Preparation method of composite aluminum current collector

Abstract

The invention discloses a preparation method of a composite aluminum current collector, which comprises the following steps: S1, selecting a polymer film material as a base film layer of the composite aluminum current collector; s2, aluminum seed layers are formed on the two sides of the base film layer through a magnetron sputtering method; s3, the aluminum seed layer is electroplated and thickened through an ionic liquid electroplating method, and aluminum-containing layers on the two sides of the base film layer are formed; in the step S3, an EMIC-chlorine salt system is selected as an electroplating solution. The composite current collector is prepared by adopting an ion electroplating method, a layer of composite aluminum foil with high tensile strength is deposited on the surface of a polymeric membrane through a magnetron sputtering and ion electroplating technology, and a plating layer with high corrosion resistance and high toughness is obtained by optimizing an electroplating liquid system.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and specifically to a method for preparing a composite aluminum current collector. Background Technology

[0002] With the rapid development of new energy and advanced manufacturing, the key performance characteristics of batteries, such as cycle life, safety, and energy density, urgently need improvement. The current collector is a core component of the battery, responsible for collecting current; its performance directly affects the battery's cycle life, energy density, safety, and other technical indicators. Furthermore, the subsequent assembly of composite current collectors into batteries involves processes such as active material coating, rolling molding, and electrode slitting, which places higher demands on the comprehensive mechanical properties of the composite current collector.

[0003] Currently, pure metal foil is commonly used for both positive and negative electrode current collectors in the battery industry. However, pure metal current collectors are costly, heavy, and perform poorly in terms of battery safety. Furthermore, their high dead weight hinders the improvement of battery energy density. The production process for composite aluminum current collectors typically involves evaporating aluminum vapor onto a polymer material in a vacuum environment. However, the temperature of the aluminum vapor in this process can reach thousands of degrees Celsius, potentially causing ablation of the polymer film during plating. This results in a narrow process window, and often requires multiple plating cycles to obtain a high-performance film. Therefore, it is necessary to develop new production processes to reduce production defects and expand the process window. Additionally, because the deposition potential of aluminum is lower than that of hydrogen, aqueous solution electroplating is not suitable for aluminum current collectors.

[0004] Traditional composite current collector aluminum foil is typically produced using vacuum evaporation. In a vacuum environment, a vacuum coating machine heats pure aluminum wire, causing aluminum vapor to cool and solidify on a polymer film, thus obtaining a composite aluminum foil that meets the process requirements. This method is simple and easy for industrial production. However, aluminum foil produced using traditional evaporation coating processes also has some unavoidable defects, such as incomplete coating, film surface burns, pinholes, and low tensile strength. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing a composite aluminum current collector, which uses magnetron sputtering + ion electroplating technology to deposit a layer of high tensile strength composite aluminum foil on the surface of a polymer film.

[0006] To achieve the above objectives, the technical solution provided by the present invention is as follows: The first aspect of this application provides a method for preparing a composite aluminum current collector, comprising the following steps: S1: Select a polymer membrane material as the base membrane layer for the composite aluminum current collector; S2: Aluminum seed layers are prepared on both sides of the base film layer by magnetron sputtering; S3: The aluminum seed layer is thickened by electroplating with ionic liquid to form aluminum-containing layers on both sides of the base film layer; In step S3, the electroplating solution for the ionic liquid electroplating method is selected as the EMIC-chloride salt system.

[0007] To optimize the above technical solution, the specific measures also include: The thickness of the aluminum seed layer on each side of the base film layer is 50~100 nm, and the thickness of the aluminum-containing layer on each side of the base film layer is 0.3~1 μm.

[0008] Furthermore, the aluminum-containing layer includes an inner aluminum alloy electroplated layer and an outer aluminum electroplated layer.

[0009] Furthermore, step S3 includes the following two steps: S3-1: An aluminum alloy electroplating layer is prepared by electroplating a polymer film with an aluminum seed layer on the outside using an ionic liquid electroplating method. S3-2: An aluminum electroplating layer is prepared by electroplating a polymer film with an outer layer of aluminum alloy electroplating layer and an aluminum seed layer in sequence using an ionic liquid electroplating method. In step S3-1, the electroplating uses the EMIC-AlCl3-ZnCl2-MgCl2 system; in step S3-2, the electroplating uses the EMIC-AlCl3 system.

[0010] In step S3, a total of 10 electroplating baths are set up, from the first to the tenth bath. The plating solution system used in the first to the fifth baths is the EMIC-AlCl3-ZnCl2-MgCl2 system; the plating solution system used in the sixth to the tenth baths is the EMIC-AlCl3 system; and the current density gradually increases from the first to the tenth bath. In step S3, the temperature range during electroplating is 26~30℃, and the electroplating linear speed is 2~5 m / min.

[0011] In the EMIC-AlCl3-ZnCl2-MgCl2 system in the first to fifth tanks, the total molar concentration ratio of EMIC to AlCl3, ZnCl2, and MgCl2 is 3:5~7; the mass ratio of AlCl3, ZnCl2, and MgCl2 is 8~10:3~4:3~4. In the EMIC-AlCl3 system in the sixth to tenth tanks, the molar concentration ratio of EMIC to AlCl3 is 3:5~7.

[0012] Furthermore, toluene was added to the sixth to tenth tanks, with the amount of toluene added being 25-35% of the volume fraction of the ionic liquid in the EMIC-AlCl3 system.

[0013] Preferably, the current densities of the first to tenth cells are 0~5, 5~10, 10~15, 15~20, and 20~25 mA / cm, respectively.2 The current densities of the sixth to tenth cells are 25~30, 30~35, 35~40, 40~45, and 45~50 mA / cm, respectively. 2 .

[0014] The second aspect of this application provides a composite aluminum current collector, prepared using the method described above.

[0015] A third aspect of this application provides an electrode comprising the aforementioned composite aluminum current collector.

[0016] A fourth aspect of this application provides a battery comprising the aforementioned electrode.

[0017] Compared with the prior art, the beneficial effects of the present invention are: Traditional electroplating methods are rarely used in the preparation of aluminum current collectors, mainly because the deposition potential of aluminum is lower than that of water. This leads to the preferential reduction of aluminum ions and the hydrogen evolution reaction of water during aqueous solution electroplating, resulting in a loose coating, poor adhesion, or even failure to form a continuous film. At the same time, conventional electroplating solutions have poor solubility for aluminum and easily form oxide films that hinder electroplating. Aluminum is easily corroded in acidic or alkaline solutions, affecting the quality of the coating. In addition, the electroplating process requires precise control of parameters such as current density, temperature, and pH value. Otherwise, defects such as uneven coating, pinholes, and incomplete plating are likely to occur. The chemically active nature of aluminum further exacerbates the difficulty of process control.

[0018] The solution proposed in this application effectively solves the above problems by combining ionic liquid electroplating with magnetron sputtering technology. Ionic liquid electroplating utilizes its wide electrochemical window, low vapor pressure, and high ionic conductivity to stabilize the aluminum ion reduction process, avoid hydrogen evolution reaction, and dissolve aluminum salts to form stable complexes, providing a sufficient aluminum source. Uniform deposition is achieved by controlling parameters such as current density and temperature. Before electroplating, a conductive seed layer is sputtered onto the surface of the polymer film using magnetron sputtering, providing a good conductive foundation for subsequent electroplating and ensuring the adhesion of the coating. By optimizing the magnetron sputtering parameters, the poor adhesion problem caused by the oxide film on the substrate surface in traditional electroplating is avoided. Finally, a high tensile strength Al-Zn-Mg alloy layer is obtained through ionic liquid electroplating to improve the support of the composite current collector, and a pure aluminum layer is wrapped on the outside of the alloy layer to balance toughness and corrosion resistance, further improving battery performance.

[0019] The proposed solution combines magnetron sputtering with ionic liquid electroplating, reducing the sensitivity of traditional electroplating to process conditions and making it suitable for industrial production. The resulting composite current collector has both high strength and corrosion resistance, which can meet the requirements of high energy density and long cycle life of batteries. Attached Figure Description

[0020] Figure 1 : A schematic diagram of the composite aluminum current collector of the present invention. In the diagram: 1-base film layer, 2-aluminum seed layer, 3-aluminum alloy electroplating layer, 4-aluminum electroplating layer. Detailed Implementation

[0021] The present invention will be further described in detail below through specific embodiments, but it should not be construed as limiting the scope of the subject matter of the present invention to the following embodiments. All technologies implemented based on the above content of the present invention fall within the scope of the present invention.

[0022] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, and the reagents, methods and equipment used are conventional reagents, methods and equipment in this technical field.

[0023] This invention provides a method for preparing a composite aluminum current collector, comprising the following steps: S1: Select a polymer thin film material as the base film layer of the composite aluminum current collector; S2: An aluminum seed layer is formed on both sides of the base film layer by magnetron sputtering; S3: The aluminum seed layer is thickened by electroplating with ionic liquid to form aluminum-containing layers on both sides of the base film layer; In step S3, the electroplating solution selected is the EMIC-chloride salt system.

[0024] In the EMIC-chloride salt system electroplating solution, the molar concentration ratio of EMIC to chloride salt is 3:5~7.

[0025] In existing technologies, electroplated aluminum current collectors are rarely used due to their low deposition potential, limited plating solutions, and difficulty in process control. This solution addresses the hydrogen evolution and passivation issues through ionic liquid electroplating and optimizes substrate surface treatment using magnetron sputtering technology, achieving the preparation of high-strength, corrosion-resistant aluminum-containing coatings and providing a new path for the green manufacturing of aluminum foil current collectors.

[0026] In some embodiments, the thickness of the aluminum seed layer on each side of the base film is 50~100 nm; the thickness of the aluminum-containing layer on each side of the base film is 0.3~1 μm.

[0027] The aluminum-containing layer includes an inner aluminum alloy electroplated layer and an outer aluminum electroplated layer; in some embodiments, the thickness of the aluminum alloy electroplated layer is 0.2~0.6μm, and the thickness of the aluminum electroplated layer is 0.2~0.6μm.

[0028] Step S3 includes the following two steps: S3-1: An aluminum alloy electroplating layer is prepared by electroplating a polymer film with an aluminum seed layer on the outside using an ionic liquid electroplating method. S3-2: An aluminum electroplating layer is prepared by electroplating a polymer film with an outer layer of aluminum alloy electroplating layer and an aluminum seed layer in sequence using an ionic liquid electroplating method. In step S3-1, the electroplating uses the EMIC-AlCl3-ZnCl2-MgCl2 system; in step S3-2, the electroplating uses the EMIC-AlCl3 system.

[0029] In some embodiments, in step S3, the temperature range during electroplating is approximately 26~30 ℃, and the electroplating line speed is 2~5 m / min.

[0030] In some embodiments, in step S3, a total of 10 electroplating solution tanks are set up, from the first tank to the tenth tank. The plating solution system used in the first to the fifth tanks is the EMIC-AlCl3-ZnCl2-MgCl2 system; the plating solution system used in the sixth to the tenth tanks is the EMIC-AlCl3 system; and the current density gradually increases from the first tank to the tenth tank.

[0031] In the EMIC-AlCl3-ZnCl2-MgCl2 system in tanks one through five, the total molar concentration ratio of EMIC to AlCl3, ZnCl2, and MgCl2 is 3:5~7; the mass ratio of AlCl3, ZnCl2, and MgCl2 is 8~10:3~4:3~4. In the EMIC-AlCl3 system in tanks six through ten, the total molar concentration ratio of EMIC to AlCl3 is 3:5~7.

[0032] In some embodiments, toluene is added to the sixth to tenth tanks, and the amount of toluene added is 25 to 35% of the volume fraction of the ionic liquid in the EMIC-AlCl3 system.

[0033] In some embodiments, the current densities of the first to tenth cells are 0~5, 5~10, 10~15, 15~20, and 20~25 mA / cm, respectively. 2 The current densities of the sixth to tenth cells are 25~30, 30~35, 35~40, 40~45, and 45~50 mA / cm, respectively. 2 .

[0034] Preferably, the current collector is flushed with EMIC ionic liquid between the fifth and sixth tanks.

[0035] Electroplating is rarely used in the preparation of aluminum current collectors in existing technologies. The deposition potential of aluminum is lower than that of water (hydrogen evolution potential). During electroplating in aqueous solutions, aluminum ions are preferentially reduced to metallic aluminum, while water undergoes hydrogen evolution, resulting in a loose coating, poor adhesion, and even the inability to form a continuous coating. Conventional electroplating solutions (such as sulfates and chlorides) have poor solubility for aluminum and easily form oxide films, hindering the electroplating process. Furthermore, aluminum is easily corroded in acidic or alkaline solutions, affecting coating quality. During electroplating, parameters such as current density, temperature, and pH value need precise control; otherwise, defects such as uneven coating, pinholes, and missed plating can easily occur. Aluminum's chemical reactivity further complicates the process requirements. This solution effectively solves the above problems by combining ionic liquid electroplating with magnetron sputtering technology. This scheme employs ionic liquid electroplating, utilizing ionic liquids with characteristics such as a wide electrochemical window, low vapor pressure, and high ionic conductivity. These characteristics stabilize the reduction process of aluminum ions and prevent hydrogen evolution reaction. The system can dissolve aluminum salts and form stable aluminum ion complexes, providing a sufficient aluminum source for electroplating. Furthermore, by controlling parameters such as current density and temperature, uniform deposition can be achieved.

[0036] Before electroplating, this method first uses magnetron sputtering to sputter a conductive seed layer on the surface of the polymer film, providing a good conductive foundation for subsequent electroplating and ensuring the adhesion of the coating. Furthermore, by optimizing the magnetron sputtering parameters, the poor adhesion problem caused by the oxide film on the substrate surface in traditional electroplating is avoided.

[0037] This method uses ionic liquid electroplating to obtain an Al-Zn-Mg alloy layer, which has high tensile strength and can improve the support of the composite current collector. A pure aluminum layer is wrapped around the outside of the alloy layer to balance toughness and corrosion resistance, further improving battery performance.

[0038] This invention combines magnetron sputtering with ionic liquid electroplating, reducing the sensitivity of traditional electroplating to process conditions and making it suitable for industrial production. The resulting composite current collector possesses both high strength and corrosion resistance, meeting the requirements of high energy density and long cycle life in batteries. The present invention also provides a composite aluminum current collector, which is prepared by the above method.

[0039] The present invention also provides an electrode comprising the above-described composite aluminum current collector.

[0040] The present invention also provides a battery comprising the above-described electrode.

[0041] The technical solution of the present invention will be further described in detail below with reference to specific embodiments: Example 1 Equipment selection: one dual-drum magnetron sputtering machine, one enclosed ten-slot winding electroplating line, and one tensile tester; Base film selection: Commercial polymer film; Target selection: Al target with a purity of 99.99%.

[0042] A method for preparing a composite aluminum current collector includes the following steps: (1) Magnetron sputtering procedure: After evacuating the sputtering chamber, start the sputtering process. After washing the target, the sputtering parameters are as follows: the background vacuum is 4×10 -3 Pa, argon flow rate is 120 sccm, sputtering main roller cooling temperature is -15 ℃, aluminum target power is 10 KW, and winding speed is 7 m / min; First, a seed layer with good conductivity and a thickness of 70 nm is sputtered on the surface of the base film to enhance the conductivity of the composite foil so as to thicken it in the subsequent electroplating process.

[0043] (2) Electroplating process: The electroplating process is carried out in a nitrogen atmosphere, and the current density gradually increases from the first tank to the tenth tank; The plating solution system used in the first five tanks was an EMIC-AlCl3-ZnCl2-MgCl2 system, and the current density increased with the increase of the plating thickness, at 2, 7, 12, 17, and 22 mA / cm², respectively. 2 The total molar concentration ratio of EMIC to AlCl3, ZnCl2, and MgCl2 is 1:2; the mass ratio of AlCl3, ZnCl2, and MgCl2 is 8:3:3. The fifth and sixth tanks are rinsed with EMIC ionic liquid to prevent liquid from being carried into the subsequent five tanks and contaminating the coating. The plating solution system used in the last five tanks was a conventional EMIC-AlCl3 system, and the current densities of the last five tanks were 27, 32, 37, 42, and 47 mA / cm². 2 Gradually increase; the molar concentration ratio of EMIC to AlCl3 is 1:2; the additive is toluene, the volume fraction of toluene is 30% of the ionic liquid, the electroplating temperature is 28 ℃, and the electroplating linear speed is 3.5 m / min; The thickness of the aluminum-containing layer (including the seed layer) on each side of the prepared base film layer is 0.5 μm. The inner side of the aluminum-containing layer is an aluminum alloy layer containing Zn and Mg, and the outer side is an Al layer.

[0044] (3) Mechanical property testing: Tensile properties are tested using a universal tensile testing machine.

[0045] Example 2 The schemes in this embodiment are basically the same as those in Embodiment 1, except that the total molar concentration ratio of EMIC to AlCl3, ZnCl2 and MgCl2 in the first five tanks is 3:5; and the molar concentration ratio of EMIC to AlCl3 in the last five tanks is 3:5.

[0046] Example 3 The schemes in this embodiment are basically the same as those in Embodiment 1, except that the total molar concentration ratio of EMIC to AlCl3, ZnCl2 and MgCl2 in the first five tanks is 3:7; and the molar concentration ratio of EMIC to AlCl3 in the last five tanks is 3:7.

[0047] Comparative Example 1 Composite current collector aluminum foil was prepared using a conventional vacuum evaporation method, with an aluminum layer thickness of 0.5 μm on each side of the base film, followed by tensile testing.

[0048] Comparative Example 2 Composite current collector aluminum foil was prepared using magnetron sputtering, with an aluminum layer thickness of 0.5 μm on each side of the base film, followed by tensile testing.

[0049] Comparative Example 3 The scheme of this comparative example is basically the same as that of Example 1, which also uses magnetron sputtering + ionic liquid electroplating to prepare composite current collectors. The only difference is that the electroplating solution system of the first to fifth tanks and the sixth to tenth tanks is the same, which is the EMIC-AlCl3 system, and the molar concentration ratio of EMIC to AlCl3 is 1:2; the additive is toluene of the same volume fraction, and the aluminum-containing layer is a pure Al layer with a thickness of 0.5 μm. Tensile test was then performed.

[0050] Comparative Example 4 The schemes in this embodiment are basically the same as those in Embodiment 1, except that the total molar concentration ratio of EMIC to AlCl3, ZnCl2 and MgCl2 in the first five tanks is 3:4; and the molar concentration ratio of EMIC to AlCl3 in the last five tanks is 3:4.

[0051] Comparative Example 5 The schemes in this embodiment are basically the same as those in Embodiment 1, except that the total molar concentration ratio of EMIC to AlCl3, ZnCl2 and MgCl2 in the first five tanks is 3:8; and the molar concentration ratio of EMIC to AlCl3 in the last five tanks is 3:8.

[0052] Table 1

[0053] Examples 1-3 all employed a composite process combining magnetron sputtering and ionic liquid electroplating. By optimizing the molar concentration ratio of EMIC to chloride salt, composite aluminum current collectors with high strength and corrosion resistance were successfully prepared. Their tensile strength ranged from 177 to 191 MPa, elongation from 11% to 15%, and corrosion resistance immersion time reached 26 to 27 days, significantly superior to traditional processes. This is because ionic liquid electroplating effectively solved the problems of hydrogen evolution and passivation, while magnetron sputtering technology ensured a strong bond between the coating and the substrate, achieving a balanced improvement in performance. Among them, Example 1 exhibited the best overall performance, which is related to its molar concentration ratio being in the middle range, ensuring both the density of the coating and avoiding increased brittleness caused by over-deposition.

[0054] Comparative Example 1 used conventional vacuum evaporation, while Comparative Example 2 used only magnetron sputtering. Both Comparative Example 2 and Comparative Example 3 showed lower tensile strength and elongation than the previous examples, and the immersion time for corrosion resistance was also significantly shorter. Vacuum evaporation struggles to control coating uniformity, and while magnetron sputtering can form a seed layer, it lacks subsequent electroplating for thickening, resulting in insufficient coating adhesion and corrosion resistance. This further validates the necessity of the composite process: in this solution, magnetron sputtering provides a conductive substrate, and ionic liquid electroplating achieves functional layer thickening; the synergistic effect of both significantly improves material performance.

[0055] Comparative Examples 3-5 showed significant performance fluctuations after adjusting the molar concentration ratio of EMIC to chloride salt. Comparative Example 3, lacking an alloy layer, exhibited tensile strength and elongation close to Example 1, but with poor corrosion resistance. The molar concentration ratios of Comparative Examples 4 and 5 deviated from the optimized range, resulting in decreased coating performance. Comparative Example 5 showed lower tensile strength and elongation, but its corrosion resistance was comparable to Comparative Example 3, indicating that both excessively high and low concentration ratios negatively impact coating quality.

[0056] In summary, based on the data in Table 1, the composite processes of Examples 1-3 are superior to the comparative examples in terms of tensile strength, elongation, and corrosion resistance. In particular, Example 1 demonstrates a tensile strength of 191 MPa and a corrosion resistance of 27 days, showcasing the synergistic advantages of magnetron sputtering and ionic liquid electroplating. The traditional single processes in Comparative Examples 1 and 2 exhibit poor performance, while the concentration ratio deviations in Comparative Examples 3-5 lead to unstable coating quality. This solution, by optimizing the molar concentration ratio and using stepwise electroplating, solves the hydrogen evolution and passivation problems inherent in traditional electroplating, providing a reliable solution for the green manufacturing of aluminum current collectors and is suitable for industrial production.

[0057] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, equivalent substitutions, and improvements made by those skilled in the art to the above embodiments without departing from the scope of the technical solution of the present invention, based on the technical essence of the present invention, shall still fall within the protection scope of the technical solution of the present invention.

Claims

1. A method for preparing a composite aluminum current collector, characterized in that, Includes the following steps: S1: Select a polymer membrane material as the base membrane layer for the composite aluminum current collector; S2: Aluminum seed layers are prepared on both sides of the base film layer by magnetron sputtering; S3: The aluminum seed layer is thickened by electroplating with ionic liquid to form aluminum-containing layers on both sides of the base film layer; In step S3, the electroplating solution for the ionic liquid electroplating method is selected as the EMIC-chloride salt system.

2. The method for preparing the composite aluminum current collector according to claim 1, characterized in that: The thickness of the aluminum seed layer on each side of the base film is 50~100 nm, and the thickness of the aluminum-containing layer on each side of the base film is 0.3~1 μm.

3. The method for preparing the composite aluminum current collector according to claim 1, characterized in that: The aluminum-containing layer includes an inner aluminum alloy electroplated layer and an outer aluminum electroplated layer. Step S3 includes the following two steps: S3-1: An aluminum alloy electroplating layer is prepared by electroplating a polymer film with an aluminum seed layer on the outside using an ionic liquid electroplating method. S3-2: An aluminum electroplating layer is prepared by electroplating a polymer film with an outer layer of aluminum alloy electroplating layer and an aluminum seed layer in sequence using an ionic liquid electroplating method. In step S3-1, the electroplating uses the EMIC-AlCl3-ZnCl2-MgCl2 system; in step S3-2, the electroplating uses the EMIC-AlCl3 system.

4. The method for preparing the composite aluminum current collector according to claim 1, characterized in that: In step S3, a total of 10 electroplating baths are set up, from the first to the tenth bath. The plating solution system used in the first to the fifth baths is the EMIC-AlCl3-ZnCl2-MgCl2 system; the plating solution system used in the sixth to the tenth baths is the EMIC-AlCl3 system; and the current density gradually increases from the first to the tenth bath. In step S3, the temperature range during electroplating is 26~30 ℃, and the electroplating linear speed is 2~5 m / min.

5. The method for preparing the composite aluminum current collector according to claim 4, characterized in that: In the EMIC-AlCl3-ZnCl2-MgCl2 system in the first to fifth tanks, the total molar concentration ratio of EMIC to AlCl3, ZnCl2, and MgCl2 is 3:5~7; the mass ratio of AlCl3, ZnCl2, and MgCl2 is 8~10:3~4:3~4. In the EMIC-AlCl3 system in the sixth to tenth tanks, the molar concentration ratio of EMIC to AlCl3 is 3:5~7.

6. The method for preparing the composite aluminum current collector according to claim 4, characterized in that: Toluene was added to tanks six through ten, at a rate of 25-35% of the volume fraction of the ionic liquid in the EMIC-AlCl3 system.

7. The method for preparing the composite aluminum current collector according to claim 4, characterized in that: The current densities of the first to tenth cells are 0~5, 5~10, 10~15, 15~20, and 20~25 mA / cm, respectively. 2 The current densities of the sixth to tenth cells are 25~30, 30~35, 35~40, 40~45, and 45~50 mA / cm, respectively. 2 .

8. A composite aluminum current collector, characterized in that: Prepared using the method described in any one of claims 1 to 7.

9. An electrode sheet, characterized in that: It includes the composite aluminum current collector as described in claim 8.

10. A battery, characterized in that: It includes the electrode sheet as described in claim 9.

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