Method for preparing humidity-sensitive polyvinyl alcohol / lithium chloride / mxene composite film

Abstract

The present application relates to the technical field of energy conversion materials and devices, and aims to provide a preparation method of a humidity-sensitive polyvinyl alcohol / lithium chloride / MXene composite film.The method comprises the following steps: dispersing lithium chloride in a polyvinyl alcohol aqueous solution to obtain a uniform polyvinyl alcohol / lithium chloride suspension, adding MXene nanosheets, and then performing chemical crosslinking under ultrasonic dispersion conditions to obtain a homogeneous sol solution; then the sol solution is applied on a clean glass sheet in a spin coating manner, and after drying and forming, a film-shaped polyvinyl alcohol / lithium chloride / MXene composite material is attached to the glass sheet.The preparation process of the composite film is simple, the product is easy to obtain, and the process is environmentally friendly; a self-powered humidity sensing device prepared based on the film application has the characteristics of high sensitivity and fast response speed, high repeatability, and reliable cycle stability of the humidity response. The synergistic effect of lithium chloride and MXene makes the humidity change response sensitivity of the composite film higher, the signal stronger, and the linear change more regular.

Description

Technical Field

[0001] This invention belongs to the field of energy conversion materials and devices, and specifically relates to a self-powered humidity sensor device with humidity-sensitive properties made of polyvinyl alcohol / lithium chloride / MXene and its preparation method. Background Technology

[0002] With the trend towards miniaturization, portability, and multifunctional integration of electronic devices, relying solely on traditional power sources such as batteries and capacitors to drive these microelectronic devices is increasingly insufficient to meet practical operational needs. In the new era of interconnectivity, distributed sensor systems play a crucial role in collecting and converting information from the surrounding environment, forming a key component of the IoT hardware foundation. Triboelectric nanogenerators, based on contact electrification and electrostatic induction coupling, have attracted significant attention because they can collect and convert low-frequency, dispersed, minute mechanical energy from daily life into electrical energy, thereby enabling self-powered wearable electronic devices and IoT devices.

[0003] Triboelectric nanogenerators, based on triboelectric generation and electrostatic induction coupling, aim to convert widely distributed and disordered low-frequency energy into usable electrical energy by utilizing the triboelectric phenomenon. Currently, they are mainly applied in four areas: micro-nano energy, self-powered sensing, blue energy, and high-voltage power supplies. However, in everyday applications, triboelectric nanogenerators are often affected by environmental humidity, resulting in charge dissipation and varying degrees of performance degradation. Therefore, it is of great significance to improve the output performance of triboelectric nanogenerators by utilizing the enhancing properties of water in the environment, developing a novel material with simple fabrication process, high humidity response sensitivity, and strong regularity, and fabricating a self-powered humidity sensor.

[0004] Based on the unique response characteristics of hydrophilic polymer polyvinyl alcohol (PVA) films to humidity changes, high-performance triboelectric nanogenerators can be fabricated using PVA composite films with abundant hydrophilic groups as the friction layer. By adjusting for ambient humidity, their output performance can be enhanced, enabling them to function as efficient and stable energy harvesting devices in high-humidity environments. However, traditional PVA films suffer from drawbacks such as low sensitivity to humidity changes, weak and inconsistent signals, and poor triboelectric properties, which hinder their ability to meet humidity sensing requirements and limit their further development and application in the sensing field. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a method for preparing a humidity-sensitive polyvinyl alcohol / lithium chloride / MXene composite film.

[0006] To solve the technical problem, the solution of the present invention is:

[0007] A method for preparing a humidity-sensitive polyvinyl alcohol / lithium chloride / MXene composite film is provided, comprising the following steps:

[0008] (1) Add polyvinyl alcohol powder to deionized water and stir continuously in a 90°C water bath for 30 min to obtain a viscous polyvinyl alcohol aqueous solution with a mass concentration of 10%; after the solution is cooled to room temperature, add lithium chloride powder and disperse it with ultrasound, and continue stirring at room temperature to obtain a uniform polyvinyl alcohol / lithium chloride suspension; control the amount of lithium chloride powder added so that its mass ratio with polyvinyl alcohol is 1:2 to 1:30.

[0009] (2) Add MXene nanosheets to the suspension obtained in step (1) and perform chemical cross-linking under ultrasonic dispersion conditions to obtain a homogeneous polyvinyl alcohol / lithium chloride / MXene sol solution; control the amount of MXene nanosheets added so that the mass ratio of MXene nanosheets to lithium chloride is 1:1 to 1:15.

[0010] (3) The sol solution obtained in step (2) is applied to a clean glass slide by spin coating and dried at 80°C for 12 hours to form a thin film of polyvinyl alcohol / lithium chloride / MXene composite material attached to the glass slide.

[0011] As a preferred embodiment of the present invention, in step (1), the ultrasonic dispersion time is 0.5h and the continuous stirring time is 12h.

[0012] As a preferred embodiment of the present invention, in step (2), the ultrasonic dispersion time is 0.5h.

[0013] The present invention further provides a self-powered humidity sensor device using a polyvinyl alcohol / lithium chloride / MXene composite film prepared by the aforementioned method as the positive electrode friction material. The self-powered humidity sensor device includes a positive electrode, a negative electrode, and an external encapsulation material.

[0014] The positive electrode has a double-layer structure formed by an FTO glass substrate and a positive electrode friction material, and a conductive aluminum tape is provided at the edge of the FTO glass substrate as an electrode terminal; the negative electrode has a sandwich structure formed by a clean glass sheet, double-sided conductive nickel paste and negative electrode friction material, and an electrode terminal is provided at the edge of the double-sided conductive nickel paste; the two electrode terminals are respectively connected to a wire, and the wire is used to connect the load to form a closed circuit.

[0015] The positive and negative electrodes are arranged in parallel, so that the positive and negative electrode friction materials are opposite each other and maintain a distance. The polyimide film, which serves as the external encapsulation material, completely wraps the positive and negative electrodes, forming a hollow structure. The longitudinal section of the hollow structure is drum-shaped. When the positive and negative electrodes are subjected to external forces, the two sides of the hollow structure can undergo elastic deformation, allowing the surfaces of the positive and negative electrode friction materials to come into contact or separate.

[0016] As a preferred embodiment of the present invention, the negative electrode friction material is a commercially available PTFE film.

[0017] As a preferred embodiment of the present invention, the thickness of the positive electrode friction material and the negative electrode friction material is 100 μm.

[0018] As a preferred embodiment of the present invention, the length, width and thickness of the FTO glass substrate are 22mm×20mm×1mm, the length, width and thickness of the clean glass sheet are 20mm×20mm×1mm, and the contact area between the positive electrode friction material and the negative electrode friction material is 20mm×20mm.

[0019] As a preferred embodiment of the present invention, the maximum distance between the positive electrode friction material and the negative electrode friction material does not exceed 4 mm.

[0020] The present invention also provides a method for preparing the aforementioned self-powered humidity sensor, comprising the following steps:

[0021] (1) A homogeneous polyvinyl alcohol / lithium chloride / MXene sol solution was prepared according to the aforementioned method;

[0022] (2) First, a conductive aluminum tape is pasted 2 mm from the edge of the FTO glass substrate to serve as the lead-out electrode; then, the sol solution is applied to the surface of the FTO glass substrate by spin coating. The resulting coating and the conductive aluminum tape are located on the same side of the FTO glass substrate and do not contact each other; after drying at 80°C for 12 h, a thin film of polyvinyl alcohol / lithium chloride / MXene composite material is formed on the FTO glass substrate to obtain a positive electrode with a double-layer composite structure.

[0023] (3) A commercial PTFE membrane was bonded onto a clean glass slide using double-sided conductive nickel paste to obtain a sandwich-structured negative electrode;

[0024] (4) Electrode terminals are set on the edges of the conductive aluminum tape and the double-sided conductive nickel adhesive respectively; the two electrode terminals are connected to wires respectively, and the wires are used to connect the load to form a closed circuit.

[0025] (5) The positive and negative electrodes are arranged in parallel, so that the positive electrode friction material and the negative electrode friction material are opposite each other and maintain a distance; a polyimide film is used as the external encapsulation material to completely wrap the positive and negative electrodes to form a hollow structure; the longitudinal section of the hollow structure is drum-shaped, and when the positive and negative electrodes are subjected to external force, the two sides of the hollow structure can undergo elastic deformation, so that the surfaces of the positive electrode friction material and the negative electrode friction material can make contact and separation operations.

[0026] Description of the invention principle:

[0027] This invention prepares a homogeneous polyvinyl alcohol / lithium chloride / MXene sol solution via chemical crosslinking, and then fabricates a composite film on an FTO glass substrate using spin coating. When used as a positive electrode material for sensor devices, the high hygroscopicity of lithium chloride allows the polyvinyl alcohol composite film to absorb moisture from the air, increasing the film's surface viscosity and thus enhancing its interaction with the PTFE film. This also significantly shortens the response time of the triboelectric nanogenerator during separation, enabling rapid transfer of induced charges and achieving a high instantaneous peak current density. Introducing two-dimensional MXene nanosheets promotes the crosslinking of polyvinyl alcohol and forms microchannels within the composite film; improving ion transport enhances the conductivity of the composite film, thereby improving the output performance of the triboelectric nanogenerator.

[0028] Compared with the prior art, the technical advantages of this invention are:

[0029] (1) The polyvinyl alcohol / lithium chloride / MXene composite film of the present invention has a simple preparation process, readily available products, and is environmentally friendly; the self-powered humidity sensor device prepared based on the application of this film has the characteristics of high sensitivity and fast response speed, high repeatability, and reliable cycle stability of humidity response.

[0030] (2) The lithium chloride in the composite film of the present invention has high hygroscopicity, which makes the composite film easy to absorb moisture from the environment, improves the adhesion characteristics of the film, increases the surface adhesion, and thus enhances the interaction with the negative electrode friction layer material when in contact, greatly shortens the response time when the triboelectric nanogenerator is separated, and thus significantly improves the electrical output performance of the energy conversion device.

[0031] (3) By introducing the two-dimensional material MXene, this invention promotes the cross-linking of polyvinyl alcohol and forms microchannels of polyvinyl alcohol molecular chains and water molecules in the composite film, thereby improving the charge transport efficiency and realizing the efficient energy conversion of the material. The synergistic effect of lithium chloride and MXene makes the humidity change response sensitivity of the composite film higher, the signal enhanced and exhibits a more regular linear change, which is conducive to the promotion and application of this humidity sensor in the field of sensing.

[0032] (4) The present invention can regulate the output performance of the triboelectric energy conversion device by adjusting the lithium chloride content and the ambient humidity.

[0033] (5) The self-powered humidity sensor of the present invention does not require an external power supply, which can realize the miniaturization and diversification of the device. It has excellent electrical output stability, which can ensure the effective collection of the neglected low-frequency energy generated by daily activities. It has great advantages in applications such as self-powered humidity sensing and human respiratory humidity detection. Attached Figure Description

[0034] Figure 1This is a schematic diagram of the structure of the self-powered humidity sensor in this invention;

[0035] The attached figures are labeled as follows: 1 FTO glass substrate, 2 conductive aluminum tape, 3 polyvinyl alcohol / lithium chloride / MXene composite film, 4 commercial PTFE film, 5 double-sided conductive nickel paste, 6 clean glass sheet, 7 MXene nanosheets, 8 lithium chloride powder, 9 polyvinyl alcohol molecular chain, 10 polyimide film.

[0036] Figure 2 This is a SEM image of the polyvinyl alcohol / lithium chloride / MXene composite film prepared according to the present invention at a relative humidity of 90%.

[0037] Figure 3 This is a graph showing the relationship between short-circuit current and time when the self-powered humidity sensor device prepared in Example 3 is operating at a relative humidity of 50-98%.

[0038] Figure 4 This is a graph showing the relationship between short-circuit current and time when the self-powered humidity sensor device prepared in Example 3 is operating at a relative humidity of 30-90%.

[0039] Figure 5 This is a graph showing the relationship between short-circuit current and time for the self-powered humidity sensor device prepared in Comparative Example 2 when operating at a relative humidity of 50-98%.

[0040] Figure 6 This is a comparison graph showing the relationship between short-circuit current and time when the self-powered humidity sensor device prepared in Example 3 and the self-powered humidity sensor devices in Comparative Examples 1 and 2 are operating at a relative humidity of 90%. Detailed Implementation

[0041] The features and advantages of the present invention are explained in detail below with reference to specific embodiments. It should be understood that the specific embodiments described below are for illustration and explanation only and are not intended to limit the present invention.

[0042] like Figure 1 As shown, the self-powered humidity sensor device provided in various embodiments of the present invention includes a positive electrode, a negative electrode, and an external encapsulation material.

[0043] The positive electrode has a double-layer structure formed by an FTO glass substrate and a positive electrode friction material, with conductive aluminum tape as electrode terminals at the edge of the FTO glass substrate. The negative electrode has a sandwich structure formed by a clean glass sheet, double-sided conductive nickel paste, and a negative electrode friction material, with electrode terminals at the edge of the double-sided conductive nickel paste. The two electrode terminals are connected to wires, which are used to connect a load to form a closed circuit. The positive and negative electrodes are arranged in parallel, with the positive and negative electrode friction materials facing each other and maintaining a distance. A polyimide film, serving as the external encapsulation material, completely encapsulates the positive and negative electrodes, forming a hollow structure. The longitudinal section of this hollow structure is drum-shaped, allowing elastic deformation on both sides of the hollow structure when the positive and negative electrodes are subjected to external forces, enabling the surfaces of the positive and negative electrode friction materials to contact or separate.

[0044] Optionally, the FTO glass substrate has a length, width, and thickness of 22mm × 20mm × 1mm, and the clean glass sheet has a length, width, and thickness of 20mm × 20mm × 1mm. The positive electrode friction material and the negative electrode friction material have a thickness of 100μm, a contact area of ​​20mm × 20mm, and a maximum spacing of no more than 4mm.

[0045] The positive electrode friction material is the core of this invention's technological innovation. This material is a humidity-sensitive polyvinyl alcohol / lithium chloride / MXene composite film. Specifically, the positive electrode is prepared by the following method:

[0046] (1) Add polyvinyl alcohol powder to deionized water and stir continuously in a 90°C water bath for 30 min to obtain a viscous polyvinyl alcohol aqueous solution with a mass concentration of 10%; after the solution is cooled to room temperature, add lithium chloride powder and disperse it ultrasonically for 0.5 h, and continue stirring at room temperature for 12 h to obtain a uniform polyvinyl alcohol / lithium chloride suspension; control the amount of lithium chloride powder added so that its mass ratio with polyvinyl alcohol is 1:2 to 1:30.

[0047] (2) Add MXene nanosheets to the suspension obtained in step (1), and disperse them by ultrasonication for 0.5 h to perform chemical cross-linking to obtain a homogeneous polyvinyl alcohol / lithium chloride / MXene sol solution; control the amount of MXene nanosheets added so that the mass ratio of MXene nanosheets to lithium chloride is 1:1 to 1:15.

[0048] (3) First, a conductive aluminum tape is pasted 2 mm from the edge of the FTO glass substrate to serve as the lead-out electrode; then, the sol solution is applied to the surface of the FTO glass substrate by spin coating. The resulting coating and the conductive aluminum tape are located on the same side of the FTO glass substrate and do not contact each other; after drying at 80°C for 12 h, a thin film of polyvinyl alcohol / lithium chloride / MXene composite material is formed on the FTO glass substrate to obtain a positive electrode with a double-layer composite structure.

[0049] The MXene nanosheets used in this invention can be prepared by referring to the method described in Chinese Invention Patent CN201610898366.4, or commercial products can be used directly.

[0050] The negative electrode friction material is a commercially available PTFE film. Specifically, a sandwich-structured negative electrode is obtained by attaching the commercial PTFE film onto a clean glass slide using double-sided conductive nickel paste.

[0051] Assembly method of self-powered humidity sensor:

[0052] (1) Connect electrode terminals to the edges of conductive aluminum tape and double-sided conductive nickel paste respectively, and then connect the two electrode terminals to wires respectively. The wires are used to connect the load to form a closed circuit.

[0053] (2) Arrange the positive and negative electrodes in parallel so that the positive electrode friction material and the negative electrode friction material are opposite each other and maintain a distance.

[0054] (3) A hollow structure is formed by completely encapsulating the positive and negative electrodes with a polyimide film as the external encapsulation material. The longitudinal section of the hollow structure is drum-shaped. When the positive and negative electrodes are subjected to external force, the two sides of the hollow structure can undergo elastic deformation, so that the surfaces of the positive electrode friction material and the negative electrode friction material can make contact and separation operations.

[0055] Example 1

[0056] This example uses lithium chloride and MXene as fillers and polyvinyl alcohol as the matrix material, employing the method used in this invention to prepare a polyvinyl alcohol / lithium chloride / MXene composite film and a self-powered humidity sensor.

[0057] The specific steps are as follows:

[0058] (1) Polyvinyl alcohol powder was added to deionized water and heated in a 90°C water bath for 30 min under continuous magnetic stirring to obtain a polyvinyl alcohol aqueous solution with a mass concentration of 10% and a certain viscosity. After the prepared aqueous solution was cooled to room temperature, lithium chloride powder was ultrasonically dispersed in the obtained solution after stirring at room temperature for 12 h, followed by magnetic stirring overnight to make it uniform. The amount of lithium chloride powder added was controlled so that the mass ratio of polyvinyl alcohol to lithium chloride was 2:1. Then, a certain amount of MXene nanosheets were ultrasonically dispersed into the solution for 0.5 h, so that the mass ratio of MXene nanosheets to lithium chloride was 1:15. A homogeneous polyvinyl alcohol / lithium chloride / MXene sol solution was prepared by chemical crosslinking.

[0059] Conductive aluminum tape was attached 2 mm from the edge of a 22 mm × 20 mm FTO glass substrate (glass / fluorine-doped tin dioxide coated glass sheet) to serve as the lead-out electrode; then, a sol solution was spin-coated onto the FTO glass substrate and dried in an oven at 80 °C for 12 h to form a thin film of polyvinyl alcohol / lithium chloride / MXene composite material on the FTO glass substrate. The composite material layer and the conductive aluminum tape were located on the same side of the FTO glass substrate and did not contact each other; thus, a double-layer composite structure positive electrode was obtained.

[0060] A sandwich-structured negative electrode is obtained by attaching a commercial PTFE membrane onto a clean glass slide using double-sided conductive nickel paste.

[0061] (2) Prepare a self-powered humidity sensor according to the above assembly method. Set the working parameters to 50N and 5Hz in the contact-separation working mode, and the positive and negative electrode separation distance is no more than 4mm. Test its electrical output performance.

[0062] The self-powered humidity sensor described in this example achieves its optimal short-circuit current, approximately 21.35 μA, when operating at a relative humidity of 70%.

[0063] Example 2

[0064] This example uses lithium chloride and MXene as fillers and polyvinyl alcohol as the matrix material, employing the method used in this invention to prepare a polyvinyl alcohol / lithium chloride / MXene composite film and a self-powered humidity sensor.

[0065] The specific steps are as follows:

[0066] (1) Polyvinyl alcohol powder was added to deionized water and heated in a 90°C water bath for 30 min under continuous magnetic stirring to obtain a polyvinyl alcohol aqueous solution with a mass concentration of 10% and a certain viscosity. After the prepared aqueous solution was cooled to room temperature, lithium chloride powder was ultrasonically dispersed in the obtained solution after stirring at room temperature for 12 h, followed by magnetic stirring overnight to make it uniform. The amount of lithium chloride powder added was controlled so that the mass ratio of polyvinyl alcohol to lithium chloride was 3:1. Then, a certain amount of MXene nanosheets were ultrasonically dispersed into the solution for 0.5 h, so that the mass ratio of MXene nanosheets to lithium chloride was 1:10. A homogeneous polyvinyl alcohol / lithium chloride / MXene sol solution was prepared by chemical crosslinking.

[0067] Following the procedure in Example 1, positive and negative electrodes were prepared.

[0068] (2) Prepare a self-powered humidity sensor according to the above assembly method. Set the working parameters to 50N and 5Hz in the contact-separation working mode, and the positive and negative electrode separation distance is no more than 4mm. Test its electrical output performance.

[0069] The self-powered humidity sensor described in this example achieves its optimal short-circuit current, approximately 23.17 μA, when operating at a relative humidity of 80%.

[0070] Example 3

[0071] This example uses lithium chloride and MXene as fillers and polyvinyl alcohol as the matrix material, employing the method used in this invention to prepare a polyvinyl alcohol / lithium chloride / MXene composite film and a self-powered humidity sensor.

[0072] The specific steps are as follows:

[0073] (1) Polyvinyl alcohol powder was added to deionized water and heated in a 90°C water bath for 30 min under continuous magnetic stirring to obtain a polyvinyl alcohol aqueous solution with a mass concentration of 10% and a certain viscosity. After the prepared aqueous solution was cooled to room temperature, lithium chloride powder was ultrasonically dispersed in the obtained solution after stirring at room temperature for 12 h, followed by magnetic stirring overnight to make it uniform. The amount of lithium chloride powder added was controlled so that the mass ratio of polyvinyl alcohol to lithium chloride was 4:1. Then, a certain amount of MXene nanosheets were ultrasonically dispersed into the solution for 0.5 h, so that the mass ratio of MXene nanosheets to lithium chloride was 2:15. A homogeneous polyvinyl alcohol / lithium chloride / MXene sol solution was prepared by chemical crosslinking.

[0074] Following the procedure in Example 1, positive and negative electrodes were prepared.

[0075] (2) Prepare a self-powered humidity sensor according to the above assembly method. Set the working parameters to 50N and 5Hz in the contact-separation working mode, and the positive and negative electrode separation distance is no more than 4mm. Test its electrical output performance.

[0076] The short-circuit current versus time graph of the self-powered humidity sensor described in this example when operating at a relative humidity of 30-90% is shown in the attached figure. Figure 4 As shown. Furthermore, it achieves its optimal short-circuit current, approximately 26.91 μA, when operating at a relative humidity of 90%.

[0077] Example 4

[0078] This example uses lithium chloride and MXene as fillers and polyvinyl alcohol as the matrix material, employing the method used in this invention to prepare a polyvinyl alcohol / lithium chloride / MXene composite film and a self-powered humidity sensor.

[0079] The specific steps are as follows:

[0080] (1) Polyvinyl alcohol powder was added to deionized water and heated in a 90°C water bath for 30 min under continuous magnetic stirring to obtain a polyvinyl alcohol aqueous solution with a mass concentration of 10% and a certain viscosity. After the prepared aqueous solution was cooled to room temperature, lithium chloride powder was ultrasonically dispersed in the obtained solution after stirring at room temperature for 12 h, and then magnetically stirred overnight to make it uniform. The amount of lithium chloride powder added was controlled so that the mass ratio of polyvinyl alcohol to lithium chloride was 5:1. Then, a certain amount of MXene nanosheets were ultrasonically dispersed into the solution for 0.5 h, so that the mass ratio of MXene nanosheets to lithium chloride was 1:6. A homogeneous polyvinyl alcohol / lithium chloride / MXene sol solution was prepared by chemical crosslinking.

[0081] Following the procedure in Example 1, positive and negative electrodes were prepared.

[0082] (2) Prepare a self-powered humidity sensor according to the above assembly method. Set the working parameters to 50N and 5Hz in the contact-separation working mode, and the positive and negative electrode separation distance is no more than 4mm. Test its electrical output performance.

[0083] The self-powered humidity sensor described in this example achieves its optimal short-circuit current, approximately 24.13 μA, when operating at a relative humidity of 80%.

[0084] Example 5

[0085] This example uses lithium chloride and MXene as fillers and polyvinyl alcohol as the matrix material, employing the method used in this invention to prepare a polyvinyl alcohol / lithium chloride / MXene composite film and a self-powered humidity sensor.

[0086] The specific steps are as follows:

[0087] (1) Polyvinyl alcohol powder was added to deionized water and heated in a 90°C water bath for 30 min under continuous magnetic stirring to obtain a polyvinyl alcohol aqueous solution with a mass concentration of 10% and a certain viscosity. After the prepared aqueous solution was cooled to room temperature, lithium chloride powder was ultrasonically dispersed in the obtained solution after stirring at room temperature for 12 h, followed by magnetic stirring overnight to make it uniform. The amount of lithium chloride powder added was controlled so that the mass ratio of polyvinyl alcohol to lithium chloride was 10:1. Then, a certain amount of MXene nanosheets were ultrasonically dispersed into the solution for 0.5 h, so that the mass ratio of MXene nanosheets to lithium chloride was 1:5. A homogeneous polyvinyl alcohol / lithium chloride / MXene sol solution was prepared by chemical crosslinking.

[0088] Following the procedure in Example 1, positive and negative electrodes were prepared.

[0089] (2) Prepare a self-powered humidity sensor according to the above assembly method. Set the working parameters to 50N and 5Hz in the contact-separation working mode, and the positive and negative electrode separation distance is no more than 4mm. Test its electrical output performance.

[0090] The self-powered humidity sensor described in this example achieves its optimal short-circuit current, approximately 19.2 μA, when operating at a relative humidity of 80%.

[0091] Example 6

[0092] This example uses lithium chloride and MXene as fillers and polyvinyl alcohol as the matrix material, employing the method used in this invention to prepare a polyvinyl alcohol / lithium chloride / MXene composite film and a self-powered humidity sensor.

[0093] The specific steps are as follows:

[0094] (1) Polyvinyl alcohol powder was added to deionized water and heated in a 90°C water bath for 30 min under continuous magnetic stirring to obtain a polyvinyl alcohol aqueous solution with a mass concentration of 10% and a certain viscosity. After the prepared aqueous solution was cooled to room temperature, lithium chloride powder was ultrasonically dispersed in the obtained solution after stirring at room temperature for 12 h, followed by magnetic stirring overnight to make it uniform. The amount of lithium chloride powder added was controlled so that the mass ratio of polyvinyl alcohol to lithium chloride was 15:1. Then, a certain amount of MXene nanosheets were ultrasonically dispersed into the solution for 0.5 h, so that the mass ratio of MXene nanosheets to lithium chloride was 1:2. A homogeneous polyvinyl alcohol / lithium chloride / MXene sol solution was prepared by chemical crosslinking.

[0095] Following the procedure in Example 1, positive and negative electrodes were prepared.

[0096] (2) Prepare a self-powered humidity sensor according to the above assembly method. Set the working parameters to 50N and 5Hz in the contact-separation working mode, and the positive and negative electrode separation distance is no more than 4mm. Test its electrical output performance.

[0097] The self-powered humidity sensor described in this example achieves its optimal short-circuit current, approximately 8.08 μA, when operating at a relative humidity of 90%.

[0098] Example 7

[0099] This example uses lithium chloride and MXene as fillers and polyvinyl alcohol as the matrix material, employing the method used in this invention to prepare a polyvinyl alcohol / lithium chloride / MXene composite film and a self-powered humidity sensor.

[0100] The specific steps are as follows:

[0101] (1) Polyvinyl alcohol powder was added to deionized water and heated in a 90°C water bath for 30 min under continuous magnetic stirring to obtain a polyvinyl alcohol aqueous solution with a mass concentration of 10% and a certain viscosity. After the prepared aqueous solution was cooled to room temperature, lithium chloride powder was ultrasonically dispersed in the obtained solution after stirring at room temperature for 12 h, followed by magnetic stirring overnight to make it uniform. The amount of lithium chloride powder added was controlled so that the mass ratio of polyvinyl alcohol to lithium chloride was 20:1. Then, a certain amount of MXene nanosheets were ultrasonically dispersed into the solution for 0.5 h, so that the mass ratio of MXene nanosheets to lithium chloride was 2:3. A homogeneous polyvinyl alcohol / lithium chloride / MXene sol solution was prepared by chemical crosslinking.

[0102] Following the procedure in Example 1, positive and negative electrodes were prepared.

[0103] (2) Prepare a self-powered humidity sensor according to the above assembly method. Set the working parameters to 50N and 5Hz in the contact-separation working mode, and the positive and negative electrode separation distance is no more than 4mm. Test its electrical output performance.

[0104] The self-powered humidity sensor described in this example achieves its optimal short-circuit current, approximately 9.31 μA, when operating at a relative humidity of 90%.

[0105] Example 8

[0106] This example uses lithium chloride and MXene as fillers and polyvinyl alcohol as the matrix material, employing the method used in this invention to prepare a polyvinyl alcohol / lithium chloride / MXene composite film and a self-powered humidity sensor.

[0107] The specific steps are as follows:

[0108] (1) Polyvinyl alcohol powder was added to deionized water and heated in a 90°C water bath for 30 min under continuous magnetic stirring to obtain a polyvinyl alcohol aqueous solution with a mass concentration of 10% and a certain viscosity. After the prepared aqueous solution was cooled to room temperature, lithium chloride powder was ultrasonically dispersed in the obtained solution after stirring at room temperature for 12 h, followed by magnetic stirring overnight to make it uniform. The amount of lithium chloride powder added was controlled so that the mass ratio of polyvinyl alcohol to lithium chloride was 25:1. Then, a certain amount of MXene nanosheets were ultrasonically dispersed into the solution for 0.5 h, so that the mass ratio of MXene nanosheets to lithium chloride was 5:6. A homogeneous polyvinyl alcohol / lithium chloride / MXene sol solution was prepared by chemical crosslinking.

[0109] Following the procedure in Example 1, positive and negative electrodes were prepared.

[0110] (2) Prepare a self-powered humidity sensor according to the above assembly method. Set the working parameters to 50N and 5Hz in the contact-separation working mode, and the positive and negative electrode separation distance is no more than 4mm. Test its electrical output performance.

[0111] The self-powered humidity sensor described in this example achieves its optimal short-circuit current, approximately 8.04 μA, when operating at a relative humidity of 90%.

[0112] Example 9

[0113] This example uses lithium chloride and MXene as fillers and polyvinyl alcohol as the matrix material, employing the method used in this invention to prepare a polyvinyl alcohol / lithium chloride / MXene composite film and a self-powered humidity sensor.

[0114] The specific steps are as follows:

[0115] (1) Polyvinyl alcohol powder was added to deionized water and heated in a 90°C water bath for 30 min under continuous magnetic stirring to obtain a 10 wt% polyvinyl alcohol aqueous solution with a certain viscosity. After the prepared aqueous solution was cooled to room temperature, lithium chloride powder was ultrasonically dispersed in the obtained solution after stirring at room temperature for 12 h, followed by magnetic stirring overnight to make it uniform. The amount of lithium chloride powder added was controlled so that the mass ratio of polyvinyl alcohol to lithium chloride was 30:1. Then, a certain amount of MXene nanosheets were ultrasonically dispersed into the solution for 0.5 h, so that the mass ratio of MXene nanosheets to lithium chloride was 1:1. A homogeneous polyvinyl alcohol / lithium chloride / MXene sol solution was prepared by chemical crosslinking.

[0116] Following the procedure in Example 1, positive and negative electrodes were prepared.

[0117] (2) Prepare a self-powered humidity sensor according to the above assembly method. Set the working parameters to 50N and 5Hz in the contact-separation working mode, and the positive and negative electrode separation distance is no more than 4mm. Test its electrical output performance.

[0118] The self-powered humidity sensor described in this example achieves its optimal short-circuit current, approximately 8.14 μA, when operating at a relative humidity of 80%.

[0119] Comparative Example 1

[0120] This example uses polyvinyl alcohol as the matrix material and employs the method used in this invention to prepare polyvinyl alcohol thin film materials and self-powered humidity sensor devices.

[0121] The specific steps are as follows:

[0122] (1) Add polyvinyl alcohol powder to deionized water and heat in a water bath at 90°C for 30 minutes under continuous magnetic stirring to obtain a 10wt% polyvinyl alcohol aqueous solution with a certain viscosity. Stir magnetically overnight to make it uniform.

[0123] Conductive aluminum tape was attached 2 mm from the edge of a 22 mm × 20 mm FTO glass substrate (glass / fluorine-doped tin dioxide coated glass sheet) to serve as the lead-out electrode; then, a polyvinyl alcohol aqueous solution was spin-coated onto the FTO glass substrate and placed in an oven to dry at 80 °C for 12 h to form a thin film of polyvinyl alcohol material on the FTO glass substrate, thereby obtaining a double-layer composite positive electrode.

[0124] Following the procedure in Example 1, a negative electrode was prepared.

[0125] (2) Prepare a self-powered humidity sensor according to the above assembly method. Set the working parameters to 50N and 5Hz in the contact-separation working mode, and the positive and negative electrode separation distance is no more than 4mm. Test its electrical output performance.

[0126] The self-powered humidity sensor described in this comparative example achieves its optimal short-circuit current, approximately 12.31 μA, when operating at a relative humidity of 90%.

[0127] Comparative Example 2

[0128] This example uses lithium chloride as a filler and polyvinyl alcohol as a matrix material, employing the method described in this invention to prepare a polyvinyl alcohol / lithium chloride composite film and a self-powered humidity sensor.

[0129] The specific steps are as follows:

[0130] (1) Polyvinyl alcohol powder was added to deionized water and heated in a water bath at 90°C for 30 min under continuous magnetic stirring to obtain a 10 wt% polyvinyl alcohol aqueous solution with a certain viscosity. After the prepared aqueous solution was cooled to room temperature, lithium chloride powder was ultrasonically dissolved in the solution for 0.5 h and then stirred at room temperature for 12 h. The solution was then magnetically stirred overnight to obtain a uniform dispersion. The amount of lithium chloride powder added was controlled so that the mass ratio of polyvinyl alcohol to lithium chloride was 4:1.

[0131] Conductive aluminum tape was attached 2 mm from the edge of an FTO glass substrate (glass / fluorine-doped tin dioxide coated glass sheet) with an area of ​​22 mm × 20 mm to serve as the lead-out electrode; then the dispersion was spin-coated onto the FTO glass substrate and placed in an oven to dry at 80 °C for 12 h to form a thin film of polyvinyl alcohol / lithium chloride composite material on the FTO glass substrate, thereby obtaining a positive electrode with a double-layer composite structure.

[0132] Following the procedure in Example 1, a negative electrode was prepared.

[0133] (2) Prepare a self-powered humidity sensor according to the above assembly method. Set the working parameters to 50N and 5Hz in the contact-separation working mode, and the positive and negative electrode separation distance is no more than 4mm. Test its electrical output performance.

[0134] The self-powered humidity sensor described in this comparative example operates with a short-circuit current versus time when the relative humidity is between 50% and 98%, as shown in the attached graph. Figure 5 As shown. The optimal short-circuit current is reached at a relative humidity of 90%, which is approximately 20.41 μA.

[0135] Comparison of implementation results:

[0136] As can be observed from the examples and comparative examples, this invention utilizes the high hygroscopicity of lithium chloride combined with the high conductivity of the two-dimensional material MXene. This improves the adhesion characteristics of the thin film, increases surface adhesion to enhance the interaction with the negative electrode friction layer material, and simultaneously promotes the cross-linking of polyvinyl alcohol, forming microchannels of polyvinyl alcohol molecular chains and water molecules in the composite film. This, in turn, improves charge transport efficiency. The synergistic effect of both enhances the electrical output performance of the self-powered humidity sensor. For example... Figure 6 As shown, under a relative humidity of 90%, the output performance of the films prepared in Examples 1 and 2 were 12.31 μA and 20.41 μA, respectively, while the output performance of the self-powered humidity sensor prepared in Example 3 was improved to 26.91 μA. Furthermore, as... Figure 5 As shown, the device described in Example 3 exhibits a relatively regular linear change within a relative humidity range of 30% to 90%, which is beneficial for the widespread application of this humidity sensor in the field of sensing.

[0137] It should be noted that the above embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

Claims

1. A method for preparing a humidity-sensitive polyvinyl alcohol / lithium chloride / MXene composite film, characterized in that, Includes the following steps: (1) Add polyvinyl alcohol powder to deionized water and stir continuously in a 90°C water bath for 30 min to obtain a viscous polyvinyl alcohol aqueous solution with a mass concentration of 10%; after the solution is cooled to room temperature, add lithium chloride powder and disperse it with ultrasound, and continue stirring at room temperature to obtain a uniform polyvinyl alcohol / lithium chloride suspension; control the amount of lithium chloride powder added so that its mass ratio with polyvinyl alcohol is 1:2 to 1:

30. (2) Add MXene nanosheets to the suspension obtained in step (1) and perform chemical cross-linking under ultrasonic dispersion conditions to obtain a homogeneous polyvinyl alcohol / lithium chloride / MXene sol solution; control the amount of MXene nanosheets added so that the mass ratio of MXene nanosheets to lithium chloride is 1:1 to 1:

15. (3) The sol solution obtained in step (2) is applied to a clean glass slide by spin coating and dried at 80°C for 12 hours to form a thin film of polyvinyl alcohol / lithium chloride / MXene composite material attached to the glass slide.

2. The method according to claim 1, characterized in that, In step (1), the ultrasonic dispersion time is 0.5 h, and the continuous stirring time is 12 h.

3. The method according to claim 1, characterized in that, In step (2), the ultrasonic dispersion time is 0.5 h.

4. A self-powered humidity sensor device using a polyvinyl alcohol / lithium chloride / MXene composite film prepared by the method of claim 1 as the positive electrode tribological material, characterized in that... The self-powered humidity sensor includes a positive electrode, a negative electrode, and an external encapsulation material; The positive electrode has a double-layer structure formed by an FTO glass substrate and a positive electrode friction material, and a conductive aluminum tape is provided at the edge of the FTO glass substrate as an electrode terminal; the negative electrode has a sandwich structure formed by a clean glass sheet, double-sided conductive nickel paste and negative electrode friction material, and an electrode terminal is provided at the edge of the double-sided conductive nickel paste; the two electrode terminals are respectively connected to a wire, and the wire is used to connect the load to form a closed circuit. The positive and negative electrodes are arranged in parallel, so that the positive and negative electrode friction materials are opposite each other and maintain a distance. The polyimide film, which serves as the external encapsulation material, completely wraps the positive and negative electrodes, forming a hollow structure. The longitudinal section of the hollow structure is drum-shaped. When the positive and negative electrodes are subjected to external forces, the two sides of the hollow structure can undergo elastic deformation, allowing the surfaces of the positive and negative electrode friction materials to come into contact or separate.

5. The self-powered humidity sensor according to claim 4, characterized in that, The negative electrode friction material is a commercially available PTFE membrane.

6. The self-powered humidity sensor according to claim 4, characterized in that, The thickness of the positive electrode friction material and the negative electrode friction material is 100 μm.

7. The self-powered humidity sensor according to claim 4, characterized in that, The FTO glass substrate has a length, width, and thickness of 22mm×20mm×1mm, the clean glass sheet has a length, width, and thickness of 20mm×20mm×1mm, and the contact area between the positive electrode friction material and the negative electrode friction material is 20mm×20mm.

8. The self-powered humidity sensor according to claim 4, characterized in that, The maximum distance between the positive electrode friction material and the negative electrode friction material shall not exceed 4 mm.

9. The method for preparing the self-powered humidity sensor according to claim 4, characterized in that, Includes the following steps: (1) A homogeneous polyvinyl alcohol / lithium chloride / MXene sol solution was prepared according to the method described in claim 1; (2) First, a conductive aluminum tape is pasted 2 mm from the edge of the FTO glass substrate to serve as the lead-out electrode; then, the sol solution is applied to the surface of the FTO glass substrate by spin coating. The resulting coating and the conductive aluminum tape are located on the same side of the FTO glass substrate and do not contact each other; after drying at 80°C for 12 h, a thin film of polyvinyl alcohol / lithium chloride / MXene composite material is formed on the FTO glass substrate to obtain a positive electrode with a double-layer composite structure. (3) A commercial PTFE membrane was bonded onto a clean glass slide using double-sided conductive nickel paste to obtain a sandwich-structured negative electrode; (4) Electrode terminals are set on the edges of the conductive aluminum tape and the double-sided conductive nickel adhesive respectively; the two electrode terminals are connected to wires respectively, and the wires are used to connect the load to form a closed circuit. (5) The positive and negative electrodes are arranged in parallel, so that the positive electrode friction material and the negative electrode friction material are opposite each other and maintain a distance; a polyimide film is used as the external encapsulation material to completely wrap the positive and negative electrodes to form a hollow structure; the longitudinal section of the hollow structure is drum-shaped, and when the positive and negative electrodes are subjected to external force, the two sides of the hollow structure can undergo elastic deformation, so that the surfaces of the positive electrode friction material and the negative electrode friction material can make contact and separation operations.

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