8-series aluminum alloy aluminum foil for solid-state battery packaging and method of making the same

Abstract

The application relates to an 8-series aluminum alloy aluminum foil for solid-state battery packaging and a preparation method thereof, relates to the non-ferrous metal processing technical field, and the aluminum foil is composed of the following components in percentage by weight: Fe: 0.7-1.8%, Si: 0.1-0.2%, Mn: 0.05-0.15%, Cu: 0.05-0.1%, Ti: 0.01-0.02%, Zr: 0.01-0.02%, Re: 0.01-0.05%, and the balance is Al and impurities. The preparation method comprises the following steps: smelting and standing, modification treatment and degassing, continuous casting, homogenizing annealing, first cold rolling, intermediate annealing, second cold rolling, co-stretching and stack rolling, separate stretching, finished product annealing and shearing. Through the component design of the aluminum foil and in combination with the co-stretching and stack rolling process, the punch formability and corrosion resistance of the aluminum foil are improved, and the aluminum foil is suitable for solid-state battery soft package packaging.

Description

Technical Field

[0001] This application relates to the field of non-ferrous metal processing technology, and in particular to 8-series aluminum alloy foil for solid-state battery packaging and its preparation method. Background Technology

[0002] With the rapid development of new energy vehicles and the energy storage industry, solid-state batteries are considered an important technological direction for the next generation of power batteries due to their high energy density and high safety. In the battery packaging process, pouch batteries generally use aluminum-plastic composite films as packaging materials, in which the inner aluminum foil directly contacts the battery cell, and its performance is crucial. An ideal packaging aluminum foil needs to have extremely high deep-drawing formability (to form the recesses to accommodate the battery cell), reliable sealing performance, excellent resistance to electrolyte corrosion, and high barrier properties.

[0003] Currently, the inner layer of the aluminum foil in conventional power battery pouch cells mostly uses 1-series or 8-series aluminum alloys. The chemical composition and heat treatment process of these aluminum foils are mainly designed for traditional liquid lithium batteries.

[0004] However, with the evolution of solid-state battery technology, the use of novel solid electrolytes such as sulfides and halides places more stringent requirements on the corrosion resistance of the encapsulating aluminum foil than on traditional liquid electrolytes. Simultaneously, to increase energy density, the cell volume or number of layers in solid-state batteries may increase, requiring the encapsulating aluminum foil to withstand deeper stamping depths, thus posing extremely high challenges to the foil's ductility, strength, and isotropy.

[0005] In practical applications, existing 8-series aluminum foil is prone to problems such as stamping cracking, wrinkling, and uneven thickness when subjected to ultra-deep drawing, leading to a decrease in yield. In addition, its long-term corrosion resistance is also insufficient to fully meet the design requirements of solid-state batteries for ultra-long lifespan.

[0006] Therefore, there is an urgent need for a special aluminum foil that combines ultra-deep drawing performance with excellent corrosion resistance to enhance the application of aluminum foil in solid-state batteries. Summary of the Invention

[0007] The technical problem to be solved by this invention is to provide an 8-series aluminum alloy foil for solid-state battery encapsulation and its preparation method, which solves the problems of stamping cracking, wrinkling, and uneven thickness that are common in existing aluminum foils. Furthermore, its long-term corrosion resistance is insufficient to fully meet the ultra-long lifespan design requirements of solid-state batteries.

[0008] To achieve the above objectives, the present invention provides the following technical solution: The 8-series aluminum alloy foil used for solid-state battery packaging has the following chemical composition by weight percentage: Fe: 0.7% - 1.8%; Si: 0.1% - 0.2%; Mn: 0.05% - 0.15%; Cu: 0.05% - 0.1%; Ti: 0.01% - 0.02%; Zr: 0.01% - 0.02%; Re: 0.01% - 0.05%; the balance being aluminum and unavoidable impurities.

[0009] Furthermore, Re is a rare earth element, and is one or a mixture of two of Ce and La.

[0010] The method for preparing 8-series aluminum alloy foil for solid-state battery encapsulation as described above includes the following sequential steps: S1. Melting and settling: Prepare the ingredients according to the stated proportions, melt them at 740-760°C to form an aluminum melt, and then set the aluminum melt at 710-730°C. S2. Modification and Degassing: Add aluminum-titanium-C-Re composite modifier to the settled aluminum melt for modification treatment, and then perform online degassing and refining of the melt. S3. Continuous casting: The aluminum melt treated in step S2 is continuously cast and rolled at a casting temperature of 690-710℃ to form a cast coil. S4. Homogenization annealing: The cast-rolled coil is subjected to homogenization annealing treatment at a temperature of 560-620℃ and a holding time of 5-15 hours. Then, it is cooled to below 300℃ at a cooling rate of ≤30℃ / h before being removed from the furnace. S5. First cold rolling: The homogeneously annealed cast-rolled coil is cold rolled to a thickness of 0.9-1.1 mm. S6. Intermediate annealing: The aluminum coil after the first cold rolling is subjected to intermediate annealing at 390-410℃ for 2-8 hours. S7. Second cold rolling: The aluminum coil after intermediate annealing is cold rolled to a thickness of 0.05-0.06mm; S8. Sheeting and Rolling: Sheet the two rolls of aluminum foil obtained in step S7 together, with their smooth surfaces facing each other, and roll them together until the total thickness is 0.07-0.09 mm. S9. Sheeting: The stacked aluminum foil is separated into two independent aluminum foils; S10. Finished product annealing: The aluminum foil after being separated is annealed at 390-410℃ for 10-30 hours. S11. Cutting: Cut the annealed aluminum foil into products of the required specifications.

[0011] Furthermore, in step S2, the mass percentages of Ti, C, and Re elements in the aluminum-titanium-C-Re composite modifier are as follows: Ti: 3-5%, C: 0.5-1.5%, Re: 1-3%, with the balance being Al.

[0012] Furthermore, in step S1, the melting temperature is 750±10℃ and the settling temperature is 720±10℃.

[0013] Furthermore, in step S4, the annealing temperature for homogeneous annealing is 580-600℃.

[0014] Furthermore, in step S6, the holding time for the intermediate annealing is 2-8 hours.

[0015] Furthermore, in step S7, the target thickness for the second cold rolling is 0.055 ± 0.005 mm.

[0016] Furthermore, in step S8, the total thickness after lamination is 0.08±0.01mm.

[0017] The above-mentioned application of 8-series aluminum alloy foil in solid-state battery soft-pack packaging.

[0018] In summary, this application includes at least the following beneficial technical effects of 8-series aluminum alloy foil for solid-state battery packaging, methods for preparing the same, and methods thereof: By designing the composition of Fe and Si, fine AlFeSi intermetallic compound particles are formed. Combined with the pinning and purifying effects of Zr and Re elements on grain boundaries, and through a multi-stage thermomechanical treatment process of "homogeneous annealing - cold rolling - intermediate annealing - cold rolling - sheet stacking rolling - finished product annealing," the recrystallization structure and texture of the aluminum foil are synergistically regulated. This meets the stamping requirements of solid-state batteries for pits and reduces problems such as cracking, wrinkling, and uneven thickness that easily occur in existing aluminum foils during stamping. The addition of rare earth elements (Re) purifies grain boundaries and reduces impurity segregation, thereby lowering the tendency for intergranular corrosion. Furthermore, the process yields a uniform and fine microstructure, reducing the active sites for electrochemical corrosion. This allows the aluminum foil to reduce mass loss when facing corrosive environments such as sulfides and halides in solid electrolytes, thus improving the long-term lifespan and safety of solid-state batteries. Through melt degassing and refining, homogenization annealing, and sheet rolling processes, the formation of microscopic defects such as pinholes and inclusions is reduced. This improves the airtightness against moisture and oxygen, achieving isolation between the cell and the external environment, enhancing the stability of the solid-state battery electrolyte, and reducing performance degradation. Attached Figure Description

[0019] Figure 1 The precipitate in this embodiment is a uniform and fine precipitate with a size of <5μm; Figure 2 These are relatively coarse precipitates in this comparative example, with most precipitates having a size >5μm and some even >10μm. Detailed Implementation

[0020] To facilitate a clear understanding of the technical means, creative features, objectives, and effects of this invention, the invention will be further described below in conjunction with specific embodiments.

[0021] The following is in conjunction with the appendix Figure 1-2 This application will be described in further detail.

[0022] This application discloses 8-series aluminum alloy foil for solid-state battery packaging and its preparation method. Example 1

[0023] The 8-series aluminum alloy foil used for solid-state battery encapsulation has the following chemical composition by weight percentage: Fe: 1.2%, Si: 0.15%, Mn: 0.1%, Cu: 0.08%, Ti: 0.015%, Zr: 0.015%, Re: 0.03%, with the balance being Al and unavoidable impurities. Preferably, Re is mixed with Ce in a 1:1 mass ratio of La.

[0024] The method for preparing 8-series aluminum alloy foil for solid-state battery encapsulation includes the following steps: Melting and settling: The ingredients are prepared according to the above proportions and melted at 750°C to form a uniform aluminum melt; then the aluminum melt is transferred to a holding furnace and settling at 720°C for 30 minutes to further homogenize the melt composition.

[0025] Modification and degassing: An aluminum-titanium-C-Re composite modifier is added to the settled aluminum melt. Preferably, the composition of the aluminum-titanium-C-Re composite modifier is as follows by mass percentage: Ti: 4%, C: 1.0%, Re: 2%, with the balance being Al. Modification treatment is performed to refine the as-cast grains. Subsequently, an online rotary degassing device is used to degas and refine the melt, controlling the hydrogen content of the melt to below 0.12 ml / 100g Al.

[0026] Continuous casting: Clean aluminum melt that has undergone modification and degassing treatment is continuously cast and rolled at a casting temperature of 700℃ to form a cast coil with a thickness of 7.0mm.

[0027] Homogeneous annealing: The cast-rolled coil is subjected to homogeneous annealing treatment at a temperature of 590℃ and a holding time of 10 hours. Then, it is cooled in the furnace to 250℃ at a cooling rate of 25℃ / h before being removed from the furnace and air-cooled.

[0028] First cold rolling: The homogenized annealed cast-rolled coil is cold rolled on a four-roll cold rolling mill to a thickness of 1.0 mm.

[0029] Intermediate annealing: The aluminum coil after the first cold rolling is subjected to intermediate annealing at a temperature of 400℃ for 5 hours, followed by air cooling.

[0030] Second cold rolling: The aluminum coil after intermediate annealing is subjected to a second cold rolling to a thickness of 0.055mm.

[0031] Sheeting and Rolling: Two rolls of 0.055mm aluminum foil obtained from the second cold rolling step are sheeted together with their smooth sides facing each other and then rolled. The total thickness is rolled to 0.08mm, that is, the thickness on one side is approximately 0.04mm.

[0032] Sheet splitting: The stacked aluminum foil is split into two independent aluminum foils of uniform thickness.

[0033] Finished product annealing: The aluminum foil after being separated is annealed at a temperature of 400℃ for 20 hours.

[0034] Cutting: Cut the annealed aluminum foil into the required width specifications.

[0035] Performance testing The performance of the aluminum foil prepared in Example 1 of this invention was tested, and the results are as follows: Mechanical properties: tensile strength is 150 MPa, elongation is 6.5%.

[0036] Forming performance: The limit drawing ratio (LDR) test reached 2.6.

[0037] Corrosion resistance: After accelerated corrosion testing in a simulated solid-state battery environment, its mass loss rate was 40% lower than that of conventional 1235 aluminum foil used as a comparison.

[0038] Microstructure: Metallographic observation shows that its grain structure is fine and uniform, with an average grain size of less than 30 μm.

[0039] Comparative Example Commercially available 1235 aluminum foil was used as a comparison. Its preparation process was a conventional cold rolling and annealing process, and the thickness of the finished product was the same as that in Example 1.

[0040] The comparative aluminum foil was subjected to performance testing under the same conditions, and the results are as follows: Mechanical properties: tensile strength is 125 MPa, elongation is 3.5%.

[0041] Forming performance: Limiting depth ratio (LDR) is 2.1.

[0042] Corrosion resistance: In the same simulated solid-state battery environment corrosion test, obvious pitting corrosion appeared on the surface, and the mass loss rate was much higher than that of the aluminum foil of the present invention. Example 2

[0043] The difference between this embodiment and Example 1 is that the alloy composition is adjusted to: Fe: 0.9%, Si: 0.18%, Mn: 0.12%, Cu: 0.06%, Ti: 0.01%, Zr: 0.02%, Re (La): 0.04%, with the balance being Al and unavoidable impurities. The preparation process parameters are the same as in Example 1.

[0044] The resulting aluminum foil has the following properties: tensile strength of 145 MPa, elongation of 6.0%, LDR value of 2.55, and corrosion resistance superior to the comparative example. Example 3

[0045] The difference between this embodiment and Embodiment 1 is that the alloy composition is adjusted to: Fe: 1.6%, Si: 0.11%, Mn: 0.08%, Cu: 0.09%, Ti: 0.018%, Zr: 0.011%, Re (Ce): 0.015%, with the balance being Al and unavoidable impurities. In the preparation process, the homogenization annealing temperature is adjusted to 580℃, and the annealing holding time for the finished product is adjusted to 15 hours.

[0046] The resulting aluminum foil has the following properties: tensile strength of 155 MPa, elongation of 5.8%, LDR value of 2.52, and corrosion resistance superior to the comparative example.

[0047] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. An 8-series aluminum alloy foil for solid-state battery encapsulation, characterized in that, Its chemical composition, by weight percentage, is as follows: Fe: 0.7% - 1.8%; Si: 0.1% - 0.2%; Mn: 0.05% - 0.15%; Cu: 0.05% - 0.1%; Ti: 0.01% - 0.02%; Zr：0.01% - 0.02%； Re: 0.01% - 0.05%; The balance is aluminum and unavoidable impurities.

2. The 8-series aluminum alloy foil for solid-state battery encapsulation according to claim 1, characterized in that, The Re is a rare earth element, and is one or a mixture of two of Ce and La.

3. A method for preparing 8-series aluminum alloy foil for solid-state battery encapsulation as described in claim 1 or 2, characterized in that, Includes the following steps: S1. Melting and settling: Prepare the ingredients according to the stated proportions, melt them at 740-760°C to form an aluminum melt, and then set the aluminum melt at 710-730°C. S2. Modification and Degassing: Add aluminum-titanium-C-Re composite modifier to the settled aluminum melt for modification treatment, and then perform online degassing and refining of the melt. S3. Continuous casting: The aluminum melt treated in step S2 is continuously cast and rolled at a casting temperature of 690-710℃ to form a cast coil. S4. Homogenization annealing: The cast-rolled coil is subjected to homogenization annealing treatment at a temperature of 560-620℃ and a holding time of 5-15 hours. Then, it is cooled to below 300℃ at a cooling rate of ≤30℃ / h before being removed from the furnace. S5. First cold rolling: The homogeneously annealed cast-rolled coil is cold rolled to a thickness of 0.9-1.1 mm. S6. Intermediate annealing: The aluminum coil after the first cold rolling is subjected to intermediate annealing at 390-410℃ for 2-8 hours. S7. Second cold rolling: The aluminum coil after intermediate annealing is cold rolled to a thickness of 0.05-0.06mm; S8. Sheeting and Rolling: Sheet the two rolls of aluminum foil obtained in step S7 together, with their smooth surfaces facing each other, and roll them together until the total thickness is 0.07-0.09 mm. S9. Sheeting: The stacked aluminum foil is separated into two independent aluminum foils; S10. Finished product annealing: The aluminum foil after being separated is annealed at 390-410℃ for 10-30 hours. S11. Cutting: Cut the annealed aluminum foil into products of the required specifications.

4. The method for preparing 8-series aluminum alloy foil for solid-state battery encapsulation according to claim 3, characterized in that, In step S2, the mass percentages of Ti, C, and Re elements in the aluminum-titanium-C-Re composite modifier are as follows: Ti: 3-5%, C: 0.5-1.5%, Re: 1-3%, with the balance being Al.

5. The method for preparing 8-series aluminum alloy foil for solid-state battery encapsulation according to claim 3, characterized in that, In step S1, the melting temperature is 750±10℃ and the settling temperature is 720±10℃.

6. The method for preparing 8-series aluminum alloy foil for solid-state battery encapsulation according to claim 3, characterized in that, In step S4, the annealing temperature for homogeneous annealing is 580-600℃.

7. The method for preparing 8-series aluminum alloy foil for solid-state battery encapsulation according to claim 3, characterized in that, In step S6, the holding time for intermediate annealing is 2-8 hours.

8. The method for preparing 8-series aluminum alloy foil for solid-state battery encapsulation according to claim 3, characterized in that, In step S7, the target thickness for the second cold rolling is 0.055 ± 0.005 mm.

9. The method for preparing 8-series aluminum alloy foil for solid-state battery encapsulation according to claim 3, characterized in that, In step S8, the total thickness after lamination is 0.08±0.01mm.

10. The application of 8-series aluminum alloy foil according to any one of claims 1-2 in solid-state battery soft-pack packaging.

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