A nitrogen-doped carbon-coated iron disulfide / gallium trisulfide composite material, a preparation method thereof and application thereof in rechargeable batteries

Abstract

The application discloses a nitrogen-doped carbon-coated ferrous disulfide / trigallic sulfide composite material and a preparation method and application thereof in a rechargeable battery. Firstly, a rice-shaped nitrogen-doped carbon-coated Fe2O3 / Ga2O3 nanorod precursor is prepared through two-step hydrothermal reaction, and then the precursor is mixed with sulfur powder and calcined in a weak reducing atmosphere to prepare a rice-shaped nitrogen-doped carbon-coated ferrous disulfide / trigallic sulfide heterojunction composite material. In the composite material, the binary metal sulfide rice-shaped FeS2 / Ga2S3 nanorod is encapsulated in a carbon layer, and a heterojunction interface between FeS2 and Ga2S3 crystals can induce an internal electric field to accelerate ion diffusion kinetics, improve conductivity and provide abundant reaction sites for sodium energy storage. When the composite material is used as a negative electrode active material to prepare a negative electrode sheet and then assembled into a sodium ion battery, the sodium ion battery has high reversible capacity, high specific capacity, stable cycle performance and robust rate performance.

Description

Technical Field

[0001] This invention belongs to the technical field of sodium-ion battery anode materials, specifically relating to a nitrogen-doped carbon-coated iron disulfide / gallium trisulfide composite material, its preparation method, and its application in rechargeable batteries. Background Technology

[0002] Sodium-ion batteries (SIBs) are considered one of the most promising alternative technologies for large-scale energy storage and low-speed electric vehicles due to their abundant sodium resources, low cost, and high safety.

[0003] However, the performance bottlenecks of existing electrode materials limit their commercialization: For cathode materials, layered oxides and polyanionic compounds face problems such as low sodium ion diffusion rates and significant volume expansion; Prussian blue materials suffer from severe capacity decay due to the presence of water of crystallization. For anode materials, hard carbon materials have limited capacity (<300 mAh / g), titanium-based materials have insufficient energy density, and while metal sulfides, such as FeS2, have a high theoretical capacity of 894 mAh / g, their poor conductivity and volume expansion rate exceeding 200% lead to a sharp decline in cycle stability.

[0004] FeS2, as a typical conversion-type anode material, involves a multi-step reaction in its sodium storage mechanism, but suffers from the following problems: Poor conductivity: FeS2 has low intrinsic conductivity, leading to slow reaction kinetics and poor rate performance. Volume expansion: Drastic volume changes during charge and discharge, causing structural collapse and active material shedding. Interfacial side reactions: The generated Na2S insulating layer hinders ion transport, further exacerbating capacity decay.

[0005] Currently, the main modification strategies for FeS2 include carbon coating and heterostructure construction, but these have the following limitations: the conductivity of carbon materials is only slightly improved, the carbon layer only provides physical support and does not fundamentally solve the intrinsic defects of FeS2; the interface control of heterostructures is insufficient, traditional composite methods are difficult to achieve uniform nanoscale coating, and the interface charge transfer efficiency is low. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a nitrogen-doped carbon-coated iron disulfide / gallium trisulfide composite material and its preparation method. The nitrogen-doped carbon-coated iron disulfide / gallium trisulfide composite material is a regular rice-shaped nanorod with a width of 100-300 nm and a length of 1-2 μm. Using it as the negative electrode active material of sodium-ion batteries greatly improves the cycle stability, lifespan, and battery capacity of sodium-ion batteries.

[0007] The present invention also provides the application of the nitrogen-doped carbon-coated iron disulfide / gallium trisulfide composite material in rechargeable batteries, which can be used as a negative electrode active material to prepare a sodium-ion battery negative electrode, and then to prepare a liquid or solid sodium-ion battery.

[0008] The present invention also provides a rechargeable battery, wherein the negative electrode active material of the rechargeable battery is the nitrogen-doped carbon-coated iron disulfide / gallium trisulfide composite material described in the present invention, and the battery has excellent cycle stability, service life and battery capacity.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0010] This invention provides a method for preparing a nitrogen-doped carbon-coated iron disulfide / gallium trisulfide composite material, the method comprising the following steps:

[0011] (1) The iron source and hexadecyltrimethylammonium bromide were dispersed in deionized water and subjected to a hydrothermal reaction to obtain rice-shaped FeOOH nanorod precursors;

[0012] (2) FeOOH nanorod precursor, organic ligand, carbon source and gallium source are mixed in a solvent and subjected to hydrothermal reaction to obtain rice-shaped nitrogen-doped carbon-coated Fe2O3 / Ga2O3 nanorod precursor;

[0013] (3) The nitrogen-doped carbon-coated Fe2O3 / Ga2O3 nanorod precursor and sulfur powder were mixed and calcined at 600-750 °C in a weak reducing atmosphere to obtain nitrogen-doped carbon-coated iron disulfide / gallium trisulfide composite material (C / FeS2 / Ga2S3 composite material).

[0014] In step (1), the molar ratio of the iron source and hexadecyltrimethylammonium bromide is 1-3:1, preferably 1.82:1; the concentration of the iron source in deionized water is 0.1-0.3 mol / L.

[0015] In step (1), the iron source is any one or both of ferric chloride or ferric nitrate.

[0016] In step (1), the hydrothermal reaction conditions are: 70-100 ℃ for 10-14 h, preferably 80 ℃ for 12 h.

[0017] In step (1), the rice-shaped FeOOH nanorod precursor has a smooth surface, a width of 100-300 nm, and a length of 1-1.5 μm.

[0018] In step (2), the organic ligand is sodium citrate; the carbon source is urea; the gallium source is gallium chloride or gallium nitrate; and the solvent is a mixed solution of deionized water and polymaleic acid in a volume ratio of 75-80:1.

[0019] In step (2), the mass ratio of FeOOH nanorod precursor, organic ligand, carbon source and gallium source is 0.03-0.1:1.5-2.0:0.1-0.2:0.1-0.5; the concentration of FeOOH nanorod precursor in solvent is 0.0015-0.005 g / mL.

[0020] In step (2), the hydrothermal reaction conditions are: 150-200 °C for 10-14 h, preferably 180 °C for 12 h.

[0021] In step (2), the width of the rice-shaped Fe2O3@Ga2O3 nanorod precursor is 100-300 nm and the length is 1-1.5 μm.

[0022] In step (3), the mass ratio of nitrogen-doped carbon-coated Fe2O3 / Ga2O3 nanorod precursor to sulfur powder is 1:8-12, preferably 1:10.

[0023] In step (3), the weak reducing atmosphere is a mixture of argon and hydrogen, wherein the volume percentages of argon and hydrogen are 95% and 5%, respectively.

[0024] In step (3), the calcination conditions are calcination at 700 °C for 2 h.

[0025] The nitrogen-doped carbon-coated iron disulfide / gallium trisulfide composite material prepared by the preparation method of the present invention is a rice-shaped nanorod with a rough surface, a width of 100-300 nm and a length of 1-1.5 μm.

[0026] The present invention also provides the application of the nitrogen-doped carbon-coated iron disulfide / gallium trisulfide composite material in rechargeable batteries.

[0027] The present invention relates to the application of nitrogen-doped carbon-coated iron disulfide / gallium trisulfide composite material in sodium-ion batteries, wherein the nitrogen-doped carbon-coated iron disulfide / gallium trisulfide composite material serves as the negative electrode active material of sodium-ion batteries.

[0028] The present invention also provides a sodium-ion battery negative electrode sheet, wherein the sodium-ion battery negative electrode sheet is prepared using the nitrogen-doped carbon-coated iron disulfide / gallium trisulfide composite material described in the present invention as the negative electrode active material.

[0029] The method for preparing the sodium-ion battery negative electrode sheet is as follows: the nitrogen-doped carbon-coated iron disulfide / gallium trisulfide composite material of the present invention is mixed with conductive carbon black and PVDF at a mass ratio of 7:2:1 and stirred magnetically for 6-8 h. The mixture is then uniformly dispersed in N-methylpyrrolidone (NMP). The uniformly mixed slurry is coated onto copper foil using a coater and placed in a vacuum drying oven at 60-80 °C for 12-24 h. After drying, the foil is pressed into sheets using a tablet press and then cut into electrode sheets using a cutting machine.

[0030] The present invention also provides a sodium-ion battery, wherein the sodium-ion battery is assembled with the sodium-ion battery negative electrode sheet as the negative electrode.

[0031] The sodium-ion battery is either a liquid sodium-ion battery or a solid sodium-ion battery.

[0032] The preparation method of the liquid sodium-ion battery is as follows: One drop of electrolyte is added to the negative electrode shell of the battery, followed by the placement of the sodium-ion battery negative electrode sheet. Then, one drop of electrolyte is added, followed by the placement of glass fiber. Three drops of electrolyte are added to the glass fiber, and a sodium sheet is placed as the counter electrode. Two pieces of nickel foam are then placed, followed by four drops of electrolyte. The positive electrode shell is then covered, and the battery is pressed and sealed using a hydraulic press. The battery is left to stand for 6-12 hours. The electrolyte is a mixture of NaPF6 and DEGDME; the sodium sheet has a purity of Na ≥ 99.99% and a thickness of 0.5 mm.

[0033] The solid-state sodium-ion battery is prepared as follows: a gasket is placed on the negative electrode shell of the battery, then the sodium-ion battery negative electrode sheet is placed on it, followed by the solid electrolyte after powder pressing. 20 microliters of electrolyte are dripped onto the electrolyte sheet for wetting, then a sodium sheet is placed as the counter electrode. The positive electrode shell is then covered, and the battery is pressed and sealed using a hydraulic press. The battery is then left to stand for 6-12 hours. The solid electrolyte is Na3PS4; the electrolyte is a mixture of NaPF6 and DEGDME.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] The present invention provides a method for preparing nitrogen-doped carbon-coated iron disulfide / gallium trisulfide composite materials. First, a rice-shaped nitrogen-doped carbon-coated Fe₂O₃ / Ga₂O₃ nanorod precursor is prepared via a two-step hydrothermal reaction. This precursor is then mixed with sulfur powder and calcined under a weakly reducing atmosphere to obtain a rice-shaped nitrogen-doped carbon-coated iron disulfide / gallium trisulfide (C / FeS₂ / Ga₂S₃) heterojunction composite material, in which bimetallic sulfide FeS₂ / Ga₂S₃ nanoparticles are encapsulated within a carbon layer. The heterojunction interface between FeS₂ and Ga₂S₃ crystals can induce an internal electric field to accelerate ion diffusion kinetics, improve conductivity, and provide abundant reaction sites for sodium energy storage. Furthermore, the carbon matrix shortens the electron / ion path and reduces strain due to volume changes. Benefiting from these advantages, the C / FeS₂ / Ga₂S₃ composite material prepared in this invention can be used as a negative electrode active material to prepare a negative electrode sheet for assembly into a sodium-ion battery. At 1.0 A g… -1 After 410 cycles at current density, the display showed 463 mAh g. -1 The high reversible capacity, high specific capacity, stable cycle performance, and robust rate performance demonstrate that the C / FeS2 / Ga2S3 composite material provided by this invention is an excellent and promising anode material for sodium-ion batteries. Furthermore, the iron, gallium, and sulfur sources used in this invention are inexpensive and readily available; carbon coating significantly improves the battery's cycle stability, extends its lifespan, and increases and stabilizes its capacity.

[0036] This invention employs a hydrothermal synthesis and in-situ sulfidation process to grow a Ga2S3 nanolayer on the surface of FeS2, avoiding the interface separation problem caused by traditional physical mixing. The formation of a thin carbon layer through carbonization enhances the conductivity of transition metal sulfides, significantly improving the electrochemical performance of the C / FeS2 / Ga2S3 composite material. The C / FeS2 / Ga2S3 composite material provided by this invention is a carbon-based composite electrode material with a nanostructure, constructed from nano-sized subunits in a specific manner. These nano-sized subunits shorten ion diffusion pathways and increase electrochemical reaction sites. Nitrogen-doped carbon coating improves electronic conductivity and buffers internal stress, which is beneficial for enhancing the electrochemical performance of sodium-ion batteries.

[0037] The C / FeS2 / Ga2S3 composite material provided by this invention is used as the negative electrode active material for sodium-ion batteries. After preparing sodium-ion battery negative electrode sheets and assembling them into sodium-ion batteries, the sodium-ion batteries can achieve 600 mAh g⁻¹. -1The initial capacity shown above exhibits a capacity retention rate exceeding 80% after 500 cycles, demonstrating excellent wide-temperature-range cycle stability and high rate performance, far superior to single FeS2 or Ga2S3 materials. During charge and discharge, the C / FeS2 / Ga2S3 composite material provides numerous active sites. The polycrystalline structure, heterogeneous interface structure, and increased conductivity after carbon layer encapsulation significantly improve cycle stability, lifespan, and battery capacity. Its unique structure allows it to withstand high current and long-term cycling, reducing active material loss during charge and discharge and buffering volume changes, thereby enhancing the electrochemical performance of the anode material. Ga2S3 semiconductor material exhibits better conductivity, facilitating sodium formation / desodium removal during the reaction process. This invention promotes rapid charge transfer through multi-component synergistic effects, resulting in excellent rate and cycle performance. The interface effect of the bimetallic sulfide introduces an internal electric field to improve reaction kinetics, while simultaneously providing abundant electrochemical reaction sites, thus enhancing reversible capacity and cycle stability. Attached Figure Description

[0038] Figure 1 This is a SEM image of the rice-shaped FeOOH nanorod precursor from Example 1.

[0039] Figure 2 This is a TEM image of the rice-shaped FeOOH nanorod precursor in Example 1;

[0040] Figure 3 This is a SEM image of the rice-shaped nitrogen-doped carbon-coated Fe2O3 / Ga2O3 nanorod precursor in Example 1.

[0041] Figure 4 This is a TEM image of the rice-shaped nitrogen-doped carbon-coated Fe2O3 / Ga2O3 nanorod precursor in Example 1;

[0042] Figure 5 Here is a SEM image of the C / FeS2 / Ga2S3 composite material in Example 1;

[0043] Figure 6 This is a TEM image of the C / FeS2 / Ga2S3 composite material in Example 1;

[0044] Figure 7 This is a mapping diagram of the C / FeS2 / Ga2S3 composite material in Example 1;

[0045] Figure 8 The image shows the XRD pattern of the C / FeS2 / Ga2S3 composite material in Example 1.

[0046] Figure 9The image shows the XRD pattern of the rice-shaped FeOOH nanorod precursor in Example 1.

[0047] Figure 10 The image shows the XRD pattern of the rice-shaped nitrogen-doped carbon-coated Fe2O3 / Ga2O3 nanorod precursor in Example 1.

[0048] Figure 11 SEM image of the rice-shaped nitrogen-doped carbon-coated Fe2O3 / Ga2O3 nanorod precursor in Comparative Example 1;

[0049] Figure 12 SEM image of the C / FeS2 / Ga2S3 composite material in Comparative Example 1;

[0050] Figure 13 SEM image of the final composite material prepared in Comparative Example 2;

[0051] Figure 14 The image shows the XRD pattern of the final composite material prepared in Comparative Example 2.

[0052] Figure 15 The image shows the XRD pattern of the final composite material prepared in Comparative Example 3.

[0053] Figure 16 SEM image of the final composite material prepared in Comparative Example 3;

[0054] Figure 17 SEM image of the final composite material prepared in Comparative Example 4;

[0055] Figure 18 TEM image of the final composite material prepared in Comparative Example 4;

[0056] Figure 19 To prepare a liquid sodium-ion battery using the C / FeS2 / Ga2S3 composite material from Example 1 as the anode material, at 1.0 A g... -1 Cyclic stability test results at current density;

[0057] Figure 20 To prepare a liquid sodium-ion battery using the C / FeS2 / Ga2S3 composite material from Example 1 as the anode material, at 1.0 A g... -1 Constant current charge-discharge curves at current density;

[0058] Figure 21 The rate capability diagram of the liquid sodium-ion battery prepared in Example 1 using the C / FeS2 / Ga2S3 composite material from Example 1 as the anode material is shown below.

[0059] Figure 22To test the liquid sodium-ion battery prepared using the C / FeS2 / Ga2S3 composite material from Example 1 as the anode material in a sodium-ion battery at 2.0 A g... -1 Cyclic stability test results at current density;

[0060] Figure 23 To test the liquid sodium-ion battery prepared using the C / FeS2 / Ga2S3 composite material from Example 1 as the anode material in a sodium-ion battery at 5.0 A g... -1 Cyclic stability test results at current density;

[0061] Figure 24 To prepare a liquid sodium-ion battery using the C / FeS2 / Ga2S3 composite material from Example 1 as the anode material, at 1.0 A g... -1 At current density and high temperature 50 o Cyclic stability test graph under C;

[0062] Figure 25 To prepare a liquid sodium-ion battery using the composite material finally prepared in Comparative Example 1 as the anode material, at 1.0 A g... -1 Cyclic stability test results at current density;

[0063] Figure 26 To prepare a liquid sodium-ion battery using the composite material finally prepared in Comparative Example 2 as the anode material, at 1.0 A g... -1 Cyclic stability test results at current density;

[0064] Figure 27 To prepare a liquid sodium-ion battery using the composite material finally prepared in Comparative Example 3 as the anode material, at 1.0 A g... -1 Cyclic stability test results at current density;

[0065] Figure 28 To prepare a liquid sodium-ion battery using the composite material finally prepared in Comparative Example 4 as the anode material, at 1.0 A g... -1 Cyclic stability test results at current density;

[0066] Figure 29 This is a schematic diagram of the solid-state sodium-ion battery in Application Example 2;

[0067] Figure 30 The XRD pattern of the Na3PS4 solid electrolyte in Application Example 2;

[0068] Figure 31 The CV diagram shows a solid-state sodium-ion battery prepared using the C / FeS2 / Ga2S3 composite material from Example 1 as the anode material.

[0069] Figure 32 To illustrate the preparation of a solid-state sodium-ion battery using the C / FeS2 / Ga2S3 composite material from Example 1 as the anode material in a 0.5 A g sample... -1 Cyclic stability test results at current density;

[0070] Figure 33 To test the solid-state sodium-ion battery prepared using the C / FeS2 / Ga2S3 composite material from Example 1 as the anode material in a sodium-ion battery at 0.1 A g... -1 Constant current charge-discharge curves at current density; Detailed Implementation

[0071] Unless otherwise specified, all test materials and reagents used in the following examples are commercially available.

[0072] Unless otherwise specified in the embodiments, the techniques or conditions described in the literature in this field or in accordance with the product manual may be followed.

[0073] The present invention will now be described in detail with reference to the embodiments.

[0074] Example 1

[0075] A method for preparing a nitrogen-doped carbon-coated iron disulfide / gallium trisulfide composite material includes the following steps:

[0076] (1) 1.62 g FeCl3·6H2O and 1.2 g hexadecyltrimethylammonium bromide were dispersed in 45 mL of deionized water, stirred and mixed for 30 min to dissolve, and then transferred to a polytetrafluoroethylene reactor. The mixture was hydrothermally reacted at 80 ℃ for 12 h, then naturally cooled to room temperature. The precursor was washed four times by deionization centrifugation and twice by ethanol, and then vacuum dried at 60 ℃ for 12 h to obtain rice-shaped FeOOH nanorods. Its SEM image is shown below. Figure 1 As shown in the figure, it can be seen that it is a smooth, rice-shaped nanorod. Its TEM image is shown below. Figure 2 As shown, its width is 100-300 nm and its length is 1-1.5 μm.

[0077] (2) 0.05 g FeOOH nanorod precursor, 1.764 g sodium citrate, 0.18 g urea, and 0.176 g GaCl3 were added to a mixed solution consisting of 19.75 mL ultrapure water and 0.25 mL polymaleic acid. The mixture was stirred for 20 min, then transferred to a polytetrafluoroethylene reactor and reacted at 180 ℃ for 12 h. After natural cooling to room temperature, the precursor was washed four times with deionized water and twice with ethanol, and then vacuum dried at 60 ℃ for 12 h. The resulting rice-shaped nitrogen-doped carbon-coated Fe2O3 / Ga2O3 nanorod precursor is shown in the SEM image below. Figure 3 As shown in the image, it can be seen that it is a rice-shaped nanorod with a rough surface. Its TEM image is shown below. Figure 4 As shown, its width is 100-300 nm and its length is 1-1.5 μm.

[0078] (3) The nitrogen-doped carbon-coated Fe2O3 / Ga2O3 nanorod precursor was mixed with sulfur powder at a mass ratio of 1:10 in a ceramic boat and calcined at 700 °C for 2 h in a mixed flowing atmosphere of 95% argon and 5% hydrogen at a heating rate of 2 °C / min. The nitrogen-doped carbon-coated iron disulfide / gallium trisulfide (C / FeS2 / Ga2S3) composite material was finally obtained. Its SEM image is shown below. Figure 5 As shown in the image, it can be seen that it is a rice-shaped nanorod with a rough surface, and its width ranges from 100 to 300 nm. Its TEM image is shown below. Figure 6 As shown, the mapping graph is as follows: Figure 7 As shown.

[0079] The XRD pattern of the C / FeS2 / Ga2S3 composite material obtained in this embodiment is as follows: Figure 8 As shown, the XRD pattern of the FeOOH nanorod precursor is as follows. Figure 9 As shown, the XRD pattern of the nitrogen-doped carbon-coated Fe2O3 / Ga2O3 nanorod precursor is as follows. Figure 10 As shown.

[0080] Comparative Example 1

[0081] The rest is the same as in Example 1, except that the amount of FeOOH nanorod precursor in step (2) is adjusted to 0.1g.

[0082] The SEM image of the nitrogen-doped carbon-coated Fe2O3 / Ga2O3 nanorod precursor prepared in this comparative example is shown below. Figure 11 As shown in the figure, it can be seen that it is a rice-shaped nanorod with a rough surface, with a width of 100-300 nm and a length of 1-1.5 μm.

[0083] The SEM image of the C / FeS2 / Ga2S3 composite material prepared in this comparative example is shown below. Figure 12As shown in the figure, it can be seen that it is a rice-shaped nanorod with a rough surface and a width of 100-300 nm.

[0084] Figure 11 It can be seen that in the comparative example, when synthesizing nitrogen-doped carbon-coated Fe2O3 / Ga2O3 nanorod precursors, the amount of FeOOH nanorod precursors added was doubled compared to that in Example 1. This resulted in less Ga layer coating on the surface of the nitrogen-doped carbon-coated Fe2O3 / Ga2O3 nanorod precursors, and severe surface agglomeration. The individual nanorods tended to stick together, leading to poor morphology.

[0085] Comparative Example 2

[0086] The rest is the same as in Example 1, except that the calcination atmosphere in step (3) is changed to argon.

[0087] The SEM image of the composite material prepared in step (3) of the comparative example is shown below. Figure 13 As shown in the figure, it can be seen that it is a rice-shaped nanorod with a rough surface, and the width is 100-300 nm. The XRD pattern is shown below. Figure 14 As shown.

[0088] It is evident that by changing the protective gas used in calcination, the final product is not Ga2S3 due to the difficulty in sulfurizing Ga and the lack of H2 reduction during high-temperature calcination. Furthermore, the oxide's performance as a negative electrode material for sodium-ion batteries is unsatisfactory.

[0089] Comparative Example 3

[0090] The process is the same as in Example 1, except that the calcination temperature in step (3) is adjusted to 500 °C. The resulting product is impure and contains a large number of compounds. The XRD pattern of the composite material prepared in step (3) of this comparative example is shown below. Figure 15 As shown. Its SEM image is as follows. Figure 16 As shown, partial sulfidation resulted in the morphology not being completely encapsulated by the outer Ga2S3 layer.

[0091] At a calcination temperature of 500 ℃, due to insufficient calcination reduction time, only a portion of Ga2O3 was sulfided to form Ga2S3, and a small amount of Fe2O3 was reduced to form FeS2. This resulted in an impure product, with the final product containing metal oxides, leading to deteriorated performance.

[0092] Comparative Example 4

[0093] The rest is the same as in Example 1, except that the calcination temperature in step (3) is adjusted to 850 °C.

[0094] The SEM image of the composite material prepared in step (3) of the comparative example is shown below. Figure 17 As shown, the TEM image is as follows Figure 18 As shown.

[0095] At a calcination temperature of 850 ℃, the calcination reduction time is too long, causing the material morphology to collapse and become undesirable. This makes it difficult to buffer the volume expansion required during battery cycling, resulting in rapid capacity decay.

[0096] Application Example 1

[0097] Using the composite materials finally prepared in Example 1 and each comparative example as negative electrode active materials, negative electrode sheets were prepared, and then assembled into liquid sodium-ion batteries, and the performance of the batteries was tested.

[0098] Specifically as follows:

[0099] The preparation process of the negative electrode is as follows:

[0100] The composite materials finally prepared in Example 1 and each comparative example were mixed with conductive carbon black and PVDF at a mass ratio of 7:2:1. After being uniformly dispersed in NMP by magnetic stirring for 6 to 8 hours, the uniformly mixed slurry was coated onto copper foil using a coater and placed in a vacuum drying oven at 60 to 80°C for 12 to 24 hours. After drying, it was pressed into tablets using a tablet press and then cut into small circular electrode sheets using a cutting machine.

[0101] The assembly method of liquid sodium-ion batteries is as follows: Assemble a button cell in a glove box filled with high-purity argon gas and where the water and oxygen levels are both ≤0.01 ppm. Specifically: Add one drop of electrolyte to the negative electrode shell, then place the electrode plate. Next, add one drop of electrolyte and place glass fiber. Add three drops of electrolyte to the glass fiber and place a sodium plate as the counter electrode. Then, place two pieces of nickel foam, add four more drops of electrolyte, cover with the positive electrode shell, and press and seal the battery using a hydraulic press. Let it stand for 6-12 hours. The electrolyte is a 1.0 mol / L NaPF6 diethylene glycol dimethyl ether solution. The sodium plate has a purity of Na ≥99.99%, a thickness of 0.5 mm, and is rolled and cut to the size of the electrode plate.

[0102] Testing Procedure: After assembling the sodium-ion half-cell, the following steps were set on the Xinwei tester: first, constant current discharge to 0.01 V, then constant current charging to 3.0 V, repeating this cycle a certain number of times. The active material loading on the electrode plates was approximately 1.1-1.3 mg / cm³. -2 .

[0103] The test results and data are as follows:

[0104] Figure 19 To prepare a liquid sodium-ion battery using the C / FeS2 / Ga2S3 composite material from Example 1 as the anode material, at 1.0 A g... -1Cyclic stability test graph at current density; as can be seen from the graph, it can be stably cycled for more than 400 cycles at this current density, showing good cyclic stability.

[0105] Figure 20 The figure shows the charge-discharge curves of a liquid sodium-ion battery prepared using the C / FeS2 / Ga2S3 composite material from Example 1 as the anode material at a current density of 1.0 A / g. As can be seen from the figure, the average discharge voltage is around 1.5 V, and the second and third curves have a high degree of overlap, indicating good reversibility.

[0106] Figure 21 The figure shows the rate capability of a liquid sodium-ion battery prepared using the C / FeS2 / Ga2S3 composite material from Example 1 as the anode material. As can be seen from the figure, the composite material can withstand a maximum current density of 10 A / g, indicating good rate performance. Furthermore, it still exhibits high capacity after two cycles of high-current rate cycling, demonstrating good electrochemical performance.

[0107] Figure 22 To test the liquid sodium-ion battery prepared using the C / FeS2 / Ga2S3 composite material from Example 1 as the anode material in a sodium-ion battery at 2.0 A g... -1 Cyclic stability test graph at current density; as can be seen from the graph, it can still be stably cycled for a long time even at higher current densities, showing good cyclic stability.

[0108] Figure 23 To test the liquid sodium-ion battery prepared using the C / FeS2 / Ga2S3 composite material from Example 1 as the anode material in a sodium-ion battery at 5.0 A g... -1 Cyclic stability test graph at current density; as can be seen from the graph, even at ultra-high current density, it can stably cycle for a long time, demonstrating a strong high-current fast charge and discharge capability.

[0109] Figure 24 To prepare a liquid sodium-ion battery using the C / FeS2 / Ga2S3 composite material from Example 1 as the anode material, at 1.0 A g... -1 At current density and high temperature 50 o Cycle stability test results at temperature C. As can be seen from the figure, this sodium-ion battery exhibits high temperature tolerance, expanding its application scenarios.

[0110] Figure 25The image shows the cycle performance of a liquid sodium-ion battery prepared using the composite material finally prepared in Comparative Example 1 as the negative electrode material. Compared with Example 1, Example 2, after doubling the FeOOH precursor in the hydrothermal reaction, resulted in less Ga2S3 coating on the surface, poorer conductivity, and severe sample agglomeration, leading to reduced capacity and fewer cycle times.

[0111] Figure 26 The graph shows the cycle performance of a liquid sodium-ion battery prepared using the composite material finally prepared in Comparative Example 2 as the anode material. Compared with Example 1, the capacity is not high and the decay is faster after the product is changed to Ga2O3. This indicates that metal oxides are not suitable as electrode materials.

[0112] Figure 27 The graph shows the cycle performance of a liquid sodium-ion battery prepared using the composite material finally prepared in Comparative Example 3 as the negative electrode material. Compared with Example 1, the calcination reduction temperature was insufficient, the oxide reduction was incomplete, and after Ga2O3 was incorporated into the product, the capacity was not high and the decay was rapid. This indicates that metal oxides are not suitable as electrode materials.

[0113] Figure 28 The image shows the cycle performance of a liquid sodium-ion battery prepared using the composite material finally prepared in Comparative Example 4 as the negative electrode material. Compared with Example 1, when the calcination reduction temperature is too high, the material morphology collapses, resulting in faster capacity decay.

[0114] Application Example 2

[0115] Using the composite material finally prepared in Example 1 as the negative electrode active material, a negative electrode sheet was prepared and then assembled into a solid-state sodium-ion battery, such as... Figure 29 As shown; and the battery performance was tested.

[0116] Specifically as follows:

[0117] The preparation process of the negative electrode is the same as in application example 1.

[0118] The assembly method of the solid-state sodium-ion battery is as follows: In a glove box filled with high-purity argon gas and where the water and oxygen values ​​are both ≤0.01 ppm, place a pad on the negative electrode shell, then place the negative electrode sheet, followed by the solid electrolyte after powder pressing. Add 20 μL of electrolyte to the electrolyte sheet for wetting, then place a sodium sheet as the counter electrode. Cover with the positive electrode shell, and use a hydraulic press to press and seal the battery. Let it stand for 6-12 hours. The solid electrolyte is Na3PS4 with a thickness of 0.97 mm, and its XRD pattern is shown below. Figure 30 As shown; the electrolyte is a 1.0 mol / L diethylene glycol dimethyl ether solution of NaPF6.

[0119] The testing process is the same as in Application Example 1.

[0120] The test results and data are as follows:

[0121] Figure 31 The figure shows the thermal conductivity CV curve of a solid-state sodium-ion battery prepared using the C / FeS2 / Ga2S3 composite material from Example 1 as the anode material. As can be seen from the figure, except for the first cycle, the plateaus where electrochemical reactions occur are almost identical to those in a liquid battery, indicating that fewer side reactions occur in the presence of a solid electrolyte. Furthermore, the curves of subsequent cycles show high overlap, indicating good reversibility of the solid-state battery.

[0122] Figure 32 To illustrate the preparation of a solid-state sodium-ion battery using the C / FeS2 / Ga2S3 composite material from Example 1 as the anode material in a 0.5 A g sample... -1 The cycle stability test graph at current density shows that the solid sodium-ion battery retains a capacity of 655.3 mAh / g after 50 cycles, and the coulombic efficiency is close to 100%. This indicates that the synthesized anode material has practical application potential.

[0123] Figure 33 To test the solid-state sodium-ion battery prepared using the C / FeS2 / Ga2S3 composite material from Example 1 as the anode material in a sodium-ion battery at 0.1 A g... -1 The constant current charge-discharge curves at current density show that the plateau position in the charge-discharge curve is consistent with the voltage peak of the CV curve of the solid-state battery, and the subsequent cycle curves have good overlap, indicating that the solid-state battery has good reversibility and high reproducibility.

[0124] The above-described detailed description of a nitrogen-doped carbon-coated iron disulfide / gallium trisulfide composite material, its preparation method, and its application in rechargeable batteries is illustrative rather than limiting. Several embodiments may be listed within the defined scope. Therefore, variations and modifications that do not depart from the overall concept of the present invention should be within the protection scope of the present invention.

Claims

1. A method for preparing a nitrogen-doped carbon-coated iron disulfide / gallium trisulfide composite material, characterized in that, The preparation method includes the following steps: (1) The iron source and hexadecyltrimethylammonium bromide were dispersed in deionized water and subjected to a hydrothermal reaction to obtain rice-shaped FeOOH nanorod precursors; (2) FeOOH nanorod precursor, organic ligand, carbon source and gallium source are mixed in a solvent and subjected to hydrothermal reaction to obtain rice-shaped nitrogen-doped carbon-coated Fe2O3 / Ga2O3 nanorod precursor; (3) The nitrogen-doped carbon-coated Fe2O3 / Ga2O3 nanorod precursor and sulfur powder were mixed and calcined at 600-750 °C in a weak reducing atmosphere to obtain C / FeS2 / Ga2S3 composite material.

2. The preparation method according to claim 1, characterized in that, In step (1), the molar ratio of the iron source and hexadecyltrimethylammonium bromide is 1-3:1; the concentration of the iron source in deionized water is 0.1-0.3 mol / L.

3. The preparation method according to claim 1, characterized in that, In step (1), the hydrothermal reaction conditions are: 70-100 ℃ for 10-14 h.

4. The preparation method according to claim 1, characterized in that, In step (2), the organic ligand is sodium citrate; the carbon source is urea; the gallium source is gallium chloride or gallium nitrate; and the solvent is a mixed solution of deionized water and polymaleic acid in a volume ratio of 75-80:

1.

5. The preparation method according to claim 1 or 4, characterized in that, In step (2), the mass ratio of FeOOH nanorod precursor, organic ligand, carbon source and gallium source is 0.03-0.1:1.5-2.0:0.1-0.2:0.1-0.5; the concentration of FeOOH nanorod precursor in solvent is 0.0015-0.005 g / mL.

6. The preparation method according to claim 1 or 4, characterized in that, In step (2), the hydrothermal reaction conditions are: 150-200 °C for 10-14 h.

7. The preparation method according to claim 1, characterized in that, In step (3), the mass ratio of nitrogen-doped carbon-coated Fe2O3 / Ga2O3 nanorod precursor to sulfur powder is 1:10; the weakly reducing atmosphere is a mixture of argon and hydrogen; and the calcination condition is calcination at 700 °C for 2 h.

8. The nitrogen-doped carbon-coated iron disulfide / gallium trisulfide composite material prepared by the preparation method according to any one of claims 1-7.

9. The application of the nitrogen-doped carbon-coated iron disulfide / gallium trisulfide composite material as described in claim 8 in a rechargeable battery, characterized in that, The nitrogen-doped carbon-coated iron disulfide / gallium trisulfide composite material can be used as the negative electrode active material for rechargeable batteries.

10. A rechargeable battery, characterized in that, The negative electrode active material of the rechargeable battery is the nitrogen-doped carbon-coated iron disulfide / gallium trisulfide composite material as described in claim 8.

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