A spherical silicon-carbon composite material, its preparation method and application

Abstract

This invention discloses a spherical silicon-carbon composite material, its preparation method, and its application. The preparation method includes: dissolving a binder in a first solvent and performing a first stirring treatment to obtain a first stirred mixture; adding graphite to the first stirred mixture and performing a second stirring treatment to obtain a second stirred mixture; adding a silicon source, a second solvent, and a conductive agent to the second stirred mixture and performing a second stirring treatment to obtain a third stirred mixture; and spray-drying the third stirred mixture to obtain the spherical silicon-carbon composite material. The spherical silicon-carbon composite material prepared by this invention has certain gaps between the graphite layers, providing space for the volume expansion of silicon. Furthermore, nano-silicon is bonded to the graphite layers, shortening the diffusion distance of lithium ions. The bonding between the two is very tight, which is beneficial to the dynamic performance of lithium-ion batteries.

Description

Technical Field

[0001] This invention relates to the field of lithium battery technology, and in particular to a spherical silicon-carbon composite material, its preparation method, and its application. Background Technology

[0002] Lithium-ion batteries possess advantages such as high energy density, environmental friendliness, and long cycle life, leading to their widespread application in energy storage fields like electric vehicles and smartphones. With the increasing demand for these electronic products, higher requirements are being placed on battery energy density. my country aims to achieve a single-cell energy density of 400 Wh / kg by 2025 and strive to reach 500 Wh / kg by 2030. However, the specific capacity of traditional graphite anodes has reached its theoretical limit, severely restricting energy density. Silicon-based anodes, on the other hand, possess extremely high theoretical specific capacity (4200 mAh / g), high safety, and a relatively low and flat operating potential, making them the most promising anode material. However, silicon-based anodes exhibit poor electronic conductivity and significant volume expansion (>300%) during charge and discharge, leading to pulverization of the active material and damage to the electrode structure, resulting in rapid capacity decay.

[0003] To overcome these problems, silicon particles can be refined to the nanoscale, reducing the diffusion path of lithium ions and alleviating the volume expansion effect. Meanwhile, carbon materials such as graphite have high conductivity and rate performance. Therefore, the nano-silicon-carbon material formed by combining the two combines the advantages of both and has high industrialization prospects.

[0004] In addition, the morphology and structure design of nano-silicon carbon materials are also a key focus of research. Studies have shown that spherical nano-silicon carbon materials can alleviate the accumulation of localized stress during silicon expansion, shorten the lithium-ion diffusion distance, and improve the kinetic performance of nano-silicon carbon materials. However, current technologies, such as conventional sand milling and carbon coating processes, cannot precisely control the morphology and structure of nano-silicon carbon materials. Controlling the spherical morphology and designing suitable structures are significant challenges we need to overcome.

[0005] Therefore, existing technologies still need to be improved and developed. Summary of the Invention

[0006] In view of the shortcomings of the prior art, the present invention provides a spherical silicon-carbon composite material, its preparation method and application, thereby solving the problem that the existing preparation methods cannot accurately control the morphology and structure of nano-silicon-carbon materials.

[0007] The technical solutions adopted by the present invention to solve the above technical problems are as follows:

[0008] In a first aspect, the present invention provides a method for preparing a spherical silicon-carbon composite material, the method comprising the following steps:

[0009] The adhesive is dissolved in a first solvent and subjected to a first stirring process to obtain a first stirred mixture;

[0010] Graphite is added to the first mixture, and a second stirring process is performed to obtain a second mixture.

[0011] A silicon source, a second solvent, and a conductive agent are added to the second mixture, and a third stirring process is performed to obtain a third mixture.

[0012] The third stirred material is spray-dried to obtain the spherical silicon-carbon composite material, which includes a spherical structure formed by stacking graphite sheets and silicon bonded to the surface of the spherical structure.

[0013] Preferably, the step of dissolving the binder in the first solvent and performing a first stirring treatment to obtain the first stirred product specifically involves: adding the first solvent and the binder to a vacuum stirring vessel, setting the parameters of the vacuum stirring vessel, performing a first stirring treatment for a time of 5-150 minutes, and obtaining the first stirred product.

[0014] The parameters of the vacuum stirring vessel include: stirring speed of 20-60 rpm and dispersion speed of 300-3000 rpm.

[0015] Preferably, the step of adding graphite to the first stirred material and performing a second stirring treatment to obtain a second stirred material specifically involves: adding graphite to a vacuum stirring vessel containing the first stirred material, setting the parameters of the vacuum stirring vessel, performing a second stirring treatment, and the second stirring treatment time being 5-150 minutes to obtain a second stirred material.

[0016] The parameters of the vacuum stirring vessel include: stirring speed of 20-60 rpm and dispersion speed of 300-3000 rpm.

[0017] Preferably, the step of adding a silicon source, a second solvent, and a conductive agent to the second stirred material and performing a third stirring treatment to obtain a third stirred material specifically involves: adding a silicon source, a second solvent, and a conductive agent to a vacuum stirring vessel containing the second stirred material, setting the parameters of the vacuum stirring vessel, performing a third stirring treatment, and the third stirring treatment time being 5-150 minutes to obtain a third stirred material.

[0018] The parameters of the vacuum stirring vessel include: stirring speed of 20-60 rpm and dispersion speed of 300-3000 rpm.

[0019] Preferably, the parameters of the spray drying process are: inlet temperature of 100-300℃, outlet temperature of 60-120℃, atomizing disc rotation speed of 150-300Hz, and fan frequency of 15-40Hz.

[0020] Preferably, in the third stirring mixture, the mass ratio of graphite to silicon source is (3-8):(3-6), the mass ratio of graphite to binder is (95-100):(1-5), and the mass ratio of graphite to conductive agent is (95-100):(1-5).

[0021] Preferably, the silicon source is selected from nano-silicon, micron-silicon, and porous silicon; the binder is selected from CMC binder, PVDF binder, and PMMA binder; the conductive agent is selected from carbon nanotubes, conductive carbon black, and graphene; the first solvent is selected from water, alcohol, and methanol; and the second solvent is selected from water, alcohol, and methanol.

[0022] Preferably, the first stirring treatment, the second stirring treatment, and the third stirring treatment are each repeated at least twice.

[0023] In a second aspect, the present invention provides a spherical silicon-carbon composite material comprising a spherical structure formed by stacking graphite sheets and silicon bonded to the surface of the spherical structure.

[0024] And / or, the spherical silicon-carbon composite material is prepared by the preparation method described above.

[0025] A third aspect of the present invention provides the application of the above-described spherical silicon-carbon composite material in the preparation of lithium-ion batteries.

[0026] Beneficial effects:

[0027] This invention discloses a spherical silicon-carbon composite material, its preparation method, and its applications. The method involves systematically mixing a silicon source and graphite, followed by spray drying to obtain the spherical silicon-carbon composite material. The spherical silicon-carbon composite material prepared by this invention consists of stacked sheet-like graphite layers, with silicon bonded to the surface of the graphite layers, forming a silicon-coated graphite spherical structure. Certain voids exist between the graphite layers, providing space for the volume expansion of silicon. Furthermore, nano-silicon is bonded to these graphite layers, shortening the diffusion distance of lithium ions. The tight bonding between the two is beneficial to the kinetic performance of lithium-ion batteries. In addition, this invention incorporates a conductive agent and a binder during the mixing of the silicon source and graphite. The binder ensures a tight bond between the two, while the presence of the conductive agent and the graphite layers significantly improves the conductivity of lithium ions, thereby enhancing diffusion kinetics. Attached Figure Description

[0028] Figure 1Here is a SEM image of the spherical silicon-carbon composite material prepared in Example 1 of this invention;

[0029] Figure 2 The XRD pattern of the spherical silicon-carbon composite material prepared in Example 1 of this invention;

[0030] Figure 3 The Raman spectrum of the spherical silicon-carbon composite material prepared in Example 1 of this invention;

[0031] Figure 4 The first cycle charge-discharge curves of the spherical silicon-carbon composite material and graphite and pure silicon prepared in Examples 1-4 of this invention are shown.

[0032] Figure 5 The cycling performance and electrode expansion rate of the spherical silicon-carbon composite material and graphite and pure silicon prepared in Examples 1-4 of this invention are shown in the first 100 cycles. Detailed Implementation

[0033] This invention provides a spherical silicon-carbon composite material, its preparation method, and its application. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention is further described in detail below. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0034] This invention provides a method for preparing spherical silicon-carbon composite materials, the method comprising the following steps:

[0035] The adhesive is dissolved in a first solvent and subjected to a first stirring process to obtain a first stirred mixture;

[0036] Graphite is added to the first mixture, and a second stirring process is performed to obtain a second mixture.

[0037] A silicon source, a second solvent, and a conductive agent are added to the second mixture, and a third stirring process is performed to obtain a third mixture.

[0038] The third stirred material is spray-dried to obtain the spherical silicon-carbon composite material, which includes a spherical structure formed by stacking graphite sheets and silicon bonded to the surface of the spherical structure.

[0039] In this invention, a silicon source and graphite are first systematically stirred and mixed, and then spherical silicon-carbon composite materials are obtained through spray drying technology. The spherical silicon-carbon composite material prepared by this invention is composed of stacked sheet-like graphite (graphite layers), with silicon bonded to the surface of the graphite layers, forming a silicon-coated graphite spherical structure. The graphite layers have certain gaps, providing space for the volume expansion of silicon, thereby reducing the probability of material cracking and pulverization. Furthermore, nano-silicon is bonded to these graphite layers, increasing the contact area between silicon and the graphite layers and shortening the diffusion distance of lithium ions. The tight bonding between the two is beneficial to the kinetic performance of lithium-ion batteries. The presence of graphite also greatly improves the conductivity of the silicon-carbon composite material, significantly enhancing the initial coulombic efficiency and cycle stability.

[0040] In this embodiment of the invention, a conductive agent and a binder are added when the silicon source and graphite are mixed. The binder can ensure a tight composite between silicon and graphite, prevent silicon from falling off the graphite, and make the overall structure more robust. The conductive agent can further increase the conductivity of the silicon-carbon composite material.

[0041] Furthermore, even if silicon expands and cracks during the cycling process of a lithium-ion battery, the detached silicon can refill the gaps between the graphite layers, thus ensuring good electrical contact and excellent capacity performance.

[0042] In some embodiments, the step of dissolving the binder in a first solvent and performing a first stirring treatment to obtain a first stirred product specifically involves: adding the first solvent and the binder to a vacuum stirring vessel, setting the parameters of the vacuum stirring vessel, performing a first stirring treatment for a time of 5-150 minutes, and obtaining the first stirred product.

[0043] The parameters of the vacuum stirring vessel include: stirring speed of 20-60 rpm and dispersion speed of 300-3000 rpm.

[0044] In some embodiments, the step of adding graphite to the first stirred material and performing a second stirring treatment to obtain a second stirred material specifically involves: adding graphite to a vacuum stirring vessel containing the first stirred material, setting the parameters of the vacuum stirring vessel, performing a second stirring treatment, and the second stirring treatment lasting for 5-150 minutes to obtain a second stirred material.

[0045] The parameters of the vacuum stirring vessel include: stirring speed of 20-60 rpm and dispersion speed of 300-3000 rpm.

[0046] In some embodiments, the step of adding a silicon source, a second solvent, and a conductive agent to the second stirred material and performing a third stirring treatment to obtain a third stirred material specifically involves: adding a silicon source, a second solvent, and a conductive agent to a vacuum stirring vessel containing the second stirred material, setting the parameters of the vacuum stirring vessel, performing a third stirring treatment, and the third stirring treatment lasting for 5-150 minutes to obtain a third stirred material.

[0047] The parameters of the vacuum stirring vessel include: stirring speed of 20-60 rpm and dispersion speed of 300-3000 rpm.

[0048] In some embodiments, the parameters of the spray drying process are: inlet temperature of 100-300℃, outlet temperature of 60-120℃, atomizing disc rotation speed of 150-300Hz, and fan frequency of 15-40Hz.

[0049] In some embodiments, the mass ratio of graphite to silicon source in the third stirrer is (3-8):(3-6), the mass ratio of graphite to binder is (95-100):(1-5), and the mass ratio of graphite to conductive agent is (95-100):(1-5). At these mass ratios, the capacity advantage of nano-silicon and the cycle stability advantage of graphite can be maximized, while also ensuring a tight bond and high conductivity between the nano-silicon and graphite. The binder tightly binds the graphite and nano-silicon, preventing the nano-silicon from detaching from the graphite. The conductive agent addresses the low conductivity of silicon, improving conductivity. If the nano-silicon content is too high, the material's cycle stability is poor, and capacity decay is severe; if the graphite content is too high, the material's capacity is too low. If the ratio of conductive agent to binder is too low, the nano-silicon can easily detach from the graphite, leading to failure, and the material's conductivity is too low; if the ratio of conductive agent to binder is too high, the specific capacity of the nano-silicon-carbon material decreases, and its capacity properties are not fully realized.

[0050] In some preferred embodiments, the third mixture contains graphite in a 1:1 mass ratio to silicon source, graphite in a 100:1 mass ratio to binder, and graphite in a 100:1 mass ratio to conductive agent.

[0051] In some embodiments, the silicon source is selected from nano-silicon, micron-silicon, and porous silicon; the binder is selected from CMC binder, PVDF binder, and PMMA binder; the conductive agent is selected from carbon nanotubes, conductive carbon black, and graphene; the first solvent is selected from water, alcohol, and methanol; and the second solvent is selected from water, alcohol, and methanol.

[0052] In this embodiment of the invention, nano-silicon is preferred as the silicon source. Compared with other silicon particles with larger sizes, nano-silicon has stronger mechanical strain resistance and reduced cracking. Nano-silicon particles have a larger specific surface area. Designing the silicon material into a nanostructure can buffer the volume expansion of the silicon-based anode.

[0053] In some embodiments, the first stirring process, the second stirring process, and the third stirring process are each repeated at least twice.

[0054] This invention also provides a spherical silicon-carbon composite material, which includes a spherical structure formed by stacking graphite sheets and silicon bonded to the surface of the spherical structure.

[0055] And / or, the spherical silicon-carbon composite material is prepared by the preparation method described above.

[0056] This invention provides the application of the above-described spherical silicon-carbon composite material in the preparation of lithium-ion batteries.

[0057] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are merely some embodiments of the present invention, not all embodiments, and are intended only to illustrate the present invention and not to limit it. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0058] Example 1

[0059] The preparation of a spherical silicon-carbon composite material includes the following steps:

[0060] (I) Dispersion process

[0061] (1) Add 1125g of pure water to a vacuum mixing vessel, and then add 5.2g (1.0%) of binder CMC powder; where 1.0% is the solid content of CMC;

[0062] (2) Set the stirring speed to 40 rpm and the dispersion speed to 500 rpm, and stir and disperse for 10 minutes. After the process is complete, open the mixing vessel and scrape off the CMC stuck to the mixer. Repeat this process twice.

[0063] (3) Close the mixing vessel and evacuate the vacuum.

[0064] (4) Set the stirring speed to 60 rpm and the dispersion speed to 2000 rpm, and stir and disperse for 60 minutes. After the process is complete, open the mixing vessel and scrape off the CMC stuck to the mixer.

[0065] (5) Take 250g of graphite and add it to the above-mentioned mixing vessel;

[0066] (6) Set the stirring speed to 40 rpm and the dispersion speed to 500 rpm, and stir and disperse for 10 minutes. After the process is complete, open the mixing vessel and scrape off the graphite stuck to the mixer. Repeat this process twice.

[0067] (7) Set the stirring speed to 60 rpm and the dispersion speed to 1500 rpm, and stir and disperse for 120 min. After the process is complete, open the mixing vessel and scrape off the slurry stuck to the mixer.

[0068] (8) Add 250g of Zhongning silicon and 250g of alcohol to the stirred tank;

[0069] (9) Add 0.5g of single-walled carbon nanotubes (0.1%) or 125g of single-walled carbon nanotube slurry;

[0070] (10) Set the stirring speed to 40 rpm and the dispersion speed to 500 rpm, and stir and disperse for 10 minutes. After the end, open the mixing vessel and scrape off the CMC stuck to the mixer. Repeat twice.

[0071] (11) Set the stirring speed to 60 rpm and the dispersion speed to 1500 rpm, and stir and disperse for 120 min. After the stirring is finished, open the mixing vessel and scrape off the slurry stuck to the mixer.

[0072] (II) Spraying Process

[0073] (1) Preparatory work for spraying - oxygen removal and temperature increase;

[0074] (2) Pour the above-dispersed solution of graphite and Zhongning silicon into the spray instrument.

[0075] (3) Set the spray parameters: inlet temperature: 200℃, outlet temperature: 90℃, atomizing disc speed: 250Hz, fan frequency: 25Hz.

[0076] (4) After 15s, a spherical silicon-carbon composite material was obtained.

[0077] Example 2

[0078] The preparation of a spherical silicon-carbon composite material is basically the same as that in Example 1, except that the amount of graphite is 450g, the amount of Zhongning silicon is 50g, and the ratio of graphite to Zhongning silicon is 9:1.

[0079] Example 3

[0080] The preparation of a spherical silicon-carbon composite material is basically the same as that in Example 1, except that the amount of graphite is 400g, the amount of Zhongning silicon is 100g, and the ratio of graphite to Zhongning silicon is 8:2.

[0081] Example 4

[0082] The preparation of a spherical silicon-carbon composite material is basically the same as that in Example 1, except that the amount of graphite is 350g, the amount of Zhongning silicon is 150g, and the ratio of graphite to Zhongning silicon is 7:3.

[0083] Performance testing experiment

[0084] (1) The spherical silicon-carbon composite material prepared in Example 1 was characterized by scanning electron microscopy (SEM), and the results are as follows: Figure 1 As shown: The overall morphology of the product is spherical, and the sphere is composed of stacked sheet graphite. There are certain gaps between the graphite layers, which provide space for the volume expansion of nano-silicon. Nano-silicon is uniformly bonded on the graphite layer, forming a spherical structure of graphite coated with nano-silicon, which shortens the diffusion distance of lithium ions. The two are very tightly bonded, which is beneficial to the dynamic performance of lithium-ion batteries.

[0085] (2) The spherical silicon-carbon composite material prepared in Example 1 was characterized by XRD and Raman spectroscopy, and the results are as follows: Figure 2 and 3 As shown, its XRD diffraction peaks precisely match those of the standard PDF cards for graphite and silicon. The Raman spectra show that at 500 cm⁻¹... -1 There is an extremely strong crystallization peak at this point, corresponding to the Raman spectrum of nano-silicon.

[0086] (3) Electrochemical characterization was performed on the spherical silicon-carbon composites with different silicon-carbon ratios in Examples 1-4. Table 1 below shows the first-cycle coulombic efficiency and first-cycle charge specific capacity of the spherical silicon-carbon composites with silicon-carbon ratios of 1:9, 2:8, 3:7, and 5:5, compared with pure silicon and graphite, in the voltage range of 0.005-1.5V.

[0087] Table 1

[0088]

[0089] Figure 4The first-cycle charge-discharge curves of spherical silicon-carbon composite materials with silicon-carbon ratios of 1:9, 2:8, 3:7, and 5:5, along with pure silicon and graphite, were presented within a voltage range of 0.005-1.5V at 0.1C. The specific capacities of the spherical silicon-carbon composite materials with silicon-carbon ratios of 1:9, 2:8, 3:7, and 5:5 were 696.2 mAh / g and 634.6 mAh / g, 1012 mAh / g and 946.2 mAh / g, 1325.9 mAh / g and 1238.8 mAh / g, and 1891.5 mAh / g and 1763 mAh / g, respectively. Pure silicon showed 3428.96 mAh / g and 3177.53 mAh / g, while graphite only showed 355.63 mAh / g and 333.49 mAh / g. The presence of silicon nanoparticles significantly improved the specific capacity of graphite, greatly increasing the energy density of lithium-ion batteries. Its initial coulombic efficiencies were 91.15%, 93.5%, 93.43%, 93.21%, 93.78% (graphite) and 92.67% (pure silicon), respectively. Figure 4 As can be seen, the spherical silicon-carbon composite material exhibits a distinct discharge plateau near 0V, corresponding to the alloying of Si and Li. Furthermore, with the increase of the silicon-to-carbon ratio, i.e., the increase of silicon content, the initial charge-discharge specific capacity increases accordingly, and the initial efficiency also improves to some extent.

[0090] (4) Table 2 below shows the capacity retention and electrode expansion rate of spherical silicon-carbon composite materials and graphite and pure silicon with silicon-carbon ratios of 1:9, 2:8, 3:7, and 5:5 after 100 charge-discharge cycles in the voltage range of 0.005-1.5V:

[0091] Table 2

[0092]

[0093] Figure 5The performance curves are for spherical silicon-carbon composite materials with silicon-to-carbon ratios of 1:9, 2:8, 3:7, and 5:5, and for graphite and pure silicon, after 100 charge-discharge cycles in the voltage range of 0.005-1.5V. The first three cycles were activated at 0.1C, and subsequent tests were conducted at 1C. As shown in the figure, after 100 cycles, the remaining discharge specific capacities are 502.9 mAh / g, 603 mAh / g, 630.3 mAh / g, 1068.7 mAh / g, 268.85 mAh / g (graphite), and 1808.01 mAh / g (pure silicon), respectively; the capacity retention rates after 100 cycles are 72.23%, 59.58%, 47.54%, 56.5%, 75.6% (graphite), and 52.72% (pure silicon), respectively; and the corresponding electrode expansion rates after 100 cycles are 31.2%, 45.6%, 57.9%, 80.2%, 20.3% (graphite), and 231.5% (pure silicon), respectively. It can be seen that when the silicon-carbon content is relatively low, i.e., when the graphite content is high, the resulting spherical silicon-carbon composite material exhibits better cycle stability; when the silicon-carbon content is relatively high, i.e., when the nano-silicon content is high, the resulting spherical silicon-carbon composite material has a larger specific capacity and higher energy density. The presence of the graphite layer can suppress silicon expansion to a certain extent.

[0094] It should be understood that the application of the present invention is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A method for preparing spherical silicon-carbon composite materials, characterized in that, The preparation method comprises the following steps: The adhesive is dissolved in a first solvent and subjected to a first stirring process to obtain a first stirred mixture; Graphite is added to the first mixture, and a second stirring process is performed to obtain a second mixture. A silicon source, a second solvent, and a conductive agent are added to the second mixture, followed by a third stirring process to obtain a third mixture. The third stirred material is spray-dried to obtain the spherical silicon-carbon composite material, which includes a spherical structure formed by stacking graphite sheets and silicon bonded to the surface of the spherical structure.

2. The method for preparing spherical silicon-carbon composite material according to claim 1, characterized in that, The step of dissolving the binder in the first solvent and performing a first stirring treatment to obtain the first stirred product is as follows: adding the first solvent and the binder to a vacuum stirring vessel, setting the parameters of the vacuum stirring vessel, performing a first stirring treatment, and the first stirring treatment time is 5-150 min to obtain the first stirred product. The parameters of the vacuum stirring vessel include: stirring speed of 20-60 rpm and dispersion speed of 300-3000 rpm.

3. The method for preparing spherical silicon-carbon composite material according to claim 1, characterized in that, The step of adding graphite to the first stirred material and performing a second stirring treatment to obtain a second stirred material is as follows: adding graphite to a vacuum stirring vessel containing the first stirred material, setting the parameters of the vacuum stirring vessel, performing a second stirring treatment, and the second stirring treatment time is 5-150 min to obtain a second stirred material. The parameters of the vacuum stirring vessel include: stirring speed of 20-60 rpm and dispersion speed of 300-3000 rpm.

4. The method for preparing spherical silicon-carbon composite material according to claim 1, characterized in that, The step of adding a silicon source, a second solvent, and a conductive agent to the second stirred material and performing a third stirring treatment to obtain a third stirred material is as follows: adding a silicon source, a second solvent, and a conductive agent to a vacuum stirring vessel containing the second stirred material, setting the parameters of the vacuum stirring vessel, and performing a third stirring treatment for a time of 5-150 minutes to obtain a third stirred material. The parameters of the vacuum stirring vessel include: stirring speed of 20-60 rpm and dispersion speed of 300-3000 rpm.

5. The method for preparing spherical silicon-carbon composite material according to claim 1, characterized in that, The parameters for the spray drying process are: inlet temperature 100-300℃, outlet temperature 60-120℃, atomizing disc rotation speed 150-300Hz, and fan frequency 15-40Hz.

6. The method for preparing spherical silicon-carbon composite material according to claim 1, characterized in that, In the third stirring mixture, the mass ratio of graphite to silicon source is (3-8):(3-6), the mass ratio of graphite to binder is (95-100):(1-5), and the mass ratio of graphite to conductive agent is (95-100):(1-5).

7. The method for preparing spherical silicon-carbon composite material according to claim 1, characterized in that, The silicon source is selected from nano-silicon, micron-silicon, and porous silicon; the binder is selected from CMC binder, PVDF binder, and PMMA binder; the conductive agent is selected from carbon nanotubes, conductive carbon black, and graphene; the first solvent is selected from water, alcohol, and methanol; and the second solvent is selected from water, alcohol, and methanol.

8. The method for preparing spherical silicon-carbon composite material according to claim 1, characterized in that, The first stirring treatment, the second stirring treatment, and the third stirring treatment were each repeated at least twice.

9. A spherical silicon-carbon composite material, characterized in that, The spherical silicon-carbon composite material comprises a spherical structure formed by stacking graphite sheets and silicon bonded to the surface of the spherical structure. And / or, the spherical silicon-carbon composite material is prepared by the preparation method according to any one of claims 1-8.

10. The application of the spherical silicon-carbon composite material according to claim 9 in the preparation of lithium-ion batteries.

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