Fe-based x Mo (1-x) Composite material of s2 and graphene laminates, method for preparing the same, battery negative electrode, lithium battery

Abstract

The application relates to a Fe x Mo (1‑x) S2 and graphene laminated composite material and a preparation method thereof, a battery negative electrode and a lithium battery, and belongs to the technical field of new battery materials. x Mo (1‑x) S2 and graphene laminated composite material, comprising a plurality of Fe x Mo (1‑x) S2 layers and graphene layers, the graphene layers are embedded between two adjacent Fe x Mo (1‑x) S2 layers to form a laminated structure; wherein x=0.1-0.4. x Mo (1‑x) S2 and graphene are stacked to form a laminated structure, which is beneficial to the rapid transmission and storage of lithium ions and improves the electrochemical performance of the battery; wherein the introduction of the graphene layer improves the overall conductivity, and the doping of Fe can further improve the conductivity of the Fe x Mo (1‑x) S2 layer and significantly improve the storage capacity of lithium ions.

Description

Technical Field

[0001] This application relates to the field of new battery materials technology, and particularly to a method based on Fe. x Mo (1-x) S2 and graphene laminate composite material and its preparation method, battery negative electrode, lithium battery. Background Technology

[0002] With rapid societal development and ever-increasing energy demands, existing non-renewable resources such as oil and coal are becoming increasingly scarce. Therefore, people are turning their attention to renewable energy sources such as solar, wind, and tidal power. However, due to the inherent limitations of these new energy sources, such as intermittency and geographical location, it is difficult for humans to effectively utilize them for daily needs. Therefore, developing new energy storage devices is urgently needed to fully utilize these recyclable energy sources. Electrochemical energy storage, as one of the most important new energy storage systems, has received widespread attention and research. Lithium-ion batteries, in particular, have advantages such as high operating voltage (~3.6V), high energy density (mass energy density 150~300Wh / kg, volumetric energy density 270~400Wh / L), long cycle life, low self-discharge rate, high safety, no memory effect, and environmental friendliness, leading to their widespread application in electric vehicles, aerospace, and other fields.

[0003] Currently, the commercially dominant graphite anode material has a relatively low theoretical capacity (372 mAh g). -1 The low rate performance of graphite is no longer sufficient to meet users' demands for higher energy density and functional density lithium-ion batteries. Researchers have conducted extensive studies on anode materials that can replace graphite. Among them, MoS2 has attracted much attention due to its graphene-like layered structure and high theoretical specific capacity (670 mAh / g). However, its poor conductivity, caused by the anisotropic ion transport channels resulting from its layered nanostructure and inherent semiconductor properties, leads to its slow lithium-ion transport rate. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the objective of this application includes providing a Fe-based... x Mo (1-x) The composite material of S2 and graphene stacked together, its preparation method, battery anode, and lithium battery are used to improve the lithium-ion transport rate of the composite material. When used as a lithium-ion battery anode, it can improve the capacity, rate performance, and cycle stability of the lithium-ion battery.

[0005] The embodiments of this application are implemented as follows:

[0006] Firstly, embodiments of this application provide a Fe-based x Mo (1-x)The composite material of S2 and graphene stack includes multiple Fe x Mo (1-x) The S2 layer and the graphene layer, with the graphene layer embedded between two adjacent Fe layers. x Mo (1-x) The S2 layer forms a stacked structure between its layers; where x = 0.1-0.4.

[0007] This composite material consists of multiple Fe... x Mo (1-x) The stacked structure is formed by stacking S2 layers and graphene layers (i.e., single-atom carbon layers), wherein the graphene layer is embedded in two adjacent Fe layers. x Mo (1-x) The S2 layer has a larger interlayer spacing compared to the traditional layered MoS2 structure. This design significantly reduces the diffusion resistance of lithium ions between layers, facilitating rapid lithium ion transport and improving battery charge / discharge efficiency. The introduction of the graphene layer effectively enhances the interlayer electron transport capability, improving overall conductivity. Graphene, as an excellent conductive material, can form a highly efficient electron conduction network in composite materials, further improving the electrochemical performance of the electrode. By introducing an iron source, Fe... x Mo (1-x) Mo in layer S2 4+ Fe 2+ or Fe 3+ Substitution, forming negatively charged Fe x Mo (1-x) The S2 layer. This change, based on the theory of like charges repelling each other, creates electrostatic repulsion between the layers, which helps to increase the Fe... x Mo (1-x) The S2 layer spacing enhances the lithium-ion transport rate. This electrostatic repulsion effect not only optimizes the ion migration path but also promotes the overall electrochemical reaction rate of the material. Fe doping can also effectively modulate the band gap of MoS2, altering its electronic structure and further improving the Fe... x Mo (1-x) The conductivity of the S2 layer; furthermore, the lattice distortion and local defects introduced during doping can serve as lithium-ion storage sites, significantly improving the lithium-ion storage capacity. This means that the composite material can accommodate more lithium ions in the same volume, increasing the energy density of the battery; moreover, the thinner monolayer Fe in this composite material... x Mo (1-x) The stacking of S2 and graphene, along with the overall embedding into an amorphous carbon substrate, effectively mitigates the volume expansion problem caused by lithium storage during charging and discharging. This design effectively prevents structural collapse or pulverization, improving the cycle stability of the electrode.

[0008] In some embodiments of this application, the total thickness of the stacked structure is 2-6 nm.

[0009] Controlling the total thickness of the stacked structure within the range of 2-6 nm can improve the ability of lithium ions to migrate rapidly during charging and discharging, thereby enhancing the battery's charging and discharging efficiency and rate. It also helps improve the battery's cycle stability, reduces material pulverization or stripping, and thus extends the battery's lifespan.

[0010] Secondly, embodiments of this application provide the above-mentioned Fe-based x Mo (1-x) A method for preparing a composite material of S2 and graphene stacks includes: mixing ammonium tetrathiomolybdate, an iron-containing compound, and an organic solvent to form a precursor liquid; placing the precursor liquid in a gas-phase high-pressure reactor at a reaction pressure of 10-100 MPa, followed by heating in a protective gas environment to obtain Fe. x Mo (1-x) A composite material of S2 and graphene stacks.

[0011] In this preparation method, after heating, the ammonium tetrathiomolybdate in the precursor liquid decomposes to form molybdenum disulfide nanosheets. The organic liquid and iron-containing compounds also decompose, and the iron ions in the iron-containing compounds replace the Mo ions on the already formed molybdenum disulfide nanosheets in situ, forming Fe. x Mo (1-x) In S2, organic solvents decompose into carbon-containing gaseous free radicals, such as OHCN:, OHC·, and ·CH3. Due to the large interlayer spacing of molybdenum disulfide (~0.62 nm), these small gaseous free radicals can insert into the interlayer of MoS2 and eventually transform into carbon atoms at higher temperatures, forming a single-atom carbon layer, i.e., a graphene layer, thus obtaining a monolayer Fe. x Mo (1-x) A layered structure of S2 and graphene. Compared with the traditional layered MoS2 structure, this structure has a larger interlayer spacing, thereby reducing the resistance to lithium-ion diffusion between layers and facilitating rapid lithium-ion transport. Therefore, Fe2+ synthesized by this method... x Mo (1-x) S2 and graphene have a single-layer structure, and when they are stacked sequentially in an orderly manner, they form a multilayer structure, which can effectively improve the lithium storage performance, cycle performance and rate performance of the composite material.

[0012] In some embodiments of this application, the iron-containing compound includes one or more of ferric naphthenate, ferric isooctanoate, ferrous oxalate, ferric nitrate, ferric acetate, and ferric acrylate.

[0013] In some embodiments of this application, the organic solvent includes one or more of dimethylpropionamide, methylpropionamide, dimethylformamide, methylformamide, and dimethylacetamide.

[0014] In some embodiments of this application, a liquid iron-containing compound is used as a reaction precursor, the precursor liquid containing an iron-containing compound, an organic solvent, and ammonium tetrathiomolybdate in a mass ratio of 1:(0.6-1):(0.4-0.7).

[0015] By controlling the mass ratio of iron-containing compounds, organic solvents, and ammonium tetrathiomolybdate within the above-mentioned range, iron ions can be effectively incorporated into Fe. x Mo (1-x) In the S2 structure, the electrochemical properties of the material, such as conductivity and lithium-ion storage capacity, can be tuned by controlling the doping amount. Furthermore, it helps to form suitable interlayer spacing, promoting rapid lithium-ion transport.

[0016] In some embodiments of this application, a solid iron-containing compound is used as a reaction precursor, and the precursor liquid contains an iron-containing compound, an organic solvent, and ammonium tetrathiomolybdate in a mass ratio of 1:(4-6):(3-5).

[0017] By controlling the mass ratio of iron-containing compounds, organic solvents, and ammonium tetrathiomolybdate within the above-mentioned range, iron ions can be effectively incorporated into Fe. x Mo (1-x) In the S2 structure, the electrochemical properties of the material, such as conductivity and lithium-ion storage capacity, can be tuned by controlling the doping amount. Furthermore, it helps to form suitable interlayer spacing, promoting rapid lithium-ion transport.

[0018] In some embodiments of this application, the heating temperature is 500–800°C and the heating time is 2–10 min.

[0019] Within a temperature range of 500–800℃ and a heating time of 2–10 minutes, it can effectively promote Fe x Mo (1-x) The formation of S2 with graphene, and the optimal doping effect of solid iron-containing compounds within this temperature range, effectively introducing iron into Fe. x Mo (1-x) In the S2 structure, its electrochemical performance is improved.

[0020] Thirdly, embodiments of this application provide a battery negative electrode, including any of the Fe-based electrodes mentioned above. x Mo (1-x) A composite material of S2 and graphene stacks.

[0021] This application is based on Fe x Mo (1-x)The composite material of S2 and graphene stacked together, when used as the negative electrode of lithium-ion batteries, has ultra-fast ion transport capability, ultra-high capacity, and excellent cycle stability.

[0022] Fourthly, embodiments of this application provide a lithium battery, including the aforementioned battery negative electrode.

[0023] Applying the above-mentioned battery negative electrode to lithium batteries can help improve the battery's electrochemical performance. Attached Figure Description

[0024] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a SEM image of the composite material obtained in Example 1 of this application;

[0026] Figure 2 This is a TEM image of the composite material obtained in Example 1 of this application;

[0027] Figure 3 The image shows the XRD pattern of the composite material obtained in Example 1 of this application.

[0028] Figure 4 The Raman spectrum of the composite material prepared in Example 1 of this application;

[0029] Figure 5 The XPS high-resolution spectrum of the Fe2p composite material prepared in Example 1 of this application;

[0030] Figure 6 This is a SEM image of the composite material obtained in Example 2 of this application;

[0031] Figure 7 This is a TEM image of the composite material obtained in Example 2 of this application;

[0032] Figure 8 The XRD pattern of the composite material obtained in Example 2 of this application;

[0033] Figure 9 The Raman spectrum of the composite material prepared in Example 2 of this application;

[0034] Figure 10 The XPS high-resolution spectrum of the Fe2p composite material prepared in Example 2 of this application;

[0035] Figure 11This is a SEM image of the composite material obtained in Example 3 of this application;

[0036] Figure 12 This is a TEM image of the composite material obtained in Example 3 of this application;

[0037] Figure 13 The image shows the XRD pattern of the composite material obtained in Example 3 of this application.

[0038] Figure 14 The Raman spectrum of the composite material obtained in Example 3 of this application;

[0039] Figure 15 The XPS high-resolution spectrum of the Fe2p composite material prepared in Example 3 of this application;

[0040] Figure 16 This is a SEM image of the composite material obtained in Example 4 of this application;

[0041] Figure 17 The XRD pattern of the composite material obtained in Example 4 of this application;

[0042] Figure 18 This is a SEM image of the composite material obtained in Example 5 of this application;

[0043] Figure 19 The XRD pattern of the composite material obtained in Example 5 of this application;

[0044] Figure 20 This is a SEM image of the composite material obtained in Example 6 of this application;

[0045] Figure 21 The XRD pattern of the composite material obtained in Example 6 of this application;

[0046] Figure 22 SEM image of the composite material prepared in Comparative Example 1 of this application;

[0047] Figure 23 TEM image of the composite material prepared in Comparative Example 1 of this application;

[0048] Figure 24 The image shows the XRD pattern of the composite material prepared in Comparative Example 1 of this application.

[0049] Figure 25 SEM image of the composite material prepared in Comparative Example 2 of this application;

[0050] Figure 26 TEM image of the composite material prepared in Comparative Example 2 of this application;

[0051] Figure 27 The image shows the XRD pattern of the composite material prepared in Comparative Example 2 of this application.

[0052] Figure 28 Thermogravimetric analysis (TGA) diagram of the composite material obtained in Example 3 of this application;

[0053] Figure 29 This is a thermogravimetric analysis diagram of the composite material obtained in Example 6 of this application. Detailed Implementation

[0054] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0055] The following describes an embodiment of this application based on Fe... x Mo (1-x) The paper provides a detailed explanation of the composite material of S2 and graphene stacks, its preparation method, battery anode, and lithium battery.

[0056] This application embodiment provides a Fe-based x Mo (1-x) The composite material of S2 and graphene stack includes multiple Fe x Mo (1-x) The S2 layer and the graphene layer, with the graphene layer embedded between two adjacent Fe layers. x Mo (1-x) The S2 layers form a stacked structure; where x = 0.1-0.4, for example, x = 0.1, 0.2, 0.3, 0.4.

[0057] This composite material consists of multiple Fe... x Mo (1-x) The stacked structure is formed by stacking S2 layers and graphene layers (carbon layers), wherein the graphene layers are embedded in two adjacent Fe layers. x Mo (1-x) The interlayer spacing of the S2 layers; compared with the traditional layered MoS2 structure, this structure has a larger interlayer spacing, thereby reducing the resistance to lithium-ion diffusion between layers and facilitating rapid lithium-ion transport. The graphene layers in the stacked structure can effectively enhance interlayer electron transport, thus effectively improving the overall conductivity of the material. Furthermore, by introducing an iron source, Mo... 4+ Fe 2+ or Fe 3+ Substitution, resulting in the formation of Fe x Mo (1-x) The S2 layer carries a negative charge. According to the theory that like charges repel each other, this leads to the formation of Fe... x Mo (1-x)Electrostatic repulsion is established between the S2 layers, which is beneficial for increasing Fe... x Mo (1-x) The interlayer spacing of S2 improves the lithium-ion transport rate. Fe doping can also effectively modulate the band gap of MoS2, change the electronic structure of MoS2, and thus improve the Fe... x Mo (1-x) The conductivity of the S2 layer. Fe doping also leads to lattice distortion and local defects, which can serve as lithium-ion storage sites, significantly improving lithium-ion storage capacity. Furthermore, the relatively thin monolayer Fe in this structure... x Mo (1-x) S2 and graphene are stacked together and embedded on an amorphous carbon substrate. This design effectively alleviates the volume expansion caused by lithium storage during charging and discharging, prevents structural collapse or pulverization, and thus improves the cycle stability of the electrode.

[0058] The total thickness of the stacked structure is 2-6 nm.

[0059] As an example, the total thickness of the stacked structure includes, but is not limited to, 2nm, 3nm, 4nm, 5nm, and 6nm.

[0060] The following discusses the above-mentioned Fe-based... x Mo (1-x) The preparation method of the composite material of S2 and graphene stack is described.

[0061] A Fe-based x Mo (1-x) The preparation method of the composite material of S2 and graphene stack includes the following steps:

[0062] S1. Mix ammonium tetrathiomolybdate, an iron-containing compound, and an organic solvent to form a precursor fluid.

[0063] The iron-containing compounds include, but are not limited to, one or more of ferric naphthenate, ferric isooctanoate, ferrous oxalate, ferric nitrate, ferric acetate, and ferric acrylate. The organic solvents include, but are not limited to, one or more of dimethylpropionylammonium, methylpropionylammonium, dimethylformamide, methylformamide, and dimethylacetamide, which are capable of readily dissolving ammonium tetrathiomolybdate.

[0064] If a liquid iron-containing compound is chosen as the reaction precursor, the precursor liquid contains an iron-containing compound, an organic solvent, and ammonium tetrathiomolybdate in a mass ratio of 1:(0.6~1):(0.4~0.7).

[0065] As an example, the mass ratio of the liquid iron-containing compound, the organic solvent, and ammonium tetrathiomolybdate includes, but is not limited to, 1:0.6:0.4, 1:0.6:0.5, 1:0.6:0.6, 1:0.6:0.7, 1:0.7:0.4, 1:0.7:0.5, 1:0.7:0.6, 1:0.7:0.7, 1:0.8:0.4, 1:0.8:0.5, 1:0.8:0.6, 1:0.8:0.7, 1:0.9:0.4, 1:0.9:0.5, 1:0.9:0.6, 1:0.9:0.7, 1:1:0.4, 1:1:0.5, 1:1:0.6, and 1:1:0.7.

[0066] If a solid iron-containing compound is chosen as the reaction precursor, the precursor liquid contains an iron-containing compound, an organic solvent, and ammonium tetrathiomolybdate in a mass ratio of 1:(4-6):(3-5).

[0067] As an example, the mass ratio of the solid iron-containing compound, the organic solvent, and ammonium tetrathiomolybdate includes, but is not limited to, 1:4:3, 1:4:4, 1:4:5, 1:5:3, 1:5:4, 1:5:5, 1:6:3, 1:6:4, and 1:6:5.

[0068] By controlling the iron doping amount within the above-mentioned mass ratio range, the electrochemical performance of the composite material can be improved. When the content of iron-containing compounds is within the above range, the electrostatic repulsion effect can increase the Fe content. x Mo (1-x) The distance between the S2 layers facilitates ion migration.

[0069] S2. The precursor liquid obtained in step S1 is placed in a gas-phase high-pressure reactor at a reaction pressure of 10-100 MPa, and then heated in a protective gas environment to obtain Fe. x Mo (1-x) A composite material of S2 and graphene stacks.

[0070] The protective gases include, but are not limited to, argon and nitrogen.

[0071] As an example, the precursor liquid obtained in step S1 is transferred to a high-pressure reactor and sealed under an argon atmosphere. The high-pressure reactor is then placed in a tube furnace and heated in an argon-filled environment to obtain Fe. x Mo (1-x) The composite material of S2 and graphene stacks. It should be noted that the high-pressure reactor used in this application can withstand a maximum temperature of 900℃ and a pressure of over 50MPa.

[0072] The heating temperature is 500–800℃, and the heating time is 2–10 minutes.

[0073] As an example, the heating temperature includes, but is not limited to, 500°C, 600°C, 650°C, 700°C, 750°C, and 800°C; the heating time includes, but is not limited to, 2 min, 3 min, 4 min, 5 min, 6 min, 7 min, 8 min, 9 min, and 10 min.

[0074] This application also provides a battery negative electrode, the preparation method of which includes the following steps:

[0075] The Fe-based preparation obtained by the above preparation scheme x Mo (1-x) The composite material of S2 and graphene stacked together was used as the active material. It was uniformly mixed and dispersed in N-methylpyrrolidone (NMP) with Super P (conductive agent) and polyvinylidene fluoride (PVDF, binder) at a mass ratio of 8:1:1. At the same time, it was magnetically stirred. After 15 hours, it was uniformly coated on copper foil and then transferred to a drying oven. It was first dried at 55°C under normal pressure for 4 hours to remove macromolecular solvents, and then dried under vacuum at 80°C for 12 hours. After the drying was completed, it was taken out and cut into round slices with a diameter of 12 mm.

[0076] This application also provides a lithium battery, the preparation method of which includes the following steps:

[0077] The lithium battery was assembled in an argon-filled glove box. The electrode shell used was a 2032 coin cell, the electrode was a disc placed in the glove box, the separator was Celgard 2500, the counter electrode and reference electrode were lithium sheets, and the electrolyte was 1M lithium hexafluorophosphate in ethylene carbonate, diethyl carbonate and dimethyl carbonate in a volume ratio of 1:1:1, with 5wt% fluoroethylene carbonate added. The supporting and conductive material was nickel foam with a diameter of 16mm and thicknesses of 1.5mm and 1mm, respectively.

[0078] The features and performance of this application will be further described in detail below with reference to the embodiments.

[0079] Example 1

[0080] This embodiment provides a Fe-based x Mo (1-x) The preparation method of the composite material of S2 and graphene stack includes the following steps:

[0081] (1) Ferrous oxalate, dimethylformamide and ammonium tetrathiomolybdate are mixed in a mass ratio of 1:4.5:3 as reaction precursors and transferred to a high-pressure reactor.

[0082] (2) The high-pressure reactor from step (1) was transferred into a tubular furnace, argon gas was introduced, and the temperature was maintained at 500°C for 2 minutes to obtain Fe. 0.35 Mo 0.65 A composite material of S2 and graphene stacks.

[0083] Example 2

[0084] This embodiment provides a Fe-based x Mo (1-x) The preparation method of the composite material of S2 and graphene stack includes the following steps:

[0085] (1) Ferric isooctanoate, dimethylformamide and ammonium tetrathiomolybdate are mixed in a mass ratio of 1:1:0.7 as reaction precursors and transferred to a high-pressure reactor.

[0086] (2) The high-pressure reactor from step (1) was transferred into a tubular furnace, argon gas was introduced, and the temperature was maintained at 800℃ for 10 minutes to obtain Fe. 0.10 Mo 0.90 A composite material of S2 and graphene stacks.

[0087] Example 3

[0088] This embodiment provides a Fe-based x Mo (1-x) The preparation method of the composite material of S2 and graphene stack includes the following steps:

[0089] (1) Ferric naphthenate, dimethylpropionamide and ammonium tetrathiomolybdate are mixed in a mass ratio of 1:0.6:0.4 as reaction precursors and transferred to a high-pressure reactor.

[0090] (2) The high-pressure reactor from step (1) was transferred into a tube furnace, argon gas was introduced, and the temperature was maintained at 600℃ for 5 minutes to obtain Fe. 0.40 Mo 0.60 A composite material of S2 and graphene stacks.

[0091] Example 4:

[0092] This embodiment is basically the same as embodiment 3, except that the heating temperature is 850℃.

[0093] Example 5

[0094] This embodiment is basically the same as Embodiment 3, except that the mass ratio of ferric naphthenate, dimethylpropionamide and ammonium tetrathiomolybdate is 1:0.5:0.3.

[0095] Example 6

[0096] This embodiment is basically the same as Embodiment 3, except that the mass ratio of ferric naphthenate, dimethylpropionamide and ammonium tetrathiomolybdate is 1:1.2:0.4.

[0097] Comparative Example 1

[0098] This comparative example is basically the same as Example 3, except that: iron naphthenate and dimethylpropionamide in step (1) are not added, only ammonium tetrathiomolybdate is added as a reaction precursor and transferred to a high-pressure reactor; then the high-pressure reactor is transferred into a tube furnace, argon gas is introduced and kept at 600°C for 5 minutes to obtain the composite material.

[0099] Comparative Example 2

[0100] This comparative example is basically the same as Example 3, except that: iron naphthenate in step (1) is not added, but dimethylpropionamide and ammonium tetrathiomolybdate in the same proportion as in Example 3 are added as reaction precursors, mixed and transferred to a high-pressure reactor, and then the high-pressure reactor is transferred into a tube furnace, argon gas is introduced and kept at 600°C for 5 minutes to obtain the composite material.

[0101] Please refer to Table 1 for some parameters of the above embodiments and comparative examples.

[0102] Table 1

[0103]

[0104] Experimental Example 1

[0105] This experiment used SEM (Scanning Electron Microscope), TEM (Transmission Electron Microscope), Raman (Raman spectra), XRD (Diffraction of Xrays), and XPS (X-ray Photoelectron Spectroscopy) to analyze the Fe-based products prepared in Examples 1-6 and Comparative Examples 1 and 2. x Mo (1-x) The composite material of S2 and graphene stack was characterized.

[0106] from Figure 1 It can be seen that particles with a diameter ranging from tens to hundreds of nanometers exhibit obvious agglomeration characteristics. Individual particles are basically irregular spherical with rough surfaces, and they are tightly packed together to form large aggregate structures. Figure 2The TEM image clearly shows relatively neat lattice fringes, which exhibit a regular arrangement of bright and dark areas. Since Fe, Mo, and S have higher atomic numbers than C, elements with higher atomic numbers scatter the electron beam more strongly, resulting in brighter images in TEM imaging. Therefore, Fe is the element with higher brightness in the image. x Mo (1-x) S2 has lower brightness, while C has lower brightness. Furthermore, the atomic sizes of Fe and Mo are significantly larger than those of C. From Figure 2 It can be seen that the two brighter layers with larger atomic sizes contain a darker layer with smaller atomic sizes, and the brightness and darkness of the layers are arranged in an orderly manner. This result proves that a monolayer Fe-based material has been successfully prepared. x Mo (1-x) The structure is a stack of MoS2 and graphene, with a thickness of 2-5 nm. The standard interplanar spacing of MoS2 is 0.62 nm, and the thickness of a single layer of graphene is approximately 0.36 nm. Therefore, the ideal interlayer spacing of the stacked structure should be 0.98 nm, but... Figure 2 The interplanar spacing of the lattice fringes is 1.07 nm, which is larger than the interlayer spacing of two MoS2 layers with a graphene layer sandwiched between them. This is because of the Fe in the introduced iron source. 2+ It will replace Mo in MoS2 in situ 4+ The location of the Fe gives the formed MoS2 layers a negative charge. According to the theory that like charges repel each other, electrostatic repulsion will occur between the MoS2 layers. Under the action of electrostatic repulsion, the spacing between the MoS2 layers will further increase. This further illustrates that Example 1 successfully prepared a Fe-based... 0.35 Mo 0.65 A composite material of S2 and graphene laminates. From Figure 3 It can be seen that a distinct diffraction peak appears at 8.0°, corresponding to the (002) crystal plane of MoS. According to Bragg's law (2dsinθ=nλ), the corresponding interlayer spacing is calculated to be 1.09 nm. This result is consistent with the TEM results, further proving the monolayer Fe. 0.35 Mo 0.65 The formation of S2 and graphene stacked structure. Figure 4 The Raman spectra show that at 374.1 and 398.5 cm⁻¹... -1 MoS2 appeared there. and A 1g The peaks indicate the presence of MoS2 material in the composite material. Furthermore, peaks at 1352.1 and 1595.2 cm⁻¹ indicate the presence of MoS₂ material. -1 The presence of typical D and G peaks for carbon materials at this location confirms the existence of free carbon in the nanocomposite material. Figure 5 The XPS high-resolution spectra of Fe2p showed that FeMoS phase Fe2p appeared at 707.6, 713.7, and 723.2 eV, respectively.3 / 2 and Fe 2p 1 / 2 The characteristic peaks indicate that Fe was successfully doped into MoS2, yielding Fe... 0.35 Mo 0.65 S2 material.

[0107] from Figure 6 The SEM images show that it exhibits a morphology similar to that of Example 1. Figure 7 The TEM image clearly shows relatively neat lattice fringes, and the lattice fringes exhibit a regular pattern of bright and dark arrangement, which is consistent with... Figure 2 The structure is similar, proving that it is based on a single layer of Fe 0.10 Mo 0.90 The formation of an S2-graphene stack structure with a thickness of 2-5 nm is achieved. The interplanar spacing of the lattice fringes is 1.10 nm, which is due to the monolayer Fe. 0.10 Mo 0.90 A layer of graphene and Fe-doped material is sandwiched between S2. 3+ This results in electrostatic repulsion between layers, which in turn increases the interlayer spacing. Figure 8 The XRD pattern showed a diffraction peak at 7.8°, and the corresponding interlayer spacing was calculated to be 1.12 nm, which is consistent with the TEM results. Figure 9 The Raman spectra show that at 374.1 and 398.5 cm⁻¹... -1 MoS2 appeared there. and A 1g The peaks indicate the presence of MoS2 material in this nanocomposite material. Furthermore, peaks at 1357.5 and 1587.3 cm⁻¹ indicate... -1 The presence of typical D and G peaks for carbon materials at this location confirms the presence of free carbon in the composite material. Figure 10 The XPS spectra show Fe2p FeMoS phase at 713.2 and 724.7 eV. 3 / 2 and Fe 2p 1 / 2 Characteristic peaks, and Figure 5 The results were similar, indicating that Fe was successfully doped into MoS2, yielding Fe... 0.10 Mo 0.90 S2 material.

[0108] from Figure 11 It can be seen that it exhibits a morphology similar to that of Example 1. Figure 12 The TEM image clearly shows relatively neat lattice fringes, which exhibit a regular pattern of bright and dark arrangement, consistent with... Figure 2 The structure is similar, proving that it is based on a single layer of Fe 0.40 Mo 0.60The formation of an S2-graphene stack structure with a thickness of 2-5 nm was observed. The interplanar spacing of the crystal fringe was 1.16 nm, which is larger than the 1.07 nm in Example 1. This is because, in addition to the monolayer Fe... 0.40 Mo 0.60 Besides the presence of a graphene layer between S2, the iron source in Example 3 has a higher mass ratio than in Example 1, thus providing more Fe. 2+ In situ replacement of Mo in MoS2 4+ The location of the crystal planes results in greater electrostatic repulsion between the layers, further increasing the interlayer spacing. Furthermore, the interplanar spacing of its crystal plane fringes is 1.16 nm, which is larger than the 1.10 nm in Example 2. This is because the iron source in Example 3 is Fe. 2+ In Example 1, the iron source is Fe. 3+ , and Fe 3+ In comparison, Fe 2+ Replace Mo 4+ This will cause the MoS2 layer to carry two negative charges (while Fe) 3+ (Substitution is a negative charge), therefore Fe 2+ In-situ substitution is better than Fe 3+ This results in greater electrostatic repulsion between layers, thereby further increasing the interlayer spacing. Figure 13 The XRD pattern showed a diffraction peak at 7.5°, and the corresponding interlayer spacing was calculated to be 1.17 nm, which is consistent with the TEM results. Figure 14 The Raman spectra show that at 374.1 and 398.5 cm⁻¹... -1 MoS2 appeared there. and A 1g The peaks indicate the presence of MoS2 material in the composite material. Furthermore, peaks at 1362.9 and 1587.3 cm⁻¹ are observed. -1 The presence of typical D and G peaks for carbon materials at this location confirms the existence of free carbon in the nanocomposite material. Figure 15 The XPS high-resolution spectrum of Fe2p shows that FeMoS phase Fe 2p appears at 712.2 and 725.9 eV, respectively. 3 / 2 and Fe 2p 1 / 2 The characteristic peaks indicate that Fe was successfully doped into MoS2, yielding Fe... 0.40 Mo 0.60 S2 material. From Figure 28 The thermogravimetric analysis (TGA) chart shows that the material loses 23.7% of its mass after being heated in air. The mass loss is mainly due to the volatilization of carbon material in the form of CO2 at high temperatures. The greater the mass loss, the higher the carbon content.

[0109] from Figure 16As can be seen, the random distribution of nanoscale irregular spherical particles and micron-scale sheet-like interwoven structures indicates that a higher reaction temperature yielded an impurity phase. Figure 17 The XRD pattern shows that, in addition to the diffraction peak corresponding to the (002) crystal plane of MoS2 at 7.7°, diffraction peaks corresponding to Fe9S3 at 33.7°, 43.7° and 53.1° were also found. 10 The diffraction peaks corresponding to the (760), (866), and (1190) crystal planes indicate that as the temperature increases, the introduced iron source contributes to the formation of Fe. 0.38 Mo 0.62 Simultaneously with S2, Fe9S is also generated. 10 ,illustrate Figure 16 The bulk impurity phase that appeared was Fe9S 10 .

[0110] from Figure 18 As can be seen, the random distribution of micron-sized bulk structures and nano-sized spherical particles indicates that excessive addition of ferric naphthenate leads to the formation of a large number of bulk impurity phases. Figure 19 The XRD pattern showed a diffraction peak at 7.8° belonging to the (002) crystal plane of MoS2. Furthermore, diffraction peaks belonging to Fe were observed at 29.9°, 33.8°, 43.8°, and 53.1°. 1-x The diffraction peaks corresponding to the (200), (205), (2010), and (220) crystal planes of S. Example 5 shows that when there is too much iron source and relatively insufficient carbon, molybdenum, and sulfur sources, the prepared product will form Fe 0.40 Mo 0.60 Simultaneously with S2, Fe is also generated. 1-x S, Explanation Figure 18 The bulk impurity phase that appears is Fe. 1-x S.

[0111] from Figure 20 As can be seen, it exhibits a morphology similar to that of Example 3, indicating that excess dimethylformamide has little effect on morphology. Figure 21 The XRD pattern shows a diffraction peak at 7.9° belonging to the (002) crystal plane of MoS2, and the calculated interplanar spacing is 1.11 nm, confirming the presence of a monolayer Fe. 0.40 Mo 0.60 The formation of the S2-graphene tandem structure. From Figure 29 The TGA plot showed that the material lost 36.4% of its mass after being heated in air, which was significantly higher than the value in Example 3, indicating that the composite material in Example 6 had a higher carbon content.

[0112] from Figure 22As can be seen, unlike the morphology of the composite material in Example 3, the sample in Comparative Example 1 has a morphology of randomly distributed micron-sized bulk particles. This indicates that the organic solvent has a significant impact on the morphology of the prepared product during the preparation process. Figure 23 The TEM images clearly show multiple layers of relatively orderly lattice fringes with uniform spacing and an interplanar spacing of approximately 0.62 nm, indicating that the prepared product is a bulk multilayer MoS2 material. Furthermore, Figure 24 The XRD pattern showed a diffraction peak at 13.9°, and the corresponding interlayer spacing was calculated to be 0.63 nm, which is consistent with the interlayer spacing of bulk multilayer MoS2 materials and is also consistent with the TEM results.

[0113] from Figure 25 It can be seen that it exhibits a morphology similar to that of Example 3. Figure 26 The TEM images clearly show relatively neat lattice fringes with uniform spacing and an interplanar spacing of approximately 0.98 nm, confirming the formation of a monolayer MoS2 and graphene stacked structure with a thickness of 2-6 nm. Furthermore... Figure 27 The XRD pattern showed a diffraction peak at 8.8°, and the corresponding interplanar spacing was calculated to be 0.99 nm, which is consistent with the TEM results, further proving the formation of the stacked structure.

[0114] Experimental Example 2

[0115] This experimental example compares the Fe-based samples prepared in Examples 1-6 and Comparative Examples 1 and 2. x Mo (1-x) A lithium-ion battery was fabricated using a composite material of S2 and graphene as the negative electrode material. The battery was then subjected to performance tests, including initial charge-discharge capacity, initial coulombic efficiency, cycle performance, and rate performance. The lithium-ion battery fabrication process is as follows: Various Fe-based composite materials were used... x Mo (1-x)The S2 and graphene laminate composite material was mixed with acetylene black and PVDF at a mass ratio of 8:1:1, and then added to NMP for magnetic stirring. After 15 hours, the mixture was evenly coated onto a copper foil current collector and transferred to a vacuum drying oven. It was first dried at 55°C under normal pressure for 4 hours to remove macromolecular solvents, and then dried under vacuum at 80°C for 12 hours. After drying, it was cut into 12mm diameter discs and placed in an argon-filled glove box. Battery assembly was then performed in an argon-filled glove box. The experiment was conducted in a box, where the electrode shell used a 2032 coin cell, the electrode sheet was the circular sheet prepared above and placed in the glove box, the separator was Celgard 2500, the counter electrode and reference electrode were lithium sheets, and the electrolyte was 1 mol of lithium hexafluorophosphide in ethylene carbonate, diethyl carbonate and dimethyl carbonate in a volume ratio of 1:1:1, with 5% fluoroethylene carbonate added. The material with supporting and conductive functions was nickel foam with a diameter of 16 mm and thicknesses of 1.5 mm and 1 mm, respectively.

[0116] Electrochemical performance testing was performed on the CT2001A Blue Battery Testing System, with a test voltage range of 0.01-3V and a current density of 0.1-20A / g.

[0117] Please refer to Table 2 for the results of the above performance tests.

[0118] Table 2

[0119]

[0120] Table 3

[0121]

[0122]

[0123] As can be seen from Table 2, the composite material provided in this application has excellent lithium storage performance and cycle performance. Among them, the composite materials in Examples 1-3 have initial discharge capacities of 1829.9 mAh / g, 1479.4 mAh / g, and 1898.9 mAh / g at a current density of 0.1 A / g, respectively, and initial charge capacities of 1387.1 mAh / g, 1085.9 mAh / g, and 1445.1 mAh / g, respectively, with initial coulombic efficiencies of 75.8%, 73.4%, and 76.1%, respectively. This indicates that the composite material provided in this application has ultra-high lithium storage capacity and good initial coulombic efficiency. Furthermore, at a current density of 0.1 A / g, the reversible capacities obtained after 100 cycles of the lithium-ion batteries prepared from the composite materials of Examples 1-3 at a current density of 0.1 A / g were 1398.2 mAh / g, 1089.2 mAh / g, and 1469.8 mAh / g, respectively; and at a current density of 5 A / g, the reversible capacities obtained after 5000 cycles were 858.7 mAh / g, 609.2 mAh / g, and 898.3 mAh / g, respectively; indicating that the composite material provided in this application has excellent cycle stability.

[0124] As can be seen from the data in Table 3, the lithium-ion batteries prepared by the composite materials of Examples 1-3 remain stable during high-rate charge and discharge processes. In particular, when the current density returns to 0.1 A / g, their reversible capacities are still as high as 1384.5 mAh / g, 1084.6 mAh / g, and 1438.5 mAh / g, respectively, indicating that the composite materials provided in this application maintain good stability during high-rate charge and discharge processes.

[0125] In Example 4, the heating temperature was increased, and the capacity obtained by this composite material at current densities of 0.1, 0.2, 0.5, 1, 2, 5, 10, and 20 A / g was lower than that obtained in Example 3 based on monolayer Fe. 0.40 Mo 0.60 The rate performance of the S2-graphene laminated nanocomposite structure is due to the formation of micron-sized sheet-like Fe9S. 10 Impurities hinder the rapid transport and storage of lithium ions, thereby reducing the corresponding capacity and rate performance.

[0126] In Example 5, when ferric naphthenate was added in excess, the capacity obtained by the composite material at current densities of 0.1, 0.2, 0.5, 1, 2, 5, 10, and 20 A / g was lower than that obtained in Example 3 based on monolayer Fe. 0.40 Mo 0.60 The rate performance of the S2-graphene laminated nanocomposite structure is due to the generation of micron-sized bulk Fe. 1-x The impurity phase of sulfur is detrimental to the rapid transport and storage of lithium ions, thereby reducing the corresponding capacity and rate performance.

[0127] In Example 6, when dimethylformamide was in excess, the capacity obtained by this composite material at current densities of 0.1, 0.2, 0.5, 1, 2, 5, 10, and 20 A / g was lower than that obtained in Example 3 based on monolayer Fe. 0.40 Mo 0.60 The rate performance of the S2-graphene multilayer nanocomposite structure is improved. This is because the carbon source in the reaction precursor is significantly increased, leading to an overall increase in the carbon content of the composite material. Furthermore, the lithium storage capacity of carbon materials is much lower than that of Fe. 0.40 Mo 0.60 Therefore, the lithium storage capacity of the composite material in Example 6 is lower than that in Example 3.

[0128] In Comparative Example 1, only ammonium tetrathiomolybdate was used as the reaction precursor. At current densities of 0.1, 0.2, 0.5, 1, 2, 5, 10, and 20 A / g, the capacity obtained by this material was lower than that obtained in Example 3 based on a monolayer Fe. 0.40 Mo 0.60 Rate performance of S2-graphene multilayer nanocomposites. This indicates that Fe doping, obtaining the multilayer structure, increasing the interlayer spacing, and achieving the desired nanostructure all contribute to improving lithium storage capacity and rate performance.

[0129] In Comparative Example 2, without the addition of ferric naphthenate, only dimethylpropionamide and ammonium tetrathiomolybdate in the same proportions as in Example 3 were added as reaction precursors. At current densities of 0.1, 0.2, 0.5, 1, 2, 5, 10, and 20 A / g, the capacity obtained by this composite material was lower than that obtained in Example 3 based on monolayer Fe. 0.40 Mo 0.60 The rate performance of the S2-graphene multilayer nanocomposite structure was also demonstrated, indicating that Fe doping and increased interlayer spacing are beneficial to improving lithium storage capacity and rate performance.

[0130] The embodiments described above are some, but not all, of the embodiments of this application. The detailed description of the embodiments of this application is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

Claims

1. A Fe-based x Mo (1-x) The method for preparing a composite material of S2 and graphene stacks is characterized by, include: Ammonium tetrathiomolybdate, an iron-containing compound, and an organic solvent are mixed to form a precursor liquid; the organic solvent includes one or more of dimethylpropionamide, methylpropionamide, dimethylformamide, methylformamide, and dimethylacetamide. The precursor liquid was placed in a gas-phase high-pressure reactor at a pressure of 10-100 MPa, and then heated in a protective gas environment at a temperature of 500-800°C for 2-10 minutes to obtain the Fe. x Mo (1-x) A composite material of S2 and graphene stacks; The Fe-based x Mo (1-x) The composite material of S2 and graphene stack includes multiple Fe x Mo (1-x) An S2 layer and a graphene layer, wherein the graphene layer is embedded in two adjacent Fe layers. x Mo (1-x) The S2 layers form a stacked structure; where x = 0.1-0.4; the total thickness of the stacked structure is 2-6 nm.

2. The preparation method according to claim 1, characterized in that, The iron-containing compounds include one or more of the following: ferric naphthenate, ferric isooctanoate, ferrous oxalate, ferric nitrate, ferric acetate, and ferric acrylate.

3. The preparation method according to claim 2, characterized in that, A liquid iron-containing compound is used as a reaction precursor, wherein the precursor liquid contains the iron-containing compound, the organic solvent, and the ammonium tetrathiomolybdate in a mass ratio of 1:(0.6~1):(0.4~0.7).

4. The preparation method according to claim 2, characterized in that, A solid iron-containing compound is used as a reaction precursor, wherein the precursor liquid contains the iron-containing compound, the organic solvent, and the ammonium tetrathiomolybdate in a mass ratio of 1:(4~6):(3~5).

5. A Fe-based preparation obtained by the preparation method according to any one of claims 1 to 4 x Mo (1-x) The composite material of S2 and graphene stack includes multiple Fe x Mo (1-x) An S2 layer and a graphene layer, wherein the graphene layer is embedded in two adjacent Fe layers. x Mo (1-x) The S2 layer forms a stacked structure between its layers; among which... x = 0.1-0.4; the total thickness of the stacked structure is 2-6 nm.

6. A battery negative electrode, characterized in that, Including the Fe-based method described in claim 5 x Mo (1-x) A composite material of S2 and graphene stacks.

7. A lithium battery, characterized in that, Includes the battery negative electrode as described in claim 6.

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