A silicon-carbon composite anode material prepared using ALD and CVD technologies, its preparation method, and a lithium battery.

Abstract

This invention discloses a silicon-carbon composite anode material, its preparation method, and a lithium battery prepared using ALD and CVD technologies. The method includes: growing a first metal oxide on the surface of a carbon substrate using ALD atomic layer deposition; reducing the first metal oxide on the surface of the carbon substrate to metal-containing nanodots in a reaction chamber; heating the carbon substrate with the nanodots in a reactor and injecting a gas mixture containing silane and an inert gas; growing silicon nanowires on the nanodots using a silane CVD pyrolysis process; heating the carbon substrate with the grown silicon nanowires in a reactor and injecting hydrocarbon gas; and coating the surface of the silicon nanowires with a carbon layer using a CVD pyrolysis process to obtain the silicon-carbon composite anode material. This method effectively prevents the volume expansion of silicon nanowires during charge and discharge, improving the cycle performance of the silicon-carbon composite anode material.

Description

Technical Field

[0001] This invention relates to the technical field of lithium-ion battery anode material preparation methods, and particularly to a silicon-carbon composite anode material prepared using ALD and CVD technologies, its preparation method, and a lithium battery. Background Technology

[0002] Lithium-ion batteries are widely used in portable electronic devices, electric vehicles, and other fields due to their high energy density, long cycle life, and environmental friendliness. The anode material is a key component of lithium-ion batteries, and its performance directly affects the battery's energy density, power density, and cycle life. Currently, graphite is the most mature anode material in commercially available lithium-ion batteries; however, the theoretical specific capacity of graphite is only 372 mAh / g, limiting further improvements in the specific energy of lithium-ion batteries.

[0003] To address this problem, researchers have begun exploring novel anode materials, such as silicon. Silicon has attracted widespread attention due to its high capacity (up to 4200 mAh / g), low delithiation potential, and abundant resources. Group14, a US company, disclosed a method in US patent US11495798B1 for depositing nano-silicon particles via silane CVD pyrolysis inside porous carbon channels, achieving good results. However, existing silicon-based anode material preparation technologies still have some problems: First, porous carbon is expensive, and the pore-forming process is very complex. Second, the pores in porous carbon are generally at the nanoscale and have uneven pore size distribution, making it difficult for deposited silicon nanoparticles to enter the channels or easily clogging the pores. These issues limit the performance of silicon-carbon anode materials. For example, Figure 23 of US Patent US11495798B1 shows that when carbon-coated silicon-carbon composite material is used as an anode, after 500 cycles at a rate of C / 2, the volumetric capacity remains at approximately 78%. Figures 18 and 19 show that when carbon-coated silicon-carbon composite material is used as an anode material, the volumetric capacity decreases by 10% to 50% after 5 cycles at 1C and 2C rates compared to 5 cycles at 0.5C rate. This is mainly because the rate at which lithium ions enter the carbon pores is limited, resulting in poor rate performance of existing silicon-carbon anodes and an inability to support fast charging.

[0004] Furthermore, although silicon nanowires have better cycling performance than silicon nanoparticles, existing silicon nanowire preparation methods, such as those disclosed in US Patent US20130220821A1, require the formation of a 2nm thick gold layer within porous alumina to catalyze the preparation of silicon nanowires with diameters of 40–100nm. This requires the porous carbon and alumina to have pore sizes of 40–100nm, classifying them as mesoporous. If the pore size of the porous carbon and alumina is microporous, existing silicon nanowire preparation processes cannot construct catalysts within the micropores. Silane molecules, typically with diameters between a few angstroms and tens of angstroms, also struggle to enter the micropores and react with the catalyst to form silicon nanowires. Therefore, existing technologies cannot prepare silicon nanowires with diameters no greater than 5nm. Summary of the Invention

[0005] The present invention aims to solve the aforementioned technical problems. To achieve the above objectives, the present invention mainly employs the following technical means:

[0006] A method for preparing silicon-carbon composite anode materials using ALD and CVD technologies includes the following steps:

[0007] Step 1. Grow a first metal oxide on the surface of a carbon substrate using ALD atomic layer deposition;

[0008] Step 2. In the reaction chamber, the first metal oxide on the surface of the carbon substrate material is reduced to nanodots containing metal elements;

[0009] Step 3. Place the carbon substrate material with the distributed nanodots in a reactor, heat it, and inject a gas mixture containing silane and inert gas to grow silicon nanowires on the nanodots based on a chemical vapor deposition process;

[0010] Step 4. Coat the silicon nanowires on the carbon substrate with a carbon layer to obtain a silicon-carbon composite anode material.

[0011] The growth of first metal oxides on the surface of carbon-based materials using ALD atomic layer deposition includes:

[0012] Step S1: Place the carbon substrate material in a porous container and place the porous container into the ALD reaction chamber, or place the carbon substrate material in the ALD reaction chamber and then repeatedly evacuate and replace the nitrogen gas at least three times.

[0013] Step S2: Fluidize the substrate material in the reaction chamber under a nitrogen or argon atmosphere at a fluidization pressure of 1-1000 torr, or achieve substrate material dispersion by rotating the porous container; the preferred fluidization pressure is 10-100 torr.

[0014] Step S3: Select the reaction precursor according to the type of first metal oxide to be deposited, and set the parameters of the ALD reaction chamber: deposition temperature 100℃-400℃, deposition pressure 0.01 torr-500 torr; precursor A is one or a mixture of several volatile metal alkylamino salts, organometallic compounds, halides, alkoxides, and metal β-diketone complexes, wherein the metal element in the metal alkylamino salt, organometallic compound, halide, alkoxide, and metal β-diketone complex is one of copper, tin, indium, gold, titanium, nickel, iron, silver, platinum, tin and gallium, cobalt, aluminum, and silicon;

[0015] Step S4: Introduce the precursor A vapor into the ALD reaction chamber under nitrogen or argon gas, and maintain it for 10-300 seconds. The flow rate of the carrier gas, nitrogen or argon, is 5-8000 sccm.

[0016] Step S5: Purge the reaction chamber with nitrogen or argon to remove the remaining precursor A. The flow rate of the carrier gas, nitrogen or argon, is 5-8000 sccm.

[0017] Step S6: Under the action of the carrier gas, oxygen source vapor is introduced into the ALD reaction chamber and held for 10-300 seconds; the oxygen source is water, hydrogen peroxide, oxygen, ozone, or atomic oxygen, and the carrier gas, nitrogen or argon, has a flow rate of 5-8000 sccm.

[0018] Step S7: Purge the reaction chamber with nitrogen or argon to remove excess oxygen vapor and byproducts;

[0019] Step S8: Repeat steps S4 to S7 until the metal oxide deposition corresponding to precursor A reaches the set coating thickness of 0.33-1nm.

[0020] Step 2 is carried out in the reaction chamber of the hydrogen reduction device.

[0021] Furthermore, the nanodots containing metallic elements are selected from one or more of copper and / or copper oxide, tin, indium, gold, titanium, nickel, iron, silver, platinum, tin and gallium, cobalt, aluminum, and silicon dioxide.

[0022] Furthermore, the thickness of the first metal oxide is 0.33–1 nm.

[0023] Furthermore, the diameter of the silicon nanowire is no greater than 5 nm.

[0024] Furthermore, the coating process is selected from one of chemical vapor deposition, plasma-enhanced chemical vapor deposition, electron beam evaporation, vacuum deposition, and atomic layer deposition.

[0025] Step 4 includes introducing hydrocarbon gas, which includes, but is not limited to, methane, propane, butane, cyclohexane, ethane, propylene, and acetylene.

[0026] Furthermore, the coating process is preferably chemical vapor deposition.

[0027] The silicon-carbon composite anode material prepared by the method includes a carbon substrate material, silicon nanowires grown on the surface of the carbon substrate material, a carbon layer coated on the surface of the silicon nanowires, and nanodots containing metal elements distributed within the silicon nanowires, wherein the nanodots containing metal elements are selected from one or more of copper and / or copper oxide, tin, and indium.

[0028] The carbon-based materials include graphite, hard carbon, soft carbon, carbon fiber, carbon nanofiber, carbon nanotube, mesophase carbon microspheres, carbon black, and Ketjen black.

[0029] A lithium-ion battery comprising the aforementioned silicon-carbon composite anode material.

[0030] Furthermore, steps 3 and 4 are further supplemented by repeating steps 1 to 2, selecting a reaction precursor according to the type of the second metal oxide to be deposited, depositing the second metal oxide on the silicon nanowires of the carbon substrate material, and then reducing it to the second metal particles. After the silicon nanowires and the second metal particles on the silicon nanowires of the carbon substrate material are processed in step 4, a carbon layer is formed on the surface of the silicon nanowires on the carbon substrate material, and carbon nanotubes are grown between the second metal particles of the silicon nanowires on the carbon substrate material.

[0031] Furthermore, the second metal oxide includes one or more of nickel oxide, iron oxide, cobalt oxide, copper oxide, chromium oxide, manganese oxide, molybdenum oxide, tungsten oxide, platinum oxide, and palladium oxide.

[0032] Furthermore, the metal in the second metal particle is selected from one or more of nickel, iron, cobalt, copper, chromium, manganese, molybdenum, tungsten, platinum, and palladium.

[0033] Furthermore, the thickness of the second metal oxide is 0.1-5 nm.

[0034] The silicon-carbon composite anode material prepared by the method includes a carbon substrate material, silicon nanowires grown on the surface of the carbon substrate material, a carbon layer coated on the surface of the silicon nanowires, carbon nanotubes formed between the silicon nanowires, metal-containing nanodots distributed within the silicon nanowires, and second metal particles distributed within the carbon nanotubes.

[0035] The carbon-based materials include graphite, hard carbon, soft carbon, carbon fiber, carbon nanofiber, carbon nanotube, mesophase carbon microspheres, carbon black, and Ketjen black.

[0036] A lithium-ion battery comprising the aforementioned silicon-carbon composite anode material.

[0037] The coating process uses a carbon source, a reaction precursor of a second metal oxide, and a co-catalyst as raw materials. The raw materials are introduced into the reactor via a carrier gas. A carbon layer is formed on the surface of silicon nanowires on a carbon substrate using a floating catalyst chemical vapor deposition method, and carbon nanotubes are grown between the silicon nanowires on the carbon substrate. The co-catalyst is selected from one or both of thiophene and sulfur. The reaction precursor of the second metal oxide is selected from a cadmium of the second metal in the second metal oxide. The carbon source includes a gaseous carbon source or a liquid carbon source, wherein the liquid carbon source is C. 1-4 alcohols and C 6-8 A mixture of hydrocarbons, wherein the gaseous carbon source comprises C 1-3 The carrier gas is a hydrocarbon, and the carrier gas includes hydrogen or an inert gas.

[0038] The C 1-4 The alcohol is selected from one or more of n-butanol, methanol, and ethanol; the C 6-8 The hydrocarbon is selected from one or more of n-hexane, benzene, toluene, and xylene; the C 1-3 Hydrocarbons include alkanes, alkenes, and alkynes.

[0039] The carbon-based materials include graphite, hard carbon, soft carbon, carbon fiber, carbon nanofiber, carbon nanotube, mesophase carbon microspheres, carbon black, and Ketjen black.

[0040] The metal in the second metal particle is selected from one or more of nickel, iron, cobalt, copper, chromium, manganese, molybdenum, tungsten, platinum, and palladium.

[0041] The silicon-carbon composite anode material prepared by the method includes a carbon substrate material, silicon nanowires grown on the surface of the carbon substrate material, a carbon layer coated on the surface of the silicon nanowires, carbon nanotubes formed between the silicon nanowires, metal-containing nanodots distributed within the silicon nanowires, and second metal particles distributed within the carbon nanotubes.

[0042] A lithium-ion battery comprising the aforementioned silicon-carbon composite anode material.

[0043] The above-described method for preparing silicon-carbon composite anode materials can effectively prevent the volume expansion of silicon nanowires during charge and discharge, thereby improving the cycle performance of the silicon-carbon composite anode materials. Through the above technical means, the technical solution of this invention successfully prepared silicon-carbon composite anode materials, solving the problems of high cost of porous carbon, complex pore-forming processes, difficulty in silicon nanoparticles entering the pores, and the limitation of silicon nanowire diameter by the size of metal catalyst particles in existing technologies.

[0044] Compared with existing technologies, the beneficial effects of the technical solution of the present invention are as follows:

[0045] 1. Cost reduction: This invention uses low-cost graphite or hard carbon as a substrate, grows metal oxides on its surface and in cracks through ALD technology, and then reduces the metal oxides into nano-metal particles as a catalyst through H2 reduction process, which greatly reduces the cost of raw materials.

[0046] 2. Optimized Structure: This invention employs a silane CVD pyrolysis process to grow silicon nanowires on a catalyst, and then uses an acetylene CVD pyrolysis process to coat the surface of the silicon nanowires with amorphous carbon or grow carbon nanotubes on the surface of the silicon nanowires, forming a novel silicon-carbon composite anode material. This structural design allows the silicon nanowires to be better dispersed in the carbon matrix, avoiding the problem of silicon nanoparticles clogging the pores, thereby improving the material's performance.

[0047] 3. Improved performance: The silicon-carbon composite anode material of the present invention has a reversible specific capacity of over 2500 mAh / g, a capacity retention rate of over 90% after 100 cycles, and a capacity retention rate of over 80% after 500 cycles. Compared with the prior art, it has higher specific capacity and better cycle performance.

[0048] 4. Achieving Small-Sized Silicon Nanowire Growth: This invention employs ALD and CVD technologies to achieve precise control over the growth of silicon nanowires. By controlling the thickness of the metal oxide film using ALD technology, the diameter of the silicon nanowires can be controlled, thus achieving the growth of silicon nanowires with a diameter of less than 5 nanometers—a feat difficult to achieve with existing technologies. The length of the silicon nanowires is controlled by adjusting the concentration and flow rate of silane using CVD.

[0049] 5. Currently, commercially available silicon-carbon nanoparticles are grown within the nanopores of porous carbon, and then coated with a carbon layer. The rate at which lithium ions enter these pores is limited, resulting in poor rate performance of existing silicon-carbon anodes and an inability to support fast charging. The silicon nanowires of this invention, after being coated with carbon, can directly contact the electrolyte, unaffected by the limitations of nanopore transport, thus exhibiting significantly better rate performance. Attached Figure Description

[0050] Figure 1 The flowcharts for the preparation of silicon-carbon composite anode materials using ALD and CVD technologies in Examples 1, 2 and 4 of this invention are shown.

[0051] Figure 2 This is a flowchart of the preparation of silicon-carbon composite anode material using ALD and CVD technologies in Example 3 of the present invention.

[0052] Figure 3 SEM image of graphite surface;

[0053] Figure 4 SEM image of copper nanoparticles formed by hydrogen reduction after copper oxide film deposition on graphite surface;

[0054] Figure 5 SEM image of silicon nanowires formed on the graphite surface;

[0055] Figure 6 This is a TEM image of a 5nm silicon nanowire.

[0056] Figure 7 The specific capacity of the silicon-carbon composite anode material in Example 1 of the present invention at a current density of 0.1C is shown.

[0057] Figure 8 The cycle life of the silicon-carbon composite anode material in Example 1 of the present invention at a current density of 0.2C is shown. Detailed Implementation

[0058] The following description provides specific application scenarios and requirements for this application, intended to enable those skilled in the art to make and use the content of this application. Various partial modifications to the disclosed embodiments will be apparent 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 this disclosure. Therefore, this disclosure is not limited to the embodiments shown, but rather to the widest scope consistent with the claims.

[0059] The technical solution of the present invention will be described in detail below with reference to the embodiments and accompanying drawings.

[0060] A method for preparing silicon-carbon composite anode materials using ALD and CVD technologies:

[0061] Step 1: Select graphite, hard carbon, soft carbon, carbon fiber, carbon nanofiber, carbon nanotube, mesophase carbon microspheres, carbon black, or Ketjen black as substrate materials, and place them in an atomic layer deposition (ALD) apparatus. Set the reaction temperature to 100℃-400℃ and the reaction pressure to 0.01 torr-500 torr. Under these conditions, use ALD technology to grow a first metal oxide, such as copper oxide, tin oxide, or indium oxide, on the surface and in the cracks of graphite. The thickness of the first metal oxide is 0.33–1 nm.

[0062] As an example of the present invention, a method for growing a first metal oxide on the surface and in cracks of graphite using ALD technology includes:

[0063] Step S1: Place the substrate material in a porous container and put the porous container into the ALD reaction chamber, or place the substrate material in the ALD reaction chamber and then repeatedly evacuate and replace the nitrogen gas at least three times.

[0064] Step S2: Fluidize the substrate material in the reaction chamber under a nitrogen or argon atmosphere at a fluidization pressure of 1-1000 torr, or achieve substrate material dispersion by rotating the porous container; the preferred fluidization pressure is 10-100 torr.

[0065] Step S3: Select the reaction precursor according to the type of first metal oxide to be deposited, and set the parameters of the ALD reaction chamber: deposition temperature 100℃-400℃, deposition pressure 0.01 torr-500 torr; precursor A is one or a mixture of several volatile metal alkylamino salts, organometallic compounds, halides, alkoxides, and metal β-diketone complexes, wherein the metal elements in the metal alkylamino salts, organometallic compounds, halides, alkoxides, and metal β-diketone complexes are copper, tin, indium, gold, titanium, nickel, iron, silver, platinum, tin and gallium, cobalt, aluminum, and silicon;

[0066] Step S4: Introduce the precursor A vapor into the ALD reaction chamber under nitrogen or argon gas, and maintain it for 10-300 seconds. The flow rate of the carrier gas, nitrogen or argon, is 5-8000 sccm.

[0067] Step S5: Purge the reaction chamber with nitrogen or argon to remove the remaining precursor A. The flow rate of the carrier gas, nitrogen or argon, is 5-8000 sccm.

[0068] Step S6: Under the action of the carrier gas, oxygen source vapor is introduced into the ALD reaction chamber and held for 10-300 seconds; the oxygen source is water, hydrogen peroxide, oxygen, ozone, or atomic oxygen, and the carrier gas, nitrogen or argon, has a flow rate of 5-8000 sccm.

[0069] Step S7: Purge the reaction chamber with nitrogen or argon to remove excess oxygen vapor and byproducts;

[0070] Step S8: Repeat steps S4 to S7 until the metal oxide deposition corresponding to precursor A reaches the set coating thickness of 0.33-1 nm; precursor A is selected from one or more of the materials in Table 1.

[0071] Table 1

[0072]

[0073] In Table 1, SnCl4 in precursor A can be replaced with other suitable tin-containing precursors, including halogenated tin-containing precursors (e.g., SnBr4) and non-halogenated tin-containing precursors (e.g., organotin compounds including alkyl-substituted tin amides). Specific examples of alkyl-substituted tin amides suitable for ALD include: tetratetra(dimethylamino)tin, tetratetra(ethylmethylamino)tin, N... 2 N 3-di-tert-butyl-butane-2,3-diaminotin(II)(N) 2 N 3 (-di-tert-butyl-butane-2,3-diamino-tin(II)) and (1,3-bis(1,1-dimethylethyl)-4,5-dimethyl-(4R,5R)-1,3,2-diazastannolidin-2-ylidine).

[0074] In Table 1, In(acac)3 is called acetylacetone indium in Chinese. It can also be replaced by other liquid compounds of indium: [(CH3CH2)2InN[Si(CH3)3]2, which is bis(trimethylsilyl)aminodiethylindium, Et2InN(TMS)2; here, TMS refers to Si(CH3)3, [(CH3)2In(CH2)3N(CH3)2; Me2In(CH2)3NMe2], which is dimethyl(3-dimethylaminopropyl)indium.

[0075] Step 2: The substrate material with grown metal oxides is placed in the reaction chamber of a hydrogen reduction apparatus. At high temperature, the metal oxides are reduced to a catalyst using a hydrogen reduction process. The catalyst's volume decreases relative to the metal oxide film, forming spaced-apart nanoparticles with a diameter of 0.5–1 nm, i.e., catalyst particles, such as copper and cuprous oxide nanoparticles, tin nanoparticles, indium nanoparticles, or composites thereof. These nanoparticles will serve as catalysts for subsequent silicon nanowire growth.

[0076] Step 3: The substrate material with the grown nano-catalyst particles is placed in the reaction chamber of a silane chemical vapor deposition (CVD) device. Silane is pyrolyzed using the CVD process to grow silicon nanowires on the nano-metal particles. During this process, the length of the silicon nanowires can be controlled by adjusting the silane flow rate and reaction time. The processing temperature and time can be varied; for example, the temperature can be between 300 and 400°C, between 400 and 500°C, between 500 and 600°C, between 600 and 700°C, between 700 and 800-900°C. The gas mixture can contain 0.1-1% silane and the remainder inert gas. Alternatively, the gas mixture can contain 1% to 10% silane and the remainder inert gas. Alternatively, the gas mixture can contain 10% to 20% silane and the remainder inert gas. Alternatively, the gas mixture can contain 20% to 50% silane and the remainder inert gas. Alternatively, the gas mixture may contain more than 50% silane and the remainder inert gas. Alternatively, the gas may be essentially 100% silane gas. The reactor for the CVD process is of various designs known in the art, such as fluidized bed reactors, static bed reactors, lifter kilns, rotary kilns, box kilns, or other suitable reactor types. Reactor materials are suitable for this task, as known in the art.

[0077] Step 4: The substrate material with grown silicon nanowires is placed in the reaction chamber of a chemical vapor deposition (CVD) apparatus. Hydrocarbon gas is introduced, and a carbon layer is deposited at a high temperature. The deposition time can be varied, for example, between 0 and 5 minutes, between 5 and 15 minutes, between 15 and 30 minutes, between 30 and 60 minutes, between 60 and 120 minutes, or between 120 and 240 minutes. In some embodiments, the deposition time is greater than 240 minutes. The deposition temperature can be varied, for example, between 350 and 1050°C, between 350 and 450°C, between 450 and 550°C, or between 550 and 650°C. The hydrocarbon gas is cracked using the chemical vapor deposition (CVD) process to coat the silicon nanowire surface with amorphous carbon. During this process, the thickness of the carbon coating layer can be controlled by adjusting the flow rate of the hydrocarbon gas and the reaction time. The hydrocarbon gas includes, but is not limited to, methane, propane, butane, cyclohexane, ethane, propylene, and acetylene.

[0078] The method for forming the carbon coating in step four is not limited to chemical vapor deposition (CVD) process, but also includes one of plasma-enhanced chemical vapor deposition, electron beam evaporation, vacuum deposition, and atomic layer deposition.

[0079] Through the above steps, this invention successfully prepared a silicon-carbon composite anode material. This material has high capacity, low lithium depletion potential, and good cycle performance. Furthermore, this invention uses graphite or hard carbon as the substrate material. The porous structure and cracks of graphite or hard carbon only serve to increase the surface area and do not act as a template for silicon nanowire growth. This invention does not use alumina or carbon materials with regular mesoporous structures as templates for silicon nanowire growth, thus avoiding the problem of using expensive porous carbon and alumina.

[0080] Existing methods for preparing silicon nanowires require the porous carbon and alumina to have mesopores. If the pore size of the porous carbon and alumina is microporous, existing silicon nanowire preparation processes cannot construct catalysts within the micropores. The diameter of silane molecules is typically between a few angstroms and tens of angstroms, making it difficult for them to enter the micropores and react with the catalyst to form silicon nanowires. Therefore, existing technologies cannot prepare silicon nanowires with a diameter no greater than 5 nm. However, when silicon nanowires have a high axis-to-diameter ratio, they can reduce the axial volume expansion of silicon during cycling. The smaller radial size of silicon nanowires can effectively prevent silicon pulverization and shorten the diffusion distance of lithium ions, allowing for full capacity release under high-rate conditions. Therefore, the pore size of porous carbon and alumina must not be larger than the mesopore size, which leads to the use of complex pore-forming processes in existing technologies to prepare porous carbon and alumina.

[0081] Furthermore, the diameter of silicon nanowires is limited by the size of the metal catalyst particles. This invention uses atomic layer deposition technology to precisely control the thickness of the copper oxide film on the substrate material, and then reduces the volume of the copper oxide film by reducing the copper oxide film, effectively controlling the size of the metal catalyst particles on the substrate material to 0.5-1 nm, and spacing them apart. Therefore, when using CVD technology to prepare silicon nanowires, silane gas can contact the metal catalyst particles, avoiding the problem of not being able to enter the micropores of the template.

[0082] As an optimized implementation, steps one and two are repeated between steps three and four to deposit a second metal particle on the silicon nanowires of the substrate material. The second metal is one of nickel, iron, cobalt, copper, chromium, manganese, molybdenum, tungsten, platinum, and palladium, including the following steps:

[0083] Step I: Place the substrate material on which silicon nanowires are grown into an atomic layer deposition (ALD) apparatus, setting the reaction temperature to 100℃-400℃ and the reaction pressure to 0.01 torr-500 torr. Under these conditions, a second metal oxide, such as nickel oxide, iron oxide, cobalt oxide, copper oxide, chromium oxide, manganese oxide, molybdenum oxide, tungsten oxide, platinum oxide, or palladium oxide, is grown on the silicon nanowires using ALD technology. The thickness of the metal oxide is 0.1-5 nm. This includes:

[0084] Step SI1: Place the substrate material in a porous container and place the porous container into the ALD reaction chamber, or place the substrate material in the ALD reaction chamber and then repeatedly evacuate and replace the nitrogen gas at least three times.

[0085] Step SI2: Fluidize the substrate material in the reaction chamber under a nitrogen or argon atmosphere at a fluidization pressure of 1-1000 torr, or achieve substrate material dispersion by rotating the porous container; the preferred fluidization pressure is 10-100 torr.

[0086] Step SI3: Select the reaction precursor according to the type of second metal oxide to be deposited, and set the parameters of the ALD reaction chamber: deposition temperature 100℃-400℃, deposition pressure 0.01 torr-500 torr; precursor B is one or a mixture of several volatile metal alkylamino salts, organometallic compounds, halides, alkoxides, and metal β-diketone complexes, wherein the metal element in the metal alkylamino salts, organometallic compounds, halides, alkoxides, and metal β-diketone complexes is nickel, iron, cobalt, copper, chromium, manganese, molybdenum, tungsten, platinum, or palladium;

[0087] Step SI4: Introduce the precursor B vapor into the ALD reaction chamber under nitrogen or argon gas, and maintain it for 10-300 seconds. The flow rate of the carrier gas, nitrogen or argon, is 5-8000 sccm.

[0088] Step SI5: Purge the reaction chamber with nitrogen or argon to remove the remaining precursor B. The flow rate of the carrier gas, nitrogen or argon, is 5-8000 sccm.

[0089] Step SI6: Under the action of the carrier gas, oxygen source vapor is introduced into the ALD reaction chamber and held for 10-300 seconds; the oxygen source is water, hydrogen peroxide, oxygen, ozone, or atomic oxygen, and the carrier gas, nitrogen or argon, has a flow rate of 5-8000 sccm.

[0090] Step SI7: Purge the reaction chamber with nitrogen or argon to remove excess oxygen vapor and byproducts;

[0091] Step SI8: Repeat steps SI4 to SI7 until the second metal oxide deposition corresponding to precursor B reaches the set coating thickness of 0.1-5 nm; precursor B is selected from one or more of the materials in Table 2, but is not limited to Table 2.

[0092] Step II: Place the product from Step I into the reaction chamber of the hydrogen reduction apparatus. At high temperature, use hydrogen reduction to reduce the metal oxide into second metal particles.

[0093] By processing the product generated in step II through step four, a carbon layer can be formed on the surface of silicon nanowires on the substrate material, and carbon nanotubes can be grown between the second metal particles of the silicon nanowires on the substrate material. The conductivity of the carbon nanotubes is due to the formation of amorphous carbon from the cracking of hydrocarbon gas, and the carbon nanotubes have a network structure that may connect multiple silicon nanowires. Table 2

[0094] Serial Number name Precursor A oxygen source reaction temperature 1 <![CDATA[Co3O4]]> <![CDATA[CoCp2]]> <![CDATA[O3]]> 250℃ 2 NiO <![CDATA[Ni(acac)2]]> <![CDATA[O3]]> 250℃ 3 <![CDATA[Fe2O3]]> <![CDATA[Fe(Cp)2]]> <![CDATA[O3]]> 230℃

[0095] As an optimized implementation, step four uses a carbon source, a reaction precursor of a second metal oxide, and a co-catalyst as raw materials. The raw materials are introduced into the reactor via a carrier gas. A carbon layer is formed on the surface of silicon nanowires on a carbon substrate using floating catalyst chemical vapor deposition, and carbon nanotubes are grown between the silicon nanowires on the carbon substrate. The co-catalyst is selected from one or both of thiophene and sulfur. The reaction precursor of the second metal oxide is selected from a cadmium of the second metal in the second metal oxide. The carbon source includes a gaseous carbon source or a liquid carbon source, wherein the liquid carbon source is C. 1-4 alcohols and C 6-8 A mixture of hydrocarbons, wherein the gaseous carbon source comprises C 1-3 The carrier gas is a hydrocarbon, and the carrier gas includes hydrogen or an inert gas.

[0096] The C 1-4 The alcohol is selected from one or more of n-butanol, methanol, and ethanol; the C 6-8 The hydrocarbon is selected from one or more of n-hexane, benzene, toluene, and xylene; the C 1-3 Hydrocarbons include alkanes, alkenes, and alkynes, such as one or two selected from methane, ethylene, acetylene, and propylene.

[0097] Example 1

[0098] by Figure 3 The method shown is to prepare silicon-carbon composite anode materials using graphite as the substrate material and ALD and CVD techniques:

[0099] Step 1: Select graphite as the substrate material and place it in an atomic layer deposition (ALD) reactor. Evacuate the reactor using an exhaust pump and fluidize the substrate material with argon gas, maintaining its temperature at 120°C. Raise the temperature of the container containing Cu(dmamb)₂ to 70°C. Regulate the reactor pressure to 5 Torr. Introduce Cu(dmamb)₂ vapor into the ALD reactor under argon gas carry-on for 10-300 seconds at a flow rate of 100 sccm. Purge the reactor with argon gas for 10 seconds. Introduce O₃ into the ALD reactor under argon gas carry-on for 10-300 seconds at a flow rate of 100 sccm. Purge the reactor with argon gas for 10 seconds. A copper oxide film with a thickness of 1 nm is formed after 30 ALD cycles using atomic layer deposition.

[0100] Step Two: The substrate material with the grown copper oxide film is placed in a hydrogen reduction reaction chamber, and the temperature is raised to 500℃ in a hydrogen atmosphere for 10 minutes. The copper oxide is reduced to copper and cuprous oxide nanoparticles using the hydrogen reduction process. Figure 4 The copper and cuprous oxide nanoparticles shown have nanometer-scale diameters and gaps between them. These copper and cuprous oxide nanoparticles serve as catalysts for subsequent silicon nanowire growth.

[0101] Step 3: The substrate material with grown copper and cuprous oxide nanoparticles is placed in a silane chemical vapor deposition (CVD) reaction chamber. The reaction chamber is evacuated using an exhaust pump, and silane gas is introduced under an inert Ar atmosphere. The reaction is carried out at 600°C for 4 hours at a reaction pressure of 1 Torr. Silicon nanowires are grown on the nano-metal particles using a silane CVD pyrolysis process. Figure 5 and Figure 6 The diameter of the silicon nanowire shown is 5 nm.

[0102] In this process, copper and cuprous oxide nanoparticles react with silane as follows to obtain a Cu3Si alloy catalyst for silicon nanowire growth: SiH4 + Cu → Cu3Si + H2

[0103] SiH4 + Cu2O → Cu3Si + H2 + H2O.

[0104] Copper and cuprous oxide nanoparticles catalyze the growth of silicon nanowires via a VSS mechanism. Dispersed copper and cuprous oxide nanoparticles can be used to catalyze the growth of dispersed silicon nanowires with a diameter of 5 nm.

[0105] Step 4: The substrate material with grown silicon nanowires is placed in a CVD reaction chamber. Acetylene is introduced into the chamber via nitrogen gas. The reaction temperature is adjusted to 700℃, and the reaction time is 6 hours. Amorphous carbon is coated onto the surface of the silicon nanowires using an acetylene CVD pyrolysis process. During this process, the temperature at which acetylene forms a carbon coating on the silicon nanowire surface is lower than the temperature at which methane forms a carbon coating on the silicon nanowire surface, thus preventing the carbon from reacting with silicon to form a silicon carbide coating layer. In this step, the thickness of the amorphous carbon coating layer is 50 nm or less.

[0106] The prepared silicon-carbon anode material was combined with lithium metal to form a half-cell for electrochemical performance testing. The charge-discharge test was conducted at a current density of C / 10 (initial) + C / 2 (cycle). The discharge performance at a rate of 5C / 0.5C was tested, and the charge-discharge voltage range was 0.005 to 2.0V. The test results are detailed in Table 3.

[0107] Example 2

[0108] A method for preparing silicon-carbon composite anode materials using hard carbon as the substrate material and ALD and CVD technologies:

[0109] Step 1: Hard carbon is selected as the substrate material and placed in an atomic layer deposition (ALD) reactor. The reactor is evacuated using an exhaust pump, and the substrate material is fluidized with argon gas. The temperature of the substrate material is maintained at 120°C. The temperature of the container containing Cu(dmamb)₂ is raised to 70°C, and the pressure inside the reactor is adjusted to 5 Torr. Cu(dmamb)₂ vapor is introduced into the ALD reactor under argon gas carry-on for 10-300 seconds at a flow rate of 100 sccm. The reactor is then purged with argon gas for 10 seconds. O₃ is then introduced into the ALD reactor under argon gas carry-on for 10-300 seconds at a flow rate of 100 sccm. The reactor is then purged with argon gas for 10 seconds. A copper oxide film with a thickness of 1 nm is formed after 30 ALD cycles using atomic layer deposition.

[0110] Step 2: The substrate material with the grown copper oxide film is placed in a hydrogen reduction reaction chamber and heated to a reaction temperature of 500°C in a hydrogen atmosphere for 30 minutes. The hydrogen reduction process reduces copper oxide to copper and cuprous oxide nanoparticles with nanometer-scale diameters and gaps between them. These copper and cuprous oxide nanoparticles serve as catalysts for subsequent silicon nanowire growth.

[0111] Step 3: The substrate material with grown copper and cuprous oxide nanoparticles was placed in a silane chemical vapor deposition (CVD) reaction chamber. The reaction chamber was evacuated using an exhaust pump, and silane gas was introduced under an inert Ar atmosphere. The reaction was carried out at 600°C for 4 hours at a reaction pressure of 1 Torr. Silicon nanowires were grown on the nanoparticles using a silane CVD pyrolysis process. The diameter of the silicon nanowires was 5 nm.

[0112] Step 4: Place the substrate material with grown silicon nanowires into the CVD reaction chamber. Acetylene is introduced into the reaction chamber via nitrogen gas. Adjust the reaction temperature inside the chamber to 700℃ and the reaction time to 6 hours. Amorphous carbon is coated onto the surface of the silicon nanowires using an acetylene CVD pyrolysis process. The thickness of the amorphous carbon coating layer is 50 nm or less.

[0113] The prepared silicon-carbon anode material was combined with lithium metal to form a half-cell for electrochemical performance testing. The charge-discharge test was conducted at a current density of C / 10 (initial) + C / 2 (cycle). The discharge performance at a rate of 5C / 0.5C was tested, and the charge-discharge voltage range was 0.005 to 2.0V. The test results are detailed in Table 3.

[0114] Example 3

[0115] A method for preparing silicon-carbon composite anode materials using graphite as the substrate and ALD and CVD technologies:

[0116] Step 1: Select graphite as the substrate material and place it in an atomic layer deposition (ALD) reactor. Evacuate the reactor using an exhaust pump and fluidize the substrate material with argon gas, maintaining its temperature at 120°C. Raise the temperature of the container containing Cu(dmamb)₂ to 70°C. Regulate the reactor pressure to 5 Torr. Introduce Cu(dmamb)₂ vapor into the ALD reactor under argon gas carry-on for 10-300 seconds at a flow rate of 100 sccm. Purge the reactor with argon gas for 10 seconds. Introduce O₃ into the ALD reactor under argon gas carry-on for 10-300 seconds at a flow rate of 100 sccm. Purge the reactor with argon gas for 10 seconds. A copper oxide film with a thickness of 0.5 nm is formed after 15 ALD cycles using atomic layer deposition.

[0117] Step 2: The substrate material with the grown copper oxide film is placed in a hydrogen reduction reaction chamber and heated to a reaction temperature of 500°C in a hydrogen atmosphere for 10 minutes. The hydrogen reduction process reduces copper oxide to copper and cuprous oxide nanoparticles with nanometer-scale diameters and gaps between them. These copper and cuprous oxide nanoparticles serve as catalysts for subsequent silicon nanowire growth.

[0118] Step 3: The substrate material with grown copper and cuprous oxide nanoparticles is placed in a silane chemical vapor deposition (CVD) reaction chamber. The reaction chamber is evacuated using an exhaust pump, and silane gas is introduced under an inert Ar atmosphere. The reaction is carried out at 600°C for 4 hours at a reaction pressure of 1 Torr. Silicon nanowires are grown on the nanoparticles using a silane CVD pyrolysis process. The diameter of the silicon nanowires is less than 5 nm.

[0119] Step 4: Place the substrate material with grown silicon nanowires into the CVD reaction chamber. Acetylene is introduced into the reaction chamber via nitrogen gas. Adjust the reaction temperature inside the chamber to 650℃ and the reaction time to 6 hours. Amorphous carbon is coated onto the surface of the silicon nanowires using an acetylene CVD pyrolysis process. The thickness of the amorphous carbon coating layer is 50 nm or less.

[0120] The prepared silicon-carbon anode material was combined with lithium metal to form a half-cell for electrochemical performance testing. The charge-discharge test was conducted at a current density of C / 10 (initial) + C / 2 (cycle). The discharge performance at a rate of 5C / 0.5C was tested, and the charge-discharge voltage range was 0.005 to 2.0V. The test results are detailed in Table 3.

[0121] Example 4

[0122] The method for preparing silicon-carbon composite anode materials using graphite as the substrate material and ALD and CVD technology is the same as that in Example 1, except that steps one to four are similar. The difference is that between steps three and four, steps one and two are repeated to deposit a second metal particle on the silicon nanowires of the substrate material. The second metal is one of nickel oxide, iron oxide, cobalt oxide, platinum oxide, and palladium oxide.

[0123] Example 5

[0124] The method for preparing silicon-carbon composite anode materials using graphite as the substrate material and ALD and CVD technologies is similar to that in Example 1, except that steps one to four are similar. The difference is that in step four, the process uses a carbon source, a reaction precursor of a second metal oxide, and a co-catalyst as raw materials. The raw materials are introduced into the reactor through a carrier gas. A carbon layer is formed on the surface of silicon nanowires on the carbon substrate material by floating catalyst chemical vapor deposition, and carbon nanotubes are grown between the silicon nanowires on the carbon substrate material. The co-catalyst is selected from thiophene, the reaction precursor of the second metal oxide is selected from ferrocene, nickel dicene, and cobalt dicene, the carbon source is ethylene, and the carrier gas is hydrogen.

[0125] Comparative Example 1

[0126] The method for preparing silicon-carbon composite anode materials using graphite as the substrate material and ALD and CVD technologies is the same as in Example 1, except that steps one to four are similar.

[0127] In step one, a copper oxide film with a thickness of 2 nm is formed by atomic layer deposition for 60 ALD cycles.

[0128] In step three, silicon nanowires with a diameter of 20–50 nm are grown on nano-metal particles using a silane CVD pyrolysis process.

[0129] The prepared silicon-carbon anode material was combined with lithium metal to form a half-cell for electrochemical performance testing. The charge-discharge test was conducted at a current density of C / 10 (initial) + C / 2 (cycle). The discharge performance at a rate of 5C / 0.5C was tested, and the charge-discharge voltage range was 0.005 to 2.0V. The test results are detailed in Table 3.

[0130] Comparative Example 2

[0131] The method for preparing silicon-carbon composite anode materials using graphite as the substrate material and ALD and CVD technologies is the same as in Example 1, except that steps one to four are similar.

[0132] In step one, a copper oxide film with a thickness of 5.5 nm is formed after 165 ALD cycles using atomic layer deposition.

[0133] In step three, silicon nanoparticles with a diameter of 50–100 nm are grown on the nano-metal particles using a silane CVD pyrolysis process.

[0134] The prepared silicon-carbon anode material was combined with lithium metal to form a half-cell for electrochemical performance testing. The charge-discharge test was conducted at a current density of C / 10 (initial) + C / 2 (cycle). The discharge performance at a rate of 5C / 0.5C was tested, and the charge-discharge voltage range was 0.005 to 2.0V. The test results are detailed in Table 3.

[0135] C / 10 (First Charge): This indicates that during the first charge, the battery is charged with one-tenth of its nominal capacity current (10% charging rate). This charging method is generally gentle and helps the battery's initial stability and long lifespan.

[0136] C / 2 (Cyclic Charge): This indicates that in the next 1 to 500 cycles, the battery will be charged with half its nominal capacity current (50% charging rate). This charging method is relatively fast and can fully charge the battery in a shorter time.

[0137] 5C / 0.5C Discharge Performance: Under these conditions, the battery is rapidly discharged at a current five times its capacity while being charged at a rate of 0.5C. This high-rate discharge test evaluates the battery's performance under extreme usage conditions.

[0138] Table 3. Results of PCR, first-efficiency, multiplier, and cycle test for the examples and comparative examples.

[0139]

[0140] Through the above steps, this invention successfully prepared a silicon-carbon composite anode material. This material exhibits high capacity, low delithiation potential, and good cycle performance, while avoiding the problems of expensive porous carbon, complex pore-forming processes, difficulty in silicon nanoparticles entering the pores, and silicon nanowire diameter limited by the size of metal catalyst particles. Example 4 improved the conductivity of the anode material and increased its cycle capacity retention by coating silicon nanowires with carbon and growing carbon nanotubes between silicon nanowires. In Comparative Examples 1 and 2, the larger silicon nanoparticle size resulted in greater volume changes during lithium-ion intercalation, causing the carbon coating layer to crack and peel off, thus reducing capacity retention. The commercial silicon-carbon anode material was purchased from Shanghai Yuling New Energy Technology Co., Ltd., and the manufacturing method followed CN114079045B.

[0141] In existing commercial silicon-carbon anode materials, nano-silicon is grown within the nanopores of porous carbon, and then coated with a carbon layer. The rate at which lithium ions enter the nanopores is limited, resulting in poor rate performance of existing silicon-carbon anodes and their inability to support fast charging. The silicon nanowires of this invention, after being coated with carbon, can directly contact the electrolyte, unaffected by the transport limitations of the nanopores, thus exhibiting better rate performance.

[0142] Due to the advanced nature of the technical solution of this invention, it has wide applications in lithium-ion battery manufacturing, new energy electric vehicles, portable electronic devices, and other fields. With the development of technology, the demand for batteries in electronic products and electric vehicles is increasing, and lithium-ion batteries have become the preferred choice due to their high energy density, long cycle life, and environmental friendliness. However, existing silicon-based anode material preparation technologies still have some problems, such as the high cost of porous carbon, complex pore-forming processes, and uneven distribution of silicon nanoparticles within the pores. This invention proposes a new method for preparing silicon-based anode materials, which can effectively solve these problems, improve the performance of silicon-carbon anode materials, and thus improve the energy density and cycle life of lithium-ion batteries. Therefore, this invention has broad market demand and good application prospects.

Claims

1. A method for preparing silicon-carbon composite anode materials using ALD and CVD technologies, characterized in that, Includes the following steps: Step 1. Grow a first metal oxide on the surface of a carbon substrate using ALD atomic layer deposition; Step 2. In the reaction chamber, the first metal oxide on the surface of the carbon substrate material is reduced to nanodots containing metal elements; Step 3. Place the carbon substrate material with the distributed nanodots in a reactor, heat it, and inject a gas mixture containing silane and inert gas to grow silicon nanowires on the nanodots based on a chemical vapor deposition process; Step 4. Coat the silicon nanowires on the carbon substrate with a carbon layer to obtain a silicon-carbon composite anode material.

2. The method according to claim 1, characterized in that, The nanodots containing metallic elements are selected from one or more of tin, indium, gold, titanium, nickel, iron, silver, platinum, tin and gallium, cobalt and aluminum; or the nanodots are copper and cuprous oxide.

3. The method according to claim 1, characterized in that, The thickness of the first metal oxide is 0.33~1nm.

4. The method according to claim 1, characterized in that, The diameter of the silicon nanowire is no greater than 5 nm.

5. The method according to claim 1, characterized in that, The coating process is selected from one of chemical vapor deposition, plasma-enhanced chemical vapor deposition, electron beam evaporation, vacuum deposition, and atomic layer deposition.

6. The method according to claim 1, characterized in that, Between steps 3 and 4, steps 1 to 2 are repeated. Depending on the type of the second metal oxide to be deposited, a reaction precursor is selected to deposit the second metal oxide on the silicon nanowires of the carbon substrate material. Then, it is reduced to the second metal particles. After the silicon nanowires and the second metal particles on the silicon nanowires of the carbon substrate material are processed in step 4, a carbon layer is formed on the surface of the silicon nanowires on the carbon substrate material, and carbon nanotubes are grown between the second metal particles of the silicon nanowires on the carbon substrate material.

7. The method according to claim 1, characterized in that, The coating process uses a carbon source, a reaction precursor of a second metal oxide, and a co-catalyst as raw materials. The raw materials are introduced into the reactor via a carrier gas. A carbon layer is formed on the surface of silicon nanowires on a carbon substrate using a floating catalyst chemical vapor deposition method, and carbon nanotubes are grown between the silicon nanowires on the carbon substrate. The co-catalyst is selected from one or both of thiophene and sulfur. The reaction precursor of the second metal oxide is selected from a cadmium of the second metal in the second metal oxide. The carbon source includes a gaseous carbon source or a liquid carbon source, wherein the liquid carbon source is C. 1-4 alcohols and C 6-8 A mixture of hydrocarbons, wherein the gaseous carbon source comprises C 1-3 The carrier gas is a hydrocarbon, and the carrier gas includes hydrogen or an inert gas.

8. The method according to any one of claims 6 to 7, characterized in that, The metal in the second metal particle and the second metal oxide is selected from one or more of nickel, iron, cobalt, copper, chromium, manganese, molybdenum, tungsten, platinum, and palladium.

9. The method according to claim 6, characterized in that, The thickness of the second metal oxide is 0.1-5 nm.

10. The silicon-carbon composite anode material prepared by the method according to any one of claims 3 to 5, characterized in that, The invention includes a carbon substrate material, silicon nanowires grown on the surface of the carbon substrate material, a carbon layer coated on the surface of the silicon nanowires, and nanodots containing metal elements distributed within the silicon nanowires, wherein the nanodots containing metal elements are selected from one or more of copper and / or cuprous oxide, tin, and indium.

11. The silicon-carbon composite anode material prepared by the method according to any one of claims 6-7, characterized in that, It includes a carbon substrate material, silicon nanowires grown on the surface of the carbon substrate material, a carbon layer coated on the surface of the silicon nanowires, carbon nanotubes formed between the silicon nanowires, nanodots containing metal elements distributed within the silicon nanowires, and second metal particles distributed within the carbon nanotubes.

12. A lithium-ion battery comprising the silicon-carbon composite anode material as described in claim 10 or claim 11.

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