Electrochemical etching preparation method of porous battery aluminum foil

Abstract

According to the electrochemical etching preparation method of the porous battery aluminum foil, the porosity, uniformity and surface performance of the aluminum foil are remarkably improved through the steps of multi-stage gradient annealing treatment, pulse voltage electrochemical etching, segmented ultrasonic cleaning, surface modification treatment and the like; according to the method, a composite electrolyte system is adopted to collaboratively optimize the etching effect, and accurate regulation and control of the aluminum foil hole structure are achieved by controlling the waveform of pulse voltage, the ratio of forward voltage to reverse voltage and illumination auxiliary conditions; in addition, the cleanliness and the interface bonding force of the aluminum foil are further improved through segmented ultrasonic cleaning and silane coupling agent surface modification, the surface activity is enhanced through low-temperature plasma treatment, and compared with a traditional method, the aluminum foil prepared through the method has higher mechanical strength, more uniform pore distribution and more excellent electrochemical performance; the energy density and the cycle life of the battery can be remarkably improved, and the method is suitable for the fields of high-performance lithium ion batteries and the like.

Description

Technical Field

[0001] This invention relates to the field of porous aluminum foil preparation technology, and more particularly to an electrochemical etching method for preparing porous battery aluminum foil. Background Technology

[0002] With the rapid development of new energy technologies, lithium-ion batteries, as core energy storage devices, have seen performance optimization become a research hotspot. Battery aluminum foil, as a key material for the positive electrode current collector, directly affects the battery's conductivity, interface stability, and energy density through its surface structure. Traditional aluminum foil preparation methods often employ mechanical punching or chemical etching. However, mechanical punching easily leads to edge burrs and stress concentration, while chemical etching suffers from uneven pore distribution and difficulty in controlling the etching rate. In recent years, electrochemical etching technology has attracted attention due to its advantage of precisely controlling the pore structure, but it still faces challenges such as a single electrolyte composition, low etching efficiency, and rough pore walls. In existing technologies, electrolytes often use strong acid systems, which easily cause excessive corrosion of the aluminum foil or irregular pore morphology; the etching process lacks dynamic control methods, resulting in poor consistency in pore size and distribution; and subsequent processing steps are simple, making it difficult to effectively remove etching residues or improve surface properties.

[0003] To address the aforementioned issues, there is an urgent need to develop an efficient and controllable aluminum foil etching method to achieve uniformity, high precision, and functionality of the hole structure.

[0004] Therefore, this invention is proposed. Summary of the Invention

[0005] To address the aforementioned technical problems, the primary objective of this invention is to provide an electrochemical etching method for preparing porous battery aluminum foil. By introducing multi-stage gradient annealing, a composite electrolyte system, dynamic pulse voltage control, and segmented cleaning-modification processes, the bottlenecks of traditional technologies are overcome. Multi-stage gradient annealing eliminates internal stress in the aluminum foil and optimizes the grain structure, providing a uniform substrate for subsequent etching. The addition of rare earth metal salts and heteropoly acids to the composite electrolyte significantly enhances etching activity and pore wall smoothness. The synergistic effect of pulse voltage and light-assisted etching enables precise control of pore morphology. Segmented ultrasonic cleaning and silane coupling agent modification ensure the cleanliness of the aluminum foil and the strength of interfacial bonding.

[0006] To achieve the objective of this invention, this invention provides an electrochemical etching preparation method for porous battery aluminum foil, comprising the following steps: after the aluminum foil undergoes multi-stage gradient annealing under inert gas protection, it is placed in an electrolyte and electrochemically etched under pulse voltage conditions; After etching, segmented ultrasonic cleaning is performed. Finally, the cleaned aluminum foil is subjected to surface modification treatment in an ethanol solution containing 0.1-0.5 wt% silane coupling agent to obtain the final product. The electrolyte comprises 0.5-1.5 mol / L phosphoric acid, 0.1-0.3 mol / L citric acid, 0.05-0.15 mol / L sodium dodecyl sulfonate, 0.01-0.1 mol / L rare earth metal salt, 0.001-0.005 mol / L heteropoly acid, 0.1-0.5 wt% ionic liquid, and pH adjuster.

[0007] Furthermore, the annealing temperature is 200-500℃ and the annealing time is 1.5h. Preferably, a three-stage gradient annealing process is performed: in the first stage, the temperature is increased to 250℃ at 5℃ / min and held for 30 minutes; in the second stage, the temperature is increased to 350℃ and held for 30 minutes; and in the third stage, the temperature is increased to 450℃ and held for 30 minutes. Furthermore, the etching temperature was 25°C and the etching time was 30 minutes.

[0008] Furthermore, the rare earth metal salt is cerium nitrate or lanthanum nitrate; the heteropoly acid is phosphotungstic acid or silicomolybdic acid; the ionic liquid is either 1-butyl-3-methylimidazolium hexafluorophosphate or 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide; and the pH adjuster is oxalic acid or tartaric acid.

[0009] Furthermore, the silane coupling agent is γ-aminopropyltriethoxysilane or γ-glycidoxypropyltrimethoxysilane.

[0010] Furthermore, the electrolyte also contains 0.001-0.01 mol / L of a transition metal complex, wherein the transition metal complex is iron acetylacetonate or cobalt acetylacetonate.

[0011] Furthermore, the ratio of the forward voltage to the reverse voltage of the pulse voltage is controlled between 3:1 and 5:1, and the ratio of the duration of the forward voltage to the duration of the reverse voltage is between 1:1.5 and 1:2.5.

[0012] Furthermore, the segmented ultrasonic cleaning includes: a first stage of cleaning in deionized water at a frequency of 40-60 kHz for 3-5 minutes, a second stage of cleaning in ethanol at a frequency of 80-100 kHz for 2-4 minutes, and a third stage of cleaning in acetone at a frequency of 60-80 kHz for 1-3 minutes.

[0013] Furthermore, the aluminum foil after surface modification is also subjected to low-temperature plasma treatment, with the treatment conditions being a power of 50-200W, a treatment time of 1-5 minutes, and argon or nitrogen gas.

[0014] Furthermore, the waveform of the pulse voltage is a square wave or a trapezoidal wave, and the pulse rise time and fall time are both less than 1ms.

[0015] Furthermore, the electrochemical etching process is assisted by light illumination, with the light source being ultraviolet or visible light, and the light intensity being 10-100 mW / cm². 2 The wavelength is 200-500nm.

[0016] The embodiments of the present invention have the following technical effects: This invention provides an electrochemical etching method for preparing porous battery aluminum foil. By introducing multi-stage gradient annealing, a composite electrolyte system, dynamic pulse voltage control, and segmented cleaning-modification processes, it solves the bottleneck problems of traditional technologies. Among them, multi-stage gradient annealing can eliminate internal stress of aluminum foil and optimize grain structure, providing a uniform substrate for subsequent etching; the addition of rare earth metal salts and heteropoly acids in the composite electrolyte significantly improves etching activity and pore wall smoothness; the synergistic effect of pulse voltage and light-assisted etching enables precise control of pore morphology; and segmented ultrasonic cleaning and silane coupling agent modification ensure the cleanliness of aluminum foil and interfacial bonding strength. Attached Figure Description

[0017] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0018] Figure 1 This is a microscopic image of the perforated battery aluminum foil prepared in Example 3 of the present invention. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0020] In a first aspect, an electrochemical etching preparation method for a porous battery aluminum foil includes the following steps: after the aluminum foil is subjected to multi-stage gradient annealing under inert gas protection, it is placed in an electrolyte and electrochemically etched under pulse voltage conditions. After etching, segmented ultrasonic cleaning is performed. Finally, the cleaned aluminum foil is subjected to surface modification treatment in an ethanol solution containing 0.1-0.5 wt% silane coupling agent to obtain the final product. The electrolyte comprises 0.5-1.5 mol / L phosphoric acid, 0.1-0.3 mol / L citric acid, 0.05-0.15 mol / L sodium dodecyl sulfonate, 0.01-0.1 mol / L rare earth metal salt, 0.001-0.005 mol / L heteropoly acid, 0.1-0.5 wt% ionic liquid, and pH adjuster.

[0021] This invention provides an electrochemical etching method for preparing porous battery aluminum foil. The technical solution, through multi-step synergistic optimization, achieves precise control of the aluminum foil's pore structure, significantly improving its mechanical properties, electrochemical stability, and interfacial bonding ability. This method is suitable for high-performance lithium-ion batteries and other energy storage devices. The core of this method lies in subjecting the aluminum foil to multi-stage gradient annealing under inert gas protection. The annealing temperature is 200-500℃, and the annealing time is 1.5 hours. Preferably, a three-stage gradient annealing process is performed, with the first stage increasing the temperature to 25℃ at a rate of 5℃ / min. The aluminum foil is annealed at 0℃ for 30 minutes, then heated to 350℃ for 30 minutes in the second stage, and then heated to 450℃ for 30 minutes in the third stage. This annealing process effectively eliminates internal stress in the aluminum foil. Subsequently, electrochemical etching is performed in a specially formulated electrolyte using pulsed voltage at 25℃ for 30 minutes. Finally, high-performance perforated aluminum foil is obtained through segmented ultrasonic cleaning and surface modification. The ultrasonic frequency is 40-100kHz, and the ultrasonic cleaning time is 6-12 minutes. Preferably, the cleaning is performed in three stages, including an inert... Multi-stage gradient annealing under gas protection effectively eliminates internal stress in aluminum foil, refines grain structure, and improves material uniformity, providing a stable substrate for subsequent etching processes and avoiding uneven etching caused by local grain boundary defects. The electrolyte contains 0.5-1.5 mol / L phosphoric acid as the main etchant, 0.1-0.3 mol / L citric acid as an inhibitor and complexing agent, 0.05-0.15 mol / L sodium dodecyl sulfate as a surfactant to improve wettability and pore wall smoothness, and 0.01-0.1 mol / L sodium dodecyl sulfate. 1 / L rare earth metal salts promote etching activity and pore structure uniformity, 0.001-0.005 mol / L heteropolyacids enhance the redox stability of the electrolyte, 0.1-0.5 wt% ionic liquids improve the conductivity and interfacial wettability of the electrolyte, and pH adjusters maintain the acid-base balance of the electrolyte, ensuring the stable progress of the etching process. This composite electrolyte system not only achieves efficient etching but also avoids the problems of excessive corrosion or rough pore walls caused by traditional strong acid systems, thereby obtaining an aluminum foil structure with uniform pore size and smooth pore walls.

[0022] In the electrochemical etching process, the application of pulsed voltage further enhances the precision and controllability of etching. This invention limits the ratio of forward voltage to reverse voltage to between 3:1 and 5:1, and the ratio of the duration of forward voltage to the duration of reverse voltage to between 1:1.5 and 1:2.5. This asymmetric pulse mode can effectively regulate the oxidation-reduction dynamic balance on the aluminum foil surface, avoiding local over-etching or passivation caused by unidirectional voltage. Simultaneously, the waveform of the pulsed voltage is preferably a square wave or trapezoidal wave, with both the rise and fall times less than 1 ms. This rapidly switching voltage mode can reduce polarization effects, improve etching efficiency, and ensure the uniformity of the hole structure. Furthermore, this invention proposes the use of light-assisted etching, with the light source being ultraviolet or visible light at an intensity of 10-100 mW / cm². 2 With a wavelength of 200-500nm, the introduction of light can stimulate photocatalytic reactions in the electrolyte, promote the generation of active substances, thereby accelerating the etching process and improving the regularity of the pore morphology.

[0023] In some embodiments, the rare earth metal salt is cerium nitrate or lanthanum nitrate; the heteropoly acid is phosphotungstic acid or silicomolybdic acid; the ionic liquid is either 1-butyl-3-methylimidazolium hexafluorophosphate or 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide; and the pH adjuster is oxalic acid or tartaric acid.

[0024] This invention further specifies the selection of key functional components in the electrolyte. Through optimization of specific combinations of rare earth metal salts, heteropoly acids, ionic liquids, and pH adjusters, the etching efficiency, stability, and environmental adaptability of the electrolyte are significantly improved, thereby ensuring that the uniformity, regularity, and surface chemical activity of the aluminum foil pore structure reach a better level. The rare earth metal salts are limited to cerium nitrate or lanthanum nitrate. These two rare earth compounds have unique catalytic and corrosion-inhibiting dual effects in the electrolyte: Ce in cerium nitrate... 3+ / Ce 4+ Redox couples can dynamically participate in the anodic oxidation process on the aluminum foil surface, regulating the local etching rate through valence state changes and avoiding pore size fluctuations caused by uneven electrolyte diffusion; while lanthanum nitrate's La... 3+It can preferentially adsorb at grain boundary defects in aluminum foil, forming a microscopic protective layer, inhibiting intergranular corrosion, and thus improving the mechanical integrity of the pore wall structure. The selection of heteropolyacids further focuses on phosphotungstic acid or silicomolybdic acid, whose multi-anionic structure exhibits supramolecular self-assembly characteristics in the electrolyte. It can form a dynamic composite interface with the alumina layer on the aluminum foil surface through electrostatic interactions, reducing the activation energy of the etching reaction on the one hand, and inhibiting excessive lateral expansion of pores through steric hindrance, ensuring narrow dispersion of the pore size distribution on the other. The specific ionic liquid chosen is 1-butyl. -3-methylimidazolium hexafluorophosphate or 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt, these two room temperature ionic liquids not only have the green chemical characteristics of low volatility and high thermal stability, but their unique synergistic effect of anions and cations can also form an "ionic lubrication effect" of electric double layer structure at the aluminum-electrolyte interface. The adsorption of large volume anions can locally shield the violent dissolution of metal ions caused by high electric field, while the planar conjugated structure of imidazole cations stabilizes the etching front through π-π stacking, thereby increasing the ratio of longitudinal hole growth rate to transverse corrosion rate.

[0025] The pH adjuster is limited to oxalic acid or tartaric acid. These two polyprotic organic acids can not only stabilize the electrolyte pH at the optimal etching window through the carboxyl dissociation equilibrium, but the unique α-hydroxy groups in their molecular structure can also form five- or six-membered ring chelates with aluminum ions, achieving efficient dissolution and mass transfer of etching products. In particular, the reducing properties of oxalic acid can neutralize the reactive oxygen free radicals generated in the electrolyte by the pulse voltage, avoiding over-passivation of the aluminum foil surface.

[0026] In some embodiments, the silane coupling agent is γ-aminopropyltriethoxysilane or γ-glycidoxypropyltrimethoxysilane.

[0027] This invention specifies two silane compounds with specific structures, γ-aminopropyltriethoxysilane or γ-glycidoxypropyltrimethoxysilane, as silane coupling agents. This allows for precise control of the chemical properties of the aluminum foil surface at the molecular level, thereby significantly improving the interfacial bonding strength and electrochemical stability between the aluminum foil and the electrode active material. From a molecular structure perspective, the primary amino group of KH-550 has lone pair electron donor characteristics, which can form coordination bonds with the hydroxyl groups on the aluminum foil surface. At the same time, its ethoxy group undergoes controlled hydrolysis in ethanol solution to generate silanol, which then forms a Si-O-Al covalent bond network with the alumina on the aluminum foil surface through a condensation reaction. This dual bonding mechanism results in a high bonding strength between the modified layer and the substrate.

[0028] In some embodiments, the electrolyte also contains 0.001-0.01 mol / L of a transition metal complex, wherein the transition metal complex is iron acetylacetonate or cobalt acetylacetonate.

[0029] This invention further specifies the addition of 0.001-0.01 mol / L of transition metal complexes to the electrolyte. Iron acetylacetonate and cobalt acetylacetonate, as classic β-diketone transition metal complexes, exhibit dynamic coordination dissociation equilibrium characteristics in the electrolyte due to their unique octahedral coordination field structure. When a pulse voltage is applied, the metal centers in the complexes form intermediates with phosphate groups in the electrolyte. These intermediates, acting as electron transfer mediators, significantly reduce the activation energy of the etching reaction, thereby increasing the etching rate under the same voltage conditions. Simultaneously, because the d-orbital electrons of the transition metal ions can delocalize with the 3p electrons of aluminum, this electron cloud rearrangement effect improves the uniformity of the current density distribution at the etching front, effectively avoiding the "crater"-like hole defects commonly found in traditional etching. Within the concentration range of the transition metal complexes, the catalytic effect is insignificant below 0.001 mol / L, while concentrations above 0.01 mol / L lead to excessive metal deposition and hole blockage.

[0030] In some embodiments, the ratio of the forward voltage to the reverse voltage of the pulse voltage is controlled between 3:1 and 5:1, and the ratio of the duration of the forward voltage to the duration of the reverse voltage is between 1:1.5 and 1:2.5.

[0031] This invention also precisely limits the pulse voltage parameters, controlling the ratio of forward voltage to reverse voltage between 3:1 and 5:1, and specifying the ratio of forward voltage duration to reverse voltage duration as 1:1.5 to 1:2.5. During the forward voltage stage, anodic dissolution occurs on the aluminum foil surface. If the forward voltage is too high or the duration is too long, an excessively thick passivation film will form at the etching front, hindering subsequent etching. The role of the reverse voltage is to locally destroy this passivation film, creating active sites for the next round of forward etching. By limiting the forward / reverse voltage ratio to this specific window of 3:1 to 5:1, sufficient driving force can be ensured to achieve a suitable dissolution rate for aluminum, while avoiding the "tunneling corrosion" phenomenon caused by excessive voltage, i.e., excessive longitudinal growth of holes with insufficient lateral expansion, resulting in a mismatch between depth and diameter.

[0032] In some embodiments, the segmented ultrasonic cleaning includes: a first stage of cleaning in deionized water at a frequency of 40-60 kHz for 3-5 minutes, a second stage of cleaning in ethanol at a frequency of 80-100 kHz for 2-4 minutes, and a third stage of cleaning in acetone at a frequency of 60-80 kHz for 1-3 minutes.

[0033] This invention also specifically defines the segmented ultrasonic cleaning process. Through a precise combination of different solvents, frequencies, and times in three stages, a progressively deepening cleaning system is constructed. This technical solution overcomes the contradiction between "surface cleanliness and deep residue" in traditional aluminum foil etching post-cleaning processes. From a microscopic cleaning mechanism perspective, the first stage involves cleaning in deionized water at a frequency of 40-60 kHz for 3-5 minutes. The energy generated by mid-frequency ultrasound acts on the macroscopic surface of the aluminum foil, physically stripping etching residues with a particle size greater than 1 μm. Simultaneously, high-frequency vibration promotes the desorption of surfactant molecules such as sodium dodecyl sulfonate from the aluminum foil surface. The second stage involves switching to ethanol and cleaning at a higher frequency of 80-100 kHz for 2-4 minutes. At this point, the ultrasound... The ultrasonic waves can penetrate the interior of the pores and perform directional cleaning of the channels. The low surface tension of ethanol makes it easier for it to penetrate into the micropores and dissolve organic residues such as ionic liquids and heteropolyacid decomposition products. In the third stage, acetone is used to clean for 1-3 minutes at a frequency of 60-80kHz. The strong polarity of acetone can effectively remove the metal-organic complexes of the monolayer on the surface of the aluminum foil. At the same time, the synergistic effect of medium and high frequency ultrasonic waves creates a vortex effect in the pores, ensuring that even small-diameter micropores can be thoroughly cleaned. Preferably, the first stage is 50kHz ultrasonic cleaning for 3 minutes to better remove residual electrolyte on the surface, the second stage is 90kHz ultrasonic cleaning for 3 minutes to further remove organic impurities, and the third stage is 70kHz ultrasonic cleaning for 2 minutes to ensure surface cleanliness.

[0034] In some embodiments, the surface-modified aluminum foil is further subjected to low-temperature plasma treatment, with a power of 50-200W and a treatment time of 1-5 minutes.

[0035] This invention further specifies that the aluminum foil after surface modification needs to undergo low-temperature plasma treatment. This technical feature fundamentally solves the key problems of insufficient surface energy and scarce chemically active sites in traditional aluminum foil. Through a physical-chemical synergistic modification mechanism, a breakthrough improvement in the interfacial performance of aluminum foil is achieved. From the perspective of plasma action mechanism, in an argon or nitrogen plasma environment with a power range of 50-200W and a treatment time of 1-5 minutes, high-energy electrons collide with gas molecules to generate a large number of active particles. These particles bombard the aluminum foil surface, resulting in modification. The ultraviolet radiation in the plasma can break the Al-O bonds in the aluminum oxide layer on the aluminum foil surface, exposing a fresh aluminum atom layer, which causes a surge in the surface hydroxyl density.

[0036] In some embodiments, the waveform of the pulse voltage is a square wave or a trapezoidal wave, and the pulse rise time and fall time are both less than 1ms.

[0037] This invention also sets crucial limitations on the pulse voltage waveform, specifying that the waveform is a square wave or trapezoidal wave with both the rise and fall times less than 1 ms. This technical feature, through precise control of the voltage transient response, fundamentally solves the problem of uncontrolled aperture morphology caused by waveform distortion in traditional electrochemical etching. Specifically, when a square wave with a rise / fall time of less than 1 ms is used, the electric field strength can reach a stable value in a short time. This allows the ion arrangement of the Helmholtz layer on the aluminum foil surface to be rapidly reorganized within each pulse cycle, thereby ensuring that the etching current density is always maintained within the optimal window. In contrast, the slow rise of conventional sine waves or gradually varying waveforms leads to lag in the reconstruction of the double electric layer, causing local current density fluctuations and resulting in uneven aperture.

[0038] In some embodiments, the electrochemical etching process is light-assisted, with the light source being ultraviolet or visible light, and the light intensity being 10-100 mW / cm². 2 The wavelength is 200-500nm.

[0039] This invention further introduces the technical features of photo-assisted electrochemical etching. By defining the synergistic mechanism of ultraviolet or visible light, it solves the industry problem of balancing etching rate and hole morphology accuracy in traditional etching processes. From the perspective of the coupling mechanism of photochemistry and electrochemistry, when photon energy of a specific wavelength acts on the electrolyte system, it triggers a triple synergistic effect. First, photons excite rare earth metal salts in the electrolyte to generate electron-hole pairs, which migrate to the aluminum foil / electrolyte interface, significantly reducing the activation energy of aluminum atom oxidation and dissolution, thus increasing the etching rate while maintaining the same voltage. Second, ultraviolet light induces ligand-metal charge transfer in heteropolyacids, generating highly oxidizing excited-state substances. These transient active species can selectively attack grain boundary defects on the aluminum foil surface, resulting in a high degree of consistency between the hole distribution and the aluminum foil grain structure. Most importantly, the visible light irradiation and pulse voltage form a spatiotemporal coupling. When the light intensity is controlled at 50-80 mW / cm², the effect is achieved. 2 At this time, a periodic photothermal gradient field can be formed on the surface of the aluminum foil. This dynamic thermal field induces micro-convection in the electrolyte, effectively eliminating the concentration polarization of etching products in the holes.

[0040] The following is a detailed explanation using specific embodiments: Example 1: The electrochemical etching method for preparing porous battery aluminum foil provided by this invention is as follows: 1. Aluminum foil pretreatment Material preparation: Select high-purity aluminum foil with a thickness of 20μm and cut it into square samples of 10cm×10cm; Surface cleaning: Immerse the aluminum foil in acetone, ethanol and deionized water in sequence, and ultrasonically clean each for 5 minutes to remove surface oil and impurities. Then dry it with nitrogen gas for later use. 2. Multi-stage gradient annealing Annealing equipment: A tubular annealing furnace is used, with high-purity argon gas introduced as a protective gas and the flow rate controlled at 1L / min; Annealing procedure: First stage: Increase the temperature to 200℃ at a rate of 5℃ / min and hold for 30 minutes; Second stage: Continue to heat to 300℃ and keep warm for 30 minutes; Third stage: Finally, raise the temperature to 400℃ and keep it warm for 30 minutes; Remove after it has cooled naturally to room temperature; Electrolyte preparation: Phosphoric acid: 0.5 mol / L Citric acid: 0.1 mol / L Sodium dodecyl sulfonate: 0.05 mol / L Cerium nitrate: 0.01 mol / L Phosphotungstic acid: 0.001 mol / L Ionic liquid (1-Butyl-3-methylimidazolium hexafluorophosphate): 0.1 wt% Oxalic acid (pH adjuster, adjusts pH to 2.5) Iron acetylacetone: 0.001 mol / L Electrochemical etching device: A dual-electrode system is adopted, with aluminum foil as the working electrode, platinum sheet as the counter electrode, and Ag / AgCl as the reference electrode; The electrolytic cell is placed in a constant temperature water bath, with the temperature controlled at 25±1℃; Etching parameters: Pulse power supply parameters: Forward voltage: 3V, reverse voltage: 1V (ratio 3:1) Forward duration: 10ms, reverse duration: 15ms (ratio 1:1.5) Pulse waveform: Square wave, rise / fall time ≤ 1ms Illumination assistance: Use ultraviolet lamps (wavelength 200nm, light intensity 10mW / cm²). 2 The light source was 10cm away from the sample. Etching time: 30 minutes; 4. Segmented ultrasonic cleaning First stage: Ultrasonic cleaning at 40kHz for 3 minutes in deionized water to remove residual electrolyte from the surface; Second stage: Ultrasonic cleaning at 80kHz for 2 minutes in anhydrous ethanol to further remove organic impurities; Third stage: Ultrasonic cleaning at 60kHz for 1 minute in acetone to ensure surface cleanliness; After cleaning, dry with nitrogen gas; 5. Surface modification treatment The cleaned aluminum foil was immersed in an ethanol solution containing 0.1 wt% γ-aminopropyltriethoxysilane (KH550) for 10 minutes, and then dried at 80°C for 10 minutes. 6. Low-temperature plasma treatment Radio frequency plasma equipment is used with an argon atmosphere (flow rate 50 sccm), power 50W, and a treatment time of 1 minute to enhance surface wettability and adhesion.

[0041] Example 2 The electrochemical etching method for preparing porous battery aluminum foil provided by this invention is as follows: 1. Aluminum foil pretreatment Material preparation: Select high-purity aluminum foil with a thickness of 20μm and cut it into square samples of 10cm×10cm; Surface cleaning: Immerse the aluminum foil in acetone, ethanol and deionized water in sequence, and ultrasonically clean each for 5 minutes to remove surface oil and impurities. Then dry it with nitrogen gas for later use. 2. Multi-stage gradient annealing Annealing equipment: A tubular annealing furnace is used, with high-purity argon gas introduced as a protective gas and the flow rate controlled at 1L / min; Annealing procedure: First stage: Increase the temperature to 300℃ at a rate of 5℃ / min and hold for 30 minutes; Second stage: Continue to heat to 400℃ and keep warm for 30 minutes; Third stage: Finally, raise the temperature to 500℃ and keep it warm for 30 minutes; Remove after it has cooled naturally to room temperature; 3. Electrochemical etching Electrolyte preparation: Phosphoric acid: 1.5 mol / L Citric acid: 0.3 mol / L Sodium dodecyl sulfonate: 0.15 mol / L Cerium nitrate: 0.1 mol / L Phosphotungstic acid: 0.005 mol / L Ionic liquid (1-Butyl-3-methylimidazolium hexafluorophosphate): 0.5 wt% Oxalic acid (pH adjuster, adjusts pH to 2.5) Iron acetylacetone: 0.01 mol / L Electrochemical etching device: A dual-electrode system is adopted, with aluminum foil as the working electrode, platinum sheet as the counter electrode, and Ag / AgCl as the reference electrode; The electrolytic cell is placed in a constant temperature water bath, with the temperature controlled at 25±1℃; Etching parameters: Pulse power supply parameters: Forward voltage: 5V, reverse voltage: 1V (ratio 5:1) Forward duration: 10ms, reverse duration: 25ms (ratio 1:2.5) Pulse waveform: Square wave, rise / fall time ≤ 1ms Illumination assistance: Use ultraviolet lamps (wavelength 500nm, light intensity 100mW / cm²). 2 The light source was 10cm away from the sample. Etching time: 30 minutes; 4. Segmented ultrasonic cleaning First stage: Ultrasonic cleaning at 60kHz for 5 minutes in deionized water to remove residual electrolyte from the surface; Second stage: Ultrasonic cleaning at 100kHz for 4 minutes in anhydrous ethanol to further remove organic impurities; Third stage: Ultrasonic cleaning in acetone at 80kHz for 3 minutes to ensure surface cleanliness; After cleaning, dry with nitrogen gas; 5. Surface modification treatment The cleaned aluminum foil was immersed in an ethanol solution containing 0.5 wt% γ-aminopropyltriethoxysilane (KH550) for 10 minutes, and then dried at 80°C for 10 minutes. 6. Low-temperature plasma treatment Radio frequency plasma equipment, argon atmosphere (flow rate 50 sccm), power 200W, and treatment time 5 minutes are used to enhance surface wettability and adhesion.

[0042] Example 3 The electrochemical etching method for preparing porous battery aluminum foil provided by this invention is as follows: 1. Aluminum foil pretreatment Material preparation: Select high-purity aluminum foil with a thickness of 20μm and cut it into square samples of 10cm × 10cm; Surface cleaning: Immerse the aluminum foil in acetone, ethanol and deionized water in sequence, and ultrasonically clean each for 5 minutes to remove surface oil and impurities. Then dry it with nitrogen gas for later use. 2. Multi-stage gradient annealing Annealing equipment: A tubular annealing furnace is used, with high-purity argon gas introduced as a protective gas and the flow rate controlled at 1L / min; Annealing procedure: First stage: Increase the temperature to 250℃ at a rate of 5℃ / min and hold for 30 minutes; Second stage: Continue to heat to 350℃ and keep warm for 30 minutes; Third stage: Finally, raise the temperature to 450℃ and keep it warm for 30 minutes; Remove after it has cooled naturally to room temperature; 3. Electrochemical etching Electrolyte preparation: Phosphoric acid: 1.0 mol / L Citric acid: 0.2 mol / L Sodium dodecyl sulfonate: 0.10 mol / L Lanthanum nitrate: 0.05 mol / L Molybdic acid: 0.003 mol / L Ionic liquid (1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide): 0.3 wt% Tartaric acid (pH adjuster, adjusts pH to 2.5) Cobalt acetylacetonate: 0.005 mol / L Electrochemical etching device: A dual-electrode system is adopted, with aluminum foil as the working electrode, platinum sheet as the counter electrode, and Ag / AgCl as the reference electrode; The electrolytic cell is placed in a constant temperature water bath, with the temperature controlled at 25±1℃; Etching parameters: Pulse power supply parameters: Forward voltage: 4V, reverse voltage: 1V (ratio 4:1) Forward duration: 10ms, reverse duration: 20ms (ratio 1:2.0) Pulse waveform: Trapezoidal wave, rise / fall time ≤ 1ms Illumination assistance: Use ultraviolet lamps (wavelength 350nm, light intensity 50mW / cm²). 2 The light source was 10cm away from the sample. Etching time: 30 minutes; 4. Segmented ultrasonic cleaning First stage: Ultrasonic cleaning at 50kHz for 4 minutes in deionized water to remove residual electrolyte from the surface; Second stage: Ultrasonic cleaning at 90kHz for 3 minutes in anhydrous ethanol to further remove organic impurities; Third stage: Ultrasonic cleaning at 70kHz for 2 minutes in acetone to ensure surface cleanliness; After cleaning, dry with nitrogen gas; 5. Surface modification treatment The cleaned aluminum foil was immersed in an ethanol solution containing 0.3wt% γ-aminopropyltriethoxysilane (KH550) for 10 minutes, and then dried at 80°C for 10 minutes. 6. Low-temperature plasma treatment Radio frequency plasma equipment, argon atmosphere (flow rate 50 sccm), power 100W, and treatment time 3 minutes are used to enhance surface wettability and adhesion.

[0043] Comparative Example 1 The specific implementation steps are the same as in Example 3, except that rare earth metal salts are not added to the electrolyte.

[0044] Comparative Example 2 The specific implementation steps are the same as in Example 3, except that the concentration of rare earth metal salt in the electrolyte is 0.5 mol / L.

[0045] Comparative Example 3 The specific implementation steps are the same as in Example 3, except that no heteropoly acid is added to the electrolyte.

[0046] Comparative Example 4 The specific implementation steps are the same as in Example 3, except that the concentration of heteropoly acid in the electrolyte is 0.1 mol / L.

[0047] Comparative Example 5 The specific implementation steps are the same as in Example 3, except that no ionic liquid is added to the electrolyte.

[0048] Comparative Example 6 The specific implementation steps are the same as in Example 3, except that the concentration of the ionic liquid in the electrolyte is 1 wt%.

[0049] Comparative Example 7 The specific implementation steps are the same as in Example 3, except that the aluminum foil is not modified with a silane coupling agent.

[0050] Comparative Example 8 The specific implementation steps are the same as in Example 3, except that no transition metal complexes are added to the electrolyte.

[0051] Experiment Example 1: Performance Comparison Experiment of Aluminum Foil for Perforated Batteries 1. Experimental objective: To test the porosity, pore size distribution uniformity, mechanical strength and electrochemical performance of the perforated aluminum foils prepared in Examples 1-3 and Comparative Examples 1-8.

[0052] 2. Experimental Procedure 2.1 Sample preparation: Perforated aluminum foil samples were prepared according to the steps of Examples 1-3 and Comparative Examples 1-8, with 3 parallel samples prepared for each condition; All samples were stored in the same environment (temperature 25±1℃, humidity 45±5%) for later use. 3. Testing Methods Porosity testing: The specific surface area of ​​the aluminum foil was measured using the nitrogen adsorption method, and the porosity was calculated using the mercury intrusion porosimetry method. Aperture distribution uniformity: Five fields of view were randomly selected using scanning electron microscopy (SEM) (100 pores were counted in each field of view), and the standard deviation of the pore size was calculated. Mechanical strength: The tensile strength of the aluminum foil was tested using a universal testing machine (tensile rate 1 mm / min). Electrochemical performance: Assemble a simulated battery (aluminum foil as the positive electrode current collector, LiFePO4 as the active material) and test its interfacial impedance (EIS) and cycle performance (1C rate, capacity retention after 100 cycles). The final test results are shown in Table 1 below.

[0053] Table 1 Test Results As can be seen from the above experimental tables, the perforated aluminum foil provided by this invention has excellent performance. Looking at the overall data of the perforated battery aluminum foil samples prepared in Examples 1-3 and Comparative Examples 1-8, Examples 1-3 show significantly better performance than the comparative examples. Example 3 achieves optimal overall performance through optimized process parameters and component combinations. Figure 1 These are microscopic images of the porous battery aluminum foil prepared in Example 3 of the present invention. In comparison, the porosity of Comparative Example 1 and Comparative Example 3 decreased to 28.5% and 30.6%, respectively, which fully demonstrates the irreplaceable role of these key components in improving etching activity and pore structure control. It is worth noting that although the porosity of Comparative Example 2 and Comparative Example 4 recovered to some extent, it was still significantly lower than that of the Example, indicating that the concentration balance of each component is crucial, and excessive addition may inhibit etching efficiency.

[0054] The test results of pore size distribution uniformity further verified the precise control capability of the process of the present invention. The pore size standard deviation of Example 3 was only 9.8 nm, while the pore size standard deviations of Comparative Example 5 and Comparative Example 7 reached 19.5 nm and 13.6 nm, respectively, indicating that the wettability of the electrolyte and subsequent surface treatment also have an important impact on the pore structure uniformity. Of particular note is that although the porosity of Comparative Example 6 is close to that of Example 1, its pore size standard deviation is still significantly higher, indicating that simply increasing the concentration of ionic liquid cannot completely reproduce the comprehensive control effect of the composite electrolyte system.

[0055] Mechanical property test data revealed the key role of multi-stage gradient annealing and surface modification treatment. The tensile strength of Example 3 reached 145 MPa, while the tensile strength of Comparative Example 7 dropped sharply to 118 MPa, which intuitively demonstrated the important influence of surface treatment on the mechanical properties of materials.

[0056] The electrochemical performance test results verified the outstanding advantages of the present invention from a practical application perspective; the interfacial impedance of Example 3 was as low as 2.38 Ω·cm.2 The capacity retention rate was as high as 97.1%, both of which were the best values ​​among all samples. In contrast, the interfacial impedance of Comparative Example 5 was as high as 4.67 Ω·cm. 2 The capacity retention rate was only 86.2%, which clearly shows that each component in the electrolyte composition makes an important contribution to the final electrochemical performance. Although the other processes of Comparative Example 8 were completely consistent with those of Example 3, its capacity retention rate was still significantly lower, proving that the special role of cobalt acetylacetone in improving etching uniformity and surface activity cannot be ignored.

[0057] Based on all the test data and technical analysis, it can be seen that the present invention has successfully solved the key problems of low porosity, uneven pore distribution, and decreased mechanical properties in traditional aluminum foil etching technology through the synergistic optimization of multiple technical means such as composite electrolyte formulation, precise pulse voltage control, and improved post-processing.

[0058] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing perforated battery aluminum foil by electrochemical etching, characterized in that, Includes the following steps: The aluminum foil was subjected to multi-stage gradient annealing under inert gas protection and then placed in an electrolyte for electrochemical etching under pulse voltage conditions. After etching, segmented ultrasonic cleaning is performed. Finally, the cleaned aluminum foil is subjected to surface modification treatment in an ethanol solution containing 0.1-0.5 wt% silane coupling agent to obtain the final product. The electrolyte comprises 0.5-1.5 mol / L phosphoric acid, 0.1-0.3 mol / L citric acid, 0.05-0.15 mol / L sodium dodecyl sulfonate, 0.01-0.1 mol / L rare earth metal salt, 0.001-0.005 mol / L heteropoly acid, 0.1-0.5 wt% ionic liquid, and pH adjuster.

2. The preparation method according to claim 1, characterized in that, The rare earth metal salt is cerium nitrate or lanthanum nitrate; the heteropoly acid is phosphotungstic acid or silicomolybdic acid; the ionic liquid is either 1-butyl-3-methylimidazolium hexafluorophosphate or 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide; and the pH adjuster is oxalic acid or tartaric acid.

3. The preparation method according to claim 1, characterized in that, The silane coupling agent is γ-aminopropyltriethoxysilane or γ-glycidoxypropyltrimethoxysilane.

4. The preparation method according to claim 1, characterized in that, The electrolyte also contains 0.001-0.01 mol / L of a transition metal complex, which is iron acetylacetone or cobalt acetylacetone.

5. The preparation method according to claim 1, characterized in that, The ratio of the forward voltage to the reverse voltage of the pulse voltage is controlled between 3:1 and 5:1, and the ratio of the duration of the forward voltage to the duration of the reverse voltage is between 1:1.5 and 1:2.

5.

6. The preparation method according to claim 1, characterized in that, The segmented ultrasonic cleaning includes: a first stage of cleaning in deionized water at a frequency of 40-60 kHz for 3-5 minutes, a second stage of cleaning in ethanol at a frequency of 80-100 kHz for 2-4 minutes, and a third stage of cleaning in acetone at a frequency of 60-80 kHz for 1-3 minutes.

7. The preparation method according to claim 1, characterized in that, The aluminum foil after surface modification is further subjected to low-temperature plasma treatment, with the treatment conditions being a power of 50-200W, a treatment time of 1-5 minutes, and the gas being argon or nitrogen.

8. The preparation method according to claim 1, characterized in that, The waveform of the pulse voltage is a square wave or a trapezoidal wave, and the pulse rise time and fall time are both less than 1ms.

9. The preparation method according to claim 1, characterized in that, The electrochemical etching process is assisted by light, with the light source being ultraviolet or visible light, the light intensity being 10-100mW / cm², and the wavelength being 200-500nm.

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