Method for preparing a material comprising silicon nanowires and tin

Abstract

A method for preparing a composite material comprising at least silicon nanowires and tin, said method comprising using tin halide, preferably tin chloride, as catalyst for the preparation of silicon nanowires.

Description

[0001] This invention relates to a method for growing silicon nanowires using tin(II) halide, preferably tin(II) chloride, as a metal seed precursor. The method is inexpensive and stable, is carried out at moderate temperatures, and allows for control of the silicon nanowire diameter. It is performed with a growth support. Silicon nanowire-based composites prepared by this method can be used in a variety of applications, such as nanoelectronics and microelectronics, spintronics, energy conversion and harvesting, sensors, or anode materials for lithium-ion batteries. Existing technology

[0002] Silicon, an element abundant on Earth, possesses unique properties and is a core material in many high-tech applications. In fact, silicon is a major component in solar cell technology and microelectronics. Silicon exhibits a low discharge potential and a very high theoretical charge capacity (>4000 mA·hg). -1 This makes it ideal for use in lithium-ion batteries. Another advantage of silicon is that its morphology can be altered through nanostructures. In fact, silicon exists in 0D (nanoparticles), 1D (nanowires), and 2D (nanofashelves) forms. It is known that nanostructuring of silicon improves its ability to withstand the mechanical strain that occurs during lithiation / delithiation processes.

[0003] Among these morphologies, silicon nanowires (SiNWs) have attracted considerable attention due to their very high aspect ratio, which is beneficial for efficient charge transport and is particularly advantageous for their application as anodes in lithium-ion batteries.

[0004] Furthermore, their conductivity can be easily improved by dopants, which can extend their applications to supercapacitors (1, 2) and thermoelectric devices (3).

[0005] The different technologies for producing SiNWs are mainly divided into two synthesis methods: bottom-up (growing nanowires from elemental silicon) and top-down (etching bulk silicon). The top-down method is characterized by considerable waste of starting silicon and the unavoidable use of hazardous chemicals. Bottom-up techniques, typically based on chemical vapor deposition (CVD), can produce high-quality nanowires. This method is advantageous for producing silicon nanowires and graphite / carbon composites. Industrializing the production of this composite material at an acceptable price is a significant challenge for the battery market.

[0006] Since the 1960s, the synthesis of SiNWs has not seen significant development, and the bottom-up production of SiNWs has been described through a gas-liquid-solid (VLS) mechanism. Currently, VLS is the most important and efficient method for synthesizing SiNWs. More precisely, VLS fabrication processes mainly focus on the combination of substrates, such as silicon wafers (2D), silicon or carbon nanoparticles (0D), and growth seeds, typically in the form of thin metal films or nanoparticles.

[0007] Gold nanoparticles (Au NPs) are considered one of the best seeds for SiNW growth. In fact, the Au-Si binary phase diagram shows a first eutectic point at 363 °C. This eutectic point allows the reaction to proceed at relatively low temperatures (compared to gold's melting point of approximately 1100 °C) and is primarily driven by the thermal decomposition of the silane precursor.

[0008] AuNP-catalyzed Si wire growth is typically achieved through chemical vapor deposition (CVD) using silicon precursors such as silanes or diphenylsilanes. However, this synthesis has only been performed on a limited scale for a limited amount of SiNWs in the laboratory. In fact, "in-house" AuNP production is both time-consuming and expensive, and difficult to scale up. This strategic material is too expensive to allow for economically viable large-scale production of SiNWs.

[0009] Other metals promote the VLS mechanism and exhibit low eutectic points with silicon and no silicide phases in their binary phase diagrams. Examples include tin, gallium, cadmium, indium, strontium, tellurium, and lead. Tin, being one of the most abundant elements on Earth, has the lowest eutectic point at 232°C.

[0010] Jeon et al. (4) reported the preparation of tin-seed SiNWs for solar cells using plasma-enhanced chemical vapor deposition (PECVD). A Sn(0) thin film was deposited in situ on a silicon wafer by thermal evaporation of metallic tin. The growth of the SiNWs was then controlled by introducing a hydrogen / SiCl4 gas flow.

[0011] Ball et al. (5) disclosed the use of Sn(0) nanoparticles (NP) as catalysts for SiNW growth, using silane as the silicon source at low pressure.

[0012] Dai et al. (6) disclosed the use of tin(II) dioxide nanoparticles (SnO2 NP) as a source of tin catalyst. In the first step, SnO2 nanoparticles were reduced to Sn(O) nanoparticles, followed by the introduction of silane at 400 °C to synthesize silicon nanowires.

[0013] Ngo et al. (7) disclosed a catalyst droplet formed by plasma-enhanced ITO reduction at 250 °C, which led to the agglomeration of metals into tin (0) and indium (0). These droplets allowed silicon nanowires to grow at 500 °C in the presence of silane.

[0014] Chockla et al. (8) described the use of bis(bis(trimethylsilyl)amino)tin (Sn(HMDS)2). Supercritical fluid-liquid-solid synthesis was performed, allowing in-situ formation of Sn(0) seed particles, followed by direct growth of SiNW using propane at 450 °C.

[0015] If these examples demonstrate that tin is an interesting candidate material as a seed for growing SiNWs, then these materials are still too expensive to allow for the mass production of silicon SiNWs.

[0016] In existing technologies, SnCl2 has been used as a precursor for the growth of tin-seed SiNWs. For example, Gérrard E.J. Poinern et al. (9) reported the use of reverse micelle reduction of tin salts to generate metallic tin nanoparticles as seeds for the growth of SiNWs. After the SnNPs were formed, silicon nanowires (SiNWs) were grown using PECVD. Although this preparation method is quite ingenious, it has its limitations because it involves many steps and is quite expensive and time-consuming.

[0017] To apply this unique related material to several industrial applications, a robust and cost-effective technology for large-scale production of SiNW is needed.

[0018] This invention describes a method for growing silicon nanowires using tin(II) halide, preferably tin(II) chloride, as a metal seed precursor. The method is simple, economical, and stable. It converts tin(II) halide, preferably tin(II) chloride, in situ into tin nanoparticles at moderate temperatures. It also allows for suitable control of the diameter of the silicon nanowires. Invention Overview

[0020] The first objective of this invention is a method for preparing a composite material comprising at least silicon nanowires and tin, said method comprising at least the following stages:

[0021] (1) Introduce at least:

[0022] - Tin halide SnX2, where X is selected from: F, Cl, Br, I, and

[0023] -Growth support,

[0024] (1') Solid / solid mixture of tin halide SnX2 and growth support

[0025] (2) Introduce at least one precursor compound of silicon nanowires into the chamber of the reactor.

[0026] (3) Reduce the oxygen content in the reactor chamber.

[0027] (4) Heat treatment is performed at temperatures ranging from 200℃ to 900℃, and

[0028] (5) Recycle products.

[0029] Steps (1), (1'), (2), (3) and (4) can be performed in this order or another order.

[0030] The present invention also relates to a method for manufacturing an electrode comprising a current collector, the method comprising (i) performing the methods disclosed above to prepare a composite material comprising at least silicon nanowires and tin as an electrode active material, and (ii) covering at least one surface of the current collector with a composition comprising the electrode active material.

[0031] The present invention also 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 at least one electrode, preferably the anode, is obtained by the method disclosed above.

[0032] According to the first variation, the method for preparing the composite material is carried out in a fixed-bed reactor.

[0033] According to the second variation, the method for preparing the composite material is carried out in the tubular chamber of a rotary drum reactor driven by a rotation and / or mixing mechanism.

[0034] According to the preferred embodiment, the tin halide is SnCl2.

[0035] According to a preferred embodiment, tin halide and growth support are mixed together before being introduced into the reactor.

[0036] According to the preferred embodiment, the heat treatment is carried out at a temperature of 200°C to 900°C, preferably 300°C to 650°C.

[0037] According to the preferred embodiment, the heat treatment is carried out for 1 minute to 5 hours, preferably 10 minutes to 2 hours, and more preferably 30 minutes to 60 minutes.

[0038] According to a preferred embodiment, the method for preparing the composite material includes a post-processing step to convert organic matter, particularly organic matter derived from precursor compounds of silicon nanowires, into carbon materials.

[0039] According to a preferred embodiment, the method for preparing the composite material includes an additional step (6) of treating the composite material obtained at the end of step (5) with an acidic solution.

[0040] According to a preferred embodiment, the precursor compound for silicon nanowires is a silane compound or a mixture of silane compounds.

[0041] According to a preferred embodiment, the precursor compound for silicon nanowires is silane (SiH4) or diphenylsilane Si(C6H5)2H2.

[0042] According to the preferred embodiment, the growth support is a carbon-based material, a silicon-based material, an ITO-based material, or a carbonaceous polymer.

[0043] The method according to the invention is based on the use of tin halides, preferably SnCl2, as a catalyst for the preparation of SiNW. Its advantage is that it can be carried out in a one-pot reaction without the need for catalyst pretreatment.

[0044] This invention is carried out in the presence of a growth support.

[0045] The combination of tin halides (preferably SnCl2) and the growth support is simple and robust. Using very stable products such as SnCl2 or another tin halide facilitates processing. In fact, SnCl2 and other tin halides only require solid / solid mixing with the growth support. SiNW growth based on methods such as gold nanoparticles requires solid / liquid preparation followed by solvent evaporation. The method according to the invention has the advantage of being carried out without any pretreatment or solvents.

[0046] The diameter of nanowires can be controlled by appropriately selecting the physical properties of the growth support. As shown in the examples, the diameter of nanowires prepared using SnCl2 is directly affected by the characteristics of the growth support.

[0047] Detailed description

[0048] The term "substantially constitutes," followed by one or more features, means that components or steps other than those expressly listed and that do not substantially affect the nature and features of the invention may be included in the methods or materials of the invention.

[0049] Unless otherwise explicitly stated, the statement "included between X and Y" includes the boundary. This statement means that the target range includes the values ​​of X and Y, as well as all values ​​from X to Y.

[0050] The primary object of this invention is a method for producing a composite material comprising silicon nanowires using a chemical vapor deposition (CVD) process. The composite material is suitable for use as an anode active material in lithium-ion batteries, and other applications are also conceivable.

[0051] The SiNW composite material obtained in this way can be used during production or can be processed after production.

[0052] This invention relates to methods for preparing silicon-based nanostructured materials. This invention also relates to methods for preparing silicon-based composite materials, said silicon-based composite materials comprising at least nanostructured silicon materials, tin, and growth support materials, and obtained by the chemical decomposition of reactive silicon-containing gaseous substances. This process is based on the principle of chemical vapor deposition (CVD).

[0053] The term "nanostructured material" is understood in the context of this invention to refer to a material containing free particles, which may be in the form of aggregates or agglomerates, wherein at least 5% by weight of the particles, relative to the total weight of the material, have at least one external size of 1 nm to 100 nm, preferably at least 10%.

[0054] "Composite material" refers to a material made of at least two constituent materials with significantly different physical or chemical properties.

[0055] The external dimensions of the particles can be measured by any known method, particularly by analyzing images obtained by scanning electron microscopy (SEM) of the composite material according to the invention.

[0056] Methods for preparing composite materials

[0057] This invention relates to a method for preparing a composite material comprising at least tin and SiNW, the method comprising at least the following steps:

[0058] (1) Introduce at least:

[0059] - Tin halide Sn(X)2, wherein X is selected from F, Cl, Br, I, and preferably tin halide is tin chloride SnCl2.

[0060] -Growth support,

[0061] (1') Solid / solid mixture of tin halide SnX2 and growth support

[0062] (2) Introduce at least one precursor compound of silicon nanowires into the chamber of the reactor.

[0063] (3) Reduce the oxygen content in the reactor chamber.

[0064] (4) Heat treatment is performed at temperatures ranging from 200℃ to 900℃, and

[0065] (5) Recycle products.

[0066] The order of steps (1) to (4) can be the order described above or another order, depending mainly on: the characteristics of the reactor in which the method is implemented, the method for reducing oxygen content, and the state (liquid or gaseous) in which the precursor compound of silicon nanowires is introduced into the reactor.

[0067] According to the first variation, the method is implemented in a fixed-bed reactor.

[0068] According to the second variation, the method is implemented in a tubular chamber of a drum reactor that includes a rotating and / or mixing mechanism.

[0069] Preferably, the reactor is closed during the process.

[0070] A closed reactor is one in which gaseous substances are introduced into the reactor at the beginning of the process, and then the reactor is shut off from the gas flow during the heat treatment step.

[0071] Process parameters

[0072] The process parameters reported below are general for all variations of this method (fixed-bed reactors, drum reactors with rotating and / or mixing mechanisms).

[0073] The method according to the invention includes introducing a growth support into the chamber of a reactor. The properties and characteristics of the growth support will be described in detail below.

[0074] The method according to the present invention includes a preparatory step of solid-solid mixing of growth support material with tin halide SnX2, hereinafter referred to as catalyst.

[0075] According to the first modification, the SnX2 catalyst (X = F, Cl, Br, I), preferably SnCl2, and the growth support are mixed together before being introduced into the reactor.

[0076] According to the second variation, after the SnX2 catalyst (X = F, Cl, Br, I), preferably SnCl2, and the growth support are introduced into the reactor as separate raw materials, they are mixed together in the reactor chamber.

[0077] Step (3) involves reducing the oxygen content in the reactor chamber, which can be done through different methods.

[0078] By placing the reactor under vacuum, preferably at a pressure of 10 or less. -1 Ba (10) -2 (MPa) can reduce the oxygen content in the reactor chamber.

[0079] Alternatively, the oxygen content in the reactor chamber can be reduced by purging the reactor chamber with an inert gas.

[0080] In the context of this invention, the expression "cleaning the chamber of the reactor with an inert gas" means injecting an inert gas stream into the chamber of the reactor so as to replace the gas present in the reactor with the injected inert gas.

[0081] Preferably, the inert gas is selected from nitrogen (N2), argon (Ar), and mixtures thereof.

[0082] Preferably, the reactor chamber is scrubbed with inert gas at least twice, more preferably at least three times.

[0083] Preferably, at the end of step (3), the oxygen content in the reactor chamber is less than or equal to 1% of the total volume of the reactor chamber.

[0084] Preferably, the heat treatment is carried out at a temperature of 200°C to 900°C, more preferably 300°C to 700°C, and even more preferably 300°C to 650°C.

[0085] Preferably, the heat treatment is carried out at low pressure, atmospheric pressure, or pressure from 0.11 MPa to 30 MPa, with the pressure parameter determined by the choice of reactor type.

[0086] In the process according to the invention, the pressure in the reactor may increase due to heat treatment. This internal pressure depends on the applied heat treatment and is not necessarily controlled or monitored.

[0087] Preferably, the heat treatment is carried out for 1 minute to 5 hours, more preferably 10 minutes to 2 hours, and even more preferably 30 minutes to 60 minutes.

[0088] According to a modified embodiment, the method according to the invention includes a post-processing step between steps (4) and (5) to convert the organic matter into carbon materials. "Organic matter" refers to organic chemical residues generated from the decomposition of silicon nanowire precursors, particularly silanes and / or diphenylsilanes. When implemented, this step primarily consists of heat treatment. Advantageously, this step is carried out under an inert atmosphere, in a carrier gas atmosphere, such as N2, Ar, or a mixture of Ar / H2, at a temperature of 500°C to 700°C, preferably 550°C to 650°C, advantageously about 600°C.

[0089] According to variations, the method according to the invention includes an additional step (6) of washing the composite material obtained at the end of step (5).

[0090] The composite material obtained at the end of step (5) can be washed with an organic solvent, preferably selected from: chloroform, ethanol, toluene, acetone, dichloromethane, petroleum ether and mixtures thereof.

[0091] Alternatively, according to a preferred embodiment, as shown in the experimental section (Example 2), the composite material obtained at the end of step (5) is washed with an acidic solution.

[0092] According to this variation, preferably, after step (6), the method further includes a supplementary step of drying the washed composite material.

[0093] Drying can be carried out, for example, by placing the composite material in an oven, preferably at a temperature of 40°C or higher, more preferably at 60°C or higher.

[0094] Preferably, the drying step lasts from 15 minutes to 12 hours, more preferably from 2 hours to 10 hours, and even more preferably from 5 hours to 10 hours.

[0095] Precursor compounds for silicon nanowires

[0096] The method according to the invention includes introducing at least one precursor compound for silicon nanowires into the chamber of a reactor. "Precursor compound for silicon nanowires" refers to a compound capable of forming silicon nanowires by implementing the method according to the invention, particularly a compound capable of forming silicon nanowires under CVD process conditions.

[0097] This compound can be introduced into the reactor chamber as either a liquid or a gas. When the compound is introduced into the reactor chamber in liquid form, it is converted into a gaseous state within the chamber by controlling the temperature and pressure. When the precursor compound for silicon nanowires is in a gaseous state, it is referred to as a reactive silicon-containing gaseous substance.

[0098] For example, if the precursor compound of SiNW is a liquid, such as diphenylsilane, the liquid precursor evaporates into a gaseous substance when the reactor reaches the appropriate temperature / pressure parameters.

[0099] Precursor compounds for silicon nanowires can be introduced into the reactor as a gas mixed with a carrier gas.

[0100] If the precursor compound is in the form of an active silicon-containing gaseous substance, it can be mixed with a carrier gas and introduced into the reactor chamber (forming an active silicon-containing gas mixture). For example, SiH4, a gas at ambient temperature / pressure, can be introduced directly into the reactor chamber alone or mixed with a carrier gas. Alternatively, liquid precursor compounds, such as diphenylsilane, Ph2SiH2, can be heated to a vapor state at the initial stage of the process and then introduced into the reactor chamber as a gas alone or mixed with a carrier gas.

[0101] Preferably, the precursor compound of the silicon nanowire or reactive silicon-containing gaseous substance is a silane compound or a mixture of silane compounds.

[0102] For the purposes of this invention, the term "silane compound" refers to a compound of formula (I):

[0103] R1-(SiR2R3) n -R4 (I)

[0104] in:

[0105] -n is an integer from 1 to 10, and

[0106] R1, R2, R3, and R4 are independently selected from hydrogen, C1 to C4. 15 Alkyl, C6 to C 12 Aryl, C7 to C 20 Aryl groups and chlorine.

[0107] According to this embodiment, preferably, the silicon-containing gaseous substance is selected from compounds of formula (I), wherein:

[0108] -n is an integer from 1 to 5, and

[0109] -R1, R2, R3 and R4 are independently selected from hydrogen, C1 to C3 alkyl, phenyl and chlorine.

[0110] 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.

[0111] According to this embodiment, preferably, the precursor compound for silicon nanowires is selected from silane, ethylsilane, propane, chlorosilane, dichlorosilane, trichlorosilane, dichlorodimethylsilane, phenylsilane, diphenylsilane, or triphenylsilane or mixtures thereof.

[0112] According to a preferred embodiment, the precursor compound for silicon nanowires is silane (SiH4) or diphenylsilane Si(C6H5)2H2. The properties and physical state of the precursor compound for silicon nanowires are selected based on the type of reactor and other parameters of the method.

[0113] Reactive silicon-containing gas mixture

[0114] The precursor compound for silicon nanowires according to the present invention can be introduced into the reactor as a gas or as a liquid converted into a gas in the reactor. The silicon nanowires are obtained by the chemical decomposition of a reactive silicon-containing gaseous substance at high temperatures, which can be mixed with a carrier gas. This mixture is hereinafter referred to as a reactive silicon-containing gas mixture.

[0115] "Carrier gas" refers to a gas selected from reducing gases, inert gases, or mixtures thereof.

[0116] Preferably, the reducing gas is hydrogen (H2).

[0117] Preferably, the inert gas is selected from argon (Ar), nitrogen (N2), helium (He), or a mixture thereof.

[0118] According to a preferred embodiment, the silicon-containing gas mixture consists of at least 1% by volume of silicon-containing gaseous material, preferably at least 10% by volume, more preferably at least 50% by volume, and even more preferably 100% by volume.

[0119] The ratio of silicon-containing gaseous material to carrier gas can be adjusted at different levels in different steps of the process.

[0120] catalyst

[0121] The method according to the invention includes introducing a SnX2 catalyst into the chamber of a reactor, wherein X is a halogen selected from F, Cl, Br and I.

[0122] In the context of this invention, "catalyst" refers to a compound selected from the formula SnX2, wherein X is a halogen selected from F, Cl, Br and I.

[0123] Preferably, in the context of this invention, "catalyst" refers to SnCl2. The role of the catalyst is to promote the growth of SiNW. Preferably, SnX2, especially SnCl2, is in particulate form.

[0124] The method according to the invention includes a solid / solid mixing step of SnX2 catalyst and growth support.

[0125] For the purposes of this invention, the term "solid / solid mixing" refers to the association and / or bonding and / or blending steps of the growth support material and the catalyst, corresponding to the mixing of the catalyst as a solid feedstock with the growth support, in order to obtain a material with substantially homogeneous composition. Solid / solid mixing is carried out without any medium or solvent.

[0126] According to a preferred embodiment of the invention, the mixture of SnX2 catalyst, preferably SnCl2 catalyst, and growth support is advantageously prepared before they are introduced into the chamber of the reactor. The resulting solid mixture is then introduced into the chamber of the reactor and steps (2) to (5) as described above are performed.

[0127] According to this embodiment, solid / solid mixing can be carried out using any industrial mixing equipment known to those skilled in the art, such as ball mills, grinding mills, hammer mills, high-energy mills, pin mills, turbine mills, fine cutting mills, impact mills, fluidized bed mills, conical screw mills, rotor mills, stirred bead mills, or jet mills. Preferably, this step of the process takes no more than 30 minutes.

[0128] According to another preferred embodiment of the invention, after the SnX2 catalyst and growth support are introduced as feedstock into the reactor chamber, solid / solid mixing of the SnX2 catalyst, preferably SnCl2, and the growth support is carried out in the reactor chamber. According to this embodiment, solid / solid mixing can be achieved, for example, by a mixing device and / or mechanism of the reactor. This may be the case, for example, when using a drum reactor with a rotating mechanism. Alternatively, solid / solid mixing can be achieved by injecting an inert gas stream into the reactor chamber, which can generate particle movement through mechanical fluidization, thereby producing their mixing.

[0129] According to the present invention, the growth support material and the catalyst are combined before or after introduction into the reactor.

[0130] For the purposes of this invention, the term "bonding" refers to a bonding step in which the growth support material and the catalyst have undergone a bonding step, which corresponds to the mixing of the catalyst with the growth support material in order to obtain a material with substantially homogeneous composition.

[0131] According to the present invention, the combination of SnX2, preferably SnCl2, and the growth support is simple and stable. Like other tin halides, SnCl2 as a raw material is a very stable product and is easier to process compared to other catalysts. In fact, SnCl2, like other tin halides, only requires solid / solid mixing with the growth support, whereas growth media based on, for example, gold nanoparticles require solid / liquid preparation followed by solvent evaporation.

[0132] When the growth support is a 2D support (e.g., ITO glass or silicon wafer), it is advantageous to use solid / solid mixing to produce a mixture of catalyst and growth support, wherein part or all of the surface of the growth support is coated with catalyst. This coating can be achieved, for example, by applying catalyst powder onto the support.

[0133] Preferably, the catalyst and growth support materials are used according to a catalyst / growth support mass ratio of 0.01:1, more preferably 0.02:0.5, and even more preferably 0.05:0.15.

[0134] The solid / solid mixing step of the catalyst and growth support material according to the present invention allows for the formation of multiple particle growth sites on the surface of the growth support material.

[0135] growth support

[0136] The method according to the invention is carried out in the presence of a growth support.

[0137] For example, the growth support can be a carbon-based material, a silicon-based material, an ITO-based material, or a carbon-containing polymer.

[0138] The growth support can be 0D, 1D, 2D or 3D material.

[0139] For example, 0D materials can be silicon nanoparticles or carbon black nanoparticles.

[0140] For example, 1D materials can be carbon polymer fibers or carbon nanotubes.

[0141] For example, 2D materials can be silicon wafers, graphene, or ITO glass.

[0142] For example, 3D materials can be powders such as silicon micron particles, graphite (natural, artificial, or expanded) or fine graphite, or carbonaceous media such as polymer materials.

[0143] The silicon-based support can be any material selected from silicon nanoparticles, silicon microparticles, and silicon wafers.

[0144] Preferably, the silicon nanoparticles have an average particle size of 1 nm to 100 nm, more preferably 30 nm to 50 nm.

[0145] Preferably, the average particle size of the silicon micron particles is from 0.1 μm to 30 μm, advantageously from 1 μm to 15 μm.

[0146] Preferably, the average width of the silicon wafer is from 1 cm to 45 cm, advantageously from 1 cm to 10 cm. The ITO-based support can be any material selected from ITO glass, with an average width of from 1 cm to 100 cm, advantageously from 1 cm to 10 cm.

[0147] 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 mixtures of two or more of them.

[0148] The average particle size of the support can be measured using laser diffraction.

[0149] When the growth support is a carbon-based support, it can be in the form of particles, particle aggregates, non-aggregate sheets, or aggregate sheets.

[0150] Advantageously, according to this deformation, the carbon-based support has a 1m 2 / g to 100m 2 / g, more preferably 1m 2 / g to 70m 2 / g, or even better 3m 2 / g to 50m 2 / g Bruner-Emmett-Teller (BET) surface area.

[0151] According to a preferred embodiment of this modification, the carbon-based material is selected from graphite, graphene, and carbon, preferably graphite powder with an average particle size of 0.01 μm to 50 μm.

[0152] According to another variation, the growth support is a carbonaceous polymer material. WO2021018598 discloses the use of polymers as growth supports.

[0153] When the growth support is a carbonaceous polymer material, preferably, the polymer material has a decomposition temperature determined by thermogravimetric analysis, which is higher than or equal to 200°C, more preferably higher than or equal to 300°C, more preferably higher than or equal to 400°C, and advantageously higher than or equal to 500°C.

[0154] Advantageously, according to this variation, the polymer material is selected from synthetic or naturally sourced fibrous polymer materials, preferably from synthetically sourced fibrous polymer materials.

[0155] More advantageously, according to this variation, the polymer material is selected from polybenzothiazole, polyamine, polyimide, polyurethane, polybenzothiazole, polyamine ... Zrazole, polyamide, polybenzimidazole and mixtures thereof, preferably selected from polyamide.

[0156] According to this variation, even more advantageously, the polymer material is poly(p-phenylene terephthalamide), also known as...

[0157] When the growth support is a polymer material, the method according to the present invention includes:

[0158] i) Prepare composite materials containing polymer materials and SiNW according to the method defined above, and

[0159] ii) Polymer materials for carbonized polymer composites. Detailed process parameters suitable for preparing silicon / polymer composites and silicon / carbon composites are disclosed in WO2021018598.

[0160] The diameter of silicon nanowires can be controlled by the physical properties of the growth support. This possibility was demonstrated in the experimental section on 3D growth supports:

[0161] As described in the experimental section, the diameter of nanowires prepared using SnCl2 is directly affected by the growth support material. In fact, it has been observed that as the specific surface area (SSA) of the growth support material increases (SSA > 5 m²), the diameter of the nanowires increases. 2 With the increase of ( / g), SiNW exhibits an average diameter of approximately 80 nm to 90 nm. However, when using materials with a lower specific surface area (SSA < 5m²), the diameter decreases. 2 When grown in the presence of a growth support material ( / g), the average diameter was found to be approximately 150 nm to 160 nm.

[0162] The morphology of the growth support material can also be used to control the diameter of the nanowires. For example, expanded graphite provided SiNWs with an average diameter of approximately 140 nm (Example 3).

[0163] Doped materials

[0164] According to one embodiment, the method according to the invention may include introducing at least one doping material into the reactor.

[0165] In the context of this invention, the term "doped material" is understood to refer to a material capable of altering the electrical conductivity of silicon. Doped materials in this context include, for example, materials rich in phosphorus, boron, or nitrogen atoms.

[0166] Preferably, according to this embodiment, the dopant material is introduced into the reactor chamber via a precursor selected from diphenylphosphine, triphenylborane, and di- and triphenylamine. According to the first variation, this introduction is achieved before SiNW growth begins.

[0167] According to another variation, the precursor of the doped material is introduced simultaneously (and possibly as part of) a mixture of gas and reactive silicon-containing gas.

[0168] Preferably, the molar ratio of the dopant material to the precursor compound of the silicon nanowire is 10. -4 mol% to 10 mol%, preferably 10 mol%. -2 mol% to 1 mol%.

[0169] reactor

[0170] According to the first variation, the method is implemented in a fixed-bed reactor.

[0171] According to the second variation, the method is carried out in a tubular chamber of a drum reactor that includes a rotating and / or mixing mechanism.

[0172] First transformation

[0173] According to the first variation, the method is implemented in a fixed-bed reactor.

[0174] • Characteristics of the reactor:

[0175] Fixed-bed reactors are preferably closed reactors.

[0176] For example, WO2019020938 discloses a reactor that can be used to implement the method according to the invention. In this document, it is used in the "closed reactor" mode.

[0177] ·parameter:

[0178] According to this first modification, the reactor is closed by placing the reactor under a vacuum, preferably less than or equal to 10. -1 Ba (10) -2 Under a pressure of MPa, the oxygen content in the reactor chamber can be reduced.

[0179] Alternatively, the oxygen content in the reactor chamber can be reduced by purging the reactor chamber with an inert gas.

[0180] In the context of this invention, the expression "cleaning the chamber of the reactor with an inert gas" means injecting an inert gas stream into the chamber of the reactor so as to replace the gas present in the reactor with the injected inert gas.

[0181] Preferably, the inert gas is selected from nitrogen (N2), argon (Ar), and mixtures thereof. Preferably, the reactor chamber is purged with an inert gas at least twice, more preferably at least three times.

[0182] Preferably, at the end of step (3), the oxygen content in the reactor chamber is less than or equal to 1% of the total volume of the reactor chamber.

[0183] Based on this variation, the precursor compound of silicon nanowires is typically introduced into the reactor as a liquid.

[0184] According to this variation, the catalyst, precursor compound of silicon nanowires, and growth support can be introduced into the reactor in the form of a mixture.

[0185] According to this modification, preferably, the reactor includes at least two loading zones, a first zone that allows the reception of precursor compounds for silicon nanowires, and a second zone that allows the reception of growth supports and catalysts.

[0186] Depending on the alternative configuration, the first and second charging zones are located at the same height within the reactor chamber.

[0187] According to the preferred alternative, the second loading zone is raised relative to the first loading zone.

[0188] • The steps of the method:

[0189] According to this modification, the method according to the invention advantageously includes:

[0190] (1') Solid / solid mixing of tin halide SnX2 and growth support in a mixing apparatus.

[0191] (1) Introduce the mixture obtained in step (1') into the chamber of the reactor.

[0192] (2) Introduce at least one precursor compound of silicon nanowires into the chamber of the reactor.

[0193] (3) Reduce the oxygen content in the reactor chamber.

[0194] (4) Heat treatment is performed at temperatures ranging from 200℃ to 900℃, and

[0195] (5) Recycle products.

[0196] Steps (1') and (1) are performed in the order stated, but steps (2), (3) and (4) may be performed in this order or another order.

[0197] Second transformation

[0198] According to a second variation, the method according to the invention is carried out in a tubular chamber of a drum reactor comprising a rotating and / or mixing mechanism.

[0199] • Characteristics of the reactor:

[0200] The aforementioned rotary drum reactor comprises at least one tubular chamber heated by a furnace, wherein the growth support material and tin halide catalyst can be loaded as separate materials or as a mixture. The reactor integrates a rotation mechanism and / or a mixing mechanism. The reactor may include two tubular chambers. The longitudinal axis of the tubular chambers is horizontal, or may be tilted at an angle of 20° to the horizontal axis. The reactor also includes a product feed system and a product discharge system, allowing for semi-continuous production of the silicon-tin and growth support composite materials. The rotary drum reactor includes reactor pressure control devices, such as needle valves or pressure controllers.

[0201] A typical mechanical rotary drum reactor is A fluidized bed reactor in which fluidization is generated by the rotation of a horizontal axis spiral in a tubular chamber.

[0202] Another typical mechanical drum reactor includes a rotating tubular chamber, in which fluidization is generated by the rotation of the tubular chamber about its longitudinal axis.

[0203] ·parameter:

[0204] This variation is particularly interesting because the fluidization generated by the reactor machinery facilitates contact between the growth support and the silicon-containing reactive gaseous material. It is also particularly interesting because it allows for the direct introduction of the catalyst and growth support, and their mixing within the reactor chamber.

[0205] According to this modification, it is preferable to introduce the precursor compound of silicon nanowires as a gas into the reactor.

[0206] • The steps of the method:

[0207] According to this modification, the method according to the invention advantageously includes:

[0208] (1A) At least SnX2 catalyst, preferably SnCl2 catalyst, and optionally growth support are introduced into the tubular chamber of the reactor.

[0209] (1B) Heating the tubular chamber under a carrier gas flow

[0210] (1') Rotate the tubular chamber and / or activate the mixing mechanism.

[0211] (2) Introduce the reactive silicon-containing gas mixture into the tubular chamber.

[0212] (3) The pressure inside the reactor chamber is controlled by the flow of a gas mixture.

[0213] (4) Heat treatment is performed in a tubular chamber under rotation and / or mixing, in the presence of a reactive silicon-containing gas mixture, at a temperature of 200°C to 900°C.

[0214] (5) Recycled products,

[0215] According to this variation, most steps must be completed in this order; however, the rotation and / or mixing in step (1') may begin before or after step (1A) or step (1B).

[0216] It should be understood, or, according to this variation, that the method can be carried out by first solid-solid mixing the SnX2 catalyst, preferably the SnCl2 catalyst, and the growth support before introducing them into the tubular chamber, and then performing the same steps (1) to (5) as described above.

[0217] At the end of step (4), the reactor can be opened and steps (2), (3) and (4) can be repeated again to continue SiNW growth before the product is recovered.

[0218] According to this deformation, the heat treatment in step (4) is carried out at low pressure (below atmospheric pressure), or at atmospheric pressure or above atmospheric pressure.

[0219] Preferably, when the reactor is a drum reactor including a rotating and / or mixing mechanism, the heat treatment in step (4) is carried out at a pressure higher than atmospheric pressure.

[0220] Material composition:

[0221] The method disclosed above provides a composite material comprising, preferably substantially composed of, a growth support, silicon nanowires, and tin particles. The material may contain trace amounts of halogens, particularly chlorine.

[0222] Advantageously, in the obtained composite material, the Si content is greater than 5% by weight of silicon relative to the total weight of the material, preferably greater than 20%.

[0223] The tin particles originate from the decomposition of tin(II) halides, particularly tin(II) chloride, during the reaction. The composite material preferably contains tin particles, with the amount of tin ranging from 1% to 10% by weight, more preferably from 1% to 5% by weight, relative to the total weight of the material.

[0224] The remaining tin halide (II), especially tin chloride, can be partially removed by acid treatment of the composite material (see Example 2 and ICP analysis).

[0225] Regarding the remaining tin(II) halides, particularly tin chloride, we mean that not all of the tin(II) halides react with silicon during the process. This observation is consistent with the study by Dusanes et al. (10) (see Example 1.d), in which the remaining tin(II) halides, particularly tin chloride, that have reacted during the process have been converted into tin (metal) bonded to SiNW.

[0226] Trace amounts of halogens, especially chlorine, can be found in composite materials. The value of halogens, especially chlorine, relative to the total weight of the material is typically less than 1% by weight, preferably less than 0.1% by weight.

[0227] Silicon materials produced by the chemical vapor phase decomposition of silicon-containing gaseous substances can be in the form of wires, worms, rods, or filaments.

[0228] According to a preferred embodiment, the silicon material is in the form of nanowires.

[0229] In the context of this invention, the term "nanowire" is understood to refer to an elongated element that is similar in shape to a wire and has a diameter on the nanometer scale.

[0230] Preferably, the diameter of the silicon nanowire is 1 nm to 250 nm, more preferably 10 nm to 200 nm, and even more preferably 30 nm to 180 nm.

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

[0232] Advantageously, silicon, preferably silicon nanowires, accounts for 1% to 70% of the total weight of the silicon-based composite material, preferably 10% to 70% of the total weight, more preferably 20% to 70% of the total weight, even more preferably 30% to 70% of the total weight, and advantageously 50% to 70% of the total weight.

[0233] Silicon-based composite materials are preferably obtained in powder form.

[0234] Applications of silicon-tin composite materials

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

[0236] The electrode, including the current collector, is prepared using methods conventionally used in the art. For example, the anolyte active material, composed of the silicon composite material of the present invention, is mixed with a binder, solvent, and conductive agent. If desired, 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] This electrode can be used to manufacture a lithium secondary battery, which includes a separator and an electrolyte solution, which are commonly used in the art and are disposed between the cathode and the anode.

[0239] Brief description of the attached figures

[0240] Figure 1 This is a photograph of the Si nanowire / KS4 graphite composite material at low magnification obtained by scanning electron microscopy (SEM) (Example 1).

[0241] Figure 2 This is a high-magnification photograph of the Si nanowire / KS4 graphite composite material obtained by scanning electron microscopy (SEM) (Example 1).

[0242] Figure 3 This is a graph showing the potential distribution of a battery prepared from Si nanowire / KS4 graphite composite material (Example 1): X = battery capacity, in mA·h, Y = battery potential, in V.

[0243] Figure 4 This is a graph showing the derivative of the potential distribution of a battery prepared from Si nanowire / KS4 graphite composite material (Example 1): X = battery capacity, in mA·h, Y = battery potential, in V.

[0244] Figure 5 This is a photograph of the Si nanowire / KS4 composite material at low magnification obtained by scanning electron microscopy (SEM) after the HCl washing step (Example 2).

[0245] Figure 6 This is a high-magnification photograph of the Si nanowire / KS4 graphite composite material after the HCl washing step, obtained by scanning electron microscopy (SEM) (Example 2).

[0246] Figure 7 This is a graph showing the potential distribution of a battery made of Si nanowire / KS4 graphite composite material after the HCl washing step (Example 2): X = battery capacity, in mA·h, Y = battery potential, in V.

[0247] Figure 8 This is a photograph of the Si nanowire / BNB90 graphite composite material at low magnification obtained by scanning electron microscopy (SEM) (Example 3).

[0248] Figure 9 This is a high-magnification photograph of the Si nanowire / BNB90 graphite composite material obtained by scanning electron microscopy (SEM) (Example 3).

[0249] Figure 10 This is a graph showing the potential distribution of a battery prepared from Si nanowire / BNB90 graphite composite material (Example 3): X = battery capacity, in mA·h, Y = battery potential, in V.

[0250] Figure 11 This is a photograph of the Si nanowire / SLP50 graphite composite material at low magnification obtained by scanning electron microscopy (SEM) (Example 4).

[0251] Figure 12 This is a high-magnification photograph of the Si nanowire / SLP50 composite material obtained by scanning electron microscopy (SEM) (Example 4).

[0252] Figure 13 This is a graph showing the potential distribution of a battery prepared from Si nanowires / SLP50 graphite composite material (Example 4): X = battery capacity, in mA·h, Y = battery potential, in V.

[0253] Figure 14 This is a photograph of the Si nanowire / Si nanoparticle composite material (Example 5) at low magnification, obtained by scanning electron microscopy (SEM).

[0254] Figure 15 This is a high-magnification photograph of the Si nanowire / Si nanoparticle composite material (Example 5) obtained by scanning electron microscopy (SEM).

[0255] Figure 16 The potential distribution of the battery prepared from the Si nanowire / Si nanoparticle composite material (Example 5) is shown (X = battery capacity, in mA·h, Y = battery potential, in V).

[0256] Figure 17 This is a low-magnification photograph of the Si nanowire / tin / KS4 composite material (Example 6) obtained by scanning electron microscopy (SEM) after SiH4 treatment.

[0257] Figure 18 This is a high-magnification photograph of the Si nanowire / tin / KS4 composite material (Example 6) obtained by scanning electron microscopy (SEM) after SiH4 treatment.

[0258] Experimental section:

[0259] In the following examples, unless otherwise stated, content and percentage are by mass.

[0260] Material

[0261] Reactor (fixed bed): Stainless steel reactor (internal volume = 1L, diameter = 100mm, height = 125mm).

[0262] - Ball mill equipment: Model PM100, sold by Retsch.

[0263] -Silicon precursor: diphenylsilane Si(C6H5)2H2, sold by Sigma-Aldrich (CAS No.: 775-12-2).

[0264] - Catalyst: SnCl2 sold by Strem Chemicals, Inc.

[0265] - Graphite growth support: Imerys sells BNB90 graphite (SSA = 21.18m). 2 / g), KS4 graphite (SSA=24.48m) 2 / g) and SLP50 graphite (SSA = 4.97m) 2 / g)

[0266] - Silicon NP: Average particle size ≤50nm, sold by GetNanoMaterials, commercial reference number Si-100

[0267] - Conductive filler: Imerys company, under the name C-NERGY TM Actilion GHDR-15-4 is a type of graphite powder sold in China.

[0268] - Carbon black, sold by Imerys, commercial reference number Tim cal C-energy C65 (CAS No.: 1333-86-4).

[0269] - Carboxymethyl cellulose (CMC) sold by Alfa-Aesar (CAS No.: 9004-32-4).

[0270] - Styrene-butadiene rubber (SBR) sold by MTI (CAS No.: 9003-55-8).

[0271] - Electrolyte: Lithium hexafluorophosphate (LiPF6) (1M) dissolved in a mixture of ethylene carbonate (EC) and diethyl carbonate (DEC) (volume ratio 1:1), the mixture containing 10% by weight of fluoroethylene carbonate (FEC) and 2% by weight of vinylene carbonate (additive), sold by Solvionic.

[0272] Example 1: Synthesis of KS4 graphite / SiNW composite material (M1)

[0273] a) KS4 graphite and SnCl2 were mixed as a precatalyst material.

[0274] Mix 3g of graphite KS4 with 0.5g of SnC l2 Mix the powder and introduce it into the steel bowl of the ball mill. Then, before tightly sealing, place 40g of 3mm steel balls into the bowl. Mix the powder at 400rpm for 10 minutes and 30 seconds.

[0275] The pre-catalyst material is recovered by extracting the balls using a sieve.

[0276] b) Growth of silicon nanowires (Process 1)

[0277] Place the material obtained at the end of step a) into a glass cup inside the fixed-bed reactor. Then pour 50 mL of diphenylsilane (Ph₂SiH₂) into the bottom of the reactor.

[0278] After sealing the reactor, the gas pipeline and temperature heating element were connected to the reactor. The reactor was then placed under vacuum and purged several times with N2 to reduce the oxygen content. Subsequently, the reactor was heated by resistance heating placed in contact with the outer surface of the reactor. The heating cycle was as follows: a gradient heating from 20°C to 430°C over 30 minutes, followed by a 60-minute resting period at 430°C, then heating was stopped, and the reactor was cooled to room temperature. Finally, the reactor was opened to recover the composite material.

[0279] c) Post-processing of graphite / tin / silicon composite materials (process 2)

[0280] The carbonization of organic matter produced by the decomposition of Ph2SiH2 is carried out by heat treatment.

[0281] The composite material obtained at the end of process 1 was placed in a crucible and then introduced into a horizontal quartz tube furnace. The furnace inlet was connected to an argon (Ar) and hydrogen (H2) gas line, with the Ar / H2 ratio controlled at 97.5:2.5 (v / v), continuously flowing through the material. The heat treatment was performed, heating to 600°C at a rate of 6°C / min for 2 hours, followed by natural cooling. Finally, the furnace was opened to recover composite M1.

[0282] Figure 1 and Figure 2This is a SEM micrograph of M1, a composite material of SiNW 101 and 201 with an average diameter of 80 nm.

[0283] d) Figure 2 Description

[0284] Figure 2 The image shows a mixture of SiNW 201 and small dots 202 dispersed on the surface of KS4 graphite 203. These small dots 202 are tin particles that are too small to react with Si during the growth of SiNW. This observation is consistent with the findings of Dusanes et al. (11).

[0285] Example 2: Synthesis of a "water-washed" KS4 graphite / tin / silicon NW composite material (M2)

[0286] Steps a), b), and c) are the same as in Example 1.

[0287] d) Cleaning of KS4 graphite / silicon composite material (process 3)

[0288] 10 g of composite M1 was introduced into a beaker equipped with a magnetic stir bar. Then, 100 mL of 5% HCl was added to the beaker. The mixture was stirred at 600 rpm for 1 hour. After one hour, the mixture was filtered through a Buchner funnel fitted with a filter and then washed with distilled water until the pH returned to 6-7. Finally, excess water was removed by adding ethanol. The filter cake was then dried overnight in a heating chamber at 60°C to recover composite M2.

[0289] Figure 5 and Figure 6 The composite material M3, consisting of SiNW501 and 601 with an average diameter of 80 nm, is shown.

[0290] Example 3: Synthesis of BNB90 graphite / tin / SiNW composite material (M3)

[0291] a) BNB90 graphite and SnCl2 were mixed as a precatalyst material.

[0292] Mix 3g of BNB90 graphite with 0.5g of SnCl2 and introduce the mixture into the steel bowl of a ball mill. Then, before tightly sealing, place 40g of 3mm steel balls into the bowl. Mix the graphite-SnCl2 material at 400rpm for 10 minutes and 30 seconds.

[0293] The pre-catalyst material is recovered by extracting the balls using a sieve.

[0294] b) Growth of silicon nanowires (Process 1)

[0295] The precatalyst material obtained at the end of step a) is placed in a glass cup inside a fixed-bed reactor. Then, 50 mL of diphenylsilane (Ph₂SiH₂) is poured into the bottom of the reactor.

[0296] After sealing the reactor, the gas pipeline and temperature heating element were connected to the reactor. The reactor was then placed under vacuum and purged several times with N2 to reduce the oxygen content. Subsequently, the reactor was heated by resistance heating placed in contact with the outer surface of the reactor. The heating cycle was as follows: a gradient heating from 20°C to 430°C over 30 minutes, followed by a 60-minute resting period at 430°C, then heating was stopped, and the reactor was cooled to room temperature. Finally, the reactor was opened to recover the composite material.

[0297] c) Post-processing of BNB90 graphite / tin / silicon composite material (process 2)

[0298] The carbonization of organic matter produced by the decomposition of Ph2SiH2 is carried out by heat treatment.

[0299] The composite material obtained at the end of process 1 was placed in a crucible and then introduced into a horizontal quartz tube furnace. The furnace inlet was connected to an argon (Ar) and hydrogen (H2) gas line, with the Ar / H2 ratio controlled at 97.5:2.5 (v / v), continuously flowing through the material. The heat treatment was performed, heating to 600°C at a rate of 6°C / min for 2 hours, followed by natural cooling. Finally, the furnace was opened to recover composite material M3.

[0300] Figure 8 and Figure 9 The composite material M3 is shown, which has SiNW801 and 901 with an average diameter of 145 nm on BNB90 graphite 802.

[0301] Table 1 shows the ICP analyses of the Si nanowire / KS4 composites from Example 1 (without post-treatment) and Example 3 (after the HCl washing step):

[0302] Table 1

[0303] Composite materials Si (% by weight) C (% by weight) Sn (% by weight) Cl (% by weight) O (% by weight) M1 20 71 4.4 0.02 5.6 M3 20.8 70 2.28 0.007 5.7

[0304] Example 4: Synthesis of SLP50 graphite / tin / SiNW composite material (M4)

[0305] a) SLP50 graphite and SnCl2 were mixed as a precatalyst material.

[0306] Mix 3g of SLP50 graphite with 0.5g of SnCl2 and introduce the mixture into the steel bowl of a ball mill. Then, before tightly sealing, place 40g of 3mm steel balls into the bowl. Mix the SLP50-SnCl2 material at 400rpm for 10 minutes and 30 seconds.

[0307] The pre-catalyst material is recovered by extracting the balls using a sieve.

[0308] b) Growth of silicon nanowires (Process 1)

[0309] The catalyst material obtained at the end of step a) is placed in a glass cup inside a fixed-bed reactor. Then, 50 mL of diphenylsilane (Ph₂SiH₂) is poured into the bottom of the reactor.

[0310] After sealing the reactor, the gas pipeline and temperature heating element were connected to the reactor. The reactor was then placed under vacuum and purged several times with N2 to reduce the oxygen content. Subsequently, the reactor was heated by resistance heating placed in contact with the outer surface of the reactor. The heating cycle was as follows: a gradient heating from 20°C to 430°C over 30 minutes, followed by a 60-minute resting period at 430°C, then heating was stopped, and the reactor was cooled to room temperature. Finally, the reactor was opened to recover the composite material.

[0311] c) Post-processing of SLP50 graphite / tin / silicon composite material (process 2)

[0312] The carbonization of organic matter produced by the decomposition of Ph2SiH2 is carried out by heat treatment.

[0313] The composite material obtained at the end of process 1 was placed in a crucible and then introduced into a horizontal quartz tube furnace. The furnace inlet was connected to an argon (Ar) and hydrogen (H2) gas line, with the Ar / H2 ratio controlled at 97.5:2.5 (v / v), continuously flowing through the material. The heat treatment was performed, heating to 600°C at a rate of 6°C / min for 2 hours, followed by natural cooling. Finally, the furnace was opened to recover composite material M4.

[0314] Figure 11 and 12 The composite material M4 is shown, consisting of Si NW 1101 and 1201 with an average diameter of 158 nm on SLP50 graphite 1102 and 1202.

[0315] Example 5: Synthesis of silicon NP / tin / silicon NW composite material (M5)

[0316] a) Si nanoparticles and SnCl2 were mixed as a precatalyst material.

[0317] 1g of silicon NP was mixed with 190mg of SnCl2 and introduced into a zirconia bowl of a ball mill. Then, 10mm zirconia balls were placed in the bowl before tightly sealing it. The Si NP-SnCl2 material was mixed at 400rpm for 10 minutes and 30 seconds.

[0318] The pre-catalyst material is recovered by extracting the balls using a sieve.

[0319] b) Growth of silicon nanowires (Process 1)

[0320] The catalyst material obtained at the end of step a) is placed in a glass cup inside a fixed-bed reactor. Then, 50 mL of diphenylsilane (Ph₂SiH₂) is poured into the bottom of the reactor.

[0321] After sealing the reactor, the gas pipeline and temperature heating element were connected to the reactor. The reactor was then placed under vacuum and purged several times with N2 to reduce the oxygen content. Subsequently, the reactor was heated by resistance heating placed in contact with the outer surface of the reactor. The heating cycle was as follows: a gradient heating from 20°C to 430°C over 30 minutes, followed by a 60-minute resting period at 430°C, then heating was stopped, and the reactor was cooled to room temperature. Finally, the reactor was opened to recover the composite material.

[0322] c) Post-processing of Si nanoparticle / tin / silicon composite materials 2)

[0323] The carbonization of organic matter produced by the decomposition of Ph2SiH2 is carried out by heat treatment.

[0324] The composite material obtained at the end of process 1 was placed in a crucible and then introduced into a horizontal quartz tube furnace. The furnace inlet was connected to an argon (Ar) and hydrogen (H2) gas line, with the Ar / H2 ratio controlled at 97.5:2.5 (v / v), continuously flowing through the material. The heat treatment was performed, heating to 600°C at a rate of 6°C / min for 2 hours, followed by natural cooling. Finally, the furnace was opened to recover composite material M5.

[0325] Figure 14 and Figure 15 An M5 composite of SiNW 1401 and 1501 is shown, with an average diameter of 165 nm.

[0326] Example 6: Synthesis of KS4 graphite / tin / SiNW composite material (M6)

[0327] a) A mixture of KS4 graphite and SnCl2 as a precatalyst material

[0328] Mix 35g of SLP50 graphite with 2.73g of SnCl2 and introduce the mixture into the steel bowl of a ball mill. Then, place 50 10mm steel balls into the bowl and seal it tightly. Mix the KS4-SnCl2 material at 300rpm for 20 minutes and 30 seconds.

[0329] The pre-catalyst material is recovered by extracting the balls using a sieve.

[0330] b) Growth of silicon nanowires (Process 1)

[0331] The precatalyst material obtained at the end of step a) is uniformly placed in a quartz tube inside a fixed-bed reactor.

[0332] After connecting the gas line to the reactor and shutting off the heating chamber, the quartz tube was flushed with N2 at a rate of 5 slm for several minutes to reduce the oxygen content. The reactor was then heated by a heating device placed in contact with the outer surface of the quartz tube. The heating and gas injection cycle was as follows: heating from 20°C to 650°C for 1 hour at a gas flow rate of 5 slm Ar / H2 2.5%, followed by standing at 650°C for 4.3 hours at 5 slm N2 / SiH4 0.9% (L / min), stopping heating, and then cooling the reactor to room temperature at a gas flow rate of 5 slm N2. Finally, the reactor was opened to recover the composite material.

[0333] Figure 17 and Figure 18 An SEM micrograph of the Si nanowire / tin / KS4 composite material M6 obtained in this embodiment is shown.

[0334] c) Figure 17 and Figure 18 Description

[0335] Figure 17 and Figure 18 A mixture of Si NW 1701 and 1801 and small dots 1803 dispersed on the surfaces of KS4 graphite 1702 and 1802 is shown. These small dots 1803 are tin particles that are too small to react with Si during the growth of SiNW. This observation is consistent with the findings of Dusanes et al. (11).

[0336] Example 7: Preparation of Lithium-ion Battery Electrodes

[0337] Electrochemical characterization of materials M1, M2, M3, M4 and M5 was carried out by preparing coin cells, wherein the anode contained one of the prepared materials as the active material.

[0338] a) Mixed with conductive filler

[0339] In the IKA Ultra-Turrax disperser, the composite material of M1, M2, M3, M4 or M5 according to the present invention is mixed with graphite powder using YSZ 3mm diameter grinding balls.

[0340] The composite material and graphite were introduced into the disperser at a weight ratio of 38:62.

[0341] Mix at 7 RPM for 10 minutes.

[0342] The mixed materials are eventually recycled for further processing or characterization.

[0343] b) Preparation of coin batteries

[0344] The synthesized material was mixed with graphite powder (Actilion GHDR-15-4) at a ratio of 38:62. Actilion graphite reference electrodes were fabricated using pure graphite as the active material. Both systems used carbon black C-NERGY C65 as a conductive additive, sodium carboxymethyl cellulose (Na-CMC) and styrene-butadiene rubber (SBR) as binders, and deionized water as a solvent. The weight ratio of active material:C65:binder was 95:1:4. Water was added to achieve a viscosity suitable for electrode processing, resulting in a dry content of approximately 40% by weight. Wet mixing was performed at speed 5 for 30 minutes. Each electrode ink was cast onto a 20 μm thick copper foil. After air drying, the electrodes were further dried in an oven at 65°C for 2 hours. The electrodes were then cut into 14 mm diameter discs at approximately 1 t / cm². 2 The mixture is rolled and weighed, and finally vacuum dried overnight at 110°C.

[0345] A half-coin cell (Kanematsu) was fabricated in an Ar glove box using metallic Li as the counter and reference electrodes, a layer of Whatman glass fiber and a layer of Celgard 2325 separator, and the electrode of interest. The company uses 316L stainless steel. The electrolyte used for impregnating the electrode and separator materials is 1M LiPF6 dissolved in EC:DEC (1 / 1 volume / volume), with 10 wt% FEC (ethylene fluoride carbonate) and 2 wt% Vc (ethylene carbonate) additives. The batteries are then sealed using an automatic press and removed from the glove box for measurement on a battery cycler. Seven formation cycles are performed before regular cycling at a 1C rate. The formation cycle consists of two cycles at C / 10 and five cycles at C / 5, using constant current and constant potential discharge (lithiation) and constant current charge (delithiation).

[0346] c) Measurement of electrochemical performance

[0347] The battery performance was measured by constant current cycling using a biological BCS-805 cycling system equipped with eight channels, each of which includes two different electrodes.

[0348] 1-Potential Distribution Diagram

[0349] During the C / 10 cycle, the potential distribution of batteries C1, C2, C3, C4, and C5 was determined by measuring the battery potential as the battery capacity changed.

[0350] Figure 3 , Figure 7 , Figure 10 , Figure 13 and Figure 16The potential distributions obtained from cells C1, C2, C3, C4, and C5 are shown, respectively, and these cells are recorded in the second cycle (third composition cycle) (third formation cycle) of C / 10.

[0351] exist Figure 3 , Figure 7 , Figure 10 and Figure 13 In the potential distribution plots of the batteries obtained from the composite materials of M1, M2, M3, and M4, the cumulative electrochemical activity of the graphite and silicon materials is shown, demonstrating that the composite materials are both electrochemically and electrochemically active. The inflection point / pseudo-plateau near 0.45V during charging (lithiation) highlights the electrochemical activity of silicon with lithium ions, which is evident in the capacity derivative plots comparing the graphite electrodes with those of the silicon-graphite composite materials. Figure 13 It is also clearly visible in the text.

[0352] exist Figure 16 Similar to other materials, composite material M5 exhibits a cumulative electrochemical activity between the growth support, silicon nanoparticles, and silicon NW material, demonstrating its electrochemical and electrochemical activity as a lithium-ion anode material. During charging (delithiation), the electrochemical activity of silicon with lithium ions is particularly prominent through an inflection point / pseudo-plateau near 0.45V.

[0353] 2-Initial reversible capacity

[0354] Table 2 shows the initial reversible capacity of the battery measured at C / 10 during the first cycle.

[0355] Table 2

[0356] Battery C1 C2 C3 C4 C5 Initial capacity (mA.h / g) 822 872 864 713 1869

[0357] Battery C1, prepared from composite material M1, and battery C2, prepared from composite material M2, have similar initial reversible capacities. Therefore, composite materials M1 and M2 have the same silicon active content (approximately 20%). However, compared to material M1, the initial capacity of material M2 is increased due to acid washing. Indeed, the capacity is increased from potentially inhibiting compounds such as unreacted SnCl2 and SnO. x The presence of SiO2 may purify the material and increase its initial capacity.

[0358] Furthermore, a comparison of C1, C3, and C4 cells from composite materials M1, M3, and M4 revealed an increase in initial capacity as the silicon active content increased (approximately 15% for 822 mA·h / g, approximately 16% for 864 mA·h / g, and approximately 11% for 713 mA·h / g, respectively).

[0359] In summary, these results demonstrate that the specific surface area and morphology of the growth support allow for tuning of the SiNW growth ratio on the growth support and for controlling the electrical and electrochemical properties of the composite material.

[0360] References

[0361] (1)ST.Lee et al., Nano Today, 2013, 8, 75-97

[0362] (2)S.Sadki et al, Nanoscale Res. Lett., 2013, 8, 1-5

[0363] (3)P.Yang et al., Nature, 2008, 45l, 163-167

[0364] (4)Jeon et al., Materials Letters 63(2009)777779

[0365] (5)Ball et al, CrystEngComm 15(2013)3808-3815

[0366] (6)Dai et al., Nanotechnology 29(2018)435301

[0367] (7)Ngo et al., MRS Proceedings 1258(2010)1258-P04-51

[0368] (8)Chockla et al., Chemistry of Materials 24(2012)378-3745

[0369] (9)Gérrard EJPoinern et al., Journal of Colloid and InterfaceScience 352(2010)259-264

[0370] (10)Dusanes et al., JNanopart Res, 2020, 22, 363.

Claims

1. A method for preparing a composite material comprising at least silicon nanowires and tin, comprising at least the following steps: (1) At least the following should be introduced into the reactor chamber: - Tin halide SnX2, where X is selected from: F, Cl, Br, I, and - Growth support, (1') Solid / solid mixed tin halide SnX2 and growth support, (2) Introduce at least one precursor compound of silicon nanowires into the chamber of the reactor. (3) Reduce the oxygen content in the reactor chamber. (4) Heat treatment is performed at temperatures ranging from 200°C to 900°C, and (5) Recycle products, Steps (1), (1'), (2), (3) and (4) are performed in this order or another order.

2. The method of claim 1, wherein it is carried out in a fixed-bed reactor.

3. The method of claim 1, wherein it is carried out in a tubular chamber of a drum reactor driven by a rotating and / or mixing mechanism.

4. The method according to any one of the preceding claims, wherein the tin halide is SnCl2.

5. The method of claim 1, wherein the tin halide and the growth support are mixed together before being introduced into the reactor.

6. The method according to claim 1, wherein the heat treatment is performed at a temperature of 300°C to 650°C.

7. The method of claim 1, wherein the heat treatment is performed for 1 minute to 5 hours.

8. The method of claim 7, wherein the heat treatment is performed for 10 minutes to 2 hours.

9. The method of claim 1, wherein it includes a post-processing step to convert the organic material generated from the precursor compound of the silicon nanowires into a carbon material.

10. The method of claim 1, wherein it comprises an additional step (6) of treating the composite material obtained at the end of step (5) with an acidic solution.

11. The method of claim 1, wherein the precursor compound of the silicon nanowire is a silane compound or a mixture of silane compounds.

12. The method according to claim 11, wherein the precursor compound of the silicon nanowire is silane SiH4 or diphenylsilane Si(C6H5)2H2.

13. The method according to claim 1, wherein the growth support is a carbon-based material, a silicon-based material, an ITO-based material, or a carbonaceous polymer.

14. A method of manufacturing an electrode comprising a current collector, the method comprising (i) carrying out the method of claim 1 to prepare a composite material comprising at least silicon nanowires and tin as an electrode active material, and (ii) covering at least one surface of the current collector with a composition comprising the electrode active material.

15. A method of manufacturing an energy storage device, the energy storage device comprising a cathode, an anode, and a partition disposed between the cathode and the anode, wherein the method comprises carrying out the method of claim 14 to manufacture at least one electrode.

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