Preparation method and application of a nickel-iron sulfide multi-channel carbon nanofiber composite material

Abstract

The application relates to the technical field of sodium ion battery electrode materials, and discloses a preparation method of a nickel-iron sulfide multi-channel carbon nanofiber composite material and application thereof, the preparation method comprising the following steps: (1) mixing and stirring a potassium ferrocyanide aqueous solution and a nickel salt solution containing a complex stabilizer, standing at room temperature for a period of time, centrifuging, washing and drying to obtain nickel-iron Prussian blue; (2) dissolving the nickel-iron Prussian blue and two immiscible polymers in N,N-dimethylformamide to form a spinning solution, and performing electrostatic spinning, pre-oxidation, carbonization and sulfidation treatment to obtain the nickel-iron sulfide multi-channel carbon nanofiber composite material. The nickel-iron Prussian blue is used as a precursor to derive a nanoscale bimetal sulfide, and the multi-channel carbon nanofiber is prepared through an electrostatic spinning technology, so that the volume effect existing in the nickel-iron sulfide in the charging and discharging process is effectively relieved, the conductivity is improved, and the nickel-iron sulfide has good electrochemical performance.

Description

Technical Field

[0001] This invention belongs to the technical field of sodium-ion battery electrode materials, and more specifically relates to a method for preparing a nickel-iron sulfide multichannel carbon nanofiber composite material and its application. Background Technology

[0002] Global economic development, while boosting energy demand, has also exacerbated environmental pollution. To find a balance between economic development and environmental protection, the development of green, efficient, and clean energy sources is urgently needed. Currently, lithium-ion batteries are widely used in commercial applications, but due to limited lithium resources and high costs, they are unlikely to meet the urgent needs of future energy storage. Sodium-ion batteries, with their lower cost, abundant raw material reserves, and similar working principle to lithium-ion batteries, are considered a promising alternative.

[0003] Transition metal sulfides are a typical class of conversion electrode materials with excellent sodium storage performance. However, transition metal sulfides still face some challenges in practical applications, such as poor conductivity, large volume changes, and slow ion migration kinetics. Designing heterojunctions by coupling two different metal sulfide components can provide abundant active sites, accelerate transport, and enhance reaction kinetics, thereby improving electrochemical performance. Furthermore, introducing highly conductive buffer matrices is also considered a useful approach; for example, introducing carbon materials can effectively suppress the dissolution of polysulfides and prevent self-aggregation, thus improving the material's cycle life. Currently, reduced graphene oxide and carbon nanotube composites have been widely used in sodium-ion battery anode materials; however, while this composite approach brings excellent electrochemical performance, it also faces high costs, hindering its further application and development. Summary of the Invention

[0004] The main objective of this invention is to address the aforementioned problems by providing a method for preparing nickel-iron sulfide / multichannel carbon nanofibers and their applications. The preparation method involved in this invention is simple, uses abundant raw materials, and is low-cost. A sugar cube-shaped nickel-iron Prussian blue is obtained using a solution co-precipitation method, which can be prepared in large quantities. In-situ carbon composite formation is achieved through electrospinning technology, which can mitigate the volume change of Prussian blue-derived metal sulfides during charge-discharge processes and improve conductivity. Furthermore, the presence of porous channels increases the contact area between the electrode material and the electrolyte, accelerating sodium ion diffusion and transfer. This composite material exhibits excellent electrochemical performance as a negative electrode material for sodium-ion batteries.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solution: a method for preparing a nickel-iron sulfide multichannel carbon nanofiber composite material, comprising the following steps:

[0006] (1) After mixing and stirring the potassium ferricyanide aqueous solution with the nickel salt solution containing the complexing stabilizer, let it stand at room temperature for a period of time, and then centrifuge, wash and dry to obtain nickel-iron Prussian blue.

[0007] (2) Nickel-iron Prussian blue and two immiscible polymers were dissolved in N,N-dimethylformamide to form a spinning solution. After electrospinning, pre-oxidation, carbonization and sulfidation treatment, nickel-iron sulfide multichannel carbon nanofiber composite material was obtained.

[0008] The main reactions occurring in the above steps are as follows: First, metal ions react with ferricyanide under the action of a complexing stabilizer to generate a nickel-iron Prussian blue precursor. The nickel-iron Prussian blue is then mixed with a polymer to prepare a spinning solution, and an organic fiber film is obtained through electrospinning. Since polyacrylonitrile (PAI) is immiscible with polystyrene or polymethyl methacrylate (PMMA), with PAI's solubility parameter being approximately three times that of PAI, each PAI fiber is embedded within a PAI fiber. Because the degradation temperature of polystyrene is 280℃ and that of PMMA is 270℃, after high-temperature carbonization, PAI decomposes into carbon, and polystyrene or PMMA decomposes to form nanochannels. Furthermore, the nickel-iron derivative sulfide has a high theoretical specific capacity, and both have similar crystal structures and lattice constants, easily forming heterostructures. Finally, a gas-phase vulcanization treatment is performed to obtain a nickel-iron sulfide / multi-channel carbon nanofiber composite material.

[0009] Preferably, in step (1), the complexing stabilizer is polyvinylpyrrolidone or trisodium citrate dihydrate, and its mass ratio with potassium ferricyanide is (1-5):1.

[0010] Preferably, in step (1), the concentration of the potassium ferricyanide aqueous solution is 0.02–0.06 mol·L⁻¹. -1 The nickel salt solution is an aqueous solution of nickel acetate, nickel chloride, nickel sulfate, or nickel nitrate, with a concentration of 0.03–0.09 mol·L⁻¹. -1 .

[0011] Preferably, in step (1), the settling time is 18 to 48 hours;

[0012] Preferably, in step (2), the two immiscible polymers are polyacrylonitrile and polymethyl methacrylate, or polyacrylonitrile and polystyrene.

[0013] Preferably, in step (2), the mass percentage of Prussian blue in the spinning solution is 3-8%, more preferably 4-7%; the total mass percentage of the polymer is 7-15%, wherein the mass ratio of polyacrylonitrile to polymethyl methacrylate or polystyrene is 10:(1-5).

[0014] The less polystyrene or polymethyl methacrylate in a polymer, the fewer the pores. When no polystyrene or polymethyl methacrylate is added, the resulting fiber is solid and has no pores.

[0015] Preferably, in step (2), the electrospinning process involves a spinning voltage of 10–18 kV and a feed rate of 0.4–1.2 mL·h. -1 .

[0016] Preferably, in step (2), the pre-oxidation temperature is 200–300°C, more preferably 260–300°C, and the holding time is 1–3 hours; the carbonization is carried out in nitrogen or argon gas at a temperature of 2–5°C / min. -1 The temperature is increased to 600-900℃ at a heating rate, and the holding time is 1-3 hours.

[0017] Pre-oxidation can promote the degradation of polystyrene or polymethyl methacrylate to form a multichannel structure.

[0018] Preferably, in step (2), the sulfidation is performed by placing the carbonization product and the sulfur source in a ceramic boat at a mass ratio of 1:(3-5), and then in a nitrogen or argon atmosphere at a temperature of 2-5°C·min. -1 The temperature is increased to 400-700℃ at a heating rate and held for 1-3 hours; the sulfur source is sulfur powder, thiourea or thioacetamide.

[0019] This invention also provides an application of the nickel-iron sulfide multichannel carbon nanofiber composite material obtained by the above preparation method as a negative electrode material for sodium-ion batteries.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] (1) The present invention prepared a nickel-iron Prussian blue precursor with uniform particles by solution coprecipitation method. The preparation method is simple, the reaction conditions are mild, and the morphology and size are controllable.

[0022] (2) The present invention uses nickel-iron Prussian blue as a precursor to derive nanoscale bimetallic sulfides. The heterogeneous interface between the two phase components can accelerate ion diffusion kinetics, reduce ion diffusion barrier, and significantly improve electrochemical performance.

[0023] (3) The present invention prepares multi-channel carbon nanofibers by electrospinning technology. The presence of carbon fibers can improve the conductivity of electrode materials. The multi-channel structure not only shortens the ion diffusion distance and increases the contact area with the electrolyte, but also suppresses the volume effect of the electrode active material and effectively improves the cycle stability of the electrode material.

[0024] (4) This invention organically combines multiple methods to alleviate the volume effect of nickel-iron sulfide during charging and discharging and improve its conductivity, so that the composite material has good electrochemical performance as a negative electrode material for sodium-ion batteries. Attached Figure Description

[0025] Figure 1 The X-ray diffraction pattern of the nickel-iron sulfide / multichannel carbon nanofiber composite material prepared in Example 1;

[0026] Figure 2 This is a scanning electron microscope image of the nickel-iron Prussian blue prepared in Example 2;

[0027] Figure 3 This is a scanning electron microscope image of the nickel-iron sulfide / multichannel carbon nanofiber composite material prepared in Example 1;

[0028] Figure 4 The image shows a scanning electron microscope (SEM) image of the nickel-iron sulfide / carbon nanofiber composite material prepared in Comparative Example 1.

[0029] Figure 5 The graph shows the cycling performance of the nickel-iron sulfide / multichannel carbon nanofiber composite material prepared in Example 1.

[0030] Figure 6 This is a rate performance diagram of the nickel-iron sulfide / multichannel carbon nanofiber composite material prepared in Example 3. Detailed Implementation

[0031] The present invention will be further described in detail below with reference to the embodiments, and the technical content and effects thereof are not limited thereto.

[0032] Example 1

[0033] (1) Weigh 0.43g of nickel chloride hexahydrate and 0.99g of trisodium citrate dihydrate and dissolve them in 30mL of water (solution A), and dissolve 0.39g of potassium ferricyanide in 30mL of water (solution B). Pour solution B into solution A and stir for 10min. Let it stand at room temperature for 24h. After centrifugation, washing and vacuum drying at 60℃, a yellow solid powder, namely nickel-iron Prussian blue (Ni-Fe PBA), is obtained.

[0034] (2) Weigh 0.3g Ni-Fe PBA and add 4.5g N,N-dimethylformamide (DMF), disperse evenly by ultrasonication, then add 0.45g polyacrylonitrile (PAN) and 0.15g polystyrene (PS) and stir vigorously to obtain spinning solution.

[0035] (3) Pour the obtained spinning solution into a 5 mL syringe, set the spinning voltage to 14 kV, and the feed rate for electrospinning to 0.7 mL·h. -1Ni-Fe PBA / PAN / PS composite nanofiber films were obtained by spinning.

[0036] (4) The obtained fiber film was first pre-oxidized in air at 260°C for 1 hour, and then in nitrogen atmosphere at 2°C·min. -1 The temperature was increased to 600℃ and held for 2 hours to obtain a black film.

[0037] (5) The obtained black film and sulfur powder were mixed at a mass ratio of 1:4 and heated in a nitrogen atmosphere at 2℃·min. -1 The temperature was increased to 500℃ and held for 2 hours to obtain a nickel-iron sulfide / carbon nanofiber composite material with hollow multi-channel structure.

[0038] Example 2

[0039] (1) Weigh 0.28g of nickel acetate tetrahydrate and 0.5g of polyvinylpyrrolidone and dissolve them in 30mL of water (solution A), and dissolve 0.13g of potassium ferricyanide in 30mL of water (solution B). Pour solution B into solution A and stir for 10min. Let it stand at room temperature for 24h. After centrifugation, washing and vacuum drying at 60℃, a yellow solid powder, namely Ni-Fe PBA, is obtained.

[0040] (2) Weigh 0.3g Ni-Fe PBA and add 3g DMF, disperse evenly by ultrasonication, then add 0.3g PAN and 0.1g PS and stir vigorously to obtain spinning solution.

[0041] (3) Pour the obtained spinning solution into a 5 mL syringe, set the spinning voltage to 12 kV, and the feed rate for electrospinning to 0.8 mL·h. -1 Ni-Fe PBA / PAN / PS composite nanofiber films were obtained by spinning.

[0042] (4) The obtained fiber film was first pre-oxidized in air at 280°C for 1 hour, and then in nitrogen atmosphere at 3°C·min. -1 The temperature was increased to 700℃ and held for 2 hours to obtain a black film.

[0043] (5) The obtained black film was mixed with thioacetamide at a mass ratio of 1:4 and heated in a nitrogen atmosphere at 5 °C·min. -1 The temperature was increased to 700℃ and held for 2 hours to obtain a nickel-iron sulfide / carbon nanofiber composite material with hollow multi-channel structure.

[0044] Example 3

[0045] (1) Weigh 0.28g of nickel chloride hexahydrate and 0.53g of trisodium citrate dihydrate and dissolve them in 20mL of water (solution A), and dissolve 0.26g of potassium ferricyanide in 20mL of water (solution B). Pour solution B into solution A and stir for 10min. After standing at room temperature for 20h, centrifuge, wash and dry under vacuum at 60℃ to obtain a yellow solid powder, namely Ni-Fe PBA.

[0046] (2) Weigh 0.2g Ni-Fe PBA and add 6g DMF, disperse evenly by ultrasonication, then add 0.6g PAN and 0.2g polymethyl methacrylate (PMMA) and stir vigorously to obtain spinning solution.

[0047] (3) Pour the obtained spinning solution into a 5 mL syringe, set the spinning voltage to 10 kV, and the feed rate for electrospinning to 0.4 mL·h. -1 Ni-Fe PBA / PAN / PMMA composite nanofiber films were obtained by spinning.

[0048] (4) The obtained fiber film was first pre-oxidized in air at 200°C for 3 hours, and then in argon atmosphere at 5°C·min. -1 The temperature was increased to 800℃ and held for 2 hours to obtain a black film.

[0049] (5) The obtained black film was mixed with thiourea at a mass ratio of 1:4 in a nitrogen atmosphere at 2℃·min. -1 The temperature was increased to 500℃ and held for 2 hours to obtain a nickel-iron sulfide / carbon nanofiber composite material with hollow multi-channel structure.

[0050] Example 4

[0051] (1) Weigh 0.53g of nickel nitrate hexahydrate and 0.99g of trisodium citrate dihydrate and dissolve them in 30mL of water (solution A), and dissolve 0.39g of potassium ferricyanide in 30mL of water (solution B). Pour solution B into solution A and stir for 10min. After standing at room temperature for 48h, centrifuge, wash and vacuum dry at 60℃ to obtain yellow solid powder, namely Ni-Fe PBA.

[0052] (2) Weigh 0.2g Ni-Fe PBA and add 4g DMF, disperse evenly by ultrasonication, then add 0.4g PAN and 0.1g PMMA and stir vigorously to obtain spinning solution.

[0053] (3) Pour the obtained spinning solution into a 5 mL syringe, set the spinning voltage to 16 kV, and the feed rate for electrospinning to 1.0 mL·h. -1 Ni-Fe PBA / PAN / PMMA composite nanofiber films were obtained by spinning.

[0054] (4) The obtained fiber film was first pre-oxidized in air at 280°C for 1 hour, and then in nitrogen atmosphere at 5°C·min. -1 The temperature was increased to 600℃ and held for 2 hours to obtain a black film.

[0055] (5) The obtained black film was mixed with thiourea at a mass ratio of 1:4 in a nitrogen atmosphere at 2℃·min. -1 The temperature was increased to 500℃ and held for 2 hours to obtain a nickel-iron sulfide / carbon nanofiber composite material with hollow multi-channel structure.

[0056] Example 5

[0057] (1) Weigh 0.45g of nickel acetate tetrahydrate and 1.0g of trisodium citrate dihydrate and dissolve them in 30mL of water (solution A). Weigh 0.3g of potassium ferricyanide and dissolve it in 30mL of water (solution B). Pour solution B into solution A and stir for 10min. After standing at room temperature for 36h, centrifuge, wash and dry under vacuum at 60℃ to obtain a yellow solid powder, namely Ni-Fe PBA.

[0058] (2) Weigh 0.3g Ni-Fe PBA and add 3g DMF, disperse evenly by ultrasonication, then add 0.3g PAN and 0.1g PS and stir vigorously to obtain spinning solution.

[0059] (3) Pour the obtained spinning solution into a 5 mL syringe, set the spinning voltage to 18 kV, and the feed rate for electrospinning to 1.2 mL·h. -1 Ni-Fe PBA / PAN / PS composite nanofiber films were obtained by spinning.

[0060] (4) The obtained fiber film was first pre-oxidized in air at 220°C for 2 hours, and then in nitrogen atmosphere at 5°C·min. -1 The temperature was increased to 800℃ and held for 2 hours to obtain a black film.

[0061] (5) The obtained black film and sulfur powder were mixed at a mass ratio of 1:4 and heated in an argon atmosphere at 2℃·min. -1 The temperature was increased to 400℃ and held for 2 hours to obtain a nickel-iron sulfide / carbon nanofiber composite material with hollow multi-channel structure.

[0062] Comparative Example 1 (Compared to Example 1: only polyacrylonitrile was added to the polymer)

[0063] (1) Weigh 0.43g of nickel chloride hexahydrate and 0.99g of trisodium citrate dihydrate and dissolve them in 30mL of water (solution A), and dissolve 0.39g of potassium ferricyanide in 30mL of water (solution B). Pour solution B into solution A and stir for 10min. Let it stand at room temperature for 24h. After centrifugation, washing and vacuum drying at 60℃, a yellow solid powder, namely Ni-Fe PBA, is obtained.

[0064] (2) Weigh 0.3g Ni-Fe PBA and add 4.5g N,N-dimethylformamide (DMF), disperse evenly by ultrasonication, and then add 0.45g PAN and stir vigorously to obtain spinning solution.

[0065] (3) Pour the obtained spinning solution into a 5 mL syringe, set the spinning voltage to 14 kV, and the feed rate for electrospinning to 0.7 mL·h. -1 Ni-Fe PBA / PAN composite nanofiber films were obtained by spinning.

[0066] (4) The obtained fiber film was first pre-oxidized in air at 260°C for 2 hours, and then in nitrogen atmosphere at 2°C·min. -1 The temperature was increased to 600℃ and held for 2 hours to obtain a black film.

[0067] (5) The obtained black film and sulfur powder were mixed at a mass ratio of 1:4 and heated in a nitrogen atmosphere at 2℃·min. -1 The temperature was increased to 500℃ and held for 2 hours to obtain a nickel-iron sulfide / carbon nanofiber composite material.

[0068] Comparative Example 2 (Nickel-Iron Sulfide Powder)

[0069] (1) Weigh 0.28g of nickel chloride hexahydrate and 0.53g of trisodium citrate dihydrate and dissolve them in 30mL of water (solution A), and dissolve 0.26g of potassium ferricyanide in 30mL of water (solution B). Pour solution B into solution A and stir for 10min. After standing at room temperature for 24h, centrifuge, wash and vacuum dry at 60℃ to obtain yellow solid powder, namely Ni-Fe PBA.

[0070] (2) Take an appropriate amount of Ni-Fe PBA and place it in a tube furnace filled with nitrogen atmosphere at 2℃·min -1 The temperature was increased to 600℃ and held for 2 hours to obtain a black powder.

[0071] (3) The black powder obtained in (2) is mixed with sulfur powder at a mass ratio of 1:4, and then heated in a nitrogen atmosphere at 2℃·min. -1 The temperature was increased to 500℃ and held for 2 hours to obtain nickel-iron sulfide powder.

[0072] The final products obtained in Examples 1-5 and Comparative Examples 1-2 were mixed with conductive agent Super P, binder polyvinylidene fluoride in a mass ratio of 7:2:1 and solvent N-methylpyrrolidone to form a homogeneous slurry. This slurry was coated onto a copper current collector and dried. After drying, it was cut into discs with a diameter of 12 mm to serve as the negative electrode, with metallic sodium as the counter electrode. 1M sodium hexafluorophosphate (NaPF6) dissolved in diethylene glycol dimethyl ether was used as the electrolyte, and glass fiber was used as the separator. The CR2025 button cell was assembled in a glove box filled with argon atmosphere and with water and oxygen values ​​of less than 0.01 ppm. After being left to stand for 24 hours, a constant current charge-discharge test was performed in the range of 0.01-3V using a Newway tester.

[0073] Figure 1 The image shows the XRD pattern of the nickel-iron sulfide / multichannel carbon nanofibers prepared in Example 1. Figure 1 It can be seen that the nickel-iron sulfide / multichannel carbon nanofibers prepared in Example 1 exhibit characteristic peaks of cubic NiS2 (JCPDS 80-0375) and pyrite FeS2 (JCPDS 71-0053), and the broad diffraction peaks that appear around 24.3° belong to amorphous carbon. Figure 2 The image shows a SEM image of the Ni-Fe PBA prepared in Example 2. It can be seen that it has a regular cubic structure with an average side length of about 100 nm. Figure 3 The image shows a SEM image of the nickel-iron sulfide / multichannel carbon nanofibers prepared in Example 1. The fibers are interwoven into a network structure with a relatively rough surface and a hollow multichannel structure inside, with a pore size of about 50 nm. Figure 4 The image shows a SEM image of the nickel-iron sulfide / carbon nanofibers prepared in Comparative Example 1. Compared with Example 1, no pores were observed inside the fibers, indicating a solid structure. Figure 5 The circuit performance graph for Example 1 shows that the sodium-ion battery operates at 1Ag... -1 After cycling 200 times at a current density, the specific capacity remained at 450 mAh g. -1 The capacity retention rate is 100%, indicating that the composite material has excellent cycle stability. Figure 6 The rate performance diagram for Example 3 is shown at 0.2 Ag. -1 0.5Ag -1 1Ag -1 2Ag -1 5Ag -1 And restore 0.2A g -1 The specific capacity at the given current density is 468.8 mAh g. -1 398.6mAh g -1 370.1mAh g -1 343.9mA hg -1270.8mAhg -1 and 420.5mAh g -1 It exhibits excellent rate performance.

[0074] The products obtained in Examples 1-5 and Comparative Examples 1-2 were used as anode materials in sodium-ion batteries and assembled into sodium-ion batteries. The performance at 1 A·g -1 The initial specific capacity at the given current density and the capacity retention after 200 cycles are shown in Table 1.

[0075] Table 1

[0076]

[0077]

[0078] As shown in Table 1, and in conjunction with Examples 1-5 and Comparative Examples 1-2, it can be seen that the sodium storage capacity of the composite material is improved after using electrospinning technology to composite multichannel carbon fibers. However, when preparing the spinning solution, excessive or insufficient addition of nickel-iron Prussian blue will affect its capacity retention rate, especially high-content PBA will exhibit partial agglomeration, leading to a decrease in capacity retention. If polystyrene or polymethyl methacrylate is not added when preparing the spinning solution, the lack of a multichannel structure will limit ion transport, thus affecting the capacity improvement.

[0079] The above embodiments of the present invention are merely illustrative examples and are not intended to limit the implementation of the invention. Those skilled in the art can make other variations and modifications based on the above description. It is impossible to exhaustively list all possible implementations here. All obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A method for preparing a nickel-iron sulfide multichannel carbon nanofiber composite material, characterized in that, The steps include the following: (1) After mixing and stirring the potassium ferricyanide aqueous solution with the nickel salt solution containing the complexing stabilizer, let it stand at room temperature for a period of time, and then centrifuge, wash and dry to obtain nickel-iron Prussian blue; (2) Nickel-iron Prussian blue and two immiscible polymers are dissolved in N,N-dimethylformamide to form a spinning solution. After electrospinning, pre-oxidation, carbonization and sulfidation treatment, nickel-iron sulfide multichannel carbon nanofiber composite material is obtained; the two immiscible polymers are polyacrylonitrile and polymethyl methacrylate, or polyacrylonitrile and polystyrene.

2. The preparation method of the nickel-iron sulfide multichannel carbon nanofiber composite material as described in claim 1, characterized in that, In step (1), the complexing stabilizer is polyvinylpyrrolidone or trisodium citrate dihydrate, and its mass ratio with potassium ferricyanide is (1~5):

1.

3. The preparation method of the nickel-iron sulfide multichannel carbon nanofiber composite material as described in claim 1, characterized in that, In step (1), the concentration of the potassium ferricyanide aqueous solution is 0.02~0.06 mol·L⁻¹. -1 The nickel salt solution is an aqueous solution of nickel acetate, nickel chloride, nickel sulfate, or nickel nitrate, with a concentration of 0.03–0.09 mol·L⁻¹. -1 .

4. The method for preparing the nickel-iron sulfide multichannel carbon nanofiber composite material as described in any one of claims 1-3, characterized in that, In step (1), the settling time is 18~48 h.

5. The method for preparing the nickel-iron sulfide multichannel carbon nanofiber composite material as described in claim 1, characterized in that, In step (2), the mass percentage of Prussian blue in the spinning solution is 3-8%, and the total mass percentage of the polymer is 7-15%, wherein the mass ratio of polyacrylonitrile to polymethyl methacrylate or polystyrene is 10:(1-5).

6. The method for preparing the nickel-iron sulfide multichannel carbon nanofiber composite material according to any one of claims 1-3, characterized in that, In step (2), the electrospinning process involves a spinning voltage of 10-18 kV and a feed rate of 0.4-1.2 mL / h. -1 .

7. The method for preparing the nickel-iron sulfide multichannel carbon nanofiber composite material as described in claim 1, characterized in that, In step (2), the pre-oxidation temperature is 200~300 ℃, and the holding time is 1~3 h; the carbonization is carried out in nitrogen or argon gas at 2~5 ℃·min. -1 The temperature is increased to 600~900℃ at a heating rate, and the holding time is 1~3 h.

8. The method for preparing the nickel-iron sulfide multichannel carbon nanofiber composite material as described in claim 1 or 7, characterized in that, In step (2), the sulfidation is performed by placing the carbonization product and the sulfur source in a ceramic boat at a mass ratio of 1:(3~5), and then heating in nitrogen or argon at 2~5 °C·min. -1 The temperature is increased to 400-700 ℃ at a heating rate, and the holding time is 1-3 h; the sulfur source is sulfur powder, thiourea or thioacetamide.

9. The application of the nickel-iron sulfide multichannel carbon nanofiber composite material obtained by the preparation method of claim 1 as a negative electrode material for sodium-ion batteries.

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