Inner-layer adhesive for aluminum-plastic film, preparation method and related application

Abstract

The invention discloses an inner-layer adhesive for an aluminum-plastic film, the inner-layer adhesive comprises matrix resin, epoxy resin and a thiol compound, and the mass ratio of the matrix resin to the epoxy resin to the thiol compound is (10-20): (0.41-1.23): (0.001-0.06). The invention also provides an aluminum plastic film which comprises the inner layer adhesive. The invention also provides a battery which comprises the inner layer adhesive. The invention further provides a preparation method of the aluminum-plastic film, which comprises the following steps: mixing the matrix resin, the epoxy resin and the thiol compound in a mass ratio of (10-20): (0.41-1.23): (0.001-0.06) to form a dispersion liquid; a curing accelerator is added, uniform stirring is performed to form an inner-layer adhesive, and the adding amount of the curing accelerator accounts for 0.1 wt%-8 wt% of the inner-layer adhesive; and coating the inner-layer adhesive between the aluminum foil layer and the heat-sealing layer, and curing at room temperature, so that the inner-layer adhesive bonds the aluminum foil layer and the heat-sealing layer to obtain the aluminum-plastic film.

Description

Technical Field

[0001] This invention relates to the field of aluminum-plastic film technology for lithium-ion batteries, specifically to a method for preparing an aluminum-plastic film using an epoxy-thiol system as the inner layer adhesive, and the battery thereof. Background Technology

[0002] Aluminum-plastic film, as an important packaging material for soft-pack lithium batteries, generally consists of an outer layer (nylon or polyester film), a middle layer (aluminum foil layer), and an inner layer (heat-sealing layer). The bonding performance and chemical resistance of the inner layer adhesive have a significant impact on the long-term performance of the aluminum-plastic film. Currently, traditional inner layer adhesives typically use polyurethane systems. These adhesives require curing treatment to achieve ideal performance, increasing production complexity and cost. Furthermore, the curing process may introduce environmental pollution.

[0003] There is an urgent need for an inner layer adhesive that does not require curing and can provide excellent bonding performance and chemical stability in order to improve the production efficiency of aluminum-plastic film and reduce production costs. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the main objective of this invention is to provide an inner layer adhesive for aluminum-plastic film, a preparation method and related applications, so as to improve the bonding strength, chemical resistance, thermal stability and mechanical properties of aluminum-plastic film structure.

[0005] In a first aspect, in some embodiments of the present invention, an inner layer adhesive for aluminum-plastic film is provided, wherein the inner layer adhesive comprises: a main resin, an epoxy resin and a thiol compound, wherein the mass ratio of the main resin, the epoxy resin and the thiol compound is (10-20):(0.41-1.23):(0.001-0.06).

[0006] In some embodiments of the present invention, the mass ratio of the main resin, epoxy resin and thiol compound is 15:0.82:0.03.

[0007] In some embodiments of the present invention, the inner layer adhesive further includes a curing accelerator, wherein the amount of the curing accelerator added is 0.1 wt% to 8 wt% of the inner layer adhesive. In some embodiments of the present invention, the amount of the curing accelerator added is 2 wt% of the inner layer adhesive.

[0008] In some embodiments of the present invention, the ratio of epoxy equivalent in the epoxy resin to hydroxyl equivalent of the host resin ranges from 2.5 to 4.5; wherein the ratio of thiol equivalent of the thiol compound to epoxy equivalent in the epoxy resin is less than or equal to 0.25.

[0009] In some embodiments of the present invention, the main resin includes at least one of acid-modified polypropylene resin, maleic anhydride-modified styrene, or polyolefin elastomer.

[0010] In some embodiments of the present invention, the epoxy resin includes at least one of bisphenol F type epoxy resin, phenolic epoxy resin, or alicyclic epoxy resin.

[0011] In some embodiments of the present invention, the thiol compound includes at least one of the following: trimercaptopropionic acid, tris[(3-mercaptopropionyloxy)-ethyl]-isocyanurate, 1,3,5-tris(3-mercaptopropyl)-1,3,5-triazine trione, mercaptosilane, trimethylolpropane tris(3-mercaptopropionate), 1,4-butanediol di(3-mercaptopropionate), pentaerythritol tetra(3-mercaptopropionate), ethylene glycol di(3-mercaptopropionate), trimercaptothiol, tetrafunctional secondary thiol PE1, and polythiols.

[0012] In some embodiments of the present invention, the curing accelerator includes at least one of tertiary amine compounds, imidazole compounds, DBU salts, BDMA, or DMP-30.

[0013] In some embodiments of the present invention, the inner adhesive layer further includes: an additive, wherein the additive is at least one selected from toughening agents, leveling agents, or weather-resistant additives. The toughening agent includes at least one selected from polymethyl methacrylate, polybutyl methacrylate, polybutyl acrylate, polyacrylate, polymethyl methacrylate, or polystyrene-methyl methacrylate copolymer. The leveling agent is a siloxane-based leveling agent. The weather-resistant additive includes at least one selected from ultraviolet absorbers or hindered amine light stabilizers.

[0014] In some embodiments of the present invention, the epoxy resin and thiol compound undergo a crosslinking reaction at room temperature.

[0015] In some embodiments of the present invention, after the aluminum foil layer, inner adhesive layer and heat-sealing layer are cured at room temperature for 5 to 19 hours, the initial peel strength between the inner adhesive layer and the aluminum foil layer and the heat-sealing layer is ≥16N / 15mm. After immersion in an electrolyte at 75 to 95°C for 0.5 to 1.5 days, the liquid resistance peel strength between the inner adhesive layer and the aluminum foil layer and the heat-sealing layer is ≥16N / 15mm.

[0016] Secondly, some embodiments of the present invention provide an aluminum-plastic film, including the inner layer adhesive provided in any embodiment of the first aspect.

[0017] Thirdly, some embodiments of the present invention provide a battery comprising the inner layer adhesive for aluminum-plastic film provided in any embodiment of the first aspect.

[0018] Fourthly, some embodiments of the present invention provide a method for preparing an aluminum-plastic film, characterized in that it includes: A dispersion is formed by mixing a main resin, an epoxy resin, and a thiol compound, wherein the mass ratio of the main resin, epoxy resin, and thiol compound is (10-20):(0.41-1.23):(0.001-0.06). A curing accelerator is added to the dispersion and stirred evenly to form an inner layer adhesive, wherein the amount of the curing accelerator added is 0.1 wt% to 8 wt% of the inner layer adhesive; and the inner layer adhesive is coated between the aluminum foil layer and the heat-sealing layer and cured at room temperature to bond the aluminum foil layer and the heat-sealing layer together to obtain an aluminum-plastic film.

[0019] In some embodiments of the present invention, the mass ratio of the main resin, epoxy resin, and thiol compound is (10-20):(0.41-1.23):(0.001-0.06). In addition, the amount of curing accelerator added accounts for 2 wt% of the inner layer adhesive, and the ratio of the epoxy equivalent in the epoxy resin to the hydroxyl equivalent of the main resin is in the range of 2.5 to 4.5; wherein the ratio of the thiol equivalent of the thiol compound to the epoxy equivalent in the epoxy resin is less than or equal to 0.25.

[0020] In some embodiments of the present invention, after the aluminum foil layer, the inner adhesive layer and the heat-sealing layer are cured at room temperature for 5 to 19 hours, the initial peel strength between the inner adhesive layer and the aluminum foil layer and the heat-sealing layer is ≥16N / 15mm. After being immersed in an electrolyte at 75 to 95°C for 0.5 to 1.5 days, the liquid-resistant peel strength between the inner adhesive layer and the aluminum foil layer and the heat-sealing layer is ≥16N / 15mm.

[0021] In some embodiments of the present invention, the heat-sealing layer is made of cast polypropylene (CPP).

[0022] In some embodiments of the present invention, the inner adhesive further includes additives.

[0023] In some embodiments of the present invention, the additives include at least one of toughening agents, leveling agents, or weather-resistant additives.

[0024] The aluminum-plastic film provided by this invention comprises an inner layer adhesive based on an epoxy-thiol system. Through cross-linking and curing reactions of the epoxy resin and thiol compounds at room temperature, highly efficient bonding is achieved between the aluminum foil layer, the inner adhesive layer, and the heat-sealing layer (i.e., high peel strength between the inner adhesive layer and the aluminum foil layer and heat-sealing layer). This eliminates the need for traditional curing processes, significantly shortening the production cycle. The inner adhesive used as the inner layer adhesive in the aluminum-plastic film imparts superior electrolyte resistance, chemical resistance, and thermal stability. Furthermore, the strong bonding force between the inner adhesive and the aluminum foil layer and heat-sealing layer further enhances the stability and safety of the lithium-ion battery encapsulated in the aluminum-plastic film.

[0025] In addition, since the aluminum-plastic film provided by this invention omits the traditional curing process, it is particularly suitable for efficient and environmentally friendly industrial production scenarios and has significant market promotion value. Attached Figure Description

[0026] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0027] Figure 1 This is a schematic diagram of the structure of an aluminum-plastic film provided in an embodiment of the present invention. The diagram shows that the aluminum-plastic film basically includes an outer layer (e.g., a nylon layer), a middle layer (e.g., an aluminum foil layer), and an inner layer (e.g., a heat-sealing layer). An inner adhesive layer is further included between the aluminum foil layer and the heat-sealing layer.

[0028] Figure 2 A process flow diagram of the method for preparing aluminum-plastic film provided in an embodiment of the present invention.

[0029] Component designation explanation:

[0030] 100 aluminum-plastic film

[0031] 101 Nylon

[0032] 102 aluminum foil layer

[0033] 103 Inner Adhesive Layer

[0034] 104 heat seal layer

[0035] S210 Step

[0036] S220 Steps

[0037] S230 Steps Detailed Implementation

[0038] To make the above and / or other objects, effects, and features of the present invention more apparent and understandable, preferred embodiments are described in detail below:

[0039] like Figure 1 As shown, the main objective of this invention is to provide an aluminum-plastic film 100, which comprises, from the outside to the inside, a nylon 101, an aluminum foil layer 102, an inner adhesive layer 103, and a heat-sealing layer 104. The inner adhesive layer comprises a base resin, an epoxy resin, and a thiol compound. In some embodiments, the inner adhesive layer comprises a base resin, an epoxy resin, a thiol compound, and a curing accelerator.

[0040] As an example, the mass ratio of the main resin, epoxy resin, and thiol compound ranges from (10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20): (0.41, 0.45, 0.50, 0.55, 0.60, 0.65, 0.70, 0.75, 0.80, 0.85, 0.90, 0.95, 1.00, 1.05, 1.10, 1.15, 1.20, 1.21, 1.22, or 1.23): (0.001, 0.005, 0.01, 0.02, 0.03, 0.04, 0.05, or 0.06). Optionally, the mass ratio of the main resin, epoxy resin and thiol compound is (10-20):(0.41-1.23):(0.001-0.06).

[0041] As an example, the amount of curing accelerator added is 0.1 wt%, 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, or 8 wt% of the inner layer adhesive. Optionally, the amount of curing accelerator added is in the range of 0.1 wt% to 8 wt% of the inner layer adhesive. Optionally, the amount of curing accelerator added is 2 wt% of the inner layer adhesive.

[0042] As an example, the ratio of epoxy equivalent in the epoxy resin to the hydroxyl equivalent of the host resin is 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.5, 4.0, 4.1, 4.2, 4.3, 4.4, or 4.5. Optionally, the ratio of epoxy equivalent in the epoxy resin to the hydroxyl equivalent of the host resin ranges from 2.5 to 4.5.

[0043] As an example, the ratio of the thiol equivalent of the thiol compound to the epoxy equivalent in the epoxy resin is less than or equal to 0.25, 0.24, 0.23, 0.22, 0.21, 0.20, 0.15, 0.10, 0.05, 0.01, 0.005, 0.001, or 0.0001. Optionally, the ratio of the thiol equivalent of the thiol compound to the epoxy equivalent in the epoxy resin is less than or equal to 0.25.

[0044] In some embodiments, the host resin includes at least one of acid-modified polypropylene resin, maleic anhydride-modified styrene, or polyolefin elastomer. Optionally, the host resin includes acid-modified polypropylene resin.

[0045] In some embodiments, the epoxy resin includes at least one of bisphenol F type epoxy resin, phenolic epoxy resin, or alicyclic epoxy resin. Optionally, the epoxy resin includes bisphenol F type epoxy resin.

[0046] In some embodiments, the thiol compound comprises multiple mercapto (-SH) groups and acts as a curing agent. Optionally, the thiol compound includes at least one of the following: trimercaptopropionic acid, tris[(3-mercaptopropionyloxy)-ethyl]-isocyanurate, 1,3,5-tris(3-mercaptopropyl)-1,3,5-triazine trione, mercaptosilane, trimethylolpropane tris(3-mercaptopropionate), 1,4-butanediol di(3-mercaptopropionate), pentaerythritol tetra(3-mercaptopropionate), ethylene glycol di(3-mercaptopropionate), trimercaptothiol, tetrafunctional secondary thiol PE1, and polythioglycolic acid polyol.

[0047] In some embodiments, the curing accelerator includes at least one of a tertiary amine compound, an imidazole compound, a DBU salt, BDMA, or DMP-30. Optionally, the curing accelerator is triethylamine. In some embodiments, the curing accelerator is used to promote the crosslinking reaction of the epoxy-thiol system; specifically, the curing accelerator is used to promote the crosslinking reaction of the epoxy resin and the thiol compound.

[0048] In some embodiments, the inner adhesive layer 103 further includes: additives. The additives are at least one of toughening agents, leveling agents, or weather-resistant additives. Toughening agents include at least one of polymethyl methacrylate, polybutyl methacrylate, polybutyl acrylate, polyacrylate, polymethyl methacrylate, or polystyrene-methyl methacrylate copolymers; leveling agents are siloxane leveling agents; and / or weather-resistant additives include at least one of ultraviolet absorbers (UV Absorbers, also known as UVA) or hindered amine light stabilizers.

[0049] In some embodiments, the epoxy resin and thiol compound undergo a crosslinking reaction at room temperature.

[0050] As an example, after the aluminum foil layer 102, the inner adhesive layer 103, and the heat-sealing layer are cured at room temperature for 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, or 19 hours, a peel strength test or an electrolyte immersion test is performed. Optionally, after the aluminum foil layer 102, the inner adhesive layer 103, and the heat-sealing layer 104 are cured at room temperature for 12 hours...

[0051] In some embodiments, after curing at room temperature for 5 to 19 hours, the inner adhesive layer 103, aluminum foil layer 102, and heat-sealing layer 104 are subjected to an electrolyte immersion test. As an example, the immersion temperature in the electrolyte is 75°C, 80°C, 85°C, 90°C, or 95°C, optionally 85°C. As an example, the immersion period in the electrolyte is 0.5 days, 1 day, or 1.5 days, optionally 1 day.

[0052] In some embodiments, after the aluminum foil layer 102, the inner adhesive layer 103, and the heat-sealing layer 104 are cured at room temperature for 12 hours, the initial peel strength of the inner adhesive layer 103 and the aluminum foil layer 102 and the heat-sealing layer and the liquid-resistant peel strength after immersion in the electrolyte are substantially unchanged.

[0053] In some embodiments, after the aluminum foil layer 102, the inner adhesive layer 103 and the heat-sealing layer are cured at room temperature for 12 hours, the initial peel strength between the inner adhesive layer 103 and the aluminum foil layer 102 and the heat-sealing layer 104 is ≥16N / 15mm. After being immersed in an electrolyte at 85°C for 1 day, the liquid-resistant peel strength between the inner adhesive layer 103 and the aluminum foil layer 102 and the heat-sealing layer 104 is ≥16N / 15mm.

[0054] As an example, the initial peel strength of the inner adhesive layer 103 to the aluminum foil layer 102 and the heat-sealing layer 104 is 16N / 15mm, 17.0N / 15mm, 17.5N / 15mm, 18.0N / 15mm, 18.5N / 15mm, 19.0N / 15mm, 19.5N / 15mm, 20.0N / 15mm, 20.5N / 15mm, 21.0N / 15mm, 21.5N / 15mm, 22.0N / 15mm, 22.5N / 15mm, 23.0N / 15mm, 23.5N / 15mm, 24.0N / 15mm, 24.5N / 15mm or 25.0N / 15mm.

[0055] As an example, the liquid peel strength of the inner adhesive layer 103 to the aluminum foil layer 102 and the heat-sealing layer 104 is 16N / 15mm, 17.0N / 15mm, 17.5N / 15mm, 18.0N / 15mm, 18.5N / 15mm, 19.0N / 15mm, 19.5N / 15mm, 20.0N / 15mm, 20.5N / 15mm, 21.0N / 15mm, 21.5N / 15mm, 22.0N / 15mm, 22.5N / 15mm, 23.0N / 15mm, 23.5N / 15mm, 24.0N / 15mm, 24.5N / 15mm or 25.0N / 15mm.

[0056] Another object of the present invention is to provide an aluminum-plastic film 100, which includes the inner layer adhesive for the aluminum-plastic film 100 as described above.

[0057] Another object of the present invention is to provide a battery comprising an inner layer adhesive for the aluminum-plastic film 100 as described above.

[0058] like Figure 2 As shown, another objective of the present invention is to provide a method for preparing the aforementioned aluminum-plastic film 100, comprising: S210, a mixture of main resin, epoxy resin and thiol compound to form a dispersion, wherein the mass ratio of main resin, epoxy resin and thiol compound is (10-20):(0.41-1.23):(0.001-0.06); S220, add a curing accelerator and stir evenly to form an inner layer adhesive, wherein the amount of curing accelerator added is in the range of 0.1wt% to 8wt% of the inner layer adhesive; and S230, coat the inner layer adhesive between the aluminum foil layer 102 and the heat-sealing layer 104, and cure it at room temperature so that the inner layer adhesive bonds the aluminum foil layer 102 and the heat-sealing layer 104 to obtain an aluminum-plastic film 100.

[0059] In some embodiments, the heat-sealing layer 104 is made of cast polypropylene (CPP).

[0060] In some embodiments, the inner adhesive further includes additives. The additives include at least one of toughening agents, leveling agents, or weather-resistant auxiliaries.

[0061] To make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer are used. Where the manufacturer of the reagents or instruments is not specified, all are conventional products that can be purchased commercially.

[0062] The above-described embodiments of the present invention are illustrated by the following examples:

[0063] Table 1. Composition of the inner layer adhesive in the aluminum-plastic films of the examples and comparative examples.

[0064] In Table 1, "EEW / HEW" represents the ratio of epoxy equivalent in the epoxy resin to the hydroxyl equivalent in the host resin. "TEW / EEW" represents the ratio of thiol equivalent in the thiol compound to the epoxy equivalent in the epoxy resin.

[0065] Table 2. Curing times of the examples and comparative examples

[0066] Example 1

[0067] In terms of composition, the inner layer adhesive for the lithium battery encapsulation aluminum-plastic film in this embodiment includes at least a main resin (taking acid-modified polypropylene resin as an example), an epoxy resin (taking bisphenol F type epoxy resin as an example), and a thiol compound (taking trimercaptopropionic acid as an example) in a mass ratio of 20:0.41:0.06, and a curing accelerator (taking triethylamine as an example) added in an amount of 2 wt% of the inner layer adhesive.

[0068] In terms of the preparation process, the main resin, epoxy resin, and thiol compound are mixed in the aforementioned mass ratio to form a dispersion. Next, triethylamine is added and stirred until homogeneous to form the inner layer adhesive. The inner layer adhesive is coated between the aluminum foil layer and the heat-sealing layer and cured at room temperature for 12 hours to obtain the composite aluminum-plastic film.

[0069] In addition, the aforementioned composite aluminum-plastic film is used to prepare lithium batteries.

[0070] Example 2

[0071] In terms of composition, the inner layer adhesive for the lithium battery encapsulation aluminum-plastic film in this embodiment includes at least a main resin (maleic anhydride modified styrene as an example), an epoxy resin (bisphenol F type epoxy resin as an example), and a thiol compound (trimercaptopropionic acid as an example) in a mass ratio of 10:1.23:0.06, and a curing accelerator (triethylamine as an example) added in an amount of 2 wt% of the inner layer adhesive.

[0072] In terms of the preparation process, the main resin, epoxy resin, and thiol compound are mixed in the aforementioned mass ratio to form a dispersion. Next, triethylamine is added and stirred until homogeneous to form the inner layer adhesive. The inner layer adhesive is coated between the aluminum foil layer and the heat-sealing layer and cured at room temperature for 12 hours to obtain the composite aluminum-plastic film.

[0073] In addition, the aforementioned composite aluminum-plastic film is used to prepare lithium batteries.

[0074] Example 3

[0075] In terms of composition, the inner layer adhesive for the lithium battery encapsulation aluminum-plastic film in this embodiment includes at least a main resin (taking polyolefin elastomer as an example), an epoxy resin (taking alicyclic epoxy resin as an example), and a thiol compound (taking trimercaptopropionic acid as an example) in a mass ratio of 15:0.82:0.03, and a curing accelerator (taking triethylamine as an example) added in an amount of 2 wt% of the inner layer adhesive.

[0076] In terms of the preparation process, the main resin, epoxy resin, and thiol compound are mixed in the aforementioned mass ratio to form a dispersion. Next, triethylamine is added and stirred until homogeneous to form the inner layer adhesive. The inner layer adhesive is coated between the aluminum foil layer and the heat-sealing layer and cured at room temperature for 12 hours to obtain the composite aluminum-plastic film.

[0077] In addition, the aforementioned composite aluminum-plastic film is used to prepare lithium batteries.

[0078] Example 4

[0079] In terms of composition, the inner layer adhesive for the lithium battery encapsulation aluminum-plastic film in this embodiment includes at least a main resin (taking acid-modified polypropylene resin as an example), an epoxy resin (taking bisphenol F type epoxy resin as an example), and a thiol compound (taking trimercaptopropionic acid as an example) in a mass ratio of 15:0.82:0.06, and a curing accelerator (taking triethylamine as an example) added in an amount of 2 wt% of the inner layer adhesive.

[0080] In terms of the preparation process, the main resin, epoxy resin, and thiol compound are mixed in the aforementioned mass ratio to form a dispersion. Next, triethylamine is added and stirred until homogeneous to form the inner layer adhesive. The inner layer adhesive is coated between the aluminum foil layer and the heat-sealing layer and cured at room temperature for 12 hours to obtain the composite aluminum-plastic film.

[0081] In addition, the aforementioned composite aluminum-plastic film is used to prepare lithium batteries.

[0082] Example 5

[0083] In terms of composition, the inner layer adhesive for the lithium battery encapsulation aluminum-plastic film in this embodiment includes at least a main resin (taking acid-modified polypropylene resin as an example), an epoxy resin (taking phenolic epoxy resin as an example), and a thiol compound (taking trimercaptopropionic acid as an example) in a mass ratio of 20:0.41:0.006, as well as a curing accelerator (taking triethylamine as an example) added in an amount of 2 wt% of the inner layer adhesive.

[0084] In terms of the preparation process, the main resin, epoxy resin, and thiol compound are mixed in the aforementioned mass ratio to form a dispersion. Next, triethylamine is added and stirred until homogeneous to form the inner layer adhesive. The inner layer adhesive is coated between the aluminum foil layer and the heat-sealing layer and cured at room temperature for 12 hours to obtain the composite aluminum-plastic film.

[0085] In addition, the aforementioned composite aluminum-plastic film is used to prepare lithium batteries.

[0086] Comparative Example 1

[0087] In terms of composition, the inner layer adhesive for the lithium battery encapsulation aluminum-plastic film in this embodiment includes at least a main resin (taking acid-modified polypropylene resin as an example), an epoxy resin (taking alicyclic epoxy resin as an example), and a thiol compound (taking trimercaptopropionic acid as an example) in a mass ratio of 40:0.41:0.06, and a curing accelerator (taking triethylamine as an example) added in an amount of 2 wt% of the inner layer adhesive.

[0088] In terms of the preparation process, the main resin, epoxy resin, and thiol compound are mixed in the aforementioned mass ratio to form a dispersion. Next, triethylamine is added and stirred until homogeneous to form the inner layer adhesive. The inner layer adhesive is coated between the aluminum foil layer and the heat-sealing layer and cured at room temperature for 12 hours to obtain the composite aluminum-plastic film.

[0089] In addition, the aforementioned composite aluminum-plastic film is used to prepare lithium batteries.

[0090] Comparative Example 2

[0091] In terms of composition, the inner layer adhesive for the lithium battery encapsulation aluminum-plastic film in this embodiment includes at least a main resin (taking acid-modified polypropylene resin as an example), an epoxy resin (taking bisphenol F type epoxy resin as an example), and a thiol compound (taking trimercaptopropionic acid as an example) in a mass ratio of 20:1.64:0.06, and a curing accelerator (taking triethylamine as an example) added in an amount of 2 wt% of the inner layer adhesive.

[0092] In terms of the preparation process, the main resin, epoxy resin, and thiol compound are mixed in the aforementioned mass ratio to form a dispersion. Next, triethylamine is added and stirred until homogeneous to form the inner layer adhesive. The inner layer adhesive is coated between the aluminum foil layer and the heat-sealing layer and cured at room temperature for 12 hours to obtain the composite aluminum-plastic film.

[0093] In addition, the aforementioned composite aluminum-plastic film is used to prepare lithium batteries.

[0094] Comparative Example 3

[0095] In terms of composition, the inner layer adhesive for the lithium battery encapsulation aluminum-plastic film in this embodiment includes at least a main resin (maleic anhydride modified styrene as an example), an epoxy resin (phenolic epoxy resin as an example), and a thiol compound (trimercaptopropionic acid as an example) in a mass ratio of 20:0.41:0.09, and a curing accelerator (triethylamine as an example) added at 1 wt% of the inner layer adhesive.

[0096] In terms of the preparation process, the main resin, epoxy resin, and thiol compound are mixed in the aforementioned mass ratio to form a dispersion. Next, triethylamine is added and stirred until homogeneous to form the inner layer adhesive. The inner layer adhesive is coated between the aluminum foil layer and the heat-sealing layer and cured at room temperature for 12 hours to obtain the composite aluminum-plastic film.

[0097] In addition, the aforementioned composite aluminum-plastic film is used to prepare lithium batteries.

[0098] Comparative Example 4

[0099] In terms of composition, the inner layer adhesive for the lithium battery encapsulation aluminum-plastic film in this embodiment includes at least a main resin (taking polyolefin elastomer as an example), isocyanate (taking toluene diisocyanate as an example), and polyol (taking polyoxypropylene glycol as an example) in a mass ratio of 10:23:100, and a curing accelerator (taking triethylamine as an example) added in an amount of 2 wt% of the inner layer adhesive.

[0100] In terms of the preparation process, the main resin, isocyanate, and polyol are mixed in the aforementioned mass ratio to form a dispersion. Next, triethylamine is added and stirred until homogeneous to form the inner layer adhesive. The inner layer adhesive is coated between the aluminum foil layer and the heat-sealing layer, and a curing process is performed at 60°C for 5 days to obtain the composite aluminum-plastic film.

[0101] In addition, the aforementioned composite aluminum-plastic film is used to prepare lithium batteries.

[0102] Comparative Example 5

[0103] In terms of composition, the inner layer adhesive for the lithium battery encapsulation aluminum-plastic film in this embodiment includes at least a main resin (taking acid-modified polypropylene resin as an example), isocyanate (taking toluene diisocyanate as an example), and polyol (not added) in a mass ratio of 100:2:12, and a curing accelerator (taking triethylamine as an example) added in an amount of 1 wt% of the inner layer adhesive.

[0104] In terms of the preparation process, the main resin, isocyanate, and polyol are mixed in the aforementioned mass ratio to form a dispersion. Next, triethylamine is added and stirred until homogeneous to form the inner layer adhesive. The inner layer adhesive is coated between the aluminum foil layer and the heat-sealing layer, and a curing process is performed at 60°C for 5 days to obtain the composite aluminum-plastic film.

[0105] In addition, the aforementioned composite aluminum-plastic film is used to prepare lithium batteries.

[0106] Test method:

[0107] 1. Peel strength test

[0108] The peel strength test is basically conducted in accordance with GB / T 8808-1988.

[0109] The peel strength test of aluminum-plastic film is divided into two stages: the initial peel strength test after curing and the liquid resistance peel strength test after immersion in electrolyte.

[0110] The electrolyte is prepared by mixing ethylene carbonate, diethyl carbonate, and dimethyl carbonate in a mass ratio of 1:1:1, and then adding 1 mol of lithium hexafluorophosphate to the mixture. The free water content of the electrolyte does not exceed 50 ppm. Furthermore, all reagents used in the electrolyte are of analytical grade purity. The immersion conditions in the electrolyte are as follows: the aluminum-plastic film is cut into 15 mm × 100 mm samples, the samples are placed in the electrolyte at 85 °C for 24 hours, and then wiped clean after being removed and allowed to cool naturally to room temperature.

[0111] All test results are shown in the table below:

[0112] Table 3. Test Results

[0113] First, as can be seen from Tables 1, 2, and 3 above, the inner layer adhesive of the present invention has high bonding performance and electrolyte resistance. It can achieve bonding and lamination between the aluminum foil layer, the inner layer adhesive layer, and the heat-sealing layer at room temperature without the need for a traditional curing process, significantly shortening the production cycle. The inner layer adhesive used in the aluminum-plastic film gives the film better electrolyte resistance, chemical resistance, and thermal stability. Furthermore, the inner layer adhesive has strong bonding force with the aluminum foil layer and the heat-sealing layer. After electrolyte immersion testing, the aluminum-plastic film maintains its integrated appearance and does not delaminate, further improving the stability of the lithium battery encapsulated in the aluminum-plastic film.

[0114] Compared to Comparative Examples 1-3 and Comparative Examples 4-5, it can be understood from Examples 1-5 that when the inner layer adhesive is an epoxy-thiol system (that is, the inner layer adhesive includes: a host resin, an epoxy resin, and a thiol compound), and the mass ratio of the host resin, epoxy resin, and thiol compound is (10-20):(0.41-1.23):(0.001-0.06), and the inner layer adhesive meets the condition that the epoxy equivalent of the epoxy resin is in the range of 2.5 to 4.5 relative to the hydroxyl equivalent of the host resin, and the thiol equivalent of the thiol compound is less than or equal to 0.25 relative to the epoxy equivalent in the epoxy resin, a better crosslinking reaction of the epoxy-thiol system can be achieved under a specific composition ratio, and the technical effect desired in this case can be achieved.

[0115] The above content involving common knowledge will not be described in detail, as those skilled in the art will understand.

[0116] The embodiments described above are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. An inner layer adhesive for aluminum-plastic film, characterized in that, The inner layer adhesive comprises a main resin, an epoxy resin, and a thiol compound, wherein the mass ratio of the main resin, epoxy resin, and thiol compound is (10-20):(0.41-1.23):(0.001-0.06).

2. The inner layer adhesive for aluminum-plastic film according to claim 1, characterized in that, The ratio of the epoxy equivalent in the epoxy resin to the hydroxyl equivalent of the host resin is in the range of 2.5 to 4.5; wherein the ratio of the thiol equivalent of the thiol compound to the epoxy equivalent in the epoxy resin is less than or equal to 0.

25.

3. The inner layer adhesive for aluminum-plastic film according to claim 1, characterized in that, The inner layer adhesive further includes a curing accelerator.

4. The inner layer adhesive for aluminum-plastic film according to claim 3, characterized in that, The curing accelerator is added at a rate of 0.1 wt% to 8 wt% of the inner layer adhesive.

5. The inner layer adhesive for aluminum-plastic film according to claim 1, characterized in that, The main resin includes at least one of acid-modified polypropylene resin, maleic anhydride-modified styrene, or polyolefin elastomer.

6. The inner layer adhesive for aluminum-plastic film according to claim 1, characterized in that, The epoxy resin includes at least one of bisphenol F type epoxy resin, phenolic epoxy resin, or alicyclic epoxy resin.

7. The inner layer adhesive for aluminum-plastic film according to claim 1, characterized in that, The thiol compounds include at least one of the following: trimercaptopropionic acid, tris[(3-mercaptopropionyloxy)-ethyl]-isocyanurate, 1,3,5-tris(3-mercaptopropyl)-1,3,5-triazine trione, mercaptosilane, trimethylolpropane tris(3-mercaptopropionate), 1,4-butanediol di(3-mercaptopropionate), pentaerythritol tetra(3-mercaptopropionate), ethylene glycol di(3-mercaptopropionate), trimercaptothiol, tetrafunctional secondary thiol PE1, and polythioglycolic acid.

8. The inner layer adhesive for aluminum-plastic film according to claim 3, characterized in that, The curing accelerator includes at least one of the following: tertiary amine compounds, imidazole compounds, DBU salts, BDMA, and DMP-30.

9. The inner layer adhesive for aluminum-plastic film according to claim 1, characterized in that, The inner layer adhesive further includes: additives, the additives including at least one of toughening agents, leveling agents or weather-resistant additives.

10. The inner layer adhesive for aluminum-plastic film according to claim 9, characterized in that, The toughening agent includes at least one of polymethyl methacrylate, polybutyl methacrylate, polybutyl acrylate, polyacrylate, polymethyl methacrylate, or polystyrene-methyl methacrylate copolymer; the leveling agent is a siloxane leveling agent; and / or the weather-resistant additive includes at least one of a UV absorber or a hindered amine light stabilizer.

11. The inner layer adhesive for aluminum-plastic film according to claim 1, characterized in that, The epoxy resin and the thiol compound undergo a crosslinking reaction at room temperature.

12. The inner layer adhesive for aluminum-plastic film according to claim 1, characterized in that, The aluminum-plastic film further includes an aluminum foil layer and a heat-sealing layer. After the aluminum foil layer, inner adhesive layer, and heat-sealing layer are cured at room temperature for 5 to 19 hours, the initial peel strength between the inner adhesive layer and the aluminum foil layer and the heat-sealing layer is ≥16N / 15mm. After immersion in an electrolyte at 75 to 95°C for 0.5 to 1.5 days, the liquid resistance peel strength between the inner adhesive layer and the aluminum foil layer and the heat-sealing layer is ≥16N / 15mm.

13. An aluminum-plastic film, comprising the inner layer adhesive for the aluminum-plastic film as described in any one of claims 1 to 12.

14. A battery comprising the aluminum-plastic film as described in claim 13.

15. A method for preparing an aluminum-plastic film, characterized in that, include: A dispersion is formed by mixing a base resin, an epoxy resin, and a thiol compound, wherein the mass ratio of the base resin, epoxy resin, and thiol compound is (10–20):(0.41–1.23). (0.001～0.06)； A curing accelerator is added to the dispersion and stirred until homogeneous to form an inner layer adhesive. The amount of the curing accelerator added is 0.1 wt% to 8 wt% of the inner layer adhesive. The inner layer adhesive is applied between the aluminum foil layer and the heat-sealing layer and cured at room temperature to bond the aluminum foil layer and the heat-sealing layer together to obtain an aluminum-plastic film.

16. The method for preparing aluminum-plastic film according to claim 15, characterized in that, The curing accelerator is added at 2 wt% of the inner layer adhesive, and the ratio of the epoxy equivalent in the epoxy resin to the hydroxyl equivalent of the host resin is in the range of 2.5 to 4.5; wherein the ratio of the thiol equivalent of the thiol compound to the epoxy equivalent in the epoxy resin is less than or equal to 0.

25.

17. The method for preparing aluminum-plastic film according to claim 15, characterized in that, After the aluminum foil layer, inner adhesive layer, and heat-sealing layer are cured at room temperature for 5 to 19 hours, the initial peel strength between the inner adhesive layer and the aluminum foil layer and the heat-sealing layer is ≥16N / 15mm. After immersion in an electrolyte solution at 75 to 95°C for 0.5 to 1.5 days, the liquid resistance peel strength between the inner adhesive layer and the aluminum foil layer and the heat-sealing layer is ≥16N / 15mm.

18. The method for preparing aluminum-plastic film according to claim 15, characterized in that, The heat-sealing layer is made of cast polypropylene (CPP).

19. The method for preparing aluminum-plastic film according to claim 15, characterized in that, The inner layer adhesive further includes additives, which include at least one of toughening agents, leveling agents, or weather-resistant additives.

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