Preparation method of anticorrosive paint and application of anticorrosive aluminum foil

Abstract

The invention relates to the technical field of batteries, and particularly discloses a preparation method of an anti-corrosion coating and application of an anti-corrosion aluminum foil. The content of the preservative in the anticorrosive paint is 70-95 wt%, the content of the adhesive is 2-5 wt%, and the content of the solvent is 3-28 wt%; according to the invention, the fluorosulfonyl material with a specific ratio is adopted as the preservative, and the optimized adhesive and solvent system are combined, so that a uniform and compact protective layer with stable chemical properties can be formed on the surface of the aluminum foil, and the corrosion of an electrolyte to an aluminum foil matrix is effectively blocked, thereby remarkably improving the corrosion resistance of the aluminum foil and prolonging the service life of the aluminum foil; meanwhile, the anti-corrosion coating is extremely thin and does not occupy the internal space of the battery additionally, so that the energy density of the battery is not influenced, and the excellent adhesive force of the anti-corrosion coating ensures that the coating does not fall off or lose efficacy in the long-term charging and discharging process; in addition, the preparation process of the anticorrosive paint is simple, raw materials are easy to obtain, and large-scale production can be achieved through a conventional coating method.

Description

Technical Field

[0001] The present invention belongs to the technical field of batteries, and particularly relates to a preparation method of an anti-corrosion coating and the application of anti-corrosion aluminum foil. Background Art

[0002] With the booming development of the new energy industry, lithium-ion batteries, as key energy storage and conversion devices, the optimization and improvement of their performance have increasingly become research hotspots. Lithium hexafluorophosphate-based electrolytes are currently the most commonly used electrolytes in lithium-ion batteries, but their poor thermal stability and easy decomposition limit the improvement of battery performance. Lithium difluoromethanesulfonimide and lithium bis(trifluoromethanesulfonyl)imide have excellent conductivity, high-temperature stability, and chemical stability, and can be used in combination with lithium hexafluorophosphate in lithium-ion battery electrolytes to improve the comprehensive performance of the electrolytes. However, lithium difluoromethanesulfonimide and lithium bis(trifluoromethanesulfonyl)imide are prone to corrode the oxide layer on the surface of aluminum foil to form aluminum salts, exposing the aluminum foil completely to the highly reactive electrolyte, resulting in a series of side reactions and causing a decline or even failure of battery performance. This severe corrosion behavior limits the application amount of lithium difluoromethanesulfonimide and lithium bis(trifluoromethanesulfonyl)imide in lithium battery electrolytes and restricts the improvement of battery performance.

[0003] Aluminum foil, as an indispensable current collector material in lithium-ion batteries, its surface properties directly affect the cycle stability, energy density, and safety performance of the battery. In order to enhance the corrosion resistance of aluminum foil, increase the application amount of lithium difluoromethanesulfonimide and lithium bis(trifluoromethanesulfonyl)imide in lithium battery electrolytes, and improve the comprehensive performance of the battery, the industry has been continuously exploring new preparation methods of anti-corrosion coatings and their applications on aluminum foil. For example, Patent CN202323052385.X discloses an anti-corrosion coated aluminum foil for lithium batteries, with MXene layers coated on both the front and back sides of the aluminum foil, graphene thin layers coated on the surface of the MXene layers, anti-corrosion layers coated on the surface of the graphite thin layers, carbon black coatings coated on the surface of the anti-corrosion layers, and flame retardant layers coated on the surface of the carbon black coatings. The anti-corrosion layer is a dopamine layer. This method can protect the aluminum foil from corrosion, but there are too many coatings, the process is too complex, the production process is too long, resulting in a significant increase in cost; at the same time, the thickness of each functional layer in this patent is greater than 2μm, and the coatings occupy too much space, affecting the energy density of the battery. At present, there is still a lack of effective solutions to the anti-corrosion problem of aluminum foil current collectors, and continuous research and improvement are still needed on how to develop high-efficiency, cost-controllable, and thin aluminum foil anti-corrosion coatings. Summary of the Invention

[0004] The purpose of the present invention is to provide a preparation method of an anti-corrosion coating and the application of anti-corrosion aluminum foil to solve the problems mentioned in the above background art.

[0005] To achieve the above purpose, the present invention provides the following technical solutions:

[0006] An anti-corrosion coating, the components of which include a solvent, a binder, and an anti-corrosion agent;

[0007] In the anti-corrosion coating, the content of the anti-corrosion agent is 70 - 95 wt%, the content of the binder is 2 - 5 wt%, and the content of the solvent is 3 - 28 wt%.

[0008] Preferably, the anti-corrosion agent is one or more of fluorosulfonyl materials such as perfluorobutanesulfonyl fluoride, perfluorohexanesulfonyl fluoride, methyl fluorosulfonyldifluoroacetate, perfluorosulfonyl vinyl ether, 4-chlorobenzenesulfonyl fluoride, fluorosulfonyldifluoroacetic acid, fluorosulfonyldifluoroacetate, fluorosulfonylbenzoic acid and its derivatives, 2,3,3,3-tetrafluoro-2-1,1,2,2-tetrafluoro-2-(fluorosulfonyl)ethoxy 1,1,2,2-tetrafluoro-2-(fluorosulfonyl)ethoxy propionyl fluoride, etc.

[0009] Preferably, the binder is one or more of polyvinylidene fluoride, styrene-butadiene rubber, fluorinated rubber, and polyurethane.

[0010] Preferably, the solvent is one or more of diethyl ether, ethyl acetate, N-methylpyrrolidone, dimethylformamide, acetonitrile, dimethyl sulfoxide, acetone, toluene, and dichloromethane.

[0011] A preparation method of an anti-corrosion coating, which is to mix the solvent, the anti-corrosion agent, and the binder in proportion, and stir evenly at 20 - 30 °C for 10 - 60 minutes to obtain the anti-corrosion coating.

[0012] An anti-corrosion aluminum foil, which includes an aluminum foil substrate and an anti-corrosion coating provided on the surface of the aluminum foil substrate. The anti-corrosion coating is an anti-corrosion coating, which is attached to the surface of the aluminum foil by dipping, spin coating, spraying, or scraping, and dried at a temperature of 60 - 140 °C for 1 - 3 hours to obtain the anti-corrosion aluminum foil; the thickness of the anti-corrosion coating is 100 - 1000 nm.

[0013] Preferably, the surface of the anti-corrosion coating is uniform and flat, without defects such as bubbles or cracks.

[0014] A preparation method of an anti-corrosion aluminum foil, which includes the following steps:

[0015] S1. Clean and dry the aluminum foil substrate;

[0016] S2. Coat the anti-corrosion coating on the surface of the aluminum foil substrate;

[0017] S3. Dry to obtain the anti-corrosion aluminum foil.

[0018] An application of the anti-corrosion aluminum foil in a lithium battery, and the anti-corrosion aluminum foil is used for a positive current collector or a negative current collector of a lithium battery.

[0019] Compared with the prior art, the beneficial effects of the present invention are:

[0020] By using a fluorosulfonyl material with a specific ratio as a preservative and combining an optimized adhesive and solvent system, a uniform, dense, and chemically stable protective layer can be formed on the surface of the aluminum foil, effectively blocking the erosion of the electrolyte on the aluminum foil substrate, thereby significantly improving the corrosion resistance of the aluminum foil and extending its service life. At the same time, the anti-corrosion coating has an extremely thin thickness, does not occupy additional internal space of the battery, ensures that the energy density of the battery is not affected, and its excellent adhesion ensures that the coating will not peel off or fail during long-term charge and discharge processes. In addition, the preparation process of this anti-corrosion coating is simple, the raw materials are easily available, it can be mass-produced by conventional coating methods, is highly compatible with the existing battery manufacturing process, greatly reduces the production cost, and provides reliable technical support for the industrial application of high-performance lithium batteries. Brief Description of the Drawings

[0021] Figure 1 is the preparation flow chart of the present invention;

[0022] Figure 2 is the surface SEM photograph of the aluminum foil coated with the anti-corrosion coating and the pure aluminum foil in Example 1;

[0023] Figure 3 is the two-electrode constant potential anodic polarization curve of the aluminum foil coated with the anti-corrosion coating and the pure aluminum foil in Example 1. Detailed Description of the Invention

[0024] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work shall fall within the protection scope of the present invention.

[0025] Example 1:

[0026] Preparation and Performance Testing of Perfluorohexylsulfonyl Fluoride-based Anti-corrosion Aluminum Foil

[0027] Step 1: Preparation of the Anti-corrosion Coating

[0028] Perfluorohexylsulfonyl fluoride (preservative, content 90 wt%), fluorinated rubber (adhesive, content 5 wt%), and ethyl acetate (solvent, content 5 wt%) are put into a stirring kettle. Stir at a speed of 500 rpm at 25°C for 30 minutes until evenly mixed to form a transparent viscous anti-corrosion coating.

[0029] Step 2: Preparation of the Anti-corrosion Aluminum Foil

[0030] The aluminum foil substrate was immersed in the above anti-corrosion coating for 30 seconds. After taking it out, it was dried in an oven at 60 °C for 1.5 hours, and finally an anti-corrosion coating with a thickness of 207 nm was formed. The obtained anti-corrosion aluminum foil was denoted as FC-Al-1.

[0031] Performance test:

[0032] Surface morphology analysis: The surface morphologies of FC-Al-1 and pure aluminum foil were observed by scanning electron microscopy (SEM). The results showed that the surface of FC-Al-1 was covered with a uniform and dense anti-corrosion coating without bubbles or cracks; while the surface of the pure aluminum foil was rough with obvious oxide layer defects.

[0033] Electrochemical performance test: A three-electrode system (the working electrode was FC-Al-1 or pure aluminum foil, the reference electrode was lithium foil, and the counter electrode was lithium foil) was used to conduct a potentiostatic anodic polarization test (polarization voltage 4.2 V, time 18000 s) in a lithium bis(trifluoromethanesulfonyl)imide-based electrolyte (1 mol / L, the solvent was DMC:EMC:EC = 1:1:1). The results showed that the polarization current of FC-Al-1 remained stable, while the current of the pure aluminum foil fluctuated violently, indicating that the anti-corrosion coating significantly inhibited the corrosion of the aluminum foil.

[0034] Example 2:

[0035] Preparation and performance test of methyl fluorosulfonyldifluoroacetate-based anti-corrosion aluminum foil

[0036] Step 1: Preparation of anti-corrosion coating

[0037] Methyl fluorosulfonyldifluoroacetate (anti-corrosion agent, content 95 wt%), polyvinylidene fluoride (adhesive, content 2.5 wt%), and dimethylformamide (solvent, content 2.5 wt%) were put into a stirring kettle. It was stirred at a speed of 400 rpm at 30 °C for 40 minutes to form a homogeneous and stable anti-corrosion coating.

[0038] Step 2: Preparation of anti-corrosion aluminum foil

[0039] The above anti-corrosion coating was evenly coated on the surface of the aluminum foil by spraying process. The spraying pressure was 0.3 MPa and the spraying distance was 20 cm. After coating, it was dried at 140 °C for 2 hours, and finally an anti-corrosion coating with a thickness of 452 nm was formed. The obtained anti-corrosion aluminum foil was denoted as FC-Al-2.

[0040] Performance test:

[0041] Coating adhesion test: The coating adhesion was tested by the cross-cut method. The results showed that the coating adhesion grade of FC-Al-2 was grade 0 (no peeling), indicating that the coating was firmly bonded to the aluminum foil substrate.

[0042] Electrolyte immersion resistance test: FC-Al-2 was immersed in a lithium bis(trifluoromethanesulfonyl)imide-based electrolyte at 60 °C for 7 days. After removal, SEM observation showed that the coating had no swelling or peeling, demonstrating its excellent corrosion resistance.

[0043] Example 3:

[0044] Preparation and performance testing of 4-chlorobenzenesulfonyl fluoride-based corrosion-resistant aluminum foil

[0045] Step 1: Preparation of the anti-corrosion coating

[0046] 4-Chlorobenzenesulfonyl fluoride (anti-corrosion agent, content 85 wt%), styrene-butadiene rubber (adhesive, content 5 wt%), and toluene (solvent, content 10 wt%) were put into a stirring kettle. Stir at a speed of 600 rpm at 20 °C for 20 minutes to form an anti-corrosion coating with moderate viscosity.

[0047] Step 2: Preparation of the anti-corrosion aluminum foil

[0048] The above anti-corrosion coating was coated on the surface of the aluminum foil by a doctor blade coating process. The coating thickness was controlled at 800 nm, and then dried at 120 °C for 2 hours to finally form an anti-corrosion coating with a thickness of 771 nm. The obtained anti-corrosion aluminum foil was designated as FC-Al-3.

[0049] Performance testing:

[0050] Battery cycle performance test: Using FC-Al-3 as the positive current collector, NMC622 as the positive electrode material, and lithium foil as the negative electrode, a lithium-ion half-cell was assembled. After 100 cycles at 4.3 V and 1C rate, the battery capacity retention rate was 87.2%, which was much higher than that of the half-cell using a pure aluminum foil current collector (capacity retention rate 51.7%), demonstrating that the anti-corrosion coating effectively improved the cycle stability of the battery.

[0051] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. An anti-corrosion coating, characterized in that: The components include a solvent, a binder, and a preservative; In the anticorrosive coating, the content of the preservative is 70 - 95 wt%, the content of the binder is 2 - 5 wt%, and the content of the solvent is 3 - 28 wt%.

2. The anti-corrosion coating according to claim 1, characterized in that: The preservative is one or more of fluorosulfonyl materials such as perfluorobutanesulfonyl fluoride, perfluorohexanesulfonyl fluoride, methyl fluorosulfonyldifluoroacetate, perfluorosulfonyl vinyl ether, 4-chlorobenzenesulfonyl fluoride, fluorosulfonyldifluoroacetic acid, fluorosulfonyldifluoroacetate, fluorosulfonylbenzoic acid and its derivatives, 2,3,3,3-tetrafluoro-2-1,1,2,2-tetrafluoro-2-(fluorosulfonyl)ethoxy-1,1,2,2-tetrafluoro-2-(fluorosulfonyl)ethoxypropionyl fluoride.

3. An anti-corrosion coating according to claim 1, characterized in that: The binder is one or more of polyvinylidene fluoride, styrene-butadiene rubber, fluorinated rubber, and polyurethane.

4. An anti-corrosion coating according to claim 1, characterized in that: The solvent is one or more of diethyl ether, ethyl acetate, N-methylpyrrolidone, dimethylformamide, acetonitrile, dimethyl sulfoxide, acetone, toluene, and dichloromethane.

5. A preparation method of an anticorrosive coating, applicable to an anticorrosive coating according to any one of claims 1 to 4, characterized in that: Mix the solvent, preservative, and binder in proportion, and stir evenly at 20 - 30 °C for 10 - 60 minutes to obtain the anticorrosive coating.

6. An anti-corrosion aluminum foil, characterized in that: It includes an aluminum foil substrate and an anticorrosive coating provided on the surface of the aluminum foil substrate. The anticorrosive coating is the anticorrosive coating described in claim 5, and is attached to the aluminum foil surface by dipping, spin coating, spraying, or scraping. The drying temperature is 60 - 140 °C, and the drying time is 1 - 3 hours to obtain the anticorrosive aluminum foil; the thickness of the anticorrosive coating is 100 - 1000 nm.

7. The anti-corrosion aluminum foil according to claim 6, wherein: The surface of the anticorrosive coating is uniformly flat without bubble or crack defects.

8. A method for preparing an anti-corrosion aluminum foil, applicable to an anti-corrosion aluminum foil as described in any one of claims 6 to 7, characterized in that, It includes the following steps: S1. Clean and dry the aluminum foil substrate; S2. Coat the anticorrosive coating described in claim 5 on the surface of the aluminum foil substrate; S3. Dry to obtain the anticorrosive aluminum foil.

9. Use of the anti-corrosion aluminum foil according to any one of claims 6 to 7 in a lithium battery, characterized in that: The anticorrosive aluminum foil is used for the positive current collector of a lithium battery.

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