Method for producing silicon nanowires and copper-containing materials

Abstract

A method for producing a composite material containing at least silicon nanowires and copper is provided, which can be carried out without pretreatment and without a solvent. The method for producing a composite material according to the present invention comprises: (A) placing at least: copper halide (CuX) in a reactor chamber; n (B) introducing a solid / solid mixture of X, Cl, Br, I, and n is an integer selected from 1 or 2; and a powdered growth support; (B) growing silicon nanowires in the reactor chamber from at least one precursor compound of the silicon nanowires selected from a silane compound or a mixture of silane compounds; and (C) recovering the product.

Description

[Technical field]

[0001] The present invention relates to a method for growing silicon nanowires using copper halides as metal seed precursors. The method is inexpensive and robust, and copper halides are converted into silicides (Cu, x S y The in-situ conversion of the silicon nanowires into silicon nanoparticles (SiO2) enables the growth of silicon nanowires. The silicon nanowire-based composites prepared by the method of the present invention can be used in a variety of applications, including nanoelectronics, microelectronics, spintronics, energy conversion and harvesting, sensors, and anode materials for lithium-ion batteries. [Background technology]

[0002] Silicon, an element with a high terrestrial abundance and unique properties, is one of the central players in many applications. Indeed, silicon is one of the main components in solar cell technology (Non-Patent Document 1 and Non-Patent Document 2) and microelectronics (Non-Patent Document 3). Silicon is also of great interest for Li-ion batteries due to its low discharge potential and extremely high theoretical charge capacity (3579 mAh / g) (Non-Patent Document 4). Another advantage of silicon is that its morphology can be modified by nanostructuring. In fact, silicon is mainly found in the form of nanoparticles, nanowires, and nanosheets. Nanostructuring of silicon has been shown to improve its resistance to mechanical strains caused by lithium insertion / extraction processes (Non-Patent Document 5).

[0003] Among these morphologies, silicon nanowires (SiNWs) have attracted much attention because their extremely high aspect ratio facilitates efficient charge transport and is extremely advantageous for use as the negative electrode of Li-ion batteries (Non-Patent Document 6).

[0004] Moreover, their electrical conductivity can be easily increased with dopants, which allows for the extension of their applications to supercapacitors (Non-Patent Documents 7 and 8) and thermoelectric materials (Non-Patent Document 9).

[0005] The synthesis of SiNWs is mainly described as a bottom-up approach via the vapor-liquid-solid (VLS) mechanism, which usually proceeds on the basis of a catalyst (i.e., growth seed). More precisely, the VLS method focuses on the combination of a substrate, such as a silicon wafer (2D substrate) or silicon or carbon nanoparticles (0D substrate), with a metal seed, usually in the form of a metal thin film or nanoparticles.

[0006] Gold is one of the most efficient growth seeds due to its chemical stability and high recombination with silicon. Gold is usually used as a thin film or nanoparticles because it allows control of the diameter of SiNWs during the growth process. Gold nanoparticles (AuNPs) are known to be one of the best seeds for SiNW growth. In fact, the Au-Si binary phase diagram has a first eutectic point at 363 °C. This low eutectic point allows the reaction to proceed at a relatively low temperature (compared to the melting point of gold: around 1100 °C), allowing most of the reaction to proceed at the decomposition temperature of the silane precursor.

[0007] Although gold can be used with versatile silicon precursors such as silane and diphenylsilane, the synthesis of AuNPs has been mostly performed on a laboratory scale due to the limited amount of SiNWs. "Homemade" preparation of AuNPs is time-consuming, costly, and expected to be difficult to scale up. This strategic material is too expensive to enable economical mass production of SiNWs.

[0008] Other materials with low eutectic points with silicon, such as tin, gallium, zinc, and cadmium, can also promote a similar VLS mechanism. However, most of these metals exhibit high vapor pressures above 500 °C (the typical temperature for the fabrication of SiNWs), making industrial-scale applications difficult. Moreover, mass production of SiNWs on an industrial scale remains a challenge for these metals. Therefore, there is a need for alternative types of growth seeds that can promote the VSS mechanism.

[0009] In the VSS mechanism, the growth of SiNWs is driven by the formation of silicide phases. For example, metals such as copper, titanium, platinum, and nickel can form silicide compounds (Non-Patent Document 10). In particular, copper exhibits a very interesting phase diagram with three eutectic points at 467 °C, 558 °C, and 802 °C. These eutectic points allow a wide variety of choices for silicon precursors and seed precursor morphologies for the fabrication of SiNWs.

[0010] Hashimi et al. (Non-Patent Document 11) reported microwave synthesis of CuNWs using an alkylamine-mediated approach. Copper(II) chloride and octadecylamine are mixed in deionized water at 65°C for 1 hour. This solution is then mixed with a glucose-based solution and reacted at 80-120°C for 2-6 hours using microwaves to form CuNWs.

[0011] Korte et al. (Non-Patent Document 12) present the synthesis of AgNWs by polyol reduction of silver nitrate catalyzed by copper(I) or copper(II) chloride. AgNWs are formed by successively mixing copper chloride with ethylene glycol, PVP / ethylene glycol solution, and AgNO3 / ethylene glycol solution at 150 °C for 1 h.

[0012] In each of these prior art documents, copper chloride is used to synthesize copper nanowires (CuNWs) and silver nanowires (AgNWs), respectively, but not SiNWs.

[0013] Wen et al. (Non-Patent Document 13) reported the growth of SiNWs by copper-seeded chemical vapor deposition (CVD) of disilane to study the formation of the η3-Cu3Si phase. A thin Cu(0) film is deposited in-situ on a thin Si(111) film by thermal evaporation. Controlled growth of SiNWs is achieved by introducing a helium / disilane gas flow at low pressure at temperatures ranging from 470°C to 550°C for 3 h.

[0014] Tuan et al. (Non-Patent Document 14) describe the use of CuS nanocrystals as a catalyst for the synthesis of SiNWs, which is a two-step in-situ reaction that is initiated by the in-situ conversion of CuS to Cu metal, which then reacts with monophenylsilane at 500 °C and 10.3 MPa pressure for 10 min to form the silicide phase and grow SiNWs.

[0015] US Patent No. 10243207 reports the production of silicon nanowires using copper-based colloidal nanoparticles deposited on a porous substrate to form a growth base. Specifically, the growth seeds are generated by colloidal synthesis of Cu nanoparticles, followed by vapor deposition, adsorption of copper ions or copper complexes, and electroless deposition onto the substrate. In one example, the growth base can be reacted with a silicon precursor at 460°C for 45 minutes at low pressure to form a SiNW-based composite.

[0016] US 2007 / 166899 A1 discloses a method for growing silicon nanowires useful in the semiconductor industry. The method comprises forming a layer of copper catalyst particles on the top surface of a two-dimensional substrate made of non-metallic materials such as silicon, silicon dioxide, quartz, glass, etc., and growing nanowires on the surface. The method disclosed in the document is typically capable of depositing 10 μg of silicon per square inch of substrate (Si wafer). However, the production of nanowires for Li-ion batteries requires a yield several orders of magnitude larger. [Prior art documents] [Patent documents]

[0017] [Patent Document 1] U.S. Patent No. 10,243,207 [Patent Document 2] U.S. Patent Application Publication No. 2007 / 166,899 [Non-Patent Document]

[0018] [Non-Patent Document 1] D. Wolf et al., Energy Environ. Sci., 2016, 9, 1552 - 1576. [Non-Patent Document 2] X. Ou et al., ACS Appl. Mater. Interfaces, 2017, 9, 34527 - 34543. [Non-Patent Document 3] Y. Bando et al., Small, 2017, 13, 1701713. [Non-Patent Document 4] R. A. Huggins et al., J. Electrochem. Soc., 1981, 128, 725 - 729. [Non-Patent Document 5] L. L. Shaw et al., Nanoscale, 2016, 8, 74 - 103. [Non-Patent Document 6] Y. Cui et al., Nat. Nanotechnol., 2008, 3, 31 - 35. [Non-Patent Document 7] S.-T. Lee et al., Nano Today, 2013, 8, 75 - 97. [Non-Patent Document 8] S. Sadki et al., Nanoscale Res. Lett., 2013, 8, 1 - 5. [Non-Patent Document 9] P. Yang et al. Nature, 2008, 451, 163 - 167. [Non-Patent Document 10] V. Schmidt et al., Chem. Rev. 2010, 110, 361-388. [Non-Patent Document 11] AS Hashimi et al., Current Applied Physics2020, 20, 205-211. [Non-Patent Document 12] KE Korte et al., J. Mater. Chem. 2008, 18, 437-441. [Non-Patent Document 13] C.-Y. Wen et al., Nano Lett. 2010, 10, 514-519. [Non-Patent Document 14] H.-Y. Tuan et al., Chem. Mater. 2008, 20, 2306-2313. [Non-Patent Document 15] Dusanes et al., J Nanopart Res, 2020, 22,363. Summary of the Invention [Problem to be solved by the invention]

[0019] Although these examples prove that copper is an attractive candidate as a seed for the growth of SiNWs, their fabrication methods are still expensive and time-consuming, and are not yet feasible for mass production of SiNWs.

[0020] The above prior art documents also show that copper-based compounds are mostly used in solution, which requires pretreatment such as deposition on a substrate before NW growth can take place.

[0021] Therefore, to enable this unique and intriguing material to be used in a number of industrial applications, including the manufacture of lithium-ion batteries, a robust, safe and economical technique for mass production of SiNWs is required. [Means for solving the problem]

[0022] This invention describes a method for growing silicon nanowires using copper halide, preferably copper chloride, as a growth seed. The method has the advantage that it can be carried out without pretreatment such as annealing or heat treatment and without solvents. The method is simple, economical and robust. The method utilizes the in situ conversion of copper halide, preferably copper chloride, to the copper component at moderate temperatures.

[0023] The method according to the invention allows the production of large quantities of nanowires in a one-pot and scalable manner by using specific starting materials, in particular the morphology and type of catalyst and growth support, which are cheap materials and do not require further processing, making the process simple and economical.

[0024] A first aspect of the present invention is a method for producing a composite material containing at least silicon nanowires and copper, the method comprising the steps of: (A) Within a reactor chamber, there is provided at least: Copper halides (CuX n ) wherein X is selected from F, Cl, Br, I, and n is an integer selected from 1 or 2; and Powdered growth carriers; introducing a solid / solid mixture of (B) growing silicon nanowires in the reactor chamber from at least one precursor compound of the silicon nanowires selected from a silane compound or a mixture of silane compounds; (C) recovering the product; The method includes at least the following:

[0025] Advantageously, step (A) of the method according to the invention comprises: (1) At least: Copper halides (CuX n) wherein X is selected from F, Cl, Br, I, and n is an integer selected from 1 or 2; and Powdered growth carriers; solid-to-solid mixing; (2) introducing the mixture obtained in step (1) into a reactor chamber; or (1') Within the reactor chamber, at least: Copper halides (CuX n ) wherein X is selected from F, Cl, Br, I, and n is an integer selected from 1 or 2; and Powdered growth carriers; and (2') solid-by-solid mixing of the copper halide and the growth support in the reactor chamber; Includes.

[0026] Advantageously, step (B) of the method according to the invention comprises: (3) introducing into the reactor chamber at least one precursor compound of the silicon nanowires selected from a silane compound or a mixture of silane compounds; (4) reducing the molecular oxygen content in the reactor chamber; and (5) performing a heat treatment at a temperature in the range of 200°C to 900°C; However, the order of steps (3) to (5) may be the above order or a different order.

[0027] In a preferred embodiment, the method according to the invention comprises the steps of: (1) At least: Copper halides (CuX n ) wherein X is selected from F, Cl, Br, I, and n is an integer selected from 1 or 2; and Powdered growth carriers; solid-to-solid mixing; (2) introducing the mixture obtained in step (1) into a reactor chamber; or (1') Within the reactor chamber, at least: Copper halides (CuX n ) wherein X is selected from F, Cl, Br, I, and n is an integer selected from 1 or 2; and Powdered growth carriers; and (2') solid-by-solid mixing of the copper halide and the growth support in the reactor chamber; and (3) introducing into the reactor chamber at least one precursor compound of the silicon nanowires selected from a silane compound or a mixture of silane compounds; (4) reducing the molecular oxygen content in the reactor chamber; (5) performing a heat treatment at a temperature in the range of 200°C to 900°C; (C) recovering the product; However, the order of steps (1) to (5) or steps (1') to (5) may be the above order or a different order.

[0028] In these embodiments, step (2) is performed after step (1) and step (2') is performed after step (1').

[0029] The present invention further relates to a method for producing an electrode including a current collector, the method comprising the steps of: (i) carrying out the above method to prepare a composite material; (ii) coating at least one surface of the current collector with a composition containing the composite material as an electrode active material; Equipped with.

[0030] The present invention further relates to a method for producing an energy storage element, such as a lithium secondary battery, comprising a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode, the method comprising the steps of: Producing at least one of these electrodes, preferably the negative electrode, by carrying out the method described above; Equipped with.

[0031] In a first example, the process for producing the composite material is carried out in a fixed bed reactor.

[0032] In a second example, the composite manufacturing process is carried out in a tubular chamber of a tumbler type reactor moved by a mechanism for rotation and / or mixing.

[0033] In a third example, the process for producing the composite material is carried out in a vertical fluidized bed reactor.

[0034] In a preferred embodiment, the copper halide is selected from copper(I) chloride (CuCl), copper(II) chloride (CuCl2), and mixtures thereof.

[0035] In a preferred embodiment, the growth support is selected from carbon-based materials and carbonaceous polymers.

[0036] Preferably, said carbon-based material is selected from carbon black nanoparticles, carbonaceous polymer fibres, carbon nanotubes, graphene, graphite, preferably from graphite powder, graphene powder and carbon powder.

[0037] The average particle size of such powders is advantageously between 0.01 μm and 100 μm, preferably between 0.01 μm and 50 μm, and more preferably between 0.05 μm and 50 μm.

[0038] In another embodiment, the growth support is selected from silicon nanoparticles or silicon microparticles.

[0039] In a preferred embodiment, the precursor compound for the silicon nanowires is silane (SiH4) or diphenylsilane ((Si(C6H5)2H2).

[0040] In a preferred embodiment, the heat treatment is carried out at a temperature in the range of 300°C to 700°C, preferably 300°C to 650°C. In a preferred embodiment, the heat treatment is carried out for 1 minute to 10 hours.

[0041] In a preferred embodiment, the method for producing the composite material further comprises: a post-treatment step for converting organic matter derived from the precursor compound of the silicon nanowires into carbon material; Equipped with. [Brief description of the drawings]

[0042] [Figure 1] 1 is a low magnification photograph obtained by scanning electron microscopy (SEM) of a Si nanowire / copper (CuCl2) / KS4 graphite composite (Example 1). [Diagram 2] 1 is a high magnification photograph obtained by scanning electron microscopy (SEM) of a Si nanowire / copper (CuCl2) / KS4 graphite composite (Example 1). [Diagram 3] 1 is a graph showing the potential profile of a battery made from a Si nanowire / copper (CuCl2) / KS4 graphite composite (Example 1) (X-axis: battery capacity (mAh), Y-axis: battery potential (V)). [Figure 4] 1 is a low magnification photograph obtained by scanning electron microscopy (SEM) of a Si nanowire / copper (CuCl2) / SFG75 graphite composite (Example 2) obtained by treatment with SiH4 at 550 °C. [Diagram 5] 1 is a high magnification photograph obtained by scanning electron microscopy (SEM) of a Si nanowire / copper (CuCl2) / SFG75 graphite composite (Example 2) obtained by treatment with SiH4 at 550 °C. [Figure 6] FIG. 1 is a graph showing the potential profile of a battery made from a Si nanowire / copper (CuCl2) / SFG75 graphite composite (Example 2) obtained by treatment with SiH4 at 550 °C (X-axis: battery capacity (mA.h), Y-axis: battery potential (V)). [Figure 7] 1 is a low magnification photograph obtained by scanning electron microscopy (SEM) of a Si nanowire / copper (CuCl2) / SFG75 graphite composite (Example 3) obtained by treatment with SiH4 at 500 °C. [Figure 8] 1 is a high magnification photograph obtained by scanning electron microscopy (SEM) of a Si nanowire / copper (CuCl2) / SFG75 graphite composite (Example 3) obtained by treatment with SiH4 at 500 °C. [Figure 9] FIG. 1 is a graph showing the potential profile of a battery made from a Si nanowire / copper (CuCl2) / SFG75 graphite composite (Example 3) obtained by treatment with SiH4 at 500 °C (X-axis: battery capacity (mA.h), Y-axis: battery potential (V)). [Figure 10] 1 is a low magnification photograph obtained by scanning electron microscopy (SEM) of a Si nanowire / copper (CuCl2) / SLP50 graphite composite (Example 4) obtained by treatment with SiH4 at 550 °C. [Figure 11] 1 is a high magnification photograph obtained by scanning electron microscopy (SEM) of a Si nanowire / copper (CuCl2) / SLP50 graphite composite (Example 4) obtained by treatment with SiH4 at 550° C. [Figure 12] FIG. 1 is a graph showing the potential profile of a battery made from a Si nanowire / copper (CuCl2) / SLP50 graphite composite (Example 4) obtained by treatment with SiH4 at 550 °C (X-axis: battery capacity (mA.h), Y-axis: battery potential (V)). [Figure 13] 1 is a low magnification photograph obtained by scanning electron microscopy (SEM) of a Si nanowire / copper (CuCl2) / SLP50 graphite composite (Example 5) obtained by treatment with SiH4 at 500 °C. [Figure 14] 1 is a high magnification photograph obtained by scanning electron microscopy (SEM) of a Si nanowire / copper (CuCl2) / SLP50 graphite composite (Example 5) obtained by treatment with SiH4 at 500 °C. [Figure 15]FIG. 1 is a graph showing the potential profile of a battery made from a Si nanowire / copper (CuCl2) / SLP50 graphite composite (Example 5) obtained by treatment with SiH4 at 500 °C (X-axis: battery capacity (mA.h), Y-axis: battery potential (V)). [Figure 16] 1 is a low magnification photograph obtained by scanning electron microscopy (SEM) of a Si nanowire / copper (CuCl2) / KS4 graphite composite (Example 6) obtained by treatment with SiH4 at 550° C. [Figure 17] 1 is a high magnification photograph obtained by scanning electron microscopy (SEM) of a Si nanowire / copper (CuCl2) / KS4 graphite composite (Example 6) obtained by treatment with SiH4 at 550° C. [Figure 18] FIG. 1 is a graph showing the potential profile of a battery made from a Si nanowire / copper (CuCl2) / KS4 graphite composite (Example 6) obtained by treatment with SiH4 at 550 °C (X-axis: battery capacity (mA.h), Y-axis: battery potential (V)). [Figure 19] 1 is a low magnification photograph obtained by scanning electron microscopy (SEM) of a Si nanowire / copper (CuCl) / SFG75 graphite composite (Example 7) obtained by treatment with SiH4 at 550° C. [Figure 20] 1 is a high magnification photograph obtained by scanning electron microscopy (SEM) of a Si nanowire / copper (CuCl) / SFG75 graphite composite (Example 7) obtained by treatment with SiH4 at 550° C. [Figure 21] FIG. 1 is a graph showing the potential profile of a battery made from a Si nanowire / copper (CuCl) / SFG75 graphite composite (Example 7) obtained by treatment with SiH4 at 550 °C (X-axis: battery capacity (mA.h), Y-axis: battery potential (V)). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0043] The phrase "consisting essentially of" means that the method or material of the invention may contain one or more components or steps other than those explicitly stated, which do not significantly affect the characteristics or properties of the invention.

[0044] The term "X to Y" is inclusive unless otherwise specified. This term means that the range includes values ​​X and Y, as well as all values ​​from X to Y.

[0045] A first aspect of the present invention is a method for producing a silicon nanowire-containing composite material by a chemical vapor deposition (CVD)-based process, which is suitable for use as an anode active material in lithium-ion batteries, although other applications are also envisaged.

[0046] The SiNW composite material obtained by this method may be used as is after production, or may be subjected to some treatment after production.

[0047] The present invention relates to a method for the preparation of silicon-based materials. The present invention relates to a method for the preparation of silicon-based composite materials containing at least nanostructured silicon materials and copper by chemical decomposition of reactive silicon-containing gaseous species. The method is based on the principle of chemical vapor deposition (CVD). The term "composite material" refers to a material made up of two or more constituent substances with significantly different physical or chemical properties.

[0048] The external dimensions of the particles can be determined by any known method, in particular by analysis of photographs of the composite material according to the invention obtained by scanning electron microscopy (SEM).

[0049] (Method of manufacturing composite materials) The present invention relates to a method for producing a composite material containing at least copper and SiNWs, the method comprising at least (A) In the reactor chamber, at least copper halide (CuX nwherein X is selected from F, Cl, Br, I, and n is an integer selected from 1 or 2, and a solid / solid mixture of a powdered growth support; (B) growing silicon nanowires in the reactor chamber from at least one precursor compound of the silicon nanowires selected from a silane compound or a mixture of silane compounds; (C) recovering the product; Equipped with.

[0050] Advantageously, step (A) comprises substeps (1) to (2) or (1') to (2') as defined herein. Advantageously, step (B) comprises substeps (3) to (5) as defined herein.

[0051] Specifically, the method according to the present invention comprises: (1) At least: Copper halides (CuX n ) wherein X is selected from F, Cl, Br, I, and n is an integer selected from 1 or 2; and Powdered growth carriers; solid-to-solid mixing; (2) introducing the mixture obtained in step (1) into a reactor chamber; or (1') Within the reactor chamber, at least: Copper halides (CuX n ) wherein X is selected from F, Cl, Br, I, and n is an integer selected from 1 or 2; and Powdered growth carriers; and (2') solid-by-solid mixing of the copper halide and the growth support in the reactor chamber; and (3) introducing into the reactor chamber at least one precursor compound of the silicon nanowires selected from a silane compound or a mixture of silane compounds; (4) reducing the molecular oxygen content in the reactor chamber; (5) performing a heat treatment at a temperature in the range of 200°C to 900°C; (C) recovering the product; Equipped with.

[0052] The order of steps (1) to (5) or steps (1') to (5) may be substantially the above order or another order, depending on the characteristics of the reactor in which the method is carried out, the method for reducing the oxygen molecular content, and the state (liquid or gas) in which the silicon nanowire precursor compound is introduced into the reactor, etc.

[0053] For example, step (3) and / or step (4) and / or step (5) may be performed before step (1) and step (2) or step (1') and step (2'). Steps (1) and step (2) or step (1') and step (2') are always in this order. For example, the method according to the present invention may be performed in the order of steps (3)-(1)-(2)-(4)-(5)-(C), or steps (4)-(3)-(1')-(2')-(5)-(C), or steps (1)-(2)-(4)-(3)-(5)-(C).

[0054] In a first example, the process is carried out in a fixed bed reactor. In a second example, the process is carried out in a tubular chamber of a tumbler type reactor equipped with a mechanism for rotation and / or mixing. In a third example, the process is carried out in a (vertical) fluidized bed reactor.

[0055] In a first embodiment, the reactor is closed during the method. In a second embodiment, the reactor is open during the process.

[0056] By open reactor is meant a reactor in which the gas flow is kept open during the process, in particular during the heat treatment step, whereas by closed reactor is meant a reactor in which the gas species are introduced at the beginning of the process and then the gas flow is closed during the heat treatment step.

[0057] Process parameters The process parameters mentioned below are common to all examples of the process (fixed bed reactor, tumbler type reactor equipped with mechanisms for rotation and / or mixing, fluidized bed reactor).

[0058] The method according to the invention comprises the step of solid-to-solid mixing of a copper halide catalyst as defined above and as detailed below, and a growth support material.

[0059] "Solid-solid mixing" refers to combining and / or associating and / or intermingling a starting solid copper halide, preferably a powdered copper halide, with a solid, powdered growth support material to obtain a material of substantially homogeneous composition. The solid / solid mixing is carried out without a solvent or carrier. The nature and characteristics of the copper halide catalyst and the growth support body are described in more detail below.

[0060] In a first example, the step of mixing the copper halide catalyst and the growth support material is carried out before they are introduced into the reactor chamber.

[0061] The solid / solid mixing can be carried out in any industrial mixing equipment known to those skilled in the art, such as mixer systems (Turbula®, Cyclomix®, Nautamix) or grinding systems, such as ball mills, attritor mills, hammer mills, high energy mills, pin mills, turbo mills, fine cutting mills, impact mills, fluidized bed mills, conical screw mills, rotor mills, stirred bead mills, jet mills, and other systems.

[0062] In a second example, the step of mixing the copper halide catalyst and the growth support material is carried out in a chamber of a reactor. This example can be carried out if the reactor has a suitable mixing function for solid / solid mixing. This can be done, for example, in a tumbler type reactor equipped with a mechanism for rotation.

[0063] The step (4) of reducing the molecular oxygen content in the reactor chamber can be accomplished in a variety of ways.

[0064] The molecular oxygen content in the reactor chamber is reduced by evacuating the reactor, preferably at 10 -1 bar(10 -2 This can be reduced by reducing the pressure to less than 100 MPa.

[0065] Additionally, the molecular oxygen content in the reactor chamber can be reduced by flushing the reactor chamber with an inert gas.

[0066] In the context of the present invention, the expression "flushing the reactor chamber with an inert gas" means injecting a flow of inert gas into the reactor chamber, thereby replacing the gas present in said reactor with the injected inert gas.

[0067] Preferably, the inert gas is selected from nitrogen gas (N2), argon gas (Ar), and mixtures thereof.

[0068] In case of a closed reactor, the reactor chamber is preferably flushed with an inert gas at least two times, more preferably at least three times.

[0069] In the case of an open reactor, an inert gas may be passed through the reactor chamber during all or part of the process.

[0070] Preferably, the molecular oxygen content in the reactor chamber at the end of step (4) is 1% by volume or less based on the total volume of the reactor chamber.

[0071] Preferably, said heat treatment is carried out at a temperature in the range of 200-900°C, preferably 300-700°C, even more preferably 300-650°C.

[0072] Applicants have surprisingly found that they can control the diameter of the SiNWs by varying the reaction temperature: in fact, increasing the applied temperature reduces the diameter of the resulting SiNWs.

[0073] Preferably, the heat treatment is carried out under low pressure, atmospheric pressure or a pressure in the range of 0.11 to 30 MPa. The pressure parameters depend on the type of reactor chosen and whether it is open or closed.

[0074] In the process of the present invention, the heat treatment may cause an increase in pressure within the reactor (especially if the reactor is closed). Such internal pressure depends on the heat treatment applied, but does not necessarily need to be controlled or monitored.

[0075] Preferably, said heat treatment is carried out for a period between 1 minute and 10 hours, preferably between 1 minute and 2 hours, more preferably between 1 minute and 30 minutes, especially when the reactor is closed during said treatment.

[0076] In an exemplary embodiment, the method according to the invention comprises a post-treatment step between steps (5) and (C) for converting organic matter into carbon material. By "organic matter" is meant organic chemical residues resulting from the decomposition of silicon nanowire precursors, such as silanes, e.g. diphenylsilane. When this step is carried out, it essentially consists of a heat treatment. Advantageously, this step is carried out in an inert atmosphere, e.g. under a carrier gas atmosphere, such as N2, Ar, Ar / H2 mixtures, etc., at a temperature in the range of 500°C to 700°C, preferably 550°C to 650°C, advantageously around 600°C.

[0077] The method according to the invention may comprise an additional step (7) of washing the composite material obtained in step (C).

[0078] The composite material obtained in step (C) may be washed with an organic solvent, preferably selected from chloroform, ethanol, toluene, acetone, dichloromethane, petroleum ether and mixtures thereof.

[0079] Alternatively, the composite material obtained in step (C) may be washed with an acid solution.

[0080] Preferably, the method further comprises, after step (7), an additional step of drying the washed composite material.

[0081] For example, the composite material is dried by placing it in an oven at a temperature preferably of 40° C. or higher, more preferably 60° C. or higher.

[0082] The drying step is preferably carried out for a period of between 15 minutes and 12 hours, more preferably between 2 hours and 10 hours, and even more preferably between 5 hours and 10 hours.

[0083] (Silicon nanowire precursor compound) In the method according to the invention, at least one precursor compound of silicon nanowires is introduced into the reactor chamber, where "precursor compound of silicon nanowires" refers to a compound capable of forming silicon nanowires when performing the method according to the invention, in particular a compound capable of forming silicon nanowires under CVD processing conditions.

[0084] The compound may be introduced into the reactor chamber as a liquid or a gas. If the compound is introduced into the reactor chamber as a liquid, the compound is converted to a gaseous state within the reactor chamber by controlling the temperature and pressure within the reactor chamber. When the silicon nanowire precursor compound is in a gaseous state, the precursor compound is referred to as a "reactive silicon-containing gas species."

[0085] For example, if the precursor compound for the SiNWs is a liquid, such as diphenylsilane, the liquid precursor will vaporize into gaseous species when the reactor is subjected to appropriate temperature / pressure parameters.

[0086] The silicon nanowire precursor compound may be introduced into the reactor as a gas mixture with a carrier gas.

[0087] When the precursor compound is in the form of a reactive silicon-containing gas species, the precursor compound may be introduced into the reactor chamber as a mixture with a carrier gas (forming a reactive silicon-containing mixed gas). For example, in the case of SiH4, which is a gas at room temperature / pressure, it can be introduced directly into the reactor chamber, either alone or as a mixture with a carrier gas. In addition, in the case of a liquid precursor compound such as diphenylsilane (Ph2SiH2), it may be heated in a previous step of the method to change it into a vapor state, and then introduced into the reactor chamber as a gas, either alone or as a mixture with a carrier gas.

[0088] Preferably, the precursor compound for silicon nanowires, i.e., the "reactive silicon-containing gas species," is a silane compound or mixture of silane compounds.

[0089] For purposes of the present invention, a "silane compound" is a compound represented by formula (I): R1-(SiR2R3) n -R4(I) (In the formula, n is an integer of 1 to 10, and R1, R2, R3 and R4 are each independently hydrogen, C1 to C 15 Alkyl groups, C6-C 12 Aryl groups, C7-C 20 aralkyl groups and chloride. This refers to the compound.

[0090] Preferably, the silicon-containing gas species of this embodiment is selected from compounds of formula (I), in which n is an integer from 1 to 5, and R1, R2, R3 and R4 are each independently selected from hydrogen, a C1-C3 alkyl group, phenyl and chloride.

[0091] More preferably, n is an integer from 1 to 3, and R1, R2, R3 and R4 are each independently selected from hydrogen, methyl, phenyl and chloride.

[0092] Preferably, the precursor compound for silicon nanowires in this embodiment is selected from silane, disilane, trisilane, chlorosilane, dichlorosilane, trichlorosilane, dichlorodimethylsilane, phenylsilane, diphenylsilane, triphenylsilane or mixtures thereof.

[0093] In a preferred embodiment, the precursor compound for silicon nanowires is silane (SiH4) or diphenylsilane (Si(C6H5)2H2). The choice of the precursor compound for silicon nanowires and its physical state depends on the type of reactor and other parameters of the method.

[0094] (Reactive silicon-containing gas mixture) The precursor compounds of silicon nanowires are introduced into the reactor as a gas or as a liquid that will be converted to a gas in the reactor. The reactive silicon-containing gas species undergo chemical decomposition at high temperature to obtain silicon nanowires. The reactive silicon-containing gas species may be in a mixture with a carrier gas. Hereinafter, such a mixture is referred to as a "reactive silicon-containing gas mixture."

[0095] "Carrier gas" refers to a gas selected from a reducing gas, an inert gas, or a mixture thereof. Preferably, the reducing gas is hydrogen (H2). Preferably, the inert gas is selected from argon (Ar), nitrogen (N2), helium (He) or mixtures thereof.

[0096] In a preferred embodiment, the silicon-containing mixed gas is composed of 1 vol% or more, preferably 10 vol% or more, more preferably 50 vol% or more, and even more preferably 100 vol% of a silicon-containing gas species.

[0097] The ratio of silicon-containing gas species to carrier gas may be adjusted to different levels at different steps of the method.

[0098] (catalyst) In the method according to the present invention, CuX n A catalyst, where X is a halide selected from the group consisting of F, Cl, Br and I, and n is an integer selected from 1 or 2, is introduced into the reactor chamber.

[0099] Preferably, the copper halide is selected from copper(I) chloride (CuCl), copper(II) chloride (CuCl2), and mixtures thereof.

[0100] In the context of the present invention, "catalyst" and "growth seed" are used interchangeably and are represented by the formula: CuX n where X is a halide selected from the group consisting of F, Cl, Br and I, and n is an integer selected from 1 or 2. The function of the catalyst is to promote the growth of SiNWs.

[0101] Copper halides (CuX n ) A solid mixture of catalyst and growth support may be prepared prior to being introduced into the reactor chamber or may be prepared within the reactor chamber.

[0102] Preferably, copper halides, in particular copper chloride, are used as raw material, in particular in powder form.

[0103] Copper halide as a raw material is a very stable product and is easier to process than other catalysts: in fact, whereas gold nanoparticle-based growth media requires a solid / liquid solution followed by evaporation of the solvent, copper halide (preferably copper chloride) can be simply mixed solid-to-solid with the growth support.

[0104] This step of the method according to the invention can be carried out in any industrial mixing device known to the person skilled in the art, such as mixers, ball mills, attritor mills, hammer mills, high energy mills, pin mills, turbo mills, fine cutting mills, impact mills, fluidized bed mills, conical screw mills, rotor mills, stirred bead mills, jet mills, etc. Alternatively, this step can be carried out in a reactor chamber, if the chamber is compatible. This step of the method takes less than 30 minutes and can be neatly carried out without aqueous or organic solvents.

[0105] The catalyst and growth support material are used according to a mass ratio (catalyst / growth support) in the range of preferably 0.01 to 1, more preferably 0.02 to 0.5, and even more preferably 0.05 to 0.15.

[0106] By associating the catalyst with the growth support material in this manner, multiple particle growth sites can be formed on the surface of the growth support material.

[0107] (Growth carrier) The method according to the invention is carried out in the presence of a powdered growth support, which may for example be a carbon-based material, a silicon-based material, an ITO-based material, a carbonaceous polymer, etc.

[0108] The growth support may be a zero-dimensional, one-dimensional, two-dimensional or three-dimensional material. For example, the zero-dimensional material may be silicon nanoparticles, carbon black nanoparticles, and the like. For example, the one-dimensional material may be a carbonaceous polymer fiber, a carbon nanotube, or the like.

[0109] For example, the two-dimensional material may be a silicon wafer, graphene, ITO glass, etc. The two-dimensional growth support may be substantially intended for nanoelectronics or microelectronics applications. For example, the three-dimensional material may be a carbonaceous material such as silicon microparticles, powders such as graphite (natural, synthetic or expanded graphite), micronized graphite, polymer bodies, etc.

[0110] For the purposes of the present invention, "powder" refers to solid growth supports broken down into very small particles, specifically particles with a size between 1 nm and 100 μm, preferably between 50 nm and 50 μm. As used herein, the term "powder" may include materials of any form (i.e., fibers, aggregates, flakes, tubes, rods, filaments) that meet the particle size criteria defined herein. Measurement of the average particle size of the supports may be performed by laser diffraction methods.

[0111] Preferably, the method according to the invention is carried out with zero, one or three dimensional materials.

[0112] The silicon-based carrier may be any material selected from the group consisting of silicon nanoparticles, silicon microparticles and silicon wafers, preferably silicon nanoparticles and silicon microparticles.

[0113] The average particle size of the silicon nanoparticles is preferably 1 to 100 nm, more preferably 30 to 50 nm. The average particle size of the silicon microparticles is preferably between 0.1 and 30 μm, advantageously between 1 and 15 μm.

[0114] The silicon wafer preferably has an average width dimension of 1 cm to 45 cm, advantageously 1 to 10 cm. The ITO-based carrier can be any material selected from the group consisting of ITO glass having an average width dimension of 1 cm to 100 cm, advantageously 1 to 10 cm. Although the disclosure refers to silicon wafers, silicon wafers are not included in the claimed invention.

[0115] The carbon-based support may be any material selected from the group consisting of graphite, graphene, carbon, in particular 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 these materials, which are generally commercially available in powder form.

[0116] If the growth support is a carbon-based support, it may be in the form of particles, particle agglomerates, non-agglomerated flakes, or agglomerated flakes.

[0117] In this example, the carbon-based support has a Brunauer-Emmett-Teller (BET) area of ​​advantageously 1 to 100 m 2 / g, more preferably 1 to 70m 2 / g, and more preferably 3 to 50 m 2 / g.

[0118] In a preferred embodiment of this example, the carbon-based material is selected from graphite powder, graphene powder, and carbon powder, preferably graphite powder having an average particle size of 0.01 to 50 μm.

[0119] In another example, the growth support is a carbonaceous polymer body. WO 2021 / 018598 discloses the use of polymers as growth supports.

[0120] When the growth support is a carbonaceous polymer body, preferably said polymer body has a decomposition temperature, as determined by thermogravimetric analysis, of 200°C or more, preferably 300°C or more, more preferably 400°C or more and advantageously 500°C or more.

[0121] In this case, said polymeric bodies are advantageously chosen from fibrous polymeric bodies of synthetic or natural origin, preferably from fibrous polymeric bodies of synthetic origin.

[0122] In this embodiment, said polymeric bodies are more advantageously selected from polybenzothiazoles, polyamines, polyimides, polyurethanes, polybenzoxazoles, polyamides, polybenzimidazoles and mixtures thereof, preferably polyamides.

[0123] In this example, even more advantageously, the polymer body is polyparaphenylene terephthalamide, also known as Kevlar®.

[0124] If the growth support is a polymeric body, the method according to the invention comprises: i) preparing a composite material containing a polymer body and SiNWs according to the method defined above; ii) carbonizing the polymer body of the polymer-based composite; Details of suitable method parameters for the preparation of silicon / polymer and silicon / carbon composites are as disclosed in WO 2021 / 018598.

[0125] As described in the Examples section, copper halides such as copper chloride (CuX n The diameter of nanowires produced using ) is directly affected by the reaction temperature. Indeed, the diameter of the resulting SiNWs decreases with increasing applied temperature.

[0126] (Doping materials) In one embodiment, in the method according to the invention, at least one doping material is introduced into the reactor.

[0127] "Doping material" in the sense of the present invention is understood to mean a material capable of modifying the conductive properties of silicon. Doping materials in the sense of the present invention are, for example, materials enriched with phosphorus, boron, nitrogen, etc. atoms.

[0128] In this embodiment, preferably the doping material is introduced into the reactor chamber with a precursor selected from diphenylphosphine, triphenylborane, diphenylamine and triphenylamine, in a first example, this introduction is performed before the start of SiNW growth.

[0129] In another example, a precursor of the doping material is introduced as a gas simultaneously with (or, in some cases, as part of) the reactive silicon-containing gas mixture.

[0130] Preferably, the molar ratio of the doping material to the precursor compound of the silicon nanowires is 10 -4 mol% to 10 mol%, preferably 10 -2 % by mole to 1% by mole.

[0131] (Reactor) In a first example, the process according to the invention is carried out in a fixed bed reactor. In a second example, the method according to the invention is carried out in the tubular chamber of a tumbler type reactor equipped with a mechanism for rotation and / or mixing. In a third example, the process according to the invention is carried out in a (vertical) fluidized bed reactor.

[0132] [First example] In a first example, the process according to the invention is carried out in a fixed bed reactor. Reactor characteristics The fixed bed reactor may be an open or closed reactor. A reactor that can be used to carry out the method according to the present invention is disclosed, for example, in WO 2019 / 020938, in which the reactor is used in the form of a "closed reactor".

[0133] In an alternative embodiment, an open fixed bed reactor is used to carry out the process according to the invention, for example the tubular chamber of a tumbler reactor used in a static manner (without rotation or mixing).

[0134] Parameters Preferably, in this first embodiment, the method according to the invention comprises the steps of: (1) At least: Copper halides (CuX n ) wherein X is selected from F, Cl, Br, I, and n is an integer selected from 1 or 2; and Powdered growth carriers; solid-to-solid mixing; (2) introducing the mixture obtained in step (1) into a reactor chamber; (3) introducing into the reactor chamber at least one precursor compound of the silicon nanowires selected from a silane compound or a mixture of silane compounds; (4) reducing the molecular oxygen content in the reactor chamber; (5) performing a heat treatment at a temperature in the range of 200°C to 900°C; (C) recovering the product; At least the following is provided.

[0135] In this first example, in the case of a closed reactor, the step of reducing the molecular oxygen content in the chamber of the reactor includes subjecting the reactor to a vacuum, preferably 10 -1 bar(10 -2 This can be achieved by applying a pressure of up to 100 MPa.

[0136] Alternatively, the step of reducing the molecular oxygen content in the reactor chamber may be performed by flushing the reactor chamber with an inert gas.

[0137] In the context of the present invention, the expression "flushing the reactor chamber with an inert gas" means injecting a flow of inert gas into the reactor chamber, thereby replacing the gas present in said reactor with the injected inert gas.

[0138] Preferably, the inert gas is selected from nitrogen gas (N2), argon gas (Ar) and mixtures thereof. In the case of a closed reactor, the reactor chamber is preferably flushed with the inert gas at least twice, more preferably at least three times. In the case of an open reactor, the inert gas may be circulated through the reactor chamber during the entire process or part of the process.

[0139] Preferably, the molecular oxygen content in the reactor chamber at the end of step (4) is 1% by volume or less, based on the total volume of the reactor chamber.

[0140] In a first embodiment of this example, which is a closed reactor, the silicon nanowire precursor compound is generally introduced into the reactor as a liquid.

[0141] In the first embodiment of this example, where the reactor is a closed type, the copper halide catalyst, the growth support and the precursor compound of silicon nanowires may be charged into the reactor in the form of a mixture.

[0142] In the first embodiment of this example, where the reactor is closed, the reactor preferably has at least two filling zones: a first zone capable of receiving a precursor compound for silicon nanowires, and a second zone capable of receiving a mixture of a growth support and a copper halide catalyst.

[0143] In a first alternative, the first and second packed zones are located at the same height within the reactor chamber.

[0144] In one preferred alternative, the second packing zone is located higher than the first packing zone.

[0145] In a second embodiment of this example, where the reactor is open, the precursor compounds for silicon nanowires are generally introduced into the reactor as a mixture with an inert gas (a "reactive silicon-containing gas mixture").

[0146] [Second example] In a second example, the method according to the invention is carried out in the tubular chamber of a tumbler type reactor equipped with a mechanism for rotation and / or mixing.

[0147] Reactor characteristics The tumbler reactor is at least composed of a tubular chamber heated by a furnace. The tubular chamber may be filled with the growth support material and the copper halide catalyst as individual raw materials or as a mixture. The reactor is equipped with a mechanism for rotation and / or mixing. The longitudinal axis of the tubular chamber may be horizontal or may be inclined to form an angle of up to 20° with the horizontal axis. The reactor further includes a product supply system and a product discharge system, which allows the semi-continuous production of silicon-copper composites. The tumbler reactor is equipped with a reactor pressure control device, such as a needle valve, a pressure controller, etc.

[0148] A typical example of a mechanical tumbler reactor is the Lodige fluidized bed reactor, in which fluidization is produced by the helical rotation of a horizontal shaft within a tubular chamber.

[0149] Another typical example of a mechanical tumbler reactor is one which comprises a tubular rotating chamber in which fluidization occurs by rotation about a longitudinal axis.

[0150] Parameters This example is unique in that the reactor mechanically generates fluidization, which is beneficial for contacting the growth support with silicon made of reactive gas species, and also in that the catalyst and growth support can be introduced directly and mixed within the reactor chamber.

[0151] In this example, the silicon nanowire precursor compound is preferably introduced into the reactor as a gas.

[0152] Each step of the method Advantageously, in this embodiment, the method according to the invention comprises: (1'A) At least: Copper halides (CuX n ) wherein X is selected from F, Cl, Br, I, and n is an integer selected from 1 or 2; and Powdered growth carriers; into a tubular chamber of a reactor; (2'A) rotating the tubular chamber and / or starting a mixing mechanism for the copper halide and the growth support; (2'B) heating the tubular chamber under a carrier gas flow; (3) introducing a reactive silicon-containing gas mixture into the tubular chamber; (4) controlling the pressure in the reactor chamber with the flow of the mixed gas; (5) performing a heat treatment in the rotating and / or mixing tubular chamber under a flow of reactive silicon-containing gas mixture at a temperature in the range of 200° C. to 900° C.; (C) recovering the resulting product; Equipped with.

[0153] In this example, the order of most of the steps must be in the order described above, but the rotation and / or mixing of step (2'A) may begin before or after step (2'B).

[0154] In this example, the heat treatment of step (5) is carried out at low pressure (lower than atmospheric pressure), atmospheric pressure, or higher than atmospheric pressure.

[0155] When the reactor is a tumbler type reactor equipped with a mechanism for rotation and / or mixing, the heat treatment in step (5) is preferably carried out at atmospheric pressure.

[0156] [Third example] In a third example, the process according to the invention is carried out in a vertical fluidized bed reactor. Reactor characteristics A vertical fluidized bed reactor generally consists of a vertical cylindrical stainless steel column. The lower part of the column is fitted with a perforated steel plate to support the powder and distribute the gas uniformly, and a water-cooled flange to avoid premature decomposition of the silane. At the outlet, the elutriated particles can be collected by a high-performance filtration cartridge. The reactor is externally heated by a two-zone electric furnace, and its wall temperature is controlled by at least two thermocouples connected to a regulator. Thermocouples are further arranged along the reactor, which monitor the axial temperature profile. Pressure sensors allow the pressure in the reactor to be controlled / monitored. Flow meters allow the flow rate of the various gases passed through the powder in the reactor to be controlled.

[0157] Parameters In a vertical fluidized bed reactor, the process according to the invention can be carried out at atmospheric pressure or at a pressure slightly higher than atmospheric pressure. 5 A pressure of at least 1000 Pa is advantageous.

[0158] Preferably, the applied temperature is within the range of 300°C to 650°C. In this example, the silicon nanowire precursor compound is preferably introduced into the reactor as a gas. In this example, both the catalyst and the growth support are in powder form.

[0159] ●Process Steps (1) introducing into a tubular chamber at least: a copper halide catalyst, preferably a copper chloride catalyst; and a growth support; (2) mixing a powder of a copper halide catalyst and a powder of the growth support solid by solid; (4) performing a seal test on the reactor using nitrogen (1 slm) (the seal test is passed if the pressure is stable after 1 minute); (4') fluidizing the powder with a neutral gas and periodically increasing the flow rate until it is equal to the desired flow rate (e.g., increasing the flow rate by 0.5 slm every 2 minutes until it is equal to the desired flow rate); (5) carrying out heat treatment (starting the heating system of the furnace and the cooling system of the flange under the floor); (3) introducing a reactive gas into the chamber after the fluidized bed has reached isothermal stability; and (C) Recovering the product (after the reaction is completed, the reactor is cooled and the resulting product is recovered: for example, the reactor is cooled to 150° C. or less and the product is recovered).

[0160] The order of most steps must be in the order shown above. Such a method is disclosed, for example, in WO 2011 / 137446.

[0161] (Material composition) The method disclosed above allows for obtaining a composite material containing silicon nanowires and a copper component.

[0162] The methods disclosed above make it possible to obtain a composite material that contains, and preferably consists essentially of, a growth support, silicon nanowires, and a copper component.

[0163] In another embodiment, the above disclosed method provides a composite material consisting essentially of silicon nanowires and copper components.

[0164] Advantageously, the Si content in the composite material obtained is greater than 5% by weight, preferably greater than 20% by weight, of silicon relative to the total weight of the material.

[0165] In the sense of the present invention, the term "copper component" or "copper" as used herein is understood to mean compounds resulting from the reaction of copper halides (especially copper chloride) with silicon precursors (especially silane gas) during the growth of silicon nanowires, as well as the remaining unreacted copper halides. Copper components include, in particular, silicides (Cu x S y Preferably, the composite material contains a copper component in an amount ranging from 0.1% to 10% by weight, preferably from 0.1% to 5% by weight, relative to the total weight of the composite material.

[0166] By remaining unreacted copper halide it is meant that not all of the copper halide introduced reacts with the silicon precursor during the process.

[0167] The material may contain minor amounts of halides, such as chlorides. Halides such as chlorides may be found as minor components in the composite material, the weight of which, in particular of chlorides, relative to the total weight of the material, is typically less than 1% by weight, preferably less than 0.01% by weight.

[0168] Advantageously, the silicon material obtained by chemical vapor decomposition of the precursor compound of silicon nanowires is in the form of a wire. Other morphologies such as worms, rods, filaments, etc. may also exist. In a preferred embodiment, the silicon material, in particular the silicon material obtained by chemical vapor decomposition of silicon-containing gas species as described above, is a mixture of nanowires and nanoparticles. Such an embodiment corresponds, for example, to the case where SiH4 is used as the precursor compound of SiNWs.

[0169] Within the meaning of the present invention, "nanowire" is understood to mean an elongated object having a shape similar to a wire and a diameter of nanometer size.

[0170] The diameter of the silicon nanowires is preferably within a range of 1 nm to 250 nm, more preferably within a range of 10 nm to 200 nm, and further preferably within a range of 30 nm to 180 nm.

[0171] The size of the silicon material can be measured by a number of techniques well known to those skilled in the art, such as, for example, by analyzing scanning electron microscopy (SEM) photographs of one or more samples of the carbon-silicon composite material.

[0172] Silicon (preferably silicon nanowires) accounts for advantageously 1% to 70% by weight, preferably 10% to 70% by weight, more preferably 20% to 70% by weight, even more preferably 30% to 70% by weight, and even more advantageously 50% to 70% by weight of the silicon-based composite material.

[0173] Advantageously, said silicon-based composite material is preferably obtained in powder form.

[0174] (Applications of carbon-silicon composite materials) The silicon composite material according to the present invention can be used as an anode active material and can be used in the manufacture of lithium ion batteries.

[0175] The electrode including the current collector is manufactured by a manufacturing method classically used in the art. For example, the negative electrode active material made of the 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. Next, the slurry is applied to a current collector and pressed to manufacture a negative electrode.

[0176] A wide variety of binder polymers can be used as binders in the present invention, such as polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HEP), polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, and the like.

[0177] The electrodes can be used to manufacture lithium secondary batteries, which are commonly used in the art and comprise a separator and an electrolyte disposed between a positive electrode and a negative electrode. EXAMPLES

[0178] (Example) In the following examples, contents and percentages are given by weight unless otherwise stated.

[0179] (Material) Reactor (fixed bed): Stainless steel reactor (internal volume = 1 L, diameter = 100 mm, height = 125 mm); Ball mill equipment: Model PM100 available from Retsch, Turbula (registered trademark) device: Model T2F, available from Wab Inc. Silicon precursor: diphenylsilane (Si(C6H5)2H2) (CAS number: 775-12-2) available from Sigma-Aldrich, SiH4 available from Messer, Catalyst: CuCl and CuCl2, available from Alfa Aesar; Graphite growth support: SFG75 graphite (SSA = 3.5 m) available from Imerys 2 / g), KS4 graphite (SSA=24.48m 2 / g) and SLP50 graphite (SSA = 4.97m 2 / g), Conductive filler: graphite powder sold under the trade names C-NERGY® Actilion GHDR-15-4 and C-NERGY® SFG15L by Imerys; Carbon black: Timcal C-NERGY C65 (CAS number: 1333-86-4), a product code available from Imerys; Sodium carboxymethylcellulose (CMC) (CAS number: 9004-32-4) available from Alfa-Aesar, Styrene butadiene rubber (SBR) (CAS number: 9003-55-8) marketed by MTI, An electrolyte solution marketed by Solvionic, which contains lithium hexafluorophosphate (LiPF6) (1M) dissolved in a mixture (volume 1:1) of ethylene carbonate (EC) and diethyl carbonate (DEC), and also contains fluoroethylene carbonate (FEC) (10% by weight) and vinylene carbonate (additive) (2% by weight).

[0180] Example 1: Synthesis of KS4 graphite / copper (CuCl2) / SiNW composite (M1) a) KS4 graphite and CuCl 2 Mixing as a pre-catalyst material 3 g of KS4 graphite is combined with 0.355 g of CuCl2 and placed in a steel container of a ball milling apparatus. Then, 3 mm steel balls (40 g) are placed in the container, which is then tightly closed. The powders are mixed at 400 rpm for 10 minutes and 30 seconds. The balls are removed through a sieve to recover the pre-catalyst material.

[0181] b) Growth of silicon nanowires (step 1) The material obtained in step a) is placed in a glass cup in a fixed-bed reactor. Then, 50 mL of diphenylsilane (PhSiH 2, ) is poured into the bottom of the reactor.

[0182] After sealing the reactor, gas lines and a heating element are connected to the reactor. The reactor is then evacuated and purged with N2 several times to reduce the oxygen level. The reactor is then heated by an electrical resistor in contact with the outer surface of the reactor. The heating cycle is as follows: ramp from 20°C to 430°C in 30 minutes, hold at 430°C for 60 minutes, stop heating, and then cool the reactor to room temperature. Finally, the reactor is opened to recover the composite material.

[0183] c) Post-processing of graphite / copper / silicon composite (step 2) The organic matter produced by the decomposition of Ph2SiH2 is carbonized by heat treatment. The composite material obtained in step 1 is placed in a crucible and then loaded into a horizontal tube furnace made of quartz. The inlet of the furnace is connected to a gas line of argon (Ar) and hydrogen gas (H2), which are continuously circulated through the material in a controlled amount with a ratio of 97.5:2.5 (v / v). The heat treatment is carried out at a temperature increase rate of 6°C / min up to 600°C for 2 hours, and then cooled naturally. Finally, the furnace is opened to recover the composite material M1.

[0184] Figures 1 and 2 are SEM micrographs of the Si nanowire / copper (CuCl2) / KS4 graphite composite M1. In Figure 1, SiNWs 101 with an average diameter of 190 nm are present on the surface of the KS4 graphite 102. In Figure 2, large twisted SiNWs 201 are present on the surface of the KS4 graphite 202.

[0185] Example 2: Synthesis of SFG75 graphite / copper (CuCl2) / SiNW composite (M2) a) SFG75 graphite and CuCl 2 Mixing as a pre-catalyst material 12.5 g of SFG75 graphite are combined with 1.48 g of CuCl2 and introduced into a Turbula® T2F mixer for 15 minutes. b) Growth of silicon nanowires (step 1) The pre-catalyst material obtained in step a) is uniformly placed in a mullite tube in a fixed bed reactor.

[0186] After connecting the gas lines to the reactor and closing the heating chamber, the oxygen level is reduced by flowing N2 (5 slm) through the quartz tube for a few minutes. The reactor is then heated by a heating device in contact with the outer surface of the quartz tube. The heating and gas injection cycle is as follows: ramp from 20°C to 650°C under Ar / H2 2.5% gas flow (5 slm) over 1 h, maintain 550°C under N2 / SiH4 0.9% (5 slm) (L / min) for 2.15 h, discontinue heating, and then cool the reactor to room temperature under N2 gas flow (5 slm). Finally, the reactor is opened to recover the composite material.

[0187] Figures 4 and 5 show SEM micrographs of the Si nanowire / copper (CuCl2) / SFG75 graphite composite M2. In each figure, long and straight SiNWs (402, 502) and Si nanoparticles (503) with an average diameter of 40 nm are present on the surface of the SFG75 graphite 401, 501.

[0188] Example 3: Synthesis of SFG75 graphite / copper (CuCl2) / SiNW composite (M3) (500°C) a) SFG75 graphite and CuCl 2 Mixing as a pre-catalyst material 12.5 g of SFG75 graphite are combined with 1.48 g of CuCl2 and introduced into a Turbula® T2F mixer for 15 minutes. b) Growth of silicon nanowires (step 1) The pre-catalyst material obtained in step a) is uniformly placed in a mullite tube in a fixed bed reactor.

[0189] After connecting the gas lines to the reactor and closing the heating chamber, the oxygen level is reduced by flowing N2 (5 slm) through the quartz tube for a few minutes. The reactor is then heated by a heating device in contact with the outer surface of the quartz tube. The heating and gas injection cycle is as follows: ramp from 20°C to 650°C under Ar / H2 2.5% gas flow (5 slm) over 1 h, hold at 500°C under N2 / SiH4 0.9% (5 slm) (L / min) for 2.15 h, discontinue heating, and then cool the reactor to room temperature under N2 gas flow (5 slm). Finally, the reactor is opened to recover the composite material.

[0190] Figures 7 and 8 show SEM micrographs of the resulting Si nanowires / copper (CuCl2) / SFG75 graphite composite M3. Short twisted SiNWs (702, 802) with an average diameter of 176 nm are obtained on the surface of the SFG75 graphite 701, 801.

[0191] Example 4: Synthesis of SLP50 graphite / copper (CuCl2) / SiNW composite (M4) (550°C) a) SLP50 graphite and CuCl 2 Mixing as a pre-catalyst material 12.5 g of SLP50 graphite are combined with 1.48 g of CuCl2 and introduced into a Turbula® T2F mixer for 15 minutes.

[0192] b) Growth of silicon nanowires (step 1) The pre-catalyst material obtained in step a) is uniformly placed in a mullite tube in a fixed bed reactor. After connecting the gas lines to the reactor and closing the heating chamber, the oxygen level is reduced by flowing N2 (5 slm) through the quartz tube for a few minutes. The reactor is then heated by a heating device in contact with the outer surface of the quartz tube. The heating and gas injection cycle is as follows: ramp from 20°C to 650°C under Ar / H2 2.5% gas flow (5 slm) over 1 h, maintain 550°C under N2 / SiH4 0.9% (5 slm) (L / min) for 2.15 h, discontinue heating, and then cool the reactor to room temperature under N2 gas flow (5 slm). Finally, the reactor is opened to recover the composite material.

[0193] Figures 10 and 11 show SEM micrographs of the obtained Si nanowires / copper (CuCl2) / SLP50 graphite composite M4. A mixture of short twisted SiNWs 1103 and long straight SiNWs 1002 with an average diameter of 68 nm is obtained on the surface of the SLP50 graphite 1001, 1101.

[0194] Example 5: Synthesis of SLP50 graphite / copper (CuCl2) / SiNW composite (M5) (500°C) a) SLP50 graphite and CuCl 2 Mixing as a pre-catalyst material 12.5 g of SLP50 graphite are combined with 1.48 g of CuCl2 and introduced into a Turbula® T2F mixer for 15 minutes. b) Growth of silicon nanowires (step 1) The pre-catalyst material obtained in step a) is uniformly placed in a mullite tube in a fixed bed reactor. After connecting the gas lines to the reactor and closing the heating chamber, the oxygen level is reduced by flowing N2 (5 slm) through the quartz tube for a few minutes. The reactor is then heated by a heater in contact with the outer surface of the quartz tube. The heating and gas injection cycle is as follows: ramp from 20°C to 650°C under Ar / H2 2.5% gas flow (5 slm) over 1 h, hold at 500°C under N2 / SiH4 0.9% (5 slm) (L / min) for 2.15 h, discontinue heating, and then cool the reactor to room temperature under N2 gas flow (5 slm). Finally, the reactor is opened to recover the composite material.

[0195] 13 and 14 are SEM micrographs of the Si nanowire / copper (CuCl2) / SLP50 graphite composite M5. Short twisted SiNWs 1302, 1402 with an average diameter of 176 nm are obtained on the surface of the SLP50 graphite 1301, 1401.

[0196] (Example 6: Synthesis of KS4 graphite / copper (CuCl2) / SiNW composite (M6) (550°C) a) KS4 graphite and CuCl 2 Mixing as a pre-catalyst material 12.5 g of KS4 graphite are combined with 1.48 g of CuCl2 and introduced into a Turbula® T2F mixer for 15 minutes. b) Growth of silicon nanowires (step 1) The pre-catalyst material obtained in step a) is uniformly placed in a mullite tube in a fixed bed reactor. After connecting the gas lines to the reactor and closing the heating chamber, the oxygen level is reduced by flowing N2 (5 slm) through the quartz tube for a few minutes. The reactor is then heated by a heating device in contact with the outer surface of the quartz tube. The heating and gas injection cycle is as follows: ramp from 20°C to 650°C under Ar / H2 2.5% gas flow (5 slm) over 1 h, maintain 550°C under N2 / SiH4 0.9% (5 slm) (L / min) for 2.15 h, discontinue heating, and then cool the reactor to room temperature under N2 gas flow (5 slm). Finally, the reactor is opened to recover the composite material.

[0197] 16 and 17 are SEM micrographs of the resulting Si nanowires (average diameter 20 nm on KS4) / copper (CuCl2) / KS4 graphite composite M6.

[0198] In each figure, long and straight SiNWs 1602, 1702 and nanoparticle aggregates 1603, 1703 are trapped on the surface of KS4 graphite 1601, 1701.

[0199] Example 7: Synthesis of SFG75 graphite / copper (CuCl) / SiNW composite (M7) (550° C.) a) Mixture of SFG75 graphite and CuCl as a pre-catalyst material 12.5 g of SFG75 graphite are combined with 1.09 g of CuCl and introduced into a Turbula® T2F mixer for 15 minutes. b) Growth of silicon nanowires (step 1) The pre-catalyst material obtained in step a) is uniformly placed in a mullite tube in a fixed bed reactor. After connecting the gas lines to the reactor and closing the heating chamber, the oxygen level is reduced by flowing N2 (5 slm) through the quartz tube for a few minutes. The reactor is then heated by a heating device in contact with the outer surface of the quartz tube. The heating and gas injection cycle is as follows: ramp from 20°C to 650°C under Ar / H2 2.5% gas flow (5 slm) over 1 h, maintain 550°C under N2 / SiH4 0.9% (5 slm) (L / min) for 2.15 h, discontinue heating, and then cool the reactor to room temperature under N2 gas flow (5 slm). Finally, the reactor is opened to recover the composite material.

[0200] Figures 19 and 20 are SEM micrographs of the Si nanowire / copper (CuCl) / SFG75 graphite composite M7. In each figure, long and straight SiNWs 1902, 2002 with an average diameter of 69 nm are present on the surface of the SFG75 graphite 1901, 2001.

[0201] (Example 8: Preparation of electrodes for lithium ion batteries) Coin batteries were fabricated using each of the prepared materials M1, M2, M3, M4, M5, M6, and M7 as the negative electrode active material, and the electrochemical properties of the materials were evaluated. a) Mixing with conductive filler The composite materials M1, M2, M3, M4, M5, M6, M7 according to the present invention were mixed with graphite powder in an Ultra-Turrax Tubedrive disperser from IKA® using YSZ grinding balls with a diameter of 3 mm. The composite material and graphite were charged into the disperser in a weight ratio of 38:62. Mixing was carried out for 10 minutes at 7 revolutions per minute. Finally, the mixed material was collected for further processing or characterization.

[0202] b) 2. Preparation of Coin Cells Each synthesized material was mixed with graphite powder (Actilion GHDR-15-4 and SFG15L) in a ratio of approximately 38:62. A reference graphite electrode was also prepared, consisting of only graphite as the active material, and its gravimetric capacity was determined. For both systems, carbon black C-NERGYC65 was added as a conductive agent, sodium carboxymethylcellulose (Na-CMC) and styrene butadiene rubber (SBR) were applied as binders, and deionized water was used as the solvent. The weight ratio of active material:C65:binder was 95:1:4. Water was added to achieve a viscosity (dry content: approximately 40 wt%) that allows electrode processing. Wet mixing was performed for 30 minutes at 5 rotations. Each electrode ink was dropped onto a 20 μm 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 disks with a diameter of 14 mm and weighed to approximately 0.6 t / cm. 2 The mixture was calendered at 400° C., weighed, and finally dried overnight in vacuum at 110° C.

[0203] In an Ar glove box, a half coin cell (Kanematsu KGK Corporation: stainless steel 316L) using metallic Li as the counter and reference electrodes was fabricated using a layer of Whatman glass fiber, a layer of Celgard 2325 separator, and an arbitrary electrode. The electrode and separator materials were impregnated with an electrolyte solution prepared by dissolving LiPF6 (1M) in EC:DEC (v / v=1 / 1) containing 10 wt% FEC (fluoroethylene carbonate) and 2 wt% VC (vinylene carbonate). The cell was then sealed using an automatic press, removed from the Ar glove box, and measured using a battery charge / discharge evaluation device. After five formation cycles, a normal charge / discharge cycle at a 1C rate was performed. The formation cycle consisted of two cycles of C / 7 and three cycles of C / 5, with constant current / constant voltage discharge (lithium insertion) and constant current charge (lithium desorption).

[0204] c) Electrochemical performance measurements The performance of the batteries is measured by constant current charge-discharge cycling using a Biologic BCS-805 charge-discharge measurement system capable of eight different configurations, each with two different electrodes. 1. Potential profile The potential profiles of batteries C1, C2, C3, C4, C5, C6, and C7 were obtained by measuring the cell potential in relation to the cell capacity during the C / 7 charge-discharge cycle.

[0205] Figures 3, 6, 9, 12, 15, 18 and 21 are the potential profiles obtained from cells C1, C2, C3, C4, C5, C6 and C7, respectively, recorded during the second cycle of C / 7.

[0206] The potential profiles of the composites M1, M2, M3, M2, M5, M4, M5, M6, M7 in Figures 3, 6, 9, 12, 15, 18 and 21 show that the electrochemical activity of the graphite material (below 0.2 V) and the electrochemical activity of the silicon material combine to make these composites electrically and electrochemically active. The electrochemical activity of silicon with lithium ions is especially evident at the inflection / pseudo-plateau around 0.45 V during charging (lithium desorption).

[0207] 2.Initial reversible capacity Table 2 shows the initial reversible capacity of the battery measured at the first cycle (C / 7).

[0208] [Table 1]

[0209] Battery C4 made from composite M4 and battery C7 made from composite M7 have similar initial reversible capacities, i.e., composites M4 and M7 have similar active silicon contents (approximately 12-13%).

[0210] Furthermore, comparing batteries C1, C2, C3, C4, C5, C6, and C7, it can be seen that the higher the active silicon content, the higher the initial capacity.

[0211] Taken together, these results demonstrate that the specific surface area and morphology of the growth support can be used to tune the shape factor of SiNWs as well as to control the electrical and electrochemical performance of the composites. [Explanation of symbols]

[0212] 101,201,402,502,702,802,1002,1102,1103,1302,1302,1402,1602,1702,1902 SiNW 503 Si nanoparticles 1603,1703 Nanoparticle aggregates 102,202,1601,1701 KS4 graphite 401,501,701,801,1901,2001 SFG75 Graphite 1001, 1101, 1301, 1401 SLP50 Graphite

Claims

1. A method for producing a composite material containing at least silicon nanowires and copper, comprising: (A) providing within a reactor chamber at least: Copper halides (CuXn), where X is selected from F, Cl, Br, and I, and n is an integer selected from 1 or 2; Powdered growth carriers introducing a solid / solid mixture; (B) growing silicon nanowires in the reactor chamber from at least one silicon nanowire precursor compound selected from a silane compound or a mixture of silane compounds; (C) recovering the product; The method comprises at least

2. 10. The method of claim 1, wherein step (A) comprises: (1) At least Copper halides (CuXn), where X is selected from F, Cl, Br, and I, and n is an integer selected from 1 or 2; A powdered growth support; solid-solid mixing; and (2) introducing the mixture obtained in step (1) into the reactor chamber; or (1') At least Copper halides (CuXn), where X is selected from F, Cl, Br, and I, and n is an integer selected from 1 or 2, and Powdered growth support into a reactor chamber; and (2') mixing the copper halide and the growth support in a solid-to-solid manner within the reactor chamber; A method comprising:

3. 3. The method of claim 1 or 2, wherein step (B) comprises: (3) introducing into the reactor chamber at least one precursor compound of the silicon nanowires selected from a silane compound or a mixture of silane compounds; (4) reducing the molecular oxygen content in the reactor chamber; and (5) heat treatment at a temperature in the range of 200°C to 900°C; A method comprising: However, steps (3) to (5) may be performed in the above order or in another order.

4. 3. The method according to claim 1 or 2, wherein the method is carried out in a fixed bed reactor, in the tubular chamber of a tumbler reactor moved by a mechanism for rotation and / or mixing, or in a vertical fluidized bed reactor.

5. 3. The method of claim 1 or 2, wherein the growth support is selected from carbon-based materials and carbonaceous polymers.

6. 6. The method of claim 5, wherein the carbon-based material is selected from carbon black nanoparticles, carbonaceous polymer fibers, carbon nanotubes, graphene, and graphite.

7. ００３７ The method of claim 6, wherein the carbon-based material has an average particle size of 0.01 μm to 100 μm.

8. ００３８ 3. The method of claim 1 or 2, wherein the growth support is selected from silicon nanoparticles or silicon microparticles.

9. A method according to claim 1 or 2, wherein the copper halide and growth support are used in a mass ratio of copper halide / growth support of 0.01 to 1.

10. A method according to claim 1 or 2, wherein the copper halide is used as a raw material.

11. The method of claim 10, wherein the copper halide is in the form of a powder.

12. 3. The method according to claim 1, wherein the copper halide is selected from the group consisting of copper (I) chloride (CuCl), copper (II) chloride (CuCl), ２ ) and mixtures thereof.

13. 3. The method of claim 1, wherein the precursor compound of the silicon nanowires is silane (SiH ４ ) or diphenylsilane (Si(C ６ H ５ ) ２ H ２ ) a method.

14. 3. The method according to claim 1, wherein the heat treatment is carried out at a temperature in the range of 300°C to 700°C.

15. 3. The method of claim 1 or 2, wherein the heat treatment is carried out for 1 minute to 10 hours.

16. The method of claim 1 or 2, further comprising: a post-treatment step for converting organic matter derived from the precursor compound of the silicon nanowires into a carbon material; A method comprising:

17. A method according to claim 1 or 2, comprising the additional step of washing the composite material obtained after completion of step (C).

18. The method of claim 1 or 2, wherein at least one doping material is introduced into the reactor.

19. A method for manufacturing an electrode including a current collector, comprising: (i) carrying out the method according to claim 1 or 2 to prepare a composite material; (ii) coating at least one surface of the current collector with a composition containing the silicon-copper composite material as an electrode active material; A method for manufacturing an electrode, comprising:

20. 1. A method for manufacturing an energy storage element such as a lithium secondary battery, comprising: a positive electrode; a negative electrode; and a separator disposed between the positive electrode and the negative electrode, the method comprising:

20. Making at least one electrode by carrying out the method of claim 19; A method for manufacturing an energy storage element, comprising:

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