Anhydrous deep eutectic solvent etchant, high voltage electronic aluminum foil and aluminum electrolytic capacitor

Abstract

This application relates to the field of aluminum foil etching technology, providing an anhydrous deep eutectic solvent etching solution, high-voltage electronic aluminum foil, and aluminum electrolytic capacitors. This etching solution completely eliminates deionized water, using three types of deep eutectic solvents as the dispersion system: L-proline and oxalic acid / malonic acid in a 1:2~2:1 ratio, β-cyclodextrin and succinic acid in a 1:3~1:5 ratio, and menthol and camphor in a 1:1~1:2 ratio; the system contains 0.4~0.6 mol / L hydrochloric acid and 3.2~3.8 mol / L sulfuric acid. Utilizing the stable hydrogen-bonded structure and suitable viscosity of the eutectic solvent, the diffusion rate of etching ions can be precisely controlled, ensuring uniform etching of the aluminum foil and eliminating problems such as localized over-etching, under-etching, and pore collapse. The finished aluminum foil exhibits regular and dense micropores, with an effective specific surface area increased by 5%~10% compared to traditional water-based processes, a specific capacity increased by 4%~10%, and significantly optimized pressure resistance and structural stability.

Description

Technical Field

[0001] This application belongs to the field of aluminum foil etching technology, and particularly relates to an anhydrous deep eutectic solvent etching solution, a method for preparing high voltage electronic aluminum foil, high voltage electronic aluminum foil and aluminum electrolytic capacitor. Background Technology

[0002] The key performance characteristics of high-voltage aluminum electrolytic capacitors are determined by the specific capacitance of the anode aluminum foil. The specific capacitance of the aluminum foil is positively correlated with its effective specific surface area. Electrochemical etching to create pores is a crucial process for expanding the specific surface area of ​​the aluminum foil and preparing high-voltage electrode aluminum foil. Currently, industrial production generally uses pure water as a solvent to prepare a composite acidic aqueous solution containing 0.4–0.6 mol / L hydrochloric acid and 3.0–4.0 mol / L sulfuric acid, and operates at 65–75℃ and 200–300 mA / cm². 2 Under certain conditions, high-purity aluminum foil is subjected to DC electrochemical corrosion. By relying on acidic electrolyte etching, tunnel micropores are constructed on the surface of the aluminum foil, thereby improving the specific surface area and specific capacity.

[0003] Existing water-based corrosion systems have several insurmountable technological shortcomings: First, after rolling and heat treatment, high-purity aluminum foil exhibits uneven grain size and significant differences in the thickness of the original oxide film on its surface. Pure water is highly polar and wets too quickly, making it difficult to control the diffusion rate of corrosion ions on the aluminum foil surface. Protruding grains are prone to over-corrosion, while recessed areas are under-corroded, resulting in a disordered micropore arrangement, large pore size dispersion, and a high proportion of local blank non-pore areas. This limits the effective specific surface area of ​​the aluminum foil, making it difficult to meet the high specific capacitance and high withstand voltage requirements of high-end high-voltage capacitors. Second, during corrosion in aqueous systems, local hydrogen evolution and acid accumulation are prone to occur, inducing micropore collapse and pore wall damage, which deteriorates the mechanical strength and withstand voltage characteristics of the aluminum foil. Third, the inorganic acids in aqueous electrolytes are highly volatile, and their concentration continuously decreases during operation, resulting in poor process repeatability and high post-treatment costs for corrosion waste.

[0004] In summary, traditional water-based etching formulations suffer from uneven corrosion pore distribution, limited improvement in specific surface area, and low porosity, making it difficult to meet the industrialization requirements of high-end high-pressure aluminum foil with high specific volume, high stability, and low cost for mass production. There is an urgent need to develop new anhydrous etching solutions to address these pain points. Summary of the Invention

[0005] The purpose of this application is to provide an anhydrous deep eutectic solvent etching solution, which aims to solve the problems of uneven pore distribution, limited specific surface area improvement, and low pore formation efficiency of pure water-based etching solutions in the prior art.

[0006] The embodiments of this application are implemented as follows: an anhydrous deep eutectic solvent etching solution is used for electrochemical etching of high-voltage electronic aluminum foil, comprising hydrochloric acid and sulfuric acid, characterized in that the etching solution system does not contain deionized water, and the dispersing solvent is a deep eutectic solvent; the deep eutectic solvent is selected from any one of L-proline-dicarboxylic acid eutectic, β-cyclodextrin-succinic acid eutectic, and menthol-camphor hydrophobic eutectic; The corrosive solution contains hydrochloric acid at a molar concentration of 0.4–0.6 mol / L and sulfuric acid at a molar concentration of 3.2–3.8 mol / L. In the L-proline-dicarboxylic acid eutectic, the molar ratio of L-proline to dicarboxylic acid is 1:2 to 2:1, and the dicarboxylic acid is oxalic acid or malonic acid. In the β-cyclodextrin-succinic acid eutectic, the molar ratio of β-cyclodextrin to succinic acid is 1:3 to 1:5. In the menthol-camphor hydrophobic eutectic, the molar ratio of menthol to camphor is 1:1 to 1:2.

[0007] Another objective of this application is a method for preparing high-voltage electronic aluminum foil, which uses the above-mentioned anhydrous deep eutectic solvent etching solution to electrochemically etch high-purity aluminum foil, including: High-purity aluminum foil with a purity of ≥99.99% was selected and ultrasonically cleaned sequentially with anhydrous ethanol and deionized water, followed by drying. The pretreated aluminum foil was used as the anode and the carbon plate as the cathode, and the electrochemical corrosion was carried out in the anhydrous deep eutectic solvent corrosion solution. The etched aluminum foil is removed, and after washing and chemical formation treatment, a high-voltage electronic aluminum foil with uniform porosity is obtained.

[0008] Another objective of this application is to provide a high-voltage electronic aluminum foil, which is prepared by the method described above.

[0009] Another objective of this application is to provide an aluminum electrolytic capacitor, wherein the anode electrode of the aluminum electrolytic capacitor is made of the aforementioned high-voltage electronic aluminum foil.

[0010] Compared with the prior art, this application has the following significant advantages: This application utilizes three types of deep eutectic solvents—L-proline-dicarboxylic acid, β-cyclodextrin-succinic acid, and menthol-camphor—to completely replace pure water in the preparation of the etching solution. Leveraging the suitable viscosity and stable hydrogen bond framework of the eutectic solvent, the diffusion rate of corrosion ions can be smoothly controlled, ensuring uniform and synchronous etching of the aluminum foil surface. This effectively avoids problems such as localized over-etching, under-etching, and pore collapse, resulting in micropores with regular diameters, dense arrangement, and intact pore walls. The effective specific surface area of ​​the aluminum foil is increased by 5%–10% compared to traditional water-based processes. The regular pore structure further enhances the energy storage capacity of the aluminum foil, increasing the specific capacity by 4%–10%. Voltage withstand performance and structural stability are simultaneously improved, meeting the requirements for manufacturing high-end high-voltage aluminum electrolytic capacitors. Furthermore, the solvent is not easily volatile at high temperatures, the electrolyte composition is stable, production repeatability is excellent, and the waste liquid can be recycled, making production environmentally friendly and cost-effective, facilitating industrial-scale mass production. Additionally, by adjusting the eutectic ratio, acid concentration, and etching process parameters, high-voltage electronic aluminum foils of various specifications and voltage withstand capabilities can be processed, demonstrating good process versatility. Detailed Implementation

[0011] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0012] To address the shortcomings of traditional hydrochloric acid-sulfuric acid aqueous solution corrosion systems, which often result in disordered pore distribution, significant pore size variations, and limited improvement in specific surface area for aluminum foil, this application replaces pure water with three types of eutectic solvents as the corrosion liquid matrix, and combines them with hydrochloric acid and sulfuric acid to form a novel corrosion system. The eutectic solvents are selected from L-proline-dicarboxylic acid, β-cyclodextrin-succinic acid, and menthol-camphor. By adjusting the eutectic ratio, acid-base concentration, and electrochemical corrosion parameters, the corrosion rate and pore uniformity of the aluminum foil are precisely controlled. Utilizing the unique hydrogen-bonding structure and adjustable viscosity of the eutectic solvent, the corrosion medium can spread uniformly on the aluminum foil surface, offsetting corrosion differences caused by uneven substrate grains and oxide films, and overcoming the drawbacks of over-corrosion and under-corrosion in traditional processes. The resulting aluminum foil exhibits uniform micropore distribution, regular pore size, and intact pore walls, with a significant improvement in effective specific surface area and finished product specific capacitance. Furthermore, the corrosion system boasts excellent thermal stability, low toxicity, environmental friendliness, and recyclable waste liquid, making it suitable for large-scale industrial production.

[0013] Specifically, this application provides an anhydrous deep eutectic solvent etching solution for electrochemical etching of high-voltage electronic aluminum foil. It contains hydrochloric acid and sulfuric acid, and the etching solution system does not contain deionized water. The dispersing solvent is a deep eutectic solvent. The deep eutectic solvent is selected from any one of L-proline-dicarboxylic acid eutectic, β-cyclodextrin-succinic acid eutectic, and menthol-camphor hydrophobic eutectic.

[0014] The corrosive solution contains hydrochloric acid with a molar concentration of 0.4-0.6 mol / L and sulfuric acid with a molar concentration of 3.2-3.8 mol / L.

[0015] In the L-proline-dicarboxylic acid eutectic, the molar ratio of L-proline to dicarboxylic acid is 1:2 to 2:1, and the dicarboxylic acid is oxalic acid or malonic acid.

[0016] In the β-cyclodextrin-succinic acid eutectic, the molar ratio of β-cyclodextrin to succinic acid is 1:3 to 1:5.

[0017] In the menthol-camphor hydrophobic eutectic, the molar ratio of menthol to camphor is 1:1 to 1:2.

[0018] Preferably, when the deep eutectic solvent is an L-proline-dicarboxylic acid eutectic, the molar concentration of hydrochloric acid in the etching solution is 0.5~0.6 mol / L and the molar concentration of sulfuric acid is 3.4~3.6 mol / L. When the hydrochloric acid concentration is below 0.5 mol / L, the supply of chloride ions in the system is insufficient, the nucleation driving force for pitting corrosion of aluminum foil is insufficient, the resulting tunnel hole diameter is small, and the corrosion uniformity of the foil surface is poor. When the sulfuric acid concentration is below 3.4 mol / L, the ability of sulfate ions to build a passivation film on the hole wall is insufficient, the lateral corrosion of the sidewall is aggravated, the hole diameter is large, and the tunnel hole density decreases. When the hydrochloric acid concentration is above 0.6 mol / L, excessive chloride ions destroy the passivation layer on the hole wall, adjacent tunnel holes are prone to interconnection, and the aluminum substrate is severely degraded by excessive dissolution.

[0019] Preferably, when the deep eutectic solvent is a β-cyclodextrin-succinic acid eutectic, the molar concentration of hydrochloric acid in the etching solution is 0.4 mol / L and the molar concentration of sulfuric acid is 3.8 mol / L. When the hydrochloric acid concentration is below 0.4 mol / L, chloride ion deficiency leads to incomplete nucleation, resulting in small tunnel pore sizes and poor corrosion uniformity on the foil surface. When the sulfuric acid concentration is below 3.8 mol / L, insufficient passivation strength of the pore walls leads to uncontrolled transverse corrosion, resulting in large pore sizes and decreased pore density. When the hydrochloric acid concentration is above 0.4 mol / L, excessive chloride ions induce numerous co-pores, causing severe over-corrosion of the aluminum substrate. When the sulfuric acid concentration is above 3.8 mol / L, excessive sulfate ions form a dense and thick passivation film on the aluminum foil surface and pore openings, preventing contact between the corrosive medium and the aluminum substrate, and inhibiting tunnel pore initiation and depth growth.

[0020] Preferably, when the deep eutectic solvent is a menthol-camphor hydrophobic eutectic, the molar concentration of hydrochloric acid in the etching solution is 0.6 mol / L and the molar concentration of sulfuric acid is 3.2 mol / L. If the hydrochloric acid concentration is below 0.6 mol / L, there are insufficient effective film-breaking ions, resulting in smaller tunnel pore sizes and uneven overall corrosion. If the sulfuric acid concentration is below 3.2 mol / L, the passivation film is not fully formed, sidewall corrosion is aggravated, and the pore size is coarser with decreased pore density. If the hydrochloric acid concentration is above 0.6 mol / L, excessive chloride ions exacerbate the co-pore phenomenon, leading to excessive dissolution and loss of the aluminum foil substrate. If the sulfuric acid concentration is above 3.2 mol / L, a thick passivation film quickly forms on the aluminum foil surface, isolating the etching solution and hindering continuous pore formation.

[0021] More preferably, the deep eutectic solvent is an L-proline-oxalic acid eutectic, and the molar ratio of L-proline to oxalic acid is 2:1. In the etching solution, the molar concentration of hydrochloric acid is 0.5 mol / L, and the molar concentration of sulfuric acid is 3.5 mol / L.

[0022] The method for preparing the deep eutectic solvent is as follows: L-proline is mixed with dicarboxylic acid, or β-cyclodextrin with succinic acid, or menthol with camphor, and stirred at 50-80°C and 300-500 r / min until the material is completely melted into a transparent and homogeneous liquid. The mixture is then cooled to room temperature to obtain a deep eutectic solvent.

[0023] The anhydrous deep eutectic solvent etching solution is obtained by slowly adding hydrochloric acid and sulfuric acid to the deep eutectic solvent and stirring at a constant temperature of 40~60℃ for 20~40 minutes until well mixed.

[0024] This application also provides a method for preparing high-voltage electronic aluminum foil, which uses the above-mentioned anhydrous deep eutectic solvent etching solution to electrochemically etch high-purity aluminum foil, including the following steps: S1. Aluminum foil pretreatment: Select high-purity aluminum foil with a purity ≥ 99.99%, and clean it with anhydrous ethanol and deionized water in sequence by ultrasonic cleaning and drying. S2. Electrochemical corrosion: The pretreated aluminum foil is used as the anode and the carbon plate is used as the cathode, and electrochemical corrosion is carried out in the anhydrous deep eutectic solvent corrosion solution. S3. Post-processing: Remove the etched aluminum foil, and after washing and chemical formation treatment, obtain high-voltage electronic aluminum foil with uniform porosity.

[0025] Preferably, the pretreated aluminum foil is used as the anode and the carbon plate as the cathode, and electrochemical corrosion is carried out in the anhydrous deep eutectic solvent etching solution, with the corrosion temperature controlled at 68~72℃ and the current density at 200~250mA / cm². 2 DC constant current corrosion for 90~110s.

[0026] More preferably, the corrosion temperature is 70°C and the current density is 250 mA / cm².2 DC constant current corrosion for 90s.

[0027] The following detailed embodiments illustrate the anhydrous deep eutectic solvent etching solution and high-voltage electronic aluminum foil provided in this application. Unless otherwise specified, the experimental methods used in the embodiments are conventional methods; and the materials and reagents used, unless otherwise specified, are commercially available conventional products.

[0028] Example 1 1. Preparation of eutectic solvent: L-proline was selected as the hydrogen bond acceptor and oxalic acid as the hydrogen bond donor. They were mixed in a molar ratio of 1:2 and placed in a constant temperature oil bath at 60℃. The mixture was stirred at 400r / min for 30min until the system was completely transparent and homogeneous. After cooling to room temperature, a novel L-proline-oxalic acid eutectic solvent was obtained.

[0029] 2. Preparation of etching solution: Slowly add hydrochloric acid and sulfuric acid to the above eutectic solvent, control the concentration of hydrochloric acid to 0.5M and the concentration of sulfuric acid to 3.5M, stir at 50℃ for 30min to obtain a homogeneous and stable anhydrous deep eutectic solvent etching solution.

[0030] 3. Aluminum foil pretreatment: Select high-purity aluminum foil with a purity of 99.99%, ultrasonically clean it with anhydrous ethanol for 10 minutes, ultrasonically clean it with deionized water for 10 minutes, and dry it for later use.

[0031] 4. Electrochemical corrosion: Using aluminum foil as the anode and carbon plate as the cathode, the sample is placed in the anhydrous deep eutectic solvent corrosion solution prepared above, with the temperature controlled at 70℃ and the current density at 250mA / cm². 2 Constant current corrosion for 90 seconds.

[0032] Example 2 1. Preparation of eutectic solvent: L-proline was selected as the hydrogen bond acceptor and oxalic acid as the hydrogen bond donor. They were mixed in a molar ratio of 2:1 and placed in a constant temperature oil bath at 60℃. The mixture was stirred at 400r / min for 30min until the system was completely transparent and homogeneous. The mixture was then cooled to room temperature to obtain a novel L-proline-oxalic acid eutectic solvent.

[0033] 2. Preparation of etching solution: Slowly add hydrochloric acid and sulfuric acid to the above eutectic solvent, control the concentration of hydrochloric acid to 0.5M and the concentration of sulfuric acid to 3.5M, stir at 50℃ for 30min to obtain a homogeneous and stable anhydrous deep eutectic solvent etching solution.

[0034] 3. Pretreatment and corrosion process: Same as in Example 1, corrosion temperature 70℃, current density 250 mA / cm². 2 Corrosion time: 90 seconds.

[0035] Example 3 1. Preparation of eutectic solvent: L-proline was selected as the hydrogen bond acceptor and malonic acid as the hydrogen bond donor. They were mixed in a molar ratio of 1:2 and placed in a constant temperature oil bath at 60℃. The mixture was stirred at 400r / min for 30min until the system was completely transparent and homogeneous. After cooling to room temperature, a novel L-proline-malonic acid eutectic solvent was obtained.

[0036] 2. Preparation of etching solution: Slowly add hydrochloric acid and sulfuric acid to the above eutectic solvent, control the concentration of hydrochloric acid to 0.5M and the concentration of sulfuric acid to 3.5M, stir at 50℃ for 30min to obtain a homogeneous and stable anhydrous deep eutectic solvent etching solution.

[0037] 3. Pretreatment and corrosion process: Same as in Example 1, corrosion temperature 70℃, current density 250 mA / cm². 2 Corrosion time: 90 seconds.

[0038] Example 4 1. Preparation of eutectic solvent: L-proline was selected as the hydrogen bond acceptor and malonic acid as the hydrogen bond donor. They were mixed in a molar ratio of 2:1 and placed in a constant temperature oil bath at 60℃. The mixture was stirred at 400r / min for 30min until the system was completely transparent and homogeneous. The mixture was then cooled to room temperature to obtain a novel L-proline-malonic acid eutectic solvent.

[0039] 2. Preparation of etching solution: Slowly add hydrochloric acid and sulfuric acid to the above eutectic solvent, control the concentration of hydrochloric acid to 0.5M and the concentration of sulfuric acid to 3.5M, stir at 50℃ for 30min to obtain a homogeneous and stable anhydrous deep eutectic solvent etching solution.

[0040] 3. Pretreatment and corrosion process: Same as in Example 1, corrosion temperature 70℃, current density 250 mA / cm². 2 Corrosion time: 90 seconds.

[0041] Example 5 1. Preparation of eutectic solvent: β-cyclodextrin was selected as hydrogen bond acceptor and succinic acid as hydrogen bond donor. They were mixed in a molar ratio of 1:3 and placed in a constant temperature oil bath at 70℃. The mixture was stirred at 450r / min for 40min. After the system became completely transparent, it was cooled to room temperature to obtain β-cyclodextrin-succinic acid eutectic solvent.

[0042] 2. Preparation of etching solution: Slowly add hydrochloric acid and sulfuric acid to the above eutectic solvent, adjust the concentration of hydrochloric acid to 0.4M and the concentration of sulfuric acid to 3.8M, stir at 45℃ for 35min to obtain a homogeneous and stable anhydrous deep eutectic solvent etching solution.

[0043] 3. Pretreatment and corrosion process: Same as in Example 1, corrosion temperature 68℃, current density 280 mA / cm². 2 Corrosion time: 80 seconds.

[0044] Example 6 1. Preparation of eutectic solvent: β-cyclodextrin was selected as hydrogen bond acceptor and succinic acid as hydrogen bond donor. They were mixed at a molar ratio of 1:4 and placed in a constant temperature oil bath at 70℃. The mixture was stirred at 450r / min for 40min. After the system became completely transparent, it was cooled to room temperature to obtain β-cyclodextrin-succinic acid eutectic solvent.

[0045] 2. Preparation of etching solution: Slowly add hydrochloric acid and sulfuric acid to the above eutectic solvent, adjust the concentration of hydrochloric acid to 0.4M and the concentration of sulfuric acid to 3.8M, stir at 45℃ for 35min to obtain a homogeneous and stable anhydrous deep eutectic solvent etching solution.

[0046] 3. Pretreatment and corrosion process: Same as in Example 1, corrosion temperature 68℃, current density 280 mA / cm². 2 Corrosion time: 80 seconds.

[0047] Example 7 1. Preparation of eutectic solvent: β-cyclodextrin was selected as hydrogen bond acceptor and succinic acid as hydrogen bond donor. They were mixed at a molar ratio of 1:5 and placed in a constant temperature oil bath at 70℃. The mixture was stirred at 450r / min for 40min. After the system became completely transparent, it was cooled to room temperature to obtain β-cyclodextrin-succinic acid eutectic solvent.

[0048] 2. Preparation of etching solution: Slowly add hydrochloric acid and sulfuric acid to the above eutectic solvent, adjust the concentration of hydrochloric acid to 0.4M and the concentration of sulfuric acid to 3.8M, stir at 45℃ for 35min to obtain a homogeneous and stable anhydrous deep eutectic solvent etching solution.

[0049] 3. Pretreatment and corrosion process: Same as in Example 1, corrosion temperature 68℃, current density 280 mA / cm². 2 Corrosion time: 80 seconds.

[0050] Example 8 1. Preparation of eutectic solvent: Menthol and camphor were mixed in a molar ratio of 1:1 and stirred at 350 r / min for 25 min at a constant temperature of 55℃ to obtain a homogeneous hydrophobic eutectic solvent.

[0051] 2. Preparation of etching solution: Slowly add hydrochloric acid and sulfuric acid to the above eutectic solvent, adjust the concentration of hydrochloric acid to 0.6M and the concentration of sulfuric acid to 3.2M, stir at 60℃ for 25 minutes to obtain a homogeneous and stable anhydrous deep eutectic solvent etching solution.

[0052] 3. Pretreatment and corrosion process: Same as in Example 1, corrosion temperature 72℃, current density 220mA / cm². 2 Corrosion time: 110s.

[0053] Example 9 1. Preparation of eutectic solvent: Menthol and camphor were mixed in a molar ratio of 1:2 and stirred at 350 r / min for 25 min at a constant temperature of 55℃ to obtain a homogeneous hydrophobic eutectic solvent.

[0054] 2. Preparation of etching solution: Slowly add hydrochloric acid and sulfuric acid to the above eutectic solvent, adjust the concentration of hydrochloric acid to 0.6M and the concentration of sulfuric acid to 3.2M, stir at 60℃ for 25 minutes to obtain a homogeneous and stable anhydrous deep eutectic solvent etching solution.

[0055] 3. Pretreatment and corrosion process: Same as in Example 1, corrosion temperature 72℃, current density 220mA / cm². 2 Corrosion time: 110s.

[0056] Example 10 1. Preparation of eutectic solvent: L-proline was selected as the hydrogen bond acceptor and oxalic acid as the hydrogen bond donor. They were mixed in a molar ratio of 1:2 and placed in a constant temperature oil bath at 60℃. The mixture was stirred at 400r / min for 30min until the system was completely transparent and homogeneous. After cooling to room temperature, a novel L-proline-oxalic acid eutectic solvent was obtained.

[0057] 2. Preparation of etching solution: Slowly add hydrochloric acid and sulfuric acid to the above eutectic solvent, control the concentration of hydrochloric acid to 0.5M and the concentration of sulfuric acid to 3.5M, and stir at 50℃ for 30 minutes to obtain a homogeneous and stable eutectic solvent etching solution.

[0058] 3. Pretreatment and corrosion process: Same as in Example 1, corrosion temperature 70℃, current density 280 mA / cm². 2 Corrosion time: 90 seconds.

[0059] Example 11 1. Preparation of eutectic solvent: L-proline was selected as the hydrogen bond acceptor and oxalic acid as the hydrogen bond donor. They were mixed in a molar ratio of 1:2 and placed in a constant temperature oil bath at 60℃. The mixture was stirred at 400r / min for 30min until the system was completely transparent and homogeneous. After cooling to room temperature, a novel L-proline-oxalic acid eutectic solvent was obtained.

[0060] 2. Preparation of etching solution: Slowly add hydrochloric acid and sulfuric acid to the above eutectic solvent, control the concentration of hydrochloric acid to 0.4M and the concentration of sulfuric acid to 3.6M, and stir at 50℃ for 30 minutes to obtain a homogeneous and stable eutectic solvent etching solution.

[0061] 3. Electrochemical corrosion: Using aluminum foil as the anode and carbon plate as the cathode, the plates are placed in a corrosion solution, with the temperature controlled at 70℃ and the current density at 250mA / cm². 2 Constant current corrosion for 90 seconds.

[0062] Example 12 1. Preparation of eutectic solvent: L-proline was selected as the hydrogen bond acceptor and malonic acid as the hydrogen bond donor. They were mixed in a molar ratio of 1:2 and placed in a constant temperature oil bath at 60℃. The mixture was stirred at 400r / min for 30min until the system was completely transparent and homogeneous. After cooling to room temperature, a novel L-proline-malonic acid eutectic solvent was obtained.

[0063] 2. Preparation of etching solution: Slowly add hydrochloric acid and sulfuric acid to the above eutectic solvent, control the concentration of hydrochloric acid to 0.6M and the concentration of sulfuric acid to 3.5M, and stir at 50℃ for 30 minutes to obtain a homogeneous and stable eutectic solvent etching solution.

[0064] 3. Electrochemical corrosion: Using aluminum foil as the anode and carbon plate as the cathode, the plates are placed in a corrosion solution, with the temperature controlled at 70℃ and the current density at 250mA / cm². 2 Constant current corrosion for 90 seconds.

[0065] Example 13 1. Preparation of eutectic solvent: L-proline was selected as the hydrogen bond acceptor and malonic acid as the hydrogen bond donor. They were mixed in a molar ratio of 1:2 and placed in a constant temperature oil bath at 60℃. The mixture was stirred at 400r / min for 30min until the system was completely transparent and homogeneous. After cooling to room temperature, a novel L-proline-malonic acid eutectic solvent was obtained.

[0066] 2. Preparation of etching solution: Slowly add hydrochloric acid and sulfuric acid to the above eutectic solvent, control the concentration of hydrochloric acid to 0.7M and the concentration of sulfuric acid to 3.5M, and stir at 55℃ for 30 minutes to obtain a homogeneous and stable eutectic solvent etching solution.

[0067] 3. Electrochemical corrosion: Using aluminum foil as the anode and carbon plate as the cathode, the plates are placed in a corrosion solution, with the temperature controlled at 70℃ and the current density at 250mA / cm². 2 Constant current corrosion for 90 seconds.

[0068] Example 14 1. Preparation of eutectic solvent: β-cyclodextrin was selected as hydrogen bond acceptor and succinic acid as hydrogen bond donor. They were mixed at a molar ratio of 1:4 and placed in a constant temperature oil bath at 70℃. The mixture was stirred at 450r / min for 40min. After the system became completely transparent, it was cooled to room temperature to obtain β-cyclodextrin-succinic acid eutectic solvent.

[0069] 2. Preparation of etching solution: Slowly add hydrochloric acid and sulfuric acid to the above eutectic solvent, adjust the concentration of hydrochloric acid to 0.4M and the concentration of sulfuric acid to 3.8M, stir at 45℃ for 35min to obtain a homogeneous and stable anhydrous deep eutectic solvent etching solution.

[0070] 3. Pretreatment and corrosion process: Same as in Example 1, corrosion temperature 70℃, current density 280 mA / cm². 2 Corrosion time: 80 seconds.

[0071] Example 15 1. Preparation of eutectic solvent: Menthol and camphor were mixed in a molar ratio of 1:1 and stirred at 350 r / min for 25 min at a constant temperature of 55℃ to obtain a homogeneous hydrophobic eutectic solvent.

[0072] 2. Preparation of etching solution: Slowly add hydrochloric acid and sulfuric acid to the above eutectic solvent, adjust the concentration of hydrochloric acid to 0.6M and the concentration of sulfuric acid to 3.2M, and stir at 60℃ for 25 minutes to prepare the etching solution.

[0073] 3. Pretreatment and corrosion process: Same as in Example 1, corrosion temperature 72℃, current density 250mA / cm². 2 Corrosion time: 90 seconds.

[0074] Example 16 1. Preparation of eutectic solvent: L-proline was selected as the hydrogen bond acceptor and oxalic acid as the hydrogen bond donor. They were mixed in a molar ratio of 1:2 and placed in a constant temperature oil bath at 60℃. The mixture was stirred at 400r / min for 30min until the system was completely transparent and homogeneous. After cooling to room temperature, a novel L-proline-oxalic acid eutectic solvent was obtained.

[0075] 2. Preparation of etching solution: Slowly add hydrochloric acid and sulfuric acid to the above eutectic solvent, control the concentration of hydrochloric acid to 0.5M and the concentration of sulfuric acid to 3.4M, and stir at 50℃ for 30 minutes to obtain a homogeneous and stable eutectic solvent etching solution.

[0076] 3. Aluminum foil pretreatment: Select high-purity aluminum foil with a purity of 99.99%, ultrasonically clean it with anhydrous ethanol for 10 minutes, ultrasonically clean it with deionized water for 10 minutes, and dry it for later use.

[0077] 4. Electrochemical corrosion: Using aluminum foil as the anode and carbon plate as the cathode, the plates are placed in a corrosion solution, with the temperature controlled at 70℃ and the current density at 250mA / cm². 2 Constant current corrosion for 90 seconds.

[0078] Comparative Example 1 (Traditional Pure Water System) A pure aqueous solution of 0.5M hydrochloric acid + 3.5M sulfuric acid was prepared for etching, and the pretreatment, etching temperature, current density, etching time and post-treatment process were exactly the same as in Example 1.

[0079] The high-voltage electronic aluminum foil samples prepared in Examples 1-15 and Comparative Example 1 were tested according to the industry standard SJ / T 11140-1997 for electrode foils for aluminum electrolytic capacitors. (The unformed foil was formed according to the formation process specified in the People's Republic of China Electronic Industry Standard SJ / T11140-1997: formation solution: deionized water (resistivity > 2 MΩ): 1000 ml; boric acid: 70 g; resistivity: (70 ℃ ± 2℃): 7500 Ω·cm ± 300 Ω·cm; pH value: (50℃ ± 2℃): 3.2 ± 1.0; formation voltage: 5200 V, to obtain high-voltage electronic aluminum foil samples). The morphology of the prepared aluminum foil samples was analyzed by scanning electron microscopy, and the specific surface area of ​​the aluminum foil tunnel pores was analyzed by Image-pro plus. The test results are shown in Table 1.

[0080] Table 1 Furthermore, in the preliminary experiments, this application conducted a series of studies on the effects of specific eutectic solvent ratios, corrosion solution concentrations, and electrochemical corrosion process parameters such as temperature, time, and current density on subsequent corrosion porosity under pre-electrochemical corrosion treatment conditions. The experimental conditions and corresponding test results are shown in Tables 2-4 below. It should be noted that the following comparative examples are all single-factor variation experiments based on the pre-electrochemical corrosion process of Example 2, including only changing the eutectic solvent ratio (Comparative Examples 2-14), or the corrosion solution concentration (Comparative Examples 14-31), or the electrochemical corrosion process parameters such as temperature, time, and current density (Comparative Examples 31-34) based on the process of Example 2.

[0081] Table 2 Table 3 Table 4 The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

[0082] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. An anhydrous deep eutectic solvent etching solution for electrochemical etching of high-voltage electronic aluminum foil, comprising hydrochloric acid and sulfuric acid, characterized in that, The corrosion solution system does not contain deionized water, and the dispersion solvent is a deep eutectic solvent; the deep eutectic solvent is selected from any one of L-proline-dicarboxylic acid eutectic, β-cyclodextrin-succinic acid eutectic, and menthol-camphor hydrophobic eutectic. The corrosive solution contains hydrochloric acid at a molar concentration of 0.4–0.6 mol / L and sulfuric acid at a molar concentration of 3.2–3.8 mol / L. In the L-proline-dicarboxylic acid eutectic, the molar ratio of L-proline to dicarboxylic acid is 1:2 to 2:1, and the dicarboxylic acid is oxalic acid or malonic acid. In the β-cyclodextrin-succinic acid eutectic, the molar ratio of β-cyclodextrin to succinic acid is 1:3 to 1:

5. In the menthol-camphor hydrophobic eutectic, the molar ratio of menthol to camphor is 1:1 to 1:

2.

2. The anhydrous deep eutectic solvent etching solution according to claim 1, characterized in that, When the deep eutectic solvent is L-proline-dicarboxylic acid eutectic, the molar concentration of hydrochloric acid in the etching solution is 0.5~0.6 mol / L and the molar concentration of sulfuric acid is 3.4~3.6 mol / L. When the deep eutectic solvent is β-cyclodextrin-succinic acid eutectic, the molar concentration of hydrochloric acid in the etching solution is 0.4 mol / L and the molar concentration of sulfuric acid is 3.8 mol / L. When the deep eutectic solvent is a menthol-camphor hydrophobic eutectic, the molar concentration of hydrochloric acid in the corrosion solution is 0.6 mol / L and the molar concentration of sulfuric acid is 3.2 mol / L.

3. The anhydrous deep eutectic solvent etching solution according to claim 1, characterized in that, The deep eutectic solvent is an L-proline-oxalic acid eutectic, and the molar ratio of L-proline to oxalic acid is 2:

1. The corrosive solution contains 0.5 mol / L hydrochloric acid and 3.5 mol / L sulfuric acid.

4. The anhydrous deep eutectic solvent etching solution according to claim 1, characterized in that, The method for preparing the deep eutectic solvent is as follows: L-proline is mixed with dicarboxylic acid, or β-cyclodextrin with succinic acid, or menthol with camphor, and stirred at 50-80°C and 300-500 r / min until the material is completely melted into a transparent and homogeneous liquid. The mixture is then cooled to room temperature to obtain a deep eutectic solvent.

5. The anhydrous deep eutectic solvent etching solution according to any one of claims 1-5, characterized in that, The anhydrous deep eutectic solvent etching solution is obtained by slowly adding hydrochloric acid and sulfuric acid to the deep eutectic solvent, stirring at a constant temperature of 40~60℃ for 20~40 minutes until well mixed.

6. A method for preparing high-voltage electronic aluminum foil, characterized in that, Electrochemical etching of high-purity aluminum foil using the anhydrous deep eutectic solvent etching solution according to any one of claims 1 to 5, comprising: High-purity aluminum foil with a purity of ≥99.99% was selected and ultrasonically cleaned sequentially with anhydrous ethanol and deionized water, followed by drying. The pretreated aluminum foil was used as the anode and the carbon plate as the cathode, and the electrochemical corrosion was carried out in the anhydrous deep eutectic solvent corrosion solution. The etched aluminum foil is removed, and after washing and chemical formation treatment, a high-voltage electronic aluminum foil with uniform porosity is obtained.

7. The method for preparing high-voltage electronic aluminum foil according to claim 6, characterized in that, Pretreated aluminum foil was used as the anode and a carbon plate as the cathode, and electrochemical corrosion was carried out in the anhydrous deep eutectic solvent etching solution. The corrosion temperature was controlled at 68~72℃ and the current density at 200~250mA / cm². 2 DC constant current corrosion for 90~110s.

8. The method for preparing high-voltage electronic aluminum foil according to claim 7, characterized in that, Corrosion temperature 70℃, current density 250mA / cm 2 DC constant current corrosion for 90s.

9. A high-voltage electronic aluminum foil, characterized in that, The high-voltage electronic aluminum foil is prepared by the method described in any one of claims 6-8.

10. An aluminum electrolytic capacitor, characterized in that, The anode electrode of the aluminum electrolytic capacitor is made of the high-voltage electronic aluminum foil as described in claim 9.

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