Preparation method and application of FeIn2S4 / FeS-CN composite material

Abstract

The invention relates to the technical field of sodium ion batteries, in particular to a preparation method and application of a FeIn2S4 / FeS-CN composite material, and the preparation method comprises the following steps: S1, mixing and quantitatively adding InCl3 into PVP, mixing and quantitatively adding thioacetamide into FeSO4. 7H2O, taking ethylene glycol into a beaker, adding PVP to fully dissolve, then sequentially adding FeSO4. 7H2O and InCl3. 4H2O, ultrasonically stirring to fully dissolve, then adding thiourea, and stirring uniformly to obtain a FeIn2S4 / FeS-CN composite material; performing ultrasonic treatment; s2, hydro-thermal treatment: pouring the solution into an inner container, putting the inner container into a drying oven for heat preservation, taking out the solution, centrifugally cleaning, putting a sample obtained by centrifugation into a vacuum drying oven for drying, and carrying out coarse grinding on all powder in a mortar to obtain precursor powder; s3, high-temperature firing: putting the raw materials into a porcelain boat at room temperature in a tubular furnace, performing high-temperature firing in an Ar atmosphere, naturally cooling to room temperature, and taking out the raw materials; by fully combining the advantages of the three materials of FeS2, C and FeIn2S4, the electrode material which is excellent in electrical property, low in manufacturing cost, high in repetition rate, safe and environment-friendly is developed.

Description

Technical Field

[0001] This invention relates to the technical field of sodium-ion batteries, and in particular to the preparation method and application of FeIn2S4 / FeS@CN composite materials. Background Technology

[0002] Lithium-ion batteries (LIBs) have been commercially applied as a mature rechargeable battery; however, the scarcity of lithium resources continues to hinder their further development. Sodium-ion batteries (SIBs), due to their low cost, abundant reserves, and similar "rocking chair" sodium-ionization / desodiumization principle to LIBs, have become a hot topic for environmentally friendly energy storage solutions. Compared to lithium ions (−3.04 V vs. Li+ / Li, 0.76 Å for Li+), the relatively large ionic radius of sodium ions (−2.71 V vs. Na+ / Na, 1.02 Å for Na+) limits their capacity and energy density in SIBs. Therefore, significant efforts have been devoted to exploring an anode material with high capacity and stable electrochemical performance for SIBs.

[0003] Recently, due to the diversity, abundant redox active sites, rich ion diffusion channels, high specific capacity, and unique synergistic effects of bimetallic sulfides, increasing efforts have focused on their use as anodes in nano-inorganic biomass (NIBs). Meanwhile, heterojunction construction is a composition-tuning method that can effectively improve conductivity and accelerate charge transfer. On the one hand, the presence of a heterojunction can generate a built-in electric field that promotes charge and ion transfer. On the other hand, abundant defects such as vacancies and dislocations at the heterojunction crystal boundaries provide rich active sites for sodium adsorption. Therefore, heterojunction structures contribute to higher conductivity and faster transfer kinetics. It can also increase the crystallinity of the heterojunction interface and induce lattice mismatch, distortion, and defects, thereby modulating the reaction kinetics of the electrode material. Due to the continuous insertion and transformation / alloying reactions in SIBs, the volume change of the electrode material is rapid.

[0004] Ferrous sulfide (FeS), as a typical TMC (tumor-terminal sulfide), boasts high theoretical specific capacity (609 mAh⋅g⁻¹), low cost, environmental friendliness, and abundant resources. However, as a common drawback of sulfides, FeS also exhibits inherently low conductivity and unavoidable volume expansion during charge and discharge, leading to poor cycle and rate performance. Due to the significant differences in electronegativity and atomic radius between In and Fe, the precursors FeS and In₂S₃ have significantly different chemical bonds and crystal structures, making it difficult to form solid solutions and more likely to form two-phase heterogeneous interfaces. Furthermore, among various bimetallic sulfides, indium-based bimetallic sulfides, due to their excellent electrochemical and catalytic activity, show high-performance potential in various energy storage applications such as lithium-ion, sodium-ion, and lithium-sulfur batteries, as well as lithium-air batteries. C and FeIn₂S₄ possess ultra-strong pseudocapacitive behavior, ultra-low charge transfer resistance, high conductivity, low Na ion diffusion barrier, superior Na ion binding kinetics, and significant strain elimination characteristics, all of which contribute to their high-capacity ultrafast and ultra-stable Na ion storage. Therefore, theoretically, introducing FeIn2S4 into FeS can form abundant heterogeneous interfaces, effectively mitigating volume expansion caused by charging and discharging, and improving the conductivity, cycle stability, and capacity of the electrode. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a method for preparing FeIn2S4 / FeS@CN composite materials, which combine the advantages of FeS2, C, and FeIn2S4 materials to develop electrode materials with excellent electrical properties, low manufacturing cost, high repeatability, and safety and environmental friendliness, as well as their applications.

[0006] The preparation method of the FeIn2S4 / FeS@CN composite material of the present invention is completed by a one-step hydrothermal method, including the following steps: S1. Add InCl3 to PVP in a mixed amount, add thioacetamide to FeSO4·7H2O in a mixed amount, put ethylene glycol in a beaker, add PVP to dissolve it completely, then add FeSO4·7H2O and InCl3·4H2O in sequence, stir ultrasonically to dissolve it completely, then add thiourea and dissolve it ultrasonically to obtain a solution. S2. Hydrothermal treatment: Pour the solution into the inner liner and place it in an oven for heat preservation. After the solution is taken out, centrifuge and wash it. Place the centrifuged sample in a vacuum drying oven to dry it. Coarsely grind all the powders in a mortar to obtain the precursor powder. S3. High-temperature firing: In a tube furnace, a porcelain boat is placed at room temperature and fired at high temperature under an Ar atmosphere. After naturally cooling to room temperature, the FeIn2S4 / FeS@CN sodium-ion battery composite material is obtained. In S1, ethylene glycol solution is used as the solvent. Its high viscosity promotes the formation of spherical and regular morphologies, and achieves the purpose of controlling the particle size of nanoparticles. In S2, In is processed by a hydrothermal method. 3+ PVP-coated nanospheres are generated by incorporating FeS2 into the crystal lattice. In S3, FeS2 undergoes a phase transformation through high-temperature sintering, transforming into a heterogeneous phase of FeS and FeIn2S4. The volume of the spheres decreases and the specific surface area increases. Under high-temperature conditions, N in thiourea and N in PVP are incorporated into the carbon layer transformed by PVP, forming a nitrogen-doped carbon composite structure. Finally, a FeIn2S4 / FeS@CN composite material with FeIn2S4 / FeS@CN as the spherical framework and CN anchored on the FeIn2S4 / FeS@CN framework is obtained. Sulfides generated from different sulfur sources can have completely different morphologies and properties. In this invention, the feeding ratio of iron and sulfur sources is strictly controlled to generate the purest FeS2, free of other iron sulfide impurities. Thioacetamide is chosen because it can generate H2S at high temperatures, and H2S decomposes into S. 2- S 2- with Fe 2+ When FeS2 is formed, if the ratio of iron to sulfur source is different, for example, if there is a slight excess of sulfur source, a complex of FeS2 and Fe7S8 will be formed, which will ultimately affect the performance of FeIn2S4 / FeS@CN composite material. If the sulfur source is slightly insufficient, it will be difficult to decompose and form enough H2S. Without enough H2S, sulfur will decompose and form sulfur. 2- with Fe 2+ When combined with the formation of FeS2, the final product will preferentially form FeS instead of FeS2. This will introduce impurities and generate other composite materials during the preparation of TiO2 / C / FeS2 composite materials, thus affecting the performance of FeIn2S4 / FeS@CN. Since the amounts of iron and sulfur sources added in S4 are very small, if the amount of InCl3 powder added is too small, it will be difficult to increase the specific capacity by increasing the heterogeneous interface and specific surface area; if too much InCl3 powder is added, it will seriously affect the structure and morphology of the material and affect the stability of the generated FeIn2S4 / FeS@CN material.

[0007] Preferably, in step S1, PVP is added first, and the mixture is sonicated for 15-30 minutes.

[0008] Preferably, in S1, the mass ratio of FeSO4·7H2O to thioacetamide is 1:0.75-1.5.

[0009] Preferably, in S1, the mass ratio of PVP to FeSO4·7H2O is 1:1.78-3, and the mass ratio of PVP to InCl3 is 1:0.3-0.8.

[0010] Preferably, in step S2, the solution obtained from step S1 is kept at 160-200°C for 15-20 hours.

[0011] Preferably, in step S3, the temperature is increased to 550-700℃ at a rate of 3.5-5℃ / min and held for 3-4 hours in an Ar atmosphere, and then decreased to 200-300℃ at a rate of 3-5℃ / min.

[0012] Preferably, the FeIn2S4 / FeS@CN sodium-ion battery composite material has a spherical morphology with a particle size of 500-800 nm.

[0013] Preferably, the FeIn2S4 / FeS@CN composite material is used as the negative electrode material of a sodium-ion battery.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) This invention first synthesizes FeIn2S4 / FeS@CN composite material as a negative electrode material for sodium-ion batteries. After cycling 100 times at a current density of 1A / g, it maintains a high specific capacity of over 600mAh / g and after cycling 12,000 times at a current density of 5A / g, it maintains a specific capacity of up to 211mAh / g, indicating that it has high specific capacitance and good long cycle performance of fast charge and discharge. (2) The raw materials used in this invention have relatively low cost, simple preparation method, safety and environmental protection, and high repeatability. Attached Figure Description

[0015] Figure 1 , Figure 2 The image shows a SEM image of the FeIn2S4 / FeS@CN composite material prepared in this embodiment. As can be seen from the image, the morphology of the composite material is uniform spherical particles.

[0016] Figure 3 Cyclic voltammetry (CV) curves of the FeIn2S4 / FeS@CN composite material prepared in Example 1 as the negative electrode of a sodium-ion battery and as the negative electrode of a lithium-ion battery during the first four charge-discharge cycles.

[0017] Figure 4 The CV curves at different scan rates are shown for the FeIn2S4 / FeS@CN composite material prepared in Example 1 when used as the anode of a sodium-ion battery.

[0018] Figure 5 The fitted line between Log(i) and Log(ν) of the CV curves measured at different scan rates when the FeIn2S4 / FeS@CN composite material prepared in Example 1 is used as the negative electrode of a sodium-ion battery.

[0019] Figure 6 When the FeIn2S4 / FeS@CN composite material prepared in Example 1 is used as the anode of a sodium-ion battery, it achieves a voltage of 0.8 mV·s. -1 The contribution ratio of the pseudo-capacitor at the specified speed.

[0020] Figure 7 The pseudo-capacitance contribution ratio at different scan rates is shown for the FeIn2S4 / FeS@CN composite material prepared in Example 1 as the negative electrode of a sodium-ion battery.

[0021] Figure 8 The specific capacity-efficiency curve of the FeIn2S4 / FeS@CN composite material prepared in Example 1 as the anode of a sodium-ion battery at a current density of 1A / g.

[0022] Figure 9 The specific capacity-efficiency curve of the FeIn2S4 / FeS@CN composite material prepared in Example 1 as the anode of a sodium-ion battery at a current density of 2A / g is shown. After 1000 cycles, its specific capacity is still 402.9mAh / g.

[0023] Figure 10 The specific capacity-efficiency curve of the FeIn2S4 / FeS@CN composite material prepared in Example 1 as the anode of a sodium-ion battery at a current density of 5 A / g.

[0024] Figure 11 The images show the XRD patterns of the FeIn2S4 / FeS@CN composite material prepared in Example 1 and the FeS material prepared in Comparative Example 1.

[0025] Figure 12 The BET diagrams are shown for the FeIn2S4 / FeS@CN composite material of the example, the FeS material prepared in Comparative Example 1, and the precursor material prepared in Comparative Example 3.

[0026] Figure 13 Scanning electron microscope (SEM) image of the FeIn2S4 / FeS@CN composite material prepared for Comparative Example 1.

[0027] Figure 14 Scanning electron microscope (SEM) image of the FeIn2S4 / FeS@CN composite material prepared for Comparative Example 2.

[0028] Figure 15 Electron microscope (SEM) image of the FeIn2S4 / FeS@CN composite precursor prepared for Comparative Example 3. Detailed Implementation

[0029] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. The present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

[0030] Example 1 The preparation method of the FeIn2S4 / FeS@CN composite material of the present invention, S1. Take 40 ml of ethylene glycol in a beaker, add 0.2 g of PVP and sonicate for 30 min to dissolve completely, then add 0.278 g of FeSO4·7H2O and 0.1105 g of InCl3 and sonicate to dissolve completely, then add 0.228 g of thiourea and sonicate for 20 min to obtain the solution. S2. Hydrothermal treatment: Pour the solution into a polytetrafluoroethylene inner liner, place it in an oven at 180℃ for 18 hours, centrifuge and wash, place the centrifuged sample in a vacuum drying oven at 80℃ for 12 hours, and coarsely grind all the powders in a mortar to obtain a certain amount of precursor powder. S3. High-temperature firing: In a tube furnace, a porcelain boat is placed at room temperature and heated to 600℃ at 4℃ / min under an Ar atmosphere and held for 3 hours. Then, the temperature is lowered to 300℃ at 5℃ / min and allowed to cool naturally to room temperature before being removed and ground to obtain FeIn2S4 / FeS@CN composite material. Figure 1 , Figure 2 The image shows a SEM image of the FeIn2S4 / FeS@CN composite material prepared in this embodiment. As can be seen from the image, the morphology of the composite material is uniform spherical particles. Figure 3 The cyclic voltammetry (CV) curves of the FeIn2S4 / FeS@CN composite material prepared in Example 1 as the negative electrode of a sodium-ion battery and the negative electrode of a lithium-ion battery during the first four charge-discharge cycles are shown in the figure. It can be seen from the figure that the peak at 0.687V generated by the formation of the SEI film during the first discharge is almost unchanged in position and highly overlapped in shape in the following two cycles, which proves that the redox reaction of the material is highly reversible. Figure 4 The CV curves at different scan rates are shown for the FeIn2S4 / FeS@CN composite material prepared in Example 1 when used as the anode of a sodium-ion battery. Figure 5The fitted line between Log(i) and Log(v) of the CV curves measured at different scan rates when the FeIn2S4 / FeS@CN composite material prepared in Example 1 is used as the anode of a sodium-ion battery is shown. The b values ​​of the four peaks (three oxidation peaks at 0.8084V, 1.1644V, and 7.7V, and one reduction peak at 1.544V) are 0.90496, 0.76083, 0.91831, and 0.80169, respectively, indicating that diffusion control and pseudocapacitive behavior coexist in the sodium storage process in the NCSs electrode. Figure 6 When the FeIn2S4 / FeS@CN composite material prepared in Example 1 is used as the anode of a sodium-ion battery, it achieves a voltage of 0.8 mV·s. -1 The contribution ratio of pseudocapacitance at the rate is as high as 80.47% for FeIn2S4 / FeS@CN electrode. Such a high contribution value indicates that the sodium storage process is dominated by pseudocapacitance behavior and tends to appear on or near the material surface. Therefore, the dominant pseudocapacitance behavior is beneficial to the rapid transfer kinetics in the sodium storage process. Figure 7 The pseudocapacitance contribution ratio of the FeIn2S4 / FeS@CN composite material prepared in Example 1 as the negative electrode of a sodium-ion battery at different scan rates shows that the pseudocapacitance contribution ratio of the electrode material is positively correlated with the increase of the scan rate. Figure 8 The specific capacity-efficiency curves of the FeIn2S4 / FeS@CN composite materials prepared in Example 1, Comparative Example 1, and Comparative Example 2 as anodes of sodium-ion batteries at a current density of 1 A / g are shown. Among them, Example 1 still showed a specific capacity of up to 609.4 mAh / g after 100 cycles, and the coulombic efficiency remained at around 100%, demonstrating good cycle stability. Figure 9 The specific capacity-efficiency curve of the FeIn2S4 / FeS@CN composite material prepared in Example 1 as the anode of sodium-ion battery at a current density of 2A / g shows that its specific capacity is still 402.9mAh / g after 1000 cycles. Figure 10 The specific capacity-efficiency curve of the FeIn2S4 / FeS@CN composite material prepared in Example 1 as the anode of sodium-ion battery is shown at a current density of 5A / g. After 12,000 cycles, its specific capacity is 211.2mAh / g, which shows that the material has good long-cycle capability. Figure 11The figures show the XRD patterns of the FeIn2S4 / FeS@CN composite material prepared in Example 1 and the FeS material prepared in Comparative Example 1. As can be seen from the figures, the FeIn2S4 / FeS@CN composite material prepared in Example 1 is composed of two phases (FeIn2S4 phase and FeS phase), while the FeS material prepared in Comparative Example 1 by the same method is pure phase FeS, indicating that the preparation method is feasible. Figure 12 The images show the BET plots of the FeIn2S4 / FeS@CN composite material of this embodiment, the FeS material prepared in Comparative Example 1, and the precursor material prepared in Comparative Example 3. It can be clearly seen from the figures that the specific surface area of ​​the FeIn2S4 / FeS@CN composite material is significantly increased compared to pure iron sulfide particles. The specific surface area of ​​the precursor material before high-temperature calcination is also increased, which is consistent with the phenomenon observed by SEM. In this embodiment, the battery testing system of model CT2001A from Wuhan Landian Electronics Co., Ltd. and the electrochemical workstation of model CHI760D from Shanghai Chenhua Instrument Co., Ltd. were used to test the electrical properties of the FeIn2S4 / FeS@CN composite material. The electrochemical characterization method was as follows: FeIn2S4 / FeS@CN composite material was mixed with conductive carbon and carboxymethyl cellulose (CMC) in a ratio of 7:2:1 in deionized water to form a uniform slurry. The slurry was then uniformly coated onto copper foil and dried in a vacuum oven at 80°C for 12 hours. The copper foil was cut into discs with a diameter of 12 mm and a loading of 1 mg / cm². The electrode materials were assembled into a 2032 type button cell. Glass fiber filter paper (Whatman GF / A) was used as the separator, and 1 M NaPF6 in 100% DME was used as the electrolyte. All cells were placed for 12 hours before testing to ensure that the electrolyte was fully permeated and reached a stable open-circuit voltage. Constant current discharge / charge cycle tests were performed at 25°C using a LANHECT2001 battery testing system in the voltage range of 0 to 3 V.

[0031] Example 2 Based on Example 1, the preparation method of the FeIn2S4 / FeS@CN composite material of the present invention involves first adding PVP to S1 and then sonicating for 15-30 minutes. In S1, the mass ratio of FeSO4·7H2O to thioacetamide is 1:0.75-1.5; In S1, the mass ratio of PVP to FeSO4·7H2O is 1:1.78-3, and the mass ratio of PVP to InCl3 is 1:0.3-0.8. In step S2, the solution obtained from step S1 is kept at 160-200℃ for 15-20 hours. In S3, the temperature is increased to 550-700℃ at 3.5-5℃ / min and held for 3-4 hours under an Ar atmosphere, and then decreased to 200-300℃ at 3-5℃ / min. The FeSO4·7H2O sodium-ion battery composite material has a spherical morphology with a particle size of 500-800 nm. The FeIn2S4 / FeS@CN composite material is used as the negative electrode material for sodium-ion batteries.

[0032] Comparative Example 1 The difference between this comparative example and Example 1 is that the amount of FeSO4·7H2O used in S1 is 0.556g, and InCl3 is not added; all other contents are exactly the same. Figure 13 The electron microscope (SEM) image of the FeIn2S4 / FeS@CN composite material prepared for this proportion shows that the morphology in this comparative example is a rough-surfaced nanosphere.

[0033] Comparative Example 2 The difference between this embodiment and Embodiment 1 is that the amount of FeSO4·7H2O used in step S1 is 0.228 g, and the amount of InCl3 used is 0.221 g; all other contents are exactly the same. Figure 14 The image shows a scanning electron microscope (SEM) image of the FeIn2S4 / FeS@CN composite material prepared in this comparative example. As can be seen from the image, when there is an excess of indium source, the prepared material has two different morphologies: relatively large nanospheres and nanoflowers attached to the nanospheres. This may be because when there is too much indium source, the excess indium source overflows from the precursor nanospheres during the annealing process, forming nanoflowers with different elemental specific gravities than the nanospheres. This structure is prone to dendrite formation during charge and discharge, which can puncture the diaphragm and cause short circuits, affecting the cycling stability of the material.

[0034] Comparative Example 3 The difference between this comparative example and Example 1 is that this comparative example does not have step S3, and the sample obtained is the precursor powder of Example 1. Figure 15 This is a SEM image of the FeIn2S4 / FeS@CN composite precursor prepared in this comparative example. The image shows smooth spheres with a larger particle size and smaller specific surface area compared to Example 1. At this stage, the PVP on the surface of the spheres has not yet been sintered at high temperature to form a carbon layer coating the spheres, resulting in small pore areas. Figure 12 The results obtained from the BET test are consistent.

[0035] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing FeIn2S4 / FeS@CN composite material, characterized in that, The process is completed using a one-step hydrothermal method, including the following steps: S1. Add InCl3 to PVP in a mixed amount, add thioacetamide to FeSO4·7H2O in a mixed amount, put ethylene glycol in a beaker, add PVP to dissolve it completely, then add FeSO4·7H2O and InCl3·4H2O in sequence, stir ultrasonically to dissolve it completely, then add thiourea and dissolve it ultrasonically to obtain a solution. S2. Hydrothermal treatment: Pour the solution into the inner liner and place it in an oven for heat preservation. After the solution is taken out, centrifuge and wash it. Place the centrifuged sample in a vacuum drying oven to dry it. "Coarsely grind" all the powders in a mortar to obtain the precursor powder. S3. High-temperature firing: In a tube furnace, a ceramic boat is placed at room temperature and fired at high temperature under an Ar atmosphere. After naturally cooling to room temperature, the FeIn2S4 / FeS@CN sodium-ion battery composite material is obtained.

2. The preparation method of the FeIn2S4 / FeS@CN composite material as described in claim 1, characterized in that, In S1, PVP is added first, and the mixture is sonicated for 15-30 minutes.

3. The preparation method of the FeIn2S4 / FeS@CN composite material as described in claim 1, characterized in that, In S1, the mass ratio of FeSO4·7H2O to thioacetamide is 1:0.75-1.

5.

4. The preparation method of the FeIn2S4 / FeS@CN composite material as described in claim 1, characterized in that, In S1, the mass ratio of PVP to FeSO4·7H2O is 1:1.78-3, and the mass ratio of PVP to InCl3 is 1:0.3-0.

8.

5. The preparation method of the FeIn2S4 / FeS@CN composite material as described in claim 1, characterized in that, In step S2, the solution obtained from S1 is kept at 160-200℃ for 15-20 hours.

6. The preparation method of the FeIn2S4 / FeS@CN composite material as described in claim 1, characterized in that, In step S3, the temperature is increased to 550-700℃ at a rate of 3.5-5℃ / min and held for 3-4 hours under an Ar atmosphere, and then decreased to 200-300℃ at a rate of 3-5℃ / min.

7. The preparation method of the FeIn2S4 / FeS@CN composite material as described in claim 1, characterized in that, The FeIn2S4 / FeS@CN sodium-ion battery composite material has a spherical morphology with a particle size of 500-800 nm.

8. Application of FeIn2S4 / FeS@CN composite material, characterized in that, The FeIn2S4 / FeS@CN composite material is used as the negative electrode material for sodium-ion batteries.

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