A core-shell structured carbon-coated FeS nanosphere, its preparation method and application

Abstract

This invention provides a core-shell structured carbon-coated FeS nanosphere, its preparation method, and its applications. The carbon-coated FeS nanosphere comprises FeS particles and a hollow carbon shell coating the FeS particles. The outer diameter of the hollow carbon shell is 0.5–1.7 μm, and the inner diameter is 0.3–1.1 μm. The particle size of the FeS particles is 50–280 nm. The preparation method includes: preparing FeOOH nanoparticles; dispersing the FeOOH nanoparticles in ethanol; dispersing n-pentane and n-dodecylamine in ethanol, adding water, adding the FeOOH dispersion, adding resorcinol, then adding ammonia and formaldehyde solution, stirring the reaction to obtain a solid product; calcining; and sulfidation. The carbon-coated FeS nanospheres prepared by this invention exhibit excellent microwave absorption performance in the resulting composite material at a low filling amount, and the carbon-coated FeS nanospheres also have good sodium ion storage performance.

Description

Technical Field

[0001] This invention belongs to the field of composite material technology, specifically relating to a core-shell structured carbon-coated FeS nanosphere, its preparation method, and its application. Background Technology

[0002] The rapid development of electrical equipment and wireless communication has led to a large output of electromagnetic radiation, resulting in electromagnetic pollution and interference under certain conditions, which can harm the environment and human health. Microwave absorbing materials can inhibit the propagation and reflection of electromagnetic waves. Developing new types of microwave absorbing materials with thin thickness, low mass density, high microwave loss, and effective absorption bandwidth is urgently needed.

[0003] Carbon-based hollow spheres have characteristics such as low mass density, high porosity, large specific surface area, and corrosion resistance. By adjusting the material size and composition of the magnetic core and the thickness and size of the carbon shell, the synergistic effect of multiple loss mechanisms can be achieved to enhance the attenuation energy of electromagnetic waves.

[0004] Furthermore, its unique structure allows for excellent performance in battery electrode materials. The abundant pores on its surface and the core material within provide more reaction sites for lithium-ion or sodium-ion batteries, thus making this type of material promising for applications in energy storage and microwave absorption, and a hot topic in nanomaterial synthesis and application research. Summary of the Invention

[0005] This invention provides a core-shell structured carbon-coated FeS nanosphere, its preparation method, and its application. The carbon-coated FeS nanospheres prepared by the method of this invention exhibit excellent microwave absorption performance in the resulting composite material at a low filling amount, and the carbon-coated FeS nanospheres also have good sodium ion storage performance.

[0006] The technical solution of the present invention is as follows: A core-shell structured carbon-coated FeS nanosphere comprises FeS particles and a hollow carbon shell covering the FeS particles. The outer diameter of the hollow carbon shell is 0.5~1.7 μm and the inner diameter is 0.3~1.1 μm. The particle size of the FeS particles is 50~280 nm.

[0007] Preferably, the hollow carbon sphere shell has cavities. These cavities can provide diffusion channels for Na ions, etc.

[0008] As a general inventive concept, this invention provides a method for preparing core-shell structured carbon-coated FeS nanospheres, comprising the following steps: (1) Preparation of FeOOH nanoparticles; (2) FeOOH nanoparticles were dispersed in ethanol to obtain FeOOH dispersion; (3) Disperse n-pentane and n-dodecylamine in ethanol, add water, stir and mix evenly, add FeOOH dispersion while stirring, stir, add resorcinol and stir, then add ammonia and formaldehyde solution dropwise, and place the resulting mixture at 22~35℃ and stir continuously to obtain solid product; (4) The solid product is placed in a tube furnace and calcined under an inert atmosphere to obtain a core-shell structured carbon-based material; (5) The carbon-based material with the core-shell structure is sulfided in a tube furnace with a flowing inert atmosphere using sulfur powder as a sulfur source to obtain carbon-coated FeS nanospheres with the core-shell structure.

[0009] In the above preparation method, FeOOH nanoparticles are used as the precursor of FeS particles, which facilitates synthesis and control of crystal size and shape, and is quick and effective. In the preparation of carbon-based hollow sphere materials, n-pentane mainly plays the role of a "soft template synergistic regulator." It synergistically constructs a soft template with n-dodecylamine (a straight-chain alkylamine), guiding the polymerization of resorcinol-formaldehyde on the periphery of the micro-region to form hollow spheres. This supports the formation of hollow carbon sphere shells from three core dimensions: "structure guidance, phase separation induction, and size control."

[0010] Furthermore, this invention first calcines the obtained solid product under an inert atmosphere before sulfiding, which yields a high-purity product. If sulfidation is performed directly, the sulfur powder will react with the gas released during the carbonization of the material, generating a large number of byproducts, which is detrimental to the carbonization process and also affects the purity of the final product.

[0011] Preferably, step (1) specifically includes the following steps: at room temperature, NaOH solution is added dropwise to FeCl3 solution to make the pH value less than 8, and the mixture is stirred continuously at 50~85℃. The product is collected and freeze-dried to obtain FeOOH nanoparticles. The concentration of the FeCl3 solution is 0.1~0.3M; the concentration of the NaOH solution is 0.1~0.3M.

[0012] Preferably, in step (2), the ratio of FeOOH nanoparticles to ethanol is 0.1g:5~10mL.

[0013] Preferably, in step (3), the volume ratio of ethanol to water is 10~20:40~70; the mass ratio of FeOOH nanoparticles, resorcinol, n-pentane, n-dodecylamine, ammonia and formaldehyde solution is 0.1:0.02~0.45:0.03~0.55:0.02~0.12:0.01~0.40:0.10~1.0; if the amount of each raw material exceeds the above range, carbon-coated FeS nanospheres with a spherical core-shell structure cannot be obtained. The stirring reaction time is ≥15 hours.

[0014] Preferably, in step (5), the mass ratio of the carbon-based material of the core-shell structure to sulfur powder is 2~20:1; Preferably, the inert atmosphere in steps (4) and (5) is at least one of nitrogen and argon.

[0015] Preferably, in step (4), the roasting temperature is 400~950℃ and the roasting time is ≥3 hours; In step (5), the vulcanization temperature is 350~550℃ and the vulcanization time is 2~4 hours; As a general inventive concept, this invention provides the application of the core-shell structured carbon-coated FeS nanospheres and the core-shell structured carbon-coated FeS nanospheres prepared by the aforementioned preparation method in microwave absorption and sodium ion storage.

[0016] The beneficial technical effects of this invention are as follows: 1. The carbon-coated FeS nanospheres provided by this invention, through the design and size control of the core-shell structure, combined with a hollow structure, possess excellent microwave absorption performance. This allows incident electromagnetic waves to undergo multiple scattering and reflections within the cavity, expanding the transmission path of the electromagnetic waves, improving the effective scattering and loss of the incident electromagnetic waves, and improving the dielectric loss and interface loss of the material. By adjusting the size of the FeS particles in the core, the magnitude of magnetic loss can be changed, achieving optimal microwave absorption matching. The microwave absorbing composite material made using the carbon-coated FeS nanospheres of this invention exhibits a reflection loss as high as -35 dB.

[0017] 2. The carbon-coated FeS nanospheres provided by this invention have a porous structure on their surface, exhibiting low density and high specific surface area, thus possessing excellent Na ion storage performance. Electrodes prepared using these carbon-coated FeS nanospheres have high specific capacity and cycling performance, and have extremely broad application prospects.

[0018] 3. In preparing carbon-coated FeS nanospheres, this invention uses FeOOH nanoparticles as FeS particle precursors and employs n-pentane and n-dodecylamine to synergistically construct a soft template to guide the polymerization of resorcinol-formaldehyde around the micro-region to form hollow spheres. Then, through calcination and sulfidation, the FeS particles are coated with hollow carbon sphere shells, and there are certain gaps between the FeS particles and the hollow carbon sphere shells. Attached Figure Description

[0019] Figure 1 The X-ray diffraction pattern of carbon-coated FeS nanospheres with a core-shell structure is shown in Example 1.

[0020] Figure 2 The X-ray diffraction pattern of carbon-coated FeS nanospheres with a core-shell structure is shown in Example 2.

[0021] Figure 3 The image shows a scanning electron microscope (SEM) image of carbon-coated FeS nanospheres with a core-shell structure, as shown in Example 1.

[0022] Figure 4 This is a TEM image of carbon-coated FeS nanospheres with a core-shell structure, as shown in Example 1.

[0023] Figure 5 The microwave absorption spectrum of carbon-coated FeS nanospheres with a core-shell structure is shown in Example 1.

[0024] Figure 6 The electrochemical spectrum of carbon-coated FeS nanospheres with a core-shell structure is shown in Example 1. Detailed Implementation

[0025] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. Obviously, the described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0026] Example 1: This embodiment provides a method for preparing core-shell structured carbon-coated FeS nanospheres, including the following steps: (1) At room temperature, 0.2M NaOH solution was added dropwise to 100 mL of 0.1M FeCl3 solution to make the pH value 4~6. The mixture was stirred continuously at 60℃ for 8 hours. The precipitate was collected by centrifugation and freeze-dried to obtain FeOOH nanoparticles. (2) Disperse 0.1g FeOOH nanoparticles in 10mL of ethanol to obtain FeOOH dispersion; (3) Disperse 0.07 g n-pentane and 0.05 n-dodecylamine in 10 ml ethanol, then add 70 ml deionized water, stir and mix evenly, and add the FeOOH dispersion obtained in step (2) while stirring; continue stirring for 30 min, then add 0.1 g resorcinol; continue stirring for 10 min, then add 0.25 g ammonia water (25~28 wt%) and 0.12 g formaldehyde solution (37 wt%) dropwise; place the resulting mixture at 30 °C and stir continuously for 15 hours to obtain a solid product; (4) The solid product obtained in step (3) is placed in a tube furnace and calcined for 3 hours under a nitrogen atmosphere at a calcination temperature of 450°C to obtain a core-shell structured carbon-based material. (5) The carbon-based material obtained in step (4) is placed in a tube furnace with a flowing inert atmosphere. 0.5 times its mass of sulfur powder is used as the sulfur source. The carbon is sulfided at 450°C for 3 hours to obtain the target product of carbon-coated FeS nanospheres, which is denoted as sample 1#.

[0027] The carbon-coated FeS nanospheres obtained in this embodiment include FeS particles and hollow carbon shells covering the FeS particles. The FeS particles have a particle size of 100~180 nm, and the hollow carbon shells have an outer diameter of 0.5~0.7 μm and an inner diameter of 0.3~0.4 μm.

[0028] The X-ray diffraction pattern of the core-shell structured carbon-coated FeS nanospheres in this embodiment is as follows: Figure 1 As shown, its scanning electron microscope (SEM) images are as follows: Figure 3 As shown. TEM image of carbon-coated FeS nanospheres. Figure 4 As shown, the hollow carbon sphere shell has cavities.

[0029] The carbon-coated FeS nanospheres of this embodiment were uniformly mixed with paraffin at a mass ratio of 4:6 after heating at 80°C. The mixture was then pressed into shape using a mold to obtain the test material. The microwave absorption performance was tested using a vector network analyzer, and the results are as follows: Maximum reflection loss of -35.24 dB was achieved when the matching thickness d was 3.2 mm, with an effective absorption bandwidth of 5.06 GHz. The microwave absorption spectrum of the core-shell structured carbon-coated FeS nanospheres of this embodiment is shown below. Figure 5 As shown.

[0030] Electrochemical tests were conducted on the carbon-coated FeS nanospheres of this embodiment. The working electrode of the sodium battery was prepared by mixing the carbon-coated FeS nanospheres with Super P and sodium carboxymethyl cellulose in a mass ratio of 8:1:1. Metallic sodium was used as the counter electrode, glass fiber as the separator, and a 1.0 M NaCF3SO3 solution in diethylene glycol dimethyl ether (DIGLYME) was used as the electrolyte. A coin cell was assembled. Electrochemical tests were performed at 30°C with a current of 100 mA·g. ‑1When the current density is tested in the constant current charge-discharge range of 0.01~3V, the first discharge capacity is 580mAh·g. ‑1 The electrochemical spectrum of the core-shell structured carbon-coated FeS nanospheres in this embodiment is as follows: Figure 6 As shown.

[0031] Example 2: This embodiment provides a method for preparing core-shell structured carbon-coated FeS nanospheres, including the following steps: (1) At room temperature, 0.2M NaOH solution was added dropwise to 100 mL of 0.1M FeCl3 solution to make the pH value 4~6. The mixture was stirred continuously at 70℃ for 16 hours. The precipitate was collected by centrifugation and freeze-dried to obtain FeOOH nanoparticles. (2) Disperse 0.1g FeOOH nanoparticles in 10mL of ethanol to obtain FeOOH dispersion; (3) Disperse 0.07 g n-pentane and 0.05 n-dodecylamine in 20 ml ethanol, then add 70 ml deionized water, stir and mix evenly, and add the FeOOH dispersion obtained in step (2) while stirring; continue stirring for 30 min, then add 0.1 g resorcinol; continue stirring for 10 min, then add 0.25 g ammonia water (25~28 wt%) and 0.12 g formaldehyde solution (37 wt%) dropwise to obtain a mixture; place the obtained mixture at 30 °C and stir continuously for 15 hours to obtain a solid product; (4) The solid product obtained in step (3) is placed in a tube furnace and calcined for 3 hours under a nitrogen atmosphere at a calcination temperature of 450°C to obtain a core-shell structured carbon-based material. (5) The carbon-based material obtained in step (4) is placed in a tube furnace with a flowing inert atmosphere. 0.4 times its mass of sulfur powder is used as the sulfur source and sulfurized at 450°C for 3 hours to obtain the target product of carbon-coated FeS nanospheres, which is denoted as sample 2#.

[0032] The carbon-coated FeS nanospheres obtained in this embodiment include FeS particles and hollow carbon shells covering the FeS particles. The FeS particles have a particle size of 120~200 nm, and the hollow carbon shells have an outer diameter of 0.5~0.7 μm and an inner diameter of 0.3~0.4 μm.

[0033] The X-ray diffraction pattern of the core-shell structured carbon-coated FeS nanospheres in this embodiment is as follows: Figure 2 As shown.

[0034] The carbon-coated FeS nanospheres of this embodiment were uniformly mixed with paraffin at a mass ratio of 4:6 at 80°C and then pressed into shape using a mold to obtain the test material. The absorption performance was tested using a vector network analyzer, and the results are as follows: the maximum reflection loss was reached when the matching thickness d was 3.0 mm, with a value of -31.24 dB and an effective absorption bandwidth of 4.86 GHz.

[0035] Electrochemical tests were performed on the carbon-coated FeS nanospheres of this embodiment. The working electrode of the sodium battery was prepared by mixing the carbon-coated FeS nanospheres with Super P and sodium carboxymethyl cellulose in a mass ratio of 8:1:1. Metallic sodium was used as the counter electrode, glass fiber as the separator, and a 1.0 M NaCF3SO3 solution in diethylene glycol dimethyl ether (DIGLYME) was used as the electrolyte. A coin cell was assembled. Electrochemical tests were conducted at 30°C with an efficiency of 100 mA·g. ‑1 When the current density is constant in the range of 0.01~3V, the first discharge capacity is 540mAh·g. ‑1 .

[0036] Example 3: This embodiment provides a method for preparing core-shell structured carbon-coated FeS nanospheres, including the following steps: (1) At room temperature, 0.2M NaOH solution was added dropwise to 150 mL of 0.1M FeCl3 solution to make the pH value 4~6. The mixture was stirred continuously at 70℃ for 24 hours. The precipitate was collected by centrifugation and freeze-dried to obtain FeOOH nanoparticles. (2) 0.1 g FeOOH nanoparticles were dispersed in 8 mL of ethanol to obtain FeOOH dispersion; (3) Disperse 0.07g n-pentane and 0.05g n-dodecylamine in 20ml ethanol, then add 70ml deionized water, stir and mix evenly, and add the FeOOH dispersion obtained in step (2) while stirring; continue stirring for 30min, then add 0.1g resorcinol; continue stirring for 10min, then add 0.25g ammonia (25~28wt%) and 0.12g formaldehyde solution (37wt%) dropwise; place the resulting mixture at 30℃ and stir continuously for 15 hours to obtain a solid product; (4) The solid product obtained in step (3) is placed in a tube furnace and calcined for 3 hours under a nitrogen atmosphere at a calcination temperature of 450°C to obtain a core-shell structured carbon-based material. (5) The carbon-based material obtained in step (4) is placed in a tube furnace with a flowing inert atmosphere. 0.5 times its mass of sulfur powder is used as the sulfur source and sulfurized at 400°C for 3 hours to obtain the target product of carbon-coated FeS nanospheres, which is denoted as sample 3#.

[0037] The carbon-coated FeS nanospheres obtained in this embodiment include FeS particles and hollow carbon shells coating the FeS particles. The FeS particles have a particle size of 160~260 nm, and the hollow carbon shells have an outer diameter of 0.5~0.7 μm and an inner diameter of 0.3~0.4 μm.

[0038] The carbon-coated FeS nanospheres of this embodiment were uniformly mixed with paraffin at a mass ratio of 4:6 after heating at 80°C, and then pressed into shape using a mold to obtain the test material. The absorption performance was tested using a vector network analyzer, and the results are as follows: the maximum reflection loss was reached when the matching thickness d was 2.8 mm, with a value of -33.24 dB and an effective absorption bandwidth of 4.66 GHz.

[0039] Electrochemical tests were performed on the carbon-coated FeS nanospheres of this embodiment. The working electrode of the sodium battery was prepared by mixing the carbon-coated FeS nanospheres with Super P and sodium carboxymethyl cellulose in a mass ratio of 8:1:1. Metallic sodium was used as the counter electrode, glass fiber as the separator, and a 1.0 M NaCF3SO3 solution in diethylene glycol dimethyl ether (DIGLYME) was used as the electrolyte. A coin cell was assembled. Electrochemical tests were conducted at 30°C with a current of 100 mA·g. ‑1 When the current density is constant in the range of 0.01~3 V for constant current charge and discharge testing, the first discharge capacity is 562 mAh·g. ‑1 .

[0040] Example 4: This embodiment provides a method for preparing core-shell structured carbon-coated FeS nanospheres, including the following steps: (1) At room temperature, 0.2M NaOH solution was added dropwise to 100 mL of 0.1M FeCl3 solution to make the pH value 4~6. The mixture was stirred continuously at 80℃ for 16 hours. The product was collected and freeze-dried to obtain FeOOH nanoparticles. (2) Disperse 0.1g of FeOOH nanoparticles in 5mL of ethanol to obtain FeOOH dispersion; (3) Disperse 0.07 g n-pentane and 0.05 n-dodecylamine in 20 ml ethanol, then add 70 ml deionized water, stir and mix evenly, and add the FeOOH dispersion obtained in step (2) while stirring; continue stirring for 30 min, then add 0.2 g resorcinol; continue stirring for 10 min, then add 0.25 g ammonia water (25~28 wt%) and 0.12 g formaldehyde solution (37 wt%) dropwise; place the resulting mixture at 30 °C and stir continuously for 15 hours to obtain a solid product; (4) The solid product obtained in step (3) is placed in a tube furnace and calcined for 3 hours under a nitrogen atmosphere at a calcination temperature of 450°C to obtain a core-shell structured carbon-based material. (5) The carbon-based material obtained in step (4) is placed in a tube furnace with a flowing inert atmosphere. 0.5 times its mass of sulfur powder is used as the sulfur source and sulfurized at 450°C for 3 hours to obtain the target product of carbon-coated FeS nanospheres, which is denoted as sample 4#.

[0041] The carbon-coated FeS nanospheres obtained in this embodiment include FeS particles and hollow carbon shells covering the FeS particles. The particle size of the FeS particles is 160~260 nm, and the outer diameter of the hollow carbon shells is 0.9~1.0 μm and the inner diameter is 0.5~0.6 μm.

[0042] The carbon-coated FeS nanospheres of this embodiment were uniformly mixed with paraffin at a mass ratio of 4:6 at 80°C and then pressed into shape using a mold to obtain the test material. The absorption performance was tested using a vector network analyzer, and the results are as follows: the maximum reflection loss was reached when the matching thickness d was 3.1 mm, with a value of -34.24 dB and an effective absorption bandwidth of 4.71 GHz.

[0043] Electrochemical tests were performed on the carbon-coated FeS nanospheres of this embodiment. The working electrode of the sodium battery was prepared by mixing the carbon-coated FeS nanospheres with Super P and sodium carboxymethyl cellulose in a mass ratio of 8:1:1. Metallic sodium was used as the counter electrode, glass fiber as the separator, and a 1.0 M NaCF3SO3 solution in diethylene glycol dimethyl ether (DIGLYME) was used as the electrolyte. A coin cell was assembled. Electrochemical tests were conducted at 30°C with an efficiency of 100 mA·g. ‑1 When the current density is constant in the range of 0.01~3V, the first discharge capacity is 522mAh·g. ‑1 .

[0044] Comparative Example 1: Unlike Example 1, step (4) is omitted. Instead, the solid product obtained in step (3) is placed in a tubular furnace with a flowing inert atmosphere, and 0.5 times its mass of sulfur powder is used as the sulfur source and calcined at 450°C for 3 hours.

[0045] The material obtained in this comparative example was mixed with paraffin at a mass ratio of 4:6 and heated to 80°C. The mixture was then pressed into shape using a mold to obtain the test material. The absorption performance was tested using a vector network analyzer, and the results are as follows: the maximum reflection loss was reached when the matching thickness d was 3.3 mm, with a value of -29.24 dB and an effective absorption bandwidth of 3.71 GHz.

[0046] Although the embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, and for those of ordinary skill in the art, various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. Therefore, the present invention is not limited to the specific details without departing from the general concept defined by the claims and their equivalents.

Claims

1. A core-shell structured carbon-coated FeS nanosphere, characterized in that, The carbon-coated FeS nanospheres include FeS particles and hollow carbon shells covering the FeS particles. The outer diameter of the hollow carbon shells is 0.5~1.7 μm and the inner diameter is 0.3~1.1 μm. The particle size of the FeS particles is 50~280 nm.

2. The core-shell structured carbon-coated FeS nanospheres as described in claim 1, characterized in that, The hollow carbon sphere shell has cavities.

3. A method for preparing core-shell structured carbon-coated FeS nanospheres as described in any one of claims 1 to 2, characterized in that, Includes the following steps: (1) Preparation of FeOOH nanoparticles; (2) FeOOH nanoparticles were dispersed in ethanol to obtain FeOOH dispersion; (3) Disperse n-pentane and n-dodecylamine in ethanol, add water, stir and mix evenly, add FeOOH dispersion while stirring, stir, add resorcinol and stir, then add ammonia and formaldehyde solution dropwise, and place the resulting mixture at 22~35℃ and stir continuously to obtain solid product; (4) The solid product is placed in a tube furnace and calcined under an inert atmosphere to obtain a core-shell structured carbon-based material; (5) The carbon-based material with the core-shell structure is sulfided in a tube furnace with a flowing inert atmosphere using sulfur powder as a sulfur source to obtain carbon-coated FeS nanospheres with the core-shell structure.

4. The preparation method according to claim 3, characterized in that, Step (1) in detail The process includes the following steps: at room temperature, NaOH solution is added dropwise to FeCl3 solution to make the pH value less than 8, and the mixture is stirred continuously at 50~85℃. The product is collected and freeze-dried to obtain FeOOH nanoparticles. The concentration of the FeCl3 solution is 0.1~0.3M; the concentration of the NaOH solution is 0.1~0.3M.

5. The preparation method according to claim 3, characterized in that, In step (2), the ratio of FeOOH nanoparticles to ethanol is 0.1g:5~10mL.

6. The preparation method according to claim 3, characterized in that, In step (3), the volume ratio of ethanol to water is 10~20:40~70; the mass ratio of FeOOH nanoparticles, resorcinol, n-pentane, n-dodecylamine, ammonia water to formaldehyde solution is 0.1:0.02~0.45:0.03~0.55:0.02~0.12:0.01~0.40:0.10~1.0; The stirring reaction time is ≥15 hours.

7. The preparation method according to claim 3, characterized in that, In step (5), the mass ratio of the carbon-based material of the core-shell structure to sulfur powder is 2~20:

1.

8. The preparation method according to claim 3, characterized in that, The inert atmosphere in steps (4) and (5) is at least one of nitrogen and argon.

9. The preparation method according to claim 3, characterized in that, In step (4), the roasting temperature is 400~950℃ and the roasting time is ≥3 hours; In step (5), the vulcanization temperature is 350~550℃ and the vulcanization time is 2~4 hours.

10. The application of carbon-coated FeS nanospheres with a core-shell structure as described in any one of claims 1 to 2, or carbon-coated FeS nanospheres with a core-shell structure prepared by the preparation method as described in any one of claims 3 to 9, in microwave absorption or sodium ion storage.

Images