Modified aluminum composite current collector and preparation method thereof

Abstract

The invention 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 carrying out alkaline degreasing, alkaline etching, bright dipping and secondary activation pretreatment on the alloy aluminum foil; chemically plating a Ni-P alloy base layer on the surface of the aluminum foil; then electroplating a graphene composite zinc layer in an acidic plating solution containing carboxylated modified graphene by taking the chemically-plated aluminum foil as a cathode and a high-purity zinc plate as an anode; and finally, washing, hot air drying and inert atmosphere annealing are performed to prepare the modified aluminum composite current collector. Through the double-layer structure of the chemical plating Ni-P layer and the electroplating graphene composite zinc layer, the problems that a traditional aluminum foil interface is large in contact resistance, low in first efficiency, poor in mechanical property and unstable in conductivity are effectively solved, the comprehensive performance of the product is excellent, the process is stable, the cost is controllable, and the method is suitable for industrial production of the lithium ion battery.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of lithium ion battery current collector materials, in particular to a modified aluminum composite current collector and a preparation method thereof. BACKGROUND

[0002] The lithium ion battery current collector as the carrier and electron transmission channel of the electrode material directly affects the energy density, cycle life and safety of the battery. The current commercialized positive electrode current collector of the lithium ion battery mainly adopts aluminum foil, which has the advantages of good electrical conductivity, low cost, lightweight, etc., but the dense oxide film is easily formed on the surface of the aluminum foil, which increases the interface contact resistance with the electrode active material, and the corrosion easily occurs under the long-term erosion of the electrolyte, which causes the performance degradation of the battery.

[0003] In the prior art, in order to improve the performance of the aluminum foil current collector, a surface plating layer is often used, but there are many limitations: when directly electroplating a metal layer, the oxide film on the surface of the aluminum foil will hinder the combination of the plating layer and the substrate, which will cause the plating layer to easily fall off; although the chemical nickel plating can solve the problem of adhesion, the high-phosphorus nickel plating layer has poor electrical conductivity and high cost; although the pure zinc plating layer can improve the corrosion resistance, the lattice matching of zinc and aluminum is poor, and direct deposition will easily cause stress cracking, which is difficult to meet the stability requirements of long-term cycle of the battery.

[0004] In addition, the mechanical properties of the traditional aluminum-based composite current collector are insufficient, and the current collector is easily wrinkled or broken in the rolling, slitting and other processes of the battery production, and the uniformity of the plating layer is difficult to control, which causes the surface resistance of the current collector to fluctuate greatly, affecting the consistency of the battery. Therefore, according to the limitations of the above-mentioned related technologies, it is urgent to develop a modified aluminum composite current collector and a preparation method thereof. SUMMARY

[0005] Therefore, the purpose of the present application is to provide a modified aluminum composite current collector and a preparation method thereof, which effectively solves the problems of large interface contact resistance, low first efficiency, poor mechanical properties and unstable electrical conductivity caused by the oxide film on the surface of the traditional aluminum foil by sequentially building a chemical Ni-P alloy primer layer and an electroplated graphene composite zinc layer on the surface of the aluminum foil.

[0006] The purpose of the present application can be achieved by the following technical solutions: On the one hand, the present application provides a preparation method of a modified aluminum composite current collector, comprising the following steps: S1: immerse the aluminum foil into the alkaline oil removal liquid and ultrasonic clean, clean the oil removal aluminum foil; immerse the oil removal aluminum foil into the alkali solution for alkali etching treatment, then take out and rinse with deionized water, obtain the alkali etching aluminum foil; immerse the alkali etching aluminum foil into the nitric acid solution for lightening treatment, then take out and rinse with deionized water, obtain the lightening aluminum foil; immerse the lightening aluminum foil into the strong alkaline zincate solution for activation treatment, obtain the activated aluminum foil; immerse the activated aluminum foil into the nitric acid solution for stripping treatment, obtain the stripping aluminum foil; carry out secondary activation treatment on the stripping aluminum foil, obtain the secondary activated aluminum foil; S2: immerse the secondary activated aluminum foil into deionized water for pre- immersion treatment, obtain the pre- immersion aluminum foil; immerse the pre- immersion aluminum foil into the preheated chemical plating liquid for chemical plating, obtain the chemical plating aluminum foil; S3: take the chemical plating aluminum foil as the cathode, take the zinc plate as the anode, preheat the electroplating liquid, then connect the power supply, start electroplating according to the set parameters, electroplate the graphene composite zinc layer on the chemical plating aluminum foil, obtain the plated aluminum foil; S4: rinse the plated aluminum foil with deionized water, then carry out hot air drying, then carry out annealing treatment, cool to room temperature in the furnace, then take out, obtain the modified aluminum composite current collector.

[0007] Further, in the step S1, the alkaline oil removal liquid is composed of 20-30 parts of NaOH, 15-25 parts of Na3PO4, 3-8 parts of surfactant and 800-1000 parts of deionized water by weight fraction, the ultrasonic cleaning temperature is 60-70℃, and the time is 5-10 min; the alkali solution used for alkali etching treatment is obtained by mixing 50-60 parts of NaOH and 1000 parts of deionized water, the alkali etching temperature is 50-60℃, and the time is 1-3 min.

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

[0009] Further, in the step S1, the lightening treatment uses the nitric acid solution composed of 300 parts of nitric acid and 700 parts of deionized water, and the immersion time at room temperature is 30-60 s.

[0010] Further, in the step S1, the strong alkaline zincate solution is composed of 400-500 parts of NaOH, 80-100 parts of ZnO, 1-3 parts of FeCl3 and 1000 parts of deionized water by weight fraction, the activation treatment is carried out at room temperature, and the immersion time is 20-60 s; the nitric acid solution used for stripping treatment is composed of 300-500 parts of nitric acid and 500 parts of deionized water by weight fraction; the secondary activation treatment has the same parameters as the first 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 carboxyl-modified graphene is as follows: first, the carboxyl-modification of graphene is carried out, the natural graphite powder is added into a mixed acid solution composed of concentrated nitric acid and concentrated sulfuric acid, stirring is carried out under ice bath condition for 20 min-30 min, then, the potassium permanganate is slowly added, the reaction temperature is controlled to be not more than 20 DEG C, the stirring is continuously carried out for 1 h-2 h, then, the temperature is increased to 35 DEG C-40 DEG C, the reaction is continuously carried out for 30 min-45 min, then, the deionized water is added, the temperature is increased to 90 DEG C-95 DEG C, the reaction is carried out for 10 min-15 min, finally, the hydrogen peroxide is added to terminate the reaction, the centrifugal separation is carried out, the deionized water is washed until neutral, and then, vacuum drying is carried out, so that the carboxyl-modified graphene is obtained.

[0015] Further, in the preparation process of the carboxyl-modified graphene, the ultrasonic dispersion power is 200 W-300 W, and the frequency is 30 kHz-40 kHz.

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

[0017] Further, the mass fraction of the concentrated nitric acid is 65%-68%.

[0018] Further, the mass fraction of the concentrated sulfuric acid is 98%.

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

[0020] Further, in the step S4, the deionized water is washed for 2-5 times, each time for 15 s-30 s, the hot air drying temperature is 60 DEG C-80 DEG C, and the time is 15 min-20 min, the annealing treatment is carried out in an inert atmosphere, the temperature is 150 DEG C-250 DEG C, and the holding time is 1 h-2 h. On the other hand, the application provides the modified aluminum composite current collector prepared by the above preparation method.

[0021] The application has the following beneficial effects: 1. The application adopts the double-layer structure design of "chemical plating Ni-P alloy base layer + electroplating graphene composite zinc layer", effectively solves the problem of large interface contact resistance caused by the surface oxidation film of the traditional aluminum foil, makes the first efficiency of the modified aluminum composite current collector much higher than that of the untreated aluminum foil and the single plating layer sample, meanwhile, the dense double-layer plating layer can isolate the erosion of the electrolyte to the aluminum matrix, greatly prolongs the cycle life, and can 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: 8 μm thick 1060 alloy aluminum foil was first immersed in an alkaline degreasing liquid prepared from 20 parts of NaOH, 15 parts of Na3PO4, 3 parts of sodium dodecyl sulfate and 800 parts of deionized water by weight, and ultrasonically cleaned at 60°C for 5 min. After taking out, it was rinsed with deionized water for 3 times. Then the degreased aluminum foil was immersed in an alkali etching liquid prepared from 50 parts of NaOH and 1000 parts of deionized water at 50°C for 1 min, and rinsed with deionized water for 3 times. Subsequently, it was immersed in a lightening liquid prepared from 300 parts of 65% by mass nitric acid and 700 parts of deionized water, and soaked at room temperature for 30 s, and rinsed with deionized water for 3 times. Then the lightened aluminum foil was immersed in a strong alkaline zincate solution prepared from 400 parts of NaOH, 80 parts of ZnO, 1 part of FeCl3 and 1000 parts of deionized water, and activated at room temperature for 20 s for one time, and rinsed with deionized water for 2 times. After that, it was immersed in a stripping liquid prepared from 300 parts of nitric acid and 500 parts of deionized water for 30 s, and rinsed with deionized water for 3 times. Finally, the activation step was repeated for one time, and the aluminum foil was rinsed with deionized water for 3 times to obtain the aluminum foil after secondary activation treatment.

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

[0028] S3: first prepare carboxylated modified graphene: 5 parts of natural graphite powder is added into 50 parts of mixed solution of 65% concentrated nitric acid and 50 parts of 98% concentrated sulfuric acid, ice bath stirring for 20 min, slowly add 15 parts of potassium permanganate, control the temperature at 19℃, stirring for 1 h, then increase the temperature to 35℃ and react for 45 min, add 200 parts of deionized water, increase the temperature to 90℃ and react for 10 min, add 5 parts of 30% hydrogen peroxide to terminate the reaction, centrifugal separation, washing to neutral, vacuum drying at 60℃ for 6 h to obtain carboxylated modified graphene. Then prepare the plating solution: 70 parts of ZnCl2, 180 parts of KCl, 25 parts of H3BO3, 5 parts of the above carboxylated modified graphene, 1 part of leveling agent (the leveling agent is composed of benzylidene acetone 0.25 parts and polyethylene glycol with molecular weight of 1200 0.75 parts) and 1000 parts of deionized water are mixed, the pH is adjusted to 4.5, preheated to 25℃ and stabilized for 15 min; the aluminum foil after chemical plating is used as cathode, the pure zinc plate with purity of 99.99% is used as anode, the area ratio of cathode to anode is 1:1, the electrode distance is 5 cm, the cathode is immersed in the plating solution for 2 min to remove bubbles, then the power is connected, under the conditions of temperature 28℃, current density 1A / dm 2 , mechanical stirring speed 200 rpm, pulse frequency 45 Hz and duty cycle 40%, the zinc layer thickness is 1.05μm, the pH value is measured every 6 min during the process and kept at 4.5, to obtain the aluminum foil after electroplating.

[0029] S4: the aluminum foil after electroplating is washed with deionized water for 2 times, each time for 15 s, hot air drying at 60℃ for 15 min, then annealing at 150℃ for 1 h in nitrogen inert atmosphere, cooling to room temperature in the furnace, to obtain the modified aluminum composite current collector.

[0030] Example 2 A method for preparing a modified aluminum composite current collector, comprising the following steps: S1: Select 3003 alloy aluminum foil with thickness of 10 μm, first immerse it in alkaline degreasing liquid prepared by 25 parts of NaOH, 20 parts of Na3PO4, 5 parts of sodium dodecyl sulfate and 900 parts of deionized water by weight, ultrasonic cleaning at 65℃ for 7 min, then take out and rinse with deionized water for 3 times; then immerse the degreased aluminum foil in 55℃ alkaline etching liquid prepared by 55 parts of NaOH and 1000 parts of deionized water for 2 min, rinse with deionized water for 3 times; then immerse it in light-out liquid prepared by 300 parts of 66% mass fraction of nitric acid and 700 parts of deionized water, soak at room temperature for 45 s, rinse with deionized water for 3 times; then immerse the light-out aluminum foil in strong alkaline zincate solution prepared by 450 parts of NaOH, 90 parts of ZnO, 2 parts of FeCl3 and 1000 parts of deionized water, soak at room temperature for 40 s for activation, rinse with deionized water for 2 times; then immerse it in stripping liquid prepared by 400 parts of nitric acid and 500 parts of deionized water for 30 s, rinse with deionized water for 3 times; finally repeat the activation step, rinse with deionized water for 3 times, and get the aluminum foil after secondary activation treatment.

[0031] S2: The electroless plating liquid prepared by 30 parts of NiSO4·6H2O, 30 parts of NaH2PO2·H2O, 50 parts of composite complexing agent (the composite complexing agent is composed of 16.7 parts of lactic acid and 33.3 parts of sodium citrate), 0.02 parts of Pb(NO3)2 and 1000 parts of deionized water by weight is adjusted to pH 9.0 with ammonia water, and heated to 85℃; immerse the aluminum foil after secondary activation in 55℃ deionized water for 40 s, then immerse it in the electroless plating liquid at 85℃ for 10 min, take out and rinse with 60℃ deionized water for 3 times, dry with cold air, the thickness of the plated layer is about 0.35 μm, and get the aluminum foil after electroless plating.

[0032] S3: first prepare carboxylated modified graphene: 7 parts of natural graphite powder is added into 55 parts of mixed solution of 66% concentrated nitric acid and 55 parts of 98% concentrated sulfuric acid, ice bath stirring for 25 min, slowly add 17 parts of potassium permanganate, control the temperature to 14℃, stirring for 1.5h, then increase the temperature to 37℃ and react for 35 min, add 225 parts of deionized water, increase the temperature to 92℃ and react for 12 min, add 7 parts of 30% hydrogen peroxide to terminate the reaction, centrifugal separation, washing to neutral, vacuum drying at 60℃ for 6h to obtain carboxylated modified graphene. Then prepare the plating solution: 85 parts of ZnCl2, 200 parts of KCl, 27 parts of H3BO3, 7 parts of the above carboxylated modified graphene, 2 parts of leveling agent (the leveling agent is composed of benzylidene acetone 0.5 parts and polyethylene glycol with molecular weight of 1500 1.5 parts) and 1000 parts of deionized water are mixed, the pH is adjusted to 5.0, preheated to 30℃ and stabilized for 17 min; the aluminum foil after chemical plating is used as cathode, the pure zinc plate with purity of 99.99% is used as anode, the area ratio of cathode to anode is 1:1.5, the pole distance is 6.5 cm, the cathode is immersed in the plating solution for 1.5 min to remove bubbles, then the power is connected, under the conditions of temperature 30℃, current density 2A / dm 2 , mechanical stirring speed 250 rpm, pulse frequency 50 Hz and duty cycle 45%, the zinc layer thickness is 2.4μm, the pH value is measured every 5 min and kept at 5.0 during the process, to obtain the aluminum foil after electroplating.

[0033] S4: the aluminum foil after electroplating is washed with deionized water for 3 times, each time for 22 s, 70℃ hot air drying for 17 min, then annealing at 200℃ for 1.5h in nitrogen inert atmosphere, cooling to room temperature in the furnace, to obtain the modified aluminum composite current collector.

[0034] Example 3 A method for preparing a modified aluminum composite current collector, comprising the following steps: S1: Select 3003 alloy aluminum foil with thickness of 12 μm, first immerse it in alkaline degreasing liquid prepared by 30 parts of NaOH, 25 parts of Na3PO4, 8 parts of sodium dodecyl sulfate and 1000 parts of deionized water by weight, ultrasonic cleaning at 70℃ for 10 min, then take out and rinse with deionized water for 3 times; then immerse the degreased aluminum foil in 60℃ alkaline etching liquid prepared by 60 parts of NaOH and 1000 parts of deionized water for 3 min, rinse with deionized water for 3 times; then immerse it in light-out liquid prepared by 300 parts of 68% mass fraction of nitric acid and 700 parts of deionized water, soak at room temperature for 60 s, rinse with deionized water for 3 times; then immerse the light-out aluminum foil in strong alkaline zincate solution prepared by 500 parts of NaOH, 100 parts of ZnO, 3 parts of FeCl3 and 1000 parts of deionized water, soak at room temperature for 60 s for activation, rinse with deionized water for 2 times; then immerse it in stripping liquid prepared by 500 parts of nitric acid and 500 parts of deionized water for 30 s, rinse with deionized water for 3 times; finally repeat the activation step, rinse with deionized water for 3 times, and get the aluminum foil after secondary activation treatment.

[0035] S2: The electroless plating liquid prepared by 35 parts of NiSO4·6H2O, 35 parts of NaH2PO2·H2O, 60 parts of composite complexing agent (the composite complexing agent is composed of 10 parts of lactic acid and 50 parts of sodium citrate), 0.03 parts of Pb(NO3)2 and 1000 parts of deionized water by weight is adjusted to pH 9.5 with ammonia water, and heated to 90℃; immerse the aluminum foil after secondary activation in deionized water at 60℃ for 50 s, then immerse it in the electroless plating liquid at 90℃ for 15 min, take out and rinse with deionized water at 60℃ for 3 times, dry with cold air, the thickness of the plated layer is about 0.5 μm, get the aluminum foil after electroless plating.

[0036] S3: First, prepare carboxylated modified graphene: add 10 parts of natural graphite powder to 60 parts of a mixture of 68% concentrated nitric acid and 60 parts of 98% concentrated sulfuric acid by weight fraction, stir for 30 min in an ice bath, slowly add 20 parts of potassium permanganate, control the temperature to be 12°C, stir for 2 h, then raise the temperature to 40°C and react for 30 min, add 250 parts of deionized water, raise the temperature to 95°C and react for 15 min, add 10 parts of 30% hydrogen peroxide to terminate the reaction, centrifuge, wash until neutral, and vacuum dry at 60°C for 6 h to obtain carboxylated modified graphene. Then prepare the electroplating solution: mix 100 parts of ZnCl2, 220 parts of KCl, 30 parts of H3BO3, 10 parts of the above carboxylated modified graphene, 3 parts of a leveling agent (the leveling agent is composed of benzylidene acetone 0.75 parts and polyethylene glycol with a molecular weight of 2200 2.25 parts), and 1000 parts of deionized water by weight fraction, adjust the pH to 5.5, preheat to 35°C and stabilize for 20 min; use the aluminum foil after chemical plating as the cathode, a pure zinc plate with a purity of 99.99% as the anode, the area ratio of the cathode to the anode is 1:2, the electrode distance is 8 cm, the cathode is immersed in the plating solution for 2 min to remove bubbles, and then the power is turned on under the conditions of a temperature of 32°C, a current density of 3 A / dm2, a mechanical stirring speed of 300 rpm, a pulse frequency of 55 Hz, and a duty cycle of 50% to electroplate for 30 min, the thickness of the zinc layer is 3.95 μm, the pH value is measured every 4 min during the process and kept at 5.5, and the aluminum foil after electroplating is obtained. 2

[0037] S4: The aluminum foil after electroplating is washed with deionized water for 5 times, each time for 30 s, dried with hot air at 80°C for 20 min, then annealed at 250°C for 2 h in a nitrogen inert atmosphere, and cooled to room temperature in the furnace to obtain the modified aluminum composite current collector.

[0038] Comparative Example 1 In this comparative example, compared with Example 2, a 3003 alloy aluminum foil with a thickness of 10 μm is selected, without any pretreatment, plating layer and post-treatment steps, and directly used as a control sample, and the remaining steps and parameters are the same. This comparative example will not be repeated here. Finally, a modified aluminum composite current collector is obtained.

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

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

[0041] Comparative example 4 The comparative example is compared with example 2, no carboxylated modified graphene is added when preparing the electroplating solution in S3, and the remaining steps and parameters are the same. The comparative example will not be repeated here. Finally, a composite current collector sample with electroplated zinc layer without graphene is obtained.

[0042] Comparative example 5 The comparative example is compared with example 2, in S3, ordinary graphene that has not been carboxylated is used to prepare the graphene dispersion solution, and the remaining steps and parameters are the same. The comparative example will not be repeated here. Finally, a composite current collector sample with electroplated zinc layer is obtained.

[0043] Comparative example 6 The comparative example is compared with example 2, after electroplating in S3, the step of annealing at 150°C in a nitrogen inert atmosphere for 1h is omitted, and direct natural cooling to room temperature is performed. The remaining steps and parameters are the same. The comparative example will not be repeated here. Finally, a modified aluminum composite current collector sample without annealing treatment is obtained.

[0044] The modified aluminum composite current collectors prepared in examples 1-3 and the modified aluminum composite current collector samples prepared in comparative examples 1-6 are subjected to performance detection, and the detailed results are shown in table 1.

[0045] Table 1: test results According to the test data analysis, the modified aluminum composite current collectors prepared in examples 1-3 have the following advantages: Excellent electrochemical performance: the first efficiency is stable at 89%-92%, higher than 72%-83% of the comparative examples, indicating that the interface contact resistance with the electrode active material is small, and the charge transfer efficiency is high; the cycle life is as long as 1480-1530 weeks, which reflects strong resistance to electrolyte corrosion, and can guarantee the long-term cycle stability of the battery.

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

[0047] High performance stability: the fluctuation range of each index of Examples 1-3 is small, such as a first efficiency difference of only 3% and a cycle life difference of 50 weeks, indicating that the process system of aluminum foil pretreatment + chemical plating of Ni-P layer + electroplating of graphene composite zinc layer + annealing treatment is highly controllable, can batch produce composite current collectors with consistent performance, and meets the consistency requirements of battery industrialization.

[0048] Comparing Comparative Example 1 and Example 2: Comparative Example 1 uses a 3003 alloy aluminum foil with a thickness of 10 μm without any pretreatment, plating layer and post-treatment. Its first efficiency is only 72%, the cycle life is only 550 weeks, the MD tensile strength is 120 MPa, the TD tensile strength is 112 MPa, the MD elongation is 3%, the TD elongation is 2%, and the puncture strength is 85 gf. Each performance index is much lower than that of Example 2, which shows that the oxide film on the untreated aluminum foil surface can significantly increase the interface contact resistance and reduce the corrosion resistance, and the mechanical properties are weak. The full process treatment of Example 2 can effectively solve these problems and greatly improve the comprehensive performance of the current collector.

[0049] Comparing Comparative Example 2 and Example 2: After completing the aluminum foil pretreatment and chemical plating of Ni-P layer in Comparative Example 2, the step of electroplating graphene composite zinc layer is omitted. Its first efficiency is 80%, the cycle life is 980 weeks, the MD tensile strength is 205 MPa, the TD tensile strength is 192 MPa, the MD elongation is 12%, the TD elongation is 10%, and the puncture strength is 180 gf, all of which are lower than those of Example 2, indicating that relying only on chemical plating of Ni-P layer cannot fully meet the needs of the current collector for high electrochemical performance and mechanical properties. The electroplating of graphene composite zinc layer plays a key role in further improving the electrolyte corrosion resistance, electrical conductivity and mechanical strength of the current collector.

[0050] Comparing Comparative Example 3 and Example 2: After completing the aluminum foil pretreatment in Comparative Example 3, the step of chemical plating of Ni-P layer is omitted, and a zinc graphene composite layer is directly electroplated. Its first efficiency is 78%, the cycle life is 850 weeks, the MD tensile strength is 184 MPa, the TD tensile strength is 171 MPa, the MD elongation is 8%, the TD elongation is 7%, and the puncture strength is 152 gf, which is significantly lower than that of Example 2. This proves that the chemical plating of Ni-P layer as a transition primer layer can effectively improve the adhesion between the aluminum foil and the subsequent zinc graphene composite layer. The lack of this transition layer will result in poor adhesion of the plating layer, which in turn will greatly degrade the performance of the current collector.

[0051] Comparative Example 4 and Example 2 can be compared: Comparative Example 4 does not add carboxylated modified graphene when preparing the electroplating solution, only forms a common zinc layer, the first efficiency is 82%, the cycle life is 1050 weeks, the MD tensile strength is 222 MPa, the TD tensile strength is 205 MPa, the MD elongation is 15%, the TD elongation is 13%, and the puncture strength is 204 gf, which is lower than Example 2. It can be seen that the modified graphene can effectively improve the conductivity, density and mechanical properties of the zinc layer. The lack of graphene will cause the performance of the plated layer to decrease, and it is unable to achieve the excellent effect of the composite plated layer in Example 2.

[0052] Comparative Example 5 and Example 2 can be compared: Comparative Example 5 uses ordinary graphene that is not modified by carboxylation when preparing the graphene dispersion solution, the first efficiency is 83%, the cycle life is 1100 weeks, the MD tensile strength is 234 MPa, the TD tensile strength is 214 MPa, the MD elongation is 18%, the TD elongation is 16%, and the puncture strength is 221 gf, which is lower than Example 2. This shows that carboxylation modification can improve the dispersibility of graphene in the electroplating solution, so that it is more uniformly integrated into the zinc layer and fully plays a reinforcing role. Ordinary graphene cannot achieve the same performance improvement effect due to poor dispersibility.

[0053] Comparative Example 6 and Example 2 can be compared: Comparative Example 6 omits the annealing treatment step under the inert atmosphere after completing electroplating and directly cools naturally, the first efficiency is 81%, the cycle life is 920 weeks, the MD tensile strength is 195 MPa, the TD tensile strength is 185 MPa, the MD elongation is 10%, the TD elongation is 9%, and the puncture strength is 173 gf, which is lower than Example 2. This shows that annealing treatment can effectively release the internal stress of the plated layer, optimize the structure of the plated layer, and improve the density and bonding strength of the plated layer. The lack of this step will cause the plated layer to be prone to cracking and the bonding force to decrease, thereby affecting the overall performance of the current collector.

[0054] The above is only an example and description of the concept of the present application. Those skilled in the art can make various modifications or supplements to the described specific embodiments or use similar ways to replace them, as long as they do not deviate from the concept of the present application or exceed the scope defined by the present claims.

Claims

1. A method of making a modified aluminum composite current collector, characterized by, The method comprises the following steps: S1: immerse the aluminum foil into an alkaline oil removal liquid and ultrasonic clean, and obtain the oil-removed aluminum foil; immerse the oil-removed aluminum foil into an alkali solution for alkali etching treatment, and then rinse with deionized water, and obtain the alkali etched aluminum foil; immerse the alkali etched aluminum foil into a nitric acid solution for lightening treatment, and then rinse with deionized water, and obtain the lightened aluminum foil; immerse the lightened aluminum foil into a strong alkaline zincate solution for activation treatment, and obtain the activated aluminum foil; immerse the activated aluminum foil into a nitric acid solution for stripping treatment, and obtain the stripped aluminum foil; and perform secondary activation treatment on the stripped aluminum foil, and obtain the secondary activated aluminum foil; S2: immerse the secondary activated aluminum foil into deionized water for pre- immersion treatment, and obtain the pre- immersed aluminum foil; immerse the pre- immersed aluminum foil into a preheated chemical plating solution for chemical plating, and obtain the chemical plated aluminum foil; S3: use the chemical plated aluminum foil as a cathode, use a zinc plate as an anode, preheat the electroplating solution, connect the power supply, start electroplating according to the set parameters, electroplate a graphene composite zinc layer on the chemical plated aluminum foil, and obtain the plated aluminum foil; S4: rinse the plated aluminum foil with deionized water, perform hot air drying, perform annealing treatment, cool to room temperature in the furnace, and obtain the modified aluminum composite current collector.

2. The method of claim 1, wherein the modified aluminum composite current collector is prepared by the steps of: In the step S1, the alkaline oil removal liquid is composed of 20-30 parts of NaOH, 15-25 parts of Na3PO4, 3-8 parts of a surfactant, and 800-1000 parts of deionized water by weight, the ultrasonic cleaning temperature is 60-70 DEG C, and the time is 5-10 min; the alkali solution used for alkali etching treatment is obtained by mixing 50-60 parts of NaOH and 1000 parts of deionized water, the alkali etching temperature is 50-60 DEG C, and the time is 1-3 min.

3. The method of claim 1, wherein the modified aluminum composite current collector is prepared by the steps of: In the step S1, the strong alkaline zincate solution is composed of 400-500 parts of NaOH, 80-100 parts of ZnO, 1-3 parts of FeCl3, and 1000 parts of deionized water by weight, the activation treatment is performed at room temperature, the soaking time is 20-60 s; the nitric acid solution used for stripping treatment is composed of 300-500 parts of nitric acid and 500 parts of deionized water by weight; the secondary activation treatment has the same parameters as the first activation treatment.

4. The method of claim 1, wherein the modified aluminum composite current collector is prepared by the steps of: In the step S2, the chemical plating solution is composed 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 by weight, and the pH value is adjusted to 8.5-9.5 by using ammonia water; the chemical plating solution heating temperature is 80-90 DEG C, and the chemical plating time is 5-15 min.

5. The method of claim 1, wherein the modified aluminum composite current collector is prepared by the steps of: In the step S3, the electroplating solution preheating temperature is 25-35℃, the electroplating solution preheating time is 15-20min; the area ratio of cathode to anode is 1:1-2, the electrode distance is kept at 5-8cm; the cathode is immersed in the electroplating solution for 1-2min before electrification; the temperature is controlled at 28-32℃ during electroplating, the current density is 1-3A / dm 2 -3A / dm 2 , mechanical stirring is adopted, the mechanical stirring speed is controlled at 200-300rpm, the pulse parameters are frequency 45-55Hz and duty cycle 40-50%; the electroplating time is 10-30min, so that the thickness of the graphene composite zinc layer reaches 1-4μm.

6. The method of claim 1, wherein the modified aluminum composite current collector is prepared by the steps of: In the step S3, the purity of the zinc plate is 99.99%; the electroplating solution is an acid zinc plating system, and is composed 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 a leveling agent, and 1000 parts of deionized water by weight, and the pH value is 4.5-5.

5.

7. The method of claim 6, wherein the modified aluminum composite current collector is prepared by the steps of: The preparation method of the carboxyl-modified graphene comprises the following steps: firstly, carboxyl-modifying graphene, adding natural graphite powder into a mixed acid solution composed of concentrated nitric acid and concentrated sulfuric acid, stirring for 20-30 minutes under ice bath condition, slowly adding potassium permanganate, controlling the reaction temperature to be not more than 20 DEG C, continuously stirring for 1-2 hours, then heating to 35-40 DEG C and continuously reacting for 30-45 minutes, subsequently adding deionized water, heating to 90-95 DEG C and reacting for 10-15 minutes, finally adding hydrogen peroxide to terminate the reaction, centrifugally separating, washing with deionized water until neutral, vacuum drying to obtain carboxyl-modified graphene; and secondly, weighing the carboxyl-modified graphene.

8. The method of claim 7, wherein the modified aluminum composite current collector is prepared by the steps of: In the preparation process of the carboxyl-modified graphene, the materials are respectively natural graphite powder 5-10 parts, concentrated nitric acid 50-60 parts, concentrated sulfuric acid 50-60 parts, potassium permanganate 15-20 parts, hydrogen peroxide 5-10 parts and deionized water 200-250 parts.

9. The method of claim 1, wherein the modified aluminum composite current collector is prepared by the steps of: In the step S4, the deionized water is washed for 2-5 times, each time for 15-30 seconds; the hot air drying temperature is 60-80 DEG C, and the time is 15-20 minutes; the annealing treatment is carried out in inert atmosphere, the temperature is 150-250 DEG C, and the holding time is 1-2 hours.

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

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