Method for preparing piezoelectric nanofiber flexible composite film with 3d conductive network

Abstract

The application discloses a preparation method of a piezoelectric nanofiber flexible composite film with a 3D conductive network, comprising the following steps: step 1, preparation of a piezoelectric / conductive nanofiber film; step 2, preparation of a CNT@piezoelectric / conductive nanofiber film; and step 3, preparation of a CNT@piezoelectric / conductive nanofiber / PDMS composite film. The application utilizes an electrospinning technology to prepare oriented nanofibers, and then utilizes a chemical vapor deposition method to uniformly grow CNT on the nanofibers, so that the long conductive nanofibers and the CNT are uniformly introduced into a dense piezoelectric nanofiber film. The long conductive nanofibers serve as vertical conductive paths in the nanofiber film, and the CNT serve as horizontal conductive paths in the nanofiber film. The two cooperate to jointly construct a well-distributed 3D conductive network among the piezoelectric nanofibers, improve the charge density, and finally improve the output performance of PENG.

Description

Technical Field

[0001] This invention relates to the field of piezoelectric materials, specifically a method for preparing a flexible composite film of piezoelectric nanofibers with a 3D conductive network (i.e., a three-dimensional conductive network). Background Technology

[0002] Piezoelectric nanogenerators (PENGs) are electronic devices that convert mechanical vibrations into electrical energy for sustainable energy supply. Considering the potential applications of PENGs in energy harvesting, health diagnostics, and motion monitoring, PENGs must possess good flexibility to withstand complex strains such as bending, stretching, and torsion. However, most materials with high piezoelectric coefficients are hard and brittle ceramics, limiting their further development. To overcome this limitation, embedding piezoelectric ceramics into flexible polymers to construct organic / inorganic composite flexible PENGs is a feasible solution. However, the polymer present in the gaps isolates the piezoelectric ceramics and restricts piezoelectric charge transfer, severely affecting the piezoelectric output performance of the PENG.

[0003] To address the aforementioned issues, an effective approach is to utilize conductive materials to construct conductive pathways between piezoelectric materials, enhancing piezoelectric charge transport and thus improving the piezoelectric output performance of PENGs. In 2012, Park et al. first proposed a strategy of incorporating multi-walled carbon nanotubes (MWCNTs) into flexible polydimethylsiloxane / barium titanate (PDMS / BaTiO3) composites to improve their piezoelectric properties. MWCNTs can form conductive pathways, thereby enhancing output performance. Based on the above research, it is evident that conductive pathways play a crucial role in charge transfer within organic / inorganic composite flexible PENGs.

[0004] While introducing conductive pathways into organic / inorganic composite piezoelectric materials to enhance charge transfer capabilities can yield high-performance PENGs, constructing well-distributed conductive pathways within ordered, dense piezoelectric nanofibers using conductive materials such as CNTs and metal nanoparticles is extremely challenging. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the technical problem this invention aims to solve is to provide a method for preparing a piezoelectric nanofiber flexible composite membrane with a 3D conductive network.

[0006] The technical solution of this invention to solve the aforementioned technical problem is to provide a method for preparing a piezoelectric nanofiber flexible composite film with a 3D conductive network, characterized in that the method includes the following steps: (1) Preparation of piezoelectric / conductive nanofiber membrane: Prepare electrospinning solution of piezoelectric material precursor and electrospinning solution of conductive material precursor, and then use the two spinning solutions as raw materials to electrospin the two syringes of the electrospinning device to form piezoelectric / conductive precursor nanofiber membrane; wherein, all precursor nanofibers in the piezoelectric / conductive precursor nanofiber membrane are arranged along the rotation direction of the collecting device of the electrospinning device; then calcine the piezoelectric / conductive precursor nanofiber membrane to decompose the polymer carrier in the membrane to obtain the piezoelectric / conductive nanofiber membrane; (2) Preparation of CNT@piezoelectric / conductive nanofiber membrane: CNTs were grown in situ on the piezoelectric / conductive nanofiber membrane by chemical vapor deposition to obtain CNT@piezoelectric / conductive nanofiber membrane; (3) Preparation of CNT@piezoelectric / conductive nanofiber / PDMS composite film: Several CNT@piezoelectric / conductive nanofiber films are stacked layer by layer to form a three-dimensional structure, and the nanofibers in each layer of CNT@piezoelectric / conductive nanofiber film are arranged in the same direction; then they are immersed in PDMS solution and left to stand, so that PDMS is attached to the inside and surface of the nanofiber film; then the PDMS is cured by curing treatment, and then the three-dimensional structure is cut along the radial direction of the nanofibers in the three-dimensional structure to obtain CNT@piezoelectric / conductive nanofiber / PDMS composite film.

[0007] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) This invention utilizes electrospinning technology to prepare oriented nanofibers, and the conductive nanofibers and piezoelectric nanofibers are mixed uniformly. Then, CNTs are uniformly grown on the nanofibers using chemical vapor deposition. Long conductive nanofibers and CNTs are uniformly introduced into the dense piezoelectric nanofiber membrane. The long conductive nanofibers serve as vertical conductive paths in the nanofiber membrane, and the CNTs serve as horizontal conductive paths in the nanofiber membrane. The two work together to construct a well-distributed 3D conductive network between the piezoelectric nanofibers, which solves the problem of constructing conductive pathways in a regularly arranged and dense piezoelectric nanofiber membrane, improves the charge density, and ultimately enhances the output performance of PENG.

[0008] (2) The 3D conductive network established by the present invention can transfer the charge generated by the piezoelectric nanofiber inside the matrix to the surface area of ​​the material, thereby inducing more induced charges on the electrode to enhance the transmission of piezoelectric charges in the nanofiber, thereby obtaining a high-performance flexible PENG.

[0009] (3) The composite membrane prepared by the present invention has broad application prospects in the field of piezoelectric nanogenerators, and its improved electrical properties also enhance its practicality in electronic textiles. Attached Figure Description

[0010] Figure 1 This is a process flow diagram of Embodiment 1 of the present invention; Figure 2 This is a SEM image of the nanofibers in the membrane (i.e., the CNT@piezoelectric / conductive nanofiber membrane) in step 2 of Example 1 of the present invention; Figure 3 This is a SEM image of the nanofibers in the membrane from step 2 of Example 2 of the present invention; Figure 4 This is a SEM image of the nanofibers in the membrane from step 2 of Example 3 of the present invention; Figure 5 This is a SEM image of the nanofibers in the membrane from step 2 of Example 4 of the present invention; Figure 6 This is a SEM image of the nanofibers in the membrane from step 2 of Example 5 of the present invention; Figure 7 This is a SEM image of the nanofibers in the membrane (i.e., the piezoelectric / conductive nanofiber membrane) of Comparative Example 1 of the present invention, in step 2. Figure 8 The graphs show the TG test results of the membranes in step 2 of Examples 1-5 and Comparative Example 1 of this invention. Figure 9 These are XRD results of the membranes from step 2 of Examples 1, 3, 5 and Comparative Example 1 of the present invention; Figure 10 The graph shows the test results of the dielectric constant of the film in step 2 of Examples 1-5 and Comparative Example 1 as a function of frequency. Figure 11 The graph shows the test results of the dielectric loss of the film in step 2 of Examples 1-5 and Comparative Example 1 as a function of frequency. Figure 12 The graph shows the test results of the conductivity of the membrane in step 2 of Examples 1-5 and Comparative Example 1 as a function of frequency. Figure 13 The graph shows the test results of dielectric constant, dielectric loss and conductivity of the composite film in Example 3 of the present invention. Figure 14 The graph shows the voltage test results of the piezoelectric properties of PENG in Examples 1-5 and Comparative Example 1 of this invention. Figure 15 The graph shows the piezoelectric performance current test results of PENG in Examples 1-5 and Comparative Example 1 of this invention. Detailed Implementation

[0011] Specific embodiments of the present invention are given below. These specific embodiments are only used to further illustrate the present invention in detail and do not limit the scope of protection of the present invention.

[0012] This invention provides a method for preparing a flexible piezoelectric nanofiber composite film with a 3D conductive network (hereinafter referred to as the method), characterized in that the method includes the following steps: (1) Preparation of piezoelectric / conductive nanofiber membrane: Prepare electrospinning solution of piezoelectric material precursor and electrospinning solution of conductive material precursor, and then use the two spinning solutions as raw materials to electrospin them in two syringes of the electrospinning device to form piezoelectric / conductive precursor nanofiber membrane; wherein, all precursor nanofibers in the piezoelectric / conductive precursor nanofiber membrane are arranged along the rotation direction of the collecting device of the electrospinning device; then calcine the piezoelectric / conductive precursor nanofiber membrane at high temperature to decompose the polymer carrier in the membrane to obtain piezoelectric / conductive nanofiber membrane; Preferably, in step (1), the piezoelectric material in the electrospinning solution of the piezoelectric material precursor refers to a material that can be used to prepare piezoelectric nanofibers by sol-gel method, electrospinning and calcination, specifically a perovskite piezoelectric material or a piezoelectric semiconductor material; the perovskite piezoelectric material is barium titanate (BaTiO3), barium zirconate titanate-barium calcium titanate (BZT-BCT), barium zirconate titanate (BCZT), barium strontium titanate (BST), bismuth titanate (BIT), sodium bismuth titanate (BNT), lead titanate (PT), lead strontium titanate (PST), lead zirconate titanate (PZT), lanthanum lead zirconate titanate (PLZT), lead magnesium niobate (PMN) or potassium sodium niobate (KNN); the piezoelectric semiconductor material is zinc oxide (ZnO); The conductive material in the electrospinning solution of the conductive material precursor refers to the material that can be used to prepare conductive nanofibers through sol-gel method, electrospinning and calcination, specifically antimony tin oxide (ATO), fluorine tin oxide (FTO), antimony fluorine tin oxide (FATO), indium tin oxide (ITO) or aluminum zinc oxide (AZO).

[0013] Preferably, in step (1), the piezoelectric material in the piezoelectric material precursor electrospinning solution is barium titanate, and the precursor electrospinning solution is prepared as follows: barium acetate and tetrabutyl titanate are dissolved in a mixture of glacial acetic acid and acetylacetone under stirring at room temperature, and then PVP (polyvinylpyrrolidone), which acts as a polymer carrier in the electrospinning process, is added. After mixing evenly, a uniform BaTiO3 precursor electrospinning solution is prepared. The mass ratio of barium acetate to tetrabutyl titanate is (1~3):1, and the volume ratio of glacial acetic acid to acetylacetone is (2~5):1; the mass fraction of barium acetate in the BaTiO3 precursor electrospinning solution is 10~20wt%; the mass fraction of PVP in the BaTiO3 precursor electrospinning solution is 2~12wt%; and the molecular weight of PVP is 300,000~1,300,000.

[0014] Preferably, in step (1), the conductive material in the electrospinning solution of the piezoelectric material precursor is antimony tin oxide. The preparation of the precursor electrospinning solution is as follows: under stirring at room temperature, tin chloride pentahydrate and antimony trichloride are dissolved in a mixture of anhydrous ethanol and DMF (N,N-dimethylformamide), and then PVP, which acts as a polymer carrier in the electrospinning process, is added. After mixing evenly, a uniform ATO precursor electrospinning solution is prepared. The mass ratio of stannous chloride pentahydrate to antimony trichloride is (8~16):1, and the volume ratio of anhydrous ethanol to DMF is 1:(1~4); the mass fraction of stannous chloride pentahydrate in the ATO precursor electrospinning solution is 6~15wt%; the mass fraction of PVP in the ATO precursor electrospinning solution is 6~18wt%; and the molecular weight of PVP is 300,000~1,300,000.

[0015] Preferably, in step (1), the electrospinning process is as follows: the spinning needles of two syringes are placed side by side and reciprocate along the axis of the collecting device during the spinning process; the ratio of precursor piezoelectric nanofibers and precursor conductive nanofibers is controlled by the extrusion rate of the precursor electrospinning solution by the syringe, the extrusion rate of the piezoelectric precursor electrospinning solution is 0.5~2.5ml / h, and the extrusion rate of the conductive precursor electrospinning solution is 0.2~2ml / h; the electric field strength is 15~40kV; the distance from the needle tip to the collecting device is 12~25cm; the rotation speed of the collecting device is 1000~4000r / min, so that the precursor nanofibers are arranged along the rotation direction; the air humidity is 10~60%, and the temperature is 20~40℃.

[0016] Preferably, in step (1), the calcination temperature is 400~1200℃, the heating rate is 0.5~8℃ / min, the holding time is 1~5h, and the calcination environment is an air atmosphere.

[0017] (2) Preparation of CNT@piezoelectric / conductive nanofiber membrane: CNT (carbon nanotubes) were grown in situ on the piezoelectric / conductive nanofiber membrane by chemical vapor deposition (CVD) to obtain CNT@piezoelectric / conductive nanofiber membrane; Preferably, step (2) specifically involves: immersing the piezoelectric / conductive nanofiber membrane in a cobalt nitrate solution and allowing it to stand so that all the cobalt nitrate adheres to the interior and surface of the nanofiber membrane; then removing the product and drying it to remove the solvent from the cobalt nitrate solution on the surface of the nanofiber membrane; then calcining the dried product and carbon source at high temperature in a H2 / Ar mixed gas to obtain a CNT@piezoelectric / conductive nanofiber membrane. Preferably, in step (2), the mass ratio of the solute in the cobalt nitrate solution to the piezoelectric / conductive nanofiber membrane is (1~20):10; Preferably, in step (2), the cobalt nitrate solution is prepared by dissolving cobalt nitrate solid particles in anhydrous ethanol, wherein the amount of anhydrous ethanol is sufficient to dissolve the cobalt nitrate solid particles.

[0018] Preferably, in step (2), the settling process is: settling at room temperature and pressure for 1 to 10 minutes.

[0019] Preferably, in step (2), the drying temperature is 40~70℃ and the drying time is 5~20min.

[0020] Preferably, in step (2), the mass ratio of carbon source to piezoelectric / conductive nanofiber membrane is 1:(1~10).

[0021] Preferably, in step (2), the carbon source is xylene.

[0022] Preferably, in step (2), the flow rate of the H2 / Ar mixed gas is 200~300 sccm.

[0023] Preferably, in step (2), the volume content of H2 in the mixed gas is 5-20%.

[0024] Preferably, in step (2), the calcination temperature is 400~1000℃, the pressure is atmospheric pressure, the heating rate is 0.5~8℃ / min, and the holding time is 1~5h.

[0025] (3) Preparation of CNT@piezoelectric / conductive nanofiber / PDMS composite film: Several CNT@piezoelectric / conductive nanofiber films are stacked layer by layer to form a three-dimensional structure, and the nanofibers in each layer of CNT@piezoelectric / conductive nanofiber film are arranged in the same direction; then they are immersed in PDMS solution and left to stand, so that PDMS is attached to the inside and surface of the nanofiber film; then the PDMS is cured by curing treatment, and then the three-dimensional structure is cut along the radial direction of the nanofibers in the three-dimensional structure to obtain CNT@piezoelectric / conductive nanofiber / PDMS composite film.

[0026] Preferably, in step (3), the mass fraction of the PDMS solution is 40~95wt%.

[0027] Preferably, in step (3), the settling process is: settling at room temperature and pressure for 1 to 8 hours.

[0028] Preferably, in step (3), the curing temperature is 40~120℃ and the curing time is 2~10h.

[0029] Preferably, a flexible piezoelectric nanogenerator is prepared by using the CNT@piezoelectric / conductive nanofiber / PDMS composite film as raw material, attaching two copper foils as electrodes to the top and bottom of the CNT@piezoelectric / conductive nanofiber / PDMS composite film, and drawing wires from the two electrodes respectively.

[0030] Example 1: (1) Preparation of BaTiO3 / ATO nanofiber membrane: First, prepare the electrospinning solution of BaTiO3 and ATO precursor. Specifically, dissolve 2.55g of barium acetate and 3.4g of tetrabutyl titanate in 6g of glacial acetic acid and 2g of acetylacetone, mix them evenly under magnetic stirring, then add 1g of PVP, stir thoroughly to prepare a uniform BaTiO3 precursor electrospinning solution; dissolve 1.7268g of tin chloride pentahydrate and 0.1274g of antimony trichloride in 4.31g of anhydrous ethanol and 10.34g of DMF, then add 2g of PVP, stir thoroughly to prepare a uniform ATO precursor electrospinning solution. Using BaTiO3 precursor electrospinning solution and ATO precursor electrospinning solution as raw materials, they were placed in two separate syringes for electrospinning to form BaTiO3 / ATO precursor nanofiber membranes; then the BaTiO3 / ATO precursor nanofiber membranes were heated to 1000℃ for 1h at a heating rate of 2℃ / min to decompose the PVP in the membrane, thus obtaining BaTiO3 / ATO nanofiber membranes. The electrospinning process conditions were as follows: the spinning needles used in the two syringes were arranged side by side and reciprocated along the axis of the collecting device during the spinning process; the extrusion rate of the BaTiO3 spinning solution was 1 ml / h, and the extrusion rate of the ATO spinning solution was 0.4 ml / h, thus controlling the content of ATO precursor nanofibers in the BaTiO3 / ATO nanofiber membrane to be 12 wt%; the electric field strength was 35 kV; the distance from the needle tip to the collecting device was 18 cm; the collecting device rotated at a speed of 2500 r / min; the air humidity was 25%, and the temperature was 20 °C. (2) Preparation of CNT@BaTiO3 / ATO nanofiber membrane: CNTs were grown in situ on BaTiO3 / ATO nanofiber membrane by CVD method. Specifically, BaTiO3 / ATO nanofiber membrane was immersed in cobalt nitrate solution and left to stand for 2 min to allow cobalt nitrate to fully penetrate the nanofiber membrane until the cobalt nitrate solution was completely absorbed. Then the product was taken out and dried at 60℃ for 5 min. Then the dried product and xylene (the mass ratio of xylene to BaTiO3 / ATO nanofiber membrane was 1:1) were placed together in a tube furnace, and H2 / Ar mixed gas (the volume ratio of H2 to Ar was 1:9) was introduced. Then the temperature was raised to 800℃ for 1 h at a heating rate of 3℃ / min to obtain CNT@BaTiO3 / ATO nanofiber membrane. The cobalt nitrate solution was prepared by dissolving cobalt nitrate solid particles in anhydrous ethanol, wherein the mass ratio of cobalt nitrate solid particles to BaTiO3 / ATO nanofiber membrane was 3:10.

[0031] (3) Preparation of CNT@BaTiO3 / ATO / PDMS composite membrane: Several CNT@BaTiO3 / ATO nanofiber membranes were stacked layer by layer to form a three-dimensional structure. The nanofibers of each CNT@BaTiO3 / ATO nanofiber membrane were arranged in the same direction. Then, the membrane was immersed in an 80wt% PDMS solution and left to stand for 2 hours to allow PDMS to adhere to the interior and surface of the nanofiber membrane. Then, the membrane was cured at 60℃ for 4 hours to cure the PDMS. The three-dimensional structure was then cut along the radial direction of the nanofibers in the three-dimensional structure to obtain the CNT@BaTiO3 / ATO / PDMS composite membrane.

[0032] Application: Flexible piezoelectric nanogenerators were fabricated by attaching two copper foils as electrodes to the top and bottom of a CNT@BaTiO3 / ATO / PDMS composite film.

[0033] Depend on Figure 1 It can be seen that a 3D conductive network was successfully constructed in the CNT@BaTiO3 / ATO nanofiber membrane, which consists of ATO nanofibers as vertical conductive paths and CNTs as horizontal interconnects.

[0034] Example 2: This embodiment is the same as that in embodiment 1, except that in step (2), the mass ratio of cobalt nitrate solid particles to BaTiO3 / ATO nanofiber membrane is 1:2.

[0035] Example 3: This embodiment is the same as that in embodiment 1, except that in step (2), the mass ratio of cobalt nitrate solid particles to BaTiO3 / ATO nanofiber membrane is 7:10.

[0036] The PENG prepared in this embodiment exhibits the best piezoelectric properties.

[0037] Example 4: This embodiment is the same as that in embodiment 1, except that in step (2), the mass ratio of cobalt nitrate solid particles to BaTiO3 / ATO nanofiber membrane is 9:10.

[0038] Example 5: This embodiment is the same as that in embodiment 1, except that in step (2), the mass ratio of cobalt nitrate solid particles to BaTiO3 / ATO nanofiber membrane is 11:10.

[0039] Comparative Example 1: This comparative example is the same as Example 1, except that in step (2), the mass ratio of cobalt nitrate solid particles to BaTiO3 / ATO nanofiber membrane is 0:1, that is, cobalt nitrate is not used.

[0040] Depend on Figure 2-7 It can be seen that as the cobalt nitrate content of the catalyst increases, the density of the generated CNTs also increases. For example... Figure 2 and Figure 3 As shown, a few sparse CNTs grew on the CNT@BaTiO3 / ATO nanofibers prepared in Examples 1 and 2; with the increase of the cobalt nitrate content in the catalyst, as... Figure 4 and Figure 5 As shown, the CNTs grown on the CNT@BaTiO3 / ATO nanofibers prepared in Examples 3 and 4 can already be connected between the fibers; as Figure 6 As shown, the surface of the CNT@BaTiO3 / ATO nanofibers prepared in Example 5 is already covered with CNTs; Figure 7 As shown, no CNTs were found on the surface of the BaTiO3 / ATO nanofibers prepared in Comparative Example 1, which also indicates that there is little difference between the fibers and the fibers that did not participate in the CVD reaction when no cobalt nitrate catalyst was added.

[0041] Depend on Figure 8 As can be seen from the TG test, since the BaTiO3 / ATO nanofiber membrane is stable at 800℃, while CNTs decompose under high temperature conditions, it can be determined that the content of CNTs in the CNT@BaTiO3 / ATO nanofiber membrane in Examples 1-5 is 4wt%, 8wt%, 14wt%, 16wt%, and 19wt%, respectively, while there is no CNT in Comparative Example 1, and the content is 0wt%.

[0042] Depend on Figure 9 It can be seen that the XRD pattern of BaTiO3 nanofibers matches well with the standard JCPDS card #05-0626, with peaks at 22.16, 31.56, 38.92, 45.34, 50.97, and 56.23 corresponding to the crystal planes of BaTiO3. Additionally, a splitting peak is observed near 45°, indicating that the BaTiO3 nanofibers exhibit tetragonal phase crystallization. The XRD pattern of ATO nanofibers matches well with the standard JCPDS card #41-1445 for SnO2, with peaks at 26.67, 33.89, 38.11, and 51.92 corresponding to the crystal planes of ATO. For the BaTiO3 / ATO nanofiber film in Comparative Example 1, their respective diffraction peaks appear simultaneously and are superimposed without interference. For the CNT@BaTiO3 / ATO nanofiber film, the peaks observed corresponded to the diffraction peaks of BaTiO3 / ATO nanofibers, without any missing peaks, thus confirming that the crystal structure did not change after the in-situ CNT growth via CVD reaction. Furthermore, from... Figure 9 As can be seen, the peak value gradually decreases with the increase of CNT content.

[0043] Depend on Figure 10 It can be seen that the dielectric constant of the nanofiber membrane increases with increasing CNT content, a phenomenon that can be explained by the principle of microcapacitors. Uniformly distributed conductive CNT fillers can form a large number of microcapacitors, and their number increases with increasing CNT content. As the CNT content increases, the isolation distance between CNTs decreases, leading to an increase in the average capacitance of the microcapacitors.

[0044] Depend on Figure 11 It can be seen that the dielectric loss of the nanofiber membrane increases with the increase of CNT content, which is due to the increased current leakage caused by the high conductivity of CNT.

[0045] Depend on Figure 12 It can be seen that as the CNT content increases, the resistance decreases, and thus the conductivity increases.

[0046] Depend on Figure 13 It can be seen that the dielectric constant, dielectric loss, and conductivity of the PDMS composite material with BaTiO3 / ATO hybrid nanofibers and 14wt% CNT are 368, 1.25, and 6.81×10⁻⁶, respectively. -11 S / m demonstrates the insulating effect of PDMS packaging on dielectric behavior.

[0047] Figure 14 and Figure 15 The voltage (Voc) and current (Isc) of PENGs during repetitive release cycles at 30 kPa pressure and 2 Hz frequency are respectively. Figure 14 and Figure 15 As can be seen, the PENG without CNTs exhibits an output of 31V and 9.6μA (corresponding to Comparative Example 1). After introducing CNTs into the PENG, the synergistic effect of CNTs and ATO nanofibers significantly improves the electrical output. With increasing CNT content, Voc and Isc gradually increase, reaching 64.5V and 29.6μA respectively when the CNT content is 14wt% (corresponding to Example 3), which are 2.08 times and 3.08 times the output performance of the pure BaTiO3 / ATO-based PENG, respectively. However, with further increases in CNT content, a decreasing trend in Voc and Isc was observed, attributed to current leakage. The test results demonstrate that CNT doping enhances the piezoelectric charge transfer capability, thereby improving the output performance of the PENG.

[0048] Any aspects not covered in this invention are applicable to existing technologies.

Claims

1. A method for preparing a piezoelectric nanofiber flexible composite film with a 3D conductive network, characterized in that, The method includes the following steps: (1) Preparation of piezoelectric / conductive nanofiber membrane: Prepare electrospinning solution of piezoelectric material precursor and electrospinning solution of conductive material precursor, and then use the two spinning solutions as raw materials to electrospin the two syringes of the electrospinning device to form piezoelectric / conductive precursor nanofiber membrane; wherein, all precursor nanofibers in the piezoelectric / conductive precursor nanofiber membrane are arranged along the rotation direction of the collecting device of the electrospinning device; then calcine the piezoelectric / conductive precursor nanofiber membrane to decompose the polymer carrier in the membrane to obtain the piezoelectric / conductive nanofiber membrane; The piezoelectric material in the electrospinning solution of the piezoelectric material precursor is a perovskite piezoelectric material or a piezoelectric semiconductor material. The conductive material in the electrospinning solution of the conductive material precursor is antimony tin oxide, fluorine tin oxide, antimony tin fluoride oxide, indium tin oxide, or aluminum zinc oxide. The electrospinning process is as follows: the spinning needles of two syringes are placed side by side and reciprocate along the axis of the collecting device during the spinning process; the extrusion rate of the electrospinning solution for the piezoelectric material precursor is 0.5~2.5 ml / h, and the extrusion rate of the electrospinning solution for the conductive material precursor is 0.2~2 ml / h; the electric field strength is 15~40 kV; the distance from the needle tip to the collecting device is 12~25 cm; the rotation speed of the collecting device is 1000~4000 r / min; the air humidity is 10~60%, and the temperature is 20~40℃. The calcination temperature is 400~1200℃, the heating rate is 0.5~8℃ / min, the holding time is 1~5h, and the calcination environment is an air atmosphere; (2) Preparation of CNT@piezoelectric / conductive nanofiber membrane: The piezoelectric / conductive nanofiber membrane was immersed in cobalt nitrate solution and allowed to stand so that all cobalt nitrate was attached to the interior and surface of the nanofiber membrane; then the product was taken out and dried to remove the solvent in the cobalt nitrate solution on the surface of the nanofiber membrane; then the dried product and carbon source were calcined in H2 / Ar mixed gas to grow CNTs in situ on the piezoelectric / conductive nanofiber membrane to obtain CNT@piezoelectric / conductive nanofiber membrane; the mass ratio of solute in cobalt nitrate solution to piezoelectric / conductive nanofiber membrane was (3~11):10; (3) Preparation of CNT@piezoelectric / conductive nanofiber / PDMS composite film: Several CNT@piezoelectric / conductive nanofiber films are stacked layer by layer to form a three-dimensional structure, and the nanofibers in each layer of CNT@piezoelectric / conductive nanofiber film are arranged in the same direction; then, they are immersed in PDMS solution and left to stand, so that PDMS is attached to the inside and surface of the nanofiber film; then, PDMS is cured by curing treatment, and then the three-dimensional structure is cut along the radial direction of the nanofibers in the three-dimensional structure to obtain CNT@piezoelectric / conductive nanofiber / PDMS composite film; in the CNT@piezoelectric / conductive nanofiber / PDMS composite film, long conductive nanofibers serve as vertical conductive paths in the nanofiber film, and CNTs serve as horizontal conductive paths in the nanofiber film.

2. The method for preparing a piezoelectric nanofiber flexible composite film with a 3D conductive network according to claim 1, characterized in that, In step (1), the perovskite piezoelectric material is barium titanate, barium zirconate titanate-barium calcium titanate, barium zirconate titanate-barium calcium titanate, barium strontium titanate, bismuth titanate, sodium bismuth titanate, lead titanate, lead strontium titanate, lead zirconate titanate, lanthanum lead zirconate titanate, lead magnesium niobate, or potassium sodium niobate; the piezoelectric semiconductor material is zinc oxide.

3. The method for preparing a piezoelectric nanofiber flexible composite film with a 3D conductive network according to claim 1 or 2, characterized in that, In step (1), the piezoelectric material in the piezoelectric material precursor electrospinning solution is barium titanate. The preparation of the precursor electrospinning solution is as follows: under stirring at room temperature, barium acetate and tetrabutyl titanate are dissolved in a mixture of glacial acetic acid and acetylacetone, and then the polymer carrier PVP is added. After mixing evenly, a uniform BaTiO3 precursor electrospinning solution is prepared. The mass ratio of barium acetate to tetrabutyl titanate is (1~3):1, and the volume ratio of glacial acetic acid to acetylacetone is (2~5):1; the mass fraction of barium acetate in the BaTiO3 precursor electrospinning solution is 10~20wt%; the mass fraction of PVP in the BaTiO3 precursor electrospinning solution is 2~12wt%; and the molecular weight of PVP is 300,000~1,300,000.

4. The method for preparing a piezoelectric nanofiber flexible composite film with a 3D conductive network according to claim 1 or 2, characterized in that, In step (1), the conductive material in the electrospinning solution of the piezoelectric material precursor is antimony tin oxide. The preparation of the precursor electrospinning solution is as follows: under stirring at room temperature, tin chloride pentahydrate and antimony trichloride are dissolved in a mixture of anhydrous ethanol and DMF, and then the polymer carrier PVP is added. After mixing evenly, a uniform ATO precursor electrospinning solution is prepared. The mass ratio of stannous chloride pentahydrate to antimony trichloride is (8~16):1, and the volume ratio of anhydrous ethanol to DMF is 1:(1~4); the mass fraction of stannous chloride pentahydrate in the ATO precursor electrospinning solution is 6~15wt%; the mass fraction of PVP in the ATO precursor electrospinning solution is 6~18wt%; and the molecular weight range of PVP is 300,000~1,300,000.

5. The method for preparing a piezoelectric nanofiber flexible composite film with a 3D conductive network according to claim 1, characterized in that, In step (2), the settling process is: settling at room temperature and pressure for 1~10 minutes; In step (2), the drying temperature is 40~70℃ and the drying time is 5~20min.

6. The method for preparing a piezoelectric nanofiber flexible composite film with a 3D conductive network according to claim 1, characterized in that, In step (2), the mass ratio of carbon source to piezoelectric / conductive nanofiber membrane is 1:(1~10); In step (2), the flow rate of the H2 / Ar mixed gas is 200~300 sccm; In step (2), the volume content of H2 in the mixed gas is 5-20%; In step (2), the calcination temperature is 400~1000℃, the pressure is atmospheric pressure, the heating rate is 0.5~8℃ / min, and the holding time is 1~5h.

7. The method for preparing a piezoelectric nanofiber flexible composite film with a 3D conductive network according to claim 1, characterized in that, In step (2), the carbon source is xylene.

8. The method for preparing a piezoelectric nanofiber flexible composite film with a 3D conductive network according to claim 1, characterized in that, In step (3), the mass fraction of the PDMS solution is 40~95 wt%; In step (3), the settling process is: settling at room temperature and pressure for 1~8 hours; In step (3), the curing temperature is 40~120℃ and the curing time is 2~10h.

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