A method for preparing carbon fiber thin film materials and their applications

Abstract

This invention discloses a method for preparing carbon fiber thin film materials and their applications. It includes the following steps: A) mixing PAN and PVP of different molecular weights in a mass ratio and dispersing them in DMF to obtain a mixed solution; B) dissolving Cu(NO3)2·3H2O in DMF and sonicating it to obtain a transparent solution; C) adding Cu(NO3)2 solution dropwise to the PAN / PVP mixed solution to obtain Cu... 2+ Step A: Spinning solution of doped PAN / PVP precursor; Step B: Obtaining composite fiber membrane by spinning; Step C: Taking the composite fiber membrane and subjecting it to multi-stage heat treatment to finally obtain Cu@CuN3 supported carbon fiber thin film material. The advantages are: when applied to stabilize the negative electrode of an aqueous zinc-ion battery as a protective layer, and assembled into an aqueous zinc-ion battery, it effectively suppresses dendrite growth in the negative electrode and improves the stable charge-discharge time of the battery, effectively solving the problem of negative electrode dendrite growth and improving the electrochemical stability of the battery, providing a new technical path for the development of high-safety, long-life aqueous zinc-ion batteries.

Description

Technical Field

[0001] This invention relates to a method for preparing carbon fiber film materials based on different molecular weight controls of polyvinylpyrrolidone (PVP) and its application, belonging to the field of new material preparation technology. Background Technology

[0002] Aqueous zinc-ion batteries (AZIBs) are considered an ideal choice for next-generation large-scale energy storage technology due to their high theoretical specific capacity (820 mAh / g), high safety, environmental friendliness, and low cost. However, zinc metal anodes face key challenges during cycling, such as uncontrolled dendrite growth, hydrogen evolution reaction (HER), and surface corrosion, which severely restrict their practical application. Disordered deposition of zinc dendrites can easily puncture the separator, leading to short circuits, while the HER not only consumes active water molecules in the electrolyte but also forms passivation products (such as Zn4(OH)6SO4·xH2O), reducing the stability of the electrode / electrolyte interface. Traditional solutions such as three-dimensional porous structure design, artificial solid electrolyte interphase (SEI) construction, and electrolyte additive optimization can partially alleviate the problems, but still have limitations such as insufficient interface stability, complex processes, or high costs.

[0003] Recent studies have shown that nanocomposite materials can optimize zinc deposition behavior through synergistic effects. For example, carbon-based materials (graphene, carbon nanotubes) can construct uniform ion channels, and metal-organic framework (MOF) derivatives can regulate zinc nucleation kinetics. However, it is difficult to achieve dual optimization of zinc deposition morphology and interfacial reaction kinetics with a single material. Therefore, how to effectively suppress dendrite growth in the anode of aqueous zinc-ion batteries and improve the stable charge-discharge time of the batteries has become an urgent technical challenge. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a method for preparing carbon fiber thin film material that can effectively suppress dendrite growth on the negative electrode of aqueous zinc-ion batteries and improve the stable charge and discharge time of the battery, as well as its application.

[0005] To solve the above-mentioned technical problems, the method for preparing carbon fiber thin film material of the present invention includes the following steps:

[0006] A. Preparation of PAN / PVP mixed solution

[0007] Polyacrylonitrile (PAN) and polyvinylpyrrolidone (PVP) of different molecular weights are mixed at a mass ratio of 2:1 to 5:1 (preferably 4:1), dispersed in N,N-dimethylformamide (DMF), and stirred in an oil bath at 30 to 60 °C and 400 to 900 rpm for 2 to 10 h to obtain a clear and transparent mixed solution.

[0008] B. Preparation of Cu(NO3)2 solution

[0009] Cu(NO3)2·3H2O is dissolved in N,N-dimethylformamide and sonicated for 10–30 min to obtain a green transparent solution with a concentration of 0.1–0.6 mmol / mL; preferably, the Cu(NO3)2 solution is prepared with a concentration of 0.25 mmol / mL and sonicated for 15 min.

[0010] Step C: Preparation of precursor spinning solution

[0011] The Cu(NO3)2 solution from step B was slowly added dropwise to the PAN / PVP mixed solution from step A at room temperature, with a volume ratio of 3:(10-15). The mixture was then magnetically stirred at room temperature for 6-12 hours until the solution became a homogeneous, green, viscous state, yielding Cu. 2+ Doped PAN / PVP precursor spinning solution;

[0012] Step D: Uniaxial electrospinning

[0013] Take Cu after step C and let it stand for 1–12 h 2+ The doped PAN / PVP precursor spinning solution was spun into a composite fiber membrane by uniaxial electrospinning.

[0014] Step E: Take the composite fiber membrane from step D and subject it to multi-stage heat treatment, including pre-oxidation, carbonization and calcination in a reducing atmosphere, to finally obtain Cu@Cu(N3)2 supported carbon fiber film material.

[0015] In step A, the molecular weight of PVP is 29,000-1,300,000, preferably 1,300,000; the mass ratio of the total solid mass of PAN and PVP to the mass of the mixed solution is 10-20 wt%, preferably 17 wt%, and the mixture is stirred at 800 rpm for 6 h at 40°C.

[0016] In step A, the oil bath temperature is 30–60 °C, the stirring rate is 400–900 rpm, and the duration is 2–10 h.

[0017] In step C, the volume of the PAN / PVP mixed solution is 10-20 mL, the volume of the Cu(NO3)2 solution is 1-5 mL, and the magnetic stirring time is 6-12 h at room temperature. Preferably, the volumes of the PAN / PVP mixed solution and the Cu(NO3)2 solution are 10 mL and 3 mL, respectively, and the stirring time is 10 h.

[0018] In step D, the precursor spinning solution is allowed to stand at 25±2 ℃ for 1–12 h to eliminate bubbles and promote homogenization. The electrospinning conditions are as follows: spinning rate of 0.6–1.0 mL / h, voltage of 15–20 kV, receiving distance of 10–20 cm, ambient temperature of 20–40 ℃, humidity of 30–60%, spinning rate of 0.8 mL / h, voltage of 16.5 kV, temperature of 30 ℃, humidity of 40%, and spinning distance of 15 cm.

[0019] The composite fiber membrane obtained in step D is vacuum dried at 60-80°C for 8-24 hours. Preferably, the film obtained after spinning is dried at 60°C for 12 hours.

[0020] In step E, the multi-stage heat treatment includes: (1) pre-oxidation: heating to 220-250 ℃ at 3 ℃ / min in an air atmosphere and holding for 1-3 h; (2) carbonization: heating to 600-900 ℃ at 3 ℃ / min in an N2 atmosphere and holding for 0.5-2 h; (3) reduction: heating to 300-500 ℃ at 3 ℃ / min in a 5% H2 / 95% Ar mixed atmosphere and holding for 0.5-2 h. Preferably, (1) pre-oxidation: heating to 240 ℃ at 3 ℃ / min in an air atmosphere and holding for 2 h; (2) carbonization: heating to 800 ℃ at 3 ℃ / min in an N2 atmosphere and holding for 1 h; (3) reduction: heating to 400 ℃ at 3 ℃ / min in a 5% H2 / 95% Ar mixed atmosphere and holding for 1 h.

[0021] In step A, when the PVP molecular weight is 29,000, electrospinning is performed for 2-3 hours, followed by multi-stage heat treatment to obtain film fibers with a diameter of 250-450 nm.

[0022] In step A, when the molecular weight of PVP is 1.3 million, electrospinning is performed for 2-3 hours, followed by multi-stage heat treatment to obtain thin film fibers with a diameter of 300-400 nm.

[0023] When the molecular weight of PVP is 29,000, the Cu@Cu(N3)2 / CFs-L film exhibits high performance at 1 mA cm⁻¹. -2 0.5mAh cm -2 The cycle was stable for 650 hours.

[0024] When the molecular weight of PVP is 1.3 million, the Cu@Cu(N3)2 / CFs-H film exhibits high performance at 1 mA cm⁻¹. -2 0.5mAh cm -2 The cycle was stable for 1200 hours.

[0025] The application of Cu@Cu(N3)2 loaded carbon fiber thin film material prepared by the above-described carbon fiber thin film material preparation method in the assembly of aqueous zinc-ion batteries.

[0026] The advantages of this invention are:

[0027] Using copper nitrate as the copper source, polyacrylonitrile polymer was employed to enhance electrospinning spinnability, and polyvinylpyrrolidone of different molecular weights was used to adjust the particle size of the product. Copper was uniformly embedded into nanofibers via uniaxial electrospinning, followed by multi-stage heat treatment to obtain Cu@Cu(N3)2 carbon nanofiber thin film material. The prepared Cu@Cu(N3)2-loaded carbon fiber thin film anode protective layer material exhibits uniform distribution and almost uniform particle size of the inorganic filler loaded in the fibers, demonstrating excellent electrochemical performance. In particular, the introduction of copper-based nanoparticles and a nitrogen-doped carbon framework facilitates zinc deposition. This method, which combines precise control of material morphology through electrospinning with targeted modification of interfacial chemistry through heat treatment, effectively suppresses dendrite growth and reduces hydrogen evolution reaction activity. When applied to the anode of a stable aqueous zinc-ion battery as a protective layer, it effectively inhibits dendrite growth and improves the battery's stable charge-discharge time. This solution addresses the dendrite growth problem and enhances the battery's electrochemical stability, providing a new technological path for the development of high-safety, long-life aqueous zinc-ion batteries. Attached Figure Description

[0028] Figure 1 These are SEM images of the Cu@Cu(N3)2 / CFs thin film materials prepared in Examples 1 and 2 of this invention;

[0029] Figure 2 The images show SEM images of the cross-sections of the Cu@Cu(N3)2 / CFs thin film materials prepared in Examples 1 and 2 of this invention.

[0030] Figure 3 The X-ray diffraction (XRD) spectra of the Cu@Cu(N3)2-loaded carbon fiber thin film materials prepared in Examples 1 and 2 of this invention based on PVP with different molecular weights are shown.

[0031] Figure 4 The images show the Raman spectra of the Cu@Cu(N3)2-loaded carbon fiber thin film materials prepared in Examples 1 and 2 of this invention, which are based on PVP with different molecular weights and controlled by different molecular weights.

[0032] Figure 5 The X-ray photoelectron spectroscopy (XPS) elemental analysis diagrams of Cu@Cu(N3)2 loaded carbon fiber thin film materials prepared in Examples 1 and 2 of this invention based on PVP of different molecular weights.

[0033] Figure 6 These are contact angle test diagrams of the aqueous zinc-ion battery negative electrode modified in Examples 1 and 2 of the present invention;

[0034] Figure 7 The Tafel curves are for the modified aqueous zinc-ion battery anodes of Examples 1 and 2 of this invention.

[0035] Figure 8 The graphs show the rate capability and long-cycle performance of the symmetrical batteries assembled in Embodiments 1 and 2 of this invention.

[0036] Figure 9 The diagram shows the long-cycle performance of the asymmetric batteries assembled in Embodiments 1 and 2 of this invention.

[0037] Figure 10 The diagram shows the long-cycle performance of the negative electrode current collector of the asymmetric battery assembled in Embodiments 1 and 2 of the present invention.

[0038] Figure 11 The cyclic voltammograms (CV), rate performance, and 1 Ag of the full cells assembled in Examples 1 and 2 of this invention are shown. -1 The following is a long-cycle diagram of constant current charge and discharge. Detailed Implementation

[0039] The method for preparing carbon fiber thin film material of the present invention mainly involves constructing a hierarchical porous structure through electrospinning technology, combined with multi-stage heat treatment to achieve Cu 2+ Reduction and nitrogen doping synergistically suppress dendrite growth and reduce hydrogen evolution activity. Experiments show that the molecular weight of PVP has a significant impact on the microstructure and electrochemical performance of the material, providing important guidance for the design of high-performance zinc-ion battery anodes. The preparation method and application of the carbon fiber thin film material of the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0040] Example 1

[0041] The preparation method of Cu@Cu(N3)2 / carbon fiber thin film material based on different molecular weight PVP in this embodiment includes the following steps:

[0042] (1) Accurately weigh 1.6 g of PAN powder and 0.4 g of PVP (Mw = 1300,000) powder and dissolve them in 9.64 g of DMF. Stir at 800 rpm for 6 h at 40 °C to obtain a PAN / PVP mixed solution with a concentration of 17 wt%.

[0043] (2) Accurately weigh 0.18 g Cu(NO3)2·3H2O and dissolve it in 3 mL DMF. Sonicate for 15 min to obtain a Cu(NO3)2 solution with a concentration of 0.25 mmol / mL.

[0044] (3) Take 3 mL of Cu(NO3)2 solution from step 2 and 10 mL of PAN / PVP mixed solution from step 1, mix and stir magnetically for 8 h until the solution is a homogeneous green viscous state, to obtain Cu 2+ Spinning solution of doped PAN / PVP precursor.

[0045] (4) Take Cu after standing for 6 hours in step 3 2+ Doped PAN / PVP precursor spinning solution. Spinning was performed using uniaxial electrospinning technology at a spinning rate of 0.8 mL / h, a voltage of 16.5 kV, a receiving distance of 15 cm, an ambient temperature of 30 ℃, and a humidity of 40%. Composite fiber films were obtained and then vacuum-dried at 60 ℃ for 12 h.

[0046] (5) The dried composite fiber film from step 4 was subjected to multi-stage heat treatment. First, it was heated to 240 °C at 3 °C / min in an air atmosphere and held for 2 h. Then, it was transferred to an N2 atmosphere and heated to 800 °C at 3 °C / min and held for 1 h. Finally, it was heated to 400 °C at 3 °C / min in a 5% H2 / 95% Ar mixed atmosphere and held for 1 h. The final Cu@Cu(N3)2 / CFs-H film was obtained.

[0047] Example 2

[0048] This embodiment provides Cu@Cu(N3)2 / carbon fiber thin film materials based on PVP with different molecular weights. The preparation steps are basically the same as those in Example 1, except that in step 1, PVP with a molecular weight of 29,000 is used.

[0049] The above embodiments were tested for morphology, structure, electrochemical performance, and cycle rate performance when assembled into batteries:

[0050] I. Surface morphology and structural element analysis of Cu@Cu(N3)2 / carbon fiber composite thin film materials with different molecular weight PVP modulation

[0051] like Figure 1-2As shown, the Cu@Cu(N3)2 / CFs-H film in Example 1 exhibits a uniform nanofiber structure with a diameter of 300–400 nm, while the Cu@Cu(N3)2 / CFs-L film in Example 2 exhibits a fiber structure of varying thickness and exhibits adhesion. This is due to the varying viscosity of the spinning solution and splashing during the spinning process. Furthermore, the films are generally of uniform thickness and free of cracks, being homogeneous and dense, with a thickness of 115–125 μm.

[0052] Figure 3 The X-ray diffraction (XRD) patterns of the Cu@Cu(N3)2-loaded carbon fiber composite thin film materials prepared show that the samples of Examples 1 and 2 both have characteristic diffraction peaks at 11.74° corresponding to the (110) crystal plane of Cu(N3)2 (PDF#76-1669), and a broad peak at 23.24° belonging to the amorphous characteristic diffraction peak of carbon fiber. In addition, the sample of Example 1 has diffraction peaks at 43.29°, 50.43° and 74.13° that correspond one-to-one with the (111), (200) and (220) crystal planes of Cu elemental (PDF#04-0836).

[0053] Figure 4 The Raman spectra of the Cu@Cu(N3)2-supported carbon fiber thin film materials are shown. Samples from Examples 1 and 2 both have a Raman value at 1362.38 cm⁻¹. -1 and 1576.63 cm -1 There are two peaks, which belong to the typical D-band defect or disordered structure and the G-band ordered graphitized structure of carbon-based materials, respectively. Among them, Sample I of Example 1... D / I G = 1.1760 indicates that the carbon-based material has a high-defect structure and a low degree of graphitization. Compared with Example 1, as the molecular weight of PVP decreases, the intensity of the characteristic peaks of the D and G bands in the Raman spectrum of the Example 2 sample weakens, and I D / I G = 0.7616 indicates that the reduction in the molecular weight of PVP results in a high degree of graphitization in this carbon-based material, giving it good electrical conductivity.

[0054] Figure 5 Energy dispersive spectroscopy (EDS) elemental analysis showed that Cu, N, C, and O were present in both Samples 1 and 2. Specifically, the copper atom content in Sample 1 was 1.32%, and in Sample 2 it was 0.91%. For Samples 1 and 2, besides Cu... 0 In addition to the characteristic peaks of Cu, two peaks corresponding to Cu appear at 934.16 and 954.57 eV in the Cu 2p XPS spectrum. 2+ The characteristic peaks, and two peaks corresponding to Cu appearing at 931.72 and 948.51 eV.+ Characteristic peaks. Further analysis of N 1s revealed higher pyridine nitrogen content in Example 1 and higher graphitic nitrogen content in Example 2, consistent with Raman spectral analysis.

[0055] II. Corrosion Resistance Testing of Cu@Cu(N3)2 / Carbon Fiber Composite Thin Films with Different Molecular Weight PVP Regulated to Aqueous Zinc-Ion Battery Anodes

[0056] like Figure 6 As shown, the zinc anode modified with Cu@Cu(N3)2 / carbon fiber composite film material regulated by high molecular weight PVP has a hydrophobic angle greater than 125 degrees, while the zinc anode modified with Cu@Cu(N3)2 / carbon fiber composite film material regulated by low molecular weight PVP has slightly lower hydrophobicity.

[0057] like Figure 7 As shown, a three-electrode method was used with silver chloride as the reference electrode and 2 M ZnSO4 solution as the electrolyte for Tafel curve testing. The calculated corrosion potentials of the two were approximately the same, but the corrosion current density of Cu@Cu(N3)2 / CFs-H@Zn was significantly lower than that of Cu@Cu(N3)2 / CFs-L@Zn. The results indicate that the zinc anode modified with the high molecular weight PVP-controlled Cu@Cu(N3)2 / carbon fiber composite film prepared in Example 1 has stronger corrosion resistance.

[0058] III. Assembly of Symmetrical Cells and Their Performance Research

[0059] like Figure 8 As shown, for the two symmetrical cells at 0.5 mA cm⁻¹ -2 Up to 10 mA cm -2 The fixed surface capacity was 1mAh cm -2 Rate performance testing was conducted. Calculations revealed that the exchange current density (i0) of Cu@Cu(N3)2 / CFs-H@Zn reached 6.34 mA cm⁻², higher than that of Cu@Cu(N3)2 / CFs-L@Zn (5.14 mA cm⁻²). Simultaneously, the Cu@Cu(N3)2 / CFs-H@Zn||Cu@Cu(N3)2 / CFs-H@Zn symmetric cell achieved a rate performance of 1 mA cm⁻². -2 and 0.5 mAh cm -2 The cell exhibited a long cycle life of 1200 h with no significant voltage fluctuations. In contrast, the Cu@Cu(N3)2 / CFs-L@Zn||Cu@Cu(N3)2 / CFs-L@Zn symmetric cell suddenly short-circuited after 650 h of cycling, and the corresponding plating peeling overpotential showed a large voltage fluctuation, indicating that disordered dendrite growth caused irreversible damage. The areal capacity was subsequently increased to 1 mAh cm⁻¹. -2Subsequent constant current charge-discharge long-cycle tests revealed that the Cu@Cu(N3)2 / CFs-H@Zn||Cu@Cu(N3)2 / CFs-H@Zn symmetric cell exhibited good performance at 1 mA cm⁻¹. -2 and 1 mAh cm -2 The Cu@Cu(N3)2 / CFs-L@Zn||Cu@Cu(N3)2 / CFs-L@Zn symmetric cells exhibited a long cycle life of ~850 h, but suddenly experienced a short circuit after ~400 h of cycling. These results verify that the Cu@Cu(N3)2 / CFs-H protective layer at the interface can establish a uniform electric field, avoid the formation of unfavorable nucleation factors, and thus extend the cycle life of the cells.

[0060] IV. Assembly of Asymmetric Cells and Their Performance Research

[0061] like Figure 9 As shown, in Example 1, the Cu@Cu(N3)2 / CFs-H thin film material was tested at 5 mA cm⁻¹. -2 The deposition overpotential and cycle number of the asymmetric cell under current conditions are superior to those of Cu@Cu(N3)2 / CFs-L thin film material, while Cu@Cu(N3)2 / CFs-H thin film material has a better effect on improving cycle performance, as shown in Table 1.

[0062] Example Example 1 Example 2 PVP molecular weight 1300,000 29,000 Asymmetric cell overpotential (mV) 35 55.8 Stable cycle count of half-cell 3200 1250

[0063] like Figure 10 As shown, this invention also provides the application of the above two thin film materials as negative electrode current collectors in aqueous zinc-ion batteries. The prepared aqueous zinc-ion battery negative electrode current collector is used as the negative electrode current collector in a zinc-ion battery, and the battery is assembled into an aqueous zinc-ion battery. Example 1: Cu@Cu(N3)2 / CFs-H thin film material negative electrode current collector at 1 mA cm⁻¹ -2 and 1 mAh cm -2 Under these conditions, the stable cycle time of the asymmetric battery is ~500 h, which is superior to that of the Cu@Cu(N3)2 / CFs-L thin film material anode current collector (~240 h). This indicates that the Cu@Cu(N3)2 / CFs-H thin film material can induce uniform zinc deposition during zinc deposition, improve charge-discharge efficiency, enhance cycle performance, and extend battery cycle life.

[0064] V. Assembly of Full Cells and Performance Research

[0065] Using α-MnO2 as the positive electrode of the full cell, and the zinc anode of the aqueous zinc-ion battery modified with the thin film material prepared in Examples 1 and 2 as the negative electrode, a glass fiber separator and 2 M ZnSO4 + 0.2 M MnSO4 as the electrolyte were used to assemble the full cell.

[0066] Figure 11 The displayed CV curves show two pairs of redox peaks, representing typical Zn. 2+ Intercalation and deintercalation processes in MnO2. (0.1–5 A g) -1 In terms of rate performance at various current densities, the Cu@Cu(N3)2 / CFs-H||MnO2 battery exhibits higher capacity values ​​than the Cu@Cu(N3)2 / CFs-L||MnO2 battery at all current density values, indicating that Zn 2+ Rapid diffusion occurs on the surface of the Cu@Cu(N3)2 / CFs-H layer. And when the current returns to 0.5 A g... -1 At that time, the zinc anode full cell modified with Cu@Cu(N3)2 / CFs-H thin film showed a capacity of 229.3 mAh g⁻¹. -1 Its high specific capacity demonstrates excellent cycle reversibility and rate performance. Furthermore, 1 A g... -1 Constant current charge-discharge tests showed that the Cu@Cu(N3)2 / CFs-H||MnO2 battery maintained a specific capacity of 132.1 mAh g⁻¹ after 2000 cycles. -1 The Cu@Cu(N3)2 / CFs-L||MnO2 battery only reaches a capacity of 106.4 mAh g after 1000 cycles. -1 The degradation begins, and it fails after 1500 cycles. This is because the modification of the Cu@Cu(N3)2 / CFs-H film effectively blocks the contact between zinc metal and electrolyte in the battery, reduces the occurrence of interfacial side reactions, and ensures that the ion transport channels are not affected during cycling. Furthermore, the presence of the coating does not affect the insertion / extraction behavior of ions.

[0067] The present invention discloses a method for preparing carbon fiber thin film materials. This method utilizes electrospinning technology combined with multi-stage heat treatment to prepare Cu@Cu(N3)2-loaded carbon fiber thin films. The molecular weight of PVP (29,000-1,300,000) is used as a key parameter to control the rheological properties of the precursor solution and the final material's microstructure. Experiments show that when the PVP molecular weight is 1.3 million, the resulting Cu@Cu(N3)2 / CFs-H film possesses a uniform fiber morphology and a high-defect structure, and achieves a cycle life of 1200 hours under conditions of 1 mA cm⁻² and 0.5 mAh cm⁻², significantly superior to the low molecular weight PVP sample film (650 hours). This material can effectively suppress zinc dendrite growth and hydrogen evolution reaction, improving battery stability and providing a new strategy for the design of anodes in aqueous zinc-ion batteries.

[0068] Of course, the above description is not intended to limit the present invention, and the present invention is not limited to the examples given above. Any changes, modifications, additions or substitutions made by those skilled in the art within the scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A method for preparing a carbon fiber thin film material, characterized in that, Includes the following steps: A. Preparation of PAN / PVP mixed solution Polyacrylonitrile and polyvinylpyrrolidone of different molecular weights were mixed in a mass ratio of 2:1 to 5:1, dispersed in N,N-dimethylformamide, and stirred in an oil bath to obtain a clear and transparent mixed solution. B. Preparation of Cu(NO3)2 solution Cu(NO3)2·3H2O was dissolved in N,N-dimethylformamide and subjected to ultrasonic treatment to obtain a green transparent solution with a concentration of 0.1–0.6 mmol / mL. Step C: Preparation of precursor spinning solution The Cu(N03)2solution in step B was slowly added dropwise into the PAN / PVP mixed solution in step A at room temperature, and mixed stirring was carried out at room temperature until the solution was uniformly green and viscous, to obtain Cu 2+ doped PAN / PVP precursor spinning solution; Step D: Uniaxial electrospinning Take the Cu after step C standing 2+ The doped PAN / PVP precursor solution is spun into a composite fiber membrane by a single-axis electrospinning method. Step E: Take the composite fiber membrane from step D and subject it to multi-stage heat treatment, including pre-oxidation, carbonization and calcination in a reducing atmosphere, to finally obtain Cu@Cu(N3)2 supported carbon fiber film material.

2. The method for preparing carbon fiber thin film material according to claim 1, characterized in that: In step A, the molecular weight of PVP is 29,000-1,300,000, and the mass ratio of the total solid mass of PAN and PVP to the mass of the mixed solution is 10-20 wt%.

3. The method for preparing carbon fiber thin film material according to claim 1 or 2, characterized in that: In step A, the oil bath temperature is 30–60°C, the stirring rate is 400–900 rpm, and the duration is 2–10 h.

4. The method for preparing carbon fiber thin film material according to claim 3, characterized in that: In step C, the volume of the PAN / PVP mixed solution is 10–20 mL, the volume of the Cu(NO3)2 solution is 1–5 mL, and the magnetic stirring time is 6–12 h at room temperature.

5. The method for preparing carbon fiber thin film material according to claim 1, 2 or 4, characterized in that: In step D, the precursor spinning solution is allowed to stand at 25±2 ℃ for 1 to 12 h to eliminate bubbles and promote homogenization. The electrospinning conditions are: spinning rate of 0.6 to 1.0 mL / h, voltage of 15 to 20 kV, receiving distance of 10 to 20 cm, ambient temperature of 20 to 40 ℃, and humidity of 30 to 60%.

6. The method for preparing carbon fiber thin film material according to claim 5, characterized in that: The composite fiber membrane obtained in step D is vacuum dried at 60–80°C for 8–24 hours.

7. The method for preparing carbon fiber thin film material according to claim 1, 2, 4 or 6, characterized in that: In step E, the multi-stage heat treatment includes: (1) pre-oxidation: heating to 220-250 ℃ at 3 ℃ / min in an air atmosphere and holding for 1-3 h; (2) carbonization: heating to 600-900 ℃ at 3 ℃ / min in a N2 atmosphere and holding for 0.5-2 h; (3) reduction: heating to 300-500 ℃ at 3 ℃ / min in a 5%H2 / 95%Ar mixed atmosphere and holding for 0.5-2 h.

8. The method for preparing carbon fiber thin film material according to claim 7, characterized in that: In step A, when the PVP molecular weight is 29,000, electrospinning is performed for 2-3 hours, followed by multi-stage heat treatment to obtain film fibers with a diameter of 250-450 nm.

9. The method for preparing carbon fiber thin film material according to claim 7, characterized in that: In step A, when the molecular weight of PVP is 1.3 million, electrospinning is performed for 2-3 hours, followed by multi-stage heat treatment to obtain thin film fibers with a diameter of 300-400 nm.

10. The method for preparing carbon fiber thin film material according to claim 8, characterized in that: Cu@Cu(N3)2 / CFs-L film with PVP of 29,000 Da has a cycle life of 650 h at 1 mA cm -2 , 0.5 mAh cm -2 .

11. The method for preparing carbon fiber thin film material according to claim 9, characterized in that: When the molecular weight of PVP is 1.3 million, the Cu@Cu(N3)2 / CFs-H film exhibits high performance at 1 mA cm⁻¹. -2 0.5mAh cm -2 The cycle was stable for 1200 hours.

12. The application of Cu@Cu(N3)2-loaded carbon fiber thin film material prepared by the method described in claims 1-11 in the assembly of aqueous zinc-ion batteries.

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