An aconitate ester-based UV-cured aluminum-based composite film, a preparation method and application thereof

Abstract

The present application relates to a kind of based on aconitate UV curing aluminum-based composite film and its preparation method and application, it solves the technical problems existing in interface bonding force, aging resistance and solidification efficiency of existing aluminum-plastic film, based on aconitate UV curing aluminum-based composite film includes aluminum base material and UV curing film layer;Aluminum base material surface is treated by vinyl silane coupling agent to form the covalent layer containing Si-O-Al covalent bond and carbon-carbon double bond;The UV curing film layer is by methacrylate, aconitate, crosslinking agent, photo-initiator is copolymerized by ultraviolet light curing;Wherein, aconitate is one or the mixture of more than two of various carbon number alkyl aconitate, cycloalkyl aconitate;The present application can be widely used in soft package battery, aluminum-plastic film, lithium battery packaging field.

Description

Technical Field

[0001] This invention relates to the field of lithium battery soft-pack packaging materials technology, and in particular to an aluminum-based composite film based on aconitate UV curing, its preparation method and application. Background Technology

[0002] Aluminum-plastic composite films for pouch cells are typically composed of a nylon layer, aluminum foil, adhesive layer, and heat-sealing layer. Traditional adhesive layers rely primarily on physical bonding, which suffers from weak interfacial adhesion, poor electrolyte resistance, easy delamination, high water and oxygen permeability, and precipitation after high-temperature aging. Conventional thermosetting processes involve high temperatures and long times, easily causing aluminum foil deformation and monomer polymerization, affecting packaging reliability. Therefore, developing aluminum-based composite films with interfacial covalent bonding, rapid room-temperature curing, and resistance to aging and precipitation is of great significance for improving the safety and lifespan of pouch cells.

[0003] Chinese invention patents or patent applications with publication numbers CN210092140U, CN112713339A and CN121307326A all disclose technical solutions related to aluminum-plastic film for soft-pack battery cells. Among them, patent CN210092140U discloses a soft-pack lithium-ion battery structure. By improving the arrangement of the adhesive layer, the traditional dot-shaped hot melt adhesive is replaced with multiple colloids arranged in a specific shape and the parameters are optimized, aiming to increase the bonding area and solve the problems of small physical bonding area and easy delamination. Patent CN112713339A discloses an aluminum-plastic soft packaging film and its application. By setting a passivation layer containing specific components on both sides of the aluminum foil layer to replace the traditional adhesive layer, it aims to improve the interlayer bonding force, resistance to electrolyte corrosion and high barrier performance. Patent CN121307326A discloses an aluminum-plastic film for high and low temperature resistant solid-state batteries. By optimizing the multi-layer nylon layer structure and adhesive formulation, it aims to solve the problems of high heat sealing temperature, easy embrittlement at high and low temperatures and poor aging resistance.

[0004] The above-mentioned techniques mainly have the following problems: (1) The fundamental nature of the interface bonding remains unchanged, and its strength is limited. Although the adhesive layer arrangement has been optimized or a passivation layer has been introduced, the core bonding mechanism is still mainly physical adhesion or weak interaction, and a stable covalent bond network has not been formed between the aluminum substrate and the film layer. Therefore, under long-term high humidity environment or electrolyte immersion, there is still an inherent risk of delamination and peeling, which cannot fundamentally guarantee the long-term reliability of soft-pack battery cell packaging.

[0005] (2) The curing process is outdated, with poor efficiency and thermal stability. All rely on traditional hot melt or heat-sealing curing processes, which have the disadvantages of high curing temperature and long time. High temperature can easily cause aluminum foil deformation and damage to the internal cell polymerization. At the same time, the production efficiency is low and cannot meet the needs of continuous and rapid mass production of modern soft pack batteries. Moreover, the long curing time also indirectly increases energy consumption and production costs.

[0006] (3) Insufficient resistance to precipitation and aging. Existing systems generally lack efficient molecular designs for resistance to precipitation and aging. Under harsh conditions such as high-temperature aging, the adhesive layer or passivation layer is prone to performance degradation and material precipitation, which leads to a decrease in the barrier performance of the aluminum-plastic film, thereby affecting the cycle life and safety of the soft-pack battery cell, making it difficult to adapt to the invention content of the invention for high-rate and long-life new energy application scenarios. Summary of the Invention

[0007] To address the technical problems of existing aluminum-plastic films in terms of interfacial adhesion, aging resistance, anti-exudation performance, and curing efficiency, this invention provides a silane-modified + aconitate ester UV-curable aluminum-based composite film with excellent interfacial adhesion, aging resistance, anti-exudation performance, and rapid curing performance, as well as its preparation method and application.

[0008] Therefore, the present invention provides an aluminum-based composite film based on aconitate UV (ultraviolet light) curing, comprising an aluminum substrate and a UV-curable film layer; the surface of the aluminum substrate is treated with a vinyl silane coupling agent to form a covalent layer containing Si-O-Al covalent bonds and carbon-carbon double bonds; the UV-curable film layer is copolymerized by curing methacrylate, aconitate, crosslinking agent, and photoinitiator under 365nm ultraviolet light; wherein, the aconitate is one or a mixture of two or more alkyl aconitate, cycloalkyl aconitate, or alkyl aconitate containing various carbon numbers.

[0009] Preferably, the aconitate is one or a mixture of two or more of aconitate, trimethyl aconitate, trioctyl aconitate, triethyl aconitate, tridecyl aconitate, and tributyl aconitate.

[0010] Preferably, the silane coupling agent is one or a mixture of two or more of vinyltrimethoxysilane, vinyltriethoxysilane, or KH-570.

[0011] Preferably, the crosslinking agent is one or a mixture of two or more of 1,6-hexanediol diacrylate (HDDA), tripropylene glycol diacrylate (TPGDA), neopentyl glycol diacrylate (NPGDA), propoxylated 1,6-hexanediol diacrylate (PO2-HDDA), and vinyltriethoxysilane.

[0012] Preferably, the photoinitiator is one or a mixture of two or more of DMPA, 184, 1173, TPO, and 819.

[0013] Preferably, the methacrylate is one or a mixture of two or more of methyl methacrylate, propyl methacrylate, and butyl methacrylate.

[0014] This invention also provides a method for preparing an aluminum-based composite film based on aconitate UV curing, comprising the following steps: Step A (aluminum substrate surface pretreatment and silane modification): (1) Aluminum foil / sheet is sequentially subjected to alkali washing, acid washing, deionized water rinsing, and drying to obtain an activated surface rich in hydroxyl groups; (2) A vinylsilane ethanol aqueous solution is prepared, the pH value is adjusted with acetic acid, hydrolyzed at room temperature, the activated aluminum substrate is immersed in or sprayed with the solution, reacted at a constant temperature, and then rinsed with ethanol, dried, and cured to form Si-O-Al covalent bonds on the aluminum surface and bonded to Dendritic carbon-carbon double bonds; Step B (Preparation of UV curing solution): By weight, 100 parts of butyl methacrylate, 25-35 parts of aconitate, 15-20 parts of crosslinking agent, and 4-6 parts of photoinitiator are placed in a stirrer and stirred at room temperature to obtain a uniform and transparent UV curing solution; Step C (Coating and UV curing): The UV curing solution is coated onto the surface of a silane-modified aluminum substrate and placed in a UV curing machine for rapid curing. The double bonds in the film layer undergo free radical copolymerization and covalent bonding with the double bonds on the aluminum surface to obtain an aluminum-based composite film based on aconitate UV curing.

[0015] Preferably, in step A, the vinylsilane ethanol aqueous solution refers to an ethanol aqueous solution with a mass fraction of 5% to 10% prepared by the vinylsilane method.

[0016] Preferably, in step C, the curing light intensity is 500–3000 mJ / cm², and the film thickness is 1–20 μm.

[0017] This invention also provides the application of aconitate-based UV-cured aluminum-based composite films in soft-pack cells, aluminum-plastic films, and lithium battery packaging.

[0018] The beneficial effects of this invention are: This invention covalently modifies the surface of an aluminum substrate using a vinyl silane coupling agent to form a transition layer containing carbon-carbon double bonds. This layer then undergoes free radical copolymerization with a UV-curable film layer doped with aconitate, forming a dual covalent bond system of Si-O-Al covalent bonds and carbon-carbon copolymer bonds. This is equivalent to introducing a "stable anchor point" between the aluminum substrate and the film layer, significantly improving the interfacial adhesion of the composite film and effectively solving the problems of easy delamination and detachment in traditional aluminum-plastic films. It is particularly suitable for the long-term packaging requirements of soft-pack batteries. The doping of aconitate effectively improves the flexibility, aging resistance, and anti-deposition properties of the composite film. With the addition of a crosslinking agent and a 365nm UV rapid curing system, the composite film can be cured within tens of seconds, avoiding the aluminum foil deformation problems caused by the high temperature of traditional thermosetting, significantly improving production efficiency and reducing production costs. The modified aluminum-based composite film has high density and low water and oxygen permeability, which can significantly improve the safety and cycle life of soft-pack batteries, making it suitable for aluminum-plastic film packaging of power and consumer soft-pack batteries. Detailed Implementation

[0020] The present invention will be further described below with reference to embodiments, so that those skilled in the art can easily implement the present invention.

[0021] Example 1 1.1 Surface pretreatment and silane modification of aluminum substrate 1) Take a 20μm thick aluminum foil for soft-pack battery cells and rinse it three times with 5% NaOH solution (65℃, 10min), 8% HNO3 solution (room temperature, 4min), and deionized water, and dry it at 120℃ for 30min to obtain an activated surface rich in hydroxyl groups. 2) Prepare a 7% (w / w) vinyltrimethoxysilane ethanol aqueous solution, adjust the pH to 4.5 with acetic acid, hydrolyze at room temperature for 20 min, immerse the activated aluminum substrate in the solution, react at 50℃ for 40 min, remove and rinse twice with anhydrous ethanol, dry and cure at 130℃ for 40 min, forming Si-O-Al covalent bonds and grafting carbon-carbon double bonds on the aluminum surface.

[0022] 1.2 UV curing solution preparation By weight, 100 parts of butyl methacrylate, 30 parts of tributyl aconitate, 18 parts of crosslinking agent HDDA, 5 parts of photoinitiator 184, and 2 parts of additive (antioxidant 1010) are placed in a stirrer and stirred at room temperature for 40 minutes to obtain a uniform and transparent UV curing solution.

[0023] 1.3 Coating and UV Curing A UV curing solution was coated onto the surface of a silane-modified aluminum substrate, with the film thickness controlled at 10 μm. The substrate was then placed in a 365 nm UV curing machine and cured for 30 s under a light intensity of 1500 mJ / cm². The double bonds in the film layer underwent free radical copolymerization and covalent bonding with the double bonds on the aluminum surface, forming a dense, strongly bonded, and water-impermeable composite film.

[0024] Example 2 2.1 Surface pretreatment and silane modification of aluminum substrate 1) The aluminum foil was successively rinsed three times with 6% NaOH solution (60℃, 12 min), 10% HNO3 solution (room temperature, 3 min), and deionized water, and dried at 110℃ for 40 min to obtain an activated surface rich in hydroxyl groups. 2) Prepare a 5% KH-570 ethanol aqueous solution, adjust the pH to 4.0 with acetic acid, hydrolyze at room temperature for 15 min, spray the activated aluminum substrate with the solution, react at 40℃ for 50 min, remove and rinse twice with anhydrous ethanol, dry and cure at 120℃ for 50 min, forming Si-O-Al covalent bonds and grafting carbon-carbon double bonds on the aluminum surface.

[0025] 2.2 UV Curing Solution Preparation By weight, 100 parts of methyl methacrylate, 25 parts of trimethyl aconitate, 15 parts of crosslinking agent TPGDA, 4 parts of photoinitiator 1173, and 1 part of additive (toughening agent) are placed in a stirrer and stirred at room temperature for 30 minutes to obtain a uniform and transparent UV curing solution.

[0026] 2.3 Coating and UV Curing A UV curing solution was coated onto the surface of a silane-modified aluminum substrate, with a film thickness of 5 μm. The substrate was then placed in a 365 nm UV curing machine and cured for 20 s under a light intensity of 1000 mJ / cm². The double bonds in the film layer and the double bonds on the aluminum surface underwent free radical copolymerization and covalent bonding, forming a dense, strongly bonded, and water-impermeable composite film.

[0027] Example 3 3.1 Surface pretreatment and silane modification of aluminum substrate 1) The aluminum foil was sequentially rinsed three times with 8% NaOH solution (70℃, 8 min), 12% HNO3 solution (room temperature, 5 min), and deionized water, and then dried at 130℃ for 20 min to obtain an activated surface rich in hydroxyl groups. 2) Prepare a 10% (w / w) vinyltriethoxysilane ethanol aqueous solution, adjust the pH to 5.0 with acetic acid, hydrolyze at room temperature for 25 min, immerse the activated aluminum substrate in the solution, react at 60℃ for 30 min, remove and rinse twice with anhydrous ethanol, dry and cure at 140℃ for 30 min, forming Si-O-Al covalent bonds and grafting carbon-carbon double bonds on the aluminum surface.

[0028] 3.2 UV curing solution preparation By weight, 100 parts of propyl methacrylate, 35 parts of trioctyl aconitate, 20 parts of crosslinking agent NPGDA, 6 parts of photoinitiator TPO, and 5 parts of additive (antioxidant 1076) were placed in a stirrer and stirred at room temperature for 50 minutes to obtain a uniform and transparent UV curing solution.

[0029] 3.3 Coating and UV Curing A UV curing solution was coated onto the surface of a silane-modified aluminum substrate, with the film thickness controlled at 15 μm. The substrate was then placed in a 365 nm UV curing machine and cured for 40 s under a light intensity of 2500 mJ / cm². The double bonds in the film layer and the double bonds on the aluminum surface underwent free radical copolymerization and covalent bonding, forming a dense, strongly bonded, and water-impermeable composite film.

[0030] Example 4 4.1 Surface pretreatment and silane modification of aluminum substrate 1) The aluminum sheet was successively rinsed three times with 7% NaOH solution (65℃, 10 min), 9% HNO3 solution (room temperature, 4 min), and deionized water, and dried at 125℃ for 25 min to obtain an activated surface rich in hydroxyl groups. 2) Prepare an ethanol-water solution containing 8% (w / w) vinyltrimethoxysilane and KH-570 (w / w) in a 1:1 ratio. Adjust the pH to 4.8 with acetic acid. After hydrolysis at room temperature for 22 min, spray the solution onto the activated aluminum substrate and react at 55°C for 35 min. After removal, rinse twice with anhydrous ethanol and dry and cure at 135°C for 35 min to form Si-O-Al covalent bonds and graft carbon-carbon double bonds on the aluminum surface.

[0031] 4.2 UV curing solution preparation By weight, 100 parts of butyl methacrylate, 32 parts of tridecyl aconitate, 17 parts of crosslinking agent PO2-HDDA, 5 parts of photoinitiator 819, and 3 parts of additive (toughening agent) were placed in a stirrer and stirred at room temperature for 45 minutes to obtain a uniform and transparent UV curing solution.

[0032] 4.3 Coating and UV Curing A UV curing solution was coated onto the surface of a silane-modified aluminum substrate, with a film thickness of 8 μm. The substrate was then placed in a 365 nm UV curing machine and cured for 25 s under a light intensity of 1800 mJ / cm². The double bonds in the film layer and the double bonds on the aluminum surface underwent free radical copolymerization and covalent bonding, forming a dense, strongly bonded, and water-impermeable composite film.

[0033] Example 5 The difference from Example 1 is as follows: 1) The silane coupling agent used is vinyltrimethoxysilane (VTMS). The silane solution has a mass fraction of 9%, the pH is adjusted to 4.8, the hydrolysis time is 28 min, the reaction temperature is 72℃, and the curing temperature is 115℃. 2) UV curing solution ratio (parts by weight): 65 parts tri-n-butyl aconitate methacrylate, 15 parts butyl methacrylate, 14 parts NPGDA crosslinking agent, 3 parts photoinitiator 819 and DMPA mixed at a mass ratio of 3:1, 1 part antioxidant 1010, and 1 part UV absorber UV-531. 3) Curing light intensity 2200mJ / cm², irradiation time 20s, film thickness 18μm.

[0034] Example 6 6.1 Surface Pretreatment and Silane Modification of Aluminum Substrate 1) The aluminum foil was sequentially rinsed three times with 6% NaOH solution (62℃, 11 min), 11% HNO3 solution (room temperature, 3.5 min), and deionized water, and then dried at 115℃ for 35 min to obtain an activated surface rich in hydroxyl groups. 2) Prepare a 6% (w / w) vinyltriethoxysilane ethanol aqueous solution, adjust the pH to 4.2 with acetic acid, hydrolyze at room temperature for 18 min, immerse the activated aluminum substrate in the solution, react at 45℃ for 45 min, remove and rinse twice with anhydrous ethanol, dry and cure at 125℃ for 45 min, forming Si-O-Al covalent bonds and grafting carbon-carbon double bonds on the aluminum surface.

[0035] 6.2 UV Curing Solution Preparation By weight, 100 parts of methyl methacrylate and butyl methacrylate (mass ratio 1:1), 28 parts of tributyl aconitate and triethyl aconitate (mass ratio 2:1), 16 parts of crosslinking agent HDDA and TPGDA (mass ratio 1:1), and 4.5 parts of photoinitiator 184 and 1173 (mass ratio 1:1) were placed in a stirrer and stirred at room temperature for 35 minutes to obtain a uniform and transparent UV curing solution.

[0036] 6.3 Coating and UV Curing A UV curing solution was coated onto the surface of a silane-modified aluminum substrate, with the film thickness controlled at 12 μm. The substrate was then placed in a 365 nm UV curing machine and cured for 35 s under a light intensity of 2000 mJ / cm². The double bonds in the film layer underwent free radical copolymerization and covalent bonding with the double bonds on the aluminum surface, forming a dense, strongly bonded, and water-impermeable composite film.

[0037] Example 7 7.1 Surface pretreatment and silane modification of aluminum substrate 1) The aluminum foil was repeatedly rinsed three times with 7.5% NaOH solution (63℃, 10.5 min), 10.5% HNO3 solution (room temperature, 3.8 min), and deionized water, and then dried at 122℃ for 28 min to obtain an activated surface rich in hydroxyl groups. 2) Prepare an ethanol-water solution containing 7.5% by mass of vinyltrimethoxysilane and vinyltriethoxysilane (mass ratio 2:1), adjust the pH to 4.4 with acetic acid, hydrolyze at room temperature for 21 min, immerse the activated aluminum substrate in the solution, react at 48℃ for 42 min, remove and rinse twice with anhydrous ethanol, dry and cure at 132℃ for 32 min, forming Si-O-Al covalent bonds and grafting carbon-carbon double bonds on the aluminum surface.

[0038] 7.2 UV Curing Solution Preparation By weight, 100 parts of methyl methacrylate, 26 parts of trimethyl aconitate and tributyl aconitate (mass ratio 1:3), 15.5 parts of crosslinking agent HDDA, and 4.2 parts of photoinitiator 184 were placed in a stirrer and stirred at room temperature for 32 minutes to obtain a uniform and transparent UV curing solution (without additives).

[0039] 7.3 Coating and UV Curing A UV curing solution was coated onto the surface of a silane-modified aluminum substrate, with the film thickness controlled at 2 μm. The substrate was then placed in a 365 nm UV curing machine and cured for 15 s under a light intensity of 600 mJ / cm². The double bonds in the film layer and the double bonds on the aluminum surface underwent free radical copolymerization and covalent bonding, forming a dense, strongly bonded, and water-impermeable composite film.

[0040] Comparative Example 1 (Traditional thermosetting instead of UV curing) The preparation method is basically the same as that in Example 1, except that in step 1.3, 365nm ultraviolet light curing is not used, but traditional thermosetting process is used, and the temperature is kept constant at 120℃ for 60 minutes.

[0041] Comparative Example 2 (Silane-free modified + UV-cured aluminum-based composite film) The difference from Example 1 is that the silane modification process on the surface of the aluminum substrate is omitted. The aluminum foil is directly coated with UV curing liquid after being alkali washed, acid washed, and dried. The other raw material ratios and process parameters are the same as in Example 1, resulting in a UV-cured aluminum-based composite film without silane modification (no covalent bond bonding at the interface).

[0042] Comparative Example 3 (Aconitate-free modified + UV-cured aluminum-based composite film) The difference from Example 1 is that an equal amount of butyl methacrylate is used to replace aconitate, while the other raw material ratios and process parameters are the same as in Example 1, resulting in a UV-curable aluminum-based composite film without aconitate modification.

[0043] The composite films / aluminum-plastic films prepared in Examples 1-7 and Comparative Examples 1-3 were subjected to performance tests according to the following standards, and the test results are shown in the table below: Sample Name Interfacial peel strength (N / mm) Curing time (s) Peel strength retention rate after electrolyte aging (%) Water permeability (×10⁻³g / (m²·d)) <![CDATA[Oxygen Permeability (×10⁻ 4 cm³ / (m²·d·atm)]]> Flexibility (bending radius, mm) Example 1 2.2 30 92 0.8 1.2 2 Example 2 1.8 20 88 1 1.5 2 Example 3 2.5 40 95 0.6 1 2 Example 4 2.3 25 93 0.7 1.1 2 Example 5 2.1 35 90 0.9 1.3 3 Example 6 2.4 50 94 0.65 1.05 2 Example 7 1.9 15 89 0.95 1.4 3 Comparative Example 1 1.6 3600 80 1.4 1.9 3 (Slight cracking after bending) Comparative Example 2 0.7 32 45 3.5 4.8 5 (Coating peels off after bending) Comparative Example 3 1.3 28 68 1.8 2.5 4 (Slight cracking of the coating after bending) The test data above show that the aconitate-based UV-cured flexible battery cell aluminum-based composite film prepared in Examples 1-7 of this invention has the following significant advantages compared with the prior art comparative examples 1-3: 1. Stronger interfacial bonding: The interfacial peel strength of Examples 1-7 is 1.8-2.5 N / mm, which is much higher than that of Comparative Example 1 (1.6 N / mm), Comparative Example 2 (0.7 N / mm), and Comparative Example 3 (1.3 N / mm). Moreover, the samples of the examples did not crack or fall off after being bent 500 times, while the comparative examples all showed cracks or falls off to varying degrees. This proves that the present invention effectively improves the interfacial bonding strength between the aluminum substrate and the film layer through the dual covalent bonding of silane modification and aconitate UV curing, and solves the problem of easy delamination and peeling of traditional aluminum-plastic films.

[0044] 2. Extremely high curing efficiency: The UV curing time of Examples 1-7 is only 15-45s, while the traditional thermal curing time of Comparative Example 1 is 60min (3600s), which greatly improves production efficiency, reduces energy consumption, and meets the requirements of continuous mass production of soft-pack battery cells; at the same time, it avoids the problem of aluminum foil deformation caused by high temperature thermal curing.

[0045] 3. Excellent aging resistance and anti-deposition performance: The peel strength retention rate after electrolyte aging in Examples 1-7 is 88%-95%, which is much higher than that of the comparative examples (45%-80%). This proves that the aconitate ester modification system introduced in this invention effectively improves the aging resistance and anti-deposition performance of the composite membrane and extends the service life of the soft-pack battery cell.

[0046] 4. Better barrier performance and flexibility: The water and oxygen permeability of Examples 1-7 is much lower than that of the comparative examples, and the bending radius is smaller and the flexibility is better, which can better adapt to the packaging requirements of soft-pack cells and improve the safety and stability of the cells.

[0047] This composite film can be used as a core material for the packaging shell of pouch cells, meeting the requirements of "protection + sealing". Specifically, it can be applied in two scenarios: First, for the main body packaging of the cell shell: after cutting and stamping, a shell blank is formed. The aluminum substrate blocks moisture and oxygen, and the UV-cured film layer is resistant to electrolyte and precipitation, preventing contamination and short circuits. The covalent layer ensures no delamination between layers, improving structural stability. Second, for tab sealing and protection: after cutting, it is UV-cured and bonded to the junction of the tab and the shell, filling gaps, improving sealing, preventing electrolyte leakage, and its aging resistance ensures long-term safety. It is suitable for pouch cells in multiple fields. Its efficient UV curing can shorten the packaging cycle, and the lightweight aluminum substrate helps to improve the energy density of the cell, making it suitable for mass production. This composite film can be used in aluminum-plastic films as a core functional layer or a modified layer to improve encapsulation reliability. Firstly, it can be used in the preparation of a novel core layer for aluminum-plastic films: constructing an "outer protective layer - aluminum-based composite film - inner heat-sealing layer" structure. The aluminum substrate acts as a barrier, the covalent layer solves the interlayer delamination problem, and the UV-cured film layer improves aging resistance, anti-deposition, and electrolyte resistance. Secondly, it can be used to modify and upgrade existing aluminum-plastic films: coating the surface of traditional aluminum foil with a UV-cured film layer significantly improves interfacial adhesion and overall performance without modifying the process, reducing production costs. Its high UV curing efficiency and good flexibility meet the cold stamping requirements of aluminum-plastic films and are suitable for various lithium battery encapsulation applications. This composite film can be applied to various types of lithium battery encapsulation, covering the entire process, such as: soft-pack lithium battery encapsulation: stamped into a packaging bag, then heat-sealed and UV-cured to complete the encapsulation, blocking moisture and oxygen, resisting electrolyte precipitation, and withstanding temperature fluctuations, suitable for high-end applications, helping to improve battery safety and energy density; auxiliary encapsulation of small cylindrical / square lithium batteries: cut and adhered to the battery casing surface, improving wear resistance, corrosion resistance, and moisture and oxidation resistance, ensuring safe and stable use; lithium battery encapsulation interface sealing: used as a sealing gasket at the interface to form a seamless seal, preventing leakage and avoiding battery failure due to seal failure. Furthermore, the type and ratio of aconitate can be adjusted according to encapsulation requirements to adapt to different lithium batteries, and its environmentally friendly, non-precipitating characteristics align with the industry's green development trend.

[0048] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the scope of the claims of the present invention should be within the protection scope of the present invention.

Claims

1. An aluminum-based composite film based on aconitate UV curing, characterized in that, The material includes an aluminum substrate and a UV-curable film layer; the surface of the aluminum substrate is treated with a vinyl silane coupling agent to form a covalent layer containing Si-O-Al covalent bonds and carbon-carbon double bonds; the UV-curable film layer is copolymerized by UV curing of methacrylate, aconitate, crosslinking agent, and photoinitiator; wherein the aconitate is one or a mixture of two or more alkyl aconitate, cycloalkyl aconitate, or alkyl aconitate containing various carbon numbers.

2. The aluminum-based composite film based on aconitate ester UV curing according to claim 1, characterized in that, The aconitate is one or a mixture of two or more of aconitate, trimethyl aconitate, trioctyl aconitate, triethyl aconitate, tridecyl aconitate, and tributyl aconitate.

3. The aluminum-based composite film based on aconitate ester UV curing according to claim 1, characterized in that, The silane coupling agent is one or a mixture of two or more of vinyltrimethoxysilane, vinyltriethoxysilane, or KH-570.

4. The aluminum-based composite film based on aconitate ester UV curing according to claim 1, characterized in that, The crosslinking agent is one or a mixture of two or more of the following: 1,6-hexanediol diacrylate (HDDA), tripropylene glycol diacrylate (TPGDA), neopentyl glycol diacrylate (NPGDA), propoxylated 1,6-hexanediol diacrylate (PO2-HDDA), and vinyltriethoxysilane.

5. The aluminum-based composite film based on aconitate ester UV curing according to claim 1, characterized in that, The photoinitiator is one or a mixture of two or more of DMPA, 184, 1173, TPO, and 819.

6. The aluminum-based composite film based on aconitate UV curing according to claim 1, characterized in that, The methacrylate is one or a mixture of two or more of methyl methacrylate, propyl methacrylate, and butyl methacrylate.

7. The method for preparing an aluminum-based composite film based on aconitate UV curing as described in any one of claims 1 to 6, characterized in that, Includes the following steps: Step A: Surface pretreatment and silane modification of aluminum substrate (1) The aluminum foil / sheet is successively subjected to alkaline washing, acid washing, deionized water rinsing and drying to obtain an activated surface rich in hydroxyl groups; (2) Prepare a vinylsilane ethanol aqueous solution, adjust the pH value with acetic acid, hydrolyze at room temperature, immerse or spray the activated aluminum substrate in the solution, react at a constant temperature, take it out, rinse with ethanol, dry and solidify, and form Si-O-Al covalent bonds and graft carbon-carbon double bonds on the aluminum surface. Step B: Preparation of UV curing solution By weight, 100 parts of butyl methacrylate, 25-35 parts of aconitate, 15-20 parts of crosslinking agent, and 4-6 parts of photoinitiator are placed in a stirrer and stirred at room temperature to obtain a uniform and transparent UV curing solution. Step C: Coating and UV Curing A UV curing solution was coated onto the surface of a silane-modified aluminum substrate and then rapidly cured in a UV curing machine. The double bonds in the film layer underwent free radical copolymerization and covalent bonding with the double bonds on the aluminum surface, resulting in an aluminum-based composite film based on aconitate UV curing.

8. The method for preparing an aluminum-based composite film based on aconitate ester UV curing as described in claim 7, characterized in that, In step A, the vinylsilane ethanol aqueous solution refers to an ethanol aqueous solution with a mass fraction of 5% to 10% prepared by the vinylsilane method.

9. The method for preparing an aluminum-based composite film based on aconitate UV curing as described in claim 7, wherein in step C, the curing light intensity is 500–3000 mJ / cm², and the film thickness is 1–20 μm.

10. The application of the aconitate-based UV-cured aluminum composite film as described in any one of claims 1 to 6 in soft-pack battery cells, aluminum-plastic films, and lithium battery packaging.