of aluminum nitrate is 0.1-2.0 wt%; in the secondary reaming corrosion treatment, the current density is controlled to be 0.05-0.13 A / cm 2 , the power-on time is 360-500 s; in the secondary reaming corrosion treatment, the temperature is controlled to be 60-80 °C; In the electrolyte, the concentration of hydrochloric acid is 1-10 wt%, the concentration of sulfuric acid is 35-60 wt%, and the concentration of aluminum trichloride is 0.5-2.0 wt%; the current density of the first-stage pore-forming corrosion treatment is 0.3-1.0 A / cm 2 , and the power-on time is 60-300 s; in the step S2, when the first-stage pore-forming corrosion treatment is carried out, the temperature is controlled at 68-85 °C.

2. The ultra-high voltage corrosion foil prepared by the pore-expanding corrosion method of the ultra-high voltage corrosion foil described in claim 1.

3. A super high voltage anode foil, characterized in that, The ultra-high voltage corrosion foil described in claim 2 is subjected to formation treatment to prepare the ultra-high voltage anode foil.

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