Aluminum-plastic composite film and preparation method thereof

Abstract

The application relates to the technical field of composite films, and particularly discloses an aluminum-plastic composite film and a preparation method thereof. The aluminum-plastic composite film comprises, from outside to inside, an outer barrier layer, a first adhesive layer, a barrier layer, a second adhesive layer, a protective layer and a heat-sealing layer; the protective layer comprises 100 parts of ternary random copolymerized polypropylene, 5-8 parts of a compatilizer, 10-25 parts of modified fillers and 1-5 parts of a nucleating agent; the modified fillers are fluorine-containing micro-powder and silicon powder treated by a silane coupling agent; and the preparation method comprises the following steps: mixing the ternary random copolymerized polypropylene, the compatilizer, the modified fillers and the nucleating agent, and then melt co-extruding to obtain the protective layer; and then, from outside to inside, the outer barrier layer, the first adhesive layer, the barrier layer, the second adhesive layer, the protective layer and the heat-sealing layer are compounded to obtain the aluminum-plastic composite film. The protective layer has good corrosion resistance, the electrolyte permeated by the heat-sealing layer continues to permeate into the second adhesive layer, and the electrolyte resistance of the aluminum-plastic composite film is improved.

Description

Technical Field

[0001] This application relates to the field of composite film technology, and more specifically, to an aluminum-plastic composite film and its preparation method. Background Technology

[0002] Aluminum-plastic composite film, or aluminum-plastic film for short, is a composite soft-pack outer shell material used for encapsulating lithium-ion batteries, commonly found in pouch batteries. Sealing the assembled individual battery cells with aluminum-plastic film plays a crucial role in protecting the internal electrodes and isolating them from the external environment.

[0003] Currently, aluminum-plastic film is composed of an outer barrier layer (nylon), a permeation barrier layer (aluminum), and a heat-sealing layer (polypropylene) bonded together with adhesives from the outside to the inside. It has good puncture resistance, high barrier properties, electrolyte resistance, high temperature insulation properties, and high cold stamping forming properties.

[0004] However, the electrolyte in lithium-ion batteries is composed of highly permeable organic solvents and readily hydrolyzed substances such as lithium hexafluorophosphate and lithium hexafluoroborate. Therefore, although the heat-sealing layer has good resistance to electrolyte corrosion, it is still easily swollen and corroded by the electrolyte after long-term contact. Consequently, some electrolyte still penetrates into the adhesive and corrodes it, causing delamination of the heat-sealing layer and the barrier layer, thus damaging the aluminum-plastic film structure and reducing the electrolyte resistance of the aluminum-plastic composite film. Summary of the Invention

[0005] To improve the electrolyte resistance of aluminum-plastic film, this application provides an aluminum-plastic composite film and its preparation method.

[0006] In a first aspect, this application provides an aluminum-plastic composite film, which adopts the following technical solution:

[0007] An aluminum-plastic composite film, from the outside to the inside, includes an outer barrier layer, a first adhesive layer, a permeation barrier layer, a second adhesive layer, a protective layer, and a heat-sealing layer;

[0008] The protective layer comprises the following components in parts by weight:

[0009] 100 parts of ternary random copolymer polypropylene;

[0010] 5-8 parts compatibilizer;

[0011] 10-25 parts of modified filler;

[0012] 1-5 parts of nucleating agent;

[0013] The modified filler is fluorine-containing micro powder and silicon powder treated with silane coupling agent.

[0014] By employing the above technical solution, fluorinated micropowder and silicon powder exhibit excellent corrosion resistance. When the fluorinated micropowder and silicon powder are mixed, the silicon powder, due to its excellent adsorption properties, can adsorb some of the smooth-surfaced fluorinated micropowder. On one hand, the fluorinated micropowder has a low surface energy; the adsorption of some fluorinated micropowder on the silicon powder surface reduces the surface energy of the silicon powder, promoting its dispersion in components such as ternary random copolymer polypropylene, thus improving the corrosion resistance of the resulting protective layer. On the other hand, the silicon powder, acting as a carrier, adsorbs some of the fluorinated micropowder, increasing the bonding strength of the fluorinated micropowder in the ternary random copolymer polypropylene, which is beneficial for the fluorinated micropowder to exert its excellent corrosion resistance in the protective layer.

[0015] Meanwhile, by using a silane coupling agent to treat the surface of the fluorine-containing micropowder and silicon powder, the dispersion and adhesion of the fluorine-containing micropowder and silicon powder in components such as ternary random copolymer polypropylene are further promoted, which is beneficial to improving the corrosion resistance of the resulting protective layer. Moreover, the coating of the fluorine-containing micropowder and silicon powder with a layer of silane coupling agent also increases the compatibility of the protective layer and the second adhesive layer, which is beneficial to improving the bonding strength of the protective layer and the second adhesive layer.

[0016] Therefore, placing the protective layer between the second adhesive layer and the heat-sealing layer is beneficial because the protective layer has good corrosion resistance, which effectively reduces the corrosion of the second adhesive layer, the first adhesive layer, and the external barrier layer by the penetrating electrolyte, thereby improving the electrolyte resistance of the aluminum-plastic film.

[0017] Preferably, the modified filler is prepared by mixing a silane coupling agent, water, and an organic solvent to obtain a mixture; adjusting the pH of the mixture to 4-5, then adding pre-mixed fluorine-containing micro powder and silicon powder, stirring and mixing, filtering, and drying to obtain the modified filler.

[0018] By adopting the above technical solution, fluorine-containing micropowder and silicon powder are first mixed, allowing the silicon powder surface to adsorb some of the fluorine-containing micropowder, which is beneficial to improving the dispersibility of silicon powder in the mixture. Then, a silane coupling agent is dissolved in water and organic solvents, and hydrolyzes to release silanol in an environment with a pH of 4-5. The silanol can bond with the silicon powder and the silicon powder surface that has adsorbed some of the fluorine-containing micropowder, forming a silane coupling agent coating layer on the surface of the fluorine-containing micropowder and silicon powder. This is beneficial to improving the dispersibility and compatibility of fluorine-containing micropowder and silicon powder in components such as ternary random copolymer polypropylene, improving the corrosion resistance of the protective layer, and thus improving the electrolyte resistance of the final aluminum-plastic film.

[0019] Preferably, the silane coupling agent is one or both of phenylsilane coupling agents and epoxy coupling agents.

[0020] By adopting the above technical solutions, the chemical structures of phenylsilane coupling agents and epoxy coupling agents contain phenyl and epoxy groups, giving them excellent resistance to chemical corrosion. Therefore, modifying fluorine-containing micropowders and silicon powder with phenylsilane coupling agents and epoxy coupling agents is beneficial to improving the corrosion resistance of the protective layer and the electrolyte resistance of the final aluminum-plastic composite film.

[0021] Preferably, the silane coupling agent is composed of a mixture of phenylsilane coupling agent and epoxy coupling agent, wherein the weight ratio of phenylsilane coupling agent to epoxy coupling agent is 1:(0.8-1.2).

[0022] By adopting the above technical solution, phenylsilane coupling agent and epoxy coupling agent are mixed and compounded to silanize fluorine-containing micro powder and silicon powder. After coating the surface of fluorine-containing micro powder and silicon powder with an organosilicon layer containing phenyl and epoxy groups, it is added to the protective layer, which helps to improve the corrosion resistance of the protective layer.

[0023] Preferably, the fluorinated micro powder is one or more of polytetrafluoroethylene micro powder, polyvinylidene fluoride micro powder, and perfluoroethylene propylene micro powder.

[0024] By adopting the above technical solutions, polytetrafluoroethylene micro powder, polyvinylidene fluoride micro powder, and perfluoroethylene propylene micro powder have good corrosion resistance. Adding the above fluorine-containing micro powders to the protective layer is beneficial to improving the electrolyte resistance of the final aluminum-plastic composite film.

[0025] Preferably, in the modified filler, the weight ratio of silane coupling agent, fluorinated micro powder and silicon powder is 1:(0.2-0.4):(0.4-0.7).

[0026] By adopting the above technical solution, the weight of silane coupling agent, fluorine-containing micro powder and silicon powder is optimized, which is conducive to the adsorption of fluorine-containing micro powder on the surface of silicon powder and the formation of organic film layer by silane coupling agent on the surface of fluorine-containing micro powder and silicon powder. This improves the dispersibility, compatibility and bonding strength of fluorine-containing micro powder and silicon powder in the protective layer, thereby improving the durable electrolyte resistance of the final aluminum-plastic composite film.

[0027] Preferably, the silicon powder is further pretreated. The pretreatment steps are as follows: adding silicon powder to an alkaline aqueous solution with a pH value of 9-11, stirring and mixing, filtering, washing with water, and drying to obtain pretreated silicon powder.

[0028] By adopting the above technical solution, micro-etching is formed on the surface of silicon powder under a strongly alkaline environment, which roughens the surface of silicon powder and increases the surface area of ​​silicon powder. This is beneficial to increasing the content of fluorine-containing micropowder adsorbed by silicon powder, increasing the bonding strength of fluorine-containing micropowder in ternary random copolymer polypropylene, and enabling fluorine-containing micropowder to exert good corrosion resistance in the protective layer, thereby improving the electrolyte resistance of aluminum-plastic composite film.

[0029] Preferably, the compatibilizer is lanthanum-grafted polypropylene, and the density of the lanthanum-grafted polypropylene is 0.92 g / cm³. 3 The melt flow index at 190℃ and 2.16Kg is 60-80g / 10min.

[0030] By adopting the above technical solution, lanthanum-grafted polypropylene exhibits high reactivity and good compatibility with fluorinated micropowder and silica powder-coated silane coupling agents. This is beneficial for improving the compatibility and bonding strength of fluorinated micropowder and silica powder in ternary random copolymer polypropylene, and enhancing the electrolyte resistance of the protective layer. Simultaneously, the lanthanum-grafted polypropylene heat-sealing layer and the second adhesive layer possess good compatibility, allowing the molecular chains at the compatibility interfaces of the protective layer, barrier layer, and heat-sealing layer to intertwine and bond, thereby improving the bonding strength between the protective layer and the barrier layer / heat-sealing layer.

[0031] Secondly, this application provides a method for preparing an aluminum-plastic composite film, which adopts the following technical solution:

[0032] A method for preparing an aluminum-plastic composite film includes the following steps:

[0033] S1: After mixing ternary random copolymer polypropylene, compatibilizer, modified filler and nucleating agent, the mixture is melt co-extruded to obtain a protective layer;

[0034] S2: From the outside to the inside, the outer barrier layer, the first adhesive layer, the barrier layer, the second adhesive layer, the protective layer obtained in S1, and the heat-sealing layer are combined to obtain an aluminum-plastic composite film.

[0035] By adopting the above technical solution, the barrier layer is directly laminated with the outer barrier layer, protective layer, and heat-sealing layer using an adhesive, reducing the need for a second high-temperature heating of the heat-sealing layer. This results in an aluminum-plastic composite film with excellent deep-drawing performance. Furthermore, the preparation methods for the protective layer and the aluminum-plastic composite film in this application are simple and suitable for large-scale production.

[0036] In summary, this application has the following beneficial effects:

[0037] 1. Because the protective layer prepared by this application using fluorine-containing micro powder and silicon powder treated with silane coupling agent has good corrosion resistance, it can prevent the permeated electrolyte from continuing to penetrate into the second adhesive layer, which is beneficial to improving the electrolyte resistance of the aluminum-plastic composite film.

[0038] 2. In the preparation method of the modified filler in this application, by pre-mixing fluorine-containing micro powder and silicon powder and then modifying with silane coupling agent, it is beneficial for the silane coupling agent to uniformly coat the silicon powder, which is beneficial for improving the dispersibility, compatibility and bonding strength of the modified filler in the protective layer, thereby enabling the protective layer to have long-lasting electrolyte resistance.

[0039] 3. The method for preparing the aluminum-plastic composite film of this application involves using a simple dry process to composite an outer barrier layer, a first adhesive layer, a barrier layer, a second adhesive layer, a protective layer obtained in S1, and a heat-sealing layer. The resulting aluminum-plastic composite film has good deep-drawing performance and electrolyte resistance. Detailed Implementation

[0040] The present application will be further described in detail below with reference to the embodiments.

[0041] Preparation Example

[0042] Preparation Example 1

[0043] A modified filler, the components and their weights (kg) are shown in the table below.

[0044]

[0045] The above-mentioned modified filler includes the following preparation steps:

[0046] A1: Fluorine-containing micro powder was added to silicon powder and ultrasonically stirred at 40 kHz for 2 hours to obtain premixed fluorine-containing micro powder and silicon powder.

[0047] In the preparation example of this application, the fluorinated micro powder is polytetrafluoroethylene propylene micro powder with a whiteness of 98%, an average particle size of 4.2 μm, a thermal weight loss of 0.05% under the condition of 150℃ for 2h, and a melting point of 264℃.

[0048] Silicon powder, with the molecular formula Ca3(Si3O9), a particle size of 325 mesh, a silicon content of >92%, a grade of SF85, a moisture content of 1.2%, and an activity index of 109.

[0049] A2: After mixing silane coupling agent, water and organic solvent, a mixture is obtained; the pH of the mixture is adjusted to 4, and after stirring for 3 hours, pre-mixed fluorine-containing micro powder and silicon powder are added, and the mixture is ultrasonically stirred at 30 kHz for 2 hours, filtered and dried to obtain the modified filler.

[0050] In the preparation example of this application, the silane coupling agent is composed of a mixture of phenylsilane coupling agent and epoxy coupling agent, with a weight ratio of 1:1 between the phenylsilane coupling agent and the epoxy coupling agent. The phenylsilane coupling agent is phenyltriethoxysilane, and the epoxy coupling agent is γ-glycidoxypropyltrimethoxysilane.

[0051] The organic solvent is ethanol.

[0052] Preparation Examples 2-5

[0053] A modified filler differs from Preparation Example 1 in that the components and their weights (kg) are shown in the table below.

[0054]

[0055] Preparation Example 6

[0056] A modified filler, which differs from Preparation Example 1, is provided in that the silane coupling agent is composed of a mixture of phenylsilane coupling agent and epoxy coupling agent in a weight ratio of 1:0.8.

[0057] Preparation Example 7

[0058] A modified filler, which differs from Preparation Example 1, is provided in that the silane coupling agent is composed of a mixture of phenylsilane coupling agent and epoxy coupling agent in a weight ratio of 1:1.2.

[0059] Preparation Example 8

[0060] A modified filler differs from Preparation Example 1 in that the silane coupling agent is composed of a mixture of a methacryloyloxysilane coupling agent and an epoxy coupling agent, with a weight ratio of 1:1 between the methacryloyloxysilane coupling agent and the epoxy coupling agent, wherein the methacryloyloxysilane coupling agent is γ-methacryloyloxypropyltrimethoxysilane.

[0061] Preparation Example 9

[0062] A modified filler, which differs from Preparation Example 1 in that the silane coupling agent is an epoxy coupling agent, wherein the epoxy coupling agent is γ-glycidoxypropyltrimethoxysilane.

[0063] Preparation Example 10

[0064] A modified filler, which differs from Preparation Example 1 in that the silane coupling agent is a phenylsilane coupling agent, wherein the phenylsilane coupling agent is phenyltriethoxysilane.

[0065] Preparation Example 11

[0066] A modified filler, which differs from Preparation Example 1, wherein the silane coupling agent is a phenylsilane coupling agent, wherein the phenylsilane coupling agent is diethoxydiphenylsilane.

[0067] Preparation Example 12

[0068] A modified filler, which differs from Preparation Example 1, is provided in that the silicon powder is pretreated. The pretreatment steps are as follows: silicon powder is added to an alkaline aqueous solution with a pH of 9, ultrasonically stirred at 40 kHz for 1.5 h, filtered, washed with water until the pH value is 7, and dried to obtain pretreated silicon powder.

[0069] Preparation Example 13

[0070] A modified filler, differing from preparation example 1, includes the following preparation steps:

[0071] After mixing silane coupling agent, water and organic solvent, a mixture was obtained. The pH of the mixture was adjusted to 4, and after stirring for 3 hours, fluorine-containing micro powder and silicon powder were added. The mixture was then ultrasonically stirred at 30 kHz for 2 hours, filtered and dried to obtain the modified filler.

[0072] Performance testing

[0073] The peel force of the aluminum-plastic composite films obtained in the embodiments and comparative examples of this application was tested, and the testing method is as follows:

[0074] The aluminum-plastic composite film was cut into 15mm wide and 150mm long pieces. The initial peel force of the barrier layer and the protective layer was tested first. Then, the cut aluminum-plastic composite film was immersed in 1mol / L lithium hexafluorophosphate electrolyte and 1% water was added. Then, it was baked in an oven at 85℃ for 24h. The final peel force of the barrier layer and the protective layer was tested. The peeling speed during the test was 50mm / min.

[0075] Example

[0076] Example 1

[0077] An aluminum-plastic composite film, from the outside to the inside, consists of an outer barrier layer, a first adhesive layer, a permeation barrier layer, a second adhesive layer, a protective layer, and a heat-sealing layer.

[0078] In this embodiment, the material of the outer barrier layer is a commercially available nylon film, customized by Suzhou Hengtuo Packaging Materials Co., Ltd., with a thickness of 20μm;

[0079] The barrier layer is a commercially available passivated aluminum foil, model 3004, with a thickness of 30μm;

[0080] The heat-sealing layer is a commercially available polypropylene insulating film, customized by Wenzhou Xintai New Material Co., Ltd., with a thickness of 20μm.

[0081] The first and second adhesive layers are polyurethane hot melt adhesives, model pur4663, with a thickness of 2μm.

[0082] The protective layer, its components, and their weights (kg) are shown in the table below.

[0083]

[0084] The preparation method of the above-mentioned aluminum-plastic composite film includes the following steps:

[0085] S1: A protective layer is obtained by melt co-extrusion of ternary random copolymer polypropylene, compatibilizer, modified filler, and nucleating agent. In this embodiment, the grade of ternary random copolymer polypropylene is 800EPS; the compatibilizer is lanthanum-grafted polypropylene, type B1, and the density of lanthanum-grafted polypropylene is 0.92 g / cm³. 3 The melt index was 60-80 g / 10 min at 190℃ and 2.16 kg; the modified filler was the modified filler prepared in Preparation Example 1; the nucleating agent was ATL-5803.

[0086] S2: From the outside to the inside, the outer barrier layer, the first adhesive layer, the barrier layer, the second adhesive layer, the protective layer obtained in S1, and the heat-sealing layer are laminated together by a dry process to obtain an aluminum-plastic composite film.

[0087] Example 2-3

[0088] An aluminum-plastic composite film differs from Example 1 in that the components and their weights (kg) in the protective layer are shown in the table below.

[0089]

[0090] The aluminum-plastic composite films obtained in Examples 2-3 of this application were subjected to peel force testing, and the test results are shown in the table below.

[0091]

[0092] Analysis of the data in the table above shows that the initial peel strength of the barrier layer and protective layer in the aluminum-plastic composite films obtained in Examples 1-3 of this application is as high as 13.0-15.8 N / 15 mm, and the final peel strength of the barrier layer and protective layer after immersion in the electrolyte for 24 hours is as high as 11.8-15.0 N / 15 mm. This indicates that the aluminum-plastic composite films obtained in Examples 1-3 of this application still exhibit high peel strength in the barrier layer and protective layer after immersion in the electrolyte for 24 hours, thus demonstrating good electrolyte resistance.

[0093] Examples 4-15

[0094] An aluminum-plastic composite film differs from Example 1 in that the modified filler in the protective layer is prepared using the preparation examples shown in the table below.

[0095] Example Preparation Example Example 4 Preparation Example 2 Example 5 Preparation Example 3 Example 6 Preparation Example 4 Example 7 Preparation Example 5 Example 8 Preparation Example 6 Example 9 Preparation Example 7 Example 10 Preparation Example 8 Example 11 Preparation Example 9 Example 12 Preparation Example 10 Example 13 Preparation Example 11 Example 14 Preparation Example 12 Example 15 Preparation Example 13

[0096] Peel force tests were performed on the aluminum-plastic composite films obtained in Examples 4-15 of this application, and the relative decrease in peel force was calculated. The calculation formula is: Relative decrease in peel force = (Initial peel force - Final peel force) / Initial peel force * 100%. The test results are shown in the table below.

[0097]

[0098]

[0099] Data analysis of the table above shows that, compared to the relative decrease in peel strength of the barrier layer and protective layer in Examples 1, 4, and 5, the relative decrease in peel strength of the barrier layer and protective layer in Examples 6 and 7 is significantly increased. This indicates that, in the total raw materials for preparing the aluminum-plastic composite film of this application, when the weight ratio of silane coupling agent, fluorinated micropowder, and silicon powder in the modified filler of the protective layer is 1:(0.2-0.4):(0.4-0.7), the electrolyte resistance of the aluminum-plastic composite film and the structural strength of the barrier layer and protective layer can be improved.

[0100] Compared to the relative decrease in peel strength of the barrier layer and protective layer in Examples 1, 8, and 9, the relative decrease in peel strength of the barrier layer and protective layer in Examples 10, 11, 12, and 13 is significantly increased. This indicates that, in the total raw materials for preparing the aluminum-plastic composite film of this application, when the modified filler in the protective layer is prepared by mixing phenylsilane coupling agent and epoxy coupling agent at a weight ratio of 1:(0.8-1.2), the electrolyte resistance of the aluminum-plastic composite film can be improved. The reason for this may be that the phenyl and epoxy groups contained in the phenylsilane coupling agent and epoxy coupling agent have good corrosion resistance. Therefore, the combined use of phenylsilane coupling agent and epoxy coupling agent improves the corrosion resistance of the protective layer, thereby improving the electrolyte resistance of the aluminum-plastic composite film.

[0101] Compared to the relative decrease in peel strength of the barrier layer and protective layer in Example 1, the relative decrease in peel strength of the barrier layer and protective layer in Example 14 is significantly lower. This indicates that in the total raw materials for preparing the aluminum-plastic composite film of this application, the silicon powder is pretreated with an alkaline aqueous solution during the preparation of the modified filler in the protective layer, which can improve the electrolyte resistance of the aluminum-plastic composite film. The reason for this may be that the alkaline aqueous solution can corrode the silicon powder, increase the surface area of ​​the silicon powder, which is beneficial to increasing the content of fluorine-containing micropowder adsorbed on the surface of the silicon powder, improving the dispersibility and compatibility of silicon powder in the protective layer components, as well as the bonding strength of fluorine-containing micropowder in the protective layer components, thereby improving the corrosion resistance of the protective layer. This allows the barrier layer and protective layer to still have high peel strength after the aluminum-plastic composite film is immersed in the electrolyte for 24 hours.

[0102] Compared to the relative decrease in peel strength of the barrier layer and protective layer in Example 1, the relative decrease in peel strength of the barrier layer and protective layer in Example 15 is significantly increased. This indicates that, in the total raw materials for preparing the aluminum-plastic composite film of this application, pre-mixing the fluorinated micropowder and silicon powder during the preparation of the modified filler in the protective layer can improve the electrolyte resistance of the aluminum-plastic composite film. The reason for this may be that pre-mixing the fluorinated micropowder and silicon powder promotes the adsorption of fluorinated micropowder by the silicon powder, reducing the surface energy of the silicon powder, promoting its full dispersion and compatibility in the protective layer components, and facilitating the adhesion of the fluorinated micropowder in the protective layer components. This improves the corrosion resistance of the protective layer, ensuring that the barrier layer and protective layer still have high peel strength after immersion in the electrolyte for 24 hours.

[0103] Example 16

[0104] An aluminum-plastic composite film differs from Example 1 in that the compatibilizer is lanthanum-grafted polypropylene, brand name Bynel 50E739, and the density of lanthanum-grafted polypropylene is 0.890 g / cm³. 3 The melt index at 190℃ and 2.16Kg is 6g / 10min.

[0105] Example 17

[0106] An aluminum-plastic composite film differs from Example 1 in that the compatibilizer is lanthanum-grafted polypropylene, type B1A, and the density of the lanthanum-grafted polypropylene is 0.92 g / cm³. 3 The melt index at 190℃ and 2.16Kg is 80-110g / 10min.

[0107] Peel force tests were performed on the aluminum-plastic composite films obtained in Examples 16-17 of this application, and the relative decrease in peel force was calculated. The calculation formula is: Relative decrease in peel force = (Initial peel force - Final peel force) / Initial peel force * 100%. The test results are shown in the table below.

[0108]

[0109] Analysis of the data in the table above shows that, compared to the relative decrease in peel strength of the barrier layer and protective layer in Example 1, the relative decrease in peel strength of the barrier layer and protective layer in Examples 16 and 17 is significantly increased. This indicates that, in the total raw materials for preparing the aluminum-plastic composite film of this application, the density of malachite anhydride-grafted polypropylene is 0.92 g / cm³. 3At 190℃ and 2.16Kg, the melt flow index is 60-80g / 10min, which can improve the corrosion resistance of the aluminum-plastic composite film. The reason for this is likely that the malachite anhydride-grafted polypropylene with the aforementioned physical properties has good compatibility with the modified filler, allowing the modified filler to be fully dispersed in the protective layer and possessing good bonding strength. This improves the corrosion resistance of the protective layer, ensuring that the barrier layer and protective layer of the aluminum-plastic composite film still have high peel strength after immersion in the electrolyte for 24 hours.

[0110] Meanwhile, compared to Examples 16 and 17, the initial peel force of the barrier layer and protective layer in Example 1 is higher. The reason for this is likely that the malachite anhydride-grafted polypropylene, with its aforementioned physical properties, not only has good processing performance but also good strength. This allows the molecular chains at the compatibility interfaces of the protective layer, the second adhesive layer, and the heat-sealing layer to intertwine and bond together during lamination, thereby improving the adhesion strength between the barrier layer and the protective layer, and between the protective layer and the heat-sealing layer.

[0111] Comparative Example

[0112] Comparative Example 1

[0113] An aluminum-plastic composite film differs from Example 1 in that, from the outside to the inside, it consists of an outer barrier layer, a first adhesive layer, a permeation barrier layer, a second adhesive layer, and a heat-sealing layer.

[0114] Comparative Example 2

[0115] An aluminum-plastic composite film differs from Example 1 in that the modified filler in the protective layer is a mixture of fluorine-containing micro powder and silicon powder.

[0116] The above-mentioned modified filler includes the following preparation steps:

[0117] Fluorine-containing micropowder was added to silicon powder and ultrasonically stirred at 40 kHz for 2 hours to obtain premixed fluorine-containing micropowder and silicon powder.

[0118] Comparative Example 3

[0119] An aluminum-plastic composite film differs from Example 1 in that the modified filler in the protective layer is a fluorinated micropowder treated with a silane coupling agent.

[0120] The above-mentioned modified filler includes the following preparation steps:

[0121] The silane coupling agent, water, and organic solvent were mixed to obtain a mixture. The pH of the mixture was adjusted to 4, and the mixture was stirred for 3 hours. Then, the pre-mixed fluorine-containing micro powder was added, and the mixture was ultrasonically stirred at 30 kHz for 2 hours. The mixture was then filtered and dried to obtain the modified filler.

[0122] Comparative Example 4

[0123] An aluminum-plastic composite film differs from Example 1 in that the modified filler in the protective layer is silicon powder treated with a silane coupling agent.

[0124] The above-mentioned modified filler includes the following preparation steps:

[0125] The silane coupling agent, water, and organic solvent were mixed to obtain a mixture. The pH of the mixture was adjusted to 4, and the mixture was stirred for 3 hours. Then, pre-mixed silicon powder was added, and the mixture was ultrasonically stirred at 30 kHz for 2 hours. The mixture was then filtered and dried to obtain the modified filler.

[0126] Peel force tests were conducted on the aluminum-plastic composite films obtained in Comparative Examples 1-4 of this application, and the relative decrease in peel force was calculated. The calculation formula is: Relative decrease in peel force = (Initial peel force - Final peel force) / Initial peel force * 100%. The test results are shown in the table below.

[0127]

[0128]

[0129] Analysis of the data in the table above shows that, compared to the relative decrease in peel strength of the barrier layer and protective layer in Example 1, the initial peel strength of the barrier layer and protective layer in Comparative Example 1 is significantly lower, while the relative decrease in peel strength of the barrier layer and protective layer is significantly higher. This indicates that the aluminum-plastic composite film, composed of an outer barrier layer, a first adhesive layer, a barrier layer, a second adhesive layer, a protective layer, and a heat-sealing layer from the outside in, can improve the electrolyte resistance of the aluminum-plastic composite film. The reason for this may be that the fluorinated micropowder and silicon powder treated with silane coupling agent in the protective layer have good corrosion resistance, preventing the electrolyte that has penetrated into the protective layer from further penetrating into the second adhesive layer, thereby improving the corrosion resistance of the aluminum-plastic composite film. Meanwhile, the lanthanum-grafted polypropylene in the protective layer exhibits good compatibility with the second adhesive layer and the heat-sealing layer, causing the molecular chains at the compatibility interface of the second adhesive layer and the heat-sealing layer to intertwine and bond together, thus improving the bonding strength between the barrier layer and the protective layer. Compared to the reduction in the peel force of the barrier layer and the protective layer in Example 1, the initial peel force of the barrier layer and the protective layer in Comparative Examples 2, 3, and 4 is significantly reduced, while the reduction in the relative peel force of the barrier layer and the protective layer is significantly increased. This indicates that in the total raw materials for preparing the aluminum-plastic composite film, the modified filler, consisting of fluorinated micropowder and silicon powder treated with silane coupling agent, can improve the electrolyte resistance of the aluminum-plastic composite film, ensuring that the barrier layer and the protective layer still possess high peel force after immersion in the electrolyte for 24 hours. The reason for this may be that the fluorine-containing micro powder and silicon powder treated with silane coupling agent have good compatibility and bonding strength in the protective layer, which makes the protective layer have long-lasting corrosion resistance. Thus, the protective layer can prevent the permeating electrolyte from continuously penetrating into the second adhesive layer, thereby improving the electrolyte resistance of the aluminum-plastic composite film.

[0130] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. An aluminum-plastic composite film, characterized in that, From the outside to the inside, it includes an outer barrier layer, a first adhesive layer, a barrier layer, a second adhesive layer, a protective layer, and a heat-sealing layer; The protective layer comprises the following components in parts by weight: 100 parts of ternary random copolymer polypropylene; 5-8 parts compatibilizer; 10-25 parts of modified filler; 1-5 parts of nucleating agent; The modified filler is fluorine-containing micro powder and silicon powder treated with silane coupling agent; The modified filler is prepared by mixing silane coupling agent, water and organic solvent to obtain a mixture; adjusting the pH of the mixture to 4-5, then adding pre-mixed fluorine-containing micro powder and silicon powder, stirring and mixing, filtering and drying to obtain the modified filler; The silane coupling agent is composed of a mixture of phenylsilane coupling agent and epoxy coupling agent, with a weight ratio of phenylsilane coupling agent to epoxy coupling agent of 1:(0.8-1.2). In the modified filler, the weight ratio of silane coupling agent, fluorinated micro powder and silicon powder is 1:(0.2-0.4):(0.4-0.7).

2. The aluminum-plastic composite film according to claim 1, characterized in that, The fluorine-containing micro powder is one or more of polytetrafluoroethylene micro powder, polyvinylidene fluoride micro powder, and perfluoroethylene propylene micro powder.

3. The aluminum-plastic composite film according to claim 1, characterized in that, The silicon powder is also pretreated. The pretreatment steps are as follows: add silicon powder to an alkaline aqueous solution with a pH value of 9-11, stir and mix, filter, wash with water, and dry to obtain pretreated silicon powder.

4. The aluminum-plastic composite film according to claim 1, characterized in that, The compatibilizer is lanthanum-grafted polypropylene, which has a density of 0.92 g / cm³ and a melt index of 60-80 g / 10 min at 190℃ and 2.16 kg.

5. The method for preparing the aluminum-plastic composite film according to any one of claims 1-4, characterized in that, Includes the following steps: S1: After mixing ternary random copolymer polypropylene, compatibilizer, modified filler and nucleating agent, the mixture is melt co-extruded to obtain a protective layer; S2: From the outside to the inside, the outer barrier layer, the first adhesive layer, the barrier layer, the second adhesive layer, the protective layer obtained in S1, and the heat-sealing layer are combined to obtain an aluminum-plastic composite film.

Images