Silicon carbon material and preparation method thereof, negative electrode material, negative electrode plate, battery and electric device

Abstract

The invention discloses a silicon-carbon material and a preparation method thereof, a negative electrode material, a negative electrode piece, a battery and an electric device, the silicon-carbon material comprises spherical porous carbon, nano silicon is deposited in pores and on the surface of the spherical porous carbon, the sphericity of the silicon-carbon material is not less than 0.85, and the BET specific surface area of the silicon-carbon material is less than or equal to 5m < 2 > / g. Therefore, the silicon-carbon material disclosed by the invention not only has a relatively low specific surface area, but also has relatively high sphericity and mechanical strength, and when the silicon-carbon material is applied to a negative pole piece, the silicon-carbon material can uniformly shrink and expand in the radial direction in the battery cycle process, so that the stability of the structure can be kept; and the capacity and the cycle performance of the battery are improved.

Description

Technical Field

[0001] This application belongs to the field of batteries. Specifically, it relates to silicon-carbon materials and their preparation methods, anode materials, anode plates, batteries, and electrical devices. Background Art

[0002] Currently, preparing silicon-carbon composite anode materials by utilizing the high specific capacity of silicon materials and the stability of carbon materials is one of the most effective ways. Among the numerous preparation processes of silicon-carbon composite anode materials, the silicon-carbon composite anode prepared by chemical vapor deposition (CVD) has received extensive attention due to its advantages such as high charge-discharge efficiency, good cycle stability, low requirements for equipment, and suitability for industrial production.

[0003] The CVD method uses porous carbon as the matrix, deposits silicon inside the porous carbon, constructs a strong conductive network while providing sufficient expansion space for silicon particles, making the prepared silicon-carbon material have a high capacity and good cycle performance. At the same time, the porous carbon plays a role of skeleton support in the whole material, and its performance parameters play a decisive role in the subsequent silicon deposition and carbon coating. Therefore, parameters such as the fluidization performance, mechanical and mechanical properties, and pore size distribution of the porous carbon are crucial for the subsequent deposition process.

[0004] However, during the silicon deposition stage of the porous carbon, due to its poor fluidity, problems such as material sticking to the wall and retention are likely to occur, which in turn cause problems such as product caking and low yield. In addition, the tiny pores of the porous carbon (especially those below 1 nm) do not contribute to the silicon hydride vapor deposition, but affect the deposition efficiency in the process of preparing silicon-carbon anode materials by chemical vapor deposition, the specific surface area of the silicon-carbon anode material product, and the final strength and structural stability of the silicon-carbon material, resulting in the collapse of the silicon-carbon material structure and the rupture of the SEI film during the charge-discharge process, leading to the infiltration of the electrolyte into the material interior and thus affecting the cycle performance of the battery.

[0005] Therefore, the existing preparation processes of silicon-carbon materials need to be improved. Summary of the Invention

[0006] The present invention aims to solve at least one of the technical problems in the related art to a certain extent.

[0007] To this end, an object of the present invention is to provide a silicon-carbon material and its preparation method, anode material, anode plate, battery, and electrical device. The silicon-carbon material not only has a high specific capacity and stability, but also has a high sphericity, so that when the silicon-carbon material is used for the anode plate, the capacity and cycle performance of the battery can be improved.

[0008] In the first aspect of the present invention, a silicon-carbon material is proposed. The silicon-carbon material includes spherical porous carbon, and nano-silicon is deposited in and on the surface of the pores of the spherical porous carbon. The sphericity of the silicon-carbon material is not less than 0.85, and the BET specific surface area of the silicon-carbon material is less than or equal to 5 m 2 / g.

[0009] Thus, the silicon-carbon material of the present application not only has a low specific surface area but also has a high sphericity, so that it has a high specific capacity and stability. When the silicon-carbon material is used for the negative electrode sheet, the silicon-carbon material can uniformly shrink and expand radially outward during the battery cycling process, so that the structural stability can be maintained, and further the possibility of electrolyte infiltration into the material due to the structural collapse of the silicon-carbon material and the rupture of the SEI film can be significantly reduced, improving the capacity and cycling performance of the battery.

[0010] In some embodiments of the present invention, the silicon-carbon material satisfies at least one of the following conditions: in the particle size distribution of the silicon-carbon material, 0.9 ≤ (Dv90 - Dv10) / Dv50 ≤ 1.1; the Dv90 of the silicon-carbon material is 11 - 16 μm; the Dv50 of the silicon-carbon material is 6 - 9 μm; the Dv10 of the silicon-carbon material is 4 - 5 μm; the Dv01 of the silicon-carbon material is not less than 2.5 μm; the micropore volume of the silicon-carbon material is not higher than 0.001 cm 3 / g. Thereby, the cycling performance of the battery can be improved.

[0011] In some embodiments of the present invention, based on the total mass of the silicon-carbon material, the mass ratio of the nano-silicon is 40wt% - 70wt%. Thereby, when the silicon-carbon material is applied to the negative electrode sheet, the capacity and cycling performance of the battery can be improved.

[0012] In some embodiments of the present invention, at least part of the surface of the silicon-carbon material has deposited carbon. Thereby, the activity of the silicon-carbon material can be reduced, thereby improving its stability and electrochemical performance.

[0013] In the second aspect of the present invention, a method for preparing a silicon-carbon material is proposed, including:

[0014] (1) Mixing spherical porous carbon with a hydrophobic polymer to obtain a mixed material;

[0015] (2) Placing the mixed material in a reactor and performing carbonization in an inert atmosphere, so that part of the micropores with a size below 1 nm on the spherical porous carbon are closed after the thermal decomposition of the hydrophobic polymer;

[0016] (3) Adjust the temperature of the reactor, introduce a mixed gas including a silicon source gas and a protective gas into the reactor, and deposit nano-silicon in and on the pores of the spherical porous carbon to obtain a silicon-carbon material.

[0017] Thus, in this method, the spherical porous carbon is first mixed with a hydrophobic polymer. Since the spherical porous carbon has high fluidization performance, it can solve the problem of material sticking to the wall and retention during the silicon deposition stage of the spherical porous carbon, reduce problems such as product caking and low yield. At the same time, the hydrophobic polymer can form a coating layer with hydrophobic and antistatic properties on the surface of the spherical porous carbon particles, which can effectively improve the adsorption of water molecules on the surface of the spherical porous carbon and the mutual adsorption between particles caused by static electricity, improve the agglomeration and moisture absorption problems of the spherical porous carbon, and further improve the fluidization of the spherical porous carbon. Then, the mixed material is carbonized. The pyrolytic carbon formed by the hydrophobic polymer can block some of the micropores with a diameter of less than 1 nm on the spherical porous carbon, improve the mechanical strength of the porous carbon itself, reduce the risk of rupture of the material during the later charge and discharge process, and at the same time improve the pore size distribution and silicon deposition efficiency. Thus, the silicon-carbon material of this application not only has a low specific surface area, but also has a high sphericity and elastic modulus. When this silicon-carbon material is used for the negative electrode sheet, during the battery cycle, the silicon-carbon material can shrink and expand uniformly along the radial direction, so as to maintain the structural stability, and further significantly reduce the possibility of electrolyte infiltration into the material due to the structural collapse of the silicon-carbon material and the rupture of the SEI film, and improve the capacity and cycle performance of the battery.

[0018] In some embodiments of the present invention, the spherical porous carbon satisfies at least one of the following conditions: the BET specific surface area of the spherical porous carbon is not less than 1500 m 2 / g, and the pore volume is 0.5 cm 3 / g - 1.8 cm 3 / g; the spherical porous carbon has a microporous and mesoporous structure, and the volume ratio of the micropores is 50% - 90%; the Dv10 of the spherical porous carbon is not less than 2.5 μm and 0.8 ≤ (Dv90 - Dv10) / Dv50 ≤ 1.05; the Dv90 of the spherical porous carbon is 10 - 15 μm; the Dv50 of the spherical porous carbon is 5 - 7 μm; the Dv10 of the spherical porous carbon is 3 - 4 μm; the sphericity of the spherical porous carbon is not less than 0.86, preferably 0.86 - 0.96, more preferably 0.86 - 0.92. Thus, the above-mentioned silicon-carbon material with a low BET specific surface area, high sphericity and good cycle performance can be prepared. And the particle size distribution of the spherical porous carbon in this application is narrow and uniform and there are no fine-grained particles, which can improve the deposition uniformity of nano-silicon on the porous carbon matrix and improve the silicon-rich surface of the silicon-carbon material.

[0019] In some embodiments of the present invention, in step (1), the hydrophobic polymer includes at least one of poly(cyclohexene oxide), poly(vinylcyclohexane), poly(adipic anhydride), poly(4-[N,N-bis(trimethylsilyl)aminomethyl]-styrene), (N-vinylcarbazole), polytetrafluoroethylene, polydimethylsiloxane, poly(vinylidene fluoride), polypropylene, polyethylene, polymethyl methacrylate, polyolefin, polyamide, polyacrylonitrile, polyester, polycarbonate, fluorosilicone resin, and poly(N-isopropylacrylamide), preferably at least one of poly(4-[N,N-bis(trimethylsilyl)aminomethyl]-styrene), poly(N-vinylcarbazole), polyamide, polyimide, poly(N-isopropylacrylamide), and polyacrylonitrile. Thus, not only can the pore size distribution in the spherical porous carbon be improved, thereby increasing the subsequent silicon deposition efficiency and reducing the specific surface area of the final product, but also the mechanical strength of the spherical porous carbon itself can be enhanced, reducing the risk of rupture of the material during the later charge and discharge process. Moreover, after the pyrolysis of the hydrophobic polymer containing N element, nitrogen atoms can be introduced onto the spherical porous carbon, which can better improve the electrical conductivity of the spherical porous carbon material, thereby enhancing the rate performance of the silicon-carbon material.

[0020] In some embodiments of the present invention, the mass ratio of the spherical porous carbon to the hydrophobic polymer is (5 - 20):1. Thus, the pore size distribution in the spherical porous carbon can be improved, thereby increasing the subsequent silicon deposition efficiency and reducing the specific surface area of the final product.

[0021] In some embodiments of the present invention, in step (2), the carbonization temperature is 500°C - 700°C and the time is 2h - 6h. Thus, under these carbonization conditions, the pyrolytic carbon formed by the hydrophobic polymer can block some of the micropores with a size below 1 nm on the spherical porous carbon, improving the pore size distribution in the spherical porous carbon, thereby increasing the subsequent silicon deposition efficiency and reducing the specific surface area of the final product.

[0022] In some embodiments of the present invention, in step (3), the silicon source gas includes at least one of silane, chlorosilane, and hydrosilane. Thus, the sources of the silicon source gas are extensive, which can meet various designs for preparing silicon-carbon materials.

[0023] In some embodiments of the present invention, in step (3), the reactor temperature is adjusted to 400°C - 600°C, and under the condition that the flow rate of the silicon source gas in the mixed gas is 2L / min - 6L / min and the total gas flow rate is 12L / min - 25L / min, the chemical vapor deposition time is 4h - 12h. Thus, the deposition efficiency of nano-silicon in the spherical porous carbon can be increased, thereby increasing the specific capacity of the silicon-carbon material.

[0024] In some embodiments of the present invention, the method further includes: introducing a mixed gas including an organic carbon source gas and a protective gas into the reactor so as to deposit carbon on at least a part of the surface of the silicon-carbon material. Thereby, by depositing carbon on the silicon-carbon material, the activity of the silicon-carbon material can be reduced, thereby improving its stability.

[0025] In some embodiments of the present invention, the method for depositing carbon on at least a part of the surface of the silicon-carbon material includes: adjusting the temperature in the reactor to 500°C - 700°C, introducing a mixed gas including an organic carbon source gas and a protective gas, controlling the flow rate of the organic carbon source in the mixed gas to be 2 L / min - 6 L / min, the volume ratio of the organic carbon source gas in the mixed gas being 15% - 40%, and the reaction time being 2 h - 5 h. Thereby, by depositing carbon on the silicon-carbon material, the activity of the silicon-carbon material can be reduced while its conductivity is improved, thereby improving the material stability and electrochemical performance.

[0026] In a third aspect of the present invention, the present invention provides a negative electrode material, which is the above-mentioned silicon-carbon material or the silicon-carbon material obtained by the above-mentioned method. Thereby, the silicon-carbon material not only has a high specific capacity and stability, but also has a high sphericity and mechanical strength. When the silicon-carbon material is used as the negative electrode material of the negative electrode sheet, the silicon-carbon material can uniformly shrink and expand radially outward during the battery cycling process, thereby being able to maintain the structural stability, and further significantly reducing the possibility of electrolyte infiltration into the material due to the structural collapse of the silicon-carbon material and the rupture of the SEI film, improving the capacity and cycling performance of the battery.

[0027] In a fourth aspect of the present invention, the present invention provides a negative electrode sheet, which includes the above-mentioned silicon-carbon material. Thereby, the structure of the negative electrode sheet is relatively stable during use, thereby improving the cycling stability of the battery.

[0028] In a fifth aspect of the present invention, the present invention provides a battery, which includes the above-mentioned negative electrode sheet. Thereby, the battery has excellent capacity and cycling stability.

[0029] In a sixth aspect of the present invention, the present invention provides an electrical device, which includes the above-mentioned battery. Thereby, the electrical device has a long battery life and a long service life of the battery, and has a high market satisfaction.

[0030] The additional aspects and advantages of the present invention will be partially given in the following description, partially become obvious from the following description, or be understood through the practice of the present invention. Description of the Drawings

[0031] The above and / or additional aspects and advantages of the present application will become obvious and easy to understand from the description of the embodiments in conjunction with the following drawings, wherein:

[0032] Figure 1 is a schematic process flow diagram of a method for preparing a silicon-carbon material according to an embodiment of the present invention;

[0033] Figure 2 is the cumulative pore volume of the porous carbon substrate in Comparative Example 2;

[0034] Figure 3 is the cumulative pore volume after pyrolysis of the spherical porous carbon hydrophobic polymer prepared in step (3) of Example 1.

[0035] Figure 4 is the pore size distribution diagram of the porous carbon substrate in Comparative Example 2;

[0036] Figure 5 is the pore size distribution diagram of the porous carbon after pyrolysis of the spherical porous carbon hydrophobic polymer prepared in step (3) of Example 1. Detailed implementation manners

[0037] The following described embodiments are exemplary and are only used to explain the present application, and should not be construed as a limitation to the present application.

[0038] In one aspect of the present invention, the present invention provides a silicon-carbon material. According to an embodiment of the present invention, the silicon-carbon material includes spherical porous carbon, and nano-silicon is deposited in and on the surface of the pores of the spherical porous carbon. The sphericity of the silicon-carbon material is not less than 0.85, and the BET specific surface area of the silicon-carbon material is less than or equal to 5 m 2 / g.

[0039] According to the silicon-carbon material of the above embodiment of the present invention, it not only has a low specific surface area, but also has a high sphericity, so that it has a high specific capacity and stability. When the silicon-carbon material is used for the negative electrode sheet, the silicon-carbon material can uniformly contract and expand radially outward during the battery cycling process, so as to maintain the structural stability, and further significantly reduce the possibility of electrolyte infiltration into the material due to the structural collapse of the silicon-carbon material and the rupture of the SEI film, improving the capacity and cycling performance of the battery.

[0040] According to an embodiment of the present invention, the BET specific surface area of the silicon-carbon material is ≤5 m 2 / g. For example, the BET specific surface area of the silicon-carbon material is 0.5 m 2 / g, 1 m 2 / g, 2 m 2 / g, 3 m 2 / g, 4 m 2 / g, 5 m 2 / g, etc.

[0041] In this application, the sphericity of the spherical porous carbon and silicon-carbon material is a value obtained by measuring using a particle shape measuring device (manufactured by SEISHIN ENTERPRISE Co., Ltd., PITA-1), with ion-exchanged water as the dispersion medium, under the condition that the volume of the sample solution is set to 1.25 μL.

[0042] In this application, Dv90 refers to the particle size corresponding to when the cumulative volume distribution percentage reaches 90%, Dv50 refers to the particle size corresponding to when the cumulative volume distribution percentage reaches 50%, Dv10 refers to the particle size corresponding to when the cumulative volume distribution percentage reaches 10%, and Dv01 refers to the particle size corresponding to when the cumulative volume distribution percentage reaches 1%.

[0043] In this application, the particle size test of the spherical porous carbon and silicon-carbon material particles is to use a Malvern particle size analyzer to test the particle size of the powder of the porous carbon material: the powder material is dispersed in an ethanol dispersant, and after ultrasonic treatment for 15 minutes, the sample is added to the Malvern particle size analyzer to test Dv01, Dv10, Dv50, and Dv90 of the powder material.

[0044] According to the embodiments of the present invention, in the particle size distribution of the silicon-carbon material, 0.9 ≤ (Dv90 - Dv10) / Dv50 ≤ 1.1; the Dv90 of the silicon-carbon material is 11 μm - 16 μm; the Dv50 of the silicon-carbon material is 6 μm - 9 μm; the Dv10 of the silicon-carbon material is 4 μm - 5 μm; the Dv01 of the silicon-carbon material is not less than 2.5 μm; the micropore volume of the silicon-carbon material is not higher than 0.001 cm 3 / g. Thus, the particle size distribution of the silicon-carbon material is narrow and uniform and there are no fine-grained particles, which can improve the deposition uniformity of nano-silicon on the porous carbon matrix, improve the silicon-rich surface of the silicon-carbon material, and thus when it is applied as the negative active material in the negative electrode sheet, the compaction density of the negative electrode sheet is moderate, so that the wettability of the electrode sheet is high, and further improve the energy density and cycle performance of the battery.

[0045] In some embodiments of the present invention, based on the total mass of the silicon-carbon material, the mass ratio of the nano-silicon is 40 wt - 70 wt%, such as 40%, 45%, 50%, 55%, 60%, 65%, 70%, etc. Thus, controlling the mass ratio of the nano-silicon in the silicon-carbon material of this application within this range can not only improve the specific capacity of the silicon-carbon material, but also control the volume expansion of the silicon-carbon material within a reasonable range, so that when the silicon-carbon material is applied to the negative electrode sheet, the capacity and cycle performance of the battery can be improved.

[0046] In this application, the test method for the BET specific surface area of the silicon-carbon material includes: using a 3H-2000PS2 type static volumetric specific surface area analyzer produced by Beijing Beishide Company. According to the nitrogen adsorption-desorption curve, the specific value of the material specific surface area is calculated using the BET (Brunauer-Emmett-Teller) specific surface area calculation method.

[0047] In some embodiments of the present invention, at least a part of the surface of the silicon-carbon material has deposited carbon. Thus, by depositing carbon on the silicon-carbon material, the activity of the silicon-carbon material can be reduced while its conductivity is increased, thereby improving the material stability and electrochemical performance.

[0048] In the second aspect of the present invention, the present invention proposes a method for preparing a silicon-carbon material. According to an embodiment of the present invention, referring to Figure 1 , the method includes:

[0049] S100: Mix the spherical porous carbon with the hydrophobic polymer

[0050] In this step, the spherical porous carbon and the hydrophobic polymer are mixed in a mixing device. For example, the mixing device may include a VC mixer, a high-speed mixer, or a conical mixer, and the mixing is carried out by stirring. The stirring speed is 300 rpm - 800 rpm, and the stirring time is 0.5 h - 1.5 h to obtain a mixed material. Since the spherical porous carbon has high fluidization performance, it can solve the problem of material sticking to the wall and retention during the silicon deposition stage, reduce problems such as product caking and low yield. At the same time, the hydrophobic polymer can form a hydrophobic and antistatic coating layer on the surface of the spherical porous carbon particles, which can effectively improve the adsorption of water molecules on the surface of the spherical porous carbon and the mutual adsorption between particles caused by static electricity, improve the agglomeration and moisture absorption problems of the spherical porous carbon, and further improve the fluidization of the spherical porous carbon.

[0051] According to an embodiment of the present invention, the spherical porous carbon can be obtained by the following method: adding a spherical porous carbon substrate to a shaping machine, and the material is shaped under the action of strong collision and vortex in the shaping machine, and then enters the subsequent air classification system. The classification frequency of the air classification system is controlled to be 100 - 180 Hz, and the particle size separation of the coarse and fine materials is carried out by a classification wheel to obtain spherical porous carbon.

[0052] According to an embodiment of the present invention, the BET specific surface area of the spherical porous carbon is not less than 1500 m 2 / g, for example 1500 m 2 / g, 1800 m 2 / g, 2000 m 2 / g, 2200 m 2 / g, 2500 m 2 / g, etc., and the pore volume is 0.5 cm 3 / g - 1.8 cm 3 / g, such as 0.5 cm 3 / g, 0.8 cm 3 / g, 1 cm 3 / g, 1.5 cm 3 / g, 1.8 cm 3 / g, etc. Thus, by using spherical porous carbon with a large BET specific surface area and a large pore volume, more nano - silicon can be deposited in the pores of the spherical porous carbon, which is conducive to obtaining the above - mentioned silicon - carbon material with a lower BET specific surface area.

[0053] According to the embodiments of the present invention, the spherical porous carbon substrate has a microporous and mesoporous structure, and the volume ratio of the micropores is 50% - 90%, such as 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, etc. In this application, a spherical porous carbon substrate with a micropore volume ratio of 50% - 90% is used, and there are mesopores. The micropores in this range make the spherical porous carbon substrate exhibit a large specific surface area, and the existence of mesopores provides more channels for the diffusion of the electrolyte when it is used for the negative electrode plate later, thereby improving the cycling performance of the battery.

[0054] In this application, the test methods for the BET specific surface area and the volume ratio of micropores in the spherical porous carbon substrate include: using a 3H - 2000PS2 type static volumetric method specific surface area and pore size analyzer produced by Beijing Beishide Company. According to the nitrogen adsorption - desorption curve, the specific value of the material specific surface area is calculated by using the BET (Brunauer - Emmett - Teller) specific surface area calculation method. The micropore volume and the total pore volume can be calculated from the amount of vapor adsorbed at different relative pressures through the adsorption isotherm. The volume ratio of micropores = micropore volume / total pore volume.

[0055] According to the embodiments of the present invention, Dv10 of the spherical porous carbon is not less than 2.5 μm and 0.8 < (Dv90 - Dv10) / Dv50 ≤ 1.05; Dv90 of the spherical porous carbon is 10 - 15 μm; Dv50 of the spherical porous carbon is 5 - 7 μm; Dv10 of the spherical porous carbon is 3 - 4 μm; the sphericity of the spherical porous carbon is not less than 0.86, preferably 0.86 - 0.96, more preferably 0.86 - 0.92. Thus, the above - mentioned silicon - carbon material with a low BET specific surface area, high sphericity and high specific capacity can be prepared. The particle size distribution of the porous carbon material is relatively narrow and there are no fine - sized particles, which can improve the deposition uniformity of nano - silicon on the porous carbon matrix, thereby improving the silicon - rich surface of the silicon - carbon material and enhancing the electrochemical performance of the silicon - carbon material.

[0056] According to an embodiment of the present invention, the hydrophobic polymer includes at least one of poly(cyclohexene oxide), poly(vinylcyclohexane), poly(adipic anhydride), poly(4-[N,N-bis(trimethylsilyl)aminomethyl]-styrene), (N-vinylcarbazole), polytetrafluoroethylene, polydimethylsiloxane, poly(vinylidene fluoride), polypropylene, polyethylene, poly(methyl methacrylate), polyolefin, polyamide, polyacrylonitrile, polyester, polycarbonate, fluorosilicone resin, and poly(N-isopropylacrylamide), preferably at least one of poly(4-[N,N-bis(trimethylsilyl)aminomethyl]-styrene), poly(N-vinylcarbazole), polyamide, polyimide, poly(N-isopropylacrylamide), and polyacrylonitrile. Thus, by mixing such a hydrophobic polymer with spherical porous carbon, a coating layer with hydrophobic and antistatic properties can be formed on the surface of the spherical porous carbon particles, which can effectively improve the adsorption of water molecules on the surface of the spherical porous carbon and the mutual adsorption between particles caused by static electricity, improve the agglomeration and moisture absorption problems of the spherical porous carbon, and further improve the fluidization property of the spherical porous carbon. According to a specific embodiment of the present invention, the hydrophobic polymer includes at least one of poly(N-vinylcarbazole), polyamide, polyimide, poly(N-isopropylacrylamide), and polyacrylonitrile. Thus, the hydrophobic polymers of this type all contain N elements, and after pyrolysis, nitrogen atoms can be introduced onto the spherical porous carbon, which can better improve the electrical conductivity of the spherical porous carbon material, thereby improving the rate performance of the silicon-carbon material.

[0057] According to an embodiment of the present invention, the mass ratio of the spherical porous carbon to the hydrophobic polymer is (5 - 20):1, such as 5:1, 10:1, 15:1, 20:1, etc. Thus, by mixing the spherical porous carbon and the hydrophobic polymer in this ratio, not only can a complete coating layer with hydrophobic and antistatic properties be formed on the surface of the spherical porous carbon particles, effectively improving the adsorption of water molecules on the surface of the spherical porous carbon and the mutual adsorption between particles caused by static electricity, improving the agglomeration and moisture absorption problems of the spherical porous carbon, and further improving the fluidization property of the spherical porous carbon, but also the pore size distribution in the spherical porous carbon can be improved, thereby improving the subsequent silicon deposition efficiency and reducing the specific surface area of the final product; moreover, during the subsequent carbonization process, the pyrolytic carbon formed by the hydrophobic polymer of this content can further block some of the micropores with a diameter of less than 1 nm on the spherical porous carbon, improving the pore size distribution in the spherical porous carbon, thereby improving the subsequent silicon deposition efficiency and reducing the specific surface area of the final product.

[0058] As an example, the spherical porous carbon substrate includes but is not limited to at least one of spherical porous carbon, spherical hard carbon, and spherical graphite. Thus, the sources of the spherical porous carbon substrate are extensive, which can meet various designs for preparing silicon-carbon materials.

[0059] S200: Place the mixed material in a reactor and carry out carbonization in an inert atmosphere

[0060] In this step, the obtained mixed material is placed in a reactor and carbonized in an inert atmosphere. The pyrolytic carbon formed by the hydrophobic polymer can block some of the micropores with a diameter of less than 1 nm on the spherical porous carbon, improve the pore size distribution in the spherical porous carbon, thereby improving the subsequent silicon deposition efficiency and reducing the specific surface area of the final product.

[0061] According to an embodiment of the present invention, the temperature of the carbonization is 500°C - 700°C, such as 500°C, 600°C, 650°C, 700°C; the time is 2h - 6h, such as 2h, 3h, 4h, 5h, 6h, etc. Thus, under such carbonization conditions, the pyrolytic carbon formed by the hydrophobic polymer can block some of the micropores with a diameter of less than 1 nm on the spherical porous carbon, and at the same time, the pore structure of the spherical porous carbon can be avoided from being damaged at this pyrolysis temperature, thereby improving the pore size distribution in the spherical porous carbon, improving the subsequent silicon deposition efficiency and reducing the specific surface area of the final product.

[0062] S300: Adjust the reactor temperature and introduce a mixed gas including a silicon source gas and a protective gas into the reactor

[0063] Specifically, adjust the temperature of the above reactor and introduce a mixed gas including a silicon source gas and a protective gas into the reactor. For example, if the reactor is a fluidized bed, heat the reactor to 400°C - 600°C, such as 400°C, 420°C, 450°C, 470°C, 500°C, 520°C, 550°C, 570°C, 600°C, etc., and then introduce a mixed gas including a silicon source gas and a protective gas. Among them, the flow rate of silane gas is 2L / min - 6L / min, such as 2L / min, 3L / min, 4L / min, 5L / min, 6L / min, etc., and the total gas flow rate is 12L / min - 25L / min, such as 12L / min, 15L / min, 17L / min, 20L / min, 22L / min, 25L / min, etc., and carry out chemical vapor deposition for 4h - 12h, such as 4h, 6h, 8h, 10h, 12h, etc. Thus, under the deposition conditions of the present application, not only can more nanosilicon be deposited in the pores of the spherical porous carbon, but also the deposition efficiency of nanosilicon in the spherical porous carbon can be improved, thereby improving the specific capacity of the silicon-carbon material.

[0064] According to an embodiment of the present invention, the silicon source gas includes at least one of silane, chlorosilane, and hydrosilane. Thus, the sources of the silicon source gas are extensive and can meet various designs for preparing silicon-carbon materials.

[0065] Thus, the method of the present application can be used to obtain the above-mentioned silicon-carbon material with a relatively low specific surface area and a relatively high sphericity. This silicon-carbon material not only has a relatively high specific capacity and stability, but also when used in the negative electrode sheet, during the battery cycling process, the silicon-carbon material uniformly shrinks and expands radially outward, thereby being able to maintain the structural stability, and further significantly reducing the possibility of electrolyte infiltration into the material due to the structural collapse of the silicon-carbon material and the rupture of the SEI film, improving the capacity and cycling performance of the battery.

[0066] In some embodiments of the present invention, after the chemical vapor deposition, it further includes: introducing a mixed gas including an organic carbon source gas and a protective gas into the reactor, so as to deposit carbon on at least a part of the surface of the silicon-carbon material. Thus, by depositing carbon on the silicon-carbon material, the activity of the silicon-carbon material can be reduced, thereby improving its stability.

[0067] In some embodiments of the present invention, the method for depositing carbon on at least a part of the surface of the silicon-carbon material includes: adjusting the temperature in the reactor to 500°C - 700°C, introducing a mixed gas including an organic carbon source gas and a protective gas, controlling the flow rate of the organic carbon source gas in the mixed gas to be 2 L / min - 6 L / min, the volume ratio of the organic carbon source gas in the mixed gas to be 15% - 40%, and the reaction time to be 2 h - 5 h. Thus, on the one hand, it avoids the generation of SiC or too large grain size due to too high temperature, and at the same time avoids the problem of low carbon source cracking efficiency due to too low temperature; on the other hand, a uniformly distributed carbon layer can be deposited on the surface of the silicon-carbon material.

[0068] In some embodiments of the present invention, the organic carbon source gas includes but is not limited to at least one of methane, propane, acetylene, propylene, and toluene.

[0069] In the third aspect of the present invention, the present invention provides a negative electrode material, which is the above-mentioned silicon-carbon material or the silicon-carbon material obtained by using the above-mentioned method. Thus, this silicon-carbon material not only has a relatively high specific capacity and stability, but also has a relatively high sphericity. When used as the negative electrode material of the negative electrode sheet, during the battery cycling process, the silicon-carbon material can uniformly shrink and expand radially outward, thereby being able to maintain the structural stability, and further significantly reducing the possibility of electrolyte infiltration into the material due to the structural collapse of the silicon-carbon material and the rupture of the SEI film, improving the capacity and cycling performance of the battery.

[0070] In the fourth aspect of the present invention, the present invention provides a negative electrode sheet, which includes the above-mentioned silicon-carbon material. Thus, the negative electrode sheet has a relatively stable structure during use, thereby improving the cycling stability of the battery.

[0071] In a fifth aspect of the present invention, the present invention provides a battery, wherein the battery comprises the above-mentioned negative electrode plate. Thus, the battery has excellent capacity and cycle stability. Specifically, the battery can be a lithium ion battery or a sodium ion battery.

[0072] In a sixth aspect of the present invention, the present invention provides an electric device, the electric device comprising the above-mentioned battery. As a result, the battery life of the electric device and the battery life are long, and the market satisfaction is high. For example, the electric device may include but is not limited to a mobile phone, a laptop computer, a pure electric vehicle, a hybrid electric vehicle, etc.

[0073] The scheme of the present application is described below by specific examples. It should be noted that the following examples are only used to illustrate the present application and should not be considered as limiting the scope of the present application. If no specific technology or conditions are specified in the examples, the technology or conditions described in the literature in this area or the product instructions are used. The reagents or instruments used are not specified by the manufacturer, and are all conventional products that can be obtained commercially.

[0074] Example 1

[0075] (1) 5 kg of porous carbon substrate was added to a spherical shaping machine. The material was processed in the shaping machine at a main engine speed of 600 r / min for 60 min to complete the shaping of the porous carbon raw material. The porous carbon raw material entered the rear air flow classification system, and the coarse and fine materials were separated by particle size by a classification wheel. The classification wheel frequency was 120 Hz to obtain spherical porous carbon (the specific surface area of ​​the spherical porous carbon was 2200 m 2 / g, pore volume is 0.85cm 3 / g, micropores account for 85%, Dv01 is 2.5 μm and (Dv90-Dv10) / Dv50 is 0.95, and the sphericity of the spherical porous carbon is 0.9);

[0076] (2) 150 g of poly(4-[N,N-bis(trimethylsilyl)aminomethyl]-styrene) and 1.5 kg of spherical porous carbon were fully mixed in a high-speed mixer at 800 r / min for 45 min to obtain a mixture of poly(4-[N,N-bis(trimethylsilyl)aminomethyl]-styrene) and spherical porous carbon;

[0077] (3) placing the poly(4-[N,N-bis(trimethylsilyl)aminomethyl]-styrene) and porous carbon mixture in a fluidized bed reactor, first introducing 5 L / min of nitrogen into the fluidized bed reactor to replace the air for 1 hour, and then heating the fluidized bed reactor to 600°C at a heating rate of 5°C / min for high-temperature carbonization for 3 hours;

[0078] (4) adjusting the temperature of the fluidized bed to 580° C., introducing a mixed gas including monosilane gas and nitrogen into the reactor, wherein the flow rate of the monosilane gas in the mixed gas is 3 L / min, the total gas rate is 18 L / min, and the chemical vapor deposition time is 5 h;

[0079] (5) After the silicon deposition reaction is completed, the fluidized bed reactor is continued to be heated at a heating rate of 5°C / min. When the temperature in the reactor rises to 600°C, a mixed gas of acetylene and nitrogen is introduced, and the flow rate of acetylene in the mixed gas is controlled to be a total gas rate of 4L / min. The volume concentration of acetylene in the mixed gas is 30%, and the reaction time is 3h. After the reaction is completed, the temperature is lowered and the material is discharged to obtain a silicon-carbon material.

[0080] Example 2

[0081] (1) 5 kg of porous carbon substrate was added to a spherical shaping machine. The material was processed in the shaping machine at a main engine speed of 700 r / min for 60 min to complete the shaping of the porous carbon raw material. The porous carbon raw material entered the air flow classification system at the rear end, and the coarse and fine materials were separated by particle size by a classification wheel. The classification wheel frequency was 100 Hz to obtain spherical porous carbon (the specific surface area of ​​the spherical porous carbon was 1500 m 2 / g, pore volume is 0.5cm 3 / g, micropores account for 50%, the spherical porous carbon Dv01 is 4 μm and (Dv90-Dv10) / Dv50 is 1.05, and the sphericity of the spherical porous carbon is 0.86);

[0082] (2) 75 g of polyacrylonitrile and 1.5 kg of spherical porous carbon were fully mixed in a high-speed mixer at 800 r / min for 0.5 h to obtain a mixture of polyacrylonitrile and spherical porous carbon;

[0083] (3) placing the polyacrylonitrile and porous carbon mixture in a fluidized bed reactor, introducing 5 L / min of nitrogen into the fluidized bed reactor for air replacement for 1 h, and then heating the fluidized bed reactor to 500 °C at a heating rate of 5 °C / min for high-temperature carbonization for 6 h;

[0084] (4) adjusting the temperature of the fluidized bed to 400° C., introducing a mixed gas including dichlorosilane gas and nitrogen into the reactor, wherein the flow rate of the dichlorosilane gas in the mixed gas is 4 L / min, the total gas rate is 20 L / min, and the chemical vapor deposition time is 12 h;

[0085] (5) After the silicon deposition reaction is completed, the fluidized bed reactor is continued to be heated at a heating rate of 5°C / min. When the temperature in the reactor rises to 700°C, a mixed gas of methane and nitrogen is introduced, and the flow rate of methane in the mixed gas is controlled to be a total gas rate of 2L / min. The volume concentration of methane in the mixed gas is 15%, and the reaction time is 5h. After the reaction is completed, the temperature is lowered and the material is discharged to obtain a silicon-carbon material.

[0086] Example 3

[0087] (1) 5 kg of porous carbon substrate was added to a spherical shaping machine. The material was processed in the shaping machine at a main engine speed of 600 r / min for 60 min to complete the shaping of the porous carbon raw material. The porous carbon raw material entered the rear air flow classification system, and the coarse and fine materials were separated by particle size by a classification wheel. The classification wheel frequency was 120 Hz to obtain spherical porous carbon (the specific surface area of ​​the spherical porous carbon was 1800 m 2 / g, pore volume is 0.7cm 3 / g, micropores account for 60%, the spherical porous carbon Dv01 is 2 μm and (Dv90-Dv10) / Dv50 is 0.8, and the sphericity of the spherical porous carbon is 0.92);

[0088] (2) 100 g of polyimide and 1.5 kg of spherical porous carbon were fully mixed in a conical mixer at 600 r / min for 50 min to obtain a mixture of polyimide and spherical porous carbon;

[0089] (3) placing the polyimide and porous carbon mixture in a fluidized bed reactor, first introducing 5 L / min of nitrogen into the fluidized bed reactor to replace the air for 1 hour, and then heating the fluidized bed reactor to 700°C at a heating rate of 5°C / min for high-temperature carbonization for 2 hours;

[0090] (4) adjusting the temperature of the fluidized bed to 600° C., introducing a mixed gas including silane gas and nitrogen into the reactor, wherein the flow rate of the silane gas in the mixed gas is 2 L / min, the total gas rate is 12 L / min, and the chemical vapor deposition time is 4 h;

[0091] (5) After the silicon deposition reaction is completed, the fluidized bed reactor is continued to be heated at a heating rate of 5°C / min. When the temperature in the reactor rises to 500°C, a mixed gas of propylene and nitrogen is introduced, and the flow rate of propylene in the mixed gas is controlled to be a total gas rate of 6L / min. The volume concentration of methane in the mixed gas is 40%, and the reaction time is 2h. After the reaction is completed, the temperature is lowered and the material is discharged to obtain a silicon-carbon material.

[0092] Example 4

[0093] (1) 5 kg of porous carbon substrate was added to a spherical shaping machine. The material was processed in the shaping machine at a main engine speed of 600 r / min for 30 min to complete the shaping of the porous carbon raw material. The porous carbon raw material entered the rear air flow classification system, and the coarse and fine materials were separated by particle size by a classification wheel. The classification wheel frequency was 180 Hz to obtain spherical porous carbon (the specific surface area of ​​the spherical porous carbon was 3000 m 2 / g, pore volume is 1.8cm 3 / g, micropores account for 90%, the spherical porous carbon Dv01 is 3 μm and (Dv90-Dv10) / Dv50 is 0.8, and the sphericity of the spherical porous carbon is 0.86);

[0094] (2) 100 g of polyisopropylacrylamide and 1.5 kg of spherical porous carbon were fully mixed in a VC mixer at 300 r / min for 1.5 h to obtain a mixture of polyisopropylacrylamide and spherical porous carbon;

[0095] (3) placing the polyisopropylacrylamide and porous carbon mixture in a fluidized bed reactor, first introducing 5 L / min of nitrogen into the fluidized bed reactor to replace the air for 1 hour, and then heating the fluidized bed reactor to 650°C at a heating rate of 5°C / min for high-temperature carbonization for 4 hours;

[0096] (4) adjusting the temperature of the fluidized bed to 500° C., introducing a mixed gas including silane gas and nitrogen into the reactor, wherein the flow rate of the silane gas in the mixed gas is 6 L / min, the total gas rate is 25 L / min, and the chemical vapor deposition time is 5 h;

[0097] (5) After the silicon deposition reaction is completed, the fluidized bed reactor is continued to be heated at a heating rate of 5°C / min. When the temperature in the reactor rises to 650°C, a mixed gas of toluene and nitrogen is introduced, and the flow rate of toluene in the mixed gas is controlled to be a total gas rate of 5L / min. The volume concentration of methane in the mixed gas is 30%, and the reaction time is 4h. After the reaction is completed, the temperature is lowered and the material is discharged to obtain a silicon-carbon material.

[0098] Example 5

[0099] (1) 5 kg of porous carbon substrate was added to a spherical shaping machine. The material was processed in the shaping machine at a main engine speed of 600 r / min for 60 min to complete the shaping of the porous carbon raw material. The porous carbon raw material entered the air flow classification system at the rear end, and the coarse and fine materials were separated by particle size by a classification wheel. The classification wheel frequency was 120 Hz to obtain spherical porous carbon (the specific surface area of ​​the spherical porous carbon was 2000 m 2 / g, pore volume is 0.85cm 3 / g, micropores account for 70%, the spherical porous carbon Dv01 is 2.5μm and (Dv90-Dv10) / Dv50 is 0.95, and the sphericity of the spherical porous carbon is 0.9);

[0100] (2) 300 g of poly(N-vinyl carbazole) and 1.5 kg of spherical porous carbon were fully mixed in a conical mixer at 800 r / min for 0.5 to obtain a mixture of poly(N-vinyl carbazole) and spherical porous carbon;

[0101] (3) placing the poly(N-vinyl carbazole) and porous carbon mixture in a fluidized bed reactor, introducing 5 L / min of nitrogen into the fluidized bed reactor for air replacement for 1 h, and then heating the fluidized bed reactor to 600 °C at a heating rate of 5 °C / min for high-temperature carbonization for 3 h;

[0102] (4) adjusting the temperature of the fluidized bed to 450° C., introducing a mixed gas including monosilane gas and nitrogen into the reactor, wherein the flow rate of the monosilane gas in the mixed gas is 3 L / min, the total gas rate is 18 L / min, and the chemical vapor deposition time is 10 h;

[0103] (5) After the silicon deposition reaction is completed, the fluidized bed reactor is continued to be heated at a heating rate of 5°C / min. When the temperature in the reactor rises to 600°C, a mixed gas of acetylene and nitrogen is introduced, and the flow rate of acetylene in the mixed gas is controlled to be a total gas rate of 2L / min. The volume concentration of acetylene in the mixed gas is 15%, and the reaction time is 5h. After the reaction is completed, the temperature is lowered and the material is discharged to obtain a silicon-carbon material.

[0104] Comparative Example 1

[0105] (1) 150 g of polyimide and 1.5 kg of unspheroidized porous carbon substrate (the specific surface area of ​​the spherical porous carbon is 2200 m 2 / g, pore volume is 0.85cm 3 / g, micropores account for 85%, Dv01 is 0.655 μm and (Dv90-Dv10) / Dv50 is 1.35, and the sphericity of the porous carbon is 0.58) is fully mixed in a high-speed mixer at 800 r / min for 45 min to obtain a polyimide and spherical porous carbon mixture;

[0106] (2) placing the polyimide and porous carbon mixture in a fluidized bed reactor, introducing 5 L / min of nitrogen into the fluidized bed reactor for air replacement for 1 h, and then heating the fluidized bed reactor to 600 °C at a heating rate of 5 °C / min for high-temperature carbonization for 3 h;

[0107] (3) Adjust the fluidized bed temperature to 580 °C, introduce a mixed gas including silane gas and nitrogen into the reactor. At a silane gas flow rate of 3 L / min in the mixed gas and a total gas velocity of 18 L / min, carry out chemical vapor deposition for 5 h;

[0108] (4) After the silicon deposition reaction ends, continue to heat the fluidized bed reactor at a heating rate of 5 °C / min. When the temperature in the reactor rises to 600 °C, start to introduce a mixed gas of acetylene and nitrogen, control the flow rate of acetylene in the mixed gas to be 4 L / min with a total gas velocity, the volume concentration of acetylene in the mixed gas is 30%, the reaction time is 3 h, and after the reaction ends, cool down and discharge to obtain a silicon-carbon material.

[0109] Comparative Example 2

[0110] (1) Add 5 kg of porous carbon substrate into a spherical shaping machine. The material is processed in the shaping machine for 60 min at a main machine speed of 600 r / min to complete the shaping of the porous carbon raw material, and then enter the subsequent air classification system. The particle size separation of coarse and fine materials is carried out by a classification wheel with a classification wheel frequency of 120 HZ to obtain spherical porous carbon (the specific surface area of the spherical porous carbon is 2200 m 2 / g, the pore volume is 0.85 cm 3 / g, the proportion of micropores is 85%, Dv01 is 2.5 μm and (Dv90 - Dv10) / Dv50 is 0.95, and the sphericity of the spherical porous carbon is 0.9);

[0111] (2) Place the spherical porous carbon in a fluidized bed reactor, first introduce nitrogen at a rate of 5 L / min to displace the air in the fluidized bed reactor for 1 h, and then heat the fluidized bed reactor at a heating rate of 5 °C / min to 580 °C. Introduce a mixed gas including silane gas and nitrogen into the reactor. At a silane gas flow rate of 3 L / min in the mixed gas and a total gas velocity of 18 L / min, carry out chemical vapor deposition for 5 h;

[0112] (3) After the silicon deposition reaction ends, continue to heat the fluidized bed reactor at a heating rate of 5 °C / min. When the temperature in the reactor rises to 600 °C, start to introduce a mixed gas of acetylene and nitrogen, control the flow rate of acetylene in the mixed gas to be 4 L / min with a total gas velocity, the volume concentration of acetylene in the mixed gas is 30%, the reaction time is 3 h, and after the reaction ends, cool down and discharge to obtain a silicon-carbon material.

[0113] Figure 2 is the cumulative pore volume of the porous carbon substrate in Comparative Example 2, Figure 3is the cumulative pore volume after pyrolysis of the spheroidized porous carbon hydrophobic polymer prepared in Example 1. In Example 1, the tiny voids on the pyrolytic carbon-encapsulated spherical porous carbon formed by the hydrophobic polymer were closed, resulting in a decrease in the pore volume of the material, indicating that the pyrolytic carbon of the hydrophobic polymer had a pore-blocking effect.

[0114] Figure 4 is the pore size distribution diagram of the porous carbon substrate in Comparative Example 2. Figure 5 is the pore size distribution diagram of the porous carbon after pyrolysis of the spheroidized porous carbon hydrophobic polymer prepared in Example 1. From these two pore size distribution diagrams, it can be seen that the pyrolytic carbon formed by the hydrophobic polymer in Example 1 played a good role in blocking the micropores below 1 nm on the spherical porous carbon while maintaining a relatively high micropore volume, thus improving the pore size distribution in the spherical porous carbon.

[0115] The following method was used to test the silicon-carbon materials prepared in Examples 1-5 and Comparative Examples 1-2:

[0116] BET specific surface area of the silicon-carbon material: It was measured using a 3H-2000PS2 type static volumetric method specific surface area and pore size analyzer produced by Beijing Beishide Company. First, the sample needed to be degassed under vacuum conditions at 110 °C for 3 h. During the degassing process, in order to better open the pores of the sample, especially for samples with a pore structure mainly composed of micropores, the degassing temperature was set on the premise of not damaging the sample structure. At 77.3 K, the nitrogen isothermal adsorption and desorption test was carried out on the degassed sample. According to the nitrogen adsorption and desorption curve, the specific value of the material specific surface area was calculated using the BET (Brunauer-Emmett-Teller) specific surface area calculation method. The pore volume and micropore volume of the silicon-carbon material were measured using the N2 gas adsorption method. After obtaining the adsorption / desorption data, the pore structure was fitted using the NRDFT model.

[0117] Characterization of the silicon content in the silicon-carbon material: The silicon content in the material was analyzed by ICP emission spectroscopy. The content of Si element in the material was tested using an inductively coupled plasma spectrometer (ICP) of model 7500ce produced by Agilent Company in the United States.

[0118] The particle strength of the silicon-carbon anode materials in each example and comparative example was tested. Nanoindentation testing is one of the common methods for characterizing the hardness and elastic modulus of materials. The specific testing method is as follows: A nanoindenter (model Hysitron TI 980) from Bruker, Germany, was used to test the hardness and elastic modulus of individual particles of the silicon-carbon anode material. The testing standard was JB / T12721-2016. Before testing, the silicon-carbon anode material powder was dispersed in epoxy resin and cured. The cured resin was cut by ion polishing. A nano-probe was used to apply pressure to individual particles, and the indentation depth on the particle surface was monitored to calculate the elastic modulus of the particles. The elastic modulus of five particles of the same sample was tested in parallel and the average value was taken to obtain the particle elastic modulus of the silicon-carbon anode material.

[0119] The following method was used to test the electrochemical performance:

[0120] Preparation of the negative electrode sheet: The silicon-carbon material was used as the negative electrode active material. A negative electrode slurry was prepared by mixing the negative electrode active material, sodium carboxymethyl cellulose (CMC), conductive carbon black (SP), and styrene-butadiene rubber (SBR) in a mass ratio of 94.5:1.5:1.5:2.5. The negative electrode slurry was coated on both sides of the copper foil current collector, and then vacuum dried to obtain the negative electrode sheet;

[0121] Preparation of the electrolyte: Ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) were mixed in a volume ratio of 1:1:1, and then the lithium salt LiPF6 was added to obtain an electrolyte with a lithium salt concentration of 1 mol / L;

[0122] The negative electrode sheet was assembled with a lithium sheet, the electrolyte, and a Celgard 2400 separator, and a button battery was assembled using a conventional production process for the outer shell.

[0123] Reversible specific capacity test: The battery was charged at a constant current of 0.1C to 2V at 25°C to obtain the first charge capacity (C c1 ); then it was discharged at a constant current of 0.1C to 0.05V to obtain the first discharge capacity (C d1 ). The first efficiency = first charge capacity / first discharge capacity × 100%; The reversible specific capacity of the silicon-carbon material from 0V to 2.0V = the first charge capacity of the button battery / the mass of the negative electrode active material.

[0124] Capacity retention rate test: The battery was cycled at 0.1C charge and discharge at a constant temperature of 25°C. The discharge capacity of the first cycle was recorded as C0, and the discharge capacity of the 300th cycle was C1. The 300-cycle capacity retention rate of the silicon-carbon material = C1 / C0 * 100%.

[0125] Rate performance test: The charge and discharge tests of the above-mentioned button batteries were carried out on the LAND battery test system of Wuhan Jinnuo Electronics Co., Ltd. The test temperature was 25°C. It was charged at a constant current of 0.5C to 4.45V, then charged at a constant voltage until the current was not greater than 0.025C. After standing for 5 minutes, it was discharged at 0.3C to 3.0V. The capacity obtained in this step was the 0.3C discharge capacity; it was charged at a constant current of 0.5C to 4.45V, then charged at a constant voltage until the current was not greater than 0.025C. After standing for 5 minutes, it was discharged at 3C to 3.0V. The capacity obtained in this way was the 3C discharge capacity; the ratio of the 3C discharge capacity to the 0.3C discharge capacity was used to characterize the rate performance.

[0126] Table 1 Various characterization data of Examples 1-5 and Comparative Examples 1-2

[0127]

[0128] It can be seen from Comparative Example 1 and Examples 1-5 in the above table that the silicon-carbon materials prepared in Examples 1-5 have excellent sphericity and a low BET specific surface area. Moreover, the rate, cycle performance, and capacity of the batteries in Examples 1-5 are significantly higher than those in Comparative Example 1, indicating that the spherical porous carbon obtained by shaping and grading treatment with a porous carbon substrate is used to prepare the silicon-carbon material. When this silicon-carbon material is used for the negative electrode sheet, the capacity, rate, and cycle performance of the battery can be improved.

[0129] It can be seen from Examples 1-5 and Comparative Example 2 that the silicon-carbon materials obtained in Examples 1-5 have a high elastic modulus, excellent sphericity, and a low BET specific surface area. Moreover, the performance, capacity, and rate performance of the batteries in Examples 1-5 are significantly higher than those in Comparative Example 2, indicating that adding a hydrophobic polymer during the preparation of the silicon-carbon material and pyrolyzing it can increase the elastic modulus of the silicon-carbon material particles. Therefore, the mechanical strength of the silicon-carbon material is improved, and thus the ability to buffer the volume expansion of the battery is improved, which is beneficial to improving the cycle performance of the battery. In addition, the pyrolytic carbon formed by the hydrophobic polymer can seal the tiny pores of the spherical porous carbon, which can improve the mechanical strength of the porous carbon itself, reduce the risk of cracking of the material during the later charge and discharge process, and at the same time improve the pore size distribution and silicon deposition efficiency. And the pyrolytic carbon introduces nitrogen atoms onto the spherical porous carbon, which can better improve the conductivity of the spherical porous carbon material, improve the electron transfer ability, and thus improve its rate performance.

[0130] In the description of this specification, the description referring to terms such as "one embodiment" and "another embodiment" means that the specific features, structures, materials, or characteristics described in connection with the embodiment are included in at least one embodiment of the present application. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, without contradiction, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples. Additionally, it should be noted that in this specification, the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features.

[0131] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be construed as limiting the present application. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present application.

Claims

1. A silicon-carbon material, characterized in that, Comprising spherical porous carbon, with nano-silicon deposited inside and on the surface of the pores of the spherical porous carbon, the sphericity of the silicon-carbon material being not less than 0.85, and the BET specific surface area of the silicon-carbon material being less than or equal to 5m 2 / g.

2. The silicon-carbon material according to claim 1, characterized in that, The silicon-carbon material satisfies at least one of the following conditions: In the particle size distribution of the silicon-carbon material, 0.9 ≤ (Dv90 - Dv10) / Dv50 ≤ 1.1; The Dv90 of the silicon-carbon material is 11 μm - 16 μm; The Dv50 of the silicon-carbon material is 6 μm - 9 μm; The Dv10 of the silicon-carbon material is 4 μm - 5 μm; The Dv01 of the silicon-carbon material is not less than 2.5 μm; The micropore volume of the silicon-carbon material is not higher than 0.001 cm 3 / g.

3. The silicon carbide material according to claim 1 or 2, characterized in that, Based on the total mass of the silicon-carbon material, the mass proportion of the nano-silicon is 40 wt% - 70 wt%.

4. The silicon carbide material according to claim 3, wherein At least part of the surface of the silicon-carbon material has deposited carbon.

5. A method for preparing the silicon-carbon material according to any one of claims 1-4, characterized in that, It includes: (1) Mix spherical porous carbon with a hydrophobic polymer to obtain a mixed material; (2) Place the mixed material in a reactor and carry out carbonization in an inert atmosphere, so that after the hydrophobic polymer is pyrolyzed, part of the micropores with a size below 1 nm on the spherical porous carbon are closed; (3) Adjust the temperature of the reactor, introduce a mixed gas including a silicon source gas and a protective gas into the reactor, and deposit nano-silicon in and on the pores of the spherical porous carbon to obtain a silicon-carbon material.

6. The method according to claim 5, wherein The spherical porous carbon satisfies at least one of the following conditions: The BET specific surface area of the spherical porous carbon is not less than 1500 m 2 / g, and the pore volume is 0.5 cm 3 / g - 1.8 cm 3 / g; The spherical porous carbon has a micropore and mesopore structure, and the volume proportion of the micropores is 50% - 90%; The Dv01 of the spherical porous carbon is not less than 2 μm and 0.8 ≤ (Dv90 - Dv10) / Dv50 ≤ 1.05; The Dv90 of the spherical porous carbon is 10 μm - 15 μm; The Dv50 of the spherical porous carbon is 5 μm - 7 μm; The Dv10 of the spherical porous carbon is 3 μm - 4 μm; The sphericity of the spherical porous carbon is not less than 0.86, preferably 0.86 - 0.96, more preferably 0.86 - 0.

92.

7. The method according to claim 5 or 6, characterized in that In step (1), the hydrophobic polymer includes at least one of poly(cyclohexene oxide), poly(vinylcyclohexane), poly(adipic anhydride), poly(4-[N,N-bis(trimethylsilyl)aminomethyl]-styrene), (N-vinylcarbazole), polytetrafluoroethylene, polydimethylsiloxane, poly(vinylidene fluoride), polypropylene, polyethylene, polymethyl methacrylate, polyolefin, polyamide, polyacrylonitrile, polyester, polycarbonate, fluorosilicone resin, and poly(isopropylacrylamide), preferably at least one of poly(4-[N,N-bis(trimethylsilyl)aminomethyl]-styrene), poly(N-vinylcarbazole), polyamide, polyimide, poly(isopropylacrylamide), and polyacrylonitrile; Optionally, the mass ratio of the spherical porous carbon to the hydrophobic polymer is (5 - 20):

1.

8. The method according to claim 5, characterized in that In step (2), the temperature of the carbonization is 500 °C - 700 °C, and the time is 2 h - 6 h.

9. The method according to claim 5, wherein In step (3), the silicon source gas includes at least one of silane, chlorosilane, and hydrosilane; Optionally, in step (3), the temperature of the reactor is adjusted to 400 °C - 600 °C, and under the condition that the flow rate of the silicon source gas in the mixed gas is 2 L / min - 6 L / min and the total gas flow rate is 12 L / min - 25 L / min, the chemical vapor deposition time is 4 h - 12 h.

10. The method according to claim 5, characterized in that It also includes: A mixed gas including an organic carbon source gas and a protective gas is introduced into the reactor so as to deposit carbon on at least a part of the surface of the silicon-carbon material; Optionally, the method for depositing carbon on at least a part of the surface of the silicon-carbon material includes: adjusting the temperature in the reactor to 500°C - 700°C, introducing a mixed gas including an organic carbon source gas and a protective gas, controlling the flow rate of the organic carbon source in the mixed gas to be 2 L / min - 6 L / min, the volume percentage of the organic carbon source gas in the mixed gas being 15% - 40%, and the reaction time being 2 h - 5 h.

11. A negative electrode material, characterized in that, The negative electrode material includes the silicon-carbon material described in any one of claims 1 - 4 or the silicon-carbon material obtained by the method described in any one of claims 5 - 10.

12. A negative electrode plate, characterized in that, The negative electrode plate includes the negative electrode material described in claim 11.

13. A battery, characterized in that, The battery includes the negative electrode plate described in claim 12.

14. An electrical device, characterized in that, The electrical device includes the battery described in claim 13.

Images