Wear-resistant and corrosion-resistant PP material for lithium battery packaging and preparation method of wear-resistant and corrosion-resistant PP material

Abstract

The invention discloses a wear-resistant and corrosion-resistant PP material for lithium battery packaging and a preparation method thereof, and belongs to the technical field of composites.The wear-resistant and corrosion-resistant PP material is prepared by taking sepiolite-reinforced silicon dioxide aerogel powder as a framework structure, loading polydopamine-coated carbon nanotubes on the surface, and carrying out ammonification reaction on hydroxyl and amino groups on the surface, so that the wear-resistant and corrosion-resistant PP material is obtained. Polydopamine provides a carbon source and a nitrogen source, carbon nanotubes are uniformly loaded on silicon dioxide aerogel and carbonized, graphite-phase carbon nitride grows on the surface, the obtained carbon nitride / graphene foam composite powder is of a three-dimensional network composite structure in the space structure, an interlayer structure of the graphite-phase carbon nitride is interspersed in the carbon nitride / graphene foam composite powder, and the carbon nitride / graphene foam composite powder has a large specific surface area. According to the present invention, the layered structure generates interlayer slippage under the action of the external force so as to disperse the stress and prevent the brittle fracture of the PP material, and the sepiolite-reinforced silica aerogel powder is adopted as the skeleton structure so as to further improve the toughness of the PP material, such that the use safety of the lithium battery is ensured.

Description

Technical Field

[0001] The present invention belongs to the technical field of composite materials, and specifically relates to a wear-resistant and corrosion-resistant PP material for lithium battery packaging and a preparation method thereof. Background Art

[0002] With the continuous development of lithium battery new energy technology, my country and even the world have set off a research boom in the lithium battery industry. With the increasing energy density of batteries and the faster charging and discharging speed, the research on new lithium battery packaging is becoming more and more important. Plastic, as a plastic product, is widely used in many aspects such as industry, construction, and packaging. However, due to the poor heat resistance and wear resistance of plastic, its application scope is subject to certain limitations. With the development of science and technology and the improvement of people's living standards, the characteristics and applications of single materials are restricted, and the performance of new materials, especially composite materials, has received more attention. Using non-metallic material surface modification technology to change the characteristics of plastics, the plastic surface is treated with chemical plating technology, which can make the plastic have good wear resistance, thermal conductivity, electrical conductivity, mechanical properties and other properties while maintaining the original light weight and corrosion resistance, making the use of plastics more extensive.

[0003] A Chinese patent with publication number CN110527183A discloses a polypropylene composite material for battery shell and a preparation method thereof. A toughening agent, glass fiber and graphene are selected to toughen and strengthen polypropylene, thereby improving the toughness while improving the mechanical properties and heat dissipation properties of polypropylene. Further, by adding a flame retardant composition, the polypropylene material has a flame retardant effect. However, in this solution, the toughening agent, dispersant, antioxidant and flame retardant composition are mixed with modified graphene treated with surfactant by a low-speed mixer and melt-extruded. There is a lack of strong interaction between the graphene, glass fiber and polypropylene treated only with a surfactant, resulting in the inability to effectively transfer stress. The interface is easily a weak area for crack expansion, resulting in a decrease in the toughness of the plastic material. When used as a packaging material for lithium batteries, the safety of the battery cannot be effectively guaranteed during the use of the battery. Summary of the invention

[0004] The purpose of the present invention is to provide a wear-resistant and corrosion-resistant PP material for lithium battery packaging and its preparation method. By using sepiolite-reinforced silica aerogel powder as the skeleton structure, carbon nanotubes coated with polydopamine are loaded on the surface, and ammoniation reaction occurs between the hydroxyl groups on the surface and the amino groups. Polydopamine provides a carbon source and a nitrogen source, uniformly loading the carbon nanotubes on the silica aerogel and carbonizing them, and growing graphitic carbon nitride on the surface. The obtained carbon nitride / graphene foam composite powder has a three-dimensional network composite structure in the spatial structure, with an interlayer structure of graphitic carbon nitride interspersed. The layered structure allows interlayer slip under external force, thereby dispersing stress and preventing brittle fracture of the PP material. Moreover, using sepiolite-reinforced silica aerogel powder as the skeleton structure can further improve the toughness of the PP material, thus ensuring the use safety of lithium batteries.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] A preparation method of a wear-resistant and corrosion-resistant PP material for lithium battery packaging, through the following steps:

[0007] Step 1: Coating carboxylated multi-walled carbon nanotubes with polydopamine, and carrying out ammoniation reaction between the hydroxyl groups on the surface and the carboxyl groups on the surface of the modified aerogel powder. After carbonization, nitrogen-doped silica / graphene foam composite powder is obtained; mixing melamine powder and nitrogen-doped silica / graphene foam composite powder evenly according to a mass ratio of 1:3, transferring them to a muffle furnace, heating at a rate of 5 - 6 °C / min to 300 - 350 °C in an argon atmosphere, holding for 1 - 1.2 h, heating at a rate of 7 - 8 °C / min to 550 - 600 °C, holding for 2 - 3 h, and naturally cooling to room temperature to obtain carbon nitride / graphene foam composite powder.

[0008] Step 2: Adding polypropylene resin and polyurethane elastic material into a reaction kettle, stirring at 150 - 160 °C for 30 - 40 min, then adding compatibilizer polyethylene glycol, carbon nitride / graphene foam composite powder, antioxidant phosphite ester, and synergistic flame retardant ammonium polyphosphate, continuing to stir for 1 - 2 h, transferring to a twin-screw extruder, extruding at 180 - 190 °C and 45 - 50 r / min, and pelletizing to obtain a wear-resistant and corrosion-resistant PP material for lithium battery packaging.

[0009] Furthermore, the dosage ratio of polypropylene resin, polyurethane elastic material, polyethylene glycol, carbon nitride / graphene foam composite powder, phosphite ester, and ammonium polyphosphate in Step 2 is 45 - 50 kg: 5 - 6 kg: 1 - 2 kg: 5 - 6 kg: 1.2 - 1.5 kg: 2.3 - 2.5 kg.

[0010] Furthermore, the specific steps of the nitrogen-doped silica / graphene foam composite powder in Step 1 are as follows:

[0011] Add carboxylated multi-walled carbon nanotubes with a length of 2.5 - 3 μm and a diameter of 6 - 8 nm, dopamine, and deionized water into a reaction kettle, stir at 20 - 25 °C and 500 - 600 r / min for 30 - 40 min, then add a Tris-HCl buffer solution with a concentration of 1 mol / L and a pH value of 8.0, heat to 80 - 85 °C, continue stirring for 20 - 22 h, then add modified aerogel powder, continue stirring for 1 - 2 h, filter, wash the filter cake with deionized water 2 - 3 times, vacuum dry at 60 - 80 °C for 1 - 2 h, transfer the product to a muffle furnace, under an argon atmosphere, heat to 800 - 850 °C at a rate of 13 - 15 °C / min, hold for 2 - 3 h, and naturally cool to room temperature to obtain nitrogen-doped silica / graphene foam composite powder.

[0012] Furthermore, the dosage ratio of carboxylated multi-walled carbon nanotubes, dopamine, deionized water, Tris-HCl buffer solution, and modified aerogel powder is 3 - 4 kg : 1 - 2 kg : 7 - 8 L : 500 - 600 mL : 2 - 3 kg.

[0013] Furthermore, the modified aerogel powder is prepared through the following steps:

[0014] Add sepiolite-reinforced silica aerogel powder, γ-aminopropyltriethoxysilane, ethanol, and deionized water into a reaction kettle, stir at 60 - 70 °C and 500 - 600 r / min for 1 - 2 h, filter, wash the filter cake with deionized water 2 - 3 times, vacuum dry at 60 - 80 °C for 1 - 2 h to obtain the modified aerogel powder.

[0015] Furthermore, the dosage ratio of sepiolite-reinforced silica aerogel powder, γ-aminopropyltriethoxysilane, ethanol, and deionized water is 3.2 - 3.6 kg : 1 - 2 L : 2 - 3 L : 3 - 4 L.

[0016] Furthermore, the sepiolite-reinforced silica aerogel powder is prepared through the following steps:

[0017] Tetraethyl orthosilicate, ethanol, and deionized water were added to a reaction kettle, stirred at 20 - 25 °C and 500 - 600 r / min for 5 - 10 min, then a 1 mol / L hydrochloric acid solution was added to adjust the pH value to 2 - 3, and stirring continued for 3 - 4 h. Pretreated sepiolite fibers were added, ultrasonically dispersed for 40 - 60 min, then ammonia water with a mass fraction of 20 - 30% was added to adjust the pH value to 7 - 8, sealed and placed in an oven at 50 - 60 °C for aging for 40 - 50 h. Trimethylchlorosilane and n - hexane were added, sealed and placed in an oven at 20 - 25 °C for constant temperature for 24 - 26 h, filtered, and the filter cake was washed 2 - 3 times with n - hexane and deionized water respectively, and vacuum - dried at 60 - 80 °C for 12 - 14 h to obtain sepiolite - reinforced silica aerogel powder with a pore size of 50 - 60 nm.

[0018] Furthermore, the dosage ratio of tetraethyl orthosilicate, ethanol, deionized water, hydrochloric acid solution, pretreated sepiolite fibers, ammonia water, trimethylchlorosilane, and n - hexane is 1 - 1.2 L : 3 - 4 L : 4 - 5 L : 250 - 300 mL : 3 - 4 kg : 200 - 300 mL : 200 - 300 mL : 1.6 - 2 L.

[0019] Furthermore, the pretreatment of sepiolite fibers is carried out through the following steps:

[0020] Sepiolite fibers with a length of 2 - 4 mm and a hydrochloric acid solution with a concentration of 3 - 4 mol / L were added to a reaction kettle according to a dosage ratio of 4 - 5 kg : 4 - 5 L, stirred at 50 - 60 °C and 500 - 600 r / min for 1 - 2 h, filtered, and the filter cake was washed with deionized water until the last washing liquid was neutral to obtain pretreated sepiolite fibers.

[0021] The beneficial effects of the present invention:

[0022] 1. A wear - resistant and corrosion - resistant PP material for lithium - battery packaging and its preparation method prepared by the present invention. Using sepiolite - reinforced silica aerogel powder as the framework structure, carbon nanotubes coated with polydopamine are loaded on the surface. The hydroxyl and amino groups on the surface undergo an ammoniation reaction. Polydopamine provides a carbon source and a nitrogen source, uniformly loading the carbon nanotubes on the silica aerogel and carbonizing them, and growing graphitic carbon nitride on the surface. The obtained carbon nitride / graphene foam composite powder has a three - dimensional network composite structure in terms of spatial structure, with an interlayer structure of graphitic carbon nitride interspersed. The layered structure allows interlayer slip under external force, thereby dispersing stress and preventing brittle fracture of the PP material. And using sepiolite - reinforced silica aerogel powder as the framework structure can further improve the toughness of the PP material. Applied in lithium - battery packaging, it has excellent corrosion resistance, wear resistance, thermal conductivity, flame retardancy, and toughness.

[0023] 2. The nitrogen-doped silica / graphene foam composite powder of the present invention uses sepiolite-reinforced silica aerogel powder as the skeleton structure. The nanofiber network of sepiolite intersects with the three-dimensional silica skeleton, which can significantly improve the structural strength of the silica aerogel. Through polydopamine as a bridge and providing a carbon source and a nitrogen source, carbon nanotubes are uniformly loaded in the skeleton structure of the aerogel. After carbonization, a nitrogen-doped silica / graphene foam is formed, which has a high specific surface area and a porous structure, can provide good mechanical support and stress buffering. Graphene itself has certain lubricating properties, which can significantly reduce the friction coefficient of the PP material and improve the wear resistance of the PP material.

[0024] 3. The carbon nitride / graphene foam composite powder of the present invention grows graphitic carbon nitride on the nitrogen-doped silica / graphene foam composite powder. The composite powder has a three-dimensional network composite structure in terms of spatial structure, in which the interlayer structure of graphitic carbon nitride is interspersed. The van der Waals force between the layers of graphitic carbon nitride is weak and easy to slide. The layered structure allows interlayer slip under the action of external force, thereby dispersing stress and avoiding local stress concentration. The three-dimensional network composite structure further uniformly transmits stress to prevent brittle fracture of the material, and can play a lubricating role synergistically with the graphene foam to further improve the wear resistance of the PP material; graphitic carbon nitride has certain flame retardancy. The nitrogen-doped three-dimensional network composite structure can release sufficient ammonia gas during decomposition, and the ceramic barrier formed by silica. The surface of the three-dimensional network composite structure is porous and rough, which can adsorb more ammonium polyphosphate, can better play a synergistic flame retardant role, promote the formation of a dense carbon layer, reduce heat transfer, and ensure the safety of lithium battery use. Detailed implementation manners

[0025] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0026] Example 1: A preparation method of a wear-resistant and corrosion-resistant PP material for lithium battery packaging, through the following steps:

[0027] S1: Add 4 kg of sepiolite fibers with a length of 2 mm and 4 L of hydrochloric acid solution with a concentration of 3 mol / L into a reaction kettle, stir at 50 °C and 500 r / min for 1 h, filter, wash the filter cake with deionized water until the last washing liquid is neutral to obtain pretreated sepiolite fibers; add 1 L of tetraethyl orthosilicate, 3 L of ethanol and 4 L of deionized water into the reaction kettle, stir at 20 °C and 500 r / min for 5 min, add 250 mL of 1 mol / L hydrochloric acid solution to adjust the pH value to 2, continue to stir for 3 h, add 3 kg of pretreated sepiolite fibers, ultrasonically disperse for 40 min, then add 200 mL of ammonia water with a mass fraction of 20% to adjust the pH value to 7, seal and place in an oven at 50 °C for 40 h, add 200 mL of trimethylchlorosilane and 1.6 L of n-hexane, seal and place in an oven at 20 °C for constant temperature for 24 h, filter, wash the filter cake with n-hexane and deionized water twice respectively, dry in vacuum at 60 °C for 12 h, grind and crush to obtain sepiolite-reinforced silica aerogel powder with a pore size of 50 - 60 nm.

[0028] Silica aerogel is brittle, has low compressive / tensile strength and is easy to break. The nanofiber network of sepiolite intersects with the three-dimensional skeleton of silica, which can significantly improve the structural strength of silica aerogel, so that it does not need to add resin materials to fix the structure of the aerogel during the regeneration process.

[0029] S2: Add 3.2 kg of sepiolite-reinforced silica aerogel powder, 1 L of γ-aminopropyltriethoxysilane, 2 L of ethanol and 3 L of deionized water into a reaction kettle, stir at 60 °C and 500 r / min for 1 h, filter, wash the filter cake with deionized water twice, dry in vacuum at 60 °C for 1 h to obtain modified aerogel powder.

[0030] The silane bonds generated by the hydrolysis of γ-aminopropyltriethoxysilane can bond with the hydroxyl groups on the surface of silica aerogel, making the surface of silica aerogel carry amino functional groups.

[0031] S3: Add 3 kg of carboxylated multi-walled carbon nanotubes with a length of 2.5 μm and a diameter of 6 nm, 1 kg of dopamine and 7 L of deionized water into a reaction kettle, stir at 20 °C and 500 r / min for 30 min, then add 500 mL of Tris-HCl buffer solution with a concentration of 1 mol / L and a pH value of 8.0, heat to 80 °C, continue to stir for 20 h, then add 2 kg of modified aerogel powder, continue to stir for 1 h, filter, wash the filter cake with deionized water twice, dry in vacuum at 60 °C for 1 h, transfer the product to a muffle furnace, under an argon atmosphere, heat to 800 °C at a rate of 13 °C / min, keep warm for 2 h, and naturally cool to room temperature to obtain nitrogen-doped silica / graphene foam composite powder.

[0032] Dopamine is rich in amino and hydroxyl groups and is dispersed in an aqueous solution. It can bond and polymerize with the carboxyl groups on the surface of carboxylated multi-walled carbon nanotubes. The surface of the carbon nanotubes modified and coated with polydopamine carries hydroxyl groups and can enter the framework of the aerogel to undergo an ammoniation reaction with the amino groups on the surface of the aerogel. In this process, this encapsulation effect not only improves the dispersion of carbon nanotubes in the silica aerogel but also enhances their binding force with the aerogel matrix. Moreover, silica can act as a catalyst to promote the reaction.

[0033] Using polydopamine as a bridge, carbon nanotubes are uniformly loaded in the aerogel framework. The carbon source and nitrogen source provided by polydopamine generate nitrogen-doped silica / graphene foam composite powder after carbonization. In the nitrogen-doped silica / graphene foam composite powder, silica, carbon nanotubes, and graphene all have excellent thermal conductivity, which can significantly increase the thermal conductivity of the PP material. The surface of the nitrogen-doped silica / graphene foam composite powder is porous and rough, which can effectively isolate the corrosive medium and improve the corrosion resistance of the composite material.

[0034] S4: Mix the melamine powder and the nitrogen-doped silica / graphene foam composite powder evenly according to a mass ratio of 1:3, transfer them to a muffle furnace, and under an argon atmosphere, heat them to 300 °C at a rate of 5 °C / min, hold for 1 h, then heat to 550 °C at a rate of 7 °C / min, hold for 2 h, and naturally cool to room temperature to obtain a carbon nitride / graphene foam composite powder with a three-dimensional network composite structure.

[0035] Based on the nitrogen-doped silica / graphene foam composite powder as the matrix, which has a high specific surface area and a porous structure, graphitic carbon nitride grows on the surface, providing good mechanical support and stress buffering. Graphitic carbon nitride has a layered structure, and the van der Waals force between layers is weak and easy to slide. The layered structure allows for interlayer slippage under external forces, thereby dispersing stress and avoiding local stress concentration. The three-dimensional network composite structure further evenly transmits stress to prevent brittle fracture of the material. The graphene foam itself has certain lubrication characteristics, combined with the layered structure of graphitic carbon nitride, can synergistically play a sliding role, significantly reducing the friction coefficient of the PP material and improving wear resistance.

[0036] Graphitic carbon nitride has excellent flame retardancy. The three-dimensional network composite structure releases an increased amount of ammonia gas during decomposition, further diluting the concentration of combustible gases. Moreover, the porous and rough surface structure can adsorb more ammonium polyphosphate, enabling better synergistic flame retardant effect.

[0037] S5: Add 45 kg of polypropylene resin and 5 kg of polyurethane elastic material into a reaction kettle, stir at 150 °C for 30 min, then add 1 kg of polyethylene glycol as compatibilizer, 5 kg of carbon nitride / graphene foam composite powder, 1.2 kg of antioxidant phosphite ester and 2.3 kg of synergistic flame retardant ammonium polyphosphate, continue to stir for 1 h, transfer to a twin-screw extruder, extrude at 180 °C and 45 r / min, and pelletize to obtain a wear-resistant and corrosion-resistant PP material for lithium battery packaging.

[0038] Example 2: A preparation method of a wear-resistant and corrosion-resistant PP material for lithium battery packaging, through the following steps:

[0039] S1: Add 4.5 kg of sepiolite fibers with a length of 3 mm and 4.5 L of hydrochloric acid solution with a concentration of 3.5 mol / L into a reaction kettle, stir at 55 °C and 550 r / min for 1.5 h, filter, wash the filter cake with deionized water until the last washing liquid is neutral to obtain pretreated sepiolite fibers; add 1.1 L of tetraethyl orthosilicate, 3.5 L of ethanol and 4.5 L of deionized water into the reaction kettle, stir at 22.5 °C and 550 r / min for 7.5 min, add 270 mL of 1 mol / L hydrochloric acid solution to adjust the pH value to 2.5, continue to stir for 3.5 h, add 3.5 kg of pretreated sepiolite fibers, ultrasonically disperse for 50 min, then add 250 mL of ammonia water with a mass fraction of 25% to adjust the pH value to 7.5, seal and place in an oven at 55 °C for 45 h, add 250 mL of trimethylchlorosilane and 1.8 L of n-hexane, seal and place in an oven at 22.5 °C for constant temperature for 25 h, filter, wash the filter cake with n-hexane and deionized water twice respectively, and dry in vacuum at 70 °C for 13 h to obtain sepiolite-reinforced silica aerogel powder with a pore size of 50 - 60 nm.

[0040] S2: Add 3.4 kg of sepiolite-reinforced silica aerogel powder, 1.5 L of γ-aminopropyltriethoxysilane, 2.5 L of ethanol and 3.5 L of deionized water into a reaction kettle, stir at 65 °C and 550 r / min for 1.5 h, filter, wash the filter cake with deionized water twice, and dry in vacuum at 70 °C for 1.5 h to obtain modified aerogel powder.

[0041] S3: Add 3.5 kg of carboxylated multi-walled carbon nanotubes with a length of 2.8 μm and a diameter of 7 nm, 1.5 kg of dopamine, and 7.5 L of deionized water into a reaction kettle, stir at 22.5 °C and 550 r / min for 35 min, then add 550 mL of Tris-HCl buffer solution with a concentration of 1 mol / L and a pH value of 8.0, heat to 82.5 °C, continue to stir for 21 h, then add 2.5 kg of modified aerogel powder, continue to stir for 1.5 h, filter, wash the filter cake with deionized water twice, dry it in vacuum at 70 °C for 1.5 h, transfer the product to a muffle furnace, under an argon atmosphere, heat it to 825 °C at a rate of 14 °C / min, hold for 2.5 h, and naturally cool to room temperature to obtain nitrogen-doped silica / graphene foam composite powder.

[0042] S4: Mix melamine powder and nitrogen-doped silica / graphene foam composite powder evenly according to a mass ratio of 1:3, transfer to a muffle furnace, under an argon atmosphere, heat it to 330 °C at a rate of 5.5 °C / min, hold for 1.1 h, heat it to 580 °C at a rate of 7.5 °C / min, hold for 2.5 h, and naturally cool to room temperature to obtain carbon nitride / graphene foam composite powder with a three-dimensional network composite structure in the spatial structure.

[0043] S5: Add 47.5 kg of polypropylene resin and 5.5 kg of polyurethane elastic material into a reaction kettle, stir at 155 °C for 35 min, then add 1.5 kg of polyethylene glycol as a compatibilizer, 5.5 kg of carbon nitride / graphene foam composite powder, 1.4 kg of antioxidant phosphite ester, and 2.4 kg of synergistic flame retardant ammonium polyphosphate, continue to stir for 1.5 h, transfer to a twin-screw extruder, extrude at 185 °C and 47.5 r / min, and pelletize to obtain a wear-resistant and corrosion-resistant PP material for lithium battery packaging.

[0044] Example 3: A preparation method of a wear-resistant and corrosion-resistant PP material for lithium battery packaging, through the following steps:

[0045] S1: Add 5 kg of sepiolite fibers with a length of 4 mm and 5 L of hydrochloric acid solution with a concentration of 4 mol / L into a reaction kettle, stir at 60 °C and 600 r / min for 2 h, filter, wash the filter cake with deionized water until the last washing liquid is neutral to obtain pretreated sepiolite fibers; add 1.2 L of tetraethyl orthosilicate, 4 L of ethanol and 5 L of deionized water into the reaction kettle, stir at 25 °C and 600 r / min for 10 min, add 300 mL of 1 mol / L hydrochloric acid solution to adjust the pH value to 3, continue to stir for 4 h, add 4 kg of pretreated sepiolite fibers, ultrasonically disperse for 60 min, then add 300 mL of ammonia water with a mass fraction of 30% to adjust the pH value to 8, seal and place in an oven at 60 °C for 50 h, add 300 mL of trimethylchlorosilane and 2 L of n-hexane, seal and place in an oven at 25 °C for constant temperature for 26 h, filter, wash the filter cake with n-hexane and deionized water 3 times respectively, and dry in vacuum at 80 °C for 14 h to obtain sepiolite-reinforced silica aerogel powder with a pore size of 50 - 60 nm.

[0046] S2: Add 3.6 kg of sepiolite-reinforced silica aerogel powder, 2 L of γ-aminopropyltriethoxysilane, 3 L of ethanol and 4 L of deionized water into a reaction kettle, stir at 70 °C and 600 r / min for 2 h, filter, wash the filter cake with deionized water 3 times, and dry in vacuum at 80 °C for 2 h to obtain modified aerogel powder.

[0047] S3: Add 4 kg of carboxylated multi-walled carbon nanotubes with a length of 3 μm and a diameter of 8 nm, 2 kg of dopamine and 8 L of deionized water into a reaction kettle, stir at 25 °C and 600 r / min for 40 min, then add 600 mL of Tris-HCl buffer solution with a concentration of 1 mol / L and a pH value of 8.0, heat to 85 °C, continue to stir for 22 h, then add 3 kg of modified aerogel powder, continue to stir for 2 h, filter, wash the filter cake with deionized water 3 times, and dry in vacuum at 80 °C for 2 h. Transfer the product to a muffle furnace, under an argon atmosphere, heat to 850 °C at a rate of 15 °C / min, hold for 3 h, and naturally cool to room temperature to obtain nitrogen-doped silica / graphene foam composite powder.

[0048] S4: Mix melamine powder and nitrogen-doped silica / graphene foam composite powder evenly according to a mass ratio of 1:3, transfer to a muffle furnace, under an argon atmosphere, heat to 350 °C at a rate of 6 °C / min, hold for 1.2 h, heat to 600 °C at a rate of 8 °C / min, hold for 3 h, and naturally cool to room temperature to obtain carbon nitride / graphene foam composite powder with a three-dimensional network composite structure in the spatial structure.

[0049] S5: Add 50 kg of polypropylene resin and 6 kg of polyurethane elastic material into the reaction kettle, stir at 160 °C for 40 min, then add 2 kg of polyethylene glycol as the compatibilizer, 6 kg of carbon nitride / graphene foam composite powder, 1.5 kg of antioxidant phosphite ester, and 2.5 kg of synergistic flame retardant ammonium polyphosphate. Continue to stir for 2 h, transfer to a twin-screw extruder, and extrude at 190 °C and 50 r / min to granulate, obtaining a wear-resistant and corrosion-resistant PP material for lithium battery packaging.

[0050] Comparative Example 1: On the basis of Example 3, replace the sepiolite-reinforced silica aerogel powder in step S2 with commercially available silica aerogel of the same mass, and keep the other steps unchanged to prepare a wear-resistant and corrosion-resistant PP material for lithium battery packaging.

[0051] Comparative Example 2: On the basis of Example 3, replace the modified aerogel powder in step S3 with sepiolite-reinforced silica aerogel powder of the same mass as in step S1, and keep the other steps unchanged to prepare a wear-resistant and corrosion-resistant PP material for lithium battery packaging.

[0052] Comparative Example 3: On the basis of Example 3, replace the melamine powder in step S3 with commercially available graphitic carbon nitride. After measuring that the actual loading amount of graphitic carbon nitride in Example 3 is 17.8%, directly mix graphitic carbon nitride and nitrogen-doped silica / graphene foam composite powder evenly according to a mass ratio of 1:5 as the carbon nitride / graphene foam composite powder in step S5, and keep the other steps unchanged to prepare a wear-resistant and corrosion-resistant PP material for lithium battery packaging.

[0053] Comparative Example 4: On the basis of Example 3, replace the nitrogen-doped silica / graphene foam composite powder in step S4 with commercially available graphene powder of the same mass, and keep the other steps unchanged to prepare a wear-resistant and corrosion-resistant PP material for lithium battery packaging.

[0054] In the examples and comparative examples:

[0055] The CAS number of carboxylated multi-walled carbon nanotubes is XFM691333-86-4, purchased from Jiangsu Xianfeng Nano Materials Technology Co., Ltd.

[0056] Sepiolite fibers are purchased from Neixiang Xinglei Sepiolite Co., Ltd.

[0057] Tris-HCl buffer solution is purchased from Thermo Fisher Scientific (China) Co., Ltd.

[0058] Melamine powder is purchased from Wujiang Huaxu Chemical Technology Co., Ltd.

[0059] The wear-resistant and corrosion-resistant PP materials for lithium battery packaging prepared in Examples 1 - 3 and Comparative Examples 1 - 4 were heated and melted by an injection molding machine, pressed into a mold, with a melting temperature of 180 °C, a pressure of 60 Mpa, and a pressing time of 30 min to obtain specimens, and the specimens were subjected to performance tests;

[0060] 1. Wear resistance test: Refer to the standard of GB / T3960-2016 "Test Method for Sliding Friction and Wear of Plastics" to detect the wear resistance of the PP material. After the PP material undergoes friction and wear, the chord length of the concave damage mark formed on the surface and the width of the wear mark are measured. The smaller the wear mark width, the better the wear resistance of the material.

[0061] 2. Mechanical property test: Refer to the standard of GB / T1040.2-2006 to test the impact strength of the PP material, and refer to the standard of GB / T9341-2008 to test the flexural strength.

[0062] 3. Flame retardancy test: Refer to the standard of UL94 to test the flame retardancy of the PP material.

[0063] 4. Corrosion resistance test: Immerse 1 kg of the wear-resistant and corrosion-resistant PP material for lithium battery packaging in a sodium hydroxide solution prepared with a mass fraction of 40%, store it in a constant temperature and humidity chamber for 90 days, take out the specimen and weigh it, and calculate the percentage change in weight before and after. The smaller the volume change, the better the corrosion resistance of the PP material.

[0064] 5. Thermal conductivity test: Refer to the standard of GB / T8722-2008 to test the thermal conductivity.

[0065] The results are shown in Table 1:

[0066] Table 1 Performance test table of wear-resistant and corrosion-resistant PP materials for lithium battery packaging

[0067]

[0068]

[0069] As can be seen from Table 1, the impact strength, flexural strength, flame retardancy grade, and thermal conductivity of the wear-resistant and corrosion-resistant PP materials for lithium battery packaging prepared in Examples 1 - 3 and Comparative Examples 1 - 3 are significantly higher than those of the comparative examples, and the wear mark width and volume change rate are significantly lower than those of the comparative examples, indicating that the PP material prepared by the present invention has excellent corrosion resistance, wear resistance, thermal conductivity, flame retardancy, and toughness.

[0070] In Comparative Example 1, the sepiolite-reinforced silica aerogel powder was replaced with commercially available silica aerogel powder of the same mass. After sintering, the silica aerogel was brittle, with low compressive and tensile strengths, and was difficult to withstand mechanical impact or shear force. Moreover, it shrank during calcination at 600 °C, and the pore structure collapsed, resulting in a sharp drop in the heat insulation performance. The high melting point of sepiolite fibers can inhibit the high-temperature shrinkage of the aerogel skeleton and maintain the structural stability of the silica aerogel.

[0071] In Comparative Example 2, the modified aerogel powder was replaced with sepiolite-reinforced silica aerogel powder of the same mass in Step S1. The sepiolite-reinforced silica aerogel powder was modified with a silane coupling agent to introduce amino groups on the surface. The amino groups can better bond with the hydroxyl groups on the surface of the subsequent polydopamine-coated carbon nanotubes, avoid carbon nanotube agglomeration, and enable them to be evenly loaded in the aerogel skeleton. Moreover, the nitrogen doping formed after the carbonization of polydopamine will be more uniform.

[0072] In Comparative Example 3, the melamine powder was replaced with graphitic carbon nitride. The graphitic carbon nitride was mixed evenly with the nitrogen-doped silica / graphene foam composite powder. During the high-temperature pyrolysis process of melamine, a polycondensation reaction occurred. The oxygen-containing functional groups on the surface of the nitrogen-doped silica / graphene foam composite powder reacted with the amino groups in the graphitic carbon nitride precursor, enhancing the interfacial bonding force and avoiding interfacial slippage in physical mixing.

[0073] In Comparative Example 4, the nitrogen-doped silica / graphene foam composite powder was replaced with commercially available graphene powder of the same mass. The addition of graphene can cause a significant decrease in the impact strength of the PP material.

[0074] It should be noted that in this article, terms such as "including", "comprising", or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article, or device including a series of elements not only includes those elements but also includes other elements not explicitly listed, or also includes elements inherent to such a process, method, article, or device.

Claims

1. A preparation method of a wear-resistant and corrosion-resistant PP material for lithium battery packaging, characterized in that, By the following steps: Step 1: Coat carboxylated multi-walled carbon nanotubes with polydopamine, and use the hydroxyl groups on the surface to undergo an ammoniation reaction with the carboxyl groups on the surface of the modified aerogel powder. After carbonization, nitrogen-doped silica / graphene foam composite powder is obtained; mix melamine powder and nitrogen-doped silica / graphene foam composite powder evenly according to a mass ratio of 1:3, transfer them to a muffle furnace, under an argon atmosphere, heat at a rate of 5-6 °C / min to 300-350 °C, keep warm for 1-1.2 h, heat at a rate of 7-8 °C / min to 550-600 °C, keep warm for 2-3 h, and cool naturally to obtain carbon nitride / graphene foam composite powder; Step 2: Add polypropylene resin and polyurethane elastic material to a reaction kettle, stir at 150-160 °C for 30-40 min, then add polyethylene glycol, carbon nitride / graphene foam composite powder, phosphite and ammonium polyphosphate, continue to stir for 1-2 h, transfer to a twin-screw extruder, and extrude at 180-190 °C and 45-50 r / min to granulate, obtaining a wear-resistant and corrosion-resistant PP material for lithium battery packaging.

2. The preparation method of a wear-resistant and corrosion-resistant PP material for lithium battery packaging according to claim 1, characterized in that, In Step 2, the dosage ratio of the polypropylene resin, polyurethane elastic material, polyethylene glycol, carbon nitride / graphene foam composite powder, phosphite and ammonium polyphosphate is 45-50 kg: 5-6 kg: 1-2 kg: 5-6 kg: 1.2-1.5 kg: 2.3-2.5 kg.

3. The preparation method of a wear-resistant and corrosion-resistant PP material for lithium battery packaging according to claim 1, characterized in that, The specific preparation steps of the nitrogen-doped silica / graphene foam composite powder in Step 1 are as follows: Add carboxylated multi-walled carbon nanotubes with a length of 2.5-3 μm and a diameter of 6-8 nm, dopamine and deionized water to a reaction kettle, stir at 20-25 °C and 500-600 r / min for 30-40 min, then add Tris-HCl buffer solution with a concentration of 1 mol / L and a pH value of 8.0, heat to 80-85 °C, continue to stir for 20-22 h, then add the modified aerogel powder, continue to stir for 1-2 h, filter, wash, vacuum dry, transfer the product to a muffle furnace, under an argon atmosphere, heat at a rate of 13-15 °C / min to 800-850 °C, keep warm for 2-3 h, and cool naturally to room temperature to obtain nitrogen-doped silica / graphene foam composite powder.

4. The preparation method of a wear-resistant and corrosion-resistant PP material for lithium battery packaging according to claim 1, characterized in that, The dosage ratio of the carboxylated multi-walled carbon nanotubes, dopamine, deionized water, Tris-HCl buffer solution and modified aerogel powder is 3-4 kg: 1-2 kg: 7-8 L: 500-600 mL: 2-3 kg.

5. The preparation method of a wear-resistant and corrosion-resistant PP material for lithium battery packaging according to claim 3, wherein, The modified aerogel powder is prepared by the following steps: Add sepiolite-reinforced silica aerogel powder, γ-aminopropyltriethoxysilane, ethanol and deionized water to a reaction kettle, stir at 60-70 °C and 500-600 r / min for 1-2 h, filter, wash, vacuum dry to obtain modified aerogel powder.

6. The preparation method of a wear-resistant and corrosion-resistant PP material for lithium battery packaging according to claim 5, characterized in that, The dosage ratio of the sepiolite-reinforced silica aerogel powder, γ-aminopropyltriethoxysilane, ethanol and deionized water is 3.2-3.6 kg: 1-2 L: 2-3 L: 3-4 L.

7. The preparation method of a wear-resistant and corrosion-resistant PP material for lithium battery packaging according to claim 5, wherein, The sepiolite-reinforced silica aerogel powder is prepared by the following steps: Add tetraethyl orthosilicate, ethanol and deionized water into a reaction kettle, stir at 20 - 25 °C and 500 - 600 r / min for 5 - 10 min, add 1 mol / L hydrochloric acid solution to adjust the pH value to 2 - 3, continue stirring for 3 - 4 h, add pretreated sepiolite fibers, ultrasonically disperse for 40 - 60 min, then add 20 - 30 wt% ammonia water to adjust the pH value to 7 - 8, seal and place in an oven at 50 - 60 °C for 40 - 50 h, add trimethylchlorosilane and n-hexane, seal and place in an oven at 20 - 25 °C for constant temperature for 24 - 26 h, filter, wash, and vacuum dry to obtain sepiolite-reinforced silica aerogel powder with a pore size of 50 - 60 nm.

8. The preparation method of a wear-resistant and corrosion-resistant PP material for lithium battery packaging according to claim 7, characterized in that, The dosage ratio of tetraethyl orthosilicate, ethanol, deionized water, hydrochloric acid solution, pretreated sepiolite fibers, ammonia water, trimethylchlorosilane and n-hexane is 1 - 1.2 L: 3 - 4 L: 4 - 5 L: 250 - 300 mL: 3 - 4 kg: 200 - 300 mL: 200 - 300 mL: 1.6 - 2 L.

9. The preparation method of a wear-resistant and corrosion-resistant PP material for lithium battery packaging according to claim 7, characterized in that, The pretreated sepiolite fibers are prepared by the following steps: Add sepiolite fibers with a length of 2 - 4 mm and 3 - 4 mol / L hydrochloric acid solution into a reaction kettle according to the dosage ratio of 4 - 5 kg: 4 - 5 L, stir at 50 - 60 °C and 500 - 600 r / min for 1 - 2 h, filter, wash the filter cake with deionized water until the last washing liquid is neutral to obtain pretreated sepiolite fibers.

10. A wear-resistant and corrosion-resistant PP material for lithium battery packaging, characterized in that, It is prepared by the preparation method described in any one of claims 1 - 9.

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