Silicon-carbon composite material and preparation method therefor

Abstract

The present application provides a silicon-carbon composite material and a preparation method therefor. The preparation method comprises: providing a porous matrix; melting and evaporating a silicon-based material, wherein the silicon-based material comprises at least one of SiOx (0<X<2), silicon, and a mixture of silicon dioxide and silicon; and introducing the molten and evaporated silicon-based material into a reaction chamber and performing a composite reaction with the porous matrix in the reaction chamber, and generating the condensate of the molten and evaporated silicon-based material in the pores of the porous matrix. The silicon-carbon composite material and the preparation method therefor in the technical solution of the present application can improve the expansion performance when the silicon-carbon composite material is used, and there is no risk associated with using hazardous chemicals.

Description

Silicon-carbon composite material and preparation method thereof TECHNICAL FIELD

[0001] The present application relates to the field of lithium ion batteries, in particular to a silicon-carbon composite material and a preparation method thereof. BACKGROUND

[0002] At present, graphite negative electrode occupies an absolute advantage in the mass-produced lithium ion battery negative electrode materials, and the main reason for limiting the large-scale use of silicon-based negative electrode is the low first efficiency and large volume expansion rate of silicon-based negative electrode material. The first efficiency of the commonly used silicon-based negative electrode material on the market can reach 90% or more, which can meet the use requirements of conventional lithium ion batteries, but the problem of excessive volume expansion of silicon-based negative electrode material has not been well solved. The excessive volume change of silicon-based negative electrode material during lithium extraction seriously limits its addition proportion in lithium ion batteries, resulting in that silicon-based negative electrode material cannot be used on a large scale.

[0003] The currently widely used processing method of silicon-carbon composite material is to prepare silicon-carbon composite material by cracking gaseous silicon source, and the gaseous silicon source is usually a silicon-containing gas such as monosilane, disilane, halosilane, etc. The silicon-containing gas will burn after leakage, and has very high requirements for storage and use environment, and there is a risk of environmental pollution. Further, the gaseous silicon source belongs to dangerous chemicals, and its processing, transportation and use all have great risks. At present, there is no good method for low-risk and high-quality processing of silicon-carbon composite material.

[0004] SUMMARY

[0005] The present application provides a silicon-carbon composite material and a preparation method thereof, which can reduce the volume expansion during lithium intercalation, and has low production risk and low production cost.

[0006] One aspect of the present application provides a preparation method of a silicon-carbon composite material, comprising:

[0007] providing a porous matrix, the electrical conductivity of the porous matrix being 1 to 100 S / cm; melting and evaporating a silicon-based material, the silicon-based material including at least one of SiOx (0X<2), silicon, and a mixture of silicon dioxide and silicon; and passing the melted and evaporated silicon-based material into a reaction chamber and allowing the melted and evaporated silicon-based material to undergo a composite reaction with the porous matrix in the reaction chamber to generate condensate of the melted and evaporated silicon-based material in the pores of the porous matrix.

[0008] In some embodiments of the present application, the method further comprises forming a carbon coating layer on the surface of the porous matrix.

[0009] In some embodiments of the present application, the molar ratio of oxygen element to silicon element in the silicon-based material is 0.0175 to 0.35.

[0010] In some embodiments of the present application, the method further comprises: introducing a carbon-containing organic gas into the reaction chamber, and making the carbon-containing organic gas undergo a pyrolysis reaction to generate pyrolytic carbon in the pores of the porous substrate.

[0011] In some embodiments of the present application, the method further comprises: introducing a carbon-containing organic gas into the reaction chamber, and making the carbon-containing organic gas undergo a pyrolysis reaction to generate pyrolytic carbon in the pores of the porous substrate.

[0012] In some embodiments of the present application, the method further comprises: introducing a carbon-containing organic gas into the reaction chamber, and making the carbon-containing organic gas undergo a pyrolysis reaction to generate pyrolytic carbon in the pores of the porous substrate.

[0013] In some embodiments of the present application, the method further comprises: introducing a carbon-containing organic gas into the reaction chamber, and making the carbon-containing organic gas undergo a pyrolysis reaction to generate pyrolytic carbon in the pores of the porous substrate.

[0014] In some embodiments of the present application, the method further comprises: introducing a carbon-containing organic gas into the reaction chamber, and making the carbon-containing organic gas undergo a pyrolysis reaction to generate pyrolytic carbon in the pores of the porous substrate.

[0015] In some embodiments of the present application, the method further comprises: introducing a carbon-containing organic gas into the reaction chamber, and making the carbon-containing organic gas undergo a pyrolysis reaction to generate pyrolytic carbon in the pores of the porous substrate.

[0016] In some embodiments of the present application, the method further comprises: introducing a carbon-containing organic gas into the reaction chamber, and making the carbon-containing organic gas undergo a pyrolysis reaction to generate pyrolytic carbon in the pores of the porous substrate.

[0017] In some embodiments of the present application, the method further comprises: introducing a carbon-containing organic gas into the reaction chamber, and making the carbon-containing organic gas undergo a pyrolysis reaction to generate pyrolytic carbon in the pores of the porous substrate.

[0018] In some embodiments of the present application, the method further comprises: introducing a carbon-containing organic gas into the reaction chamber, and making the carbon-containing organic gas undergo a pyrolysis reaction to generate pyrolytic carbon in the pores of the porous substrate. 2 / g, pore volume is 0.005-2.0 ml / g.

[0019] In some embodiments of the present application, the method further comprises: introducing a carbon-containing organic gas into the reaction chamber, and making the carbon-containing organic gas undergo a pyrolysis reaction to generate pyrolytic carbon in the pores of the porous substrate.

[0020] In some embodiments of the present application, the method further comprises: introducing a carbon-containing organic gas into the reaction chamber, and making the carbon-containing organic gas undergo a pyrolysis reaction to generate pyrolytic carbon in the pores of the porous substrate.

[0021] In some embodiments of the present application, the carbon-containing organic gas includes hydrocarbon CxHy(x≥2, y≥7) or CxHyNz(x≥2, y≥7, z≥1) with a boiling point lower than 200°C.

[0022] In some embodiments of the present application, the silicon element in the silicon-carbon composite material has a mass percentage content of 1.7-68%, and the pyrolytic carbon has a mass percentage content of 1-10%.

[0023] In some embodiments of the present application, the carbon source gas for forming the carbon coating layer includes hydrocarbon CxHy(x≥2, y≥7) or CxHyNz(x≥2, y≥7, z≥1) with a boiling point lower than 200°C.

[0024] In some embodiments of the present application, the carbon coating layer has a thickness of 1-100 nm.

[0025] The present application also provides a silicon-carbon composite material, comprising: a porous substrate, wherein the pores of the porous substrate are filled with a condensate after melting and evaporation of a silicon-based material, and the silicon-based material includes at least one of SiOx(0

[0026] In some embodiments of the present application, the silicon-carbon composite material further comprises a carbon coating layer on the surface of the porous substrate.

[0027] In some embodiments of the present application, the molar ratio of oxygen element to silicon element in the silicon-based material is 0.0175-0.35.

[0028] Compared with the prior art, the silicon-carbon composite material and the preparation method thereof have the following beneficial effects:

[0029] By adjusting the oxygen content in the silicon-based material, the oxygen content of the filling substance in the pores of the porous substrate can be adjusted, thereby reducing the volume expansion of the material during lithium intercalation, and further slowing down the particle breakage caused by frequent lithium deintercalation.

[0030] If Si is oxidized in an oxygen-containing atmosphere, not only the structure of the porous carbon substrate will be changed, but also Si will be directly oxidized to SiO2, and the atomic ratio of silicon and oxygen cannot be controlled, resulting in problems such as impedance rise and low capacity of the formed silicon-carbon composite material during use. In the embodiments of the present application, the silicon-based material including at least one of SiOx(0

[0031] The embodiment of the present application continuously / intermittently introduces the carbon-containing organic gas when the carbon-containing organic gas is introduced into the reaction cavity, forms pyrolytic carbon in the pores of the porous substrate, and synchronously condenses and deposits the molten evaporated substance of the silicon-based material into the interstices of the porous substrate. This not only buffers the volume expansion caused by lithium intercalation of the silicon-carbon composite material, but also improves the contact between the pyrolytic carbon particles and the particles formed after condensation of the molten evaporated substance of the silicon-based material, reduces the interface impedance, and further improves the rate performance of the silicon-carbon composite material.

[0032] Further, the embodiment of the present application uses a silicon-based material including at least one of SiOx(0X<2), silicon, and a mixture of silicon dioxide and silicon as a raw material. The risk is low, which greatly reduces the danger of the production process and further reduces the production cost. The porous carbon is used as the porous substrate, and the heat treatment is performed in a hydrogen atmosphere. The number of oxygen-containing functional groups (i.e., the oxygen content) on the surface of the porous substrate can be reduced. Moreover, the reduction of the oxygen content of the porous carbon is beneficial to the reduction of the overall oxygen content in the silicon-carbon composite material, which in turn reduces the degree of oxidation of silicon during the composite reaction, and is beneficial to improving the first charge-discharge effect of the silicon-carbon composite material. DETAILED DESCRIPTION

[0033] The following description provides specific application scenarios and requirements of the present application, which aims to enable those skilled in the art to manufacture and use the content of the present application. Various local modifications of the disclosed embodiments are obvious to those skilled in the art, and the general principles defined herein can be applied to other embodiments and applications without departing from the spirit and scope of the present application. Therefore, the present application is not limited to the shown embodiments, but to the widest scope consistent with the claims.

[0034] The volume expansion of the prior art silicon-based negative electrode material during lithium extraction severely limits the large-scale production and application of the material. The existing silicon-based negative electrode material uses gaseous silicon source as a raw material, which results in high production cost and high risk. Therefore, the present application provides a silicon-carbon composite material and a preparation method thereof. The preparation method directly uses an oxygen-containing silicon-based material as a raw material, which reduces the production cost and production risk. Further, by controlling the oxygen content in the silicon-based material, a silicon-carbon composite material with different silicon-oxygen ratios is prepared, which reduces the expansion performance of the silicon-carbon composite material during use. Furthermore, by introducing silicon-based materials with different silicon-oxygen ratios at different stages of the reaction, a concentration difference of oxygen elements is formed in the silicon-carbon composite material, which further reduces the expansion performance of the composite material during use.

[0035] The method for preparing the silicon-carbon composite material according to the embodiments of the present application comprises the following steps:

[0036] Step S1: providing a porous substrate, the conductivity of the porous substrate being 1-100 S / cm;

[0037] Step S2: evaporating a silicon-based material, the silicon-based material comprising at least one of SiOx (0X<2), silicon, and a mixture of silicon dioxide and silicon;

[0038] Step S3: introducing the evaporated silicon-based material into a reaction chamber and allowing the evaporated silicon-based material to react with the porous substrate in the reaction chamber to form a condensate of the evaporated silicon-based material in the pores of the porous substrate. Optionally, a carbon-containing organic gas can be introduced into the porous substrate to form pyrolytic carbon inside the porous substrate.

[0039] Optionally, the method can further comprise Step S4: forming a carbon coating layer on the surface of the porous substrate.

[0040] Referring to Step S1, the porous substrate according to the embodiments of the present application is, for example, amorphous carbon, and the porous substrate comprises pores with a pore size of less than 5 nm, the number of the pores accounting for more than 80%, and the pores providing a reaction site for the reaction in Step S3. The size of the pores is conducive to controlling the size of the pyrolytic carbon and the silicon-based material formed in the pores.

[0041] In some embodiments of the present application, the conductivity of the porous substrate is 1-100 S / cm, the specific surface area of the porous substrate is 2-3000 m 2 / g, and the pore volume is 0.005-2.0 ml / g. Optionally, the conductivity of the porous substrate is 20-70 S / cm, the specific surface area of the porous substrate is 500-2000 m 2 / g, and the pore volume is 0.4-2.0 ml / g. Since the pores provide a reaction site for the reaction in Step S3, the large specific surface area and pore volume of the porous substrate can improve the capacity of the silicon-carbon composite material.

[0042] Continuing Step S2, the silicon-based material is prepared, and in some embodiments of the present application, the silicon-based material comprises silicon and oxygen elements, and the molar ratio of the oxygen element to the silicon element in the silicon-based material is 0.0175-0.35. Optionally, the molar ratio of the silicon element to the oxygen element is 0.02-0.3, or 0.15-0.25, etc. That is, the content of the oxygen element in the silicon-based material as a raw material is greater than or equal to 0 and less than 53.3%.

[0043] In some embodiments of the present application, the silicon-based material comprises at least one of SiOx(0X<2), silicon, and a mixture of silicon dioxide and silicon, for example, the silicon-based material is SiOx(0X<2), and the silicon-based material can also comprise a mixture of silicon dioxide and silicon, and when the silicon-based material is the mixture of silicon dioxide and silicon, the molar ratio of silicon dioxide to silicon is (0.008-0.150:1). The silicon-based material can also comprise a mixture of SiOx(0X<2), silicon, and silicon dioxide, and the molar ratio of SiOx, silicon, and silicon dioxide can be set as required, for example, the molar ratio of SiOx(0X<2), silicon, and silicon dioxide is 1:5.55:0.24, provided that the molar ratio of oxygen to silicon in the silicon-based material is 0.0175-0.35. By selecting and controlling the content of oxygen in the silicon-based material, the volume expansion of the formed silicon-carbon composite material during lithium intercalation can be reduced, and the particle breakage of the silicon-carbon composite material caused by frequent lithium deintercalation can be slowed down.

[0044] Subsequently, the silicon-based material is evaporated by melting, and in some embodiments of the present application, the silicon-based material can be heated by electromagnetic induction, silicon-carbon rod, or molybdenum wire to a temperature of 1000-2500°C and evaporated by melting, or the silicon-based material can be heated by a high-temperature plasma torch to a temperature of 1000-2500°C and evaporated by melting. Optionally, the silicon-based material is heated to a temperature of 1200-2000°C and evaporated by melting.

[0045] In the process of evaporating the silicon-based material by melting, the pressure in the reaction chamber is 0.01 Pa-200,000 Pa, and optionally, the pressure is 0.1-100,000 Pa. The use of the above range can reduce the evaporation temperature of the silicon-based material, thereby further reducing energy consumption.

[0046] In some embodiments of the present application, inert gas is introduced during the process of evaporating the silicon-based material by melting to increase the flow rate of the silicon-based material after evaporation by melting. The inert gas comprises nitrogen or argon.

[0047] Subsequently, step S3 is performed: the evaporated silicon-based material by melting is introduced into the reaction chamber and reacts with the porous matrix in the reaction chamber to generate condensate of the evaporated silicon-based material by melting in the pores of the porous matrix. After step S3 is performed, the formed silicon-carbon composite material comprises the porous matrix, and the pores of the porous matrix are filled with condensate of the evaporated silicon-based material by melting. In the silicon-carbon composite material, the mass percentage content of silicon is 1.7-68%.

[0048] In some embodiments of the present application, the molten evaporated silicon-based material is introduced into the reaction cavity and reacts with the porous substrate in the reaction cavity to form condensate of the molten evaporated silicon-based material in the pores of the porous substrate, including: step S31, placing the porous substrate in the reaction cavity; step S32, introducing the molten evaporated silicon-based material into the reaction cavity; and step S34, reacting at a temperature of 300-1000°C until the pore filling rate of the porous substrate is greater than 20%. In some embodiments of the present application, step S33 can also be included, i.e., introducing a carbon-containing organic gas into the reaction cavity to cause pyrolysis of the carbon-containing organic gas and form pyrolytic carbon in the pores of the porous substrate. Step S33 can be performed simultaneously with step S32 or sequentially, and the reaction for forming pyrolytic carbon in the pores of the porous substrate can be performed simultaneously with the reaction for forming condensate of the molten evaporated silicon-based material in the pores of the porous substrate.

[0049] In some embodiments of the present application, the reaction cavity of step S31 is a deposition reaction region of a deposition device, and pyrolytic carbon can be formed in the reaction cavity by thermal pyrolysis, or the molten evaporated silicon-based material can be physically adsorbed and deposited in the pores of the porous substrate to form condensate in the pores of the porous substrate. The reaction device can be a horizontal static furnace, a dynamic furnace, or a vertical dynamic furnace, such as a tube furnace, a rotary furnace, a fluidized bed, etc.

[0050] In some embodiments of the present application, step S32 can continuously introduce the same oxygen-containing silicon-based material into the reaction cavity throughout the entire reaction process, or the composition and content of the silicon-based material can be adjusted throughout the entire process to adjust the oxygen content of the condensate filled in the pores. For example, in some embodiments of the present application, the silicon-based material is SiOx(0X<2), and the flow rate of the molten evaporated silicon-based material introduced into the reaction cavity is 0.1-500 cm / s, and the ratio of the flow rate to the length-diameter ratio of the reaction cavity is 0.01-300. In some other embodiments of the present application, the molten evaporated silicon-based material with a component of Si is first introduced, then the molten evaporated silicon-based material with a component of SiOx(0X<2) is introduced after 7.5 h, and the reaction time is 2.5 h until the end of the reaction. In some other embodiments of the present application, the molten evaporated silicon-based material with a component of SiOx(0X<2) is introduced for 2 h, then the molten evaporated silicon-based material with a component of Si is introduced, and after 6 h, the component of the molten evaporated silicon-based material is adjusted to a mixture of silicon dioxide and silicon (for example, the mass ratio of silicon dioxide to silicon is 1:2) until the end of the reaction.

[0051] By controlling the mass percentage content of oxygen element in the silicon-based material, the content of oxygen element in the formed silicon-carbon composite material can be adjusted, the volume expansion of the formed silicon-carbon composite material when lithium is inserted can be reduced, and then the particle breakage of the silicon-carbon composite material caused by frequent de-insertion of lithium can be slowed down. By introducing materials with different oxygen element contents at different stages of the reaction, the condensate of the silicon-based material melted and evaporated from the substance filled in the pores of the porous matrix has different oxygen element contents, which is beneficial to reducing the expansion performance of the silicon-carbon composite material in use.

[0052] In some embodiments of the present application, the mass ratio of silicon element in the melted and evaporated silicon-based material introduced in the composite reaction process to the mass of carbon element in the porous matrix is 0.01-5, so that the filling rate of the pores in the formed silicon-carbon composite material can reach a set value.

[0053] Step S33: introducing the carbon-containing organic gas into the reaction cavity can be performed simultaneously with step S32 or after step S32, and the present application does not limit the execution order too much. In some embodiments of the present application, the carbon-containing organic gas includes hydrocarbons CxHy or CxHyNz (x≥2, y≥7, z≥1) with a boiling point lower than 200°C. For example, ethylamine, aniline, etc.

[0054] In some embodiments of the present application, the carbon-containing organic gas can be continuously introduced into the reaction cavity, and the flow rate of the carbon-containing organic gas is 0.1-500 cm / s. The carbon-containing organic gas can also be introduced into the reaction cavity in an intermittent manner. For example, the carbon-containing organic gas is introduced into the reaction cavity at a flow rate of 10 cm / s for 10 min, then stopped for 20 min, and then introduced into the reaction cavity at a flow rate of 30 cm / s for 10 min.

[0055] Step S34: reacting at a temperature of 300-1000℃ until the porosity filling rate of the porous substrate is greater than 20%. After the melt-evaporated silicon-based material is introduced into the reaction chamber, the silicon-based material is physically deposited or physically adsorbed in the pores of the porous substrate, gradually filling the pores. After the carbon-containing organic gas is introduced into the reaction chamber, pyrolysis reaction occurs in the pores of the porous substrate, thereby generating pyrolytic carbon in the pores. During the reaction, the temperature in the reaction chamber ranges from 300 to 1000℃, and a high temperature is conducive to further reducing the size of the nanoparticles during condensation of the steam, reducing the difficulty of condensate of the pyrolytic carbon and the melt-evaporated silicon-based material entering the pores of the porous substrate, reducing the proportion of particles that are not adsorbed in the pores of the porous substrate, and further, controlling the temperature in the reaction chamber can also control the size of the particles filled in the pores of the porous substrate, thereby improving the initial coulomb efficiency of the material. In some embodiments of the present application, the temperature in the reaction chamber ranges from 500 to 900℃.

[0056] In some embodiments of the present application, during the process of introducing the melt-evaporated silicon-based material and / or the carbon-containing organic gas into the reaction chamber, a reducing gas can also be introduced into the reaction chamber. After the reducing gas introduced fills the pores of the porous substrate, it can reduce the oxygen content of the porous substrate, which is conducive to improving the initial coulomb efficiency of the silicon-carbon composite material formed.

[0057] In some embodiments of the present application, during the process of introducing the melt-evaporated silicon-based material and / or the carbon-containing organic gas into the reaction chamber, a nitrogen source gas can also be introduced into the reaction chamber, and the nitrogen source gas includes at least one of nitrogen, ammonia, or a nitrogen-containing organic gas, and the nitrogen-containing organic gas includes at least one of methylamine, ethylamine, or aniline. Among them, the nitrogen source gas introduced can react with elemental silicon in the melt-evaporated silicon-based material to generate amorphous silicon nitride, which can further improve the structural stability of the silicon-carbon composite material formed and reduce the lithium intercalation expansion rate of the silicon-carbon composite material.

[0058] The embodiments of the present application can also perform step S4: forming a carbon coating layer on the surface of the porous substrate. In some embodiments of the present application, the carbon source gas used to form the carbon coating layer includes a hydrocarbon CxHy or CxHyNz (x≥2, y≥7, z≥1) with a boiling point lower than 200℃. To ensure the quality of the carbon coating layer, the temperature range for forming the carbon coating layer is 500-1000℃, and the thickness of the carbon coating layer formed is 1-100nm.

[0059] In some embodiments of the present application, the silicon-carbon composite material has a mass percentage of silicon of 1-70%, and a mass percentage of carbon of 1-10%, wherein the carbon includes carbon in a carbon coating layer and pyrolytic carbon filled in the pores.

[0060] In some embodiments of the present application, the silicon-carbon composite material has a mass percentage of silicon of 1-70%, and a mass percentage of carbon of 1-10%, wherein the carbon includes carbon in a carbon coating layer and pyrolytic carbon filled in the pores. 2 2 In some embodiments of the present application, the silicon-carbon composite material has a mass percentage of silicon of 1-70%, and a mass percentage of carbon of 1-10%, wherein the carbon includes carbon in a carbon coating layer and pyrolytic carbon filled in the pores.

[0061] In some embodiments of the present application, the silicon-carbon composite material further includes a carbon coating layer on the surface of the porous matrix. The carbon coating layer has a thickness of 1-100 nm.

[0062] In some embodiments of the present application, the silicon-carbon composite material has a mass percentage of silicon of 1-70%, and a mass percentage of carbon of 1-10%, wherein the carbon includes carbon in a carbon coating layer and pyrolytic carbon filled in the pores.

[0063] In some embodiments of the present application, the silicon-carbon composite material has a mass percentage of silicon of 1-70%, and a mass percentage of carbon of 1-10%, wherein the carbon includes carbon in a carbon coating layer and pyrolytic carbon filled in the pores.

[0064] In some embodiments of the present application, the silicon-carbon composite material has a mass percentage of silicon of 1-70%, and a mass percentage of carbon of 1-10%, wherein the carbon includes carbon in a carbon coating layer and pyrolytic carbon filled in the pores.

[0065] In some embodiments of the present application, the silicon-carbon composite material has a mass percentage of silicon of 1-70%, and a mass percentage of carbon of 1-10%, wherein the carbon includes carbon in a carbon coating layer and pyrolytic carbon filled in the pores.

[0066] ​The silicon-carbon composite material obtained by the above preparation method mainly comprises silicon elements, oxygen elements and carbon elements, the content of the oxygen elements affects the volume expansion of the silicon-carbon composite material when lithium is inserted, and thus the particle breakage of the silicon-carbon composite material caused by frequent de-insertion of lithium can be slowed down.

[0067] In some embodiments, before carbon coating, the particle size of the porous matrix can also be adjusted through a crushing process to reduce the specific surface area of the porous matrix and improve the dispersion performance when a lithium ion battery is made.

[0068] Embodiment 1

[0069] A reaction device comprising an evaporation zone and a deposition zone is selected, and a porous carbon with a specific surface area of 2000 m 2 / g, a pore volume of 1.00 ml / g, an electrical conductivity of 1 S / cm and a deposition weight of 1 kg is placed in the deposition zone as a porous matrix;

[0070] The temperature of the evaporation zone is 1700℃, the system pressure is 1 Pa, elemental silicon and SiOx(x=0.9) are selected as silicon-based materials, the total mass of the silicon-based materials is 1 kg, and Msi / Mc is 0.1 / h, wherein M Si refers to the evaporation rate of the silicon-based materials (kg / h), Mc refers to the mass of the porous matrix (kg), 0.75 kg of elemental silicon is first sent into the evaporation zone as a silicon-based material, and after complete melting and evaporation, 0.25 kg of SiOx(x=0.9) is sent into the evaporation zone as a silicon-based material until complete melting and evaporation of the SiOx(x=0.9);

[0071] The silicon-based materials including elemental silicon and SiOx(x=0.9) that are melted and evaporated are introduced into the deposition zone, and the porous carbon is sent into the deposition zone, the temperature of the deposition zone is maintained at 600℃ in a vacuum atmosphere, and the silicon-based materials that are melted and evaporated are filled and adsorbed in the pores of the porous carbon;

[0072] 0.5 L / min of C2H2 is introduced into the deposition zone as a carbon source of the carbon coating layer, the reaction time is 5 h, and after cooling, the silicon-based composite material of embodiment 1 is obtained.

[0073] Embodiment 2

[0074] A reaction device comprising an evaporation zone and a deposition zone is selected, and a porous carbon with a specific surface area of 2000 m 2 / g, a pore volume of 1.00 ml / g, an electrical conductivity of 1 S / cm and a deposition weight of 1 kg is placed in the deposition zone as a porous matrix;

[0075] The temperature of the evaporation zone is 1700℃, the system pressure is 1 Pa, 1 kg of elemental silicon is selected as a silicon-based material, kg, and Msi / Mc is 0.1 / h, wherein M SiThe evaporation rate of the silicon-based material refers to the evaporation rate of the silicon-based material (kg / h), and Mc refers to the mass of the porous substrate (kg). 1 kg of elemental silicon is sent into the evaporation zone as the silicon-based material, and after complete melting and evaporation, the deposition zone is passed through, and the porous carbon is sent into the deposition zone. Under a vacuum atmosphere, the temperature of the deposition zone is maintained at 600°C, the molten and evaporated silicon-based material is filled and adsorbed in the pores of the porous carbon, and after cooling and condensation, a silicon-carbon composite material is formed.

[0076] Example 3

[0077] 1 kg of SiOx (x = 0.9) is selected as the silicon-based material, and the remaining conditions are the same as in Example 1.

[0078] Example 4

[0079] During the process of passing the molten and evaporated silicon-based material into the deposition zone for reaction, 0.1 L / min of carbon-containing organic gas C2H4 is introduced into the deposition zone for the generation of pyrolytic carbon, and the remaining conditions are the same as in Example 1.

[0080] Example 5

[0081] Msi / Mc is 0.05, and during the process of passing the molten and evaporated silicon-based material into the deposition zone for reaction, 0.1 L / min of carbon-containing organic gas C2H4 is introduced into the deposition zone for the generation of pyrolytic carbon, and the remaining conditions are the same as in Example 1.

[0082] Example 6

[0083] Elemental silicon and SiOx (x = 0.9) are selected as the silicon-based material, which contains 0.375 kg of elemental silicon and 0.125 kg of SiOx (x = 0.9), and the remaining conditions are the same as in Example 5.

[0084] Example 7

[0085] Elemental silicon and SiOx (x = 0.9) are selected as the silicon-based material, which contains 1.125 kg of elemental silicon and 0.375 kg of SiOx (x = 0.9), and the remaining conditions are the same as in Example 5.

[0086] Example 8

[0087] The system pressure is 100000 Pa, and during the process of passing the molten and evaporated silicon-based material into the deposition zone for reaction, 0.1 L / min of carbon-containing organic gas C2H4 is introduced into the deposition zone for the generation of pyrolytic carbon, and the remaining conditions are the same as in Example 1.

[0088] Example 9

[0089] The specific surface area of the porous carbon is 3000 m 2The porous carbon with a pore volume of 2.00 ml / g, a conductivity of 1 S / cm and a deposition weight of 1 kg is used as the porous matrix, and the other conditions are the same as those in Example 8.

[0090] Example 10

[0091] The system pressure is 100000 Pa, and a nitrogen-hydrogen mixed gas containing 2% hydrogen by volume is used as the carrier gas, and the other conditions are the same as those in Example 8.

[0092] Example 11

[0093] The system pressure is 100000 Pa, and 0.1 L / min of a carbon-containing organic gas C2H7N is introduced into the deposition zone for generating pyrolytic carbon during the process of reacting the molten and evaporated silicon-based material in the deposition zone, and the other conditions are the same as those in Example 10.

[0094] Example 12

[0095] 0.5 L / min of C6H7N is introduced into the deposition zone as the carbon source for the carbon coating layer, and the reaction time is 5 h, and the other conditions are the same as those in Example 10.

[0096] Example 13

[0097] The system pressure is 0.01 Pa, and the other conditions are the same as those in Example 1.

[0098] Example 14

[0099] The system pressure is 100000 Pa, the evaporation temperature is 2500℃, and 0.1 L / min of a carbon-containing organic gas C2H4 is introduced into the deposition zone for generating pyrolytic carbon during the process of reacting the molten and evaporated silicon-based material in the deposition zone, and the other conditions are the same as those in Example 1.

[0100] Example 15

[0101] The system pressure is 0.01 Pa, and elemental silicon and SiOx (x=0.9) are selected as the silicon-based material, and the total mass of the silicon-based material is 1 kg, and Msi / Mc is 0.1 / h, wherein, M Si M refers to the evaporation rate of the silicon-based material (kg / h), and Mc refers to the mass of the porous matrix (kg). 0.75 kg of elemental silicon is first sent into the evaporation zone as the silicon-based material, the evaporation zone temperature is 1500℃, and after complete melting and evaporation, 0.25 kg of SiOx (x=0.9) is sent into the evaporation zone as the silicon-based material, and the evaporation zone temperature is adjusted to 1200℃ until the SiOx (x=0.9) is completely melted and evaporated.

[0102] Example 16

[0103] 1 kg of SiOx(x=0.9) was selected as the silicon-based material, the system pressure was 5 Pa, the evaporation temperature was 1200 °C, and the other conditions were the same as in Example 1.

[0104] Example 17

[0105] The system pressure was 0.01 Pa, the evaporation temperature was 1700 °C, and the other conditions were the same as in Example 1.

[0106] Example 18

[0107] The system pressure was 5, the evaporation temperature was 1700 °C, the temperature of the deposition zone was maintained at 300 °C, 0.1 L / min of a carbon-containing organic gas C2H4was introduced into the deposition zone during the process of passing the molten and evaporated silicon-based material into the deposition zone to react, the reaction time was 5 h, pyrolytic carbon was generated, no carbon coating layer was deposited, and the other conditions were the same as in Example 1.

[0108] Example 19

[0109] A reaction device comprising an evaporation zone and a deposition zone was selected, and 1 kg of porous carbon with a specific surface area of 2 m 2 / g, a pore volume of 0.005 ml / g, and an electrical conductivity of 100 S / cm was placed in the deposition zone as a porous substrate;

[0110] The evaporation zone temperature was 2000 °C, the system pressure was 200000 Pa, 0.02 kg of elemental silicon was selected as the silicon-based material, the evaporation rate MSi was 0.1 kg / h, and Msi / Mc was 5. After 0.02 kg of elemental silicon was fed into the evaporation zone as the silicon-based material and was completely molten and evaporated;

[0111] The molten and evaporated silicon-based material was passed into the deposition zone, and the porous carbon was fed into the deposition zone. Under a vacuum atmosphere, the temperature of the deposition zone was maintained at 1000 °C, 0.1 L / min of a carbon-containing organic gas C2H4was introduced into the deposition zone, the reaction time was 5 h, and pyrolytic carbon was generated.

[0112] 0.5 L / min of C2H2was introduced into the deposition zone as the carbon source for the carbon coating layer, the reaction time was 5 h, and after cooling, the silicon-based composite material of Example 13 was obtained.

[0113] Example 20

[0114] 1 kg of porous carbon with a specific surface area of 2 m 2 / g, a pore volume of 0.011 ml / g, and an electrical conductivity of 100 S / cm was placed in the deposition zone as a porous substrate, and the other conditions were the same as in Example 19.

[0115] Example 21

[0116] Msi / Mc is 0.01, 0.1 L / min of carbon-containing organic gas C2H4 is introduced into the deposition zone during the process of the molten and evaporated silicon-based material into the deposition zone, and the reaction is carried out for 5 h to generate pyrolytic carbon, and the remaining conditions are the same as those in Example 13.

[0117] Example 22

[0118] Elemental silicon, SiOx(x = 0.9), and a mixture of elemental silicon and silicon dioxide are selected as the silicon-based material, the total mass of the silicon-based material is 1 kg, the evaporation rate Msi / Mc is 0.1 kg / h, 0.2 kg of SiOx(x = 0.9) is first sent into the evaporation zone as the silicon-based material, after the SiOx(x = 0.9) is completely molten and evaporated, 0.6 kg of elemental silicon is sent into the evaporation zone as the silicon-based material, and after the elemental silicon is completely molten and evaporated, 0.2 kg of the mixture of elemental silicon and silicon dioxide (the mass ratio of elemental silicon to silicon dioxide is 2:1) is sent into the evaporation zone as the silicon-based material, so that the mixture of elemental silicon and silicon dioxide is completely molten and evaporated. Si Si The remaining conditions are the same as those in Example 1.

[0119] In the process of the molten and evaporated silicon-based material into the deposition zone, 0.1 L / min of carbon-containing organic gas C2H4 is introduced into the deposition zone, and the reaction is carried out for 5 h to generate pyrolytic carbon, and the remaining conditions are the same as those in Example 1.

[0120] Example 23

[0121] Elemental silicon and SiOx(x = 0.9) are selected as the silicon-based material, the total mass of the silicon-based material is 1 kg, the evaporation rate Msi / Mc is 0.1 kg / h, 0.25 kg of elemental silicon is first sent into the evaporation zone as the silicon-based material, after being completely molten and evaporated, it is introduced into the deposition zone, 0.1 L / min of carbon-containing organic gas C2H4 is introduced into the deposition zone, and the reaction is carried out for 5 h to generate pyrolytic carbon, 0.25 kg of SiOx(x = 0.9) is sent into the evaporation zone as the silicon-based material, and after the SiOx(x = 0.9) is completely molten and evaporated, it is introduced into the deposition zone, 0.25 kg of elemental silicon is continuously sent into the evaporation zone as the silicon-based material, after being completely molten and evaporated, it is introduced into the deposition zone, 0.1 L / min of carbon-containing organic gas C2H4 is introduced into the deposition zone, and the reaction is carried out for 5 h to generate pyrolytic carbon, 0.25 kg of SiOx(x = 0.9) is sent into the evaporation zone as the silicon-based material, and after the SiOx(x = 0.9) is completely molten and evaporated, it is introduced into the deposition zone, and 0.25 kg of elemental silicon is sent into the evaporation zone as the silicon-based material, after being completely molten and evaporated, it is introduced into the deposition zone. 0.1 L / min of carbon-containing organic gas C2H4 is introduced into the deposition zone, and the reaction is carried out for 5 h to generate pyrolytic carbon.

[0122] The remaining conditions are the same as those in Example 1.

[0123] ​Example 24

[0124] The total mass of the silicon-based material is 1 kg, the evaporation rate M Si is 0.1 kg / h, 0.25 kg of SiOx(x=0.9) is first sent into the evaporation zone as the silicon-based material, and after the SiOx(x=0.9) is completely melted and evaporated, it is introduced into the deposition zone; 0.25 kg of elemental silicon is sent into the evaporation zone as the silicon-based material, and after it is completely melted and evaporated, it is introduced into the deposition zone, 0.1 L / min of carbon-containing organic gas C2H4 is introduced into the deposition zone for 5 h to generate pyrolytic carbon; 0.25 kg of SiOx(x=0.9) is sent into the evaporation zone as the silicon-based material, and after the SiOx(x=0.9) is completely melted and evaporated, it is introduced into the deposition zone; 0.25 kg of elemental silicon is sent into the evaporation zone as the silicon-based material, and after it is completely melted and evaporated, it is introduced into the deposition zone, 0.1 L / min of carbon-containing organic gas C2H4 is introduced into the deposition zone for 5 h to generate pyrolytic carbon; and then 0.25 kg of SiOx(x=0.9) is sent into the evaporation zone as the silicon-based material, and after it is completely melted and evaporated, it is introduced into the deposition zone. The remaining conditions are the same as in Example 1.

[0125] Example 25

[0126] 1 kg of elemental silicon is selected as the silicon-based material

[0127] A reaction device comprising an evaporation zone and a deposition zone is selected, and a porous carbon with a specific surface area of 2000 m 2 / g, a pore volume of 1.00 ml / g, and an electrical conductivity of 1 S / cm is placed in the deposition zone as a porous substrate, and the mass of the porous substrate is 1 kg;

[0128] The temperature of the evaporation zone is 1700°C, the system pressure is 1 Pa, 1 kg of elemental silicon is selected as the silicon-based material, kg, Msi / Mc is 0.1 kg / h, wherein, M Si refers to the evaporation rate of the silicon-based material (kg / h), and Mc refers to the mass of the porous substrate (kg), 0.2 kg of elemental silicon is first sent into the evaporation zone as the silicon-based material, and after it is completely melted and evaporated, it is introduced into the deposition zone, 1 L / min of C2H2 is introduced into the deposition zone to generate pyrolytic carbon, and the porous carbon is sent into the deposition zone, the temperature of the deposition zone is maintained at 600°C under a vacuum atmosphere, and the reaction is carried out for 1 h to enable the silicon-based material that is melted and evaporated to fill and adsorb in the pores of the porous carbon; then the process of sending 0.2 kg of elemental silicon into the evaporation zone as the silicon-based material, completely melting and evaporating it, introducing it into the deposition zone, introducing 1 L / min of C2H2 into the deposition zone to generate pyrolytic carbon, and sending the porous carbon into the deposition zone is repeated under a vacuum atmosphere, the temperature of the deposition zone is maintained at 600°C, and the reaction is carried out for 1 h to enable the silicon-based material that is melted and evaporated to fill and adsorb in the pores of the porous carbon, and so on until all of the silicon-based material is introduced.

[0129] Comparative Example 1:

[0130] Using a fluidized bed, using a porous carbon with a specific surface area of 2000 m 2 / g, a pore volume of 1.00 ml / g, and a conductivity of 1 S / cm as a porous substrate, the mass of the porous carbon was 1 kg, using silane as the silicon source, setting the deposition zone at 600 ℃, and passing in silane at a flow rate of 0.1 kg / h of elemental silicon, depositing for a total of 10 h, continuing to pass in 0.5 L / min of C2H2 gas as a silicon source for forming a carbon coating layer in the deposition zone, and reacting for 5 h, to obtain a silicon-based composite material after cooling.

[0131] Comparative Example 2: Based on Comparative Example 1, 0.1 L / min of C2H4 was passed in as a silicon source for forming pyrolytic carbon, and the other conditions were the same.

[0132] The process parameters of all of the examples and comparative examples are compared in Table 1:

[0133] Table 1

[0134] The silicon-carbon composite material formed in the examples was used as a negative electrode material, and a lithium ion battery was formed using the same lithium ion battery preparation process. The electrochemical performance of the silicon-carbon composite material and the lithium ion battery was tested, and the test data are shown in Table 2. As can be seen from Table 2, compared with Comparative Examples 1 and 2, the composite material prepared in the examples has a large degree of improvement and enhancement in terms of full charge expansion and 50-week capacity retention rate under similar capacity efficiency, which further reduces the difficulty of the material in the application of lithium ion batteries.

[0135] In the examples, the filling rate of silicon in the silicon-carbon composite material per gram of the silicon-carbon composite material, i.e. wherein V0 is the total pore volume of the porous material, in cm 3 ; is the true density of silicon, in g / cm 3 .

[0136] In some examples, the detection method of the silicon content is, for example, as follows: 1 g of the silicon-based composite material is taken, and is calcined in an air atmosphere at 800 ℃ or above until the mass is constant to obtain a mass M1, which is multiplied by a coefficient of 0.467 to obtain the silicon content, in g.

[0137] Table 2

[0138] Finally, it should be understood that the embodiments of the application disclosed herein are illustrative of the principles of the present application. Other modifications that are obvious within the spirit and principles of the application are intended to be within the scope of the application. Accordingly, the disclosure of embodiments is intended to be illustrative, but not limiting, of the scope of the application. Those of ordinary skill in the art can readily devise alternative arrangements, which are intended to fall within the scope of the application, without departing from the spirit and principles of the application. Thus, the embodiments disclosed herein are merely exemplary and are not intended to limit the scope of the application.

Claims

1. A method for producing a silicon-carbon composite material, characterized by, The method comprises: providing a porous substrate; fusing and evaporating a silicon-based material, the silicon-based material comprising at least one of SiOx (0 introducing the fusing and evaporated silicon-based material into a reaction chamber and allowing the fusing and evaporated silicon-based material to react with the porous substrate in the reaction chamber to form a condensate of the fusing and evaporated silicon-based material in the pores of the porous substrate.

2. The method of claim 1, wherein the silicon-carbon composite material is prepared by a process comprising: Further comprising: forming a carbon coating layer on the surface of the porous substrate.

3. The method for preparing the silicon-carbon composite material according to claim 1, characterized in that, The molar ratio of oxygen and silicon in the silicon-based material is 0.0175 to 0.

35.

4. The method of claim 1, wherein the silicon-carbon composite material is prepared by a process comprising: The method of introducing the fusing and evaporated silicon-based material into the reaction chamber and allowing the fusing and evaporated silicon-based material to react with the porous substrate in the reaction chamber to form a condensate of the fusing and evaporated silicon-based material in the pores of the porous substrate comprises: placing the porous substrate in the reaction chamber; introducing the fusing and evaporated silicon-based material into the reaction chamber; and reacting at a temperature of 300-1000°C until the porosity filling rate of the porous substrate is greater than 20%.

5. The method of claim 4, wherein the silicon-carbon composite material is prepared by a process comprising: Further comprising: introducing a carbon-containing organic gas into the reaction chamber to allow the carbon-containing organic gas to undergo a pyrolysis reaction to form pyrolytic carbon in the pores of the porous substrate.

6. The method of claim 5, wherein the silicon-carbon composite material is prepared by a process comprising: The method of introducing the carbon-containing organic gas into the reaction chamber comprises: introducing the carbon-containing organic gas in an intermittent manner; or continuously introducing the carbon-containing organic gas into the reaction chamber at a flow rate of 0.1-500 cm / s.

7. The method of making a silicon-carbon composite of claim 4, wherein, The method further comprises: introducing a reducing gas into the reaction chamber.

8. The method of making a silicon-carbon composite of claim 4, wherein, The method further comprises: introducing a nitrogen source gas into the reaction chamber, the nitrogen source gas comprising at least one of nitrogen, ammonia, or a nitrogen-containing organic gas comprising at least one of methylamine, ethylamine, or aniline.

9. The method of making a silicon-carbon composite of claim 4, wherein, The flow rate of the fusing and evaporated silicon-based material introduced into the reaction chamber is 0.1-500 cm / s, and the ratio of the flow rate to the length-diameter ratio of the reaction chamber is 0.01-300.

10. The method of claim 4, wherein the silicon-carbon composite material is prepared by a process comprising: The mass ratio of silicon atoms in the fusing and evaporated silicon-based material to the mass of the porous substrate is 0.01-5.

11. The method of making a silicon-carbon composite of claim 1, wherein, The specific surface area of the porous matrix is from 2 to 3000 m 2 / g, and the pore volume is from 0.005 to 2.0 ml / g.

12. The method for preparing the silicon-carbon composite material according to claim 1, characterized in that, The temperature for fusing and evaporating the silicon-based material is 1000-2500°C, and the pressure range is 0.01 Pa-200,000 Pa.

13. The method for preparing the silicon-carbon composite material according to claim 1, characterized in that, An inert gas is introduced during the process of fusing and evaporating the silicon-based material, and the inert gas comprises nitrogen or argon.

14. The method for preparing the silicon-carbon composite material according to claim 1, characterized in that, The mass percentage of silicon in the silicon-carbon composite material is 1.7-68%.

15. The method for preparing silicon-carbon composite material according to claim 2, characterized in that, The thickness of the carbon coating layer is 1 nm-100 nm.

16. A silicon-carbon composite material, characterized by, The method comprises: a porous substrate, the pores of the porous substrate being filled with a condensate of a fusing and evaporated silicon-based material, the silicon-based material comprising at least one of SiOx (0 17. The silicon-carbon composite of claim 16, wherein, The pores of the porous substrate are filled with pyrolytic carbon.

18. The silicon-carbon composite of claim 16, wherein, Further comprising a carbon coating layer on the surface of the porous substrate.

19. The silicon-carbon composite of claim 16, wherein, The molar ratio of oxygen and silicon in the silicon-based material is 0.0175 to 0.

35.

20. The silicon-carbon composite of claim 17, wherein, The mass percentage of silicon in the silicon-carbon composite material is 1.7-68%, and the mass percentage of pyrolytic carbon is 1-10%.

Images