High strength solid state battery packaging nylon film and method of production thereof

Abstract

The application discloses a high-strength solid-state battery packaging nylon film, which comprises a nylon layer, an aluminum foil layer and a heat-sealing layer, the nylon layer is prepared by a two-way stretching process after polyamide 66 and metal chloride are solution-blended, the metal chloride is a compound of calcium chloride and lanthanum chloride; the surface of the nylon layer is subjected to fluorination modification treatment, the fluorination modification treatment is grafting trifluoropropyltrimethoxysilane on the surface of the nylon layer; the heat-sealing layer is a polypropylene film, which is prepared by a flow casting process after a polypropylene matrix and a composite additive are melt-blended, and the composite additive is composed of an antioxidant, a stabilizer and an organic silicon polymer anti-blocking agent; and the nylon film prepared by the application has high strength and good comprehensive performance.

Description

Technical Field

[0001] This invention relates to the field of solid-state battery encapsulation film technology, specifically a high-strength solid-state battery encapsulation nylon film and its production method. Background Technology

[0002] With the rapid development of new energy vehicles and consumer electronics, the demand for high-energy-density and high-safety batteries is becoming increasingly urgent. Solid-state and semi-solid-state batteries, due to their use of solid or semi-solid electrolytes, offer higher safety and energy density, making them an important direction for the development of next-generation battery technology. However, solid-state batteries place more stringent requirements on the mechanical properties and water-blocking properties of encapsulation materials.

[0003] Existing lithium battery packaging films generally consist of a nylon layer, an aluminum foil layer, and a heat-sealing layer, and can be prepared using dry or thermal processes. Among them, the nylon layer (usually BOPA film) serves as the outer protective layer, playing a role in scratch resistance and providing structural support. However, traditional nylon materials (such as PA6 and PA66) have the following technical defects: (1) insufficient strength, making it difficult to meet the high mechanical performance requirements of solid-state batteries for the packaging film; (2) insufficient barrier properties against moisture.

[0004] Meanwhile, existing performance testing methods typically separate mechanical performance testing from water-blocking performance and other performance tests, failing to reflect the combined conditions under which the encapsulation film simultaneously withstands mechanical stress and water vapor permeation in actual use. Therefore, developing a nylon layer material with both high strength and high water-blocking properties, and establishing a performance evaluation method capable of simulating actual service conditions, is of significant practical importance. Summary of the Invention

[0005] In view of the above-mentioned deficiencies of the prior art, one object of the present invention is to provide a high-strength solid-state battery encapsulation nylon film.

[0006] To solve the above problems, the technical solution of the present invention is: a high-strength solid-state battery encapsulation nylon film, comprising a nylon layer, an aluminum foil layer, and a heat-sealing layer;

[0007] The nylon layer is prepared by biaxial stretching after solution blending of polyamide 66 and metal chloride. The metal chloride is a compound of calcium chloride and lanthanum chloride. The surface of the nylon layer is fluorinated, which involves grafting trifluoropropyltrimethoxysilane onto the surface of the nylon layer.

[0008] The heat-sealing layer is a polypropylene film, which is prepared by melt blending of polypropylene matrix and composite additives and then casting process. The composite additives consist of antioxidants, stabilizers and organosilicon polymer antiblocking agents.

[0009] Furthermore, the nylon layer is composed of the following components by mass ratio: polyamide 66 90.9%, calcium chloride 4.55%, and lanthanum chloride 4.55%.

[0010] The components of the heat-sealing layer by mass ratio are: 99.7% ternary random copolymer polypropylene, 0.1% antioxidant, 0.1% stabilizer, and 0.1% organosilicon polymer antiblocking agent.

[0011] This invention also provides a method for producing a high-strength solid-state battery encapsulation nylon film, comprising the following steps:

[0012] (1) Preparation of modified nylon granules: Polyamide 66 was dissolved in formic acid, and calcium chloride and lanthanum chloride were added. The mass ratio of polyamide 66 to metal chloride was 100:10, and the mass ratio of calcium chloride to lanthanum chloride was 1:1. The mixture was stirred and dissolved for 4.5 h. The solution was placed in an evaporating dish and evaporated at room temperature for 12 h. Then, it was slowly heated to 100°C in a vacuum oven and dried for 8 h to obtain dry modified nylon granules.

[0013] (2) Preparation of nylon layer: The modified nylon granules obtained in step (1) are formed by biaxial stretching process;

[0014] (3) Decomplexation treatment: The nylon film obtained in step (2) is immersed in deionized water for 4 hours to restore hydrogen bonds. After being taken out, it is vacuum dried at 50°C for 6 hours.

[0015] (4) Fluorination modification treatment of nylon layer surface: The nylon layer film obtained in step (3) is placed in formaldehyde-phosphoric acid solution and soaked at 60°C for 12h for hydroxylation pretreatment. After taking it out, it is rinsed with water and dried. Prepare fluorination modification solution by mixing trifluoropropyltrimethoxysilane, anhydrous ethanol, deionized water and 0.1mol / L hydrochloric acid in a molar ratio of 1.000:0.044:0.031:0.0057 and stirring evenly. Immerse the hydroxylated nylon layer film in the modification solution and react at 30°C for 24h. After taking it out, wipe off the excess solution on the surface and place it in a vacuum drying oven to dry at 30°C for 24h to obtain a nylon film with fluorination modification on the surface.

[0016] (5) Preparation of aluminum foil layer: The surface of aluminum foil is degreased and subjected to corrosion-resistant treatment to obtain aluminum foil layer;

[0017] (6) Preparation of heat-sealing layer: Ternary random copolymer polypropylene is mixed with composite additives and formed by casting process. The casting temperature is controlled at 230°C and the cooling roller temperature is 35°C to prepare a heat-sealing layer film with a thickness of 60 micrometers.

[0018] (7) Composite: The nylon film obtained in step (4), the aluminum foil layer obtained in step (5), and the heat-sealing layer obtained in step (6) are composited using a dry process.

[0019] Furthermore, it also includes step (8): performing performance tests on the obtained nylon film, including the following steps:

[0020] (81) Verification test of hydrogen bond shielding and recovery of nylon layer: Before the fluorination modification treatment, the nylon layer film obtained in step (2) was cut into small pieces and its infrared spectrum was tested by Fourier transform infrared spectrometer. The peak position changes of amide I band and amide II band were recorded. Its melting and crystallization behavior was tested by differential scanning calorimeter. The heating rate was 10℃ / min and the temperature range was 30℃ to 280℃. The nylon film after decomplexation treatment was tested again by infrared spectroscopy and DSC. The characteristic peak shifts and crystallization behavior changes before and after hydrogen bond shielding were compared to verify the shielding effect of metal chloride on hydrogen bonds and the recovery effect after decomplexation.

[0021] (82) Mechanical property test of nylon layer: Before fluorination modification, the nylon layer film obtained in step (2) was cut into dumbbell-shaped samples and subjected to tensile test on an electronic universal testing machine. The tensile speed was 50 mm / min, and the tensile strength, elongation at break and elastic modulus were recorded.

[0022] (83) Overall tensile properties test of composite film: The final composite nylon film was cut into dumbbell-shaped specimens and subjected to tensile test on an electronic universal testing machine at a tensile speed of 50 mm / min. The tensile strength, elongation at break and elastic modulus were recorded.

[0023] (84) Water vapor barrier performance test: The water vapor transmission rate of the composite nylon membrane was tested at 38℃ and 90%RH using a water vapor transmission rate tester for 7 consecutive days and the steady-state transmission rate value was recorded. At the same time, the composite nylon membrane was placed in a constant temperature and humidity chamber at 85℃ and 85%RH for 30 days. The water vapor transmission rate was tested every 5 days and the curve of water vapor transmission rate change over time was plotted to evaluate the water barrier stability of the material under long-term humid and hot environment. The initial water vapor transmission rate was required to be ≤0.72g / (m²·24h) and the water vapor transmission rate after 30 days was required to be ≤1.2g / (m²·24h).

[0024] (85) Solid electrolyte compatibility test: The composite nylon film and the solid electrolyte sheet are tightly bonded together and hot-pressed at 60℃ and 0.5MPa for 24h. After taking it out, observe the changes in the contact surface between the composite nylon film and the solid electrolyte, and test the tensile strength retention rate of the composite nylon film after hot pressing. At the same time, the bonded sample is placed in a 60℃ environment and left to stand for 30 days. Every 5 days, it is taken out to observe whether there are bubbles, delamination, discoloration and other phenomena at the interface, and evaluate the interface compatibility between the composite nylon film and the solid electrolyte. The tensile strength retention rate after hot pressing is required to be ≥95%, and there should be no bubbles, no delamination and no obvious discoloration after 30 days of standing.

[0025] (86) High and low temperature cycle durability test: The composite nylon membrane is placed in a temperature cycling chamber and cycled between -40℃ and 85℃. Each temperature point is kept for 2 hours, the heating and cooling rate is 2℃ / min, and the cycle is repeated 100 times. After the test, the appearance of the composite nylon membrane is observed, and the tensile strength retention rate and water vapor transmission rate are tested. It is required that there is no cracking, no delamination, and no whitening after the cycle. The tensile strength retention rate is ≥90%, and the increase in water vapor transmission rate is ≤0.3g / (m²·24h).

[0026] (87) Heat-sealing layer performance test: Take the heat-sealing layer film obtained in step (6), cut it into appropriate sizes, and test it according to the following method:

[0027] (87a) Heat seal strength and initial heat seal temperature test: The heat seal film is placed in pairs and heat-sealed at different temperatures (100℃ to 130℃, with an interval of 5℃). The heat seal pressure is 0.3MPa and the heat seal time is 1s. The film is cut into 15mm wide samples and the heat seal strength is tested on a tensile testing machine at a speed of 300mm / min. The heat seal strength-temperature curve is plotted and the temperature corresponding to the strength of 2.5N / 15mm is defined as the initial heat seal temperature.

[0028] (87b) Friction coefficient test: Place the heat-sealing film on the friction coefficient tester to test the dynamic friction coefficient and static friction coefficient. The dynamic friction coefficient is required to be ≤0.8.

[0029] (88) Tensile-corrosion coupled accelerated aging test: The composite nylon film was cut into dumbbell-shaped samples. A pre-tension stress equivalent to 50% of its tensile strength was applied first. Under the stress condition, it was placed in an environment of 85℃ and 85%RH for 1 day, 3 days, 7 days, 14 days and 28 days respectively. After the stress was released, the overall tensile strength, elongation at break and elastic modulus of the composite film were tested. At the same time, in-situ X-ray diffraction test was performed to record the crystal form change of the nylon layer.

[0030] The cross-section of the tensile fractured specimen was observed by scanning electron microscopy to analyze the changes in the bonding state of the interface between the nylon layer and the fluorinated modified layer, and between the nylon layer and the aluminum foil layer before and after aging. It was required that the strength retention rate be ≥80% after 28 days of coupled aging, and the cross-section SEM image showed no delamination at the interface and no peeling of the protective layer.

[0031] (89) Pack the qualified products after testing.

[0032] The beneficial effects of this invention are:

[0033] The nylon layer uses a metal chloride system composed of calcium chloride and lanthanum chloride, which significantly increases the elongation at break and greatly improves the stretchability of the material, making it easy to process in both directions. After decomplexing treatment, the tensile strength is significantly improved and the mechanical strength is enhanced.

[0034] Fluorination modification is performed on the surface of the nylon layer by grafting fluorinated silanes to form a dense fluorinated hydrophobic layer on the surface of the nylon layer. By utilizing the low surface energy characteristics of fluorine atoms, the adsorption and penetration of water vapor on the surface of the nylon layer are significantly reduced without reducing the mechanical properties of the nylon layer.

[0035] The heat-sealing layer is modified by blending ternary random copolymer polypropylene with a composite additive system. Among them, the organosilicon polymer anti-blocking agent forms a micro-nano structure on the film surface, which significantly reduces the coefficient of friction and prevents the film from sticking together during the storage and transportation of the roll material;

[0036] The tensile-corrosion coupled accelerated aging test method was adopted, which takes into account the dual effects of mechanical stress and water vapor permeation on the encapsulation film during use, providing a basis for material performance evaluation and life prediction. Detailed Implementation

[0037] To provide a more intuitive and complete understanding of the technical solution of this invention, the following non-limiting features are described:

[0038] Example 1:

[0039] A high-strength solid-state battery encapsulation nylon film includes a nylon layer, an aluminum foil layer, and a heat-sealing layer;

[0040] The nylon layer is prepared by biaxial stretching after solution blending of polyamide 66 and metal chloride. The metal chloride is a compound of calcium chloride and lanthanum chloride. The surface of the nylon layer is fluorinated, which involves grafting trifluoropropyltrimethoxysilane onto the surface of the nylon layer.

[0041] The heat-sealing layer is a polypropylene film, which is prepared by melt blending of polypropylene matrix and composite additives and then casting process. The composite additives consist of antioxidants, stabilizers and organosilicon polymer antiblocking agents.

[0042] The thicknesses of the nylon layer, aluminum foil layer, and heat-sealing layer are 20μm, 40μm, and 60μm, respectively.

[0043] The nylon layer is composed of the following components by mass ratio: polyamide 66 90.9%, calcium chloride 4.55%, and lanthanum chloride 4.55%.

[0044] The components of the heat-sealing layer, by mass ratio, are: 99.7% ternary random copolymer polypropylene, 0.1% antioxidant, 0.1% stabilizer, and 0.1% silicone polymer antiblocking agent. The antioxidant is antioxidant 1010, the stabilizer is antioxidant 168, and the silicone polymer antiblocking agent is polymethylsilsesquioxane microspheres.

[0045] The process parameters for fluorination modification were as follows: the molar ratio of trifluoropropyltrimethoxysilane, ethanol, water, and hydrochloric acid was 1.000:0.044:0.031:0.0057, the reaction temperature was 30℃, and the reaction time was 24h.

[0046] This invention also provides a method for producing a high-strength solid-state battery encapsulation nylon film, comprising the following steps:

[0047] (1) Preparation of modified nylon granules: Polyamide 66 was dissolved in formic acid, and calcium chloride and lanthanum chloride were added. The mass ratio of polyamide 66 to metal chloride was 100:10, and the mass ratio of calcium chloride to lanthanum chloride was 1:1. The mixture was stirred and dissolved for 4.5 h. The solution was placed in an evaporating dish and evaporated at room temperature for 12 h. Then, it was slowly heated to 100°C in a vacuum oven and dried for 8 h to obtain dry modified nylon granules.

[0048] (2) Preparation of nylon layer: The modified nylon granules obtained in step (1) are formed by biaxial stretching process; the specific process is as follows: the modified nylon granules are melt-extruded into a casting, the casting temperature is controlled at 235℃, and the casting thickness is 300 micrometers; after cooling the casting to 40℃, longitudinal stretching is performed, the longitudinal stretching temperature is 70℃, and the stretching ratio is 5 times; after longitudinal stretching, transverse stretching is performed, the transverse stretching temperature is 90℃, and the stretching ratio is 5 times; after stretching, heat setting treatment is performed, the heat setting temperature is 190℃, and the heat setting time is 20 seconds; after heat setting, the film is cooled, trimmed, and rolled up to obtain a nylon layer film with a thickness of 20 micrometers;

[0049] (3) Decomplexation treatment: The nylon film obtained in step (2) is immersed in deionized water for 4 hours to restore hydrogen bonds. After being taken out, it is vacuum dried at 50°C for 6 hours.

[0050] (4) Fluorination modification treatment of nylon layer surface: The nylon layer film obtained in step (3) is placed in formaldehyde-phosphoric acid solution and soaked at 60°C for 12h for hydroxylation pretreatment. After taking it out, it is rinsed with water and dried. Prepare fluorination modification solution by mixing trifluoropropyltrimethoxysilane, anhydrous ethanol, deionized water and 0.1mol / L hydrochloric acid in a molar ratio of 1.000:0.044:0.031:0.0057 and stirring evenly. Immerse the hydroxylated nylon layer film in the modification solution and react at 30°C for 24h. After taking it out, wipe off the excess solution on the surface and place it in a vacuum drying oven to dry at 30°C for 24h to obtain a nylon film with fluorination modification on the surface.

[0051] (5) Preparation of aluminum foil layer: The surface of aluminum foil is degreased and subjected to corrosion-resistant treatment to obtain aluminum foil layer;

[0052] (6) Preparation of heat-sealing layer: Ternary random copolymer polypropylene is mixed with composite additives and formed by casting process. The casting temperature is controlled at 230°C and the cooling roller temperature is 35°C to prepare a heat-sealing layer film with a thickness of 60 micrometers.

[0053] (7) Composite: The nylon film obtained in step (4), the aluminum foil layer obtained in step (5) and the heat-sealing layer obtained in step (6) are composited using a dry process. Polyurethane adhesive is used for the composite process. The adhesive coating amount is 5g / m², the composite pressure is 0.5MPa, the curing temperature is 50°C, and the curing time is 60h.

[0054] Step (8): Perform performance tests on the obtained nylon film, including the following steps:

[0055] (81) Verification test of hydrogen bond shielding and recovery of nylon layer: Before the fluorination modification treatment, the nylon layer film obtained in step (2) was cut into small pieces and its infrared spectrum was tested by Fourier transform infrared spectrometer. The peak position changes of amide I band and amide II band were recorded. Its melting and crystallization behavior was tested by differential scanning calorimeter. The heating rate was 10℃ / min and the temperature range was 30℃ to 280℃. The nylon film after decomplexation treatment was tested again by infrared spectroscopy and DSC. The characteristic peak shifts and crystallization behavior changes before and after hydrogen bond shielding were compared to verify the shielding effect of metal chloride on hydrogen bonds and the recovery effect after decomplexation.

[0056] (82) Mechanical property test of nylon layer: Before fluorination modification, the nylon layer film obtained in step (2) was cut into dumbbell-shaped samples and subjected to tensile test on an electronic universal testing machine. The tensile speed was 50 mm / min, and the tensile strength, elongation at break and elastic modulus were recorded.

[0057] (83) Overall tensile properties test of composite film: The final composite nylon film was cut into dumbbell-shaped specimens and subjected to tensile test on an electronic universal testing machine at a tensile speed of 50 mm / min. The tensile strength, elongation at break and elastic modulus were recorded.

[0058] (84) Water vapor barrier performance test: The water vapor transmission rate of the composite nylon membrane was tested at 38℃ and 90%RH using a water vapor transmission rate tester for 7 consecutive days and the steady-state transmission rate value was recorded. At the same time, the composite nylon membrane was placed in a constant temperature and humidity chamber at 85℃ and 85%RH for 30 days. The water vapor transmission rate was tested every 5 days and the curve of water vapor transmission rate change over time was plotted to evaluate the water barrier stability of the material under long-term humid and hot environment. The initial water vapor transmission rate was required to be ≤0.72g / (m²·24h) and the water vapor transmission rate after 30 days was required to be ≤1.2g / (m²·24h).

[0059] (85) Solid electrolyte compatibility test: The composite nylon film and the solid electrolyte sheet are tightly bonded together and hot-pressed at 60℃ and 0.5MPa for 24h. After taking it out, observe the changes in the contact surface between the composite nylon film and the solid electrolyte, and test the tensile strength retention rate of the composite nylon film after hot pressing. At the same time, the bonded sample is placed in a 60℃ environment and left to stand for 30 days. Every 5 days, it is taken out to observe whether there are bubbles, delamination, discoloration and other phenomena at the interface, and evaluate the interface compatibility between the composite nylon film and the solid electrolyte. The tensile strength retention rate after hot pressing is required to be ≥95%, and there should be no bubbles, no delamination and no obvious discoloration after 30 days of standing.

[0060] (86) High and low temperature cycle durability test: The composite nylon membrane is placed in a temperature cycling chamber and cycled between -40℃ and 85℃. Each temperature point is kept for 2 hours, the heating and cooling rate is 2℃ / min, and the cycle is repeated 100 times. After the test, the appearance of the composite nylon membrane is observed, and the tensile strength retention rate and water vapor transmission rate are tested. It is required that there is no cracking, no delamination, and no whitening after the cycle. The tensile strength retention rate is ≥90%, and the increase in water vapor transmission rate is ≤0.3g / (m²·24h).

[0061] (87) Heat-sealing layer performance test: Take the heat-sealing layer film obtained in step (6), cut it into appropriate sizes, and test it according to the following method:

[0062] (87a) Heat seal strength and initial heat seal temperature test: The heat seal film is placed in pairs and heat-sealed at different temperatures (100℃ to 130℃, with an interval of 5℃). The heat seal pressure is 0.3MPa and the heat seal time is 1s. The film is cut into 15mm wide samples and the heat seal strength is tested on a tensile testing machine at a speed of 300mm / min. The heat seal strength-temperature curve is plotted and the temperature corresponding to the strength of 2.5N / 15mm is defined as the initial heat seal temperature.

[0063] (87b) Friction coefficient test: Place the heat-sealing film on the friction coefficient tester to test the dynamic friction coefficient and static friction coefficient. The dynamic friction coefficient is required to be ≤0.8.

[0064] (88) Tensile-corrosion coupled accelerated aging test: The composite nylon film was cut into dumbbell-shaped samples. A pre-tension stress equivalent to 50% of its tensile strength was applied. Under the stress condition, the samples were placed in an environment of 85℃ and 85%RH for 1 day, 3 days, 7 days, 14 days, and 28 days, respectively. After the stress was released, the overall tensile strength, elongation at break, and elastic modulus of the composite film were tested. At the same time, in-situ X-ray diffraction tests were performed to record the crystal form changes of the nylon layer. The strength retention rate after coupled aging was calculated according to the following formula:

[0065] ;

[0066] The cross-section of the tensile fractured specimen was observed by scanning electron microscopy to analyze the changes in the bonding state of the interface between the nylon layer and the fluorinated modified layer, and between the nylon layer and the aluminum foil layer before and after aging. It was required that the strength retention rate be ≥80% after 28 days of coupled aging, and the cross-section SEM image showed no delamination at the interface and no peeling of the protective layer.

[0067] (89) Pack the qualified products after testing.

[0068] The purpose of the nylon layer hydrogen bond shielding and recovery verification test is to verify the shielding effect of metal chlorides on hydrogen bonds and the recovery effect after decomplexation. The nylon layer mechanical property test measures the mechanical properties of the nylon layer itself. The overall tensile performance test of the composite membrane verifies the overall mechanical properties after lamination. The water vapor barrier performance test measures the water vapor permeability and water barrier stability under long-term humid and hot conditions. The solid electrolyte compatibility test verifies the interfacial compatibility between the composite membrane and the solid electrolyte. The high and low temperature cycle durability test verifies the performance stability of the composite membrane under alternating temperature environments. The heat seal layer performance test measures the heat seal strength, initial heat seal temperature, and coefficient of friction. The tensile-corrosion coupled accelerated aging test simulates the combined conditions of mechanical stress and humid and hot environments to verify long-term service performance.

[0069] Comparative Example 1: The difference between Comparative Example 1 and Example 1 is that the nylon layer of Comparative Example 1 is made of conventional PA66 and has not undergone fluorination modification; the heat-sealing layer is made of conventional ternary copolymer polypropylene and no composite additive system has been added.

[0070] The performance comparison between Example 1 and Comparative Example 1 is shown in the table below:

[0071] Test Project Example 1 Comparative Example 1 Increase Tensile strength of nylon layer (MPa) 85.2 72.3 +17.8% Tensile strength of composite membrane (MPa) 102.5 85.6 +19.7% Initial water vapor transmission rate (g / (m²·24h)) 0.72 2.15 -66.5% Initial heat-sealing temperature of the heat-sealing layer (°C) 111 118 -7℃ Dynamic friction coefficient of heat seal layer 0.75 1.099 -31.7% Strength retention rate after 28 days of coupling aging (%) 86.5 65.8 +20.7% Interface aging state No layering, no peeling Slight stratification Significant improvement

[0072] As can be seen from the comparison, Example 1 uses metal chloride hydrogen bond regulation technology to prepare a nylon layer and performs fluorination modification treatment on its surface. At the same time, a low-friction heat-sealing layer is used. Compared with Comparative Example 1, the tensile strength of the nylon layer is increased by 17.8%, the water vapor barrier performance is increased by 66.5%, the friction coefficient is reduced by 31.7%, and the overall performance is comprehensively improved.

[0073] The nylon layer of this invention employs a metal chloride system composed of calcium chloride and lanthanum chloride, resulting in a significant increase in elongation at break and greatly improving the material's stretchability, facilitating biaxial stretching. After decomplexing treatment, the tensile strength is significantly enhanced, and the mechanical strength is strengthened. This is because the complexation effect of the metal chloride effectively regulates the hydrogen bonding of PA66, thereby affecting its crystallization behavior. Shielding the hydrogen bonds enhances the stretchability of PA66, thus facilitating biaxial stretching. Furthermore, the film recovers hydrogen bonds through decomplexing, which is beneficial to its mechanical properties. The fundamental reason for the increased tensile strength is that water dissolves the chlorides in the fiber, allowing the hydrogen bonds between amide bonds to recover, which has a positive effect on improving mechanical properties. (The film's orientation increases significantly after stretching, undergoing a transformation from α-crystal to γ-crystal under stress-induced conditions, with a slight increase in relative crystallinity. After decomplexing, the sample reverts to the α-crystal form without significant deorientation. At this point, due to the combined effects of high orientation and hydrogen bond recovery, the material's relative crystallinity increases significantly, and the mechanical strength is also enhanced.) The shielding and inhibition effects of calcium chloride and lanthanum chloride on hydrogen bonds have a synergistic effect. In other words, the nylon layer of this invention uses a metal chloride system composed of calcium chloride and lanthanum chloride to decomplex the bonds, which significantly improves the stretchability of the material during the processing stage, facilitating high-ratio biaxial stretching. This also ensures high strength of the nylon layer in the finished product stage. This reversible hydrogen bond control strategy achieves two goals at once: solving the problem of high-ratio stretching during processing and ensuring the high mechanical properties of the final product.

[0074] This invention modifies the surface of a nylon layer by fluorination. By grafting fluorinated silanes, a dense fluorinated hydrophobic layer is formed on the nylon surface. Utilizing the low surface energy of fluorine atoms, the adsorption and permeation of water vapor on the nylon surface are significantly reduced without compromising the mechanical properties of the nylon layer. Fluorination successfully introduces fluorosilane groups onto the nylon membrane surface, thereby reducing its hydrophilicity and solubility in water, greatly weakening the water absorption capacity of nylon and enhancing its water barrier properties. This invention employs hydroxylation and fluorination methods to modify the nylon layer. First, active hydroxyl groups are introduced onto the nylon surface. Then, hydrolyzed fluorinated silanes undergo dehydration condensation with the hydroxyl groups, allowing highly water-resistant fluorocarbon chains to be firmly grafted onto the nylon layer through a chemical reaction. The reaction conditions are mild, the steps are simple, and the fluorination does not alter the mechanical properties of the membrane itself.

[0075] The heat-sealing layer is modified by blending ternary random copolymer polypropylene with a composite additive system. Among them, the organosilicon polymer anti-blocking agent forms a micro-nano structure on the film surface, which significantly reduces the coefficient of friction and prevents the film from sticking together during the storage and transportation of the roll material.

[0076] The tensile-corrosion coupled accelerated aging test method was adopted, which takes into account the dual effects of mechanical stress and water vapor permeation on the encapsulation film during use, providing a basis for material performance evaluation and life prediction.

Claims

1. A high-strength solid-state battery encapsulation nylon film, comprising a nylon layer, an aluminum foil layer, and a heat-sealing layer, characterized in that: The nylon layer is prepared by biaxial stretching after solution blending of polyamide 66 and metal chloride. The metal chloride is a compound of calcium chloride and lanthanum chloride. The surface of the nylon layer is fluorinated, which involves grafting trifluoropropyltrimethoxysilane onto the surface of the nylon layer. The heat-sealing layer is a polypropylene film, which is prepared by melt blending of polypropylene matrix and composite additives and then casting process. The composite additives consist of antioxidants, stabilizers and organosilicon polymer antiblocking agents.

2. The high-strength solid-state battery encapsulation nylon film according to claim 1, characterized in that: The nylon layer is composed of the following components by mass ratio: polyamide 66 90.9%, calcium chloride 4.55%, and lanthanum chloride 4.55%. The components of the heat-sealing layer by mass ratio are: 99.7% ternary random copolymer polypropylene, 0.1% antioxidant, 0.1% stabilizer, and 0.1% organosilicon polymer antiblocking agent.

3. The method for producing a high-strength solid-state battery encapsulation nylon film according to claim 1, characterized in that... Includes the following steps: (1) Preparation of modified nylon granules: Polyamide 66 was dissolved in formic acid, and calcium chloride and lanthanum chloride were added. The mass ratio of polyamide 66 to metal chloride was 100:10, and the mass ratio of calcium chloride to lanthanum chloride was 1:

1. The mixture was stirred and dissolved for 4.5 h. The solution was placed in an evaporating dish and evaporated at room temperature for 12 h. Then, it was slowly heated to 100°C in a vacuum oven and dried for 8 h to obtain dry modified nylon granules. (2) Preparation of nylon layer: The modified nylon granules obtained in step (1) are formed by biaxial stretching process; (3) Decomplexation treatment: The nylon film obtained in step (2) is immersed in deionized water for 4 hours to restore hydrogen bonds. After being taken out, it is vacuum dried at 50°C for 6 hours. (4) Fluorination modification treatment of nylon layer surface: The nylon layer film obtained in step (3) is placed in formaldehyde-phosphoric acid solution and soaked at 60°C for 12h for hydroxylation pretreatment. After taking it out, it is rinsed with water and dried. Prepare fluorination modification solution by mixing trifluoropropyltrimethoxysilane, anhydrous ethanol, deionized water and 0.1mol / L hydrochloric acid in a molar ratio of 1.000:0.044:0.031:0.0057 and stirring evenly. Immerse the hydroxylated nylon layer film in the modification solution and react at 30°C for 24h. After taking it out, wipe off the excess solution on the surface and place it in a vacuum drying oven to dry at 30°C for 24h to obtain a nylon film with fluorination modification on the surface. (5) Preparation of aluminum foil layer: The surface of aluminum foil is degreased and subjected to corrosion-resistant treatment to obtain aluminum foil layer; (6) Preparation of heat-sealing layer: Ternary random copolymer polypropylene is mixed with composite additives and formed by casting process. The casting temperature is controlled at 230°C and the cooling roller temperature is 35°C to prepare a heat-sealing layer film with a thickness of 60 micrometers. (7) Composite: The nylon film obtained in step (4), the aluminum foil layer obtained in step (5), and the heat-sealing layer obtained in step (6) are composited using a dry process.

4. The method of producing a high-strength solid-state battery packaging nylon film according to claim 3, characterized by It also includes step (8): performing performance tests on the obtained nylon film, including the following steps: (81) Verification test of hydrogen bond shielding and recovery of nylon layer: Before the fluorination modification treatment, the nylon layer film obtained in step (2) was cut into small pieces and its infrared spectrum was tested by Fourier transform infrared spectrometer. The peak position changes of amide I band and amide II band were recorded. Its melting and crystallization behavior was tested by differential scanning calorimeter. The heating rate was 10℃ / min and the temperature range was 30℃ to 280℃. The nylon film after decomplexation treatment was tested again by infrared spectroscopy and DSC. The characteristic peak shifts and crystallization behavior changes before and after hydrogen bond shielding were compared to verify the shielding effect of metal chloride on hydrogen bonds and the recovery effect after decomplexation. (82) Mechanical property test of nylon layer: Before fluorination modification, the nylon layer film obtained in step (2) was cut into dumbbell-shaped samples and subjected to tensile test on an electronic universal testing machine. The tensile speed was 50 mm / min, and the tensile strength, elongation at break and elastic modulus were recorded. (83) Overall tensile properties test of composite film: The final composite nylon film was cut into dumbbell-shaped specimens and subjected to tensile test on an electronic universal testing machine at a tensile speed of 50 mm / min. The tensile strength, elongation at break and elastic modulus were recorded. (84) Water vapor barrier performance test: The water vapor transmission rate of the composite nylon membrane was tested at 38℃ and 90%RH using a water vapor transmission rate tester for 7 consecutive days and the steady-state transmission rate value was recorded. At the same time, the composite nylon membrane was placed in a constant temperature and humidity chamber at 85℃ and 85%RH for 30 days. The water vapor transmission rate was tested every 5 days and the curve of water vapor transmission rate change over time was plotted to evaluate the water barrier stability of the material under long-term humid and hot environment. The initial water vapor transmission rate was required to be ≤0.72g / (m²·24h) and the water vapor transmission rate after 30 days was required to be ≤1.2g / (m²·24h). (85) Solid electrolyte compatibility test: The composite nylon film and the solid electrolyte sheet are tightly bonded together and hot-pressed at 60℃ and 0.5MPa for 24h. After taking it out, observe the changes in the contact surface between the composite nylon film and the solid electrolyte, and test the tensile strength retention rate of the composite nylon film after hot pressing. At the same time, the bonded sample is placed in a 60℃ environment and left to stand for 30 days. Every 5 days, it is taken out to observe whether there are bubbles, delamination, discoloration and other phenomena at the interface, and evaluate the interface compatibility between the composite nylon film and the solid electrolyte. The tensile strength retention rate after hot pressing is required to be ≥95%, and there should be no bubbles, no delamination and no obvious discoloration after 30 days of standing. (86) High and low temperature cycle durability test: The composite nylon membrane is placed in a temperature cycling chamber and cycled between -40℃ and 85℃. Each temperature point is kept for 2 hours, the heating and cooling rate is 2℃ / min, and the cycle is repeated 100 times. After the test, the appearance of the composite nylon membrane is observed, and the tensile strength retention rate and water vapor transmission rate are tested. It is required that there is no cracking, no delamination, and no whitening after the cycle. The tensile strength retention rate is ≥90%, and the increase in water vapor transmission rate is ≤0.3g / (m²·24h). (87) Heat-sealing layer performance test: Take the heat-sealing layer film obtained in step (6), cut it into appropriate sizes, and test it according to the following method: (87a) Heat seal strength and initial heat seal temperature test: The heat seal film is placed in pairs and heat-sealed at different temperatures (100℃ to 130℃, with an interval of 5℃). The heat seal pressure is 0.3MPa and the heat seal time is 1s. The film is cut into 15mm wide samples and the heat seal strength is tested on a tensile testing machine at a speed of 300mm / min. The heat seal strength-temperature curve is plotted and the temperature corresponding to the strength of 2.5N / 15mm is defined as the initial heat seal temperature. (87b) Friction coefficient test: Place the heat-sealing film on the friction coefficient tester to test the dynamic friction coefficient and static friction coefficient. The dynamic friction coefficient is required to be ≤0.

8. (88) Tensile-corrosion coupled accelerated aging test: The composite nylon film was cut into dumbbell-shaped samples. A pre-tension stress equivalent to 50% of its tensile strength was applied first. Under the stress condition, it was placed in an environment of 85℃ and 85%RH for 1 day, 3 days, 7 days, 14 days and 28 days respectively. After the stress was released, the overall tensile strength, elongation at break and elastic modulus of the composite film were tested. At the same time, in-situ X-ray diffraction test was performed to record the crystal form change of the nylon layer. The cross-section of the tensile fractured specimen was observed by scanning electron microscopy to analyze the changes in the bonding state of the interface between the nylon layer and the fluorinated modified layer, and between the nylon layer and the aluminum foil layer before and after aging. It was required that the strength retention rate be ≥80% after 28 days of coupled aging, and the cross-section SEM image showed no delamination at the interface and no peeling of the protective layer. (89) Pack the qualified products after testing.