A method for producing microporous aluminum foil using an additive

Abstract

The application provides a micro-porous aluminum foil preparation method using an additive and relates to the technical field of lithium ion batteries. The micro-porous aluminum foil is prepared by a ternary synergistic etching system, and the number of pores per unit area of the micro-porous aluminum foil is 5812-7681 / cm 2 , the pore size is 4.52-6.14 microns, the porosity is 0.13%-0.25%, and the tensile strength retention rate is greater than or equal to 83%. In the ternary synergistic etching system, sodium chloride provides a basis for destroying the aluminum surface oxide film to initiate pitting, ammonium chloride provides a buffering effect and assists in regulating the pitting process, and trimethyl phosphate serves as an interface regulator to realize micro-porous morphology regulation by reducing surface tension, promoting bubble detachment, homogenizing current distribution, and synergistically passivating the pore wall. By using a ternary electrolyte, combining pretreatment and chromium-free fluorine post-treatment, green production, controllable micro-pore size, reduced production cost, easy mass production, improved micro-pore anchoring adhesion, and effectively prolonged battery life are achieved.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, specifically to a method for preparing microporous aluminum foil using additives. Background Technology

[0002] With the booming development of the new energy industry, lithium-ion batteries, as high-efficiency energy storage devices, face increasingly higher requirements for energy density, cycle life, and safety. The positive electrode current collector is a key component of lithium-ion batteries, serving the dual functions of carrying the positive electrode active material and conducting current. Currently, aluminum foil is commonly used as the positive electrode current collector in lithium-ion batteries, primarily due to its advantages such as low density, excellent conductivity, and the ease with which a dense oxide film can be formed on its surface, resulting in good corrosion resistance at the positive electrode potential.

[0003] However, the interfacial bonding between traditional smooth aluminum foil and the positive electrode active material mainly relies on physical coating, lacking an effective mechanical interlocking structure. During charging and discharging, due to the volume expansion and contraction of the active material, microcracks easily form at the interface, leading to problems such as active layer peeling and powder shedding, directly causing battery capacity decay and shortened cycle life. Unlike copper foil, aluminum foil has a more reactive surface chemistry, readily forming a natural oxide film. While this oxide film imparts corrosion resistance to the aluminum foil, it also makes its surface chemically inert, increasing the difficulty of surface modification. How to effectively overcome the limitations of the oxide layer and construct a microscopic anchoring structure while maintaining the inherent performance of the aluminum foil is a key challenge in the research and development of aluminum foil current collectors.

[0004] Existing aluminum foil surface roughening technologies mainly include mechanical embossing, chemical etching, laser etching, and electrochemical etching. Among these, mechanical embossing easily causes localized thinning and stress concentration, reducing the mechanical properties of the aluminum foil; chemical etching involves a violent reaction that is difficult to control precisely, easily leading to a significant decrease in the mechanical properties of the aluminum foil; laser etching, due to the low melting point of aluminum, easily produces heat-affected zones and burrs, and its high equipment cost makes large-scale production difficult. Electrochemical etching has advantages such as controllable etching rate, minimal damage to the aluminum foil, and simple process, making it the most promising surface roughening technology. However, the aluminum oxide film significantly affects the uniformity of current distribution in the early stages of corrosion, easily leading to localized over-corrosion or pinhole formation, making it difficult to obtain a microporous structure with uniform pore size and high pore density.

[0005] Studies have shown that the nucleation and growth of micropores in the electrochemical corrosion of aluminum foil are strongly dependent on the interfacial properties of the electrolyte. Introducing functional additives to regulate these interfacial properties holds promise for overcoming existing bottlenecks. Trimethyl phosphate (TMP), as a polar organophosphorus compound, possesses excellent surface activity and has been widely used as a flame-retardant additive in lithium-ion battery electrolytes; however, its application in the electrochemical corrosion of aluminum foil has not yet been reported.

[0006] Application publication number CN107658470A discloses an electrochemical etching method for preparing microporous battery aluminum foil, which uses Cl-containing... - Fe 3+ Cu 2+ Electrochemical etching is performed using a salt-based etching solution, followed by a brightening solution containing chromium and fluoride to improve surface smoothness. While this method can produce microporous aluminum foil with uniform pore size, it has the following significant drawbacks: First, the use of a brightening solution containing chromium and fluoride poses serious environmental and safety risks; second, the process is lengthy, involves numerous formulation components, requires high control precision, and necessitates a corresponding etching solution circulation system, resulting in high production costs and management difficulty; third, the wide pore size distribution range can introduce fluctuations in battery consistency. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides a method for preparing microporous aluminum foil using additives, which solves the problems of poor adhesion, difficulty in modification, and various roughening processes of traditional aluminum foil, as well as the environmental problems, high costs, and uneven pore size of comparative patents.

[0008] To achieve the above objectives, the present invention provides the following technical solution: a microporous aluminum foil using additives, comprising microporous aluminum foil: The microporous aluminum foil is passed through The microporous aluminum foil was prepared using a ternary synergistic etching system, and the number of pores per unit area was 5812–7681 / cm². 2 The pore size is 4.52–6.14 μm, the porosity is 0.13%–0.25%, and the tensile strength retention rate is ≥83%. The In the ternary synergistic etching system, sodium chloride provides the basic... Ammonium chloride is used to break the oxide film on the aluminum surface and induce pitting corrosion. It provides a buffering effect and helps to regulate the pitting corrosion process. Trimethyl phosphate, as an interface regulator, achieves micropore morphology regulation by reducing surface tension, promoting bubble desorption, homogenizing current distribution, and synergistically passivating the pore walls.

[0009] Preferably, the number of pores per unit area of ​​the microporous aluminum foil is 7306 to 7681. The preferred aperture is 4.52–5.61 mm. The porosity is preferably 0.15% to 0.25%. This parameter range corresponds to the optimal preparation effect when the amount of trimethyl phosphate added is 0.2% to 0.8% of the total mass of the electrolyte. At this time, the micropore distribution is the most uniform and there is no obvious pore co-occurrence.

[0010] Preferably, the tensile strength of the microporous aluminum foil is 264.15–285.91 kJ. Its areal density is 39.79–41.38 g / L. The tensile strength retention rate can reach up to 90.67%, which is much higher than that of microporous aluminum foil prepared by traditional electrochemical corrosion process, and can meet the stringent requirements of mechanical properties for positive electrode current collectors of lithium-ion batteries and electrode materials of electrolytic capacitors.

[0011] Preferably, the porosity P of the microporous aluminum foil is calculated using the following formula: Where N is the number of holes per unit area, in units of 1 / 2000 pores. The number of transmitted points was obtained by counting the number of light-transmitting points using the transmission light source mode of a Keyence super depth-of-field 3D microscope; d is the average aperture, in units of m is obtained by taking the arithmetic mean of the diameters of at least 100 micropores; A is the test area, in units of m². , where is the actual area of ​​the area observed under the microscope.

[0012] Preferably, the surface roughness of the microporous aluminum foil is detected by the three-dimensional profile measurement function of the Keyence ultra-depth-of-field three-dimensional microscope or a dedicated roughness tester. The microporous aluminum foil is suitable for lithium-ion battery positive electrode current collectors or electrolytic capacitor electrode materials, which can significantly improve the interfacial bonding force between the active material and the current collector and reduce the risk of active layer peeling off during charging and discharging.

[0013] A method for preparing microporous aluminum foil using additives includes the following steps: S1: Aluminum foil pretreatment, which involves alkali washing, water washing, activation, water washing and drying in sequence to remove residual rolling oil, lubricant and naturally formed loose oxide layer on the surface of aluminum foil, and obtain a clean and uniform initial surface. S2: Electrolyte preparation, with a resistivity ≥ 18.2 Using deionized water as a solvent, an aqueous solution containing sodium chloride, ammonium chloride, and trimethyl phosphate was prepared as a ternary synergistic etching electrolyte. S3: Electrolytic etching, using pretreated aluminum foil as the anode and a corrosion-resistant metal plate as the cathode, constant current electrolytic etching is performed using a DC power supply, the aluminum foil passes continuously in the electrolyte and the upper and lower surfaces are simultaneously immersed in the electrolyte; S4: Post-processing involves sequentially cleaning the etched aluminum foil with deionized water, anhydrous ethanol, and vacuum drying to remove residual electrolyte, reaction products, and adsorbed trimethyl phosphate from the surface, resulting in a clean microporous aluminum foil product.

[0014] Preferably, the electrolyte in step S2 has the following components: Sodium chloride: 0.5-3 Too low a concentration will lead to poor conductivity of the solution, increased tank pressure, and Cl... -Insufficient supply makes pitting corrosion difficult, while excessively high concentrations will increase solution viscosity, affect ion migration and additive diffusion, and reduce corrosion uniformity. Ammonium chloride: 0.2–2.0 Too low a concentration can lead to insufficient buffering capacity, difficulty in initiating pitting corrosion, severe lateral corrosion, and sparse micropores; too high a concentration can... The formation of complexes increases viscosity, weakens the adsorption regulation effect of trimethyl phosphate, and reduces pore size uniformity; Trimethyl phosphate: 0.1% to 5.0% of the total mass of the electrolyte. When the amount added is too low, the interface control effect is not obvious and the bubble desorption promotion effect is weak. When the amount added is too high, the viscosity of the electrolyte increases, ion migration is hindered, and corrosion reaction is excessively inhibited. Solvent: Resistivity ≥ 18.2 Use deionized water to avoid impurity ions interfering with the uniformity of the corrosion reaction.

[0015] Preferably, the electrolyte preparation method in step S2 is as follows: Take approximately 80% of the prepared volume of deionized water, add weighed sodium chloride and ammonium chloride while stirring, and continue stirring until the solids are completely dissolved; slowly add weighed trimethyl phosphate while continuing to stir, and continue stirring for 5-10 minutes to ensure uniform mixing; add deionized water to bring the volume to 100% of the prepared volume, and stir for another 10-15 minutes to fully homogenize the solution; after standing for 30 minutes, test the pH, conductivity, and surface tension of the solution; finally, use 5-10... The filter cartridges with a precision of m remove insoluble impurities and are stored in sealed, corrosion-resistant containers for later use.

[0016] Preferably, the process parameters for electrolytic etching in step S3 are as follows: Current density: 1.5~2.5A / Preferably 2A / ; Electrolysis temperature: 20~50℃, with water bath heating to maintain stable electrolyte temperature; Etching time: 1-10 Adjustments are made based on the target pore size and porosity; Plate spacing: 2-8 The cathode and aluminum foil are arranged in parallel and opposite directions; The electrolyte circulates on the upper and lower surfaces of the aluminum foil in a circulating manner. The flow direction is perpendicular or parallel to the running direction of the aluminum foil, ensuring that fresh electrolyte is continuously replenished to the surface of the aluminum foil and promptly carrying away reaction products and hydrogen bubbles.

[0017] Preferably, the specific parameters for the aluminum foil pretreatment in step S1 are as follows: Alkaline washing: A mixed alkaline solution of sodium hydroxide and sodium carbonate is used, with the temperature controlled at 45±5℃ and the treatment time at 6~20s, to remove rolling oil and lubricant from the surface of aluminum foil; First wash: Use a material with a conductivity ≤10 Rinse with deionized water spray for 5-10 seconds to remove residual alkaline solution and saponification products from the surface. Activation: Immerse the aluminum surface in dilute nitric acid solution at room temperature for 5-15 seconds to remove oxide film residue and activate the surface. Second rinse: Rinse thoroughly with deionized water for 5-10 seconds to remove residual acid and prevent contamination of subsequent corrosion solutions; Drying: Use hot air drying at a temperature of 80-120℃ for 10-30 seconds to prevent the aluminum foil from oxidizing again.

[0018] This invention provides a method for preparing microporous aluminum foil using additives. It has the following beneficial effects: 1. This invention constructs The ternary composite electrolyte system, combined with a simple post-treatment process of water washing and ethanol drying, achieves green preparation effects without chromium and fluorine additives. It eliminates the need for brightening liquid materials containing chromium compounds and fluorides, which are found in the patented materials. This also eliminates waste liquid pollution and production safety hazards caused by heavy metals and fluorides, simplifies waste liquid disposal procedures, and meets the industry development needs of green production of new energy materials.

[0019] 2. This invention utilizes the interfacial activation and regulation effect of trimethyl phosphate, combined with the controlled design of electrolyte component concentration and electrolysis parameters, to achieve a precisely controllable micropore size, solving the problems of uneven current and localized over-etching caused by the natural oxide film on aluminum foil. The product pore size is 4.52–6.14 mm. The pore size and pore density are significantly improved, effectively narrowing the pore size distribution and solving the problem of product performance fluctuation.

[0020] 3. This invention simplifies the reagent ratio system and post-processing steps, and combines standardized electrolyte preparation and filtration with continuous electrolytic etching process to achieve the effect of streamlining the process and reducing costs. It eliminates the need for multiple types of metal salt additives and dedicated large-scale corrosion cycle equipment, reduces production control points, lowers raw material input and equipment operation and maintenance costs, and facilitates the continuous mass production of microporous aluminum foil.

[0021] 4. This invention utilizes a ternary etching system to construct a densely packed microporous structure and combines it with graded pretreatment to protect the strength of the aluminum foil substrate, thereby achieving a high-adhesion current collector preparation effect. The micropores form a mechanically interlocked anchoring structure, which significantly improves the bonding strength of the positive electrode active material, improves the coating peeling and powder shedding caused by charge and discharge expansion and contraction, delays lithium battery capacity decay, and extends the cycle life of the battery cell. Attached Figure Description

[0022] Figure 1 This is an overall flow chart of the preparation method of the present invention; Figure 2 This is a diagram illustrating the ternary synergistic etching mechanism of the present invention; Figure 3 This is a comparative schematic diagram of the micropore morphology of the present invention; Figure 4 This is a graph showing the effect of the amount of TMP added on the number of pores per unit area in this invention. Figure 5 This is a graph showing the effect of the amount of TMP added on the average pore size according to the present invention. Figure 6 This is a graph showing the effect of the amount of TMP added on porosity according to the present invention; Figure 7 This is a graph showing the effect of the amount of TMP added in this invention on tensile strength; Figure 8 This is a graph showing the effect of the amount of TMP added on the surface density in this invention. Figure 9 This is a schematic diagram of the electrolytic etching apparatus of the present invention. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] Example: like Figure 1-9 As shown, an embodiment of the present invention provides a microporous aluminum foil using additives, comprising microporous aluminum foil: Microporous aluminum foil through The ternary synergistic etching system was used to prepare microporous aluminum foil with a pore number of 5812–7681 per unit area. The pore size is 4.52–6.14 μm, the porosity is 0.13%–0.25%, the tensile strength retention rate is ≥83%, and the preferred number of pores per unit area of ​​the microporous aluminum foil is 7306–7681 pores / unit. The preferred pore size is 4.52–5.61 μm, and the preferred porosity is 0.15%–0.25%. This parameter range corresponds to the optimal preparation effect when the amount of trimethyl phosphate added is 0.2%–0.8% of the total mass of the electrolyte. At this point, the micropore distribution is most uniform, with no obvious pore aggregation, and the tensile strength of the microporous aluminum foil is 264.15–285.91 MPa, and the areal density is 39.79–41.38 g / L. The tensile strength retention rate can reach up to 90.67%, which is much higher than that of microporous aluminum foil prepared by traditional electrochemical corrosion process, and can meet the stringent mechanical performance requirements of lithium-ion battery positive electrode current collector and electrolytic capacitor electrode materials. In the ternary synergistic etching system, sodium chloride provides the basic... Ammonium chloride is used to break down the oxide film on the aluminum surface and induce pitting corrosion. It provides a buffering effect and helps regulate the pitting corrosion process. Trimethyl phosphate, as an interface regulator, controls the micropore morphology by reducing surface tension, promoting bubble desorption, homogenizing current distribution, and synergistically passivating the pore walls. The porosity P of the microporous aluminum foil is calculated using the following formula: , Where N is the number of pores per unit area, measured in pores / cm², obtained by counting the number of light-transmitting points using the transmission light source mode of a Keyence super depth-of-field 3D microscope; d is the average pore diameter, measured in μm, obtained by taking the arithmetic mean of the diameters of at least 100 micropores; and A is the test area, measured in μm. , which is the actual area of ​​the microscope observation area. The surface roughness of the microporous aluminum foil is detected by the three-dimensional profile measurement function of the Keyence ultra-depth-of-field three-dimensional microscope or a dedicated roughness tester. The microporous aluminum foil is suitable for lithium-ion battery positive electrode current collectors or electrolytic capacitor electrode materials. It can significantly improve the interfacial bonding force between the active material and the current collector and reduce the risk of active layer peeling off during charging and discharging.

[0025] Specifically: This microporous aluminum foil passes through A ternary synergistic etching system was prepared. In the actual preparation process, when the amount of trimethyl phosphate added was 0.2% of the total mass of the electrolyte, the number of pores per unit area of ​​the microporous aluminum foil was 6532 / ... The average pore size is 5.53 μm, the porosity is 0.20%, the tensile strength is 279.36 MPa, and the areal density is 40.77 g / L. When the amount of trimethyl phosphate added was increased to 0.5%, the micropore nucleation density reached its peak, and the number of pores per unit area increased to 7681 / unit. The average pore size was narrowed to 4.52 μm, the porosity was 0.15%, the tensile strength was 264.15 MPa, and the areal density was 39.79 g / L. ; When the trimethyl phosphate content was 0.8%, the porosity reached its maximum value of 0.25%, while the number of pores per unit area remained at 7306 / m². The average pore size is 5.61 μm, the tensile strength is 270.59 MPa, and the areal density is 40.25 g / L. When the amount of trimethyl phosphate added was further increased to 1.2%, the number of pores per unit area decreased to 5812 / 500. The average pore size is 6.14 μm, the porosity is 0.13%, the tensile strength is 285.91 MPa, and the areal density is 41.38 g / L. .

[0026] In summary, the number of pores per unit area of ​​this microporous aluminum foil is 5812–7681. The pore size is 4.52–6.14 μm, the porosity is 0.13%–0.25%, the tensile strength retention rate is ≥83%, and the preferred pore number per unit area is 7306–7681 pores / unit. The preferred pore size is 4.52–5.61 μm, and the preferred porosity is 0.15%–0.25%. This parameter range corresponds to the optimal preparation effect when the trimethyl phosphate addition is 0.2%–0.8% of the total electrolyte mass. At this level, the micropore distribution is most uniform, with no obvious pore aggregation, and the tensile strength retention rate can reach up to 90.67%, which is far higher than that of microporous aluminum foil prepared by traditional electrochemical etching processes. This meets the stringent mechanical performance requirements of lithium-ion battery cathode current collectors and electrolytic capacitor electrode materials. In this ternary synergistic etching system, sodium chloride provides the basic Cl... - Ammonium chloride is used to break the oxide film on the aluminum surface and induce pitting corrosion. It provides a buffering effect and helps to regulate the pitting corrosion process. Trimethyl phosphate, as an interface regulator, achieves micropore morphology regulation by reducing surface tension, promoting bubble desorption, homogenizing current distribution, and synergistically passivating the pore walls.

[0027] The porosity P of the microporous aluminum foil is expressed by the formula... Calculate, where N is the number of holes per unit area, in units of 1 / 2. The number of transmitted points was obtained by counting the number of points of light transmitted through the transmission light source mode of a Keyence super depth-of-field 3D microscope. d represents the average aperture in μm, obtained by taking the arithmetic mean of the diameters of at least 100 micropores. A represents the test area in μm. , where is the actual area of ​​the microscopic observation region. The surface roughness of this microporous aluminum foil is detected using the 3D profile measurement function of a Keyence ultra-depth-of-field 3D microscope or a dedicated roughness tester. It is suitable for lithium-ion battery cathode current collectors or electrolytic capacitor electrode materials, and can significantly improve the interfacial bonding force between the active material and the current collector, reducing the risk of active layer peeling during charging and discharging.

[0028] A method for preparing microporous aluminum foil using additives includes the following steps: S1: Aluminum foil pretreatment involves sequential alkaline washing, water washing, activation, water washing, and drying to remove residual rolling oil, lubricant, and naturally formed loose oxide layer from the aluminum foil surface, resulting in a clean and uniform initial surface. Specific parameters for aluminum foil pretreatment are as follows: Alkaline washing: Using a mixed alkaline solution of sodium hydroxide and sodium carbonate, the temperature is controlled at 45±5℃, and the treatment time is 6–20 seconds to remove rolling oil and lubricant from the aluminum foil surface; First water washing: Using deionized water with a conductivity ≤10μS / cm for spray rinsing for 5–10 seconds to remove residual alkaline solution and saponification products from the surface; Activation: Immersing in a dilute nitric acid solution at room temperature for 5–15 seconds to remove oxide film residue and activate the aluminum surface; Second water washing: Thoroughly rinsing with deionized water for 5–10 seconds to remove residual acid and prevent contamination of subsequent etching solutions; Drying: Using hot air drying at a temperature of 80–120℃ for 10–30 seconds to prevent the aluminum foil from oxidizing again.

[0029] S2: Electrolyte preparation. Using deionized water with a resistivity ≥18.2 MΩ·cm as the solvent, prepare an aqueous solution containing sodium chloride, ammonium chloride, and trimethyl phosphate as the ternary synergistic etching electrolyte. Sodium chloride concentration: 0.5–3 mol / L. Too low a concentration will lead to poor solution conductivity, increased tank voltage, and Cl... - Insufficient supply leads to difficulties in pitting corrosion; excessively high concentrations increase solution viscosity, affect ion migration and additive diffusion, and reduce corrosion uniformity. Ammonium chloride: 0.2–2.0 mol / L; too low a concentration leads to insufficient buffering capacity, difficulty in initiating pitting corrosion, severe lateral corrosion, and sparse micropores; too high a concentration forms complexes with Al3+, increasing viscosity, weakening the adsorption regulation effect of trimethyl phosphate, and reducing pore size uniformity. Trimethyl phosphate: 0.1%–5.0% of the total electrolyte mass; too low a concentration results in insignificant interface regulation and weak bubble desorption promotion; too high a concentration increases electrolyte viscosity, hinders ion migration, and excessively inhibits corrosion reactions. Solvent: resistivity. Use deionized water with a strength ≥18.2 MΩ·cm to avoid interference from impurity ions on the uniformity of the corrosion reaction; take approximately 80% of the prepared volume of deionized water, and while stirring, add the weighed sodium chloride and ammonium chloride, continuing to stir until the solids are completely dissolved; under continuous stirring, slowly add the weighed trimethyl phosphate, and continue stirring for 5–10 minutes to ensure uniform mixing; add deionized water to bring the volume to 100% of the prepared volume, and stir for another 10–15 minutes to fully homogenize the solution; after standing for 30 minutes, test the pH, conductivity, and surface tension of the solution; finally, filter using a 5–10 μm precision filter cartridge to remove insoluble impurities, and store in a sealed corrosion-resistant container for later use.

[0030] S3: Electrolytic etching, using pretreated aluminum foil as the anode and a corrosion-resistant metal plate as the cathode, employs a DC power supply for constant current electrolytic etching. The aluminum foil continuously passes through the electrolyte, with both its upper and lower surfaces simultaneously immersed in the electrolyte. The process parameters for electrolytic etching are: current density: 1.5~2.5A / Preferably 2A / Electrolysis temperature: 20~50℃, using water bath heating to maintain stable electrolyte temperature; Etching time: 1~10min, adjusted according to target pore size and porosity; Electrode spacing: 2~8cm, with the cathode and aluminum foil arranged parallel to each other; The electrolyte circulates on the upper and lower surfaces of the aluminum foil, with the flow direction perpendicular or parallel to the aluminum foil's running direction, ensuring a continuous supply of fresh electrolyte to the aluminum foil surface and timely removal of reaction products and hydrogen bubbles.

[0031] S4: Post-processing involves sequentially cleaning the etched aluminum foil with deionized water, anhydrous ethanol, and vacuum drying to remove residual electrolyte, reaction products, and adsorbed trimethyl phosphate from the surface, resulting in a clean microporous aluminum foil product.

[0032] Specifically, high-performance microporous aluminum foil was prepared through a standardized pretreatment process, ternary synergistic etching electrolyte preparation, constant current electrolytic etching, and post-cleaning treatment. First, commercially available 12μm thick battery-grade smooth aluminum foil was pretreated by sequentially treating it with a mixed alkaline solution of sodium hydroxide and sodium carbonate at 45±5℃ for 6–20s to remove surface rolling oil and lubricant. Then, it was rinsed with deionized water with a conductivity ≤10μS / cm for 5–10s to remove residual alkaline solution and saponification products. Next, it was immersed in dilute nitric acid solution at room temperature for 5–15s to remove oxide film residue and activate the aluminum surface. After being thoroughly rinsed with deionized water for 5–10s, it was dried with hot air at 80–120℃ for 10–30s to prevent the aluminum foil from oxidizing again, thus obtaining a clean and uniform initial surface. Next, a ternary synergistic etching electrolyte was prepared using deionized water with a resistivity ≥18.2 MΩ·cm as the solvent. The sodium chloride concentration was controlled between 0.5 and 3 mol / L, a range that ensured sufficient Cl. - The supply method aims to disrupt the aluminum oxide film, initiating pitting corrosion. However, it avoids excessively high concentrations that could increase solution viscosity, hindering ion migration and additive diffusion. The ammonium chloride concentration is controlled between 0.2 and 2.0 mol / L to provide a suitable buffering effect, assisting in regulating the pitting corrosion process and preventing severe lateral corrosion and microporous sparseness due to excessively low concentrations, or excessively high concentrations that clash with Al. 3+To address the issue of increased viscosity due to the formation of complexes and the weakening of the adsorption regulation effect of trimethyl phosphate, the amount of trimethyl phosphate added is 0.1% to 5.0% of the total mass of the electrolyte. In actual preparation, it can be precisely adjusted according to the target microporous structure. When preparing the solution, first take about 80% of the preparation volume of deionized water, and add the weighed sodium chloride and ammonium chloride while stirring until completely dissolved. Then, slowly add the corresponding mass of trimethyl phosphate while continuously stirring, and continue stirring for 5 to 10 minutes to ensure uniform mixing. Add deionized water to make up to 100% of the preparation volume, and then stir for 10 to 15 minutes to fully homogenize the solution. After standing for 30 minutes, test the pH value, conductivity, and surface tension. After filtering through a 5 to 10 μm precision filter to remove insoluble impurities, store in a sealed corrosion-resistant container for later use. Subsequently, using the pretreated aluminum foil as the anode and the corrosion-resistant metal plate as the cathode, constant current electrolytic etching was performed using a DC power supply, with the current density controlled between 1.5 and 2.5 A / s. Preferably 2A / The electrolysis temperature was maintained at 20–50℃, and a water bath was used to maintain system stability. The etching time was adjusted to 1–10 min according to the target pore size and porosity. The electrode spacing was set to 2–8 cm, and the cathode was arranged parallel to the aluminum foil. The electrolyte circulated on the upper and lower surfaces of the aluminum foil, with the flow direction perpendicular or parallel to the aluminum foil's running direction. This ensured a continuous supply of fresh electrolyte to the aluminum foil surface and timely removal of reaction products and hydrogen bubbles. The aluminum foil continuously passed through the electrolyte, with both upper and lower surfaces simultaneously immersed to ensure uniform etching on both sides. Finally, the etched aluminum foil was sequentially cleaned with deionized water, anhydrous ethanol, and vacuum dried to thoroughly remove residual electrolyte, reaction products, and adsorbed trimethyl phosphate, resulting in a clean microporous aluminum foil product. By adjusting the amount of trimethyl phosphate added, products with different performance gradients could be obtained. When the addition amount was 0.2%, the microporous aluminum foil had 6532 pores per unit area. Average pore size 5.53 μm, porosity 0.20%, tensile strength 279.36 MPa, areal density 40.77 g / L When the addition amount is 0.5%, the microporous nucleation density reaches its peak, and the number of pores per unit area increases to 7681 / unit. The average pore size was reduced to 4.52 μm, the porosity was 0.15%, the tensile strength was 264.15 MPa, and the areal density was 39.79 g / L. When the addition amount is 0.8%, the porosity reaches its maximum value of 0.25%, and the number of pores per unit area remains at 7306 / %. Average pore size: 5.61 μm; tensile strength: 270.59 MPa; areal density: 40.25 g / L When the addition amount is 1.2%, the number of pores per unit area decreases to 5812 / 1000. Average pore size 6.14 μm, porosity 0.13%, tensile strength 285.91 MPa, areal density 41.38 g / L All products retain ≥83% of their tensile strength, with a maximum of 90.67%, meeting the stringent requirements for mechanical properties and interfacial bonding performance of lithium-ion battery cathode current collectors and electrolytic capacitor electrode materials.

[0033] The raw materials used in the embodiments and comparative examples of this invention are all commercially available industrial-grade products. The aluminum foil is a commercially available 12μm thick battery-grade smooth aluminum foil; sodium chloride, ammonium chloride, and trimethyl phosphate (TMP) are all analytical grade reagents; and the resistivity of deionized water is ≥18.2MΩ·cm.

[0034] Performance testing methods must be strictly followed in accordance with regulations: 1. Micropore morphology detection: Using the Keyence super depth-of-field 3D microscope in transmission light source mode, the number and diameter of light-transmitting points per unit area were counted, and the average pore diameter and porosity were calculated; 2. Tensile strength test: A universal testing machine was used, with a tensile rate of 5 mm / min and a sample size of 150 mm × 25 mm. 3. Areal density test: An electronic balance with an accuracy of 0.001g was used, and the sample size was 50mm × 50mm; 4. Porosity calculation formula: Where N is the number of holes per unit area (holes / ), d is the average pore size (μm), A is the test area ( ).

[0035] Example 1:

[0036] S1: Aluminum foil pretreatment: 12μm thick commercial aluminum foil is subjected to alkaline washing (mixed alkaline solution of sodium hydroxide and sodium carbonate, 45℃, 15s), deionized water spray rinsing (conductivity ≤10μS / cm, 8s), dilute nitric acid room temperature activation (10s), deionized water rinsing again (8s), and hot air drying (100℃, 20s) to remove surface rolling oil, lubricant and loose oxide layer.

[0037] S2: Electrolyte preparation: Weigh 600g of sodium chloride and 300g of ammonium chloride, dissolve them in 8L of deionized water, and stir until completely dissolved; slowly add 50g of trimethyl phosphate (accounting for 0.5% of the total mass of the electrolyte), and continue stirring for 10min; add deionized water to make up to 10L, and stir for another 15min; after standing for 30min, test the pH value, conductivity and surface tension, and filter through a 5μm filter cartridge for later use.

[0038] S3: Electrolytic Etching: Using pretreated aluminum foil as the anode and a stainless steel plate as the cathode, constant current electrolysis is performed with a DC power supply at a current density of 2A / m³. The electrolysis temperature was 25℃, the etching time was 90s, the electrode spacing was 5cm, and the electrolyte circulation direction was perpendicular to the aluminum foil running direction.

[0039] S4: Post-processing: Rinse the etched aluminum foil three times with deionized water (30s each time), clean it once with anhydrous ethanol, and dry it for 30min at 60℃ and 0.09MPa vacuum to obtain the microporous aluminum foil product.

[0040] Example 2:

[0041] The only difference between this embodiment and Example 1 is that the amount of trimethyl phosphate added in step S2 is 20g (accounting for 0.2% of the total mass of the electrolyte), and the other steps and parameters are the same as in Example 1.

[0042] Example 3:

[0043] The only difference between this embodiment and Example 1 is that the amount of trimethyl phosphate added in step S2 is 80g (accounting for 0.8% of the total mass of the electrolyte), and the other steps and parameters are the same as in Example 1.

[0044] Example 4:

[0045] The only difference between this embodiment and Example 1 is that the amount of trimethyl phosphate added in step S2 is 120g (accounting for 1.2% of the total mass of the electrolyte), and the other steps and parameters are the same as in Example 1.

[0046] Comparative Example 1: The only difference between this comparative example and Example 1 is that trimethyl phosphate was not added in step S2; all other steps and parameters are the same as in Example 1.

[0047] Comparative Example 2: The only difference between this comparative example and Example 1 is that ammonium chloride was not added in step S2; all other steps and parameters are the same as in Example 1.

[0048] Comparative Example 3: The only difference between this comparative example and Example 1 is that the amount of ammonium chloride added in step S2 is 800g, while the other steps and parameters are the same as in Example 1.

[0049] Test Results and Analysis 1. Microporous structure performance testing The performance test results of the microporous structures in each embodiment and comparative example are shown in Table 1. Figure 3-5 Performance change trends.

[0050] The performance test results of the microporous structures in each embodiment and comparative example are shown in Table 1. Figure 3-5 Performance change trend: From Table 1 and Appendix Figure 3-5 It can be seen that as the TMP addition amount increases from 0 to 0.5%, the number of pores per unit area increases from 3125 pores / cm². 2 Increased to 7681 / cm 2 The average pore size decreased from 10.92 μm to 4.52 μm. When the TMP addition exceeded 0.5%, the number of pores per unit area gradually decreased, while the average pore size increased slightly. The porosity of Example 3 reached the highest value of 0.25%, at which point the overall performance of the microporous structure was optimal.

[0051] Comparative Example 1, without TMP, showed fewer micropore nucleation sites, severe pore aggregation, and large, unevenly distributed pore sizes. Comparative Example 2, without ammonium chloride, had insufficient buffering capacity, making pitting corrosion difficult to initiate, and resulting in sparse micropores. Comparative Example 3, with excessive ammonium chloride, weakened the adsorption-regulating effect of TMP, leading to decreased pore size uniformity. These results validated... The necessity of a ternary synergistic etching system.

[0052] Appendix Figure 3 This is a schematic diagram comparing the micropore morphology of Example 1 and Comparative Example 1. It can be seen that the microporous aluminum foil prepared in Example 1 has small and uniform pore size and no obvious pore coalescence. In contrast, the micropore size of Comparative Example 1 varies greatly, and there are a large number of large pores formed by coalescence.

[0053] The mechanical properties and areal density test results of each embodiment and comparative example are shown in Table 2, with corresponding appendices. Figure 6-7 Performance change trend: From Table 2 and Appendix Figure 6-7 As can be seen, the microporous aluminum foil prepared by this invention retains ≥83% of its tensile strength, meeting the mechanical performance requirements of lithium-ion battery cathode current collectors. With increasing TMP addition, the corrosion degree of the aluminum foil gradually decreases, while the tensile strength and areal density gradually increase, forming a good match with the performance of the microporous structure.

[0054] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A microporous aluminum foil using additives, comprising microporous aluminum foil, characterized in that: The microporous aluminum foil is passed through The microporous aluminum foil was prepared using a ternary synergistic etching system, and the number of pores per unit area was 5812–7681 / cm². 2 The pore size is 4.52–6.14 μm, the porosity is 0.13%–0.25%, and the tensile strength retention rate is ≥83%. The In the ternary synergistic etching system, sodium chloride provides the basic... Ammonium chloride is used to break the oxide film on the aluminum surface and induce pitting corrosion. It provides a buffering effect and helps to regulate the pitting corrosion process. Trimethyl phosphate, as an interface regulator, achieves micropore morphology regulation by reducing surface tension, promoting bubble desorption, homogenizing current distribution, and synergistically passivating the pore walls.

2. The microporous aluminum foil using additives according to claim 1, characterized in that: The preferred number of pores per unit area of ​​the microporous aluminum foil is 7306–7681. The preferred aperture is 4.52–5.61 mm. The porosity is preferably 0.15% to 0.25%. This parameter range corresponds to the optimal preparation effect when the amount of trimethyl phosphate added is 0.2% to 0.8% of the total mass of the electrolyte. At this time, the micropore distribution is the most uniform and there is no obvious pore co-occurrence.

3. The microporous aluminum foil using additives according to claim 1, characterized in that: The tensile strength of the microporous aluminum foil is 264.15–285.

91. Its areal density is 39.79–41.38 g / L. The tensile strength retention rate can reach up to 90.67%, which is much higher than that of microporous aluminum foil prepared by traditional electrochemical corrosion process, and can meet the stringent requirements of mechanical properties for positive electrode current collectors of lithium-ion batteries and electrode materials of electrolytic capacitors.

4. The microporous aluminum foil using additives according to claim 1, characterized in that: The porosity P of the microporous aluminum foil is calculated using the following formula: Where N is the number of holes per unit area, in units of 1 / 2000 pores. The number of transmitted points was obtained by counting the number of light-transmitting points using the transmission light source mode of a Keyence super depth-of-field 3D microscope; d is the average aperture, in units of m is obtained by taking the arithmetic mean of the diameters of at least 100 micropores; A is the test area, in units of m². , where is the actual area of ​​the area observed under the microscope.

5. A microporous aluminum foil using additives according to claim 1, characterized in that: The surface roughness of the microporous aluminum foil is detected by the three-dimensional profile measurement function of the Keyence ultra-depth-of-field three-dimensional microscope or a dedicated roughness tester. The microporous aluminum foil is suitable for lithium-ion battery positive electrode current collectors or electrolytic capacitor electrode materials, which can significantly improve the interfacial bonding force between the active material and the current collector and reduce the risk of active layer peeling off during charging and discharging.

6. A method for preparing microporous aluminum foil using additives, comprising using a microporous aluminum foil using additives as described in any one of claims 1 to 5, characterized in that, Includes the following steps: S1: Aluminum foil pretreatment, which involves alkali washing, water washing, activation, water washing and drying in sequence to remove residual rolling oil, lubricant and naturally formed loose oxide layer on the surface of aluminum foil, and obtain a clean and uniform initial surface. S2: Electrolyte preparation, with a resistivity ≥ 18.2 Using deionized water as a solvent, an aqueous solution containing sodium chloride, ammonium chloride, and trimethyl phosphate was prepared as a ternary synergistic etching electrolyte. S3: Electrolytic etching, using pretreated aluminum foil as the anode and a corrosion-resistant metal plate as the cathode, constant current electrolytic etching is performed using a DC power supply, the aluminum foil passes continuously in the electrolyte and the upper and lower surfaces are simultaneously immersed in the electrolyte; S4: Post-processing involves sequentially cleaning the etched aluminum foil with deionized water, anhydrous ethanol, and vacuum drying to remove residual electrolyte, reaction products, and adsorbed trimethyl phosphate from the surface, resulting in a clean microporous aluminum foil product.

7. The method for preparing microporous aluminum foil using additives according to claim 1, characterized in that: The electrolyte in step S2 has the following components: Sodium chloride: 0.5-3 Too low a concentration will lead to poor conductivity of the solution, increased tank pressure, and Cl... - Insufficient supply makes pitting corrosion difficult, while excessively high concentrations will increase solution viscosity, affect ion migration and additive diffusion, and reduce corrosion uniformity. Ammonium chloride: 0.2–2.0 Too low a concentration can lead to insufficient buffering capacity, difficulty in initiating pitting corrosion, severe lateral corrosion, and sparse micropores; too high a concentration can... The formation of complexes increases viscosity, weakens the adsorption regulation effect of trimethyl phosphate, and reduces pore size uniformity; Trimethyl phosphate: 0.1% to 5.0% of the total mass of the electrolyte. When the amount added is too low, the interface control effect is not obvious and the bubble desorption promotion effect is weak. When the amount added is too high, the viscosity of the electrolyte increases, ion migration is hindered, and corrosion reaction is excessively inhibited. Solvent: Resistivity ≥ 18.2 Use deionized water to avoid impurity ions interfering with the uniformity of the corrosion reaction.

8. The method for preparing microporous aluminum foil using additives according to claim 1, characterized in that: The electrolyte preparation method in step S2 is as follows: Take approximately 80% of the prepared volume of deionized water, and while stirring, add the weighed sodium chloride and ammonium chloride, continuing to stir until the solids are completely dissolved; under continuous stirring, slowly add the weighed trimethyl phosphate, and continue stirring for 5-10 minutes to ensure uniform mixing; add deionized water to bring the volume to 100% of the prepared volume, and stir for another 10-15 minutes to fully homogenize the solution; after standing for 30 minutes, test the pH, conductivity, and surface tension of the solution; finally, use 5-10... The filter cartridges with a precision of m remove insoluble impurities and are stored in sealed, corrosion-resistant containers for later use.

9. The method for preparing microporous aluminum foil using additives according to claim 1, characterized in that: The process parameters for electrolytic etching in step S3 are as follows: Current density: 1.5~2.5A / Preferably 2A / ; Electrolysis temperature: 20~50℃, with water bath heating to maintain stable electrolyte temperature; Etching time: 1-10 Adjustments are made based on the target pore size and porosity; Plate spacing: 2-8 The cathode and aluminum foil are arranged in parallel and opposite directions; The electrolyte circulates on the upper and lower surfaces of the aluminum foil in a circulating manner. The flow direction is perpendicular or parallel to the running direction of the aluminum foil, ensuring that fresh electrolyte is continuously replenished to the surface of the aluminum foil and promptly carrying away reaction products and hydrogen bubbles.

10. The method for preparing microporous aluminum foil using additives according to claim 1, characterized in that: The specific parameters for the aluminum foil pretreatment in step S1 are as follows: Alkaline washing: A mixed alkaline solution of sodium hydroxide and sodium carbonate is used, with the temperature controlled at 45±5℃ and the treatment time at 6~20s, to remove rolling oil and lubricant from the surface of aluminum foil; First wash: Use a material with a conductivity ≤10 Rinse with deionized water spray for 5-10 seconds to remove residual alkaline solution and saponification products from the surface. Activation: Immerse the aluminum surface in dilute nitric acid solution at room temperature for 5-15 seconds to remove oxide film residue and activate the surface. Second rinse: Rinse thoroughly with deionized water for 5-10 seconds to remove residual acid and prevent contamination of subsequent corrosion solutions; Drying: Use hot air drying at a temperature of 80-120℃ for 10-30 seconds to prevent the aluminum foil from oxidizing again.

Images