Graphene-coated AgI composite fiber membrane as well as preparation method and application thereof

Abstract

The invention relates to the technical field of nanofiber materials and energy storage, in particular to a graphene and AgI composite fiber membrane and a preparation method and application thereof. The method comprises the following steps: preparing an aqueous dispersion of graphene oxide into graphene oxide fibers; the preparation method comprises the following steps: cutting the graphene oxide fiber short, and placing the cut graphene oxide fiber in an ethanol solution of CaCl2 for solvent exchange to form a graphene oxide gel fiber; after reduced-pressure suction filtration and hot-pressing drying, the graphene fiber membrane is placed in an acetic acid solution of HI to be subjected to a reduction reaction, and a graphene fiber membrane is obtained; the graphene fiber membrane is soaked in soluble silver salt, I <-> and Ag < + > react to generate AgI nano-particles, the AgI nano-particles are attached to the graphene fiber membrane, the graphene and AgI nano-particles are taken out and dried, and the graphene and AgI composite fiber membrane is obtained. According to the preparation method, the problem that in the prior art, due to pi-pi interaction, a graphene sheet layer is prone to agglomeration to form a close packing structure is solved, and the specific surface area of the graphene fiber membrane is also increased.

Description

Technical Field

[0001] The present invention relates to the field of nanofiber materials and energy storage technology, and in particular to a graphene@AgI composite fiber membrane and a preparation method and application thereof. Background Art

[0002] With the rapid development of portable flexible electronic devices, the demand for flexible and efficient energy storage technologies is rapidly increasing. Compared to batteries, supercapacitors offer advantages such as high power density and excellent cycling stability, and have been widely researched and applied in portable energy devices, hybrid electric vehicles, and backup energy systems. Various fiber, membrane, and fabric-based electrodes have been widely used in flexible electronic devices.

[0003] In recent years, two-dimensional materials have shown great potential for application in electrochemical energy storage devices due to their large specific surface area and abundant active sites. Graphene, in particular, has been investigated for its high specific surface area, high conductivity, and excellent flexibility, and is being used in flexible supercapacitors. Gao Chao's team at Zhejiang University cut continuous graphene fibers into short graphene fibers, filtered them, and applied them to supercapacitors, resulting in flexible supercapacitors with high specific capacitance. This demonstrates the broad application prospects of graphene fiber membranes in high-area-capacitance supercapacitors.

[0004] However, since graphene sheets can easily agglomerate to form a densely packed structure due to the π-π interaction between the sheets, the transmission of electrolyte ions between the electrodes is greatly hindered, resulting in a significant reduction in the area of ​​direct contact between the electrolyte ions and the electrode material, seriously affecting the energy storage performance of the graphene fiber membrane electrode. Summary of the Invention

[0005] In response to the problems existing in the prior art, the present invention provides a graphene@AgI composite fiber membrane and its preparation method and application. The present invention uses graphene oxide as the starting material and adopts a wet spinning process to obtain graphene oxide fiber; the graphene oxide fiber is placed in a CaCl2 ethanol solution for solvent exchange, and then the solvent is separated and hot-pressed to dry to obtain a graphene oxide fiber membrane; then the graphene oxide fiber membrane is reduced using an acetic acid solution of HI to obtain a graphene fiber membrane; finally, the graphene fiber membrane is immersed in a soluble silver salt, I - With Ag +The reaction generates AgI nanoparticles, which adhere to the graphene fiber membrane and are then dried to produce a graphene@AgI composite fiber membrane. By in-situ generating AgI nanoparticles on the graphene fiber membrane, this method not only overcomes the prior art problem of graphene sheets easily agglomerating to form a densely packed structure due to π-π interactions, but also increases the specific surface area of ​​the graphene fiber membrane, thereby significantly enhancing the electrochemical performance of the graphene@AgI composite fiber membrane.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] The first object of the present invention is to provide a method for preparing a graphene@AgI composite fiber membrane, comprising the following steps:

[0008] S1. Dispersing graphene oxide in water to obtain a graphene oxide dispersion; and wet spinning the graphene oxide dispersion into graphene oxide fibers.

[0009] S2. After cutting the graphene oxide fiber short, place it in a CaCl2 ethanol solution for solvent exchange. During the solvent exchange process, the graphene oxide sheets on the graphene oxide fiber undergo a phase transition through hydrogen bonds or ionic bonds with Ca ions, changing from a homogeneous phase to a gel state, forming a structurally stable graphene oxide gel fiber; after separating the solvent, the graphene oxide fiber membrane is obtained by hot pressing and drying.

[0010] S3, placing the graphene oxide fiber membrane in HI acetic acid solution to perform a reduction reaction. During the reduction reaction, the oxygen-containing functional groups in the graphene oxide sheet are ring-opened, and the purpose of eliminating the oxygen-containing functional groups is finally achieved to obtain a graphene fiber membrane. At this time, I - Attached to the surface of graphene fiber membrane, I - Intercalated between the layers of graphene fiber membranes. Currently, there are no reports on the reduction of other iodides. HI has a strong reducing property and can remove oxygen-containing functional groups in graphene oxide. Other iodides are not sufficiently reducing.

[0011] S4, soaking the graphene fiber membrane in soluble silver salt, I - With Ag + The reaction generates AgI nanoparticles, which are attached to the graphene fiber membrane. After being taken out and dried, a graphene@AgI composite fiber membrane is obtained.

[0012] Preferably, the number of layers of graphene oxide is 1 to 3 layers, the average lateral size is 10 μm to 40 μm, and the Zeta potential of the graphene oxide dispersion is negative. Graphene oxide is a two-dimensional sheet structure with a thickness of about 1 nm. Compared with a multilayer structure (>5 layers), 1 to 3 layers of graphene oxide have less lattice distortion, which is beneficial to maintaining the intrinsic conductivity of graphene in the reduced graphene fiber membrane; the ultra-thin sheets are more easily oriented by shear force during the wet spinning process to form an ordered fiber structure. At the same time, the number of layers of graphene oxide is 1 to 3 layers, and its specific surface area is larger, providing sufficient interface for subsequent AgI nanoparticle loading.

[0013] Preferably, the reduction reaction is carried out at 80° C. to 100° C. for 6 h to 12 h.

[0014] Preferably, the hot press drying conditions are: at 40°C to 60°C, 0.2N / m 2 ~1N / m 2 wherein, the applied gravity mainly affects the thickness of the graphene fiber membrane, and the greater the gravity applied per unit area, the smaller the thickness of the graphene fiber membrane.

[0015] Preferably, the mass fraction of CaCl2 in the ethanol solution is 5wt% to 15wt%, and the volume ratio of anhydrous ethanol to water in the ethanol solution is 1 to 3:1. Ethyl acetate is also used for solvent exchange in the prior art. The present invention uses a 5wt% CaCl2 ethanol solution as the coagulation bath, which is environmentally friendly and low-cost.

[0016] Preferably, the specific operation of shortening is: using scissors to cut the graphene oxide fibers into short graphene oxide fibers of 1 mm to 2 mm.

[0017] Preferably, graphene oxide is prepared according to the following steps:

[0018] S1. Pre-oxidized graphite is mixed with a mixed solution of H2SO4 and H3PO4, and then a KMnO4 solution is added dropwise to initiate an oxidation reaction to produce graphene oxide. The goal is to insert oxygen-containing functional groups between the graphite flakes, increasing the interlayer spacing between the flakes and facilitating the exfoliation of single-layer graphene during the subsequent oxidation process.

[0019] S2. After mixing the pre-oxidized graphite with a mixed solution of H2SO4 and H3PO4, slowly add KMnO4 to initiate an oxidation reaction, inserting oxygen-containing functional groups into the graphite flakes, breaking C=C bonds and generating CO or C=O, thereby obtaining graphene oxide. The mixed solution of H2SO4 and H3PO4 provides a strong acidic environment, allowing the pre-oxidized graphite to be oxidized by KMnO4 into graphene oxide. During the oxidation reaction, potassium permanganate should not be added all at once, as this can cause a violent reaction and explosion.

[0020] Preferably, the mass volume ratio of flake graphite, potassium persulfate and concentrated sulfuric acid is 2g-10g:0.5g-5g:5mL-20mL.

[0021] Preferably, the mixing conditions for preparing pre-oxidized graphite are: reacting at 65° C. to 80° C. for 3 h to 6 h.

[0022] Preferably, in the mixed solution of H2SO4 and H3PO4, the ratio of H2SO4 to H3PO4 is 0-150 mL: 10 mL-30 mL.

[0023] Preferably, the oxidation reaction conditions are: first stirring the reaction at -3°C to 3°C for 0.5h to 1.5h, and then stirring the reaction at 30°C to 40°C for 1h to 3h.

[0024] Preferably, the prepared graphene oxide is further post-treated, and the specific operation of the post-treatment is: adding 20wt% to 40wt% of H2O2 to the graphene oxide until no bubbles are generated, so as to eliminate unreacted KMnO4.

[0025] Preferably, in the HI acetic acid solution, the volume ratio of HI to acetic acid is 20-30:60-90. The HI acetic acid solution has a high HI content and a relatively fast reduction rate.

[0026] Preferably, Ag in the soluble silver salt + The concentration of Ag is 0.8mol / L~1.2mol / L. + Is to ensure that the residual I in the graphene fiber membrane - It can be completely converted into AgI nanoparticles, and the influence of its concentration is negligible.

[0027] The second object of the present invention is to provide a graphene@AgI composite fiber membrane prepared by the above preparation method.

[0028] Preferably, the graphene@AgI composite fiber membrane has a dense structure and a complete membrane layer. The graphene@AgI composite fiber membrane is composed of a graphene fiber membrane and AgI nanoparticles. The AgI nanoparticles are attached to the surface of the graphene fiber membrane and intercalated between the layers of the graphene fiber membrane.

[0029] Preferably, the thickness of the graphene@AgI composite fiber membrane is 250 μm to 300 μm.

[0030] The third object of the present invention is to provide an application of graphene@AgI composite fiber membrane in the preparation of flexible supercapacitors.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] 1. The present invention provides a method for preparing a graphene@AgI composite fiber membrane, which comprises the following steps: using an aqueous dispersion of graphene oxide as a raw material, wet spinning is performed to prepare graphene oxide fibers; placing the graphene oxide fibers in a CaCl2 ethanol solution for solvent exchange, during which the graphene oxide sheets on the graphene oxide fibers are transformed from a homogeneous phase to a gel state through hydrogen bonds or crosslinking with ionic bonds of Ca ions, thereby forming graphene oxide gel fibers; separating the solvent and then hot-pressing and drying to obtain a graphene oxide fiber membrane; placing the graphene oxide fiber membrane in an acetic acid solution of HI for reduction reaction, during which the oxygen-containing functional groups in the graphene oxide sheets are ring-opened to obtain a graphene fiber membrane, at which point I - Attached to the surface of graphene fiber membrane, I - Inserted between the layers of graphene fiber membrane; soaking the graphene fiber membrane in soluble silver salt, I - With Ag + The reaction generates AgI nanoparticles, which are attached to the graphene fiber membrane. After being taken out and dried, a graphene@AgI composite fiber membrane is obtained.

[0033] The present invention utilizes the residual I in the reduction process - AgI nanoparticles are generated in situ and attached to a graphene fiber membrane to form a graphene@AgI composite fiber membrane. The present invention effectively inhibits the re-stacking of graphene sheets through the "interlayer support effect" of AgI nanoparticles, forming a three-dimensional, interconnected, multi-level pore structure. This not only overcomes the densely packed structure problem of graphene sheets caused by π-π agglomeration in the prior art, significantly improves the electrolyte ion transport efficiency, but also greatly increases the specific surface area of ​​the graphene@AgI composite fiber membrane. In addition, the synergistic conductive network of AgI nanoparticles and graphene fiber membrane is utilized to significantly enhance the charge transfer dynamics.

[0034] 2. This invention utilizes a wet spinning process in conjunction with a CaCl₂ ethanol solution system to precisely construct the microstructure of the graphene oxide fiber membrane through a dual mechanism of solvent exchange and gravity densification. The solvent exchange process renders the graphene oxide fibers continuous and uniform. After solvent separation and hot-press drying, the graphene oxide fiber membrane achieves a dense, well-defined, and intact membrane structure.

[0035] 3. The present invention soaks the graphene fiber membrane obtained by the reduction reaction in a soluble silver salt solution without washing, so that the residual I - With Ag + reaction to generate AgI nanoparticles. - The residual problem is solved, and the washing steps are reduced, thus avoiding the generation of waste water.

[0036] 4. The electrode material prepared using the graphene@AgI composite fiber membrane of the present invention has excellent mechanical properties and electrical conductivity, can maintain stable electrochemical properties in a bent state, and has excellent cycle stability. It has broad application prospects in the fields of wearable electronic devices, energy conversion and storage devices, and flexible electronics. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is an AFM image of graphene oxide prepared in Example 1 of the present invention.

[0038] Figure 2 This is a diagram of the graphene@AgI composite fiber membrane prepared in Example 1 of the present invention, wherein a is a physical diagram of the graphene@AgI composite fiber membrane, and b is a display diagram of the graphene@AgI composite fiber membrane wound onto a glass rod.

[0039] Figure 3 This is an SEM image of the graphene@AgI composite fiber membrane prepared in Example 1 of the present invention, where a is 200 μm and b is 50 μm.

[0040] Figure 4 This is a CV curve diagram of the graphene@AgI composite fiber membrane prepared in Example 1 of the present invention.

[0041] Figure 5 This is a GCD curve diagram of the graphene@AgI composite fiber membrane prepared in Example 1 of the present invention.

[0042] Figure 6 Graphs showing the BET curves of the graphene fiber membrane and graphene@AgI composite fiber membrane prepared in Example 1 of the present invention.

[0043] Figure 7 CV curve and GCD curve of the graphene fiber membrane prepared in Example 1 of the present invention, wherein a is the CV curve and b is the GCD curve.

[0044] Figure 8 CV curves of the graphene@AgI composite fiber membrane flexible supercapacitor prepared in Example 1 of the present invention at different bending angles. DETAILED DESCRIPTION

[0045] The following will clearly and completely describe the technical solution of the present invention in conjunction with the data in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0046] 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 scope of protection of the present invention. Unless otherwise specified, the various raw materials, reagents, instruments and equipment used in the following embodiments of the present invention can be purchased from the market or prepared by existing methods.

[0047] In the existing technology, since graphene sheets can easily agglomerate to form a densely packed structure due to the π-π interaction between the sheets, the transmission of electrolyte ions between the electrodes is greatly hindered, resulting in a significant reduction in the area of ​​direct contact between the electrolyte ions and the electrode material, seriously affecting the energy storage performance of the graphene fiber membrane electrode.

[0048] In view of the problems existing in the above-mentioned prior art, the present invention provides a method for preparing a graphene@AgI composite fiber membrane, comprising the following steps: using an aqueous dispersion of graphene oxide as a raw material, adopting a wet spinning method to prepare graphene oxide fibers; placing the graphene oxide fibers in an ethanol solution of CaCl2 for solvent exchange, during which the graphene oxide sheets on the graphene oxide fibers are transformed from a homogeneous phase to a gel state through hydrogen bonds or ionic bonds with Ca ions to form graphene oxide gel fibers; separating the solvent and then hot-pressing and drying to obtain a graphene oxide fiber membrane; placing the graphene oxide fiber membrane in an acetic acid solution of HI for reduction reaction, during which the oxygen-containing functional groups in the graphene oxide sheets are ring-opened to obtain a graphene fiber membrane, at which time I - Attached to the surface of graphene fiber membrane, I - Inserted between the layers of graphene fiber membrane; soaking the graphene fiber membrane in soluble silver salt, I - With Ag + The reaction generates AgI nanoparticles, which are attached to the graphene fiber membrane. After being taken out and dried, a graphene@AgI composite fiber membrane is obtained.

[0049] The present invention is based on the residual I in the reduction process - , achieving in-situ uniform loading of AgI nanoparticles on the surface and between layers of graphene fibers. Through the "interlayer support effect" of AgI nanoparticles, the densification stacking of graphene sheets caused by π-π interactions is effectively suppressed, and a three-dimensional multi-level pore structure is constructed. This significantly improves the problem of electrolyte ion transport obstruction caused by the dense stacking structure of traditional graphene fiber membranes, and has fundamentally solved the problem of limited effective contact area of ​​electrode materials caused by sheet agglomeration.

[0050] The technical solution of the present invention is further explained by using embodiments below, which are as follows:

[0051] Example 1

[0052] A method for preparing a graphene@AgI composite fiber membrane comprises the following steps:

[0053] S1. Preparation of graphene oxide dispersion:

[0054] 3.0 g of flake graphite and 2.5 g of potassium persulfate were weighed and added to 10 mL of concentrated sulfuric acid. The temperature was raised to 80 ° C and stirred for 4.5 h. After cooling to room temperature, vacuum filtration was performed and the filtrate was washed with deionized water until the pH value of the filtrate reached 7. The pre-oxidized graphite was then dried at 50 ° C for 24 h.

[0055] Pre-oxidized graphite was added to a mixed solution of 120 mL of H₂SO₄ and 30 mL of H₃PO₄. The mixture was cooled to -3°C using a cold trap and stirred for 0.5 h. Then, 12.0 g of KMnO₄ was slowly added. After all the KMnO₄ was added, the mixture was stirred at -3°C for 1.0 h to thoroughly mix the mixture. The mixture was then heated to 35°C and allowed to react for 2 h. After the reaction was complete, 250 mL of deionized water was added for dilution, causing the reaction solution to change from dark green to dark brown. 20 mL of 30% H₂O₂ was then added dropwise until no bubbles formed. The reaction solution changed from dark brown to reddish brown and then to golden yellow, resulting in a graphene oxide dispersion.

[0056] S2. Preparation of graphene oxide fiber membrane:

[0057] 5 mL of graphene oxide dispersion (10 mg / mL) was added to a syringe fixed on a syringe pump. The spinning solution in the syringe was squeezed out from the needle at an injection speed of 100 μL / min into a coagulation bath with a rotation speed of about 6 rpm. The coagulation bath was a 5 wt% CaCl2 ethanol solution (V 水 :V 无水乙醇 =3:1), solvent exchange occurs in a coagulation bath to form graphene oxide gel fibers; after spinning, the graphene oxide gel fibers are immersed in the coagulation bath for 0.5 h, cut into 2 mm short fibers with scissors, filtered under reduced pressure, washed with water three times, and then a 50 g weight is placed on the graphene oxide gel fibers, and dried in a vacuum oven at 50° C. to obtain a graphene oxide fiber membrane.

[0058] S3. Preparation of graphene@AgI composite fiber membrane:

[0059] The graphene oxide fiber membrane was placed in a 40% HI acetic acid solution and heated to 90°C for reduction for 6 hours to obtain a graphene fiber membrane; then, the graphene fiber membrane was directly immersed in a 1 mol / L AgNO3 aqueous solution without washing with water. After standing for 2.5 hours, it was washed with water three times and then placed in a vacuum oven at 50°C for drying to obtain a graphene@AgI composite fiber membrane, which was recorded as Ag@rGOFF.

[0060] Example 2

[0061] A method for preparing a graphene@AgI composite fiber membrane comprises the following steps:

[0062] S1. Preparation of graphene oxide dispersion:

[0063] Weigh 2 g of flake graphite and 0.5 g of potassium persulfate into 5 mL of concentrated sulfuric acid, heat to 65°C, and stir for 6 h. After cooling to room temperature, vacuum filter the mixture and wash with deionized water until the filtrate reaches a pH of 7. Dry the mixture at 50°C for 24 h to obtain pre-oxidized graphite.

[0064] Pre-oxidized graphite was added to a mixed solution of 120 mL of H₂SO₄ and 30 mL of H₃PO₄. The mixture was cooled to -3°C using a cold trap and stirred for 0.5 h. Then, 12.0 g of KMnO₄ was slowly added. After the KMnO₄ was completely added, the mixture was stirred at -3°C for 0.5 h to thoroughly mix. The mixture was then heated to 30°C and allowed to react for 3 h. After the reaction was complete, 250 mL of deionized water was added for dilution, causing the reaction solution to change from dark green to dark brown. 20 mL of 20% H₂O₂ was then added dropwise until no bubbles formed. The reaction solution changed from dark brown to reddish brown and then to golden yellow, resulting in a graphene oxide dispersion.

[0065] S2. Preparation of graphene oxide fiber membrane:

[0066] 5 mL of graphene oxide dispersion (10 mg / mL) was added to a syringe fixed on a syringe pump. The spinning solution in the syringe was squeezed out from the needle at an injection speed of 100 μL / min into a coagulation bath with a rotation speed of about 6 rpm. The coagulation bath was a 5 wt% CaCl2 ethanol solution (V 水 :V 无水乙醇 =1:1), solvent exchange occurs in a coagulation bath to form graphene oxide gel fibers; after spinning, the graphene oxide gel fibers are immersed in the coagulation bath for 0.5 h, cut into 2 mm short fibers with scissors, filtered under reduced pressure, washed with water three times, and then a 20 g weight is placed on the graphene oxide gel fibers, and dried in a vacuum oven at 40° C. to obtain a graphene oxide fiber membrane.

[0067] S3. Preparation of graphene@AgI composite fiber membrane:

[0068] The graphene oxide fiber membrane was placed in a 40% HI acetic acid solution and heated to 80°C for reduction for 12 hours to obtain a graphene fiber membrane; then, the graphene fiber membrane was directly immersed in a 0.8 mol / L AgNO3 aqueous solution without washing with water. After standing for 2.5 hours, it was washed with water three times and then placed in a vacuum oven at 50°C for drying to obtain a graphene@AgI composite fiber membrane.

[0069] Example 3

[0070] A method for preparing a graphene@AgI composite fiber membrane comprises the following steps:

[0071] S1. Preparation of graphene oxide dispersion:

[0072] Weigh 10 g of flake graphite and 5 g of potassium persulfate and add them to 20 mL of concentrated sulfuric acid. Heat to 80 °C and stir for 3 h. Cool to room temperature and then vacuum filter. Wash with deionized water until the pH value of the filtrate reaches 7, and then dry at 50 °C for 24 h to obtain pre-oxidized graphite.

[0073] Pre-oxidized graphite was added to a mixed solution of 130 mL of H₂SO₄ and 20 mL of H₃PO₄. The mixture was cooled to 3°C using a cold trap and stirred for 0.5 h. Then, 12.0 g of KMnO₄ was slowly added. After all the KMnO₄ was added, the mixture was stirred at 3°C ​​for 1 h to thoroughly mix. The mixture was then heated to 40°C and allowed to react for 1 h. After the reaction was complete, 250 mL of deionized water was added for dilution, causing the reaction solution to change from dark green to dark brown. 10 mL of 40% H₂O₂ was then added dropwise until no bubbles formed. The reaction solution changed from dark brown to reddish brown and then to golden yellow, resulting in a graphene oxide dispersion.

[0074] S2. Preparation of graphene oxide fiber membrane:

[0075] 5 mL of graphene oxide dispersion (10 mg / mL) was added to a syringe fixed on a syringe pump. The spinning solution in the syringe was squeezed out from the needle at an injection speed of 100 μL / min into a coagulation bath with a rotation speed of about 6 rpm. The coagulation bath was a 5 wt% CaCl2 ethanol solution (V 水 :V 无水乙醇 =3:1), solvent exchange occurs in a coagulation bath to form graphene oxide gel fibers; after spinning, the graphene oxide gel fibers are immersed in the coagulation bath for 0.5 h, cut into 2 mm short fibers with scissors, filtered under reduced pressure, washed with water three times, and then a 100 g weight is placed on the graphene oxide gel fibers, and the fibers are dried in a vacuum oven at 60° C. to obtain a graphene oxide fiber membrane.

[0076] S3. Preparation of graphene@AgI composite fiber membrane:

[0077] The graphene oxide fiber membrane was placed in a 40% HI acetic acid solution and heated to 100°C for 6 hours to obtain a graphene fiber membrane. Then, the graphene fiber membrane was directly immersed in a 1.2 mol / L AgNO3 aqueous solution without washing. After standing for 2.5 hours, it was washed with water three times and then dried in a vacuum oven at 50°C.

[0078] Comparative Example 1

[0079] A method for preparing a graphene oxide fiber membrane comprises the following steps:

[0080] S1. Preparation of graphene oxide dispersion:

[0081] Weigh 3 g of flake graphite and 2.5 g of potassium persulfate and add them to 10 mL of concentrated sulfuric acid. Heat to 80 °C and stir for 4.5 h. Cool to room temperature and then vacuum filter. Wash with deionized water until the pH value of the filtrate reaches 7, and then dry at 50 °C for 24 h to obtain pre-oxidized graphite.

[0082] The pre-oxidized graphite was added to a mixed solution of 120 mL of H₂SO₄ and 30 mL of H₃PO₄. The mixture was cooled to -3°C using a cold trap and stirred for 0.5 h. Then, 12.0 g of KMnO₄ was carefully and slowly added. After the KMnO₄ was completely added, the mixture was stirred at -3°C for 1.0 h to thoroughly mix, then heated to 35°C for 2 h. 250 mL of deionized water was then added for dilution, causing the reaction solution to change from dark green to dark brown. 20 mL of 30% H₂O₂ was then added dropwise until no bubbles formed, causing the reaction solution to change from dark brown to reddish brown and then to golden yellow, resulting in a graphene oxide dispersion.

[0083] S2. Preparation of graphene oxide fiber membrane:

[0084] 5 mL of graphene oxide dispersion (10 mg / mL) was added to a syringe fixed on a syringe pump. The spinning solution in the syringe was squeezed out from the needle at an injection speed of 100 μL / min into a coagulation bath with a rotation speed of about 6 rpm. The coagulation bath was a 5 wt% CaCl2 ethanol solution (V 水 :V 无水乙醇 =3:1), solvent exchange occurs in the coagulation bath to form graphene oxide gel fibers; after spinning, the graphene oxide gel fibers are immersed in the coagulation bath for 0.5 h, cut into 2 mm short fibers with scissors, filtered under reduced pressure, washed with water three times, and then a 50 g weight is placed on the graphene oxide gel fibers, and dried in a vacuum oven at 50°C to obtain a graphene oxide fiber membrane.

[0085] observe Figure 1 It was concluded that the obtained graphene oxide was a single layer or a few layers, indicating that the graphite layer was successfully peeled off and graphene oxide was prepared.

[0086] observe Figure 2 It was found that the obtained graphene@AgI composite fiber membrane was dark gray and could be bent and wound around a glass rod without any damage or creases, showing good flexibility.

[0087] Figure 3The results show that the graphene@AgI composite fiber membrane is composed of interwoven fibers, with AgI nanoparticles evenly distributed throughout the graphene fiber membrane. This unique structure of graphene fibers coated with AgI nanoparticles successfully creates a three-dimensional through-pore network, significantly improving the transport kinetics of electrolyte ions and effectively optimizing the electrochemical performance of the graphene@AgI composite fiber membrane.

[0088] Graphene@AgI composite fiber membranes were prepared in Examples 1 to 4 of the present invention, and the effects were similar. The electrochemical properties of the graphene@AgI composite fiber membrane prepared in Example 1 and the graphene oxide fiber membrane prepared in Comparative Example 1 were studied as examples.

[0089] The graphene@AgI composite fiber membrane and the graphene oxide fiber membrane prepared in Comparative Example 1 were cut into 1 cm × 1.5 cm sizes and used as working electrodes, platinum sheets as counter electrodes, Ag / AgCl electrodes as reference electrodes, and 0.8 mol / L H2SO4 as electrolyte to assemble a three-electrode system for CV testing.

[0090] The test conditions are as follows: the selected voltage window is 0 V to -0.8 V, and the scan rates are 10 mV / s, 20 mV / s, 50 mV / s, 80 mV / s, 100 mV / s, and 200 mV / s.

[0091] At current densities of 1 A / cm 2 , 3A / cm 2 , 5A / cm 2 , 8mA / cm 2 Perform GCD test below.

[0092] The area specific capacitance of the thin film electrode is calculated according to the following formula: Among them, C A is the area specific capacitance of the thin film electrode, I is the current, t is the discharge time, U is the voltage, and S is the area of ​​the electrode material.

[0093] observe Figure 4 The CV curve is rectangular, indicating double-layer capacitance. Capacitors are classified as double-layer capacitors and pseudocapacitors. Graphene fiber film-based capacitors, which are carbon-based materials, exhibit a rectangular CV curve without the redox peaks of pseudocapacitors.

[0094] observe Figure 5 It is concluded that GCD is a symmetrical isosceles triangle and the surface has good specific capacitance performance. 2 At a current density of 1.5 GHz, its area specific capacitance is 1106.56 mF / cm 2 .

[0095] Figure 6The results show that the specific surface area of ​​graphene@AgI composite fiber membrane is greatly improved compared with pure graphene fiber membrane, providing a theoretical basis for improving capacitance performance.

[0096] Depend on Figure 7 As shown in Figure a, the charge and discharge time of the graphene@AgI composite fiber membrane is much longer than that of the pure graphene fiber membrane, indicating that the specific capacitance of the graphene@AgI composite fiber membrane is greatly improved. 2 At a current density of 1.5 GHz, the area specific capacitance of the graphene@AgI composite fiber membrane is 1106.56 mF / cm 2 , while the area specific capacitance of pure graphene fiber membrane is only 62.23mF / cm 2 .

[0097] Taking the graphene@AgI composite fiber membrane prepared in Example 1 of the present invention as an example, it was applied to prepare a PVA-H2SO4 gel electrolyte. The specific operation was as follows:

[0098] Weigh 3g of PVA powder into a beaker and add 15mL of deionized water. Stir continuously at room temperature until the PVA powder dissolves. Measure 1mL of concentrated H2SO4 and slowly add it dropwise to the PVA aqueous solution at room temperature. Stir for 8 minutes, then at 100°C for 40 minutes to obtain a transparent, uniform PVA-H2SO4 colloidal solution. Ultrasonicate the colloidal solution in an ultrasonic cleaner for 12 minutes to remove any bubbles. Pour the PVA-H2SO4 colloidal solution into a clean glass Petri dish and freeze it at -20°C. After 50 minutes, remove it and air-dry it at room temperature to obtain the PVA-H2SO4 gel electrolyte.

[0099] The graphene@AgI composite fiber membrane prepared in Example 1 and the graphene oxide fiber membrane prepared in Comparative Example 1 were used as electrodes, and PVA-H2SO4 gel electrolyte was used as solid electrolyte to assemble them into flexible supercapacitors.

[0100] Mechanical bending strain was applied to the flexible supercapacitor and CV testing was performed. Specifically, the bending angles of the flexible supercapacitor were kept at 0, 45°, 90°, 135°, and 180°, respectively, and the voltage window was selected from 0V to -0.8V, with a scan rate of 10mV / s, for CV testing.

[0101] Depend on Figure 8 It was found that under different bending angles, the CV curves are almost the same, indicating that the flexible supercapacitor has stable electrochemical properties in the bent state, can meet the flexibility requirements of wearable energy storage devices, and further shows that the device has potential practical application value.

[0102] Compared with the graphene oxide fiber membrane prepared in Comparative Example 1, the graphene@AgI composite fiber membrane electrode in the present invention is assembled into a structure similar to a commercial capacitor, and the electrochemical performance test is carried out under the action of external mechanical strain, which proves the excellent capacitance retention and cycle stability under strain of the graphene@AgI composite fiber membrane electrode, demonstrating the unique advantages of this composite film material.

[0103] It should be noted that when the present invention involves numerical ranges, it should be understood that both endpoints of each numerical range and any value between the two endpoints can be selected. Since the steps and methods used are the same as those in the embodiments, in order to avoid redundancy, the present invention describes preferred embodiments. Although preferred embodiments of the present invention have been described, those skilled in the art will be able to make additional changes and modifications to these embodiments once they understand the basic inventive concepts. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

Claims

1. A method for preparing a graphene@AgI composite fiber membrane, characterized in that: The following steps are involved: Graphene oxide fibers are prepared by wet spinning using a water dispersion of graphene oxide as a raw material; The graphene oxide fiber is placed in a CaCl2 ethanol solution for solvent exchange. During the solvent exchange process, the graphene oxide sheets on the graphene oxide fiber are transformed from a homogeneous phase to a gel through hydrogen bonds or ionic bonds with Ca ions to form a graphene oxide gel fiber. After separating the solvent, the graphene oxide fiber is hot-pressed and dried to obtain a graphene oxide fiber membrane. The graphene oxide fiber membrane is placed in an acetic acid solution of HI for reduction reaction. During the reduction reaction, the oxygen-containing functional groups in the graphene oxide sheet are ring-opened to obtain a graphene fiber membrane. At this time, I - Attached to the surface of graphene fiber membrane, I - Intercalated between graphene fiber membrane layers; The graphene fiber membrane is immersed in soluble silver salt. - With Ag + The reaction generates AgI nanoparticles, which are attached to the graphene fiber membrane. After being taken out and dried, a graphene@AgI composite fiber membrane is obtained.

2. The method for preparing a graphene@AgI composite fiber membrane according to claim 1, wherein: The number of graphene oxide layers is 1 to 3.

3. The method for preparing a graphene@AgI composite fiber membrane according to claim 1, wherein: Graphene oxide is prepared according to the following steps: flake graphite, potassium persulfate and concentrated sulfuric acid are mixed, filtered, washed and dried to obtain pre-oxidized graphite; After pre-oxidized graphite is mixed with a mixed solution consisting of H2SO4 and H3PO4, KMnO4 solution is added dropwise to carry out an oxidation reaction to obtain graphene oxide.

4. The method for preparing a graphene@AgI composite fiber membrane according to claim 1, wherein: The conditions for the reduction reaction are: reaction at 80°C to 100°C for 6h to 12h.

5. The method for preparing a graphene@AgI composite fiber membrane according to claim 1, characterized in that: Hot press drying conditions are: 40℃~60℃, 0.2N / m 2 ~1N / m 2 Dry under.

6. The method for preparing a graphene@AgI composite fiber membrane according to claim 1, characterized in that: In the ethanol solution of CaCl2, the mass fraction of CaCl2 is 5wt% to 15wt%.

7. A graphene@AgI composite fiber membrane prepared by the preparation method according to any one of claims 1 to 6.

8. The graphene@AgI composite fiber membrane according to claim 7, characterized in that The graphene@AgI composite fiber membrane is composed of graphene fiber membrane and AgI nanoparticles. The AgI nanoparticles are attached to the surface of the graphene fiber membrane and intercalated between the layers of the graphene fiber membrane.

9. The graphene@AgI composite fiber membrane according to claim 7, characterized in that The thickness of the graphene@AgI composite fiber membrane is 250μm to 300μm.

10. Use of the graphene@AgI composite fiber membrane according to claim 7 in preparing a flexible supercapacitor.

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