Low pinhole type battery foil of high-energy density battery

Abstract

The invention provides a low pinhole type battery foil of a high-energy density battery, and a preparation method comprises the following steps: S1, carrying out degreasing treatment on the surface of an aluminum foil, and cleaning the surface of the aluminum foil by adopting an alkaline degreasing agent and a surfactant; s2, cold rolling machining is conducted, a roller with the surface roughness lower than 0.02 micrometer is used, the rolling speed is 200-300 m / min, the total compression ratio is controlled to range from 40% to 50%, the cold rolling machining is divided into 4-6 passes, then annealing treatment is conducted, the annealing temperature ranges from 250 DEG C to 300 DEG C, and the heat preservation time ranges from 2 hours to 4 hours; and S3, the surface of the aluminum foil is coated with a composite coating of aluminum fluoride and aluminum oxide according to the proportion of 1: 1, the thickness of the composite coating ranges from 20 nm to 30 nm, and after coating, drying and curing are conducted through a tunnel type hot air dryer. By optimizing the degreasing, cold rolling and coating processes, the surface quality and electrochemical stability of the aluminum foil are remarkably improved, the pinhole rate is reduced, the comprehensive performance of the aluminum foil in the high-energy-density lithium ion battery is improved, and reliable guarantee is provided for improvement of the battery performance.

Description

Technical Field

[0001] The invention relates to the field of preparation of battery foil, and more particularly to a low pinhole type battery foil for a high energy density battery. Background Art

[0002] With the growth of global energy demand and the enhancement of environmental protection awareness, electrochemical energy storage technology, especially lithium-ion battery technology, has become the core support in the field of new energy. High-energy-density batteries are increasingly used in new energy vehicles, energy storage power stations, and portable electronic devices. As one of the key materials for lithium-ion batteries, aluminum foil has become the main choice for positive electrode current collectors due to its high conductivity, light weight, and low cost. However, in practical applications, traditional aluminum foil has the following technical difficulties:

[0003] In the production process of aluminum foil, processes such as cold rolling and annealing are prone to introduce microscopic pinholes, which can lead to electrolyte penetration during lithium battery assembly and long-term use, further causing aluminum foil corrosion, affecting the battery's cycle performance and safety. The control and repair of pinholes have become the focus of aluminum foil technology optimization. As a positive electrode current collector, aluminum foil is prone to surface oxidation and corrosion reactions when in contact with high-voltage positive electrode materials and electrolytes, resulting in increased interface impedance and decreased battery performance. Summary of the invention

[0004] The present invention provides a method for preparing a low pinhole battery foil for high energy density batteries, which significantly improves the pinhole control ability, corrosion resistance and electrochemical stability of the aluminum foil by precisely degreasing the surface of the aluminum foil, optimizing the cold rolling process and using a composite coating of aluminum fluoride and aluminum oxide. The specific scheme is as follows:

[0005] A low pinhole battery foil for a high energy density battery, wherein the preparation method of the battery foil comprises the following steps:

[0006] S1. Degreasing the surface of the aluminum foil; cleaning the surface of the aluminum foil with an alkaline degreasing agent and a surfactant;

[0007] S2, cold rolling: using a roller with a surface roughness of <0.02μm, the rolling speed is 200-300m / min; the total compression rate is controlled at 40%-50%; divided into 4-6 passes, followed by annealing treatment, the annealing temperature is 250-300℃; the holding time is 2-4h;

[0008] S3. A composite coating of aluminum fluoride and aluminum oxide is applied on the surface of the aluminum foil.

[0009] Furthermore, the ratio of aluminum fluoride to aluminum oxide in S3 is 1:1, and the thickness of the composite coating is 20 to 30 nm.

[0010] Furthermore, S3 also includes the following sub-steps:

[0011] S301: Activate the surface of the aluminum foil with a weak acid solution of 0.1% nitric acid for 3 minutes; and dry after activation;

[0012] S302: preparing an aluminum fluoride aqueous solution with a concentration of 5%, preparing a sodium aluminate solution with a concentration of 3%, and adjusting the pH to 8-9; mixing the aluminum fluoride solution and the aluminum oxide precursor solution in a volume ratio of 1:1;

[0013] S303: Use precision coating machine, the gap of blade coating head is set to 10-50μm; coating speed is 5-15m / min

[0014] Furthermore, the composite coating after coating in S3 is dried by a tunnel-type hot air drying machine, the hot air flow rate is 2-4 m / s, the temperature is 150-180°C, the drying time is 3-5 minutes, and after drying, it is cured at a curing temperature of 180-200°C and a curing time of 2 minutes.

[0015] Furthermore, the compression ratio of each pass during cold rolling is as follows: the first pass: 10% to 15%; the second pass: 10% to 15%; the third to fifth passes: gradually decreasing, 5% to 10% each time.

[0016] Furthermore, the heating rate during annealing is 5 to 10° C. / min.

[0017] Furthermore, the alkaline degreasing agent is 3% sodium hydroxide.

[0018] Furthermore, the viscosity of the cold rolling oil is 10 to 15 cSt.

[0019] Beneficial effects:

[0020] The present invention provides a low pinhole type battery foil for a high energy density battery and a preparation method thereof, which has the following beneficial effects:

[0021] (1) The present invention effectively reduces the pinhole defects on the surface of the aluminum foil by optimizing the cold rolling process parameters, including allocating the compression ratio, optimizing the rolling roller parameters, and optimizing the annealing temperature and time, thereby significantly improving the density and mechanical properties of the aluminum foil and ensuring its long-term stability in a high voltage environment.

[0022] (2) The aluminum fluoride and aluminum oxide composite coating is uniform and has strong adhesion, which can effectively isolate the direct contact between the aluminum foil and the electrolyte, enhance its corrosion resistance and chemical stability, and reduce the interface impedance, thereby extending the service life of the lithium battery.

[0023] (3) By activating the aluminum foil surface and optimizing the coating thickness, the bonding strength between the coating and the aluminum foil substrate is improved, the electrode interface performance is optimized, and the incidence of interfacial side reactions is reduced, thereby improving the capacity retention rate and cycle stability of lithium-ion batteries. DETAILED DESCRIPTION

[0024] In order to deepen the understanding of the present invention, the present invention will be further described in detail below in conjunction with examples. The examples are only used to explain the present invention and do not constitute a limitation on the protection scope of the present invention.

[0025] Example 1

[0026] A method for preparing a low pinhole battery foil for a high energy density battery:

[0027] S1. Surface degreasing treatment

[0028] Preparation of degreasing solution: Use 3% sodium hydroxide NaOH solution as alkaline degreasing agent and add 0.5% nonionic surfactant nonylphenol polyoxyethylene ether.

[0029] Solution temperature: maintained at 55°C.

[0030] Conductivity: controlled at 700μS / cm.

[0031] Aluminum foil immersion degreasing: Soak the aluminum foil in the degreasing solution for 20 minutes with a stirring rate of 80 rpm.

[0032] Neutralization treatment: After degreasing, the aluminum foil was neutralized with 0.1% nitric acid solution for 3 minutes at a solution temperature of 35°C.

[0033] Deionized water rinsing: rinse 3 times, 1 minute each time, the water temperature is controlled at 30℃, and the conductivity is ≤20μS / cm.

[0034] Drying: Use hot air drying equipment, the air temperature is 50℃, and the drying time is 3 minutes.

[0035] S2. Cold rolling treatment

[0036] High-precision rollers with a roughness of <0.02μm are used, and the viscosity of the cold rolling oil is 12cSt.

[0037] Cold rolling process parameters:

[0038] Rolling speed: 250m / min.

[0039] Total compression ratio: 45%, completed in 5 passes.

[0040] Compression ratio:

[0041] First pass: 13%.

[0042] Second pass: 12%.

[0043] The third to fifth passes: each pass gradually decreases to 7%, 6%, and 7%.

[0044] Annealing treatment: After cold rolling, the aluminum foil is placed in an annealing furnace with the following parameters:

[0045] Heating rate: 8℃ / min.

[0046] Annealing temperature: 275℃.

[0047] Keep warm time: 3 hours.

[0048] Cooling method: Inert gas cooling, rate 10℃ / min.

[0049] S3, surface coating composite coating

[0050] S301, activation treatment:

[0051] The aluminum foil was immersed in a 0.1% nitric acid solution for 3 minutes at a solution temperature of 30°C. The drying condition was hot air at 50°C.

[0052] S302, preparing coating solution:

[0053] A 5% aluminum fluoride aqueous solution and a 3% sodium aluminate aqueous solution were prepared, and the pH was adjusted to 8.5. The two solutions were mixed at a volume ratio of 1:1 and stirred at a speed of 200 rpm.

[0054] S303, coating:

[0055] A blade coater was used with a gap setting of 30 μm and a coating speed of 10 m / min. The coating thickness was controlled at 25 nm.

[0056] Drying and curing:

[0057] Drying was carried out in a tunnel-type hot air dryer with a hot air velocity of 3 m / s, a temperature of 170°C and a drying time of 4 minutes.

[0058] Curing with infrared curing equipment, temperature 190℃, time 2 minutes.

[0059] Example 2

[0060] A method for preparing a low pinhole battery foil for a high energy density battery:

[0061] S1. Surface degreasing treatment

[0062] Prepare degreasing solution: 3% sodium hydroxide, 0.3% nonylphenol polyoxyethylene ether, solution temperature 50°C, conductivity 600μS / cm.

[0063] The aluminum foil was immersed for 15 minutes and stirred at 70 rpm.

[0064] Neutralization treatment: 0.1% nitric acid solution, 3 minutes, temperature 30°C.

[0065] Rinse with deionized water 3 times at 25°C.

[0066] Drying: Use hot air drying in a dust-free environment, the air temperature is 45℃, and the time is 2 minutes.

[0067] S2. Cold rolling treatment

[0068] Rolling speed: 220m / min.

[0069] Total compression rate: 40%, completed in 4 passes. Compression ratio distribution: 15%, 12%, 8%, 5%.

[0070] Annealing parameters:

[0071] Heating rate: 5℃ / min.

[0072] Temperature: 250℃.

[0073] Keep warm time: 2 hours.

[0074] S3, surface coating composite coating

[0075] Activation treatment: using 0.1% nitric acid solution, time 2 minutes, drying temperature 40°C.

[0076] Preparation of coating solution: 4% aluminum fluoride solution, 3% sodium aluminate solution, mixing ratio 1:1, pH adjusted to 9.

[0077] Coating parameters: blade gap 25 μm, coating speed 8 m / min, coating thickness 20 nm.

[0078] Drying and curing: hot air temperature 160℃, time 5 minutes, curing temperature 180℃, time 2 minutes.

[0079] Example 3

[0080] A method for preparing a low pinhole battery foil for a high energy density battery:

[0081] S1. Surface degreasing treatment

[0082] Preparation of degreasing solution: Use 3% sodium hydroxide solution and 0.4% nonylphenol polyoxyethylene ether, solution temperature 60°C, conductivity 900μS / cm.

[0083] The aluminum foil was soaked for 25 minutes with a stirring rate of 90 rpm.

[0084] Neutralization: 0.1% nitric acid solution, 4 minutes, solution temperature 40°C.

[0085] Drying: hot air temperature 55°C, time 4 minutes.

[0086] S2. Cold rolling treatment

[0087] Rolling speed: 300m / min.

[0088] Total compression rate: 50%, completed in 6 passes. Compression ratio distribution: 15%, 12%, 10%, 7%, 3%, 3%.

[0089] Annealing parameters:

[0090] Heating rate: 10℃ / min.

[0091] Temperature: 300℃.

[0092] Keep warm time: 4 hours.

[0093] S3, surface coating composite coating

[0094] Activation treatment: using 0.1% nitric acid solution, time 3 minutes, drying temperature 50°C.

[0095] Coating solution: aluminum fluoride concentration 5%, sodium aluminate concentration 3%, mixing ratio 1:1, pH adjusted to 8.5.

[0096] Coating parameters: blade gap 50 μm, coating speed 12 m / min, coating thickness 30 nm.

[0097] Drying and curing: hot air temperature 180℃, time 3 minutes; curing temperature 200℃, time 2 minutes.

[0098] The surfaces of the battery foils prepared in Examples 1 to 3 were observed using an electron microscope. The observation results showed that there were no pinholes, cracks or uneven coating on the surfaces of the battery foils.

[0099] As a further improvement, the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A low pinhole battery foil for a high energy density battery, characterized in that: The preparation method of the battery foil comprises the following steps: S1. Degreasing the surface of the aluminum foil; cleaning the surface of the aluminum foil with an alkaline degreasing agent and a surfactant; S2, cold rolling: using a roller with a surface roughness of <0.02μm, the rolling speed is 200-300m / min; the total compression rate is controlled at 40%-50%; divided into 4-6 passes, followed by annealing treatment, the annealing temperature is 250-300℃; the holding time is 2-4h; S3. A composite coating of aluminum fluoride and aluminum oxide is applied on the surface of the aluminum foil.

2. A low pinhole type battery foil for a high energy density battery according to claim 1, characterized in that: The ratio of aluminum fluoride to aluminum oxide in S3 is 1:1, and the thickness of the composite coating is 20 to 30 nm.

3. The low pinhole battery foil for a high energy density battery according to claim 1, characterized in that: S3 also includes the following sub-steps: S301: Activate the surface of the aluminum foil with a weak acid solution of 0.1% nitric acid for 3 minutes; and dry after activation; S302: preparing an aluminum fluoride aqueous solution with a concentration of 5%, preparing a sodium aluminate solution with a concentration of 3%, and adjusting the pH to 8-9; mixing the aluminum fluoride solution and the aluminum oxide precursor solution in a volume ratio of 1:1; S303: A precision coating machine is used, and the gap of the blade coating head is set to 10-50 μm; the coating speed is 5-15 m / min.

4. The low pinhole battery foil for a high energy density battery according to claim 1, characterized in that: The composite coating after coating in S3 is dried by a tunnel-type hot air drying machine, the hot air flow rate is 2-4 m / s, the temperature is 150-180°C, the drying time is 3-5 minutes, and after drying, it is cured at a curing temperature of 180-200°C and a curing time of 2 minutes.

5. The low pinhole battery foil for a high energy density battery according to claim 1, characterized in that: The compression ratio of each pass during cold rolling is as follows: the first pass: 10% to 15%; the second pass: 10% to 15%; the third to fifth passes: gradually decreasing, 5% to 10% each time.

6. The low pinhole battery foil for a high energy density battery according to claim 1, characterized in that: The heating rate during annealing is 5 to 10°C / min.

7. The low pinhole battery foil for a high energy density battery according to claim 1, characterized in that: The alkaline degreasing agent is 3% sodium hydroxide.

8. The low pinhole battery foil for a high energy density battery according to claim 1, characterized in that: The viscosity of cold rolling oil is 10-15 cSt.