Silicon-carbon composite material, preparation method and application thereof

Abstract

The application discloses a silicon-carbon composite material and a preparation method and application thereof, and relates to the technical field of battery negative electrode materials.The silicon-carbon composite material comprises active material particles, and the active material particles comprise a skeleton of spherical porous carbon and nano silicon particles.The silicon-carbon composite material has high sphericity, and the problem that the poor compression resistance caused by many edges and corners is avoided in the rolling process, the problem that the solid electrolyte interface (SEI) film is continuously generated due to low strength, the capacity is weakened, and the cycle is deteriorated can be improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of battery negative electrode materials, in particular to a silicon-carbon composite material and a preparation method and application thereof. BACKGROUND

[0002] Nowadays, lithium ion batteries are indispensable in the fields of traditional 3C consumer electronics, new energy power batteries, large power generation plants, large-scale energy storage power stations and the like. As a traditional battery negative electrode material, the actual capacity of graphite has gradually approached its theoretical true capacity with the progress of technology. Under this background, silicon negative electrode with higher theoretical capacity is considered to be the best candidate for the next generation of high-capacity batteries. In order to inhibit the expansion of silicon during charging and discharging and improve the conductivity of silicon element, it is necessary to coat silicon in a porous carbon substrate with high specific surface.

[0003] In the process of battery production, the strength of the silicon-carbon composite material has certain requirements to prevent the particles from being broken due to rolling, so that the silicon particles are exposed and serious volume expansion occurs during charging and discharging, affecting the performance of the battery. The strength of the silicon-carbon composite material is related to various factors, such as material particle size, silicon content, morphology, etc. The particle breakage caused by rolling is greatly related to the morphology of the silicon-carbon material. Irregular silicon-carbon composite material will cause mutual extrusion between particles during rolling, resulting in the breakage of irregular edges and corners, and the shedding of internal active substances, which is not conducive to the formation of stable SEI film.

[0004] In view of this, the present application is proposed. SUMMARY

[0005] The purpose of the present application is to provide a silicon-carbon composite material, a preparation method and application thereof, and a detection method of the silicon-carbon composite material. The silicon-carbon composite material has high sphericity, avoids poor compression resistance caused by many edges and corners during rolling, prevents particle breakage, and can improve the problem of continuous formation of solid electrolyte interface (SEI) film due to low strength, capacity weakening and cycle deterioration.

[0006] In order to achieve the above purpose, the present application adopts the following technical solutions:

[0007] In a first aspect, the present application provides a silicon-carbon composite material, which comprises active material particles, and the active material particles comprise a skeleton of spherical porous carbon and nano-silicon particles.

[0008] The strength of the silicon-carbon composite material is defined by the following formula:

[0009]

[0010] Wherein, P represents the strength of the silicon-carbon composite material, %; S2 represents the specific surface area of the silicon-carbon composite material after pressing, m2 S1 represents the specific surface area of the silicon-carbon composite material before pressing, m 2 / g.

[0011] Preferably, the specific surface area of the silicon-carbon composite material is 2-5 m 2 / g.

[0012] Preferably, the strength of the silicon-carbon composite material under a pressure of 450 MPa for 30 s is above 90%.

[0013] Preferably, the sphericity of the spherical porous carbon is ≥80%.

[0014] Preferably, the spherical porous carbon contains uniformly distributed micropores and / or mesopores inside.

[0015] Preferably, the total pore volume of the spherical porous carbon with an average pore diameter less than 4 nm is ≥0.7 cm 3 / g.

[0016] Preferably, the mesopore ratio of the spherical porous carbon is <20%, and the micropore ratio is >80%.

[0017] Preferably, the particle size of the spherical porous carbon is 1-60 μm; wherein the D 10 particle size is 3-7 μm; the D 50 particle size is 8-13 μm; and the D 90 particle size is 15-40 μm.

[0018] Preferably, the nano-silicon particles are deposited in the pores of the spherical porous carbon.

[0019] Preferably, the content of silicon in the silicon-carbon composite material is 40-60%.

[0020] Preferably, the specific capacity of the silicon-carbon composite material is >1500 mAh / g, and preferably the specific capacity is >1800 mAh / g.

[0021] Preferably, the capacity retention rate of the silicon-carbon composite material after 200 cycles is >90%.

[0022] In a second aspect, the present application provides a preparation method of the silicon-carbon composite material according to the first aspect, and the preparation method comprises the following steps:

[0023] Mixing low-carbon source microspheres, high-carbon source resin and solvent to obtain a mixed solution;

[0024] Spray drying the mixed solution to obtain small spherical particles;

[0025] Carrying out carbonization treatment and activation treatment on the small spherical particles in sequence to obtain spherical porous carbon;

[0026] The spherical porous carbon is subjected to vapor phase deposition to obtain the silicon-carbon composite material.

[0027] Preferably, the residual carbon content of the low carbon source microspheres is ≤40%.

[0028] Preferably, the residual carbon content of the high carbon source resin is 50-70%.

[0029] Preferably, the low-carbon source microspheres include any one or a combination of at least two of polystyrene microspheres, polylactic acid microspheres, or polyvinylidene fluoride microspheres.

[0030] Preferably, the high carbon source resin is a phenolic resin and / or a phenolic resin derivative.

[0031] Preferably, the mass ratio of the low-carbon source microspheres to the high-carbon source resin is 1:(1-5).

[0032] Preferably, the solvent includes an alcohol solvent, and more preferably ethanol.

[0033] Preferably, the solid content of the mixture is 30-60 wt%.

[0034] Preferably, the mixture further includes 5-10 wt% carbon nanotubes.

[0035] Preferably, the mixture further includes a conductive polymer, which includes any one or a combination of at least two of polyacetylene, polythiophene, polypyrrole, or polyaniline.

[0036] Preferably, the spray drying process parameters include: centrifugal disc rotation speed of 24,000 to 30,000 rpm; air inlet temperature of 160 to 230°C; feed rate of 1.2 to 4 L / h; and induced draft fan frequency of 40 to 50 Hz.

[0037] Preferably, the carbonization temperature is 400–900°C, and the carbonization time is 3–10 hours.

[0038] Preferably, the activation treatment is performed using a physical activation method.

[0039] Preferably, the physical activation step is as follows: physical activation is performed by introducing an activation gas into the carbon microspheres obtained after carbonization treatment.

[0040] Preferably, the activating gas includes carbon dioxide and / or water vapor.

[0041] Preferably, the temperature for physical activation is 800–1000°C, and the time for physical activation is 7–20 h.

[0042] Preferably, the activation treatment further includes a step of removing impurities: the activated porous carbon microspheres are acid-washed to remove impurities, then washed with water and dried.

[0043] Preferably, the pickling is performed using a 5-8 wt% hydrochloric acid solution.

[0044] Preferably, the pickling temperature is 20–100°C, and the pickling time is 1–24 hours.

[0045] Preferably, the drying temperature is 70–90°C.

[0046] Preferably, the deposition gas source for the vapor deposition is a mixture of protective gas and silicon source gas.

[0047] Preferably, the protective gas includes any one or a combination of at least two of nitrogen, neon, argon, krypton, xenon, or radon.

[0048] Preferably, the silicon source gas includes any one or a combination of at least two of silane, disilane, dichlorosilane, or trichlorosilane.

[0049] Preferably, the silicon source gas further includes a carbon source gas, which includes any one or a combination of at least two of methane, ethane, acetylene, or ethylene.

[0050] Preferably, the volume ratio of the protective gas to the silicon source gas is (10-30):(70-90).

[0051] Preferably, the content of the carbon source gas accounts for 0-30% of the total volume of the silicon source gas.

[0052] Preferably, the ratio of the amount of vapor deposition to the amount of material fed is (0.4-1.5):1.

[0053] Preferably, the temperature of the vapor deposition is 300–800°C, and the time of the vapor deposition is 5–10 hours.

[0054] Thirdly, the present invention provides an application of the silicon-carbon composite material as described in the first aspect in the preparation of battery anode materials.

[0055] Fourthly, the present invention provides a method for detecting silicon-carbon composite materials, the method comprising the following steps:

[0056] The specific surface area of ​​the silicon-carbon composite material before pressure is obtained and denoted as S1;

[0057] The silicon-carbon composite material was compacted to break the sample, and the specific surface area of ​​the broken silicon-carbon composite material after compaction was obtained and denoted as S2.

[0058] The specific surface area change rate of the silicon-carbon composite material is calculated using the following formula to characterize the strength of the silicon-carbon composite material;

[0059] The strength of the silicon-carbon composite material is defined by the following formula:

[0060]

[0061] Wherein, P represents the strength of the silicon-carbon composite material, %; S2 represents the specific surface area of ​​the silicon-carbon composite material before compression, m². 2 / g; S1 represents the specific surface area of ​​the silicon-carbon composite material after compression, in m² 2 / g.

[0062] Preferably, the compaction rate is 8-12 mm / min, and more preferably 10 mm / min.

[0063] Preferably, the holding time for the compaction process is 10 to 50 seconds, and more preferably 30 seconds.

[0064] Preferably, the compaction pressure is 450–500 MPa.

[0065] Compared with the prior art, the present invention has the following beneficial effects:

[0066] (1) This invention utilizes the morphology of carbon microspheres and the high carbon content of phenolic resin to synthesize carbon substrates with good sphericity. The particle size of carbon microspheres can be well controlled by spray drying technology, and the particle size uniformity is good.

[0067] (2) Compared with irregular resin-based silicon-carbon composite materials, the silicon-carbon materials synthesized by this method have higher strength and do not have the large pores naturally present in biomass-based materials.

[0068] (3) The silicon-carbon anode material of the present invention has high sphericity, which avoids poor compressive strength caused by having many sharp edges during the rolling process. It can improve the situation where the solid electrolyte interphase (SEI) film is continuously generated due to low strength, resulting in reduced capacity and poor cycle performance.

[0069] (4) This invention compares the change rate of specific surface area before and after pressing to quantify the strength of silicon-carbon composite materials. It uses a formula to characterize the strength and limit the strength range of silicon-carbon composite materials. This avoids the problems of traditional nanoindentation instruments used to detect the strength of silicon-carbon anode materials, such as the lack of adhesion of the sample, easy crushing and running, plateau period, erroneous data, and the fact that only a single particle can be evaluated. Attached Figure Description

[0070] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0071] Figure 1 The image shown is a scanning electron microscope (SEM) image of the silicon-carbon anode material prepared in Example 1.

[0072] Figure 2 The image shown is a scanning electron microscope (SEM) image of the silicon-carbon anode material prepared in Example 2.

[0073] Figure 3 The image shown is a scanning electron microscope (SEM) image of the silicon-carbon anode material prepared in Example 3.

[0074] Figure 4 The image shown is a scanning electron microscope (SEM) image of the silicon-carbon anode material prepared in Comparative Example 1.

[0075] Figure 5 The image shown is a scanning electron microscope (SEM) image of the silicon-carbon anode material prepared in Comparative Example 2.

[0076] Figure 6 The image shows a scanning electron microscope (SEM) image of the carbonized microspheres prepared in Comparative Example 3.

[0077] Figure 7 The image shown is a scanning electron microscope (SEM) image of the silicon-carbon anode material prepared in Comparative Example 4.

[0078] Figure 8 The particle size distribution diagram is shown for the silicon-carbon anode material prepared in Example 1.

[0079] Figure 9 The image shows the N2 adsorption-desorption isotherm of the silicon-carbon anode material prepared in Example 1. Detailed Implementation

[0080] Unless otherwise defined herein, the scientific and technical terms used in conjunction with this invention shall have the meanings commonly understood by one of ordinary skill in the art. The meaning and scope of terms shall be clear; however, in any case of potential ambiguity, the definitions provided herein shall prevail over any dictionary or foreign definitions. In this application, unless otherwise stated, the use of "or" means "and / or". Furthermore, the use of the term "comprising" and other forms is non-limiting.

[0081] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. 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.

[0082] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0083] In a first aspect, the present invention provides a silicon-carbon composite material, the silicon-carbon composite material comprising active material particles, the active material particles comprising a spherical porous carbon framework and nano-silicon particles;

[0084] The strength of the silicon-carbon composite material is defined by the following formula:

[0085]

[0086] Wherein, P represents the strength of the silicon-carbon composite material, %; S2 represents the specific surface area of ​​the silicon-carbon composite material after compression, m². 2 / g; S1 represents the specific surface area of ​​the silicon-carbon composite material before compression, in m² 2 / g.

[0087] In this invention, silicon-carbon composite materials with high sphericity are prepared by chemically depositing nano-silicon particles into the pores of a spherical porous carbon framework. Simultaneously, the silicon-carbon composite material is compacted. After compaction, electron microscopy characterization revealed that most particles of the silicon-carbon composite material broke down, mainly through-cracks, which increased the specific surface area of ​​the particles. Thus, the degree of particle breakage can be quantified by characterizing the specific surface area before and after compaction. Furthermore, it was found that the compaction density and the applied pressure have a good linear correlation with the specific surface area after compaction. Therefore, the change rate of specific surface area before and after compaction is used to characterize the strength.

[0088] In an optional embodiment, the specific surface area of ​​the silicon-carbon composite material is 2–5 m². 2 / g, for example, could be 2m 2 / g, 2.5m 2 / g、3m 2 / g, 3.5m 2 / g、4m 2 / g, 4.5m 2 / g、5m 2 / g etc.

[0089] In an optional embodiment, the silicon-carbon composite material has a strength of over 90% when compressed under a pressure of 450 MPa for 30 seconds, for example, it can be 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, etc.

[0090] In an optional embodiment, the sphericity of the spherical porous carbon is ≥80%, for example, it can be 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, etc.

[0091] In an optional embodiment, the interior of the spherical porous carbon contains uniformly distributed micropores and / or mesopores.

[0092] In an optional embodiment, the spherical porous carbon has an average pore diameter of less than 4 nm and a total pore volume ≥ 0.7 cm³. 3 / g, for example, could be 0.7cm 3 / g, 0.75cm 3 / g, 0.8cm 3 / g, 0.85cm 3 / g, 0.9cm 3 / g, 1.0cm 3 / g etc.

[0093] In an optional embodiment, the mesoporous carbon of the spherical porous carbon is <20%, for example, it can be 19%, 18%, 17%, 16%, 15%, 14%, 12%, 10%, 8%, 6%, 4%, 2%, 1%, etc.

[0094] In an optional embodiment, the microporosity of the spherical porous carbon is >80%, for example, it can be 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, etc.

[0095] In an optional embodiment, the particle size of the spherical porous carbon is 1 to 60 μm, for example, it can be 1 μm, 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, etc.

[0096] In an optional embodiment, the D of the spherical porous carbon 10 The particle size is 3 to 7 μm, for example, it can be 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, etc.

[0097] In an optional embodiment, the D of the spherical porous carbon 50 The particle size is 8–13 μm, for example, it can be 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, etc.

[0098] In an optional implementation, D 90 The particle size is 15–40 μm, for example, it can be 15 μm, 18 μm, 20 μm, 22 μm, 24 μm, 26 μm, 28 μm, 30 μm, 32 μm, 34 μm, 36 μm, 38 μm, 40 μm, etc.

[0099] In an optional embodiment, the nano-silicon particles are deposited in the pores of the spherical porous carbon.

[0100] In an optional embodiment, the silicon content in the silicon-carbon composite material is 40% to 60%, for example, it can be 40%, 42%, 44%, 46%, 48%, 50%, 52%, 54%, 56%, 58%, 60%, etc.

[0101] In optional embodiments, the specific capacity of the silicon-carbon composite material is >1500mAh / g, for example, it can be 1501mAh / g, 1505mAh / g, 1510mAh / g, 1550mAh / g, 1600mAh / g, 1650mAh / g, 1700mAh / g, 1750mAh / g, 1780mAh / g, 1790mAh / g, 1800mAh / g, 1820mAh / g, 1830mAh / g, 1840mAh / g, 1850mAh / g, 1860mAh / g, 1870mAh / g, 1880mAh / g, 1890mAh / g, 1900mAh / g, etc., preferably with a specific capacity >1800mAh / g.

[0102] In an optional embodiment, the capacity retention rate of the silicon-carbon composite material after 200 cycles is >90%, for example, it can be 90%, 92%, 94%, 95%, 96%, 98%, 99%, etc.

[0103] In a second aspect, the present invention provides a method for preparing a silicon-carbon composite material as described in the first aspect, the method comprising the following steps:

[0104] Low-carbon-source microspheres, high-carbon-source resin and solvent are mixed to obtain a mixture;

[0105] The mixture was spray-dried to obtain small spherical particles;

[0106] The small spherical particles were sequentially subjected to carbonization and activation treatments to obtain spherical porous carbon.

[0107] The spherical porous carbon is subjected to vapor phase deposition to obtain the silicon-carbon composite material.

[0108] This invention utilizes a mixture of low-carbon-content microspheres and a high-carbon-source resin liquid, followed by spray drying to form small spheres. The particle size of the spherical carbon is controlled by adjusting the curing conditions of the spray drying process, resulting in spherical carbon with high carbon content and good sphericity. Further, pores are created using chemical and physical methods. During the carbonization and activation pore-forming process, there is no hollowing, and large internal pores prevent strength reduction, thus producing spherical porous carbon with high sphericity and high strength. Finally, nano-silicon particles are deposited into the pores of the spherical porous carbon framework via vapor deposition, yielding a silicon-carbon composite material with high sphericity. Higher sphericity also avoids poor compressive strength due to numerous sharp edges during rolling, mitigating the effects of low strength leading to continuous formation of the solid electrolyte interphase (SEI) film, reduced capacity, and poor cycle life. Specifically, the spherical silicon-carbon composite material retains over 90% of its strength under 450 MPa pressure for 30 seconds, while irregularly shaped silicon-carbon composite materials have a strength less than 90%.

[0109] In an optional embodiment, the residual carbon content of the low carbon source microspheres is ≤40%, for example, it can be 40%, 35%, 30%, 25%, 20%, 15%, 10%, 5%, etc.

[0110] In an optional embodiment, the residual carbon content of the high carbon source resin is 50-70%, for example, it can be 50%, 55%, 60%, 65%, 70%, etc.

[0111] In an optional embodiment, the low-carbon source microspheres include any one or a combination of at least two of polystyrene microspheres, polylactic acid microspheres, or polyvinylidene fluoride microspheres. The high-carbon source resin is a phenolic resin and / or a phenolic resin derivative.

[0112] In an optional embodiment, the mass ratio of the low-carbon source microspheres to the high-carbon source resin is 1:(1-5), for example, it can be 1:1, 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5, 1:5, etc.

[0113] In an optional embodiment, the solvent includes an alcohol solvent, preferably ethanol;

[0114] In an optional embodiment, the solid content of the mixture is 30-60 wt%, for example, it can be 30 wt%, 32 wt%, 34 wt%, 36 wt%, 38 wt%, 40 wt%, 42 wt%, 44 wt%, 46 wt%, 48 wt%, 50 wt%, 52 wt%, 54 wt%, 56 wt%, 58 wt%, 60 wt%, etc.

[0115] In an optional embodiment, the mixture may further include 5 to 10 wt% carbon nanotubes, for example, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, etc.

[0116] It should be noted that in this invention, in addition to the fusion of microspheres with a high carbon source resin, a certain amount of carbon nanotubes can also be added to further increase the conductivity of the silicon-carbon composite material.

[0117] In an optional embodiment, the mixture further includes a conductive polymer, which includes any one or a combination of at least two of polyacetylene, polythiophene, polypyrrole, or polyaniline.

[0118] It should be noted that in this invention, in addition to the fusion of microspheres with high carbon source resin, a certain amount of conductive polymer can also be added to increase active defects, thereby further increasing the conductivity of silicon-carbon composite material.

[0119] In an optional embodiment, the spray drying process parameters include: centrifugal disc rotation speed of 24,000 to 30,000 rpm; inlet air temperature of 160 to 230°C; feed rate of 1.2 to 4 L / h; and induced draft fan frequency of 40 to 50 Hz.

[0120] In an optional embodiment, the centrifugal disc rotates at a speed of 24,000 to 30,000 rpm, for example, 24,000 rpm, 25,000 rpm, 26,000 rpm, 27,000 rpm, 28,000 rpm, 29,000 rpm, 30,000 rpm, etc.

[0121] In an optional embodiment, the air inlet temperature is 160-230°C, for example, it can be 160°C, 170°C, 180°C, 190°C, 200°C, 210°C, 220°C, 230°C, etc.

[0122] In an optional embodiment, the feeding rate is 1.2 to 4 L / h, for example, it can be 1.2 L / h, 1.4 L / h, 1.6 L / h, 1.8 L / h, 2 L / h, 2.2 L / h, 2.4 L / h, 2.6 L / h, 2.8 L / h, 3 L / h, 3.2 L / h, 3.4 L / h, 3.6 L / h, 3.8 L / h, 4 L / h, etc.

[0123] In an optional embodiment, the frequency of the induced draft fan is 40-50Hz, for example, it can be 40Hz, 42Hz, 44Hz, 46Hz, 48Hz, 50Hz, etc.

[0124] In an optional embodiment, the carbonization temperature is 400–900°C, for example, it can be 400°C, 450°C, 500°C, 550°C, 600°C, 620°C, 640°C, 660°C, 680°C, 700°C, 720°C, 740°C, 760°C, 780°C, 800°C, 820°C, 840°C, 860°C, 880°C, 900°C, etc.

[0125] In an optional embodiment, the carbonization treatment time is 3 to 10 hours, for example, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, etc.

[0126] In an optional embodiment, the activation treatment includes physical activation and / or chemical activation.

[0127] In an optional implementation, the activation process is performed using a physical activation method.

[0128] In an optional embodiment, the physical activation step is as follows: an activation gas is introduced into the carbon microspheres obtained after carbonization treatment for physical activation.

[0129] In an optional embodiment, the activating gas includes carbon dioxide and / or water vapor.

[0130] In an optional embodiment, the temperature for physical activation is 800 to 1000°C, for example, it can be 800°C, 820°C, 840°C, 860°C, 880°C, 900°C, 920°C, 940°C, 960°C, 980°C, 1000°C, etc.

[0131] In an optional implementation, the physical activation time is 7 to 20 hours, for example, 7 hours, 8 hours, 9 hours, 10 hours, 12 hours, 14 hours, 16 hours, 18 hours, 20 hours, etc.

[0132] In an optional embodiment, the activation treatment further includes a step of removing impurities: the activated porous carbon microspheres are acid-washed to remove impurities, then washed with water and dried.

[0133] In an optional embodiment, the pickling uses a 5-8 wt% hydrochloric acid solution, for example, 5 wt%, 5.5 wt%, 6 wt%, 6.5 wt%, 7 wt%, 7.5 wt%, 8 wt%, etc.

[0134] In an optional embodiment, the pickling temperature is 20 to 100°C, for example, it can be 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C, etc.

[0135] In an optional embodiment, the pickling time is 1 to 24 hours, for example, it can be 1 hour, 2 hours, 4 hours, 6 hours, 8 hours, 10 hours, 12 hours, 14 hours, 16 hours, 18 hours, 20 hours, 22 hours, 24 hours, etc.

[0136] In an optional embodiment, the drying temperature is 70-90°C, for example, 70°C, 75°C, 80°C, 85°C, 90°C, etc.

[0137] In an optional embodiment, the deposition gas source for the vapor deposition is a mixture of protective gas and silicon source gas.

[0138] In an optional embodiment, the protective gas includes any one or a combination of at least two of nitrogen, neon, argon, krypton, xenon, or radon.

[0139] In an optional embodiment, the silicon source gas includes any one or a combination of at least two of silane, disilane, dichlorosilane, or trichlorosilane.

[0140] In an optional embodiment, the volume ratio of the protective gas to the silicon source gas is (10-30):(70-90);

[0141] Among them, "10 to 30" can be, for example, 10, 12, 15, 18, 20, 22, 25, 28, 30, etc.

[0142] Among them, "70-90" can be, for example, 70, 72, 75, 78, 80, 82, 85, 88, 90, etc.

[0143] In an optional embodiment, the ratio of the amount of vapor deposition to the amount of feed material is (0.4 to 1.5):1, for example, it can be 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, etc.

[0144] In an optional embodiment, the temperature of the vapor deposition is 300 to 800°C, for example, 300°C, 350°C, 400°C, 450°C, 500°C, 550°C, 600°C, 650°C, 700°C, 750°C, 800°C, etc.

[0145] In an optional embodiment, the vapor deposition time is 5 to 10 hours, for example, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, etc.

[0146] In an optional embodiment, the method for preparing the silicon-carbon composite material includes the following steps:

[0147] S1. Preparation of low-carbon-source microspheres / high-carbon-source resin mixture:

[0148] Low-carbon-source microspheres and high-carbon-source resin are mixed and dispersed in a solvent to obtain a mixture;

[0149] S2, Spray drying:

[0150] The mixture obtained in S1 was spray-dried to obtain small spherical particles with a sphericity >80%.

[0151] S3, carbonization treatment:

[0152] The small spherical particles obtained in S2 were carbonized under an inert atmosphere to obtain carbonized carbon microspheres.

[0153] S4. Activation treatment:

[0154] The carbonized carbon microspheres obtained from S3 were activated to obtain porous carbon microspheres.

[0155] S5. Impurity Removal:

[0156] The porous carbon microspheres obtained from S4 were acid-washed to remove impurities, and then washed with water and dried.

[0157] S6, Chemical Vapor Deposition:

[0158] The porous carbon microspheres obtained after impurity removal in S5 were subjected to chemical vapor deposition to obtain the silicon-carbon composite material.

[0159] Thirdly, the present invention provides an application of the silicon-carbon composite material in the preparation of battery anode materials.

[0160] Fourthly, the present invention provides a method for detecting silicon-carbon composite materials, the method comprising the following steps:

[0161] The specific surface area of ​​the silicon-carbon composite material before pressure is obtained and denoted as S1;

[0162] The silicon-carbon composite material was compacted to break the sample, and the specific surface area of ​​the silicon-carbon composite material after crushing under test was obtained and recorded as S2.

[0163] The specific surface area change rate of the silicon-carbon composite material is calculated using the following formula to characterize the strength of the silicon-carbon composite material;

[0164] The strength of the silicon-carbon composite material is defined by the following formula:

[0165]

[0166] Wherein, P represents the strength of the silicon-carbon composite material, %; S2 represents the specific surface area of ​​the silicon-carbon composite material after compression, m².2 / g; S1 represents the specific surface area of ​​the silicon-carbon composite material before compression, in m² 2 / g.

[0167] This invention does not limit the testing method for the specific surface area of ​​silicon-carbon composite materials; for example, the BET method can be used for testing.

[0168] The present invention does not limit the instrument used for compaction of silicon-carbon composite materials. Preferably, a compaction density meter is used for compaction.

[0169] In this invention, a compaction density meter and a specific surface area meter are combined to quantify the strength of the silicon-carbon composite anode material by comparing the rate of change of specific surface area before and after compaction. Electron microscopy characterization of the silicon-carbon material after compaction revealed that most particles broke apart, primarily through-cracks, while the specific surface area of ​​the particles increased. Therefore, the degree of particle breakage is quantified by characterizing the specific surface area of ​​the particles before and after compaction.

[0170] In an optional implementation, a laser particle size analyzer can also be used to test the particle size distribution of silicon-carbon powder in accordance with GB / T 19077. During the testing of the particle size of silicon-carbon composite materials, if two identical samples are compared, D(50) can be controlled to be the same.

[0171] In an optional implementation, the compaction process must meet the following conditions to break the sample: setting appropriate pressurization and depressurization displacements, holding pressure and holding time, so that the sample particles break under the same pressure (i.e., ensuring that the pressurization time and holding time can crush the sample).

[0172] In an optional embodiment, the specific process of the compaction treatment is as follows: weigh an appropriate amount of silicon carbide powder sample into the sample chamber of the compaction density meter; set the compaction test conditions: set appropriate pressurization and depressurization displacements, holding pressure and holding time, so that the sample particles break under the same pressure (ensure that the pressurization time and holding time can crush the sample); after the test, use the rod ejector to remove the sample and collect the sample after compression; mix the collected samples for testing.

[0173] In an optional embodiment, the compaction rate is 8 to 12 mm / min, for example, 8 mm / min, 9 mm / min, 10 mm / min, 11 mm / min, 12 mm / min, etc., preferably 10 mm / min.

[0174] In an optional embodiment, the holding time of the compaction process is 10 to 50 seconds, for example, 10 seconds, 15 seconds, 20 seconds, 25 seconds, 30 seconds, 35 seconds, 40 seconds, 45 seconds, 50 seconds, etc., preferably 30 seconds.

[0175] In an optional embodiment, the compaction pressure is 450-500 MPa, for example, 450 MPa, 460 MPa, 470 MPa, 480 MPa, 490 MPa, 500 MPa, etc.

[0176] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0177] Some raw material parameters are shown below in the following examples:

[0178] Low-carbon source carbon microspheres: Beijing Deco Island Gold Technology Co., Ltd.; Model: PSC002000, residual carbon content is 15-20%, particle size is 2um.

[0179] High carbon source solid resin: Guangzhou Shuangli Rubber Raw Material Trading Co., Ltd.; Model: 9003-35-4, residual carbon content is 50-70%.

[0180] Example 1

[0181] This embodiment provides a silicon-carbon composite material, which is prepared by the following steps:

[0182] S1. Carbon microspheres with a residual carbon content of 15% and resin with a residual carbon content of 55% are mixed and dispersed in anhydrous ethanol at a mass ratio of 1:1 to form a spray liquid with a solid content of 30%.

[0183] S2. Conduct a spraying experiment on the above spray liquid: Spray curing conditions: atomizing disc speed: 28000rpm, air inlet temperature: 175℃, feed rate: 1.8L / h, fan frequency: 50Hz, sprayed carbon microspheres with a particle size of 5~20μm.

[0184] S3. The solidified carbon microspheres are heat-treated in a nitrogen atmosphere at a heating rate of 10 / min and a heat treatment temperature of 400°C for 5 hours to obtain carbonized carbon microspheres.

[0185] S4. Place the carbonized carbon microspheres into a well-sealed rotary kiln, rotate the kiln at a frequency of 30Hz, introduce steam at a flow rate of 12L / min, and raise the temperature of the rotary kiln to 900℃ at a rate of 10℃ / min. Hold the temperature for 8 hours, and then cool to room temperature to obtain the material.

[0186] S5. Soak the material obtained from S4 in 6.5% HCl and heat it to 60°C and stir for 1 hour. Then wash it with pure water until neutral and dry it at 80°C to obtain spherical porous carbon.

[0187] The spherical porous carbon has a sphericity of 92.5%; the interior of the spherical porous carbon contains uniformly distributed micropores and mesopores, and the average pore size of the spherical porous carbon is 1.89 nm; the total pore volume of the spherical porous carbon with an average pore size of less than 4 nm is 0.84 cm³. 3 / g; the spherical porous carbon has a mesoporous ratio of 19% and a microporous ratio of 81%; the particle size of the spherical porous carbon is 8.3μm; wherein, the D of the spherical porous carbon... 10 Particle size is 3.5 μm; D 50 Particle size is 8.3 μm; D 90 The particle size is 19.8 μm.

[0188] S6. Place the spherical porous carbon material obtained in S5 into a well-sealed rotary kiln, rotate the kiln at a frequency of 40Hz, and introduce a mixture of protective gas and silicon source gas: nitrogen and silane (the volume ratio of nitrogen to silane is 20:80). The deposition amount to the material feed ratio is 0.6, the deposition temperature is 500℃, and the deposition time is 6h to obtain the silicon-carbon composite material.

[0189] Figure 1 This is a scanning electron microscope (SEM) image of the silicon-carbon composite material prepared in Example 1. Figure 1 As shown, low-carbon source microspheres are combined with high-carbon source resin matrix, and the particle size of spherical carbon is controlled by spray drying to prepare a high-carbon carbon substrate with good sphericity. Moreover, when carbon substrate microspheres are prepared using this method, there is no hollow phenomenon during carbonization and alkali activation pore-forming process, and there are no large pores inside that would weaken the strength.

[0190] Example 2

[0191] This embodiment provides a silicon-carbon composite material, which differs from Embodiment 1 only in that the spray curing conditions in S2 are different, as detailed below:

[0192] S2. Conduct a spraying experiment on the above spray liquid: Spray curing conditions: atomizing disc speed: 28000rpm, inlet air temperature: 190℃, feed rate: 2.3L / h, induced draft fan frequency: 50Hz, sprayed carbon microspheres with a particle size of 6~40μm.

[0193] Figure 2 The image shown is a scanning electron microscope (SEM) image of the silicon-carbon composite material prepared in Example 2. Figure 1 As shown, low-carbon source microspheres are combined with high-carbon source resin matrix, and the particle size of spherical carbon is controlled by spray drying to prepare a high-carbon carbon substrate with good sphericity. Moreover, when carbon substrate microspheres are prepared using this method, there is no hollow phenomenon during carbonization and alkali activation pore-forming process, and there are no large pores inside that would weaken the strength.

[0194] Example 3

[0195] This embodiment provides a silicon-carbon composite material, which differs from Embodiment 1 only in that the spray curing conditions in S2 are different, as detailed below:

[0196] S2. Conduct a spraying experiment on the above spray liquid: Spray curing conditions: atomizing disc speed: 28000rpm, air inlet temperature: 200℃, feed rate: 3.2L / h, fan frequency: 50Hz, sprayed carbon microspheres with a particle size of 5~20μm.

[0197] Figure 3 The image shown is a scanning electron microscope (SEM) image of the silicon-carbon composite material prepared in Example 3. Figure 1 As shown, low-carbon source microspheres are combined with high-carbon source resin matrix, and the particle size of spherical carbon is controlled by spray drying to prepare a high-carbon carbon substrate with good sphericity. Moreover, when carbon substrate microspheres are prepared using this method, there is no hollow phenomenon during carbonization and alkali activation pore-forming process, and there are no large pores inside that would weaken the strength.

[0198] Example 4

[0199] This embodiment provides a silicon-carbon composite material. The difference from Embodiment 1 is that in S1, the mass ratio of the low-carbon source microspheres to the high-carbon source resin is 1:5, while the other steps are completely consistent with Embodiment 1.

[0200] Example 5

[0201] This embodiment provides a silicon-carbon composite material, which differs from Embodiment 1 in that the S3 carbonization treatment temperature is 600℃; the carbonization treatment time is 10h, and the other steps are completely consistent with Embodiment 1.

[0202] Example 6

[0203] This embodiment provides a silicon-carbon composite material, which differs from Embodiment 1 in that the S3 carbonization treatment temperature is 900℃; the carbonization treatment time is 3 hours, and the other steps are completely consistent with Embodiment 1.

[0204] Example 7

[0205] This embodiment provides a silicon-carbon composite material, which differs from Embodiment 1 in that the activation temperature in S4 is 800°C and the activation time is 20 hours, while the other steps are completely consistent with Embodiment 1.

[0206] Example 8

[0207] This embodiment provides a silicon-carbon composite material, which differs from Embodiment 1 in that the activation temperature in S4 is 1000℃ and the activation time is 7h, while the other steps are completely consistent with Embodiment 1.

[0208] Example 9

[0209] This embodiment provides a silicon-carbon composite material, which differs from Embodiment 1 in that the deposition amount to feed material ratio is 0.4, the deposition temperature is 300℃, and the deposition time is 10h. The other steps are completely the same as in Embodiment 1.

[0210] Example 10

[0211] This embodiment provides a silicon-carbon composite material, which differs from Embodiment 1 in that the deposition amount to feed material ratio is 1.5, the deposition temperature is 800℃, and the deposition time is 5h. The other steps are completely consistent with Embodiment 1.

[0212] Comparative Example 1

[0213] This comparative example provides a silicon-carbon composite material, which is prepared by the following steps:

[0214] S1. Disperse resin with a residual carbon content of 55% in anhydrous ethanol to form a spray liquid with a solid content of 30%.

[0215] S2. Conduct a spraying experiment on the above spray liquid: Spray curing conditions: atomizing disc speed: 28000rpm, inlet air temperature: 175℃, feed rate: 1.8L / h, induced draft fan frequency: 50Hz, sprayed carbon microspheres with a particle size of 5~20μm and a sphericity of 70~80%.

[0216] S3. The solidified carbon microspheres are heat-treated in a nitrogen atmosphere at a heating rate of 10 / min and a heat treatment temperature of 400°C for 5 hours to obtain carbonized carbon microspheres.

[0217] S4. Place the carbonized carbon microspheres into a well-sealed rotary kiln, rotate the kiln at a frequency of 30Hz, introduce steam at a flow rate of 12L / min, and raise the temperature of the rotary kiln to 900℃ at a rate of 10℃ / min. Hold the temperature for 8 hours, and then cool to room temperature to obtain the material.

[0218] S5. Soak the material obtained from S4 in 6.5% HCl and heat it to 60°C and stir for 1 hour. Then wash it with pure water until neutral and dry it at 80°C to obtain spherical porous carbon.

[0219] S6. Place the spherical porous carbon material obtained in S5 into a well-sealed rotary kiln, rotate the kiln at a frequency of 40Hz, and introduce a mixture of protective gas and silicon source gas: nitrogen and silane (the volume ratio of nitrogen to silane is 20:80). The deposition amount to the material feed ratio is 0.6, the deposition temperature is 500℃, and the deposition time is 6h to obtain the silicon-carbon composite material.

[0220] Figure 4 Here is an electron microscope image of the silicon-carbon composite material prepared in Comparative Example 1, as shown. Figure 4 As shown, without adding low-carbon source microspheres, but only using high-carbon source resin liquid for spray drying granulation, the sphericity of the silicon-carbon composite material prepared by this method is poor.

[0221] Comparative Example 2

[0222] This comparative example provides a silicon-carbon composite material, which is prepared by the following steps:

[0223] S1. Dissolve the resin with a residual carbon content of 55% in anhydrous ethanol to form a resin liquid with a solid content of 30%. Then, cure the resin liquid in a vacuum oven at 120°C for 4 hours.

[0224] S2. The solidified carbon particles are heat-treated in a nitrogen atmosphere at a heating rate of 10 / min and a heat treatment temperature of 400°C for 5 hours to obtain the pre-carbonized material.

[0225] S3. Crush the pre-carbonized material into uniform particles at the millimeter level using a crusher for later use.

[0226] S4. Place the carbonized carbon microspheres into a well-sealed rotary kiln, rotate the kiln at a frequency of 30Hz, introduce steam at a flow rate of 12L / min, and raise the temperature of the rotary kiln to 900℃ at a rate of 10℃ / min. Hold the temperature for 8 hours, and then cool to room temperature to obtain the material.

[0227] S5. Soak the material obtained from S4 in 6.5% HCl and heat it to 60°C and stir for 1 hour. Then wash it with pure water until neutral and dry it at 80°C.

[0228] S6. Use an air jet mill to pulverize the material in S5 to D50 = 5~12μm.

[0229] S7. Place the material obtained in S6 into a well-sealed rotary kiln, rotate the kiln at a frequency of 40Hz, and introduce a mixture of protective gas and silicon source gas: a mixture of nitrogen and silane (the volume ratio of nitrogen to silane is 20:80). The ratio of deposition amount to material added is 0.6, the deposition temperature is 500℃, and the deposition time is 6h to obtain the silicon-carbon composite material.

[0230] Figure 5 The image shows an electron microscope image of the silicon-carbon composite material prepared in Comparative Example 2. Figure 5 As shown, without adding low-carbon source microspheres and without using spray drying, the obtained silicon-carbon composite material exhibits an irregular state.

[0231] Comparative Example 3

[0232] This comparative example provides a carbon microsphere particle, which is prepared by the following steps:

[0233] S1. Carbon microspheres with a residual carbon content of 15% are directly cured in a vacuum oven at 120°C for 4 hours.

[0234] S2. The solidified carbon microspheres are then heat-treated in a nitrogen atmosphere at a heating rate of 10℃ / min and a heat treatment temperature of 400℃ for 5 hours to achieve carbonization.

[0235] Figure 6 Here is an electron microscope image of the silicon material prepared in Comparative Example 3, as shown. Figure 6 As shown, the spheres collapsed and became hollow after carbonization.

[0236] Comparative Example 4

[0237] This comparative example provides a silicon-carbon composite material. The difference from Example 1 is that in S1, the mass ratio of carbon microspheres with a residual carbon content of 15% to resin with a residual carbon content of 55% is 2:1. The other steps are completely consistent with Example 1.

[0238] Comparative Example 5

[0239] This comparative example provides a silicon-carbon composite material, which differs from Example 1 in that, in S1, the mass ratio of carbon microspheres with a residual carbon content of 15% to resin with a residual carbon content of 55% is 1:6, while the other steps are completely consistent with Example 1.

[0240] Comparative Example 6

[0241] This comparative example provides a silicon-carbon composite material, which is prepared by the following steps:

[0242] S1. Carbon microspheres with a residual carbon content of 15% and resin with a residual carbon content of 55% are mixed and dispersed in anhydrous ethanol at a mass ratio of 1:1 to form a spray liquid with a solid content of 30%.

[0243] S2. Stir the above mixture and heat it for 8 hours to form carbon microspheres with a sphericity of 60-70%.

[0244] S3. The solidified carbon microspheres are heat-treated in a nitrogen atmosphere at a heating rate of 10 / min and a heat treatment temperature of 400°C for 5 hours to obtain carbonized carbon microspheres.

[0245] S4. Place the carbonized carbon microspheres into a well-sealed rotary kiln, rotate the kiln at a frequency of 30Hz, introduce steam at a flow rate of 12L / min, and raise the temperature of the rotary kiln to 900℃ at a rate of 10℃ / min. Hold the temperature for 8 hours, and then cool to room temperature to obtain the material.

[0246] S5. Soak the material obtained from S4 in 6.5% HCl and heat it to 60°C and stir for 1 hour. Then wash it with pure water until neutral and dry it at 80°C to obtain spherical porous carbon.

[0247] S6. Place the spherical porous carbon material obtained in S5 into a well-sealed rotary kiln, rotate the kiln at a frequency of 40Hz, and introduce a mixture of protective gas and silicon source gas: nitrogen and silane (the volume ratio of nitrogen to silane is 20:80). The deposition amount to the material feed ratio is 0.6, the deposition temperature is 500℃, and the deposition time is 6h to obtain the silicon-carbon composite material.

[0248] Figure 7 Here is an electron microscope image of the silicon carbide material prepared in Comparative Example 4, as shown. Figure 7 As shown, without spray drying, the silicon-carbon composite material has a low sphericity.

[0249] Comparative Example 7

[0250] This comparative example provides a silicon-carbon composite material. The difference from Example 1 is that in S2, the spray drying process parameters include: centrifugal disc speed of 20,000 rpm; air inlet temperature of 250°C; feed rate of 4.5 L / h; and induced draft fan frequency of 35 Hz. Other steps are completely consistent with Example 1.

[0251] Comparative Example 8

[0252] This comparative example provides a silicon-carbon composite material. The difference from Example 1 is that, in S2, the spray drying process parameters include: centrifugal disc speed of 32000 rpm; air inlet temperature of 150℃; feed rate of 1.0 L / h; and induced draft fan frequency of 55 Hz. Other steps are completely consistent with Example 1.

[0253] Test Example 1

[0254] Test samples: silicon-carbon composite materials provided in Examples 1-10 and composite materials provided in Comparative Examples 1-8;

[0255] Test method:

[0256] (1) Particle size testing:

[0257] The particle size distribution of the powder was tested using a laser particle size analyzer in accordance with GB / T 19077, and the particle size of the silicon-carbon composite material was also tested.

[0258] (2) Strength test:

[0259] The specific surface area of ​​the silicon-carbon composite material before compaction was measured using a specific surface area meter and recorded as S1. The silicon-carbon composite material was placed in the sample chamber of a compaction density meter and compacted (compaction conditions: 10 mm / min, holding time: 60 s, pressure: 450 MPa) to break the sample. The specific surface area of ​​the broken silicon-carbon composite material after compaction was measured using a specific surface area meter and recorded as S2. The specific surface area change rate of the silicon-carbon composite material was calculated using the following formula to characterize the strength of the silicon-carbon composite material.

[0260] The strength of the silicon-carbon composite material is defined by the following formula:

[0261]

[0262] Wherein, P represents the strength of the silicon-carbon composite material, %; S2 represents the specific surface area of ​​the silicon-carbon composite material after compression, m². 2 / g; S1 represents the specific surface area of ​​the silicon-carbon composite material before compression, in m² 2 / g.

[0263] (3) Capacity: At 25℃, first discharge to 0.005V at 0.1C, then discharge to 0.001V at 0.08C, then discharge to 0.001V at 0.05C, then discharge to 0.001V at 0.02C, and let stand for 10 minutes; then charge to 1.5V at 0.1C, let stand for 10 minutes, and record the charge and discharge capacity after the first cycle.

[0264] (4) 200-cycle capacity retention rate: Cycle 200 times in the above manner, record the charge and discharge capacity after 200 cycles, and calculate the capacity retention rate after 200 cycles. 200-cycle capacity retention rate = discharge capacity of the 200th cycle / discharge capacity of the first cycle × 100%.

[0265] The specific test results are shown in Table 1:

[0266] Table 1

[0267]

[0268]

[0269] As shown in Table 1, the specific surface area of ​​the silicon-carbon composite material of the present invention is 2–5 m². 2 / g; the silicon-carbon composite material retains over 90% of its strength after 30 seconds of compression at 450 MPa; the specific capacity of the silicon-carbon composite material is >1500 mAh / g, and the capacity retention rate after 200 cycles is >90%. This demonstrates that the silicon-carbon composite material of this invention has high sphericity, avoiding poor compressive strength caused by numerous sharp edges during rolling, and improving the problem of continuous formation of a solid electrolyte interphase (SEI) film due to low strength, resulting in reduced capacity and poorer cycle life.

[0270] in, Figure 8 The particle size distribution diagram is shown for the silicon-carbon composite material prepared in Example 1. Figure 9 The image shows the N2 adsorption-desorption isotherm of the silicon-carbon composite material prepared in Example 1. Figure 8 and Figure 9 As shown, the single-point BET specific surface area of ​​the silicon-carbon composite material is 0.20000:1014.12875 (m²) at a P / Po ratio of 0.20000:1014.12875 (m²). 2 / g); Total pore volume: 0.84cm 3 / g; Micropore volume: 0.68cm³ 3 / g; Average pore size: 1.89nm; Mesoporosity: 19%; Microporosity: 81%.

[0271] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A silicon-carbon composite material, characterized in that, The silicon-carbon composite material includes active material particles, which include a spherical porous carbon framework and nano-silicon particles. The strength of the silicon-carbon composite material is defined by the following formula: in, P The strength of the silicon-carbon composite material is represented by % %. S 2 represents the specific surface area of ​​the silicon-carbon composite material after compression, in m². 2 / g; S 1 represents the specific surface area of ​​the silicon-carbon composite material before compression, in m². 2 / g; The silicon-carbon composite material retains more than 90% of its strength under a pressure of 450 MPa for 30 seconds. The silicon-carbon composite material is prepared by the following steps: A mixture is prepared by mixing low-carbon source microspheres, high-carbon source resin, and solvent; wherein the residual carbon content of the low-carbon source microspheres is ≤40%; the residual carbon content of the high-carbon source resin is 50-70%; the mass ratio of the low-carbon source microspheres to the high-carbon source resin is 1:(1-5); wherein the low-carbon source microspheres include any one or a combination of at least two of polystyrene microspheres, polylactic acid microspheres, or polyvinylidene fluoride microspheres; the high-carbon source resin is phenolic resin and / or phenolic resin derivatives; and the solid content of the mixture is 30-60 wt%. The mixture is spray-dried to obtain small spherical particles; wherein the spray-drying process parameters include: centrifugal disc speed of 24,000~30,000 rpm; inlet air temperature of 160~230℃; feed rate of 1.2~4 L / h; and induced draft fan frequency of 40~50 Hz. The small spherical particles were sequentially subjected to carbonization and activation treatments to obtain spherical porous carbon. The spherical porous carbon is subjected to vapor phase deposition to obtain the silicon-carbon composite material.

2. The silicon-carbon composite material according to claim 1, characterized in that, The specific surface area of ​​the silicon-carbon composite material is 2~5 m². 2 / g.

3. The silicon-carbon composite material according to claim 1, characterized in that, The sphericity of the spherical porous carbon is ≥80%.

4. The silicon-carbon composite material according to claim 1, characterized in that, The spherical porous carbon contains uniformly distributed micropores and / or mesopores inside.

5. The silicon-carbon composite material according to claim 1 or 4, characterized in that, The spherical porous carbon has an average pore size of less than 4 nm and a total pore volume ≥ 0.7 cm³. 3 / g.

6. The silicon-carbon composite material according to claim 1 or 4, characterized in that, The spherical porous carbon has a mesoporous rate of <20% and a microporous rate of >80%.

7. The silicon-carbon composite material according to claim 1 or 4, characterized in that, The spherical porous carbon has a particle size of 1~60 μm; wherein, the D of the spherical porous carbon is... 10 Particle size is 3~7 μm; D 50 Particle size is 8~13 μm; D 90 The particle size is 15~40 μm.

8. The silicon-carbon composite material according to claim 1, characterized in that, The nano-silicon particles are deposited in the pores of the spherical porous carbon.

9. The silicon-carbon composite material according to claim 1, characterized in that, The silicon content in the silicon-carbon composite material is 40-60%.

10. The silicon-carbon composite material according to claim 1, characterized in that, The specific capacity of the silicon-carbon composite material is >1500 mAh / g.

11. The silicon-carbon composite material according to claim 1 or 10, characterized in that, The specific capacity of the silicon-carbon composite material is >1800 mAh / g.

12. The silicon-carbon composite material according to claim 1, characterized in that, The silicon-carbon composite material has a capacity retention rate of >90% over 200 cycles.

13. A method for preparing a silicon-carbon composite material according to any one of claims 1 to 12, characterized in that, The preparation method includes the following steps: A mixture is prepared by mixing low-carbon source microspheres, high-carbon source resin, and solvent; wherein the residual carbon content of the low-carbon source microspheres is ≤40%; the residual carbon content of the high-carbon source resin is 50-70%; the mass ratio of the low-carbon source microspheres to the high-carbon source resin is 1:(1-5); wherein the low-carbon source microspheres include any one or a combination of at least two of polystyrene microspheres, polylactic acid microspheres, or polyvinylidene fluoride microspheres; the high-carbon source resin is phenolic resin and / or phenolic resin derivatives; and the solid content of the mixture is 30-60 wt%. The mixture is spray-dried to obtain small spherical particles; wherein the spray-drying process parameters include: centrifugal disc speed of 24,000~30,000 rpm; inlet air temperature of 160~230℃; feed rate of 1.2~4 L / h; and induced draft fan frequency of 40~50 Hz. The small spherical particles were sequentially subjected to carbonization and activation treatments to obtain spherical porous carbon. The spherical porous carbon is subjected to vapor phase deposition to obtain the silicon-carbon composite material.

14. The method for preparing the silicon-carbon composite material according to claim 13, characterized in that, The solvent includes alcohol solvents.

15. The method for preparing the silicon-carbon composite material according to claim 14, characterized in that, The solvent is ethanol.

16. The method for preparing the silicon-carbon composite material according to claim 13, characterized in that, The mixture also includes 5-10 wt% carbon nanotubes.

17. The method for preparing the silicon-carbon composite material according to claim 13, characterized in that, The mixture also includes a conductive polymer, which includes any one or a combination of at least two of polyacetylene, polythiophene, polypyrrole, or polyaniline.

18. The method for preparing the silicon-carbon composite material according to claim 13, characterized in that, The carbonization treatment temperature is 400~900℃; the carbonization treatment time is 3~10 h.

19. The method for preparing the silicon-carbon composite material according to claim 13, characterized in that, The activation treatment is carried out using a physical activation method.

20. The method for preparing the silicon-carbon composite material according to claim 19, characterized in that, The physical activation step is as follows: an activation gas is introduced into the carbon microspheres obtained after carbonization to perform physical activation.

21. The method for preparing the silicon-carbon composite material according to claim 20, characterized in that, The activating gas includes carbon dioxide and / or water vapor.

22. The method for preparing the silicon-carbon composite material according to claim 19, characterized in that, The physical activation temperature is 800~1000℃, and the physical activation time is 7~20 h.

23. The method for preparing the silicon-carbon composite material according to claim 13, characterized in that, The activation treatment also includes a step of removing impurities: the activated porous carbon microspheres are acid-washed to remove impurities, then washed with water and dried.

24. The method for preparing the silicon-carbon composite material according to claim 23, characterized in that, The pickling process uses a 5-8 wt% hydrochloric acid solution.

25. The method for preparing the silicon-carbon composite material according to claim 23, characterized in that, The pickling temperature is 20~100℃, and the pickling time is 1~24 h.

26. The method for preparing the silicon-carbon composite material according to claim 23, characterized in that, The drying temperature is 70~90℃.

27. The method for preparing the silicon-carbon composite material according to claim 13, characterized in that, The deposition gas source for the vapor phase deposition is a mixture of protective gas and silicon source gas.

28. The method for preparing the silicon-carbon composite material according to claim 27, characterized in that, The protective gas includes any one or a combination of at least two of nitrogen, neon, argon, krypton, xenon, or radon.

29. The method for preparing the silicon-carbon composite material according to claim 27, characterized in that, The silicon source gas includes any one or a combination of at least two of the following: silane, disilane, dichlorosilane, or trichlorosilane.

30. The method for preparing the silicon-carbon composite material according to claim 27, characterized in that, The silicon source gas also includes a carbon source gas, which includes any one or a combination of at least two of methane, ethane, acetylene, or ethylene.

31. The method for preparing the silicon-carbon composite material according to claim 27, characterized in that, The volume ratio of the protective gas to the silicon source gas is (10~30):(70~90).

32. The method for preparing the silicon-carbon composite material according to claim 30, characterized in that, The carbon source gas accounts for 0-30% of the total volume of the silicon source gas.

33. The method for preparing the silicon-carbon composite material according to claim 13, characterized in that, The ratio of the amount of vapor deposition to the amount of feed material is (0.4~1.5):

1.

34. The method for preparing the silicon-carbon composite material according to claim 13, characterized in that, The vapor deposition temperature is 300~800℃, and the vapor deposition time is 5~10 h.

35. The application of the silicon-carbon composite material according to any one of claims 1 to 12 in the preparation of battery anode materials.

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