Battery foil for preventing dense pinholes and manufacturing method thereof

Abstract

The invention provides a battery foil for preventing dense pinholes and a manufacturing method thereof. The manufacturing method comprises the following steps: preparing 0.12-0.165% of Si, 0.520-0.550% of Fe, 0.160-0.180% of Cu, less than or equal to 0.030% of Mn, less than or equal to 0.030% of Zn, less than or equal to 0.015-0.030% of Ti, more than or equal to 99.00% of Al and the balance of other unavoidable impurities in parts by weight; the weighed raw materials are placed in a smelting furnace to be smelted, the highest smelting molten aluminum temperature is controlled to be smaller than or equal to 760 DEG C, the smelting time is controlled to be smaller than or equal to 12 hours, the turning-down temperature ranges from 740 DEG C to 750 DEG C, double filtration is conducted through a tubular filter box and a ceramic filter piece, and the filtration temperature ranges from 710 DEG C to 730 DEG C; the temperature of the heat preservation furnace is controlled to be 730-740 DEG C, and it is guaranteed that the temperature fluctuation of the heat preservation furnace is within + / -5 DEG C; a refining agent is added into the smelting furnace twice, a refining agent is added into the heat preservation furnace once, the refining time of each time is 18-22 min, and the refining pressure is 0.2-0.5 MPa; the length of a cast-rolling area is 50-65 mm, the cast-rolling speed is 710-750 mm / min, and a cast-rolling coil of about 7.5-7.8 mm is obtained; and step 6, carrying out surface corona treatment on the cast-rolled foil. Therefore, the problem that the pinhole density of the battery foil exceeds the standard is effectively solved.

Description

Technical Field

[0001] This invention relates to a battery foil for preventing dense pinholes and a method for manufacturing the same. Background Technology

[0002] With the rapid development of new energy vehicles and large-scale energy storage equipment, the demand for lithium-ion batteries is constantly increasing. As an indispensable component of lithium-ion batteries, aluminum foil materials for the positive electrode current collector play an increasingly important role in the development of lithium-ion batteries. However, current battery foil products have relatively high requirements for pinholes, plate shape, and microstructure. In particular, pinhole problems lead to low product yield, high cost, and low efficiency, seriously affecting customer use.

[0003] Pinholes are difficult to detect, invisible on the surface of the foil, and only revealed through surface inspection. They are internal defects in the aluminum foil structure and are fatal to customers. Existing aluminum foil production processes for lithium batteries have several problems, such as the high energy consumption and pollution associated with traditional hot rolling technology. Furthermore, the temperature control and purity of the molten aluminum in current technologies are not ideal, leading to dense pinholes in the battery foil, affecting product quality and production efficiency. In addition, the current process involves a short filtration time for the molten aluminum, resulting in insufficient purity and a high density of pinholes.

[0004] Therefore, there is an urgent need for a method that can effectively prevent dense pinholes in battery foil in order to improve product yield and reduce production costs. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a battery foil for preventing dense pinholes and its manufacturing method. By optimizing the temperature control process of the holding furnace, the temperature control of the molten aluminum and the purity of the melt are improved, effectively solving the problem of dense pinholes in the battery foil, significantly improving the product yield, and reducing production costs and efficiency. This objective of the invention is achieved as follows:

[0006] On one hand, another invention proposes a battery foil for preventing dense pinholes, comprising the following mass percentages: Si 0.12-0.165%, Fe 0.520-0.550%, Cu 0.160-0.180%, Mn≤0.030%, Zn≤0.030%, Ti≤0.015-0.030%, Al≥99.00%, with the balance being other unavoidable impurities.

[0007] On the other hand, a method for manufacturing battery foil to prevent dense pinholes includes the following steps: Step 1, preparing a mixture of Si 0.12-0.165%, Fe 0.520-0.550%, Cu 0.160-0.180%, Mn≤0.030%, Zn≤0.030%, Ti≤0.015-0.030%, Al≥99.00% by weight, with the balance being unavoidable other impurities; Step 2, placing the weighed raw materials in a melting furnace for melting, controlling the maximum melting temperature of molten aluminum to ≤760℃, the melting time to ≤12 hours, and the furnace turning temperature to 740-750℃, through a pipe... The process involves two steps: 1) Dual filtration using a filter box and ceramic filter sheets, with a filtration temperature of 710-730℃; 2) Maintaining the temperature of the holding furnace at 730-740℃, ensuring temperature fluctuations within ±5℃; 3) Adding refining agent twice to the smelting furnace and once to the holding furnace, with each refining process lasting 18-22 minutes and the refining pressure at 0.2-0.5MPa; 4) Using a casting and rolling zone with a length of 50-65mm and a casting and rolling speed of 710-750mm / min, resulting in a cast and rolled coil of approximately 7.5-7.8mm; 5) Performing surface corona treatment on the cast and rolled foil.

[0008] Furthermore, step two also includes the following step: when the temperature of the molten aluminum reaches 680-700℃, argon gas with a purity ≥99.99% is introduced into the molten aluminum at a flow rate of 0.3-0.5 m³ / h for 15-20 minutes. The argon gas is dispersed into bubbles with a diameter of 2-5 mm by a graphite rotor to remove dissolved hydrogen gas from the molten aluminum.

[0009] Furthermore, between steps two and three, the following step is also included: adding Al-Ti-B modifier to the molten aluminum, with an addition amount of 0.05-0.1% of the weight of the molten aluminum, and stirring with a stirrer at 300-500 r / min for 5-8 minutes to refine the aluminum crystal particles to 50-80 μm.

[0010] Furthermore, between steps five and six, the following step is also included: placing the cast-rolled coil in a four-roll cold rolling mill for initial rolling, with a rolling reduction rate of 30-40% and a rolling speed of 300-500 m / min, to obtain a billet with a thickness of 4.5-5.5 mm, and using rolling oil with a viscosity of 20-30 cSt and a temperature of 40°C for lubrication during rolling.

[0011] Furthermore, before the corona treatment in step six, a surface pretreatment step is added: the surface of the cast-rolled coil is cleaned with a 10-15MPa high-pressure water jet at a 45° angle, and after 3-5 seconds, it is cleaned with 60-80℃ hot air at a wind speed of 10-15m / s to ensure that the residual oil on the surface is ≤0.3mg / m².

[0012] Furthermore, during the heat preservation process in step three, an online stirring step is added: using a silicon nitride stirring paddle, stirring for 5 minutes every 30 minutes at 100-200 r / min, to control the uniformity deviation of the aluminum molten material composition within ±0.01%.

[0013] Furthermore, in step five of the casting and rolling process, a temperature control step for the casting roll is added: the temperature of the casting roll is controlled at 200-220℃, monitored by an infrared thermometer, and adjusted using 50-80L / min circulating heat transfer oil.

[0014] Furthermore, in the raw material preparation of step one, a pretreatment step is added: crush the raw materials such as Si, Fe, and Cu to 5-10 mm and dry them at 120-150℃ for 4-6 hours to make the moisture content of the raw materials ≤0.05%.

[0015] Compared with the prior art, the beneficial effects of the present invention are: by optimizing the alloy composition ratio and manufacturing process parameters, and by adopting measures such as dual filtration, precise temperature control and grain refinement, the problem of excessive pinhole density in battery foil is effectively solved, which has the advantages of improving product qualification rate, reducing energy consumption and improving material performance. Attached Figure Description

[0016] Figure 1 This is a flowchart illustrating a method for manufacturing battery foil to prevent dense pinholes. Detailed Implementation

[0017] To enhance understanding of the present invention, the present invention will be further described in detail below with reference to embodiments and accompanying drawings. These embodiments are only used to explain the present invention and do not constitute a limitation on the scope of protection of the present invention.

[0018] In one aspect, embodiments of the present invention provide a battery foil for preventing dense pinholes, comprising the following mass percentages: Si 0.12-0.165%, Fe 0.520-0.550%, Cu 0.160-0.180%, Mn ≤ 0.030%, Zn ≤ 0.030%, Ti ≤ 0.015-0.030%, Al ≥ 99.00%, with the balance being other unavoidable impurities.

[0019] Specifically, controlling the Si content within the range of 0.12-0.165% effectively improves the alloy's casting properties while avoiding increased brittleness due to excessive Si. Limiting the Fe content to 0.520-0.550% helps improve the material's strength, but excessive Fe can form coarse intermetallic compounds. The Cu content of 0.160-0.180% improves the material's electrical conductivity and corrosion resistance. Both Mn and Zn contents are controlled to ≤0.030% to minimize their adverse effects on material properties. The Ti content, limited to 0.015-0.030%, helps refine the grain size. Al, as the matrix material, is maintained at ≥99.00% to ensure good electrical conductivity and ductility.

[0020] Further, the Si content is preferably 0.135-0.155%, the Fe content is preferably 0.530-0.540%, the Cu content is preferably 0.165-0.175%, and the Ti content is preferably 0.020-0.025%. As a preferred embodiment, the Si content is 0.145%, the Fe content is 0.535%, the Cu content is 0.170%, and the Ti content is 0.022%.

[0021] Therefore, by strictly controlling the content range of each element, especially the ratio of key elements such as Si, Fe, Cu, and Ti, the microstructure of aluminum foil can be effectively improved, reducing the formation of internal defects. Specifically, the synergistic effect of Si and Fe optimizes the mechanical properties of the material, the appropriate addition of Cu helps improve conductivity, and the addition of Ti refines the grains, thereby reducing the probability of pinhole formation. This alloy formulation design can fundamentally solve the problem of dense pinholes in battery foil, improving product yield and quality stability.

[0022] On the other hand, the present invention proposes a method for manufacturing battery foil to prevent dense pinholes, comprising the following steps: Step 1, preparing a mixture of Si 0.12-0.165%, Fe 0.520-0.550%, Cu 0.160-0.180%, Mn≤0.030%, Zn≤0.030%, Ti≤0.015-0.030%, Al≥99.00% by weight, with the balance being unavoidable other impurities; Step 2, placing the weighed raw materials in a melting furnace for melting, controlling the maximum melting temperature of molten aluminum to ≤760℃, the melting time to ≤12 hours, and the furnace turning temperature to 740-750℃. Double filtration is performed using a tubular filter box and ceramic filter sheets at a filtration temperature of 710-730℃; Step 3: The temperature of the holding furnace is controlled at 730-740℃, ensuring that the temperature fluctuation is within ±5℃; Step 4: Refining agent is added twice to the smelting furnace and once to the holding furnace, with each refining time being 18-22 minutes and the refining pressure being 0.2-0.5MPa; Step 5: The length of the casting and rolling zone is 50-65mm, and the casting and rolling speed is 710-750mm / min, resulting in a cast and rolled coil of approximately 7.5-7.8mm; Step 6: The cast and rolled foil is subjected to surface corona treatment.

[0023] It should be noted that the smelting process employs a dual filtration system using both tubular filter boxes and ceramic filter sheets. The tubular filter boxes intercept large inclusions, while the ceramic filter sheets, with a pore size of 20-30 ppi, remove minute impurities. The refining agent is preferably a mixture of sodium fluoroaluminate and cryolite at a ratio of 1:1.5. A rotating nozzle is used during refining to enhance the dispersion effect. The casting rolls are made of high thermal conductivity alloy steel with a hard chrome plating to improve wear resistance, and the rolling force is controlled within the range of 800-1000 kN. The corona treatment parameters are set to a voltage of 8-12 kV and an electrode spacing of 2-3 mm, with the treatment speed synchronized with the casting speed.

[0024] Therefore, this embodiment effectively reduces the gas and inclusion content in molten aluminum by precisely controlling alloy composition and process parameters, combined with multi-stage filtration and phased refining. Specifically, the dual filtration system controls inclusion size to below 5μm, and the refining process ensures hydrogen content ≤0.12ml / 100gAl. Coordinated control of the length and speed of the casting and rolling zone homogenizes grain size, achieving an average grain diameter of 60-80μm. Compared to conventional single-stage refining processes, three-stage refining increases the purity of molten aluminum by over 40%, reducing pinhole density to ≤5 pins / m². Corona treatment achieves a surface tension of 32-35mN / m, improving adhesion in subsequent coating processes.

[0025] Furthermore, step two also includes the following steps: when the temperature of the molten aluminum reaches 680-700℃, argon gas with a purity ≥99.99% is introduced into the molten aluminum at a flow rate of 0.3-0.5 m³ / h for 15-20 minutes. The argon gas is dispersed into bubbles with a diameter of 2-5 mm by a graphite rotor to remove dissolved hydrogen gas from the molten aluminum.

[0026] It should be noted that argon, as an inert gas, effectively prevents the oxidation of molten aluminum, and the graphite rotor disperses the argon into micron-sized bubbles, increasing the gas-liquid contact area. Controlling the bubble diameter to 2-5 mm balances rising speed and hydrogen removal efficiency; excessively large bubbles reduce the hydrogen removal effect, while excessively small bubbles are easily entrained by the molten aluminum. A gas flow rate of 0.3-0.5 m³ / h combined with a processing time of 15-20 minutes can reduce the hydrogen content of the molten aluminum to below 0.12 ml / 100g. As a preferred implementation, a porous graphite rotor with a porosity of 15-20% and a pore size of 0.5-1 mm can be used, with the rotor speed maintained at 200-300 r / min. Furthermore, the choice of a temperature range of 680-700℃ is based on the balance point between the viscosity of the molten aluminum and the solubility of hydrogen; too low a temperature results in slow hydrogen diffusion, while too high a temperature easily leads to component segregation.

[0027] Therefore, this embodiment effectively removes dissolved hydrogen during the smelting process by precisely controlling the argon gas treatment parameters. With a reduced hydrogen content in the molten aluminum, pinhole defects caused by hydrogen accumulation are less likely to form during subsequent rolling. Compared to conventional methods relying solely on refining agents for hydrogen removal, this approach reduces pinhole density by approximately 40% without introducing new inclusions. The hydrogen content fluctuation range of the treated molten aluminum can be controlled within ±0.02 ml / 100 g, significantly improving melt purity.

[0028] Furthermore, between steps two and three, the following step is also included: adding Al-Ti-B modifier to the molten aluminum, the amount of which is 0.05-0.1% of the weight of the molten aluminum, and stirring with a stirrer at 300-500 r / min for 5-8 minutes to refine the aluminum crystal particles to 50-80 μm.

[0029] It should be noted that the Al-Ti-B modifier is composed of an Al-5Ti-1B master alloy, in which TiB2 particles act as nucleation cores, and the TiAl3 phase promotes grain refinement. A propeller-type stirrer is used during the stirring process, with a blade diameter to furnace diameter ratio of 1:3. During stirring, a 10-15 cm vortex is formed on the liquid surface, but gas entrainment is avoided. Grain size is detected using a metallographic microscope. After sampling the molten aluminum, the microstructure is rapidly water-quenched to fix it, and the determination is performed according to GB / T 3246.1 standard.

[0030] Thus, this step works through the following mechanisms: TiB2 particles provide heterogeneous nucleation sites, the TiAl3 phase reduces the undercooling of aluminum, and mechanical stirring promotes the uniform distribution of the modifier and breaks up the dendritic network. Compared with no modifier added, the grain size is reduced from 150-200 μm to 50-80 μm, the total grain boundary area increases by 2-3 times, and the segregation of solute elements during subsequent casting and rolling is reduced by more than 40%. Experimental data show that when using these parameters, the pinhole density can be reduced from 8-12 pins / m² to 3-5 pins / m², and the standard deviation of the grain size is controlled within ±5 μm.

[0031] As a preferred embodiment, the stirring speed is preferably 400 r / min, at which point the melt convection intensity and grain fragmentation efficiency reach the optimal balance. The modifier is added 20 minutes before the furnace is turned over to ensure complete dissolution without causing TiB2 particles to settle due to prolonged standing. To this end, a preheated graphite bell jar is used to force the modifier into the middle of the molten aluminum to avoid the formation of slag.

[0032] Furthermore, between steps five and six, the following step is also included: placing the cast-rolled coil in a four-roll cold rolling mill for initial rolling, with a rolling reduction rate of 30-40% and a rolling speed of 300-500 m / min, to obtain a billet with a thickness of 4.5-5.5 mm. During rolling, rolling oil with a viscosity of 20-30 cSt and a temperature of 40°C is used for lubrication.

[0033] It should be noted that rolling reduction rate refers to the percentage reduction in material thickness during the rolling process. Controlling the reduction rate to 30-40% can effectively eliminate internal defects in cast-rolled coils. The selection of rolling speed must balance production efficiency and material deformation uniformity; a speed range of 300-500 m / min ensures rolling stability. For rolling oil, a viscosity of 20-30 cSt forms a stable oil film, and an operating temperature of 40℃ maintains optimal lubrication performance. The use of a four-roll cold rolling mill ensures uniform distribution of rolling force; the work roll diameter is typically 400-600 mm, while the support roll diameter can reach 1200-1500 mm.

[0034] As a preferred implementation, the rolling process can employ a segmented reduction mode: the first segment uses a reduction rate of 35-40% to eliminate casting structures, and the second segment uses a reduction rate of 30-35% to improve surface quality. The rolling oil can be a mineral oil-based product with added extreme pressure additives, where the sulfur-based extreme pressure additive content is controlled at 1-2%. It is recommended that the roll surface roughness be maintained within the range of 0.2-0.4 μm, and the rolling force be controlled at 800-1200 tons.

[0035] Therefore, this embodiment effectively improves the internal microstructure of the cast-rolled coil through a precisely controlled cold rolling process. An appropriate reduction rate breaks down coarse grains, and the combination of rolling speed and lubrication conditions reduces surface defects. Compared to direct corona treatment, this step significantly reduces stress concentration and micro-defects within the material, providing a more uniform substrate for subsequent processing. Through optimized combinations of rolling process parameters, production efficiency is ensured while achieving a denser microstructure and more uniform thickness distribution in the billet.

[0036] Furthermore, before the corona treatment in step six, a surface pretreatment step is added: the surface of the cast-rolled coil is cleaned with a 10-15MPa high-pressure water jet at a 45° angle, and after 3-5 seconds, it is cleaned with 60-80℃ hot air at a wind speed of 10-15m / s to ensure that the residual oil on the surface is ≤0.3mg / m².

[0037] Understandably, high-pressure water jet cleaning achieves efficient decontamination through a specific combination of angle and pressure, with a 45° incident angle balancing the impact force and the risk of material damage. A water pressure range of 10-15 MPa effectively peels off the rolled oil film without damaging the microstructure of the aluminum foil surface. The hot air drying process employs coordinated temperature and airflow control; 60-80℃ hot air combined with a 10-15 m / s airflow speed can complete moisture evaporation within 10 seconds, avoiding secondary contamination. Oil stain detection can be performed in real-time using infrared spectroscopy or gravimetric methods.

[0038] This pretreatment replaces traditional chemical cleaning with physical cleaning, eliminating pinhole defects caused by solvent residue. High-pressure water jets remove contaminants that have penetrated into micron-level pits from rolling oil, while the directional airflow generated by hot air drying carries away surface-attached particles. Experimental results show that this combined process achieves Sa1-level cleanliness on the substrate surface before corona treatment, reducing pinhole incidence by 37%. The pretreatment temperature and time parameters were optimized through orthogonal experiments to ensure cleaning effectiveness while preventing abnormal grain growth in the aluminum foil.

[0039] Furthermore, in the heat preservation process of step three, an online stirring step is added: a silicon nitride stirring paddle is used to stir for 5 minutes every 30 minutes at 100-200 r / min to control the uniformity deviation of the aluminum molten composition within ±0.01%.

[0040] Furthermore, in step five of the casting and rolling process, a temperature control step for the casting roll is added: the temperature of the casting roll is controlled at 200-220℃, monitored by an infrared thermometer, and adjusted using 50-80L / min circulating heat transfer oil.

[0041] It should be noted that in the temperature control process of the casting roll, the temperature control range of 200-220℃ is achieved through a heat transfer oil circulation system, with the heat transfer oil flow rate adjustable from 50-80 L / min. An infrared thermometer monitors the roll surface temperature in real time and feeds back to the control system to automatically adjust the heat transfer oil flow rate. As a preferred embodiment, the heat transfer oil can be mineral oil or synthetic oil, with a flash point higher than 250℃. Furthermore, a spiral flow channel can be installed inside the casting roll to enhance heat exchange efficiency. The temperature control accuracy can reach ±2℃, thereby ensuring the stability of heat conduction in the casting zone.

[0042] To address this issue, this embodiment effectively solves the problem of uneven grain size caused by temperature fluctuations during aluminum foil casting by precisely controlling the temperature of the casting rolls. When the roll temperature is below 200°C, the rapid cooling rate of the molten aluminum can easily generate internal stress; above 220°C, it may lead to grain coarsening. By combining infrared thermometry with heat transfer oil control, the roll surface temperature is stabilized within the optimal range, thereby obtaining cast-rolled strip blanks with uniform grain size. Compared with existing technologies, this solution significantly improves the microstructure uniformity of the cast-rolled strip, providing high-quality blanks for subsequent cold rolling.

[0043] Furthermore, in the raw material preparation of step one, a pretreatment step is added: crush the raw materials such as Si, Fe, and Cu to 5-10 mm and dry them at 120-150℃ for 4-6 hours to make the moisture content of the raw materials ≤0.05%.

[0044] Specifically, raw material crushing is achieved using a jaw crusher or roller crusher. The crushed particles are then graded by a vibrating screen to ensure uniform particle size. The drying process takes place in a hot air circulating oven, with the hot air velocity controlled at 1.5-2 m / s. After drying, the raw material is immediately transferred to a drying container for sealed storage. As a preferred embodiment, the crushed raw material can first undergo magnetic separation to remove iron impurities before entering the drying process. Moisture content is measured using a Karl Fischer moisture analyzer, with sampling points at the top, middle, and bottom layers of each batch of raw material.

[0045] Therefore, this embodiment reduces gas introduction during the smelting process by controlling the physical state and moisture content of the raw materials. Crushing the raw materials results in a more uniform distribution of alloying elements, preventing localized component segregation; low-temperature, long-term drying effectively removes adsorbed water and crystal water from the raw materials, reducing hydrogen generation during smelting. Compared to directly feeding in lumpy raw materials, the pre-treated raw materials increase the dissolution rate of alloying elements by approximately 30% during smelting, and reduce the hydrogen content of the melt by 15-20%, thereby reducing the core factor contributing to pinhole formation. This step synergizes with subsequent smelting processes, significantly improving the purity of the molten aluminum without excessively increasing energy consumption.

[0046] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. 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 be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A battery foil for preventing dense pinholes, characterized in that, It consists of the following mass percentages: Si 0.12-0.165%, Fe 0.520-0.550%, Cu 0.160-0.180%, Mn≤0.030%, Zn≤0.030%, Ti≤0.015-0.030%, Al≥99.00%, with the balance being other unavoidable impurities.

2. A method for manufacturing battery foil to prevent dense pinholes, characterized in that, Includes the following steps: Step 1: Prepare a mixture according to the following weight proportions: Si 0.12-0.165%, Fe 0.520-0.550%, Cu 0.160-0.180%, Mn≤0.030%, Zn≤0.030%, Ti≤0.015-0.030%, Al≥99.00%, with the balance being unavoidable impurities. Step 2: Place the weighed raw materials in a melting furnace for melting. Control the maximum molten aluminum temperature to ≤760℃, the melting time to ≤12 hours, and the furnace temperature to 740-750℃. Use a tubular filter box with ceramic filter plates for further processing. The process involves: 1) Double filtration at a temperature of 710-730℃; 2) Maintaining the temperature of the holding furnace at 730-740℃, ensuring temperature fluctuations within ±5℃; 3) Adding refining agent twice to the smelting furnace and once to the holding furnace, with each refining process lasting 18-22 minutes and under a pressure of 0.2-0.5 MPa; 4) Using a casting and rolling zone with a length of 50-65 mm and a casting and rolling speed of 710-750 mm / min to obtain a cast and rolled coil of approximately 7.5-7.8 mm; 5) Performing surface corona treatment on the cast and rolled foil.

3. A method for manufacturing battery foil to prevent dense pinholes according to claim 2, characterized in that, Step two further includes the following step: when the temperature of the molten aluminum reaches 680-700℃, argon gas with a purity ≥99.99% is introduced into the molten aluminum at a flow rate of 0.3-0.5 m³ / h for 15-20 minutes. The argon gas is dispersed into bubbles with a diameter of 2-5 mm by a graphite rotor to remove dissolved hydrogen gas from the molten aluminum.

4. A method for manufacturing battery foil to prevent dense pinholes according to claim 2, characterized in that, Between steps two and three, the following step is also included: adding Al-Ti-B modifier to the molten aluminum, the amount of which is 0.05-0.1% of the weight of the molten aluminum, and stirring with a stirrer at 300-500 r / min for 5-8 minutes to refine the aluminum crystal particles to 50-80 μm.

5. A method for manufacturing battery foil to prevent dense pinholes according to claim 2, characterized in that, Between steps five and six, the following step is also included: placing the cast-rolled coil in a four-roll cold rolling mill for initial rolling, with a rolling reduction rate of 30-40% and a rolling speed of 300-500 m / min, to obtain a billet with a thickness of 4.5-5.5 mm. During rolling, rolling oil with a viscosity of 20-30 cSt and a temperature of 40°C is used for lubrication.

6. A method for manufacturing battery foil to prevent dense pinholes according to claim 2, characterized in that, Before the corona treatment in step six, a surface pretreatment step is added: the surface of the cast-rolled coil is cleaned with a 10-15MPa high-pressure water jet at a 45° angle, and after 3-5 seconds, it is cleaned with 60-80℃ hot air at a wind speed of 10-15m / s to ensure that the residual oil on the surface is ≤0.3mg / m².

7. A method for manufacturing battery foil to prevent dense pinholes according to claim 2, characterized in that, In the heat preservation process of step three, an online stirring step is added: use a silicon nitride stirring paddle to stir for 5 minutes every 30 minutes at 100-200 r / min, so that the uniformity deviation of the aluminum molten composition is controlled within ±0.01%.

8. A method for manufacturing a battery foil to prevent dense pinholes according to claim 2, characterized in that, In step five of the casting and rolling process, a temperature control step for the casting roll is added: the temperature of the casting roll is controlled at 200-220℃, monitored by an infrared thermometer, and adjusted using 50-80L / min circulating heat transfer oil.

9. A method for manufacturing a battery foil to prevent dense pinholes according to claim 2, characterized in that, In the raw material preparation of step one, a pretreatment step is added: crush the raw materials such as Si, Fe, and Cu to 5-10 mm and dry them at 120-150℃ for 4-6 hours to make the moisture content of the raw materials ≤0.05%.

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