A method for preparing fiber electrodes by using magnet-induced Fe3O4@GO to arrange them in a directional manner

Abstract

The present invention discloses a method for preparing fiber electrodes by using a magnet to induce the directional arrangement of Fe3O4@GO, belonging to the field of functional material technology. The present invention first disperses Fe3O4 nanoparticles in a GO suspension, and controls the distribution of Fe3O4 nanoparticles on the surface of GO nanosheets by adding EDA to form a Fe3O4@GO liquid crystal solution; then, the Fe3O4@GO liquid crystal solution is extruded into a coagulation bath through a spinneret of a spinning device, and at the same time, a magnet is used to rotate above the spinneret to drive the Fe3O4@GO to rotate and unfold in the solution for bidirectional directional arrangement, forming Fe3O4@GO gel fiber filaments; finally, drying, stretching, and winding to obtain a fiber electrode. The fiber electrode prepared by the present invention can take into account both electrochemical and mechanical properties, and can be used to prepare fiber-shaped batteries, supercapacitors, etc.

Description

Technical Field

[0001] The present invention relates to a method for preparing a fiber electrode by using a magnet to induce the directional arrangement of Fe3O4@GO, and belongs to the technical field of functional materials. Background Art

[0002] In recent years, demand for multifunctional structural composite materials has steadily increased, especially for structural energy storage composite materials, which have attracted attention due to their ability to withstand heavy loads and possess electrical energy storage functions (such as batteries and supercapacitors). The potential application scenarios of flexible supercapacitors generally require thinness, strong deformation capability, and high deformation cycle stability. This places new demands on the electromechanical properties of supercapacitors, such as capacity retention, voltage output stability, structural cycle stability, and electrical properties. In this context, one-dimensional fiber supercapacitors can perfectly fill this gap and provide diverse possibilities in the field of flexible wearable electronics.

[0003] To date, the fabrication of fiber-based lithium-ion battery electrodes has achieved tremendous innovation, from the optimized design of active materials to device configurations. Traditionally, fiber electrodes have been prepared by selecting a suitable linear substrate or current collector, such as metal wire, polymer-based fibers, carbon fibers, and carbon nanotube / graphene-based fibers, as a supporting backbone to coat or deposit the active material. A variety of active materials (e.g., MnO2, MoS, Fe2O3, etc.) have been incorporated into fiber electrodes to achieve high specific capacities. Meanwhile, novel coaxial / twisted structures have been employed to enhance electrochemical performance, but the improvement in energy density remains far from satisfactory. Generally speaking, fiber electrodes fabricated via such surface coating methods suffer from two major drawbacks: the additional substrate weight reduces the effective mass loading of the active material, which severely limits their overall energy density; and the interfacial adhesion between the active layer and the fiber substrate is loose, which easily leads to detachment of the active material under deformation, resulting in unstable energy output. Therefore, fiber electrodes that combine excellent flexibility with high linear / volumetric specific capacity have become a rarely achieved but urgently needed attribute for flexible fiber supercapacitors.

[0004] Due to its two-dimensional structure and excellent physical and chemical properties, graphene is primarily used as an anode material in energy storage devices, particularly in lithium-ion batteries. Its high electrical conductivity, extremely high specific surface area, and good lithium compatibility significantly improve the battery's charging speed, cycling stability, and energy storage capacity. Its ability to facilitate the rapid transfer of electrons and lithium ions significantly enhances the battery's power density and cycle life. Graphene's versatility and broad application prospects demonstrate its importance as both an anode and potential cathode material in supercapacitor technology, depending on specific battery technology and design requirements. Therefore, it is necessary to design a fibrous electrode material with an oriented morphology based on graphene fibers to address the aforementioned technical challenges. Summary of the Invention

[0005] [Technical Issues]

[0006] The mechanical and electrochemical properties of general structural energy storage composite materials are poor;

[0007] Conventional composite materials cannot take into account both electrochemical and mechanical properties.

[0008] [Technical solution]

[0009] To address the above issues, the present invention first disperses Fe3O4 nanoparticles in a GO (graphene oxide) suspension, then regulates the distribution of Fe3O4 nanoparticles on the surface of GO nanosheets by adding ethylenediamine (EDA), forming a Fe3O4-modified graphene oxide (Fe3O4@GO) liquid crystal solution. The Fe3O4-modified graphene oxide (Fe3O4@GO) liquid crystal solution is then extruded through a spinneret of a spinning device into a coagulation bath. A magnet is then rotated above the spinneret, causing the Fe3O4@GO to rotate and expand in the solution for bidirectional alignment, forming Fe3O4@GO gel fibers. Finally, the fibers are dried, stretched, and wound to obtain fiber electrodes. The fiber electrodes prepared by the present invention offer both electrochemical and mechanical properties and can be used to prepare batteries, supercapacitors, and the like.

[0010] The first object of the present invention is to provide a method for preparing a fiber electrode by using a magnet to induce the oriented arrangement of Fe3O4@GO, comprising the following steps:

[0011] (1) Fe3O4 nanoparticles were dispersed in a GO (graphene oxide) suspension, and the distribution of Fe3O4 nanoparticles on the surface of GO nanosheets was regulated by adding ethylenediamine (EDA). The mixture was then mixed uniformly to form a Fe3O4-modified graphene oxide (Fe3O4@GO) liquid crystal solution.

[0012] (2) extruding a Fe3O4-modified graphene oxide (Fe3O4@GO) liquid crystal solution through a spinneret of a spinning device into a coagulation bath, and simultaneously, before spinning, rotating a magnet above the spinneret to drive the Fe3O4@GO to rotate and expand in the solution for bidirectional orientation, thereby forming Fe3O4@GO gel fibers; wherein the rotation speed of the magnet is 0.5-10 rpm;

[0013] (3) drying, stretching, and winding the Fe3O4@GO gel fiber to obtain fibers;

[0014] (4) The fiber is reduced and calcined to obtain a fiber electrode.

[0015] In one embodiment of the present invention, in step (1), GO (graphene oxide) is prepared by using a modified Hummers method.

[0016] In one embodiment of the present invention, the Fe3O4 nanoparticles in step (1) are prepared by a hydrothermal method.

[0017] In one embodiment of the present invention, the particle size of GO (graphene oxide) in step (1) is 0.5 to 50 μm.

[0018] In one embodiment of the present invention, the average particle size of the Fe3O4 nanoparticles in step (1) is 220 nm.

[0019] In one embodiment of the present invention, the concentration of the GO (graphene oxide) suspension in step (1) is 10-20 mg / mL, and the solvent is water.

[0020] In one embodiment of the present invention, the concentration of Fe3O4 nanoparticles in the GO (graphene oxide) suspension in step (1) is 1-30 wt%, further optimized to 5-20 wt%.

[0021] In one embodiment of the present invention, the volume ratio of GO (graphene oxide) suspension to ethylenediamine (EDA) in step (1) is 10 mL:40-100 μL.

[0022] In one embodiment of the present invention, the uniform mixing in step (1) is achieved by vigorous stirring, specifically stirring at 800 rpm for 100-150 min.

[0023] In one embodiment of the present invention, the Fe3O4-modified graphene oxide (Fe3O4@GO) liquid crystal solution in step (2) needs to be degassed before spinning, and the degassing is performed by centrifugation at 200-4000 rpm for 5-15 minutes.

[0024] In one embodiment of the present invention, the coagulation bath in step (2) is a mixture of ethanol, water and CaCl2 or pure ethyl acetate; wherein the volume ratio of ethanol to water in the mixture is 3:1, and the concentration of CaCl2 is 5wt%.

[0025] In one embodiment of the present invention, the specifications of the magnet in step (2) are annular perforated neodymium magnets with an outer diameter of 20 mm, an inner diameter of 18 mm, and a ring thickness of 2 mm.

[0026] In one embodiment of the present invention, the spinneret in step (2) is a 22G hole spinneret with a needle inner diameter of 0.4 mm and an outer diameter of 0.7 mm.

[0027] In one embodiment of the present invention, the magnet in step (2) improves the sheet order of the fiber cross section through the rotational shear flow, thereby significantly promoting the transverse fiber arrangement.

[0028] In one embodiment of the present invention, in step (2), the Fe3O4@GO fluid is transformed into gel fibers by double diffusion between water (water in the GO (graphene oxide) suspension) and a coagulation bath.

[0029] In one embodiment of the present invention, the drying in step (3) is performed at 60-80° C. for 24 h.

[0030] In one embodiment of the present invention, the stretching ratio in step (3) is 1.5-2.5 times.

[0031] In one embodiment of the present invention, the diameter of the fiber in step (3) is 40-70 microns.

[0032] In one embodiment of the present invention, the reduction in step (4) is to place the fiber in a straight state and reduce it in a hydroiodic acid (HI) aqueous solution with a mass concentration of 47 wt% at 90° C. for 360-480 min.

[0033] In one embodiment of the present invention, the calcination in step (4) is to heat the reduced fiber from room temperature to 450°C at a rate of 5°C / min, and then maintain it at 800°C and 1200°C for 1 hour respectively at a rate of 10°C / min in an argon flow.

[0034] In one embodiment of the present invention, the diameter of the fiber electrode in step (4) is 40-70 microns.

[0035] The second object of the present invention is a fiber electrode prepared by the method of the present invention.

[0036] The third object of the present invention is to provide an electrode material, which is obtained by weaving the fiber electrode described in the present invention.

[0037] The fourth object of the present invention is the application of the fiber electrode or electrode material of the present invention in the field of electricity.

[0038] A fifth object of the present invention is to provide a lithium electronic battery, which uses the fiber electrode or electrode material described in the present invention.

[0039] A sixth object of the present invention is to provide a supercapacitor, which uses the fiber electrode or electrode material described in the present invention.

[0040] The seventh object of the present invention is to provide a method for simultaneously improving the electrochemical properties and mechanical properties of an electrode material, which uses the fiber electrode or electrode material described in the present invention.

[0041] An eighth object of the present invention is to provide a structural energy storage composite material, which uses the fiber electrode or electrode material described in the present invention.

[0042] [Beneficial Effects]

[0043] (1) The tensile strength of the fiber electrode prepared by the present invention can reach above 225 MPa and can be as high as 928.8 MPa.

[0044] (2) The volumetric capacitance of the fiber supercapacitor electrode prepared by the present invention is 2mV s -1 Up to 1237.0Fcm -3 The assembled fiber supercapacitor achieved a power output of 30.1 mW cm -3 40.0 mWh cm -3 The energy density of the battery is 100%, and it exhibits almost 100% capacitance retention under mechanical bending at different angles.

[0045] (3) The volumetric capacity of the flexible fiber-shaped lithium-ion battery prepared by the present invention is 2mV s -1 Up to 162mAhcm -3 The assembled fiber supercapacitor achieved a power output of 625.3 mW cm -3 32mWh cm -3 The energy density of the battery is significantly improved, and it exhibits almost 100% capacity retention under mechanical bending at different angles.

[0046] (4) By modifying the graphene fiber to make it magnetic, it has the concept of bidirectionally promoting the assembly order during the spinning process, so that the graphene fiber can achieve synergistically improved mechanical and electrochemical properties. The concentric arrangement of the graphene oxide sheets on the cross section and the arrangement along the fiber axis are achieved through multiple shear flow fields. This bidirectional promotion promotes the directional arrangement of the graphene sheets in the prepared macroscopic graphene fiber, resulting in a dense and crystalline graphite structure and improving its performance. The development of new functional fibers with good energy storage performance, high conductivity and strong mechanical properties and the assembly of supercapacitors provide feasibility for solving these problems. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 : TEM image of graphene oxide (GO).

[0048] Figure 2 : Actual picture of the fiber bundle after preliminary spinning.

[0049] Figure 3 : SEM of fibers with biaxial orientation, where (a) is 500 μm and (b) is 3 μm.

[0050] Figure 4 : Stress-strain curves of fiber electrodes prepared with different contents of Fe3O4.

[0051] Figure 5: Tensile strength results of fiber electrodes prepared at different rotation speeds.

[0052] Figure 6 :(a) Fiber supercapacitor at 2mV s -1 CV curves of (a) fiber supercapacitor at 2 mV s -1 CV curves at different bending angles, (c) fiber-shaped lithium-ion battery at 2mV s -1 CV curves of lithium-ion batteries at 2mV s -1 CV curves at different bending angles.

[0053] Figure 7 : Cyclic charge-discharge performance of flexible fiber supercapacitors prepared using fiber electrodes. DETAILED DESCRIPTION

[0054] The following describes preferred embodiments of the present invention. It should be understood that the embodiments are for better explanation of the present invention and are not intended to limit the present invention.

[0055] Test method:

[0056] 1. Diameter and cross-sectional area test:

[0057] The diameter and cross-sectional area of ​​the prepared fibers were measured according to the standard GB / T 29762-2013 for the determination of diameter and cross-sectional area of ​​carbon fiber.

[0058] 2. Stress-strain curve test:

[0059] The tensile properties test was carried out according to the GB / T 31290-2022 standard for the determination of tensile properties of carbon fiber monofilaments, and the stress-strain curve was plotted based on the load-displacement curve.

[0060] The raw materials used in the embodiment are:

[0061] GO (graphene oxide) was prepared using the modified Hummers method as follows:

[0062] 400 mL of sulfuric acid and phosphoric acid (9:1 by volume) were added to a beaker and mechanically stirred at 100 rpm to mix thoroughly. 21 g of expandable graphite and potassium permanganate (1:6 by mass) were slowly added in batches, releasing a small amount of heat. The beaker was placed in a 50°C water bath and stirred at 200 rpm at 50°C for 12 hours. After the reaction was complete, the reaction solution was cooled to room temperature. 200 mL of ice and 20 mL of 30% hydrogen peroxide solution were slowly added simultaneously to prevent the temperature from rising until bubbles ceased. The solution was then cooled externally with ice and sonicated for 1 hour. The solution was then centrifuged at 1000 rpm for 6 minutes, the supernatant removed, and the precipitate collected after subsequent centrifugation at 8000 rpm for 6 minutes. Finally, the solution was washed three times with 30% HCl solution, anhydrous ethanol, and deionized water to obtain graphene oxide (GO).

[0063] Ferroferric oxide (Fe3O4) nanoparticles were prepared by a hydrothermal method as follows:

[0064] Under continuous stirring (500 rpm), 0.07M FeCl3·4H2O and 0.14M FeCl3·6H2O were dissolved in deionized water to form a homogeneous solution. An appropriate amount of 30% ammonia solution was added dropwise to 80 mL of the homogeneous solution, and the pH of the solution was measured using a pH meter to 9. The solution was then stirred at 80°C for 1 hour under constant stirring (500 rpm). After the reaction, a black precipitate formed. The resulting precipitate was washed three times with distilled water and calcined at 300°C for 3 hours. The prepared sample was collected as Fe3O4 nanoparticles.

[0065] Graphene oxide (GO): specifications are 0.5 to 50 μm;

[0066] Fe3O4 nanoparticles: The specification is an average particle size of 220nm.

[0067] Example 1

[0068] A method for preparing a fiber electrode by using a magnet to induce the oriented arrangement of Fe3O4@GO comprises the following steps:

[0069] (1) Fe3O4 nanoparticles were dispersed in 10 mL of a 10 mg / mL GO (graphene oxide) suspension. 50 μL of ethylenediamine (EDA) was used in an ultrasonic cleaner to adjust the distribution of Fe3O4 nanoparticles on the surface of GO nanosheets. The reaction was carried out by ultrasonication at 40 W for 30 min. After the reaction was completed, the solution was vigorously stirred at 1000 rpm for 120 min to make it completely uniform, thereby forming an Fe3O4-modified graphene oxide (Fe3O4@GO) liquid crystal solution. The concentration of Fe3O4 nanoparticles in the GO (graphene oxide) suspension was 20 wt%.

[0070] (2) The Fe3O4-modified graphene oxide (Fe3O4@GO) liquid crystal solution was degassed by centrifugation at 1500 rpm for 10 minutes, and then placed in a spinning device. It was extruded into a coagulation bath (pure ethyl acetate) through a spinneret (22G hole spinneret, needle inner diameter 0.4 mm, outer diameter 0.7 mm) at an extrusion speed of 0.2 mL / min. Before spinning, a magnet (specification: annular neodymium magnet with holes, outer diameter 20 mm, inner diameter 18 mm, ring thickness 2 mm) was used to rotate above the spinneret (speed of 8 rev / s) to drive the Fe3O4@GO to rotate and expand in the solution for bidirectional orientation. The Fe3O4@GO fluid was double diffused between water and the coagulation bath to become gel fiber filaments. The fiber filaments were pulled out of the coagulation bath to form Fe3O4@GO gel fiber filaments (diameter of 200-300 μm).

[0071] (3) The Fe3O4@GO gel fibers were dried at 60 °C for 24 h and directed onto a polytetrafluoroethylene roller (with the same size and rotation speed). The fibers were stretched (stretching ratio of 1.2 times) by adjusting the latter roller to a higher speed. Subsequently, the fibers were further stretched (stretching ratio of 1.5 times) and finally collected on a drum for winding to obtain fibers.

[0072] (4) The fiber was straightened and reduced in a 47 wt% hydroiodic acid (HI) aqueous solution at 90°C for 360 min. After the reduction was completed, the fiber was taken out and heated from room temperature to 450°C at a rate of 5°C / min, and then maintained at 800°C and 1200°C for 1 h in an argon flow at a rate of 10°C / min. A fiber electrode (diameter of 40-70 μm) was obtained.

[0073] Example 2

[0074] The concentration of Fe3O4 nanoparticles in the GO (graphene oxide) suspension in step (1) of Example 1 was adjusted to 0, 5, 10, 15, 20, 25, and 30 wt%; at the same time, the rotation speed of the magnet in step (2) was adjusted to 5 rpm; the rest was kept consistent with Example 1 to obtain a fiber electrode.

[0075] The obtained fiber electrode performance was tested, and the test results are as follows:

[0076] Figure 4 The stress-strain curves of fiber electrodes prepared with different contents of Fe3O4. Figure 4It can be seen that the tensile strength of pure graphene fiber is 106.8 MPa. After adding different amounts of magnetic material to promote bidirectional alignment, the tensile strength is increased several times. Among them, the tensile strengths of Fe3O4@GO hybrid fibers with 5, 10, 15, 20, and 25 wt% content are 328.4, 747.9, 855.7, 928.8, and 722.7 MPa, respectively. After adding 25 wt% Fe3O4, the excessive amount of magnetic material makes the mixture uneven, resulting in a decrease in fiber orientation and tensile strength. Therefore, adding 20 wt% Fe3O4 can achieve the maximum mechanical properties of the hybrid fiber.

[0077] Example 3

[0078] The rotation speed of the magnet in step (2) of Example 1 was adjusted to 0.5, 1, 2, 5, 8, 10, and 15 rpm; at the same time, the concentration of Fe3O4 nanoparticles in the GO (graphene oxide) suspension in step (1) was 20 wt %, and the rest was kept consistent with Example 1 to obtain a fiber electrode.

[0079] The obtained fiber electrode performance was tested, and the test results are as follows:

[0080] Figure 5 The tensile strength results of the fiber electrodes prepared at different rotation speeds are shown in Figure 2. Figure 5 It can be seen that both high and low rotation speeds of the magnet ring lead to disordered or random arrangement of the Fe3O4@GO sheets, resulting in poor orientation order and smaller crystallite size. The tensile strengths of the composite graphene fibers at rotation speeds of 0.5, 1, 2, 5, 8, 10, and 15 rpm / s were 225.3, 291.2, 559.6, 929.8, 1104.4, 886.3, and 562.3 MPa, respectively. This shows that an appropriate rotation speed can enhance the orderly arrangement of graphene sheets. However, when the magnet ring rotates too quickly, the stress on the sheets can become uneven, causing large graphene sheets to break into smaller ones, resulting in a decrease in mechanical properties.

[0081] Example 4

[0082] A flexible fiber supercapacitor is prepared using the fiber electrode of Example 3 (the rotation speed of the magnet is 5 rpm, and the concentration of Fe3O4 nanoparticles in the GO (graphene oxide) suspension is 20 wt%);

[0083] The preparation method is as follows:

[0084] 1 g of polyvinyl alcohol (PVA) powder was added to 10 mL of deionized water and then vigorously stirred at 90 °C for 30 min until a clear solution was obtained to obtain a mixture;

[0085] When the temperature of the mixture dropped to ambient temperature, 1 g of H3PO4 was added to the mixture and mixed well to obtain a PVA / H3PO4 gel electrolyte;

[0086] A flexible fiber supercapacitor was assembled using two fiber electrodes of Example 3 and PVA / H3PO4 gel electrolyte.

[0087] The fiber electrode was immersed in PVA / H3PO4 gel electrolyte for 1 hour, taken out, and dried in air for 8 hours;

[0088] Two fiber electrodes coated with electrolyte are placed in parallel on a flexible PET substrate, and the electrolyte is re-coated until the fiber surface is completely wrapped with electrolyte, and then a flexible fiber supercapacitor is made.

[0089] The obtained flexible fiber supercapacitor was tested for electrochemical properties using an electrochemical workstation (CHI 660D), including cyclic voltammetry (CV) and other tests.

[0090] The test results are as follows:

[0091] from Figure 6 From (a) and (b), it can be seen that the volumetric capacitance of the fiber supercapacitor electrode is 2mV s -1 Up to 1237.0F cm -3 The assembled fiber supercapacitor has a power output of 30.1 mW cm -3 40.0 mWh cm -3 The energy density of the battery is 100%, and it exhibits almost 100% capacitance retention under mechanical bending at different angles.

[0092] Figure 7 The cyclic charge-discharge performance of flexible fiber supercapacitors prepared using fiber electrodes. Figure 7 It can be seen that the fiber electrode exhibits excellent electrochemical performance as well as excellent flexibility and stability.

[0093] It can be seen that the flexible fiber supercapacitor prepared using the fiber electrode of the present invention can have excellent electrochemical and cycling performance. The fiber supercapacitor not only has the characteristics of large capacitance, high power density, and long cycle life, but also has the advantages of small size, light weight, good flexibility, and strong deformability. Therefore, the fiber supercapacitor can meet the high flexibility, weavability, and wearability requirements of flexible devices such as wearable smart devices, making it an ideal choice for wearable smart device energy storage systems.

[0094] Example 5

[0095] A flexible fiber lithium-ion battery is prepared using the fiber electrode of Example 3 (the rotation speed of the magnet is 5 rpm, and the concentration of Fe3O4 nanoparticles in the GO (graphene oxide) suspension is 20 wt%):

[0096] The details are as follows:

[0097] First, polyvinylidene fluoride-co-hexafluoropropylene (PVDF-HFP) was added to an N-methylpyrrolidone (NMP) solution to prepare a mixed solution with a mass fraction of 15 wt%, and magnetic stirring was carried out overnight to obtain a PVDF-HFP / NMP solution.

[0098] Then, lithium iron phosphate, carbon black, and PVDF-HFP were dispersed into a PVDF-HFP / NMP solution in a mass ratio of 7:2:1 and stirred for 1 hour using a high-speed disperser to obtain a uniformly dispersed mixed liquid; wherein the concentration of lithium iron phosphate in the PVDF-HFP / NMP solution was 70wt%;

[0099] The mixed liquid was extruded at a high speed of 8 mm / s and immersed in an ethanol coagulation bath;

[0100] After thorough solvent exchange, the fiber electrode was placed in an open container and dried naturally at room temperature to obtain the lithium iron phosphate fiber electrode.

[0101] The preparation of fiber-shaped lithium-ion batteries is as follows:

[0102] Lithium iron phosphate fiber and graphene fiber electrodes were immersed in PVDF-HFP acetone solution (0.5wt%) three times, a PVDF-HFP separation membrane was evenly coated on the surface, and then they were twisted to serve as cathode and anode, respectively;

[0103] The potential window of the fiber-type full cell is 1-2.5V;

[0104] A current collector (aluminum foil for cathode electrode and copper foil for anode electrode) was attached to the end of each fiber electrode, and then the injection and encapsulation process of ethylene carbonate (EC) liquid electrolyte containing 1M lithium hexafluorophosphate (LiPF6) was completed in a glove box.

[0105] The test results are as follows:

[0106] from Figure 6 (c) and (d) show that the volumetric capacity of the fiber supercapacitor electrode is 2mVs -1 Up to 162mAh cm -3 The assembled fiber supercapacitor achieved a power output of 625.3 mW cm -3 32mWh cm -3The energy density of the prepared fiber electrode showed almost 100% capacity retention under mechanical bending at different angles. The prepared fiber electrode showed excellent electrochemical performance as well as excellent flexibility and stability.

[0107] As can be seen, the flexible fiber-shaped lithium-ion battery prepared using the fiber electrodes of the present invention can have excellent electrochemical and cycling performance. The fiber-shaped lithium-ion battery not only has the characteristics of large capacity, high power density, and long cycle life, but also has the advantages of small size, light weight, good flexibility, and strong deformability. Therefore, the fiber-shaped lithium-ion battery can also meet the high flexibility, weavability, and wearability requirements of flexible devices such as wearable smart devices, making it an ideal choice for wearable smart device energy storage systems.

[0108] Comparative Example 1

[0109] The magnet in step (2) of Example 1 was omitted, and the rest of the steps remained the same as in Example 1 to obtain a fiber electrode.

[0110] The results showed that the mechanical properties of the prepared fiber electrode decreased by about 85% compared with those in Example 1. The electrical conductivity also decreased by 32%.

[0111] Comparative Example 2

[0112] The fiber electrode of Comparative Example 1 was used to prepare a fiber supercapacitor according to Example 4.

[0113] The results showed that compared with the fiber supercapacitor prepared in Example 4, its electrochemical performance decreased by approximately 42%. At the same time, when conducting electrochemical performance tests at different angles, the fiber supercapacitor short-circuited when bent to 120°. This shows that rotating the graphene mixed solution at different rates in a magnetic field during the spinning process can not only increase the mechanical properties of the prepared fiber electrode material, but also improve its electrochemical performance.

[0114] Comparative Example 3

[0115] The fiber electrode of Comparative Example 1 was used to prepare a fiber-shaped lithium-ion battery according to Example 5.

[0116] The results showed that compared with the fiber-shaped lithium-ion battery prepared in Example 5, its specific capacity was 64 mAh cm -3 Compared to the fiber-shaped lithium-ion battery prepared in Example 5, its specific capacity decreased by approximately 60%. Although no short circuit occurred during bending, its specific capacity gradually decreased with increasing bending angle. This comparative example also confirmed that rotating the graphene mixed solution at different speeds in a magnetic field during the spinning process not only increases the mechanical properties of the prepared fiber electrode material, but also improves its electrochemical performance.

[0117] Comparative Example 4

[0118] The magnet in Example 1 was replaced with a thin rod for stirring in the capillary to prepare Fe3O4@GO fibers;

[0119] The details are as follows:

[0120] First, a graphene solution was injected into a 300 mm diameter capillary tube. A 100 mm diameter stainless steel strip was inserted into the center of the capillary tube and rotated uniformly at 8 rpm / s for 60 minutes before being removed. The rotation of the stainless steel strip resulted in a uniform and horizontal alignment of the graphene solution in the capillary tube. One end of the capillary tube was then inserted into the spinning apparatus used in Example 1, and the graphene solution was extruded from the capillary tube at the same speed. All other conditions were the same as in Example 1, yielding Fe3O4@GO fibers.

[0121] The tensile strength of the fiber was tested for its mechanical properties, and the results showed that its tensile strength was only 428 MPa, which was about 77% lower than the 1104.4 MPa of Fe3O4@GO fiber prepared by magnet rotation under the same conditions.

[0122] Although the present invention has been disclosed above in terms of preferred embodiments, it is not intended to limit the present invention. Anyone familiar with this technology can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be based on the definition of the claims.

Claims

1. A method for preparing fiber electrodes by using magnet-induced Fe3O4@GO to align the electrodes, characterized in that: The steps include: (1) Fe3O4 nanoparticles were dispersed in a GO (graphene oxide) suspension, and the distribution of Fe3O4 nanoparticles on the surface of GO nanosheets was regulated by adding ethylenediamine (EDA). The mixture was then mixed uniformly to form a Fe3O4-modified graphene oxide (Fe3O4@GO) liquid crystal solution. (2) extruding a Fe3O4-modified graphene oxide (Fe3O4@GO) liquid crystal solution through a spinneret of a spinning device into a coagulation bath, and simultaneously, before spinning, rotating a magnet above the spinneret to drive the Fe3O4@GO to rotate and expand in the solution for bidirectional orientation, thereby forming Fe3O4@GO gel fibers; wherein the rotation speed of the magnet is 0.5-10 rpm; (3) drying, stretching, and winding the Fe3O4@GO gel fiber to obtain fibers; (4) The fiber is reduced and calcined to obtain a fiber electrode.

2. The method according to claim 1, characterized in that In step (1), the concentration of Fe3O4 nanoparticles in the GO (graphene oxide) suspension is 1-30 wt%.

3. The method according to claim 1, characterized in that In step (2), the coagulation bath is a mixture of ethanol, water and CaCl2 or pure ethyl acetate; wherein the volume ratio of ethanol to water in the mixture is 3:1, and the concentration of CaCl2 is 5wt%.

4. A fiber electrode prepared by the method according to any one of claims 1 to 3.

5. An electrode material, characterized in that The fiber electrode according to claim 4 is woven into the fiber electrode.

6. Use of the fiber electrode according to claim 4 or the electrode material according to claim 5 in the field of electricity.

7. A lithium-ion battery, characterized in that: The fiber electrode according to claim 4 or the electrode material according to claim 5 is used.

8. A supercapacitor, characterized in that: The fiber electrode according to claim 4 or the electrode material according to claim 5 is used.

9. A method for simultaneously improving the electrochemical and mechanical properties of an electrode material, characterized in that: The fiber electrode according to claim 4 or the electrode material according to claim 5 is used.

10. A structural energy storage composite material, characterized in that: The fiber electrode according to claim 4 or the electrode material according to claim 5 is used.

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