Preparation method and application of nitrogen-doped carbon-coated iron sulfide hollow tubular negative electrode material

Abstract

The present invention relates to the field of sodium ion batteries, and discloses a preparation method and application of a nitrogen-doped carbon-coated iron sulfide hollow tubular negative electrode material. The nitrogen-doped carbon-coated iron sulfide hollow tubular negative electrode material developed by the present invention, wherein an iron coordination polymer with nitrilotriacetic acid as a ligand is subjected to high-temperature annealing treatment to form a nitrogen-doped carbon-coated structure, thereby increasing the conductivity of the material; the hollow tubular structure obtained by amidation treatment with dopamine hydrochloride exposes more active sites and increases the contact area with the electrolyte; while the amidation reaction is being carried out, polydopamine also coats the outer layer of the hollow tubular iron sulfide and forms a nitrogen-doped carbon coating layer after high-temperature annealing treatment, thereby further improving the structural stability of the material and effectively solving the problem of volume expansion. When the above materials are used as negative electrode materials for sodium ion batteries, they have high specific capacity, cycle life and rate performance.

Description

Technical Field

[0001] The present invention relates to the field of sodium ion batteries, and in particular to a preparation method and application of a nitrogen-doped carbon-coated iron sulfide hollow tubular negative electrode material. Background Art

[0002] Sodium-ion batteries (SIBs), due to their abundant resources, low cost, and similar performance to lithium-ion batteries, are expected to become a strong contender for large-scale stationary energy storage. In recent years, SIB anode materials have garnered significant research attention and development. However, due to the larger radius of sodium ions (0.102 nm) compared to lithium ions (0.076 nm), SIBs exhibit disadvantages such as low specific capacity, poor cycling stability, and poor rate performance. Therefore, the development of high-performance SIB anode materials is urgently needed.

[0003] In recent years, researchers have conducted extensive research on the application of transition metal sulfides in sodium-ion battery anode materials. Transition metal sulfides have high electrochemical activity and thermodynamic stability, and the metal-sulfur bond is weaker than the metal-oxygen bond. Therefore, they have attracted widespread attention as anode materials for sodium-ion batteries. The metal sulfides currently studied by researchers include FeS2, ZnS, etc., which generally have high theoretical capacity, low price, and environmental friendliness. However, transition metal sulfides have defects similar to many metal compounds, and there is a problem of large volume expansion during the energy storage process. Summary of the Invention

[0004] To address the above technical issues, the present invention provides a method for preparing a nitrogen-doped carbon-coated hollow tubular iron sulfide anode material and its application. Using an iron coordination polymer as a precursor, the present invention employs a strategy involving amidation, high-temperature annealing, and vapor-phase vulcanization to design and prepare a hollow tubular structure of nitrogen-doped carbon-coated iron sulfide. This hollow tubular structure is then used as the anode material for sodium-ion batteries, effectively addressing the volume expansion issue and exhibiting high specific capacity, cycle life, and rate capability.

[0005] The specific technical solutions of the present invention are:

[0006] In a first aspect, the present invention provides a method for preparing a nitrogen-doped carbon-coated iron sulfide hollow tubular negative electrode material, comprising the following steps:

[0007] (1) Dissolve the metallic iron salt in a mixed solution of water and isopropanol, continue stirring, and then add nitrilotriacetic acid to obtain reaction solution A.

[0008] (2) Solvent-thermally treating the reaction solution A obtained in step (1), cooling it, centrifuging it, washing it, and drying it to obtain an iron coordination polymer.

[0009] (3) The iron coordination polymer obtained in step (2) is dispersed in water and stirred, tris(hydroxymethyl)aminomethane and dopamine hydrochloride are added, and the pH of the mixed solution is adjusted to 8.1-8.9. After the stirring is completed, the mixture is thoroughly washed with water and ethanol, and vacuum dried to obtain a composite precursor.

[0010] (4) The composite precursor in step (3) is subjected to calcination and carbonization treatment under a protective atmosphere, and a black powder is obtained after cooling.

[0011] (5) The sulfur powder and the black powder in step (4) are subjected to high-temperature sulfurization treatment under a protective atmosphere, and after cooling, a nitrogen-doped carbon-coated iron sulfide hollow tubular negative electrode material is obtained.

[0012] In the above preparation process, the present invention uses nitrilotriacetic acid with chelating ability as an organic ligand to form an iron coordination polymer with metal ions through a solvent thermal method to prepare a nanorod precursor; thereafter, the precursor is subjected to an amidation reaction with dopamine hydrochloride in tris(hydroxymethyl)aminomethane, so that the carboxyl group in the nitrilotriacetic acid replaces the hydrogen atom of the amino group on the dopamine. During the amidation reaction, dopamine first undergoes an amidation reaction with the nitrilotriacetic acid on the surface of the nanorod precursor. When the reaction proceeds to a certain extent, the nitrilotriacetic acid inside the nanorod is promoted to overflow. The organic ligand and the polydopamine layer are further amidated with dopamine to form a hollow tubular structure precursor, and due to the self-polymerization property of dopamine itself, a polydopamine layer is formed on the outer layer of the hollow tubular structure precursor. After a series of reactions, a composite precursor is obtained; the composite precursor is annealed at high temperature under the protection of an inert atmosphere to convert the organic ligand and the polydopamine layer into nitrogen-doped carbon in situ. In addition, the carbon thermal reaction at high temperature induces the reduction of metal ions; finally, iron sulfide is formed by a gas phase sulfidation method to obtain a nitrogen-doped carbon-coated iron sulfide hollow tubular material.

[0013] In summary, the present invention uses an iron coordination polymer as a precursor and designs and prepares a hollow tubular structure nitrogen-doped carbon-coated iron sulfide through strategies such as amidation reaction, high-temperature annealing, and vapor-phase vulcanization. The iron coordination polymer with nitrilotriacetic acid as a ligand is subjected to high-temperature annealing treatment to form a nitrogen-doped carbon-coated structure, which increases the conductivity of the material; the hollow tubular structure is exposed to more active sites by amidation treatment with dopamine hydrochloride, which increases the contact area with the electrolyte; while the amidation reaction is being carried out, polydopamine also coats the outer layer of the hollow tubular iron sulfide and forms a nitrogen-doped carbon coating layer after high-temperature annealing treatment, which further improves the structural stability of the material and can effectively solve the volume expansion problem. When the above materials are used as negative electrode materials for sodium ion batteries, they have high specific capacity, cycle life and rate performance.

[0014] Preferably, in step (1), the volume ratio of water to isopropanol in the reaction solution A is 1:(1-3), the molar ratio of the metal ion in the metal iron salt to nitrilotriacetic acid is 1:(0.5-4), and the mass ratio of the metal iron salt to the sum of water and isopropanol is 1:(40-150).

[0015] Preferably, in step (1), the metal iron salt is one or both of ferric chloride and ferric nitrate.

[0016] Preferably, in step (1), the stirring time is 10 to 30 minutes.

[0017] Preferably, step (2) is as follows: reaction solution A is reacted at 150-200°C for 6-30 h, cooled to room temperature, centrifuged, washed repeatedly, and vacuum dried at 50-80°C for 10-30 h.

[0018] Preferably, in step (3), the mass ratio of the iron coordination polymer to water is 1:(1000-2000), and the mass ratio of the iron coordination polymer, tris(hydroxymethyl)aminomethane and dopamine hydrochloride is 1:(3-6):(1.5-3).

[0019] Preferably, in step (3), the stirring time is 2 to 5 h, the pH value is maintained at 8.1 to 8.9, and the vacuum drying time is 6 to 24 h.

[0020] To better form the ideal hollow tubular structure, the solution pH and reaction time must be strictly controlled during the amidation reaction. The inventors found that the solution pH should be maintained between 8.1 and 8.9. Too low or too high a pH value will prevent the amidation reaction from proceeding smoothly and prevent dopamine from self-polymerizing to form a polydopamine layer. At the same time, the reaction time should be controlled between 2 and 5 hours. Too long a time will lead to the formation of excess polydopamine spheres, while too short a time will result in insufficient amidation reaction and unclear hollow tubular structure.

[0021] Preferably, in step (4), the calcination atmosphere is nitrogen, the temperature is 400-600°C, the heating rate is 1-5°C / min, and the holding time is 1-3 h. Preferably, in step (5), the high-temperature sulfurization atmosphere is nitrogen, the mass ratio of black powder to sulfur powder is 1:(2.5-6), the temperature is 400-600°C, the heating rate is 2-5°C / min, and the holding time is 1-3 h.

[0022] The temperature setting and heating rate during high-temperature annealing and vapor-phase vulcanization will also affect the final product. During high-temperature annealing, the temperature should be maintained at 400-600°C. Too low a temperature will result in incomplete carbonization of the material, while too high a temperature may cause morphological collapse and recrystallization during the annealing process. The heating rate should not be too fast and should be maintained at 1-5°C. If the temperature changes too quickly, the material may lose weight rapidly, leading to structural deformation. During vapor-phase vulcanization, the amount of sulfur powder is a key factor in the success of vulcanization. The mass ratio of material to sulfur powder should be controlled at 1:(2.5-6). Too little sulfur powder will result in incomplete vulcanization of the material and cause phase separation. Conversely, too little sulfur powder will cause sulfur powder residue to contaminate the sample.

[0023] In a second aspect, the present invention provides a nitrogen-doped carbon-coated iron sulfide hollow tubular negative electrode material prepared by the above-mentioned preparation method. The hollow tubular structure exhibits a hollow tubular structure before calcination and maintains a complete hollow tubular structure after calcination. The hollow tubular structure has a diameter of approximately 200 to 400 nm and is coated with a nitrogen-doped carbon coating layer with a thickness of 20 to 50 nm. In a third aspect, the present invention provides the use of the nitrogen-doped carbon-coated iron sulfide hollow tubular negative electrode material prepared by the above-mentioned preparation method in a sodium ion battery.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] (1) The present invention adopts a simple solvent thermal method, high temperature annealing and vapor phase sulfurization treatment to prepare nitrogen-doped carbon-coated iron sulfide hollow tubular materials. The synthesis method is simple, effective and low-cost.

[0026] (2) The present invention uses an iron coordination polymer as a precursor for derivatization treatment, thereby retaining the porous structure and large specific surface area characteristics of the iron coordination polymer. Nitrilotriacetic acid, as an organic ligand of the iron coordination polymer, is subjected to high-temperature annealing treatment to form a nitrogen-doped carbon coating structure, thereby increasing the conductivity of the material.

[0027] (3) The hollow tubular structure obtained by amidation treatment with dopamine hydrochloride in the present invention exposes more active sites and increases the contact area with the electrolyte.

[0028] (4) In the present invention, polydopamine is also coated on the outer layer of the iron coordination polymer hollow tube while the amidation reaction is carried out, and a nitrogen-doped carbon coating layer is formed after high-temperature annealing and vapor-phase sulfurization treatment, which can further improve the structural stability of the material. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is the X-ray diffraction (XRD) pattern of the nitrogen-doped carbon-coated iron disulfide hollow tubular material prepared in Example 1;

[0030] Figure 2(a) and (b) are scanning electron microscope (SEM) images of the nanorods prepared in Example 2 at different magnifications;

[0031] Figure 3 (a) and (b) are SEM images of the composite precursor prepared in Example 3 at different magnifications;

[0032] Figure 4 (a) and (b) are SEM images of the nitrogen-doped carbon-coated iron disulfide hollow tubular material prepared in Example 1 at different magnifications;

[0033] Figure 5 (a) and (b) are SEM images of the nitrogen-doped carbon-coated nickel-iron sulfide hollow tubular material prepared in Example 3 at different magnifications;

[0034] Figure 6 (a) and (b) are SEM images of the nitrogen-doped carbon-coated iron disulfide hollow tubular material prepared in Example 6 at different magnifications;

[0035] Figure 7 (a) and (b) are SEM images of the nitrogen-doped carbon-coated iron disulfide hollow tubular material prepared in Example 7 at different magnifications;

[0036] Figure 8 The battery cycle performance of the nitrogen-doped carbon-coated iron disulfide hollow tubular material prepared in Example 1;

[0037] Figure 9 This is the battery rate performance of the nitrogen-doped carbon-coated iron disulfide hollow tubular material prepared in Example 1. DETAILED DESCRIPTION

[0038] The present invention will be further described below with reference to the embodiments.

[0039] Example 1

[0040] (1) Dissolve 0.399 g of FeCl3 in 30 mL of deionized water and 30 mL of isopropanol, continue stirring, add 1.2 g of nitrilotriacetic acid, and stir thoroughly to obtain reaction solution A;

[0041] (2) The reaction solution A obtained in step (1) was transferred to a 100 mL reactor and reacted at 180 °C for 24 h. After cooling to room temperature, the white product nanorod precursor was collected by centrifugation, washed thoroughly with deionized water and ethanol, and dried in a vacuum oven at 60 °C for 12 h.

[0042] (3) 100 mg of the nanorod precursor obtained in step (2) was dispersed in 100 mL of deionized water by ultrasonication at room temperature for 30 min, and then 200 mg of tris(hydroxymethyl)aminomethane was added and dissolved with continuous stirring to obtain a mixed solution B. The pH value of the solution was measured to be about 8.6;

[0043] (4) Add 150 mg of dopamine hydrochloride to the mixed solution B in step (3) to carry out an amidation reaction, and reduce the pH value to about 8.2. After stirring at room temperature for 3 h, the black product was collected by centrifugation and thoroughly washed with deionized water and ethanol. After drying in a vacuum oven for 6 h, a composite precursor was obtained;

[0044] (5) annealing the composite precursor prepared in step (4) at 400°C for 3 h at a heating rate of 1°C / min under a nitrogen atmosphere to carbonize the composite precursor to obtain black powder α;

[0045] (6) The black powder α (0.3 g) and sulfur powder (1.2 g) prepared in step (5) were placed in a quartz boat (sulfur powder was placed upstream) and kept at 500 °C for 2 h under nitrogen flow at a heating rate of 2 °C / min to obtain a nitrogen-doped carbon-coated iron disulfide hollow tubular material.

[0046] Example 2

[0047] (1) Dissolve 0.994 g of Fe(NO3)3·9H2O in 30 mL of deionized water and 30 mL of isopropanol. Add 1.2 g of nitrilotriacetic acid while stirring continuously. Stir thoroughly to obtain reaction solution A.

[0048] (2) The reaction solution A obtained in step (1) was transferred to a 100 mL reactor and reacted at 150 °C for 30 h. After cooling to room temperature, the light green nanorod precursor product was collected by centrifugation, washed thoroughly with deionized water and ethanol, and dried in a vacuum oven at 80 °C for 18 h.

[0049] (3) 100 mg of the nanorod precursor obtained in step (2) was dispersed in 100 mL of deionized water by ultrasonication at room temperature for 40 min, followed by the addition of 300 mg of tris(hydroxymethyl)aminomethane and continuous stirring to dissolve to obtain a mixed solution B. The pH value of the solution was measured to be approximately 8.6.

[0050] (4) Add 150 mg of dopamine hydrochloride to the mixed solution B in step (3) to carry out an amidation reaction, and reduce the pH value to about 8.1. Stir at room temperature for 3 h, collect the black product by centrifugation, and thoroughly wash with deionized water and ethanol. After drying in a vacuum oven for 12 h, a composite precursor is obtained;

[0051] (5) annealing the composite precursor prepared in step (4) at 500°C for 3 h at a heating rate of 5°C / min under a nitrogen atmosphere to carbonize the composite precursor to obtain black powder α;

[0052] (6) The black powder α (0.3 g) and sulfur powder (1.2 g) prepared in step (5) were placed in a quartz boat (sulfur powder was placed upstream) and kept at 600 °C for 1 h under a nitrogen flow at a heating rate of 4 °C / min to obtain a nitrogen-doped carbon-coated iron disulfide hollow tubular material.

[0053] Example 3

[0054] (1) Dissolve 0.399 g of FeCl3 in 30 mL of deionized water and 30 mL of isopropanol, continue stirring, add 1.2 g of nitrilotriacetic acid, and stir thoroughly to obtain reaction solution A;

[0055] (2) The reaction solution A obtained in step (1) was transferred to a 100 mL reactor and reacted at 150 °C for 30 h. After cooling to room temperature, the white product nanorod precursor was collected by centrifugation, washed thoroughly with deionized water and ethanol, and dried in a vacuum oven at 80 °C for 15 h.

[0056] (3) 100 mg of the nanorod precursor obtained in step (2) was dispersed in 100 mL of deionized water by ultrasonication at room temperature for 40 min, and then 300 mg of tris(hydroxymethyl)aminomethane was added and dissolved by continuous stirring to obtain a mixed solution B. The pH value of the solution was measured to be about 8.8;

[0057] (4) Add 150 mg of dopamine hydrochloride to the mixed solution B in step (3) to carry out an amidation reaction, and reduce the pH value to about 8.2. Stir at room temperature for 5 h, collect the black product by centrifugation, and thoroughly wash with deionized water and ethanol. After drying in a vacuum oven for 18 h, a composite precursor is obtained;

[0058] (5) annealing the composite precursor prepared in step (4) at 600°C for 2 h at a heating rate of 5°C / min under a nitrogen atmosphere to carbonize the composite precursor to obtain a black powder α;

[0059] (6) The black powder α (0.3 g) and sulfur powder (1.5 g) prepared in step (5) were placed in a quartz boat (sulfur powder was placed upstream) and kept at 500 °C for 3 h under nitrogen flow at a heating rate of 5 °C / min to obtain a nitrogen-doped carbon-coated iron disulfide hollow tubular material.

[0060] Example 4

[0061] (1) Dissolve 0.266 g of FeCl3 in 20 mL of deionized water and 20 mL of isopropanol, continue stirring, add 0.2 g of nitrilotriacetic acid, and stir thoroughly to obtain reaction solution A;

[0062] (2) The reaction solution A obtained in step (1) was transferred to a 100 mL reactor and reacted at 200 °C for 18 h. After cooling to room temperature, the white product nanorod precursor was collected by centrifugation, washed thoroughly with deionized water and ethanol, and dried in a vacuum oven at 80 °C for 18 h.

[0063] (3) 100 mg of the nanorod precursor obtained in step (2) was dispersed into 150 mL of deionized water by ultrasonication at room temperature for 30 min, and then 400 mg of tris(hydroxymethyl)aminomethane was added and dissolved with continuous stirring to obtain a mixed solution B. The pH value of the solution was measured to be about 8.9;

[0064] (4) Add 150 mg of dopamine hydrochloride to the mixed solution B in step (3) to carry out an amidation reaction, and reduce the pH value to about 8.4. Stir at room temperature for 5 h, collect the black product by centrifugation, and thoroughly wash with deionized water and ethanol. After drying in a vacuum oven for 18 h, a composite precursor is obtained;

[0065] (5) annealing the composite precursor prepared in step (4) at 600°C for 1 h at a heating rate of 5°C / min under a nitrogen atmosphere to carbonize the composite precursor to obtain a black powder α;

[0066] (6) The black powder α (0.4 g) and sulfur powder (1.0 g) prepared in step (5) were placed in a quartz boat (sulfur powder was placed upstream) and kept at 600 °C for 1 h under a nitrogen flow at a heating rate of 3 °C / min to obtain a nitrogen-doped carbon-coated iron disulfide hollow tubular material.

[0067] Example 5

[0068] (1) Dissolve 0.532 g of FeCl3 in 40 mL of deionized water and 40 mL of isopropanol, continue stirring, add 1.6 g of nitrilotriacetic acid, and stir thoroughly to obtain reaction solution A;

[0069] (2) The reaction solution A obtained in step (1) was transferred to a 100 mL reactor and reacted at 180 °C for 24 h. After cooling to room temperature, the white product nanorod precursor was collected by centrifugation, washed thoroughly with deionized water and ethanol, and dried in a vacuum oven at 50 °C for 24 h.

[0070] (3) 100 mg of the nanorod precursor obtained in step (2) was dispersed in 200 mL of deionized water by ultrasonication at room temperature for 60 min, and then 600 mg of tris(hydroxymethyl)aminomethane was added and dissolved with continuous stirring to obtain a mixed solution B. The pH value of the solution was measured to be about 8.9;

[0071] (4) Add 300 mg of dopamine hydrochloride to the mixed solution B in step (3) to carry out an amidation reaction, and reduce the pH value to about 8.5. Stir at room temperature for 2 h, collect the black product by centrifugation, and thoroughly wash with deionized water and ethanol. After drying in a vacuum oven for 24 h, a composite precursor is obtained;

[0072] (5) annealing the composite precursor prepared in step (4) at 500°C for 2 h at a heating rate of 2°C / min under a nitrogen atmosphere to carbonize the composite precursor to obtain a black powder α;

[0073] (6) The black powder α (0.3 g) and sulfur powder (1.8 g) prepared in step (5) were placed in a quartz boat (sulfur powder was placed upstream) and kept at 500 °C for 1 h under a nitrogen flow at a heating rate of 3 °C / min to obtain a nitrogen-doped carbon-coated iron disulfide hollow tubular material.

[0074] Experimental example

[0075] The nitrogen-doped carbon-coated hollow tubular iron disulfide material prepared in Example 1 was mixed with a conductive agent, Super P, and a binder, polyvinylidene fluoride (PVDF), in a ratio of 8:1:1 to form a slurry. This slurry was then coated on a copper current collector. The coated copper foil was placed in a vacuum drying oven and dried at 80°C for 12 hours. After punching, the resulting electrode was used as the working electrode of the battery. A sodium metal sheet was used as the counter electrode, and a Whatman glass fiber (Ø = 19 mm) was used as the separator. The electrolyte was 1 M NaPF6 dissolved in diethylene glycol dimethyl ether. The resulting CR2025 button half-cell was assembled. The reversible charge-discharge specific capacitance, charge-discharge cycle performance, and rate characteristics of the nitrogen-doped carbon-coated hollow tubular iron disulfide were measured in a 25°C environment with a charge-discharge voltage of 0.01-3.0 V.

[0076] In order to explore the factors affecting the changes in material properties, further research was carried out using characterization methods such as SEM and XRD. Figure 1 This is the XRD pattern of the nitrogen-doped carbon-coated iron disulfide hollow tubular material prepared in Example 1, and its peak position corresponds well to the JCPDS standard card of FeS2. Figure 2 This is the SEM image of the nanorod precursor in Example 1. It can be seen from the figure that its diameter distribution is relatively uniform. Figure 3 、 4 This is an SEM image of the composite precursor and the final product after the reaction with dopamine in Example 1. It can be seen from the figure that the hollow tubular structure is obvious. After high-temperature annealing and vapor phase sulfurization, the hollow tubular structure remains intact, and the diameter of the hollow tubular structure is approximately 30~50 nm. Figure 5 This is the SEM image of the final product in Example 3. It is found that when the type of metal salt is changed, its morphology can still maintain a hollow tubular structure. Figure 6 、 7 These are SEM images of the final products in Examples 4 and 5. It is found that when the amount of dopamine changes, the wall thickness of the tubular material also changes accordingly.

[0077] Figure 8 、 9 The figure shows the cycle performance and rate performance of the nitrogen-doped carbon-coated iron disulfide hollow tubular material of Example 1. Figure 8 It can be seen that the nitrogen-doped carbon-coated hollow tubular iron disulfide of the present invention has a high -1 After 1000 cycles at high current, the capacity is still 418.7 mAh g -1 , only 8.3% of the initial capacity was decayed, showing excellent cycle stability and long cycle life. Figure 9 It can be seen that at 0.2 A g -1 , 0.5 A g -1 , 1 A g -1 , 2 A g -1 and 5 A g -1 At current densities of 100 and 100 nm, the specific capacities of the nitrogen-doped carbon-coated hollow tubular iron disulfide materials are 721 mAh g -1 , 675 mAh g -1 , 658mAh g -1 , 618 mAh g -1 and 569 mAh g -1 , showing excellent rate performance.

[0078] In summary, this is because the nitrilotriacetic acid as an organic ligand is derivatized to form a nitrogen-doped carbon coating structure, which increases the conductivity of the material; the hollow tubular structure obtained by amidation treatment with dopamine hydrochloride exposes more active sites and increases the contact area with the electrolyte; while the amidation reaction is taking place, dopamine hydrochloride is also coated on the outer layer of the nanotube, and after derivatization treatment, a nitrogen-doped carbon coating layer is formed, which improves the structural stability of the material.

[0079] Therefore, the nitrogen-doped carbon-coated iron sulfide hollow tubular material of the present invention has high specific capacity, high cycle life, and high rate performance, and has broad application prospects in small mobile grid energy storage, electronic equipment, electric vehicles, aerospace and other fields.

[0080] Unless otherwise specified, the raw materials and equipment used in the present invention are commonly used in the art; the methods used in the present invention are conventional methods in the art unless otherwise specified.

[0081] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent transformation made to the above embodiment based on the technical essence of the present invention still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A method for preparing a nitrogen-doped carbon-coated iron sulfide hollow tubular negative electrode material, characterized in that The following steps are involved: (1) dissolving a metallic iron salt in a mixed solution of water and isopropyl alcohol, and adding nitrilotriacetic acid after continuous stirring to obtain a reaction solution A; The metallic iron salt is one or both of ferric chloride and ferric nitrate; The volume ratio of water to isopropanol in the reaction solution A is 1:(1-3), the molar ratio of the metal ion in the metal iron salt to nitrilotriacetic acid is 1:(0.5-4), and the mass ratio of the metal iron salt to the sum of water and isopropanol is 1:(40-150); (2) subjecting the reaction solution A obtained in step (1) to solvent thermal treatment at 150-200°C for 6-30 h, cooling to room temperature, centrifuging, repeatedly washing, and vacuum drying at 50-80°C for 10-30 h to obtain an iron coordination polymer; (3) dispersing the iron coordination polymer obtained in step (2) in water and stirring, adding tris(hydroxymethyl)aminomethane and dopamine hydrochloride, adjusting the pH of the mixed solution to 8.1-8.9, and after the stirring is completed, washing thoroughly with water and ethanol, and vacuum drying to obtain a composite precursor; The mass ratio of the iron coordination polymer to water is 1:(1000-2000), and the mass ratio of the iron coordination polymer, tris(hydroxymethyl)aminomethane, and dopamine hydrochloride is 1:(3-6):(1.5-3); (4) The composite precursor in step (3) is subjected to calcination and carbonization treatment under a protective atmosphere, and a black powder is obtained after cooling; (5) The sulfur powder and the black powder in step (4) are subjected to high-temperature sulfurization treatment under a protective atmosphere, and after cooling, a nitrogen-doped carbon-coated iron sulfide hollow tubular negative electrode material is obtained.

2. The preparation method according to claim 1, wherein: In step (1), the stirring time is 10 to 30 minutes.

3. The preparation method according to claim 1, wherein: In step (3), the stirring time is 2 to 5 h, the pH value is maintained at 8.1 to 8.9, and the vacuum drying time is 6 to 24 h.

4. The preparation method according to claim 1, wherein: In step (4), the calcination atmosphere is nitrogen, the temperature is 400~600℃, the heating rate is 1~5℃ / min, and the holding time is 1~3h.

5. The preparation method according to claim 1, wherein: In step (5), the high-temperature vulcanization atmosphere is nitrogen, the mass ratio of black powder to sulfur powder is 1:(2.5~6), the temperature is 400~600℃, the heating rate is 2~5℃ / min, and the holding time is 1~3h.

6. A nitrogen-doped carbon-coated iron sulfide hollow tubular negative electrode material prepared by the preparation method according to any one of claims 1 to 5, characterized in that: The diameter of the hollow tube is 200~400 nm, and the outer layer is a nitrogen-doped carbon coating with a thickness of 20~50 nm.

7. Use of the nitrogen-doped carbon-coated iron sulfide hollow tubular negative electrode material prepared by the preparation method according to any one of claims 1 to 5 in a sodium ion battery.

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