Method for producing silicon nanowires and tin-containing materials

Abstract

A method for producing silicon nanowires reliably at low cost is provided. [Solution] The method of the present invention includes at least the steps of introducing at least a tin halide (SnX2: where X is selected from F, Cl, Br, and I) and a growth support material into a reactor chamber, mixing the tin halide (SnX2) and the growth support material solid-to-solid, introducing at least one precursor compound of the silicon nanowires into the reactor chamber, reducing the oxygen molecular weight in the reactor chamber, performing a heat treatment at a temperature in the range of 200°C to 900°C, and recovering the product. Each step may be performed in this order or in a different order.

Description

[Technical field]

[0001] The present invention relates to a method for growing silicon nanowires using tin(II) halides, preferably tin(II) chloride, as metal seed precursors. The method is inexpensive, robust, proceeds at moderate temperatures, and allows control of the diameter of the silicon nanowires. The method is carried out in the presence of a growth support material. Silicon nanowire-based composites produced by this method can be used in a variety of applications, including nanoelectronics, microelectronics, spintronics, energy conversion, energy scavenging, sensors, and anode materials for lithium-ion batteries. [Background technology]

[0002] Silicon, an element with unique properties and abundant on Earth, is one of the strategic materials for many high-tech applications. In fact, silicon is one of the main components in solar cell technology and microelectronics. Silicon has attracted great interest for use in lithium-ion batteries due to its low discharge potential and extremely high theoretical charge capacity (more than 4000 mAh / g). Another advantage of silicon is that its morphology can be modified by nanostructuring. In fact, silicon is available in zero-dimensional (nanoparticles), one-dimensional (nanowires) and two-dimensional (nanosheet) forms. It has been shown that nanostructuring silicon increases its ability to withstand the mechanical strains that occur during lithium insertion / extraction processes.

[0003] Among these morphologies, silicon nanowires (SiNWs) have attracted much attention because their extremely high aspect ratio facilitates efficient charge transport, making them extremely advantageous for application to the negative electrodes of lithium-ion batteries.

[0004] Moreover, their electrical conductivity can be easily increased with dopants, which allows their use in supercapacitors (Non-Patent Documents 1 and 2) and thermoelectric materials (Non-Patent Document 3).

[0005] The various techniques for producing SiNWs can be broadly divided into two synthesis methods: bottom-up (growing nanowires from elemental silicon) and top-down (etching bulk silicon). Top-down methods waste a lot of the starting silicon and require the use of hazardous chemicals. Bottom-up methods, typically based on chemical vapor deposition (CVD), can produce high-quality nanowires. This method is well suited to producing silicon nanowires and graphite / carbon composites. The industrial production of such composites at an acceptable cost is a key challenge for the battery market.

[0006] The synthesis of SiNWs has not evolved much since the appearance of bottom-up fabrication of SiNWs by the vapor-liquid-solid growth (VLS) mechanism in the 60s. Currently, VLS is the most prominent and efficient method for synthesizing SiNWs. More specifically, VLS fabrication is dominated by combining a substrate, such as a silicon wafer (2D) or silicon or carbon nanoparticles (0D), with a growth seed, usually in the form of a metal thin film or metal nanoparticles.

[0007] Gold nanoparticles (AuNPs) are known to be the best seeds for SiNW growth. In fact, the Au-Si binary phase diagram shows the first eutectic point at 363 °C. This low eutectic point allows the reaction to proceed at relatively low temperatures (compared to the melting point of gold, which is around 1100 °C), and most of the reaction can proceed via the thermal decomposition of the silane precursor.

[0008] Typically, the growth of Si wires catalyzed by AuNPs is performed by chemical vapor deposition (CVD) using silicon precursors such as silane or diphenylsilane. However, such synthesis has only been performed on a laboratory scale with small quantities of SiNWs. Indeed, in-house production of AuNPs is time-consuming, costly and difficult to scale up. This strategic material is too expensive to make mass production of SiNWs economically feasible.

[0009] Other metals that promote the VLS mechanism also have low eutectic points with silicon and no silicide phases in their binary phase diagrams, such as tin, gallium, cadmium, indium, strontium, tellurium, and lead. Tin is abundant on Earth and has one of the lowest eutectic temperatures, at 232 °C.

[0010] Jeon et al. (Non-Patent Document 4) reported the synthesis of tin-seeded SiNWs for solar cell applications by plasma-enhanced chemical vapor deposition (PECVD). A thin film of Sn(0) is deposited in situ on a Si wafer by thermal evaporation of metallic tin. A hydrogen / SiCl4 gas flow is then introduced to control the growth of the SiNWs.

[0011] Ball et al. (Non-Patent Document 5) disclosed the use of Sn(0) nanoparticles (NPs) as catalysts for the synthesis of SiNWs using silane as a silicon source at low pressure.

[0012] Dai et al. (Non-Patent Document 6) disclosed that tin dioxide nanoparticles (SnO2NPs) were used as the tin catalyst material. Silicon nanowires were synthesized by first reducing SnO2NPs to Sn(0)NPs and then introducing silane at 400 °C.

[0013] (Non-Patent Document 7) disclose the plasma-induced reduction of ITO at 250° C. to condense it into catalytic droplets of tin(0) and indium(0). These droplets can be used to grow silicon nanowires at 500° C. in the presence of silane.

[0014] Chockla et al. (Non-Patent Document 8) reported that SiNWs could be grown directly using trisilane at 450 °C after in situ formation of Sn(0) seed particles using supercritical fluid-liquid-solid synthesis using bis(bis(trimethylsilyl)amino)tin (Sn(HMDS)2).

[0015] Although the above examples show that tin is a promising choice as a seed for SiNW growth, these materials are still expensive and do not enable mass production of SiNWs.

[0016] Currently, SnCl2 is used as a precursor for the growth of Sn-seeded SiNWs. For example, Gerrard EJ Poinern et al. (Non-Patent Document 9) reported the preparation of Sn metal nanoparticles as seeds for SiNW growth by the reduction of tin salts using a reverse micelle method. After the formation of SnNPs, the silicon nanowires (SiNWs) are grown using PECVD. Although this preparation method is excellent, it involves many steps, is very expensive and time-consuming, and has limitations. [Prior art documents] [Patent documents]

[0017] [Patent Document 1] International Publication No. 2021 / 018598 [Patent Document 2] International Publication No. 2019 / 020938 [Non-patent literature]

[0018] [Non-Patent Document 1] S.-T. Lee et al., Nano Today, 2013, 8, 75-97 [Non-Patent Document 2] S. Sadki et al., Nanoscale Res. Lett., 2013, 8, 1-5 [Non-Patent Document 3] P. Yang et al., Nature, 2008, 451, 163-167 [Non-Patent Document 4] Jeon et al., Materials Letters 63 (2009) 777-779 [Non-Patent Document 5] Ball et al., CrystEngComm 15 (2013) 3808-3815 [Non-Patent Document 6] Dai et al., Nanotechnology 29 (2018) 435301 [Non-Patent Document 7] Ngo et al., MRS Proceedings 1258 (2010) 1258-P04-51 [Non-Patent Document 8] Chockla et al., Chemistry of Materials 24 (2012) 3738-3745 [Non-Patent Document 9] Gerrard EJ Poinern et al., Journal of Colloid and Interface Science 352 (2010) 259-264 [Non-Patent Document 10] Dusanes et al. J Nanopart Res, 2020, 22, 363. Summary of the Invention [Problem to be solved by the invention]

[0019] To harness this unique and versatile material for a variety of industrial applications, robust and economical technologies for mass production of SiNWs are required. [Means for solving the problem]

[0020] This invention describes a method for growing silicon nanowires using tin(II) halide, preferably tin(II) chloride, as a seed metal precursor. This method is simple, cost-effective, and robust. This method utilizes the in situ conversion of tin(II) halide, preferably tin(II) chloride, to tin nanoparticles at moderate temperatures. In addition, it allows satisfactory control of the diameter of silicon nanowires.

[0021] A first aspect of the present invention is a method for producing a composite material containing at least silicon nanowires and tin. The method includes the steps of: (1) introducing at least a tin halide (SnX2, where X is selected from F, Cl, Br and I) and a growth support into a reactor chamber; (1') mixing the tin halide (SnX2) and the growth support in a solid-solid state; (2) introducing at least one precursor compound of the silicon nanowires into the chamber of the reactor; (3) reducing the molecular weight of oxygen in the chamber of the reactor; (4) a step of performing a heat treatment at a temperature in the range of 200°C to 900°C; (5) recovering the product; and The steps (1), (1'), (2), (3) and (4) may be carried out in this order or in a different order.

[0022] The present invention further relates to a method for producing an electrode having a current collector, the method comprising the steps of: (i) carrying out the above method to prepare a composite material containing at least silicon nanowires and tin as an electrode active material; (ii) coating at least one surface of the current collector with a composition containing the electrode active material; Includes.

[0023] 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, wherein at least one of the electrodes, preferably the negative electrode, is obtained by the method described above.

[0024] In a first example, the process for producing a composite material is carried out in a fixed bed reactor. 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.

[0025] In a preferred embodiment, the tin halide is SnCl2. In a preferred embodiment, the tin halide and the growth support are mixed together before being introduced into the reactor.

[0026] In a preferred embodiment, the heat treatment is carried out at a temperature in the range of 200°C to 900°C, preferably 300°C to 650°C. In a 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.

[0027] In a preferred embodiment, the method for producing a composite material further comprises a post-treatment step for converting organic matter, in particular organic matter resulting from the precursor compound of the silicon nanowires, into a carbon material.

[0028] In a preferred embodiment, the method for producing a composite material further comprises an additional step (6) of treating the composite material obtained in step (5) with an acidic solution.

[0029] In a preferred embodiment, the precursor compound of the silicon nanowires is a silane compound or a mixture of silane compounds.

[0030] In a preferred embodiment, the precursor compound of the silicon nanowires is silane (SiH4) or diphenylsilane (Si(C6H5)2H2).

[0031] In a preferred embodiment, the growth support material is a carbon-based material, a silicon-based material, an ITO-based material, or a carbonaceous polymer material.

[0032] The method according to the present invention is based on a tin halide, preferably SnCl2, as a catalyst for the production of SiNWs, which has the advantage that it can be carried out in a one-pot reaction without pretreatment of the catalyst.

[0033] The present invention is practiced in the presence of a growth support. The combination of tin halide (preferably SnCl2) with the growth support is simple and robust. The use of very stable products such as SnCl2 or other tin halides allows for a simplified procedure. In fact, SnCl2 or other tin halide and said growth support only need to be mixed solid-to-solid. Methods for growing SiNWs based on, for example, gold nanoparticles, require the preparation of a solid / liquid followed by evaporation of the solvent. The method according to the invention has the advantage that it can be carried out without pretreatment or solvent.

[0034] By appropriately selecting the physical properties of the growth support, the diameter of the nanowires can be controlled. As shown in the examples, the diameter of nanowires produced using SnCl2 is directly affected by the properties of the growth support. [Brief description of the drawings]

[0035] [Figure 1] 1 is a low magnification photograph of a Si nanowire / KS4 graphite composite (Example 1) obtained by scanning electron microscopy (SEM). [Diagram 2] 1 is a high magnification photograph of a Si nanowire / KS4 graphite composite (Example 1) obtained by scanning electron microscopy (SEM). [Diagram 3] 1 is a graph showing the potential profile of a battery made from a Si nanowire / KS4 graphite composite (Example 1) (X-axis: battery capacity (mAh), Y-axis: battery potential (V)). [Figure 4] 1 is a graph showing a differential plot of the potential profile (X-axis = battery capacity (mAh), Y-axis: battery potential (V)) of a battery made from a Si nanowire / KS4 graphite composite (Example 1). [Diagram 5] 1 is a low magnification photograph of the Si nanowire / KS4 composite (Example 2) after the HCl cleaning step obtained by scanning electron microscopy (SEM). [Figure 6]1 is a high magnification photograph of the Si nanowire / KS4 graphite composite (Example 2) after the HCl cleaning step obtained by scanning electron microscopy (SEM). [Figure 7] 1 is a graph showing the potential profile of a battery made from a Si nanowire / KS4 graphite composite (Example 2) after a cleaning process with HCl (X-axis: battery capacity (mAh), Y-axis: battery potential (V)). [Figure 8] 1 is a low magnification photograph of a Si nanowire / BNB90 graphite composite (Example 3) obtained by scanning electron microscopy (SEM). [Figure 9] 1 is a high magnification photograph of a Si nanowire / BNB90 graphite composite (Example 3) obtained by scanning electron microscopy (SEM). [Figure 10] 1 is a graph showing the potential profile of a battery made from a Si nanowire / BNB90 graphite composite (Example 3) (X-axis: battery capacity (mAh), Y-axis: battery potential (V)). [Figure 11] 1 is a low magnification photograph of a Si nanowire / SLP50 graphite composite (Example 4) obtained by scanning electron microscopy (SEM). [Figure 12] 1 is a high magnification photograph of a Si nanowire / SLP50 composite (Example 4) obtained by scanning electron microscopy (SEM). [Figure 13] 1 is a graph showing the potential profile of a battery made from a Si nanowire / SLP50 graphite composite (Example 4) (X-axis: battery capacity (mAh), Y-axis: battery potential (V)). [Figure 14] 1 is a low magnification photograph of a Si nanowire / Si nanoparticle composite (Example 5) obtained by scanning electron microscopy (SEM). [Figure 15] 1 is a high magnification photograph of a Si nanowire / Si nanoparticle composite (Example 5) obtained by scanning electron microscopy (SEM). [Figure 16] 1 is a graph showing the potential profile of a battery made from a Si nanowire / Si nanoparticle composite (Example 5) (X-axis: battery capacity (mAh), Y-axis: battery potential (V)). [Figure 17] 1 is a low magnification photograph of a Si nanowire / Sn / KS4 composite (Example 6) treated with SiH4 obtained by scanning electron microscopy (SEM). [Figure 18] 1 is a high magnification photograph of a Si nanowire / Sn / KS4 composite (Example 6) treated with SiH4 obtained by scanning electron microscopy (SEM). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0036] The phrase "consisting essentially of" means that the method or material of the invention may contain other components or steps, other than one or more components or steps specified, that do not significantly affect the characteristics or properties of the invention.

[0037] The term "X to Y" is inclusive unless otherwise specified. This term means that the range includes X and Y, as well as all values ​​from X to Y.

[0038] The first aspect of the present invention is a method for producing a composite material containing silicon nanowires by a process based on chemical vapor deposition (CVD). The composite material is suitable for use as an anode active material in lithium ion batteries, but other uses are also envisioned.

[0039] The SiNW composite material obtained by this method may be used as is after production or may be subjected to post-treatment after production.

[0040] The present invention relates to a method for producing silicon-based nanostructured materials. The present invention relates to a method for producing silicon-based composite materials, which contain at least a nanostructured silicon material, tin and a growth support material, and which are obtained by chemical decomposition of reactive silicon-containing gaseous species. The method is based on the principle of chemical vapor deposition (CVD).

[0041] The term "nanostructured material" in the sense of the present invention is to be understood as meaning a material comprising individual particles, possibly in the form of aggregates or agglomerates, in which at least one dimension of the outer shape of at least 5% by weight, preferably at least 10% by weight, based on the total weight of the material, of the particles ranges from 1 nm to 100 nm.

[0042] "Composite material" refers to a material made up of two or more constituent substances that have significantly different physical or chemical properties. The external dimensions of the particles can be determined by any known method, in particular by analysis of images of the composite material according to the invention obtained by scanning electron microscopy (SEM).

[0043] (Method of manufacturing composite materials) The present invention relates to a method for producing a composite material containing at least tin and SiNWs, the method comprising the steps of: (1) introducing at least a tin halide (Sn(X)2, where X is selected from F, Cl, Br and I, preferably tin chloride (SnCl2)) and a growth support into a reactor chamber; (1') mixing the tin halide (SnX2) and the growth support in a solid-solid state; (2) introducing at least one precursor compound of the silicon nanowires into the chamber of the reactor; (3) reducing the molecular weight of oxygen in the chamber of the reactor; (4) a step of performing a heat treatment at a temperature in the range of 200°C to 900°C; (5) recovering the product; and At least

[0044] The order of steps (1) to (4) may essentially be 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 molecular weight of oxygen, and the state (liquid or gas) in which the silicon nanowire precursor compound is introduced into the reactor.

[0045] In a first example, the process is carried out in a fixed bed reactor. In a second example, the process is carried out in the tubular chamber of a tumbler type reactor equipped with a mechanism for rotation and / or mixing.

[0046] Preferably, the reactor is closed during the process. By closed reactor, it is meant that the introduction of gaseous species occurs at the beginning of the process and then the reactor is closed to gas flow during the heat treatment step.

[0047] (Process parameters) The process parameters described below are common to all examples of this process (fixed bed reactor, tumbler reactor equipped with mechanisms for rotation and / or mixing).

[0048] In the method according to the invention, a growth support is introduced into the reactor chamber, the form and nature of which will be described in more detail below.

[0049] The method according to the invention involves a preparatory step of solid-to-solid mixing of a growth support and a tin halide (SnX2), hereafter referred to as the catalyst.

[0050] In a first example, the catalyst (SnX2) (wherein X is F, Cl, Br, I) (preferably SnCl2) and the growth support are mixed and then introduced into the reactor.

[0051] In a second example, the catalyst (SnX2) (wherein X is F, Cl, Br, I) (preferably SnCl2) and the growth support are introduced into the reactor separately as feedstocks and then mixed in the reactor chamber.

[0052] The step (3) of reducing the molecular weight of oxygen within the reactor chamber can be carried out in a variety of different ways. The oxygen molecular weight in the reactor chamber is preferably adjusted to 10 -1 bar(10 -2This can be reduced by reducing the pressure to below 100 MPa.

[0053] Alternatively, the oxygen molecular weight within the reactor chamber can be reduced by flushing the reactor chamber with an inert gas. 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 pre-chamber of the reactor, thereby replacing the gas present in the reactor with the injected inert gas.

[0054] Preferably, the inert gas is selected from nitrogen gas (N2), argon gas (Ar), and mixtures thereof.

[0055] Preferably, the reactor chamber is flushed with the inert gas at least twice, more preferably at least three times.

[0056] Preferably, at the end of step (3), the molecular weight of oxygen in the reactor chamber is 1% by volume or less, based on the total volume of the reactor chamber.

[0057] Preferably, the heat treatment is carried out at a temperature in the range of 200 to 900°C, preferably 300 to 700°C, more preferably 300 to 650°C.

[0058] Preferably, the heat treatment is carried out under low pressure, atmospheric pressure or at a pressure in the range of 0.11 to 30 MPa, the pressure parameters being determined by the type of reactor chosen.

[0059] During the process of the present invention, the pressure inside the reactor may increase due to the heat treatment, this pressure depends on the heat treatment being applied and does not necessarily need to be controlled or monitored. Preferably, the heat treatment is carried out for 1 minute to 5 hours, preferably 10 minutes to 2 hours, more preferably 30 minutes to 60 minutes.

[0060] In one embodiment, the method according to the invention comprises a post-treatment step between steps (4) and (5) for converting the organic matter into carbon material. By "organic matter" is meant the organic chemical residues resulting from the decomposition of the precursors of silicon nanowires (in particular silanes and / or diphenylsilane). When carried out, the step essentially consists of a heat treatment. Advantageously, the step is carried out in an inert atmosphere, for example under a carrier gas atmosphere such as N2, Ar, mixtures of Ar / H2, etc., at a temperature in the range of 500°C to 700°C, preferably 550°C to 650°C, advantageously around 600°C.

[0061] In one embodiment, the method according to the invention comprises the additional step (6) of washing the composite material obtained in step (5). The composite material obtained at the end of step (5) may be washed with an organic solvent, preferably selected from chloroform, ethanol, toluene, acetone, dichloromethane, petroleum ether and mixtures thereof.

[0062] Alternatively, in a preferred embodiment, the composite material obtained in step (5) is washed with an acidic solution as described in the Experimental Examples section (Example 2). In this variant, preferably the method further comprises, after step (6), the auxiliary step of drying the washed composite material.

[0063] 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 a temperature of 60° C. or higher. Preferably, the drying step may last for 15 minutes to 12 hours, more preferably 2 hours to 10 hours, and even more preferably 5 hours to 10 hours.

[0064] (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. By "precursor compound of silicon nanowires" is meant a compound capable of forming silicon nanowires by carrying out the method according to the invention, in particular a compound capable of forming silicon nanowires under the conditions of the CVD process.

[0065] 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 liquid is converted into 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, it is referred to as a "reactive silicon-containing gas species."

[0066] For example, if the precursor compound for SiNWs is a liquid, such as diphenylsilane, the liquid precursor will vaporize into gaseous species when the reactor reaches the appropriate temperature / pressure parameters.

[0067] The precursor compound for silicon nanowires may be introduced into the reactor as a mixed gas with a carrier gas. 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 gas mixture with a carrier gas (forming a reactive silicon-containing gas mixture). For example, SiH4, which is a gas at room temperature / pressure, can be introduced directly into the reactor chamber, either alone or in a mixture with a carrier gas. Alternatively, a liquid precursor compound such as diphenylsilane (Ph2SiH2) can be heated in a pretreatment step of the process to change it to a vapor state, and then introduced into the reactor chamber as a gas, either alone or in a mixture with a carrier gas.

[0068] Preferably, the silicon nanowire precursor compound or "reactive silicon-containing gas species" is a silane compound or mixture of silane compounds. For purposes of the present invention, the term "silane compound" refers to 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

[0069] In this embodiment, the silicon-containing gas species is preferably selected from compounds represented by formula (I), wherein n is an integer of 1 to 5, and R1, R2, R3 and R4 are each independently selected from hydrogen, a C1 to C3 alkyl group, phenyl and chloride. 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.

[0070] In this embodiment, the precursor compound of silicon nanowires is preferably selected from silane, disilane, trisilane, chlorosilane, dichlorosilane, trichlorosilane, dichlorodimethylsilane, phenylsilane, diphenylsilane, triphenylsilane or mixtures thereof.

[0071] In a preferred embodiment, the silicon nanowire precursor compound is silane (SiH4) or diphenylsilane (Si(C6H5)2H2). The morphology and physical state of the silicon nanowire precursor compound is selected depending on the type of reactor and other process parameters.

[0072] (Reactive silicon-containing gas mixture) The precursor compound of silicon nanowires according to the present invention can be introduced into the reactor as a gas or as a liquid that changes into a gas in said reactor. The silicon nanowires are obtained by chemical decomposition at high temperature of reactive silicon-containing gas species. The reactive silicon-containing gas species may be in a mixture with a carrier gas. Hereinafter, this mixture is referred to as "reactive silicon-containing gas mixture".

[0073] "Carrier gas" refers to a gas selected from a reducing gas, an inert gas, or a mixture thereof. Preferably, the reducing gas is hydrogen gas (H2). Preferably, the inert gas is selected from argon gas (Ar), nitrogen gas (N2), helium gas (He) or a mixture thereof.

[0074] In a preferred embodiment, the silicon-containing mixed gas contains silicon-containing gas species at 1 vol % or more, preferably 10 vol % or more, more preferably 50 vol % or more, and even more preferably 100 vol %. The ratio of silicon-containing gas species to carrier gas may be modulated to different levels at different steps of the method.

[0075] (catalyst) In the process according to the invention, a catalyst (SnX2), where X is a halide selected from the group consisting of F, Cl, Br and I, is introduced into the reactor chamber.

[0076] In the context of the present invention, "catalyst" refers to a compound selected from compounds of the formula: SnX2, where X is a halide selected from the group consisting of F, Cl, Br and I.

[0077] Preferably, in the context of the present invention, "catalyst" refers to SnCl2. The function of the catalyst is to promote the growth of SiNWs. SnX2 (especially SnCl2) is preferably in the form of particles. The process according to the invention comprises a step of mixing the catalyst (SnX2) and the growth support in a solid-to-solid manner.

[0078] For the purposes of the present invention, the term "solid-state mixing" refers to the mixing of a catalyst and a growth support as raw materials in a solid state, and means associating and / or combining and / or subjecting said growth support and said catalyst to a blending process, to obtain a material of substantially homogeneous composition. The solid-state mixing is carried out without the use of a medium or solvent.

[0079] In a preferred embodiment of the present invention, a mixture of the catalyst (SnX2) (preferably SnCl2) and the growth support is advantageously prepared prior to introduction into the reactor chamber, after which the resulting solid-phase mixture is introduced into the reactor chamber and steps (2) to (5) above are carried out.

[0080] In this embodiment, the solid-solid mixing can be carried out by any industrial mixing equipment known to those skilled in the art, such as ball mills, attrition 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. This step in the process preferably does not last more than 30 minutes.

[0081] In another preferred embodiment of the present invention, the solid-solid mixing of the catalyst (SnX2) (preferably SnCl2) and the growth support material is carried out in the reactor chamber after the catalyst (SnX2) and the growth support material are introduced as raw materials into the reactor chamber. In this embodiment, the solid-solid mixing can be carried out, for example, by the mixing means and / or mechanism of the reactor. This is the case, for example, when a tumbler type reactor equipped with a rotation mechanism is used. Alternatively, the solid-solid mixing can be carried out by injecting an inert gas flow into the reactor chamber, which mechanically fluidizes and moves the particles, thereby mixing them.

[0082] In the present invention, the growth support and catalyst are associated with each other either before or after introduction into the reactor. For purposes of the present invention, the term "associated" means that the growth support and the catalyst have been subjected to an association process that corresponds to mixing of the growth support and the catalyst to obtain a material of substantially homogeneous composition.

[0083] The combination of SnX2 (preferably SnCl2) and the growth support according to the present invention is simple and reliable. SnCl2 and other tin halides as raw materials are very stable substances, which simplifies the processing compared to other catalysts. In fact, SnCl2 and other tin halides only need to be mixed solid-to-solid with the growth support, whereas growth media based on, for example, gold nanoparticles, require the preparation of a solid / liquid followed by evaporation of the solvent.

[0084] When the growth support is a two-dimensional support (e.g., ITO glass, Si wafer, etc.), the solid-to-solid mixture advantageously results in a mixture of catalyst and growth support in which the surface of the growth support is partially or entirely coated with the catalyst, for example by dropping a powder of the catalyst onto the support.

[0085] Preferably, the catalyst and growth support are used according to a catalyst / growth support mass ratio in the range of 0.01 to 1, more preferably 0.02 to 0.5, even more preferably 0.05 to 0.15.

[0086] The solid-solid mixing process of the catalyst and growth support according to the present invention can form a plurality of particle growth sites on the surface of the growth support.

[0087] (growth support material) The method according to the invention is carried out in the presence of a growth support. For example, the growth support may be a carbon-based material, a silicon-based material, an ITO-based material, or a carbonaceous polymer material.

[0088] The growth support may be a zero dimensional object, a one dimensional object, a two dimensional object, or a three dimensional object. For example, the zero-dimensional object may be a silicon nanoparticle, a carbon black nanoparticle, etc. For example, the one-dimensional object may be a carbonaceous polymer fiber, a carbon nanotube, or the like. For example, the two-dimensional object may be a silicon wafer, graphene, ITO glass, etc. For example, the three-dimensional object may be a carbonaceous medium, such as silicon microparticles, powders such as graphite (natural, synthetic or expanded graphite), micronized graphite, or polymeric materials.

[0089] The silicon-based support material may be any material selected from the group consisting of silicon nanoparticles, silicon microparticles, and silicon wafers.

[0090] Preferably, the silicon nanoparticles have an average particle size of 1 to 100 nm, more preferably 30 to 50 nm. Preferably, the silicon microparticles have an average particle size of 0.1 to 30 μm, advantageously 1 to 15 μm. Preferably, the silicon wafer has an average width dimension between 1 cm and 45 cm, advantageously between 1 and 10 cm. The ITO-based support may be any material selected from the group consisting of ITO glass with an average width dimension between 1 cm and 100 cm, advantageously between 1 and 10 cm.

[0091] The carbon-based support material may be any material selected from the group consisting of graphite, graphene, carbon, more specifically natural graphite, artificial graphite, hard carbon, soft carbon, carbon nanotubes or amorphous carbon, carbon nanofibers, carbon black, expanded graphite, graphene, or a mixture of two or more thereof.

[0092] The average particle size of the support material can be measured by laser diffraction methods. When the growth support is a carbon-based support, the growth support may be in the form of particles, particle agglomerates, non-agglomerated flakes, or agglomerated flakes.

[0093] In this example, the carbon-based support has a Brunauer-Emmett-Teller (BET) area of ​​1 to 100 m 2 / g, more preferably 1 to 70 m 2 / g, more preferably 3 to 50 m 2 / g range.

[0094] In a preferred embodiment of this example, the carbon-based material is selected from graphite, graphene, and carbon, preferably graphite powder having an average particle size of 0.01 to 50 μm.

[0095] In another example, the growth support is a carbonaceous polymer material. The use of polymers as growth supports is disclosed in WO 2021 / 018598.

[0096] When the growth support is a carbonaceous polymeric material, preferably the polymeric material has a decomposition temperature, measured 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.

[0097] In this case, advantageously, the polymeric material is selected from fibrous polymeric materials of synthetic or natural origin, preferably from fibrous polymeric materials of synthetic origin.

[0098] More advantageously in this case, the polymeric material is selected from polybenzothiazoles, polyamines, polyimides, polyurethanes, polybenzoxazoles, polyamides, polybenzimidazoles and mixtures thereof, preferably polyamides. In this example, even more advantageously, the polymeric material is polyparaphenylene terephthalamide, also known as Kevlar®.

[0099] When the growth support is a polymeric material, the method according to the invention comprises: i) preparing a composite material containing a polymeric material and SiNWs according to the method defined above; ii) carbonizing the polymer material of the polymer-based composite material; Includes. Details of suitable process parameters for the preparation of silicon / polymer and silicon / carbon composites are disclosed in WO 2021 / 018598.

[0100] The diameter of the silicon nanowires can be controlled via the physical properties of the growth support, and this controllability is illustrated in the Examples section for three-dimensional growth supports.

[0101] As will be shown in the Examples section, the diameter of nanowires produced using SnCl2 is directly affected by the growth support. In fact, the larger the specific surface area of ​​the growth support (SSA>5m 2 / g), the average diameter of SiNWs was found to be around 80-90 nm. 2 It was found that when grown in the presence of ZnO (ZnS) and ZnO (ZnO), the average diameter was around 150 to 160 nm.

[0102] The morphology of the growth support can also control the diameter of the nanowires: for example, the use of expanded graphite yields SiNWs with an average diameter of around 140 nm (Example 3).

[0103] (Doping materials) In one embodiment, the process according to the invention may include introducing at least one doping material into the reactor. The term "doping material" in the sense of the present invention is understood to mean a material capable of modifying the electrical conductivity of silicon. A doping material in the sense of the present invention is, for example, a material rich in phosphorus, boron or nitrogen atoms.

[0104] In this embodiment, the doping material is introduced into the reactor chamber, preferably by a precursor selected from diphenylphosphine, triphenylborane, diphenylamine and triphenylamine, in a first example, before the start of the growth of the SiNWs.

[0105] In another example, a precursor of the doping material is introduced as a gas along with (or, in some cases, as part of) a reactive silicon-containing gas mixture.

[0106] 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.

[0107] (Reactor) 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.

[0108] [First example] In a first example, the process is carried out in a fixed bed reactor. ● Reactor characteristics Preferably, the fixed bed reactor is a closed type reactor. A reactor that can be used to carry out the method according to the present invention is, for example, as disclosed in International Publication No. 2019 / 020938. In this document, a "closed reactor" embodiment is used.

[0109] ● Parameters In this first example, the reactor is closed and the reactor is subjected to a vacuum, preferably for 10 -1 bar(10 -2 By applying a pressure of up to 1000 psi (100 psi) to the reactor chamber, a reduction in the molecular weight of oxygen can be achieved.

[0110] Alternatively, the molecular weight of oxygen within the reactor chamber may be reduced by flushing the reactor chamber with an inert gas. 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 the reactor with the injected inert gas.

[0111] Preferably, the inert gas is selected from nitrogen gas (N2), argon gas (Ar) and mixtures thereof. Preferably, the reactor chamber is flushed with the inert gas at least twice, more preferably at least three times.

[0112] Preferably, at the end of step (3), the molecular weight of oxygen in the reactor chamber is 1% by volume or less, based on the total volume of the reactor chamber.

[0113] In this example, the silicon nanowire precursor compounds are generally introduced into the reactor as liquids. In this example, the catalyst, silicon nanowire precursor compounds, and growth support materials may be introduced into the reactor in the form of a mixture.

[0114] In this example, the reactor preferably has at least two input zones: a first zone capable of receiving a precursor compound for the silicon nanowires, and a second zone capable of receiving a growth support and a catalyst.

[0115] In one option, the first and second input zones are located at the same height within the reactor chamber. In one preferred option, the second input zone is located higher than the first input zone.

[0116] ● Each step of the manufacturing process In this example, advantageously, the process according to the invention comprises: (1') mixing tin halide (SnX2) and a growth support material in a solid-solid state using a mixer; (1) introducing the mixture obtained in step (1') into a reactor chamber; (2) introducing at least one precursor compound of the silicon nanowires into the chamber of the reactor; (3) reducing the molecular weight of oxygen in the chamber of the reactor; (4) a step of performing a heat treatment at a temperature in the range of 200°C to 900°C; (5) recovering the product; and wherein steps (1′) and (1) are performed in the order stated above, while steps (2), (3) and (4) may be performed in this order or in another order.

[0117] [Second example] In a second example, the method according to the invention is carried out in a tubular chamber of a tumbler type reactor equipped with a mechanism for rotation and / or mixing.

[0118] ● Reactor characteristics The tumbler reactor described above is composed of at least a tubular chamber heated by a furnace. The growth support and the tin halide catalyst can be charged into the tubular chamber as raw materials, either individually or as a mixture. The reactor is equipped with a mechanism for rotation and / or a mechanism for mixing. The reactor may comprise two tubular chambers. The longitudinal axis of the tubular chambers may be horizontal or inclined to an angle of up to 20° with the horizontal axis. The reactor further comprises a product supply system and a product discharge system, allowing the semi-continuous production of the silicon-tin / growth support composite. The tumbler reactor is equipped with a reactor pressure control device, such as a needle valve, a pressure controller, etc.

[0119] A typical mechanical tumbler reactor is a Lödige fluidized bed reactor in which fluidization is achieved by the helical rotation of a horizontal shaft within a tubular chamber.

[0120] Another typical mechanical tumbler reactor comprises a tubular rotating chamber in which fluidization occurs by rotation about a longitudinal axis.

[0121] ● Parameters This embodiment is extremely advantageous in that the reactor mechanically generates fluidization beneficial for contacting the growth support material with silicon, which constitutes the reactive gas species, and also in that the catalyst and growth support material can be directly introduced and mixed within the reactor chamber.

[0122] In this example, the silicon nanowire precursor compound is preferably introduced into the reactor as a gas.

[0123] ● Each step of the manufacturing process In this example, advantageously, the process according to the invention comprises: (1A) introducing at least the catalyst (SnX) (preferably SnCl) and optionally the growth support into the tubular chamber of the reactor; (1B) heating the tubular chamber under a carrier gas flow; (1') rotating the tubular chamber and / or activating the mixing mechanism; (2) introducing a reactive silicon-containing gas mixture into the tubular chamber; (3) controlling the pressure in the chamber of the reactor with a flow of mixed gas; (4) subjecting the tubular chamber to a heat treatment at a temperature in the range of 200° C. to 900° C. while rotating and / or mixing the tubular chamber under a reactive silicon-containing mixed gas flow; (5) recovering the resulting product; and Includes.

[0124] In this example, most of the steps must be performed in this order, however, said rotating and / or mixing of step (1') may commence before or after step (1A) or step (1B).

[0125] In this example, it should be appreciated that, as a variant, the method may be carried out by first mixing the catalyst (SnX2) (preferably SnCl2) and the growth support solid by solid and then introducing the mixture into the tubular chamber, followed by carrying out steps (1)-(5) as described above.

[0126] After step (4) is completed, the reactor may be opened and steps (2), (3) and (4) may be further repeated to continue the growth of SiNWs and then the product may be recovered.

[0127] In this example, the heat treatment in step (4) is carried out at low pressure (subatmospheric pressure), atmospheric pressure, or superatmospheric pressure.

[0128] When the reactor is a tumbler type reactor equipped with a mechanism for rotation and / or mixing, it is preferred to carry out the heat treatment in step (4) at a pressure higher than atmospheric pressure.

[0129] (Material composition) The above method results in a composite material containing, preferably consisting essentially of, a growth support material, silicon nanowires and tin particles, which may also contain a halide, in particular a chloride, as a minor component.

[0130] Advantageously, the Si content in the resulting composite material is greater than 5% by weight, preferably greater than 20% by weight, based on the total weight of said material.

[0131] The tin particles originate from the decomposition of tin(II) halides, in particular tin(II) chloride, during the reaction. Preferably, the composite material contains tin particles (tin) in an amount ranging from 1% to 10% by weight, preferably from 1% to 5% by weight, based on the total weight of the material.

[0132] Residual tin(II) halides, especially tin chloride, can be partially removed by acidic treatment of the composite material (see Example 2 and ICP analysis).

[0133] The fact that tin(II) halides, particularly tin chloride, remain indicates that not all tin(II) halides react with silicon during the process. This view is consistent with the work of Dusanes et al. (see details in Non-Patent Document 10: Example 1.d), in which the remaining tin(II) halides, particularly tin chloride, are converted to tin (metal) bound to the SiNWs by the reaction in the process.

[0134] Trace amounts of halides, particularly chlorides, may be found in the composite material, usually less than 1% by weight, preferably less than 0.1% by weight, based on the total weight of the material.

[0135] The silicon material obtained by chemical vapor deposition of silicon-containing gaseous species may be in the form of a wire, worm, rod or filament.

[0136] In a preferred embodiment, the silicon material is in the form of nanowires. The term "nanowire" within the meaning of the present invention is to be understood to mean an elongated object having a wire-like shape and a diameter of nanometers.

[0137] Preferably, the silicon nanowires have a diameter in the range of 1 nm to 250 nm, more preferably in the range of 10 nm to 200 nm, and even more preferably in the range of 30 nm to 180 nm.

[0138] The size of the silicon material can be measured by various methods known to those skilled in the art, for example: It may be measured by analyzing images obtained by scanning electron microscopy (SEM) of one or more samples of the carbon-silicon composite material.

[0139] Advantageously, the silicon, preferably the silicon nanowires, constitutes 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, advantageously 50% to 70% by weight, based on the total weight of the silicon-based composite material. Preferably, the silicon-based composite material is obtained in the form of a powder.

[0140] (Applications of silicon-tin composite materials) The silicon composite material according to the present invention can be used as an anode active material and in the manufacture of lithium ion batteries.

[0141] The electrode having a current collector is manufactured by a manufacturing method conventionally 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.

[0142] As the binder in the present invention, various types of binder polymers can be used, such as polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HEP), polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, and the like.

[0143] The electrodes are commonly used in the art and can be used to manufacture lithium secondary batteries comprising a separator and an electrolyte disposed between a positive electrode and a negative electrode. EXAMPLES

[0144] (Example) In the following examples, unless otherwise specified, the contents and percentages are expressed on a mass basis.

[0145] (Experimental 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. Silicon precursor: diphenylsilane (Si(C6H5)2H2) (CAS number: 775-12-2) available from Sigma-Aldrich. Catalyst: SnCl2 available from Strem Chemicals. Graphite growth support: Imerys' BNB90 graphite (SSA = 21.18 m 2 / g), KS4 graphite (SSA=24.48m 2 / g) and SLP50 graphite (SSA = 4.97m 2 / g).

[0146] Silicon NP: Product code Si-100 (average particle size = 50 nm or less) sold by GetNanoMaterials. Conductive filler: graphite powder sold by Imerys under the trade name C-NERGY® Actilion GHDR-15-4. Carbon black: Timcal C-NERGY C65 (CAS number: 1333-86-4), a product code available from Imerys. Carboxymethylcellulose (CMC): Carboxymethylcellulose (CMC) (CAS number: 9004-32-4) available from Alfa-Aesar. Styrene butadiene rubber (SBR): Styrene butadiene rubber (SBR) sold by MTI (CAS number: 9003-55-8). Electrolyte: An electrolyte solution marketed by Solvionic, comprising lithium hexafluorophosphate (LiPF6) (1M) dissolved in a mixture (volume 1:1) of ethylene carbonate (EC) and diethyl carbonate (DEC), and also containing fluoroethylene carbonate (FEC) (10% by weight) and vinylene carbonate (additive) (2% by weight).

[0147] Example 1: Synthesis of KS4 graphite / SiNW composite (M1) a) KS4 Graphite and SnCl 2 Mixing as a pre-catalyst material 3 g of KS4 graphite is combined with 0.5 g of SnCl2 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.

[0148] b) Silicon nanowire growth (process 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. After sealing the reactor, gas lines and heating elements are connected to the reactor. The reactor is then evacuated and purged with N2 several times to reduce the oxygen concentration. 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.

[0149] c) Post-treatment of graphite / tin / silicon composites (Process 2) The organic matter produced by the decomposition of Ph2SiH2 is carbonized by heat treatment. The composite material obtained in process 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 gas lines of argon (Ar) and hydrogen gas (H2), and the ratio of argon to hydrogen is controlled to 97.5:2.5 (v / v) and is continuously flowed through the material. The heat treatment is performed by increasing the temperature to 600°C at a rate of 6°C / min for 2 hours, and then allowing it to cool naturally. Finally, the furnace is opened to recover the composite material M1. Figures 1 and 2 are SEM photographs of composite material M1 containing SiNWs 101,201 with an average diameter of 80 nm.

[0150] d) Description of Figure 2 Figure 2 shows a mixture of SiNWs 201 and small dots 202 distributed on the surface of KS4 graphite 203. These small dots 202 are tin particles that were too small to react with Si during the growth of the SiNWs. This interpretation is consistent with the work of Dusanes et al.

[0151] Example 2: Synthesis of KS4 graphite / tin / silicon NW "cleaned" composite (M2) Steps a), b) and c) are the same as in Example 1. d) Cleaning of KS4 graphite / silicon composite (Process 3) 10 g of composite material M1 is placed in a beaker with a magnet. Then, 100 ml of HCl (5% by volume) is added to the beaker. The mixture is stirred at 600 rpm for 1 hour. After 1 hour, the mixture is filtered through a Büchner funnel equipped with a filter and then washed with distilled water until the pH is 6-7. Finally, the excess water is removed by adding ethanol. The filter cake is then dried overnight in a thermostatic bath at 60°C to recover composite material M2. Figures 5 and 6 show composite material M3 containing SiNWs 501,601 with an average diameter of 80 nm.

[0152] Example 3: Synthesis of BNB90 graphite / tin / SiNW composite (M3) a) BNB90 graphite and SnCl 2 Mixing as a pre-catalyst material 3 g of BNB90 graphite is combined with 0.5 g of SnCl2 and placed in the steel container of a ball milling apparatus. 3 mm steel balls (40 g) are then placed in the container, which is then tightly closed. The graphite-SnCl2 material is mixed at 400 rpm for 10 minutes and 30 seconds. The balls are removed through a sieve to recover the pre-catalyst material.

[0153] b) Silicon nanowire growth (process 1) The pre-catalyst material obtained in step a) is placed in a glass cup in a fixed-bed reactor. Then, 50 mL of diphenylsilane (PhSiH 2, ) into the bottom of the reactor.

[0154] After sealing the reactor, gas lines and heating elements are connected to the reactor. The reactor is then evacuated and purged with N2 several times to reduce the oxygen concentration. 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, turn off the heating, and then cool the reactor to room temperature. Finally, the reactor is opened to recover the composite material.

[0155] c) Post-treatment of BNB90 graphite / tin / silicon composite (Process 2) The organic matter produced by the decomposition of Ph2SiH2 is carbonized by heat treatment. The composite material obtained in process 1 is placed in a crucible, and then the crucible is loaded into a horizontal tube furnace made of quartz. The inlet of the furnace is connected to gas lines of argon (Ar) and hydrogen gas (H2), and the ratio of argon to hydrogen is controlled to 97.5:2.5 (v / v) and is continuously flowed through the material. The heat treatment is performed by increasing the temperature to 600°C at a rate of 6°C / min for 2 hours, and then allowing it to cool naturally. Finally, the furnace is opened to recover the composite material M3. 8 and 9 show a composite material M3 containing SiNWs 801,901 of average diameter 145 nm on BNB90 graphite 802.

[0156] Table 1 shows the ICP analysis results of the Si nanowire / KS4 composites of Example 1 (without post-treatment) and Example 3 (with HCl washing process).

[0157] [Table 1]

[0158] Example 4: Synthesis of SLP50 graphite / tin / SiNW composite (M4) a) SLP50 Graphite and SnCl 2 Mixing as a pre-catalyst material 3 g of SLP50 graphite is combined with 0.5 g of SnCl2 and placed in the steel container of a ball milling apparatus. 3 mm steel balls (40 g) are then placed in the container, which is then tightly closed. The SLP50-SnCl2 material is mixed at 400 rpm for 10 minutes and 30 seconds. The balls are removed through a sieve to recover the pre-catalyst material.

[0159] b) Silicon nanowire growth (process 1) The pre-catalyst 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.

[0160] After sealing the reactor, gas lines and heating elements are connected to the reactor. The reactor is then evacuated and purged with N2 several times to reduce the oxygen concentration. 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, maintain 430°C for 60 minutes, then discontinue heating and allow the reactor to cool to room temperature. Finally, the reactor is opened to recover the composite material.

[0161] c) Post-treatment of SLP50 graphite / tin / silicon composite (Process 2) The organic matter produced by the decomposition of Ph2SiH2 is carbonized by heat treatment. The composite material obtained in process 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), and the ratio of argon to hydrogen is controlled to 97.5:2.5 (v / v) and is continuously flowed through the material. The heat treatment is performed by increasing the temperature to 600°C at a rate of 6°C / min for 2 hours, and then allowing it to cool naturally. Finally, the furnace is opened to recover the composite material M4. 11 and 12 show a composite material M4 containing SiNWs 1101, 1201 of average diameter 158 nm on SLP50 graphite 1102, 1202.

[0162] Example 5: Synthesis of silicon NP / tin / silicon NW composite (M5) a) Si nanoparticles and SnCl 2 Mixing as a pre-catalyst material 1 g of silicon NPs is combined with 190 mg of SnCl2 and placed into the zirconia container of a ball milling machine. Then, a 10 mm zirconia ball is placed into the container, which is then tightly closed. The SiNP-SnCl2 material is mixed at 400 rpm for 10 min 30 s. The balls are removed through a sieve to recover the pre-catalyst material.

[0163] b) Silicon nanowire growth (process 1) The pre-catalyst 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.

[0164] 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 concentration. The reactor is then heated by an electrical resistor in contact with the outer surface of the reactor. The heating cycle is as follows: increase from 20°C to 430°C in 30 minutes, maintain 430°C for 60 minutes, then stop heating and allow the reactor to cool to room temperature. Finally, the reactor is opened to recover the composite material.

[0165] c) Post-treatment of Si nanoparticle / tin / silicon composite (Process 2) The organic matter produced by the decomposition of Ph2SiH2 is carbonized by heat treatment. The composite material obtained in process 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), and the ratio of argon to hydrogen is controlled to 97.5:2.5 (v / v) and is continuously flowed through the material. The heat treatment is performed by increasing the temperature to 600°C at a rate of 6°C / min for 2 hours, and then allowing it to cool naturally. Finally, the furnace is opened to recover the composite material M5. 14 and 15 show composite material M5 containing SiNWs 1401, 1501 with an average diameter of 165 nm.

[0166] Example 6: Synthesis of KS4 graphite / tin / SiNW composite (M6) a) KS4 graphite and SnCl 2 Mixing as a pre-catalyst material 35 g of SLP50 graphite is combined with 2.73 g of SnCl2 and placed in the steel container of a ball milling apparatus. 50 10 mm steel balls are then placed in the container, which is then tightly closed. The KS4-SnCl2 material is mixed at 300 rpm for 20 minutes and 30 seconds. The balls are removed through a sieve to recover the pre-catalyst material.

[0167] b) Silicon nanowire growth (process 1) The pre-catalyst material obtained in step a) is evenly distributed inside a quartz tube in a fixed bed reactor. After connecting the gas lines to the reactor and closing the heating chamber, N2 (5 slm) is flushed through the quartz tube for a few minutes to reduce the oxygen concentration. The reactor is then heated by a heating device in contact with the outer surface of the quartz tube. The heating and gas injection cycles are as follows: ramp from 20°C to 650°C over 1 h with a gas flow of 5 slm Ar / H2 2.5%, hold at 650°C for 4.3 h with a gas flow of 5 slm N2 / SiH4 0.9%, turn off the heating, and then cool the reactor to room temperature with a gas flow of 5 slm N2. Finally, the reactor is opened to recover the composite material. 17 and 18 are SEM images of the Si nanowire / tin / KS4 composite material M6 obtained in this example.

[0168] c) Description of Figure 17 and Figure 18 Figures 17 and 18 show a mixture of SiNWs 1701, 1801 and small dots 1803 distributed on the surface of KS4 graphite 1702, 1802. These small dots 1803 are tin particles that were too small to react with Si during the growth of SiNWs. This interpretation is consistent with the work of Dusanes et al.

[0169] (Example 7: Preparation of electrodes for lithium batteries) A coin battery is fabricated using one of the prepared materials M1, M2, M3, M4, and M5 as the negative electrode active material, and the electrochemical properties of the material are evaluated.

[0170] a) Mixing with conductive filler The composite materials M1, M2, M3, M4, M5 according to the invention are mixed with graphite powder in an Ultra-Turrax disperser from the company IKA® using grinding balls made of YSZ and having a diameter of 3 mm. The disperser is charged with the composite material and graphite in a weight ratio of 38:62. Mix for 10 minutes at RPM=7. Finally, the mixed material is collected for further processing or characterization.

[0171] b) 2. Preparation of Coin Cells The synthesized materials were mixed with graphite powder (Actilion GHDR-15-4) in a ratio of approximately 38:62. A control graphite electrode of Actilion material was also made with graphite as the only active material. Carbon black C-NERGYC65 was added as a conductive agent to both electrodes, sodium carboxymethylcellulose (Na-CMC) and styrene butadiene rubber (SBR) were used 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 that allows electrode processing (dry content: approximately 40 wt%). Wet mixing was performed for 30 minutes at 5 rotations. Each electrode ink was dropped onto a 20 μm copper foil. The electrodes were dried in air and then further dried in an oven at 65 °C for 2 hours. The electrodes were then cut into 14 mm diameter disks and spun to approximately 1 t / cm. 2 The mixture was calendered at 400° C., weighed, and finally dried overnight in vacuum at 110° C.

[0172] In an Ar glove box, a half coin battery (Kanematsu KGK Corporation: stainless steel 316L) was fabricated using metallic Li as the counter and control electrode, a layer of Whatman glass fiber, a layer of Celgard 2325 separator, and the electrode to be inspected. The electrolyte to be impregnated into the electrode and separator material was 1M LiPF6 dissolved in EC:DEC (v / v=1 / 1) with 10 wt% FEC (fluoroethylene carbonate) and 2 wt% VC (vinylene carbonate). The battery was then sealed with an automatic press, removed from the glove box, and measured with a charge / discharge evaluation device. Seven formation cycles were performed before the normal cycle at 1C rate. The formation cycle consisted of two cycles of C / 10 and five cycles of C / 5 by constant current constant voltage discharge (lithium insertion) and constant current charge (lithium desorption).

[0173] 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.

[0174] 1. Potential Profile The potential profiles of cells C1, C2, C3, C4, and C5 were obtained by measuring the cell potential as a function of cell capacity during C / 10 charge-discharge cycles.

[0175] Figures 3, 7, 10, 13 and 16 are potential profiles recorded at the second cycle (third formation cycle) of C / 10 obtained from cells C1, C2, C3, C4 and C5, respectively.

[0176] In Figures 3, 7, 10 and 13, the potential profiles of the cells obtained from composites M1, M2, M3 and M4 show the superposition of the electrochemical activity of the graphite and silicon materials, confirming that these composites are electrically and electrochemically active. The electrochemical activity of silicon with lithium ions is evident from the inflection / pseudo plateau around 0.45 V during charging (lithium desorption), which is also evident in the capacity derivative plot (Figure 13) comparing the graphite electrode profile with the Si-graphite composite profile.

[0177] In Figure 16, composite M5, like the other materials, shows a superposition of electrochemical activity of the growth support, silicon nanoparticles, and silicon NW materials, and is confirmed to be electrically and electrochemically active as a Li-ion anode material. The electrochemical activity of silicon by lithium ions is particularly evident from the inflection / pseudo-plateau around 0.45 V upon charging (lithium desorption).

[0178] 2.Initial reversible capacity Table 2 shows the initial reversible capacity of the battery measured at the first cycle (C / 10).

[0179] [Table 2]

[0180] The battery C1 made from the composite material M1 and the battery C2 made from the composite material M2 have similar initial reversible capacities. That is, the composite materials M1 and M2 have similar active silicon contents (about 20%). However, the material M2 has a higher initial capacity than the material M1 because it has been subjected to acid washing. In fact, the unreacted SnCl2, SnO x The initial capacity of the material is increased by removing potentially inhibitory compounds such as SiO2.

[0181] Furthermore, when comparing batteries C1, C3, and C4, it can be seen that the initial capacity (822 mAh / g, 864 mAh / g, and 713 mAh / g, respectively) increases with increasing active silicon content (approximately 15%, approximately 16%, and approximately 11%) in composite material M1, composite material M3, and composite material M4.

[0182] In summary, these results demonstrate that the growth rate of SiNWs on the growth support can be adjusted by the specific surface area and morphology of the growth support, and the electrical and electrochemical performance of the composite can be manipulated. [Explanation of symbols]

[0183] 101,102,501,601,801,901,1101,1201,1401,1501,1701,1801 Silicon Nanowires (SNW) 202,1803 Tin particles 203,820,1102,1202,1702,1802 Graphite

Claims

1. A method for producing a composite material containing at least silicon nanowires and tin, comprising: (1) At least tin halide (SnX ２ : wherein X is selected from F, Cl, Br and I) and a growth support material are introduced into a chamber of a reactor, and (1') A step of mixing the tin halide (SnX ２ ) and the growth support material in solid form with each other; (2) A step of introducing at least one precursor compound of the silicon nanowires into the chamber of the reactor; (3) A step of reducing the oxygen molecular weight in the chamber of the reactor; (4) A step of performing heat treatment at a temperature in the range of 200°C to 900°C; (5) A step of recovering the product; A method comprising at least the above steps. However, steps (1), (1'), (2), (3) and (4) may be carried out in this order, or in another order.

2. The method according to claim 1, wherein the method is carried out in a fixed bed reactor.

3. The method according to claim 1, wherein the method is carried out in a tubular chamber of a tumbler reactor driven by a mechanism for rotation and / or mixing.

4. In the method according to any one of claims 1 to 3, wherein the tin halide is SnCl 2 a method.

5. The method according to claim 1, wherein the tin halide and the growth support material are mixed and then introduced into the reactor.

6. The method according to claim 1, wherein the heat treatment is carried out at a temperature in the range of 200°C to 900°C.

7. The method according to claim 6, wherein the heat treatment is carried out at a temperature in the range of 300°C to 650°C.

8. The method according to claim 1, wherein the heat treatment is carried out for 1 minute to 5 hours.

9. The method according to claim 8, wherein the heat treatment is carried out for 10 minutes to 2 hours.

10. The method according to claim 1, further comprising: A post-treatment step for converting the organic matter generated from the precursor compound of the silicon nanowires into a carbon material; A method comprising the above step.

11. The method according to claim 1, further comprising: An additional step (6) of treating the composite material obtained in step (5) with an acidic solution; A method comprising the above step.

12. The method according to claim 1, wherein the precursor compound of the silicon nanowires is a silane compound or a mixture of silane compounds.

13. In the method according to claim 12, the precursor compound of the silicon nanowire is silane (SiH ４ ), or diphenylsilane (Si(C ６ H ５ )) ２ H ２ ).

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

15. A method for producing an electrode having a current collector, comprising: (i) A step of carrying out the method according to claim 1 to prepare a composite material containing at least silicon nanowires and tin as an electrode active material; Step (ii) of coating at least one surface of the current collector with the composition containing the electrode active material; A method comprising the above.

16. A method for manufacturing an energy storage device, comprising a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode, the method comprising: A step of manufacturing at least one electrode by implementing the method according to claim 15; A method comprising the above.

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