A preparation method and product of electromagnetic shielding sheet for wireless charging of new energy vehicles

Abstract

This invention discloses a method and product for preparing an electromagnetic shielding sheet for wireless charging of new energy vehicles. The method comprises the following steps: preparing electromagnetic shielding materials, selecting magnetic conductive materials, winding, hot pressing, spraying, gluing, laminating multiple layers, and stamping. The stamped magnetic conductive sheet is then laminated to a coil to form an electromagnetic shielding sheet assembly. The electromagnetic shielding sheet prepared by the invention has low magnetic loss, low heat generation, and high module charging efficiency, making it suitable for high-power wireless charging.

Description

Technical Field

[0001] The present invention relates to the technical field of electromagnetic shielding sheets, and in particular to a preparation method and product of an electromagnetic shielding sheet for wireless charging of new energy vehicles. Background Art

[0002] Wireless charging, also known as inductive charging or contactless charging, is a new charging technology derived from wireless power transmission (WPT). It utilizes near-field induction to transfer energy from a wireless charger to the device being charged. As wireless charging power increases, so do the requirements for magnetic conductive sheets. While magnetic conductive sheets for wireless charging provide magnetic isolation, conduction, and shielding, they also introduce magnetic losses. These losses include hysteresis and eddy current losses within the sheet itself, as well as leakage losses caused by insufficient shielding.

[0003] While traditional magnetic fragmentation processes can reduce magnetic losses to a certain extent, they also reduce magnetic conductivity. Therefore, the search for electromagnetic shielding materials that can both reduce the hysteresis and eddy current losses of the magnetic sheet itself and enhance its shielding properties is a research and development trend. MXenes, a new type of two-dimensional structural material discovered in 2011 by Professor Yury Gogotsi's research group at Drexel University, possess high specific surface area and high electrical conductivity, and hold great promise for application in electromagnetic shielding.

[0004] Patent CN108045063A discloses a method for preparing an electromagnetic shielding sheet for wireless charging, which uses a roll-to-roll process to pattern a soft magnetic material, resulting in a more uniform pattern. Patent CN108990398A discloses a composite electromagnetic shielding sheet and its preparation method, which is formed by combining a composite nanocrystalline alloy ceramic sheet and a thermally conductive sheet, also patterned. Both of these processes suffer from complex processes and difficult pattern control. To address these issues, the present invention provides a method for preparing an electromagnetic shielding sheet for wireless charging of new energy vehicles and the resulting product. Summary of the Invention

[0005] In order to solve the problem that the traditional magnetic crushing process can reduce magnetic loss to a certain extent but also reduces magnetic conductivity, the present invention provides a method for preparing an electromagnetic shielding sheet for wireless charging of new energy vehicles and a product.

[0006] In one aspect, the present invention provides a method for preparing an electromagnetic shielding sheet for wireless charging of new energy vehicles, comprising the following steps:

[0007] 1) Preparation of electromagnetic shielding material: a) Immersing a MAX phase material and an inorganic fluoride in a 10-12 mol / L HCl solution for etching to obtain a MXenes solution of electromagnetic shielding material; b) Mixing the prepared MXenes solution with polyvinyl alcohol, adding a thermally conductive filler during stirring to obtain a preliminary dispersion, and ultrasonically dispersing the preliminary dispersion to obtain an electromagnetic shielding material;

[0008] As a preferred technical solution, the MAX phase material is Ti3AlC2;

[0009] As a preferred technical solution, the inorganic fluoride includes at least one of LiF, NaF, and KF. Preferably, the inorganic fluoride is LiF and NaF, and the weight ratio of the two is 1:1.

[0010] As a preferred technical solution, the etching treatment is to stir the mixed solution at 40°C for 30-35 hours, ultrasonically vibrate for 20-25 minutes, and then centrifuge to remove surface impurities. After repeated washing with deionized water, the supernatant is obtained, which is the MXenes material, and is placed in an inert gas for storage.

[0011] As a preferred technical solution, the weight ratio of the MAX phase material, the inorganic fluoride, and the HCl solution is 1:(1-2):(5-9). Preferably, the weight ratio of the MAX phase material, the inorganic fluoride, and the HCl solution is 1:1:7.

[0012] As a preferred technical solution, the thermally conductive filler is an inorganic thermally conductive filler, including at least one of nano-oxides, nano-carbides, and nano-nitrides; preferably, the thermally conductive filler is a nano-nitride, and the nano-nitride is at least one of nano-aluminum nitride and nano-boron nitride; more preferably, the thermally conductive filler is nano-aluminum nitride with a particle size of 50 nm, model ZH-AlN-01, purchased from Hefei AVIC Nano Technology Development Co., Ltd.; preferably, the polyvinyl alcohol is PVA17-88.

[0013] The thermally conductive filler selected for addition to this system is an inorganic thermally conductive filler nano-nitride, including at least one of nano-aluminum nitride, nano-titanium nitride, and nano-boron nitride, which has extremely high insulating thermal conductivity. When filled in this system, it can transfer heat in a timely manner and effectively improve the thermal conductivity of the electromagnetic shielding sheet; in particular, the particle size of the nano-aluminum nitride selected for addition to the inorganic thermally conductive filler is 50nm. The smaller particle size allows it to be fully mixed with the MXenes solution and fully filled in the MXenes layer structure to form a connected thermal conduction path, which can reduce the contact area between the layered structures, increase the contact resistance, further improve the thermal conductivity of the system, and minimize eddy current loss.

[0014] As a preferred technical solution, the weight ratio of the MXenes solution, polyvinyl alcohol and thermally conductive filler is (2-4): (0.2-0.5): (4-7); preferably, the weight ratio of the MXenes solution, polyvinyl alcohol and thermally conductive filler is 3: (0.3-0.5): (4-7); more preferably, the weight ratio of the MXenes solution, polyvinyl alcohol and thermally conductive filler is 3: 0.4: 6.

[0015] The inventors found that the weight ratio of MXenes solution, polyvinyl alcohol and thermal conductive filler used in this system is (2-4): (0.2-0.5): (4-7). Through ultrasonic treatment, the MXenes material can be well dispersed, which is conducive to subsequent coating or spraying. Moreover, the well-dispersed electromagnetic shielding material can significantly reduce magnetic loss and reduce heat generation. This may be because the electromagnetic shielding material presents a regular layered structure, and the layered structure is evenly filled with thermal conductive fillers. The special layered structure causes electromagnetic waves to repeatedly undergo a process of reflection and scattering in the material, thereby significantly attenuating the intensity of the electromagnetic waves. At the same time, the thermal conductive filler filled inside can conduct heat away in time to avoid reducing the shielding efficiency due to heat concentration. The three work synergistically in the system to achieve the purpose of reducing electromagnetic waves and reducing magnetic losses. More preferably, the weight ratio of the MXenes solution, polyvinyl alcohol and thermal conductive filler is 3:0.4:6. At this time, the three in the system work synergistically, so that the prepared electromagnetic shielding material has extremely strong magnetic shielding performance, reduces magnetic loss, and generates less heat, making it suitable for high-power wireless charging.

[0016] 2) Selection of magnetic conductive materials: Amorphous or nanocrystalline strips are used as the magnetic conductive materials of the magnetic conductive sheets, and double-sided tape is used for bonding and bearing.

[0017] As a preferred technical solution, the magnetic conductive material comprises ordinary or high-Bs nanocrystalline soft magnetic material. Preferably, each layer of the magnetic conductive material of the electromagnetic shielding sheet comprises one or more nanocrystalline ribbons used simultaneously; more preferably, the magnetic conductive material is a high-Bs nanocrystalline soft magnetic material.

[0018] 3) Winding: Wind the magnetic material into small rolls for use in subsequent processes;

[0019] 4) Hot pressing treatment: The rolled magnetic conductive material is first compacted under a pressure of 750-800 MPa, and then placed in a heat treatment furnace for heat treatment. The heat treatment temperature includes pretreatment and heat treatment: pretreatment: 400-450℃, holding time 1-150min; heat treatment: 550-650℃, holding time: 60-150min;

[0020] In this system, the nanocrystalline ribbons are subjected to a hot pressing process, which can increase the magnetic induction intensity and magnetic permeability, and can also eliminate the residual internal stress inside the nanocrystalline ribbons, further improve the magnetic properties, and reduce magnetic losses.

[0021] 5) attaching the electromagnetic shielding material prepared in step 1) to one side of the hot-pressed magnetic conductive material by spraying or coating;

[0022] As a preferred technical solution, the thickness of the electromagnetic shielding material sprayed or coated is 1-10 μm; preferably, the thickness of the electromagnetic shielding material sprayed or coated is 3-8 μm; further preferably, the thickness of the electromagnetic shielding material sprayed or coated is 5 μm.

[0023] 6) Glue coating: Glue coating is performed on one side of the magnetic conductive material to which the electromagnetic shielding material was attached in step 5);

[0024] 7) Multi-layer lamination: Laminating the adhesive-coated side of the magnetic conductive material in step 6) to the unadhesive surface of another roll of magnetic conductive material to obtain laminate A. Repeat this operation based on laminate A to obtain the required number of layers as required to obtain a multi-layer magnetic conductive material roll;

[0025] As a preferred technical solution, the number of layers of the multi-layer magnetic conductive material coil is 2-7 layers.

[0026] In the system of the present invention, the applicant uses a multi-layer lamination process to obtain an Oreo structure formed by magnetic conductive materials and electromagnetic shielding materials. Through this structural design, electromagnetic waves will undergo multiple reflection and scattering processes within the material, achieving complete attenuation, greatly improving the magnetic conductive and electromagnetic shielding performance. In the system of the present invention, the electromagnetic shielding material is attached to the surface of the magnetic conductive material by spraying or coating, which can well control the coating thickness. The resulting electromagnetic shielding sheet is thin and light. Combined with the multi-layer lamination process, the Oreo multi-layer structure is obtained, which not only ensures good electromagnetic shielding performance but also has the characteristics of lightness and thinness, making it suitable for high-power wireless charging.

[0027] 8) punching the multi-layer magnetic conductive material coil described in step 7) according to size requirements to obtain magnetic conductive sheets of a certain size;

[0028] 9) Laminating the magnetic conductive sheet and the coil described in step 8) to obtain the final electromagnetic shielding sheet assembly

[0029] Another aspect of the present invention provides an electromagnetic shielding sheet for wireless charging of new energy vehicles, which is obtained by the above-mentioned preparation method.

[0030] Beneficial effects:

[0031] 1) The electromagnetic shielding material prepared by the preparation method in the system does not go through the traditional magnetic crushing process, which reduces magnetic loss without weakening the magnetic conductivity. This improves the magnetic conductivity and shielding performance, reduces magnetic loss, generates less heat, and improves module charging efficiency, making it suitable for high-power wireless charging.

[0032] 2) By adding inorganic thermally conductive fillers, they are fully filled into the MXenes layer structure to form a connected thermal conduction path, which can reduce the contact area between the layered structures, increase the contact resistance, further improve the thermal conductivity of the system, and minimize eddy current losses;

[0033] 3) The weight ratio of MXenes solution, polyvinyl alcohol, and thermally conductive filler used in this system is (2-4):(0.2-0.5):(4-7). Ultrasonic treatment can achieve good dispersion of the MXenes material, which is beneficial for subsequent coating or spraying. In addition, the well-dispersed electromagnetic shielding material can significantly reduce magnetic loss and heat generation.

[0034] 4) The electromagnetic shielding material prepared in the present invention is relatively thin. The electromagnetic shielding sheet obtained after multi-layer bonding with the magnetic conductive material has the characteristics of being light and thin while ensuring good electromagnetic shielding performance. It is suitable for high-power wireless charging. At the same time, different electromagnetic shielding sheets can be obtained according to the degree of coating and the number of bonding layers to adapt to different application scenarios. DETAILED DESCRIPTION

[0035] Example 1

[0036] Embodiment 1 of the present invention specifically provides a method for preparing an electromagnetic shielding sheet for wireless charging of new energy vehicles, comprising the following steps:

[0037] 1) Preparation of electromagnetic shielding material: a) Immersing a MAX phase material and an inorganic fluoride in a 12 mol / L HCl solution for etching to obtain a MXenes solution of electromagnetic shielding material; b) Mixing the prepared MXenes solution with polyvinyl alcohol, adding a thermally conductive filler during stirring to obtain a preliminary dispersion, and ultrasonically dispersing the preliminary dispersion to obtain an electromagnetic shielding material;

[0038] The MAX phase material is Ti3AlC2, purchased from Laizhou Kaiyi Ceramic Materials Co., Ltd.

[0039] The inorganic fluoride is LiF and NaF, and the weight ratio of the two is 1:1; the LiF is purchased from Sigma-Aldrich (Shanghai) Trading Co., Ltd., and the NaF is purchased from Jinan Huifengda Chemical Co., Ltd.;

[0040] The etching treatment comprises stirring the mixed solution at 40° C. for 33 hours, ultrasonically vibrating the solution for 23 minutes, and then centrifuging the solution to remove surface impurities. The solution is then repeatedly washed with deionized water to obtain a supernatant, which is the MXenes material. The supernatant is then stored in an inert gas for later use.

[0041] The weight ratio of the MAX phase material, the inorganic fluoride and the HCl solution is 1:1:7.

[0042] The thermal conductive filler is nano-aluminum nitride with a particle size of 50 nm and model ZH-ALN-01, purchased from Hefei AVIC Nanotechnology Development Co., Ltd.; the polyvinyl alcohol is PVA17-88, purchased from Guangzhou Yinhuan Chemical Co., Ltd.

[0043] The weight ratio of the MXenes solution, polyvinyl alcohol and thermal conductive filler is 3:0.4:6.

[0044] 2) Selection of magnetic conductive materials: Amorphous or nanocrystalline strips are used as the magnetic conductive materials for the magnetic conductive sheets, and double-sided tape is used for bonding and bearing.

[0045] The magnetic conductive material is a high Bs nanocrystalline soft magnetic material, model 1K107B, with a thickness of 23 μm, purchased from Guangzhou Jingci Electronic Technology Co., Ltd.

[0046] 3) Winding: Wind the magnetic material into small rolls for use in subsequent processes;

[0047] 4) Hot pressing treatment: The rolled magnetic conductive material is first compacted under a pressure of 780 MPa, and then placed in a heat treatment furnace for heat treatment. The heat treatment temperature includes pretreatment and heat treatment: pretreatment: 420°C, holding time: 90 minutes; heat treatment: 600°C, holding time: 120 minutes;

[0048] 5) attaching the electromagnetic shielding material prepared in step 1) to one side of the hot-pressed strip by spraying or coating;

[0049] The thickness of the electromagnetic shielding material sprayed is 5 μm.

[0050] 6) Glue coating: Glue coating is performed on one side of the magnetic conductive material to which the electromagnetic shielding material was attached in step 5);

[0051] 7) Multi-layer lamination: Laminating the adhesive-coated side of the magnetic conductive material in step 6) to the adhesive-free surface of another roll of magnetic conductive material to obtain laminate A. Repeat this process using laminate A as a base until five layers of magnetic conductive material rolls are obtained;

[0052] 8) Punching the five layers of magnetic conductive material coils described in step 7) according to size requirements to obtain the desired nanocrystalline magnetic conductive sheets;

[0053] 9) The nanocrystalline magnetic conductive sheet punched out in step 8) is assembled with the FPC coil to obtain an electromagnetic shielding sheet.

[0054] An electromagnetic shielding sheet for wireless charging of new energy vehicles is obtained by the above-mentioned preparation method.

[0055] Example 2

[0056] Example 2 of the present invention specifically provides a method for preparing an electromagnetic shielding sheet for wireless charging of new energy vehicles. The specific implementation method is the same as that of Example 1, except that the thermal conductive filler is nano-boron nitride with a particle size of 50 nm, model ZH-BN-01, purchased from Hefei AVIC Nanotechnology Development Co., Ltd.

[0057] Example 3

[0058] Example 3 of the present invention specifically provides a method for preparing an electromagnetic shielding sheet for wireless charging of new energy vehicles. The specific implementation method is the same as that of Example 1, except that the weight ratio of the MXenes solution, polyvinyl alcohol and thermal conductive filler is 2:0.3:4.

[0059] Example 4

[0060] Example 4 of the present invention specifically provides a method for preparing an electromagnetic shielding sheet for wireless charging of new energy vehicles. The specific implementation method is the same as that of Example 1, except that the thickness of the electromagnetic shielding material sprayed is 7 μm.

[0061] Comparative Example 1

[0062] Comparative Example 1 of the present invention specifically provides a method for preparing an electromagnetic shielding sheet for wireless charging of new energy vehicles. The specific implementation method is the same as that of Example 1, except that the prepared MXenes solution is not added to the system.

[0063] Comparative Example 2

[0064] Comparative Example 2 of the present invention specifically provides a method for preparing an electromagnetic shielding sheet for wireless charging of new energy vehicles. The specific implementation method is the same as Example 1, except that no thermal conductive filler is added to the system.

[0065] Comparative Example 3

[0066] Comparative Example 3 of the present invention specifically provides a method for preparing an electromagnetic shielding sheet for wireless charging of new energy vehicles. The specific implementation method is the same as that of Example 1, except that the prepared electromagnetic shielding material is not added.

[0067] Performance Testing

[0068] The electromagnetic shielding sheets prepared in Examples 1-4 and Comparative Examples 1-3 were assembled into a module and tested for charging efficiency at 85 kHz according to standard SJ / T10298-91, with the current of the transmitter being 10 A and the voltage of the transmitter being 400 V. The test results are shown in Table 1.

[0069] Table 1

[0070] efficiency(%) Example 1 94.93 Example 2 94.89 Example 3 94.91 Example 4 94.86 Comparative Example 1 92.11 Comparative Example 2 93.02 Comparative Example 3 92.95

Claims

1. A method for preparing an electromagnetic shielding sheet for wireless charging of new energy vehicles, characterized in that: The steps include: 1) Preparation of electromagnetic shielding material: a) Immersing a MAX phase material and an inorganic fluoride in a 10-12 mol / L HCl solution for etching to obtain a MXenes solution of electromagnetic shielding material; b) Mixing the prepared MXenes solution with polyvinyl alcohol, adding a thermally conductive filler during stirring to obtain a preliminary dispersion, and ultrasonically dispersing the preliminary dispersion to obtain an electromagnetic shielding material; 2) Selection of magnetic conductive materials: Amorphous or nanocrystalline strips are used as the magnetic conductive materials of the magnetic conductive sheets, and double-sided tape is used for bonding and bearing; 3) Winding: Wind the magnetic material into small rolls for use in subsequent processes; 4) Hot pressing treatment: The rolled magnetic conductive material is first compacted under a pressure of 750-800 MPa, and then placed in a heat treatment furnace for heat treatment. The heat treatment temperature includes pretreatment and heat treatment: pretreatment: 400-450 ° C, holding time 1-150 min; Heat treatment: 550-650℃, holding time: 60-150min; 5) attaching the electromagnetic shielding material prepared in step 1) to one side of the hot-pressed magnetic conductive material by spraying or coating; 6) Glue coating: Glue coating is performed on one side of the magnetic conductive material to which the electromagnetic shielding material was attached in step 5); 7) Multi-layer lamination: Laminating the adhesive-coated side of the magnetic conductive material in step 6) to the unadhesive surface of another roll of magnetic conductive material to obtain laminate A. Repeat this operation based on laminate A to obtain the required number of layers as required to obtain a multi-layer magnetic conductive material roll; 8) punching the multi-layer magnetic conductive material coil described in step 7) according to size requirements to obtain magnetic conductive sheets of a certain size; 9) Laminating the magnetic conductive sheet described in step 8) to the coil to obtain a final electromagnetic shielding sheet assembly; In step 1), the MAX phase material is Ti3AlC2; the inorganic fluoride is LiF and NaF, and the weight ratio of the two is 1:1; The weight ratio of the MAX phase material, the inorganic fluoride and the HCl solution in step 1) is 1:(1-2):(5-9); The weight ratio of the MXenes solution, polyvinyl alcohol and thermal conductive filler in step 1) is 3:(0.3-0.5):(4-7); The thermal conductive filler in step 1) is nano-aluminum nitride or nano-boron nitride, and the particle size is 50 nm.

2. The method for preparing an electromagnetic shielding sheet for wireless charging of new energy vehicles according to claim 1, wherein: The magnetic conductive material in step 2) includes ordinary or high Bs nanocrystalline soft magnetic material.

3. The method for preparing an electromagnetic shielding sheet for wireless charging of new energy vehicles according to claim 1, characterized in that: The thickness of the electromagnetic shielding material sprayed or coated in step 5) is 1-10 μm.

4. The method for preparing an electromagnetic shielding sheet for wireless charging of new energy vehicles according to claim 1, wherein: Step 7) The number of layers of the multi-layer magnetic conductive material coil is 2-7 layers.

5. An electromagnetic shielding sheet obtained by the preparation method of the electromagnetic shielding sheet for wireless charging of new energy vehicles according to any one of claims 1 to 4.