High-strength high-voltage-resistant positive current collector aluminum foil for solid-state battery and preparation method thereof

Abstract

The invention discloses a high-strength high-voltage-resistant positive current collector aluminum foil for a solid-state battery and a preparation method thereof, and relates to the technical field of lithium ion battery materials, the aluminum foil comprises the following alloy components in percentage by weight: 0.8-1.2% of Fe, 0.10-0.20% of Si, 0.05-0.12% of Cu, 0.01-0.03% of Ti, and the balance of Al and inevitable impurities, in the inevitable impurities, the content of a single impurity element is less than or equal to 0.03%, and the content of a single impurity element is less than or equal to 0.03%. The thickness of the aluminum foil is 9-20 microns, the tensile strength is larger than or equal to 280 MPa, the ductility is larger than or equal to 3.5%, and the volume resistivity is smaller than or equal to 3.2 n omega.m. According to the high-strength and high-voltage-resistant positive current collector aluminum foil for the solid-state battery and the preparation method of the high-strength and high-voltage-resistant positive current collector aluminum foil, through the synergistic effect of Fe, Si and Cu elements, a fine and dispersively distributed strengthening phase is formed in an aluminum matrix, the strength is remarkably improved, meanwhile, the scattering effect on electrons is small, and low resistivity is guaranteed.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery materials technology, specifically to a high-strength, high-voltage resistant positive electrode current collector aluminum foil for solid-state batteries and its preparation method. Background Technology

[0002] Solid-state batteries, using non-flammable solid electrolytes, are considered a key technology for next-generation high-safety, high-energy-density energy storage devices. However, solid-state batteries, especially those based on sulfide or oxide electrolytes, place far more stringent requirements on their cathode current collectors than liquid batteries: First, they require extremely high mechanical strength to withstand the significant volume changes and stresses caused by lithium-ion insertion / extraction during charging and discharging, preventing electrode structure damage; second, they need excellent chemical and electrochemical interfacial stability with the solid electrolyte to avoid the formation of a high-resistivity interfacial reaction layer; and finally, the solid-solid interface contact needs to be optimized to reduce interfacial impedance.

[0003] Currently, commercially available aluminum foil for cathode current collectors is primarily designed for liquid electrolyte systems. Its strength, elongation, and surface properties are insufficient to meet the demands of high-performance solid-state batteries. Especially with the trend towards ultra-thin designs, the tensile strength and elongation of aluminum foil often exhibit a "seesaw" effect, making it difficult to achieve both simultaneously. This leads to low processing yield and rapid degradation of battery cycle performance. Furthermore, the poor compatibility between the natural oxide layer on the surface of ordinary aluminum foil and the solid electrolyte results in excessively high interfacial impedance.

[0004] Therefore, in view of this, we have studied and improved the existing structure and its shortcomings, and proposed a high-strength, high-voltage resistant positive electrode current collector aluminum foil for solid-state batteries and its preparation method. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a high-strength, high-voltage resistant positive electrode current collector aluminum foil for solid-state batteries and its preparation method, thus solving the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solution: a high-strength, high-voltage resistant positive electrode current collector aluminum foil for solid-state batteries, wherein the alloy composition of the aluminum foil, by weight percentage, includes: Fe: 0.8-1.2%, Si: 0.10-0.20%, Cu: 0.05-0.12%, Ti: 0.01-0.03%, with the balance being Al and unavoidable impurities.

[0007] Furthermore, among the unavoidable impurities, the content of a single impurity element is ≤0.03%, and the total amount of impurities is ≤0.15%.

[0008] Furthermore, the aluminum foil has a thickness of 9-20 μm, a tensile strength ≥280 MPa, an elongation ≥3.5%, and a volume resistivity ≤3.2 nΩ·m.

[0009] Furthermore, a method for preparing a high-strength, high-voltage resistant positive electrode current collector aluminum foil for solid-state batteries, applicable to the preparation of the aforementioned high-strength, high-voltage resistant positive electrode current collector aluminum foil for solid-state batteries, includes the following steps: Smelting and casting: The raw materials are smelted according to the above composition ratio, and after refining, degassing and filtering, they are cast into aluminum flat ingots; Homogenization annealing: The aluminum flat ingot is held at 540-580℃ for 6-10 hours, and then cooled to room temperature at a rate of ≤50℃ / h; Hot rolling: The homogenized annealed flat ingot is heated to 480-520℃ and hot rolled. The final rolling temperature is not lower than 300℃ to obtain a hot-rolled plate with a thickness of 2.5-4.0mm. Cold rough rolling: Cold rolling of hot-rolled plates to produce intermediate billets with a thickness of 0.8-1.2 mm; Intermediate annealing: The intermediate billet after cold rough rolling is held at 320-360℃ for 5-8 hours, and then air-cooled; Foil rolling: The intermediate annealed billet is subjected to multiple cold finishing rolling passes to achieve a target thickness of 9-20μm; water-based rolling fluid is used during the rolling process; Slitting and Packaging: Aluminum foil is slitting, inspecting, and packaging in a clean environment with a relative humidity of ≤30%.

[0010] Furthermore, the aqueous rolling fluid contains a 1-3 wt% diimidazoline quaternary ammonium salt corrosion inhibitor, and the rolling fluid temperature is controlled at 40-60℃.

[0011] Furthermore, the bisimidazoline quaternary ammonium salt corrosion inhibitor is 1-hydroxyethyl-2-heptadecenylimidazoline quaternary ammonium salt.

[0012] Furthermore, the preferred process for homogenization annealing is to hold at 550-570°C for 7-9 hours, and then cool at a rate of 20-40°C / h.

[0013] Furthermore, the preferred process for intermediate annealing is to hold at 330-350℃ for 6-7 hours.

[0014] Furthermore, the total processing rate of the foil rolling is controlled between 85% and 95%, and the single-pass processing rate of the last three passes is no more than 15%.

[0015] This invention provides a high-strength, high-voltage resistant positive electrode current collector aluminum foil for solid-state batteries and its preparation method, which has the following beneficial effects: through the synergistic effect of Fe, Si and Cu, a fine and dispersed reinforcing phase (such as AlFeSi) is formed in the aluminum matrix, which significantly improves the strength while having a small scattering effect on electrons and ensuring low resistivity. The specific homogenization process and intermediate annealing regime effectively control the size and distribution of the second phase particles, avoiding the generation of coarse and brittle phases, thereby ensuring excellent elongation while obtaining high strength, and solving the contradiction between strength and elongation of ultra-thin aluminum foil. The rolling fluid containing bisimidazoline quaternary ammonium salt corrosion inhibitor not only provides good lubrication and cooling effects, but more importantly, the corrosion inhibitor can form a dense molecular protective film on the aluminum foil surface. On the one hand, it improves the corrosion resistance (high pressure oxidation resistance) of the aluminum foil, and on the other hand, its functional groups are expected to form good compatibility with the components in the solid electrolyte, effectively reducing the interfacial contact resistance. The aluminum foil prepared by this invention has high strength, high elongation and low resistivity. Its performance surpasses that of conventional alloy aluminum foils such as 1235 and 8079. It is particularly suitable as a positive electrode current collector for high-performance solid-state batteries and can effectively improve the cycle life and rate performance of the battery. Attached Figure Description

[0016] Figure 1 This refers to the nano-AlFeSi phase formed in this embodiment.

[0017] Figure 2 The image shows a coarse AlFeSi phase in the comparative example. Detailed Implementation

[0018] The embodiments of the present invention will be described in further detail below with reference to examples. These examples are for illustrative purposes only and should not be construed as limiting the scope of the invention.

[0019] Example 1 Batching and casting: The aluminum flat ingot is obtained by smelting, refining and casting according to the following proportions: Fe: 1.0%, Si: 0.15%, Cu: 0.08%, Ti: 0.02%, with the balance being Al and unavoidable impurities (total impurities <0.1%).

[0020] Homogenization annealing: The aluminum flat ingot is held at 560℃ for 8 hours, and then cooled to room temperature in the furnace at a rate of 30℃ / h.

[0021] Hot rolling: The homogenized flat ingot is heated to 500℃ and hot rolled. The final rolling temperature is controlled at 320℃ to obtain a hot-rolled plate with a thickness of 3.0mm.

[0022] Cold roughing: Cold rolling of hot-rolled plates to produce intermediate billets with a thickness of 1.0 mm.

[0023] Intermediate annealing: The intermediate billet is held at 340℃ for 6 hours, and then removed from the furnace and air-cooled.

[0024] Foil rolling: The intermediate-annealed billet is subjected to multiple cold finishing rolls. An aqueous rolling fluid containing 2 wt% 1-hydroxyethyl-2-heptadecenylimidazoline quaternary ammonium salt corrosion inhibitor is used during the rolling process, and the temperature of the rolling fluid is controlled at 50°C. The final thickness is 12 μm.

[0025] Slitting and Packaging: The aluminum foil is slitting and inspected in a clean environment with a relative humidity of <25%, and then vacuum-packed using aluminum-plastic composite moisture-proof bags.

[0026] Performance testing: The obtained aluminum foil was tested for performance, and the results are as follows: tensile strength (Rm) is 295MPa, elongation (A50mm) is 4.0%, and volume resistivity is 3.15nΩ·m.

[0027] Comparative Example 1 The conventional 1235 alloy aluminum foil (composition: Fe+Si≈1.0%, balance Al and impurities) is rolled to a thickness of 12μm using traditional processes (including hot rolling, cold rolling, intermediate annealing, etc., but excluding the specific homogenization system and foil rolling process containing special corrosion inhibitors of this invention).

[0028] Performance test results: tensile strength is 245 MPa, elongation is 2.8%, and volume resistivity is 3.40 nΩ·m.

[0029] The aluminum foils of Example 1 and Comparative Example 1 were used as current collectors to fabricate symmetrical or full cells with a sulfide solid electrolyte (such as Li6PS5Cl) and a positive electrode active material (such as NCM811). The interfacial impedance was tested by electrochemical impedance spectroscopy (EIS). The results showed that, under the same test conditions, the interfacial charge transfer impedance of the cell using the aluminum foil of Example 1 was about 40% lower than that of the cell using the aluminum foil of Comparative Example 1, proving that the aluminum foil of the present invention has superior interfacial compatibility.

[0030] Example 2 The alloy composition was adjusted to: Fe: 0.9%, Si: 0.18%, Cu: 0.06%, Ti: 0.025%, with the balance being Al. The preparation process parameters were adjusted adaptively: homogenization annealing was 550℃ / 9h with a cooling rate of 40℃ / h; intermediate annealing was 335℃ / 7h; the corrosion inhibitor concentration in the foil rolling solution was 1.5%. A 15μm thick aluminum foil was finally obtained, with a tensile strength of 285MPa, an elongation of 3.7%, and a volume resistivity of 3.18 nΩ·m.

[0031] Example 3 The alloy composition was adjusted to: Fe: 1.15%, Si: 0.12%, Cu: 0.11%, Ti: 0.015%, with the balance being Al. The preparation process parameters were: homogenization annealing at 575℃ for 6.5h with a cooling rate of 25℃ / h; intermediate annealing at 355℃ for 5.5h; and a corrosion inhibitor concentration of 2.8% in the foil rolling solution. A 10μm thick aluminum foil was finally obtained, with a tensile strength of 305MPa, an elongation of 3.6%, and a volume resistivity of 3.22 nΩ·m.

[0032] Compared with the battery test results of Comparative Example 1, the corrosion inhibitor protective film effectively suppressed the harmful side reactions between the aluminum foil surface and the solid electrolyte (especially the highly active sulfide electrolyte) at high potential; the high strength and good ductility of the aluminum foil itself enabled it to maintain a closer and more stable contact with the solid electrolyte under battery stacking pressure, reducing contact resistance; the bisimidazoline quaternary ammonium salt molecular film may have some interaction between its functional groups and the electrolyte interface, playing a "bridge" effect to improve interfacial ion transport.

[0033] The embodiments of the present invention are given for illustrative and descriptive purposes only, and are not intended to be exhaustive or to limit the invention to the forms disclosed. Many modifications and variations will be apparent to those skilled in the art. The embodiments were chosen and described in order to better illustrate the principles and practical application of the invention, and to enable those skilled in the art to understand the invention and to design various embodiments with various modifications suitable for a particular purpose.

Claims

1. A high-strength, high-pressure-resistant positive electrode current collector aluminum foil for a solid-state battery, characterized by: The alloy composition of the aluminum foil comprises, by weight percentage: Fe: 0.8-1.2%, Si: 0.10-0.20%, Cu: 0.05-0.12%, Ti: 0.01-0.03%, and the balance being Al and inevitable impurities.

2. A high strength, high pressure resistant cathode current collector aluminum foil for solid state batteries according to claim 1, characterized in that: In the inevitable impurities, the content of a single impurity element is ≤0.03%, and the total amount of impurities is ≤0.15%.

3. A high strength, high pressure resistant cathode current collector aluminum foil for solid state batteries according to claim 1, characterized in that: The aluminum foil has a thickness of 9-20 μm, a tensile strength of ≥280 MPa, an elongation of ≥3.5%, and a volume resistivity of ≤3.2 nΩ·m.

4. A method for preparing a high-strength high-voltage-resistant positive electrode current collector aluminum foil for solid-state batteries, applied to the preparation of a high-strength high-voltage-resistant positive electrode current collector aluminum foil for solid-state batteries according to any one of claims 1-3, characterized in that: The method comprises the following steps: Smelting and casting: smelting raw materials according to the above component ratio, and after refining, degassing and filtering, pouring into aluminum slab ingots; Homogenization annealing: the aluminum slab ingot is kept at 540-580 ℃ for 6-10 hours, and then cooled to room temperature at a rate of ≤50 ℃ / h; Hot rolling: the homogenization annealed slab ingot is heated to 480-520 ℃, and hot rolling is performed, with a final rolling temperature of not less than 300 ℃, to obtain a hot-rolled plate with a thickness of 2.5-4.0 mm; Cold rough rolling: the hot-rolled plate is cold-rolled to an intermediate blank with a thickness of 0.8-1.2 mm; Intermediate annealing: the cold-rough-rolled intermediate blank is kept at 320-360 ℃ for 5-8 hours, and then air-cooled; Foil rolling: the intermediate annealed blank is cold-precision-rolled in multiple passes to a target thickness of 9-20 μm; wherein an aqueous rolling liquid is used during rolling; Slitting and packaging: the aluminum foil is slitted, inspected and packaged in a clean environment with a relative humidity of ≤30%.

5. A method of producing a high-strength, high-pressure-resistant positive current collector aluminum foil for a solid-state battery according to claim 4, characterized by: The aqueous rolling liquid contains a double imidazoline quaternary ammonium salt corrosion inhibitor with a concentration of 1-3 wt%, and the rolling liquid temperature is controlled at 40-60 ℃.

6. A method of producing a high-strength, high-pressure-resistant cathode current collector aluminum foil for a solid-state battery according to claim 5, characterized by: The double imidazoline quaternary ammonium salt corrosion inhibitor is 1-hydroxyethyl-2-heptadecenyl imidazoline quaternary ammonium salt.

7. A method of making a high strength, high pressure resistant cathode current collector aluminum foil for solid state batteries as claimed in claim 4, wherein: The preferred process of the homogenization annealing is keeping at 550-570 ℃ for 7-9 hours, and then cooling at a rate of 20-40 ℃ / h.

8. A method of making a high strength, high pressure resistant cathode current collector aluminum foil for solid state batteries as claimed in claim 4, wherein: The preferred process of the intermediate annealing is keeping at 330-350 ℃ for 6-7 hours.

9. A method of making a high strength, high pressure resistant cathode current collector aluminum foil for solid state batteries as claimed in claim 4, wherein: The total processing rate of the foil rolling is controlled between 85% and 95%, and the single-pass processing rate of the last three passes is not more than 15%.

Images