Film-shaped friction nano-generator and preparation method and application thereof

Abstract

The invention discloses a film-like friction nano generator and a preparation method and application thereof, and the preparation method comprises the steps: uniformly dispersing polyvinylidene fluoride-hexafluoropropylene in a first solvent to form a polymer solution; adding polyimide and molybdenum disulfide into the polymer solution, and uniformly dispersing to obtain a spinning solution; the first solvent is prepared from polyvinylidene fluoride-hexafluoropropylene, polyimide and molybdenum disulfide according to a mass part ratio of (0.9-1.05): (0.2-1.05): (0.03-0.06), the first solvent is prepared from N, N-dimethylformamide and acetone, the first solvent is prepared from polyvinylidene fluoride-hexafluoropropylene, polyimide and molybdenum disulfide according to a mass part ratio of (0.9-1.05): (0.2-1.05): (0.03-0.06), and the second solvent is prepared from a second solvent, a third solvent and a fourth solvent. The maximum open-circuit voltage of the film-shaped friction nano generator obtained by taking the MoS2 / PVDF-HFP / PI composite fiber film as the negative friction electric layer is 327 V, the maximum short-circuit current of the film-shaped friction nano generator is 42 nA, the electric output performance is optimized, and the energy conversion efficiency is improved.

Description

Technical Field

[0001] This invention belongs to the field of flexible electronic devices and smart textile technology, specifically relating to a film-like triboelectric nanogenerator (TENG), its preparation method, and its application. Background Technology

[0002] With the development of the Internet of Things, smart wearables, and flexible electronics, a large number of distributed sensing nodes, emergency monitoring terminals, and smart textiles have placed demands on batteries that are "lightweight, thin, flexible, bendable, and provide stable power over long periods." While existing batteries can provide high energy density, they generally suffer from problems such as incompatibility between rigid structures and flexible devices, limited capacity requiring frequent replacement or charging, high maintenance costs, and reduced reliability under conditions of moisture, sweat, or repeated deformation. These issues make it difficult to meet the long-term, continuous, and low-maintenance power supply requirements of wearable systems.

[0003] Triboelectric nanogenerators (TENGs), as a novel energy harvesting device, can efficiently convert mechanical energy (such as low-frequency dispersed mechanical energy from human movement and environmental vibration) in the environment into electrical energy through the coupling effect of triboelectric charging and electrostatic induction. Their advantages include simple structure, flexible material selection, high output voltage, and flexible design for integration with fabrics. Among them, triboelectric nanogenerators based on the vertical contact-separation mode are widely used because they can generate periodic potential differences and achieve alternating current output. To improve the electrical output performance, two main approaches are used: first, selecting combinations of triboelectric materials with significant differences in electron affinity to enhance interfacial charge transfer; second, introducing a composite dielectric layer to enhance interfacial charging and dielectric polarization capabilities, thereby improving surface charge density and energy conversion efficiency.

[0004] However, existing flexible triboelectric nanogenerators (TENGs) still face multiple bottlenecks in practical applications: On the one hand, single polymer triboelectric layers often suffer from low dielectric constants and insufficient fatigue and environmental resistance, leading to output degradation with varying cycle counts and operating conditions; on the other hand, while simply increasing filler content can improve dielectric properties, it easily causes filler agglomeration, interface defects, and film embrittlement, resulting in decreased flexibility, insufficient structural reliability, and poor processing consistency. Furthermore, under complex service conditions such as repeated contact friction, sweat wetting, humid heat, and temperature fluctuations, existing flexible triboelectric nanogenerators struggle to achieve a balance between high output, high flexibility, and high stability in their material systems and structural designs. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a method for preparing MoS2 / PVDF-HFP / PI composite fiber membranes. This method improves the dielectric constant and β-phase content by doping molybdenum disulfide (MoS2) into polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), and introduces polyimide (PI) to enhance mechanical strength and thermal stability.

[0006] Another object of the present invention is to provide a MoS2 / PVDF-HFP / PI composite fiber membrane obtained by the above method.

[0007] Another objective of this invention is to provide a membrane-based triboelectric nanogenerator, which is assembled based on a MoS2 / PVDF-HFP / PI composite fiber membrane, achieving a balance between the electrical output performance and mechanical properties of the triboelectric nanogenerator (TENG) in a composite system reinforced with molybdenum disulfide and polyimide.

[0008] The objective of this invention is achieved through the following technical solution.

[0009] A method for preparing a MoS2 / PVDF-HFP / PI composite fiber membrane includes: uniformly dispersing polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) in a first solvent to form a polymer solution; adding polyimide (PI) and molybdenum disulfide (MoS2) to the polymer solution and uniformly dispersing them to obtain a spinning solution; spinning the spinning solution into a membrane; and drying the membrane after spinning to obtain a MoS2 / PVDF-HFP / PI composite fiber membrane, wherein the ratio of polyvinylidene fluoride-hexafluoropropylene, polyimide, and molybdenum disulfide by mass parts is (0.9~1.05):(0.2~1.05):(0.03~0.06), and the first solvent includes N,N-dimethylformamide (DMF) and acetone.

[0010] In the above technical solution, the ratio of polyvinylidene fluoride-hexafluoropropylene, polyimide and molybdenum disulfide by mass parts is (0.9~1.05):(0.5~0.7):(0.03~0.06).

[0011] In the above technical solution, the ratio of N,N-dimethylformamide to acetone in the first solvent by volume is (1~3):(1~3).

[0012] In the above technical solution, the ratio of polyvinylidene fluoride-hexafluoropropylene to the first solvent by mass parts is (15~18):(85~82).

[0013] In the above technical solution, the molybdenum disulfide is polycrystalline and its microstructure is flower-like.

[0014] In the above technical solution, the preparation method of molybdenum disulfide (MoS2) includes: mixing thiourea, ammonium molybdate and water evenly to obtain a mixed solution; adjusting the pH of the mixed solution to 1.5~2.5; adding hexadecyltrimethylammonium bromide (CTAB) to obtain a reactant; transferring the reactant to a reaction vessel, sealing it, and reacting it at a constant temperature of 180~220℃ for 22~26h; after the reaction is completed, cooling it to room temperature, centrifuging, washing, and drying to obtain molybdenum disulfide (MoS2); wherein the mass fractions of thiourea, ammonium molybdate, hexadecyltrimethylammonium bromide and water are in the ratio of (3~5):(2~3):(0.1~0.3):(90~100), where the mass fractions are in g and the volume fractions are in mL.

[0015] In the above technical solution, the reactants are transferred to the reaction vessel, so that the reactants occupy 60-80% of the internal volume of the reaction vessel, and then the vessel is sealed.

[0016] In the above technical solution, the method of spinning the spinning solution into a film is electrospinning, the voltage applied to the electrospinning is 20~22kV, and the feed flow rate of the electrospinning is 0.3~0.8mL / h.

[0017] The above technical solution yields a MoS2 / PVDF-HFP / PI composite fiber membrane.

[0018] A membrane-like triboelectric nanogenerator includes: a negative electrode layer, a positive triboelectric layer, and a negative triboelectric layer, which are arranged in parallel, with the positive and negative triboelectric layers spaced apart. The negative electrode layer is connected to the side of the negative triboelectric layer away from the positive triboelectric layer. The negative triboelectric layer is a MoS2 / PVDF-HFP / PI composite fiber membrane.

[0019] In the above technical solution, the positive triboelectric layer is aluminum foil.

[0020] In the above technical solution, the negative electrode layer includes a copper electrode.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] 1. The maximum open-circuit voltage of the film triboelectric nanogenerator of the present invention is 327V, and the maximum short-circuit current is 42nA, which optimizes the electrical output performance and improves the energy conversion efficiency.

[0023] 2. The MoS2 / PVDF-HFP / PI composite fiber membrane of the present invention improves the dielectric constant and β phase content by doping molybdenum disulfide (MoS2), and introduces polyimide (PI) to enhance mechanical strength and thermal stability, thereby achieving a balance between electrical output performance and mechanical properties in the composite system reinforced by doping molybdenum disulfide and introducing polyimide. Attached Figure Description

[0024] Figure 1 The XRD pattern of molybdenum disulfide (MoS2) in Example 1;

[0025] Figure 2 The images show (a) a morphology image, (b) a magnified view, and (c) an EDS image of the MoS2 / PVDF-HFP / PI composite fiber membrane obtained in Example 1.

[0026] Figure 3 The open-circuit voltage and short-circuit current of the film-type TENGs obtained in Examples 2-1 to 2-5 are shown in Figure 2-1 to 2-5.

[0027] Figure 4 The β phase fraction of the MoS2 / PVDF-HFP / PI composite fiber membranes obtained in Examples 3-1 to 3-5;

[0028] Figure 5 The dielectric constant and dielectric loss of the MoS2 / PVDF-HFP / PI composite fiber membranes obtained in Examples 3-1 to 3-5 are shown in Figures 3-1 to 3-5.

[0029] Figure 6 The open-circuit voltage and short-circuit current of the film-type TENGs obtained in Examples 3-1 to 3-5 are shown in Figure 3-1 to 3-5.

[0030] Figure 7 The TG curves are for the PVDF-HFP membrane obtained in Example 2-1, polyimide, the MoS2 / PVDF-HFP composite fiber membrane obtained in Example 2-3, and the MoS2 / PVDF-HFP / PI composite fiber membrane obtained in Example 3-3.

[0031] Figure 8 Stress-strain curves of the PVDF-HFP membrane obtained in Example 2-1, the MoS2 / PVDF-HFP composite fiber membrane obtained in Example 2-3, and the MoS2 / PVDF-HFP / PI composite fiber membrane obtained in Example 3-3 are shown.

[0032] Figure 9 This is a schematic diagram of the structure of a membrane triboelectric nanogenerator. Detailed Implementation

[0033] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0034] This invention uses polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) as a substrate and prepares a MoS2 / PVDF-HFP / PI composite fiber membrane by doping molybdenum disulfide (MoS2) and polyimide (PI), which is then assembled into a triboelectric nanogenerator (TENG).

[0035] Sources of materials used in this invention:

[0036] Polyvinylidene fluoride-hexafluoropropylene (granules, PVDF-HFP, Mw=455000), thiourea (CH4N2S), ammonium molybdate tetrahydrate ((NH4)6Mo7O) 24 • 4H2O) and polyimide (PI, number average molecular weight 70,000) were purchased from Shanghai Aladdin Biochemical Technology Co., Ltd. (analytical grade).

[0037] The supplier of hexadecyltrimethylammonium bromide (CTAB) was Shanghai Maclean Biochemical Co., Ltd. (analytical grade).

[0038] The hydrochloric acid and N,N-dimethylformamide (DMF) were purchased from Tianjin Jiangtian Chemical Technology Co., Ltd. (analytical grade), and the concentration of HCl in the hydrochloric acid was 36 wt%.

[0039] The aluminum foil was purchased from the High Purity Metal Materials Research Institute (thickness 0.01mm, purity 99.9%).

[0040] The source of the instruments used in this invention:

[0041] The electrospinning machine (model JDF05) was purchased from Changsha Nayi Instrument Technology Co., Ltd.

[0042] The electrometer (model Keithley 6517B) was purchased from Keithley Instruments, Inc., USA.

[0043] The thermal field emission scanning electron microscope (model Gemini SEM500) was purchased from ZEISS GmbH, Germany.

[0044] The X-ray diffractometer (model D8 Discover) was purchased from BRUKER GmbH, Germany.

[0045] The dielectric impedance spectrometer (model Alpha-A) was purchased from Novocontrol GmbH, Germany.

[0046] The Fourier transform infrared spectrometer (model Nicolet iS10) was purchased from Thermo Fisher Scientific, Inc., USA.

[0047] The thermogravimetric analyzer (model TG 209 F3 Tarsus) was purchased from NETZSCH GmbH, Germany.

[0048] The universal power press (model HT-2402) was purchased from Hongda Instruments Co., Ltd. in Taiwan, China.

[0049] Example 1

[0050] A method for preparing a MoS2 / PVDF-HFP / PI composite fiber membrane includes: mixing polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP, granules) and a first solvent, and magnetically stirring at 60°C for 4 hours until the PVDF-HFP is uniformly dispersed in the first solvent to form a polymer solution; adding polyimide (PI, powder) to the polymer solution, continuing stirring for 2 hours until dissolved, then adding molybdenum disulfide and ultrasonicating for 30 minutes (ultrasonic cleaning machine power is 300W, frequency is 40kHz) until uniformly dispersed to obtain a spinning solution; and spinning the spinning solution into a membrane using an electrospinning machine (the voltage applied during electrospinning is 20kV). The fiber feed rate was 0.5 mL / h. After spinning, the fiber was dried in a vacuum drying oven at 60℃ for 12 h to remove residual solvent, resulting in a MoS2 / PVDF-HFP / PI composite fiber membrane. The membrane contained in the following composition: by mass, the ratio of polyvinylidene fluoride-hexafluoropropylene, polyimide, and molybdenum disulfide was 1:0.6:0.05; the first solvent was a mixture of N,N-dimethylformamide (DMF) and acetone, with a volume ratio of 2:1; and the ratio of polyvinylidene fluoride-hexafluoropropylene to the first solvent was 16:84. The molybdenum disulfide was polycrystalline with a flower-like microstructure.

[0051] The preparation method of molybdenum disulfide (MoS2) includes: mixing thiourea (4.5g), ammonium molybdate, and deionized water, and stirring magnetically for 35min until completely dissolved to obtain a mixed solution; adjusting the pH of the mixed solution to 2 with hydrochloric acid, then adding hexadecyltrimethylammonium bromide (CTAB), stirring for 10min until uniformly dispersed, transferring to a 50mL polytetrafluoroethylene liner, adding deionized water to 70% of the liner volume, and sealing in a stainless steel reactor; placing the stainless steel reactor in an oven and reacting at a constant temperature of 200℃ for 24h. After the reaction was completed, the mixture was naturally cooled to room temperature, centrifuged at 8000 r / min for 10 min, washed three times each with deionized water and anhydrous ethanol, and dried under vacuum at 60℃ for 12 h to obtain molybdenum disulfide (MoS2). The mass ratio of thiourea, ammonium molybdate, hexadecyltrimethylammonium bromide, and deionized water in the mixed solution was 4.5:2.5:0.3:100. The mass fractions are in g and the volume fractions are in mL. The ammonium molybdate was ammonium molybdate tetrahydrate.

[0052] X-ray diffraction analysis was performed on molybdenum disulfide (MoS2) (monomer) in Example 1, and its XRD pattern is shown below. Figure 1 As shown. By Figure 1 It can be seen that characteristic peaks appear at 2θ=14.01°, 33.45°, 39.74° and 58.91° in the XRD test results, which correspond to the (002), (100), (103) and (110) crystal planes of molybdenum disulfide. There are no impurity peaks, indicating that the molybdenum disulfide monomer product was successfully prepared and has high purity.

[0053] The MoS2 / PVDF-HFP / PI composite fiber membrane obtained in Example 1 was tested by scanning electron microscopy, and the SEM results are as follows: Figure 2 As shown. (a) is a morphology diagram of the MoS2 / PVDF-HFP / PI composite fiber membrane, (b) is a magnified view of (a), and (c) is an elemental distribution (EDS) diagram of the MoS2 / PVDF-HFP / PI composite fiber membrane. Figure 2 (a) and Figure 2 As shown in (b), the MoS2 / PVDF-HFP / PI composite fiber membrane obtained in Example 1 exhibits a uniform nanofiber network structure, with molybdenum disulfide displaying a flower-like morphology and uniformly loaded on the surface and interior of the fibers, forming a rough surface to increase the specific surface area (specific surface area is positively correlated with electrical output performance); Figure 2 As shown in (c), C, F, Mo and S elements are uniformly distributed in the MoS2 / PVDF-HFP / PI composite fiber membrane, proving that molybdenum disulfide was successfully doped.

[0054] Example 2-1

[0055] like Figure 9 As shown, a film-like triboelectric nanogenerator (film TENG) includes: a negative electrode layer, a positive triboelectric layer, and a negative triboelectric layer. The negative electrode layer, positive triboelectric layer, and negative triboelectric layer are arranged in parallel, with the positive and negative triboelectric layers spaced apart. The negative electrode layer is connected to the side of the negative triboelectric layer away from the positive triboelectric layer. The negative triboelectric layer is a PVDF-HFP film. The positive triboelectric layer is an aluminum foil (3×3cm). 2 The negative electrode layer is a copper electrode (3×3cm). 2 The positive triboelectric layer also functions as a positive electrode layer.

[0056] The above-mentioned method for preparing a film-shaped triboelectric nanogenerator includes: attaching an acrylic substrate to the top surface of the positive triboelectric layer and the bottom surface of the negative electrode layer, and placing the negative triboelectric layer on the top surface of the negative electrode layer to obtain a film-shaped triboelectric nanogenerator.

[0057] The method for preparing the PVDF-HFP membrane is basically the same as that in Example 1, “Method for preparing MoS2 / PVDF-HFP / PI composite fiber membrane”. The only difference is that molybdenum disulfide (MoS2) and polyimide are not added in this example, that is, “the polymer solution is used as the spinning solution”.

[0058] Examples 2-2 to 2-5

[0059] A membrane-like triboelectric nanogenerator is basically the same as that in Example 2-1, except that the negative triboelectric layer is a MoS2 / PVDF-HFP composite fiber membrane. The method for preparing the MoS2 / PVDF-HFP composite fiber membrane is basically the same as that in Example 1, “Method for preparing MoS2 / PVDF-HFP / PI composite fiber membrane”. The only difference is that polyimide is not added in Examples 2-2 to 2-5, and the amount of molybdenum disulfide (MoS2) added is different, that is, “the ratio of polyvinylidene fluoride-hexafluoropropylene and molybdenum disulfide by mass parts is X”, where X is shown in Table 1.

[0060] Table 1

[0061]

[0062] The dielectric properties of the PVDF-HFP membrane obtained in Example 2-1 and the MoS2 / PVDF-HFP composite fiber membranes obtained in Examples 2-2 to 2-5 were tested, as shown in Table 2. It was found that the MoS2 / PVDF-HFP composite fiber membrane obtained in Example 2-3 had the highest dielectric constant of 3.36. When the amount of molybdenum disulfide added was greater than that in Examples 2-3, the resulting MoS2 / PVDF-HFP composite fiber membrane exhibited agglomeration and localized clustering due to the excessive molybdenum disulfide content, resulting in a decrease in dielectric properties.

[0063] Table 2

[0064]

[0065] The electrical output performance of the film-shaped TENGs (triboelectric nanogenerators) obtained in Examples 2-1 to 2-5 was tested under the following conditions: An acrylic substrate with a positive triboelectric layer attached to the film-shaped TENG was fixed to a linear motor moving part, with the positive and negative triboelectric layers facing each other. The acrylic substrate with the negative electrode layer attached was fixed. The positive triboelectric layer (positive electrode layer) of the film-shaped TENG was connected to the positive terminal of an electrometer via a copper wire, and the negative electrode layer was connected to the negative terminal of the electrometer via another copper wire. The linear motor was started to cause the positive and negative triboelectric layers to periodically contact and separate. The open-circuit voltage and short-circuit current were obtained through the electrometer. The linear motor was set to a frequency of 3Hz and provided a pressure of 25N.

[0066] The open-circuit voltage and short-circuit current of the film-type TENGs obtained in Examples 2-1 to 2-5 are shown in Table 2 and Figure 3 As shown. Among them, Figure 3 (a) is the open-circuit voltage. Figure 3 (b) represents the short-circuit current. From... Figure 3 It was found that when the mass ratio of polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) to molybdenum disulfide in the spinning solution was 1:0.05, the open-circuit voltage of the film-shaped TENG obtained in Examples 2-3 increased to 208V, and the short-circuit current increased to 31µA. That is, the film-shaped TENG obtained in Examples 2-3 exhibited the best electrical output performance. The improvement in the electrical output performance of the film-shaped TENG is mainly attributed to the increase in the β-phase fraction (F) in PVDF-HFP after the addition of molybdenum disulfide. β The increase of β phase fraction (F) and the improvement of dielectric constant of MoS2 / PVDF-HFP composite fiber membrane, in which the β phase fraction (F) β The electrical output performance of the film-like TENG is positively correlated (measured by Fourier transform infrared spectroscopy at 840 cm⁻¹ of the negative triboelectric layer). -1 and 1276cm -1 The intensity of the characteristic peak of the β phase was determined, and the β phase fraction was calculated. For details on the calculation method of the β phase fraction, please refer to the references "KAVARTHAPU VS, GRAHAM SA, MANCHI P, et al. Electrospun ZnSnO3 / PVDF-HFP Nanofibrous Triboelectric Films for Efficient Mechanical Energy Harvesting [J]. Advanced Fiber Materials, 2023, 5(5): 1685-98." and "MANCHI P,GRAHAM SA, PATNAM H, et al. High-efficiency Poly(vinylidene fluoride-co-hexafluoropropylene) loaded 3D marigold flower-like bismuth tungstate triboelectric films for mechanical energy harvesting and sensing applications[J]. Small, 2022, 18(20), 2200822.").

[0067] Furthermore, when the amount of molybdenum disulfide added to the spinning solution exceeded that in Examples 2-3, the electrical output performance of the resulting film-like TENG gradually decreased to 132V and 21µA (film-like TENGs of Examples 2-5 in Table 2). Thus, the film-like TENGs obtained in Examples 2-3 exhibited the highest electrical output performance.

[0068] Example 3-1

[0069] A membrane-like triboelectric nanogenerator is basically the same as in Example 2-1, except that the negative triboelectric layer in this example is a MoS2 / PVDF-HFP / PI composite fiber membrane. The method for preparing the MoS2 / PVDF-HFP / PI composite fiber membrane is basically the same as in Example 1, except that the amount of molybdenum disulfide (MoS2) and polyimide (PI) added is different, that is, "by mass parts, the ratio of polyvinylidene fluoride-hexafluoropropylene, polyimide and molybdenum disulfide is 1:0.2:0.05".

[0070] Example 3-2

[0071] A membrane-like triboelectric nanogenerator is basically the same as that in Example 3-1, except that the amount of molybdenum disulfide and polyimide added in the "method for preparing MoS2 / PVDF-HFP / PI composite fiber membrane" in this example is different, that is, "by mass parts, the ratio of polyvinylidene fluoride-hexafluoropropylene, polyimide and molybdenum disulfide is 1:0.4:0.05".

[0072] Example 3-3

[0073] A membrane-like triboelectric nanogenerator is basically the same as that in Example 3-1, except that the MoS2 / PVDF-HFP / PI composite fiber membrane in this example is the MoS2 / PVDF-HFP / PI composite fiber membrane obtained in Example 1.

[0074] Examples 3-4

[0075] A membrane-like triboelectric nanogenerator is basically the same as that in Example 3-1, except that the amount of molybdenum disulfide and polyimide added in the "method for preparing MoS2 / PVDF-HFP / PI composite fiber membrane" in this example is different, that is, "by mass parts, the ratio of polyvinylidene fluoride-hexafluoropropylene, polyimide and molybdenum disulfide is 1:0.8:0.05".

[0076] Examples 3-5

[0077] A membrane-like triboelectric nanogenerator is basically the same as that in Example 3-1, except that the amount of molybdenum disulfide and polyimide added in the "method for preparing MoS2 / PVDF-HFP / PI composite fiber membrane" in this example is different, that is, "by mass parts, the ratio of polyvinylidene fluoride-hexafluoropropylene, polyimide and molybdenum disulfide is 1:1:0.05".

[0078] Figure 4 The β phase fraction (F) of the MoS2 / PVDF-HFP / PI composite fiber membranes obtained in Examples 3-1 to 3-5 is given. β From Table 3 and Figure 4 It can be seen that the β-phase content in the MoS2 / PVDF-HFP / PI composite fiber membrane obtained in Examples 3-3 reached a peak of 75.09%. This is because the polar groups in polyimide can promote the orderly arrangement of PVDF molecular chains in polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), which is beneficial to improving the β-phase content and the corresponding electrochemical output performance of the membrane-like TENG. However, excessive polyimide (Examples 3-4 and 3-5) inhibited the formation of the β-phase due to phase separation and the increased rigidity of the PVDF molecular chains. This indicates that the addition of polyimide can synergistically increase the β-phase content with molybdenum disulfide.

[0079] Table 3

[0080]

[0081] The dielectric properties of the MoS2 / PVDF-HFP / PI composite fiber membranes obtained in Examples 3-1 to 3-5 were tested at 1 Hz, and the results are as follows: Figure 5 As shown, (a) is the dielectric constant, and (b) is the dielectric loss. The numerical values ​​of the dielectric constant are detailed in Table 3. From Table 3 and... Figure 5 It can be seen that the MoS2 / PVDF-HFP / PI composite fiber membrane obtained in Example 3-3 has the highest dielectric constant of 6.24, mainly attributed to the increased dipole moment due to the enhanced polar groups in the polyimide and the increased β-phase content. Furthermore, the MoS2 / PVDF-HFP / PI composite fiber membranes obtained in Examples 3-1 to 3-5 maintain low loss (dielectric loss <0.1) across the entire frequency range, demonstrating good dielectric balance. Among them, the dielectric loss of the MoS2 / PVDF-HFP / PI composite fiber membrane obtained in Example 3-3 is less than 0.02.

[0082] The electrical output performance of the membrane-like TENGs obtained in Examples 3-1 to 3-5 was tested, and the results are shown in Table 3 and 3. Figure 6 As shown. Among them, Figure 6 (a) is the open-circuit voltage. Figure 6 (b) represents the short-circuit current. (From Table 3 and...) Figure 6It can be seen that, based on mass fractions, when the ratio of polyvinylidene fluoride-hexafluoropropylene, polyimide and molybdenum disulfide is 1:0.6:0.05, the electrical output performance of the film-like TENG obtained in Examples 3-3 reaches the optimal level, with open-circuit voltage and short-circuit current reaching 327V and 42μA, respectively. Figure 6 The diagram illustrates the trends in open-circuit voltage and short-circuit current of the membrane-like TENGs obtained in Examples 3-1 to 3-5: With increasing polyimide (PI) content, the electrical output performance of the membrane-like TENGs initially increases and then decreases. This trend is consistent with the trend of β-phase content in the MoS2 / PVDF-HFP / PI composite fiber membrane; that is, the β-phase content in the MoS2 / PVDF-HFP / PI composite fiber membrane obtained in Example 3-3 is the highest at 75.09%. When the amount of polyimide added is greater than that corresponding to Example 3-3, the β-phase content in the obtained MoS2 / PVDF-HFP / PI composite fiber membrane decreases.

[0083] Thermogravimetric analysis (TG) was performed on the PVDF-HFP membrane obtained in Example 2-1, the polyimide (PI, powder) membrane obtained in Example 2-3, the MoS2 / PVDF-HFP composite fiber membrane obtained in Example 3-3, and the MoS2 / PVDF-HFP / PI composite fiber membrane obtained in Example 3-3. Their TG curves are shown below. Figure 7 As shown. By Figure 7 It can be seen that the PVDF-HFP membrane obtained in Example 2-1 ( Figure 7 "PVDF-HFP" in the text, polyimide ( Figure 7 The thermal stability of the MoS2 / PVDF-HFP composite fiber membrane obtained in Examples 2-3 and 3-3 differs significantly. In comparison, the PVDF-HFP membrane obtained in Example 2-1 begins to lose mass at 430°C, while polyimide begins to lose mass at 380°C, indicating a lower decomposition temperature than the PVDF-HFP membrane obtained in Example 2-1. However, polyimide exhibits less mass loss at higher temperatures (above 600°C), suggesting it is less prone to decomposition at high temperatures. The thermal stability of the MoS2 / PVDF-HFP composite fiber membrane obtained in Example 2-3 is slightly improved compared to the PVDF-HFP membrane obtained in Example 2-1 at high temperatures. The MoS2 / PVDF-HFP / PI composite fiber membranes obtained in Examples 3-3 exhibited excellent thermal stability with minimal mass loss. Their thermal stability at high temperatures was not significantly different from that of polyimide, indicating that polyimide played a significant reinforcing role in the MoS2 / PVDF-HFP / PI composite fiber membrane, thereby improving its heat resistance.

[0084] Tensile tests were conducted on the PVDF-HFP membrane obtained in Example 2-1, the MoS2 / PVDF-HFP composite fiber membrane obtained in Example 2-3, and the MoS2 / PVDF-HFP / PI composite fiber membrane obtained in Example 3-3, respectively, as test membranes. The tensile test conditions were as follows: at room temperature, an 80mm × 20mm test membrane was fixed on the clamps at both ends of a universal tensile testing machine (HT-2402), with a clamp spacing of 50mm. The membrane was stretched at a loading speed of 100mm / min until it fractured, and the stress-strain curves were recorded. The test membrane was one of the PVDF-HFP membrane obtained in Example 2-1, the MoS2 / PVDF-HFP composite fiber membrane obtained in Example 2-3, and the MoS2 / PVDF-HFP / PI composite fiber membrane obtained in Example 3-3. The obtained stress-strain curves are shown below. Figure 8 As shown, by Figure 8 It can be seen that the MoS2 / PVDF-HFP / PI composite fiber membrane obtained in Example 3-3 has a tensile strength of 1.2 MPa and a tensile strain of 81.3%, which is 15 times higher than the tensile strength of the PVDF-HFP membrane obtained in Example 2-1. In contrast, the MoS2 / PVDF-HFP composite fiber membrane obtained in Example 2-3 has a tensile strength of only 0.7 MPa and low ductility. This indicates that the addition of polyimide binds the fibers to form a stable network structure, thereby alleviating stress concentration.

[0085] This invention optimizes dielectric properties by doping with molybdenum disulfide, while simultaneously introducing polyimide (PI) to improve mechanical properties and thermal stability. Studies have shown that the introduction of molybdenum disulfide increases the β-phase content and dielectric constant in PVDF-HFP, while polyimide significantly enhances the tensile strength and thermal stability of the composite fiber membrane. Furthermore, polyimide synergistically enhances dielectric properties with molybdenum disulfide, thereby improving the electrical output performance and environmental adaptability of TENG.

[0086] The present invention has been described above by way of example. It should be noted that any simple modifications, alterations or other equivalent substitutions that can be made by those skilled in the art without creative effort without departing from the core of the present invention fall within the protection scope of the present invention.

Claims

1. A method for preparing a MoS2 / PVDF-HFP / PI composite fiber membrane, characterized in that, include: Polyvinylidene fluoride-hexafluoropropylene is uniformly dispersed in a first solvent to form a polymer solution; Polyimide and molybdenum disulfide were added to the polymer solution and dispersed uniformly to obtain a spinning solution; The spinning solution is spun into a membrane, and after spinning, it is dried to obtain a MoS2 / PVDF-HFP / PI composite fiber membrane. The ratio of polyvinylidene fluoride-hexafluoropropylene, polyimide and molybdenum disulfide by mass is (0.9~1.05):(0.2~1.05):(0.03~0.06). The first solvent includes N,N-dimethylformamide and acetone.

2. The method according to claim 1, characterized in that, The ratio of polyvinylidene fluoride-hexafluoropropylene, polyimide and molybdenum disulfide by mass parts is (0.9~1.05):(0.5~0.7):(0.03~0.06).

3. The method according to claim 1, characterized in that, The ratio of N,N-dimethylformamide to acetone in the first solvent is (1~3):(1~3) by volume.

4. The method according to claim 1, characterized in that, The ratio of the polyvinylidene fluoride-hexafluoropropylene to the first solvent by mass parts is (15~18):(85~82).

5. The method according to claim 1, characterized in that, The method for preparing molybdenum disulfide includes: mixing thiourea, ammonium molybdate, and water evenly to obtain a mixed solution; adjusting the pH of the mixed solution to 1.5-2.5; adding hexadecyltrimethylammonium bromide to obtain a reactant; transferring the reactant to a reaction vessel, sealing it, and reacting it at a constant temperature of 180-220℃ for 22-26 hours; after the reaction is completed, cooling it to room temperature, centrifuging, washing, and drying to obtain molybdenum disulfide; wherein the mass fractions of thiourea, ammonium molybdate, hexadecyltrimethylammonium bromide, and water are in the ratio of (3-5):(2-3):(0.1-0.3):(90-100), where mass fractions are in g and volume fractions are in mL.

6. The method according to claim 5, characterized in that, The reactants are transferred to a reaction vessel, making the reactants occupy 60-80% of the internal volume of the reaction vessel, and then sealed.

7. The method according to claim 1, characterized in that, The method for spinning the spinning solution into a film is electrospinning, wherein the voltage applied during electrospinning is 20~22kV, and the feed flow rate during electrospinning is 0.3~0.8mL / h.

8. The MoS2 / PVDF-HFP / PI composite fiber membrane obtained by the method according to any one of claims 1 to 7.

9. A film-like triboelectric nanogenerator, characterized in that, include: The membrane comprises a negative electrode layer, a positive triboelectric layer, and a negative triboelectric layer, arranged in parallel, with the positive and negative triboelectric layers spaced apart. The negative electrode layer is connected to the side of the negative triboelectric layer away from the positive triboelectric layer. The negative triboelectric layer is the MoS2 / PVDF-HFP / PI composite fiber membrane as described in claim 8.

10. The film-like triboelectric nanogenerator according to claim 9, characterized in that, The positive triboelectric layer is an aluminum foil, and the negative electrode layer includes a copper electrode.

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