Corrosion and heat resistant flame-retardant pet-based film for composite current collector and preparation method thereof

Abstract

The application relates to the field of composite current collector base film materials, and particularly discloses a corrosion-resistant and heat-resistant flame-retardant PET base film for composite current collectors and a preparation method thereof.The preparation raw materials of the base film include the following in parts by weight: 70-90 parts of PET resin, 6-18 parts of PPS resin, 1.5-4 parts of a compatilizer, 0.5-2 parts of a lubricant, 1-3 parts of a crosslinking agent and 20-35 parts of a flame-retardant multi-effect filler.In the application, the corrosion resistance of the PET base film can be remarkably improved by adding the PPS resin into the PET base material, and the heat stability and the flame-retardant property can also be improved.The self-prepared flame-retardant and heat-resistant synergistic filler is assembled and compounded by cross treatment of cerium and aluminum co-doped mesoporous SiO2 and basalt fibers through a coupling agent, and then is obtained by antioxidant loading functionalization and phosphorus-containing flame-retardant copolymer grafting, so that the flame-retardant property, the high-temperature resistance, the corrosion resistance and the antioxidant property of the base film can be comprehensively improved.

Description

Technical Field

[0001] This invention relates to the field of composite current collector base film materials. In particular, it relates to a corrosion-resistant, heat-resistant, and flame-retardant PET base film for composite current collectors and its preparation method. Background Technology

[0002] Composite current collectors are core components in battery systems that carry electrode active materials and collect current. They employ a three-layer structure design of "metal-polymer-metal". Compared to the copper and aluminum foils used in traditional lithium-ion batteries, composite current collectors have significant advantages in improving battery energy density, safety, and material cost, and are currently widely used in lithium / sodium-ion batteries and energy storage devices.

[0003] Composite current collector base film materials mainly use polymer materials such as PET, PP, or PI. Among them, PET (polyethylene terephthalate) has advantages such as high tensile strength, excellent mechanical properties, and good copper adhesion as a composite current collector base film. For example, patent CN121004784A discloses a production method of a high mechanical performance PET composite current collector base film, and patent CN117946500B discloses a conductive composite current collector base film and its preparation method. However, PET film has poor heat resistance and resistance to strong acids and alkalis. The corrosiveness of electrolytes and the high-temperature environment of batteries in composite current collector applications pose challenges to the base film, and traditional PET films cannot meet the application requirements. On the other hand, traditional PET films have poor flame retardant properties, and their direct application in composite current collectors may pose safety hazards.

[0004] Basalt fiber is a continuous fiber drawn from natural basalt. It is a new type of inorganic, environmentally friendly, high-performance fiber material composed of oxides such as silicon dioxide, aluminum oxide, calcium oxide, magnesium oxide, iron oxide, and titanium dioxide. Basalt fiber possesses excellent corrosion resistance and flame retardancy, high strength and high modulus, high thermal stability, and a significant cost advantage, costing approximately 1 / 10 of carbon fiber, making it a promising candidate for use as a filler in PET. However, its poor compatibility with polymers such as PET limits its application. Therefore, it is now necessary to improve existing technologies to provide more reliable solutions. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a corrosion-resistant, heat-resistant, and flame-retardant PET base film for composite current collectors and its preparation method, in order to address the shortcomings of the prior art.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a corrosion-resistant, heat-resistant, and flame-retardant PET base film for composite current collectors and its preparation method, wherein the raw materials for preparation include, by weight: 70-90 parts of PET resin, 6-18 parts of PPS resin, 1.5-4 parts of compatibilizer, 0.5-2 parts of lubricant, 1-3 parts of crosslinking agent, and 20-35 parts of flame-retardant multi-effect filler; The flame-retardant multi-effect filler is prepared through the following steps: S1. Basalt fibers are modified by using silane coupling agent 1 containing double bonds to obtain modified basalt fibers. S2. Prepare cerium-aluminum co-doped mesoporous SiO2, and then modify it with silane coupling agent 2 to obtain modified composite mesoporous SiO2. S3. Modified composite mesoporous SiO2 is grafted onto the surface of modified basalt fiber to obtain SiO2-grafted basalt fiber composite. S4. An antioxidant was loaded onto the SiO2-grafted basalt fiber composite by impregnation to obtain an intermediate product. S5. Grafting phosphorus-containing flame-retardant copolymers onto the intermediate product yields a flame-retardant multi-effect filler.

[0007] Preferably, the silane coupling agent 1 is at least one of the following: silane coupling agent KH570, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltri(β-methoxyethoxy)silane, and acryloyloxysilane coupling agent.

[0008] Preferably, the silane coupling agent 2 is at least one of silane coupling agent KH550 and silane coupling agent KH560.

[0009] Preferably, the antioxidant is at least one of antioxidant 168 and antioxidant TH-1790.

[0010] Preferably, the flame-retardant multi-effect filler is prepared through the following steps: S1. Add KH570 to a mixture of ethanol and deionized water, stir and react to obtain a hydrolysate. Add basalt fiber to the hydrolysate, heat and stir to separate the basalt fiber, dry it to obtain modified basalt fiber. S2. Preparation of modified composite mesoporous SiO2: S2-1, Preparation of cerium-aluminum co-doped mesoporous SiO2: Add CTAB, Ce(NO3)3·6H2O, and Al(NO3)3 to deionized water, stir, and simultaneously add tetraethyl orthosilicate and urea solution. After stirring, transfer the resulting mixture to a reaction vessel and react at 120-160℃ for 6-20 h. After centrifugation, wash and dry the solid, and calcine at 500-650℃ for 2-8 h to obtain cerium-aluminum co-doped mesoporous SiO2. S2-2, Coupling agent modification: Cerium-aluminum co-doped mesoporous SiO2 and deionized water were added to ethanol, ultrasonically dispersed, and then coupling agent KH560 was added. The mixture was heated and stirred to react, centrifuged and filtered, and dried to obtain modified composite mesoporous SiO2. S3. Modified composite mesoporous SiO2 and modified basalt fiber are added to toluene, ultrasonically dispersed, heated and stirred under reflux, cooled, washed and dried to obtain SiO2 grafted basalt fiber composite. S4. The SiO2-grafted basalt fiber composite was added to an acetone solution of antioxidant TH-1790, stirred, shaken, centrifuged, and the precipitate was washed and dried to obtain the intermediate product. S5, Grafted phosphorus-containing flame-retardant copolymer: S5-1. Add the intermediate product to tetrahydrofuran, sonicate under nitrogen gas to obtain an intermediate product dispersion; S5-2. Styrene, glycidyl methacrylate, maleic anhydride, isooctyl acrylate, dimethyl vinylphosphonate and emulsifier are added to tetrahydrofuran and stirred with nitrogen gas to obtain a monomer mixture. S5-3. Add the monomer mixture to the intermediate product dispersion under stirring, stir, add initiator 1 and initiator 2, stir under nitrogen protection and heating, cool, filter, wash and dry the solid product to obtain basalt fiber-based composite filler.

[0011] Preferably, in step S3, the mass ratio of modified composite mesoporous SiO2 to modified basalt fiber is 0.2-0.8:1.

[0012] Preferably, the initiator 1 is at least one selected from n-butyllithium, sec-butyllithium, phenyllithium, potassium amino, sodium methoxide, and potassium ethoxide; Initiator 2 is at least one of azobisisobutyronitrile, azobisisoheptanenitrile, dimethyl azobisisobutyrate, benzoyl peroxide, di-tert-butyl peroxide, tert-butyl hydroperoxide, and cumene hydroperoxide.

[0013] Preferably, the flame-retardant multi-effect filler is prepared through the following steps: S1, Basalt fiber coupling agent modification: KH570 was added at a mass concentration of 1.5-6% to a mixture of ethanol and deionized water at a volume ratio of 9:1. The mixture was stirred at 20-40℃ for 0.5-2 hours to obtain a hydrolysate. Basalt fiber was added to the hydrolysate at a mass ratio of 0.3g to 10mL. The mixture was stirred at 50-70℃ for 1-4 hours to separate the basalt fiber. The basalt fiber was then vacuum dried to obtain modified basalt fiber. S2. Preparation of modified composite mesoporous SiO2: S2-1, Preparation of cerium-aluminum co-doped mesoporous SiO2: Add 1.25-5g CTAB, 0.25-1g Ce(NO3)3·6H2O, and 0.75-2.5g Al(NO3)3 to 40-160mL of deionized water and stir for 15-60min. Then, simultaneously add 4-16mL of tetraethyl orthosilicate and 10-40mL of urea solution with a concentration of 2-8mol / L. After stirring for 1-4h, transfer the resulting mixture to a reaction vessel and react at 120-160℃ for 6-20h. After cooling and centrifugation, wash the solid with deionized water, dry it, and calcine it in a muffle furnace at 500-650℃ for 2-8h. After cooling and grinding, obtain cerium-aluminum co-doped mesoporous SiO2. S2-2, Coupling agent modification: Add 0.5-2g of cerium-aluminum co-doped mesoporous SiO2 and 2.5-10mL of deionized water to 20-90mL of ethanol, and ultrasonically disperse for 0.5-2h. Then add 0.01-0.04g of coupling agent KH560, stir and react at 60-80℃ for 1-4h, centrifuge, filter, and dry to obtain modified composite mesoporous SiO2. S3, Modified composite mesoporous SiO2 grafted with modified basalt fiber: Add 0.2-0.8g of modified composite mesoporous SiO2 and 1g of modified basalt fiber to 50-200mL of toluene, ultrasonically disperse for 0.5-2h, then stir and reflux at 60-75℃ for 6-24h, cool to room temperature, wash with ethanol, and dry to obtain SiO2 grafted basalt fiber composite. S4, Antioxidant Loading: Add 2.5-10g of SiO2-grafted basalt fiber composite to 75-300mL of acetone solution containing antioxidant TH-1790 at a concentration of 0.05-0.5g / mL, stir for 0.5-2h, then shake in a shaker at 50-70℃ for 8-30h, centrifuge, wash the precipitate with acetone and ethanol sequentially, and dry to obtain the intermediate product; S5, Grafted phosphorus-containing flame-retardant copolymer: S5-1. Add 4-16g of intermediate product to 60-250mL of tetrahydrofuran, and sonicate under nitrogen for 0.5-2h to obtain an intermediate product dispersion. S5-2. Add 6-24g styrene, 3.5-15g glycidyl methacrylate, 2-8g maleic anhydride, 1.5-7g isooctyl acrylate, 6.5-26g dimethyl vinylphosphonate and 1-4g emulsifier SDBS to 100-300mL of tetrahydrofuran, stir under nitrogen for 15-60min to obtain a monomer mixture. S5-3. Add the monomer mixture to the intermediate product dispersion under stirring, stir for 0.5-2 h, add 0.075-0.3 g sec-butyllithium and 0.12-0.5 g azobisisobutyronitrile, under nitrogen protection, stir and react at 50-70 °C for 5-20 h, cool to room temperature, filter, wash the solid product with ethanol, dry, and obtain basalt fiber-based composite filler.

[0014] Preferably, the compatibilizer is at least one selected from PP-g-MAH, PE-g-MAH, SOG-03, SOG-02, and POE-g-GMA. The lubricant is at least one of silicone oil, polyethylene wax, polyamide wax, calcium stearate, magnesium stearate, and barium stearate; The crosslinking agent is at least one of diphenylmethane diisocyanate, pentaerythritol tetraacrylate, and pentaerythritol triacrylate.

[0015] The present invention also provides a method for preparing the corrosion-resistant, heat-resistant, and flame-retardant PET-based film for composite current collectors as described above, comprising the following steps: PET resin, PPS resin, compatibilizer, lubricant, crosslinking agent, and flame-retardant multi-effect filler are mixed evenly according to the weight ratio. The resulting mixture is melt-extruded at 275-300℃, cooled, and cast into sheets. After preheating, the cast sheets are stretched longitudinally and transversely in sequence to obtain a corrosion-resistant, heat-resistant, and flame-retardant PET base film for composite current collectors.

[0016] The beneficial effects of this invention are: In this invention, by compounding PPS resin into PET substrate, the corrosion resistance of PET film can be significantly improved, as well as its thermal stability and flame retardant properties can be enhanced. The flame-retardant and heat-resistant synergistic filler in this invention is assembled and composited from cerium-aluminum co-doped mesoporous SiO2 and basalt fiber through a coupling agent cross-treatment method, and then functionalized by antioxidant loading and grafted with phosphorus-containing flame-retardant copolymer. It can comprehensively improve the flame-retardant performance, high-temperature resistance, corrosion resistance and oxidation resistance of the base film. In this invention, by loading antioxidants onto the mesoporous structure of modified composite mesoporous SiO2 nanoparticles, the antioxidants can be released in a sustained manner, thereby prolonging their effect. Furthermore, by combining the effect of basalt fibers on improving the dispersibility of modified composite mesoporous SiO2 nanoparticles, the antioxidants can be more evenly dispersed in the base film, allowing the antioxidants to exert their effects more fully.

[0017] Both basalt fiber and cerium-aluminum co-doped mesoporous SiO2, as inorganic fillers, suffer from poor dispersion and incompatibility with PET resin systems. In this invention, the two are assembled into a composite: during the SiO2-grafted basalt fiber composite process, the dispersibility of both can be improved to some extent through coupling agent modification. Furthermore, by using styrene, glycidyl methacrylate, maleic anhydride, isooctyl acrylate, and dimethyl vinylphosphonate as mixed monomers, and grafting a phosphorus-containing flame-retardant copolymer onto the composite through in-situ polymerization, its dispersibility in PET resin systems can be significantly improved.

[0018] In the basalt fiber-based composite filler of the present invention, the synergistic effect of the components such as basalt fiber, cerium-aluminum co-doped mesoporous SiO2, antioxidant, and phosphorus-containing flame-retardant copolymer can enhance the flame retardant performance, corrosion and heat resistance, mechanical properties and antioxidant properties of the base film through the mutual cooperation between the components. Furthermore, the combination of basalt fiber-based composite filler and PPS resin can further enhance the corrosion resistance and heat resistance of the base film. Attached Figure Description

[0019] Figure 1 The infrared absorption spectra of the basalt fibers in Example 1 and the prepared SiO2-grafted basalt fiber composite (BF-CeAl@SiO2); Figure 2 The results of the sustained-release performance test of the basalt fiber-based composite filler prepared in Example 1; Figure 3 The flame retardant performance test results are for the examples and comparative examples; Figure 4 The results of heat resistance tests for the examples and comparative examples are shown. Figure 5 The results of electrolyte corrosion resistance tests are for the examples and comparative examples; Figure 6 The tensile strength test results are for the examples and comparative examples; Figure 7 The results of heat aging performance tests are for the examples and comparative examples. Detailed Implementation

[0020] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the materials and reagents used in the following examples are commercially available. For examples where specific conditions are not specified, conventional conditions or conditions recommended by the manufacturer are followed. For reagents or instruments whose manufacturers are not specified, they are all commercially available products.

[0022] This invention provides a corrosion-resistant, heat-resistant, and flame-retardant PET base film for composite current collectors and its preparation method. The raw materials for preparation include, by weight, 70-90 parts of PET resin, 6-18 parts of PPS resin, 1.5-4 parts of compatibilizer, 0.5-2 parts of lubricant, 1-3 parts of crosslinking agent, and 20-35 parts of flame-retardant multi-effect filler. The preparation method of this base film includes the following steps: PET resin, PPS resin, compatibilizer, lubricant, crosslinking agent, and flame-retardant multi-effect filler are mixed evenly according to the weight ratio. The resulting mixture is melt-extruded at 275-300℃, cooled, and cast into sheets. After preheating, the cast sheets are stretched longitudinally and transversely in sequence to obtain a corrosion-resistant, heat-resistant, and flame-retardant PET base film for composite current collectors.

[0023] In this invention, the flame-retardant multi-effect filler is prepared through the following steps: S1, Basalt fiber coupling agent modification: Coupling agent KH570 was added at a mass concentration of 1.5-6% to a mixture of ethanol and deionized water at a volume ratio of 9:1. The mixture was stirred at 20-40℃ for 0.5-2 hours to obtain a hydrolysate. Basalt fiber was added to the hydrolysate at a mass ratio of 0.3g to 10mL. The mixture was stirred at 50-70℃ for 1-4 hours, and the basalt fiber was separated and vacuum dried to obtain modified basalt fiber. S2. Preparation of modified composite mesoporous SiO2: S2-1, Preparation of cerium-aluminum co-doped mesoporous SiO2: Add 1.25-5g CTAB (hexadecyltrimethylammonium bromide), 0.25-1g Ce(NO3)3·6H2O, and 0.75-2.5g Al(NO3)3 to 40-160mL of deionized water and stir for 15-60min. Then, simultaneously add 4-16mL of tetraethyl orthosilicate and 10-40mL of urea solution with a concentration of 2-8mol / L. After stirring for 1-4h, transfer the resulting mixture to a reaction vessel and react at 120-160℃ for 6-20h. After cooling and centrifugation, wash the solid with deionized water, dry it, and calcine it in a muffle furnace at 500-650℃ for 2-8h. After cooling and grinding, obtain cerium-aluminum co-doped mesoporous SiO2. S2-2, Coupling agent modification: Add 0.5-2g of cerium-aluminum co-doped mesoporous SiO2 and 2.5-10mL of deionized water to 20-90mL of ethanol, and ultrasonically disperse for 0.5-2h. Then add 0.01-0.04g of coupling agent KH560, stir and react at 60-80℃ for 1-4h, centrifuge, filter, and dry to obtain modified composite mesoporous SiO2. S3, Modified composite mesoporous SiO2 grafted with modified basalt fiber: Add 0.2-0.8g of modified composite mesoporous SiO2 and 1g of modified basalt fiber to 50-200mL of toluene, ultrasonically disperse for 0.5-2h, then stir and reflux at 60-75℃ for 6-24h, cool to room temperature, wash with ethanol, and dry to obtain SiO2 grafted basalt fiber composite. S4, Antioxidant Loading: Add 2.5-10g of SiO2-grafted basalt fiber composite to 75-300mL of acetone solution containing antioxidant TH-1790 at a concentration of 0.05-0.5g / mL, stir for 0.5-2h, then shake in a shaker at 50-70℃ for 8-30h, centrifuge, wash the precipitate with acetone and ethanol sequentially, and dry to obtain the intermediate product; S5, Grafted phosphorus-containing flame-retardant copolymer: S5-1. Add 4-16g of intermediate product to 60-250mL of tetrahydrofuran, and sonicate under nitrogen for 0.5-2h to obtain an intermediate product dispersion. S5-2. Add 6-24g styrene, 3.5-15g glycidyl methacrylate, 2-8g maleic anhydride, 1.5-7g isooctyl acrylate, 6.5-26g dimethyl vinylphosphonate and 1-4g emulsifier SDBS (sodium dodecylbenzene sulfonate) to 100-300mL tetrahydrofuran, stir under nitrogen for 15-60min to obtain a monomer mixture; S5-3. Add the monomer mixture to the intermediate product dispersion under stirring, stir for 0.5-2 h, add 0.075-0.3 g sec-butyllithium and 0.12-0.5 g azobisisobutyronitrile, under nitrogen protection, stir and react at 50-70 °C for 5-20 h, cool to room temperature, filter, wash the solid product with ethanol, dry, and obtain basalt fiber-based composite filler.

[0024] Invention Mechanism PPS resin (polyphenylene sulfide resin) has a stable backbone composed of high-bond-energy CS and CC aromatic bonds, and has high crystallinity and low polarity, giving it excellent resistance to acids, alkalis and solvents. At the same time, it also has good heat resistance and certain flame retardant properties. When compounded and added to PET, it can significantly improve the corrosion resistance of PET base film, as well as improve thermal stability and flame retardant properties.

[0025] In this invention, the flame-retardant and heat-resistant synergistic filler is assembled and composited from cerium-aluminum co-doped mesoporous SiO2 and basalt fibers through a coupling agent cross-treatment method, and then functionalized by antioxidant loading and grafted with phosphorus-containing flame-retardant copolymer. It can comprehensively improve the flame-retardant performance, high-temperature resistance, corrosion resistance and oxidation resistance of the base film. The preparation and mechanism of action are explained in more detail below to facilitate understanding of this invention.

[0026] 1. Preparation mechanism: First, basalt fibers were surface-modified using a silane coupling agent KH570 containing double bonds to obtain modified basalt fibers. Simultaneously, cerium-aluminum co-doped mesoporous SiO2 was prepared using CTAB as a template agent and Ce(NO3)3·6H2O and Al(NO3)3 as cerium and aluminum sources, respectively, through hydrothermal reaction and high-temperature calcination. This was then surface-modified using coupling agent KH560 to obtain modified composite mesoporous SiO2. Next, the modified basalt fibers and the modified composite mesoporous SiO2 were blended and reacted, and the modified composite mesoporous SiO2 was grafted onto the surface of the modified basalt fibers to obtain a SiO2-grafted basalt fiber composite. In the above preparation process, the silanol produced by KH570 hydrolysis dehydrates and condenses with Si-OH on the surface of basalt fiber to achieve connection; similarly, the silanol produced by KH560 hydrolysis dehydrates and condenses with Si-OH on the surface of mesoporous SiO2 to achieve connection; then, Si-O-Si bonds are formed by the condensation of mesoporous SiO2 and silanol on basalt fiber, thus achieving the grafting of modified composite mesoporous SiO2 onto basalt fiber.

[0027] Then, by impregnation, antioxidants were loaded onto the mesoporous SiO2 in the SiO2-grafted basalt fiber composite through the mesoporous structure, and an intermediate product was obtained. Finally, styrene, glycidyl methacrylate, maleic anhydride, and isooctyl acrylate were used as the main monomers, and dimethyl vinyl phosphonate was used as the doped phosphorus-containing flame retardant monomer to perform in-situ copolymerization grafting on the intermediate product to obtain the final basalt fiber-based composite filler. During the grafting process, coupling agent KH570 introduced a large number of double bonds on the surface of basalt fibers. These double bonds participated in the copolymerization reaction, thereby realizing the chemical connection between the polymer and the basalt fibers.

[0028] 2. Mechanism of action Basalt fiber has high tensile strength and high modulus, and is heat-resistant, acid and alkali-resistant, as well as non-flammable. It can improve the mechanical strength, corrosion resistance, heat resistance and flame retardancy of the base film, and also has the advantages of being natural and environmentally friendly.

[0029] In the cerium-aluminum co-doped mesoporous SiO2 of the present invention: SiO2 can enhance mechanical properties: improve the hardness, wear resistance, scratch resistance and toughness of PET film, and improve heat resistance and weather resistance. In addition, the silica particles form a micro-rough structure on the surface of PET film, which can reduce the actual contact area and improve anti-adhesion performance. Doped CeO2 can have a synergistic effect of flame retardancy and anti-aging: CeO2 can penetrate the Ce surface... 3+ / Ce 4+ The redox cycle captures free radicals, interrupts the chain reaction, and thus inhibits the spread of flames. At the same time, it can also catalyze the formation of a carbon layer, which improves the flame retardant performance through physical isolation. CeO2 inhibits the oxidative degradation of PET molecular chains by scavenging free radicals, thereby improving the anti-aging performance. Doped Al₂O₃ improves thermal stability, mechanical strength, and chemical inertness, reduces the collapse of mesoporous structures, and enhances the heat resistance, mechanical properties, and corrosion resistance of the base film. Meanwhile, the loading of silica promotes the dispersion of cerium oxide, while the thermal stability of alumina inhibits the grain growth of cerium oxide particles at high temperatures, thus maintaining its high specific surface area and catalytic activity, and helping to maintain flame-retardant properties at higher temperatures. Therefore, in cerium-aluminum co-doped mesoporous SiO₂, the synergistic effect of each component can enhance its flame-retardant properties and mechanical strength. In this invention, by grafting modified composite mesoporous SiO2 onto the surface of basalt fibers, the mechanical interlocking force between the basalt fiber-based composite filler and the membrane matrix can be enhanced, and the interfacial bonding strength between the basalt fiber-based composite filler and the matrix can be improved. This is beneficial for improving the overall strength of the base membrane and fully utilizing the reinforcing performance of the basalt fiber-based composite filler. Simultaneously, during the grafting reaction between the modified composite mesoporous SiO2 and basalt fibers, the modified composite mesoporous SiO2 can act as connecting nodes, allowing the basalt fibers to interweave and form a network structure, thereby further enhancing its mechanical properties and also improving its barrier properties. Grafting modified composite mesoporous SiO2 nanoparticles onto the surface of basalt fibers with a high aspect ratio also improves the dispersion performance of the modified composite mesoporous SiO2 nanoparticles.

[0030] In this invention, by loading antioxidants onto the mesoporous structure of modified composite mesoporous SiO2 nanoparticles, the antioxidants can be released in a sustained manner, thereby prolonging their effect. Furthermore, by combining the effect of basalt fibers on improving the dispersibility of modified composite mesoporous SiO2 nanoparticles, the antioxidants can be more evenly dispersed in the base film, allowing the antioxidants to exert their effects more fully.

[0031] Both basalt fiber and cerium-aluminum co-doped mesoporous SiO2, as inorganic fillers, suffer from poor dispersion and incompatibility with PET resin systems. In this invention, the two are assembled into a composite: during the SiO2-grafted basalt fiber composite process, the dispersibility of both can be improved to some extent through coupling agent modification. Furthermore, by using styrene, glycidyl methacrylate, maleic anhydride, isooctyl acrylate, and dimethyl vinylphosphonate as mixed monomers, and grafting a phosphorus-containing flame-retardant copolymer onto the composite through in-situ polymerization, its dispersibility in PET resin systems can be significantly improved.

[0032] Among the monomers mentioned above: glycidyl methacrylate contains epoxy groups, which can chemically react with the terminal hydroxyl or carboxyl groups of PET to form an in-situ copolymer at the blending interface, thereby enhancing the compatibility of the two phases; maleic anhydride has a strongly polar reactive group, which can chemically react or strongly interact with the terminal hydroxyl (-OH) or carboxyl (-COOH) groups of PET molecular chains, thereby improving interfacial adhesion, reducing interfacial tension, and enhancing compatibility.

[0033] Meanwhile, PPS resin and PET resin have poor compatibility, and the aforementioned grafted phosphorus-containing flame-retardant copolymer can also improve the compatibility between PPS resin and PET resin.

[0034] Furthermore, isooctyl acrylate, styrene, and glycidyl methacrylate can also toughen and strengthen the PET matrix and improve interfacial adhesion. Therefore, in addition to improving compatibility, the grafted polymers can also toughen and strengthen the PET matrix. In particular, this invention introduces phosphorus-containing dimethyl vinylphosphonate into the monomer, which can further enhance flame retardancy. Dimethyl vinylphosphonate releases phosphoric acid and metaphosphoric acid free radicals at high temperatures. These free radicals can capture highly reactive H· and OH· free radicals in the combustion chain reaction, thereby interrupting the chain oxidation reaction required for flame propagation and playing a gas-phase flame-retardant role. Phosphorus compounds can catalyze the dehydration and carbonization of polymers, forming a dense carbon layer (coke layer). This layer has the functions of heat insulation, oxygen isolation, and preventing the escape of combustible gases, thus achieving flame retardancy. Furthermore, in this invention, dimethyl vinylphosphonate is chemically grafted into the polymer system. With the enhanced compatibility of glycidyl methacrylate and maleic anhydride in the polymer monomers with PET, dimethyl vinylphosphonate can be better dispersed in the PET matrix and is difficult to migrate, thus avoiding the decrease in flame retardant effect and aging time caused by the migration of phosphorus-containing monomers.

[0035] In summary, the basalt fiber-based composite filler of the present invention, through the synergistic interaction among components such as basalt fiber, cerium-aluminum co-doped mesoporous SiO2, antioxidant, and phosphorus-containing flame-retardant copolymer, can achieve a synergistic enhancement effect in improving the flame retardant performance, corrosion and heat resistance, mechanical properties, and oxidation resistance of the base film; and through the combination of basalt fiber-based composite filler and PPS resin, the corrosion resistance and heat resistance of the base film can be further enhanced.

[0036] The above is the general concept of the present invention. Based on this, detailed embodiments and comparative examples are provided below to further illustrate the present invention.

[0037] The main sources of raw materials in the following examples and comparative examples are explained below: PET resin, brand: DuPont, USA, grade SST35NC010, Shanghai Yilida Plastics Co., Ltd.; PPS resin, grade SH-080W, Dongguan Shenghao Plastic Raw Materials Co., Ltd. PP-g-MAH (maleic anhydride grafted polypropylene), model XH3221C2DPAV, Dongguan Shenghao Plastic Raw Materials Co., Ltd.; Polyethylene wax, model AC-6, Shanghai Hongzhuang Chemical Technology Co., Ltd.; Diphenylmethane diisocyanate, Jiangsu Bost Chemical Technology Co., Ltd.; Antioxidant TH-1790, Nanxing Chemical (Jiangsu) Co., Ltd.; Basalt fiber, average length 1mm, Jiangxi Shuobang New Material Technology Co., Ltd. Coupling agent KH560, coupling agent KH570, Nanjing Chemical Reagent Co., Ltd.; Styrene, glycidyl methacrylate, maleic anhydride, isooctyl acrylate, Nantong Runfeng Petrochemical Co., Ltd.; Dimethyl vinylphosphonate, Shanghai Yiji Industrial Co., Ltd.

[0038] In the following examples and comparative examples, the basalt fibers were pretreated using the following method before use: Basalt fibers were added to a mixture of acetone and ethanol in a volume ratio of 1:1, with the solid-liquid ratio controlled at 1g:30mL. The mixture was ultrasonically treated for 1 hour, then removed and heat-treated at 200℃ for 45 minutes to complete the pretreatment. The mixture was then ready for use.

[0039] Example 1: A composite current collector with corrosion resistance, heat resistance and flame retardant PET base film and its preparation method. The raw materials for preparation include, by weight, 86 parts of PET resin, 14 parts of PPS resin, 2 parts of compatibilizer, 1 part of lubricant, 1.5 parts of crosslinking agent and 25 parts of flame retardant multi-effect filler. The compatibilizer is PP-g-MAH (maleic anhydride-grafted polypropylene), the lubricant is polyethylene wax, and the crosslinking agent is diphenylmethane diisocyanate.

[0040] The preparation method of this base film is as follows: Step 1: Vacuum dry PET resin and PPS resin at 120℃ for 6 hours, then mix them with compatibilizer, lubricant, crosslinking agent and flame-retardant multi-effect filler at 60℃ (800 rpm) for 45 minutes. Add the resulting mixture to a twin-screw extruder, melt extrude at 290℃, cool, and cast into sheets. Step 2: After preheating the cast sheet at 90℃, it is longitudinally stretched at 110℃ with a stretching ratio of 3.5 times; then it is transversely stretched at 115℃ with a stretching ratio of 3 times; after cooling, a corrosion-resistant, heat-resistant, and flame-retardant PET base film for composite current collectors is obtained.

[0041] In this embodiment, the flame-retardant multi-effect filler is prepared through the following steps: S1, Basalt fiber coupling agent modification: KH570 was added at a mass concentration of 4% to a mixture of ethanol and deionized water at a volume ratio of 9:1. The mixture was stirred at 25°C for 1 hour to obtain a hydrolysate. Basalt fiber was added to the hydrolysate at a mass ratio of 0.3 g to 10 mL. The mixture was stirred at 60°C for 2 hours to separate the basalt fiber. The basalt fiber was then vacuum dried at 100°C for 6 hours to obtain modified basalt fiber. S2. Preparation of modified composite mesoporous SiO2: S2-1, Preparation of cerium-aluminum co-doped mesoporous SiO2: 2.5g CTAB, 0.57g Ce(NO3)3·6H2O, and 1.25g Al(NO3)3 were added to 80mL of deionized water and stirred for 0.5h. Then, 8mL of tetraethyl orthosilicate and 20mL of 4mol / L urea solution were added dropwise. After stirring for 2h, the resulting mixture was transferred to a reaction vessel and reacted at 150℃ for 10h. After cooling to room temperature, the mixture was centrifuged, the solid was washed with deionized water, dried at 120℃ for 8h, and then calcined in a muffle furnace at 600℃ for 4h. After cooling and grinding, cerium-aluminum co-doped mesoporous SiO2 was obtained, denoted as CeAl@SiO2. S2-2, Coupling agent modification: 1g of cerium-aluminum co-doped mesoporous SiO2 and 5mL of deionized water were added to 45mL of ethanol and ultrasonically dispersed for 1h. Then, 0.02g of coupling agent KH560 was added, and the mixture was stirred at 70℃ for 2h. After centrifugation and filtration, the mixture was vacuum dried at 100℃ for 6h to obtain modified composite mesoporous SiO2. S3, Modified composite mesoporous SiO2 grafted with modified basalt fiber: 0.45 g of modified composite mesoporous SiO2 and 1 g of modified basalt fiber were added to 100 mL of toluene and ultrasonically dispersed for 1 h. Then, the mixture was stirred and refluxed at 70 °C for 10 h, cooled to room temperature, washed with ethanol, and vacuum dried at 100 °C overnight to obtain the SiO2-grafted basalt fiber composite, denoted as BF-CeAl@SiO2. S4, Antioxidant Loading: 5g of SiO2-grafted basalt fiber composite was added to 150mL of acetone solution containing 0.1g / mL antioxidant TH-1790. After stirring for 1h, the mixture was shaken on a shaker at 60℃ for 12h. After centrifugation, the precipitate was washed with acetone and ethanol in sequence and dried under vacuum at 80℃ for 10h to obtain the intermediate product. S5, Grafted phosphorus-containing flame-retardant copolymer: S5-1. Add 8g of intermediate product to 150mL of tetrahydrofuran, sonicate under nitrogen for 1h to obtain intermediate product dispersion; S5-2. Add 12g styrene, 7.5g glycidyl methacrylate, 4g maleic anhydride, 3.5g isooctyl acrylate, 13g dimethyl vinylphosphonate and 2g emulsifier SDBS to 170mL tetrahydrofuran, stir under nitrogen for 30min to obtain monomer mixture. S5-3. The monomer mixture was added to the intermediate product dispersion under stirring. After stirring for 1 hour, 0.15 g of sec-butyllithium and 0.25 g of azobisisobutyronitrile were added. The mixture was stirred at 65 °C for 14 hours under nitrogen protection. After cooling to room temperature, the mixture was filtered. The solid product was washed with ethanol and dried under vacuum at 80 °C for 10 hours to obtain basalt fiber-based composite filler.

[0042] The infrared absorption spectra of the basalt fiber and the prepared SiO2-grafted basalt fiber composite (BF-CeAl@SiO2) in this example are as follows: Figure 1 As shown, compared with BF, 3410 cm⁻¹ in BF-CeAl@SiO₂ -1 The newly appearing peak in the vicinity is due to the -OH absorption peak formed by the silane coupling agent on the surface of SiO2 and basalt fibers, at 1020 cm⁻¹. -1 and 785cm -1 The significantly enhanced characteristic peaks originating from Si−O−Si in the vicinity are due to the grafting of SiO2 onto the BF-bound surface, while the appearance of Al-O and Ce-O characteristic peaks indicates the successful doping of Al and Ce into SiO2.

[0043] Example 2 is basically the same as Example 1, with only the differences listed below: The raw materials for preparing the corrosion-resistant, heat-resistant, and flame-retardant PET base film for composite current collectors in this example include, by weight, 88 parts of PET resin, 12 parts of PPS resin, 2 parts of compatibilizer, 1 part of lubricant, 1.5 parts of crosslinking agent, and 25 parts of flame-retardant multi-effect filler.

[0044] Example 3 is basically the same as Example 1, with only the differences listed below: The raw materials for preparing the corrosion-resistant, heat-resistant, and flame-retardant PET base film for composite current collectors in this example include, by weight, 84 parts of PET resin, 16 parts of PPS resin, 2 parts of compatibilizer, 1 part of lubricant, 1.5 parts of crosslinking agent, and 25 parts of flame-retardant multi-effect filler.

[0045] In this example, the flame-retardant multi-effect filler is prepared through the following steps: S1. Basalt fiber coupling agent modification, the specific method is the same as in Example 1; S2. Prepare modified composite mesoporous SiO2, using the same method as in Example 1; S3, Modified composite mesoporous SiO2 grafted with modified basalt fiber: 0.55 g of modified composite mesoporous SiO2 and 1 g of modified basalt fiber were added to 100 mL of toluene and ultrasonically dispersed for 1 h. Then, the mixture was stirred and refluxed at 70 °C for 10 h, cooled to room temperature, washed with ethanol, and vacuum dried at 100 °C overnight to obtain the SiO2-grafted basalt fiber composite, denoted as BF-CeAl@SiO2. S4. Loading antioxidants, the specific method is the same as in Example 1; S5, Grafted phosphorus-containing flame-retardant copolymer: S5-1. Add 8g of intermediate product to 150mL of tetrahydrofuran, sonicate under nitrogen for 1h to obtain intermediate product dispersion; S5-2. Add 11g styrene, 8.5g glycidyl methacrylate, 4.5g maleic anhydride, 3g isooctyl acrylate, 13g dimethyl vinylphosphonate and 2g emulsifier SDBS to 170mL tetrahydrofuran, stir under nitrogen for 30min to obtain monomer mixture. S5-3. The monomer mixture was added to the intermediate product dispersion under stirring. After stirring for 1 hour, 0.15 g of sec-butyllithium and 0.25 g of azobisisobutyronitrile were added. The mixture was stirred at 65 °C for 14 hours under nitrogen protection. After cooling to room temperature, the mixture was filtered. The solid product was washed with ethanol and dried under vacuum at 80 °C for 10 hours to obtain basalt fiber-based composite filler.

[0046] Comparative Example 1 is basically the same as Example 1; the differences are listed below: The raw materials for preparing the corrosion-resistant, heat-resistant, and flame-retardant PET base film for composite current collectors in this example include, by weight, 100 parts of PET resin, 2 parts of compatibilizer, 1 part of lubricant, 1.5 parts of crosslinking agent, and 25 parts of flame-retardant multi-effect filler.

[0047] Comparative Example 2 is basically the same as Example 1; the differences are listed below: The raw materials for preparing the corrosion-resistant, heat-resistant, and flame-retardant PET base film for composite current collectors in this example include, by weight: 86 parts PET resin, 14 parts PPS resin, 2 parts compatibilizer, 1 part lubricant, 1.5 parts crosslinking agent, and 1.5 parts antioxidant TH-1790.

[0048] The preparation method of this base film is as follows: Step 1: Vacuum dry PET resin and PPS resin at 120℃ for 6 hours, then mix with compatibilizer, lubricant, crosslinking agent and antioxidant TH-1790 at 60℃ (800 rpm) for 45 minutes. Add the resulting mixture to a twin-screw extruder, melt extrude at 290℃, cool and cast into sheets. Step 2: After preheating the cast sheet at 90℃, it is longitudinally stretched at 110℃ with a stretching ratio of 3.5 times; then it is transversely stretched at 115℃ with a stretching ratio of 3 times; after cooling, a corrosion-resistant, heat-resistant, and flame-retardant PET base film for composite current collectors is obtained.

[0049] Comparative Example 3 is basically the same as Example 1; the differences are listed below: In this example, Ce(NO3)3·6H2O is not added in step S2-1 of the preparation of the flame-retardant multi-effect filler.

[0050] Comparative Example 4 is basically the same as Example 1; the differences are listed below: In this example, Al(NO3)3 is not added in step S2-1 of the preparation of the flame-retardant multi-effect filler.

[0051] Comparative Example 5 is basically the same as Example 1; the differences are listed below: The raw materials for preparing the corrosion-resistant, heat-resistant, and flame-retardant PET base film for composite current collectors in this example include, by weight: 86 parts PET resin, 14 parts PPS resin, 2 parts compatibilizer, 1 part lubricant, 1.5 parts crosslinking agent, and 5 parts intermediate product; The preparation method of this base film is as follows: Step 1: Vacuum dry PET resin and PPS resin at 120℃ for 6 hours, then mix them with compatibilizer, lubricant, crosslinking agent and intermediate product at 60℃ (800 rpm) for 45 minutes. Add the resulting mixture to a twin-screw extruder, melt extrude at 290℃, cool and cast into sheets. Step 2: After preheating the cast sheet at 90℃, it is longitudinally stretched at 110℃ with a stretching ratio of 3.5 times; then it is transversely stretched at 115℃ with a stretching ratio of 3 times; after cooling, a corrosion-resistant, heat-resistant, and flame-retardant PET base film for composite current collectors is obtained.

[0052] The preparation method of the intermediate product is the same as in Example 1.

[0053] Comparative Example 6 is basically the same as Example 1; the differences are listed below: In this example, the preparation step S5-2 of the flame-retardant multi-effect filler is as follows: 17g of styrene, 10.5g of glycidyl methacrylate, 6.5g of maleic anhydride, 5g of isooctyl acrylate and 2g of emulsifier SDBS are added to 170mL of tetrahydrofuran, and stirred under nitrogen for 30min to obtain a monomer mixture.

[0054] Comparative Example 7: A composite current collector with corrosion resistance, heat resistance and flame retardancy PET base film and its preparation method. The raw materials for preparation include, by weight, 86 parts of PET resin, 14 parts of PPS resin, 2 parts of compatibilizer, 1 part of lubricant, 1.5 parts of crosslinking agent, 17.2 parts of basalt fiber base filler and 7.8 parts of mesoporous SiO2 base filler. The compatibilizer is PP-g-MAH (maleic anhydride-grafted polypropylene), the lubricant is polyethylene wax, and the crosslinking agent is diphenylmethane diisocyanate.

[0055] The preparation method of this base film is as follows: Step 1: Vacuum dry PET resin and PPS resin at 120℃ for 6 hours, then mix them with compatibilizer, lubricant, crosslinking agent and flame-retardant multi-effect filler at 60℃ (800 rpm) for 45 minutes. Add the resulting mixture to a twin-screw extruder, melt extrude at 290℃, cool, and cast into sheets. Step 2: After preheating the cast sheet at 90℃, it is longitudinally stretched at 110℃ with a stretching ratio of 3.5 times; then it is transversely stretched at 115℃ with a stretching ratio of 3 times; after cooling, a corrosion-resistant, heat-resistant, and flame-retardant PET base film for composite current collectors is obtained.

[0056] In this example, the basalt fiber-based filler was prepared by the following method: S1-1, Basalt fiber coupling agent modification: KH570 was added at a mass concentration of 4% to a mixture of ethanol and deionized water at a volume ratio of 9:1. The mixture was stirred at 25°C for 1 hour to obtain a hydrolysate. Basalt fiber was added to the hydrolysate at a mass ratio of 0.3 g to 10 mL. The mixture was stirred at 60°C for 2 hours to separate the basalt fiber. The basalt fiber was then vacuum dried at 100°C for 6 hours to obtain modified basalt fiber. S1-2, Grafted phosphorus-containing flame-retardant copolymer: S1-2-1. Add 8g of modified basalt fiber to 130mL of tetrahydrofuran, and sonicate under nitrogen for 1h to obtain an intermediate product dispersion. S1-2-2, Add 12g styrene, 7.5g glycidyl methacrylate, 4g maleic anhydride, 3.5g isooctyl acrylate, 13g dimethyl vinylphosphonate and 2g emulsifier SDBS to 170mL tetrahydrofuran, stir under nitrogen for 30min to obtain monomer mixture. S1-2-3. The monomer mixture was added to the intermediate product dispersion under stirring. After stirring for 1 hour, 0.15 g of sec-butyllithium and 0.25 g of azobisisobutyronitrile were added. The mixture was stirred at 65 °C for 14 hours under nitrogen protection. After cooling to room temperature, the mixture was filtered. The solid product was washed with ethanol and dried under vacuum at 80 °C for 10 hours to obtain basalt fiber-based filler.

[0057] In this example, the mesoporous SiO2-based filler was prepared by the following method: S2-1, Preparation of cerium-aluminum co-doped mesoporous SiO2: 2.5g CTAB, 0.57g Ce(NO3)3·6H2O, and 1.25g Al(NO3)3 were added to 80mL of deionized water and stirred for 0.5h. Then, 8mL of tetraethyl orthosilicate and 20mL of 4mol / L urea solution were added dropwise. After stirring for 2h, the resulting mixture was transferred to a reaction vessel and reacted at 150℃ for 10h. After cooling to room temperature, the mixture was centrifuged, the solid was washed with deionized water, dried at 120℃ for 8h, and then calcined in a muffle furnace at 600℃ for 4h. After cooling and grinding, cerium-aluminum co-doped mesoporous SiO2 was obtained. S2-2, Coupling agent modification: 1g of cerium-aluminum co-doped mesoporous SiO2 and 5mL of deionized water were added to 45mL of ethanol and ultrasonically dispersed for 1h. Then, 0.02g of coupling agent KH570 was added, and the mixture was stirred at 70℃ for 2h. After centrifugation and filtration, the mixture was vacuum dried at 100℃ for 6h to obtain modified composite mesoporous SiO2. S2-3, Antioxidant Loading: Add 5g of modified composite mesoporous SiO2 to 150mL of acetone solution of antioxidant TH-1790 with a concentration of 0.1g / mL, stir for 1h, shake on a shaker at 60℃ for 12h, centrifuge, wash the precipitate with acetone and ethanol in sequence, and vacuum dry at 80℃ for 10h to obtain the intermediate product. S2-4, Grafted phosphorus-containing flame-retardant copolymer: S2-4-1. Add 8g of intermediate product to 150mL of tetrahydrofuran, sonicate under nitrogen for 1h to obtain intermediate product dispersion; S2-4-2. Add 12g styrene, 7.5g glycidyl methacrylate, 4g maleic anhydride, 3.5g isooctyl acrylate, 13g dimethyl vinylphosphonate and 2g emulsifier SDBS to 170mL tetrahydrofuran, stir under nitrogen for 30min to obtain monomer mixture. S2-4-3. The monomer mixture was added to the intermediate product dispersion under stirring. After stirring for 1 hour, 0.15 g of sec-butyllithium and 0.25 g of azobisisobutyronitrile were added. The mixture was stirred at 65 °C for 14 hours under nitrogen protection. After cooling to room temperature, the mixture was filtered. The solid product was washed with ethanol and dried under vacuum at 80 °C for 10 hours to obtain mesoporous SiO2-based filler.

[0058] The base films prepared in the examples and comparative examples were subjected to the following performance tests: 1. Flame retardant properties The limiting oxygen index is tested using the standard JIS-K7201-3-2008. The higher the value, the better the flame retardant performance.

[0059] 2. Heat resistance The longitudinal thermal shrinkage rate of the base film was tested according to ASTM D2732 (150℃×30min).

[0060] 3. Resistance to electrolyte corrosion The composite current collector base films prepared in each example were cut into 40mm*40mm test samples, weighed (m0), and the data was recorded. They were then placed in aluminum-plastic bags, filled with electrolyte at 50 times the weight of the base film, and sealed. The sealed aluminum-plastic bags were transferred to a 50℃ oven and baked for 20 days. The base film inside the aluminum-plastic bag was removed, rinsed with deionized water, and then dried at 50℃ to constant weight. Its weight (m1) was measured, and the weight change rate (η) was calculated. η=(m0-m1) / m0*100%, the smaller the weight change rate, the stronger the resistance to electrolyte corrosion; The electrolyte consists of a 1.5 mol / L LiPF6 solution of ethylene carbonate and diethyl carbonate, with a mass ratio of ethylene carbonate to diethyl carbonate of 2:1.

[0061] 4. Tensile strength The tensile breaking strength of the base film was tested using a universal tensile testing machine in accordance with the standard ASTM D882-12, "Standard Test Methods for Tensile Properties of Films and Sheets".

[0062] 5. Heat aging resistance The base film was placed in hot air at 120°C for 240 hours for artificial accelerated aging. After cooling to room temperature, the longitudinal tensile strength was measured. The retention rate of longitudinal tensile strength was used to measure the heat aging resistance. The retention rate of longitudinal tensile strength = (longitudinal tensile strength after aging / longitudinal tensile strength before aging) × 100%. The larger the value, the better the heat aging resistance.

[0063] Sustained-release performance verification 10g of the basalt fiber-based composite filler prepared in Example 1 was added to 500mL of acetone solution and stirred for 30min to obtain the test solution. The concentration of antioxidant TH-1790 in the test solution was measured every 12h (initially every 6h) using high-performance liquid chromatography (HPLC) for 240h. The cumulative release percentage of antioxidant TH-1790 at different release times was calculated (cumulative mass percentage of release amount to total load), and a release curve was plotted. The test results are as follows: Figure 2 As shown, the basalt fiber-based composite filler can achieve good sustained release of the antioxidant TH-1790.

[0064] The results of the above performance tests are shown in Table 1 and below. Figure 3-7 As shown: Table 1 The test results show that the base films prepared in Examples 1-3 have excellent flame retardant properties, heat resistance, corrosion resistance, mechanical strength and aging resistance. In Comparative Example 1, no PPS resin was added to the raw materials, and the flame retardant properties, heat resistance, and corrosion resistance all decreased significantly. In Comparative Example 2, no basalt fiber-based composite filler was added, and all properties decreased significantly. Although antioxidants were added to the raw materials, its aging resistance was significantly worse than that of Example 1. This was mainly due to the inability to achieve sustained release of antioxidants in Comparative Example 2 and the inferior uniform dispersion effect of antioxidants compared to Example 1.

[0065] The results of Comparative Example 3 show that Ce doping in modified composite mesoporous SiO2 has a significant effect on improving flame retardancy and aging resistance. The results of Comparative Example 4 show that Al doping in modified composite mesoporous SiO2 has a certain effect on improving flame retardancy, heat resistance and mechanical strength. In Comparative Example 5, the ungrafted phosphorus-containing flame-retardant copolymer not only failed to achieve uniform dispersion of the filler, but also lost the flame-retardant performance improvement effect of the phosphorus-containing monomer, resulting in a significant decrease in overall performance.

[0066] The results of Comparative Example 6 show that the introduction of dimethyl vinylphosphonate into the monomer grafted onto the intermediate product can significantly improve the flame retardant properties.

[0067] In Comparative Example 7, the cerium-aluminum co-doped mesoporous SiO2 and basalt fibers did not assemble to form a complex, which affected the dispersion of the cerium-aluminum co-doped mesoporous SiO2 and reduced the uniform dispersion of its slow-release antioxidant, resulting in a decrease in its improvement effect on aging resistance, flame retardancy, etc. At the same time, due to the decrease in the bonding strength between basalt fibers and the base film, its improvement effect on mechanical strength decreased.

[0068] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A corrosion-resistant, heat-resistant, and flame-retardant PET-based film for composite current collectors and its preparation method, characterized in that, The raw materials for its preparation include, by weight: 70-90 parts PET resin, 6-18 parts PPS resin, 1.5-4 parts compatibilizer, 0.5-2 parts lubricant, 1-3 parts crosslinking agent, and 20-35 parts flame-retardant multi-effect filler. The flame-retardant multi-effect filler is prepared through the following steps: S1. Basalt fibers are modified by using silane coupling agent 1 containing double bonds to obtain modified basalt fibers. S2. Prepare cerium-aluminum co-doped mesoporous SiO2, and then modify it with silane coupling agent 2 to obtain modified composite mesoporous SiO2. S3. Modified composite mesoporous SiO2 is grafted onto the surface of modified basalt fiber to obtain SiO2-grafted basalt fiber composite. S4. An antioxidant was loaded onto the SiO2-grafted basalt fiber composite by impregnation to obtain an intermediate product. S5. Grafting phosphorus-containing flame-retardant copolymers onto the intermediate product yields a flame-retardant multi-effect filler.

2. The corrosion-resistant, heat-resistant, and flame-retardant PET base film for composite current collectors according to claim 1, characterized in that, Silane coupling agent 1 is at least one of silane coupling agent KH570, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltri(β-methoxyethoxy)silane, and acryloyloxysilane coupling agent.

3. The corrosion-resistant, heat-resistant, and flame-retardant PET base film for composite current collectors according to claim 1, characterized in that, Silane coupling agent 2 is at least one of silane coupling agent KH550 and silane coupling agent KH560.

4. The corrosion-resistant, heat-resistant, and flame-retardant PET base film for composite current collectors according to claim 1, characterized in that, The antioxidant is at least one of antioxidant 168 and antioxidant TH-1790.

5. The corrosion-resistant, heat-resistant, and flame-retardant PET base film for composite current collectors according to claim 1, characterized in that, The flame-retardant multi-effect filler is prepared through the following steps: S1. Add KH570 to a mixture of ethanol and deionized water, stir and react to obtain a hydrolysate. Add basalt fiber to the hydrolysate, heat and stir to separate the basalt fiber, dry it to obtain modified basalt fiber. S2. Preparation of modified composite mesoporous SiO2: S2-1, Preparation of cerium-aluminum co-doped mesoporous SiO2: Add CTAB, Ce(NO3)3·6H2O, and Al(NO3)3 to deionized water, stir, and simultaneously add tetraethyl orthosilicate and urea solution. After stirring, transfer the resulting mixture to a reaction vessel and react at 120-160℃ for 6-20 h. After centrifugation, wash and dry the solid, and calcine at 500-650℃ for 2-8 h to obtain cerium-aluminum co-doped mesoporous SiO2. S2-2, Coupling agent modification: Cerium-aluminum co-doped mesoporous SiO2 and deionized water were added to ethanol, ultrasonically dispersed, and then coupling agent KH560 was added. The mixture was heated and stirred to react, centrifuged and filtered, and dried to obtain modified composite mesoporous SiO2. S3. Modified composite mesoporous SiO2 and modified basalt fiber are added to toluene, ultrasonically dispersed, heated and stirred under reflux, cooled, washed and dried to obtain SiO2 grafted basalt fiber composite. S4. The SiO2-grafted basalt fiber composite was added to an acetone solution of antioxidant TH-1790, stirred, shaken, centrifuged, and the precipitate was washed and dried to obtain the intermediate product. S5, Grafted phosphorus-containing flame-retardant copolymer: S5-1. Add the intermediate product to tetrahydrofuran, sonicate under nitrogen gas to obtain an intermediate product dispersion; S5-2. Styrene, glycidyl methacrylate, maleic anhydride, isooctyl acrylate, dimethyl vinylphosphonate and emulsifier are added to tetrahydrofuran and stirred with nitrogen gas to obtain a monomer mixture. S5-3. Add the monomer mixture to the intermediate product dispersion under stirring, stir, add initiator 1 and initiator 2, stir under nitrogen protection and heating, cool, filter, wash and dry the solid product to obtain basalt fiber-based composite filler.

6. The corrosion-resistant, heat-resistant, and flame-retardant PET base film for composite current collectors according to claim 5, characterized in that, In step S3, the mass ratio of modified composite mesoporous SiO2 to modified basalt fiber is 0.2-0.8:

1.

7. The corrosion-resistant, heat-resistant, and flame-retardant PET base film for composite current collectors according to claim 5, characterized in that, Initiator 1 is at least one of n-butyllithium, sec-butyllithium, phenyllithium, potassium amino, sodium methoxide, and potassium ethoxide; Initiator 2 is at least one of azobisisobutyronitrile, azobisisoheptanenitrile, dimethyl azobisisobutyrate, benzoyl peroxide, di-tert-butyl peroxide, tert-butyl hydroperoxide, and cumene hydroperoxide.

8. The corrosion-resistant, heat-resistant, and flame-retardant PET base film for composite current collectors according to claim 5, characterized in that, The flame-retardant multi-effect filler is prepared through the following steps: S1, Basalt fiber coupling agent modification: KH570 was added at a mass concentration of 1.5-6% to a mixture of ethanol and deionized water at a volume ratio of 9:

1. The mixture was stirred at 20-40℃ for 0.5-2 hours to obtain a hydrolysate. Basalt fiber was added to the hydrolysate at a mass ratio of 0.3g to 10mL. The mixture was stirred at 50-70℃ for 1-4 hours to separate the basalt fiber. The basalt fiber was then vacuum dried to obtain modified basalt fiber. S2. Preparation of modified composite mesoporous SiO2: S2-1, Preparation of cerium-aluminum co-doped mesoporous SiO2: Add 1.25-5g CTAB, 0.25-1g Ce(NO3)3·6H2O, and 0.75-2.5g Al(NO3)3 to 40-160mL of deionized water and stir for 15-60min. Then, simultaneously add 4-16mL of tetraethyl orthosilicate and 10-40mL of urea solution with a concentration of 2-8mol / L. After stirring for 1-4h, transfer the resulting mixture to a reaction vessel and react at 120-160℃ for 6-20h. After cooling and centrifugation, wash the solid with deionized water, dry it, and calcine it in a muffle furnace at 500-650℃ for 2-8h. After cooling and grinding, obtain cerium-aluminum co-doped mesoporous SiO2. S2-2, Coupling agent modification: Add 0.5-2g of cerium-aluminum co-doped mesoporous SiO2 and 2.5-10mL of deionized water to 20-90mL of ethanol, and ultrasonically disperse for 0.5-2h. Then add 0.01-0.04g of coupling agent KH560, stir and react at 60-80℃ for 1-4h, centrifuge, filter, and dry to obtain modified composite mesoporous SiO2. S3, Modified composite mesoporous SiO2 grafted with modified basalt fiber: Add 0.2-0.8g of modified composite mesoporous SiO2 and 1g of modified basalt fiber to 50-200mL of toluene, ultrasonically disperse for 0.5-2h, then stir and reflux at 60-75℃ for 6-24h, cool to room temperature, wash with ethanol, and dry to obtain SiO2 grafted basalt fiber composite. S4, Antioxidant Loading: Add 2.5-10g of SiO2-grafted basalt fiber composite to 75-300mL of acetone solution containing antioxidant TH-1790 at a concentration of 0.05-0.5g / mL, stir for 0.5-2h, then shake in a shaker at 50-70℃ for 8-30h, centrifuge, wash the precipitate with acetone and ethanol sequentially, and dry to obtain the intermediate product; S5, Grafted phosphorus-containing flame-retardant copolymer: S5-1. Add 4-16g of intermediate product to 60-250mL of tetrahydrofuran, and sonicate under nitrogen for 0.5-2h to obtain an intermediate product dispersion. S5-2. Add 6-24g styrene, 3.5-15g glycidyl methacrylate, 2-8g maleic anhydride, 1.5-7g isooctyl acrylate, 6.5-26g dimethyl vinylphosphonate and 1-4g emulsifier SDBS to 100-300mL of tetrahydrofuran, stir under nitrogen for 15-60min to obtain a monomer mixture. S5-3. Add the monomer mixture to the intermediate product dispersion under stirring, stir for 0.5-2 h, add 0.075-0.3 g sec-butyllithium and 0.12-0.5 g azobisisobutyronitrile, under nitrogen protection, stir and react at 50-70 °C for 5-20 h, cool to room temperature, filter, wash the solid product with ethanol, dry, and obtain basalt fiber-based composite filler.

9. The corrosion-resistant, heat-resistant, and flame-retardant PET base film for composite current collectors according to claim 1, characterized in that, The compatibilizer is at least one of PP-g-MAH, PE-g-MAH, SOG-03, SOG-02, and POE-g-GMA. The lubricant is at least one of silicone oil, polyethylene wax, polyamide wax, calcium stearate, magnesium stearate, and barium stearate; The crosslinking agent is at least one of diphenylmethane diisocyanate, pentaerythritol tetraacrylate, and pentaerythritol triacrylate.

10. A method for preparing a corrosion-resistant, heat-resistant, and flame-retardant PET-based film for composite current collectors as described in any one of claims 1-9, characterized in that, Includes the following steps: PET resin, PPS resin, compatibilizer, lubricant, crosslinking agent, and flame-retardant multi-effect filler are mixed evenly according to the weight ratio. The resulting mixture is melt-extruded at 275-300℃, cooled, and cast into sheets. After preheating, the cast sheets are stretched longitudinally and transversely in sequence to obtain a corrosion-resistant, heat-resistant, and flame-retardant PET base film for composite current collectors.

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