Silicon-carbon composite material containing carbon nanotubes, method for preparing the same, and applications

Abstract

The objective is to provide silicon-carbon composite materials containing carbon nanotubes, methods for preparing the same, and applications thereof. [Solution] The silicon-carbon composite material comprises a porous composite hard carbon material containing carbon nanotubes and silicon nanoparticles. The interior of the porous composite hard carbon material is supported by carbon nanotubes, the silicon-carbon composite material uses the porous composite hard carbon material as a substrate, and the silicon nanoparticles are distributed within the pores of the porous composite hard carbon material. The particle size of the silicon-carbon composite material is 1 μm to 100 μm, and the pore diameter of the porous composite hard carbon material is 1 nm to 7 nm. This composite material limits the size and uniform dispersion of silicon nanoparticles, reduces the expansion effect, avoids the problem of repeated formation of SEI films due to the micronization of silicon crystal grains, reduces material fracture due to silicon expansion, and ultimately improves the battery's cycle characteristics. The carbon nanotubes enhance the compressive and tensile properties of the matrix, maintain the stability of the material structure, and provide high-speed conduction channels for lithium ion conduction, thereby ensuring the material's rated properties.

Description

Technical Field

[0001] (Cross - reference to related applications) This application claims the priority of Chinese Patent Application No. 202310884957.6, titled "Silicon - Carbon Composite Material Containing Carbon Nanotubes, Its Preparation Method, and Applications", filed on July 18, 2023.

[0002] (Technical Field) The present invention relates to the technical field of hard carbon anode materials, and particularly to a silicon - carbon composite material containing carbon nanotubes, its preparation method, and applications.

Background Art

[0003] The anode materials widely used in lithium - ion batteries are mainly composed of carbon materials such as artificial graphite and natural graphite, and their theoretical capacity is 372 mAh / g, which cannot meet the demand for high - capacity batteries. On the other hand, silicon has extremely high theoretical reversible capacity as an anode material for lithium - ion batteries, reaching up to 4200 mAh / g at most. However, the main problem of silicon is its large volume expansion coefficient. In lithium - ion batteries, during the charge - discharge process, lithium ions move between the positive and negative electrodes. When lithium ions are inserted into the silicon anode, a large volume change occurs in the silicon crystal.

[0004] During the initial charge-discharge process of a lithium-ion battery, lithium ions are inserted into and removed from the silicon anode. This causes expansion and contraction of the silicon crystal, and this volume change leads to stress concentration and the formation of microcracks in the silicon crystal. As the charge-discharge cycle progresses, these cracks gradually enlarge, eventually leading to the pulverization of the silicon crystal. The silicon nanoparticles generated by this pulverization react with components in the electrolyte to form a thin film called the solid electrolyte interface (SEI). The SEI film is a thin film formed by the reaction of solvent decomposition products in the electrolyte with the electrode material, and it plays an important role in lithium ion transport and battery stability.

[0005] However, since the micronization of the silicon anode occurs repeatedly, new silicon crystal grains are formed and micronized with each charge-discharge cycle. These newly generated silicon microparticles continuously react with components in the electrolyte, causing the SEI film to be constantly formed and reconstructed. Such constant formation and reconstruction of the SEI film may lead to a decrease in the battery's cycle life.

[0006] Currently, research on the modification of silicon-based materials is ongoing. Research has shown that by nano-processing silicon particles, the volume effect can be reduced, mitigating the problem of repeated SEI film formation due to the pulverization of silicon crystal grains during the charge-discharge process, improving the cycle characteristics of silicon-based anode materials, and maintaining high reversible capacity. Further preparation of silicon-carbon composite materials and construction of cage-like structures can effectively mitigate the volume effect of silicon-based anodes. However, the preparation cost of nanosilicon particles is high, and the dispersibility of the nanoparticles themselves is poor. This makes them prone to aggregation during the silicon-carbon anode composite and preparation process, resulting in an uneven distribution that affects the cycle characteristics of the composite material, and preventing the full advantages of nano-processing from being realized. [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] The embodiments of the present invention provide a silicon-carbon composite material containing carbon nanotubes, a method for preparing the same, and applications to solve the problem that nanosilicon particles have poor dispersibility, tend to aggregate easily in the silicon-carbon anode composite and preparation process, resulting in a non-uniform distribution, affecting the cycle properties of the composite material, and preventing the full realization of the advantages of nanotechnology. [Means for solving the problem]

[0008] In a first embodiment, the present invention provides a silicon-carbon composite material containing carbon nanotubes, wherein the silicon-carbon composite material comprises a porous composite hard carbon material containing carbon nanotubes and silicon nanoparticles, wherein the interior of the porous composite hard carbon material is supported by the carbon nanotubes. The silicon-carbon composite material uses the porous composite hard carbon material as a base material, and the silicon nanoparticles are distributed within the pores of the porous composite hard carbon material. The particle size of the silicon-carbon composite material is 1 μm to 100 μm. The pore size of the porous composite hard carbon material is 1 nm to 7 nm.

[0009] Preferably, the silicon nanoparticles account for 10% to 70% of the mass of the silicon-carbon composite material.

[0010] Preferably, the diameter of the carbon nanotube is 1 μm or less, and the length is 50 μm or less.

[0011] In a second embodiment, the present invention provides a method for preparing a silicon-carbon composite material as described in the first embodiment, the preparation method being: A carbonized precursor containing carbon nanotubes is obtained by uniformly mixing a resin, carbon nanotubes, and nano-water-soluble salt particles and subjecting them to a thermosetting treatment. The carbonization precursor containing the carbon nanotubes is introduced into a reaction apparatus, subjected to carbonization treatment, pulverized, washed with water, filtered, and dried to obtain a composite hard carbon matrix containing carbon nanotubes with a particle size of 1 μm to 100 μm. By subjecting the aforementioned composite hard carbon matrix containing carbon nanotubes to a pore-forming treatment, a porous composite hard carbon material containing carbon nanotubes is obtained. Using the aforementioned porous composite hard carbon material containing carbon nanotubes as a base material, and introducing a silicon-containing gas as a silicon source into a reaction furnace with a protective gas, a silicon-carbon composite material containing carbon nanotubes is obtained by performing gas-phase deposition. Includes.

[0012] Preferably, the mass ratio of the resin, the carbon nanotubes, and the nano-water-soluble salt particles is [50%~95%]:[3%~10%]:[2%~40%].

[0013] Preferably, the temperature of the heat curing treatment is 100°C to 300°C, and the duration is 1 to 5 hours. The temperature of the carbonization treatment is 600°C to 900°C, and the duration is 0.5 hours to 15 hours. The temperature of the aforementioned pore-forming treatment is 800°C to 1200°C, and the duration is 6 hours to 50 hours. The temperature of the gas phase deposition is 500°C to 1500°C, and the time is 1 hour to 20 hours.

[0014] Preferably, the protective gas contains one or two of nitrogen gas and argon gas, and the flow rate is 1 to 5 L / min.

[0015] Preferably, the silicon-containing gas contains one or more of monosilane, trisilane, dichlorosilane, trichlorosilane, and tetrachlorosilane, and the flow rate is 2 to 10 L / min.

[0016] In a third embodiment, the present invention provides a negative electrode plate comprising the silicon-carbon composite material described in the first embodiment.

[0017] In a fourth embodiment, the present invention provides a lithium battery, the lithium battery comprising the negative electrode plate described in the third embodiment. [Effects of the Invention]

[0018] Compared to conventional technologies, nanosilicon particles in silicon-carbon composite materials containing carbon nanotubes are uniformly distributed within the pore structure of porous composite hard carbon materials containing carbon nanotubes by gas-phase deposition. On the one hand, the porous composite hard carbon material containing carbon nanotubes limits the size of silicon crystal grains formed after the decomposition and deposition of silicon-containing gas, maintaining them at the nanoscale. On the other hand, it uniformly disperses the silicon nanotubes within the porous composite hard carbon material containing carbon nanotubes, reducing the expansion effect and avoiding the problem of repeated formation of SEI films due to the pulverization of silicon particles during the charge-discharge process. On the other hand, it limits the expansion of silicon, reduces the damage to the silicon-carbon composite material due to silicon expansion, and ultimately improves the battery's cycle characteristics. At the same time, porous composite hard carbon materials can improve the energy density of batteries by effectively increasing the compaction density of the electrode plates after coating. The pore walls of these porous composite hard carbon materials have excellent pressure resistance, and the addition of carbon nanotubes can, on the one hand, improve the tensile strength of the pore wall structure and prevent fracture due to stress during the expansion process of silicon crystal grains. On the other hand, the electrical conductivity of carbon nanotubes (>100 S / m) becomes much higher than that of porous composite hard carbon materials (<10 S / m), improving the rate properties of the material.

[0019] The technical proposal of the embodiment of the present invention will be described in more detail below with reference to the drawings and examples. [Brief explanation of the drawing]

[0020] [Figure 1]It is a schematic diagram of the structure of a silicon-carbon composite material containing carbon nanotubes according to an embodiment of the present invention. [Figure 2] It is a flowchart of a method for preparing a silicon-carbon composite material containing carbon nanotubes according to an embodiment of the present invention.

Mode for Carrying Out the Invention

[0021] Hereinafter, the present invention will be further described with reference to the drawings and specific examples. However, it should be understood that these examples are only for explaining the present invention in more detail and are not intended to limit the present invention in any way, that is, they are not intended to limit the protection scope of the present invention.

[0022] The present invention provides a silicon-carbon composite material containing carbon nanotubes. As shown in FIG. 1, the silicon-carbon composite material includes a porous composite hard carbon material containing carbon nanotubes and silicon nanoparticles. Here, the inside of the porous composite hard carbon material is supported by carbon nanotubes. The silicon-carbon composite material is based on the porous composite hard carbon material, and the silicon nanoparticles are distributed in the pores of the porous composite hard carbon material. The particle size of the silicon-carbon composite material is 1 μm to 100 μm. The pore diameter of the pores of the porous composite hard carbon material is 1 nm to 7 nm.

[0023] The silicon nanoparticles account for 10% to 70% of the mass of the silicon-carbon composite material.

[0024] The diameter of the carbon nanotubes is 1 μm or less, and the length is 50 μm or less.

[0025] The present invention further provides a method for preparing a silicon-carbon composite material containing the above-mentioned carbon nanotubes, wherein the preparation method is a water-soluble salt template method, and in the preparation process, nano-water-soluble salt particles are used as a template, and as shown in Figure 2, the preparation method includes the following steps.

[0026] In step 110, the resin, carbon nanotubes, and nano-water-soluble salt particles are uniformly mixed and subjected to a thermosetting treatment to obtain a carbonized precursor containing carbon nanotubes.

[0027] The resin contains one or more of the following: phenolic resin, epoxy resin, and furfural resin. The carbon nanotubes have a diameter of 1 μm or less and a length of 50 μm or less, while the nano-water-soluble salt particles have a particle size of 20 nm to 100 nm.

[0028] Here, the mass ratio of resin, carbon nanotubes, and nano-water-soluble salt particles is [50%~95%]:[3%~10%]:[2%~40%].

[0029] The temperature for the heat curing treatment is 100°C to 300°C, and the duration is 1 to 5 hours.

[0030] In step 120, a carbonization precursor containing carbon nanotubes is introduced into a reactor, subjected to carbonization treatment, pulverized, washed with water, filtered, and dried to obtain a composite hard carbon matrix containing carbon nanotubes with a particle size of 1 μm to 100 μm.

[0031] The carbonization treatment temperature is 600°C to 900°C, and the duration is 0.5 to 15 hours.

[0032] In this step, nano-water-soluble salt particles are removed by washing.

[0033] In step 130, a porous composite hard carbon material containing carbon nanotubes is obtained by subjecting a composite hard carbon matrix containing carbon nanotubes to a pore-forming treatment.

[0034] The composite hard carbon matrix containing carbon nanotubes obtained in step 120 is subjected to a pore-forming treatment. The gas source used includes one or two of oxygen, carbon dioxide, and water vapor. The pore-forming treatment temperature is 800°C to 1200°C, and the duration is 6 to 50 hours.

[0035] In step 140, a porous composite hard carbon material containing carbon nanotubes is used as the base material, and a silicon-containing gas is introduced into the reactor using a protective gas to perform gas-phase deposition, thereby obtaining a silicon-carbon composite material containing carbon nanotubes.

[0036] The silicon-containing gas includes one or more of the following: monosilane, trisilane, dichlorosilane, trichlorosilane, and tetrachlorosilane, with a flow rate of 2 to 10 L / min. The protective gas includes one or two of the following: nitrogen gas and argon gas, with a flow rate of 1 to 5 L / min. The temperature for gas-phase deposition is 500°C to 1500°C, and the time is 1 to 20 hours.

[0037] Compared to conventional technologies, nanosilicon particles in silicon-carbon composite materials containing carbon nanotubes are uniformly distributed within the pore structure of porous composite hard carbon materials containing carbon nanotubes by gas-phase deposition. On the one hand, the porous composite hard carbon material containing carbon nanotubes limits the size of silicon crystal grains formed after the decomposition and deposition of silicon-containing gas, maintaining them at the nanoscale. On the other hand, it uniformly disperses the silicon nanotubes within the porous composite hard carbon material containing carbon nanotubes, reducing the expansion effect and avoiding the problem of repeated formation of SEI films due to the pulverization of silicon particles during the charge-discharge process. On the other hand, it limits the expansion of silicon, reduces the damage to the silicon-carbon composite material due to silicon expansion, and ultimately improves the battery's cycle characteristics. At the same time, porous composite hard carbon materials can improve the energy density of batteries by effectively increasing the compaction density of the electrode plates after coating. The pore walls of these porous composite hard carbon materials have excellent pressure resistance, and the addition of carbon nanotubes can, on the one hand, improve the tensile strength of the pore wall structure and prevent fracture due to stress during the expansion process of silicon crystal grains. On the other hand, the electrical conductivity of carbon nanotubes (>100 S / m) becomes much higher than that of porous composite hard carbon materials (<10 S / m), improving the rate properties of the material.

[0038] The silicon-carbon composite material containing carbon nanotubes provided by the present invention can be used as a negative electrode plate and is further applicable to liquid, semi-solid, quasi-solid, and all-solid electrolyte lithium-ion batteries.

[0039] To better understand the proposed technology according to the present invention, several specific examples are given below to describe the specific process for preparing a silicon-carbon composite material containing carbon nanotubes using the method provided in the above-mentioned embodiments of the present invention, and the properties of the silicon-carbon composite material containing carbon nanotubes obtained therefrom.

[0040] (Example 1) In Step 1, phenolic resin, carbon nanotubes, and nano-water-soluble salt particles are uniformly mixed in a mass ratio of 50%:10%:40%, and then cured by heating at 100°C for 5 hours to obtain a carbonized precursor containing carbon nanotubes. In step 2, a carbonization precursor containing carbon nanotubes is placed in a reactor, heated to 600°C, and maintained at that temperature for 15 hours to carbonize the carbonization precursor containing carbon nanotubes. After pulverization, the material is washed, filtered, and dried to obtain a composite hard carbon matrix containing 12 μm carbon nanotubes. In step 3, a porous composite hard carbon material containing carbon nanotubes is obtained by subjecting a composite hard carbon matrix containing carbon nanotubes to a pore-forming treatment. The gas source used is oxygen, the gas flow rate is 10 L / min, the pore-forming treatment temperature is 900°C, and the duration is 6 hours. In step 4, a porous composite hard carbon material containing carbon nanotubes is used as the substrate, dichlorosilane gas is used as the silicon source, the flow rate is 2 L / min, and nitrogen gas is introduced into the reactor as a protective gas, the flow rate is 2 L / min, the gas phase deposition temperature is 500°C, and the gas phase deposition time is 2 hours.

[0041] The silicon-carbon composite material containing the obtained carbon nanotubes is used as the negative electrode material. The negative electrode material, the conductive additive carbon black, and the adhesive (carboxymethylcellulose sodium and styrene-butadiene rubber in a 1:1 mass ratio) are weighed in a 96%:2%:2% ratio, and a slurry is prepared at room temperature using a beater. The prepared slurry is uniformly applied to copper foil and dried in a forced-air dryer at 80°C for 2 hours. It is then cut into 16mm diameter circular electrode plates and dried in a vacuum dryer at 90°C for 5 hours. For battery assembly, the dried electrode plates are immediately transferred to a glove box and set aside.

[0042] The simulated battery was assembled in a glove box with a high-purity Ar atmosphere. A metallic lithium electrode was used as the counter electrode, and an ethylene carbonate (EC) / diethyl carbonate (DEC) solution containing 1 mol / L LiPF6 was used as the electrolyte. Constant current charge-discharge mode tests were performed using a charge / discharge device. The discharge termination voltage was 0.005V, the charge termination voltage was 1.5V, and the charge / discharge tests were performed at a C / 10 current density. The test results are shown in Table 1.

[0043] (Comparative Example 1) In Step 1, phenolic resin and nanosilicon particles are uniformly mixed in a mass ratio of 70%:30%, and then cured by heating at 100°C for 5 hours to obtain a silicon-carbon material precursor. In step 2, the silicon-carbon material precursor is placed in a reactor, heated to 900°C, maintained at that temperature for 6 hours, subjected to carbonization treatment, and then pulverized to obtain a 12 μm silicon-carbon composite material.

[0044] (Comparative Example 2) In Step 1, phenolic resin and nano-water-soluble salt particles are uniformly mixed in a 50%:50% mass ratio, and then cured by heating at 100°C for 5 hours to obtain a carbonization precursor. In step 2, the carbonization precursor is placed in a reactor, heated to 900°C, and maintained at that temperature for 6 hours to carbonize the carbonization precursor. After pulverization, washing, filtering, and drying, a 12 μm composite hard carbon matrix is ​​obtained. In step 3, a porous composite hard carbon material is obtained by subjecting the composite hard carbon matrix to a pore-forming treatment. The gas source used is oxygen, the gas flow rate is 10 L / min, the pore-forming treatment temperature is 800°C, and the duration is 8 hours. In step 4, a porous composite hard carbon material is used as the substrate, dichlorosilane gas is used as the silicon source, the flow rate is 2 L / min, and nitrogen gas is introduced into the reactor as a protective gas, the flow rate is 2 L / min, the gas phase deposition temperature is 500°C, and the gas phase deposition time is 2 hours.

[0045] (Example 2) In Step 1, phenolic resin, carbon nanotubes, and nano-water-soluble salt particles are uniformly mixed in a mass ratio of 50%:9%:41%, and then cured by heating at 120°C for 5 hours to obtain a carbonized precursor containing carbon nanotubes. In step 2, a carbonization precursor containing carbon nanotubes is placed in a reactor, heated to 900°C, and maintained at that temperature for 0.5 hours to carbonize the carbonization precursor containing carbon nanotubes. The carbonization precursor is then pulverized to obtain a composite hard carbon matrix containing 16 μm carbon nanotubes. In step 3, a porous composite hard carbon material containing carbon nanotubes is obtained by subjecting a composite hard carbon matrix containing carbon nanotubes to a pore-forming treatment. The gas source used is water vapor, the gas flow rate is 0.5 L / min, the pore-forming treatment temperature is 1200°C, and the duration is 6 hours. In step 4, a porous composite hard carbon material containing carbon nanotubes is used as the substrate, monosilane gas is used as the silicon source at a flow rate of 0.5 L / min, and nitrogen gas is introduced into the reactor as a protective gas at a flow rate of 1 L / min. The gas phase deposition temperature is 1500°C, and the gas phase deposition time is 1 hour.

[0046] (Example 3) In Step 1, phenolic resin, carbon nanotubes, and nano-water-soluble salt particles are uniformly mixed in a mass ratio of 50%:7%:33%, and then cured by heating at 100°C for 5 hours to obtain a carbonized precursor containing carbon nanotubes. In step 2, a carbonization precursor containing carbon nanotubes is placed in a reactor, heated to 600°C, and maintained at that temperature for 15 hours to carbonize the carbonization precursor containing carbon nanotubes. The carbonization precursor is then pulverized to obtain a composite hard carbon matrix containing 85 μm carbon nanotubes. In step 3, a porous composite hard carbon material containing carbon nanotubes is obtained by subjecting a composite hard carbon matrix containing carbon nanotubes to a pore-forming treatment. The gas source used is carbon dioxide, the gas flow rate is 20 L / min, the pore-forming treatment temperature is 950°C, and the duration is 48 hours. In step 4, a porous composite hard carbon material containing carbon nanotubes is used as the base material, monosilane gas and trichlorosilane gas are used as silicon sources at a flow rate of 5 L / min, and nitrogen gas is introduced into the reactor as a protective gas at a flow rate of 3 L / min. The temperature for gas phase deposition is 500°C, and the time for gas phase deposition is 18 hours.

[0047] (Example 4) In Step 1, phenolic resin, carbon nanotubes, and nano-water-soluble salt particles are uniformly mixed in a mass ratio of 60%:10%:30%, and then cured by heating at 100°C for 5 hours to obtain a carbonized precursor containing carbon nanotubes. In step 2, a carbonization precursor containing carbon nanotubes is placed in a reactor, heated to 700°C, and maintained at that temperature for 15 hours to carbonize the carbonization precursor containing carbon nanotubes. The carbonization precursor is then pulverized to obtain a composite hard carbon matrix containing 1 μm carbon nanotubes. In step 3, a porous composite hard carbon material containing carbon nanotubes is obtained by subjecting a composite hard carbon matrix containing carbon nanotubes to a pore-forming treatment. The gas source used is carbon dioxide, the gas flow rate is 9 L / min, the pore-forming treatment temperature is 880°C, and the duration is 22 hours. In step 4, a porous composite hard carbon material containing carbon nanotubes is used as the base material, trisilane gas and dichlorosilane gas are used as silicon sources at a flow rate of 10 L / min, and nitrogen gas is introduced into the reactor as a protective gas at a flow rate of 4.5 L / min. The gas phase deposition temperature is 1350°C, and the gas phase deposition time is 10 hours.

[0048] (Example 5) In Step 1, epoxy resin, carbon nanotubes, and nano-water-soluble salt particles are uniformly mixed in a mass ratio of 70%:5%:25%, and then cured by heating at 300°C for 1 hour to obtain a carbonized precursor containing carbon nanotubes. In step 2, a carbonization precursor containing carbon nanotubes is placed in a reactor, heated to 1250°C, and maintained at that temperature for 10 hours to carbonize the carbonization precursor containing carbon nanotubes. The precursor is then pulverized to obtain a composite hard carbon matrix containing 38 μm carbon nanotubes. In step 3, a porous composite hard carbon material containing carbon nanotubes is obtained by subjecting a composite hard carbon matrix containing carbon nanotubes to a pore-forming treatment. The gas source used is water vapor, the gas flow rate is 7.5 L / min, the pore-forming treatment temperature is 1050°C, and the duration is 29 hours. In step 4, a porous composite hard carbon material containing carbon nanotubes is used as the substrate, trisilane gas is used as the silicon source at a flow rate of 3.5 L / min, and nitrogen gas is introduced into the reactor as a protective gas at a flow rate of 4.5 L / min. The gas phase deposition temperature is 1450°C, and the gas phase deposition time is 12 hours.

[0049] (Example 6) In Step 1, epoxy resin, carbon nanotubes, and nano-water-soluble salt particles are uniformly mixed in a mass ratio of 95%:3%:2%, and then cured by heating at 100°C for 5 hours to obtain a carbonized precursor containing carbon nanotubes. In step 2, a carbonization precursor containing carbon nanotubes is placed in a reactor, heated to 850°C, and maintained at that temperature for 15 hours to carbonize the carbonization precursor containing carbon nanotubes. The carbonization precursor is then pulverized to obtain a composite hard carbon matrix containing 72 μm carbon nanotubes. In step 3, a porous composite hard carbon material containing carbon nanotubes is obtained by subjecting a composite hard carbon matrix containing carbon nanotubes to a pore-forming treatment. The gas source used is carbon dioxide, the gas flow rate is 12 L / min, the pore-forming treatment temperature is 1350°C, and the duration is 7 hours. In step 4, a porous composite hard carbon material containing carbon nanotubes is used as the substrate, tetrachlorosilane gas is used as the silicon source at a flow rate of 3.5 L / min, and nitrogen gas is introduced into the reactor as a protective gas at a flow rate of 2 L / min. The gas phase deposition temperature is 600°C, and the gas phase deposition time is 20 hours.

[0050] (Example 7) In Step 1, epoxy resin, carbon nanotubes, and nano-water-soluble salt particles are uniformly mixed in a mass ratio of 75%:10%:15%, and then cured by heating at 100°C for 5 hours to obtain a carbonized precursor containing carbon nanotubes. In step 2, a carbonization precursor containing carbon nanotubes is placed in a reactor, heated to 900°C, and maintained at that temperature for 8 hours to carbonize the carbonization precursor containing carbon nanotubes. The carbonization precursor is then pulverized to obtain a composite hard carbon matrix containing 15 μm carbon nanotubes. In step 3, a porous composite hard carbon material containing carbon nanotubes is obtained by subjecting a composite hard carbon matrix containing carbon nanotubes to a pore-forming treatment. The gas source used is carbon dioxide, the gas flow rate is 9 L / min, the pore-forming treatment temperature is 800°C, and the duration is 25 hours. In step 4, a porous composite hard carbon material containing carbon nanotubes is used as the substrate, monosilane gas is used as the silicon source at a flow rate of 1.5 L / min, and nitrogen gas is introduced into the reactor as a protective gas at a flow rate of 1 L / min. The temperature for gas phase deposition is 800°C, and the time for gas phase deposition is 10 hours.

[0051] (Example 8) In Step 1, epoxy resin, carbon nanotubes, and nano-water-soluble salt particles are uniformly mixed in a mass ratio of 70%:5%:25%, and then cured by heating at 150°C for 5 hours to obtain a carbonized precursor containing carbon nanotubes. In step 2, a carbonization precursor containing carbon nanotubes is placed in a reactor, heated to 750°C, and maintained at that temperature for 3 hours to carbonize the carbonization precursor containing carbon nanotubes. The carbonization precursor is then pulverized to obtain a composite hard carbon matrix containing 44 μm carbon nanotubes. In step 3, a porous composite hard carbon material containing carbon nanotubes is obtained by subjecting a composite hard carbon matrix containing carbon nanotubes to a pore-forming treatment. The gas source used is oxygen, the gas flow rate is 3 L / min, the pore-forming treatment temperature is 850°C, and the duration is 15 hours. In step 4, a porous composite hard carbon material containing carbon nanotubes is used as the substrate, monosilane gas is used as the silicon source at a flow rate of 8 L / min, and is introduced into the reactor by argon gas as a protective gas at a flow rate of 5 L / min. The gas phase deposition temperature is 800°C, and the gas phase deposition time is 10 hours.

[0052] (Example 9) In Step 1, furfural resin, carbon nanotubes, and nano-water-soluble salt particles are uniformly mixed in a mass ratio of 90%:5%:5%, and then cured by heating at 200°C for 5 hours to obtain a carbonized precursor containing carbon nanotubes. In step 2, a carbonization precursor containing carbon nanotubes is placed in a reactor, heated to 900°C, and maintained at that temperature for 2 hours to carbonize the carbonization precursor containing carbon nanotubes. The carbonization precursor is then pulverized to obtain a composite hard carbon matrix containing 56 μm carbon nanotubes. In step 3, a porous composite hard carbon material containing carbon nanotubes is obtained by subjecting a composite hard carbon matrix containing carbon nanotubes to a pore-forming treatment. The gas source used is water vapor, the gas flow rate is 13 L / min, the pore-forming treatment temperature is 1050°C, and the duration is 27 hours. In step 4, a porous composite hard carbon material containing carbon nanotubes is used as the substrate, trisilane gas is used as the silicon source at a flow rate of 5 L / min, and argon gas is introduced into the reactor as a protective gas at a flow rate of 2.5 L / min. The gas phase deposition temperature is 1200°C, and the gas phase deposition time is 4 hours.

[0053] (Example 10) In Step 1, furfural resin, carbon nanotubes, and nano-water-soluble salt particles are uniformly mixed in a mass ratio of 60%:5%:35%, and then cured by heating at 100°C for 5 hours to obtain a carbonized precursor containing carbon nanotubes. In step 2, a carbonization precursor containing carbon nanotubes is placed in a reactor, heated to 750°C, and maintained at that temperature for 8 hours to carbonize the composite carbonization precursor containing carbon nanotubes. The carbonization process is then performed, and a composite hard carbon matrix containing 12 μm carbon nanotubes is obtained. In step 3, a porous composite hard carbon material containing carbon nanotubes is obtained by subjecting a composite hard carbon matrix containing carbon nanotubes to a pore-forming treatment. The gas source used is oxygen, the gas flow rate is 3 L / min, the pore-forming treatment temperature is 1150°C, and the duration is 18 hours. In step 4, a porous composite hard carbon material containing carbon nanotubes is used as the base material, trisilane gas and dichlorosilane gas are used as silicon sources at a flow rate of 6 L / min, and argon gas is introduced into the reactor as a protective gas at a flow rate of 2.5 L / min. The gas phase deposition temperature is 1350°C, and the gas phase deposition time is 2.5 hours.

[0054] Under the same conditions, button-type batteries were assembled using the materials obtained in Comparative Examples 1-2 and Examples 2-10 according to the method of Example 1, and tests were conducted to evaluate their electrochemical properties. The test results are shown in Table 1.

[0055] [Table 1]

[0056] As can be seen from the data in Table 1, although there is no significant difference in charge ratio capacity and first cycle Coulomb efficiency between Examples 1-10 and Comparative Examples 1-2, the rate characteristics of Examples 1-10 are significantly superior to those of Comparative Examples 1-2, and the electrode expansion rate in the fully charged state is significantly lower than that of Comparative Examples 1-2. Comparative Example 1 is a general silicon-carbon structure made by mixing nanosilicon and carbon matrix and then firing it. Its nanoparticles are not uniformly dispersed, resulting in a large expansion effect, and the electrode plate expansion rate in the fully charged state was 46.25%. Comparative Example 2 is a vapor-deposited silicon-carbon composite structure. In contrast, the silicon-carbon composite material provided in Example 1 suppresses stress-induced fracture during the expansion process of silicon particles by adding carbon nanotubes, reducing the expansion rate of the electrode plate in a fully charged state from 15.93% to 8.35%, further improving the structural stability of the particles during the charge-discharge process, preventing the repeated formation of SEI films due to the pulverization of silicon crystal grains during the charge-discharge process, improving the battery's cycle characteristics, effectively improving the material's conductivity, and ultimately enhancing its rate characteristics.

[0057] Compared to conventional technologies, the nanosilicon particles in the silicon-carbon composite material containing carbon nanotubes provided by the present invention are uniformly distributed within the pore structure of the porous composite hard carbon material containing carbon nanotubes by gas-phase deposition. On the one hand, the porous composite hard carbon material containing carbon nanotubes limits the size of the silicon crystal grains formed after the decomposition and deposition of silicon-containing gas, maintaining them at the nanoscale, and uniformly disperses them within the porous composite hard carbon material containing carbon nanotubes, reducing the expansion effect and avoiding the problem of repeated formation of SEI films due to the pulverization of silicon particles during the charge-discharge process. On the other hand, it limits the expansion of silicon, reduces the damage to the silicon-carbon composite material due to silicon expansion, and ultimately improves the battery's cycle characteristics. At the same time, porous composite hard carbon materials can improve the energy density of batteries by effectively increasing the compaction density of the electrode plates after coating. The pore walls of these porous composite hard carbon materials have excellent pressure resistance, and the addition of carbon nanotubes can, on the one hand, improve the tensile strength of the pore wall structure and prevent fracture due to stress during the expansion process of silicon crystal grains. On the other hand, the electrical conductivity of carbon nanotubes (>100 S / m) becomes much higher than that of porous composite hard carbon materials (<10 S / m), improving the rate properties of the material.

[0058] The above specific embodiments further describe the objectives, technical proposals, and beneficial effects of the present invention. It should be understood that these are merely specific embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention shall all be included within the scope of protection of the present invention.

[0059] (Note) (Note 1) A silicon-carbon composite material containing carbon nanotubes, wherein the silicon-carbon composite material comprises a porous composite hard carbon material containing carbon nanotubes and silicon nanoparticles, wherein the interior of the porous composite hard carbon material is supported by the carbon nanotubes. The silicon-carbon composite material uses the porous composite hard carbon material as a base material, and the silicon nanoparticles are distributed within the pores of the porous composite hard carbon material. The particle size of the silicon-carbon composite material is 1 μm to 100 μm. The pore size of the porous composite hard carbon material is 1 nm to 7 nm. A silicon-carbon composite material containing carbon nanotubes, characterized by the following features.

[0060] (Note 2) The silicon-carbon composite material according to Appendix 1, characterized in that the silicon nanoparticles account for 10% to 70% of the mass of the silicon-carbon composite material.

[0061] (Note 3) The silicon-carbon composite material according to Appendix 1, characterized in that the diameter of the carbon nanotubes is 1 μm or less and the length is 50 μm or less.

[0062] (Note 4) A method for preparing a silicon-carbon composite material containing carbon nanotubes as described in any one of the above appendices 1 to 3, wherein the preparation method is: A carbonized precursor containing carbon nanotubes is obtained by uniformly mixing a resin, carbon nanotubes, and nano-water-soluble salt particles and subjecting them to a thermosetting treatment. The carbonization precursor containing the carbon nanotubes is introduced into a reaction apparatus, subjected to carbonization treatment, pulverized, washed with water, filtered, and dried to obtain a composite hard carbon matrix containing carbon nanotubes with a particle size of 1 μm to 100 μm. By subjecting the aforementioned composite hard carbon matrix containing carbon nanotubes to a pore-forming treatment, a porous composite hard carbon material containing carbon nanotubes is obtained. Using the aforementioned porous composite hard carbon material containing carbon nanotubes as a base material, and introducing a silicon-containing gas as a silicon source into a reaction furnace with a protective gas, a silicon-carbon composite material containing carbon nanotubes is obtained by performing gas-phase deposition. including, A preparation method characterized by the above.

[0063] (Note 5) The preparation method according to Appendix 4, characterized in that the mass ratio of the resin, the carbon nanotubes, and the nano-water-soluble salt particles is [50%~95%]:[3%~10%]:[2%~40%].

[0064] (Note 6) The temperature of the aforementioned heat curing treatment is 100°C to 300°C, and the duration is 1 to 5 hours. The temperature of the carbonization treatment is 600°C to 900°C, and the duration is 0.5 hours to 15 hours. The temperature of the aforementioned pore-forming treatment is 800°C to 1200°C, and the duration is 6 hours to 50 hours. The temperature of the gas phase deposition is 500°C to 1500°C, and the time is 1 to 20 hours. The preparation method described in Appendix 4, characterized by the features described herein.

[0065] (Note 7) The preparation method according to Appendix 4, characterized in that the protective gas comprises one or two of nitrogen gas and argon gas, and the flow rate is 1 to 5 L / min.

[0066] (Note 8) The preparation method according to Appendix 7, characterized in that the silicon-containing gas contains one or more of monosilane, trisilane, dichlorosilane, trichlorosilane, and tetrachlorosilane, and the flow rate is 2 to 10 L / min.

[0067] (Note 9) A negative electrode plate characterized by containing a silicon-carbon composite material as described in any one of the above appendices 1 to 3.

[0068] (Note 10) A lithium battery characterized by including the negative electrode plate described in Appendix 9 above.

Claims

1. A silicon-carbon composite material containing carbon nanotubes, wherein the silicon-carbon composite material comprises a porous composite hard carbon material containing carbon nanotubes and silicon nanoparticles, wherein the interior of the porous composite hard carbon material is supported by the carbon nanotubes. The silicon-carbon composite material uses the porous composite hard carbon material as a base material, and the silicon nanoparticles are distributed within the pores of the porous composite hard carbon material. The particle size of the silicon-carbon composite material is 1 μm to 100 μm. The pore size of the porous composite hard carbon material is 1 nm to 7 nm. A silicon-carbon composite material containing carbon nanotubes, characterized by the following features.

2. The silicon-carbon composite material according to claim 1, characterized in that the silicon nanoparticles account for 10% to 70% of the mass of the silicon-carbon composite material.

3. The silicon-carbon composite material according to claim 1, characterized in that the diameter of the carbon nanotube is 1 μm or less and the length is 50 μm or less.

4. A method for preparing a silicon-carbon composite material containing carbon nanotubes according to any one of claims 1 to 3, wherein the preparation method is: A carbonized precursor containing carbon nanotubes is obtained by uniformly mixing a resin, carbon nanotubes, and nano-water-soluble salt particles and subjecting them to a thermosetting treatment. The carbonization precursor containing the carbon nanotubes is introduced into a reaction apparatus, subjected to carbonization treatment, pulverized, washed with water, filtered, and dried to obtain a composite hard carbon matrix containing carbon nanotubes with a particle size of 1 μm to 100 μm. By subjecting the aforementioned composite hard carbon matrix containing carbon nanotubes to a pore-forming treatment, a porous composite hard carbon material containing carbon nanotubes is obtained. Using the aforementioned porous composite hard carbon material containing carbon nanotubes as a base material, and introducing a silicon-containing gas as a silicon source into a reaction furnace with a protective gas, a silicon-carbon composite material containing carbon nanotubes is obtained by performing gas-phase deposition. including, A preparation method characterized by the above.

5. The preparation method according to claim 4, characterized in that the mass ratio of the resin, the carbon nanotubes, and the nanowater-soluble salt particles is [50% to 95%]:[3% to 10%]:[2% to 40%].

6. The temperature of the aforementioned heat curing treatment is 100°C to 300°C, and the duration is 1 to 5 hours. The temperature of the carbonization treatment is 600°C to 900°C, and the duration is 0.5 hours to 15 hours. The temperature of the aforementioned pore-forming treatment is 800°C to 1200°C, and the duration is 6 hours to 50 hours. The temperature of the gas phase deposition is 500°C to 1500°C, and the time is 1 hour to 20 hours. The preparation method according to feature 4.

7. The preparation method according to claim 4, characterized in that the protective gas comprises one or two of nitrogen gas and argon gas, and the flow rate is 1 to 5 L / min.

8. The preparation method according to claim 7, characterized in that the silicon-containing gas comprises one or more of monosilane, trisilane, dichlorosilane, trichlorosilane, and tetrachlorosilane, and the flow rate is 2 to 10 L / min.

9. A negative electrode plate characterized by comprising the silicon-carbon composite material described in any one of claims 1 to 3 above.

10. A lithium battery characterized by including the negative electrode plate described in claim 9 above.

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