An electromagnetic shielding composite film for new energy vehicles and preparation method thereof

Abstract

The present invention discloses an electromagnetic shielding composite film and its preparation method and application, which belong to the field of polymer science and technology. A shape memory polyimide (PI) fiber membrane with lightness, flexibility and corrosion resistance is prepared by electrostatic spinning technology, and a few layers of MXene nanosheets and silver nanowires (AgNWs) are prepared respectively by in-situ HF etching method and polyol method. MXene and AgNWs are first mixed in different proportions and vacuum filtered on the surface of PI fiber membrane to obtain PI / MXene‑AgNWs composite film, and then MXene and melamine cyanurate (MCA) are mixed in different proportions and vacuum filtered on the surface of another PI fiber membrane to obtain PI / MXene‑MCA composite film. Finally, PI / MXene‑AgNWs and PI / MXene‑MCA composite film are stacked in sequence with PI fiber membrane and hot-pressed, thereby obtaining an electromagnetic shielding composite film integrating lightness, flexibility, corrosion resistance, ultra-high electromagnetic shielding effectiveness, flame retardancy and shape memory performance, which is suitable for electromagnetic protection of new energy vehicles.

Description

Technical Field

[0001] The present invention belongs to the field of polymer science and technology, and specifically relates to an electromagnetic shielding composite film for new energy vehicles and a preparation method thereof. Background Art

[0002] The rapid development of new energy vehicles inevitably generates significant electromagnetic radiation, primarily from batteries and motors. This not only impacts ride comfort and poses a threat to human health, but also interferes with onboard electronic systems, even causing system freezes and compromising driving safety. Currently, commercially available electromagnetic shielding films boast high shielding effectiveness and stability, enjoying widespread application in the new energy vehicle sector. However, they still have some significant drawbacks.

[0003] Some electromagnetic shielding films, particularly metal-based ones, suffer from high density, heavy weight, susceptibility to corrosion, poor flexibility, and high cost. This not only increases the overall weight and production cost of new energy vehicles, but also affects the vehicle's energy efficiency and driving performance, and is susceptible to damage in harsh environments. Furthermore, vehicles experience various vibrations and shocks during operation, making electromagnetic shielding films with poor flexibility more susceptible to damage or failure.

[0004] To sum up, although electromagnetic shielding films for new energy vehicles have broad application prospects and market demand, some key technical problems still need to be solved to improve their performance and reduce costs. Summary of the Invention

[0005] The purpose of this section is to summarize some aspects of the embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the abstract and title of this application to avoid obscuring the purpose of this section, the abstract and the title of the invention, and such simplifications or omissions should not be used to limit the scope of the present invention.

[0006] In view of the above problems and / or the problems existing in the prior art, the present invention is proposed.

[0007] Therefore, the purpose of the present invention is to overcome the deficiencies in the prior art and provide a method for preparing an electromagnetic shielding composite film for new energy vehicles.

[0008] In order to solve the above technical problems, the present invention provides the following technical solutions: a method for preparing an electromagnetic shielding composite film for new energy vehicles, characterized in that: comprising:

[0009] Pretreatment: preparation of polyamic acid PAA spinning solution, few-layer MXene nanosheets and silver nanowires AgNWs;

[0010] PAA fiber membrane was prepared by electrospinning PAA spinning solution, and the PAA fiber membrane was heat-treated to prepare shape memory polyimide PI fiber membrane;

[0011] MXene and AgNWs were mixed and ultrasonically dispersed to obtain a mixed solution of MXene and AgNWs, which was then vacuum filtered onto the surface of the PI fiber membrane to obtain a PI / MXene-AgNWs composite membrane.

[0012] MXene and melamine cyanurate (MCA) were mixed and ultrasonically dispersed to obtain a mixed solution of MXene and MCA, which was then vacuum filtered onto the surface of a PI fiber membrane to obtain a PI / MXene-MCA composite membrane.

[0013] The PI / MXene-AgNWs composite film, the PI / MXene-MCA composite film and the PI fiber film are stacked in sequence and hot pressed to obtain an electromagnetic shielding composite film for new energy vehicles with a multi-level layered structure.

[0014] As a preferred embodiment of the preparation method of the present invention, the PAA spinning solution is electrospun to prepare a PAA fiber membrane, and the PAA fiber membrane is heat-treated, wherein the electrospinning voltage is 16 to 20 kV, the heat treatment temperature is 200 to 300°C, and the heat treatment time is 1.5 to 2 hours.

[0015] As a preferred embodiment of the preparation method of the present invention, MXene and AgNWs are mixed, wherein the mass ratio of MXene to AgNWs is 5-0:0-5.

[0016] As a preferred embodiment of the preparation method of the present invention, MXene and melamine cyanurate MCA are mixed, wherein the mass ratio of MXene to MCA is 5-0:0-5.

[0017] As a preferred embodiment of the preparation method of the present invention, the ultrasonic dispersion is carried out in an ice bath for 2 to 3 hours.

[0018] As a preferred embodiment of the preparation method of the present invention, the polyamic acid PAA spinning solution is prepared by stirring diaminodiphenyl ether (ODA), phthalic anhydride (PMDA) and N,N-dimethylformamide (DMF) in an ice bath for 10 hours.

[0019] As a preferred embodiment of the preparation method of the present invention, the mass ratio of ODA, PMDA and DMF is 2:2.18:19.04.

[0020] As a preferred embodiment of the preparation method of the present invention, the preparation method of the few-layer MXene nanosheets is to first etch away the Al layer in the MAX phase using HCl and lithium fluoride LiF, and then obtain the few-layer MXene nanosheets after ultrasonic exfoliation and centrifugation.

[0021] As a preferred embodiment of the preparation method of the present invention, the preparation method of the silver nanowires AgNWs is as follows: AgNO3 is dissolved in ethylene glycol to prepare a silver ion solution, which is heated to 160°C, and a silver precursor solution coated with polyvinyl pyrrolidone (PVP) is slowly added to reduce the silver ions to silver atoms, which are aggregated to form nanowires, and then separated, washed, and dried after cooling to obtain AgNWs.

[0022] As a preferred embodiment of the preparation method of the present invention, the hot pressing comprises the following steps: the hot pressing pressure is 1 MPa, the hot pressing temperature is 120° C., and the hot pressing time is 3 min.

[0023] Beneficial effects of the present invention:

[0024] The electromagnetic shielding composite film prepared by electrospinning, vacuum filtration and hot pressing technology of the present invention overcomes the shortcomings of traditional automotive electromagnetic shielding films and has a huge improvement in overall performance and intelligent design.

[0025] (1) The PI fiber membrane prepared by electrospinning technology has extremely low mass and excellent flexibility, and can fit tightly with the battery or motor. On the one hand, it does not take up too much space, and on the other hand, it does not significantly increase the overall mass of the car and affect normal driving.

[0026] (2) The excellent corrosion resistance and high temperature resistance enable the composite film to be used for a long time in harsh environments, extending the service life of the automotive electromagnetic shielding film.

[0027] (3) The design of the multi-level layered structure can give the composite film an ultra-high electromagnetic shielding performance, while greatly reducing the agglomeration and oxidation of nanofillers and improving their utilization rate.

[0028] (4) The accompanying flame retardancy and shape memory properties can not only protect the safety of cars and people, but also give the composite film the ability to deform, broadening its intelligent application areas.

[0029] (5) This new multifunctional intelligent electromagnetic shielding composite film has great research significance and application value for my country's huge new energy vehicle market. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. Those skilled in the art can also derive other drawings based on these drawings without inventive effort. Among them:

[0031] Figure 1 Schematic diagram of the preparation method of PI / MXene-AgNWs and PI / MXene-MCA composite films in the present invention.

[0032] Figure 2 It is a schematic diagram of the preparation method of the electromagnetic shielding composite film for new energy vehicles according to the present invention.

[0033] Figure 3 It is the electromagnetic shielding effectiveness of the electromagnetic shielding composite film prepared in Example 1. DETAILED DESCRIPTION

[0034] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the embodiments of the specification.

[0035] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0036] Secondly, the term "one embodiment" or "embodiment" herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in various places throughout this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive of other embodiments.

[0037] The raw materials used in this invention were obtained from: Ti3AlC2 powder (99% purity, 400 mesh) purchased from Jilin 11 Technology Co., Ltd.; hydrochloric acid (HCl, 37 wt%), N,N-dimethylformamide (DMF), silver nitrate (AgNO3), ferric chloride hexahydrate (FeCl3·6H2O), ethanol (C2H6O), and acetone (C3H6O) purchased from China National Pharmaceutical Group Chemical Reagent Co., Ltd.; and 99% pure lithium fluoride (LiF), diaminodiphenyl ether (ODA), phthalic anhydride (PMDA), ethylene glycol (EG), polyvinylpyrrolidone (PVP, Mw = 30,000 g / mol), and melamine cyanurate (MCA) provided by Aladdin Reagent Co., Ltd.

[0038] Instruments used in the examples of the present invention: (FE-SEM, Sigma 300, Carl Zeiss Co., Germany): Field emission scanning electron microscope (FE-SEM), model Sigma 300, manufactured by Carl Zeiss Co., Germany. (TEM, FEI Tecnai G2 F20, USA): Transmission electron microscope (TEM), model FEI Tecnai G2 F20, manufactured by the United States. (FT-IR, Nicolet-10, American Thermo Fisher Scientific Co., Ltd., China): Fourier transform infrared spectrometer (FT-IR), model Nicolet-10, manufactured by Thermo Fisher Scientific Co., Ltd., China. (XRD, D2 PHASER, Brooke AXS Co., Ltd., Germany): X-ray diffractometer (XRD), model D2 PHASER, manufactured by Brooke AXS Co., Germany. (DSC, Q200, TA Instruments, USA): Differential Scanning Calorimeter (DSC), Model Q200, manufactured by TA Instruments, USA. (UTM2203, Sanshi Zongheng Technology Co., Ltd., China): Universal Testing Machine, Model UTM2203, manufactured by Sanshi Zongheng Technology Co., Ltd., China. (E8, FLIR Systems, Ltd., USA): Infrared Thermal Imager, Model E8, manufactured by FLIR Systems, Inc., USA. (PNA-N5244A, Agilent Technologies Ltd., USA): Vector Network Analyzer, Model PNA-N5244A, manufactured by Agilent Technologies, Inc., USA. (DMA, Q800, TA Instruments, USA): Dynamic Mechanical Analyzer (DMA), Model Q800, manufactured by TA Instruments, USA.

[0039] The electromagnetic shielding effectiveness testing method of the product in the embodiment of the present invention is as follows: the scattering parameters (S parameters) of the electromagnetic shielding composite film in the X-band (8.2-12.4GHz) are measured by a vector network analyzer through a waveguide transmission line method, and the electromagnetic shielding effectiveness is calculated based on these parameters. The specific testing method is as follows: a vector network analyzer (VNA) is used as an electromagnetic wave transmitter and receiver; a coaxial cable is connected to ensure that the electromagnetic wave can be transmitted to the rectangular waveguide; relevant parameters and calibration before the test are adjusted, and the composite film is placed in the middle of the fixture; the vector network analyzer transmits an incident electromagnetic wave, which is transmitted to the rectangular waveguide through a coaxial cable; the electromagnetic wave passes through the sample to be tested, the incident end detects the reflected wave, and the receiving end detects the transmitted wave; the scattering parameters (S parameters) of the two ports are recorded, including S 11(reflection coefficient), S 21 (transmission coefficient), etc. These parameters will be used in subsequent data analysis and shielding performance calculation.

[0040] The shape memory performance testing method of the product in the embodiment of the present invention is as follows: the composite film is cut into rectangular sizes using a DMA machine. The length, width, thickness and other relevant parameters are input into the machine and the length of the sample at this time is recorded, which is set as L1. The sample is heated to above the glass transition temperature, and then stress is applied to the sample. The length after stretching is L2. At this time, the stress is kept constant, and the temperature is quickly lowered to room temperature. After cooling for a period of time, the sample is heated again to above the glass transition temperature. The sample length becomes L3. The measurement is repeated 3 times. The shape fixation rate (R) of the sample can be calculated based on the relevant data. f ) and shape recovery rate (R r ).

[0041] The flame retardant performance testing method of the product in the embodiment of the present invention is as follows: applying a flame and recording the time when the flame is completely extinguished.

[0042] The corrosion resistance testing method of the product in the embodiment of the present invention is as follows: after being placed in a strong acid and strong alkali solution, the electromagnetic shielding effectiveness of the composite film is determined to see whether it changes. If it remains substantially unchanged, the composite film is qualified.

[0043] The method for measuring the thickness of the product in the embodiment of the present invention is as follows: the thickness gauge is used for measurement, the composite film is placed between the upper and lower probes of the thickness gauge, and the thickness of the composite film can be directly obtained by reading the data on the thickness gauge screen.

[0044] Example 1

[0045] A novel electromagnetic shielding composite film for new energy vehicles and its preparation technology, the preparation process sequence includes:

[0046] (1) 2.0 g of diaminodiphenyl ether (ODA), 2.18 g of phthalic anhydride (PMDA), and 19.04 g of N,N-dimethylformamide (DMF) were placed in a three-necked round-bottom flask and stirred in an ice bath for 10 h to prepare a 16 wt% polyamic acid (PAA) spinning solution.

[0047] (2) The PAA spinning solution obtained in step (1) is electrospun at a voltage of 20 kV to obtain a PAA fiber membrane, and then the PAA fiber membrane is placed in a 300° C. oven for 2 h for thermal imidization to obtain a shape memory polyimide (PI) fiber membrane.

[0048] (3) Few-layer MXene nanosheets were prepared by in-situ HF etching. The Al layer in the MAX phase was first etched away using HCl and LiF (lithium fluoride), and then the few-layer MXene nanosheets were obtained after ultrasonic stripping and centrifugation.

[0049] (4) Silver nanowires (AgNWs) were prepared by the polyol method. AgNO3 was dissolved in ethylene glycol to prepare a silver ion solution, which was heated to 160°C and slowly added with a silver precursor solution coated with polyvinyl pyrrolidone (PVP). The silver ions were reduced to silver atoms, which aggregated to form nanowires. After cooling, the solution was separated, washed, and dried to obtain AgNWs.

[0050] (5) The MXene and AgNWs prepared in step (3) and step (4) were mixed to control the total mass to 50 mg and the mass ratio of the two to 3:2, and ultrasonic dispersion was performed to obtain a mixed solution of MXene and AgNWs.

[0051] (6) The mixed solution of MXene and AgNWs prepared in step (5) was vacuum filtered onto the surface of the PI fiber membrane obtained in step (2) to obtain PI / MXene-AgNWs composite membranes with different mass ratios.

[0052] (7) The MXene prepared in step (3) and melamine cyanurate (MCA) were mixed to control the total mass to be 50 mg and the mass ratio of the two to be 4:1, and ultrasonic dispersion was performed to obtain a mixed solution of MXene and MCA.

[0053] (8) The mixed solution of MXene and MCA prepared in step (7) was vacuum filtered onto the surface of the PI fiber membrane obtained in step (2) to obtain PI / MXene-MCA composite membranes with different mass ratios.

[0054] (9) The composite membrane prepared in step (6) and step (8) and the PI fiber membrane prepared in step (2) are Figure 2 As shown, they are stacked together in sequence to prepare a new electromagnetic shielding composite film with a multi-level layered structure through a hot pressing process.

[0055] The electromagnetic shielding performance of the composite film prepared in Example 1 was tested, and the test results are as follows: Figure 3 As shown, it can be seen that the total electromagnetic shielding effectiveness (SET) is as high as 95.8dB, which is nearly 5 times the commercial standard value (20dB). Among them, the absorption shielding effectiveness (SEA) contributes more to SET, indicating that the composite film has ultra-high electromagnetic shielding effectiveness.

[0056] Example 2

[0057] The difference between this embodiment and embodiment 1 is that the mass ratio of MXene and MCA in step (7) is replaced with 3:2, and the remaining steps are the same as those in embodiment 1 to prepare an electromagnetic shielding composite film.

[0058] Example 3

[0059] The difference between this embodiment and embodiment 1 is that the mass ratio of MXene and MCA in step (7) is replaced with 2:3, and the remaining steps are the same as those in embodiment 1 to prepare an electromagnetic shielding composite film.

[0060] Comparative Example 1

[0061] The difference between this comparative example and Example 1 is that MCA in step (7) is replaced by hexabromocyclododecane, and the remaining steps are the same as those in Example 1 to prepare an electromagnetic shielding composite film.

[0062] Comparative Example 2

[0063] The difference between this comparative example and Example 1 is that MCA in step (7) is replaced by tetrabromobisphenol A, and the remaining steps are the same as those in Example 1 to prepare an electromagnetic shielding composite film.

[0064] Comparative Example 3

[0065] The difference between this comparative example and Example 1 is that the mass ratio of MXene and MCA in step (7) is replaced with 6:1, and the remaining steps are the same as in Example 1 to prepare an electromagnetic shielding composite film.

[0066] Comparative Example 4

[0067] The difference between this comparative example and Example 1 is that the mass ratio of MXene and MCA in step (7) is replaced with 1:6, and the remaining steps are the same as in Example 1 to prepare an electromagnetic shielding composite film.

[0068] Performance testing of the electromagnetic shielding composite films produced in Examples 1-3 and Comparative Examples 1-4 was conducted. The test results are shown in Table 1. It can be seen that the MCA flame retardant used in this solution significantly improves the flame retardancy of the material at a very low dosage. It contains no harmful substances such as bromine and chlorine, and is non-toxic to the environment and human body. When used in conjunction with MXene, it can reduce the agglomeration of MXene nanosheets and simultaneously intercalate the MXene nanosheets, improving their electromagnetic shielding performance. Due to the synergistic effect of the two, it exhibits excellent flame retardancy. This effect cannot be achieved with other flame retardants, such as hexabromocyclododecane and tetrabromobisphenol A.

[0069] Table 1

[0070]

[0071] Example 4

[0072] The difference between this embodiment and embodiment 1 is that the mass ratio of MXene and AgNWs in step (5) is replaced with 4:1, and the remaining steps are the same as those in embodiment 1 to prepare an electromagnetic shielding composite film.

[0073] Example 5

[0074] The difference between this embodiment and embodiment 1 is that the mass ratio of MXene and AgNWs in step (5) is replaced with 2:3, and the remaining steps are the same as those in embodiment 1 to prepare an electromagnetic shielding composite film.

[0075] Example 6

[0076] The difference between this embodiment and embodiment 1 is that the mass ratio of MXene and AgNWs in step (5) is replaced with 5:0, and the remaining steps are the same as those in embodiment 1 to prepare an electromagnetic shielding composite film.

[0077] Example 7

[0078] The difference between this embodiment and embodiment 1 is that the mass ratio of MXene and AgNWs in step (5) is replaced with 0:5, and the remaining steps are the same as those in embodiment 1 to prepare an electromagnetic shielding composite film.

[0079] Comparative Example 5

[0080] The difference between this comparative example and Example 1 is that the AgNWs in step (5) are replaced by carbon nanotubes CNTs, and the remaining steps are the same as those in Example 1 to prepare an electromagnetic shielding composite film.

[0081] Comparative Example 6

[0082] The difference between this comparative example and Example 1 is that the mass ratio of MXene and AgNWs in step (5) is replaced with 1:6, and the remaining steps are the same as in Example 1 to prepare an electromagnetic shielding composite film.

[0083] Comparative Example 7

[0084] The difference between this comparative example and Example 1 is that the mass ratio of MXene and AgNWs in step (5) is replaced with 6:1, and the remaining steps are the same as in Example 1 to prepare an electromagnetic shielding composite film.

[0085] Performance testing of the electromagnetic shielding composite films prepared in Examples 1, 4-7, and Comparative Examples 5-7 was conducted. The test results are shown in Table 2. It can be seen that the ratio of MXene to AgNWs is crucial for improving electromagnetic shielding and flame retardancy. When the ratio is 3:2, the best overall performance is achieved. This is because a reasonable ratio reduces the agglomeration of MXene nanosheets and facilitates the construction of a continuous and complete three-dimensional conductive and thermal network between the two. The excellent electrical and thermal conductivity of the two work synergistically, achieving efficient electromagnetic shielding and flame retardancy with low nanofiller content. At the same time, the composite film also has an extremely low thickness, excellent shape memory properties, and corrosion resistance.

[0086] When AgNWs were replaced with conventional nanofillers, such as CNTs, the study found that compared to Example 1, electromagnetic shielding performance was significantly reduced, and other properties, such as flame retardancy, also declined to varying degrees. This is because CNTs are highly susceptible to aggregation, have high rigidity, and have limited conductivity, making it difficult to achieve a synergistic effect when combined with MXene. Therefore, combining MXene with AgNWs in a ratio of 3:2 can maximize the performance of the composite film while effectively reducing the tendency of nanofillers to agglomerate in the polymer.

[0087] Table 2

[0088]

[0089] Example 8

[0090] The difference between this embodiment and embodiment 1 is that the hot pressing temperature in step (9) is replaced with 100° C., and the remaining steps are the same as those in embodiment 1 to obtain an electromagnetic shielding composite film.

[0091] Example 9

[0092] The difference between this embodiment and embodiment 1 is that the hot pressing temperature in step (9) is replaced with 140° C., and the remaining steps are the same as those in embodiment 1 to obtain an electromagnetic shielding composite film.

[0093] Example 10

[0094] The difference between this comparative example and Example 1 is that the hot pressing time in step (9) is replaced with 1 min, and the remaining steps are the same as those in Example 1 to obtain an electromagnetic shielding composite film.

[0095] Example 11

[0096] The difference between this comparative example and Example 1 is that the hot pressing time in step (9) is replaced with 5 minutes, and the remaining steps are the same as those in Example 1 to obtain an electromagnetic shielding composite film.

[0097] The electromagnetic shielding composite films prepared in Examples 1 and 8 to 11 were tested for performance. The test results are shown in Table 3. It can be seen that changing the hot pressing temperature and time during the hot pressing process affects the performance of the final composite film. By comparison, it was found that when the hot pressing temperature and hot pressing time were set to 120°C and 3 minutes, respectively, the composite film had the best overall performance. However, randomly changing the hot pressing temperature and hot pressing time had a significant impact on the shape memory performance of the composite film, significantly reducing it. Therefore, the hot pressing conditions proposed in the present invention are the optimal values, giving the composite film the best overall performance.

[0098] Table 3

[0099]

[0100]

[0101] The novel electromagnetic shielding composite film proposed in this invention features lightweight, flexible, corrosion-resistant, ultra-high electromagnetic shielding effectiveness, flame retardancy, and shape memory properties. It not only effectively addresses the shortcomings of current electromagnetic shielding films for new energy vehicles but also promotes their development towards high performance and intelligent technology. Key advantages include: With the rapid development of modern new energy vehicles, larger battery capacities, and increasingly sophisticated motor and electronic equipment, electromagnetic shielding composite films with ultra-high electromagnetic shielding effectiveness are needed to shield virtually all electromagnetic waves. Its excellent shape memory properties, flexibility, and corrosion resistance allow the composite film to fit tightly to vehicle equipment, making it less susceptible to damage, saving costs, and significantly extending its service life. Furthermore, the composite film is flame-retardant, effectively delaying vehicle combustion and protecting people in the event of an accident. Through the rational selection of materials and the ingenious design of its layered structure, the novel electromagnetic shielding composite film will provide safe and reliable electromagnetic protection for new energy vehicles while ensuring the stability and reliability of the vehicle's electronic systems. Compared to conventional automotive electromagnetic shielding films, the electromagnetic shielding composite film prepared in this invention offers higher shielding effectiveness, fire protection, shape change, and cost savings. The successful implementation of this invention is expected to provide new ideas and methods for the development of electromagnetic protection technology in the new energy vehicle industry, and promote the sustainable and healthy development of the industry.

[0102] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, and all of these should be included in the scope of the present invention.

Claims

1. A method for preparing an electromagnetic shielding composite film for new energy vehicles, characterized in that: include, Pretreatment: preparation of polyamic acid PAA spinning solution, few-layer MXene nanosheets and silver nanowires AgNWs; PAA fiber membrane was prepared by electrospinning PAA spinning solution, and the PAA fiber membrane was heat-treated to prepare shape memory polyimide PI fiber membrane; MXene and AgNWs were mixed and ultrasonically dispersed to obtain a mixed solution of MXene and AgNWs, which was then vacuum filtered onto the surface of the PI fiber membrane to obtain a PI / MXene-AgNWs composite membrane. MXene and melamine cyanurate (MCA) were mixed and ultrasonically dispersed to obtain a mixed solution of MXene and MCA, which was then vacuum filtered onto the surface of a PI fiber membrane to obtain a PI / MXene-MCA composite membrane. The PI / MXene-AgNWs composite film, the PI / MXene-MCA composite film, and the PI fiber film are stacked in sequence and hot-pressed to obtain an electromagnetic shielding composite film for new energy vehicles with a multi-level hierarchical structure. The MXene and AgNWs are mixed, wherein the mass ratio of MXene to AgNWs is 4-2:1-3; The MXene and melamine cyanurate MCA are mixed, wherein the mass ratio of MXene to MCA is 4-2:1-3.

2. The preparation method according to claim 1, wherein: The PAA spinning solution is electrospun to prepare a PAA fiber membrane, and the PAA fiber membrane is heat-treated, wherein the electrospinning voltage is 16-20 kV, the heat treatment temperature is 200-300° C., and the heat treatment time is 1.5-2 h.

3. The preparation method according to claim 1, wherein: The ultrasonic dispersion was performed in an ice bath for 2 to 3 hours.

4. The preparation method according to claim 1, wherein: The preparation method of the polyamic acid PAA spinning solution comprises the following steps: stirring diaminodiphenyl ether (ODA), phthalic anhydride (PMDA) and N,N-dimethylformamide (DMF) in an ice bath for 10 hours.

5. The preparation method according to claim 4, wherein: The mass ratio of the ODA, PMDA and DMF is 2:2.18:19.

04.

6. The preparation method according to claim 1, wherein: The preparation method of the few-layer MXene nanosheets is to first etch away the Al layer in the MAX phase using HCl and lithium fluoride LiF, and then obtain the few-layer MXene nanosheets after ultrasonic stripping and centrifugation.

7. The preparation method according to claim 1, wherein: The preparation method of the silver nanowires AgNWs is as follows: AgNO3 is dissolved in ethylene glycol to prepare a silver ion solution, which is heated to 160°C, and a silver precursor solution coated with polyvinyl pyrrolidone (PVP) is slowly added to reduce the silver ions to silver atoms, which are aggregated to form nanowires. After cooling, the solution is separated, washed, and dried to obtain AgNWs.

8. The preparation method according to claim 1, wherein: The hot pressing process comprises the following steps: the hot pressing pressure is 1 MPa, the hot pressing temperature is 100-140° C., and the hot pressing time is 1-5 min.

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