阅读说明：本技术 一种固态铝电解电容器用电极箔的制造方法 (Method for manufacturing electrode foil for solid aluminum electrolytic capacitor ) 是由 孙新明 吴春春 于 2021-09-13 设计创作，主要内容包括：本发明涉及一种固态铝电解电容器用电极箔的制造方法,包括以下步骤：将铝箔浸于盐酸溶液；将其再次浸于酸性溶液中,且施加高频脉冲电流进行预电解；顺序执行第一次电解腐蚀、第二次电解腐蚀；重复第一次电解腐蚀和第二次电解腐蚀操作至少三次；纯水冲洗；化学清洗液清洗；再次纯水冲洗；高温热处理、冷却。通过前期酸蚀处理与预电解配合,从而可有效地改善铝箔表面所形成初始腐蚀点的分布均匀性,进而大幅地提升后续电解腐蚀的均匀性。另外,在几次不同的电腐蚀操作中,分别施于不同频率、不同波形的交流电,从而有效地改善了电解腐蚀过程电流与特定腐蚀液的配合度,利于实现铝箔经电解腐蚀后其自身的高厚度腐蚀层特性以及超高容量特性。(The invention relates to a method for manufacturing an electrode foil for a solid-state aluminum electrolytic capacitor, which comprises the following steps: soaking the aluminum foil in a hydrochloric acid solution; immersing the membrane in an acid solution again, and applying high-frequency pulse current to perform pre-electrolysis; sequentially performing first electrolytic etching and second electrolytic etching; repeating the first electrolytic etching and the second electrolytic etching at least three times; washing with pure water; cleaning with chemical cleaning liquid; washing with pure water again; and (4) performing high-temperature heat treatment and cooling. Through the cooperation of the early-stage acid etching treatment and the pre-electrolysis, the distribution uniformity of initial corrosion points formed on the surface of the aluminum foil can be effectively improved, and the uniformity of subsequent electrolytic corrosion is greatly improved. In addition, in several different electroerosion operations, alternating currents with different frequencies and different waveforms are respectively applied, so that the matching degree of the current and a specific corrosive liquid in the electrolytic corrosion process is effectively improved, and the characteristics of a high-thickness corrosion layer and ultrahigh capacity of the aluminum foil after electrolytic corrosion are facilitated.)

1. A method for manufacturing an electrode foil for a solid aluminum electrolytic capacitor, comprising the steps of:

s1, soaking the aluminum foil in a hydrochloric acid solution with the temperature controlled at 50-70 ℃ and the volume percentage concentration of 0.1-1%, wherein the soaking time is controlled at 0.5-2 min;

s2, soaking the aluminum foil obtained in the step S1 in a phosphoric acid solution with the temperature controlled at 20-40 ℃ and the volume percentage concentration of 0.1-0.5%; or the temperature is controlled to be 20-40 ℃, and the volume percentage concentration is 0.1-0.5% in the sulfuric acid solution; or controlling the temperature to be 20-40 ℃, and mixing the phosphoric acid solution with the volume percentage concentration of 0.1-0.5% and the sulfuric acid solution with the volume percentage concentration of 0.1-0.5%; applying high-frequency pulse current for pre-electrolysis, wherein the time is controlled to be 30-60 s, and the frequency is controlled to be 12-16 KHz;

s3, placing the aluminum foil obtained in the step S2 in a mixed solution of hydrochloric acid, sulfuric acid, oxalic acid and copper sulfate for first electrolytic corrosion, controlling the reaction temperature to be 20-40 ℃, controlling the applied current to be sine wave alternating current, controlling the frequency to be 40-70 Hz, and controlling the electrolysis time to be 1.5-2 min;

s4, placing the aluminum foil obtained in the step S3 in a mixed solution of hydrochloric acid, sulfuric acid, oxalic acid and copper sulfate for chemical corrosion, controlling the reaction temperature to be 40-60 ℃ and the reaction time to be 25-45S; introducing current into a mixed solution of hydrochloric acid, sulfuric acid, oxalic acid and copper sulfate for second electrolytic corrosion, controlling the reaction temperature to be 20-40 ℃, controlling the applied current to be square wave alternating current, controlling the frequency to be 60-90 Hz, and controlling the electrolysis time to be 2-4 min;

s5, repeating the steps S3 and S4 at least three times;

s6, placing the aluminum foil obtained in the step S5 in pure water for washing for not less than 2min;

s7, placing the aluminum foil obtained in the step S6 in a chemical cleaning solution for post-treatment cleaning, wherein the temperature of the post-treatment cleaning solution is controlled to be 60-80 ℃, and the reaction time is 2-4 min;

s8, putting the aluminum foil obtained in the step S7 into pure water again for washing, wherein the water temperature is controlled to be 30-40 ℃, and the time duration is controlled to be 7-10 min;

s9, placing the aluminum foil obtained in the step S8 in an oven, controlling the temperature to be 480-520 ℃ and the time duration to be 40-60S;

and S10, cooling the aluminum foil obtained in the step S9 to obtain the product.

2. The method for producing an electrode foil for a solid-state aluminum electrolytic capacitor as claimed in claim 1, wherein the chemical cleaning liquid used in step S7 is a mixed solution of nitric acid having a concentration of 2% to 5% by volume and thiourea having a concentration of 0.1 to 0.5% by weight.

3. The method of manufacturing an electrode foil for a solid-state aluminum electrolytic capacitor as recited in claim 1, wherein in step S9, an inert gas is introduced into the oven.

4. The method of manufacturing an electrode foil for a solid aluminum electrolytic capacitor as claimed in claim 1, wherein in step S9, the inside of the oven is evacuated and the degree of vacuum is controlled to 0.12 to 0.15 pa.

5. The method of manufacturing an electrode foil for a solid aluminum electrolytic capacitor as claimed in claim 1, wherein in step S10, the aluminum foil heat-treated in step S9 is continuously placed in an oven, and an inert gas having a temperature of less than 10 ℃ is directly introduced into an inner cavity of the oven.

6. The method for producing an electrode foil for a solid aluminum electrolytic capacitor as claimed in any one of claims 1 to 5, wherein the thickness of the aluminum foil which has not been subjected to etching is controlled to 100 to 120 μm and the purity is not less than 99.95%.

Technical Field

The invention relates to the technical field of electrode foil manufacturing, in particular to a manufacturing method of an electrode foil for a solid-state aluminum electrolytic capacitor.

Background

The solid-state aluminum electrolytic capacitor uses the solid electrolyte, the solid electrolyte is not easy to flow in the nano-micropore structure of the electrode foil, the holes cannot be completely filled, the problem of capacity extraction rate is caused when the solid electrolyte is used, special requirements are provided for the micropore shape of the aluminum electrode foil, and the reduction of ineffective holes is required to improve the capacity extraction rate. Meanwhile, the solid aluminum electrolytic capacitor needs to be subjected to a carbonization high-temperature heat treatment step in the manufacturing process, and higher requirements are put forward on the high-temperature resistance of the aluminum electrode foil.

The manufacturing method of the electrode foil for the general solid aluminum electrolytic capacitor comprises the following steps: the aluminum foil is placed in a solution containing hydrochloric acid, sulfuric acid, nitric acid or phosphoric acid for chemical or electrochemical corrosion, which is disclosed in chinese patent CN110517892B for a manufacturing method of an electrode foil for a solid aluminum electrolytic capacitor. Because the corrosion layer of the low-voltage corrosion foil is a sponge layer, the power frequency alternating current corrosion cannot deeply corrode, and higher capacity cannot be obtained. Meanwhile, the traditional method has the problems that the pretreatment before the aluminum foil hole is not in place, the corrosion is not uniform in the later corrosion process, the obtained capacity is low, the capacity dispersion is large, and the like. The solid capacitor manufactured by the manufacturing method of the low-voltage corrosion foil has low capacity and cannot meet the requirement of high specific volume of the solid aluminum foil. Thus, a skilled person is urgently needed to solve the above problems.

Disclosure of Invention

Therefore, in view of the above-mentioned problems and drawbacks, the present inventors have collected relevant information, evaluated and considered in many ways, and made continuous experiments and modifications by skilled technicians engaged in the industry for years of research and development, which finally resulted in the emergence of the manufacturing method of the electrode foil for solid aluminum electrolytic capacitors.

In order to solve the above technical problems, the present invention relates to a method for manufacturing an electrode foil for a solid aluminum electrolytic capacitor, comprising the steps of:

s1, soaking the aluminum foil in a hydrochloric acid solution with the temperature controlled at 50-70 ℃ and the volume percentage concentration of 0.1-1%, wherein the soaking time is controlled at 0.5-2 min;

s2, soaking the aluminum foil obtained in the step S1 in a phosphoric acid solution with the temperature controlled at 20-40 ℃ and the volume percentage concentration of 0.1-0.5%, or a sulfuric acid solution with the temperature controlled at 20-40 ℃ and the volume percentage concentration of 0.1-0.5%, or a mixed solution of a phosphoric acid solution with the temperature controlled at 20-40 ℃ and the volume percentage concentration of 0.1-0.5% and a sulfuric acid solution with the volume percentage concentration of 0.1-0.5%, and applying high-frequency pulse current to pre-electrolyze for 30-60S, wherein the frequency is controlled at 12-16 KHz;

s3, placing the aluminum foil obtained in the step S2 in a mixed solution of hydrochloric acid, sulfuric acid, oxalic acid and copper sulfate for first electrolytic corrosion, controlling the reaction temperature to be 20-40 ℃, controlling the applied current to be sine wave alternating current, controlling the frequency to be 40-70 Hz, and controlling the electrolysis time to be 1.5-2 min;

s4, placing the aluminum foil obtained in the step S3 in a mixed solution of hydrochloric acid, sulfuric acid, oxalic acid and copper sulfate for chemical corrosion, controlling the reaction temperature to be 40-60 ℃ and the reaction time to be 25-45S; introducing current into a mixed solution of hydrochloric acid, sulfuric acid, oxalic acid and copper sulfate for second electrolytic corrosion, controlling the reaction temperature to be 20-40 ℃, controlling the applied current to be square wave alternating current, controlling the frequency to be 60-90 Hz, and controlling the electrolysis time to be 2-4 min;

s5, repeating the steps S3 and S4 at least three times;

s6, placing the aluminum foil obtained in the step S5 in pure water for washing for not less than 2min;

s7, placing the aluminum foil obtained in the step S6 in a chemical cleaning solution for post-treatment cleaning, wherein the temperature of the post-treatment cleaning solution is controlled to be 60-80 ℃, and the reaction time is 2-4 min;

s8, putting the aluminum foil obtained in the step S7 into pure water again for washing, wherein the water temperature is controlled to be 30-40 ℃, and the time duration is controlled to be 7-10 min;

s9, placing the aluminum foil obtained in the step S8 in an oven, controlling the temperature to be 480-520 ℃ and the time duration to be 40-60S;

and S10, cooling the aluminum foil obtained in the step S9 to obtain the product.

As a further improvement of the technical scheme of the invention, the chemical cleaning solution used in the step S7 is a mixed solution of nitric acid with the volume percentage concentration of 2-5% and thiourea with the volume percentage concentration of 0.1-0.5 wt%.

As a further improvement of the technical solution of the present invention, in step S9, an inert gas is charged into the oven.

Of course, as another modification of the above technical solution, in step S9, the oven cavity may also be vacuumized, and the vacuum degree is controlled to be 0.12 to 0.15 pa.

As a further improvement of the technical scheme of the invention, in step S10, the aluminum foil heat-treated in step S9 is continuously placed in the oven, and inert gas with the temperature lower than 10 ℃ is directly filled into the inner cavity of the oven.

As a further improvement of the technical scheme of the invention, the thickness of the aluminum foil which is not corroded is controlled to be 100-120 mu m, and the purity is not lower than 99.95%.

Compared with the traditional method for manufacturing the electrode foil for the solid aluminum electrolytic capacitor, in the technical scheme disclosed by the invention, firstly, the aluminum foil is sequentially impregnated by two different types of acid liquids in the early stage, and before the electrolytic etching operation is formally executed, high-frequency pulse current is applied to the acid liquid used in the second impregnation operation for pre-electrolysis. Through the cooperation of the early-stage acid etching treatment and the pre-electrolysis, the distribution uniformity of initial corrosion points formed on the surface of the aluminum foil can be effectively improved, the uniformity of subsequent electrolytic corrosion is greatly improved, and the consistency of the capacity of the electrode foil is finally improved. In addition, in several different electroerosion operations, alternating currents with different frequencies and different waveforms are respectively applied, so that the matching degree of the current and a specific corrosive liquid in the electrolytic corrosion process is effectively improved, and the characteristics of a high-thickness corrosion layer and ultrahigh capacity of the aluminum foil after electrolytic corrosion are favorably realized on the premise of ensuring higher corrosion rate, so that the requirements of the solid aluminum electrolytic capacitor on the electrode foil are met.

Detailed Description

For the purpose of enhancing understanding of the present invention, the present invention will be further described in detail with reference to the following examples, which are provided for illustration only and are not to be construed as limiting the scope of the present invention. The methods are conventional methods, not specifically described.

Example 1

Dipping a 120-micron-thickness soft aluminum foil with the purity of 99.98% in a hydrochloric acid solution with the temperature of 70 ℃ and the volume percentage concentration of 0.1% for 2min, then placing the pre-treated aluminum foil in a phosphoric acid solution with the temperature of 40 ℃ and the volume percentage concentration of 0.5%, and then applying high-frequency pulse current for pre-electrolysis, wherein the time is controlled at 30s, and the frequency is controlled at 12 KHz;

placing the pre-electrolyzed aluminum foil in a mixed solution (formed by mixing hydrochloric acid, sulfuric acid, oxalic acid and copper sulfate in a mass ratio of 1: 1: 1: 1) for carrying out first electrolytic corrosion, applying sine wave alternating current with the frequency of 40Hz, wherein the reaction temperature is 40 ℃, and the reaction time is 2 min:

then placing the mixture in a middle treatment mixed solution (formed by mixing hydrochloric acid, sulfuric acid, oxalic acid and copper sulfate according to the mass ratio of 1: 1: 1: 1) for chemical corrosion, wherein the reaction temperature is 60 ℃, and the reaction time is 25 s;

continuously placing the mixture in the treated mixed solution (formed by mixing hydrochloric acid, sulfuric acid, oxalic acid and copper sulfate in a mass ratio of 1: 1: 1: 1) for carrying out second electrolytic corrosion, applying square wave alternating current with the frequency of 90Hz, and carrying out reaction at the temperature of 20 ℃ for 2min;

repeating each of the first electrolytic etching step and the second electrolytic etching step 3 times;

placing the etched foil in pure water and washing for 2min;

placing the etched foil in a chemical cleaning solution (a mixed solution of 2-5% nitric acid and 0.1-0.5 wt% thiourea in volume percentage concentration) for post-treatment cleaning, wherein the temperature of the post-treatment cleaning solution is 60 ℃, and the reaction time is 4 min;

washing in pure water at 30 deg.C for 8 min;

and (3) placing the aluminum foil in an oven, and carrying out heat treatment at 520 ℃, wherein the heat treatment process is carried out in an inert gas protective atmosphere or vacuum, and the treatment time is 40s to obtain the product.

Example 2

Dipping a 120-micron-thickness soft aluminum foil with the purity of 99.98% in a hydrochloric acid solution with the temperature of 60 ℃ and the volume percentage concentration of 0.5% for 1min, then placing the pre-treated aluminum foil in a sulfuric acid solution with the temperature of 20 ℃ and the volume percentage concentration of 0.3%, and then applying high-frequency pulse current for pre-electrolysis, wherein the time is controlled at 40s, and the frequency is controlled at 14 KHz;

placing the pre-electrolyzed aluminum foil in a mixed aqueous solution (formed by mixing hydrochloric acid, sulfuric acid, oxalic acid and copper sulfate in a mass ratio of 1: 1: 1: 1) for carrying out first electrolytic corrosion, applying sine wave alternating current with the frequency of 60Hz, and carrying out reaction at the temperature of 30 ℃ for 2 min:

then placing the mixture into a middle-treatment mixed aqueous solution (prepared by mixing hydrochloric acid, sulfuric acid, oxalic acid and copper sulfate in a mass ratio of 1: 1: 1: 1) for chemical corrosion, wherein the reaction temperature is 50 ℃, and the reaction time is 30 s;

continuously placing the mixture in the treated mixed aqueous solution (formed by mixing hydrochloric acid, sulfuric acid, oxalic acid and copper sulfate in a mass ratio of 1: 1: 1: 1) to perform second electrolytic corrosion, applying square wave alternating current with the frequency of 80Hz, and performing reaction at the temperature of 30 ℃ for 3 min;

repeating each of the first electrolytic etching step and the second electrolytic etching step 3 times;

placing the etched foil in pure water and washing for 2min;

placing the etched foil in a chemical cleaning solution (a mixed solution of 2-5% nitric acid and 0.1-0.5 wt% thiourea in volume percentage concentration) for post-treatment cleaning, wherein the temperature of the post-treatment cleaning solution is 70 ℃, and the reaction time is 3 min;

washing in pure water at 35 deg.C for 9 min;

placing the aluminum foil in an oven, and carrying out heat treatment at 510 ℃, wherein the heat treatment process is carried out in an inert gas protection atmosphere or vacuum for 50s, so as to obtain a product;

example 3

Dipping a 120-micron-thickness soft aluminum foil with the purity of 99.98% in a hydrochloric acid solution with the temperature of 50 ℃ and the volume percentage concentration of 1% for 2min, then placing the pre-treated aluminum foil in a phosphoric acid solution with the temperature of 30 ℃ and the volume percentage concentration of 0.4%, and then applying high-frequency pulse current for pre-electrolysis, wherein the time is controlled at 50s, and the frequency is controlled at 16 KHz;

placing the pre-electrolyzed aluminum foil in a mixed aqueous solution (formed by mixing hydrochloric acid, sulfuric acid, oxalic acid and copper sulfate in a mass ratio of 1: 1: 1: 1) for carrying out first electrolytic corrosion, applying sine wave alternating current with the frequency of 70Hz, wherein the reaction temperature is 20 ℃, and the reaction time is 1.5 min:

then placing the mixture into a middle-treatment mixed aqueous solution (prepared by mixing hydrochloric acid, sulfuric acid, oxalic acid and copper sulfate in a mass ratio of 1: 1: 1: 1) for chemical corrosion, wherein the reaction temperature is 40 ℃, and the reaction time is 45 s;

continuously placing the mixture in the treated mixed aqueous solution (formed by mixing hydrochloric acid, sulfuric acid, oxalic acid and copper sulfate in a mass ratio of 1: 1: 1: 1) to perform second electrolytic corrosion, applying square wave alternating current with the frequency of 60Hz, and performing reaction at the temperature of 40 ℃ for 4 min;

repeating each of the first electrolytic etching step and the second electrolytic etching step 3 times;

placing the etched foil in pure water and washing for 2min;

placing the etched foil in a chemical cleaning solution (a mixed solution of 2-5% nitric acid and 0.1-0.5 wt% thiourea in volume percentage concentration) for post-treatment cleaning, wherein the temperature of the post-treatment cleaning solution is 80 ℃, and the reaction time is 4 min;

washing in pure water at 40 deg.C for 10 min;

placing the aluminum foil in an oven, and carrying out heat treatment at 490 ℃, wherein the heat treatment process is carried out in an inert gas protective atmosphere or vacuum for 60s, so as to obtain a product;

example 4

Dipping a 120-micron-thickness soft aluminum foil with the purity of 99.98% in a hydrochloric acid solution with the temperature of 50 ℃ and the volume percentage concentration of 1% for 2min, then placing the pre-treated aluminum foil in a mixed solution of a phosphoric acid solution with the volume percentage concentration of 0.4% and a sulfuric acid solution with the volume percentage concentration of 0.4% at the temperature of 30 ℃, and then applying high-frequency pulse current for pre-electrolysis, wherein the time is controlled at 50s, and the frequency is controlled at 16 KHz;

placing the pre-electrolyzed aluminum foil in a mixed aqueous solution (formed by mixing hydrochloric acid, sulfuric acid, oxalic acid and copper sulfate in a mass ratio of 1: 1.2: 1.5: 2) for first electrolytic corrosion, applying sine wave alternating current with the frequency of 70Hz, and reacting at the temperature of 20 ℃ for 1.5 min:

then placing the mixture into a middle-treatment mixed aqueous solution (prepared by mixing hydrochloric acid, sulfuric acid, oxalic acid and copper sulfate in a mass ratio of 1: 1: 1: 1) for chemical corrosion, wherein the reaction temperature is 40 ℃, and the reaction time is 45 s;

then continuously placing the mixture into the treated mixed aqueous solution (which is formed by mixing hydrochloric acid, sulfuric acid, oxalic acid and copper sulfate according to the mass ratio of 1: 1.2: 1.5: 2) to carry out second electrolytic corrosion, applying square wave alternating current with the frequency of 60Hz, and reacting at the temperature of 40 ℃ for 4 min;

repeating each of the first electrolytic etching step and the second electrolytic etching step 3 times;

placing the etched foil in pure water and washing for 2min;

placing the etched foil in a chemical cleaning solution (a mixed solution of 2-5% nitric acid and 0.1-0.5 wt% thiourea in volume percentage concentration) for post-treatment cleaning, wherein the temperature of the post-treatment cleaning solution is 80 ℃, and the reaction time is 4 min;

washing in pure water at 40 deg.C for 10 min;

placing the aluminum foil in an oven, and carrying out heat treatment at 490 ℃, wherein the heat treatment process is carried out in an inert gas protective atmosphere or vacuum for 60s, so as to obtain a product;

example 5

Dipping a 100-micron-thickness soft aluminum foil with the purity of 99.98% in a hydrochloric acid solution with the temperature of 50 ℃ and the volume percentage concentration of 1% for 2min, then placing the pre-treated aluminum foil in a mixed solution of a phosphoric acid solution with the volume percentage concentration of 0.4% and a sulfuric acid solution with the volume percentage concentration of 0.4% at the temperature of 30 ℃, and then applying high-frequency pulse current for pre-electrolysis, wherein the time is controlled at 50s, and the frequency is controlled at 16 KHz;

placing the pre-electrolyzed aluminum foil in a mixed aqueous solution (formed by mixing hydrochloric acid, sulfuric acid, oxalic acid and copper sulfate in a mass ratio of 1: 1.2: 1.5: 2) for first electrolytic corrosion, applying sine wave alternating current with the frequency of 70Hz, and reacting at the temperature of 20 ℃ for 1.5 min:

then placing the mixture into a middle-treatment mixed aqueous solution (prepared by mixing hydrochloric acid, sulfuric acid, oxalic acid and copper sulfate in a mass ratio of 1: 1: 1: 1) for chemical corrosion, wherein the reaction temperature is 40 ℃, and the reaction time is 45 s;

then continuously placing the mixture into the treated mixed aqueous solution (which is formed by mixing hydrochloric acid, sulfuric acid, oxalic acid and copper sulfate according to the mass ratio of 1: 1.2: 1.5: 2) to carry out second electrolytic corrosion, applying square wave alternating current with the frequency of 60Hz, and reacting at the temperature of 40 ℃ for 4 min;

repeating each of the first electrolytic etching step and the second electrolytic etching step 3 times;

placing the etched foil in pure water and washing for 2min;

placing the etched foil in a chemical cleaning solution (a mixed solution of 2-5% nitric acid and 0.1-0.5 wt% thiourea in volume percentage concentration) for post-treatment cleaning, wherein the temperature of the post-treatment cleaning solution is 80 ℃, and the reaction time is 4 min;

washing in pure water at 40 deg.C for 10 min;

placing the aluminum foil in an oven, and carrying out heat treatment at 490 ℃, wherein the heat treatment process is carried out in an inert gas protective atmosphere or vacuum for 60s, so as to obtain a product;

example 6

Dipping a 100-micron-thickness soft aluminum foil with the purity of 99.98% in a hydrochloric acid solution with the temperature of 50 ℃ and the volume percentage concentration of 1% for 2min, then placing the pre-treated aluminum foil in a mixed solution of a phosphoric acid solution with the volume percentage concentration of 0.4% and a sulfuric acid solution with the volume percentage concentration of 0.4% at the temperature of 30 ℃, and then applying high-frequency pulse current for pre-electrolysis, wherein the time is controlled at 50s, and the frequency is controlled at 16 KHz;

placing the pre-electrolyzed aluminum foil in a mixed aqueous solution (formed by mixing hydrochloric acid, sulfuric acid, oxalic acid and copper sulfate in a mass ratio of 1: 1.2: 1.5: 2) for first electrolytic corrosion, applying sine wave alternating current with the frequency of 70Hz, and reacting at the temperature of 20 ℃ for 1.5 min:

then placing the mixture into a middle-treatment mixed aqueous solution (prepared by mixing hydrochloric acid, sulfuric acid, oxalic acid and copper sulfate in a mass ratio of 1: 1: 1: 1) for chemical corrosion, wherein the reaction temperature is 40 ℃, and the reaction time is 45 s;

then continuously placing the mixture into the treated mixed aqueous solution (which is formed by mixing hydrochloric acid, sulfuric acid, oxalic acid and copper sulfate according to the mass ratio of 1: 1.2: 1.5: 2) to carry out second electrolytic corrosion, applying square wave alternating current with the frequency of 60Hz, and reacting at the temperature of 40 ℃ for 4 min;

repeating each of the first electrolytic etching step and the second electrolytic etching step 3 times;

placing the etched foil in pure water and washing for 2min;

placing the etched foil in a chemical cleaning solution (a mixed solution of 2-5% nitric acid and 0.1-0.5 wt% thiourea in volume percentage concentration) for post-treatment cleaning, wherein the temperature of the post-treatment cleaning solution is 80 ℃, and the reaction time is 4 min;

washing in pure water at 40 deg.C for 10 min;

placing the aluminum foil in an oven, and carrying out heat treatment at 490 ℃, wherein the heat treatment process is carried out in an inert gas protective atmosphere or vacuum for 60 s;

and then, continuously placing the aluminum foil subjected to heat treatment in an oven, directly filling inert gas with the temperature lower than 10 ℃ into the inner cavity of the oven, and waiting for a period of time to obtain a cooled product.

Table 1 shows the results of specific volume test of the etched foil obtained in examples 1 to 6

TABLE 1

Remarking: the general etching foil was fabricated according to the examples described in chinese patent CN 110517892B.

In the technical scheme disclosed by the invention, firstly, the aluminum foil is sequentially impregnated by two different types of acid liquor in the early stage, and before the electrolytic corrosion operation is formally executed, high-frequency pulse current is applied to the acid liquor used in the second impregnation operation for pre-electrolysis. Through the cooperation of the early-stage acid etching treatment and the pre-electrolysis, the distribution uniformity of initial corrosion points formed on the surface of the aluminum foil can be effectively improved, the uniformity of subsequent electrolytic corrosion is greatly improved, and the consistency of the capacity of the electrode foil is finally improved.

In addition, in several different electroerosion operations, alternating currents with different frequencies and different waveforms are respectively applied, so that the matching degree of the current and a specific corrosive liquid in the electrolytic corrosion process is effectively improved, and the characteristics of a high-thickness corrosion layer and ultrahigh capacity of the aluminum foil after electrolytic corrosion are favorably realized on the premise of ensuring higher corrosion rate, so that the requirements of the solid aluminum electrolytic capacitor on the electrode foil are met.

The following points need to be explained here:

1) after the etched foil is washed by pure water, a plurality of chemical cleaning solutions can be adopted to carry out post-treatment cleaning on the etched foil, but a chemical cleaning solution formula which is easy to match, high in cleaning efficiency and good in cleaning effect is recommended, and the chemical cleaning solution formula is preferably prepared by mixing 2-5% of nitric acid and 0.1-0.5 wt% of thiourea in percentage by volume.

2) When the etched foil is subjected to a heat treatment, cooling is required. The following two common ways are available: a. and transferring the corrosion foil after the heat treatment to the external environment, and naturally cooling. Then the surface of the electrode foil is seriously oxidized due to the action of oxygen in the transfer process and the subsequent cooling process, so that the structural strength and the specific volume performance of the formed electrode foil are influenced; b. the corrosion foil after heat treatment is directly sealed in the oven for cooling, so that the oxidation phenomenon can be effectively avoided, but the equipment utilization rate of the oven is extremely low due to the fact that a large amount of time is consumed, and the purchase number and the cost of the equipment are increased. In view of this, a preferred cooling solution is proposed here, in particular as follows: the aluminum foil after high-temperature heat treatment is continuously kept in the oven, and inert gases (such as nitrogen and argon) with the temperature lower than 10 ℃ are directly filled into the inner cavity of the oven, so that the cooling time can be greatly shortened, and the oxidation phenomenon is avoided;

3) compared with the phosphoric acid solution and the sulfuric acid solution, the phosphoric acid solution and the sulfuric acid solution with the same volume percentage concentration have better corrosion effect, and are beneficial to ensuring that the electrode foil obtains higher specific volume;

4) the difference of example 6 compared with example 5 lies in the difference of cooling means after the electrode foil is corroded, and the inert gas in a low temperature state is introduced into the oven on the premise of not taking out the electrode foil, so that the electrode foil can be effectively prevented from being subjected to air oxygen, and the cooling time is greatly reduced. But the specific value of the electrode foil is basically not influenced.

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.