Aluminum material with high corrosion resistance for cover plates of new energy lithium batteries and its preparation method

Abstract

This invention belongs to the field of aluminum material technology, specifically relating to an aluminum material for a high corrosion-resistant cover plate of a new energy lithium battery and its preparation method. The preparation method includes the following steps: (1) Weighing aluminum material components according to the following mass percentage ratio: Fe 1.21-1.84%, Si 0.12-0.28%, Mn 0.22-0.47%, Ca 0.01-0.05%, Ti 0.03-0.05%, Sr 0.02-0.07%, Cu 0.35-0.62%, Cr 0.08-0.24%, V 0.01-0.07%, with the balance being Al and unavoidable impurities; (2) Heating and melting the aluminum material components, and refining them; (3) Casting and rolling; (4) Homogenization treatment; (5) Cold rolling; (6) Annealing treatment to obtain the aluminum material for a high corrosion-resistant cover plate of a new energy lithium battery. The aluminum material of this invention has strong corrosion resistance and excellent mechanical properties.

Description

Technical Field

[0001] This invention belongs to the field of aluminum material technology, specifically relating to an aluminum material for a highly corrosion-resistant cover plate of a new energy lithium battery and its preparation method. Background Technology

[0002] Aluminum materials used in the cover plates of new energy lithium batteries are one of the key components in lithium battery manufacturing. They not only seal the battery but also play a crucial role in protecting the internal cells, providing electrical connections, and ensuring battery safety. Choosing the right aluminum material is essential for improving the performance, reliability, and safety of lithium batteries.

[0003] Lithium battery covers typically use aluminum alloys as the base material, with common alloy series including the 5000 series (such as 5052, 5083) and the 6000 series (such as 6061). These alloys have good mechanical strength and processing performance, making them suitable for manufacturing complex cover structures. However, they also face some technical challenges and problems that may affect the performance, safety, and reliability of the battery: (1) Insufficient corrosion resistance. Although aluminum alloys have a certain degree of corrosion resistance, they may still corrode when in contact with the electrolyte inside the lithium battery for a long time, especially when the electrolyte leaks or the internal environment of the battery changes. Corrosion can lead to a decrease in the mechanical strength of the cover, and may even cause short circuits or leakage, affecting the safety of the battery. 2. Mechanical strength and toughness. Lithium batteries will experience slight expansion and contraction during charging and discharging. Long-term cyclic use may lead to fatigue damage to the cover material. Especially in applications such as electric vehicles, the battery may be subjected to external forces such as vibration and impact, further aggravating the fatigue problem. 3. Impact Resistance: Although aluminum alloys have good toughness, under extreme conditions (such as impacts or drops), the cover may still crack or deform, affecting battery safety. Impact resistance is a crucial consideration, especially for thin-walled cover designs. 4. Low-Temperature Brittleness: Some aluminum alloys may become brittle at low temperatures (such as below -40°C), leading to a decrease in their mechanical properties. This poses a potential risk for electric vehicles or energy storage systems used in cold regions. 5. Conductivity and Resistance: While aluminum alloys have good conductivity, their resistance is still relatively high compared to highly conductive materials like copper. In high-current applications, higher contact resistance leads to increased heat generation, affecting battery efficiency and lifespan. Furthermore, fluctuations in contact resistance can cause voltage drops, impacting battery stability.

[0004] Lithium-ion battery electrolytes are mainly composed of organic solvents, and their pH value is generally between 5.5 and 6.5, making them acidic. Therefore, the corrosion resistance of the battery cover in acidic environments is crucial and can significantly extend the lifespan of lithium-ion batteries. Current technologies improve the corrosion resistance of aluminum materials through process modifications, but this often results in a loss of mechanical properties, failing to meet consumer demands.

[0005] Therefore, there is an urgent need for an aluminum material with high corrosion resistance for cover plates of new energy lithium batteries and its preparation method. Summary of the Invention

[0006] The purpose of this invention is to provide an aluminum material for a highly corrosion-resistant cover plate of a new energy lithium battery and its preparation method.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] This invention provides a method for preparing aluminum material for high corrosion resistance cover plates of new energy lithium batteries, comprising the following steps:

[0009] (1) Weigh the aluminum material components according to the following mass percentage ratio: Fe 1.21-1.84%, Si 0.12-0.28%, Mn 0.22-0.47%, Ca 0.01-0.05%, Ti 0.03-0.05%, Sr 0.02-0.07%, Cu 0.35-0.62%, Cr 0.08-0.24%, V 0.01-0.07%, with the balance being Al and unavoidable impurities;

[0010] (2) The aluminum material components are heated and melted to obtain a melt. A refining agent is added under a nitrogen atmosphere to refine the aluminum material melt.

[0011] (3) Casting and rolling the molten aluminum material to obtain a cast-rolled coil;

[0012] (4) Homogenize the cast-rolled coil to obtain a semi-finished product;

[0013] (5) The semi-finished product is cold-rolled to a thickness of 1.5-2.0 mm to obtain cold-rolled sheet and strip;

[0014] (6) Annealing the cold-rolled strip to obtain aluminum material for high corrosion resistance cover plates of new energy lithium batteries.

[0015] Further, in step (1), the mass percentage ratio of Fe, Mn and Cu is (1.3-1.5):(0.3-0.4):(0.5-0.6).

[0016] This invention improves the corrosion resistance of aluminum materials by carefully selecting their components and composition. However, it was found that only when the mass percentage ratio of Fe, Mn, and Cu is (1.3-1.5):(0.3-0.4):(0.5-0.6) can the aluminum material simultaneously maintain excellent mechanical properties and acid corrosion resistance. Analysis shows that under this condition, the formation of harmful phases can be better suppressed, the precipitation of fine, dispersed phases can be promoted, and the strength and toughness of the material can be improved. The optimal ratio of Fe, Mn, and Cu can alter the electrochemical behavior of aluminum alloys, reduce their corrosion rate in acidic environments, improve electrochemical behavior, enhance the material's acid corrosion resistance, optimize the microstructure, and form a uniform grain structure and fine second-phase distribution.

[0017] Furthermore, the homogenization process in step (4) specifically involves: first heating to 460℃-480℃ and holding for 5-7 hours, then heating to 560℃-580℃ and holding for 17-19 hours.

[0018] Further, the annealing process in step (6) specifically involves: heating to 450-470℃ at a heating rate of 20-30℃ / s and holding for 4-6 hours, then heating to 530-550℃ at a heating rate of 20-30℃ / s and holding for 7-9 hours, then heating to 570-590℃ at a heating rate of 20-30℃ / s and holding for 11-13 hours, and then cooling to 60-80℃ at a rate of 30-40℃ / s.

[0019] This invention, through specific homogenization and annealing conditions, not only further optimizes the mechanical properties and acid corrosion resistance of aluminum materials but also improves their electrical conductivity. The homogenization process allows alloying elements to diffuse fully within the matrix, eliminating component segregation, promoting the formation of a uniform microstructure, reducing the formation of harmful phases, and improving the overall material performance. Impurities and coarse second phases (such as β-Fe phase and CuAl2 phase) in aluminum alloys scatter electrons, increasing resistance and reducing conductivity. Homogenization and annealing reduce the content of these impurities and second phases, thereby reducing electron scattering and improving conductivity.

[0020] Furthermore, in step (2), the refining agent is hexachloroethane, and the amount added is 0.25-0.3% of the melt weight.

[0021] Furthermore, in step (2), the aluminum material components are heated and melted at 1500-1550°C.

[0022] Furthermore, in step (3), a cast-rolled coil with uniform grain size of grade 1 is obtained on both the upper and lower plates. The grain size is checked by EBSD metallographic examination of the cast-rolled coil. The grain size ratio at 1 / 2 distance from the center of the cast-rolled plate on the surface is 0.07-0.09, and the grain size ratio at the middle position of the cast-rolled plate is 0.15-0.18.

[0023] Furthermore, in step (5), the crown of the cold rolling mill work roll is controlled at 0.01-0.03 mm, and the roughness Ra value is 0.16-0.18 μm.

[0024] Furthermore, in step (5), the total cold rolling deformation is controlled to be 60-70%.

[0025] This invention provides an aluminum material for a highly corrosion-resistant cover plate of a new energy lithium battery prepared by the aforementioned method.

[0026] Compared with the prior art, the advantages and beneficial effects of the present invention are as follows:

[0027] 1. This invention improves the corrosion resistance of aluminum materials by carefully selecting the types and composition of aluminum materials. However, it has been found that only when the mass percentage of Fe, Mn and Cu is (1.3-1.5):(0.3-0.4):(0.5-0.6) can the aluminum material maintain excellent mechanical properties and acid corrosion resistance at the same time.

[0028] 2. Through specific homogenization and annealing conditions, this invention can not only further optimize the mechanical properties and acid corrosion resistance of aluminum materials, but also improve their electrical conductivity. Detailed Implementation

[0029] 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.

[0030] Example 1

[0031] This embodiment provides an aluminum material for a highly corrosion-resistant cover plate of a new energy lithium battery, and its preparation method includes the following steps:

[0032] (1) Weigh the aluminum material components according to the following mass percentage ratio: Fe 1.45%, Si 0.24%, Mn 0.36%, Ca 0.04%, Ti 0.04%, Sr 0.05%, Cu 0.55%, Cr 0.13%, V 0.05%, with the balance being Al and unavoidable impurities;

[0033] (2) The aluminum material components are heated to 1520℃ to melt and obtain a melt. Under a nitrogen atmosphere, a refining agent is added for refining. The refining agent is hexachloroethane, and the amount added is 0.28% of the melt weight to obtain the aluminum material melt.

[0034] (3) The aluminum material melt is cast and rolled to obtain a cast and rolled coil with uniform grain size of grade 1 on both the upper and lower plates. The grain size is checked by metallographic EBSD sample preparation of the cast and rolled coil. The grain size ratio is 0.08 at 1 / 2 of the distance from the center of the cast and rolled plate on the surface and 0.16 at the middle position of the cast and rolled plate.

[0035] (4) The cast-rolled coil is homogenized by first heating it to 470℃ and holding it for 6 hours, then heating it to 570℃ and holding it for 18 hours to obtain a semi-finished product.

[0036] (5) The semi-finished product is cold-rolled to a thickness of 1.8 mm, the crown of the cold rolling mill roll is controlled at 0.02 mm, the roughness Ra value is 0.17 μm, and the total cold rolling deformation is controlled at 66% to obtain cold-rolled sheet and strip.

[0037] (6) The cold-rolled sheet and strip are annealed. The annealing process is as follows: the temperature is raised to 460°C at a heating rate of 25°C / s and held for 5 hours, then raised to 540°C at a heating rate of 25°C / s and held for 8 hours, then raised to 580°C at a heating rate of 25°C / s and held for 12 hours, and then cooled to 70°C at a rate of 35°C / s to obtain aluminum material for high corrosion resistance cover plates of new energy lithium batteries.

[0038] Example 2

[0039] This embodiment provides an aluminum material for a highly corrosion-resistant cover plate of a new energy lithium battery, and its preparation method includes the following steps:

[0040] (1) Weigh the aluminum material components according to the following mass percentage ratio: Fe 1.3%, Si 0.28%, Mn 0.4%, Ca 0.01%, Ti 0.05%, Sr 0.02%, Cu 0.6%, Cr 0.08%, V 0.07%, with the balance being Al and unavoidable impurities;

[0041] (2) The aluminum material components are heated to 1550℃ to melt and obtain a melt. Under a nitrogen atmosphere, a refining agent is added for refining. The refining agent is hexachloroethane, and the amount added is 0.3% of the melt weight to obtain the aluminum material melt.

[0042] (3) The aluminum material melt is cast and rolled to obtain a cast and rolled coil with uniform grain size of grade 1 on both the upper and lower plates. The grain size is checked by metallographic EBSD sample preparation of the cast and rolled coil. The grain size ratio is 0.08 at 1 / 2 of the distance from the center of the cast and rolled plate on the surface and 0.16 at the middle position of the cast and rolled plate.

[0043] (4) The cast-rolled coil is homogenized by first heating it to 480℃ and holding it for 7 hours, then heating it to 560℃ and holding it for 19 hours to obtain a semi-finished product.

[0044] (5) The semi-finished product is cold-rolled to a thickness of 1.8 mm, the crown of the working roll of the cold rolling mill is controlled at 0.02 mm, the roughness Ra value is 0.17 μm, and the total deformation of cold rolling is controlled at 70% to obtain cold-rolled sheet and strip;

[0045] (6) The cold-rolled sheet and strip are annealed. The annealing process is as follows: the temperature is raised to 450°C at a heating rate of 30°C / s and held for 6 hours, then raised to 550°C at a heating rate of 20°C / s and held for 7 hours, then raised to 570°C at a heating rate of 30°C / s and held for 13 hours, and then cooled to 80°C at a rate of 30°C / s to obtain aluminum material for high corrosion resistance cover plates of new energy lithium batteries.

[0046] Comparative Example 1

[0047] The difference between this comparative example and Example 1 is that the aluminum material components were weighed according to the following mass percentage ratios: Fe 1.95%, Si 0.34%, Mn 0.16%, Ca 0.04%, Ti 0.01%, Sr 0.08%, Cu 0.25%, Cr 0.03%, V 0.05%, with the balance being Al and unavoidable impurities.

[0048] Comparative Example 2

[0049] The difference between this comparative example and Example 1 is that the aluminum material components were weighed according to the following mass percentage ratios: Fe 1.15%, Si 0.24%, Mn 0.56%, Ca 0.04%, Ti 0.04%, Sr 0.05%, Cu 0.65%, Cr 0.13%, V 0.05%, with the balance being Al and unavoidable impurities.

[0050] Comparative Example 3

[0051] The difference between this comparative example and Example 1 is that the homogenization treatment specifically involves heating to 500°C and holding at that temperature for 24 hours.

[0052] Comparative Example 4

[0053] The difference between this comparative example and Example 1 is that the homogenization treatment is as follows: first, the temperature is raised to 430°C and kept at that temperature for 2 hours, then the temperature is raised to 590°C and kept at that temperature for 22 hours.

[0054] Comparative Example 5

[0055] The difference between this comparative example and Example 1 is that the annealing treatment is as follows: the temperature is increased to 430°C at a heating rate of 15°C / s and held for 10 hours, then increased to 570°C at a heating rate of 15°C / s and held for 5 hours, then increased to 600°C at a heating rate of 15°C / s and held for 10 hours, and then cooled to 70°C at a rate of 50°C / s.

[0056] Comparative Example 6

[0057] The difference between this comparative example and Example 1 is that the annealing treatment is as follows: the temperature is raised to 560°C at a heating rate of 25°C / s and held for 25 hours, and then cooled to 70°C at a rate of 50°C / s.

[0058] Performance testing

[0059] The aluminum materials prepared in Examples 1-2 and Comparative Examples 1-6 were subjected to performance tests.

[0060] 1. Mechanical properties were tested in accordance with GB / T228.1-2021 "Metallic materials - Tensile testing - Part 1: Test method at room temperature".

[0061] 2. Conduct conductivity tests according to GB / T3956-2008;

[0062] 3. Corrosion resistance: The sample was sprayed with hydrochloric acid at pH 6 for 48 hours and left to stand for 12 hours. The weight of the sample before and after corrosion was calculated. The weight gain of corrosion products and the area fraction of white spots on the sample surface were statistically analyzed. If the weight gain of corrosion products was ≤0.015% and the area fraction of white spots was ≤10%, it was considered qualified; otherwise, it was considered unqualified.

[0063] The results are shown in Table 1.

[0064] Table 1 Performance Test Results

[0065]

[0066] As can be seen from the above performance test results, Examples 1-2 have excellent mechanical properties, high electrical conductivity, and good acid corrosion resistance. In particular, Example 1 has the most outstanding comprehensive performance, which is mainly due to the synergistic effect of the aluminum material composition and preparation conditions.

[0067] The comparative examples, lacking the necessary technical solutions, showed significantly inferior performance compared to the original examples in relevant tests. Comparative Example 1, by altering the composition of the aluminum material, exhibited a marked decrease in overall performance. Comparative Example 2, by changing the contents of Fe, Mn, and Cu, also showed a decline in mechanical properties and corrosion resistance. Changes in the homogenization treatment conditions in Comparative Examples 3-4 and the annealing treatment conditions in Comparative Examples 5-6 all affected the mechanical properties, electrical conductivity, and corrosion resistance of the aluminum material to varying degrees. These experimental results further demonstrate the importance of the technical solutions defined in this invention for its technical effectiveness.

[0068] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing an aluminum material for a highly corrosion-resistant cover plate of a new energy lithium battery, characterized in that, Includes the following steps: (1) Weigh the aluminum material components according to the following mass percentage ratio: Fe 1.21-1.84%, Si 0.12-0.28%, Mn 0.22-0.47%, Ca 0.01-0.05%, Ti 0.03-0.05%, Sr 0.02-0.07%, Cu 0.35-0.62%, Cr 0.08-0.24%, V 0.01-0.07%, with the balance being Al and unavoidable impurities; the mass percentage ratio of Fe, Mn, and Cu is (1.3-1.5):(0.3-0.4):(0.5-0.6); (2) The aluminum material components are heated and melted to obtain a melt. A refining agent is added under a nitrogen atmosphere to refine the aluminum material melt. (3) The aluminum material melt is cast and rolled to obtain a cast and rolled coil; the cast and rolled coil is a cast and rolled coil with uniform grain size of grade 1 on both the upper and lower plates. The grain size is checked by metallographic EBSD sample preparation of the cast and rolled coil. The grain size ratio at 1 / 2 of the distance from the center of the cast and rolled plate on the surface is 0.07-0.09, and the grain size ratio at the middle position of the cast and rolled plate is 0.15-0.

18. (4) Homogenize the cast-rolled coil to obtain a semi-finished product; the homogenization process is as follows: first heat up to 460℃-480℃ and keep it at that temperature for 5-7 hours, then heat up to 560℃-580℃ and keep it at that temperature for 17-19 hours. (5) The semi-finished product is cold-rolled to a thickness of 1.5-2.0 mm to obtain cold-rolled sheet and strip; (6) The cold-rolled sheet and strip are annealed to obtain aluminum material for high corrosion resistance cover plates of new energy lithium batteries. The annealing process is as follows: the temperature is raised to 450-470℃ at a heating rate of 20-30℃ / s and held for 4-6 hours, then raised to 530-550℃ at a heating rate of 20-30℃ / s and held for 7-9 hours, then raised to 570-590℃ at a heating rate of 20-30℃ / s and held for 11-13 hours, and then cooled to 60-80℃ at a rate of 30-40℃ / s.

2. The method for preparing aluminum material for high corrosion resistance cover plates of new energy lithium batteries according to claim 1, characterized in that, In step (2), the refining agent is hexachloroethane, and the amount added is 0.25-0.3% of the melt weight.

3. The method for preparing aluminum material for high corrosion resistance cover plates of new energy lithium batteries according to claim 2, characterized in that, In step (2), the aluminum material components are heated and melted at 1500-1550℃.

4. The method for preparing aluminum material for high corrosion resistance cover plates of new energy lithium batteries according to claim 3, characterized in that, In step (5), the crown of the cold rolling mill work roll is controlled at 0.01-0.03 mm, and the roughness Ra value is 0.16-0.18 μm.

5. The method for preparing aluminum material for high corrosion resistance cover plates of new energy lithium batteries according to claim 4, characterized in that, In step (5), the total cold rolling deformation is controlled to be 60-70%.

6. An aluminum material for a highly corrosion-resistant cover plate of a new energy lithium battery prepared by the preparation method according to any one of claims 1-5.

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