Electromagnetic shielding-heat conducting multifunctional composite film of electric insulation type and preparation method and application thereof

Abstract

The application belongs to the technical field of electromagnetic shielding-thermal management multifunctional materials, and discloses an electrically insulating electromagnetic shielding-thermal conductive multifunctional composite film and a preparation method and application thereof. A metal phase / semiconductor vanadium oxide nanowire / sheet / belt is prepared by using a one-step hydrothermal method, and then a vanadium oxide / polymer composite film is obtained by using a vacuum filtration-packaging and hot pressing process. The one-step hydrothermal method is simple in operation, the obtained product is adjustable in morphology, phase structure and performance, the raw materials are cheap and easy to obtain, the energy consumption is small, the method is green and environmentally friendly, the repeatability is good, the precision requirement of the instrument is low, the yield is high, and the method has good industrial application potential. The vacuum filtration-packaging and hot pressing process is simple in operation, low in cost and easy to scale up. The obtained vanadium oxide / polymer composite film has good electromagnetic shielding, thermal conductive and electrically insulating properties, and has good industrial application potential in the fields of electromagnetic shielding, thermal management, sensors and the like.

Description

Technical Field

[0001] This invention belongs to the field of electromagnetic shielding-thermal management multifunctional materials technology, and relates to the preparation and film formation process of a low-dimensional metallic phase / semiconductor vanadium oxide filler and its application in electromagnetic shielding, thermal management, sensors, supercapacitors, photocatalysis and batteries. Background Technology

[0002] Among various novel ceramic materials, heterostructured vanadium oxide nanowires / belts / sheets exhibit low density, high specific surface area, large shape anisotropy, and unique mechanical, electrical, and thermal properties, showing promising application prospects in thermal management, energy, electronic devices, and electromagnetic protection. Vanadium ions possess multiple oxidation states (+5, +4, +3, +2, +1), and can form different monovalent vanadium oxides (such as V₂O₅, VO₂, V₂O₃, VO, V₂O) and mixed-valence vanadium oxides, namely the Magnéli phase V₂O₅. n O 2n-1 (3≤n≤9) and the V of Wadsley phase n O2 n+1 (n = 2, 3, 6). The transition of vanadium ions from a high oxidation state to a low oxidation state is usually accompanied by the generation of oxygen vacancies and free electrons, which is beneficial to dipole / defect polarization loss; therefore, VO2, V2O3, V2O5, VOOH and their complexes have been studied as microwave absorbers.

[0003] Currently, vanadium oxides are mainly reported as composites with other materials, used alone as electromagnetic wave shielding, absorption, and heat conduction materials. Among them, Chinese patent CN109502578A discloses a method for preparing vanadium oxide-graphene intercalated composite material. This method uses vanadium pentoxide and graphene as raw materials, and obtains the final product through ice-water bath, pH adjustment, aging, and high-temperature calcination, which can be used as an electromagnetic shielding material. This method uses high temperatures and is complex. Chinese patent CN119240788A discloses a microwave absorbing material of nitrogen-doped vanadium oxide and its preparation method. This method uses ammonium metavanadate, guanidine carbonate, and glucose as raw materials, and requires subsequent steps such as pH adjustment, hydrothermal treatment, and calcination, which is cumbersome. Chinese patent CN114574169A discloses a vanadium dioxide-boron nitride phase change thermally conductive composite material and its preparation method and application. This method uses ammonium metavanadate, oxalic acid, hexagonal boron nitride, ammonium tungstate, and / or tellurium dioxide as raw materials. This method is obtained through steps such as stirring, hydrothermal treatment, centrifugation, and calcination. This method is divided into two steps, which is time-consuming, high-temperature, and complex.

[0004] Therefore, how to develop a multifunctional material that is easy to process, easy to industrialize, has controllable morphology and size, has a high specific surface area, and is electromagnetic shielding / wave absorption-thermal conduction is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide an electrically insulating electromagnetic shielding-thermal conductive multifunctional composite membrane, its preparation method, and its application. This electromagnetic shielding-thermal conductive multifunctional filler is simple to operate and produces a novel product morphology. Furthermore, the vanadium oxide / polymer composite membrane is obtained using a vacuum filtration-encapsulation and hot pressing process, overcoming the shortcomings of previous preparation methods, such as harsh reaction conditions, difficulty in controlling the morphology of the reaction products, and poor experimental repeatability. The obtained vanadium oxide / polymer composite membrane possesses good electromagnetic shielding, thermal conductivity, and electrical insulation properties, and has good industrial application potential in the fields of electromagnetic shielding, thermal management, and sensors.

[0006] To achieve the above objectives, the present invention discloses the following technical content:

[0007] The primary technical objective of this invention is to provide an electrically insulating electromagnetic shielding-thermal conductive multifunctional composite membrane. This composite membrane is obtained by vacuum filtration, encapsulation, and hot pressing of an electromagnetic shielding-thermal conductive multifunctional filler. The electromagnetic shielding-thermal conductive multifunctional filler is a metallic vanadium oxide / semiconductor vanadium oxide nanowire / sheet / ribbon; the vanadium oxide is VO2(A), VO2(P), V2O5, or V3O7; the nanowire / sheet / ribbon has an average diameter of 51.2–798.0 nm, an average length of 35.8–1116.8 μm, and an aspect ratio of 50.4–13739.7. Furthermore, the metallic vanadium oxide / semiconductor vanadium oxide nanowire / sheet / ribbon contains V and O elements, as can be seen from the EDX image.

[0008] Furthermore, the multifunctional composite film exhibits excellent thermal conductivity and shielding properties, with a thermal conductivity of 2.36–4.25 W / (m·K); electromagnetic interference shielding effectiveness of 12.1–46.9 dB; and a sample thickness of 3 mm.

[0009] It should be noted that VO2 has ten phase structures (M1, M2, B, A, R, P, T, etc.). Among them, due to its high stability and metal-insulator transition properties, the M1 and R phases of VO2 and their complexes (VO2(M) / Ti3C2T) are particularly important. xCellulose nanofibers / VO2(R), VO2 / graphene, and VO2 / CNF have been the most studied intelligent electromagnetic wave absorbing / shielding materials, while VO2, V2O5, and their composites have also been studied individually as thermally conductive fillers. While heterogeneous interfaces are beneficial for microwave absorption / shielding, phonon mismatch at these interfaces is detrimental to the thermal conduction of heterogeneous structures. Therefore, we selected low-dimensional metallic phase VO2(A) with good phonon matching to construct heterogeneous nanofibers / ribbons / sheets with semiconductor vanadium oxide. To our knowledge, current research mainly focuses on vanadium oxide as an electromagnetic wave absorbing / shielding or thermally conductive material, while research on VO2(A), especially low-dimensional metallic phase VO2(A) / semiconductor vanadium oxide composite films, as multifunctional electromagnetic wave shielding, thermal conductivity, and electrical insulation materials is rarely reported. Furthermore, the incompatibility of electromagnetic wave shielding, thermal conductivity, and electrical insulation properties poses a significant challenge to the synergistic improvement of these properties.

[0010] The second technical objective of this invention is to provide a method for preparing the electrically insulating electromagnetic shielding-thermal conductive multifunctional composite film as described above. The multifunctional composite film is prepared by vacuum filtration-encapsulation and hot pressing of an electromagnetic shielding-thermal conductive multifunctional filler. The specific steps are as follows:

[0011] (1) Vacuum filtration to form a membrane: Weigh a certain mass of electromagnetic shielding-thermal conductive multifunctional filler and add it to water. Disperse it ultrasonically for 10-30 mins to obtain an aqueous solution of multifunctional filler. Pour the dispersed solution into a vacuum filtration device to filter it into a pure membrane. Place the membrane between two glass plates and dry it at 50-80℃ for 6-12 hours for later use.

[0012] (2) Membrane encapsulation process: A thin layer of thermoplastic polyurethane (TPU) and 1,4-dioxane solution is applied to one of the glass slides. The dried membrane is then placed between the two glass slides. The excess air bubbles are removed by vacuuming in a vacuum drying oven, and the solvent is evaporated to complete the TPU encapsulation of one side of the membrane. The other side of the membrane is encapsulated with TPU using the same method to obtain the electrically insulating electromagnetic shielding-thermal conductive multifunctional composite membrane.

[0013] (3) Hot pressing process of the membrane: The obtained electrically insulating electromagnetic shielding-thermal conductive multifunctional composite membrane is placed between two glass plates, and then hot pressing is performed for 10 minutes at 90-110℃ using an electric iron.

[0014] Preferably, the electromagnetic shielding-thermal conductive multifunctional filler is prepared by a hydrothermal method, which involves mixing vanadium pentoxide, polyethylene glycol of different molecular weights, and water, stirring, and then pouring the mixture into a reaction vessel. The mixture is then reacted at 200°C for 48 hours. The mass ratio of vanadium pentoxide to surfactant is 11:18, and the mass ratio of vanadium pentoxide to water is 1:320 to 1:50. After the reaction is completed and the mixture is allowed to cool naturally to room temperature, the sample is washed alternately with water and ethanol, filtered, and dried to obtain vanadium oxide nanowires / sheets / belts of different aspect ratios, which are the electromagnetic shielding-thermal conductive multifunctional fillers.

[0015] It is worth noting that the electromagnetic shielding-thermal conductive multifunctional filler disclosed in this invention, prepared by hydrothermal method, not only has a novel structure and formation mechanism, but can also prepare a series of metallic vanadium oxide / semiconductor vanadium oxide nanowires / sheets / ribbons by changing the hydrothermal reaction time. The nanowires / sheets / ribbons prepared by this invention show great potential in the field of electromagnetic shielding. Furthermore, the electrically insulating electromagnetic shielding-thermal conductive multifunctional composite film prepared in this invention has excellent thermal conductivity-shielding properties.

[0016] Furthermore, the preparation method disclosed in this invention is simple to operate and produces novel product morphology. It overcomes the shortcomings of previous preparation processes, such as harsh reaction conditions, difficulty in controlling the morphology of reaction products, and poor experimental repeatability, and has good potential for industrial application.

[0017] Furthermore, the polyethylene glycol has molecular weights of 400 g / mol, 2000 g / mol, 6000 g / mol, 10000 g / mol, and 20000 g / mol.

[0018] Furthermore, the reaction temperature is 120–220°C, the stirring time is 0.5–1.0 h, and the reaction time is 3–72 h.

[0019] Preferably, in step (1), the concentration of the multifunctional filler aqueous solution is 0.019 mol / L to 0.076 mol / L; in step (2), the concentration of the 1,4-dioxane solution of thermoplastic polyurethane (TPU) is 0.083 to 0.125 g / mL.

[0020] The third technical objective of this invention is to provide the application of the above-mentioned electrically insulating electromagnetic shielding-thermal conductive multifunctional composite film in the fields of electromagnetic shielding, thermal management, sensors, supercapacitors, photocatalysis, and batteries.

[0021] As can be seen from the above technical solution, compared with the prior art, the present invention provides an electrically insulating electromagnetic shielding-thermal conductive multifunctional composite film, its preparation method and application, which has the following excellent effects:

[0022] 1) This invention uses water as a solvent, vanadium pentoxide as a raw material, polyethylene glycol as a surface active agent, and a one-step hydrothermal method to prepare vanadium oxide nanowires / sheets / belts with unique morphologies in the metal phase / semiconductor phase. The synthesis method is simple, has high yield, and the morphology, phase structure, and properties of the obtained products are adjustable.

[0023] 2) The electrically insulating electromagnetic shielding-thermal conductive multifunctional composite film prepared by the present invention has good electrical insulation, excellent thermal conductivity, hydrophobicity, electromagnetic shielding, Joule heating and sensing properties, and shows great application potential in the fields of electromagnetic shielding, thermal management and sensing, especially in extreme environments.

[0024] 3) The vacuum filtration-encapsulation and hot pressing process of the electrically insulating electromagnetic shielding-thermal conductive multifunctional composite membrane of the present invention is simple and unique, and the raw materials are cheap and readily available. The reaction process is simple, time-consuming, energy-efficient, low-risk, environmentally friendly, has good repeatability, low requirements for instrument precision, and considerable output, and has good potential for industrial application. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0026] Figures 1-3 The phase and morphology of the product obtained in Example 1 of this invention were measured under XRD, EDX and scanning electron microscope, respectively.

[0027] Figures 4-6 The phase and morphology of the product obtained in Example 2 of this invention were measured under XRD, EDX and scanning electron microscope, respectively.

[0028] Figures 7-9 The phase and morphology of the product obtained in Example 3 of this invention were measured under XRD, EDX and scanning electron microscope, respectively.

[0029] Figure 10 The morphology of the product obtained in Example 4 of this invention was measured under a scanning electron microscope.

[0030] Figure 11 The morphology of the product obtained in Example 5 of this invention was measured under a scanning electron microscope.

[0031] Figure 12 The morphology of the product obtained in Example 6 of this invention was measured under a scanning electron microscope.

[0032] Figure 13 The morphology of the product obtained in Example 7 of this invention was measured under a scanning electron microscope.

[0033] Figure 14 The morphology of the product obtained in Example 8 of this invention was measured under a scanning electron microscope.

[0034] Figure 15 The morphology of the product obtained in Example 9 of this invention was measured under a scanning electron microscope. Detailed Implementation

[0035] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. 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.

[0036] This invention discloses an electrically insulating electromagnetic shielding-thermal conductive multifunctional composite film with simple processing, controllable size, and good electromagnetic shielding properties, as well as its preparation method and application.

[0037] To better understand the present invention, the following embodiments are provided for further detailed description of the present invention, but they should not be construed as limiting the present invention. Any non-essential improvements and adjustments made by those skilled in the art based on the above-described invention are also considered to fall within the protection scope of the present invention.

[0038] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0039] Example 1

[0040] A method for preparing an electrically insulating electromagnetic shielding-thermal conductive multifunctional composite film specifically includes the following steps:

[0041] 0.55g of vanadium pentoxide and 0.9g of PEG 2000 were added to 80mL of water and magnetically stirred at room temperature for 1h, until the solution turned bright orange. The solution was then placed in a high-pressure reactor and hydrothermally reacted at 200℃ for 48h. After the reaction was completed, the solution was cooled to room temperature and filtered out by washing with water and ethanol several times alternately. The sample was then dried in an oven at 60℃ for 12h to obtain the electromagnetic shielding-thermal conductive multifunctional filler.

[0042] Take 0.5g of dried sample and add it to 100mL of water for ultrasonic dispersion for 30mins. Pour the dispersed solution into a vacuum filtration device and filter it into a pure membrane. Place it between two glass slides and dry it at 60℃ for 6 hours. Coat a thin layer of thermoplastic polyurethane (TPU) and 1,4-dioxane solution on one of the glass slides. Place the dried membrane between the two glass slides and remove excess air bubbles in a vacuum drying oven. Evaporate the solvent at 60℃ to complete the TPU encapsulation of one side of the membrane. Use the same method to encapsulate the other side of the membrane with TPU to finally obtain an electrically insulating electromagnetic shielding-thermal conductive multifunctional composite membrane.

[0043] The obtained electrically insulating electromagnetic shielding-thermal conductive multifunctional composite film was placed between two glass plates and then hot-pressed at approximately 100°C for 10 minutes. This hot-pressing process ensures that the TPU matrix is ​​fully impregnated and penetrates into the gaps between the fillers, making the composite film smoother and thus effectively improving its thermal conductivity.

[0044] The phase composition, morphology, and other properties of the obtained filler material as measured by XRD, EDX, and scanning electron microscopy are as follows: Figures 1-3 As shown.

[0045] The product is V3O7·H2O and VO2(A) nanowires / belts with an average length of 567.3 μm and an average diameter of 116 nm. The EDX plot shows that it contains V and O elements.

[0046] As shown in Table 1, the obtained electrically insulating electromagnetic shielding-thermal conductive multifunctional composite film exhibits excellent electromagnetic shielding characteristics. Specifically, the 3mm thick film demonstrates an electromagnetic interference shielding effectiveness (SE) in the 2–18GHz range. T ≥20dB, maximum SE T It is 46.9 dB; thermal conductivity is 3.22 W / (m·K).

[0047] Example 2

[0048] A method for preparing an electrically insulating electromagnetic shielding-thermal conductive multifunctional composite film, with other conditions remaining unchanged, except that the molecular weight of polyethylene glycol is changed to 400 g / mol based on Example 1.

[0049] The phase composition, morphology, and other properties of the obtained filler material as measured by XRD, EDX, and scanning electron microscopy are as follows: Figures 4-6 As shown.

[0050] The product is V3O7·H2O and VO2(A) nanoribbons with an average length of 40.2 μm and an average diameter of 798.0 nm. The EDX plot shows that it contains V and O elements.

[0051] As shown in Table 1, the obtained electrically insulating electromagnetic shielding-thermal conductive multifunctional composite film exhibits excellent electromagnetic shielding characteristics. Specifically, the 3mm thick film demonstrates an electromagnetic interference shielding effectiveness (SE) of [missing value] in the 5.8–18GHz range. T ≥20dB, maximum SE T It is 33.3 dB; thermal conductivity is 2.89 W / (m·K).

[0052] Example 3

[0053] A method for preparing an electrically insulating electromagnetic shielding-thermal conductive multifunctional composite film, with other conditions remaining unchanged, except that the molecular weight of polyethylene glycol is changed to 20000 g / mol based on Example 1.

[0054] The phase composition, morphology, and other properties of the obtained filler material as measured by XRD, EDX, and scanning electron microscopy are as follows: Figures 7-9 As shown.

[0055] The products are V2O5·1.6H2O and V3O7·H2O nanowires / belts with an average length of 1116.8 μm and an average diameter of 92 nm. The EDX plot shows that they contain V and O elements.

[0056] As shown in Table 1, the obtained electrically insulating electromagnetic shielding-thermal conductive multifunctional composite film exhibits excellent electromagnetic shielding characteristics. Specifically, the 3mm thick film demonstrates an electromagnetic interference shielding effectiveness (SE) of [missing value] in the 4.4–18GHz range. T ≥20dB, maximum SE T It is 40.1 dB; thermal conductivity is 4.25 W / (m·K).

[0057] Example 4

[0058] A method for preparing an electrically insulating electromagnetic shielding-thermal conductive multifunctional composite film, with other conditions remaining unchanged, except that the hydrothermal time is changed to 3 hours based on Example 1.

[0059] The morphology of the obtained filler measured under a scanning electron microscope is as follows: Figure 10 As shown.

[0060] The products are V2O5·1.6H2O, V3O7·H2O and V2O5·H2O nanowires / belts with an average length of 147.7 μm and an average diameter of 118 nm.

[0061] As shown in Table 1, the obtained electrically insulating electromagnetic shielding-thermal conductive multifunctional composite film exhibits excellent electromagnetic shielding characteristics. Specifically, the 3mm thick film demonstrates an electromagnetic interference shielding effectiveness (SE) of [missing information - likely a specific value] in the 16–18GHz range. T ≥20dB, maximum SE T It is 23.1 dB; thermal conductivity is 2.37 W / (m·K).

[0062] Example 5

[0063] A method for preparing an electrically insulating electromagnetic shielding-thermal conductive multifunctional composite film, with other conditions remaining unchanged, except that the hydrothermal time is changed to 72h based on Example 1.

[0064] The morphology of the obtained filler measured under a scanning electron microscope is as follows: Figure 11 As shown.

[0065] The products are V3O7·H2O and VO2(A) nanowires / belts with an average length of 584.9 μm and an average diameter of 106 nm.

[0066] As shown in Table 1, the obtained electrically insulating electromagnetic shielding-thermal conductive multifunctional composite film exhibits excellent electromagnetic shielding characteristics. Specifically, the 3mm thick film demonstrates an electromagnetic interference shielding effectiveness (SE) in the 2–18GHz range. T ≥20dB, maximum SE T It is 43.7 dB; thermal conductivity is 3.86 W / (m·K).

[0067] Example 6

[0068] A method for preparing an electrically insulating electromagnetic shielding-thermal conductive multifunctional composite film, with other conditions remaining unchanged, except that the hydrothermal temperature is changed to 120°C based on Example 1.

[0069] The morphology of the obtained filler measured under a scanning electron microscope is as follows: Figure 12 As shown.

[0070] The product is V2O5·1.6H2O nanosheets with an average diameter of 522.9 nm.

[0071] As shown in Table 1, the obtained electrically insulating electromagnetic shielding-thermal conductive multifunctional composite film exhibits excellent electromagnetic shielding properties, with a maximum SE value of 3 mm. T It is 12.1 dB; thermal conductivity is 2.36 W / (m·K).

[0072] Example 7

[0073] A method for preparing an electrically insulating electromagnetic shielding-thermal conductive multifunctional composite film, with other conditions remaining unchanged, except that the hydrothermal temperature is changed to 220℃ based on Example 1.

[0074] The morphology of the obtained filler measured under a scanning electron microscope is as follows: Figure 13 As shown.

[0075] The products are V3O7·H2O and VO2(A) nanowires / belts with an average length of 22.9 μm and an average diameter of 280 nm.

[0076] As shown in Table 1, the obtained electrically insulating electromagnetic shielding-thermal conductive multifunctional composite film exhibits excellent electromagnetic shielding characteristics. Specifically, the 3mm thick film demonstrates an electromagnetic interference shielding effectiveness (SE) of [missing information - likely a specific value] in the 4.8–18GHz range. T ≥20dB, maximum SE T It is 37.7 dB; thermal conductivity is 2.90 W / (m·K).

[0077] Example 8

[0078] A method for preparing an electrically insulating electromagnetic shielding-thermal conductive multifunctional composite film, with other conditions remaining unchanged, except that the mass ratio of vanadium pentoxide to water is changed to 11:3200 based on Example 1.

[0079] The morphology of the obtained filler measured under a scanning electron microscope is as follows: Figure 14 As shown.

[0080] The products are V3O7·H2O and VO2(A) nanowires / belts with an average length of 477.4 μm and an average diameter of 144 nm.

[0081] As shown in Table 1, the obtained electrically insulating electromagnetic shielding-thermal conductive multifunctional composite film exhibits excellent electromagnetic shielding characteristics. Specifically, the 3mm thick film demonstrates an electromagnetic interference shielding effectiveness (SE) of [missing value] in the 5.6–18GHz range. T ≥20dB, maximum SE T It is 39.3 dB; thermal conductivity is 3.12 W / (m·K).

[0082] Example 9

[0083] A method for preparing an electrically insulating electromagnetic shielding-thermal conductive multifunctional composite film, with other conditions remaining unchanged, except that the mass ratio of vanadium pentoxide to water is changed to 11:800 based on Example 1.

[0084] The morphology of the obtained filler measured under a scanning electron microscope is as follows: Figure 15 As shown.

[0085] The products are V3O7·H2O and VO2(A) nanowires / belts with an average length of 703.5 μm and an average diameter of 51.2 nm.

[0086] As shown in Table 1, the obtained electrically insulating electromagnetic shielding-thermal conductive multifunctional composite film exhibits excellent electromagnetic shielding characteristics. Specifically, the 3mm thick film demonstrates an electromagnetic interference shielding effectiveness (SE) of [missing value] in the 4.2–18GHz range. T ≥20dB, maximum SE T It is 44.2 dB; thermal conductivity is 3.49 W / (m·K).

[0087] Table 1 shows the electromagnetic shielding and thermal conductivity properties of the products obtained in Examples 1-9 of this invention.

[0088]

[0089] Analysis of the above data shows that the electrically insulating electromagnetic shielding-thermal conductive multifunctional composite film prepared by this invention has good thermal conductivity and shielding performance.

[0090] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A multifunctional composite film for electromagnetic shielding and thermal conductivity with electrical insulation properties, characterized in that, The composite membrane is obtained by vacuum filtration, encapsulation and hot pressing of an electromagnetic shielding-thermal conductive multifunctional filler. The electromagnetic shielding-thermal conductive multifunctional filler is metallic vanadium oxide / semiconductor vanadium oxide nanowires / belts. The vanadium oxide is VO2(A) or V3O7·H2O. The nanowires / belts have an average diameter of 51.2~798.0 nm, an average length of 22.9~703.5 µm, and an aspect ratio of 50.4~13739.

7.

2. The electrically insulating electromagnetic shielding-thermal conductive multifunctional composite film according to claim 1, characterized in that, The multifunctional composite film has a thermal conductivity of 2.36~4.25 W / (m·K), an electromagnetic interference shielding effectiveness of 12.1~46.9 dB, and a thickness of 3 mm.

3. A method for preparing an electrically insulating electromagnetic shielding-thermal conductive multifunctional composite film as described in claim 1, characterized in that, The multifunctional composite membrane is prepared by vacuum filtration, encapsulation, and hot pressing of an electromagnetic shielding and thermally conductive multifunctional filler. The specific steps are as follows: (1) Vacuum filtration to form a membrane: Weigh a certain mass of electromagnetic shielding-thermal conductive multifunctional filler and add it to water. Disperse it ultrasonically for 10~30 mins to obtain an aqueous solution of the multifunctional filler. Pour the dispersed solution into a vacuum filtration device to filter it into a pure membrane. Place the membrane between two glass plates and dry it at 50~80 ℃ for 6~12 hours for later use. (2) Membrane encapsulation process: A thin layer of thermoplastic polyurethane (TPU) and 1,4-dioxane solution is coated on one of the glass slides. The dried membrane is then placed between the two glass slides. The excess air bubbles are removed by vacuuming in a vacuum drying oven, and the solvent is evaporated to complete the TPU encapsulation of one side of the membrane. The other side of the membrane is encapsulated with TPU using the same method to obtain the electrically insulating electromagnetic shielding-thermal conductive multifunctional composite membrane. (3) Hot pressing process of the membrane: The obtained electrically insulating electromagnetic shielding-thermal conductive multifunctional composite membrane is placed between two glass plates, and then hot pressing is performed at 90~110℃ for 10 minutes.

4. The method for preparing the electrically insulating electromagnetic shielding-thermal conductive multifunctional composite film according to claim 3, characterized in that, The electromagnetic shielding-thermal conductive multifunctional filler is prepared by a hydrothermal method, and the specific steps are as follows: Vanadium pentoxide, surfactant, and water were mixed and stirred, and then reacted at a certain temperature for different times. After the reaction was completed, the mixture was allowed to cool naturally to room temperature. The sample was then washed with water and ethanol alternately and filtered out. After drying, metallic vanadium oxide / semiconductor vanadium oxide nanowires / belts with different aspect ratios were obtained, which are the electromagnetic shielding-thermal conductive multifunctional fillers.

5. The method for preparing the electrically insulating electromagnetic shielding-thermal conductive multifunctional composite film according to claim 4, characterized in that, The surfactant is polyethylene glycol with a molecular weight of 400 g / mol or 2000 g / mol; the mass ratio of vanadium pentoxide to surfactant is 11:18, and the mass ratio of vanadium pentoxide to water is 1:320 to 1:

50.

6. The method for preparing the electrically insulating electromagnetic shielding-thermal conductive multifunctional composite film according to claim 4, characterized in that, The reaction temperature is 120~220 ℃, the stirring time is 0.5~1.0 h, and the reaction time is 3~72 h.

7. The method for preparing the electrically insulating electromagnetic shielding-thermal conductive multifunctional composite film according to claim 3, characterized in that, In step (1), the concentration of the aqueous solution of the multifunctional packing material is 0.019 mol / L to 0.076 mol / L.

8. The method for preparing the electrically insulating electromagnetic shielding-thermal conductive multifunctional composite film according to claim 3, characterized in that, In step (2), the concentration of the 1,4-dioxane solution of the thermoplastic polyurethane (TPU) is 0.083~0.125 g / mL.

9. The application of an electrically insulating electromagnetic shielding-thermal conductive multifunctional composite film as described in claim 1 or an electromagnetic shielding-thermal conductive multifunctional composite film prepared by the method described in any one of claims 3 to 8 in the fields of electromagnetic shielding, thermal management, sensors, supercapacitors, photocatalysis, and batteries.

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