A modified aluminum composite current collector and a method for preparing the same

Abstract

The application discloses a modified aluminum composite current collector and a preparation method thereof, and relates to the field of lithium ion battery current collector materials. The method comprises the following steps: sequentially performing alkaline oil removal, alkali etching, light extraction and secondary activation pretreatment on an alloy aluminum foil; performing chemical plating of a Ni-P alloy on the surface of the aluminum foil to form a primer layer; then taking the chemically plated aluminum foil as a cathode, a high-purity zinc plate as an anode, and performing electroplating of a graphene composite zinc layer in an acid plating solution containing carboxyl-modified graphene; and finally performing rinsing, hot air drying and inert atmosphere annealing to obtain the modified aluminum composite current collector. The double-layer structure of the chemical plating Ni-P layer and the electroplated graphene composite zinc layer effectively solves the problems of large interface contact resistance, low initial efficiency, poor mechanical property and unstable conductivity of the traditional aluminum foil, the product has excellent comprehensive performance, the process is stable, the cost is controllable, and the method is suitable for industrialized production of lithium ion batteries.

Description

Technical Field

[0001] This invention relates to the field of current collector materials for lithium-ion batteries, specifically to a modified aluminum composite current collector and its preparation method. Background Technology

[0002] As the carrier of electrode materials and the electron transport channel, the current collector in lithium-ion batteries directly affects the energy density, cycle life, and safety of the battery. Currently, commercially available lithium-ion battery cathode current collectors mainly use aluminum foil, which has advantages such as good conductivity, low cost, and lightweight. However, a dense oxide film easily forms on the surface of aluminum foil, leading to increased interfacial contact resistance with the electrode active materials. Furthermore, it is prone to corrosion under long-term electrolyte erosion, causing battery performance degradation.

[0003] In existing technologies, surface plating is often used to improve the performance of aluminum foil current collectors, but this method has many limitations: when directly electroplating a metal layer, the oxide film on the surface of the aluminum foil will hinder the bonding between the plating and the substrate, causing the plating to easily peel off; although electroless nickel plating can solve the bonding problem, the conductivity of high-phosphorus nickel plating is poor and the cost is high; although simple zinc plating can improve corrosion resistance, the lattice matching between zinc and aluminum is poor, and direct deposition is prone to stress cracking, making it difficult to meet the stability requirements of long-term battery cycling.

[0004] Furthermore, traditional aluminum-based composite current collectors suffer from insufficient mechanical properties, making them prone to wrinkling or breakage during battery production processes such as rolling and slitting. Additionally, the uniformity of the coating is difficult to control, resulting in significant fluctuations in the current collector surface resistance and affecting battery consistency. Therefore, given the limitations of the aforementioned technologies, there is an urgent need to develop a modified aluminum composite current collector and its preparation method. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide a modified aluminum composite current collector and its preparation method. By sequentially constructing a chemically plated Ni-P alloy underlayer and an electroplated graphene composite zinc layer on the surface of aluminum foil, the problems of high interfacial contact resistance, low initial efficiency, poor mechanical properties and unstable conductivity caused by the oxide film on the surface of traditional aluminum foil are effectively solved.

[0006] The objective of this invention can be achieved through the following technical solutions: On one hand, the present invention provides a method for preparing a modified aluminum composite current collector, comprising the following steps: S1: Immerse aluminum foil in an alkaline degreasing solution and ultrasonically clean it to obtain degreased aluminum foil; immerse the degreased aluminum foil in an alkaline solution for alkaline etching treatment, then rinse it with deionized water to obtain alkaline etched aluminum foil; immerse the alkaline etched aluminum foil in a nitric acid solution for brightening treatment, then rinse it with deionized water to obtain bright aluminum foil; immerse the bright aluminum foil in a strongly alkaline zincate solution for activation treatment to obtain activated aluminum foil; immerse the activated aluminum foil in a nitric acid solution for stripping treatment to obtain stripped aluminum foil; perform a second activation treatment on the stripped aluminum foil to obtain second-activated aluminum foil. S2: The secondary activated aluminum foil is immersed in deionized water for pre-immersion treatment to obtain pre-immersion aluminum foil; the pre-immersion aluminum foil is immersed in a preheated chemical plating solution for chemical plating to obtain chemically plated aluminum foil; S3: Using electroless aluminum foil as the cathode and zinc plate as the anode, after the electroplating solution is preheated, the power is turned on and electroplating is started according to the set parameters. A graphene composite zinc layer is electroplated on the electroless aluminum foil to obtain coated aluminum foil. S4: After rinsing the coated aluminum foil with deionized water, it is dried with hot air and then annealed. After cooling to room temperature in the furnace, the modified aluminum composite current collector is obtained.

[0007] Further, in step S1, the alkaline degreasing solution, by weight, consists of 20-30 parts NaOH, 15-25 parts Na3PO4, 3-8 parts surfactant, and 800-1000 parts deionized water. The ultrasonic cleaning temperature is 60℃-70℃, and the time is 5min-10min. The alkaline solution used for alkaline etching is a mixture of 50-60 parts NaOH and 1000 parts deionized water. The alkaline etching temperature is 50℃-60℃, and the time is 1min-3min.

[0008] Furthermore, in step S1, the aluminum foil is selected from 1060 or 3003 alloy aluminum foil.

[0009] Furthermore, in step S1, the nitric acid solution used for the light extraction process consists of 300 parts nitric acid and 700 parts deionized water, and the soaking time at room temperature is 30-60 seconds.

[0010] Further, in step S1, the strongly alkaline zincate solution, by weight, consists of 400-500 parts NaOH, 80-100 parts ZnO, 1-3 parts FeCl3, and 1000 parts deionized water. The activation treatment is carried out at room temperature, and the soaking time is 20-60 seconds. The nitric acid solution used for the stripping treatment, by weight, consists of 300-500 parts nitric acid and 500 parts deionized water. The parameters for the secondary activation treatment are the same as those for the primary activation treatment. Further, in step S2, the electroless plating solution, by weight, consists of 25-35 parts of NiSO4·6H2O, 25-35 parts of NaH2PO2·H2O, 40-60 parts of a composite complexing agent, 0.01-0.03 parts of a stabilizer, and 1000 parts of deionized water, and the pH value is adjusted to 8.5-9.5 with ammonia water; the electroless plating solution is heated at 80℃-90℃, and pre-immersion is carried out in deionized water at 50℃-60℃ for 30s-50s; the electroless plating time is 5min-15min. Furthermore, in step S2, the complexing agent is composed of lactic acid and sodium citrate, with a weight ratio of lactic acid to sodium citrate of 1:2-5.

[0011] Furthermore, in step S2, the stabilizer is lead nitrate or thiourea.

[0012] Further, in step S3, the preheating temperature of the electroplating solution is 25℃-35℃, and the preheating time is 15min-20min; the cathode to anode area ratio is 1:1-2, and the electrode distance is maintained at 5cm-8cm; the cathode is immersed in the electroplating solution for 1min-2min before energizing; the temperature is controlled at 28℃-32℃ during electroplating, and the current density is 1A / dm³. 2 -3A / dm 2 Mechanical stirring is employed, with the stirring speed controlled at 200rpm-300rpm and the pulse parameters being a frequency of 45Hz-55Hz and a duty cycle of 40%-50%. The electroplating time is 10min-30min, resulting in a graphene composite zinc layer thickness of 1μm-4μm. Furthermore, in step S3, the zinc plate has a purity of 99.99%; the electroplating solution is an acidic zinc plating system, which, by weight, consists of 70-100 parts of ZnCl2, 180-220 parts of KCl, 25-30 parts of H3BO3, 5-10 parts of carboxylated modified graphene, 1-3 parts of leveling agent, and 1000 parts of deionized water, with a pH value of 4.5-5.5.

[0013] Furthermore, in step S3, the leveling agent is composed of benzyl acetone and polyethylene glycol, with a weight ratio of benzyl acetone to polyethylene glycol of 1:3, and the molecular weight range of polyethylene glycol is 1200-2200.

[0014] Further, the preparation method of the carboxylated modified graphene is as follows: First, the carboxylation modification of graphene is carried out by adding natural graphite powder into a mixed acid solution composed of concentrated nitric acid and concentrated sulfuric acid, stirring under ice bath conditions for 20 min-30 min, then slowly adding potassium permanganate, controlling the reaction temperature not to exceed 20℃, stirring continuously for 1 h-2 h, then raising the temperature to 35℃-40℃ and continuing the reaction for 30 min-45 min, then adding deionized water, raising the temperature to 90℃-95℃ and reacting for 10 min-15 min, finally adding hydrogen peroxide to terminate the reaction, centrifuging separation, washing with deionized water until neutral, and vacuum drying to obtain carboxylated modified graphene.

[0015] Furthermore, during the preparation of the carboxylated modified graphene, the ultrasonic dispersion power is 200W-300W and the frequency is 30kHz-40kHz.

[0016] Furthermore, in the preparation process of the carboxylated modified graphene, the materials are as follows by weight: 5-10 parts of natural graphite powder, 50-60 parts of concentrated nitric acid, 50-60 parts of concentrated sulfuric acid, 15-20 parts of potassium permanganate, 5-10 parts of hydrogen peroxide, and 200-250 parts of deionized water.

[0017] Furthermore, the concentrated nitric acid has a mass fraction of 65%-68%.

[0018] Furthermore, the concentrated sulfuric acid has a mass fraction of 98%.

[0019] Furthermore, the mass fraction of the hydrogen peroxide is 30%.

[0020] Furthermore, in step S4, the number of times of rinsing with deionized water is 2 to 5 times, each time for 15 to 30 seconds; the hot air drying temperature is 60℃ to 80℃, and the time is 15 to 20 minutes; the annealing treatment is carried out in an inert atmosphere at a temperature of 150℃ to 250℃ and a holding time of 1 to 2 hours. On the other hand, the present invention provides a modified aluminum composite current collector prepared by the above-mentioned method.

[0021] The beneficial effects of this invention are: 1. This invention effectively solves the problem of high interfacial contact resistance caused by the oxide film on the surface of traditional aluminum foil through a double-layer structure design of "chemically plated Ni-P alloy base layer + electroplated graphene composite zinc layer". This makes the first-time efficiency of the modified aluminum composite current collector much higher than that of untreated aluminum foil and single-layer samples. At the same time, the dense double-layer coating can isolate the electrolyte from the corrosion of the aluminum substrate, greatly extend the cycle life, and fully meet the stability requirements of long-term cycle of lithium-ion batteries.

[0022] 2. The modified composite current collector has significantly improved longitudinal and transverse tensile strength, and also has high strength and good toughness. It can resist the mechanical stress of rolling and slitting processes in battery production and avoid wrinkles or breakage. In addition, its puncture strength is greatly improved, which can reduce the safety risk of short circuit caused by external force puncture during battery assembly and meet the stringent requirements of industrial production for the mechanical properties of current collectors.

[0023] 3. This invention precisely defines the key parameters for each stage of aluminum foil pretreatment, chemical plating, electroplating and post-treatment. Moreover, the performance indicators of multiple embodiments show small fluctuations, indicating that the process system has high stability, can achieve mass production, ensures consistent performance of each batch of composite current collectors, avoids the impact of performance fluctuations on battery consistency, and meets the standardized production requirements of the lithium-ion battery industry.

[0024] 4. This invention uses conventional alloy aluminum foil as the substrate. This type of aluminum foil has low cost and is commercially available. The agents used in the chemical plating and electroplating processes are all conventional chemical raw materials, which are easy to obtain and have controllable costs, making them more economical than high-cost precious metal coatings. At the same time, by optimizing the dispersion process of modified graphene, graphene agglomeration and waste can be avoided. While ensuring high performance, cost is also taken into account, and it has the potential for large-scale application. Detailed Implementation

[0025] The technical solutions in the embodiments of the present invention will be clearly and completely described below. 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.

[0026] Example 1 A method for preparing a modified aluminum composite current collector includes the following steps: S1: Select 1060 alloy aluminum foil with a thickness of 8μm. First, immerse it in an alkaline degreasing solution prepared by weight of 20 parts NaOH, 15 parts Na3PO4, 3 parts sodium dodecyl sulfate, and 800 parts deionized water, and ultrasonically clean it at 60℃ for 5 minutes. After removal, rinse it three times with deionized water. Then, immerse the degreased aluminum foil in an alkaline etching solution prepared by 50 parts NaOH and 1000 parts deionized water at 50℃ for 1 minute, and rinse it three times with deionized water. Subsequently, immerse it in 300 parts of 65% nitric acid and 700 parts of... The aluminum foil was immersed in a brightening solution containing deionized water for 30 seconds at room temperature and then rinsed three times with deionized water. Next, the brightened aluminum foil was immersed in a strongly alkaline zincate solution prepared with 400 parts NaOH, 80 parts ZnO, 1 part FeCl3 and 1000 parts deionized water for 20 seconds at room temperature for the first activation and then rinsed twice with deionized water. After that, it was immersed in a stripping solution composed of 300 parts nitric acid and 500 parts deionized water for 30 seconds and then rinsed three times with deionized water. Finally, the activation step was repeated and the aluminum foil was rinsed three times with deionized water to obtain the aluminum foil after the second activation treatment.

[0027] S2: The chemical plating solution, prepared by weight of 25 parts NiSO4·6H2O, 25 parts NaH2PO2·H2O, 40 parts composite complexing agent (composed of 13.3 parts lactic acid and 26.7 parts sodium citrate), 0.01 parts Pb(NO3)2 and 1000 parts deionized water, is adjusted to pH 8.5 with ammonia water and heated to 80℃. The aluminum foil after secondary activation is pre-immersed in 50℃ deionized water for 30s, then immersed in the 80℃ chemical plating solution for 5min. After removal, it is rinsed 3 times with 60℃ deionized water and dried with cold air. The coating thickness is about 0.2μm, and the chemically plated aluminum foil is obtained.

[0028] S3: First, prepare carboxylated modified graphene: By weight, add 5 parts of natural graphite powder to a mixture of 50 parts of concentrated nitric acid (65% by mass) and 50 parts of concentrated sulfuric acid (98% by mass), stir in an ice bath for 20 minutes, slowly add 15 parts of potassium permanganate, control the temperature at 19℃, stir for 1 hour, then raise the temperature to 35℃ and react for 45 minutes, add 200 parts of deionized water, raise the temperature to 90℃ and react for 10 minutes, add 5 parts of hydrogen peroxide (30% by mass) to terminate the reaction, centrifuge, wash until neutral, and vacuum dry at 60℃ for 6 hours to obtain carboxylated modified graphene. The electroplating solution was then prepared as follows: 70 parts by weight of ZnCl2, 180 parts by weight of KCl, 25 parts by weight of H3BO3, 5 parts by weight of the above-mentioned carboxylated modified graphene, 1 part by weight of a leveling agent (composed of 0.25 parts by weight of benzyl acetone and 0.75 parts by weight of polyethylene glycol with a molecular weight of 1200), and 1000 parts by weight of deionized water were mixed. The pH was adjusted to 4.5, and the solution was preheated to 25°C and stabilized for 15 minutes. The electroless plated aluminum foil was used as the cathode, and a 99.99% pure zinc plate was used as the anode. The cathode-to-anode area ratio was 1:1, and the electrode distance was 5 cm. After immersing the cathode in the plating solution for 2 minutes to remove air bubbles, the power was turned on, and the solution was applied at a temperature of 28°C and a current density of 1 A / dm³. 2 Electroplating was performed for 10 minutes under the conditions of mechanical stirring speed of 200 rpm, pulse frequency of 45 Hz and duty cycle of 40%, with a zinc layer thickness of 1.05 μm. During the process, the pH value was measured every 6 minutes and kept at 4.5 to obtain the electroplated aluminum foil.

[0029] S4: Rinse the electroplated aluminum foil twice with deionized water for 15 seconds each time, dry it with hot air at 60°C for 15 minutes, and then anneal it at 150°C for 1 hour in a nitrogen inert atmosphere. Cool it to room temperature with the furnace to obtain the modified aluminum composite current collector.

[0030] Example 2 A method for preparing a modified aluminum composite current collector includes the following steps: S1: Select 10μm thick 3003 alloy aluminum foil. First, immerse it in an alkaline degreasing solution prepared by weight of 25 parts NaOH, 20 parts Na3PO4, 5 parts sodium dodecyl sulfate, and 900 parts deionized water, and ultrasonically clean it at 65℃ for 7 minutes. After removal, rinse it three times with deionized water. Then, immerse the degreased aluminum foil in an alkaline etching solution prepared by 55 parts NaOH and 1000 parts deionized water at 55℃ for 2 minutes, and rinse it three times with deionized water. Subsequently, immerse it in 300 parts of 66% nitric acid and 700 parts of... The aluminum foil was immersed in a brightening solution containing deionized water for 45 seconds at room temperature and rinsed three times with deionized water. Then, the brightened aluminum foil was immersed in a strongly alkaline zincate solution prepared with 450 parts NaOH, 90 parts ZnO, 2 parts FeCl3 and 1000 parts deionized water for 40 seconds at room temperature for the first activation and rinsed twice with deionized water. After that, it was immersed in a stripping solution composed of 400 parts nitric acid and 500 parts deionized water for 30 seconds and rinsed three times with deionized water. Finally, the activation step was repeated and the aluminum foil was rinsed three times with deionized water to obtain the aluminum foil after the second activation treatment.

[0031] S2: The chemical plating solution, prepared by weight of 30 parts NiSO4·6H2O, 30 parts NaH2PO2·H2O, 50 parts composite complexing agent (composed of 16.7 parts lactic acid and 33.3 parts sodium citrate), 0.02 parts Pb(NO3)2 and 1000 parts deionized water, is adjusted to pH 9.0 with ammonia water and heated to 85°C. The aluminum foil after secondary activation is pre-immersed in deionized water at 55°C for 40 seconds, then immersed in the chemical plating solution at 85°C for 10 minutes. After removal, it is rinsed three times with deionized water at 60°C and dried with cold air. The coating thickness is about 0.35 μm, and the chemically plated aluminum foil is obtained.

[0032] S3: First, prepare carboxylated modified graphene: By weight, add 7 parts of natural graphite powder to a mixture of 55 parts of concentrated nitric acid (66% by mass) and 55 parts of concentrated sulfuric acid (98% by mass), stir in an ice bath for 25 minutes, slowly add 17 parts of potassium permanganate, control the temperature at 14℃, stir for 1.5 hours, then raise the temperature to 37℃ and react for 35 minutes, add 225 parts of deionized water, raise the temperature to 92℃ and react for 12 minutes, add 7 parts of hydrogen peroxide (30% by mass) to terminate the reaction, centrifuge, wash until neutral, and vacuum dry at 60℃ for 6 hours to obtain carboxylated modified graphene. The electroplating solution was then prepared as follows: 85 parts by weight of ZnCl2, 200 parts by weight of KCl, 27 parts by weight of H3BO3, 7 parts by weight of the above-mentioned carboxylated modified graphene, 2 parts by weight of a leveling agent (composed of 0.5 parts by weight of benzyl acetone and 1.5 parts by weight of polyethylene glycol with a molecular weight of 1500), and 1000 parts by weight of deionized water were mixed. The pH was adjusted to 5.0, and the solution was preheated to 30°C and stabilized for 17 minutes. The electroless plated aluminum foil was used as the cathode, and a 99.99% pure zinc plate was used as the anode. The cathode-to-anode area ratio was 1:1.5, and the electrode distance was 6.5 cm. After immersing the cathode in the plating solution for 1.5 minutes to remove air bubbles, the power was turned on, and the solution was applied at a temperature of 30°C and a current density of 2 A / dm³. 2 Electroplating was performed for 20 minutes under the conditions of mechanical stirring speed of 250 rpm, pulse frequency of 50 Hz and duty cycle of 45%, with a zinc layer thickness of 2.4 μm. During the process, the pH value was measured every 5 minutes and kept at 5.0 to obtain the electroplated aluminum foil.

[0033] S4: Rinse the electroplated aluminum foil three times with deionized water for 22 seconds each time, dry it with hot air at 70°C for 17 minutes, and then anneal it at 200°C for 1.5 hours in a nitrogen inert atmosphere. Cool it to room temperature with the furnace to obtain the modified aluminum composite current collector.

[0034] Example 3 A method for preparing a modified aluminum composite current collector includes the following steps: S1: Select 12μm thick 3003 alloy aluminum foil. First, immerse it in an alkaline degreasing solution prepared by weight of 30 parts NaOH, 25 parts Na3PO4, 8 parts sodium dodecyl sulfate, and 1000 parts deionized water, and ultrasonically clean it at 70℃ for 10 minutes. After removal, rinse it three times with deionized water. Then, immerse the degreased aluminum foil in an alkaline etching solution prepared by 60 parts NaOH and 1000 parts deionized water at 60℃ for 3 minutes, and rinse it three times with deionized water. Finally, immerse it in 300 parts by mass of 68% nitric acid and 700... The aluminum foil was immersed in a brightening solution containing 500 parts NaOH, 100 parts ZnO, 3 parts FeCl3, and 1000 parts deionized water for 60 seconds at room temperature, followed by rinsing with deionized water three times. Then, the brightened aluminum foil was immersed in a strongly alkaline zincate solution containing 500 parts NaOH, 100 parts ZnO, 3 parts FeCl3, and 1000 parts deionized water for 60 seconds at room temperature for the first activation, followed by rinsing with deionized water twice. After that, it was immersed in a stripping solution containing 500 parts nitric acid and 500 parts deionized water for 30 seconds, followed by rinsing with deionized water three times. Finally, the activation step was repeated once, followed by rinsing with deionized water three times, to obtain the aluminum foil after the second activation treatment.

[0035] S2: The chemical plating solution, prepared by weight of 35 parts NiSO4·6H2O, 35 parts NaH2PO2·H2O, 60 parts composite complexing agent (composed of 10 parts lactic acid and 50 parts sodium citrate), 0.03 parts Pb(NO3)2 and 1000 parts deionized water, is adjusted to pH 9.5 with ammonia water and heated to 90℃. The aluminum foil after secondary activation is pre-immersed in deionized water at 60℃ for 50s, and then immersed in the chemical plating solution at 90℃ for 15min. After removal, it is rinsed 3 times with deionized water at 60℃ and dried with cold air. The coating thickness is about 0.5μm, and the chemically plated aluminum foil is obtained.

[0036] S3: First, prepare carboxylated modified graphene: By weight, add 10 parts of natural graphite powder to a mixture of 60 parts of concentrated nitric acid (68% by mass) and 60 parts of concentrated sulfuric acid (98% by mass), stir in an ice bath for 30 minutes, slowly add 20 parts of potassium permanganate, control the temperature at 12℃, stir for 2 hours, then raise the temperature to 40℃ and react for 30 minutes, add 250 parts of deionized water, raise the temperature to 95℃ and react for 15 minutes, add 10 parts of hydrogen peroxide (30% by mass) to terminate the reaction, centrifuge, wash until neutral, and vacuum dry at 60℃ for 6 hours to obtain carboxylated modified graphene. The electroplating solution was then prepared as follows: 100 parts by weight of ZnCl2, 220 parts by weight of KCl, 30 parts by weight of H3BO3, 10 parts by weight of the above-mentioned carboxylated modified graphene, 3 parts by weight of a leveling agent (composed of 0.75 parts by weight of benzyl acetone and 2.25 parts by weight of polyethylene glycol with a molecular weight of 2200), and 1000 parts by weight of deionized water were mixed. The pH was adjusted to 5.5, and the solution was preheated to 35°C and stabilized for 20 minutes. Using the electroless plated aluminum foil as the cathode and a 99.99% pure zinc plate as the anode, the cathode-to-anode area ratio was 1:2, and the electrode distance was 8 cm. After immersing the cathode in the plating solution for 2 minutes to remove air bubbles, the power was turned on, and the plating was performed at a temperature of 32°C and a current density of 3 A / dm³. 2 Electroplating was performed for 30 minutes under the conditions of mechanical stirring speed of 300 rpm, pulse frequency of 55 Hz and duty cycle of 50%, with a zinc layer thickness of 3.95 μm. During the process, the pH value was measured every 4 minutes and kept at 5.5 to obtain the electroplated aluminum foil.

[0037] S4: Rinse the electroplated aluminum foil 5 times with deionized water for 30 seconds each time, dry it with hot air at 80°C for 20 minutes, and then anneal it at 250°C for 2 hours in a nitrogen inert atmosphere. Cool it to room temperature with the furnace to obtain the modified aluminum composite current collector.

[0038] Comparative Example 1 Compared with Example 2, this comparative example uses 3003 alloy aluminum foil with a thickness of 10μm. No pretreatment, coating or post-treatment steps are performed. It is used directly as a control sample. All other steps and parameters are the same. This comparative example will not be repeated. Finally, the modified aluminum composite current collector is obtained.

[0039] Comparative Example 2 Compared with Example 2, this comparative example omits the step of S3 electroplating zinc-graphene composite layer after completing S1 aluminum foil pretreatment and S2 chemical plating of Ni-P layer. Instead, it directly performs S4 deionized water rinsing, hot air drying and annealing treatment. The remaining steps and parameters are the same, and will not be repeated in this comparative example. Finally, a modified aluminum composite current collector sample containing only chemically plated Ni-P layer is obtained.

[0040] Comparative Example 3 Compared with Example 2, this comparative example omits the S2 electroless Ni-P layer plating step after completing the S1 aluminum foil pretreatment, and directly proceeds to the S3 electroplating of zinc graphene composite layer and subsequent S4 post-treatment. The remaining steps and parameters are the same, and will not be repeated in this comparative example. Finally, a modified aluminum composite current collector sample containing only the electroless Ni-P layer is obtained.

[0041] Comparative Example 4 Compared with Example 2, this comparative example does not add carboxylated modified graphene when preparing the electroplating solution in S3. All other steps and parameters are the same, and will not be repeated here. The final result is a composite current collector sample with an electroplated zinc layer without graphene.

[0042] Comparative Example 5 Compared with Example 2, in S3, ordinary graphene without carboxylation modification was used to prepare the graphene dispersion. The remaining steps and parameters were the same, and will not be repeated in this comparative example. Finally, the electroplated zinc layer composite current collector sample was obtained.

[0043] Comparative Example 6 Compared with Example 2, this comparative example omits the step of annealing at 150°C for 1 hour in a nitrogen inert atmosphere after S3 electroplating, and directly cools to room temperature naturally. The remaining steps and parameters are the same, and will not be repeated in this comparative example. Finally, a modified aluminum composite current collector sample without annealing treatment is obtained.

[0044] The performance of the modified aluminum composite current collectors prepared in Examples 1-3 and the modified aluminum composite current collectors prepared in Comparative Examples 1-6 were tested, and the detailed results are shown in Table 1.

[0045] Table 1: Test Results Based on the analysis of test data, the modified aluminum composite current collectors prepared in Examples 1-3 of this invention have the following advantages: Excellent electrochemical performance: The initial efficiency is consistently 89%-92%, higher than the comparative ratio of 72%-83%, indicating that it has low interfacial contact resistance with electrode active materials and high charge transfer efficiency; the cycle life is as long as 1480-1530 cycles, demonstrating extremely strong resistance to electrolyte corrosion and ensuring the long-term cycle stability of the battery.

[0046] Outstanding mechanical properties: MD (longitudinal) tensile strength reaches 292MPa-305MPa, and TD (transverse) tensile strength reaches 275MPa-285MPa, which can effectively resist the mechanical stress of rolling and slitting processes in battery production and avoid wrinkles or breakage; MD elongation is 31%-34%, and TD elongation is 28%-31%, combining strength and toughness; puncture strength is 310gf-325gf, which can reduce the risk of short circuit caused by external force puncture during battery assembly.

[0047] High performance stability: The fluctuation range of various indicators in Examples 1-3 is small, such as the difference in first-efficiency value of only 3% and the difference in cycle life of 50 weeks. This shows that the process system of aluminum foil pretreatment + chemical plating of Ni-P layer + electroplating of graphene composite zinc layer + annealing treatment has strong controllability and can mass-produce composite current collectors with consistent performance to meet the consistency requirements of battery industrialization.

[0048] A comparison of Comparative Example 1 and Example 2 shows that: Comparative Example 1 uses 10μm thick 3003 alloy aluminum foil without any pretreatment, coating, or post-treatment. Its initial efficiency is only 72%, its cycle life is only 550 cycles, its MD tensile strength is 120MPa, its TD tensile strength is 112MPa, its MD elongation is 3%, its TD elongation is 2%, and its puncture strength is 85gf. All performance indicators are far lower than those of Example 2. This indicates that the oxide film on the surface of the untreated aluminum foil will significantly increase the interfacial contact resistance, reduce corrosion resistance, and has weak mechanical properties. The full process treatment of Example 2 can effectively solve these problems and greatly improve the overall performance of the current collector.

[0049] A comparison of Comparative Example 2 and Example 2 shows that: Comparative Example 2, after completing the aluminum foil pretreatment and electroless Ni-P layer plating, omitted the step of electroplating the graphene composite zinc layer. Its initial efficiency (80%), cycle life (980 cycles), tensile strength (MD) of 205 MPa, tensile strength (TD) of 192 MPa, elongation (MD) of 12%, elongation (TD) of 10%, and puncture strength (180 gf) are all lower than those of Example 2. This indicates that relying solely on electroless Ni-P layer plating cannot fully meet the current collector's requirements for high electrochemical and mechanical properties. The electroplated graphene composite zinc layer plays a key role in further improving the current collector's resistance to electrolyte corrosion, conductivity, and mechanical strength.

[0050] Comparing Comparative Example 3 and Example 2, it can be seen that: After completing the aluminum foil pretreatment, Comparative Example 3 omitted the step of electroless Ni-P plating and directly electroplated the zinc-graphene composite layer. Its first-time efficiency of 78%, cycle life of 850 cycles, MD tensile strength of 184 MPa, TD tensile strength of 171 MPa, MD elongation of 8%, TD elongation of 7%, and puncture strength of 152 gf were significantly lower than those of Example 2. This proves that the electroless Ni-P plating layer, as a transitional underlayer, can effectively improve the bonding force between the aluminum foil and the subsequent zinc-graphene composite layer. The lack of this transitional layer will lead to weak coating bonding, which in turn will significantly deteriorate the current collector performance.

[0051] Comparing Comparative Example 4 and Example 2, it can be seen that: Comparative Example 4 did not add carboxylated modified graphene when preparing the electroplating solution, and only formed a normal zinc layer. Its initial efficiency was 82%, cycle life was 1050 cycles, MD tensile strength was 222 MPa, TD tensile strength was 205 MPa, MD elongation was 15%, TD elongation was 13%, and puncture strength was 204 gf, which were lower than those of Example 2. It can be seen that modified graphene can effectively improve the conductivity, density and mechanical properties of the zinc layer. The lack of graphene will cause the coating performance to decline and cannot achieve the excellent effect of the composite coating in Example 2.

[0052] A comparison between Comparative Example 5 and Example 2 shows that: Comparative Example 5 used ordinary graphene without carboxylation modification when preparing the graphene dispersion. Its initial efficiency was 83%, cycle life was 1100 cycles, MD tensile strength was 234 MPa, TD tensile strength was 214 MPa, MD elongation was 18%, TD elongation was 16%, and puncture strength was 221 gf, which were lower than those of Example 2. This indicates that carboxylation modification can improve the dispersibility of graphene in the electroplating solution, allowing it to be more uniformly integrated into the zinc layer and fully exert its reinforcing effect. Ordinary graphene, due to its poor dispersibility, cannot achieve the same performance improvement effect.

[0053] Comparing Comparative Example 6 and Example 2, it can be seen that after electroplating, Comparative Example 6 omitted the annealing process under an inert atmosphere and directly cooled naturally. Its initial efficiency was 81%, cycle life was 920 cycles, MD tensile strength was 195 MPa, TD tensile strength was 185 MPa, MD elongation was 10%, TD elongation was 9%, and puncture strength was 173 gf, which were lower than those of Example 2. This shows that the annealing process can effectively release the internal stress of the coating, optimize the coating structure, and improve the density and bonding strength of the coating. The absence of this step will lead to easy cracking of the coating and a decrease in bonding strength, which will affect the overall performance of the current collector.

[0054] The above description is merely an example and illustration of the concept of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described or use similar methods to replace them, as long as they do not deviate from the concept of the invention or exceed the scope defined in the claims, they should all fall within the protection scope of the present invention.

Claims

1. A method for preparing a modified aluminum composite current collector, characterized in that, Includes the following steps: S1: Immerse aluminum foil in an alkaline degreasing solution and ultrasonically clean it to obtain degreased aluminum foil; immerse the degreased aluminum foil in an alkaline solution for alkaline etching treatment, then rinse it with deionized water to obtain alkaline etched aluminum foil; immerse the alkaline etched aluminum foil in a nitric acid solution for brightening treatment, then rinse it with deionized water to obtain bright aluminum foil; immerse the bright aluminum foil in a strongly alkaline zincate solution for activation treatment to obtain activated aluminum foil; immerse the activated aluminum foil in a nitric acid solution for stripping treatment to obtain stripped aluminum foil; perform a second activation treatment on the stripped aluminum foil to obtain second-activated aluminum foil. S2: The secondary activated aluminum foil is immersed in deionized water for pre-immersion treatment to obtain pre-immersion aluminum foil; the pre-immersion aluminum foil is immersed in a preheated chemical plating solution for chemical plating to obtain chemically plated aluminum foil; S3: Using electroless aluminum foil as the cathode and zinc plate as the anode, after the electroplating solution is preheated, the power is turned on and electroplating is started according to the set parameters. A graphene composite zinc layer is electroplated on the electroless aluminum foil to obtain coated aluminum foil. S4: After rinsing the coated aluminum foil with deionized water, it is dried with hot air and then annealed. After cooling to room temperature in the furnace, it is taken out to obtain the modified aluminum composite current collector. In step S2, the chemical plating solution, by weight, consists of 25-35 parts of NiSO4·6H2O, 25-35 parts of NaH2PO2·H2O, 40-60 parts of a composite complexing agent, 0.01-0.03 parts of a stabilizer, and 1000 parts of deionized water, and the pH value is adjusted to 8.5-9.5 with ammonia. In step S3, the electroplating solution is an acidic zinc plating system, which consists of 70-100 parts by weight of ZnCl2, 180-220 parts by weight of KCl, 25-30 parts by weight of H3BO3, 5-10 parts by weight of carboxylated modified graphene, 1-3 parts by weight of leveling agent and 1000 parts by weight of deionized water, with a pH value of 4.5-5.

5.

2. The method for preparing a modified aluminum composite current collector according to claim 1, characterized in that, In step S1, the alkaline degreasing solution, by weight, consists of 20-30 parts NaOH, 15-25 parts Na3PO4, 3-8 parts surfactant, and 800-1000 parts deionized water. The ultrasonic cleaning temperature is 60℃-70℃, and the time is 5-10 minutes. The alkaline solution used for alkaline etching is a mixture of 50-60 parts NaOH and 1000 parts deionized water. The alkaline etching temperature is 50℃-60℃, and the time is 1-3 minutes.

3. The method for preparing a modified aluminum composite current collector according to claim 1, characterized in that, In step S1, the strongly alkaline zincate solution, by weight, consists of 400-500 parts NaOH, 80-100 parts ZnO, 1-3 parts FeCl3, and 1000 parts deionized water. The activation treatment is carried out at room temperature, and the immersion time is 20-60 seconds. The nitric acid solution used for the stripping treatment, by weight, consists of 300-500 parts nitric acid and 500 parts deionized water. The parameters for the secondary activation treatment are the same as those for the primary activation treatment.

4. The method for preparing a modified aluminum composite current collector according to claim 1, characterized in that, In step S2, the heating temperature of the chemical plating solution is 80℃-90℃, and the chemical plating time is 5min-15min.

5. The method for preparing a modified aluminum composite current collector according to claim 1, characterized in that, In step S3, the preheating temperature of the electroplating solution is 25℃-35℃, and the preheating time is 15min-20min; the cathode to anode area ratio is 1:1-2, and the electrode distance is maintained at 5cm-8cm; the cathode is immersed in the electroplating solution for 1min-2min before energizing; the temperature is controlled at 28℃-32℃ during electroplating, and the current density is 1A / dm³. 2 -3A / dm 2 Mechanical stirring is employed, with the stirring speed controlled at 200rpm-300rpm and the pulse parameters being a frequency of 45Hz-55Hz and a duty cycle of 40%-50%. The electroplating time is 10min-30min, resulting in a graphene composite zinc layer thickness of 1μm-4μm.

6. The method for preparing a modified aluminum composite current collector according to claim 1, characterized in that, In step S3, the zinc plate has a purity of 99.99%.

7. The method for preparing a modified aluminum composite current collector according to claim 1, characterized in that, The preparation method of the carboxylated modified graphene is as follows: First, the carboxylation modification of graphene is carried out by adding natural graphite powder into a mixed acid solution composed of concentrated nitric acid and concentrated sulfuric acid, stirring under ice bath conditions for 20 min-30 min, then slowly adding potassium permanganate, controlling the reaction temperature not to exceed 20℃, stirring continuously for 1 h-2 h, then raising the temperature to 35℃-40℃ and continuing the reaction for 30 min-45 min, then adding deionized water, raising the temperature to 90℃-95℃ and reacting for 10 min-15 min, finally adding hydrogen peroxide to terminate the reaction, centrifuging separation, washing with deionized water until neutral, and vacuum drying to obtain carboxylated modified graphene; then weigh the above carboxylated modified graphene.

8. The method for preparing a modified aluminum composite current collector according to claim 7, characterized in that, In the preparation process of carboxylated modified graphene, the materials are as follows by weight: 5-10 parts of natural graphite powder, 50-60 parts of concentrated nitric acid, 50-60 parts of concentrated sulfuric acid, 15-20 parts of potassium permanganate, 5-10 parts of hydrogen peroxide, and 200-250 parts of deionized water.

9. The method for preparing a modified aluminum composite current collector according to claim 1, characterized in that, In step S4, the deionized water rinsing is performed 2 to 5 times, each time for 15 to 30 seconds; the hot air drying temperature is 60℃ to 80℃, and the time is 15 to 20 minutes; the annealing treatment is carried out in an inert atmosphere at a temperature of 150℃ to 250℃ for 1 to 2 hours.

10. A modified aluminum composite current collector prepared by the method of any one of claims 1-9.

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