Aluminum-plastic film for packaging lithium battery and preparation method of aluminum-plastic film

Abstract

The invention belongs to the technical field of aluminum plastic films, and particularly relates to an aluminum plastic film for packaging a lithium battery and a preparation method of the aluminum plastic film. The aluminum plastic film is sequentially composed of a protective layer, an upper bonding layer, a modified aluminum foil layer, a lower bonding layer and a heat sealing layer from top to bottom. The modified aluminum foil layer is prepared through the following preparation processes that in the inert gas atmosphere, Al, Fe, Ni, Nb and Er are mixed and smelted, and aluminum base alloy is obtained after cooling; and under the inert gas atmosphere, the aluminum-based alloy serves as a target material, and after magnetron sputtering is conducted on the two faces of the aluminum foil, the modified aluminum foil layer is obtained. The aluminum plastic film disclosed by the invention has excellent mechanical properties, corrosion resistance and flame retardance.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of aluminum-plastic film, and particularly relates to an aluminum-plastic film for lithium battery packaging and a preparation method thereof. BACKGROUND

[0002] Lithium batteries have the advantages of small volume, light weight, good durability, etc., and are widely used in electronic fields such as mobile phones, video cameras, etc., and gradually penetrate into the field of new energy vehicles, and are currently the mainstream power supply of electronic equipment. In recent years, the popularity of new energy vehicles has remained high, and the entire battery industry chain has also entered a stage of rapid development. As the outer packaging material of the lithium battery cell, the packaging material plays a crucial role in the performance and safety of the cell, and the performance requirements have also improved significantly. The packaging forms of lithium batteries mainly include cylindrical lithium batteries packaged with stainless steel materials, square lithium batteries packaged with aluminum alloy materials, and soft-packaged lithium batteries packaged with aluminum-plastic composite films. Among them, the aluminum-plastic film has the advantages of light weight, good plasticity, good air and moisture barrier properties, etc. The shape and size of the soft-packaged lithium battery are flexible, which can meet the higher energy density requirements, and are widely used in the battery packaging industry.

[0003] The aluminum-plastic film is usually composed of aluminum foil, multiple plastics and adhesive, and the common structure is protective layer + adhesive + aluminum foil layer + adhesive + heat-sealing layer. The protective layer is usually a nylon layer to improve the strength and ductility of the aluminum layer. The aluminum foil layer mainly plays a role in isolating water vapor and electrolyte. The heat-sealing layer plays a role in packaging and blocking water and solvents. The current domestic aluminum-plastic film for soft-packaged batteries mainly faces the following problems: poor barrier performance, affecting the service life and safety of the battery; poor ductility, small shell depth after forming; poor electrolyte resistance, easy to form corrosion and cause battery failure. In order to improve the above problems, it is usually necessary to improve the design of the composite layer and the selection of each layer of substrate to obtain an aluminum-plastic film with excellent comprehensive performance. SUMMARY

[0004] The first object of the present application is to provide an aluminum-plastic film for lithium battery packaging, which has excellent mechanical properties, corrosion resistance and flame retardance.

[0005] The second object of the present application is to provide a preparation method of the above-mentioned aluminum-plastic film for lithium battery packaging.

[0006] In order to achieve the above objects, the technical scheme adopted by the present application is as follows: An aluminum-plastic film for lithium battery packaging, which is composed of a protective layer, an upper adhesive layer, a modified aluminum foil layer, a lower adhesive layer and a heat-sealing layer from top to bottom. The modified aluminum foil layer is prepared by the following process: (1) In an inert gas atmosphere, Al, Fe, Ni, Nb and Er are mixed and smelted, and an aluminum-based alloy is obtained after cooling; (2) under the inert gas atmosphere, the aluminum-based alloy is used as a target material to perform magnetron sputtering on both sides of the aluminum foil to obtain a modified aluminum foil layer; The protective layer is prepared by the following preparation process: (a) aluminum nitrate, magnesium nitrate, zinc nitrate, vanadium nitrate and scandium nitrate are added to water, the pH is adjusted to 9.5-11, stirring, standing and aging, filtration, washing, drying, calcination to obtain a high-entropy metal oxide; (b) nylon 66, high-entropy metal oxide, antioxidant, plasticizer are mixed, added to a twin-screw extruder, melt extrusion, cast into a film to obtain a protective layer.

[0007] Further, the molar ratio of Al, Fe, Ni, Nb and Er in step (1) is (12-14):(2-3):(1-2):(1-2):(1-2).

[0008] Further, in step (2), the sputtering power of magnetron sputtering is 80-100W, the deposition rate is 2-4nm / min, the deposition temperature is 0-10℃, and the sputtering thickness is 0.2-0.8μm; the aluminum foil is any one of 8021 aluminum foil and 8079 aluminum foil.

[0009] Further, in step (a), the molar ratio of aluminum nitrate, magnesium nitrate, zinc nitrate, vanadium nitrate and scandium nitrate is 1:1:1:1:1, the concentration of aluminum nitrate in water is 0.2-0.6mol / L; the stirring time is 3-5h; the standing and aging time is 2-5h; the calcination temperature is 900-1150℃, and the time is 5-8h.

[0010] Further, in step (b), the mass ratio of nylon 66, high-entropy metal oxide, antioxidant and plasticizer is 1:(0.08-0.12):(0.01-0.03):(0.02-0.05); the melt extrusion temperature is 220-240℃; the antioxidant is antioxidant 1010; and the plasticizer is plasticizer JZ-218.

[0011] Further, the materials of the upper adhesive layer and the lower adhesive layer are independently selected from any one or more of polyurethane adhesive, polyolefin adhesive, and epoxy resin adhesive; and the material of the heat-sealing layer is polypropylene.

[0012] Further, the thickness of the protective layer is 22-30μm, the thickness of the upper adhesive layer is 2-5μm, the thickness of the aluminum foil layer is 30-45μm, the thickness of the lower adhesive layer is 2-5μm, and the thickness of the heat-sealing layer is 40-65μm.

[0013] The preparation method of the above-mentioned aluminum-plastic film for lithium battery packaging comprises the following steps: The protective layer, the upper adhesive layer, the modified aluminum foil layer, the lower adhesive layer and the heat-sealing layer are laminated to obtain the aluminum-plastic film after heating and curing.

[0014] Further, the step of heating and curing is: firstly, curing at 65-75 DEG C for 4-5h, then increasing the temperature to 85-100 DEG C for 65-70h, and finally decreasing the temperature to 60-70 DEG C for 62-64h The beneficial technical effects of the present application are: 1. The Al-Fe-Ni-Nb-Er amorphous alloy coating is sputtered on the surface of the aluminum foil, the atoms in the amorphous alloy are arranged in a long-range disordered and short-range ordered structure, and there are no defects such as grain boundaries and dislocations in the crystal alloy, so the amorphous alloy has excellent mechanical strength and corrosion resistance. The Al-based alloy combines the uniformity of the amorphous structure and the easy passivation advantage of aluminum element, as the coating of the aluminum foil, not only has good combination with the substrate, but also can form a passivation film on the surface of the aluminum foil, enhance the corrosion resistance and mechanical strength of the aluminum foil, and effectively improve the mechanical properties and stability in the electrolyte of the aluminum foil.

[0015] 2. The high-entropy metal oxide modified nylon material is used as the protective layer, compared with ordinary metal oxide fillers such as Al2O3 and MgO, the high-entropy metal oxide has high configuration entropy and multi-element synergistic effect, so it has excellent thermal stability and high strength and hardness, and the surface of the high-entropy metal oxide has multi-element active sites, the interface combination and dispersion with the substrate are better, as the filler of the nylon film, it can improve the heat resistance, flame retardance and mechanical properties of the nylon, and as the protective layer of the aluminum-plastic film, it can improve the safety performance of the battery. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 The XRD pattern of the modified aluminum foil layer in the aluminum-plastic film prepared in Example 1 of the present application is shown in the figure. Figure 2 The scanning electron microscope pattern of the protective layer in the aluminum-plastic film prepared in Example 1 of the present application is shown in the figure. DETAILED DESCRIPTION

[0017] The following is a further detailed description of the present application in combination with specific preferred embodiments, which cannot be considered as limiting the specific implementation of the present application to these descriptions. For ordinary skilled persons in the technical field to which the present application belongs, without departing from the concept of the present application, a number of simple deductions or substitutions can be made, which should be considered as belonging to the protection scope of the present application. The specific conditions not mentioned in the examples are carried out according to the conventional conditions or the conditions recommended by the manufacturer. The reagents or instruments used, such as those not specifically mentioned, are conventional products obtained through market channels.

[0018] (I) Examples Example 1 Example 1 provides an aluminum-plastic film for lithium battery packaging, which is composed of a protective layer with a thickness of 25 μm, a polyurethane adhesive layer with a thickness of 3 μm, a modified aluminum foil layer with a thickness of 40 μm, a polyurethane adhesive layer with a thickness of 3 μm, and a polypropylene film with a thickness of 55 μm from top to bottom; The modified aluminum foil layer is prepared by the following process: (1) Under an argon atmosphere, arc melting is performed according to a molar ratio of Al, Fe, Ni, Nb, and Er of 13:2:1:1:1, and an aluminum-based alloy is obtained after cooling; (2) Under an argon atmosphere, using 8021 aluminum foil as the substrate and the aluminum-based alloy as the target material, the double sides of the aluminum foil are subjected to magnetron sputtering using a radio frequency power source to obtain a modified aluminum foil layer; the sputtering power is 100 W, the deposition temperature is 5°C, the deposition rate is 3 nm / min, and the sputtering thickness is 0.4 μm. The XRD of the modified aluminum foil layer is shown in Figure 1 .

[0019] The protective layer is prepared by the following process: (a) Equal molar ratios of aluminum nitrate, magnesium nitrate, zinc nitrate, vanadium nitrate, and scandium nitrate are weighed and added to water to make the concentration of metal cations 0.4 mol / L. A 0.1 mol / L NaOH solution is added dropwise to adjust the pH to 10. After stirring for 4 h, it is left to age for 4 h. After filtration, washing, and drying, it is calcined at 1000°C for 6 h to obtain a high-entropy metal oxide; (b) Nylon 66, high-entropy metal oxide, antioxidant 1010, and plasticizer JZ-218 are mixed uniformly according to a mass ratio of 1:0.1:0.02:0.03. They are added to a twin-screw extruder and melted and extruded at 230°C. After casting into a film, a protective layer is obtained. The scanning electron microscope image of the protective layer is shown in Figure 2 .

[0020] This embodiment also provides a preparation method of the above-mentioned aluminum-plastic film for lithium battery packaging. The specific steps are as follows: Polyurethane adhesive is coated on both sides of the modified aluminum foil layer as the upper and lower adhesive layers. Then the protective layer is attached to the surface of the upper adhesive layer, and the heat-sealing layer is attached to the surface of the lower adhesive layer to obtain an aluminum-plastic film primary product. The aluminum-plastic film primary product is placed in an oven, first aged at 70°C for 5 h, then aged at 90°C for 70 h, and finally aged at 60°C for 62 h to obtain an aluminum-plastic film.

[0021] Example 2 Example 2 provides an aluminum-plastic film for lithium battery packaging, which is composed of a protective layer with a thickness of 22 μm, a polyurethane adhesive layer with a thickness of 2 μm, a modified aluminum foil layer with a thickness of 30 μm, a polyurethane adhesive layer with a thickness of 2 μm, and a polypropylene film with a thickness of 40 μm from top to bottom; The modified aluminum foil layer is prepared by the following preparation process: (1) Under an argon atmosphere, arc melting is performed according to a molar ratio of Al, Fe, Ni, Nb and Er of 12:2:1:1:1, and an aluminum-based alloy is obtained after cooling; (2) Under an argon atmosphere, 8021 aluminum foil is used as a substrate, and the aluminum-based alloy is used as a target material, and the double sides of the aluminum foil are subjected to magnetron sputtering by using a radio frequency power source to obtain a modified aluminum foil layer; wherein the sputtering power is 80 W, the deposition temperature is 0°C, the deposition speed is 2 nm / min, and the sputtering thickness is 0.2 μm.

[0022] The protective layer is prepared by the following preparation process: (a) Equal molar ratios of aluminum nitrate, magnesium nitrate, zinc nitrate, vanadium nitrate and scandium nitrate are weighed and added to water to make the concentration of metal cations 0.2 mol / L, and a 0.05 mol / L NaOH solution is added dropwise to adjust the pH to 9.5, stirred for 3 h and aged for 2 h, then filtered, washed and dried, and then calcined at 900°C for 5 h to obtain a high-entropy metal oxide; (b) Nylon 66, high-entropy metal oxide, antioxidant 1010, plasticizer JZ-218 are mixed in a mass ratio of 1:0.08:0.01:0.02, added to a twin-screw extruder, melted and extruded at 220°C, and then cast into a film to obtain a protective layer.

[0023] The present embodiment also provides a preparation method of the above-mentioned aluminum-plastic film for packaging lithium batteries, and the specific steps are as follows: Polyurethane adhesives are coated on both sides of the modified aluminum foil layer as upper and lower adhesive layers, then the protective layer is attached to the surface of the upper adhesive layer, and the heat-sealing layer is attached to the surface of the lower adhesive layer to obtain an aluminum-plastic film initial product; the aluminum-plastic film initial product is placed in an oven, first aged at 65°C for 4 h, then aged at 85°C for 65 h, and finally aged at 60°C for 62 h to obtain an aluminum-plastic film.

[0024] Example 3 Example 3 provides an aluminum-plastic film for packaging lithium batteries, which is composed of, from top to bottom, a protective layer with a thickness of 30 μm, a polyurethane adhesive layer with a thickness of 5 μm, a modified aluminum foil layer with a thickness of 45 μm, a polyurethane adhesive layer with a thickness of 5 μm, and a polypropylene film with a thickness of 65 μm; The modified aluminum foil layer is prepared by the following preparation process: (1) Under an argon atmosphere, arc melting is performed according to a molar ratio of Al, Fe, Ni, Nb and Er of 14:3:2:2:2, and an aluminum-based alloy is obtained after cooling; (2) Under an argon atmosphere, 8079 aluminum foil is used as a substrate, and an aluminum-based alloy is used as a target material. The double sides of the aluminum foil are subjected to magnetron sputtering by using a radio frequency power source to obtain a modified aluminum foil layer; wherein the sputtering power is 100 W, the deposition temperature is 10℃, the deposition speed is 4 nm / min, and the sputtering thickness is 0.8 μm.

[0025] The protective layer is prepared by the following preparation process: (a) Equal-molar-ratio aluminum nitrate, magnesium nitrate, zinc nitrate, vanadium nitrate and scandium nitrate are weighed and added to water, so that the concentration of metal cations is 0.6 mol / L. A 0.15 mol / L NaOH solution is added dropwise to adjust the pH to 11. After stirring for 5 h, it is left to stand for 5 h. After filtration, washing and drying, it is calcined at 1150℃ for 8 h to obtain a high-entropy metal oxide; (b) Nylon 66, high-entropy metal oxide, antioxidant 1010 and plasticizer JZ-218 are mixed uniformly according to a mass ratio of 1:0.12:0.03:0.05. A double-screw extruder is added, and melt extrusion is carried out at 240℃. After flow casting, the protective layer is obtained.

[0026] The embodiment also provides a preparation method of the above-mentioned aluminum-plastic film for lithium battery packaging, and the specific steps are as follows: A polyurethane adhesive is coated on both sides of the modified aluminum foil layer as upper and lower adhesive layers. Then, the protective layer is attached to the surface of the upper adhesive layer, and the heat-sealing layer is attached to the surface of the lower adhesive layer to obtain an aluminum-plastic film initial product. The aluminum-plastic film initial product is placed in an oven, and is first aged at 75℃ for 5 h, then heated to 100℃ for 70 h, and finally cooled to 70℃ for 64 h to obtain the aluminum-plastic film.

[0027] (II) Comparative Examples Comparative Example 1 Comparative Example 1 and Example 1 are basically the same in content, except that the modified aluminum foil layer in Example 1 is replaced by 8021 aluminum foil.

[0028] Comparative Example 2 Comparative Example 2 and Example 1 are basically the same in content, except that the high-entropy metal oxide is omitted when preparing the protective layer.

[0029] Comparative Example 3 Comparative Example 3 and Example 1 are basically the same in content, except that the high-entropy metal oxide is replaced by aluminum oxide when preparing the protective layer.

[0030] (III) Test Examples The aluminum-plastic films prepared in Examples 1-3 and Comparative Examples 1-3 are subjected to performance tests.

[0031] Mechanical property test: according to GB / T 228.1-2021 “Metallic materials-Tensile testing-Part 1: Method of test at room temperature”, the mechanical properties of the aluminum-plastic films of Examples 1-3 and Comparative Examples 1-3 were tested, and the results are shown in Table 1.

[0032] Corrosion resistance test: the aluminum-plastic films prepared in Examples 1-3 and Comparative Examples 1-3 were cut into 15 mm long strips, and then immersed in an electrolyte (EC:DEC = 1:1, 1M LiPF6) at 80℃ for 24h. After drying, the peel strength between the aluminum foil layer and the heat-seal layer was measured, and the results are shown in Table 1.

[0033] Flame resistance test: lithium ion batteries were assembled using the aluminum-plastic films prepared in Examples 1-3 and Comparative Examples 1-3. The positive electrode was lithium cobaltate, and the negative electrode was graphite. The battery was charged to 4.2V voltage and placed in an oven at 200℃. The ignition data was recorded, and the results are shown in Table 1.

[0034] Table 1: Test results of mechanical properties, corrosion resistance and flame resistance of aluminum-plastic films As shown in Table 1, the aluminum-plastic films prepared in Examples 1-3 have excellent mechanical properties, corrosion resistance and flame resistance.

[0035] Compared with Example 1, Comparative Example 1 replaced the modified aluminum foil layer in Example 1 with 8021 aluminum foil, and the mechanical properties and corrosion resistance were decreased to different degrees, which indicated that the modification of the aluminum foil layer could significantly improve the mechanical properties and corrosion resistance of the aluminum-plastic film. According to the specific analysis, the Al-Fe-Ni-Nb-Er amorphous alloy coating was prepared on the surface of the aluminum foil, and the atoms in the amorphous alloy were arranged in a long-range disorder and short-range order structure, without defects such as grain boundaries and dislocations in the crystal alloy. Therefore, it has the advantages of high strength, high hardness, wear resistance and corrosion resistance. The Al-based alloy combines the uniformity of amorphous structure and the easy passivation advantage of aluminum element. As a coating of aluminum foil, it not only has good adhesion to the substrate, but also can form a passivation film on the surface of the aluminum foil, enhancing the corrosion resistance and mechanical strength of the aluminum foil, and effectively improving the mechanical properties and stability in electrolyte of the aluminum foil.

[0036] Compared with example 1, the mechanical properties and flame-retardant properties of comparative example 2 and comparative example 3 are decreased to different degrees, which shows that the mechanical properties and corrosion resistance of the aluminum-plastic film can be obviously improved by introducing the high-entropy metal oxide into the protective layer. According to specific analysis, the nylon material modified by the high-entropy metal oxide is used as the protective layer in the application. Compared with the ordinary metal oxide fillers such as Al2O3 and MgO, the high-entropy metal oxide has high configuration entropy and multi-element synergistic effect, and therefore has excellent thermal stability and high strength and hardness. The surface of the high-entropy metal oxide has multi-element active sites, and the interface bonding and dispersibility with the matrix are better. As the filler of the nylon film, the high-entropy metal oxide can improve the heat resistance, flame-retardant property and mechanical property of the nylon. As the protective layer of the aluminum-plastic film, the high-entropy metal oxide can improve the safety performance of the battery.

[0037] Finally, it should be pointed out that the above embodiments are only used to illustrate the technical solutions of the application, but not to limit the application. The basic principles and main features of the application have been described above with specific embodiments. Based on the application, some modifications or replacements can be made, but these modifications or replacements do not make the corresponding technical solutions deviate from the scope of the application.

Claims

1. An aluminum-plastic film for lithium battery encapsulation, characterized in that, The aluminum-plastic film consists of a protective layer, an upper adhesive layer, a modified aluminum foil layer, a lower adhesive layer, and a heat-sealing layer from top to bottom. The modified aluminum foil layer is prepared by the following process: (1) Under an inert gas atmosphere, Al, Fe, Ni, Nb and Er are mixed and smelted, and then cooled to obtain an aluminum-based alloy; (2) In an inert gas atmosphere, the aluminum-based alloy is used as the target material to perform magnetron sputtering on both sides of the aluminum foil to obtain a modified aluminum foil layer; The protective layer is prepared by the following process: (a) Add aluminum nitrate, magnesium nitrate, zinc nitrate, vanadium nitrate and scandium nitrate to water, adjust the pH to 9.5-11, stir, let stand and age, filter, wash, dry and calcine to obtain high entropy metal oxide; (b) Nylon 66, high-entropy metal oxide, antioxidant and plasticizer are mixed and added to a twin-screw extruder. After melt extrusion and casting, a protective layer is obtained.

2. The aluminum-plastic film for lithium battery packaging according to claim 1, characterized in that, The molar ratio of Al, Fe, Ni, Nb and Er in step (1) is (12-14): (2-3): (1-2): (1-2): (1-2).

3. The aluminum-plastic film for lithium battery packaging according to claim 1, characterized in that, In step (2), the magnetron sputtering has a sputtering power of 80-100W, a deposition rate of 2-4nm / min, a deposition temperature of 0-10℃, and a sputtering thickness of 0.2-0.8μm; the aluminum foil is either 8021 aluminum foil or 8079 aluminum foil.

4. The aluminum-plastic film for lithium battery packaging according to claim 1, characterized in that, In step (a), the molar ratio of aluminum nitrate, magnesium nitrate, zinc nitrate, vanadium nitrate, and scandium nitrate is 1:1:1:1:1, and the concentration of aluminum nitrate in water is 0.2-0.6 mol / L; the stirring time is 3-5 h; the standing aging time is 2-5 h; and the calcination temperature is 900-1150℃ for 5-8 h.

5. The aluminum-plastic film for lithium battery packaging according to claim 1, characterized in that, In step (b), the mass ratio of nylon 66, high-entropy metal oxide, antioxidant, and plasticizer is 1:(0.08-0.12):(0.01-0.03):(0.02-0.05); the melt extrusion temperature is 220-240℃; the antioxidant is antioxidant 1010; and the plasticizer is plasticizer JZ-218.

6. The aluminum-plastic film for lithium battery encapsulation according to claim 1, characterized in that, The materials of the upper adhesive layer and the lower adhesive layer are each independently selected from one or more of polyurethane adhesives, polyolefin adhesives, and epoxy resin adhesives; the material of the heat-sealing layer is polypropylene.

7. The aluminum-plastic film for lithium battery packaging according to claim 1, characterized in that, The protective layer has a thickness of 22-30 μm, the upper adhesive layer has a thickness of 2-5 μm, the aluminum foil layer has a thickness of 30-45 μm, the lower adhesive layer has a thickness of 2-5 μm, and the heat-sealing layer has a thickness of 40-65 μm.

8. A method for preparing an aluminum-plastic film for lithium battery encapsulation according to any one of claims 1-7, characterized in that, Includes the following steps: The protective layer, upper adhesive layer, modified aluminum foil layer, lower adhesive layer and heat-sealing layer are laminated together and heated to cure, thus obtaining the aluminum-plastic film.

9. The method for preparing the aluminum-plastic film for lithium battery packaging according to claim 8, characterized in that, The heating and cooking step is as follows: First, mature at 65-75℃ for 4-5 hours, then raise the temperature to 85-100℃ and mature for 65-70 hours, and finally lower the temperature to 60-70℃ and mature for 62-64 hours.

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