Aramid paper-based friction nano power generation material with sandwich gradient structure and preparation method of aramid paper-based friction nano power generation material

Abstract

The invention relates to the field of friction nano power generation and paper-based functional materials, in particular to an aramid paper-based friction nano power generation material with a sandwich gradient structure and a preparation method of the aramid paper-based friction nano power generation material. According to the material, a paper base obtained by synergistic papermaking of para-aramid fiber and meta-aramid fibrid which are subjected to acetone and ethanol cleaning and H2O2 oxidation modification is taken as a core layer, and polar groups such as hydroxyl and carboxyl are introduced into the surface of the modified fiber, so that the electronegativity and interfacial activity of the paper base are enhanced. And a continuous charge conduction path is formed in the paper base through micro MXene impregnation, so that the charge capture and migration efficiency is improved. The aramid nanofiber membrane which is blade-coated on the outer layer serves as a high-friction functional layer, a higher interface potential difference is formed between rich hydrogen bond sites of the aramid nanofiber membrane and the PTFE negative electrode, and the electron transfer amount can be increased. The obtained modified aramid paper base layer-MXene transport layer-ANF friction layer sandwich structure is light and flexible, large-area processing can be achieved, synergistic enhancement of triboelectrification and charge conduction is achieved on the microscopic level, the output performance is obviously better than that of a traditional paper-based triboelectricity material, and the modified aramid paper base layer-MXene transport layer-ANF friction layer sandwich structure is suitable for application such as flexible wearing, self-powered sensing and micro-nano energy collection.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of friction nanogenerator, flexible electronic material, special paper-based functional material, in particular to an aramid paper-based friction nanogenerator material with sandwich gradient structure and a preparation method thereof. BACKGROUND

[0002] With the rapid development of triboelectric nanogenerator (TENG) in the fields of flexible electronics, intelligent paper-based devices, environmental energy harvesting, etc., how to construct a paper-based triboelectric material with lightweight, flexibility, large-scale preparation, controllable cost and high output performance has become a key problem in current research. Traditional paper-based TENG usually relies on natural fibers or unmodified synthetic fibers as the positive electrode material. Due to the strong surface chemical inertness, insufficient controllable functional groups, limited charge transfer path between fibers, etc., the contact electrification ability, charge retention ability and overall output power of the material are all significantly limited. Under this background, it is particularly important to construct a new type of paper-based triboelectric structure material with chemical adjustability, interface controllability and internal charge transport function.

[0003] Para-aramid fibers have basic advantages in the field of special paper processing and manufacturing due to their high crystallinity, high strength and high thermal stability, but their surface itself lacks sufficient active sites, which is not conducive to forming a strong enough potential difference with the negative electrode material (such as polytetrafluoroethylene). The present application first introduces H2O2 oxidation regulation strategy to generate more active groups such as carboxyl, hydroxyl and amino on the surface of para-aramid fibers. While maintaining the intrinsic mechanical properties of the fibers, the electronegativity and interface chemical activity of the fibers are significantly improved, which significantly moves the position of the fibers in the triboelectric series, thereby facilitating effective electron transfer during contact separation. Subsequently, the modified para-aramid fibers are co-pulped with meta-aramid fibers to obtain a composite paper with toughness, strength and chemical activity, which provides a positive electrode basis with better performance for TENG.

[0004] However, simply increasing the polar functional groups is still insufficient to solve the inherent limitations of the internal charge transfer path of the paper-based material and the loss of charge transfer between fibers. Therefore, the present application further impregnates and couples the modified aramid paper with a small amount of MXene. MXene has high electrical conductivity and abundant surface groups, and by forming a continuous charge transfer network inside the paper-based material, it can significantly improve the rapid transmission and temporary storage capacity of charges inside, making the charge accumulation in the triboelectric process more efficient and more directional.

[0005] Further, the key innovation of the present application is the design of the sandwich structure. Inspired by the multi-scale sandwich structure of bamboo joints and wood fiber-gel-fiber, the present application adopts the synergistic mechanism of outer layer responsible for tribocharging and inner layer responsible for charge transport to form a functional division mode of surface friction layer and internal transport layer. Specifically, a uniform and dense aramid nanofiber (ANF) film is coated on the internal transport layer of MXene, which has a smaller fiber diameter and a larger specific surface area, can form a stronger interface charge attraction effect with the negative PTFE film, and make the electron more easily transfer from the positive electrode surface to the negative electrode, thereby significantly enhancing the overall triboelectric output capacity of the material. At the same time, the ANF nanofilm and the MXene impregnated layer are stably coupled through hydrogen bonds, van der Waals forces and a small amount of residual functional groups, making the sandwich structure more compact and reducing the interlayer charge loss. SUMMARY

[0006] In view of the problems that the contact electrification ability, charge retention ability and overall output power of traditional paper-based materials are significantly limited, the present application provides an aramid paper-based friction nanogenerator material with sandwich gradient structure and a preparation method thereof.

[0007] The present application is realized by the following technical solutions: An aramid paper-based friction nanogenerator material with sandwich gradient structure, the preparation method comprising the following steps: Step 1: The para-aramid fibers are sequentially cleaned with acetone and ethanol by ultrasonic, and then dried and placed in a H2O2 solution, and ultrasonic and heated stirring are performed to introduce active functional groups such as hydroxyl and carboxyl groups on the surface of the fibers to obtain modified para-aramid fibers; Step 2: The modified para-aramid fibers are mixed with meta-aramid fibrids in a certain proportion, and a uniform slurry is formed by mechanical stirring and defibration, and a uniform and dense aramid paper is prepared by using a wet papermaking forming process; Step 3: The aramid paper is immersed in a MXene nanosheet water dispersion, and after adsorption and drying, the MXene layers are embedded between the fiber pores to form a good charge transport network; Step 4: A uniform aramid nanofiber gel is coated on the surface of the MXene impregnated paper, and a dense surface layer is formed after drying to obtain an aramid paper-based friction nanogenerator material with sandwich gradient structure.

[0008] Preferably, in step 1, the para-aramid fibers have a diameter of 12-15 um and a length of 3-12 mm; the meta-aramid fibrids have a specific surface area of 6-12 m 2 / g, a fiber length of 0.7-1.2 mm, and a Schopper beating degree of 45-60°SR.

[0009] Preferably, in step 1, the para-aramid fiber is cleaned with acetone at 100-400W ultrasonic for 3-5h, then cleaned with ethanol at 100-400W ultrasonic for 3-5h, and dried at 60-80℃ for 8-12h.

[0010] Preferably, in step 1, the concentration of H2O2 solution is 20%-30%, ultrasonic for 2-3h, and heated and stirred at 60℃ for 3-5h, and dried at 60-80℃ for 8-12h.

[0011] Preferably, in step 2, the modified para-aramid fiber and the meta-aramid fiber are mixed in a ratio of 70:30-50:50, and mechanically stirred and defibered for 20000-30000 revolutions to form a uniform slurry, and the paper basis weight is 70-80g / m 2 .

[0012] Preferably, in step 2, the wet-laid paper must be subjected to cold pressing and vacuum drying, the cold pressing pressure is 0.8-1.0MPa, the time is 10-15min; the vacuum drying temperature is 105-120℃, the vacuum degree is 0.7-0.9MPa, and the time is 8-10min.

[0013] Preferably, in step 3, the MXene aqueous dispersion is prepared by acid etching method, the concentration of MXene dispersion is 20-25mg / mL, the immersion time is 3-5min, and the drying temperature is 60-80℃ for 3-5h.

[0014] Preferably, in step 4, the preparation of aramid nanofiber mixed dispersion is as follows: first, the alkaline solution, para-aramid fiber and dimethyl sulfoxide are stirred and mixed to obtain dispersion A; wherein the mass ratio of para-aramid fiber and dimethyl sulfoxide is 2-3:200-300, the solute of alkaline solution is potassium hydroxide, the concentration of solute in alkaline solution is 0.3-0.6g / mL, and the ratio of alkaline solution and para-aramid fiber is 1-2mL:2-3g; The dispersion A is uniformly dispersed into deionized water, then placed and filtered to obtain para-aramid nanofiber dispersion B; wherein the volume ratio of water and dispersion A is 1000-1500:50-100, and the para-aramid nanofiber gel is obtained by filtering through a 2800 mesh filter screen.

[0015] Preferably, in step 4, the MXene is uniformly coated on the surface of the paper by scraping, the scraping thickness is 60-80um, and the drying temperature is 60-80℃ for 6-8h.

[0016] A product obtained by the preparation method of the aramid paper-based friction nanogenerator material according to the sandwich gradient structure Compared with the prior art, the present application has the following beneficial effects:

[0017] (1) The surface of para-aramid fibers is modified by hydrogen peroxide (H2O2). The oxidation reaction of H2O2 is significantly enhanced under the high-temperature and high-pressure environment generated by ultrasonic waves around the bubbles. The surface of the fibers is effectively etched, and polar functional groups such as carboxyl, hydroxyl, and amino groups are generated, thereby imparting higher surface activity to the fibers. Compared with the traditional unmodified aramid paper-based positive electrode, the potential position of the modified fibers in the triboelectric series is significantly shifted upwards, which can form a larger interfacial potential difference, thereby achieving higher charge transfer efficiency in the contact-separation process. On the other hand, the newly generated functional groups enhance the hydrogen bonding between fibers, making the paper-based network structure more compact, avoiding problems such as insufficient charge retention and serious interface loss due to the inertness of the fiber surface, and increasing the amount of charge transfer, thereby significantly improving the open-circuit voltage and short-circuit current.

[0018] (2) The internal structure of the traditional paper-based fiber network is a porous insulating structure, and the migration path of the charge between the fibers is long and has high resistance, making it difficult to form rapid and directional charge transport. By impregnating with a small amount of MXene dispersion liquid, the highly conductive Ti3C2T x nanosheets are uniformly embedded in the fiber pores and distributed along the fiber surface, thereby constructing a three-dimensional charge transport network inside the paper-based material. This network, on the one hand, increases the charge capture and storage capacity inside the paper-based material through its high specific surface area, and on the other hand, shortens the effective path of electron migration, thereby reducing the interface charge loss from a micro-mechanism. Compared with the traditional paper-based TENG which relies solely on the fiber structure, the continuous nanoscale conductive channels inside the paper-based material enable the device to output higher charge density and more stable voltage signals under the same mechanical excitation, thereby improving the overall energy utilization rate of the triboelectric output.

[0019] (3) Constructing a biomimetic “sandwich gradient structure” to achieve functional synergy between the triboelectric layer and the transport layer. Inspired by the “fiber bundle-gel-fiber bundle” sandwich structure of bamboo and wood in nature, where the outer layer undertakes the interface function and the inner layer provides transport support, this invention forms a gradient functional partition of “modified aramid paper base layer-MXene transport layer-ANF triboelectric layer” by coating a highly uniform aramid nanofiber (ANF) film on the outside of the MXene transport layer. The aramid nanofiber has a small diameter and a large specific surface area, forming a stronger interfacial charge attraction effect with the PTFE negative electrode, making the interface contact more fully charged, and effectively solving the problems of surface fuzzing, fiber shedding, and internal charge leakage that are prone to occur in traditional paper-based triboelectric materials during long-term use; the MXene layer provides a continuous charge transport path, enabling the charge generated on the surface to migrate quickly to the electrode, avoiding output saturation due to insufficient charge accumulation; the ANF layer and the MXene layer form a stable coupling through hydrogen bonds and van der Waals interactions, making energy loss lower during the interface transfer process. Compared to traditional single-layer paper-based materials, this invention integrates three functions: triboelectric charging, charge transfer, and structural support. This results in a significant improvement in output performance during triboelectric testing, enhanced voltage stability, and lower attenuation after 5000 repeated triboelectric cycles.

[0020] (4) Relying on the lightweight, flexible, porous and high-strength fiber network of aramid paper, a three-dimensional synergistic structure of triboelectric layer-charge transport layer-reinforcing paper base can be achieved through wet papermaking, gradient impregnation and low-temperature drying. It does not require the solvent curing, high-temperature crosslinking or complex molding process commonly found in the preparation of traditional PTFE, PDMS and PI films. The preparation process is highly compatible with the papermaking industry chain and has the advantages of rapid prototyping, continuous scale-up and low-cost manufacturing. The introduction of trace amounts of MXene and the construction of an efficient charge transport network inside the paper base fundamentally improves the problems of long migration paths and weak charge retention in traditional paper bases. Furthermore, the hydrogen bonds and van der Waals interactions between MXene and the surface of aramid fibers and the surface ANF protective layer enable the structure to maintain stable triboelectric output capability in high humidity, high salt spray or sweat environments. Paper-based materials can be cut, folded, and molded, and can be directly attached to fabrics, skin, packaging shells, book structures, and even disposable labels, enabling rapid deployment in various scenarios such as flexible wearable sensing, self-powered tags, breathing and motion monitoring, structural health monitoring, and wind / water wave energy harvesting. At the same time, due to its natural porous fiber network, it has excellent corrosion resistance and damp heat resistance, and can work stably in environments such as sweat, dust, rain, high humidity storage, and outdoor vibration, making it suitable for complex working conditions such as wearable health monitoring, smart packaging, environmental sensing, agricultural monitoring, and low-power energy harvesting. Attached Figure Description

[0021] Figure 1This is a structural diagram of an aramid paper-based triboelectric nanomaterial with a sandwich gradient structure according to the present invention. Figure 2 This is the Fourier transform infrared spectrum of an aramid paper-based triboelectric nanomaterial with a sandwich gradient structure according to the present invention. Figure 3 This is a SEM cross-sectional image of H2O2 oxidation-modified aramid fibers in an aramid paper-based triboelectric nanomaterial with a sandwich gradient structure according to the present invention. Figure 4 The open-circuit voltages of Examples 1-5 of the aramid paper-based triboelectric nanomaterial with a sandwich gradient structure according to the present invention are shown.

[0022] Figure 5 The short-circuit currents of Examples 1-5 of the aramid paper-based triboelectric nanomaterial with a sandwich gradient structure according to the present invention are shown.

[0023] Figure 6 The transferred charge amounts in Examples 1-5 of the aramid paper-based triboelectric nanomaterial with a sandwich gradient structure according to the present invention are shown. Detailed Implementation

[0024] The present invention will be further described in detail below with reference to specific embodiments. These descriptions are for explanation purposes only and are not intended to limit the scope of the invention.

[0025] This invention also discloses a sandwich gradient structure aramid paper-based triboelectric nanomaterial for generating electricity, with reference to... Figure 1 This includes the following steps: Step 1: The para-aramid fibers with a diameter of 12-15 μm and a length of 3-12 mm are ultrasonically cleaned at 100-400 W for 3-5 h, then ultrasonically cleaned with ethanol at 100-400 W for 3-5 h, and dried at 60-80 °C for 8-12 h. After drying, they are placed in a 20%-30% H2O2 solution and ultrasonically cleaned for 2-3 h, heated and stirred at 60 °C for 3-5 h, and dried at 60-80 °C for 8-12 h to obtain modified para-aramid fibers. Step 2: Modified para-aramid fibers with a specific surface area of ​​6~12 m² 2 The pulp, with a fiber length of 0.7~1.2mm and a Shore freeness of 45~60 °, is mixed with SR meta-aramid precipitated fibers in a ratio of 70:30~50:50 and mechanically stirred for 20,000~30,000 revolutions to form a uniform pulp. The basis weight of the paper is 70~80 g / m³. 2 The paper is cold-pressed at 0.8~1.0MPa for 10~15min and dried at 105℃ for 8~10min, and a uniform and dense aramid paper is obtained by wet papermaking process. Step 3: Immerse the aramid paper in an aqueous dispersion of MXene nanosheets with a concentration of 20-25 mg / mL for 3-5 min, and dry it at 60-80℃ for 3-5 h. The MXene sheets are embedded in the fiber pores to form a good charge transport network. Step 4: A 60-80 μm thick aramid nanofiber gel is uniformly coated onto the surface of MXene-impregnated paper and dried at 60-80 °C for 6-8 h to obtain a sandwich gradient structure aramid paper-based triboelectric nanomaterial.

[0026] Figure 1 This is a structural diagram of a sandwich gradient structure aramid paper-based triboelectric nanomaterial for generating electricity. H2O2-modified para-aramid fibers and meta-aramid precipitated fibers are interwoven to form a flexible aramid paper substrate. MXene nanosheets are uniformly arranged in the aramid fibers to form charge transport channels. The aramid nanofiber film on the surface is conducive to generating more surface charge through friction. The outer layer is responsible for triboelectric charging, and the inner layer is responsible for charge transport. This forms a sandwich gradient structure aramid paper-based triboelectric nanomaterial for generating electricity, with functional partitions of a surface friction layer and an internal transport layer.

[0027] Figure 2 This is the Fourier transform infrared spectrum of an aramid paper-based triboelectric nanomaterial with a sandwich gradient structure according to the present invention. By modifying the para-aramid fibers, the C=O, CO, and NH bond positions increase, indicating an increase in active groups such as carboxyl, hydroxyl, and amino groups. After the aramid paper is impregnated with MXene, an additional C-Ti bond appears at the 620 peak position. After further coating the aramid paper with an MXene-impregnated aramid nanofiber film, the CO and CH bond positions increase further.

[0028] Figure 3 This is a SEM cross-sectional image of H2O2-oxidized aramid fibers in a sandwich gradient structure aramid paper-based triboelectric nanomaterial of the present invention. The surface of the oxidized para-aramid fibers is swollen and has many open aramid fiber filaments, but the overall structure of the fiber is not destroyed, and its mechanical strength and temperature resistance are not affected. However, the surface of the oxidized fiber will generate more active functional groups, which is conducive to forming a larger potential difference with the negative electrode material, promoting charge transfer, and improving triboelectric output performance.

[0029] Figure 4 The open-circuit voltages of the sandwich gradient structure aramid paper-based triboelectric nanomaterials of the present invention (Examples 1-5) are shown. The open-circuit voltage of the oxidized para-aramid fiber paper is higher than that of the unmodified aramid fiber paper (open-circuit voltage of about 50V). As the concentration of impregnated MXene increases and the coating thickness of aramid nanofibers increases, i.e. the charge transport layer and the triboelectric layer are strengthened, the open-circuit voltage gradually increases. However, if the coating thickness is too high, it will also hinder the charge transport and cause the triboelectric output performance to gradually decrease.

[0030] Figure 5 The short-circuit current of the sandwich gradient structure aramid paper-based triboelectric nanomaterials of the present invention, in Examples 1-5, gradually increases with the increase of MXene impregnation concentration and aramid nanofiber coating thickness.

[0031] Figure 6 The amount of transferred charge in Examples 1-5 of the aramid paper-based triboelectric nanomaterial with a sandwich gradient structure of the present invention gradually increases with the increase of MXene impregnation concentration and aramid nanofiber coating thickness.

[0032] Example 1 Step 1: The para-aramid fiber with a diameter of 12 μm and a length of 5 mm was ultrasonically cleaned at 300 W for 3 h, then ultrasonically cleaned with ethanol at 300 W for 3 h, and dried at 60 °C for 10 h. After drying, it was placed in a 20% H2O2 solution, ultrasonicated for 2 h, heated and stirred at 60 °C for 3 h, and dried at 60 °C for 10 h to obtain the modified para-aramid fiber. Step 2, mix the modified para-aramid fiber with a specific surface area of ​​8m² 2 The pulp, with a fiber length of 1.2 mm and a Shore freeness of 60 °, is a 70:30 mixture of meta-aramid precipitated fibers. The mixture is mechanically stirred for 30,000 revolutions to form a homogeneous pulp, and the paper basis weight is 80 g / m³. 2 The paper was cold-pressed at 1.0 MPa for 10 min and dried at 105℃ for 10 min, and a uniform and dense aramid paper was produced by wet papermaking process. Step 3: Immerse the aramid paper in an aqueous dispersion of MXene nanosheets with a concentration of 20 mg / mL for 5 min, and dry it at 60 °C for 3 h. The MXene sheets are embedded in the fiber pores to form a good charge transport network. Step 4: A 60µm thick aramid nanofiber gel is uniformly coated onto the surface of MXene-impregnated paper and dried at 70℃ for 6 hours to obtain a sandwich gradient structure aramid paper-based triboelectric nanomaterial.

[0033] In this embodiment 1, a sandwich gradient structure aramid paper-based triboelectric nanomaterial is used as the positive electrode, and a PTFE film is used as the negative electrode. A 2*2cm sample is taken. 2 The sample was sized and a grid-like copper foil was attached to the back as a current collector. Using an electrometer 6514, the open circuit voltage was 101.3V, the short circuit current was 136.7nA, and the transferred charge was 10.3nC during the contact separation process at a frequency of 2Hz without additional pressure.

[0034] Example 2 Step 1: The para-aramid fiber with a diameter of 12 μm and a length of 5 mm was ultrasonically cleaned at 300 W for 3 h, then ultrasonically cleaned with ethanol at 300 W for 3 h, and dried at 60 °C for 10 h. After drying, it was placed in a 20% H2O2 solution, ultrasonicated for 2 h, heated and stirred at 60 °C for 3 h, and dried at 60 °C for 10 h to obtain the modified para-aramid fiber. Step 2, mix the modified para-aramid fiber with a specific surface area of ​​8m² 2 The pulp, with a fiber length of 1.2 mm and a Shore freeness of 60 °, is a 60:40 mixture of meta-aramid precipitated fibers. The mixture is mechanically stirred for 30,000 revolutions to form a homogeneous pulp, and the paper basis weight is 80 g / m³. 2 The paper was cold-pressed at 1.0 MPa for 10 min and dried at 105℃ for 10 min, and a uniform and dense aramid paper was produced by wet papermaking process. Step 3: Immerse the aramid paper in an aqueous dispersion of MXene nanosheets with a concentration of 20 mg / mL for 5 min, and dry it at 60 °C for 3 h. The MXene sheets are embedded in the fiber pores to form a good charge transport network. Step 4: A 65µm thick aramid nanofiber gel is uniformly coated onto the surface of MXene-impregnated paper and dried at 70℃ for 7 hours to obtain a sandwich gradient structure aramid paper-based triboelectric nanomaterial.

[0035] In this embodiment 2, a sandwich-graded aramid paper-based triboelectric nanomaterial is used as the positive electrode, and a PTFE film is used as the negative electrode. A 2*2cm sample is taken. 2 The sample was sized and a grid-like copper foil was attached to the back as a current collector. Using an electrometer 6514, the open circuit voltage was 115.0V, the short circuit current was 140.9nA, and the transferred charge was 12.0nC during the contact separation process at a frequency of 2Hz without additional pressure.

[0036] Example 3 Step 1: The para-aramid fiber with a diameter of 12 μm and a length of 5 mm was ultrasonically cleaned at 300 W for 3 h, then ultrasonically cleaned with ethanol at 300 W for 3 h, and dried at 60 °C for 10 h. After drying, it was placed in a 25% H2O2 solution, ultrasonicated for 2 h, heated and stirred at 60 °C for 3 h, and dried at 60 °C for 10 h to obtain the modified para-aramid fiber. Step 2, mix the modified para-aramid fiber with a specific surface area of ​​8m² 2 / g, fiber length 1.2mm, Shore freeness 60 °SR meta-aramid precipitated fibers are mixed in a 50:50 ratio and mechanically stirred for 30,000 revolutions to form a homogeneous pulp. The basis weight of the paper is 80g / m³. 2The paper was cold-pressed at 1.0 MPa for 10 min and dried at 105℃ for 10 min, and a uniform and dense aramid paper was produced by wet papermaking process. Step 3: Immerse the aramid paper in an aqueous dispersion of MXene nanosheets with a concentration of 23 mg / mL for 5 min, and dry it at 60 °C for 3 h. The MXene sheets are embedded in the fiber pores to form a good charge transport network. Step 4: A 70µm thick aramid nanofiber gel is uniformly coated onto the surface of MXene-impregnated paper and dried at 70℃ for 8 hours to obtain a sandwich gradient structure aramid paper-based triboelectric nanomaterial.

[0037] In this embodiment 3, a sandwich gradient structure aramid paper-based triboelectric nanomaterial is used as the positive electrode, and a PTFE film is used as the negative electrode. A 2*2cm sample is taken. 2 The sample was sized and a grid-like copper foil was attached to the back as a current collector. Using an electrometer 6514, the open circuit voltage was 135.9V, the short circuit current was 180.9nA, and the transferred charge was 13.6nC during the contact separation process at a frequency of 2Hz without additional pressure.

[0038] Example 4 Step 1: The para-aramid fibers with a diameter of 12 μm and a length of 5 mm were ultrasonically cleaned at 300 W for 3 h, then ultrasonically cleaned with ethanol at 300 W for 3 h, and dried at 60 °C for 10 h. After drying, they were placed in a 30% H2O2 solution, ultrasonicated for 2 h, heated and stirred at 60 °C for 3 h, and dried at 60 °C for 10 h to obtain modified para-aramid fibers. Step 2, mix the modified para-aramid fiber with a specific surface area of ​​8m² 2 The pulp, with a fiber length of 1.2 mm and a Shore freeness of 60 °, is a 70:30 mixture of meta-aramid precipitated fibers. The mixture is mechanically stirred for 30,000 revolutions to form a homogeneous pulp, and the paper basis weight is 80 g / m³. 2 The paper was cold-pressed at 1.0 MPa for 10 min and dried at 105℃ for 10 min, and a uniform and dense aramid paper was produced by wet papermaking process. Step 3: Immerse the aramid paper in an aqueous dispersion of MXene nanosheets with a concentration of 25 mg / mL for 5 min, and dry it at 60 °C for 3 h. The MXene sheets are embedded in the fiber pores to form a good charge transport network. Step 4: A 75µm thick aramid nanofiber gel is uniformly coated onto the surface of MXene-impregnated paper and dried at 80℃ for 7 hours to obtain a sandwich gradient structure aramid paper-based triboelectric nanomaterial.

[0039] In this embodiment 4, a sandwich-graded aramid paper-based triboelectric nanomaterial is used as the positive electrode, and a PTFE film is used as the negative electrode. A 2*2cm sample is taken. 2 The sample was sized and a grid-like copper foil was attached to the back as a current collector. Using an electrometer 6514, the open circuit voltage was 160.8V, the short circuit current was 249.9nA, and the transferred charge was 17.1nC during the contact separation process at a frequency of 2Hz without additional pressure.

[0040] Example 5 Step 1: The para-aramid fibers with a diameter of 12 μm and a length of 5 mm were ultrasonically cleaned at 300 W for 3 h, then ultrasonically cleaned with ethanol at 300 W for 3 h, and dried at 60 °C for 10 h. After drying, they were placed in a 30% H2O2 solution, ultrasonicated for 2 h, heated and stirred at 60 °C for 3 h, and dried at 60 °C for 10 h to obtain modified para-aramid fibers. Step 2, mix the modified para-aramid fiber with a specific surface area of ​​8m² 2 / g, fiber length 1.2mm, Shore freeness 60 °SR meta-aramid precipitated fibers are mixed in a 50:50 ratio and mechanically stirred for 30,000 revolutions to form a homogeneous pulp. The basis weight of the paper is 80g / m³. 2 The paper was cold-pressed at 1.0 MPa for 10 min and dried at 105℃ for 10 min, and a uniform and dense aramid paper was produced by wet papermaking process. Step 3: Immerse the aramid paper in an aqueous dispersion of MXene nanosheets with a concentration of 25 mg / mL for 5 min, and dry it at 60 °C for 3 h. The MXene sheets are embedded in the fiber pores to form a good charge transport network. Step 4: A aramid nanofiber gel with a thickness of 80 μm is uniformly coated on the surface of MXene impregnated paper and dried at 80 °C for 8 h to obtain a sandwich gradient structure aramid paper-based triboelectric nanomaterial.

[0041] In this embodiment 5, a sandwich gradient structure aramid paper-based triboelectric nanomaterial is used as the positive electrode, and a PTFE film is used as the negative electrode. A 2*2cm sample is taken. 2 The sample was sized and a grid-like copper foil was attached to the back as a current collector. Using an electrometer 6514, the open circuit voltage was 140.9V, the short circuit current was 201.7nA, and the transferred charge was 14.2nC during the contact separation process at a frequency of 2Hz without additional pressure.

[0042] Table 1. Technical parameters of the sandwich gradient structure aramid paper-based triboelectric nanomaterials obtained in Examples 1-5 During the triboelectric voltage test, a 2*2cm piece of aramid paper-based triboelectric nanomaterial with a sandwich gradient structure was first cut. 2Divide the square pieces into small squares, and then attach 2*0.5cm square pieces to the back of each piece in a grid pattern. 2 Copper foil tape and wires were used to prepare the positive electrode device of a triboelectric nanogenerator, and in the same way, a polytetrafluoroethylene film was used to prepare the negative electrode device. The positive and negative electrode materials were connected to a Keithley electrometer 6514, and a linear motor was used to control the contact separation of the positive and negative electrodes at a frequency of 2 Hz without additional pressure, resulting in charge transfer and generating triboelectric output voltage, short-circuit current, and amount of transferred charge.

[0043] Table 1 shows the technical parameters of the sandwich gradient structure aramid paper-based triboelectric nanomaterials prepared in Examples 1-5. It can be seen that the triboelectric materials prepared by the process route provided by this invention benefit from the application of aramid nanofibers as the contact friction layer and MXene-impregnated aramid paper as the charge transport layer, exhibiting both good triboelectric generation and charge transfer capabilities, which is conducive to generating high triboelectric output performance. Furthermore, as the concentration of impregnated MXene gradually increases and the thickness of the ANF coating increases, the charge transfer efficiency improves, and the triboelectric output performance gradually improves. However, when the ANF coating thickness in Example 5 is relatively thick, although more charge can be generated through friction, it is not conducive to charge transport within the internal aramid paper layer, and the performance gradually decreases. Overall, the sandwich gradient structure aramid paper-based triboelectric nanomaterials, through a 2*2cm... 2 The small area achieved an output voltage of 101~160V, a short-circuit current of 136~250nA, and a transferred charge of 10~17nC, demonstrating very high triboelectric output performance. This lays the foundation for the large-scale fabrication of paper-based triboelectric sensors and micro-nano energy harvesting devices.

[0044] The above description is merely a preferred embodiment of the present invention and is not intended to limit the technical solution of the present invention in any way. Those skilled in the art should understand that, without departing from the spirit and principles of the present invention, the technical solution can be modified and replaced in several simple ways, and these modifications and replacements are all within the scope of protection covered by the claims.

Claims

1. A method for preparing a sandwich gradient structure aramid paper-based triboelectric nanomaterial, characterized in that, Includes the following steps: Step 1: The para-aramid fiber is ultrasonically cleaned with acetone and ethanol in sequence, dried and placed in H2O2 solution, and ultrasonically and heated and stirred to introduce active functional groups such as hydroxyl and carboxyl groups on the fiber surface to obtain modified para-aramid fiber. Step 2: Modified para-aramid fibers and meta-aramid precipitated fibers are mixed in proportion and mechanically stirred to form a uniform slurry. The uniform and dense aramid paper is then produced by wet papermaking process. Step 3: Immerse aramid paper in an aqueous dispersion of MXene nanosheets. After adsorption and drying, the MXene sheets are embedded in the pores of the fibers to form a good charge transport network. Step 4: Aramid nanofiber gel is uniformly coated onto the surface of MXene-impregnated paper. After drying, a dense surface layer is formed, resulting in an aramid paper-based triboelectric nanomaterial with a sandwich gradient structure.

2. The method for preparing aramid paper-based triboelectric nanomaterials with a sandwich gradient structure according to claim 1, characterized in that, In step 1, the para-aramid fibers have a diameter of 12-15 μm and a length of 3-12 mm; the meta-aramid precipitated fibers have a specific surface area of ​​6-12 m². 2 / g, fiber length is 0.7~1.2mm, Shore freeness is 45~60 °SR.

3. The method for preparing aramid paper-based triboelectric nanomaterials with a sandwich gradient structure according to claim 1, characterized in that, In step 1, the para-aramid fibers are ultrasonically cleaned with acetone at 100-400W for 3-5 hours, then ultrasonically cleaned with ethanol at 100-400W for 3-5 hours, and dried at 60-80℃ for 8-12 hours.

4. The method for preparing aramid paper-based triboelectric nanomaterials with a sandwich gradient structure according to claim 1, characterized in that, In step 1, the concentration of H2O2 solution is 20%~30%, ultrasonicated for 2~3 hours, heated and stirred at 60℃ for 3~5 hours, and dried at 60~80℃ for 8~12 hours.

5. The method for preparing aramid paper-based triboelectric nanomaterials with a sandwich gradient structure according to claim 1, characterized in that, In step 2, modified para-aramid fibers and meta-aramid precipitated fibers are mixed in a ratio of 70:30 to 50:50, and mechanically stirred for 20,000 to 30,000 revolutions to form a homogeneous slurry. The basis weight of the paper is 70 to 80 g / m³. 2 .

6. The method for preparing aramid paper-based triboelectric nanomaterials with a sandwich gradient structure according to claim 1, characterized in that, In step 2, the wet-processed paper must undergo cold pressing dehydration and vacuum drying. The cold pressing pressure is 0.8~1.0MPa and the time is 10~15min; the vacuum drying temperature is 105~120℃, the vacuum degree is 0.7~0.9MPa, and the time is 8~10min.

7. The method for preparing aramid paper-based triboelectric nanomaterials with a sandwich gradient structure according to claim 1, characterized in that, In step 3, the MXene aqueous dispersion is prepared by acid etching. The concentration of the MXene dispersion is 20-25 mg / mL, the immersion time is 3-5 min, and it is dried at 60-80℃ for 3-5 h.

8. The method for preparing aramid paper-based triboelectric nanomaterials with a sandwich gradient structure according to claim 1, characterized in that, In step 4, the preparation of the aramid nanofiber mixed dispersion is as follows: First, an alkaline solution, para-aramid fibers, and dimethyl sulfoxide are stirred and mixed to obtain dispersion A; wherein, the mass ratio of para-aramid fibers to dimethyl sulfoxide is 2~3:200~300, the solute in the alkaline solution is potassium hydroxide, the concentration of the solute in the alkaline solution is 0.3~0.6g / mL, and the ratio of alkaline solution to para-aramid fibers is 1~2mL:2~3g; Dispersion A was uniformly dispersed in deionized water, and then allowed to stand and filtered to obtain para-aramid nanofiber dispersion B; wherein the volume ratio of water to dispersion A was 1000~1500:50~100, and the dispersion was filtered through a 2800 mesh filter to obtain para-aramid nanofiber gel.

9. The method for preparing aramid paper-based triboelectric nanomaterials with a sandwich gradient structure according to claim 2, characterized in that, In step 4, aramid nanofiber gel is uniformly coated onto the surface of MXene-impregnated paper to a thickness of 60-80 μm, and then dried at 60-80°C for 6-8 hours.

10. A product obtained by a method for preparing aramid paper-based triboelectric nanomaterials with a sandwich gradient structure according to any one of claims 1 to 9.

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