A high-ductility aluminum foil for battery positive electrode and its production method

Abstract

The application relates to the technical field of aluminum foils for batteries, in particular to a high-ductility aluminum foil for battery positive electrodes and a production method thereof, which comprises the following components in percentage by mass: copper 0.05-0.2%, rare earth elements 0.01-0.1%, iron 0.08-0.2%, silicon 0.01-0.05%, titanium 0.005-0.02%, boron 0.002-0.005%, zirconium 0.08-0.12% and the balance of aluminum. The high-ductility aluminum foil for battery positive electrodes and the production method thereof are used, the rare earth elements can refine the grains, and the rare earth elements and other elements can synergistically act, so that the aluminum foil has relatively high tensile strength and good ductility, the aluminum foil can effectively avoid cracking and breaking, and the production yield and cycle stability of lithium batteries are improved.

Description

Technical Field

[0001] This invention relates to the field of aluminum foil technology for batteries, and in particular to a high-ductility aluminum foil for battery positive electrodes and its production method. Background Technology

[0002] Lithium-ion batteries, with their advantages of high energy density and long cycle life, are widely used in new energy vehicles, energy storage, and other fields. The positive electrode current collector, as a key component, plays a crucial role in conducting current and supporting the active material; its performance is vital to the overall battery performance. Currently, aluminum foil is commonly used as the current collector for battery positive electrodes. However, as batteries develop towards higher energy density and higher power density, more stringent requirements are placed on the performance of aluminum foil. Traditional aluminum foil for battery positive electrodes is mostly made from pure aluminum or low-alloy aluminum. While it possesses certain conductivity and formability, it has significant limitations in the following aspects: insufficient ductility leads to processing and usage risks. During the coating and winding process of lithium-ion battery positive electrodes, the aluminum foil must withstand repeated mechanical stress (such as bending and stretching). Traditional aluminum foil, due to its coarse grains and internal stress concentration, is prone to cracking and breakage, reducing production efficiency and product quality. Summary of the Invention

[0003] The purpose of this invention is to provide a high-ductility aluminum foil for battery cathodes and its production method. Rare earth elements can refine the grains and work synergistically with other elements to give the aluminum foil both high tensile strength and good ductility, effectively preventing cracking and breakage of the aluminum foil and improving the production yield and cycle stability of lithium batteries.

[0004] To achieve the above objectives, the present invention provides a highly ductile aluminum foil for a battery positive electrode, comprising the following components by mass percentage: 0.05-0.2% copper, 0.01-0.1% rare earth elements, 0.08-0.2% iron, 0.01-0.05% silicon, 0.005-0.02% titanium, 0.002-0.005% boron, 0.08-0.12% zirconium, and the balance aluminum;

[0005] Rare earth elements include one or more of lanthanum, cerium, europium, yttrium, and scandium.

[0006] A method for producing a high-ductility aluminum foil for a battery positive electrode includes the following steps:

[0007] S1. After emptying and preheating the smelting furnace, add aluminum ingots and other raw materials to smelt, stir until uniformly mixed, add refining agent and continue stirring to obtain the first aluminum mixture;

[0008] S2. Add a refining agent to the first aluminum mixture obtained in S1 to obtain a second aluminum mixture, and then cast and roll it to obtain an ingot.

[0009] S3. Remove the segregation layer on the surface of the ingot obtained in S2, and then perform a stepped heating homogenous annealing operation in a heating furnace to obtain the annealed ingot.

[0010] S4. The annealed ingot obtained in S3 is subjected to three cold rolling passes, followed by intermediate annealing, and then two more cold rolling passes to obtain aluminum strip.

[0011] S5. After the aluminum strip obtained in S4 is trimmed and inspected, it is rolled into foil in 4-6 passes to obtain an aluminum foil with a thickness of 8-15μm. After low-speed heating and recrystallization annealing, the finished aluminum foil is obtained.

[0012] Preferably, in S1, after the smelting furnace is emptied, it is heated by purging the furnace chamber with a nitrogen-argon mixture and preheating it to 400-500°C.

[0013] Preferably, in S1, the temperature during stirring is 700-800℃, and the stirring time is 10-45 minutes. After removing surface impurities, the mixture is transferred to a heat preservation furnace and processed online through an SNIF rotary jet degassing device and a ceramic plate filter to obtain the first aluminum mixture.

[0014] Preferably, in S2, the amount of refining agent added is 0.1%-0.3% of the mass of the first aluminum mixture.

[0015] More preferably, in S2, the refining agent is an Al-Ti-C-RE composite refining agent, and the mass ratio of Ti:C:RE is 5:1:2.

[0016] More preferably, in S2, the refining agent includes one or more of Al-Ti-C-La composite refining agent, Al-Ti-C-Ce composite refining agent, and Al-Ti-C-Sc composite refining agent.

[0017] Preferably, in S2, the second aluminum mixture is filtered and then added to the casting and rolling mill at a casting and rolling speed of 0.8-1.5 m / min and a roll gap of 6-10 mm.

[0018] Preferably, in S3, during the step-by-step heating and homogenization process, the ingot after removing the segregation layer is sent to a continuous heating furnace, heated to 480-500℃ at 3-5℃ / min, held for 2 hours, and then heated to 540-560℃ at 1-2℃ / min, held for 6-10 hours, and then cooled with the furnace.

[0019] Preferably, in S4, the first cold rolling in the three cold rolling processes rolls the ingot to 2.0-3.0 mm at a rolling speed of 300-500 m / min;

[0020] The second cold rolling process produces a thickness of 0.8-1.2 mm at a speed of 500-800 m / min.

[0021] The third cold rolling process reduces the thickness to 0.3-0.5 mm at a speed of 800-1200 m / min.

[0022] Preferably, in S4, the intermediate annealing temperature is 350-400℃, and the holding time is 2-4 hours;

[0023] In the two-pass cold rolling after intermediate annealing, the first pass is rolled to 0.1-0.15mm at a rolling speed of 1000-1500m / min;

[0024] The second cold rolling process reduces the thickness to 0.05-0.08 mm at a speed of 1200-1800 m / min.

[0025] Therefore, the present invention employs the above-mentioned high-ductility aluminum foil for battery positive electrodes and its production method, the beneficial effects of which are:

[0026] 1. The rare earth elements used in this invention can refine the grains and work synergistically with other elements to give the aluminum foil both high tensile strength and good ductility, which can effectively prevent the aluminum foil from cracking and breaking, and improve the production yield and cycle stability of lithium batteries.

[0027] 2. The preparation method provided by this invention, from melting, refining, casting and rolling, to stepped heating homogeneous annealing, multi-pass cold rolling and foil rolling, and then to low-speed heating recrystallization annealing of the finished product, achieves precise control over the microstructure and properties of aluminum foil.

[0028] 3. In this invention, boron and zirconium are used to synergistically improve the performance of aluminum foil. Zirconium forms dispersed nano-sized Al3Zr particles, which can strongly pin grain boundaries and dislocations, significantly increase recrystallization temperature, refine grains and improve strength and ductility. Boron forms stable borides with impurities such as titanium and vanadium inherent in the raw materials, and removes them from the aluminum solid solution.

[0029] 4. The aluminum foil prepared by this invention maintains high tensile strength while possessing extremely high ductility, which greatly reduces the breakage rate of the foil during coating, rolling and slitting processes in battery factories, and meets the higher mechanical requirements of high-density cathode materials for current collectors.

[0030] The technical solution of the present invention will be further described in detail below through embodiments. Detailed Implementation

[0031] The present invention will be further described below with reference to embodiments. Unless otherwise defined, the technical or scientific terms used in this invention should have the ordinary meaning understood by one of ordinary skill in the art. The features mentioned above or in the specific examples mentioned in this invention can be combined arbitrarily, and these specific embodiments are only used to illustrate the invention and are not intended to limit the scope of the invention.

[0032] This invention provides a method for producing high-ductility aluminum foil for battery positive electrodes, comprising the following steps:

[0033] S1. After emptying and preheating the smelting furnace, add aluminum ingots and other raw materials to smelt, stir until uniformly mixed, add refining agent and continue stirring to obtain the first aluminum mixture;

[0034] S2. Add a refining agent to the first aluminum mixture obtained in S1 to obtain a second aluminum mixture, and then cast and roll it to obtain an ingot.

[0035] S3. Remove the segregation layer on the surface of the ingot obtained in S2, and then perform a stepped heating homogenous annealing operation in a heating furnace to obtain the annealed ingot.

[0036] S4. The annealed ingot obtained in S3 is subjected to three cold rolling passes, followed by intermediate annealing, and then two more cold rolling passes to obtain aluminum strip.

[0037] S5. After the aluminum strip obtained in S4 is trimmed and inspected, it is rolled into foil in 4-6 passes to obtain an aluminum foil with a thickness of 8-15μm. After low-speed heating and recrystallization annealing, the finished aluminum foil is obtained.

[0038] In some embodiments of the present invention, in step S1, after emptying the smelting furnace, heating is performed by purging the furnace chamber with nitrogen and preheating to 400-500°C. A nitrogen-argon mixture replaces the air in the furnace chamber, preventing O2 and H2 from reacting with the molten aluminum to generate Al2O3 and H2 bubbles, thus avoiding pinhole defects in the subsequent aluminum foil. Preheating also prevents excessive local temperature differences caused by directly adding aluminum ingots to a cold furnace, thus preventing cracks in the aluminum ingots due to excessive temperature variations.

[0039] In some embodiments of the present invention, in step S1, the stirring temperature is 700-800°C, and the stirring time is 10-45 minutes. After removing surface impurities, the mixture is transferred to a holding furnace and subjected to online treatment using an SNIF rotary jet degassing device and a ceramic plate filter to obtain a first aluminum mixture. At this stirring temperature, the aluminum liquid has good fluidity, the raw materials are easily dissolved, and stirring ensures uniform dispersion of copper, rare earth elements, and other alloying elements, avoiding component segregation. Efficient online purification can greatly improve the purity of the melt, removing hydrogen and oxide inclusions, providing a foundation for high ductility.

[0040] In some embodiments of the present invention, the refining agent includes one or more of hexachloroethane and magnesium chloride. The refining agent reacts with H2 in the molten aluminum to generate HCl gas, which escapes with bubbles and simultaneously adsorbs Al2O3 inclusions. This removes surface scum Al2O3, impurity oxides, and other contaminants from the molten aluminum, purifying the aluminum melt, reducing internal defects in the subsequent aluminum foil, such as porosity and inclusions, and improving the ductility and conductivity of the finished aluminum foil.

[0041] In some embodiments of the present invention, in step S2, the amount of refining agent added is 0.1%-0.3% of the mass of the first aluminum mixture. The refining agent is an Al-Ti-C-RE composite refining agent, including one or more of Al-Ti-C-La composite refining agents, Al-Ti-C-Ce composite refining agents, and Al-Ti-C-Sc composite refining agents.

[0042] In the Al-Ti-C-RE composite refining agent, Ti preferentially reacts with Al in the first aluminum mixture to form the Al3Ti phase, which has a crystal structure very similar to that of the aluminum matrix α-Al. 22 With its ordered structure and very small lattice mismatch, it is an excellent heterogeneous nucleation substrate. Aluminum atoms readily attach to its surface and begin crystallization, significantly increasing the nucleation rate. C reacts with Ti to form TiC particles, which have high thermal stability, are not easily dissolved or aggregated, and their microstructure is easier to control. Rare earth elements are highly surface-active elements that can adsorb onto the surface of TiC particles, significantly reducing the interfacial energy between TiC and the aluminum melt, improving wettability, and thus dispersing more uniformly in the aluminum melt. At the same time, they inhibit the excessively rapid growth of TiC particles, promoting the formation of finer, more nano-sized TiC particles. Rare earth elements can react with impurities such as hydrogen, oxygen, and sulfur to achieve refining and purification, preventing grain agglomeration and maintaining a fine-grained structure. They can also change the morphology of iron-rich impurity phases, transforming them from coarse needle-like or flaky phases into fine spherical phases, reducing the cutting effect on the aluminum matrix, indirectly improving the ductility of aluminum foil, and facilitating subsequent rolling production.

[0043] In some embodiments of the present invention, in step S2, the second aluminum mixture is filtered and then added to a casting and rolling mill at a speed of 0.8-1.5 m / min and a roll gap of 6-10 mm. Filtration removes undissolved refining agent agglomerates and residual inclusions from the second aluminum mixture, preventing hard particles from entering the ingot and thus preventing scratches on the aluminum foil surface or wear on the rolls during subsequent cold rolling. The casting and rolling speed controls the solidification rate of the second aluminum mixture, resulting in a refined grain structure and crack-free ingot.

[0044] In some embodiments of the present invention, during step-by-step heating and homogenization in step S3, the ingot after removing the segregation layer is fed into a continuous heating furnace, heated to 480-500°C at a rate of 3-5°C / min, held for 2 hours, and then heated to 540-560°C at a rate of 1-2°C / min, held for 6-10 hours, and then cooled with the furnace. The segregation layer on the surface of the ingot is enriched with alloying elements such as copper and iron. This layer has an uneven structure and is brittle. Removing the segregation layer improves the uniformity of cold rolling and prevents local cracking of the finished aluminum foil. In the low-temperature stage, the coarse second phase (such as AlFeSi) of the non-equilibrium eutectic is partially dissolved and fragmented, preparing for more sufficient diffusion and spheroidization in the subsequent high-temperature stage. This process can more effectively spheroidize the coarse second phase, eliminate intragranular segregation, and greatly improve the plasticity of subsequent processing. 520-560°C is the recrystallization temperature range of aluminum. Holding at this temperature can eliminate the casting stress of the ingot, allow the various alloying elements to diffuse evenly, and refine the grains. Slow cooling avoids generating thermal stress again, while maintaining the stability of the refined grain structure.

[0045] In some embodiments of the present invention, in S4, the first cold rolling in the three-pass cold rolling process rolls the ingot to 2.0-3.0 mm at a rolling speed of 300-500 m / min;

[0046] The second cold rolling process produces a thickness of 0.8-1.2 mm at a speed of 500-800 m / min.

[0047] The third cold rolling process reduces the thickness to 0.3-0.5 mm at a speed of 800-1200 m / min.

[0048] The three-stage cold rolling process avoids excessive deformation in a single cold rolling process, which could lead to cracking of the aluminum strip. By gradually accumulating deformation through multiple passes, the strength and toughness of the aluminum strip are improved.

[0049] In some embodiments of the present invention, in S4, the intermediate annealing temperature is 350-400℃ and the holding time is 2-4h; intermediate annealing eliminates the work hardening caused by cold rolling, and the aluminum strip hardness increases and ductility decreases after cold rolling. At the same time, it promotes recrystallization, forms fine and uniform grains, restores the ductility of the aluminum strip, and prepares it for subsequent second cold rolling.

[0050] In the two-pass cold rolling after intermediate annealing, the first pass is rolled to 0.1-0.15mm at a rolling speed of 1000-1500m / min;

[0051] The second cold rolling process reduces the thickness to 0.05-0.08 mm at a speed of 1200-1800 m / min.

[0052] The subsequent second cold rolling further reduces the thickness of the aluminum strip, while introducing a small amount of work hardening through moderate cold rolling to improve the strength of the aluminum strip. This provides a billet with uniform thickness and moderate strength for foil rolling, ensuring that foil rolling can be stably rolled to 8-15μm.

[0053] In some embodiments of the present invention, in step S5, the first foil is rolled to 0.035-0.05 mm at a rolling speed of 1500-1800 m / min;

[0054] The second foil is rolled to 0.025-0.035mm at a rolling speed of 1800-2000m / min;

[0055] The third foil is rolled to 0.018-0.025mm at a rolling speed of 2000-2200m / min;

[0056] The fourth foil is rolled to 0.013-0.018 mm at a rolling speed of 2200-2400 m / min;

[0057] The fifth foil is rolled to 0.010-0.013mm at a rolling speed of 2400-2500m / min;

[0058] The sixth foil is rolled to 8-10μm at a rolling speed of 2400-2500m / min.

[0059] Cold-rolled aluminum strip often exhibits edge cracks and wavy defects. These defects can rapidly propagate due to stress concentration during foil rolling, leading to strip breakage. Edge trimming completely removes these defective areas, resulting in neat, defect-free edges. Online quality inspection removes aluminum strips with thickness deviations or surface scratches, preventing these defects from being amplified after foil rolling. Before each rolling pass, the rolls undergo ultra-precision grinding and ultrasonic cleaning to remove residual aluminum powder. Low-viscosity rolling oil is used during foil rolling, employing a 5μm precision filter and circulating 5-8 times per hour to ensure that impurity particles in the oil are smaller than 3μm. Finished product annealing eliminates residual stress, improves ductility, stabilizes surface condition, and reduces contact resistance, which is beneficial for improving the high-rate discharge performance of batteries.

[0060] In some embodiments of the present invention, low-rate recrystallization annealing involves slowly heating to 260-300°C at a rate of 10-20°C / h under a nitrogen-hydrogen protective atmosphere and holding at that temperature for 10-15 hours. The extremely slow heating rate is beneficial for the formation of a large number of fine recrystallization nuclei, thereby obtaining uniform and fine recrystallized grains. Rapid heating, on the other hand, can easily lead to abnormal grain growth, and coarse grains will reduce ductility.

[0061] Example 1

[0062] A high-ductility aluminum foil for battery cathodes comprises the following components by mass percentage: 0.1% copper, 0.05% rare earth elements (cerium and yttrium in a mass ratio of 2:1), 0.1% iron, 0.025% silicon, 0.01% titanium, 0.003% boron, 0.08% zirconium, and the balance aluminum. The refining agent is an Al-Ti-C-La composite refining agent.

[0063] The preparation of the above-mentioned high-ductility aluminum foil for battery positive electrode includes the following steps:

[0064] S1. The smelting furnace is purged with a nitrogen-argon mixture and preheated to 500°C. Aluminum ingots and other raw materials are added and smelted, stirred until uniformly mixed. Hexachloroethane, a refining agent, is added and stirring continues at 750°C for 30 minutes. After removing surface impurities, the mixture is transferred to a holding furnace and treated online using an SNIF rotary jet degassing device and a ceramic plate filter to obtain the first aluminum mixture.

[0065] S2. Add 0.3% of a refining agent by mass of the first aluminum mixture obtained in S1 to obtain the second aluminum mixture. After filtering the second aluminum mixture, add it to the casting and rolling mill. The casting and rolling speed is 1.2 m / min and the roll gap is 8 mm. Casting and rolling yields an ingot.

[0066] S3. Remove the segregation layer from the surface of the ingot obtained in S2, and then perform a stepped heating homogenous annealing operation in a heating furnace. During the stepped heating homogenous annealing, the ingot after removing the segregation layer is sent to a continuous heating furnace and heated to 480°C at a rate of 4°C / min, held for 2 hours, then heated to 560°C at a rate of 2°C / min, held for 6 hours, and then cooled with the furnace to obtain the annealed ingot.

[0067] S4. The annealed ingot obtained in S3 is subjected to three cold rolling passes. The first cold rolling pass rolls the ingot to 3.0 mm at a rolling speed of 500 m / min. The second cold rolling pass rolls it to 1.2 mm at a rolling speed of 600 m / min. The third cold rolling pass rolls it to 0.5 mm at a rolling speed of 1000 m / min. Then, intermediate annealing is performed at 400℃ for 3 hours. Next, two more cold rolling passes are performed. The first cold rolling pass rolls the ingot to 0.15 mm at a rolling speed of 1200 m / min. The second cold rolling pass rolls it to 0.08 mm at a rolling speed of 1500 m / min to obtain aluminum strip.

[0068] S5. After quality inspection of the trimmed aluminum strip obtained in S4, perform six foil rolling passes. The first pass rolls the foil to 0.05 mm at a rolling speed of 1700 m / min. The second pass rolls the foil to 0.035 mm at a rolling speed of 2000 m / min. The third pass rolls the foil to 0.025 mm at a rolling speed of 2200 m / min. The fourth pass rolls the foil to 0.018 mm at a rolling speed of 2400 m / min. The fifth pass rolls the foil to 0.013 mm at a rolling speed of 2500 m / min. The sixth pass rolls the foil to 9 μm at a rolling speed of 2500 m / min, resulting in a 9 μm thick aluminum foil. Low-speed recrystallization annealing is performed under a nitrogen-hydrogen protective atmosphere, with the temperature slowly increased to 280 °C at a rate of 15 °C / h and held for 12 h to obtain the finished aluminum foil.

[0069] Example 2

[0070] A high-ductility aluminum foil for battery cathodes comprises, by mass percentage: 0.05% copper, 0.1% rare earth elements (lanthanum and europium mass ratio 1.5:1), 0.08% iron, 0.01% silicon, 0.02% titanium, 0.005% boron, 0.12% zirconium, and the balance aluminum. The refining agent is an Al-Ti-C-Ce composite refining agent.

[0071] The preparation of the above-mentioned high-ductility aluminum foil for battery positive electrode includes the following steps:

[0072] S1. The smelting furnace is purged with a nitrogen-argon mixture and preheated to 500°C. Aluminum ingots and other raw materials are added and smelted, stirred until uniformly mixed. Hexachloroethane, a refining agent, is added and stirring continues at 750°C for 30 minutes. After removing surface impurities, the mixture is transferred to a holding furnace and treated online using an SNIF rotary jet degassing device and a ceramic plate filter to obtain the first aluminum mixture.

[0073] S2. Add 0.1% of a refining agent by mass of the first aluminum mixture obtained in S1 to obtain the second aluminum mixture. After filtering the second aluminum mixture, add it to the casting and rolling mill. The casting and rolling speed is 1.2 m / min and the roll gap is 8 mm. Casting and rolling yields an ingot.

[0074] S3. Remove the segregation layer from the surface of the ingot obtained in S2, and then perform a stepped heating homogenous annealing operation in a heating furnace. During the stepped heating homogenous annealing, the ingot after removing the segregation layer is sent to a continuous heating furnace and heated to 480°C at a rate of 4°C / min, held for 2 hours, then heated to 560°C at a rate of 2°C / min, held for 6 hours, and then cooled with the furnace to obtain the annealed ingot.

[0075] S4. The annealed ingot obtained in S3 is subjected to three cold rolling passes. The first cold rolling pass rolls the ingot to 3.0 mm at a rolling speed of 500 m / min. The second cold rolling pass rolls it to 1.2 mm at a rolling speed of 600 m / min. The third cold rolling pass rolls it to 0.5 mm at a rolling speed of 1000 m / min. Then, intermediate annealing is performed at 400℃ for 3 hours. Next, two more cold rolling passes are performed. The first cold rolling pass rolls the ingot to 0.15 mm at a rolling speed of 1200 m / min. The second cold rolling pass rolls it to 0.08 mm at a rolling speed of 1500 m / min to obtain aluminum strip.

[0076] S5. After edge trimming and quality inspection of the aluminum strip obtained in S4, perform six foil rolling passes. The first pass rolls the foil to 0.05 mm at a rolling speed of 1700 m / min. The second pass rolls the foil to 0.035 mm at a rolling speed of 2000 m / min. The third pass rolls the foil to 0.025 mm at a rolling speed of 2200 m / min. The fourth pass rolls the foil to 0.018 mm at a rolling speed of 2400 m / min; the fifth pass rolls the foil to 0.013 mm at a rolling speed of 2500 m / min. The sixth pass rolls the foil to 8 μm at a rolling speed of 2500 m / min, resulting in an 8 μm thick aluminum foil. Low-speed recrystallization annealing is performed under a nitrogen-hydrogen protective atmosphere, with the temperature slowly increased to 280 °C at a rate of 15 °C / h and held for 12 h to obtain the finished aluminum foil.

[0077] Example 3

[0078] A high-ductility aluminum foil for battery cathodes comprises, by mass percentage, the following components: 0.2% copper, 0.01% rare earth elements (lanthanum, yttrium, and scandium in a mass ratio of 3:1:1), 0.2% iron, 0.05% silicon, 0.005% titanium, 0.002% boron, 0.08% zirconium, and the balance aluminum. The refining agent is an Al-Ti-C-Ce composite refining agent.

[0079] The preparation of the above-mentioned high-ductility aluminum foil for battery positive electrode includes the following steps:

[0080] S1. The smelting furnace is purged with a nitrogen-argon mixture and preheated to 500°C. Aluminum ingots and other raw materials are added and smelted, stirred until uniformly mixed. Hexachloroethane, a refining agent, is added and stirring continues at 750°C for 30 minutes. After removing surface impurities, the mixture is transferred to a holding furnace and treated online using an SNIF rotary jet degassing device and a ceramic plate filter to obtain the first aluminum mixture.

[0081] S2. Add 0.2% of a refining agent by mass of the first aluminum mixture obtained in S1 to obtain the second aluminum mixture. After filtering the second aluminum mixture, add it to the casting and rolling mill. The casting and rolling speed is 1.2m / min and the roll gap is 8mm. Casting and rolling yields an ingot.

[0082] S3. Remove the segregation layer from the surface of the ingot obtained in S2, and then perform a stepped heating homogenous annealing operation in a heating furnace. During the stepped heating homogenous annealing, the ingot after removing the segregation layer is sent to a continuous heating furnace and heated to 480°C at a rate of 4°C / min, held for 2 hours, then heated to 560°C at a rate of 2°C / min, held for 6 hours, and then cooled with the furnace to obtain the annealed ingot.

[0083] S4. The annealed ingot obtained in S3 is subjected to three cold rolling passes. The first cold rolling pass rolls the ingot to 3.0 mm at a rolling speed of 500 m / min. The second cold rolling pass rolls it to 1.2 mm at a rolling speed of 600 m / min. The third cold rolling pass rolls it to 0.5 mm at a rolling speed of 1000 m / min. Then, intermediate annealing is performed at 400℃ for 3 hours. Next, two more cold rolling passes are performed. The first cold rolling pass rolls the ingot to 0.15 mm at a rolling speed of 1200 m / min. The second cold rolling pass rolls it to 0.08 mm at a rolling speed of 1500 m / min to obtain aluminum strip.

[0084] S5. After quality inspection of the trimmed aluminum strip obtained in S4, perform five foil rolling passes. The first pass rolls the foil to 0.05 mm at a rolling speed of 1700 m / min. The second pass rolls the foil to 0.035 mm at a rolling speed of 2000 m / min. The third pass rolls the foil to 0.025 mm at a rolling speed of 2200 m / min. The fourth pass rolls the foil to 0.018 mm at a rolling speed of 2400 m / min. The fifth pass rolls the foil to 0.013 mm at a rolling speed of 2500 m / min, resulting in an aluminum foil with a thickness of 0.013 mm. Low-speed recrystallization annealing is performed under a nitrogen-hydrogen protective atmosphere, with the temperature slowly increased to 280 °C at a rate of 15 °C / h and held for 12 h to obtain the finished aluminum foil.

[0085] Example 4

[0086] A high-ductility aluminum foil for battery cathodes comprises the following components by mass percentage: 0.12% copper, 0.1% rare earth elements (lanthanum, cerium, and europium mixed in a mass ratio of 1:1:1), 0.08% iron, 0.01% silicon, 0.01% titanium, 0.004% boron, 0.1% zirconium, and the balance aluminum. The refining agent is an Al-Ti-C-Sc composite refining agent.

[0087] The preparation of the above-mentioned high-ductility aluminum foil for battery positive electrode includes the following steps:

[0088] S1. The smelting furnace is purged with a nitrogen-argon mixture and preheated to 500°C. Aluminum ingots and other raw materials are added and smelted, stirred until uniformly mixed. Hexachloroethane, a refining agent, is added and stirring continues at 750°C for 30 minutes. After removing surface impurities, the mixture is transferred to a holding furnace and treated online using an SNIF rotary jet degassing device and a ceramic plate filter to obtain the first aluminum mixture.

[0089] S2. Add 0.2% of a refining agent by mass of the first aluminum mixture obtained in S1 to obtain the second aluminum mixture. After filtering the second aluminum mixture, add it to the casting and rolling mill. The casting and rolling speed is 1.2m / min and the roll gap is 8mm. Casting and rolling yields an ingot.

[0090] S3. Remove the segregation layer from the surface of the ingot obtained in S2, and then perform a stepped heating homogenous annealing operation in a heating furnace. During the stepped heating homogenous annealing, the ingot after removing the segregation layer is sent to a continuous heating furnace and heated to 480°C at a rate of 4°C / min, held for 2 hours, then heated to 560°C at a rate of 2°C / min, held for 6 hours, and then cooled with the furnace to obtain the annealed ingot.

[0091] S4. The annealed ingot obtained in S3 is subjected to three cold rolling passes. The first cold rolling pass rolls the ingot to 3.0 mm at a rolling speed of 500 m / min. The second cold rolling pass rolls it to 1.2 mm at a rolling speed of 600 m / min. The third cold rolling pass rolls it to 0.5 mm at a rolling speed of 1000 m / min. Then, intermediate annealing is performed at 400℃ for 3 hours. Next, two more cold rolling passes are performed. The first cold rolling pass rolls the ingot to 0.15 mm at a rolling speed of 1200 m / min. The second cold rolling pass rolls it to 0.08 mm at a rolling speed of 1500 m / min to obtain aluminum strip.

[0092] S5. After quality inspection of the trimmed aluminum strip obtained in S4, perform five foil rolling passes. The first pass rolls the foil to 0.05 mm at a rolling speed of 1700 m / min. The second pass rolls the foil to 0.035 mm at a rolling speed of 2000 m / min. The third pass rolls the foil to 0.025 mm at a rolling speed of 2200 m / min. The fourth pass rolls the foil to 0.018 mm at a rolling speed of 2400 m / min. The fifth pass rolls the foil to 0.010 mm at a rolling speed of 2500 m / min, resulting in an aluminum foil with a thickness of 0.010 mm. Low-speed recrystallization annealing is performed under a nitrogen-hydrogen protective atmosphere, with the temperature slowly increased to 280 °C at a rate of 15 °C / h and held for 12 h to obtain the finished aluminum foil.

[0093] Example 5

[0094] A high-ductility aluminum foil for battery cathodes comprises the following components by mass percentage: 0.08% copper, 0.08% rare earth elements (cerium, europium, and yttrium mixed in a mass ratio of 1:1:1), 0.08% iron, 0.02% silicon, 0.008% titanium, 0.003% boron, 0.09% zirconium, and the balance aluminum. The refining agent is an Al-Ti-C-La composite refining agent.

[0095] The preparation of the above-mentioned high-ductility aluminum foil for battery positive electrode includes the following steps:

[0096] S1. The smelting furnace is purged with a nitrogen-argon mixture and preheated to 500°C. Aluminum ingots and other raw materials are added and smelted, stirred until uniformly mixed. Hexachloroethane, a refining agent, is added and stirring continues at 750°C for 30 minutes. After removing surface impurities, the mixture is transferred to a holding furnace and treated online using an SNIF rotary jet degassing device and a ceramic plate filter to obtain the first aluminum mixture.

[0097] S2. Add 0.15% of a refining agent by mass of the first aluminum mixture obtained in S1 to obtain the second aluminum mixture. After filtering the second aluminum mixture, add it to the casting and rolling mill. The casting and rolling speed is 1.2 m / min and the roll gap is 8 mm. Casting and rolling yields an ingot.

[0098] S3. Remove the segregation layer from the surface of the ingot obtained in S2, and then perform a stepped heating homogenous annealing operation in a heating furnace. During the stepped heating homogenous annealing, the ingot after removing the segregation layer is sent to a continuous heating furnace and heated to 480°C at a rate of 4°C / min, held for 2 hours, then heated to 560°C at a rate of 2°C / min, held for 6 hours, and then cooled with the furnace to obtain the annealed ingot.

[0099] S4. The annealed ingot obtained in S3 is subjected to three cold rolling passes. The first cold rolling pass rolls the ingot to 3.0 mm at a rolling speed of 500 m / min. The second cold rolling pass rolls it to 1.2 mm at a rolling speed of 600 m / min. The third cold rolling pass rolls it to 0.5 mm at a rolling speed of 1000 m / min. Then, intermediate annealing is performed at a temperature of 350-400℃ for 2-4 hours. Next, two more cold rolling passes are performed. The first cold rolling pass rolls the ingot to 0.15 mm at a rolling speed of 1200 m / min. The second cold rolling pass rolls it to 0.08 mm at a rolling speed of 1500 m / min to obtain aluminum strip.

[0100] S5. After quality inspection of the trimmed aluminum strip obtained in S4, perform six foil rolling passes. The first pass rolls the foil to 0.05 mm at a rolling speed of 1700 m / min. The second pass rolls the foil to 0.035 mm at a rolling speed of 2000 m / min. The third pass rolls the foil to 0.025 mm at a rolling speed of 2200 m / min. The fourth pass rolls the foil to 0.018 mm at a rolling speed of 2400 m / min. The fifth pass rolls the foil to 0.013 mm at a rolling speed of 2500 m / min. The sixth pass rolls the foil to 10 μm at a rolling speed of 2500 m / min, resulting in a 10 μm thick aluminum foil. Low-speed recrystallization annealing is performed under a nitrogen-hydrogen protective atmosphere, with the temperature slowly increased to 280 °C at a rate of 15 °C / h and held for 12 h to obtain the finished aluminum foil.

[0101] Application Example 1

[0102] Using the finished aluminum foil from Example 4 as the positive electrode, a lithium battery was prepared.

[0103] Comparative Example 1

[0104] An aluminum foil for a battery positive electrode comprises, by weight percentage: 0.1% copper, 0.18% iron, 0.05% silicon, 0.01% titanium, 0.002% boron, and the balance aluminum. The refining agent is an Al-Ti-C composite refining agent.

[0105] The preparation of the above-mentioned high-ductility aluminum foil for battery positive electrode includes the following steps:

[0106] S1. The smelting furnace is purged with a nitrogen-argon mixture and preheated to 500°C. Aluminum ingots and other raw materials are added and smelted, stirred until uniformly mixed. Hexachloroethane, a refining agent, is added and stirring continues at 750°C for 30 minutes. After removing surface impurities, the mixture is transferred to a holding furnace and treated online using an SNIF rotary jet degassing device and a ceramic plate filter to obtain the first aluminum mixture.

[0107] S2. After filtering the first aluminum mixture in S1, add it to the casting and rolling mill. The casting and rolling speed is 1.2m / min and the roll gap is 8mm. Casting and rolling yields ingots.

[0108] S3. Remove the segregation layer from the surface of the ingot obtained in S2, and then perform a stepped heating homogenous annealing operation in a heating furnace. During the stepped heating homogenous annealing, the ingot after removing the segregation layer is sent to a continuous heating furnace and heated to 480°C at a rate of 4°C / min, held for 2 hours, then heated to 560°C at a rate of 2°C / min, held for 6 hours, and then cooled with the furnace to obtain the annealed ingot.

[0109] S4. The annealed ingot obtained in S3 is subjected to three cold rolling passes. The first cold rolling pass rolls the ingot to 3.0 mm at a rolling speed of 500 m / min. The second cold rolling pass rolls it to 1.2 mm at a rolling speed of 600 m / min. The third cold rolling pass rolls it to 0.5 mm at a rolling speed of 1000 m / min. Then, intermediate annealing is performed at 400℃ for 3 hours. Next, two more cold rolling passes are performed. The first cold rolling pass rolls the ingot to 0.15 mm at a rolling speed of 1200 m / min. The second cold rolling pass rolls it to 0.08 mm at a rolling speed of 1500 m / min to obtain aluminum strip.

[0110] S5. After quality inspection of the trimmed aluminum strip obtained in S4, perform six foil rolling passes. The first pass rolls the foil to 0.05 mm at a rolling speed of 1700 m / min. The second pass rolls the foil to 0.035 mm at a rolling speed of 2000 m / min. The third pass rolls the foil to 0.025 mm at a rolling speed of 2200 m / min. The fourth pass rolls the foil to 0.018 mm at a rolling speed of 2400 m / min. The fifth pass rolls the foil to 0.013 mm at a rolling speed of 2500 m / min. The sixth pass rolls the foil to 9 μm at a rolling speed of 2500 m / min, resulting in a 9 μm thick aluminum foil. Low-speed recrystallization annealing is performed under a nitrogen-hydrogen protective atmosphere, with the temperature slowly increased to 280 °C at a rate of 15 °C / h and held for 12 h to obtain the finished aluminum foil.

[0111] Comparative Example 2

[0112] The difference from Application Example 1 is that the lithium battery is prepared using the finished aluminum foil from Comparative Example 1, while everything else is the same as in Application Example 1.

[0113] Test case

[0114] a. Mechanical property testing

[0115] The mechanical properties of the aluminum foils in Examples 1-5 and Comparative Example 1 were tested, and the results are shown in Table 1.

[0116] Table 1. Mechanical property data of Examples 1-5 and Comparative Example 1

[0117] ;

[0118] As shown in Table 1, in Examples 1-5, rare earth elements act as heterogeneous nucleation sites during aluminum foil preparation, inhibiting the growth of aluminum grains in the ingot. The addition of rare earth elements results in a fine-grained structure. During subsequent processing, the grain boundaries in this fine-grained structure hinder dislocation movement under stress, requiring greater external force to deform the aluminum foil, thus improving its tensile strength and yield strength. In contrast, Comparative Example 1 lacks the effect of rare earth elements, resulting in relatively coarse grains and weaker resistance to deformation at the grain boundaries, leading to lower strength. Furthermore, the fine-grained structure promotes more uniform deformation, reduces stress concentration, and improves the material's elongation.

[0119] b. Electrochemical performance testing

[0120] Electrochemical performance tests were conducted on the lithium batteries obtained in Application Example 1 and Comparative Example 2. After 300 charge-discharge cycles, the capacity retention rate of the lithium battery in Application Example 1 remained at 85%, while the capacity retention rate of the lithium battery in Comparative Example 2 was 70%. After 1000 charge-discharge cycles, the aluminum foil in Application Example 1 did not break, while the aluminum foil in Comparative Example 2 broke after 430 cycles.

[0121] Therefore, the present invention adopts the above-mentioned high-ductility aluminum foil for battery cathode and its production method. Rare earth elements can refine the grains and work synergistically with other elements to make the aluminum foil have both high tensile strength and good ductility, which can effectively avoid cracking and breakage of aluminum foil and improve the production yield and cycle stability of lithium battery.

[0122] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for producing an aluminum foil for a high-ductility battery positive electrode, characterized by: The high-ductility aluminum foil for battery cathode includes the following components by mass percentage: copper 0.05-0.2%, rare earth elements 0.01-0.1%, iron 0.08-0.2%, silicon 0.01-0.05%, titanium 0.005-0.02%, boron 0.002-0.005%, zirconium 0.08-0.12%, and the balance of aluminum; The rare earth elements include one or more of lanthanum, cerium, europium, yttrium, and scandium; The production method of the high-ductility aluminum foil for battery cathode includes the following steps: S1, after emptying the smelting furnace, preheat, add aluminum ingots and the rest of the raw materials for smelting, stir until mixed evenly, add a refining agent and continue stirring to obtain a first aluminum mixed solution; S2, add a refiner to the first aluminum mixed solution obtained in S1 to obtain a second aluminum mixed solution, and then cast and roll to obtain a cast ingot; The refiner is an Al-Ti-C-RE composite refiner, the mass ratio of Ti:C:RE is 5:1:2, and the Al-Ti-C-RE composite refiner includes one or more of an Al-Ti-C-La composite refiner, an Al-Ti-C-Ce composite refiner, and an Al-Ti-C-Sc composite refiner; In S2, the amount of the refiner added is 0.1%-0.3% of the mass of the first aluminum mixed solution; S3, remove the segregation layer on the surface of the cast ingot obtained in S2, and then perform a stepwise temperature increasing homogenization annealing operation in a heating furnace to obtain an annealed cast ingot; In S3, the cast ingot after removing the segregation layer is sent into a continuous heating furnace for temperature increasing at 3-5 ℃ / min to 480-500 ℃, and then kept for 2 h, and then increased at 1-2 ℃ / min to 540-560 ℃, and then kept for 6-10 h, and then cooled with the furnace; S4, the annealed cast ingot obtained in S3 is sequentially subjected to three cold rolling, then intermediate annealing, and then two cold rolling to obtain an aluminum strip; In S4, the first cold rolling in the three cold rolling rolls the cast ingot to 2.0-3.0 mm, and the rolling speed is 300-500 m / min; The second cold rolling is rolled to 0.8-1.2 mm, and the rolling speed is 500-800 m / min; The third cold rolling is rolled to 0.3-0.5 mm, and the rolling speed is 800-1200 m / min; In S4, the temperature of the intermediate annealing is 350-400 ℃, and the holding time is 2-4 h; In the two cold rolling after the intermediate annealing, the first cold rolling is rolled to 0.1-0.15 mm, and the rolling speed is 1000-1500 m / min; The second cold rolling is rolled to 0.05-0.08 mm, and the rolling speed is 1200-1800 m / min; S5, the aluminum strip obtained in S4 is cut and inspected, and then subjected to 4-6 foil rolling to obtain an aluminum foil with a thickness of 8-15 μm, and then subjected to low-speed temperature increasing recrystallization annealing to obtain a finished aluminum foil; The low-speed temperature increasing recrystallization annealing is slowly increased to 260-300 ℃ at a rate of 10-20 ℃ / h under a nitrogen-hydrogen protective atmosphere, and then kept for 10-15 h.

2. The method of producing a high-ductility aluminum foil for a battery positive electrode according to claim 1, characterized by: In S1, after heating after emptying the smelting furnace, the furnace chamber is purged with a mixture of nitrogen and argon, and preheated to 400-500 ℃.

3. The method of producing a high-ductility aluminum foil for a battery positive electrode according to claim 1, characterized by: In S1, the temperature is 700-800 DEG C during stirring, and stirring is performed for 10-45 min, and after removing surface impurities, the first aluminum mixture is transferred into a holding furnace, and is treated on line through a SNIF rotating blowing degassing device and a ceramic plate filter, to obtain the first aluminum mixture.

4. The method of producing a high-ductility aluminum foil for a battery positive electrode according to claim 1, characterized by: In S2, the second aluminum mixture is filtered and is added into a casting and rolling machine, the casting and rolling speed is 0.8-1.5 m / min, and the roll gap is 6-10 mm.