A high specific capacity aluminum electrode foil based on composite etching and electrochemical deposition and a preparation method thereof

Abstract

The application relates to a high specific capacity aluminum electrode foil based on composite etching and electrochemical deposition and a preparation method thereof, and belongs to the technical field of electrode foils. First, step-by-step composite etching is adopted, that is, etching in a hydrochloric acid solution, then hole expansion and activation in a composite acid system containing specific surfactants and other additives, and then electrochemical deposition is carried out on the activated etching foil, so that the aluminum electrode foil with high specific capacity, firm structure and good pressure resistance is finally prepared.

Description

Technical Field

[0001] This invention belongs to the field of electrode foil technology, and relates to a high specific capacitance aluminum electrode foil based on composite etching and electrochemical deposition and its preparation method. Background Technology

[0002] Aluminum electrode foil is the core electrode material of aluminum electrolytic capacitors, and its performance directly determines key indicators such as capacitance, voltage withstand, and stability. As electronic components continue to evolve towards miniaturization, lightweighting, and high power density, improving the specific capacitance of aluminum electrode foil has become a crucial issue.

[0003] Currently, the main methods to improve specific capacitance are etching and the addition of high-dielectric materials. However, in terms of etching technology, traditional processes typically use acid systems to perform DC electrochemical etching on high-purity aluminum foil, which has the following problems: pitting corrosion initiation is random, the distribution of etched pits is not uniform, and local over-corrosion areas appear; in the subsequent hole enlargement stage, the hole walls between adjacent tunnel holes are easily broken down, leading to co-existing holes, which not only reduces the effective specific surface area but also weakens the residual bending strength of the aluminum foil; existing composite acid hole enlargement systems have limited ability to differentiate the reaction rates at the hole opening and inside the hole during the hole enlargement process, making it difficult to effectively guide the hole enlargement current to concentrate in the depth of the hole while suppressing surface over-corrosion.

[0004] In terms of introducing materials with high dielectric constants, the main methods include sol-gel method, hydrolysis deposition method, and electrochemical deposition method. Among them, electrochemical deposition method has received widespread attention due to its ability to selectively deposit materials onto the inner wall of the etched pit, its strong process controllability, and its relatively simple equipment. However, it has the following main problems: existing electrodeposition processes are mostly simple serial combinations with upstream etching-hole enlargement processes, lacking systematic interface functional synergy design. The chemical state of the inner wall of the etched tunnel is not compatible with the deposition solution system, resulting in limited continuous coverage of the deposition layer within the pit depth. The electrodeposition process requires the consumption of a titanium source on the counter electrode side, and the uniformity and long-term stability of the anode configuration are required for process scale-up, making large-scale production difficult to engineer. Summary of the Invention

[0005] The purpose of this invention is to provide a high specific capacitance aluminum electrode foil based on composite etching and electrochemical deposition and its preparation method. The prepared aluminum electrode foil has high specific capacitance, a robust structure, and good pressure resistance.

[0006] The objective of this invention can be achieved through the following technical solutions: A method for preparing a high-specific-capacitance aluminum electrode foil based on composite etching and electrochemical deposition includes the following steps: S1, First Etching: The aluminum foil was placed in an etching solution for electrochemical etching, and then rinsed with anhydrous ethanol after etching was completed. S2, Composite Pore Enlargement and Activation: The aluminum foil after one etching is placed in a mixed pore-expanding solution containing surfactant and compound acid, and treated at 60~80℃ for 60~180s for pore-expanding and activation treatment. S3, Electrochemical Deposition: The aluminum foil that has undergone step S2 is used as the cathode and placed in a deposition solution for electrochemical deposition. The deposition solution is a homogeneous solution composed of a titanium source, an organic solvent, a conductive additive polystyrene sulfonic acid, and water. S4. Heat annealing: The aluminum foil that has undergone step S3 is annealed at 400~600℃ for 30~120s; S5. Formation treatment: The aluminum foil obtained in step S4 is subjected to a formation treatment in an aqueous solution containing boric acid with a concentration of 30-80 g / L or ammonium adipate with a concentration of 50-100 g / L to obtain the aluminum electrode foil.

[0007] In a preferred embodiment of the present invention, in step S1, the etching solution is hydrochloric acid with a concentration of 1-3 mol / L, and the current density during electrochemical etching is 0.1-0.5 A / cm². 2 Temperature 60~80℃, time 30~120s.

[0008] As a preferred embodiment of the present invention, in step S2, the mixed pore-expanding solution contains 0.5~2 mol / L sulfuric acid, 0.1~1 mol / L hydrochloric acid, 0.05~0.5 mol / L phosphoric acid and 0.5~2 g / L surfactant.

[0009] As a preferred technical solution of the present invention, in step S2, the mixed pore-expanding liquid further includes 1.5~3.5% of a modified corrosion inhibitor by weight of the total mass of the mixed pore-expanding liquid. The modified corrosion inhibitor is polyacrylic acid, polyether-modified polysiloxane and isopropanol in a weight ratio of 1:(0.3~0.5):(0.5~1.0).

[0010] As a preferred embodiment of the present invention, in step S2, the surfactant is at least one of sodium dodecyl sulfate, hexadecyltrimethylammonium bromide, and Triton X-100.

[0011] As a preferred technical solution of the present invention, in step S3, the electrochemical deposition conditions are: temperature 10~50℃, voltage 30~100V, and time 30~60min.

[0012] As a preferred embodiment of the present invention, in step S3, the deposition solution contains, by weight, 3-5 parts of titanium-derived ammonium fluorotitanate, 0.5-1.5 parts of polystyrene sulfonic acid, 0.5-2.0 parts of polyvinylpyrrolidone, 75-90 parts of ethylene glycol, 5-10 parts of deionized water, and 0.5-1 parts of polyethylene glycol-400.

[0013] As a preferred technical solution of the present invention, in step S3, the preparation method of the deposition solution is as follows: first, the titanium source is dissolved in ethylene glycol to form solution A, then polystyrene sulfonic acid, polyvinylpyrrolidone, polyethylene glycol-400 and deionized water are mixed to form solution B, solution B is added to solution A and stirred thoroughly to obtain the deposition solution.

[0014] As a preferred technical solution of the present invention, in step S5, the conditions for the formation treatment are: temperature 70~95℃, voltage 50~150V, and time 10~40min.

[0015] A high-capacitance aluminum electrode foil based on composite etching and electrochemical deposition is obtained according to any one of the above preparation methods.

[0016] In this invention, step S1 forms initial holes on the aluminum foil surface through a single etching process, followed by a composite hole-expanding process in step S2. A ternary corrosion inhibitor, composed of polyacrylic acid, polyether-modified polysiloxane, and isopropanol in a specific weight ratio of 1:(0.3~0.5):(0.5~1.0), plays a synergistic role: polyacrylic acid forms a protective layer on the aluminum foil surface through carboxyl chemical adsorption, inhibiting excessive corrosion in the hole opening area; the polyether-modified polysiloxane, due to its low surface tension, rapidly penetrates deep into the micropores and forms a hydrophobic shielding layer at the hole opening, guiding the hole-expanding current preferentially into the depth of the tunnel hole for longitudinal hole expansion; isopropanol modulates the molecular conformation of polyacrylic acid through hydrogen bonding, exposing more carboxyl active sites. The three components synergistically enhance the hole-expanding effect, providing a larger deposition substrate for subsequent electrochemical deposition. After the synergistic treatment of S1 and S2, the hole density on the aluminum foil surface can reach 10. 7 ~10 8 pcs / cm 2 Hole depth uniformity is less than 20%.

[0017] After pore enlargement in step S2, the carboxyl active sites left on the pore walls by polyacrylic acid can serve as adsorption binding sites for polystyrene sulfonic acid and polyvinylpyrrolidone in the deposition solution in step S3. Polystyrene sulfonic acid is added to the deposition solution in step S3 as a strong polyelectrolyte, ionizing in water to produce H+ and negatively charged long-chain polystyrene sulfonate ions, providing ionic conductivity. Simultaneously, the long chains of polystyrene sulfonic acid can adsorb onto the aluminum surface and the inner walls of the pores, acting as a film-forming template to induce uniform deposition of the titanium source. Polyvinylpyrrolidone contains amide groups, which can form a hydrogen bond network with the carboxyl groups remaining on the pore walls from step S2, thereby improving the wettability and spreadability of the deposition solution within the pores. After annealing in step S4 and formation treatment in step S5, there is no delamination or peeling between the TiO2 / Al2O3 composite layer and the aluminum substrate, and the interfacial bonding strength is improved.

[0018] In step S3, ammonium fluorotitanate was used as the titanium source in the deposition solution, which exhibits high chemical stability in an ethylene glycol / water mixed solvent and is not prone to hydrolysis and precipitation. Furthermore, polystyrene sulfonic acid also serves as a high-molecular-weight conductive additive, simultaneously functioning as an electrolyte and dispersant, improving the conductivity of the deposition solution and inhibiting the aggregation of titanium precursors. Polyvinylpyrrolidone and polyethylene glycol-400 synergistically regulate the rheological properties and film-forming behavior of the deposition solution. This deposition solution system can be stably stored for more than 48 hours within a temperature range of room temperature to 50°C without precipitation or phase separation.

[0019] The beneficial effects of this invention are: This invention improves performance through the synergistic use of etching and deposition processes, enhancing both structural compatibility and surface modification. First, a stepwise composite etching process is employed: etching is first performed in a hydrochloric acid solution, followed by pore expansion and activation in a composite acid system containing specific surfactants and other additives. Subsequently, the activated etched foil undergoes electrochemical deposition, ultimately yielding an aluminum electrode foil with high specific capacity, robust structure, and good voltage resistance. The entire process of this invention is simple to operate, requires low equipment investment, and is suitable for large-scale production. Detailed Implementation

[0020] To further illustrate the technical means and effects adopted by the present invention to achieve the intended purpose, the following detailed description of the specific implementation methods, structures, features and effects of the present invention, in conjunction with embodiments, is provided below.

[0021] It should be noted that, unless otherwise specified, the present invention does not specifically limit the source of the raw materials used in the following embodiments. Commercially available products or products prepared by conventional preparation methods that are well known to those skilled in the art can be used. Experimental methods that do not specify specific conditions are all conventional methods and conditions well known in the art.

[0022] The polyether-modified polysiloxane was purchased from Nanjing Tianyou Chemical Co., Ltd., A0002 organosilicon superwetting agent (polyether-modified polysiloxane); the weight-average molecular weight of polyacrylic acid is 5000~15000.

[0023] Example 1 S1, First Etching: The aluminum foil was subjected to electrochemical etching in a 2 mol / L hydrochloric acid etching solution at a current density of 0.3 A / cm². 2 The etching process was carried out at 70°C for 90 seconds, followed by rinsing with anhydrous ethanol. S2, Composite Pore Enlargement and Activation: The aluminum foil after one etching was placed in a mixed pore-expanding solution containing surfactant and compound acid, and treated at 70℃ for 120s for pore-expanding and activation treatment. The mixed pore-expanding solution contained 1 mol / L sulfuric acid, 0.5 mol / L hydrochloric acid, 0.2 mol / L phosphoric acid and 1 g / L Triton X-100, and a modified corrosion inhibitor accounting for 2.5% of the total mass of the mixed pore-expanding solution. The modified corrosion inhibitor was polyacrylic acid, polyether modified polysiloxane and isopropanol in a weight ratio of 1:0.4:0.8. S3, Electrochemical Deposition: By weight, 4 parts of ammonium fluorotitanate are dissolved in 80 parts of ethylene glycol to form solution A. Then, 1 part of polystyrene sulfonic acid, 1 part of polyvinylpyrrolidone, 0.8 parts of polyethylene glycol-400 and 8 parts of deionized water are mixed to form solution B. Solution B is added to solution A and stirred thoroughly to obtain a deposition solution. The aluminum foil obtained in step S2 is used as the cathode and placed in the deposition solution for electrochemical deposition. The electrochemical deposition conditions are: temperature 30℃, voltage 80V, and time 50min. S4. Heat annealing: The aluminum foil that has undergone step S3 is annealed at 500°C for 90 seconds. S5. Formation treatment: The aluminum foil that has undergone step S4 is subjected to a formation treatment in an aqueous solution containing 80 g / L ammonium adipate to obtain the aluminum electrode foil. The temperature is 85°C, the voltage is 100 V, and the time is 30 min.

[0024] Example 2 The process is basically the same as in Example 1, except that the modified corrosion inhibitor in step S2 is polyacrylic acid, alkyl-terminated polyether modified polysiloxane and isopropanol in a weight ratio of 1:0.3:0.5.

[0025] Example 3 The process is basically the same as in Example 1, except that the modified corrosion inhibitor in step S2 is polyacrylic acid, alkyl-terminated polyether modified polysiloxane and isopropanol in a weight ratio of 1:0.5:1.0.

[0026] Example 4 It is basically the same as Example 1, except that the modified corrosion inhibitor accounts for 1.5% of the total mass of the mixed pore-expanding liquid in step S2.

[0027] Example 5 It is basically the same as Example 1, except that the modified corrosion inhibitor accounts for 3.5% of the total mass of the mixed pore-expanding liquid in step S2.

[0028] Example 6 It is basically the same as Example 1, except that the modified corrosion inhibitor accounts for 0.5% of the total mass of the mixed pore-expanding liquid in step S2.

[0029] Comparative Example 1 It is basically the same as Example 1, except that the modified corrosion inhibitor is not included in the pore-expanding solution in step S2.

[0030] Comparative Example 2 The process is basically the same as in Example 1, except that in step S2, the modified corrosion inhibitor is polyacrylic acid, Triton X-100 and isopropanol in a weight ratio of 1:0.4:0.8 (i.e., the polyether modified polysiloxane is replaced by a conventional surfactant).

[0031] Comparative Example 3 It is basically the same as Example 1, except that the modified corrosion inhibitor in step S2 does not contain polyacrylic acid, but is a polyether-modified polysiloxane and isopropanol with a weight ratio of 0.4:0.8.

[0032] Comparative Example 4 It is basically the same as Example 1, except that the modified corrosion inhibitor in step S2 is polyacrylic acid and isopropanol in a weight ratio of 1:0.8.

[0033] Comparative Example 5 It is basically the same as Example 1, except that the modified corrosion inhibitor in step S2 is polyacrylic acid, alkyl-terminated polyether modified polysiloxane and ethanol in a weight ratio of 1:0.4:0.8.

[0034] Comparative Example 6 It is basically the same as Example 1, except that polystyrene sulfonic acid was not added in step S3.

[0035] Comparative Example 7 It is basically the same as Example 1, except that the surfactant Triton X-100 was not added in step S2.

[0036] Performance testing: 1. Specific volume: Refer to SJ / T1140-2012 and use a specific volume tester to determine the specific volume; 2. Referring to SJ / T11140-2022, the withstand voltage value was tested, and the test results are shown in the table below:

[0037] Based on the data above, it can be seen that Example 1 has the highest specific volume, reaching 1.26 μF / cm³. 2 This achieved optimal pore-expansion effect and synergy with subsequent deposition. In Example 2, the proportion of polyether-modified polysiloxane was too low, resulting in insufficient hydrophobic shielding effect and thus a reduced specific volume. The specific volume of Example 3 was 1.19 μF / cm³. 2 Because the proportion of polyether-modified polysiloxane was too high, the orifices were excessively passivated. In Example 4, the total amount of corrosion inhibitor was lower than in Example 1, resulting in weaker surface corrosion control. In Example 5, the total amount of corrosion inhibitor was higher than in Example 1, therefore the adsorption layer was slightly thicker, and thus the specific volume was reduced. In Example 6, the total amount of corrosion inhibitor added was 0.5%, and the specific volume was only 1.02 μF / cm. 2 The values ​​were below the optimal range, demonstrating that a total addition of 1.5-3.5% is crucial for ensuring the quality of the expanded pores. Comparative Example 1 had the lowest specific volume, indicating that the modified corrosion inhibitor is indispensable; the specific volumes of Comparative Examples 2-5 were all lower than those of Example 1, indicating that the modified corrosion inhibitor used in this invention has a synergistic effect.

[0038] The withstand voltage values ​​of all examples and comparative examples were within the range of 618~627V, showing overall stable withstand voltage. Comparative Example 7 had the lowest withstand voltage at 618V, and was the only one below 620V among all groups. This indicates a synergistic wetting effect between Triton X-100 and the polyether-modified polysiloxane. Without Triton X-100, the dispersibility and stability of the polyether-modified polysiloxane in the pore-expanding solution decreased, resulting in insufficient wetting of some pores, poor coverage of the subsequent electrodeposition layer, and the formation of weak points for breakdown, thus reducing the withstand voltage. In Comparative Example 6, the lack of polystyrene sulfonic acid led to a decrease in the conductivity of the deposition solution, poor uniformity of the deposition layer, and the presence of localized micropores or defects, thereby reducing the withstand voltage.

[0039] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for preparing high-specific-capacitance aluminum electrode foil based on composite etching and electrochemical deposition, characterized in that, Includes the following steps: S1, First Etching: The aluminum foil was placed in an etching solution for electrochemical etching, and then rinsed with anhydrous ethanol after etching was completed. S2, Composite Pore Enlargement and Activation: The aluminum foil after one etching is placed in a mixed pore-expanding solution containing surfactant and compound acid, and treated at 60~80℃ for 60~180s for pore-expanding and activation treatment. S3, Electrochemical Deposition: The aluminum foil that has undergone step S2 is used as the cathode and placed in a deposition solution for electrochemical deposition. The deposition solution is a homogeneous solution composed of a titanium source, an organic solvent, a conductive additive polystyrene sulfonic acid, and water. S4. Heat annealing: The aluminum foil that has undergone step S3 is annealed at 400~600℃ for 30~120s; S5. Formation treatment: The aluminum foil obtained in step S4 is subjected to a formation treatment in an aqueous solution containing boric acid with a concentration of 30-80 g / L or ammonium adipate with a concentration of 50-100 g / L to obtain the aluminum electrode foil.

2. The method for preparing high-specific-capacitance aluminum electrode foil based on composite etching and electrochemical deposition according to claim 1, characterized in that, In step S1, the etching solution is hydrochloric acid with a concentration of 1~3 mol / L, and the current density during electrochemical etching is 0.1~0.5 A / cm. 2 Temperature 60~80℃, time 30~120s.

3. The method for preparing high-specific-capacitance aluminum electrode foil based on composite etching and electrochemical deposition according to claim 1, characterized in that, In step S2, the mixed pore-expanding solution contains 0.5~2 mol / L sulfuric acid, 0.1~1 mol / L hydrochloric acid, 0.05~0.5 mol / L phosphoric acid and 0.5~2 g / L surfactant.

4. The method for preparing high-specific-capacitance aluminum electrode foil based on composite etching and electrochemical deposition according to claim 1, characterized in that, In step S2, the mixed pore-expanding liquid further includes 1.5~3.5% of a modified corrosion inhibitor by weight of the total mass of the mixed pore-expanding liquid. The modified corrosion inhibitor is polyacrylic acid, polyether-modified polysiloxane and isopropanol in a weight ratio of 1:(0.3~0.5):(0.5~1.0).

5. The method for preparing high-specific-capacitance aluminum electrode foil based on composite etching and electrochemical deposition according to claim 1, characterized in that, In step S2, the surfactant is at least one of sodium dodecyl sulfate, hexadecyltrimethylammonium bromide, and Triton X-100.

6. The method for preparing high-specific-capacitance aluminum electrode foil based on composite etching and electrochemical deposition according to claim 1, characterized in that, In step S3, the electrochemical deposition conditions are: temperature 10~50℃, voltage 30~100V, and time 30~60min.

7. The method for preparing high-specific-capacitance aluminum electrode foil based on composite etching and electrochemical deposition according to claim 1, characterized in that, In step S3, the deposition solution contains, by weight, 3-5 parts of titanium-derived ammonium fluorotitanate, 0.5-1.5 parts of polystyrene sulfonic acid, 0.5-2.0 parts of polyvinylpyrrolidone, 75-90 parts of ethylene glycol, 5-10 parts of deionized water, and 0.5-1 parts of polyethylene glycol-400.

8. The method for preparing high-specific-capacitance aluminum electrode foil based on composite etching and electrochemical deposition according to claim 1, characterized in that, In step S3, the preparation method of the deposition solution is as follows: first, the titanium source is dissolved in ethylene glycol to form solution A, then polystyrene sulfonic acid, polyvinylpyrrolidone, polyethylene glycol-400 and deionized water are mixed to form solution B, solution B is added to solution A and stirred thoroughly to obtain the deposition solution.

9. The method for preparing high-specific-capacitance aluminum electrode foil based on composite etching and electrochemical deposition according to claim 1, characterized in that, In step S5, the conditions for the formation treatment are: temperature 70~95℃, voltage 50~150V, and time 10~40min.

10. A high-specific-capacitance aluminum electrode foil based on composite etching and electrochemical deposition, characterized in that, The preparation method according to any one of claims 1 to 9 is used.

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