High-ductility battery aluminum foil and preparation method therefor

Abstract

A high-ductility battery aluminum foil and a preparation method therefor. The high-ductility battery aluminum foil comprises the following components in mass fraction: Si: 0.25-0.40%, Fe: 0.30-0.50%, Cu: 0.02-0.10%, and the balance being Al, wherein the amount of an iron-containing second phase in the section of the high-ductility battery aluminum foil is 1.1×102-4×104 per mm2; the amount of intermetallic compounds formed by the elements other than the element Fe with the element Al in the section of the high-ductility battery aluminum foil is less than or equal to 1.1×102 per mm2; the amount of elemental silicon particles in the section of the high-ductility battery aluminum foil is less than or equal to 1.1×10 2 per mm2. The high-ductility battery aluminum foil has a thickness less than or equal to 13 μm, a tensile strength greater than or equal to 250 MPa, and an elongation rate greater than or equal to 5%.

Description

High-ductility battery aluminum foil and preparation method thereof

Technical field

[0001] The present invention relates to the technical field of aluminum processing, and in particular to a high-ductility battery aluminum foil and a preparation method thereof. [Background Technology]

[0002] With the continuous development of power batteries, in order to achieve higher energy density, the aluminum foil needs to be thinned while the compaction density needs to be continuously increased to avoid belt breakage during the compaction process. In order to reduce the number of belt breaks, one of the most effective methods is to simultaneously increase the tensile strength and elongation of the battery aluminum foil. However, there is an "inverted" relationship between tensile strength and elongation, that is, the higher the tensile strength, the lower the elongation. Therefore, a feasible technical route to break this "inverted" relationship is to refine the grains. However, under industrial production conditions, there is a clear "ceiling" in grain refinement, and it is particularly difficult to increase the elongation after reaching the "ceiling".

[0003] To improve the tensile strength of battery aluminum foil, elements such as Mg, Cu, and Mn can be added to the foil. This coordinated effect of these elements increases the tensile strength of the foil while maintaining an elongation of more than 2%. This is a commonly used method in related technologies. However, there are no published reports on how to significantly increase the elongation (elongation ≥5%) of thinned aluminum foil (thickness ≤ 13μm) while maintaining high strength (tensile strength ≥ 250MPa).

[0004] Patent document (201110076608.9) provides a method for manufacturing pure aluminum hard foil for battery collectors. By adding elements such as iron, copper, and manganese, controlling the silicon content, refining the grains during intermediate annealing, and controlling the number of subgrains in the cross section, the battery aluminum foil maintains a tensile strength of 220 to 270 MPa while having an elongation of more than 4%.

[0005] Patent document (201510415406.0) discloses a method for producing aluminum foil for lithium batteries. The method adds copper elements during the casting and smelting process to change the synergistic effect between different elements. At the same time, the grains are refined through two intermediate annealing treatments to produce battery aluminum foil with a tensile strength of 160-190 MPa and an elongation of ≥1.5%.

[0006] Patent document (201710317640.9) provides a method for producing high-performance aluminum foil for batteries. By adding copper elements and further controlling the iron and silicon content, the aluminum foil produced has a tensile strength of ≥230MPa and an elongation of ≥2.5%.

[0007] In summary, in the solutions of the related art, no matter what attempts are made, it is impossible to produce a battery aluminum foil with a thickness less than or equal to 13 μm, a tensile strength greater than or equal to 250 MPa, and an elongation greater than or equal to 5%.

[0008] Therefore, it is necessary to provide a highly ductile battery aluminum foil and a preparation method thereof to solve the above-mentioned defects.

[0009] [Summary of the invention]

[0010] The purpose of the embodiments of the present invention is to provide a highly ductile battery aluminum foil and a preparation method thereof, so as to solve the problem that the prior art cannot obtain a battery aluminum foil with a thickness less than or equal to 13 μm, a tensile strength greater than or equal to 250 MPa, and an elongation greater than or equal to 5%.

[0011] In a first aspect, an embodiment of the present invention provides a highly ductile battery aluminum foil, the composition and mass fraction of which are: Si 0.25-0.40%, Fe 0.30-0.50%, Cu 0.02-0.10%, and the balance Al; wherein the mass fraction ratio of element Fe to element Si is: 1.0-2.0; the presence of an iron-containing second phase with an equivalent circular diameter of 0.2-3 μm in the cross section of the highly ductile battery aluminum foil is 1.1×10 2 ~4×10 4 Pieces / mm 2 The presence of intermetallic compounds formed by elements other than Fe and Al with an equivalent circular diameter of 0.2 to 3 μm in the cross section of the high ductility battery aluminum foil is less than or equal to 1.1×10 2 Pieces / mm 2 The number of elemental silicon particles with an equivalent circular diameter of 0.2 to 3 μm in the cross section of the high ductility battery aluminum foil is less than or equal to 1.1×10 2 Pieces / mm 2 .

[0012] Preferably, the components of the high-ductility battery aluminum foil also include a first group of elements, and the components and mass fractions of the first group of elements in the high-ductility battery aluminum foil are: Mg≤0.20%, Mn≤0.20%, and one or more rare earth elements≤0.15%.

[0013] Preferably, the components of the high ductility battery aluminum foil also include one or more elements of the second group of elements, and the components and mass fractions of the second group of elements in the high ductility battery aluminum foil are Cr≤0.20%, Zn≤0.20%, Ni≤0.20% and V≤0.20%.

[0014] Preferably, the components of the high ductility battery aluminum foil further include one or more elements of the third group of elements, and the components and mass fractions of the third group of elements in the high ductility battery aluminum foil are Ti≤0.20%, Zr≤0.20% and Co≤0.20%.

[0015] Preferably, the components of the high ductility battery aluminum foil also include one or more elements of the third group of sub-elements, and the components and mass fractions of the third group of sub-elements in the high ductility battery aluminum foil are Ti≤0.20%, Zr≤0.20% and Co≤0.20%.

[0016] Preferably, the components of the high ductility battery aluminum foil also include one or more elements of the fourth group of elements, and the components and mass fractions of the fourth group of elements in the high ductility battery aluminum foil are Be≤0.15%, Bi≤0.15%, Sr≤0.15% and In≤0.15%.

[0017] Preferably, the components of the high-ductility battery aluminum foil also include one or more elements of the fourth group of first sub-elements, and the composition and mass fraction of the fourth group of first sub-elements in the high-ductility battery aluminum foil are Be≤0.15%, Bi≤0.15%, Sr≤0.15% and In≤0.15%.

[0018] Preferably, the components of the high ductility battery aluminum foil also include one or more elements of the fourth group of second sub-elements, and the composition and mass fraction of the fourth group of second sub-elements in the high ductility battery aluminum foil are Be≤0.15%, Bi≤0.15%, Sr≤0.15% and In≤0.15%.

[0019] Preferably, the components of the high-ductility battery aluminum foil also include one or more elements of the fourth group of third sub-elements, and the composition and mass fraction of the fourth group of third sub-elements in the high-ductility battery aluminum foil are Be≤0.15%, Bi≤0.15%, Sr≤0.15% and In≤0.15%.

[0020] In a second aspect, an embodiment of the present invention provides a method for preparing a highly ductile battery aluminum foil, the preparation method comprising the following steps:

[0021] S1. Preparing a cast-rolled coil by a twin-roll continuous casting method according to the composition and mass fraction of the above-mentioned high-ductility battery aluminum foil;

[0022] S2. cold rolling the cast-rolled coil to obtain an aluminum foil blank;

[0023] S3, rolling the aluminum foil blank to obtain the high-ductility battery aluminum foil having a thickness of less than or equal to 13 μm;

[0024] Before cold rolling, the thickness of the cast coil is h0, and after foil rolling, the thickness of the high-ductility battery aluminum foil is h, and the equivalent strain coefficient ln(h0 / h) is ≥3.9.

[0025] Preferably, the subcrystalline grain diameter of the high-ductility battery aluminum foil is less than or equal to 2.5 μm, and the subcrystalline grain area ratio of the high-ductility battery aluminum foil is greater than or equal to 55%.

[0026] Compared with the prior art, the high-ductility battery aluminum foil in the present invention is prepared by limiting its components and mass fractions as well as the existence range of each element in the cross-section of the high-ductility battery aluminum foil, and is prepared by the preparation method of the relevant technology to obtain a high-ductility battery aluminum foil with a thickness less than or equal to 13 μm, a tensile strength greater than or equal to 250 MPa, and an elongation greater than or equal to 5%.

Brief Description of the Drawings

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. Those skilled in the art can also derive other drawings based on these drawings without inventive work, among which:

[0028] FIG1 is a schematic flow chart of the steps of a method for preparing a highly ductile battery aluminum foil provided by an embodiment of the present invention;

[0029] FIG2 is a color subgrain distribution cloud diagram of a high-ductility battery aluminum foil provided in an embodiment of the present invention. [Specific implementation method]

[0030] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0031] Example 1

[0032] An embodiment of the present invention provides a highly ductile battery aluminum foil, the composition and mass fraction of which are: Si 0.25-0.40%, Fe 0.30-0.50%, Cu 0.02-0.10%, and the balance Al; wherein the mass fraction ratio of element Fe to element Si is 1.0-2.0; the presence of an iron-containing second phase with an equivalent circular diameter of 0.2-3 μm in the cross section of the highly ductile battery aluminum foil is 1.1×10 2 ~4×10 4Pieces / mm 2 The presence of intermetallic compounds formed by elements other than Fe (such as Si and Cu) and Al with an equivalent circular diameter of 0.2 to 3 μm in the cross section of the high ductility battery aluminum foil is less than or equal to 1.1×10 2 Pieces / mm 2 The number of elemental silicon particles with an equivalent circular diameter of 0.2 to 3 μm in the cross section of the high ductility battery aluminum foil is less than or equal to 1.1×10 2 Pieces / mm 2 .

[0033] Among them, the above components and mass fractions can be regarded as main elements.

[0034] As an optional embodiment of the present invention, the components of the high ductility battery aluminum foil further include a first group of elements, and the composition and mass fraction of the first group of elements in the high ductility battery aluminum foil are: Mg ≤ 0.20%, Mn ≤ 0.20%, and one or more rare earth elements ≤ 0.15%; wherein, the presence of intermetallic compounds formed by element Mg, element Mn, and rare earth elements with an equivalent circular diameter of 0.2 to 3 μm and element Al in the cross section of the high ductility battery aluminum foil is less than or equal to 1.1×10 2 Pieces / mm 2 .

[0035] Wherein, no matter whether the rare earth elements are selected alone or in combination, the mass fraction thereof is ≤0.15%.

[0036] As an optional embodiment of the present invention, the components of the high ductility battery aluminum foil also include one or more elements of the second group of elements, and the components and mass fractions of the second group of elements in the high ductility battery aluminum foil are one or more of Cr≤0.20%, Zn≤0.20%, Ni≤0.20% and V≤0.20%.

[0037] As an optional embodiment of the present invention, the components of the high-ductility battery aluminum foil also include one or more elements from the third group of elements, and the components and mass fractions of the third group of elements in the high-ductility battery aluminum foil are one or more of Ti≤0.20%, Zr≤0.20% and Co≤0.20%.

[0038] As an optional embodiment of the present invention, the components of the high ductility battery aluminum foil also include one or more elements of the fourth group of elements, and the composition and mass fraction of the fourth group of elements in the high ductility battery aluminum foil are one or more of Be≤0.15%, Bi≤0.15%, Sr≤0.15% and In≤0.15%.

[0039] Specifically, the main element can be used in any combination with the above-mentioned first group of elements, second group of elements, third group of elements and fourth group of elements according to actual conditions, such as the main element is used in combination with the first group of elements, the main element is used in combination with the first group of elements and the second group of elements, the main element is used in combination with the first group of elements, the second group of elements and the third group of elements, the main element is used in combination with the first group of elements, the second group of elements, the third group of elements and the fourth group of elements, the main element is used in combination with the second group of elements, the main element is used in combination with the second group of elements and the third group of elements, the main element is used in combination with the second group of elements, the third group of elements and the fourth group of elements, the main element is used in combination with the third group of elements, the main element is used in combination with the third and fourth group of elements, and the main element is used in combination with the fourth group of elements.

[0040] Specifically, the iron-containing second phase having an equivalent circle diameter of 0.2 to 3 μm includes an iron-containing multicomponent phase formed by elements such as Mn and rare earth elements.

[0041] Specifically, the presence of intermetallic compounds formed by elements selected from the second group of elements, the third group of elements, and the fourth group of elements with an equivalent circular diameter of 0.2 to 3 μm and element Al in the cross section of the high ductility battery aluminum foil is less than or equal to 1.1×10 2 Pieces / mm 2 .

[0042] Specifically, the subcrystalline grain diameter of the high-ductility battery aluminum foil is less than or equal to 2.5 μm, and the subcrystalline grain area ratio of the high-ductility battery aluminum foil is greater than or equal to 55%.

[0043] The high-ductility battery aluminum foil in this embodiment is prepared by limiting its components and mass fractions as well as the presence range of each element in the cross-section of the high-ductility battery aluminum foil, and using the preparation method of the relevant technology to obtain a high-ductility battery aluminum foil with a thickness less than or equal to 13 μm, a tensile strength greater than or equal to 250 MPa, and an elongation greater than or equal to 5%.

[0044] Example 2

[0045] An embodiment of the present invention provides a method for preparing a highly ductile battery aluminum foil. As shown in FIG1 , the method comprises the following steps:

[0046] S1. Prepare cast-rolled coils by twin-roll continuous casting and rolling according to the raw material formula.

[0047] The raw material formula adopts the components and mass fractions of the high ductility battery aluminum foil in the above-mentioned embodiment 1.

[0048] Specifically, step S1 includes the following sub-steps:

[0049] S11, melting the raw material formula into molten aluminum;

[0050] Among them, the element Si is prepared using AlSi20 master alloy, the element Fe is prepared using aluminum-type iron agent 80FeAl, and the element Cu is prepared using AlCu20 master alloy; if the raw material formula contains the element Ti and other elements, the element Ti is prepared by adding the grain refiner aluminum titanium boron wire online, and the other alloys are not prepared and added separately.

[0051] The content of element Si is significantly increased compared to the existing 1060 alloy power battery aluminum foil with element Si less than 0.15%. This can effectively form an AlFeSi phase with the melt element Fe to reduce the formation of large-sized needle-shaped Al3Fe phases. The formed AlFeSi phase can be more easily broken during the subsequent rolling deformation process, which significantly improves the strength and elongation of the finished material.

[0052] The elemental Cu content is controlled to be lower than the 0.05% elemental Cu in the existing 1060 alloy power battery aluminum foil. Elemental Cu exists in the matrix as a solid solution. Increasing the Cu content significantly improves the material's strength, but it also makes rolling the aluminum foil difficult and reduces its elongation. Using a low Cu content here can effectively reduce the impact of elemental Cu on the elongation of the finished product. Table 1 below compares the performance of the finished aluminum foil with different Cu content levels:

[0053] Table 1. Comparison of the performance of finished aluminum foil with different Cu content

[0054] The step of melting and casting includes the following sub-steps in sequence:

[0055] Prepare the raw materials according to the raw material formula;

[0056] Using a smelting furnace to smelt the raw materials according to the raw material formula;

[0057] Adding the element Si, the element Fe, and the element Cu for alloying; if other elements are present, adding them together for alloying;

[0058] Perform the first refining;

[0059] Carry out the first slag removal;

[0060] Conduct component analysis;

[0061] Perform a second refining to obtain aluminum liquid;

[0062] transferring the aluminum liquid into a refining furnace;

[0063] Performing a third refining, a second slagging and a standing state to obtain the molten aluminum;

[0064] The first refining and the second refining are respectively performed using a granular refining agent combined with argon gas, and the refining time is 12 to 25 minutes respectively.

[0065] By adopting two refining steps in the smelting furnace, and limiting the two refining steps to be respectively performed using a granular refining agent combined with argon gas and controlling the refining time to be 12 to 25 minutes, it is possible to ensure that the added elements can be uniformly dissolved.

[0066] S12, injecting the molten aluminum into the casting nozzle of the casting mill through the launder, and cooling the molten aluminum through the rolling rollers of the casting mill to obtain the cast-rolled coil.

[0067] The front box temperature of the casting and rolling mill is 690±3°C, and the temperature of the coolant used in the casting and rolling mill is less than 30°C.

[0068] The casting and rolling mill adopts a large casting and rolling mill, and the roller diameter of the rolling roller is greater than 800 mm. Such a setting can effectively improve the cooling intensity of the molten aluminum and achieve the purpose of refining the initial grains and the second phase.

[0069] The rolling speed of the casting and rolling mill is 700±200 mm / min, which is significantly slower than the rolling speed of 1000±30 mm / min of the existing 1060 alloy power battery aluminum foil. By controlling the casting and rolling speed, the liquid cavity depth during the solidification process of the molten aluminum can be reduced, thereby reducing the center layer segregation and agglomeration problems.

[0070] S2. Cold rolling the cast-rolled coil to obtain an aluminum foil blank.

[0071] Specifically, the cold rolling is performed using a four-roll cold rolling mill.

[0072] Compared with the existing production process of power battery foil, which performs intermediate annealing when cold rolling to an intermediate thickness to eliminate internal stress during the rolling process, this embodiment adopts a process route without intermediate annealing. Through large rolling deformation, the degree of dislocation and second phase fragmentation in the material structure can be improved, thereby ensuring the high strength and high elongation of the finished material.

[0073] Specifically, the cold rolling process is performed in eight passes. When the cast coil is cold-rolled to its intermediate and final thicknesses, it is trimmed. Due to the increased alloying of the material, the cracks generated during the cold-rolling thinning process are wider than those in existing power battery processes. Therefore, two trimming passes are required to ensure that the end faces of the cold-rolled coil are free of gaps and ensure stability during the subsequent foil rolling process.

[0074] S3. Foil rolling is performed on the aluminum foil blank to obtain the high-ductility battery aluminum foil having a thickness less than or equal to 13 μm.

[0075] Among them, foil rolling is carried out using a foil rolling mill.

[0076] Before cold rolling, the thickness of the cast coil is h0. After foil rolling, the thickness of the high-ductility battery aluminum foil is h, and the equivalent strain coefficient ln(h0 / h) is ≥3.9.

[0077] In this embodiment, the subcrystalline grain diameter of the high-ductility battery aluminum foil is less than or equal to 2.5 μm, and the subcrystalline grain area ratio of the high-ductility battery aluminum foil is greater than or equal to 55%.

[0078] The method for measuring the subgrains and calculating the area ratio of the prepared high ductility battery aluminum foil is as follows:

[0079] The high-ductility battery aluminum foil was cut into samples of appropriate sizes, mechanically polished, and then ion-etched using an ion etcher. The samples were then analyzed using a scanning electron microscope equipped with an EBSD system, and the data were analyzed using Channel 5 software. Specifically, subgrains are grains composed of small-angle grain boundaries with an orientation difference of 5° or less. Subgrains with the same orientation difference share the same color, with different colors representing the range from 0° to 5°, forming a colored subgrain distribution cloud map. When the orientation difference exceeds 5°, all subgrains are marked in yellow. The area percentage of the subgrains is calculated by comparing the area of ​​the colored subgrains with the area of ​​the yellow subgrains.

[0080] Specifically, the foil rolling process is performed in five passes; the rolling mill's roll roughness is 0.06±0.01μm, and the rolling speed is 500-700m / min. By using precision rolling rollers and reducing the rolling speed, the microscopic flatness of the aluminum foil surface can be controlled, preventing localized microscopic irregularities in the foil from causing performance degradation in cathode fluid applications. Table 2 below compares the performance of battery aluminum foil under different rolling parameters:

[0081] Table 2. Comparison of different rolling parameters on the performance of battery aluminum foil

[0082] The method for preparing the high-ductility battery aluminum foil in this embodiment adopts the components and mass fraction of the high-ductility battery aluminum foil in the above-mentioned embodiment 1, so the high-ductility battery aluminum foil prepared by it can achieve the technical effect achieved by the high-ductility battery aluminum foil in the above-mentioned embodiment 1, which will not be elaborated here; in addition, the above-mentioned preparation method does not require intermediate annealing throughout the entire process, and the preparation process is short, the energy consumption is low, and the carbon emissions during the preparation cycle are less than those of similar products.

[0083] The mass fraction of element Si is 0.23%, the mass fraction of element Fe is 0.32%, the mass fraction of element Cu is 0.34%, and the mass fraction ratio of element Fe to element Si is 1.39. Through the above preparation method, a high-ductility battery aluminum foil with a thickness of 13 μm can be obtained, and the equivalent strain coefficient of the high-ductility battery aluminum foil is ln(h0 / h) = 6.26, the tensile strength is 254 MPa, and the elongation is 5.5%; in addition, through the above-mentioned subgrain measurement method of the high-ductility battery aluminum foil, the corresponding color subgrain distribution cloud map can be obtained (as shown in Figure 2), and then through calculation, it can be concluded that the average subgrain grain diameter of the high-ductility battery aluminum foil is 1.89 μm, and the subgrain area accounts for 61.9%.

[0084] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention description and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A highly ductile battery aluminum foil, characterized in that, the components and mass fractions of the highly ductile battery aluminum foil are: Si 0.25 - 0.40%, Fe 0.30 - 0.50%, Cu 0.02 - 0.10%, and the balance is Al; wherein, the mass fraction ratio of element Fe to element Si is: 1.0 - 2.0; The presence of the iron-containing second phase with an equivalent circular diameter of 0.2 to 3 μm in the cross-section of the high-ductility battery aluminum foil is 1.1×10 2 ~4×10 4 pieces / mm 2 ; The presence of intermetallic compounds formed by elements other than element Fe with element Al, each having an equivalent circular diameter of 0.2 to 3 μm, in the cross-section of the high-ductility battery aluminum foil is less than or equal to 1.1×10 2 pieces / mm 2 ; The presence of elemental silicon particles with an equivalent circular diameter of 0.2 to 3 μm in the cross-section of the high-ductility battery aluminum foil is less than or equal to 1.1×10 2 pieces / mm 2 .

2. The highly ductile battery aluminum foil according to claim 1, characterized in that, the components of the highly ductile battery aluminum foil further include a first group of elements, and the components and mass fractions of the first group of elements in the highly ductile battery aluminum foil are: Mg ≤ 0.20%, Mn ≤ 0.20%, one or more of rare earth elements ≤ 0.15%.

3. The highly ductile battery aluminum foil according to claim 1 or 2, characterized in that, the components of the highly ductile battery aluminum foil further include one or more elements of a second group of elements, and the components and mass fractions of the second group of elements in the highly ductile battery aluminum foil are: Cr ≤ 0.20%, Zn ≤ 0.20%, Ni ≤ 0.20% and V ≤ 0.20%.

4. The highly ductile battery aluminum foil according to claim 1 or 2, characterized in that, the components of the highly ductile battery aluminum foil further include one or more elements of a third group of elements, and the components and mass fractions of the third group of elements in the highly ductile battery aluminum foil are Ti ≤ 0.20%, Zr ≤ 0.20% and Co ≤ 0.20%.

5. The highly ductile battery aluminum foil according to claim 3, characterized in that, the components of the highly ductile battery aluminum foil further include one or more elements of a third subgroup of elements, and the components and mass fractions of the third subgroup of elements in the highly ductile battery aluminum foil are Ti ≤ 0.20%, Zr ≤ 0.20% and Co ≤ 0.20%.

6. The highly ductile battery aluminum foil according to claim 1 or 2, characterized in that, the components of the highly ductile battery aluminum foil further include one or more elements of a fourth group of elements, and the components and mass fractions of the fourth group of elements in the highly ductile battery aluminum foil are Be ≤ 0.15%, Bi ≤ 0.15%, Sr ≤ 0.15% and In ≤ 0.15%.

7. The highly ductile battery aluminum foil according to claim 3, characterized in that, the components of the highly ductile battery aluminum foil further include one or more elements of a first subgroup of the fourth group of elements, and the components and mass fractions of the first subgroup of the fourth group of elements in the highly ductile battery aluminum foil are Be ≤ 0.15%, Bi ≤ 0.15%, Sr ≤ 0.15% and In ≤ 0.15%.

8. The highly ductile battery aluminum foil according to claim 4, characterized in that, the components of the highly ductile battery aluminum foil further include one or more elements of a second subgroup of the fourth group of elements, and the components and mass fractions of the second subgroup of the fourth group of elements in the highly ductile battery aluminum foil are Be ≤ 0.15%, Bi ≤ 0.15%, Sr ≤ 0.15% and In ≤ 0.15%.

9. The highly ductile battery aluminum foil according to claim 5, characterized in that, The components of the high-ductility battery aluminum foil further include one or more elements in the third sub-element of the fourth group, and the components and mass fractions of the third sub-element of the fourth group in the high-ductility battery aluminum foil are Be≤0.15%, Bi≤0.15%, Sr≤0.15%, and In≤0.15%.

10. A preparation method of a high-ductility battery aluminum foil, characterized in that, the preparation method of the high-ductility battery aluminum foil includes the following steps: S1. Prepare a continuous cast-rolled coil by means of double-roll continuous casting and rolling according to the components and mass fractions of the high-ductility battery aluminum foil described in any one of claims 1 to 9; S2. Cold-roll the continuous cast-rolled coil to obtain an aluminum foil blank; S3. Foil-roll the aluminum foil blank to obtain the high-ductility battery aluminum foil with a thickness less than or equal to 13 μm; Among them, before cold rolling, the thickness of the cast-rolled coil is h 0 , after foil rolling, the thickness of the high-ductility battery aluminum foil is h, and the equivalent strain coefficient ln(h 0 / h) ≥ 3.

9.

11. The preparation method of the high-ductility battery aluminum foil according to claim 10, characterized in that, the diameter of the sub-grain crystal of the high-ductility battery aluminum foil is less than or equal to 2.5 μm, and the proportion of the area of the sub-grain crystal of the high-ductility battery aluminum foil is greater than or equal to 55%.

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