Polyimide and potassium-sodium niobate composite film, preparation method and piezoelectric nanogenerator

Abstract

This invention discloses a polyimide-potassium sodium niobate composite film, its preparation method, and a piezoelectric nanogenerator, belonging to the field of nanogenerator technology. The method includes: ball milling and mixing Nb₂O₅, Na₂CO₃, and K₂CO₃ until uniform and drying; grinding, sieving, calcining, and grinding again to obtain potassium sodium niobate ceramic nanoparticle fillers; mixing anhydrous N,N-dimethylformamide solution and 4,4'-diaminodiphenyl ether powder until uniform; adding pyromellitic dianhydride powder in multiple batches; stirring thoroughly after reaction; adding potassium sodium niobate ceramic nanoparticle fillers; repeated ultrasonication and stirring; heating and stirring reaction; casting; vacuum drying; gradient temperature calcination; and cooling to obtain a polyimide-potassium sodium niobate composite film; the assembled piezoelectric nanogenerator combines... d 31 and d 33 With dual operating modes, it can collect and utilize micro-energy in various application environments, and its power density is significantly enhanced compared to the traditional single operating mode; it also maintains excellent operating stability at a high temperature of 150℃.

Description

Technical Field

[0001] This invention belongs to the field of nanogenerator technology, specifically relating to a polyimide-potassium sodium niobate composite film and its preparation method, and a piezoelectric nanogenerator. Background Technology

[0002] The global energy crisis and the growing demand for sustainable energy solutions have fueled significant interest in piezoelectric energy harvesting technology. Among these technologies, the piezoelectric nanogenerator (PENG) can directly convert environmental mechanical energy into usable electrical energy through piezoelectric conversion. It features a simple structure, high energy conversion efficiency, and can harvest energy from various sources, including biomechanical motion, acoustic vibration, and environmental mechanical disturbances. This versatility, along with compatibility with various electronic systems, makes the PENG an ideal candidate for self-powered sensor networks and implantable medical devices.

[0003] However, achieving reliable performance under harsh conditions, especially at high temperatures, remains a significant challenge for applications such as industrial monitoring, aerospace systems, and fire early warning sensors. To address these issues, developing material systems with high thermal stability and mechanical toughness is crucial for the development of PENGs. Polyimide, due to its excellent thermal stability (decomposition temperature > 400°C) and mechanical robustness, has become an ideal matrix material for high-temperature applications. Chinese patent application CN106380845B discloses a sandwich-structured polyimide composite film co-doped with layered boron nitride and spherical alumina, which significantly improves insulation and mechanical properties; however, its purpose is not piezoelectric applications, nor does it involve piezoelectric fillers or dual-mode output. Chinese patent application CN104046023B proposes a method for preparing a high-dielectric polyimide / barium titanate composite film, aiming to improve the dielectric constant; however, its filler system does not possess piezoelectric response, and it does not address high-temperature piezoelectric properties. Chinese patent application CN117362720A improves the energy storage performance of polyimide by introducing strontium niobate and titanium dioxide nanosheets, but its focus is on improving dielectric energy storage density rather than piezoelectric power generation capability, and it does not involve the crystal structure control and working mode design of piezoelectric fillers.

[0004] Traditional polyimide-based composites still use lead-based ceramics, while among lead-free alternatives, potassium sodium niobate ceramics are preferred due to their high piezoelectric response. d 33 ≈120-150 pC / N) and a relatively high Curie temperature (T cPotassium sodium niobate ceramics show particular application potential at temperatures above 300℃. When combined with polyimide materials, they exhibit the potential as high-temperature stable piezoelectric composites. However, usually only a single type can be obtained. d 33 The electrical output of the mode cannot be obtained simultaneously in d 31 Evaluation of electrical output performance under operating mode. Summary of the Invention

[0005] To overcome the shortcomings of the prior art, the present invention aims to provide a polyimide-potassium sodium niobate composite film, its preparation method, and a piezoelectric nanogenerator, thereby addressing the issues of low stability and inability to simultaneously achieve the desired performance in existing piezoelectric nanogenerators operating at high temperatures. d 31 and d 33 Technical issues related to the working mode.

[0006] To achieve the above objectives, the present invention employs the following technical solution: This invention discloses a method for preparing a polyimide-sodium niobate composite film, comprising the following steps: 1) Solid Nb2O5, solid Na2CO3 and solid K2CO3 were ball-milled and mixed evenly, and then dried, ground, sieved, calcined and ground again to obtain potassium sodium niobate ceramic nanoparticle filler. 2) Add the potassium sodium niobate ceramic nanoparticle filler obtained in step 1) to the polyamic acid solution, and perform ultrasonic stirring multiple times until the mixture is uniform. After heating and stirring reaction, a binary casting precursor solution of polyamic acid and potassium sodium niobate is obtained. After casting treatment of the binary casting precursor solution of polyamic acid and potassium sodium niobate, a composite film of polyamic acid and potassium sodium niobate is obtained. After vacuum drying treatment of the composite film of polyamic acid and potassium sodium niobate, it is calcined by gradient temperature rise treatment. After cooling, a composite film of polyimide and potassium sodium niobate is obtained.

[0007] Preferably, in step 1), the molar ratio of solid Nb2O5, solid Na2CO3 and solid K2CO3 is (1.9-2.1):(0.95-1.05):(0.95-1.05).

[0008] Preferably, in step 1), the conditions for ball milling include: adding ball stones and alcohol to the ball mill jar, and ball milling them thoroughly for 6-12 hours; The calcination conditions include: starting from room temperature, heating to 850-950℃ at a rate of 3-6℃ / min, and holding the temperature for 4-8 hours; the time for re-grinding is 10-30 minutes.

[0009] Preferably, in step 2), the method for preparing the polyamic acid solution includes: mixing anhydrous N,N-dimethylformamide solution and 4,4'-diaminodiphenyl ether powder evenly to obtain a mixed solution; adding pyromellitic dianhydride powder to the mixed solution in multiple portions; and stirring the mixture thoroughly to obtain the polyamic acid solution. The ratio of anhydrous N,N-dimethylformamide solution, 4,4'-diaminodiphenyl ether powder, and pyromellitic dianhydride powder is (35~50) mL : (3~5) g : (3.28~4.28) g; the method of adding pyromellitic dianhydride powder is: add 1 g of pyromellitic dianhydride powder every 20 min; the reaction time is 1~2 h with thorough stirring.

[0010] Preferably, in step 2), the volume of the potassium sodium niobate ceramic nanoparticle filler is 5% to 30% of the total volume of the 4,4'-diaminodiphenyl ether powder, pyromellitic dianhydride powder, and potassium sodium niobate ceramic nanoparticle filler.

[0011] Preferably, in step 2), the conditions for repeated sonication and stirring include: sonication for 10-30 minutes, followed by stirring for 10-30 minutes, and repeating this cycle 5-10 times; then continue stirring for 6-12 hours, followed by sonication at room temperature for 0.5-1 hour; The conditions for heating and stirring the reaction include: heating and stirring at 30~60℃ for 10~30 min.

[0012] Preferably, in step 2), the casting conditions include: injecting a binary casting precursor solution of polyamic acid and potassium sodium niobate into the guide plate of an adjustable doctor blade, adjusting the doctor blade height to 10~20 μm, and casting on a clean glass plate at a speed of 10~20 cm / min.

[0013] Preferably, in step 2), the vacuum drying conditions include: evacuating at 0.4-0.8 MPa for 8-12 hours at 30-60°C; the gradient heating calcination conditions include: calcining at 80°C, 100°C, 120°C, 150°C, 180°C and 300°C for 1-2 hours respectively.

[0014] The present invention also discloses a polyimide-potassium sodium niobate composite film, which is prepared by the above-described method for preparing polyimide-potassium sodium niobate composite films.

[0015] This invention also discloses a piezoelectric nanogenerator, comprising the aforementioned polyimide and potassium sodium niobate composite film; the piezoelectric nanogenerator combines... d 31 Work mode and d 33 Work mode.

[0016] Compared with the prior art, the present invention has the following beneficial effects: This invention discloses a method for preparing a polyimide-potassium sodium niobate composite film. By integrating a polyimide matrix with R-T biphase potassium sodium niobate ceramic nanoparticles containing both trigonal (R-phase) and tetragonal (T-phase) crystal structures, it effectively solves the problems of insufficient device stability and single operating mode under high-temperature environments. Specifically, in the preparation of the potassium sodium niobate ceramic nanoparticles, solid Nb₂O₅, solid Na₂CO₃, and solid K₂CO₃ are ball-milled, mixed uniformly, and dried. After grinding, sieving, calcination, and further grinding, the potassium sodium niobate ceramic nanoparticles are ensured to form an R-T biphase structure, which simultaneously supports… d 31 Work mode and d 33 The key foundation of the working mode is that the R phase and T phase are two key piezoelectric phases of potassium sodium niobate near the quasi-isomorphic phase boundary. This coexistence of two phases lowers the energy barrier during polarization, making it easier for the domains to orient and move when the material is subjected to external stress. The coupling of the R phase and T phase at the lattice scale allows the filler particles to respond simultaneously to stress perpendicular to the film direction. d 33 (pattern) and in-plane tensile or bending stress ( d 31 This approach fundamentally solves the problem of the single working mode of traditional piezoelectric composite materials. Simultaneously, the high Curie temperature characteristics of potassium sodium niobate ceramic nanoparticle fillers provide material assurance for high-temperature stability. The polyimide-potassium sodium niobate composite film maintains structural integrity and piezoelectric activity at high temperatures, supporting… d 31 Work mode and d 33 Synergistic output of operating modes. The introduction of R and T biphase potassium sodium niobate ceramic nanoparticle fillers effectively solves the problem of single operating modes, enabling the device to simultaneously activate transverse and longitudinal piezoelectric responses under bending or compressive deformation; the excellent thermal stability of the polyimide matrix combined with the optimized fabrication process ensures that the device maintains reliable performance in high-temperature environments, thereby significantly broadening the application scenarios of energy harvesting.

[0017] This invention discloses a polyimide-potassium sodium niobate composite film. By employing potassium sodium niobate ceramic nanoparticles with an R and T dual-phase crystal structure as piezoelectric fillers and utilizing an optimized preparation process, highly uniform dispersion and strong interfacial bonding of the filler within the polyimide matrix are achieved. This composite film not only inherits the excellent high-temperature thermal stability and mechanical toughness of polyimide but also possesses… d 31 Work mode and d33 The synergistic output capability of its operating modes enables it to efficiently harvest energy under multi-dimensional mechanical deformations such as bending and compression. Furthermore, precisely controlled casting and gradient heat treatment processes ensure the density and thickness uniformity of the thin film structure, significantly improving its dielectric strength and environmental adaptability. This polyimide-potassium sodium niobate composite film, as the core functional material of a piezoelectric nanogenerator, successfully solves the key technical challenges of insufficient device stability and limited operating modes under high-temperature environments, providing a high-performance, environmentally friendly material solution for demanding applications such as high-temperature self-powered sensing, industrial monitoring, and aerospace.

[0018] This invention discloses a piezoelectric nanogenerator. In the assembly step, after the polyimide and potassium sodium niobate composite film is cut, the copper electrode can be specifically a circular metal foil. The wire is spirally wound and attached to the electrode, and the assembly is completed together with the polyimide encapsulation layer. The encapsulation layer provides additional thermal and mechanical protection. By integrating the polyimide matrix with the R and T biphase potassium sodium niobate ceramic filler through a synergistic design, the low stability and inability to achieve both at high temperature operating environments are effectively solved. d 31 Work mode and d 33 The issue of operating mode. The introduction of R and T dual-phase potassium sodium niobate ceramic fillers ensures simultaneous activation in the composite material. d 31 Work mode and d 33 The operating mode enables the device to harvest mechanical energy from multiple dimensions; the excellent thermal stability of the polyimide matrix, combined with the optimized fabrication process, provides stable structural support for high-temperature environments, thereby achieving the effect of stable dual-mode power output within the range of 50~180°C. Attached Figure Description

[0019] Figure 1 X-ray diffraction patterns of polyimide-potassium sodium niobate composite films with different potassium sodium niobate doping amounts according to the present invention; Figure 2 Infrared spectra of polyimide-potassium sodium niobate composite films with different potassium sodium niobate doping amounts according to the present invention; Figure 3 Scanning electron microscope image (a) of pure polyimide film and scanning electron microscope image (b) of polyimide and potassium sodium niobate composite film prepared in Example 1. Figure 4 To provide the piezoelectric nanogenerators of this invention with different potassium, sodium, and niobate doping amounts in d 33 Operating cycle diagram under the mode (a); short-circuit current under 5Hz and 10N load (b); and open-circuit voltage under 5Hz and 10N load (c). Figure 5 To provide the piezoelectric nanogenerators of this invention with different potassium, sodium, and niobate doping amounts in d 31 Operating cycle diagram under the mode (a); short-circuit current under 5Hz and 10N load (b); and open-circuit voltage under 5Hz and 10N load (c). Figure 6 This invention discloses the working mechanism of the piezoelectric nanogenerator in different piezoelectric modes; Figure 7 The piezoelectric nanogenerator prepared in Example 1 of this invention is shown in the following figures: open-circuit voltage output at different operating temperatures under test force conditions of 5N and 10Hz (a); short-circuit current output at different operating temperatures under test force conditions of 5N and 10Hz (b); voltage response and recovery time test figures at operating temperatures of room temperature and 150℃ (c); and long-term voltage output stability test figure at operating temperature of 150℃ (d). Detailed Implementation

[0020] The technical solution of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] Unless otherwise specified, all embodiments and preferred embodiments mentioned herein can be combined to form new technical solutions.

[0022] Unless otherwise specified, all the technical features and preferred features mentioned herein can be combined to form new technical solutions.

[0023] In this invention, unless otherwise specified, percentage (%) or parts refer to weight percentage or parts relative to the composition.

[0024] Unless otherwise specified, the components or preferred components involved in this invention can be combined with each other to form new technical solutions.

[0025] In this invention, unless otherwise specified, the numerical range "a~b" is an abbreviation for any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "6~22" indicates that the real numbers between "6~22" are already included in this document, and "6~22" is simply an abbreviation for these numerical combinations.

[0026] The "scope" disclosed in this invention can be in the form of a lower limit and an upper limit, and can be one or more lower limits and one or more upper limits, respectively.

[0027] In this invention, the term "and / or" as used herein refers to any combination of one or more of the associated listed items, as well as all possible combinations, and includes such combinations.

[0028] Unless otherwise stated, the technical and scientific terms used herein have the same meanings as those familiar to those skilled in the art. Any methods or materials similar to or equivalent to those described herein may also be used in this invention.

[0029] In this invention specification, PI represents polyimide (PI); KNN represents sodium potassium niobate (KNN); PI-5KNN represents a polyimide-sodium potassium niobate composite film with a total volume doping amount of 5 vol.% of sodium potassium niobate (KNN); PI-10KNN represents a polyimide-sodium potassium niobate composite film with a total volume doping amount of 10 vol.% of KNN; PI-15KNN represents a polyimide-sodium potassium niobate composite film with a total volume doping amount of 15 vol.% of KNN; PI-20KNN represents a polyimide-sodium potassium niobate composite film with a total volume doping amount of 20 vol.% of KNN; and PI-30KNN represents a polyimide-sodium potassium niobate composite film with a total volume doping amount of 30 vol.% of KNN.

[0030] The dij disclosed in this invention specification is the piezoelectric constant, which has two subscripts. The first subscript i indicates the polarization direction of the crystal, denoted as i, and i can take the values ​​1, 2, and 3. The second subscript j, which can take the values ​​1, 2, 3, 4, 5, and 6, indicates the direction of the force applied to the material. d 31 Pattern and d 33 These are two common operating vibration modes of piezoelectric vibration energy harvesters. d 31 The polarization direction of the mode is 3, which utilizes the force or deformation in the 1 direction; energy conversion occurs between perpendicular directions. d 33 The polarization direction of the mode is 3, and it also utilizes the force or deformation in the 3rd direction. Energy conversion occurs in parallel or in the same direction. The R and T dual-phase KNN ceramic nanoparticle filler is a potassium sodium niobate (KNN) based ceramic filler containing two crystal structures: trigonal (R phase) and tetragonal (T phase).

[0031] This invention provides a method for preparing a piezoelectric nanogenerator, comprising the following steps: Step 1: Preparation of potassium sodium niobate ceramic nanoparticle fillers by solid-state method Add 13.6982g of solid Nb₂O₅, 2.7229g of solid Na₂CO₃, and 3.5789g of solid K₂CO₃ to a ball mill jar, making the molar ratio of solid Nb₂O₅, solid Na₂CO₃, and solid K₂CO₃ (1.9-2.1):(0.95-1.05):(0.95-1.05). Simultaneously, add 40.0-80.0g of grinding stones and 60.0-80.0g of alcohol to the ball mill jar, mix thoroughly, and then place the ball mill jar on a ball mill. The mixture was ball-milled for 6–12 hours. Afterward, the mixture was dried in an oven to allow the alcohol to evaporate completely. It was then ground in a grinding bowl, and the powder was separated from the grinding stones using a sieve. The separated powder was poured into a crucible, covered, and placed in a muffle furnace for firing. The muffle furnace temperature was set to 850–950℃, the heating rate was 3–6℃ / min, and the holding time was 4–8 hours. The fired powder was then removed and ground in a grinding bowl for 10–30 minutes to ensure complete dispersion. Finally, potassium-sodium niobate ceramic nanoparticle filler was obtained.

[0032] Optimizing the ratio of solid Nb₂O₅, solid Na₂CO₃, and solid K₂CO₃ ensures the formation of a high-purity R / T dual-phase structure during the high-temperature reaction, avoiding the formation of impurity phases and thus providing a stable piezoelectric performance foundation for piezoelectric nanogenerators. During ball milling and calcination, optimizing the atomic ratio of sodium, potassium, and niobium effectively promotes the directional growth of potassium sodium niobate crystals. Under solid-state reaction conditions, side reactions are suppressed, ensuring the phase purity and crystal quality of the potassium sodium niobate ceramic particles. Subsequently, during doping in the polyimide matrix, the high-purity potassium sodium niobate particles can be uniformly dispersed, forming an effective piezoelectric network, supporting… d 31 and d 33 The synergistic output of dual operating modes significantly improves the stability and energy conversion efficiency of the device in high-temperature environments.

[0033] Sufficient ball milling for 6–12 hours ensures deep homogenization of the solid raw material under the impact of the ball mills and solvent dispersion, effectively overcoming component segregation caused by short-time mixing. Calcination using a slow heating rate of 3–6 °C / min significantly reduces the rate of thermal stress accumulation, allowing the potassium sodium niobate crystals to fully complete phase transformation and stabilize the R and T dual-phase structure within the optimized temperature range of 850–950 °C. A second grinding time of 10–30 minutes avoids lattice damage caused by over-grinding and particle coarsening caused by under-grinding. This ensures that the potassium sodium niobate ceramic nanoparticle filler possesses high crystallinity and a narrow particle size distribution, providing a structurally stable piezoelectric functional phase for piezoelectric nanogenerators.

[0034] Step 2: Preparation of polyamic acid solution Add 35-50 mL of anhydrous N,N-dimethylformamide solution and 3-5 g of 4,4'-diaminodiphenyl ether powder to a three-necked flask and stir for 10 min. Add 1 g of pyromellitic dianhydride powder every 20 min in sequence. Slowly add the remaining 0.28 g of pyromellitic dianhydride powder, and control the total mass of PMDA to 3.28-4.28 g. Stir thoroughly for 1-2 h to prepare a polyamic acid solution.

[0035] The ratio of anhydrous N,N-dimethylformamide solution, 4,4'-diaminodiphenyl ether powder, and pyromellitic dianhydride powder was (35~50) mL : (3~5) g : (3.28~4.28) g; this ensured a stable stoichiometric environment in the initial stage of the reaction, promoting efficient monomer condensation to form polyamic acid chains with uniform molecular weight distribution. The method for adding pyromellitic dianhydride powder was as follows: 1 g of pyromellitic dianhydride powder was added every 20 min; controlling the addition interval and dosage ensured a stable release of reaction heat, maintained a stable temperature in the reaction system, and reduced side reactions. The reaction was stirred thoroughly for 1~2 h; this provided sufficient assurance for the amidation reaction. This effectively avoided local overheating and concentration fluctuations during the reaction process, optimized the uniformity and structural integrity of the polyamic acid solution, and thus created ideal conditions for the uniform dispersion of potassium sodium niobate ceramic nanoparticles in the solution.

[0036] Step 3: Preparation of the binary casting precursor solution of polyamic acid and potassium sodium niobate Pour the polyamic acid solution into a container; then add 0-30 vol.% of potassium sodium niobate ceramic nanoparticle filler, mix, and sonicate for 10-30 min, then stir for 10-30 min. Repeat this cycle 5-10 times. Transfer the mixture to a magnetic stirrer and continue stirring for 6-12 h. Afterward, sonicate at room temperature for 0.5-1 h, then heat and stir at 30-60℃ for 10-30 min to obtain a binary casting precursor solution of polyamic acid and potassium sodium niobate. The binary casting precursor solution of polyamic acid and potassium sodium niobate is a mixed solution of polyamic acid and potassium sodium niobate.

[0037] The volume of the potassium sodium niobate ceramic nanoparticle filler is 5%~30% of the total volume of 4,4'-diaminodiphenyl ether powder, pyromellitic dianhydride powder, and potassium sodium niobate ceramic nanoparticle filler. This ensures uniform dispersion of the filler in the polyamic acid solution and effectively suppresses particle aggregation that easily occurs at high proportions. During subsequent multiple ultrasonic stirring and heating reactions, the uniformly distributed filler can fully combine with the polyamic acid molecular chains, thus forming a continuous and stable piezoelectric phase network structure during the casting and gradient temperature calcination stages. This structure retains the piezoelectric properties of the R and T biphase potassium sodium niobate ceramics to support multidimensional mechanical energy harvesting, while ensuring the mechanical flexibility and interfacial bonding strength of the polyimide-potassium sodium niobate composite film under high temperature conditions, thereby maintaining its stability over a wide temperature range of 50~180°C. d 31 and d 33 The stress transfer mechanism and charge separation capability required for the operating mode.

[0038] The conditions for repeated sonication and stirring include: sonication for 10-30 min, followed by stirring for 10-30 min, repeated 5-10 times; utilizing the cavitation effect of ultrasound to break up agglomerates and combining it with stirring shear force to achieve uniform distribution; continuing stirring for 6-12 h to allow the nanoparticles to reach a state of dynamic equilibrium in suspension, reducing the risk of sedimentation; subsequently, sonication at room temperature for 0.5-1 h to eliminate residual bubbles and micro-agglomerates; the conditions for the heated and stirred reaction include: heating and stirring at 30-60℃ for 10-30 min, which provides sufficient energy to promote the interfacial bonding between polyamic acid and potassium sodium niobate ceramic nanoparticle fillers, while avoiding potential damage to the material structure from high temperatures, ensuring the stability of the precursor solution during the subsequent imidization process, and ultimately providing a reliable foundation for the preparation of composite films with both high thermal stability and excellent piezoelectric properties.

[0039] Step 4: Preparation of polyimide-potassium sodium niobate composite films A binary casting precursor solution of polyamic acid and potassium sodium niobate is injected into the guide plate of an adjustable doctor blade. The doctor blade height is adjusted to 10~20 μm, and the casting is carried out on a clean glass plate at a speed of 10~20 cm / min to obtain a composite film of polyamic acid and potassium sodium niobate.

[0040] The polyamic acid and potassium sodium niobate composite film was placed in an oven at 30-60℃ and vacuumed at 0.4-0.8 MPa for 8-12 hours to remove air. Then, the polyamic acid and potassium sodium niobate composite film, along with a glass plate, was transferred into a muffle furnace and fired sequentially at 80℃, 100℃, 120℃, 150℃, 180℃, and 300℃ for 1-2 hours each to complete the imidization process. Afterward, the film, along with the glass plate, was cooled in cold water, and the polyamic acid and potassium sodium niobate composite film was removed from the glass surface, finally yielding the polyimide and potassium sodium niobate composite film. The polyimide and potassium sodium niobate composite film is a composite film of polyimide and potassium sodium niobate.

[0041] The casting conditions include: injecting a binary casting precursor solution of polyamic acid and potassium sodium niobate into the guide plate of an adjustable doctor blade, adjusting the doctor blade height to 10~20 μm to adapt the film thickness to the high-temperature bending deformation requirements, thus ensuring... d 31 The required lateral strain transfer efficiency for the operating mode, while maintaining d 33 The longitudinal piezoelectric activity in the working mode is achieved by casting the solution on a clean glass plate at a speed of 10~20cm / min to ensure that the solution spreads smoothly to form a dense and defect-free thin film structure, thereby enhancing the structural stability during high-temperature cycling and providing a key guarantee for the consistency of piezoelectric performance in both working modes.

[0042] Vacuum drying conditions include: evacuating at 0.4-0.8 MPa for 8-12 hours at 30-60℃ to ensure slow solvent removal and maintain the density and uniformity of the composite film; gradient heating calcination conditions include: calcining at 80℃, 100℃, 120℃, 150℃, 180℃, and 300℃ for 1-2 hours respectively; allowing the polyimide to fully remove moisture below 150℃ and complete the imidization reaction above 180℃, while meeting the thermal stability requirements of potassium sodium niobate ceramics, effectively coordinating the thermal expansion behavior between materials, avoiding thermal stress concentration, and ultimately forming a structurally stable and defect-free polyimide and potassium sodium niobate composite film.

[0043] Step 5: Fabrication of piezoelectric nanogenerators A circular film with a radius of 1.6 cm was cut from a polyimide-potassium sodium niobate composite film. Then, two copper electrodes with a radius of 1.2 cm were cut. Next, two 20 cm long wires were cut, and 5 cm of the outer insulation layer of the two wires was removed to expose the conductive copper wires inside. These wires were then spirally coiled and attached to the two copper electrodes. They were then attached to both sides of the circular polyimide-potassium sodium niobate composite film in a completely aligned manner. After the attachment was completed, a 5 cm × 5 cm square of polyimide encapsulation layer with high temperature resistance was cut. The encapsulation layer polyimide was then adhered to the top and bottom sides of the polyimide-potassium sodium niobate composite film to obtain a piezoelectric nanogenerator. This piezoelectric nanogenerator is designed for high-temperature working environments.

[0044] The piezoelectric nanogenerator assembled from a polyimide and potassium sodium niobate composite film effectively ensures the uniform bonding quality between the electrodes and the film, enhances the mechanical stability of the wire connections, and achieves tight coverage of the encapsulation layer. This allows the piezoelectric nanogenerator to maintain structural reliability in high-temperature operating environments, ensuring... d 31 and d 33 The coordinated implementation of dual working modes enables the stable harvesting of multi-dimensional mechanical energy.

[0045] This invention synthesizes potassium sodium niobate ceramic particles using a solid-state method and prepares a piezoelectric nanogenerator based on a polyimide-potassium sodium niobate composite film for micro-energy harvesting. The prepared polyimide-potassium sodium niobate composite film exhibits good heat resistance, hydrophobicity, mechanical strength, and lightweight structure. The open-circuit voltage of the piezoelectric nanogenerator was then investigated. V oc ) and short circuit current, I sc Piezoelectric nanogenerators have achieved high performance in a temperature range of 50–150°C. V oc and I sc Furthermore, the assembled PI-20KNN piezoelectric nanogenerator exhibits fast response and recovery times (82 ms and 83 ms) even at high temperatures and excellent durability under long-term operation. The piezoelectric nanogenerator prepared in this invention demonstrates high operational stability at high temperatures, compared to traditional piezoelectric nanogenerators which only have a single... d 31 work mode or d 33In terms of operating modes, the piezoelectric nanogenerator prepared by this invention provides a coexistence of two operating modes. Both the polyimide material and the potassium sodium niobate ceramic nanoparticle filler can provide high-temperature stability. The R and T biphase potassium sodium niobate ceramic nanoparticle filler enables the piezoelectric nanogenerator to have both longitudinal and transverse dual operating modes.

[0046] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0047] Example 1 A method for fabricating a piezoelectric nanogenerator includes the following steps: Step 1: Preparation of potassium sodium niobate ceramic nanoparticle fillers by solid-state method 13.6982g of solid Nb₂O₅, 2.7229g of solid Na₂CO₃, and 3.5789g of solid K₂CO₃ were added to a ball mill jar, along with 40.0g of grinding stones and 60.0g of alcohol. The mixture was thoroughly mixed, and then the jar was placed in a ball mill and milled for 12 hours. After milling, the resulting mixture was dried in an oven to allow the alcohol to evaporate completely. The mixture was then ground in a grinding bowl to pulverize the Nb₂O₅, Na₂CO₃, and K₂CO₃ powder. The powder was then separated from the grinding stones using a sieve. The separated powder was poured into a crucible, covered, and placed in a muffle furnace for firing at 910℃ with a heating rate of 3℃ / min for 4 hours. The fired powder was then removed and ground in a grinding bowl for 30 minutes to ensure thorough dispersion, yielding potassium sodium niobate ceramic nanoparticle fillers.

[0048] Step 2: Preparation of polyamic acid solution Add 35 mL of anhydrous DMF solution and 3 g of 4,4'-diaminodiphenyl ether powder to a three-necked flask and stir for 10 min. Then, add 1 g of pyromellitic dianhydride powder every 20 min. Finally, slowly add the remaining 0.28 g of pyromellitic dianhydride powder, controlling the total mass of PMDA to 3.28 g, and stir thoroughly for 2 h to prepare a polyamic acid solution.

[0049] Step 3: Preparation of the binary casting precursor solution of polyamic acid and potassium sodium niobate 12g of polyamic acid solution was poured into a container; then 20 vol.% of potassium sodium niobate ceramic nanoparticle filler was added, mixed and sonicated for 30 min, then stirred for 30 min, and this cycle was repeated 10 times. Finally, the mixture was transferred to a magnetic stirrer and stirred for 12 h. After sonicating at room temperature for 1 h, it was stirred for 30 min under heating at 50 °C to obtain a binary casting precursor solution of polyamic acid and potassium sodium niobate. Step 4: Preparation of polyimide-potassium sodium niobate composite films A binary casting precursor solution of polyamic acid and potassium sodium niobate was injected into the guide plate of an adjustable doctor blade. The doctor blade height was adjusted to 20 μm, and casting was performed on a clean glass plate at a speed of 10 cm / min. After casting, a polyamic acid and potassium sodium niobate composite film was obtained. The film was then placed in an oven at 30°C and vacuumed at 0.8 MPa for 12 h to remove air. The film, along with the glass plate, was then transferred to a muffle furnace and fired at 80°C, 100°C, 120°C, 150°C, 180°C, and 300°C for 1 h to complete the imidization process. The film, along with the glass plate, was then cooled in cold water, and the film was removed from the glass surface, finally yielding a polyimide and potassium sodium niobate composite film.

[0050] Step 5: Fabrication of piezoelectric nanogenerators for high-temperature operating environments A circular film with a radius of 1.6 cm was cut from a polyimide and potassium sodium niobate composite film. Two copper electrodes with a radius of 1.2 cm were then cut, followed by two 20 cm long wires. The insulation layer of the two wires was removed by 5 cm to expose the conductive copper wires, which were then spirally coiled and attached to the two copper electrodes. These were then perfectly aligned and attached to both sides of the circular composite film. After attachment, a 5 cm × 5 cm square of high-temperature resistant polyimide encapsulation layer was cut and adhered to both the top and bottom surfaces of the polyimide and potassium sodium niobate composite film. This resulted in a piezoelectric nanogenerator designed for high-temperature operating environments.

[0051] Figure 1 The images show X-ray diffraction patterns of polyimide-sodium niobate composite films with different potassium sodium niobate doping amounts according to the present invention. As can be seen from the images, the polyimide-sodium niobate composite films of the present invention do not exhibit any characteristic peaks of other crystal phases except for the characteristic peaks of potassium sodium niobate, indicating that the polyimide-sodium niobate composite films have high purity characteristics and that potassium sodium niobate is successfully loaded into the polyimide matrix.

[0052] Figure 2The images show the infrared spectra of polyimide and potassium sodium niobate composite films with different potassium sodium niobate doping amounts according to the present invention; it can be seen from the figures that at 731 cm⁻¹... 1 1380 cm 1 1727 cm 1 and 1778 cm 1 Characteristic peaks of polyimide were observed at all locations, indicating the successful synthesis of polyimide.

[0053] Figure 3 The images show a scanning electron microscope (SEM) image of a pure polyimide film (a) and a scanning electron microscope (SEM) image of a polyimide-sodium niobate composite film prepared in Example 1 of this invention (b). As can be seen from the images, compared with the pure polyimide film, the polyimide-sodium niobate composite film has a large number of potassium sodium niobate ceramic particles loaded in the polyimide matrix, which can provide multiple working modes and high voltage properties of the piezoelectric nanogenerator.

[0054] Figure 4 To provide the piezoelectric nanogenerators of this invention with different potassium, sodium, and niobate doping amounts in d 33 Operating cycle diagram under the mode (a); short-circuit current under 5Hz and 10N load (b); and open-circuit voltage under 5Hz and 10N load (c). Figure 5 To provide the piezoelectric nanogenerators of this invention with different potassium, sodium, and niobate doping amounts in d 31 Operating cycle diagram under the mode (a); short-circuit current under 5Hz and 10N load (b); and open-circuit voltage under 5Hz and 10N load (c). Figure 6 The figure shows the working mechanism of the piezoelectric nanogenerator disclosed in this invention in different piezoelectric modes. As can be seen from the figure, the piezoelectric nanogenerator prepared by this invention has multiple working modes and can work alone or in combination, which greatly improves the energy harvesting efficiency.

[0055] Figure 7The piezoelectric nanogenerator prepared in Example 1 of this invention is shown in the following figures: open-circuit voltage output at different operating temperatures under test force conditions of 5N and 10Hz (a); short-circuit current output at different operating temperatures under test force conditions of 5N and 10Hz (b); voltage response and recovery time test figures at operating temperatures of room temperature and 150℃ (c); and long-term voltage output stability test figure at operating temperature of 150℃ (d). As can be seen from the figure, the piezoelectric nanogenerator prepared in Example 1 of this invention can operate at different temperatures, and its electrical output is relatively stable at most temperatures. It can also be seen that as the operating temperature increases, the piezoelectric output of the piezoelectric nanogenerator first increases and then decreases. The increase is mainly due to the adjustment of the effective piezoelectric coefficient and internal stress, that is, the appropriate increase in temperature will improve the stress transmission efficiency of the matrix. The decrease above 150°C is due to the thermal depolarization effect of the potassium sodium niobate ceramic nanoparticle filler. Although there is a certain decrease, the polyimide and potassium sodium niobate high-temperature resistant piezoelectric nanogenerator still exhibits excellent electrical output performance over a wide range of temperatures. Even at a high temperature of 150°C, it still exhibits good voltage response and recovery time, demonstrating its sensitivity at high temperatures. Furthermore, it can still perform long-term energy harvesting at a high temperature of 150°C, demonstrating its application potential in harsh high-temperature working environments.

[0056] Example 2 The difference from Example 1 is as follows: Step 2: Add 50 mL of anhydrous DMF solution and 5 g of 4,4'-diaminodiphenyl ether powder to a three-necked flask and stir for 10 min. Then, add 1 g of pyromellitic dianhydride powder every 20 min. Finally, slowly add the remaining 0.28 g of pyromellitic dianhydride powder, controlling the total mass of PMDA to 4.28 g, and stir thoroughly for 2 h to prepare a polyamic acid solution.

[0057] Example 3 The difference from Example 1 is as follows: Step 1: Add 13.6982g of solid Nb2O5, 2.7229g of solid Na2CO3 and 3.5789g of solid K2CO3 to a ball mill jar, along with 40.0g of ball stones and 60.0g of alcohol. Mix them thoroughly, then place the ball mill jar on a ball mill and mill for 12 hours. After milling, place the resulting mixture in an oven to dry, allowing the alcohol to evaporate completely. The resulting mixture was then placed in a grinding mortar and ground to crush the mixed powder of Nb2O5, Na2CO3, and K2CO3. The mixed powder was then separated from the grinding stone using a sieve. The separated mixed powder was poured into a crucible, covered, and placed in a muffle furnace for firing. The temperature of the muffle furnace was set to 950℃, the heating rate was 3℃ / min, and the holding time was 4h. After firing, the powder was removed and poured into a grinding mortar for 30min of grinding to ensure that the powder was fully dispersed. Finally, potassium sodium niobate ceramic nanoparticle filler was obtained.

[0058] Step 2: Add 35 mL of anhydrous DMF solution and 4 g of 4,4'-diaminodiphenyl ether powder to a three-necked flask and stir for 10 min. Then, add 1 g of pyromellitic dianhydride powder every 20 min. Finally, slowly add the remaining 0.28 g of pyromellitic dianhydride powder, controlling the total mass of PMDA to 3.78 g, and stir thoroughly for 2 h to prepare a polyamic acid solution.

[0059] Example 4 The difference from Example 1 is as follows: Step 1: Add 13.6982g of solid Nb2O5, 2.7229g of solid Na2CO3 and 3.5789g of solid K2CO3 to a ball mill jar. At the same time, add 40.0g of ball stones and 60.0g of alcohol to the ball mill jar. Mix them thoroughly. Then place the ball mill jar on a ball mill and mill for 10 hours. After that, put the mixture obtained after milling into an oven to dry it so that the alcohol can be fully evaporated. The resulting mixture was then placed in a grinding mortar and ground to crush the mixed powder of Nb2O5, Na2CO3, and K2CO3. The mixed powder was then separated from the grinding stone using a sieve. The separated mixed powder was poured into a crucible, covered, and placed in a muffle furnace for firing. The temperature of the muffle furnace was set to 850℃, the heating rate was 4℃ / min, and the holding time was 4h. After firing, the powder was removed and poured into a grinding mortar for 30min of grinding to ensure that the powder was fully dispersed. Finally, potassium sodium niobate ceramic nanoparticle filler was obtained.

[0060] Step 2: Add 40 mL of anhydrous DMF solution and 3 g of 4,4'-diaminodiphenyl ether powder to a three-necked flask and stir for 10 min. Then, add 1 g of pyromellitic dianhydride powder every 20 min. Finally, slowly add the remaining 0.28 g of pyromellitic dianhydride powder, controlling the total mass of PMDA to 3.28 g, and stir thoroughly for 2 h to prepare a polyamic acid solution.

[0061] Example 5 A method for fabricating a piezoelectric nanogenerator includes the following steps: Step 1: Preparation of potassium sodium niobate ceramic nanoparticle fillers by solid-state method 13.732g of solid Nb₂O₅, 2.875g of solid Na₂CO₃, and 3.392g of solid K₂CO₃ were added to a ball mill jar, along with 60.0g of grinding stones and 70.0g of alcohol. The mixture was thoroughly combined, and the jar was then placed in a ball mill and milled for 10 hours. The resulting mixture was then dried in an oven to allow the alcohol to evaporate completely. The mixture was then ground in a grinding bowl to pulverize the Nb₂O₅, Na₂CO₃, and K₂CO₃ powder. The powder was separated from the grinding stones using a sieve. The separated powder was poured into a crucible, covered, and placed in a muffle furnace for firing at 910℃ with a heating rate of 4℃ / min for 5 hours. The fired powder was then removed and ground in a grinding bowl for 10 minutes to ensure thorough dispersion, yielding potassium sodium niobate ceramic nanoparticle fillers.

[0062] Step 2: Preparation of polyamic acid solution Add 35 mL of anhydrous DMF solution and 3 g of 4,4'-diaminodiphenyl ether powder to a three-necked flask and stir for 5 min. Then, add 1 g of pyromellitic dianhydride powder every 20 min. Finally, slowly add the remaining 0.28 g of pyromellitic dianhydride powder, controlling the total mass of PMDA to 3.28 g, and stir thoroughly for 1 h to prepare a polyamic acid solution.

[0063] Step 3: Preparation of the binary casting precursor solution of polyamic acid and potassium sodium niobate Pour 6g of polyamic acid solution into a container; then add 30 vol.% of potassium sodium niobate ceramic nanoparticle filler, mix, sonicate for 10 min, stir for 10 min, repeat this cycle 5 times, and finally transfer to a magnetic stirrer to continue stirring for 6 h. After sonicating at room temperature for 0.5 h, stir at 50℃ for 30 min to obtain a binary casting precursor solution of polyamic acid and potassium sodium niobate. Step 4: Preparation of polyimide-potassium sodium niobate composite films A binary casting precursor solution of polyamic acid and potassium sodium niobate was injected into the guide plate of an adjustable doctor blade. The doctor blade height was adjusted to 20 μm, and casting was performed on a clean glass plate at a speed of 10 cm / min. After casting, a polyamic acid and potassium sodium niobate composite film was obtained. The film was then placed in an oven at 40°C and vacuumed at 0.4 MPa for 8 hours to remove air. The film, along with the glass plate, was then transferred to a muffle furnace and fired at 80°C, 100°C, 120°C, 150°C, 180°C, and 300°C for 1 hour to complete the imidization process. The film, along with the glass plate, was then cooled in cold water, and the film was removed from the glass surface, finally yielding a polyimide and potassium sodium niobate composite film.

[0064] Step 5: Same as Example 1.

[0065] Example 6 A method for fabricating a piezoelectric nanogenerator includes the following steps: Step 1: Preparation of potassium sodium niobate ceramic nanoparticle fillers by solid-state method 13.682g of solid Nb₂O₅, 2.591g of solid Na₂CO₃, and 3.735g of solid K₂CO₃ were added to a ball mill jar, along with 60.0g of grinding stones and 70.0g of alcohol. The mixture was thoroughly combined, and the jar was then placed in a ball mill and milled for 10 hours. The resulting mixture was then dried in an oven to allow the alcohol to evaporate completely. The mixture was then ground in a grinding bowl to pulverize the Nb₂O₅, Na₂CO₃, and K₂CO₃ powder. The powder was separated from the grinding stones using a sieve. The separated powder was poured into a crucible, covered, and placed in a muffle furnace for firing at 910℃ with a heating rate of 4℃ / min for 5 hours. The fired powder was then removed and ground in a grinding bowl for 10 minutes to ensure thorough dispersion, yielding potassium sodium niobate ceramic nanoparticle fillers.

[0066] Step 2: Preparation of polyamic acid solution Add 35 mL of anhydrous DMF solution and 3 g of 4,4'-diaminodiphenyl ether powder to a three-necked flask and stir for 5 min. Then, add 1 g of pyromellitic dianhydride powder every 20 min. Finally, slowly add the remaining 0.28 g of pyromellitic dianhydride powder, controlling the total mass of PMDA to 3.28 g, and stir thoroughly for 1 h to prepare a polyamic acid solution.

[0067] Step 3: Preparation of the binary casting precursor solution of polyamic acid and potassium sodium niobate Pour 6g of polyamic acid solution into a container; then add 5 vol.% of potassium sodium niobate ceramic nanoparticle filler, mix, sonicate for 10 min, stir for 10 min, repeat this cycle 5 times, and finally transfer to a magnetic stirrer to continue stirring for 6 h. After sonicating at room temperature for 0.5 h, stir at 50℃ for 30 min to obtain a binary casting precursor solution of polyamic acid and potassium sodium niobate. Step 4: Preparation of polyimide-potassium sodium niobate composite films A binary casting precursor solution of polyamic acid and potassium sodium niobate was injected into the guide plate of an adjustable doctor blade. The doctor blade height was adjusted to 20 μm, and casting was performed on a clean glass plate at a speed of 10 cm / min. After casting, a polyamic acid and potassium sodium niobate composite film was obtained. The film was then placed in an oven at 40°C and vacuumed at 0.4 MPa for 8 hours to remove air. The film, along with the glass plate, was then transferred to a muffle furnace and fired at 80°C, 100°C, 120°C, 150°C, 180°C, and 300°C for 1 hour to complete the imidization process. The film, along with the glass plate, was then cooled in cold water, and the film was removed from the glass surface, finally yielding a polyimide and potassium sodium niobate composite film.

[0068] Step 5: Same as Example 1.

[0069] Example 7 A method for fabricating a piezoelectric nanogenerator includes the following steps: Step 1: Preparation of potassium sodium niobate ceramic nanoparticle fillers by solid-state method 13.6982g of solid Nb₂O₅, 2.7229g of solid Na₂CO₃, and 3.5789g of solid K₂CO₃ were added to a ball mill jar, along with 70.0g of grinding stones and 75.0g of alcohol. The mixture was thoroughly mixed, and then the jar was placed in a ball mill and milled for 8 hours. After milling, the resulting mixture was dried in an oven to allow the alcohol to evaporate completely. The mixture was then ground in a grinding bowl to pulverize the Nb₂O₅, Na₂CO₃, and K₂CO₃ powder. The powder was then separated from the grinding stones using a sieve. The separated powder was poured into a crucible, covered, and placed in a muffle furnace for firing at 910℃ with a heating rate of 5℃ / min for 6 hours. The fired powder was then removed and ground in a grinding bowl for 15 minutes to ensure thorough dispersion, ultimately yielding potassium sodium niobate ceramic nanoparticle fillers.

[0070] Step 2: Preparation of polyamic acid solution Add 35 mL of anhydrous DMF solution and 3 g of 4,4'-diaminodiphenyl ether powder to a three-necked flask and stir for 5 min. Then, add 1 g of pyromellitic dianhydride powder every 20 min. Finally, slowly add the remaining 0.28 g of pyromellitic dianhydride powder, controlling the total mass of PMDA to 3.28 g, and stir thoroughly for 1 h to prepare a polyamic acid solution.

[0071] Step 3: Preparation of the binary casting precursor solution of polyamic acid and potassium sodium niobate Pour 6g of polyamic acid solution into a container; then add 10 vol.% of potassium sodium niobate ceramic nanoparticle filler, mix, sonicate for 20 min, stir for 20 min, repeat this cycle 5 times, and finally transfer to a magnetic stirrer to continue stirring for 6 h. After sonicating at room temperature for 0.5 h, stir at 50℃ for 30 min to obtain a binary casting precursor solution of polyamic acid and potassium sodium niobate. Step 4: Preparation of polyimide-potassium sodium niobate composite films A binary casting precursor solution of polyamic acid and potassium sodium niobate was injected into the guide plate of an adjustable doctor blade. The doctor blade height was adjusted to 20 μm, and casting was performed on a clean glass plate at a speed of 10 cm / min. After casting, a polyamic acid and potassium sodium niobate composite film was obtained. The film was then placed in an oven at 40°C and vacuumed at 0.4 MPa for 8 hours to remove air. The film, along with the glass plate, was then transferred to a muffle furnace and fired at 80°C, 100°C, 120°C, 150°C, 180°C, and 300°C for 1 hour to complete the imidization process. The film, along with the glass plate, was then cooled in cold water, and the film was removed from the glass surface, finally yielding a polyimide and potassium sodium niobate composite film.

[0072] Step 5: Same as Example 1.

[0073] Example 8 A method for fabricating a piezoelectric nanogenerator includes the following steps: Step 1: Preparation of potassium sodium niobate ceramic nanoparticle fillers by solid-state method 13.6982g of solid Nb₂O₅, 2.7229g of solid Na₂CO₃, and 3.5789g of solid K₂CO₃ were added to a ball mill jar, along with 70.0g of grinding stones and 75.0g of alcohol. The mixture was thoroughly mixed, and then the jar was placed in a ball mill and milled for 8 hours. After milling, the resulting mixture was dried in an oven to allow the alcohol to evaporate completely. The mixture was then ground in a grinding bowl to pulverize the Nb₂O₅, Na₂CO₃, and K₂CO₃ powder. The powder was then separated from the grinding stones using a sieve. The separated powder was poured into a crucible, covered, and placed in a muffle furnace for firing at 910℃ with a heating rate of 5℃ / min for 6 hours. The fired powder was then removed and ground in a grinding bowl for 15 minutes to ensure thorough dispersion, ultimately yielding potassium sodium niobate ceramic nanoparticle fillers.

[0074] Step 2: Preparation of polyamic acid solution Add 35 mL of anhydrous DMF solution and 3 g of 4,4'-diaminodiphenyl ether powder to a three-necked flask and stir for 7 min. Then, add 1 g of pyromellitic dianhydride powder every 20 min. Finally, slowly add the remaining 0.28 g of pyromellitic dianhydride powder, controlling the total mass of PMDA to 3.28 g, and stir thoroughly for 1.5 h to prepare a polyamic acid solution.

[0075] Step 3: Preparation of the binary casting precursor solution of polyamic acid and potassium sodium niobate Pour 8g of polyamic acid solution into a container; then add 15 vol.% of potassium sodium niobate ceramic nanoparticle filler, mix, sonicate for 20 min, stir for 20 min, repeat this cycle 6 times, and finally transfer to a magnetic stirrer to continue stirring for 8 h. After sonicating at room temperature for 0.7 h, stir for 30 min under heating at 50 °C to obtain a binary casting precursor solution of polyamic acid and potassium sodium niobate. Step 4: Preparation of polyimide-potassium sodium niobate composite films A binary casting precursor solution of polyamic acid and potassium sodium niobate was injected into the guide plate of an adjustable doctor blade. The doctor blade height was adjusted to 10 μm, and casting was performed on a clean glass plate at a speed of 20 cm / min. After casting, a polyamic acid and potassium sodium niobate composite film was obtained. The film was then placed in an oven at 50°C and vacuumed at 0.5 MPa for 9 hours to remove air. The film, along with the glass plate, was then transferred to a muffle furnace and fired at 80°C, 100°C, 120°C, 150°C, 180°C, and 300°C for 1 hour to complete the imidization process. The film, along with the glass plate, was then cooled in cold water and removed from the glass surface, finally yielding a polyimide and potassium sodium niobate composite film.

[0076] Step 5: Same as Example 1.

[0077] Example 9 A method for fabricating a piezoelectric nanogenerator includes the following steps: Step 1: Preparation of potassium sodium niobate ceramic nanoparticle fillers by solid-state method 13.6982g of solid Nb₂O₅, 2.7229g of solid Na₂CO₃, and 3.5789g of solid K₂CO₃ were added to a ball mill jar, along with 80.0g of grinding stones and 80.0g of alcohol. The mixture was thoroughly mixed, and then the jar was placed in a ball mill and milled for 8 hours. After milling, the resulting mixture was dried in an oven to allow the alcohol to evaporate completely. The mixture was then ground in a grinding bowl to pulverize the Nb₂O₅, Na₂CO₃, and K₂CO₃ powder. The powder was then separated from the grinding stones using a sieve. The separated powder was poured into a crucible, covered, and placed in a muffle furnace for firing at 910℃ with a heating rate of 5℃ / min for 6 hours. The fired powder was then removed and ground in a grinding bowl for 15 minutes to ensure thorough dispersion, ultimately yielding potassium sodium niobate ceramic nanoparticle fillers.

[0078] Step 2: Preparation of polyamic acid solution Add 35 mL of anhydrous DMF solution and 3 g of 4,4'-diaminodiphenyl ether powder to a three-necked flask and stir for 7 min. Then, add 1 g of pyromellitic dianhydride powder every 20 min. Finally, slowly add the remaining 0.28 g of pyromellitic dianhydride powder, controlling the total mass of PMDA to 3.28 g, and stir thoroughly for 1.5 h to prepare a polyamic acid solution.

[0079] Step 3: Preparation of the binary casting precursor solution of polyamic acid and potassium sodium niobate Pour 8g of polyamic acid solution into a container; then add 5 vol.% of potassium sodium niobate ceramic nanoparticle filler, mix, sonicate for 20 min, stir for 20 min, repeat this cycle 6 times, and finally transfer to a magnetic stirrer to continue stirring for 8 h. After sonicating at room temperature for 0.7 h, stir for 30 min under heating at 50 °C to obtain a binary casting precursor solution of polyamic acid and potassium sodium niobate. Step 4: Preparation of polyimide-potassium sodium niobate composite films A binary casting precursor solution of polyamic acid and potassium sodium niobate was injected into the guide plate of an adjustable doctor blade. The doctor blade height was adjusted to 15 μm, and casting was performed on a clean glass plate at a speed of 15 cm / min. After casting, a polyamic acid and potassium sodium niobate composite film was obtained. The film was then placed in an oven at 50°C and vacuumed at 0.5 MPa for 9 hours to remove air. The film, along with the glass plate, was then transferred to a muffle furnace and fired at 80°C, 100°C, 120°C, 150°C, 180°C, and 300°C for 1 hour to complete the imidization process. The film, along with the glass plate, was then cooled in cold water and removed from the glass surface, finally yielding a polyimide and potassium sodium niobate composite film.

[0080] Step 5: Same as Example 1.

[0081] Example 10 A method for fabricating a piezoelectric nanogenerator includes the following steps: Step 1: Preparation of potassium sodium niobate ceramic nanoparticle fillers by solid-state method 13.6982g of solid Nb₂O₅, 2.7229g of solid Na₂CO₃, and 3.5789g of solid K₂CO₃ were added to a ball mill jar, along with 80.0g of grinding stones and 80.0g of alcohol. The mixture was thoroughly mixed, and then the jar was placed in a ball mill and milled for 6 hours. After milling, the resulting mixture was dried in an oven to allow the alcohol to evaporate completely. The mixture was then ground in a grinding bowl to pulverize the Nb₂O₅, Na₂CO₃, and K₂CO₃ powder. The powder was then separated from the grinding stones using a sieve. The separated powder was poured into a crucible, covered, and placed in a muffle furnace for firing at 910℃ with a heating rate of 6℃ / min for 8 hours. The fired powder was then removed and ground in a grinding bowl for 20 minutes to ensure thorough dispersion, ultimately yielding potassium sodium niobate ceramic nanoparticle fillers.

[0082] Step 2: Preparation of polyamic acid solution Add 35 mL of anhydrous DMF solution and 3 g of 4,4'-diaminodiphenyl ether powder to a three-necked flask and stir for 7 min. Then, add 1 g of pyromellitic dianhydride powder every 20 min. Finally, slowly add the remaining 0.28 g of pyromellitic dianhydride powder, controlling the total mass of PMDA to 3.28 g, and stir thoroughly for 1.5 h to prepare a polyamic acid solution.

[0083] Step 3: Preparation of the binary casting precursor solution of polyamic acid and potassium sodium niobate Pour 10g of polyamic acid solution into a container; then add 20 vol.% of potassium sodium niobate ceramic nanoparticle filler, mix, sonicate for 25 min, stir for 25 min, repeat this cycle 6 times, and finally transfer to a magnetic stirrer to continue stirring for 10 h. After sonicating at room temperature for 0.7 h, stir at 50℃ for 30 min to obtain a binary casting precursor solution of polyamic acid and potassium sodium niobate. Step 4: Preparation of polyimide-potassium sodium niobate composite films A binary casting precursor solution of polyamic acid and potassium sodium niobate was injected into the guide plate of an adjustable doctor blade. The doctor blade height was adjusted to 20 μm, and casting was performed on a clean glass plate at a speed of 10 cm / min. After casting, a polyamic acid and potassium sodium niobate composite film was obtained. The film was then placed in a 60°C oven and vacuumed at 0.6 MPa for 10 h to remove air. The film, along with the glass plate, was then transferred to a muffle furnace and fired at 80°C, 100°C, 120°C, 150°C, 180°C, and 300°C for 2 h to complete the imidization process. The film, along with the glass plate, was then cooled in cold water and removed from the glass surface to obtain the final polyimide and potassium sodium niobate composite film.

[0084] Step 5: Same as Example 1.

[0085] Example 11 A method for fabricating a piezoelectric nanogenerator includes the following steps: Step 1: Preparation of potassium sodium niobate ceramic nanoparticle fillers by solid-state method 13.6982g of solid Nb₂O₅, 2.7229g of solid Na₂CO₃, and 3.5789g of solid K₂CO₃ were added to a ball mill jar, along with 80.0g of grinding stones and 80.0g of alcohol. The mixture was thoroughly mixed, and then the jar was placed in a ball mill and milled for 6 hours. After milling, the resulting mixture was dried in an oven to allow the alcohol to evaporate completely. The mixture was then ground in a grinding bowl to pulverize the Nb₂O₅, Na₂CO₃, and K₂CO₃ powder. The powder was then separated from the grinding stones using a sieve. The separated powder was poured into a crucible, covered, and placed in a muffle furnace for firing at 910℃ with a heating rate of 6℃ / min for 8 hours. The fired powder was then removed and ground in a grinding bowl for 20 minutes to ensure thorough dispersion, ultimately yielding potassium sodium niobate ceramic nanoparticle fillers.

[0086] Step 2: Preparation of polyamic acid solution Add 35 mL of anhydrous DMF solution and 3 g of 4,4'-diaminodiphenyl ether powder to a three-necked flask and stir for 8 min. Then, add 1 g of pyromellitic dianhydride powder every 20 min. Finally, slowly add the remaining 0.28 g of pyromellitic dianhydride powder, controlling the total mass of PMDA to 3.28 g, and stir thoroughly for 1.8 h to prepare a polyamic acid solution.

[0087] Step 3: Preparation of the binary casting precursor solution of polyamic acid and potassium sodium niobate Pour 10g of polyamic acid solution into a container; then add 20 vol.% of potassium sodium niobate ceramic nanoparticle filler, mix, sonicate for 25 min, stir for 25 min, repeat this cycle 8 times, and finally transfer to a magnetic stirrer to continue stirring for 10 h. After sonicating at room temperature for 0.8 h, stir for 10 min under heating at 30 °C to obtain a binary casting precursor solution of polyamic acid and potassium sodium niobate. Step 4: Preparation of polyimide-potassium sodium niobate composite films A binary casting precursor solution of polyamic acid and potassium sodium niobate was injected into the guide plate of an adjustable doctor blade. The doctor blade height was adjusted to 20 μm, and casting was performed on a clean glass plate at a speed of 10 cm / min. After casting, a polyamic acid and potassium sodium niobate composite film was obtained. The film was then placed in a 60°C oven and vacuumed at 0.6 MPa for 10 h to remove air. The film, along with the glass plate, was then transferred to a muffle furnace and fired at 80°C, 100°C, 120°C, 150°C, 180°C, and 300°C for 1.5 h to complete the imidization process. The film, along with the glass plate, was then cooled in cold water, and the film was removed from the glass surface, finally yielding a polyimide and potassium sodium niobate composite film.

[0088] Step 5: Same as Example 1.

[0089] Example 12 A method for fabricating a piezoelectric nanogenerator includes the following steps: Step 1: Preparation of potassium sodium niobate ceramic nanoparticle fillers by solid-state method 13.6982g of solid Nb₂O₅, 2.7229g of solid Na₂CO₃, and 3.5789g of solid K₂CO₃ were added to a ball mill jar, along with 80.0g of grinding stones and 80.0g of alcohol. The mixture was thoroughly mixed, and then the jar was placed in a ball mill and milled for 6 hours. After milling, the resulting mixture was dried in an oven to allow the alcohol to evaporate completely. The mixture was then ground in a grinding bowl to pulverize the Nb₂O₅, Na₂CO₃, and K₂CO₃ powder. The powder was then separated from the grinding stones using a sieve. The separated powder was poured into a crucible, covered, and placed in a muffle furnace for firing at 910℃ with a heating rate of 6℃ / min for 8 hours. The fired powder was then removed and ground in a grinding bowl for 20 minutes to ensure thorough dispersion, ultimately yielding potassium sodium niobate ceramic nanoparticle fillers.

[0090] Step 2: Preparation of polyamic acid solution Add 35 mL of anhydrous DMF solution and 3 g of 4,4'-diaminodiphenyl ether powder to a three-necked flask and stir for 8 min. Then, add 1 g of pyromellitic dianhydride powder every 20 min. Finally, slowly add the remaining 0.28 g of pyromellitic dianhydride powder, controlling the total mass of PMDA to 3.28 g, and stir thoroughly for 1.8 h to prepare a polyamic acid solution.

[0091] Step 3: Preparation of the binary casting precursor solution of polyamic acid and potassium sodium niobate Pour 10g of polyamic acid solution into a container; then add 20 vol.% of potassium sodium niobate ceramic nanoparticle filler, mix, sonicate for 25 min, stir for 25 min, repeat this cycle 8 times, and finally transfer to a magnetic stirrer to continue stirring for 10 h. After sonicating at room temperature for 0.8 h, stir at 60℃ for 20 min to obtain a binary casting precursor solution of polyamic acid and potassium sodium niobate. Step 4: Preparation of polyimide-potassium sodium niobate composite films The polyamic acid and potassium sodium niobate binary casting precursor solution is injected into the guide plate of an adjustable scraper, and the scraper is adjusted. A polyamic acid and potassium sodium niobate composite film was cast on a clean glass plate at a height of 20 μm and a speed of 10 cm / min. After casting, the film was obtained. The film was then placed in an oven at 60°C and vacuumed at 0.6 MPa for 10 h to remove air. The film and glass plate were then transferred to a muffle furnace and fired at 80°C, 100°C, 120°C, 150°C, 180°C and 300°C for 1.5 h to complete the imidization process. The film and glass plate were then cooled in cold water and the film was removed from the glass surface to obtain the polyimide and potassium sodium niobate composite film.

[0092] Step 5: Same as Example 1.

[0093] Table 1 Comparison of maximum longitudinal mode open-circuit voltage and corresponding maximum open-circuit voltage operating temperature in different embodiments

[0094] Table 1 compares the maximum open-circuit voltage in the longitudinal mode and the corresponding operating temperature at the maximum open-circuit voltage for different embodiments. The table shows significant differences in voltage output and high-temperature resistance among the different embodiments. Embodiments 1-4 maintain a high open-circuit voltage at a high temperature (110℃), demonstrating good high-temperature stability. In contrast, Embodiments 5-9 exhibit relatively low open-circuit voltages at lower temperatures (70℃), indicating that their material combinations or structural designs are limited in performance at high temperatures. This table clearly demonstrates the differences in performance optimization among the different embodiments, providing a reference for subsequent implementation scheme selection.

[0095] In summary, this invention provides a polyimide-potassium sodium niobate composite film, its preparation method, and a piezoelectric nanogenerator. The piezoelectric nanogenerator is small in size and low in cost. First, potassium sodium niobate ceramic nanoparticles were synthesized using a solid-state method. Then, a polyamic acid solution, a precursor for the polyimide film, was synthesized using 4,4'-diaminodiphenyl ether and pyromellitic dianhydride. After thoroughly mixing the polyamic acid solution and the potassium sodium niobate ceramic nanoparticles, the film was imidized through a casting method and high-temperature heat treatment. Finally, a piezoelectric nanogenerator for micro-energy harvesting was preliminarily prepared. The prepared polyimide-potassium sodium niobate composite film exhibits good heat resistance, hydrophobicity, mechanical strength, and lightweight structure. The open-circuit voltage of the piezoelectric nanogenerator was also investigated. V oc ), short-circuit current ( I sc Output performance, etc. Due to the presence of potassium sodium niobate ceramic nanoparticle fillers... R and T Dual-phase, thus enabling the device to have both d 33 and d 31 The dual operating modes enable piezoelectric nanogenerators to harvest and utilize micro-energy in various application environments. Furthermore, the synergistic effect of the dual operating modes significantly enhances the power density of our fabricated piezoelectric nanogenerators compared to traditional single-mode piezoelectric nanogenerators. Additionally, the high-temperature resistance of the polyimide matrix allows the fabricated polyimide-potassium sodium niobate piezoelectric nanogenerator to achieve high power density within a temperature range of 50–180°C. V oc and I sc Furthermore, the assembled polyimide and potassium sodium niobate piezoelectric sensor exhibits excellent operational stability even at a high temperature of 150°C. Due to these characteristics, the high-temperature multi-mode piezoelectric sensor constructed in this invention possesses superior performance. By integrating the high-temperature operational stability and multi-mode operation of the piezoelectric nanogenerator, polyimide provides excellent thermal stability, while the added R and T biphase potassium sodium niobate ceramic particles can be effectively loaded within the polyimide matrix, providing good piezoelectric properties and offering… d 33 as well as d 31 The dual operating modes enable PENG to harvest weak mechanical energy from nature from multiple dimensions, significantly reducing the limitations of energy harvesting. Simultaneously, the fabricated nanogenerator exhibits excellent piezoelectric properties at high temperatures. The concept of this invention is simple and clear, and the prepared product possesses sufficient thermal stability, demonstrating broad application prospects.

[0096] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a polyimide-sodium niobate composite film, characterized in that, Includes the following steps: 1) Solid Nb2O5, solid Na2CO3 and solid K2CO3 were ball-milled and mixed evenly, and then dried, ground, sieved, calcined and ground again to obtain potassium sodium niobate ceramic nanoparticle filler. 2) Add the potassium sodium niobate ceramic nanoparticle filler obtained in step 1) to the polyamic acid solution, and perform ultrasonic stirring multiple times until the mixture is uniform. After heating and stirring reaction, a binary casting precursor solution of polyamic acid and potassium sodium niobate is obtained. After casting treatment of the binary casting precursor solution of polyamic acid and potassium sodium niobate, a composite film of polyamic acid and potassium sodium niobate is obtained. After vacuum drying treatment of the composite film of polyamic acid and potassium sodium niobate, it is calcined by gradient temperature rise treatment. After cooling, a composite film of polyimide and potassium sodium niobate is obtained.

2. The method for producing a polyimide / potassium-sodium niobate composite film according to claim 1, characterized by, In step 1), the molar ratio of solid Nb2O5, solid Na2CO3 and solid K2CO3 is (1.9-2.1):(0.95-1.05):(0.95-1.05).

3. The method for preparing the polyimide-potassium sodium niobate composite film according to claim 1, characterized in that, In step 1), the conditions for ball milling include: adding ball stones and alcohol to the ball mill jar, and mixing them thoroughly for 6-12 hours; The calcination conditions include: starting from room temperature, heating to 850-950°C at a rate of 3-6°C / min, and holding the temperature for 4-8 hours; the re-grinding time is 10-30 minutes.

4. The method for preparing the polyimide-potassium sodium niobate composite film according to claim 1, characterized in that, In step 2), the preparation method of polyamic acid solution includes: mixing anhydrous N,N-dimethylformamide solution and 4,4'-diaminodiphenyl ether powder evenly to obtain a mixed solution; adding pyromellitic dianhydride powder to the mixed solution in multiple batches; and stirring the reaction thoroughly to obtain polyamic acid solution. The ratio of the amount of anhydrous N,N-dimethylformamide solution, 4,4'-diaminodiphenyl ether powder, and pyromellitic dianhydride powder is (35~50) mL : (3~5) g : (3.28~4.28) g; the method of adding pyromellitic dianhydride powder is: add 1 g of pyromellitic dianhydride powder every 20 min; the reaction time for thorough stirring is 1~2 h.

5. The method for preparing the polyimide-sodium niobate composite film according to claim 1, characterized in that, In step 2), the volume of the potassium sodium niobate ceramic nanoparticle filler is 5% to 30% of the total volume of 4,4'-diaminodiphenyl ether powder, pyromellitic dianhydride powder and potassium sodium niobate ceramic nanoparticle filler.

6. The method for preparing the polyimide-potassium sodium niobate composite film according to claim 1, characterized in that, In step 2), the conditions for repeated sonication and stirring include: sonication for 10-30 minutes, followed by stirring for 10-30 minutes, and repeating this cycle 5-10 times; then continue stirring for 6-12 hours, followed by sonication at room temperature for 0.5-1 hour; The conditions for the heating and stirring reaction include: heating and stirring at 30~60℃ for 10~30 min.

7. The method for preparing the polyimide-potassium sodium niobate composite film according to claim 1, characterized in that, In step 2), the casting conditions include: injecting a binary casting precursor solution of polyamic acid and potassium sodium niobate into the guide plate of an adjustable doctor blade, adjusting the doctor blade height to 10~20 μm, and casting on a clean glass plate at a speed of 10~20 cm / min.

8. The method for preparing the polyimide-potassium sodium niobate composite film according to claim 1, characterized in that, In step 2), the vacuum drying conditions include: evacuating at 0.4-0.8 MPa for 8-12 hours at 30-60℃; the gradient heating calcination conditions include: calcining at 80℃, 100℃, 120℃, 150℃, 180℃ and 300℃ for 1-2 hours respectively.

9. A polyimide and potassium-sodium niobate composite film, characterized by, The polyimide-sodium niobate composite film was prepared using the method described in any one of claims 1 to 8.

10. A piezoelectric nanogenerator, characterized in that, Including the polyimide and potassium sodium niobate composite film as described in claim 9; the piezoelectric nanogenerator also has d 31 Work mode and d 33 Work mode.

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