Method for preparing silicon-carbon composite

Abstract

A process for preparing a carbon-silicon composite material comprising a carbon-based material and a silicon nanomaterial, in particular nanowires or nanoislands, where the process is carried out in a rotating tubular chamber of a reactor.

Description

[0001] This application is a divisional application of Chinese invention patent application No. 202280038260.0, filed on May 20, 2022, entitled "Method for Preparing Silicon-Carbon Composite Materials". Technical Field

[0002] This invention relates to a method for preparing composite carbon-silicon materials comprising carbon-based materials and silicon nanomaterials, particularly nanowires or nanoislands, wherein the method is carried out in a tubular chamber of a rotary reactor at pressures above atmospheric pressure. The invention also relates to a method for manufacturing electrodes for lithium-ion batteries. Background Technology

[0003] Since its commercialization in 1991, lithium-ion battery (LIB) technology has continuously improved its energy storage capabilities. However, next-generation LIBs require higher energy densities for a given battery capacity (kWh / L) and a lower price ($ / kWh), especially for electric vehicle applications. Current battery active materials (including anode and cathode components) have reached their theoretical limits, and battery manufacturers need more efficient materials to meet market demands.

[0004] Graphite, currently used almost exclusively as the anode material, is a weak point in batteries, taking up more space than any other component. Over the past two decades, several anode materials with improved storage capacity have been developed. Among them, silicon (Si) is the most promising candidate as a novel anode material because it can store nearly 10 times more energy than graphite. Along with its high theoretical specific capacity, silicon exhibits high volume expansion, leading to poor stability during lithiation and degradation processes.

[0005] Silicon nanowires (SiNWs) are excellent candidates for lithium-ion battery anode materials in terms of specific capacity and cycle life due to their excellent strain and volume regulation properties. Cui et al. have already disclosed a high-performance lithium-ion battery anode using silicon nanowires grown directly on current collectors in Nature Nanotechnology, 2008, 31-35. However, this novel electrode technology requires serious effort from battery manufacturers to match current battery production lines. In contrast, the co-utilization of silicon nanowires and graphite / carbon could be one of the preferred strategies as a fully "droplet" approach. Industrializing this composite material at an acceptable price is a significant challenge for the battery market.

[0006] The different techniques used for SiNW fabrication are mainly divided into two synthesis methods: bottom-up (growing nanowires from elemental silicon) and top-down (bulk silicon etching). Top-down methods are characterized by significant waste of starting silicon and the unavoidable use of hazardous chemicals. Bottom-up techniques are typically based on chemical vapor deposition (CVD) and can produce high-quality nanowires.

[0007] Currently, the "fixed-bed" CVD equipment used for SiNW growth results in limited contact between the 2D surface decorated with metal nanoseeds and the gas precursor, thus only allowing for the production of small quantities, which is insufficient to meet market demand.

[0008] Several attempts have been made to synthesize SiNW using vertical “fluidized bed” CVD reactors to increase the contact surface in 3D form (e.g., US 2011 / 0309306). Unfortunately, the application of conventional “fluidized bed” CVD reactors on an industrial scale has shown very limited technical and economic feasibility because 1 / the volumetric method rate (product quality per reactor volume) decreases as production scale increases, and 2 / extremely large quantities of reactants / carrier gas and complexes need to be processed, making the separation of gases and nano- and micro-sized objects on an industrial scale very costly.

[0009] WO 2018 / 013991 discloses the preparation of carbon-SiNW composite materials in a mechanically rotating fluidized bed reactor, which can be used in batch or semi-continuous mode. The method is based on the use of a rotating drum filled with carbon-based material. The method is carried out under low pressure. The method provides kilogram-scale materials containing up to 32% by mass of Si. Several major limitations exist with this method: the reaction zone of the CVD chamber is limited by the reduced size of the rotating drum; from a technical, procedural, and economic perspective, the orbital, gas input, gas output, and gear systems, as well as the pressure regulation devices required for connecting and controlling the rotating drum, result in a complex apparatus. The system is equipped with a cyclone separator for collecting panned particles larger than 5 µm, thus limiting the range of powders usable in the process.

[0010] Another example of preparing carbon-SiNW composites was recently reported (Energy & Fuels, 2021, 35275-2765). The authors demonstrated the possibility of preparing SiNW / graphite composites from chloromethylsilane and graphite powder using a simple rotary furnace. Under the reported conditions, a significant portion of the silicon / graphite composite was lost during the reaction. Besides the low yield, an inconvenience is that a gas-solid separation device is required at the exhaust of the gas pipeline (filters and / or cyclones) for an industrial version of this method.

[0011] WO2013 / 016339 discloses a method for preparing nanostructures from copper-based catalyst materials, particularly silicon NW. The reaction can be carried out under mixing or stirring while controlling the pressure. Very low pressure is disclosed.

[0012] Therefore, there is a need for new, efficient methods that can prepare high-performance silicon-graphite anode materials in high yields for use as anode active materials in lithium-ion batteries, and that can be implemented on an industrial scale.

[0013] There is a need for methods that allow for minor improvements to existing industrial reactors / equipment.

[0014] A method is needed that can easily separate powders and clumps after synthesis.

[0015] This invention describes a novel method for preparing silicon-nanowire-carbon / graphite composite materials, namely LIB, for energy storage. This composite material can be prepared on a large / industrial scale at a competitive price. Summary of the Invention

[0016] The first object of the present invention is a method for preparing carbon-silicon composite materials, wherein the method is carried out in a tubular chamber of a reactor, wherein the tubular chamber is rotatable about its longitudinal axis (XX), the method comprising:

[0017] (1) Introduce at least a carbon-based material comprising a carbon support and an optional catalyst into the tubular chamber;

[0018] (2) Heating the tubular chamber under a carrier gas flow.

[0019] (3) Rotating tubular chamber,

[0020] (4) Introduce a gas mixture containing reactive silicon into a rotating tubular chamber.

[0021] (5) In a rotating tubular chamber, under a flow of a gas mixture containing reactive silicon, at a temperature of 200°C to 900°C, at a temperature higher than 1.02 × 10⁻⁶. 5 Pa or equal to 1.02 × 10 5 Heat treatment is performed under Pa pressure.

[0022] (6) The recycled products

[0023] It should be understood that step (3) may begin before or after step (1) or step (2).

[0024] Another object of the present invention is a method for preparing an electrode comprising a current collector, the method comprising (i) carrying out the method disclosed above for preparing a carbon-silicon composite material, and (ii) covering at least one surface of the current collector with a composition comprising the carbon-silicon composite material as an electrode active material.

[0025] According to another aspect, the present invention relates to a method for manufacturing an energy storage device, such as a lithium secondary battery, the energy storage device comprising a cathode, an anode, and a separator disposed between the cathode and the anode, wherein the method comprises carrying out the methods disclosed above for manufacturing at least one of the electrodes, preferably the anode.

[0026] According to the preferred embodiment, the pressure in step (5) is 1.05 × 10⁻⁶. 5 Pa to 10 6 Pa.

[0027] According to the preferred embodiment, the temperature of step (5) is 350°C to 850°C.

[0028] According to the preferred embodiment, the carbon-based material is selected from graphite, graphene, and carbon, preferably graphite powder with an average particle size of 0.01µm to 50µm.

[0029] According to a preferred embodiment, the carbon-based material has catalyst particles on its surface.

[0030] According to a preferred variation of this embodiment, the catalyst is selected from metals, bimetallic compounds, metal oxides, metal nitrides, metal salts, and metal sulfides.

[0031] According to a preferred embodiment, the gas mixture stream containing reactive silicon includes at least a reactive silicon substance and a carrier gas.

[0032] According to a preferred embodiment, the reactive silicon material is selected from silane compounds, and preferably the reactive silicon material is silane SiH4.

[0033] According to a preferred embodiment, the volume ratio of the carbon-based material comprising the carbon support and optional catalyst to the volume of the tubular chamber is 10% to 60%, more preferably 20% to 50%, and even more preferably 30% to 50%.

[0034] According to a preferred embodiment, in step (5), the flow rate of the gas mixture containing reactive silicon is 0.1 SLM to 50 SLM (standard cubic meters per minute), more preferably 0.5 SLM to 40 SLM.

[0035] According to the variation, in step (5), the flow rate of the gas mixture containing reactive silicon is 0.1 SLM to 10 SLM (standard cubic meters per minute), more preferably 0.5 SLM to 5 SLM.

[0036] According to the preferred embodiment, the rotation speed of the tubular chamber is from 1 RPM to 40 RPM (revolutions per minute).

[0037] According to the preferred embodiment, the angle between the longitudinal axis XX of the tubular chamber and the horizontal axis is 0° to 20°.

[0038] According to a preferred embodiment, the method includes applying at least one loop following step (6):

[0039] (1') Reload the new carbon-based material into the tubular chamber.

[0040] (2') Heating the tubular chamber under a carrier gas flow

[0041] (3') Rotating tubular chamber,

[0042] (4') Introduce a gas mixture containing reactive silicon into a rotating tubular chamber.

[0043] (5) In a rotating tubular chamber, under a flow of a gas mixture containing reactive silicon, at a temperature of 200°C to 900°C, at a temperature higher than 1.02 × 10⁻⁶. 5 Pa or equal to 1.02 × 10 5 Heat treatment is performed under Pa pressure.

[0044] (6') The products obtained from recycling.

[0045] According to a preferred embodiment, the silicon-carbon composite material comprises carbon-based materials and nano-silicon materials.

[0046] According to the preferred embodiment, the nano-silicon material is a nanowire or a nanoisland, or even more preferably a nanowire.

[0047] The method according to the invention provides an anodic active material comprising a carbon-based support and silicon nanomaterials, particularly silicon nanowires, grown on the carbon-based support. The material may also include a carbon coating formed on the surface of the carbon-based support and the silicon nanomaterials, particularly the silicon nanowires.

[0048] The method according to the invention has many advantages: the rotating mechanical fluidized bed reactor is more flexible than conventional reactors. If heat and mass transfer are lower than in conventional fluidized bed configurations, the rotating reactor allows for chemical vapor deposition reactions using particles smaller than 30 µm or even 5 µm with good efficiency. Solid behavior is independent of or less dependent on gas flow, depending on the column arrangement—horizontal or inclined—resulting in longer residence times for reactants, lower gas consumption, and the absence or non-existence of gas-solid separation devices. In fact, the generation of fine particles is significantly reduced in such a reactor. It also offers higher pressure resistance and a less complex overall system, making it easier to scale up for industrial production. The inventors have demonstrated that implementing this method at pressures above atmospheric pressure yields very high chemical yields of the final composite material. This approach also reduces the need to collect particles and fine particles at the reactor exhaust.

[0049] The method according to the invention provides an anodic active material comprising a carbon-based support and silicon nanomaterials, particularly silicon nanowires, deposited on the carbon-based support. Direct growth of silicon nanomaterials, particularly silicon nanowires, on the carbon-based support can suppress silicon / carbon contact losses during battery charging and discharging. When the material also includes a carbon coating formed on the surfaces of the carbon-based support and the silicon nanomaterials, particularly the silicon nanowires, this additional layer increases the bonding strength between the silicon nanomaterials, particularly the silicon nanowires, and the carbon-based support, thus further improving battery performance.

[0050] The advantage of the method according to the invention is that, depending on the size of the equipment, it can be carried out at the laboratory scale (up to 1 kg per day), pilot scale (up to 100 kg per day), and industrial scale (several tons per day).

[0051] The method according to the invention provides an anodic active material having uniform silicon nanomaterials, particularly silicon nanowires, deposited on the surface of a carbon-based material, preferably graphite, which can be prepared in an industrially feasible and economically viable manner. The deposition of uniform silicon nanomaterials, particularly silicon nanowires, improves the conductivity of the final silicon-carbon composite material, preferably a silicon-graphite composite material, thereby improving the cyclability of the secondary battery.

[0052] The term “substantially constitutes” followed by one or more features means that, in addition to the expressly listed components or steps that do not substantially affect the nature and features of the invention, it may also be included in the methods or materials of the invention.

[0053] Unless otherwise explicitly stated, the expression "includes X to Y" includes the boundary. This expression means that the target range includes the values ​​of X and Y, as well as all values ​​from X to Y.

[0054] The first object of the present invention is a method for preparing silicon-carbon composite materials by a chemical vapor deposition (CVD) process carried out in a rotating fluidized bed reactor, the silicon-carbon composite materials being suitable for use as anode active materials in lithium-ion batteries.

[0055] The silicon-carbon composite material obtained by this method can be used as a silicon-carbon composite anode material during preparation or after post-preparation treatment.

[0056] This invention relates to a method for preparing silicon-based nanostructured materials. Specifically, it relates to a method for preparing silicon-carbon composite materials comprising nanostructured silicon materials and carbon-based materials, obtained at high temperatures by the chemical decomposition of a reactive silicon-containing gaseous substance mixed with a carrier gas. This mixture is hereinafter referred to as a reactive silicon-containing gaseous mixture. Therefore, this method is based on the principle of chemical vapor deposition (CVD).

[0057] The term "nanostructured material" should be understood within the meaning of this invention as a material containing free particles in the form of aggregates or clusters, wherein at least 5% by weight, preferably at least 10% by weight, of the external dimensions of the particles are 1 nm to 100 nm.

[0058] The term "composite material" refers to a material made of at least two constituent materials with significantly different physical or chemical properties.

[0059] The external dimensions of the particles can be measured by any known method, particularly by analyzing images of the composite material according to the invention obtained by scanning electron microscopy (SEM). Attached Figure Description

[0060] Figure 1 This is a schematic cross-sectional view of a rotating fluidized bed reactor.

[0061] Figure 2 This is a schematic diagram of a method for preparing silicon-carbon composite materials in a rotating fluidized bed reactor.

[0062] Figure 3 This is a nanoscale micrograph of the first (comparative) embodiment of the microstructure of silicon-carbon composite material.

[0063] Figure 4 This is a millimeter-scale micrograph of the first (comparative) embodiment of the microstructure of silicon-carbon composite material.

[0064] Figure 5 The image shows a nanoscale micrograph of the microstructure of the silicon-carbon composite material obtained by the method of the present invention (Example 2).

[0065] Figure 6These are millimeter-scale micrographs of the microstructure of silicon-carbon composite materials obtained by the method according to the present invention (Example 2).

[0066] Figure 7 This is a schematic cross-sectional view of a Lödige type rotating fluidized bed reactor.

[0067] Figure 8 This is a schematic diagram of a method for preparing silicon-carbon composite materials in a rotating Lödige-type fluidized bed reactor.

[0068] Figure 9 This is a schematic cross-sectional view of a deformed industrial rotating Lödige type fluidized bed reactor.

[0069] Figure 10 Is Figure 9 A schematic diagram of a method for preparing silicon-carbon composite materials in a modified rotating Lödige fluidized bed reactor. Detailed Implementation

[0070] carbon-based materials

[0071] The method according to the invention includes using at least one carbon-based material as a starting material.

[0072] Carbon-based materials are advantageously composed of micron-sized carbon in powder form, including “carbon supports” or “carbon-based supports”, which are optionally associated with a catalyst.

[0073] According to the present invention, carbon-based materials are used as carriers for the growth of silicon nanomaterials, particularly silicon nanoislands or silicon nanowires, preferably silicon nanowires.

[0074] The carbon-based support can be any material selected from graphite, graphene, carbon, and more specifically, natural graphite, artificial graphite, hard carbon, soft carbon, carbon nanotubes or amorphous carbon, carbon nanofibers, carbon black, expanded graphite, graphene, or a mixture of two or more of them.

[0075] An advantage of this invention is that ultrafine graphite powder, a byproduct of graphite manufacturing (grinding and spheroidizing processes), can be used as a carbon-based carrier. In fact, rotary chamber reactors are well-suited for the use of this material, whereas other types of reactors equipped with filters and / or cyclone separators encounter operational difficulties when introducing particles smaller than 5µm into their reaction chambers.

[0076] Preferably, the carbon carrier material is composed primarily of natural or artificial graphite, and more preferably solely of natural or artificial graphite.

[0077] Preferably, at least 75% by mass, more preferably at least 80% by mass, even more preferably at least 90% by mass, and even more preferably at least 95% by mass, and advantageously at least 99% by mass of the carbon support are composed of graphite relative to the total mass of the carbon support.

[0078] Preferably, the carbon support is micrometer-sized. Advantageously, the average particle size of the carbon support is from 0.01 µm to 50 µm, more preferably from 0.05 µm to 40 µm, even more preferably from 0.1 µm to 30 µm, and advantageously from 0.1 µm to 20 µm. For example, the average particle size of the carbon support can be measured using laser diffraction.

[0079] Preferably, the carbon support is in the form of particles, particle aggregates, non-agglomerated sheets, or aggregated sheets.

[0080] Advantageously, the specific surface area (BET) of the carbon support is from 1 m² / g to 100 m² / g, more preferably from 3 m² / g to 70 m² / g, and even more preferably from 5 m² / g to 50 m² / g.

[0081] According to a preferred variation, the surface of the carbon-based material is coated with catalyst particles. More advantageously, when a catalyst is present, the surface of the carbon-based material is uniformly modified by nanocatalyst particles or their precursors.

[0082] catalyst

[0083] The method according to the invention can be implemented with or without a catalyst.

[0084] According to a preferred variation, the method according to the invention includes introducing at least one catalyst into the rotating chamber of a reactor.

[0085] The role of the catalyst is to create growth sites on the surface of the carbon support.

[0086] Preferably, according to this variation, the catalyst is selected from metals, bimetallic compounds, metal oxides, metal nitrides, metal salts, metal sulfides, and organometallic compounds.

[0087] Among metal catalysts, gold (Au), cobalt (Co), nickel (Ni), bismuth (Bi), tin (Sn), iron (Fe), indium (In), aluminum (Al), manganese (Mn), iridium (Ir), silver (Ag), copper (Cu), calcium (Ca), and mixtures thereof can be mentioned.

[0088] In bimetallic compounds, manganese and platinum (MnPt3) or iron and platinum (FePt) can be mentioned.

[0089] Among metal sulfides, tin sulfide (SnS) can be mentioned.

[0090] Among metal oxides, iron oxide (Fe₂O₃) and tin oxide (SnO) can be mentioned. 2-x (0≤x<2).

[0091] More preferably, according to this variation, the catalyst is selected from metals and metal oxides.

[0092] Preferably, when a catalyst is present, it is selected from gold (Au), tin (Sn), and tin dioxide (SnO2).

[0093] Advantageously, when a catalyst is present, it is tin dioxide (SnO2).

[0094] Preferably, according to this modification, the catalyst is in particulate form, more preferably in nanoparticle form.

[0095] Preferably, according to this variation, the longest size of the catalyst nanoparticles is 1 nm to 100 nm, more preferably 1 nm to 50 nm, and even more preferably 5 nm to 30 nm.

[0096] Advantageously, the catalyst nanoparticles are spherical when the catalyst is present.

[0097] According to a preferred embodiment, the catalyst is in the form of nanospheres with a diameter of 1 nm to 30 nm, preferably 5 nm to 30 nm.

[0098] Gold nanoparticles that can be used in the methods of this invention are prepared and disclosed, for example, in M. Brust et al., J. Chemical Society, Chemical Communications, 7(7):801-802, 1994.

[0099] The metal forming the catalyst is preferably introduced in the form of a thin metal layer that is liquefied by heat at the start of the process and then separated from its support by forming liquid metal droplets. Alternatively, the metal can be introduced in the form of a metal salt layer coated on a growth substrate, which is reduced at the start of the growth process by a reducing gas such as dihydrogen (H2).

[0100] Metals can be introduced in the form of organometallic compounds, which decompose during particle growth and deposit the metal onto a carbon support in the form of nanoparticles or droplets.

[0101] Preferably, according to this modification, the catalyst nanoparticles are dispersed on the surface of the carbon support.

[0102] The catalyst and the carbon support may or may not be in contact.

[0103] According to a preferred embodiment, the carbon support and catalyst are associated before being introduced into the reactor.

[0104] For the purposes of this invention, the term "association" refers to a prior association step between the carbon support and the catalyst, which corresponds to the attachment or deposition of at least a portion of the catalyst on at least a portion of the surface of the carbon support. In other words, at least a portion of the catalyst is attached to the surface of the carbon support, for example, through physical bonding or adsorption.

[0105] Preferably, according to this variation, the catalyst and carbon support are used according to a catalyst / carbon support mass ratio of 0.01 to 1, more preferably 0.02 to 0.5, and even more preferably 0.05 to 0.1.

[0106] The association between the catalyst and the carbon support allows multiple particle growth sites to be formed on the surface of the carbon support.

[0107] According to another variation, the method according to the invention is carried out without a catalyst.

[0108] Precursor compounds of silicon nanomaterials, especially nanowires

[0109] The method according to the invention includes introducing a precursor composition of a nano-silicon material into a rotating fluidized bed reactor, referred to as a "reactive silicon-containing gaseous material", preferably a precursor composition of silicon nano-islands or nanowires, and even more preferably a precursor composition of silicon nanowires.

[0110] The precursor composition for silicon particles contains at least one precursor compound of silicon nanomaterials, particularly silicon nanowires.

[0111] The term "precursor compound of nano-silicon material" or "precursor compound of silicon nanomaterial" refers to a nano-silicon material that can be formed on the surface of a carbon carrier material by implementing the method according to the present invention.

[0112] The term "precursor compound of silicon nano islands or nanowires" refers to a compound that can form silicon nano islands or nanowires on the surface of a carbon carrier material by implementing the method according to the present invention.

[0113] Preferably, the precursor compound is in the form of a reactive silicon-containing gaseous substance mixed with a carrier gas (forming a reactive silicon-containing gaseous mixture).

[0114] Preferably, the precursor compound of the nano-silicon material, particularly silicon nanowires, or "gaseous substance containing reactive silicon," is a silane compound or a mixture of silane compounds.

[0115] For the purposes of this invention, the term "silane compound" refers to a compound of formula (I):

[0116] R1-(SiR2R3) n -R4(I)

[0117] in:

[0118] - n is an integer from 1 to 10, and

[0119] - R1, R2, R3, and R4 are independently selected from hydrogen, C1 to C4, respectively. 15 Alkyl, C6 to C 12 Aryl, C7 to C 20 Aryl groups and chlorine.

[0120] According to this embodiment, preferably, the silicon-containing gaseous substance is selected from compounds of formula (I), wherein:

[0121] - n is an integer from 1 to 5, and

[0122] - R1, R2, R3 and R4 are independently selected from hydrogen, C1 to C3 alkyl, phenyl and chlorine.

[0123] Even more preferably, n is an integer from 1 to 3, and R1, R2, R3 and R4 are independently selected from hydrogen, methyl, phenyl and chlorine.

[0124] According to this embodiment, preferably, the gaseous substance containing reactive silicon is selected from silane, ethylsilane, propane, chlorosilane, dichlorosilane, trichlorosilane, dichlorodimethylsilane, phenylsilane, diphenylsilane or triphenylsilane or mixtures thereof.

[0125] According to the preferred embodiment, the gaseous substance containing reactive silicon is silane (SiH4).

[0126] According to the preferred embodiment, the reactive silicon-containing gaseous substance is substantially composed of one or more precursor compounds of nano-silicon materials, particularly silicon nanowires, or better yet, it is composed of only one or more precursor compounds of nano-silicon materials, particularly silicon nanowires.

[0127] According to a preferred embodiment, a gaseous substance containing reactive silicon is mixed with a carrier gas and introduced into the reactor.

[0128] Gas mixture containing reactive silicon

[0129] Silicon materials are obtained by the chemical decomposition of a gaseous substance containing reactive silicon at high temperatures, which can be mixed with a carrier gas. This mixture is referred to below as a "gas mixture containing reactive silicon".

[0130] The term "carrier gas" refers to a gas selected from reducing gases, inert gases, or mixtures thereof.

[0131] Preferably, the reducing gas is hydrogen (H2).

[0132] Preferably, the inert gas is selected from argon (Ar), nitrogen (N2), helium (He), or a mixture thereof.

[0133] Preferably, the carrier gas composition consisting of a reducing gas and an inert gas contains 0% to 99% by volume of the reducing gas, more preferably 20% to 99% by volume of the reducing gas.

[0134] According to a preferred embodiment, the silicon-containing gas mixture consists of at least 0.5% by volume, preferably at least 10% by volume, more preferably at least 50% by volume, and even more preferably 100% by volume of silicon-containing gaseous material.

[0135] The carrier gas used in step (2) of the method may be the same as or different from the carrier gas used in step (5) when mixed with the silicon-containing gaseous substance.

[0136] The ratio of silicon-containing gaseous material to carrier gas can be adjusted at different levels in different steps of the process.

[0137] Rotary fluidized bed reactor

[0138] The rotating fluidized bed reactor mentioned above and described below consists at least of a tubular chamber therein loaded with carbon-based material, which is heated by a furnace. The reactor integrates a rotating mechanism. The reactor may include two tubular chambers. The tubular chambers may be tilted. The reactor also includes a product feed system and a product discharge system, allowing for semi-continuous production of silicon-carbon composites. The rotating fluidized bed reactor includes reactor pressure control devices, such as needle valves or pressure controllers.

[0139] Unlike traditional fluidized bed reactors, mechanical fluidized bed reactors utilize external forces other than gas flow, including rotation of the reactor along its longitudinal axis, to fluidize the powder bed. A typical mechanical fluidized bed reactor is the rotating Lödige-type fluidized bed reactor, where fluidization is generated by the rotation of a tubular chamber.

[0140] The advantage of the method according to the invention lies in the expanded possibility of preparing carbon-silicon composite materials on an industrial scale using a rotating Lödige-type fluidized bed reactor based on chemical vapor deposition (CVD).

[0141] Fluidized bed reactor - batch processing mode

[0142] Figure 1A rotating fluidized bed reactor apparatus is shown. The reactor consists of a tubular quartz chamber 106 extending along a central longitudinal axis XX. Chamber 106 is surrounded and heated by a furnace 107. The furnace is heated by resistance heating, induction heating, or infrared lamp heating. After carbon powder material 108 is loaded, chamber 106 is closed by two flanges 103 and 109 at the ends of chamber 106. Each flange is located on bearing systems 104 and 110. Bearing system 104 is connected to an electric motor 105. Electric motor 105 allows chamber 106 to rotate about the longitudinal axis XX via bearing system 104. The rotating fluidized bed reactor includes a carrier gas inlet 101 at one end of chamber 106 (also referred to as the inlet of chamber 106) and a reactive silicon-containing gas mixture inlet 102 at the same end of chamber 106 as the carrier gas inlet 101. At the other end of chamber 106, also referred to as the outlet of chamber 106, there is a tubular gas cooling device 111 and a needle valve 112 for perfect reactor pressure control. A dual-container liquid trap 114a and 114b are placed between the needle valve 112 and the gas tubular cooling device 111 for valve protection and collection of fine / silane byproducts, with one of the containers 114a filled with oil. The total gas output 113 is located at the outlet of the needle valve 112, and a pressure indicator 115 is located at the outlet of chamber 106 to measure the reactor pressure. The reactor control unit monitors process parameters such as temperature, carrier gas flow rate, flow rate of the reactive silicon-containing gas mixture, and rotational speed. Figure 1 As shown in the image.

[0143] Continuous mode reactor

[0144] Figure 7An industrial rotating Lödige-type fluidized bed reactor is shown. The reactor consists of a tubular chamber 701 extending along a central longitudinal axis XX. Chamber 701 is surrounded and heated by a single-zone or multi-zone furnace 702. The furnace is heated by resistance heating, induction heating, or infrared lamp heating. The tubular chamber 701 is closed by at least two boundary systems 703 at the ends of chamber 701. Carbonaceous material 704 is loaded by a product feed system 705 at the first end of chamber 701. A generator 706 allows chamber 701 to rotate while the boundary systems 703 remain stationary. The furnace 702 remains mounted on a device support 707. The rotating Lödige-type fluidized bed reactor can be tilted by a tilting system 708. Preferably, the tilt angle α between the reactor longitudinal axis XX and the horizontal plane is less than or equal to 20°. The tilting system 708 allows the carbonaceous material to slide from the product feed system 705 to the product discharge system 709 located at the opposite end of chamber 701 at a speed depending on the rotation speed and the tilt angle. The rotating Lödige-type fluidized bed reactor includes a carrier gas inlet 710, at least one inlet 711 containing a reactive silicon gas mixture, and an inert gas inlet 712, all located at the end of chamber 701 opposite to product feed system 705, and a total gas outlet 713 located at the same end as product feed system 705. These gas inlets and outlets can be preheated by corresponding systems and can integrate valves 714 and 718. Valve 718 at the total gas outlet 713 allows for reactor pressure control and can be managed by at least one reactive silicon gas detector 715, depending on the number of reactive silicon gas sources used. A pressure indicator 719 provides the reactor pressure. A gas safety tank 717 is connected to tubular chamber 701 via a burst disc safety system 716 placed on boundary system 703, and the burst disc safety system 716 can integrate a pressure sensor (not shown). The pressure sensor in the bursting disc safety system 716 allows for control of valve 714 at the inlet 711 of the reactive silicon-containing gas mixture, ensuring safety, process efficiency, and flexibility. In effect, increasing the pressure of the silicon-containing gaseous substance within the tubular chamber 701 allows for controlled silicon material growth, thereby controlling the structure. The product collection tank and reactor control unit monitor process parameters such as temperature, carrier gas and reactive silicon-containing gas mixture flow rate, inclination angle, and rotational speed. Figure 7 As shown in the image.

[0145] The product feeding system 705 can be a headless screw feeding system, a metering system, or a funnel-type system. The same applies to the product discharge system 709. The latter may include a cooling system.

[0146] The rotating tubular chamber 701 and / or process support 707 and / or boundary system 703 can be integrated with other devices to accommodate the complexity of production operations. These devices include thermocouples for gas or product control, pressure sensors, optics, sealing systems, sampling systems, and analytical instruments.

[0147] The rotating tubular chamber 701 may include internal components such as fixed fins, movable rods, or movable balls. The geometry, layout, and number of fins, as well as the size and number of rods and balls, depend on the physical properties of the carbon-based material powder 704.

[0148] One advantage of the method of this invention is that mechanical fluidized bed reactors are easier to scale up for industrial production than conventional fluidized bed reactors. Powders with particle sizes smaller than 30 µm (from Group C of the Geldart powder classification) can be easily processed using this type of fluidized bed reactor, which remains difficult in classical fluidized bed reactors. Furthermore, the residence time of reactants in a rotating fluidized bed reactor is much higher, which, from a chemical perspective, allows for better production efficiency and thus cost savings, because the behavior of solid particles is independent of or only minimally correlated with gas flow rate. The movement of solid particles is provided by the reactor motion.

[0149] Dual-chamber reactor

[0150] Figure 9A variation of the aforementioned industrial rotating Lödige-type fluidized bed reactor is shown. In this case, the reactor consists of two tubular chambers 901.a and 901.b extending along the central longitudinal axis XX, each heated by a single-zone or multi-zone furnace 902. Tubular chambers 901.a and 901.b are enclosed by at least two fixed boundary systems 903 and separated by a separation system 918. Tubular chamber 901.a is dedicated to the preparation of silicon-carbon composite materials. It is loaded with carbon material via a product feed system 905. Tubular chamber 901.b, hereinafter referred to as the granulation chamber, is dedicated to the granulation of silicon-carbon composite materials. Granulation is the process of forming particles from powdered material, thereby preparing particulate material. The granulation chamber is loaded with fresh silicon-carbon composite material 904 via the separation system 918 to obtain silicon-carbon composite material particles 919. A generator 906 allows the chamber to rotate. The furnace 902 remains fixed on the process support 907. The rotating Lödige-type fluidized bed reactor can be tilted via a tilting system 908. A tilting system 908 allows carbon-based materials to diffuse into tubular chamber 901.a. Silicon-carbon composite material 904 slides from chamber 901.a to chamber 901.b via a separation system 918. Silicon-carbon composite particles 919 slide towards product discharge system 909 at a speed depending on the rotation speed and tilt angle. The rotating Lödige-type fluidized bed reactor includes a carrier gas inlet 910, at least one inlet 911 for a reactive silicon-containing gas mixture connected to preparation chamber 901.a, an inert gas inlet 912, and total gas outlets 913a and 913b. These gas inlets and outlets can be preheated by corresponding systems and can be integrated with valves 914a, 914b, and 914c. Valve 918 at the total gas outlet 913b of chamber 901.a allows for perfect reactor pressure control and can be managed by at least one reactive silicon-containing gas detector 915, depending on the number of reactive silicon-containing gas sources used. A pressure indicator 919 detects the reactor pressure. Gas safety tank 917 is connected to tubular chamber 901.a via a burst disc safety system 916 placed on boundary system 903, and the burst disc safety system 916 can integrate a pressure sensor. Through the pressure sensor of the burst disc safety system 916, valve 914c at the inlet 911 of the reactive silicon-containing gas mixture can be controlled for safety, process efficiency, and flexibility. In effect, increasing the pressure of the silicon-containing gaseous substance within tubular chamber 901.a allows for controlled silicon material growth, thereby controlling the structure. Product collection tanks and reactor control devices monitor process parameters such as temperature, carrier gas and reactive silicon-containing gas mixture flow rate, inclination angle, and rotational speed. Figure 9 As shown in the image.

[0151] Product feeding system 905 can be a headless screw feeding system, a metering system, or a funnel-type system. The same applies to product discharge system 909. The latter may include a cooling system.

[0152] The separation system 918 acts as a connection between tubular chambers 901.a and 901.b and is rotated by a motor 906. It integrates a three-layer gear system that remains closed while the preparation and granulation steps occur in tubular chambers 901.a and 901.b, respectively, and opens upon completion of these steps, allowing the silicon-carbon composite material to slide from one chamber to another. Therefore, batches of silicon-carbon composite material can be granulated in tubular chamber 901.b while another batch is prepared in tubular chamber 901.a.

[0153] The rotating tubular chamber 901 and / or process support 907 and / or boundary system 903 can be integrated into devices according to the complexity of the production operation. These devices include thermocouples for gas or product control, pressure sensors, optics, sealing systems, sampling systems, and analytical instruments.

[0154] Tubular chamber 901.a may include internal components such as movable rods or movable balls. The size and number of rods and balls depend on the physical properties of the initial carbon-based material powder. Tubular chamber 901.b may include internal components such as fixed fins. The geometry, layout, and number of fins depend on the physical properties of the silicon-carbon composite material 904.

[0155] Methods for preparing carbon-silicon composite materials

[0156] The process according to the present invention includes:

[0157] (1) Introduce at least a carbon-based material and an optional catalyst into the tubular chamber;

[0158] (2) Heating the tubular chamber under a carrier gas flow.

[0159] (3) Rotating tubular chamber,

[0160] (4) Introduce a gas mixture containing reactive silicon into a rotating tubular chamber.

[0161] (5) In a rotating tubular chamber, under a flow of a gas mixture containing reactive silicon, at a temperature of 200°C to 900°C, at a temperature higher than 1.02 × 10⁻⁶. 5 Pa or equal to 1.02 × 10 5 Heat treatment is performed under Pa pressure.

[0162] (6) Products recovered from recycling,

[0163] Most steps must be completed in this order, but the rotation in step (3) can begin before or after step (1) or step (2).

[0164] Step (1)

[0165] Preferably, the volume ratio of the carbon-based material (including a carbon support and optional catalyst) to the volume of the tubular chamber is 10% to 60%, more preferably 20% to 50%, and even more preferably 30% to 50%.

[0166] Steps (2) to (5)

[0167] Preferably, the temperature ramp in step (2) is from 1°C / minute to 50°C / minute, more preferably from 5°C / minute to 30°C / minute, and even more preferably about 10°C / minute, until the room reaches the desired value.

[0168] In step (5), the temperature of the tubular chamber is maintained at 200°C to 900°C, preferably 350°C to 850°C, and even more preferably 450°C to 750°C.

[0169] The furnace can be heated by resistance heating, induction heating or infrared lamp heating.

[0170] In step (5), the pressure in the tubular chamber can be controlled, and preferably is 1.02 × 10⁻⁶. 5 Pa to 5×10 6 Pa, more preferably 1.05 × 10 Pa. 5 Pa to 10 6 Pa, or even more preferably 1.1 × 10 Pa. 5 Pa to 10 6 Pa.

[0171] The duration of the treatment, which combines the treatment with the gas mixture containing reactive silicon and the heating in the rotating chamber, is preferably 1 minute to 10 hours, advantageously 5 minutes to 5 hours, and even more preferably 15 minutes to 10 hours.

[0172] Preferably, in step (2), the carrier gas flow rate is 0.1 SLM to 50 SLM (standard liters / minute), more preferably 0.5 SLM to 40 SLM.

[0173] According to the variation, in step (2), the flow rate of the gas mixture containing reactive silicon is 0.1 SLM to 10 SLM (standard cubic meters per minute), more preferably 0.5 SLM to 5 SLM.

[0174] Preferably, in step (5), the flow rate of the gas mixture containing reactive silicon is 0.1 SLM to 50 SLM (standard cubic meters per minute), more preferably 0.5 SLM to 40 SLM.

[0175] According to the variation, in step (5), the flow rate of the gas mixture containing reactive silicon is 0.1 SLM to 10 SLM (standard cubic meters per minute), more preferably 0.5 SLM to 5 SLM.

[0176] The carrier gas flow rate and the flow rate of the gas mixture containing reactive silicon can be the same or different.

[0177] The carrier gas used in step (2) of the method may be the same as or different from the carrier gas used in step (5) when mixed with the silicon-containing gaseous substance.

[0178] The gas flow rate in step (2) leads to a decrease in the oxygen content in the reaction chamber.

[0179] The gas flow rate in step (5) causes the growth of silicon nanostructures on a carbon-based support in the reaction chamber.

[0180] Preferably, at the end of step (5), the flow of the gas mixture containing reactive silicon is stopped, and the tubular chamber is cooled to room temperature under the flow of carrier gas.

[0181] Preferably, the rotational speed of the tubular chamber is 1 to 40 RPM (revolutions per minute), more preferably 1 to 30 RPM, even more preferably 1 to 20 RPM, and even more preferably 1 to 15 RPM.

[0182] Depending on the configuration, the rotational speed of the tubular chamber is from 1 RPM to 40 RPM, preferably from 10 RPM to 30 RPM, and even more preferably from 15 RPM to 25 RPM.

[0183] According to the first implementation plan, the longitudinal axis XX of the tubular chamber is horizontal.

[0184] According to the second embodiment, the longitudinal axis XX of the tubular chamber is inclined and forms an angle α with the horizontal plane. Advantageously, according to this embodiment, the inclination angle is 1 degree to 20 degrees, more preferably 5 degrees to 15 degrees, and advantageously about 10 degrees.

[0185] According to an advantageous embodiment, the method according to the invention includes applying at least one cycle following step (6):

[0186] (1') Fresh carbon-based material (including carbon support and optional catalyst) is reloaded into the tubular chamber.

[0187] (2') Heating the tubular chamber under a carrier gas flow

[0188] (3') Rotating tubular chamber,

[0189] (4') Introduce a gas mixture containing reactive silicon into a rotating tubular chamber.

[0190] (5) In a rotating tubular chamber, under a flow of a gas mixture containing reactive silicon, at a temperature of 200°C to 900°C, at a temperature higher than 1.02 × 10⁻⁶. 5 Pa or equal to 1.02 × 10 5Heat treatment is performed under Pa pressure.

[0191] (6') The products obtained from recycling.

[0192] The preferred embodiments of steps (1') to (6') are the same as the preferred embodiments of steps (1) to (6).

[0193] Advantageously, between the two cycles, the tubular chamber continues to be heated, the rotation of the tubular chamber can be reduced or completely stopped, and the airflow can continue as a carrier gas flow.

[0194] The rotation in step (3') can begin before or after step (1') or step (2'). Alternatively, the rotation from one cycle to another can be continuous, and the rotation speed can vary between cycles.

[0195] Other steps

[0196] According to some implementations, additional steps may optionally be performed between steps (5) and (6), such as forming a carbon coating on the surface of the silicon-carbon composite material. In this case, one or more additional integrated gas inlet valves may be added for the carbonaceous gaseous material.

[0197] For example, the method may include additional steps of heat-treating the silicon-carbon composite material obtained at the end of step (5) in the presence of a carbon source.

[0198] For example, the method may include additional steps such as injecting an inert gas into the tubular chamber prior to step (6) to avoid oxygen contamination.

[0199] According to one embodiment, the method according to the invention further includes a step (G) of granulating the product obtained at the end of step (5) or step (5'). According to this embodiment, the product obtained in step (5) or (5') is introduced into a granulation chamber and the granulation chamber is rotated for a predetermined period of time. After granulation is considered complete, the product (6) is recovered and may be subjected to further post-processing steps, such as heat treatment.

[0200] Method - Batch Processing Mode

[0201] Figure 2 This illustrates the use of a rotating Lödige-type fluidized bed reactor, such as Figure 1 A method for preparing silicon-carbon composite materials in a reactor. In step 201, a carbon-based powder material 108, optionally containing a catalyst, is loaded into a tubular quartz chamber 106 by removing a flange 109. When the carbon-based powder material 108 is loaded, the chamber 106 is closed by the flange 109, and the flange 109 is mounted in a bearing system 110. Then, according to... Figure 1The arrangement shown connects the tubular cooling device 111, needle valve 112, and main gas outlet 113 to flange 109. In step 202, carrier gas is supplied to chamber 106 through carrier gas inlet 101. Rotation and heating of chamber 106 begin in steps 203 and 204, respectively. When the desired reactor temperature is reached, it is stabilized for a certain period of time in step 205.

[0202] In step 206, the carrier gas inlet 101 is closed, and the inlet 102 containing the reactive silicon gas mixture is opened. During heating under an inert gas flow, the pressure is monitored using a needle valve 112. The flow rate of the reactive silicon gas mixture can be the same as the carrier gas flow rate in step 202. During step 207, the silicon source from the reactive silicon gas mixture reacts with the carbon-based powder material for a predetermined time to form a silicon-carbon composite material. The duration of the treatment depends on the silicon source and its concentration in the gas flow. After the silicon-carbon composite material is prepared, in step 208, the inlet 102 containing the reactive silicon gas mixture is closed, and the carrier gas inlet 101 is opened. The carrier gas flow rate can be the same as in step 202. Simultaneously, the furnace 107 is closed, and the chamber 106 is cooled to room temperature under the action of the carrier gas flow (step 209). When room temperature is reached, rotation is stopped (step 210), and in step 211 the silicon-carbon composite material is unloaded by disconnecting the tubular cooling device 111 from the flange 109 and removing the flange 109 from the bearing system 110 and the chamber 106.

[0203] Method - Continuous Mode

[0204] Figure 8 This illustrates a rotating Lödige-type fluidized bed reactor, for example... Figure 7A method for preparing a silicon-carbon composite material in the reactor shown. The preparation method begins in step 801, where a process support 707 is tilted via a tilting system 708. Then, rotation of the tubular chamber 701 is initiated at a desired rotational speed, and the chamber is heated to a desired temperature. Then, in step 802, a carbon-based powder material 704, optionally containing a catalyst, is loaded into the tubular quartz chamber 701 by opening the product feed system 705. In step 803, the product feed system 705 is closed, while a carrier gas is supplied to the rotating tubular chamber 701 through a carrier gas inlet 710. The temperature stabilizes over a period of time. When the desired reactor temperature is reached, in step 804, the carrier gas inlet 710 is automatically closed, and the inlet 711 for a gas mixture containing reactive silicon is opened. The flow rate of the gas mixture containing reactive silicon can have the same value as the carrier gas flow rate in step 801. During step 805, the silicon source from the reactive silicon-containing gas mixture reacts with the carbon-based powder material for a predetermined amount of time, based on the silicon source and its concentration in the gas stream, to form a silicon-carbon composite material. The total gas output 713 can be kept closed to increase the pressure of the reactive silicon-containing gas within the tubular chamber 716. Once the preparation of the silicon-carbon composite material is considered complete, the reactive silicon-containing gas mixture input 711 is closed, while the inert gas input 712 and the total gas output 713 are opened to purge the rotating tubular chamber 701 and any remaining reactive gaseous material from the silicon-carbon composite material.

[0205] In steps 803 and / or 804 and / or 806, the inert gas and carrier gas flow rates, as well as the flow rate of the reactive silicon-containing gas mixture, can have the same value. In step 807, the silicon-carbon composite material is unloaded by opening the product discharge system 709.

[0206] At this point, a semi-continuous preparation mode 809 can be adopted by repeating all the above steps starting from step 802: the carbon-based material powder 704 is reloaded into the rotating tubular chamber 701 by opening the product feed system 705. The temperature of the chamber 701 is maintained, but its rotation can be slowed down or stopped between two cycles.

[0207] Step 808 allows the preparation process to be stopped for system maintenance or safety reasons. Under an inert atmosphere, furnace 702 is shut off, tubular chamber 701 is cooled to room temperature while rotation is stopped, and the reactor is tilted back to horizontal if necessary.

[0208] Methods - Granulation Mode

[0209] Figure 10 It shows that in relation to Figure 9A method for preparing silicon-carbon composite materials in a modified rotating Lödige fluidized bed reactor. The preparation method begins in step 1001 by tilting the process support 907 via a tilting system 908 to rotate tubular chambers 901.a and 901.b at a desired rotational speed and heating each to a desired temperature. In step 1002, inert gas is supplied to both chambers through an inert gas inlet 912, and the temperature stabilizes over a period of time. Then, in step 1003, carbon-based powder material is loaded into the first tubular chamber 901.a by opening the product feed system 905. In step 1004, the product feed system 905 is closed, while a carrier gas is supplied to the rotating tubular chamber 901.a through a carrier gas inlet 910. In step 1005, when the desired temperature is reached, the carrier gas inlet 910 is closed, and the inlet 911 containing a reactive silicon gas mixture is opened. During step 1006, a silicon source from a reactive silicon-containing gas mixture reacts with a carbon-based powder material for a predetermined time to form a silicon-carbon composite material. The reaction time depends on the silicon source and its concentration in the gas. The total gas output 913 is closed to increase the pressure of the reactive silicon-containing gas within the tubular chamber 901.a. In step 1007, after the preparation of the silicon-carbon composite material 904 is considered complete, the reactive silicon-containing gas mixture input 911 is closed, while the inert gas input 912 and the total gas output 913 are opened to purge the rotating tubular chamber 901.a and the silicon-carbon composite material from any remaining reactive gaseous material.

[0210] In step 1008, when the tubular chamber 901.a is purged with an inert gas, the separation system 918 is opened, and the silicon-carbon composite material 904 is transferred to the granulation chamber 901.b. At this time, a semi-continuous preparation 1012 can be carried out by repeating the method from step 1002 to step 1008.

[0211] In step 1009, granulation of the silicon-carbon composite material 904 begins. Inert gas or carrier gas is supplied as needed through inert gas and carrier gas inlets 910 and 912, and the process is run for a predetermined amount of time. The resulting silicon-carbon composite material particles 919 are then unloaded from the granulation chamber 901.b via the product discharge system 909. At this point, semi-continuous granulation 1013 is performed by repeating the process from steps 1009 to 1010.

[0212] Step 1011 allows the preparation process to be stopped for system maintenance or safety reasons. Under an inert atmosphere, furnace 902 is shut off, tubular chamber 901 is cooled to room temperature while rotation is stopped, and the reactor is tilted back to horizontal if necessary.

[0213] Silicon-carbon composite materials

[0214] The present invention provides a silicon-carbon composite material, which can be obtained by the above-described method.

[0215] The silicon-carbon composite material obtainable by this method comprises carbon-based materials and nano-silicon materials. The carbon-based materials comprise the aforementioned carbon support and, optionally, a catalyst.

[0216] The catalyst and the carbon support may or may not be in contact. Preferably, when the catalyst is present, it is in contact with the surface of the carbon support. The contact between the catalyst and the carbon support can be achieved through chemisorption or physisorption.

[0217] More preferably, when the catalyst is present, it is well dispersed in particulate form on the surface of the carbon support.

[0218] Preferably, the nanostructured silicon material is composed of silicon particles, at least one of which has an external size of 10 nm to 500 μm, more preferably 10 nm to 500 nm.

[0219] Silicon materials are produced by the chemical vapor phase decomposition of silicon-containing gaseous substances, and they can take the form of threads, worms, rods, filaments, islands, granules, films, sheets, or spheres.

[0220] The presence or absence of a catalyst affects the type of silicon particles obtained.

[0221] According to a preferred embodiment, the silicon particles are in the form of nanowires. The Si nanowires are preferably obtained by a method involving the use of a catalyst.

[0222] The term "nanowire" should be understood, within the meaning of this invention, to refer to a slender element that is similar in shape to a wire and has a diameter on the nanometer scale.

[0223] Preferably, the diameter of the silicon nanowire is 1 nm to 100 nm, more preferably 10 nm to 100 nm, and even more preferably 10 nm to 50 nm.

[0224] Preferably, the average diameter of the silicon nanowires is 5 nm to 5 μm, more preferably 10 nm to 50 nm.

[0225] Preferably, the average length of the silicon nanowires is between 50 nm and 500 nm.

[0226] Nanoworms are a special, preferred subgroup of nanowires characterized by their aspect ratio (the ratio of average length to average diameter), which is in the lower range of the nanowire group, i.e., an L / D ratio of less than 10 or equal to 10, more preferably less than 5 or equal to 5, and advantageously less than 2 or equal to 2.

[0227] According to another embodiment, the silicon particles are in the form of nanoislands. The Si nanoislands are preferably obtained by a method performed in the absence of a catalyst.

[0228] The term "nano island" should be understood, within the meaning of this invention, to refer to a circular element with a diameter on the nanometer scale.

[0229] Preferably, the diameter of the silicon nanoislands is 1 nm to 100 nm, more preferably 10 nm to 100 nm, and even more preferably 10 nm to 50 nm.

[0230] Preferably, the average diameter of the silicon nanoislands is 5 nm to 5 μm, more preferably 10 nm to 50 nm.

[0231] The dimensions of silicon materials can be measured using several techniques well known to those skilled in the art, such as by analyzing images obtained from one or more samples of carbon-silicon composites using a scanning electron microscope (SEM).

[0232] Silicon particles, preferably silicon nanowires or silicon nanoislands, account for 1% to 70% of the weight of the silicon-carbon composite material, preferably 10% to 70% of the weight, more preferably 20% to 70% of the weight, even more preferably 30% to 70% of the weight, and advantageously 50% to 70% of the weight.

[0233] Preferably, the silicon-carbon composite material is obtained in powder form.

[0234] Applications of carbon-silicon composite materials

[0235] The silicon-carbon composite material according to the present invention can be used as an anode active material and for manufacturing lithium-ion batteries.

[0236] Electrodes comprising current collectors are prepared using methods typically employed in the art. For example, an anode active material composed of the carbon-silicon composite material of the present invention is mixed with a binder, a solvent, and a conductive agent. If necessary, a dispersant may be added. The mixture is stirred to prepare a slurry. The slurry is then coated onto the current collector and pressed to prepare the anode.

[0237] Various types of adhesive polymers can be used as adhesives in this invention, such as polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HEP), polyvinylidene fluoride, polyacrylonitrile, and polymethyl methacrylate.

[0238] The electrode can be used to manufacture a lithium secondary battery comprising a separator and an electrolyte solution, which are commonly used in the art and disposed between the cathode and the anode.

[0239] Example

[0240] Two examples of preparing silicon-carbon composite materials are given below.

[0241] The example preparation was carried out in a Nabertherm RSRB120-750 / 11 articulated rotary tube furnace equipped with a 4L quartz tube as the reaction chamber.

[0242] In both embodiments, silane was used as the silicon source and mixed with nitrogen gas at a concentration of 0.9 vol% silane to obtain the silicon-carbon composite material. Nitrogen gas was also used alone as a carrier gas during heating (steps 202, 203, 204, and 205) and cooling (steps 208 and 209) of the rotating fluidized bed reactor. Both the carrier gas flow rate and the flow rate of the gas mixture containing reactive silicon had a value of 1 SLM. Pressure was controlled. Both preparations were achieved within 6 hours. The rotation speed was 20 RPM, and the temperature ramp was 10 °C / min, reaching a temperature of 650 °C. In both embodiments, the micron-sized graphite support in the carbon-based material of the silicon-carbon composite was KS4 (Imerys) graphite. It was uniformly coated with catalytic nanoparticles. Operation was achieved using 30 g of carbon-based material. For both embodiments, the target silicon value was 10% by mass. For both embodiments, the diameter of the silicon nanowires was 20 nm to 50 nm.

[0243] Example 1 (Comparative)

[0244] In this first embodiment, the pressure P = 1.013 × 10 5 Pa (atmospheric pressure).

[0245] Figure 3 and Figure 4 A first embodiment of a silicon-carbon composite material is shown. Silicon nanowires 303 are synthesized on a micron-sized KS4 graphite support (30g) 301 uniformly covered by catalytic gold nanoparticles 302. The gold / graphite mass ratio is 0.05.

[0246] As confirmed by MEB, Si nanowires were obtained. Figure 3 ). Figure 4 The granulation phenomenon that occurs during this process is explained. The size of the spherical agglomerates 401 ranges from 1 mm to 3 mm. The size of the larger "burr-like" agglomerates 402 ranges from 3 mm to 5 mm.

[0247] Example 2 (according to the present invention)

[0248] Implement the same conditions as in Example 1:

[0249] T=650℃, t=6 h, rotation 20 rpm, gas flow rate of nitrogen and nitrogen / silane mixture (silane=0.9 vol%)=1 slm, powder=graphite KS4 and gold nanoparticles, the same amount of KS4=30g.

[0250] The difference from Example 1 is that in Example 2, the pressure P = 1.2 × 10⁻⁶. 5 Pa. Figure 5 A second embodiment of a silicon-carbon composite material is shown. Silicon nanowires 503 are synthesized on a micron-sized KS4 graphite support 501 uniformly covered by catalytic gold nanoparticles 502. The gold / graphite mass ratio is 0.05. As confirmed by MEB, Si nanowires ( Figure 5 Estimated diameter: 50nm to 100nm. Estimated length: 100nm. Figure 6 A second embodiment of the silicon-carbon composite material is shown. In this micrograph, one can observe the particulate phenomenon that occurs during the process. Spherical aggregates 601 with a size of 1 mm to 3 mm are present.

[0251] result

[0252]

[0253] The comparison shows that implementing the process according to the protected parameters yields a higher yield of composite materials.

Claims

1. A method for preparing a carbon-silicon composite material, wherein the method is carried out in a tubular chamber of a reactor, wherein the tubular chamber is rotatable about its longitudinal axis (XX), the method comprising: (1) Introduce at least a carbon-based material comprising a carbon support and an optional catalyst into the tubular chamber; (2) Heating the tubular chamber under a carrier gas flow. (3) Rotating tubular chamber, (4) Introduce a gas mixture containing reactive silicon into a rotating tubular chamber. (5) In a rotating tubular chamber, under a flow of a gas mixture containing reactive silicon, at a temperature of 200°C to 900°C, at a temperature higher than 1.02 × 10⁻⁶. 5 Pa or equal to 1.02 × 10 5 Heat treatment is performed under Pa pressure. (6) The recycled products It should be understood that step (3) may begin before or after step (1) or step (2).

2. The method according to claim 1, wherein the pressure in step (5) is 1.05 × 10⁻⁶. 5 Pa to 10 6 Pa.

3. The method according to claim 1 or claim 2, wherein the temperature of step (5) is 350°C to 850°C.

4. The method according to any one of the preceding claims, wherein the carbon-based material is selected from graphite, graphene, and carbon, preferably graphite powder with an average particle size of 0.01µm to 50µm.

5. The method according to any one of the preceding claims, wherein the carbon-based material has catalyst particles on its surface.

6. The method according to any one of the preceding claims, wherein the catalyst is selected from metals, bimetallic compounds, metal oxides, metal nitrides, metal salts, and metal sulfides.

7. The method according to any one of the preceding claims, wherein the gas mixture stream containing reactive silicon comprises at least a reactive silicon substance and a carrier gas.

8. The method according to any one of the preceding claims, wherein the reactive silicon material is selected from silane compounds, preferably silane SiH4.

9. The method according to any one of the preceding claims, wherein the volume ratio of the carbon-based material comprising the carbon support and optional catalyst to the volume of the tubular chamber is 10% to 60%, more preferably 20% to 50%, and even more preferably 30% to 50%.

10. The method according to any one of the preceding claims, wherein in step (5), the flow rate of the gas mixture containing reactive silicon is 0.1 SLM to 50 SLM (standard cubic meters per minute), more preferably 0.5 SLM to 40 SLM.

11. The method according to any one of the preceding claims, wherein the rotational speed of the tubular chamber is from 1 RPM to 40 RPM (revolutions per minute).

12. The method according to any one of the preceding claims, wherein the method comprises applying at least one loop following the order of steps (6): (1') Reload fresh carbon-based material into the tubular chamber. (2') Heating the tubular chamber under a carrier gas flow (3') Rotating tubular chamber, (4') Introduce a gas mixture containing reactive silicon into a rotating tubular chamber. (5') In a rotating tubular chamber, under a flow of a gas mixture containing reactive silicon, at temperatures ranging from 200°C to 900°C, at a concentration above 1.02 × 10⁻⁶ 5 Pa or equal to 1.02 × 10 5 Heat treatment is performed under Pa pressure. (6') The products obtained from recycling.

13. The method according to any one of the preceding claims, wherein the silicon-carbon composite material comprises a carbon-based material and a nano-silicon material, preferably, the nano-silicon material is a nanowire or a nano-island, or even more preferably, a nanowire.

14. A method for preparing an electrode comprising a current collector, the method comprising (i) carrying out a method for preparing a carbon-silicon composite material according to any one of claims 1 to 13, and (ii) covering at least one surface of the current collector with a composition comprising the carbon-silicon composite material as an electrode active material.

15. A method for manufacturing an energy storage device such as a lithium secondary battery, the energy storage device comprising a cathode, an anode, and a separator disposed between the cathode and the anode, wherein the method comprises the method of claim 14 for manufacturing at least one electrode, preferably an anode.

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