Super-soft, electricity-conducting and heat-conducting film electrode and preparation method thereof

Abstract

The invention belongs to the technical field of composite films, and particularly relates to a super-soft, electricity-conducting and heat-conducting film electrode and a preparation method thereof. The preparation method comprises the following main preparation steps: firstly, preparing a single-layer boron nitride nanosheet BNNS from a two-dimensional heat conduction material hexagonal boron nitride BN through an ultrasonic stripping technology, and then carrying out hydroxylation treatment on the BNNS to form a hydroxylated boron nitride nanosheet HO-BNNS; the preparation method comprises the following steps: mixing a HO-BNNS aqueous solution with a silver nanowire (AgNWs) or copper nanowire (CuNWs) aqueous solution, mixing with a polyvinyl alcohol (PVA) polymer substrate material to form a uniform dispersion liquid, pouring the mixed solution on the surface of a prefabricated metal nanowire thin film electrode (a substrate can be a flat substrate such as a PET flexible polymer or a silicon wafer rigid substrate), and performing high-temperature curing to obtain the metal nanowire thin film electrode. And finally, the cured film is peeled off from the substrate, so that the super-soft film electrode with excellent electric conduction and heat conduction performance is prepared, and the film can be repeatedly folded and has super-flexibility.

Description

Technical Field

[0001] The present invention belongs to the technical field of composite films, and in particular relates to an ultra-flexible, electrically and thermally conductive film electrode and a preparation method thereof. Background Art

[0002] As electronic devices continue to develop towards integration and miniaturization, the demand for thermal interface materials is growing. The heat generated by these devices during operation can seriously affect their normal operation, reduce efficiency and shorten their service life. Therefore, the development of effective thermal management strategies has become crucial. One effective method is to build a filler network by adding high thermal conductivity materials to enhance the thermal conductivity of composite materials or films, thereby effectively managing the heat generated by electronic devices. However, most thermally conductive films often do not have conductive properties at the same time and their lack of flexibility limits their application in various optoelectronic devices.

[0003] Chinese patent publication CN 109627471A discloses a method for preparing a highly thermally conductive flexible membrane and its application. The method involves first preparing an aqueous dispersion of hydroxylated boron nitride nanosheets and an aqueous dispersion of nanocellulose. The aqueous dispersion of hydroxylated boron nitride nanosheets and the aqueous dispersion of nanocellulose are then mixed, stirred, and ultrasonicated to obtain a uniformly dispersed aqueous dispersion of hydroxylated boron nitride nanosheets / nanocellulose. A film is then prepared by filtration and air-dried in a natural environment, ultimately yielding a highly thermally conductive flexible membrane composed of a composite of hydroxylated boron nitride nanosheets and nanocellulose. However, the thermal conductivity and mechanical properties of this highly thermally conductive flexible membrane still do not meet requirements, and conductive materials cannot be loaded onto the membrane. Summary of the Invention

[0004] One of the objectives of the present invention is to provide a method for preparing an ultra-flexible, electrically conductive and thermally conductive thin film electrode. The preparation method improves the thermal conductivity of the polymer matrix by adding a highly thermally conductive two-dimensional BN material to the polymer matrix material, and uses a one-dimensional metal nanowire material as a thermal bridge of the BN material to further increase the thermal conductivity of the PVA matrix; and loads AgNWs or CuNWs electrode materials on the surface of the film to increase the conductivity of the film, thereby preparing an ultra-flexible, electrically conductive and thermally conductive thin film electrode material.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: a method for preparing an ultra-flexible, electrically and thermally conductive thin film electrode, comprising the following steps:

[0006] S1. Dispersing hexagonal boron nitride (BN) in a mixed solvent of water and isopropyl alcohol, subjecting the mixture to ultrasonic exfoliation to obtain a mixed solution containing boron nitride (BN) and boron nitride nanosheets (BNNS), centrifuging, collecting the supernatant, and washing to obtain a BNNS dispersion.

[0007] S2, drying the BNNS dispersion to obtain BNNS powder, adding the BNNS powder to a 3-10 M NaOH ethanol solution to disperse it evenly, and then heating and drying it to obtain hydroxylated BNNS powder, which is recorded as HO-BNNS powder;

[0008] S3. Dispersing HO-BNNS powder uniformly in deionized water to obtain a HO-BNNS aqueous solution, adding a metal nanowire aqueous solution to the HO-BNNS aqueous solution, and stirring uniformly to obtain a metal nanowire / HO-BNNS mixed solution; the metal nanowire aqueous solution is an AgNWs aqueous solution or a CuNWs aqueous solution;

[0009] S4. Add PVA polymer matrix material to the metal nanowire / HO-BNNS mixed solution and stir until the PVA is completely dissolved to obtain a mixed uniform dispersion; pour the mixed uniform dispersion onto a flat substrate prefabricated with a metal nanowire thin film electrode, and perform high-temperature curing again to form a cured film; peel the cured film together with the metal nanowire thin film electrode from the flat substrate to obtain an ultra-flexible, electrically conductive and thermally conductive thin film electrode with a thickness of 20-60 μm.

[0010] Further improvements to the preparation method of ultra-flexible, electrically and thermally conductive thin film electrodes:

[0011] Preferably, the particle size of the boron nitride BN in step S1 is 1-15 μm, and the particle size of the boron nitride nanosheets BNNS is about 1-3 μm and the thickness is 10-300 nm.

[0012] Preferably, in step S1, water and isopropanol are mixed in a volume ratio of 1:1 to form a mixed solvent; the dispersion concentration of hexagonal boron nitride (BN) in the mixed solvent is 1-5 g / ml, the power of ultrasonic stripping is 50-300 W, and the time is 4-12 h; the mixed solution of BN and BNNS is separated by centrifugation at a speed of 1500-3500 rpm for 3-5 min.

[0013] Preferably, in step S2, the BNNS dispersion is dried at 60-90° C. for 6-12 h to obtain BNNS powder; the BNNS powder is added to the NaOH ethanol solution at a concentration of 3-5 g / ml, ultrasonically dispersed at a power of 50-300 W for 10-30 min until uniformly dispersed, and then heated at 80-120° C. for 8-24 h to obtain hydroxylated BNNS powder.

[0014] Preferably, the dispersion concentration of HO-BNNS powder in deionized water in step S3 is 8-10 mg / ml; the concentration of the metal nanowire aqueous solution is 2-6 mg / ml, and the mass of HO-BNNS in the HO-BNNS aqueous solution is 1-2 times the mass of the metal nanowires in the metal nanowire aqueous solution.

[0015] Preferably, in step S3, the average length of the metal nanowires in the metal nanowire aqueous solution is 50-100 um, the diameter is 20-100 nm, and the aspect ratio is 500-1500.

[0016] Preferably, in step S4, a PVA polymer matrix material is added to the metal nanowire / HO-BNNS mixed solution, stirred at 90-100° C. until the PVA is completely dissolved, and vacuumed to remove bubbles to obtain a uniformly mixed dispersion.

[0017] Preferably, in step S4, the amount of the PVA polymer matrix material added to the metal nanowire / HO-BNNS mixed solution is 10-30 mg / ml, and the molar mass of the PVA polymer matrix material is 150,000-180,000.

[0018] Preferably, the preparation method of the metal nanowire thin film electrode in step S4 is as follows: metal nanowires AgNWs or CuNWs with an aspect ratio of 500-1500 are dispersed in a solvent, wherein the solvent is water, anhydrous ethanol or isopropanol, and the dispersion concentration is 2-8 mg / ml. A film is formed on a flat substrate by a film forming method, and the film is cured in an oven at 60-100°C for 5-20 minutes to form a metal nanowire thin film electrode on the flat substrate.

[0019] A second object of the present invention is to provide an ultra-flexible, electrically conductive and thermally conductive thin film electrode produced by any of the above-mentioned methods for producing the ultra-flexible, electrically conductive and thermally conductive thin film electrode.

[0020] The beneficial effects of the present invention compared to the prior art are:

[0021] 1) This invention provides a method for preparing ultra-flexible, electrically and thermally conductive thin-film electrodes. This method utilizes a cross-dimensional nano-percolation system to achieve ultra-flexibility and successfully load electrode materials, creating a high-performance thin film that is both electrically and thermally conductive. The specific steps are as follows:

[0022] BN has a high thermal conductivity and is inexpensive. BN is dispersed in a mixture of water and isopropyl alcohol. Ultrasonic exfoliation is performed to obtain a mixed solution containing BN and a monolayer of BNNS. After centrifugation, the supernatant is collected and washed to remove the isopropyl alcohol residue on the surface, yielding a BNNS dispersion.

[0023] The BNNS dispersion is dried to obtain BNNS powder; in order to increase the dispersibility of BNNS in water, the BNNS is hydroxylated; the BNNS powder is added to an ethanol solution of sodium hydroxide, ultrasonically dispersed, and then the hydroxylated BNNS is added to obtain HO-BNNS. HO-BNNS is used as a high thermal conductive filling material, and the hydroxylated BNNS does not change its original morphology.

[0024] In step S3, a bridging effect is formed by connecting the isotropic thermally conductive filler and the anisotropic thermally conductive filler, so that the thermal conductive path is completed between the thermally conductive fillers, thereby having a higher thermal conductivity coefficient in the longitudinal direction.

[0025] The HO-BNNS solution is added to a metal nanowire aqueous solution (AgNWs aqueous solution or CuNWs aqueous solution), and a PVA polymer matrix material is added to form a uniformly mixed dispersion. The solution is then mechanically stirred under heating conditions, and vacuumed to remove bubbles. Finally, the solution is poured onto a metal nanowire conductive thin film electrode based on an organic polymer or a rigid substrate. After solidification, the solidified film with the metal nanowire thin film electrode is peeled off from the substrate, thereby preparing an ultra-flexible, electrically conductive and thermally conductive thin film electrode material.

[0026] 2) Polyvinyl alcohol (PVA) has good film-forming properties, ideal mechanical strength, and good biocompatibility, but its low thermal conductivity makes it difficult to meet the requirements of rapid heat dissipation. The thermal conductivity of the PVA substrate can be improved by adding thermal conductive materials. Hexagonal boron nitride (h-BN) is a two-dimensional (2D) material similar to graphite, with high thermal conductivity, wide band gap, oxidation resistance, high elastic modulus, low friction coefficient, and excellent electrical insulation properties. These unique properties enable hydroxylated monolayer boron nitride to effectively enhance the thermal conductivity of polymer materials without affecting the insulation properties of the polymer substrate. Metal nanowires such as silver nanowires (AgNWs) and copper nanowires (CuNWs) are one-dimensional nanomaterials that have shown broad application potential in multiple fields due to their unique physical, chemical, optical, and mechanical properties. In addition to their excellent electrical conductivity, the above-mentioned metal nanowires exhibit excellent light transmittance and flexural resistance due to the nanoscale size effect. At the same time, as a metal material, it has high thermal conductivity. Therefore, adding high aspect ratio AgNWs or CuNWs can increase the contact area of BNNS filler and increase the thermal conductivity and mechanical properties of the film.

[0027] In the present invention, the BN used is not only low-cost, but also BNNS can be easily obtained by ultrasonic stripping technology. After hydroxylation, HO-BNNS shows better dispersibility in aqueous solution, which is beneficial to improving the thermal conductivity of the film. The improvement of thermal conductivity depends not only on the dispersibility and content of the thermally conductive filling material, but also on the continuity of the material. In the film structure, a one-dimensional and two-dimensional material hybrid structure is adopted. After the organic polymers such as PVA are completely dissolved in the solution, the viscosity of the solution will increase, which can further slow down the time for the filling material to be delaminated, so that the thermally conductive filling material can be continuously and evenly dispersed in all corners of the film. This hybrid structure can achieve rapid and uniform heat transfer. The present invention forms a bridging effect through the connection of an isotropic thermally conductive filler and an anisotropic thermally conductive filler, so that the thermal conductive path is completed between the thermally conductive fillers, thereby having a higher thermal conductivity coefficient in the longitudinal direction.

[0028] Large-area conductive films can be fabricated on PDMS or rigid substrates through spraying or doctor blade coating. Leveraging the polymer's bonding properties, the thermally conductive mixed solution can be poured onto the electrode, effectively bonding the conductive material. This allows the fabrication of large-area flexible, electrically and thermally conductive thin-film electrodes. The film has a thermal conductivity of 0.79-1.16 W / mK, exhibiting high electrical conductivity. Its sheet resistance ranges from 10-26 Ω, and its bending radius is less than 1 mm.

[0029] 3) The electrode film prepared by the present invention has the advantages of light weight, controllable thickness, simple structure, and certain flexibility. It can also achieve high thermal conductivity with less filler material, and has good flexibility and electrical conductivity. The present invention can be used for heat dissipation and cooling in devices such as semiconductor chips, OLED displays, and high-power power supplies, ensuring long-life, efficient and stable operation of the devices.

[0030] Cross-dimensional nanostructure achieves ultra-flexibility: The present invention combines two-dimensional boron nitride with one-dimensional metal nanowires, and through cross-dimensional design, achieves ultra-flexibility of electrode materials while maintaining excellent electrical and thermal conductivity.

[0031] Ultrasonic exfoliation and hydroxylation treatment: Ultrasonic exfoliation technology is used to obtain a single layer of boron nitride, and hydroxylation treatment is used to improve its dispersibility and interfacial bonding ability, thereby enhancing the overall performance of the electrode material.

[0032] Integrated preparation and flexible substrate peeling: The innovative integrated preparation process and flexible substrate peeling technology simplify the production process, ensure the firm adhesion of electrode materials on the flexible substrate, and provide technical support for the production of flexible electronic products. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1(a) and (b) are the diameter SEM images and length SEM images of the AgNWs used in the above examples and comparative examples. Figure 1 (c) is the morphology characterization of HO-BNNS prepared in Example 1.

[0034] Figure 2 This is the cross-sectional SEM morphology characterization of the PVA&AgNWs thin film electrode prepared in Comparative Example 1 of the present invention.

[0035] Figure 3 (a) is the SEM cross-sectional characterization of the PVA&AgNWs thin film electrode prepared in Comparative Example 2, (b) is the SEM cross-sectional characterization of the PB-120&AgNWs prepared in Example 1, (c) is the SEM cross-sectional characterization of the PAB-80&AgNWs thin film electrode prepared in Example 2, and (d) is the SEM characterization of the AgNWs electrode loaded on the PAB-120&AgNWs thin film prepared in Example 3.

[0036] Figure 4 SEM characterization and EDS characterization of the PAB-120&AgNWs film obtained in Example 3; (a) is the cross-sectional characterization of the PAB-120&AgNWs film, (b) is the SEM morphology characterization of the thickness of the PAB-120&AgNWs film; (c) shows the surface structure of the PAB-120&AgNWs film by planar SEM morphology characterization, and (d) is the elemental analysis by energy dispersive X-ray spectroscopy (EDS), showing the distribution of B, N, and Ag elements on the cross section of the film.

[0037] Figure 5 A thermal imager was used to monitor the surface temperature changes of PAB-120 and AgNWs films when LED lamp beads were in operation and in the off state. (a) Thermal imaging images of different films first heated up for 120 seconds and then cooled down for 120 seconds; (b) Temperature changes of different films during the heating and cooling processes over time.

[0038] Figure 6 This is the square resistance distribution diagram of the PAB-120 & AgNWs film loaded electrode in Example 3 of the present invention.

[0039] Figure 7 This is a graph showing the change in conductivity of the PAB-120&AgNWs film during the bending process as the number of bending times increases in Example 3 of the present invention. DETAILED DESCRIPTION

[0040] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the embodiments. All other embodiments obtained by persons of ordinary skill in the art based on the embodiments of the present invention without creative work are within the scope of protection of the present invention. The chemical reagents used in the following examples are all conventional chemical reagents and can be purchased through commercial channels.

[0041] Comparative Example 1

[0042] This embodiment provides a method for preparing a PVA&AgNWs thin film electrode, and the specific steps are as follows:

[0043] 1) Add 0.2 g of PVA particles into 10 ml of dispersed aqueous solution, heat and stir at 95° C. for 4 h to obtain a PVA aqueous solution.

[0044] 2) An AgNWs aqueous solution was sprayed on a PDMS substrate and cured to form a conductive film containing the electrode material AgNWs. A PVA aqueous solution was then poured on the conductive film and cured at 80°C to form a PVA film on the conductive film. The cured composite film was peeled off from the PDMS substrate as a whole and recorded as a PVA & AgNWs thin film electrode.

[0045] Comparative Example 2

[0046] This embodiment provides a method for preparing a PA&AgNWs thin film electrode, and the specific steps are as follows:

[0047] 1) 0.2 g of PVA particles were added to 10 ml of a 0.4 mg / ml AgNWs aqueous solution, and the mixture was heated and stirred at 95 °C for 4 h to obtain a PVA / AgNW mixed solution, which was recorded as the PA mixed solution.

[0048] 2) An AgNWs aqueous solution was sprayed on the PDMS film and cured to form a conductive film; a PA mixed solution was poured on the conductive film and cured at 80°C to form a PA film on the conductive film. The cured composite film was peeled off from the PDMS substrate as a whole and recorded as a PA&AgNWs thin film electrode.

[0049] Example 1

[0050] This embodiment provides a method for preparing a PB-120&AgNWs / HO-BNNS thin film electrode, and the specific steps are as follows:

[0051] 1) Weigh 6 g of BN and add it to 200 ml of a mixed solution of deionized water and isopropyl alcohol. Ultrasonic exfoliate at 500 W for 6 h. Centrifuge at 2000 rpm and wash thoroughly to obtain a BNNS dispersion.

[0052] 2) The BNNS dispersion was oven-dried at 60°C to obtain BNNS powder. 80 mg of BNNS powder was evenly dispersed in 100 ml of 5 M NaOH ethanol solution, followed by heating at 120°C for 24 h. The product was washed with deionized water and vacuum-dried at 60°C for 6 h to obtain hydroxylated BNNS powder, designated as HO-BNNS powder.

[0053] 3) Weigh 120 mg of HO-BNNS powder and disperse it in 10 ml of aqueous solution. Mechanically stir for 1 h to form a uniformly dispersed solution. Add 0.2 g of PVA particles to the uniformly dispersed solution and stir at 95°C for 4 h to obtain a uniformly dispersed PVA / HO-BNNS-120 (abbreviated as PB-120, where X in PB-X represents the mass of HO-BNNS) mixed solution.

[0054] 4) An aqueous solution of AgNWs was sprayed on a PDMS substrate and cured to form a conductive film. The mixed solution from step 4 was cast on the conductive film and cured at 80°C to form a PB-120 film on the conductive film. The cured composite film was mechanically peeled off from the PDMS substrate, and the electrode material was loaded in the PB-120 film, which was recorded as a PB-120 & AgNWs / HO-BNNS thin film electrode.

[0055] Example 2

[0056] This embodiment provides a method for preparing a PAB-80 & AgNWs / HO-BNNS thin film electrode, and the specific steps are as follows:

[0057] 1) 80 mg of the HO-BNNS powder obtained in step 2) of Example 1 was weighed and dispersed in 10 ml of aqueous solution, mechanically stirred for 1 h, 1 ml of a 4 mg / ml AgNWs aqueous solution was added, and stirred at 95 ° C for 4 h to obtain a uniformly dispersed AgNWs / HO-BNNS mixed solution, 0.2 g of PVA particles was added to the AgNWs / HO-BNNS mixed solution, and stirred at 95 ° C for 4 h to form a PVA / AgNWs / HO-BNNS-80 (abbreviated as PAB-80) mixed solution.

[0058] 2) An AgNWs aqueous solution was sprayed on a PDMS film and cured to form a conductive film. A PAB-80 mixed solution was poured on the conductive film and cured at 80°C to form a PAB-80 film on the conductive film. The cured composite film was mechanically peeled off from the PDMS substrate, and the electrode material was coated in the PAB-80 film, which was recorded as a PB-80 & AgNWs / HO-BNNS thin film electrode.

[0059] Example 3

[0060] This embodiment provides a method for preparing a PAB-120 & AgNWs / HO-BNNS thin film electrode, and the specific steps are as follows:

[0061] 1) 120 mg of the HO-BNNS powder obtained in step 2) of Example 1 was weighed and dispersed in 10 ml of aqueous solution and mechanically stirred for 1 h. 1 ml of a 4 mg / ml aqueous solution of AgNWs was added and stirred at 95° C. for 4 h to obtain a uniformly dispersed AgNWs / HO-BNNS mixed solution. 0.2 g of PVA particles was added to the AgNWs / HO-BNNS mixed solution and stirred at 95° C. for 4 h to form a PVA / AgNWs / HO-BNNS-120 (abbreviated as PAB-120) mixed solution.

[0062] 2) A AgNWs conductive film was sprayed on a PDMS substrate and cured to form a conductive film; a PAB-120 mixed solution was poured on the conductive film and cured at 80°C to form a PAB-120 film on the conductive film; the cured composite film was mechanically peeled off from the PDMS substrate, and the electrode material was loaded in the PAB-120 film, recorded as a PAB-120 & AgNWs / HO-BNNS thin film electrode.

[0063] Figure 1 (a) and (b) are SEM images of AgNWs used in the above examples and comparative examples. Figure 1 Measurements show that the length of AgNWs is about 50 μm and the diameter is 90 nm. Figure 1 (c) shows the morphology of HO-BNNS in Example 1. The HO-BNNS after hydroxylation and exfoliation does not change its sheet structure.

[0064] Figure 2 is the thickness of the PVA&AgNWs thin film electrode prepared in Comparative Example 1, such as Figure 2 Tests show that the thickness of the PVA&AgNWs thin film electrode is 50-60um.

[0065] Figure 3 (a) is the SEM cross-sectional characterization of the PVA&AgNWs thin film electrode prepared in Comparative Example 2. It can be seen that the thickness of the obtained thin film electrode is about 40 μm, and the longitudinal thermal conductivity is 0.89 W / (m·K). Figure 3 (b) is the SEM cross-sectional characterization of PB-120&AgNWs prepared in Example 1. It can be seen that the thickness of the obtained thin film electrode is about 40 μm, and the longitudinal thermal conductivity is 0.79 W / (m·K). Figure 3 (c) is the cross-sectional SEM characterization of the PAB-80&AgNWs thin film electrode prepared in Example 2, and it can be seen that the thickness of the obtained thin film electrode is about 40 μm. Figure 3 (d) is the SEM characterization of the AgNWs electrode loaded on the PAB-120&AgNWs film prepared in Example 3. The electrode is completely loaded on the surface of the film and forms a network-like interlaced structure.

[0066] Figure 4 SEM and EDS characterizations of the PAB-120 & AgNWs film obtained in Example 3. (a)-(b) show cross-sectional images of the PAB-120 & AgNWs film, which is approximately 40 μm thick. (c) shows the surface structure of the PAB-120 & AgNWs film, showing a chaotic arrangement of HO-BNNS and AgNWs within the film. (d) shows elemental analysis by energy-dispersive X-ray spectroscopy (EDS), which reveals the distribution of B, N, and Ag elements across the film's cross-section. Testing indicates that the longitudinal thermal conductivity of the PAB-120 & AgNWs film prepared in Example 3 is 1.16 W / (m·K).

[0067] The PAB-120 & AgNWs film prepared in Example 3 was pasted on the back of the LED lamp bead, and a thermal imager was used to monitor the changes in the surface temperature of the LED lamp bead when it was working and when it was turned off. Figure 5 As shown in (a), the temperature change of PAB-120&AgNWs film during the cooling process is the most significant. Figure 5 Panel (b) details the time-dependent surface temperature variations of various films. Increasing the HO-BNNS thermal conductive material content enhances the film's thermal conductivity. Furthermore, mixing high-aspect-ratio AgNWs with HO-BNNS further improves overall thermal conductivity. For the PAB-120 & AgNWs film, we observed a relatively slow temperature rise and a relatively rapid temperature drop.

[0068] The conductivity of the PAB-120 & AgNWs film prepared in Example 3 was measured using a four-probe method. Figure 6 As shown in the figure, the square resistance at different points is between 10-26Ω, proving that the film can not only carry conductive electrode materials but also has excellent electrical conductivity. Testing has shown that the bending radius of the film can reach 1mm, demonstrating excellent flexibility. Film flexibility plays an important role in practical applications, and its unique properties give it a wide range of application potential in multiple fields. Figure 7 The study further revealed changes in the conductivity of the loaded electrode material during repeated bending of the film. The decrease in conductivity was minimal with increasing bending cycles; even after 2,000 bends, the conductivity dropped by only 0.08%, further confirming the stability and durability of the PAB-120 and AgNWs film's conductivity in practical applications.

[0069] In summary, the present invention relates to a method for preparing an ultra-flexible, electrically conductive and thermally conductive thin film electrode. This technology is consistent with the development trend of modern electronic products towards high integration, lightweight and flexibility. The film not only has excellent thermal conductivity and can effectively cope with the heat management challenges in modern electronic products, but also in the field of environmentally friendly materials, polyvinyl alcohol (PVA) film, as a non-toxic, pollution-free new green packaging material, has become the focus of research on heat dissipation substrates for electronic devices at home and abroad due to its excellent properties such as water solubility, barrier properties and degradability. The film of the present invention not only achieves a breakthrough in technology, but also has significant advantages in environmental protection and sustainability, and is expected to bring revolutionary progress to the electronics industry.

[0070] Those skilled in the art will appreciate that the foregoing descriptions are merely specific embodiments of the present invention, and not exhaustive. It should be noted that numerous variations and modifications are possible for those skilled in the art, and all such variations and modifications that do not exceed the scope of the claims should be considered within the scope of protection of the present invention.

Claims

1. A method for preparing an ultra-flexible, electrically and thermally conductive thin film electrode, characterized in that: The steps include: S1. Dispersing hexagonal boron nitride (BN) in a mixed solvent of water and isopropyl alcohol, subjecting the mixture to ultrasonic exfoliation to obtain a mixed solution containing boron nitride (BN) and boron nitride nanosheets (BNNS), centrifuging, collecting the supernatant, and washing to obtain a BNNS dispersion. S2, drying the BNNS dispersion to obtain BNNS powder, adding the BNNS powder to a 3-10 M NaOH ethanol solution to disperse it evenly, and then heating and drying it to obtain hydroxylated BNNS powder, which is recorded as HO-BNNS powder; S3. Dispersing HO-BNNS powder uniformly in deionized water to obtain a HO-BNNS aqueous solution, adding a metal nanowire aqueous solution to the HO-BNNS aqueous solution, and stirring uniformly to obtain a metal nanowire / HO-BNNS mixed solution; the metal nanowire aqueous solution is an AgNWs aqueous solution or a CuNWs aqueous solution; S4. Add PVA polymer matrix material to the metal nanowire / HO-BNNS mixed solution and stir until the PVA is completely dissolved to obtain a mixed uniform dispersion; pour the mixed uniform dispersion onto a flat substrate prefabricated with a metal nanowire thin film electrode, and perform high-temperature curing again to form a cured film; peel the cured film together with the metal nanowire thin film electrode from the flat substrate to obtain an ultra-flexible, electrically conductive and thermally conductive thin film electrode with a thickness of 20-60 μm.

2. The method for preparing the ultra-flexible, electrically and thermally conductive thin film electrode according to claim 1, characterized in that: In step S1 , the particle size of the boron nitride BN is 1-15 μm, and the particle size of the boron nitride nanosheets BNNS is about 1-3 μm and the thickness is 10-300 nm.

3. The method for preparing the ultra-flexible, electrically and thermally conductive thin film electrode according to claim 1, characterized in that: In step S1, water and isopropanol are mixed in a volume ratio of 1:1 to form a mixed solvent; the dispersion concentration of hexagonal boron nitride (BN) in the mixed solvent is 1-5 g / ml, the ultrasonic stripping power is 50-300 W, and the time is 4-12 hours; the mixed solution of BN and BNNS is separated by centrifugation at a speed of 1500-3500 rpm for 3-5 minutes.

4. The method for preparing the ultra-flexible, electrically and thermally conductive thin film electrode according to claim 1, characterized in that: In step S2, the BNNS dispersion is dried at 60-90°C for 6-12 hours to obtain BNNS powder; the BNNS powder is added to the NaOH ethanol solution at a concentration of 3-5 g / ml, ultrasonically dispersed at a power of 50-300 W for 10-30 minutes until uniformly dispersed, and then heated at 80-120°C for 8-24 hours to obtain hydroxylated BNNS powder.

5. The method for preparing an ultra-flexible, electrically and thermally conductive thin film electrode according to claim 1, characterized in that: In step S3, the dispersion concentration of HO-BNNS powder in deionized water is 8-10 mg / ml; the concentration of the metal nanowire aqueous solution is 2-6 mg / ml, and the mass of HO-BNNS in the HO-BNNS aqueous solution is 1-2 times the mass of the metal nanowires in the metal nanowire aqueous solution.

6. The method for preparing the ultra-flexible, electrically and thermally conductive thin film electrode according to claim 1 or 5, characterized in that: In step S3, the average length of the metal nanowires in the metal nanowire aqueous solution is 50-100 um, the diameter is 20-100 nm, and the aspect ratio is 500-1500.

7. The method for preparing an ultra-flexible, electrically and thermally conductive thin film electrode according to claim 1, characterized in that: In step S4, PVA polymer matrix material is added to the metal nanowire / HO-BNNS mixed solution, stirred at 90-100° C. until the PVA is completely dissolved, and vacuumed to remove bubbles to obtain a uniformly mixed dispersion.

8. The method for preparing an ultra-flexible, electrically and thermally conductive thin film electrode according to claim 1, characterized in that: In step S4, the amount of the PVA polymer matrix material added to the metal nanowire / HO-BNNS mixed solution is 10-30 mg / ml, and the molar mass of the PVA polymer matrix material is 150,000-180,000.

9. The method for preparing an ultra-flexible, electrically and thermally conductive thin film electrode according to claim 1, characterized in that: The preparation method of the metal nanowire thin film electrode described in step S4 is as follows: metal nanowires AgNWs or CuNWs with an aspect ratio of 500-1500 are dispersed in a solvent, wherein the solvent is water, anhydrous ethanol or isopropanol, and the dispersion concentration is 2-8 mg / ml. A film is formed on a flat substrate by a film forming method, and then cured in an oven at 60-100°C for 5-20 minutes to form a metal nanowire thin film electrode on the flat substrate.

10. An ultra-flexible, electrically conductive and thermally conductive thin film electrode produced by the method for producing an ultra-flexible, electrically conductive and thermally conductive thin film electrode according to any one of claims 1 to 9.

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