High-performance ultrathin aluminum foil and preparation method thereof

Abstract

The invention relates to the technical field of aluminum processing, and provides a high-performance ultrathin aluminum foil and a preparation method thereof.The preparation method comprises the following steps that S1, a raw material formula is smelted into molten aluminum through a smelting furnace; s2, the molten aluminum is injected into a casting nozzle of a casting and rolling machine through a runner, the molten aluminum is cooled through a rolling roller of the casting and rolling machine, and a cast-rolled coil with the thickness of 6.4 + / -0.3 mm is obtained; s3, the cast-rolled coil is subjected to cold rolling through a four-roller cold rolling mill, and a cold-rolled coil with the thickness ranging from 0.18 mm to 0.21 mm is obtained; s4, foil rolling is conducted on the cold-rolled coil through a foil rolling machine, and a high-performance ultrathin aluminum foil coil with the thickness smaller than or equal to 10 micrometers is obtained; and S5, the high-performance ultra-thin aluminum foil roll is subjected to fine cutting after being slit, and the high-performance ultra-thin aluminum foil is obtained. The high-performance ultrathin aluminum foil is thin, the tensile strength is larger than or equal to 265 MPa, the percentage elongation after fracture is larger than or equal to 3.5%, and the collapse value is smaller than or equal to 5 mm.

Description

Technical Field

[0001] This invention relates to the field of aluminum processing technology, and in particular to a high-performance ultrathin aluminum foil used in the positive electrode current collector of power batteries and its preparation method. Background Technology

[0002] With the rapid development of new energy vehicles, portable electronic devices, and large-scale energy storage systems, the market is placing ever-increasing demands on the energy density of lithium-ion batteries. Improving battery energy density is one of the core driving forces of technological innovation in the industry. In the structure of lithium-ion batteries, the positive electrode current collector is typically made of aluminum foil, which, as an "inactive material" that does not participate in electrochemical reactions, accounts for a significant proportion of the battery's total weight. Currently, the thickness of commercially available positive electrode aluminum foil is mostly between 10 and 15 μm, and this portion of the current collector can account for more than 10% of the total mass of the positive electrode sheet, severely restricting further improvements in battery mass energy density. Therefore, reducing the mass proportion of the current collector aluminum foil by thinning it has become a direct and effective technical path for improving energy density in the industry. Theoretically, reducing the aluminum foil thickness from 15 μm to 10 μm can significantly reduce the weight of the current collector, thereby creating space within the same volume or weight of battery to accommodate more electrochemically active positive electrode materials (such as lithium iron phosphate, ternary materials, etc.), directly improving the battery's mass energy density. However, reducing the thickness of aluminum foil faces severe technical challenges: reduced thickness inevitably leads to decreased mechanical strength and reduced ductility, and makes it more prone to problems such as strip breakage, wrinkling, and perforation during subsequent battery fabrication processes (e.g., coating, rolling, slitting, and winding / stacking). This severely restricts the industrial application and reliability of ultra-thin aluminum foil. Therefore, developing a high-performance ultra-thin aluminum foil that combines excellent mechanical properties and stability while achieving thinner profiles is crucial for overcoming the current energy density bottleneck of lithium-ion batteries.

[0003] In related technologies, aluminum foil production methods generally include smelting and casting / rolling processes: lithium battery components and their mass percentages are heated and smelted with aluminum foil to form an aluminum alloy melt; then, refining, slag removal, grain refinement, degassing, slag removal, and filtration are performed sequentially; the filtered aluminum alloy melt is then continuously cast and rolled into a billet of 6.0-8.0 mm; cold rolling process: the billet is first cold rolled to 4.0-5.0 mm, then subjected to a first annealing treatment; the billet after the first annealing treatment is rough rolled to 0.25-0.3 mm, followed by a second annealing treatment; foil pressing treatment: the aluminum foil after the second annealing treatment is finely rolled into aluminum foil rolls with a thickness of 0.01-0.05 mm, and the aluminum foil rolls are slit to obtain the finished aluminum foil for lithium batteries. However, by adding copper during the casting and smelting process, the synergistic effect between different elements was changed, and the grains were refined through two intermediate annealing treatments, resulting in battery aluminum foil with a tensile strength of 160-190 MPa and an elongation at break of ≥1.5%.

[0004] However, the aluminum foil produced above has a large thickness, low tensile strength, and small elongation, resulting in poor performance. Summary of the Invention

[0005] The purpose of this invention is to provide a high-performance ultra-thin aluminum foil to solve the problems of large thickness and poor performance of existing battery aluminum foils.

[0006] To address the aforementioned technical problems, in a first aspect, embodiments of the present invention provide a method for preparing high-performance ultrathin aluminum foil, the method comprising the following steps: Step S1: Melt the raw materials into molten aluminum using a smelting furnace; The composition and mass percentage of the raw material formula are as follows: Si: 0.4%~0.6%, Fe: 0.5%~0.7%, Cu≤0.15%, Ti≤0.05%, with the balance being Al; wherein, Al is obtained from aluminum ingots with an aluminum content greater than or equal to 99.70%, Si is prepared using AlSi20 master alloy, Fe is prepared using iron additives, Cu is prepared using AlCu50 master alloy, and Ti is prepared by adding aluminum-titanium-boron wire at the outlet of the holding furnace. Step S2: The molten aluminum is injected into the casting nozzle of the casting and rolling mill through a flow channel, and the molten aluminum is cooled by the rolling rolls of the casting and rolling mill to obtain a cast coil with a thickness of 6.4±0.3mm. The casting nozzle has an opening of 13±1mm. Before being injected into the nozzle, the molten aluminum passes through a degassing box and a filter box. The degassing box uses a silicon carbide rotor with a rotation speed of 500±50rpm and a temperature of 725±3℃. The argon gas flow rate is 20±2mL / min. The filter box uses a 50mm thick, 60ppi+70ppi dual-stage ceramic filter plate. At the outlets of the degassing box and the filter box, the hydrogen content of the molten aluminum is ≤0.1mL / (100gAl), and the slag content is ≤0.05mm. 2 / kg; Step S3: The cast-rolled coil is cold-rolled using a four-roll cold rolling mill to obtain a cold-rolled coil with a thickness of 0.18~0.21mm; Step S4: The cold-rolled coil is foil-rolled using a foil rolling mill to obtain a high-performance ultra-thin aluminum foil coil with a thickness ≤10μm; Step S5: After the high-performance ultra-thin aluminum foil roll is slit, it is precision cut to obtain the finished aluminum foil product.

[0007] Preferably, step S1 specifically includes the following steps: The raw materials are smelted in the furnace according to the raw material formula to obtain a melt; The melt is stirred; Perform the first refining; Perform the first slag removal; Perform the first settling process; Turn the furnace over; Perform a second refining; Perform a second slag removal; The mixture is allowed to stand for a second time to obtain the molten aluminum. Specifically, when the melt temperature reaches 730~750℃, additives and intermediate alloys are added. The melting time in the smelting furnace is ≥20min, and electromagnetic stirring is simultaneously activated for ≥30min. In the smelting furnace refining process, 10~15Kg of granular refining agent is used, and refining is performed for 20~25min using argon gas injection. In the holding furnace, argon gas is used for refining for 15~20min. After refining, the slag is removed, and the mixture is allowed to stand for 30~40min. After the aluminum liquid has remained in the holding furnace for ≥6 hours, argon gas is used for supplementary refining for 10~15min. After refining in the holding furnace, the hydrogen content of the molten aluminum is ≤0.2mL / (100gAl), and the slag content is ≤0.05mm. 2 / kg.

[0008] Preferably, in step S2, the following conditions are met during casting and rolling: The temperature of the front chamber of the smelting furnace is 693~697℃, the length of the casting and rolling zone is 50~60mm, the temperature of the cooling water is 30~38℃, the temperature difference between the inlet and outlet of the cooling water is 2~3℃, the cooling water flow rate is 90~100m3 / h, the roll gap is 3.5~4.0mm, the strip speed is 750~850mm / min, and the diameter of the casting and rolling roll is ≥800mm.

[0009] Preferably, the cold rolling process includes seven passes; wherein, the first pass of the cold rolling process is 6.80±3mm→4.00mm, and the uncoiling tension is 0.45~0.60kg / mm. 2 The curling tension is 1.30~1.45 kg / mm. 2 The rolling speed is 230~270m / min, and the rolling force is 590~600t; the second pass of the cold rolling is 4.00mm→2.50mm, and the uncoiling tension is 0.90~1.10kg / mm. 2 The curling tension is 1.80~2.00 kg / mm. 2 The rolling speed is 280~320m / min, and the rolling force is 530~540t; the third pass of the cold rolling is 2.50mm→1.45mm, and the uncoiling tension is 1.60~1.80kg / mm. 2 The curling tension is 2.00~2.22 kg / mm. 2The rolling speed is 320~360m / min, and the rolling force is 460~470t; the fourth pass of the cold rolling is 1.45mm→0.85mm, and the uncoiling tension is 1.80~2.00kg / mm. 2 The curling tension is 2.40~2.60 kg / mm. 2 The rolling speed is 470~510m / min, and the rolling force is 470~480t; the fifth pass of the cold rolling is 0.85mm→0.55mm, and the uncoiling tension is 2.20~2.40kg / mm. 2 The curling tension is 2.70~2.90 kg / mm. 2 The rolling speed is 490~530m / min, and the rolling force is 400~410t; the sixth pass of the cold rolling is 0.55mm→0.33mm, and the uncoiling tension is 2.50~2.70kg / mm. 2 The curling tension is 2.80~3.00 kg / mm. 2 The rolling speed is 495~535m / min, and the rolling force is 430~440t; the seventh pass of the cold rolling is 0.33mm→0.18~0.21mm, and the uncoiling tension is 2.50~2.80kg / mm. 2 The curling tension is 3.00~3.40 kg / mm. 2 The rolling speed is 520~560m / min and the rolling force is 370~380t.

[0010] Preferably, edge trimming is performed after the second and seventh passes of the cold rolling process.

[0011] Preferably, the foil rolling process includes five passes; wherein, the first pass of the foil rolling process is 0.200mm → 0.100mm, and the unwinding tension is ≥35kg / mm. 2 The curling tension is 35~40 kg / mm 2 The rolling speed is ≤750m / min, the rolling force is 200~300t, the roll surface roughness is 0.16um, and the roll crown is 0.045mm; the second pass of the foil rolling is 0.100mm→0.048mm, and the uncoiling tension is ≥40kg / mm. 2 The curling tension is 35~40 kg / mm 2 The rolling speed is ≤900m / min, the rolling force is 220~320t, the roll surface roughness is 0.16um, and the roll crown is 0.045mm; the third pass of the foil rolling is 0.048mm→0.026mm, and the uncoiling tension is ≥50kg / mm. 2 The curling tension is 40~45 kg / mm. 2The rolling speed is ≤950m / min, the rolling force is 220~300t, the roll surface roughness is 0.12um, and the roll crown is 0.065mm; the fourth pass of the foil rolling is 0.026mm→0.015±0.001mm, and the uncoiling tension is ≥50kg / mm. 2 The curling tension is 40~50 kg / mm 2 The rolling speed is ≤800m / min, the rolling force is 230~320t, the roll surface roughness is 0.10um, and the roll crown is 0.065mm; the fifth pass of the foil rolling is 0.015±0.001mm→0.009mm, and the uncoiling tension is ≥60kg / mm. 2 The curling tension is 40~65 kg / mm 2 The rolling speed is ≤800m / min, the rolling force is 220~360t, the surface roughness of the roll is 0.06~0.07um, and the crown of the roll is 0.065mm.

[0012] Preferably, during the fifth pass of the foil rolling mill, the inlet air flotation angle of the foil rolling mill is 30°~60°.

[0013] Preferably, the rolling oil used in the first, second, and third passes of foil rolling contains 0.15-0.2 mg KOH / g of acid, 1.2-1.5% of alcohol, 5.5-7.5% of ester, and ≤400 mg / 100 mL of gum; the rolling oil used in the fourth and fifth passes of foil rolling contains 0.25-0.3 mg KOH / g of acid, 2.6-2.9% of alcohol, 6.0-8.0% of ester, and ≤400 mg / 100 mL of gum.

[0014] Preferably, step S5 specifically involves: slitting the high-performance ultra-thin aluminum foil roll using a slitting machine, and then precision cutting it using a precision cutter to obtain the high-performance ultra-thin aluminum foil; wherein the blade angle of the precision cutter is 15°; The preparation method further includes corona treatment of the precision-cut high-performance ultrathin aluminum foil using a corona device; wherein the power of the corona device is 88±5kW, and the speed of the precision cutter is ≤200m / min.

[0015] Secondly, embodiments of the present invention provide a high-performance ultra-thin aluminum foil, which is made by the above-described method for preparing high-performance ultra-thin aluminum foil, and is used as a positive electrode current collector in a lithium-ion battery.

[0016] Compared with existing technologies, the high-performance ultra-thin aluminum foil of this invention is produced by melting the raw material formula into molten aluminum in a melting furnace; injecting the molten aluminum into the casting nozzle of a casting and rolling mill through a flow channel, and cooling the molten aluminum through the rolling rolls of the casting and rolling mill to obtain a cast-rolled coil with a thickness of 6.4±0.3mm; cold rolling the cast-rolled coil through a four-roll cold rolling mill to obtain a cold-rolled coil with a thickness of 0.18~0.21mm; foil rolling the cold-rolled coil through a foil rolling mill to obtain a high-performance ultra-thin aluminum foil coil with a thickness of ≤10μm; and precision cutting the high-performance ultra-thin aluminum foil coil after slitting to obtain high-performance ultra-thin aluminum foil. In this way, through composition design and process route adjustment, the aluminum foil achieves a thickness of ≤10μm, tensile strength ≥265MPa, elongation after fracture ≥3.5%, and slump value ≤5mm, thereby improving the performance of the high-performance ultra-thin aluminum foil. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort, wherein: Figure 1 A flowchart illustrating the method for preparing high-performance ultrathin aluminum foil according to an embodiment of the present invention; Figure 2 A schematic diagram of the surface of the 0.021 mm diameter foil-rolled product of the method for preparing high-performance ultrathin aluminum foil provided in the embodiments of the present invention; Figure 3 A schematic diagram of the surface of the 0.015mm finished foil product of the high-performance ultrathin aluminum foil preparation method provided in the embodiments of the present invention; Figure 4 A schematic diagram of the surface of the 0.009 mm diameter foil-rolled product from the method for preparing high-performance ultrathin aluminum foil provided in this embodiment of the invention; Figure 5 A microscopic schematic diagram of the cutting edge of the precision cutting blade with an angle of 15° in the preparation method of high-performance ultrathin aluminum foil provided in the embodiments of the present invention; Figure 6 This is a microscopic schematic diagram of the cutting edge of a precision cutting blade with a cutting edge angle of 30°, used in a common method for preparing high-performance ultrathin aluminum foil. Detailed Implementation

[0018] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. 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.

[0019] Example 1 Please see the appendix Figures 1-6 As shown in the figure, this invention provides a method for preparing high-performance ultrathin aluminum foil, the method comprising the following steps: Step S1: Melt the raw material formula into molten aluminum in a smelting furnace.

[0020] The raw material formulation comprises the following components and mass percentages: Si: 0.4%~0.6%, Fe: 0.5%~0.7%, Cu≤0.15%, Ti≤0.05%, with the balance being Al. Specifically, Al is obtained from aluminum ingots with an aluminum content greater than or equal to 99.70%; Si is prepared using AlSi20 master alloy; Fe is prepared using an iron-based agent; Cu is prepared using AlCu50 master alloy; and Ti is prepared by adding aluminum-titanium-boron wire (AlTi5B0.6) to the inlet of the holding furnace. In the aluminum alloy production process, the melting furnace and holding furnace are the core collaborative equipment for front-end melting and back-end refining liquid supply. Through clear functional division, strict process parameter matching, and seamless connection logic, they jointly ensure the compositional uniformity, purity, and forming stability of the aluminum alloy billet. The raw material formulation comprises elements from two sources. One source is commonly used 1xxx series (1060, 1100, etc.) recycled aluminum alloys (substandard products generated during the processing of aluminum alloy sheets, strips, and foils), accounting for ≤10%. Using 1xxx series recycled aluminum alloys will not introduce non-formula chemical components or non-Al-Fe and Al-Fe-Si second phases. Any inclusions resulting from appropriate additions are removed through slag removal processes and online filtration, without negatively impacting the aluminum foil. Adding recycled materials not only improves raw material utilization but also reduces production costs and energy consumption. The other source is aluminum ingots with an aluminum content ≥99.70%.

[0021] Step S2: The molten aluminum is injected into the casting nozzle of the casting and rolling mill through a flow channel, and the molten aluminum is cooled by the rolling rolls of the casting and rolling mill to obtain a cast and rolled coil with a thickness of 6.4±0.3mm.

[0022] The casting nozzle has an opening of 13±1mm. Before being injected into the nozzle, the molten aluminum passes through a degassing box and a filter box. The degassing box uses a silicon carbide rotor with a rotation speed of 500±50rpm and a temperature of 725±3℃. The argon gas flow rate is 20±2mL / min. The filter box uses a 50mm thick, 60ppi+70ppi dual-stage ceramic filter plate. At the outlets of the degassing box and the filter box, the hydrogen content of the molten aluminum is ≤0.1mL / (100gAl), and the slag content is ≤0.05mm. 2 / kg. The 60ppi (60 pores per square inch) filter can first intercept larger inclusions (such as unremoved oxide slag and refining agent residue) to prevent clogging of the subsequent finer 70ppi filter plate; the 70ppi filter can intercept fine inclusions (particle size ≤10μm), achieving dual protection of coarse and fine filtration. Through a degassing box and dual-stage filtration, the hydrogen and slag content are controlled below the "critical value" in aluminum foil production, avoiding core defects such as pinholes and pores from the source.

[0023] Step S3: The cast-rolled coil is cold-rolled using a four-roll cold rolling mill to obtain a cold-rolled coil with a thickness of 0.18~0.21mm.

[0024] Step S4: The cold-rolled coil is foil rolled using a foil rolling mill to obtain a high-performance ultra-thin aluminum foil coil with a thickness ≤10μm.

[0025] Step S5: After the high-performance ultra-thin aluminum foil roll is slit, it is precision cut to obtain high-performance ultra-thin aluminum foil.

[0026] Specifically, the raw material formula is smelted into molten aluminum in a melting furnace; the molten aluminum is then poured into the casting nozzle of a casting and rolling mill through a flow channel, and cooled by the rolling rolls of the casting and rolling mill to obtain a cast-rolled coil with a thickness of 6.4±0.3mm; the cast-rolled coil is then cold-rolled using a four-roll cold rolling mill to obtain a cold-rolled coil with a thickness of 0.18~0.21mm; the cold-rolled coil is then foil-rolled using a foil rolling mill to obtain a high-performance ultra-thin aluminum foil coil with a thickness of ≤10μm; the high-performance ultra-thin aluminum foil coil is then slit and precision-cut to obtain high-performance ultra-thin aluminum foil; thus, through composition design and process route adjustment, the aluminum foil ultimately achieves a thickness of ≤10μm, a tensile strength of ≥265MPa, an elongation at break of ≥3.5%, and a slump value of ≤5mm, thereby improving the performance of the high-performance ultra-thin aluminum foil.

[0027] In this embodiment, step S1 specifically includes the following steps: The raw materials are smelted in the furnace according to the raw material formula to obtain a melt; the melt is stirred; a first refining is performed; a first slag removal is performed; a first settling is performed; the furnace is turned over; a second refining is performed; a second slag removal is performed; and a second settling is performed to obtain the molten aluminum.

[0028] Specifically, when the melt temperature reaches 730~750℃, additives and intermediate alloys are added. The melting time in the smelting furnace is ≥20min, and electromagnetic stirring is simultaneously activated for ≥30min. In the smelting furnace refining process, 10~15Kg of granular refining agent is used, and refining is performed for 20~25min using argon gas injection. In the holding furnace, argon gas is used for refining for 15~20min. After refining, the slag is removed, and the mixture is allowed to stand for 30~40min. After the aluminum liquid has remained in the holding furnace for ≥6 hours, argon gas is used for supplementary refining for 10~15min. After refining in the holding furnace, the hydrogen content of the molten aluminum is ≤0.2mL / (100gAl), and the slag content is ≤0.05mm. 2 / kg.

[0029] Specifically, 730~750℃ is the optimal temperature range for smelting aluminum and aluminum alloys. This range ensures melt fluidity for proper mixing while preventing excessive oxidation and burn-off caused by high temperatures, and also prevents insufficient dissolution of additives at low temperatures. A furnace simmering period of ≥20 minutes isolates the furnace from air, reducing the reaction loss of additives and intermediate alloys with oxygen, ensuring stable dissolution and effectiveness. Electromagnetic force drives the melt to flow without dead zones, breaking up areas of component segregation and ensuring uniform distribution of additives and intermediate alloys in the molten aluminum. Simultaneously, it breaks up oxide inclusions generated in the melt, creating conditions for impurity removal in subsequent refining processes. Granular refining agents can chemically react with alkali metals, alkaline earth metals (Ca), and oxide inclusions in the molten aluminum to generate low-melting-point, low-density compounds, facilitating subsequent slag removal. Argon, as an inert gas, acts as a carrier for the refining agent, uniformly injecting it into the depths of the melt; it also forms bubbles during its ascent, adsorbing hydrogen and fine inclusions from the molten aluminum, which float to the melt surface with the bubbles. A refining time of 20-25 minutes ensures sufficient reaction between the refining agent and impurities, and optimizes the efficiency of impurity adsorption by bubbles. Argon refining in the holding furnace is a secondary refining process, further removing trace amounts of hydrogen and inclusions remaining after refining in the smelting furnace; simultaneously, the argon atmosphere prevents the molten aluminum from absorbing hydrogen again and oxidizing during the holding process. A 30-40 minute settling period utilizes density differences to allow small inclusions that haven't floated to the surface to slowly settle to the bottom of the furnace; at the same time, it allows sufficient time for dissolved hydrogen in the molten aluminum to diffuse to the surface and escape, reducing the hydrogen content of the molten aluminum. Holding the molten aluminum for ≥6 hours achieves long-term homogenization, eliminating localized composition and temperature differences; simultaneously, it allows inclusions in the melt to settle fully, further purifying the molten aluminum. Supplemental argon refining provides final purification for trace amounts of hydrogen that may be re-adsorbed by the molten aluminum during long-term holding and for the formation of oxide slag, ensuring stable molten aluminum quality. Low hydrogen content (≤0.2mL / (100gAl) after settling): Hydrogen is the core factor causing pinholes and bubbles during aluminum foil rolling. Low-hydrogen molten aluminum will not form micro-voids due to hydrogen evolution during rolling, ensuring the surface smoothness and density of the aluminum foil and preventing the finished aluminum foil from being scrapped due to pinholes. Low slag content (≤0.05mm² / kg): Slag inclusions in molten aluminum are the main cause of scratches, cracks, and delamination on the surface of aluminum foil. Controlling the slag content to an extremely low level can prevent slag inclusions from being pressed into the aluminum foil matrix during rolling or causing damage to the rolling roll surface, thereby ensuring the mechanical properties and surface quality of the aluminum foil. Therefore, the synergistic control of these parameters can obtain high-purity molten aluminum with uniform composition, extremely low hydrogen content, and minimal slag inclusions, providing high-quality raw materials for subsequent casting (or hot rolling) into aluminum billets and then cold rolling into aluminum foil, ultimately resulting in uniform and stable mechanical properties of the aluminum foil such as tensile strength and elongation.

[0030] In this embodiment, during step S2, the following conditions are met during casting and rolling: The furnace front chamber temperature is 693~697℃, the casting and rolling zone length is 50~60mm, the cooling water temperature is 30~38℃, the cooling water inlet and outlet temperature difference is 2~3℃, the cooling water flow rate is 90~100m³ / h, the roll gap is 3.5~4.0mm, the strip speed is 750~850mm / min, and the casting roll diameter is ≥800mm. This parameter adjustment improves the casting and rolling cooling intensity and controls the center layer segregation of the cast billet. Reducing the roll gap eliminates the increase in plate thickness caused by low strip speed, thereby improving the casting and rolling cooling intensity. The casting rolls are old rolls, and before use, the roll sleeves need to be cleaned with alkaline detergent to remove scale, as scale affects the thermal conductivity of the casting rolls.

[0031] In this embodiment, the high casting and rolling cooling capacity of this method results in a high degree of solid solution of Fe and Si elements in the cast and rolled billet, which can effectively avoid premature softening during processing, leading to low tensile strength and elongation after fracture of the aluminum foil.

[0032] In this embodiment, the cold rolling process includes seven passes; wherein, the first pass of the cold rolling process is 6.80±3mm→4.00mm, and the uncoiling tension is 0.45~0.60kg / mm. 2 The curling tension is 1.30~1.45 kg / mm. 2 The rolling speed is 230~270m / min, and the rolling force is 590~600t; the second pass of the cold rolling is 4.00mm→2.50mm, and the uncoiling tension is 0.90~1.10kg / mm. 2 The curling tension is 1.80~2.00 kg / mm. 2 The rolling speed is 280~320m / min, and the rolling force is 530~540t; the third pass of the cold rolling is 2.50mm→1.45mm, and the uncoiling tension is 1.60~1.80kg / mm. 2 The curling tension is 2.00~2.22 kg / mm. 2 The rolling speed is 320~360m / min, and the rolling force is 460~470t; the fourth pass of the cold rolling is 1.45mm→0.85mm, and the uncoiling tension is 1.80~2.00kg / mm. 2 The curling tension is 2.40~2.60 kg / mm. 2 The rolling speed is 470~510m / min, and the rolling force is 470~480t; the fifth pass of the cold rolling is 0.85mm→0.55mm, and the uncoiling tension is 2.20~2.40kg / mm. 2 The curling tension is 2.70~2.90 kg / mm. 2The rolling speed is 490~530m / min, and the rolling force is 400~410t; the sixth pass of the cold rolling is 0.55mm→0.33mm, and the uncoiling tension is 2.50~2.70kg / mm. 2 The curling tension is 2.80~3.00 kg / mm. 2 The rolling speed is 495~535m / min, and the rolling force is 430~440t; the seventh pass of the cold rolling is 0.33mm→0.18~0.21mm, and the uncoiling tension is 2.50~2.80kg / mm. 2 The curling tension is 3.00~3.40 kg / mm. 2 The rolling speed is 520~560m / min, and the rolling force is 370~380t. This achieves a large reduction in thickness while ensuring the stability of the strip, correcting defects in the cast-rolled coil, and laying a foundation for uniform microstructure and strip shape for subsequent multi-pass cold rolling.

[0033] In this embodiment, the rolling conditions for cold rolling are shown in Table 1; Table 1 - Rolling conditions for cold rolling

[0034] In this embodiment, conventional cast-rolled aluminum foil blanks undergo intermediate annealing (recrystallization annealing, incomplete annealing) or even homogenization annealing during production. However, the high-performance ultra-thin aluminum foil of this invention is produced without heat treatment throughout the entire process. During the production of aluminum foil in the H19 state, by controlling the Si content and avoiding intermediate annealing, processing softening occurs during foil rolling, thereby improving the elongation at break of the aluminum foil.

[0035] In this embodiment, edge trimming is performed after the second and seventh passes of cold rolling. Specifically, edge trimming is performed at the intermediate thickness of 2.5 mm and the finished thickness of 0.18-0.21 mm. Due to the high degree of material alloying, the cracks generated during the cold rolling thinning process are larger than in traditional battery aluminum foil processes, necessitating two edge trimming operations to ensure that the end face of the finished cold-rolled coil (i.e., aluminum foil blank) is free of gaps, ensuring stability in subsequent foil rolling processes.

[0036] In this embodiment, the foil rolling process includes five passes; wherein, the first pass of the foil rolling process is 0.200mm → 0.100mm, and the unwinding tension is ≥35kg / mm. 2 The curling tension is 35~40 kg / mm 2 The rolling speed is ≤750m / min, the rolling force is 200~300t, the roll surface roughness is 0.16um, and the roll crown is 0.045mm; the second pass of the foil rolling is 0.100mm→0.048mm, and the uncoiling tension is ≥40kg / mm. 2The curling tension is 35~40 kg / mm 2 The rolling speed is ≤900m / min, the rolling force is 220~320t, the roll surface roughness is 0.16um, and the roll crown is 0.045mm; the third pass of the foil rolling is 0.048mm→0.026mm, and the uncoiling tension is ≥50kg / mm. 2 The curling tension is 40~45 kg / mm. 2 The rolling speed is ≤950m / min, the rolling force is 220~300t, the roll surface roughness is 0.12um, and the roll crown is 0.065mm; the fourth pass of the foil rolling is 0.026mm→0.015±0.001mm, and the uncoiling tension is ≥50kg / mm. 2 The curling tension is 40~50 kg / mm 2 The rolling speed is ≤800m / min, the rolling force is 230~320t, the roll surface roughness is 0.10um, and the roll crown is 0.065mm; the fifth pass of the foil rolling is 0.015±0.001mm→0.009mm, and the uncoiling tension is ≥60kg / mm. 2 The curling tension is 40~65 kg / mm 2 The rolling speed is ≤800m / min, the rolling force is 220~360t, the surface roughness of the roll is 0.06~0.07um, and the crown of the roll is 0.065mm.

[0037] In this embodiment, the rolling conditions for the foil are shown in Table 2; Table 2 - Foil Rolling Conditions

[0038] Specifically, the thickness of the semi-finished product pass is 0.0155±0.001mm. If the semi-finished product pass thickness is too small, it will be difficult to thread the finished product pass during rolling; if the semi-finished product pass thickness is too large, it will be difficult to roll the finished product pass to the target thickness. The finished foil pass rolling requires the use of new rolls with a surface roughness of 0.06~0.07μm. The speed of both the finished and semi-finished product passes must be strictly controlled, using low speeds. This is because the surface quality of the aluminum foil in the earlier passes is less affected by the parameters, but the surface quality of the finished and semi-finished product passes is greatly affected by the foil rolling parameters. Poor surface quality will act as a crack initiation during deformation, thereby reducing the elongation at break of the aluminum foil.

[0039] In this embodiment, compressed air is added below the roll exit for both the semi-finished and finished product passes to cause slight oscillations on the aluminum foil surface. A flattening roll with a convexity of 0.03~0.05mm is used. By adjusting the pressure of the flattening roll, the occurrence of bulging defects can be effectively reduced.

[0040] In this embodiment, during the fifth pass of foil rolling, the inlet air flotation angle of the foil rolling mill is 30°~60°. The inlet air flotation angle of the foil rolling mill for the finished product pass is also 30°~60°. A smaller air flotation angle is not conducive to threading the strip, while a larger air flotation angle can easily lead to strip breakage during threading.

[0041] In this embodiment, the rolling oil used in the first, second, and third passes of foil rolling contains 0.15-0.2 mg KOH / g of acid, 1.2-1.5% of alcohol, 5.5-7.5% of ester, and ≤400 mg / 100 mL of gum; the rolling oil used in the fourth and fifth passes contains 0.25-0.3 mg KOH / g of acid, 2.6-2.9% of alcohol, 6.0-8.0% of ester, and ≤400 mg / 100 mL of gum. Because aluminum foil has high strength, further thinning is difficult, and the oil film strength needs to be improved by adjusting the oil content.

[0042] In this embodiment, as Figures 5-6 As shown, step S5 specifically involves: slitting the high-performance ultra-thin aluminum foil roll using a slitting machine, and then precision cutting it using a precision cutter to obtain the high-performance ultra-thin aluminum foil; wherein the blade angle of the precision cut is 15°. A 15° blade angle is preferred over a 30° blade angle, which is commonly used in the industry. The 15° blade angle provides superior quality and effectively reduces the risk of tape breakage during subsequent coating and rolling processes. According to production data, there is no significant difference in service life between a 15° and a 30° blade.

[0043] The preparation method further includes corona treatment of the precision-cut high-performance ultrathin aluminum foil using a corona treatment device; wherein the power of the corona treatment device is 88±5kW, and the speed of the precision cutter is ≤200m / min. Because the rolling oil has a high additive content, corona treatment using a slitting machine and a precision cutter disperses and evaporates some of the oil droplets on the aluminum foil surface. A corona treatment device power of 88±5kW and a precision cutter speed not exceeding 200m / min effectively improve the surface wetting tension of the aluminum foil.

[0044] Example 2 This invention provides a high-performance ultrathin aluminum foil, which is manufactured using the aforementioned method for preparing high-performance ultrathin aluminum foil. This high-performance ultrathin aluminum foil is used as a positive electrode current collector in lithium-ion batteries. Since the high-performance ultrathin aluminum foil in this embodiment is manufactured using the method described in the previous embodiments, it achieves the same technical effects as those achieved by the method described in the previous embodiments, and will not be elaborated upon further here.

[0045] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0046] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A method for preparing high-performance ultrathin aluminum foil, characterized in that, The preparation method includes the following steps: Step S1: Melt the raw materials into molten aluminum using a smelting furnace; The composition and mass percentage of the raw material formula are as follows: Si: 0.4%~0.6%, Fe: 0.5%~0.7%, Cu≤0.15%, Ti≤0.05%, with the balance being Al; wherein, Al is obtained from aluminum ingots with an aluminum content greater than or equal to 99.70%, Si is prepared using AlSi20 master alloy, Fe is prepared using iron additives, Cu is prepared using AlCu50 master alloy, and Ti is prepared by adding aluminum-titanium-boron wire at the outlet of the holding furnace. Step S2: The molten aluminum is injected into the casting nozzle of the casting and rolling mill through a flow channel, and the molten aluminum is cooled by the rolling rolls of the casting and rolling mill to obtain a cast coil with a thickness of 6.4±0.3mm. The casting nozzle has an opening of 13±1mm. Before being injected into the nozzle, the molten aluminum passes through a degassing box and a filter box. The degassing box uses a silicon carbide rotor with a rotation speed of 500±50rpm and a temperature of 725±3℃. The argon gas flow rate is 20±2mL / min. The filter box uses a 50mm thick, 60ppi+70ppi dual-stage ceramic filter plate. At the outlets of the degassing box and the filter box, the hydrogen content of the molten aluminum is ≤0.1mL / (100gAl), and the slag content is ≤0.05mm. 2 / kg; Step S3: The cast-rolled coil is cold-rolled using a four-roll cold rolling mill to obtain a cold-rolled coil with a thickness of 0.18~0.21mm; Step S4: The cold-rolled coil is foil-rolled using a foil rolling mill to obtain a high-performance ultra-thin aluminum foil coil with a thickness ≤10μm; Step S5: After the high-performance ultra-thin aluminum foil roll is slit, it is precision cut to obtain the high-performance ultra-thin aluminum foil.

2. The method for preparing high-performance ultrathin aluminum foil according to claim 1, characterized in that, Step S1 specifically includes the following steps: The raw materials are smelted in the furnace according to the raw material formula to obtain a melt; The melt is stirred; Perform the first refining; Perform the first slag removal; Perform the first settling process; Turn the furnace over; Perform a second refining; Perform a second slag removal; The mixture is allowed to stand for a second time to obtain the molten aluminum. Specifically, when the melt temperature reaches 730~750℃, additives and intermediate alloys are added. The melting time in the smelting furnace is ≥20min, and electromagnetic stirring is simultaneously activated for ≥30min. In the smelting furnace refining process, 10~15Kg of granular refining agent is used, and refining is performed for 20~25min using argon gas injection. In the holding furnace, argon gas is used for refining for 15~20min. After refining, the slag is removed, and the mixture is allowed to stand for 30~40min. After the aluminum liquid has remained in the holding furnace for ≥6 hours, argon gas is used for supplementary refining for 10~15min. After refining in the holding furnace, the hydrogen content of the molten aluminum is ≤0.2mL / (100gAl), and the slag content is ≤0.05mm. 2 / kg.

3. The method for preparing high-performance ultrathin aluminum foil according to claim 1, characterized in that, In step S2, the following conditions are met during casting and rolling: The temperature of the front chamber of the smelting furnace is 693~697℃, the length of the casting and rolling zone is 50~60mm, the temperature of the cooling water is 30~38℃, the temperature difference between the inlet and outlet of the cooling water is 2~3℃, and the cooling water flow rate is 90~100m³ / h. 3 / h, roll gap is 3.5~4.0mm, strip speed is 750~850mm / min, and casting roll diameter is ≥800mm.

4. The method for preparing high-performance ultrathin aluminum foil according to claim 1, characterized in that, The cold rolling process comprises seven passes; wherein, the first pass of the cold rolling process is 6.80±3mm→4.00mm, and the uncoiling tension is 0.45~0.60kg / mm. 2 The curling tension is 1.30~1.45 kg / mm. 2 The rolling speed is 230~270m / min, and the rolling force is 590~600t; the second pass of the cold rolling is 4.00mm→2.50mm, and the uncoiling tension is 0.90~1.10kg / mm. 2 The curling tension is 1.80~2.00 kg / mm. 2 The rolling speed is 280~320m / min, and the rolling force is 530~540t; the third pass of the cold rolling is 2.50mm→1.45mm, and the uncoiling tension is 1.60~1.80kg / mm. 2 The curling tension is 2.00~2.22 kg / mm. 2 The rolling speed is 320~360m / min, and the rolling force is 460~470t; the fourth pass of the cold rolling is 1.45mm→0.85mm, and the uncoiling tension is 1.80~2.00kg / mm. 2 The curling tension is 2.40~2.60 kg / mm. 2 The rolling speed is 470~510m / min, and the rolling force is 470~480t; the fifth pass of the cold rolling is 0.85mm→0.55mm, and the uncoiling tension is 2.20~2.40kg / mm. 2 The curling tension is 2.70~2.90 kg / mm. 2 The rolling speed is 490~530m / min, and the rolling force is 400~410t; the sixth pass of the cold rolling is 0.55mm→0.33mm, and the uncoiling tension is 2.50~2.70kg / mm. 2 The curling tension is 2.80~3.00 kg / mm. 2 The rolling speed is 495~535m / min, and the rolling force is 430~440t; the seventh pass of the cold rolling is 0.33mm→0.18~0.21mm, and the uncoiling tension is 2.50~2.80kg / mm. 2 The curling tension is 3.00~3.40 kg / mm. 2 The rolling speed is 520~560m / min and the rolling force is 370~380t.

5. The method for preparing high-performance ultrathin aluminum foil according to claim 4, characterized in that, After the second and seventh passes of the cold rolling process, edge trimming is performed respectively.

6. The method for preparing high-performance ultrathin aluminum foil according to claim 1, characterized in that, The foil rolling process comprises five passes; wherein, the first pass of the foil rolling process is 0.200mm → 0.100mm, and the unwinding tension is ≥35kg / mm. 2 The curling tension is 35~40 kg / mm 2 The rolling speed is ≤750m / min, the rolling force is 200~300t, the roll surface roughness is 0.16um, and the roll crown is 0.045mm; the second pass of the foil rolling is 0.100mm→0.048mm, and the uncoiling tension is ≥40kg / mm. 2 The curling tension is 35~40 kg / mm 2 The rolling speed is ≤900m / min, the rolling force is 220~320t, the roll surface roughness is 0.16um, and the roll crown is 0.045mm; the third pass of the foil rolling is 0.048mm→0.026mm, and the uncoiling tension is ≥50kg / mm. 2 The curling tension is 40~45 kg / mm. 2 The rolling speed is ≤950m / min, the rolling force is 220~300t, the roll surface roughness is 0.12um, and the roll crown is 0.065mm; the fourth pass of the foil rolling is 0.026mm→0.015±0.001mm, and the uncoiling tension is ≥50kg / mm. 2 The curling tension is 40~50 kg / mm 2 The rolling speed is ≤800m / min, the rolling force is 230~320t, the roll surface roughness is 0.10um, and the roll crown is 0.065mm; the fifth pass of the foil rolling is 0.015±0.001mm→0.009mm, and the uncoiling tension is ≥60kg / mm. 2 The curling tension is 40~65 kg / mm 2 The rolling speed is ≤800m / min, the rolling force is 220~360t, the surface roughness of the roll is 0.06~0.07um, and the crown of the roll is 0.065mm.

7. The method for preparing high-performance ultrathin aluminum foil according to claim 6, characterized in that, During the fifth pass of the foil rolling mill, the inlet air flotation angle is 30°~60°.

8. The method for preparing high-performance ultrathin aluminum foil according to claim 6, characterized in that, The rolling oil used in the first, second, and third passes of foil rolling contains 0.15-0.2 mg KOH / g of acid, 1.2-1.5% of alcohol, 5.5-7.5% of ester, and ≤400 mg / 100 mL of gum. The rolling oil used in the fourth and fifth passes of foil rolling contains 0.25-0.3 mg KOH / g of acid, 2.6-2.9% of alcohol, 6.0-8.0% of ester, and ≤400 mg / 100 mL of gum.

9. The method for preparing high-performance ultrathin aluminum foil according to claim 1, characterized in that, Step S5 specifically involves: slitting the high-performance ultra-thin aluminum foil roll using a slitting machine, and then precision cutting it using a precision cutter to obtain the high-performance ultra-thin aluminum foil; wherein the blade angle of the precision cutter is 15°. The preparation method further includes corona treatment of the precision-cut high-performance ultrathin aluminum foil using a corona device; wherein the power of the corona device is 88±5kW, and the speed of the precision cutter is ≤200m / min.

10. A high-performance ultrathin aluminum foil, characterized in that, The high-performance ultrathin aluminum foil is made by the preparation method of the high-performance ultrathin aluminum foil according to any one of claims 1-9, and the high-performance ultrathin aluminum foil is used as the positive electrode current collector of a lithium-ion battery.

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