Method for preparing silicon-carbon material for lithium-ion batteries

Abstract

The application relates to the field of battery materials, in particular to a preparation method of a silicon-carbon material. The preparation method of the silicon-carbon material comprises the following steps: a synthesis step of a metal organic framework material; an activation step of the metal organic framework material; and a nano-silicon deposition step: placing the activated metal organic framework material in a silicon-containing gas, using laser to induce dissociation of the silicon-containing gas, so as to deposit nano-silicon on the activated metal organic framework material. Through the preparation method of the silicon-carbon material provided in the application, uniform distribution and controllable growth of silicon nanoparticles in MOF channels can be realized, and the electrochemical performance and cycle stability of the material are significantly improved.

Description

Technical Field

[0001] This application relates to the field of battery materials, specifically to a method for preparing silicon-carbon materials for lithium-ion batteries. Background Technology

[0002] Lithium-ion batteries are widely used in portable electronic devices, electric vehicles, and other fields due to their high energy density and long cycle life. Currently, the main negative electrode active material in commercial lithium-ion batteries is graphite, but its theoretical specific capacity is only 372 mAh / g, which is insufficient to meet the demands of high-energy-density batteries. Silicon-based materials, with a theoretical specific capacity as high as 4200 mAh / g, are considered the most promising next-generation negative electrode active materials for lithium-ion batteries. However, silicon undergoes a huge volume change (>300%) during charge and discharge, leading to electrode structure damage and active material shedding, resulting in rapid capacity decay. Furthermore, the low electronic and ionic conductivity of silicon also limits its electrochemical performance.

[0003] To address these issues, researchers have developed various nanostructured silicon materials, such as silicon nanowires and porous silicon. These nanostructures can alleviate volume expansion and improve cycle stability to some extent. However, nanomaterials have a large specific surface area, making them prone to side reactions with the electrolyte, forming a thick SEI film and reducing coulombic efficiency. Furthermore, the fabrication processes of nanomaterials are complex and costly, hindering large-scale applications.

[0004] In recent years, metal-organic frameworks (MOFs) have attracted widespread attention in the field of energy storage due to their high specific surface area and tunable pore structure. Confining silicon nanoparticles within MOF channels can effectively suppress silicon volume expansion, while the MOF framework can provide electron transport channels, improving the material's conductivity. However, MOF-confined silicon materials in related technologies suffer from problems such as uneven silicon distribution and low silicon loading. Summary of the Invention

[0005] This application addresses at least one of the problems of the related technology in the following aspects.

[0006] The first aspect of this application provides a method for preparing a silicon-carbon material, comprising:

[0007] Synthesis steps of metal-organic framework materials;

[0008] Activation steps for metal-organic framework materials; and

[0009] The nano-silicon deposition step includes: placing an activated metal-organic framework material in a silicon-containing gas, using a laser to induce the dissociation of the silicon-containing gas, thereby depositing nano-silicon on the activated metal-organic framework material.

[0010] The silicon-carbon anode active material provided in this application embodiment solves the problem of electrode structure damage and active material shedding caused by volume expansion of silicon-based materials in lithium-ion batteries, while improving its electronic conductivity and ionic conductivity to meet the requirements of high energy density batteries.

[0011] This application provides a silicon-carbon material exhibiting both high specific capacity and cycling stability by incorporating carbon nanotubes into the synthesis of a metal-organic framework and using laser-induced silicon-containing gas dissociation. Furthermore, the preparation method provided in this application avoids the carbonization of the metal-organic framework material at high temperatures, which would affect the cycling stability of the resulting material. Instead, it synergistically improves the electrochemical performance of the obtained material through the steps of adding carbon nanotubes and laser-induced silicon-containing gas dissociation to deposit nano-silicon.

[0012] In some embodiments, the metal-organic framework material is selected from one or more of the following: MIL-101, UiO-66, ZIF-8, IRMOF-1, NKMOF-1, and PCN-333.

[0013] In some embodiments, the metal center of the metal-organic framework material is selected from one or more of the following: Ce, Cr, La, Fe, Al.

[0014] In some embodiments, the organic ligands of the metal-organic framework material are selected from one or more of the following: polycyclic aromatic hydrocarbons, porphyrins, phthalocyanines, pyridines, biphenyls, and thiophenes.

[0015] In some embodiments, the metal-organic framework material is MIL-101, and the specific surface area of ​​the metal-organic framework material is 3000-4500 m². 2 / g, pore volume 1.5-2.5cm 3 / g, pore size is 3.2-3.6nm.

[0016] In some embodiments, the silicon-carbon material comprises 50-80 wt% of a metal-organic framework, 10-30 wt% of nano-silicon, and 0.1-3 wt% of carbon nanotubes. In some embodiments, the synthesis steps of the metal-organic framework include: preparing MIL-101 using a dispersion of nitrate, terephthalic acid, 2-aminoterephthalic acid, hydrofluoric acid, and carbon nanotubes.

[0017] The nitrates are selected from: cerium nitrate, chromium nitrate, lanthanum nitrate, ferric nitrate, and aluminum nitrate.

[0018] The molar ratio of the nitrate, terephthalic acid, 2-aminoterephthalic acid, and hydrofluoric acid is 1:(0.5-2):(0.1-1):(1-3).

[0019] The carbon nanotube dispersion contains 60-90 wt%, optionally 75-85 wt%, of carbon nanotubes.

[0020] Based on the nitrate content of the metal-organic framework material, the amount of carbon nanotube dispersion used is 0.15-6 wt%.

[0021] In some embodiments, the synthesis steps of the metal-organic framework material include: preparing MIL-101 by reacting a dispersion of nitrate, terephthalic acid, 2-aminoterephthalic acid, hydrofluoric acid, and carbon nanotubes at 180-250°C for 4-12 hours.

[0022] The nitrates are selected from: cerium nitrate, chromium nitrate, lanthanum nitrate, ferric nitrate, and aluminum nitrate.

[0023] The molar ratio of the nitrate, terephthalic acid, 2-aminoterephthalic acid, and hydrofluoric acid is 1:(0.5-2):(0.1-1):(1-3).

[0024] The carbon nanotube dispersion contains 60-90 wt%, optionally 75-85 wt%, of carbon nanotubes.

[0025] The amount of carbon nanotube dispersion used is 0.15-6 wt%, based on the mass of nitrate in the metal-organic framework material.

[0026] In some embodiments, the synthesis steps of the metal-organic framework material include: preparing MIL-101 using nitrates, terephthalic acid, 2-aminoterephthalic acid, carbon nanotube dispersions, hydrofluoric acid, and modifying compounds.

[0027] The nitrates are selected from: cerium nitrate, chromium nitrate, lanthanum nitrate, ferric nitrate, and aluminum nitrate.

[0028] The modified compound is selected from one or more of the following: nitrogen-containing compounds, sulfur-containing compounds, fluorine-containing compounds, phosphorus-containing compounds, and boron-containing compounds.

[0029] The molar ratio of nitrogen to metal in the modified compound is (0.1-1):1, and / or the molar ratio of sulfur to metal in the modified compound is (0.01-0.1):1, and / or the molar ratio of fluorine to metal in the modified compound is (0.01-0.1):1, and / or the molar ratio of phosphorus to metal in the modified compound is (0.05-0.2):1, and / or the molar ratio of boron to metal in the modified compound is (0.01-0.1):1.

[0030] The embodiments of this application significantly improve the electrochemical performance of silicon-carbon materials by adding an appropriate proportion of modifying compounds during the metal-organic framework process.

[0031] In some embodiments, the synthesis steps of the metal-organic framework material include: using nitrates, terephthalic acid, 2-aminoterephthalic acid, carbon nanotube dispersion, hydrofluoric acid, and a modified compound, reacting at 180-250°C for 4-12 hours to prepare MIL-101.

[0032] The nitrates are selected from: cerium nitrate, chromium nitrate, lanthanum nitrate, ferric nitrate, and aluminum nitrate.

[0033] The modified compound is selected from one or more of the following: nitrogen-containing compounds, sulfur-containing compounds, fluorine-containing compounds, phosphorus-containing compounds, and boron-containing compounds, wherein the nitrogen-containing compound is selected from one or more of the following: ethylenediamine, ammonia, and urea; the sulfur-containing compound is sulfur dioxide; the fluorine-containing compound is hydrogen fluoride; the phosphorus-containing compound is phosphoric acid and / or metaphosphoric acid; and the boron-containing compound is boric acid and / or sodium borohydride.

[0034] The molar ratio of nitrogen to metal in the modified compound is (0.1-1):1, and / or the molar ratio of sulfur to metal in the modified compound is (0.01-0.1):1, and / or the molar ratio of fluorine to metal in the modified compound is (0.01-0.1):1, and / or the molar ratio of phosphorus to metal in the modified compound is (0.05-0.2):1, and / or the molar ratio of boron to metal in the modified compound is (0.01-0.1):1.

[0035] In some embodiments, the activation step of the metal-organic framework material includes: adding MIL-101 to anhydrous ethanol and activating it at 80-150°C for 8-15 hours.

[0036] In some embodiments, the nano-silicon deposition step includes: placing the activated metal-organic framework material in a silicon-containing gas at a power of 800-1400 W / cm². 2 The laser induces the dissociation of the silicon-containing gas, thereby depositing nano-silicon on the activated metal-organic framework material.

[0037] In some embodiments, the silicon-containing gas is silicon tetrachloride or silane.

[0038] The second aspect of this application provides a negative electrode active material comprising silicon-carbon material and graphite prepared according to the preparation method of any of the first aspects described above, wherein the mass ratio of silicon-carbon material to graphite is (0.4-1.2):1.

[0039] Compared with related technologies, the embodiments of this application achieve at least the following beneficial effects:

[0040] The silicon-carbon anode active material provided in this application solves the problems of electrode structure damage and active material shedding caused by volume expansion of silicon-based materials in lithium-ion batteries, while improving its electronic and ionic conductivity to meet the requirements of high-energy-density batteries. This application also develops a simple and efficient method for preparing MOF-confined silicon materials, achieving in-situ growth and uniform distribution of silicon in MOF channels, which is of great significance for improving the electrochemical performance of silicon-based anode active materials. Furthermore, this application proposes a novel method for preparing lithium-ion battery anode active materials using MOF-confined silicon, which can achieve uniform distribution and controllable growth of silicon nanoparticles in MOF channels, significantly improving the electrochemical performance and cycle stability of the material. Detailed Implementation

[0041] The present application will now be described in further detail with reference to specific embodiments. The embodiments given are merely illustrative of the present application and are not intended to limit the scope of the present application. The embodiments provided below can serve as a guide for further improvements by those skilled in the art and do not constitute a limitation on the present application in any way.

[0042] This application is based on the inventor's following understanding:

[0043] 1) A method for in-situ growth of metal-organic frameworks (MOFs) on carbon nanotubes was designed. Through optimization of the metal center and ligand design, the pore size of the MOF was precisely controlled, achieving uniform distribution and controllable growth of silicon nanoparticles. To achieve effective confinement of the nano-silicon, the specific surface area, pore volume, and pore size range of the MOF material used are as follows: specific surface area > 1000 m² / g. 2 / g, optional >1500m 2 / g; pore volume > 0.5cm 3 / g, optional >1.0cm 3 / g; pore size 1-5mm, 2-4mm optional.

[0044] 2) The three-dimensional confinement of nano-silicon using MOF cages provides ample expansion space for silicon under the support of the MOF framework, effectively mitigating volume changes and significantly improving the cycling stability of the material.

[0045] 3) A laser-induced silane dissociation method was developed to generate nano-silicon particles in situ within the MOF confinement space, achieving a tight bond between nano-silicon and MOF.

[0046] 4) The mass ratio of MOF, silicon, and carbon nanotubes is: MOF (50-80%), nano-silicon (10-30%), and carbon nanotubes (0.1-3%). Alternatively, MOF (68%), nano-silicon (30%), and carbon nanotubes (2%) can be used.

[0047] 5) Introduce one or more non-metallic elements into the MOF framework to adjust the electronic structure and improve the electronic conductivity and electrochemical activity of the material, such as nitrogen doping (0.5-2%), phosphorus doping (0.1-3%), fluorine doping (0.1-2%), boron doping (0.5-5%), etc.

[0048] 6) A three-dimensional ordered composite structure of carbon nanotubes, MOFs, and nano-silicon was designed. MOFs were grown in situ on the surface of carbon nanotubes, and nano-silicon particles were confined within the mesoporous cages of the MOFs. In this structure: a) carbon nanotubes provide a one-dimensional electron transport highway; b) the MOF framework provides a three-dimensional electron / ion transport network; c) nano-silicon particles are uniformly distributed as active materials. This three-dimensional ordered network structure not only solves the volume expansion problem of nano-silicon but also improves the electron and ion transport properties of the material.

[0049] The first aspect of this application provides a method for preparing a silicon-carbon material, comprising: a metal-organic framework material synthesis step; a metal-organic framework material activation step; and a nano-silicon deposition step, comprising: placing the activated metal-organic framework material in a silicon-containing gas, using a laser to induce the dissociation of the silicon-containing gas, thereby depositing nano-silicon on the activated metal-organic framework material.

[0050] Understandably, metal-organic frameworks are porous materials with nano-silicon uniformly deposited on their outer and inner surfaces.

[0051] The silicon-carbon anode active material provided in this application embodiment solves the problem of electrode structure damage and active material shedding caused by volume expansion of silicon-based materials in lithium-ion batteries, while improving its electronic conductivity and ionic conductivity to meet the requirements of high energy density batteries.

[0052] This application provides a silicon-carbon material exhibiting both high specific capacity and cycling stability by incorporating carbon nanotubes into the synthesis of a metal-organic framework and using laser-induced silicon-containing gas dissociation. Furthermore, the preparation method provided in this application avoids the carbonization of the metal-organic framework material at high temperatures, which would affect the cycling stability of the resulting material. Instead, it synergistically improves the electrochemical performance of the obtained material through the steps of adding carbon nanotubes and laser-induced silicon-containing gas dissociation to deposit nano-silicon.

[0053] In some embodiments, the metal-organic framework material is selected from one or more of the following: MIL-101, UiO-66, ZIF-8, IRMOF-1, NKMOF-1, and PCN-333.

[0054] In some embodiments, the metal center of the metal-organic framework material is selected from one or more of the following: Ce, Cr, La, Fe, Al.

[0055] In some embodiments, the organic ligands of the metal-organic framework material are selected from one or more of the following: polycyclic aromatic hydrocarbons, porphyrins, phthalocyanines, pyridines, biphenyls, and thiophenes.

[0056] In some embodiments, the metal-organic framework material is MIL-101, and the specific surface area of ​​the metal-organic framework material is 3000-4500 m². 2 / g (e.g., 3200m) 2 / g、3400m 2 / g、3600m 2 / g、3800m 2 / g、4000m 2 / g、4200m 2 / g、4400m 2 / g), pore volume is 1.5-2.5cm 3 / g (e.g., 1.6cm) 3 / g, 1.7cm 3 / g, 1.8cm 3 / g, 1.9cm 3 / g, 2.0cm 3 / g, 2.1cm 3 / g, 2.2cm 3 / g, 2.3cm 3 / g, 2.4cm 3 / g), with pore sizes of 3.2-3.6nm (e.g., 3.3nm, 3.4nm, 3.5nm).

[0057] In some embodiments, the silicon-carbon material comprises 50%-80 wt% (e.g., 55 wt%, 60 wt%, 65 wt%, 70 wt%, 75 wt%), optionally 68 wt%, of a metal-organic framework material, 10-30 wt% (e.g., 15 wt%, 20 wt%, 25 wt%), optionally 30 wt%, of nano-silicon, and 0.1-3 wt% (e.g., 0.5 wt%, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%), optionally 2 wt%, of carbon nanotubes.

[0058] In some embodiments, the synthesis steps of the metal-organic framework material include: preparing MIL-101 using nitrates, terephthalic acid, 2-aminoterephthalic acid, hydrofluoric acid, and a carbon nanotube dispersion.

[0059] The nitrates are selected from: cerium nitrate, chromium nitrate, lanthanum nitrate, ferric nitrate, and aluminum nitrate.

[0060] The molar ratio of the nitrate, terephthalic acid, 2-aminoterephthalic acid, and hydrofluoric acid is 1:(0.5-2):(0.1-1):(1-3) (e.g., 1:0.5:0.1:1, 1:1:0.1:1, 1:1.5:0.1:1, 1:2:0.1:1, 1:0.5:0.5:1, 1:0.5:1:1, 1:0.5:0.1:2, 1:0.5:0.1:3).

[0061] The carbon nanotube dispersion contains 60-90 wt% (e.g., 65 wt%, 70 wt%, 75 wt%, 80 wt%, 85 wt%), optionally 75-85 wt% carbon nanotubes.

[0062] Based on the mass of the nitrate in the metal-organic framework material, the amount of carbon nanotube dispersion is 0.15wt%-6wt% (e.g., 0.5wt%, 1wt%, 1.5wt%, 2wt%, 2.5wt%, 3wt%, 3.5wt%, 4wt%, 4.5wt%, 5wt%, 5.5wt%).

[0063] In some embodiments, the synthesis step of the metal-organic framework material includes: preparing MIL-101 by reacting a dispersion of nitrate, terephthalic acid, 2-aminoterephthalic acid, hydrofluoric acid, and carbon nanotubes at 180-250°C (e.g., 190°C, 200°C, 210°C, 220°C, 230°C, 240°C) for 4-12 hours (e.g., 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours).

[0064] The nitrates are selected from: cerium nitrate, chromium nitrate, lanthanum nitrate, ferric nitrate, and aluminum nitrate.

[0065] The molar ratio of the nitrate, terephthalic acid, 2-aminoterephthalic acid, and hydrofluoric acid is 1:(0.5-2):(0.1-1):(1-3) (e.g., 1:0.5:0.1:1, 1:1:0.1:1, 1:1.5:0.1:1, 1:2:0.1:1, 1:0.5:0.5:1, 1:0.5:1:1, 1:0.5:0.1:2, 1:0.5:0.1:3).

[0066] The carbon nanotube dispersion contains 60-90 wt% (e.g., 65 wt%, 70 wt%, 75 wt%, 80 wt%, 85 wt%), optionally 75-85 wt% carbon nanotubes.

[0067] Based on the mass of the nitrate in the metal-organic framework material, the amount of carbon nanotube dispersion is 0.15wt%-6wt% (e.g., 0.5wt%, 1wt%, 1.5wt%, 2wt%, 2.5wt%, 3wt%, 3.5wt%, 4wt%, 4.5wt%, 5wt%, 5.5wt%).

[0068] In some embodiments, the synthesis step of the metal-organic framework material includes: preparing MIL-101 using nitrates, terephthalic acid, 2-aminoterephthalic acid, carbon nanotube dispersion, hydrofluoric acid, and a modifying compound, wherein the nitrate is selected from: cerium nitrate, chromium nitrate, lanthanum nitrate, ferric nitrate, and aluminum nitrate, wherein the modifying compound is selected from one or more of the following: nitrogen-containing compounds, sulfur-containing compounds, fluorine-containing compounds, phosphorus-containing compounds, and boron-containing compounds, wherein the molar ratio of nitrogen element in the modifying compound to the metal element in the nitrate is (0.1-1):1 (e.g., 0.2:1, 0.3:1, 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1), and / or the molar ratio of sulfur element in the modifying compound to the metal element in the nitrate is (0.01-0.1):1 (e.g., 0.02:1, 0.03:1, 0.04:1, 0.05:1, 0.06). The modified compound contains fluorine in a molar ratio of 1, 0.07:1, 0.08:1, or 0.09:1, and / or the molar ratio of fluorine to metal in the nitrate is (0.01-0.1):1 (e.g., 0.02:1, 0.03:1, 0.04:1, 0.05:1, 0.06:1, 0.07:1, 0.08:1, or 0.09:1), and / or the modified compound contains phosphorus in a molar ratio of 0.05 to metal in the nitrate is (0.05:1, 0.07:1, 0.08:1, or 0.09:1). -0.2):1 (e.g., 0.06:1, 0.08:1, 0.1:1, 0.12:1, 0.14:1, 0.16:1, 0.18:1), and / or the molar ratio of boron to metal in the nitrate in the modified compound is (0.01-0.1):1 (e.g., 0.02:1, 0.03:1, 0.04:1, 0.05:1, 0.06:1, 0.07:1, 0.08:1, 0.09:1).

[0069] In some embodiments, the synthesis step of the metal-organic framework material includes: preparing MIL-101 by reacting nitrates, terephthalic acid, 2-aminoterephthalic acid, carbon nanotube dispersions, hydrofluoric acid, and modifying compounds at 180-250°C (e.g., 190°C, 200°C, 210°C, 220°C, 230°C, 240°C) for 4-12 hours (e.g., 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours), wherein the nitrates are selected from: cerium nitrate, chromium nitrate, lanthanum nitrate, ferric nitrate, and aluminum nitrate, and wherein the modifying compounds are selected from the following... One or more: nitrogen-containing compounds, sulfur-containing compounds, fluorine-containing compounds, phosphorus-containing compounds, boron-containing compounds, wherein the nitrogen-containing compound is selected from one or more of the following: ethylenediamine, ammonia, and urea; the sulfur-containing compound is sulfur dioxide; the fluorine-containing compound is hydrogen fluoride; the phosphorus-containing compound is phosphoric acid and / or metaphosphoric acid; the boron-containing compound is boric acid and / or sodium borohydride; wherein the molar ratio of nitrogen to metal in the nitrate in the modified compound is (0.1-1):1 (e.g., 0.2:1, 0.3:1, 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0. The modified compound contains sulfur in a molar ratio of 8:1 or 0.9:1 to the metal element in the nitrate, and / or the modified compound contains sulfur in a molar ratio of (0.01-0.1):1 (e.g., 0.02:1, 0.03:1, 0.04:1, 0.05:1, 0.06:1, 0.07:1, 0.08:1, 0.09:1), and / or the modified compound contains fluorine in a molar ratio of fluorine in the nitrate, and / or the modified compound contains fluorine in a molar ratio of (0.01-0.1):1 (e.g., 0.02:1, 0.03:1, 0.04:1, 0.05:1, 0.06:1, 0.07:1, 0.07:1, 0.08:1). 1. 0.09:1), and / or the molar ratio of phosphorus in the modified compound to the metal element in the nitrate is (0.05-0.2):1 (e.g., 0.06:1, 0.08:1, 0.1:1, 0.12:1, 0.14:1, 0.16:1, 0.18:1), and / or the molar ratio of boron in the modified compound to the metal element in the nitrate is (0.01-0.1):1 (e.g., 0.02:1, 0.03:1, 0.04:1, 0.05:1, 0.06:1, 0.07:1, 0.08:1, 0.09:1).

[0070] In some embodiments, the activation step of the metal-organic framework material includes: adding the MIL-101 to anhydrous ethanol and activating it at 80-150°C (e.g., 90°C, 100°C, 110°C, 120°C, 130°C, 140°C) for 8-15 hours (e.g., 9 hours, 10 hours, 11 hours, 12 hours, 13 hours, 14 hours).

[0071] In some embodiments, the nano-silicon deposition step includes: placing the activated metal-organic framework material in a silicon-containing gas at a power of 800-1400 W / cm². 2 (e.g., 900W / cm) 2 1000W / cm 2 1100W / cm 2 1200W / cm 2 1300W / cm 2 The laser induces the dissociation of the silicon-containing gas, thereby depositing nano-silicon on the activated metal-organic framework material.

[0072] In some embodiments, the silicon-containing gas is silicon tetrachloride or silane.

[0073] The second aspect of this application provides a negative electrode active material comprising silicon-carbon material and graphite prepared by the preparation method of any of the first aspects described above, wherein the mass ratio of silicon-carbon material to graphite is (0.4-1.2):1 (e.g., 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1.0:1, 1.1:1).

[0074] The following embodiments are used to further illustrate the advantages and features of this method, and are not intended to limit this application. Unless otherwise specified, the experimental methods in the following embodiments are conventional methods, performed according to the techniques or conditions described in the literature in this field or according to the product instructions.

[0075] Unless otherwise specified, the quantitative analysis experiments in the following examples are all repeated three times, and the results are averaged.

[0076] Example 1

[0077] 1.1 MIL-101 Synthesis:

[0078] One or more of the following nitrates (Ce, Cr, La, Fe, Al, etc.) were selected (see Table 1 below for specific experimental group parameters) and dissolved in 6000 ml of deionized water at a dosage of 1.5 mol. 1.0 mol of terephthalic acid, 0.5 mol of 2-aminoterephthalic acid, a carbon nanotube dispersion (OCSiAl single-walled carbon nanotube dispersion, 80% solid content, 49 wt% HF) with a nitrate mass of 3.5 wt% and modified compounds (nitrogen-containing compounds (ethylenediamine, ammonia, urea), sulfur-containing compounds (carbon disulfide), fluorine-containing compounds (hydrogen fluoride), phosphorus-containing compounds (phosphoric acid or metaphosphoric acid), boron-containing compounds (boric acid or sodium borohydride)) were added, and the mixture was stirred for 15 minutes. 2 mol of hydrofluoric acid was added dropwise, and the mixture was stirred continuously for 30 minutes to obtain the first mixture.

[0079] The first mixture was transferred to a polytetrafluoroethylene-lined high-pressure reactor and crystallized at 200°C for 10 hours. After the reaction was completed, it was cooled to room temperature at a cooling rate of 10°C / h to obtain the first suspension.

[0080] 1.2 MIL-101 purification:

[0081] Washed sequentially with N'N-dimethylformamide (DMF) and anhydrous ethanol, specifically:

[0082] The first suspension was mixed with N,N-dimethylformamide (DMF) and stirred for 30 minutes. After centrifugation (2500 rad / min) for 5 minutes, the supernatant was discarded, and the sample was washed with anhydrous ethanol under the same conditions. The washed sample was dried at 150°C to obtain the first precipitate.

[0083] 1.3 MIL-101 Activation:

[0084] The first precipitate was mixed with 5000 ml of anhydrous ethanol to obtain a second mixture. The second mixture was placed in a high-pressure reactor and activated at 120 °C for 12 hours to obtain a second suspension. The second suspension was centrifuged and filtered to precipitate the second precipitate. The precipitate was dried at 150 °C for 12 hours to obtain the MIL-101 organic framework (Experimental Group 1).

[0085] 1.4 nm silicon deposition:

[0086] The MIL-101 organic framework was kept in a silane atmosphere for 60 minutes to completely replace the air in the MIL-101 organic framework with silane gas. The MIL-101 organic framework was then irradiated with a high-energy laser of a specific wavelength to induce silane dissociation, resulting in a silicon-carbon anode active material (experimental group 1). Elemental analysis was used to determine the mass percentage of nano-silicon in the obtained silicon-carbon anode material.

[0087] The silicon-carbon anode active materials of experimental groups 1-8 and control groups 1-3 were prepared using the same method as steps 1.1-1.4 above, and their specific parameters are shown in Table 1 below.

[0088] Table 1

[0089]

[0090]

[0091] Test Example 1

[0092] The silicon-carbon materials and graphite prepared in each experimental and control group in Example 1 were mixed at a mass ratio of 1:1 to serve as negative electrode materials. The negative electrode active material was prepared by mixing SBR and CMC-Na at a ratio of 97:1.5:1.5. NCM811 material was used as the positive electrode active material, mixed with conductive carbon black and PVDF at a ratio of 96:2:2 to prepare the positive electrode material. The resulting cells were fabricated into soft-pack wound cells with a thickness of 4 mm, a width of 85 mm, and a length of 115 mm. The ratio of positive to negative electrode active materials was 1:1.1, and the electrolyte was (EC:DMC at a volume ratio of 1:1, containing 1 M LiPF6).

[0093] The prepared battery cells were charged at 1C (charging cutoff voltage is 4.2V) and discharged at 1C (discharge cutoff voltage is 2.75V). The initial specific capacity was calculated by taking the first discharge capacity. Then, a 25℃ cycle test was performed. The test results are shown in Table 2 below.

[0094] Table 2

[0095]

[0096]

[0097] As shown in Table 1 above, the anode materials prepared using the silicon-carbon anode active materials of experimental groups 1-8 provided in the embodiments of this application have higher specific capacity while maintaining excellent cycle performance.

[0098] Comparing the test results of experimental groups 1-8 with those of control group 1, it can be seen that the modified compound simultaneously improves the specific capacity and capacity retention of silicon-carbon anode active materials.

[0099] Comparing the test results of experimental groups 1-8 with those of control group 2, it can be seen that although the metal-organic carbide framework improves the initial specific capacity of silicon-carbon anode active materials, it significantly reduces their cycle performance.

[0100] Comparing the test results of experimental groups 1-8 with those of control group 2, it can be seen that adding carbon nanotubes to the synthesis of metal-organic framework can simultaneously improve the specific capacity and capacity retention of silicon-carbon anode active materials.

[0101] In summary, the preparation method of this application provides a silicon-carbon anode active material that combines high specific capacity and excellent cycle stability.

[0102] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0103] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A method for preparing a silicon-carbon material, characterized in that, include: Synthesis steps of metal-organic framework materials; Activation steps for metal-organic framework materials; and The nano-silicon deposition step includes: placing an activated metal-organic framework material in a silicon-containing gas, using a laser to induce the dissociation of the silicon-containing gas, thereby depositing nano-silicon on the activated metal-organic framework material.

2. The preparation method according to claim 1, characterized in that, The metal-organic framework material is selected from one or more of the following: MIL-101, UiO-66, ZIF-8, IRMOF-1, NKMOF-1, PCN-333; Optionally, the metal center of the metal-organic framework material is selected from one or more of the following: Ce, Cr, La, Fe, Al; Optionally, the organic ligands of the metal-organic framework material are selected from one or more of the following: polycyclic aromatic hydrocarbons, porphyrins, phthalocyanines, pyridines, biphenyls, and thiophenes; Optionally, the metal-organic framework material is MIL-101, and the specific surface area of ​​the metal-organic framework material is 3000-4500 m². 2 / g, pore volume 1.5-2.5cm 3 / g, pore size is 3.2-3.6nm; Optionally, the silicon-carbon material comprises 50-80 wt% of a metal-organic framework, 10-30 wt% of nano-silicon, and 0.1-3 wt% of carbon nanotubes.

3. The preparation method according to claim 1, characterized in that, The synthesis steps of the metal-organic framework material include: preparing MIL-101 using nitrates, terephthalic acid, 2-aminoterephthalic acid, hydrofluoric acid, and a carbon nanotube dispersion. The nitrates are selected from: cerium nitrate, chromium nitrate, lanthanum nitrate, ferric nitrate, and aluminum nitrate. The molar ratio of the nitrate, terephthalic acid, 2-aminoterephthalic acid, and hydrofluoric acid is 1:(0.5-2):(0.1-1):(1-3). The carbon nanotube dispersion contains 60-90 wt%, optionally 75-85 wt%, of carbon nanotubes. Based on the nitrate content of the metal-organic framework material, the amount of carbon nanotube dispersion used is 0.15-6 wt%.

4. The preparation method according to claim 1, characterized in that, The synthesis steps of the metal-organic framework material include: preparing MIL-101 by reacting a dispersion of nitrate, terephthalic acid, 2-aminoterephthalic acid, hydrofluoric acid, and carbon nanotubes at 180-250°C for 4-12 hours. The nitrates are selected from: cerium nitrate, chromium nitrate, lanthanum nitrate, ferric nitrate, and aluminum nitrate. The molar ratio of the nitrate, terephthalic acid, 2-aminoterephthalic acid, and hydrofluoric acid is 1:(0.5-2):(0.1-1):(1-3). The carbon nanotube dispersion contains 60-90 wt%, optionally 75-85 wt%, of carbon nanotubes. The amount of carbon nanotube dispersion used is 0.15-6 wt%, based on the mass of nitrate in the metal-organic framework material.

5. The preparation method according to claim 3, characterized in that, The synthesis steps of the metal-organic framework material include: preparing MIL-101 using nitrates, terephthalic acid, 2-aminoterephthalic acid, carbon nanotube dispersion, hydrofluoric acid, and modifying compounds. The nitrates are selected from: cerium nitrate, chromium nitrate, lanthanum nitrate, ferric nitrate, and aluminum nitrate. The modified compound is selected from one or more of the following: nitrogen-containing compounds, sulfur-containing compounds, fluorine-containing compounds, phosphorus-containing compounds, and boron-containing compounds. The molar ratio of nitrogen to metal in the modified compound is (0.1-1):1, and / or the molar ratio of sulfur to metal in the modified compound is (0.01-0.1):1, and / or the molar ratio of fluorine to metal in the modified compound is (0.01-0.1):1, and / or the molar ratio of phosphorus to metal in the modified compound is (0.05-0.2):1, and / or the molar ratio of boron to metal in the modified compound is (0.01-0.1):

1.

6. The preparation method according to claim 4, characterized in that, The synthesis steps of the metal-organic framework material include: using nitrates, terephthalic acid, 2-aminoterephthalic acid, carbon nanotube dispersion, hydrofluoric acid, and modifying compounds, reacting at 180-250℃ for 4-12 hours to prepare MIL-101. The nitrates are selected from: cerium nitrate, chromium nitrate, lanthanum nitrate, ferric nitrate, and aluminum nitrate. The modified compound is selected from one or more of the following: nitrogen-containing compounds, sulfur-containing compounds, fluorine-containing compounds, phosphorus-containing compounds, and boron-containing compounds, wherein the nitrogen-containing compound is selected from one or more of the following: ethylenediamine, ammonia, and urea; the sulfur-containing compound is sulfur dioxide; the fluorine-containing compound is hydrogen fluoride; the phosphorus-containing compound is phosphoric acid and / or metaphosphoric acid; and the boron-containing compound is boric acid and / or sodium borohydride. The molar ratio of nitrogen to metal in the modified compound is (0.1-1):1, and / or the molar ratio of sulfur to metal in the modified compound is (0.01-0.1):1, and / or the molar ratio of fluorine to metal in the modified compound is (0.01-0.1):1, and / or the molar ratio of phosphorus to metal in the modified compound is (0.05-0.2):1, and / or the molar ratio of boron to metal in the modified compound is (0.01-0.1):

1.

7. The preparation method according to any one of claims 3 to 6, characterized in that, The activation step of the metal-organic framework material includes: adding MIL-101 to anhydrous ethanol and activating it at 80-150°C for 8-15 hours.

8. The preparation method according to any one of claims 1 to 7, characterized in that, The nano-silicon deposition step includes: placing the activated metal-organic framework material in a silicon-containing gas at a power of 800-1400 W / cm². 2 The laser induces the dissociation of the silicon-containing gas, thereby depositing nano-silicon on the activated metal-organic framework material.

9. The preparation method according to any one of claims 1 to 8, characterized in that, The silicon-containing gas is silicon tetrachloride or silane.

10. A negative electrode active material comprising silicon-carbon material prepared by any one of claims 1 to 9 and graphite, wherein the mass ratio of silicon-carbon material to graphite is (0.4-1.2):1.

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