A method for producing aluminum foil for new energy applications using asynchronous rolling process

Abstract

This invention proposes a method for producing aluminum foil for new energy applications using an asynchronous rolling process, belonging to the field of aluminum rolling technology. The method includes the following steps: S1. Surface treatment of pure aluminum foil to remove oxides, followed by cooling in a cryogenic chamber; S2. Removal of the cooled pure aluminum foil and cryogenic asynchronous rolling; S3. High-temperature homogenization annealing of the rolled strip, followed by multiple asynchronous rolling processes without intermediate annealing; S4. Re-cooling the rolled strip, performing cryogenic asynchronous rolling, slitting, finished product annealing, and shearing to obtain aluminum foil for new energy applications. This invention, using an asynchronous rolling process to produce aluminum foil for new energy applications, significantly improves the mechanical and electrical properties of the aluminum foil through special cryogenic, asynchronous rolling, and annealing processes, greatly enhancing the performance of the aluminum foil and the yield of lithium-ion batteries. Furthermore, the preparation method is simple, lower in cost, and results in superior subsequent coating performance of the battery aluminum foil, leading to better characteristics of the resulting new energy batteries.

Description

Technical Field

[0001] This invention relates to the field of aluminum rolling technology, and specifically to a method for producing aluminum foil for new energy applications using an asynchronous rolling process. Background Technology

[0002] Asynchronous rolling, as an advanced high-plasticity deformation process, can be achieved by modifying synchronous rolling mills. Its main rolling methods include same-diameter, different-speed asynchronous rolling (upper and lower rolls have the same diameter but different rotational speeds) and different-diameter, same-speed asynchronous rolling (upper and lower rolls have different diameters but the same rotational speed). During asynchronous rolling, the asymmetry in deformation of the workpiece by the upper and lower rolls leads to intense additional shear deformation within the workpiece, thereby improving the uniformity of deformation along the thickness direction and contributing to the improvement of the overall performance of the sheet metal. Based on the advantages of asynchronous rolling technology in improving the uniformity of microstructure and enhancing the performance of metals and alloys, this technology has been widely used in the rolling research and production of metals and alloys such as aluminum / magnesium, achieving good results.

[0003] Invention patents (CN101524707A, CN105603341A) disclose a metal rolling process that utilizes asynchronous rolling to achieve fine grains and significantly improved formability and strength. Invention patents (such as CN201210590806.1, CN200410021496.7, CN200510046810.1) have improved the properties of grain-oriented silicon steel using asynchronous rolling technology. Invention patent (CN201010524366.0) utilizes asynchronous rolling technology to achieve nano-scale material surface treatment. However, due to the asymmetry in the deformation of the metal or alloy in contact with the upper and lower rolls during rolling, asynchronously rolled plates exhibit upward or downward bending, making it difficult for the plate to continuously bite into the rolls, reducing rolling efficiency. Severe warping can even cause the plate to stick to the rolls, damage the rolling mill equipment, and increase production costs. Currently, research on the application of asynchronous rolling technology is still focused on thin plates and strips. This is because the coiling tension applied by the coiler significantly suppresses warping in thin plates and strips, and therefore, the related warping problem has not received much attention. However, in the asynchronous rolling process of medium and heavy plates, there is no longer tension provided by the coiler on both sides of the rolls. Therefore, how to improve or optimize the plate shape of asynchronously rolled medium and heavy plates and reduce / eliminate the warping problem caused by asynchronous rolling is particularly prominent and important. This problem is generally addressed by modifying the rolling mill equipment, such as adding a horizontal hydraulic bending roll system to the rolling mill or adding forced straightening equipment to the rolling production line. However, this involves huge investments and is difficult to achieve in the short term. To address the warping problem in asynchronous rolling of medium-thick plates, invention patent CN104624664A proposes a method to control the warping of the roughing head of a 400mm billet by adjusting the rolling line height and the bite speed of the upper / lower work rolls. Invention patents (CN03114584.1 and CN200520079602.7) disclose a method to solve the warping problem in asynchronous rolling by adjusting the height of the mill guide plates and utilizing a designed variable infeed angle device. However, in actual production lines, the mill roller table systems are long and fixed, making it difficult to achieve continuous asynchronous rolling of plates using the methods provided by the aforementioned invention patents.

[0004] Currently, ultra-high strength metal foils are receiving increasing attention. For many metal materials, prices rise exponentially as foil thickness decreases. This is mainly because reduced foil thickness significantly increases processing difficulty. Simultaneously, during the rolling process of some difficult-to-deform metal foils, when the deformation resistance and hardness of the rolled material far exceed the hardness of the rolls, the rolls may crack during rolling, causing processing accidents and resulting in substantial losses for enterprises. Summary of the Invention

[0005] The purpose of this invention is to propose a method for producing aluminum foil for new energy applications using an asynchronous rolling process. This asynchronous rolling process, through special cryogenic rolling and annealing techniques, significantly improves the mechanical and electrical properties of the aluminum foil. Its tensile strength is ≥280MPa, and its elongation is ≥3.5%, far exceeding the performance of aluminum foils of other thicknesses used in batteries. This greatly improves the performance of the aluminum foil and the yield of lithium-ion batteries. Furthermore, the preparation method is simple and lower in cost, and the areal density of the produced aluminum foil is ≥35g / m³. 2 With a thickness tolerance of ≤±1.0%, the subsequent coating performance of the battery aluminum foil is better, resulting in new energy batteries with better characteristics.

[0006] The technical solution of this invention is implemented as follows:

[0007] This invention provides a method for producing aluminum foil for new energy applications using an asynchronous rolling process, comprising the following steps:

[0008] S1. Surface-treat the pure aluminum foil to remove oxides, and then place it in a cryogenic chamber for cooling;

[0009] S2. Take out the cooled pure aluminum foil and perform cryogenic asynchronous rolling;

[0010] S3. The rolled strip is subjected to high-temperature homogenization annealing and multiple asynchronous rolling processes without intermediate annealing;

[0011] S4. The rolled strip is cooled again, subjected to cryogenic asynchronous rolling, slitting, finished product annealing and shearing to obtain aluminum foil for new energy.

[0012] As a further improvement of the present invention, a novel rolling oil is used in the rolling process. The rolling oil is prepared by adding 5-10 wt% fatty acids and 3-5 wt% alcohol to paraffin oil and mixing them evenly.

[0013] As a further improvement of the present invention, the fatty acid is selected from at least one of butyric acid, caprylic acid, lauric acid, myristic acid, stearic acid, nonanoic acid, and palmitic acid; the alcohol is selected from at least one of glycerol, ethylene glycol, ethanol, resveratrol, butylene glycol, and sorbitol.

[0014] As a further improvement of the present invention, the fatty acid is a mixture of caprylic acid and lauric acid in a mass ratio of 4-6:3; the alcohol is a mixture of glycerol and sorbitol in a mass ratio of 5-7:2.

[0015] As a further improvement of the present invention, the injection volume of the novel rolling oil is 20-40 mL / m. 2 The viscosity of the novel rolling oil is 6-7 mm at 40℃. 2 / s.

[0016] As a further improvement of the present invention, the temperature of the cryogenic chamber in step S1 is -85 to -80°C, and the cryogenic treatment time is 10-20 minutes.

[0017] As a further improvement of the present invention, the velocity ratio of the cryogenic asynchronous rolling in step S2 is 1.2-1.4, the rolling is performed 2-4 times, the relative deformation of each pass is 40-55%, and the sample is immersed in liquid nitrogen for 10-15 minutes before each rolling pass.

[0018] As a further improvement of the present invention, the high-temperature homogenization annealing temperature in step S3 is 550-650℃, the time is 0.5-1h, the number of asynchronous rolling processes is 5-7, the speed ratio is 1.0-1.6, and the relative deformation per pass is 20-30%.

[0019] As a further improvement of the present invention, the cooling in step S4 is cooling at -85 to -80°C for 10-20 minutes, the differential speed ratio of the cryogenic asynchronous rolling is 1.2-1.3, the number of times is 1-2, the temperature of the finished product annealing is 430-470°C, and the holding time is 25-50 hours.

[0020] This invention further protects an aluminum foil for new energy obtained by the above-described method.

[0021] This invention has the following beneficial effects: A novel rolling oil is prepared in this invention. When it comes into contact with a metal surface, it lacks permanent dipoles; instead, transient dipoles appear within the molecules due to the asymmetric movement of electrons and atomic nuclei. The dispersion force generated by these transient dipoles causes the mineral oil molecules to adsorb onto the metal surface, forming a nonpolar molecular boundary lubricating film. Fatty acids and alcohols are used as additives to the base oil, and their main function is to assist in the adsorption of the base oil. One end of fatty acids and alcohols is a nonpolar hydrocarbon group (R-); the other end of fatty acids is a polar group (-COOH), while alcohols are (-OH). When polar molecules approach nonpolar molecules, in addition to the dispersion force, the nonpolar molecules generate induced dipoles due to the influence of the electric field of the polar molecules. The attractive force between these induced dipoles and the polar molecules is called the inductive force. Simultaneously, the induced dipoles act on the polar molecules, increasing their dipole moments, thereby further strengthening the attraction between them. Furthermore, by adding appropriate amounts of fatty acids and alcohols, this invention can effectively adjust the viscosity of the rolling oil, preventing incomplete degreasing of the aluminum foil during annealing and avoiding residual butter spots on the surface of the aluminum foil after annealing. Simultaneously, the additives lauric acid and sorbitol provide excellent antioxidant effects, preventing the oil film formed after aging from becoming too weak and breaking during rolling, thus avoiding bright spots on the aluminum foil.

[0022] This invention utilizes an asynchronous rolling process to produce aluminum foil for new energy applications. Through a special cryogenic, asynchronous rolling, and annealing process, the mechanical and electrical properties of the aluminum foil are significantly improved. Its tensile strength is ≥280MPa, and its elongation is ≥3.5%, far exceeding the performance of aluminum foils of other thicknesses used in batteries. This greatly improves the performance of the aluminum foil and the yield of lithium-ion batteries. Furthermore, the preparation method is simple and cost-effective, and the areal density of the produced aluminum foil is ≥35g / m³. 2 With a thickness tolerance of ≤±1.0%, the subsequent coating performance of the battery aluminum foil is better, resulting in new energy batteries with better characteristics. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art 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.

[0024] Figure 1 This is a SEM image of the stretched port of the aluminum foil for new energy prepared in Example 1. Detailed Implementation

[0025] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] Preparation Example 1: Novel Rolling Oil

[0027] The rolling oil is prepared by adding 5 wt% fatty acid and 3 wt% alcohol to paraffin oil, mixing them evenly, and obtaining a viscosity of 6.12 mm at 40℃. 2 / s. The fatty acid is a mixture of caprylic acid and lauric acid in a mass ratio of 4:2; the alcohol is a mixture of glycerol and sorbitol in a mass ratio of 5:2.

[0028] Preparation Example 2: Novel Rolling Oil

[0029] The rolling oil is prepared by adding 10 wt% fatty acid and 5 wt% alcohol to paraffin oil, mixing them evenly, and obtaining a viscosity of 6.32 mm at 40℃. 2 / s. The fatty acid is a mixture of caprylic acid and lauric acid in a mass ratio of 6:2; the alcohol is a mixture of glycerol and sorbitol in a mass ratio of 7:2.

[0030] Preparation Example 3: Novel Rolling Oil

[0031] The rolling oil is prepared by adding 7 wt% fatty acid and 4 wt% alcohol to paraffin oil, mixing them evenly, and obtaining a viscosity of 6.26 mm at 40℃. 2 / s. The fatty acid is a mixture of caprylic acid and lauric acid in a mass ratio of 5:2; the alcohol is a mixture of glycerol and sorbitol in a mass ratio of 6:2.

[0032] Comparative Preparation Example 1

[0033] The difference from Preparation Example 3 is that the fatty acid is a single type of octanoic acid.

[0034] Comparative Preparation Example 2

[0035] The difference from Preparation Example 3 is that the fatty acid is a single type of lauric acid.

[0036] Comparative preparation example 3

[0037] The difference from Preparation Example 3 is that the alcohol is a single type of glycerol.

[0038] Comparative preparation example 4

[0039] The difference from Preparation Example 3 is that the alcohol is a single sorbitol.

[0040] Example 1

[0041] This embodiment provides a method for producing aluminum foil for new energy applications using an asynchronous rolling process, including the following steps:

[0042] S1. Treat the surface of pure aluminum foil to remove oxides, and then cool it in a -85℃ cryogenic chamber for 10 minutes;

[0043] S2. Take out the cooled pure aluminum foil and perform deep cryogenic asynchronous rolling with a speed ratio of 1.2. Roll twice, with a relative deformation of 40% per pass. Before each pass, immerse the sample in liquid nitrogen for 10 minutes.

[0044] S3. The rolled strip is homogenized and annealed at 550℃ for 0.5h, and then subjected to multiple asynchronous rolling processes, with a total of 5 times, a speed ratio of 1.0, and a relative deformation of 20% per pass, without intermediate annealing.

[0045] S4. The rolled strip is cooled at -85℃ for 10 minutes, then subjected to cryogenic asynchronous rolling at a speed ratio of 1.2, once per cycle. The strip is then spun into coils, annealed at 430℃ for 25 hours, and sheared to obtain aluminum foil for new energy applications. SEM images of the stretched ends after breakage are shown below. Figure 1 As shown, the fracture surface has dense and deep dimples with large size, and there is significant necking before the sample breaks, indicating that the aluminum foil for new energy has good plasticity.

[0046] The novel rolling oil prepared in Preparation Example 1 was used during the rolling process, and the injection rate of the novel rolling oil was 20 mL / m. 2 .

[0047] Example 2

[0048] This embodiment provides a method for producing aluminum foil for new energy applications using an asynchronous rolling process, including the following steps:

[0049] S1. Surface-treat the pure aluminum foil to remove oxides, and then cool it in a -80℃ cryogenic chamber for 20 minutes;

[0050] S2. Take out the cooled pure aluminum foil and perform deep cryogenic asynchronous rolling with a speed ratio of 1.4. Roll 4 times, with a relative deformation of 55% per pass. Before each pass, immerse the sample in liquid nitrogen for 15 minutes.

[0051] S3. The rolled strip is homogenized and annealed at 650℃ for 1 hour, and then subjected to multiple asynchronous rolling processes, with a total of 7 times, a speed ratio of 1.6, and a relative deformation of 30% per pass, without intermediate annealing.

[0052] S4. Cool the rolled strip at -80℃ for 20 minutes, perform deep cryogenic asynchronous rolling with a speed ratio of 1.3 and 2 times, spool, anneal the finished product at 470℃ for 50 hours, and shear to obtain aluminum foil for new energy.

[0053] The novel rolling oil prepared in Preparation Example 2 was used during the rolling process, and the injection rate of the novel rolling oil was 40 mL / m. 2 .

[0054] Example 3

[0055] This embodiment provides a method for producing aluminum foil for new energy applications using an asynchronous rolling process, including the following steps:

[0056] S1. Surface-treat pure aluminum foil to remove oxides, and then cool it in a -82℃ cryogenic chamber for 15 minutes;

[0057] S2. Take out the cooled pure aluminum foil and perform deep cryogenic asynchronous rolling with a speed ratio of 1.3. Roll 3 times, with a relative deformation of 47% per pass. Before each pass, immerse the sample in liquid nitrogen for 12 minutes.

[0058] S3. The rolled strip is homogenized and annealed at 600℃ for 1 hour, and then subjected to multiple asynchronous rolling processes, with a total of 6 times, a speed ratio of 1.3, and a relative deformation of 25% per pass, without intermediate annealing.

[0059] S4. The rolled strip is cooled at -82℃ for 15 minutes, then subjected to cryogenic asynchronous rolling with a speed ratio of 1.25 and 2 times. The strip is then spun into coils, annealed at 450℃ for 37 hours, and sheared to obtain aluminum foil for new energy applications.

[0060] The novel rolling oil prepared in Preparation Example 3 was used during the rolling process, and the injection rate of the novel rolling oil was 30 mL / m. 2 .

[0061] Comparative Example 1

[0062] The difference from Example 3 is that the novel rolling oil was prepared from Comparative Preparation Example 1.

[0063] Comparative Example 2

[0064] The difference from Example 3 is that the novel rolling oil was prepared from Comparative Preparation Example 2.

[0065] Comparative Example 3

[0066] The difference from Example 3 is that the novel rolling oil was prepared from Comparative Preparation Example 3.

[0067] Comparative Example 4

[0068] The difference from Example 3 is that the novel rolling oil was prepared from Comparative Preparation Example 4.

[0069] Comparative Example 5

[0070] The difference from Example 3 is that step S2 was not performed.

[0071] Comparative Example 6

[0072] The difference from Example 3 is that step S3 was not performed.

[0073] Test Example 1

[0074] The performance of the aluminum foils for new energy prepared in Examples 1-3 and Comparative Examples 1-6 of this invention was tested, and the results are shown in Table 1.

[0075] The hardness of the interface region of the composite plate was measured using a 402-MVD Vickers microhardness tester under the following conditions: load of 0.25 N and duration of 25 s.

[0076] The tensile strength and elongation of the composite plate were tested on a SANSCMT5000 material testing machine. The tensile speed was 1 mm / min, and the dimensions of the tensile specimens were specified according to standard GB / T228-2002, with a gauge length of 20 mm × 10 mm.

[0077] Table 1

[0078]

[0079] As shown in the table above, the unequal thickness double-rolled ultrathin aluminum foil obtained by this invention has high hardness, good mechanical properties, small thickness tolerance, and high areal density.

[0080] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for producing aluminum foil for new energy applications using an asynchronous rolling process, characterized in that, Includes the following steps: S1. Surface-treat the pure aluminum foil to remove oxides, and then place it in a cryogenic chamber for cooling; the temperature of the cryogenic chamber is -85 to -80°C. S2. Take out the cooled pure aluminum foil and perform cryogenic asynchronous rolling; the rate ratio of the cryogenic asynchronous rolling is 1.2-1.4, the rolling is performed 2-4 times, the relative deformation of each pass is 40-55%, and the sample is immersed in liquid nitrogen for 10-15 minutes before each rolling pass. S3. The rolled foil is homogenized and annealed at high temperature, and then subjected to multiple asynchronous rolling processes without intermediate annealing; S4. The rolled foil is cooled again, subjected to cryogenic asynchronous rolling, slitting, finished product annealing and shearing to obtain aluminum foil for new energy; the cooling is performed at -85 to -80℃ for 10-20 minutes.

2. The method for producing aluminum foil for new energy applications using asynchronous rolling process according to claim 1, characterized in that, Rolling oil is used in the rolling process. The rolling oil is prepared by adding 5-10 wt% fatty acids and 3-5 wt% alcohol to paraffin oil and mixing them evenly.

3. The method for producing aluminum foil for new energy using asynchronous rolling process according to claim 2, wherein the fatty acid is selected from at least one of butyric acid, caprylic acid, lauric acid, myristic acid, stearic acid, nonanoic acid, and palmitic acid; and the alcohol is selected from at least one of glycerol, ethylene glycol, ethanol, resveratrol, butylene glycol, and sorbitol.

4. The method for producing aluminum foil for new energy using asynchronous rolling process according to claim 3, wherein the fatty acid is a mixture of octanoic acid and lauric acid in a mass ratio of 4-6:3; and the alcohol is a mixture of glycerol and sorbitol in a mass ratio of 5-7:

2.

5. The method for producing aluminum foil for new energy applications using asynchronous rolling process according to claim 2, wherein the injection volume of the rolling oil is 20-40 mL / m 2 The viscosity of the rolling oil is 6-7 mm at 40℃. 2 / s.

6. The method for producing aluminum foil for new energy using asynchronous rolling process according to claim 1, wherein the cryogenic treatment time in step S1 is 10-20 min.

7. The method for producing aluminum foil for new energy using asynchronous rolling process according to claim 1, wherein the high-temperature homogenization annealing temperature in step S3 is 550-650℃, the time is 0.5-1h, the number of asynchronous rolling processes is 5-7, the speed ratio is 1.0-1.6, and the relative deformation per pass is 20-30%.

8. The method for producing aluminum foil for new energy using asynchronous rolling process according to claim 1, wherein the differential speed ratio of the cryogenic asynchronous rolling in step S4 is 1.2-1.3, the number of times is 1-2, the annealing temperature of the finished product is 430-470℃, and the holding time is 25-50h.

9. A new energy aluminum foil prepared by the method according to any one of claims 1-8.

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