Cellulose-based aerogel triboelectric material and preparation method thereof

Abstract

The invention belongs to the technical field of friction power generation materials, and particularly relates to a cellulose-based aerogel triboelectric material and a preparation method thereof. Comprising the following steps: gelatinizing first chitosan, and adding a first cross-linking agent for reaction to obtain first chitosan fibers; gelatinizing second chitosan, then carrying out homogenization treatment, adding a second cross-linking agent, and carrying out a reaction to obtain second chitosan fibers; sequentially adding a first chitosan fiber and a second chitosan fiber into the homogenized cellulose fiber dispersion liquid, sequentially adding a water-soluble metal salt and a third cross-linking agent, stirring and dispersing, carrying out a cross-linking reaction, and freezing to obtain a cellulose-based aerogel precursor; immersing into a solvent for solvent replacement, and extruding and drying to obtain the cellulose-based aerogel triboelectric material. According to the invention, the dielectric property of the cellulose-based triboelectric material is improved, the mechanical stability and humidity adaptability of the material are enhanced, and the energy efficiency of the material in a self-powered process in a high-humidity environment is enhanced.

Description

Technical Field

[0001] The present invention belongs to the technical field of triboelectric materials, and particularly relates to a cellulose-based aerogel triboelectric material and a preparation method thereof. Background Art

[0002] With the development of industries such as the Internet of Things and smart home, the scope of use of sensors has been significantly expanded, but their wide applicability is usually limited by external power sources and complex manufacturing processes. The invention of triboelectric nanogenerators provides an effective solution for realizing the self-driving of sensors and simplifying the manufacturing process. The English abbreviation of triboelectric nanogenerator is TENG; TENG is a convenient and sustainable green energy device that converts low-frequency and irregular mechanical energy into electrical energy based on the triboelectric effect and electrostatic induction, and has the advantages of high energy conversion efficiency, high output power, wide material selection range, high reliability, and low cost. The core component of TENG is triboelectric material, which plays a key role in determining the output power of TENG.

[0003] In the prior art, the commonly used triboelectric material is a petroleum-based synthetic polymer. The main advantages of this type of material are stable properties, but the disadvantages are that it is generally non-renewable and non-biodegradable, which has an adverse impact on the environment and the comprehensive benefits of applications.

[0004] Cellulose is one of the most abundant natural polysaccharides in the world and has a series of advantageous characteristics such as being renewable, biodegradable, chemically modifiable, and low-cost; a large number of oxygen atoms with lone electron pairs are contained on the surface of cellulose. The oxygen atoms have a high electronegativity and can attract electrons from adjacent other atoms, thereby forming negative local dipoles in the highest occupied molecular orbital band composed of non-bonding electrons and providing more electrons during the contact electrification process of cellulose. Therefore, cellulose is a good environmentally friendly triboelectric positive electrode material. However, in the process of using cellulose to prepare triboelectric materials in the prior art, due to the highly crystalline structure of cellulose, more hydroxyl groups are wrapped to form hydrogen bonds and cannot lose electrons during the contact electrification process, thus reducing the polarity and electron-losing ability of cellulose molecules. The abundant hydroxyl groups in the cellulose molecular weight are prone to adsorbing too much water, resulting in charge dissipation of the triboelectric material in a high-humidity environment and reducing the surface charge density of the cellulose material; the water molecules induce an electrostatic shielding effect, resulting in the dissipation of the surface charge of the friction layer material and the reduction of power output, which seriously deteriorates the performance of cellulose-based TENG and hinders its practical application. The prior art also points out that in the process of using cellulose to prepare triboelectric materials, the triboelectric output characteristics of cellulose can be enhanced by adding chitosan. However, due to the characteristics of both cellulose and chitosan having high resistivity and low dielectric constant, there is a problem of hindering the transfer and accumulation of charges in TENG devices, making the energy efficiency of the self-powered process of TENG in a high-humidity environment low. Summary of the Invention

[0005] To solve the above problems, the present invention provides a cellulose-based aerogel triboelectric material and a preparation method thereof, so as to improve the dielectric properties of the cellulose-based triboelectric material, enhance the mechanical stability and wet stability of the material, and enhance the energy efficiency of the self-powered process of the material in a high-humidity environment.

[0006] The present invention solves the above technical problems through the following technical solutions.

[0007] On the one hand, the present invention provides a preparation method of a cellulose-based aerogel triboelectric material, comprising the following steps: Step 1: Dissolve the first chitosan in the first acid solution to form a first precursor solution, stir and adjust the pH value to alkaline for gelation, then add a first cross-linking agent for the first cross-linking reaction to obtain first chitosan fibers.

[0008] Step 2: Dissolve the second chitosan in the second acid solution to form a second precursor solution, stir and adjust the pH value to alkaline for gelation, then perform homogenization treatment and add a second cross-linking agent for the second cross-linking reaction to obtain second chitosan fibers.

[0009] Step 3: Sequentially add the first chitosan fibers and the second chitosan fibers to the homogenized cellulose fiber dispersion liquid. After mixing evenly, sequentially add a water-soluble metal salt and a third cross-linking agent, stir and disperse, and then perform a third cross-linking reaction. After the reaction is completed, perform freezing to obtain a cellulose-based aerogel precursor.

[0010] Step 4: Immerse the cellulose-based aerogel precursor in a solvent for solvent replacement, and obtain a cellulose-based aerogel triboelectric material after extrusion and drying.

[0011] It should be noted that in the present invention, the first chitosan is gelated and crosslinked with the first crosslinking agent to form an amide structure, thereby forming chitosan microscale fibers; the second chitosan is gelated and homogenized, and crosslinked with the second crosslinking agent to form an amide structure, thereby forming chitosan micro / nanoscale fibers; through the homogenization, a multi-scale fiber entanglement framework is constructed by cellulose fibers, chitosan microscale fibers and chitosan micro / nanoscale fibers, and a chelation bond is formed through the complexation of water-soluble metal salt ions, and a multi-network structure is constructed by means of chemical crosslinking and hydrogen bond crosslinking. Then, through solvent exchange, extrusion rapid desolvation and environmental drying, a cellulose-based aerogel triboelectric material in the form of aerogel is formed. This aerogel has the characteristics of low apparent density, high specific surface area and adjustable surface chemical properties. Its porous structure helps to increase the effective contact area and provide abundant active sites for water molecules in a high-humidity environment. The prepared cellulose-based aerogel has a large number of water molecule active sites and a multi-network structure system with fast adsorption and desorption of water molecules, endowing the material with excellent humidity adaptability; the constructed multi-crosslinking network system of hydrogen bond crosslinking, chemical covalent crosslinking and ionic coordination endows the material with excellent mechanical properties and wet stability; metal ions improve the dielectric properties of the material, endowing the material with excellent triboelectric output characteristics, forming a material system with high stability, triboelectric characteristics and humidity adaptability.

[0012] Furthermore, the present invention provides a method for preparing a cellulose-based aerogel triboelectric material. First, the first chitosan is dissolved in an acid solution, and gelation transformation is induced by adjusting the pH value, so that an amide structure is formed between the active groups on the first cross-linking agent and the amino groups on the chitosan chain, realizing the cross-linking of chitosan molecular chains to form chitosan microscale fibers; second, the second chitosan is dissolved in an acid solution, and gelation transformation is induced by adjusting the pH value, and further homogenization treatment is carried out to improve the rheological properties of the polymer solution. The molecular chains are stretched and arranged along the flow direction under the action of shear force, reducing the entanglement density of the molecular chains. Then, an amide structure is formed between the active groups on the second cross-linking agent and the amino groups on the chitosan chain, realizing the cross-linking of chitosan molecular chains to form chitosan micro / nanoscale fibers; second, after the cellulose fiber dispersion is homogenized, multi-level dispersion is realized to construct cellulose fibers with a multi-scale structure. Then, using cellulose fibers and chitosan microscale fibers as the matrix skeleton, chitosan micro / nanoscale fibers as the reinforcing skeleton, and metal ions in the water-soluble metal salt as the reinforcing bridging points, chelation bonds can be formed with the active groups in chitosan and cellulose fibers. On the basis of the third cross-linking agent, a multi-network structure composite aerogel is formed through a multiple combination of chemical cross-linking, ion complexation, and hydrogen bond cross-linking. Finally, through solvent exchange, extrusion rapid desolvation, and environmental drying, a cellulose-based aerogel triboelectric material with a multi-network structure is constructed. This aerogel has the characteristics of a porous structure with a low apparent density and a high specific surface area. The porous structure is used to increase the effective contact area and free volume effect, and at the same time helps to form more active sites for water molecules in a high-humidity environment.

[0013] In some embodiments, the mass-volume ratio of the first chitosan, the first cross-linking agent, and the first acid solution is 0.5 g to 0.9 g: 0.1 g to 0.18 g: 40 mL. The first acid solution is hydrochloric acid, and the concentration of hydrochloric acid is 0.05 M to 0.2 M.

[0014] In some embodiments, the mass-volume ratio of the second chitosan, the second cross-linking agent, and the second acid solution is 0.05 g to 0.1 g: 0.01 g to 0.02 g: 20 mL. The second acid solution is hydrochloric acid, and the concentration of hydrochloric acid is 0.05 M to 0.2 M.

[0015] In some embodiments, the mass ratio of cellulose fibers, the first chitosan, and the second chitosan in the cellulose fiber dispersion is 1 g: 0.5 g to 0.9 g: 0.05 g to 0.1 g.

[0016] In some embodiments, the mass ratio of cellulose fibers and the soluble water-soluble metal salt in the cellulose fiber dispersion is 1 g: 0.04 g to 0.12 g, and the mass ratio of cellulose fibers and the third cross-linking agent in the cellulose fiber dispersion is 1 g: 0.1 g to 0.2 g.

[0017] It should be noted that the formulation of the technical solution of the present invention has the characteristics of low cost, simple process and environmental friendliness. Taking the multi-scale entanglement structure of cellulose fiber and chitosan micro / nanofiber as the skeleton, using chemical covalent crosslinking, ionic coordination and hydrogen bond crosslinking, combined with multiple strategies of freezing, solvent replacement, extrusion to remove solvent and normal temperature drying, a cellulose-based aerogel triboelectric material with excellent wet structural stability, mechanical properties, humidity adaptability and high triboelectric output characteristics is obtained. Chitosan is rich in amino groups with excellent electron-donating properties, which is beneficial to improving the dielectric properties of the aerogel. Introducing metal ions can improve the structural stability of the aerogel, reduce the crystallinity of cellulose and chitosan, further enhance the interfacial polarization effect, improve the transport characteristics of electrons and ions, increase the charge center spacing, and increase the dipole moment of the aerogel component molecules. The multi-crosslinked network structure helps to construct channels for water molecule adsorption, transport and desorption, improving the humidity adaptability and durability of the aerogel. The porous structure, molecular entanglement structure and solution exchange process of the aerogel contribute to the formation of a rough micro / nano surface, increasing the effective contact area and forming a larger number of electrostatic induction sites.

[0018] In some embodiments, the water-soluble metal salt is at least one of water-soluble copper salt, water-soluble aluminum salt, water-soluble magnesium salt, water-soluble calcium salt, water-soluble sodium salt, water-soluble iron salt, and water-soluble potassium salt.

[0019] It should be noted that the metal ions such as K + , Ca 2+ , Zn 2+ , Cu 2 + , Al 3+ and Fe 3+ produced by the hydrolysis of the water-soluble metal salt in the present invention can form chelation bonds with the active groups in chitosan and cellulose fibers, strengthening the molecular network structure. The present invention does not limit the specific types of its water-soluble copper salt, water-soluble aluminum salt, water-soluble magnesium salt, water-soluble calcium salt, water-soluble sodium salt, water-soluble iron salt or water-soluble potassium salt, as long as the metal ions such as K + , Ca 2+ , Zn 2+ , Cu 2+ , Al 3+ and Fe 3+ can be produced. Its copper salt, aluminum salt, magnesium salt, calcium salt, sodium salt, iron salt, and potassium salt are all water-soluble metal salts. For example, the copper salt can be CuCl2, etc., the aluminum salt can be AlCl3, etc., the magnesium salt can be MgCl2, etc., the calcium salt can be CaCl2, etc., the iron salt can be FeCl3, etc., the potassium salt can be KCl, etc., and the sodium salt can be NaCl, etc.

[0020] In some embodiments, the first crosslinking agent, the second crosslinking agent, and the third crosslinking agent are all glycidyl ethers, and the glycidyl ether is ethylene glycol diglycidyl ether or polyethylene glycol diglycidyl ether; the temperatures of the first crosslinking reaction, the second crosslinking reaction, and the third crosslinking reaction are all 50°C to 70°C, and the reaction times are all 4 h to 6 h.

[0021] It should be noted that during the first crosslinking reaction and the second crosslinking reaction, the epoxy groups on the glycidyl ether molecules open the ring and form amide structures with the amino groups on the chitosan chains, realizing the crosslinking of the chitosan molecular chains. During the third crosslinking reaction, the epoxy groups on the glycidyl ether molecules open the ring and crosslink with the amino groups on the chitosan chains and the hydroxyl groups on the cellulose chains respectively.

[0022] In some embodiments, the stirring rate of the first precursor solution is 1000 rpm to 2000 rpm, and the stirring rate of the second precursor solution is 500 rpm to 1000 rpm.

[0023] It should be noted that in the present invention, by means of high-speed shearing, chitosan fibers are formed into multi-scale fibers during the gelation transition process.

[0024] In some embodiments, the freezing temperature is -2°C to -10°C, the time is 1 h to 3 h, and the solvent replacement is to immerse the cellulose-based aerogel precursor in absolute ethanol and let it stand for 2 h to 4 h.

[0025] It should be noted that the present invention adopts the freezing method. Since hydrogen bond interaction dominates in the low-temperature environment, the strong lateral aggregation of cellulose chains is further promoted. During the freezing process, water molecules form ice crystals, resulting in further compression of the framework and more voids formed between the fibers. Through ethanol substitution and rapid desolvation, the water content is greatly reduced, the capillary force during the drying process is reduced, and the formation of physical crosslinking domains in the framework is promoted; then drying is carried out at room temperature environment, and finally a lightweight and porous cellulose-based aerogel triboelectric material is obtained. By means of freezing, solvent replacement, and room-temperature drying, the present invention effectively improves the disadvantages of high cost and high technical requirements existing in the methods of freeze-drying and supercritical drying in the process of preparing biomass aerogels in the prior art, as well as the problems of brittleness, poor flexibility, low physical strength, and small specific surface area of cellulose and its derivative aerogels due to low solid content.

[0026] Aiming at the problem that in the prior art, in order to reduce the surface tension of water and prevent the collapse of the gel structure during environmental drying, the preparation methods using surfactants such as sodium dodecyl sulfate and octylamine result in unstable aerogels and cause harm to the environment and ecology, the preparation process of the present invention adopts the method of solvent exchange. This method has the effects of being easy to expand and relatively environmentally friendly, and is conducive to industrial recycling.

[0027] In some embodiments, the cellulose fiber is one or a mixture of two of hardwood cellulose fibers and softwood cellulose fibers.

[0028] It should be noted that to disperse the cellulose fiber to form a cellulose fiber dispersion liquid, the solvent used is deionized water, and the concentration of the cellulose fiber dispersion liquid is not specifically limited. Only the amount of cellulose fiber used needs to be determined. After dispersing the hardwood cellulose fiber and softwood cellulose fiber raw materials in deionized water, use a homogenizer to homogenize for 10 min to 20 min at a rotation speed of 11000 rpm to 20000 rpm to obtain a dispersion liquid. After subjecting the dispersion liquid to suction filtration treatment, dry the residue to obtain cellulose fibers. Then disperse the cellulose fibers in deionized water to form a cellulose fiber dispersion liquid.

[0029] In some embodiments, the regulator used to adjust the pH value to alkaline is one or a mixture of several of NaOH, KOH or NH3·H2O. Prepare a pH adjustment solution with the regulator and add it to the first precursor solution or the second precursor solution in portions to adjust the pH value to 10.5 to 11.5.

[0030] On the other hand, the present invention provides a cellulose-based aerogel triboelectric material prepared by the above preparation method. The method for preparing the cellulose-based triboelectric material does not require any special equipment, and greatly shortens the time required for environmental drying. For example, an aerogel with a volume of 50 mm × 50 mm × 25 mm can be dried in just 3 h. The preparation process has low energy consumption, simple operation, the solvent is easy to recycle, and it is easy to expand. The triboelectric material assembled from the composite aerogel has good triboelectric output performance and durability, and the maximum output voltage is 205.8 V; in the humidity range of 40% RH to 95% RH, the TENG exhibits good wet response cycle characteristics and reversibility, and can accurately and stably detect different biological and non-biological sound signals and identify the electrical signals written by humans; this composite aerogel-based TENG can be applied to fields such as sound recognition, self-powered writing boards and identity recognition. This composite aerogel has good recyclability, durability and degradability.

[0031] The present invention has the following beneficial effects compared with the prior art: The preparation method of the cellulose-based aerogel triboelectric material provided by the present invention uses a first chitosan for gelation, crosslinks with a first crosslinking agent to form an amide structure, and forms chitosan micron-scale fibers; uses a second chitosan for gelation and homogenization treatment, crosslinks with a second crosslinking agent to form an amide structure, and forms chitosan micro / nano-scale fibers; constructs a multi-scale fiber entanglement framework through homogenized cellulose fibers, chitosan micron-scale fibers and chitosan micro / nano-scale fibers, and forms chelation bonds through ion complexation with water-soluble metal salts, and constructs a multi-network structure through chemical crosslinking and hydrogen bond crosslinking methods. Then, through solvent exchange, extrusion and rapid desolvation, and ambient drying, a cellulose-based aerogel triboelectric material in the form of an aerogel is formed. This aerogel has the characteristics of low density, high specific surface area, adjustable surface chemical properties and porous structure. Its porous structure helps to form additional active sites for water molecules in a high-humidity environment. Due to the large number of water molecule active sites in the prepared cellulose-based aerogel, it has a multi-network system for rapid adsorption and desorption of water molecules, making the material have excellent humidity adaptability; the constructed multi-crosslink network structure of hydrogen bond crosslinking, chemical covalent crosslinking and ion coordination endows the material with excellent mechanical properties and wet stability; metal ions improve the dielectric properties of the material, making the material have excellent triboelectric output characteristics, forming a material system with high stability, triboelectric characteristics and humidity adaptability.

[0032] The preparation process of the present invention is simple and can be completed using existing simple conventional equipment without using special equipment. Moreover, the prepared cellulose-based aerogel triboelectric material has excellent mechanical properties, moisture resistance, recyclability and degradability, and has the characteristics of low cost, greenness and good biocompatibility.

[0033] The present invention adopts a freezing method. Due to the dominant role of hydrogen bonds in a low-temperature environment, the strong lateral aggregation of cellulose chains is further promoted. During the freezing process, water molecules form ice crystals, resulting in further compression of the framework and forming more voids between the fibers. Through ethanol substitution and rapid desolvation, the water content is greatly reduced, reducing the capillary force during drying and promoting the formation of physical crosslinking domains in the framework; then ambient drying is carried out to finally obtain a lightweight and porous cellulose-based aerogel triboelectric material. This technology effectively improves the disadvantages of high cost and high technical requirements that usually exist when using freeze-drying and supercritical drying methods to prepare biomass aerogels in the prior art, and improves the problems that cellulose and its derivative aerogels are usually brittle, poor in flexibility, low in physical strength and small in specific surface area due to low solid content. Description of the Drawings

[0034] Figure 1 It is a physical diagram of the moldability of the cellulose-based aerogel prepared in Example 1 of the present invention. Figure 1In Figure i, it is the aerogel on the flower; in Figure ii, it is the aerogels of various shapes; in Figure iii, it is the aerogels in different twisted states; in Figure iv, it is the aerogels in different bent states.

[0035] Figure 2 They are the infrared spectra of the T2-M aerogel prepared in Examples 1 to 5 of the present invention, the CS-0.5 aerogel prepared in Example 12, the CS-0.7 aerogel prepared in Example 13, the CF / CS aerogel prepared in Comparative Example 1, and CF.

[0036] Figure 3 It is the Mg 2+ 2-M aerogel, CS powder, the X-ray diffraction patterns of the CF / CS aerogel prepared in Comparative Example 1, and the CF fibers prepared in Comparative Example 2.

[0037] Figure 4 They are the surface scanning electron microscope images of the T2-M aerogel prepared in the examples of the present invention and the CF / CS aerogel prepared in Comparative Example 1. Figure 4 In Figure a, it is the surface scanning electron microscope image of Comparative Example 1 at a size of 200 μm; in Figure b, it is the surface scanning electron microscope image of Example 1 at a size of 200 μm; in Figure c, it is the surface scanning electron microscope image of Example 2 at a size of 200 μm; in Figure d, it is the surface scanning electron microscope image of Example 3 at a size of 200 μm; in Figure e, it is the surface scanning electron microscope image of Example 4 at a size of 200 μm; in Figure f, it is the surface scanning electron microscope image of Example 5 at a size of 200 μm; in Figure a1, it is the surface scanning electron microscope image of Comparative Example 1 at a size of 50 μm; in Figure b1, it is the surface scanning electron microscope image of Example 1 at a size of 50 μm; in Figure c1, it is the surface scanning electron microscope image of Example 2 at a size of 50 μm; in Figure d1, it is the surface scanning electron microscope image of Example 3 at a size of 50 μm; in Figure e1, it is the surface scanning electron microscope image of Example 4 at a size of 50 μm; in Figure f1, it is the surface scanning electron microscope image of Example 5 at a size of 50 μm.

[0038] Figure 5 They are the cross-sectional scanning electron microscope images of the T2-M aerogel prepared in the examples of the present invention and the CF / CS aerogel prepared in Comparative Example 1. Figure 5In the figure, Figure a is the scanning electron microscope image of the cross-section of Comparative Example 1 at a size of 200 μm, Figure b is the scanning electron microscope image of the cross-section of Example 1 at a size of 200 μm, Figure c is the scanning electron microscope image of the cross-section of Example 2 at a size of 200 μm, Figure d is the scanning electron microscope image of the cross-section of Example 3 at a size of 200 μm, Figure e is the scanning electron microscope image of the cross-section of Example 4 at a size of 200 μm, Figure f is the scanning electron microscope image of the cross-section of Example 5 at a size of 200 μm, Figure a1 is the scanning electron microscope image of the cross-section of Comparative Example 1 at a size of 50 μm, Figure b1 is the scanning electron microscope image of the cross-section of Example 1 at a size of 50 μm, Figure c1 is the scanning electron microscope image of the cross-section of Example 2 at a size of 50 μm, Figure d1 is the scanning electron microscope image of the cross-section of Example 3 at a size of 50 μm, Figure e1 is the scanning electron microscope image of the cross-section of Example 4 at a size of 50 μm, and Figure f1 is the scanning electron microscope image of the cross-section of Example 5 at a size of 50 μm.

[0039] Figure 6 Mg prepared in Example 3 of the present invention 2+ Energy dispersive X-ray spectroscopy analysis diagram of 2-M aerogel. Figure 6 In the figure, Figure a is the scanning electron microscope image selected for the surface energy dispersive X-ray spectroscopy analysis of Example 3, Figure b is the C element distribution diagram of Figure a, Figure c is the N element distribution diagram of Figure a, Figure d is the Mg element distribution diagram of Figure a, Figure a1 is the scanning electron microscope image selected for the cross-section energy dispersive X-ray spectroscopy analysis of Example 3, Figure b1 is the C element distribution diagram of Figure a1, Figure c1 is the N element distribution diagram of Figure a1, and Figure d1 is the Mg element distribution diagram of Figure a1.

[0040] Figure 7 Compression stress-strain and compression modulus diagrams of T2-M aerogel prepared in the examples of the present invention and CF / CS aerogel prepared in Comparative Example 1. Figure 7 In the figure, (a) is the compression stress-strain diagram, and (b) is the compression modulus diagram.

[0041] Figure 8 Single compression cycle test diagram and residual stress diagram at different strains of T2-M aerogel prepared in the examples of the present invention and CF / CS aerogel prepared in Comparative Example 1. Figure 8 In the figure, (a) is the single compression cycle test diagram at different strains, and (b) is the residual stress diagram.

[0042] Figure 9 Before and after the wet stability test of T2-M aerogel prepared in the examples and CF / CS aerogel prepared in Comparative Example 1. Figure 9 In the figure, Figure a is the initial state diagram in water, Figure b is the state diagram after stirring and shaking in water, and Figure c is the comparison diagram before and after drying after continuous immersion in deionized water for 40 days.

[0043] Figure 10 Comparison diagram of output voltages of TENG prepared from T6-M aerogel in embodiments of the present invention under different external conditions. Figure 10 In figure (a), it is the output voltage diagram under the action of an external force of 7 Hz and 15 N. In figure (b), it is the output voltage diagram under the action of external forces of 3 Hz, 5 N and 7 Hz, 5 N. In figure (c), it is the output voltage diagram under the action of external forces of 3 Hz, 5 N and 3 Hz, 15 N.

[0044] Figure 11 Comparison diagram of output voltages of cellulose aerogel-based TENG prepared in embodiments 3, 6 and 7 of the present invention at different thicknesses. Figure 11 In figure (a), it is the output voltage diagram. In figure (b), it is the diagram of output performance vs. contact area. In figure (c), it is the diagram of thickness relationship. In figure (d), it is the diagram of output voltage and output power density with an external load resistance.

[0045] Figure 12 For TENG prepared from 7Mg 2+ 6-M aerogel, triboelectric output performance diagram under different humidity environments. Figure 12 In figure (a), it is the output voltage diagram. In figure (b), it is the data fitting diagram of output voltage. In figure (c), it is the output current diagram.

[0046] Figure 13 For TENG prepared from 7Mg 2+ 6-M aerogel, fitting diagram of output voltage for continuous humidity cycle test of TENG.

[0047] Figure 14 For TENG prepared from 7Mg 2+ 6-M aerogel, comparison diagram of detected electrical signals of TENG with different biological and non-biological sound audio signals. Figure 14 In figure (a), it is the comparison diagram of drum beating sound signal. In figure (b), it is the comparison diagram of dog barking sound signal. In figure (c), it is the comparison diagram of thunder and lightning sound signal. In figure (d), it is the comparison diagram of wood burning sound signal. In figure (e), it is the comparison diagram of a continuous section of piano sound signal.

[0048] Figure 15 For TENG prepared from 7Mg 2+ 6-M aerogel, recyclability comparison diagram. Figure 15 In figure (a), it is the comparison diagram of output voltages of different aerogel-based TENGs. In figure (b), it is the output current diagram of new and old aerogel-based TENGs. In figure (c), it is the transferred charge diagram of new and old aerogel-based TENGs.

[0049] Figure 16 Degradation process diagram of aerogels in embodiments 1 to 3 of the present invention and comparative example CF / CS aerogel.Figure 16 Figure i shows the initial state diagram, Figure ii shows the state diagram after 30 days of placement in the container, Figure iii shows the state diagram after 10 days of transfer to the natural environment, and Figure iv shows the state diagram after 30 days of transfer to the natural environment. Detailed implementation mode

[0050] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0051] It should be noted that the professional terms used in the present invention are only for the purpose of describing specific embodiments, and are not intended to limit the protection scope of the present invention. Unless otherwise specifically stated, various raw materials, reagents, instruments, and equipment used in the following embodiments of the present invention can be obtained through market purchase or prepared by existing methods.

[0052] The following will be further described through specific embodiments.

[0053] Example 1 A preparation method of a cellulose-based aerogel triboelectric material, comprising the following steps: S1. Immerse the softwood pulp paper in deionized water to fully absorb water and expand, and homogenize it with a homogenizer for 15 min at a rotation speed of 11000 rpm to obtain a pulp dispersion. After filtering the dispersion by suction filtration, dry the residue to obtain cellulose fibers. Take 1 g of cellulose fibers and add them to 200 mL of deionized water, and disperse them fully to obtain a cellulose fiber dispersion.

[0054] S2. Weigh 0.9 g of chitosan and dissolve it in 40 mL of a hydrochloric acid solution with a concentration of 0.1 M, and mechanically dissolve it to fully dissolve the chitosan to form a first precursor solution. Then, add a NaOH solution with a concentration of 1 M to adjust the pH value to 11, and at the same time, use mechanical stirring with a rotation speed controlled at 1500 rpm. Then, add 0.18 g of ethylene glycol diglycidyl ether and react at a temperature of 60 °C for 5 h to obtain the first chitosan fiber.

[0055] S3. Weigh 0.1 g of chitosan and dissolve it in 20 mL of hydrochloric acid solution with a concentration of 0.1 M. Through mechanical dissolution, make the chitosan fully dissolved to form a second precursor solution. Then, add a NaOH solution with a concentration of 1 M to adjust the pH value to 11, and at the same time, use magnetic stirring with the rotation speed controlled at 800 rpm. Then, use a homogenizer to homogenize for 3 min at a rotation speed of 11000 rpm. After that, add 0.02 g of ethylene glycol diglycidyl ether and react at a temperature of 60 °C for 5 h to obtain second chitosan fibers.

[0056] S4. Mix the cellulose fiber dispersion obtained in S1, the first chitosan fibers obtained in S2, and the second chitosan fibers obtained in S3. After mixing evenly, add 0.04 g of sodium chloride and 0.2 g of ethylene glycol diglycidyl ether in sequence, and stir for 30 min. Then, use ultrasonic dispersion for 1 h. After that, conduct the third reaction at a temperature of 60 °C for 5 h. After completion, place it in a filter screen to drain water and let it stand still. After no water droplets naturally drip down, freeze it at a temperature of -5 °C for 2 h to obtain a cellulose-based aerogel precursor. S5. Immerse the cellulose-based aerogel precursor in absolute ethanol at 60 °C and let it stand still for 3 h for solvent replacement. Then, place it between two glass flat plates and squeeze it. After squeezing, let it stand still and dry to obtain a cellulose-based aerogel triboelectric material; name it Na + 2-M aerogel.

[0057] Example 2 A preparation method of a cellulose-based aerogel triboelectric material, which is different from the preparation method of Example 1 in that: in S4, 0.04 g of calcium chloride and 0.2 g of ethylene glycol diglycidyl ether are added in sequence. The obtained cellulose-based aerogel triboelectric material is named Ca 2+ 2- M aerogel.

[0058] Example 3 A preparation method of a cellulose-based aerogel triboelectric material, which is different from the preparation method of Example 1 in that: in S4, 0.04 g of magnesium chloride and 0.2 g of ethylene glycol diglycidyl ether are added in sequence. The obtained cellulose-based aerogel triboelectric material is named Mg 2+ 2-M aerogel.

[0059] Example 4 A preparation method of a cellulose-based aerogel triboelectric material, which is different from the preparation method of Example 1 in that: in S4, 0.04 g of ferric chloride and 0.2 g of ethylene glycol diglycidyl ether are added in sequence. The obtained cellulose-based aerogel triboelectric material is named Fe 3+ 2-M aerogel.

[0060] Example 5 A preparation method of a cellulose-based aerogel triboelectric material. The difference in the preparation method of Example 1 is that in S4, 0.04 g of aluminum chloride and 0.2 g of ethylene glycol diglycidyl ether are added successively. The obtained cellulose-based aerogel triboelectric material is named Al 3+ 2-M aerogel.

[0061] Example 6 A preparation method of a cellulose-based aerogel triboelectric material. The basic difference from the preparation method of Example 3 is that the dosage of magnesium chloride in S4 is 0.08 g. The obtained cellulose aerogel triboelectric material is named Mg 2+ 4-M aerogel.

[0062] Example 7 A preparation method of a cellulose-based aerogel triboelectric material. The basic difference from the preparation method of Example 3 is that the dosage of magnesium chloride in S4 is 0.12 g. The obtained cellulose-based aerogel triboelectric material is named Mg 2+ 6-M aerogel.

[0063] Example 8 A preparation method of a cellulose-based aerogel triboelectric material. The basic difference from the preparation method of Example 1 is that the dosage of sodium chloride in S4 is 0.12 g. The obtained cellulose-based aerogel triboelectric material is named Na 2+ 6-M aerogel.

[0064] Example 9 A preparation method of a cellulose-based aerogel triboelectric material. The basic difference from the preparation method of Example 2 is that the dosage of calcium chloride in S4 is 0.12 g. The obtained cellulose-based aerogel triboelectric material is named Ca 2+ 6-M aerogel.

[0065] Example 10 A preparation method of a cellulose-based aerogel triboelectric material. The basic difference from the preparation method of Example 4 is that the dosage of ferric chloride in S4 is 0.12 g. The obtained cellulose-based aerogel triboelectric material is named Fe 3+ 6-M aerogel.

[0066] Example 11 A preparation method of a cellulose-based aerogel triboelectric material. The basic difference from the preparation method of Example 5 is that the dosage of aluminum chloride in S4 is 0.12 g. The obtained cellulose-based aerogel triboelectric material is named Al 3+ 6-M aerogel.

[0067] Example 12 A preparation method of a cellulose-based aerogel triboelectric material includes the following steps: S1. Soak the softwood pulp paper in deionized water to fully absorb water and swell, use a homogenizer for 15 minutes at a speed of 11000 rpm to obtain a pulp dispersion. After the dispersion is filtered, the residue is dried to obtain cellulose fibers; take 1g of cellulose fibers, add them into 200ml of deionized water, and fully disperse them to obtain a cellulose fiber dispersion.

[0068] S2, weigh 0.5g chitosan, dissolve it in 40mL of 0.1M hydrochloric acid solution, dissolve the chitosan fully by mechanical dissolution, and form a first precursor solution. Then, add 1M NaOH solution to adjust the pH value to 11, and use mechanical stirring at the same time, and control the speed at 1500rpm. Then, add 0.14g of ethylene glycol diglycidyl ether, react at 60°C for 5h, and obtain the first chitosan fiber.

[0069] S3, take 0.07g chitosan and dissolve it in 10ml 0.1M hydrochloric acid solution, dissolve the chitosan fully by mechanical dissolution to form a second precursor solution. Then add 1M NaOH solution to adjust the pH value to 11, and use magnetic stirring at the same time, and control the speed at 800rpm. Then use a homogenizer to homogenize for 3min at a speed of 11000rpm, then add 0.01g of ethylene glycol diglycidyl ether, react at a temperature of 60°C for 5h to obtain the second chitosan fiber.

[0070] S4, the cellulose fiber dispersion obtained in S1, the first chitosan fiber obtained in S2 and the second chitosan fiber obtained in S3 are mixed, and after mixing evenly, 0.04g magnesium chloride and 0.2g ethylene glycol diglycidyl ether are added in sequence, and stirred for 30min, and then ultrasonically dispersed for 1h. Then, the third reaction is carried out at a temperature of 60°C for 5h. After completion, it is placed in a filter to drain and stand, and after no water drops naturally drip, it is frozen at a temperature of -5°C for 2h to obtain a cellulose-based aerogel precursor.

[0071] S5. Immerse the cellulose-based aerogel precursor in anhydrous ethanol at 60°C, stand for 3 hours for solvent replacement, and squeeze it between two glass flat plates. After squeezing, stand and dry to obtain a cellulose-based aerogel triboelectric material; named CS-0.5 aerogel.

[0072] Example 13 A method for preparing a cellulose-based aerogel triboelectric material is different from the method for preparing the material in Example 12 in that: In S2, 0.7 g of chitosan is weighed and dissolved in 40 ml of a 0.1 M hydrochloric acid solution, and the amount of ethylene glycol diglycidyl ether used is 0.1 g.

[0073] 0.05 g of chitosan was weighed in S3 and dissolved in 10 ml of hydrochloric acid solution with a concentration of 0.1 M, and the amount of ethylene glycol diglycidyl ether used was 0.015 g.

[0074] The obtained cellulose-based aerogel triboelectric material was named CS-0.7 aerogel.

[0075] Comparative Example 1 A preparation method of a cellulose-based aerogel triboelectric material, which is different from the preparation method of Example 1 in that: only 0.2 g of ethylene glycol diglycidyl ether was used in S4.

[0076] The obtained cellulose-based aerogel triboelectric material was named CF / CS aerogel.

[0077] Comparative Example 2 A preparation method of cellulose fibers includes the following steps: The softwood pulp paper was soaked in deionized water to fully absorb water and swell, and homogenized with a homogenizer for 15 min at a rotation speed of 11,000 rpm to obtain a pulp dispersion. After the dispersion was filtered by suction, the residue was dried to obtain cellulose fibers; named CF fibers.

[0078] For Examples 1 to 5, the structures of the cellulose-based aerogels prepared in Comparative Example 1 and the cellulose fibers prepared in Comparative Example 2 were tested. Among them, Examples 1 to 5 were collectively referred to as T2-M aerogels, and T refers to metal ions. The results are as follows: Figure 1 This is a physical diagram of the moldability of the cellulose-based aerogel prepared in Example 1 of the present invention. Figure 1 In i of, the aerogel on the flower, ii of are aerogels of various shapes, iii of are aerogels in different twisted states, and iv of are aerogels in different bent states. As Figure 1 shown, the prepared aerogel is light in weight, and its apparent density is 0.066 g / cm 3 , and has good moldability. The aerogel can be bent and twisted, showing good flexibility.

[0079] Figure 2 This is the infrared spectrogram of T2-M aerogels prepared in Examples 1 to 5 of the present invention, CS-0.5 aerogel prepared in Example 12, CS-0.7 aerogel prepared in Example 13, CF / CS aerogel prepared in Comparative Example 1, and CF. As Figure 2 shown, for CF, the broad absorption band in the range of 3200 cm -1 ~3500 cm -1 and the peak near 2900 cm -1 are caused by the stretching vibrations of O-H and -CH-, respectively. At 1030 cm -1, 897 cm -1 and 1156 cm -1 The absorption peaks at indicate the stretching vibrations of C-O-C, β-glycosidic bonds, and the pyranose ring skeleton vibrations, respectively, which are characteristic peaks unique to the cellulose macromolecular structure. In the CF / CS aerogel, the absorption band near 3200 cm -1 becomes broader and its intensity decreases, and the peak near 2900 cm -1 increases in width, which is caused by the introduction of -NH2 in chitosan and the cross-linking of ethylene glycol diglycidyl ether with the two components; the peak intensity near 1646 cm -1 increases, and a new peak appears at 1584 cm -1 , which are caused by the stretching vibration of C=O in -NHCO and the bending of N-H in -NH2, respectively; at the same time, it is observed that the characteristic peak of C-O at 1065 cm -1 ~1024 cm -1 is broader and more prominent, indicating that the added cross-linking agent ethylene glycol diglycidyl ether has cross-linked with CF and chitosan. In the T2-M aerogel, the peak at 1646 cm -1 is enhanced, and the peak at 1584 cm -1 is weakened, indicating that metal ions complex with -NH2 and at the same time more -NHCO is formed. In the Na + 2-M aerogel triboelectric material, the complexation between Na + and -OH and -NH2 reduces the groups that can form hydrogen bonds. Therefore, the absorption band intensity weakens in the range of 3200 cm -1 ~3500 cm -1 . In the Mg 2+ 2-M, Fe 3+ 2-M, and Al 3+ 2-M aerogels, the absorption band intensity in the range of 3200 cm -1 ~3500 cm -1 increases because divalent and trivalent metal ions have a stronger binding ability with cellulose, improving the dispersibility of cellulose in the solution, increasing the intermolecular chain distance, and resulting in more active groups being exposed. The characteristic peak positions of CS-0.5 and CS-0.7 are basically the same as those of the Mg 2+ 2-M aerogel, but there are obvious changes in the peak intensity, which is caused by the change in the relative proportion of each component, resulting in changes in the proportion of hydrogen bonds, covalent cross-linking, and ionic complexation.

[0080] Figure 3 is the X-ray diffraction pattern of the Mg 2+ 2-M aerogel prepared in Example 3 of the present invention, CS powder, the CF / CS aerogel prepared in Comparative Example 1, and the CF fiber prepared in Comparative Example 2. As Figure 3As shown, the crystal structure evolution of CS powder, CF fiber, CF / CS aerogel and Mg 2+ 2-M aerogel was studied by X-ray diffraction patterns. First, similar diffraction peaks were shown at 10.5° and 20° in the X-ray diffraction patterns of chitosan powder and chitosan fiber, but the diffraction peak intensity of chitosan fiber decreased significantly; typical cellulose I phase diffraction peaks appeared at 16.5° and 22.5° in the X-ray diffraction pattern of CF fiber. All diffraction peaks of CF and CS could be observed in CF / CS aerogel and Mg 2+ 2-M aerogel, but the peak intensities decreased, indicating that the crystallinity of CF and CS in the composite aerogel decreased, which was beneficial to the formation and stability of the multi-crosslinked network structure.

[0081] Figure 4 Figure 8 is the surface scanning electron microscope image of the T2-M aerogel prepared in the embodiment of the present invention and the CF / CS aerogel prepared in Comparative Example 1. Figure 4 In Figure 8, Figure a is the surface scanning electron microscope image of Comparative Example 1 at a size of 200 μm, Figure b is the surface scanning electron microscope image of Example 1 at a size of 200 μm, Figure c is the surface scanning electron microscope image of Example 2 at a size of 200 μm, Figure d is the surface scanning electron microscope image of Example 3 at a size of 200 μm, Figure e is the surface scanning electron microscope image of Example 4 at a size of 200 μm, Figure f is the surface scanning electron microscope image of Example 5 at a size of 200 μm, Figure a1 is the surface scanning electron microscope image of Comparative Example 1 at a size of 50 μm, Figure b1 is the surface scanning electron microscope image of Example 1 at a size of 50 μm, Figure c1 is the surface scanning electron microscope image of Example 2 at a size of 50 μm, Figure d1 is the surface scanning electron microscope image of Example 3 at a size of 50 μm, Figure e1 is the surface scanning electron microscope image of Example 4 at a size of 50 μm, Figure f1 is the surface scanning electron microscope image of Example 5 at a size of 50 μm. As Figure 4 shown, the fibers on the surface of CF / CS aerogel were loosely distributed, some fibers agglomerated, and the pores were large; Na + 2-M aerogel triboelectric material showed a large number of fiber adhesions on the surface; Ca 2+ 2-M aerogel triboelectric material had the fibers arranged more closely and a small amount of fiber aggregation appeared; in Mg 2+ 2-M, Fe 3+ 2-M, Al 3+ 2-M aerogel triboelectric material, a large number of fibers could be observed, the degree of fiber adhesion decreased, and the stacking between fibers was relatively dense.

[0082] Figure 5 Figure 26 is the cross-section scanning electron microscope image of the T2-M aerogel prepared in the embodiment of the present invention and the CF / CS aerogel prepared in Comparative Example 1. Figure 5In the figure, Figure a is a scanning electron microscope image of the cross-section of Comparative Example 1 at a size of 200 μm, Figure b is a scanning electron microscope image of the cross-section of Example 1 at a size of 200 μm, Figure c is a scanning electron microscope image of the cross-section of Example 2 at a size of 200 μm, Figure d is a scanning electron microscope image of the cross-section of Example 3 at a size of 200 μm, Figure e is a scanning electron microscope image of the cross-section of Example 4 at a size of 200 μm, Figure f is a scanning electron microscope image of the cross-section of Example 5 at a size of 200 μm, Figure a1 is a scanning electron microscope image of the cross-section of Comparative Example 1 at a size of 50 μm, Figure b1 is a scanning electron microscope image of the cross-section of Example 1 at a size of 50 μm, Figure c1 is a scanning electron microscope image of the cross-section of Example 2 at a size of 50 μm, Figure d1 is a scanning electron microscope image of the cross-section of Example 3 at a size of 50 μm, Figure e1 is a scanning electron microscope image of the cross-section of Example 4 at a size of 50 μm, and Figure f1 is a scanning electron microscope image of the cross-section of Example 5 at a size of 50 μm. As Figure 5 shown, the scanning electron microscope images of the cross-section of the CF / CS aerogel show that the fibers are stacked layer by layer and in a low-order state, resulting in a limited number of formed pores and a rather large range of pore sizes. Na + 2-M aerogel and Ca 2+ 2-M aerogel lack order, and the formation of multi-level pores is observed in some regions. In contrast, Mg 2+ 2-M aerogel, Fe 3+ 2-M aerogel, and Al 3+ 2-M aerogel triboelectric materials show obvious stratification phenomena and form many multi-level pores. The fibers in the Mg 2+ 2-M aerogel triboelectric materials show obvious order, the formed pore arrangement is more regular, and the structure is relatively complete. The layered stacking between the fibers is due to the formation of hydrogen bonds between the fibers. While forming the solid aerogel skeleton, multi-level pores are also formed by combining multiple strategies; and the complexation properties of different metal ions with CF and CS are significantly different.

[0083] Figure 6 This is the energy-dispersive X-ray spectroscopy analysis diagram of the Mg 2+ 2-M aerogel prepared in Example 3 of the present invention. Figure 6 In the figure, Figure a is the scanning electron microscope image selected for the surface energy-dispersive X-ray spectroscopy analysis of Example 3, Figure b is the C element distribution diagram of Figure a, Figure c is the N element distribution diagram of Figure a, Figure d is the Mg element distribution diagram of Figure a, Figure a1 is the scanning electron microscope image selected for the cross-section energy-dispersive X-ray spectroscopy analysis of Example 3, Figure b1 is the C element distribution diagram of Figure a1, Figure c1 is the N element distribution diagram of Figure a1, and Figure d1 is the Mg element distribution diagram of Figure a1. As Figure 6 shown, Mg 2+A large amount of N and Mg elements exist in the 2-M aerogel skeleton and the inner wall of the pores, further proving that multi-stage crosslinking has occurred.

[0084] Figure 7 This is the compressive stress-strain and compressive modulus diagram of the T2-M aerogel prepared in the embodiment of the present invention and the CF / CS aerogel prepared in Comparative Example 1. Figure 7 In the figure (a) is the compressive stress-strain diagram, and the figure (b) is the compressive modulus diagram. As Figure 7 shown, under the same strain condition, the CF / CS aerogel and Ca 2+ The 2-M aerogel triboelectric material has a relatively high compressive strength. However, the maximum compressive strains of the two are 40% and 36% respectively, lower than those of other aerogel triboelectric materials. The two show relatively large compressive moduli and elastic strain energies. The compressive moduli are 0.29 MPa and 0.17 MPa respectively, and the elastic strain energies are 8.72 kJ / m 3 and 40.43 kJ / m 3 . The CF / CS aerogel shrinks severely during the preparation process. The shrinkage of the internal structure results in its dense structure and the largest apparent density, which is 0.232 g / cm. Among the Ca 2+ 2-M, Na + 2-M, Mg 2+ 2-M, Fe 3+ 2-M and Al 3+ 2-M aerogel triboelectric materials, the internal structure of the Mg 2+ 2-M aerogel triboelectric material is more ordered, has a better support skeleton, shows better mechanical properties, its compressive stress is 0.37 MPa, and the maximum compressive modulus at 50% strain is 0.14 MPa.

[0085] Figure 8 This is the single compression cycle test diagram and residual stress diagram of the T2-M aerogel prepared in the embodiment of the present invention and the CF / CS aerogel prepared in Comparative Example 1 under different strains, Figure 8 In the figure (a) is the single compression cycle test diagram under different strains, and the figure (b) is the residual stress diagram. As Figure 8As shown, compression tests were carried out on the aerogel samples of Examples 1 to 5 and Comparative Example 1 under different compression strains of 10% to 50% respectively. When performing the compression external force loading-unloading test, all aerogels showed insufficient compression recovery performance. However, for the CF / CS aerogel, when the strain conditions were preset to 10% and 20%, the hysteresis loop of the aerogel increased slowly. When the strain was 30% and 40%, the hysteresis loop of the aerogel increased significantly. At 40% strain, the residual strain energy reached 27.44%. When the strain setting was further increased, the deformation and rebound of the aerogel could no longer meet the requirements of the testing instrument, so the hysteresis loop under larger strain setting conditions could not be obtained. Combining the surface and cross-section SEM results of the CF / CS aerogel, it can be seen that there are a large number of large pores and voids inside the aerogel, the interaction between fibers is weak, and the compression resistance of the aerogel is limited, indicating that its elasticity is poor. Under the same compression strain conditions, the residual strain of the aerogel after introducing metal ions is less than that of the CF / CS aerogel. Ca 2+ For the Ca2-M aerogel, at low strain settings of 10% and 20%, its residual strain value is basically close to that of the aerogels added with other metal ions, showing better resilience compared to the CS / CF aerogel. That is to say, at small strains, it has good elasticity. When the strain increases to 30% or even higher, its hysteresis loop increases significantly, and the compression strength of the aerogel increases sharply, indicating that the aerogel structure may be significantly densified at this time, and its resilience becomes worse. For the remaining ion-complexed aerogels, when the strain > 30%, the hysteresis loop increases significantly. But Al 3+ The change of the hysteresis loop of the Al2-M aerogel is relatively slow as a whole, remains relatively stable, and has a low residual strain, indicating that in the strain range of 10%-50%, the permanent deformation of the aerogel is relatively small, and the resilience of the aerogel is good. And Mg 2+ The Mg2-M aerogel shows the smallest residual strain of 5.22% under 10% compression strain at small strains, showing the best resilience under small strain conditions. This is caused by the combined action of the different interaction forces between different ions and the micro / nano fiber molecular chains and the microscale hierarchical pore structure of the aerogel.

[0086] The wet stability test was carried out on the cellulose-based aerogels prepared in Examples 1 to 5 and Comparative Example 1, including the following steps: Take the CF / CS aerogel, and Na + 2-M aerogel, Ca 2+ 2-M aerogel, Mg 2+ 2-M aerogel, Fe 3+ 2-M aerogel and Al 3+The 2-M aerogel was cut into samples of 15 mm × 15 mm × 4 mm, immersed in water, and photographed to record its initial state. After that, it was magnetically stirred for 30 min and then manually shaken in the same way for 2 min, and the dispersion of each sample in water was observed and photographed. After 30 days of placement, each sample was manually shaken in the same way for 2 min, and the dispersion of the sample was photographed and recorded.

[0087] Figure 9 Front and back views of the wet stability test of the T2-M aerogel prepared in the example and the CF / CS aerogel prepared in Comparative Example 1. Figure 9 In Figure a, it is the initial state diagram in water. In Figure b, it is the state diagram after stirring and shaking in water. In Figure c, it is the comparison diagram before and after drying after continuously soaking in deionized water for 40 days. As Figure 9 shown, after the sample was completely water-absorbed, it was mechanically stirred and shaken in the same way, and it was observed that the CF / CS and Na + 2-M aerogel triboelectric materials showed obvious delamination and finally dissociation, losing their initial complete structure. While Ca 2+ 2-M, Mg 2+ 2-M, Fe 3+ 2-M and Al 3+ 2-M aerogel triboelectric materials swelled in water and could always maintain their complete structure, showing no obvious change compared with the initial state. This phenomenon is because the intermolecular force in the CF / CS aerogel is not strong enough to resist the water and vortex shear forces, resulting in dissociation. Metal ion complexation can enhance the force, but the complexation ability of metal ions varies. In Na + 2-M aerogel, the binding energy of Na + with CF and CS is relatively low. Therefore, in water, water molecules can easily break the complexation between alkali metals and molecular chains, making the aerogel show poor water stability. Ca 2+ , Mg 2+ , Fe 3+ , Al 3+ has a strong complexation with the molecular chain, so it shows excellent water stability. The T2-M aerogel triboelectric material was continuously soaked in deionized water for 40 days, then mechanically stirred for 30 min, and the aerogel triboelectric materials added with Ca 2+ , Mg 2+ , Fe 3+ , Al 3+ did not show dissociation, and their structures were always consistent with the initial state. After the samples were taken out of deionized water and put into a drying oven for drying, the structures of the aerogel triboelectric materials were complete and basically the same size as the initial state.

[0088] The self-powered performance of the cellulose-based aerogels prepared in Examples 7 to 11 and Comparative Example 1 was tested. The cellulose-based aerogels prepared in Examples 7 to 11 were named T6-M. Using the T6-M cellulose-based aerogel and a perfluoroethylene propylene copolymer film as the triboelectric positive and negative electrode materials respectively, two copper sheets were pasted on the T6-M aerogel and the commercial FEP film as the back electrodes and connected to an external circuit. An EVA sponge was used as the spacer to separate the two electrodes, and a TENG in contact-separation mode was assembled to measure its electrical output to evaluate the triboelectric performance of the T6-M aerogel. At the same time, for easy comparison, a TENG based on a CF / CS aerogel was assembled using the same method.

[0089] Figure 10 This is a comparison chart of the output voltages of the TENG prepared with the T6-M aerogel of the embodiments of the present invention under different external conditions. Figure 10 In Figure (a), it is the output voltage chart under the action of an external force of 7 Hz and 15 N. In Figure (b), it is the output voltage chart under the action of external forces of 3 Hz, 5 N and 7 Hz, 5 N. In Figure (c), it is the output voltage chart under the action of external forces of 3 Hz, 5 N and 3 Hz, 15 N. As Figure 10 shown in Figure (a), under the conditions of an operating frequency of 7 Hz and an applied force of 15 N, the output voltages of the CF / CS aerogel-based TENG, Na + 6-M aerogel-based TENG, Ca 2 + 6-M aerogel-based TENG, Mg 2+ 6-M aerogel-based TENG, Fe 3+ 6-M aerogel-based TENG and Al 3+ 6-M aerogel-based TENG were 78.9 V, 116.6 V, 73.3 V, 205.1 V, 184.1 V and 118.5 V respectively. The output voltage of the Ca 2+ 6-M aerogel-based TENG was 7.6% lower than that of the CF / CS aerogel-based TENG, while the output voltage of the Mg 2+ 6-M aerogel-based TENG was the highest, showing a 259.9% increase compared to it, demonstrating excellent electrical output performance. Under different applied force and frequency conditions, the effects of different metal ions on improving the output voltage of the TENG device were Ca 2+ <Na + <Al 3+ <Fe 3+ <Mg 2+ . As Figure 10As shown in Figures (b) and (c), as the operating frequency and applied force increase, the output voltage of the TENG increases significantly. Induced charges exist at both the contact surface of the aerogel and the interface of the structural network. In this composite aerogel, CS is rich in amino groups with excellent electron-donating properties and a large number of hydroxyl groups, which is beneficial to enhancing the dielectric properties of the composite aerogel. The high specific surface area of the aerogel enables more sites for electrostatic induction to form. Molecular entanglement and liquid-phase exchange cause the aerogel to form a rough micro / nano surface, further increasing the effective contact area. After the introduction of metal ions, the crystallinity of CS and CF decreases, further enhancing the interfacial polarization effect, and forming nanopores by complexing with molecular chains, providing a stable charge migration path for the free movement of electrons and improving the transport performance of electrons and ions. Hybridization of ions with CF and CS molecules expands the distance between charge centers, causing electrons to deviate from CF molecules and CS molecules, increasing the dipole moment. Na + There is a large amount of fiber adhesion on the surface of the 6-M aerogel, and relatively few surface pores. Ca 2+ The structure of the 6-M aerogel is relatively dense, but the compressive performance of the aerogel is poor, and the resilience of both is low, which is not conducive to charge accumulation. While adding Mg 2+ 、Fe 3+ and Al 3+ In the aerogels, metal ions form a stable multi-network complex hierarchical pore structure with CF and CS. Especially in the Mg 2+ 6-M aerogel, a relatively complete ordered hierarchical pore structure is formed inside, the structure is dense, and it has good resilience. During the working process, it can generate a larger deformation, resulting in an increase in the potential difference between the upper and lower electrodes during release, generating more additional triboelectric charges and enhancing the electrostatic effect.

[0090] Figure 11 This is a comparison chart of the output voltages of the cellulose aerogel-based TENGs prepared in Example 3, Example 6, and Example 7 of the present invention at different thicknesses. Figure 11 In Figure (a), it is the output voltage chart, in Figure (b), it is the chart of output performance and contact area, in Figure (c), it is the chart of thickness relationship, and in Figure (d), it is the chart of output voltage and output power density of the external load resistance. As Figure 11 shown in Figure (a), the more metal ions in the aerogel, the stronger the surface polarity, thus improving the output performance of the TENG. As Figure 11 shown in Figure (b), the output voltage of the TENG device increases proportionally with the effective contact area. In addition, the thickness of the aerogel also affects the output performance of the TENG. As Figure 11 shown in Figure (c), when Mg 2+When the thicknesses of the 6-M aerogel are 2 mm, 3 mm, 4 mm, and 5 mm, the output voltages of the TENG are 97.9 V, 117.7 V, 205.8 V, and 171.9 V in sequence. When the aerogel thickness is 4 mm, the output voltage of the TENG is the highest. When the aerogel thickness is 2 mm, the specific surface area is relatively small, the number of active sites is limited, the electrode charge accumulation is less, and the output performance of the TENG is relatively weak. With the increase of the aerogel thickness, the specific surface area of the aerogel also increases, which is conducive to generating additional charges through electrostatic storage and electrostatic induction. However, when the thickness exceeds 4 mm, due to the further stacked aerogel structure being far from the contact active interface, the accumulated induced charge density is low, the deformation amplitude of the aerogel structure decreases, and the charge transfer is blocked, resulting in the decline of the output performance of the TENG. In summary, based on Mg 2+ The TENG based on 6-M aerogel has the best triboelectric output performance. When the working frequency is 7 Hz, the external force is 15 N, the contact area is 5 cm × 5 cm, and the thickness is 4 mm, the electrical output performance of the TENG is the best, and the output voltage reaches 205.8 V. To explore its output performance in the actual circuit with an external load, the Mg 2+ 6-M aerogel-based TENG is connected to resistors with different resistance values (10 4 Ω to 10 7 Ω) to test its output voltage and power. As shown in Fig. (d) from Figure 11 , with the increase of the load resistance value, the output voltage increases with the increase of the resistance. The output power density of the TENG (P = U 2 / (RS), where U, R, and S are the output voltage, the resistance value of the external resistor, and the contact area of the triboelectric electrode respectively) shows a trend of first increasing and then decreasing. It reaches its maximum power density of 581.16 mW / m 7 ² at 1 × 10 2 . After 5000 cycles, the Mg 2+ 6-M aerogel-based TENG still has stable electrical output performance, and with the extension of the test time, the output voltage of the TENG increases from the initial 169.1 V and remains at 202.8 V.

[0091] Using the Mg 2+ 6-M aerogel with a size of 5 cm × 5 cm as the triboelectric positive electrode material and FEP as the negative electrode material, a TENG is assembled and its triboelectric output performance is tested under different humidity environments at a working frequency of 1 Hz and an applied force of 20 N.

[0092] Figure 12 This is the triboelectric output performance diagram of the TENG prepared from the Mg 2+ 6-M aerogel in Example 7 of the present invention under different humidity environments. Figure 12Figure (a) is the output voltage diagram, Figure (b) is the fitting diagram of output voltage data, and Figure (c) is the output current diagram. As Figure 12 shown in Figure (a) therein, when the humidity change range is from 40%RH to 70%RH, the output voltage of the TENG slightly decreases, from 165.9V to 148.2V. When the humidity increases from 70%RH to 90%RH, the output voltage decreases more significantly, from 148.2V to 73.9V. As Figure 12 shown in Figure (b) therein, in the linear fitting of the output voltage and the relative humidity change, R1 2 and R2 2 can reach 0.972 and 0.998 respectively. This is because although free water has a dissipative effect on charges, the accumulation of water molecules will form a "water bridge", thus increasing the electron capacity. Under low humidity conditions, a large number of water molecules will be adsorbed on the surface to form a gas-liquid interface, thereby reducing the dissipation of free water molecules on charges. At the same time, the diffusion of water molecules into the aerogel can effectively improve the ability of electron donors, which is conducive to charge transfer, and thus can inhibit the dissipative effect of free water to a certain extent, and the voltage output of the aerogel decreases less. However, with the continuous increase of humidity, especially when the environmental humidity reaches more than 80%RH, the excessive free water molecules on the surface and inside of the aerogel will lead to an increase in charge dissipation and an enhancement of the electrostatic shielding effect, thus causing a significant decrease in the voltage output of the TENG, which is consistent with Figure 12 the law of the change of the output current of the TENG with humidity shown in Figure (c) therein.

[0093] Figure 13 This is the fitting diagram of the output voltage of the TENG prepared by the 7Mg 2+ 6-M aerogel in Example 7 of the present invention for continuous humidity cycle testing. As Figure 13 shown, by maintaining continuous contact-separation cycles and adjusting the environmental humidity from 40%RH to 95%RH, it can be observed that as the environmental humidity increases, the output voltage of the TENG decreases from 161.9V at the beginning to 41.8V. Thereafter, by quickly reducing the humidity to 40%RH, the output voltage of the TENG rises to 162.6V, showing good wet response cycle characteristics and reversibility.

[0094] A single-electrode mode TENG was constructed using Mg 2+ 6-M aerogel. A copper electrode and an acrylic plate were sequentially arranged above the Mg 2+ 6-M aerogel, and then a speaker was arranged below the Mg 2+ 6-M aerogel to form a single-electrode mode TENG. Subsequently, the speaker was connected to a computer via Bluetooth, an audio signal was played through the computer, and an electrometer was used to record the electrical output signal of the TENG, so as to evaluate the sound recognition characteristics of the TENG.

[0095] Figure 14 For Example 7 Mg of the present invention 2+ Comparison diagram of the TENG detection electrical signal and the audio signals of different biological and non-biological sounds constructed by 6-M aerogel. Figure 14 In Figure (a), it is the comparison diagram of the drum-beating sound signal. In Figure (b), it is the comparison diagram of the barking sound signal of a dog. In Figure (c), it is the comparison diagram of the thunder and lightning sound signal. In Figure (d), it is the comparison diagram of the firewood burning sound signal. In Figure (e), it is the comparison diagram of a continuous section of the piano sound signal. As Figure 14 shown, after comparing the conversion waveform curves of non-biological and biological audio signals with different characteristics with the output voltage signal of the TENG, it is found that the TENG responds quickly to these sounds. In addition, the output voltage signal shows a high degree of consistency, stability and repeatability with the audio signal.

[0096] The Mg 2+ 6-M aerogel that has been assembled into a TENG and tested is placed normally for 30 days, then cut and mixed, deionized water is added and stirred at high speed to make the mixture uniform, and then 50% of the newly prepared CF / CS solution, 50% of the cross-linking agent and metal ions are added to re-prepare the aerogel sample, named Mg 2+ 6-M-M O-N and assembled into a vertical contact detachable TENG.

[0097] Figure 15 For Example 7 Mg of the present invention 2+ Recyclability comparison diagram of 6-M aerogel of the present invention Figure 15 In Figure (a), it is the comparison diagram of the output voltage of different aerogel-based TENGs. In Figure (b), it is the output current diagram of the new and old aerogel-based TENGs. In Figure (c), it is the transferred charge diagram of the new and old aerogel-based TENGs. As Figure 15 shown, the output voltage of the TENG constructed by Mg 2+ 6-M-M O-N aerogel is 205.5 V, which is basically the same as that of the TENG based on Mg 2+ 6-M aerogel, and the output current and transferred charge are also basically the same.

[0098] Figure 16 Degradation process diagram of the aerogels of Examples 1 to 3 and the comparative example CF / CS aerogel of the present invention. Figure 16 In Figure i, it is the initial state diagram. In Figure ii, it is the state diagram after being placed in the container for 30 days. In Figure iii, it is the state diagram after being transferred to the natural environment for 10 days. In Figure iv, it is the state diagram after being transferred to the natural environment for 30 days. As Figure 16 shown, fresh soil is placed in a dry plastic container, and then CF / CS, Na + 2-M, Mg 2+ 2-M and Ca2+ The 2-M aerogel was separately buried in dry plastic containers to observe the degradation of the gel. After 20 days, the aerogel was dry but its structure remained intact. After 30 days, it became brittle and the Ca 2+ in the 2-M aerogel was significantly fractured. Then the samples were directly buried in outdoor soil. After 10 days, the samples further shrank and the added Ca 2+ in the 2-M aerogel fragmented into small pieces. After continuing to bury for 30 days, all the aerogels degraded and disappeared. Thus, it can be seen that the aerogel has good recyclability, durability and biodegradable characteristics.

[0099] It should be noted that when the present invention involves a numerical range, it should be understood that any value between the two endpoints of each numerical range and the two endpoints themselves can be selected. Since the step methods adopted are the same as those in the embodiments, in order to avoid repetition, the present invention describes the preferred embodiments. Although the preferred embodiments of the present invention have been described, those skilled in the art can make additional changes and modifications to these embodiments once they know the basic creative concept. Therefore, the appended claims are intended to be construed as including the preferred embodiments and all changes and modifications falling within the scope of the present invention.

[0100] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention also intends to include these changes and modifications.

Claims

1. A preparation method of a cellulose-based aerogel triboelectric material, characterized in that, It includes the following steps: Dissolve the first chitosan in the first acid solution to form a first precursor solution, stir and adjust the pH value to alkaline for gelation, and then add a first cross-linking agent for the first cross-linking reaction to obtain first chitosan fibers; Dissolve the second chitosan in the second acid solution to form a second precursor solution, stir and adjust the pH value to alkaline for gelation, and then perform homogenization treatment and add a second cross-linking agent for the second cross-linking reaction to obtain second chitosan fibers; Sequentially add the first chitosan fibers and the second chitosan fibers to the homogenized cellulose fiber dispersion liquid. After mixing evenly, sequentially add a water-soluble metal salt and a third cross-linking agent, stir and disperse, and then perform a third cross-linking reaction. After the reaction ends, perform freezing to obtain a cellulose-based aerogel precursor; Immerse the cellulose-based aerogel precursor in a solvent for solvent replacement, and obtain a cellulose-based aerogel triboelectric material after extrusion and drying.

2. The preparation method of the cellulose-based aerogel triboelectric material according to claim 1, wherein, The mass-volume ratio of the first chitosan, the first cross-linking agent, and the first acid solution is 0.5 g - 0.9 g: 0.1 g - 0.18 g: 40 mL. The first acid solution is hydrochloric acid, and the concentration of hydrochloric acid is 0.05 M - 0.2 M.

3. The preparation method of the cellulose-based aerogel triboelectric material according to claim 1, characterized in that, The mass-volume ratio of the second chitosan, the second cross-linking agent, and the second acid solution is 0.05 g - 0.1 g: 0.01 g - 0.02 g: 20 mL. The second acid solution is hydrochloric acid, and the concentration of hydrochloric acid is 0.05 M - 0.2 M.

4. The preparation method of the cellulose-based aerogel triboelectric material according to claim 1, characterized in that The mass ratio of the cellulose fibers, the first chitosan, and the second chitosan in the cellulose fiber dispersion liquid is 1 g: 0.5 g - 0.9 g: 0.05 g - 0.1 g.

5. The preparation method of the cellulose-based aerogel triboelectric material according to claim 1, wherein The mass ratio of the cellulose fibers and the water-soluble metal salt in the cellulose fiber dispersion liquid is 1 g: 0.04 g - 0.12 g, and the mass ratio of the cellulose fibers and the third cross-linking agent in the cellulose fiber dispersion liquid is 1 g: 0.1 g - 0.2 g.

6. The preparation method of the cellulose-based aerogel triboelectric material according to claim 1, characterized in that, The water-soluble metal salt is at least one of a water-soluble copper salt, a water-soluble aluminum salt, a water-soluble magnesium salt, a water-soluble calcium salt, a water-soluble sodium salt, a water-soluble iron salt, and a water-soluble potassium salt.

7. The preparation method of the cellulose-based aerogel triboelectric material according to claim 1, characterized in that The first cross-linking agent, the second cross-linking agent, and the third cross-linking agent are all glycidyl ethers. The glycidyl ether is ethylene glycol diglycidyl ether or polyethylene glycol diglycidyl ether; the temperatures of the first cross-linking reaction, the second cross-linking reaction, and the third cross-linking reaction are all 50°C - 70°C, and the reaction times are all 4 h - 6 h.

8. The preparation method of the cellulose-based aerogel triboelectric material according to claim 1, wherein, The stirring rate of the first precursor solution is 1000 rpm - 2000 rpm, and the stirring rate of the second precursor solution is 500 rpm - 1000 rpm.

9. The preparation method of the cellulose-based aerogel triboelectric material according to claim 1, wherein, The freezing temperature is -2°C - -10°C, and the time is 1 h - 3 h. The solvent replacement is to immerse the cellulose-based aerogel precursor in absolute ethanol and let it stand for 2 h - 4 h.

10. A cellulose-based aerogel triboelectric material, characterized in that, It is prepared by using the preparation method described in any one of claims 1 - 9.

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