Process for producing a formation foil and a formation foil produced thereby

Abstract

The application provides a preparation process of a formation foil and the formation foil prepared by the preparation process, and the preparation process comprises a formation pretreatment, and the formation pretreatment comprises the following steps: S100: performing at least one first film forming treatment on an etching foil, and the first film forming treatment comprises sequentially performing a first boiling treatment, a first weak acid washing treatment and a heating treatment on the etching foil; and S200: performing a second film forming treatment on the etching foil, and the second film forming treatment comprises performing a second boiling treatment and a second weak acid washing treatment on the etching foil. The preparation process of the formation foil and the formation foil prepared by the preparation process can form a hydrated oxide film with a relatively large thickness, no feather-shaped outer layer and uniform crystal nucleus distribution in etching holes, can greatly improve the subsequent formation treatment efficiency, and can effectively reduce the energy consumption of the subsequent multi-stage formation treatment.

Description

TECHNICAL FIELD

[0001] The present application generally relates to the technical field of aluminum electrolytic capacitor, and particularly relates to a preparation process of formation foil and the formation foil prepared by the same. BACKGROUND

[0002] The formation foil is prepared by etching foil through formation treatment, and in order to reduce the formation energy consumption of the formation foil, the etching foil usually needs to be pre-treated. The existing formation pretreatment is usually one-time water boiling-heating-two-time water boiling, such as Chinese patent (publication number CN119964988A).

[0003] However, how to further reduce the formation treatment energy consumption of the formation foil is still a technical problem to be solved in the field. SUMMARY

[0004] In view of the above defects or deficiencies in the prior art, it is desirable to provide a preparation process of formation foil and the formation foil prepared by the same.

[0005] In a first aspect, the present application provides a preparation process of formation foil, which comprises formation pretreatment, and the formation pretreatment comprises:

[0006] S100: performing first film forming treatment on the etching foil, and the first film forming treatment comprises sequentially performing first water boiling treatment, first weak acid washing treatment and heating treatment on the etching foil;

[0007] S200: performing second film forming treatment on the etching foil, and the second film forming treatment comprises performing second water boiling treatment and second weak acid washing treatment on the etching foil.

[0008] Further, in S100, the first film forming treatment is performed on the etching foil for multiple times.

[0009] Further, in S100, the total time length of the first water boiling treatment is 16-20 min, and the heating temperature of the heating treatment is 500-600℃ and the total time length of the heating treatment is 80-90s.

[0010] Further, the heating treatment specifically comprises: heating the etching foil by a heating furnace, wherein high-temperature dry gas is input during the heating process, and the high-temperature dry gas blows the surface of the etching foil.

[0011] Further, the high-temperature dry gas is nitrogen, and the flow rate of the high-temperature dry gas is 0.8-1.0m / s.

[0012] Further, the water boiling time length of the second water boiling treatment is 6-10min.

[0013] Further, the first weak acid washing treatment and the second weak acid washing treatment both use an ammonium dihydrogen phosphate solution to soak the etching foil, wherein the soaking temperature is 40-60°C and the soaking time is 1-3 min, and the concentration of the ammonium dihydrogen phosphate is 2-5 wt%.

[0014] Further, the etching foil after the pre-treatment is subjected to a multi-stage formation treatment, and the multi-stage formation treatment comprises:

[0015] First-stage formation: the etching foil after the pre-treatment is subjected to a formation treatment in a formation solution, wherein the formation voltage is 200-220 V, the current density is 50-60 mA / cm 2 , and the formation time is 10-12 min;

[0016] Second-stage formation: the etching foil after the first-stage formation is subjected to a formation treatment in a formation solution, wherein the formation voltage is 380-400 V, the current density is 50-60 mA / cm 2 , and the formation time is 10-12 min;

[0017] Third-stage formation: the etching foil after the second-stage formation is subjected to a formation treatment in a formation solution, wherein the formation voltage is 550 V, the current density is 50-60 mA / cm 2 , and the formation time is 10-12 min;

[0018] Fourth-stage formation: the etching foil after the third-stage formation is subjected to a formation treatment in a formation solution, wherein the formation voltage is 610-630 V, the current density is 50-60 mA / cm 2 , and the formation time is 10-12 min.

[0019] Further, the etching foil after the multi-stage formation treatment is subjected to a multi-stage repair formation treatment, and the multi-stage repair formation treatment comprises:

[0020] The repair formation treatment is repeatedly performed for multiple times, and the repair formation treatment comprises:

[0021] The etching foil is soaked in a phosphoric acid solution for 3-5 min, and the concentration of the phosphoric acid is 5-7 wt%;

[0022] The etching foil is subjected to an annealing treatment, and the annealing temperature is 300-500°C and the annealing time is 2-3 min;

[0023] The etching foil is placed in a repair solution for repair formation, wherein the formation voltage is 610-630 V, the current density is 50-60 mA / cm 2 , and the repair formation time is 10-12 min;

[0024] After the multiple repair chemical conversion treatments, the etching foil is immersed in an ammonium dihydrogen phosphate solution for 2-5 min, wherein the concentration of the ammonium dihydrogen phosphate is 2-5 wt%.

[0025] In a second aspect, the present application further provides a chemical conversion foil, which is prepared by the above chemical conversion foil preparation process.

[0026] The chemical conversion foil preparation process and the chemical conversion foil prepared thereby provided by the present application can form a hydrated oxide film with a relatively thick outer layer and uniform crystal nucleus distribution in the etching holes, which can greatly improve the subsequent chemical conversion treatment efficiency and effectively reduce the energy consumption of the subsequent multi-stage chemical conversion treatment. BRIEF DESCRIPTION OF DRAWINGS

[0027] Other features, objects, and advantages of the present application will become more apparent from the following detailed description of non-limiting embodiments thereof, read in conjunction with the accompanying drawings:

[0028] Figure 1 A schematic diagram of the chemical conversion foil preparation process provided by the embodiments of the present application. DETAILED DESCRIPTION

[0029] The present application will be further described in detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely intended for the purpose of interpretation of the related application, and are not limiting of the application. In addition, it should be noted that only the parts related to the application are shown in the drawings for the purpose of description.

[0030] Reference should be made to the accompanying drawings Figure 1 The embodiments of the present application provide a chemical conversion foil preparation process, which includes chemical pretreatment and multi-stage chemical conversion treatment performed in sequence.

[0031] The chemical pretreatment includes:

[0032] S100: performing first film formation treatment on the etching foil;

[0033] S200: performing second film formation treatment on the etching foil.

[0034] In step S100, the first film forming treatment includes a first boiling treatment, a first weak pickling treatment and a heating treatment, which are sequentially performed on the etching foil. The first boiling treatment is to immerse the etching foil in pure water at a temperature of 98℃ or above, so as to form a first hydrated oxide film on the surface of the etching foil. The first hydrated oxide film can be divided into a main body layer and an outer layer located outside the main body layer. The outer layer is in a loose feather shape, and the main body layer is relatively dense in structure compared with the outer layer. The first weak pickling treatment is to immerse the etching foil after the first boiling treatment in a weak acid solution. The weak acid solution can react with the outer layer to dissolve and remove the feather-shaped outer layer of the first hydrated oxide film. It should be understood that the weak acid solution is weakly acidic and the pickling treatment time is short, which is basically harmless to the main body layer of the first hydrated oxide film, that is, the main body layer is retained. The heating treatment is to perform high-temperature heating treatment on the etching foil after the first weak pickling treatment. The first hydrated oxide film is dehydrated and converted to form γ-Al2O3nuclei under the action of high temperature, and the first hydrated oxide film is more dense, so as to reduce the energy consumption of subsequent multi-stage formation treatment. During the heating treatment, the first hydrated oxide film will shrink in volume, resulting in structural defects such as cracks in the first hydrated oxide film.

[0035] In step S200, the second film forming treatment includes a second boiling treatment and a second weak pickling treatment, which are sequentially performed on the etching foil after the first film forming treatment. The second boiling treatment is to immerse the etching foil in pure water at a temperature of 98℃ or above. During the second boiling treatment, a second hydrated oxide film will continue to grow on the first hydrated oxide film. The second hydrated oxide film not only can repair the structural defects on the first hydrated oxide film, but also can increase the thickness of the hydrated oxide film on the surface of the etching foil. The second weak pickling treatment is to immerse the etching foil after the second boiling treatment in a weak acid solution. The weak acid solution can dissolve and remove the feather-shaped outer layer of the second hydrated oxide film. Similarly, the weak acid solution is weakly acidic and the pickling treatment time is short, which is basically harmless to the main body layer of the second hydrated oxide film, that is, the main body layer of the second hydrated oxide film is retained. The first hydrated oxide film and the second hydrated oxide film constitute a formation pretreatment to form a hydrated oxide film on the surface of the etching foil.

[0036] The formation pretreatment provided by the embodiment has at least the following beneficial effects:

[0037] In the first aspect, by performing the weak pickling treatment on the etching foil after the second boiling treatment, the feather-shaped outer layer of the hydrated oxide film located in the etching hole can be removed. This not only ensures the required effective inner diameter of the etching hole, avoids the feather-shaped outer layer from blocking the formation solution from entering the etching hole, improves the efficiency of subsequent formation treatment, but also eliminates the energy consumption occupied by the feather-shaped outer layer of the hydrated oxide film in the subsequent formation treatment, so as to reduce the energy consumption of the subsequent formation treatment.

[0038] In the second aspect, the first hydrated oxide film in the corrosion hole can be formed to have a feathered outer layer after the first water boiling treatment. The feathered outer layer of the first hydrated oxide film can be removed by the first weak acid washing treatment after the first water boiling treatment. The water vapor generated in the subsequent heating treatment process does not affect the crystallization efficiency of the inner layer of the first hydrated oxide film. The efficiency of generating crystal nucleus of the first hydrated oxide film in the heating treatment process is improved.

[0039] In the third aspect, the required effective radius of the corrosion hole is ensured. The thickness of the hydrated oxide film in the corrosion hole can be set to be relatively large. The thicker hydrated oxide film can form more crystal nucleus in the subsequent heating process. The energy consumption of the subsequent formation treatment can be reduced.

[0040] Therefore, compared with the existing formation pretreatment, the corrosion foil can be formed to have a thicker hydrated oxide film without a feathered outer layer and with uniform distribution of crystal nucleus in the corrosion hole after the formation pretreatment provided in the embodiment. The efficiency of the subsequent formation treatment can be greatly improved. The energy consumption of the subsequent multi-stage formation treatment can be effectively reduced.

[0041] Optionally, in the step S100, the total time length of the first water boiling treatment is 16-20 min. The water boiling time length of the second water boiling treatment is 6-10 min. The structure defects of the first hydrated oxide film can be completely filled and repaired by the second hydrated oxide film. The hydrated oxide film formed in the formation pretreatment has a complete structure. The leakage current can be effectively reduced. The water boiling time length in the formation pretreatment of the present application is longer than that in the existing formation pretreatment. A thicker hydrated oxide film is formed.

[0042] For example, the inner diameter of the target corrosion hole on the corrosion foil (such as a corrosion foil used to prepare a formation foil with a withstand voltage of 600 V) before the formation pretreatment is about 2 μm. After the first water boiling treatment, the target corrosion hole is basically filled with the first hydrated oxide film. The thickness of the feathered outer layer of the first hydrated oxide film is about 1200 nm. The thickness of the inner layer of the first hydrated oxide film is about 800 nm. In addition, it is found that the thickness of the inner layer of the first hydrated oxide film does not change when the time length of the first water boiling treatment is prolonged. That is, the thickness of the first hydrated oxide film formed by the first film forming treatment of the present embodiment basically reaches the maximum. The energy saving ability is better at this time.

[0043] Optionally, the corrosion foil is soaked in a weak acid solution in the first weak acid washing treatment and the second weak acid washing treatment. The weak acid solution can be an ammonium dihydrogen phosphate solution. The concentration of the ammonium dihydrogen phosphate is 2-5 wt%. The soaking temperature is 40-60 ℃. The soaking time length is 1-3 min. Further preferably, the concentration of the ammonium dihydrogen phosphate is 3 wt%. The soaking temperature is 50 ℃. The soaking time length is 3 min.

[0044] In some embodiments of this application, in step S100, the etched foil is subjected to multiple first film-forming processes, preferably 2 or 3 times in a cycle.

[0045] The first boiling treatment takes a long time, resulting in a thicker first hydrated oxide film and increased dehydration, necessitating a longer subsequent heating time. A longer heating time significantly reduces the bending strength of the etched foil, affecting its mechanical properties. In this embodiment, the etched foil undergoes multiple first film-forming treatments. Each first film-forming treatment forms a hydrated film layer on the etched foil, and these multiple hydrated film layers are stacked together to ultimately form the first hydrated oxide film. After each hydrated film layer is formed, it undergoes weak acid washing and heating treatment to ensure the formation of crystal nuclei within each layer. Compared to a single first film-forming treatment, this approach reduces the overall difficulty of dehydration within the first hydrated oxide film, improves dehydration efficiency, reduces heating time, and thus increases the bending strength of the etched foil after heating treatment. Furthermore, it increases the number of crystal nuclei within the first hydrated oxide film, ensuring a more uniform distribution of crystal nuclei along the thickness direction, thereby further reducing the energy consumption of subsequent formation processes.

[0046] In the process of performing multiple first film-forming treatments, the total duration of the first boiling treatment is 16-20 minutes, and the heating temperature of the heating treatment is 500-600℃ with a total heating time of 80-90 seconds. In step S200, the duration of the second boiling treatment is preferably 8 minutes. Preferably, the total duration of the first boiling treatment is 18 minutes, and the heating temperature of the heating treatment is 550℃ with a total heating time of 90 seconds. Taking two first film-forming treatments as an example, the boiling treatment time for each first film-forming treatment can be 9 minutes, and the heating treatment time can be 45 seconds. Of course, the boiling time and heating time in the two first film-forming treatments can be different; for example, the heating time in the first first film-forming treatment is shorter than the heating time in the second first film-forming treatment. It should be understood that when performing a single first film-forming treatment during the formation pretreatment, the heating treatment time can be selected as 100-120 seconds.

[0047] In some embodiments of this application, the heat treatment specifically includes: heating the etched foil in a heating furnace, and during the heating process, introducing high-temperature dry gas to purge the surface of the etched foil. The aforementioned high-temperature dry gas not only reduces moisture in the heating furnace, but also, especially when flowing on the surface of the etched foil, utilizes gas pressure to rapidly expel water vapor from the etched holes, improving the dehydration efficiency of the first hydrated oxide film located within the etched holes, thereby contributing to improved crystallization efficiency.

[0048] Optionally, the high-temperature drying gas is nitrogen, with a temperature of 480-500℃ and a flow rate of 0.8-1.0 m / s. This configuration allows for relatively stable humidity within the furnace, resulting in effective moisture removal.

[0049] In some embodiments of this application, the etching foil after the formation pretreatment is further subjected to a multi-stage formation process, the multi-stage formation process including:

[0050] First-stage formation: The etched foil, after pretreatment, is placed in a formation solution for formation treatment, wherein the formation voltage is 200-220V and the current density is 50-60mA / cm². 2 The formation time is 10-12 minutes, and the formation solution is a mixed aqueous solution containing boric acid and ammonium pentaborate, wherein the concentration of boric acid is 5 wt% and the concentration of ammonium pentaborate is 0.3 wt%.

[0051] Secondary formation: The etched foil after primary formation is placed in a formation solution for further formation treatment, wherein the formation voltage is 380-400V and the current density is 50-60mA / cm². 2 The formation time is 10-12 minutes, and the formation solution is a mixed aqueous solution containing boric acid and ammonium pentaborate, wherein the concentration of boric acid is 5 wt% and the concentration of ammonium pentaborate is 0.15 wt%.

[0052] Third-stage formation: The etched foil, after second-stage formation, is placed in a formation solution for formation treatment, wherein the formation voltage is 550V and the current density is 50-60mA / cm². 2 The formation time is 10-12 minutes, and the formation solution is a mixed aqueous solution containing boric acid and ammonium pentaborate, wherein the concentration of boric acid is 5 wt% and the concentration of ammonium pentaborate is 0.1 wt%.

[0053] Fourth-stage formation: The etched foil, after three-stage formation, is placed in a formation solution for formation treatment, wherein the formation voltage is 610-630V and the current density is 50-60mA / cm². 2 The formation time is 10-12 minutes, and the formation solution is a mixed aqueous solution containing boric acid and ammonium pentaborate, wherein the concentration of boric acid is 5 wt% and the concentration of ammonium pentaborate is 0.05 wt%.

[0054] In some embodiments of this application, a multi-stage repair formation process is also included for the etched foil after the multi-stage formation process. The multi-stage repair formation process includes:

[0055] The process involves multiple repair formation processes, which include:

[0056] The etched foil was immersed in a phosphoric acid solution with a concentration of 5-7 wt% for 3-5 minutes.

[0057] The etched foil is annealed at a temperature of 300-500℃ for 2-3 minutes.

[0058] The etched foil is placed in a repair solution for repair formation, wherein the formation voltage is 610-630V and the current density is 50-60mA / cm². 2 Furthermore, the repair formation time is 10-12 minutes, and the repair solution can be the above-mentioned four-stage formation solution;

[0059] After multiple repair and formation processes, the etched foil is immersed in an ammonium dihydrogen phosphate solution for 2-5 minutes, where the concentration of ammonium dihydrogen phosphate is 2-5 wt%.

[0060] This application also provides a chemically formed foil, which is prepared from an etched foil according to the above-described chemically formed process.

[0061] To better demonstrate the effectiveness of this application, the following test is provided: Comparative Examples

[0062] The etched foil was subjected to a first boiling treatment, a heating treatment, and a second boiling treatment in sequence. In both the first and second boiling treatments, the etched foil was immersed in pure water at 98°C. The duration of the first boiling treatment was 4 minutes and the duration of the second boiling treatment was 8 minutes. The heating temperature was 550°C and the heating time was 90 seconds. Example 1

[0063] The etched foil was subjected to a first film-forming treatment and a second film-forming treatment in sequence. In the first and second water boiling treatments, the etched foil was immersed in pure water at 98°C for 18 minutes and the second water boiling treatment for 8 minutes. The heating temperature was 550°C and the heating time was 90 seconds. In the first and second weak acid washing treatments, the etched foil was immersed in 3.5 wt% ammonium dihydrogen phosphate solution for 3 minutes. Example 2

[0064] The etched foil was subjected to two first film-forming treatments and one second film-forming treatment. In both the first and second water boiling treatments, the etched foil was immersed in pure water at 98°C. The duration of each first water boiling treatment was 9 minutes and the duration of each second water boiling treatment was 8 minutes. The heating temperature was 550°C and the heating time was 45 seconds each time. In both the first and second weak acid washing treatments, the etched foil was immersed in a 3.5 wt% ammonium dihydrogen phosphate solution for 3 minutes.

[0065] The etched foils in the above comparative examples, Examples 1 and 2, and the pre-treated foils were all prepared using the same formation process. The energy consumption, withstand voltage, and specific volume of the formed foils during the multi-stage formation process were measured, and the results are shown in the table below:

[0066]

[0067] Based on the above test results, it is evident that, compared to existing formation pretreatment processes, the formation pretreatment process provided in this application can significantly reduce the energy consumption of subsequent formation processes, while ensuring the specific volume and withstand voltage of the formed foil. Furthermore, the formation pretreatment process provided in this application resolves the influence of the feather-like outer layer of the hydrated oxide film on the effective inner diameter of the corrosion pores, thereby improving the specific volume value.

[0068] It should be understood that the terms "first" and "second" used above are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature specified with "first" or "second" may explicitly or implicitly include one or more of that feature.

[0069] The above description is merely a preferred embodiment of this application and an explanation of the technical principles employed. Those skilled in the art should understand that the scope of the invention involved in this application is not limited to technical solutions formed by specific combinations of the above-described technical features, but should also cover other technical solutions formed by arbitrary combinations of the above-described technical features or their equivalents without departing from the inventive concept. For example, technical solutions formed by substituting the above features with (but not limited to) technical features with similar functions disclosed in this application.

Claims

1. A process for preparing electrolytic foil, characterized in that, include: Formation pretreatment, the formation pretreatment including: S100: Perform a first film-forming treatment on the etched foil, the first film-forming treatment including a first boiling water treatment, a first weak acid washing treatment and a heat treatment performed sequentially on the etched foil; S200: The etched foil is subjected to a second film-forming treatment, the second film-forming treatment including a second boiling water treatment and a second weak acid washing treatment of the etched foil; The etched foil after the formation pretreatment is subjected to a multi-stage formation process, the multi-stage formation process including: First-stage formation: The etched foil, after the aforementioned formation pretreatment, is placed in a formation solution for formation treatment, wherein the formation voltage is 200-220V and the current density is 50-60mA / cm². 2 And the transformation time is 10-12 minutes; Secondary formation: The etched foil after primary formation is placed in a formation solution for formation treatment, wherein the formation voltage is 380-400V and the current density is 50-60mA / cm². 2 And the transformation time is 10-12 minutes; Third-stage formation: The etched foil, after the second-stage formation, is placed in a formation solution for formation treatment, wherein the formation voltage is 550V and the current density is 50-60mA / cm². 2 And the transformation time is 10-12 minutes; Fourth-stage formation: The etched foil, after the three-stage formation, is placed in a formation solution for formation treatment, wherein the formation voltage is 610-630V and the current density is 50-60mA / cm². 2 And the transformation time is 10-12 minutes; The etched foil after the multi-stage formation process is subjected to a multi-stage repair formation process, which includes: The repair and formation process is performed repeatedly in cycles, and the repair and formation process includes: The etched foil is immersed in a phosphoric acid solution with a concentration of 5-7 wt% for 3-5 minutes. The etched foil is annealed at a temperature of 300-500℃ for 2-3 minutes. The etched foil is placed in a repair solution for repair formation, wherein the formation voltage is 610-630V and the current density is 50-60mA / cm. 2 The repair process takes 10-12 minutes. After the repeated repair and formation processes, the etched foil is immersed in an ammonium dihydrogen phosphate solution for 2-5 minutes, wherein the concentration of ammonium dihydrogen phosphate is 2-5 wt%.

2. The preparation process of the electroformed foil according to claim 1, characterized in that, In S100, the first film-forming process is performed on the etched foil multiple times.

3. The preparation process of the electroformed foil according to claim 2, characterized in that, In S100, the total duration of the first boiling treatment is 16-20 min, and the heating temperature of the heating treatment is 500-600℃ with a total heating duration of 80-90 s.

4. The preparation process of the electroformed foil according to claim 1, characterized in that, The heat treatment specifically includes: heating the etched foil in a heating furnace, wherein high-temperature dry gas is introduced during the heating process, and the high-temperature dry gas is used to purge the surface of the etched foil.

5. The preparation process of the electroformed foil according to claim 4, characterized in that, The high-temperature drying gas is nitrogen, and the flow rate of the high-temperature drying gas is 0.8-1.0 m / s.

6. The preparation process of the electroformed foil according to claim 1, characterized in that, The boiling time for the second boiling treatment is 6-10 minutes.

7. The preparation process of the electroformed foil according to claim 1, characterized in that, In both the first and second weak acid pickling processes, the etched foil is immersed in ammonium dihydrogen phosphate solution at a temperature of 40-60°C for 1-3 minutes, and the concentration of the ammonium dihydrogen phosphate is 2-5 wt%.

8. A type of electrolytic foil, characterized in that, It is prepared by the preparation process described in any one of claims 1-7.

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