Battery aluminum foil and cast-rolling production method thereof

Abstract

The application discloses a battery aluminum foil and a cast-rolling production method thereof, and belongs to the technical field of battery aluminum foils. The battery aluminum foil comprises Si, Cu, Fe, Mg, Zn, Mn, Zr, Ti and Al. The cast-rolling production method comprises the following steps: obtaining an aluminum alloy melt through smelting, refining, online degassing, filtering and wire feeding refining treatment, and then performing ultra-thin rapid casting and rolling on the aluminum alloy melt through a double-roller casting and rolling machine to obtain a cast-rolled blank with a thickness of 1.5-3 mm; performing cold rolling treatment on the cast-rolled blank, and the cold rolling treatment comprises twice intermediate annealing; and finally performing finished product aging treatment to obtain the battery aluminum foil. Through the synergistic effect of alloy component regulation, ultra-thin rapid casting and rolling and two-step intermediate annealing process, the battery aluminum foil with high strength and high elongation can be stably produced while the number of cold rolling passes is reduced.

Description

Technical Field

[0001] This invention relates to the field of battery aluminum foil technology, specifically to a battery aluminum foil and its casting and rolling production method. Background Technology

[0002] In recent years, with the rapid development of new energy vehicles in my country, lithium batteries, as the core power source, have driven the booming growth of the entire lithium battery industry. As the positive electrode current collector in lithium batteries, aluminum foil has the dual function of carrying the positive electrode active material and collecting conductive current. It requires high tensile strength and excellent conductivity, making it one of the key materials determining the performance and safety of lithium batteries.

[0003] Compared to traditional aluminum foil, battery aluminum foil has much stricter technical requirements, demanding thinner thickness, higher strength, better surface wettability, and high cleanliness and shape. Currently, the thickness requirement for aluminum foil in power batteries is maintained at 10-15μm, with some high-end power batteries using even thinner foil. Tensile strength requirements are ≥200MPa, elongation ≥3%, excellent surface quality with no color difference, and a surface wetting tension value greater than 32×10⁻⁶. -3 N / m, number of pinholes less than 3 per square meter, and plate collapse less than 8mm.

[0004] Reducing the thickness of aluminum foil can help improve the energy density of batteries, but it also places higher demands on the rolling process and increases the difficulty of rolling aluminum foil. In addition, since there is a mutually restrictive relationship between strength and plasticity, it is difficult to balance the strength and plasticity of aluminum foil. Therefore, how to improve the strength and plasticity of aluminum foil by adjusting the alloy composition and optimizing casting and rolling is the key to obtaining high-performance battery aluminum foil. Summary of the Invention

[0005] To address the aforementioned problems, the present invention aims to provide a battery aluminum foil and its casting and rolling production method, which can stably produce ultra-thin battery aluminum foil with both high strength and high elongation while reducing the number of cold rolling passes.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: a battery aluminum foil, comprising the following components by weight percentage: Fe: 0.1-0.15%, Si: 0.08-0.12%, Cu: 0.05-0.1%, Mg: ≤0.02%, Zn: ≤0.03%, Mn: 0.03-0.05%, Zr: 0.05-0.1%, Ti: 0.015-0.025%, with the remainder being Al and unavoidable impurities.

[0007] A method for producing battery aluminum foil by casting and rolling includes the following steps:

[0008] Step S1: Add aluminum ingots and metal alloys to the melting furnace according to the mixing direction, heat to 730-750℃ and melt to obtain aluminum alloy melt;

[0009] Step S2: High-purity argon gas is used to inject refining agent into the furnace for refining. After refining, the furnace is allowed to stand and the slag is removed.

[0010] Step S3: After the melt is introduced into the degassing device for online degassing, Al-5Ti-1B wire is added online through the wire feeder, and then filtered to obtain purified aluminum alloy melt;

[0011] Step S4: The purified aluminum alloy melt flows into the twin-roll casting mill, is distributed through the casting nozzle, and is rapidly cast and rolled through the rolls to obtain a cast and rolled billet with a thickness of 1.5-3 mm and then coiled up.

[0012] Step S5: The cast-rolled billet is cold-rolled to 0.6-0.8mm and then subjected to an intermediate annealing. After cold rolling to 0.1-0.15mm, it is subjected to a second intermediate annealing and then precision cold rolling to obtain a foil material with a thickness of 0.01-0.015mm.

[0013] Step S7: Cut the foil and age the finished product to obtain battery aluminum foil.

[0014] Furthermore, the cavity of the casting nozzle is a gradually changing cross-section flow distribution cavity, with five 15° rounded corner flow dividers inside the cavity. The length of the casting nozzle cavity is 50-60 mm, and the opening degree of the casting nozzle cavity is 1.8-2.5 mm.

[0015] Furthermore, the temperature of the front box of the casting and rolling mill is 695-705℃, the liquid level height of the front box of the casting and rolling mill is 10-15mm, the casting and rolling speed is 4-6m / min, the rolling zone length is 40-50mm, and the average cooling rate of the casting and rolling mill is 600-800℃ / s.

[0016] Furthermore, the roller sleeve of the rolling roller is a copper roller sleeve, and the roller gap of the rolling roller is 1.5-3.2 mm.

[0017] Furthermore, the cooling water flow rate of the single roller of the rolling roller is 150-200 m³ / h, the water pressure in the cooling zone is 0.5-0.7 MPa, the water inlet temperature of the rolling roller is controlled at 20-25℃, and the water outlet temperature of the rolling roller is controlled at 35-45℃.

[0018] Furthermore, the single-pass reduction rate of the cold rolling is controlled at 30%-60%.

[0019] Furthermore, the temperature of the first intermediate annealing is 500-550℃, the annealing time is 4-5 hours, and the annealing process is protected by a nitrogen atmosphere.

[0020] Furthermore, the intermediate annealing temperature is 400-450℃, the annealing time is 5-6 hours, and the annealing process is protected by a nitrogen atmosphere.

[0021] Furthermore, the aging treatment temperature of the finished product is 180-230℃, and the treatment time is 4-6 hours.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] In this invention, lithium battery aluminum foil is obtained by adjusting the raw material formula and using smelting, refining, online degassing and filtration, casting, cold rolling, and finished product annealing. In the casting stage, a rapid cooling process is used to obtain ultra-thin cast-rolled billets. In the cold rolling stage, rough rolling is performed first, followed by an intermediate annealing treatment, then cold rolling again, followed by a second intermediate annealing treatment, and finally fine rolling to obtain foil. This reduces the number of cold rolling passes and enables stable long-term production of ultra-thin aluminum sheets. After finished product annealing, the resulting battery aluminum foil has a pinhole rate (DPU) ≤ 0.1%, tensile strength ≥ 220 MPa, elongation ≥ 5%, grain size grade ≤ 1, surface dyne value ≥ 35 mN / m, and aluminum foil strip flatness with a collapse amount ≤ 3 mm under a 6 N horizontal force. Detailed Implementation

[0024] The specific embodiments of the present invention will be further described below with reference to examples.

[0025] Example 1

[0026] The battery aluminum foil of this embodiment comprises the following components by weight percentage: Fe: 0.1%, Si: 0.08%, Cu: 0.05%, Mg: ≤0.02%, Zn: ≤0.03%, Mn: 0.03%, Zr: 0.05%, Ti: 0.015%, with the remainder being Al and unavoidable impurities.

[0027] The casting and rolling production method for battery aluminum foil includes the following steps:

[0028] Step S1: Add aluminum ingots and metal alloys to the melting furnace according to the mixing direction, heat to 740℃ and melt to obtain aluminum alloy melt;

[0029] Step S2: Use high-purity argon gas to inject 0.1% refining agent into the furnace to refine the aluminum alloy melt, and then let it stand to remove slag.

[0030] Step S3: The melt is introduced into the degassing device for online degassing and filtration. Al-5Ti-1B wire is added online through the wire feeder at a feeding speed of 1.5 m / min to obtain purified aluminum alloy melt.

[0031] Step S4: The purified aluminum alloy melt flows into a twin-roll casting mill, is distributed through the casting nozzle, and is rapidly cast through the rolls to obtain a cast billet with a thickness of 2mm and is then coiled; the temperature of the front box of the casting mill is 700℃, the liquid level height of the front box of the casting mill is 12mm, the casting speed is 5m / min, the rolling zone length is 45mm, and the average cooling rate of the casting mill is 700℃ / s;

[0032] The casting nozzle has a gradually changing cross-section flow distribution cavity with five 15° rounded corner flow dividers inside. The nozzle cavity length is 55mm, and the opening diameter is 2.2mm. The rolling roller has a copper sleeve and a 2mm gap. The single-roller cooling water flow rate is 180 m³ / h, the cooling zone water pressure is 0.6MPa, the inlet water temperature is controlled at 25℃, and the outlet water temperature is controlled at 45℃.

[0033] Step S5: The cast-rolled billet is subjected to two passes of cold rolling, with the single pass reduction rate controlled at 40%. After cold rolling to 0.72 mm, an intermediate annealing is performed. The temperature of the intermediate annealing is 550℃ and the annealing time is 4 hours. The annealing process is protected by a nitrogen atmosphere.

[0034] After two more cold rolling passes to 0.115 mm, a second intermediate annealing is performed. The single-pass reduction rate is controlled at 60%. The temperature of the second intermediate annealing is 450℃ and the annealing time is 5 hours. The annealing process is protected by a nitrogen atmosphere.

[0035] Five more precision cold rolling passes are then performed, with the single-pass reduction rate controlled at 36%, to obtain 0.012mm foil.

[0036] Step S7: Cut the foil and age the finished product. The aging treatment temperature is 200℃ and the treatment time is 5h to obtain battery aluminum foil.

[0037] The battery aluminum foil finished product has a pinhole rate (DPU) ≤ 0.1%, a tensile strength of 220 MPa, an elongation of 5.3%, a grain size grade ≤ 1, a surface dyne value of 35 mN / m, and an aluminum foil strip flatness with a sagging amount ≤ 3 mm under a 6 N horizontal force.

[0038] Example 2

[0039] The battery aluminum foil of this embodiment comprises the following components by weight percentage: Fe: 0.1%, Si: 0.08%, Cu: 0.05%, Mg: ≤0.02%, Zn: ≤0.03%, Mn: 0.05%, Zr: 0.075%, Ti: 0.02%, with the remainder being Al and unavoidable impurities. Its casting and rolling production method is the same as in Example 1.

[0040] The battery aluminum foil finished product has a pinhole rate (DPU) of ≤0.1%, a tensile strength of 225MPa, an elongation of 5.2%, a grain size grade of ≤1, a surface dyne value of 36mN / m, and an aluminum foil strip flatness with a sag of 3mm under a 6N horizontal force.

[0041] Example 3

[0042] The battery aluminum foil of this embodiment comprises the following components by weight percentage: Fe: 0.15%, Si: 0.12%, Cu: 0.1%, Mg: ≤0.02%, Zn: ≤0.03%, Mn: 0.05%, Zr: 0.1%, Ti: 0.025%, with the remainder being Al and unavoidable impurities. Its casting and rolling production method is the same as in Example 1.

[0043] The battery aluminum foil finished product has a pinhole rate (DPU) of ≤0.1%, a tensile strength of 228MPa, an elongation of 5.1%, a grain size grade of ≤1, a surface dyne value of 37mN / m, and an aluminum foil strip flatness with a sagging amount of ≤3mm under a 6N horizontal force.

[0044] Example 4

[0045] The composition of the battery aluminum foil in this embodiment is the same as that in Example 1.

[0046] The casting and rolling production method for battery aluminum foil includes the following steps:

[0047] Step S1: Add aluminum ingots and metal alloys to the melting furnace according to the mixing direction, heat to 740℃ and melt to obtain aluminum alloy melt;

[0048] Step S2: Use high-purity argon gas to inject 0.1% refining agent into the furnace to refine the aluminum alloy melt, and then let it stand to remove slag.

[0049] Step S3: The melt is introduced into the degassing device for online degassing and filtration. Al-5Ti-1B wire is added online through the wire feeder at a feeding speed of 1.5 m / min to obtain purified aluminum alloy melt.

[0050] Step S4: The purified aluminum alloy melt flows into a twin-roll casting mill, is distributed through the casting nozzle, and is rapidly cast through the rolls to obtain a cast billet with a thickness of 1.5 mm, which is then coiled. The temperature of the front box of the casting mill is 700℃, the liquid level height of the front box is 15 mm, the casting speed is 6 m / min, the rolling zone length is 45 mm, and the average cooling rate of the casting mill is 800℃ / s.

[0051] The casting nozzle has a gradually changing cross-section flow distribution cavity with five 15° rounded corner flow dividers inside. The cavity length is 55mm, and the opening is 2.2mm. The rolling roller has a copper sleeve and a 2mm gap. The single-roller cooling water flow rate is 200 m³ / h, the cooling zone water pressure is 0.6MPa, the inlet water temperature is controlled at 25℃, and the outlet water temperature is controlled at 45℃.

[0052] Step S5: The cast-rolled billet is subjected to two passes of cold rolling, with the single pass reduction rate controlled at 35%. After cold rolling to 0.63 mm, an intermediate annealing is performed. The temperature of the intermediate annealing is 550℃ and the annealing time is 4 hours. The annealing process is protected by a nitrogen atmosphere.

[0053] After three more cold rolling passes to 0.1 mm, a second intermediate annealing is performed. The single-pass reduction rate is controlled at 45%. The temperature of the second intermediate annealing is 450℃ and the annealing time is 5 hours. The annealing process is protected by a nitrogen atmosphere.

[0054] Then, continue with 5 more precision cold rolling passes, with the single-pass reduction rate controlled at 36%, to obtain 0.01mm foil;

[0055] Step S7: Cut the foil and age the finished product. The aging treatment temperature is 230℃ and the treatment time is 4h to obtain battery aluminum foil.

[0056] The battery aluminum foil finished product has a pinhole rate (DPU) of 0.1%, a tensile strength of 226 MPa, an elongation of 5.2%, a grain size grade of ≤1, a surface dyne value of 35 mN / m, and an aluminum foil strip flatness with a sagging amount of ≤3 mm under a 6N horizontal force.

[0057] The above description is a detailed description of the preferred embodiments of the present invention. However, the embodiments are not intended to limit the scope of the patent application of the present invention. All equivalent changes or modifications made under the technical spirit of the present invention should be covered by the patent of the present invention.

Claims

1. A battery aluminum foil, characterized in that, The composition includes the following components by weight percentage: Fe: 0.1-0.15%, Si: 0.08-0.12%, Cu: 0.05-0.1%, Mg: ≤0.02%, Zn: ≤0.03%, Mn: 0.03-0.05%, Zr: 0.05-0.1%, Ti: 0.015-0.025%, with the remainder being Al and unavoidable impurities.

2. A method for casting and rolling battery aluminum foil as described in claim 1, characterized in that, Includes the following steps: Step S1: Add aluminum ingots and metal alloys to the melting furnace according to the mixing direction, heat to 730-750℃ and melt to obtain aluminum alloy melt; Step S2: High-purity argon gas is used to inject refining agent into the furnace for refining. After refining, the furnace is allowed to stand and the slag is removed. Step S3: After the melt is introduced into the degassing device for online degassing, Al-5Ti-1B wire is added online through the wire feeder, and then filtered to obtain purified aluminum alloy melt; Step S4: The purified aluminum alloy melt flows into the twin-roll casting mill, is distributed through the casting nozzle, and is rapidly cast and rolled through the rolls to obtain a cast and rolled billet with a thickness of 1.5-3 mm and then coiled up. Step S5: The cast-rolled billet is cold-rolled to 0.6-0.8mm and then subjected to an intermediate annealing. After cold rolling to 0.1-0.15mm, it is subjected to a second intermediate annealing and then precision cold rolling to obtain a foil material with a thickness of 0.01-0.015mm. Step S7: Cut the foil and age the finished product to obtain battery aluminum foil.

3. The method for casting and rolling battery aluminum foil as described in claim 2, characterized in that, The casting nozzle cavity is a gradually changing cross-section flow distribution cavity, with 5 15° rounded corner flow dividers inside the cavity. The length of the casting nozzle cavity is 50-60 mm, and the opening degree of the casting nozzle cavity is 1.8-2.5 mm.

4. The method for casting and rolling battery aluminum foil as described in claim 2, characterized in that, The temperature of the front box of the casting and rolling mill is 695-705℃, the liquid level in the front box of the casting and rolling mill is 10-15mm, the casting and rolling speed is 4-6m / min, the rolling zone length is 40-50mm, and the average cooling rate of the casting and rolling mill is 600-800℃ / s.

5. The method for casting and rolling battery aluminum foil as described in claim 2, characterized in that, The roller sleeve of the rolling roller is a copper roller sleeve, and the roller gap of the rolling roller is 1.5-3.2 mm.

6. The method for casting and rolling battery aluminum foil as described in claim 2, characterized in that, The cooling water flow rate of the single roller of the rolling mill is 150-200 m³ / h, the water pressure in the cooling zone is 0.5-0.7 MPa, the inlet water temperature of the rolling mill is controlled at 20-25℃, and the outlet water temperature of the rolling mill is controlled at 35-45℃.

7. The method for casting and rolling battery aluminum foil as described in claim 2, characterized in that, The single-pass reduction rate of cold rolling is controlled at 30%-60%.

8. The method for casting and rolling battery aluminum foil as described in claim 2, characterized in that, The intermediate annealing temperature is 500-550℃, the annealing time is 4-5 hours, and the annealing process is protected by a nitrogen atmosphere.

9. The method for casting and rolling battery aluminum foil as described in claim 2, characterized in that, The intermediate annealing temperature is 400-450℃, the annealing time is 5-6 hours, and the annealing process is protected by a nitrogen atmosphere.

10. The method for casting and rolling battery aluminum foil as described in claim 2, characterized in that, The aging treatment temperature for the finished product is 180-230℃, and the treatment time is 4-6 hours.